高原短期暴露人群返回低海拔地区后脱适应期血清皮质醇水平的变化

目的了解高原短期暴露人群返回低海拔地区后脱适应期皮质醇水平的变化。方法对参加高原(海拔3 700m以上)军事任务116天后返回平原的官兵在返回后的第2天、第15天和第30天分别采集清晨空腹静脉血,采用放射免疫法分析血清皮质醇浓度。未上高原的140例官兵作为对照,进行同样的检测。结果高原短期暴露人群,血清皮质醇呈先升高后下降趋势。官兵返回平原第2、15天时的皮质醇水平明显高于对照人群和返回平原后第30天的水平(P<0.05),且第15天时明显高于第2天(P<0.05)。官兵返回平原后第30天时与对照人群比较,差异无统计学意义(P>0.05)。结论高原短期暴露人群返回平原初期皮质醇水平变化明显,且与高原脱适应症状相关。     

White blood cell and hormonal responses to 4300 m altitude before and after intermittent altitude exposure

Recent studies have demonstrated that brief daily IAE (intermittent altitude exposure) was equally as effective as continuous altitude residence in inducing physiological adaptations consistent with altitude acclimatization. Although the positive benefits of IAE have been clearly defined, the potential negative consequences of IAE on health, specifically the immune system, remain undefined. The present study determined the effects of IAE on WBC (white blood cell) and hormonal responses during rest and exercise at 4300 m altitude. Six lowlanders (age, 23+/-2 years; body weight, 77+/-6 kg; values are means+/-S.E.M.) completed a VO(2)max (maximal O(2) uptake) and submaximal cycle ergometer test during a 30-h SL (sea level) exposure and during a 30 h exposure to 4300 m altitude-equivalent once before (PreIAE) and once after (PostIAE) a 3-week period of IAE (4 hxday(-1), 5 daysxweek(-1), 4300 m). The submaximal cycle ergometer test consisted of two consecutive 15-min work bouts at 40% and 70% of altitude-specific VO(2)max. Blood samples were obtained at rest and during both exercise work bouts for measurements of WBC count, leucocyte subset counts, cortisol, adrenaline (epinephrine) and noradrenaline (norepinephrine). WBC, neutrophil and lymphocyte counts increased significantly (P<0.05) during rest and exercise from SL to PreIAE and decreased (P<0.05) during rest and exercise from PreIAE to PostIAE. Monocyte counts decreased (P<0.05) during rest and exercise from PreIAE to PostIAE, but eosinophil and basophil counts did not change. Cortisol, adrenaline and noradrenaline did not change during rest or exercise from SL to PreIAE or PostIAE, but all increased significantly (P<0.05) from rest during the two work bouts. In conclusion, this type of IAE stimulus did not induce a hormonal stress response and did no harm in terms of activation of the immune system at altitude, as measured by WBC and leucocyte subset counts. This method of pre-acclimatization can therefore be highly recommended for inducing altitude acclimatization without the 'altitude residency' requirement.     

尿微量蛋白联合检测对高原短期暴露人群返回低海拔地区后肾脏脱适应损伤的判定

目的通过对高原短期暴露人群尿微量蛋白变化规律分析,探讨高原脱适应对肾脏的影响。方法高原短期暴露（116d）人员738例,根据返至富氧环境后晨尿中微量蛋白检测时间依次将受检者分为第2、15、30天组,并分别于上述时间检测其尿液中α1-微球蛋白（α—microglobulin,α1—MG）、p2微球蛋白（β2 microglobulin,β2-MG）、尿微量白蛋白（urinary microalbumin,mAlb）水平。结果第2、15、30天组α1-MG持续升高,β2-MG呈先降低后升高趋势,mAlb呈先升高后降低趋势;第30天组α1-MG、β2—MG异常率高于第2天组与第15天组（P〈0．05）,mAlb水平低于第15天组,高于第2天组（P均〈0．05）,第15天组第α1-MG、mAlb异常率高于第2天组,β2-MG异常率低于第2天组（P〈0．05）。结论高原低氧对肾功能有一定损伤,且返至富氧环境后脱适应对肾功能的损伤有所加剧。     

Sensitivity and specificity of a self-administered questionnaire of tobacco use; including the Fagerström test

Background

Preventing tobacco consumption and promoting cessation among health professionals are of great significance as their habits can influence their patients’ attitudes. Knowledge of the prevalence and characteristics of tobacco use in a specific population is important for the design of efficient strategies for preventing people from acquiring the habit and persuading them to stop. Self-administered questionnaires are a very common method for determining tobacco use, but assessment is needed of their validity for specific groups, such as occasional smokers or students of health sciences.

Objectives

The aim of this study was to determine the sensitivity and specificity of a self-administered questionnaire for determining tobacco use among a population of young female students of health sciences. As a gold standard, we used a measure of the concentration of cotinine in saliva with different cut-off points. We also analysed the influence on sensitivity and specificity of the questionnaire of nicotine dependence and exposure to secondary smoke.

Design

This is an internal validity study (sensitivity and specificity) of a self-administered questionnaire.

Settings

The study was carried out in the School of Health Sciences of the University of León, at its centres in León and Ponferrada.

Participants

Data were collected on 432 of a total of 480 women aged under 25 who were studying Health Sciences at the University of León in 2007.

Methods

The self-administered questionnaire included data concerning demography, education, tobacco habits and exposure to environmental smoke. Saliva cotinine concentration was determined with an EIA kit.

Results

The questionnaire used showed high values of sensitivity and specificity (85.3% and 95.3%) and a very good correlation (Kappa = 81.0%) with cotinine values of 10 ng/ml or higher. Discrepancies in the test results for those who declared themselves to be smokers only occurred in women with a low nicotine dependency. Among those who did not declare themselves smokers, those exposed to second-hand smoke were 7 times more frequently classified erroneously as smokers than those who had not been exposed.

Conclusion

The self-administered questionnaire used showed a very good internal validity and a good correlation with cotinine levels of 10 ng/mg, and therefore seems to be a good instrument for measuring tobacco use in this population. The availability of information on passive smoking and nicotine dependence is essential for the correct interpretation of the discrepancies.     

The haematological and cardiac patterns of adaptation of rabbits to 4,500 m simulated altitude and of readaptation to 400 m

The haemoglobin (Hb), red blood cell count (RBC) and haematocrit (Hct) of 11 male rabbits were measured at weekly intervals during a 5-week exposure period to hypobaric hypoxia (simulated altitude, 4,500 m) and the following 4 weeks after restoring normoxic conditions in a climatic chamber at constant temperature. RBC showed the slowest response, Hct the fastest during adaptation to hypoxia and readaptation to normoxia. The body weight decreased during the 1st week at hypoxia and remained at a reduced level for 2 weeks after the return to normoxia. In female rabbits exposed up to 43 days to hypoxia the heart ventricle quotient (HVQ) (weights of left ventricle + septum/right ventricle) was determined. There was a gradual decrease of HVQ expressing the development of right heart hypertrophy which was not stabilised within the observation period.     

Atrial performance in healthy subjects following high altitude exposure at 4100 m: 2D speckle-tracking strain analysis

The International Journal of Cardiovascular Imaging - High altitude (HA) exposure has been considered as a cardiac stress and might impair ventricular diastolic function. Atrial contraction is...     

In vitro effect on Cryptosporidium parvum of short-term exposure to cathelicidin peptides

Two laboratory methods, a cell culture system and double fluorogenic staining, were used to study the viability and infective ability of Cryptosporidium parvum sporozoites and oocysts after short-term exposure to four cathelicidin peptides. The compounds, SMAP-29, BMAP-28, PG-1 and Bac7(1-35), exerted a strong cytotoxic effect on sporozoites, but did not affect the viability and function of oocysts consistently. Overall, in the sporozoite series, a percentage of the viable population decreased rapidly to less than detectable levels after 15 and 60 min exposure to the peptides at concentrations of 100 and 10 micro g/mL, respectively. In the oocyst series, no compound produced complete inhibition of parasite growth: 60-85% of the oocyst population was viable after 180 min exposure at 100 micro g/mL. SMAP-29 exerted the highest activity against both sporozoites and oocysts.     

Bactericidal activities of five antibiotics during short-term exposure to coagulase-negative staphylococci.

After a 1-h exposure to concentrations used for topical prophylaxis in neurosurgical procedures, bacitracin, vancomycin, and oxacillin were bactericidal against more than 90% of 48 body fluid isolates of coagulase-negative staphylococci. More than 10% of isolates survived despite exposure for 4 h to concentrations of gentamicin and streptomycin greater than those employed for topical prophylaxis.     

Selective growth of epithelial-like clear cells from adult rat liver by short-term exposure to glucocorticoids in primary culture

Isolated liver cells, which were prepared from adult rats by a trypsin-liver-perfusion technique, were treated with dexamethasone or hydrocortisone at a concentration of 7.7 X 10(-6) M for 8 days in primary culture. The treated cultures displayed homogeneous population consisting of epithelial-like clear cells, while the untreated cultures displayed mixed population consisting of epithelial-like clear cells and fibroblast-like cells. The epithelial-like clear cells, which proliferated in the cultures treated with glucocorticoids for 8 days in primary culture, did not show any morphological changes following cultivation in glucocorticoid-free medium. After continuous glucocorticoid-treatment for more than 1 month, the treated cultures showed relatively low cell densities at confluence. The surface area of individual epithelial-like clear cells in the cultures treated with glucocorticoids for long periods of time was evidently greater than that in the cultures treated for only 8 days. The epithelial-like clear cells had glucose 6-phosphatase and tyrosine aminotransferase activities even though the levels of these enzyme-activities were very low compared with those in rat liver homogenates.     

Cardiac baroreflex control in humans during and immediately after brief exposure to simulated high altitude

To examine the baroreflex response in humans during and immediately after acute hypoxia exposure, the cardiac baroreflex sensitivity (BRS) was studied using adaptation of RR intervals in response to spontaneous systolic blood pressure fluctuations (sequences methodology) in 11 unacclimatized subjects. All measurements were made under fixed breathing rate, and realized consecutively at baseline level (20 min), at an inspired oxygen concentration of 11% (15 min) and again under normoxic conditions (20 min; recovery period). The spontaneous baroreflex response decreases progressively during hypoxic exposure, causing a tachycardic response at this FiO2 without any significant alteration of the systolic or diastolic blood pressure. The magnitude of decrease for this variable at the end of exposure averaged 42.9 +/- 15.6%. The simultaneous spectral analysis of heart rate (HR) variability in hypoxic condition confirmed an alteration in the parasympathetic activity (HFnu: -17.8 +/- 30.9% versus basal conditions, P < 0.01) counterbalanced by an exaggerated sympathetic activity (LFnu: +33 +/- 42.4%, P < 0.05) at the sinus node. Interestingly, we could observe an enhanced cardiac baroreflex response during the period following the inhalation of the hypoxic mixture (+130.6 +/- 15.6% of basal conditions, P < 0.001). There is a relationship with a significant and abrupt increase in the parasympathetic control of HR (mean HR reached 111 +/- 8.1% of the mean basal HR, P < 0.01). These results suggest that brief exposure to hypoxia under rate-controlled ventilation is associated with a significant alteration in the spontaneous cardiac baroreflex. This important cardiac autonomic imbalance is followed by a significant increase in the cardiac parasympathetic drive even after the disappearance of the hypoxic stimulus.     

Persistence of a reduced-collagen-producing phenotype in cultured scleroderma fibroblasts after short-term exposure to interferons

Transient exposure to inflammation-associated, fibroblast-stimulatory factors appears to initiate fibrosis by inducing the persistently activated phenotypes displayed by fibroblast cultures derived from scleroderma skin and other fibrotic tissues. To determine whether one class of fibroblast-inhibitory factors, the interferons (IFNs), plays a role in terminating fibrosis by acting as persistent fibroblast deactivators, we inhibited (40-60%) the growth and collagen production of normal dermal fibroblasts and hypercollagen-producing scleroderma fibroblasts by short-term exposure to IFN-alpha, beta, or gamma. During subsequent subculture in the absence of IFNs, the growth and collagen production of normal fibroblasts and the growth of scleroderma fibroblasts increased to untreated control levels after two to three passages. In contrast, collagen production by scleroderma fibroblasts remained inhibited for at least five passages (18 cell doublings) and was not further suppressed by subsequent IFN exposure. These data suggest that IFNs may help terminate fibrosis by suppressing persistently activated fibroblast functions.     

Comparison of the pharmacokinetics of sulfamethoxazole in male chinese volunteers at low altitude and acute exposure to high altitude versus subjects living chronically at high altitude: An open-label,controlled, prospective study

Background: Sulfamethoxazole is an antibacterial sulfonamide used primarily for the treatment of a wide variety of bacterial infections in combination with trimethoprim. Despite being used as prophylactic treatment for respiratory infections associated with high altitude, little information is available on the pharmacokinetic properties of sulfamethoxazole in subjects living at high altitude, especially in a Chinese population.Objective: This study was conducted to investigate the pharmacokinetics of sulfamethoxazole in healthy Chinese subjects after acute and chronic exposure to high altitude.Methods: An open-label, controlled, prospective study was conducted in healthy Chinese male volunteers. Sulfamethoxazole 1200 mg was administered orally to volunteers in 3 groups: those residing at low altitude (~400 m [~1300 ft]); these same volunteers after 16 hours (acute) of exposure to high altitude (~3780 m [~12,400 ft]); and a separate group of volunteers who had been living at high altitude (~3780 m) for ≥1 year (chronic). The phases of the low-altitude and acute-exposure groups were separated by a 1-week washout period. Blood samples were collected from an indwelling venous catheter into heparinized tubes before (baseline) study drug administration and at 0.25, 0.5, 0.75, 1, 1.5, 2, 3, 4, 6, 8, 12, 24, 36, and 48 hours after study drug administration. Sulfamethoxazole in whole blood, plasma, and plasma water, and its metabolite, N⁴-acetyl-sulfamethoxazole, in plasma were determined by HPLC. Tolerability was determined using blood chemistry testing, continuous 12-lead ECG, and blood pressure monitoring.Results: A total of 23 healthy Chinese male volunteers living at low altitude (race, all Han Chinese; mean [SD] age, 20.4 [1.1] years [range, 19–24 years]; weight, 64.2 [5.9] kg [range, 56.0–75.0 kg]; and height, 172.1 [4.9] cm [range, 163.0–180.0 cm]) and 21 healthy Chinese male volunteers living at high altitude (race, all Han Chinese; mean [SD] age, 21.2 [1.3] years [range, 19–24 years]; weight, 62.4 [8.2] kg [range, 50.0–75.0 kg]; and height, 171.4 [5.8] cm [range, 162.0–182.0 cm]) were enrolled in the study; 20 from each group completed the study. Concentration of sulfamethoxazole in plasma water decreased significantly after exposure to high altitude; therefore, the protein binding was significantly higher in the acute- (80.4%) and chronic-exposure (72.5%) groups compared with the low-altitude group (65.7%; both, P < 0.001). The binding of sulfamethoxazole to red blood cells was 6.0%, 6.9%, and 9.3% in the low-altitude, acute-, and chronic-exposure groups, respectively. The chronic-exposure group was 55% higher than the low-altitude group (P < 0.001). The following values were recorded in the low-altitude, acute-, and chronic-exposure groups after administration of sulfamethoxazole, respectively: mean (SD) t_½, 9.30 (1.11), 10.37 (0.88), and 11.15 (1.53) hours; mean residence time (MRT_0–48), 12.06 (0.94), 13.15 (0.67), and 13.00 (1.01) hours; elimination rate constant (k_e), 0.076 (0.010), 0.067 (0.006), and 0.063 (0.009) hours^?1; AUC_0–48, 1202.5 (238.3), 1416.3 (202.6), and 1298.5 (256.0) μ/mL/h; and clearance (CL), 1.01 (0.22), 0.83 (0.13), and 0.92 (0.22) L/kg/h. The t_½ was 11.5% and 19.9% higher in the acute- and chronic-exposure groups, respectively, compared with the low-altitude group, and 7.5% higher in the chronic-exposure group than in the acute-exposure group. MRT was 9.0% and 7.8% higher in the acute- (P < 0.05) and chronic-exposure (P < 0.001) groups, respectively, than in the low-altitude group. AUC_0–48 was 17.8% higher and CL was 17.8% lower in the acute-exposure group compared with the low-altitude group (both, P < 0.05).Conclusion: This study found significant changes in the disposition of sulfamethoxazole in these healthy male Chinese subjects after either acute or chronic exposure to an altitude of ~3780 m in comparison to those residing at an altitude of ~400 m.