低氧耐受动物细胞的耐低氧策略

一些脊椎动物通过进化可以耐受长期低氧 ,龟作为一种所谓的兼性耐低氧生物 (ｆａｃｕｌｔａ ｔｉｖｅａｎａｅｒｏｂｅｓ)能通过多种机制对低氧适应。其中最为重要的是急剧下调能量转换和上调ＡＴＰ生成通路的能效[1 ] ,后一机制是在低氧条件下从每摩尔Ｏ2 最大限度地获取ＡＴＰ ,而在无氧条件下 ,则通过无氧代谢通路 ,从发酵形成的每摩尔Ｈ+最大限度地获取ＡＴＰ[2～ 9] 。主要根据近年对龟的神经元与肝细胞的研究 ,可以列出以下的几种策略或机制。1　ＡＴＰ供需的平衡实验表明 ,低氧时肝细胞的能量转换低达1 0倍[2～ 3] ,在其他条件等同的…     

低氧感受及其信号转导机制研究进展

氧是机体及细胞进行有效能量代谢不可缺少的物质,低氧使机体及细胞的生理功能发生改变,严重时可引起一系列损伤和疾病。为适应低氧环境,生物经过长期进化,已形成一套完整的氧感受机制及在不同氧环境下的基因表达调控机制,以适应低氧环境,达到生存的目的。生物体对外界环境刺激作出反应,普遍的机制是通过配体-受体结合,引发细胞内一系列生化级联反应,最后调控相关基因表达的升高或降低,机体和细胞对低氧信号的识别及对基因表达的调控也遵循这一机制[1]。基于这一点,人们研究低氧对机体影响的热点集中在:探讨机体及细胞是如何感受周围环境氧浓…     

血型与高原血氧饱和度的观测

目的：探讨人体进入高原低氧环境初期和移居６个月与居住２年后血型与血氧饱和率（ＳａＯ２）之间的内在关系，为高原低氧生理积累资料；方法：对初入海拔５３８０ｍ３天￣７天和居住６个月的１９８名边防军人及移居海拔４３００ｍ２年的４８名健康青年在静息上进行ＡＢＯ血型鉴定同时检测ＳａＯ２；结果：初入海拔５３８０ｍ３天￣７天的健康青年Ｏ、Ａ血型的ＳａＯ２含量显著高于Ｂ、ＡＢ型血的青年（Ｐ〈０．０１或Ｐ〈０．０５）     

低氧条件下增加血氧饱和度的实验研究

低压舱模拟急性低氧３０００ｍ和日喀则高原３８３６ｍ条件下，以４１名健康成年人为被试对象，经１５ｍｉｎ健身顺运动使血氧饱和度明显增加，运动后３ｍｉｎ血氧饱和度仍比对照有显著意义的增加。结果提示：在低氧条件下进行健身运动确有提高血氧饱和度的功效，是克服生低氧反应的一各肯效措施。本文对此类健身器运动后增加血氧饱和度的可能性进行了分析。     

低氧诱导因子-1结构、活性调节及其靶基因的研究进展

低氧诱导因子-1(hypoxia-inducible factor 1，HIF-1)是由低氧等诱导细胞产生的一种转录因子。通过调控近50种靶基因，引起细胞对低氧发生一系列适应性反应，以实现其主要调节氧稳态的功能，说明其在低氧信号转导过程中起关键作用，具有重要的生理学和病理生理学意义。本文综述了HIF-1的结构、活性调节及其靶基因等方面的研究进展。     

低氧血症导致肥胖者急性高原反应:个案分析

<正>随着我国经济的发展,到高原地区旅游的人日益增多,急性高原反应(AMS)的防治成为重要的研究课题,而提高高原旅居人群的健康水平和生活质量也一直是医学工作者追求的目标[1]。急性严重缺氧易导致器官功能障碍和代偿不全,甚至引起不可逆损伤而导致机体死亡。目前研究得到的     

低氧、运动对大鼠骨骼肌细胞凋亡及bcl-2、bax表达的影响

目的:观察低氧和运动刺激后大鼠骨骼肌细胞凋亡及bcl-2b、ax表达情况,为探讨运动与低氧适应机理提供依据。方法:7周龄雄性SD大鼠56只,平均体重220±28克。随机分成7组:(1)对照组;(2)低氧对照组,包括4天和7天组;(3)常氧训练组,包括4天和7天组;(4)低氧训练组,包括4天和7天组。对照组不安排任何形式的运动训练。常氧训练组在常氧条件下进行上坡跑训练,每天1h,跑速为20m/min,坡度+10°。低氧对照组不安排任何形式的训练,生活在低氧舱内,低氧舱内氧分压为12.7%(相当于海拔4000米高度),每天在常氧下生活1h。低氧训练组生活环境同低氧对照组,训练方案同常氧训练组。4天组和7天组分别进行为期4天与7天的训练。实验后取材,采用HE染色、原位末端脱氧核糖核苷酸转移酶介导的dUTP缺口末端标记法(TUNEL)、DNA电泳及蛋白免疫组织化学法检测各组大鼠骨骼肌凋亡和bcl-2、bax表达。结果:(1)低氧对照7天组及低氧运动7天组大鼠骨骼肌bcl-2表达显著低于对照组,bax表达无明显变化;(2)低氧对照7天组与低氧运动7天组大鼠骨骼肌细胞凋亡较对照组明显增加,但两组之间无显著性差异,提示低氧和运动的双重作用不会加重细胞凋亡;(3)常氧运动组运动后未出现明显的骨骼肌细胞凋亡,提示运动诱导骨骼肌细胞凋亡可能与运动强度和/或运动量有关。     

低氧适应兔肺超微结构观察

家兔暴露于低压舱,每天4h,连续2周。第一周与第二周的模拟海拔高度分别为3800m和5000m。阶梯低氧适应后,适应组与急性低氧组家兔一同暴露于模拟海拔5000m,停留3h。暴露后家兔和正常对照家兔(n=5)均进行了电镜观察。结果发现,急性低氧兔肺毛细血管内皮明显肿胀,有时因毛细血管内皮明显隆出而使毛细血管腔变小。而在低氧适应组,肺毛细血管内皮肿胀程度减轻,同时也未见因内皮膨出而使毛细血管腔变小的现象。文章还讨论了本观察结果的生理意义。     

两种缺氧刺激对大学生红细胞生成素及有氧能力的影响

目的:探讨缺氧刺激对血清红细胞生成素(EPO)和转铁蛋白受体(sTfR)的影响,观察在低氧刺激环境下血液EPO分泌和血清sTfR浓度的变化规律.方法:受试者为20名身体健康的男性大学生,随机分为3组:间歇吸低氧组(n=7)、模拟高住组(n=5)和对照组(n=8).间歇吸低氧组每天30分钟吸低氧,模拟高住组每天8小时低氧环境睡眠.所有受试者在实验期均从事相同的体育技术课和理论课学习及相同的生活作息,全部实验共包括4周试验期和2周恢复期.结果:(1)对照组血清EPO浓度在实验前、中和恢复期均无明显变化.间歇吸低氧组血清EPO浓度在实验第3天、第17天、第22天,模拟高住组血清EPO浓度在实验第15天、第17天、第22天、第24天及恢复期均显著高于实验前(P＜0.05),(2)间歇吸低氧组血清sTfR浓度在实验第3天、第10天、第17天及恢复期结束均显著高于实验前(P＜0.05),而模拟高住组和对照组血清sTfR浓度在实验期和恢复期均未发生明显变化.(3)实验后间歇吸低氧组受试者VO2max与实验前比较明显增加(P＜0.05).(4)除对照组外,实验后间歇吸低氧组、模拟高住组在定量负荷运动中的心率、血乳酸与实验前相比显著下降(P＜0.05).结论:血清EPO、sTfR浓度的变化受不同低氧浓度刺激时间和方式的影响,间歇吸低氧与运动刺激相结合可增加VO2max.     

高原环境对机体免疫功能的影响机制

高原地区所处的环境为低氧、低温、强辐射等因素对人体各系统均有明显的影响作用，包括生理和心理影响，越来越多的研究表明低氧、低温、强辐射等环境因素会引起机体免疫功能的变化，其中低氧是主要的影响因素。主要是引起机体免疫抑制，增加机体的易感性。机体的免疫功能分为非特异性免疫和特异性免疫，前者主要包括红细胞(RBC)、中性     

在长期航天中利用紫外线辐射的展望

随着航天员在太空停留的时间逐渐延长,各种航天环境因素对航天员的影响更加显著,紫外线缺乏也成为一个重要因素。研究表明,低剂量（10mJ/cm2)的紫外线照射对人体是有益的而且是必需的,它可增强机体免疫功能;改善载人航天时周围环境的卫生条件,提高机体的工作能力和航天中不利因素的抵抗力,预防航天员飞行中矿物质丢失,治疗皮肤化脓性疾病和变态反应性疾病;对变态源的脱敏等。所以,对长期航天时的航天员适当进行紫外线照射是十分必要的。     

失重和缺氧的复合生理效应

失重和缺氧的复合生理效应张汝果（北京航天医学工程研究所１０００９４）１引言失重是航天中特有的、持续的因素，低氧或缺氧是航天器座舱内可能出现的环境因素。缺氧对失重效应的影响理应为航天医学专家们重视，这不仅对保障航天员的身体健康、工作效率有重要意义，同时...     

Advantages of a low-oxygen environment in space cabins

The advantages of having a low-oxygen environment in space cabins are discussed. The major advantage is a sharply reduced fire hazard, which is a major threat in manned space flights. At 1 atm, for example, 15% O2 (9,000 ft altitude equivalent) would not support most fires and could accommodate the crew with respect to hypoxia, decompression sickness (DCS), and other requirements. Chronic exposure to such a hypoxic environment (altitude acclimatization) could improve major areas of crew health and safety including alleviating deconditioning effects, decreasing susceptibility to DCS, and improving tolerance to severe hypoxia.     

Hypobaric nitrogen-oxygen atmosphere as a method of preventing altitude decompression sickness]

It has been shown experimentally that the development of altitude decompression disease at 250 and 180 mm Hg can be prevented by preliminary desaturation in the nitrogen-oxygen hypobaric atmosphere (60% N2 and 40% O2 at 550 mm Hg). This has been demonstrated in 38 experiments on 21 test subjects. The use of this atmosphere in space cabin prevents the development of decompression disease upon a decrease of the cabin pressure to 250 mm Hg and upon extravehicular activity in a space suit with 180--200 mm Hg.     

Cabin air quality: an overview

In recent years, there have been increasing complaints from cockpit crew, cabin crew, and passengers that the cabin air quality of commercial aircraft is deficient. A myriad of complaints including headache, fatigue, fever, and respiratory difficulties among many others have been registered, particularly by flight attendants on long-haul routes. There is also much concern today regarding the transmission of contagious disease inflight, particularly tuberculosis. The unanswered question is whether these complaints are really due to poor cabin air quality or to other factors inherent intlight such as lowered barometric pressure, hypoxia, low humidity, circadian dysynchrony, work/rest cycles, vibration, etc. This paper will review some aspects relevant to cabin air quality such as volatile organic compounds (VOCs), carbon dioxide (CO2), carbon monoxide (CO), ozone (O3), particulates, and microorganisms, as well as the cabin ventilation system, to discern possible causes and effects of illness contracted inflight. The paper will conclude with recommendations on how the issue of cabin air quality may be resolved.     

固态胺二氧化碳去除系统中反应罐的设计

目的 设计一种能满足长期载人航天器内固态胺吸附／水蒸气解吸CO2控制系统要求的反应罐。方法 根据系统要求及固态胺本身特性,解决如下关键问题：（1）额定的阻力损失需要减少床高与吸附,浓缩需要增加床高的问题;（2）有限的解吸热量与一定解吸温度保持的问题;（3）微重力下如何适应固态胺的膨胀与收缩的问题。结果 成功地实现了CO2的吸附,解吸及浓缩,系统可控制座舱CO2浓度在0．5％以下,浓缩的CO2浓度＞95％,可直接进入CO2还原系统,系统阻力低于160mmH2O,解吸能耗降到650W以下,结论 设计的反应罐能满足微重力条件下固态胺二氧化碳去除系统的要求。     

Cerebral oxygenation in awake rats during acclimation and deacclimation to hypoxia: an in vivo electron paramagnetic resonance study

Exposure to high altitude or hypobaric hypoxia results in a series of metabolic, physiologic, and genetic changes that serve to acclimate the brain to hypoxia. Tissue Po(2) (Pto(2)) is a sensitive index of the balance between oxygen delivery and utilization and can be considered to represent the summation of such factors as cerebral blood flow, capillary density, hematocrit, arterial Po(2), and metabolic rate. As such, it can be used as a marker of the extent of acclimation. We developed a method using electron paramagnetic resonance (EPR) to measure Pto(2) in unanesthetized subjects with a chronically implanted sensor. EPR was used to measure rat cortical tissue Pto(2) in awake rats during acute hypoxia and over a time course of acclimation and deacclimation to hypobaric hypoxia. This was done to simulate the effects on brain Pto(2) of traveling to altitude for a limited period. Acute reduction of inspired O(2) to 10% caused a decline from 26.7?±?2.2 to 13.0?±?1.5?mmHg (mean?±?SD). Addition of 10% CO(2) to animals breathing 10% O(2) returned Pto(2) to values measured while breathing 21% O(2,) indicating that hypercapnia can reverse the effects of acute hypoxia. Pto(2) in animals acclimated to 10% O(2) was similar to that measured preacclimation when breathing 21% O(2). Using a novel, individualized statistical model, it was shown that the T(1/2) of the Pto(2) response during exposure to chronic hypoxia was approximately 2 days. This indicates a capacity for rapid adaptation to hypoxia. When subjects were returned to normoxia, there was a transient hyperoxygenation, followed by a return to lower values with a T(1/2) of deacclimation of 1.5 to 3 days. These data indicate that exposure to hypoxia results in significant improvements in steady-state oxygenation for a given inspired O(2) and that both acclimation and deacclimation can occur within days.     

Toxicologic evaluation of the space shuttle "Columbia"

Atmospheric contamination of spacecraft crew cabins has been a toxicological concern since this country began its efforts in manned space flight (1). Procedures have been developed and utilized for determining the identities and quantities of contaminant gases present in the crew cabin environment. Methods have also been developed for assessing and controlling the trace gas contaminant buildup within the closed environment of spacecraft cabins. Although nearly one hundred contaminant gases have been detected in the Shuttle crew cabin, for the most part, the concentrations of these gases have been maintained below a toxicity hazard level.     

Loss of cabin pressurization in U.S. Naval aircraft: 1969-90.

During the 22-year period from 1 January 1969 to 31 December 1990, there were 205 reported cases of loss of cabin pressure in US Naval aircraft; 21 were crew-initiated and 184 were deemed accidental. The ambient altitudes varied from 10,000 ft (3048 m) to 40,000 ft. (12192 m). The most common reason for crew-initiated decompression was to clear smoke and fumes from the cockpit/cabin (95%). The most common cause for accidental loss of cabin pressure was mechanical (73.37%), with aircraft structural damage accounting for the remaining 26.63%. Serious physiological problems included 1 pneumothorax, 11 cases of Type I decompression sickness, 23 cases of mild to moderate hypoxia with no loss of consciousness, 18 cases of hypoxia with loss of consciousness, and 3 lost aircraft with 4 fatalities due to incapacitation by hypoxia. In addition, 12 ejections were attributed to loss of cockpit pressure. Nine of the ejections were deliberate and three were accidental, caused by wind blast activation of the face curtain. Three aviators lost their lives following ejection and seven aircraft were lost. While the incidence of loss of cabin pressure in Naval aircraft appears low, it none-the-less presents a definite risk to the aircrew. Lectures on the loss of cabin/cockpit pressurization should continue during indoctrination and refresher physiology training.     

Normobaric hypoxia inhalation test vs. response to airline flight in healthy passengers

INTRODUCTION: There is little data available to determine the normal response to normobaric hypoxia inhalation testing (NHIT) and air travel. Quantifying a healthy response may assist in the evaluation of passengers considered at risk for air travel. The aims of this study were: (1) to quantify the degree of desaturation in healthy subjects during a NHIT and air travel; and (2) assess the validity of the NHIT when compared with actual in-flight responses. METHODS: There were 15 healthy adults (age 23-57; 10 women) who volunteered for this study. Preflight tests included lung function, arterial blood gas, pulse oximetry (SpO2), and NHIT (inspired oxygen 15%). SpO2 and cabin pressure were measured continuously on each subject during a commercial air flight (mean cabin altitude 2178 m; range 1719-2426 m). In-flight oxygenation was compared with the preflight NHIT. RESULTS: Lung function testing results were normal. There was significant desaturation (SpO2) during the NHIT (pre: 98 +/- 2%; post: 92 +/- 2%) and at cruising altitude (pre: 97 +/- 1%; cruise: 92 +/- 2%). There was no difference between the final NHIT SpO2 and the mean in-flight SpO2. There was a significant difference between the lowest in-flight SpO2 (88 +/- 2%) vs. the lowest NHIT SpO2, (90 +/- 2%). DISCUSSION: Oxygen saturation decreases significantly during air travel in normal individuals. In this group of healthy passengers the NHIT approximates some, but not all, aspects of in-flight oxygenation. These results can be used to describe a normal response to the NHIT and air-travel.