Biomedical subjects

X Lin

Publications and source records attributed to X Lin.

At least 181 records · Page 10Linked to original sources

PubMed1999

Sensitivity comparison for detection of respiratory bovine coronaviruses in nasal samples from feedlot cattle by ELISA and isolation with the G clone of HRT-18 cells.

A monoclonal antibody-based capture enzyme-linked immunosorbent assay (ELISA) was developed to detect respiratory bovine coronavirus (RBCV) antigens in nasal swabs collected from cattle showing signs of respiratory tract disease following shipping. These samples had been previously tested for RBCV by inoculation of G clone cultures of human rectal tumor cells (HRT-18G) and for bovine herpes virus 1, parainfluenza virus 3, bovine adenovirus, bovine respiratory syncytial virus, and bovine viral diarrhea virus on other specifically permissive cell cultures. RBCV has not previously been recognized as an important etiological factor in the bovine respiratory disease complex of feedlot cattle. Thirty of 100 samples tested positive for RBCV antigen by capture ELISA in contrast to 38 of 100 samples that yielded RBCV isolates in G clone cells. Samples yielding other bovine respiratory viruses in the absence of RBCV were negative in the capture ELISA, which was based on the use of a single monoclonal antibody that recognizes one RBCV epitope on the S glycoprotein with the broadest reactivity with different strains of RBCV tested. Some RBCV strains may not be detected by this ELISA, which may account for the higher percentage of RBCV-infected cattle detected by RBCV isolation. However, the ELISA was simple to perform, sensitive, and specific and was more rapid than virus isolation. This assay will be useful for processing large numbers of field samples in future epidemiologic and diagnostic studies of RBCV infections of cattle.

Animals↗

PubMed1999

Do market-level hospital and physician resources affect small area variation in hospital use?

This study evaluates the effect of market-level physician and hospital resources on hospital use. It is anticipated that higher hospital discharges are associated with (1) greater hospital and physician resources, (2) more differentiated hospital and physician resources, and (3) higher levels of teaching intensity in the community. Data on 14 modified diagnostically related groups (DRGs) and 58 hospital market communities in Michigan are analyzed during a 7-year period. Findings indicate that physician resources, hospital resources, differentiation of hospital and physician resources, and teaching intensity contribute only modestly to discharges, holding constant the socioeconomic attributes of the community and adjusting for the variation in hospital use over time. With the inclusion of hospital and physician resource variables, socioeconomic factors remain important determinants of the variation across market communities. Findings are discussed in terms of their implications for health care organizations, managed care programs, and cost control efforts in general.

Adult↗

PubMed1999

Toxicity Screening of a Combinatorial Library: Correlation of Cytotoxicity and Gene Induction to Compound Structure.

Combinatorial chemistry has increased the number of compounds available for efficacy and safety assessment by several orders of magnitude and has made high throughput assays essential. To test whether higher throughput toxicity assays could be of utility in screening compounds in early development, a selected set of combinatorial chemistry compounds was screened for induction of 70-Kd heat shock protein (HSP70) and 45-Kd growth arrest and DNA damage protein (GADD45) mRNA levels as well as cytotoxicity, in HepG2 cells, using a 96-well microtiter plate format. Both assays, the branched DNA (Quantigene) assay for mRNA levels and MTT for cytotoxicity, were robust enough to be incorporated into a screening format using a single replicate and a single concentration of compound. Significantly, a structure/toxicity correlation was established with this set of compounds with cytotoxicity and gene induction patterns linked to compound structure. Therefore, this type of early screening may be useful in identifying toxic substituents, enabling the design of libraries with less potential for toxicity. While structure/toxicity correlations were observed, no relationship was observed between GADD45 gene induction and mutagenesis as measured by the Ames bacterial reverse mutation assay.

Journal Article↗

PubMed1999

Transcriptional activation of gonadotropin-releasing hormone (GnRH) receptor gene by GnRH: involvement of multiple signal transduction pathways.

Previous studies have shown that GnRH activates transcriptional activity of its own receptor (GnRHR) gene in part through the cAMP signal transduction pathway. In the present study we explored the possible involvement of multiple signal transduction pathways in GnRH regulation of GnRHR gene transcription; these studies relied upon a luciferase reporter gene vector (GnRHR-pXP2) containing a 1226-bp promoter fragment (-1164 to +62, relative to the major transcription start site) of the mouse GnRHR gene in GGH3 cells (GH3 cells stably expressing rat GnRHR). Activation of protein kinase C (PKC) by phorbol myristic acid significantly stimulated GnRHR-luciferase reporter gene (GnRHR-Luc) activity, but did not potentiate the stimulation of GnRHR-Luc activity by the GnRH agonist, buserelin (GnRH-A). Inhibition of PKC by PKC inhibitor (GF 109203X) or depletion of PKC blocked phorbol myristic acid- or GnRH-A-stimulated GnRHR-Luc activity, but did not affect (Bu)2cAMP-stimulated GnRHR-Luc activity. In addition, GnRH-A-stimulated GnRHR-Luc activity was inhibited by preventing external Ca2+ influx with the external Ca2+ chelator EGTA or the Ca2+ ion channel antagonist, D600. Surprisingly, overexpression of the mitogen-activated protein kinase (MAPK) kinase kinase (Raf-1) inhibited GnRHR-Luc activity and partially blocked GnRH-A-stimulated GnRHR-Luc activity. In contrast, inhibition of MAPK activity by MAPK kinase inhibitor (PD 98059) or by overexpression of kinase-deficient MAPKs activated basal and GnRH-A-stimulated GnRHR-Luc activity. These results suggested that PKC- and Ca2+-dependent signal transduction pathways participate in the GnRH activation of GnRHR promoter activity, and that the MAPK cascade is involved in the negative regulation of basal and GnRH-stimulated GnRHR transcriptional activity conferred by the 1226-bp promoter fragment.

Animals↗

PubMed1999

Molecular cloning and expression of two type one somatostatin receptors in goldfish brain.

Somatostatin (SRIF or SS) exerts diverse inhibitory actions through binding to specific receptors. In this study, two SRIF receptor complementary DNAs (cDNAs) were cloned and sequenced from goldfish brain using PCR and cDNA library screening. The two cDNAs share 92% similarity in nucleotide sequence and 98% similarity in the deduced amino acid sequences and are presumably derived from duplicate genes, as goldfish are tetraploid. Two cDNAs encode two 367-amino acid goldfish type one SRIF receptors (designated as sst1A and sst1B, respectively), with seven putative transmembrane domains (TMD) and YANSCANP motif in the 7th TMD, a signature sequence for mammalian SRIF receptor (sst) family. In addition, the amino acid sequences of two receptors have 76% and 75% similarity to human or rat sst1, respectively, and 39-55% similarities to other mammalian sst subtypes (sst2-5), suggesting that the two receptors could be the goldfish homologs of mammalian sst1. The difference between goldfish and mammalian sst1 is mainly reflected by the extreme divergence in their extracellular N termini. Both SRIF-14 and [Pro2]SRIF-14, two of the native goldfish SRIF forms, significantly inhibited forskolin-stimulated cAMP release in COS-7 cells transiently expressing goldfish sSt1A or sst1B, suggesting functional coupling of the two receptors to adenylate cyclase. Northern blot and RT-PCR showed that messenger RNAs (mRNAs) for both receptors are widely distributed throughout goldfish brain, whereas only one receptor mRNA is expressed in the pituitary. RT-PCR analysis also detected sst1 receptor mRNAs in several peripheral tissues. These findings provide fundamental information for studying the mechanism of SRIF actions in vertebrates and structural analysis of mammalian sst receptors.

Amino Acid Sequence↗

PubMed1999

Expression of three distinct somatostatin messenger ribonucleic acids (mRNAs) in goldfish brain: characterization of the complementary deoxyribonucleic acids, distribution and seasonal variation of the mRNAs, and action of a somatostatin-14 variant.

In this study, three somatostatin (SRIF) complementary DNAs (cDNAs) were characterized from goldfish brain. The cDNAs encode three distinct preprosomatostatins (PSS), designated as PSS-I, PSS-II, and PSS-III. The goldfish PSS-I, PSS-II, and PSS-III contain enzymatic cleavage recognition sites, potentially yielding SRIF-14 with sequence identical to mammalian SRIF-14, SRIF-28 with [Glu1, Tyr7, Gly10]SRIF-14 at its C-terminus, and [Pro2]SRIF-14, respectively. The brain distribution of the three SRIF messenger RNAs (mRNAs) were differential but overlapping in the telencephalon, hypothalamus and optic tectum-thalamus regions. Seasonal variations in the levels of the three mRNAs were observed, with differential patterns between the three mRNAs and differences between the sexes. However, only the seasonal alteration in the levels of the mRNA encoding PSS-I showed close association with the seasonal variation in brain contents of immunoreactive SRIF-14 and inversely correlated with the seasonal variation in serum GH levels described in the previous studies, suggesting that SRIF-14 is involved in the control of the seasonal variation in serum GH levels. The putative SRIF-14 variant, [Pro2]SRIF-14, inhibited basal GH secretion from in vitro perifused goldfish pituitary fragments, with similar potency to SRIF-14; [Pro2]SRIF-14 also inhibited stimulated GH release from the pituitary fragments, supporting that [Pro2] SRIF-14 is a biologically active form of SRIF in goldfish.

Amino Acid Sequence↗

PubMed1999

Simultaneous and independent visualization of the gonadotropin-releasing hormone receptor and its ligand: evidence for independent processing and recycling in living cells.

The first step in GnRH signaling is binding by the peptide to its plasma membrane receptor (GnRHR). The receptor is a member of the seven transmembrane G protein-coupled class but lacks the characteristic C-terminal cytoplasmic tail, making it among the smallest receptors in this superfamily. It has been known since 1980 that agonist occupancy of the GnRHR results in patching, capping, and internalization, although it has not been possible to localize the unoccupied GnRHR, because elaboration of receptor antisera has not been easy to achieve. The recent production of a green fluorescent protein (GFP) conjugate of the GnRHR ("rGnRHR-C-tail-GFP") that is expressed in cells, targeted to the plasma membrane, binds GnRH analogs and couples to G proteins has made it possible to monitor movement of the unoccupied receptor by confocal microscopy. In the present study, we used this probe, along with Texas Red conjugates of a GnRH agonist, to examine simultaneous processing of the receptor and its ligands. The preparation of the GFP GnRHR chimera has been described. A Texas Red conjugate was made from the GnRH agonist D-Lys6-Pro9-des-Gly10EA-GnRH by standard procedures. Bioactivity of this conjugate was confirmed. Confocal fluorescence images of living GGH3 cells showed that the agonist binds the GFP-GnRH receptor construct on the cell membrane and causes the internalization of vesicles delimited by a membrane. Shortly after internalization, the agonist separates from receptor inside the vesicle, although it is still enclosed in membranes containing free receptor. As the vesicles approach the perinuclear space, the separation between receptor and agonist is more pronounced. Free receptor appears at the cell membrane after the internalization of agonist has been completed. The protein synthesis inhibitor, cycloheximide (1 mM) did not inhibit this process, suggesting that the free receptor results from the recycling of previously internalized vesicles rather than from newly synthesized receptor. These studies show visual evidence for recycling of the GnRH receptor in cultured cells.

Animals↗

PubMed1999

Heparan sulfate proteoglycans are essential for FGF receptor signaling during Drosophila embryonic development.

The Drosophila sugarless and sulfateless genes encode enzymes required for the biosynthesis of heparan sulfate glycosaminoglycans. Biochemical studies have shown that heparan sulfate glycosaminoglycans are involved in signaling by fibroblast growth factor receptors, but evidence for such a requirement in an intact organism has not been available. We now demonstrate that sugarless and sulfateless mutant embryos have phenotypes similar to those lacking the functions of two Drosophila fibroblast growth factor receptors, Heartless and Breathless. Moreover, both Heartless- and Breathless-dependent MAPK activation is significantly reduced in embryos which fail to synthesize heparan sulfate glycosaminoglycans. Consistent with an involvement of Sulfateless and Sugarless in fibroblast growth factor receptor signaling, a constitutively activated form of Heartless partially rescues sugarless and sulfateless mutants, and dosage-sensitive interactions occur between heartless and the heparan sulfate glycosaminoglycan biosynthetic enzyme genes. We also find that overexpression of Branchless, the Breathless ligand, can partially overcome the requirement of Sugarless and Sulfateless for Breathless activity. These results provide the first genetic evidence that heparan sulfate glycosaminoglycans are essential for fibroblast growth factor receptor signaling in a well defined developmental context, and support a model in which heparan sulfate glycosaminoglycans facilitate fibroblast growth factor ligand and/or ligand-receptor oligomerization.

Amidohydrolases↗

PubMed1999

Analysis of repeated hemoglobin measures in full-term, normal birth weight Kenyan children between birth and four years of age. III. The Asemobo Bay Cohort Project.

Anemia is an important public health problem. During very early childhood numerous factors affect hemoglobin (Hb) concentration over time, making single cross-sectional measurements difficult to interpret when studying the natural history of anemia or evaluating anemia control strategies. We analyzed repeated Hb measures contributed by 942 Kenyan children between birth and 48 months of life using a mixed effects model, with a regression spline used to describe the population mean Hb profile, and random intercepts and slopes and first-order autoregressive correlation structure to accommodate the within-individual correlation among the repeated Hb measures. The approach facilitates the study of time-stationary and time-varying covariates that influence Hb in early life. The fitted mean Hb profile obtained from the analytic model is consistent with the observed mean Hb of the study population. Village of residence was associated with greatest difference in mean Hb at time of birth (16 versus 19 g/dL; P < 0.0001). Monthly weight-for-age was also associated with mean Hb after 3 months of age. This is the first description of an analysis strategy specifically for repeated Hb measures collected in a longitudinal field study in Africa. The strategy will facilitate improved study of time-varying covariates thought to influence pediatric anemia.

Adolescent↗

PubMed1999

[Cost-effectiveness analysis of treatment of chronic hepatitis B with interferon in Chinese city].

OBJECTIVE: In this article, we evaluated the economic significance of treating HBeAg-positive chronic hepatitis B with interferon in Chinese population. METHODS: Cohort of 1,000 hypothetical HBeAg-positive chronic hepatitis B patients treated with interferon was compared to patients with routine treatment in respect of cost and effectiveness. The costs of routine treatment were estimated by surveys in four Chinese cities (Beijing, Shanghai, Nanning and Shijiazhuang). Natural history of HBeAg-positive chronic hepatitis B and the efficacy of interferon were determined by meta-analysis. Outcome of the disease and medical cost of the two cohorts were predicted over a period of 30 years using survival analysis. Thus, cost per life year and cost per QALY(Quality adjusted life year) with the interferon treatment were calculated. Sensitivity analysis was performed to test the firmness of the conclusion. RESULTS: Costs per life year and per QALY saved were no more than 2,359 Yuan(RMB) and 1,775 Yuan (RMB) respectively. In Shanghai and Beijing, medical costs could be saved due to the use of interferon. CONCLUSIONS: Treatment of chronic hepatitis B with interferon was cost-effective and should be considered in the allocation of health resource in Chinese cities.

Antiviral Agents↗

PubMed1999

[Long-term efficacy study of hepatitis B vaccination in newborns--results of 11 years' follow-up].

OBJECTIVE: To evaluate the long-term efficacy of hepatitis B(HB) vaccination in newborns and the need for a booster dose. This research is one of the longest HB vaccine follow-up studies in the world with its subjects came from a program of universal infant HB vaccination. METHODS: Children who were born in 1986 and immunized with hepatitis B vaccine at birth were followed up at least once a year. Serum HBsAg, anti-HBc and anti-HBs were tested. At the 5th year after the first dose the prevalence of hepatitis B infection in the children in other district who were also born in 1986 and remained unvaccinated was surveyed as external controls. Random sampling was applied and the possible bias was analyzed. The trends of the positive rates of serum HBsAg, anti-HBs and anti-HBc in the immunized cohort were studied. With external control, the long-term efficacy of HB vaccination was calculated. RESULTS: The positive rates of HBsAg in the vaccine group from the first to eleventh year were 0.46%-0.98% and were below than those of baseline and external control. HBsAg rates in the cohort at different ages were similar with an average of 0.70%(25/3 578). The long-term efficacy of newborn vaccination was 85.42% (95% confidant interval: 70.11%-100%). CONCLUSIONS: The efficacy of HB vaccine was long-lasting and a booster dose was not necessary at least up to age 11 years.

Female↗

PubMed1999

Experimental studies on topoisomerase inhibitor camptothecin as an antipsoriatic agent.

OBJECTIVES: To elucidate the therapeutic mechanism of topical camptothecin (CPT) in treating psoriasis and to detect the effects of CPT on keratinocyte proliferation, differentiation and apoptosis. METHODS: Mitotic numbers in mouse vaginal epithelium at estrus and numbers of scale with granular layer per 100 scales in mouse tail epidermis were determined in vivo. Experiments on cultured normal human keratinocytes were performed using the methods of crystal violet staining, absorbance-cell number converting, cell counting and quantitation of morphologic changes during differentiation, transglutaminase assay and nucleosomal enrichment assay. RESULTS: Inhibition of cell proliferation and promotion of cell differentiation by camptothecin were showed in animal models and were reconfirmed in cultured keratinocytes. Apoptosis was induced by camptothecin and was showed by activation of "tissue" transglutaminase and increase in nucleosomes. The endonuclease activity was reduced by an endonuclease inhibitor aurintricarboxylic acid. CONCLUSION: The therapeutic effects of camptothecin on psoriasis can at least partly be explained by its multiple effects on DNA as a topoisomerase inhibitor.

Animals↗

PubMed1999

[Effect of Yiqi Zishen granule on ultrastructure of glomeruli of IgA nephropathy in mice].

OBJECTIVE: To study the effect and therapeutical mechanism of Yiqi Zishen granule (YQZSG) in treating IgA nephropathy. METHODS: One hundred and fifty mice were divided into 5 groups randomly, in every treatment group, the relevant drugs were given. Their kidney tissues were observed with light microscope and electron microscope in batches at the 3rd, 6th, 9th and 12th week. RESULTS: The glomerular mesangial cells and mesangial matrix were proliferative in the model group at the 6th, 9th and 12th week. The light density of glomeruli, the mesangial area, the numeral density of mesangial cells and the light density of mesangial matrix in the model group were obviously higher, the change of large and small dosage YQZSG group and positive Chinese drug group were similar, but milder in pathological degree. The light density of glomerulus area, the mesangial area, the numeral density of mesangial cells and the light density of mesangial matrix in large dosage YQZSG group were significantly lower than those in the model group (P < 0.05 or P < 0.01). CONCLUSION: YQZSG could inhibit the proliferation of mesangial cells and the mesangial matrix in IgA nephropathy.

Animals↗

PubMed1999

[Applying combination of ultrasound and CT to diagnose paralaryngeal space tumor].

OBJECTIVE: To explore an effective way to diagnose parapharyngeal space tumor. METHODS: The clinical data of 25 cases of this type of tumor, diagnosed by combinating ultrasound examination and CT scan, were analysed. RESULTS: The diagnosis correspondence rate by the combinating way of ultrasound and CT is 92%. The combination of the two methods is likely able to reveal the overall shape, extend and feature of tumor, and to assist us in decision of the entrance of operation. CONCLUSION: The combination of ultrasound diagaosis and CT scan is of satisfactory clinical value in diagnosis of parapharyngeal space tumor.

Adolescent↗

PubMed1999

[Detection of circulating antigen in serum and cerebrospinal fluid for diagnosis of cerebral cysticercosis].

AIM: To detect circulating antigen(CAg) in serum and cerebrospinal fluid(CSF) from patients with cerebral cysticercosis with specific antiserum by sandwich ELISA. METHODS: Antisera were prepared from rabbits immunized respectively with 3 antigens with molecule weights of 64 kDa, 53 kDa, 32 kDa-30 kDa extracted from Cysticercus cellulosae and purified by SDS-PAGE. RESULTS: When samples from patients were tested with antiserum against 53 kDa antigen, the CAg positive rate was 93.8% in serum and 91.7% in CSF of 32 patients with active cysticercosis, whereas only one positive was found in CSF in 16 patients with inactive cysticercosis. The detection rate of CAg was significantly higher with anti-53 kDa antiserum than with anti-64 kDa and anti-32 kDa-30 kDa antiserum. CONCLUSION: Sandwich-ELISA using antiserum against 53 kDa antigen to detect CAg was found to be a promising assay for diagnosis and evaluation of treatment efficacy of active cerebral cysticercosis in terms of its high sensitivity and specificity.

Animals↗

PubMed1999

[The prognostic value of virology and immunology markers in Chinese HIV-1 infected people].

OBJECTIVE: To study the prognostic value of virology and immunology markers in Chinese HIV-1 infected people and their correlation. METHODS: We studied 190 HIV infected people/AIDS patients' samples from China. Plasma viral load, P24 antigen, virus culture, CD4 positive T lymphocyte (CD4) count and CD8 positive T lymphocyte(CD8) count were tested. Test groups were divided according to clinical staging diagnosis from physicians. The data were analyzed in aspects of their relations with clinical status and correlations among all the above markers. RESULTS: Plasma viral load, CD4 count and CD4/CD8 ratio showed significant difference between asymptomatic stage and symptomatic stages (P < 0.01), also between asymptomatic and AIDS stages(P < 0.001). Virus culture positive rate increased significantly from asymptomatic to symptomatic stage. No significant clinical change was observed associating with P24 antigen positive rate. CD8 count decreased slightly when AIDS occurred (P < 0.001). Close correlation was observed between plasma viral load, CD4 count and CD4/CD8 ratio. CONCLUSION: Viral load, CD4 count and CD4/CD8 ratio are useful indicators to AIDS prognosis and virus culture can be a supplementary marker. p24 antigen detection seems no diagnostic value to disease progress. The significance of CD8 change will be further studied.

Biomarkers↗

PubMed1998

Biodegradable positively charged ion exchange beads: a novel biomaterial for enhancing soft tissue repair.

Previous work in the area of vulnerary agents is extensive. One material of focus has been positively charged ion exchange beads, which have been shown to promote a variety of wound-healing responses in several models. The goal of this work was to improve upon the clinical utility of positively charged dextran beads by creating a biodegradable version that maintains the material's inherent efficacy. A chemical method consisting of a sodium periodate oxidation was used to create a degradable diethylaminoethanol crosslinked dextran bead. The ability of this process to create a degradable bead was verified in vitro and in vivo. Furthermore, efficacy was shown in a rat linear incision model for a variety of beads exhibiting different degradation rates. The results show that efficacy is maintained by a degradable bead, but there is a diminution of the magnitude of the response as the mass loss rate is increased. Efficacy also was investigated for a moderate but completely degrading bead material over time and dose. Wound breaking strength was evaluated at days 7, 10, 14, 21, and 28 for degradable beads at doses of 10 mg/mL and 50 mg/mL. Although little difference in efficacy was noted for the increased dose, statistically significant increases over control were seen at days 7, 10, and 14 for the 10 mg/mL dose and at days 10 and 14 for the 50 mg/mL dose. At days 21 and 28 there were no differences between treated and control wounds.

Animals↗

PubMed1998

Visualization of unoccupied and occupied gonadotropin-releasing hormone receptors in living cells.

Three chimeras of the rat GnRH receptor (rGnRHR) and an enhanced green fluorescent protein (GFP) were assessed to examine their suitability as probes of the receptor in transfected GH3 cells. Direct fusion of GFP to the N or C terminus of the rGnRHR abolished the receptor ligand binding affinity and the chimeric receptors were intracellularly localized. In contrast, rGnRHR-Ctail-GFP, a fusion of the N-terminus of the GFP to the C-terminus of the rGnRHR with the intracellular C-terminal tail of the catfish GnRHR as an intermediate spacer, was functional in terms of plasma membrane localization, ligand binding ability, receptor-mediated signal transduction and pattern of homologous down-regulation. The functional chimera of GnRHR and GFP provided a useful model for observation of GnRHR distribution and agonist-stimulated trafficking in living cells.

Animals↗