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X Min

Publications and source records attributed to X Min.

11 recordsLinked to original sources
PubMed2000

Molecular cloning and expression patterns of three putative functional aldehyde oxidase genes and isolation of two aldehyde oxidase pseudogenes in tomato.

The final steps in the biosynthesis of the plant hormones abscisic acid (ABA) and indole-3-acetic acid (IAA) have been shown to be catalyzed by aldehyde oxidases (AO). We have cloned three putative functional AO genes (TAO1, TAO2 and TAO3) and two putative AO pseudogenes (TAO4 and TAO5) in tomato. The TAO1 cDNA described here includes the correct amino terminus of the encoded TAO1 protein and is different at the 5'-end from the TAO1 sequence in GenBank (accession number U82558). Northern analysis shows that TAO1 is expressed mainly in vegetative tissues and TAO2 is expressed in both vegetative and reproductive tissues. TAO3 expression was not detectable by Northern hybridization. These results suggest that each AO may play different roles in the regulation of tomato growth and development.

Aldehyde Oxidase↗
PubMed1998

Conformational basis of the phospholipid requirement for the activity of SR Ca(2+)-ATPase.

The delipidated sarcoplasmic reticulum (SR) Ca(2+)-ATPase was reconstituted into proteoliposomes containing different phospholipids. The result demonstrated the necessity of phosphatidylcholine (PC) for optimal ATPase activity and phosphatidylethanolamine (PE) for the optimal calcium transport activity. Fluorescence intensity of Fluorescein 5-isothiocyanate (FITC)-labeled enzyme at Lys515 as well as the measurement of the distance between 5-((2-[(iodoacetyl) amino] ethyl) amino)naphthalene-1-sulphonic acid (IAEDANS) label sites (Cys674/670) and Pr3+ demonstrated a conformational change of cytoplasmic domain, consequently, leading to the variation of the enzyme function with the proteoliposomes composition. Both the intrinsic fluorescence of Trp and its dynamic quenching by HB decreased with increasing PE content, revealing the conformational change of transmembrane domain. Time-resolved fluorescence study characterized three classes of Trp residues, which showed distinctive variation with the change in phospholipid composition. The phospholipid headgroup size caused the conformational change of SR Ca(2+)-ATPase, subsequent the ATPase activity and Ca2+ uptake.

Animals↗
PubMed1998

Finite element analysis of defibrillation fields in a human torso model for ventricular defibrillation.

In order to optimize defibrillation electrode systems for ventricular defibrillation thresholds (DFTs), a Finite Element Torso model was built from fast CT scans of a patient who had large cardiac dimensions (upper bound of normal) but no heart disease. Clinically used defibrillation electrode configurations, i.e. Superior Vena Cava (SVC) to Right Ventricle (RV) (SVC-RV), left pectoral Can to RV (Can-RV) and Can + SVC-RV, were analyzed. The DFTs were calculated based on 95% ventricular mass having voltage gradient > 5 V/cm and these results were also compared with clinical data. The low voltage gradient regions with voltage gradient < 5 V/cm were identified and the effect of electrode dimension and location on DFTs were also investigated for each system. A good correlation between the model results and the clinical data supports the use of Finite Element Analysis of a human torso model for optimization of defibrillation electrode systems. This correlation also indicates that the critical mass hypothesis is the primary mechanism of defibrillation. Both the FEA results and the clinical data show that Can + SVC-RV system offers the lowest voltage DFTs when compared with SVC-RV and Can-RV systems. Analysis of the effect of RV, SVC and Can electrode dimensions and locations can have an important impact on defibrillation lead designs.

Computational Biology↗
PubMed1998

Effect of the Yang tonifying herbs on myocardial beta-adrenoceptors of hypothyroid rabbits.

New Zealand White female rabbits were randomly divided into three groups, each contained six rabbits, i.e. thyroidectomized and untreated rabbits (group 1), thyroidectomized rabbits treated by the Yang tonifying herbs (group 2) and sham thyroidectomized rabbits as controls (group 3). The myocardial beta-adrenoceptor density (Bmax) and affinity (Kd) of each group of rabbits were determined by radioligand binding assay technique on the thirtieth postoperative day and the data were handled by using a computer program of the Woolf plot with weight regression. Moreover, the serum levels of thyroxine (T4) and triiodothyronine (T3) of each group of rabbits were measured by radioimmunoassay technique and their heart rates (HR) were also recorded on the preoperative and thirtieth postoperative day. The results showed that the Bmax, T4, T3 and HR in group 1 were lower significantly than that in group 3 (P < 0.01-0.001), but the change of Kd in group 1 was not significant; the deviation of the indices from the normal value in group 2 was less remarkably than in group 1 other than T4.

Adrenergic beta-Antagonists↗
PubMed1997

An integral equation model for intracardiac electrogram sensing.

Electrogram sensed by an intracardiac electrode has long been characterized based on two approaches: 1) presume that the electrode is very small and does not disturb the potential prior to applying the electrode, and 2) take an average of the prior potential over the electrode surface. In fact, any intracardiac sensing electrode has a finite surface area where electrical charges are induced and disturb the external potential field, thus, the sensed potential is different from the potential prior to placing the electrode. In this paper, an integral equation model is proposed based on the current continuity equation in homogeneous myocardial medium. The new model can accurately characterize the electrogram sensed by an electrode with a non-negligible surface area and a load impedance. The new model can be solved numerically via the method of moments to obtain the potential induced on the electrode surface by an arbitrary dipole volume source. As an application of the proposed theory, several electrode configurations with different loads have been analyzed with an intent to show that a finite electrode surface will significantly reduce the electrogram peak amplitude and slope, and a load impedance lower than 20 k omega will also degrade the electrogram sensitivity.

Electrocardiography↗
PubMed1992

Random mutagenesis of the human immunodeficiency virus type-1 trans-activator of transcription (HIV-1 Tat).

A new method is described for the direct construction of randomly mutagenized genes by applying the polymerase chain reaction (PCR) to an oligonucleotide synthesized using doped nucleotide reservoirs. We have demonstrated the utility of this method by generating a library of mutant HIV-1 tat genes. Several arbitrarily selected, inactive tat clones were sequenced to evaluate the extent of the mutagenesis. Moreover, fourteen recombinants encoding varying levels of transcriptional trans-activator activity were isolated by transient transfection of sub-library pools into a HeLa cell line bearing an HIV-LTR-chloramphenicol acetyltransferase (CAT) reporter gene. Sequence data revealed a spectrum of alterations including nucleotide substitutions, insertions, and deletions, suggesting that mutations arose from both the doped DNA synthesis and the subsequent PCR 'rescue' of full-length product. Sequence comparison between inactive and active Tat clones revealed a selection pressure against amino-acid substitutions within the N-terminal domains of Tat, indicating the importance of this region to trans-activation competence. In addition, single and double missense mutations within the basic-rich, TAR RNA-binding domain were seen to be tolerated within active Tat clones.

Amino Acid Sequence↗
PubMed1991

Expansion of myelopoietic precursors and inhibition of B-cell precursors in mice that express a T-cell receptor gamma (V gamma 1.1J gamma 4C gamma 4) transgene.

Knowledge of the genetic determinants that can affect renewal of multipotential stem cells and their commitment to specific cell lineages is essential to our understanding of multicellular development. However, despite the vast amount of accumulated knowledge in this area, genetic determinants that affect renewal and commitment of precursor cells are unknown. In this study, we demonstrate that three independently derived founder mouse strains, transgenic for the TcR V gamma 1.1J gamma 4C gamma 4 (TcR gamma 4) chain gene, differed significantly from normal mice in their development of T and B cells as well as myelopoietic precursor cells. Ontogenic programs consistent with an acceleration of T-cell development and a delayed appearance and suppressed levels of pre-B- and B-cell precursors were evident in these transgenic mice. In addition, TcR gamma 4 transgenic mice possessed a significantly elevated level of myelopoietic pluripotential precursors. 3H-thymidine cell suicide studies suggest that higher percentages of pluripotent precursors from the bone marrow of the TcR gamma 4 transgenic mice were in the S phase of the cell cycle. These modulations of the lymphoid and myelopoietic compartments, however, were not found in other T-cell receptor transgenic mice (e.g., TcR V gamma 1.2J gamma 2C gamma 2, TcR gamma 2; or V beta 8.1D beta J beta 2.4C beta 2, TcR beta) constructed with the same or similar cDNA expression vector. The results suggest that the expression of a specific T-cell receptor gamma chain gene, and/or an elevated level of particular subset of TcR gamma delta cells, may affect the proliferation and relative proportions of haemopoietic and lymphoid precursors.

Aging↗
PubMed1991

Detection of amplified Wuchereria bancrofti DNA in mosquitoes with a nonradioactive probe.

A technique to identify Wuchereria bancrofti larvae in mosquito vectors with an enzyme-labeled DNA probe is described. To overcome the low sensitivity of nonradioactive detection methods, analyte DNA was amplified by polymerase chain reaction (PCR). Oligonucleotide primers were used to amplify W. bancrofti-specific DNA fragments of 380 and 650 bp, respectively. Parasite DNA in mosquito extracts was isolated free of inhibitors of the PCR by hybridization to a biotinylated DNA fragment (IWb 67), which hybridizes to DNA from most filarial species, followed by absorption of the resulting DNA hybrids onto avidin-coated acrylic beads. PCR-amplified DNA was detected with a biotin-labeled W. bancrofti-specific repeat DNA (IWb 35) coupled to avidin-alkaline phosphatase and the chemiluminescent substrate, AMPPD. The DNA equivalent of less than one larva can be detected by this method in mosquito extracts. The sensitivity of detection was comparable to that of radioactive probes and the assay is suitable for field application in endemic countries.

Animals↗