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Biomedical subjects

L Su

Publications and source records attributed to L Su.

At least 127 records · Page 7Linked to original sources
PubMed1993

Expression of keratin 14 and 19 mRNA and protein in normal oral epithelia, hairy leukoplakia, tongue biting and white sponge nevus.

This study was undertaken to analyze keratin gene expression at both the mRNA and protein level in oral hairy leukoplakia (OHL). Comparisons were made with normal lingual epithelium from a similar site, tongue biting, normal buccal mucosa and another condition which disturbs oral epithelial differentiation, white sponge nevus. Combined immunocytochemical and in situ hybridization studies for keratins 14 and 19 were carried out on 2 specimens of OHL from HIV-positive males and one sample each of the other cases. Keratin 14 protein expression was uniform throughout all the epithelia. In normal epithelia and in lesions other than OHL, keratin 14 mRNA was most strongly expressed in basal cells with weaker but still significant amounts in the spinous cell layer. In both cases of OHL there was weaker basal cell expression of keratin 14 mRNA and frequent absence in koilocytoid cells. Keratin 19 protein expression was heterogeneous in the basal layer of all specimens with suprabasal staining of occasional groups of cells. Its mRNA was uniformly distributed in all cases. The findings indicate the keratin mRNA expression does not always parallel that of protein and that, in the case of keratin 14, expression may be influenced by the presence of EBV.

AIDS-Related Opportunistic Infections↗
PubMed1993

Yeast phenotype classifies mammalian protein kinase C cDNA mutants.

The phorbol ester receptor protein kinase C (PKC) gene family encodes essential mediators of eukaryotic cellular signals. Molecular dissection of their mechanisms of action has been limited in part by the lack of random mutagenesis approaches and by the complexity of signaling pathways in mammalian cells which involve multiple PKC isoforms. Here we present a rapid screen which permits the quantification of mammalian PKC activity phenotypically in the yeast Saccharomyces cerevisiae. Bovine PKC alpha cDNA is functionally expressed in S. cerevisiae. This results in a phorbol ester response: a fourfold increase in the cell doubling time and a substantial decrease in yeast colony size on agar plates. We have expressed pools of bovine PKC alpha cDNAs mutagenized by Bal 31 deletion of internal, amino-terminal, or carboxyl-terminal sequences and have identified three classes of mutants on the basis of their distinct yeast phenotypes. Representatives of each class were analyzed. An internal deletion of amino acids (aa) 172 to 225 displayed ligand-dependent but reduced catalytic activity, an amino-terminal truncation of aa 1 to 153 displayed elevated and ligand-independent activity, and a carboxyl-terminal 26-aa truncation (aa 647 to 672) lacked activity under any conditions. Additional mutations confirmed the distinct functional characteristics of these classes. Our data show that deletion of the V1 and C1 regions results in elevated basal catalytic activity which is still Ca2+ responsive. Internal deletions in the V2 and C2 regions do not abolish phorbol ester or Ca2+ regulation of PKC activity, suggesting that most of the C2 domain is not essential for phorbol ester stimulation and most of the regulatory domain is dispensable for Ca2+ regulation of PKC activity. These distinct activities od the PKC mutants correlate with a specific and proportional yeast phenotype and are quantified on agar plates by yeast colony size. This provides a phenotypic screen which is suitable to identity rare, randomly altered but active mammalian PKC mutants. It quantifies their catalytic and biological activities in response to PKC activators or inhibitors for a systematic mapping of PKC structure and function or PKC-drug interaction.

Animals↗
PubMed1993

Functional carboxyl terminal deletion map of protein kinase C alpha.

The phorbol ester receptor protein kinase C (PKC) gene family encodes essential mediators of various eukaryotic cellular signals. Based on the predicted amino acid (aa) sequence homology of more than ten distinct PKC gene coding sequences, four highly conserved regions C1-C4 and five variable regions V1-V5 have been defined for the different PKC subtypes. Some of these regions, such as C1 and C3/V4/C4, have been correlated with specific PKC functions, such as activator binding and enzymatic activity, respectively, while the biological role of others is unknown. The biological significance of the PKC carboxyl terminus is unclear and the predicted boundary of the catalytic C4 region is controversial due to different interpretations of aa sequence comparisons. We explored the PKC alpha carboxyl terminal requirement for basic PKC function and mapped the boundary of the sequences essential for enzymatic activity based on functional criteria. cDNAs encoding normal and random carboxyl terminal truncations of bovine PKC alpha were introduced into Saccharomyces cerevisiae, allowing its rapid functional expression and characterization for catalytic as well as biological activity. We found that deletion of up to 11 carboxyl terminal aa still results in a phorbol ester-responsive, biologically active enzyme in vivo which is dependent on calcium and phospholipids for catalytic activation in vitro. Deletion of 15 and 23 aa results in marginal and total loss of catalytic activity, respectively, and in complete loss of biological activity for both truncations.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

[Assay of negative inotropism of bepridil on isolated guinea pig left atrial myocardium by simulating constant rate of absorption and elimination].

The pharmacodynamic characteristic of negative inotropic effect of bepridil on isolated guinea pig cardiac atrium was conducted by gradient perfusion with constant rate of bepridil ranging from 0-20 mumol.L-1 and inverse, simulating a fixed pharmacokinetic parameters of K(a) and K(e), respectively. A counter-clockwise hysteresis loop of negative inotropism of bepridil was presented. Fixing Cp, T, and E by pharmacokinetics/pharmacodynamics (PK/PD) non-parameter model, the hysteresis loop was collapsed in figure plotting C(e) against E. The estimated K(eo) = 0.03 +/- 0.023 h-1, an apparent T1/2 of pharmacological effect was measured, and about 80-fold as long as the pharmacokinetic T1/2. It was suggested that the long-lasting effect of bepridil was partly due to the slow elimination rate from the effect compartment.

Absorption↗
PubMed1992

Genomic organization of the mouse granzyme A gene. Two mRNAs encode the same mature granzyme A with different leader peptides.

Granzyme A is a serine protease that, together with the other granular components of cytotoxic T lymphocyte (CTL) cells, has been implicated in the cytolysis process. We report here two different messages and the genomic organization of the mouse granzyme A gene. The granzyme A gene is composed of six exons spanning 7 kilobases. Alternative splicing of the second exon results in the two transcripts. The two mRNA species encode the same mature granzyme A protein but with different leader sequences. The first (HF1) encodes a typical leader signal sequence similar to other granzymes, but the second (HF2) putative leader sequence is different and less hydrophobic. Both messages are present in cultured CTL cell lines and in normal lymphoid tissues. They are both induced when CTL cells are activated in vitro or in vivo. Both messages can be translated in vitro, although the HF1 message appears to be much more efficient as a template. The putative 5' promoter region of the HF gene sequenced (500 base pairs of upstream sequences) contains no well defined promoter sequences aside from the TATA box. The results suggest that (a) granzyme A may be produced with putative different leader sequences from two different mRNAs; (b) this may provide a model system for studying alternate splicing and the evolution of a complex enzymatic system in an organelle; and (c) the genomic DNA reported will be useful for studying transcription regulations involved in controlling the specific expression pattern of this gene.

Amino Acid Sequence↗
PubMed1992

Cytotoxicity with target DNA breakdown by rat basophilic leukemia cells expressing both cytolysin and granzyme A.

The noncytotoxic rat mast cell tumor line RBL was transfected with genes for the cytotoxic lymphocyte granule proteins cytolysin (perforin) and granzyme A, giving transfectants with mRNA and protein expression levels comparable with cloned cytotoxic T lymphocytes. Both RBL-cytolysin and RBL-cytolysin-granzyme A transfectants showed extremely potent killing of red cell targets and lysed 20%-60% of EL4 lymphoma targets at an effector-to-target ratio of 30. RBL transfectants expressing only granzyme A were not cytotoxic. Significant EL4 DNA breakdown accompanying lysis was observed only with RBL that was transfected with both cytolysin and granzyme A. These results support the granule-exocytosis model for lymphocyte cytotoxicity and show that effector granzyme A plays a role in target cell DNA breakdown.

Animals↗
PubMed1991

Three rapid immunoassays for the determination of creatine kinase MB: an analytical, clinical, and interpretive evaluation.

We present analytical and clinical studies of three commercial immunoassays for the determination of the creatine kinase MB isoenzyme (CK-MB). All methods are compared with the presently-accepted reference method, agarose gel electrophoresis. We find that each of the immunoassay methods offers diagnostic sensitivity and specificity similar to those of electrophoresis, while none experiences detectable interference from high concentrations of the creatine kinase BB isoenzyme (CK-BB) or the so-called "atypical" bands. The presence of atypical bands can cause electrophoresis to yield inaccurate quantification or even misidentification of CK-MB. Because the immunoassay approaches are more rapid than electrophoresis and require less technical expertise, it is possible to evaluate patients in a more timely and cost-effective manner. Further, since immunoassay results can be available in approximately 1/2 hour, rapid real-time decisions can be made regarding the desirability of initiating or continuing such valuable but dangerous procedures as thrombolytic therapy.

Antibodies, Monoclonal↗
PubMed1991

[Effect of alcohol-extract from scorpion on checking externally active cysticerus cellulosae].

Putting the alcohol-extract from scorpion in the ordinary aqueous solution of 15% pork bile and having it cultured at the temperature of 37 degrees C have proved for the first time that in contrast with the chemical albendazole, Scorpion has a conspicuous effect on the external killing of the cysticercus cellulosae, The action of killing cysticercus cellulosae has almost nothing to do with the difference of processed products or of the parts used in medicine.

Animals↗
PubMed1989

Crosslinking of extracellular matrix proteins: a preliminary report on a possible mechanism of argon laser welding.

In order to elucidate the biochemical mechanism of laser welding of tissues, we have compared protein profiles from argon laser-treated specimens with controls. Extracellular matrix components from untreated and laser-welded skin and blood vessels were extracted with guanidine hydrochloride and separated by SDS polyacrylamide gel electrophoresis. When compared with matched, untreated tissues, protein electrophoretic profiles from laser-treated samples showed several changes. In both tissue types, argon laser treatment decreased the concentration of a 235 kd protein that migrates between the alpha and beta chains of type I collagen. Laser-treated blood vessels showed significantly more low molecular weight protein at the dye front than in control tissue, whereas significantly more high molecular weight protein appeared in laser-treated skin samples when compared with untreated tissue. These results suggest that the argon laser may either degrade or crosslink proteins in vivo. Laser-induced protein crosslinks may be the biochemical basis of argon laser welding.

Animals↗
PubMed1989

Herpes simplex virus alpha protein ICP27 can inhibit or augment viral gene transactivation.

Three of the five alpha (immediate early) gene products of herpes simplex virus, infected cell proteins (ICPs) 4, 0, and 27 play a role in the control of expression of viral beta (delayed-early) and gamma (late) genes. We report here that ICP27 can inhibit or augment the individual or combined abilities of ICP4 and ICP0 to stimulate expression of chimeric genes containing viral gene promoters in a transient expression system. The specific effect of ICP27 was dependent on the viral gene promoter in the chimeric gene. ICP27 inhibited the ability of ICP4 and ICP0 to activate some beta gene promoters but augmented their ability to activate other beta or gamma 1 gene promoters when they were used in the target genes. Activation of the target genes by adenovirus E1A was not affected by ICP27 under the same conditions. ICP27 also repressed the ability of ICP0 to stimulate expression of a chimeric gene containing an alpha gene promoter. Insertion of a termination codon in the middle of the ICP27 coding region severely reduced the inhibitory effect of the plasmid, indicating that this activity requires expression of functional ICP27 polypeptide. This report focuses on the ICP27 activity that negatively regulates ICP4 transactivation of a chimeric gene containing the upstream sequences of the HSV beta gene ICP8. ICP27 decreased the level of mRNA initiated at the transcriptional start site of the ICP8 gene. The level of expression of the ICP4 gene was not changed by ICP27 but an alteration in the electrophoretic mobility of ICP4 expressed was observed. The modulatory effect of ICP27 on HSV transactivators may control the progress of the lytic cycle or provide a balance that varies in different cell types to affect whether lytic or latent infection ensues.

Animals↗
PubMed1989

Immunopathological study on human cartilage allografts.

The fate of human cartilage allografts and the mechanism of its kinetical development were studied histopathologically and immunohistologically. After transplantation, the grafts underwent necrosis, calcification and were partially invaded by osteoplastic tissue of the host and eventually replaced by bone tissue. Thus, the contour of the transplanted cartilage was kept partially by the living cartilage and the newly-formed osseous tissue. The grafts were surrounded initially by granular tissue and then by scar tissue, in which numerous T cells and a few macrophage infiltrates were noted. In T cells, T4+ lymphocytes predominated but T8+ cells accounted for a small number. B cells were not found within the infiltrates. Most of the infiltrating cells expressed 12 antigens, indicating that the majority of T cells were activated. It was concluded that T lymphocytes mediated cellular immunity played an important role. The chondrocytes of the cartilage did not express HLA I and II antigens before transplantation, but one month later, the living chondrocytes became HLA I and II antigens positive, and the antigen expression became stronger with the elapse of time; this might be induced by lymphokins, especially by interferon produced by the infiltrating lymphocytes. Such an expression of MHC antigens on chondrocytes might contribute to the further enhancement of immunorejection.

Adult↗
PubMed1988

Physiology of behavioral mutants of Rhizobium meliloti: evidence for a dual chemotaxis pathway.

Wild-type and nonchemotactic mutant strains of Rhizobium meliloti were tested for attraction to localized sites on alfalfa roots and for attraction to numerous small molecules, including sugars, amino acids, and two fractions derived from alfalfa root extracts. Four strains (carrying mutations che-6, che-11, che-12, and che-26) lost all responses and were classified as generally nonchemotactic mutants. One strain (carrying mutation che-7) lost responses to a group of structurally unrelated amino acids but retained all other responses and was classified as a putative sensory transducer mutant. Two strains (carrying mutations che-1 and che-3) lost responses to all the amino acids and sugars tested but retained normal responses to localized sites on roots and to the root fractions. These two mutant strains could not be classified according to the generally accepted model for a sensory pathway, derived from studies of enteric bacteria, and provided evidence for a dual chemotaxis pathway in R. meliloti.

Amino Acids↗
PubMed1987

Mapping of the transcriptional initiation site of the herpes simplex virus type 1 ICP8 gene in infected and transfected cells.

The initiation site for transcription of the herpes simplex virus type 1 (HSV-1) gene encoding the major DNA-binding protein. ICP8, was mapped by nuclease S1 analysis of RNA-DNA hybrids. When RNA isolated from cells infected with HSV-1 was used, one major start site of ICP8 gene transcription was mapped at 89 base pairs to the right of the BstEII site at 0.409 map units. In cells transfected with a cloned ICP8 gene, the same major start site was detected either in the presence or absence of the immediate-early (alpha) genes encoding ICP4 or ICP0, which have been shown to stimulate ICP8 gene expression in transfected cells. Both ICP4 and ICP0 stimulated the accumulation of the ICP8 gene transcripts in the transient expression system, and their effects were synergistic. By comparison of the sequence of the putative promoter region of the ICP8 gene with the promoter of the HSV-1 TK gene, a significant similarity was detected between the three transcriptional regulatory signals of the TK gene and the upstream sequences of the ICP8 gene. Analysis of promoters of other delayed-early (beta) genes showed that they all contained regions of significant homology with the distal signals of the upstream sequences of the TK or ICP8 gene.

Animals↗