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  • 11
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary As has been previously shown, non-shivering thermogenesis is the prevailing mechanism of heat production in the newborn guinea pig exposed to a cool environment. In the course of the first two to three weeks of life, non-shivering thermogenesis is reduced and replaced by shivering. In the present study this process has been shown to be linked with morphological and functional alterations in the multilocular adipose tissue. The functional changes have been evidenced by the following experiments: In two groups of guinea pigs, 0–2, and 25 to 42 days of age, respectively, the local temperature and blood flow were measured in the large fat pad located between the scapulae, in addition to gaseous metabolism, electrical activity of the sceletal musculature and colon temperature. In the young animals the rise of O2-consumption as occuring on cold exposure was accompanied by a temperature rise in the fat tissue (absolute and relative to the colon temperature), whereas electrical activity of the musculature remained low. Blood flow of the fat tissue increased at the same time. In the older animals, the temperature difference between the fat tissue and colon remained low but it occurred shivering. The increase of temperature difference and blood flow was reduced or abolished in the young animals by Alderlin, an adrenergic β-receptor blocking agent that has been previously shown to block non-shivering thermogenesis; on the other hand, the blockade of non-shivering thermogenesis caused an onset of shivering. Further, noradrenaline and adrenaline have been shown to increase blood flow of the fat tissue in the young animals. The results indicate. 1. that the brown adipose tissue can be considered an important site of non-shivering thermogenesis in the newborn guinea pig, and 2. that the thermogenic capacity of the brown fat is diminished with increasing age.
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  • 12
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    Pflügers Archiv 266 (1957), S. 39-40 
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 13
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 14
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    Pflügers Archiv 272 (1960), S. 27-28 
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 15
    ISSN: 1432-2013
    Keywords: Temperature Regulation ; Control of Shivering ; Central Thermosensitive Structures ; Spinal Cord ; Diencephalon ; Temperaturregulation ; Steuerung des Kältezitterns ; zentrale thermosensitive Strukturen ; Rückenmark ; Zwischenhirn
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary In young guinea pigs the ascending pathways from the spinal thermosensitive region were studied by means of 1. microelectrode recording and 2. micro-electrocoagulation. In the first series of studies, impulse frequency was recorded from single units of the spinothalamic tract which responded to a temperature rise in the spinal segments C5-T2 with an increase of discharge frequency. At a spinal cord temperature of 38–39° C these units showed a firing rate of 1–5 imp./sec; local heating of the spinal cord (dT/dt=0.1° C/sec) to 40–41° C caused an increase in discharge frequency to 20–25 imp./sec. The mean static impulse frequency was 3 imp./sec at a spinal cord temperature of 39° C, and 10 imp./sec at a spinal cord temperature of 42.5° C. In the second series of studies bilateral RF-coagulations were carried out in different sites of the diencephalon. These experiments showed that the ascending fibres from the spinal thermosensitive region connect the thermosensitive spinal region with a hypothalamic “temperature control centre”.
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  • 16
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Zusammenfassung Bei Meerschweinchen im Alter von 0 Tagen bis durchschnittlich 11 Monaten wurde die Altersabhängigkeit des maximalen Ausmaßes der zitterfreien Thermogenese mit folgenden Methoden bestimmt: 1. Mit dem Noradrenalintest, das ist Bestimmung der O2-Aufnahmesteigerung nach Noradrenalininjektion, 2. mit dem „Blockadetest“, d.h. durch quantitative Erfassung der Beziehung zwischen elektrischer Muskelaktivität und O2-Aufnahme vor und nach Blockade der zitterfreien Thermogenese mit einem β-Receptorenblocker. Die zitterfreie Thermogenese betrug beim neugeborenen Meerschweinchen rund 250% des Grundumsatzes. Bei Aufzucht in warmer Umgebung nahm sie im Verlauf von 4 Wochen bis auf 10 bis 15% ab. Bei Aufzucht in kalter Umgebung (+3° C) bzw. vierwöchiger Adaptation an + 3° C nach vorheriger Aufzucht in wärmerer Umgebung betrug die zitterfreie Thermogenese im Alter von 3 Monaten noch ca. 60%, im Alter von 9 Monaten nur noch 40% des Grundumsatzes. Bei tieferer Adaptationstemperatur, wurden keine höheren, sondern sogar geringere Werte erhalten. Der Abbau der zitterfreien Thermogenese war von einem Schwund an braunem Fettgewebe begleitet.
    Notes: Summary In guinea pigs, 0 days to, on the average, 11 months of age, the age-dependency was determined of the maximum extent of non-shivering thermogenesis, using the following methods: 1. The noradrenaline-test: measurement of the increase in oxygen uptake on a noradrenaline injection. 2. The “blocking test”: quantitative evaluation of the relationship between electrical activity of the musculature and oxygen uptake before and after blockade of non-shivering thermogenesis by a β-receptor blocking agent. In the newborn guinea pig non-shivering thermogenesis amounted to 250% of the basal metabolic rate. It decreased to 10–15% within four weeks in animals which were reared in a warm environment. In animals reared in the cold or adapted to a cold environment (+3° C) after having been reared in a warm environment the non-shivering thermogenesis amounted to about 60% at the age of 3 months and to no more than 40% at the age of 9 months. With lower adaptation temperatures no larger but smaller amounts of non-shivering thermogenesis were obtained. The loss of non-shivering thermogenesis was accompanied by a reduction of the brown adipose tissue.
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  • 17
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Zusammenfassung An nichtnarkotisierten Katzen wurden die Hypothalamustemperatur, die Hautdurchblutung am Ohr und die Rectaltemperatur fortlaufend registriert. Die Registrierung der Hypothalamustemperatur erfolgte mit Thermonadeln, die mittels einer modifizierten Hessschen Technik eingeführt wurden, die Hautdurchblutung wurde mit dem Wärmeleitmesser nach Hensel aufgezeichnet. Bei 22–23° C Raumtemperatur traten in der Ruhe rhythmische Durchblutungsänderungen der Haut mit einer Frequenz von 1–2/min auf, diesen Durchblutungsschwankungen folgten mit großer Regelmäßigkeit Veränderungen der Hypothalamustemperatur bis zu 0,2° C, und zwar nach constrictorischen Phasen Erhöhung, nach dilatatorischen Phasen Senkung. Bei Kälte- und Wärmereizen an den Extremitäten trat eine reflektorische Vasoconstriction bzw. Dilatation ein, bevor sich die Hypothalamustemperatur geändert hatte. Erst im Gefolge der Hautdurchblutungsänderungen kam es zu Temperaturänderungen bis zu 0,4° C im Hypothalamus, und zwar zu Anstiegen bei Kaltreizen und zu Senkungen bei Warmreizen. Die Rectaltemperatur verhielt sich in allen Versuchen gleichsinnig wie die Hypothalamustemperatur, der zeitliche Verlauf der Rectaltemperatur war jedoch gegenüber dem der Hypothalamustemperatur erheblich verzögert.
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  • 18
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 19
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    Springer
    Pflügers Archiv 270 (1959), S. 54-55 
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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  • 20
    ISSN: 1432-2013
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
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