Biomedical subjects

Y Lin

Publications and source records attributed to Y Lin.

At least 91 records · Page 5Linked to original sources

PubMed2001

Different effects of conjugated linoleic acid isomers on lipoprotein lipase activity in 3T3-L1 adipocytes.

Conjugated linoleic acids (CLAs) are the positional and geometric isomers of linoleic acid. In the present study the effects of cis-9, trans-11 CLA (c9,t11 CLA) and trans-10, cis-12 CLA (t10,c12 CLA ) on intracellular and heparin-releasable (HR-) lipoprotein lipase (LPL) activity in 3T3-L1 adipocytes were investigated. Cells were exposed to the two CLA isomers and linoleic acid, which were bound to bovine serum albumin (BSA). In the adipocytes insulin up-regulated and tumor necrosis factor alpha (TNFalpha) down-regulated HR-LPL activity, which corresponds with the findings in vivo. The experimental fatty acids at low concentrations (<30 µmol/L) moderately increased intracellular and HR-LPL activity. At a concentration of 100 µmol/L, c9,t11 CLA and t10,c12 CLA suppressed HR-LPL activity to 20 and 24% below the BSA control level, respectively, while linoleic acid had no effect unless its concentration was as high as 1000 µmol/L. Insulin abolished the inhibitory effect of c9,t11 CLA, but not of t10,c12 CLA. In the presence of insulin, t10,c12 CLA inhibited HR-LPL activity by 41% compared to BSA control. In contrast to TNFalpha, which suppressed both intracellular LPL and HR-LPL activity, CLAs suppressed HR-LPL activity without decreasing intracellular LPL activity. Additionally, t10,c12 CLA (100 µmol/L) partially prevented TNFalpha-induced decrease of intracellular LPL activity. These results indicate that CLAs differ from linoleic acid in regulating HR-LPL activity, and t10,c12 CLA appeared to be more effective than c9,t11 CLA.

Journal Article↗

PubMed2001

Seasonal allergic rhinoconjunctivitis and fatty acid intake: a cross-sectional study in Japan.

PURPOSE: To investigate the associations of fatty acid intake with seasonal allergic rhinoconjunctivitis. METHODS: The study subjects consisted of 1012 women aged 22 to 57 years (mean age +/- SD: 36.5+/-7.7 years), who had graduated from the Aichi Prefectural Junior College of Nursing, Nagoya, Japan. They completed a self-administered questionnaire on symptoms of the disease in August 1998. Symptoms of seasonal allergic rhinoconjunctivitis in spring were determined by response to the questionnaire, and fatty acid intake was estimated using a food frequency questionnaire. Odds ratios (ORs) were computed using unconditional logistic models to assess the strength of associations between the symptoms and fatty acid intake. RESULTS: An increasing trend in the ORs was observed with increasing dietary intake of n-6 polyunsaturated fatty acids. After adjustment for potential confounders, the ORs for the second, third, and highest quartiles of intake relative to the lowest were 1.28 [95% confidence interval (CI), 0.78-2.10], 1.55 (0.96-2.50), and 1.74 (1.09-2.77), respectively (trend p = 0.015). Consumption of saturated, monounsaturated, and n-3 polyunsaturated fatty acids was not significantly related to the symptoms. CONCLUSIONS: Dietary intake of n-6 polyunsaturated fatty acids was positively associated with seasonal allergic rhinoconjunctivitis in spring.

Adult↗

PubMed2001

Factors affecting phantom scores at annual mammography facility inspections by the U.S. Food and Drug Administration.

RATIONALE AND OBJECTIVES: The authors performed this study to evaluate the factors affecting phantom image score at the annual inspection of mammography facilities. MATERIALS AND METHODS: In 1997, three U.S. Food and Drug Administration (FDA)-trained inspectors performed inspections of all mammography facilities in North Carolina. All federal and state inspection data were collected and evaluated by using linear regression analysis. Factors affecting the American College of Radiology phantom scores were assessed. RESULTS: Phantom score was affected by inspector identity, view box luminance, and optical density. All of these factors had a statistically significant effect on mass score (P < .05). Inspector identity yielded a statistically significant effect on speck group score, fibril score, and total score. Luminance yielded a statistically significant effect on both speck group score and total score. CONCLUSION: Phantom scoring should be automated to allow for more consistent interobserver scoring. In addition, radiology facilities can improve the likelihood of receiving a passing phantom score by reducing the ambient light and increasing the view box luminance in the location where the images are evaluated and the phantom is scored routinely. Radiologists should also consider increasing phantom and clinical image optical density to allow for improved phantom testing outcomes.

Breast Diseases↗

PubMed2001

Regulation of PTEN transcription by p53.

PTEN tumor suppressor is frequently mutated in human cancers and is a negative regulator of PI3'K/PKB/Akt-dependent cellular survival. Investigation of the human genomic PTEN locus revealed a p53 binding element directly upstream of the PTEN gene. Deletion and mutation analyses showed that this element is necessary for inducible transactivation of PTEN by p53. A p53-independent element controlling constitutive expression of PTEN was also identified. In contrast to p53 mutant cell lines, induction of p53 in primary and tumor cell lines with wild-type p53 increased PTEN mRNA levels. PTEN was required for p53-mediated apoptosis in immortalized mouse embryonic fibroblasts. Our results reveal a unique role for p53 in regulation of cellular survival and an interesting connection in tumor suppressor signaling.

Animals↗

PubMed2001

Quantitative evaluation of thalami and basal ganglia in infants with periventricular leukomalacia.

Quantitative analyses of cross-sectional areas of the thalami, caudate nuclei, and lentiform nuclei were performed in 29 preterm infants (16 males, 13 females; mean age 29.6 weeks, age range 27 to 24 weeks,) with periventricular leukomalacia (PVL). MRI was carried out in the infants between 9 and 18 months of corrected age and in 16 control infants. Bilateral thalami, caudate nuclei, lentiform nuclei, cerebral hemispheres, and cerebellum were measured by computer. Ratios of the areas of the thalami (Th), caudate nuclei (Ca), lentiform nuclei (Le), and cerebral hemispheres (CH) to that of the cerebellum (Ce) were calculated in each infant. The ratio of Th:Ce was significantly smaller in infants with moderate and severe PVL than in the control group bilaterally. Abnormal intensity areas were not observed in the thalami in any infants with PVL. CH:Ce was also smaller in infants with severe PVL than in the control group. No significant difference was observed between the groups in ratios Le:Ce or Ca:Ce. Results of our study suggest that the volume of the thalami is reduced and that thalamic involvement is present in infants with white matter lesions who have moderate to severe PVL.

Basal Ganglia↗

PubMed2001

Protein kinase C modulates NMDA receptor trafficking and gating.

Regulation of neuronal N-methyl-D-aspartate receptors (NMDARs) by protein kinases is critical in synaptic transmission. However, the molecular mechanisms underlying protein kinase C (PKC) potentiation of NMDARs are uncertain. Here we demonstrate that PKC increases NMDA channel opening rate and delivers new NMDA channels to the plasma membrane through regulated exocytosis. PKC induced a rapid delivery of functional NMDARs to the cell surface and increased surface NR1 immunofluorescence in Xenopus oocytes expressing NMDARs. PKC potentiation was inhibited by botulinum neurotoxin A and a dominant negative mutant of soluble NSF-associated protein (SNAP-25), suggesting that receptor trafficking occurs via SNARE-dependent exocytosis. In neurons, PKC induced a rapid delivery of functional NMDARs, assessed by electrophysiology, and an increase in NMDAR clusters on the surface of dendrites and dendritic spines, as indicated by immunofluorescence. Thus, PKC regulates NMDAR channel gating and trafficking in recombinant systems and in neurons, mechanisms that may be relevant to synaptic plasticity.

Animals↗

PubMed2001

Sequence diversity in CYP3A promoters and characterization of the genetic basis of polymorphic CYP3A5 expression.

Variation in the CYP3A enzymes, which act in drug metabolism, influences circulating steroid levels and responses to half of all oxidatively metabolized drugs. CYP3A activity is the sum activity of the family of CYP3A genes, including CYP3A5, which is polymorphically expressed at high levels in a minority of Americans of European descent and Europeans (hereafter collectively referred to as 'Caucasians'). Only people with at least one CYP3A5*1 allele express large amounts of CYP3A5. Our findings show that single-nucleotide polymorphisms (SNPs) in CYP3A5*3 and CYP3A5*6 that cause alternative splicing and protein truncation result in the absence of CYP3A5 from tissues of some people. CYP3A5 was more frequently expressed in livers of African Americans (60%) than in those of Caucasians (33%). Because CYP3A5 represents at least 50% of the total hepatic CYP3A content in people polymorphically expressing CYP3A5, CYP3A5 may be the most important genetic contributor to interindividual and interracial differences in CYP3A-dependent drug clearance and in responses to many medicines.

Alleles↗

PubMed2001

The essential role of MEKK3 in TNF-induced NF-kappaB activation.

Activation of IkappaB kinase (IKK) is the key step in stimulation of the transcription factor NF-kappaB, which regulates many genes in the inflammatory response pathway. The molecular mechanism that underlies IKK activation in response to tumor necrosis factor (TNF) is still unknown. Using mitogen-activated protein kinase kinase kinase 3 (MEKK3)-deficient fibroblast cells, we found that MEKK3 plays a critical role in TNF-induced NF-kappaB activation. We have shown that MEKK3 is required for IKK activation and functions downstream of receptor-interacting protein (RIP) and TNF receptor- associated factor 2. We have also shown that MEKK3 interacts with RIP and directly phosphorylates IKK. The kinase activity of MEKK3 is pivotal to its function and, therefore, MEKK3 links RIP and IKK in TNF-induced NF-kappaB activation.

Animals↗

PubMed2001

Mutational analysis of the structure and functions of hepatitis C virus RNA-dependent RNA polymerase.

The hepatitis C virus (HCV) nonstructural protein 5B (NS5B) is an RNA-dependent RNA polymerase (RdRP), a central catalytic enzyme for HCV replication. To further understand the structure and functions of NS5B, we introduced a series of 27 clustered and 19 point substitution mutations within and outside the well-known motifs conserved among RdRP by alanine scanning and investigated effects of these mutants on enzymatic activity of NS5B. Surprisingly, most of the mutations (22 of 27 clustered mutants) do not affect RdRP activity at all, indicating that the side chains of the corresponding amino acid residues are dispensable for the catalytic activity. On the other hand, 4 mutants, cm20t, cm194t, cm2t, and cm3t, are defective in RdRP activity. By further analysis with point mutations within these regions, E18, Y191, C274, Y276, and H502 were determined to be critical for the RdRP activity. Y276 was also shown to be critical for RNA template/primer association, although 3 amino acid sequences were identified to be important for RNA template binding by RNA-filter binding assays. Finally, 4 discontinuous sequences of NS5B (aa139-145, aa149-155, aa 365-371, and aa 382-388) were found to be essential for binding to NS5A as determined by glutathione S-transferase (GST)-pull down assays using GST-NS5A and FLAG-NS5B expressed in cotransfected cells, and GST-pull down assay in vitro. In light of the crystal structure models of NS5B recently reported, our results indicate that the RdRP activity of NS5B requires the longer loop and the helix located at the distal of the thumb, which are unique among RdRPs as well as reverse transcriptases.

Amino Acid Sequence↗

PubMed2001

Prevalence of naturally occurring surface gene variants of hepatitis B virus in nonimmunized surface antigen-negative Chinese carriers.

Previous studies have suggested that hepatitis B virus (HBV) variants may account for the presence of HBV DNA in hepatitis B surface antigen (HBsAg)-negative patients (occult HBV infection). However, it is not known how widespread these variants are and how they influence the course of liver disease. To determine the prevalence of variants within the major hydrophilic region (MHR) of HBsAg, we investigated 2,565 subjects, including subjects with chronic hepatitis, cryptogenic cirrhosis, hemodialysis patients, and blood donors. Fifty-one of them had occult HBV infection. The entire S gene from 46 of these patients was sequenced from amplified serum HBV DNA. Forty-three percent (20 of 46) had mutations in the MHR of HBsAg. Thirty-two amino acid substitutions between positions 100-160 of the MHR of HBsAg were detected in 18 patients, and these ranged from 1 to 4 per patient. These changes involved 11 positions inside and 5 outside of the historical first and second loops of the "a" determinant, and included the following: Q101K, T115A, K122N, T123A, T126N, Q129N, G130R, T131I, M133T, F134L, C138Y, K141E, P142S, G145R, N146S, and C147F/R. Combinations of mutations were detected in 9 patients, and 7 of these have not been described before. Two further patients had insertion mutations immediately before the "a" determinant. Monoclonal antibody binding tests with the Royal Free hepatitis B surface (RFHBs) panel of antibodies revealed decreased immunoreactivity in 6 novel variants of HBsAg. The existence of patients with occult HBV infection caused by HBsAg variants, therefore, has implications for their possible transmission through sexual contact and by blood transfusion.

Alanine Transaminase↗

PubMed2001

Preclinical evaluation of a humanized NR-LU-10 antibody-streptavidin fusion protein for pretargeted cancer therapy.

A humanized single chain Fv antibody fragment specific to the EGP40 antigen was genetically engineered as a streptavidin fusion (scFvSA) for use in pretargeted radioimmunotherapy. The scFvSA construct was expressed as a soluble, tetrameric species in the Escherichia coli periplasm at 110-140 mg/liter. The fusion protein was purified from crude lysates by iminobiotin affinity chromatography with an overall yield of 50-60%. Characterization of the purified protein by SDS-PAGE, light scattering, and size exclusion chromatography demonstrated that the fusion protein was tetrameric with a molecular weight of approximately 172,000. Competitive immunoreactivity assays showed a two-fold greater binding to the antigen than the comparable whole antibody. The purified protein had a biotin disassociation rate identical to recombinant streptavidin and bound an average of three of four possible biotins per molecule. The radiolabeled fusion protein showed a faster blood clearance rate in normal mice than the corresponding whole antibody-streptavidin chemical conjugate. Tumor-specific targeting of a subsequently administered radionuclidechelate/biotin molecule was demonstrated in nude mice bearing SW1222 human colon carcinoma xenografts. A single dose of 800 microCi of 90Y-DOTA-biotin produced cures in mice with established subcutaneous human small cell lung or colon cancer xenografts.

Animals↗

PubMed2001

Statistical properties of the traditional algorithm-based designs for phase I cancer clinical trials.

Although there are several new designs for phase I cancer clinical trials including the continual reassessment method and accelerated titration design, the traditional algorithm-based designs, like the '3 + 3' design, are still widely used because of their practical simplicity. In this paper, we study some key statistical properties of the traditional algorithm-based designs in a general framework and derive the exact formulae for the corresponding statistical quantities. These quantities are important for the investigator to gain insights regarding the design of the trial, and are (i) the probability of a dose being chosen as the maximum tolerated dose (MTD); (ii) the expected number of patients treated at each dose level; (iii) target toxicity level (i.e. the expected dose-limiting toxicity (DLT) incidences at the MTD); (iv) expected DLT incidences at each dose level and (v) expected overall DLT incidences in the trial. Real examples of clinical trials are given, and a computer program to do the calculation can be found at the authors' website approximately linyo" locator-type="url">http://www2.umdnj.edu/ approximately linyo.

Journal Article↗

PubMed2001

Capture of DNA sequences at double-strand breaks in mammalian chromosomes.

To study double-strand break (DSB)-induced mutations in mammalian chromosomes, we transfected thymidine kinase (tk)-deficient mouse fibroblasts with a DNA substrate containing a recognition site for yeast endonuclease I-SceI embedded within a functional tk gene. To introduce a genomic DSB, cells were electroporated with a plasmid expressing endonuclease I-SceI, and clones that had lost tk function were selected. Among 253 clones analyzed, 78% displayed small deletions or insertions of several nucleotides at the DSB site. Surprisingly, approximately 8% of recovered mutations involved the capture of one or more DNA fragments. Among 21 clones that had captured DNA, 10 harbored a specific segment of the I-SceI expression plasmid mapping between two replication origins on the plasmid. Four clones had captured a long terminal repeat sequence from an intracisternal A particle (an endogenous retrovirus-like sequence) and one had captured what appears to be a cDNA copy of a moderately repetitive B2 sequence. Additional clones displayed segments of the tk gene and/or microsatellite sequences copied into the DSB. This first systematic study of DNA capture at DSBs in a mammalian genome suggests that DSB repair may play a considerable role in the evolution of eukaryotic genomes.

Animals↗

PubMed2001

Women on the editorial boards of major journals.

PURPOSE: To determine the percentages of women on the editorial boards of general and specialty medical journals in comparison with the numbers of women physicians in the journals' respective specialties. METHOD: The numbers of women editors, deputy editors, assistant editors, and members of editorial boards of 12 major journals in 1999 were counted and compared with the percentages of women physicians in the journals' specialties, as published by the American Medical Association. RESULTS: Parity between the percentages of women on editorial boards of specialty journals and women physicians in the journals' specialties was found for five journals. Only one journal had more women on the editorial board than there were women physicians in the specialty. CONCLUSIONS: Fewer than half of the journals studied had parity between the percentages of women members of editorial boards and the percentages of women physicians in the specialties. Parity should be maintained to accurately reflect the numbers of women physicians in these fields.

American Medical Association↗

PubMed2001

Dynamic localization of rop GTPases to the tonoplast during vacuole development.

Vacuoles are essential pleomorphic organelles that undergo dynamic changes during cell growth and differentiation in plants. How developmental signals are linked to vacuole biogenesis and development is poorly understood. In this report, we show that a Rop GTPase is localized to developing vacuoles in pea (Pisum sativum cv Extra Early Alaska). Rop belongs to the RHO family of Ras-related small GTP-binding proteins that are key molecular switches in a wide variety of eukaryotic signal transduction pathways. Using indirect immunofluorescence and an anti-Rop antibody, we showed that Rop proteins accumulate to high levels in rapidly growing tapetal cells of pea anthers. In these cells, Rop is localized to an endomembrane system that exists as dynamic pleomorphic networks: a perinuclear fine network decorated with punctate dots, a network composed of small spheres and tubules, and interconnected chambers. Colocalization with a tonoplast annexin VCaB42 shows that these dynamic networks represent the tonoplast. Our results suggest that the dynamic Rop-containing tonoplast networks represent a unique stage of vacuole development. The specific localization of Rop to developing vacuoles supports a role for Rop in signal transduction that mediates vacuole development in plants.

Endoplasmic Reticulum↗

PubMed2001

The Rop GTPase switch controls multiple developmental processes in Arabidopsis.

G proteins are universal molecular switches in eukaryotic signal transduction. The Arabidopsis genome sequence reveals no RAS small GTPase and only one or a few heterotrimeric G proteins, two predominant classes of signaling G proteins found in animals. In contrast, Arabidopsis possesses a unique family of 11 Rop GTPases that belong to the Rho family of small GTPases. Previous studies indicate that Rop controls actin-dependent pollen tube growth and H(2)O(2)-dependent defense responses. In this study, we tested the hypothesis that the Rop GTPase acts as a versatile molecular switch in signaling to multiple developmental processes in Arabidopsis. Immunolocalization using a general antibody against the Rop family proteins revealed a ubiquitous distribution of Rop proteins in all vegetative and reproductive tissues and cells in Arabidopsis. The cauliflower mosaic virus 35S promoter-directed expression of constitutively active GTP-bound rop2 (CA-rop2) and dominant negative GDP-bound rop2 (DN-rop2) mutant genes impacted many aspects of plant growth and development, including embryo development, seed dormancy, seedling development, lateral root initiation, morphogenesis of lateral organs in the shoot, shoot apical dominance and growth, phyllotaxis, and lateral organ orientation. The rop2 transgenic plants also displayed altered responses to the exogenous application of several hormones, such as abscisic acid-mediated seed dormancy, auxin-dependent lateral shoot initiation, and brassinolide-mediated hypocotyl elongation. CA-rop2 and DN-rop2 expression had opposite effects on most of the affected processes, supporting a direct signaling role for Rop in regulating these processes. Based on these observations and previous results, we propose that Rop2 and other members of the Rop family participate in multiple distinct signaling pathways that control plant growth, development, and responses to the environment.

Arabidopsis↗

PubMed2001

Reduced antibody response to streptavidin through site-directed mutagenesis.

Streptavidin provides an effective receptor for biotinylated tumoricidal molecules, including radionuclides, when conjugated to an antitumor antibody and administered systemically. Ideally, one would like to administer this bacterial protein to patients repeatedly, so as to maximize the antitumor effect without eliciting an immune response. Therefore, we attempted to reduce the antigenicity of streptavidin by mutating surface residues capable of forming high energy ionic or hydrophobic interactions. A crystallographic image of streptavidin was examined to identify residues with solvent-exposed side chains and residues critical to streptavidin's structure or function, and to define loops. Mutations were incorporated cumulatively into the protein sequence. Mutants were screened for tetramer formation, biotin dissociation, and reduced immunoreactivity with pooled patient sera. Patient antisera recognized one minor continuous epitope with binding locus at residue E101 and one major discontinuous epitope involving amino acid residues E51 and Y83. Mutation of residues E51, Y83, R53, and E116 reduced reactivity with patient sera to <10% that of streptavidin, but these mutations were no less antigenic in rabbits. Mutant 37, with 10 amino acid substitutions, was only 20% as antigenic as streptavidin. Rabbits immunized with either streptavidin or mutant 37 failed to recognize the alternative antigen. Biotin dissociated from mutant 37 four to five times faster than from streptavidin. Residues were identified with previously undescribed impact on biotin binding and protein folding. Thus, substitution of charged, aromatic, or large hydrophobic residues on the surface of streptavidin with smaller neutral residues reduced the molecule's ability to elicit an immune response in rabbits.

Amino Acid Sequence↗

PubMed2001

Associations of alcohol drinking and nutrient intake with chronic pancreatitis: findings from a case-control study in Japan.

OBJECTIVE: The aim of this study was to examine the association of alcohol drinking and nutrient intake with chronic pancreatitis in a hospital-based case-control study. METHODS: From July, 1997, to December, 1998, 91 male patients, who were newly diagnosed as having chronic pancreatitis, were recruited as cases, and 175 controls were individually matched to each case for gender, age (+/-5 yr), hospital, and time of the first visit to a hospital (+/-1 yr). Information on demographic characteristics, smoking and drinking, and dietary habits were collected by a self-administered questionnaire. The strength of associations was examined by odds ratios (ORs) and 95% CIs calculated from conditional logistic regression models. RESULTS: Our study showed that the more the daily amount of alcohol drinking, the larger the OR. Men who consumed > or =100 g ethanol/day were at an approximately 11-fold increased risk as compared with nondrinkers. Long-term alcohol consumption (>35 yr) was associated with the increased risk (OR = 4.0). Risk of chronic pancreatitis remarkably increased with increasing cumulative alcohol consumption (trend p = 0.0001). Intakes of saturated fatty acid and vitamin E were negatively associated with the risk (trend p = 0.05 for saturated fatty acid and 0.03 for vitamin E). CONCLUSION: Our study clearly demonstrated that prolonged heavy alcohol consumption was an important and independent risk factor, and suggested a role of lower nutrient intakes in the development of chronic pancreatitis.

Adult↗