The milky spots in omentum are atypical lymphoid tissues that play a pivotal role in regulating immune responses in the peritoneal cavity. The milky spots act as central hubs for collecting antigens and particles from the peritoneal cavity, regulating lymphocyte trafficking, promoting the differentiation and self-renewal of immune cells, and supporting the local germinal centre response. In addition, the milky spots exhibit unique developmental characteristics that combine the features of secondary and tertiary lymphoid tissues. These structures are innately programmed to form during foetal development; however, they can also be formed postnatally in response to peritoneal irritation such as inflammation, infection, obesity, or tumour metastasis. In this review, I discuss emerging perspectives on homeostatic development and organization of the milky spots.

Chronic liver disease results from the orchestrated interplay of components of innate and adaptive immunity in response to liver tissue damage. Recruitment, positioning, and activation of immune cells can contribute to hepatic cell death, inflammation, and fibrogenesis. With disease progression and increasing portal pressure, repeated translocation of bacterial components from the intestinal lumen through the epithelial and vascular barriers leads to persistent mucosal, hepatic, and systemic inflammation which contributes to tissue damage, immune dysfunction, and microbial infection. It is increasingly recognised that innate-like and adaptive T-cell subsets located in the liver, mucosal surfaces, and body cavities play a critical role in the progression of advanced liver disease and inflammatory complications of cirrhosis. Mucosal-associated invariant T cells, natural killer T cells, γδ T cells, and tissue-resident memory T cells in the gut, liver, and ascitic fluid share certain characteristic features, which include that they recognise microbial products, tissue alarmins, cytokines, and stress ligands in tissues, and perform effector functions in chronic liver disease. This review highlights recent advances in the comprehension of human tissue-resident and unconventional T-cell populations and discusses the mechanisms by which they contribute to inflammation, fibrosis, immunosuppression, and antimicrobial surveillance in patients with cirrhosis. Understanding the complex interactions of immune cells in different compartments and their contribution to disease progression will provide further insights for effective diagnostic interventions and novel immunomodulatory strategies in patients with advanced chronic liver disease.

In recent years, significant advances have been made in the study of lymphatic vessels with the identification of their specific markers and the development of research tools that have accelerated our understanding of their role in tissue homeostasis and disease pathogenesis in many organs. Compared to other organs, the lymphatic system in the liver is understudied despite its obvious importance for hepatic physiology and pathophysiology. In this review, we describe fundamental aspects of the hepatic lymphatic system and its role in a range of liver-related pathological conditions such as portal hypertension, ascites formation, malignant tumours, liver transplantation, congenital liver diseases, non-alcoholic fatty liver disease, and hepatic encephalopathy. The article concludes with a discussion regarding the modulation of lymphangiogenesis as a potential therapeutic strategy for liver diseases.

Euthanasia is one of the most commonly performed procedures in biomedical research, involving tens of millions of animals in North America and Europe every year. The use of sodium pentobarbital, injected intraperitoneally, for killing rodents is described as an acceptable technique by the AVMA and CCAC euthanasia guidelines. This drug and route are recommended over inhalant anesthetics, carbon dioxide, and physical methods for ethical and aesthetic reasons as well as efficiency. However, a growing body of evidence challenges the efficacy and utility of intraperitoneal pentobarbital. This methodology has been described as inconsistent and may induce pain and stress. With these considerations in mind, a review of the literature is needed to assess the evidence surrounding this killing method, the associated welfare implications, and potential for refinement.

The interest in approaches to deliver therapeutics to the lymphatic system has increased in recent years as the lymphatics have been discovered to play an important role in a range of disease states such as cancer metastases, inflammatory and metabolic disease, and acute and critical illness. Therapeutic delivery to lymph has the potential to enhance treatment of these conditions. Currently much of the existing data explores therapeutic delivery to the lymphatic vessels and nodes that drain peripheral tissues and the intestine. Relatively little focus has been given to understanding the anatomy, function and therapeutic delivery to the peritoneal lymphatics. Gaining a better understanding of peritoneal lymphatic structure and function would contribute to the understanding of disease processes involving these lymphatics and facilitate the development of delivery systems to target therapeutics to the peritoneal lymphatics. This review explores the basic anatomy and ultrastructure of the peritoneal lymphatics system, the lymphatic drainage pathways from the peritoneum, and therapeutic and delivery system characteristics (size, lipophilicity and surface properties) that favour lymph uptake and retention after intraperitoneal delivery. Finally, techniques that can be used to quantify uptake into peritoneal lymph are outlined, providing a platform for future studies.

William Hunter along with his brother, John, and their colleagues William Hewson, William Cruikshank and John Sheldon made a large contribution to understanding of lymphatic vessels. Hewson, Cruikshank and Sheldon all carried out mercury injections and made much progress in mapping the distribution of lymphatics in the human body. William Hunter appreciated that lymphatics absorbed fluid from the tissues of the body and that lacteals of the intestine and lymphatics are similar structures. John Hunter carried out an elegant series of experiments that proved that lacteals absorb products of digestion. The Hunters, however, were wrong in dismissing absorption by blood vessels and missed the importance of blood capillaries. William Hewson showed that lymphatics were not confined to mammals but that they are present in reptiles, birds and fish. Hewson also demonstrated that tracheobronchial glands are lymph nodes and not mucus-secreting glands as previously thought. Although William Hunter appreciated that tuberculosis and venereal diseases might involve the regional lymph nodes, he does not seem to have fully grasped that malignant disease might involve the local nodes or the concept that knowledge of lymph drainage could be used to define the likely site of a primary malignancy.

Steroids play an important role in mammalian reproduction and early pregnancy. Although systemic changes in steroid concentrations have been well documented, it is not clear how these correlate with local steroid concentrations in the genital tract. We hypothesised that, in the horse, the preimplantation embryo may be subjected to high local steroid concentrations for several days. Therefore, we measured progesterone, 17-hydroxyprogesterone, 17?-oestradiol, testosterone and 17?-testosterone concentrations in equine oviductal tissue by ultra-HPLC coupled with tandem mass spectrometry, and progesterone, 17?-oestradiol, oestrone and testosterone concentrations in oviduct fluid by radioimmunoassay, with reference to cycle stage and side of ovulation. Progesterone concentrations were high in oviductal tissue and fluid ipsilateral to the ovulation side during dioestrus, whereas other steroid hormone concentrations were not influenced by the side of ovulation. These results suggest that the high ipsilateral progesterone concentration is caused by: (1) contributions from the follicular fluid in the oviduct and diffusion of follicular fluid steroids after ovulation; (2) local transfer of steroids via blood or lymph; (3) local synthesis of progesterone in the oviduct, as evidenced by the expression of steroidogenic enzymes; and (4) a paracrine contribution from follicular cells. These data provide a basis for the study of the importance of endocrine and paracrine signalling during early embryonic development in the horse.

Lymphatic stomata are small openings of lymphatic capillaries on the surface of the mesothelium that lines the serous cavity and have the function of active absorption. They play an important role in physiological and pathological conditions. The cavity of the tunica vaginalis is a typical serous cavity of the testis, but the lymphatic stomata of the tunica vaginalis of humans have never been reported. Here, we studied their ultrastructure by scanning and transmission electron microscopy. The submesothelial connective tissue with foramina was investigated after the mesothelial cells were digested using NaOH solution. We found the lymphatic stomata in cuboidal mesothelial cell regions of the parietal layer of the tunica vaginalis of humans with a diameter of about 1-2 μm. Sometimes, closed lymphatic stomata could be observed. Our study is the first to report the existence of lymphatic stomata of the tunica vaginalis of humans. We found that the tunica vaginalis cavity is connected with the lymphatic system through the stomata, which might provide a morphological basis for the drainage of hydrocele and tumor metastasis of the tunica vaginalis of humans.

Peritoneal dysfunction is a major factor leading to treatment failure of peritoneal dialysis (PD). However, the precise mechanism of the peritoneal diffusion changes related to PD remains to be elucidated. To this end, we have established a novel peritoneal diffusion model in vitro, which consists of a three-dimensional culture system using a collagen vitrigel membrane chamber and a fluid-stream generation system. This artificial peritoneal model revealed that high-glucose culture medium and fluid flow stress promoted the epithelial-mesenchymal transition (EMT) process of mesothelial cells and that endothelial cells inhibited this mesothelial EMT process. Mesothelial cells in the EMT state showed high expression of connective tissue growth factor and low expression of bone morphogenic protein-7, while non-EMT mesothelial cells showed the opposite expression pattern of these two proteins. In addition, these protein expressions were dependent on the presence of endothelial cells in the model. Our model revealed that the endothelial slit function was predominantly dependent on the covering surface area, while the mesothelial layer possessed a specific barrier function for small solutes independently of the surface area. Notably, a synergic barrier effect of mesothelial cells and endothelial cells was present with low-glucose pretreatment, but high-glucose pretreatment abolished this synergic effect. These findings suggest that the mesothelial slit function is not only regulated by the high-glucose-induced EMT process but is also affected by an endothelial paracrine effect. This peritoneal diffusion model could be a promising tool for the development of PD.

The communicating hydrocele is caused by the failure of the processus vaginalis closure. After the patent processus vaginalis is closed, the hydrocele can subside spontaneously, but the mechanism responsible for the drainage of hydrocele has not been expounded. Former studies showed that lymphatic stomata between the mesothelial cells lining the peritoneum and pleura were responsible for the drainage of ascites and pleural effusion. Although the tunica vaginalis is also lined by mesothelial cells, the existence of lymphatic stomata in it has never been reported. Therefore, we investigated the presence and ultrastructure of lymphatic stomata in mouse tunica vaginalis.

We studied the ultrastructure of mouse tunica vaginalis by scanning and transmission electron microscopy. The submesothelial connective tissue with foramina were investigated after the mesothelial cells were digested by NaOH solution. Typan blue was used as a tracer to show the absorptive function of lymphatic stomata.

The lymphatic stomata were found between the mesothelial cells. The trypan blue was directly absorbed by the lymphatic stomata. Milky spots which possessed immune function were observed, and the lymphatic stomata were found within the milky spots.

Our study is the first to report the presence and ultrastructure of lymphatic stomata in mouse tunica vaginalis. They might be related to the lymphatic drainage in the tunica vaginalis cavity.

Recalling the evolutionary sequence of development first of gonad and subsequently of oviducts, ovarian endocrine regulation of all known components of oviduct physiology is reviewed. Ovaries not only influence oviducts via the systemic blood circulation, but also locally by counter-current transfer of relatively high concentrations of steroid hormones and prostaglandins between the ovarian vein and oviduct branch of the ovarian artery. The efficiency and impact of such counter-current transfer is greatest around the time of ovulation, the transfer process receiving further inputs from hormones present in peritoneal fluid. Classical oviduct physiology is summarised, and the potential molecular consequences of temperature gradients within the duct lumen examined. At ovulation, an oocyte-cumulus complex is displaced in minutes from the follicular surface to the site of fertilisation at the ampullary-isthmic junction of the oviduct. This rapid initial phase is contrasted with the subsequent slow progression of embryos to the uterus in days, still encompassed within a zona pellucida. Regarding transport of spermatozoa, the formation of a pre-ovulatory reservoir in the caudal portion of the oviduct isthmus is noted, with suppression of motility and sperm-head binding to epithelial organelles acting to maintain fertilising ability. Completion of capacitation is prompted shortly before ovulation, predominantly by Ca(2+) influx into bound spermatozoa. A controlled release of spermatozoa coupled with their hyperactivation results in initial sperm:egg ratios at the site of fertilisation close to unity, thereby avoiding the pathological condition of polyspermy. Both the oviduct milieu and embryonic development are influenced by paracrine activity of follicular granulosa cells released at ovulation and remaining in suspension in the vicinity of the oocyte or embryo. These cells may amplify early pregnancy signals from a zygote to the endosalpinx. Beneficial effects of the oviduct on domestic animal embryos are contrasted with anomalies arising as a consequence of in vitro culture. Primate embryos do not require exposure to an oviduct for normal development, perhaps due to overlapping compositions of endosalpingeal and endometrial secretions. Additionally, primate endometrial secretions may be modified by viable gametes or an embryo in the presence of a cumulus cell suspension.

Lymphatic stomata are small openings of lymphatic capillaries on the free surface of the mesothelium. The peritoneal cavity, pleural cavity, and pericardial cavity are connected with lymphatic system via these small openings, which have the function of active absorption. The ultrastructure of the lymphatic stomata and their absorption from the body cavities are important clinically, such as ascites elimination, neoplasm metastasis, and inflammatory reaction. The lymphatic stomata play an important role in the physiological and pathological conditions. Our previous study indicated for the first time that nitric oxide (NO) could regulate the opening and absorption of the lymphatic stomata. It could decrease the level of free intracellular calcium [Ca(2+)] through increasing the cyclic guanosine monophosphate (cGMP) level in the rat peritoneal mesothelial cells, thus regulating the lymphatic stomata. This process is related with the NO-cGMP-[Ca(2+)] signal pathway. In this review, we summarize the recent advances in understanding the development and the function of the lymphatic stomata. The ultrastructure and regulations of the lymphatic stomata are also discussed in this review.

The lymphatic system plays important roles in maintaining tissue fluid homeostasis, immune surveillance of the body, and the taking up dietary fat and fat-soluble vitamins A, D, E and K. The lymphatic system is involved in many pathological conditions, including lymphedema, inflammatory diseases, and tumor dissemination. A clear understanding of the organization of the lymphatic vessels in normal conditions would be critically important to develop new treatments for diseases involving the lymphatic vascular system. Therefore, the present paper reviews the organization of the lymphatic vascular system of a variety of organs, including the thyroid gland, lung and pleura, small intestine, cecum and colon in the rat, the diaphragm in the rat, monkey, and human, Peyer's patches and the appendix in the rabbit, and human tonsils. Methods employed include scanning electron microscopy of lymphatic corrosion casts and tissues with or without treatment of alkali maceration technique, transmission electron microscopy of intact tissues, confocal microscopy in conjunction with immunohistochemistry to some lymphatic-specific markers (i.e., LYVE-1 and VEGFR-3), and light microscopy in conjunction with enzyme-histochemistry to 5'-nucleotidase. Some developmental aspects of the lymphatic vessels and lymphedema are also discussed.

We report a patient methicillin-resistant Staphylococcus aureus pneumonia who developed fluid collections in three spaces in the thorax, the pleural space, the pericardial space, and a pre-existing bulla, in addition to mediastinal oedema. We discuss the universal pathogenesis for the development of these fluid collections and the explanation for the most common presentation being a parapneumonic effusion.

Lymphangioleiomyomatosis (LAM) affects exclusively women of reproductive age, involves the lungs and axial lymphatic system, and is frequently complicated with renal angiomyolipomas. LAM lesions are generated by the proliferation of LAM cells with mutations of one of the tuberous sclerosis complex (TSC) genes. Recent studies indicate that LAM cells can migrate or metastasize to form new lesions in multiple organs, although they show a morphologically benign appearance. In the previous study, we reported LAM-associated lymphangiogenesis and implicated its role in the progression of LAM. In this study, we further focused on the lymphatic abnormalities in LAM: LAM-associated chylous fluid (5 pleural effusion and 2 ascites), surgically resected diaphragm (1 patient), and axial lymphatic system including the thoracic duct, lymph nodes at various regions, and diaphragmatic lymphatic system (5 autopsy cases). We demonstrated that LAM cell clusters enveloped by lymphatic endothelial cells (LCC) in all chylous fluid examined. We identified LAM lesion in the diaphragm (2 of 5 autopy cases and one surgical specimen), thoracic duct (5 of 5), and lymph nodes (retroperitoneal (5 of 5), mediastinal (4 of 5), left venous angle (5 of 5) with total positive rate of 68% to 88% at each region of the lymph node, but less frequent or none at remote lymph nodes located away from the axial lymph trunk (cervical [1 of 5] and axillary [0 of 5]). LCCs were identified in intra-LAM lesional lymphatic channels where LAM cells proliferate along lymphatic system. In in vitro culture system, LCC can fragment into each proliferating LAM cell. These findings suggest that LAM-associated lymphangiogenesis demarcates LAM lesion into bundle- or fascicle-like structure and eventually shed LCC into the lymphatic circulation and that LCCs play a central role in the dissemination of LAM lesion.

Occasional reports describe various aspects of the fine morphology of the pelvic peritoneum, but its complete organ characteristics remain undefined. The peritoneal covering of the urinary bladder, rectum, uterus, uterine tube, ovary, broad ligament (BL) and testis in Wistar rats was examined by means of transmission and scanning electron microscopy (TEM, SEM). Unusually complicated relief and stomata between the cubic mesothelial cells characterized the surface of the BL. Deep, parallel furrows separated the wide longitudinal folds over the entire length of the uterine tube. The uterus and the ovary formed less numerous, shallow or extremely deep crypt-like invaginations, as well as serous villus-like or papilla-like evaginations. The flat cells were the predominant cell type over the BL, while the cubic mesothelium was the basic covering of the organs. Most of the cubic cells were located in the invagination of the submesothelial layer (SML). Such cells formed an almost smooth surface over the urinary bladder or formed larger areas of the rectum and the testis surfaces. Numerous microvilli, ciliae, round evaginations and complex lamellar bodies characterized their apical plasmalemma. In conclusion, the mesothelial heterogeneity is a stable feature of the lesser pelvis peritoneum, confirmed by TEM and SEM. The cubic mesothelium characterizes the organ peritoneum, while the BL plays the role of the parietal sheet, involving lymphatic units in the SML. The different types of contacts between the mesothelio-endothelial cells, large lymphatic vessels and occasional stomata are the usual components of the lymphatic units in norm, visible by TEM. Images of stomata, seen by SEM, demonstrate oval-shaped deep channel-like gaps surrounded by cubic mesothelium. The last data extend the evidence on stomata regions, which resemble the diaphragmatic ones. Clusters of cells (macrophages, mastocytes and Lymphocytes), small vessels (blood or lymphatic) and nerve fibers (unmyelinated and rare myelinated) form highly specialized complexes in the SML of the ovary, the uterus and the testis.

The conspicuous presence of primary cilia, a small immotile cilium present on most cell types, left researchers with little doubt of their functional relevance. Recently mechanosensitive functional significance was established and a link with the pathogenesis of polycystic kidney disease. Together these discoveries have raised the profile of this, previously considered "vestigial", organelle. Primary cilia are expressed on the apical surface of serosal mesothelium and display regional variation but are more abundant on biosynthetically active cells. Adult mesothelial cells are highly biosynthetic producing a phospholipid rich surfactant that lubricates and protects the visceral organs. The mesothelium is utilized as a semipermeable membrane during peritoneal dialysis for patients with end stage renal failure. However, little is known about the functional role of primary cilia on this highly specialized cell type. The present review, examines the significance of the primary cilium in serosal mesothelial cell biology with an emphasis on ciliary location, structure, form and function. Future research is identified and discussed in view of the emerging role cilia have in other cells and the established function of the serosal mesothelium in development, normal function, peritoneal dialysis and pathology of the serosal membranes.

The pleural space separating the lung and chest wall of mammals contains a small amount of liquid that lubricates the pleural surfaces during breathing. Recent studies have pointed to a conceptual understanding of the pleural space that is different from the one advocated some 30 years ago in this journal. The fundamental concept is that pleural surface pressure, the result of the opposing recoils of the lung and chest wall, is the major determinant of the pressure in the pleural liquid. Pleural liquid is not in hydrostatic equilibrium because the vertical gradient in pleural liquid pressure, determined by the vertical gradient in pleural surface pressure, does not equal the hydrostatic gradient. As a result, a viscous flow of pleural liquid occurs in the pleural space. Ventilatory and cardiogenic motions serve to redistribute pleural liquid and minimize contact between the pleural surfaces. Pleural liquid is a microvascular filtrate from parietal pleural capillaries in the chest wall. Homeostasis in pleural liquid volume is achieved by an adjustment of the pleural liquid thickness to the filtration rate that is matched by an outflow via lymphatic stomata.

The generation and development of the peritoneal lymphatic stomata (PLS) and lymphatic vessels of the diaphragm were studied in mice at gestational ages from the embryonic to the postnatal period with TEM, SEM and enzyme histochemistry and the PLS data were quantitatively analyzed with computer-assisted image processing technology (Elescope image analysis software). The results showed that the diaphragmatic mesothelium was covered only by flattened mesothelial cells (FMC) at the 13th embryonic day (ED 13). At ED 15, some cuboidal mesothelial cells (CMC) and immature lymphatic stomata (NLS) were found scattered on the diaphragmatic mesothelium. The sub-peritoneal lymphatic capillaries did not appear until ED 18. However, no absorptive function was observed in NLS when trypan blue granules were injected into the peritoneal cavity. At postnatal day 1 (PND 1), the endothelial cytoplasm processes of the diaphragm lymphatic capillaries span the connective tissue fibers and the basal membrane of CMC to form the subperitoneal channels. These channels were connected with NLS and serve as the absorptive route between the peritoneal cavity and the sub-peritoneal lymphatic vessels. The trypan blue absorption test demonstrated that postnatal PLS possessed an absorptive function and had transformed to mature lymphatic stomata (MLS) by PND 1. Thus, NLS were renamed of MLS. At PND 5, the cuboidal mesothelial cell ridge (CMCR) appeared with increased CMC areas. At PND 10, CMCR were fused to form the band-like CMC area with much more MLS distributed in the muscular portion of the diaphragm. With distribution area and density of PLS increasing and growth of lymphatic vessels, an increased absorptive function from the peritoneal cavity was observed in the experiment.

Application of india ink to the peritoneal and pleural surfaces of the adult human diaphragm allowed visualization of the distribution and morphology of the lymphatic vessels by light microscopy and scanning electron microscopy. The diaphragms examined had been fixed and stored in 10% formalin. Numerous lymphatic vessels were stained black with india ink, presenting reticular, radial-meshwork, ladder-like and lacy patterns. They were distributed throughout the entire sternocostal part. Analysis by light and scanning electron microscopy of the areas indicated by india ink revealed the presence of primary lymphatic vessels that formed lymphatic lacunae and stomatal openings to the peritoneal cavity. A layer of secondary collecting lymphatic vessels was located cranially with respect to the layer of primary lymphatic vessels. Thus, the peritoneum had at least two layers of lymphatic vessels. These lymphatic vessels were not tubular vessels but resembled flat cisternae, as has been suggested in the case of the mouse diaphragm. The pleura lacked lymphatic stomata and had no such double-layered lymphatic organization. This is the first report that showed distribution and morphology of the lymphatic vessels in the diaphragmatic peritoneum of the formalin-fixed, adult human diaphragm. The method and results in the present study may contribute to morphological analysis of the lymphatic system in the wall of the human body cavity.

The mesothelium is composed of an extensive monolayer of specialized cells (mesothelial cells) that line the body's serous cavities and internal organs. Traditionally, this layer was thought to be a simple tissue with the sole function of providing a slippery, non-adhesive and protective surface to facilitate intracoelomic movement. However, with the gradual accumulation of information about serosal tissues over the years, the mesothelium is now recognized as a dynamic cellular membrane with many important functions. These include transport and movement of fluid and particulate matter across the serosal cavities, leucocyte migration in response to inflammatory mediators, synthesis of pro-inflammatory cytokines, growth factors and extracellular matrix proteins to aid in serosal repair, release of factors to promote both the deposition and clearance of fibrin, and antigen presentation. Furthermore, the secretion of molecules, such as glycosaminoglycans and lubricants, not only protects tissues from abrasion, but also from infection and possibly tumour dissemination. Mesothelium is also unlike other epithelial-like surfaces because healing appears diffusely across the denuded surface, whereas in true epithelia, healing occurs solely at the wound edges as sheets of cells. Although controversial, recent studies have begun to shed light on the mechanisms involved in mesothelial regeneration. In the present review, the current understanding of the structure and function of the mesothelium and the biology of mesothelial cells is discussed, together with recent insights into the mechanisms regulating its repair.

We present de novo studies and review published efforts from our laboratory, spanning 12 years (from 1988 to 2000), where we have used ultrastructural approaches to study the functional anatomy of the microvasculature in man and animals in health and disease. These efforts have defined a new endothelial cell organelle, termed the vesiculo-vacuolar organelle (VVO), which participates in the regulated transendothelial cell passage of soluble macromolecules. The studies defining this organelle utilized ultrathin serial sections, three-dimensional computer-assisted reconstructions, and ultrastructural electron-dense tracers to establish luminal to abluminal transendothelial cell continuity of VVOs. Commonality of VVOs and caveolae is suggested by the ultrastructural anatomy of individual units of VVOs and caveolae, the presence of caveolin in both structures, and a mathematical analysis of morphometric data, all of which suggest that VVOs form from fusions of individual size units equivalent to vesicles of caveolar size. Ultrastructural studies have localized potent permeability factors and their specific receptors to VVOs in in vivo tumor and allergic inflammation models. Regulation of permeability through VVOs has been quantified and shown to be increased in tumor microvessels and in control vessels exposed to potent permeability-inducing mediators. The transendothelial cell passage of particulate macromolecules occurs by vacuolar transport in tumor vessels; in permeability factor-exposed control vessels, colloidal carbon traversed endothelial cells via the development of pores that did not communicate with or disrupt intercellular junctions by gap formation. Serial section and computer-assisted reconstructions established these findings and suggested the possible development of transendothelial cell pores from VVOs. Serial sectioning and computer-assisted three-dimensional reconstructions of ultrastructural samples of an acute inflammation model revealed a transendothelial cell traffic route for motile neutrophils and platelets in the absence of classical ultrastructural criteria for regulated secretion from either cell.

To study the mechanism of Chinese herbal medicine (CHM), the prescription consists of Radix Salviae Miltiorrhizae, Radix Codonopsitis Pilosulae, Rhizoma Atractylodis Alba and Rhizoma Alismatis, Leonurus Heterophyllus Sweet,etc on the regulation of the peritoneal lymphatic stomata and the ascites drainage.

The mouse model of live fibrosis was established with the application of intragastric installations of carbon tetrachloride once every three days; scanning electron microscope and computer image processing were used to detect the area and the distributive density of the peritoneal lymphatic stomata; and the concentrations and NO in the serum were measured and analyzed in the experiment.

Two different doses of CHM could significantly increase the area of the peritoneal lymphatic stomata, promote its distributive density and enhance the drainage of urinary ion such as sodium, potassium and chlorine. Meanwhile, the NO concentration of two different doses of CHM groups was 133.52+/-23.57 micromol/L and 137.2+/-26.79 micromol/L respectively. In comparison with the control group and model groups (48.36+/-6.83 micromol/L and 35.22+/-8.94 micromol/L, P<0.01),there existed significantly marked difference, this made it clear that Chinese herbal medicine could induce high endogenous NO concentration. The effect of Chinese herbal medicine on the peritoneal lymphatic stomata and the drainage of urinary ion was altered by adding NO donor(sodium nitropurruside,SNP) or NO synthase (NOS) inhibitor (N(G)-monomethyl-L-arginine, L-NMMA) to the peritoneal cavity.

There existed correlations between high NO concentration and enlargement of the peritoneal lymphatic stomata, which result in enhanced drainage of ascites. These data supported the hypothesis that Chinese herbal medicine could regulate the peritoneal lymphatic stomata by accelerating the synthesis and release of endogenous NO.

This paper reports on how lymphatic vessels and their smooth muscle cells develop in the diaphragm of postnatal rats. Lymphatic endothelial cells in the diaphragm were labeled by an intraperitoneal injection of DiI-labeled acetylated low-density lipoprotein (DiIac-LDL). During postnatal week 1, DiI-ac-LDL was detected in many free cells in addition to distinct endothelial cells that formed lymphatic vessels. Occasionally, saccular lymphatics isolated from previously formed lymphatics were recognized; these were referred to as lymphatic islands. The DiI-ac-LDL-labeled free and lymphatic endothelial cells showed immunoreactivity for CD 34 and Flt-4, but most of them did not express either OX 62 or ED 1 immunoreactivity, with only some showing ED 1 immunoreactivity. This suggests that most of the DiI-ac-LDL-labeled elements were lymphatic endothelial cells, and that some were macrophages. After postnatal week 1, the DiI-ac-LDL positive cells were restricted to lymphatic vessels. Until postnatal week 6, lymphatic vessels increased as the diaphragm enlarged. Towards the end of postnatal week 2, free cells expressing alpha-smooth muscle actin (alpha-SMA) immunoreactivity increased in the diaphragm, and some of these were in contact with lymphatics. A coarse plexus of smooth muscle cells surrounding the lymphatic vessels first appeared at postnatal week 2, and this plexus became denser with age. Our findings indicate that lymphatic vessels are formed not only by sprouting from previously formed lymphatic vessels but also by migrating endothelial cells, and that smooth muscle cells may be differentiated from mesenchymal cells to form a plexus surrounding the lymphatic vessels.

Numerous investigations concerning the fine morphology of diaphragmatic stomata have been performed, but its ultrastructural changes in experimental conditions remain unclear. The present study demonstrates the peritoneal side of the diaphragm in adult Wistar rats by transmission electron microscopy. Ten experimental animals were observed 5 and 8 days after Pseudomonas aeuriginosa instillation (PI) into the peritoneal cavity. A control group of 6 rats showed flat mesothelial covering on basal lamina (BL) and connective tissue layer, as well as cubic mesothelial cells, single stomata over underlying lymphatic lacunae (LL). Five days after PI the mesothelial cells had more numerous microvilli, microvesicles, vacuoles, lysosomes and a lesser number of specialized contacts. The multiplication of the extravasal cells and larger intercellular spaces lead to thickenings of the connective tissue around LL. LL were larger and located in close proximity of the mesothelium. Intercellular spaces in the mesothelial layer and different types of contacts between mesothelial cells and endothelial protrusions of LL (with common BL or without BL) were encountered. Eight days after PI the mesothelium, endothelium of LL, their BL and surrounding connective tissue were interrupted and structurally modified to form typical new channels--stomata. The larger portion of the channels were formed of mesothelial cells, while the endothelial cells participated in the submesothelial part. LL were more numerous than in the previous period, and were arranged in groups. LL increased their vertical (50.59 microm) and horizontal (155.57 microm) diameter, as compared with control animals (respectively 12.37 microm and 74.08 microm). Neighbouring LL were separated by thin or thick septae. Peristomatal mesothelial cells or more rarely endothelium formed valve- or bridge-like structures. Valves on the opposite side of LL were observed. Groups of electron-dense bodies characterized some tall endothelial cells of LL. Cubic mesothelium, endothelium of the LL, both BL, the cell connections that formed new stomata, LL and surrounding connective tissue underwent rapid and parallel changes after PI. Among these elements of the lymphatic regions mentioned above, the mesothelium and endothelium of LL had a main role in experimental conditions.

The visceral peritoneum of intraabdominal organs (spleen, stomach, liver, small intestine), omentum majus and the parietal peritoneum of the anterior abdominal wall and the diaphragm were studied in adult Wistar rats by combined scanning and transmission electron microscopy (SEM, TEM). In general, the peritoneal surface consisted of a mesothelium composed of cubic, flat or intermediate cell types delimited by a basal lamina. Cubic mesothelial cells predominated in parenchymal organs (spleen, liver) and were characterized by prominent and indentated nuclei, a cytoplasm richly supplied with organelles, a dense microvillous coat, basal invaginations and elaborate intercellular contacts. Flat mesothelial cells were observed in the intestinal, omental and parietal peritoneum (tendinous diaphragm, abdominal wall) and showed elongated nuclei, scant cytoplasm, a poorly developed organelle apparatus and sparsely distributed microvilli. An intermediate mesothelial cell type was described within the gastric peritoneum characterized by a central cytoplasmic protrusion at the nuclear region containing most of the cytoplasmic organelles and by thin finger-like cytoplasmic processes. The submesothelial connective tissue layer was composed of collagen fiber bundles, fibroblasts and free cells (macrophages, granulocytes, mast cells) and contained blood and lymphatic vessels. In the spleen, elastic fibers formed a membranous structure with intercalated smooth muscle cells. Mesothelial openings were observed as tunnel-like invaginations within the hepatic peritoneum and as clusters of peritoneal stomata within the parietal peritoneum of the anterior abdominal wall and the muscular diaphragm. The round or oval openings of the peritoneal stomata were frequently occluded by overlapping adjacent mesothelial cells and their microvillous coat or obstructed by cellular material. At the side of the peritoneal stomata the mesothelial cell layer was interrupted to allow a direct access to the underlying submesothelial lymphatic system. The mesothelium and lymphatic endothelium shared a common basal lamina. The endothelial cells were discontinuous and displayed valve-like plasmalemmatic interdigitations facilitating an intercellular transport of fluids and corpuscular elements from the peritoneal cavity to the submesothelial lymphatic lacunae. The findings underline the morphological heterogeneity of the peritoneum in visceral and parietal regions, suggesting different functional implications, and further support the presence of extra-diaphragmatic peritoneal stomata.

A 3-day-old premature infant with meconium peritonitis, periventricular leukomalacia, and pulmonary hypertension died with respiratory insufficiency. An autopsy disclosed intravascular squamous cells in the lungs, brain, liver, pancreas, and kidneys. Numerous pulmonary capillaries and arterioles were occluded by squamous cells, accounting for pulmonary hypertension. Brain parenchyma surrounding occluded cerebral vessels showed infarct and gliosis. A mediastinal lymph node filled with squamous cells alluded to the mechanism by which these cells from the peritoneal cavity likely entered the bloodstream--namely, via diaphragmatic pores connecting with lymphatics. Thus, disseminated intravascular meconium rarely may complicate meconium peritonitis and have devastating consequences.

We studied the absorbing peripheral lymphatic vessel with the light microscope, the transmission electron microscope, the scanning electron microscope, and three-dimensional models of the diaphragm of several rodents and insectivores under normal and experimental conditions (lymphatic stasis and dehydration). To clarify the delicate and complex mechanism that permits drainage of the abdominal cavity contents into the lymphatic circulatory system, we introduced Polystyrene latex spherules, China ink, and Trypan blue into the abdominal cavities. After anatomical comparisons of the superficial and deep networks of absorbing peripheral lymphatic vessels at the tendinous and muscular portions of the diaphragm and after classification of lymphatic vessels into absorbing and conducting functions, we examined the stomata, which, owing to morphologic and topographic findings, we defined as stable structures. Furthermore, we observed that the stomata and submesothelial connective channel are fundamental elements that facilitate the flow of the corpuscular and liquid contents of the peritoneal cavity to the submesothelial absorbing lymphatic vessel wall. Also, we underlined that the genesis of the connective channel depends on the secondary cytoplasm extensions of two distinct adjacent endothelial cells, which, to facilitate the flow of the absorbed abdominal contents, completely coat this channel. Additionally, our observations illustrate that the secondary cytoplasm extensions do not engage in continuous relationships with the basal lamina of the mesothelium and with the margins of the stoma, and, hence, the hypothesis of "lymphatic stomata" as an expression of the anchoring of the borders of the open interendothelial junctions to the orifice margins of the stoma cannot be confirmed. Moreover, we describe the presence and formation of intraendothelial channels in the lymphatic endothelial wall. We affirm that this morphological entity is a dynamic unit, because its numerical density varies according to different physiological and experimental conditions to degrees of hydrostatic and colloidal osmotic pressure and, perhaps, also to the particular characteristics of the substances that the connective channel liberates into the endothelial wall of the lymphatic vessel. In conclusion, we affirm that the absorbing peripheral lymphatic vessels of the diaphragm, by way of intraendothelial channel formations, membrane diffusion, and the vesicular path of the endothelial cells, constitute the fundamental draining elements for the corpuscular and liquid contents of the abdominal cavity.

The influence of the route of administration (i.v., i.p. and s.c.) on pharmacokinetics and tissue distribution of bovine testicular hyaluronidase and vinblastine was studied in mice (plasma, skeletal muscle, liver, kidney and human melanoma). After i.v. injection, hyaluronidase was accumulated in liver and kidney, whereas i.p. and s.c. administration led to almost equal distribution in plasma, muscle, liver and kidney. In melanoma, the highest levels of hyaluronidase were found after s.c. injection of the enzyme close to the tumor. Hyaluronidase s.c. increased the intratumoral concentration of s.c. co-administered vinblastine most efficiently, making local simultaneous application as in interstitial chemotherapy most promising.

Peritoneal stomata constitute the principal pathways for the drainage of intraperitoneal contents from the peritoneal cavity to the lymphatic system and have been claimed to be exclusively restricted to the peritoneal surface of the diaphragm. This concept has been revised by the demonstration of peritoneal stomata in the omental, mesenteric, ovaric and pelvic peritoneum. Therefore, the aim of this study was to further assess peritoneal surfaces of several other abdominal organs and of the abdominal wall with special reference to the occurrence of peritoneal stomata. The peritoneum covering the spleen, stomach, intestine, liver, diaphragm and anterior abdominal wall obtained from rats was examined by scanning electron microscopy. Whereas the splenic and hepatic peritoneal surfaces were composed of uniformly distributed cuboidal mesothelial cells, the gastric and intestinal peritoneal surfaces were arranged in parallel folds composed of prominent mesothelial cells with elongated finger-like cytoplasmic processes. In addition to diaphragmatic peritoneal stomata, mesothelial openings were also found on the peritoneal surfaces covering the anterior abdominal wall and the liver. The parietal peritoneal stomata were arranged in clusters, oval in shape and delimited by flattened mesothelial cells exposing the underlying submesothelial connective tissue. The hepatic mesothelial openings formed by deep channel-like gaps of adjacent cuboidal mesothelial cells were almost completely occluded by a dense microvillous coat. As the submesothelial connective tissue was not identifiable with certainty, the mesothelial openings were regarded as corresponding to stoma-like structures. These findings yield further evidence that peritoneal stomata are obviously not confined to the diaphragmatic area but extend to other peritoneal regions. It is therefore suggested that these extra-diaphragmatic parietal and visceral peritoneal surfaces contribute to the absorption capacity of the entire peritoneum and are subsequently involved in either therapeutic procedures or pathological processes affecting the peritoneal cavity.

The distribution of lymphatic stomata that open to the pleural cavity is unclear. The distribution and the surface topography of the pleural and visceral pleurae are key factors in the turnover of pleural fluid and respiration physiology.

Nine golden hamsters (Mesocricetus auratus) from 26 to 33 weeks of age were used for the study. The gross anatomy of the thorax and the arterial supply to the lung were studied in four hamsters. Five thoracic hemispheres, three diaphragms, and tissue blocks of the heart and lung were prepared from the remaining five hamsters. The thoracic hemispheres were fixed in 2.5% glutaraldehyde and the muscular bands at each intercostal space were carefully cut along the costae. The intercostal bands were processed for scanning electron microscopy (SEM) and the localization and the number of lymphatic stomata were recorded. The diaphragms and blocks of the lung and heart were also processed for SEM and the surface topography was observed.

The right and left superior lobes of the lung were supplied by the bronchial artery that originated from the right costocervical trunk and left internal thoracic artery, respectively. Lymphatic stomata and mesothelial discontinuities (pores and gaps) were predominantly located in areas lined with cuboidal cells. The areas of cuboidal cells occupied approximately 4.6 mm2, namely, 1% of the total area of the thoracic hemisphere. There were about 1,000 lymphatic stomata per thoracic hemisphere. About 15% of lymphatic stomata were distributed in the ventro-cranial regions of the thoracic wall, with about 85% in the dorsocaudal region. In the former region, lymphatic stomata were found along the costal margins. In the latter, they were predominantly located in the pre- and paravertebral fatty tissue. There were also areas of cuboidal cells on the pleural surface of the diaphragm. Some mesothelial pores and gaps were found, but no lymphatic stomata opened on the pleural surface of the diaphragm. The pleural surface of the lung and that of the heart were lined with flattened polygonal cells. The topography of the surface varied, but there were no mesothelial discontinuities of the type commonly found in the parietal pleura.

1) The parietal pleura has a surface structure that is more permeable and absorptive for fluid and particulate matter than the visceral pleura. 2) The distribution of lymphatic stomata does not correspond directly to the pleural liquid pressures that have been reported. 3) The functions of lymphatic stomata should be considered not only in terms of fluid turnover but also in terms of self-defense mechanisms. 4) The presence or absence of lymphatic stomata on the diaphragmatic pleura should be re-examined and determined in a variety of animal species.

The diaphragm has a unique system that collects peritoneal fluid and carries it into the lymphatic system. However, our understanding of the morphology and function of this system is still incomplete.

Twelve C57BL/6 mice of 13 to 25 weeks of age were used without regard to sex. In one series of experiments, the diaphragm was isolated and fixed 10-15 minutes after injection of india ink into the peritoneal cavity and then the peritoneal mesothelium was peeled off from the submesothelial connective tissue. The lymphatic vessels attached to the mesothelial strip were examined by scanning electron microscopy. The diaphragm was also observed in plastic-embedded semithin and ultrathin sections. In another series of experiments, the diaphragm was stained by 5'-nucleotidase histochemistry (Wachstein and Meizel, 1957a. Am. J. Clin. Pathol., 27:13-23), and several microdrops of india ink were placed on the peritoneal or pleural surface to reveal the profile of the lymphatic vessels.

The lymphatic vessels on the peritoneal side of the diaphragm were flattened. They usually ranged from several to 100 microns in width and from close to zero to a few micrometers in thickness. In other words, they formed extremely flat lumina, differing from the more usual tubular lymphatic vessels. Several lymphatic vessels extended radially and parallel to one another from the central tendon to the thoracic wall, with numerous connecting branches, forming an area of lymphatic vessels. The india ink that had been injected intraperitoneally and the staining with 5'-nucleotidase revealed that there were seven to nine such lymphatic areas in one hemisphere of the diaphragm. The lymphatic areas spread in parallel with the peritoneal surface of the diaphragm and all the areas together appeared to occupy more than half the surface area of the sternocostal part of the diaphragm. Each area was a relatively distinct functional unit with respect to the draining of india ink. Microdrops of india ink placed on the pleural surface did not enter the lymphatic vessels, while those placed on the peritoneal surface immediately entered the peritoneal lymphatic vessels and migrated to the pleural lymphatic vessels via the transmuscular lymphatic branches.

The peritoneal lymphatic vessels of the diaphragm have extremely flat lumina that spread in parallel with the peritoneal surface of the diaphragm and form a lymphatic sieve that covers approximately half or more of the surface area of the sternocostal region for drainage of fluid and particulate matter from the peritoneal cavity. The lymphatic system has been characterized by the presence of openings (= stomata) to the peritoneal cavity and the amplitude of the lumina (= lacunae). However, the fundamental characteristic of the system is the extremely flat lumen (= vadum), which facilitates the formation of the lymphatic sieve.

The lymphatic stomata in the pelvic peritoneum of human fetuses and mature mice were initially observed and studied quantitatively by using computer image processing (C.I.P.) attached to a scanning electron microscope (SEM). Two types of mesothelial cells were found in the pelvic peritoneum of human fetuses and mature mice, i.e. flattened and cuboidal cells. The lymphatic stomata, arranged in clusters, were only found irregularly distributed among the cuboidal cells. The divergence of stoma area in the pelvic peritoneum of human fetuses varied greatly, ranging from 0.8 micron2 to 43.4 microns2. The average area of the lymphatic stomata in human fetuses was 10.00 +/- 9.44 microns2. The variation coefficient was 94.40. The standard deviations and standard errors were 9.44 and 0.98 respectively. Most of the lymphatic stomata in human fetuses were between 1.34 microns2 and 32.11 microns2 in size (accounting for 90%), with maximum and minimum values of 43.4 microns2 and 0.8 micron2. The average distribution density of the lymphatic stomata in human fetuses was 7.2% and the maximum density was 11.6%, which means that the average and the maximum absorption rates of the human pelvic peritoneum from the peritoneal cavity were 7.2% and 11.6% respectively. Therefore, it is suggested that the lymphatic stomata in pelvic peritoneum play an important role in draining materials from the peritoneal cavity, and that the absorption effect of the pelvic peritoneum is similar to that of the diaphragmatic peritoneum.

Lymphatic stomata are channels connecting the peritoneal cavity with the lymphatics in the diaphragm. The process of sequential formation of the stomata has not been studied. The objective of this study was to examine the morphogenesis of the lymphatic stomata in mice.

Ultrathin sections of diaphragms from ddY mice obtained on embryonic day 18 and postnatal days 0, 4, and 10 were observed with a transmission electron microscope.

By embryonic day 18 and postnatal day 0, lymphatics were already observed in the submesothelial connective tissue on the peritoneal side of the fetal diaphragm. The lymphatic endothelial cells, but not the mesothelial cells covering the diaphragm, protruded short cytoplasmic processes into the submesothelial connective tissue, and these almost reached the basal surfaces of individual mesothelial cells. By postnatal days 4 and 10, the lymphatic endothelial cells frequently protruded cytoplasmic processes into the submesothelial connective tissue, and the endothelial cell processes broke the continuity of both the basal lamina beneath the mesothelial cells and the submesothelial connective tissue. Neighboring endothelial processes formed a pair of U-shaped folds that were connected with each other via intercellular junctions at the apexes of the U-shaped folds. The disassembly of the intercellular junctions between the U-shaped folds was observed, and the basal surface of the mesothelial cell faced the lymphatic lumen. Dehiscence of the intercellular junctions between the mesothelial cells overlaying the lymphatics was observed, and lymphatic stomata were present. On the pleural side of the diaphragm, lymphatics were already present on embryonic day 18, but it was not observed that the endothelial process spanned the submesothelial connective tissue to the basal surface of the mesothelial cell.

These results suggest the following process of the formation of the lymphatic stomata. (1) Neighboring lymphatic endothelial cells span the submesothelial connective tissue to the basal surfaces of mesothelial cells. (2) The lymphatic stomata are formed by the disassembly of the intercellular junctions between the neighboring endothelial cells and between the mesothelial cells overlying the endothelial cells.

The peritoneal stomata, lymphatic drainage units and subperitoneal terminal lymphatics, called lymphatic lacunae, form a specialized drainage system in the diaphragm, by which absorption of fluid in bulk, particles and cells is carried out in the peritoneal cavity. The aim of this study is to elucidate the three-dimensional organization and function of the subperitoneal lymphatic lacunae and lymphatic drainage units by using lymphatic casts in the scanning electron microscope (SEM), ODO (OsO4-DMSO-OsO4) freeze fracture, conventional SEM and the transmission electron microscope (TEM). The subperitoneal lymphatic lacuna is unique for its large size and its multiple morphology and can be recognized by its broad, flattened enlargement and the blind-ends of lymphatic vessels, from which extend numerous main lymphatic vessels and side branches. These lymphatic vessels communicate with each other and form a rich lymphatic plexus under the diaphragmatic peritoneum. Two layers of lymphatic networks, i.e. the subperitoneal plexus and the deeper plexus are found in the muscular portion. Only one layer is present in the tendinous portion of the human diaphragm. The lymphatic plexus is denser in the tendinous portion than that in the muscular portion. The lymphatic lacunae occur exclusively in the muscular portion of the human diaphragm. The lumina of lymphatic lacunae are separated from the peritoneal cavity by a barrier consisting of cuboidal mesothelial cells, endothelial cells of the lymphatic lacunae and intervening connective tissue forming a lymphatic drainage unit. All these three components of the lymphatic drainage unit abut upon each other, but are not linked by specialized junctions. The cuboidal mesothelial cells frequently extend valve-like cytoplasmic processes that bridge the subperitoneal channel and make give it a tortuous course. The fibrous layer of the connective tissue is arranged in fiber bundles and gives a three-dimensional network forming the floor of the peritoneal stomata and the roof of the lymphatic lacunae. Via the fibrous network, the cuboidal mesothelial cells and the endothelial cells of the lacunae come into close contact with each other and form short subperitoneal channels which connect the peritoneal cavity with the subperitoneal lymphatic lacunae. The lymphatic drainage units may regulate the material absorption of the peritoneal stomata from the peritoneal cavity. It is suggested that the peritoneal stomata together with the subperitoneal channels, lymphatic drainage units and lymphatic lacunae comprise an important diaphragmatic lymphatic drainage system which plays an important role in the absorption of materials from the peritoneal cavity.

Visceral and parietal pleura, peritoneum and pericardium of 26 adult cats were studied by means of transmission electron microscopy. The main components of the three serous membranes follow a general plan: mesothelium, basal lamina (BL) and submesothelial connective tissue layer. They show significant diversities in both sheets of the three serous membranes in the different organs and regions. The elastic membrane under the BL is an obligatory component of the visceral pleura. Two basic cell types - high and flat, as well as intermediate and degenerative cell forms are described in the mesothelial layer. The high cells are especially characteristic of the visceral sheets, while the flat cells predominate in the parietal sheets. The involvement of the mesothelium in the homeostasis in the cavities is discussed. A detailed characteristic of the BL of both sheets and its variation in individual organs is presented. Varieties of cells, collagen and elastic fibers, blood and lymph capillaries of the connective tissue layers of the visceral and parietal sheets are described with special reference to their relation to different underlying tissues. An attempt to find a structure-functional correlation of these observations is made. The transport capability of the pleura and peritoneum is investigated by the intrapleural and intraperitoneal application of horseradish peroxidase (HRP).

The experiment on mice was carried out by injecting intraperitoneally Chinese materia medica for treating hepatocirrhosis with ascites. Observations and a quantitative analysis were carried out on the pharmacological regulation of the peritoneal stomata by using a scanning electron microscope (SEM) and a computer image processing system attached to the SEM. There was a significant increase in both the diameter (P < 0.05) and distribution density (P < 0.01) of the peritoneal stomata in the red sage root and alismatis rhizome groups, whereas the effect of poria and poria peel was not significant compared with the control group (P > 0.05). Our findings confirm the effect of red sage root and alismatis rhizome on the regulation of the peritoneal stomata, which can enhance the absorption of ascitic fluid, taking into consideration the absorbent function of these stomata. They indicate that the patency of peritoneal stomata can vary in response to the effect of some Chinese materia. They also suggest that the ascites is drained mainly by means of enhancing the patency of the stomata and lymphatic absorption of the stomata during the process of treatment by traditional Chinese medicine.

Fluid and free cells in the peritoneal cavity enter the lymphatics through the lymphatic stomata which are channels connecting the lymphatics in the peritoneal side of the diaphragm with the peritoneal cavity. While the stomata thus play a very important in the physiology of the peritoneal cavity, it is unclear when they appear or how they are distributed on the diaphragm. We therefore conducted an embryological study of the process and timing of mouse lymphatic stomata development in the peritoneal surface of the diaphragm.

The mouse diaphragm, at stage ranging from embryonic day 18 (ED18) to postnatal week 10 (PW10), was observed by scanning electron microscopy, and the number of lymphatic stomata was counted on each observation day. A map of the data was constructed to illustrate the process of appearance of lymphatic stomata.

Lymphatic stomata were not found on ED18. They were first found on PD0 and their number increased exponentially until PW10. Lymphatic stomata were usually located in cuboidal cell areas but not in the areas lined with flattened cells. The cuboidal cell area with several lymphatic stomata was first found in the retroparasternal region on PD0, followed by in the muscular portion, as "ridges" on PD4 and "bands" on PD6 or up to a few days later. The long axis of the ridges and bands was oriented from the center to periphery of the diaphragm. Subsequently, cuboidal cell areas with lymphatic stomata formed along the border between the central tendon and the muscular portion, most frequently on PD10. Another cuboidal cell area with lymphatic stomata appeared rather suddenly ventral to the inferior vena cava on PD10. This was the full complement of cuboidal cell areas seen in the adult of PW10.

These results verified that the course of the change of the shape and distribution of cuboidal cell areas parallels that of the underlying lymphatic lacunae, suggesting the delivery of some stimuli from the lymphatic lacunae to the overlying mesothelial cells that results in alternation of their cell shape.

The peritoneal-plasma barrier is a pharmacologic entity of importance for treatment planning in patients with malignant tumours confined to the abdominal cavity. This physiologic barrier limits the resorption of drugs from the peritoneal cavity into the blood. The sequestration of chemotherapeutic agents improves their locoregional cytotoxicity and reduces their systemic toxicity. The physical nature of the peritoneal-plasma barrier has not been clearly defined. Further pharmacologic studies need to be performed in order to achieve a better understanding of this interesting metabolic phenomenom. At present, it is suspected that a diffusion barrier exists that consists of subserosal tissues or blood vessel walls. As postulated by Maher [29], the capillary wall appears to offer the dominant resistance to the transfer of larges solutes. The mesothelium and intersitium impede their movement to a lesser extent, and their removal during cytoreductive surgery does not affect the pharmacology of postoperative intraperitoneal chemotherapy.