Expression of caveolin-1 in rat Leydig cells

Caveolin-1, the first member of caveolin family reported, is recognized as the structural component of caveola, a plasma membrane invagination or vesicles that are a subcompartment distinct from clathrin-coated pits. This protein is also known to be involved in cholesterol trafficking. The aim of this study was to determine the expression of caveolin-1 in adult rat Leydig cells. Testis sections incubated with an antibody to caveolin-1 showed, by immunohistochemistry, a moderate number of Leydig cells with different degrees of immunoreaction and a strong reaction in endothelial cells and in the lamina propia of seminiferous tubules. Caveolin- 1 was detected in the cell cytoplasm with a granular pattern and on the cell surface of Leydig cells cultured 24 h on uncoated, laminin-1 or type IV collagen coated coverslips. We also observed a milder reaction in 3 h cultures. Immunoreaction was also detected in Leydig cells with an antibody to tyrosine-phosphorylated caveolin-1. By double immunofluorescent technique, we observed co-localization of caveolin- I and 313-hydroxysteroid dehydrogenase. Western blot analysis revealed a band of about 22 kDa molecular weight that was recognized with both caveolin-1 and tyrosine-phosphocaveolin-1 antibodies. Caveolin-l is one of a few proteins with a demonstrated ability to bind cholesterol in vivo. In this context, the presence of caveolin- in Leydig cells may be related to cholesterol traffic--a rate limiting step in steroid biosynthesis.

Immunodetection of cell adhesion molecules in rat Sertoli cell cultures

PROBLEM

The presence of cell adhesion molecules (CAMs) in Sertoli cells has not been explored extensively. The expression of CAMs involved in cell-matrix and cell-to-cell interactions in Sertoli cell cultures was examined.

METHOD OF STUDY

Immunohistochemical and Western blot techniques were applied to rat Sertoli cell cultures using specific antibodies to alpha 3, alpha 5, and alpha 6 integrin subunits; NCAM; and cadherins.

RESULTS

Expression of alpha 3 and alpha 6 integrin subunits (mainly laminin receptors) and lack of expression of alpha 5 integrin subunit (fibronectin receptor) was observed in Sertoli cells by immunohistochemistry. These cells also expressed neural CAM (NCAM) and N-cadherin. By Western blot analysis, Sertoli cell extracts reacted with antibodies to alpha 3 integrin subunit revealed a band approximately 130 kDa, whereas no expression of alpha 5 integrin subunit was detected. Cell extracts incubated with antibodies to pan cadherin exhibited a band approximately 120 kDa, whereas bands of 180, 140, and 120 kDa were observed with antibodies to NCAM.

CONCLUSION

New data about the expression of receptors for extracellular matrix proteins (alpha 3 and alpha 6 integrin subunits) as well as cell-to-cell adhesion molecules (NCAM and cadherins) are reported in rat Sertoli cell cultures.

Immunodetection of cell adhesion molecules and extracellular matrix proteins in rat Leydig cell cultures

Cell adhesion molecules (CAMs) as well as extracellular matrix (ECM) proteins were identified in Leydig cell cultures using immunohistochemical and Western blot analysis. Leydig cells were isolated from 60-day-old rats and cultured for 4 days. For immunofluorescence and immunoperoxidase techniques, Leydig cells were incubated with antisera to ECM proteins (antibodies to laminin, type IV collagen and fibronectin); antisera to integrins (antibodies to beta 1, alpha 3, alpha 5 and alpha 6 integrin subunits) and antisera to cell-to-cell adhesion molecules (antibodies to N-CAM and N-cadherin). Results of the two immunohistochemical techniques were similar. Laminin and type IV collagen were detected in the perinuclear area of Leydig cell cytoplasm and cell processes as bright granular immunofluorescence or as a brown reaction product using the immunoperoxidase technique. Leydig cells expressed alpha 3 and alpha 6 integrin subunits (mainly laminin receptors), while no reaction was detected with antibodies to the alpha 5 integrin subunit (fibronectin receptor). Leydig cells also expressed cell-to-cell adhesion molecules such as N-CAM and N-cadherin. Using Western blot analysis, Leydig cell extracts incubated with antibodies to laminin revealed two bands of around 200 kDa, which is characteristic of laminin 1 light chains. A band with electrophoretic mobility similar to that of the alpha 2 (IV) collagen chain from EHS sarcoma and a band of around 230 kDa similar to fibronectin were also detected in Leydig cell extracts using specific antisera. Leydig cells incubated with antibodies to the alpha 3 integrin subunit revealed two bands below 120 kDa. Finally, Western blot results showed that Leydig cells expressed N-CAM as two faint bands of around 140 kDa and N-cadherin as a 120 kDa band. The present data suggest that Leydig cells in culture are able to synthesize ECM proteins and express ECM receptors (integrins), as well as cell-to-cell adhesion molecules such as N-CAM and N-cadherin.

Cryostat sections with tissue amastigotes of Trypanosoma cruzi as a substrate for Chagas' disease serology

Sera from 30 chronic chagasic patients together with 52 control samples (34 with other pathological conditions and 18 from normal individuals) were titrated by the indirect immunofluorescent technique (IFA) on Trypanosoma cruzi amastigotes. Acetone-fixed cryostat sections of skeletal muscle of Rockland mice 10 days post-infection with the RA isolate of T. cruzi were used as substrate. Results were compared with titres obtained by conventional IFA on epimastigotes. All 52 control sera had amastigote titres less than or equal to 2 double dilutions (dd) as compared with epimastigote values. Out of the 30 chagasic samples, differences were greater than or equal to 4 dd (less than or equal to 1 log) for 22, 3 dd for 5 and less than or equal to 2 dd for the remaining 3, when comparing amastigote and epimastigote titres. These results show that the use of amastigotes in cryostat sections of infected tissue for performing Chagas' serology in a simple, adequate and sensitive method.

Experimental myocarditis induced in Swiss mice by homologous heart immunization resembles chronic experimental Chagas' heart disease

The Swiss mouse is considered a satisfactory model for experimental chronic chagasic myocarditis and there is some evidence of an immunopathologic mechanism in the development of this disease. To further support this conjecture, 45-day-old albino Swiss mice (40 animals) were immunized with homologous heart in complete Freund's adjuvant. As controls, 20 animals were likewise inoculated with allogeneic testis, as "non-related" antigen. Three mice from the former group died suddenly at 19-21 days postinoculation while the survivors were sacrificed at 60 days for serum samples, and histologic analysis of the heart and skeletal muscle. Electrocardiographic records were taken at Days 0, 30, and 60 postinoculation. Of myocardium-inoculated animals and testis-inoculated mice 33/37 (89%) and 1/20 (5%), respectively, exhibited myocarditis (P less than 0.001). Histologic lesions were highly reminiscent of those observed in chronic experimental Chagas' disease of Swiss mice. Antimuscle antibodies were seen, by indirect immunofluorescence employing cryostat sections, in 30/33 (91%) of the former group and in 3/20 (15%) of the latter (P less than 0.001), some of which recognized a surface antigen of primary cultured fetal rat myocardiocytes. Mice inoculated with myocardium also exhibited electrocardiographic abnormalities consisting in QRS interval widening. Results show that following an autoimmune experimental design the main features of chronic chagasic myocarditis may be reproduced in the Swiss mouse. This agrees with the likely role of an immunopathologic mechanism in heart damage due to Trypanosoma cruzi infection.

Immunofluorescent anti-Junin virus antibodies in Argentine hemorrhagic fever

Immunofluorescent anti-Junin virus antibodies were detected in 15 nonfatal cases of Argentine hemorrhagic fever between the 2nd and 3rd week after onset of symptoms. In most cases, antibodies appeared by the day of clinical improvement, or between 2 and 4 days later. It was interesting to note that in 5 of 11 cases studied, the first positive serum sample presented anti-Junin virus immunofluorescent antibodies in IgA. In 2 of these 5 cases, IgA was the only immunoglobulin with antibody activity in the early positive serum sample.

Ultrastructural and immunohistochemical studies in five cases of Argentine hemorrhagic fever

Ultrastructural and immunohistochemical studies on tissues from five patients with Argentine hemorrhagic fever revealed previously undetected lesions caused by the viral infection. Two types of particle were seen in the cells of all organs examined. The particles had some characteristics similar to those described for arenaviruses. However, the virus-like particles were intracellular, had a single membrane, and apparently originated by a process of budding into the endoplasmic reticulum cisternae. Intranuclear bodies and three types of cytopolasmic change were observed in conjunction with the virus-like particles; Antigenic determinants of Junin virus were demonstrated in cells of all organs examined. Immunohistochemical experiments also indicated alterations in the cellular mechanisms of protein synthesis. Until now the pathogenesis of human diseases produced by arenaviruses has not been established. The results of this study suggest that in Argentine hemorrhagic fever the virus is responsible for a direct pathogenic action.