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Biomedical subjects

Y Sun

Publications and source records attributed to Y Sun.

At least 973 records · Page 54Linked to original sources
PubMed1991

Isolation and Characterization of a UDPGlucose: Flavonol O-Glucosyltransferase from Illuminated Red Cabbage (Brassica oleracea cv Red Danish) Seedlings.

A UDPGlc:flavonol O(3)-glucosyltransferase (EC 2.4.1.91) that catalyzes the formation of quercetin and kaempferol O(3)-glucosides has been purified about 1450-fold from illuminated red cabbage (Brassica oleracea cv Red Danish) seedlings with a 3.3% yield. Purification of the enzyme was achieved by (NH(4))(2)SO(4)-precipitation, gel-filtration, ion-exchange chromatography on DEAE-Bio-Gel and Q-Sepharose, chromatofocusing, and electrophoresis in nondenaturing polyacrylamide (10%) gels. The enzyme preparation had a pH optimum between 5.8 and 6.2, isoelectric point in the pH range 4.25 to 4.55, a M(r) of 59,000, and it was composed of two similar subunits of M(r) 29,500. The glucosyltransferase reached half substrate saturation at 180 micromolar (UDPGlc) and 7 micromolar (quercetin) concentrations. Kaempferol, which was glucosylated at a relative rate of 87%, had a lesser affinity for the enzyme (K(m)~12 micromolar). Flavanones, flavanols, flavones, dihydroflavonols, and anthocyanidins were not readily utilized as substrates, suggesting that the enzyme is specific for flavonol glucoside biosynthesis.

Journal Article↗
PubMed1991

Changes in cardiac angiotensin converting enzyme after myocardial infarction and hypertrophy in rats.

1. Cardiac angiotensin-converting enzyme (ACE) is localized in high concentration in cardiac valves, coronary vessels, right and left atrium and right and left ventricle. 2. Cardiac ACE is functionally active in converting angiotension I to angiotensin II. 3. The level of cardiac ACE measured by radioinhibitor binding or by quantitative in vitro autoradiography was greatly increased after experimental myocardial infarction in the rat. The increase was greatest in the fibrous scar tissue of the free left ventricular wall infarct, but there were also significant increases in the ACE concentration in the four chambers of the heart. 4. Treatment with enalapril for 4 weeks following coronary ligation inhibited cardiac ACE, including the high levels found in the scar in the left ventricular free wall. 5. There was a close relationship between the systolic blood pressure and left ventricular mass in several models of experimental hypertension, despite varying degrees of activation of the renin-angiotensin system. However no relationship between the degree of left ventricular hypertrophy and changes in cardiac ACE could be determined. 6. Inhibition of cardiac ACE may contribute to the beneficial effect of ACE inhibitors in cardiac hypertrophy and remodelling, and may play a part in the cardioprotective role of ACE inhibitor.

Animals↗
PubMed1991

Effect of loading doses of L-valine on relative contributions of valine derived from protein degradation and plasma to the precursor pool for protein synthesis in rat brain.

"Flooding" amino acid pools with high doses of labeled amino acids of low specific activity has been proposed to minimize the effects of recycling of amino acids derived from protein degradation on the specific activity of the amino acid precursor pool for protein synthesis. We have examined the influence of recycling on the precursor pool for protein synthesis under conditions in which plasma valine concentrations were normal (0.19 mM) and "flooded" (10-28 mM) by comparing the steady-state specific activity of the tRNA-bound valine with that of the plasma valine. Under normal and "flooding" conditions, the relative contributions of valine from protein degradation to the precursor pool were 63 and 26%, respectively; "flooding" with a plasma level of 28 mM raised the brain acid-soluble pool level to 3.1 mM but was no more effective in decreasing the relative contribution of valine from protein degradation to the precursor pool than "flooding" with a plasma level of 17 mM valine, which raised the brain acid-soluble level only to 2.3 mM. The results of these studies show that "flooding" amino acid pools does indeed reduce the effect of recycling on the precursor amino acid pool for protein synthesis, but it does not totally eliminate it.

Animals↗
PubMed1991

Modeling the dynamic interaction between left ventricle and intra-aortic balloon pump.

An analog model is developed to characterize how alterations of some intra-aortic balloon pump (IABP) parameters affect the coupling between left ventricle (LV) and aorta. The time-varying elastance concept is applied to modeling both active components (LV and IABP) in the assisted circulation. Pressure and flow waveforms in the system are determined by numerically integrating five simultaneous state equations that represent the system dynamics. Validity of the model is supported by good agreement between model predictions and published data on LV pressure-volume (P-V) loops, end-systolic P-V relations, and hemodynamic consequences of adjusting IABP timing and speed. The model also predicts that increasing balloon volume increases the diastolic aortic pressure augmentation but has a negative effect of increasing LV load. Increasing balloon diameter over length ratio and holding a constant volume increases the diastolic augmentation and decreases the LV demand. Positioning the balloon closer to the heart improves systolic unloading but affects neither diastolic augmentation nor cardiac output. These results suggest that occlusivity is a major determinant of IABP effectiveness and plays a more important role than balloon volume and position.

Animals↗
PubMed1991

The association between cervical carcinoma and human papilloma virus (HPV) in Xiangyuan County.

A mass survey was conducted to investigate the association between cervical carcinoma and human papilloma virus (HPV) infection in a high-risk area, Xiangyuan County, Shanxi Province. Fifty-four cases of cervical cancer in situ (CIS), including severe dysplasia (CIN III), 14 cases of invasive cervical carcinoma, 28 cases of mild cervical dysplasia (CIN I), and 13 cases of moderate cervical dysplasia (CIN II) were identified among 6710 women examined. One hundred and sixty-nine punch biopsies from abnormal cervix and genital tract were examined for the presence of HPV 6B/11, 16 and 18 DNA sequences by dot blot hybridization: The positive rates of HPV infection in cervicitis, CIN I, II, III, CIS and invasive cervical carcinoma specimens were 35.06% (27/77), 25% (2/8), 33.33% (2/6), 40% (2/5), 70.58% (24/34) and 40% (4/10), respectively. Among these groups, there was no regular distribution of HPV types except for HPV 16, the positive rate of which was increased from 25% in CIN I to 46.15% in CIS: HPV 16 was also the only type seen in the invasive cervical cancer group. Distribution analysis of HPV types in HPV-positive cervical cancer tissues uncovered an HPV 16 positive rate of 59.4%; 3.7 and 2.4 times higher than those of HPV 6B/11 and HPV 18, respectively. These data confirm the close association between cervical cancer and HPV 16 infection.

Adult↗
PubMed1991

[Epidemiological and serological study on hepatitis C virus infection in plasmapheresis donors].

An epidemic of hepatitis C virus infection in plasmapheresis donors which occurred in 1985 in Gu-An county, Hebei province, was studied. A total of 3,496 persons in five villages were investigated. The prevalence rates of viral hepatitis and elevated ALT levels alone in plasmapheresis donors were 17.10% and 23.23%, respectively, which were significantly higher than these of whole blood donors and controls. 59 sera collected from plasmapheresis donors with viral hepatitis and elevated ALT levels alone were sent to the Centers for Disease Control, USA, for detection of anti-HCV with Chiron C100 (EIA). The positivity rates of anti-HCV were 97.06% and 100%, respectively, indicating that the epidemic was caused by hepatitis C virus.

Adult↗
PubMed1991

[Dihydroetorphine hydrochloride for moderate and severe cancer pain].

One hundred and three patients with moderate and severe cancer pain were given a sublingual analgesic agent--dihydroetorphine hydrochloride (DHE). Relief of cancer pain was moderate or complete in 89.3% (92/103). The average relief time (ART) was 3.9 hours and the average time before effectiveness was 20 minutes. In patients with acute or chronic cancer pain, moderate and complete pain-relief rates were 91.3% and 82.2% (P = 0.237). Difference of ART between them was insignificant (P = 0.299). The main clinical side-effects were somnolence (60%), dizziness (72%), nausea (30%), vomiting (16.5%), constipation (5%) and shortness of breath (8%). In two of the patients, the administration of DHE had to be stopped due to its side-effects. Age, sex and site of cancer pain were not related to the analgesic effects of DHE, but the pain-relief in patients with bladder cancer was poor (P less than 0.001). Within certain range, increase in dose was able to enhance its analgesic effect (P less than 0.001) and reduce drug resistance (P less than 0.001).

Administration, Sublingual↗
PubMed1991

The 1958 and 1987 ARA revised criteria for rheumatoid arthritis in Chinese patients. A comparative study.

The American Rheumatism Association (ARA) 1958 and 1987 criteria for the classification of rheumatoid arthritis (RA) were applied to 111 consecutive RA patients and 54 patients with non-RA connective tissue diseases from three hospitals of tertiary level in Beijing. Comparison of the two criteria showed that the specificity was the same, being 88% for both, whereas the sensitivity varied from 94% of the 1958 criteria to 91% of the 1987 criteria. Factors affecting the sensitivity were morning stiffness for more than one hour and increase of number of swollen joints from one to three in the 1987 revised criteria.

Adolescent↗
PubMed1991

[Study of exercise and serum lipids in puberty].

For determining the relationship between serum lipids and exercise, an investigation was carried out, 275 students (mean age, 16.33 years) acted as an exercise group from Anhui province physical training school and Hefei physical training middle school exercise classes, and 309 students (mean age, 16.96 years) as a control group from Hefei normal school and Hefei physical training middle school general classes. The variables were studied which included age, height, body weight, Quetlete index, energy expenditure, TC, TG, and HDL-C. The survey shows that exercise may lower serum TG, increase TC and HDL-C levels. Energy expenditure, age, and height were identified as the most important predictors by the multiple linear regression analyses. These findings suggest that exercise may play significant role in primary prevention of the cardiovascular diseases.

Adolescent↗
PubMed1990

Heme oxygenase-2 mRNA: developmental expression in the rat liver and response to cobalt chloride.

We have previously identified two isozymes of heme oxygenase, HO-1 and HO-2, in the rat liver exhibiting vastly different molecular biochemical properties, including their responses to various chemical inducers. In the present study of the livers of fetal and newborn rats (-1 day to 21 days) we observed marked differences in the developmental pattern of expression of the transcripts for the two forms of heme oxygenase. In addition, the transcripts for HO-1 and HO-2 vary in their number and response to treatment with cobalt chloride. Specifically, using a full length cDNA probe for HO-2, we observed the 1.3-kb mRNA previously shown to encode HO-2 in the testis, as well as a second less abundant transcript of 1.9 kb. An HO-1 cDNA probe detected only the anticipated single transcript of 1.8 kb. The abundance of each HO-2 homologous transcript was unaffected by cobalt chloride treatment (4 or 24 h) in newborn (7 days old) and adult rats. The 1.8-kb HO-1 mRNA, however, was markedly increased in abundance in both age groups by this treatment. The 1.3-kb HO-2 mRNA level nearly doubled after parturition, but remained essentially unchanged during the first 2 weeks of life, and only modestly increased by age 21 days. At all stages of development, the relative abundance of the 1.3- and 1.9-kb transcripts remained unchanged. In the case of 1.8-kb HO-1 mRNA, the level of mRNA was relatively constant during the first week of life, but was substantially reduced by age 14 days, and was further decreased by age 21 days and in the adult animals. In adult rats, the abundance of the 1.3-kb HO-2 mRNA did not markedly increase over that detected in the course of the early postparturition developmental period. The data suggest that the abundance of the two HO-2 homologous transcripts is not readily subject to regulation by chemicals at any stage of development. The expression of HO-1, on the other hand, is subject to such regulation throughout life, and its high transcript abundance in newborn rats may well reflect availability of an endogenous inducer.

Animals↗
PubMed1990

Vasoactive intestinal peptide increases intracellular cAMP and gonadotropin-alpha gene activity in JEG-3 syncytial trophoblasts. Constraints posed by desensitization.

Expression of the human chorionic gonadotropin (hCG)-alpha gene in placental trophoblasts is markedly stimulated by cAMP, a property preserved in a reporter plasmid containing its cAMP response elements (CREs) linked to the chloramphenicol acetyltransferase coding sequence (CRE alpha CAT). In search of a potential physiologic regulator of hCG gene expression via cAMP, we found that JEG-3 syncytial trophoblast cells have specific binding sites for vasoactive intestinal peptide (VIP) with dissociation constant of 1 nM. VIP maximally increased the transient expression of CRE alpha CAT and the expression of endogenous hCG-alpha mRNA in JEG-3 cells by 4- and 9-fold, respectively. Exposure of JEG-3 cells to 30 nM VIP increased cAMP levels 60-fold after 10-30 min, but cAMP rapidly declined thereafter. As a consequence of this desensitization, the effect of VIP on stimulation of both CRE alpha CAT and endogenous hCG-alpha and hCG-beta mRNA levels more closely resembled that of forskolin or 8-br-cAMP at time points much less than 24 h. Moreover, transient exposure to 8-br-cAMP was much less effective than 24 h of continuous incubation on CRE alpha CAT activity. We conclude that VIP rapidly increases cAMP content and activates hCG-alpha gene expression in JEG-3 cells, but sustained elevations in cAMP are necessary for maximal accumulation of this CRE-regulated gene product.

8-Bromo Cyclic Adenosine Monophosphate↗
PubMed1990

Developmental expression of heme oxygenase isozymes in rat brain. Two HO-2 mRNAs are detected.

Blot hybridization of RNA isolated from rat brain revealed the presence of two HO-2 homologous transcripts (1.3 and 1.9 kilobases (kb] at all stages of development ranging from 1 day before birth to adulthood. The level of both HO-2 messages appeared to be developmentally regulated and a gradual increase was observed from prenatal day 1 to adulthood. The two transcripts were highly homologous as assayed through hybridization studies using probes derived from the 5' end, middle, and 3' end of a cloned rat testis HO-2 cDNA. The 1.3-kb mRNA was essentially identical in size to the testis HO-2 cDNA. The message was efficiently translated in the brain, and is believed to encode the HO-2 protein. It seems unlikely that the 1.9-kb species represents a precursor of the 1.3-kb mRNA, as it was also translated in vivo, although less efficiently than the smaller mRNA species. Neither of the two HO-2 mRNA species were induced by bacterial endotoxin. Unlike HO-2, only one HO-1 transcript of approximately 1.8 kb could be detected. This transcript was of very low abundance and was not developmentally regulated, but could be increased by bacterial endotoxin. The product of this induced message, however, was not detectable by Western immunoblot analysis using antibody raised against liver HO-1. An immunoprecipitate could be detected in brain microsomes by radioimmunoassay using the same antibody. This protein, however, exhibited antigenic properties different from that of the purified liver HO-1 or that of spleen microsomal HO-1. Brain heme oxygenase activity correlated well with the amount of immunoreactive HO-2 protein and both reflect the abundance of the 1.3-kb mRNA message over the course of development.

Animals↗
PubMed1990

Oxygen toxicity in control and H2O2-resistant Chinese hamster fibroblast cell lines.

Following exposure to 95% oxygen, clonogenic cell survival was assayed and qualitative morphologic changes were observed in a Chinese hamster fibroblast cell line (HA-1). The time in 95% O2 necessary to clonogenically inactivate 90% of the cells was inversely related to the cell density of the cultures at the beginning of hyperoxic exposure (from 1 to 6 X 10(4) cells/cm2). The O2-induced loss in clonogenicity and evidence of morphologic injury were shown to be significantly delayed (17-22 h) in an H2O2-resistant variant of the parental HA-1 cell line. After the delay in onset of clonogenic cell killing or morphologic injury, the process of injury proceeded in a similar fashion in both cell lines. The H2O2-resistant cell line demonstrated significantly greater catalase activity (20-fold), CuZn superoxide dismutase activity (2-fold), and Se-dependent glutathione peroxidase activity (1.5-fold). The greater activities of CuZn superoxide dismutase and catalase were accompanied by similarly greater quantities of immunoreactive protein as determined by immunoblotting. These data demonstrate that the cells adapted and/or selected for growth in a highly peroxidative environment also became refractory to O2-induced toxicity, which may be related to increased expression of antioxidant enzymes. However, the magnitude of this cross-resistance to O2 toxicity was less than the magnitude of the cellular resistance to the toxicity of exogenous H2O2, suggesting that in this system the toxicity of 95% oxygen is not identical to H2O2-mediated cytotoxicity.

Animals↗