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31.
Allan K. Stobart W. Trevor Griffiths Ibraheem Ameen-Bukhari Robert P. Sherwood 《Physiologia plantarum》1985,63(3):293-298
The effect of cadmium on the biosynthesis of chlorophyll has been investigated in the leaves of dark-grown seedlings of barley ( Hordeum vulture L. cv. Proctor). Cd2+ inhibited the production of chlorophyll by affecting 1) the synthesis of 5-aminolacvulinic acid and 2) the protoehlorophyllide reductase ternary complex with its substrates. Cd2+ had no effect on the constituent enzymes that catalyse the synthesis of free protoehlorophyllide from 5-aminolaevulinic acid. The results obtained are consistent with Cd2+ inhibiting the formation of chlorophyll by reacting with essential thiol groups in both the protochlorophyllide reductase protein and the enzyme(s) involved in the light dependent synthesis of 5-aminolaevulinic acid. 相似文献
32.
Summary The enzyme protochlorophyllide (pchlide) reductase has been identified amongst the peptides, resolved by sodium dodecyl sulphate
polyacrylamide gel electrophoresis (SDS-PAGE), of chloroplast membranes from oat and barley plants. In support of this identification
the enzymic activity associated with the enzyme has also been measured in the same preparations. A higher level of enzyme
was found in plants which had been darkened prior to extraction. Based on this data, mechanisms for the light regulated diurnal
variation of the reductase are discussed. 相似文献
33.
Insertion of a foreign nucleotide sequence into mitochondrial DNA causes senescence in Neurospora intermedia 总被引:9,自引:0,他引:9
The kalilo variants of Neurospora contain a cytoplasmic genetic factor that causes senescence. This factor is a 9.0 kb transposable element (kalDNA) that lacks nucleotide sequence homology with mtDNA and is inserted into the mitochondrial chromosome, often at sites located within the open reading frame in the intron-DNA of the mitochondrial 25S-rRNA gene. Genomes containing the "foreign" DNA insert accumulate during growth, and death occurs as the cells become deficient in functional large and small subunits of mitochondrial ribosomes. The kalDNA transposon may be an "activator" element that causes breaks in mtDNA. Nonsenescing [+] strains of Neurospora do not contain kalDNA. 相似文献
34.
An immunogenetic analysis of the progeny of F1, F2, and (F1 x parental strain) test cross-matings between the CIA-susceptible DA(RT1av1) and the CIA-resistant BN(RT1n) rat strains was performed. Hybrid progeny were tested for susceptibility to CIA as induced by native calf type II collagen, and for immune response to native rat and calf type II collagens. The results show a minimum of one non-RT1-linked gene which modifies susceptibility to CIA in RT1a/a hybrid progeny. These hybrids have anti-collagen immune responses equivalent to those of the parental DA strain as measured by skin testing and IgG antibody titers. An affect of sex hormones on susceptibility to CIA is indicated, because hybrid females were more susceptible than were hybrid males of equivalent RT1 allotypes. 相似文献
35.
The Catalasemetre, for assessing the quality of raw and pasteurized milk, has been studied. No correlation was found between catalase activity and bacterial counts for farm bulk tank milks within the range 5.2 ± 102 -5.4 ± 105 cfu/ml. Similarly, no relation was observed between catalase activity and somatic cell counts of milk (range of counts from 0.08 to 3.5). However, the catalase activity and bacterial count of pasteurized milks which had been pre-incubated at 21.C for 25 h in the presence of crystal violet-penicillin-nisin to inhibit Gram-positive bacterial growth were significantly related. Thus, the use of this pre-incubation procedure coupled with the Catalasemetre to estimate bacterial growth, has potential in assessing the keeping quality of pasteurized milk samples within 25.5 h of production. Results on the thermostability of native milk catalase are also presented. 相似文献
36.
37.
Abstract: The concentration of γ-aminobutyrate (GABA) and the activity of glutamate decarboxylase and GABA-transaminase were measured in extracts of mouse brain before the onset and during the course of generalized seizures induced by systemic administration of homocysteine thiolactone. The results indicate that whole brain GABA metabolism is unaffected by subconvulsive and convulsive doses of homocysteine at all stages of the generalized seizure. Electroencephalographic monitoring of rat brain electrical activity via hippocampal electrode implantation allowed the course of homocysteine-induced seizures to be followed and afforded a means of quantifying such seizures. 相似文献
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A. G. Nash D. R. Dance V. R. McCready J. D. Griffiths 《BMJ (Clinical research ed.)》1972,3(5825):508-510
The uptake of 67Ga in biopsy specimens of normal and abnormal tissue was measured in 20 cases of colonic and rectal disease and the ratio between the 67Ga uptake in these diseases and in the normal colon or rectum was determined. Uptake of the isotope was high in most of the 14 primary malignant tumours, being highest in poorly differentiated tumours. This uptake was found to be concentrated at the active tumour edge. Uptake of the isotope was generally low in non-malignant lesions. 相似文献