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Biomedical subjects

H Xu

Publications and source records attributed to H Xu.

At least 775 records · Page 43Linked to original sources
PubMed1990

[Studies on structure-activity relationships and receptor binding feature for 3-methylfentanyl derivatives].

Ohmefentanyl is not only a potent analgesic agent, but also a selective ligand for mu opioid receptor. In order to search for more potent analgesics, more selective ligands and long duration of analgesic action in 3-methylfentanyl derivatives, we made modifications of the 1-phenethyl and 4-N-propionyl groups in 3-methylfentanyl and synthesized 15 new compounds. The analgesic activity, duration of analgesic action, receptor binding affinity and opioid sub-receptor selectivity of some of these compounds were measured. Primary pharmacological results showed that most of the compounds in this series possessed morphine-like effects. The analgesic activities of them were about 2-180 times more potent than that of morphine. The duration of analgesic action of the tested compounds was 6-10 times longer than that of fentanyl. The receptor binding affinities (IC50) of compounds 1-4 were 10(-7)-10(-8) mol. Compound 13 displayed the best binding selectivity on mu opioid receptor site with ratio mu/delta greater than 700 in rat brain membrane and mu/delta = 1000 in mouse brain membrane. The new compound may be proposed as a useful tool in studying the opioid receptor. According to the result of equations in reference 11, compounds 7-14 were designed and prepared. The observed log 1/c values of them were much closer to the calculated values.

Analgesics↗
PubMed1990

[Extraction technology of radix Isatidis].

The indigotin and indirubin contents of Radix Isatidis, its aqueous extract and residues, as well as extract with 95%, 50% alcohol were determined by TLC-densitometry. The authors throw doubt upon the current processes of extracting with water and precipitating with alcohol for Radix Isatidis, and indicate that the method of extraction with alcohol can give more indigotin and indirubin.

Antibiotics, Antineoplastic↗
PubMed1990

[Possible mechanisms of the action of lymphocyte proliferation-inhibitory factor(s) in rat serum receiving electroacupuncture stimulation].

Previous reports showed that EA stimulation (3V, 2Hz, 30 min/d, 5 d) induced the production of one or more lymphocyte proliferation-inhibitory factor(s) in the rat serum. In this paper, the mechanisms of the action for the inhibitory factor(s) to suppress lymphocyte proliferation were studied. (1) the lymphocytes from different immune organs of the mice were prepared and cultured with the rat serum stimulated by EA. The results show that the serum not only inhibited the mouse lymph node T cell proliferation induced by Con A, but also inhibited the mouse thymocyte and spleen T cell proliferation induced by Con A. When B cells were stimulated by LPS, the proliferative effect can also be inhibited significantly by the rat serum stimulated by EA. This implies that the effect of the lymphocyte proliferation-inhibitory factor(s) has no specificity. (2) Incubation of the mouse lymph node cell with serum for one hour is enough to cause an inhibitory effect on Con A stimulated lymphocyte proliferation. However, no inhibitory effect was observed if the mouse lymph node cells were incubated with Con A for 15 min or 30 min before the addition of rat serum. The results demonstrate that the lymphocyte proliferation-inhibitory factor(s) act on the early events of T lymphocyte activation induced by Con A. (3) Protein kinase C (PKC) is a key link in the activation of T and B lymphocyte proliferation by Con A and LPS respectively. So it would be interesting to learn whether the inhibitory effect of the lymphocyte proliferation-inhibitory factor(s) is caused by the inhibition of PKC activity.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1989

Opioids can enhance and inhibit the electrically evoked release of methionine-enkephalin.

The stimulated (40 Hz) release of enkephalin from the myenteric plexus can be modulated by multiple types of opiate receptor. The direction of the modulation is not fixed but is bimodal. Both an inhibition and an enhancement of evoked release is observed depending on the concentration of opioid agonist that is used. Each of these effects can be antagonized by naloxone. Following pretreatment of guinea pig myenteric plexus in vitro with forskolin (0.5 microM) or the lipid soluble cAMP analog 8-(4-chlorphenylthio)-cAMP (8-CPT-cAMP; 100 microM) the inhibition of stimulated Met-enkephalin release that is produced by sufentanil (10(-8) M), [D-Pen2-D-Pen5]enkephalin (DPDPE, 10(-8) M) or dynorphin (10(-7) M) is no longer observed. On the contrary, in forskolin- or 8-CPT-cAMP treated myenteric plexus a previously inhibitory concentration of the above opioids now produces an enhancement of the magnitude of the stimulated Met-enkephalin release. Excitatory responses (enhanced release) to lower concentrations of sufentanil (1 nM) or DPDPE (5 nM) are not affected by pretreatment with the same concentration of forskolin or 8-CPT-cAMP. These data suggest that the ability of opioids to enhance or inhibit evoked enkephalin release is mediated via different biochemical processes (separate second messenger systems). This could imply that the opioid enhancement of enkephalin release is due to a direct facilitation of release and not to disinhibition. The ability of opioids to enhance the release of at least some neurotransmitters should be taken into account when attempting to explain the physiological sequelae of the acute and chronic effects of narcotics.

Action Potentials↗
PubMed1989

Schistosoma mansoni tropomyosin: cDNA characterization, sequence, expression, and gene product localization.

We have defined the polypeptide pattern of 3-hr Schistosoma mansoni schistosomula on nonequilibrium two-dimensional gels (NEPHGE). An acidic group of polypeptides with a molecular weight of about 40 kDa and a pI value of around 5.0 (numbered 48/59/53) were identified as antigens on Western blots probed with chronic human infection sera or vaccinated mouse sera. Polypeptides 48/49/53 from silver-stained NEPHGE gels produced antisera that were specific as demonstrated by Western blot analysis and immunoprecipitations of in vitro translation products. A cDNA clone (clone 1) from a S. mansoni adult worm pBR322 library was isolated by using cDNA probes made from size-fractionated mRNA and defined as encoding polypeptide 49 by hybridization selection of the mRNA which was in vitro translated and immunoprecipitated with specific mouse antiserum. A lambda gt 11 expression clone which contained an insert close to the full length mRNA was isolated from a S. mansoni cercariae library. The complete sequence of the mRNA was determined by sequencing the insert of this clone as well as primer extension of total RNA. The only open reading frame coding for 284 amino acids in the 1316 nucleotide sequence showed a 44.76 to 55.44% homology with the amino acid sequences of 18 different tropomyosins from various species. Computer-predicted secondary structure of schistosome tropomyosin was mainly alpha-helix which was very similar to other tropomyosins. Northern analysis showed the mRNA to be about 1.5 kb in size and detectable at much higher levels in the adult worm stage as compared to the cercariae and the egg stages. Western blot analysis likewise showed that greater amounts of tropomyosin were detected in extracts from adult worm stage as compared to extracts from cercariae and egg stages. Immunocytochemical analysis shows that tropomyosin is strongly associated with the tegument of adult worms. The restriction digestion pattern given by genomic Southern analysis suggests the existence of introns and/or multiple gene copies. Thus polypeptide 49, an immunodominant antigen, represents schistosome tropomyosin.

Amino Acid Sequence↗
PubMed1989

The protein kinase C inhibitor H-7 inhibits concanavalin A induced T-lymphocyte activation.

1. 1-(5-isoquinoline sulfonyl)-2-methylpiperazine (H-7), a protein kinase C inhibitor, was found to inhibit con A stimulated [3H]thymidine incorporation and cytosolic protein kinase C (PKC) activation in T-lymphocytes of mouse spleen. 2. The inhibitory effect of H-7 was both concentration and time-dependent. 3. H-7 exerted no inhibition when T-lymphocytes have been preincubated with con A for 10 hours or longer. 4. These results support the notion that PKC is an important element of the con A mitogenic signal transduction mechanism and the PKC signal is completed within the first 10 hr of con A incubation.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1989

Negative transcriptional regulation in the Caulobacter flagellar hierarchy.

The Caulobacter crescentus flagellum is formed at a specific time in the cell cycle and its assembly requires the ordered expression of a large number of genes. These genes are controlled in a positive trans-acting hierarchy that reflects the order of assembly of the flagellum. Using plasmids carrying transcriptional fusions of either a neo or a lux reporter gene to the promoters of three flagellar genes representing different ranks in the hierarchy (the hook operon, a basal body gene flbN, and the flaO gene), we have measured the level of chimeric gene expression in 13 flagellar mutant backgrounds. Mutants in the hook operon or in basal body genes caused overproduction of both hook operon and basal body gene chimeric mRNAs, suggesting that negative regulation is superimposed on the positive trans-acting control for these early events in the flagellar hierarchy. Mutants in the structural genes and in genes involved in flagellar assembly had no effect on flaO expression, placing the flaO gene near the top of the hierarchy. However, flaO expression appears to be under negative control by two regulatory genes flaS and flaW. Negative control, as a response to the completion of specific steps in the assembly process, may be an important mechanism used by the cell to turn off flagellar gene expression once the gene product is no longer needed.

Bacteria↗
PubMed1989

Comparisons of the electrophysiological effects of intravenous sotalol and propranolol on the immature mammalian heart.

Sotalol is a beta blocker that has also been reported to exert class III antiarrhythmic effects. To evaluate the effects of sotalol on the immature heart, and specifically to assess the relative importance of its class III action, the electrophysiologic effects of incremental doses of intravenous dl-sotalol (cumulative dose of 8 mg/kg) were studied in 11 intact canines (ages 4-15 days) utilizing intracardiac programmed stimulation and electrogram recording techniques. These results were compared to the electrophysiologic effects obtained in an additional 14 neonatal canines given 0.6 mg/kg of the beta blocker propranolol intravenously. Sotalol caused a greater increase than propranolol in the resting sinus cycle length (45 vs. 4%). Importantly, sotalol resulted in greater increases in atrial and ventricular muscle refractoriness than did propranolol (AERP--77 vs. 4%, AFRP--57 vs. 6%; VERP--53 vs. 4%, VFRP--51 vs. 7%). Thus, the electrophysiologic effects of sotalol include large changes in myocardial refractoriness that are not observed with simple beta blockade induced by propranolol. These results suggest that sotalol exerts a significant class III effect in the immature mammalian heart, and thus may be useful as an antiarrhythmic agent in the neonate.

Analysis of Variance↗
PubMed1989

Clinicopathological analysis of causes of perinatal death.

The perinatal mortality rates and causes of deaths in our hospital within the three 5-year periods (1955-1959, 1976-1980, 1981-1985) were reported as well as the total number of births (16,846), deaths (457), and autopsies (393, autopsy rate 85.9%). The perinatal mortality for the three 5-year periods was 44.5%, 23.8%, and 17.2% respectively; it declined more significantly in 1981-1985 than in 1976-1980. Anoxia was the first cause of death for the three 5-year periods. Other causes in sequence in 1955-1959 were traumatic intracranial hemorrhage and pulmonary diseases, in 1976-1980 malformation and pulmonary diseases, and in 1981-1985 anoxia, pulmonary diseases and hyaline membrane disease. Results suggest that accurate analysis of causes of deaths depends on meticulous systematic fetal and neonatal autopsy, including macerated fetuses, extensive discussion by pathologists, obstetricians and neonatalogists, and indispensable placental examination.

Cause of Death↗
PubMed1989

[A survey on Campylobacter jejuni high infection in a nursery].

An epidemiologic survey on Campylobacter jejuni infection in a nursery was made in April 1987. It was found that there was a spread of C. jejuni high infection. Two cooks affected by enteritis of C. jejuni were considered to be a reservoir of the infection. Stool cultures were positive for C. jejuni in 43 out of 187 children, with a positive rate of 23%. Eight of the 43 had diarrhea and the others were asymptomatic carriers (24.3%). Controls were set up in another nursery with 238 healthy children and 201 non-diarrheal outpatients; C. jejuni was positive for 11.4% and 7.5%, respectively. The difference was quite significant (P less than 0.005). Results of biotyping on the strains isolated from the two cooks and the children in the nursery showed that all were of C. jejuni biotype 1, except two (4.7%) of the strains from the children, which were E. coli. The authors have suggested that transmission of C. jejuni in the nursery may be caused by contaminated food or person-to-person contact.

Adult↗
PubMed1989

[Survey of Campylobacter jejuni/coli infection and risk factors in children].

From March to May 1987, 798 children under 7 years of the outpatients in Chengdu district were examined and their stool samples cultured for Campylobacter jejuni/coli. C. jejuni/coli was isolated from 31 (9.51%) of 326 children with diarrhea and 22 (4.66%) of 472 children with non-diarrhea. The difference was significant (P less than 0.05). This result indicated that C. jejuni/coli is an important pathogen of children diarrhea in Chengdu district. Meanwhile, by inquiry we investigated risk factors related with C. jejuni/coli infections. Case group was consisted of 53 children with C. jejuni/coli positive. For each case, 3 controls were chosen from 745 children with C. jejuni/coli negative and matched according to age (less than 6 month), sex, living place (city or countryside), way of feeding, and whether to have diarrhea or not. The results has shown that contact with animals a week before being ill and habit of intake of food with hands are risk factors of C. jejuni/coli infection of childhood in Chengdu, with an odd ratio of 2.97 and 2.71 respectively. This provides valuable information about the prevention of C. jejuni/coli infection.

Campylobacter Infections↗
PubMed1988

Phase metastability and supercooled metastable state of diundecanoylphosphatidylethanolamine bilayers.

Aqueous dispersons of L-alpha-phosphatidylethanolamine (PE) with identical saturated acyl chains are known to exhibit gel-state metastability. It is also known that the metastability in PE becomes more pronounced with decreasing acyl chain-length. In an attempt to study the metastable phase behavior of PE, we have synthesized diundecanoylphosphatidylethanolamine (diC11PE) and examined its polymorphic phase behavior. A single endothermic transition at 38 degrees C is detected between 10 and 55 degrees C by DSC for the nonheated sample of diC11PE in excess water. An immediate second heating scan done after cooling slowly of the same sample from the liquid-crystalline state shows a smaller endothermic transition at a lower temperature, 18 degrees C. However, the high-temperature transition at 38 degrees C can be detected, if the sample which has been heated above 38 degrees C is quench cooled from the liquid-crystalline to a temperature between 18 and 38 degrees C. Furthermore, two endothermic transitions at 18 and 38 degrees C and an exothermic transition at 19 degrees C are recorded for diC11PE after quench supercooling of the sample from the liquid-crystalline state to an appropriate temperature below 10 degrees C. The gel-state metastability of diC11PE can be most appropriately explained in terms of changes in interbilayer headgroup-headgroup interactions. It is suggested that the kinetically trapped supercooled metastable state may be a multilamellar structure with melted acyl chains but with strong interbilayer headgroup-headgroup interactions.

Calorimetry↗