Inner acrosomal membrane of mammalian spermatozoa: its properties and possible functions in fertilization

The inner acrosomal membrane (IAM) develops during the spermatid stage of differentiation as that portion of the Golgi-derived acrosome granule that tightly associates with the condensing sperm nucleus. In some mammalian species, an electron-dense proteinaceous material accumulates between the IAM and the nuclear envelope, collectively comprising the "perforatorium." Evidence, including its partial purification and its structural resistance to detergents and sonication, suggests that the IAM is an unusually resiliant membrane. Dense paracrystalline arrays of intramembranous particles, a lack of lectin-mediated receptor modulation, and its lack of participation in sperm-egg fusion suggest that the IAM lacks the same degree of fluidity as the egg surface plasmalemma. Observations using monoclonal antibodies, however, suggest that some specific antigenic modulations may be possible within the IAM. Its structural rigidity is of obvious mechanical value during sperm penetration through the zone pellucida. An additional role as a scaffold for putative zona lysin material remains controversial. Biochemical evidence suggests that acrosin, for example, is not entirely soluble and that some remains sperm-associated, depending on the conditions of acrosome disruption. Nevertheless, morphological studies do not agree on acrosin's specific localization to the IAM. Currently there is only very limited information concerning the localization of the other acrosomal enzymes to the IAM. Another possible role for the IAM in some species may be in recognizing the zona pellucida. Evidence for this derives from the observation that fucoidin, a fucose heteropolysaccharide, inhibits guinea pig sperm-zona binding, and bound fucoidin can be localized to the IAM and equatorial regions of the living acrosome-reacted spermatozoa. Finally, the IAM may have a role in early recognition/adhesion with the colemma.     

Degradation of Dehydrodivanillin by Anaerobic Bacteria from Cow Rumen Fluid

Dehydrodivanillin (DDV; 0.15 g/liter) was biodegradable at 37°C under strictly anaerobic conditions by microflora from cow rumen fluid to the extent of 25% within 2 days in a yeast extract medium. The anaerobes were acclimated on DDV for 2 weeks, leading to DDV-degrading microflora with rates of degradation eight times higher than those initially. Dehydrodivanillic acid and vanillic acid were detected in an ethylacetate extract of a DDV-enriched culture broth by thin-layer, gas, and high-performance liquid chromatographies and by mass spectrometry.     

Chemical transformation of eremofortin C into PR toxin.

The natural products of both eremofortin C (EC) and PR toxin are secondary metabolites of Penicillium roqueforti. Because the chemical structures of EC and PR toxin are closely related to each other and differ only by a hydroxyl functional group in EC and an aldehyde functional group in PR toxin at the C-12 position, the chemical transformation of EC into PR toxin was investigated. Oxidation with a chromic anhydride-pyridine complex was found to be the most satisfactory method.     

Covalent structure of three phase-1 flagellar filament proteins of Salmonella

Using recombinant DNA techniques, the covalent structure was determined for three flagellar filament proteins produced by Salmonella serotypes with phase-1 antigens a, c and d. Comparison of the results obtained, together with previous results for antigen i, indicated an overall structure in which conservation of amino acid sequence was absolute at both ends of the molecule and proceeded inwards with progressively greater variation. Very few differences in nucleotide sequence were detected in regions of amino acid conservation, which suggested that these areas of the gene may be involved in regulatory functions.     

Sodium arsenite enhances the cytotoxicity, clastogenicity, and 6-thioguanine-resistant mutagenicity of ultraviolet light in Chinese hamster ovary cells

Cytotoxicity, chromosome aberrations, and mutations to 6-thioguanine resistance were synergistically increased by incubating the ultraviolet light (UV)-irradiated Chinese hamster ovary (CHO) cells in medium containing sodium arsenite. However, the frequencies of sister-chromatid exchanges and mutations to ouabain resistance induced by UV were not synergistically increased by sodium arsenite. The synergistic effect of sodium arsenite on UV-induced chromosome aberrations varied with cell-harvesting time and decreased with increasing time intervals between UV and sodium arsenite treatments.     

The Hypersensitive Reaction of Tobacco to Pseudomonas syringae pv. pisi: Activation of a Plasmalemma K/H Exchange Mechanism

Net electrolyte efflux from suspension-cultured tobacco cells undergoing the hypersensitive reaction to Pseudomonas syringae pv. pisi resulted from a specific efflux of K⁺ which was accompanied by an equimolar net influx of H⁺. These fluxes began 60 to 90 minutes after inoculation of tobacco cells with bacteria, reached maximum rates of 6 to 9 micromoles per gram fresh weight tobacco cells per hour within 2.5 to 3 hours, and dropped below 4 micromoles per gram per hour within 5 hours. Tobacco cells lost approximately 35% of total K⁺ during this period, and average cellular pH declined by approximately 0.75 pH unit. These events were accompanied by a 30% decrease in cellular ATP. K⁺ and H⁺ fluxes were inhibited by the protonophore (p-trifluoromethoxy)carbonyl cyanide phenylhydrazone and by increasing the K⁺ concentration of the external solution. Tobacco leaf discs inoculated with the bacterium also exhibited a specific net K⁺ efflux and H⁺ influx. These results suggest that induction of the hypersensitive reaction in tobacco proceeds through the activation of a passive plasmalemma K⁺/H⁺ exchange mechanism. It is hypothesized that activation of this exchange is a major contributing factor in hypersensitive plant cell death.     

Relationship between bacteriophage T4 and T6 DNA topoisomerases. T6 39-protein subunit is equivalent to the combined T4 39- and 60-protein subunits

T6 DNA topoisomerase has been purified from bacteriophage T6 infected Escherichia coli. Unlike the T4 DNA topoisomerase which has three subunits, it consists of two subunits of molecular weights 75,000 and 51,000. They are the products of T6 genes 39 and 52, respectively. The purified T6 enzyme can stimulate in vitro T6 DNA replication. It has an ATP-dependent DNA relaxation activity similar to the T4 enzyme. Either ATP or dATP can be used in both reactions. Using a "Western blotting" and radioimmuno-detection methods, we show that T6 39 subunit contains protein sequences specified by both the T4 39 and 60 genes. The 52-proteins of both phages appear to be identical. The T4 and T6 topoisomerase genes represent a naturally occurring example of gene separation or fusion.     

Glucagon-stimulated phosphorylation of rat liver glycogen synthase in isolated hepatocytes

Addition of glucagon (20 nM) to the isolated hepatocytes from 24-h starved male rats results in an inactivation of glycogen synthase. The A0.5 for glucose-6-P is increased 2-fold over the control but the S0.5 for UDP-glucose is not significantly affected. The glucagon-stimulated inactivation of glycogen synthase is also accompanied by a 60-120% increase in the phosphorylation of the synthase. Glycogen synthase labeled with 32P by incubation of the hepatocytes with [32P] PO4(3-) was recovered by immunoprecipitation and the resulting immunoprecipitate was subjected to tryptic digestion. Analysis of the 32P-labeled peptides reveals that the sites corresponding to those phosphorylated by cAMP-dependent protein kinase and glycogen synthase (casein) kinase-1 (Itarte, E., and Huang, K.-P. (1979) J. Biol. Chem. 254, 4052-4057) are rapidly phosphorylated in response to glucagon. These results demonstrate that glucagon not only triggers the activation of cAMP-dependent protein kinase through an increase in the intracellular level of cAMP but also, by an unknown mechanism, activates a Ca2+- and cAMP-independent protein kinase.     

Reconstruction of the pharyngoesophagus following pharyngoesophagectomy and irradiation therapy

During the 5-year period between 1978 and 1983, a total of 56 individuals have undergone pharyngoesophageal reconstruction at our hospitals. To restore the continuity of the upper enteric tract, conventional skin flaps with or without the underlying muscle were used in 27 and a segmental free intestinal graft by means of microvascular technique was used in 29. Two-thirds of both groups received irradiation therapy before surgery. Fistula formation was encountered in 8 individuals who received a skin flap. This incidence was found to increase with the use of preoperative irradiation. In contrast, no patient developed a fistula among the 29 patients who received the segmental free intestinal graft.