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Biomedical subjects

J Wu

Publications and source records attributed to J Wu.

At least 1,567 records · Page 87Linked to original sources
PubMed1984

Enteric neural pathways inhibitory to rabbit duodenal serotonin release.

Previous studies have shown that adrenergic and cholinergic neural pathways mediate duodenal serotonin (5-HT) release from the mucosal surface after a luminal acid stimulus. To examine the overall neural contribution to 5-HT release, we studied the effects of tetrodotoxin (TTX), a nerve-conduction blocker, added to mucosal and/or serosal surfaces of rabbit duodenal mucosa in a modified Ussing chamber at both neutral and acid (pH 5) luminal pH. A specific radioimmunoassay was used to measure 5-HT. TTX (2 X 10(-7) M) increased mucosal 5-HT release significantly at luminal pH 7.4 and 5 when it was added to both mucosal and serosal surfaces (2.7- and 1.9-fold at pH 7.4 and pH 5, respectively; p less than 0.05 for each) or when it was added to the serosal surface only (3.4- and 1.8-fold; p less than 0.02 and p less than 0.01, respectively). TTX added only to the mucosal surface, however, reduced 5-HT release by 48.5% at pH 5 (p less than 0.01) and had no effect at pH 7.4. Since adenosine triphosphate (ATP) and vasoactive intestinal polypeptide are the two proposed mediators of a nonadrenergic, noncholinergic inhibitory neural system, we studied the effects of each on mucosal 5-HT release. While vasoactive intestinal polypeptide had no significant effect at either pH, ATP (10(-7)M) reduced acid-stimulated 5-HT release by approximately 50% (p less than 0.02). We conclude that a nonadrenergic, noncholinergic neural pathway that is inhibitory to mucosal 5-HT release resides primarily on the basal surface of mucosal cells. ATP is the most likely neurotransmitter involved in this response.

Adenosine Triphosphate↗
PubMed1983

Differences in de novo cholesterol synthesis between the intact male and female rat.

Three different isotopes were used to quantify de novo sterologenesis in intact male and female rats. All three substrates (i.e. [14C]acetate, [14C]octanoate, and [3H]water) were incorporated into nonsaponifiable lipids and cholesterol at significantly greater rates in males than in females. Even with cholesterol feeding, male animals synthesized significantly more cholesterol and nonsaponifiable lipids than females. The primary site of this sex difference in sterologenesis is extrahepatic, extraintestinal tissues (e.g. carcass). In the carcass this sex difference is chiefly due to an enhancement of sterol synthesis in the skin of male rats. Cholesterol synthesis is 73% greater and nonsaponifiable lipid synthesis is 85% greater in the skin of males than in females. Moreover, de novo sterologenesis in skin is hormonally dependent. In castrated females, testosterone treatment results in a 2-fold stimulation of skin sterol synthesis compared to that in animals administered estradiol or oil vehicle alone. In castrated males, estradiol treatment caused a 30% reduction in skin cholesterol and nonsaponifiable lipid synthesis compared to that in animals administered testosterone. The effects of sex steroid hormones on skin are, therefore, probably responsible for mediating the observed sex difference in de novo sterol synthesis. Additionally, this study demonstrates that the administration of estradiol and testosterone in physiological doses to castrated animals has no effect on cholesterol or nonsaponifiable lipid synthesis in liver, intestine, or other nondermal tissues.

Animals↗
PubMed1982

Diet and vitamin nutrition of the high esophageal cancer risk population in Linxian, China.

In order to examine the nutritional status of the population of Linxian (in Henan, China) known to be at high risk for esophageal cancer (EC), we analyzed blood samples and conducted 3-day dietary surveys on 3 groups of normal adults, age 40-50, from Henan province. Two groups were from Linxian, where the EC mortality rate is about 138/100,000 (Group C, consisting of volunteers with a family history of EC, and Group NC, consisting of those who did not have a family history of EC). The third group, Group F, was from Fanxian, where the EC mortality rate is about 24/100,000. The average plasma retinol level was found to be about 0.27 micrograms/ml in all 3 groups; about 13%-20% of the individuals had a level less than 0.2 micrograms/ml. The average plasma carotene level of all 3 groups appeared to be adequate, ranging from 0.5-1.0 micrograms/ml. About 23% of the subjects in both Groups C and NC had low (less than 2 micrograms/ml) plasma ascorbate levels; in Group F, 16% had low ascorbate levels. Less than 12% of the individuals in each of the 3 groups had erythrocyte glutathione reductase activation coefficients less than 1.2, indicating a widely occurring riboflavin deficiency. Consumption of alcoholic beverages was not found to be a contributing factor to EC. The results of the present study reveal a deficiency of vitamins in the study populations, but do not indicate that the average nutritional status of the volunteers in Group C was worse than that of Groups NC and F with regard to vitamin A, ascorbate, and riboflavin.

Adult↗
PubMed1981

Demonstration and characterization of opiate inhibition of the striatal adenylate cyclase.

The conditions in which Leu(5)-enkephalin inhibition of striatal adenylate cyclase was observed were defined. It was determined that enkephalin inhibition was dependent on GTP. The apparent K(m) for GTP in opiate inhibition was determined to be 0.5 and 2 micrometer when 0.1 mM- and 0.5 mM-ATP were used as substrate. ITP, but not CTP or UTP, could substitute for GTP in the reaction. Though the addition of monovalent cations-Na+, K+, Li+, Cs+, and choline+--stimulated striatal adenylate cyclase activity, enkephalin inhibition of striatal adenylate cyclase did not require Na+ when theophylline was used as the phosphodiesterase inhibitor. Under optimal conditions, i.e., 20 micrometer-GTP and 100 mM-Na+, Leu(5)-enkephalin inhibited the strial adenylate cyclase activity by 23-27%. When the enkephalin regulation of the cyclase activity was further characterized, it was observed that Leu(5)-enkephalin inhibited the rate of the enzymatic reaction. Kinetic analysis revealed that the opioid peptide decreases V (max) values but not the K(m) values for the substrates Mg2+ and Mg-ATP. Agents such as MnCl(2), NaF, and guanyl-5'-ylimido-diphosphate, which directly activated the adenylate cyclase, antagonized the opiate inhibition. Levorphanol and (-)naloxone were more potent than dextrorphan and (+) naloxone in inhibiting adenylate cyclase and in reversing the enkephalin inhibition, respectively. There were differences in the potencies of various opiate peptides in their inhibition of striatal adenylate cyclase activity, with Met5- > Leu(5)-enkephalin > beta-endorphin. The opiate receptor through which the enkephalin inhibition was observed is most likely delta in nature, since in the presence of either Na+ or K+, the magnitude of the alkaloid inhibition was reduced, whereas the peptide inhibition was either potentiated or not affected.

Adenylyl Cyclase Inhibitors↗
PubMed1981

Microbial transformations of 7,2-dimethylbenz[a]anthracene.

Microbial transformations of 7,12-dimethylbenz[a]anthracene, a carcinogenic polycyclic aromatic hydrocarbon, in cultures of Pseudomonas aeruginosa and Penicillium notatum were studied by high performance liquid chromatographic separation of metabolic fractions followed by gas chromatographic-mass spectrometric analysis of the metabolites. Two methyl-hydroxylated metabolites were identified in each of the incubations. The metabolic activation of the polycyclic aromatic hydrocarbon suggests a possible involvement of microorganisms in environmental carcinogenesis.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1981

Estrogen regulation of follicle-stimulating hormone production in vitro: species variation.

Pituitary cell cultures were used to investigate factors, such as species, sex, and age, which might be associated with differences in FSH regulation by estrogens. 17 beta-Estradiol at 10(-9) M inhibited spontaneous secretion of FSH in sheep, pig, and cow cell cultures (65-95%), had no detectable effect on rabbit cell cultures, and stimulated spontaneous secretion of FSH in rat cell cultures (1.5- to 5-fold). These differential effects of 17 beta-estradiol were not due to changes in cell division; gonadotrophs did not divide in culture, and general cell division was unaffected by 17 beta-estradiol. Differences in 17 beta-estradiol action on FSH secretion were not associated wih age or sex. Spontaneous secretion of FSH from pituitary cell cultures also varied according to species and was ranked: rabbit approximately equal to sheep > pig > rat > cow. Secretion and synthesis of FSH were tightly coupled in at least three of these species. Nonestrogenic steroids, such as androgens, progestins, and corticosterone, exhibited only minor effects on spontaneous secretion of FSH in either male or female sheep cell culture. These results clearly show that estrogens are capable of altering FSH secretion and synthesis differentially in pituitary cell cultures from different species. It is possible that the differences noted in pituitary cell cultures from various species also exist in vivo.

Age Factors↗
PubMed1980

Brain locations controlling the behavioral effects of chronic amphetamine intoxication.

Rats were administered D-amphetamine repeatedly for 4 days. After day 1 of treatment, the amphetamine-induced increases in ambulation, rearing, and stereotyped activity were augmented. However, after 4 days treatment, the rearing and ambulatory responses became attenuated while the stereotyped activities remained augmented. Micro-injection studies revealed that both the augmentation and attenuation of nonstereotyped ambulation were generated from the nucleus accumbens. The augmentation of stereotyped behaviors was generated from the caudate nucleus. Chronically treated animals who were administered 0.7 but not 1.0 mg/kg apomorphine showed augmented behavioral response. Chronic amphetamine treatment significantly decreased (3H) spiroperidol binding in both the nucleus accumbens and caudate nucleus. However, no effect on the DA-stimulated adenyl cyclase activity was observed in either brain region. It is concluded that repeated D-amphetamine administration selectively augments and attenuates D-amphetamine-induced behaviors and that these selective effects are mediated by different dopamine systems.

Adenylyl Cyclases↗
PubMed1980

Radiolabeled adrenergi neuron-blocking agents: adrenomedullary imaging with [131I]iodobenzylguanidine.

The tissue distributions of three radioiodinated neuron-blocking agents have been determined in dogs. Iodine-125-labeled meta- and para-iodobenzylguanidines show a striking affinity for, and retention in, the adrenal medulla. Peak concentrations of the two isomers exceed those of previously reported adrenophilic compounds. High myocardial concentrations were also observed at early time intervals. Images of the dog's adrenal medullae have been obtained with para [131I]iodobenzylguanidine.

3-Iodobenzylguanidine↗
PubMed1978

Haemoglobin A1, blood glucose, and high-density lipoprotein cholesterol in insulin-requiring diabetics.

In forty insulin-requiring diabetics there was a significant correlation between haemoglobin A1 (HbA1) and blood-glucose measured at the same time and mean clinic blood-glucose measured over the previous year. There was no significant correlation between high-density lipoprotein (H.D.L.) cholesterol concentration and HbA1 or blood-glucose. HbA1 is not a good predictor of H.D.L. cholesterol concentration in insulin-requiring diabetics.

Adolescent↗
PubMed1978

Silica gel radioimmunoassay for myelin basic protein.

1. A radioimmunoassay which relies upon the capacity of silica gel to absorb free human basic protein of myelin (BP) is described. 2. Reagents involved in the assay include unlabelled BP, I-BP, and rabbit anti-BP. The assay is performed in excess normal rabbit serum, and uses 3-4% silica gel for absorption of free I-BP. 3. The assay is simple, reproducible and not particularly time-consuming. It is capable of detecting BP at a level of 1-10 or more nanograms in samples containing varying amounts of serum. The assay is thus highly suitable as a routine test in clinical laboratories interested in detecting BP in cerebrospinal fluid in patients with suspected or proven demyelination.

Gels↗