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Biomedical subjects

W Zhu

Publications and source records attributed to W Zhu.

At least 253 records · Page 14Linked to original sources
PubMed1997

Existence of an abnormal nitric oxide metabolism seen in glomeruli and inner medullary collecting duct in diabetic rat.

OBJECTIVE: To investigate the nitric oxide (NO)-dependent 3', 5'-cyclic guanosine monophosphate (cGMP) stimulation or inhibition in isolated glomeruli and inner medullary collecting duct (IMCD) cells from normal and diabetic rats for elucidating the probable role of NO in diabetic nephropathy. METHODS: Glomeruli and IMCD cells were obtained from anesthetized diabetic rats, 2 weeks after streptozotocin-induction, and normal rats, and incubated for 10 minutes under basal state or adding different drugs. cGMP was measured by radioimmunoassay. RESULTS: Diabetic glomeruli had a higher generation of cGMP under basal state but failed to further response of L-arginine, which was contrary to the glomeruli from normal rats. NG-monomethyl-L-arginine prevented the elevation of cGMP after L-arginine stimulation in normal rats but not in diabetic rats. Acetylcholine produced a concentration-dependent of cGMP accumulation in the glomeruli of both groups, but the extent was relatively smaller in diabetic than in normal. A similar tendency was also observed in sodium nitroprusside treated glomeruli. However the cGMP increment in response to atrial natriuretic peptide was identical in the two groups. For the IMCD cells, neither the difference of basal cGMP nor those responses related to acetylcholine or sodium nitroprusside could be observed. But the attenuated response to L-arginine also existed in diabetic IMCD cells. CONCLUSION: Both diabetic glomeruli and IMCD cells have an abnormal NO metabolism, which may account in part for the disturbance of renal hemodynamics.

Animals↗
PubMed1997

Post-hoc Rasch analysis of optimal categorization of an ordered-response scale.

The purpose of this study was to determine the optimal categorization of a self-efficacy ordered-response scale using the Rasch analysis and compare the performance of the Rasch statistics and parameter estimates with conventional statistics. A 50-item scale to measure psychomotor self-efficacy was administered to a total of 2,022 children, including 1,009 boys and 1,013 girls. The data analysis started by collapsing the original five adjacent categories into two, three, and four categories, and a total of 14 data sets were derived. Each of these data sets, including the original one, was analyzed using the Rasch rating scale model, and a set of Rasch model-data fit, category, and separation statistics and parameter estimates, as well as three conventional statistics, were computed and compared. It was found that, instead of the five-category construct designed, the best order of category meanings of the scale in respondents' perceptions was a three-category construct. The Rasch threshold estimates were sensitive indexes in determining the order of the categorization, and that item separation statistics were useful in determining the optimal categorization after its order was confirmed. The commonly used coefficient alpha was found not helpful at all in determining the optimal categorization. The Rasch analysis was demonstrated to be a useful post-hoc analytic approach in determining the optimal categorization of an ordered-response scale.

Adolescent↗
PubMed1997

[Partial nucleotide sequencing of 7 hepatitis E virus strains isolated from sera of patients with acute sporadic hepatitis E in China].

OBJECTIVE: To compare partial nucleotide and amino acid sequences between epidemic and sporadic hepatitis E viruses (HEV) in China and their relation to the frequency of hepatitis E (HE). METHODS: A reverse transcription nested polymerase chain reaction (RT-nPCR) was used for the amplication of HEV open reading frame 2 (ORF2) cDNA from sera of patients with acute sporadic HE. The RT-nPCR products of HEV ORF2 cDNA were directly sequenced using a sequenase version 2.0 kit with the dideoxy sequencing method. RESULTS: 28 of 41 sera of patients with acute sporadic HE obtained from Shenzhen, Changchun, Hangzhou, Xian and Beijing by RT-nPCR were HEV ORF2 cDNA positive, and 7 of them were sequenced. The nucleotide homology of the seven HEV ORF2 cDNA was 78.9%-80.2%, as compared with the Mexico strain of HEV (M); 93.1%-95.1% with the Burma epidemic strain of HEV (B) (Ep); 92.3%-94.2% with the Burma sporadic strain of HEV (B) (Sp); 96.5%-98.9% with the Xinjiang epidemic strain of HEV CH 1.1; and 95.7%-100.0% between them. CONCLUSIONS: The seven strains of HEV ORF2 cDNA isolated from sera of acute sporadic HE cases have a higher degree of homology with the HEV CH 1.1 and the HEV (B), and may belong to HEV (B) subtype, as the HEV CH1.1 does.

Amino Acid Sequence↗
PubMed1996

Bcl-2 mutants with restricted subcellular location reveal spatially distinct pathways for apoptosis in different cell types.

Human Bcl-2 is located in multiple intracellular membranes when expressed in MDCK and Rat-1/myc cells. We restricted expression to the endoplasmic reticulum or mitochondria by exchanging the Bcl-2 carboxy-terminal insertion sequence for an equivalent sequence from cytochrome b5 or ActA, respectively. MDCK cells are protected from serum deprivation-induced apoptosis by both wild-type Bcl-2 and the mutant targeted to mitochondria but not by the mutant targeted to endoplasmic reticulum. In contrast, when expressed in Rat-1/myc cells, the Bcl-2 mutant located at the endoplasmic reticulum is more effective than that targeted to mitochondria. In MDCK cells both mutants bind Bax as effectively as wild-type, demonstrating that Bax binding is not sufficient to prevent apoptosis.

Amino Acid Sequence↗
PubMed1996

Evolutionary strategies for the elucidation of cis and trans factors that regulate the developmental switching programs of the beta-like globin genes.

We describe three strategies for the identification of specific cis and trans factors that regulate globin gene expression, all three of which are based on the evolution of the globin genes and their expression patterns. The first approach, phylogenetic footprinting, relies on a search for sequence similarities and is designed to elucidate the factors that control those expression patterns which are shared by orthologous globin genes of all eutherian mammals (e.g., the expression of the epsilon globin genes in the embryonic yolk sac and its repression in fetal and adult hematopoietic tissues). The second approach, differential phylogenetic footprinting, relies on a search for sequence differences. This approach may be of value in identifying the mechanisms underlying the generation of novel expression patterns in specific lineages (e.g., the expression of gamma as a fetal gene in the simian primates in contrast with the embryonic expression of gamma in all other mammals). Finally, motif-based phylogenetic analysis takes into consideration the fact that many transcription factors are quite flexible in the recognition of their cognate sites. The approach allows the detection of functionally conserved binding sites despite their sequence variation.

Adult↗
PubMed1996

Regulation of ionic conductances and gene expression by hypoxia in an oxygen sensitive cell line.

We have shown that the PC12 cell line is an excellent model system for investigations of the molecular and cellular processes involved in O2-chemosensitivity. We have identified an O2-sensitive K channel in this cell line that mediates membrane depolarization, an increase in intracellular free Ca2+, and dopamine release during hypoxia. We also presented evidence which shows that expression of the gene for tyrosine hydroxylase, the rate-limiting enzyme in dopamine biosynthesis, is stimulated by reduced O2 tension in PC12 and type I carotid body cells. In addition, we have successfully identified the DNA sequences and trans-acting protein factors that regulate transcription of the TH gene during hypoxia. The mechanisms by which a reduction in O2 tension is transduced into alter cell function including increased gene expression remain unknown. Unpublished results from our laboratory show that the increased TH gene expression during hypoxia does not require activation of the cAMP-PKA signal transduction pathway. We propose that the increase in intracellular free Ca2+ that occurs as a result of membrane depolarization might play an important role. Preliminary findings from our laboratory show that blockade of the voltage operated Ca2+ channel or chelation of intracellular Ca2+ prevent full activation of the TH gene during hypoxia.

Animals↗
PubMed1996

Determination of collagen-proteoglycan interactions in vitro.

The objective of this study was to characterize the physical interactions of the molecular networks formed by mixtures of collagen and proteoglycan in vitro. Pure proteoglycan aggrecan solutions, collagen (type II) suspensions and mixtures of these molecules in varying proportions and concentrations were subjected to viscometric flow measurements using a cone-on-plate viscometer. Linear viscoelastic and non-Newtonian flow properties of these solutions and suspensions were described using a second-order statistical network theory for polymeric fluids (Zhu et al., 1991, J. Biomechanics 24, 1007-1018). This theory provides a set of material coefficients which relate the macroscopic flow behavior of the fluid to an idealized molecular network structure. The results indicated distinct differences between the flow properties of pure collagen suspensions and those of pure proteoglycan solutions. The collagen network showed much greater shear stiffness and more effective energy storage capability than the proteoglycan network. The relative proportion of collagen to proteoglycan is the dominant factor in determining the flow behavior of the mixtures. Analysis of the statistical network theory indicated that the collagen in a collagen-proteoglycan mixture enhances molecular interactions by increasing the amount of entanglement interactions and/or the strength of interaction, while aggrecan acts to reduce the number and/or strength of molecular interactions. These results characterize the physical interactions between type II collagen and aggrecan and provide some insight into their potential roles in giving articular cartilage its mechanical behavior.

Aggrecans↗
PubMed1996

A review of the statistical analysis used in papers published in Clinical Radiology and British Journal of Radiology.

Statistical analysis such as significance testing have become essential features of published medical studies. This has resulted in an increased frequency with which statistics are used, making the interpretation of scientific publications more difficult. There is an extensive array of tests and techniques. The aim of this study is to identify which statistical tests are used in radiology publications. All major articles published in Clinical Radiology and British Journal of Radiology in one year were reviewed. The frequency of statistical methods used was as follows: no statistical method or descriptive statistics only 103 (47%), one type of statistical method 67 (31%), and two or more methods 47 (22%). Statistics dealing with basic inference, decisions, contingency tables or correlation/regression techniques were found in 124 (53%) in which a procedure had been used. Advanced statistics including receiver operating characteristics (ROC), odds ratio, regression techniques, multiway ANOVA, and nonparametric ANOVA studies accounted for only 41 (19%) in which a procedure had been used. We conclude that descriptive analysis and basic statistical techniques account for most of the statistical tests reported. Physicians should concentrate on improving their understanding of basic statistics but advice should be sought from professionals in the fields of biostatistics and epidemiology as to whether the use of more advanced techniques would be more appropriate.

Humans↗
PubMed1996

Many-faceted Rasch calibration of a gross motor instrument.

The purpose of this study was to recalibrate a well-developed motor development instrument (Ulrich, 1985) using the many-faceted Rasch model and to examine its advantages and application potential. The instrument was administered to a total of 909 children from a national multistage sampling across 9 states. These children included 451 boys and 458 girls ranging in age from 3-10 years. The instrument was recalibrated using the many-faceted Rasch model with 8 defined facets. The primary advantages of the many-faceted Rasch calibration are (a) that estimations of parameters are independent of both the examinees and testing items employed, (b) that all facets involved in the calibration can be taken into account, (c) that the calibrated facets share the same metric, and (d) that the measurement scales are additive. These advantages, together with goodness-of-fit statistics generated from the calibration, provided a convenient way to examine the appropriateness of the testing items and related facets and to determine examinees' strengths and weaknesses of their measured ability. Finally, through a step-by-step example, it was shown that applying the many-faceted Rasch calibrated instrument can be both simple and practical.

Calibration↗
PubMed1996

A novel neutralization epitope on the 'thumb' subdomain of human immunodeficiency virus type 1 reverse transcriptase revealed by a monoclonal antibody.

We have prepared a MAb, 7C4, which inhibits the RNA-dependent DNA polymerase activity of human immunodeficiency virus type 1 (HIV- 1) reverse transcriptase (RT); this MAb has allowed identification of a previously unknown neutralizing epitope of RT. Analysis of the epitope and of the mechanism of polymerase inhibition revealed that 7C4 acts by interfering with the interaction between RT and the template-primer. 7C4 recognizes a discontinuous epitope on the two alpha-helices, alphaH and alpha(I), that make up the 'thumb' subdomain of RT. The existing crystallographic model of HIV-1 RT suggests that the 'thumb' subdomain, together with the 'fingers' and 'palm', form a nucleic-acid-binding cleft in the 66 kDa subunit of RT and that alphaH is in contact with the primer strand of the template-primer. The extent of inhibition of enzyme activity produced by 7C4 correlates with the reported primer-length-dependency of template-primer binding to RT. Inhibition by 7C4 was competitive with respect to the template-primer and mixed with respect to the substrate. Binding of 7C4 to RT was prevented by preincubation of the enzyme with high concentrations of template-primer but not with substrate. Thus, the 7C4 epitope apparently exists on part of the template-primer binding site of the alphaH and alpha(I) regions of the 'thumb' subdomain. This neutralization epitope is a logical target for the development of new types of HIV-1 RT inhibitors.

Animals↗