慢性低氧大鼠肾上腺皮质球状带的变化

将Ｗｉｓｔａｒ大鼠喂养在逐渐降低的常压低氧条件下，用氮气和空气的混合气体调节氧含量。氧浓度由正常逐步降低为１５％、１２％、１０％、８％，最后降至７％，实验共进行１１２ｄ，结果显示低氧动物体重下降，肾上腺重量减少，肾上腺皮质球状带萎缩，脂质丢失，球状带细胞线粒体肿胀和空泡变性，溶酶体增多，表明在慢性常压低氧中，当吸入气氧含量降至７％时，可导致肾上腺皮质球状带细胞超微结构改变，从而影响醛固酮的合成与分     

Pathogenesis of the low cardiac output syndrome in postresuscitation states

Acute hypervolemia induced in experiments on dogs by infusion of dextran, did not produce decompensation of the circulation in animals whose cardiac output was sharply depressed in the postresuscitation period after circulatory arrest lasting 15 min. The increase in the venous return and change in the conditions of the peripheral circulation as a result of dextran administration temporarily increased the central venous pressure, caused a lasting increase in the arterial pressure, cardiac output, stroke volume, work of the left ventricle, and total oxygen consumption by the body, and lowered the peripheral vascular resistance. In model experiments on dogs subjected to isolated compression ischemia of the brain for 20 min, a low cardiac output syndrome also developed.Presented by Academician of the Academy of Medical Sciences of the USSR N. A. Fedorov.Translated from Byulleten' Éksperimental'noi Biologii i Meditsiny, Vol. 82, No. 7, pp. 787–789, July, 1976.     

Changes in Hemodynamics and Respiration in Rats with Different Resistance to Acute Hypoxia

Effects of acute hypoxia on hemodynamics and respiration were studied in acute experiments on narcotized rats. The animals were divided into groups characterized by high, low-, and medium- resistance to hypoxia by the time of respiration arrest during inhalation of gas mixture containing 3% O2. Hemodynamic parameters of highly resistant animals were higher than in low-resistant rats throughout the entire hypoxic period. The development of a rare (with prolonged inspiratory phase) respiratory rhythm in highly resistant rats is an adaptive reaction, which allows them longer tolerate hypoxia compared to low-resistant animals.     

Influence of hypobaric hypoxia in infancy on the subsequent development of vasoconstrictive pulmonary vascular disease in the Wistar albino rat

A group of Wistar albino rats was injected subcutaneously with monocrotaline to induce vasoconstrictive hypertensive pulmonary vascular disease characterized by medial hypertrophy of small pulmonary arteries, the appearance of muscular pulmonary arterial vessels of arteriolar dimensions (less than 20 microns) in diameter), and exudative changes in the lung parenchyma. The vascular abnormalities were quantified by measuring the percentage medial thickness of small pulmonary arteries, the number of muscular pulmonary arterial vessels below 20 microns in diameter per cm2 of lung section and by determining the smallest arterial vessels in each case showing muscularity. A second group of rats was born in a decompression chamber and kept in hypobaric hypoxia for a month of the neonatal period, developing hypoxic hypertensive pulmonary vascular disease as a consequence. The animals in this group were allowed to recover in room air for a period of 3 months and were then injected with the same dose of monocrotaline as that given to the first group. The rats previously exposed to hypoxia exhibited an exaggerated response to the alkaloid, showing in particular many more small muscular pulmonary arterial vessels which were of a smaller diameter than those found in the eupoxic rats treated with the alkaloid. The experiment demonstrates the perinatal hypoxia exaggerates the effects of agents inducing vasoconstrictive pulmonary hypertension with a shift of the segment of the pulmonary arterial tree involved to the periphery as in hypoxia. Reports of a similar phenomenon are noted as occurring in babies born at high altitude, spending their infancy there and subsequently developing primary pulmonary hypertension later in life.     

Power and peak blood lactate at 5050 m with 10 and 30 s ‘all out’ cycling

Anecdotal observations suggest that the reduction in peak lactate accumulation in blood ([La]_{b peak}) after exhausting exercise, in chronic hypoxia vs. normoxia, may be related to the duration of the exercise protocol, being less pronounced after short supramaximal exercise than after incremental exercise (IE) lasting several minutes. To test this hypothesis, six healthy male Caucasians (age 36.8 ± 7.3, x¯ ± SD) underwent three exercise protocols on a cycle ergometer, at sea level (SL) and after 21 ± 10 days at 5050 m altitude (ALT): (1) 10 s, (2) 30 s ‘all out’ exercise and (3) IE leading to exhaustion in ～20–25 min. ‘Average’ power output (p¯) was calculated for 10 or 30 s ‘all out’; maximal power output (P_max) was determined for IE. Lactate concentration in arterialized capillary blood ([La]_b) was measured at rest and at different times during recovery; the highest [La]_b during recovery was taken as [La]_{b peak}. No significant differences in p¯ were observed between SL and ALT, for either 10 or 30 s ‘all out’ exercise; P_max during IE was significantly lower at ALT than at SL. [La]_{b peak} after 10 s ‘all out’ was unaffected by chronic hypoxia (7.0 ± 0.9 at ALT vs. 6.3 ± 1.8 mmol L^–1 at SL). After 30 s ‘all out’ the [La]_{b peak} decrease, at ALT (10.6 ± 0.6 mmol L^–1) vs. SL (12.9 ± 1.4 mmol L^–1), was only ～50% of that observed for IE (6.7 ± 1.6 mmol L^–1 vs. 11.3 ± 2.8 mmol L^–1). Muscle power output and blood lactate accumulation during short supramaximal exercise are substantially unaffected by chronic hypoxia.     

低氧致鼠腺泡内肺动脉PDGF—B链蛋白表达的变化

目的：探讨血小板源性生长因子（ＰＤＧＦ）在低氧肺动脉高压血管构形重建发生中的作用。方法：应用免疫组化技术结合计算机图像分析，检测了低氧大鼠腺泡内肺动脉（ＩＡＰＡ）ＰＤＧＦ－Ｂ链蛋白表达水平。结果：常氧时，ＩＡＰＡ仅有ＰＤＧＦ－Ｂ链蛋白弱表达；低氧１天时，ＩＡＰＡ便有较强的ＰＤＧＦ－Ｂ链蛋白表达，定位于ＩＡＰＡ的内皮和中膜，低氧３天至１４天仅分布于中膜；低氧１、３、５、７、１４天各时间点ＰＤＧＦ－Ｂ链蛋白表达分别为常氧组的１．５３、１．５９、１．５６、１．６２和１．４２倍，差异有显著性（Ｐ＜０．０１）。结论：ＰＤＧＦ－Ｂ链蛋白可能参与了低氧肺动脉高压血管构形重建的发病过程     

MORPHOLOGICAL DIFFERENCES IN HEARTS OF RATS WELL ADAPTED AND POORLY ADAPTED TO CHRONIC HYPOXIA

We carried out an experiment to analyze morphological differences in hearts of rats well adapted and poorly adapted to chronic hypoxia. Male and female Wistar rats, 1 week, 4 weeks and 9 weeks old, were employed on the assumption that adaptive ability was dependent on age and sex. These rats were raised at an altitude of 2,400 m and were kept for 7 to 9 weeks. Control groups were maintained at an altitude of 600 m during the same period of time. Each group consisted of 4 to 6 rats. At the end of the experiment, body weight, heart weight, ratio of heart weight to body weight and hematocrit were measured, and ventricular wall thickness, myocardial fiber diameter, capillary supply and mitochondria were morphometrically studied. Of the 6 experimental groups, the 4-week-old male rats (M2) had the highest body weight, as compared with the other experimental groups. In addition, relative to these other experimental groups, the following features were found for M2. Heart weight was intermediate, heart weight/body weight ratio was low and hematocrit was also low. Ventricular wall thickness was intermediate in the right ventricle (RV) and interventricular septum (IVS) but was thin in the left ventricle (LV). Myocardial fiber diameter was intermediate in the RV, large in the IVS and small in the LV. Capillary supply was intermediate in the RV and dense in the IVS and LV. Mitochondria were small but cristal density and percentage area, estimated from electron micrographs, were found to be high. These data showed that in well developed rats under chronic hypoxia, there is good development of capillary supply with corresponding restriction of cardiac hypertrophy, while hematocrit count and mitochondria are also affected.     

Operation Everest II: Alterations in the immune system at high altitudes

We investigated the effects on immune function after progressive hypobaric hypoxia simulating an ascent to 25,000 ft (7620 m) over 4 weeks. Multiple simultaneousin vitro andin vivo immunologic variables were obtained from subjects at sea level, 7500 ft (2286 m), and 25,000 ft during a decompression chamber exposure. Phytohemag-glutinin-stimulated thymidine uptake and protein synthesis in mononuclear cells were reduced at extreme altitudes. Mononuclear-cell subset analysis by flow cytometry disclosed an increase in monocytes without changes in B cells or T-cell subsets. Plasma IgM and IgA but not IgG levels were increased at altitudes, whereas pokeweed mitogen-stimulatedin vitro IgG, IgA, and IgM secretion was unchanged. During exposure to 25,000 ft,in vitro phytohemagglutinin-stimulated interferon production and natural killer-cell cytotoxicity did not change statistically, but larger intersubject differences occurred. IgA and lysozyme levels (nasal wash) and serum antibodies to nuclear antigens were not influenced by altitude exposure. These results suggest that T-cell activation is blunted during exposure to severe hypoxemia, whereas B-cell function and mucosal immunity are not. Although the mechanism of alteredin vitro immune responsiveness after exposure to various environmental stressors has not been elucidated in humans, hypoxia may induce alterations in immune regulation as suggested byin vitro immune assays of effector-cell function.Some of this study's results were presented as an abstract at the FASEB meeting in St. Louis, Missouri, 1986.