Search PubMed⌕ Search

Biomedical subjects

C Zhang

Publications and source records attributed to C Zhang.

At least 721 records · Page 40Linked to original sources
PubMed1991

Naloxone-sensitive inhibition of nicotinic transmission in the superior cervical ganglion of the cat.

In anesthetized, artificially ventilated cats, pretreated with the muscarinic antagonist scopolamine, the effect of naloxone on the efficacy of nicotinic transmission in the superior cervical ganglion was used as a test of endogenous opioid release by the preganglionic axons. The cervical sympathetic trunk (CST) was split into two bundles. The compound action potential (CAP), evoked by supramaximal low-frequency stimulation (0.25 Hz) of one CST bundle, was recorded from a postganglionic nerve of the superior cervical ganglion. Partial block with hexamethonium was used to reduce the 'safety factor' of nicotinic transmission. A conditioning train (5 Hz, 40 s, supramaximal) to the other CST bundle (heterosynaptic conditioning) inhibited the CAP. At the peak of the inhibition the CAP was attenuated by 51 +/- 4%. Recovery was 90% complete in 201 +/- 28 s. The inhibition was antagonized in a dose-dependent manner by i.v. naloxone with an apparent IC50 of 60 +/- 12 micrograms/kg. The maximum effect obtained with naloxone was an 80% decrease in the magnitude of the inhibition. Magnitude and duration of the heterosynaptic inhibition were related to frequency, duration and intensity of the conditioning train. Naloxone-sensitive inhibition was observed with frequencies of the conditioning train as low as 0.5 Hz. A train (5 Hz, 40 s) to the postganglionic nerves produced a naloxone-insensitive depression of the orthodromic test CAP which was of smaller amplitude and duration than when the conditioning train was applied to the preganglionic axons.(ABSTRACT TRUNCATED AT 250 WORDS)

Action Potentials↗
PubMed1991

PAF-induced bowel necrosis. Effects of vasodilators.

Ischemic bowel necrosis in the rat is produced by injecting platelet-activating factor (PAF) intravenously. Since intestinal hypoperfusion is observed after PAF injection, we hypothesize that mesenteric vasoconstriction is the mechanism of bowel injury. We thus studied the effects of vasodilators in this model. We found that: (1) Phenoxybenzamine, prazosin, ICI 198615 (leukotriene antagonist) and PGE1 counteracted the PAF-induced mesenteric flow reduction and ameliorated the bowel injury. However, phenoxybenzamine and prazosin were relatively ineffective in correcting PAF-induced hypotension, showing that bowel injury can be prevented independently of the hypotensive state. (2) Nitroglycerin failed to prevent bowel injury, although it improved the mesenteric blood flow. Thus, in opposition to our initial hypothesis, correction of the mesenteric flow reduction induced by PAF does not always prevent intestineal necrosis. (3) Only phenoxybenzamine, prazosin, ICI 198615, and PGE1 ameliorated PAF-induced hemoconcentration and bowel injury. This suggests a correlation between vascular injury (expressed by "leaky" vessels and the consequent hemoconcentration) and bowel necrosis. (4) Although both nitroglycerin and hydralazine relax smooth muscle, hydralazine seemed to aggravate bowel necrosis. The mechanism remains unclear.

Alprostadil↗
PubMed1991

Platelet activating factor-induced shock and intestinal necrosis in the rat: role of endogenous platelet-activating factor and effect of saline infusion.

BACKGROUND AND METHODS: The mechanism of ischemic bowel necrosis induced by platelet-activating factor is unclear. Since intestinal hypoperfusion is observed after platelet-activating factor injection, we hypothesized that mesenteric vasoconstriction is the mechanism of bowel injury. The present study investigated the effects of saline infusion on platelet activating factor-induced bowel necrosis and its mechanism. Male Sprague-Dawley rats were divided into four groups: group A consisted of sham-operated rats; group B received platelet-activating factor (1.5 micrograms/kg iv); group C received platelet-activating factor and saline (0.097 mL/min iv); group D received platelet-activating factor and WEB 2086 (platelet-activating factor antagonist). RESULTS: Saline infusion largely reversed platelet activating factor-induced hypotension, hemoconcentration, and reduction of the superior mesenteric arterial blood flow. Saline infusion also ameliorated platelet activating factor-induced bowel injury, although a mild-to-moderate degree of necrosis still developed focally. In addition, saline prevented the platelet activating factor-induced increase in intestinal platelet-activating factor production. Saline also prevented the increase in intestine leukocyte number, as estimated by myeloperoxidase activity. CONCLUSIONS: Saline infusion is an effective treatment for platelet activating factor-induced shock and intestinal necrosis. However, focal bowel injury is still observed, suggesting that other factors besides hemodynamic changes contribute to the development of tissue injury. We also showed that, in vivo, platelet-activating factor stimulates its own synthesis via a positive feedback loop, which could be blocked by intravascular volume expansion with saline.

Animals↗
PubMed1991

Case-control study of cigarette smoking and primary hepatoma in an aflatoxin-endemic region of China: a protective effect.

Aflatoxin is believed to be a major causative agent in the high incidence of primary liver cancer seen in certain regions of the world. In Fujian Province, an aflatoxin-endemic region of China, we compared the cigarette smoking habits of 200 primary hepatoma patients with those of 200 matched nonhepatoma controls. We excluded from our study all individuals with evidence of hepatitis B virus serum antigen and/or alcoholic cirrhosis. Interestingly, two groups of hepatoma patients could be discerned. In patients more than 50 years of age, a significantly higher number of cases of primary hepatoma was found among nonsmokers than smokers (odds ratio = 2.06; 95% confidence interval = 1.32-3.20). In patients less than 50 years of age, this difference was not seen. Previous studies in the rat, mouse and duck had suggested that agents present in cigarette smoke might induce a cytochrome P450-mediated detoxication pathway, leading to protection against aflatoxin-induced primary liver cancer. Our clinical data in the present study are therefore consistent with the previous laboratory animal experiments.

Adult↗
PubMed1991

Isoflurane alters the kinetics of oral cyclosporine.

Cyclosporine is an important immunosuppressive agent often given orally preoperatively to patients undergoing organ transplantation. The aim of the present study was to evaluate the effects of anesthesia on the pharmacokinetics of orally administered cyclosporine. Sixty unanesthetized fasting female Lewis rats were given 25 mg/kg cyclosporine by gastric tube and were then randomized to immediately receive an isoflurane anesthetic (n = 30) or to serve as nonanesthetized controls. At 1, 2, 3, 4, and 6 h after the administration of the cyclosporine, six animals from each group (while still anesthetized for those in the anesthesia group) were killed, and arterial blood and the entire bowel from the esophagogastric junction to the ileocecal junction were removed for measurement of cyclosporine concentrations. A subsequent study with six animals in each group was performed to examine more closely the distribution of cyclosporine in the stomach and small intestine 4 h after the oral dose. In these animals the cyclosporine concentration in the stomach and in five 10-cm-long segments of small bowel was assayed. In all studies of gastrointestinal specimens, the cyclosporine extracted is a combination of that contained in the lumen and the wall. At all times except at 6 h, the blood cyclosporine levels were significantly higher in the control group than in the isoflurane group. Conversely, the amount of cyclosporine in the distal small bowel of control rats was increased as compared with the anesthetized animals. In the animals studied at 4 h, the amount of cyclosporine in the stomach of control rats was significantly lower than that in the anesthetized animals.(ABSTRACT TRUNCATED AT 250 WORDS)

Administration, Oral↗
PubMed1991

Impaired secretion of growth hormone-releasing hormone, growth hormone and IGF-I in elderly men.

The GHRH test and L-dopa test were performed in 12 normal young men (24.1 +/- 1.1 years) and 12 normal elderly men (77.8 +/- 1.4 years) to investigate age-related changes in secretion of GHRH, GH and IGF-I. The basal plasma levels of GHRH and GH were not significantly different in young and elderly men, but the basal plasma level of IGF-I was higher in the young men (159.0 +/- 11.7 vs 86.7 +/- 11.6 micrograms/l). The area under the curve for plasma GH in the GHRH test was less in the elderly group (35.1 +/- 5.9 vs 11.2 +/- 2.1 micrograms.h-1.l-1, p less than 0.001). The AUCs for the plasma GHRH and GH responses in the L-dopa test in young and elderly men were 32.0 +/- 2.7 vs 20.3 +/- 1.8 ng.h-1.l-1 (p less than 0.001), and 21.8 +/- 4.6 vs 5.4 +/- 1.1 micrograms.h-1.l-1 (p less than 0.01), respectively, indicating decreased releases of GHRH and GH in the elderly. Correlations between the AUCs for plasma GHRH and GH responses in L-dopa were found in both groups, but the ratio of the AUCs for GH/GHRH was lower in the elderly group. The elderly group showed a significant correlation between the basal plasma IGF-I level and the AUCs for plasma GH in the GHRH and L-dopa tests. These results suggest that elderly men have a decreased reserve of hypothalamic GHRH, resulting in secondarily impaired GH release, which may lead to a lower level of IGF-I than in young men.

Adult↗
PubMed1991

[A study on the effectiveness of three common stabilizers of peracetic acid].

This paper reports the effectiveness of 0.1% (W/V) quinoline-8-ol, 0.5% (V/V) phosphoric acid and 0.5% (W/V) sodium pyrophosphate as stabilizers of stock solutions on peracetic acid. The three solutions were put separately as stabilizers into stock solutions of peracetic acid in the laboratory. They were stored at room temperature for approximately one year, and the percent of peracetic acid content was determined at regular intervals. Also, we made studies on different concentrations of phosphoric acid for different prescriptions of peracetic acid. The results show that 0.1%, 0.3% and 0.5% (V/V) phosphoric acid and 0.5% (W/V) sodium pyrophosphate were not effective stabilizers for the stock solutions of peracetic acid. Therefore, phosphoric acid or sodium pyrophosphate is not an effective stabilizer in stockpiling stock solutions of peracetic acid.

Diphosphates↗
PubMed1991

[The report of organophosphorus pesticides cause delayed nervous system diseases (143 cases)].

This article reports delayed dysneuria 143 cases, 54 cases in male and 89 cases in female, age 8-59 years old. They are treated by atropine. After the cholinesterase inhibited symptoms had vanished or had improved and after the other factors had been eliminated the delayed dysneurias occur after poisoning 5.42 days. They are the peripheral neuritis, the amyotrophic lateral sclerosis, the myasthenic crisis, the peptic neuritis, the encephalitis, the mixed aphasia and the symptoms like Guillain-Barre's syndrome. Their death rates are higher in two months to the types of the myasthenic crisis, the encephalitis and the amyotrophic lateral sclerosis and to the other types of disease and the cases. Poisoned two months later, their prognosis are better and the mechanism are not very clear now.

Adolescent↗
PubMed1991

Chemical synthesis, cloning and expression of human epidermal growth factor gene in Saccharomyces cerevisiae.

A gene coding for human epidermal growth factor (hEGF) has been chemically synthesized by solid-phase phosphoramidite method. The 173 base-pair synthetic DNA duplex consists of a structural gene encoding hEGF, a stop codon TGA at 3' end and some convenient restriction sites at both ends of the gene. The synthesis of the gene involved enzymatic joining of 8 oligonucleotides to form a DNA duplex which was cloned into vector M13mp18. The recombinant colonies were identified by dot hybridization and restriction enzyme digestion. Its accuracy was confirmed by DNA sequence analysis. The hEGF DNA was inserted into yeast secretory vector YFD59. The resulting expression plasmid YFD104 was introduced into yeast Saccharomyces cerevisiae. The binding assay showed that the yeast transformants could express and secrete hEGF.

Amino Acid Sequence↗
PubMed1991

[Analysis of outer membrane proteins from eight strains of Campylobacter in SDS-PAGE].

The outer membrane proteins (OMPs) from 8 strains of Campylobacter, including 5 reference strains and 3 local strains, were isolated and examined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE). The results showed that the population distributions of molecular weight of OMPs from different species and sources were alike based on the Rank Sum Test analysis. The number of bands of major OMP was around 2-3, the molecular weight of which varied from 33-68 kd. Moreover, three C. jejuni local strains isolated from patients in China showed common characteristics of OMPs to the reference strains. It is suggested that the OMPs of Campylobacter are of a conservative and stable structure.

Bacterial Outer Membrane Proteins↗
PubMed1991

[A investigation on the types of chromosomes and epidemiology of Paragonimus westermanni in Huadian city of Jilin Province].

An investigation on the types of chromosomes and epidemiology of Paragomanni westermanni in five Villages and towns of Huadian city was carried out. The data showed that the infection rate of crayfish, the first intermediate host, was 100% and the infectiosities varied from 99 to 160/per crayfish in the five areas. The genetic patterns of all the cysticercus, ovum and imagoes had been proved to be diploid by morphological and genetic studies. The infection rate of animal final host such as dogs and cats reached as highly as 94.3%, and all the infected animals presented typical pathological changes. Among the total 1008 examined people, the positive rate of skin test of hypersensitivity was 25.1%, and only 0.4% was positive sputum test. Moreover, very few infected people had remarkable clinical expressions, suggesting that the infection of most people was only "transient", or of the larval parasitisim. The results showed that diploid Paragonimus westermanni were not strongly pathogenic to human beings.

Animals↗
PubMed1991

[The study on calcium ion concentration specificity in meridian and acupoint in rabbit].

Ion selected "Acupuncture electrode" was introduced for detection of calcium ion concentration in meridians and acupoints in rabbit. It was demonstrated that the calcium ion concentration was significant higher than that in the location of non-meridian and non-acupoint. This is the first and important finding of physicochemical characteristics of meridians.

Acupuncture Points↗
PubMed1991

Pylorus and antroseromuscular flap-preserving gastrectomy--a new type of reconstruction after subtotal gastrectomy for treatment of gastroduodenal ulcer: clinical and experimental study.

To avoid motility disturbances after Billroth gastrectomy, the authors designed pylorus and antroseromuscular flap-preserving subtotal gastrectomy (PAFPG). Results showed that gastric motility and emptying time of dogs after PAFPG were close to normal. PAFPG was applied to 125 consecutive patients with gastroduodenal ulcers (gastric ulcer, 15 patients; duodenal ulcer, 94 patients; and combined ulcers, 16 patients) confirmed by barium examination and fibro-gastroendoscopy. All patients recovered smoothly, none of them had postoperative complication. Gastric acid output reduction rates were as follows: basal acid output, 85.05% +/- 8.13%; maximal acid output, 81.76% +/- 10.85%; peak acid output, 81.42% +/- 10.15%. The incidence of postoperative enterogastric reflux (endoscopically) and the concentration of cholic acids in gastric juice were significantly lower in patients after PAFPG than after Billroth I or II gastrectomy. Results suggest that PAFPG reduced gastric acid outputs definitely and overcame adverse motility consequences after Billroth I or II gastrectomy desirably.

Animals↗