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871.
The Role of Dissolved Organic Material in the Nutrition of Pelagic Larvae: Amino Acid Uptake by Bivalve Veligers 总被引:1,自引:1,他引:0
SYNOPSIS. Studies on the role of dissolved organic materialin the nutrition of marine invertebrates have largely been confinedto adults. However larval forms, with a higher surface areato volume ratio, have a greater weight specific capacity forabsorbing dissolved organic material than adults. Autoradiographic,biochemical, and kinetic experiments with bivalve larvae allindicate that amino acid uptake and translocation mechanismscan operate efficiently at naturally occurring substrate concentrations.The mechanisms operate throughout the life-span of the animal,from fertilized egg to adult. Experimental evidence is presentedto show that the kinetics of uptake by larvae allow them tocompete with bacteria for dissolved organic material in seawater. In larvae, supplementary sources of energy may be moreimportant than in adults since larvae are provided with minimalfood reserves by the parent and must pass through periods whenpaniculate feeding cannot occur. 相似文献
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Sixty male Friesian calves were weaned from milk at 5 weeks of age. From 3 to 11 weeks of age, the calves were offered a diet of barley, meat meal, urea and 15% oat straw, supplemented with sodium chloride (NaCl) or sodium bicarbonate (NaHCO3). The sodium (Na) contents of the diets supplemented with NaCl were 0.3, 1.1, 1.9 and 2.8%. The sodium contents of the diets supplemented with NaHCO3 were 1.1 and 1.9%.The performance of the calves fed on the diets containing 0.3, 1.1 and 1.9% Na from NaCl was similar, but the organic matter intake and weight gains of the calves fed on the diet containing 2.8% Na were significantly lower between 5 and 11 weeks of age. The feed intake of the calves fed on the diets containing 1.1 and 1.9% Na from NaHCO3 was 8 and 15% greater than the feed intake of the calves fed on the diet containing 0.3% Na. However, there was no significant difference in the intake of organic matter, the efficiency of feed conversion ratios or the weight gains of the calves.The sodium treatments resulted in no significant differences in the concentration of volatile fatty acids in the rumen. The addition of NaHCO3 to the diets altered in acid—base balance in jugular blood. 相似文献
874.
Morphological pathway of flagellar assembly in Salmonella typhimurium. 总被引:14,自引:0,他引:14
The process of flagellar assembly was investigated in Salmonella typhimurium. Seven types of flagellar precursors produced by various flagellar mutants were purified by CsCl density gradient protocol. They were characterized morphologically by electron microscopy, and biochemically by two-dimensional gel electrophoresis. The MS ring is formed in the absence of any other flagellar components, including the switch complex and the putative export apparatus. Four proteins previously identified as rod components, FlgB, FlgC, FlgF, FlgG, and another protein, FliE, assemble co-operatively into a stable structure. The hook is formed in two distinct steps; formation of its proximal part and elongation. Proximal part formation occurs, but elongation does not occur, in the absence of the LP ring. FlgD is necessary for hook formation, but not for LP-ring formation. A revised pathway of flagellar assembly is proposed based on these and other results. 相似文献
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J M Al-Hassan M Afzal M Ali M Thomson T Fatima S Fayad R S Criddle 《Comparative biochemistry and physiology. B, Comparative biochemistry》1986,85(1):41-47
Lipids associated with a threat induced epidermal gel secretion from the catfish, Arius thalassinus, have been analyzed. Phospholipids, neutral lipids and glycolipids are all present and each of these subclasses has been analyzed by thin layer and gas chromatography with a general similarity with membrane lipids being noted. The epidermal gel lipids differed from total liver lipids of the catfish. Fatty acid analysis showed the gel lipid to be rich in the unsaturated fatty acids: oleate (omega 7, C18:1), arachidonate (omega 6, C20:4), and docosahexaenoate (omega 3, C22:6). Some prostaglandins were quantitated in lipid extracts from the epidermal gel. 相似文献
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The arid zone scorpion Urodacus yaschenkoi (Birula 1903) is shown to have six instars. Instars can be recognized by measuring the claws and the carapace plus first five tail segments. A population study, carried out at Coombah, NSW, showed that the life history consisted of mating in September–October, 18 month gestation, birth in February-March, moult to second instar March-April and annual moults to sixth instar in December–February. The minimum generation time was 6 y, and the population appeared to be stable. The calendar of catches method was used to determine the population size (about 400 animals in 2240 m2) but required some extra assumptions to cope with loss of marks from individuals when they moulted. 相似文献