Purification and characterization of two plasma membrane domains from ejaculated bull spermatozoa

Plasma membranes were detached from ejaculated bull spermatozoa by a brief sonication in a moderately hypotonic medium, and the released plasma membranes were partially purified by differential centrifugation. The resulting fraction was enriched 8- and 15-fold in alkaline phosphatase and 5' nucleotidase activities, respectively, compared with the starting sonicated spermatozoa. This total plasma membrane fraction was separated into two distinct fractions by equilibrium density centrifugation on a continuous linear sucrose gradient. Two peaks of light scattering material were formed at densities of 1.117 and 1.148 g/ml. The denser peak contained most of the protein of the plasma membrane fraction, whereas nearly all the concanavalin A binding activity was found in the lighter peak. The two bands had distinctly different polypeptide compositions when analyzed by SDS PAGE. Polyclonal antibodies were raised in rabbits against a major integral membrane glycoprotein of each fraction (Mr of 92,000 in the light peak and 98,000 in the dense peak). The two antigens were detected on the surface of intact spermatozoa by indirect immunofluorescence microscopy. The 92-kD protein (present in the lighter band) was detected only on the plasma membrane of the acrosomal and anterior postacrosomal regions of the head. The 98-kD antigen, present in the heavier band, was localized to the surface of the postacrosomal region of the head, to the principal piece of the tail, and to the connecting piece between the head and tail. The exclusive localization of the 92-kD polypeptide to the surface of the anterior portion of the head was confirmed by immunoelectron microscopy. These data show that the two fractions isolated on the sucrose gradient originate from different regions of the sperm cell plasma membrane.     

Effect of prolonged bed rest on lung volume in normal individuals

Pulmonary function was assessed in supine subjects before, during, and after three separate bed-rest studies of 11 and 12 days duration. Forced vital capacity (FVC) increased during bed rest in each subject. Total lung capacity (TLC) was measured by helium dilution in one bed-rest study and increased in each subject, while residual volume and functional residual capacity of the respiratory system did not change. No change in FVC was found in an ambulatory control group using identical measurement techniques. Maintaining base-line plasma volume during one bed rest by the use of exogenous estrogen did not prevent an increase in FVC, and decreasing plasma volume with diuretics in ambulatory subjects to the same degree as seen in the bed rests did not cause an increase in FVC. We conclude that prolonged bed rest results in a small significant increase in TLC and that this change is not dependent on alterations in plasma volume.     

Pathophysiologic alterations in Biomphalaria glabrata infected with Angiostrongylus costaricensis

Hemolymph glucose, alkaline phosphatase, lactic dehydrogenase, and creatine phosphokinase in Biomphalaria glabrata infected with Angiostrongylus costaricensis were significantly higher on day 27 postinfection (PI) than in uninfected snails. Hemolymph total calcium from infected snails was less on days 6, 12, and 27 PI than that from controls. Total hemolymph protein was similar for controls and infected animals during the entire study. Throughout the study the mean number of amoebocytes/mm³ hemolymph from infected snails was significantly less than that for controls. Mean total wet weights of digestive gland and foot muscle from infected and uninfected snails was similar throughout the study. Mean μg glycogen/mg wet weight of digestive gland from infected snails was significantly greater on days 24, 27, and 28 PI than that from controls. Mean μg glycogen/mg wet weight of foot muscle from infected snails was significantly reduced between days 12 and 28 PI from that of uninfected snails. It is suggested that hemolymph glucose and digestive gland glycogen in infected snails are augmented by glycogen breakdown in the foot muscle of parasitized animals. Elevations in hemolymph enzymes are due to tissue destruction by larvae emerging from the foot muscle of infected snails. Parasite-induced derangements in shell metabolism underlie observed changes in hemolymph calcium in infected snails.     

Insulin regulation of protein biosynthesis in differentiated 3T3 adipocytes. Regulation of glyceraldehyde-3-phosphate dehydrogenase

The effect of insulin on protein biosynthesis was examined in differentiated 3T3-L1 and 3T3-F442A adipocytes. Insulin altered the relative rate of synthesis of specific proteins independent of its ability to hasten conversion of the fibroblast (preadipocyte) phenotype to the adipocyte phenotype. Although more than one pattern of response to insulin was observed, we focused on the induction of a Mr 33,000 protein which was identified as the glycolytic enzyme glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Exposure of 3T3 adipocytes to insulin throughout differentiation specifically increased GAPDH activity and protein content by 2- to 3-fold as compared to 3T3 adipocytes differentiated in the absence of insulin. These changes in enzyme activity and content could be accounted for by a 4-fold increase in the relative rate of synthesis of GAPDH and a 9-fold increase in hybridizable mRNA levels. Within 2 h of insulin addition to 3T3 adipocytes differentiated in the absence of hormone, hybridizable GAPDH mRNA levels increased 3-fold, and within 24 h GAPDH mRNA levels increased 8-fold, and [35S] methionine incorporation into GAPDH protein increased 5-fold. The increase in GAPDH mRNA and GAPDH biosynthesis could be demonstrated using physiologic concentrations of insulin (0.24 nM), indicating that these effects are mediated through a specific interaction with the insulin receptor. These studies demonstrate that insulin, as the sole hormonal perturbant, can increase the synthesis of certain 3T3 adipocyte proteins by altering the cellular content of a specific mRNA.     

Dependence of phytoplankton assimilation quotients on light and nitrogen source: implications for oceanic primary productivity

Photosynthetic production of oxygen by phytoplankton assemblagedominated by Peridinium in Lake Kinneret, Israel, generallyexceeds the molar equivalent rate of carbon assimilation. Carbonassimilation occurs only if oxygenic photosynthesis exceedsa light-dependent threshold. Assimilation quotients (mol C molO₂^–1) are a variable function of irradiance, and typicallyonly about one-half of the photoreductant produced during oxygenicphotosynthesis is used for reduction of carbon dioxide. Mostof the residual oxygenic photoreductant probably is used forlight-dependent reduction of nitrate, which competes with carbondioxide for oxygenic photoreductant. Nitrate is an importantsource of nitrogen for this algal assemblage, and light-dependentnitrate reduction probably is much larger than carbon dioxidereduction at lowest irradiances in the euphotic zone. Oxygenproduction also may be much larger than carbon assimilationat low light levels in other environments where oxidized formsof nitrogen are important nitrogenous nutrients for phytoplankton,as in the lower euphotic zone of the sea, where low rates ofcarbon assimilation by phytoplankton have been thought to beinconsistent with the amount of oxygen that accumulates duringsummer.     

Microfluorometric estimates of proteins associated with murine hepatocyte and thymocyte nuclei, residual structures, and nuclear matrix derivatives

Isolated diploid hepatocyte and thymocyte nuclei and their derivatives ("residual structures" and nuclear matrices, as defined by Kaufmann et al. 1981) were evaluated by microfluorometry following reaction with the following fluorochromes: brilliant sulfaflavine (BSF) used at pH 2.8 for the demonstration of total protein; acridine orange (AO) used at pH 9.0 to reveal acidic groups of proteins; and 3-(4-maleimidylphenyl)-7-diethylamino-4-methylcoumarin (CPM) used under conditions required to demonstrate the sum of sulfhydryl (SH) and disulfide (SS) groups of proteins. The results suggested that the proteins reacting with AO and CPM differed from each other and from those revealed by fluorochroming with BSF. In every comparison, hepatocyte nuclei and their derivatives were more fluorescent than the respective populations of thymocyte nuclei and their derivatives. In material fluorochromed with BSF and AO, nuclear matrices were less fluorescent than residual structures, which, in turn, were less fluorescent than intact nuclei. In contrast, nuclear matrices fluorochromed with CPM were less fluorescent than intact nuclei but more fluorescent (paradoxically) than residual structures. The ratios of the total fluorescence values of hepatocyte and thymocyte nuclei fluorochromed with BSF changed significantly during extractions required to produce residual structures and nuclear matrices, while comparable ratios in material fluorochromed with AO or CPM did not change significantly. Comparisons of the ratios of the fluorescence values of intact nuclei and their derivatives in a variety of combinations yielded complex and variable results.(ABSTRACT TRUNCATED AT 250 WORDS)     

On the diphasic nature of vasovagal fainting associated with blood-injury-illness phobia

A detailed psychophysiologic analysis of a vasovagal faint occurring in a "blood-injury-illness" phobic demonstrated that the syncopal episode consisted of a diphasic response. This lends support to the hypothesis that vasovagal fainting in these patients is caused by an overcompensating rebound parasympathetic activation following sympathetic arousal. Treatment and research implications of this finding are discussed.     

Analysis of Cell Types Identifiable In Air-Dried Cell Preparations of Human Testis

Abstract. The mixed cell population of the testicular epithelium has been studied in air-dried cell preparations obtained from a testicular biopsy. Observed cell types are defined, quantified and assigned to cell stages of the spermatogenic cycle. Studies with tritiated thymidine helped to categorize the spermatogonial cell types. Variation in cell size within cell categories, variation in frequency of cells in different categories within individuals, and variation in frequency of cells within categories between individuals were subjected to quantitative analysis.