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排序方式: 共有433条查询结果,搜索用时 13 毫秒
1.
Murthy S. D. S.; Sabat Surendra Chandra; Mohanty Prasanna 《Plant & cell physiology》1989,30(8):1153-1157
Addition of low concentrations of mercury chloride (HgCl2 tointact cells of the cyanobacterium, Spirulina platensis causedan enhancement in the intensity of fluorescence emitted fromphycocyanin at room temperature and induced blue shifts in theemission peak suggestive of changes in energy transfer withinthe phycobilisomes. HgCl2 also suppressed the whole-chain electrontransport activity (H2O methylviologen) at much lower concentrationsthan that required to inhibit Hill activity supported by para-benzoquinone.The extent of inhibition of Hill activity was much higher underhigh-intensity light than that under low-intensity light. Ourresults indicate that mercury ions at low concentrations affectthe transfer of energy within phycobilisomes and at high concentrationsthey inhibit electron transport in this cyanobacterium. (Received February 21, 1989; Accepted October 2, 1989) 相似文献
2.
Urea metabolism in the cyanobacterium Anabaena cycadeae: regulation of urea uptake and urease by ammonia 总被引:1,自引:0,他引:1
Surendra Singh 《FEMS microbiology letters》1991,84(2):177-182
A total of 160 Escherichia coli positive for F165 fimbrial antigen and isolated from diarrheic and septicemic animals, were examined for the presence of the pap, afa, and sfa/foc operons or related nucleotide sequences using colony hybridization. Most isolates shared DNA sequences with the pap operon sequences alone or in association with afa or sfa. Thus, our results indicate that F165-positive E. coli from diseased animals share DNA sequences with operons coding for adhesins important in human extra-intestinal disease and that multiple adhesin systems are often found in single isolates. However, 20% of the F165-positive isolates did not show any homology with the probes representing the three adhesin systems, suggesting that one of the operons responsible for F165 production could be different from the pap, sfa/foc, and afa operons. 相似文献
3.
The role of intracellular glutamine concentration in the regulation of14C-glutamine uptake was studied in a diazotrophic cyanobacteriumAnabaena 7120. The uptake pattern was found to be biphasic, consisting of a rapid first phase lasting up to 60 s followed by a slower second phase. Azaserine, which could not inhibit in vitro and in vivo glutamine synthetase (GS) activity effectively, inhibited the14C-glutamine uptake. Glutamine uptake was also not significantly affected when glutamate, methylglutamate, aspartate, arginine, lysine, hydroxylysine, ornithine, and GS inhibitor,L-methionine-DL-sulfoximine (MSX) were simultaneously available during uptake assay, suggesting that glutamine uptake takes place via a general amino acid permease which does not, however, transport basic and acidic amino acids. The azaserine-treated cells had increased and decreased levels of glutamine and glutamate, respectively, suggesting that the increased intracellular glutamine level is responsible for the inhibition of14C-glutamine uptake and provides evidence here for the role of an intracellular glutamine pool in the regulation of14C-glutamine uptake inAnabaena 7120. 相似文献
4.
Mei-Ling Siu-Caldera Jeffrey W. Clark Anabela Santos-Moore Sara Peleg Yan Yun Liu Milan R. Uskokovi Surendra Sharma G. Satyanarayana Reddy 《The Journal of steroid biochemistry and molecular biology》1996,59(5-6)
1α,25(OH)2-16-ene-D3, a synthetic analog of the steroid hormone, 1α,25(OH)2D3, has great potential to become a drug in the treatment of leukemia and other proliferative disorders, because of its minimal in vivo calcemic activity associated with a potent inhibitory effect on cell growth. However, at present, the mechanisms through which 1α,25(OH)2-16-ene-D3 expresses its biological activities are still not completely understood. Our previous in vitro study in a perfused rat kidney indicated for the first time that 1α,25(OH)2-16-ene-D3 and 1α,25(OH)2D3 are metabolized differently. 1α,25(OH)2-24-oxo-16-ene-D3, an intermediary metabolite of 1α,25(OH)2-16-ene-D3 formed through the C-24 oxidation pathway, accumulated significantly in the perfusate when compared to 1α,25(OH)2-24-oxo-D3, the corresponding intermediary metabolite of 1α,25(OH)2D3. In a subsequent in vivo study, we also reported that 1α,25(OH)2-24-oxo-16-ene-D3 exerted immunosuppressive activity equal to its parent, without causing significant hypercalcemia. In order to establish further the critical role of 1α,25(OH)2-24-oxo-16-ene-D3, in generating some of the key biological activities ascribed to its parent, we performed the present in vitro study using a human myeloid leukemic cell line (RWLeu-4) as a model. Comparative target tissue metabolism studies indicated that 1α,25(OH)2-16-ene-D3 and 1α,25(OH)2D3 are metabolized differently in RWLeu-4 cells, and the differences were similar to the ones we previously observed in the rat kidney. The significant finding was the accumulation of 1α,25(OH)2-24-oxo-16-ene-D3 in RWLeu-4 cells because of its resistance to further metabolism. Biological activity studies indicated that both 1α,25(OH)2-16-ene-D3 and its 24-oxo metabolite produced growth inhibition and promoted differentiation of RWLeu-4 cells to the same extent, and these activities were several fold higher than those exerted by 1α,25(OH)2D3. In addition, the genomic action of each vitamin D compound was assessed in a rat osteosarcoma cell line (ROS 17/2.8) by measuring its ability to transactivate a gene construct containing the vitamin D response element of the osteocalcin gene linked to the growth hormone reporter gene. In these studies, both 1α,25(OH)2-16-ene-D3 and its 24-oxo metabolite exerted similar but potent transactivation activity which was several fold greater than that exerted by 1α,25(OH)2D3 itself. In summary, our results indicate that the production and slow clearance of the bioactive intermediary metabolite, 1α,25(OH)2-24-oxo-16-ene-D3, in RWLeu-4 cells contributes significantly to the final expression of the enhanced biological activities ascribed to its parent analog, 1α,25(OH)2-16-ene-D3. 相似文献
5.
Determination of anteroposterior and dorsoventral axes is an important early event in the development of vertebrates involving
extensive cellular interactions including inductive events. Recently we showed that insulin plays an essential role in prepancreatic
development of the frogMicrohyla ornata. In the present study we have investigated the effects of immunoneutralization of endogenous insulin on the process of pattern
formation. Treatment of neurulating embryos with antiserum to insulin caused abnormal pattern formation. The defects included
loss of normal architecture of the neural tube, reduction in the size of the neural tube and, most conspicuously, rotation
of the dorsoventral axis of the neural tube, notochord and adjoining mesodermal elements. The effects could be alleviated
partially by pretreatment of embryos with exogenous insulin. This supports our belief that insulin plays an important role
in induction and pattern formation of the amphibian nervous system.
In addition, using 2-deoxy-α-D-glucose, an inhibitor of glucose metabolism, it is shown that the stimulatory effects of exogenous
insulin on developing frog embryos are, at least partially, through the glucose metabolism pathway.
Preliminary results of this study were presented at the National Symposium on Genes and Human Environment, held at Hyderabad,
February 1994 and DAE Symposium on Stress and Adaptive Responses in Biological Systems, held at Vadodara, March 1994. 相似文献
6.
To study the effects of varying mineral content and various trace elements in bone composities on its electrical behavior and possible use in design of transducers, various physical, dielectric, piezoelectric, and electromechanical parameters have been measured. For electrical characterization of various such composites in the high-frequency region (1–108 MHz), variation of impedance (Z), phase angle (tan ), and relative output voltage with frequency has been examined. Furtherfore, the Curie temperature has been determined and the temperature variation of capacitance and loss factor (tan ) studied (24–225°C). Two types of bone composites were prepared and studied. First, powdered collagen and apatite obtained from full bone were mixed intimately in various proportions by weight to prepare eleven bone compositions. Second, such bone materials were made to contain 5–10% various doping foreign additives (A1Br3, Na2CO3, SrCO3, LiCO3, Sb2O3, ZnO, Nb2O5, piezoelectric ceramic (PZT), and Pb(NO3)2. It has been observed that a bone composition of 50% collagen + 50% apatite has possible piezoelectric application and other compositions [85% collagen + 15% apatite, 90% collagen + 10% ZnO, and 90% bone + 10% Ba(OH)2] have a sharp rise in capacitance near the Curie temperature. The Curie temperature is generally shifted towards higher values by additives. It is expected that such results will be relevant in characterizing bone behavior. 相似文献
7.
8.
Ravindra N. Kharwar Surendra K. Gond Anuj Kumar Ashish Mishra 《World journal of microbiology & biotechnology》2010,26(11):1941-1948
Eucalyptus citriodora Hook, is frequently cultivated tree in India for its wood and medicinal usages. The endophytic and epiphytic fungi were estimated
from healthy leaves of E. citriodora growing in the premise of Banaras Hindu University, Varanasi, India. A total of 33 fungal species were isolated from leaf
segments. Of 33 taxa, 20 were recorded as endophytes, while 22 as epiphytes. Nine, out of 33 species were found to be common
in leaf tissues and surfaces (Alternaria alternata, Aspergillus fumigatus, A. terreus, Cladosporium cladosporioides, Drechslera rostrata, Humicola grisea, Nigrospora oryzae, Penicillium
cristata, and Pestalotia sp.). Out of 478 fungal isolates, 279 were epiphytic while only 199 were endophytic. Most isolates were anamorphic filamentous
fungi which often don’t produce sexual spores. The Sorensen’s index of similarity between endophytes and epiphytes (leaf surface
colonizers) was found to be at 0.300. Diversity index of fungal species was higher in endophytes than epiphytes. The frequency
of colonization differs greatly in both myco-populations. Cladosporium cladosporioides (26%) was dominant species on leaf surfaces while Botrytis cinerea (10.5%) was dominant in leaf tissues. Out of 16 endophytic isolates evaluated for antagonistic test, 8 (50%) gave the antagonistic
activity against variety of fungi representing pathogens to both humans and plants. 相似文献
9.
Surendra K. Gond Ashish Mishra Vijay K. Sharma Satish K. Verma Jitendra Kumar Ravindra N. Kharwar Anuj Kumar 《Mycoscience》2012,53(2):113-121
Endophytic fungi from Nyctanthes arbor-tristis were isolated and evaluated for their antimicrobial activity. A total of 19 endophytic fungi were isolated from 400 segments
of healthy leaf and stem tissues of N. arbor-tristis. Eighteen endophytic fungi were obtained from leaf, while only ten from stem. Alternaria alternata had the highest colonization frequency (15.0%) in leaf, whereas Cladosporium cladosporioides ranked first in stem with a colonization frequency of 12%. The diversity and species richness were found higher in leaf tissues
than in stem. The similarity indices between leaf and stem were 0.473 for Jaccard’s and 0.642 for the Sorenson index, respectively.
Of 16, 12 (75%) endophytic fungal extracts showed antibacterial activity against either one or more pathogenic bacteria. The
endophytic Nigrospora oryzae showed maximum inhibition against Shigella sp. and Pseudomonas aeruginosa. The leaf endophytes Colletotrichum dematium and Chaetomium globosum exhibited a broad range of anibacterial activity and were active against Shigella flexnii, Shigella boydii, Salmonella enteritidis, Salmonella paratyphi, and P. aeruginosa. Nine out of 16 (56.25%) endophytic fungi exhibited antifungal activity to one or more fungal pathogens. Colletotrichum dematium inhibited 55.87% of the radial growth of the phytopathogen Curvularia lunata. The antimicrobial activity of these endophytic microorganisms could be exploited in the biotechnological, medicinal, and
agricultural industries. 相似文献
10.
Kulsoom Zahra Sandeep Patel Tulika Dey Uma Pandey Surendra Pratap Mishra 《Biochemistry and Biophysics Reports》2021
Cervical cancer is the second most common cause of cancer-related death among women worldwide, especially in developing countries. Oxidative stress has been associated with cervical cancer. Many studies demonstrated that the low level of antioxidants induces the production of free radicals that cause lipid peroxidation, DNA, and protein damage leading to mutations that favors malignant transformation. This is a case-control institutional study conducted to evaluate the level of oxidative stress in cervical cancer patients and the age-matched healthy controls. We measured level of TBARS expressed as MDA, activity of SOD and GSH level by the spectrophotometric method, and level of 8-OHdG was estimated using a competitive sandwich ELISA assay. Our results showed a significant increase in the level of lipid peroxidation in group IV when compared to the control, group II and group III (p < 0.001). The activity of SOD was also significantly higher in group IV when compared to the control group (p < 0.001), group II (p < 0.001), and group III (p < 0.001). The level of GSH was also significantly lower in group IV when compared to the control group (p < 0.01), group II (p < 0.01), and group III (p < 0.01). The level of 8-OHdG was significantly higher in group IV than in the other groups (p < 0.01). The results suggest that oxidative stress is involved in the pathogenesis of cervical cancer, which is demonstrated by an increased level of lipid peroxidation and higher levels of 8-OHdG and an altered antioxidant defense system. 相似文献