Thirty-eight carbamates and thiocarbamates were evaluated for the production of delayed neurotoxicity in the mature White Leghorn hen. Several thiocarbamates including phenyl-N-ethylthiocarbamate and s-2,3-dichloroallyl diisopropylthiocarbamate (diallate) produced symptoms of severe delayed neurotoxicity following repeated oral administration. The results of these experiments do not preclude the possibility that neurotoxic carbamates and organophosphorous compounds may share a common site of action. 相似文献
There were 6 treatments in each of 2 series covering the range from 1–6 fruit trusses per plant. The terminal growing-points were removed 2 leaves above the last inflorescence of each treatment in the “limited-stem” series, and 2 leaves above inflorescence 6 with inflorescences removed as necessary in the “full-stem” series.The yield of trusses 2–5 in the “full-stem” and of truss 2 in the “limited-stem” series was reduced by the presence of subsequent trusses. Similar trends were apparent with trusses 3–5 of the “limited-stem” series. It was suggested that the reduction in yield was due to competition between trusses for assimilates resulting in smaller and/or fewer fruit per truss.Data is presented to suggest that the net assimilation rate in the tomato plant can be reduced due to lack of fruit load and that fruit yield can be limited simultaneously by lack of both source and sink strength. 相似文献
1. Male broilers (0 to 35 d) were given foods with two types of yellow sorghum substituted for maize in isonutrient diets. Sorghum-based foods were also supplemented with extra phosphorus, to provide a total P of about 8 g/kg; the P being from either orthophosphoric acid or food grade dicalcium phosphate. 2. Both sorghums depressed growth and food:gain ratio and increased the incidence of locomotor disorder to about 0.50 (maize control = 0). Sorghum from Sudan, with higher concentrations of both tannin and phytate, caused more severe anti-nutritive effects than sorghum from Egypt. 3. Within the limits of statistical significance the growth depressing effect of sorghum was completely reversed by extra P. With the more toxic Sudanese sorghum this amelioration was numerically less than complete (growth = 0.94, maize control = 1). Locomotor disorders were also virtually, but not completely, eliminated by phosphorus treatment. 4. Treatment of sorghum by dry-mixing with dicalcium phosphate could form the basis of a simple and economic method for extending the use of high-tannin sorghum in poultry foods. The mode of action of the treatment remains to be determined. 相似文献
A method for the determination of amino acid requirements of laying hens is described. This involves the dilution of a high protein “ summit” diet with an isocaloric nitrogen‐free mixture. By ensuring that the amino acid to be assayed is first‐limiting in the summit diet, the response to dilution can be interpreted as a response to a single amino acid.
The method is applied to the determination of methionine requirement and it is shown that the response to methionine obtained is virtually independent of the protein level of the diet and is not influenced by direct effects of the dilution mixture.
From the results of the present and other published experiments, the “ available “ methionine required for maximum egg yield of pullets in the early stages of lay is estimated to be 275 mg per bird per day. 相似文献
Clover is frequently grown in rotation with cereals in order to increase soil nitrogen. The systemic fungicide triadimefon, widely used against cereal pathogens, is readily taken up from soil by clover and degraded to a single major metabolite. Plant weight and symbiotic nitrogen fixation by Rhizobium trijolii are affected only by concentrations of triadimefon in soil that are much in excess of those likely to be encountered in practice. Triadimefon residues are thus unlikely to affect nitrogen fixation by clover under field conditions. 相似文献
Cytochrome b from yeast (Saccharomyces cerevisiae Meyer ex Hansen) provides a convenient model system for the study of Qo-site inhibitor (QoI) resistance mutations from a variety of organisms. QoI resistance mutations from fungal plant pathogens (G143A and F129L), malaria agent Plasmodium sp (Y279C/S), and Pneumocystis carinii (L275F), an opportunistic pathogenic fungus of man, were introduced into yeast cytochrome b and their effect on the binding of a variety of natural (myxothiazol and stigmatellin) and synthetic (atovaquone, azoxystrobin and pyraclostrobin) inhibitors to the bc1 complex monitored. L275S (from a myxothiazol-resistant yeast) was also re-examined. Stigmatellin binding was relatively unaffected by the introduction of these mutations. Significant increases in resistance were observed for the strobilurin-class inhibitors myxothiazol, azoxystrobin and pyraclostrobin, with the largest increase in resistance conferred by G143A. In contrast, atovaquone binding was most effected by Y279C/S and L275S. Notably, F129L, G143A and L275S had a minor effect on bc1 activity, and so are unlikely to confer significant fitness penalties in vivo. These data are discussed in the light of the atomic structures for myxothiazol- and azoxystrobin-inhibited bovine bc1 which have recently become available. We propose that QoI resistance due to G143A arises from steric hindrance between the inhibitor and cytochrome b, whereas the mechanism of resistance for the other mutations is due to an increase in binding energy between the protein and inhibitor molecule. Site-directed mutagenesis was also used to model selected regions of the mammalian Qo site in yeast cytochrome b in order to further understand the differential efficacy of these QoI in the mammalian and pathogen bc1 complexes. 相似文献
A model which describes the response of groups of laying hens to different levels of amino acid intake is presented. The model is based on the assumption of simple linear relationships between amino acid intake and the output characteristics, egg production and maintenance, for individual birds. The response for a group of birds is then derived as the average of the individual responses. The shape of this flock—response curve depends on seven parameters, namely the mean maximum egg output (ēmax), variation in Emax, mean body weight (W), variation in W, the correlation between egg output and body weight, and two constants (a and b) representing respectively the quantities of amino acid required for unit egg output and for maintenance of unit body weight.
Three methods of manipulating the model are described. These use (i) a computer simulation procedure; (ii) the exact solution for the model and (iii) some reasonable approximations for practical application.
The use of the model for describing experimental data and for predicting amino acid requirements is discussed, and the main limiting assumptions and some possible extensions of the principles involved are pointed out. 相似文献