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21.
The algal and cyanobacterial flora and the chemical environment of six freshwater streams of Schirmacher Oasis, Antarctica were investigated. Over 30 species of algae, predominantly cyanobacteria (Cyanophyceae), were recorded. N2-fixing species, both heterocystous and unicellular diazotrophs, contributed more than 50% to the counts and their dominance was greatest in the middle of the stream where nitrogen and other nutrients were low. Green algae and diatoms also contributed to the flora. The species composition varied between streams. Glacial and snow drift meltwater streams contained a distinctive community. Based on diversity indices, these streams could be classified into two clusters. 相似文献
22.
Evidence for intracellular formation of angiotensins: coexistence of renin and angiotensin-converting enzyme in Leydig cells of rat testis 总被引:7,自引:0,他引:7
K N Pandey K S Misono T Inagami 《Biochemical and biophysical research communications》1984,122(3):1337-1343
Leydig cells were purified from rat testes by discontinuous metrizamide density gradient and were shown to contain renin (EC 3.4.99.1), angiotensin-converting enzyme (dipeptidyl carboxypeptidase, (EC 3.4.15.1), and the peptide hormone angiotensins I, II and III as determined by the combined HPLC and radioimmunoassay. In germinal cells only angiotensin II (AII) was found at a significant level. These findings provide evidence for intracellular formation of AII in testicular cells and demonstrate that an intracellular renin-angiotensin system exists in normal non-transformed cells. 相似文献
23.
A NaCl-tolerant callus line of Cicer arietinum has been isolated, as a spontaneous variant, on agar-solidified MS-medium supplemented with 100 mM NaCl. The growth of this line, in the presence of 100 mM NaCl, was comparable to that of the NaCl-sensitive callus line growing in the absence of NaCl. Regarding relative tolerance of the two callus lines towards NaCl (0 to 200 mM), the tolerant line performed poorly in the absence of NaCl and exhibited optimal growth at 50 mM NaCl. The tolerance persisted even after three passages of 4-wk each, tested so far, away from the selective agent. 相似文献
24.
25.
Pandey K. K. 《TAG. Theoretical and applied genetics. Theoretische und angewandte Genetik》1977,50(2):89-101
Summary The restriction of sexual pairing by a specificity gene is considered to be an ancient development in the plant kingdom. The diversity and general parallelism of incompatibility systems seen amongst the phyla at the present time can be rationalized in terms of the association of various derived forms of the ancestral specificity unit with differing spectra of accessory factors controlling sexual physiology in the different phyla. Sexual morphogenesis has become divided into distinct phases under the control of complementary genes. These phases are initiated by a regulatory system of Co-ordinator genes which control the order in which groups of morphogenetic genes are expressed during development. The entire sexual cycle will be completed only if all the complementary groups are activated in the appropriate sequence. The present article discusses essential features of the evolution of the breeding locus in different phyla. These features are consistent in themselves with the present data and are not dependent on the proposed ancient origin of the specificity gene.The above hypothesis throws light on the (1) evolution of the complex mating loci in flowering plants and fungi; (2) evolution of complementary incompatibility and heteromorphic incompatibility in flowering plants; (3) anomalous cross-compatibility behaviour of mutants in the fungus Schizophyllum commune; (4) nature of homothallism in higher fungi; (5) mode of origin of new functional self-incompatibility alleles; and (6) homogenic and heterogenic incompatibility. 相似文献
26.
Antiulcerogenic and anti-inflammatory effects of emodin, isolated from Rhamnus triquerta wall 总被引:3,自引:0,他引:3
Emodin, an anthraquinone derivative, isolated from the whole plant of R. triquerta, in 15 mg/kg dose (ip) exhibited anti-inflammatory activity against carrageenin-induced pedal inflammation in rats. In the same dosage it also showed antiulcer activity against 4 hr pylorus-ligated, aspirin and immobilization stress-induced gastric ulcers in rats. It decreased acid and pepsin output and augmented mucus secretion in terms of total carbohydrate: protein ratio in the gastric juice of aspirin treated pylorus-ligated rats, indicating that the antiulcerogenic effect of emodin may be due to its effect on gastric secretion. 相似文献
27.
Abstract. Four humid grassland communities at three different locations in Meghalaya, India were analysed during 1988 and 1989 for species and life-form composition, diversity and dominance in relation to altitude, soil and prevailing disturbances. Due to the adverse interactive influences of exceptionally high annual rainfall (> 10 000 mm), topography and human interference on soil fertility, the grassland at Cherrapunji, at 1300 m altitude, had a low species diversity (H'= 1.74) and was dominated by three perennial grass species. Similar grasslands, at both higher and lower altitudes on fertile soil and with lower rainfall (ca. 2000 mm), showed higher diversity values (H'= 2.28 at Burnihat and 2.31 at Upper Shillong). The proportion of perennial species and chamaephytes increased with elevation. At the high altitude site a grassland under short-term protection from fires and grazing had a higher species richness, density and basal cover than an unprotected grassland. All grasslands show a clear seasonality, albeit with different patterns, with a maximum in density and basal cover in August. The differences in structure and seasonality are discussed in terms of different levels of stress. 相似文献
28.
Abstract. Savanna vegetation and pertinent soil features were studied on 43 sites in a dry tropical forest region of India. Grazing intensity ranged from 0.68 to 0.98. Soil moisture was positively related to the proportion of fine soil particles (< 0.1 mm), and the latter decreased while the proportion of coarse particles (2.0-0.5 mm) increased with increasing grazing intensity. Canopy biomass ranged from 28 to 104 g/m2 in grazed communities and from 230 to 337 g /m2 in ungrazed communities and was positively related to vegetation cover which ranged between 30–72 % in grazed and 68 - 91 % in ungrazed communities. Vegetation cover was negatively related to grazing intensity. Species richness and diversity were highest at low grazing intensity. Using community coefficients and Detrended Correspondence Analysis, the grazed stands were clustered into six and the ungrazed ones into three communities. The grazed communities were recognised as degradation stages and the ungrazed ones as recovery stages. Only five grass species, in various combinations were able to dominate in one of the different stages. Evidently the harsh climatic conditions (high temperatures, high variability in rainfall and a long dry period) in the region permit only a few species already adapted to these conditions to participate in the succession. 相似文献
29.
P Srivastava S K Puri G P Dutta V C Pandey 《International journal for parasitology》1992,22(2):243-245
Plasmodium knowlesi (a simian malarial parasite) infection resulted in elevation of hepatic oxidative stress in monkeys. Further, the antioxidant defence system of the host was also noticeably affected. The infected monkeys showed a marked increase in the levels of superoxide (O2-), lipid peroxidation (LPO), glutathione (GSH) and xanthine oxidase (XO), and decreased levels of superoxide dismutase (SOD) and catalase. Oral administration of chloroquine (20 mg kg body wt-1 for 3 days) to infected monkeys caused recovery trends in oxidative stress and antioxidant defences to almost normal a week after cessation of drug treatment. 相似文献
30.
F M Salzano F L Black S M Callegari-Jacques S E Santos T A Weimer M A Mestriner R R Kubo J P Pandey M H Hutz 《American journal of physical anthropology》1991,85(1):51-60
Data on 31 genetic systems were obtained for 421 individuals belonging to the Arara, Araweté, Mundurucu, and Jamamadi tribes of northern Brazil. The Jamamadi depart farthest, and the Mundurucu least, from South American Indian averages. These data are analyzed together with those of 24 other Amazonian groups. Genetic distances and corresponding dendrograms indicate a cluster of 14 related tribes living north of the Amazon river. These genetic results show only a modest correlation with linguistic and geographic relationships among these groups. 相似文献