Biomedical subjects

H Cheng

Publications and source records attributed to H Cheng.

At least 91 records · Page 5Linked to original sources

PubMed2001

[Prevalent forecast of kiwifruit bacterial canker caused by Pseudomonas syringae pv. actinidiae].

The prevalent analysis of kiwifruit bacterial canker for several years showed that the effective ecological factors of severe degree were the precipitation (x1) in the second and last ten-days of March, and the average temperature (x2) of January. The model was y = 2.1359 + 0.0107x1 - 0.6061x2. The main factor of the prevalence was the relative variation of ten-days average temperature and precipitation in Winter and in early Spring, and the regression equation was y = -8.127 + 22.739x - 13.254x2. The forecast effect of the equation was obviously significant after testing.

Actinidia↗

PubMed2001

[Ecological factors affecting prevalence of kiwifruit bacterial canker and bacteriostatic action of bacteriocides on Pseudomonas syringae pv. actinidae].

According to the systematic study for 5 years, this paper dealt with the ecological factors affecting prevalence of kiwifruit bacterial canker. The disease was more serious in the orchards with above 750 m in elevation, and more serious at mountain slope facing south than facing north. Incidence differed significantly among cultivars, with easy disease infection for Jinfeng, and strong disease resistance for Jinkui. The older the trees, the more the diseased plants. The one year old twigs had highest death twig incidence of diseased twigs and death twig incidence than other twigs. Among 6 tested bacteriocides, Jiaruinong and streptomycin showed best bacteriostatic effect.

Actinidia↗

PubMed2001

Effects of acute or prolonged exposure to leptin on hepatic glucose oxidation.

OBJECTIVE: To observe the short-term and long-term effects of leptin on hepatic glucose oxidation and glucokinase gene expression. METHODS: Rat hepatic cell line BRL was incubated with leptin of different doses (range from 10 ng/ml-200 ng/ml) for 1 h or 24 h. Glucose oxidation was determined by liquid scintillation counting. Glucokinase gene expression (corrected by beta-actin) was determined by reverse transcription semi-quantitative polymerase chain reaction. RESULTS: Treatment with leptin 10 ng/ml for 1 h had no significant effects on glucose oxidation in hepatic cells. However, at the doses ranging from 50 ng/ml to 200 ng/ml, leptin significantly inhibited glucose oxidation. These effects disappeared when the hepatic cells were exposed to leptin for 24 h. Glucokinase mRNA expression was reduced significantly after both 1 h and 24 h exposure to leptin (100 ng/ml) as compared to that of the control group. CONCLUSION: A low dose of leptin has no significant effect on glucose oxidation in hepatic cells. A relatively high dose of leptin has an acute inhibitory effect on the glucose oxidation in hepatic cells. This effect may likely involve the inhibition of glucokinase gene expression. The inhibitory effect on glucose oxidation is transient and disappears with prolonged exposure time.

Animals↗

PubMed2001

Relationship of large multifunctional proteasome 7 gene polymorphism with susceptibility to type 1 diabetes mellitus and DR3 gene.

OBJECTIVE: To study the relationship of the large multifunctional proteasome 7 (LMP7) gene polymorphism with susceptibility to type 1 diabetes mellitus (DM-1) and the DR3 gene in south Chinese Han population. METHODS: LMP7 genotypes and the DR3 gene were identified in 71 DM-1 patients and 86 healthy persons (as controls) by polymerase chain reaction-restriction fragment length polymorphism. DM-1 patients and controls were divided into DR3-positive and DR3-negative subjects. The frequencies of LMP7 genotypes and alleles were compared between DM-1 patients and controls respectively in the random subjects and in the DR3-matched subjects. Furthermore, DM-1 patients were divided into 3 groups according to the age of diabetic onset: group A < or = 14 years, group B 15-30 years, group C > or = 31 years. RESULTS: In the random subjects, the frequency of LMP7-B/B was lower (39% vs 58%, P < 0.05) and that of LMP7-B/A was higher (54% vs 31%, P < 0.01) in DM-1 patients than that in controls. In DR3-positive subjects, the frequencies of LMP7 genotypes and alleles showed no differences between DM-1 patients and controls. In DR3-negative subjects, the frequency of LMP7-B/B was decreased (40% vs 61%) and that of LMP7-B/A was increased (55% vs 28%, P < 0.01) in DM-1 patients. The frequencies of LMP7 genotypes and alleles showed no significant differences among different ages of diabetic onset. CONCLUSIONS: LMP7-B/B may be the protective genotype, and LMP7-B/A may be the susceptible genotype of DM-1, and this may not be affected by the DR3 gene. Persons with LMP7-B/B may have a decreased risk, and those with LMP7-B/A have an increased risk suffering from DM-1. The LMP7 gene may not be associated with the age of diabetic onset.

Adolescent↗

PubMed2001

[Estimation of insulin secretion rate in multiple sampled intravenous glucose tolerance test].

OBJECTIVE: To measure and calculate insulin secretion rate(ISR) in multiple sampled intravenous glucose tolerance test (FSIVGTT) according to the two compartment model and standard parameters of the kinetics of connecting peptide (C-P) in vivo. METHODS: 15 subjects with normal glucose tolerance and 11 type 2 diabetic patients took part in the study. Oral glucose tolerance test (OGTT) and FSIVGTT were performed. Glucose concentrations were measured by hexokinase method. Insulin (INS) and C-P concentrations were measured by radioimmunoassay. A computer procedure devised by our laboratory was used to calculate the value of ISR at each time point. RESULTS: In the control group, serum INS and C-P concentrations reached the peak at 4 min, the second peak was not obvious. In type 2 diabetes, only 5 subjects had a small peak within 4 min, two curves reached its peak between 60 and 80 min. In the control group, ISR reached its peak 2 min after injection of glucose, that was earlier than INS and C-P curves in time sequence (P = 0.000), the second obvious peak was shown at 22 min. In type 2 diabetes, an obvious but small peak of ISR was shown at 2 min and all the patients had this peak. CONCLUSIONS: It is necessary to take the process of metabolic clearance of INS and C-P into consideration, when blood concentration of INS and C-P were used as indexes to evaluate the secretion function of beta-cells. The ISR profile is more sensitive for investigation of the second phase of insulin secretion in the control group and the first phase in type 2 diabetes group.

Blood Glucose↗

PubMed2001

[Pre- and post-contrast multiphase helical CT in the diagnosis of hepatic focal nodular hyperplasia].

OBJECTIVE: To analyse the pre- and post-contrast CT findings of liver focal nodular hyperplasia (FNH), so as to improve its diagnostic accuracy. METHODS: Pre-contrast scan and post-contrast tri-phase scan (arterial phase, portal venous phase and delayed phase) were performed in 21 patients with FNH which were proved surgically and pathologically. Transcatheter arterial angiography was performed in 2 patients. RESULTS: On pre-contrast scans, 16 of 21 lesions were hypodense, 5 of 21 were isodense. Twelve of 21 lesions showed punctate, streak and radial scar. On the arterial phase scans, all the lesions were markedly and homogeneously enhanced, except for the central scar. Nine of 21 lesions showed dilated and tortuous arteries at the central or peripheral area. On the portal venous phase scans, focal density was decreased, but still showing hyperdense or slightly hyperdense relative to the normal liver. On the delay phase scans, the lesions changed to isodense or slightly hypodense. Enhanced capsule was observed in 3 patients. On the angiography images, dilated arteries and drainage veins were seen. CONCLUSION: FNH has its special characteristics on the multiphasic helical CT scan. It is of great value in diagnosing the FNH and in choosing the appropriate therapy.

Adolescent↗

PubMed2001

[Study on variation and interrelations of characteristics at ginseng germplasms].

The variation and interrelations of some characteristics of Panax ginseng germplasms(lines), which were five selfmating generations of some single plants were studied. Methods of multivariate analysis, such as correlation, regression, or clustering, and coefficient of variation were used. The results were of benefit to the breeding and standardized planting of Panax ginseng.

Genetic Variation↗

PubMed2001

[An exponential universal formula and evaluation model of sustainable development for cities].

In order to study an evaluation model of sustainable development for cities, analysis was performed to study the features of indicator system of community, economy and environment. Based on the genetic algorithms optimum, an exponential universal formula of single indicator was proposed. Evaluation model of sustainable development about the coordinative development of community, economy and environment was developed using weighting method combining the general contrast algorithm with analytic hierarchy process for different structure. The evaluation results of sustainable development for examples using this model showed that the exponential formula of single indicator based on parameters optimum and the evaluation model are not only simple and practical, but also comparisonable, realizable and general.

City Planning↗

PubMed2001

[Relation between transcatheter arterial chemoembolization and time of death in patients with hepatic carcinoma].

OBJECTIVE: To evaluate the relationship between transcatheter arterial chemoembolization (TACE) and time of death in hepatic carcinoma patients. METHODS: One hundred and ninety-five patients (male 188, female 7) with liver cancer underwent TACE with patients dying at different intervals after treatment. Dose of antitumor drugs, amount of iodized oil, liver function, size, recurrence of surgical resection, pattern of tumor, metastasis, presence of portal vein thrombosis, post TACE relapse, post TACE liver function and AFP, etc, altogether 15 variables were subjected to statistical analysis with the Cox's hazard proportional model. RESULTS: According to univariate and forward stepwise regression analysis, factors associated with significantly worse survival were diffused type, multi-nodular growth of tumor, and tumor embolus in the portal vein (P < 0.0001). Before death, most patients had symptoms of chest oppression, shortness of breath, ascites, abdominal distension, jaundice, hepatic failure and hematemesis. Causes of death were hepatic coma (27.2%, n = 53), hepatic failure (23.1%, n = 45), hemorrhage from the digestive tract (36.9%, n = 72), multiple organ failure (5.1%, n = 10) and others (7.2%, n = 14). CONCLUSION: Several factors of TACE may lead to failure in liver function and death. TACE may hasten death in patients with severe liver functional embarrassment. Before instituting TACE, careful weighing the pros and cons of the general condition and liver function is important for patients with portal vein embolism, multiple tumors or diffused lesions. Tolerance of liver to the drug, time, dose and method of treatment should be meticulously and carefully planned. Post TACE protection of liver is also very important.

Adolescent↗

PubMed2001

[Etiological study on human rotavirus infections in children with acute gastroenteritis].

OBJECTIVE: To understand the etiology of human rotavirus infections in children with acute gastroenteritis in China. METHODS: The investigation covered 1968 feces infants and children with acute gastroenteritis in 19 provinces and cities in China. Feces samples collected from 1968 infants and children with diarrhea, 148 children, 135 newborns and 37 adults without diarrhea, 36 adults with diarrhea were examined by polyacrylamide gel electrophoresis (PAGE). 1493 feces samples were examined by ELISA; 388 feces samples from sick children and 57 feces samples from children and adults without diarrhea were examined by EM. Bacterial culture were analyzed in 645 feces samples. RESULTS: Human rotavirus RNA (HRV RNA) was detected in 804(40.9%) of 1968 feces samples examined. No virus was detected in the feces samples of children and adults without diarrhea. Rotavirus antigen was detected in 500 (33.5%) of the 1493 feces samples. According to the genome profile of PAGE, 801 (99.6%) of the 804 rotavirus RNA positive belonged to group A virus, and the other 3 (0.4%) belonged to group C virus. According to the different migration of 10 and 11 segments on PAGE, the RNA pattern of group A rotavirus could be subdivided into two patterns: long and short patterns. The 527 (66.8%) positive HRV RNA was in the long pattern, while the 267 (33.3%) positive were in the short pattern. Among the rest 6 appeared to be mixed types, and the examined one was uncertain. Four different genotypes of HRV RNA in long and short patterns were identified respectively. They were types 4232, 4222, 3232 and 3222. The eight electropherotype genomes of HRV RNA varied not only in different years or seasons but also with the ages of patients and regions where the patients live. CONCLUSION: Rotavirus infections are the major cause of diarrhea of infants and young children throughout China.

Acute Disease↗

PubMed2001

[Expression of KDR in medulloblastoma and its clinical implication].

OBJECTIVE: To gain an insight into the possible relationship between the expression of kinase insert domain-containning receptor (KDR) and the prognosis of medulloblastoma. METHODS: Fifty cases of medulloblastoma of the posterior fossa and ten cases of normal cerebellar tissue were studied via a combination of immunnohistochemical staining in formalin fixed paraffin-embedded sections. RESULTS: KDR was expressed weakly in 1 of 10 normal cerebellar tissues, while KDR was either moderately or strongly expressed in most of the medulloblastomas (49 of 50 cases). Moreover, KDR was expressed not only in the endothelial cells of tumor vasculature, but also in tumor cells. Correlation analysis indicated that expression of KDR was correlated significantly with survival time (r = -0.527, P < 0.01). CONCLUSION: KDR was expressed in most of the medulloblastomas, not only in the endothelial cells of tumor vasculature, but also in tumor cells. The expression level of KDR had a negative correlation with the survival time, thus it might be used as one of the prognosticators of medulloblastoma.

Adolescent↗

PubMed2001

[Expression and significance of urokinase-type plasminogen activator in medulloblastoma].

OBJECTIVE: To detect the expression and evaluate the clinical significance of urokinase-type plasminogen activator (uPA) in medulloblastoma. METHODS: LSAB (labelled streptavidin biotin method) immunohistochemical technique was applied for detecting the expression of uPA in 50 patients with medulloblastoma, and a follow-up survey with Cox regression analysis was made. RESULTS: The staining for uPA was localized on tumor cells and endothelial cells. Cox regression analysis showed that uPA was an independent prognostic factor affecting survival and it had a negative correlation with the prognosis. CONCLUSION: uPA appears to be an independent marker for predicting the prognosis of medulloblastoma.

Adolescent↗

PubMed2000

gamma-phosphate protonation and pH-dependent unfolding of the Ras.GTP.Mg2+ complex: a vibrational spectroscopy study.

The interdependence of GTP hydrolysis and the second messenger functions of virtually all GTPases has stimulated intensive study of the chemical mechanism of the hydrolysis. Despite numerous mutagenesis studies, the presumed general base, whose role is to activate hydrolysis by abstracting a proton from the nucleophilic water, has not been identified. Recent theoretical and experimental work suggest that the gamma-phosphate of GTP could be the general base. The current study investigates this possibility by studying the pH dependence of the vibrational spectrum of the Ras.GTP.Mg(2+) and Ras.GDP.Mg(2+) complexes. Isotope-edited IR studies of the Ras.GTP.Mg(2+) complex show that GTP remains bound to Ras at pH as low as 2.0 and that the gamma-phosphate is not protonated at pH > or = 3.3, indicating that the active site decreases the gamma-phosphate pK(a) by at least 1.1 pK(a) units compared with solution. Amide I studies show that the Ras.GTP.Mg(2+) and Ras.GDP.Mg(2+) complexes partially unfold in what appear to be two transitions. The first occurs in the pH range 5.4-2.6 and is readily reversible. Differences in the pH-unfolding midpoints for the Ras.GTP.Mg(2+) and Ras.GDP.Mg(2+) complexes (3.7 and 4.8, respectively) reveal that the enzyme-gamma-phosphoryl interactions stabilize the structure. The second transition, pH 2.6-1.7, is not readily reversed. The pH-dependent unfolding of the Ras.GTP.Mg(2+) complex provides an alternative interpretation of the data that had been used to support the gamma-phosphate mechanism, thereby raising the issue of whether this mechanism is operative in GTPase-catalyzed GTP hydrolysis reactions.

Escherichia coli↗

PubMed2000

Principles of hydroxamate inhibition of metalloproteases: carboxypeptidase A.

Hydroxamic acids of structure RCON(OH)CH(2)CH(CH(2)C(6)H(5))CO(2)H induce micromolar competitive inhibition of catalysis for the enzyme carboxypeptidase A. Enzyme affinity depends on the nature of the acyl group, for RCO equaling HCO, CH(3)CO, FCH(2)CO, F(2)CHCO, F(3)CCO, CH(3)OCH(2)CO, or CH(3)OCO. In acid dissociation these residues yield hydroxamic acid pK(a) values that vary from 7.6 to 10.3. Profiles of inhibitory pK(i) plotted versus pH indicate characteristically a maximum effectiveness near neutrality. Weaker binding to enzyme is generally displayed in either acidic or alkaline solution, with the position of the alkaline limb of the profiles depending on the pK(a) of the inhibitor. A reverse-protonation pattern of association with the enzyme is indicated, in which the hydroxamate anion of the inhibitor displaces a relatively acidic H(2)O ligand (pK(a) of 6) from the active-site zinc ion of carboxypeptidase A. The metal-coordinating, N-substituted hydroxamic acid functional groups exist in solution as a mixture of syn and anti rotamers, with relative abundances that depend on their pK(a). A pyrrolidinone analogue having a conformationally syn-fixed cyclohydroxamic acid was not an especially potent inhibitor. Structure-activity relationships suggest design criteria for hydroxamic acid inhibitors in order to provide most effective binding with metalloenzymes.

Animals↗

PubMed2000

Competing drug-drug interactions among multidrug antiretroviral regimens used in the treatment of HIV- infected subjects: ACTG 884.

OBJECTIVE: To evaluate the steady state concentrations of saquinavir, ritonavir, nelfinavir, delavirdine, and adefovir in six different three- and four-drug combination regimens. DESIGN: Randomized, partially double-blinded, multicenter study in a population of indinavir-experienced subjects with virologic failure. The first seven subjects enrolled in each of the six treatment arms from 10 participating sites were entered into this pharmacokinetic evaluation. SETTING: Multicenter study of the AIDS Clinical Trials Group (ACTG). PATIENTS: HIV-infected subjects. INTERVENTIONS: A 12-hour pharmacokinetic study was conducted after 2 weeks of drug administration. MAIN OUTCOME MEASURES: Area under the concentration-time curve with statistical comparisons to evaluate the effect of the second protease inhibitor and the effect of the non-protease inhibitors. RESULTS: There was no difference in saquinavir concentrations according to whether the second protease inhibitor was ritonavir or nelfinavir. Saquinavir concentrations in the groups receiving the combination of delavirdine plus adefovir dipivoxil were reduced by approximately 50% compared with those receiving delavirdine. Delavirdine concentrations were reduced by approximately 50%, in the delavirdine plus adefovir dipivoxil arms compared with the delavirdine arms. CONCLUSIONS: Saquinavir concentrations were significantly lower in the arms containing the combination of delavirdine and adefovir dipivoxil compared with the arms containing delavirdine. Delavirdine concentrations were significantly lower when coadministered with adefovir dipivoxil. These drug-drug interactions were not expected, the mechanism(s) is (are) not clear, and additional studies are warranted. This study illustrates the need to understand more fully the pharmacokinetic characteristics of complex combination antiretroviral regimens prior to use in patient management.

Adenine↗

PubMed2000

Direct evidence for the cooperative unfolding of cytochrome c in lipid membranes from H-(2)H exchange kinetics.

The interaction of cytochrome c (cyt c) with anionic lipid membranes is known to disrupt the tightly packed native structure of the protein. This process leads to a lipid-inserted denatured state, which retains a native-like alpha-helical structure but lacks any specific tertiary interactions. The structural and dynamic properties of cyt c bound to vesicles containing an anionic phospholipid (DOPS) were investigated by amide H-(2)H exchange using two-dimensional NMR spectroscopy and electrospray ionisation mass spectrometry. The H-(2)H exchange kinetics of the core amide protons in cyt c, which in the native protein undergo exchange via an uncorrelated EX2 mechanism, exchange in the lipid vesicles via a highly concerted global transition that exposes these protected amide groups to solvent. The lack of pH dependence and the observation of distinct populations of deuterated and protonated species by mass spectrometry confirms that exchange occurs via an EX1 mechanism with a common rate of 1(+/-0.5) h(-1), which reflects the rate of transition from the lipid-inserted state, H(l), to an unprotected conformation, D(i), associated with the lipid interface.

Amides↗

PubMed2000

Sinoatrial node pacemaker activity requires Ca(2+)/calmodulin-dependent protein kinase II activation.

Cardiac beating arises from the spontaneous rhythmic excitation of sinoatrial (SA) node cells. Here we report that SA node pacemaker activity is critically dependent on Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). In freshly dissociated rabbit single SA node cells, inhibition of CaMKII by a specific peptide inhibitor, autocamtide-2 inhibitory peptide (AIP, 10 micromol/L), or by KN-93 (0.1 to 3.0 micromol/L), but not its inactive analog, KN-92, depressed the rate and amplitude of spontaneous action potentials (APs) in a dose-dependent manner. Strikingly, 10 micromol/L AIP and 3 micromol/L KN-93 completely arrested SA node cells, which indicates that basal CaMKII activation is obligatory to the genesis of pacemaker AP. To understand the ionic mechanisms of the CaMKII effects, we measured L-type Ca(2+) current (I(Ca, L)), which contributes both to AP upstroke and to pacemaker depolarization. KN-93 (1 micromol/L), but not its inactive analog, KN-92, decreased I:(Ca, L) amplitude from 12+/-2 to 6+/-1 pA/pF without altering the shape of the current-voltage relationship. Both AIP and KN-93 shifted the midpoint of the steady-state inactivation curve leftward and markedly slowed the recovery of I(Ca, L) from inactivation. Similar results were observed using the fast Ca(2+) chelator BAPTA, whereas the slow Ca(2+) chelator EGTA had no significant effect, which suggests that CaMKII activity is preferentially regulated by local Ca(2+) transients. Indeed, confocal immunocytochemical imaging showed that active CaMKII is highly localized beneath the surface membrane in the vicinity of L-type channels and that AIP and KN-93 significantly reduced CaMKII activity. Thus, we conclude that CaMKII plays a vital role in regulating cardiac pacemaker activity mainly via modulating I(Ca, L) inactivation and reactivation, and local Ca(2+) is critically involved in these processes.

Action Potentials↗

PubMed2000

Randomized study of saquinavir with ritonavir or nelfinavir together with delavirdine, adefovir, or both in human immunodeficiency virus-infected adults with virologic failure on indinavir: AIDS Clinical Trials Group Study 359.

This study compared antiretroviral activity among 6 "salvage" therapy regimens. The study was a prospective, randomized, 2x3 factorial, multicenter study of the AIDS Clinical Trials Group. The study enrolled 277 human immunodeficiency virus (HIV)-infected patients naive to nonnucleoside analogues who had taken indinavir >6 months. The patients had 2000-200,000 HIV RNA copies/mL. Patients received saquinavir with ritonavir or nelfinavir together with delavirdine and/or adefovir and were followed for safety and antiretroviral response between baseline and week 16. At week 16, 30% (77/254) of patients had </=500 HIV RNA copies/mL. Virologic response did not differ significantly between pooled ritonavir and nelfinavir groups (28% vs. 33%; P=.50) or between pooled delavirdine and delavirdine/adefovir groups (40% vs. 33%; P=.42). Pooled delavirdine groups had a greater virologic response rate than did adefovir groups (40% vs. 18%; P=.002). Overall, one-third of patients who experienced virologic failure on an indinavir-containing regimen suppressed virus load levels while they were taking a new salvage regimen.

Adenine↗