scholarly journals Oxygen metabolism of mammalian spermatozoa. Generation of hydrogen peroxide by rabbit epididymal spermatozoa

1981 ◽  
Vol 198 (2) ◽  
pp. 273-280 ◽  
Author(s):  
Michael K. Holland ◽  
Bayard T. Storey
Keyword(s):  
Molecular Weight ◽  
Plasma Membrane ◽  
Cell Concentration ◽  
Oxygen Metabolism ◽  
Low Molecular Weight ◽  
H2o2 Production ◽  
Epididymal Spermatozoa ◽  
Cell Concentrations ◽  
Osmotic Treatment ◽  
Rabbit Spermatozoa

Rabbit spermatozoa from the cauda epididymis produced 0.7–0.8nmol of H2O2/min per 108 cells at cell concentrations below 107 cells/ml with linear dependence on cell concentration. Above 2 × 107 cells/ml, the rate again became linear with cell concentration but decreased to 0.1–0.2nmol/min per 108 cells. Spermatozoa treated with amphotericin B, which makes the plasma membrane highly permeable to low-molecular-weight compounds, showed a similar dependence of H2O2 production rate on cell concentration; below 107 cells/ml the rate was 0.3–0.4nmol/min per 108 cells; above 2 × 107 cells/ml, the rate was 0.1–0.2nmol/min per 108 cells. Hypo-osmotically treated rabbit epididymal spermatozoa, a preparation useful for studying mitochondrial function in sperm [Keyhani & Storey (1973) Biochim. Biophys. Acta305, 557–565] produced 0.1–0.2nmol/min per 108 cells in the absence of added substrates. The dependence of rate on cell concentration was linear from 107 to 2.2 × 108 cells/ml. This endogenous rate was unaffected by rotenone, but stimulated 4-fold by antimycin A. Addition of the mitochondrial substrates lactate plus malate increased the rate of H2O2 production to 0.3nmol/min per 108 cells. The decreased rate of H2O2 production observed with intact sperm at high cell concentrations is attributed to reaction of H2O2 with the cells, possibly with the plasma membrane, which is lost after hypo-osmotic treatment. Rabbit spermatozoa have glutathione peroxidase and glutathione reductase activities, but these seem to play little role in removal of H2O2 generated. The rate at low cell concentration is taken to be the unperturbed rate. The sources of H2O2 production in rabbit spermatozoa have been tentatively resolved into a low-molecular-weight component, lost after amphotericin treatment, a mitochondrial component and a rotenone-insensitive component that has not been identified.

Ca2+-sensitive permeability changes caused by influenza virus

1983 ◽  
Vol 3 (8) ◽  
pp. 749-755 ◽  
Author(s):  
Kalpana Patel ◽  
Charles A. Pasternak
Keyword(s):  
Molecular Weight ◽  
Influenza Virus ◽  
Plasma Membrane ◽  
Trypan Blue ◽  
Low Molecular Weight ◽  
Permeability Change ◽  
Permeability Changes ◽  
Phosphorylated Compounds

Influenza virus added to Lettré cells at pH 5.3 induces a permeability change similar to that elicited by Sendal virus at pH 7.4: K+ and Na+ equilibrate across the plasma membrane and low-molecular-weight phosphorylated compounds leak out of cells, which remain impermeable to trypan blue.

Trypsin-uncoupled synthesis and secretion of yeast invertase: implications for the mechanism of secretion

1979 ◽  
Vol 25 (4) ◽  
pp. 528-534 ◽  
Author(s):  
Bruce E. Holbein ◽  
Denis K. Kidby
Keyword(s):  
Molecular Weight ◽  
Plasma Membrane ◽  
Subcellular Distribution ◽  
Plasma Membranes ◽  
External Surface ◽  
Internal Surface ◽  
Low Molecular Weight ◽  
Synthetase Activity ◽  
Trypsin Treatment ◽  
Yeast Invertase

The subcellular distribution of invertase was examined after synthesis and secretion by sphaeroplasts had been uncoupled by the addition of 30 μg mL−1 trypsin. Sphaeroplasts secreted only the high molecular weight invertase during uncoupling by trypsin. The level of low molecular weight, 'small' invertase in the soluble internal pool was found to be elevated by over fivefold, and the membrane-associated pool was found to contain low molecular weight invertase in addition to intermediate molecular weight invertase, after 1.5 h of trypsin treatment. Purified plasma membranes from trypsin-treated sphaeroplasts had no detectable mannan synthetase activity. On the basis of these and previous findings, a working hypothesis wherein invertase is synthesized on the internal surface of the plasma membrane and glycosylated during its transit to the external surface is presented.

scholarly journals Effect of extender supplementation with low-molecular-weight antioxidants on selected quality parameters of cryopreserved canine spermatozoa

2018 ◽  
Vol 62 (2) ◽  
pp. 221-227 ◽  
Author(s):  
Marek Lecewicz ◽  
Rafał Strzeżek ◽  
Władysław Kordan ◽  
Anna Majewska
Keyword(s):  
Molecular Weight ◽  
Plasma Membrane ◽  
Sperm Quality ◽  
Membrane Integrity ◽  
Quality Parameters ◽  
Freezing Process ◽  
Low Molecular Weight ◽  
Synergistic Activity ◽  
Enzymatic Antioxidants ◽  
Vitamins E And C

AbstractIntroduction The addition of low-molecular-weight antioxidants during the freezing process improves post-thaw sperm quality. The high antioxidant potential of cryopreserved semen could have a positive effect on the motility, viability, and energy status of sperm cells and their ability to bind to the zona pellucida of oocytes. The aim of the study was to determine the effects of different concentrations and combinations of vitamins E and C in a semen extender on selected quality parameters of frozen-thawed canine spermatozoa.Material and Methods The experimental material was the semen of four mixed-breed dogs. Sperm viability (motility, plasma membrane integrity, and mitochondrial function) was examined at 0, 60, and 120 min in semen samples supplemented with the extender and in the controls.Results Combined supplementation with vitamins C + E at a concentration of 200 + 200 μM /1 × 109 spermatozoa had the most profound effect on total sperm motility, linear motility, and the percentage of spermatozoa with intact plasma membrane and active mitochondria.Conclusion The synergistic activity of vitamins E and C had a more beneficial influence on the quality of frozen–thawed sperm than these non-enzymatic antioxidants applied separately.

A modified procedure for studying enzyme secretion in yeast sphaeroplasts: subcellular distribution of invertase

1976 ◽  
Vol 22 (7) ◽  
pp. 989-995 ◽  
Author(s):  
Bruce E. Holbein ◽  
Cecil W. Forsberg ◽  
Denis K. Kidby
Keyword(s):  
Molecular Weight ◽  
Plasma Membrane ◽  
High Molecular Weight ◽  
Subcellular Distribution ◽  
Invertase Activity ◽  
Enzyme Secretion ◽  
Low Molecular Weight ◽  
Triton X

A significantly modified procedure for investigating enzyme secretion from yeast sphaeroplasts, and results from its application are described. Sphaeroplasts were derepressed for invertase biosynthesis in the presence of helicase and fractionated to reveal the distribution of high and low molecular weight forms of invertase. Secreted enzyme was found to be of high molecular weight, exclusively. Less than 10% of the total invertase activity was present in washed sphaeroplasts and of this, 43% was soluble, consisting of both high and low molecular weight forms of invertase. Washed membranes retained 32% of the internal invertase activity, and on solubilization with Triton X-100 the enzyme was found to be of an intermediate molecular weight. These results are consistent with the hypothesis that invertase is glycosylated at the plasma membrane.

A high-performance oil-free backing pump for electron microscopes

1978 ◽  
Vol 36 (1) ◽  
pp. 110-111
Author(s):  
G.K.W. Balkau ◽  
E. Bez ◽  
J.L. Farrant
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Hot Spots ◽  
High Performance ◽  
Carbonaceous Material ◽  
Contamination Rate ◽  
Low Molecular Weight ◽  
Principal Source ◽  
Rotary Pumps ◽  
Electron Microscopes

The earliest account of the contamination of electron microscope specimens by the deposition of carbonaceous material during electron irradiation was published in 1947 by Watson who was then working in Canada. It was soon established that this carbonaceous material is formed from organic vapours, and it is now recognized that the principal source is the oil-sealed rotary pumps which provide the backing vacuum. It has been shown that the organic vapours consist of low molecular weight fragments of oil molecules which have been degraded at hot spots produced by friction between the vanes and the surfaces on which they slide. As satisfactory oil-free pumps are unavailable, it is standard electron microscope practice to reduce the partial pressure of organic vapours in the microscope in the vicinity of the specimen by using liquid-nitrogen cooled anti-contamination devices. Traps of this type are sufficient to reduce the contamination rate to about 0.1 Å per min, which is tolerable for many investigations.

Low-molecular-weight heparin in the prevention and treatment of thromboembolic disorders

1998 ◽  
Vol 1 (5) ◽  
pp. 166-174 ◽  
Author(s):  
Evelyn R Hermes De Santis ◽  
Betsy S Laumeister ◽  
Vidhu Bansal ◽  
Vandana Kataria ◽  
Preeti Loomba ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Low Molecular Weight ◽  
Prevention And Treatment
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