Estradiol phase shifts circannual body mass rhythms of male ground squirrels

1998 ◽  
Vol 274 (3) ◽  
pp. R754-R759
Author(s):  
Sara M. Hiebert ◽  
Theresa M. Lee ◽  
Paul Licht ◽  
Irving Zucker
Keyword(s):  
Mass Loss ◽  
Body Mass ◽  
Sexual Differentiation ◽  
Statistical Significance ◽  
Mass Gain ◽  
Hormone Treatment ◽  
Estradiol Benzoate ◽  
Ground Squirrels ◽  
Circannual Rhythm ◽  
Spermophilus Lateralis

Gonadectomized male golden-mantled ground squirrels ( Spermophilus lateralis) were implanted with estradiol benzoate (EB)-filled or empty capsules. Body mass was monitored before, during, and for at least 1 yr after hormone treatment. EB treatment during the mass-gain phase of the annual cycle significantly decelerated increases in body mass; the period of the circannual rhythm (CAR) of body mass was 54 days longer in EB- than blank-treated squirrels. Hormone treatment during the mass-loss phase accelerated mass loss; although this effect only approached statistical significance, some phase markers of the CAR were significantly advanced in subsequent cycles. We conclude that, as in females, estradiol affects the waveform of the CAR of males differently at different phases of the circannual cycle. Sexual differentiation does not eliminate responsiveness of CARs of squirrels to estradiol; sex differences, if any, are subtle rather than absolute and, in this respect, differ from circadian rhythms.

Estradiol phase-shifts circannual rhythms of golden-mantled ground squirrels

1992 ◽  
Vol 262 (6) ◽  
pp. R1096-R1099
Author(s):  
T. M. Lee ◽  
I. Zucker
Keyword(s):  
Weight Loss ◽  
Weight Gain ◽  
Hormone Treatment ◽  
Estradiol Benzoate ◽  
Ground Squirrels ◽  
Circannual Rhythm ◽  
Response Curves ◽  
Pharmacological Manipulation ◽  
Spermophilus Lateralis ◽  
Peak Weight

Ovariectomized golden-mantled ground squirrels (Spermophilus lateralis) were implanted with estradiol benzoate (EB)-filled or empty capsules. Body weight was monitored for at least 1 yr before, during, and after hormone treatment. EB treatment of 6-7 mo duration, restricted to the weight-gain phase, decelerated weight gain and delayed attainment of peak weight by 34 days; the period of the circannual rhythm, measured between successive trough weights, was 36 days longer in squirrels treated with estradiol than in untreated animals. EB treatment of 2- to 4-mo duration, restricted to the weight-loss phase, accelerated weight loss, advanced attainment of trough weights by 57 days, and decreased the period of the circannual rhythm by 66 days. Estradiol-induced phase delays and advances were preserved in the year after discontinuation of hormone treatment. These results favor the existence of circannual phase-response curves to hormones and provide a system for pharmacological manipulation of circannual rhythms.

Increased heat loss affects hibernation in golden-mantled ground squirrels

2004 ◽  
Vol 287 (1) ◽  
pp. R167-R173 ◽  
Author(s):  
Alexander S. Kauffman ◽  
Matthew J. Paul ◽  
Irving Zucker
Keyword(s):  
Food Intake ◽  
Heat Loss ◽  
Body Mass ◽  
Complete Removal ◽  
Ground Squirrels ◽  
Control Procedure ◽  
Ambient Temperatures ◽  
Spermophilus Lateralis ◽  
Maintain Body Temperature ◽  
Body Heat

During hibernation at ambient temperatures (Ta) above 0°C, rodents typically maintain body temperature (Tb) ∼1°C above Ta, reduce metabolic rate, and suspend or substantially reduce many physiological functions. We tested the extent to which the presence of an insulative pelage affects hibernation. Tb was recorded telemetrically in golden-mantled ground squirrels ( Spermophilus lateralis) housed at a Ta of 5°C; food intake and body mass were measured at regular intervals throughout the hibernation season and after the terminal arousal. Animals were subjected to complete removal of the dorsal fur or a control procedure after they had been in hibernation for 3–4 wk. Shaved squirrels continued to hibernate with little or no change in minimum Tb, bout duration, duration of periodic normothermic bouts, and food intake during normothermia. Rates of rewarming from torpor were, however, significantly slower in shaved squirrels, and rates of body mass loss were significantly higher, indicating increased depletion of white adipose energy stores. An insulative pelage evidently conserves energy over the course of the hibernation season by decreasing body heat loss and reducing energy expenditure during periodic arousals from torpor and subsequent intervals of normothermia. This prolongs the hibernation season by several weeks, thereby eliminating the debilitating consequences associated with premature emergence from hibernation.

Circannual variations in circadian rhythms of ground squirrels

1986 ◽  
Vol 250 (5) ◽  
pp. R831-R836 ◽  
Author(s):  
T. M. Lee ◽  
M. S. Carmichael ◽  
I. Zucker
Keyword(s):  
Activity Rhythm ◽  
Active Phase ◽  
Ground Squirrels ◽  
Circadian Activity ◽  
Circannual Rhythm ◽  
Light Onset ◽  
Spermophilus Lateralis ◽  
Activity Onset ◽  
The Times ◽  
Phase Angles

There was a circannual rhythm in the times of activity onset (psi o) and activity termination (psi T) and in the duration of the active phase (alpha) in female ground squirrels (Spermophilus lateralis) maintained in a light-dark (LD) 14:10 photoperiod for 22 mo. Activity onset occurred 2.3 h after light onset in the 4 mo before estrus, 0.5 h before light onset during the month encompassing estrus, and progressively later during each of the ensuing 4 mo. Termination of activity occurred later during the month of estrus than in the 4 mo preceding estrus; alpha nearly doubled during the month of estrus and decreased gradually over the next 3 mo. The psi o and psi T remained entrained to the daily illumination cycle, but the phase angles of activity onset and offset and the duration of the active phase varied seasonally and recurred with a circannual period of 9-11 mo. The LD 14:10 photoperiod entrained the circadian activity rhythm throughout the year; however, circannual variations in activity as well as in estrus and body mass were not entrained by this photoperiod but free-ran with periods of less than 12 mo.

scholarly journals IMPACT OF CREATINE MONOHYDRATE ON BODY MASS OF SWIMMERS

2020 ◽  
Vol 11 (2) ◽  
Author(s):  
Goran Grahovac ◽  
Bojan Guzina ◽  
Milomir Trivun ◽  
Goran Pašić
Keyword(s):  
Water Temperature ◽  
Body Mass ◽  
Motor Development ◽  
Statistical Significance ◽  
Good Health ◽  
Mass Gain ◽  
Creatine Monohydrate ◽  
The Subject ◽  
Research Show

The subject of the research is impact of creatine monohydrate on a mass of swimmers. The test was performed on a sample of 60 swimmers among members of the Academic Swimming Club „22. April“ divided into two groups aged between 21 and 25. All respondents are male and in good health. The respondents belonging to this population are at the zenith of morphological and motor development and are well motivated to advance in swimming. The measurement was carried out at the end of May and half of June 2008 at the premises of the Recreation Center Srpske Toplice (water temperature 28°C). The respondents were measured for body mass at baseline and after 21 days of taking creatine. The main objective of the paper is to determine whether taking creatine for three weeks shows significant differences in a mass gain of swimmers. The results of the research show that the differences in body mass between the two measurements have statistical significance.

Circannual body weight rhythms of ground squirrels: role of gonadal hormones

1982 ◽  
Vol 243 (5) ◽  
pp. R546-R551 ◽  
Author(s):  
I. Zucker ◽  
M. Boshes
Keyword(s):  
Body Weight ◽  
Sex Difference ◽  
Estradiol Benzoate ◽  
Gonadal Hormones ◽  
Ground Squirrels ◽  
Gonadal Hormone ◽  
Spermophilus Lateralis ◽  
Body Weights ◽  
Hormone Secretions

The influence of ovarian and testicular hormones on circannual body weight cycles was assessed in golden-mantled ground squirrels (Spermophilus lateralis), maintained in a LD 14:10 photoperiod at 23 degrees C. Animals were gonadectomized or sham operated at 47 days of age and implanted with empty capsules or capsules filled with estradiol benzoate (EB) or testosterone propionate (TP). Body weight, food intake, and reproductive condition were recorded at weekly intervals. Gonadectomized and intact squirrels of both sexes manifested robust circannual rhythms of body weight; cyclic secretion of gonadal hormones was not necessary for the expression of this circannual cycle. Intact and gonadectomized males weighed substantially more than their female counterparts but only during part of the annual cycle. This sex difference waxed and waned on a circannual basis in the absence of concurrent gonadal hormone secretions. EB phase-delayed attainment of peak body weights in ovariectomized squirrels but did not affect timing of trough body weights. EB increased the amount of food consumed by ovariectomized squirrels particularly during the weight gain phase. TP accelerated attainment of trough body weights in orchidectomized animals. Gonadal hormones modify the magnitude and timing of body weight peaks and troughs but are not necessary for the generation or expression of the circannual body weight cycle or for the sex difference in this cycle.

scholarly journals Bottlenecks and rescue effects in a fluctuating population of golden-mantled ground squirrels (Spermophilus lateralis)

2010 ◽  
Vol 12 (1) ◽  
pp. 285-296 ◽  
Author(s):  
Mary Brooke McEachern ◽  
Dirk H. Van Vuren ◽  
Chris H. Floyd ◽  
Bernie May ◽  
John M. Eadie
Keyword(s):  
Ground Squirrels ◽  
Spermophilus Lateralis

Effects of neurosecretory protein GL on food intake and fat accumulation under different dietary nutrient compositions in rats

2021 ◽  
Author(s):  
Keisuke Fukumura ◽  
Kenshiro Shikano ◽  
Yuaki Narimatsu ◽  
Eiko Iwakoshi-Ukena ◽  
Megumi Furumitsu ◽  
...  
Keyword(s):  
Food Intake ◽  
Feeding Behavior ◽  
Body Mass ◽  
Mass Gain ◽  
Chow Diet ◽  
Tissue Mass ◽  
Fat Accumulation ◽  
Intracerebroventricular Infusion ◽  
Body Mass Gain ◽  
Sucrose Diet

Abstract We recently identified a novel hypothalamic small protein, named neurosecretory protein GL (NPGL), which is involved in energy homeostasis in birds and mammals. However, whether the action of NPGL is influenced by nutritional composition remains unknown. Thus, we investigated the effect of chronic intracerebroventricular infusion of NPGL for 13 days on feeding behavior and body mass gain under a normal chow diet (NC), high-fat diet, high-sucrose diet (HSD), and medium-fat/medium-sucrose diet (MFSD) in rats. NPGL stimulated food intake of NC and MFSD, especially during the light period. By contrast, NPGL decreased body mass gain under NC and increased total white adipose tissue mass in HSD- and MFSD-fed rats. These data suggest that the effects of NPGL on feeding behavior, body mass gain, and fat accumulation depend on nutrient type. Among them, sucrose in diets seems to contribute to fat accumulation elicited by NPGL.

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