Biomedical subjects

X Lin

Publications and source records attributed to X Lin.

At least 37 records · Page 2Linked to original sources

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↗

PubMed2001

A case of cutaneous disseminated sporotrichosis.

We described a case of cutaneous disseminated sporotrichosis. The condition was diagnosed based on isolation and identification of Sporothrix schenckii from the lesions. The patient was otherwise normal, including a negative HIV test. The blood culture did not grow S. schenckii. However, spores were detected in the biopsy histological sections and stained positively with PAS staining and ConA and LCA lectin histochemistry.

Abdomen↗

PubMed2001

Infectivity-neutralizing and hemagglutinin-inhibiting antibody responses to respiratory coronavirus infections of cattle in pathogenesis of shipping fever pneumonia.

Respiratory bovine coronaviruses (RBCV) emerged as an infectious agent most frequently isolated from respiratory tract samples of cattle with acute respiratory tract diseases. Infectivity-neutralizing (IN) and hemagglutinin-inhibiting (HAI) antibodies induced by RBCV infections were monitored in sequential serum samples collected from cattle during a naturally evolving and experimentally monitored epizootic of shipping fever pneumonia (SFP). Cattle nasally shedding RBCV at the beginning of the epizootic started with low levels of serum IN and HAI antibodies. An increase in serum IN antibody after day 7 led to reduction of virus shedding in nasal secretions by the majority of the cattle between days 7 and 14. A substantial rise in the serum HAI antibody was observed during the initial phase among the sick but not the clinically normal cattle which were infected with RBCV. The RBCV isolation-positive cattle that developed fatal SFP had minimal serum IN and HAI antibodies during the course of disease development. Cattle that remained negative in RBCV isolation tests entered this epizootic with high levels of serum IN and HAI antibodies, which dramatically increased during the next two weeks. Protection against SFP was apparently associated with significantly higher levels of serum IN antibodies at the beginning of the epizootic. The RBCV-neutralizing activity is associated with serum immunoglobulin G (IgG), particularly the IgG2 subclass, while RBCV-specific HAI antibody is related to both serum IgG and IgM fractions.

Animals↗

PubMed2001

Quantitative diffusion weighted magnetic resonance imaging, cerebral atrophy, and disability in multiple sclerosis.

OBJECTIVES: To investigate the relations between quantitative diffusion coefficient MRI histograms, clinical variables, and cerebral atrophy. METHODS: Twenty two patients with clinically definite multiple sclerosis and 11 healthy volunteers were studied. Histograms of apparent diffusion coefficient (ADC) from a volume of interest that included multiple slices encompassing the lateral ventricles were processed from diffusion weighted MRI. In addition, total lesion load was measured on T2 weighted dual echo images, and cerebral volume from 3D magnetisation prepared rapid acquisition gradient echo scans. All patients underwent neurological assessment, including disability on the expanded disability status scale (EDSS). RESULTS: Histograms from the patient group showed a reduced peak height and a "right shift" compared with healthy controls. Peak height of the diffusion histogram correlated with both EDSS (r=-0.54, p=0.0101) and disease duration (r=-0.52, p=0.0140), but not with age. Brain volume correlated with peak height of the ADC histogram (r=0.55, p=0.0129), but not with disability. Total lesion load also correlated moderately with EDSS (r=0.46, p=0.03). CONCLUSIONS: This study shows for the first time that quantitative MRI measures of diffusion correlate with clinical variables (disability, disease duration) and cerebral atrophy in multiple sclerosis. Cerebral atrophy and fixed neurological deficit may be attributed to axonal loss, which would be expected to have a significant effect on ADC. Extension of this method to more patients and longitudinal studies will further elucidate its sensitivity, reproducibility, and potential role in clinical practice and treatment trials.

Adult↗

PubMed2001

Abnormal gastric slow waves in patients with functional dyspepsia assessed by multichannel electrogastrography.

The aim of this study was to utilize multichannel electrogastrography to investigate whether patients with functional dyspepsia had impaired propagation or coordination of gastric slow waves in the fasting state compared with healthy controls. The study was performed in 10 patients with functional dyspepsia and 11 healthy subjects. Gastric myoelectrical activity was measured by using surface electrogastrography with a specially designed four-channel device. The study was performed for 30 min or more in the fasting state. Special computer programs were developed for the computation of the propagation and coupling of the gastric slow wave. It was found that, compared with the healthy controls, the patients showed a significantly lower percentage of slow wave propagation (58.0 +/- 8.9 vs. 89.9 +/- 2.6%, P < 0.002) and a significantly lower percentage of slow wave coupling (46.9 +/- 4.4 vs. 61.5 +/- 6.9%, P < 0.04). In addition, the patients showed inconsistencies in the frequency and regularity of the gastric slow wave among the four-channel electrogastrograms (EGGs). It was concluded that patients with functional dyspepsia have impaired slow wave propagation and coupling. Multichannel EGG has more information than single-channel EGG for the detection of gastric myoelectrical abnormalities.

Adult↗

PubMed2001

Calcium dynamics and electrophysiological properties of cerebellar Purkinje cells in SCA1 transgenic mice.

Cerebellar Purkinje cells (PCs) from spinocerebellar ataxia type 1 (SCA1) transgenic mice develop dendritic and somatic atrophy with age. Inositol 1,4,5-trisphosphate receptor type 1 and the sarco/endoplasmic reticulum Ca(2+) ATPase pump, which regulate [Ca(2+)](i), are expressed at lower levels in these cells compared with the levels in cells from wild-type (WT) mice. To examine PCs in SCA1 mice, we used whole-cell patch clamp recording combined with fluorometric [Ca(2+)](i) and [Na(+)](i) measurements in cerebellar slices. PCs in SCA1 mice had Na(+) spikes, Ca(2+) spikes, climbing fiber (CF) electrical responses, parallel fiber (PF) electrical responses, and metabotropic glutamate receptor (mGluR)-mediated, PF-evoked Ca(2+) release from intracellular stores that were qualitatively similar to those recorded from WT mice. Under our experimental conditions, it was easier to evoke the mGluR-mediated secondary [Ca(2+)](i) increase in SCA1 PCs. The membrane resistance of SCA1 PCs was 3.3 times higher than that of WT cells, which correlated with the 1.7 times smaller cell body size. Most SCA1 PCs (but not WT) had a delayed onset (about 50--200 ms) to Na(+) spike firing induced by current injection. This delay was increased by hyperpolarizing prepulses and was eliminated by 4-aminopyridine, which suggests that this delay was due to enhancement of the A-like K(+) conductance in the SCA1 PCs. In response to CF stimulation, most PCs in mutant and WT mice had rapid, widespread [Ca(2+)](i) changes that recovered in <200 ms. Some SCA1 PCs showed a slow, localized, secondary Ca(2+) transient following the initial CF Ca(2+) transient, which may reflect release of Ca(2+) from intracellular stores. Thus, with these exceptions, the basic physiological properties of mutant PCs are similar to those of WT neurons, even with dramatic alteration of their morphology and downregulation of Ca(2+) handling molecules.

Action Potentials↗

PubMed2001

Salt-inducible kinase is involved in the ACTH/cAMP-dependent protein kinase signaling in Y1 mouse adrenocortical tumor cells.

The involvement of salt-inducible kinase, a recently cloned protein serine/threonine kinase, in adrenal steroidogenesis was investigated. When Y1 mouse adrenocortical tumor cells were stimulated by ACTH, the cellular content of salt-inducible kinase mRNA, protein, and enzyme activity changed rapidly. Its level reached the highest point in 1-2 h and returned to the initial level after 8 h. The mRNA levels of cholesterol side-chain cleavage cytochrome P450 and steroidogenic acute regulatory protein, on the other hand, began to rise after a few hours, reaching the highest levels after 8 h. The salt-inducible kinase mRNA level in ACTH-, forskolin-, or 8-bromo-cAMP-treated Kin-7 cells, mutant Y1 with less cAMP-dependent PKA activity, remained low. However, Kin-7 cells, when transfected with a PKA expression vector, expressed salt-inducible kinase mRNA. Y1 cells that overexpressed salt-inducible kinase were isolated, and the mRNA levels of steroidogenic genes in these cells were compared with those in the parent Y1. The level of cholesterol side-chain cleavage cytochrome P450 mRNA in the salt-inducible kinase-overexpressing cells was markedly low compared with that in the parent, while the levels of Ad4BP/steroidogenic factor-1-, ACTH receptor-, and steroidogenic acute regulatory protein-mRNAs in the former were similar to those in the latter. The ACTH-dependent expression of cholesterol side-chain cleavage cytochrome P450- and steroidogenic acute regulatory protein-mRNAs in the salt-inducible kinase-overexpressing cells was significantly repressed. The promoter activity of the cholesterol side-chain cleavage cytochrome P450 gene was assayed by using Y1 cells transfected with a human cholesterol side-chain cleavage cytochrome P450 promoter-linked reporter gene. Addition of forskolin to the culture medium enhanced the cholesterol side-chain cleavage cytochrome P450 promoter activity, but the forskolin-dependently activated promoter activity was inhibited when the cells were transfected with a salt-inducible kinase expression vector. This inhibition did not occur when the cells were transfected with a salt-inducible kinase (K56M) vector that encoded an inactive kinase. The salt-inducible kinase's inhibitory effect was also observed when nonsteroidogenic, nonAd4BP/steroidogenic factor-1 -expressing, NIH3T3 cells were used for the promoter assays. These results suggested that salt-inducible kinase might play an important role(s) in the cAMP-dependent, but Ad4BP/steroidogenic factor-1-independent, gene expression of cholesterol side-chain cleavage cytochrome P450 in adrenocortical cells.

Adrenal Cortex Neoplasms↗

PubMed2001

Heparan sulfate proteoglycans are critical for the organization of the extracellular distribution of Wingless.

Recent studies in Drosophila have shown that heparan sulfate proteoglycans (HSPGs) are required for Wingless (Wg/Wnt) signaling. In addition, genetic and phenotypic analyses have implicated the glypican gene dally in this process. Here, we report the identification of another Drosophila glypican gene, dally-like (dly) and show that it is also involved in Wg signaling. Inhibition of dly gene activity implicates a function for DLY in Wg reception and we show that overexpression of DLY leads to an accumulation of extracellular Wg. We propose that DLY plays a role in the extracellular distribution of Wg. Consistent with this model, a dramatic decrease of extracellular Wg was detected in clones of cells that are deficient in proper glycosaminoglycan biosynthesis. We conclude that HSPGs play an important role in organizing the extracellular distribution of Wg.

Amino Acid Sequence↗

PubMed2001

[Studies on the supercritical-CO2 fluid extraction of complex prescription Danshen-Jiangxiang].

This paper first reported the supercritical-CO2 fluid extraction of complex prescription Danshen-Jiangxiang. With the active constituents and yield of extracts as index, the each other effect of each drug and effect on total complex prescription in extraction were studied. And the effects of pressure and temperature were also studied. The results showed the effects were different in complex prescription extraction and single prescription. Active constituents can be extracted, but a obvious effect exist each other and effects together the yield of extract, extraction rate and content of active constituents of complex prescription extraction, which are concerned in extraction conditions. These study results have important reference on the modernization of traditional Chinese medicines.

Carbon Dioxide↗

PubMed2001

Full-length genomic analysis of hepatitis B virus isolates in a patient progressing from hepatitis to hepatocellular carcinoma.

In hepatitis B virus (HBV)-endemic countries, the majority of hepatocellular carcinoma (HCC) arises in HBV carriers. High frequency of mutations at nucleotides 1762(A-->T) and 1764(G-->A) in the core promoter region have been described in HCC. Due to the differences in genetic backgrounds, environmental risk factors and random cellular insertion sites, it is difficult to analyze the possible roles of HBV variants detected in different HCC patients. In a follow-up cohort study, an HBsAg-positive asymptomatic carrier was diagnosed HCC within 4 years. Eleven full-length HBV isolates, three from the first serum sample obtained 4 years pre-HCC, and eight from serum sample, peri-tumor and tumor tissue post-HCC of this individual were sequenced and used to transfect HepG2 cells. When sequences were compared between pre- and post-HCC isolates, no single mutation common to all post-HCC isolates that differed from pre-HCC isolates was found. Among all 11 isolates, there were 20 predicted amino acid substitutions shared by two or more post-HCC isolates. These were located in the S(5), X(4), core(4), polymerase(4), pre-S1(2) and pre-S2(1) proteins. Possible roles of amino acid substitutions and enhanced replication efficiency in cells transfected by post-HCC isolates are discussed.

Amino Acid Substitution↗

PubMed2001

Full-length genomic analysis of hepatitis B virus isolates in a patient progressing from hepatitis to hepatocellular carcinoma.

Amino Acid Substitution↗

PubMed2000

Sequence and analysis of chromosome 1 of the plant Arabidopsis thaliana.

The genome of the flowering plant Arabidopsis thaliana has five chromosomes. Here we report the sequence of the largest, chromosome 1, in two contigs of around 14.2 and 14.6 megabases. The contigs extend from the telomeres to the centromeric borders, regions rich in transposons, retrotransposons and repetitive elements such as the 180-base-pair repeat. The chromosome represents 25% of the genome and contains about 6,850 open reading frames, 236 transfer RNAs (tRNAs) and 12 small nuclear RNAs. There are two clusters of tRNA genes at different places on the chromosome. One consists of 27 tRNA(Pro) genes and the other contains 27 tandem repeats of tRNA(Tyr)-tRNA(Tyr)-tRNA(Ser) genes. Chromosome 1 contains about 300 gene families with clustered duplications. There are also many repeat elements, representing 8% of the sequence.

Arabidopsis↗

PubMed2000

Smurf2 is a ubiquitin E3 ligase mediating proteasome-dependent degradation of Smad2 in transforming growth factor-beta signaling.

Smads are important intracellular signaling effectors for transforming growth factor-beta (TGF-beta) and related factors. Proper TGF-beta signaling requires precise control of Smad functions. In this study, we have identified a novel HECT class ubiquitin E3 ligase, designated Smurf2, that negatively regulates Smad2 signaling. In both yeast two-hybrid and in vitro binding assays, we found that Smurf2 could interact with receptor-activated Smads (R-Smads), including Smad1, Smad2, and Smad3 but not Smad4. Ectopic expression of Smurf2 was sufficient to reduce the steady-state levels of Smad1 and Smad2 but not Smad3 or Smad4. Significantly, Smurf2 displayed preference to Smad2 as its target for degradation. Furthermore, Smurf2 exhibited higher binding affinity to activated Smad2 upon TGF-beta stimulation. The ability of Smurf2 to promote Smad2 destruction required the HECT catalytic activity of Smurf2 and depended on the proteasome-dependent pathway. Consistent with these results, Smurf2 potently reduced the transcriptional activity of Smad2. These data suggest that a ubiquitin/proteasome-dependent mechanism is important for proper regulation of TGF-beta signaling.

Cell Line↗

PubMed2000

The NF-kappa B-inducing kinase induces PC12 cell differentiation and prevents apoptosis.

NF-kappa B has been implicated in the survival and differentiation of PC12 cells. In this study, we examined the effect of the NF-kappa B-inducing kinase (NIK) on these processes. When inducibly expressed in PC12 cells, a kinase-proficient but not -deficient form of NIK promoted neurite process formation and mediated anti-apoptotic signaling. As expected, NIK expression led to I kappa B kinase activation and induced nuclear translocation of NF-kappa B. However, NIK-induced neurite outgrowth was only partially blocked by concomitant expression of a nondegradable form of I kappa B alpha that completely blocks NF-kappa B induction. In search of additional signaling pathways activated by NIK, we now demonstrate that NIK activates MEK1 phosphorylation and induces the Erk1/Erk2 MAPK pathway. Treatment of PC12 cells with PD98059, a MEK1 inhibitor, potently blocked neurite process formation; however, a dominantly interfering mutant of the upstream Shc adapter failed to alter this response. These findings reveal a new function for NIK as a MEK1-dependent activator of the MAPK pathway and implicate both the I kappa B kinase and MAPK signaling cascades in NIK-induced differentiation of PC12 cells.

Animals↗

PubMed2000

Mild and efficient functionalization at C6 of purine 2'-deoxynucleosides and ribonucleosides.

[reaction: see text] Treatment of sugar-protected inosine and 2'-deoxyinosine derivatives with a cyclic secondary amine or imidazole and I(2)/Ph(3)P/EtN(i-Pr)(2)/(CH(2)Cl(2) or toluene) gave quantitative conversions into 6-N-(substituted)purine nucleosides. S(N)Ar reactions with 6-(imidazol-1-yl) derivatives gave 6-(N, O, or S)-substituted products. The 6-(benzylsulfonyl) group underwent S(N)Ar displacement with an arylamine at ambient temperature.

Deoxyribonucleosides↗