The disruption of sodium balance in brook charr, Salvelinus fontinalis (Mitchill), by manganese and iron

A primary toxic action of manganese to brook charr, Sulvelinusjonfinalis, at concentrations near or above the 96 h LC₅₀ was the disruption of sodium regulation. Body and plasma sodium concentrations of brook charr declined by 52 and 40%, respectively, during exposure to 10.9 mM manganese (in 250 PM CaCI), and all fish died within 36 h. Sodium balance was less severely affected by 2.7 and 5.5 mM manganese. An increase in the external calcium concentration from 0.05 to 1.0 mM raised the LC₅₀ for manganese from 4.9 to 5.8 mM, and a further increase to 2.5 mM calcium almost doubled it to 10.2 mM. An examination of stable manganese uptake by the gills revealed that accumulation was inversely correlated with body sodium concentration (r =−0.77). Radioactive J4Mn entered the bloodstream in low levels and accumulated in the liver. Thus manganese may have systemic effects as well as those attributable to surface binding on the gill. Studies of the mechanism ofdissolved iron toxicity were less conclusive, but it did not appear to involve extensive disruption of sodium balance. There was about a 15% drop in body sodium concentration when the trout were exposed for 48 h to the 96 h LC₅₀ level of iron, but plasma sodium was unaffected. Also, an iron concentration at twice the LC₅₀ did not escalate the loss of body sodium, and increasing the water calcium concentration did not raise the LC₅₀.     

Calcium transport in intact human erthrocytes

Intact human erythrocytes can be readily loaded with calcium by incubation in hypersomotic media at alkaline pH. Erythrocyte calcium content increases from 15-20 to 120-150 nmol/g hemoglobin after incubation for 2 h at 20 degree C in a 400 mosmol/kg, pH 7.8 solution containing 100 mM sodium chloride, 90 mM tetramethylammonium chloride, 1 mM potassium chloride, and 10 mM calcium chloride. Calcium uptake is a time-dependent process that is associated with an augmented efflux of potassium. The ATP content in these cells remains at more than 60% of normal and is not affected by calcium. Calcium uptake is influenced by the cationic composition of the external media. The response to potassium is diphasic. With increasing potassium concentrations, the net accumulation of calcium initially increases, becoming maximal at 1 mM potassium, then diminishes, falling below basal levels at concentrations above 3 mM potassium. Ouabain inhibits the stimulatory effect of low concentrations of potassium. The inhibitory effects of higher concentrations of potassium are ouabain insensitive and independent of the external calcium concentration. Sodium also inhibits calcium uptake but this inhibition can be modified by altering the external concentration of calcium. The effux of calcium from loaded erythrocytes is not significantly altered by changes in osmolality, medium ion composition, or ouabain. It is concluded that hypertonicity increases the net uptake of calcium by increasing the influx of calcium and that some part of the sodium potassium transport system is involved in this influx process.     

Osmoregulatory action of 17beta-estradiol in the gilthead sea bream Sparus auratus

The osmoregulatory action of 17beta-estradiol (E2) was examined in the euryhaline teleost Sparus auratas. In a first set of experiments, fish were injected once with vegetable oil containing E2 (1, 2 and 5 microg/g body weight), transferred 12h after injection from sea water (SW, 38 ppt salinity) to hypersaline water (HSW, 55 ppt) or to brackish water (BW, 5 ppt salinity) and sampled 12h later (i.e. 24 h post-injection). In a second experiment, fish were injected intraperitoneally with coconut oil alone or containing E2 (10 microg/g body weight) and sampled after 5 days. In the same experiment, after 5 days of treatment, fish of each group were transferred to HSW, BW and SW and sampled 4 days later (9 days post-implant). Gill Na+,K+ -ATPase activity, plasma E2 levels, plasma osmolality, and plasma levels of ions (sodium and calcium), glucose, lactate, protein, triglyceride, and hepatosomatic index were examined. Transfer from SW to HSW produced no significant effects on any parameters assessed. E2 treatment did not affect any parameter. Transfer from SW to BW resulted in a significant decrease in plasma osmolality and plasma sodium but did not affect gill Na+,K+ -ATPase activity. A single dose of E2 attenuated the decrease in these parameters after transfer from SW to BW, but was without effect on gill Na+,K+ -ATPase activity. An implant of E2 (10 microg/g body weight) for 5 days significantly increased plasma calcium, hepatosomatic index, plasma metabolic parameters, and gill Na+,K+ -ATPase activity. In coconut oil-implanted (sham) fish, transfer from SW to HSW or BW during 4 days significantly elevated gill Na+,K+ -ATPase. Gill Na+,K+ -ATPase activity remained unaltered after transfer of E2-treated fish to HSW or BW. However, in E2-treated fish transferred from SW to SW (9 days in SW after E2-implant), gill Na+,K+ -ATPase activity decreased with respect to HSW- or BW-transferred fish. Shams transferred to HSW showed increased levels of lactate, protein, and trygliceride in plasma, while those transferred to BW only displayed increased trygliceride levels. E2-treated fish transferred to HSW showed higher protein levels without any change in other plasmatic parameters, while those transferred to BW displayed elevated plasma glucose levels but decreased osmolality and protein levels. These results substantiate a chronic stimulatory action of E2 on gill Na+,K+ -ATPase activity in the euryhaline teleost Sparus auratas.     

Mechanisms of regulation of erythrocyte volume in common carp <Emphasis Type="Italic">Cyprinus carpio</Emphasis> (Cyprinidae) at increase in the osmotic concentration of blood plasma within the zone of critical water salinity

In common carp Cyprinus carpio, acclimated to NaCl content in water of 0–6 g/L, the concentration of sodium in blood plasma was relatively constant (130.8 ± 0.7 mM/L). In the fish acclimated to 6?12 g/L NaCl, which corresponds to critical water salinity, plasma sodium content rose to the maximal value of 205.6 ± 1.3 mM/L. Within the interval of water salinity of 0–6 g/L NaCl, the content of potassium in erythrocytes exhibits a trend to gradual decrease from 104.8 ± 1.6 mM/L to 96 ± 1.5 mM/L. In the zone of critical salinity, potassium content increases exponentially to 130.3 ± 2.9 mM/L. The erythrocytes adapted to the increase in osmotic concentration of plasma by accumulation of potassium ions. According to published data on the studies in vitro, the erythrocytes adapt to hypertonic solutions by means of increase in intracellular sodium concentration. Possible reasons for discrepancy between the results of in vivo and in vitro studies are discussed in the present paper.     

High dietary sodium chloride and body temperature in the domestic fowl and the Glaucous-winged gull

Arad and Skadhauge (1986) correlated plasma sodium to calcium ratio and body temperature in domestic fowl (Gallus domesticus) during increased dietary sodium chloride intake which increased plasma sodium concentration. During acclimation to high dietary NaCl, body temperature should increase in proportion to the increase in plasma sodium concentration, and body temperature should increase less in gulls than in chickens because salt gland secretion of NaCl by gulls should prevent elevation of plasma sodium concentration. Plasma osmolality, plasma sodium concentration, plasma concentrations of total calcium and ionized calcium, and body temperature and panting threshold were measured in domestic roosters and Glaucous-winged gulls before and after exposure to high NaCl diets. Gull body temperature (40.4±0.2 °C) increased significantly (PM0.05) during salt acclimation. Rooster body temperature (41.0±0.2 °C) did not increase significantly. Plasma sodium concentration increased in gulls (5.4±0.5%, P<0.01) and was correlated with body temperature (r=0.497, P<0.05); the 3.8±1.0% increase in plasma sodium concentration in roosters (P<0.01) was not, suggesting that change in body temperature might be a response to the magnitude of increase in plasma sodium concentration. Plasma ionized calcium concentration increased by 12.9±4.6% (P<0.01) in gulls and by 5.3±1.0% (P<0.01) in roosters. Plasma sodium concentration was correlated with calcium ion concentration in both gulls (r=0.635, P<0.05) and roosters (r=0.664, P<0.05). In neither species were ratios of sodium to total calcium plasma concentration or sodium to ionized calcium concentration altered or related to body temperature. Panting threshold increased significantly in roosters following salt acclimation, but not in gulls due to high variability in response. The increase in gull plasma sodium concentration was small compared to previously reported (Saxena 1976; Denbow and Edens 1980, 1981; Maki et al. 1988) increases in hypothalamic and intraventricular sodium concentration following infusion of Na⁺, yet the effect on body temperature was similar in both types of studies. This suggests that sodium may have peripheral effects that augment the central effects imposed by altered hypothalamic interstitial sodium and calcium concentration.Abbreviations [Ca]_p1 total calcium concentration in plasma - [Ca²⁺] ionized calcium concentration in plasma - [Cl]_p1 chloride concentration in plasma - f respiratory frequency - Hct hematocrit - [K]_p1 potassium concentration in plasma - [Na]_p1 sodium concentration in plasma - osm_p1 plasma osmolality - PT panting threshold - T _a ambient temperature - T _b body temperature - V _t tidal volume     

Effects of ingestion of cadmium-polluted rice or low-dose cadmium-supplemented diet on the endogenous metal balance in female rats

The concentrations of endogenous metal ions in liver, kidney, and bone tissues of female rats were measured after ingestion of cadmium-polluted rice (1.24 ppm as Cd) or cadmium-supplemented rice (1.24 and 4.96 ppm) for 2 or 4 mo. The metal accumulated mainly in the kidneys and in the liver. The concentration of cadmium (Cd) in the kidneys of rats fed a 1.24-ppm Cd-supplemented diet was significantly higher than in the Cd-polluted rice group. After 2 mo, the levels of iron and sodium in the liver were elevated in the Cd-polluted rice group, but not in the 1.24-ppm Cd-supplemented group, as compared to controls. The zinc concentration in the Cd-polluted rice group was decreased. The concentration of copper in the kidneys was increased for all Cd-containing diet groups. After 4 mo, the effects of Cd on essential metals in the Cd-polluted and 1.24-ppm Cd-supplemented groups had almost disappeared, although several metal ions in selected organs in the 4.96-ppm Cd-supplemented group showed more prominent changes than in the group exposed for 2 mo. These results suggest that the effects of short-term exposure to Cd on essential metal balance are stronger for rice-bound Cd than for inorganic Cd, although the absorption rate of Cd in Cd-polluted rice may be lower than that of cadmium chloride added to rice.     

The decrement of carcinogenesis by dietary selenium and expression of placental form of glutathione-S-transferase in rat glioma

Supranutrition dietary levels of the element selenium (Se) that have been shown to reduce or retard tumor development resulting from transplantation. The rat placental form of glutathione-S-transferase (GST-p) has been reported to be a good marker for preneoplastic or neoplastic lesions. Four groups of rats with glioma were exposed to Se-free, 0.05, 2.0, and 4.0 ppm sodium selenite GST-p was investigated. Normal brain tissue did not differ significantly in all groups. In contrast, GST-p in tumor was significantly higher in Se-free and 4.0-ppm groups compared to 0.5- and 2.0-ppm groups. The concentration of Se in normal brain tissue did not differ significantly in Se-supplement groups. By contrast, Se in tumors was significantly higher in the 0.5- and 2.0-ppm groups compared to the Se-free and 4.0-ppm groups. Mean group survival at 30 d after treatment was determined and compared with previous dietary Se. Survival was significantly longer in the 0.5- and 2.0-ppm groups than in the Se-free and 4.0-ppm groups. The 2.0-ppm group had enhanced survival, similar to the 0.5-ppm group. The Se-free and 4.0-ppm groups might have no protection against carcinogenesis.     

Differential effect of extracellular calcium on the Na(+)-K+ pump activity in intact polymorphonuclear leucocytes and erythrocytes

The effect of extracellular calcium on the Na(+)-K+ pump activity in human polymorphonuclear leucocytes and erythrocytes was studied and compared with the activity in mixed peritoneal leucocytes from rats. While there was maximal decrease in the pump activity (25-30%) of leucocytes from both rat and human by calcium 0.6 mM, a concentration of 0.1 mM caused a substantial decrease indicating a high sensitivity for extracellular calcium. In contrast, calcium had no effect on the pump activity in erythrocytes. The effect of calcium on the pump activity in leucocytes may be due to regulation of the influx of sodium across the plasma membrane, since in human leucocytes calcium had no effect on the pump activity if the cells were loaded with sodium.     

Interactions of dietary lead with fish oil and antioxidant in chicks

Two experiments were conducted with day-old broiler chicks reared to 18 or 19 d of age. The objectives were: (1) to examine the effects of the antioxidant ethoxyquin (EQ) on peroxidation in feeds containing fish oil (FO) or lead (Pb), and (2) to determine whether systemic effects of Pb, which are attributed to tissue peroxidation, can be reversed by dietary EQ. Experiment 1 was a 2 x 2 factorial arrangement with the factors being 4% dietary cottonseed oil (CSO) vs FO and dietary Pb as lead acetate trihydrate (0 vs 1000 ppm). Feed was mixed 1 d prior to initiation of the experiment and stored at 4 degrees C until it was placed in the feeders. Experiment 2 was a 2 x 2 x 2 factorial arrangement with the factors being 3.5% dietary oil (CSO vs FO), dietary Pb (0 vs 1000 ppm), and EQ (0 vs 75 ppm). Feed was mixed 1 d prior to initiation of the experiment and held at room temperature thereafter. Growth depression by FO and Pb was less pronounced in Experiment 1 than in Experiment 2. In Experiment 2, FO and Pb increased the concentration of feed peroxide, and the increases were prevented by EQ. The growth depression by FO was completely reversed by EQ. EQ reversal of Pb-induced growth depression, although substantial, was not complete. The FO diet without Pb had a peroxide content (12.4 meq/kg feed) similar to the CSO + Pb diet (12.3 meq/kg feed); however, growth was not similar (407 vs 213 g body weight at 19 d, respectively). The results suggest that the toxic effects of Pb are mediated by peroxidative alterations both in the feed and in tissues. The ability of EQ to reverse significantly Pb effects on growth suggests a systemic action of this antioxidant.     

Selenium-mediated biochemical changes in Japanese quails

The effect of selenium (Se) on collagen characteristics and glutathione peroxidase (GSH-Px) activity in the skin of Japanese quailsCoturnix coturnix japonica fed a formulated, semipurified, low-Se diet (basal) (0.05 ppm) was investigated. The quails exhibited severe Se-deficiency symptoms and significant reduction in skin GSH-Px activity at the end of 30 d. Selenium supplementation at a 2-ppm level restored the normal skin conditions and enhanced skin GSH-Px activity significantly. But a dietary Se level of 0.1 ppm was found to be inadequate in restoring the general skin conditions and GSH-Px activity. A markedly low total collagen content of about 23% was observed in the skin of quails fed the basal diet, compared to 39% of total collagen content in the skin of the 2-ppm Se-supplemented group. Molecular organization of skin collagen of quails on the basal and 0.1-ppm Se diet showed an abundance of monomeric forms with less crosslinks, compared to the presence of polymeric forms with more crosslinks, indicating enhanced stability in the skin collagen of quails on the 2-ppm diet. The delay in the in vitro fibril formation of collagen from the basal and 0.1-ppm Se groups, compared to a relatively faster rate in the case of the 2-ppm Se group, indicates a disturbance in the aggregation phenomenon of collagen. The increase in skin GSH-Px activity and concurrent increase in polymeric collagen on increasing the dietary Se level suggest a possible role for Se in collagen metabolism.     

Endocrine, osmoregulatory, respiratory and haematological parameters in flounder exposed to the water soluble fraction of crude oil

Flounders Pleuronectes flesus with an implanted vascular catheter were exposed to a 50% dilution of the water soluble fraction (WSF) of Omani crude oil (c. 6ppm total aromatic hydrocarbons) and serial blood samples taken to determine their endocrine status (cortisol, catecholamines and thyroid hormones) and the resultant and/or causal physiological (haematological, ionoregulatory and respiratory) disturbances. This resulted in a progressive increase in plasma cortisol concentrations from 3 h onwards (rising from 18 to 51 ng ml⁻¹ after 48-h exposure), and increased plasma glucose concentrations indicating a generalized stress response. Plasma T3 and T4 concentrations of both control and WSF-exposed groups declined progressively over the experimental period; exposure to the WSF of crude oil further depressed plasma T4 concentrations but not plasma T₃ concentrations relative to those of control fish. Plasma osmolality and sodium and chloride concentrations were stable in WSF-exposed fish, however, plasma potassium concentrations were increased significantly at the 24-and 48-h sampling points. The most profound physiological disturbance in WSF-exposed fish was a dramatic decline in blood oxygen content (CvO₂) (from 2–8 to 0–8 ml 100 ml⁻¹ after 48-h exposure), which is likely to be the cause of the increased plasma noradrenaline concentrations from 3 h onwards. Increased noradrenaline is likely in turn to have been responsible for the significant increase in blood haematocrit and blood haemoglobin at the 3-h sampling point, although the dominant effect in the longer-term was a significant decline in both of these haematological parameters.     

Effect of ethanol on serum electrolytes and osmolality

Rats and rabbits were injected ethanol 2 g/kg intraperitoneally. One hour after injection blood was analyzed for serum electrolytes and osmolality. Administration of ethanol caused decrease in serum sodium (p less than 0.0005), potassium (p less than 0.0005), calcium (p less than 0.0005), chloride (p less than 0.005), magnesium (p less than 0.0005) in rabbits. Further studies of intraperitoneal administration of ethanol in rats showed decrease in concentration of sodium (p less than 0.025), potassium (p less than 0.025), calcium (p less than 0.01) chloride (p less than 0.005) magnesium (p less than 0.005), phosphorus (p less than 0.025) and glucose (p less than 0.005). Administration of ethanol caused an increase in serum osmolality in both rabbits and rats (p less than 0.005, p less than 0.05). It is concluded that ethanol ingestion is probably the commonest cause of the hyperosmolar state. Although the osmotic and sedative effects of ethanol are pharmacologically unrelated, the presence of ethanol should be considered in comatose patients in whom the measured plasma osmolality appreciably exceeds that predicted on the basis of plasma glucose, urea and electrolytes concentration.     

X-ray microanalysis of elemental changes in human parathyroid glands in primary and secondary hyperparathyroidism

The elemental composition of chief cells of parathyroid glands from patients with adenomatous primary hyperparathyroidism (HPT) and uremic secondary HPT was studied by X-ray microanalysis. Glands histologically deemed normal were used as controls. The analyses were also carried out on tissue specimens incubated in hypo-, normo- and hypercalcemic media (0.5, 1.25, and 3.0 mM calcium concentration). Analysis of chief cells from normal glands did not reveal any significant differences in ionic composition after exposure to the different calcium concentrations. In chief cells from adenomatous and uremic hyperplastic glands, elemental changes were noted. In comparison with specimens incubated in 1.25 mM calcium medium, cells in 0.5 mM calcium medium had a lower content of potassium and phosphorus. After stimulation with increasing extracellular concentration, an increase in the K/Na ratio was observed, due to a marked decrease of sodium and an increase of potassium: the calcium concentration was almost unchanged. Our findings indicate that in HPT an increase in serum calcium concentration might exert a stimulatory effect on the Na/K pump (sodium pump) and on the calcium-activated potassium channels. Either of these mechanisms might contribute to a lowering of cytoplasmic calcium. Our observations suggest that changes in ionic content of the parathyroid cells may be of importance for the stimulus secretion process in the cells.     

Effect of blood withdrawal and angiotensin II on prolactin release in the tilapia,Oreochromis mossambicus

Repeated blood withdrawal (5% of estimated blood volume at 0, 1, 4, 8, 24, 48 and 76 h) from tilapia acclimated to fresh water (FW) resulted in a marked increase in plasma levels of prolactin (PRL) during the first 8 h, reaching a peak above 300 ng/ml after 4 h. The increase in plasma PRL levels was significant except for the level after 72 h. A slight but significant decrease in plasma osmolality was observed at all time points after the blood withdrawal. Repeated blood withdrawal from fish acclimated to seawater (SW) resulted in a marked increase in plasma osmolality after 4 and 8 h. A significant increase was observed in plasma growth hormone (GH) in the fish in SW until the end of the experiment, but there was no change in plasma PRL. Plasma levels of cortisol were significantly higher in the fish in SW than in those in FW during the first 24 h. Blood withdrawal resulted in a significant reduction in hematocrit values in both FW- and SW-adapted fish, suggesting hemodilution. In a separate experiment, a single blood withdrawal (20% of total blood) stimulated drinking after 5 h, regardless of whether the fish were held in FW or SW. Plasma PRL level was also elevated following a single blood withdrawal in the fish acclimated to FW, but not in the fish in SW. Intraperitoneal injection of ANG II (1.0 microg/g) into the fish in FW significantly increased plasma PRL levels after 1 h. Activation of the renin-angiotensin system after blood withdrawal and the dipsogenic action of angiotensin II (ANG II) are well established in fish. The reduction in plasma osmolality after repeated blood withdrawal in FW and the increased osmolality in SW suggest that blood volume is restored, at least in part, by drinking environmental water. These results suggest that the marked increase in PRL concentration after blood withdrawal from the fish in FW is due, at least in part, to a facilitative effect between ANG II and reduced plasma osmolality.     

Response of prolactin cells to environmental calcium in the eel (Anguilla anguilla L.)

Prolactin (PRL) cell activity was investigated in eels kept in fresh water (FW), deionized water (DW) supplemented or not with Ca (2 mM), in Ca-enriched FW (10 mM), in normal (Ca 3.4 mM) or Ca-free 1/3 sea water (SW), and in SW (Ca 10.2 mM) or Ca-free SW (Ca 0.15 mM). Light-microscopic studies, including measurement of the nuclear area and cell height, showed that PRL cell activity, reduced in DW, is not affected by Ca supplementation. Activity is reduced in Ca-enriched FW, in 1/3 SW and in SW, conditions inducing an increase in the plasma sodium level. The lack of calcium in saline environments partly suppresses the nuclear atrophy occurring in SW. There is no significant correlation between external or total plasma calcium concentration and PRL cell activity. In artificial Ca-free SW, eels show a rapid increase in plasma osmolarity and sodium levels; there is a significant negative correlation between these two plasma values and the nuclear area or cell height of PRL cells. As in some other teleosts, plasma osmolarity and plasma sodium seem to play a more important role than external or internal calcium in controlling PRL secretion. This correlation is not apparent in eels kept in SW, having unstimulated PRL cells but active calcium-sensitive (Ca-s) cells in the pars intermedia.     

The effect of intravenous hypertonic saline infusion on renal function and vasopressin excretion in sheep.

Conscious Merino ewes were given an intravenous hypertonic sodium chloride load of 4 mmol.min-1 for 100 min. This resulted in increases in urine flow, sodium and potassium excretion and plasma sodium concentration and osmolality. Urinary vasopressin output and solute-free water reabsorption increased and plasma renin activity declined. Renal plasma flow and glomerular filtration rate (GFR) rose, as did the solute clearance. The change in urinary osmolality was related to the initial urine osmolality such that when the initial urine osmolality was high the urine became more dilute, and vice versa. Tubular sodium reabsorption increased but the fractional reabsorption rate fell. It is suggested that the increase in GFR was at least partly due to the increase in AVP and that the electrolyte loss can be accounted for by the increase in GFR without necessarily involving AVP or other hormonal effects at the tubular level.     

Osmoregulation and muscle water control of the Amazon fish Oscar Astronotus ocellatus (Cichlidae) when facing salinity stress

Specimens of Oscar Astronotus ocellatus from a fish farm were abruptly submitted to salt stress of 14 ppt and 20 ppt, for 3 and 8 h to determine their plasma osmolality. Muscle wet body mass change in vitro was analyzed from control freshwater animals. Fish in 14 ppt presented no osmolality distress even after 8 h. In 20 ppt, a slight increase (10%) in plasma osmolality was observed for both times of exposure when compared to control fish. Muscle slices submitted in vitro to hyper-osmotic saline displayed decreased body mass after 75 min, and slices submitted to hypo-osmotic saline displayed increased body mass after 45 min when compared to control (isosmotic saline). These results reinforce A. ocellatus’s euryhalinity. The fish were able to regulate its internal medium and tolerate 14 ppt, but presented an intense osmotic challenge and low muscle hydration control when facing salinities of 20 ppt.     

Short-term physiological changes in turbot and seabream juveniles exposed to exogenous ammonia

Seabream and turbot juveniles (40-520 g) were exposed to constant exogenous NH5-N concentrations (1.27-4.27 mmol/l; pH, 8.15). In 96 hr acclimated fish, plasma TA-N (total ammonia nitrogen) contents were positively correlated to ambient ammonia concentrations. The LD50 were 2.2-2.5 mmol/l TA-N in both species. There were no marked osmoregulatory disturbances and plasma urea-N, thyroid hormones levels and gill (Na-K)-ATPase activities were only affected at the highest concentrations. Liver GOT, GPT and GIDH activity dose-response were low and species dependent. In cannulated and non-cannulated turbot exposed to half 96 hr LC50 (lethal ambient concentration for 50% of the population), there was a rapid, pronounced and prolonged increase in plasma TA-N, followed by an immediate decline when exogenous ammonia supply was stopped. Maximum loading and unloading were observed within 1-3 hr. Plasma cortisol levels indicated a stressful situation in exposed fish (150 ng/ml) and a quick recovery capacity. In dose and time response experiments, the most relevant physiological indicator of ammonia stress was blood TA-N content. Other parameters tested led either to transient or low amplitude responses except when fish approached death.     

Semen of Perca fluviatilis L.: sperm volume and density, seminal plasma indices and effects of dilution ratio, ions and osmolality on sperm motility

The objectives of the present study were to characterize sperm volume and density, seminal plasma indices (ionic contents and osmolality) and to study the effects of dilution ratio, ions and osmolality on sperm motility parameters (percentage of motile sperm and sperm velocity) in farmed European perch (Perca fluviatilis L.). The means of sperm volume (ml), sperm density (x10(9)spermml(-1)) and total number of sperm (volumexdensity) per fish were 2.75+/-0.51, 29.19+/-3.15 and 82.19+/-15.26. The seminal plasma osmolality (mOsmkg(-1)), sodium, chloride, potassium and calcium ions concentrations (mM) were measured to be 298.07+/-5.09, 130.97+/-2.19, 106.75+/-2.37, 10.70+/-0.61 and 2.41+/-0.09, respectively. At 15s post-activation of stripped sperm, the percentage of motile sperm (%) and sperm velocity (mums(-1)) were 91.90+/-1.27 and 115.54+/-1.25, respectively, and decreased significantly following sperm activation (P<0.05). The optimal sperm motility was observed when the sperm was prediluted in immobilizing solution (IS) at a ratio 1:50. Prediluted sperm showed the maximum velocity when activated in 2.5mM Ca(2+), 50mM K(+) and sucrose with osmolality 100mOsmkg(-1). Neither Ca(2+) nor K(+) showed a significant effect on the percentage of motile sperm at 15s post-activation. Osmolality higher than 200mOsmkg(-1) significantly decreased the percentage of motile sperm, while osmolality of 300mOsmkg(-1) or above totally suppressed sperm motility.     

The distribution of zinc and copper in plasma, erythrocytes and erythrocyte membranes of rainbow trout (Salmo gairdneri)

1. The zinc and copper concentration of plasma was determined in rainbow trout, lake trout, walleye and whitefish. 2. These fish had mean plasma zinc concentrations ranging from 9.3 to 15.1 ppm and copper concentrations from 0.6 to 1.3 ppm. 3. In rainbow trout, the concentration of zinc and copper is greater in the erythrocyte membrane than in the total erythrocyte. 4. Ultrafilterable plasma zinc and copper concentration in rainbow trout was determined to be 0.03 and 0.019 ppm, respectively. 5. Dialysis of rainbow trout plasma against 20 mM EDTA results in removal of 99% of the zinc and 88% of the copper from plasma proteins.