Effect of ascorbic acid on the binding of 3H-GABA and 3H-glutamic acid to synaptosomes of the rat cerebral cortex

The effects of different concentrations of L-ascorbic acid (Asc) on Na+-dependent binding of 3H-GABA and 3H-DL-glutamic acid to rat brain cortical synaptosomes were studied. Asc, at a concentration nearly equal to brain extracellular one (3 X 10(-4) M), had no effect on specific and nonspecific 5H-GABA binding. At higher concentrations (10(-3) M) Asc strongly inhibited, and at lower concentrations (10(-6) M) considerably stimulated 3H-GABA binding. At a concentration of 10(-5)-10(-3) M Asc tended to decrease 3H-DL-glutamic acid binding.     

Range of the antigenic specificity of peptidoglycan in Staphylococcus aureus compared to other representatives of the Staphylococcus genus

In investigations based on the use of a highly sensitive test system permitting the detection of normal human antibodies to S. aureus peptidoglycan, the antigenic relationships between the peptidoglycans of S. aureus and other representatives of the genus Staphylococcus have been studied. Among other staphylococcal species, S. simulans, S. xylosus, S. hyicus, S. cohnii, S. hyicus s. s. chromogenes have been found to possess peptidoglycans most closely related to S. aureus peptidoglycans, while S. warneri and S. epidermidis peptidoglycans have proved to be least closely related to it.     

CHELATOR: an improved method for computing metal ion concentrations in physiological solutions.

An algorithm is presented for the calculation of metal ion concentrations from given total metal concentrations (and vice versa) in physiological media containing metal-chelating compounds. In such media, conditions differ from those used for stability constant determination of metal-chelator equilibria; therefore calculated metal ion concentrations are incorrect. We recompute stability constants to reflect the effects of ionic strength and temperature of physiological solutions. Twelve different equilibria can be considered per metal-chelator pair. The computer program also calculates the contribution of ionized species of metals, chelator, complexes and pH buffers to ionic strength. Measurements with a Ca-selective electrode and with fura-2 show that calculated ionic Ca2+ concentrations are correct from 10 nM up to the millimolar range. The importance of the correct calculation of metal ion concentrations in physiological experiments is demonstrated by data, and derived kinetic parameters, on Na+/Ca2+ exchange and the ATP-dependent Ca2+ pump of enterocyte plasma membrane vesicles. The program is written in Turbo Pascal and will run on IBM-compatible computers. It is menu-driven and supports the use of a Microsoft mouse.     

Influence of age,weaning, season and body weight on the levels of progesterone,oestradiol-17β and luteinizing hormone in growing buffalo heifers (Bubalus bubalis)

The influence of age, weaning, season of the year and body weight on the peripheral levels of progesterone, oestradiol-17β and luteinizing hormone (LH) were studied during neonatal, perinatal and peripubertal periods in buffalo heifers. The buffalo heifers exhibited oestrus only after 30 months of age and had higher levels of LH and oestradiol-17β and a lower level of progesterone on the day of oestrus. The progesterone concentration was affected significantly (P < 0.01) by different seasons, by weaning (P < 0.05) and varied between pubertal and neonatal periods (P < 0.01), whereas the oestradiol-17β level was affected significantly (P < 0.01) by weaning and varied at different seasons and with body weight. However, the LH concentration was greater during the neonatal period than the pre- and peripubertal periods and changed significantly (P < 0.01) between groups of ages and body weights. The results suggest that increases in the levels of oestradiol-17β and progesterone after 30 months of age are probably indicative of the onset of puberty in buffalo heifers. However, a further increase in oestradiol-17β, LH, and a decrease in progesterone are essential for oestrus and cyclicity to be exhibited in buffalo heifers.     

Volume and density changes of biological fluids with temperature

High-precision (10(-5) g/ml) mass density measurements on human blood, plasma, plasma ultrafiltrate (using PM-10 membranes), and erythrocyte concentrate samples were performed with the mechanical oscillator technique. Measurement temperatures varied between 4 and 48 degrees C and were accurate to +/- 1 X 10(-2) K. The coefficient of thermal expansion (beta), defined as relative volume change with temperature, was calculated. It was shown that beta increases with temperature in these fluid samples over the entire temperature range investigated; the magnitude of this increase declines with increasing temperature; beta increases with density at temperatures below 40 degrees C but is independent of density above 40 degrees C; and the beta of the intracellular fluid has about twice the value of the beta for extracellular fluid at low (4-10 degrees C) temperatures but is equal for both fluids at greater than or equal to 40 degrees C. The mechanical oscillator technique provides data with an accuracy sufficient to perform precise (10(-5) K) calculations of beta of small volumes of biological fluids.     

Antigen-specific T helper clones in a nonresponder strain require augmentation for expression of helper activity. Evidence for a possible antigen presentation defect in B cells

Hen egg-white lysozyme (HEL)-specific Thy-1+, Lyt-1+2- T cell lines and clones were derived from the nonresponder C57BL/6 strain. Although the antigen-specific proliferative response of these T cells in the presence of syngeneic irradiated spleen cells as a source of antigen-presenting cells (APC) was normal, the same cells were incapable of stimulating B cells to secrete antibody in vitro. This deficiency could, however, be corrected by the addition of an excess of normal T cells or a supernatant from concanavalin A-stimulated rat spleen cells. Alternatively, the use of highly cross-reactive ring-necked pheasant lysozyme in the cultures allowed expression of efficient help, ruling out any inherent deficiency in the T cells. The antibody response was specific and required MHC compatibility between the T lines and responding B cells. By using (H-2b X H-2d)F1 B cells and another H-2d-restricted HEL-specific T line, it was shown that only the H-2b-restricted T-B collaboration required exogenous factors, and the H-2d-restricted collaboration did not. Because both proliferative and helper responses are dependent upon MHC-restricted antigen presentation by macrophage-APC and B cells, respectively, these results suggest that the defect in the nonresponder H-2b-restricted T-B collaborative pathway may relate to the inability of B cells to adequately process and present HEL to clonal T cells.