Biomedical subjects

H Lin

Publications and source records attributed to H Lin.

At least 199 records · Page 11Linked to original sources

PubMed1999

[Variations of the middle meatus mucosa ultrastructure after endoscopic sinus surgery].

OBJECTIVE: To explore the variations of middle meatus ultrastructure after endoscopic sinus surgery. METHOD: 10 cases whose middle meatus mucosa recovered well after undergoing endoscopic sinus surgery were screened, and postoperative electron microscope examinations of middle meatus mucosa were made in the first, second, third and forth month. RESULT: In the first month after operation, there was obvious fibre proliferation in the mucosa. In the second month, there was fibre proliferation and dissolution existing simultaneously. In the third month, the mucosa's structure resumed fundamentally to normal, but its function was not perfect. In the forth month, the mucosa was completely normal and can function normally. CONCLUSION: The mucosa of middle meatus can resume completely after endoscopic sinus surgery but need at least four months. It is very important to have a long time reexamination for improving therapeutic effect.

Adult↗

PubMed1998

Application of magnetic field-induced heat shock protein 70 for presurgical cytoprotection.

To develop an alternative to hyperthermia for the induction of hsp70 for presurgical cytoprotection, we investigated the optimal exposure conditions for magnetic field induction of hsp70. Normal human breast cells (HTB124) were exposed to 60-Hz magnetic fields and hsp70 levels were measured following three different exposure conditions: continuous exposure up to 3 h, a single 20-min exposure, and a single 20-min exposure followed by repeated 20-min exposures at different field strengths. In cells exposed continuously for 3 h, hsp70 levels peaked (46%) within 20 min and returned to control levels by 2 h. Following a single 20-min exposure, the return of hsp70 levels to control values extended to more than 3 h. When cells underwent a 20-min exposure followed by repeated 20-min exposures (restimulation) with different field strengths, additional increases in hsp70 levels were induced: 31% at 1 h, 41% at 2 h, and 30% at 3 h.

Breast↗

PubMed1998

A novel class of evolutionarily conserved genes defined by piwi are essential for stem cell self-renewal.

Germ-line stem cells (GSCs) serve as the source for gametogenesis in diverse organisms. We cloned and characterized the Drosophila piwi gene and showed that it is required for the asymmetric division of GSCs to produce and maintain a daughter GSC but is not essential for the further differentiation of the committed daughter cell. Genetic mosaic and RNA in situ analyses suggest that piwi expression in adjacent somatic cells regulates GSC division. piwi encodes a highly basic novel protein, well conserved during evolution. We isolated piwi homologs in Caenorhabditis elegans and humans and also identified Arabidopsis piwi-like genes known to be required for meristem cell maintenance. Decreasing C. elegans piwi expression reduces the proliferation of GSC-equivalent cells. Thus, piwi represents a novel class of genes required for GSC division in diverse organisms.

Amino Acid Sequence↗

PubMed1998

Phosphoinositide-specific phospholipase C interacts with phosphatidylinositol kinase homolog TOR2.

The Saccharomyces cerevisiae PLC1 gene encodes a homolog of the delta isoform of mammalian phosphoinositide-specific phospholipase C. Cells deleted for PLC1 gene (plc1Delta) are viable but display several phenotypes, including temperature and osmotic sensitivity and defects in utilization of carbon sources other than glucose. We have used the two hybrid screen to identify Plc1p-interacting proteins. One of the identified proteins was Tor2p, a putative phosphatidylinositol (PtdIns) kinase involved in regulation of protein synthesis, cell cycle progression and organization of the actin cytoskeleton. This interaction was confirmed biochemically by coprecipitation of Plc1p and Tor2p. The results suggest that Tor2p, as a PtdIns kinase, produces phosphorylated PtdIns, which is then hydrolyzed by the associated Plc1p. The proximity of Tor2p to Plc1p may therefore result in a regulated spatial and temporal coupling of synthesis and hydrolysis of phosphorylated forms of PtdIns.

Animals↗

PubMed1998

Comparison of the mode of action of a dinuclear platinum complex containing a pyridine derivative with its monomeric analog.

The DNA binding and interstrand cross-linking properties of the dinuclear platinum complex [¿cis-Pt(NH3)2Cl¿2bpsu](NO3)2 (bpsu is 4,4'-dipyridyl sulfide) (II) and the mononuclear complex [cis-Pt(NH3)2Cl(4-methylpyridine)]NO3 (I) were compared with those of [¿cis-Pt(NH3)2Cl¿2H2N(CH2)4NH2](NO3)2 (III) in order to understand the mode of action of complexes I and II. Both compound I and compound II caused significantly different changes of conformation in poly(dG-dC) x poly(dG-dC) than compound III did. Studies of DNA binding, interstrand cross-linking and fluorescence assay suggest that compound I monofunctionally binds to DNA and compound II bifunctionally binds to DNA, that the dinuclear platinum complex II more efficiently interacts with DNA compared to its monomeric analog, and that platinum I and II complexes both interact with DNA in a non-intercalative mode. All the results indicate that the mode of action of the dinuclear complex II is different from that of the mononuclear complex I.

Animals↗

PubMed1998

Uncoupling activation-dependent HS1 phosphorylation from nuclear factor of activated T cells transcriptional activation in Jurkat T cells: differential signaling through CD3 and the costimulatory receptors CD2 and CD28.

CD3, CD2, and CD28 are functionally distinct receptors on T lymphocytes. Engagement of any of these receptors induces the rapid tyrosine phosphorylation of a shared group of intracellular signaling proteins, including Vav, Cbl, p85 phosphoinositide 3-kinase, and the Src family kinases Lck and Fyn. Ligation of CD3 also induces the tyrosine phosphorylation of HS1, a 75-kDa hematopoietic cell-specific intracellular signaling protein of unknown function. We have examined changes in HS1 phosphorylation after differential stimulation of CD3, CD2, and CD28 to elucidate its role in T cells and to further delineate the signaling pathways recruited by these receptors. Unlike ligation of CD3, stimulation with anti-CD28 mAb or CHO cells expressing the CD28 ligands CD80 or CD86 did not lead to tyrosine phosphorylation of HS1 in Jurkat T cells. Additionally, no tyrosine phosphorylation of HS1 was induced by mitogenic pairs of anti-CD2 mAbs capable of activating the transcription factor NFAT (nuclear factor of activated T cells). Costimulation through CD28 and/or CD2 did not modulate the CD3-dependent phosphorylation of HS1. In vivo studies indicated that CD3-induced HSI phosphorylation was dependent upon both the Src family tyrosine kinase Lck and the tyrosine phosphatase CD45, did not require MEK1 kinase activity, and was regulated by protein kinase C activation. Thus, although CD3, CD28, and CD2 activate many of the same signaling molecules, they differed in their capacity to induce the tyrosine phosphorylation of HSI. Furthermore, activation-dependent tyrosine phosphorylation of HS1 was not required for NFAT transcriptional activation.

Adaptor Proteins, Signal Transducing↗

PubMed1998

[Identify influential points].

Influential points are the points with excessive influence on result and detected by influential function theta-theta(i). theta-theta(i) is a multidimensional vector. For convenience, people always consider some quantitative function g (theta-theta(i)) to measure the vector theta-theta(i), but how to define g is a difficult problem. This paper proposes a new quantitative diagnostic statistics for identifying influential points for all parametrical statistical analysis. The method is more appropriate than cook's method for regression analysis. In this study an example is used to illustrate the procedure in COX proportional hazard model.

Proportional Hazards Models↗

PubMed1998

Magnetic field activation of protein-DNA binding.

The mechanisms involved in sensing, signaling, and coordinating changes resulting from magnetic field-induced stress show substantial similarities to those of heat shock, e.g., magnetic field-induced heat shock 70 gene (HSP70) expression involves heat shock factor (HSF) activation and heat shock element binding. However, an additional requirement for transactivation of HSP70 expression by magnetic fields is the binding of Myc protein, indicating that additional elements and/or pathways are involved in the induction of HSP70 expression by magnetic fields. To investigate the possible participation of additional genetic elements in magnetic field-induced HSP70 expression, we examined both magnetic field exposure and heat shock on protein-DNA binding of the transcription factors HSF, AP-1, AP-2, and SP-1 in four human cell lines. The binding sites for these transcription factors are present in the HSP70 promoter. AP-1 binding activity, normally not increased by heat shock, was increased by magnetic fields; heat shock induced an increase only in HSF binding. Although intersecting and converging signaling pathways could account for the multiplicity of elements involved in magnetic field-induced HSP70 transcription, direct interaction of magnetic fields with DNA is also a possible mechanism. Because magnetic fields penetrate the cell, they could well react with conducting electrons present in the stacked bases of the DNA.

Binding, Competitive↗

PubMed1998

A unifying Tm diagram for phosphatidylethanolamines with sn-1 C20 saturated and sn-2 C18 unsaturated acyl chains.

We have determined calorimetrically the phase transition temperature (Tm) values of five sn-1 saturated/sn-2 unsaturated phosphatidylethanolamines (PE) in which the sn-1 acyl chain has 20 carbons and the sn-2 acyl chain has 18 carbons with different number and position of the cis double bond. When these Tm values are combined with the five published Tm values of related unsaturated PE, a unifying Tm diagram is generated for the first time. Moreover, as the molecular mechanics simulated structures of these lipids are taken into consideration, this unifying Tm diagram provides insight into how variations in the number and position of the cis double bond in the lipid's sn-2 acyl chain can influence the phase transition behavior of the lipid bilayer.

Calorimetry, Differential Scanning↗

PubMed1998

Apolipoprotein E and longevity among Han Chinese population.

The apolipoprotein E gene (APOE), which locates on chromosome 19, has three common APOE alleles encoding APOE*2, APOE*3, APOE*4. It has been considered to be closely associated with human longevity among Western population. However, the allele frequency varies among racial and ethnic groups. We studied the relationship between APOE and longevity among 1562 Han Chinese (246 female and 1316 male) whose ages ranged from 20-108 years old in Shanghai metropolitan area and Lian Yungang, Jiangsu province. APOE was amplified by one-stage PCR using the forward primer: 5'-GGC ACG GCT GTC CAA GGA GCT-3' and reverse primer: 5'-GAT GGC GCT GAG GCC GCG CT-3'. The PCR product was digested directly with 5 U of CfoI and separated by a 20% polyacrylamide (acrylamide:bisacrylamide = 29:1) nondenaturing gel. The allele frequency of APOE*4 in thevery old age group (> or = 85 years) was significantly different from that in the youth (20-39 years), middle (40-59 years) and old (60-84 years) age group (2.5% vs 8.4, 7.9 or 7.6%; P < 0.05), respectively.

Adult↗

PubMed1998

Association of p59(fyn) with the T lymphocyte costimulatory receptor CD2. Binding of the Fyn Src homology (SH) 3 domain is regulated by the Fyn SH2 domain.

Human CD2 is a 50-55-kDa cell surface receptor specifically expressed on the surface of T lymphocytes and NK cells. Stimulation of human peripheral blood T cells with mitogenic pairs of anti-CD2 monoclonal antibodies (mAbs) is sufficient to induce interleukin-2 production and T cell proliferation in the absence of an antigen-specific signal through the T cell receptor. CD2 has been shown previously to associate physically with the Src family protein-tyrosine kinases p56(lck) and p59(fyn). We now report that stimulation of T cells with mitogenic pairs of anti-CD2 mAbs enhanced the association of the Fyn polypeptide with the CD2 complex, whereas stimulation with single anti-CD2 mAb had minimal effect. Using glutathione S-transferase (GST) fusion proteins, we found that CD2 bound to the Src homology (SH) 3 domain of Fyn. Interestingly, the CD2-Fyn association was negatively regulated by the Fyn SH2 domain; CD2 bound poorly to GST fusion proteins expressing both the SH2 and SH3 domains of Fyn. However, the inhibitory effect of the Fyn SH2 domain on binding of the Fyn SH3 domain to CD2 was relieved by peptides containing a phosphorylated YEEI sequence that bound directly to the Fyn SH2 domain. In addition, we found that the ability of the Fyn SH2 domain to precipitate tyrosine-phosphorylated proteins, including the CD3zeta chain, was enhanced after T cell stimulation with mitogenic pairs of CD2 mAbs. Finally, overexpression of a mutated Fyn molecule, in which the ability of the Fyn SH2 domain to bind phosphotyrosine-containing proteins was abrogated, inhibited CD2-induced transcriptional activation of the nuclear factor of activated T cells (NFAT), suggesting a functional involvement of the Fyn SH2 domain in CD2-induced T cell signaling. We thus propose that stimulation through the CD2 receptor leads to the tyrosine phosphorylation of intracellular proteins, including CD3zeta itself, which in turn bind to the Fyn-SH2 domain, allowing the direct association of the Fyn SH3 domain with CD2 and the initiation of downstream signaling events.

Antibodies↗

PubMed1998

Calorimetric studies of phosphatidylethanolamines with saturated sn-1 and dienoic sn-2 Acyl chains.

We have semi-synthesized 18 species of mixed chain phosphatidylethanolamines (PE) in which the sn-1 acyl chain is derived from stearic, arachidic, and behenic acids, and the sn-2 acyl chain is originated from cis,cis-octadecadienoic and cis, cis-eicosadienoic acids with the two methylene-interrupted double bonds located at various positions. These PEs constituting the bilayers in the aqueous dispersion were subjected to differential scanning calorimetric experiments. The Tm values associated with the gel-to-liquid crystalline phase transitions for these PEs are found to be significantly smaller than those of the saturated counterparts. Moreover, the magnitude of the Tm-lowering effect of acyl chain diunsaturation depends critically on the positions of the two methylene-interrupted cis double bonds in the sn-2 acyl chain. Specifically, if the sn-2 acyl chain is derived from cis, cis-octadecadienoic acid, the Tm-lowering effect has the following decreasing order: Delta9,12 > Delta6,9 > Delta12,15. For cis, cis-eicosadienoyl acyl chain, the Tm-lowering effect is stronger in the order of Delta10,13 > Delta11,14 > Delta8,11 > Delta5,8 > Delta14,17. Finally, a refined molecular model is presented that can adequately explain the Tm-lowering effect of sn-2 acyl chain diunsaturation. Moreover, this same refined molecular model can also be invoked to better interpret the Tm-lowering effect observed for sn-1 saturated/sn-2 monoenoic PE.

Calorimetry, Differential Scanning↗

PubMed1998

NADH fluorescence in isolated guinea-pig and rat cardiomyocytes exposed to low or high stimulation rates and effect of metabolic inhibition with cyanide.

In this study we investigated whether NADH fluorescence levels changed in response to low or high rates of electrical stimulation in single ventricular myocytes isolated from rat and guinea-pig hearts, either during a single contraction or upon sustained electrical stimulation of cells. NADH levels were determined from cell autofluorescence and cell length monitored using an edge-tracking device. NADH/NAD+ was obtained by addition of cyanide, 100% NADH, and carbonylcyanide-p-trifluoromethoxy phenylhydrazone (FCCP), 100% NAD+. Rat myocytes exhibited slightly higher resting fluorescence levels than guinea-pig cells; however, NADH/NAD+ was higher in rat than guinea-pig cells (P < 0.05), 24.3+/-4.3 (N = 17) vs 14.6+/-1.6 (N = 17), respectively. There was no change in NADH fluorescence during a single contraction when cells were stimulated at either low (0.2 Hz) or high (3 Hz) rates in either species. Furthermore, NADH levels did not change upon sustained stimulation at 3 Hz in either species. Metabolic blockade with cyanide induced a dose dependent rise in NADH fluorescence which was similar for both rat and guinea-pig myocytes and reached a maximum at > or = 1 mM of cyanide. Although a full recovery of NADH fluorescence was seen in both types of cells after brief exposure to cyanide, the rate of recovery was significantly slower in rat myocytes; times to 90% recovery were 110+/-29 sec, N = 6, and 264+/-50 sec, N = 6, for guinea-pig and rat cells, respectively. This work demonstrates that although rat and guinea-pig myocytes have different resting NADH/NAD+, their response to electrical stimulation is the same, whereas in response to metabolic inhibition subtle differences are seen.

Animals↗

PubMed1998

Cytotoxic T lymphocyte antigen 4 (CTLA4) blockade accelerates the acute rejection of cardiac allografts in CD28-deficient mice: CTLA4 can function independently of CD28.

Cytotoxic T lymphocyte antigen 4 (CTLA4) appears to negatively regulate T cell activation. One mechanism by which CTLA4 might antagonize T cell function is through inhibition of CD28 signaling by competing for their shared ligands B7-1 and B7-2. In addition, CTLA4 ligation could initiate a signaling cascade that inhibits T cell activation. To address whether CTLA4 could inhibit immune responses in the absence of CD28, rejection of heart allografts was studied in CD28-deficient mice. H-2(q) hearts were transplanted into allogeneic wild-type or CD28-deficient mice (H-2(b)). Graft rejection was delayed in CD28-deficient compared with wild-type mice. Treatment of wild-type recipients with CTLA4-immunoglobulin (Ig), or with anti-B7-1 plus anti-B7-2 mAbs significantly prolonged allograft survival. In contrast, treatment of CD28-deficient mice with CTLA4-Ig, anti-B7-1 plus anti-B7-2 mAbs, or a blocking anti-CTLA4 mAb induced acceleration of allograft rejection. This increased rate of graft rejection was associated with more severe mononuclear cell infiltration and enhanced levels of IFN-gamma and IL-6 transcripts in donor hearts of untreated wild-type and CTLA4-Ig- or anti-CTLA4 mAb-treated CD28-deficient mice. Thus, the negative regulatory role of CTLA4 extends beyond its potential ability to prevent CD28 activation through ligand competition. Even in the absence of CD28, CTLA4 plays an inhibitory role in the regulation of allograft rejection.

Abatacept↗

PubMed1998

Light and electron microscopic study of neuronal nitric oxide synthase-immunoreactive neurons in the rat subiculum.

Neurons in the rat subiculum that are capable of producing nitric oxide were studied by using an antibody to the neuronal isoform of nitric oxide synthase (nNOS). In the light microscope, the staining pattern with the nNOS antibody closely resembled that seen following histochemical processing with nicotinamide adenine dinucleotide phosphate diaphorase. Immunostained neurons were found in all layers, and, in addition, large dendrites in the apical dendrite layer were also immunopositive. Although a few immunolabelled cells had the typical morphology of interneurons, most were found to have the characteristics of pyramidal neurons. In the subiculum, these immunoreactive pyramidal neurons were concentrated mainly in the most superficial cell layers and closest to the CA1 region, but pyramidal neurons in the CA1 layer of the hippocampus were consistently immunonegative. Immunopositive profiles in the subiculum were studied in the electron microscope and compared with unlabelled structures. Ultrastructural criteria suggest that both pyramidal and nonpyramidal subicular neurons are immunopositive for nNOS. Large, spiny dendrites and smaller, varicose dendrites were found to be immunoreactive for nNOS. Vesicle-containing profiles were probably presynaptic axons, and immunopositive boutons were seen to make symmetrical and asymmetrical synaptic contacts.

Animals↗

PubMed1998

Dilated cardiomyopathy in transgenic mice expressing a dominant-negative CREB transcription factor in the heart.

Idiopathic-dilated cardiomyopathy (IDC) is a common primary myocardial disease of unknown etiology characterized by progressive biventricular failure, cardiac dilatation, and premature mortality. Here we show that transgenic mice expressing a dominant-negative form of the CREB transcription factor (CREBA133) under the control of the cardiac myocyte-specific alpha-MHC promoter develop dilated cardiomyopathy that closely resembles many of the anatomical, physiological, and clinical features of human IDC. Between 2 and 20 wk of age, these mice develop four chamber cardiac dilatation, decreased systolic and diastolic left ventricular function, and attenuated contractile responses to the beta-adrenergic agonist, isoproterenol. Histologically, the CREBA133 hearts demonstrated both atrophic and hypertrophied fibers as well as significant interstitial fibrosis. These anatomical and hemodynamic changes were associated with hepatic congestion and peripheral edema, intracardiac thrombi, and premature mortality. Taken together, these results implicate CREB as an important regulator of cardiac myocyte function and provide a genetic model of dilated cardiomyopathy which should facilitate studies of both the pathogenesis and therapy of this clinically important disorder.

Animals↗

PubMed1998

Myc-mediated transactivation of HSP70 expression following exposure to magnetic fields.

We investigated c-myc protein-binding sites on the HSP70 promoter as modulators of the induction of HSP70 gene expression in response to magnetic field stimulation (8microT at 60Hz) and whether the presence of c-myc protein potentiates transactivation of HSP70 expression. A 320 base pair region in the HSP70 promoter (+1 to -320) was analyzed. This region contains two c-myc-protein binding sites with consensus sequences located at -230 and -160 nucleotide positions (relative to the transcription initiation site) and overlapping with the region reported for the regulation of HSP70 gene expression by c-myc protein. This promoter region is upstream of other regulatory sequences, including the heat shock element (HSE), AP-2, and serum response element (SRE). Transfectants containing both c-myc protein-binding sites, HSP-MYC A and HSP-MYC B, and exposed to magnetic fields showed a 3.0-fold increase in expression of CAT activity as compared with sham-exposed control transfectants. Transfectants containing one c-myc binding site, HSP-MYC A, and exposed to magnetic fields showed a 2.3-fold increase in CAT expression. Transfectants in which both HSP-MYC A and HSP-MYC B binding sites were deleted showed no magnetic field sensitivity; values were virtually identical with sham-exposed controls. If the c-myc expression vector was not co-transfected with the constructs containing myc-binding sites, there was no difference in the expression of CAT activity between magnetically stimulated and sham-exposed controls, although both responded to heat shock. These data suggest that endogenous elevated levels of myc protein contribute to the induction of HSP70 in response to magnetic field stimulation.

Electromagnetic Fields↗

PubMed1998

DNA requirements in vivo for phage T4 packaging.

Phage T4 terminase, comprising the products of genes 16 and 17, packages headfuls of DNA from a concatemer but its mechanism of DNA recognition remains to be determined. Phage T4 terminase gene sequences were introduced into prophage lambda imm434 and plasmids in order to assess their effect on packaging as measured by transduction frequency and DNA content of T4-transducing particles. Multiple copy prophage lambda imm434 genes were transduced at 100-fold higher frequency, and high copy plasmids were transduced at 1000-fold higher frequency than single copy prophage or chromosomal genes T4 16 gene inserts enhanced both prophage and plasmid packaging; terminase gene-containing plasmid DNA in T4 transducing particles could exceed 10% of the total. Deletion or base change of the 24-bp gene 16 3' region which is required for sequence specific amplification of terminase gene 17 (Hp 17 mutations) depressed these elevated plasmid transduction frequencies, suggesting that this is a preferred T4 pac sequence. Moreover, a specific gene 16-containing pac fragment could be detected in mature, packaged phage T4 DNA following restriction endonuclease digestion. We conclude that both the copy number of homologous sequences and the DNA pac sequence(s) themselves are important for packaging, consistent with a synapsis model for regulation of terminase cutting and packaging in phage T4.

Bacteriophage T4↗