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PubMedDate not supplied

Dehydration and symptoms of delayed-onset muscle soreness in normothermic men.

CONTEXT: A dehydrated individual who performs eccentric exercise may exacerbate skeletal muscle damage, leading to structural, contractile, and enzymatic protein denaturation, in addition to the myofiber and connective damage resulting from the eccentric muscle tension. OBJECTIVE: To identify the effects of dehydration on 5 physiologic characteristics of delayed-onset muscle soreness (DOMS) in normothermic men after an eccentric exercise perturbation. DESIGN: Randomized group test-retest design. SETTING: Laboratory. PATIENTS OR OTHER PARTICIPANTS: Ten healthy male volunteers randomly assigned to either a euhydration (age = 26.2 +/- 4.9 years, height = 174.1 +/- 6.0 cm, mass = 86.5 +/- 15.3 kg) or dehydration (age = 25.8 +/- 2.2 years, height = 177.2 +/- 3.1 cm, mass = 84.4 +/- 3.8 kg) group. INTERVENTION(S): Subjects performed treadmill walking for 45 minutes in either a thermoneutral (euhydration) or a hot, humid (dehydration) environment. After a rest period to allow for return to the normothermic condition, DOMS was induced with a 45-minute downhill run. MAIN OUTCOME MEASURES: We assessed 5 physiologic characteristics of DOMS before and at intervals after the eccentric exercise. The characteristics were perceived pain of the bilateral quadriceps and overall body, bilateral punctate tenderness of the superficial quadriceps muscles, bilateral knee-flexion passive range of motion, bilateral thigh circumference, and bilateral isometric quadriceps muscle strength. Thermoregulatory and cardiovascular measures were obtained to monitor participants' heat load during exercise. RESULTS: The experimental protocol produced a 0.9% increase in body mass of the euhydration group and a significant 2.7% decrease in body mass of the dehydration group. The downhill-running exercise perturbation induced DOMS in both the euhydrated and dehydrated participants, based on increased bilateral quadriceps and overall body perceived pain and punctate tenderness of the bilateral vastus medialis muscle. The signs and symptoms of DOMS after an eccentric exercise perturbation were not exacerbated by moderate dehydration of 2.7% body mass after rest and return to the normothermic condition. CONCLUSIONS: Significantly dehydrated participants who rested and returned to a normothermic condition did not experience increased characteristics of DOMS.

Journal Article↗

PubMed2002

Rehospitalization for neonatal dehydration: a nested case-control study.

OBJECTIVES: To determine the incidence of neonatal dehydration leading to rehospitalization, whether clinical and health services data could predict its occurrence, and the outcome of dehydrated infants. METHODS: We employed a retrospective case-control design nested within a cohort of 51 383 newborns weighing 2000 g or more, with a gestational age of 36 weeks or more born at 11 Kaiser Permanente hospitals during 1995 and 1996. Cases were 110 infants who were rehospitalized within 15 days of discharge with dehydration, and who either had 12% or greater weight loss or a serum sodium level of 150 mEq/L or greater. Controls were 402 randomly selected infants. We reviewed subjects' paper medical records and telephoned their families at 24 to 36 months of age to ascertain neurological outcomes. RESULTS: Rehospitalization for dehydration occurred in 2.1 per 1000 live births (95% confidence interval [CI], 1.8-2.6). Among vaginal births, the most important risk factors were being born of a first-time mother (adjusted odds ratio [AOR], 5.5; 95% CI, 3.1-9.6); exclusive breastfeeding (AOR, 11.2; 95% CI, 3.9-32.6); maternal age equal to or older than 35 years (AOR, 3.0; 95% CI, 1.5-6.0); and gestational age younger than 39 weeks (AOR, 2.0, 95% CI, 1.2-3.5). Among cesarean births, having a birth hospitalization length of stay less than 48 hours was associated with dehydration (odds ratio [OR], 14.8; 95% CI, 1.4-154.1). Adherence to the American Academy of Pediatrics follow-up guideline did not decrease risk of readmission. Among surviving infants, 1 of 110 cases and 12 of 400 controls had evidence of possible neurological problems 24 to 36 months after discharge (P =.3). No cases of limb gangrene, amputation, or intracranial infarction occurred. CONCLUSIONS: In this population with good access to medical care, serious sequelae of neonatal dehydration are rare. Interventions to decrease the frequency of neonatal dehydration should focus on first-time mothers and those who breastfeed exclusively.

Birth Weight↗

PubMed1989

Thermal panting in dehydrated dogs: effects of plasma volume expansion and drinking.

Dehydrated mammals reduce thermoregulatory evaporation and regulate deep body temperature (Tb) at elevated levels when they are exposed to heat. These experiments were designed to study the effects of plasma volume (PV) replacement and the effects of drinking H2O or 0.9% NaCl on thermal panting in dehydrated dogs resting at Ta 40-41 degrees C. Five dogs were studied when they were hydrated (control) and in 4 different experiments when they had been dehydrated (D) by removal of drinking water: (1) D, no treatment; (2) D + intravenous dextran infusion; (3) D + drinking H2O; (4) D + drinking NaCl. Compared to controls, dehydrated dogs had lower respiratory frequency (f), higher Tb, lower PV and blood volume (BV) and higher plasma osmolality (pOsmol). Intravenous dextran infusion restored BV to the control level without reducing pOsmol; but f and Tb remained at dehydrated levels after the infusion. When the dogs drank either H2O or NaCl,f increased significantly during the first minute after drinking. pOsmol decreased by 6 min after drinking H2O but did not change after drinking NaCl. BV measured 5 min after the end of drinking H2O was not different from dehydrated BV. It is concluded that (1) Restoration of BV to hydrated levels in dehydrated, heat-exposed dogs with elevated pOsmol does not restore f or Tb to hydrated levels; (2) There is a rapid recovery of thermal panting after drinking which is not dependent on changes in pOsmol or in BV.

Animals↗

PubMed2003

Achievement of rapid osmotic dehydration at specific temperatures could maintain high Saccharomyces cerevisiae viability.

Various methods have been tried to prevent cell mortality during dehydration, but the reasons why microorganisms die when submitted to dehydration and rehydration are not well understood. The aim of this study was to further investigate the reasons for yeast mortality during dehydration. Osmotic dehydration and rehydration of Saccharomyces cerevisiae W303-1A were performed at different temperatures. Two different approaches were used: isothermic treatments (dehydration and rehydration at the same temperature), and cyclic treatments (dehydration at an experimental temperature and rehydration at 25 degrees C), with significant differences in viability found between the different treatments. Dehydration at lower and higher temperatures gave higher viability results. These experiments allowed us to propose a hypothesis that relates mortality to a high water flow through an unstable membrane during phase transition.

Dehydration↗

PubMed1985

Redistribution of cardiac output in anesthetized thermally dehydrated rats.

Cardiac output (CO) and its distribution were studied in dehydrated (37 degrees C) anesthetized (Na thiopentone) rats prior to and following heat acclimation (at 34 degrees C), using 57Co 15 micron microspheres. In non-acclimated dehydrated rats, CO decreased while heart rate (HR) increased significantly. Following acclimation CO increased without any change in HR; during dehydration CO remained elevated together with a significant increase in HR. In non-acclimated rats at low dehydration blood perfusion to peripheral thermoregulatory areas increased while perfusion of splanchnic area decreased; at high dehydration level peripheral blood flow decreased whereas splanchnic blood flow was augmented. In acclimated dehydrated rats, CO distribution to thermoregulatory areas did not change while perfusion of the splanchnic area decreased. It is suggested that following acclimation, the increased CO contributes to maintenance of thermoregulatory peripheral blood flow; in non-acclimated rats severe dehydration leads to augmented blood flow in the permeable splanchnic vascular bed, increasing efflux of plasma protein and failure of plasma volume conservation.

Acclimatization↗

PubMed1992

The effect of dehydration on brain temperature regulation in Japanese quail (Coturnix coturnix japonica).

1. The effect of dehydration and heat exposure on body and brain temperature was studied in quail exposed to increasing ambient temperatures within the range of 25-40 degrees C. 2. The body-to-brain temperature difference was not affected by increasing ambient temperature or hydration state. A mean body-to-brain temperature difference of 0.96 +/- 0.64 degrees C and 0.85 +/- 0.65 degrees C was found in normally hydrated and dehydrated quail, respectively. 3. The slope of the relation between brain temperature to body temperature (0.77) was significantly lower than 1.0 (P less than 0.001), when the results of the two hydration states were pooled. This indicates increased brain cooling with increased body temperature. 4. Body and brain temperatures of water-deprived quail were significantly higher (P less than 0.05) than those of hydrated birds during exposure to ambient temperatures of 35 and 40 degrees C. 5. Respiration frequency increased during exposure to 35 (four birds) and 40 degrees C (six birds) in the normally hydrated quail, while in the dehydrated quail, respiration frequency increased only in three birds during exposure to 35 degrees C, and four birds during exposure to 40 degrees C, the frequencies were lower during dehydration. 6. Plasma osmolality and chloride concentration were significantly higher in the dehydrated quail (P less than 0.05). 7. The present findings show that dehydration and heat exposure resulted in a relative hyperthermy, and thus implying a reduced evaporative cooling. The quail appears to be well adapted to dehydrating conditions.

Animals↗

PubMed1986

Effect of intraperitoneal and intragastric loading with water and isosmotic solutions of saline and glucose on water intake of dehydrated rats.

Female rats, dehydrated with food available for 24 hr, lost 6 to 8% of body weight. When allowed access to water, 40 to 60% of the weight deficit was replaced within the first hr. Either intraperitoneal (IP) or intragastric (IG) water loads (3% of body weight) administered just prior to return of water inhibited water intake of dehydrated rats nearly completely during the first hr of access to water. In contrast, similar loads of isotonic saline were much less effective. Even when 0.5 and 1.0 hr elapsed between IP loading (3% of body weight) with isotonic saline and access to water, water intake was not significantly different from that of untreated, dehydrated controls. In contrast, a similar IP load of water at these times completely inhibited water intake. Because of the contrasting effects of similar loads of water and isotonic saline on water intake of dehydrated rats, additional studies were carried out with an isosmotic solution of glucose (5%). IG administration (3% of body weight) of glucose inhibited water intake of dehydrated rats. IP administration (3% of body weight) attenuated the drinking response but did not reduce it to the level observed in dehydrated rats given an IP water load. When isosmotic glucose was administered at 0.5, 1.0, and 2.0 hr prior to allowing access to water, water intake was reduced significantly below that of dehydrated controls and to the same extent regardless of time of administration of the glucose load.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1992

Reevaluation of the plasticity in the rat supraoptic nucleus after chronic dehydration using immunogold for oxytocin and vasopressin at the ultrastructural level.

It has been shown that during physiological stimuli, such as dehydration, supraoptic nucleus (SON) neurons undergo profound morphological changes. However, little is known about how much each type of cell, oxytocin (OT) or vasopressin (VP), contributes to this plasticity during dehydration. Using postembedding immunogold cytochemistry for both OT and VP hormones at the electron microscopic level, we address this question. Rats were chronically dehydrated (given 2% saline to drink for 10 days) and their SON neurons were studied morphologically. The results were compared to control animals with free access to water. Both VP and OT somata showed an enlargement in size in dehydrated animals. Percentage of somasomatic/dendritic membrane contact increased significantly in both VP and OT neurons, with no significant changes in percentage of coverage of the cells by astrocytic membrane. Only the VP cells had a lesser amount of axosomatic membrane contact after dehydration, possibly due to an increase in cell size rather than a decrease in synaptic contact. Multiple synapses (MSs) (i.e., terminals that form more than one synapse with adjacent somata and or dendrites) occurred only between positively labeled cells and between negatively labeled cells, but not between positively and negatively labeled cells. The number of MSs per 100 microns OT somatic membrane or per 100 OT cells was significantly higher in dehydrated rats but was unchanged with regard to VP neurons. These findings indicate that both VP and OT neurons undergo morphological changes during chronic dehydration and, thus, that plasticity is not limited to OT cells as some earlier reports have suggested.

Animals↗

PubMed2004

Postmortem diagnosis of hypertonic dehydration.

Beside morphological signs of hypertonic dehydration as tinting of skin, sunken eyes, dry surface of the galea or dry cutting areas of organs, a chemical profile of vitreous humor was proposed as a diagnostic tool for the diagnosis of hypertonic dehydration. The profile consists of an elevation of sodium >155 mmol/l, chloride >135 mmol/l and urea >40 mg/dl. This profile was named dehydration pattern. The value of this dehydration pattern for the diagnosis of hypertonic dehydration will be discussed by a short review of the literature and case reports. So far, the published literature on the dehydration pattern is not a sound scientific basis for the diagnosis of dehydration.

Chlorides↗

PubMedDate not supplied

Intra- and extracellular dehydration-induced thirst-related behavior in an amphibian.

The behavioral response to dehydration is critical to an animal's survival. Because of their permeable skin, amphibians are particularly sensitive to dehydrating conditions. We tested the hypothesis that different forms of dehydration induce water absorption response (WR) behavior in the desert spadefoot toad, Scaphiopus couchii. First, we determined the behavioral response to intracellular dehydration by treating fully hydrated toads with increasing concentrations of hypertonic solutions of NaCl or sucrose via intraperitoneal injection (i.p.). Animals that were treated to induce intracellular dehydration with either solute exhibited a significant increase in WR behavior compared to vehicle-treated controls. To distinguish that the response was a result of an increased osmotic gradient between the intra- and extracellular compartments, we treated fully hydrated animals i.p. with urea, which freely passes into the intracellular compartment and increases overall animal osmolarity. Urea treatment did not induce WR behavior. To determine the response to extracellular dehydration, the blood volume of fully hydrated toads was reduced via cardiac puncture, and the WR behavior was measured. Animals who had a reduction in blood volume exhibited a significant increase in WR behavior compared to sham-punctured controls. Our results are the first to demonstrate that multiple forms of dehydration can induce thirst-related behavior in amphibians.

Animals↗

PubMed2002

Effects of dehydration on renal aminopeptidase activities in adult male and female rats.

Aminopeptidases (APs) are important regulators of peptides directly involved in water homeostasis such as angiotensins (Ang) and vasopressin (AVP). Sex differences in water balance and differences in the effects of gonadal steroids on osmotic stimulation of vasopressin secretion have been reported. Since sex steroids may be involved, the gonadotropin response to osmotic stimuli may be different between males and females. The purpose of this study was to determine the behavior of angiotensinases, vasopressin-degrading activity and gonadotropin-releasing hormone (GnRH)-degrading activity in the cortex and medulla of the kidney of dehydrated male and female rats. In the renal cortex, our results demonstrated an increase in Ang III-degrading activity in dehydrated males but not in females. This response may lead to an increased formation of Ang IV. This occurs with an increase in AspAP activity (which metabolizes Ang I to des-Asp(1)-Ang I), with no changes in Ang II-degrading activity and also with increased levels of AVP-degrading activity in dehydrated animals. These results may suggest an increased cortical blood flow due to enhanced formation of Ang IV together with reduced availability of the vasoconstrictor agents Ang II and AVP in the renal cortex of dehydrated males. The results obtained in the renal medulla suggest the inhibition of the metabolism of Ang I to des-Asp(1)-Ang I, together with a reduced metabolism of Ang II and AVP in dehydrated males but not in females. These results suggest a prolonged action of Ang II and AVP, which could stimulate sodium and water reabsorption in the medulla of dehydrated males. Changes in APs after dehydration occur preferentially in males, which may explain in part the reported sex differences in water homeostasis. The present results suggest a physiologically relevant role for AP activities in water homeostasis.

Aging↗

PubMed2001

Effects of fluid ingestion on cognitive function after heat stress or exercise-induced dehydration.

This study investigated the effects of heat exposure, exercise-induced dehydration and fluid ingestion on cognitive performance. Seven healthy men, unacclimatized to heat, were kept euhydrated or were dehydrated by controlled passive exposure to heat (H, two sessions) or by treadmill exercise (E, two sessions) up to a weight loss of 2.8%. On completion of a 1-h recovery period, the subjects drank a solution containing 50 g l(-1) glucose and 1.34 g l(-1) NaCl in a volume of water corresponding to 100% of his body weight loss induced by dehydration. (H1 and E1) or levels of fluid deficit were maintained (H0, E0). In the E0, H0 and control conditions, the subject drank a solution containing the same quantity of glucose diluted in 100 ml of water. Psychological tests were administered 30 min after the dehydration phase and 2 h after fluid ingestion. Both dehydration conditions impaired cognitive abilities (i.e. perceptive discrimination, short-term memory), as well as subjective estimates of fatigue, without any relevant differences between the methods. By 3.5 h after fluid deficit, dehydration (H0 and E0) no longer had any adverse effect, although the subjects felt increasingly tired. Thus, there was no beneficial effect of fluid ingestion (H1 and E1) on the cognitive variables. However, long-term memory retrieval was impaired in both control and dehydration situations, whereas there was no decrement in performance in the fluid ingestion condition (H1, E1).

Adult↗

PubMed1992

Effect of dehydration on cardiovascular responses and electrolytes after hypertonic saline/dextran treatment for moderate hemorrhage.

STUDY OBJECTIVE: To determine if hypertonic saline/dextran (HSD) is effective in treating hemorrhage in the presence of dehydration. DESIGN: After surgical preparation, swine were euhydrated or dehydrated for 24 or 48 hours. Animals were bled 25 mL/kg over 60 minutes and treated with HSD. SETTING: Laboratory. PARTICIPANTS: Seventeen immature Yorkshire pigs. INTERVENTIONS: 4 mL/kg HSD (7.5% NaCl in 6% dextran-70) administered over one minute. MEASUREMENTS AND MAIN RESULTS: All euhydrated animals survived; 100% of the pigs survived 180 minutes after treatment. Two animals dehydrated for 24 hours and three animals dehydrated for 48 hours died within three hours of HSD treatment. In all groups, plasma potassium was reduced significantly and equally; cardiac output was increased; mean arterial pressure rose rapidly within first five minutes, but was sustained only in euhydrated animals; hematocrit, hemoglobin, and plasma total protein levels were reduced; and plasma glucose increased with persistent between-group differences. RESULTS: HSD immediately rectified the decreases in mean arterial pressure and cardiac output incurred during hemorrhage; over time, however, the improvement in pressure was not sustained in dehydrated pigs. Parallel increases in plasma osmolality and sodium concentrations were offset by the initial group differences resulting from dehydration. CONCLUSION: Dehydration does not compromise the efficacy of HSD as a resuscitation treatment for hemorrhagic shock.

Animals↗

PubMed1996

Outpatient rapid intravenous rehydration to correct dehydration and resolve vomiting in children with acute gastroenteritis.

STUDY OBJECTIVE: To determine the efficacy of outpatient rapid i.v. rehydration in correcting dehydration and resolving vomiting in children with mild to moderate dehydration resulting from acute gastroenteritis. METHODS: We carried out a prospective cohort study in an urban children's hospital. A convenience sample of 58 children aged 6 months to 13 years, with acute gastroenteritis and clinically estimated dehydration of 5% to 10% body weight, was assembled. All patients had been vomiting for less than 48 hours, had vomited at least five times in the 24 hours preceding presentation, and had metabolic acidosis (serum bicarbonate concentration, 18 mEq/L or less). Each patient received an i.v. infusion of 20 to 30 mL/kg isotonic crystalloid solution over 1 to 2 hours, followed by the oral administration of 1 to 3 ounces of clear fluid. Patients who subsequently vomited were admitted for continued i.v. fluid therapy. Patients who tolerated oral fluid were discharged; their caregivers were contacted by telephone 24 to 48 hours after discharge. RESULTS: All patients had improved hydration status after rapid i.v. rehydration. Sixteen patients (28%) did not tolerate oral fluids after rapid i.v. rehydration and were admitted; 11 of these patients had a serum bicarbonate concentration of 13 mEq/L or less. The other 42 patients (72%) tolerated oral fluids after rapid i.v. rehydration and were discharged; 41 of these patients had a serum bicarbonate concentration greater than 13 mEq/L. The frequency of serum bicarbonate concentration of 13 mEq/L or less on presentation was significantly greater (P = .001) in patients requiring hospitalization than in those discharged from the emergency department after rapid i.v. rehydration. Of 40 patients whose caregivers were contacted after discharge, 34 (85%) required no further medical evaluation or treatment for any reason, including inadequate hydration; 29 of these patients vomited no more than once. Six of the discharged patients (15%) required further medical evaluation and were admitted; four had recurrent vomiting and dehydration, two had not vomited but were dehydrated as a result of diarrheal fluid loss or inadequate oral fluid intake. CONCLUSION: Outpatient rapid i.v. rehydration is safe and effective in correcting dehydration and resolving vomiting in selected children with acute gastroenteritis and mild to moderate dehydration. In our study, most children who presented with a serum bicarbonate concentration greater than 13 mEq/L tolerated oral fluids after rapid i.v. rehydration and were further managed as outpatients without complications. By contrast, most children with a serum bicarbonate concentration of 13 mEq/L or less usually did not tolerate oral fluids after rapid i.v. rehydration and required more prolonged i.v. fluid therapy. All discharged patients, regardless of their serum bicarbonate concentration, demonstrated the ability to tolerate orally administered fluid.

Adolescent↗

PubMed1983

The neurohypophysial axons in normal and dehydrated rats: an electron microscopic study including ZIO-staining method.

The neurohypophysial axons from normal rats and those dehydrated for 4 and 12 days were investigated by means of conventional glutaraldehyde fixation and the zinc-iodide-osmium (ZIO) staining technique. Conventionally fixed axons from dehydrated rats revealed depletion of dense core of neurosecretory granules, more frequent occurrence of microvesicles, proliferation of smooth endoplasmic reticulum or accumulation of lysosomes. It has been disclosed that the ZIO reaction product has the ability to stain microvesicles (normal rats) and smooth endoplasmic reticulum, lysosomes, some neurosecretory granules and some parts of stromal inclusion at the release site (dehydrated rats). Quantitative data are also presented. They indicate a significantly decreased number of both neurosecretory granules (NSG) and ZIO-positive microvesicles (MV) in dehydrated rats. Equally, the value of the median of the MV/NSG ratio was significantly increased from 1.38 in normal rats to 5.50 and 7.50 in rats dehydrated for 4 and 12 days, respectively. Thus, the possible involvement of ZIO-positive microvesicles in a process associated with neurosecretion is suggested. While in normal rats a correlation was found between the number of neurosecretory granules and the area of sectioned profiles of the axons, no evidence was obtained for it in 12-day dehydrated rats. Conversely, no evidence for a relationship between the axon area and the number of ZIO-positive microvesicles was obtained in normal rats, while in rats dehydrated for 12 days a correlation was found.

Animals↗

PubMed2004

Economic burden of dehydration among hospitalized elderly patients.

PURPOSE: The cost of unnecessary hospitalizations associated with dehydration in elderly patients was studied. METHODS: The study involved a retrospective examination of 1999 data on hospital discharges from the Healthcare Cost and Utilization Project Nationwide Inpatient Sample. The procedure code for volume depletion was used to extract hospitalization episodes for patients > or = 65 years of age who had a principal diagnosis of dehydration and were discharged alive. Hospitalizations with procedure codes unrelated to dehydration were omitted. RESULTS: The descriptive findings indicated that hospitalized older patients with a principal diagnosis of dehydration averaged 80.4 years of age, were primarily white (82.5%), and were more likely to live in the community than in a nursing home. Hospitalizations for dehydration were more common in the South and less common in the West. The average length of stay (LOS) was 4.6 days. The average total hospital charge was dollars 7,442, and the average per diem charge was dollars 1,628. Regression analysis explained nearly half of the variation in charges for dehydration (R2 = 0.457). Average LOS and number of diagnoses were directly related to hospital charges, and age was inversely related. Higher charges were associated with being nonwhite, entering the hospital via the emergency room, having private insurance, having no insurance, having comorbidities, and being hospitalized in the West or in teaching or urban hospitals. In 1999, the potential national saving from avoidable hospitalizations in these patients could have been as much as dollars 1.14 billion. CONCLUSION: The economic burden associated with avoidable hospitalizations due to dehydration in elderly patients was substantial.

Aged↗

PubMed1997

The relationship between dehydration and parotid salivary gland function in young and older healthy adults.

BACKGROUND: Saliva is essential for the maintenance of oral health. The primary constituent of saliva is water and, traditionally, decreased body water homeostasis has been linked with salivary dysfunction. This is consistent with the greater prevalence of dehydration and salivary gland dysfunction among the elderly. However, this association between dehydration and salivary dysfunction has never been tested using objective criteria. The purpose of this study was to determine the effect of body dehydration upon parotid salivary flow rates in young and older healthy adults. METHODS: Twelve young (20-40 years) and 12 older (60-80 years) healthy subjects abstained from food and beverage intake for 24 h (dehydration) and then underwent intravenous rehydration to replace all lost weight. Unstimulated and stimulated parotid salivary flow rates, weight, hematocrit, hemoglobin, serum sodium, plasma protein, creatinine, serum, and urine osmolality values were assessed at baseline, 24 h, and 1 h after the completion of rehydration. RESULTS: All subjects experienced a significant decrease in weight and increased levels of hematocrit, hemoglobin, plasma protein, and creatinine during dehydration with few age-related differences. Intravenous fluid replacement increased weight and decreased hematocrit, hemoglobin, plasma protein, and creatinine back to baseline values, demonstrating that subjects were metabolically rehydrated. Unstimulated (young and older, p = .0001) and stimulated (young, p > .05; older, p = .03) parotid flow rates decreased during the 24-h dehydration period, yet did not completely return (young and older unstimulated, p < .001; young and older stimulated, p > .05) to baseline values after rehydration. CONCLUSIONS: These findings suggest that body dehydration is associated with decreased parotid salivary gland flow rates, and that these changes are generally age-independent in healthy adults. Furthermore, although subjects were metabolically rehydrated, unstimulated salivary flow rates remained significantly lower than baseline levels.

Adult↗

PubMed2004

Dietary exposure to aroclor 1254 alters central and peripheral vasopressin release in response to dehydration in the rat.

Central vasopressin (VP) release from magnocellular neuroendocrine cells (MNCs) in the supraoptic nucleus (SON) occurs from their somata and dendrites within the SON several hours after acute dehydration, and is an important autoregulatory mechanism influencing the systemic release of VP from MNC terminals in the posterior pituitary. To begin to explore the impact of polychlorinated biphenyls (PCBs) on brain mechanisms of body fluid regulation, both central and systemic VP release in response to acute dehydration were assessed in adult male rats fed the commercial PCB mixture Aroclor 1254 (30 mg/kg/day) for 15 days. Water intake and body weight were recorded daily, and on day 15 rats were dehydrated by intraperitoneal injection of 3.5 M saline (controls received physiological saline) and sacrificed 4-6 h later. Intranuclear VP release was measured in SON tissue punches in vitro, and systemic VP release was measured in the same rats. SON prepared from dehydrated PCB-naive rats released significantly more VP than did SON from control rats (4.9 +/- 0.8 vs. 2.7 +/- 0.4 pg/ml/microg). In contrast, while Aroclor 1254 exposure had no effect on baseline water intake, weight gain, or plasma osmolality responses to dehydration in PCB-fed rats, the SON failed to respond with increased VP release during dehydration. Consistent with previous studies showing an inhibitory effect of central VP on plasma VP output, dehydrated PCB-fed rats had an exaggerated 863% increase in plasma VP over basal levels, compared to a 241% increase in PCB-naive rats, suggesting that the MNC system is subtly disrupted.

Animals↗