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1.
Dynamics of the thiol status of rat spermatozoa during maturation: analysis with the fluorescent labeling agent monobromobimane 总被引:4,自引:0,他引:4
Mammalian spermatozoa undergo maturation as they pass through the epididymis. Maturation is accompanied by the oxidation of thiols to disulfides. Disulfides are probably involved in sperm chromatin condensation and tail structure stabilization. In this work, we used the fluorescent thiol-labeling agent monobromobimane to determine the changes occurring in thiols and disulfides in rat sperm heads and tails during maturation. Spermatozoa were obtained from testis, epididymis (caput, corpus, cauda, and vas deferens), and ejaculate. Intact spermatozoa were labeled with monobromobimane, with or without pretreatment with dithiothreitol. Labeling was evaluated microscopically, and quantitative analysis was carried out spectrofluorimetrically with labeled globin used as a standard. Samples were also analyzed by gel electrophoresis. The total amount of thiols and disulfides remained the same during the entire period of sperm maturation (26 +/- 0.5 nmoles thiols + disulfides/10(6) spermatozoa). However, the reactive thiols decreased markedly between the corpus and the cauda (from greater than 90% of total in testis and 75% in corpus to about 25% in cauda), with little or no further change in vas deferens and ejaculated sperm. Trypsin treatment followed by sucrose gradient was used to separate the heads from the tails. Thiols comprised 84% of the total SH + SS in the heads and 74% in the tails of caput spermatozoa, decreasing to 14% and 45%, respectively, in cauda sperm. Thus, the decrease in reactive thiols involved both heads and tails-oxidation to disulfides being very marked in the head. Electrophoresis revealed that oxidation of thiols to disulfides occurred in many protein fractions during maturation in the epididymis. 相似文献
2.
THE SEPARATION OF DIFFERENT CELL CLASSES FROM LYMPHOID ORGANS : III. The Purification of Erythroid Cells by pH-Induced Density Changes
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1. Mammalian erythrocytes swell as the pH of the isotonic suspending medium is lowered, as a direct consequence of the specialized permeability properties of the erythrocyte membrane. Lymphocytes and granulocytes from a variety of sources did not exhibit this property. 2. The behaviour of mouse bone marrow erythroid cells at various stages of differentiation was studied by using a change in buoyant density with pH as an index of swelling. The ability to swell with a pH drop was acquired while the cell was still nucleated. All non-nucleated cells showed swelling. Most small erythroblasts shared this property, whereas most large erythroblasts did not. 3. The density shift with pH was used to provide a purification scheme specific for erythroid cells. The bone marrow cells were first centrifuged to equilibrium in an isotonic albumin density gradient at neutral pH. Regions of the gradient containing the erythroid cells were collected, and the cells were recovered and redistributed in an albumin gradient at acid pH. The erythroid cells showed a specific density shift which removed them from contaminants. Preparations containing 90–97% erythroblasts were obtained by this technique. 4. Differentiation within the erythroid series was accompanied by a general increase in cell buoyant density at neutral pH. This density increase may have been a discontinuous process, since erythroid cells appeared to form a number of density peaks. 5. The pH shift technique, in association with established density distribution and sedimentation velocity procedures, provides a range of cell separation techniques for biological or biochemical studies of erythroid cell differentiation in the complex cell mixtures in bone marrow or spleen. 相似文献
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Excess amino acid polymorphism in mitochondrial DNA: contrasts among genes from Drosophila, mice, and humans 总被引:13,自引:3,他引:10
Recent studies of mitochondrial DNA (mtDNA) variation in mammals and
Drosophila have shown an excess of amino acid variation within species
(replacement polymorphism) relative to the number of silent and replacement
differences fixed between species. To examine further this pattern of
nonneutral mtDNA evolution, we present sequence data for the ND3 and ND5
genes from 59 lines of Drosophila melanogaster and 29 lines of D. simulans.
Of interest are the frequency spectra of silent and replacement
polymorphisms, and potential variation among genes and taxa in the
departures from neutral expectations. The Drosophila ND3 and ND5 data show
no significant excess of replacement polymorphism using the
McDonald-Kreitman test. These data are in contrast to significant
departures from neutrality for the ND3 gene in mammals and other genes in
Drosophila mtDNA (cytochrome b and ATPase 6). Pooled across genes, however,
both Drosophila and human mtDNA show very significant excesses of amino
acid polymorphism. Silent polymorphisms at ND5 show a significantly higher
variance in frequency than replacement polymorphisms, and the latter show a
significant skew toward low frequencies (Tajima's D = -1.954). These
patterns are interpreted in light of the nearly neutral theory where mildly
deleterious amino acid haplotypes are observed as ephemeral variants within
species but do not contribute to divergence. The patterns of polymorphism
and divergence at charge-altering amino acid sites are presented for the
Drosophila ND5 gene to examine the evolution of functionally distinct
mutations. Excess charge-altering polymorphism is observed at the carboxyl
terminal and excess charge-altering divergence is detected at the amino
terminal. While the mildly deleterious model fits as a net effect in the
evolution of nonrecombining mitochondrial genomes, these data suggest that
opposing evolutionary pressures may act on different regions of
mitochondrial genes and genomes.
相似文献
6.
D D Pietronigro J E McGinness M J Koren R Crippa M L Seligman H B Demopoulos 《Physiological chemistry and physics》1979,11(5):405-414
Adriamycin semiquinone radicals are spontaneously generated by adriamycin solutions at physiologic pH. Rate of radical formation and equilibrium-state radical yield increase with increasing pH from 7.4 to 8.85. The radicals are oxygen sensitive, but the mechanism of radical formation is oxygen independent and associated with proton removal from the dihydroquinone of adriamycin. The less cardiotoxic and non-mutagenic (Ames test) anthracycline 5-iminodaunorubicin does not form semiquinone radicals spontaneously at physiologic pH. 相似文献
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Sara Santarossa Alexandra R. Sitarik Christine Cole Johnson Jia Li Susan V. Lynch Dennis R. Ownby Alex Ramirez Germaine LM. Yong Andrea E. Cassidy-Bushrow 《Journal of Exercise Nutrition & Biochemistry》2021,25(4):24
[Purpose] To determine whether physical activity (PA), primarily the recommended 60 minutes of moderate-to-vigorous PA, is associated with gut bacterial microbiota in 10-year-old children.[Methods] The Block Physical Activity Screener, which provides minutes/day PA variables, was used to determine whether the child met the PA recommendations. 16S rRNA sequencing was performed on stool samples from the children to profile the composition of their gut bacterial microbiota. Differences in alpha diversity metrics (richness, Pielou’s evenness, and Faith’s phylogenetic diversity) by PA were determined using linear regression, whereas beta diversity (unweighted and weighted UniFrac) relationships were assessed using PERMANOVA. Taxon relative abundance differentials were determined using DESeq2.[Results] The analytic sample included 321 children with both PA and 16S rRNA sequencing data (mean age [SD] =10.2 [0.8] years; 54.2% male; 62.9% African American), where 189 (58.9%) met the PA recommendations. After adjusting for covariates, meeting the PA recommendations as well as minutes/day PA variables were not significantly associated with gut richness, evenness, or diversity (p ≥ 0.19). However, meeting the PA recommendations (weighted UniFrac R2 = 0.014, p = 0.001) was significantly associated with distinct gut bacterial composition. These compositional differences were partly characterized by increased abundance of Megamonas and Anaerovorax as well as specific Christensenellaceae_R-7_group taxa in children with higher PA.[Conclusion] Children who met the recommendations of PA had altered gut microbiota compositions. Whether this translates to a reduced risk of obesity or associated metabolic diseases is still unclear. 相似文献
10.
A balanced psychology and a full life 总被引:3,自引:0,他引:3
Seligman ME Parks AC Steen T 《Philosophical transactions of the Royal Society of London. Series B, Biological sciences》2004,359(1449):1379-1381
Psychology since World War II has been largely devoted to repairing weakness and understanding suffering. Towards that end, we have made considerable gains. We have a classification of mental illness that allows international collaboration, and through this collaboration we have developed effective psychotherapeutic or pharmacological treatments for 14 major mental disorders. However, while building a strong science and practice of treating mental illness, we largely forgot about everyday well-being. Is the absence of mental illness and suffering sufficient to let individuals and communities flourish? Were all disabling conditions to disappear, what would make life worth living? Those committed to a science of positive psychology can draw on the effective research methods developed to understand and treat mental illness. Results from a new randomized, placebo-controlled study demonstrate that people are happier and less depressed three months after completing exercises targeting positive emotion. The ultimate goal of positive psychology is to make people happier by understanding and building positive emotion, gratification and meaning. Towards this end, we must supplement what we know about treating illness and repairing damage with knowledge about nurturing well-being in individuals and communities. 相似文献