Biomedical subjects

X Lin

Publications and source records attributed to X Lin.

At least 19 recordsLinked to original sources

PubMed2001

A comparison of three different sleep schedules for reducing daytime sleepiness in narcolepsy.

STUDY OBJECTIVE: To determine if the combination of scheduled sleep periods and stimulant medications were more effective than stimulant medications alone in controlling the excessive daytime sleepiness experienced by narcoleptic patients. DESIGN: Twenty-nine treated narcoleptic subjects were randomly assigned to one of three treatment groups: 1) two 15-minute naps per day; 2) a regular schedule for nocturnal sleep; or 3) a combination of scheduled naps and regular bedtimes. Measures of symptom severity and unscheduled daytime were obtained at baseline and at the end of the two-week treatment period, using the Narcolepsy Symptom Status Questionnaire (NSSQ) and 24-hour ambulatory polysomnographic monitoring. No alterations were made in stimulant medications during the study period. SETTING: N/A. PATIENTS OR PARTICIPANTS: N/A. INTERVENTIONS: N/A. MEASUREMENTS AND RESULTS: The addition of two-15 minute naps did not alter either symptom severity or the duration of unscheduled daytime sleep. Regular times for nocturnal sleep reduced perceived symptom severity, but did not reduce the amount of unscheduled daytime sleep. Only the combination of scheduled naps and regular nocturnal sleep times, significantly reduced both symptom severity and the amount of unscheduled daytime sleep in treated narcoleptic subjects. The type of sleep schedule prescribed, however, was less important than the severity of the patients' pre-treatment daytime sleepiness. Subjects with severe daytime sleepiness benefited from the addition of scheduled sleep periods, while those who were only moderately sleepy or able to maintain alertness did not benefit from scheduled sleep periods. CONCLUSIONS: Scheduled sleep periods are helpful for only those patients who remain profoundly sleepy despite stimulant medications and should not be prescribed for all patients with narcolepsy.

Adult↗

PubMed2001

Modulation of docetaxel-induced apoptosis and cell cycle arrest by all- trans retinoic acid in prostate cancer cells.

We report that all- trans retinoic acid (ATRA) enhanced the toxicity of docetaxel against DU145 and LNCaP prostate cancer cells, and that the nature of the interaction between ATRA and docetaxel was highly synergistic. Docetaxel-induced apoptotic cell death was associated with phosphorylation and hence inactivation of Bcl-2. ATRA enhanced docetaxel-induced apoptosis and combined treatment with ATRA and docetaxel resulted in down-regulation of Bcl-2. Docetaxel caused phosphorylation and hence inactivation of cdc2 kinase result ing in G2/M arrest. ATRA inhibited docetaxel-induced phosphorylation of cdc2 resulting in activation of cdc2 kinase and partial reversal of the G2/M arrest. ATRA also inhibited docetaxel-induced activation of MAPK indicating that the effects of docetaxel and ATRA on cdc2 phosphorylation are dependent on MAPK. We conclude that ATRA synergistically enhances docetaxel toxicity by down-regulating Bcl-2 expression and partially reverses the docetaxel-induced G2/M arrest by inhibiting docetaxel-induced cdc2 phosphorylation in a pathway that is dependent on MAPK.

Antineoplastic Agents↗

PubMed2001

Physical and radiation hybrid mapping of canine chromosome 12, in a region corresponding to human chromosome 6p12-q12.

The positional cloning of the hypocretin receptor 2, the gene for autosomal recessive canine narcolepsy, has led to the development of a physical map spanning a large portion of canine chromosome 12 (CFA12), in a region corresponding to human chromosome 6p12-q13. More than 40 expressed sequence tags (ESTs) were used in homology search experiments, together with chromosome walking, to build both physical and radiation hybrid maps of the CFA12 13-21 region. The resulting map of bacterial artificial chromosome ends, ESTs, and microsatellite markers represents the longest continuous high-density map of the dog genome reported to date. These data further establish the dog as a system for studying disease genes of interest to human populations and highlight feasible approaches for positional cloning of disease genes in organisms where genomic resources are limited.

Animals↗

PubMed2001

GeneSplicer: a new computational method for splice site prediction.

GeneSplicer is a new, flexible system for detecting splice sites in the genomic DNA of various eukaryotes. The system has been tested successfully using DNA from two reference organisms: the model plant Arabidopsis thaliana and human. It was compared to six programs representing the leading splice site detectors for each of these species: NetPlantGene, NetGene2, HSPL, NNSplice, GENIO and SpliceView. In each case GeneSplicer performed comparably to the best alternative, in terms of both accuracy and computational efficiency.

Algorithms↗

PubMed2001

The sequence of the human genome.

A 2.91-billion base pair (bp) consensus sequence of the euchromatic portion of the human genome was generated by the whole-genome shotgun sequencing method. The 14.8-billion bp DNA sequence was generated over 9 months from 27,271,853 high-quality sequence reads (5.11-fold coverage of the genome) from both ends of plasmid clones made from the DNA of five individuals. Two assembly strategies-a whole-genome assembly and a regional chromosome assembly-were used, each combining sequence data from Celera and the publicly funded genome effort. The public data were shredded into 550-bp segments to create a 2.9-fold coverage of those genome regions that had been sequenced, without including biases inherent in the cloning and assembly procedure used by the publicly funded group. This brought the effective coverage in the assemblies to eightfold, reducing the number and size of gaps in the final assembly over what would be obtained with 5.11-fold coverage. The two assembly strategies yielded very similar results that largely agree with independent mapping data. The assemblies effectively cover the euchromatic regions of the human chromosomes. More than 90% of the genome is in scaffold assemblies of 100,000 bp or more, and 25% of the genome is in scaffolds of 10 million bp or larger. Analysis of the genome sequence revealed 26,588 protein-encoding transcripts for which there was strong corroborating evidence and an additional approximately 12,000 computationally derived genes with mouse matches or other weak supporting evidence. Although gene-dense clusters are obvious, almost half the genes are dispersed in low G+C sequence separated by large tracts of apparently noncoding sequence. Only 1.1% of the genome is spanned by exons, whereas 24% is in introns, with 75% of the genome being intergenic DNA. Duplications of segmental blocks, ranging in size up to chromosomal lengths, are abundant throughout the genome and reveal a complex evolutionary history. Comparative genomic analysis indicates vertebrate expansions of genes associated with neuronal function, with tissue-specific developmental regulation, and with the hemostasis and immune systems. DNA sequence comparisons between the consensus sequence and publicly funded genome data provided locations of 2.1 million single-nucleotide polymorphisms (SNPs). A random pair of human haploid genomes differed at a rate of 1 bp per 1250 on average, but there was marked heterogeneity in the level of polymorphism across the genome. Less than 1% of all SNPs resulted in variation in proteins, but the task of determining which SNPs have functional consequences remains an open challenge.

Algorithms↗

PubMed2001

Quantification of tumor cell injury in vitro and in vivo using expression of green fluorescent protein under the control of the GADD153 promoter.

The GADD153 gene is strongly transcriptionally activated by many types of cellular injury and the magnitude of the change in GADD153 expression is proportional to the extent of damage. We developed a novel reporter system in which a chimeric gene containing the GADD153 promoter linked to the coding region of an enhanced green fluorescent protein (EGFP) gene was stably integrated into the genome of a clone of UMSCC10b head and neck carcinoma cells. Activation of the exogenous GADD153 promoter was quantified using flow cytometric measurement of EGFP expression following drug exposure. The exogenous GADD153 promoter in this clone was activated by N-methl-N'-nitro-N-nitrosoguanidine (MNNG) in a concentration-dependent manner with kinetics that closely paralleled perturbation of cell cycle phase distribution. EGFP expression was strongly activated by a variety of genotoxic agents including DNA cross-linking and methylating agents, oxygen free radicals, DNA intercalator, UV and gamma-radiation and hypoxia. When grown as a xenograft in nude mice, the stably transfected clone also demonstrated dose-dependent EGFP expression when measured 4 days after cisplatin treatment. The reporter system accurately categorized the relative potency of adducts produced by 6 related platinum-containing drugs. In conclusion, this reporter system can facilitate in vitro and in vivo screening for agents capable of producing cytotoxicity via a wide variety of different mechanisms, and can be utilized to investigate the relative potency of structurally related DNA adducts.

Animals↗

PubMed2001

P53 modulates the effect of loss of DNA mismatch repair on the sensitivity of human colon cancer cells to the cytotoxic and mutagenic effects of cisplatin.

This study examined how the DNA mismatch repair (MMR) system and p53 interact to maintain genomic integrity in the presence of the mutagenic stress induced by cisplatin (DDP). Sensitivity to the cytotoxic and mutagenic effect of DDP was assessed using a panel of sublines of the MMR-deficient HCT116 colon carcinoma cells in which MMR function had been restored by transfer of a copy of MLH1 on chromosome 3 or in which p53 function had been disabled by expression of HPV-16 E6. Loss of p53 function by expression of E6 in MMR-proficient HCT116+ ch3 cells conferred only 1.1-2.0-fold resistance to a panel of commonly used chemotherapeutic agents, whereas disruption of p53 in MMR-deficient HCT116 cells resulted in substantial levels of resistance to some agents (paclitaxel, 1.9-fold; gemcitabine, 2.7-fold; 6-thioguanine, 3.3-fold; and etoposide, 4.4-fold) but sensitization to other agents (topotecan, 2.5-fold; and DDP, 3.3-fold). Loss of MMR or p53 alone had only a minor effect on sensitivity to the mutagenic effect of DDP as measured by the appearance of variants resistant to 6-thioguanine, etoposide, topotecan, gemcitabine, and paclitaxel in the population 10 days later (1.0-2.4-fold), whereas loss of both p53 and MMR had a more profound effect (1.7-6.5-fold). Loss of both p53 and MMR increased the basal frequency insertion/deletion mutations detected by a shuttle vector-based assay to a greater extent than loss of either alone. In association with DDP-induced injury, loss of p53 or MMR alone resulted in 1.2- and 1.7-fold more mutations, whereas loss of both resulted in a 5.1-fold increase in mutant frequency. Examination of the impact of loss of p53 and/or MMR on the DDP-induced cell cycle checkpoint activation, p53 induction, ability of the cell to tolerate adducts in its DNA, and the rate of disappearance of platinum from genomic DNA indicated the effects of the loss of p53 and/or MMR on all of these parameters, suggesting a multifactorial etiology for the changes in sensitivity to the cytotoxic and mutagenic effects of DDP. These results indicate that p53 and MMR can cooperate to control sensitivity to the cytotoxic effect of DDP and to limit its mutagenic potential in the colon cancer cells.

Antineoplastic Agents↗

PubMed2001

Complex HLA-DR and -DQ interactions confer risk of narcolepsy-cataplexy in three ethnic groups.

Human narcolepsy-cataplexy, a sleep disorder associated with a centrally mediated hypocretin (orexin) deficiency, is tightly associated with HLA-DQB1*0602. Few studies have investigated the influence that additional HLA class II alleles have on susceptibility to this disease. In this work, 1,087 control subjects and 420 narcoleptic subjects with cataplexy, from three ethnic groups, were HLA typed, and the effects of HLA-DRB1, -DQA1, and -DQB1 were analyzed. As reported elsewhere, almost all narcoleptic subjects were positive for both HLA-DQA1*0102 and -DQB1*0602. A strong predisposing effect was observed in DQB1*0602 homozygotes, across all ethnic groups. Relative risks for narcolepsy were next calculated for heterozygous DQB1*0602/other HLA class II allelic combinations. Nine HLA class II alleles carried in trans with DQB1*0602 were found to influence disease predisposition. Significantly higher relative risks were observed for heterozygote combinations including DQB1*0301, DQA1*06, DRB1*04, DRB1*08, DRB1*11, and DRB1*12. Three alleles-DQB1*0601, DQB1*0501, and DQA1*01 (non-DQA1*0102)-were found to be protective. The genetic contribution of HLA-DQ to narcolepsy susceptibility was also estimated by use of lambda statistics. Results indicate that complex HLA-DR and -DQ interactions contribute to the genetic predisposition to human narcolepsy but that additional susceptibility loci are also most likely involved. Together with the recent hypocretin discoveries, these findings are consistent with an immunologically mediated destruction of hypocretin-containing cells in human narcolepsy-cataplexy.

Black or African American↗

PubMed2001

Signal via lymphotoxin-beta R on bone marrow stromal cells is required for an early checkpoint of NK cell development.

NK cells play an important role in the immune system but the cellular and molecular requirements for their early development are poorly understood. Lymphotoxin-alpha (LTalpha)(-/-) and LTbetaR(-/-) mice show a severe systemic reduction of NK cells, which provides an excellent model to study NK cell development. In this study, we show that the bone marrow (BM) or fetal liver cells from LTalpha(-/-) or LTbetaR(-/-) mice efficiently develop into mature NK cells in the presence of stromal cells from wild-type mice but not from LTalpha(-/-) or LTbetaR(-/-) mice. Direct activation of LTbetaR-expressing BM stromal cells is shown to promote to early NK cell development in vitro. Furthermore, the blockade of the interaction between LT and LTbetaR in adult wild-type mice by administration of LTbetaR-Ig impairs the development of NK cells in vivo. Together, these results indicate that the signal via LTbetaR on BM stromal cells by membrane LT is an important pathway for early NK cell development.

Adoptive Transfer↗

PubMed2001

Identification of a human brain-specific gene, calneuron 1, a new member of the calmodulin superfamily.

The calmodulin superfamily includes the calmodulins, calcium-binding proteins, and related genes. Herein, we describe the cloning and characterization of human calneuron 1 (CALN1). CALN1 encodes a novel neuron-specific protein that maps to chromosome 7q11. CALN1 spans a large genomic region (>360 kb). Sequence comparison shows significant similarity with the calmodulin superfamily of genes, especially in the two conserved EF-hand motifs. The mouse orthologous gene (Caln1) shows little prenatal expression, with highest expression at Postnatal Day 21. In situ hybridization to adult mouse brain shows high expression in the cerebellum, hippocampus, and cortex. The high expression of this gene exclusively in brain, the developmental changes in expression levels, the high homology with calmodulin which indicates a potential role in signal transduction, and the cellular localization of the mRNA suggest that CALN1 has a significant role in the physiology of neurons and is potentially important in memory and learning.

Amino Acid Sequence↗

PubMed2001

Overexpression of phosphatidylinositol 3-kinase in human lung cancer.

BACKGROUND: This study was conducted to investigate the expression of phosphatidylinositol 3-kinase (PI3K) and AKT2, a downstream effector, in primary human lung carcinomas of different histological type. METHODS: Specimens from 105 human lung carcinomas and their corresponding lymph nodes and liver metastases were examined using immunohistochemistry and Northern-blot assays to study the PI3K p85 and p110 subunits and the AKT2-expression patterns. RESULTS: The p85 and p110 subunits of PI3K were overexpressed at the protein level in 77% and 59% of 80 primary lung carcinomas, respectively, irrespective of the histological type. PI3K overexpression was correlated with tumor grading. In contrast, no overexpression of PI3K subunits was observed in normal lung tissue and benign lung tumors. Consistent with these findings, upregulation of p110 mRNA transcripts was restricted to primary lung carcinomas. Overexpression of AKT2 was observed in 10% of the investigated lung tumor specimens, but in none of the healthy lung sections. A profound increase of PI3K expression was uniformly observed in lung tissue specimens and in corresponding extra-pulmonary lymph-node and liver metastases with low-differentiation grades. CONCLUSION: PI3K appears to be associated with the process of tumor-cell transformation and proliferation. One of its major downstream effector molecules, AKT2, which contributes to apoptotic cell death, was not upregulated by PI3K overexpression in primary lung carcinomas.

Adult↗

PubMed2001

Computer-simulation studies on roles of potassium currents in neurotransmission of the auditory nerve.

Our previous work showed that action potentials (APs) fired in spiral ganglion (SG) neurons broaden gradually as a result of cumulative inactivation of the potassium current (I(K)), or with the application of a tinnitus-inducing drug (quinine). These results led us to speculate that AP width could affect neurotransmission of the auditory nerve under both normal and pathological conditions. This study used both experimental and theoretical approaches to test this hypothesis. We first measured the effect of AP broadening on Ca2+ entry into SG neurons. The effect of pre-synaptic AP broadening on post-synaptic responses was then assessed using computer-simulations. Results showed that wider presynaptic APs augmented responses of all types of postsynaptic glutamatergic receptors mainly by amplifying responses of postsynaptic receptors whose locations were not well aligned with the presynaptic release sites. A cumulative inactivation of I(K) in SG neurons significantly enhanced the responses of kainate receptors at all spike rates, while the augmentations for the alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid and N-methyl-D-aspartic acid receptors were most prominent below 100 spikes/s. These modeling results suggest that, in addition to the AP firing rate and timing, the width of APs could affect the neurotransmission of the auditory nerve under both normal and pathological conditions.

Action Potentials↗

PubMed2001

Adverse events associated with hepatitis B vaccine in U.S. children less than six years of age, 1993 and 1994.

PURPOSE: This study evaluated infrequent adverse reactions to hepatitis B vaccine by investigating the association of this vaccine with adverse health outcomes for U.S. children less than six years of age. The evaluation of the association between hepatitis B vaccine and chronic arthritis provides needed data, relevant to the Institute of Medicine's Report that there are inadequate data available to assess the causal relationship of hepatitis B vaccine to arthritis risk. METHODS: The 1993 (n = 5505 children) and 1994 (n = 6515 children) National Health Interview Survey (NHIS) datasets were analyzed to provide post-marketing surveillance data from probability samples of the U.S. population. Incident cases of adverse events were determined from the temporal association between the hepatitis B vaccination and the adverse events. Logistic regression modeling was used to adjust for potential confounding. RESULTS: Controlling for age, race, and gender simultaneously in the 1994 NHIS, hepatitis B vaccine was found to be associated with prevalent arthritis [odds ratio (OR) = 5.91, 95% confidence interval (CI) = 1.05-33.14], incident acute ear infections (OR = 1.60, 95% CI = 1.00-2.58), and incident pharyngitis/nasopharyngitis (OR = 1.41, 95% CI = 0.95-2.09). CONCLUSIONS: Evidence from this study suggests that hepatitis B vaccine is positively associated with adverse health outcomes in the general population of US children.

Arthritis↗

PubMed2001

Somatostatins and their receptors in fish.

Somatostatin (SRIF) is a multigene family of peptides. SRIF-14 is conserved with identical primary structure in species across the vertebrates. The presence of multiple SRIF genes has been demonstrated in a number of fish species. Notably, three distinct SRIF genes have been identified in goldfish. One of these genes, which encodes [Pro(2)]SRIF-14, has also been identified in sturgeon and African lungfish, and is closely associated with the amphibian [Pro(2),Met(13)]SRIF-14 gene and mammalian cortistatin gene. The main neuroendocrine role of SRIF-14 peptide that has been determined in fish is the inhibition of pituitary growth hormone secretion. The functions of SRIF-14 variant or larger forms of SRIF peptide and the regulation of SRIF gene expression remain to be explored. Type one and two SRIF receptors have been identified from goldfish and type three SRIF receptor from an electric fish. Fish SRIF receptors display considerable homology to mammalian counterparts in terms of primary structure and negative coupling to adenylate cyclase. The identification of the multiple gene family of SRIF peptides and multiple types of SRIF receptors in fish opens a new avenue for the study of physiological roles of SRIF, and the molecular and cellular mechanisms of SRIF actions in fish.

Animals↗

PubMed2001

Covalent modification of glassy carbon electrode with glutamic acid for simultaneous determination of uric acid and ascorbic acid.

A novel covalently modified glassy carbon electrode with glutamic acid has been fabricated via an electrochemical oxidation procedure and was applied to the catalytic oxidation of uric acid (UA) and ascorbic acid (AA), reducing the overpotentials by about 0.2 V and 0.3 V, respectively. Based on its strong catalytic function toward the oxidation of UA and AA, the modified electrode resolved the overlapping voltammetric response of UA and AA into two well-defined voltammetric peaks with both cyclic voltammetry (CV) and differential pulse voltammetry (DPV), which can be used for the simultaneous determination of these species in a mixture. The catalytic peak current obtained from DPV was linearly dependent on the UA and AA concentration in the range 2 x 10(-6)-4 x 10(-4) mol L-1 and 1.0 x 10(-6)-4 x 10(-4) mol L-1 with correlation coefficients of 0.996 and 0.997, respectively. The detection limits (3 delta) for UA and AA were 1.1 x 10(-6) mol L-1 and 9.2 x 10(-7) mol L-1, respectively. The modified electrode shows good sensitivity, selectivity and stability, and has been applied to the determination of UA and AA simultaneously in human urine samples with satisfactory results.

Ascorbic Acid↗

PubMed2001

Chemiluminescence of Ce(IV) and surfactant Tween 20.

It was found that cerium(IV) reacted with surfactant Tween 20 in acidic medium to generate green chemiluminescence. The maximum emission wavelength was about 478 nm. The enhancement and inhibition of the CL reaction by some polyphenols and anilines was studied and the possibility of analytical application was explored.

Journal Article↗

PubMed2001

Selective determination of dopamine in the presence of ascorbic acid at an over-oxidized poly(N-acetylaniline) electrode.

An over-oxidized poly(N-acetylaniline) (PNAANI)/GCE was used to determine dopamine (DA) in a large excess of ascorbic acid (AA) by differential pulse voltammetry. A linear relation between Ip and DA concentration was found over the range 5.0 x 10(-7) to 2.0 x 10(-5) M. The detection limit was 1.68 x 10(-8) M for S/N = 3 and 400 microM AA did not interfere with the DA determination. The high sensitivity was due to accumulation and selectivity was due to charge discrimination. The mechanism of selective determination of DA at over-oxidized PNAANI/GCE was also proposed.

Ascorbic Acid↗

PubMed2001

Identification and functional analysis of mutations in the hypocretin (orexin) genes of narcoleptic canines.

Narcolepsy is a sleep disorder affecting animals and humans. Exon skipping mutations of the Hypocretin/Orexin-receptor-2 (Hcrtr2) gene were identified as the cause of narcolepsy in Dobermans and Labradors. Preprohypocretin (Hcrt) knockout mice have symptoms similar to human and canine narcolepsy. In this study, 11 sporadic cases of canine narcolepsy and two additional multiplex families were investigated for possible Hcrt and Hcrtr2 mutations. Sporadic cases have been shown to have more variable disease onset, increased disease severity, and undetectable Hypocretin-1 levels in cerebrospinal fluid. The canine Hcrt locus was isolated and characterized for this project. Only one novel mutation was identified in these two loci. This alteration results in a single amino acid substitution (E54K) in the N-terminal region of the Hcrtr2 receptor and autosomal recessive transmission in a Dachshund family. Functional analysis of previously-described exon-skipping mutations and of the E54K substitution were also performed using HEK-293 cell lines transfected with wild-type and mutated constructs. Results indicate a truncated Hcrtr2 protein, an absence of proper membrane localization, and undetectable binding and signal transduction for exon-skipping mutated constructs. In contrast, the E54K abnormality was associated with proper membrane localization, loss of ligand binding, and dramatically diminished calcium mobilization on activation of the receptor. These results are consistent with a loss of function for all three mutations. The absence of mutation in sporadic cases also indicates genetic heterogeneity in canine narcolepsy, as reported previously in humans.

Amino Acid Sequence↗