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1.
The purpose of this experiment was to determine if tolerance to exercise in the heat is related to maximal oxygen uptake (max 02) and sweating. Seven men with max 02 between 42 and 66 ml/(min·kg) underwent one 2-hr exposure at 24°C Tq while working on a bicycle ergometer at rel 02 of 28% ( 02 = 1.23 1/min). In the hot exposures the high capacity subjects had maximal sweat rates of 800 to 1,000 g/(hr·m2) while the lower capacity men sweated 300 to 400 g/(hr·m2). These differences in sweating were not related to neuromuscular stimuli, 02 (metabolic rate), Tre, Tre, s, s or tolerance time. Tolerance to exercise in the heat was not related to maximal 02 capacity when the subjects worked at the same relative load in spite of large differences in sweating. These results question the importance of the rate of sweating for predicting work performance in hot environments.
Zusammenfassung Das Ziel dieser Untersuchung war, zu prüfen, ob die Toleranz bei Arbeit in der Hitze in einer Beziehung steht zur maximalen O2-Aufnahme und Schwitzen. Sieben Männer mit V02 zwischen 42 – 66 ml/(min·kg) wurden belastet während 2 Stunden bei Ta 24°C und 3 × 2 Stunden bei 47°C mit Arbeit auf dem Fahrrad-Ergometer bei im Mittel von 28% V02 = 1.23 1/min. Während der Hitzebelastung zeigten die leistungsfähigen Personen Schweissekretionsraten von 800 – 1000 g/(hr·m2) und die wenig leistungsfähigen 300 – 400 g/(hr·m2). Diese Unterschiede waren ohne Beziehung zu neuromuskulären Stimuli, Stoffwechselrate, Tre, Tre, s, s oder der Toleranzzeit. Ausdauer bei Arbeit in der Hitze war ohne Beziehung zur maximalen V02-Kapazität, wenn die Personen bei der gleichen relativen Belastung arbeiteten tro grosser Unterschiede im Schwitzen. Die Ergebnisse stellen den Wert der Schweissekretionsrate zur Voraussage der Arbeitsleistung in der Hitze in Frage.

Resume Dans cette étude, on a cherché à voir si la tolérance au travail sous contrainte de chaleur était en relation avec la possibilité maximum d'absorption de O2 ( 02) d'une part, de transpirer d'autre part. 7 hommes présentant des 02 compris entre 42 et 66 ml/(min · kg) ont pédalé sur un ergomètre pendant 2 heures par une Ta de 24°C et 3 × 2 heures par 47°C et cela par une 02 relative de 28% ( 02 = 1,25 1/min). Durant l'effort sous contrainte de chaleur, les plus actifs ont eu des sécrétions de sueur de 800 à 1.000 g h–1 m–2 et les moins actifs de 300 à 400 g/h · m2. Ces différences étaient sans rapport avec les stimulus neuro-musculaires, le taux de métabolisme, Tre, Tre, Ts et Ts ou la durée de tolérance. L'endurance au travail sous contrainte de chaleur n'a pas été fonction de la capacité maximum de 02, lorsque les personnes travaillaient dans des conditions analogues, même si l'on a noté de grandes différences dans la transpiration. Ces résultats mettent en doute la représentativité du taux de sécrétion de sueur comme indicatif des possibilités de travailler en atmosphère chaude.
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2.
Rectal (Tre), mean skin temperature ( sk) and sweating rate ( ) were measured in 4 residents of temperate climate under acute moderate heat exposure (designated EE in such an experimental situation), after 3 weeks in India (designated as EI) and in 8 Indian residents (designated as II) both at rest and during submaximal exercises at 2 different intensities. At rest, Tre is higher in EI (37.6°C) than in EE (36.8°C, P<0.01) and reaches 37.8°C in II. At the end of exercise, the increment in Tre seems to depend on work load only and to be independent of thermal environment; S follows a similar pattern in the 3 groups of subjects: sk is altered neither by exercise nor acclimatization. Under chronic heat exposure compared to acute conditions: (1) identical is achieved with higher Tre and similar sk so that the linear relationships vs Tre is shifted to the right. (2) the Tresk difference is greater at rest and during exercise: hence, skin blood flow, calculated from heat balance equation diminishes. In hot climate, a rise in Tre seems to be an adaptive response which allows the body to reduce skin blood flow.  相似文献   

3.
In separate experiments dogs and men were exposed to various combinations of dry-bulb (DB) and wet-bulb (WB) temperatures (DB 37.8 to 54.4°C, WB 23.9 to 47.2°C). Rectal temperature (Tr), tolerance time (TT) and incidence of tetany were noted. In some experiments total plasma catecholamines and blood(venous or arterial) pH and were also measured. Dogs were removed from the heat when Tr reached 42.0°C and men were removed when Tr reached 39.2°C or for other reasons.Dog and man, when exposed to particular environmental conditions, hyperventilate to the extent that, in man blood CO2 and pH approximate 20 mm Hg and 7.6 respectively and, in the dog 10 mm Hg and 7.7 respectively. When the heat load is very high,both dog and man hyperventilate earlier and the changes in blood pH and CO2 are more rapid. However, whereas man experiences intense carpopedal spasm, the dog does not, even though the changes in pH and CO2 are greater in the dog. There was no significant change in plasma catecholamines during heat stress.
Zusammenfassung In verschiedenen Experimenten wurden Hunde und junge Männer Hitze von verschiedener Trocken- und Feuchttemperatur (TT 37, 8-54, 4°C, FT 23,9-47, 2°C) exponiert und die Rektaltemperatur (Tr),Toleranzzeit (TT) und Tetaniehäufigkeit gemessen. In einigen Experimenten wurden zusätzlich die PlasmaKatecholamine, Blut pH und (arteriell und venös) bestimmt.Die Exponierung wurde unterbrochen,wenn bei Hunden die Tr 42,0°C und bei Männern 39,2°C erreicht hatte. Hunde und Männer hyperventilieren unter den Hitzebedingungen in solchem Ausmass, dass sich beim Hund Blut 10 mm Hg und pH 7,7 nähern, beim Mann 20 mm Hg und pH 7,6.Bei sehr starker Hitzebelastung erfolgt bei beiden die Hyperventilation früher und die Blut-Veränderungen erscheinen früher.Beim Menschen tritt ausserdem Carpopedalspasmus auf,nicht beim Hund, obwohl die Blut pH und CO2 Veränderungen extremer sind.Die Plasmakatecholamine waren während der Hitzebelastung nicht signifikant verändert.

Resume On a exposé séparément des chiens et des êtres humains à différentes combinaisons de températures sèche (TS) et du thermomètre mouillé (TM) (TS de 37,8 à 54,4°C, TM de 23,9 à 47,2°C). On a noté dans chaque cas la température rectale(Tr) et le temps de tolérance (TT) ainsi que l'incidence des conditions ambiantes sur la tétanie. Dans quelques cas, on a en outre déterminé la catécholamine plasmatique totale ainsi que le pH et la du sang aussi bien artériel que veineux.On a interrompu l'expérience lorsque Tr a atteint 42,0°C chez le chien et 39,2°C chez l'homme. La respirations augmente sous l'effet de la chaleur et cela aussi bien chez le chien que chez l'homme si bien que, pour le premier, atteint 10 mm Hg et pH 7,7,respectivement 20 mm Hg et 7,6 pour le second. Si la charge due à la chaleur est très élevée, l'augmentation de la vitesse de respiration et les modifications sanguines se manifestent plus rapidement. On constate en outre chez l'homme des spasmes carpopédaliques, ce qui ne se produit pas chez le chien bien que les modifications du pH et du CO2 soient plus marquées dans le second cas que dans le premier. On discute enfin les répercussions futures de ces résultats ainsi que d'autres.


Paper presented at the Fourth International Biometeorological Congress, New Brunswick, N.J., 26 August – 2 September 1966.  相似文献   

4.
Thermoregulatory responses to exercise in relation to the phase of the menstrual cycle were studied in ten women taking oral contraceptives (P) and in ten women not taking oral contraceptives (NP). Each subject was tested for maximal aerobic capacity ( ) and for 50% exercise in the follicular (F) and luteal (L) phases of the menstrual cycle. Since the oral contraceptives would have prevented ovulation a quasi-follicular phase (q-F) and a quasi-luteal phase (q-L) of the menstrual cycle were assumed for P subjects. Exercise was performed on a cycle ergometer at an ambient temperature of 24° C and relative air humidity of 50%. Rectal (T re), mean skin ( ), mean body ( ) temperatures and heart rate (f c) were measured. Sweat rate was estimated by the continuous measurement of relative humidity of air in a ventilated capsule placed on the chest, converted to absolute pressure (PH2Ochest). Gain for sweating was calculated as a ratio of increase inPH2Ochest to the appropriate increase inT re for the whole period of sweating (G) and for unsteady-state (Gu) separately. The did not differ either between the groups of subjects or between the phases of the menstrual cycle. In P, rectal temperature threshold for sweating (T re, td) was 37.85° C in q-L and 37.60° C in q-F (P < 0.01) and corresponded to a significant difference fromT re at rest. TheT re, andf c increased similarly during exercise in q-F and q-L. No menstrual phase-related differences were observed either in the dynamics of sweating or in G. In NP,T re, td was shorter in L than in F (37.70 vs 37.47° C,P<0.02) with a significantly greater value fromT re at rest. The dynamics and G for sweating were also greater in L than in F. The Gu was 36.8 versus 16.6 kPa · ° C–1 (P<0.01) while G was 6.4 versus 3.8 kPa · ° C–1 (P<0.05), respectively. TheT re, andf c increased significantly more in phase F than in phase L. It was concluded that in these women performing moderate exercise, there was a greater temperature threshold and larger gains for sweating in phase L than in phase F. Intake of oral contraceptives reduced the differences in the gains for sweating making the thermoregulatory responses to exercise more uniform.  相似文献   

5.
Summary D. melanogaster males of bb/O genetic constitution undergoing rDNA magnification were mated singly to XXbb +/O females, yielding bb/O male progeny, and to XNO-w sn bb + fameles, yielding bb/XNO- females. The male and female offspring were scored for the bb + phenotype.Results show that there is a higher percentage of bb + flies in the bb/O male progeny than in bb/XNO- females progeny, in single crosses as well as in the combined data. rRNA/DNA hybridization experiments agree with this observation, by showing that the rDNA content in the progeny of premagnified flies was higher in the sons than in the daughters.These data indicate that the increase of ribosomal RNA genes is not due to a stable event such as an unequal mitotic sister exchange, whereas they do not contrast with the extracopy model.  相似文献   

6.
A study was conducted on 30 healthy soldiers (age: 40–46 years) to assess the effect of selected yogic exercises (asanas) on some physiological responses to cold exposure. They were randomly divided into two groups of 15 each. One group performed regular physical exercises of physical training (PT), while the other group practised yogic exercises. At the end of 6 months of training, both the groups were exposed together to cold stress at 10°C for 2 h, and the following parameters were periodically monitored during cold exposure: heart rate (fH), blood pressure (BP), cardiac output , oral temperature (Tor), skin temperature (T sk), respiratory rate (fR), minute ventilation , oxygen consumption , and shivering response by integrated electromyogram (EMG). There were progressive increases inBP, fR, , , and and decreases infH,T or andT sk during cold exposure in both the groups. However, the decrease inT or and the increases in and were relatively lower (P<0.01) in the yoga group as compared to the PT group. The shivering response appeared much earlier and was more intense in the PT group. These findings suggest that practice of yoga exercises may improve cold tolerance.  相似文献   

7.
Based on the hypothesis that the relation between sweating rate and body temperature should be different during exercise and rest after exercise, we compared the sweating response during exercise and recovery at a similar body temperature. Healthy male subjects performed submaximal exercise (Experiment 1) and maximal exercise (Experiment 2) in a room at 27° C and 35% relative humidity. During exercise and recovery of 20 min after exercise, esophageal temperature (Tes), mean skin temperature, mean body temperature ( ), chest sweating rate ( ), and the frequency of sweat expulsion (F SW) were measured. In both experiments, andF SW were clearly higher during exercise than recovery at a similar body temperature (Tes, ). was similar during exercise and recovery, or a little less during the former, at a similarF SW. It is concluded that the sweating rate during exercise is greater than that during recovery at the same body temperature, due to greater central sudomotor activity during exercise. The difference between the two values is thought to be related to non-thermal factors and the rate of change in mean skin temperature.  相似文献   

8.
Physiological and metabolic output responses to facial cooling during a graded maximal exercise and a prolonged submaximal exercise lasting 30 min at 65% max were investigated in five male subjects. Pedalling on a cycle ergometer was performed both with and without facial cooling (10°C, 4.6 m s–1). Facial cooling at the end of graded maximal exercise apparently had no effect on plasma lactate (LA), maximal oxygen consumption ( max), maximal heart rate (HR max), rectal temperature (T re), work-load, lactate threshold (LT), ventilatory threshold (VT) and onset of blood lactate accumulation (OBLA). However, the response to facial cooling after prolonged submaximal exercise is significantly different for heart rate and work-load. The results suggest that facial wind stimulation during maximal exercise does not produce a stress high enough to alter the metabolic and physiological responses.  相似文献   

9.
The hand blood flow ( ) was investigated in response to a wide range of general and local cutaneous thermal stimuli (0–36°C and 4–42°C respectively), the local stimulus consisting of a thermostatically controlled water bath for the right hand (Tw), and the general stimulus, the ambient room temperature (Ta). was measured at the right wrist by strain gauge plethysmography; it was seen to respond more significantly to variations in Tw than to those in Ta at cold to comfortable ambient temperatures (Ta<22°C). A paradoxical vasodilatation was observed at Tw=4°C (Lewis' hunting phenomenon). The graphs of versus T at average to high local cutaneous temperatures (Tw > 33°C) are remarkably similar, except for an upward shift at successively higher values of Tw. The slope (or vasomotor reactivity) is interpreted as being controlled by variations in Ta. The curves exhibited maximum values at Ta = 31°C. Their subsequent decrease could represent a thermoregulatory adaptation to environment-organism heat transfer, the relative vasoconstriction tending to reduce the transfer. Although the qualitative response was the same for both sexes, the absolute value of was generally greater in male than in female subjects.  相似文献   

10.
Summary Seedlings of paper birch (Betula papyrifera Marsh.), green ash (Fraxinus pennsylvanica Marsh.), and red pine (Pinus resinosa Ait.) fumigated with 0.2 ppm SO2 for 30 h at 30° C had higher leaf diffusive conductances (LDC) and absorbed more sulfur than seedlings fumigated at 12° C. Comparisons among the three species fumigated at the same temperature, however, do not support the view that a plant with higher LDC should absorb more SO2 than a plant with lower LDC. Mean relative growth rates ( ) of seedlings grown at 21° C after fumigation were variously affected by SO2. of green ash was not inhibited by SO2, but of roots of red pine seedlings was reduced by SO2, with greater inhibition in seedlings fumigated at 30° C. Root and shoot of paper birch seedlings were lowered by SO2, and effects of SO2 were about equal at both exposure temperatures. The data indicate that temperature can affect mechanisms of SO2 avoidance, tolerance, or both to various degrees in different species. Thus generalizations on the influence of exposure temperature on resistance of plants to SO2 may be inappropriate.Research supported by the College of Agricultural and Life Sciences, University of Wisconsin-Madison.  相似文献   

11.
Summary Adelie penguins (Pygoscelis adeliae) experience a wide range of ambient temperatures (T a) in their natural habitat. We examined body temperature (T b), oxygen consumption ( ), carbon dioxide production ( ), evaporative water loss ( ), and ventilation atT a from –20 to 30 °C. Body temperature did not change significantly between –20 and 20°C (meanT b=39.3°C).T b increased slightly to 40.1 °C atT a=30°C. Both and were constant and minimal atT a between –10 and 20°C, with only minor increases at –20 and 30°C. The minimal of adult penguins (mean mass 4.007 kg) was 0.0112 ml/[g·min], equivalent to a metabolic heat production (MHP) of 14.9 Watt. The respiratory exchange ratio was approximately 0.7 at allT a. Values of were low at lowT a, but increased to 0.21 g/min at 30°C, equivalent to 0.3% of body mass/h. Dry conductance increased 3.5-fold between –20 and 30°C. Evaporative heat loss (EHL) comprised about 5% of MHP at lowT a, rising to 47% of MHP atT a=30°C. The means of ventilation parameters (tidal volume [VT], respiration frequency [f], minute volume [I], and oxygen extraction [ ]) were fairly stable between –20 and 10°C (VT did not change significantly over the entireT a range). However, there was considerable inter- and intra-individual variation in ventilation patterns. AtT a=20–30°C,f increased 7-fold over the minimal value of 7.6 breaths/min, and I showed a similar change. fell from 28–35% at lowT a to 6% atT a=30°C.Abbreviations C thermal conductance - EHL evaporative heat loss - oxygen extraction - f respiratory frequency - MHP metabolic heat production - evaporative water loss - LCT lower critical temperature - RE respiratory exchange ratio - T a ambient temperature - T b body temperature - rate of oxygen consumption - rate of carbon dioxide production - I inspiratory minute volume - VT tidal volume  相似文献   

12.
Summary The effects of ambient temperature (T a) on ventilation and gas exchange in chukar partridges (Alectoris chukar) were determined after acclimation to low and high altitute (LA and HA; 340 and 3,800 m, respectively).At both LA and HA, oxygen consumption ( ) increased with decreasingT a atT a from 20 to –20°C. AtT a of 35 to 40°C, increased above thermoneutral values at HA but remained constant and minimal at LA. Water loss rates increased rapidly atT a>30°C at both altitudes as birds began to pant. Ventilation rates (f) during panting were 5-to 23-fold greater than the minimalf at thermoneutralT a.Increased atT a below thermoneutrality was supported by increased minute volume (V i) at both altitudes. The change inV i was primarily a function of changing tidal volume (V t), althoughf increased slightly asT a declined. Oxygen extraction ( ) remained fairly constant atT a below 20°C at both altitudes. BothV t and were considerably lower when birds were panting than at lowerT a.Chukars showed few obvious ventilatory adaptations to HA. The 35% change in between 340 and 3,800 m was accommodated by a corresponding change inV i (btps), most of which was accomplished by increasedf at HA, along with a slight increase in .Abbreviations and symbols HA high altitude - LA low altitude - rate of evaporative water loss - oxygen extraction efficiency - f respiratory frequency - V t tidal volume - V i minute volume - BMR basal metabolic rate - MHP metabolic heat production  相似文献   

13.
Summary The resting membrane potential data existing in the literature for the giant axon of the squid, frog muscle and barnacle muscle have been analyzed from the standpoint of the theory of membrane potential due to Kobatake and co-workers. The average values derived for the effective charge density (where is a constant, , and represents the fraction of counterions that are free, and is the stoichiometric charge density in the membrane) present on the different biomembranes existing in their normal ionic environment are 0.3, 0.325 and 0.17 M for the squid axon, frog and barnacle muscles, respectively. On the assumption that the values of are 0.4 and 0.2 for nerve and muscle membranes, respectively, values of 0.75, 1.62 and 0.85 M have been derived for the stoichiometric charge density present in the respective biological membranes. These correspond to 1 negative charge per 222, 103 and 195 Å of the membrane area of the squid axon, frog and barnacle muscles, respectively.  相似文献   

14.
The aim of this study was to evaluate the thermoregulatory changes induced by 27-h of sleep deprivation (SD) in men at rest both in a comfortable ambient temperature and in cold air. A group of 12 male subjects were placed in a comfortable ambient temperature (dry bulb temperature,T db = 25° C, relative humidity, rh = 40%–50% , clothing insulation = 1 clo) for 1 h and then they were submitted to a standard cold air test in a climatic chamber for 2h (T db=1° C, rh = 40%–50%, wind speed = 0.8 m·s–1, nude), before and after 27 h of sleep deprivation. Thermoregulatory changes (rectal temperature,T re; mean skin temperature, sk; metabolic heat production ) were monitored continuously. At comfortable ambient temperature, no significant change was observed after SD forT re, sk and . During the cold test,T re did not change but sk and were higher after SD (P<0.05). Increased (+ 6%,P < 0.05) was related to earlier and higher shivering, with a possible increase in the sensitivity of the thermoregulatory system as shown by the shorter time to onset of continous shivering (d): 8.66 (SEM 1.33) min versus 28.20 (SEM 1.33) min (P < 0.001) and by a higher sk observed at d: 27.60 (SEM 1.40)° C versus 21.40 (SEM 0.60)° C (P < 0.001). These results were associated with higher cold sensations and shivering following SD. They also suggested that SD modified thermoregulatory responses at a central level especially in a cold environment.  相似文献   

15.
To examine cardiopulmonary function during exercise in a mountainous region at moderate altitude, we measured cardiac frequency, oxygen consumption , and percentage arterial hemoglobin oxygen saturation (%SaO2) before and after a bicycle race with a starting point at 638 m and finishing point at 1980 m. The time required to ascend an elevation of 10 m was prolonged with increasing altitude, and heart rate also increased with altitude. The %SaO2 at the starting point and at the finishing point differed significantly (P<0.01). Faster cyclists exhibited higher %SaO2 and lower , while slower cyclists exhibited a reduction in %SaO2 and an increase in immediately after the race. The %SaO2 recovery time was significantly correlated with the racing time (r=0.54,P<0.001). Therefore, the faster cyclists' oxygen debt upon completion of the race may be small and recovery of cardiopulmonary function may be fast, while the slower cyclists' oxygen debt may be large and recovery of cardiopulmonary function may be slow.  相似文献   

16.
Zusammenfassung Durch simultane visuelle Bewegungsreize, die von mehreren Beutetieren (z.B. Mehlkäferlarven) ausgehen, wird der Beutefang der Erdkröte (Bufo bufo L.) gehemmt. An diese Verhaltensheobaehtung anknüpfend, wurde die Abhängigkeit dieses inhibitorischen Umfeldeffektes von verschiedenen visuellen Reizparametern im Attrappen versuch quantitativ gemessen: Im frontalen Gesichtsfeld der Kröte rotierte vor dunklem Hintergrund eine weiße, rechteckige, 2,5 × 20° große Beuteattrappe (Zentralattrappe, z) mit dem Rechteckzentrum im Drehpunkt. Zusätzlich konnten mehrere Kreisscheiben von 5 bzw. 10° (Peripherattrappen, p) um die Zentralattrappe bewegt werden.Die Beutefangaktivität R z [Beutefangreaktionen x min–1] auf die allein gebotene Zentralattrappe war bei einer Sehwinkelgeschwindigkeit v s der distalen Attrappenkanten 10v s30 [grad x see–1] maximal und sank für kleinere oder größere Winkelgeschwindigkeiten wieder ab. Eine mit v s=25 [grad x sec–1] allein bewegte Peripherattrappe löste maximale Beutefangaktivität R p aus. Mit zunehmender Anzahl n p simultan bewegter Peripherattrappen sank die Beutefangaktivität ab.Mehrere, um den gleichen Drehpunkt bewegte Peripherattrappen, deren Abstand untereinander =10° betrug, blieben von der Kröte unbeantwortet. Sie bildeten ein inhibitorisches Umfeld und hemmten dadurch die Reaktion auf die gleichzeitig bewegte Zentralattrappe z. — Die im Simultanreizungsversuch gemessene Beutefangaktivität R zp war abhängig vom Abstand [grad] zwischen Zentralattrappe und Peripherattrappen ( : Kürzester Abstand zwischen z und p): Für =10° war R zp0 und stieg für >10° an. — Kontrollversuche, die jeweils auf die Simultanreizung mit z allein folgten (R z), ließen eine -abhängige Nachhemmung erkennen. — Die hemmende Wirkung auf die Beantwortung von z war auch von der Sehwinkelgeschwindigkeit v s der Peripherattrappen abhängig; sie war bei derjenigen Sehwinkelgeschwindigkeit (v s=25 [grad × sec–1]) maximal, mit der die Zentralattrappe, allein geboten, maximale Beutefangaktivität auslöste; für v sg25 [grad × sec–1] nahm die Hemmung wieder ab.Die Versuchsergebnisse lassen auf inhibitorische Verknüpfungen innerhalb des zentralen visuellen Systems schließen. Es wird vermutet, daß die Reiz-Verhaltens-reaktionsbeziehungen in den visuellen Simultanreizungsversuchen durch eine Art zentrale laterale Inhibition bestimmt werden.
Inhibitory effect of simultaneously moved prey dummies on the prey catching behaviour of the common toad (Bufo bufo L.)
Summary The prey catching behaviour of the toad (Bufo bufo L.) is generally inhibited by simultaneously visual moving stimuli caused by a group of prey animals (mealworms). According to this behavioural observation the dependence of this inhibitory effect on several visual parameters were quantitatively measured in dummy experiments: in the frontal visual field of the toad a white rectangular prey dummy of 2,5×20° (central dummy, z) was rotating in a centre against dark background. In addition several disks of 5 or 10° diameter (peripheral dummies, p) could simultaneously rotate around the central dummy (Figs. 1 and 7).The prey catching activity R z [catching reactions x min–1] released by rotation of only the central dummy z increased with increasing angular velocity v s of the stimulus distal edges, reaching a maximum for 10vs30 [degrees x sec–1] and decreasing for v s>30 [degrees x sec–1] (Fig. 5).A single peripheral dummy p, moved at v s=25 [degrees x sec–1], released maximal catching activity R p. The activity R p decreased with the increasing number n p of simultaneously offered dummies (Fig. 6).The prey catching behaviour of the toad was inhibited, when several peripheral dummies p were moved around the centre with a distance =10° from each other. They caused an inhibitory field and they also inhibited the response to a simultaneously moved central dummy z. The prey catching activity, measured in experiments in which z and p rotated simultaneously, depends on the distance [degrees] between z and p ( being the shortest distance between z and p). For =10°, R zp was zero; R zp increased for >10° (Figs. 9 and 10). — Control experiments carried out with z allone — after having applied the simultaneous stimulation — showed a - dependent after-inhibition (Fig. 9). — The inhibitory effect on the response to z also depended on the angular velocity v s of p; the inhibition was at a maximum for v s25 [degrees x sec–1], and it decreased for v s25 [degrees x sec–1] (Fig. 11).The experimental results suggest inhibitory interactions within the central visual system. It is supposed that the relation between stimulus and behavioural reaction in simultaneous stimulating experiments results from some kind of central nervous lateral inhibition.


Mit Unterstützung der Deutschen Forschungsgemeinschaft (Ew 7/4+5).  相似文献   

17.
The aim of this study was to measure running times to exhaustion (Tlim) on a treadmill at 100% of the minimum velocity which elicits max max in 38 elite male long - distance runners max = 71.4 ± 5.5 ml.kg–1.min–1 and max = 21.8 ± 1.2 km.h–1). The lactate threshold (LT) was defined as a starting point of accelerated lactate accumulation around 4 mM and was expressed in max. Tlim value was negatively correlated with max (r = -0.362, p< 0.05) and max (r = –0.347, p< 0.05) but positively with LT (%v max) (r = 0.378, p < 0.05). These data demonstrate that running time to exhaustion at max in a homogeneous group of elite male long-distance runners was inversely related to max and experimentally illustrates the model of Monod and Scherrer regarding the time limit-velocity relationship adapted from local exercise for running by Hughson et al. (1984) .  相似文献   

18.
Body weight loss was measured continuously for 24 hours in lightly clothed subjects at a room temperature of 26°C and relative humidity of 60% using the bed scale (model 33B, James Addison Potter). One male, aged 38 years and four females, aged 22 years served as subjects. Skin temperatures of the chest, thigh, leg and arm were measured every ten min. and mean skin temperature was calculated. Water loss through the skin was estimated by deducting body weight loss due to respiratory gas exchange and respiratory water loss from total weight loss. Respiratory water loss was estimated by using the formula (44-Pa) where e is the rate of evaporative water loss in the expired air (g/min), the oxygen uptake (L/min STPD) and Pa is the ambient water vapor pressure. Insensible water loss through skin was found to be significantly lower between 2:00–5:00 h than in the daytime. These findings contradict the results that the value of insensible water loss was higher at night than during the day.  相似文献   

19.
In this investigation, we assessed the effects of physical training on exercise-induced systemic and pulmonary hemodynamic changes under hypobaric hypoxia in catheter-implanted rats. We made continuous measurements of pulmonary and systemic arterial pressures during progressive treadmill exercises under hypobaric hypoxia (equivalent to altitudes of 2500 and 5500 m) in 46 control and 41 trained rats. Trained rats were exercised on two running schedules: 4 weeks (4-trained) and 6 weeks (6-trained). Both these groups of trained rats were exercised for the same length of running time each day. The increase in resting mean pulmonary arterial pressure with increasing equivalent altitude was lower in the two trained groups than in the control group. The increase in with progressive intensity of exercise was lower in the 6-trained than in the 4-trained and control groups at 610 and 2500 m. The 6-trained rats showed higher pH,P a CO 2 and O2 saturation in their blood than did the control group, whereas theP a O 2 was less. Lung tissue cyclic AMP concentration at rest was higher in the 6-trained than in the control group. Finally, it may be noted that exercise-induced lung tissue vasodilator responses seem to be enhanced in well-trained rats under both normobaric normoxia and hypobaric hypoxia. This study indicates that exercise training may be useful in preventing pulmonary hypertension resulting from both hypoxia and exercise.  相似文献   

20.
The electrochemical potential differences for potassium, between excised barley (Hordeum vulgare L.) roots and external media containing 0.05 mM KCl+0.5 mM CaSO4, were determined over a 4-h period during which initially low-K+ roots accumulated K+ by pretreatment in 50 mM KCl plus 0.5 mM CaCl2. This pretreatment resulted in increased internal [K+], decreased K+ influx (as measured from 0.05 mM KCl+0.5 mM CaSO4) and decreased values of . These observations indicate that the decline of K+ influx associated with increased internal K+ concentration cannot be accounted for by passive adjustment to the electrochemical gradient for this ion.  相似文献   

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