Regional differences in fat pad responses to short days in Siberian hamsters

1989 ◽  
Vol 257 (6) ◽  
pp. R1533-R1540 ◽  
Author(s):  
T. J. Bartness ◽  
J. M. Hamilton ◽  
G. N. Wade ◽  
B. D. Goldman
Keyword(s):  
Body Weight ◽  
Body Fat ◽  
Subcutaneous Fat ◽  
Short Photoperiod ◽  
Fat Pad ◽  
Initial Exposure ◽  
Short Day ◽  
Siberian Hamsters ◽  
Long Day ◽  
Induced Changes

Siberian hamsters exhibit decreased body weight and fat after initial exposure to short photoperiods and increased body weight and fat after extended short photoperiod exposure. The purpose of the present experiments was to determine if uniform changes in white adipose tissue (WAT) pad weights and lipid metabolism correspond to these short photoperiod-induced changes in body fat. Carcass lipid content and testes and fat pad weights [retroperitoneal WAT (RWAT), epididymal WAT (EWAT), and inguinal and dorsal subcutaneous WAT, respectively] were decreased in male hamsters relative to their long day counterparts after 6 and 12 wk of short-day exposure. Moreover, EWAT and RWAT weight, EWAT specific lipoprotein lipase activity, and specific and total lipogenesis were disproportionately decreased relative to the subcutaneous fat pads. The changes in fat pad weight and metabolism were generally reversed coincident with the return to a long-day-like reproductive status after prolonged short-day exposure (24 and 30 wk). In a less detailed experiment, female Siberian hamsters had decreased body, fat pad, and uterine weights after 6 wk of short-day exposure; however, no fat pad-specific changes in weight were observed. The results of these experiments demonstrate that short-day-exposed male Siberian hamsters may be a useful model for examining mechanisms underlying fat pad-specific responses. In addition, gender appears to influence the pattern of short-day-induced lipid depletion in this species.

Control of torpor and body weight patterns by a seasonal timer in Siberian hamsters

1989 ◽  
Vol 257 (1) ◽  
pp. R142-R149 ◽  
Author(s):  
T. J. Bartness ◽  
J. A. Elliott ◽  
B. D. Goldman
Keyword(s):  
Body Weight ◽  
Food Intake ◽  
Implant Removal ◽  
Daily Torpor ◽  
Short Day ◽  
Siberian Hamsters ◽  
Long Day ◽  
Preparatory Phase ◽  
Pelage Color ◽  
Seasonal Responses

Two experiments were designed to assess whether the short-day-induced patterns of shallow daily torpor, body weight, and other seasonal responses (food intake and pelage pigmentation) exhibited by Siberian hamsters (Phodopus sungorus sungorus) are under the control of a "seasonal timekeeping mechanism" that is independent of reproductive status [testosterone, (T)]. We examined whether the patterning and expression of these seasonal responses were altered by decreases in serum T that accompany gonadal regression during the first 8 wk of short-day exposure (i.e., the "preparatory phase" of the torpor season) or by experimental increases in serum T after this phase. Short-day-housed, castrated hamsters bearing T implants had long-day levels of the hormone and did not exhibit torpor. Appropriate seasonal patterns and levels of torpor, body weight, pelage color stage, and food intake were exhibited after T implant removal although serum T was clamped to long-day levels during the preparatory phase. In animals that were gonad intact during the preparatory phase and were subsequently castrated and given T implants, torpor did not occur as long as the implants were in place. However, the patterns and levels of daily torpor, food intake, and body weight rapidly returned to appropriate seasonal values compared with the castrated, blank-implanted controls on T implant removal; these effects occurred whether the T implants were removed when torpor frequency was increasing, at its peak, or decreasing across the torpor season. T did not affect pelage color stage under any condition.(ABSTRACT TRUNCATED AT 250 WORDS)

Short-day-like body weight changes do not prevent fat pad compensation after lipectomy in Siberian hamsters

1997 ◽  
Vol 272 (1) ◽  
pp. R68-R77 ◽  
Author(s):  
M. M. Mauer ◽  
T. J. Bartness
Keyword(s):  
Body Weight ◽  
Food Restriction ◽  
Adipocyte Size ◽  
Weight Changes ◽  
Fat Pad ◽  
Body Weight Changes ◽  
Siberian Hamsters ◽  
Long Day ◽  
Long Duration ◽  
Short Days

Long-day (LD)-housed Siberian hamsters show compensatory increases in white adipose tissue (WAT) weight after lipectomy, whereas hamsters exposed to short days (SDs) for a long duration (22 wk) do not. We tested whether SD-induced body weight changes prevent fat pad compensation after lipectomy. In experiment 1, hamsters with lesions of the paraventricular nucleus of the hypothalamus (PVNx) rapidly increased body weight similarly to 22-wk SD-exposed hamsters. In experiment 2, LD-housed hamsters were food restricted for 22 wk and then pair fed with SD-housed hamsters for 12 wk to produce body weight changes mimicking those of ad libitum-fed SD-exposed animals. Epididymal WAT (EWAT) lipectomy (EWATx) of PVNx or food-restricted hamsters elicited compensatory increases in retroperitoneal and inguinal WAT (RWAT and IWAT) weights. Unlike other fat pads, EWAT was less affected by food restriction or PVNx than by SD exposure. In general, food restriction decreased adipocyte number, whereas SD exposure decreased adipocyte size. PVNx increased RWAT adipocyte size and IWAT adipocyte number. These results suggest that the lack of body fat compensation by EWATx hamsters exposed to SDs for a long duration is due to SD-associated responses other than body weight changes per se.

Gonadal and photoperiodic control of seasonal body weight changes in male voles

1984 ◽  
Vol 247 (1) ◽  
pp. R84-R88 ◽  
Author(s):  
J. Dark ◽  
I. Zucker
Keyword(s):  
Body Weight ◽  
Body Mass ◽  
Late Summer ◽  
Short Photoperiod ◽  
Late Winter ◽  
Weight Changes ◽  
Short Day ◽  
Long Day ◽  
Principal Factors ◽  
Gonadal Recrudescence

After 15 wk in a short photoperiod (10 h of light/day), adult male voles weighed 25% less and consumed 33% less food than did voles in a long photoperiod (14 h light/day). Neither body weight nor food intake differed among long- and short-day castrated voles. After 19 wk, castrated long-day voles weighed less than did intact animals. Voles reduced their body weight during the first 15 wk in the short photoperiod and increased their body mass during the succeeding 15 wk. Body mass of short-day voles was positively correlated with combined testes weight. Voles in the short photoperiod collected less nesting material than did their long-day counterparts at week 31. Pelage characteristics at week 32 were not affected by castration or by photoperiod. We conclude that the decreased body mass of male voles during the late summer, fall, and early winter reflects a decrease in circulating levels of testicular hormones; gonadal recrudescence and increased circulating androgen levels are in part responsible for the subsequent seasonal increase in body weight. Part of the increased body mass in late winter in field populations or in laboratory voles after 15 wk in the short photoperiod is independent of the resumption of gonadal activity. Fluctuations in neural and endocrine processes, rather than availability of food, are the principal factors underlying seasonal changes in energy balance.

Body fat regulation after partial lipectomy in Siberian hamsters is photoperiod dependent and fat pad specific

1994 ◽  
Vol 266 (3) ◽  
pp. R870-R878 ◽  
Author(s):  
M. M. Mauer ◽  
T. J. Bartness
Keyword(s):  
Body Fat ◽  
Fat Pad ◽  
Compensatory Response ◽  
Initial Exposure ◽  
Fat Loss ◽  
Fat Depots ◽  
Siberian Hamsters ◽  
Total Body Fat ◽  
Total Body ◽  
Fat Pads

Siberian hamsters exhibit seasonal fluctuations in body weight (fat). Initial exposure to a short photoperiod results in body fat loss that reverses after approximately 22 wk of short-day exposure. The purpose of this study was to determine whether Siberian hamsters are able to recover body fat after surgical reduction of total lipid stores and if so, whether this ability is photoperiod dependent and fat pad specific. Either the largest pair of internal fat pads, the epididymal white adipose tissue (EWAT) or one pair of two large external depots, the inguinal (IWAT) fat pads, were removed from male hamsters housed for 22 wk in a long (LD) or short (SD) photoperiod. Retroperitoneal fat pad (RWAT) mass was increased in LD EWAT- and IWAT-lipectomized hamsters. IWAT mass also was increased in the LD EWAT-lipectomized hamsters. Neither SD-lipectomized group compensated for body fat loss in any of the measured fat pads. Increased food intake was not necessary for total body fat recovery, but undereating partially may be responsible for the lack of recovery in SDs. The results of these experiments demonstrate a photoperiod-dependent ability of male Siberian hamsters to regulate total body fat after partial lipectomy. In addition, recovery involves a fat pad-specific compensatory response to partial lipectomy, rather than a general increase in lipid deposition in all fat depots.

Effects of melatonin on long-day responses in short-day housed adult Siberian hamsters

1988 ◽  
Vol 255 (5) ◽  
pp. R823-R830 ◽  
Author(s):  
T. J. Bartness ◽  
B. D. Goldman
Keyword(s):  
Short Photoperiod ◽  
Serum Prolactin ◽  
Short Day ◽  
Siberian Hamsters ◽  
Long Day ◽  
Secretion Profile ◽  
Total Body Fat ◽  
Photoperiodic Responses ◽  
Epididymal White Adipose Tissue ◽  
Total Body

Testis growth is stimulated when short photoperiod-regressed Siberian hamsters are exposed to a lengthening photoperiod, an effect presumably mediated by the pineal gland through a decrease in the peak nocturnal duration of secretion of its hormone melatonin (MEL)(D. S. Carter and B. D. Goldman, Endocrinology 113: 1268-1273, 1983). We examined this stimulatory or "progonadal" effect of MEL in short photoperiod-regressed, adult male Siberian hamsters that were pinealectomized (PINX) and given timed daily subcutaneous 1) injections of MEL (1 or 10 micrograms/day) or saline or 2) infusions of MEL that were "long day-like" (4 h, 10 or 100 ng/day), "short day-like" (10 h, 10 ng/day), or control saline infusions (4 h/day). Photoregressed sham PINX hamsters were transferred to long days at this time. After 5 wk of treatment, 1-microgram MEL-injected hamsters and both groups of 4-h MEL-infused hamsters had stimulatory responses that mimicked those of the long-day-exposed, sham PINX group [i.e., increased testes, body, and epididymal white adipose tissue (EPIWAT) weights, total body fat, EPIWAT lipoprotein lipase activity, and serum prolactin and follicle-stimulating hormone levels]. These effects were not observed in 10-micrograms MEL- or saline-injected and 10-h MEL- or saline-infused hamsters. Thus the peak nocturnal duration of serum MEL is the critical parameter of the MEL secretion profile for stimulating a variety of photoperiodic responses when photoregressed hamsters are exposed to lengthening daylengths.

Photoperiod-dependent fat pad mass and cellularity changes after partial lipectomy in Siberian hamsters

1996 ◽  
Vol 270 (2) ◽  
pp. R383-R392 ◽  
Author(s):  
M. M. Mauer ◽  
T. J. Bartness
Keyword(s):  
Adipose Tissue ◽  
Body Fat ◽  
White Adipose Tissue ◽  
Present Experiment ◽  
Inhibitory Effect ◽  
Adipocyte Size ◽  
Fat Pad ◽  
Siberian Hamsters ◽  
Long Day ◽  
Short Days

Long day (LD)-housed Siberian hamsters show compensatory mass increases in nonexcised white adipose tissue (WAT) after partial lipectomy, whereas hamsters exposed to short days (SDs) for 22 wk do not. The purpose of this experiment was to determine the cellularity changes underlying lipectomy-induced WAT compensation and whether the duration of SD exposure affects this compensation. Male Siberian hamsters were epididymal (E) or inguinal (I) WAT lipectomized (x) or sham-lipectomized (Sham) and either remained in LDs or were transferred to SDs and killed 6 or 12 wk later. In LDs, lipectomized hamsters showed compensatory mass increases in retroperitoneal WAT (RWAT) due to hyperplasia. IWAT mass also was increased by approximately 40% in LD-housed EWATx hamsters because of nonsignificant increases in adipocyte size and number at weeks 6 and 12, respectively. SD-housed hamsters responded to lipectomy by delaying the SD-associated body fat loss so that RWAT mass was reduced only one-third as much in lipectomized as in Sham hamsters, and the IWAT adipocytes of EWATx hamsters were larger than in Sham hamsters at week 6. At week 12, there was little indication of fat pad compensation by SD-housed hamsters. Collectively, the results of the present experiment and our previous study (16) suggest that the inhibitory effect of SDs on fat pad compensation after lipectomy increases with prolonged SD exposure.

Fat pad-specific compensatory mass increases after varying degrees of lipectomy in Siberian hamsters

1997 ◽  
Vol 273 (6) ◽  
pp. R2117-R2123 ◽  
Author(s):  
Mary Margaret Mauer ◽  
Timothy J. Bartness
Keyword(s):  
Adipose Tissue ◽  
Body Fat ◽  
White Adipose Tissue ◽  
Fat Content ◽  
Fat Pad ◽  
Siberian Hamsters ◽  
Long Day ◽  
Body Fat Content ◽  
Fat Removal ◽  
Fat Pads

Long day-housed Siberian hamsters show compensatory mass increases in inguinal (I) white adipose tissue (WAT) after epididymal WAT pad (EWAT) removal (x) but do not increase EWAT mass after IWATx. This study tested whether EWAT is specifically unresponsive to IWATx or whether EWAT lacks responsiveness to body fat deficits in general. We also tested whether the compensatory mass increases that occur after side-specific body fat removal are unilateral or bilateral. Therefore EWAT and/or IWAT was removed unilaterally or bilaterally. The compensatory changes in WAT mass by the intact fat pads were measured 12 wk later. EWAT did not compensate for removal of its contralateral mate. Retroperitoneal WAT and IWAT showed greater compensatory mass increases ipsilateral to the side of fat pad removal when EWAT or IWAT pads were removed unilaterally but not after removal of larger amounts of body fat. These results suggest the following: 1) in general, the greater the lipectomy-induced lipid deficit, the greater is the relative fat pad mass compensation; 2) the restoration of body fat content after lipectomy may involve mechanisms that can detect the side of the lipid deficit and enhance fat deposition on this side; and 3) EWAT does not show compensatory mass increases after lipectomy.

SCN lesions block responses to systemic melatonin infusions in Siberian hamsters

1991 ◽  
Vol 260 (1) ◽  
pp. R102-R112 ◽  
Author(s):  
T. J. Bartness ◽  
B. D. Goldman ◽  
E. L. Bittman
Keyword(s):  
Serum Prolactin ◽  
Suprachiasmatic Nuclei ◽  
Fat Pad ◽  
Short Day ◽  
Siberian Hamsters ◽  
Long Day ◽  
Testicular Regression ◽  
Body Weights ◽  
Short Days

The role of the suprachiasmatic nuclei (SCN) in the response to short-day melatonin (MEL) signals was examined in long-day-housed pinealectomized (PINX) Siberian hamsters. Five- or ten-hour MEL infusions that mimicked the peak nocturnal durations of serum MEL levels in long or short days, respectively, or control saline infusions were given for 5 wk. Half the hamsters in each infusion group also received bilateral electrolytic SCN lesions. The 10-h MEL infusions reduced testes weight, body and fat pad weights, and serum prolactin (PRL) and follicle-stimulating hormone (FSH) concentrations in unoperated controls. These short-day-type effects were blocked by SCN lesions, which often produced hyperprolactinemia. Circadian rhythms of locomotor activity were disrupted or sparse in hamsters with lesions in or near the SCN. In a second experiment, 5 wk of long-day-like, short-duration (5-h) MEL infusions were administered to hamsters that had been PINX after 8 wk of short-day exposure. Control hamsters given 5-h MEL infusions, but not 10-h MEL or saline infusions, exhibited testicular growth and increased serum PRL levels. Hamsters with SCN lesions showed similar responses, regardless of the duration or type of infusion. Although the blockade of 10-h MEL infusion-induced testicular regression by SCN lesions in experiment 1 may have been due to stimulation of the testes by PRL, it is unlikely that the hyperprolactinemia accounted for the ability of SCN lesions to block effects of 10-h MEL infusions on fat pad and body weights. Therefore, the SCN and/or neighboring structures may participate in the response to short-day MEL signals in Siberian hamsters.

Lower limit of body fat in healthy active men

1994 ◽  
Vol 77 (2) ◽  
pp. 933-940 ◽  
Author(s):  
K. E. Friedl ◽  
R. J. Moore ◽  
L. E. Martinez-Lopez ◽  
J. A. Vogel ◽  
E. W. Askew ◽  
...  
Keyword(s):  
Weight Loss ◽  
Body Weight ◽  
Lower Limit ◽  
Body Fat ◽  
Fat Mass ◽  
Subcutaneous Fat ◽  
Fat Free Mass ◽  
Energy Deficit ◽  
Strenuous Exercise ◽  
Healthy Men

We examined body composition changes in 55 normal young men during an 8-wk Army combat leadership training course involving strenuous exercise and low energy intake, with an estimated energy deficit of 5.0 +/- 2.0 MJ/day and a resultant 15.7 +/- 3.1% weight loss. Percent body fat (BF) measured by dual-energy X-ray absorptiometry (DEXA) averaged 14.3% (range 6–26%) and 5.8 +/- 1.8% (range 4–11%) at the beginning and end of the course, respectively. Men who achieved a minimum percent BF (4–6%) by 6 wk demonstrated only small additional total and subcutaneous fat losses in the final 2 wk and sacrificed increasingly larger proportions of fat-free mass. Percent BF estimated from skinfold thicknesses reflected relative changes in fat mass, although actual percent BF was overestimated. Instead of reaching a plateau after fat stores were substantially depleted, abdominal, hip, and thigh girths continued to decline with body weight loss. Final percent BF for the leanest men was similar to that observed after a 25% body weight reduction in the 1950 Minnesota study (5.2% by underwater weighting), and height-corrected final fat mass was the same (1.0 +/- 0.2 vs. 0.9 +/- 0.7 kg fat/m2), suggesting that these values represent a minimal body fat content in healthy men and that weight loss subsequent to achieving this level is contributed from the fat-free mass. Our results suggest that 4–6% BF or approximately 2.5 kg fat represents the lower limit for healthy men, as assessed by DEXA or by underwater weighing.

Photoperiod modulates the effects of norepinephrine on lymphocyte proliferation in Siberian hamsters

2003 ◽  
Vol 285 (4) ◽  
pp. R873-R879 ◽  
Author(s):  
Gregory E. Demas ◽  
Timothy J. Bartness ◽  
Randy J. Nelson ◽  
Deborah L. Drazen
Keyword(s):  
Lymphocyte Proliferation ◽  
Splenic Tissue ◽  
Splenocyte Proliferation ◽  
Short Day ◽  
Siberian Hamsters ◽  
Long Day ◽  
Β Adrenergic Receptors ◽  
Short Days

Siberian hamsters ( Phodopus sungorus) rely on photoperiod to coordinate seasonally appropriate changes in physiology, including immune function. Immunity is regulated, in part, by the sympathetic nervous system (SNS), although the precise role of the SNS in regulating photoperiodic changes in immunity remains unspecified. The goal of the present study was to examine the contributions of norepinephrine (NE), the predominant neurotransmitter of the SNS, to photoperiodic changes in lymphocyte proliferation. In experiment 1, animals were maintained in long [16:8-h light-dark cycle (16:8 LD)] or short days (8:16 LD) for 10 wk, and splenic NE content was determined. In experiment 2, in vitro splenocyte proliferation in response to mitogenic stimulation (concanavalin A) was assessed in spleen cell suspensions taken from long- or short-day hamsters in which varying concentrations of NE were added to the cultures. In experiment 3, splenocyte proliferation was examined in the presence of NE and selective α- and β-noradrenergic receptor antagonists (phenoxybenzamine and propranolol, respectively) in vitro. Short-day animals had increased splenic NE content compared with long-day animals. Long-day animals had higher proliferation compared with short-day animals independent of NE. NE (1 μM) further suppressed splenocyte proliferation in short but not long days. Last, NE-induced suppression of proliferation in short-day hamsters was blocked by propranolol but not phenoxybenzamine. The present results suggest that NE plays a role in photoperiodic changes in lymphocyte proliferation. Additionally, the data suggest that the effects of NE on proliferation are specific to activation of β-adrenergic receptors located on splenic tissue. Collectively, these results provide further support that photoperiodic changes in immunity are influenced by changes in SNS activity.

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