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81.
The process of spermiation and sperm transport was studied using specific inhibitors of cytoskeletal elements. Within 12-24 hr after the intratesticular injection of taxol, a compound that acts to stabilize microtubules and inhibit microtubule-related processes, an unusually large number of microtubules was seen within the body of the Sertoli cell. At the same time, transport of elements within the seminiferous epithelium was affected. At the end of stage VI of the cycle, step 19 spermatids were maintained in the deep recesses of the Sertoli cell and not transported to the rim of the seminiferous tubule lumen. At stage VIII, residual bodies remained at, or near, the rim of the tubule and were not transported to the base of the tubule. They underwent only partial degradation at this site, indicating that there may have been two phases involved in their dissolution--one autophagic and one phagocytic, but the latter did not occur since the residual bodies were not transported to Sertoli lysosomes at the base of the tubule. The observations suggest that microtubules are involved in transport processes within the seminiferous epithelium. Within 1-12 hr after the intratesticular injection of 500 microM cytochalasin D, a compound which interferes with actin-related processes, normal appearing tubulobulbar complexes were not present. The tubular portion (distal tube) of the complex did not initiate development. It was assumed that filaments (which were identified as such using NBD-phallacidin and the S-1 fragment of myosin) played an important role in the development of this portion of the complex. Cells did not eliminate cytoplasm normally, as evidenced by an enlarged cytoplasmic droplet, further emphasizing the published role for tubulobulbar complexes in cytoplasmic elimination. Although sperm were released normally from stage VIII tubules, many remained within the tubular lumen and did not traverse the duct system. Cytochalasin did not inhibit fluid secretion by the Sertoli cell, as demonstrated by efferent duct ligation, but did alter myoid cell actin cytoskeletal organization, suggesting that myoid cell contractility is primarily responsible for transport of sperm. Overall, the observations suggest that cytoskeletal activity of the Sertoli cell is important for several aspects of the spermiation process as well as sperm transport. 相似文献
82.
Two monensin-sensitive bacteria which utilized carbohydrates poorly and grew rapidly on amino acids were isolated from the bovine rumen. The short rods (strain SR) fermented arginine, serine, lysine, glutamine, and threonine rapidly (greater than 158 nmol/mg of protein per h) and grew faster on casein digest containing short peptides than on free amino acids ().34 versus 0.29 h(-1)). Gelatin hydrolysate, an amino acid source containing an abundance of long peptides, was unable to support growth or ammonia production, but there was a large increase in ammonia production if strain SR was cocultured with peptidase-producing ruminal bacteria (Bacteroides ruminicola or Streptococcus bovis). Cocultures showed no synergism with short peptides. Strain SR washed out of continuous culture ().1 h(-1)) at pH 5.9. The irregularly shaped organisms (strain F) deaminated glutamine, histidine, glutamate, and serine rapidly (greater than 137 nmol/mg of protein per min) and grew faster on free amino acids than on short peptides ().43 versus 0.21 h(-1)). When strain F was provided with casein or gelatin hydrolysate and cocultured with peptidase-producing bacteria, there was a more than additive increase in ammonia production. Strain F grew in continuous culture (0.1 h(-1)) when the pH was as low as 5.3. The irregularly shaped cells and short rods were present at less than 10(9)/ml in vivo, but they ahd very high specific activities of ammonia production (greater than 310 nmol of ammonia/mg of protein per min) and could play an important role in ruminal amino acid fermentation. 相似文献
83.
84.
A J Grant P J Russell D Raghavan 《Biochemical and biophysical research communications》1989,162(1):308-315
Elastase activities in intact human bladder cancer cell lines, established from three patients, were measured using a fluorogenic substrate highly specific for elastase, under conditions of physiological pH and ionic strength. This method allowed separation of cell-associated from secreted enzyme activity. As secreted elastase accounted for only 8% of the total, we concluded that the elastases were present at the cell surface. Inhibition studies using extracts of cell-surface elastases showed them to be serine proteinases which were also inhibited by alpha 1-antitrypsin. Partially purified fractions showing the highest specific activity towards the fluorogenic substrate hydrolysed insoluble elastin thus confirming the presence of elastases. This is the first time that elastase activity has been demonstrated in human bladder cancer cells and may represent a mechanism involved in tumour invasion. 相似文献
85.
D B Evans R G Russell B L Brown P R Dobson 《Biochemical and biophysical research communications》1989,164(3):1076-1085
The stimulation of osteocalcin synthesis by human osteoblast-like cells in response to 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) is antagonised by several bone regulatory agents. We have shown that agents which activate adenylate cyclase inhibit this action of 1,25(OH)2D3 on human osteoblast-like cells. Activation of adenylate cyclase, either via the stimulatory GTP-binding protein using cholera toxin, or directly at the catalytic via the stimulatory GTP-binding protein using cholera toxin, or directly at the catalytic subunit using forskolin, results in a suppression of osteocalcin synthesis. Whilst the activation of adenylate cyclase induces this inhibitory response, neither exogenous dibutyryl cyclic AMP nor the phosphodiesterase inhibitor, IBMX, exerted any apparent effect on the production of osteocalcin. The tumour promoting phorbol ester, 4 beta-phorbol 12,13-dibutyrate, also inhibited 1,25(OH)2D3-stimulated osteocalcin production. This was not apparent in response to the non-tumour promoting phorbol ester 4 beta-phorbol suggesting the involvement of protein kinase C. 相似文献
86.
H J Andrews R A Bunning C A Dinarello R G Russell 《Biochimica et biophysica acta》1989,1012(2):128-134
Human articular chondrocytes in monolayer culture and fragments of human articular cartilage were treated with recombinant human interferon gamma (IFN-gamma) both alone and in combination with interleukin 1 (IL-1). IFN-gamma alone inhibits metalloproteinase production, as measured in the caseinase assay, and decreases glycosaminoglycan release from cartilage fragments in culture. The synthesis of DNA, as measured by [3H]thymidine incorporation, is stimulated by IFN-gamma. Similar effects are seen in the presence of IL-1. Thus, IFN-gamma opposes the stimulatory effect of IL-1 on caseinase production and decreases IL-1-stimulated cartilage degradation, as measured by glycosaminoglycan release. In contrast, IFN-gamma has no effect on IL-1-stimulated prostaglandin production, and acts synergistically with IL-1 to cause a large stimulation of DNA synthesis. These results show that IFN-gamma has a number of effects on articular chondrocytes in-vitro and suggest a possible role for IFN-gamma in limiting cartilage degradation in inflammatory joint conditions. 相似文献
87.
We report the first study of the effect of NaCl on the double-bond isomeric composition of fatty acids and theirsn-1/sn-2 positional distribution in the membrane phospholipids of a moderately halophilic eubacterium. The major phospholipids, phosphatidylethanolamine and phosphatidylglycerol, ofVibrio costicola grown in 1M or 3M NaCl both have ansn-1 saturated,sn-2 unsaturated distribution of fatty acids. There is a greater effect of salinity on the fatty acid composition of phosphatidylglycerol compared with phosphatidylethanolamine. The fatty acids in phosphatidylethanolamine of cultures grown in 1M compared with 3M NaCl have the same unsaturation index and average chain length, but different double-bond isomeric compositions. In comparison, the fatty acid composition of phosphatidylglycerol is more unsaturated, with a different double-bond isomeric distribution, and has a shorter average chain length in cultures grown in 3M compared with 1M NaCl. The pattern of fatty acid isomers of 16:1 and 18:1 shows thatV. costicola uses the anaerobic pathway of fatty acid biosynthesis. The presence of the isomers 16:1c11 and 18:1c13 in the phospholipids of cultures grown in 3M but not in 1M NaCl indicates that external salinity affects the specificity of fatty acid synthetase in this moderately halophilic bacterium. 相似文献
88.
1. Dopaminergic neurotransmission in brain is receiving increased attention because of its known involvement in Parkinson's disease and new methods for the treatment of this disorder and because of hypotheses relating several psychiatric disorders to abnormalities in brain dopaminergic systems. 2. Chemical assessment of brain dopamine metabolism has been attempted by measuring levels of its major metabolite, homovanillic acid (HVA), in cerebrospinal fluid, plasma, or urine. Because HVA is derived in part from dopamine formed in noradrenergic neurons, plasma levels and urinary excretion rates of HVA do not adequately reflect solely metabolism of brain dopamine. 3. Using debrisoquin, the peripheral contributions of HVA to plasma or urinary HVA can be diminished, but the extent of residual HVA formation in noradrenergic neurons is unknown. By measuring the levels of methoxy-hydroxyphenylglycol (MHPG) in plasma or of urinary norepinephrine metabolites (total MHPG in monkeys; the sum of total MHPG and vanillyl mandelic acid (VMA) in humans) along with HVA, it is possible to estimate the degree of impairment by debrisoquin of HVA formation from noradrenergic neuronal dopamine and thereby better assess brain dopamine metabolism. 4. This method was applied to a monkey before and after destruction of the nigrostriatal pathway by the administration of MPTP. 相似文献
89.
90.
Internal waves, primary production and the compensation depth of marine phytoplankton 总被引:2,自引:0,他引:2
Internal waves increase the average light intensity experiencedby phytoplankton and augment the compensation depth below whichno net photosynthesis occurs. These effects may be quite largein eutrophic waters with moderate or high light attenuationcoefficients. Data on internal waves and light attenuation canbe used to correct standard estimates of (new) primary productionin the lower euphotic zone based on uptake rates of carbon ornitrogen isotopes. 相似文献