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Biomedical subjects

F Tang

Publications and source records attributed to F Tang.

102 records · Page 6Linked to original sources
PubMed1983

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↗
PubMed1982

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↗
PubMed1978

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↗
PubMedDate not supplied

Age-related changes in the contents of neuropeptides in the rat brain and pituitary.

beta-Endorphin, Leu-enkephalin, Met-enkephalin, substance P, somatostatin, and cholecystokinin were measured in the brain and the pituitary of male Sprague-Dawley rats aged 3 months, 12 months, and 22 months. beta-Endorphin, Met-enkephalin and Leu-enkephalin contents in the neurointermediate lobe, and the enkephalin levels in the anterior lobe of the pituitary increased with age. The increases in contents were both in the day and at night for beta-endorphin and Met-enkephalin. However, the increase for Leu-enkephalin content was in the day only. Hypothalamic beta-endorphin content decreased with age only in the day. beta-Endorphin and Leu-enkephalin contents in the brain stem, and Leu-enkephalin levels contents in the cortex decreased with age at night. Leu-enkephalin in the striatum decreased with age in the day. There was also an age-related decrease for somatostatin and substance P contents in the striatum and the hypothalamus in the day, and in cholecystokinin levels in the hippocampus, and the hypothalamus at night. It is concluded that there are age differences in neuropeptide levels, and that these changes may differ according to diurnal rhythms.

Aging↗
PubMedDate not supplied

Use of dithiodiglycolic acid as a tether for cationic lipids decreases the cytotoxicity and increases transgene expression of plasmid DNA in vitro.

Two major barriers that limit cationic lipids in gene delivery are low transfection efficiency and toxicity. In the present studies, we used dithiodiglycolic acid as a new tether for the polar and hydrophobic domains of a cationic lipid, cholesteryl hemidithiodiglycolyl tris(aminoethyl)amine (CHDTAEA). We compared the transfection activity and toxicity of CHDTAEA with its nondisulfide analogue and cholesteryl N-(dimethylaminoethyl) carbamate (DC-Chol). The liposomes of CHDTAEA had more than 2 orders of magnitude greater transfection activity than DC-Chol in CHO cells and 7 times greater transfection activity in SKnSH cells. CHDTAEA also demonstrated much less toxicity than the other two lipids. Dithiodiglycolic acid may act as an excellent linker in the application of cationic lipid syntheses.

Animals↗
PubMedDate not supplied

Chronic exposure to hypergravity affects thyrotropin-releasing hormone levels in rat brainstem and cerebellum.

In studies to determine the neurochemical mechanisms underlying adaptation to altered gravity we have investigated changes in neuropeptide levels in brainstem, cerebellum, hypothalamus, striatum, hippocampus, and cerebral cortex by radioimmunoassay. Fourteen days of hypergravity (hyperG) exposure resulted in significant increases in thyrotropin-releasing hormone (TRH) content of brainstem and cerebellum, but no changes in levels of other neuropeptides (beta-endorphin, cholecystokinin, met-enkephalin, somatostatin, and substance P) examined in these areas were found, nor were TRH levels significantly changed in any other brain regions investigated. The increase in TRH in brainstem and cerebellum was not seen in animals exposed only to the rotational component of centrifugation, suggesting that this increase was elicited by the alteration in the gravitational environment. The only other neuropeptide affected by chronic hyperG exposure was met-enkephalin, which was significantly decreased in the cerebral cortex. However, this alteration in met-enkephalin was found in both hyperG and rotation control animals and thus may be due to the rotational rather than the hyperG component of centrifugation. Thus it does not appear as if there is a generalized neuropeptide response to chronic hyperG following 2 weeks of exposure. Rather, there is an increase only of TRH and that occurs only in areas of the brain known to be heavily involved with vestibular inputs and motor control (both voluntary and autonomic). These results suggest that TRH may play a role in adaptation to altered gravity as it does in adaptation to altered vestibular input following labyrinthectomy, and in cerebellar and vestibular control of locomotion, as seen in studies of ataxia.

Adaptation, Physiological↗
PubMedDate not supplied

Pituitary contents of beta-endorphin, dynorphin, substance P, cholecystokinin and somatostatin in rats with streptozotocin-induced diabetes.

The effects of streptozotocin-induced diabetes on pituitary neuropeptides were studied. Substance P, dynorphin and beta-endorphin in both pituitary lobes and cholecystokinin and somatostatin in the neurointermediate lobe (NIL) were measured 4 weeks after streptozotocin treatment in adult male rats. There were significant decreases of substance P levels in both the anterior lobe (AL) and NIL, and of cholecystokinin, dynorphin and beta-endorphin in the NIL, whereas the dynorphin content in the AL increased, when values were expressed on a per-lobe basis. On a per-milligram-protein basis, however, only beta-endorphin in the NIL showed a significant decrease, while AL beta-endorphin and dynorphin were increased. Correlated with these changes were a drastic decrease in the serum insulin level and a marked increase in serum glucose and corticosterone levels. All these changes were reversible with insulin treatment. It is suggested that the decrease in NIL contents of neuropeptides demonstrated (except for beta-endorphin) might be due to mechanisms other than a change in synthesis.

Animals↗