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Biomedical subjects

L Jin

Publications and source records attributed to L Jin.

At least 55 records · Page 3Linked to original sources
PubMed2003

Expression profile of mRNAs from human pancreatic islet tumors.

In order to understand the tIssue specificity of the endocrine pancreas, it is important to clarify the expression profile of mRNAs in various states of the tIssue. A total of approximately 9000 non-redundant expressed genes from human pancreatic islets and insulinoma have so far been determined as expressed sequence tags (ESTs) and deposited in public databases. In the present study towards the identification of a complete set of genes expressed in human pancreatic islets, we have determined 3'-ESTs of 21267 clones randomly selected from a cDNA library of human pancreatic islet tumors. Clustering analysis generated 6157 non-redundant sequences comprising 2323 groups and 3834 singletons. Nucleotide and peptide database searches show that 3103 of them represent known human sequences or homologs of genes identified in other species and 58 are new members of structurally related families. The sequences were classified on the basis of the putative protein functions encoded, and were assigned to the respective chromosome by database analysis. The sequences were also compared with the EST databases (dbEST and EPConDB) including ESTs from normal pancreatic islet, insulinoma, and fetal pancreas. Since 3384 genes were newly found to be expressed in human pancreatic islets and 587 of them were unique to the islets, this study has considerably expanded the catalog of genes expressed in the endocrine pancreas. The larger collection of pancreatic islet-related ESTs should provide a better genome source for molecular studies of differentiation, tIssue-specific functions, and tumorigenesis of the endocrine pancreas as well as for genetic studies of diabetes mellitus.

Cloning, Molecular↗
PubMed2002

An RT-PCR assay using oral fluid samples to detect rubella virus genome for epidemiological surveillance.

A reverse transcription nested polymerase chain reaction (RT-PCR) method was developed for detecting rubella virus (RV) RNA using primer pairs which targeted a variable region of the E1 gene. RV genome was detected in oral fluid, throat swabs, serum and tissue samples. This is the first report to show that RV genome can be detected in oral fluid samples, including acute cases < or = 2 days after onset of symptoms, which have previously only been used for antibody testing. This suggests that PCR is useful for assisting with early diagnosis when a sufficient IgM response may not have been mounted. The PCR amplicon of 553 nucleotides was also useful for molecular genotyping, which contributes to RV epidemiological surveillance.

Body Fluids↗
PubMed2002

Characterization of measles virus strains causing SSPE: a study of 11 cases.

Eleven subacute sclerosing panencephalitis (SSPE) cases diagnosed in the UK between 1965 and 2000 were investigated. The entire or partial matrix (M), hemagglutinin (H), and nucleoprotein (N) genes of measles virus (MV) were sequenced following direct RT-PCR amplification from brain tissues. All the M genes showed the characteristic biased hypermutations and a premature termination codon was detected in 5/11 M sequences. Based on the more highly conserved H and N genes observed in persistent MV studies, phylogenetic analysis showed that two of three strains from patients likely to have acquired infection in the 1950s were related to clade C (WHO designation) and one appears to be a novel genotype. Three strains from patients infected in the 1960s and 1970s were clearly related to a MV strain isolated in 1974 belonging to genotype D1. Four strains from patients infected in the 1980s clustered with genotype D7 strains. One sequence from a patient infected in 1990s was identified as genotype D6. No vaccine strains were detected although five of these patients had been previously immunized. The sequence data obtained from these historic strains do not support the view that vaccine strains are associated with SSPE and provide valuable information for further studies of MV epidemiology, evolution, and pathogenesis in SSPE.

Adolescent↗
PubMed2002

Linkage disequilibrium mapping of quantitative trait loci under truncation selection.

As a dense map of single nucleotide polymorphism (SNP) markers are available, population-based linkage disequilibrium (LD) mapping or association study is becoming one of the major tools for identifying quantitative trait loci (QTL) and for fine gene mapping. However, in many cases, LD between the marker and trait locus is not very strong. Approaches that maximize the potential of detecting LD will be essential for the success of LD mapping of QTL. In this paper, we propose two strategies for increasing the probability of detecting LD: (1) phenotypic selection and (2) haplotype LD mapping. To provide the foundations for LD mapping of QTL under selection, we develop analytic tools for assessing the impact of phenotypic selection on allele and haplotype frequencies, and LD under three trait models: single trait locus, two unlinked trait loci, and two linked trait loci with or without epistasis. In addition to a traditional chi(2) test, which compares the difference in allele or haplotype frequencies in the selected sample and population sample, we present multiple regression methods for LD mapping of QTL, and investigate which methods are effective in employing phenotypic selection for QTL mapping. We also develop a statistical framework for investigating and comparing the power of the single marker and multilocus haplotype test for LD mapping of QTL. Finally, the proposed methods are applied to mapping QTL influencing variation in systolic blood pressure in an isolated Chinese population.

Chi-Square Distribution↗
PubMed2002

Generation of recombinant virus-like particles of human and non-human polyomaviruses in yeast Saccharomyces cerevisiae.

OBJECTIVES: Non-viral methods of gene transfer have been preferred in gene therapy approaches for several reasons, particularly for their safety, simplicity and convenience in introducing heterologous DNA into cells. Polyomavirus virus-like particles (VLPs) represent a promising carrier for encapsidation of foreign nucleic acids for gene therapy. For the development of such gene delivery systems as well as for providing reagents for improving virus diagnostics, an efficient yeast expression system for the generation of different polyomavirus VLPs was established. METHODS: A galactose-inducible Saccharomyces cerevisiae yeast expression system was used. Formation of empty VLPs was confirmed by cesium chloride ultracentrifugation, agarose gel electrophoresis and electron microscopy. Cross-reactivity of the major capsid proteins (VP1) of different polyomaviruses was analyzed by Western blot using rabbit and mice sera raised against the VP1 proteins. RESULTS: VP1 of polyomaviruses from humans (JC polyomavirus and serotypes AS and SB of BK polyomavirus), rhesus monkeys (simian virus 40), hamsters (hamster polyomavirus), mice (murine polyomavirus) and birds (budgerigar fledgling disease virus) were expressed at high levels in yeast. Empty VLPs formed by all yeast-expressed VP1 proteins were dissociated into pentamers and reassociated into VLPs by defined ion and pH conditions. Different patterns of cross-reactivity of the VP1 proteins with heterologous mice and rabbit sera were observed. CONCLUSION: The developed heterologous yeast expression system is suitable for high-level production of polyomavirus VLPs. Yeast-derived VLPs are generally free of toxins, host cell DNA and proteins. These VLPs might be useful for the generation of new diagnostical tools, gene delivery systems and antiviral vaccines.

Amino Acid Sequence↗
PubMed2001

Crystallization and preliminary X-ray crystallographic studies of a macromolecular antitumour antibiotic, C1027.

C1027 is a macromolecular antitumour antibiotic produced by Streptomyces globispourus C1027 and consists of an apoprotein and a non-protein labile chromophore. Little is known about how the thermally unstable chromophore is stabilized by the apoprotein. The purified C1027 was monodisperse according to dynamic light-scattering measurements and crystallized in two different crystal forms from two different starting conditions using the vapour-diffusion method. Condition I yielded hexagonal prism crystals having space group P3(1)/P3(2) and unit-cell parameters a = b = 66.8, c = 55.4 A. Diffraction data were collected to 2.1 A resolution using an in-house Rigaku rotating Cu anode X-ray generator. Another condition produced rod-like crystals with space group P3(1)21/P3(2)21 and unit-cell parameters a = b = 55.15, c = 55.87 A. A data set to 1.8 A resolution was collected from a rod-like crystal using a MAR CCD detector at the SRS synchrotron source.

Aminoglycosides↗
PubMed2001

Mammalian Bax-induced plant cell death can be down-regulated by overexpression of Arabidopsis Bax Inhibitor-1 (AtBI-1).

We recently isolated the AtBI-1 (Arabidopsis Bax Inhibitor-1) gene, the expression of which suppressed Bax-induced cell death in yeast. To determine whether the same is true in the plant system, transgenic Arabidopsis plants overexpressing Bax protein under a dexamethasone (DEX)-inducible promoter were generated. On DEX treatment, such transgenic plants exhibited marked cell death at the whole-plant level, cell shrinkage, membranous destruction, and other apoptotic phenotypes. Transgenic Bax plants were retransformed with a vector containing the AtBI-1 gene (tagged with green fluorescent protein) under the control of the cauliflower mosaic virus 35S promoter. Plants expressing both Bax and AtBI-1 were able to maintain growth on DEX-treatment by sustaining intracellular integrity. Thus, we present here direct genetic evidence that the plant antiapoptotic protein AtBI-1 is biologically active in suppressing the mammalian Bax action in planta.

Animals↗
PubMed2001

The Eurasian heartland: a continental perspective on Y-chromosome diversity.

The nonrecombining portion of the human Y chromosome has proven to be a valuable tool for the study of population history. The maintenance of extended haplotypes characteristic of particular geographic regions, despite extensive admixture, allows complex demographic events to be deconstructed. In this study we report the frequencies of 23 Y-chromosome biallelic polymorphism haplotypes in 1,935 men from 49 Eurasian populations, with a particular focus on Central Asia. These haplotypes reveal traces of historical migrations, and provide an insight into the earliest patterns of settlement of anatomically modern humans on the Eurasian continent. Central Asia is revealed to be an important reservoir of genetic diversity, and the source of at least three major waves of migration leading into Europe, the Americas, and India. The genetic results are interpreted in the context of Eurasian linguistic patterns.

Adult↗
PubMed2001

MMR vaccine in HIV-infected children -- potential hazards?

Although given routinely as prophylaxis against wild-type measles to HIV-infected children, the live attenuated measles component of the MMR triple vaccine also possesses potential for disease. We document a case of measles proven to be caused by vaccine strain in a HIV-infected child here in the UK and discuss the clinical and immunological aspects. We also consider the new guidelines for MMR vaccination in HIV-infected children adopted last year in the USA.

Antiretroviral Therapy, Highly Active↗
PubMed2001

Receptor specificity in the self-renewal and differentiation of primary multipotential hemopoietic cells.

To determine whether cytokine-induced signals generate unique responses in multipotential hemopoietic progenitor cells, the signaling domains of 3 different growth factor receptors (Mpl, granulocyte-colony-stimulating factor [G-CSF] receptor, and Flt-3) were inserted into mouse primary bone marrow cells. To circumvent the activation of endogenous receptors, each signaling domain was incorporated into an FK506 binding protein (FKBP) fusion to allow for its specific activation using synthetic FKBP ligands. Each signaling domain supported the growth of Ba/F3 cells; however, only Mpl supported the sustained growth of transduced marrow cells, with a dramatic expansion of multipotential progenitors and megakaryocytes. These findings demonstrate that the self-renewal and differentiation of multipotential progenitor cells can be influenced through distinct, receptor-initiated signaling pathways.

Animals↗
PubMed2001

Dopamine beta-monooxygenase signal/anchor sequence alters trafficking of peptidylglycine alpha-hydroxylating monooxygenase.

Dopamine beta-monooxygenase (DBM) and peptidylglycine alpha-hydroxylating monooxygenase (PHM) are essential for the biosynthesis of catecholamines and amidated peptides, respectively. The enzymes share a conserved catalytic core. We studied the role of the DBM signal sequence by appending it to soluble PHM (PHMs) and expressing the DBMsignal/PHMs chimera in AtT-20 and Chinese hamster ovary cells. PHMs produced as part of DBMsignal/PHMs was active. In vitro translated and cellular DBMsignal/PHMs had similar masses, indicating that the DBM signal was not removed. DBMsignal/PHMs was membrane-associated and had the properties of an intrinsic membrane protein. After in vitro translation in the presence of microsomal membranes, trypsin treatment removed 2 kDa from DBMsignal/PHMs while PHMs was entirely protected. In addition, a Cys residue in DBMsignal/PHMs was accessible to Cys-directed biotinylation. Thus the chimera adopts the topology of a type II membrane protein. Pulse-chase experiments indicate that DBMsignal/PHMs turns over rapidly after exiting the trans-Golgi network. Although PHMs is efficiently localized to secretory granules, DBMsignal/PHMs is largely localized to the endoplasmic reticulum in AtT-20 cells. On the basis of stimulated secretion, the small amount of PHMs generated is stored in secretory granules. In contrast, the expression of DBMsignal/PHMs in PC12 cells yields protein that is localized to secretory granules.

Amino Acid Sequence↗
PubMed2001

Cell proliferation through forced engagement of c-Kit and Flt-3.

To investigate the potential for functional interactions between heterologous receptors, the cytoplasmic domains of 2 different receptors (c-Kit and Flt-3) were coexpressed in the interleukin-3-dependent cell line Ba/F3. The receptor signaling domains were presented in the context of fusion proteins, with c-Kit linked to the FK506 binding protein (FKBP12) and Flt-3 linked to the FRB domain of the FKBP12-rapamycin-associated protein. The fusions were brought into apposition with the use of chemical inducers of dimerization (CIDs). Two classes of CID were employed. FK1012 and its synthetic analogue AP1510 bring together 2 copies of the FKBP12 domain, thereby inducing homodimerization of the c-Kit(FKBP12) fusion. A second type of CID, rapamycin, brings together one FKBP12 domain and one FRB domain, resulting in heterodimerization of the c-Kit(FKBP12) and Flt-3(FRB) fusions. Ba/F3 cell growth was promoted not only by FK1012- or AP1510-induced homodimerization of the c-Kit(FKBP12) fusion (as reported previously), but also by rapamycin-induced c-Kit(FKBP12)-Flt-3(FRB) heterodimerization. These findings demonstrate the potential for a direct functional interaction between c-Kit and Flt-3. (Blood. 2001;97:3662-3664)

Animals↗
PubMed2001

The effect that genotyping errors have on the robustness of common linkage-disequilibrium measures.

The rapid development of a dense single-nucleotide-polymorphism marker map has stimulated numerous studies attempting to characterize the magnitude and distribution of background linkage disequilibrium (LD) within and between human populations. Although genotyping errors are an inherent problem in all LD studies, there have been few systematic investigations documenting their consequences on estimates of background LD. Therefore, we derived simple deterministic formulas to investigate the effect that genotyping errors have on four commonly used LD measures-D', r, Q, and d-in studies of background LD. We have found that genotyping error rates as small as 3% can have serious affects on these LD measures, depending on the allele frequencies and the assumed error model. Furthermore, we compared the robustness of D', r, Q, and d, in the presence of genotyping errors. In general, Q and d are more robust than D' and r, although exceptions do exist. Finally, through stochastic simulations, we illustrate how genotyping errors can lead to erroneous inferences when measures of LD between two samples are compared.

Chromosome Mapping↗
PubMed2001

African origin of modern humans in East Asia: a tale of 12,000 Y chromosomes.

To test the hypotheses of modern human origin in East Asia, we sampled 12,127 male individuals from 163 populations and typed for three Y chromosome biallelic markers (YAP, M89, and M130). All the individuals carried a mutation at one of the three sites. These three mutations (YAP+, M89T, and M130T) coalesce to another mutation (M168T), which originated in Africa about 35,000 to 89,000 years ago. Therefore, the data do not support even a minimal in situ hominid contribution in the origin of anatomically modern humans in East Asia.

Africa↗
PubMed2001

Miniaturized amperometric biosensor based on xanthine oxidase for monitoring hypoxanthine in cell culture media.

Fabrication and characterization of miniaturized amperometric hypoxanthine biosensors are described and demonstrated for monitoring hypoxanthine in myocardial cell culture media. The sensors are based on xanthine oxidase (XO) immobilized on carbon fiber microelectrodes (CFMEs) using a composite film of Nafion and electropolymerized phenol (PPh). Nafion was used for XO immobilization because of its film hydrophobicity, enzyme-favored environment, and electrostatic interaction with XO, which was dispersed in Nafion film by immersing the Nafion-coated CFMEs in XO solution for 5 h. PPh film was formed as an overlay on Nafion and XO-modified CFMEs via electropolymerization. Hypoxanthine was measured with the sensor by the oxidation of enzymatic reaction products, hydrogen peroxide (H(2)O(2)), and uric acid (UA) at +0.60 V (vs Ag/AgCl). The use of Nafion and PPh as a matrix for XO immobilization yields enhanced specificity, sensitivity, and linearity toward hypoxanthine. A dynamic linear range of 5.0 microM to 1.8 mM was achieved with a calculated detection limit of 1.5 microM (S/N = 3) and a sensitivity of 3.144 nA/mM. In addition, the measurement was virtually interference-free from easily oxidizable species such as UA, ascorbic acid, physiological levels of neurotransmitters, and their principal metabolites. The biosensor was used to monitor hypoxanthine accumulation in myocardial cell culture media, in which the level of extracellular hypoxanthine was found to increase with ischemic tolerance.

Animals↗
PubMed2001

Modulation of the neuronal glutamate transporter EAAT4 by two interacting proteins.

Glutamate is the main excitatory neurotransmitter in the mammalian central nervous system and is removed from the synaptic cleft by sodium-dependent glutamate transporters. To date, five distinct glutamate transporters have been cloned from animal and human tissue: GLAST (EAAT1), GLT-1 (EAAT2), EAAC1 (EAAT3), EAAT4, and EAAT5 (refs 1-5). GLAST and GLT-1 are localized primarily in astrocytes, whereas EAAC1 (refs 8, 9), EAAT4 (refs 9-11) and EAAT5 (ref 5) are neuronal. Studies of EAAT4 and EAAC1 indicate an extrasynaptic localization on perisynaptic membranes that are near release sites. This localization facilitates rapid glutamate binding, and may have a role in shaping the amplitude of postsynaptic responses in densely packed cerebellar terminals. We have used a yeast two-hybrid screen to identify interacting proteins that may be involved in regulating EAAT4--the glutamate transporter expressed predominately in the cerebellum--or in targeting and/or anchoring or clustering the transporter to the target site. Here we report the identification and characterization of two proteins, GTRAP41 and GTRAP48 (for glutamate transporter EAAT4 associated protein) that specifically interact with the intracellular carboxy-terminal domain of EAAT4 and modulate its glutamate transport activity.

Amino Acid Sequence↗
PubMed2001

Carbon-11 labelled cholecystokininB antagonists: radiosynthesis and evaluation in rats.

Three cholecystokinin type B (CCKB) receptor antagonists were labelled with 11C and evaluated ex vivo in rat biodistribution studies. The CCKB antagonists were YF 476 and two other compounds of the basic 3-ureido-1,4-benzodiazepine class. Following tail-vein administration of [11C]-YF 476 exceedingly low levels of radioactivity were found in all brain regions from 5 to 60 min post-injection. Similar results were obtained using the other two 11C-labelled CCKB antagonists. In light of the very poor brain penetration of these compounds, reports on the central nervous system activity of this class of CCKB antagonists should be viewed with caution.

Animals↗