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71.
本文比较了中药灵香草Lysimachia foenum-graecum Hance及其混淆品种垂花香草Lysimaehia nutantiflora Chen et C.M.Hu的植物形态、药材性状以及茎、叶组织显微特征。指出垂花香草无灵香草特有的芳香。也无药用记载。应仔细区别,不宜混用。 相似文献
72.
9-β-
-Arabinofuranosyl-2-fluoroadenine (F-ara-A) and 9-β-
-arabinofuranosyladenine (ara-A) are purine nucleoside analogues which are incorporated into nucleic acids. This study demonstrates the mutagenic properties of F-ara-A and ara-A and provides evidence for mechanisms by which the arabinosyl nucleosides induce mutation. At the drug dosages that evoked exponential cell killing, F-ara-A and ara-A caused a significant increase in the number of 6-thioguanine-resistant mutants in Chinese hamster ovary cells. Southern analyses showed that 15 of 16 drug-induced mutants had lost all or part of the HPRT gene, whereas no loss of the gene was found in 4 spontaneous mutants. We conclude that both F-ara-A and ara-A induced mutation predominantly by causing deletion of genetic method. The remarkable frequency of gene deletion among these drug-induced mutations is discussed with respect to possible mechanisms of action of arabinosyl nucleosides in mutational studies. 相似文献
73.
Maintenance of low cl concentrations in mesophyll cells of leaf blades of barley seedlings exposed to salt stress
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The concentrations of vacuolar Na+ and Cl− in the epidermal and mesophyll cells of the leaf blade and sheath of Hordeum vulgare seedlings (cv California Mariout and Clipper) were measured by means of quantitative electron probe x-ray microanalysis. A preferential accumulation of Cl− in vacuoles of epidermal cells in both blade and sheath and a low level in mesophyll cells of the blade were evident in plants grown in full strength Johnson solution. The concentration of Cl− in the mesophyll cells of the blade remained at a low level after exposure to 50 or 100 millimolar NaCl for 1 day or to 50 millimolar for 4 days, while at the same time the concentration of Cl− in the epidermis and mesophyll of the sheath showed a dramatic increase. Clipper generally contained more Cl− in the mesophyll cells of the blade than California Mariout. A greater accumulation of Na+ in the mesophyll of the sheath relative to that of the blade was only apparent after treatment with 100 millimolar NaCl for 1 day or 50 millimolar for 4 days. These results confirm the suggestion that sheath tissue is capable of accumulating excess Cl− (and to a lesser extent Na+) and suggest that the site of regulation of Cl− concentration in the barley leaf is located in the mesophyll cells of the blade. 相似文献
74.
Lysophosphatidate acyltransferase activities in the microsomes from palm endosperm, maize scutellum, and rapeseed cotyledon of maturing seeds 总被引:8,自引:5,他引:3
Lysophosphatidate (LPA) acyltransferase (EC 2.3.1.51) in the microsomes from palm endosperm (Syagrus cocoides Martius), maize scutellum (Zea mays L.), and rapeseed cotyledon (Brassica napus L.) of maturing seeds were studied for their specificities toward the acyl moiety of the substrates lysophosphatidate and acyl coenzyme A (CoA). The LPA acceptor greatly influenced the acyl CoA specificity of the enzyme and vice versa. With 1-oleoyl-lysophosphatidate (LPA-18:1), the palm enzyme was equally active on oleoyl CoA and lauroyl CoA, whereas the maize and rapeseed enzymes were more active on oleoyl CoA than on lauroyl CoA. With 1-lauroyl-lysophosphatidate (LPA-12), which generated less activity than LPA-18:1, the palm enzyme was three times more active on lauroyl CoA than on oleoyl CoA. LPA-12 was an inactive substrate for the maize and rapeseed enzymes. The selectivity of the enzymes was also studied using a mixture of LPA-18:1 and LPA-12, as well as lauroyl CoA and oleoyl CoA. Under this selectivity condition and compared to the specificity condition, the enzymes from all the three seeds exerted stronger preference for oleoyl moiety in either the LPA or acyl CoA, and again, only the palm enzyme could act on LPA-12. Similar studies, although in lesser detail, showed that the enzymes from soybean and castor bean were similar to the maize and rapeseed enzymes in having little activity on substrates containing lauroyl moiety. The results demonstrate the importance of the acyl group in the sn-1 position of LPA in determining the acyl preference in the sn-2 position in phosphatidate synthesis. The palm enzyme appears to be the only one capable of synthesizing phosphatidates containing high amounts of lauric moieties. 相似文献
75.
Two structural genes on different chromosomes are required for encoding the major subunit of human red cell glucose-6-phosphate dehydrogenase 总被引:6,自引:0,他引:6
Structural analysis revealed the existence of two types of subunits in human red cell glucose-6-phosphate dehydrogenase. The two subunits have the same COOH region consisting of 479 amino acid residues, but their NH2-terminal regions are different in size and sequence. The minor subunit can be fully encoded by the X-linked G6PD cDNA, but the NH2-terminal region of the major subunit cannot. The cDNA and the gene for the NH2-terminal region of the major subunit were cloned and characterized. Southern blot hybridization indicated that the gene for the NH2-terminal region is on chromosome 6, not on the X chromosome. Northern blot hybridization demonstrated an existence of two separate mRNA components, one for the COOH-terminal region and the other for the NH2-terminal region. Two separate structural genes, the X-linked and chromosome 6-linked genes, must be coresponsible for encoding the single chain subunit. Either cross-translation of two mRNAs, or transpeptidation, or some other mechanism must be involved in the synthesis of human red cell G6PD. 相似文献
76.
Vasoactive intestinal peptide (VIP) and peptide histidine isoleucine (PHI) are homologous neuropeptides which share vasodilatory properties. This paper addresses the question of whether PHI exerts its vascular action via a receptor distinct from that for VIP. Radioligand binding experiments were done using [Tyr(125I)10]VIP, [Tyr(125I)22]porcine PHI, [Tyr(125I)10]rat PHI and arterial preparations from rat, bovine and porcine species. The radioiodination of rat PHI by the lactoperoxidase-glucose oxidase method and analysis of the structure of the major radiolabeled derivatives were described. All the receptor binding experiments identified a VIP-preferring receptor irrespective of which radioligand or arterial preparation was utilized. VIP and PHI peptides demonstrated cross-desensitization in studies of relaxation of porcine coronary arterial strips in vitro. The present results favor the conclusion that the vascular actions of the PHI peptides are best explained by binding to a VIP-preferring receptor. 相似文献
77.
Genetic Analysis of Olfactory Behavior in Drosophila: A New Screen Yields the Ota Mutants 总被引:5,自引:3,他引:2
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A simple means of measuring Drosophila olfactory response is described, and the behavior which it measures is characterized. The assay was used to screen for X-linked mutants defective in olfactory function. Six ota mutants were isolated and characterized (ota = olfactory trap abnormal). Four of the mutants were found to be abnormal in another chemosensory behavior as well. Two of the mutant phenotypes extend to include another sensory system: they are defective in visual system physiology. All were normal, however, in a test of giant fiber system physiology. Two of the mutations are dominant, and the recessive mutations define two complementation groups. Mutations representing each complementation group, as well as one of the dominant mutations, were mapped. For the mutants with defective visual system physiology, the visual defects were shown to cosegregate with olfactory phenotypes. 相似文献
78.
Molecular genetics of phenylketonuria in Orientals: linkage disequilibrium between a termination mutation and haplotype 4 of the phenylalanine hydroxylase gene. 总被引:11,自引:8,他引:3
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T Wang Y Okano R Eisensmith S Z Huang Y T Zeng W H Lo S L Woo 《American journal of human genetics》1989,45(5):675-680
Phenylketonuria (PKU) is a common metabolic disorder among Chinese, with a prevalence of about 1 in 16,500 births. This frequency is very similar to that among Caucasians. Individual exons of the phenylalanine hydroxylase (PAH) gene with flanking introns were amplified by polymerase chain reaction and cloned into M13 for sequence analysis. An Arg111-to-Ter111 mutation has been identified in exon 3 of the PAH gene in a Chinese PKU patient. The mutation is in linkage disequilibrium with the mutant haplotype 4 alleles which are the most prevalent haplotype among the Orientals. The mutation accounts for about 10% of the Chinese PKU alleles and is absent from the Caucasians, demonstrating that independent mutational events have occurred in the PAH locus after racial divergence. 相似文献
79.
Tyrosine phosphorylation in human neutrophil 总被引:9,自引:0,他引:9
J Gomez-Cambronero C K Huang V A Bonak E Wang J E Casnellie T Shiraishi R I Sha'afi 《Biochemical and biophysical research communications》1989,162(3):1478-1485
Protein tyrosine phosphorylation in human neutrophils was examined by immunoblotting with antibodies specific for phosphotyrosine. The addition of the human hormone granulocyte-macrophage colony stimulating factor to human neutrophils caused an increase in the tyrosine phosphorylation levels of several proteins. The increases in at least two of these proteins having molecular masses of 40 kDa (p40) and 54 kDa (p54) were rapid and were inhibited in pertussis toxin treated cells. The newly synthesized tyrosine kinase inhibitor ST 638 inhibited the increases in the levels of the tyrosine phosphorylation in p92, p78, p54 and p40 proteins. The epidermal growth factor receptor tyrosine kinase inhibitors were less effective. The addition of the chemotactic factor fMet-Leu-Phe to human neutrophils also caused an increase in tyrosine phosphorylation in some of these proteins. The pattern of the fMet-Leu-Phe-induced tyrosine phosphorylation was different from that produced by GM-CSF. The increases were also inhibited by ST 638. In addition, ST 638 inhibited superoxide production but not actin polymerization in control and GM-CSF-treated cells stimulated with fMet-Leu-Phe. Moreover, the active but not inactive phorbol esters increase the tyrosine phosphorylation only in the 40 kDa protein. These results suggest several points: (a) some of the responses produced by GM-CSF and fMet-Leu-Phe are mediated through tyrosine phosphorylation, (b) the GM-CSF receptor is coupled to a pertussis toxin sensitive G-protein, (c) the 40 kDa protein is probably the Gi alpha 2, and (d) the 78 or the 92 kDa protein is most likely the receptor for GM-CSF, which indicates that the receptor may have a tyrosine kinase domain. 相似文献
80.
A new compound, withangulatin A, promotes type II DNA topoisomerase-mediated DNA damage 总被引:1,自引:0,他引:1
J K Juang H W Huang C M Chen H J Liu 《Biochemical and biophysical research communications》1989,159(3):1128-1134
Withangulatin A, a new compound with a known chemical structure and from the antitumor Chinese herb Physalis angulata L, was found to act on topoisomerase II to induce topoisomerase II-mediated DNA damage in vitro. It has two effective dosage ranges of approximate 0.5 and 20 microM, with about one-third the activity of 20 microM VM-26. 相似文献