Diurnal rhythm of the in vivo release of enkephalin from the globus pallidus of the rat

The in vivo spontaneous release of enkephalin in the globus pallidus of the rat increases from noon to evening by 100%; during this period the local release of exogenous gamma-aminobutyric acid (GABA) decreases by 60%. These diurnal rhythms are more marked in the K+-stimulated release: enkephalin-induced output increases 6-fold while GABA decreases 10-fold during the afternoon and evening hours. Since pallidal enkephalin and GABA are involved in the control of locomotor activity we suggest that these rhythms may be linked to the circadian changes of activity in the rat.     

Some aspects of social problems facing conservation in Brazil

There has been growing concern in Brazil for environmental issues in the last two decades. The conservation policies for Amazonia, which still represents the largest portion of forests of the country, are still based on isolated decisions made in the late 1970's. Among these policies there is, for instance, the plan for the establishment of a net of National Parks, proposed by Wetterberg et al. (1), based on the 'Pleistocene refugia' model. These refugia are areas of high species endemism, representing forest islands formed during the dry periods of the Pleistocene age, constituting the center of evolution and dispersal of Amazonian species (2). A number of parks and biological reserves have since been established and the decreese of laws protecting some elements of the fauna have been implemented. In 1979, studies for a more comprehensive plan for the conservation and development of Brazilian Amazonia were carried out in several institutions committed to research in Amazonia. As a result, several documents were handed to the government, but nothing has yet been implemented. Indeed, no environmental policy for Amazonia will succeed without an effective and comprehensive social plan, and the latter has yet to be formulated.     

Immunofluorescence of the microtubular skeleton in growing and drug-treated yeast protoplasts

The microtubular system in growing protoplasts of Saccharomyces uvarum was visualized by immunofluorescence using the monoclonal antitubulin antibody TU 01. We confirmed the coexistence of regular spindle configuration and extensive cytoplasmic networks in growing protoplasts and also observed a distinct distortion of cytoplasmic microtubules in association with wall removal. After a short period for recovery of protoplasts in nutrient medium a restitution of cytoplasmic microtubules and their resumed contact with the protoplast surface was observed. Treatment of growing protoplasts with nocodazole resulted in the disappearance of spindle and cytoplasmic microtubules in the relevant fraction of the protoplast population. In carbendazime (MBC)-arrested protoplasts spindle microtubules were absent but cytoplasmic microtubules associated with spindle pole bodies were clearly visible. Microtubule reassembly on spindle pole bodies occurred within 30 min after washing out nocodazole as well as carbendazime. The approach using protoplasts suggests a simple way in which the differential effect of antimicrotubule agents can be experimentally tested and the microtubule organizing activity of yeast protoplasts visualized at the population level.     

Interaction between prostacyclin and colchicine on the gastric mucosa of rat in different experimental ulcer models

The effect of prostacyclin and colchicine on the fundic gastric mucosa of adult female Wistar rats was investigated in stress (immobilization) and indomethacin induced ulcer models. Under prostacyclin treatment the ulcer index decreased significantly in both ulcer models. This effect was inhibited by colchicine. The nuclear volume of fundic epithelial cells increased significantly after application of either type of ulcerogenic stimulus. Prostacyclin did not influence the nuclear volume changes in stress ulcer, while it prevented this phenomenon in indomethacin-induced ulceration. Following colchicine treatment the nuclear volume decreased in both ulcer models. After combined prostacyclin and colchicine treatment the nuclear shrinkage remained unaltered in stress ulcer, while in indomethacin ulcer the nuclear volume decreasing effect of the separately administered drugs disappeared after combined treatment. The latter phenomenon was interpreted as an antagonistic interaction between prostacyclin and colchicine.     

Modification of 144Ce tissue deposition by mixed ligand complex treatment in mice

The individual effect of desferrioxamine-B (DFOA), Na3Ca-diethylene-triaminepentaacetic acid (DTPA), DL-penicillamine (PA) and Na-salicylate (SA) has been examined as well as the effect of mixed-ligand treatment on the retention and elimination of 144Ce in mice. It was found that 144Ce could easily be mobilized by a single dose of DTPA. Mixed-ligand (MLCs) treatment did not change the deposition characteristics and translocation kinetics of 144Ce.     

Effects of arginine-vasopressin and ACTH 4-10 on acquisition of active avoidance response in rats with alcohol pretreatment in prenatal and adult age

Alcohol administration in drinking water to mother rats during gestation resulted in a permanent learning deficit of the offspring when behavioural reactions were tested in active avoidance conditioned reflex situation in adult age. A similar deficit of learning capacity was observed in adult rats following alcohol administration for two weeks; the acquisition of active avoidance response was tested later. Administration of arginine-vasopressin and ACTH 4-10 during behavioural test led to a significant improvement of learning ability of the animals pretreated with alcohol. The observations indicate that the ethanol-induced deficit of learning capacity involves peptidergic mechanisms and the behavioural manifestations following chronic alcohol treatment are not irreversible processes.     

Effects of L-carnitine in acute myocardial ischaemia

Data in the literature suggest that exogenous L-carnitine improves the metabolic function of ischaemic heart cells: it enhances the transport of long-chain fatty acids into the mitochondria, stimulates the slowed beta-oxidation, and moderates the accumulation of amphiphilic acyl esters. A study has therefore been made of the cardiac effects of L-carnitine in dog experiments (n = 8). The left anterior descending coronary artery (LAD) was isolated in anaesthetized, thoracotomized animals in situ. After a control occlusion and equilibration period, the LAD was again ligated at the time of L-carnitine infusion (100 mg/kg iv. during 10 min). The agent diminished the maximal conduction delay and the degree of epicardial ST-segment elevation in the ischaemic myocardial region, and the free fatty acid concentration of the arterial blood, but it did not influence the frequency of ventricular extrasystoles. The anti-ischaemic effect of L-carnitine was manifest only during the infusion, and its discontinuation was immediately followed by an enhanced ST-segment elevation. In the dose applied, the substance did not affect the heart rate, systemic mean arterial pressure, left ventricular end-diastolic pressure (LVEDP), or left ventricular contractility (LV dP/dtmax). In the canine myocardial infarction model employed it was observed that the duration of the anti-ischaemic effect of L-carnitine (100 mg/kg iv.) is very short, and it has no significant antiarrhythmic action.