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Biomedical subjects

Y L Li

Publications and source records attributed to Y L Li.

At least 91 records · Page 5Linked to original sources
PubMed1993

[The studies on electronic structure and structure-activity relationships of [Leu5]-enkephalin].

The quantum chemical (INDO) calculations have been undertaken for [Leu5]-enkephalin. The electronic structure was investigated, the active site, the way of action and structure-activity relationship were discussed. It was found that the region of N(1) is the main active site for acceptance of electron, the region of O(51) and O(52) is the main active site for providing electron when interacting with the opiate receptor. [Leu5]-enkephalin was compared with morphine and R31833 in electronic and spatial structure of active site. Study of the results showed that the N(1) in [Leu5]-enkephalin corresponds to the N in morphine and the N(9) in R31833, phenyl of Tyr1 in [Leu5]-enkephalin corresponds to the phenyl in morphine and the phenyl of phenylethyl in R31833, the O(51) and O(52) in [Leu5]-enkephalin corresponds to the O(3) in morphine and the O(25) in R31833, the O(4) in [Leu5]-enkephalin corresponds to the O(29) or O(27) in R31833. On the basis of these studies, it was inferred that these compounds have common feature in pharmacophore. They not only have the same way of action but also have common site of action in the receptor when they interact with the opiate receptor.

Analgesics, Opioid↗
PubMed1993

Electrophysiological effects of N6-cyclopentyl-adenosine and [-]-N6-[phenylisopropyl]-adenosine on pacemaker cells in sinoatrial node of guinea pigs.

The electrophysiological effects of N6-cyclopentyladenosine (CPA) and [-]-N6-[phenylisopropyl]adenosine (R-PIA) (both are selective adenosine A1 receptor agonists) on pacemaker cells in sinoatrial (SA) node of guinea pigs were investigated using intracellular microelectrodes. CPA and R-PIA increased the amplitude of action potential, amplitude of the maximal diastolic potential and maximal rate of depolarization (phase 0), but decreased the velocity of diastolic (phase 4) depolarization, the rate of pacemaker firing, and the duration of 90% repolarization in pacemaker cells of guinea pigs. 8-Phenyltheophylline (a nonselective antagonist of adenosine receptors) and glibenclamide (a potent blocker of ATP-sensitive K+ channels) inhibited the electrophysiological responses of pacemaker cells to CPA. These results suggest that the electrophysiological changes induced by CPA are adenosine receptor-dependent and mainly mediated by activation of ATP-sensitive K+ channels coupled to adenosine receptors.

Action Potentials↗
PubMed1993

[Purification of 31/32 kDa proteins of adult Schistosoma japonicum and studies on their protective immunity].

Schistosoma japonicum adult worm 31/32 kDa proteins (Sj 31/32) were separated on polyacrylamide slab gels and purified by electrophoretic elution. These purified proteins were used to immunize mice in order to observe their protective immunity against challenge. The results of SDS-PAGE,EITB and ELISA indicated that the 31/32 kDa proteins separated and purified by means of these methods were pure and active. It was assumed that Sj 31/32 proteins could reduce worm burden and inhibit the fecundity of schistosome and formation of egg granuloma. The results suggested that 31/32 kDa S. japonicum proteins might be an important component of a multivalent vaccine against schistosomiasis japonica (Figs. 1-4).

Animals↗
PubMed1993

[Synthesis and analgesic activity of non-aryl analogues of 4-methoxycarbonyl fentanyl].

In this paper, the synthesis and analgesic activities of some derivatives of 4-methoxycarbonyl fentanyl are reported, in which the 4-N-phenyl group or both the 4-N-phenyl group and the 1-beta-phenyl group were replaced by some nonaromatic groups. In the last case, some compounds showed very strong analgesic activity. For example, the analgesic activities of compounds 4 and 6 were shown to be 695 and 818 times more potent than that of morphine respectively. The structure-analgesic activity relationships were discussed.

Analgesics, Opioid↗
PubMed1993

[A histogenetic study on the carcinogenesis of colonic mucous membrane glands induced by 1,2-dimethylhydrazine in rats].

The relationship between atypical proliferation and carcinogenesis of colonic mucous membrane glands induced by different doses of 1,2-dimethylhydrazine (DMH) was studied by use of histopathological methods and sequential endoscopic observation. The results showed a significant increase of atypical glands in the flat mucosa with the increase in number of DMH injections, the degree of atypical proliferation becoming more serious with the increase of glandular ducts. The following changes were observed under sequential endoscopy: small elevations were first seen on the flat mucosa, then in sequence-flat elevations, hemisphere elevations, substem elevations and finally, stemmed elevations. At the same time, changes such as rubifaction, erosion, central depression and hemorrhage on the tumor surface were frequently encountered. It is concluded that atypical glandular proliferation in the flat mucosa of the colon is a precancerous lesion of colonic carcinoma.

Animals↗
PubMed1993

[The effects of angiotensin II and other vasoactive agents on the blood flow in Yoshida ascites hepatoma].

The effects of angiotensin II and other six vasoactive agents on tissue blood flow of Yoshida rat ascites hepatoma AH109A and normal liver were measured by the hydrogen clearance method. The mean blood flow in the tumor peripheral part under normotensin was 11.9 +/- 8.2 ml/min/100 g tissue and was not influenced by tumor size. Tumor blood flow was more significantly increased in infusion angiotensin II than 0.5 mg/ml methoxamine; however, normal liver blood flow of tumor-bearing rats was unchanged in contrast to an increase seen in the tumor. A Pronounced reduction of tumor blood flow was found after administration of epinephrine, norepinephrine and ethylphenylephrine. In addition, metaraminol, phenylephrine as well as 1.0 and 2.5 mg/ml methoxamine were not found to significantly change the blood flow of the tumor.

Angiotensin II↗
PubMed1992

Occupational dimethylformamide exposure. 3. Health effects of dimethylformamide after occupational exposure at low concentrations.

A factory survey was conducted in a plant where N,N-dimethylformamide (DMF) was in use during the production of polyurethane plastics and related materials. In all, 318 DMF-exposed workers (195 men and 123 women) and 143 non-exposed controls (67 men and 76 women) were examined for time-weighted average exposure (to DMF and other solvents by diffusive sampling), hematology, serum biochemistry, subjective symptoms, and clinical signs. Most of the exposed workers were exposed only to DMF, whereas others were exposed to a combination of DMF and toluene. DMF exposure in the former group was up to 7.0 ppm (geometric mean on a workshop basis), whereas it was up to 2.1 ppm in combination with 4.2 ppm toluene. Both hematology and serum biochemistry, results (including aspartate and alanine aminotransferases, gamma-glutamyl transpeptidase and amylase) were essentially comparable among the 3 groups. There was, however, a dose-dependent increase in subjective symptoms, especially during work, and in digestive system-related symptoms such as nausea and abdominal pain in the past 3-month period. The prevalence rate of alcohol intolerance complaints among male (assumedly) social drinkers was also elevated in relation to DMF dose.

Adolescent↗
PubMed1992

Studies of the synthesis of biomarkers. XI. Synthesis of 4,5-secocholestane and 4-methyl-4,5-secocholestane.

4,5-Secocholestane (1a) and 4-methyl-4,5-secocholestane (1b) were synthesized from cholesterol (2) in five and seven steps, respectively. The key intermediate, 5-oxo-4,5-secocholestan-4-al (7) was reduced by the Clemmensen method to afford 1a. Meanwhile, 7 underwent selective Wittig reaction, Clemmensen reduction, and hydrogenation to give another target molecule, 1b. The structure of an unknown biomarker was shown to be different from the proposed 1a by gas chromatographic and mass spectrometric comparison.

Cholestanes↗
PubMed1992

Studies of the synthesis of biomarkers. X. Synthesis of 13,17-secodiacholestanes.

13,17-Secodiacholestanes (6) were synthesized from cholesterol (1) in six steps. The key intermediates, (20R)- and (20S)-diacholest-13(17)-enes (3a and 3b), underwent ozonization and reduction to provide (20R)- and (20S)-13,17-secodiacholesta-13,17-dione (5a and 5b), respectively. On Clemmensen reduction, the diones (5a and 5b) yielded the target molecule 6. The structure of an unknown biomarker was shown to be different from the proposed 6 by gas chromatographic/mass spectrometric comparison.

Cholestanes↗
PubMed1992

Synthesis, characterization, and antibacterial activity of transition metal complexes with 5-hydroxy-7,4'-dimethoxyflavone.

Complexes of CuII, NiII, CoII, ZnII, FeIII, CrIII, CdII, and MnII with the natural product 5-hydroxy-7,4'-dimethoxyflavone have been synthesized and the probable structures of these complexes have been proposed on the basis of elemental analyses, molecular weight determination, magnetic moments, and electronic and IR spectral data. The presence of coordinated and crystal water molecules was demonstrated by thermal studies. The antibacterial activity of the ligand and all the complexes has been determined on gram positive and gram negative bacteria.

Apigenin↗
PubMed1992

[Three-dimensional microstructure and its significance of pseudotubular formation in the crescents of rapidly progressive glomerulonephritis].

Tubuloid structure of the crescents in rapidly progressive glomerulonephritis (RPGN) was studied in order to detect its morphological features and functional significance by using three-dimensional microstructure method. The results showed that the tubuloid structure was actually pseudotubular formation in the crescents. Their inner lumens were communicating between the Bowman's capsular space and lumens of the renal tubules. It indicated that pseudotubular formation in the crescents may play an important role in repairing the damaged structure of those injured glomeruli.

Glomerulonephritis↗
PubMed1991

Distribution of hantavirus serotypes Hantaan and Seoul causing hemorrhagic fever with renal syndrome and identification by hemagglutination inhibition assay.

An epidemiologic evaluation of patients with hemorrhagic fever with renal syndrome from different locations in the People's Republic of China was conducted to define the prevalence of two Hantavirus serotypes, Seoul (SEO) and Hantaan (HTN). Serum specimens were collected between 5 and 14 days after the onset of illness and were tested for antibodies by both hemagglutination inhibition (HI) and plaque reduction neutralization (PRN). By the HI test, the geometric mean titer (GMT) of antibodies to SEO in the sera from individuals from Kaifeng City of Henan Province was five times higher than that to HTN. In contrast, by the HI test, the sera from individuals from Jiande County of Zhejiang Province had a GMT of antibodies to HTN that was seven times higher than that to SEO. In the sera from individuals from Shanghai, only a twofold difference was observed in HI antibody titers to the two hemagglutinins by the HI test, with that to HTN being higher than that to SEO. By the PRN test, the GMT ratios of antibody between HTN and SEO strains from individuals in Kaifeng, Jiande, and Shanghai were found to be 1:13, 14:1, and 2:1 respectively. A close correlation (r = 0.8219) and concordance rate (78.3%) were observed between the PRN and HI tests for the identification of the serotypes of individual cases of hemorrhagic fever with renal syndrome. The hantavirus serotypes from individuals in Kaifeng and Jiande were identified as predominantly SEO and HTN, respectively, and those from individuals in Shanghai had an indeterminant serotype defined by these two techniques. The HI test appears to be a simple and reliable way of determining the predominant hantavirus that causes HFRS in a given geographic area.

Antibodies, Viral↗
PubMed1991

Dissociation of tubular cell detachment and tubular cell death in clinical and experimental "acute tubular necrosis".

"Acute tubular necrosis" in humans is often characterized histologically by tubular cell loss and nonreplacement rather than by frank cellular necrosis. It has been assumed that tubular cells detach from the tubular basement membrane after the occurrence of irreversible cell injury and/or cell death. We examined voided urine from patients with native kidney and transplant kidney "acute tubular necrosis" and found significant tubular cell shedding with up to 100% viability of voided tubular cells, as determined by exclusion of trypan blue. Histochemical stains for the brush border enzyme gamma-glutamyl transpeptidase and electron microscopy of cell isolates demonstrated that 30 to 100% of the voided cells were of proximal tubule origin. Moreover, epithelial cell cultures were readily established from noncontaminated voided specimens, and more than 80% of the cells in monolayers expressed gamma-glutamyl transpeptidase activity in vitro. Electron microscopy of cell monolayers confirmed proximal tubular differentiation in the majority of cells in the monolayer, with the remainder having an appearance more consistent with distal origin. In rabbit models of acute ischemic (pedicle clamp) and toxic (HgCl2 and glycerol-induced) injury, tubular cell shedding was also significant, with a mean of 25 to 30% of the voided cells viable. Epithelial cells were successfully cultured and passed from animals with ischemic renal injury. In vitro studies were carried out in cultured human proximal tubular cells to assess suitability of this system for more direct study of the phenomenon of cell detachment in response to injury. We found significant changes in cell shape in response to exposure to anoxia and HgCl2 in these cultures, with extensive cell rounding and retraction at times when cell viability remained high. This in vitro system could prove useful for defining mechanisms of renal tubular cell detachment in response to injury and for examining potential interventions to prevent epithelial disruption and loss of functional integrity. These strategies may ultimately have clinical relevance in patients with "acute tubular necrosis".

Acute Kidney Injury↗
PubMed1991

[Cohort study of seroepidemiology on hemorrhagic fever with renal syndrome].

A cohort study of seroepidemiology on hemorrhagic fever with renal syndrome (HFRS) was carried out in two villages, Jiande County, Zhejiang Province. 1325 persons who had not had antibodies to HFRS in 1987 were interviewed and re-examined in 1988. Seroconversion to HFRS antibodies was found in 30 persons (2.26%). Among them, were two clinical cases with an incidence rate of 0.151% and the rate of inapparent infection was 2.12%. Ratio of apparent to inapparent infection was 1:14. No infection was observed in children aged 2-4 years and subjects aged 60 years and over. The rate was lower in 5-14 years age group (1.42%) than in those of 15-59 age groups (1.47-4.26%). The infection rate in males (2.57%) was slightly higher than in females (1.96%). Results of stratified analysis and logistic regression analysis showed that living in houses located at the village periphery, having straw stack out of the house and rearing cat were risk factors of HFRS infection and their ORs were 3.0932, 3.3629, and 4.9970 respectively. Antibodies and antigens of HFRS were detected in A. agrarius and R. norvegicus captured in the villages.

Adolescent↗
PubMed1991

Transcoronary ethanol ablation of experimental ventricular tachycardia after epicardial ice mapping and localizing.

Thirty-seven reproducible ventricular tachycardias (VTs) were induced in 19 dogs after the onset of myocardial infarction. The site of origin of VT was localized in 19 (59%) of 32 VTs by ice epicardial mapping. After 0.3-1.2 ml of 95% ethanol was injected into a small coronary artery supplying the arrhythmogenic area, VT was no longer inducible in 10 of 14 dogs. Intramyocardial ethanol (1-3 ml) was injected into the site of origin of VT in 9 dogs including 4 with VTs reinduced after intracoronary ethanol. Six of these VTs were not reinduced. Thus, the total efficacy rate was 84%. In 7 dogs, after injection of 0.4-1.2 ml (mean 0.5 ml) of 95% ethanol into a small normal coronary artery, the extent of the changes in ECG, CK-MB and pathology was found to be related to the size of myocardial damage and to the dose of ethanol. The smaller the dose of ethanol was given and the more distal the branch of coronary artery into which the ethanol was injected, the smaller the myocardial damage was. The data demonstrated that intracoronary or intramyocardial injection of ethanol may ablate the experimental VT induced by programmed heart stimulation in dogs after myocardial infarction, indicating that this approach may be useful and meaningful in some selected instances. However, it is necessary to limit the myocardial damage as far as possible.

Animals↗
PubMed1991

[Clinical and experimental study on the treatment of children diarrhea by granule of children-diarrhea fast-stopping].

Granule of children-diarrhea fast-stopping is a proved recipe composed of seven medical herbs such as Poria cocos, haw charcoal, Euphorbia humifusa, etc. After more 20 years' clinical application of 419 cases, the total effective rate proved to be 96.4% and the cure rate 90%, much better than the control groups [TCM: gelian san and shenglingbaizhu san; WM: gentamycin and PPA]. It had the effect of fast-stopping diarrhea and shortening the recovery period. It also had excellent curative effect for acute and chronic diarrhea, for noninfective and infective diarrhea with virus or germs, and for the diarrhea due to moist heat and spleen weakness in TCM. Clinical tests and experiments showed that this medicine had no toxic or side effects. The diarrhea-cure mechanisms were (1) Inhibiting germs so as to eliminate pathogeny. (2) Adjusting and improving organism immunity function. (3) Accelerating the recovery of intestinal digestion and absorption functions. (4) Inhibiting intestinal movement.

Animals↗
PubMed1990

Schistosoma japonicum: an ultraviolet-attenuated cercarial vaccine applicable in the field for water buffaloes.

Water buffaloes were vaccinated three times with 10,000 Schistosoma japonicum cercariae irradiated with ultraviolet (uv) light at a dose of 400 microW x min/cm2. The irradiation was performed with cheap, simple, and portable equipment in a rural area of Hubei Province (People's Republic of China). A challenge infection of 1000 untreated cercariae was given to six vaccinated and six naive control buffaloes, while two vaccinated animals were not challenged. The experiment was terminated 6 weeks after the challenge. Control animals had lost body weight and harbored a mean of 110 worms and 37 eggs per gram of liver. The vaccinated animals gained weight after the challenge and developed 89% resistance to infection with S. japonicum. Since schistosomiasis japonica is nowadays transmitted in China predominantly by domestic livestock, a uv-attenuated cercarial vaccine for bovines may contribute to the control of this disease.

Animals↗