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PubMed1975

Fluid balance, renal function, and blood pressure.

After many detours in the search for the basic mechanism of hypertension, evidence now seems to corroborate the earliest concept that developed in the 1800's, namely, that hypertension almost always results from a tendency of the kidneys to retain water and salt. Animal studies show that the amount of excess body water and salt required to cause hypertension is exceedingly small, and that the hypertensive effect of the excess water and salt may not develop for days or weeks. When vascular constriciton occurs simultaneously, as occurs in the presence of large quantities of angiotensin, the blood volume may be less than normal, but even in these circumstances the fluid volume is relatively increased and is responsible for the hypertension because the vascular constrictont has decreased the capacity of the circulation to a greater extent than the decrease in blood volume.

Angiotensin II↗
PubMed1984

Neuroendocrine mechanisms mediating fluid intake during the estrous cycle.

Gonadal steroids appear to influence fluid-electrolyte homeostasis through behavioral as well as renal mechanisms. The marked fluctuations in drinking behavior observed during the estrous cycle of the female rat may be due to an interaction between estrogen and the dipsogenic peptide hormone, angiotensin II, at the level of basal forebrain receptors. The preoptic region in particular may play an important integrative role in the maintenance of extracellular fluid balance in synchrony with the estrous cycle, since it contains receptors for angiotensin and estrogen. Prolactin may also directly participate in mechanisms of extracellular thirst, while an exact role for vasopressin has yet to be established. Recent studies also suggest that estrogens may influence body fluid regulation by interacting with several neurotransmitters, including serotonin, dopamine and noradrenaline.

Angiotensin II↗
PubMed2005

Perioperative bioelectrical impedence analysis in neurosurgery.

The use of bioelectrical impedence (BI) measurement to assess body composition has recently attracted the attention of anesthesiologists. Analysis of BI provides a non-invasive method to quantify fluid distribution in different body compartments. This study was designed to assess whether BI analysis reflects fluid depletion in neurosurgical patients with moderate blood loss. Six adult male patients scheduled for elective craniotomy under general anesthesia were studied. Exclusion criteria included patients with cardio-respiratory disease. BI analysis was performed at three stages, A, day before operation, B, during surgery and C, on the first postoperative day. Total body resistivity was measured by BI analysis with a four-terminal portable impedence analyzer. At each frequency, impedence was calculated as resistance (Rx)2 + reactance (Rc)2. The mean values of total body water (TBW) at stages A, B and C were 39.8 L (range: 33.1-46.7 L), 43.2 L (range: 33.1-66.2 L) and 36.8 L (range: 22.4-36.3 L) respectively with significant differences (P<0.05). The impedence at the three frequencies during stages A, B and C showed significant differences (P<0.05). In conclusion, we have found that in male neurosurgical patients multiple frequency BI measurements has reflected fluid balance perioperatively. Whether this observation remains true for other surgical procedures with massive blood loss, yet to be further investigated.

Anesthesia, General↗
PubMed2000

Regulation and distribution of body fluid during a 6-day head-down tilt study in a randomized cross-over design.

Head down tilt (-6 degrees HDT) examinations are commonly used simulation models for various microgravity induced changes in body functions. Body fluid distribution (by means of dye dilution and two independent multifrequency impedance techniques), water- and sodium-handling, and the plasma/serum concentrations of fluid balance related hormones have been determined in a randomized, controlled, cross-over study in 8 healthy test subjects. The comparison of responses to HDT and an upright control position with respective experiences from space shows some similarities but also various discrepancies between the terrestrial simulation and real microgravity.

Bed Rest↗
PubMed1981

Body fluid composition in chronic renal failure.

Studies were performed to assess body fluid composition alterations occurring in 10 patients undergoing chronic hemodialysis. Red cell mass (RCM), plasma volume (PV), extracellular fluid volume (ECF), and total body water (TBW) were assessed 24 hours following hemodialysis to dry weight, following infusion of normal saline to increase body weight by approximately 2 kg, and following hemodialysis to decrease body weight by approximately 2 kg. Results demonstrate that TBW constituted from 48.5 to 51.0% of body weight. The ECF constituted from 41.8 to 46.3% of the total body water. The ratio of PV to interstitial fluid (ISF) volume (ISF = ECF - PV) approximated 1.1 to 1.2:3. Salt and water alterations (isotonic saline infusion and ultrafiltration) were restricted to the ECF component of the TBW. In the ECF, it was principally the ISF that buffered salt and water expansion or depletion. There was no evidence for volume alterations in the intracellular fluid (ICF = TBW - ECF). We conclude that the ISF is the buffer zone which maintains the proper balance and relationship between vascular capacity and volume.

Adult↗
PubMed2005

Role of dehydroepiandrosterone sulfate levels on body composition after laparoscopic adjustable gastric banding in pre-menopausal morbidly obese women.

UNLABELLED: In humans, dehydroepiandrosterone (DHEAS) has been postulated to have anabolic and lipolytic properties that could potentially counteract the catabolic effect of cortisol. DHEAS secretion is reduced in morbid obesity, likely due to hyperinsulinemia, and laparoscopic adjustable gastric banding (LASGB), by inducing considerable and rapid weight loss, reduces insulin levels. To investigate the role of decreased insulin levels after LASGB-induced weight loss on DHEAS levels and on body composition changes, we studied 30 pre-menopausal morbidly obese women (BMI ranging 37-62 kg/m2) before, 6, 12 and 24 months after LASGB. Total body water (TBW), fat-free mass (FFM) and fat mass (FM) were measured by bioelectrical impedance analysis; tissue hydration was also assessed by impedance vector analysis. At study ending, the subjects had a total weight loss of 28% of baseline body weight (15% after 6 months). After LASGB, weight loss was mainly due to decreased FM, and TBW, FFM, and body hydration were not significantly reduced. Weight loss was associated with an 82% rise in serum DHEAS already after 6 months while cortisol, cortisol/DHEAS molar ratio, and insulin levels fell by 5.5, 62 and 50%, respectively, after 6, 12 and 24 months (p<0.05). CONCLUSIONS: LASGB associated with a well balanced low-calorie diet permits a satisfactory 2-yr weight loss, sparing FFM and without body fluid alterations. As the result of a stable weight reduction program weight loss is associated to decrease in cortisol, cortisol/DHEAS molar ratio, and insulin plasma levels with marked rise in DHEAS. Higher cortisol/DHEAS molar ratio values at baseline are also associated to lower weight loss after LASGB, with lower decrease in FM and higher reduction in FFM and body cell mass, in spite of no differences in dietary regimes. Cortisol/DHEAS molar ratio is likely to represent a reliable marker of favourable modifications in body composition.

Adult↗
PubMed2004

TIMPs as multifacial proteins.

Tissue inhibitors of metalloproteinases (TIMPs) are natural inhibitors of matrix metalloproteinases (MMPs) found in most tissues and body fluids. By inhibiting MMPs activities, they participate in tissue remodeling of the extracellular matrix (ECM). The balance between MMPs and TIMPs activities is involved in both normal and pathological events such as wound healing, tissue remodeling, angiogenesis, invasion, tumorigenesis and metastasis. The intracellular signalling controlling both TIMPs and MMPs expression begins to be elucidated and gaining insights into the molecular mechanisms regulated by TIMPs and MMPs could represent a new approach in the development of potential therapeutics. Numerous investigations have pointed out that TIMPs exhibit multifunctional activities distinct from MMP inhibition. In this review, we detailed the multiple activities of TIMPs in vivo and in vitro and we reported their implication in physiological and pathological processes. Further, we documented recent studies of their role in hematopoiesis and we itemized the different signalling pathways they induced.

Animals↗
PubMed1997

Water channels and urea transporters.

1. It now appears that when water crosses an endothelium which is not fenestrated, or an epithelium with tight junctions, it does so rapidly, and with low energy cost, only if the cell membrane contains an adequate number of specific water channels, encoded by one of at least six different genes. 2. The water channel genes so far cloned encode a series of integral membrane proteins called aquaporins, all of approximately 30 kDa (265-282 amino acids), in the unglycosylated state. All but one (AQP3) are specific water channels and all but one (AQP4) are inactivated by mercurial compounds. 3. Aquaporin 0 is the major (60%) intrinsic protein (MIP) of lens fibre cells of the eye. Mutations in this gene are associated with cataract formation in mice. 4. Aquaporin 1, also called CHIP-28, exists in the membrane as a homotetramer, and is present in red blood cells, the choroid plexus, the proximal tubule and descending limb of the loop of Henle in the kidney as well as in many other sites. Surprisingly, no pathological consequence is known in patients lacking a functional AQP1 gene. 5. Aquaporin 2, also called WCH-CD, is the water channel of the principal cell of the cortical and medullary collecting duct, and is located in cytoplasmic vesicles unless arginine vasopressin is acting, when it is translocated to the apical membrane by synaptobrevins or vesicle associated membrane protein 2 (VAMP2). Lack of a functional AQP2 gene leads to a rare form of nephrogenic diabetes insipidus. 6. Aquaporins 3, 4, and 5 are located in many tissues-AQP3 and AQP4 being in the basolateral membrane of the renal cortical and medullary principal cell, as well as in the gastrointestinal tract (AQP3) and the brain (AQP4). 7. Four sequences are known for urea transporters HUT11-the urea transporter of the human red cell membrane, and HUT2, rUT2, rbUT2-the arginine vasopressin inducible urea transporters of the human, rat and rabbit kidney. They are specifically permeable to urea, not to water, and are claimed to be inhibited by phloretin. 8. The water channel proteins contain six membrane-spanning regions, whilst the urea transporters are thought to contain at least 10 membrane spanning segments. 9. Very little work has examined the ontogeny of these proteins, except in the rat, and virtually nothing is known of the expression of these genes in pregnancy or in any disorder of fluid balance in the mother or foetus.

Animals↗
PubMed1999

Appetite at "high altitude" [Operation Everest III (Comex-'97)]: a simulated ascent of Mount Everest.

We hypothesized that progressive loss of body mass during high-altitude sojourns is largely caused by decreased food intake, possibly due to hypobaric hypoxia. Therefore we assessed the effect of long-term hypobaric hypoxia per se on appetite in eight men who were exposed to a 31-day simulated stay at several altitudes up to the peak of Mt. Everest (8,848 m). Palatable food was provided ad libitum, and stresses such as cold exposure and exercise were avoided. At each altitude, body mass, energy, and macronutrient intake were measured; attitude toward eating and appetite profiles during and between meals were assessed by using questionnaires. Body mass reduction of an average of 5 +/- 2 kg was mainly due to a reduction in energy intake of 4.2 +/- 2 MJ/day (P < 0.01). At 5,000- and 6,000-m altitudes, subjects had hardly any acute mountain sickness symptoms and meal size reductions (P < 0.01) were related to a more rapid increase in satiety (P < 0.01). Meal frequency was increased from 4 +/- 1 to 7 +/- 1 eating occasions per day (P < 0. 01). At 7,000 m, when acute mountain sickness symptoms were present, uncoupling between hunger and desire to eat occurred and prevented a food intake necessary to meet energy balance requirements. On recovery, body mass was restored up to 63% after 4 days; this suggests physiological fluid retention with the return to sea level. We conclude that exposure to hypobaric hypoxia per se appears to be associated with a change in the attitude toward eating and with a decreased appetite and food intake.

Adult↗
PubMed2000

Comparison of 2 methods of managing gastric residual volumes from feeding tubes.

BACKGROUND: Research-based standards do not exist for the management of gastric residual volumes from feeding tubes. Withdrawing and returning residual volumes can lead to clogged tubes and exposes patients to possible contamination of the feeding system. However, discarding residual volumes may place patients at risk for electrolyte imbalance and may alter fluid or nutritional balance. OBJECTIVES: To investigate the effects of discarding versus returning gastric residual volumes on body weight, serum electrolyte levels, and the rate of complications associated with tube feeding. METHODS: Thirty-five subjects receiving enteral feedings were recruited from intensive care units at 3 Midwest hospitals and randomized to a discard group or a return group. Eighteen sets of usable data were obtained. RESULTS: Repeated-measures analysis of variance indicated no significant differences between the 2 groups for any of the variables. Complications related to enteral feedings were more common in the return group (n = 8), which had 2 episodes of tube clogging and 1 episode of diarrhea and nausea. None of these complications were experienced by patients in the discard group (n = 10). CONCLUSIONS: Both groups had significant numbers of complications, including a total of 15 episodes, 7 in the discard group and 8 in the return group, of feeding delays due to high gastric residual volumes. Although serum electrolyte levels did not differ significantly between the 2 groups, potassium levels tended to be lower in the discard group. Considerations for the care of critically ill patients with feeding tubes are discussed in light of these findings.

Adolescent↗