Isosmotic Water Research Articles

Does Metabolism Regulate Cardiac Repair in the Regeneration Competent Axolotl Salamander?

Adult human hearts form permanent scar tissue after a myocardial infarction, leaving millions of survivors in western societies with ongoing heart complications and increased risk of heart failure. Unlike, humans and other mammals, axolotl salamanders have an extraordinary ability to repair similar cardiac injuries. After forming an initial collagenous scar in response to a cryo‐infarction, axolotls completely repair their heart, with existing cardiomyocytes dedifferentiating and proliferating, with the transient scar tissue eventually completely replaced by new functioning myocardium. The mechanisms leading to this immense discrepancy in capacity for repair within vertebrates is not fully understood, although the proliferative capacity of cardiomyocytes are a perquisite for regeneration. In recent years, research across species has demonstrated that metabolism may be instrumental in regulating cardiomyocyte proliferation and regeneration. In both adult and neonatal mice as well as zebrafish, studies have shown that a pro‐glycolytic metabolic profile is favorable to regeneration, although the mechanisms involved are unclear. We hypothesize that metabolic adaptations are an instrumental part of the regenerative response in the axolotl and that thereby altering metabolism can both promote and inhibit cardiac regeneration in this animal model. In this currently ongoing study, we are employing a range of methods to uncover the interplay between metabolism and regeneration in the axolotl, combining whole‐animal and high resolution cardiac respirometry as well as autoradiography to assess glucose and acetate consumption, metabolite analysis, immunochemistry and enzyme histochemistry. We are currently exploring if specific metabolic adaptations occur after injury both in the animal as a whole and locally in the different regions of the heart, which could help facilitate cardiac regeneration. In addition, we are looking at how altering axolotl metabolism can support or inhibit regeneration. For this purpose, axolotls are given the same type of cryoinjury and housed at different rearing temperatures (10 ◦C, 20 ◦C or 30 ◦C), or kept in isosmotic water, or fasted for the duration of regeneration which takes 60 ‐ 90 days. By augmenting metabolism in this way in a regenerative animal model, we hope to uncover key insights about how metabolism affects cardiac regenerative ability.

Oxygen Uptake and Osmotic Balance of Atlantic Salmon in Relation to Exercise and Salinity Acclimation

The fish gill is subject to an osmorespiratory compromise in physiologically demanding situations where conditions that favour gas exchange may compromise osmotic balance, especially when large gradients between the blood and the aquatic environment are present. Fish in isosmotic water should therefore be less restricted by an osmorespiratory compromise, which should improve aerobic performance. To investigate this hypothesis, Atlantic salmon were acclimated to freshwater, near isosmotic brackish water or sea water, and tested in groups of 10 in a large swim tunnel respirometer to assess metabolic rates, swimming capacity and haematological parameters. Oxygen uptake rates and the critical swimming speed were similar between treatments. However, osmolality and plasma [ions] before and after swim trials, and subsequent recovery differed. Fish in sea water experienced a substantially larger osmotic disturbance in the swim trials, which had increased further 3 hours post-fatigue, while fish in lower salinities were approaching full recovery. Swim trials increased plasma cortisol levels, which may modulate increased gas transfer and facilitate beneficial ion regulation in both low and high salinities. Swimming also increased haematocrit and haemoglobin concentration that returned to control levels after recovery, suggesting recruitment of erythrocytes via splenic contraction. These results show that Atlantic salmon do not elicit a clear salinity optimum in terms of metabolic and locomotory advantages. Although, swimming in sea water imposes larger osmoregulatory challenges which may have implications for repeated swim challenges. Hence, Atlantic salmon are well-equipped to minimize the potential restrictions of an osmorespiratory compromise on aerobic performance, and more so in brackish and freshwater.

Effects of salinity on growth and metabolism in blue tilapia (Oreochromis aureus)

Tilapia were acclimated to the water source which had 8 precipitation (ppt) of salinity in the experimental unit before the experiment started and then, they were transfered to five different saltwater (SW) treatments: SW (8 ppt), 50% SW (12 ppt), 100% SW (16 ppt), 150% SW (20 ppt), and 200% SW (24 ppt). The objectives of this study were; to investigate the effects of five different salinities on specific growth rate (SGR), weight gain (WG), food intake (FI) and survival of tilapia in the long term trial (30 days) and find out how salinity affects muscle water content, hematosomatic index (HSI), and blood chemistry (sodium, chloride, potassium, glucose, total protein and triglycerides) in the short term trial (6 to 12 h). In the long-term trial, six fish were stocked in each aquarium. They were fed with commercial feed (Bagci trout) to satiation twice a day and individually weighed at ten-days interval. Growth rate was highest in the 50% SW (SGR 0.95 ± 0.18% per day); there was no significant difference among the first three treatments. Growth rate was lowest in 200% SW (SGR 0.23 ± 0.08% per day). Weight gain and food intake showed identical results as SGR. Survival was high in the first three groups (72.2 ±1 9.2 to 100.0 ± 0.0) but it was lowest in the 200% SW treatment (22.2±19.2%). In the short-term trial, six tilapia were placed per aquarium. They were exposed to SW, 50, 100, 150 and 200% SW treatments and the fish were gradually acclimated to salt water. Blood samples were taken to analyse plasma sodium, chloride, potassium, total protein and triglycerides. Liver and muscle samples were collected for HSI and moisture values. Plasma sodium chloride increased in parallel with salinity rise. Total protein and triglycerides significantly reduced as salinity increased. Glucose and potassium were not altered significantly. HSI and muscle water content decreased when salinity concentration was elevated. Blood chemistry demonstrated that isosmotic water concentration was between 8 and 12 ppt. Salinity did not affect HSI and moisture until it reached as much as 16 ppt (100% SW). The results show that the optimum condition for farming blue tilapia, Oreochromis aureus, both with respect to growth rate and metabolic parameters is at salinities lower than 12 ppt. This is an important finding for the tilapia industry. Keywords : Tilapia, salinity, growth, survival, metabolism African Journal of Biotechnology Vol. 12(19), pp. 2715-2721

Life on the edge: physiological problems in penaeid prawns Litopenaeus stylirostris, living on the low side of their thermopreferendum

The underlying physiological mechanisms explaining why the adult penaeid prawn Litopenaeus stylirostris cannot successfully face heavy stressful events on the low edge of its thermopreferendum (20–22°C) were studied during the austral winter. Prawns were studied during recovery from net fishing and rapid transfer from outdoor earthen ponds into indoor facilities. This was assimilated to a predator–prey interaction. O2-consumption, hemolymph osmotic pressure (OPh), arterial O2 partial pressure (PO2), a–v O2-capacitance and mortality rates were analysed. Data were compared to similar challenges performed at 28°C during the austral summer. At 20–22°C, mortality of up to 70% was observed after 2 days whereas at 28°C, maximum mortality was 3–5%. Mortality occurred when OPh shifted towards equilibrium with seawater, the resting O2-consumption, the a–v O2-capacitance and the arterial PO2 went down to minimal values. These events can be counterbalanced by transiently hyper-oxygenating the hemolymph or by blocking the OPh shift in isosmotic water (Wabete et al. in Aquaculture 260:181–193, 2006): both led to a dramatic decrease in mortality. It is concluded that in penaeid prawns L. stylirostris, a mismatch between O2-demand and O2-supply contributes to setting the geographical limits for this animal species through an impairment of their hemolymph O2-carrying capacity during heavy stressful events like chasing by predators.

A soft technology to improve survival and reproductive performance of Litopenaeus stylirostris by counterbalancing physiological disturbances associated with handling stress

The consequences of handling stress (fishing, transfer, eyestalk ablation) on shrimp broodstock are poorly documented. The weakness of farmed shrimp, Litopenaeus stylirostris, during winter is a major problem in New Caledonia, because of seasonal climate (tropical–sub-temperate). The transfer of broodstock in winter from earthen outdoor ponds to indoor maturation tanks in the hatchery ( T = 20 °C, Salinity = 35‰, fed shrimp) usually leads, after 48 h, to high mortality (up to 70%). Eyestalk ablation to induce ovarian maturation in females leads to further mortality. Starting from a background analysis of physiological disturbances (initial osmoregulatory imbalance) associated with handling stress (Wabete, N., Chim, L., Lemaire, P., Massabuau, J.-C., 2004. Caractérisation de problèmes de physiologie respiratoire et d'échanges ioniques associés à la manipulation chez la crevette pénéide Litopenaeus stylirostris à 20 °C. Styli 2003. Trente ans de crevetticulture en Nouvelle-Calédonie. Ed. Ifremer. Actes Colloq. 38, 75-84.), we developed a protocol using a soft technology, based on modifications of water salinity, temperature and feeding regime. The aim was to minimize problems of osmoregulatory imbalance and associated mortalities. The protocol we developed, called the LSD OT protocol (Low Salinity and Diet, Optimal Temperature), was first evaluated on sub-adult shrimp (20–25 g) and then applied to broodstock. Survival after transfer and following eyestalk ablation, as well as reproductive achievement (spawning rate, nauplii number) was considerably improved when shrimps were transferred under “physiological comfort” i.e. warmed isosmotic water (26 °C and 26‰) and unfed for 3 d. This new handling protocol, based on a better control of salinity, temperature and feeding conditions, has been transferred successfully to private hatcheries and already contributes to an increased profitability of New-Caledonian shrimp industry.

MR enteroclysis imaging of Crohn disease.

Magnetic resonance (MR) enteroclysis imaging is emerging as a technique for evaluation of the small bowel in patients with Crohn disease. Administration of 1.5-2 L of isosmotic water solution through a nasojejunal catheter ensures distention of the bowel and facilitates identification of wall abnormalities. True fast imaging with steady-state precession (FISP), half-Fourier acquisition single-shot turbo spin-echo (HASTE), and postgadolinium T1-weighted three-dimensional fast low-angle shot sequences can be employed in a comprehensive and integrated MR enteroclysis examination protocol to overcome specific disadvantages of each of the sequences involved. Superficial abnormalities that are ideally delineated with conventional enteroclysis are not consistently depicted with MR enteroclysis. The characteristic transmural abnormalities of Crohn disease such as bowel wall thickening, linear ulcers, and cobblestoning are accurately shown with MR enteroclysis imaging, especially with the true FISP sequence. MR enteroclysis is comparable to conventional enteroclysis in the detection of the number and extent of involved small bowel segments and in the disclosure of luminal narrowing or prestenotic intestinal dilatation. The clinical utility of MR enteroclysis in Crohn disease has not been fully established. At present, the method may be used for follow-up studies of known disease, estimation of disease activity, and determination of the extramucosal extent and spread of the disease process.

Physiological aspects of molting in the blue crabCallinectes sapidus

Synopsis. From a respiratory and metabolic standpoint, a blue crab is in an extremely precarious condition during a molt. A molt is physiolog? ically possible for two major reasons. First, a premolt alkalosis anticipates the acidosis that arises during actual exuviation when the gas exchanger and ventilatory appendage are impaired and thus anaerobic metabolism must be activated. Second, the crab is able to revert to more primitive forms of skeletal support and, immediately after exuviation, gas exchange. These mechanisms are very fragile, however, as are the cardiovascular mechanisms that provide the force for exuviation; any one may fail. Changes in various enzyme activities and in free amino acid content of the tissues, which are usually associated with osmotic challenges, are associated specifically with a molt as well. I suggest that they are related to isosmotic water uptake and cell volume regulation.

The dynamics of vasopressin release and blood volume regulation during fetal hemorrhage in the lamb fetus.

Summary: Experiments were performed on 11 long-term fetal lamb preparations (103–138 days of gestation) to investigate the sensitivity and relative responsiveness of the fetal volume receptors in modulating fetal plasma arginine vasopressin (pAVP) secretion and plasma renin activity (PRA) secretion during fetal hypovolemia and after fetal blood volume replacement. During fetal hemorrhage there were significant decreases (P < 0.05) in fetal hematocrit (34.7 ± 2.58 to 27.0 ± 1.64%), plasma proteins (3.14 ± 0.15 to 2.78 ± 0.19 g/100 ml), mean arterial blood pressure (MABP) (58.1 ± 2.59 to 52.2 ± 2.60 mmHg) and fetal arterial pH (7.38 ± 0.01 to 7.35 ± 0.01). A significant increase in fetal pAVP concentration from 0.73 ± 0.21 to 34.9 ± 10.04 μU/ml (P < 0.01) and fetal PRA from 4.78 ± 2.22 to 40.4 ± 18.31 ng/ml/hr (P < 0.05) was demonstrated at the peak of fetal hemorrhage. Two hr after correction of the fetoplacental blood volume, these values were back to base line levels. No change in either maternal pAVP or PRA was seen during fetal hemorrhage. When individual values for log pAVP and log PRA were plotted as a function of percent of fetoplacental blood volume removed the correlation coefficients were 0.82 and 0.60, respectively. A multiple regression analysis showed a high correlation of log pAVP and log PRA with the volume of blood removed and a low partial correlation with the fetal MABP. This suggests the decrease in fetal MABP was not the primary factor explaining the increase in pAVP and PRA during fetoplacental blood volume depletion. The data indicate that the fetal volume receptors for control of arginine vasopressin secretion are fully functional in the last trimester of gestation and suggests that fetal pAVP and PRA are released as an exponential function of the percent of fetoplacental blood volume depletion. Finally, an isosmotic water shift from the fetal interstitial space to the fetal vascular space is described during fetal hemorrhage.Speculation: It is suggested that a change in the equilibrium between the forces regulating fluid movement through the fetal capillary membranes, in accordance with Starling's principle, activates isosmotic water fluxes from the fetal interstitial space to the fetal vascular compartment counteracting the effects of fetal blood volume depletion. Therefore, the role of arginine vasopressin (AVP) release during fetal hemorrhage, if any, will be to act as a pressor substance helping to maintain fetal blood pressure. No major effect of AVP on placental membranes was demonstrated in vivo.

Thermal preference in relation to salinity in the threespine stickleback, Gasterosteus aculeatus L., with an interpretation of its significance

Thermal preferences were determined in spacious thermal gradients of fresh water and sea water (32‰ salinity (S))for acclimations of 5, 15, and 25 °C in sea water, for samples of threespine stickleback Gasterosteus aculeatus L. Preferred temperatures increased through acclimations of 5–25 °C, with those for the freshwater tests being about 2 °C lower at each acclimation. Final preferenda were 16 and 18 °C for freshwater tests and seawater tests, respectively. The final preferendum in such haloplastic species is defined as the highest obtainable preferendum that equals acclimation temperature. A later series of disjunct preference determinations in approximately isosmotic water (10.5‰ S) for subjects acclimated to 7, 15, and 20 °C yielded mean values of 17.7, 18.2, and 18.7 °C, respectively. A final preferendum has not been designated since the samples were of separate origins. A parallel exists between these responses and the response of this and other haloplastic species in the determination of upper lethal temperatures. The immediate cause appears to be differentials in metabolic loading occasioned by l stresses.

Intestinal salt and water transport in a euryhaline teleost, Aphanius dispar (Cyprinodontidae)

1. 1. The transmural Na +, K +, Cl − and water flow in the total intestine of Aphanius dispar was measured by an in vitro in situ perfusion technique. 2. 2. A neutral NaCl absorption without a net K + flow was observed; this occurred in the absence of a transmural osmotic difference followed by an isosmotic water absorption. 3. 3. The osmotic permeability coefficient and the NaCl mobility of the intestinal wall seemed high.