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1.
Some properties of hexameric purine nucleoside phosphorylase II (EC 2.4.2.1) from Escherichia coli K-12 were studied. The enzyme obeys the Michaelis-Menten kinetics with respect to purine substrates (Km for inosine, deoxyinosine and hypoxanthine are equal to 492, 106 and 26.6 microM, respectively) and exhibits negative kinetic cooperativity towards phosphate and ribose-1-phosphate. The Hill coefficient is equal to approximately 0.5 for both substrates. Hexameric purine nucleoside phosphorylase II is not a metal-dependent enzyme; its activity is inhibited by Cu2+, Zn2+, Ni2+ and SO4(2-). The enzyme is the most stable at pH 6.0; it contains essential thiol groups. All substrates partly protect the enzyme against inactivation by 5.5'-dithiobis(2-nitrobenzoic acid) and heat-inactivation and, with the exception of phosphate-against inactivation by p-chloromercuribenzoate. Hypoxanthine, especially in combination with phosphate, afford the best protection against inactivation. 相似文献
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A S Agabalian R A Zakharian S M Akopian K A Bakunts Iu A Israelian 《Mikrobiologiia》1978,47(1):97-100
Physico-chemical characteristics of plasmid DNAs isoalted from Pseudomonas putida G7 were studied as well as the behavior of these DNAs in th eourse of chromatography on columns with Sepharose 4B and kieselguhr with methylated albumin (MAC). This strain was found to contain several plasmid DNAs having molecular weights of 33-36X10(6), 15-18X10(6), and 3-5X10(6) dalton. The plasmid DNAs of biodegradation are supposed to be located in the vicinity of chromosomes, and only a small part of them is characterized by extrachromosomal localization. 相似文献
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Harsh Sancheti Garnik Akopian Fei Yin Roberta D. Brinton John P. Walsh Enrique Cadenas 《PloS one》2013,8(7)
Alzheimer’s disease is a progressive neurodegenerative disease that entails impairments of memory, thinking and behavior and culminates into brain atrophy. Impaired glucose uptake (accumulating into energy deficits) and synaptic plasticity have been shown to be affected in the early stages of Alzheimer’s disease. This study examines the ability of lipoic acid to increase brain glucose uptake and lead to improvements in synaptic plasticity on a triple transgenic mouse model of Alzheimer’s disease (3xTg-AD) that shows progression of pathology as a function of age; two age groups: 6 months (young) and 12 months (old) were used in this study. 3xTg-AD mice fed 0.23% w/v lipoic acid in drinking water for 4 weeks showed an insulin mimetic effect that consisted of increased brain glucose uptake, activation of the insulin receptor substrate and of the PI3K/Akt signaling pathway. Lipoic acid supplementation led to important changes in synaptic function as shown by increased input/output (I/O) and long term potentiation (LTP) (measured by electrophysiology). Lipoic acid was more effective in stimulating an insulin-like effect and reversing the impaired synaptic plasticity in the old mice, wherein the impairment of insulin signaling and synaptic plasticity was more pronounced than those in young mice. 相似文献
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The differentiation of rhythmogenic characteristics of the ureter's different regions in guinea pigs
Kazarian KV Vantsian VTs Meliksetian IB Tiraian AS Akopian RR 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2002,88(7):925-931
Characteristics of rhythmogenic pacemakers of the ureter's perirenal middle and peribladder region morphologically and electrophysiologically are analysed in guinea pigs both in presence of spreading activity and breach of conductivity. It was shown that the action potential's amplitude of the middle region is the highest and duration of the spike activities from perirenal zone is maximal and all three regions are characterised by different functional conditions. 相似文献
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Kazarian KV Vantsian VTs Meliksetian IB Tiraian AS Akopian AA 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2003,89(2):200-206
Histamine changed characteristics of the perinephric spontaneous spike activity and of the spreading electrical wave. It was shown that histamine could activate latent pacemakers of the ureter's middle area. Morphological picture of the histamine effect was also shown. 相似文献
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Kazarian KV Vanzian VTs Tiraian AS Akopian RR 《Rossi?skii fiziologicheski? zhurnal imeni I.M. Sechenova / Rossi?skaia akademiia nauk》2000,86(12):1656-1661
The rhythm generated by the peribladder area was found to be slower than that generated by the basis perirenal pacemaker in cats and rats. The antiperistaltic waves' frequency of the peribladder area was the lowest within the range of all the recorded rhythms. 相似文献