[An improved paw-pressure test for nociception].
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Acupuncture Therapy↗
Biomedical subjects
F Tang
Publications and source records attributed to F Tang.
Age attenuation in the rat of pituitary-thyroid response to cold.
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Aging↗
Effect of sex and age on serum aldosterone and thyroid hormones in the laboratory rat.
Serum levels of aldosterone, tri-iodo thyronine (T3) and thyroxine (T4) were measured in male and female rats aged 3 months, 12 months, and 18 months. Female rats were found to have higher aldosterone and T3 levels, and lower T4 level than the male. No age-related change was observed in serum aldosterone in either sex. In contrast, serum T4 were found to decrease with age in both sexes while serum T3 showed an age-associated diminution in the male only. Serum testosterone was also measured in the male rats and was found to decline with age.
Aging↗
Alloxan-induced diabetes and the pineal gland: differential effects on the levels of pineal N-acetylserotonin, pineal melatonin, and serum melatonin.
Effects of alloxan treatment on the levels of pineal melatonin, pineal N-acetylserotonin, and serum melatonin were investigated. Male rats were housed under a photoperiod of 12 h light: 12 h darkness and a temperature of 23 +/- 3 degrees C. Three weeks after alloxan (170 mg/kg) or carrier injection (s.c.), the animals were killed at mid-light (1200 h) and mid-dark (2400 h). Pineal and serum indoles were extracted and quantified by radioimmunoassays. It was found that pineal levels of N-acetylserotonin in the diabetic rats were significantly higher (P less than 0.05) than those of the controls. Conversely, pineal and serum levels of melatonin in the control rats were significantly higher (P less than 0.05) than those of the alloxan-induced diabetics. Our results suggest that alloxan-induced diabetes may decrease pineal melatonin synthesis in rats by reducing the activity of hydroxyindole-O-methyltransferase, resulting in a decrease in pineal melatonin secretion.
Acetylserotonin O-Methyltransferase↗
Aging and diurnal rhythms of pineal serotonin, 5-hydroxyindoleacetic acid, norepinephrine, dopamine and serum melatonin in the male rat.
Pineal serotonin (5-HT), 5-hydroxyindoleacetic acid (5-HIAA), norepinephrine (NE) and dopamine (DA) were measured by high-pressure liquid chromatography with electrochemical detection and serum melatonin was measured by radioimmunoassay in rats aged 3 weeks, 8 weeks and 18 months. They were killed either at mid-light or mid-dark of a 12 h light:12 h dark cycle. Diurnal rhythms were observed for 5-HT and 5-HIAA in all ages studied while those for NE and DA were not observed in the 18-month-old animals. Pineal 5-HT and 5-HIAA were higher in 3-week-old rats at mid-dark, and lower at mid-light than in older animals. The pineal content of NE was lower in the 3-week-old rats at mid-dark and mid-light compared with that in the 8-week-old while the DA content was lower at mid-dark. In addition, pineal 5-HT, 5-HIAA, NE and DA were lower in the 18-month-old than in the 8-week-old animals at mid-dark. At mid-dark serum melatonin levels showed an age-related decrease. This study shows that an age-related decrease of pineal 5-HT, 5-HIAA, NE and DA can only be demonstrated at mid-dark and that the age-related decrease of melatonin may not be due to a decrease in sympathetic activity.
Aging↗
Further regression of seminal vesicles of castrated guinea pig by administration of cyproterone acetate.
It has been established that a low level of secretory activity persisted in seminal vesicles of guinea pigs long after castration and that this may be due to a higher extratesticular androgen level in this animal. A RIA study revealed that the normal serum testosterone concentration of the guinea pigs was comparable to that of the rats, but the basal serum testosterone level after castration was ten times higher than rats under a similar condition. It was also shown that cyproterone acetate did not significantly lower the basal serum testosterone concentration in the castrated guinea pigs. The higher basal serum testosterone level is believed to be responsible for the slow and incomplete regression of this gland in the guinea pigs. There was a significant reduction in wet weight of the seminal vesicles after the treatment of castrated guinea pigs with cyproterone acetate. Ultrastructural study showed that there were both qualitative and quantitative changes in the cytoplasmic organelles. The Golgi apparatus further reduced in size and in the number of associated vesicles and vacuoles. There was a marked decrease in the number and size of secretory granules and lysosomes and an increase in the degree of undulation of the basement membrane. Accumulation of lipid droplets and glycogen was commonly observed. All these morphological evidences showed that further regression of the castrated guinea pig seminal vesicles can be achieved by cyproterone acetate treatment.
Animals↗
Age-related and diurnal changes in Met5-Enk-Arg6-Phe7 and Met5-enkephalin contents of pituitary and rat brain structures.
The beta-endorphin, met5-enkephalin-arg6-phe7 (MEAP) and met5-enkephalin (ME) changes related to age and diurnal rhythms were studied in various regions of rat brain and in the pituitary by specific radioimmunoassays. The contents of MEAP, met5-enkephalin and beta-endorphin were higher in the pituitary of old rats (18 months old) than that of young rats (23 days old) while the content of these opioid peptides was higher in the hypothalamus of young rats than in that of old rats. Beta-endorphin was also higher in the striatum of 23 days old rats, but no age-associated changes were observed in the hippocampus, brain stem or cortex. In the diurnal rhythm study, it was found that in the hypothalamus and striatum of the adult rat (2-3 months old), both MEAP and ME contents were higher at mid-dark than at mid-light and that in the intermediate posterior lobe of the pituitary, the ME content was also higher at mid-dark.
Age Factors↗
Immunoactive TSH in the amniotic fluid of the rat.
Amniotic fluid was obtained from 19-day-old rat fetuses by aspiration. Pooled samples measured at 4 different dilutions demonstrated parallelism with standard rat TSH. It is concluded that rat amniotic fluid has TSH immunoactivity.
Amniotic Fluid↗
Negative correlation of age and the levels of pineal melatonin, pineal N-acetylserotonin, and serum melatonin in male rats.
Pineal concentrations of N-acetylserotonin and melatonin and serum levels of melatonin were studied in 3-wk-old (prepubertal), 8-wk-old (adult), and 17-mo-old (senile) male rats. They were adapted to a photoperiod of 12 h light/12 h darkness for a minimum of 1 wk and killed at mid-light and mid-dark. Melatonin and N-acetylserotonin were determined by radioimmunoassay. The concentrations of pineal N-acetylserotonin and melatonin were high in the dark period and low in the light period. Statistical analysis indicated that pineal N-acetylserotonin and melatonin levels per 100 gm body weight declined with age. Similarly, serum melatonin demonstrated diurnal changes in all the age groups studied. In addition, there was a significant reduction in the levels of serum melatonin with age. The parallel patterns of decrease in pineal and serum melatonin levels with age suggest a decline in pineal secretion of melatonin in the older animals.
Age Factors↗
Interaction of cold and starvation in the regulation of plasma corticosterone levels in the male rat.
Plasma corticosterone levels were determined in serial samples obtained from 3 groups of rats: 1) starved, 2) cold-treated (4 degrees C), and 3) starved and cold treated (4 degrees C). Starvation resulted in an increase of plasma corticosterone on the 3rd day and the increase henceafter was linear with the number of days of treatment up to day 13 whereas upon cold exposure, the plasma corticosterone levels first increased on day 1 up to day 3, and then declined on day 9. Cold and starvation in combination led to a greater elevation of plasma corticosterone level than cold or starvation alone. It is concluded that the increase of plasma corticosterone during starvation or cold may be related to altered metabolism under such circumstances, and that the effect of cold and starvation are synergistic and may be mediated by different neural mechanisms.
Animals↗
Serum potassium and aldosterone levels in gossypol-treated rats.
Male rats fed with 30 mg/kg gossypol for 2 or 4 weeks exhibited a decrease in growth but showed no change from control in serum potassium levels. Serum aldosterone levels remained unchanged, but serum testosterone levels were significantly reduced after 4 weeks of treatment. Serum T3 was significantly increased after 2 or 4 weeks of treatment, while serum T4 was not different from control. It is concluded that gossypol at a dose that is sufficient to produce sterility in rats did not change serum potassium and aldosterone levels.
Aldosterone↗
Sex differences in the serum concentrations of testosterone in mice and hamsters during their critical periods of neural sexual differentiation.
Male and female mice and hamsters were decapitated 1-5 days after birth and serum concentrations of testosterone determined by radioimmunoassay. In the two species studied, serum levels of testosterone in male pups were significantly (P less than 0.05) higher than those obtained in female neonates. This lends support to the hypothesis that circulating levels of testosterone play an important role in the process of neural sexual differentiation in rodents. Moreover, the sex differences in serum concentrations of testosterone in neonatal rodents together with the detectable levels of testosterone in female neonates may suggest that androgenization is a dose-dependent phenomenon. Alternatively, they may indicate that a minimum concentration of the steroid must be present for androgenization to occur during the critical period of neural sexual differentiation and that this 'threshold' is exceeded in male but not in female rodents.
Animals↗
Cyclic-AMP-mediated modulation of gene expression in adrenal chromaffin cell cultures.
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8-Bromo Cyclic Adenosine Monophosphate↗
Enkephalin biosynthesis in adrenal medulla. Modulation of proenkephalin mRNA content of cultured chromaffin cells by 8-bromo-adenosine 3',5'-monophosphate.
Incubation of primary cultures of chromaffin cells from bovine adrenal medulla with 8-bromo-adenosine 3',5'-monophosphate (8-Br-cyclic AMP) resulted in an increase in proenkephalin mRNA content. The mRNA that increased was detected by hybridization analysis using a cDNA probe and migrated with an apparent size of approximately 1400 bases. The increase in proenkephalin mRNA following 8-Br-cyclic AMP treatment was apparent in 12 hr and continued over 2 days. Corresponding changes were detected in enkephalin-like immunoreactivity but with a 24-hr lag: the cellular content increased significantly after 2 days of treatment and continued to rise over the next 2 days, whereas changes in the amount released to the medium followed the same time course. Dose-response curves for the increase in the content of proenkephalin mRNA and of enkephalin-containing peptides were essentially identical. Chromatographic characterization of the enkephalin-like peptides demonstrated that 8-Br-cyclic AMP increased both the high molecular weight fraction and the low molecular weight fraction, which was shown by high-pressure liquid chromatography to contain Met5-enkephalin, Leu5-enkephalin, and Met5-enkephalin-Arg6-Phe7. Previous results in chromaffin cells have demonstrated that the synthesis of tyrosine hydroxylase is also regulated by cyclic AMP, with a similar time course. These results therefore suggest the possibility of coordinate regulation by cyclic AMP of the expression of the cotransmitters, catecholamines and enkephalin peptides, in the adrenal medulla.
8-Bromo Cyclic Adenosine Monophosphate↗
Increase of proenkephalin mRNA and enkephalin content of rat striatum after daily injection of haloperidol for 2 to 3 weeks.
Proenkephalin mRNA has been detected in striatum, hypothalamus, cortex, cerebellum, hippocampus, midbrain, and brain stem of rat by RNA ("Northern") blot analysis using a 918-base-pair DNA hybridization probe complementary to proenkephalin mRNA [Comb, M., Seeburg, P. H., Adelman, J., Eiden, L. & Herbert, E. (1982) Nature (London) 295, 663-666]. The size of the mRNA species in all brain regions is approximately 1,400 bases, and it was found to be comparable with that of bovine adrenal medulla and human pheochromocytoma. The data were quantified by densitometric scanning of the autoradiograms: the area under the peak is proportional to the amount of standard proenkephalin mRNA from bovine adrenal medulla. The relative content of proenkephalin mRNA in the various brain regions correlates generally with the content of [Met5]enkephalin-like immunoactivity of these regions. Rats receiving daily intraperitoneal injection of haloperidol (1 or 2 mg/kg) show a fourfold increase of proenkephalin mRNA content in striatum but not other brain regions. In agreement with previous reports, [Met5]enkephalin-like immunoactivity increased twofold in striatum.
Animals↗
Effect of N-acetylserotonin on the serum level of thyroid-stimulating hormone in the male rat.
The effect of N-acetylserotonin (NAS) on serum levels of thyroid-stimulating hormone (TSH) in the male rat was investigated. In the first experiment, NAS and carrier were injected intraperitoneally into rats. The animals were sacrificed 30 and 60 min after injection. It was found that NAS (100 micrograms/rat) significantly depressed serum TSH 60 Min after injection when compared with saline-injected controls. In another experiment in which samples were obtained from rats at 0, 30, 60, 90 and 120 min after injection, significant decrease in serum TSH was observed at all time intervals after NAS (100 micrograms/rat) injection while no such difference was observed in the saline-injected groups. It is suggested that NAS may exert an inhibitory effect on TSH secretion.
Animals↗
Inhibition of catechol-O-methyltransferase by gossypol: the effect of plasma proteins.
Catechol-O-methyltransferase (COMT) is a key enzyme in the metabolism of catecholamines. As gossypol, a recent male contraceptive, has been reported to inhibit some respiratory enzymes in vitro, we have studied its effect on rat liver COMT activity. Varying concentrations of gossypol acetic acid were incubated with 3H-methyl-S-adenosyl-methionine, COMT, a different concentrations of norepinephrine. It was found that addition of gossypol into the incubation medium greatly depressed COMT activity, with an I50 of 0.01 mM. A series of inhibitory curves constructed from using different concentrations of the substrate suggested that the inhibition was non-competitive. Addition of blood serum or BSA significantly reduced the inhibitory effect of gossypol. We concluded that gossypol may markedly decrease COMT activity through non-competitive inhibition. Since various organs of the rat have been shown to accumulate gossypol, ingestion of gossypol for the purpose of fertility control may have important effect on the metabolism of catecholamine.
Animals↗
Some age-related changes in pituitary-adrenal function in the male laboratory rat.
Changes in the pituitary-adrenal axis have been investigated as a function of age (2 1/2 to 26 mo) in the male laboratory rat (CFY-Sprague Dawley). Ether stress was used to challenge the pituitary-adrenal axis and blood samples (peripheral and adrenal venous effluent) taken for measurement of corticosterone using the competitive protein-binding assay and ACTH by the increase in corticosteroidogenesis in isolated rat adrenal cells. The results show that there was an increase of basal ACTH levels with increase in age which might be correlated with the degenerative changes in the adrenal cortex at old age. No age difference was observed in the 2 1/2-min stress levels. However, 15-min stress resulted in a further increment of ACTH levels, which was not found in old animals. No age-related differences in the basal and stress levels of corticosterone was observed, and, hence, adrenocortical function would seem not to be impaired in old age.
Adrenal Glands↗