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KURZFASSUNG: Quantitative Aspekte der K~ilteadaptation und ihres Thyroxin-Modells I N T R O D U C T I O NBetween several tissues of unadapted cold-and warm-blooded animals e. g, frogs and mice exist certain metabolic differences (LocKER 1962(LocKER , 1964. These can be disclosed by the action of a substance stimulating metabolism, namely 4.6-dinitro-o-cresol (DNOC). Under the influence of DNOC the percentage O2-consumption of brain, liver and heart in winter-frogs increases progressively with increasing temperatures in vitro, whereas in the remaining frog tissues and in all tissues of mice, a decrease in the percentage increment of O2-uptake occurs (LocKEX 1962). The question now arises whether a chronic stimulus, like exposure to cold, intensifies these metabolic differences between poikilothermic and homoiothermic animals or whether it alters them in a somewhat characteristic way. Since the adaptive changes of metabolism due to cold are connected with an activated thyroid gland, the problem gains interest whether chronic treatment with thyroxine exerts similar or even identical metabolic effects. The search for such effects has been performed on the whole animal metabolism and the respiration of all relevant tissues as well, together with the recording of changes

Specialia 771 carbohydrate coat, containing sialic acid among other chemical constituents, cannot be related to morphological findings. den als Reste der Glycocalyx yon Endothel-beziehungsweise Epithelzellen angesehen und zeigen einen partiku-l~iren Aufbau dieser Kohlenhydratschicht an.Zusammen/assung. An der Oberfl~iche isolierter Glomerulus-Basalmembranen des Schweins konnten dutch GefrierXtzung und durch Negativkontrastierung unregel-m~issig verteilte Partikel nachgewiesen werden. Sie wer-

Total metabolism and summated tissue respiration in relation to body size. Recording weight-specific total body metabolism of the mouse at two ambient temperatures (22.5 °, 350 C) and plotting the resulting data on a double logarithmic grid revealed a cyclic allometry with a positive constant between 1.3 and 5 g body weight (cycle I) and a negative constant between 5 (or 7) and 23 g (cycle II). Similar cycles concerning the weight-allometry of the mass of several organs (brain, heart, liver, skin) and the tissue respiration of brain, liver, intestine and kidneys are statistically significant. If the summated tissue respiration is determined over the entire body size range --by summing up tissue respiration for several individual body weights and calculating the regression lines-two cycles are, again, observable; their slopes cannot be distinguished statistically from those of the cycles of total body 02-uptake at 35 ° C. Its intensity, however, is considerably lower than that of the directly measured total body metabolism. If certain corrections are applied (inclusion of skin respiration and extrapolation of respiration in vitro to tO the intensity of summated tissue respiration as well as its slope coincide well with the BMR obtained from literature.

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