Several focal adhesion proteins are known to cooperate with integrins to link the extracellular matrix to the actin cytoskeleton; as a result, many intracellular signaling pathways are activated and several focal adhesion complexes are formed. However, how these proteins function in mammalian spermatozoa remains unknown. We confirm the presence of focal adhesion proteins in guinea pig spermatozoa, and we explore their role during capacitation and the acrosome reaction, and their relationship with the actin cytoskeleton. Our results suggest the presence of a focal adhesion complex formed by β1-integrin, focal adhesion kinase (FAK), paxillin, vinculin, talin, and α-actinin in the acrosomal region. Inhibition of FAK during capacitation affected the protein tyrosine phosphorylation associated with capacitation that occurs within the first few minutes of capacitation, which caused the acrosome reaction to become increasingly Ca2+ dependent and inhibited the polymerization of actin. The integration of vinculin and talin into the complex, and the activation of FAK and paxillin during capacitation, suggests that the complex assembles at this time. We identify that vinculin and α-actinin increase their interaction with F-actin while it remodels during capacitation, and that during capacitation focal adhesion complexes are structured. FAK contributes to acrosome integrity, likely by regulating the polymerization and the remodeling of the actin cytoskeleton.

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The one-and two-dimensional protein patterns of Streptococcus thermophi/us PB18 in the exponential and stationary phases of growth were analysed. Onedimensional SDS-PAGE showed that a 16 kDa protein was overexpressed in stationary phase as well as 2 h after an acid shock, and that it was not expressed when the bacteria reached the stationary phase in medium with limiting lactose concentrations (5 or 10 g P), in which the pH (55) was not as acid as in control cultures (pH 4-78 lactose 20 g [-I). The results support the idea that this protein is expressed in response to the acidic environment and not in response to the growth phase. Two-dimensional PAGE showed that nine proteins were expressed only during the exponential phase and ten others only during the stationary phase. The 16 kDa band seen in one-dimensional SDS-PAGE corresponded to a 16 kDa protein family observed on twodimensional SDS-PAGWIEF gels, whose expression was increased 85-fold when the extracellular pH reached a critical value below 59. The N-terminal sequences of proteins from two spots on the two-dimensional gels (members of the 16 kDa family) were determined and found to be identical. The physiological role of this protein family has not yet been elucidated.

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SummaryMalnutrition is distributed widely throughout the world and is a particular problem in developing countries. Laboratory animals have been very useful in studying the effects of varying levels of malnutrition because non-nutritional factors that affect humans may be controlled. The objective of the present study was to determine the effects of moderate and severe malnutrition on lymphocyte proportions and activation markers of T cells in experimentally malnourished rats during lactation by flow cytometry. Lower absolute (total) and relative (%) numbers of CD3 + and CD4 + lymphocyte subpopulations were observed in moderately (second degree) and severely (third degree) malnourished rats compared with well-nourished rats (P < 0·05). Both groups of malnourished rats showed a significant decrease in the percentage of CD71 + cells at 24 h post-activation with phytohaemagglutinin (PHA). After 24 h activation of spleen cells with PHA, a lower percentage of CD25+ cells was observed in malnourished than well-nourished rats (P < 0·05). In conclusion, the results of this study indicated an altered expression of CD71 and CD25 during activation of T lymphocytes in malnourished rats and may partially explain increased susceptibility to infection associated with malnutrition. Moreover, these results demonstrated that moderate malnutrition affects the response of T lymphocytes as much as severe malnutrition.