Axonal transport of the voltage-dependent Na+ channel protein identified by its tetrodotoxin binding site in rat sciatic nerves.

Na+ channels levels were measured in different segments of rat vagus and sciatic nerves by in vitro binding using a tritiated ethylene-diamine tetrodotoxin derivative ([3H]en-TTX). Binding sites were found to accumulate on both sides of a ligature tied on the sciatic nerve indicating an anterograde and retrograde axoplasmic transport of Na+ channels. Accumulation of Na+ channels at the ligature was time-dependent and appeared to occur through fast axoplasmic transport mechanisms. This accumulation on both sides of a ligature was also visualized by autoradiographic studies in longitudinal sections of sciatic nerves using [3H]en-TTX.

Identification in mammalian brain of an endogenous substance with Na+ channel blocking activities similar to those of tetrodotoxin.

A substance with Na+ channel blocking activities has been isolated from pig brain after extraction and purification on sulfopropyl-Sephadex C-25, reversed-phase and carboxymethyl Synchropak high pressure liquid chromatography columns. The peptidic material i) displaces [3H]ethylenediamine tetrodotoxin ([3H]en-TTX) from its binding sites on rat brain membranes, (ii) it blocks 22Na+ influx induced by veratridine and sea anemone toxin on neuroblastoma and embryonic chick heart cells in culture, (iii) it specifically decreases the height of the action potential generated in frog sciatic nerve, and (iv) it blocks the fast Na+ current in voltage-clamped neuroblastoma cells. These properties are similar to those of tetrodotoxin while the endogenous factor is a peptide that is destroyed by proteases. These results suggest the presence in pig brain of a potent Na+ channel modulation activity.

Axonal transport of Na+,K+-ATPase identified as a ouabain binding site in rat sciatic nerve.

Na+,K+-ATPase levels were measured in different segments of rat sciatic nerves by in vitro binding of [3H]ouabain. Binding sites were found to accumulate on both sides of a ligature tied on the sciatic nerve, indicating an anterograde and retrograde axoplasmic transport of Na+,K+-ATPase. Accumulation of Na+,K+-ATPase at the ligature was time dependent and appeared to occur through fast axoplasmic transport mechanisms. This accumulation on both sides of the ligature was also visualized by autoradiographic studies in longitudinal section of sciatic nerves using [3H]ouabain.

Clinical pharmacology of nicardipine in liver transplant patients.

Slow calcium channel antagonists are widely used among transplanted patients suffering from hypertension, although some of them tend to reduce hepatic blood flow. The aim of our study was to determine the pharmacological properties of nicardipine in transplanted patients with hypertension. Ten hours after liver transplantation, six patients (three men, three women) received 5 mg of intravenous nicardipine to prevent high blood pressure during intensive care. Prior to the administration and during the study (at the completion of the infusion, 3, 5, 10, 15, 20, 30, 45, and 60 min after infusion), the systemic and splanchnic parameters were measured (Swan Ganz catheter). Blood samples were drawn simultaneously from radial artery and free hepatic veins, in order to obtain the hepatic extraction of nicardipine. The hepatic extraction ratio was around 70% for the first 3 min, then decreased and remained stable thereafter, around 45%, showing a non linear first-pass metabolism pattern. Plasma hepatic clearance of nicardipine (699-850 ml/min) was close to total plasma clearance throughout the study (978 +/- 222 ml/min, from 71 to 87%) and half of the estimated hepatic plasma flow values at the same times (1467-1770 ml/min, from 44 to 51%). No statistically significant changes were observed in cardiac output and hepatic blood flow during the study, although there was a decrease in mean arterial blood pressure from 87 +/- 6 mmHg baseline level to 76 +/- 3 mmHg, 60 min after administration. Nicardipine chlorhydrate seems to be appropriate in post operative liver transplant patients when blood pressure must be decreased. Nicardipine safely lowers peripheral resistance, and does not induce changes in hepatic blood flow.(ABSTRACT TRUNCATED AT 250 WORDS)

Circadian rhythm in plasma noradrenaline of healthy sleep-deprived subjects.

Under normal sleep-wake conditions, noradrenaline (NA) secretions in supine subjects exhibit a weak circadian variation with a peak that occurs around noon; the sleep span is characterized by reduced NA secretion. Some investigators have reported that the circadian NA rhythm is completely obliterated during sleep deprivation. In our laboratory, plasma NA was assayed every hour for 24 h in nine healthy men 20-23 years of age. All men were deprived of sleep and were required to eat and walk around every hour to prevent sleep. However, subjects remained supine for 20 min before blood samples were collected to eliminate the effect of activity. Persistence of a slight decrease in the night concentration in several subjects, despite sleep deprivation, suggests that NA secretion may be influenced by a biological clock whose activity becomes visible when the influence of posture is removed.

Acute arsenic intoxication: forensic and toxicologic aspects (an observation).

The authors report on an acute suicidal arsenic intoxication (di-arsenic-trioxide). Death can occur one week after ingestion, despite intensive care. The forensic, anatomopathological and toxicologic aspects are reported. Forty titrations are realized at the level of the biologic fluid in viscera, by absorption spectrophotometry. These data are compared with those in standing literature, especially with the rates determined in normal subjects, following simple environmental impregnation.

[Subacute arsenic poisoning]. / Intoxication suraiguë à l'arsenic.

A cas is reported of a 23-year-old man who voluntarily took a massive dose of arsenic (at least 8 g). In spite of the ingested amount and the acute nature of the poisoning, the patient survived 8 days. Gastrointestinal, neurologic and cardiac features were predominant including nausea, vomiting, choleroid diarrhoea, encephalopathy, peripheral neuropathy, and finally a fatal toxic cardiomyopathy. Metabolic acidosis, moderate cytolysis and an anticoagulant effect were also observed. This unique characteristic was partly due to a circulating anticoagulant with prothrombinase activity, as well as direct antivitamin K activity. Postmortem examination revealed: a congestive oesophagitis; a necrosing gastritis involving all the stomach wall; diffuse hepatic steatosis; skin lesions with vascular congestion and dermoepidermal detachment; discrete subepicardial congestive lesions. Arsenic was found in all tissues.

Is verapamil also a non-selective beta blocker?

Verapamil is a calcium channel blocker widely used as an antihypertensive agent, and its pharmacological effects may partly be due to some degree of beta blockade. In order to evaluate the changes occurring in beta-2 adrenoceptor density, 40 patients with mild to moderate hypertension received verapamil 240 mg (once a day) or captopril 20 mg (twice a day) during 30 days, in a double-blind randomized study, after a placebo run-in period. The lymphocytic membrane beta-2 adrenoceptor density (Bmax) was determined before the administration of active drugs and after a 15-day treatment. After a month of treatment, most patients showed a marked reduction of their diastolic blood pressure: from 98.2 +/- 3.2 mmHg to 81.2 +/- 4.0 mmHg (p < 0.05), in the verapamil group, and from 95.0 +/- 6.0 mmHg to 82.5 +/- 4.8 mmHg (p < 0.05) in the captopril group. After 15 days of treatment, verapamil induced an up-regulation of beta-2 adrenoceptors from 39.5 +/- 8.3 fmol/mg protein to 58.5 +/- 12.0 fmol/mg protein (p < 0.05), whereas the Bmax in the captopril group did not significantly change. No significant change occurred in the two dissociation constants. This up-regulation phenomenon, common among beta-2 blockers, supports the hypothesis of verapamil's beta blockade potency.

Minocycline induces an increase in the number of excreting pilosebaceous follicles in acne vulgaris. A randomised study.

The effects of treatment with minocycline 100 mg per day on sebaceous excretion in acne vulgaris using lipometry and Sebutape were studied in 45 patients in an open study as well as in a randomised placebo-controlled study. In both studies a subclinical increase in sebaceous excretion was noted from the 28th day of treatment. This effect continued for 1 month after the end of treatment. The increase in sebaceous excretion was concomitant with an increase in the number of excreting pilosebaceous follicles. Minocycline may cause the follicles to become unblocked by acting on the factors responsible for ostial hyperkeratosis, in addition to an antibacterial effect on retentional acne lesions.

Clinical and biological evaluation of dilevalol vasodilating properties in mild to moderate hypertension.

Dilevalol is a vasodilating beta-blocker with proven antihypertensive activity. In this study, 28 patients with mild-to-moderate uncomplicated hypertension underwent 2 submaximal exercise tests, each consisting of progressive steps of 20 watts for 2 minutes or up to 85% theoretical maximum heart rate. Five minutes after the first test, patients received either placebo or dilevalol 200 mg, 400 mg or 600 mg. The second exercise test was performed 3 hours later. Diastolic blood pressure, systolic blood pressure, heart rate and norepinephrine plasma levels were assessed before and after exercise. Dilevalol at all doses caused a significant decrease in heart rate and blood pressure both at rest and during exercise, compared to placebo. Dilevalol 600 mg had a greater effect on diastolic blood pressure than dilevalol 200 mg and 400 mg. Administration of dilevalol 200 mg and 400 mg enabled 42% of patients to increase their maximal exercise level by 20 to 60 watts. Dilevalol increased plasma norepinephrine levels at the 100 watts exercise levels from 5.1 +/- 4.0 nmol/l to 7.6 +/- 4.3 nmol/l (p less than 0.05). No adverse effects were observed during dilevalol treatment. This study shows that dilevalol is an effective antihypertensive agent that blunts heart rate and blood pressure risings during exercise.

Simple column liquid chromatographic assay for serum neopterin.

A simple high-performance liquid chromatographic assay for serum neopterin with highly sensitive fluorimetric detection (limit 1 nM) is proposed. Comparison with results obtained by radioimmunoassay revealed a good correlation between the two techniques. The potential use of this method for the follow-up of liver transplant patients is discussed.