Effect of ambient temperature on learning

After a three week exposure at 34, 25 or 10°C, three strains of mice (C57BL/6, BALB/c and A/J) underwent a conventional active two-way avoidance task. As compared to 25°C of ambient temperature, acquisition on the first day was severely impaired in the three strains at 34°C and in the C57BL/6, and A/J mice at 10°C. Learning scores on the second day were diminished in the C57BL/6 strain at 34°C and 10°C and in the BALB/c strain at 34°C. The mechanisms of such an impairment in learning at high or low temperature are discussed.     

基于形态学的均值平移算法的神经元干细胞图像的自动分割

在神经元干细胞的图像分析中,准确快速的图像分割是干细胞分化增值自动追踪系统的基础。为了准确地分割低对比度的灰度神经元干细胞图像,本研究提出一种基于形态学运算和均值平移算法的神经元干细胞分割方法,称其为形态学的均值平移算法。此算法可以快速地获得任意形状细胞的图像,并且能检测到图像中多连接边缘不封闭的细胞。将此方法应用于神经元干细胞序列图像分割中并且将其与门限分割、水线分割和活动轮廓进行对比。实验结果证明,与其它的方法相比,此方法获得的细胞分割形状更接近于真实细胞的形状,并且能获得或接近于原始图像中准确的独立细胞数目。此方法可以获得正确的分割结果,为进一步图像处理奠定了良好的基础。     

Different thermal conditions of the extremities affect thermoregulation in clothed man

The effects of different types of clothing on human deep body temperature were studied with six healthy male subjects in a supine posture. Two clothing ensembles were employed for the present study: A covered the whole body area with garments except the face (1.97 clo) and B covered only the trunk and the upper half of the extremities with garments (1.53 clo). The experiment was carried out in a climatic chamber at 55% ± 5% relative humidity under cooling and warming temperatures: the temperature was changed from 22°C to 10°C (cooling) and returned to 22°C again (warming). The major findings were: rectal temperature (T _re) continued to decrease gradually in A throughout the experiment, whereas in B it increased during cooling, and returned to previous levels during warming. As a result, Tre and chest skin temperature were maintained at a higher level in B than in A. Internal tissue conductances were greater in A than in B both during cooling and during warming. Thermal comfort appeared to have been influenced more by the rate of skin temperature change than by the level of skin temperature per se. It was concluded that peripheral vasoconstriction in B induced less heat flow from core to shell, and, thus, the core temperature was maintained at a higher level in B than in A.     

Physiological responses and manual performance in humans following repeated exposure to severe cold at night

We evaluated human physiological responses and the performance of manual tasks during exposure to severe cold (–25°C) at night (0300–0500 hours) and in the afternoon (1500–1700 hours). Thirteen male students wearing standard cold protective clothing occupied a severely cold room (–25°C) for 20 min, and were then transferred to a cool room (10°C) for 20 min. This pattern of exposure was repeated three times, for a total time of exposure to extreme cold of 60 min. The experiments were started either at 1500 hours or 0300 hours and measurements of rectal temperature, skin temperature, blood pressure, performance in a counting task, hand tremor, and subjective responses were made in each condition. At the end of the experiment at night the mean decrease in rectal temperature [0.68 (SEM 0.04)°C] was significantly greater than that at the end of the experiment in the afternoon [0.55 (SEM 0.08)°C, P<0.01]. After the second cold exposure at night the mean increase in diastolic blood pressure [90 (SEM 2.0) mmHg] was significantly greater than that at the end of the second cold exposure in the afternoon [82 (SEM 2.8) mmHg, P<0.01]. At the end of the second cold exposure at night, mean finger skin temperature [11.8 (SEM 0.8)°C] was significantly higher than that at the comparable time in the afternoon [9.0 (SEM 0.7)°C, P<0.01]. Similarly for the toe, mean skin temperature at the start of the second cold exposure at night [25.6 (SEM 1.5)°C] was significantly higher than in the afternoon [20.1 (SEM 0.8)°C, P<0.01]. The increased skin temperatures in the periphery resulted in increased heat loss. Since peripheral skin temperatures were highest at night, the subjects noted diminished sensations of thermal cold and pain at that time. Manual dexterity at the end of the first cold exposure at night [mean 83.7 (SEM 3.6) times·min^–1] had decreased significantly more than at the end of the first cold exposure in the afternoon [mean 89.4 (SEM 3.5) times·min^–1, P<0.01]. These findings of a lowered rectal temperature and diminished manual dexterity suggest that there is an increased risk of both hypothermia and accidents for those who work at night. Electronic Publication     

Hand and finger skin temperatures in convective and contact cold exposure

The present study aimed at investigating the spatial variability of skin temperature (T _sk) measured at various points on the hand during convective and cold contact exposure. A group of 8 subjects participated in a study of convective cooling of the hand (60 min) and 20 subjects to contact cooling of the finger pad (5 min). Experiments were carried out in a small climatic chamber into which the hand was inserted. For convective cold exposure,T _sk was measured at seven points on the palmar surface of the fingers of the left hand, one on the palmar surface and one on the dorsal surface of the hand. The air temperature inside the mini-chamber was 0, 4, 10 and 16°C. With the contact cold exposure, the subjects touched at constant pressures an aluminium cube cooled to temperatures of –7, 0 and 7°C in the same mini-chamber. ContactT _sk was measured on the finger pad of the index finger of the left hand. TheT _sk of the proximal phalanx of the index finger (on both palm and back sides), and of the middle phalanx of the little finger was also measured. The variation ofT _sk between the proximal and the distal phalanx of the index finger was between 1.5 to 10°C during the convective cold exposure to an air temperature of 0°C. Considerable gradients persisted between the hand and fingers (from 2 to 17°C at 0°C air temperature) and between the phalanges of the finger (from 0.5 to 11.4°C at 0°C air temperature). The onset of cold induced vasodilatation (CIVD) on different fingers varied from about 5 to 15 min and it did not always appear in every finger. For contact cold exposure, whenT _sk on the contact skin cooled down to nearly 0°C, the temperature at the area close to the contact skin could still be 30°C. Some cases of CIVD were observed in the contact skin area, but not on other measuring points of the same finger. These results indicated that local thermal stimuli were the main determinents of CIVD. Representative hand skin temperature may require five or more measuring points. Our results strongly emphasised a need to consider the large spatial and individual variations in the prediction and modelling of extremity cooling.     

Recruitment of fibre types and quadriceps muscle portions during repeated, intense knee-extensor exercise in humans

To investigate recruitment of slow-twitch (ST) and fast-twitch (FT) muscle fibres, as well as the involvement of the various quadriceps femoris muscle portions during repeated, intense, one-legged knee-extensor exercise, 12 healthy male subjects performed two 3-min exercise bouts at ~110% maximum thigh O₂ consumption (EX1 and EX2) separated by 6 min rest. Single-fibre metabolites were determined in successive muscle biopsies obtained from the vastus lateralis muscle (n=6) and intra-muscular temperatures were continuously measured at six quadriceps muscle sites (n=6). Creatine phosphate (CP) had decreased (P<0.05) by 27, 73 and 88% in ST fibres and 25, 71 and 89% in FT fibres after 15 and 180 s of EX1 and after 180 s of EX2, respectively. CP was below resting mean–1 SD in 15, 46, 84 and 100% of the ST fibres and 9, 48, 85 and 100% of the FT fibres at rest, after 15 and 180 s of EX1 and after 180 s of EX2, respectively. A significant muscle temperature increase (T_m) occurred within 2–4 s at all quadriceps muscle sites. T_m varied less than 10% between sites during EX1, but was 23% higher (P<0.05) in the vastus lateralis than in the rectus femoris muscle during EX2. T_m in the vastus lateralis was 101 and 109% of the mean quadriceps value during EX1 and EX2, respectively. We conclude that both fibre types and all quadriceps muscle portions are recruited at the onset of intense knee-extensor exercise, that essentially all quadriceps muscle fibres are activated during repeated intense exercise and that metabolic measurements in the vastus lateralis muscle provide a good indication of the whole-quadriceps muscle metabolism during repeated, intense, one-legged knee-extensor exercise.     

Brain mapping analysis in patients with hepatic encephalopathy

Summary Topographical analysis of cerebral electrical activity was performed in 44 patients with hepatic encephalopathy. These patients were classified in 5 groups according to clinical criteria. Eight healthy subjects were used as a control group. All were studied in an awake, eyes closed, condition and some [Control Group (CG), Group 0 (G0), Group 1 (G1) and Group 2 (G2)] also in an awake, eyes open, condition. The awake, eyes closed, maps showed marked differences in the power spectral density (PSD) of the different bands, when comparing normal subjects with patients with several degrees of hepatic encephalopathy. These differences were related to the degree of clinical involvement, mainly in the alpha and delta PSD bands. The combination of a decreased alpha PSD, increased delta PSD, and decreased mean dominant frequency (MDF) allowed a clear discrimination between the different clinical groups. The differences observed between awake, eyes closed, and awake, eyes open, conditions were especially helpful to discriminate between CG subjects and G0, G1 and G2 patients.     

人体体温下UHMWPE人工髋臼材料压缩性能的试验研究

模拟人体体温下对超高分子量聚乙烯（UHMWPE）人工髋臼材料进行了压缩力学性能的试验研究,并与室温下的试验结果进行了对比.当由室温22℃升高到体温37℃和40℃时,其屈服应力呈明显的下降趋势,分别下降了23.1%和31.9%,由体温37℃升高到40℃时,二者仅差3℃,其屈服应力亦下降了11.5%.同时还对不同加载速度下UHMWPE试件压缩变形过程进行了红外辐射温度的监测与分析.不同加载速度下试件压缩变形过程中的红外辐射温度均有明显升高,加载时间越长,试件平均红外辐射温度越高.试验结果分析表明,不能忽视植入人体后UHMWPE人工髋臼局部受压时温度的升高,特别不能忽视植入人体后在人体体温作用下其力学性能的改变和下降,人体体温的作用是UHMWPE人工髋臼出现过早失效的原因之一.本试验研究为UHMWPE材料在人体环境中的应用研究提供了参考.     

Periovulatory increase in temperature difference within the rabbit oviduct

BACKGROUND: Earlier studies demonstrated a small temperature difference between the sperm storage and fertilization sites within the oviducts of rabbits and pigs. Our aim was to reveal the time dependence of this temperature difference relative to ovulation, and to determine how this difference is generated-by temperature elevation at one of these sites or by temperature decrease at the other site. METHODS: The temperature at the sperm storage site (at the isthmus near the uterotubal junction) and at the fertilization site (the isthmic-ampullary junction) of rabbit oviducts were measured before, during, and after ovulation by two probes, connected to digital thermometers. Rectal temperature was constantly measured and served as a control for body temperature. RESULTS: The temperature difference between the fertilization site and the storage site was 0.8+/-0.2 degrees C before ovulation. This difference increased at ovulation, reaching 1.6+/-0.1 degrees C after ovulation (P<0.03). This increased difference was mainly due to temperature decrease in the sperm storage site. CONCLUSION: The temperature-difference increase within the rabbit oviduct is generated at ovulation by a reduced temperature at the sperm storage site. This temperature gradient may play a role in mammalian reproduction via sperm thermotaxis.     

Local thermal unpleasantness and discomfort prediction in the vicinity of thermoneutrality

This work emphasizes a better understanding of the origin of human thermal discomfort under heterogeneous but steady environments, in subjects in the vicinity of physiological and sensory thermoneutrality. The knowledge of skin temperatures allows a psychophysiological study aiming at linking the body thermal state (local and global) to thermal sensation (perceptive and affective judgements). By using two driving simulators, 345 subjects were exposed to different thermal environments, modulated by factors such as the air distribution in the automotive cockpit or the clothing insulation (winter or summer). This work shows that consideration of the local thermal state is essential for the evaluation of thermal comfort in the case of non-uniform environments. Our experimental conditions point out that the overall sensation of discomfort is quantitative, with local unpleasantness needing to be felt for a certain number of body surfaces. A local origin is suggested for cold discomfort, in opposition to the global characteristics of warm discomfort.