The effects of central nervous system administration of morphine on secretion of luteinizing horm... more The effects of central nervous system administration of morphine on secretion of luteinizing hormone (LH), follicle-stimulating hormone, and prolactin were investigated in ovariectomized gilts stereotaxically implanted with lateral ventricular cannulas. In Experiment 1, mean serum LH and follicle-stimulating hormone concentrations and serum LH pulse frequency were unaffected by artificial cerebrospinal fluid administration (P greater than 0.1), but decreased (P less than 0.01) in 8 of 11 gilts when 500 micrograms of morphine were given 3 hr later. Serum LH pulse amplitude was unaffected (P greater than 0.1) by cerebrospinal fluid or morphine injection. In Experiment 2, luteinizing hormone concentrations decreased (P less than 0.0001) and prolactin concentrations increased (P less than 0.0001), but follicle-stimulating hormone concentrations did not change (P greater than 0.1) after 500 micrograms of morphine. Gonadotropin responses to 10 micrograms of gonadotropin-releasing hormone, given 2 hr after intraventricular injection, were similar (P greater than 0.1) for morphine- and cerebrospinal fluid-treated gilts. These results indicate that morphine inhibits LH secretion at the level of the central nervous system, and are consistent with the concept that endogenous opioid peptides participate in the regulation of gonadotropin and prolactin release in pigs.
... in subcutaneous fat thickness (Fig. 1). Moreover, plasma glucose and serum insulin concentrat... more ... in subcutaneous fat thickness (Fig. 1). Moreover, plasma glucose and serum insulin concentrations were lower in fasted ani-mals compared to fed controls (Barb et al., un-published data). Dyer et al. (1 997) reported that in ...
Two experiments were conducted with laying hens fed a corn-soy basal diet or diets containing fis... more Two experiments were conducted with laying hens fed a corn-soy basal diet or diets containing fish meal, distillers dried grains with solubles (DDGS) or torula yeast formulated to be isocaloric and isonitrogenous with the basal diet. One half of the hens were kept at a temperature range of 13-24 degrees and the other half at 24-35 degrees for 49 days in experiment 2. Liver lipid content was significantly lower in hens fed DDGS (experiment 1) and DDGS or fish meal (experiment 2) than in hens fed the corn-soy basal diet, but it was not influenced by environmental temperature. Feeding DDGS or fish meal reduced lipoprotein lipase activity in adipose tissue. High temperature reduced plasma estradiol level but not thyroid hormone levels. Plasma estradiol in the hens fed DDGS or fish meal (experiment 1) and DDGS, fish meal or torula yeast (experiment 2) an plasma thyroxine and triiodothyronine in hens fed the DDGS or fish meal at 24-35 degrees in experiment 2 were significantly lower than that of hens fed the corn-soy basal diet. Significant correlations were observed between liver lipid content and plasma estradiol or thyroxine concentrations. These findings show that plasma estrogen and thyroxine levels were influenced by diet composition and that these hormones have a close relation to induction of fatty livers in laying hens.
Transition from the fed to fasted state occurs more rapidly in prepubertal pigs than in mature pi... more Transition from the fed to fasted state occurs more rapidly in prepubertal pigs than in mature pigs. Insulin-like growth factor I (IGF-I), leptin and specific metabolites, such as glucose and free fatty acids (FFA), play a role in signalling metabolic status to the brain-pituitary axis. High serum concentrations of FFA or glucose suppressed the growth hormone (GH) response to GH releasing hormone (GHRH), whereas glucose inhibited and FFA enhanced pituitary LH response to GnRH. The site of action of FFA and glucose on LH and GH secretion is at the pituitary cell. In cultured pig pituitary cells, IGF-I suppressed the GH response to GHRH and enhanced basal LH secretion. However, intracerebroventricular injection of IGF-I failed to affect LH or GH secretion in prepubertal gilts. Acute fasting suppressed leptin secretion without affecting LH or GH secretion. Metabolic fuel restriction by decreasing glucose availability increased GH secretion, but decreased LH secretion in prepubertal gilts. However, serum leptin concentrations were unchanged. Thus, the effects of acute energy deprivation on LH and GH secretion are independent of changes in leptin secretion. Serum leptin concentrations, hypothalamic leptin receptor mRNA and oestrogen-induced leptin gene expression in fat increased with age and adiposity in pigs. This increase occurred at the time of expected puberty in intact pigs. An intracerebroventricular injection of leptin suppressed feed intake, but stimulated GH secretion in prepubertal gilts. Leptin stimulated GnRH release from hypothalamic tissue in vitro. These results identify putative signals that link metabolic status and neuroendocrine control of appetite, growth and reproduction and have implications for nutrition-related human health problems due to high fat diets.
The effect of prostaglandin F2 alpha (PGF2 alpha) on luteinizing hormone (LH) receptors, weight a... more The effect of prostaglandin F2 alpha (PGF2 alpha) on luteinizing hormone (LH) receptors, weight and progesterone content of corpora lutea (CL), and serum progesterone concentrations was studied in gilts. Fifteen gilts were hysterectomized between Days 9 to 11 of the estrous cycle. Twelve gilts were injected i.m. with 10 mg of PGF2 alpha and 3 with saline on Day 20. Ovaries were surgically removed from each of 3 gilts at 4, 8, 12 and 24 h following PGF2 alpha treatment and from the 3 control gilts 12 h following saline injection. Jugular blood samples for progesterone analysis were collected from all gilts at 0, 2 and 4 h following treatment and at 8, 12 and 24 h for gilts from which ovaries were removed at 8, 12 and 24 h, respectively. Mean serum progesterone and CL progesterone concentrations decreased within 4 h after PGF2 alpha treatment (P less than 0.05) and remained low through 24 h after treatment. The number of unoccupied LH receptors decreased by 4 h (P less than 0.05) and this trend continued through 24 h. There were no differences in luteal weight or affinity of unoccupied LH receptors of luteal tissue at 4, 8 12 and 24 h after PGF2 alpha when compared to luteal tissue from controls. These data indicate that during PGF2 alpha-induced luteolysis in the pig, luteal progesterone, serum progesterone concentrations and the number of LH receptors decrease simultaneously.
Nutritional signals are detected by the central nervous system (CNS) and translated by the neuroe... more Nutritional signals are detected by the central nervous system (CNS) and translated by the neuroendocrine system into signals that alter secretion of LH and growth hormone (GH). Furthermore, these signals directly affect the activity of the pituitary gland independently of CNS input. Insulin-like growth factor I (IGF-I), insulin, leptin and specific metabolites, such as glucose and free fatty acids (FFA), are potential signals of the metabolic status to the brain-pituitary axis. Intravenous injection of a lipid emulsion or glucose suppressed the GH and LH response to GH releasing hormone (GHRH) and GnRH, respectively. Insulin and IGF-I regulation of LH and GH secretion occur at the pituitary gland. Feed deprivation for 24 h suppressed leptin secretion without affecting LH or GH secretion, whereas central administration of leptin resulted in a decrease in feed intake and an increase in GH secretion. Oestrogen-induced leptin gene expression in adipose tissue increased with age and adiposity in pigs. Leptin stimulated GnRH release from hypothalamic tissue in vitro. These results identify putative signals that link metabolic status and neuroendocrine control of growth and reproduction by altering endocrine function during periods of fasting, feed restriction and lactation.
The effects of central nervous system administration of morphine on secretion of luteinizing horm... more The effects of central nervous system administration of morphine on secretion of luteinizing hormone (LH), follicle-stimulating hormone, and prolactin were investigated in ovariectomized gilts stereotaxically implanted with lateral ventricular cannulas. In Experiment 1, mean serum LH and follicle-stimulating hormone concentrations and serum LH pulse frequency were unaffected by artificial cerebrospinal fluid administration (P greater than 0.1), but decreased (P less than 0.01) in 8 of 11 gilts when 500 micrograms of morphine were given 3 hr later. Serum LH pulse amplitude was unaffected (P greater than 0.1) by cerebrospinal fluid or morphine injection. In Experiment 2, luteinizing hormone concentrations decreased (P less than 0.0001) and prolactin concentrations increased (P less than 0.0001), but follicle-stimulating hormone concentrations did not change (P greater than 0.1) after 500 micrograms of morphine. Gonadotropin responses to 10 micrograms of gonadotropin-releasing hormone, given 2 hr after intraventricular injection, were similar (P greater than 0.1) for morphine- and cerebrospinal fluid-treated gilts. These results indicate that morphine inhibits LH secretion at the level of the central nervous system, and are consistent with the concept that endogenous opioid peptides participate in the regulation of gonadotropin and prolactin release in pigs.
... in subcutaneous fat thickness (Fig. 1). Moreover, plasma glucose and serum insulin concentrat... more ... in subcutaneous fat thickness (Fig. 1). Moreover, plasma glucose and serum insulin concentrations were lower in fasted ani-mals compared to fed controls (Barb et al., un-published data). Dyer et al. (1 997) reported that in ...
Two experiments were conducted with laying hens fed a corn-soy basal diet or diets containing fis... more Two experiments were conducted with laying hens fed a corn-soy basal diet or diets containing fish meal, distillers dried grains with solubles (DDGS) or torula yeast formulated to be isocaloric and isonitrogenous with the basal diet. One half of the hens were kept at a temperature range of 13-24 degrees and the other half at 24-35 degrees for 49 days in experiment 2. Liver lipid content was significantly lower in hens fed DDGS (experiment 1) and DDGS or fish meal (experiment 2) than in hens fed the corn-soy basal diet, but it was not influenced by environmental temperature. Feeding DDGS or fish meal reduced lipoprotein lipase activity in adipose tissue. High temperature reduced plasma estradiol level but not thyroid hormone levels. Plasma estradiol in the hens fed DDGS or fish meal (experiment 1) and DDGS, fish meal or torula yeast (experiment 2) an plasma thyroxine and triiodothyronine in hens fed the DDGS or fish meal at 24-35 degrees in experiment 2 were significantly lower than that of hens fed the corn-soy basal diet. Significant correlations were observed between liver lipid content and plasma estradiol or thyroxine concentrations. These findings show that plasma estrogen and thyroxine levels were influenced by diet composition and that these hormones have a close relation to induction of fatty livers in laying hens.
Transition from the fed to fasted state occurs more rapidly in prepubertal pigs than in mature pi... more Transition from the fed to fasted state occurs more rapidly in prepubertal pigs than in mature pigs. Insulin-like growth factor I (IGF-I), leptin and specific metabolites, such as glucose and free fatty acids (FFA), play a role in signalling metabolic status to the brain-pituitary axis. High serum concentrations of FFA or glucose suppressed the growth hormone (GH) response to GH releasing hormone (GHRH), whereas glucose inhibited and FFA enhanced pituitary LH response to GnRH. The site of action of FFA and glucose on LH and GH secretion is at the pituitary cell. In cultured pig pituitary cells, IGF-I suppressed the GH response to GHRH and enhanced basal LH secretion. However, intracerebroventricular injection of IGF-I failed to affect LH or GH secretion in prepubertal gilts. Acute fasting suppressed leptin secretion without affecting LH or GH secretion. Metabolic fuel restriction by decreasing glucose availability increased GH secretion, but decreased LH secretion in prepubertal gilts. However, serum leptin concentrations were unchanged. Thus, the effects of acute energy deprivation on LH and GH secretion are independent of changes in leptin secretion. Serum leptin concentrations, hypothalamic leptin receptor mRNA and oestrogen-induced leptin gene expression in fat increased with age and adiposity in pigs. This increase occurred at the time of expected puberty in intact pigs. An intracerebroventricular injection of leptin suppressed feed intake, but stimulated GH secretion in prepubertal gilts. Leptin stimulated GnRH release from hypothalamic tissue in vitro. These results identify putative signals that link metabolic status and neuroendocrine control of appetite, growth and reproduction and have implications for nutrition-related human health problems due to high fat diets.
The effect of prostaglandin F2 alpha (PGF2 alpha) on luteinizing hormone (LH) receptors, weight a... more The effect of prostaglandin F2 alpha (PGF2 alpha) on luteinizing hormone (LH) receptors, weight and progesterone content of corpora lutea (CL), and serum progesterone concentrations was studied in gilts. Fifteen gilts were hysterectomized between Days 9 to 11 of the estrous cycle. Twelve gilts were injected i.m. with 10 mg of PGF2 alpha and 3 with saline on Day 20. Ovaries were surgically removed from each of 3 gilts at 4, 8, 12 and 24 h following PGF2 alpha treatment and from the 3 control gilts 12 h following saline injection. Jugular blood samples for progesterone analysis were collected from all gilts at 0, 2 and 4 h following treatment and at 8, 12 and 24 h for gilts from which ovaries were removed at 8, 12 and 24 h, respectively. Mean serum progesterone and CL progesterone concentrations decreased within 4 h after PGF2 alpha treatment (P less than 0.05) and remained low through 24 h after treatment. The number of unoccupied LH receptors decreased by 4 h (P less than 0.05) and this trend continued through 24 h. There were no differences in luteal weight or affinity of unoccupied LH receptors of luteal tissue at 4, 8 12 and 24 h after PGF2 alpha when compared to luteal tissue from controls. These data indicate that during PGF2 alpha-induced luteolysis in the pig, luteal progesterone, serum progesterone concentrations and the number of LH receptors decrease simultaneously.
Nutritional signals are detected by the central nervous system (CNS) and translated by the neuroe... more Nutritional signals are detected by the central nervous system (CNS) and translated by the neuroendocrine system into signals that alter secretion of LH and growth hormone (GH). Furthermore, these signals directly affect the activity of the pituitary gland independently of CNS input. Insulin-like growth factor I (IGF-I), insulin, leptin and specific metabolites, such as glucose and free fatty acids (FFA), are potential signals of the metabolic status to the brain-pituitary axis. Intravenous injection of a lipid emulsion or glucose suppressed the GH and LH response to GH releasing hormone (GHRH) and GnRH, respectively. Insulin and IGF-I regulation of LH and GH secretion occur at the pituitary gland. Feed deprivation for 24 h suppressed leptin secretion without affecting LH or GH secretion, whereas central administration of leptin resulted in a decrease in feed intake and an increase in GH secretion. Oestrogen-induced leptin gene expression in adipose tissue increased with age and adiposity in pigs. Leptin stimulated GnRH release from hypothalamic tissue in vitro. These results identify putative signals that link metabolic status and neuroendocrine control of growth and reproduction by altering endocrine function during periods of fasting, feed restriction and lactation.
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