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81.
L Prakash 《Mutation research》1977,45(1):13-20
The ability to remove ultraviolet (UV)-induced pyrimidine dimers was examined in four radiation-sensitive mutants of Saccharomyces cerevisiae. The susceptibility of DNA from irradiated cells to nicking by either the T4 UV-endonuclease or an endonuclease activity found in crude extracts of Micrococcus luteus was used to measure the presence of dimers in DNA. The rad3 and rad4 mutants are shown to be defective in dimer excision whereas the rad6 and rad9 mutants are proficient in dimer excision. 相似文献
82.
Diamine oxidase was purified separately from cotyledon and embryo of pea seedlings germinated for 6 days. The Km of the cotyledon enzyme for putrescine was 1.6 × 10?4M while that for the embryo enzyme was 9 × 10?5M. On heating for 15 min at 70° the embryo enzyme retained about 90% activity whereas the cotyledon enzyme retained only 20% activity. The electrophoretic mobility of the cotyledon enzyme was ca twice that of the enzyme from embryo. 相似文献
83.
The activity of cotyledon and embryo diamine oxidase was reduced by feeding ethrel and chloroethanol to the seedlings. The inhibitory effect of 2,4-D on the activity of enzyme in the cotyledon which may be mediated through ethylene was reversed by exposure of seeds to red light. 相似文献
84.
85.
Summary In a pot culture experiment on a sierozem sandy soil (pH 8.2) rates of added B at 3 ppm although decreased root yield significantly
but shoot and grain yield was unaffected even at 6 ppm added B, even though shoot B concentration was as high as 360 ppm and
Ca/B ratio as low as 11. At 6 ppm applied B, shoot yield was increased by 18.5 per cent, whereas grain yield was at par with
control. The results suggested that Ca/B ratio in barley straw was not a reliable index for determing the magnitude of B problem
in the soil. 相似文献
86.
Structure and function in galactosyltransferase. Sequence locations of alpha-lactalbumin binding site, thiol groups, and disulfide bond 总被引:4,自引:0,他引:4
The region(s) of bovine galactosyltransferase that interacts with the lactose synthase regulatory protein alpha-lactalbumin was investigated using trace 3H acetylation to probe the effects of alpha-lactalbumin on the reactivities of the individual amino groups of galactosyltransferase. In the presence of Mn2+, alpha-lactalbumin was found to reduce the reactivities of lysines 93 and 181 and to increase the reactivities of one or more of lysines 230, 237, and 241. The addition of N-acetylglucosamine (20 mM), which enhances complex formation between the two proteins, did not significantly alter the pattern of perturbation. These results indicate that the NH2-terminal region of the catalytic domain of galactosyltransferase, and possibly part of the proline-rich "stem" region, is affected by the association with alpha-lactalbumin and is therefore implicated in the binding of acceptor substrates. In a separate study only cysteines 176, 266, and 342 of galactosyltransferase were found to react with [3H]iodoacetic acid under denaturing conditions. From their lack of reactivity it is deduced that the remaining two cysteines, residues 134 and 247, are joined in a disulfide linkage. From these results and those of a previous study of UDP-galactose binding (Yadav, S., and Brew, K. (1990) J. Biol. Chem. 265, 14163-14169) it appears that the soluble form of galactosyltransferase is composed of two domains, the NH2-terminal 150 residues containing the Cys134-Cys247 disulfide bond, which functions in alpha-lactalbumin and acceptor binding, and the COOH-terminal region, which is involved in UDP-galactose binding. 相似文献
87.
A highly sensitive and specific assay based on gas chromatography/electron capture negative ion chemical ionization mass spectrometry has been developed for the analysis of the enantiomers of hexobarbital and its major metabolites in human urine and plasma. S-(+)-(5-2H3)hexobarbital and R-(-)-(5-2H3)hexobarbital were synthesized for clinical studies along with (+/-)-(1,5-2H6)hexobarbital and the deuterated major metabolites for use as internal and reference standards. Hexobarbital enantiomers and their metabolites were analyzed after pentafluorobenzyl and trimethylsilyl derivatization, following solid-phase extraction from plasma and urine. Intense negative ion spectra were observed for all of the derivatives. The base peak in the spectra corresponded to the M-pentafluorobenzyl anion [M-PFB]- except for 1,5-dimethylbarbituric acid, where M-. was the most abundant ion. The applicability of the method was demonstrated by following the plasma concentration-time profiles and urinary excretion in a male extensive metabolizer of mephenytoin who was given a pseudoracemic oral dose of hexobarbital containing equal 50 mg amounts of S-(+)-2(H0)hexobarbital and R-(-)-(2H3)hexobarbital. Marked stereoselective disposition was observed, with the R-(-)-enantiomer being more efficiently metabolized, primarily by alicyclic oxidation and ring cleavage. 相似文献
88.
Five commercial preparations of natural pesticides were tested for in vitro compatibility with muscardine fungi, Beauveria brongniartii and Metarhizium anisopliae. Neemark (azadirachtin) was found compatible with both the fungi. Phytoallexin, the natural fungicide, significantly inhibited the growth of both the fungi, while other natural pesticides showed moderate to severe inhibition. 相似文献
89.
90.
The effects of cardiogenic and noncardiogenic pulmonary edema on the activities of rapidly adapting receptors (RARs) and pulmonary C-fibre receptors were investigated in dogs anaesthetized with chloralose. Cardiogenic pulmonary edema was produced by elevating the mean left atrial pressure by 25 mmHg (1 mmHg = 133.32 Pa) above the control value for a period of 45 min, by partial obstruction of the mitral valve. Noncardiogenic pulmonary edema was produced by injecting alloxan (100 mg/kg) intravenously. The effect of the latter was examined on RARs alone. Cardiogenic edema activated RARs (n = 8) and the activity was greatest during the first few minutes after elevation of mean left atrial pressure. The pulmonary C-fibre receptors (n = 6) were also activated by cardiogenic edema, but these responses were variable. Noncardiogenic pulmonary edema also activated RAR (n = 6), and this response was maintained during the entire recording period (20 min). The extravascular lung water (%), measured 15 min (n = 5) and 45 min (n = 5) after the elevation of the mean left atrial pressure, was significantly elevated above control values. However, these two values were not significantly different from each other. The extravascular lung water increased significantly after the injection of alloxan also (n = 5). These results show that during pulmonary edema, there is significant stimulation of the RARs and the pulmonary C-fibre receptors. It is suggested that the reflex respiratory responses observed in pulmonary edema may be due to the activation of both the RARs and the pulmonary C-fibre receptors. 相似文献