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-1 and 3β-hydroxysteroid dehydrogenase. Western blot analysis revealed a band of about 22 kDa molecular weight that was recognized with both caveolin-1 and tyrosinephosphocaveolin-1 antibodies. Caveolin-1 is one of a few proteins with a demonstrated ability to bind cholesterol in vivo. In this context, the presence of caveolin-1 in Leydig cells may be related to cholesterol traffic -a rate limiting step in steroid biosynthesis.     

EFFECT OF SOLID CONTENT AND SUGAR COMBINATIONS ON THE QUALITY OF SOYMILK-BASED YOGURT

A research to evaluate the effect of two levels of solids and two sugar combinations in the quality of a soymilk yogurt-type food was carried out. Yogurts were elaborated by inoculating lactic cultures ( Lactobacillus dellbruckii spp. bulgaricus and Streptococcus salivarius spp. thermophilus ) into soymilk with 8% and 11% solid levels and glucose/sucrose and glucose/fructose mixtures. Also, a control treatment with cow milk was prepared. Yogurts were analyzed after two days of preparation for their chemical (protein, lipids, titrable acidity and pH), physical (syneresis and viscosity) and sensory characteristics (quality and acceptability). Protein content of soymilk based yogurts ranged between 3.56 and 4.45 g/100 g. The higher titrable acidities (0.66% and 0.63% lactic acid) were shown by treatments with higher solids level, which also shown the lowest syneresis. All soymilk yogurts were yellowier than the control. The highest sensory acceptability was for the 8% solids treatment enriched with glucose and sucrose.

PRACTICAL APPLICATIONS

There are an increasing number of people suffering of lactose intolerance, which need an alternative product to milk. Besides, some people have adopted a strictly vegetarian way of life. Soymilk has been used for a long time by this part of the population; however, it usually has a beany flavor, which can cause some rejection among occidental consumers. A fermented product from soymilk, such as soymilk yogurt, may offer a good alternative for those people. In soymilk production it is necessary to carefully adjust the amount of solids and the sugar used in fermentation in order to obtain a well accepted commercial product. Soy yogurt could be used to formulate a number of different new products like desserts, high fiber yogurt, fruit-added yogurt and so on.