Decreased testosterone levels do not mediate short-photoperiod-induced brown fat changes

1986 ◽  
Vol 251 (5) ◽  
pp. R963-R970 ◽  
Author(s):  
K. S. Kott ◽  
B. J. Moore ◽  
B. A. Horwitz
Keyword(s):  
Testosterone Level ◽  
Citrate Synthase ◽  
Hormone Secretion ◽  
Gonadal Hormones ◽  
Brown Fat ◽  
Short Photoperiod ◽  
Gonadal Hormone ◽  
Hydroxyacyl Coa Dehydrogenase ◽  
Long Photoperiod ◽  
Thermogenic Capacity

Previous studies showed that short photoperiod increased brown fat (BAT) mass and reduced gonadal size and gonadal hormone secretion in hamsters. The present study investigated the possibility that the effects on BAT were dependent on reduced levels of gonadal hormones. BAT from male Syrian hamsters exposed to short photoperiod for 10 wk was significantly greater in mass, protein content, and total maximal citrate synthase and beta-hydroxyacyl-CoA dehydrogenase activities than was BAT from long-photoperiod hamsters, These differences between short- and long-photoperiod exposure were observed in hamsters housed at 21 as well as at 8 degrees C. Short photoperiod also increased the total recovered mitochondrial GDP binding, a finding consistent with increased BAT thermogenic capacity. These short-photoperiod effects were neither mimicked by castration of long-photoperiod hamsters nor prevented by high levels of testosterone administered to short-photoperiod animals. Castration did attenuate the effects of short photoperiod on BAT growth if, after surgery and prior to short-photoperiod exposure, the animals were housed at a long photoperiod for 2-3 wk. In contrast, in hamsters immediately placed at short photoperiod after surgery, castration did not inhibit short-photoperiod effects. The present three experiments demonstrate that, in addition to increasing BAT mass, short photoperiod elevates the thermogenic capacity of BAT, and this elevation does not require the absence or a much reduced testosterone level.

GDP binding to hamster brown fat mitochondria is reduced during hibernation

1985 ◽  
Vol 249 (6) ◽  
pp. R689-R693 ◽  
Author(s):  
B. A. Horwitz ◽  
J. S. Hamilton ◽  
K. S. Kott
Keyword(s):  
Binding Sites ◽  
Mitochondrial Protein ◽  
Substantial Reduction ◽  
Brown Fat ◽  
Short Photoperiod ◽  
Syrian Hamsters ◽  
Hydroxyacyl Coa Dehydrogenase ◽  
Brown Fat Mitochondria ◽  
Important Site ◽  
Thermogenic Capacity

Preparation for hibernation is accompanied by increased thermogenic capacity of brown fat (BAT), an important site of thermogenesis during arousal from hibernation. This study examined whether that thermogenic capacity is reduced in hibernation and reactivated during arousal. In one set of experiments, Syrian hamsters were exposed to short photoperiod (10:14 light-dark) and cold (7 degrees C). Those not hibernating at death (n = 10) served as controls for those that were (n = 9). A third group (n = 10) was killed 80–90 min after arousal was initiated by manual perturbation. Mitochondrial GDP binding (nmol/mg mitochondrial protein) was used to estimate thermogenic capacity. In a second experimental series, BAT citrate (si)-synthase and 3-hydroxyacyl-CoA dehydrogenase activities were measured in hibernating and nonhibernating hamsters. Although there were no differences in the maximum activities of these enzymes, GDP binding was markedly lower in the hibernators relative to the nonhibernators (0.214 +/- 0.031 vs. 0.535 +/- 0.039). However, in the partially aroused hamsters, GDP binding had doubled (0.438 +/- 0.04). Thus hibernation is accompanied by a substantial reduction of BAT thermogenic capacity (as manifested by GDP binding), which is reversed during arousal. The rapidity of this reversal indicates that it does not involve the synthesis of new GDP binding sites.

Hyperprolactinemia prevents short photoperiod-induced changes in brown fat

1989 ◽  
Vol 256 (1) ◽  
pp. R174-R180
Author(s):  
K. S. Kott ◽  
B. J. Moore ◽  
L. Fournier ◽  
B. A. Horwitz
Keyword(s):  
Protein Content ◽  
Fat Mass ◽  
Carcass Composition ◽  
Brown Fat ◽  
Short Photoperiod ◽  
Necessary Condition ◽  
Tissue Mass ◽  
The Right ◽  
Induced Changes ◽  
Thermogenic Capacity

Previous studies demonstrated that short photoperiod exposure significantly decreases circulating prolactin levels. The present study investigated the possibility that concomitant changes in brown fat tissue mass, protein content, thermogenic capacity, and carcass composition are dependent on this change in prolactin levels. Male golden (Syrian) hamsters were sham operated and exposed to a short (10L:14D) or long (14L:10D) photoperiod. A third group was implanted with exogenous pituitaries under the right kidney capsule and exposed to a short photoperiod. In experiment I, 4 wk of short- vs. long-photoperiod exposure did not result in significant changes in circulating prolactin levels, nor was there an increase in brown fat mass, protein content, or thermogenic capacity. Four weeks of short-photoperiod exposure did significantly increase carcass lipid content. However, this increase did not occur in hamsters exposed to 4 wk of short photoperiod but made hyperprolactinemic (implanted with two exogenous pituitaries). Ten weeks of short photoperiod significantly reduced circulating prolactin levels. Concomitantly, brown fat mass, protein content, and thermogenic capacity, as well as carcass fat, were increased. These short-photoperiod-induced changes were not observed in similarly exposed hamsters that were made hyperprolactinemic via two implanted pituitaries. In experiment II, similar changes in brown fat and body composition occurred in sham-operated hamsters exposed to 10 wk of short photoperiod. These changes were prevented in hamsters exposed to 10 wk of short photoperiod but made hyperprolactinemic via only one implanted pituitary. These results suggest that decreased prolactin is a necessary condition for the increased brown fat mass, protein content, and thermogenic capacity that occurs when golden hamsters are exposed to short photoperiod.

Metabolic organization of muscle and brown fat of normal and dystrophic hamsters

1983 ◽  
Vol 244 (3) ◽  
pp. R407-R411
Author(s):  
S. J. Wickler ◽  
B. A. Horwitz
Keyword(s):  
Cardiac Tissue ◽  
Citrate Synthase ◽  
Tricarboxylic Acid Cycle ◽  
Tricarboxylic Acid ◽  
Brown Fat ◽  
Nonshivering Thermogenesis ◽  
Beta Oxidation ◽  
Hydroxyacyl Coa Dehydrogenase ◽  
Metabolic Organization ◽  
Thermogenic Response

The thermogenic response to catecholamines, i.e., regulatory nonshivering thermogenesis (NST), is significantly reduced in dystrophic hamsters (BIO 14.6) compared with age-matched normals. The possibility that this reduction reflects, in part, lower levels of enzymes in those tissues implicated in NST has been examined by assaying citrate synthase (CS), beta-hydroxyacyl CoA dehydrogenase (HOAD), and phosphofructokinase (PFK), enzymes whose activity reflect the potential flux of substrates through the tricarboxylic acid cycle, beta-oxidation, and glycolysis, respectively. Each enzyme was assayed in brown fat, heart, gastrocnemius, and semitendinosus of 3-mo-old normal (n = 15) and dystrophic (n = 18) hamsters. Brown fat masses from interscapular, cervical, and scapular-axillary regions of dystrophics averaged only 50% those of normals (424 vs. 890 mg). Additionally, markers of aerobic metabolism (CS and HOAD) were significantly reduced in the brown fat from dystrophic animals. (CS activities averaged 59% of normal, whereas HOAD activities averaged 75% of normal). In dystrophic animals CS and HOAD levels were similar to those of normals in cardiac tissue but were significantly elevated in skeletal muscle samples. Tissue PFK activities were reduced only in cardiac tissue of the more affected dystrophics. Thus decreased NST capacity in dystrophic hamsters is accompanied by reduced masses and CS values in brown fat but not by decreases in the aerobic markers in skeletal or cardiac muscle.

Photoperiodic regulation of body mass, food intake, and reproduction in meadow voles

1983 ◽  
Vol 245 (3) ◽  
pp. R334-R338 ◽  
Author(s):  
J. Dark ◽  
I. Zucker ◽  
G. N. Wade
Keyword(s):  
Adipose Tissue ◽  
Food Intake ◽  
Lean Body Mass ◽  
Body Mass ◽  
Hormone Secretion ◽  
Gonadal Hormone ◽  
Meadow Voles ◽  
Short Day ◽  
Brown Adipose ◽  
Long Photoperiod

Adult male voles were maintained for 10 wk in long or short photoperiods (14 or 10 h of light/day). A third group of animals housed in the long photoperiod was implanted with capsules containing melatonin. Body weight and food intake were measured weekly; various tissues were weighed and analyzed at the time of autopsy. After 10 wk, voles in the short photoperiod weighed 20% less and consumed 30% less food than those housed in the long photoperiod. Total body water and lean body mass were reduced in the short-day animals, although the size of the brown adipose tissue was not affected. White adipose tissue lipoprotein lipase (LPL) activity was markedly reduced in the short-day voles who also manifested gonadal regression and suppression of spermatogenesis. Melatonin mimicked the effects of short photoperiods on LPL activity and on lean body mass; other parameters for melatonin-treated animals were intermediate between those of untreated long- and short-day voles. We hypothesize that winter weight losses experienced by meadow voles in the field are mediated by decreases in the duration of the daily photophase and that the reduction in body mass permits overwintering voles to reduce their energy requirements and the amount of time devoted to foraging. At least part of the seasonal decline in body mass appears due to a decrease in gonadal hormone secretion.

Short photoperiod and cold activate brown fat lipoprotein lipase in the Djungarian hamster

1989 ◽  
Vol 257 (5) ◽  
pp. R1123-R1127 ◽  
Author(s):  
M. Klingenspor ◽  
S. Klaus ◽  
H. Wiesinger ◽  
G. Heldmaier
Keyword(s):  
Ambient Temperature ◽  
Cold Acclimation ◽  
Lipoprotein Lipase ◽  
Brown Fat ◽  
Short Photoperiod ◽  
Slight Reduction ◽  
Nonshivering Thermogenesis ◽  
Djungarian Hamster ◽  
Substrate Supply ◽  
Long Photoperiod

Activation of lipoprotein lipase (LPL) in brown fat of the Djungarian hamster ensures substrate supply for nonshivering thermogenesis. Cold acclimation [5 degrees C ambient temperature (Ta)] in long photoperiod [light-dark (LD) 16:8] increased brown fat LPL activity from 4.7 to 22.7 nmol oleate.mg-1.min-1 within 1 day. Slight reduction of this high LPL activity was observed during prolonged cold exposure for up to 4 wk. Deacclimation (transfer from 5 to 23 degrees C Ta) caused total inactivation of brown fat LPL within 4 days. Short photoperiod (LD 8:16) also stimulates brown fat LPL activity. Its effect can be summarized by three different observations. At thermoneutrality short photoperiod elevated LPL activity to 7.1 instead of 4.7 nmol.mg-1.min-1 observed in long photoperiod. Second, at low ambient temperature short photoperiod reinforces the effect of cold acclimation. Maximum LPL activity of cold-exposed Djungarian hamsters averaged 23.7 nmol.mg-1.min-1 in long photoperiod and was elevated to 35.5 nmol.mg-1.min-1 in short photoperiod. Third, inactivation of LPL during deacclimation was delayed in short photoperiod. These results demonstrate that photoperiod as well as ambient temperature may be cooperatively used as environmental cues for seasonal acclimation of brown fat substrate supply for nonshivering thermogenesis.

scholarly journals A Role for Androgens in Regulating Circadian Behavior and the Suprachiasmatic Nucleus

Endocrinology ◽  
2007 ◽  
Vol 148 (11) ◽  
pp. 5487-5495 ◽  
Author(s):  
Ilia N. Karatsoreos ◽  
Alice Wang ◽  
Jasmine Sasanian ◽  
Rae Silver
Keyword(s):  
Suprachiasmatic Nucleus ◽  
Light Pulse ◽  
Fluorescent Protein ◽  
Hormone Secretion ◽  
Gonadal Hormones ◽  
Gonadal Hormone ◽  
Gastrin Releasing Peptide ◽  
Late Night ◽  
Green Fluorescent ◽  
Circadian Behavior

The suprachiasmatic nucleus (SCN) of the hypothalamus is the locus of a master circadian clock controlling behavioral and physiological rhythms, including rhythmic secretion of gonadal hormones. Gonadectomy results in marked alteration of circadian behaviors, including lengthened free-running period, decreased precision of daily onset of running, and elimination of early-evening but not late-night activity bouts. Androgen replacement restores these responses. These aspects of rhythmicity are thought to be regulated by the brain clock, although the site of androgen action remains unknown. Anatomically, the rodent SCN is composed of a ventrolateral core and a dorsomedial shell, and the present studies show that androgen receptors (AR) are localized to the ventrolateral core SCN. Using a transgenic mouse bearing dual reporter molecules driven by the AR targeted to both membrane and nucleus, we find that projections of AR-containing cells form a dense plexus in the core, with their fibers appearing to exit the SCN dorsally. In a second transgenic strain, in which the retinorecipient gastrin-releasing peptide cells express a green fluorescent protein reporter, we show that gastrin-releasing peptide cells contain AR. Through immunocytochemistry, we also show that SCN AR cells express FOS after a light pulse. Importantly, gonadectomy reduces the FOS response after a phase-shifting light pulse, whereas androgen replacement restores levels to those in intact animals. Taken together, the results support previous findings of a hypothalamic neuroendocrine feedback loop. As such, the SCN regulates circadian rhythms in gonadal hormone secretion, and in turn, androgens act on their receptors within the SCN to alter circadian function.

Influence of training on skeletal muscle enzymatic adaptations in normal and diabetic rats

1985 ◽  
Vol 249 (4) ◽  
pp. E360-E365 ◽  
Author(s):  
E. G. Noble ◽  
C. D. Ianuzzo
Keyword(s):  
Skeletal Muscle ◽  
Exercise Training ◽  
Citrate Synthase ◽  
Diabetic Rats ◽  
Muscle Fiber Types ◽  
Fiber Types ◽  
Marker Enzymes ◽  
Oxidative Potential ◽  
Hydroxyacyl Coa Dehydrogenase ◽  
Fast Twitch

Muscle homogenates representing slow-twitch oxidative, fast-twitch oxidative-glycolytic, fast-twitch glycolytic, and mixed fiber types were prepared from normal, diabetic, and insulin-treated diabetic rats. Diabetes was induced by injection of 80 mg . kg-1 of streptozotocin. The activities of citrate synthase, succinate dehydrogenase, and 3-hydroxyacyl-CoA dehydrogenase were employed as markers of oxidative potential, whereas phosphorylase, hexokinase, and phosphofructokinase activities were used as an indication of glycolytic capacity. Diabetes was associated with a general decrement in the activity of oxidative marker enzymes for all fiber types except the fast-twitch glycolytic fiber. In contrast, the fast-twitch glycolytic fibers demonstrated the greatest decline in glycolytic enzymatic activity. Insulin-treated animals, either trained or untrained, exhibited enzyme activities similar to their normal counterparts. Exercise training of diabetic rats mimicked the effect of insulin treatment and caused a near normalization of the activity of the marker enzymes. These findings suggest that the enzymatic potential of all skeletal muscle fiber types of diabetic rats may be normalized by exercise training even in the absence of significant amounts of insulin.

scholarly journals Probability of pregnancy before ninety days postpartum in water buffaloes

2021 ◽  
Vol 30 (1) ◽  
pp. 29-34
Author(s):  
Hector Nava-Trujillo ◽  
Robert Valeris-Chacin ◽  
Adriana Morgado-Osorio ◽  
Javier Hernández ◽  
Janeth Caamaño ◽  
...  
Keyword(s):  
Mixed Model ◽  
Linear Mixed Model ◽  
Water Buffalo ◽  
Mixed Effects ◽  
Short Photoperiod ◽  
Water Buffaloes ◽  
Negative Effect ◽  
Log Odds ◽  
First 90 Days ◽  
Long Photoperiod

This study aimed to determine the effect of parity and season of calving on the probability of water buffalo cows becoming pregnant before 90 days postpartum. A retrospective analysis of reproductive records of 1,465 water buffaloes with 3,181 pregnancies was carried out. Buffaloes were grouped according to parity in one, two, or three and more calvings. Season of calving was created with the following values: long photoperiod (March-August) and short photoperiod (September-February) and predicted probabilities from the mixed-effects logistic regression model were calculated, and a generalized linear mixed model was fitted with random intercepts to calculate the log odds of becoming pregnant ≤90 days postpartum. The probability of pregnancy ≤90 days postpartum was 0.3645, and this was lower in primiparous (0.2717) in comparison with two-calved (0.3863) and three or more calving buffaloes (0.5166). Probability of pregnancy ≤90 days postpartum increased 1.77 odds by each increase in parity. The probability of becoming pregnant ≤90 days postpartum was higher in water buffaloes calving during the short photoperiod season (0.4239 vs. 0.2474, P>0.000), and water buffaloes calving during the long photoperiod season only had 0.2645 odds to become pregnant than those calving during the short photoperiod season. The negative effect of long photoperiod was observed indifferently of parity. In conclusion, primiparity and the long photoperiod affect water buffalo cow's reproductive performance, decreasing pregnancy probability during the first 90 days postpartum.

Photoperiodic Control of Diapause Induction in the Larva of Lucilia Caesar L. (Diptera: Calliphoridae)

1967 ◽  
Vol 46 (1) ◽  
pp. 117-122
Author(s):  
R. A. RING
Keyword(s):  
Direct Effect ◽  
Diapause Induction ◽  
Short Photoperiod ◽  
Photoperiodic Control ◽  
One Stage ◽  
Photoperiod Regime ◽  
Absolute Length ◽  
The Absolute ◽  
Diapause Incidence ◽  
Long Photoperiod

1. It has been shown that photoperiod has a direct effect on the larva of Lucilia casear L. in the induction of diapause. 2. Transference of larvae from long to short photoperiod conditions during the 1st, 2nd, or 3rd instar increases their tendency to enter diapause. Conversely, transfer from short to long photoperiod conditions decreases their tendency to enter diapause. 3. Larvae are sensitive to changes in the absolute length of the photoperiod during all instars. The reaction is not restricted to any one stage but tends to be cumulative; thus the earlier the larvae are transferred from one photoperiod regime to another then the greater the contrast in diapause incidence between experimental groups and controls.

CIRCA-ANNUAL RHYTHMS OF PROLACTIN SECRETION IN EWES AND THE EFFECT OF PINEALECTOMY

1980 ◽  
Vol 84 (1) ◽  
pp. 83-89 ◽  
Author(s):  
C. J. MUNRO ◽  
K. P. McNATTY ◽  
L. RENSHAW
Keyword(s):  
Plasma Concentration ◽  
Pineal Gland ◽  
Seasonal Variations ◽  
Reproductive Tract ◽  
Plasma Concentrations ◽  
Prolactin Secretion ◽  
Transitional Period ◽  
Short Photoperiod ◽  
Winter Period ◽  
Long Photoperiod

Changes in the plasma concentration of prolactin in intact, pinealectomized, shampinealectomized, ovariectomized and hysterectomized ewes were investigated over a period of 11 months. The concentrations of prolactin were consistently low (<20 ng/ml) during the winter months (short photoperiod) in the intact, sham-pinealectomized, ovariectomized and hysterectomized animals. In contrast, the concentrations of prolactin were consistently raised (> 50 ng/ml) during the summer months (long photoperiod) in the same groups. During the transitional period from winter to summer the concentrations of prolactin were correlated with the reproductive status of the animals. In the pregnant animals, the prolactin concentrations increased from low values during pregnancy to high values at parturition. During lactation, the concentrations of prolactin in these animals remained high, although they were lower than those found subsequently during the summer months when the ewes were no longer lactating. In the non-pregnant ewes (i.e. the ovariectomized and hysterectomized animals), the prolactin concentrations increased more gradually during the transitional period from winter to summer than was the case in the parturient animals. In the pinealectomized ewes, the plasma concentrations of prolactin were raised throughout the year, irrespective of whether the animals were pregnant, lactating or in anoestrus. In these animals, the only occasion when prolactin concentrations were consistently low was during the mid-winter period, although they were also low at times during the period of oestrous activity. It was concluded that the circa-annual pattern of prolactin concentrations in ewes is primarily determined by the photoperiod, and that the pineal gland in the ewe is an important translator of the photoperiod. Parturition and suckling have important, but secondary, influences. Moreover, it was concluded that the secretions from the reproductive tract and the seasonal variations in temperature normally have little influence by themselves on the circa-annual rhythm of prolactin.

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