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11.
Erythrocyte membranes and their liposomes were prepared from clinically normal dogs and Labrador retrievers with hereditary muscular dystrophy. The static and dynamic components of fluidity of each membrane were then assessed by steady-state fluorescence polarization techniques using limiting hindered fluorescence anisotropy and order parameter values of 1,6-diphenyl-1,3,5-hexatriene (DPH) and fluorescence anisotropy values ofdl-2-(9-anthroyl)-stearic acid anddl-12-(9-anthroyl)-stearic acid, respectively. Membrane lipids were extracted and analyzed by thin-layer chromatography and gas chromatography. The results of these studies demonstrated that the lipid fluidity of erythrocyte membranes, and their liposomes, prepared from dystrophic dogs were found to possess significantly lower static and dynamic components of fluidity than control counterparts. Analysis of the composition of membranes from dystrophic dogs revealed a higher ratio of saturated fatty acyl chain/unsaturated chains (w/w) and lower double-bond index. Alterations in the fatty acid composition such as decrease in levels of linoleic (18:2) and arachidonic (20:4) acids and increase in palmitic (16:0) and stearic (18:0) acids were also observed in the membranes of dystrophic animals. These associated fatty acyl alterations could explain, at least in part, the differences in membrane fluidity between dystrophic and control dogs.  相似文献   
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Summary In order to study the Mn nutrition ofbidi tobacco plant (Nicotiana tabacum L. aromatic strain 2-1) when it is supplied with nutrient solutions containing different ratios of Mn with Fe, P, K and Ca, a sand-culture experiment was carried out in four different series viz. Fe-Mn, K-Mn, P-Mn and Ca-Mn. No characteristic deficiency symptoms except general loss of green colour and diminished growth were observed at 0.1 ppm Mn in the nutrient solution. Toxicity was observed when Mn in the nutrient solution was 100 ppm and severity of the symptoms decreased with increase in Fe-Mn or K-Mn ratios, but it increased when P-Mn ratio increased while in Ca-Mn series it first decreased and then increased at still higher concentration of Ca on account of chloride ion effect as CaCl2 had to be added to bring about 500 ppm concentration of Ca necessary for the treatment. No symptoms of deficiency or toxicity were observed when Mn in nutrient solution varied from 1 to 10 ppm and Fe-Mn ratio for the leaf varied from 0.4 to 6.1 and its Mn content varied from 190 to 1575 ppm. Slight loss of green colour and plant vigour appeared when Fe-Mn ratio for the leaf was higher than 12.8 even though the Mn content was as high as 90 ppm. Toxic effect due to excessive Mn was felt when Fe-Mn ratio was 0.35 or less and leaf content 1875 ppm or more. Nicotine content was inversely related to the intensity of Mn-toxicity.Contribution from the Agricultural Chemistry and Soil Science Division, Institute of Agriculture, Anand, G.S., India.Prof. and Head of the Agricultural Chemistry and Soil Science Division, and Lecturer in Agricultural Chemistry, respectively.  相似文献   
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The relationships between structure and inhibitory potency toward microsomal cytochrome P-450 (P-450)-mediated androst-4-ene-3,17-dione hydroxylase activities were investigated in rat liver with a series of 5 alpha- and 5 beta-androstane derivatives. 5 beta-Reduced steroids (containing a cis-A/B ring junction) were more potent inhibitors than the 5 alpha-reduced epimers (containing a trans-A/B ring junction) except in the case of the 17 beta-hydroxy-substituted derivatives. The most effective inhibitor was 5 beta-androstane-3 beta-ol which exhibited I50 values of 7 and 27 microM against androstenedione 16 alpha- and 6 beta-hydroxylase activities, which are catalysed by P-450 IIC11 and IIIA2, respectively. In general, these two pathways of steroid hydroxylation were more susceptible to inhibition than the 7 alpha- and 16 beta-hydroxylase pathways. The 7 alpha-hydroxylase enzyme (P-450 IIA1) was only inhibited by 5 beta-reduced steroids that contained an oxygenated function at C17. All of the test compounds elicited type I spectral binding interactions with P-450 in oxidised microsomes. The most effective steroid inhibitors generally exhibited the greatest capacity to interact with P-450. Additional studies with one of the more potent compounds, 5 beta-androstane-3 beta-ol-17-one, revealed that the inhibition kinetics were competitive and that preincubation of the inhibitor with NADPH-supplemented microsomes prior to substrate (androstenedione) addition decreased the extent of inhibition observed. These findings are consistent with the assertion that the inhibition of hepatic steroid hydroxylases by 5 beta-androstanes involves an effective competitive interaction with the steroid substrate at the P-450 active site. Since the relative overproduction of 5 beta-reduced metabolites of certain androgens has been reported in clinical conditions, such as androgen insensitivity, it now appears important to investigate the hepatic drug oxidation capacity of patients with hormonal abnormalities.  相似文献   
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Retinoic acid (a possible morphogen), its biological precursor retinol, and certain synthetic derivatives of retinol profoundly change junctional intercellular communication and growth (saturation density) in 10T 1/2 and 3T3 cells and in their transformed counterparts. The changes correlate: growth decreases as the steady-state junctional permeability rises, and growth increases as that permeability falls. Retinoic acid and retinol exert quite different steady-state actions on communication at noncytotoxic concentrations in the normal cells: retinoic acid inhibits communication at 10(-10)-10(-9) M and enhances at 10(-9)-10(-7) M, whereas retinol only enhances (10(-8)-10(-6) M). In v-mos-transformed cells the enhancement is altogether lacking. But regardless of the retinoid or cell type, all growth responses show essentially the same dependence on junctional permeability. This is the expected behavior if the cell-to-cell channels of gap junctions disseminate growth-regulating signals through cell populations.  相似文献   
17.
Evaluation of three portable samplers for monitoring airborne fungi   总被引:3,自引:0,他引:3  
Airborne fungi were monitored at five sample sites with the Burkard portable, the RCS Plus, and the SAS Super 90 air samplers; the Andersen 2-stage impactor was used for comparison. All samplers were calibrated before being used simultaneously to collect 100-liter samples at each site. The Andersen and Burkard samplers retrieved equivalent volumes of airborne fungi; the SAS Super 90 and RCS Plus measurements did not differ from each other but were significantly lower than those obtained with the Andersen or Burkard samplers. Total fungal counts correlated linearly with Cladosporium and Penicillium counts. Alternaria species, although present at all sites, did not correlate with total count or with amounts of any other fungal genera. Sampler and location significantly influenced fungal counts, but no interactions between samplers and locations were found.  相似文献   
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A gene responsible for the degradation of ß-N-Oxalyl diaminopropionic acid (ODAP) was fused to the maIE gene, which codes for maltose binding protein, by cloning into an expression vector pMAL c2. The gene has been expressed as fusion protein of mol wt approximately 62 kD. It has been purified by affinity chromatography. The fusion protein has been cleaved by an endoprotease factor Xa and the presence of maltose binding protein and the product of the cloned gene confirmed. SDS-PAGE has shown that the product of the ODAP degrading gene is a single polypeptide of mol wt of about 20.7 kD.  相似文献   
19.
We have employed a genetic approach to study the resistance of tomato to the phytopathogenic bacterium Pseudomonas syringae pv tomato. Resistance to P. s. tomato depends upon expression of the Pto locus in tomato, which encodes a protein with similarity to serine/threonine protein kinases and recognizes pathogen strains expressing the avirulence gene avrPto. Eleven tomato mutants were isolated with altered resistance to P. s. tomato strains expressing avrPto. We identified mutations both in the Pto resistance locus and in a new locus designated Prf (for Pseudomonas resistance and fenthion sensitivity). The genetic approach allowed us to dissect the roles of these loci in signal transduction in response to pathogen attack. Lines carrying mutations in the Pto locus vary 200-fold in the degree to which they are susceptible to P. s. tomato strains expressing avrPto. The pto mutants retain sensitivity to the organophosphate insecticide fenthion; this trait segregates with Pto in genetic crosses. This result suggested that contrary to previous hypotheses, the Pto locus controls pathogen recognition but not fenthion sensitivity. Interestingly, mutations in the prf locus result in both complete susceptibility to P. s. tomato and insensitivity to fenthion, suggesting that Prf plays a role in tomato signaling in response to both pathogen elicitors and fenthion. Because pto and prf mutations do not alter recognition of Xanthomonas campestris strains expressing avrBsP, an avirulence gene recognized by all tested tomato cultivars, Prf does not play a general role in disease resistance but possibly functions specifically in resistance against P. s. tomato. Genetic analysis of F2 populations from crosses of pto and prf homozygotes indicated that the Pto and Prf loci are tightly linked.  相似文献   
20.
The formation of intracellular amorphous calcium carbonates (iACC) has been recently observed in a few cultured strains of Microcystis, a potentially toxic bloom-forming cyanobacterium found worldwide in freshwater ecosystems. If iACC-forming Microcystis are abundant within blooms, they may represent a significant amount of particulate Ca. Here, we investigate the significance of iACC biomineralization by Microcystis. First, the presence of iACC-forming Microcystis cells has been detected in several eutrophic lakes, indicating that this phenomenon occurs under environmental conditions. Second, some genotypic (presence/absence of ccyA, a marker gene of iACC biomineralization) and phenotypic (presence/absence of iACC) diversity have been detected within a collection of strains isolated from one single lake. This illustrates that this trait is frequent but also variable within Microcystis even at a single locality. Finally, one-third of publicly available genomes of Microcystis were shown to contain the ccyA gene, revealing a wide geographic and phylogenetic distribution within the genus. Overall, the present work shows that the formation of iACC by Microcystis is common under environmental conditions. While its biological function remains undetermined, this process should be further considered regarding the biology of Microcystis and implications on the Ca geochemical cycle in freshwater environments.  相似文献   
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