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Biomedical subjects

Z H Zhong

Publications and source records attributed to Z H Zhong.

5 recordsLinked to original sources
PubMed2001

Insulin binding monitored by fluorescence correlation spectroscopy.

AIM/HYPOTHESIS: The characteristics of insulin binding to its receptors have been extensively studied by the radioligand binding assay. We used fluorescence correlation spectroscopy to determine the distribution of diffusion times and further novel data on the kinetics of insulin's binding to its receptor. METHODS: Cultured human renal tubular cells (HRTC) were incubated with tetramethyl rhodamine labelled insulin (Rh-Ins) for 60 min. Fluorescence intensity fluctuations and autocorrelation functions for Rh-Ins, free in the incubation medium and bound to the cell membrane, were studied at single-molecule detection sensitivity in a 0.2 fL confocal volume. RESULTS: Measurements at the cell membrane revealed Rh-Ins binding with at least two diffusion components (diffusion times tauD1 = 0.8 ms, tauD2 = 20 ms) and corresponding weight fractions of y1 = 0.43 and y2 = 0.42. Specificity of the binding was shown by the dislocation of bound Rh-Ins when excess unlabelled insulin was added. Scatchard analysis showed a nonlinear plot, revealing two binding processes with different affinities (Kass approximately 2 x 10(10) M(-1) and approximately 1 x 10(9) M(-1), respectively). CONCLUSION/INTERPRETATION: The fluorescence correlation spectroscopy results show two classes of binding sites with different affinities for insulin, or interactions between receptor sites consistent with negative cooperativity. This conclusion is in agreement with studies of insulin binding using radioligand binding assays. Because of its high sensitivity (single molecule detection), FCS, provides additional data allowing a more precise evaluation of the kinetics of ligand-receptor interactions at low expression levels in living cells.

Cell Membrane↗
PubMed2001

Detection and differentiation of CAV-1 and CAV-2 by polymerase chain reaction.

Canine adenovirus type 1 (CAV-1) and type 2 (CAV-2) can be categorized in the laboratory by haemagglutination and neutralization tests, but they are difficult to differentiate from each other in specimens, especially when infection occurs in the digestive tract. The object of this study was to develop a simple method of detecting and differentiating them. One pair of common primers was designed and synthesized according to the sequences of the E3 and flanking regions and a polymerase chain reaction (PCR) assay was established using these two primers to amplify the virus-specific DNA fragment from clinical specimens as well as from cell cultures. After elecctrophoresis, under the same amplification conditions, 508 bp and 1030 bp PCR products were observed for CAV-1 and CAV-2, respectively. These were further shown to be adenovirus specific by dot hybridization and sequencing. As only one pair of primers was involved in the PCR procedure, it was faster and easier to perform than any of the other assays used for detecting canine adenovirus, making it applicable in the rapid confirmation of diagnosis and differentiation of the two types of canine adenoviruses.

Adenoviridae Infections↗
PubMed1998

Pharmacokinetics of nortriptyline and its 10-hydroxy metabolite in Chinese subjects of different CYP2D6 genotypes.

OBJECTIVES: To study the impact of the CYP2D6*10 allele on the disposition of nortriptyline in Chinese subjects. METHODS: A single dose of 25 mg nortriptyline was given orally to 15 healthy Chinese volunteers who were classified as extensive metabolizers after phenotyping with debrisoquin (INN, debrisoquine) and who were genotyped by allele-specific polymerase chain reaction. Five subjects were homozygous for CYP2D6*1, 5 subjects were homozygous for CYP2D6*10, and 5 subjects were heterozygous for these 2 alleles. Plasma concentrations of nortriptyline and its main metabolite 10-hydroxynortriptyline were measured by liquid chromatography-mass spectrometry, and the pharmacokinetics were studied during 168 hours after the dose. RESULTS: Subjects who were homozygous for CYP2D6*10 had significantly higher total areas under the plasma concentration-time curve (AUC), lower apparent oral clearances, and longer mean plasma half-life of nortriptyline than subjects in the CYP2D6*1/*1 and the heterozygous groups. For 10-hydroxynortriptyline, the AUC was lower and the plasma half-life was longer in subjects who were homozygous for CYP2D6*10 than in subjects in the other 2 groups. CONCLUSION: The CYP2D6*10 allele in Chinese subjects was associated with significantly higher plasma levels of nortriptyline compared with the CYP2D6*1 allele because of an impaired metabolism of nortriptyline to 10-hydroxynortriptyline, particularly in the subjects with the CYP2D6*10/*10 genotype. The results suggest that genotyping of CYP2D6 may be a useful tool in predicting the pharmacokinetics of nortriptyline.

Adult↗