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11.
Two apparently distinct types of inhibition of the synthesis of U1, U2, U3, U4, and U5 small nuclear RNA, induced by ultraviolet (UV) radiation, have been described before: immediate and delayed. Our present observation can be summarized as follows: a) neither the immediate nor the delayed inhibition appear to be mediated by the formation of cyclobutane pyrimidine dimers, since they were not prevented by photoreactivating light, in ICR 2A frog cells; b) the inhibition of U1 RNA synthesis, monitored in HeLA cells within the first few minutes after irradiation, extrapolated to a substantial suppression at time zero of postirradiation cell incubation, providing further support for the proposal that the immediate inhibition is a reaction separate from the delayed UV light-induced inhibition of U1 RNA synthesis; c) the transition from the pattern of the immediate inhibition to that of the delayed inhibition (disappearance of the UV-resistant fraction of U1 RNA synthesis and increased rate of inhibition) occurred gradually, without an apparent threshold, within the first 2 hr of incubation after irradiation; and d) the incident UV dose that resulted in a 37% level of residual U1 RNA synthesis (D37) during the delayed inhibition was about 7 J/m2, with an apparent UV dose threshold, and was about 60 J/m2 for the immediate inhibition. 相似文献
12.
The effects of kinetin (Kn) on pigment content and electron transport activities (ETA) in wheat leavesin vivo and chloroplastsin vitro aging in light was investigated. Excised wheat leaves were infiltrated with Kn for 3 h under irradiation. The treatment increased
zeaxanthin (Zx) content by 40% and also increased chlorophyll (Chia, Chib) and major carotenoid (Car) contents in the leaves (per fresh mass unit). Chloroplasts isolated from Kn treated leaves, when
incubated in light for 4 h showed relatively lower pigment loss and slower loss of ETA compared to the chloroplasts of untreated
leaves. These observations suggest photoprotective action of Kn. The photoprotection was more prominent when Kn was applied
directly to the irradiated chloroplastsin vitro. Moreover, chloroplasts agingin vitro under irradiation without Kn treatment lost pigments and ETA. Within 3 h of irradiation, both whole chain (H2O to methylviologen) electron transport as well as photosystem (PS) 2 activity were completely lost. However, in the chloroplasts
treated with Kn, the loss of pigments was slow and even after 4 h of irradiation the chloroplasts retained 15 % of PS 2 and
9 % of whole chain ETA. In the untreated chloroplasts, the loss of Zx after 4 h of irradiation was 49 % whereas in Kn treated
samples its level was 1.3 times higher than that of control. Since a higher level of Zx was maintained in Kn treated chloroplasts,
photoprotective action of Kn is possibly mediated through Zx.
One of us (NKC) thanks Sambalpur University for study leave and Department of Biological Sciences, Mankato State University,
Mankato for labortory facilities. 相似文献
13.
Summary Semi-pilot scale production of citric acid was investigated with a gamma-ray induced mutant (HB3) of Aspergillus niger using 500, 1000 and 1500 ml medium in 51 fermentation jars. Yield of citric acid was found to be seven-fold higher compared to the parent in 1000 ml medium and the corresponding increase was two-fold in the 500 ml medium. With 1500 ml/fermentation jar the yield was low with both the parent and the mutant strain though the mutant gave higher yield compared to the parent. 相似文献
14.
15.
From the unripe fruits of Sapium indicum, three aliphatic esters of the tigliane nucleus were isolated. These compounds were derivatives of 4-deoxyphorbol. Sapatoxin A was identified as 12-O-[n-deca-2,4,6-trienoyl]-4-deoxyphorbol-13-acetate, B as 12-O-[n-deca-2,4,6-trienoyl]-4-deoxy-5-hydroxyphorbol-13-acetate and C as 12-O-[n-deca-2,4,6-trienoyl]-4,20-dideoxy-5-hydroxyphorbol-13-acetate, by spectroscopic analysis and hydrolysis reactions. 相似文献
16.
G G Choudhury V L Sylvia A Y Sakaguchi 《The Journal of biological chemistry》1991,266(34):23147-23151
Receptor tyrosine kinases couple to multiple intracellular effector molecules that are crucial for normal cell growth and transformation. Stimulation of membrane phospholipid hydrolysis by receptor tyrosine kinases is one such pathway for generating intracellular second messengers that may be important for mitogenesis. Certain receptor tyrosine kinases tyrosine phosphorylate a phosphoinositide-specific phospholipase C that hydrolyses the membrane phospholipid phosphatidylinositol 4,5-bisphosphate. In contrast, the glycoprotein receptor for colony stimulating factor 1, a transmembrane tyrosine kinase, does not utilize this pathway, but rather stimulates the hydrolysis of phosphatidylcholine. Here we show that eluates of antiphosphotyrosine affinity purified lysates of colony-stimulating factor 1-stimulated cells contain elevated levels of phosphatidylcholine-specific phospholipase C activity. The affinity-purified activity is sensitive to tyrosine-specific T-cell phosphatase, and is detected in the membrane fraction of stimulated cells. Recovery of phospholipase C activity in the antiphosphotyrosine protein fraction is reduced by pertussis toxin pretreatment of cells. The phosphatidylcholine phospholipase C activity in isolated membranes of colony-stimulating factor 1-treated cells was also reduced by pertussis toxin treatment and stimulated by guanosine 5'-3-O-(thio)triphosphate. These results indicate that colony stimulating factor 1 receptor-mediated stimulation of phosphatidylcholine-specific phospholipase C requires tyrosine phosphorylation, and might be affected by a G-protein coupled pathway. 相似文献
17.
N.A. Chowdhury M. Moniruzzaman N. Nahar N. Choudhury 《World journal of microbiology & biotechnology》1991,7(6):603-606
A locally isolated strain of Micromonospora sp. when grown on different natural cellulosic substrates gave the highest activity of carboxymethylcellulase (34 U/ml) and Avicelase (0.9 U/ml) on rice straw. Sugar cane bagasse was also a good substrate for growth and cellulase production. With commercial cellulosic substrates, highest carboxymethylcellulase (90 U/ml) and Avicelase (2.8 U/ml) activities were when the organism grew on xylan. Saccharification of sugar cane bagasse and rice straw by enzyme preparations of the organism grown on the respective substrates released 5.6 and 5.8 mg reducing sugar/ml. With all enzyme preparations, bagasse was more easily saccharified than rice straw.The authors are with the Atomic Energy Research Establishment, GPO Box 3787, Dhaka 1000, Bangladesh; N.A. Chowdhury, M. Moniruzzaman, and N. Choudhury in the Institute of Food and Radiation Biology, and N. Nahar in the Institute of Nuclear Science and Technology. 相似文献
18.
Post-transfusion malaria in thalassaemia patients 总被引:1,自引:0,他引:1
A total of 125 beta-thalassaemia patients receiving repeated blood transfusions were screened by Giemsa stain, Acridine-orange stain and antigen detection for evidence of malaria infection on each visit. A total of 8 (6.4%) of the patients developed post-transfusion malaria (PMT) as confirmed by tracing the infected blood donors. A high incidence of PTM in thalassaemia patients appears to be due to the use of fresh blood and the high frequency of blood transfusions required by these patients. Antigen detection using monoclonal antibody was found to be more sensitive for diagnosis of PTM and for screening suspected donors than the conventional blood smear examination methods and is therefore recommended for routine blood donor screening to rule out malaria infection. 相似文献
19.
Despite convincing physiological evidences for vasopressin (VP) autoregulation in the supraoptic (SON) and paraventricular (PVN) nuclei, the morphological demonstration of VP synapses has lagged behind. The present work investigates the possible existence of such synapses in the SON and PVN of the rat. Electron microscopy of sections immunostained with VP antibody (1:5,000) and conjugated with avidin-biotin demonstrated presynaptic terminals containing neurosecretory granule (NSG)-like bodies, 80-100 nm in diameter. The terminals formed axodendritic, axosomatic and axoaxonic synapses, though the postsynaptic elements remained largely unidentified. Other ultrastructural features of synaptic specialization were evident. The NSG-like bodies exhibited a varying and dynamic relationship to the presynaptic membrane, suggesting their involvement in synaptic mechanisms. 相似文献
20.
A. M. Choudhury K. Y. Chu G. W. Kenner S. Moore K. L. Ramachandran R. Ramage 《Bioorganic chemistry》1979,8(4):471-483
The synthesis of fragments corresponding to the N-terminal region of porcine big gastrin is described. Radioimmunoassay using synthetic peptides supports the revised structure for the hormone. 相似文献