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51.
Bioaccumulation of nickel and vanadium in the tissues of the liver, kidney, gill, and intestine has been studied following 4 days and 30 days of exposure at sublethal concentrations of nickel and vanadium compounds in the catfish Clarias batrachus. Nickel and vanadium have been found to accumulate in all four tissues observed. High concentrations of nickel and vanadium have been found in the order kidney greater than gill greater than liver greater than intestine during the 4 days and 30 days treatment. A dose-response effect was seen, as the concentration of metals in the tissues increased with concentration and exposure time. The effect on bioaccumulation in the specific tissue provides a better basis for monitoring exposures than whole-body analysis. 相似文献
52.
S. K. Soni I. K. Sandhu K. S. Bath U. C. Banerjee P. R. Patnaik 《Folia microbiologica》1996,41(3):243-248
A strain of starch-assimilating yeast,Saccharomycopsis capsularis, isolated from Indian cereal-based fermented foods, produced significant levels of extracellular α-amylase and glucoamylase.
The enzymes reached their peak activities during the stationary phase at the end of the 5th and 4th day of cultivation, respectively.
The amylase yields were maximized by a proper choice of carbon and nitrogen sources, starting pH of the culture medium and
growth temperature. High activities of the enzymes were obtained through inexpensive agricultural commodities, such as wheat
bran and corn meal as carbon sources, and defatted soybean meal and peanut meal as nitrogen sources. A temperature of 28–32°C
and an initial pH of 4.5–5.0 were optimum. The crude amylase mixture could liquefy and saccharify a 1% starch solution completely
in 24 h at 50°C. 相似文献
53.
54.
Kanika Misra Arun B. Banerjee Subhankar Ray Manju Ray 《Molecular and cellular biochemistry》1996,156(2):117-124
Two enzymes, one NADPH-dependent and another NADH-dependent which catalyze the reduction of methylglyoxal to acetol have been isolated and substantially purified from crude extracts of Escherichia coli K12 cells. Substrate specificity and formation of acetol as the reaction product by both the enzymes, reversibility of NADH-dependent enzyme with alcohols as substrates and inhibitor study with NADPH-dependent enzyme indicate that NADPH-dependent and NADH-dependent enzymes are identical with an aldehyde reductase (EC 1.1.1.2) and alcohol dehydrogenase (EC 1.1.1.1) respectively. The Km for methylglyoxal have been determined to be 0.77 mM for NADPH-dependent and 3.8 mM for NADH-dependent enzyme. Stoichiometrically equimolar amount of acetol is formed from methylglyoxal by both NADPH- and NADH-dependent enzymes. In phosphate buffer, both the enzymes are active in the pH range of 5.8–6.6 with no sharp pH optimum. Molecular weight of both the enzymes were found to be 100,000 ± 3,000 by gel filtration on a Sephacryl S-200 column. Both NADPH- and NADH-dependent enzymes are sensitive to sulfhydryl group reagents. 相似文献
55.
Dr P. P. Srivastava A. K. Bansal R. M. Shukla N. D. Banerjee N. N. Saxena S. S. Sinha 《Mycopathologia》1994,128(2):81-84
The major cuticular components of Indian tasar silkworm,Antheraea mylitta Drury, were sequentially extracted and estimated to ascertain preferential utilization of these components for growth by the entomopathogenic fungusPenicillium citrinum Thom. Proteins which constituted 61.64% dry weight of cuticule were found to play a key role in the growth ofP. citrinum whereas lipids (7.15%) and chitin (30.02%) were least involved. Also, this study suggests absence of any mycocidal substance in the cuticle ofA. mylitta. 相似文献
56.
The 2,053-bp broad-host-range incompatibility group N replicon of plasmid pCU1 has two components: a region of 1,200 bp that is sufficient for its replication in Escherichia coli PolA+ and PolA- hosts and a regulatory region called the group I iteron region that contains 13 39-bp iterons. Within the 1,200-bp region, there are three replication origins, two of which, called oriB and oriS, function in PolA+ and PolA- hosts and a third, called oriV, which functions only in PolA+ hosts. The region also specifies a protein called RepA. We now show that both oriB and oriS can function in a delta polA strain but that in such a strain, only oriB has an absolute requirement for RepA. oriS can function without RepA and polymerase I provided that the iteron region is deleted and that in this circumstance, it is the only origin, the usage of which is detected. The requirements for oriB usage can thus be distinguished from those for oriS usage. The oriB region can be recovered as a plasmid only if RepA is provided in trans. These complex features of this replicon are also shown to be shared by the IncN replicons of other antibiotic resistance plasmids. Functionally distinguishable origins in a small replicon may be a way of endowing such a replicon with a broad host range. 相似文献
57.
The frequency and accuracy of replication past a thymine-thymine cyclobutane dimer are very different in Saccharomyces cerevisiae and Escherichia coli. 总被引:5,自引:0,他引:5 下载免费PDF全文
We have compared the mutagenic properties of a T-T cyclobutane dimer in baker's yeast, Saccharomyces cerevisiae, with those in Escherichia coli by transforming each of these species with the same single-stranded shuttle vector carrying either the cis-syn or the trans-syn isomer of this UV photoproduct at a unique site. The mutagenic properties investigated were the frequency of replicational bypass of the photoproduct, the error rate of bypass, and the mutation spectrum. In SOS-induced E. coli, the cis-syn dimer was bypassed in approximately 16% of the vector molecules, and 7.6% of the bypass products had targeted mutations. In S. cerevisiae, however, bypass occurred in about 80% of these molecules, and the bypass was at least 19-fold more accurate (approximately 0.4% targeted mutations). Each of these yeast mutations was a single unique event, and none were like those in E. coli, suggesting that in fact the difference in error rate is much greater. Bypass of the trans-syn dimer occurred in about 17% of the vector molecules in both species, but with this isomer the error rate was higher in S. cerevisiae (21 to 36% targeted mutations) than in E. coli (13%). However, the spectra of mutations induced by the latter photoproduct were virtually identical in the two organisms. We conclude that bypass and error frequencies are determined both by the structure of the photoproduct-containing template and by the particular replication proteins concerned but that the types of mutations induced depend predominantly on the structure of the template. Unlike E. coli, bypass in S. cerevisiae did not require UV-induced functions. 相似文献
58.
Ibuprofen, a unique anti-inflammatory compound with antifungal activity against dermatophytes 总被引:2,自引:2,他引:0
Ibuprofen showed significant antifungal activity in vitro against dermatophytes at pH 5 (MIC: 5–40 μg ml-1 ). In this respect it is comparatively more efficient than two well known and medically used antifungal compounds, benzoic and salicylic acids. This compound with anti-inflammatory activity which is not found in any other conventional antifungal organic acids, may have clinical prospects. 相似文献
59.
The optical density (450 nm) of samples of homogenized fungal biomass correlated linearly with the dry weight of the biomass in the samples. As shown for broths of the filamentous microfungus Neurospora sitophila, the sensitivity of the technique depended on the extent of fragmentation of fungal hyphae during homogenization: increased fragmentation increased sensitivity. The method applied during all phases of growth, was as accurate as the conventional dry weight technique and permitted rapid and simple measurement of biomass concentration. 相似文献
60.