Blood Plasma Osmolality Research Articles

Seawater tolerance in first-time migrants of anadromous Arctic charr (Salvelinus alpinus)

Anadromous juvenile Arctic charr (Salvelinus alpinus) were caught in the Sila River (66°21′N, 13°10′E, Nordland County, Norway) by use of a fish trap during their migration towards the sea in May/June. The absence of tags (not captured before) and examination of otoliths from sacrificed fish revealed that none of the experimental charr had previously encountered seawater. During 4 days of exposure to seawater, only minor changes in blood plasma osmolality, and blood plasma concentrations of Na+, Cl– and Mg2+ were detected. An increase in Na+-K+-ATPase activity was measured during the exposure period. These results verified that first-time migrants exhibit hypoosmoregulatory capacity similar to that of smoltified Atlantic salmon (Salmo salar). Accordingly, the Arctic charr first-time migratory behaviour, including late descent and a possible stay within an estuary, cannot be taken as evidence of a poorly developed seawater tolerance.

The physiological response to capture and handling stress in the Atlantic sharpnose shark, Rhizoprionodon terraenovae

Secondary effects of capture and handling stress in the Atlantic sharpnose shark, Rhizoprionodon terraenovae, were investigated in this study. Twenty-four sharks were serially bled and changes in several hematological parameters were monitored over a 1-h time period, following capture by hook-and-line. Blood samples were obtained from each shark at 0, 15, 30, 45 and 60 min. All 0-min (initial) blood samples were obtained within 3 min of capture. Blood glucose (9.2–13.1 mmol l−1), lactate (1.5–28.9 mmol l−1), and plasma osmolality (871–929 mOsm kg−1) all increased after capture, whereas blood pH (6.86–6.78) declined. Hematocrit values (initial = 25.1%) remained unchanged throughout the 1-h stress period. Due to the short amount of time it took to obtain the initial sample and the lack of a significant relationship between the initial time and the initial parameter levels, all initial samples are considered the best approximation of the predisturbance resting levels. The use of repeated measures in this study enables us to describe the dynamics of the secondary stress response in the Atlantic sharpnose shark.

Problems and solutions for artificial kidney

The uremic syndrome is the prototype of a slowly progressive endogenous intoxication, when a detoxifying organ (in this case the kidney) fails. It is characterized by the gradual retention of a host of metabolites, which is in part corrected by dialysis, allowing survival with an acceptable quality of life. This paper reviews the main problems of hemodialysis today, and possible solutions. Adequacy of dialysis is estimated currently from the concentration of urea, which is used as a marker molecule. The problem is that urea is not really toxic by itself. Other markers with known toxicity, such as middle molecules (300-12,000 D) and protein bound compounds should be considered. The question then arises whether the classical dialytic concept based on diffusion should be modified. Adsorptive systems may be strong binders of protein bound solutes. Other concepts that are now arising, and that may add to toxin removal, are slow and daily dialysis. Another question that could be raised is whether it would not be possible to support toxin removal, by administering peroral sorbants. Dialysis patients are prone to vascular disease and die early from cardio-vascular complications. One of the solutions for this problem could be to bring the blood of dialyzed patients into contact with antioxidants (e.g. vitamin C or E). The risk for perdialytic hemodynamic instability is increased in many dialysis patients. The ideal solution would be to develop an "intelligent" dialysis system, whereby blood volume and plasma osmolality are sensed continuously, and ultrafiltration and dialysate sodium concentration are adapted in function of this evolution. An adequate vascular access is indispensable to perform adequate dialysis, but thrombotic/stenotic complications are frequent. This could be prevented by molecular biological modification of vascular grafts, whereby genetic information is entered into the cells, blocking the natural chain of events that otherwise unavoidably leads to neointimal hyperplasia and atherosclerosis. Another old dream is to develop a wearable artificial kidney, whereby patients can move around, and be treated 24 hours per 24 hours, in stead of being treated intermittently at a specific location by the dialysis machine. According to some authors, part of the natural renal function could be replaced by cultured renal tubular cells, which are brought in contact with the blood of the patients. It is concluded that thrilling improvements lie ahead in the future, but the following questions arise: 1) What is the cost of all these improvements? 2) Will it remain possible to reimburse all this? 3) What is going to happen in transplantation, mainly regarding improvements in immunosuppression and the development of xenotransplantation?

Vasopressin V1a receptor antagonism does not reverse adrenocorticotrophin-induced hypertension in the rat.

1. The role of arginine vasopressin (AVP) was examined in adrenocorticotrophin (ACTH)-induced hypertension in Sprague-Dawley rats using the non-peptide AVP V1a receptor antagonist OPC 21268. 2. In an acute study, six rats were pretreated with ACTH for 11 days and direct arterial blood pressure (4 h), plasma osmolality and electrolyte concentrations were measured after OPC 21268 gavage. In a chronic study, 40 rats were randomly divided into four groups: (i) sham injection + sham gavage; (ii) ACTH + sham gavage; (iii) sham injection + OPC 21268; or (iv) ACTH + OPC-21268 for 16 days. Systolic blood pressure (SBP), water intake, urine volume (UV), urine osmolality and electrolytes, food intake, bodyweight and plasma osmolality and electrolyte concentrations were measured. 3. In the acute study, direct mean arterial blood pressure did not change with OPC 21268 (122+/-2 and 120+/-3 mmHg at 0 and 240 min, respectively). 4. In the chronic study, OPC 21268 did not affect ACTH-induced rises in blood pressure (from 125+/-2 (control) to 145+/-5 mmHg (group 4) compared with 122+/-3 (control) to 149+/-5 mmHg (group2)). Water intake and UV increased (from 29+/-2 to 83+/-6 mL/day; and from 5+/-1 to 36+/-5 mL/day, respectively) and the change in bodyweight decreased from 0+/-2 to -107+/-7 g. 5. These results suggest that AVP (at the V1a receptor) does not play a significant role in the maintenance of ACTH-induced hypertension.

Effects of anesthesia, surgery, and intravenous administration of fluids on plasma antidiuretic hormone concentrations in healthy dogs.

To evaluate effects of anesthesia, surgery, and intravenous administration of fluids on plasma concentrations of antidiuretic hormone (ADH), concentration of total solids (TS), PCV, arterial blood pressure (BP), plasma osmolality, and urine output in healthy dogs. 22 healthy Beagles. 11 dogs did not receive fluids, and 11 received 20 ml of lactated Ringer's solution/kg of body weight/h. Plasma ADH adn TS concentrations, PCV, osmolality, and arterial BP were measured before anesthesia (T0) and after administration of preanesthetic agents (T1), induction of anesthesia (T2), and 1 and 2 hours of surgery (T3 and T4, respectively). Urine output was measured at T3 and T4. ADH concentrations increased at T1, T3, and T4, compared with concentrations at T0. Concentration of TS and PCV decreased at all times after administration of preanesthetic drugs. Plasma ADH concentration was less at T3 in dogs that received fluids, compared with those that did not. Blood pressure did not differ between groups, and osmolality did not increase > 1% from To value at any time. At T4, rate of urine production was less in dogs that did not receive fluids, compared with those that did. Plasma ADH concentration increased and PCV and TS concentration decreased in response to anesthesia and surgery. Intravenous administration of fluids resulted in increased urine output but had no effect on ADH concentration or arterial BP. The causes and effects of increased plasma ADH concentrations may affect efficacious administration of fluids during the perioperative period in dogs.

Acute Responses to Salinity for Sunshine Bass and Palmetto Bass

Abstract Differences in salinity tolerance and osmoregulatory performance between sunshine bass (white bass Morone chrysops ♀ × striped bass M. saxatilis ♂) and palmetto bass (striped bass ♀ × white bass ♂) were evaluated by using direct-transfer toxicity testing and monitoring of plasma osmolality during salinity elevation. The 24-h LC50 (concentration lethal for 50% of test animals) for sunshine bass was a salinity of 27.9‰ with a 95% lower and upper confidence interval (CI) of 24.5‰ to 36.2‰. The 24-h LC50 for palmetto bass was 28.0‰ with a 95% CI of 26.2‰ to 30.8‰. Test temperatures during this interval ranged from 19.6°C to 21.7°C, and the LC50 values for both crosses did not differ significantly. Differences in osmoregulatory performance were determined by sampling blood plasma osmolality (mmol/kg) during a stepwise elevation in salinity from freshwater to 52‰. Plasma osmolality of sunshine bass was significantly higher at 11‰, but osmolality of palmetto bass was higher at 41‰ and 52‰. Sunshine bass...

Comparative study on the regulation of body fluids and mammary circulation at different stages of lactation in crossbred Holstein cattle feeding on different types of roughage

SummaryThe present study was carried out to evaluate the effect of prolonged feeding of urea‐treated rice straw, compared with feeding of hay, on the regulation of body fluids, milk yield and mammary circulation at early lactation (30 days postpartum), mid‐lactation (120 days postpartum) and late lactation (210 days postpartum) in crossbred Holstein Friesians. Sixteen first lactating crossbred Holstein Friesians (HF), consisting of eight animals of two breed types, 87.5%HF and 50%HF, were selected and each breed was randomly allocated into two groups. Each group, consisting of four animals from the same breed, was fed either 5% urea‐treated rice straw or pangola hay (Digitaria decumbens) as the source of roughage in combination with a similar concentrate throughout the experiments. During the course of lactation there were no significant differences in body weight, heart rate, mean arterial blood pressure, plasma osmolality, plasma volume and blood volume among groups of 87.5%HF animals and 50%HF animals fed either hay or urea‐treated rice straw. Water turnover rate, total body water space and total body water as a percentage of body weight of 50%HF animals were significantly higher than those of 87.5%HF animals fed either hay or urea‐treated rice straw. The packed cell volume was significantly higher in all lactating periods of both groups of 50%HF animals in comparison with 87.5%HF animals. The ratio of DM intake to milk production for 87.5%HF animals fed either hay or urea‐treated rice straw was significantly lower than that of 50%HF animals in early lactation. The udder blood flow and milk secretion of 87.5%HF were significantly higher in early lactation and markedly declined when lactation advanced in comparison with those of 50%HF animals fed either hay or urea‐treated rice straw. The ratio of mammary blood flow to milk yield for all groups was in a similar range during early lactation although it significantly increased in mid‐ and late lactation for both groups of 87.5%HF animals. From these results it can be concluded that both 50%HF and 87.5%HF animals feeding on urea‐treated rice straw as a roughage source do not show any undernutritional effects in comparison with those fed with hay during the course of lactation. The physiological response differences between breeds are that 87.5%HF animals, which have a genetic makeup closer to the exotic bos taurus breed and a high milk yield, show a poor adjustment to the tropical environment and poorer lactation persistency in comparison with 50%HF animals.

Interaction between AVP and sympathetic system in subtotal nephrectomy-saline hypertension: role of α and V 1 receptors

The development process of subtotal nephrectomy-salt hypertension is still unclear. The aim of the present study was to determine the role of the interaction between vasopressin and sympathetic system in the development of this hypertension by using AVP V 1 antagonist and α blocker phentolamine under anesthesia condition. For this purpose, we carried out about 73% subtotal nephrectomy on male Wistar rats. One group of these rats (normotensive group) was given a low-salt diet and the other group (hypertensive group) was given a high-salt diet for 4 weeks. Finally, eight groups of rats were formed according to the kind(s) of the injected drug(s): (1) normotensive and hypertensive groups injected only V 1 antagonist, (2) normotensive and hypertensive groups injected only phentolamine, (3) normotensive and hypertensive groups injected first V 1 antagonist and then phentolamine, (4) normotensive and hypertensive groups injected first phentolamine and then V 1 antagonist. Either V 1 or α blockage separately led to a higher reduction in the mean blood pressure (MAP) of the hypertensives than, of the normotensives ( p<0.05). The combined blockage of V 1 and α receptors, also caused a higher decrease in the MAP of hypertensive group than, of normotensive group, not depending on the order of the injections ( p<0.01). The heart rate increase recorded as a response to the phentolamine injection in normotensive group, did not develop in hypertensive group ( p<0.05). There was no significant difference between the two groups with regard to plasma electrolytes and osmolality. A positive correlation was found between systolic blood pressure and plasma osmolality in hypertensive group ( r=0.40, p<0.05), but not in normotensive group. We conclude that the increase in V 1 and α pressor activities contributes to the subtotal nephrectomy-saline hypertension and the augmentation of α pressor activity by vasopressin may participate in this contribution.

Distended, water‐filled stomach in seawater farmed rainbow trout, Oncorhynchus mykiss (Walbaum), provoked experimentally by osmoregulatory stress

The present study evaluates if abdominal dis‐tension caused by a water‐filled stomach in seawater farmed rainbow trout, Oncorhynchus mykiss (Walbaum), and Atlantic salmon, Salmo salar L., could be provoked experimentally by live chilling in sea water (0.5 °C). Fifty rainbow trout and 50 salmon were visually classified, either as normal or suffering from the condition. Prior to chilling, no rainbow trout or salmon suffered from a water‐filled stomach. During chilling, 25% of the rainbow trout and 2.5% of the salmon developed water‐filled stomach. Affected rainbow trout had significantly higher blood plasma osmolality and significantly lower body weight than normal trout. The frequency of trout with a water‐filled stomach increased significantly with increasing chilling time and increasing plasma osmolality. The regression coefficients revealed that the proportion of affected rainbow trout in‐creased by 0.82% h−1 of chilling and by 0.46% per unit increase in mosmol L−1. The present study revealed that abdominal distension in seawater farmed rainbow trout was far more severe than in Atlantic salmon and could be provoked experimentally by osmoregulatory stress. This is consistent with the observation that water‐filled stomach appear only occasionally in seawater farmed Atlantic salmon.

Chronic animal health assessment during axial ventricular assistance: importance of hemorheologic parameters.

Chronic testing of the Nimbus/UOP Axial Flow Pump was performed on 22 calves for periods of implantation ranging from 27 to 226 days (average, 74 days). The following parameters were measured: plasma free hemoglobin, blood and plasma viscosity, erythrocyte deformability and mechanical fragility, oxygen delivery index (ODI), blood cell counts, hematocrit, hemoglobin, blood urea nitrogen, creatinine, bilirubin, total protein, fibrinogen, and plasma osmolality. Most of the above parameters were stable during the full course of support. Compared with baseline, statistically significant differences during the entire period of implantation were only found in: hematocrit (p<0.001), hemoglobin (p<0.005), red blood cell (RBC) count (p<0.001), and whole blood viscosity (p<0.01). Plasma viscosity and ODI were mostly stable during the period of implantation. In some animals, an acute increase in fibrinogen concentration, plasma and blood viscosity, and a decrease in ODI were found to be early signs of the onset of infection. A small (10%) decrease in deformability of RBCs was found during the first 2 weeks after implantation. This alteration in RBC deformability was highly correlated (r = 0.793) with changes in total plasma protein concentration that fell more than 15% (p<0.001) during the same period. Mechanical fragility of RBCs was found to be slightly increased after implantation. Plasma free hemoglobin remained close to baseline level (p>0.2). After the first 2 weeks of the postoperative period, pump performing parameters for all animals were consistent and stable. In general, the Nimbus/UOP Axial Flow Pump demonstrated basic reliability and biocompatibility and did not produce significant alterations in the mechanical properties of blood or animal health status. The pump provided adequate hemodynamics and was well tolerated by the experimental animal for periods as long as 7.5 months. Monitoring rheologic parameters of blood is very helpful for evaluation of health during heart-assist device application.

Effects of Feed and Water Intakes on Whole Blood Viscosity and Plasma Osmolality in Broiler Chickens.

Two experiments were carried out to determine the effect of feed and water intakes on whole blood viscosity in broiler chickens. In experiment 1, three feeding levels (25, 50 and 75g/bird) were provided to three groups of birds at 08.00h, respectively. After feeding, each bird was allowed to drink 100ml water at 09.00h. In experiment 2, two levels of water (50 and 150ml/bird) were given to two group birds, after 50g/bird feed was taken, at 09.00h. WBV and plasma osmolality (PO) increased with the increase of feed intake, and decreased with time after feeding. However, in 25g feed intake birds, PO increased with time after feeding. Plasma protein concentration (PPC) was (P<0.05) higher at 50 and 75g than at 25g feeding level. No significant differences were found in haematocrit (HCT) and plasma viscosity (PV) between feeding levels. There was no significant difference in PPC, HCT or PV between the two drinking levels. PO had a significantly (P<0.05) lower value at 150ml compared to at 50ml at 09.30h, although no significant difference was found in WBV. Moreover, WBV and PO tended to decrease with time at 50ml, while to increase at 150ml. As described above, WBV and PO increased with the increase of feed intake, but their changes with time after feeding were related to a water/feed ratio.

Summer seawater tolerance of small-sized Arctic charr, Salvelinus alpinus , on Svalbard

Migrating Arctic charr (Salvelinus alpinus) parr (118 ± 34.4 mm) were caught close to the rivermouth of the Dieset river on Spitsbergen (79°10′N), Svalbard. When subjected to a seawater tolerance test (34 ppt at 6°C) their blood plasma osmolality and sodium and magnesium concentrations increased significantly. After 90 h of exposure, average plasma osmolality was 410 (±54.1) mOsmol. Corresponding sodium and magnesium concentrations were 207 (±35.9) mmol l−1 and 2.7 (±1.36) mmol l−1, respectively. Survival at this time was only 12.5%. When smaller fish (96 ± 26.6 mm) were exposed to seawater, mortality was 100% within 72 h. We conclude that small-sized Svalbard charr may survive only short periods in seawater. Therefore, the lack of adequate hypoosmoregulatory capacity limits their access to marine food resources.

Daily hyperhydration effect on electrolyte deficiency of endurance-trained subjects during prolonged hypokinesia.

The aim of this study was to evaluate the effect of a daily intake of fluid and salt supplementation (FSS) on the deficiency of electrolytes, which is characterized by higher rather than lower plasma concentration of electrolytes during prolonged hypokinesia (HK) (decreased number of km taken per day). Forty long distance runners aged 22-25 yr with a peak VO2 65.4 mL min(-1) kg(-1) with an average 14.2 km d running distance were selected as subjects. They were equally divided into four groups: 1) unsupplemented control subjects (UCS); 2) unsupplemented hypokinetic subjects (UHS); 3) supplemented hypokinetic subjects (SHS), and 4) supplemented control subjects (SCS). During the investigation of 364 d, groups 2 and 3 maintained an average running distance of less than 4.7 km per day, groups 1 and 4 did not experience any modification in their normal training routines and diets. During the preexperimental period of 60 d and during the experimental period of 364 d urinary excretion of electrolytes and concentrations of sodium, potassium, calcium, and magnesium in plasma were determined. Whole blood hemoglobin, hematocrit index, plasma osmolality, and plasma protein concentration were measured. In the UHS plasma concentration of electrolytes and urinary excretion thereof, fluid elimination, hematocrit, whole blood hemoglobin, plasma osmolality, and plasma protein concentration increased significantly (p < 0.05) when compared with the UCS, SCS, and SHS groups. In the SHS plasma concentration of electrolytes and urinary excretion thereof, fluid excretion, whole blood hemoglobin, hematocrit, plasma osmolality, and plasma protein concentration decreased when compared with the UHS and increased insignificantly when compared with the UCS and SCS groups. It was concluded that FSS may be used to prevent or minimize electrolyte deficiency in endurance-trained volunteers during prolonged restriction of muscular activity.

Effects of glucose in drinking water on the changes in whole blood viscosity and plasma osmolality of broiler chickens during high temperature exposure

This study was conducted to elucidate the influence of glucose in drinking water on whole blood viscosity and plasma osmolality of broilers during high temperature exposure. Two groups of birds, which had ad libitum access to either a 4% glucose-water solution (Group G) or tap water (Group W), were exposed simultaneously to 30 C from 0300 h for 12 h each day for 3 d. During the experimental period, Group G birds had greater metabolic energy intake and body weight gain than Group W. Hematocrit and whole blood viscosity decreased significantly at 30 C compared to controls at 20 C in Group W, whereas, in Group G, no changes were found for these two variables. Plasma osmolality also decreased at 30 C compared to 20 C in Group W, whereas no change was noted in this variable in Group G. However, at 20 C, plasma osmolality was significantly higher in Group W than in Group G, but no difference was observed between the two groups at 30 C. Plasma protein concentration decreased during exposure to 30 C in both groups, but the decrease tended to be greater in Group W than in Group G. These results suggest that glucose intake may alleviate the influence of heat stress on whole blood viscosity and plasma osmolality.

Dehydration in soldiers during walking/running exercise in the heat and the effects of fluid ingestion during and after exercise.

The aim of this study was to examine whether ingesting water alone, or dextrose (7.5 g x 100 ml(-1)) with electrolytes, or fructose/corn solids (7.5 g x 100 ml(-1)) (400 ml every 20 min) would reduce the perceived exertion associated with 16 km (3 h) walking/running in the heat compared with that perceived during exercise with no fluid intake. Perceived exertion was assessed at 1-h intervals during exercise. Blood samples, required for analysis of blood glucose, plasma sodium, plasma osmolality and plasma volume, were obtained prior to exercise and at 1-h intervals during the exercise; further samples were obtained 1-h intervals for 3 h following the exercise. Drinking fluids at regular intervals reduced the level of perceived exertion. In the test during which no fluid was ingested, body mass decreased by 4.9 (0.4) kg [mean (SEM)], but decreased less with ingestion of either the dextrose/electrolytes or fructose/corn solids solutions, or water alone [1.3 (0.2) kg, 1.6 (0.3) kg and 2.0 (0.1) kg, respectively]. Plasma volume fell by 17% when taking no fluid, but fell less when ingesting fluids. Blood glucose fell significantly (P < 0.01) when taking no fluid and rose to 8.4 (1.3) mmol x l(-1) (P < 0.001) and 6.8 (1.1) mmol x l(-1) (P < 0.01) with ingestion of the dextrose/electrolytes or fructose/corn solids solutions, respectively. Urine output was greater with ingestion of water than with any of the other drinks. Six subjects experienced fatigue during exercise with no fluid and failed to complete the exercise. These results suggest that fatigue was caused by several interacting factors: a fall in blood glucose and plasma volume, dehydration, and neuroglycopenia. Taking fluids during exercise reduced the strain and the rating of perceived exertion; this was better achieved by ingesting a dextrose/electrolytes solution.

Summer osmoregulatory capacity of the world's northernmost living salmonid.

Anadromous Arctic charr (Salvelinus alpinus L.) were caught on their way to and from the sea with the use of a fish trap placed in the Dieset watercourse located on the Spitsbergen Island (79 degrees 10' Northern latitude) within the high-Arctic Svalbard archipelago. When subjected to a seawater challenge test (34 parts/thousand at 4-5 degrees C), charr on their way to the sea showed only minor and temporary changes in blood plasma osmolality and Na+ and Mg2+ concentrations. The seawater tests also revealed good hypoosmoregulatory capacity for Arctic charr returning from the marine environment 4 wk later. A progressive decrease in seawater tolerance was first documented 7-11 days after their return to the freshwater habitat. Thus the Svalbard charr, being the northernmost anadromous salmonid and probably a direct descendant from the first Salvelinus immigrants to freshwater systems, undergoes a preparatory increase of hypoosmoregulatory capacity (smoltification) before entering the oceanic water bodies. Furthermore, the termination of their short annual seawater stay is probably elicited by factors controlling body systems other than osmoregulation.

Vasopressin and atrial natriuretic hormone response to hypertonic saline during the follicular and luteal phases of the menstrual cycle.

We studied the hormonal responses to hypertonic saline during the follicular (days 2-9) and luteal (days 21-28) phases of the menstrual cycle in nine healthy young women, aged 19-25 years. On both study days, each woman was infused with 5% hypertonic saline for 1 h at the rate of 0.1 ml/kg/min. Serum progesterone and oestradiol concentrations confirmed the reported stage of the menstrual cycle. No difference in weight or haematocrit was observed between the two stages of the study for each woman. Baseline blood pressure, serum sodium, plasma osmolality, plasma vasopressin and thirst levels were almost identical for both stages, and changed to the same degree during infusion of hypertonic saline. Baseline atrial natriuretic hormone concentrations were higher during the follicular phase and became significantly higher than during the luteal phase following infusion of hypertonic saline. We concluded that the intravascular volume during the luteal phase may be effectively decreased in comparison to the follicular phase.

Toxicity of ammonia to Atlantic salmon ( Salmo salar L.) in seawater—Effects on plasma osmolality, ion, ammonia, urea and glucose levels and hematologic parameters

Atlantic salmon ( Salmo salar L.) (369 ± 70 g) were exposed to nominal water ammonia levels of 0.5 (control), 3, 22, 40, 112 and 255 μg/l NH 3-N (0.05–25.3 mg/l TA-N; total ammonia-N) in running seawater at 8–9°C, 33–35% salinity, pH 7.8–7.9 and 6.3–9.7 mg/l O 2. Blood plasma TA, urea, glucose, osmolality and ion levels and blood hematocrit (Hct), erythrocyte osmotic fragility (EOF), red blood cell count (RBC) and mean cell volume (MCV) were measured after 2–3 and 14–15 days of exposure. Plasma TA increased linearly with the water TA level. Plasma urea generally decreased with increasing water ammonia level, except for at 225 μg/l NH 3-N. At this acutely toxic ammonia level, plasma osmolality, Na +, Cl −, Mg 2+, urea and TA levels were largely increased; plasma glucose and Ca 2+ moderately increased and Hct decreased; and all fish were dead within 6 days of exposure. Plasma glucose, osmolality and ion levels, and blood Hct, RBC, EOF and MCV were not affected within 14–15 days of exposure to 22 μg/l NH 3-N.

Brain edema and neurological status with rapid infusion of lactated Ringer's or 5% dextrose solution following head trauma.

Rapid infusion of 0.25 ml/g of 0.9% saline over 30 minutes has been shown to have no effect on electrolyte balance, neurological severity score (NSS), or brain edema, following closed head trauma (CHT). Rapid infusion of the same volume of 5% dextrose solution decreased blood sodium concentration, increased edema, and decreased NSS following CHT. In the present study the authors examined the effect of rapid infusion (30 minutes) of smaller volumes of 5% dextrose (0.08 ml/g and 0.16 ml/g) and of 0.25 ml/g lactated Ringer's solution on blood electrolyte concentrations, plasma osmolality, brain edema, and NSS. The purposes of this study were to determine whether rapid infusion of a large volume of lactated Ringer's solution could be given after CHT without increasing mortality or brain edema or producing electrolyte disturbances, and whether small volumes of 5% dextrose could be infused with few or none of the deleterious effects expected from large volumes of 5% dextrose. One hundred eighteen rats, which survived halothane anesthesia and CHT, were randomly assigned to one of 15 experimental groups. Fluids were administered beginning 1 hour after scalp incision or CHT. The NSS, extent of edema, blood electrolyte concentrations, and plasma osmolality in the groups treated with lactated Ringer's solution were not significantly different from those values in the nontreated groups. In addition, the mortality rate after CHT was not increased by administration of lactated Ringer's solution. The groups treated with 5% dextrose solution showed a significantly higher mortality rate, but the NSSs of the surviving rats were not different from controls. None of the groups treated with 0.16 ml/g 5% dextrose solution survived 24 hours. Although blood glucose concentration increased to 1126 +/- 102 g% (mean +/- standard deviation) and 1568 +/- 283 g% and blood sodium concentration decreased to 110.4 +/- 4.6 mEq/L and 92.0 +/- 5.2 mEq/L in the groups treated with 0.08 ml/g and 0.16 ml/g of 5% dextrose solution, respectively, plasma osmolality was normal and no significant difference could be found between the brain tissue specific gravity of animals in the nontreated and 5% dextrose treatment groups. It is concluded that in the CHT model used in this study, the large volume of lactated Ringer's solution did not affect blood electrolyte concentration, neurological outcome, or formation of brain edema, whereas smaller volumes of 5% dextrose solution increased blood glucose and decreased blood sodium concentrations, did not affect plasma osmolality, and had a deleterious effect on neurological outcome.

Effect of acute manipulation of blood volume and osmolality on plasma [AVT] in seawater flounder

Chronically cannulated seawater (SW)-adapted flounder (Platichthys flesus) were used unanesthetized and unrestrained in an experimental series that acutely manipulated blood volume and plasma osmolality to determine their influence on plasma arginine vasotocin (AVT) concentrations. Immunoreactive AVT was measured using a radioimmunoassay validated for flounder and other teleosts. After hemorrhage-induced hypovolemia or hypervolemia produced by saline infusion, no major changes in plasma AVT concentrations were detected. Raising plasma osmolality by intraperitoneal injection of 1 M NaCl compared with control 150 mM NaCl-injected fish (329.4 +/- 3.4 vs. 320.4 +/- 3.0 mosmol/kgH2O, P < 0.05) produced an increase in plasma AVT concentration (6.7 +/- 1.2 vs. 4.2 +/- 0.2 fmol/ml, P < 0.05). In a separate study, plasma composition in a large number of uncannulated SW-adapted flounder was determined. This demonstrated a positive linear relationship between the natural variation in plasma AVT concentrations and plasma osmolality and Na+ and Cl- concentrations observed between fish. These data indicate that AVT secretion in SW-adapted flounder is closely related and perhaps directly sensitive to changes in plasma tonicity.