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Biomedical subjects

N Mrosovsky

Publications and source records attributed to N Mrosovsky.

At least 109 records · Page 6Linked to original sources
PubMed1980

Animal anorexias.

Eating very little in the presence of food or failure to serach for food has been documented in various species during the hibernation season, incubation, molting, and defense of the territory or harem. At these times feeding competes with other, more important activities. One way to avoid conflicts between feeding and these other activities to lower the programmed weight or set-point for body fat. Experiments on mammalian hibernators and incubating birds provide evidence that set-points are indeed lowered. Failure to eat in these two examples depends on anorexia, loss of appetite. A review of other examples suggests that conceptualization in terms of lowered set-points provides a unified and testable way of understanding many naturally occurring instances of fasting in the animal kingdom. Finally, spontaneous animal anorexias are contrasted with attempts by people to lose weight.

Animals↗
PubMed1979

Seaward orientation of hatchling turtles: turning systems in the optic tectum.

This paper reports studies on the mechanisms underlying seaward orientation in hatchling turtles. The particular aim was to investigate whether activity in different regions of the retina and associated tectal areas, as assessed by some comparator mechanism, results in turning in different directions. Hatchling green turtles (Chelonia mydas) were tested for sea-finding ability in a natural situation on the beach following lesions of the optic tectum. Asymmetrical bilateral lesions resulted in a number of turtles making circles in the direction of the tectum with the posterior lesion and in other turtles deviated in this direction. Bilaterally lesioned turtles were also slower and less consistent in their sea-finding behaviour. No major disruptions of sea finding were detected in animals with unilateral tectal lesions. By suspending lights in the nasal visual field of unilaterally blindfolded green and leatherback turtles (Dermochelys coriacea) it was possible to produce circling in the direction of the covered eye; in contrast, with the light suspended in the temporal field, turning was always in the direction of the uncovered eye. The results are consistent with the view that sea finding depends on a complex phototropotactic system with stimulation in different parts of a single retina being associated with turning in opposite directions.

Animals↗
PubMed1977

Hibernation and body weight in dormice: a new type of endogenous cycle.

Under conditions unfavorable to hibernateion (22 degrees C), the body-weight cycles of dormice are only a few weeks long, but under conditions in which dormice hibernate (5 degrees C), the cycles can last many months; the more the animals hibernate, the longer are the cycles. Such cycles contrast with the relative independence from torpor of the period of circannual cycles in other hibernating rodents and with the temperature compensation of circannual and circadian cycles in general.

Animals↗
PubMed1977

Individual differences in the sea-finding mechanism of hatchling leatherback turtles.

When hatchling leatherback turtles, Dermochelys coriacea, are unilarerally blindfolded, some circle toward their open eyes and some toward their covered eyes. If tests were performed immediately after one eye had been blindfolded, in cases where the turtle circled toward the open eye there was a transient potentiation of circling at the start of the test. In contrast, in cases where the turtle circled toward the covered eye, circling was decreased at the start of the test. Similar transient phenomena occurred when the position of a blindfold was reversed from one eye to another. Following removal of a blindfold, circling toward the previously covered eye was increased. The transient effects in all these tests waned by about 2 min. There was no evidence of transient circling tendencies in turtles that were tested after a unilateral blindfold had been in position for 4 min. The results suggest that ipsilateral and contralateral retinotectal turning systems differ in strength among individual turtles and individual eyes, and that following unilateral blindfolding there is a potentiation only of the ipsilateral turning system associated with stimulation of the still open eye.

Animals↗
PubMed1975

The amplitude and period of circannual cycles of body weight in golden-mantled ground squirrels with medial hypothalamic lesions.

Golden-mantled ground squirrels, Citellus lateralis, were kept for several years in conditions of constant temperature and photoperiod. Control animals showed the expected circannual cycles of body weight, becoming fat in the autumn and thin in the spring. Animals with lesions in the ventromedial region of the hypothalamus also had circannual cycles of weight but in most animals the amplitude was increased. At one time of year the lesioned ground squirrels were grossly obese while often at other times their weight was close to that of control animals or their own preoperative weights. There were unusually early peaks in weight after the lesion in some animals and it is probable that a phase shift occurred. Observations on hibernation, food intake, transient weight gains and delayed weight gains following the lesions are also reported. Evidently during the winter phase of the annual cycle in these ground squirrels there exist mechanisms that lead not only to a loss of weight gained naturally before the time for hibernation but also to a temporary attenuation of additional obesity produced by ventromedial hypothalamic lesions.

Animals↗