The effect of leptin on the tonic secretion of gonadotropins in the female rats.

OBJECTIVES: This study is an attempt to determine, the in vivo action of leptin on this hypophysiotropic hypothalamic area, by evaluating the concentrations of luteinizing hormone (LH) and follicular stimulating hormone (FSH) in the serum. METHODS: The experiments were done by stereotaxic injection of recombinant rat leptin (rrleptin) into the third cerebral ventricle (V3) of adult female Wistar rats. Subjects were divided into five groups. Group A included normal intact animals. In Group B, the rats were stereotaxically administered with rrleptin in the V3. The rats, in Groups C, D and E, were subjected to electrolytic lesion of the arcuate nucleus (ARC), of the ventromedial nucleus (VMH) and of both of these hypothalamic nuclei, respectively. Immediately after the electric lesion, they were intracranially injected with rrleptin. Blood samplings for serum LH and FSH levels estimation were performed three times: 1) just before any stereotaxic procedure, 2) six hours, and 3) twenty-four hours after leptin administration. RESULTS: The results showed that serum LH levels increased dramatically in group B, six hours after leptin administration. The LH levels in Groups C, D and E presented the same pattern with a lower peak. The FSH levels were doubled six hours after leptin administration in all groups without any exception. Both LH and FSH serum levels reverted to the initial basic levels after 24 hours. DISCUSSION: The significant conclusion derived from this study is that ARC and VMH, which are responsible for controlling the tonic secretion of gonadotropins, respond in a different way for the FSH and LH secretion. This also suggests that some other mechanism(s) or factor(s) may additionally participate in the control of the tonic component of FSH secretion.

Erythropoietin prevents long-term sensorimotor deficits and brain injury following neonatal hypoxia-ischemia in rats.

Perinatal asphyxia accounts for behavioral dysfunctions that often manifest as sensorimotor, learning or memory disabilities throughout development and into maturity. Erythropoietin (Epo) has been shown to exert neuroprotective effects in different models of brain injury including experimental models of perinatal asphyxia. However, the effect of Epo on functional abilities following cerebral hypoxia-ischemia (HI) in neonatal rats is not known. The aim of the present study is to investigate the effect of Epo on sensorimotor deficits and brain injury induced by hypoxia-ischemia. Seven-day-old rats underwent unilateral, permanent carotid artery ligation followed by 1 h of hypoxia. Epo was administered as a single dose immediately after the hypoxic insult (2000 U/kg). The neuroprotective effect of Epo was evaluated at postnatal day 42 by using a battery of behavioral tests and histological analysis. The results of the present study suggest that Epo treatment immediately after HI insult significantly facilitated recovery of sensorimotor function. Consistently, histopathological evaluation demonstrated that Epo significantly attenuated brain injury and preserved the integrity of cerebral cortex. These findings indicate that long-term neuroprotective effect of Epo on neonatal HI-induced brain injury might be associated with the preservation of sensorimotor functions.

Maximum cognitive performance and physiological time trend measurements after caffeine intake.

The effect of caffeine on the central nervous system and cardiorespiratory system was tested under resting conditions and while undertaking a multitask performance test. The subjects abstained from caffeine for a week before the study. Each subject performed the test after oral administration of 90 and 250 mg of caffeine on two separate days. Sum of Squares was recorded during the whole period of the study. Heart rate (HR) and respiration rates (RR) were continuously recorded and blood pressure (BP) was recorded before and after each stage of the experiment (Test(0), Test(1), Test(2), Test(3)). Sixteen healthy volunteers participated in the study divided into three groups: Group A, non-smokers and non-coffee drinkers; Group B, smokers and coffee drinkers; and Group C, non-smokers and coffee drinkers. Comparison of the performance of each stage with the resting conditions revealed statistically significant differences of group B compared to the other two groups and no significant differences between Groups A and C in both doses of caffeine. Non-coffee drinkers needed a low dose of caffeine for their optimal performance while a higher dose significantly increased their blood pressure. Coffee drinkers and smokers needed a higher dose of caffeine for optimal performance, which increased very quickly, but did not last and increased their BP. This increase in BP was not statistically significant, probably because of nicotine's effect. Heart rate was decreased and respiration rate increased significantly. The optimal performance was dose-dependent, increasing significantly with the higher dose of caffeine but with adverse effects on BP and RR.

Hypoxia-ischemia affects erythropoietin and erythropoietin receptor expression pattern in the neonatal rat brain.

Erythropoietin (EPO), known for its role in erythroid differentiation, has been suggested to have non-hematopoietic functions in the brain, especially during development. In the present study, we investigated the expression of erythropoietin and erythropoietin receptor (EPOR) in the developing rat brain following hypoxia-ischemia. Seven-day-old rats underwent unilateral, permanent carotid artery ligation followed by 1 h of hypoxia, and their brains were examined immediately, 24 h or 4 days after hypoxia-ischemia. RT-PCR and Western blot analysis revealed that hypoxia-ischemia only marginally affected EPO expression. Immunohistochemical study of brains 4 days after hypoxia showed that 60 min of hypoxia (resulting in cortical infarction and severe neuronal loss in other regions) led to the increased EPO immunoreactivity, especially in the boundaries of the damaged cerebral cortex, associated with astrocytosis. In contrast, EPOR was dramatically upregulated within 24 h after hypoxia-ischemia. These results suggest that there is a rapid response of EPOR to the hypoxic-ischemic stimulus, which seems to precede that of EPO, leading to the hypothesis that the EPO/EPOR system is implicated in the processes of neuroprotection from hypoxia-ischemia.

Erythropoietin prevents hypoxia/ischemia-induced DNA fragmentation in an experimental model of perinatal asphyxia.

Erythropoietin (EPO) prevents neuronal damage following ischemic, metabolic and excitotoxic stress. Recent studies have shown that EPO plays a significant role in the developing brain. The present study investigates the effect of EPO administration on hypoxic-ischemic brain injury and the possibility that its neuroprotective action may be associated with anti-apoptotic activity. Seven-day-old rats were treated with EPO (2000 U/kg) and subjected to a modified Levine procedure. EPO administration before the hypoxic-ischemic insult significantly reduces the severity of brain damage and improved the short-term functional brain recovery. Terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling and DNA electrophoresis displayed no evidence of DNA fragmentation in EPO-treated animals. These results suggest that EPO might protect the neonatal rat brain by anti-apoptotic mechanisms.

Morphological, histochemical, and interstitial pressure changes in the tibialis anterior muscle before and after aortofemoral bypass in patients with peripheral arterial occlusive disease.

BACKGROUND: Morphological and electrophysiological studies of ischemic muscles in peripheral arterial disease disclosed evidence of denervation and fibre atrophy. The purpose of the present study is to describe morphological changes in ischemic muscles before and after reperfusion surgery in patients with peripheral occlusive arterial disease, and to provide an insight into the effect of reperfusion on the histochemistry of the reperfused muscle. METHODS: Muscle biopsies were obtained from the tibialis anterior of 9 patients with chronic peripheral arterial occlusive disease of the lower extremities, before and after aortofemoral bypass, in order to evaluate the extent and type of muscle fibre changes during ischemia and after revascularization. Fibre type content and muscle fibre areas were quantified using standard histological and histochemical methods and morphometric analysis. Each patient underwent concentric needle electromyography, nerve conduction velocity studies, and interstitial pressure measurements. RESULTS: Preoperatively all patients showed muscle fibre atrophy of both types, type II fibre area being more affected. The mean fibre cross sectional area of type I was 3,745 microm2 and of type II 4,654 microm2. Fibre-type grouping, great variation in fibre size and angular fibres were indicative of chronic dennervation-reinnervation, in the absence of any clinical evidence of a neuropathic process. Seven days after the reperfusion the areas of both fibre types were even more reduced, being 3,086 microm2 for type I and 4,009 microm2 for type II, the proportion of type I fibres, and the interstitial pressure of tibialis anterior were increased. CONCLUSIONS: The findings suggest that chronic ischemia of the leg muscles causes compensatory histochemical changes in muscle fibres resulting from muscle hypoxia, and chronic dennervation-reinnervation changes, resulting possibly from ischemic neuropathy. Reperfusion seems to bring the oxidative capacity of the previously ischemic muscle closer to normal.

Electrophysiological, histochemical, and hormonal adaptation of rat muscle after prolonged hindlimb suspension.

The perspective of long-duration flights for future exploration, imply more research in the field of human adaptation. Previous studies in rat muscles hindlimb suspension (HLS), indicated muscle atrophy and a change of fibre composition from slow-to-fast twitch types. However, the contractile responses to long-term unloading is still unclear. Fifteen adult Wistar rats were studied in 45 and 70 days of muscle unweighting and soleus (SOL) muscle as well as extensor digitorum longus (EDL) were prepared for electrophysiological recordings (single, twitch, tetanic contraction and fatigue) and histochemical stainings. The loss of muscle mass observed was greater in the soleus muscle. The analysis of electrophysiological properties of both EDL and SOL showed significant main effects of group, of number of unweighting days and fatigue properties. Single contraction for soleus muscle remained unchanged but there was statistically significant difference for tetanic contraction and fatigue. Fatigue index showed a decrease for the control rats, but increase for the HLS rats. According to the histochemical findings there was a shift from oxidative to glycolytic metabolism during HLS. The data suggested that muscles atrophied, but they presented an adaptation pattern, while their endurance in fatigue was decreased.

Resveratrol ameliorates hypoxia/ischemia-induced behavioral deficits and brain injury in the neonatal rat brain.

Hypoxia-ischemia (HI) induced injury of the neonatal brain accounts for behavioral deficits concerning mainly neurological reflexes, sensorimotor functions and learning/memory disabilities that may evolve throughout development. The positive biological effects of resveratrol, a natural compound with anti-oxidant/anti-inflammatory properties found mainly in red wine have been indicated recently. Aim of this study was to investigate the delayed outcome of early administration of resveratrol in an experimental model of hypoxic-ischemic encephalopathy, by means of behavioral analysis and late neuropathological examination. Seven-day-old (P7) rats were separated into 3 groups: Group 1 underwent HI and treated with resveratrol. Group 2 (HI-treated) was subjected to HI and received same volume of saline. Group 3 (sham-operated) was the control group. A battery of behavioral tests was performed from days P8-P66, during which early reflexes (righting reflex, gait, geotaxis), sensorimotor (rope suspension, beam walking, rotarod) and learning/memory function (passive avoidance, Morris water-maze) were examined. Significant difference among the groups was observed in righting reflex, rotarod and water maze tests in which the resveratrol group almost reached the performance of the control animals. The other behavioral tests showed that control and resveratrol groups were better compared to HI, although not significant. Neuropathology study revealed a remarkable reduction of the infarct and preservation of myelination after resveratrol treatment, which was in most cases correlated with the better performance of the resveratrol group. These findings indicate that long-term neuroprotective effect of resveratrol on neonatal HI-induced gray and white matter damage might be associated with the preservation of behavioral functions.

Evaluation of long-lasting sensorimotor consequences following neonatal hypoxic-ischemic brain injury in rats: the neuroprotective role of MgSO4.

Perinatal asphyxia (PA) is a major determinant for long-term sensorimotor and locomotor deficits. The model of neonatal hypoxia-ischemia (HI) in 7-day-old rats produces sensorimotor cortex, thalamus and striatum injury, which are all critical for the maintenance of sensory motor function. The aim of this study was to evaluate the long-term neurodevelopmental disturbances in the above experimental model and to assess the neuroprotective effect of MgSO(4) in terms of long-term behavioral and morphological changes. Seven-day-old rats were separated into three groups: A (control), neither ligated nor exposed to hypoxia; B (HI/MgSO(4)) ligated, exposed to hypoxia and treated with MgSO(4) (2 g/kg b.w., i.p.), and C (HI) ligated and exposed to hypoxia. At the age of 42 days, the behavior of the rats was evaluated using 5 sensorimotor tests. Muscle power, motor coordination, reflexes, and limb placing were tested to different sensory stimuli. The study was completed with the histopathological evaluation of brain tissue damage. In all individual tests the HI-treated rats performed significantly worse than the control and MgSO(4)-treated rats and this difference was more pronounced in the limb placing tests. Additionally, neonatal HI resulted in extensive neuronal damage that was limited after MgSO(4) administration. Behavioral alterations represent a useful endpoint for studying the consequences of a perinatal HI insult and the efficacy of potential neuroprotective treatments. MgSO(4) administration resulted in prevention of HI-induced sensorimotor deficits and brain injury.

Neuroprotective effect of long-term MgSO4 administration after cerebral hypoxia-ischemia in newborn rats is related to the severity of brain damage.

Previous studies have shown contradictory results regarding magnesium-mediated neuroprotection in animal models of perinatal asphyxia. The aim of this study is to investigate the effects of MgSO(4) postasphyxial treatment on hypoxia-ischemia (HI)-induced brain injury in neonatal rats and the possibility that this effect is related to the severity of brain damage. Seven-day-old rats underwent unilateral carotid artery ligation followed by 1 or 2 hours of hypoxia (8% O(2)) and MgSO(4) administration. Adenosine triphosphate/phosphocreatine and glutamate/glutamine measurements and neuropathological evaluation of the hippocampus were used to assess the effects of HI and MgSO(4). HI caused time-dependent changes in energy stores, amino acid concentrations, and brain damage. Administration of MgSO(4) after 1 hour but not after 2 hours of hypoxia resulted in significant prevention of HI-induced brain injury. MgSO(4) administration results in a significant protection against moderate HI-induced brain damage, whereas it fails to offer a similar effect against severe brain damage.

Erythropoietin attenuates renal injury in experimental acute renal failure ischaemic/reperfusion model.

BACKGROUND: Erythropoietin (EPO), originally identified for its critical role in promoting erythrocyte survival and differentiation, has been shown to exert multiple paracrine/autocrine functions. Protective effects of EPO have been demonstrated in various tissues and experimental models of ischaemia-induced injury. In the present study, we investigated the effect of EPO on an in vivo rat model of renal ischaemia/reperfusion (I/R) injury and the possible mechanisms implicated in the EPO-mediated anti-apoptotic action. METHODS: Male Wistar rats, subjected to renal ischaemia for 45 min, were administered either saline or EPO (500 U/kg, i.p.) 20 min prior to I/R. A sham-operated group served as the control. At 48 h of reperfusion, the renal dysfunction and injury was assessed by measurement of serum biochemical markers (urea, creatinine) and histological grading. Apoptosis was assessed by the TUNEL method and morphological criteria. Expression of Bax and NF-kappaB (p65) was also evaluated. RESULTS: High levels of serum urea and creatinine were identified at 48 h after ischaemia. The EPO-treated group had significantly lower serum and creatinine levels. Semi-quantitative assessment of the histological lesions showed that rats subjected to I/R developed marked structural damage, whereas significantly less tubular damage was observed in the EPO-treated group. I/R caused an increase in TUNEL-positive cells that was accompanied by morphological evidence of apoptosis. In the EPO-treated rats only a few scattered TUNEL-positive cells were observed. Up-regulation of Bax in the tubular epithelial cells and increased expression of NF-kappaB was observed in the I/R-treated rats, while diminished expression of Bax and positive immunostaining of NF-kappaB was observed in the EPO-treated rats. CONCLUSION: Administration of EPO as a single dose before the onset of ischaemia produced a significant reduction in tubular injury, which was accompanied by a marked amelioration of renal functional impairment. The cytoprotective action of EPO against I/R injury seems to be associated with its anti-apoptotic action. Moreover, transcription factor NF-kappaB is likely to play a pivotal role in the pathophysiology of I/R renal injury and might have a key role in EPO-mediated protective effects.