首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献,搜索用时 15 毫秒
1.
Analysis of 2-year myocardial infarct deaths in subtropical Brisbane shows an increase in mortality rate within a temperature range normally considered mild in mid-latitude locations. During both the coldest and warmest season, the relationship is a strong one, especially with temperatures that are below neutrality for the population.  相似文献   

2.
Daily myocardial infarct deaths for Auckland (36° 51S, 20 m above sea-level) show an increase in mortality rate with decreasing temperatures over the entire thermal range. Parallel studies in Brisbane and Montreal predicted a minimum death temperature between 21 and 24° C, but no such point was apparent. Lack of temperatures above 21° C, together with the small overall thermal range, is thought responsible.  相似文献   

3.
Abstract Death-rate determinations indicated that a temperature a few tenths of a degree higher than Tmax was more deleterious to Klebsiella terrigena (ATCC 33257) than a somewhat higher temperature. The death rate at 40°C (Tmax+ 0.5°C) was approximately 0.2 log units per h but about 0.01 log units per h between 42°C and 44°C. Sequential temperature-gradient and constant temperature incubations showed the same phenomenon qualitatively among 14 Enterobacteriaceae strains representing different species.  相似文献   

4.
This paper reviews studies that have been conducted to determine how environmental temperature affects productivity of poultry and how these effects can be alleviated so that the bird will realise its full productive capacity. It is shown that temperature primarily affects production of poultry meat and eggs through food consumption. A key factor in efficient weight gain and/or egg production of poultry is optimum nutrient intake. High environmental temperatures cause food intake to decrease and often result in inadequate nutrient intake contributing to poor performance. When nutrient intake is shifted by the influence of temperature on food intake, the adverse effect on productivity (growth or egg output) may be alleviated through improved feed formulation by adjusting the nutrient density to compensate for the altered intake of food. Improved feed management and better housing systems can partially compensate for low feed intake caused by high environmental temperatures.  相似文献   

5.
杜抱朴  杜靖 《人类学学报》2021,40(4):644-652
观察中国不同区域内现代人群四肢形态变化是否与艾伦法则相一致。本文搜集中国各区域102处地点的现代人群上、下肢测量性状中17项指标,探讨其与温度(年平均温度、年最高温度、年最低温度和气温年较差)间的线性关系。结果表明,随着环境温度降低,中国现代人的上肢相对长度逐渐变短,前臂和手则逐渐增粗;下肢(下肢全长、大腿长和小腿长)逐渐变长,且下肢相对长度同样渐增。手长、手宽、上臂围和前臂围与气温年较差呈正相关,而身高上肢长指数与气温年较差呈负相关;下肢全长、大腿长、足长和小腿围与气温年较差呈正相关。环境温度作为一项选择性压力,作用于上肢发育或形态塑造过程的显著程度上要高于下肢。中国现代人群的四肢形态变化规律并不完全符合艾伦法则,可能与遗传、地理环境、功能性需求、生存策略和营养等因素共同影响现代人群的四肢发育密切相关。  相似文献   

6.
Effects of temperature on O2 consumption by mitochondria of the Antarctic fish Trematomus bernacchii were compared with effects obtained with mitochondria from tropical (Sarotheridon mossambica) and temperate zone fishes (Sebastes carnatus and Sebastes mystinus). Arrhenius plots of O2 consumption versus temperature exhibited slope discontinuities (“breaks”) at temperatures (Arrhenius break temperatures: ABTs) reflective of the species' adaptation temperatures. The ABT for mitochondria of T. bernacchii is the lowest reported for any animal and is ∼12 °C below the value predicted by a regression equation based on ABT data for several invertebrates and fishes. The temperature at which the acceptor control ratio (ACR), an index of efficiency of coupling of electron transport to synthesis of ATP, began to decrease with rising temperature also reflected adaptation temperature. The decrease in ACR with rising temperature began at ∼18 °C for mitochondria of T. bernacchii, in contrast to ∼35 °C for mitochondria of Sarotheridon mossambica. Maintaining T. bernacchii at 4 °C for 2 weeks led to no changes in ABT or in the response of ACR to temperature. The thermal sensitivities of mitochondria of T. bernacchii reflect the high level of cold adaptation and stenothermy that is characteristic of Antarctic Notothenioid fishes. Accepted: 5 January 1998  相似文献   

7.
Daily myocardial infarct deaths from Brisbane, 29°28 S, and Montreal, 45°30 N, were used to derive a pool of susceptible individuals. Pool size had no effect on the minimum death temperature but large pools increased the value of the acceleration temperature in Brisbane and the maximum death temperature in Montreal. Moderately sized pools in Montreal appeared to produce reduced death rates in cold conditions from both cold avoidance and habituation. A generalized relationship between temperature and myocardial infarct death is postulated.  相似文献   

8.
人类白细胞抗原(HLA)的检测最初用于器官移植,但近年来,HLA作为免疫遗传基因在与免疫调节有关的疾病中所扮演的重要角色愈来愈受到重视。本就HLA的检测方法以及与某些临床疾病的关系加以论述。  相似文献   

9.
The pulse rates of atmospherics at 10 and 28 kHz have been compared with the variations of outside air temperature up to a height of 7 km. In the 10 kHz band the pulse rate showed a strong statistically significant correlation with air temperature for all heights up to 7 km, the maximum correlation coefficient beingr=0.78 at a level of significanceP0.001. In the 28 kHz band the correlation is weaker: up to a height of 3 km the correlation coefficient ranges from 0.17 to 0.3 (P 0.001 and 0.02, respectively) and above 3 kmr ranges from 0.15 to 0.17 (P 0.02 and 0.05, respectively).As the outdoor absolute humidity depends mainly on the air temperature, it is now clear why previous investigations showed strong correlations between the difference (S) of the atmospherics pulse rates at 10 and 28 kHz, the absolute humidity (AH) outdoors and the diffusion time (T D ) of ions in gelatin films, measured in a fully air-conditioned working-room.  相似文献   

10.
Summary Yellow-bellied marmots characteristically live in montane-mesic environments, but in several areas in western North America, this species extended its range into lowland-xeric habitats. Body mass was significantly smaller in the lowland-xeric population from eastern Washington at 393 m than in the montane-mesic population from western Colorado at 2900 m. Oxygen consumption of marmots from montane-mesic and lowland-xeric environments was signiflcantly affected by ambient temperature (TA) water regimen, population, and a population x water regimen x temperature interaction. Lowland-xeric animals had a higher metabolic rate at low TAs, but a lower metabolic rate at higher TAs than the montane-mesic aminals. Oxygen consumption was lower on a restricted-water regimen than on ad libitum water in both populations. Coefficients relating oxygen consumption to body mass were affected by TA, water regimen, and population. These intraspecific coefficients are larger than the interspecific coefficients for all mammals. Body temperature (TB) was affected significantly by TA, water regimen, and population. TA body mass, and a population x water regimen interaction significantly affected conductance. Conductance generally was higher in the lowland-xeric than in the montane-mesic marmots. Both populations increased conductance at high TA, but the lowland-xeric population dissipated a much higher proportion of the heat by evaporative water loss (EWL) than did the montane-mesic population. Metabolic water production exceeded or equaled EWL at 5–20°C. Smaller body size, reduced metabolism at high TA, and increased EWL at high TA characterized the lowland-xeric population.Metabolic rates of yellow-bellied marmots were higher than predicted from body size during the reproductive season but decreased to 67% of that predicted from the Kleiber curve by late summer. Marmots minimize thermoregulatory costs by concentrating activity at times when the microclimate is favorable, by tolerating hyperthermia at high TA in the field, and by having a conductance lower than that predicted from body size.Abbreviations DHC dry-heat conductance - EHL evaporative heat loss - EWL evaporative water loss - HP heat produced - T A ambient temperature - T n body temperature - M body mass  相似文献   

11.
韩宝瑜  陈宗懋  张钟宁 《生态学报》2001,21(12):2131-2135
触角电位(EAG)研究和选择性行为反应表明茶梢受茶蚜(Toxoptera aurantti Boyer)为害后能释放引诱异色瓢虫LLeis axyridis(Pallas)]的互利素,茶蚜、萝卜蚜Lipaphis erystmi(Kaltenbach)体表和茶蚜蜜露中含有吸引异色瓢虫的利它素,其中的少数特异性组分引诱活性较强.源于茶园、桑园和菜园的互利素或利它素对各自生境中的异色瓢虫更具刺激性,显示了生境特定性.EAG剂量反应表明茶园中的显明变种比显现变种稍敏感,这可能是由于前者触角上的化感器数量较多所致.  相似文献   

12.
BACKGROUND: A picornavirus (Ljunganvirus [LV]) has recently been associated with disease during pregnancy in its natural rodent reservoir and in humans. A study of laboratory mice infected under controlled conditions was therefore undertaken. METHODS: CD-1 female mice were infected gestational day two and subjected to varying regimes of stress. RESULTS: LV infection in combination with stress resulted in uterine resorptions, malformations, and neonatal death. A short delay in time to first pregnancy and births was observed in pairs infected in utero. CONCLUSIONS: LV is found in different species of native animals in both Europe and the United States and human epidemiological evidence connects LV and human reproduction, while the observations here indicate that LV is responsible for reproductive problems in a laboratory mouse model. The current findings suggest that the hypothesis that LV also causes disease in pregnant women and their offspring deserves further study.  相似文献   

13.
微生态制剂在室温存放过程中的活菌数变化规律   总被引:1,自引:0,他引:1  
目的检测自制微生态制剂在室温存放过程中的活菌数变化规律。方法在存放的8个月中,采用平板计数法对存放不同时间的菌群活菌数进行统计。结果活菌数量呈动态变化,经历了增殖、迅速下降、相对稳定、又下降、又稳定的过程。存放10d活菌数高达8.9×10^10/ml,之后活菌数呈下降趋势,30d时降至7.85×10^10/ml:50d时,降至2.14×10^10/ml;保存4个月时,活菌数降为6.1×10^8/ml;8个月时,下降到1.5×10^8/ml。结论本研究对于微生态制剂的实际应用具有重要参考价值。  相似文献   

14.
Coping with cold winter conditions is a major challenge for many insects.In early spring we observed newly emerged Drosophila subobscura, which had overwintered as larvae and pupae. As temperatures increase during spring these flies are faced with higher minimum and maximum temperatures in their natural microhabitat. Thus, there is a potential costly mismatch between winter and early spring acclimatization and the increased ambient temperatures later in adult life.We obtained individuals from a natural Danish population of D. subobscura and acclimated them in the laboratory to 20 °C for one generation, and compared critical thermal maximum (CTmax) and minimum (CTmin) to that of individuals collected directly from their natural microhabitat. The two populations (laboratory and field) were subsequently both held in the laboratory at 20 °C and tested for their CTmax and CTmin every third day for 28 days.At the first day of testing, field acclimatized D. subobscura had both higher heat and cold resistance compared to laboratory flies, and thereby a considerable larger thermal scope. Following transfer to the laboratory, cold and heat resistance of the field flies decreased over time relative to the laboratory flies. Despite the substantial decrease in thermal tolerances the thermal scope remained larger for field acclimatized individuals for the duration of the experiment.We conclude that flies acclimatized to their natural microhabitat had increased cold resistance, without a loss in heat tolerance. Thus while a negative correlation between cold and heat tolerance is typically observed in laboratory studies in Drosophila sp., this was not observed for field acclimatized D. subobscura in this study. We suggest that this is an adaptation to juvenile overwintering in temperate cold environments, where developmental (winter) temperatures can be much lower than temperatures experienced by reproducing adults after emergence (spring). The ability to gain cold tolerance through acclimatization without a parallel loss of heat tolerance affects thermal scope and suggests that high and low thermal tolerance act through mechanisms with different dynamics and reversibility.  相似文献   

15.
D. H. Greer  W. A. Laing 《Planta》1988,174(2):159-165
Recovery of photoinhibition in intact leaves of shade-grown kiwifruit was followed at temperatures between 10° and 35° C. Photoinhibition was initially induced by exposing the leaves for 240 min to a photon flux density (PFD) of 1 500 mol·m-2·s-1 at 20° C. In additional experiments to determine the effect of extent of photoinhibition on recovery, this period of exposure was varied between 90 and 400 min. The kinetics of recovery were followed by chlorophyll fluorescence at 77K. Recovery was rapid at temperatures of 25–35° and slow or negligible below 20° C. The results reinforce those from earlier studies that indicate chilling-sensitive species are particularly susceptible to photoinhibition at low temperatures because of the low rates of recovery. At all temperatures above 15° C, recovery followed pseudo first-order kinetics. The extent of photoinhibition affected the rate constant for recovery which declined in a linear fashion at all temperatures with increased photoinhibition. However, the extent of photoinhibition had little effect on the temperature-dependency of recovery. An analysis of the fluorescence characteristics indicated that a reduction in non-radiative energy dissipation and repair of damaged reaction centres contributed about equally to the apparent recovery though biochemical studies are needed to confirm this. From an interpretation of the kinetics of photoinhibition, we suggest that recovery occurring during photoinhibition is limited by factors different from those that affect post-photoinhibition recovery.Abbreviations and symbols F o, F m, F v instantaneous, maximum, variable fluorescence - K D, K F, K P, K T rate constants for non-radiative energy dissipation, fluorescence, photochemistry, transfer to photosystem I - K(PI), k(R) rate constants for photoinhibition and recovery - PFD photon flux density - PSI, II photosystem I, II - i photon yield of photosynthesis (incident light)  相似文献   

16.
In this study, objective differences between the Cold (Han) and Hot (Re) nature of traditional Chinese medicines, e.g. Strobal and Rhubarb, are determined by using a cold/hot plate differentiation technology. A novel, self-designed cold/hot plate differentiating instrument, with methodological study, was used to investigate the intervention of Strobal and Rhubarb on the temperature tropism of mice. Compared with the ICR and BALB/c mice, it was found that KM mice on the cold/hot plate were more sensitive to the change of temperature, within the tolerant temperature range of 15—40℃. The temperature tropism behavior of mice is influenced by treatment with Rhubarb and Strobal, as is the activity of ATPase in liver tissue. These trends are consistent with the definition of the Cold/Hot nature of Chinese medicines based on traditional Chinese medicinal theory. This study showed that the differences of the Cold/Hot nature of traditional Chinese medicines. might be objectively represented by the temperature tropism of animal by means of cold/hot differentiating assay.  相似文献   

17.
18.
本研究分析近年来上海市境外输入性传染病的病例特点,为上海市输入性传染病的防控提供依据。对上海市某三甲医院2012—2019年报告的所有法定及重点监测传染病中确定为境外感染的305例传染病病例进行回顾性分析。采用WPS Office 2019和 SPSS17.0软件对所收集病例的病种、数量、输入时间、病例人口学特征以及输入地区等进行整理分析。结果显示,2012—2019年该院报告境外输入性传染病11种,分别为疟疾、登革热、肺结核、麻疹、甲型肝炎、戊型肝炎、伤寒、人类免疫缺陷病毒(human immunodeficiency virus,HIV)感染、黄热病、白喉、隐性梅毒。确诊的305例病例中,疟疾226例,占74.10%;登革热68例,占22.30%;其他9种疾病共11例,占3.6%。疟疾、登革热全年均有输入,其中6月、9月和11月为疟疾输入高峰,6~8月为登革热输入高峰,肺结核、麻疹、甲型肝炎、戊型肝炎、伤寒、HIV感染、黄热病、白喉、隐性梅毒无明显季节性分布特征。输入性病例中,中国籍多于外籍,男性多于女性,以青壮年为主;主要职业为商业服务和工人;主要输入地为非洲。本研究结果提示境外输入性传染病以疟疾、登革热等虫媒传染病为主,病种呈现多样化的变化趋势,输入高峰主要在夏秋季。应加强非洲、东南亚劳务和旅游人群的健康教育,做好病例监管和防蚊、灭蚊,减少二代病例。  相似文献   

19.
The two Pseudomonas aeruginosa lectins PA-IL and PA-IIL, which are very similar in subunit size, composition and properties, but differ in carbohydrate specificity, were shown to exhibit opposite temperature profiles in hemagglutination tests. The galactophilic PA-IL, which interacts with the erythrocyte I antigen (together with B or P system antigens), resembles Ii system-specific 'cold hemagglutinins' (including antibodies and lectins of animals and plants) in low (4 degrees C) temperature optimum, while the hemagglutination by the fucose- and mannose-binding PA-IIL (like that of antibodies and lectins which do not bind to these antigens) increases on raising the temperature from 4 to 37 degrees C and even to 42 degrees C. The preferential production of both P. aeruginosa lectins at 28 degrees C and their much stronger interaction with enzyme (protease or sialidase)-damaged cells, as well as the lower temperature optimum (4 degrees C) of PA-IL-binding to the host cells, may be associated with the saprophytic rather than parasitic designation of this bacterium.  相似文献   

20.
The incidence of mortality from myocardial infarction over a 2-year period in Montreal is examined in relation to temperatures and snowfall. Mortality is seen to increase with deviations from seasonally determined thermally neutral conditions, although compared to observations of a parallel study in subtropical Brisbane, death rates are lower with similar falls in temperature. In Montreal, mortality is also seen to increase with snow during the previous day. During anomalous cold spells death frequencies decrease, a phenomenon interpreted as the behavioural thermoregulatory process of cold avoidance.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号