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Biomedical subjects

E Cogan

Publications and source records attributed to E Cogan.

At least 55 records · Page 3Linked to original sources
PubMed1992

Movement disorders due to cerebral Toxoplasma gondii infection in patients with the acquired immunodeficiency syndrome (AIDS).

Hemichorea and parkinsonism are unusual manifestations of cerebral toxoplasmosis in patients with AIDS. We here describe two such cases and we reviewed extensively the literature (through computer searches using MEDLINE) for other reported instances. In our patients, unlike the other neurological symptoms, the response of the movement disorders to anti-toxoplasmosis therapy was delayed and only partial. We demonstrate that tetrabenazine is a valuable additional symptomatic treatment for choreic movements in one of our patients. We emphasize that, among patients suffering from AIDS, particularly in countries with high prevalence of toxoplasmosis, the occurrence of movement disorders should first suggest the diagnosis of cerebral toxoplasmosis.

Acquired Immunodeficiency Syndrome↗
PubMed1991

Atrial natriuretic factor and the endocrine control of electrolyte homeostasis.

The potent diuretic and natriuretic properties of atrial natriuretic factor (ANF) suggest that atrial hormones may participate to the regulation of salt and water excretion under physiological conditions. ANF, via the increase of its intracellular second messenger cGMP, has been recently shown to inhibit the apical sodium channel of the inner medullary collecting tubule (IMCD). In addition, ANF inhibits renin and aldosterone synthesis and antagonizes the antinatriuretic effects of angiotensin II. ANF may also contribute to the excretion of free water by inhibiting both the secretion of vasopressin and its antidiuretic action. ANF appears to play an important physiological role in sodium repleted states, or when the effective plasma volume is increased. On the contrary, when the effective plasma volume is decreased or in sodium depleted states, the natriuretic effect of both endogenous and exogenous ANF is severely blunted. That ANF-resistance may be related to the activation of the renin-angiotensin-aldosterone axis, increased circulating catecholamines, renal sympathetic nerve stimulation, changes in renal hemodynamics or increased degradation of ANF. All these factors could explain the lack of significant natriuretic effect of both endogenous and exogenous ANF in some pathological conditions such as heart failure or liver cirrhosis. ANF may also been concerned in water homeostasis. In addition to the well-known osmoregulatory pathways of water metabolism, we recently found that ANF could be involved in the volume adjustment to acute water intake in normal man.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Impaired hydroosmotic response to vasopressin of cortical collecting tubules from lithium-treated rabbits.

The hydroosmotic action of [arginine]vasopressin (vasopressin, 25 microU/ml) and of 8-Br-cAMP (10(-4)M) was studied in vitro in perfused cortical collecting tubules (CCT) isolated from rabbits fed with lithium chloride for 3 weeks. Vasopressin-dependent water reabsorption was significantly inhibited by 65% although no lithium was used in the in vitro experiments. The hydroosmotic action of 8-Br-cAMP was also inhibited by previous Li treatment, but the effect was smaller in magnitude. Water intake, diuresis, and urinary osmolality were no different in the lithium-treated animals as compared with respective pretreatment values or with control animals given an equivalent amount of sodium chloride. Neither the creatinine clearance nor the maximal urinary concentrating ability were modified by lithium treatment. A mathematical model simulating water reabsorption along the CCT predicts that a 65% reduction of vasopressin-stimulated hydraulic conductivity, as observed in the Li group, may not be sufficient to prevent a complete osmotic equilibration at the end of the CCT in vivo. We conclude that: (a) in the rabbit, lithium administration induces an impairment of the hydroosmotic action of vasopressin in the CCT, which is due to an inhibition of pre- and post-cAMP events. (b) The inhibition of vasopressin action can be demonstrated in vitro at a time when no detectable impairment of the water conservation process occurs in vivo.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1989

Correction of low circulating levels of 1,25-dihydroxyvitamin D by 25-hydroxyvitamin D during reversal of hypomagnesaemia.

The effect of 25-hydroxyvitamin D (25OHD), given orally during the reversal of hypomagnesaemia, was studied in five patients with hypomagnesaemic hypocalcaemia and low serum levels of 25OHD and 1,25-dihydroxyvitamin D (1,25(OH)2D). The results were compared to those obtained in five other patients with similar initial levels of magnesium, calcium, 25OHD and 1,25(OH)2D who did not receive 25OHD. Serum levels of 1,25(OH)2D in the ten hypomagnesaemic patients were lower than in ten control subjects with low serum levels of 25OHD. The reversal of hypomagnesaemia was similar in the two groups of patients and elicited a similar increase of circulating iPTH levels. The expected increase of circulating 25OHD was observed in patients supplemented with 25OHD; their circulating 1,25(OH)2D rose within 48 h to normal levels, contrasting with the delayed and poor increase of 1,25(OH)2D in patients receiving no 25OHD. The evolution of serum calcium was however identical in the two groups. Our results suggest that vitamin D deficiency was a significant factor leading to low circulating levels of 1,25(OH)2D in hypomagnesaemic hypocalcaemic patients. The biological consequences of low serum 1,25(OH)2D in these patients remain unclear, but clearly, normal levels of 1,25(OH)2D are not essential for the correction of hypomagnesaemic hypocalcaemia.

Adult↗
PubMed1988

Natriuresis and atrial natriuretic factor secretion during inappropriate antidiuresis.

The mechanisms responsible for the natriuresis encountered in the syndrome of inappropriate secretion of antidiuretic hormone (SIADH) are not fully understood. The present study explores the role of atrial natriuretic factor (ANF). Eight subjects unable to excrete ingested free water normally (three patients with SIADH and five healthy humans after intranasal administration of desmopressin) underwent a standard oral water loading test. Plasma ANF level and urinary sodium excretion increased during water retention, whereas plasma aldosterone value decreased later. The increment of urinary sodium excretion rate was significantly correlated with that of plasma ANF. In two patients with hyponatremia due to SIADH, plasma ANF levels were increased during the hyponatremic phase of their condition and decreased under water restriction. In one of them, marked natriuresis was observed when the plasma ANF level was high. It is concluded that secretion of ANF is acutely and chronically stimulated during water retention in SIADH and that ANF may be in part responsible for the natriuresis encountered in inappropriate antidiuresis.

Adult↗
PubMed1987

Mechanisms of lithium-vasopressin interaction in rabbit cortical collecting tubule.

In single cortical collecting tubules (CCT) of the rabbit, guanosine 5'-triphosphate (GTP) increased the arginine vasopressin (AVP)-stimulated adenylate cyclase (AC) by 60% (P less than 0.05). In contrast, guanosine 5' O-(2-thio)-diphosphate (GDP-beta S), a competitive inhibitor of GTP action on the stimulatory guanine regulatory protein (Ns), reduced the AVP-stimulated AC activity by 72% (P less than 0.001), indicating the presence of endogenous GTP in the cells under study. That inhibitory effect was reversed by the addition of GTP to the incubation medium. In isolated perfused CCT, cholera toxin (CT) induced a significant increase in water permeability in the absence of AVP. In contrast, Bordetella pertussis toxin (BPT) did not modify the low AVP-independent water permeability. Lithium, an inhibitor of the hydrosmotic action of AVP, also inhibits the hydrosmotic action of CT by 70% (P less than 0.05) but not that of forskolin. The conclusions of the present study are Ns is required for AVP stimulation of AC in the CCT; Ns is functionally active in this system as evidenced by the hydrosmotic effect of CT; the lack of effect of BPT suggests that the low AVP-independent water permeability in the CCT is not the result of a tonic inhibition of the AC operating through the inhibitory guanine nucleotide regulatory protein; and the inhibition by lithium of the hydrosmotic action of AVP in the CCT appears to involve an interaction with the regulatory proteins (probably Ns) or with their binding to the catalytic unit of AC.

Adenylyl Cyclases↗
PubMed1986

Inhibition by lithium of the hydroosmotic action of vasopressin in the isolated perfused cortical collecting tubule of the rabbit.

Because treatment with lithium salts may impair renal concentrating ability, we investigated the possibility of a direct effect of lithium ions on the permeability to water of the collecting duct epithelium. The coefficient of hydraulic conductivity (Lp) of isolated perfused rabbit cortical collecting tubules (CCT) was measured in the presence and absence of arginine-8-vasopressin (AVP), or 8-bromo (Br) cyclic AMP (cAMP) and/or lithium chloride (Li 10 mM). In the absence of AVP, Li in the lumen for 30 min failed to affect basal water permeability; however, in tubules preincubated with Li in the lumen for 80 min, basal water permeability was reduced to 30% of the value found in control tubules (P less than 0.01). In CCT incubated at 25 degrees C with Li in the lumen for 3 h, the hydroosmotic response to 2.5 microU X ml-1 AVP (Lp = 6.88 +/- 1.54 nl X cm-2 X s-1 X atm-1) was significantly lower than that in the control tubules (13.98 +/- 1.59, P less than 0.01); the inhibition was not reversible. When Li was present in the peritubular medium only, the hydroosmotic effect of AVP was not different from that of the controls. The hydroosmotic effect of 25 microU/ml AVP was investigated at 37 degrees C. CCT exposed to Li in the lumen had a 49% inhibition of peak Lp under AVP (Lp = 10.98 +/- 1.17) as compared with control tubules (Lp = 21.39 +/- 1.51; P less than 0.005). In contrast, the hydroosmotic response to 8-Br-cAMP was not affected by lithium. The results are compatible with the view that Li inhibits the action of AVP at the level of the regulating protein or the catalytic unit of the membrane adenylate cyclase and that the site of the interaction can be reached by lithium only from the cytoplasmic side. The Li-antidiuretic hormone (ADH) interaction found here may represent the earliest pathophysiological event underlying the renal concentrating defect observed after Li administration.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1986

Transient hyperthyroxinemia in symptomatic hyponatremic patients.

Twenty-two patients with severe hyponatremia were divided into 12 patients with and ten without associated neurologic manifestations (groups 1 and 2, respectively). Marked hyperthyroxinemia was demonstrated in seven patients in group 1 but in none in group 2. The triiodothyronine concentration was also higher than normal in two patients in group 1. All serum iodothyronine concentrations in group 1 were significantly higher than in group 2. Thyrotropin and thyroxine-binding globulin levels were normal in both groups. The differences between groups were apparent only in the acute phase, and there were no clinical manifestations of hyperthyroidism. All iodothyronine concentrations returned to normal within two weeks after the correction of the hypo-osmolar disorder. Our results indicate that a transient asymptomatic increase in serum iodothyronine levels occurs during hyponatremia. Thus, thyroid test results should be interpreted cautiously in patients with acute, severe, symptomatic hyponatremia.

Aged↗
PubMed1985

Azathioprine. An alternative treatment for recurrent idiopathic retroperitoneal fibrosis.

Ureteral obstruction resulting from idiopathic retroperitoneal fibrosis (IRF) generally requires a surgical approach sometimes associated with the administration of a corticosteroid. Corticosteroids alone have also been used successfully for recurrences of IRF after the surgical procedure; however, their success is not uniform. We treated a patient with IRF and ureteral obstruction who showed a dramatic recurrence soon after treatment with prednisone was discontinued. Azathioprine was then considered as an alternative treatment. A six-week course of azathioprine (150 mg/day) resolved all the biologic signs of inflammation, normalized renal function, and greatly improved ureteral obstruction. We discuss the choice of immunosuppressive drugs in the management of the disease and propose azathioprine treatment for the recurrent forms.

Azathioprine↗
PubMed1985

Magnesium administration reverses the hypocalcaemia secondary to hypomagnesaemia despite low circulating levels of 25-hydroxyvitamin D and 1,25-dihydroxy vitamin D.

The effect of parenteral administration of magnesium was studied in five patients with hypomagnesaemic hypocalcaemia. The initial metabolic state was characterized by a normal level of serum immunoreactive parathyroid hormone (iPTH), and by low or undetectable serum 25-hydroxyvitamin D (25OHD) and 1,25-dihydroxyvitamin D (1,25 (OH)2D). A parathyroid response was elicited by the acute intravenous injection of magnesium chloride. In contrast, 1,25(OH)2D did not change up to 24 h after the injection. Intramuscular magnesium sulphate restored serum magnesium and calcium to normal, whereas iPTH was transiently increased. 25OHD remained low and unchanged. 1,25(OH)2D rose very slowly, but the correction of hypocalcemia began before any change in 1,25(OH)2D levels could be demonstrated. Thus, the early correction of hypocalcemia mainly depended on the restoration of an adequate parathyroid function independently of the secretion of 1,25(OH)2D.

25-Hydroxyvitamin D 2↗