The influence of size on ion regulation and sea-water survival of acid-exposed coho salmon smolts (Oncorhynchus kisutch)

1. Evidence of a size-related influence on sea-water adaptation in salmonids has led to a concern that acid exposure prior to entry into sea-water may further influence the sea-water adaptability of smaller fish.2. Coho salmon smolts (Oncorhynchus kisutch) were exposed to acidified soft waters for up to three weeks.3. Subsamples of these fish were subjected to a sea-water challenge test after 1, 2 or 3 weeks.4. Larger fish were found to tolerate longer periods of acid exposure. This size-dependent survival of larger fish was further influenced as fish were subjected to a sea-water challenge test.5. Ion regulatory mechanisms were also shown to be related to size and duration of acid exposure.     

Effects of acute exposures to elevated temperatures on rat embryo growth and development in vitro

Day 10 rat embryos (8-12 somites) cultured in vitro were exposed to elevated temperatures (41-43 degrees C) for varying lengths of time. A 15-minute exposure to a temperature of 43 degrees C (109.4 degrees F) was sufficient to produce malformed embryos when observed on day 11. Longer exposures at this temperature produce higher incidences of malformed embryos and also more severely affected embryos. Temperatures of 42 degrees C (107.6 degrees F) or 41 degrees C (105.8 degrees F) also produced malformed embryos, but the required length of exposure was increased compared to 43 degrees C. The minimal length of exposure at 42 degrees C was 60 minutes, while at 41 degrees C it was increased to 4 hours. The central nervous system was particularly sensitive to increased temperatures, and embryos exposed to "teratogenic doses" of hyperthermia exhibited primarily microcephaly and microphthalmia. In addition, histological analyses revealed that at 4.5 hours after a 30-minute exposure to 43 degrees C, necrotic debris was prevalent in the neuroepithelium, less prevalent in the surrounding mesenchyme and surface ectoderm, and absent in the tissues of the heart.     

Osmotic regulation in aqueous humor and blood in the euryhaline fish,Eugerres plumieri

• 1.1. The estuarine fish Eugerres plumieri was acclimated to sea-water concentrations ranging from 6 to 85% sea-water.
• 2.2. Serum and aqueous humor osmolalities were moderately well regulated over the range of concentrations studied.
• 3.3. Serum osmolality and aqueous humor osmolalities conformed to the following relations: serum osmolality = (319 ± 3) + (0.56 ± 0.03) (% sea-water); aqueous humor osmolality = (314 ± 4) + (0.35 ± 0.04) (% sea-water).
• 4.4. Aqueous humor osmolality was more strictly regulated than that of serum, indicating that the retina and nervous system of the fish, which are encased in inextensible structures, are well protected from variations in sea-water concentration in order to minimize osmotically induced changes in cell volume.

     

Surface disinfection of Atlantic halibut Hippoglossus hippoglossus eggs with ozonated sea-water inactivates nodavirus and increases survival of the larvae

Disinfection by ozonation of sea-water may reduce the risk of transmission of nodavirus, a major fish pathogen, via Atlantic halibut Hippoglossus hippoglossus eggs. In the present study, eggs at 4 d prior to hatching were exposed to nodavirus and then to ozonated sea-water using different concentrations (0.3 to 10 mg l-1) and exposure times (0.5 to 10 min). None of the larvae from virus-exposed eggs washed with ozonated sea-water developed viral encephalopathy and retinopathy (VER), which was detected in all dead larvae from eggs exposed to nodavirus but not washed with ozonated sea-water. In the non-treated control group about 20% of the dead larvae developed the disease. This suggests that the halibut eggs taken from a large-scale production facility were already contaminated with nodavirus. The egg groups which had been treated with 4 mg O3 l-1 for 0.5 min or with lower total ozone exposures had a higher survival and no adverse effects on the development of the larvae after hatching were observed. Although a slight delay in hatching was found, after 2 d the cumulative hatching had normalised. In the egg groups with high total exposure (4 mg O3 l-1 for 1 min or higher total ozone exposures) a pronounced negative effect on hatching was observed. Our results indicate that the egg surface may be important in the transfer of nodavirus and that nodavirus associated with the surface of the egg may be inactivated by ozonated sea-water.     

Effect of different environmental temperatures on the serotonin concentration and turnover in the brain stem of a hibernator.

The serotonin (5-HT) and 5-hydroxyindoleacttic acid (5-HIAA) levels and 5-HT turnover were studies in the brain stem of warm- (+30 degrees C) and cold- (+6 degrees C) acclimated golden hamsters, exposed for 3 hours to temperatures of +6 degrees C, +30 degrees C and +37 degrees C, respectively. In war-acclimated hamsters kept under conditions the 5-HT level in the brain did not change significantly during the year. The 5-HIAA level was slightly higher in the winter. The 5-HT turnover varied within limits of 0.071 to 0.180 mug/g/hour-1. Three hours' exposure of warm-acclimated golden hamsters to cold (6 degrees C) increased the concentrations of 5-HT and 5-HIAA and the 5-HT turnover in the brain. After long-term adaptation to cold (6 degrees C) the 5-HT level, and the 5-HT turnover returned to the original level. Three hours' exposure of golden hamsters to higher environmental temperatures (warm-acclimated individuals to 37 degrees C and cold-acclimated individuals to 30 degrees C) also increased the 5-HT turnover. The concentrations of 5-HT and 5-HIAA increased in cold-acclimated golden hamsters exposed to 30 degrees C and was not changed in warm-acclimated ones, exposed to 37 degrees C. Although the elevated temperatures induce greater changes in serotonin metabolism than lowered temperatures, the serotonin pathways in the brain do not seem to be affected by short-term temperature changes specifically. The findings are rather indicative that changes in 5-HT turnover may be the primary reaction to stressful conditions.     

Sodium and calcium balance in Mozambique tilapia, Oreochromis mossambicus, raised at different salinities

Mozambique tilapia, Oreochromis mossambicus, born and raised in five salinities, viz. (relatively soft) fresh water, 25, 50, 75% and full-strength sea-water, were analyzed for ionoregulatory performance (in particular sodium and calcium handling) and growth. This tilapia regulates its blood serum mineral composition rather effectively; however, in sea-water serum concentrations of sodium, chloride and calcium (in males only) were increased, as was the serum osmolarity. In sea-water, the total body sodium pool was significantly enlarged. With increasing salinity, sodium turnover increased. Serum calcium levels and the total body calcium pool were more strictly controlled than those of sodium. The lowest density of chloride cells in opercular epithelium and the lowest branchial Na+-K+-ATPase activity were observed in 50% sea-water; these values were higher in fish kept in waters of lower or higher salinities. Fish grew more rapidly in brackish water. Fish kept in brackish water appeared to depend on food-related calcium for growth as branchial calcium uptake provides no more than 20% of growth related Ca-accumulation.     

Effects of hyperthermia on fetal and maternal plasma prostaglandin concentrations and uterine activity in sheep

The exposure of pregnant sheep to high ambient temperatures (43 degrees C) for 8 hours, sufficient to significantly elevate maternal and fetal body temperature +2.0 degrees C (p less than 0.001) and +1.9 degrees C (p less than 0.001) respectively, resulted in significant increases in PGE2 plasma concentrations in both the maternal and fetal circulations. Plasma PGF2 alpha concentrations were significantly raised in the fetal circulation but not the maternal during hyperthermia. The increase in prostaglandin concentrations were correlated with the magnitude of the increase in maternal and fetal body temperature. Uterine activity also increased during hyperthermia, probably as a result of the increase in prostaglandin concentrations. We propose that increased synthesis and release of prostaglandins from the uterus and/or placenta is an adaptive response to hyperthermia, and may protect the fetus from the consequences of heat stress.     

Effects of methylglyoxal bis(guanylhydrazone) on tumour and skin responses to hyperthermia in mice

Effects of methylglyoxal bis(guanylhydrazone) (MGBG) on tumour and skin responses to hyperthermia (42 degrees C) were examined in C3H mice. MGBG (50 mg/kg) was administered intraperitoneally to mice 4 hours before hyperthermic treatment. The tumour (FM3A) growth time was elongated by an amount dependent on the exposure time of treatment at 42 degrees C (60, 90 and 120 min). Pre-treatment of mice with MGBG (50 mg/kg, i.p.) apparently further lengthened the tumour growth time after treatment at 42 degrees C. No significant damage of foot skin was caused by 42 degrees C hyperthermia. Pre-treatment with MGBG did not make the foot skin susceptible to the heating. From these findings, it can be considered that MGBG or related less-toxic compounds may have a clinical advantage for the mild (42 degrees C) hyperthermic treatment in cancer therapy.     

Hyperthermia as a teratogen: parameters determining hyperthermia-induced head defects in the rat

This study determined the relationship between the duration and extent of temperature elevation, during a critical period of rat embryonic development, and the induction of congenital malformations. Pregnant Sprague-Dawley rats, at 9 days 12 hours gestation (gastrulation stage), were partially immersed in a water bath until their core temperature, monitored by a rectal thermistor probe, was elevated to a nominated temperature. Seven temperatures were tested from 40.5 degrees C to 43.5 degrees C, elevations of 2.0-5.0 degrees C in core temperature. Various durations at each of these temperatures were tested for potential teratogenicity. A single elevation of 5.0 degrees C or 4.5 degrees C needed only a "spike" in duration to be teratogenic, 4.0 degrees C was teratogenic within 5 minutes, 3.5 degrees C within 10 minutes, 3.0 degrees C within 20 minutes, and 2.5 degrees C within 1 hour. An elevation of 2.0 degrees C for 8 hours was not teratogenic. Microphthalmia was the most common malformation at all teratogenic temperatures and was frequently the only malformation seen at the shortest time exposure for a particular temperature. Encephalocele, facial clefting, and maxillary hypoplasia were the other frequently seen malformations. Five control rats were placed in the water bath for 2 hours at 38 degrees C so that their core temperature was not elevated. All the control fetuses were normal. An elevation of 2.5 degrees C for 1 hour was the threshold combination for teratogenesis. As the temperature increased above a 2.5 degrees C elevation the necessary duration of exposure for teratogenesis decreased.     

Metabolic effects in rats drinking increasing concentrations of sea-water

Research on laboratory rats confirmed that drinking sea-water when dehydrated, was not beneficial and caused impaired renal function. When the concentration of sea-water in the drinking water is gradually increased there is a gradual increase in water uptake and corresponding urine excretion. At 50% sea-water the maximum uptake and excretion is reached. Following this there is a decline in appetite, water uptake and urine secretion. When on 100% sea-water, the creatinine clearances were greater than on tap water, while urine/plasma osmolalities (U/P) averaged 7. The only higher U/P was found in animals drinking sea-water when dehydrated, i.e. a U/P of 11. The urea metabolism appears to be suited to either the need to conserve body water, up to 50% sea-water, or to guarantee an adequate urine production, from 50% sea-water to pure sea-water. It is suggested that when a man is stranded at sea it is not advisable to drink all the fresh water and then be compelled to drink sea-water when dehydrated. It is better to slowly increase the sea-water uptake. This will prolong the time before sea-water needs to be drunk and result in only minor metabolic changes. Return to fresh water will be followed by an immediate return to normal homeostasis.     

Circadian variations in psychophysiological responses to heat exposure and exercise

Ten healthy men were tested at 0600, 1200, 1800 and 2400 hours on different days at rest in a laboratory at room temperature followed by 1 h of heat exposure in a climatic chamber at 42 degrees C, 60% rh (50 min rest and 10 min exercise on a cycle ergometer at 50% VO2max). Heart rate, blood pressure, rectal temperature Tre, metabolic rate, number connection test, visual and auditory reaction time, flicker test and catecholamine excretion were measured. Heat exposure and exercise caused lower heart rate acceleration at 2400 hours than at 0600 and 1200 hours, the smallest increase of Tre at 1800 hours, and an increase in metabolic rate greater at 1200 than at 1800 hours. In the afternoon, when, according to the circadian rhythm, the body temperature is highest, the additional heat load produced the smallest physiological effects. Performance efficiency, after heat exposure combined with physical exercise, improved slightly, but diurnal variations did not show significant circadian rhythm.     

Temperature-dependence of ATP level, organic phosphate production and Na,K-ATPase in human lymphocytes

It was previously shown that human lymphocytes maintain a normal accumulation of K+ and exclusion of Na+ between 37 degrees and 10 degrees C., and a significant net accumulation of K+ and exclusion of Na+ at even lower temperatures. The studies reported here show that the level of ATP is near-normal for at least 24 hours between 37 degrees and 10 degrees C., but that ATP synthesis and utilization are progressively and markedly decreased with decreasing temperatures below 37 degrees C. The activities of the membrane Na+- and K+-activated ATPases have typical marked temperature-dependences. Therefore, the normal accumulation of K+ and exclusion of Na+ between 37 degrees and 10 degrees C., and the normal rate of Na+ efflux at these temperatures, do not correlate with properties of the Na+,K+-ATPase or with rates of synthesis and utilization of ATP.     

Adrenal catecholamine synthesis rate changes induced by combined thermal and immobilization stress in fed and 24 hour fasted rats

The combined stress of acute immobilization (IM) at high and low ambient temperature has been used to determine its influence on adrenal catecholamine (CA) content assassed histofluorimetrically in fed and 24 hour fasted rats. The general course of changes obtained after the arrangement of adrenal strips deriving from the adrenals of rats exposed to cold and IM stress (CIMS) at +10 degrees C to -25 degrees C during the different time fragments presented the adrenal CA depletion events followed sometimes by the adrenal CA content increase after the longer stress exposure or/and stronger CIMS and WIMS conditions. It was found that this depletion-stimulated increase of adrenal Ca synthesis rate had been accelerated in 24 h fasted rats compared to satiated ones exposed to the same stress conditions, especially after the CIMS exposure. Moreover the survival time duration at first lethal temperature (-5 degrees C and +45 degrees C) was significantly higher in fasted rats. The possible hypothalamic regulation of adrenal CA synthesis rate accordingly to the actual metabolism needs and beta-adrenoceptor sensitivity changes depending on satiety state have been discussed and the necessity of further investigations concerning the specificity of stress-induced metabolism changes in 24 h starved rats has been suggested.     

Sea-water tolerance in freshwater-resident arctic charr (Salvelinus alpinus)

• 1.1. Freshwater-resident Arctic charr acclimated for 2 months at 8°C, 15% were divided into four experimental groups in July and exposed to 1 and 8°C in 15 and 34% salinity.
• 2.2. Only slight changes in gill Na-K-ATPase activity, blood plasma osmolality and blood plasma concentrations of Cl⁻ and Mg²⁺ were found for the fish exposed to 1 or 8°C in brackish water.
• 3.3. When exposed to sea-water at 8°C, an increase in osmolality and in concentrations of Cl⁻ and Mg²⁺ took place during the first 2–3 days, after which it levelled off.
• 4.4. If exposed to sea-water at 1°C, however, marked increases were found for all parameters measured and all the fish were dead within 5 days of exposure.
• 5.5. These results show that freshwater-resident Arctic charr—if acclimated to brackish water—can survive in sea-water during summer if the environmental temperature is not too low.

     

Effect of some autonomic drugs on heat defence in the pigeon.

As compared to the time of median control death (i.e. the time inducing 50% death in untreated birds at 50 degrees C), exogenous noradrenaline afforded 100% survival in the blue rock pigeon, Columba livia. The survival percentages with the other autonomic drugs were: chlorpromazine 70%; reserpine 60%; adrenaline 60%; pentolinium 50% and dihydroergotamine 30%. The time of median control death at 50 degrees C was found to be 3.5 hours in the pigeon. During 10-day exposure at 45 degrees C all the birds pre-treated with noradrenaline survived, and 47% of those treated with adrenaline and 42% of the untreated birds survived the stress. It is concluded that noradrenaline acts definitely as a "heat protective" hormone in the pigeon.     

Varying patterns of protein synthesis in bread wheat during heat shock

High temperatures during seedling growth are considered as one of the factors that can modify surviving properties in wheat (Triticum aestivum L.) plant. This work attempts to evaluate the heat shock responses of seedling of winter wheat (Bezostaya-1) using growth parameters (seedling length, embryonal root length and embryonal root number), membrane stability index (MSI) and two dimensional (2D) gel electrophoresis analysis of heat shock proteins (HSPs) during heat shock. Seedlings grown until first leaf opening at controlled conditions (23 degrees C, 200 micromol m(-2) s(-1), 16h day/8h night, 50-60% humidity) were exposed to 37 degrees C or 45 degrees C high temperatures for 2, 4 and 8 hours. While 37 degrees C did not cause any significant change, 45 degrees C heat treatments caused significant decrease in terms of seedling and root length, and leaf MSI for all exposure times. However, all the plants from 45 degrees C heat treatments continued to grow during recovery period. 2D protein analysis indicated that 37 degrees C, 8 hours exposure caused stronger and more diverse heat shock response than the other treatments, followed by 37 degrees C, 4 hours, 45 degrees C, 8 hours, 45 degrees C, 4 hours, 45 degrees C, 2 hours treatments. 5 protein spots, ranging from 6-7.8 pl (isoelectric point) and 27-31.7 kDA molecular weight, were expressed at 37 degrees C, 2 hours and continued at 37 and 45 degrees C for all exposure times. This suggests that these early proteins and other newly synthesized proteins may have protective effects at 37 and 45 degrees C and provide plants for healthy growth during the recovery period.     

Thermal, metabolic, and cardiovascular responses to various degrees of cold stress.

The metabolic, thermal, and cardiovascular responses of two male Caucasians to 1 2 h exposure to ambient temperature ranging between 28 degrees C and 5 degrees C were studied and related to the respective ambient temperatures. The metabolic heat production increased linearly with decreasing ambient temperature, where heat production (kcal times m- minus 2 times h- minus 1) = minus 2.79 Ta degrees C + 103.4, r = -0.97, P smaller than 0.001. During all exposures below 28 degrees C, the rate of decrease in mean skin temperature (Tsk) was found to be an exponential function dependent upon the ambient temperature (Ta) and the time of exposure. Reestablishment of Tsk steady state occurred at 90-120 min of exposure, and the time needed to attain steady state was linearly related to decreasing Ta. The net result was that a constant ratio of 1.5 of the external thermal gradient to the internal thermal gradient was obtained, and at all experimental temperatures, the whole body heat transfer coefficient remained constant. Cardiac output was inversely related to decreasing Ta, where cardiac output (Q) = minus 0.25 Ta degrees C + 14.0, r = minus 0.92, P smaller than 0.01. However, the primary reason for the increased Q, the stroke output, was also described as a third-order polynomial, although the increasing stroke volume throughout the Ta range (28-5 degrees C) was linearly related to decreasing ambients. The non-linear response of this parameter which occurred at 20 degrees C larger than or equal to Ta larger than or equal to 10 degrees C suggested that the organism's cardiac output response was an integration of the depressed heart rate response and the increasing stroke output at these temperatures.     

A laboratory study of the copper and nickel uptake and regulation in a copper-tolerant decapod, Cambarus bartoni (Fabricius) (Decapoda, Crustacea)

Tissue copper concentration in whole Cambarus bartoni, exposed for four weeks to 0.125, 0.25 and 0.5 mg Cu/litre and 0.2, 0.4 and 0.8 mg Ni/litre in the laboratory at 18 degrees C, showed a linear relationship with exposure time at 0.25 and 0.5 mg Cu/litre; the regression slope at 0.5 mg Cu/litre (r2 = 0.218; 0.001 less than P less than or equal to 0.05) was approximately two times higher than that at 0.25 mg Cu/litre (r2 = 0.148; 0.025 less than P less than or equal to 0.05). Regression analysis of nickel concentrations in whole crayfish as a function of exposure time showed a third degree polynomial relationship at 0.4 (y = 49.989 + 14.77x - 15.395x2 + 3.194x3) and 0.8 (y = 52.053 + 37.05x - 28.933x2 + 5.133x3) mg Ni/litre, as well as in the control (y = 49.126 + 27.253x - 23.468x2 + 4.168x3) (y = Ni concentration; x = exposure time in weeks), suggesting the occurrence of a Ni flux every 4 weeks.     

Thermoregulation in chickens subjected to hypoalimentation

Calculation of the body temperature of 4 chickens, 14 days old, submitted during 26 days to a reduced nourishment so that their growing up was stopped. Morning temperature diminished, in comparison with checkings, of 0,78 degrees in the first week, of 1,57 degrees in the second week and of 1,80 degrees in the last days. After 1 and 2 hours of reduced meal, the temperature generally increases 0,76 degrees and 1,39 degrees respectively when chickens are hypo-nourished, while in the checkins it is almost unchanged, +0,02 degrees and +0,07 degrees. 5 hours after the meal, the temperature of hypo-nourished chickens increases 0,24 degrees, in checkings 0,30 degrees. AA thinks that hypotalamic thermoregulating centers always work and that the thermic differences between hypo-nourished and checkings are caused by percentage variations of metabolic substances put in circulation during digestion.     

Osmoregulation of the cane toad, Bufo marinus, in salt water

Adult cane toads, B. marinus, survived in salinities up to 40% sea-water (SW). Pre-exposure to 30, then 40% SW, increased the survival time of toads in 50% SW. Plasma from toads acclimated to salt water is hyperosmotic to the environment--a result of increased plasma sodium, chloride and urea concentrations. When toads were placed in tap-water and 20% SW, all significant changes to plasma sodium, chloride, urea and osmotic pressure occurred within the first 2 days of exposure. When toads were placed in 30 and 40% SW environments, the increases in plasma sodium and chloride concentrations occurred within the first 2 days of exposure while urea and total osmotic pressure continued to rise until some time between 2 and 7 days exposure.