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151.
Karoly Jakab Brook Damon Françoise Marga Octavian Doaga Vladimir Mironov Ioan Kosztin Roger Markwald Gabor Forgacs 《Developmental dynamics》2008,237(9):2438-2449
The Differential Adhesion Hypothesis (DAH) posits that differences in adhesion provide the driving force for morphogenetic processes. A manifestation of differential adhesion is tissue liquidity and a measure for it is tissue surface tension. In terms of this property, DAH correctly predicts global developmental tissue patterns. However, it provides little information on how these patterns arise from the movement and shape changes of cells. We provide strong qualitative and quantitative support for tissue liquidity both in true developmental context and in vitro assays. We follow the movement and characteristic shape changes of individual cells in the course of specific tissue rearrangements leading to liquid-like configurations. Finally, we relate the measurable tissue-liquid properties to molecular entities, whose direct determination under realistic three-dimensional culture conditions is not possible. Our findings confirm the usefulness of tissue liquidity and provide the scientific underpinning for a novel tissue engineering technology. Developmental Dynamics 237:2438-2449, 2008. (c) 2008 Wiley-Liss, Inc. 相似文献
152.
John E. Burnes David C. Kaelber Bruno Taccardi Robert L. Lux Philip R. Ershler Yoram Rudy 《Annals of biomedical engineering》1998,26(1):37-47
Mapping of bioelectric potentials over a given surface (e.g., the torso surface, the scalp) often requires interpolation of potentials into regions of missing data. Existing interpolation methods introduce significant errors when interpolating into large regions of high potential gradients, due mostly to their incompatibility with the properties of the three-dimensional (3D) potential field. In this paper, an interpolation method, inverse-forward (IF) interpolation, was developed to be consistent with Laplace's equation that governs the 3D field in the volume conductor bounded by the mapped surface. This method is evaluated in an experimental heart–torso preparation in the context of electrocardiographic body surface potential mapping. Results demonstrate that IF interpolation is able to recreate major potential features such as a potential minimum and high potential gradients within a large region of missing data. Other commonly used interpolation methods failed to reconstruct major potential features or preserve high potential gradients. An example of IF interpolation with patient data is provided to illustrate its applicability in the actual clinical setting. Application of IF interpolation in the context of noninvasive reconstruction of epicardial potentials (the inverse problem) is also examined. © 1998 Biomedical Engineering Society.
PAC98: 8710+e, 0260Ed 相似文献
153.
Summary The data collected by the authors in four experimental series have been analysed together with data from the literature, to
study the relationship between mean skin temperature and climatic parameters, subject metabolic rate and clothing insulation.
The subjects involved in the various studies were young male subjects, unacclimatized to heat. The range of conditions examined
involved mean skin temperatures between 33‡ C and 38‡ C, air temperatures (Ta) between 23‡ C and 50‡ C, ambient water vapour pressures (Pa) between 1 and 4.8 kPa, air velocities (Va) between 0.2 and 0.9 m · s−1, metabolic rates (M) between 50 and 270 W · m−2, and Clo values between 0.1 and 0.6. In 95% of the data, mean radiant temperature was within ±3‡ C of air temperature. Based
on 190 data averaged over individual values, the following equation was derived by a multiple linear regression technique:
ˉTsk=30.0+0.138Ta+0.254Pa−0.57Va+1.28 · 10−3 M−0.553 Clo. This equation was used to predict mean skin temperature from 629 individual data. The difference between observed
and predicted values was within ±0.6‡ C in 70% of the cases and within ±1‡ C in 90% of the cases. It is concluded that the
proposed formula may be used to predict mean skin temperature with satisfactory accuracy in nude to lightly clad subjects
exposed to warm ambient conditions with no significant radiant heat load. 相似文献
154.
Levente Kaps Ferenc Obl Jr. Mark R. Opp Lars Johannsen James M. Krueger 《Physiology & behavior》1991,50(6):1241-1244
Cholecystokinin (CCK) reduces food intake and promotes non-rapid-eye-movement sleep (NREMS) in rats. The purpose of present experiments was to determine if CCK is somnogenic in rabbits; another species in which CCK suppresses feeding. White New Zealand rabbits were treated intracerebroventricularly (ICV; 0.05, 0.5 and 2 μg) or intraperitoneally (IP; 2.5, 10 and 40 μg/kg) with CCK or saline, and sleep-wake activity and brain temperature (Tbr) were recorded for 6 h. Injections of 10 and 40 μg/kg CCK IP elicited a decrease in wakefulness and an increase in NREMS during the first hour postinjection. The hypnogenic effects were accompanied by a decrease in Tbr. After the IP injection of a lower dose (2.5 μg/kg) a slight, nonsignificant increase in NREMS during the first hour postinjection was followed by a decrease in NREMS. ICV injections of CCK had relatively small inhibitory effects on sleep. We conclude that circulating, hormone CCK might be a hypnogenic signal with a peripheral site of action. 相似文献
155.
The effect of temperature and sex on spatial distribution ofDrosophila melanogaster adults was studied in a specially designed apparatus. It was observed that individuals tend to aggregate in sections of the sphere independently of sex and temperature. Nevertheless, decrease in temperature increase aggregation. The mobility of both males and females indicates a megative geotactic tendency. 相似文献
156.
Hubert Walter Hideo Matsumoto Heidi Danker-Hopfe Kailash C. Malhotra Biswa N. Mukherjee 《Journal of human genetics》1997,42(1):193-203
Summary Serum samples from eight endogamous Indian tribal populations of Madhya Pradesh (Dhurwa, Halba, Bhatra, Muria, Maria) and
Orissa (Deshia Khond, Binjhal, Kisan) with a total of n=731 unrelated individuals were typed for G1M (1,2,3,17), G3M (5,10,11,13,14,15,16,21,26),
and KM (1). In seven of these populations five different GM haplotypes were found:GM*1,17;21,26; GM*1,17;10,11,13,15,16; GM*1,2,17;21,26; GM*1,3;5,10,11,13,14,26; andGM*3;5,10,11,13,14,26. In the Kisan sample the haplotypeGM*1,2,17; 21,26 is absent. The intergroup variability in the distribution of these haplotypes is considerable and statistically highly significant.
The reasons for that can be attributed to the ethnohistory and to the genetic isolation of these eight endogamous tribal populations.
The GM haplotype distribution pattern of all these groups is quite different from that of the non-tribal populations of India,
whereas it is in good agreement with that of the so far tested other tribal populations from India. This can be explained
by different origin and history of the Indian tribal and non-tribal populations. In the KM system, too, remarkable variability
is seen in the distribution of phenotype and allele frequencies among the eight tribal populations under study. 相似文献
157.
Satoshi Takahashi Dawn D. Tooley Levente Kapás Jidong Fang Jerome M. Seyer James M. Krueger 《Pflügers Archiv : European journal of physiology》1995,431(2):155-160
Tumor necrosis factor (TNF) is a cytokine that possesses many biological activities, including enhancement of non-rapid-eye-movement sleep (NREMS). The role of endogenous TNF in the regulation of spontaneous sleep is unknown. If TNF is involved in sleep regulation, then reduction of endogenous TNF should suppress spontaneous sleep. A soluble TNF-binding protein I (TNF-BP I) and a synthetic fragment of TNF-BP I, TNF-R-(159–178), that contains the biologically active region of TNF-BP I, were used. These substances bind TNF and possess TNF-inhibitory activity; their effects on rabbit sleep after intracerebroventricular injection were determined across a 6-h recording period. Two doses of TNF-BP I (0.05 g and 0.5 g) were administered; the higher dose of TNF-BP I significantly decreased NREMS. Four doses of TNF-R-(159–178) (0.25 g, 2.5 g, 25 g and 50 g) were used. The 25 g and 50 g doses significantly suppressed NREMS. The highest dose (50 g) also decreased REM sleep. These results are consistent with the hypothesis that endogenous brain TNF is involved in the regulation of normal sleep. 相似文献
158.
Yoshimitsu Inoue Mikio Nakao Syozo Okudaira Hiroyuki Ueda Tsutomu Araki 《European journal of applied physiology》1995,70(1):6-12
Eight older (60–65 years) and six younger (20–25 years) men were exposed to a standard heat stress for 60 min in summer, autumn, winter, and spring. The test consisted of placing the lower legs and feet in a 42°C water bath while sitting in constant environmental conditions (30°C and 45% relative humidity). The increase of rectal temperature (T
re) was significantly greater (P < 0.05) in autumn, winter, and spring than in summer for the older group, but significantly greater only in winter than in summer for the younger group (P < 0.05). The T
re was greater for the older group in all seasons, but of significance only in autumn and spring (P < 0.01). There were no significant season-related differences for metabolic heat production (m) and mean skin temperature (
sk) during the heat test in the respective groups, although the m and
sk were lower for the older group in all seasons (P < 0.01). In the older group total body sweating rate (msw) divided by T
re (total msw/T
re) decreased from summer to winter (P < 0.02) and did not differ between winter and spring, whereas total msw/T
re in the younger group increased in spring after decreasing from autumn to winter (P < 0.03). The variations of the value, local sweating rate on the back and thigh divided by T
re (back msw/T
re and thigh msw/T
re), were similar to those of the total msw/T
re in each group, except for back msw/T
re in the younger group, which did not increase from winter to spring. The total msw/T
re, back msw/T
re and thigh msw/T
re were significantly less for the older group in summer, autumn and spring (P < 0.05). The range of seasonal variations was significantly less for the older group (P < 0.001). The results indicated that, compared with younger men in older men, the enhancement of sweating function toward summer occurred later and its reduction toward winter occurred earlier despite a smaller range of seasonal variation and that older men had a somewhat lesser capability to maintainT
re when challenged by heat stress in all seasons. 相似文献
159.
The contributions of the autonomic nervous system and the cardiac pacing cells in the development of heat-acclimation-induced bradycardia were analyzed, and the effect of heat acclimation on the chronotropic response of the heart to heat stress (40° C) was studied. Rats were acclimated at 34° C for 0, 5, 14, 30 and 60 days. Heart rate (HR) was measured in conscious animals, using chronic subcutaneous electrodes. Sympathetic and parasympathetic influences were studied by IP administration of 0.1 and 1 mg/100 g body weight atropine and propranolol respectively, while intrinsic HR (HRi) was measured following administration of both drugs simultaneously. The effects of carbamylcholine and norepinephrine on the beating rate of isolated rat atria were investigated to study pacemaker responsiveness to neutrotransmitters. Up to day 14 of heat acclimation, bradycardia was attained by tonic parasympathetic acceleration (18%) and temporal sympathetic withdrawal (0.8% on day 14), to compensate for the gradually augmented HRi (2.5% and 8% on days 5 and 14, respectively). Following long-term acclimation HRi declined below pre-acclimation rate. This was associated with resumed sympathetic activity (16% and 10% on days 30 and 60 respectively) while parasympathetic activity continued to be high (18%). Tachycardia, known to occur with severe uncontrolled body hyperthermia, was attenuated following heat acclimation by 42%. It was concluded that during the initial phase of heat acclimation bradycardia is achieved primarily by changes in autonomic influences, while following long-term acclimation, changes in the intrinsic properties of the pacing cells (HRi) and the autonomic system both play a role. 相似文献
160.
Frantiek Moravec Isaure de Buron Tiffany G. Baker David González-Solís 《Acta parasitologica / Witold Stefański Institute of Parasitology, Warszawa, Poland》2008,53(4):382-391
Three gonad-infecting species of Philometra Costa, 1845 were, for the first time, recorded from perciform fishes from estuarine and marine waters in South Carolina and
Georgia, USA: Philometra charlestonensis sp. nov. from the scamp Mycteroperca phenax (Jordan et Swain) (Serranidae), P. saltatrix Ramachandran, 1973 from the bluefish Pomatomus saltatrix (Linnaeus) (Pomatomidae), and Philometra sp. from the Atlantic croaker Micropogonias undulatus (Linnaeus) (Sciaenidae). The new species is characterized mainly by males (body length 2.65–3.14 mm) with equally long, needle-like
spicules (length 132–141 μm) and the gubernaculum (81–93 μm) bearing dorsal transverse lamella-like structures on its distal
portion, the body length of gravid females (168–247 mm), the presence of a well-developed anterior bulbous inflation on the
female oesophagus, and by the length of the first-stage larvae (544–597 μm). A key to gonad-infecting species of Philometra parasitizing marine and brackish-water fishes is provided. 相似文献