马拉维Nyika高原三种溪流鱼类的生境类型

本研究调查了生活在非洲马拉维北部Nyika高原三种溪流鱼类的栖息地.分3个时期选择3条河流的24个地点进行取样,每个样点长100 m左右;分急流和回水湾两种生境类型作为独立的栖息地单元取样,据此观察研究对象和物理环境间的关系;用喜好指数和逻辑回归分析每种鱼重要栖息地是否稳定.瞻星平鳍鲇(Amphilius uranoscopus)通常喜欢生活在水深小于50 cm、流速0.4-1 m/s的缓流河段,这里水色较深,河底多卵石.黄鱼(Labeobarbus johnstonii)常被发现在水深大于50 cm的河段,河水流速中等或较急.引入种虹鳟(Oncorhynchus mykiss)的活动范围常局限在水温低于20℃的河段,这些河段水深中等,流速较快,沿河多植物.虹鳟栖息地与土著种相似,可能与同域分布的土著种,特别是与广泛分布的瞻星平鳍鲇存在生存竞争.     

Variation of vertebral number in juvenile Oncorhynchus mykiss in relation to upstream distance from the ocean

Vertebral counts in fishes are set early in development by a complex interaction of genetic and environmental factors. Recently, R. M. McDowall showed that vertebral counts can differ between diadromous and non-diadromous galaxiids, and suggested similar life history-based variation might also occur in the closely related Salmonidae. We examined variation in vertebral counts of juvenile rainbow trout, Oncorhynchus mykiss, from within a single large basin where anadromous and non-anadromous forms co-occur. Juveniles were collected at 29 sites within the Klamath River basin using a nested sampling design. Mean vertebral counts varied among regions, among complexes within regions, and among sites within complexes. Regression showed that mean vertebral counts decreased with increasing distance from the ocean. This decrease could not be explained by differences in temperature within the basin during early development. However, the decrease is consistent with the expectation that non-anadromous forms have fewer vertebrae and are more common at sites distant from the ocean, and suggests that further study of the relationship between vertebral counts and life history form in O. mykiss is warranted.

A cDNA microarray assessment of gene expression in the liver of rainbow trout (Oncorhynchus mykiss) in response to a handling and confinement stressor

A purpose-designed microarray platform (Stressgenes, Phase 1) was utilised to investigate the changes in gene expression within the liver of rainbow trout during exposure to a prolonged period of confinement. Tissue and blood samples were collected from trout at intervals up to 648 h after transfer to a standardised confinement stressor, together with matched samples from undisturbed control fish. Plasma ACTH, cortisol, glucose and lactate were analysed to confirm that the neuroendocrine response to confinement was consistent with previous findings and to provide a phenotypic context to assist interpretation of gene expression data. Liver samples for suppression subtractive hybridisation (SSH) library construction were selected from within the experimental groups comprising “early” stress (2–48 h) and “late” stress (96–504 h). In order to reduce redundancy within the four SSH libraries and yield a higher number of unique clones an additional subtraction was carried out. After printing of the arrays a series of 55 hybridisations were executed to cover 6 time points. At 2 h, 6 h, 24 h, 168 h and 504 h 5 individual confined fish and 5 individual control fish were used with control fish only at 0 h. A preliminary list of 314 clones considered differentially regulated over the complete time course was generated by a combination of data analysis approaches and the most significant gene expression changes were found to occur during the 24 h to 168 h time period with a general approach to control levels by 504 h. Few changes in expression were apparent over the first 6 h. The list of genes whose expression was significantly altered comprised predominantly genes belonging to the biological process category (response to stimulus) and one cellular component category (extracellular region) and were dominated by so-called acute phase proteins. Analysis of the gene expression profile in liver tissue during confinement revealed a number of significant clusters. The major patterns comprised genes that were up-regulated at 24 h and beyond, the primary examples being haptoglobin, β-fibrinogen and EST10729. Two representative genes from each of the six k-means clusters were validated by qPCR. Correlations between microarray and qPCR expression patterns were significant for most of the genes tested. qPCR analysis revealed that haptoglobin expression was up-regulated approximately 8-fold at 24 h and over 13-fold by 168 h.     

Temperature,contractility and high energy phosphates in anoxic fish heart muscle

Summary Isolated, electrically paced ventricular tissue of rainbow trout, Oncorhynchus mykiss, was examined at 20 and 10°C for the effects of different metabolic inhibitions on isometric force development and cellular content of phosphocreatine, creatine, ATP, ADP and AMP. At 20 relative to 10°C, twitch force was the same, but both twitch development and relaxation occurred over a shorter time and at a considerably higher maximal rate. Inhibition of cellular respiration caused twitch force and phosphocreatine to decrease, both about twice as fast at 20 as at 10°C. This doubling of energy degradation, i.e. in decrease of phosphocreatine, ATP, and loss of twitch force also occurred in preparations in which the energy liberation was totally blocked by iodoacetate in combination with N₂ and cyanide; both anaerobic energy degradation and anaerobic energy liberation expressed as lactate production were doubled. The similar effect of temperature on degradation and liberation of energy might explain why loss of twitch force during a 1-h period of anoxia was the same at both temperatures. The latter result was also found in the myocardium of eel Anguilla anguilla. In spite of its large influence on the time-course of twitch force development, the difference in temperature had no evident effects on the relationship between twitch force and phosphocreatine.Abbreviation Cr_t total creatine (creatine and phosphocreatine) - EDTA ethylenediminetetra-acetate - IAA iodoacetate - PCr phosphocreatine - TPT time-to-peak force - TR ₇₅ time for relaxation - V _F maximal rate of force development - V _R maximal rate of relaxation     

Differential responses to copper in rainbow trout (Oncorhynchus mykiss) acclimated to sea water and brackish water

Rainbow trout, Oncorhynchus mykiss, acclimated to 33% sea water (12 mg·ml^-1 salinity) experienced significant (10 meq·1^-1) increases in plasma [Na⁺] and [Cl^-] within 5 h of exposure to 6.3 mol copper·1^-1 indicating severe impairment of branchial ionoregulatory capacity. All plasma ion levels subsequently stabilised once the transbranchial [Na⁺] gradient was reduced to zero. The similar ionic strength of the external medium and their body fluids appeared to protect trout maintained in 33% sea water from further ionoregulatory stress and any secondary physiological disturbances during exposure to copper. Despite three- and fourfold greater transbranchial [Na⁺] and [Cl^-] gradients, trout acclimated to full-strength sea water (35 mg·ml^-1 salinity) suffered no major changes in plasma Na⁺, Cl^-, K⁺, or Ca²⁺, blood gases or haematology during 24 h exposure to 6.3 mol copper·1^-1. This reduction in toxicity in full strength sea water cannot be explained by differences in copper speciation. We suggest that during acute exposure to waterborne copper, active NaCl extrusion is unaffected due to the basolateral location of the gill Na⁺/K⁺-ATPase, but that ionoregulatory disturbances can occur due to gill permeability changes secondary to the displacement of surface-bound Ca²⁺. However, in full strength sea water the three-fold higher ambient [Ca²⁺] and [Mg²⁺] appear to be sufficient to prevent any detrimental permeability changes in the presence of 6.3 mol copper·1^-1. Plasma [NH ₊ ⁴ ] and [HCO _- ³ ] were both significantly elevated during exposure to copper, indicating that some aspects of gill ion transport (specifically the apical Na⁺/NH ₊ ⁴ and Cl^-/HCO _- ³ exchanges involved in acid/base regulation and nitrogenous waste excretion) are vulnerable to inhibition in the presence of waterborne copper.Abbreviations C _aO₂ arterial oxygen content - Hb haemoglobin - Hct haematocrit - MABP mean arterial blood pressure - MCHC mean cell haemoglobin content - MO₂ rate of oxygen consumption - P _a CO₂ arterial carbon dioxide tension - P _aO₂ arterial oxygen partial pressure - S salinity - SW sea water - T _Amm total ammonia (=NH₃+NH ₊ ⁴ ) - T _{CO 2} total carbon dioxide - TEP transepithelial potential - TOC total organic carbon - %Hb-O₂ percentage of haemoglobin saturated with oxygen     

Evidence of partial anadromy and resident-form dispersal bias on a fine scale in populations of Oncorhynchus mykiss

We examine sympatric anadromous (steelhead) and nonanadromous (resident) rainbow trout (Oncorhynchus mykiss) from neighboring locations to test three hypotheses: (1) the sympatric life history types are not genetically different; (2) fine-scale dispersal is the same for both sexes, and (3) fine-scale dispersal is the same for steelhead and resident individuals. Data from 13 microsatellite loci reveal no genetic difference between sympatric steelhead and resident O. mykiss but moderate population structure (F _ST=0.019–0.028) between adjacent samples, regardless of life history type. Our results provide further evidence of partial anadromy and suggest that geographic proximity and genetic history, more than migratory type, should be considered when identifying populations for use in restoration of local genetic diversity. We find evidence of resident-form dispersal bias on a fine spatial scale, however, we find no evidence that fine-scale dispersal varies by gender. Conservation strategies should aim to maintain resident and anadromous forms when they occur in sympatry, as they may be important in facilitating gene flow on small and large spatial scales, respectively.     

Effect of starvation and refeeding on digestive enzyme activities in sturgeon (Acipenser naccarii) and trout (Oncorhynchus mykiss)

The digestive enzyme activities were determined in Adriatic sturgeon and rainbow trout during starvation and refeeding period. Overall, the digestive enzyme activities are affected in the same sense in both species. The protease and lipase activities were decreased later than amylase activity. Even after 1 month of starvation, both species would be prepared to digest protein and lipids in an effective way. After 72 days of starvation, the digestive machinery of the sturgeon and of the trout shows an altered capacity to digest macronutrients. The capacity to digest proteins and lipids, after 60 days of refeeding, begins to become re-established in sturgeon and trout. In contrast, in this period, the capacity to digest carbohydrates remains depressed in both species.     

Innate immune responses in rainbow trout (Oncorhynchus mykiss, Walbaum) induced by probiotics

Carnobacterium maltaromaticum B26 and Carnobacterium divergens B33, which were isolated from the intestine of healthy rainbow trout (Oncorhynchus mykiss, Walbaum), were selected as being potentially useful as probiotics with effectiveness against Aeromonas salmonicida and Yersinia ruckeri. Thus, rainbow trout administered with feed supplemented with B26 or B33 dosed at >10(7) cells g(-1) feed conferred protection against challenge with virulent cultures of the pathogens. Moreover, both cultures persisted in the gut for up to 3 weeks after administration. The cultures enhanced the cellular and humoral immune responses. Specifically, fish fed with B26 demonstrated significantly increased phagocytic activity of the head kidney macrophages, whereas the use of B33 led to significant increases in respiratory burst and serum lysozyme activity. Also, the gut mucosal lysozyme activity for fish fed with both cultures was statistically higher than the controls.     

Effect of acute and chronic epinephrine administration on clearance and metabolism of [3H]-epinephrine in trout (Oncorhynchus mykiss)

Several studies have measured the rate of catecholamine clearance, metabolism, and tissue accumulation in fish. However, no information is available on the effect of repeated stress or high circulating catecholamine levels on catecholamine clearance and metabolism. We measured the clearance and metabolism of [³H]-epinephrine (approximately 0.1 g·kg^-1) in SW-acclimated rainbow trout subjected to acute (five injections in 1 day) and chronic (4 days; five injections per day) administration of 4.0 g·kg^-1 epinephrine or saline. In addition, a saturation experiment, where 4.0 g·kg^-1 of unlabelled epinephrine was injected concurrently with [³H]-epinephrine, investigated whether catecholamine clearance and metabolism are affected by high circulatin levels. Neither the rate constants for catecholamine clearance, nor the post-injection proportions of unmetabolised [³H]-epinephrine, deaminated [³H]-epinephrine and O-methylated [³H]-epinephrine were affected by the acute or chronic injection protocols. The concurrent injection of [³H]-epinephrine and 4.0 g·kg^-1 of unlabelled epinephrine resulted in an elevated postinjection ³H:¹⁴C ratio, but increased proportions of O-methylated [³H]-epinephrine and reduced proportions of unmetabolised [³H]-epinephrine. We conclude that in fish (1) catecholamine clearance and metabolism are unlikely to be compromised by repeated exposure to acute stressors; (2) catecholamine extraction and/or metabolism is enhanced when circulating levels are high; and (3) there is a marked capacity to rapidly (minutes) clear and inactivate catecholamines that are released in response to stressful stimuli.Abbreviations CA catecholamines - dpm disintegrations per minute - MAO monoamine oxidase - COMT catecholamine-O-methyltransferase - MOPEG 3-methoxy-4-hydroxyphenylglycol - VMA 3-methoxy-4-hydroxymendelic acid - SW seawater - HPLC high-performance liquid chromatography     

Diversity of juvenile fish assemblages in the pelagic waters of Lebanon (eastern Mediterranean)

Oxygen consumption rates of nauplii of the brine shrimp Artemia franciscana Kellogg 1906 were determined over a range of salinities from 10 to 110 ppm, in temperatures from 0 to 30°C, using a multi-factorial design. The oxygen micro-sensors employed have a fast response time and are capable of accurately measuring oxygen concentrations at temperatures well below 0°C. Oxygen uptake rate ranged from 0.03 to 0.66 μmol O₂ mg⁻¹ h⁻¹ and was sensitive to changes in both salinity and temperature. Temperature was the dominant factor affecting oxygen consumption rates, which showed a significant increase with increasing temperature. A slight decrease was measured in oxygen consumption with increasing salinity related to differential solubility of oxygen in waters of different salinities. Thermal sensitivity of oxygen consumption determined from calculations of Q ₁₀, indicated physiological adaptation of Artemia nauplii to the ranges of temperatures tested. Handling editor: A. van Kerchove     

基于标志重捕法的高原鼢鼠种群动态及其环境影响因子

高原鼢鼠（Eospalax baileyi）是青藏高原优势地下啮齿动物,研究其种群数量变化规律及其与环境因子关系,对于保护高寒草地生物多样性和科学防控草原鼠害具有重要意义。于2014-2019年在天祝县抓喜秀龙乡高原鼢鼠分布区,采用标志重捕法调查每年5月和10月高原鼢鼠种群密度、存活率、补充量及体重,利用样方法调查各植物功能群地上、地下生物量,并从中国气象数据中心获取同期气象数据。通过灰色关联度分析,探究高原鼢鼠种群特征变化与环境因子关联程度。结果表明：高原鼢鼠种群数量存在年际和季节性变化规律,年际间高原鼢鼠种群数量总体呈下降趋势,秋季高原鼢鼠种群数量高于春季种群数量;灰色关联分析表明,春季高原鼢鼠种群数量变化与降雨量、极端温度和杂类草生物量关联程度较高,而秋季高原鼢鼠种群数量与环境因子关联程度较低。研究结果不仅为今后构建高原鼢鼠种群数量预测预报模型提供基础依据,也为适时防控高原鼢鼠危害提供有益参考。     

The mucous coat on gill lamellae of rainbow trout (Oncorhynchus mykiss)

The existence of a layer of mucus covering the gill lamellae of healthy rainbow trout (Oncorhynchus mykiss) was investigated. Using cryo-scanning electron microscopy, a smooth, undulating, thin layer was observed which completely covered gill filaments and lamellae, thereby obscuring epithelial microridges. After processing cryopreserved gill arches in glutaraldehyde for conventional scanning electron microscopy, the layer was no longer present and epithelial microridges were clearly visible. The identity of this layer was investigated using cryopreserved gills which were treated in one of two ways. First, gills were incubated with a rabbit antiserum to gill mucus, with normal rabbit serum, or with phosphate-buffered saline. Following fixation in glutaraldehyde and processing, only the gill tissue incubated with the mucus-specific antiserum was still covered with the smooth layer. The layer was also retained on the gills of fish anesthetized in a solution containing mucusspecific antiserum and then processes in glutaraldehyde for conventional scanning electron microscopy. The tenacious nature of the mucous layer was demonstrated by its stability following exposure to formalin and a cationic detergent. Second, the presence of this layer was confirmed on gill tissue which was cryopreserved, followed by freeze-substitution and vapor fixation, and then examined by transmission electron microscopy.     

Ion movements associated with chorion elevation during egg laying in trout (Oncorhynchus mykiss) in fresh water

Within 1 min of transfer from coelomic fluid to fresh water, eggs of rainbow trout (Oncorhynchus mykiss) underwent a transient loss of Na⁺ and K⁺ coupled with an elevation of the chorionic envelope. Both mechanisms were blocked by adding a monovalent cation Li⁺ or K⁺ (140 mmol·l^-1) to the fresh water, but the divalent ion Mg²⁺ (100 mmol MgCl₂·l^-1) or elevating the osmotic pressure to 300 mOsmol·l^-1 with glycine had no inhibitory effect. The blocking of Na⁺ loss occurred at external monovalent cation (LiCl) concentrations above 70 mmol·l^-1. A 20-s exposure of eggs to fresh water was sufficient to trigger Na⁺ loss and chorion elevation, even when the eggs were subsequently transferred to fresh water containing 140 mmol LiCl·l^-1. Eggs placed in a medium containing 140 mmol LiCl·l^-1 and 2 mmol Ca(NO₃)₂·l^-1 showed chorion elevation and associated Na⁺ loss after addition of calcium ionophore (20 mol·l^-1 A.23187). This activation by calcium ionophore was supressed in a Ca²⁺-free medium containing 5 mmol EGTA·l^-1.     

Seasonal dynamics of Bythonomus lemani and Bothrioneurum vejdovskyanum (Oligochaeta, Annelida) in relation to environmental variables

The seasonal dynamics of Bythonomus lemani (Lumbriculidae) were studied for the first time and the knowledge of Bothrioneurum vejdovskyanum (Tubificidae) was extended based on four quantitative samples of oligochaetes taken monthly in the Rokytná River (Czech Republic) during a two-year study (April 1999–April 2001). The influence of water temperature, velocity, depth, discharge, pH, conductivity, dissolved oxygen amount and biochemical oxygen demand (BOD) on their life cycles was evaluated. Habitat preferences of the juvenile and adult stages were recorded. Time series analysis was used to determine the worm densities, seasonality and trends. For Byth. lemani one distinct reproduction cycle per year was found and this was regulated by temperature, while Both. vejdovskyanum showed a one-year cycle not significantly dependent on measured environmental variables. The overall trend was an increase in density for Byth. lemani and a decrease in density for Both. vejdovskyanum. Byth. lemani showed a significant negative correlation between the trend of its density and BOD concentration.     

高原鼢鼠干扰下高寒草甸大型土壤动物多样性对环境因子的响应

为研究高寒草甸大型土壤动物群落组成和分布对环境因子的响应,选取祁连山东段的甘肃省天祝县高原鼢鼠典型分布区域,以鼠丘密度代表干扰强度设置4个干扰区。调查各干扰区植被群落特征、土壤理化性质、大型土壤动物类群组成及其数量,采用约束性排序方法分析环境因子对大型土壤动物类群组成和分布的影响。结果表明：高原鼢鼠干扰下高寒草甸大型土壤动物优势类群为瓦娄蜗牛科、象甲科和短角亚目幼虫;极重度干扰区大型土壤动物类群的丰度、丰富度、Shannon指数显著高于重度干扰区（P<0.05）;多元回归分析表明大型土壤动物类群丰度、丰富度和Shannon指数与土壤温度呈显著负相关（P<0.05）,丰富度与土壤含水量呈显著负相关（P<0.05）,丰度与土壤紧实度呈显著负相关（P<0.05）,丰富度和Shannon指数与植物Shannon指数呈显著负相关（P<0.05）;冗余分析和偏冗余分析表明,土壤温度、紧实度和含水量是影响高寒草甸大型土壤动物类群组成和分布的主要环境因子。     

Calcium signalling in isolated single chromaffin cells of the rainbow trout (Oncorhynchus mykiss)

Chromaffin cells were isolated from the posterior cardinal vein of rainbow trout (Oncorhynchus mykiss) to assess their suitability as a model system for studying mechanisms of catecholamine secretion in fish and to evaluate intracellular calcium changes associated with cholinoreceptor stimulation. Immunocytochemistry in concert with fluorescence microscopy was employed to identify characteristic chromaffin cell proteins and thus to confirm the presence of these specific cells in suspensions and cultures. Dopamine-β-hydroxylase, an enzyme of the catecholamine-synthesising Blaschko pathway, was identified in cytoplasmic vesicles of the isolated chromaffin cells. The actin filament-severing protein, scinderin, was co-localized with actin in the sub-plasmalemmal membrane of these chromaffin cells. Intracellular calcium [Ca²⁺]_i was measured in single chromaffin cells by microspectrofluorometry using the fluorescent dye Fura-2. Significant increases in [Ca²⁺]_i were observed in chromaffin cells in response to depolarisation of the cell membrane by high concentrations of K⁺ or by the stimulation of the cell by the cholinergic receptor agonists, nicotine, acetylcholine or carbachol. The response to the reversible agonist, nicotine, was attenuated following addition of the nicotinic receptor blocker hexamethonium. Such attenuation, however, did not occur when hexamethonium was added after stimulation with the non-specific irreversible cholinergic agonist, carbachol. These results demonstrate the presence of functional cholinoreceptors, linked to intracellular calcium signalling, on isolated trout chromaffin cells and reveal the potential of these cells as a model system for studying aspects of catecholamine secretion in fish.     

Plasma ghrelin levels in rainbow trout in response to fasting, feeding and food composition, and effects of ghrelin on voluntary food intake

Ghrelin, a peptide hormone which stimulates growth hormone (GH) release, appetite and adiposity in mammals, was recently identified in fish. In this study, the roles of ghrelin in regulating food intake and the growth hormone (GH)-insulin-like growth factor I (IGF-I) system of rainbow trout (Oncorhynchus mykiss) were investigated in three experiments: 1) Pre- and postprandial plasma levels of ghrelin were measured in relation to dietary composition and food intake through dietary inclusion of radio-dense lead-glass beads, 2) the effect of a single intraperitoneal (i.p.) injection with rainbow trout ghrelin on short-term voluntary food intake was examined and 3) the effect of one to three weeks fasting on circulating ghrelin levels and the correlation with plasma GH and IGF-I levels, growth and lipid content in the liver and muscle was studied. There was no postprandial change in plasma ghrelin levels. Fish fed a normal-protein/high-lipid (31.4%) diet tended to have higher plasma ghrelin levels than those fed a high-protein/low-lipid (14.1%) diet. Plasma ghrelin levels decreased during fasting and correlated positively with specific growth rates, condition factor, liver and muscle lipid content, and negatively with plasma GH and IGF-I levels. An i.p. ghrelin injection did not affect food intake during 12-hours post-injection. It is concluded that ghrelin release in rainbow trout may be influenced by long-term energy status, and possibly by diet composition. Further, in rainbow trout, ghrelin seems to be linked to growth and metabolism, but does not seem to stimulate short-term appetite through a peripheral action.     

Interstitial cells from the testis of the trout (Oncorhynchus mykiss) in vivo and in primary culture

Summary In the testis of the trout, while no changes are apparent in myoid cells at any stage of maturation, Leydig cells display striking structural alterations when observed at different periods of the reproductive cycle. Spermiating testes contain fully differentiated Leydig cells. In regressed testes and those involved in spermatogenesis, poorly differentiated Leydig cells are mixed with cells ranging structurally from normal Leydig cells to fibroblast-like elements. After 3–4 days in culture the myoid cells/fibroblasts progressively acquire the ability to proliferate and then show a positive reaction for 3-hydroxysteroid dehydrogenase. During the same period they undergo structural changes reflecting the emergence of a steroidogenic activity. These changes occur concomitantly with an increase in progestagen secretion. These data suggest that, in vivo, Leydig cells degenerate at the end of a cycle, being then replaced by fibroblastic precursor cells capable of division and differentiation into steroidogenic cells.     

The energetic cost of protein synthesis in isolated hepatocytes of rainbow trout (Oncorhynchus mykiss)

Summary To establish the energetic cost of protein synthesis, isolated trout hepatocytes were used to measure protein synthesis and respiration simultaneously at a variety of temperatures. The presence of bovine serum albumin was essential for the viability of isolated hepatocytes during isolation, but, in order to measure protein synthesis rates, oxygen consumption rates and RNA-to-protein ratios, BSA had to be washed from the cells. Isolated hepatocytes were found to be capable of protein synthesis and oxygen consumption at constant rates over a wide range of oxygen tension. Cycloheximide was used to inhibit protein synthesis. Isolated hepatocytes used on average 79.7±9.5% of their total oxygen consumption on cycloheximide-sensitive protein synthesis and 2.8±2.8% on maintaining ouabain-sensitive Na⁺/K⁺-ATPase activity. The energetic cost of protein synthesis in terms of moles of adenosine triphosphate per gram of protein synthesis decreased with increasing rates of protein synthesis at higher temperatures. It is suggested that the energetic cost consists of a fixed (independent of synthesis rate) and a variable component (dependent on synthesis rate).Abbreviations BSA bovine serum albumin - dpm disintegrations per min - k _s fractional rate of protein synthesis - HEPES N-2-hydroxyethylpiperazine-N-2-ethane sulphonic acid - PHE phenylalanine; PO₂ oxygen tension - PCA perchloric acid