The renin-angiotensin system in the perinatal period in rats

Plasma concentrations of renin, angiotensinogen, kininogen, total protein, and renal renin concentration were measured in rats before spontaneous birth, immediately after vaginal delivery, during the subsequent 48 h, as well as at the ages of 10, 20 and 80 days. Preterm rats had a plasma renin concentration about 15 times higher than adults, which increased further in 1 h-old vaginally-delivered rats. Thereafter renin fell to very low levels within 2 h, rose again during the first day and remained at 4 times the adults level until day 10. Renal renin content and concentration increased over the whole observation period, except for a slight fall of renin concentration in the first 3 h after birth. In pre- and full-terms rats, angiotensinogen concentration was only 20% that of adults, reaching even lower values immediately after delivery, due to excessive consumption by renin. Thereafter, angiotensinogen increased more than 10 fold within 48 h. Kininogen concentration in plasma was higher than in adults and stable up to the 10th postnatal day. We conclude that vaginal delivery is a strong stimulus for renin release, the resulting high concentration of renin being responsible both for the increased turnover of angiotensinogen and the subsequent inhibition of renin release. The cause and biological significance of the dramatic increase of angiotensinogen during the first 48 h of life remains obscure.     

Effect of rhodium (III) complex on experimental carcinogenesis in the livers of rats treated with thioacetamide

Enzyme activities and protein content were determined in the cytosolic and mitochondrial fractions of liver homogenates obtained from Rh(III) complex-, thioacetamide- and thioacetamide + Rh(III) complex-treated rats. The Rh(III) complex administered to nonthioacetamide-treated rats produced no significant changes either in the enzymatic activities assayed or in the protein concentration. The Rh(III) complex administered to thioacetamide-treated rats produced significant restoration of the following altered values: cytosolic and mitochondrial aspartate aminotransferase, glutamate dehydrogenase, NADP-isocitrate dehydrogenase, and protein concentration. However, a further increase was produced in the activities of glucose-6-phosphate dehydrogenase and malic enzyme. These increases can be interpreted in terms of an enhancement of the NADPH-dependent detoxifying processes and of nucleic acid synthesis and repair.     

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.     

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.     

Further data on the origin of gonadotropin releasing hormone in the median eminence of the rat hypothalamus

Gonadotropin releasing hormone (GnRH) content of the two halves of the median eminence of the rat hypothalamus was determined by radioimmunoassay three weeks after three different unilateral knife cuts around the preoptic area. A unilateral cut in front or above the area caused a more than 25% decrease in the GnRH content of the two halves of the median eminence. A cut lateral to the preoptic region had only a slight effect similar to that observed after sham operations. The data suggest that probably more than 50% of the rat median eminence GnRH derives from outside the preoptic-suprachiasmatic region. The GnRH fibres projecting to the median eminence but arising from outside the preoptic region, probably mainly from GnRH perikarya in the limbs of the diagonal band of Broca and septum, enter this area partly from rostral and partly from above, but not from lateral direction. partly from rostral and partly from above, but not from lateral direction. Several of these fibres probably cross before terminating in the median eminence.