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Dehydration-induced cross-regulation of apelin and vasopressin immunoreactivity levels in magnocellular hypothalamic neurons.

Apelin, a neuropeptide recently identified as the endogenous ligand for the G protein-coupled receptor APJ, is highly concentrated in brain structures involved in the control of body fluid homeostasis including the supraoptic (SON) and paraventricular (PVN) hypothalamic nuclei. To clarify the implication of apelin in the regulation of water balance, we sought to determine whether apelin colocalized with arginine vasopressin (AVP) in the rat SON and PVN. We also investigated the effects of water deprivation on the levels of apelin within these two nuclei by comparison with those of AVP. Using dual immunolabeling confocal microscopy, we found that a large proportion of apelin-immunoreactive neurons colocalized AVP within both the SON and PVN, but that the two peptides were segregated within distinct subcellular compartments inside these cells. Both the number and labeling intensity of magnocellular apelin-immunoreactive cells increased significantly after 24- or 48-h dehydration, whereas the number and labeling density of AVP-immunoreactive neurons significantly decreased. The dehydration-induced increase in apelin immunoreactivity was markedly diminished by central injection of a selective vasopressin-1 receptor antagonist. Conversely, the effect of dehydration was mimicked by a 16-min intracerebroventricular infusion of AVP, again in a vasopressin-1 receptor antagonist-reversible manner. These results provide additional evidence for the involvement of the neuropeptide apelin in the control of body fluid homeostasis. They further suggest that the dehydration-induced release of AVP from magnocellular hypothalamic neurons may be responsible for the observed increase in immunoreactive apelin levels within the same neurons and thus that the release of one peptide may block that of another peptide synthesized in the same cells.

Animals↗

Fluid calories and energy balance: the good, the bad, and the uncertain.

Energy-yielding fluids are a large and growing proportion of daily energy intake. The specific form and nutrient composition of fluids may hold divergent implications for energy balance. Ethanol elicits a weak compensatory dietary response, resulting in positive energy balance. However, its impact on body weight is unclear, possibly due to metabolic inefficiencies. In contrast, the weak dietary compensation for clear beverages containing other energy sources is associated with weight gain. How these beverages elude satiety mechanisms has not been studied. Soups hold higher satiating value, at least in part, due to cognitive factors. Nutrient dense beverages have been used successfully in meal replacement regimens for weight management, but due to their relatively weak satiety value, are widely consumed for weight gain and as nutrient supplements. A better understanding of the role of fluid calories in the diet is needed to improve dietary guidelines.

Beverages↗

Regulation of body water balance in reedfrogs (superspecies Hyperolius viridiflavus and Hyperolius marmoratus: Amphibia, Anura, Hyperoliidae) living in unpredictably varying savannah environments.

The regulation of body water balance was examined in the reedfrogs Hyperolius marmoratus taeniatus and Hyperolius viridiflavus ommatostictus. Temperature and stage of post-metamorphic development significantly affected the rate of water uptake. Hydrated reedfrogs prevented hyperhydration by voiding diluted urine when obtaining water. Within 48 hr after rehydration, body fluid osmolality remained at low levels, which may be supportive to counter excessive cutaneous water influx in hydrated frogs. Once evaporative water loss exceeded 10-12% total body mass, reedfrogs became anuric. The rate of water uptake strongly increased with increasing body water deficit. Both the anuric response and the increased rate of water uptake are assumed to strongly enhance the efficacy of using very briefly available water sources during dry-period conditions. Dry-adapted and estivating reedfrogs survived evaporative water losses between 40 and 55% total body mass. Bladder fluid stores contributed substantially to this desiccation tolerance. During a 16-day period of desiccation, H. v. ommatostictus could replace approximately 25% of evaporative water loss from the bladder fluid store. During desiccation, the level of free amino acids selectively increased in the gastrocnemius muscle tissue, which may support cell volume regulation and/or protect cellular structures from osmotic stresses. Even strongly dehydrated reedfrogs rehydrated quickly with no obvious osmoregulatory problem. Rehydration was associated with a higher than expected decrease of free amino acids in the gastrocnemius muscle tissue, a response that may help to protect cells from bursting during fast rehydration.

Amino Acids↗

Aqueous vasopressin infusion during chemotherapy in patients with diabetes insipidus.

BACKGROUND: Patients who have suprasellar germinomas in childhood often present with central diabetes insipidus (CDI). The authors investigated the use of aqueous vasopressin (AVP) by continuous infusion to control the fluid and electrolyte balance in germinoma patients with CDI during aggressive fluid hydration as a part of a preirradiation chemotherapy protocol. METHODS: Three patients with suprasellar germinomas and CDI were treated with four courses of preirradiation chemotherapy. Two patients were treated with a continuous AVP infusion at an initial rate of 0.08-0.10 mU/kg per hour during hydration. Fluid intake, urine output, body weight, urine specific gravity, and serum electrolyte concentrations were monitored closely, and the infusion rate was adjusted accordingly. RESULTS: Very low dose AVP infusion controlled fluid balance while allowing appropriate diuresis during chemotherapy. Fluid intake and output were markedly less in the AVP-treated patients (3.8 L/m2 per day) than in the untreated patient (20 L/m2 per day). CONCLUSIONS: The use of very low dose AVP infusion at an initial rate of 0.08-0.10 mU/kg per hour during hydration therapy allowed easily titratable control of fluid and electrolyte balance in the patients studied and avoided the complications associated with desmopressin acetate antidiuresis or withholding antidiuretic treatment altogether.

Adolescent↗

Post-exercise rehydration in man: effects of electrolyte addition to ingested fluids.

This study examined the effects on water balance of adding electrolytes to fluids ingested after exercise-induced dehydration. Eight healthy male volunteers were dehydrated by approximately 2% of body mass by intermittent cycle exercise. Over a 30-min period after exercise, subjects ingested one of the four test drinks of a volume equivalent to their body mass loss. Drink A was a 90 mmol.l-1 glucose solution; drink B contained 60 mmol.l-1 sodium chloride; drink C contained 25 mmol.l-1 potassium chloride; drink D contained 90 mmol.l-1 glucose, 60 mmol.l-1 sodium chloride and 25 mmol.l-1 potassium chloride. Treatment order was randomised. Blood and urine samples were obtained at intervals throughout the study; subjects remained fasted throughout. Plasma volume increased to the same extent after the rehydration period on all treatments. Serum electrolyte (Na+, K+ and Cl-) concentrations fell initially after rehydration before returning to their pre-exercise levels. Cumulative urine output was greater after ingestion of drink A than after ingestion of any of the other drinks. On the morning following the trial, subjects were in greater net negative fluid balance [mean (SEM); P < 0.02] on trial A [745 (130) ml] than on trials B [405 (51) ml], C [467 (87) ml] or D [407 (34) ml]. There were no differences at any time between the three electrolyte-containing solutions in urine output or net fluid balance. One hour after the end of the rehydration period, urine osmolality had fallen, with a significant treatment effect (P = 0.016); urine osmolality was lowest after ingestion of drink A.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

Laparoscopic gastric banding and body composition in morbid obesity.

BACKGROUND AND AIM: Gastric banding induced considerable and rapid weight loss in morbid obesity. Nevertheless data on changes in body composition following gastric banding are scanty. In this study, we evaluated the 2-year changes in body composition in a small group of morbidly obese women treated by laparoscopic adjustable gastric banding (LAGB) associated with a well balanced low-calorie diet. METHODS AND RESULTS: We studied 20 premenopausal morbid obese women with BMI ranging from 35 to 57 (kg/m2) before, and 6, 12 and 24 months after laparoscopic adjustable gastric banding (LAGB). A well balanced 5.4 MJ/day hypocaloric diet was prescribed after surgery. Total body water (TBW), fat-free mass (FFM) and fat mass (FM) were investigated using conventional bioelectrical impedance analysis (BIA). Tissue hydration was also assessed by impedance vector analysis and the RXc graph method. The subjects showed a total weight loss of 28% of baseline body weight. In the first 6 months after surgery, patients lost 18.5+/-5.9 kg of body weight (17.6+/-6.2 kg of FM and 0.7+/-1.4 kg of FFM). From 6 to 12 months, a further 12.5+/-7.5 kg of body weight was lost (10.5+/-8.2 kg of FM and 2.2+/-3.8 kg of FFM). During the last 12 months, weight loss was 3.0+/-2.3 kg (1.9+/-3.7 kg of FM and 1.1+/-2.9 kg of FFM). The weight loss observed after LAGB was mainly due to a decrease in FM, whereas TBW, FFM and BCM were only slightly and non-significantly reduced. No changes in body hydration status were observed after surgery. CONCLUSIONS: LAGB associated with a well balanced low-calorie diet achieved a satisfactory 2-year weight loss, while sparing FFM and not causing body fluid alterations.

Adipose Tissue↗

Fluid volume measurements in normal subjects to disclose body hydration during acute bed rest.

Measuring intercompartmental, blood and urinary biochemical parameters during acute bed rest (ABR) and rigorous bed rest (RBR) the aim of this work was to disclose if ABR or RBR could influence significantly more and significantly faster the body hydration level in normal subjects. Studies conducted during pre-bed rest (BR) period of 3-days and during 7-days period of ABR and RBR. Thirty normal male individuals 24.6 +/- 5.7 years of age were chosen as subjects. They were divided into three groups: unrestricted active control subjects (UACS), acute bed rested subjects (ABRS) and rigorous bed rested subjects (RBRS). Acute bed rested subjects confined abruptly to RBR, while they did not have any prior knowledge of the exact date and time when they would be subjected to RBR. RBRS were submitted to RBR in a predetermined date and time known to them right from the start of the study. UACS were not subjected to any form of BR. Fluid loss, urinary and plasma sodium (Na+) and potassium (K+), plasma osmolality, whole blood hematocrit (Hct) and hemoglobin (Hb), and total plasma protein level increased significantly (p < 0.05), while urinary osmolality, extracellular volume (ECV), plasma volume (PV), red cell volume (RCV), blood volume (BV), interstitial volume (IV) and fluid consumption decreased significantly (p < 0.05) in ABRS and RBRS compared with their pre-BR values and their control (UACS). However, the measured variables changed significantly (p < 0.05) more and significantly faster in ABRS than RBRS. Conversely, whole blood Hct and Hb levels, fluid consumption and fluid loss, urinary and plasma osmolality, urinary and plasma electrolytes, plasma protein, ECV, PV, RCV, BV and IV levels were not change in UACS compared with their pre-BR values. Significantly greater and significantly faster intercompartmental, blood and urinary biochemical changes were observed in ABRS than RBRS. Body hydration was affected significantly more and significantly faster in ABR than RBR. It was concluded, the more abruptly normal activity is restricted the smaller the body hydration in bed rested subject is, and probably in patients who are abruptly confined to RBR.

Adolescent↗

Involvement of the renal natriuretic peptide urodilatin in body fluid regulation.

Urodilatin, a 32-aminoacid peptide, is expressed in distal tubular cells of the human kidney and presumably released into the luminal part of the nephron to exert its effect via activation of membrane-bound guanylyl cyclases (type A) at the medullary collecting duct. Thereby, the tubular reabsorption of sodium is inhibited and natriuresis is stimulated. The peptide is derived from the same gene and propeptide as the atrial natriuretic peptide (ANP), a more N-terminal cleavage in the human kidney than in other body tissues may be responsible for the existence of this renal natriuretic peptide and its increased stability in the extreme environment of the kidney and primary urine. The results of a sequence of human and animal physiology experiments has suggested that the renal natriuretic peptide, rather than its cardiac analog ANP, may play an essential role in mediating urinary sodium excretion. First observations are made suggesting a contribution of the renal natriuretic peptide also to disturbed sodium handling under pathophysiological conditions.

Animals↗

Nutritional support of the chronically ill elderly female at risk for elective or urgent surgery.

Among the elderly, those at highest risk are the chronically ill, inactive patients. Assessing macronutrient requirements and outcome depends on longitudinal studies. Seven chronically ill, elderly female patients suffering from persistent infections, were studied monthly, over a 6-month period to determine their protein and energy requirements. Calorie and protein requirements were based on clinical status. The results of the nutrition support program were monitored using: weight change, nitrogen balance, serum albumin levels, alterations in anthropometric measurements (triceps skinfold thickness and arm muscle circumference), and immune function tests. Based on the 6-month study period data, the calculated mean energy requirement for weight maintenance was 98% of calculated basal energy expenditure (BEE) and the mean protein required for nitrogen balance, 0.8 g/kg desired body weight (DBW). Excess caloric administration resulted in weight gain, determined to be fat (and/or fluid) but not lean body mass. When surgery is contemplated, there should be a 30% (factorial) increase over these base-line values. It is inadvisable to allow elderly patients to sustain any starvation, period given their inability to produce increases in body cell mass even in this 6-month period.

Aged↗

Endocrine control of salt and water excretion: the role of vasopressin in DOCA-salt hypertension.

Arginine-vasopressin (AVP), the antidiuretic hormone, not only regulates water balance but may also exert direct and indirect effects on blood pressure by influencing systemic vascular resistance and body fluid volumes. Recently, specific competitive antagonists of AVP at its vascular and tubular receptors have been described. We used d(CH2)5Tyr(Me) AVP, a vascular (V1) antagonist, and d(CH2)5-D-Tyr(Et) VAVP, a vascular and tubular (V1V2) antagonist, for studies on the role of AVP in deoxycorticosterone acetate (DOCA)-salt hypertension. The antagonists were infused intravenously via osmotic minipumps in unilaterally nephrectomized rats for 6 weeks after the beginning of the DOCA-salt treatment. At the end of the experiment, blood pressure was 15 mm Hg lower in the rats receiving the V1 antagonist than in those in which the vehicle was infused. In the rats receiving the V1V2 antagonist, blood pressure was reduced by 38 mm Hg. However, these rats were in poor general condition and gained no body weight. Their plasma sodium concentration was markedly increased throughout the duration of the experiment. These results suggest that AVP contributes to the development of DOCA-salt hypertension not only through its vascular but also through its renal tubular effects. Thus AVP may act as an impormediator of volume changes associated with alterations in sodium intake or excretion and thereby affect blood pressure.

Animals↗

Bioimpedance assessment of hypohydration.

PURPOSE: This study examined the utility of bioimpedance spectroscopy (BIS) for assessing total body water (TBW) changes associated with moderate (6-7% TBW), hypertonic (HH), and isotonic (IH) hypohydration. METHODS: The TBW of nine men was measured using BIS (TBWBIS) when euhydrated (EU) and during HH and IH. These measurements were compared with TBW measurements obtained using isotope dilution (deuterium oxide; TBWD20) during EU, and the estimated TBWD20 during hypohydration calculated from body weight change. RESULTS: Body weight loss was similar (P > 0.05) for HH (3.4 +/- 0.7 kg) and IH (2.9 +/- 0.7 kg). Plasma osmolality was higher (P < 0.05) on HH (292 +/- 4 mOsmol x kg(-1)) than EU (280 +/- 4 mOsmol x kg(-1)) and IH (284 +/- 3 mOsmol x kg(-1)), and higher (P < 0.05) during IH than EU. The measurements reflected a similar decrease (P < 0.05) in TBW during HH (TBWD20: 45.4 +/- 7.3 L, TBWBIS: 42.2 +/- 5.1 L) and IH (TBWD20: 45.8 +/- 7.5 L, TBWBIS: 42.0 +/- 4.9 L), compared with EU (TBWD20: 48.8 +/- 7.5 L, TBWBIS: 44.3 +/- 5.0 L), but TBWD20 was consistently higher (3.9 +/- 4.0 L, P < 0.05) than TBWBIS during all tests. TBWD20 and TBWBIS were correlated (P < 0.05) during EU (r = 0.87), HH (r = 0.84), and IH (r = 0.84). The change in TBW from EU during HH was greater (P < 0.05) for TBWD20 (3.5 +/- 0.8 L) than TBWBIS (2.1 +/- 0.9 L), but during IH the change in TBW reflected by TBWD20 (3.0 +/- 0.6 L) and TBWBIS (2.3 +/- 0.8 L) did not differ. The change in TBWD20 and TBWBIS between EU and hypohydration was correlated for HH (r = 0.77, P < 0.05), but not IH. CONCLUSION: These findings indicate that BIS is sufficiently sensitive to detect moderate hypohydration; however, the resolution of this technique diminished with isotonic fluid loss.

Adolescent↗

A case of alveolar cell carcinoma accompanied by fluid and electrolyte depletion through production of voluminous amounts of lung liquids.

A patient is described who showed typical features of alveolar cell carcinoma, including production of a huge amount of clear frothy lung liquid (as much as 4 liter per day), diffuse dissemination of nodular lesions throughout the lung, and tall columnar cell proliferation outlining the alveolar walls uniformly without architectural destruction in the terminal lung unit. From the results of comparative serial analyses of biochemical components in the liquid and the serum, it is suggested that the excessive liquid production in this case should be due to abnormal secretory functioning of diffusely proliferated carcinoma cells.

Adenocarcinoma, Bronchiolo-Alveolar↗