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41.
42.
Comparative Cytochrome Oxidase and Superoxide Dismutase Analyses on Strains of Azotobacter vinelandii and Other Related Free-Living Nitrogen-Fixing Bacteria 总被引:4,自引:3,他引:1 下载免费PDF全文
Quantitative N,N,N′,N′-tetramethyl-p-phenylenediamine (TMPD) oxidase and superoxide dismutase (SOD) analyses were performed on representative organisms of the family Azotobacteraceae. Azotobacter vinelandii, Azotobacter chroococcum, Azotobacter paspali, and Derxia gummosa exhibited high quantitative TMPD oxidase activities, and their extracts possessed very active and electrophoretically homogeneous (single gel band) Fe-type SODs. Azomonas macrocytogenes extracts had similar single Fe-type SODs, and their cells exhibited no TMPD-dependent cytochrome oxidase activity. Nitrogen-fixing cells of Beijerinckia indica, Beijerinckia derxii, and Beijerinckia mobilis exhibited minimal TMPD oxidation capabilities (rates equivalent to the TMPD autooxidation reaction), and these extracts also possessed very active SODs but only of the Mn metallotype. 相似文献
43.
Edward A. Bayer Ehud Skutelsky T. Viswanatha Meir Wilchek 《Molecular and cellular biochemistry》1978,19(1):23-29
Summary Two approaches are described for the localization and quantification of biotin transport components in yeast cells. One approach is based on tracing the fate of a radioactive affinity label for the biotin transport system, [14C]-biotinyl-p-nitrophenyl ester (pBNP), through various stages of subcellular fractionations. A complementary method involves the use of a biotinderivatized, impermeant, electron-dense, affinity-cytochemical label (ferritin-biotin conjugates) for subsequent visualization by electron microscopy. Values of approximately 8,000 and 4,000 sites/cell, respectively, were achieved by the two methods. Complicating factors, future perspectives and the relevance of the two methods to the isolation of transport components are discussed. 相似文献
44.
Estimation of the Number of Sex Alleles and Queen Matings from Diploid Male Frequencies in a Population of APIS MELLIFERA 总被引:9,自引:3,他引:6 下载免费PDF全文
The distribution of diploid males in a population of Apis mellifera was obtained by direct examination of the sexual phenotypes of the larvae. Using these data, estimates are derived for the number of sex alleles and the number of matings undergone by the queen. The number of sex alleles is estimated to be 18.9. The estimate is larger than previous ones, which have ranged between 10 and 12. However, the increase in the number of sex alleles can be explained by the large effective population number for our data. The best estimator of the number of matings by a queen is a maximum likelihood type that assumes a prior distribution on the number of matings. For the data presented here, this estimate is 17.3. This estimate is compared to others in the literature obtained by different approaches. 相似文献
45.
Edward G. Durbin 《Journal of phycology》1977,13(2):150-155
The effect of cell size on growth rates and some cellular contents of Thalassiosira nordenskioeldii Cleve has been measured at 0 and 10 C. At 0 C the growth rate did not vary with cell size. The 2 smallest clones at this temperature had reduced growth rates because of the induction of sexuality in that size range. The clones grown at 10 C showed a significant negative relationship between growth rate and valve diameter with the cell surface area/volume ratio positively related to growth rate. At both temperatures the smaller cells had proportionately more carbon and nitrogen/unit cell volume. The amount of chlorophyll a and silica/unit cell surface area increased with increasing cell surface area at both 0 and 10 C. Both the C/N and C/chl a ratios showed no significant change with cell size at either temperature but there was a significant increase in the C/chl a ratio at 0 C. The C/Si ratio decreased with increasing cell size at both 0 and 10 C. 相似文献
46.
Steven G. Chrysant M.D.Ph.D. Susan M. Townsend B.S. Robert D. Lindeman M.D. Edward D. Frohlich M.D. 《Life sciences》1977,20(12):1953-1960
The possible effects of renal vasoconstriction from anesthesia and surgery on water excretion after hypotonic volume expansion (HVE) were studied in 18 well conditioned anesthetized dogs, with and without the infusion of phenoxybenzamine and acetylcholine into the renal artery of the cannulated kidney. In 6 dogs (Group 1 - Control) whose renal artery was infused with isosmotic saline, HVE resulted in a bilateral increase in GFR and UV (p < .05). ERPF, Cosm, CH2O, UNaV, UKV, RBF, RVR and MAP did not change significantly. In 6 other dogs (Group 2), whose cannulated kidney was infused with phenoxybenzamine 50 μg/min before and during HVE, GFR increased on the infused side while CH2O and UV increased bilaterally (p < .05). ERPF, Cosm, UNaV, UKV, RBF, RVR and MAP were not affected significantly. The addition of ADH, 2 mu/min into the phenoxybenzamine infusate, decreased ERPF, RBF and RVR bilaterally and CH2O on the infused side (p < .05). It had no effect upon GFR, Cosm, UNaV, UKV and MAP. In another 6 dogs, (Group 3), whose cannulated renal artery was infused with acetylcholine (20 μg/min) before and during HVE, CH2O, UV and RVR increased bilaterally (p < .05). ERPF and RBF decreased bilaterally (p < .05), whereas GFR, Cosm, UNaV and MAP were unaffected. UKV decreased on the infused side (p < .05). The addition of ADH (2 mu/min)_into the acetylcholine infusate, decreased CH2O bilaterally and increased Cosm and UKV on the control side (p < .05). It had no effect on ERPF, GFR, UV, UNaV, RBF, RVR and MAP. These observations suggest that anesthesia and surgery produce renal vasoconstriction and this together with increased ADH release, interfere with water excretion by the kidney. Previous renal vasodilation prevents these influences of anesthesia and surgery. 相似文献
47.
We examined the effects of isopropanol (ISOP) pretreatment on the metabolism of 14CCl4 to 14CO2 and CHCl3 exhaled in the breath, to 14C metabolite excreted in 24 hr urine and feces from 0 to 24 hr, and to 14C metabolite bound to liver at 24 hr. Fasted male rats were given 0.1 or 2.0 mmoles 14CCl4/kg. ISOP pretreatment, which markedly enhanced the hepatotoxicity of CCl4, selectively enhanced the rate and total extent of 14CO2 and CHCl3 metabolite exhalation. The pathways of CCl4 metabolism leading to CO2 and CHCl3 metabolite formation may be more relevant to the hepatotoxicity of CCl4 than the pathways leading to urinarym fecal or covalently bound metabolites. 相似文献
48.
Edward G. Kirby 《Physiologia plantarum》1982,56(1):114-117
In order to establish rapidly growing, friable cell cultures of Douglas-fir ( Pseudotsuga menziesii [Mirb. (Franco)], the effects of organic sources of nitrogen on growth were investigated. Of the nitrogen sources studied, including allantoin, allantoic acid, glutamine and glutamic acid, all were capable of increasing growth. Glutamine (50 m M ) produced the most marked increase in growth boosting dry weight production to a level of four times that of controls. Glutamine additions also eliminated the lag phase of growth and caused cells to become densely cytoplasmic. Results are discussed in relation to the pathway for assimilation of nitrogen. 相似文献
49.
Graham S. Baldwin Alphonse Galdes H.Allen O. Hill Stephen G. Waley Edward P. Abraham 《Journal of inorganic biochemistry》1980,13(3):189-204
β-Lactamase II has two metal-binding sites. The electronic spectra of Cd(II)- and Co(II)-substituted β-lactamase II have been investigated. It is suggested that a thiol ligand is involved in metal binding at the first site. The stoichiometric dissociation constants for Co(II) binding to β-lactamase II were estimated to be 0.13 and 2.66 mM (pH 6.0, 4°C, 1 M NaCl) by equilibrium dialysis. Competition between Zn(II) and Co(II) for the first metal binding site suggests a value of 0.7 μM (pH 6.0, 30°C, 1 M NaCl) for the dissociation constant o Zn(II).The electronic spectra of the Co(II) enzyme lead to the suggestion that the coordination geometries around the metal ions in the first and second sites are related to those of a distorted tetrahedron and octahedron, respectively. 相似文献
50.
A novel procedure is described for preparing a plasma membrane fraction from skeletal muscle (i.e., sarcolemma). The procedure entails evacuating the myoplasm from muscle slices as a preliminary step to homogenization and fractionation. The evacuated muscle slices are composed of a stroma-containing sarcolemma, which is then homogenized and fractionated, utilizing a sequence of differential and discontinuous sucrose density gradient centrifugations. On the basis of electron microscopy, selective enzyme markers and α-bungarotoxin binding in innervated and denervated muscles, the fraction most enriched with sarcolemma is recovered from the 0.5/0.7 M interface of a discontinuous sucrose gradient. 相似文献