Revista espanola de fisiologia最新文献

Anorexia inducing lithium chloride is believed to involve descending projections from hypothalamus to preganglionic autonomic output neurons. A multiple-labelling technique has presently been used to analyze the anatomical projections of lithium chloride sensitive neurons in the hypothalamus. Immunolabelling of c-fos was performed to stain neurons activated after LiCl administration, while neurons projecting toward vagal parasympathetic preganglionic levels were identified by injection of diamidino yellow in the dorsal motor nucleus of the vagus. Perikarya of descending neurons were mainly observed in the ventral and lateral areas of the paraventricular hypothalamic nucleus. In contrast, lithium chloride activated neurons were observed mainly in the magnocellular division of the paraventricular nucleus and supraoptic nucleus. Double-labelled neurons were not observed. These data provide evidence that lithium chloride sensitive neurons in the paraventricular nucleus are clearly different from those descending toward preganglionic vagal outflow neurons.

When exposed to hypoxia, the isolated atria from fed rats released lactate into the medium and underwent a decline of the peak developed tension and pacemaker frequency. The atria from 24-h fasted rats showed a rise in the resting tension together with a greater decline of the pacemaker rate and a lower lactate output than those from fed rats. The exposure to 5 mM 3-hydroxybutyrate caused only a small and brief decline in the pacemaker rate in the fed rats atria indicating that ketone bodies are able to exert only a minor detrimental effect on the hypoxic atria. Since the lactate output remained unaffected, this effect cannot be ascribed to a lowering in the energy supply from anaerobic glycolysis. On the contrary, 3-hydroxybutyrate improved the post-hypoxic recovery of the peak tension in the atria from fasted rats. This finding may be reflecting an anaplerotic role of 3-hydroxybutyrate, thus suggesting that in addition to glucose a second substrate is needed to meet the energy demand in the reoxygenated atria from fasted rats.

Creatine supplementation has been shown by several authors to improve physical performance in very high intensity, intermittent, exercises. The effect on performance, as well as in plasma creatine and lactate concentrations has been studied in a group of twelve sprinters of national class when running a distance of 150 m on two occasions, before and after creatine (or placebo) supplementation for the previous three days. The most important differences in the biochemical parameters analyzed have been in plasma creatinine concentration, which increased substantially both before and after the race in the group that had received a daily supplement of 25 grams of creatine monohydrate for the previous three days. Creatine supplementation, therefore, did not improve physical performance, in the conditions, when running a 150 m distance.

Short-circuit current (Isc) and transepithelial potential difference (PD) of the rat distal colon mucosa are sensitive to acute hypoxia in vitro. The relative contribution of luminal and serosal oxygenation in sustaining Isc and PD was assessed. Rat distal colon Isc and PD responses to hypoxia and reoxygenation of preparations of mucosa-submucosa, and of isolated mucosa (with and without the mucus gel layer), mounted in an Ussing chamber, and of sacs of everted and non-everted isolated mucosa, were measured. In Ussing chambers, a 5-min total (bilateral) hypoxia reduces Isc and PD by 50 to 70%, while an overshoot was observed on reoxygenation. Serosal hypoxia caused about the same effect as total hypoxia, with complete recovery on reoxygenation. Luminal hypoxia had no effect in either Isc or PD. After total hypoxia, selective serosal reoxygenation allowed complete recovery of Isc and PD; addition of luminal reoxygenation did not further increase Isc and PD. Luminal reoxygenation after total hypoxia did not modify the decrease in Isc and PD, but addition of serosal reoxygenation led to complete recovery. A similar behaviour was seen in isolated mucosa preparations without the mucus gel layer. Baseline Isc and PD of everted sacs were about 45% of those of non-everted sacs, but their response to a hypoxic challenge was slightly attenuated. On reoxygenation, both everted and non-everted sacs showed complete recovery. Summing up: serosal oxygenation is both necessary and sufficient to sustain rat distal colon Isc and PD, while luminal oxygenation is not; there seems to exist a barrier, different from the mucus gel layer, for oxygen access from the luminal side of the epithelium; and distal colon isolated mucosa everted sac preparations are suboptimally oxygenated.

The effect of 10 day-low dosage of n-3 long chain fatty acids (390 mg/day of EPA and 252 mg/day of DHA) on lipid and apolipoprotein (Apo) concentrations has been studied in nine normolipidaemic women aged 28.9 +/- 4.2 years. n-3 fatty acid supplementation did not significantly decrease total cholesterol and triglyceride levels but markedly decreased the Apo A1 and Apo B concentrations (12.7%, p < 0.01 and 23.1%, p < 0.001, respectively), while the Apo A1/Apo B ratio significantly increased (14.8%, p < 0.02). In contrast to the individual variations found for triglycerides and cholesterol, Apo changes indicate a fairly homogeneous response to the fish oil supplement. In seven women Apo A1 decreased (> 10%), whereas Apo B decreased (> 10%) in all of them. The Apo A1/Apo B ratio increased (> 10%) in five of these nine women. Changes in Apo A-1 and Apo B did not significantly correlate with changes in serum lipids. These findings suggest that short-term supplementation with low amount of n-3 long chain fatty acids, EPA and DHA, influences the serum Apo content more than the lipid levels in normolipidaemic women.

Several reports have shown the importance of MHC class I antigens in enabling the host to regulate tumour growth in vivo. Glucocorticoid hormones have strong immunosuppressive effects and are known to be regulators of gene transcription. In this report the expression of Major Histocompatibility Complex (MHC) class I antigens in six breast carcinoma cell lines have been studied before and after treatment with the synthetic glucocorticoid dexamethasone. Hence, HLA class I expression in the MCF-7 cell line was down-regulated in the presence of dexamethasone. This down-modulation of expression appeared to be mediated by transcriptional mechanisms, as revealed by HLA-class I mRNA levels.

The effect of melatonin administration on the oxidative stress induced by a high dose of Adriamycin (AD, doxorubicin hydrochloride) in plasma, hypothalamus and brain cortex of rats, as well as lipoperoxide changes, and catalase activity (CAT) levels have been studied. After administration of a single high AD dosis (25 mg/kg, i.p.), melatonin was injected daily three days before and after oxidative stress induction. The AD injection produced a significant lipoperoxide increase in plasma, hypothalamus and brain cortex, which was prevented by melatonin. CAT activity mean values decreased in hypothalamus by AD, effect which was reverted and increased by simultaneous melatonin administration. CAT activity was not changed after AD, melatonin or AD + melatonin administration in plasma and brain cortex. These results, especially those concerning lipoperoxide content changes, showed a powerful antioxidative effect of melatonin at both neural and extraneural levels in rats. CAT changes in the presence of melatonin suggest that there is a relationship between a scavenger role of the pineal hormone and a high oxidative activity in the brain hypothalamy area. When these results are taken together, they also show that melatonin, besides, producing the extraneural effect, can act as a powerful antioxidative agent in organs such as the brain, very rich in lipid susceptible to oxidation in the neuronal as well as the extraneuronal tissues.

The anaerobic threshold (AT) was calculated in 23 swimmers by field methods: MADER (MM) and modified exponential MADER (EM) and laboratory methods: SKINNER (SM), ROBERGS (RM), CONCONI (CM), and ventilatory (VM). Two types of test were designed. The first in a swimming pool (test 1), performing four series of increasing intensity swims, and the second on a cycle ergometer increasing until exhaustion (test 2). In both tests the heart rate (HR) was recorded in beats per minute by telemetry. Despite the different HR at the AT: 180.0 +/- 2.7 (MM), 179.1 +/- 2.4 (EM), 166.0 +/- 2.9 (SM), 157.0 +/- 2.8 (RM), 167.6 +/- 2.7 (VM) and 168.8 +/- 2.2 (CM), and the different maximum HR (HRmax) in the two tests: 201.6 +/- 2.0 in Test 1 and 188.5 +/- 1.6 in Test 2; the percentage HR in the AT/HRmax proved to be similar for all the methods except RM (88.0%-89.2%). The mechanism of organic control in progressive exercise can therefore have, in this test, a "threshold" zone at a given percentage of the maximum capacity of adaptation, both when the exercise is carried out in a pool and also on a cycle ergometer.