The interaction of temperature and fish size on growth of juvenile turbot

Growth rate of tagged juvenile turbot was significantly influenced by the interaction of temperature and fish size. The results suggest the optimum temperature for growth of juvenile turbot in the size range 25–75 g is between 16 and 19°C. Optimal temperature for growth decreased rapidly with increasing size, and is between 13 and 16°C for 100 g turbot. Although individual growth rates varied highly at all times within the temperature treatments, significant size rank correlations were maintained during the experimental period. The study confirms that turbot exhibit ontogenetic variation in temperature optimum, which might partly explain different spatial distribution of juvenile and adult turbot in ocean waters.     

The effect of temperature and fish size on growth and feed efficiency ratio of juvenile spotted wolffish Anarhichas minor

The growth properties of juvenile spotted wolffish Anarhichas minor reared at 4, 6, 8 and 12° C, and a group reared under 'temperature steps', (T‐step) i.e . with temperature reduced successively from 12 to 9 and 6° C were investigated. Growth rate and feed efficiency ration was significantly influenced by temperature and fish size. Overall growth rate was highest at 6° C (0·68% day⁻¹) and lowest at 12° C (0·48% day⁻¹), while the 4 and 8° C, and the T‐step groups had similar overall growth rates, i.e . 0·59, 0·62 and 0·51% day⁻¹ respectively. Optimal temperature for growth ( T _{opt G} ) and feed efficiency ratio (T_{opt FCE}) decreased as fish size increased, indicating an ontogenetic reduction in T _{opt G} and T _{opt FCE}. The results suggest a T _{opt G} of juvenile spotted wolffish in the size range 135–380 g, dropping from 7·9° C for 130–135 g to 6·6° C for 360–380 g juveniles. The T _{opt FCE} dropped from 7·4° C for 120–150 g to 6·5° C for 300–380 g juveniles. A wider parabolic regression curve between growth, feed efficiency ratio and temperature as fish size increased, may indicate increased temperature tolerance with size. Individual growth rates varied greatly at all time periods within the experimental temperatures, but at the same time significant size rank correlations were maintained and this may indicate stable size hierarchies in juvenile spotted wolffish.     

The effects of temperature and size on growth and mortality of cod larvae

The optimal temperatures for growth of four groups of hatchery-reared cod larvae (geometric mean weight: 73, 191, 249 and 251 μg), reared on rotifers at four or five constant temperatures between 4 and 16° C for 14, 12, 9 and 16 days were 9.7, 12.3, 12.7 and 13.4° C, respectively. The maximum growth rate also increased with size and was 6.5, 9.6, 11.7 and 11.3% day⁻¹ for the respective size groups. The optimal temperature for survival was 8.5–8.8° C for all size groups. The results indicate an opposite relationship between (1) size and optimal temperature for growth and (2) size and maximum growth rate of cod larvae, to that observed for juvenile and immature cod.     

The effect of different initial size distributions on the growth of Atlantic halibut

Growth rate of individually tagged medium–sized (249±6·9 g) juvenile halibut was 18% lower when medium sized fish were reared alone (treatment Mm) as compared with rearing with either large/dominant (382±12·1 g) (Ml) or small/subordinate (158±3·1 g) (Ms) conspecifics. The coefficient of variation of weight of medium–sized fish increased with weight in both the Mm and the Ml group whereas it was stable in the Ms group. Size rank correlation between initial and final weight was highest in the Mm group and lowest in Ms. A negative rank correlation was found also between initial weight and overall growth rate for the Ms treatment groups but not the other groups. It is hypothesized that interactions between similar–sized individuals in the Mm treatment group had an inhibiting effect on growth as social hierarchies were being resolved.     

Effects of salinity on the ionic balance and growth of juvenile turbot

The effects of salinity changes (27, 19 and 10‰) on seawater-adapted juvenile turbot were studied on their plasma osmolarity and ion concentrations, on oxygen consumption, on gill Na⁺,K⁺-ATPase activity after 3 months and on growth parameters. All plasma concentrations (except chloride) were unchanged, suggesting that fish were well adapted to their environment. Oxygen consumption was significantly decreased in the 19 and 10‰ groups, where fish weighed significantly more 105 days after transfer than fish maintained in sea water. These results, and the fact that apparent food conversion rates were lower in a diluted environment, suggest that on a long term schedule growth conditions could be improved by adaptation to brackish waters (salinities between 10 and 19‰). The effects of transfer from sea water to 27, 19, 10 and 5‰ were also followed during the first 3 weeks. With salinity 10‰ a steady state was reached on day 21 with all plasma values within the same range. The significant differences observed in osmolarity, plasma ion concentrations and Na⁺,K⁺-ATPase activity 3 weeks after transfer of juveniles to 5‰ salinity, compared with transfers in higher salinities, suggest that there is a threshold of acclimation of turbot to a hypotonic environment.     

低氧及酸化胁迫对大黄鱼幼鱼离子调节与鳃组织结构的影响

为探讨大黄鱼幼鱼在低氧及酸化胁迫下机体离子调节情况,本研究探讨了低氧(溶解氧量DO 3.5 mg·L-1,pH 8.1)、酸化(DO 7.0 mg·L-1,pH 7.35)以及低氧酸化协同胁迫(DO3.5 mg·L-1,pH 7.35)对大黄鱼幼鱼鳃组织结构以及离子调节相关生理指标的影响.结果 表明:低氧胁迫下,大黄鱼...     

Antagonistic anticancer effect of paclitaxel and digoxin combination

Despite the growing interest in the antitumor effect of cardiotonic steroids, combination treatments with well-established chemotherapy drugs like paclitaxel have been rarely investigated. Moreover, paclitaxel has been suggested as a Na⁺/K⁺-ATPase inhibitor. Here we investigated the effect of paclitaxel and digoxin alone or in combination on the viability of human lung (A549) and cervical cancer (HeLa) cell lines and the inhibitory effect of paclitaxel on several mammalian Na⁺/K⁺-ATPases. Although the viability of both tumor cell lines was concentration-dependently affected by digoxin treatment after 48 hours (A549 IC₅₀ = 31 nM and HeLa IC₅₀ = 151 nM), a partial effect was observed for paclitaxel, with a maximal inhibitory effect of 45% at 1000 nM with A549 and around 70% with HeLa cells (IC₅₀ = 1 nM). Although the two drugs were cytotoxic, their combined effect in HeLa cells was revealed to be antagonistic, as estimated by the combination index. No direct inhibitory effect of paclitaxel was detected in human, pig, rat, and mouse Na⁺/K⁺-ATPase enzymes, but high concentrations of paclitaxel decreased the Na⁺/K⁺-ATPase activity in HeLa cells after 48 hours without affecting protein expression. Our findings demonstrate that, under our conditions, paclitaxel and digoxin cotreatment produce antagonistic cytotoxic effects in HeLa cells, and the mechanism of action of paclitaxel does not involve a direct inhibition of Na⁺/K⁺-ATPase. More studies shall be designed to evaluate the consequences of the interaction of cardiotonic steroids and chemotherapy drugs.     

Effects of temperature, salinity, and fish size on growth and consumption of juvenile bluefish

Consumption and growth rates of juvenile bluefish Pomatomus saltatrix increased with increasing temperature and decreased with increasing fish size in short-term (7 days) experiments. Salinity had no effect on growth or consumption rate in a short-term experiment. In a long-term (90 days) mesocosm experiment, consumption and growth rates declined with increasing body size. Predictive equations developed from short-term experiments did not adequately predict observed consumption rates in the mesocosm experiment. However, growth in the mesocosm experiment was similar to field growth. Also, mesocosm consumption rates and consumption rates calculated using field growth and mesocosm growth efficiencies were similar to published independent field estimates of consumption rate. Our results indicate that experiments to determine the effects of temperature and the allometry of body size on growth and consumption rates should be conducted over long time periods simulating field conditions. Juvenile bluefish have rapid growth and their individual cumulative consumption is large. This result suggests that bluefish may have a large effect on their prey populations. This effect has yet to be quantified.     

氯化钾对长春花盛花期盐胁迫效应和生物碱含量的影响

在温室土培条件下,研究了不同浓度KCl处理对长春花盛花期盐胁迫效应以及对文多灵、长春质碱、长春碱和长春新碱等生物碱含量的影响.结果现实:(1)3‰ NaCl胁迫下,施入一定量KCl,将Na+/K+调为20:1(K2)时可显著缓解盐胁迫对长春花的危害,与不施KCl(K1)相比,长春花的鲜质量、株高、根长和相对含水量均显著提高,而长春花叶片丙二醛含量显著下降,超氧化物歧化酶(SOD)、过氧化氢酶(CAT)、过氧化物酶(POD)活性在Na+/K+为20:1(K2)时显著高于其它处理,但当Na+/K+为10:1(K3)与5:1(K4)时,盐胁迫的危害又显著加剧.(2)Na+/K+为20:1处理的长春花盛花期文多灵、长春质碱、长春碱和长春新碱含量显著高于其它处理,分别为20.88、30.18、2.53和5.12 mg·g-1.研究表明,Na+/K+为20:1比例施用钾肥可最大限度地降低NaCl胁迫对盛花期长春花生长造成的伤害,并显著促进其生物碱的代谢,显著提高长春花盛花期4种主要生物碱的含量.     

盐胁迫下囊果碱蓬出苗状况及苗期抗盐性

研究了盐胁迫对囊果碱蓬出苗、幼苗生长、离子积累以及光合放氧速率的影响.囊果碱蓬生长的最适盐浓度在200 mmol/L NaCl左右.高浓度NaCl(400 mmol/L和600 mmol/L)没有显著降低其出苗率,200 mmol/L NaCl对出苗率具有促进作用.400 mmol/L和600 mmol/L NaCl显著降低了光合放氧速率.囊果碱蓬在高浓度NaCl处理下能够维持叶片较高的K+/Na+ 及含水量可能是其适应高盐生境的重要机制.     

Geographic variation in growth and food conversion efficiency of juvenile Atlantic halibut related to latitude

Higher growth capacity and food conversion efficiency was observed in populations of juvenile halibut from high Hippoglossus hippoglossus compared lower latitudes. In addition, temperature adaptation shown by the lower temperature optimum for growth in the Norwegian population (mean±S.E. 12·9±0·10 C) compared with the Icelandic and Canadian populations (14·2±0·2 and 13·9±0±30 C respectively), seems to occur. Overall the data support the hypothesis of countergradient variation in growth. These results have implications firstly for selection focusing on growth performance in halibut culture; and secondly, for safe prediction of growth, since if countergradient variation in growth performance occurs one cannot assume automatically that a species will respond to the same set of physiological parameters in the same way throughout its range.     

Genetic differences in physiology, growth hormone levels and migratory behaviour of Atlantic salmon smolts

Out of five strains of Atlantic salmon Salmo salar of 1+ years released upstream of a fyke net in the River Gudenaa in 1996, three, Lagan, Ätran and Corrib, migrated immediately, 50% of the recaptured fish reaching the net in 3–6 days. Burrishoole and Conon fish migrated with a 15–19 day delay. Smolt development in 1997 at the hatchery showed a spring surge in gill Na⁺, K⁺-ATPase activity in all strains which was correlated with increased seawater tolerance. Differences in the timing of gill enzyme development matched the observed migration pattern well. Lagan, Ätran and Corrib strains reached high enzyme activity earlier than the Burrishoole and Conon strains, and strains with delayed enzyme development and migration showed a delayed regression of seawater tolerance compared with the early strains. Inter-strain differences in plasma growth hormone profiles could not be related to the observed patterns of Na⁺, K⁺-ATPase and seawater tolerance development. The study gives evidence of genetic influence on the timing and intensity of smolting and subsequent migration in Atlantic salmon.     

The gene sll0273 of the cyanobacterium Synechocystis sp. strain PCC6803 encodes a protein essential for growth at low Na+/K+ ratios

A mutant of Synechocystis sp. strain PCC6803 was obtained by random cartridge mutagenesis, which could not grow at low sodium concentrations. Genetic analyses revealed that partial deletion of the sll0273 gene, encoding a putative Na ⁺ /H ⁺ exchanger, was responsible for this defect. Physiological characterization indicated that the sll0273 mutant exhibited an increased sensitivity towards K ⁺ , even at low concentrations, which was compensated for by enhanced concentrations of Na ⁺ . This enhanced Na ⁺ demand could also be met by Li ⁺ . Furthermore, addition of monensin, an ionophore mediating electroneutral Na ⁺ /H ⁺ exchange, supported growth of the mutant at unfavourable Na ⁺ /K ⁺ ratios. Measurement of internal Na ⁺ and K ⁺ contents of wild‐type and mutant cells revealed a decreased Na ⁺ /K ⁺ ratio in mutant cells pre‐incubated at a low external Na ⁺ /K ⁺ ratio, while it remained at the level of the wild type after pre‐incubation at a high external Na ⁺ /K ⁺ ratio. We conclude that the Sll0273 protein is required for Na ⁺ influx, especially at low external Na ⁺ concentrations or low Na ⁺ /K ⁺ ratios. This system may be part of a sodium cycle and may permit re‐entry of Na ⁺ into the cells, if nutrient/Na ⁺ symporters are not functional or operating.     

The co-presence of Na+/Ca2+-K+ exchanger and Na+/Ca2+ exchanger in bovine adrenal chromaffin cells

We have previously shown that there is high Na(+)/Ca(2+) exchange (NCX) activity in bovine adrenal chromaffin cells. In this study, by monitoring the [Ca(2+)](i) change in single cells and in a population of chromaffin cells, when the reverse mode of exchanger activity has been initiated, we have shown that the NCX activity is enhanced by K(+). The K(+)-enhanced activity accounted for a significant proportion of the Na(+)-dependent Ca(2+) uptake activity in the chromaffin cells. The results support the hypothesis that both NCX and Na(+)/Ca(2+)-K(+) exchanger (NCKX) are co-present in chromaffin cells. The expression of NCKX in chromaffin cells was further confirmed using PCR and northern blotting. In addition to the plasma membrane, the exchanger activity, measured by Na(+)-dependent (45)Ca(2+) uptake, was also present in membrane isolated from the chromaffin granules enriched fraction and the mitochondria enriched fraction. The results support that both NCX and NCKX are present in bovine chromaffin cells and that the regulation of [Ca(2+)](i) is probably more efficient with the participation of NCKX.     

Extracellular ionic and acid-base adjustments of Atlantic salmon presmolts and smolts in fresh water and after transfer to sea water: the effects of ovine growth hormone on the acquisition of euryhalinity

In order to better understand the basis for the acquisition of euryhalinity by juvenile salmon and the role of endogeneous stimuli, experiments have been carried out to examine the dynamics of ionic and acid-base adjustments in fresh water (FW) and after direct transfer to full salinity (32 g l⁻¹) sea water (SW) (1) on Atlantic salmon smolt during the natural period of smoltification in spring, (2) on presmolt salmon in autumn, after intraperitoneal implantation of pellets containing ovine growth hormone (oGH). During parr-smolt transformation in FW, gill Na⁺/K⁺ ATPase activity gradually rises, the plasma osmolality (Posm) is unaffected and the total CO₂ of the plasma decreases significantly while whole blood pH fluctuates slightly. Direct transfer of smolt from FW to SW provokes only a slight increase in Posm and emphasizes the acid-base balance disruptions shown in FW. An oGHimplant in a presmolt stimulates gill Na⁺/K⁺ ATPase activity in FW, and affects the acid-base balance. After SW transfer (12 days after implantation), oGH treatment prevents the increase of osmotic pressure and the restoration of the acid-base, ionic equilibrium was faster for oGH-implanted fish than for sham-operated fish. These observations show that in FW smelting salmon develop most of the systems they need for migration and growth in SW and that oGH implants induce the development of physiological characteristics of smolts in a non-natural period of smolting.     

Changes in gill Na+, K+ -ATPase specific activity during seaward migration of wild juvenile chinook salmon

Migration of wild juvenile chinook salmon Oncorhynchus tshawytscha during the first 80 km of their 254 km migration through the Rogue River, Oregon, was significantly slower than that during the last 170 km. Gill Na⁺, K⁺ -ATPase specific activity did not increase significantly during the first 38 km of migration. Specific activities during the next 43 km did increase significantly. Specific activities continued to increase as the fish moved downstream, reaching a maximum within 44 km from the Pacific Ocean.     

Digestive tract ontogeny of Dicentrarchus labrax: implication in osmoregulation

The ontogeny of the digestive tract (DT) and of Na(+)/K(+)-ATPase localization was investigated during the early postembryonic development (from yolk sac larva to juvenile) of the euryhaline teleost Dicentrarchus labrax reared at two salinities: seawater and diluted seawater. Histology, electron microscopy and immunocytochemistry were used to determine the presence and differentiation of ion transporting cells. At hatching, the DT is an undifferentiated straight tube over the yolk sac. At the mouth opening (day 5), it comprises six segments: buccopharynx, esophagus, stomach, anterior intestine, posterior intestine and rectum, well differentiated at the juvenile stage (day 72). The enterocytes displayed ultrastructural features similar to those of mitochondria-rich cells known to be involved in active ion transport. At hatching, ion transporting cells lining the intestine and the rectum exhibited a Na(+)/K(+)-ATPase activity which increased mainly after the larva/juvenile (20 mm) metamorphic transition. The immunofluorescence intensity was dependent upon the stage of development of the gut as well as on the histological configuration of the analyzed segment. The appearance and distribution of enteric ionocytes and the implication of the DT in osmoregulation are discussed.     

青藏高原东缘11种小檗属(Berberis)植物种子萌发特性

在实验室条件下研究了青藏高原东缘11种小檗属(Berberis)植物的种子萌发特性,并分析了种子萌发能力与种子大小和海拔之间的关系。结果表明,11种植物中,仅有5种植物(金花小檗、匙叶小檗、锥花小檗、鲜黄小檗和刺黄花)种子萌发率超过50%,其中金花小檗最高(86.7%);有2种植物(巴东小檗、华西小檗)种子始终没有萌发,其余4种植物种子萌发率均在10%以下;种子萌发开始时间均在10d以后,匙叶小檗种子萌发的持续时间最长(40d)。11种植物种子萌发率、萌发速率、萌发持续时间与种子大小均呈显著负相关,而萌发开始时间与种子大小之间具有显著的正相关关系。萌发率、萌发速率、萌发持续时间与海拔均有较弱的正关联,萌发开始时间与海拔有较弱的负关联。     

温度对水螅种群增长和个体大小的影响

应用群体累积培养法,以枝角类为食物,在10℃、20℃和30℃三种温度下,研究了温度对水螅(Hydra sp．)种群密度、种群增长率和个体大小的影响。结果表明温度对水螅种群密度和个体体积由极显著影响。在培养初期,30℃下的水螅种群密度最大;而在培养后期,20℃下的水螅种群密度则显著大于30℃下的值;10℃下的值则始终最小。在同一温度下,种群增长率均与时间呈曲线相关,10℃、20℃、30℃的回归方程分别为：Y=0．000433X^2-0．00262X 0．00332、Y=-0．003367X^2 0．068335X-0．066489、Y=-0．018469X^2 0．188952X-0．030933。在研究范围内,30℃的水螅个体最小。