大鼠在模拟5 000米低氧下心力储备的动态变化

目的和方法：采用电刺激大鼠坐骨神经引起心阴抗图相应参数变化来测算心力储备的方法,测定了大鼠在模拟５０００ｍ氏氧下不同时间心力储备的动态变化。结果：心力储备在低氧３ｄ已开始增加,７ｄ增加显著（Ｐ〈０．０５）,低氧１０ｄ及１４ｄ又降至接近正常组水平,低氧３０ｄ略低于正常水平;每搏储备的变化规律和变化量均与心力领略相近,低氧７ｄ增加显著（Ｐ〈０．０１）,人低氧１４ｄ仍显著地对照组（Ｐ〈０．０５）;心率储     

Antihypoxic and antioxidative properties of bemitil

The authors discovered antihypoxic properties of the bemitil (pretreatment injections 50 mg/kg intraperitoneally) in the experiments on rats with the circulatory or hypoxic hypoxia. There was limitation of pO decrease and diene conjugates and Schiff bases production increase with the drug in the circulatory hypoxia conditions. Bemitil restricted malondialdehyde accumulation in the rat brain homogenate under the activation of free radicals processes. In the mitochondrial suspension incubation similar effect of the medicine was accompanied with limitation of organelle degradation. Bemitil showed no antiradical activity.     

Nicotine reduces mortality of developing rats exposed to high-altitude hypoxia and partially suppresses the duration of cortical epileptic afterdischarges

Nicotine has been repeatedly reported as substance possessing neuroprotective properties. This study focused on the possible beneficial effects of nicotine against the high-altitude hypoxia (9000 m for one hour). 15 min prior to hypoxia exposition rats (12- and 35-day-old) were treated with nicotine. Next day electrodes have been implanted and the effects of nicotine and hypoxia (or both factors) on duration of afterdischarges (ADs) were tested. Administration of nicotine declined the hypoxia-induced mortality in 35-day-old animals. Nicotine pretreatment had no effect on ADs duration in 12-day-old pups, therefore brought about suppression of ADs in 35-day-old animals. Taken together, our data show that nicotine exhibits an anticonvulsant effect that is age-dependent. The mechanisms of nicotine neuroprotective properties include probably the influence of calcium homeostasis, increase synthesis of variety of growth factors, inhibition of the caspase cascades and antioxidant capability of nicotine.     

Response of the rat cardiovascular system to a moderate altitude in connection with endurance training

The authors investigated whether an altitude of 1,350 m would affect the rat cardiovascular system in the same way as genuine altitude hypoxia and the way it would take effect when combined with endurance training in the form of swimming It was found that 8 weeks spent at this altitude led to an increase in absolute and relative heart weight, to right ventricular hypertrophy, and to increased resistance of the myocardium to acute anoxia. Physical training at a moderate altitude resulted in an increase in the relative weight of the musculature of both the right and the left ventricle and of the septum. Unlike low altitude training, however, growth of the two compartments of the heart was proportional. The resistance of the myocardium of trained animals against anoxia was the same, irrespective of whether they trained at a low or a high altitude. The results show that even a moderate altitude is not a matter of indifference for the rat organism, but that it leads to characteristic manifestations of altitude hypoxia in the cardiovascular system.     

Effects of acute hypobaric hypoxia and exhaustive exercise on AMP-activated protein kinase phosphorylation in rat skeletal muscle

The present study was aimed to explore the changes of phosphorylated AMP-activated protein kinase (pAMPK) level in skeletal muscle after exposure to acute hypobaric hypoxia and exhaustive exercise. Thirty-two male Sprague-Dawley (SD) rats were randomly divided into sea level and high altitude groups. The rats in high altitude group were submitted to simulated 5 000 m of high altitude in a hypobaric chamber for 24 h, and sea level group was maintained at normal conditions. All the rats were subjected to exhaustive swimming exercise. The exhaustion time was recorded. Before and after the exercise, blood lactate and glycogen content in skeletal muscle were determined; AMPK and pAMPK levels in skeletal muscle were detected by Western blot. The results showed that the exhaustion time was significantly decreased after exposure to high altitude. At the moment of exhaustion, high altitude group had lower blood lactate concentration and higher surplus glycogen content in gastrocnemius compared with sea level group. Exhaustive exercise significantly increased the pAMPK/AMPK ratio in rat skeletal muscles from both sea level and high altitude groups. However, high altitude group showed lower pAMPK/AMPK ratio after exhaustion compared to sea level group. These results suggest that, after exposure to acute hypobaric hypoxia, the decrement in exercise capacity may not be due to running out of glycogen, accumulation of lactate or disturbance in energy status in skeletal muscle.     

模拟高原环境下高原肺水肿大鼠模型的建立

目的在人工实验舱模拟高原环境下,探讨建立高原肺水肿大鼠模型的条件。方法 Wistar大鼠,雌雄各半,随机分为5组:空白对照组、低氧24 h组、低氧48 h组、低氧72 h组、低氧7 d组,测定大鼠肺组织含水量,肺组织中TNF-α、IL-6含量及病理改变。结果与正常对照组相比,低氧24、48、72 h组大鼠肺组织含水量依次为(81.58±0.86)%、(82.13±0.57)%、(82.21±0.88)%,高于正常对照组(78.72±0.52)%,肺组织中IL-6依次为(329.30±133.58)、(323.92±127.42)、(506.29±197.19)pg/mL,TNF-α依次(221.08±20.26)、(208.05±20.33)、(244.63±51.53)pg/mL,高于正常对照组IL-6(187.26±69.49)pg/mL,TNF-α为(91.81±22.24)pg/mL。低氧7d组肺组织含水量(81.47±0.65)%、肺组织中IL-6(241.33±83.60)pg/mL、TNF-α(109.99±31.98)pg/mL,均显著低于低氧72h组,病理学结果显示72h组肺组织有炎性细胞浸润,肺泡壁有明显的充血和水肿。结论模拟海拔5000 m环境,建立大鼠肺水肿模型的较好的时间为72 h。     

Effects of adaptation to intermittent high altitude hypoxia on ischemic ventricular arrhythmias in rats

We compared the effects of adaptation to intermittent high altitude (IHA) hypoxia of various degree and duration on ischemia-induced ventricular arrhythmias in rats. The animals were exposed to either relatively moderate hypoxia of 5000 m (4 or 8 h/day, 2-3 or 5-6 weeks) or severe hypoxia of 7000 m (8 h/day, 5-6 weeks). Ventricular arrhythmias induced by coronary artery occlusion were assessed in isolated buffer-perfused hearts or open-chest animals. In the isolated hearts, both antiarrhythmic and proarrhythmic effects were demonstrated depending on the degree and duration of hypoxic exposure. Whereas the adaptation to 5000 m for 4 h/day decreased the total number of premature ventricular complexes (PVCs), extending the daily exposure to 8 h and/or increasing the altitude to 7000 m led to opposite effects. On the contrary, the open-chest rats adapted to IHA hypoxia exhibited an increased tolerance to arrhythmias that was even more pronounced at the higher altitude. The distribution of PVCs over the ischemic period was not altered by any protocol of adaptation. It may be concluded that adaptation to IHA hypoxia is associated with enhanced tolerance of the rat heart to ischemic arrhythmias unless its severity exceeds a certain upper limit. The opposite effects of moderate and severe hypoxia on the isolated hearts cannot be explained by differences in the occluded zone size, heart rate or degree of myocardial fibrosis. The proarrhythmic effect of severe hypoxia may be related to a moderate left ventricular hypertrophy (27 %), which was present in rats adapted to 7000 m but not in those adapted to 5000 m. This adverse effect can be overcome by an unknown protective mechanism(s) that is absent in the isolated hearts.     

Age-dependent influence of a moderate altitude (1,350 m) on the rat cardiopulmonary system

The aim of the study was to determine whether a moderate altitude (1,350 m, Strbské Pleso, High Tatras) would act as a hypoxic stimulus on the cardiopulmonary system of young and adult rats. We used three experimental groups of animals differing in the duration of time for which they were kept at the given altitude (60 and 120 days) and the age at which they were acclimatized (from the 5th and the 60th day of life). The controls were kept at an altitude of 200 m (Prague). We found that an altitude of 1,350 m produced a significant increase in blood pressure in the lesser circulation; this response did not depend on the animals' age. Right ventricular enlargement occurred at the same time and was more pronounced in rats which had been acclimatized from infancy. The systemic blood pressure fell mildly, but significantly, only in animals exposed to altitude from adulthood; elevation of the haematocrit was likewise recorded only in this group. The results show that even a moderate altitude influences the cardiopulmonary system of the rat in a manner characteristic of the effect of chronic hypoxic hypoxia.     

低氧暴露条件下高原鼠兔和大鼠HPA轴活动的比较

采用人工模拟低气压低氧的方法比较研究了不同程度（模拟海拔5 km和7 km)和不同时间（24d和5d）低氧暴露,对大鼠和高原鼠兔（Ochotona curzoniae）下丘脑-垂体-肾上腺皮质 (hypothalamo-pituitary-adrenalcortex,HPA)轴活动的影响。结果如下：7 km低氧暴露24 h,大鼠下丘脑的促肾上腺皮质激素释放激素（corticotropin-releasing actor,CRF）和肾上腺皮质激素皮质酮分泌显著增加,大鼠HPA低氧暴露对大鼠HPA 轴活动无显著差异。低氧暴露5天后,大鼠7 km、5 km组的HPA轴活动与对照相比无明显差异。低氧暴露对高原鼠兔的HPA轴无明显影响。上述结果表明：低氧暴露的时间和程度与大鼠HPA的活动密切相关;从HPA的活动来看,高原鼠兔表现出较强的低氧耐受性。     

Dizocilpine pretreatment suppresses the action of hypoxia on hippocampal epileptic afterdischarges in immature rats

Effect of dizocilpine (0.5 mg/kg i.p.) on epileptic afterdischarges elicited by low-frequency electrical stimulation of the dorsal hippocampus was studied in rat pups aged 12 and 18 days. Repeated elicitation of afterdischarges (ADs) in control animals resulted in a progressive increase of the duration of ADs in both age groups. Dizocilpine (MK-801) injected after the first afterdischarge suppressed this prolongation in 12-day-old rats only. Hypobaric hypoxia (simulated altitude of 9000 m for one hour) led to a marked prolongation of the first afterdischarge in both age groups with a tendency to shorter ADs after repeated stimulations. Dizocilpine potentiated this tendency in 12-day-old rat pups so that it became statistically significant. Administration of dizocilpine before hypoxia prevented the increase in duration of the first afterdischarge in both age groups.     

Effects of increased swimming costs on foraging behavior and efficiency of captive Steller sea lions: Evidence for behavioral plasticity in the recovery phase of dives

A significant component of foraging energetics is the cost of locomotion, which for marine animals, is the cost of swimming. Increases in the cost of swimming may have significant impacts on foraging efficiency. Minimizing the cost of swimming can contribute to the optimization of foraging strategies by reducing the energetic cost of foraging. Results of several field studies suggest that an increase in the cost of locomotion may have comparable effects on foraging behavior and efficiency to a decrease in prey availability. We tested the hypothesis that an increased cost of swimming, brought on by increased hydrodynamic drag, has the same effect on dive behavior and efficiency as reduced prey availability under standard locomotion. Experiments were performed using two adult female Steller sea lions at the Alaska SeaLife Center in Seward, AK, using the same animals and general experimental design previously used to test the effects of reduced prey encounter rate on dive behavior and efficiency. Animals were fitted with a drag-inducing harness for half of the 500 simulated foraging dives in order to increase the cost of swimming. Individual dive duration and foraging time were significantly reduced in all cost-increased dives, comparable to the effects of reduced prey encounter rate. However, on a bout-by-bout basis, dive and foraging efficiency were only slightly reduced, which is likely due to an average 50% reduction in post-dive surface recovery duration during cost-increased dives. Increased heat flux across the body surface measured in a parallel study confirmed a significant increase in work during drag-increased dives. These results suggest that sea lions are able to compensate for changes in the cost of foraging and maintain their foraging efficiency by altering their dive strategy over an entire bout of dives when operating well within their aerobic scope.     

Experimental study of the immunostimulating properties of tomitsid

Tomicide, a preparation with antibacterial properties, accumulates in the culture medium during the growth of one of streptococcal strains. The injection of the preparation into mice simultaneously with the antigen (sheep red blood cells) produces an adjuvant effect. Tomicide has been found capable of inducing the production of interferon detected in the serum of the animals. During experimental stress created by intensive exercise tomicide prevented a decrease in the normal (anamnestic) level of antibodies, produced an immunostimulating effect and, at the same time, enhanced the total physical endurance of the animals, manifested by an increased duration of swimming.     

Effects of antidepressive agents on tolerance of hypoxia and physical exercise]

In experiments on mice and rats we studied the influence of antidepressants on hypoxic and physical tolerance. The antidepressants pyrazidol, azaphen, imipramine and moclobemide as well as the nootropic drug piracetam prolonged the life of animals in conditions of hypoxic and hemic hypoxia and increased the survival rate of rats in circulatory hypoxia. In experiments on mice antidepressants increased also the time of swimming.     

Certain mechanisms of development of types of body tolerance to acute hypobaric hypoxia

The regulatory mechanisms of individual rat resistance to acute hypobaric hypoxia were studied using the functional indices of the central nervous system (neurochemical and behavioral) and the hematopoietic system. The resistance to hypoxia was evaluated by the time of attitudinal reflex maintenance and recovery after decompression to a simulated altitude of 11 200 m. Animals with different types of tolerance to hypoxia demonstrated different metabolic backgrounds of neurochemical processes (which were most balanced in moderately resistant rats). This agrees with the differences in active behavior and adaptive efficiency of these animals exposed to mild open-field stress. High functional activity of erythropoiesis and early leukocytic response were observed in hypoxia-tolerant rats.     

兴奋性氨基酸加强高原低氧大鼠下丘脑前生长抑素原mRNA的表达

目的和方法：应用大鼠高原低氧模型及原位杂交技术和氨基酸测定法,研究下丘脑前生长抑素原（ＰＰＳ）ｍＲＮＡ表达和谷氨酸（Ｇｌｕ）、天门冬氨酸（Ａｓｐ）含量的变化。结果：高原低氧组大鼠下丘脑Ｇｌｕ和Ａｓｐ的含量明显增多,室周核、室旁核、弓状核ＰＰＳ－ｍＲＮＡ阳性神经元数目显著增加;而ＮＭＤＡ受体拮抗抗剂氯铵酮,虽然对Ｇｌｕ和Ａｓｐ含量无明显影响,但可使高原低氧大鼠下丘脑ＰＰＳ－ｍＲＮＡ阳性神经元数目减少     

Effects of endotoxin on oxidative metabolism of polymorphonuclear leukocytes

The influence of endotoxin on rat polymorphonuclear leucocytes (PMN) ability to generate oxygen free radicals (OFR) has been studied by chemiluminescence method. PMNs derived from intact animals were used as a control. PMNs derived from animals with 1.5 h endotoxemia increased OFR production after stimulation by latex. In contrast, PMNs derived from intact animals and preincubated with endotoxin for 1.5 h decreased OFR production after stimulation bw latex. It was proposed that stimulating effect of endotoxin on PMNs in vivo was mediated by plasma components.     

Effect of mediodorsal thalamic nucleus on the respiratory neurons from medulla oblongata and the rat respiration during hypoxia]

In the normal as well as in the oxygen deficiency conditions the research has been conducted to study the influence of associative mediodorsal (MD) nucleus of thalamus on impulsive activity of respiratory neurons of medulla oblongata of respiration. In conditions of normal atmospheric pressure, before the uplift of the animals, the electrical stimulation of MD of nucleus of thalamus has had mainly inhibiting influence. In the initial phase, on 4-5 thousand meter altitude, activation of frequent discharge of neurons occurred, the respiration has become frequent as well. In this situation the inhibiting influence of stimulation of MD nucleus of thalamus was more accentuated than in conditions of normoxia. In the second phase, 7.5-8 thousand meters, the opposite occurred, i.e. reduction of respiratory center activity of medulla oblongata and thalamus. In this difficult conditions of hypoxia, a reduction of impulsive activity of neurons has been observed; the respiration was becoming slower and surface. Meanwhile, the inhibiting influence of thalamus was not significant.     

The oxygen consuming systems of the liver of mice exposed to simulated high altitude

Altitude hypoxia does not induce any changes in the enzymatic systems related to oxygen consumption in guinea pigs native of the Peruvian high altitudes. The biochemical changes frequently found in high altitude animals are the result of exposure to the low temperature of this environment rather than to hypoxia. In the present work, mice were chronically exposed to hypobaric hypoxia and maintained at equal temperature as the sea level control group, and measurements of enzymatic activities of the three major oxygen consuming systems of the liver were carried out, i.e., mitochondria, microsomes and peroxisomes. The results obtained have confirmed that hypoxia has no apparent influence on these enzymatic systems.     

Increased somatostatin mRNA expression in periventricular nucleus of rat hypothalamus during hypoxia

We reported that hypoxia inhibited the growth hormone (GH) and induced somatostatin (SS) release from the hypothalamic median eminence (ME) of rats. This study is designed to examine the SS mRNA alterations in the periventricular nucleus (PeN) of the hypothalamus in rats and the possible involvement of glucocorticoid (GC) during hypoxia. Rats were exposed to hypoxia in a simulated hypobaric chamber. SS mRNA levels in the PeN were tested by in situ hybridization. Hypoxia of 5-km altitude (10.8% O(2)) for 2, 5 and 24 h increased the SS mRNA expression by 34.72%, 50.31% and 95.05% (p<0.05), respectively. Severe hypoxia of 7-km altitude (8.2% O(2)) enhanced the SS expression by 79.08% (p<0.01), 74.90% (p<0.01) and 71.40% (p<0.05), respectively. Prolonged hypoxia (5 km for 5 days) exposure augmented a 2.5-fold SS mRNA (p<0.001). One week post adrenalectomy (ADX), SS mRNA level was significantly increased. During hypoxia, 5 km for 5 h, SS mRNA in ADX rats was not further increased. An increased SS mRNA was showed by pretreatment with low dose of dexamethasone (DEX) (125 microg/kg, i.p.) to ADX animals but this increase was depressed by a high dose of DEX (500 microg/kg, i.p.). The data suggested that (1) hypoxia stimulated the expression of SS mRNA in the PeN of rat hypothalamus. (2) Increased circulating GC levels might play a role in upregulating the SS mRNA in the rat PeN during hypoxia.