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Drinking and osmoregulation in the mangrove crab Ucides cordatus following exposure to benzene.

In benzene-exposed Ucides cordatus acclimated for 96 h to 9 and 34 per thousand SW, haemolymph, urine and gastric juice are isosmotic with each other, but differ significantly in osmolality from external media. In both salinities, under benzene action, urine K+ excretion and calcium absorption are increased significantly, whereas Na+ absorption and Mg2+ excretion show U/B ratios similar to control values. In 9 per thousand SW, some ionic exchanges via benzene-exposed gills are possibly hastened. Benzene exposure decreases significantly branchial chamber water osmolality, [Na+] and [K+], whereas [Ca2+] and [Mg2+] are unaffected. However, faster medium exchange presumably occurs in 34 per thousand SW, both crab groups show branchial chamber water osmotic and ionic concentrations similar to surrounding medium. Benzene exposure unaffected gastric juice composition. In both media, [Ca2+] and [Mg2] accumulate several times higher than surrounding media, and [Na+] and [K+] are significantly hypo-ionic to haemolymph. Na+ and K+ G/H ratios are lower in crabs acclimated to 34 per thousand SW than in crabs acclimated to 9 per thousand SW. Drinking rates are enhanced by benzene exposure and are higher at 34 per thousand SW than in seawater isosmotic with the haemolymph (26 per thousand SW). Benzene exposure affects significantly osmoregulatory capability, slowing haemolymph dilution after transfer to clean 9 per thousand SW. Lower haemolymph dilution rate accounts for higher osmolality, but 48 h after transfer there is no recovery like in control crabs. Haemolymph transfusion experiments suggest an interaction among effects of benzene and hormonal factors, possibly on water influx.

Animals↗

Neurohormonal consequences of diuretics in different cardiovascular syndromes.

Diuretics have long been used to lower blood pressure in hypertensive patients or to control body fluid and electrolyte homeostasis in diseases such as congestive heart failure, chronic renal failure or cirrhosis. The initial response to diuretics is a negative sodium and fluid balance. The diuretic-induced loss of salt and water activates several hormonal systems such as vasopressin, the renin-angiotensin-aldosterone system or the sympathetic nervous system which tend to compensate for the changes in sodium and water balance. This neurohormonal response may have important clinical implications. Thus, the activation of the renin-angiotensin-aldosterone cascade appears to be partially responsible for the flat dose-blood pressure response curve of thiazides in hypertensive patients. It may also be responsible for the difference between responders and non-responders to diuretic therapy and for the development of side-effects such as hypokalaemia, metabolic alkalosis or hyponatraemia. There are several ways to prevent the undesirable consequences of the neurohormonal responses to diuretics. The first is to use low doses of these agents. It is also possible to combine them with agents that block the activity of the renin-angiotensin-aldosterone system such as ACE inhibitors or in combination with drugs that reduce aldosterone secretion such as calcium antagonists. The development of drugs able to enhance urinary sodium excretion and to reduce simultaneously the activity of the renin-angiotensin-aldosterone system may offer a new interesting alternative. This might perhaps be achieved in the future with the administration of neutral endopeptidase inhibitors which interfere with the enzymatic degradation of atrial natriuretic peptide.

Animals↗

TERATOGENIC SIGNIFICANCE OF IONIC AND FLUID IMBALANCES.

Some agents teratogenic to the chick embryo cause serum electrolyte and fluid inmbalances which initiate an edema syndrome leading to malformations. Differences in ionic composition of serum and yolk of normal chicks help explain how these imbalances can be produced.

Animals↗

Segmental chloride reabsorption during volume expansion and recovery.

Clearance and micropuncture studies were performed in Sprague-Dawley and Munich-Wistar rats to examine the nephron sites of chloride reabsorption in animals undergoing sustained volume expansion (SVE) (10% of body wt) with isotonic saline and in animals in which the extracellular fluid volume was expanded to 10% of body wt over 60 min, after which the sustaining saline volume was abruptly discontinued (recovery) (R). Net sodium and chloride balances were not significantly different in R compared with SVE. The fractional excretion of chloride, however, was significantly lower (2.62 +/- 0.25 vs. 4.18 +/- 0.62%, P less than 0.05). In the Sprague-Dawley rats, chloride delivery to the early distal tubule average 18% in both groups. Chloride delivery to the late distal tubule was significantly lower in R (4.39 +/- 0.79%) than in SVE (8.55 +/- 0.76%, P less than 0.005). In the Munich-Wistar rats, samples were obtained from the late distal tubule and base and tip of the papilla. Chloride delivery to the base did not differ from that to the late distal tubule in either group, but was significantly lower in R compared with SVE. These results indicate that the so-called "post-volume expansion" antinatriuresis is the result, at least in part, of enhanced reabsorption in the distal tubule.

Absorption↗

Lithium in depression: a biochemical study.

Two groups of depressed subjects, one with a history of recurrent depression, the other with a history of persistent apathy, were given lithium carbonate 1,200 mg q.i.d. and supplementart potassium 1,200 mg t.d.s. for 1 week. Measurements were made before and after the lithium treatment of total body water (tritium space), extracellular fluid (sulphate space), total exchangeable sodium (Nae) and total exchangeable potassium (Ke) using sodium-24 and potassium-42 multiple isotope dilution techniques. Prior to treatment when compared with a group of normal subjects, both depressed groups showed changes in body fluid volumes and electrolyte levels. Total body water, intracellular fluid and intracellular potassium were lowered, while electrolyte levels. Total body water, intracellular fluid and intracellular potassium were lowered, while intracellular sodium was raised. After treatment with lithium the values in the apathetic group showed little change but the group with recurrent depression showed a significant increase in intracellular fluid (p less than 0.025), Ke (p less than 0.001), intracellular potassium (p less than 0.025) and a significant decrease in Nae (p less than 0.05). There was a marked increase in mood in the group with recurrent depression but not in the apathetic group following lithium treatment. These findings suggest that recurrent depression, both in clinical improvement, mood and also correction of water and also correction of water and electrolyte disturbances arise, but not in patients with long-standing apathy.

Aged↗

Factors affecting bioelectrical impedance measurements in humans.

In several groups of young healthy subjects the effect of the ingestion of a meal, of drinking normal tea or beef tea, of exercise and of the menstrual cycle on body impedance was assessed. The day-to-day reproducibility of the method was also investigated under standardized conditions. Two to four hours after ingestion of a meal, body impedance had decreased by about 13-17 Ohms in comparison with body impedance in the fasting state. Drinking 200 ml of normal tea did not result in a change of body impedance, but drinking 200 ml beef tea lowered the body impedance significantly by 4 +/- 4 Ohms. Moderate exercise on a bicycle ergometer (90 min, 100 W) did not influence body impedance, but strenuous exercise (90 min, 175 W) resulted in a decrease of 9 +/- 11 Ohms in body impedance. In general, changes in body impedance during the menstrual cycle were small, and only the difference between measurements of body impedance 1 week before the onset of the menstruation and again 1 week after menstruation (8 +/- 9 Ohms) was statistically significant. Under standardized conditions (in the morning, in the fasting state after emptying the bladder) the within-person between-day variation was found to be 2.8 per cent (13 Ohms).

Adipose Tissue↗