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71.
Male and female meiosis in grasshoppers 总被引:2,自引:2,他引:0
Male meiosis in the grasshopper Stethophyma grossum is well known as an example of proximal chiasma localisation. An investigation of female meiosis in oocytes of this species shows that both the frequency and distribution of chiasmata are quite different from the male situation. Mean chiasma frequency per cell (14.98) in considerably higher in females than in males (11.28) which agrees with the trend established in other comparative studies of male and female meiosis. More strikingly, males and females also show not only different but quite opposite patterns of chiasma distribution. In spermatocytes of males, chiasmata are strictly localised proximally in most bivalents, but in oocytes of females very few chiasmata form in proximal regions and nearly all chiasmata form either in distal or interstitial regions. The genetical significance of these findings is considered. 相似文献
72.
73.
Divergent Metabolic Pathways for Propane and Propionate Utilization by a Soil Isolate 总被引:14,自引:9,他引:5 下载免费PDF全文
The metabolism of propane and propionate by a soil isolate (Brevibacterium sp. strain JOB5) was investigated. The presence of isocitrate lyase in cells grown on isopropanol, acetate, or propane and the absence of this inducible enzyme in n-propanol- and propionate-grown cells suggested that propane is not metabolized via C-terminal oxidation. Methylmalonyl coenzyme A mutase and malate synthase are constitutive in this organism. The incorporation of 14CO2 into pyruvate accumulated during propionate utilization suggests that propionate is metabolized via the methyl-malonyl-succinate pathway. These results were further substantiated by radiorespirometric studies with propionate-1-14C, -2-14C, and -3-14C as substrate. Propane -2-14C was shown, by unlabeled competitor experiments, to be oxidized to acetone; acetone and isopropanol are oxidized in this organism to acetol. Cleavage of acetol to acetate and CO2 would yield the inducer for the isocitrate lyase present in propane-grown cells. 相似文献
74.
Toxicity of dimethyl sulfoxide on HeLa cells 总被引:2,自引:0,他引:2
75.
Effect of Substrate on the Fatty Acid Composition of Hydrocarbon-utilizing Microorganisms 总被引:2,自引:0,他引:2
The fatty acid pattern in three hydrocarbon-utilizing bacteria during growth on various substrates was examined. The predominant fatty acids in acetate-grown cells were C(16), C(16:1), C(18:1), and Br-C(19) and the major fatty acids in propane-grown cells were C(15), C(17), C(17:1), C(18:1), and Br-C(18). When one organism (Mycobacterium sp. strain OFS) was grown on the n-alkanes from C(13) to C(17), the major fatty acid in the cells was of the same chain length as the substrate. Studies on the incorporation of acetate into the cellular fatty acids of microorganisms growing on C(15) and C(17)n-alkanes suggest that the oxidative products of the substrate are incorporated into the cellular fatty acids without degradation to acetate. 相似文献
76.
A new glycolipid sulfate ester in Halobacterium cutirubrum 总被引:7,自引:0,他引:7
77.
A protein factor inhibiting the magnesium-activated adenosine triphosphatase of desensitized-actomyosin 总被引:7,自引:7,他引:0 下载免费PDF全文
1. The preparation and properties of a myofibrillar protein factor which inhibits the Mg(2+)-activated adenosine triphosphatase of desensitized actomyosin is described. 2. This factor had negligible effect on the Mg(2+)-activated adenosine triphosphatase of natural actomyosin and on the Ca(2+)-activated adenosine triphosphatases of desensitized actomyosin and myosin. 3. The Mg(2+)-activated inosine triphosphatase activity of desensitized actomyosin was not affected by the factor. 4. The inhibitory effect was sensitive to ionic strength. In addition to their ionic effects Mg(2+) and Ca(2+) appeared to have a specific action in reducing the effect of the inhibitor. 5. F-actin reduced the inhibition whereas Bailey-type tropo-myosin had little effect. 6. As far as can be judged from the reported experiments this factor is different from any of the previously described myofibrillar components. 相似文献
78.
3-Methylhistidine in actin and other muscle proteins 总被引:13,自引:10,他引:3
1. By the use of the extended elution system for basic amino acid analysis, 3-methylhistidine has been detected in hydrolysates of actin isolated from mammalian, fish and bird skeletal muscle. 2. Evidence is presented to indicate that 3-methylhistidine forms part of the primary structure and that in rabbit actin this residue is restricted to one peptide fraction obtained from the tryptic digest. 3. Rabbit skeletal-muscle actin has a 3-methylhistidine:histidine ratio 1:7.6, indicating a minimum molecular weight of 47600. 4. Adult rabbit myosin contains approximately 2 3-methylhistidine residues/mol. These residues are localized in the heavy meromyosin part of the molecule, and are restricted to the major component obtained after succinylation. 相似文献
79.
80.
Anita B. Williams G.R. Stirling † A.C. Hayward J. Perry 《Journal of applied microbiology》1989,67(2):145-156
When they were subjected to a range of physical and chemical treatments, spores of Pasteuria penetrans showed properties similar to those of other endospore-forming bacteria. The spores did not take up some stains, were resistant to desiccation and sonication and showed extrusion of spore contents ('spore popping') on prolonged exposure to 0.1% KMnO4 in 0.3 n HNO3 . Calcium and dipicolinic acid (DPA) were present at concentrations of 0.28% and 0.96% of the spore dry weight respectively, giving a Ca: DPA molar ratio of 1.2. The infectivity of P. penetrans spores was reduced to a low level after heating at 100°C for 5 min, but spore attachment was not markedly affected by heating at 100°C for 15 min. Evidence for the presence of catalase in P. penetrans spores was equivocal because the low levels of catalase activity observed in spore suspensions may have been due to contamination from catalase-positive nematode tissue. When P. penetrans spores were exposed to a range of substances known to act as germinants for spores of Bacillus spp., germination or loss of refractility was not observed by phase microscopy. In vitro culture of P. penetrans was attempted by inoculating either spores or vegetative mycelial bodies onto a diverse range of simple and complex media and incubating them in aerobic, reduced oxygen, anaerobic and increased CO2 environments. Signs of spore germination or growth of vegetative stages were never observed. 相似文献