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Biomedical subjects

N Zhu

Publications and source records attributed to N Zhu.

At least 19 recordsLinked to original sources
PubMed1998

Hepatitis C virus core protein binds to the cytoplasmic domain of tumor necrosis factor (TNF) receptor 1 and enhances TNF-induced apoptosis.

The hepatitis C virus (HCV) core protein is known to be a multifunctional protein, besides being a component of viral nucleocapsids. Previously, we have shown that the core protein binds to the cytoplasmic domain of lymphotoxin beta receptor, which is a member of tumor necrosis factor receptor (TNFR) family. In this study, we demonstrated that the core protein also binds to the cytoplasmic domain of TNFR 1. The interaction was demonstrated both by glutathione S-transferase fusion protein pull-down assay in vitro and membrane flotation method in vivo. Both the in vivo and in vitro binding required amino acid residues 345 to 407 of TNFR 1, which corresponds to the "death domain" of this receptor. We have further shown that stable expression of the core protein in a mouse cell line (BC10ME) or human cell lines (HepG2 and HeLa cells) sensitized them to TNF-induced apoptosis, as determined by the TNF cytotoxicity or annexin V apoptosis assay. The presence of the core protein did not alter the level of TNFR 1 mRNA in the cells or expression of TNFR 1 on the cell surface, suggesting that the sensitization of cells to TNF by the viral core protein was not due to up-regulation of TNFR 1. Furthermore, we observed that the core protein blocked the TNF-induced activation of RelA/NF-kappaB in murine BC10ME cells, thus at least partially accounting for the increased sensitivity of BC10ME cells to TNF. However, NF-kappaB activation was not blocked in core protein-expressing HeLa or HepG2 cells, implying another mechanism of TNF sensitization by core protein. These results together suggest that the core protein can promote cell death during HCV infection via TNF signaling pathways possibly as a result of its interaction with the cytoplasmic tail of TNFR 1. Therefore, TNF may play a role in HCV pathogenesis.

Animals↗
PubMed1997

Synthesis, structure, dopamine transporter affinity, and dopamine uptake inhibition of 6-alkyl-3-benzyl-2-[(methoxycarbonyl)methyl]tropane derivatives.

A series of 6-alkyl-3 beta-benzyl-2-[(methoxycarbonyl)methyl]tropane analogues were synthesized and evaluated as cocaine binding site ligands at the dopamine transporter (DAT). The in vitro affinity (Ki) for the DAT of the 6-alkyl-3 beta-benzyl-2-[(methoxycarbonyl) methyl]tropane analogues was determined by inhibition of [3H]WIN 35,428 in rat caudate putamen tissue. The inhibition of dopamine uptake (IC50) was also measured for selected compounds which demonstrated moderate affinity for the dopamine transporter. The unsubstituted enantiopure analogues (-)-19a (Ki = 33 nM) and surprisingly (+)-20a (Ki = 60 nM) were found to be almost equipotent with the high-affinity binding components of cocaine and WIN 35,065-2 and exhibited slightly more potent dopamine uptake inhibition than both cocaine and WIN 35,065-2. In general, substitution at the 6-position of racemic 19a and 20a with alkyl groups was found to result in decreased activity relative to increased chain length of the substituent. The 3 beta-benzyl-2 beta-[(methoxycarbonyl)methyl]-6 beta-methyltropane (21b; Ki = 57 nM) was the only 6-alkyl derivative to exhibit moderately potent activity. The 6 beta-isomer 21b was 4-fold more potent than the 6 alpha-isomer 19b (Ki = 211 nM) and was nearly equipotent with (-)-19a and (+)-20a as well as with cocaine and WIN 35,065-2. The results of this study further demonstrate the steric constraints associated with the C(6)-C(7) methylene bridge of the tropane ring system for molecular recognition of cocaine analogues at the cocaine binding site(s) on the DAT.

Animals↗
PubMed1997

Cutaneous malignant melanoma in the young.

Between the years 1967 and 1993, 3246 patients were diagnosed with malignant melanoma at Frenchay Hospital, Bristol. This paper reports 47 patients, 21 years of age or under, including 10 preadolescent cases under 14 years of age. It represents a further follow-up of a cohort originally published from this centre in 1986 in addition to 18 new cases. Most (89%) of the lesions occurred on the trunk and extremities, with females showing a predominance of lesions on the lower limbs. 83% of the melanomas were of the superficial spreading type: 72% invaded to Clark level III and IV. Thickness ranged from 0.29 mm to 50.00 mm (median 1.20 mm). Ulceration was present in 17% of cases and 32% of melanomas arose within a pre-existing small congenital melanocytic naevus. Overall 5-year survival was 81%, with a mean follow-up of 8.5 years. Ulceration and tumour thickness of greater than 1.5 mm were associated with a poor prognosis.

Adolescent↗
PubMed1997

Hepatitis C virus core protein interacts with the cytoplasmic tail of lymphotoxin-beta receptor.

Hepatitis C virus (HCV) core protein is a multifunctional protein. We examined whether it can interact with cellular proteins, thus contributing to viral pathogenesis. Using the HCV core protein as a bait to screen a human liver cDNA library in a yeast two-hybrid screening system, we have isolated several positive clones encoding cellular proteins that interact with the HCV core protein. Interestingly, more than half of these clones encode the cytoplasmic domain of lymphotoxin-beta receptor (LT betaR), which is a member of the tumor necrosis factor receptor family. Their binding was confirmed by in vitro glutathione S-transferase fusion protein binding assay and protein-protein blotting assay to be direct and specific. The binding sites were mapped within a 58-amino-acid region of the cytoplasmic tail of LT betaR. The binding site in the HCV core protein was localized within amino acid residues 36 to 91 from the N terminus, corresponding to the hydrophilic region of the protein. In mammalian cells, the core protein was found to be associated with the membrane-bound LT betaR. Since the LT betaR is involved in germinal center formation and developmental regulation of peripheral lymphoid organs, lymph node development, and apoptotic signaling, the binding of HCV core protein to LT betaR suggests the possibility that this viral protein has an immunomodulating function and may explain the mechanism of viral persistence and pathogenesis of HCV.

Binding Sites↗
PubMed1997

Evidence that complex formation by Bas1p and Bas2p (Pho2p) unmasks the activation function of Bas1p in an adenine-repressible step of ADE gene transcription.

Bas1p and Bas2p (Pho2p) are Myb-related and homeodomain DNA binding proteins, respectively, required for transcription of adenine biosynthetic genes in Saccharomyces cerevisiae. The repression of ADE genes in adenine-replete cells involves down-regulation of the functions of one or both of these activator proteins. A LexA-Bas2p fusion protein was found to activate transcription from a lexAop-lacZ reporter independently of both BAS1 function and the adenine levels in the medium. In contrast, a LexA-Bas1p fusion activated the lexAop reporter in a BAS2-dependent and adenine-regulated fashion. The DNA binding activity of Bas2p was not needed for its ability to support activation of the lexAop reporter by LexA-Bas1p, indicating that LexA-Bas1p recruits Bas2p to this promoter. The activation functions of both authentic Bas1p and LexA-Bas1p were stimulated under adenine-repressing conditions by overexpression of Bas2p, suggesting that complex formation by these proteins is inhibited in adenine-replete cells. Replacement of Asp-617 with Asn in Bas1p or LexA-Bas1p allowed either protein to activate transcription under repressing conditions in a manner fully dependent on Bas2p, suggesting that this mutation reduces the negative effect of adenine on complex formation by Bas1p and Bas2p. Deletions of N-terminal and C-terminal segments from the Bas1p moiety of LexA-Bas1p allowed high-level activation by the truncated proteins independently of Bas2p and adenine levels in the medium. From these results we propose that complex formation between Bas1p and Bas2p unmasks a latent activation function in Bas1p as a critical adenine-regulated step in transcription of the ADE genes.

Adenine↗
PubMed1997

Abnormal phospholipid molecular species of erythrocytes in sickle cell anemia.

As the lipid composition of cell membranes has significant effects upon cellular function, we hypothesized that the membranes of sickle cells might have a distorted lipid composition. Accordingly, we analyzed the molecular species of the choline and ethanolamine glycerophospholipids, the fatty acid composition of the total phospholipids and of the five major individual phospholipids of erythrocytes from 8 patients with sickle cell anemia and from 14 normal subjects. Of the 31 molecular species identified for each subclass of the glycerophospholipids, 12 were found to be distinctly abnormal. Sickle cells contained more molecular species with saturated and monounsaturated fatty acid at the sn-2 position and fewer molecular species with polyunsaturated fatty acids at the sn-2 position. The values ranged from 20 to 60% above or below normal values. In diacyl choline glycerophospholipids (outer membrane leaflet), sickle erythrocytes contained lower amounts of the 16:0-18:2 species and higher 16:0-18:1 and 16:0-16:0 species. In diacyl ethanolamine glycerophospholipid (inner membrane leaflet), sickle erythrocytes had lower amounts of 18:0-22:6; 16:0-22:4; 18:0-18:2; 18:1-18:2; and 18:1-20:3. In phosphatidylcholine and phosphatidylethanolamine, sickle erythrocytes contained less linoleic acid, less docosahexaenoic acid (30-40%) and more oleic and palmitic acids (20-30%) compared to normal erythrocytes. These same differences were seen also in the total phospholipids. Our data demonstrated distinct abnormalities of the phospholipid molecular species composition in the membrane lipids of sickle erythrocytes. These defects might have a role in one or more known metabolic abnormalities of sickle cell disease including cation imbalance, dehydration, disturbed membrane phospholipid asymmetry, and hypercoagulability. Furthermore, detailed information of the phospholipid molecular species composition of normal erythrocytes was provided.

Anemia, Sickle Cell↗
PubMed1997

[Screening and genetic analysis of fragile X syndrome in Tongling Anhui province of China].

OBJECTIVE: To investigate the prevalence of fragile X syndrome in the Chinese. METHODS: Fragile X syndrome was screened from 172,600 people living in Tongling city, Anhui province. Suspected patients were tested by PCR and Southern Blotting. RESULTS: Seven of 88 mental handicap children were found with fra (X), including 3 female and 4 male patients. Six patients, 3 normal transmitting males and 5 carriers were found in detailed search in these 6 fra (X) families. Genetic linkage analyses of 2 of the families were reported here. CONCLUSION: The prevalence of fragile X syndrome in the Chinese is not apparently different from the previous reports on the Caucasian population.

Child, Preschool↗
PubMed1996

Synthesis and dopamine transporter affinity of 2-(methoxycarbonyl)-9-methyl-3-phenyl-9-azabicyclo[3.3.1]nonane derivatives.

A series of 9-methyl-3 beta-phenyl-2-substituted-9-azabicyclo[3.3.1]nonane derivatives were synthesized and evaluated as cocaine-binding site ligands at the dopamine transporter (DAT). The conformation of the bicyclic structures and the stereochemistry of the substituents were determined by NMR and X-ray crystallography. The in vitro binding affinity (Ki) of the 9-azabicyclo[3.3.1]nonane derivatives was measured in rat caudate-putamen tissue, and they were found to be 100-fold (Ki = 2-14 microM) less potent than cocaine and other tropane analogs. From these results it is evident that the cocaine-binding site at the DAT is very sensitive to structural modifications of the unsubstituted methylene bridge [C(6)-C(7)] of cocaine and cocaine-like compounds.

Animals↗
PubMed1996

Homotypic interaction and multimerization of hepatitis C virus core protein.

Hepatitis C virus (HCV) core protein constitutes a viral nucleocapsid and may possess multiple functions. In this study, we demonstrated the homotypic interaction and multimerization of HCV core protein in vitro and in vivo. By using a yeast two-hybrid system, we showed that the amino-terminal hydrophilic portion (amino acids 1-115) of the core protein could interact with itself. Deletion analysis mapped the interacting domain within amino acid residues 36-91. The homotypic interaction of the core protein was also confirmed by in vitro protein-protein blotting assay using the recombinant HCV core proteins and by its binding to the glutathione S-transferase core fusion protein. The biological significance of the core protein self-interactions was demonstrated by the detection of multimeric forms of the core protein in mammalian cells. The domain responsible for multimerization was determined to be within the amino-terminal hydrophilic region (amino acids 1-115). Both the membrane-bound and the free core proteins exist in dimeric and multimeric forms, suggesting that multimerization of the HCV core protein occurred at an early stage of viral assembly and that the multimer forms may be involved in multiple functions of the core protein.

Animals↗
PubMed1996

[Evaluation of levator palpebrae superioris muscle resection in 500 cases].

We sum up the effects of levator palpebrae superioris muscle resection to correct congenital ptosis in 500 cases. The surgical results in 369 cases (73.8%) are excellent; ninety-six cases (19.2%) are good and 35 cases (7%) are poor. The operative result depends on the amount of muscle resection. We believe that the levator palpebrae superioris muscle resection is the first choice of treatment for a patient whose levator has no function. The operation method is described and the indications of the operation and related problems are discussed.

Blepharoptosis↗
PubMed1996

Community-based health insurance in China: bending to the wind of change.

China's Cooperative Medical System, a community-based health insurance scheme, declined markedly after the economic restructuring of rural communities and the development of a private market in the health sector during the late 1970s. However, a study of the modified system in Taichang County, where it remains popular, has revealed that insurance premiums (calculated as a percentage of household income), copayments, the inclusion of non-agricultural workers, and strong political support not only favoured the system but also increased its efficiency and effectiveness.

China↗
PubMed1996

[Middle ear function in children with cleft palate].

Middle ear problems in patients with cleft palate have for a long time received insufficient attention. The present study was designed to evaluate middle ear function in 56 children with cleft palate and in a control group of 50 children without cleft palate. The age ranging between 5 and 14 years was similar in both groups. All children underwent routine otoscopic examinations of ear, nose and throat, and were also examined using the Madsen acoustic impedance audiometer. Four major parameters (static compliance, middle ear pressure, acoustic stapedius reflex and Eustachian tube function) were analyzed. It was found that the negative middle ear pressures were higher and the static compliance, which reflected the elasticity of the conducting mechanism of the middle ear, was poorer in children with cleft palate than in the controls. The proportion of children with cleft palate who showed the presence of the acoustic stapedius reflex was also lower than in the control children. Children with cleft palate have a limited ability to actively open the Eustachian tube by swallowing, as evidenced by a poor ability to equilibrate applied positive or negative middle ear pressure. A multidisciplinary approach should be adopted for the complete overall rehabilitation of children with cleft palate. Plastic surgeons to whom most of the treatment is entrusted should be concerned not only with achieving palatal function and acceptable speech, but also with the various other problems associated with cleft palate, especially those affecting the middle ear.

Abnormalities, Multiple↗
PubMed1995

Synthesis and antimicrobial activity of 6,7-annulated pyrido[2,3-d]pyrimidines.

Four new 6H-indeno[2',1':5,6]pyrido[2,3-d]pryimidines (10-13) were synthesized via cyclocondensation reactions involving chlorovinyl aldehyde 1 or ketoaldehyde 3 and appropriately substituted 6-aminopyrimidines. The regiochemistry of the compounds was established by 1H NMR and 13C NMR spectral data as well as X-ray crystal data. Compounds 10 and 11 and previously reported homologues 14 and 15 were screened for antimicrobial activity. Moderate antimicrobial activity was observed for some of these compounds. Compound 14 was especially active against Staphylococcus aureus. Crystal data for 13 (C14H7N3Cl2) follows: monoclinic space group, P21/n; Unit cell dimensions, a = 7.284(1) A, b = 12.800(1) A, c = 13.108(1) A, beta = 93.98(1) degree, V = 1219.2(2) A3, Z = 4.

Anti-Bacterial Agents↗
PubMed1995

Myocardial venous O2 saturation becomes more heterogeneous during hypoxic and carbon monoxide hypoxia.

The hypothesis tested was that myocardial venous O2 saturation (SvO2) heterogeneity, a measure of microregional O2 supply/consumption balance, would increase under hypoxic and CO-hypoxia conditions. Since we are able to determine both O2 supply and the O2 supply/consumption ratio, we could also determine whether regional myocardial O2 consumption was heterogeneous. Twenty open-chest anesthetized dogs were studied under control and four hypoxic conditions, hypoxic hypoxia induced by ventilation with either an 8% O2 (SaO2 = 56%) or a 6% O2 (SaO2 = 40%) gas mixture for 20 min, or CO hypoxia induced by ventilation with a 1% CO gas mixture for either 7 min (SaO2 = 67%) or 20 min (SaO2 = 40%). Regional myocardial blood flow was measured using radioactive microspheres in 40 pieces (approximately 0.5 g) of the left ventricular free wall. Arterial and venous O2 saturations were determined with a four-wavelength microspectrophotometric method. A total of 28 veins (20-100 microns) were examined to determine SvO2 for each condition within each animal. The coefficient of variation (CV = SD/mean x 100), an index of heterogeneity, was calculated for both flow and SvO2 under each condition. Flow increased with increasing severity of hypoxia but its heterogeneity did not change with hypoxic or CO hypoxia. However, SvO2 heterogeneity significantly increased with increasing severity of hypoxia. A linear regression of SvO2 CV and mean SvO2 showed a significant correlation (CV = -0.84 (mean SvO2) + 51.1, R = 0.59). All possible myocardial O2 consumptions were calculated by multiplying all of the flows and O2 extractions. In 53 subepicardial and subendocardial measurements, only 10% of the flow and O2 supply/consumption heterogeneity observations could be explained by uniform O2 consumption if our acceptance criterion was 0.06-0.1 ml O2/min/100 g, and 50% could be explained with an acceptance criterion of 0.3-0.4 ml O2/min/100 g. Therefore, there must be some regional myocardial O2 consumption heterogeneity. The increase in venous O2 saturation heterogeneity during hypoxia may be due to increased variation in regional myocardial O2 consumption or variation in the control of O2 supply/consumption coupling.

Animals↗
PubMed1995

[Detection of FMR-1 gene expression by RT-PCR].

Fragile X syndrome [FRA(X)] as the most common form of inherited mental retardation in man has an incidence of one per 1250 and is associated with a fragile site at Xq27.3. A gene was identified at the fragile X locus and was designated Fragile X Mental Retardation-1 (FMR-1). FRA(X) resulted from expansion of (CGG)n trinucleotide repeat in 5' untranslated region of the human FMR-1 gene, and was associated with abnormal methylation of a CpG island 250 bp proximal to this (CGG)n repeat. Males with typical FRA(X) showed repression of FMR-1 transcription and absence of FMR-1 protein, which was believed to contribute to the fragile X phenotype. FMR-1 mRNA extracted from leukocytes in normal and clinically suspected males were detected by RT-PCR. The methylation status and CGG expansion were also studied by PCR and Southern blot. Two of 10 clinically suspected males were found devoid of FMR-1 expression and accompanied with hypermethylation of the CpG island and CGG trinucleotide repeat expansion.

CpG Islands↗
PubMed1994

(-)-Norcocaine.

The title compound, [2R,3S-(2 beta,3 beta)]-methyl 3-(benzoyloxy)-8-azabicyclo[3.2.1]octane-2-carboxylate, C16H19NO4, is a metabolite of the tropane alkaloid cocaine. The molecule crystallized as the free base with the piperidine ring in a chair conformation. The tropane ring system and its methoxycarbonyl and benzoyl groups are rigid; only rotational flexibility is allowed in the conformation of the substituents.

Cocaine↗