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PubMed1980

Ultrastructural variations following use of several weakly protic alcohols as dehydration agents.

Evaluation has been made of ultrastructural variations which obtain following dehydration and infiltration of glutaraldehyde plus osmium fixed CHO cells with the weakly protic alcohols (methanol, ethanol, ethylene glycol, 1-propanol, 2-propanol, propylene glycol and glycerine), acetone alone, and with use of acetone and propylene oxide as transition solvents subsequent to dehydration with ethanol, methanol and ethylene glycol. It appears that the weakly protic alcohols, applied without transition solvent, in addition to some extraction by themselves, variously condition the components of membranes, etc, for possible further extraction by the embedment resin. Extraction by embedment consists mainy of removal of aggregate or 'corpuscular' units from regions assumed to have originally consisted of endomembrane. Relatively discrete extraction pits in membranes are noted in the cases of methanol and ethylene glycol dehydration without transition solvent; whereas use of the other alcohols such as 1-propanol and 2-propanol accentuate the visualization and staining of mitochondrial ribosomes. Cytoplasmic ribosomes stain more strongly when acetone or ethylene glycol are employed as dehydration agents, but some size (length) differences obtain. Apparently, acetone or propylene oxide transition following dehydration with ethanol or methanol (but not the glycols) assists in, or fixes, alterations of endomembrane components into the familiar 'unit membrane' orientation upon which the embedding substances have little discernible effect. Glycol dehydration and infiltration regimens (especially ethylene glycol alone and as a dehydration agent in the application of Bernhard's (1969) staining technique) result in lesser electron density of heterochromatin while accentuating RNP particles. The increased electron density of heterochromatin while accentuating RNP particles. The increased electron density of the RNP particles and the decrease in density of the heterochromatin result in improved visualization of the relationships among nucleolar RNP particles and the nuclear pore complexes.

Alcohols↗
PubMed1981

Osmolar relationships in infantile dehydration.

We studied serum osmolality in 167 consecutive infants admitted for gastroenteritis with 5% or more dehydration. Osmolality was determined by the freezing-point method in a 0.2-mL sample of serum immediately on admission. Forty-one patients (24.6%) had hypo-osmolar dehydration, with a mean osmolality of 257 mOsm/kg (range, 234 to 270 mOsm/kg). Eleven patients (6.5%) had hyperosmolar dehydration, with a mean osmolality of 329 mOsm/kg (range, 312 to 369 mOsm/kg). Simultaneous serum and CSF osmolalities were determined in 14 patients with hypo-osmolar and eight with hyperosmolar dehydration. In patients with hyperosmolar dehydration, serum osmolality correlated well with CSF osmolality, but a poor correlation was seen between serum and CSF sodium levels. Convulsions occurred in two patients in whom the CSF osmolality was greater than the serum osmolality by more than 10 mOsm/kg. Convulsions also occurred in two patients with hypo-osmolar dehydration in whom the CSF osmolality was lower than the serum osmolality by more than 13 mOsm/kg.

Child, Preschool↗
PubMed1998

The region of the pontine parabrachial nucleus is a major target of dehydration-sensitive CRH neurons in the rat lateral hypothalamic area.

Neurons in a restricted part of the lateral hypothalamic area (LHA) show increased expression of corticotropin-releasing hormone (CRH) mRNA as a consequence of cellular dehydration. In the present study, we have investigated the organization of their efferent projections by using anterograde and retrograde tracing techniques. Additionally, we have compared the distribution of CRH mRNA-containing neurons after cellular dehydration and intraventricular (i.c.v.) colchicine injections. Our results show that cellular dehydration activates a more restricted neuronal population than does i.c.v. colchicine. Iontophoretic injections of Phaseolus vulgaris leucoagglutinin (PHAL) were placed in the LHA of animals drinking hypertonic saline and their proximity to activated CRH neurons determined by in situ hybridization for CRH mRNA. Although labelled fibers from these injections were seen throughout the brain, the region of the parabrachial nucleus and nucleus of the solitary tract (NTS) were most conspicuous in also having CRH immunoreactive fibers. Injections of Fluoro-Gold placed in these two structures were used to confirm these findings in dehydrated animals. Significant numbers of neurons containing both Fluoro-Gold and CRH mRNA were seen in the lateral hypothalamus after injections in the lateral and medial parts of the parabrachial nucleus; far fewer were seen after injections in the NTS. These results strongly suggest that the CRH neurons in the LHA activated by cellular dehydration provide an input to the region of the parabrachial nucleus. The altered biochemical composition of this pathway may well be able to modify sensory and motor patterns both during and after dehydration.

Animals↗
PubMed2000

Intra- and extracellular dehydration has no effect on plasma levels of angiotensin II in an amphibian.

Previous studies have demonstrated that both dehydration (intra and extracellular) and treatment with angiotensin II (A-II) induce changes in thirst-related behavior in the spadefoot toad, Scaphiopus couchii. One of the steps in determining a causal relationship between a hormone and a behavior is to determine that there is association between an animal's performance of the behavior and changes in endogenous hormonal concentrations. The hypothesis tested that plasma levels of the peptide hormone A-II would change as a result of dehydration known to induce water absorption response (WR) behavior in the spadefoot toad. Plasma samples were taken from toads dehydrated intracellularly by injection of hypertonic solutions of NaCl or sucrose at levels known to induce WR behavior. As an osmotic control, a group of animals was injected with urea, which has been demonstrated to not induce WR behavior. In order to determine the effects of extracellular dehydration on plasma, A-II levels in toads dehydrated by plasma volume depletion via cardiac puncture were compared to sham-punctured controls. None of the treatments in any experiment resulted in significant differences in plasma levels of angiotensin II among groups sampled at the time when WR behavior occurs. These results do not support the hypothesis that dehydration-induced thirst is stimulated by changes in plasma A-II concentrations at the onset of WR behavior. J. Exp. Zool. 286:343-349, 2000.

Angiotensin II↗
PubMed1998

Dehydration and rehydration selectively and reversibly alter glial fibrillary acidic protein immunoreactivity in the rat supraoptic nucleus and subjacent glial limitans.

Ultrastructural studies of the supraoptic nucleus (SON) of the hypothalamus suggest that an active retraction and extension of astrocytic processes (structural plasticity) from between magnocellular neuroendocrine neurons plays a role in the release of oxytocin, vasopressin, or both peptides that accompanies parturition, lactation, and dehydration. In support of this, Salm et al. (1985) previously demonstrated a lactation-associated reduction in immunoreactive glial fibrillary acidic protein (GFAP), an astrocyte-specific cytoskeletal constituent. To determine if similar changes occur in response to dehydration, and if they are reversible, the present study examined GFAP-immunoreactivity (IR) in the SON under various hydration states. Rats were dehydrated for 7 days by substitution of drinking water with 2% saline (n = 3), or dehydrated for 7 days followed by 7 days of rehydration (n = 3). A control group (n = 3) with free access to tap water was used for comparisons. The optical density of GFAP-IR was obtained from the SON, globus pallidus, and lateral hypothalamic regions. The areas of the ventral glial limitans subjacent to the SON (SON-VGL) and of linearly equivalent segments of glial limitans more distant from the SON were also determined. Dehydration resulted in a significant reduction in GFAP-IR in the SON compared to control and rehydrated levels. We also found that the area of the SON-VGL was significantly larger than that of linearly equivalent segments of glial limitans elsewhere and that it was significantly reduced in dehydrated rats, returning to control levels with rehydration. GFAP-IR and glial limitans thickness in regions unrelated to body fluid homeostasis lateral to the SON, overlying to dorsal cortex, and subjacent to the optic chiasm were not significantly changed by hydration state. These results are similar to the changes of GFAP-IR reported for lactating rats and provide further evidence for a role of structural plasticity of astrocytes in events surrounding the selective functional activation of local neurons.

Animals↗
PubMed2003

Freeze or dehydrate: only two options for the survival of subzero temperatures in the arctic enchytraeid Fridericia ratzeli.

Hygrophilic soil animals, like enchytraeids, overwintering in frozen soil are unlikely to base their cold tolerance on supercooling of body fluids. It seems more likely that they will either freeze due to inoculative freezing, or dehydrate and adjust their body fluid melting point to ambient temperature as has been shown for earthworm cocoons and Collembola. In the present study we tested this hypothesis by exposing field-collected adult Fridericia ratzeli from Disko, West Greenland, to freezing temperatures under various moisture regimes. When cooled at -1 degrees C min(-1) under dry conditions F. ratzeli had a mean temperature of crystallisation ( T(c)) of -5.8 degrees C. However, when exposed to temperatures above standard T(c) for 22 h, at -4 degrees C, most individuals (90%, n= 30) remained unfrozen. Slow cooling from -1 degrees C to -6 degrees C in vials where the air was in equilibrium with the vapour pressure of ice resulted in freezing in about 65% of the individuals. These individuals maintained a normal body water content of 2.7-3.0 mg mg(-1) dry weight and had body fluid melting points of about -0.5 degrees C with little or no change due to freezing. About 35% of the individuals dehydrated drastically to below 1.1 mg mg(-1) dry weight at -6 degrees C, and consequently had lowered their body fluid melting point to ca. -6 degrees C at this time. Survival was high in both frozen and dehydrated animals at -6 degrees C, about 60%. Approximately 25% of the animals (both frozen and dehydrated individuals) had elevated glucose concentrations, but the mean glucose concentration was not increased to any great extent in any group due to cold exposure. The desiccating potential of ice was simulated using aqueous NaCl solutions at 0 degrees C. Water loss and survival in this experiment were in good agreement with results from freezing experiments. The influence of soil moisture on survival and tendency to dehydrate was also evaluated. However, soil moisture ranging between 0.74 g g(-1) and 1.15 g g(-1) dry soil did not result in any significant differences in survival or frequency of dehydrated animals even though the apparent wetness and structure of the soil was clearly different in these moisture contents.

Adaptation, Physiological↗
PubMed2002

Dehydration modifies guanidino compound concentrations in the different zones of the rat kidney.

Guanidino compounds (GCs) related to arginine (Arg) are unevenly distributed along the cortico-papillary axis of the rat kidney. Inasmuch as the concentration of alpha-keto-delta-guanidinovaleric acid (alpha-keto-delta-GVA), guanidinosuccinic acid (GSA), creatinine (CTN), gamma-guanidinobutyric acid (gamma-GBA) and methylguanidine (MG) increased steeply along the inner medulla in parallel to the urea and osmotic gradients, the question arose as to whether dehydration enhances their renal content and distribution. To examine this possibility, adult male rats were dehydrated by removing the drinking water for 24 or 48 h. The kidneys were sliced and cut in seven sections along the cortico-papillary axis. Twelve GCs were determined by liquid chromatography in each renal zone. Dehydration modified GC concentrations and regional distribution. The renal content of Arg, guanidine and MG was decreased while that of alpha-keto-delta-GVA, gamma-GBA, alpha- N-acetyl-arginine and homoarginine remained unchanged. In contrast, GSA, guanidinoacetic acid (GAA), creatine (CT), CTN and beta-guanidinopropionic acid (beta-GPA) concentrations were enhanced significantly in different renal zones after 24 and 48 h dehydration. In addition, the tissue level of GCs supplying energy, such as CT and beta-GPA, the precursor of CT (GAA) and its metabolite (CTN) were enhanced under dehydration. Arg and CT account for 80-90% of the GCs located in the renal cortex. Variations of some GC levels under dehydration may modify enzyme activities, renal metabolism and cell function.

Animals↗
PubMed1997

When to treat dehydration in a terminally ill patient?

The need to treat dehydration in terminally ill patients has become a very controversial topic. Numerous reports in the literature illustrate opposing view-points from both clinical and ethical perspectives. Arguments for the maintenance of hydration in terminally ill patients have tended to come from "the traditional medical model". Many health care professionals looking after terminally ill patients have reacted to the generalized use of intravenous fluids in dying patients and the perceived negative effects of this management. Our palliative care group has argued that the viewpoint that dehydration in dying patients is not a cause of symptom distress overlooks commonly reported problems, such as agitated delirium, that can be prevented or reversed by the management of dehydration. This review presents a summary of the traditional arguments, a different perspective on the controversy, biochemical parameters reported in terminally ill cancer patients, recent dehydration research, and the use of hypodermoclysis and rectal hydration. We conclude that the data reported to date are insufficient to allow a final conclusion on the benefit or harm of dehydration in terminally ill patients. Nevertheless, it is worth considering that while some dying patients may not suffer any ill effects from dehydration, there may be others who do manifest symptoms, such as confusion or opioid toxicity, that might be alleviated or prevented by parenteral hydration.

Dehydration↗
PubMed1992

Opioid modulation of thermal dehydration-induced thirst in rats.

Male Sprague-Dawley rats were utilized to study the effects of the opioid receptor antagonists, naloxone and naltrexone, on thirst induced by thermal dehydration. In an initial experiment, the depressant effect of naloxone (1.0 mg/kg, IP) on the water intake of rats deprived of water for 24 h was confirmed. In subsequent experiments, rats were thermally dehydrated by exposing them without water to a 40 degrees C environment for 1-4 h. Following heat exposure, rats were injected with either naloxone or naltrexone either IP or ICV. Fifteen minutes later, rats were provided with water and water intake was measured for 2 h. Both naloxone and naltrexone had dose (0.1-5.0 mg/kg, IP)-dependent effects of reducing water intake of rats thermally dehydrated for 3 h. Water intake of rats thermally dehydrated for 2 or 4 h was also attenuated by pretreatment with naloxone. Rats thermally dehydrated for 3 h exhibited decreases in water intake following ICV injection of either naloxone or naltrexone at a dose of 50 micrograms. Neither naloxone nor naltrexone had an effect on urine output in any experiment. The water intake data support the hypothesis that thirst induced by thermal dehydration in rats is modulated by an opioid mechanism.

Animals↗
PubMed1994

Proto-oncogene c-fos and the regulation of vasopressin gene expression during dehydration.

Secretion of the antidiuretic hormone (ADH) vasopressin is increased when body fluid homeostasis is disturbed by dehydration. Associated with this increased secretion is an elevation of vasopressin mRNA in magnocellular hypothalamic neurons projecting to the posterior pituitary. The proto-oncogene c-fos codes for a nuclear phospho-protein Fos which binds to specific DNA elements and acts as a transcriptional regulator coupling short-term extracellular stimuli to long-term responses by altering secondary target gene expression. This study in rats examined the time courses of dehydration induced c-fos expression and the change of vasopressin gene expression in the magnocellular neurons of the hypothalamus. Immunocytochemical and in situ hybridization study demonstrated that c-fos was induced by acute intracellular dehydration in the hypothalamic magnocellular nuclei of paraventricular (PVN), supraoptic (SON), and accessory groups such as nucleus circularis. Double-label immunocytochemical study co-localized Fos and vasopressin-neurophysin immunoreactivity in the same magnocellular neurons in the SON and PVN. In situ hybridization analysis after acute dehydration revealed a rapid and transient c-fos induction followed by a persistent increase in vasopressin mRNA for up to 2 days even after rehydration. Furthermore, prevention of c-fos translation by pretreatment with protein synthesis inhibitor cycloheximide attenuated this dehydration induced increase in vasopressin mRNA. This study demonstrated that an increase in vasopressin transcription after acute dehydration is dependent on an early phase of protein synthesis.

Animals↗
PubMed2006

Clinical manifestations and MRI findings of patients with hydrated and dehydrated lumbar disc herniation.

RATIONALE AND OBJECTIVES: In addition to the expected appearance of degenerated discs that become dehydrated, hydrated intervertebral disc herniations are sometimes encountered in radiologic practice. This study was undertaken to evaluate the clinical manifestations and MRI findings of hydrated and dehydrated herniated intervertebral discs. MATERIALS AND METHODS: This cross-sectional single-institution study included 73 patients with dehydrated (group I) and hydrated (group II) lumbar disk herniation. The criteria for hydrated and dehydrated disc herniation were subjective criteria compared to the normal signal of intervertebral discs. A herniated disc has been regarded to be hydrated if more than two thirds of it was hypersignal in T2-weighted images, while more than two thirds of a dehydrated disc was hyposignal on T2-weighted images. RESULTS: The mean weight of patients in group I was greater than that of patients in group II (69.3 versus 64.2 kg, P < 0.05). Also, patients in group I tended to be older than those in group II (35.2 versus 28.9 years). Regarding physical activity, a greater number of patients in group II had intense physical activity compared to group I patients (25% versus 13.2%, respectively; P < 0.05). The duration of radicular pain and back pain was significantly greater in group I than in group II (485 versus 202 and 1346 versus 242 days, respectively; P < 0.05). CONCLUSION: Hydrated intervertebral disc herniation tends to be associated with younger age, lighter body weight, shorter duration of radicular pain, and more intense physical activity compared to dehydrated intervertebral disc herniation. These findings may suggest other mechanisms rather than degenerative changes for hydrated disc herniation.

Adult↗
PubMed2005

Potassium intake during cell dehydration.

Isotonic NaCl is ingested in addition to water by cell-dehydrated rats in two-bottle tests. The objective of the present work was to find out whether mineral intake in the cell-dehydrated rat is specific to NaCl in a five-bottle test. Adult male Sprague Dawley rats had distilled water and four mineral solutions at palatable concentrations (0.01 M KCl, 0.05 mM CaCl2, 0.15 M NaHCO3, 0.15 M NaCl) simultaneously available for consumption. Cell-dehydration was produced infusing 1.5 ml of NaCl solution (0.15, 0.25, 0.5, 1.0, 2.0, 4.0 M) intravenously for 10 min and intakes were recorded for the next hour. It was observed a NaCl concentration-dependent increase in 0.01 M KCl intake. The ingestion of the other mineral solutions was not significantly altered compared to infusion of 0.15 M NaCl. The ingestion of KCl was not related to changes in serum potassium concentration. The ingestion of KCl was reduced in half and water was the preferred fluid when the five-bottle test was performed with mineral solutions at isomolar (0.15 M) concentrations. There was no increase in intake of other mineral solution in the isomolar test. No preference was observed for palatable or isomolar solutions during early extracellular dehydration until 4 h after subcutaneous injection of furosemide, in spite of the increase in total volume intake. Therefore, mineral intake induced by cell dehydration is not specific for NaCl solution. The type of mineral solution available influences the choice and KCl is the preferred solution of the cell-dehydrated rat in the conditions of the present study.

Analysis of Variance↗
PubMed1999

Tissue norepinephrine turnover and cardiovascular responses during intermittent dehydration in the rat.

We investigated the central and peripheral sympathetic responses to intermittent dehydration in rats. The norepinephrine (NE) turnover, a biochemical index correlated with noradrenergic neuronal activity, was measured. The modification of blood pressure was also determined by telemetry during the different cycles of dehydration. Dehydration caused a decrease of NE turnover in A2, A5 and A6 nuclei and in peripheral organs. The vasopressinergic level of dehydrated rats decreased in hypophysis and hypothalamus, and increased in plasma. A repeated gradual increase of arterial blood pressure during the first three days of dehydration, followed by a sudden drop when the rats were rehydrated on the fourth day was observed. In conclusion, our study revealed an increase in blood pressure and in central sympathetic activity during dehydration.

Animals↗
PubMed1998

Risk factors for development of dehydration in children aged under five who have acute watery diarrhoea: a case-control study.

OBJECTIVE: To identify factors for development of dehydration in under five year olds with acute watery diarrhoea. DESIGN: Hospital based unmatched case-control study. SETTING: Diarrhoea Treatment Unit, Government Medical College Hospital, Nagpur, India. PARTICIPANTS: The study included 387 cases of diarrhoea having severe or moderate dehydration and 387 controls suffering from diarrhea with mild or no dehydration. RISK FACTORS: The study included infancy, female sex, religion, residing in urban slums or rural area, under nutrition, cessation of breast feeding during diarrhoeal episode, fluid intake decrease/stopped during diarrhoea, ORS not received, home available funds (HAF) not received, both ORS and HAF not received, non-washing of hands by mother before preparation of food, after defaecation, after disposal of faeces, history of measles in the previous six months, frequency of stools > 8/d, frequency of vomiting more than twice per day and temperature more than 99 degrees F, as risk factors for development of dehydration. STATISTICAL ANALYSIS: Univariate analysis included OR, 95% CI for OR and Chi-square test. Multivariate analysis was carried out by unconditional multiple logistic regression (MLR). RESULTS: This study identified the significance of infancy, religion, severe undernutrition, non-washing of hands by mother before preparation of food, frequency of stool > 8/d, frequency of vomiting > 2/d, history of measles in previous six months, withdrawal of breast feeding during diarrhoea, withdrawal of fluids during diarrhoea and not giving ORS, HAF or both during diarrhoea, in the outcome of development of moderate or severe dehydration. CONCLUSIONS: Timely intervention in the preventable risk factors included in this study may prevent the development of moderate or severe dehydration in the children suffering form acute watery diarrhoea.

Case-Control Studies↗
PubMed1989

Clinical signs of dehydration in children.

102 children with acute gastroenteritis were thought by the admitting junior doctors to be 5% or more dehydrated. As judged by subsequent weight recovery in hospital, the main indicators of mild to moderate dehydration were decreased peripheral perfusion, deep breathing, decreased skin turgor, high urea, low pH, and a large base deficit; a history of increased thirst was just short of statistical significance. Dehydration was not indicated by a history of oliguria, by the presence of restlessness or lethargy, sunken eyes, dry mouth, or a sunken fontanelle or by the absence of tears. Clinical signs of dehydration became apparent at 3-4% rather than 5% dehydration. The degree of dehydration was overestimated by a mean of 3.2%; this caused unnecessary hospital admissions and overtreatment with intravenous fluid.

Acute Disease↗
PubMed1997

Are mu-opioid receptors involved in the control of endothelin-1 release from the pituitary gland in normal and dehydrated rats?

UNLABELLED: The objective of the present study was to investigate whether the endogenous opioids are involved in the control of endothelin-1 release from the pituitary gland. To test this hypothesis we have measured the peripheral plasma concentration of ET-1 as well as the content of immunoreactive ET-1 (irET-1) in the pituitary in response to opioid receptors blockade in euhydrated and 24 h water-deprived Wistar-Kyoto rats. Placebo or naltrexone (50 micrograms/kg body wt.) were given i.v. in both groups. Trunk blood was collected to determine hematocrit, plasma sodium and ET-1 levels (RIA). Immunostaining of ET-1 in the whole pituitary glands was performed by colloidal gold labeling. The quantitative analysis of irET-1 was carried out under a light microscope using a computerized image analyzer (MultiScan). RESULTS: (1) Twenty-four-hour dehydration resulted in marked increase of peripheral concentration of ET-1. Naltrexone injection induced a significant elevation of ET-1 plasma concentration in both, dehydrated and control animals. (2) The content of irET-1 in anterior and intermediate lobes of the pituitary in dehydrated rats was markedly higher than in control group. (3) Naltrexone injection caused a rapid and significant reduction irET-1 within the anterior, intermediate and posterior lobes in dehydrated and control animals. CONCLUSIONS: (1) An elevation of irET-1 in the pituitary gland and peripheral circulation in dehydrated animals may play a role in maintaining of water-electrolyte balance. (2) The mu-opioid system appears to control the ET-1 release from the pituitary in normal and dehydrated animals.

Animals↗
PubMed1998

Effect of dehydration on the pharmacokinetics of oxytetracycline hydrochloride administered intravenously in goats (Capra hircus).

1. The effects of various levels of dehydration induced by water deprivation were studied in six Nubian goats on the pharmacokinetics of oxytetracycline after intravenous administration (5 mg/kg). 2. In goats that had lost an average of 7.6% body weight after 2 days of water deprivation, the elimination rate constant of the drug was significantly decreased (P<0.01) and the total body clearance was significantly slower (P<0.001). No statistically significant changes were observed in the pharmacokinetic parameters describing the distribution of the drug at this dehydration level. 3. Water deprivation for 3 or 4 days resulted in a level of dehydration at which the goats lost an average of 10.3% or 12.7% of their body weight, respectively; significant changes were observed in the pharmacokinetic distribution and elimination parameters of oxytetracycline. The volume of distribution at steady state was significantly decreased (P<0.01). Significantly slower total body clearance (P<0.001) and subsequent prolongation of the elimination half-life were found at these dehydration levels. 4. The alterations caused by dehydration on the disposition kinetics of the drug should be considered for better definition of dosage regimens for sick, dehydrated animals.

Animals↗
PubMed1998

Role of antioxidant defenses in the tolerance of severe dehydration by anurans. The case of the leopard frog Rana pipiens.

Many anurans have excellent dehydration tolerance that allows endurance of the loss of up to 50-60% of total body water. One of the effects of severe dehydration is circulatory impairment due the reduced volume and increased viscosity of blood, which leads to organ hypoxia. The rehydration situation, therefore, involves a reoxygenation of tissues that may include elements of oxidative stress that resemble the injury in post-ischemic reperfusion of mammalian organs. The role of endogenous defenses against oxygen radicals in the tolerance of severe dehydration by leopard frogs, Rana pipiens, was investigated by monitoring the activities of antioxidant enzymes and glutathione levels (reduced GSH and oxidized GSSG) in leg muscle and liver of control, 50%-dehydrated, and fully rehydrated frogs. The maximal activities of muscle catalase and liver glutathione peroxidase, measured per mg soluble protein, increased significantly by 52 and 74%, respectively, after dehydration whereas muscle superoxide dismutase and glutathione reductase activities responded oppositely, decreasing by 32 and 35%, respectively. Enzyme activities returned to control levels after full rehydration. Hepatic GSH and GSSG increased early in the rehydration process (30% recovery of total body water), but returned to control levels after full recovery. A similar trend was observed for liver GSSG. The elevation of antioxidant defenses against peroxides during dehydration could provide protection against post-hypoxic oxyradical stress during rehydration. Indeed, analysis of one product of lipid peroxidation, thiobarbituric acid reactive substances, in frog tissues gave no indication of oxidative stress during the dehydration/rehydration cycle.

Animals↗