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91.
试验研究了半胱胺(Cs)对藏绵羊断奶羔羊瘤胃pH值、总脱氢酶及TVFA的影响。将10只(公母各半)80日龄左右、体重平均为(16.00±0.31)kg、装有永久性瘤胃瘘管的藏绵羊断奶羔羊随机分为2组(试验组和对照组),在日粮精料中添加300 mg/(kg·BW)的Cs,隔日添加1次,试验期42 d。正式试验当日及试验第7、14、21、28、35天的7:00、9:00、11:00、13:00、15:00、17:00、19:00、21:00、23:00、1:00、3:00、5:00于颈静脉采血样10 mL,同时采集瘤胃液10 mL,测定瘤胃pH值、总脱氢酶的活性和TVFA。检测结果表明,试验组精料中添加Cs使藏绵羊断奶羔羊瘤胃液pH值升高;血清尿素氮浓度降低,与对照组相比差异极显著(P0.01);瘤胃液总脱氢酶活力提高极其明显(P0.01);整个试验期内,半胱胺对瘤胃TVFA的影响极显著(P0.01)。 相似文献
92.
Salmonid sperm pre-incubated at extracellular pH (pHe) values less than about 7.4 do not become motile upon water activation whereas sperm maintained above about pH 8.0 demonstrate maximal motility upon activation. The basis for this permissive effect of elevated pHe on sperm motility is not known. Since it is conceivable that the pH sensitivity of dyneinATPase (the molecular motor that drives flagellar movement) could be the basis of, or contribute to this pH dependency, the pH sensitivity of this enzymatic activity was evaluated in membrane-permeabilized axonemes (isolated flagella) ofsteelhead sperm. DyneinATPase activity was found to be sensitive to pH. This activity in permeabilized axonemes was about 3.5-fold higher at pH 7.6 compared to 7.0. To determine whether the pH sensitivity ofATP regeneration might affect the interpretation of the effect of pH on dyneinATPase activity, the pH sensitivities of creatine kinase and adenylate kinase were established. The rates ofATP generation by these enzymes were insensitive to pH between 6.5 and 8.0. The results of these studies are consistent with the hypothesis that prior maintenance at pHe, in part, controls the potential for sperm motility upon water activation via an influence on dyneinATPase activity. However, the potential for motility ofsteelhead sperm is particularly sensitive to prior maintenance at pHe values between about 7.4 and 8.0 whereas the dyneinATPase activity of permeabilized axonemes was particularly sensitive to pH values between 7.0 and 7.6. Phosphorus NMR spectroscopy was used to determine that sperm intracellular pH (pHi) increased with increasing pHe between 7.0 and 8.5 and pHi was, on average 0.4–0.5 pH units lower than pHe. Therefore the pHe sensitivity of the potential for motility appears to correspond to the pHi sensitivity of dyneinATPase activity. The data indicate that pHi is directly related to pHe and that prior incubation at pHe may, in part, control the sperm's potential for motility upon water activation via an influence on dyneinATPase activity. 相似文献
93.
Proteolytic activity of sea trout hatching liquid was examined towards casein and azocazein as a function of pH and temperature.
The optimum pH for caseinolytic and azocaseinolytic activities were 9.4, and 9.0, respectively. At alkaline pH the enzyme
was activated by low concentrations of Zn2+ ions (10−5 M). Maximum proteolytic activity of the hatching liquid was observed at 25°C. Temperatures exceeding 30°C caused a rapid
reduction in enzyme activity. Proteolytic activity observed at 10°C was approximately 50% of that observed at 25°C. In general,
a pseudo-Arrhenius plot indicated a Q10 of 1.6 between 6 and 25°C. 相似文献
94.
We investigated ventillatory responses to a plasma alkaloids and hypocapnia,a nd the basis for the ventilatory response to sodium bicarbonate (NaHCO3) infusion in rainbow trout. Plasma alkalosis and hypocapnia created by infusion of sodium hydroxide (NaOH) did not cause hypoventilation, whereas infusion of hydrochloric acid (HCl) caused vigorous hyperventilation, associated with an acidosis, a reduction in blood O2 content (CaO
2) and a release of circulating catecholamines. Infusion of NaHCO3 stimulated ventilation and caused an increase in plasma pH, total carbon dioxide content (CaCO
2) and catecholamine levels, and a reduction in oxygen tension (PaO
2). Infusion of ammonium bicarbonate (NH 4HCO3) caused hyperventilation and was associated with an increase in CaCO
2 and plasma total ammonia (Camm) and ammonia gas (NH3) concentration. Infusion of sodium chloride (NaClI) and Cortland's saline had no effect on ventilation. The results indicate that trout do not exhibit the ventilatory sensitivity to pH seen in terrestrial vertebrates. Ventilatory responses to NaHCO3 appear to have been a result of reductions in PaO
2, a release of catecholamines and an increase in CaCO
2 whereas responses to NH4HCO3 appear to have been a result of increases in CaCO
2 and Camm. 相似文献
95.
S Y Yacoob K Anraku T Marui T Matsuoka G Kawamura & M Vazquez Archdale 《Aquaculture Research》2001,32(3):217-222
The gustatory sensitivity of the Nile tilapia, Oreochromis niloticus L., to different amino acids was studied using an electrophysiological approach. The electrical responses were recorded from a branch of the facial nerve innervating the external taste buds of the upper lip. The relative stimulatory effectiveness (RSE) of nine amino acids and betaine were determined at a concentration of 1 mm and all of them elicited neural responses. This species responded well to the neutral, basic and acidic amino acids. The most stimulatory amino acids were L‐histidine, L‐arginine, L‐serine, L‐methionine and L‐glutamine; L‐proline and betaine were the least stimulatory. The results of this study suggest that the Nile tilapia has high external gustatory sensitivity to some amino acids as a physiological adaptation to search effectively for their sources. The effect of the pH, ranging from 4.0 to 9.0, on the RSE of three neutral amino acids and artificial pond water (APW) was also studied. The RSE increased below pH 6.0 and was relatively unaffected from 7.0 to 9.0, indicating that acidified stimulants are highly stimulatory in this species. Nile tilapia did not discriminate the pH of APW as effectively as some of the species studied earlier. 相似文献
96.
Ammonia distribution and excretion in fish 总被引:6,自引:0,他引:6
This paper reviews the literature concerning ammonia production, storage and excretion in fish. Ammonia is the end product of protein catabolism and is stored in the body of fish in high concentrations relative to basal excretion rates. Ammonia, if allowed to accumulate, is toxic and is converted to less toxic compounds or excreted. Like other weak acids and bases, ammonia is distributed between tissue compartments in relation to transmembrane pH gradients. NH3 is generally equilibrated between compartments but NH4
+ is distributed according to pH. Ammonia is eliminated from the blood upon passage through the gills. The mechanisms of branchial ammonia excretion vary between different species of fish and different environments, and primarily involves NH3 passive diffusion and NH4
+/Na+ exchange. Water chemistry near the gill surface may also be important to ammonia excretion, but a more accurate measurement of the NH3 gradient across the gill epithelium is required before a more detailed analysis of NH3 and NH4
+ excretion can be made. 相似文献
97.
C.S. Carvalho 《Aquaculture (Amsterdam, Netherlands)》2006,251(1):109-117
Copper sulfate has been widely used to control algae and pathogens in fish culture ponds. However, its toxic effects on fish depend not only on its concentration in water but also on water quality. The susceptibility of the neotropical freshwater fish Prochilodus scrofa to copper was evaluated at two temperatures with low and high water pH. Juvenile fish were acclimated at 20 and 30 °C and exposed to copper (static bioassay system) in water with pH 4.5 and 8.0. The 96 h-LC50 were determined at each temperature and pH, as were the hematological parameters. The 96 h-LC50 for copper (98 and 88 μg Cu L− 1 in water with pH 4.5 and 16 and 14 μg Cu L− 1 in water with pH 8.0 for fish kept at 20 and 30 °C, respectively) was significantly dissimilar in pH 4.5 and 8.0, but no difference was found between 20 and 30 °C in the same water pH. At 20 °C, regardless of the water pH, the hematocrit (Hct) increased while the red blood cells (RBC) and hemoglobin (Hb) concentration decreased compared to control pH 7.0. Copper exposure in water pH 4.5 and 8.0 causes an increase on the Hct, RBC and Hb concentrations in relation to the controls pH 4.5 and 8.0. At 30 °C, the changes on the blood parameters depended on the water pH and, after copper exposure at low and high pH, the blood changes indicated more complex responses. The changes in hematological parameters of the fish, regardless of the pH and water temperature, indicate ionoregulatory or respiratory disturbances that imply an increase in energy consumption to restore homeostasis instead of other physiological functions such as weight gain and growth. 相似文献
98.
I.J. Morgan L.M. D-Cruz J.J. Dockray T.K. Linton D.G. McDonald C.M. Wood 《Fish physiology and biochemistry》1998,19(4):377-389
Appetite, growth, and protein turnover (synthesis, growth and degradation) of liver and gills were measured in juvenile rainbow trout (Oncorhynchus mykiss) fed to satiation, and exposed for 90 days to elevated winter temperatures (+2 °C above ambient) and either low pH (5.2) in softwater or 70 M total ammonia (TAmm) in hardwater. All fish increased in weight during the experiments, but those exposed to +2°C grew significantly more than those at ambient temperature due to a stimulation of appetite. During the relatively constant temperature of the first 75 days, +2 °C caused a significant increase in the rates of protein synthesis and degradation in the liver of hardwater-acclimated fish, as a result of an increase in RNA translational efficiency (KRNA). The elevated temperature also induced an increase in gill protein synthesis in softwater-acclimated fish but in this case the underlying mechanism was an increase in Cs, the capacity for protein synthesis (RNA:protein) rather than in KRNA. The addition of 70 M TAmm had no effect on protein turnover in either liver or gills of hardwater-acclimated fish. Low pH inhibited protein growth in the liver of softwater-acclimated fish at day 90 under both temperature regimes. This inhibition was effected via a decrease in protein synthesis at control temperature but via an increase in protein degradation when the fish were exposed to both low pH and +2 °C. From these results we conclude that a simulated global warming scenario has potentially beneficial rather than detrimental effects on protein turnover and growth of freshwater fish during winter. 相似文献
99.
Three species of fish were studied: Atlantic cod (Gadus morhua), sculpin (Myoxocephalus scorpius) (from the North Sea, temperature 2 to 12°C) andNotothenia neglecta (from Antarctica, temperature –2 to +2°C). Single fast muscle fibres were isolated from anterior myotomes and skinned with detergent in order to directly determine the effects of pH and temperature on force production and shortening velocity.In all species maximum force production (Po) was independent of pH over the range 7.3–8.0. Decreasing the pH from 7.3 to 6.6 reduced maximum force by 28% in fibres fromG. morhua andN. neglecta but had no effect on fibres fromM. scorpius. The depression in maximum force with acidosis was accompanied by a proportional decrease in stiffness and an increase in the rate of force recovery after stretch.Unloaded contraction velocity of cod fibres (Vmax) showed a pH optimum at around pH 7.6 decreasing by 31% at pH 6.6. Vmax of fibres from the other species was independent of pH over the range 6.6–8.0.The effects of pH on Po and Vmax were similar at 0 and 10°C. Thus for maximally activated fibres both force and contraction velocity are independent of temperature induced changes in pH. In some species acidosis depresses contractility and is likely to be a contributory factor to muscle fatigue. 相似文献
100.