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Biomedical subjects

T Berl

Publications and source records attributed to T Berl.

At least 91 records · Page 5Linked to original sources
PubMed1978

The role of renal nerves and prostaglandins in control of renal hemodynamics and plasma renin activity during hypotensive hemorrhage in the dog.

The effects of hypotensive hemorrhage (HH) on renal hemodynamics and plasma renin activity (PRA) during prostaglandin (PG) synthesis inhibition were examined in three groups of dogs. In each group of animals arterial blood pressure was lowered by a 30% decrement. In the first group of eight control animals, HH was not associated with a significant change in glomerular filtration rate (GFR, 42-36 ml/min, NS); renal blood flow (RBF) declined significantly, from 234 to 171 ml/min, P < 0.05. In the second group of eight animals, pretreated with RO 20-5720 (RO, 2 mg/kg), a competitive inhibitor of PG synthesis, HH was associated with a significant fall in GFR (43-17 ml/min, P < 0.001) and RBF (195-89 ml/min, P < 0.001). In the third group of eight animals, pretreatment with indomethacin (IN, 10 mg/kg), a chemically dissimilar PG inhibitor, HH was also associated with a significant fall in GFR (38-8 ml/min, P < 0.001) and RBF (150-30 ml/min, P < 0.001). Renal denervation attenuated this renal ischemic effect of HH in the presence of PG inhibition. In the RO group, GFR (34 vs. 17 ml/min, P < 0.005) and RBF (145 vs. 89 ml/min, P < 0.025) were significantly greater in denervated vs. innervated kidneys during HH. Similarly, in animals treated with IN, a significantly higher GFR (28 vs. 8 ml/min, P < 0.005) and RBF (101 vs. 30 ml/min, P < 0.005) occurred in denervated as compared to innervated kidneys during HH. With HH, the increase in PRA in the control group (3.34-11.68 ng/ml per h, P < 0.005) was no different than that observed in the RO group (4.96-18.9 ng/ml per h, P < 0.001) or IN group (4.71-17.8 ng/ml per h, P < 0.001). In summary, the present results indicate that renal PG significantly attenuate the effect of HH to decrease GFR and RBF. Furthermore, renal denervation exerts a protective effect against the enhanced renal ischemic effects which occur in the presence of PG inhibition during HH. Finally, PG inhibition does not alter the effect of HH to cause an increase in PRA.

Animals↗
PubMed1978

1,25 dihydroxycholecalciferol effects in chronic dialysis. A double-blind controlled study.

1,25 dihydroxycholecalciferol [1,25(OH)2D3] was studied in a double-blind controlled fashion in patients on chronic dialysis. Serum calcium was unchanged in 16 patients on vitamin D3 (D3) (400 to 1200 IU/day). In 15 patients on 1,25(OH)2D3 (0.5 to 1.5 microgram/day), serum calcium increased from 9.05 +/- .15 to 10.25 +/- .20 mg/dl (p less than 0.001), returning to 9.37 +/- .16 mg/dl (p less than 0.001) in the post control period. Patients on D3 showed no reversible decrease in immunoreactive parathyroid hormone levels, but patients on 1,25(OH)2D3 did, from a control of 1077 +/- 258 to 595 +/- 213 microliter equivalents/ml (p less than 0.01), and returned to 1165 +/- 271 microliter equivalents/ml (p less than 0.005). Nine of 12 patients on D3 who underwent serial iliac-crest biopsies showed histologic deterioration, and six of seven who received 1,25(OH)2D3 were improved or unchanged (p less than 0.025). Bone mineral and calcium decreased in patients on D3 (p less than 0.05) but not in those on 1,25(OH)2D3. Hypercalcemia occurred in five of 15 patients. We conclude that 1,25(OH)2D3 has a calcemic effect in chronic dialysis patients, decreases levels of immunoreactive parathyroid hormone, and is associated with histologic improvement in bone disease. Thus, 1,25(OH)2D3 is a valuable adjunct to the management of renal osteodystrophy but requires monitoring of serum calcium to avoid hypercalcemia.

Adult↗
PubMed1977

In vivo effect of indomethacin to potentiate the renal medullary cyclic AMP response to vasopressin.

In a previous study we demonstrated that indomethacin potentiated the hydro-osmotic action of vasopressin in vivo. It was hypothesized that this action of indomethacin was due to its ability to suppress renal medullary prostaglandin synthesis, since in vitro studies have suggested that prostaglandins interfere with the ability of vasopressin to stimulate production of its intracellular mediator, cyclic AMP. In the present study this hypothesis was tested in vivo. Anesthetized rats undergoing a water diuresis were studied. In a control group, bolus injections of 200 muU of vasopressin caused a rise in urinary osmolality (Uosm) from 124 +/- 6 to 253 +/- 20 mosmol/kg H2O (P less than 0.005). In a group treated with 2 mg/kg of indomethacin the same dose of vasopressin caused a significantly greater (P less than 0.001) rise in Uosm from 124 +/- 7 to 428 +/- 19 mosmol/kg H2O. Medullary tissue cyclic AMP rose from 9.4 +/- 0.9 to 13.4 +/- 1.7 (P less than 0.05) pmol/mg tissue protein after vasopressin administration in animals receiving no indomethacin, while in indomethacin-treated animals there was a significantly greater rise (P less than 0.001) in medullary cyclic AMP from 10.4 +/- 0.9 to 21.6 +/- 2.1 pmol/mg tissue protein in response to the vasopressin injections. In neither control animals nor indomethacin-treated animals were there significant changes in renal hemodynamics, as measured by clearance techniques. Indomethacin, when given alone, had no effect on Uosm or medullary tissue cyclic AMP. Indomethacin did, however, reduce medullary prostaglandin E content from 84.7 +/- 15.0 to 15.6 +/- 4.3 pg/mg tissue. This study has shown that indomethacin, in a dose which suppresses medullary prostaglandin content, potentiates the ability of vasopressin to increase the tissue content of its intracellular mediator, cyclic AMP. Indomethacin caused no demonstrable inhibition of cyclic AMP phosphodiesterase. Therefore, it seems likely that indomethacin enhanced the ability of vasopressin to increase medullary cyclic AMP levels by causing an increased production rather than decreased destruction of the nucleotide. We conclude that this action of indomethacin contributes to its ability to potentiate the hydro-osmotic action of vasopressin in vivo. A corollary to this conclusion is that endogenous medullary prostaglandin E's may be significant physiological modulators of the renal response to vasopressin.

Animals↗
PubMed1977

On the mechanism of polyuria in potassium depletion. The role of polydipsia.

The association of potassium (K) depletion with polyuria and a concentrating defect is established, but the extent to which these defects could be secondary to an effect of low K on water intake has not been systematically investigated. To determine whether hypokalemia has a primary effect to increase thirst and whether any resultant polyuria and polydipsia contribute to the concentrating defect, we studied three groups of rats kept in metabolic cages for 15 days. The groups were set up as follows: group 1, normal diets and ad lib. fluids (n = 12); group 2, K-deficient diet on ad lib. fluids (n = 12); and group 3, K-deficient diet and fluid intake matched to group 1 (n = 14). Daily urine flow and urinary osmolality of groups 1 and 3 were not significantly different throughout the study. In contrast, as of day 6, group 2 rats consistently had a higher fluid intake (P < 0.0025), higher urine flow (P < 0.001), and lower urinary osmolality (P < 0.001) than the other two groups. These alterations in fluid intake and urine flow preceded a defect in maximal concentrating ability. On day 7, maximal urinary osmolality was 2,599+/-138 msmol/kg in rats on K-deficient intake and 2,567+/-142 msmol/kg in controls. To determine whether this primary polydipsia is itself responsible for the development of the concentrating defect, the three groups of rats were dehydrated on day 15. Despite different levels of fluid intake, maximal urinary osmolality was impaired equally in groups 2 and 3 (1,703 and 1,511 msmol/kg, respectively), as compared to rats in group 1 (2,414 msmol/kg), P < 0.001. We therefore conclude that K depletion stimulates thirst, and the resultant increase in water intake is largely responsible for the observed polyuria. After 15 days of a K-deficient diet, the impaired maximal urinary concentration in hypokalemia, however, was not related to increased water intake, since fluid restriction did not abolish the renal concentrating defect.

Animals↗
PubMed1976

Osmotic control of prolactin release and its effect on renal water excretion in man.

Prolactin appears to play a role in osmoregulation of fishes and birds and a possible contribution of this hormone to the regulation of salt and water excretion in mammals has been suggested as well. The present studies were undertaken to investigate the role of osmotic pressure on the secretion of prolactin and the effect of the hormone on renal water excretion in man. The i.v. administration of synthetic thyrotropin releasing hormone (TRH) (7 mug/kg) to five subjects undergoing a maximal sustained water diuresis increased serum prolactin to supraphysiologic levels in all as mean concentration rose from 30.2 +/- 2.9 to 60.2 +/- 5.0 ng/ml (P less than 0.005). This increase was not associated with either significant alterations in renal hemodynamics or sodium excretion and water excretion. The osmoregulation of prolactin release was then investigated by the oral administration of 20 ml/kg of water to seven subjects in 11 studies. While the water load decreased serum osmolality from 293 +/- 285 +/- 1.5 mOsm/kg H2O (P less than 0.001), there was no significant change in prolactin level, 28+/- 1.8 to 30 +/- 2.4 ng/ml. Serum hypertonicity was achieved in six subjects with the infusion of 5% NaCl which increased serum osmolality from 287 +/- 1.8 to 298 +/- 1.4 mOsm/kg (P less than 0.001). While the hypertonic state caused a marked antidiuresis as urinary osmolality rose from 62 +/- 5.9 to 480 +/- 48 mOsm/kg (P less than 0.001), the concentration of prolactin remained unchanged at 28 ng/ml. We conclude that supraphysiologic levels of prolactin have no antidiuretic properties in a vasopressin-free state and that acute alterations in serum tonicity within the range observed do not affect the release of prolactin in man.

Adolescent↗
PubMed1976

Hypercalcemia of acute renal failure. Clinical significance and pathogenesis.

Hypocalcemia is a frequent accompaniment of acute renal failure, but paradoxically hypercalcemia also has been described in association with acute renal failure. In this paper we describe two patients who provide some insights into both the potential clinical importance and mechanism of the hypercalcemia associated with acute renal failure. The clinical significance is emphasized by the presence of diffuse metastatic calcification observed at postmortem examination in one patient. In both patients the increase in serum calcium concentration was not coincident with a decrease in serum phosphorus concentration; when measured in one patient, serum levels of parathyroid hormone were undetectable. These findings, along with the consistent association with rhabdomyolosis, support the proposal that the hypercalcemia of acute renal failure is caused by dissolution of dystrophic calcifications in traumatized muscle and may lead to severe metastatic calcifications.

Acute Kidney Injury↗
PubMed1975

Parasympathetic pathways, renin secretion and vasopressin release.

1. The interrelationship between parasympathetic neural tone, renin secretion and vasopressin release was examined by observing the effect of bilateral cervical vagotomy on renin secretion in intact and acutely hypophysectomized dogs undergoing a water diuresis. 2. In intact dogs bilateral cervical vagotomy decreased the mean renin secretion from 1245 to 682 units/min (P less than 0.01) as urinary osmolality increased from 95 to 414 mosmol/kg (P less than 0.001). In contrast, in acutely hypophysectomized dogs cervical vagotomy failed to alter renin secretion significantly (834 to 893 units/min) and urinary osmolality was also unchanged (78 to 71 mosmol/kg). 3. The results suggest that a diminution in vagal tone may significantly alter renin secretion by stimulating vasopressin release. Exogenous vasopressin was associated with changes in urinary osmolality and renin secretion which were qualitatively similar to those seen after servical vagotomy. 4. We suggest that there is a neurohumoral reflex mechanism by which a fall in parasympathetic tone increases the release of vasopressin, which, in turn, suppresses renin secretion. The results are also compatible with the hypothesis that vasopressin inhibits renin release by a direct effect on the juxtaglomerular cells.

Animals↗
PubMed1975

Catecholamines and renal water excretion.

The in vivo mechanisms whereby systemic alpha- and beta-adrenergic stimulation exert opposing effects on renal water excretion are reviewed. An extrarenal mechanism is suggested since the effect of intravenous infusion of norepinephrine or isoproterenol on water excretion cannot be mimicked by the intrarenal administration of these agents. A ROLE OF VASOPRESSIN IS IMPLICATED SINCE NEITHER MAN NOR DOG WITHOUT A PITUITARY SOURCE OF VASOPRESSIN DEMONSTRATE THE SAME EFFECT OF CATECHOLAMINES ON WATER EXCRETION AS OBSERVED IN INTACT MAN AND DOG. Evidence also is presented that systemic alpha- and beta-adrenergic stimulation affect vasopressin release primarily by altering baroreceptor tone. The potential role of the autonomic nervous system in mediating other nonosmotic stimuli for vasopressin is discussed.

Animals↗
PubMed1975

Evidence for an in vivo antagonism between vasopressin and prostaglandin in the mammalian kidney.

These studies were undertaken to examine whether an antagonism between vasopressin and prostaglandin occurs in vivo in the mammalian kidney. All experiments were performed in steroid-replaced hypophysectonized dogs undergoing a water diuresis. In the first group of studied the effect of two consecutive intravenous doses (100 mU) of vasopressin was examined. The second dose of vasopressin was preceded by an injection of the carrier solution for solubilizing indomethacin or neclofenamate. No enhancement of the antidiuretic effect of the second dose of vasopressin was observed as urinary osmolality (Uosm) increased from 92 +/- 5 to 252 +/- 18 mosmol/kg H2O (P less than 0.0001) after the first dose and from 109 +/- 8 to 209 +/- 10 mosmol/kg H2O (P less than 0.001) after the second dose of vasopressin. In another group of studies the second dose of vasopressin was preceded by the administration of a potent inhibitor of prostaglandin synthesis, indomethacin (2 mg/kg). The Uosm increased from 93 +/- 9 to 244 +/- 33 mosmol/kg H2O (P less than 0.001) after the first dose of vasopressin, but after the second dose of vasopressin the Uosm increased to a significantly greater degree from 106 +/- 14 to 702 +/- 69 mosmol/kg H2O (P less than 0.001). In a third group of studies the antidiuretic effect of the same 100-mU dose of vasopressin was examined before and after the administration of meclofenamate (2 mg/kg), an inhibitor of prostaglandin synthesis which is chemically dissimilar from indomethacin. Uosm increased from 83+/-7 to 216+/-16 mosmol/kg H2O (P less than 0.001) after the first dose and from 101 +/- 8 to 734 +/- 86 mosomol/kg H2O (P less than 0.001) after the second dose of vasopressin. As in the indomethacin studies this enhancement in the antidiuretic effects of vasopressin after inhibition of prostaglanding synthesis was highly significant (P less than 0.001). These results therefore implicate a physiological role of prostaglandin in modulating the hydroosmotic effect of vasopressin in the mammalian kidney.

Animals↗