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Biomedical subjects

M Li

Publications and source records attributed to M Li.

At least 1,063 records · Page 59Linked to original sources
PubMed1991

[A study on the male DNA special restricted fragment of bovine].

Bkm, which is related to sexes, is a satellite DNA of the female snake. After the genomic DNA of bovine was digested by Pst I, it was hybridized with Bkm sequence probe (p184) and subcloned in the vector pUC19. Recombinants were identified by the colony in situ and Southern blot hybridization. When we determined genomic DNA of bovine using the male DNA fragment, it was observed that the pattern of hybridization was different because of different sexes. The results showed that we could identify the sex of bovine by Southern blot hybridization with recombinants of male DNA special restricted fragment of bovine origin.

Animals↗
PubMed1991

[Experimental study on the principal effects and dependence potential of thiofentanil].

Thiofentanil is a synthetic analgesic with pharmacological effects similar to etorphine hydrochloride (M99). The aim of the present study was to assess its analgesic and immobilization effects and to evaluate its dependence potential in comparison with morphine. The median analgesic dose (AD50) was measured by hot plate method in mice. The median paralytic dose (PD50), as an indicator of immobilization, was tested in rats, rabbits, dogs and monkeys. Results showed that the analgesic potency of this drug was 3260 times that of morphine, 22 times that of fentanyl and 1.5 times that of M99 and the immobilization effect was 2-3 times that of M99. Results from jumping test in mice and physical dependence-producing test in rats (the drug was dissolved in drinking water) showed that thiofentanil possessed physical dependence liability weaker than morphine. Physical dependence was not observed in rats with intravenous injection of one dose each h over a period of 72 h, and also in monkey with 20-week drug medication. The LD50 of thiofentanil was also determined in mice, rats, rabbits, dogs and monkeys in comparison with M99. Results suggest that it should be valuable to develop thiofentanil as an analgesic for clinical use.

Analgesics, Opioid↗
PubMed1991

[Experimental research of the effect of polysaccharides in semen Ziziphis Spinosae and Ziziphis Spinosae on enhancing the immune function of mice injured by radiation].

This article surveys the pharmacological effect of the polysaccharides in Semen Ziziphis Spinosae and Ziziphis Spinosae. The result shows that oral administration of this polysaccharide (0.1g/kg/d) can strengthen the immune function of cells nd body fluids and to a certain extent protect mice from radioactive injuries.

Animals↗
PubMed1991

Synthesis of (+/-)-N-2-methylpropyl-N-1'-methylacetonyl-nitrosamine.

N-2-methylpropyl-N-1-methylacetonyl-nitrosamine (NMAMPA), first isolated from moldy and normal foods, was synthesized by chemical means. The structure and molecular weight of the synthetic NMAMPA were elucidated by spectrometry. A combination of spectral and chromatographic data indicated that the synthetic NMAMPA is identical to that obtained naturally. Synthetic NMAMPA is a racemic modification, and a carcinogen which can induce esophageal and forestomach cancer in rats.

Carcinogens↗
PubMed1991

[Effects of phencyclidine on rabbit basilar artery in vitro and rabbit cerebral blood flow in vivo].

The effect of phencyclidine [1-(1-phenylcyclohexyl)piperidine, PCP] on rabbit basilar arteries was studied with an in vitro model of ring segment arteries. PCP 0.05-500 mumol.L-1 caused vasoconstriction of basilar arteries in a concentration-dependent manner. Its maximal effect (Emax) was 94 +/- 21 mg and the concentration causing half maximal effect (EC50) was 25 +/- 18 mumol.L-1. PCP 0.01-10 mumol.L-1 also concentration-dependently augmented the vasoconstriction induced by electric stimulation in rabbit basilar arteries. Its Emax was 91 +/- 18 mg and EC50 was 0.27 +/- 0.17 mumol.L-1. The effects of PCP on mean arterial blood pressure (MABP) and heart rate (HR) of rabbits were observed. PCP iv 4 mg.kg-1 reduced MABP from 14.3 +/- 0.8 to 12.2 +/- 1.0 kPa and HR from 300 +/- 0 to 278 +/- 5 bpm in 5 min. Using the technique of radionuclide imaging in rabbit brain in vivo, we studied the effect of PCP on cerebral blood flow. After iv PCP 4 mg.kg-1, the tp of radiocerebrogram was increased from 4.5 +/- 1.1 to 6.1 +/- 1.0 s, the tg of radiocerebrogram was increased from 11.7 +/- 0.6 to 18.2 +/- 3.3 s and the rate of clearance was decreased. After iv PCP 2 mg.kg-1, only tg increased from 12.6 +/- 2.1 to 15.9 +/- 0.6 s. Hence PCP increased the transit time of nondiffusible indicators (99mTc) through the cerebral circulation. These results suggest that PCP causes constriction of basilar artery and slows down the cerebral blood flow.

Animals↗
PubMed1991

[Measurement of intracellular free Ca2+ concentration in dissociated rat brain cells using Fura-2/AM].

The intracellular free Ca2+ concentration was measured in freshly dissociated brain cells prepared from neonatal rats using the fluorescent Ca2+ indicator Fura-2/AM. Cytosolic Ca2+ concentration of resting cells was calculated to be 240 +/- 5 nmol/L. Depolarization with high K+ resulted in an over 100% increase in intracellular Ca2+ concentration, and this increase could be prevented or reversed by verapamil or nifedipine known to block voltage-sensitive Ca channels. These results suggest that the adoption of Fura-2/AM method in freshly dissociated rat brain cells is a useful and relatively easily applicable technique for monitoring intracellular Ca2+ changes.

Animals↗
PubMed1991

[Studies of pickled vegetables and cause of esophageal cancer in Linxian. II. Determination of nitrosamines and their precursors].

Pickled vegetables are daily food consumed in the high-risk areas for esophageal cancer in China. We analyzed the nitrosamine content of Linxian pickles by GC/TEA and found that trace amounts of six nitrosamines (NDMA, NDEA, NMBA, NMAMBA, NDPA, NPYR) were present, with the highest concentrations being NDMA and NDEA (1.7 and 1.9 micrograms/kg wet weight respectively). The average level of nitrosamine precursors, such as nitrate (111.22 mg/L), nitrite (0.152 mg/L) and secondary amines (4.223 mg/L), in pickled vegetables were determined, and their pH values ranged from 3 to 5.

Diethylnitrosamine↗
PubMed1991

Distribution of m2 muscarinic receptors in rat brain using antisera selective for m2 receptors.

The DNA fragment encoding the third intracellular loop of rat m2 muscarinic receptor was fused to the gene for staphylococcal Protein A. The resultant fusion protein, expressed in bacteria, was purified via IgG affinity chromatography and used as an antigen to raise a polyclonal antiserum. Chinese hamster ovary cells transfected with cDNA coding for a single muscarinic receptor subtype were used as tissue sources to screen antisera. The antiserum was shown to immunoprecipitate quantitatively (greater than 90%) m2 receptors but not to precipitate m1, m3, m4, or m5 receptors. Additionally, immunoprecipitation by m2 antiserum could be inhibited by protein containing the third intracellular loop of the m2 receptor. This selective m2 antiserum was then used to study the distribution and density of m2 receptors in rat brain and heart. In agreement with previous studies, m2 receptors were found to be abundant in heart and comprise at least 92% of the total muscarinic receptor density. Hindbrain, brain stem, and midbrain regions such as cerebellum (75%), pons/medulla (70%), and thalamus/hypothalamus (43%) are also enriched in m2 receptors. In contrast, forebrain regions contain markedly lower percentages of m2 receptors, with cortex expressing 20%, hippocampus 19%, striatum 12%, and olfactory tubercle 20% of the total receptor density. Although the density of m2 receptors expressed as a percentage of total varied considerably from brain region to brain region, the absolute density of these receptors appeared relatively uniform throughout the brain. This study demonstrates that a gene fusion system can be used for efficient antibody production. The use of similar fusion protein antisera directed against other subtypes of muscarinic receptors should prove useful in future studies on regulation, function, and structure of muscarinic receptors.

Animals↗
PubMed1991

[Eighty cases of alveolar hydatid disease treated with albendazole].

Alveolar hydatid disease occurs frequently in Xiji County of Ningxia. 80 cases of the disease were treated orally with albendazole from 1985 to 1988 and the short-term results proved satisfactory. The treatment consisted of two groups. Group I included 72 cases which were orally given 8-10 mg/kg.d of albendazole 2 to 3 times a day after each meal for 30 days and then stop taking the medicine for 10 days as one treatment course. The treatment continued 3-12 months comprising about 24 courses were given with the highest dosage of 412g. Group II included 8 cases who were given 15.6-20 mg/kg.d of the medicine for 14 days (one course) and every two weeks with a 10 days interval. The treatment of group II continued 3-6 months which totalled 19-24 courses with the highest dosage of 270g. All the treated patients tolerate well except that a few of them felt giddy and had diarrhoea which disappeared after the withdrawal of medicine. Through 3-5 years, follow-up observation, it was found that the gener alsymptoms of the treated patients improved and their body weight increased by 2-9.5 kg, some of them could take part in light physical labour. The jaundice index in 80% of them returned to normal. SGPT in 86.4% decreased to within normal range. The enlarged livers in half of the patients decreased by 1-6 cm. 23.7% of the patients were reexamined by B ultrasound scanning which revealed that their enlarged liver reduced in size while the liquifaction area and the shadows of calcification in the livers in 42.5% patients increased obviously.

Adolescent↗
PubMed1991

[Preliminary investigation of liver alveolar echinococcosis and liver cystic, echinococcosis in Xiji County, Ningxia].

This article reports on the result of an investigation on the prevalence of liver alveolar echinococcosis (LAE) and liver cystic echinococcosis (LCE) in the peasants and the residents of Xiji County, Ningxia Hui Autonomous Region. Among 2,389 selected persons examined with B-ultrasound, 197 cases were diagnosed to have LAE or LCE; the prevalence being 8.2%. Of the 197 cases, 141 (5.9%) had LAE; 56 (2.3%) had LCE. Among 1,413 peasants, 9.7% had LAE; 3.8% had LCE. Among 976 residents, 0.4% had LAE, 0.2% had LCE. Obviously, the peasants were more prone to be infected with the disease, suggesting LAE had much to do with the job of hunting the fox and capturing the Citellus dauricus, while the infectious source of LCE was mainly the domestic dog.

Adolescent↗
PubMed1991

[An investigation on the resources of medicinal fungi in Sichuan].

This paper reports the classification, distributional traits, new distribution, specific species of medicinal fungi, as well as the status of anticancer medications and edible and medicinal fungi in Sichuan. Rational suggestions have been made with regard to the cultivation, development and utilization of those important species with proven curative effect.

Conservation of Natural Resources↗
PubMed1991

[A study on components and compound prescription of huangqin decoction].

The results obtained from the pharmacological experiments have preliminarily demonstrated that the compound prescription is better than its individual component drug in the range and potency of pharmacological activities. In the prescription Radix Scutellariae plays a principal role in pharmacological effects. Radix Scutellariae and Radix Paeoniae Alba can potentiate each other. Radix Glycyrrhizae and Fructus Jujubae in the compound prescription also exhibit biological activities to some extent. The relieving effect of the prescription for spasm and pain may result from the synergistic interaction between Radix Paeoniae Alba and Radix Glycyrrhiza, and the heat clearing and diarrhea stopping action is due to the biological activity of Radix Scutellariae.

Animals↗
PubMed1991

[Endoscopic retrograde cholangiopancreatography in children].

Endoscopic retrograde cholangiopancreatography (ERCP) was performed less in children than in adults. Twenty-seven children, aged from 56 days to 14 years (average 6 years), received ERCP from August 1989 to December 1990. The cannulation into the papilla of Vater was successful in 24 children (88.9%) and their pancreaticobiliary ductal system was visualized clearly. Congenital biliary dilatation (CBD) was diagnosed in 16 patients and other biliary disorders in 8 patients. The APBD was confirmed in almost all CBD patients, showing a close etiological relation. It was concluded that ERCP is helpful to diagnose and differentiate pediatric biliary diseases and to study the etiology and pathophysiology of CBD.

Adolescent↗
PubMed1991

Development of an antiserum against m3 muscarinic receptors: distribution of m3 receptors in rat tissues and clonal cell lines.

A synthetic oligopeptide (QCDKRKRRKQQYQQRQSV) corresponding to a carboxyl-terminal sequence of the rat m3 receptor (amino acids 561-578) was coupled to carrier proteins and used to generate a polyclonal antiserum. This serum selectively immunoprecipitates at least 90% of the m3 receptors expressed by A9 cells transfected with the cDNA encoding the m3 muscarinic receptor but does not precipitate receptors from cells transfected with cDNA encoding m1, m2, m4, or m5 receptors. Using this m3 antiserum, the density of m3 receptors in various regions of rat brain was quantified. Areas expressing the highest density of m3 receptors are the cortex, hippocampus, striatum, and olfactory tubercle, with 232 fmol/mg, 197 fmol/mg, 140 fmol/mg, and 130 fmol/mg, respectively. Hindbrain regions (i.e., cerebellum, thalamus/hypothalamus, and pons/medulla) expressed fewer m3 receptors, both as a percentage of total muscarinic receptors (5-6%) and in terms of absolute receptor density (12-70 fmol/mg). A panel of subtype-selective antisera (m1, m2, and m3) was used to determine receptor distribution in several peripheral tissues of the rat (lung, ileum, and bladder). The m2 receptor subtype constitutes the majority of total receptors in the bladder (86%), lung (91%), and ileum (69%). The m3 receptor was found at lower densities in these tissues (5-11%), whereas the m1 receptor is present in highest amounts in the ileum (17%). Human clonal cell lines, in which regulation of muscarinic receptors has been commonly studied, were also examined. The SK-N-SH neuroblastoma line, which has been reported to express M3 receptors, on the basis of pharmacology and molecular size, was found to express a mixture of subtypes (m1 = 31%, m2 = 21%, m3 = 43%). Interestingly, SH-SY-5Y and SH-IN cells, both derived from SK-N-SH cells, exhibit predominantly m3 receptors (74% for SH-SY-5Y; 58% for SH-IN), with lower levels of m1 and m2 receptors (5% and 8% for SH-SY-5Y; 4% and 23% for SH-IN, respectively.) Another commonly studied cell line, 132-1-N1 astrocytoma cells, reportedly expressing M3 receptors, based upon mRNA measurements and second messenger linkage, also expresses a predominance of m3 receptors (91% of total). This m3-selective antiserum should prove useful not only for localizing and quantifying m3 muscarinic receptors but also for examining mechanisms involved in the regulation of receptor expression in human tissues or animal models of disease, as well as in cell culture.

Amino Acid Sequence↗
PubMed1990

The aggregation and dissociation properties of a low molecular weight mannose 6-phosphate receptor from bovine testis.

The aggregation state of low molecular weight mannose 6-phosphate receptor from bovine testis was determined in membrane preparations and in purified soluble preparations. The effect of aggregation on binding of the receptor to immobilized pentamannose 6-phosphate was also examined. Nonreducing SDS-PAGE followed by immunoblotting revealed that interchain disulfide bonds exist in detergent-solubilized and purified receptor preparations, but not in membrane-associated receptor. Reduction of the receptor with dithiothreitol abolished its ligand binding activity and drastically altered its ability to bind antibodies. The results of receptor crosslinking and molecular sieving chromatography studies suggest that the receptor exists in membranes as a noncovalently linked dimer and in solution as oligomeric forms, largely as a tetramer. The formation of the tetramer is affected by the concentration of the receptor, but not by its solubilization from membranes with detergent, nor by the presence of mannose 6-phosphate. Mono-, di-, and tetramer forms of 125I-labeled receptor were separated by molecular sieving chromatography and examined for their ability to bind to immobilized ligand, agarose-pentamannose-phosphate. The order of binding observed was tetramer greater than dimer greater than monomer. Binding of the monomer and dimer to immobilized ligand was dependent on the presence of divalent cations while the tetramer had little requirement for divalent cations.

Animals↗
PubMed1990

Obstructive jaundice promotes bacterial translocation from the gut.

Experiments were performed to determine if obstructive jaundice promotes the translocation of bacteria from the gastrointestinal tract to visceral organs. Three groups of mice were studied: control (n = 20), sham ligated (n = 28), and bile duct ligated (n = 33). The sham-ligated group underwent laparotomy and manipulation of the portal region, whereas the ligated group had their common bile ducts ligated. Seven days later, the mice were killed, their organs cultured, and the gastrointestinal tract examined histologically. The bilirubin levels of the ligated group (18.7 mg/dL) were elevated compared with the other groups (0.5 mg/dL) (p less than 0.05). The incidence of bacterial translocation was higher in the ligated (33%) than in the control (5%) or sham-ligated (7%) groups (p less than 0.05). Since bile is important in binding endotoxin and maintaining a normal intestinal microflora, cecal bacterial populations were quantitated. The cecal levels of gram-negative, enteric bacilli were 100-fold higher in the bile duct-ligated mice in which bacterial translocation occurred (p less than 0.05), indicating that intestinal bacterial overgrowth was a major factor responsible for bacterial translocation. The mucosal appearance of the intestines from the control and sham-ligated groups was normal. In contrast, subepithelial edema involving the ileal villi was present in the ligated group. In conclusion, the absence of bile within the gastrointestinal tract allows intestinal overgrowth with enteric bacilli and the combination of bacterial overgrowth and mucosal injury appears to promote bacterial translocation.

Animals↗