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Summary Based on a dose-survival curve, a radiation dose of 3.99 C/kg was used to induce antibiotic-resistant mutants inBacteroides fragilis. Escherichia coli B/r membrane fragments were employed as a reducing agent. Antibiotic-resistant mutants ofB. fragilis were utilized to study the mechanism by which these organisms become resistant to selected chemotherapeutic agents. Decreased accumulation of tetracycline by resistant mutants ofB. fragilis suggests that the resistance to this antibiotic is associated with the outer membrane permeability. There is a marked difference in the inhibitory action of rifampicin on RNA polymerase activity in rifampicin-sensitive and-resistant strains ofB. fragilis. This enzyme is, therefore, the likely target for inhibition of bacterial growth in this anaerobe by rifampicin. 相似文献
74.
Serum antioxidant enzyme activity in Parkinson's disease 总被引:2,自引:0,他引:2
Jawahar Kalra Ali H. Rajput Subrahmanyam V. Mantha Kailash Prasad 《Molecular and cellular biochemistry》1992,110(2):165-168
Summary The activities of superoxide dismutase (SOD; EC 1.15.1.1) and glutathione peroxidase (GSHPx; EC 1.11.1.9.), the enzymes that metabolize the superoxide anion and hydrogen peroxide, respectively, were measured in serum
from healthy subjects and patients with Parkinson's disease (PD). The activities of SOD and GSHPx in patients with PD were higher than those in normal healthy individuals. These results suggest that the increased activities
of these enzymes could be due to oxidative stress in the initial stages of this disease. 相似文献
75.
We have identified by immunoblotting and ADP-ribosylation by cholera toxin and pertussis toxin the presence of Mr 43 and 46 KDa Gs, and 39 and 41 KDa Gi;.. subunits in rat parotid gland plasma membranes but not in granule membranes. A Mr 28 KDa polypeptide that served as substrate for ADP-ribosylation by both cholera toxin and pertussis toxin was present exclusively in granule membranes. Photoaffinity crosslinking of [-32P]GTP showed the presence of high molecular weight GTP-binding proteins (Mr 160,100 KDa) in granule membranes. Six low molecular weight GTP-binding proteins (Mr 21–28 KDa) were differentially distributed in both plasma membranes and granule membranes. The present study identifies various GTP-binding proteins in rat parotid gland plasma membranes and granule membranes, and demonstrates the presence of distinct molecular weight GTP-binding proteins in granule membranes. These granule-associated GTP-binding proteins may be involved in secretory processes. 相似文献
76.
77.
Growth ofPseudomonas testosteroni in a medium containing 1mm Cu(II) causes a color change from blue to green. The spectrum of the supernatant solution from the blue culture shows an absorption at 660 nm, identical to that of 1mm [Cu(II)] in the medium. The green supernatant solution shows a UV absorption, which tails into the visible and so is responsible for the green color, and ad-d absorption at 720 nm. The absorption at 660 nm for the blue supernatant solution is probably due to [Cu(NH3)3(H2O)3]2+. Growth of the organism causes loss of ammonia and a speciation change to [Cu(NH3)2(H2O)4]2+, with a shift in absorption maximum from 660 to 720 nm. These conclusions are based upon the spectra of known aquaammine complexes of Cu(II) and calculations of the speciation of Cu(II) before and after growth. Change in metal speciation owing to nutrient uptake by an organism does not appear to have been recognized previously. 相似文献
78.
Nicholas F. Hughes 《Environmental Biology of Fishes》1992,33(3):299-305
Synopsis Length-frequency data suggest Nile perch, Lates niloticus, from the Nyanza Gulf grew to a total length of 9 cm by age 118 days and 23 cm by age 287 days. A modified von Bertalanffy growth curve t = 1.35·L(1-e–K(t-t
o)) with the parameters L = 93.1, K = 0.272 and to = 0.046, is suggested to describe growth up to 5 years of age and the relationship t = 1.35·(31.96 + 7.681t) for fish aged 6 years and above. Length-weight relationships were = 0.0234·-gt2.74 for fish between 7 and 15.9 cm total length, = 0.0151·2.94 for fish between 16 and 45.9 cm total length, and = 0.0023·3.44 for fish between 46 and 120 cm total length. Male Nile perch first matured between 50 and 55 cm total length when they were probably 2 years old; female Nile perch first matured between 80 and 85 cm total length when they were probably 4 years old. Small males were common, large males were rare, with the reverse holding for females. Sex change, from male to female, is a possible explanation for this size dimorphism. 相似文献
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80.
The relative contributions made by the l-arginine/agmatine/N-carbamoylputrescine/putrescine and the l-ornithine/putrescine pathways to hyoscyamine formation have been investigated in a transformed root culture of Datura stramonium. The activity of either arginine decarboxylase (EC 4.1.1.19) or ornithine decarboxylase (EC 4.1.1.17) was suppressed in vivo by using the specific irreversible inhibitors of these activities, dl--difluoromethylarginine or dl--difluoromethylornithine, respectively. It was found that suppression of arginine decarboxylase resulted in a severe decrease in free and conjugated putrescine and in the putrescine-derived intermediates of hyoscyamine biosynthesis. In contrast, the suppression of ornithine decarboxylase activity stimulated an elevation of arginine decarboxylase and minimal loss of metabolites from the amine and alkaloid pools. The stimulation of arginine decarboxylase was not, however, sufficient to maintain the same potential rate of putrescine biosynthesis as in control tissue. It is concluded that (i) in Datura the two routes by which putrescine may be formed do not act in isolation from one another, (ii) arginine decarboxylase is the more important activity for hyoscyamine formation, and (iii) the formation of polyamines is favoured over the biosynthesis of tropane alkaloids. An interaction between putrescine metabolism and other amines is also indicated from a stimulation of tyramine accumulation seen at high levels of dl--difluoromethylornithine.Abbreviations ADC
arginine decarboxylase
- DFMA
dl--dif-luoromethylarginine
- DFMO
dl--difluoromethylornithine
- MPO
N-methylputrescine oxidase
- ODC
ornithine decarboxylase
- PMT
putrescine N-methyltransferase
We are indebted to Dr. E.W.H. Bohme of Merrell Dow Research Laboratories (Cincinnati, Ohio, USA) for kind gifts of DFMO and DFMA and to Dr. M.J.C. Rhodes for helpful advice and discussion. 相似文献