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L Lin

Publications and source records attributed to L Lin.

At least 37 records · Page 2Linked to original sources
PubMed1999

The lack of extracellular laminin beta2 chain deposition correlates to the loss of conjunctival epithelial keratin K4 localization in culture.

PURPOSE: To examine the effects of external modulation of epithelial-mesenchymal interaction on conjunctival epithelial cell differentiation characteristics. METHODS: Keratin K4 and laminin beta2 chain protein localization was examined in an organotypic model which facilitates the comparison of differentiation characteristics of conjunctival epithelium interacting with conjunctival basement membrane or corneal basement membrane. In addition, keratin K4 and laminin beta2 chain localization was examined in primary cultures of conjunctival epithelial cells and fibroblasts. The synthesis and secretion of laminin beta2 chain by conjunctival fibroblasts in culture was determined by western blot analysis and immunoprecipitation. The ability of conjunctival epithelium to respond to exogenous laminin beta2 chain was assayed by culturing epithelial cells on a laminin matrix isolated from human placenta. RESULTS: In culture, conjunctival fibroblasts synthesize and secrete laminin beta2 chain but do not deposit this chain into an extracellular matrix substrate or basement membrane-like structure. The lack of extracellular deposition of this chain correlates to the gradual loss of keratin K4 protein in conjunctival epithelial cell culture. Conjunctival epithelium remains responsive to laminin beta2 chain in vitro because keratin K4 localization can be rescued in these cells by culture on a substrate of exogenous placental laminin. CONCLUSIONS: In vitro, alterations in native conjunctival epithelial-mesenchymal interactions results in aberrant basement membrane laminin isoform composition. This, in turn, leads to the loss of adult epithelial cell phenotype characteristics, suggesting that at least some aspects of conjunctival epithelial cell differentiation are regulated by the extracellular matrix.

Animals↗
PubMed1999

Differential rapid adhesion of bovine ocular surface epithelial cells to laminin isoforms.

PURPOSE: To examine the ability of bovine corneal and conjunctival epithelial cells to adhere to different types of exogenous laminin preparations. METHODS: The ability of bovine corneal and conjunctival epithelial cells in primary culture to attach to laminin isolated from human placenta or from mouse EHS tumor was measured using a short-term colorimetric adhesion assay. Focal adhesion formation in response to interaction with laminins was determined by immunofluorescence microscopy using antibodies to vinculin and morphometric analysis. The influence of laminin on the secretion of adhesion complex proteins by bovine corneal epithelial cells in culture was analyzed using immunofluorescence microscopy. RESULTS: In short-term assays, primary bovine corneal epithelial cells demonstrate rapid and efficient adhesion to placental laminin, and significantly more cells contain focal adhesions, compared to those incubated on EHS laminin. In contrast, primary bovine conjunctival epithelial cells adhere equally well to placental and EHS laminin over a range of substrate concentrations. Additionally, the percentage of cells containing focal adhesions is not significantly different. In primary bovine corneal epithelium, the deposition of collagen type IV and collagen type VII into extracellular network-like structures is inhibited in cells cultured on placental laminin compared to cells cultured on EHS laminin. CONCLUSIONS: In vitro, bovine corneal epithelial cells attach more rapidly and efficiently to exogenous placental laminin compared to EHS laminin. However, this isoform inhibits the ready formation of adhesion complex-like structures in culture. The laminin isoform found in human placental preparations may therefore modulate corneal epithelial cell motility as opposed to permanent adhesion.

Animals↗
PubMed1999

Identification of a stress-induced protein during human trophoblast differentiation by differential display analysis.

Differentiation of human placental trophoblast is characterized by a process during which mononuclear villous cytotrophoblasts fuse to form a multinucleate syncytium. This event is associated with dramatic changes in gene expression. In the present study, we have applied a sensitive approach-differential display analysis-to evaluate changes in gene expression during in vitro forskolin-induced differentiation of a model of human trophoblast, the choriocarcinoma BeWo. We identified seven genes that were up-regulated; their expression and function have not previously been reported in trophoblast. Four up-regulated genes were novel upon comparison of their sequences to the GenBank database. The other three genes encode human cytochrome p450 IIC, inosine monophosphate dehydrogenase type II, and reducing agent and tunicamycin-responsive protein (RTP). Northern blot analysis revealed that RTP mRNA expression was induced to 3-fold in BeWo after 24-h incubation with forskolin and increased up to 11-fold by 72 h of forskolin treatment. The expression pattern of RTP was further investigated by in situ hybridization on second trimester and term placenta tissues. RTP mRNA was predominantly expressed in syncytiotrophoblasts in both second trimester and term placentae. The expression of RTP gene in BeWo cells was protein kinase C dependent. This is the first description of RTP gene expression in placenta and the first study elucidating the signaling pathway involved in the regulation of RTP gene expression. These results suggest that RTP may play a role in trophoblast cell proliferation and differentiation.

Blotting, Northern↗
PubMed1999

A human period gene (HPER1) polymorphism is not associated with diurnal preference in normal adults.

Mammalian circadian rhythmicity has recently been shown to be regulated at the genetic level by transcription--translation feed-back loops. Key molecular components such as Clock, Bmal-1, Timeless and three Period proteins have been isolated in mammals. In this study, we hypothesized that polymorphisms at the level of one of these genes--HPER1--could be associated with differential morningness-eveningness tendencies. The sample comprised 463 middle-aged participants enrolled in the Wisconsin Sleep Cohort Study. Diurnal preferences were evaluated using the Horne-Ostberg questionnaire. An A to G synonymous substitution at position 2548 was identified in HPER1 c-DNA sequence by comparing available sequence data. This polymorphism was verified by sequencing and typed using established oligotyping techniques in all subjects, yielding allele frequencies of 0.85 and 0.15 for HPER1 2548G and HPER1 2548A, respectively. Morningness-eveningness scores were then compared between genotype groups. In contrast to data previously published using a Clock polymorphism, scores did not differ significantly across HPER1 groups. These results suggest that polymorphism at the level of HPER1 does not significantly modulate morningness-eveningness tendencies in the general population.

Adult↗
PubMed1999

PCR assay for detecting porcine cytomegalovirus.

This is the first published report of a PCR assay for detecting porcine cytomegalovirus (PCMV), the causative agent of inclusion body rhinitis in pigs. The DNA to be tested was extracted directly from lungs and nasal scrapings of pigs with various clinical syndromes. Fifty-nine percent (74 of 126) of tested pigs with various clinical syndromes were found to be PCR positive for PCMV. It is hoped that veterinary diagnostic laboratories will benefit by using this PCR assay for routine testing and surveillance of PCMV in pigs.

Animals↗
PubMed1999

Gender differences in cellular response.

Autoimmune and other diseases frequently manifest a sexual discordance that cannot be explained by hormonal differences. Although there is evidence for gender skewing being caused by gonadal hormones, such skewing does not explain an increase of frequency rather than of severity of such diseases in women. To examine if skewing might have a genetic explanation, we have asked how male and female cells devoid of hormonal differences respond to challenges. We used mouse embryonic cells from heart, liver and brain and assessed cellular responsiveness by cell survival. We find that female cells in general show more sensitivity to challenges, such as ethanol, hydrogen peroxide, and camptothecin. Our findings indicate that there is a differential behavior to challenges, in male vs female cells, which may be due to differences in the biological make-up of the cells with regard to gender, and provide preliminary information regarding the feasibility of this type of approach.

Animals↗
PubMed1999

Selective activation of the probasin androgen-responsive region by steroid hormones.

Glucocorticoid and androgen receptors have been shown to function through the same palindromic glucocorticoid response element (GRE) and yet have differential effects on gene transcription. In this study, we examined the functional and structural relationship of the androgen and glucocorticoid receptors with the androgen responsive region (ARR) of the probasin (PB) gene containing two androgen receptor binding sites, ARBS-1 and ARBS-2. Transfection studies indicated that one copy of each cis-acting DNA element was essential for maximal androgen-induced chloramphenicol acetyltransferase (CAT) activity and that androgen selectivity was maintained when multiple copies of the minimal wild type (wt) androgen responsive region containing both ARBS-1 and ARBS-2 (-244 to -96) were subcloned in front of the thymidine kinase promoter. Furthermore, replacing the androgen response region with 1, 2 or 3 copies of either ARBS-1 or ARBS-2 restored less than 4% of the biological activity seen with the wt PB ARR. Multiple copies of either ARBS-1 or ARBS-2 did not result in glucocorticoid-induced CAT gene activity. By comparison, 1 or 2 copies of the tyrosine aminotransferase (TAT) GRE, as well as the mouse mammary tumour virus GRE, were strong inducers of CAT activity in response to both androgen and glucocorticoid treatment. In addition, band shift assays demonstrated that although the synthetic glucocorticoid receptor, GR-DNA binding domain (GR-DBD), and the synthetic androgen receptor, AR2, could interact with the TAT GRE (dissociation constants Kd of 63.9 and 14.1 respectively), only AR2 but not GR-DBD binding could be detected on ARBS-1 and ARBS-2. Our findings provide further evidence that androgen-induced regulation of gene transcription can occur through androgen-specific DNA binding sites that are distinct from the common GRE.

Androgen-Binding Protein↗
PubMed1999

Frequency and pattern of p53 gene mutation in a cohort of Spanish women with node-negative breast cancer.

Ethnic, racial and regional differences in the frequency and pattern of p53 gene mutations have been well documented. Some of these differences have been shown to have an impact on the survival of patients with breast cancer. In this study we explored the frequency and pattern of p53 abnormality in a cohort of Spanish women with node-negative breast cancer using PCR, subcloning and DNA sequencing of archival tumors. One hundred and seventy-eight cases of breast cancer diagnosed between 1981 and 1986 at the University of Oviedo Hospital in Oviedo, Spain were subjects of this study. Sequence analysis of exons 5 through 8 of p53 was performed on subcloned PCR-amplified DNA, extracted from formalin-fixed, paraffin-embedded tumors. Appropriate positive, negative, PCR, and polymerase controls were utilized and evaluated. Duplicate samples of the genomic DNA were re-evaluated on all cases showing more than one mutation. One hundred and five out of 178 breast cases (59%) carried one or more p53 gene mutations. Mutations were distributed randomly from codon 128 to 305. There were 123 (88%) transition, 10 (7%) transversion, 5 (3.5%) splice junction mutations, and 2 (1.5%) deletions. Eighty-three cases (61.5%) had missense mutation, 45 (33.5%) silent, 5 (3.5%) nonsense and 2 (1.5%) frameshifts. Eighty (75%) of 120 transitions were G:C to A:T, 11 (25%) of which occurred at CpG sites. Sixteen mutations were in novel codons not reported in breast cancers previously. Codons with the highest frequency of mutations in this group were 278, 273, 213 and 227. We also detected 27 tumors with more than one mutation within a single exon or in different exons in the same patient. These findings suggest that the frequency and pattern of p53 mutations in this group of Spanish women with breast cancer is different than those reported in the United States and Northern Europe.

Breast Neoplasms↗
PubMed1999

Comparative analysis of HPLC profile of cytosolic thymidine kinase activity between hepatoma and regenerating liver in rat with reference to phosphorylation.

Thymidine kinase (TK) activity in rat hepatoma JB1 and AH136B was mainly due to cytosolic TK and was much higher than that in rat regenerating liver. Two forms of cytosolic TK, designated as TK-I and TK-II, were revealed in addition to mitochondrial TK in anion-exchange high performance liquid chromatography (HPLC) of the enzyme extract from hepatoma JB1. During incubation of the enzyme extract at 20 degrees C in the presence of phosphatase inhibitor NaF, TK-II activity remained while TK-I activity almost disappeared. Thus, TK-II appeared to be more stable than TK-I. In Western blot analysis, TK-II was much more phosphorylated and exhibiting higher specific activity than TK-I. Meanwhile, regenerating liver derived from the rat 24 h after partial hepatectomy showed only TK-I activity, which completely disappeared after incubation at 20 degrees C even in the presence of NaF. Consequently, the presence of TK-II might account for the higher TK activity in hepatomas than in regenerating liver.

Animals↗
PubMed1999

[A preliminary study on the genetic susceptibility of asthma in a Chinese population].

OBJECTIVE: To study the asthma genetic susceptibility by way of ccandidate region so as to accumulate data on the related loci in Chinese population and determine whether genetic susceptibility to asthma is linked to the chromosome region. METHODS: One hundred ninety-two samples from 32 families were collected from Zhaoan county in Fujian province. Two Rsa I polymorphic sites within uncoded region of the high-affinity IgE receptor beta chain gene (Fc(epsilon) RI-beta) located on chromosome 11q13 were detected by PCR/Rsa I restriction endonuclease digestion. The polymorphic markers D5S436 and D5S393 within chromosome 5q31-33 were amplified by PCR incorporated with radioactive isotope. The asthma family samples were compared with unrelated samples randomly selected from general population. RESULTS: Genotypes containing A allele within intron 2 polymorphic site of Fc(epsilon) RI-beta gene were associated with asthma (P<0.05,OR = 2.039). Significant difference in the level of total serum IgE was noted among three genotypes of intron 2 polymorphic site of Fc(epsilon) RI-beta gene (P<0.05). The association between A allele and elevated total serum IgE was also significant (P<0.05, RR = 1.361). No relationship between exon 7 polymorphic site of Fc epsilonRI-beta gene and asthma was shown. By sib-pair analysis, significant evidence for linkage to asthma was observed with D5S436 (P<0.05) but not with D5S393. No significant linkage to total serum IgE was identified with both of these markers. CONCLUSION: The above-accumulated data suggested that both Fc epsilonRI-beta gene and chromosome 5q31-33 could be very attractive candidate gene and region for further studies in Chinese population, and to confirm these preliminary results, more markers within these regions merit testing in additional population samples.

Adolescent↗
PubMed1998

The effect of 4,4'-diisothiocyanato-stilbene-2,2'-disulfonate on CO2 permeability of the red blood cell membrane.

It has long been assumed that the red cell membrane is highly permeable to gases because the molecules of gases are small, uncharged, and soluble in lipids, such as those of a bilayer. The disappearance of 12C18O16O from a red cell suspension as the 18O exchanges between labeled CO2 + HCO3- and unlabeled HOH provides a measure of the carbonic anhydrase (CA) activity (acceleration, or A) inside the cell and of the membrane self-exchange permeability to HCO3- (Pm,HCO-3). To test this technique, we added sufficient 4, 4'-diisothiocyanato-stilbene-2,2'-disulfonate (DIDS) to inhibit all the HCO3-/Cl- transport protein (Band III or capnophorin) in a red cell suspension. We found that DIDS reduced Pm,HCO-3 as expected, but also appeared to reduce intracellular A, although separate experiments showed it has no effect on CA activity in homogenous solution. A decrease in Pm,CO2 would explain this finding. With a more advanced computational model, which solves for CA activity and membrane permeabilities to both CO2 and HCO3-, we found that DIDS inhibited both Pm,HCO-3 and Pm,CO2, whereas intracellular CA activity remained unchanged. The mechanism by which DIDS reduces CO2 permeability may not be through an action on the lipid bilayer itself, but rather on a membrane transport protein, implying that this is a normal route for at least part of red cell CO2 exchange.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1998

cDNA sequence and chromosomal localization of mouse Dlgh3 gene adjacent to the BRCA1 tumor suppressor locus.

Membrane associated guanylate kinase homologues (MAGUKs) function in tumor suppression and receptor clustering pathways presumably by modulating signaling events at the interface of the membrane cytoskeleton. The p55 subclass of MAGUKs includes two novel cDNAs that were originally identified by virtue of their genomic location to human chromosome 17q12-21 where the BRCA1 tumor suppressor gene has been mapped. The predicted primary structure of the human MPP3 contains a single copy of the PDZ domain, an SH3 motif, and a carboxy-terminal guanylate kinase-like domain. Here we report the full-length coding cDNA sequence of the mouse homologue of MPP3. The translated amino acid sequence of murine Dlgh3 contains 568 amino acids that show 87% sequence identity with the human MPP3 protein. Northern blot analysis shows abundant expression of a approximately 3.0 kb transcript of Dlgh3 in mouse brain and skeletal muscle, and a relatively less abundant approximately 5.0 kb transcript in skeletal muscle, testis, kidney, and lung. Using an interspecific backcross panel, the Dlgh3 gene was mapped to a segment of mouse chromosome 11 that is conserved with human chromosome 17q12-21. The close proximity of murine Dlgh3 gene to the BRCA1 locus and the high conservation of the primary structure of human and murine proteins provide a framework for testing the role of Dlgh3 in cell proliferation pathways using the mouse as a model system.

Amino Acid Sequence↗
PubMed1998

At least four loci and gender are associated with susceptibility to the chemical induction of lung adenomas in A/J x BALB/c mice.

Four putative quantitative trait loci (QTLs) that influence susceptibility to the induction of lung adenomas by urethane in an F2 cross between A/J and BALB/cOlaHsd have been mapped. Following microsatellite typing of mice with resistant and susceptible phenotypes at 97 microsatellite marker loci, a major locus was identified on chromosome 18 with a lod score of 15. This was responsible for an 8- to 10-fold increase in tumor multiplicity in males and females, respectively, having the AA and CC genotypes at the D18Mit188 marker locus. It mapped close to Dcc (deleted in colorectal cancer). A locus on chromosome 4 (lod score 6.5) had the resistant allele in strain A/J and the susceptible allele in BALB/c, with a 14-fold difference in tumor multiplicity between mice of the AA and CC genotypes. This mapped close to the Cdkn2a (cyclin-dependent kinase inhibitor 2A) locus, which is commonly deleted in mouse lung tumors. Two loci with smaller effects (lod scores 3.03 and 3.25) were identified on chromosomes 1 and 11. There was also significant sexual dimorphism in tumor multiplicity both among 151 F2 hybrids and among 52 mice resulting from a backcross to strain A/J, with males having higher tumor counts than females.

Adenoma↗
PubMed1998

A CLOCK polymorphism associated with human diurnal preference.

A single nucleotide polymorphism located in the 3' flanking region of the human CLOCK gene was investigated as a predictor of diurnal preference in a population-based random sample of 410 normal adults. Morningness-eveningness preferences were determined using the 19-item Home-Ostberg questionnaire. Subjects carrying one of the two CLOCK alleles, 3111C, had a significantly lower mean Horne-Ostberg score. The distribution of scores was clearly shifted toward eveningness for these subjects. The score difference was independent of age, sex and ethnic heritage, thus making population stratification effects unlikely to explain this difference. These subjects had a substantial 10- to 44-minute delay in preferred timing for activity or sleep episodes. We suggest that the identified polymorphism or another tightly linked polymorphism within the CLOCK gene or its regulatory elements may be responsible for the finding.

Adult↗
PubMed1998

In vitro anti-human immunodeficiency virus (HIV) activity of the chromanone derivative, 12-oxocalanolide A, a novel NNRTI.

The three chromanone derivatives, (+)-, (-)-, and (+/-)-12-oxocalanolide A (2), were evaluated for in vitro antiviral activities against HIV and simian immunodeficiency virus (SIV). The compounds were determined to be inhibitors of HIV-1 reverse transcriptase (RT) and exhibited activity against a variety of viruses selected for resistance to other HIV-1 nonnucleoside RT inhibitors. They are the first reported calanolide analogues capable of inhibiting SIV.

Acquired Immunodeficiency Syndrome↗
PubMed1998

Thin-layer chromatography of mycotoxins and comparison with other chromatographic methods.

This paper highlights the status of thin-layer chromatography (TLC) of mycotoxins in various sample matrices. The outstanding merits of TLC in the field of the qualitative and quantitative determination of mycotoxins have been briefed. A comparison between different TLC methods and TLC with HPLC, enzyme-linked immunosorbent assay and GC methods, etc. is made, in general.

Chromatography↗
PubMed1998

Constitutive expression of HGF modulates renal epithelial cell phenotype and induces c-met and fibronectin expression.

Hepatocyte growth factor (HGF) is a potent renotropic factor that has been shown to play important roles in kidney development and recovery from acute renal injury. To examine the effects of HGF on renal tubular epithelium, we generated HGF-producing renal epithelial cells by stably transfecting mIMCD-3 and OK cells with an expression plasmid containing human HGF cDNA. Expression of HGF in the transfected cells was confirmed by detection of HGF mRNA by Northern blot analysis and detection of HGF secretion into the conditioned medium by ELISA. HGF-transfected cells exhibited fibroblast-like scattered morphology and increased cell motility. They formed branching tubules when grown in 3-D collagen gel. In addition, HGF-producing cells grew faster than their parental cells, but failed to form colonies in soft agar. These phenotypic changes were inhibited by a specific, neutralizing anti-HGF antibody. Interestingly, both c-met transcript and c-met protein were increased in HGF-transfected cells, suggesting that HGF amplifies its own action via stimulation of c-met expression. Autocrine expression of HGF and c-met in renal epithelial cells also stimulated fibronectin gene expression, which was totally blocked by incubation with a neutralizing anti-HGF but not a pan-specific anti-TGF-beta antibody, suggesting that it is independent of TGF-beta production. Our data demonstrate that HGF as a single factor stimulates renal epithelial cell proliferation, migration, differentiation, and extracellular matrix remodeling, making it uniquely suited to promote renal tubulogenesis during development, as well as to reconstitute tubular integrity following acute injury.

Animals↗