Ultrastructure of the lymphatic capillaries of the diaphragm and their interrelationship with peritoneal mesothelium

In 28 mature rats, ultrastructure of the diaphragmal lymphatic capillaries and mesothelial tegmen was studied. Interrelation of their cellular elements and possible ways of metabolic absorbtion from the abdomen were clarified. The diaphragmal lymphatic capillaries were demonstrated to situate under mesothelial cells and they are separated by a thin layer of longitudial collagenic fibers. As cross section of the lymphatic capillary demonstrates, the capillary wall consists of 3--6 endothelial cells with a set of organelles, among which are: mitochondria, Golgi's complex, some pinocytotic vesicles.     

A scanning electron microscope study of mouse peritoneal mesothelium.

As seen in the scanning electron microscope, peritoneal mesothelial cells of the mouse diaphragm, anterior abdominal wall and intestinal serosa carry numerous microvilli. These microvilli are absent over certain areas of the cell surface and are sometimes, interlocked in meshwork patterns or coronal formation. The apical cell membranes of the mesothelium at the base of the microvilli, are invaginated by many plasmalemmal vesicles and vacuoles and carry a number of protruding spherical structures. Deep circular craters, giving the impression of stomata, are also visible.     

Organization of cell junctions in the peritoneal mesothelium

Intercellular junctions in the mesothelium of the visceral (mesentery and omentum), and parietal (diaphragm, pre-aortic, and iliac region) peritoneum were examined in rats and mice by using freeze-cleaved preparations. In addition to usual intercellular junctions (cell body junctions), special junctions are found between cell processes and the surface of the neighboring cell (cell process junctions). Cell body junctions are provided with tight junctions and communicating (gap) junctions. The former consist of one to two junctional strands which show a characteristic staggered arrangement, and focal discontinuities. In cell process junctions, the strands form loops or appear as short, free-ending elements; their polymorphism suggests considerable lability, probably in connection with their assembly and disassembly. The existence of free-ending strands indicates that such structures can be used as attachment devices without being concomitantly involved in the formation of occluding zonules. In both types of junctions, the strands can be resolved into bars, approximately 80- 100nm long, frequently provided with terminal enlargements and intercalated particles which occur singly or in small clusters. These particles are morphologically similar to those present in communicating (gap) junctions. The mesothelium is also provided with isolate composite macular junctions. Throughout the mesothelium, the cleavage plane follows the outer contour of junctional strands and particles, suggesting that strand-to-strand interactions in the apposed membranes are weaker than interactions between each strand and underlying cytoplasmic structures. In their general geometry and cleavage characteristics, the mesothelial junctions resemble the junctions found in the venular endothelium.     

Morphogenesis of tight junctions in the peritoneal mesothelium of the mouse embryo

The peritoneal mesothelium of mouse embryos (12 to 18 day of gestation) was studied by freeze-fracture and in sections in order to reveal the initial formation of the tight junctions. Freeze-fracture observations showed three types of tight junctions. Type I consists of belt-like meshworks of elevations on the P face and of shallow grooves on the E face. No tight junctional particle can be seen either on the elevations or in the grooves. Type II shows rows of discontinuous particles on the elevations on the P face. Type III consists of strands forming ridges on the P face. On the E face, the grooves of Type II and III appear to be narrower and sharper than those of Type I. Quantitatively, Type I junctions are most numerous during the early stages (day 12-13) of embryonic development, while Type III junctions become more common in the later stages, and are the only type seen by day 18. Observations on sections, however, fail to distinguish between the three types. The results suggest that an initial sign of tight junction formation is close apposition of the two cell membranes in the junctional domain, without tight junctional particles. Later, the particles appear to be incorporated in the tight junctions and the strands form by fusion of the particles.     

Macrophage growth inhibitors derived from the murine peritoneal cavity

Summary The murine peritoneal cavity contains factors that inhibit the in vitro growth and colony formation of macrophages. The inhibition of macrophage growth is not due to cell death. In the presence of inhibitors, the growth of colony-forming macrophages is suppressed, and small clusters are formed as a result of limited proliferation. The more mature mono-nuclear phagocytes (blood monocytes and peritoneal exudate macrophages) are more sensitive to the overall inhibitory effect of the peritoneal inhibitors than the less mature bone marrow mononuclear phagocytes. Furthermore, using dialysis and Amicon ultrafiltration, at least two inhibitors with differential inhibitory effects can be demonstrated. The colony formation of bone marrow mononuclear phagocytes is suppressed mainly by a protease-resistant, small molecular weight (<1,000) dialyzable inhibitor. In contrast, peritoneal exudate macrophages are sensitive to both the small molecular weight inhibitor and a protease-sensitive, large molecular weight (>12,000), nondialyzable inhibitor. The data suggest a possible existence of a dual inhibitor control on the proliferation of mononuclear phagocytes in vivo. In addition, the in vitro cultured peritoneal exudate cells are capable of producing inhibitors that mimic the activity of the in vivo inhibitors. This investigation was supported by Grants CA 09 11(SY) and AI15563(CCS) from the National Institutes of Health, Bethesda, MD     

Isolation and characterization of rabbit ovarian surface epithelium,granulosa cells,and peritoneal mesothelium in primary culture

Summary Mammalian ovarian surface epithelial (OSE) cells and peritoneal mesothelial (PM) cells have a common embryologic origin, yet certain morphologic and histochemical characteristics are different in the adult. In this study, a two-step culture method was developed to examine the characteristics of these two cell types in vitro. OSE, PM, and ovarian granulosa (GC) cells were isolated from estrous rabbits and cultured for 6 d in 5% serum-supplementedd-valine medium (to inhibit fibroblast growth), then incubated for a further 2 d in serum-free McCoy's 5A medium. This study showed that rabbit OSE and PM cells in vitro maintained certain in vivo morphologic characteristics; OSE cells exhibited distinct cell borders and abundant microvilli of homogeneous size and shape, whereas PM cells were characterized by obscure cell borders and abundant microvilli of heterogeneous form. GC in vitro exhibited overlapping cell borders and sparse microvilli of homogeneous structure. This study showed for the first time that cultured rabbit OSE and PM cells, but not GC, contain distinct filaments of cytokeratin 18. In addition, rabbit OSE cells and GC, but not PM cells, contained 17β-hydroxysteroid dehydrogenase. However, only GC contained delta 5-3β hydroxysteroid dehydrogenase. OSE, PM, and GC maintained their ultrastructural and histochemical characteristics in serum-free medium. These results suggest that rabbit OSE cells in vitro could be distinguished from PM cells by histochemical and ultrastructural differences. Furthermore, because these characteristics were not altered in serum-free medium, the two-step culture method will be valuable in further hormonal studies of these cells in vitro. This work was supported in part by Grant No. 202-3192 from the University of South Dakota Parsons Fund     

Diagnostic utility of sialosyl-Tn in discriminating carcinomatous cells from benign mesothelium in body cavity effusions

OBJECTIVE: Detecting malignant cells in the setting of reactive mesothelium can be difficult. Several techniques have been tried but without widespread acceptance. Sialosyl-Tn (STn) is an aberrantly glycosylated precursor of the MN blood group antigen frequently expressed in carcinomas and dysplastic epithelium. We investigated the STn monoclonal antibody for its clinical utility as an isolated stain to discriminate benign mesothelium from malignant cells. STUDY DESIGN: Cell block material from 72 cases of body cavity fluids were immunostained for STn using the avidin-biotin complex method without antigen retrieval. Slides were incubated overnight at 4 degrees C in a humidified chamber. RESULTS: Strong immunoreactivity was noted in 31/40 (77%) carcinomatous cases. Only moderate staining was noted in 1 of 28 (4%) benign effusions and weak staining in 5 (18%) additional benign cases. Specificity was 100%, sensitivity 78%, positive predictive value 100% and negative predictive value 76%. No staining was noted in four noncarcinomatous malignant effusions. CONCLUSION: STn may have diagnostic value in this cytologic setting as part of a diagnostic panel but not as an isolated stain.     

Characterization of the nonphagocytic adherent cell from the peritoneal cavity of normal and BCG-treated mice.

A distinctive subpopulation of nonphagocytic, tightly adherent cells (NPAC) comprised approximately 6% of the adherent peritoneal cells from untreated mice, and about 18% of those from mice previously given BCG i.p. A separation procedure based on adherence and lack of phagocytosis was devised. Isolated NPAC were morphologically intermediate between small lymphocytes and macrophages. They were positive for nonspecific esterase, negative for peroxidase, positive for surface IgM, and negative for surface IgG1, IgG2 and IgA. When capped, their surface IgM regenerated in vitro. NPAC had demonstrable Fc receptors but not EAC receptors. They resisted killing by an anti-macrophage serum, were negative by immunofluorescence with an anti-T cell reagent, and incorporated increased amounts of thymidine in response to LPS but not to PHA. They were more readily killed with anti-Ia serum and complement than macrophages, but less readily than splenic B cells. NPAC appeared to represent a subpopulation of B lymphocytes which contaminates some preparations previously regarded as "macrophages" and which may be ressponsible for some of the activities previously ascribed to "macrophages".     

The architecture of the gill surface of the catfish, Heteropneutes fossilis (Bloch): SEM study.

A scanning electron microscopical examination of the gills of H. fossilis is described. The surface architecture of gill filaments and secondary gill lamellae showed the presence of various features such as indentations, micropits and crevices. The possible functions of these morphological adaptations are discussed in relation to physiology of the gill.     

Experimental adhesion model: effect of viscosities of fluids put in the peritoneal cavity on preventing peritoneal adhesions.

In this study we assessed the effectiveness of fluid viscosities placed in the peritoneal cavity to prevent postoperative peritoneal adhesions. Thirty-six Wistar albino female rats (average weight: 160 +/- 30 g, average age: 6.5 months) were divided into three groups of equal number. A standard adhesion pattern was formed in each group. Then, 3 ml isotonic sodium chloride solution (relative viscosity value: 1) was added into the peritoneal cavity of group 1; 3 ml standard 6% hydroxy ethyl starch solution (HES) (relative viscosity value: 2.9) was added into the peritoneal cavity of group 2; and a standard HES solution that was concentrated by dehydration (relative viscosity value: 249.7) was added into the peritoneal cavity of group 3. All rats were sacrificed on postoperative day 10 and the adhesions that formed were graded. In group 1, grade-3 adhesions developed in 9 (75%) rats, and grade-2 developed in 3 (25%) rats. In group 2, grade-3 adhesions developed in 1 (8.3%) rat, grade-2 developed in 6 (50%) rats, and grade-1 developed in 5 (41.6%) rats; in group 3, grade-3 adhesions developed in 9 (75%) rats, and grade-2 developed in 3 (25%) rats. The adhesion scores of group 3 and group 1 were equal to each other (P=1), while the adhesion score of group 2 was significantly less (chi(2): 18.23, P<0.001). Increasing the viscosity of fluids that are inserted in the peritoneal cavity may reduce the formation of postoperative peritoneal adhesions till a critical value of unknown viscosity is achieved. The mechanism behind this process remains unclear.     

SEM study on the dorsal lingual surface of the common tree shrew, Tupaia glis.

The dorsal lingual surface of the common tree shrew was examined by SEM after treating it with HCl to remove the mucous substance. Filiform (FI), fungiform (FU) and circumvallate papillae (CI) were observed. The FI exhibited a small circular bulge surrounded by anterior and posterior filamentous processes. FU were scattered among the FI. There were 3 CI separating the anterior 4/5 from the posterior 1/5 of the tongue. In addition, a group of conical projections with caudal orientation was found anterior to the palatoglossal fold on each side of the tongue. Microridges were widely observed on the entire dorsal lingual surface, except on the free surface of FI processes.