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Biomedical subjects

Q S Zhu

Publications and source records attributed to Q S Zhu.

At least 19 recordsLinked to original sources
PubMed2001

A case-control study of microsomal epoxide hydrolase, smoking, meat consumption, glutathione S-transferase M3, and risk of colorectal adenomas.

We estimated associations between polymorphisms in the gene encoding microsomal epoxide hydrolase (mEH) among 464 cases diagnosed with first occurrence of colorectal adenoma and 510 matched controls. In an analysis controlling only for the matching variables, we found little or no association between adenoma and mEH genotypes defined by polymorphisms at either codon 113 and 139 or mEH activity predicted by both polymorphisms. However, in subsequent analyses, high predicted mEH activity was significantly associated with adenoma among certain subgroups defined by smoking history [odds ratio (OR), 4.27; 95% confidence interval (CI), 1.68-10.81 among current smokers; interaction, P = 0.11], meat consumption (OR, 2.47; CI, 0.99-6.19 among individuals who regularly eat well-done meat; interaction, P = 0.03), and genotypes for the *A/*B polymorphism in the gene encoding glutatione S-transferase M3 (OR, 2.60; CI, 1.28-5.28 among individuals with *A*A genotype; interaction, P = 0.03). These findings are consistent with causal roles for environmental polycyclic aromatic hydrocarbons and genetically encoded variants in enzymes whose actions lead to the production of activated polycyclic aromatic hydrocarbon metabolites.

Adenoma↗
PubMed1996

Monoamine oxidase gene transcription in human cell lines: treatment with psychoactive drugs and ethanol.

In the present study transcriptional activities has been measured with different fragments of the 5'-flanking sequence of the human monoamine oxidase (MAO) genes linked to human growth hormone which was used as a reporter gene. SH-SY5Y neuroblastoma cells and 1242 MG glioma cells were compared under basal conditions as well as after treatments with different drugs. Under basal conditions, the relative reporter activities of the different promoter fragments were similar for both cell lines. No changes in promoter activities, were observed when cells were treated with L-deprenyl, lithium chloride or raclopride. In contrast, increases (2-3-fold) in both reporter gene expression and enzyme activity were observed after ethanol treatment of cells transfected with MAO-B fragments. Gel retardation analysis showed that ethanol caused changes in transcription factor binding to the MAO-B core promoter in both the SH-SY5Y and 1242 MG cell lines in a cell-type specific fashion.

Alcohol Drinking↗
PubMed1995

Characterization of the human 5-HT2A receptor gene promoter.

The regulation of 5-HT2A receptor (5-HT2AR) expression has been implicated in a variety of pathological processes and has been shown to be extremely complicated and controversial. In order to understand the mechanisms of regulation of this receptor, it is important to characterize its promoter. In this report, the 5' end of the human 5-HT2AR gene was cloned and characterized. Anchored PCR mapped multiple transcription initiation sites at nucleotides -1157, -1137, -1127, and -496. Transfection of chimeric growth hormone plasmids containing various DNA fragments into 5-HT2AR-positive human cell lines (SHSY-5Y, neuroblastoma; HeLa, cervix carcinoma) showed that the 0.74 kb HaeIII/PvuII fragment, which encompasses the initiation sites between -1157 and -1127 and 5' of the downstream initiation site (at -496), exhibited significant promoter activity. This promoter activity was not affected by the sequence upstream of the 0.74 kb fragment. The sequence downstream (the 0.45 kb PvuII/SmaI fragment) strongly repressed this promoter activity, suggesting the presence of a silencer. Sequence analysis combined with gel retardation and Dnase 1 footprinting assay identified multiple cis and trans elements for this fragment, including Sp1, PEA3, cyclic AMP response element (CRE)-like sequence, and E-boxes. Two novel transcription factors have been detected by gel retardation and DNase 1 footprinting assay; one of them may be specific for human. The transcription factors and promoter activities were low in the negative cell line NCI-H460 (human lung large cell carcinoma). Interestingly, the 0.39 kb fragment, isolated from the 3' end of the 0.74 kb fragment, exhibited the highest promoter activity. The possibility that this 0.39 kb fragment may be an alternative promoter is discussed. These new data are essential for further study of the regulation of 5-HT2AR gene expression.

Base Sequence↗
PubMed1994

Identification of human monoamine oxidase (MAO) A and B gene promoters.

The promoter of human monoamine oxidase (MAO) A and B genes have been identified. The core promoter region of MAO A is comprised of two 90 bp repeats each of which contains two Sp1 elements and lacks a TATA box. The MAO B core promoter region contains two sets of overlapping Sp1 sites which flank a CACCC element all upstream of a TATA box. The different organization of the MAO A and B promoters may underlie their different cell and tissue specific expression.

Base Sequence↗
PubMed1994

Development of a real-time adaptive current tomograph.

Following the successful development of a multiple-drive electrical impedance tomography system OXPACT-II featuring a voltage-driven current method for in vitro studies, research work currently being undertaken at the EIT research group in Oxford is aimed at developing a real-time multiple-drive adaptive system, called the Oxford Brookes Adaptive Current Tomograph Mark-III (OXBACT-III) which will operate at several frequencies in between 10-160 kHz. The objective of this system development is to enable EIT clinical studies to be undertaken based on the adaptive current method. One of the most important issues addressed in the new system design is to achieve high data acquisition speed while maintaining sufficient system accuracy. This paper will describe the overall data acquisition system structure and relevant system performance specifications.

Data Display↗
PubMed1994

A high output impedance current source.

A high output impedance current source was required for electrical impedance tomography (EIT) applications capable of operating up to 200 kHz. The architecture is based on operational-amplifier power-supply current sensing and produces a predominantly capacitive output impedance, which for the design presented is approximately 1.2 pF.

Amplifiers, Electronic↗
PubMed1994

[The measurement of collagen and proteoglycan contents in nucleus pulposus of lumbar intervertebral disc].

The collagen and proteoglycan contents were determined in lumbar intervertebral disc nucleus from 50 cases normal Chinese with accidental death and in that of 50 cases of prolapsed lumbar intervertebral disc (PID). The significance of the work rested with. (1) The normal range of the collagen and proteoglycan contents in the nucleus pulposus of normal Chinese was defined, therefore, it provided a normal parameter and laid a foundation for the study of collagen and proteoglycan metabolic changes in the nucleus pulposus of lumbar intervertebral disc under pathological condition. (2) By comparison of contents between collagen and proteoglycan in the nucleus pulposus of PID, the physiopathology of PID was confirmed further, that is, the content of proteoglycan of the nucleus pulposus in PID decreased, however, that of collagen increased. (3) The collagen contents between fibrocartilage and nucleus pulposus in normal chinese were compared. Analyses were made biomechanically and biochemically.

Adolescent↗
PubMed1994

[Cytogenetic analyses on giant cell tumor of bone].

Over a 3 year period, 19 surgically resected giant cell tumors of bone and cell lines from 4 cases were analysed cytogenetically. The results indicate that most of the tumor cells are heteroploid, the chromosome model number is predominantly hypodiploid. Karyotypic analysis demonstrated that the loss of chromosome #17, #18 appears more frequently (with a loss rate of 60% and 45% respectively), terminal deletion and telomeric fusion were the most common cytogenetic aberrations. We compared highly nonrandom tumor cell chromosome breakpoints and the same patient's somatic cell chromosome fragile sites with published oncogenes and found that 7q32, 13q13, 22q12 were coincident with MET, FLT, YES2/PDGFB (sis) respectively. Whether these loci abnormalities correlate with tumorgenesis needs further investigation.

Aneuploidy↗
PubMed1994

Bidirectional promoter of human monoamine oxidase A (MAO A) controlled by transcription factor Sp1.

The core promoter region of human monoamine oxidase (MAO) A has been identified in the two 90 bp repeat sequences, which can be further divided into four imperfect tandem repeats, each containing an Sp 1 binding site in the reversed orientation. Gel retardation and DNase 1 footprinting assays identified Sp 1 to be the major transcription factor binding to MAO A core promoter. In addition, positive association has been observed between cellular Sp1 concentration and MAO A promoter or catalytic activity, indicating that Sp1 is a controlling factor for human MAO A expression. DNA fragments from MAO A core promoter exhibit promoter activity in both orientations in a transient transfection assay, using human growth hormone as the reporter gene. A DNA probe isolated from upstream of the core promoter detected positive signals in a Northern analysis, suggesting that the reverse promoter activity may endogenously transcribe a new gene located upstream of MAO A.

Base Sequence↗
PubMed1993

[Measurement of collagen content in articular cartilage of normal Chinese].

We determine the collagen contents of fresh articular cartilage from 188 normal Chinese who died in accidents. Among them, the collagen content of femoral head cartilage (104 cases) was 496 +/- 35mg/g, femoral condyle cartilage (62) 456 +/- 38mg/g, and humeral head cartilage 588 +/- 42mg/g. The normal range of collagen contents in Chinese articular cartilage was defined for the pathological studies of collagen metabolic changes in cartilage. The collagen contents of the non-loading areas were evidently higher than those of the loading ones. The more pressure the cartilage beared, the less collagen contents it contained. In our experiment, the disturbances of "free" hydroxyproline were eliminated by analysing hydroxyproline with rehydrolysis after extraction with heated trichloroacetic acid.

Adolescent↗
PubMed1993

Structure and promoter organization of the human monoamine oxidase A and B genes.

Monoamine oxidase (MAO) A and B play an important role in regulating levels of biogenic amines. MAO A and B cDNAs have been cloned and the deduced amino acids share 73% sequence identity. The genes for MAOA and B are comprised of 15 exons interspersed by 14 introns, span at least 60 kb and exhibit identical exon-intron organization. These findings suggest that the MAOA and MAOB genes are derived from the duplication of a common ancestral gene. The core promoter region of MAOA is comprised of two 90 bp repeats, each of which contains two Spl elements and lacks a TATA box. The MAOB core promoter region contains two sets of overlapping Spl sites which flank a CACCC element all upstream of a TATA box. The different organization of the MAOA and MAOB promoters may underlie their different cell and tissue specific expression.

Base Sequence↗
PubMed1992

Direct interaction between the internal NADH: ubiquinone oxidoreductase and ubiquinol:cytochrome c oxidoreductase in the reduction of exogenous quinones by yeast mitochondria.

The reduction of duroquinone (DQ) and 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone (DB) by NADH and ethanol was investigated in intact yeast mitochondria with good respiratory control ratios. In these mitochondria, exogenous NADH is oxidized by the NADH dehydrogenase localized on the outer surface of the inner membrane, whereas the NADH produced by ethanol oxidation in the mitochondrial matrix is oxidized by the NADH dehydrogenase localized on the inner surface of the inner membrane. The reduction of DQ by ethanol was inhibited 86% by myxothiazol; however, the reduction of DQ by NADH was inhibited 18% by myxothiazol, suggesting that protein-protein interactions between the internal (but not the external) NADH: ubiquinone oxidoreductase and ubiquinol:cytochrome c oxidoreductase (the cytochrome bc1 complex) are involved in the reduction of DQ by NADH. The reduction of DQ and DB by NADH and ethanol was also investigated in mutants of yeast lacking cytochrome b, the iron-sulfur protein, and ubiquinone. The reduction of both quinone analogues by exogenous NADH was reduced to levels that were 10 to 20% of those observed in wild-type mitochondria; however, the rate of their reduction by ethanol in the mutants was equal to or greater than that observed in the wild-type mitochondria. Furthermore, the reduction of DQ in the cytochrome b and iron-sulfur protein lacking mitochondria was myxothiazol sensitive, suggesting that neither of these proteins is an essential binding site for myxothiazol. The mitochondria from the three mutants also contained significant amounts of antimycin- and myxothiazol-insensitive NADH:cytochrome c reductase activity, but had no detectable succinate:cytochrome c reductase activity. These results suggest that the mutants lacking a functional cytochrome bc1 complex have adapted to oxidize NADH.

Antimycin A↗
PubMed1992

Electrical impedance tomography. Electrode current determination from programmable voltage sources.

The accuracy requirements for adaptive current electrical impedance tomography (EIT) measurements exceed the capability of available current sources. A new architecture for an EIT system is described in which the electrode current is set indirectly from a voltage-drive structure. A numerically inverted admittance matrix, obtained from current measurements and driving voltages, has been used to achieve the desired current pattern from programmable voltage sources.

Electric Conductivity↗
PubMed1992

[Peripheral nerves injection injury: the clinical and experimental study].

The results of operative management of peripheral nerve postinjection injuries in 58 patients are reported. Neurolysis is one effective method in treating nerve postinjection injuries with excellent and good results observed in 64.6 percent of patients in this series. We also investigated the early changes in neurophysiological, histological and ultrastructural studies in the peroneal nerve of the rabbit. The results from early exploration and 0.9% NaCl irrigation were compared with those from late extraneural and intraneural neurolysis. The results showed that the injury occurs early in the nerve following intrafacicular injection and may proceed quickly to a certain degree of severity, so timely operation is advisable early incision of the epineurium with saline irrigation is superior to the neurolysis in treating nerve injuries as proved by the experimental study which suggests that the former can be used as an emergency operation for the management of this type of nerve injuries.

Adolescent↗
PubMed1992

Promoter organization and activity of human monoamine oxidase (MAO) A and B genes.

Monoamine oxidase A and B (MAO A and B) play important roles in the metabolism of biogenic and dietary amines and are encoded by two genes derived from a common ancestral gene. The promoter regions for human MAO A and B genes have been characterized using a series of 5' flanking sequences linked to a human growth hormone reporter gene. When these constructs were transfected into NIH3T3, SHSY-5Y, and COS7 cells, the maximal promoter activity for MAO A was found in a 0.14 kilobase (kb) PvuII/DraII fragment (A0.14) and in a 0.15 kb PstI/NaeI fragment (B0.15) for MAO B. Both fragments are GC-rich, contain potential Sp1 binding sites, and are in the region where the MAO A and B 5' flanking sequences share the highest identity (approximately 60%). However, the organization of the transcription elements is distinctly different between these two promoters. Fragment A0.14 consists of three Sp1 elements, all in reversed orientations, and lacks a TATA box. Two of the Sp1 sites are located within the downstream 90 base pair (bp) direct repeat, and the third is located at the 3' end of the upstream 90 bp direct repeat. Fragment B0.15 contains an Sp1-CACCC-Sp1-TATA structure; deletion of any of these elements reduced promoter activity. Additional Sp1 sites, CACCC elements, CCAAT boxes, and direct repeats (four 30 bp direct repeats in MAO A and two 29 bp direct repeats in MAO B) are found in farther-upstream sequences of both genes (1.27 kb for MAO A and mostly in 0.2 kb for MAO B). Inclusion of these sequences decreased promoter activity. The different promoter organization of MAO A and B genes provides the basis for their different tissue- and cell-specific expression.

3T3 Cells↗
PubMed1990

Unique organization of the human BCR gene promoter.

The promoter of the human BCR gene, regulating the transcription of the chimeric BCR/ABL mRNA in leukemia, has been isolated and characterized. A region of 1.1 kb immediately 5' to the transcription start site was analyzed in detail by sequencing, DNase 1 footprinting, gel retardation and functional studies. These experiments localized a minimal promoter to a 650 bp sequence, composed of 270 bp of 5' flanking sequences and 380 bp of exon 1 transcribed sequences. The promoter region includes a TTTAA box, one Sp1 site and a novel protein-binding sequence absolutely necessary for efficient transcription in vivo. Six additional protein-binding regions were identified more to the 5'. Of these, one is found in an inverted repeat in the 3' coding and splice donor region of BCR exon 1.

Animals↗