Core temperature in the female rat: effect of pinealectomy or altered lighting

1976 ◽  
Vol 231 (2) ◽  
pp. 355-360 ◽  
Author(s):  
F Spencer ◽  
HW Shirer ◽  
JM Yochim
Keyword(s):  
Core Temperature ◽  
Continuous Light ◽  
Mature Female ◽  
Female Rats ◽  
Female Rat ◽  
Light Phase ◽  
Continuous Darkness ◽  
Temperature Rhythm ◽  
Two Component ◽  
Lighting Regimen

Radiotelemetry of core temperature in unrestrained, mature female rats revealed the existence of a 24-h rhythm that was bimodal. The principal peak occurred during the night under control conditions of 14 h light and 10 h darkness, and a less pronounced, secondary peak occurred 3-4 h after the onset of the light phase. Shifts in the phase of the photoperiod or alteration of the proportion of light per day revealed that the temperature rhythm was entrained by light, but that the two component peaks were governed by different aspects of the lighting regimen. Exposure of rats to continuous darkness, continuous light, or to a 20-h photoperiod revealed that the primary rhythm was endogenous, entrained by circadian photoperiods only, whereas the secondary rhythm was exogenous, requiring a circadian light/dark rhythm. A relationship between mean core temperature and ttion pressure, end-systolic L was constant, despite variations in filling and therefore independent of initial L and delta L; moreover, the L to which the ventricle shortened was determined by the course of the systolic force L-relation. Thus, irrespective of loading, delta L occurs within the confines of the contractile state-depdendent isovolumic force-L relation and where the latter is equivalent to the end-systolic force-length relation.

Stimulation of food intake and weight gain in mature female rats by bovine prolactin and bovine growth hormone

1993 ◽  
Vol 264 (6) ◽  
pp. E986-E992 ◽  
Author(s):  
J. C. Byatt ◽  
N. R. Staten ◽  
W. J. Salsgiver ◽  
J. G. Kostelc ◽  
R. J. Collier
Keyword(s):  
Growth Hormone ◽  
Body Weight ◽  
Weight Gain ◽  
Food Intake ◽  
Body Weight Gain ◽  
Mature Female ◽  
Female Rats ◽  
Bovine Growth Hormone ◽  
Female Rat ◽  
Moisture Percentage

Recombinant bovine prolactin (rbPRL) or bovine growth hormone (rbGH) was administered to mature female rats (10/treatment group) by daily subcutaneous injection for 10 days. Doses ranged from 7 to 5,000 micrograms/day (0.03-24 mg/kg body wt). Both rbPRL and rbGH increased body weight gain and food intake, but these parameters were increased at lower doses of rbPRL (7-63 micrograms/day) than rbGH (> 190 micrograms/day). Weight gain and food intake were maximally stimulated by 190 micrograms/day rbPRL, whereas maximal increased weight gain was obtained with the highest dose of rbGH (5,000 micrograms/day). Total carcass protein was increased by both hormones; however, protein as a percentage of body weight was unchanged. Similarly, neither rbPRL nor rbGH changed the percentage of carcass moisture. Percentage of body fat was increased by rbPRL but was decreased by rbGH. Weight of the gastrointestinal tract and kidneys was increased by both hormones, but increases were in proportion to body weight gain. These data confirm that ungulate prolactin is a hyperphagic agent in the female rat. In addition, they suggest that, while prolactin stimulates growth in mature female rats, this growth is probably not via a somatogenic mechanism.

Melatonin administration entrains female rat activity rhythms in constant darkness but not in constant light

1988 ◽  
Vol 255 (2) ◽  
pp. R237-R242
Author(s):  
E. M. Thomas ◽  
S. M. Armstrong
Keyword(s):  
Estrous Cycle ◽  
Activity Rhythm ◽  
Onset Time ◽  
Circadian System ◽  
Female Rats ◽  
Male Rats ◽  
Constant Darkness ◽  
Female Rat ◽  
Continuous Darkness ◽  
Activity Rhythms

In female rats the luteinizing hormone (LH) is timed by the circadian system and is followed by a display of intense, estrogen-induced running behavior. This proestrous running on the night of ovulation can be used as a marker of the estrous cycle. Entrainment of the mammalian circadian system by exogenous melatonin (MT) has been demonstrated only in the activity rhythms of male rats. The present experiments were designed to study the effect of daily MT injections on activity rhythms and proestrous running of female rats in 1) continuous dim white light (LL) and 2) continuous darkness (DD). In LL, MT injections (50 micrograms/kg or 1 mg/kg) had no discernible effect on activity rhythms. In DD, four of the six MT-treated rats (100 micrograms/kg) entrained to the injection, and a fifth animal showed phase advances in its activity rhythm when onset of activity passed through injection time. The sixth animal was not injected with MT at activity onset time. None of the six control animals showed either effect. MT had no effect on the length of the estrous cycle. Thus MT injections can entrain circadian rhythms of activity and proestrous running in female rats in DD but not in LL.

OSTEOPOROSIS AFTER OOPHORECTOMY IN THE MATURE FEMALE RAT AND THE EFFECT OF OESTROGEN AND/OR PROGESTOGEN REPLACEMENT THERAPY IN ITS PREVENTION

1972 ◽  
Vol 55 (1) ◽  
pp. 79-87 ◽  
Author(s):  
J. M. AITKEN ◽  
E. ARMSTRONG ◽  
J. B. ANDERSON
Keyword(s):  
Replacement Therapy ◽  
Mineral Content ◽  
Unit Length ◽  
Hormone Replacement ◽  
Mature Female ◽  
Relative Increase ◽  
Female Rats ◽  
Female Rat ◽  
New Bone Formation ◽  
Femoral Morphology

SUMMARY Fifty-two mature female rats on a controlled diet were studied to compare the effects of oophorectomy, and hormone replacement therapy after oophorectomy, on femoral morphology and mineral content. Oophorectomy was followed by the development of osteoporosis after 11 months of observation. This was characterized by a reduction in ash per unit length of bone and a diminution of mid-shaft femoral cortical width. The administration of a progestogen (9 μg ethynodiol diacetate/rat/day) for 10 months after oophorectomy prevented the reduction in ash per unit length from occurring, whereas an oestrogen (0·9 μg mestranol/rat/day) had no significant effect on either parameter of osteoporosis. The progestogen appeared to produce this effect by a relative increase in periosteal new bone formation at the expense of increased loss of bone from the endosteal surface.

Change from beta- to alpha-adrenergic glycogenolysis induced by corticosteroids in female rat liver

1997 ◽  
Vol 273 (1) ◽  
pp. R153-R160
Author(s):  
M. Moriyama ◽  
Y. Nakanishi ◽  
S. Tsuyama ◽  
Y. Kannan ◽  
M. Ohta ◽  
...  
Keyword(s):  
Glucose Production ◽  
Plasma Corticosterone ◽  
Mature Female ◽  
Female Rats ◽  
Male Rats ◽  
Female Rat ◽  
Circadian Variations ◽  
Male And Female ◽  
Male And Female Rats ◽  
The Difference

The conversion of beta- to alpha-adrenergic glycogenolysis by corticosteroids was studied in perfused livers of mature female rats. Isoproterenol stimulated glucose production more effectively in female rats than in male rats, but the difference in its stimulatory effect disappeared in adrenalectomized (ADX) rats, whereas it remained in adrenodemedulated rats. When ADX female rats were treated with dexamethasone sulfate, alpha-responses increased and beta-responses decreased, depending on the concentration of dexamethasone sulfate. The treatment of female rats with 1.5 mg/kg dexamethasone sulfate changed the levels of the alpha- and beta-responses to those observed in male rats, and the changes were associated with changes in the number of receptors. Although periodicity of changes in plasma corticosterone levels was observed in both male and female rats, the extent of circadian variations was significantly lower in female rats during the estrous cycle than in male rats. The variations in plasma corticosterone levels and in both alpha- and beta-responses after ovariectomy approached those in male rats. The results suggest that the level of plasma corticosterone might play an important role in the regulation of the relative levels of alpha- and beta-adrenergic responses in female rats.

Induction of prolactin receptors in the liver is more closely related to the growth-promoting than to the lactogenic potency of peptides

1987 ◽  
Vol 114 (3) ◽  
pp. 350-356 ◽  
Author(s):  
G. Norstedt ◽  
B. Husman ◽  
A. Mode ◽  
P. Eneroth ◽  
U.J. Lewis ◽  
...  
Keyword(s):  
Time Course ◽  
Mature Female ◽  
Female Rats ◽  
Male Rats ◽  
Female Rat ◽  
Hypophysectomized Rats ◽  
Liver Membranes ◽  
Growth Promoting ◽  
Rat Livers

Abstract. The sex differentiated binding 125I-human prolactin (PRL) to rat liver membranes was studied and the present results extend our previous studies on induction of hepatic PRL receptors by growth hormone (GH). In prepubertal female rats, PRL receptor levels are low compared with those in mature female rat livers. Infusion of hGH during one week to 17-day-old female rats resulted in a receptor level typical of adult female rats. The time course of receptor disappearance in male rats treated with hGH was also studied. When the receptor-inducing hormone was removed, receptor levels in hGH-treated male rats returned to the normal level characteristic of male rats after approximately 96 h. The specificity of various GH-like and PRL-like hormones in PRL receptor induction was studied in hypophysectomized rats. The PRL-like hormones were identified by measuring their potency to displace 125I-hPRL from a receptor preparation obtained from female rat livers, and the GH-like hormones were identified by their potency to increase body weight in hypophysectomized rats. Using similar doses of hormones it was found that in vivo administration of growth-promoting peptides (rGH, hGH, bGH) induced PRL receptors, whereas lactogenic hormones (rPRL, hPL) had a very small or no effect on PRL receptor induction. This suggests that binding to a type of GH receptor is the first step in PRL receptor induction.

Hindlimb unloading has a greater effect on cortical compared with cancellous bone in mature female rats

2003 ◽  
Vol 94 (2) ◽  
pp. 642-650 ◽  
Author(s):  
Matthew R. Allen ◽  
Susan A. Bloomfield
Keyword(s):  
Cortical Bone ◽  
Bone Mineral ◽  
Cancellous Bone ◽  
Proximal Tibia ◽  
Mature Female ◽  
Hindlimb Unloading ◽  
Female Rats ◽  
Female Rat ◽  
Mineral Density ◽  
Tibia Bone

This study was designed to determine the effects of 28 days of hindlimb unloading (HU) on the mature female rat skeleton. In vivo proximal tibia bone mineral density and geometry of HU and cage control (CC) rats were measured with peripheral quantitative computed tomography (pQCT) on days 0and 28. Postmortem pQCT, histomorphometry, and mechanical testing were performed on tibiae and femora. After 28 days, HU animals had significantly higher daily food consumption (+39%) and lower serum estradiol levels (−49%, P = 0.079) compared with CC. Proximal tibia bone mineral content and cortical bone area significantly declined over 28 days in HU animals (−4.0 and 4.8%, respectively), whereas total and cancellous bone mineral densities were unchanged. HU animals had lower cortical bone formation rates and mineralizing surface at tibial midshaft, whereas differences in similar properties were not detected in cancellous bone of the distal femur. These results suggest that cortical bone, rather than cancellous bone, is more prominently affected by unloading in skeletally mature retired breeder female rats.

THE EFFECT OF PROGESTERONE ON THE QUANTITY AND DISTRIBUTION OF BODY FAT IN THE FEMALE RAT

1964 ◽  
Vol 46 (3) ◽  
pp. 379-386 ◽  
Author(s):  
F. Galletti ◽  
A. Klopper
Keyword(s):  
Body Fat ◽  
Adult Female ◽  
Mature Female ◽  
Fat Deposition ◽  
Female Rats ◽  
Weight Increase ◽  
Female Rat ◽  
Additional Weight ◽  
Extra Weight

ABSTRACT Mature female rats given 3.14 mg progesterone daily for 20 days gained more weight than controls. Carcase analysis showed this extra weight to be due to an increased fat deposition. Immature females did not gain weight faster than controls and showed no enhanced fat deposition. When adult female rats were castrated they gained weight faster than intact animals but treating such castrated animals with progesterone did not cause an additional weight increase.

Adrenergic Regulation of “Synaptic” Ribbon Populations in the Rat Pinealocyte

1980 ◽  
Vol 38 ◽  
pp. 512-513
Author(s):  
T. S. King ◽  
T. M. Holt ◽  
W. J. Dougherty
Keyword(s):  
Continuous Light ◽  
Neonatal Rat ◽  
Synaptic Ribbons ◽  
Female Rat ◽  
Synaptic Ribbon ◽  
Continuous Darkness ◽  
Adrenergic Regulation ◽  
Morphometric Analyses ◽  
Adrenergic Mechanism ◽  
Cervical Ganglia

“Synaptic” ribbons (SR) are functionally enigmatic organelles characteristic of a number of neuroreceptor cells including the mammalian pinealocyte. SR appear to be responsive to a number of physiological stimuli, both normal and experimental. During the first days after birth, an initial, non-rhythmic rise in SR numbers nocturnally and diurnally (King and Dougherty, 1980) appeared to reflect a similar non-rhythmic increase in norepinephrine (NE) content in the neonatal rat (Moore and Smith, 1969). During the second postnatal week, both SR numbers (fig. 1) and NE content developed circadian rhythms, being high nocturnally and low diurnally. Our observations suggested that the circadian rhythm in SR numbers is regulated or influenced directly by an adrenergic mechanism via the superior cervical ganglia. Morphometric analyses of SR populations in female rat pinealocytes were performed to determine changes related to (1) continuous light, (2) continuous darkness, (3) isoproterenol, isoproterenol-propranolol and isoproterenol-phentolamine administration and (4) bilateral superior cervical ganglionectomy (SCGx) and SCGx-isoproterenol administration. Comparison of this data to that obtained from SR populations during the course of so-called “normal” 12 hours light:12 hours darkness cycles was made (fig. 2).

THE MODIFICATION OF LACTATION IN THE ALBINO RAT BY ENVIRONMENTAL FACTORS

1951 ◽  
Vol 7 (3) ◽  
pp. 280-287 ◽  
Author(s):  
J. T. EAYRS
Keyword(s):  
Food Intake ◽  
Mature Female ◽  
Female Rats ◽  
Total Darkness ◽  
Female Rat ◽  
Newborn Rats ◽  
Albino Rat ◽  
Natural Lighting ◽  
Daily Food ◽  
The Mean

The growth and food consumption of mature female rats and of lactating rats and their litters reared under various conditions of illumination have been measured. Mature female rats grew less when kept in the dark than in the light. Newborn rats reared in total darkness by does which were allowed in the light for only 1½ hr. daily grew less during the first 18 days of life than their litter-mate controls. Newborn rats reared under natural lighting by does with both eyes removed did not grow as well as litter-mates reared by does with one eye removed. The mean weight of food eaten daily by mature female rats when in the dark did not differ significantly from that eaten when in natural lighting. Lactating does and their litters confined in total darkness and bilaterally enucleated does ate significantly less food than their controls. The reduction in food intake was apparent by the third day after parturition. On the other hand, when the doe received 1½ hr. illumination daily, the daily food intake of the experimental litters was depressed only during the latter part of lactation. The discussion suggests a possible way in which the effects of darkness on the normal adult female rat and on the lactating rat may be interrelated.

Stimulation of body weight gain of the mature female rat by bovine GH and bovine placental lactogen

1991 ◽  
Vol 130 (1) ◽  
pp. 11-19 ◽  
Author(s):  
J. C. Byatt ◽  
N. R. Staten ◽  
J. J. Schmuke ◽  
F. C. Buonomo ◽  
S. S. Galosy ◽  
...  
Keyword(s):  
Weight Gain ◽  
Body Weight Gain ◽  
Mature Female ◽  
Female Rats ◽  
Placental Lactogen ◽  
Feed Consumption ◽  
Female Rat ◽  
Binding Studies ◽  
Response Curves ◽  
Igf I

ABSTRACT Mature female rats (200 g) were treated for 10 days with either recombinant bovine GH (bGH) or recombinant bovine placental lactogen (bPL) to compare the somatogenic responses elicited by these hormones. The treatments were administered by daily s.c. injection at four dose levels (0·19, 0·56, 1·67 and 5·0 mg/day). Both bGH and bPL stimulated significant increases in weight gain, but the slopes of the dose–response curves were different (P<0·05). Bovine PL was more potent than bGH (P<0·01) at the lowest dose, although there were no differences between treatment groups at the three higher doses. Feed consumption was stimulated more by bPL than bGH at all doses (P<0·001). The concentration of insulin-like growth factor-I (IGF-I) in blood plasma was increased by bGH in a dose-responsive manner and was higher than control at doses of 1·67 and 5 mg/day (P<0·05). Low doses of bPL stimulated increases in IGF-I similar to those with bGH. At the highest dose of bPL, however, there was no concomitant increase in plasma IGF-I. Nevertheless, the growth rate of the animals in this group matched that of the group given the highest dose of bGH. Receptor binding studies indicated that bPL bound to both GH and prolactin receptors. This is consistent with the growth data which suggest that bPL stimulated weight gain through a somatogenic mechanism as well as by another route, possibly mediated by lactogenic receptors. Journal of Endocrinology (1991) 130, 11–19

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