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Biomedical subjects

N Zhu

Publications and source records attributed to N Zhu.

At least 55 records · Page 3Linked to original sources
PubMed1999

Application of capillary nongel sieving electrophoresis for gene analysis.

Capillary electrophoresis (CE) has proved to be a strong tool for DNA analysis and has found abundant applications in the fields of restriction fragment sizing, mutation screening, polymerase chain reaction (PCR) product characterizing and forensic identifying. CE may be the main alternative to slab gel electrophoresis. Capillary nongel electrophoresis is the most favorable mode when aiming for this purpose because of its advantages of long lifetime, easy operation, good reproducibility, and low expense. In this paper, a new kind of sieving matrix, with mannitol as the additive for capillary electrophoresis, as well as related methods and their application for gene analysis were reported. Nine DNA fragments amplified by multiplex PCR from a normal dystrophin gene were well separated by this system. Three different deletions were found in Duchenne muscular dystrophy (DMD) patients. Three to four copies of the sex-determination region of the Y chromosome (SRY) gene, as well as the phenylalanine hydroxylase (PAH) gene, could be detected in mixed samples. The frequencies of short tandem repeats (STR) in PAH genes was analyzed in 61 normal Chinese individuals and 6 phenylketonuria families. One case of prenatal gene diagnosis was performed. By using this matrix, CE coupled with reverse transcription PCR (RT-PCR), the analysis of the alternative splicing expression pattern of the fragile X mental retardation 1 (FMR1) gene in adult lung tissue was achieved.

Adult↗
PubMed1999

Two C21-steroidal glycosides isolated from Cynanchum stauntoi.

Studies on the roots of Cynanchum stauntoi led to the isolation of two C21-steroidal glycosides, formally named stauntosides A and B. Their structures were elucidated on the basis of spectroscopic evidence, especially that from analysis of 2D-NMR spectra. They were found to possess an unusual skeleton and were identified as stauntogenin 3-O-alpha-L-diginopyranosyl-(1-4)-beta-L-cymaropyranosyl-(1- 4)-beta-D- digitoxopyranosyl-(1-4)-beta-D-thevetopyranoside and stauntogenin 3-O-alpha-L-cymaropyranosyl-(1-4)-beta-D-digitoxopyranosyl-( 1-4)-beta-D-3- demethyl-2-deoxy-thevetopyranoside.

Carbohydrate Conformation↗
PubMed1999

Antioxidative phenolic glycosides from sage (Salvia officinalis).

An investigation of Salvia officinalis L. has led to the isolation of three new phenolic glycosides, 6-O-caffeoyl-beta-D-fructofuranosyl-(2-->1)-alpha-D-glucopyranosid e (1), 1-O-caffeoyl-beta-D-apiofuranosyl-(1-->6)-beta-D-glucopyrano side (2), and 1-O-p-hydroxybenzoyl-beta-D-apiofuranosyl-(1-->6)-beta-D-glucop yranos ide (3). Elucidation of the structures of 1-3 was based on the interpretation of FABMS and 1D and 2D NMR spectra. Compounds 1 and 2 were found to be moderately active as antioxidants in the DPPH test and metmyoglobin test.

Antioxidants↗
PubMed1999

[Cloning of full-length Dnmt3b cDNA and its alternative splicing isoforms in mouse embryo].

OBJECTIVE: To clone the novel full-length cDNA related to mouse embryonic development. METHODS: Starting from a new expression sequence (clone 2 #) out of a mouse embryonic cDNA library, its full-length cDNA were obtained by rapid amplification of cDNA ends with polyA RNA isolated from mouse 8-9 day embryonic tissue as template, combined with screening of mouse embryonic cDNA library by PCR. Based on the sequences at the two ends of the cDNA, the primers for long range RT-PCR were designed to confirm its factuality. RESULTS: The cDNA isolated in our hands was one of the alternative splicing isoforms of mouse de novo DNA cytosine 5'-specific methyltransferase gene (Dnmt3b) reported in July, 1998. A new alternative splicing region upstream of its initiate codon was found 5' forwards 152 bp over the Dnmt3b cDNA sequence. Eight alternative splicing isoforms of Dnmt3b from mouse embryonic tissue were cloned (Genbank accession number are AF151969, AF151970, AF151971, AF151972, AF151973, AF151974, AF151975, AF151976 respectively). CONCLUSIONS: The 4 kb full-length Dnmt3b cDNA was isolated. Dnmt3b may have novel exons at its 5' upstream and present a complex alternative splicing pattern during mouse embryonic development.

Alternative Splicing↗
PubMed1998

A crystallographic and molecular modeling study of butyrophenones.

The X-ray crystal structures of four butyrophenone analogues have been completed and are reported herein. These include spiperone hydrochloride (I), N-methylspiperone hydrochloride (II), pimozide (III), and fluspirilene (IV). These structures were compared to other structurally similar molecules with similar pharmacological activity. In addition, a molecular modeling study was done in order to determine the low energy conformations of these molecules. It was found that calculations of parameters that describe the molecular conformations showed that all four molecules were structurally similar. Crystallographic data: [see text]

Butyrophenones↗
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↗
PubMed1998

Calreticulin: an intracellular Ca++-binding protein abundantly expressed and regulated by androgen in prostatic epithelial cells.

Calreticulin was identified in a screen for androgen-response genes in the rat ventral prostate. Northern blot and Western blot analyses in the rat model showed that both calreticulin messenger RNA and protein are down-regulated by castration and up-regulated by androgen replacement in the prostate. Northern blot analysis showed that calreticulin expression level in the prostate is much higher than that in seminal vesicles, heart, brain, muscle, kidney, and liver. The regulation of calreticulin expression by androgen is only observed in the prostate and seminal vesicles, two male secondary sex organs. The induction of calreticulin by androgen in prostate organ culture partially resists protein synthesis inhibition, suggesting that calreticulin is a direct androgen-response gene. In situ hybridization and immunohistochemistry studies showed that calreticulin is an intracellular protein in prostatic epithelial cells. Because calreticulin is a major intracellular Ca++-binding protein with 1 high-affinity and 25 low-affinity Ca binding sites, our observations suggest that calreticulin is a promising candidate that mediates androgen regulation of intracellular Ca++ levels and/or signals in prostatic epithelial cells. The expression of calreticulin is also regulated by androgen in the mouse and human prostate, suggesting that androgen regulation and function of calreticulin in the prostate are conserved evolutionarily.

Androgens↗
PubMed1998

PET quantification of specific binding of carbon-11-nicotine in human brain.

UNLABELLED: Previous work on the PET measured uptake of (S)-[11C]nicotine presents conflicting findings as to whether it reflects specific binding. METHODS: We studied the uptake of (R)-[11C]nicotine and (S)-[11C]nicotine in normal volunteers at baseline conditions and after a challenge with unlabeled (S)-nicotine to decrease the concentration of free binding sites or with CO2 to increase perfusion. We analyzed the data using two- and three-compartment models. RESULTS: We found tissue pharmacokinetics of (R)- and (S)-[11C]nicotine are adequately described by the two-compartment model. (S)-nicotine challenge induced small but statistically significant reductions in distribution volume (DV) of both (R)- and (S)-[11C]nicotine. The changes in DV could not be attributed to perfusion changes because DV was not affected by CO2 challenge. Although the reduction in DV indicates sensitivity of [11C]nicotine to status of nicotinic binding sites, the small magnitude of the reduction suggests that most nicotine uptake is nonspecific. CONCLUSION: Although differences in DV attributable to specific binding were detected, (R)- and (S)-[11C]nicotine are relatively poor tracers for studying nicotinic binding sites using PET.

Blood-Brain Barrier↗
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

Reliability of telemedicine examination.

OBJECTIVES: To assess the reliability of telemedicine examination and identify the issues to be addressed if the conduct of physical examination and the reading of images and tracings by telemedicine are to be as reliable as conventional examination and reading. METHODS: Patients were examined both conventionally and by telemedicine in 12 clinics, and the results were compared. There were 1826 matched pairs of observations. Cardiac auscultation, echocardiography, electrocardiography, electroencephalography, obstetric ultrasonography, ophthalmologic examination, physical therapy assessment, pulmonary auscultation, and the reading of chest radiographs with telemedicine cameras and monitors were studied. The main outcome measure was agreement between the telemedicine findings and a criterion standard. RESULTS: For ophthalmology, physical therapy, and cardiac auscultation, 91.2% of the conventional findings and 86.5% of the telemedicine findings were identical or similar to the criterion standard. The kappa coefficient on matched-pair analysis was 0.66. For pulmonary auscultation and reading of chest films with a telemedicine camera and monitor abnormalities were suppressed at default settings but subsequently revealed with extensive manipulation of system settings. For tracings and images, both conventional and telemedicine findings showed 92% reliability, with a kappa coefficient of 0.87. CONCLUSIONS: On the basis of these observations and the methods used, reliability varied with the type of examination, clinician experience with telemedicine, and participant knowledge of system limitations. Clinicians without experience or knowledge of system limitations missed findings of clinical importance. Improvements in equipment since the clinics were conducted in 1994 may have resolved some of these problems. Our findings raise doubts about the reliability of occasional telemedicine consultations by clinicians inexperienced in the technology.

Bias↗
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↗