Struggles to correct published errors.
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Kinetics↗
Biomedical subjects
A Haim
Publications and source records attributed to A Haim.
The relative importance of photoperiod and temperature as cues for seasonal acclimation of thermoregulation in pouched mice (Saccostomus campestris: Cricetidae) from southern Africa.
The effect of short photoperiod and cold on metabolism and thermoregulation was investigated in pouched mice (Saccostomus campestris: Cricetidae) from three localities in southern Africa which experience contrasting climatic conditions. Mice were initially acclimated to long photoperiod (14L: 10D) at 25 degrees C, followed first by a decline in photoperiod (to 10L: 14D) and then by a fall in temperature (to 10 degrees C). Minimum observed metabolic rate (identical to basal metabolic rate) was unaffected by the decline in photoperiod but increased significantly following cold acclimation. Because minimal thermal conductance remained constant throughout the study the increase in minimum observed metabolic rate caused a decline in lower critical temperature to around 26 degrees C. In contrast to minimum observed metabolic rate, regulatory non-shivering thermogenesis improved significantly following the decline in both photoperiod and temperature. However, pouched mice from the warmest locality were significantly less responsive to photoperiod than those from the other two localities whose survival might depend upon their ability to accurately predict seasonal changes in temperature. Neither photoperiod nor temperature had any effect on body mass, yet pouched mice from the most arid locality, where food supply might be unpredictable, were significantly smaller and had lower total energy requirements than those from areas experiencing higher annual rainfall. These results indicate that S. campestris displays considerable geographical variation in energy requirements together with differences in the use of photoperiod as an anticipatory cue for predicting the onset of winter. These differences appear to be related to the availability of energy and the relative severity of climatic conditions in each locality.
Africa↗
Burrowing and huddling in newborn porcupine: the effect on thermoregulation.
The newborn cape porcupine Hystrix africaeaustralis is a precocial rodent. However, the newborn spends its first 9 weeks in the burrow. Heat production (oxygen consumption--VO2) and body temperature (Tb) were measured at various ambient temperatures (Ta) in newborn (4-8-week-old) porcupines, with a body mass between 1340-1993 g during summer, from the colony kept at the Mammal Research Institute, University of Pretoria. To assess the effect of huddling, these parameters were also measured in adult pairs of porcupines (Ta = 15 and 25 degrees C) kept together in the metabolic chamber and the values were compared with those obtained from single porcupines. Overall minimal thermal conductance was calculated for newborn and paired adult porcupines. The newborn porcupines can regulate their body temperature at Tas between 10-28 degrees C. VO2 measured at lower critical point is 0.602 +/- 0.08 ml/O2/g.h. At Ta = 10 degrees C, VO2 oscillated with a characteristic amplitude and frequency, while body temperature was well regulated. Huddling decreases the lower critical point. The overall minimal thermal conductance (0.044 +/- 0.002 ml O2/g.h.1 degree C) is higher than expected from body mass, so that the young are liable to lose heat rapidly. It is well known that the newborn porcupine spends a long period in the burrow and the results of this study suggest that this may be in order to conserve energy and presumably allocate it to growth. Apart from decreasing vulnerability, delaying foraging also avoids heat loss in the newborn porcupine.
Animals↗
Daily rhythms of metabolic rate and body temperature of two murids from extremely different habitats.
Daily circadian rhythms of body temperature (Tb) and oxygen consumption (VO2) were measured in two murid species, which occupy extremely different habitats in Israel. The golden spiny mouse (Acomys russatus) is a diurnal murid distributed in arid and hot parts of the great Syrio-African Rift Valley, while the broad-toothed field mouse (Apodemus mystacinus) is a nocturnal species that inhabits the Mediterranean woodlands. In both species, the daily rhythms of Tb and VO2 are entrained by the photoperiod. Under laboratory experimental conditions (ambient temperature Ta = 33 degrees C and photoperiod regime of 12L:12D), Acomys russatus exhibits a tendency towards a nocturnal activity pattern, compared to the diurnal activity displayed by this species under natural conditions. Under the same photoperiod regime and at Ta = 28 degrees C, Apodemus mystacinus displays nocturnal activity, as observed under natural conditions. The maximal values of Tb were recorded in Acomys russatus at midnight (23:50 h), while the maximal values of VO2 were recorded at the beginning of the dark period (18:20 h). In Apodemus mystacinus, the maximal values of Tb and VO2 were recorded at 23:40 and 20:00 h, respectively. The ecophysiological significance of these results is discussed further.
Animals↗
Behavior patterns of cold-resistant golden spiny mouse Acomys russatus.
Nesting behavior and food storage were studied in a cold-resistant (CR) population of the golden spiny mouse, Acomys russatus, in Southern Sinai at an altitude of 1600 m. CR-mice, in contrast to cold-sensitive (CS) ones, built nests in which they stored food. Such mice were found to be winter-solitary. These results show that food supply is an essential parameter for the survival of CR-mice during winter. Therefore, it is suggested that food supply rather than energy conservation was the main driving force in the selection of a solitary behavior pattern of CR-mice.
Animals↗
Thermoregulatory circadian rhythms in the pouched mouse (Saccostomus campestris).
1. Circadian rhythms of body temperature (Tb), oxygen consumption (VO2), and minimal thermal conductance (C) were studied in the pouched mouse, Saccostomus campestris under natural photoperiod during February at a constant ambient temperature of 28 degrees C. 2. Circadian rhythms of body temperature were also studied under natural photoperiod and laboratory temperatures (Max: 28.1 degrees C; Min: 23.2 degrees C) during February. 3. The results of the present study suggest that changes in ambient temperature are not the main "zeitgeber" for body temperature rhythm, and it seems that photoperiod plays a major role in this species. 4. The relationship between the rhythms of Tb, VO2, and C are further discussed.
Animals↗
Urine analysis of European moles Talpa europaea and white rats Rattus norvegicus kept on a carnivore's diet.
1. The urine compositions of the European mole Talpa europaea and of the white rat Rattus norvegicus (albino) kept on a carnivore's diet were compared. 2. The urine of moles contained bicarbonate while that of rats kept on a carnivore's diet did not. 3. Urine volume per 100 g body mass over 24 hr was significantly higher in the mole than in the rat. 4. The results of this study suggest that the mole, like other subterranean mammals on the one hand and caecal fermenters on the other, may use its kidneys as a pathway for releasing bicarbonate in its hypercapnic environment.
Animals↗
Geographical variations in heat production and dissipation within two populations of Rhabdomys pumilio (Muridae).
A comparative study of heat production and dissipation was carried out on Rhabdomys pumilio from two extremely different climatic zones. Our results show higher oxygen consumption (Vo2) values for the desert population at Ta = 5 degrees C when compared to the mesic population. The overall thermal conductance is also higher for the desert population. It seems as though penetration into mesic areas of R. pumilio, which originated in an arid zone, was accompanied by an increase in body mass.
Acclimatization↗
Enzymatic activity in crude oil contaminated rats.
The activity of enzymes found in the plasma, malate dehydrogenase (MDH) and lactate dehydrogenase (LDH), and enzymes from erythrocytes, glucose-6-phosphate dehydrogenase (G-6-PDH) and catalase, was studied in rats contaminated by crude oil. Crude oil (tube fed) contamination caused a significant increase in MDH and LDH activity 96 hr after contamination while a decrease in activity was noted in 6-6-PDH and catalase. An additional contamination (1 week after the first contamination), measured 96 hr after contamination, caused a relative decrease in MDH and LDH activity while there was a contrasting relative increase in G-6-PDH and catalase activity. After a recovery period of 3 weeks the only significant change was an increase in catalase activity.
Animals↗
Urine analysis of three rodent species with emphasis on calcium and magnesium bicarbonate.
The urine composition of three rodent species, mole rat Spalax ehrenbergi, the golden hamster Mesocricetus auratus and the white rat Rattus norvegicus was studied. These three species represent different degrees of fossoriality. The results show that the urine of the species that show a higher degree of fossoriality, the mole rat and the hamster, contain high values of calcium and magnesium bicarbonates when compared with the white rat. From these results it may be assumed that the mole rat as well as the hamster can use the kidney as a pathway for releasing bicarbonate and carbonate. This mechanism may reduce the CO2 concentration in their hypercapnic environment.
Animals↗
Non shivering thermogenesis and implication of the thyroid in cold labile and cold resistant populations of the golden spiny mouse (Acomys russatus).
The golden spiny mouse is dependent on non shivering thermogenesis (N.S.T.) for thermoregulation at cool ambient temperatures. Mice from the shores of the Dead Sea (Ein-Gedi, EG-mice) lose body heat when exposed to 6 degrees C. Their rate of cooling is linearly correlated to the magnitude of N.S.T. This is true for mice acclimated to 28 degrees C, born in the laboratory or freshly captured. Mice from the high mountains of South Sinai (S-mice) resist cooling under the same conditions and their N.S.T. is about twice that of EG-mice. EG-mice did not acclimate to cold. However thyroxine injections made them cold resistant and their N.S.T. rose to values close to that of S-mice. Light and electronmicroscopy of the thyroids in mice acclimated to 28 degrees C and exposed to 6 degrees C, or injected with TRH suggested intense activity in S-mice and little activity in EG-mice.
Acclimatization↗
Thermoregulation and nonshivering thermogenesis as factors limiting distribution of the golden spiny mouse (Acomys russatus).
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Animals↗
Size and activity of a cold resistant population of the golden spiny mouse (Acomys russatus: Muridae).
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Animals↗
Urinary characteristics of the Cape porcupine Hystrix africaeaustralis: effects of photoperiod and temperature.
The Cape porcupine Hystrix africaeaustralis is a large (11-18 kg), nocturnal, burrowing and group-living rodent. It experiences a metabolic response to seasonal acclimatization and is a hind gut fermenter. Changes in the urinary electrolyte and free urinary catecholamine concentrations of Cape porcupines were related to combined changes of ambient temperature and photoperiod regime. Three groups, A) Ta = 25 degrees C, 12L:12D; B) Ta = 32 degrees C, 16L:8D; C) Ta = 10 degrees C, 8L:16D, were studied to assess the influence of seasonal acclimatization on urinary bicarbonate and catecholamine concentrations. Urine volume was significantly (p < 0.001) higher in group C than in the other two groups. In groups B and C urinary pH was above 7 and this was associated with high concentrations of HCO3-. The total amount of catecholamines was higher in groups B and C than in group A. It is apparent that seasonal acclimatization of the Cape porcupine is also reflected by these parameters.
Acclimatization↗