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H Shao

Publications and source records attributed to H Shao.

At least 55 records · Page 3Linked to original sources
PubMed1998

[Computerized transformation of the cardiotocographic paper record to its digital equivalent for computerised analysis].

OBJECTIVE: To analyze cardiotocograph by computer, the tracings recorded in paper form must first be converted into their digital equivalent. We developed a method by which this process may be performed. METHODS: Paper recordings were first scanned using a conventional flat bed scanner to obtain a digital image. Each image was firstly corrected for rotational misalignment error during scanning and, sceondly the grid was removed by performing logistic contrast enhancement to leave the discrete fetal heart rate and tocographic tracings. The method was validated by comparing differences between the fetal heart rate obtained from the paper record with that directly obtained from the fetal monitor. RESULTS: Forty recordings were analyzed. The mean difference per recording between the actual and derived values ranged from -0.26(-)-1.26 beats per minute. The 95% confidence interval for the pooled differences between the derived and actual fetal heart rate values was--7-5 beats per minute. CONCLUSION: By using the techniques described in this paper, it is now possible to convert the large number of paper records available so that they can be analyzed by computerized cardiotocograph interpreters.

Cardiotocography↗
PubMed1998

[Regulating function of enzymization and deenzymization of the lactate dehydrogenase isozymes in the mouse tissues during hypoxia].

OBJECTIVE: Study the characteristics of changes of LDH enzyme map of mouse under slight hypoxia. METHODS: Treated mouse with artificial hypoxia, various tissue biopsies were made for the test of LDH enzymatic activity by specific staining technical LDH(1-5)relative percent enzymatic activity were measured with CS-910 dual-wavelength thin-layer chromatography scanner. RESULTS: The relative percent enzymatic activity of LDH isozymes of various tissues after slight hypoxia shift to the isozymes LDH1 and LDH2, whose principal subunits are H subunits, and the relative percent enzymatic activity of LDH1 (H4), LDH2-(H3M) increased (the relative percent enzymatic activity of LDH2 increased markedly, P < 0.05), while LDH (M4) in various tissues decreased prominently except the cardiac muscle, and that of LDH4 (HM3) decreased as well. After the PAGE of the hypoxia treated cardiac muscle specimen was made, activity subbands originated regularly in the isozyme pattern of LDH, with the regularity of LDH1 (0 subband), LDH2 (0-1 subbands), LDH3 (0-2 subbands), LDH4 (1-3 subbands), LDH5 (2-4 subbands). After adding appropriate amount of NAD+ to mouse cardiac muscle specimen with hypoxia, PAGE showed the numbers of subbands of four kinds of isozymes (LDH2-LDH5) decreased even totally disappeared in the isozyme pattern. CONCLUSIONS: The negative feedback regulation of enzymization and deenzymization of LDH isozymes is one of mouse stress responses to slight hypoxia.

Animals↗
PubMed1997

A role for Ras signaling in coreceptor regulation during differentiation of a double-positive thymocyte cell line.

Evidence suggests that the Ras/mitogen-activated protein kinase signaling pathway is required for positive selection of thymocytes. We have asked whether Ras activation is also sufficient to mediate changes in gene expression that are associated with positive selection. To accomplish this, we expressed a constitutively active form of Ras in the immature CD4+ 8+ DPK thymocyte cell line. DPK cells that express active Ras have reduced levels of CD8alpha and CD8beta at the level of cell surface protein and mRNA. These data provide evidence of a direct link between Ras signaling pathways and coreceptor regulation during positive selection. They also suggest that a sustained or potent Ras signal may play a critical role in directing thymocytes into the CD4 lineage. DPK cells that express active Ras, however, were not fully differentiated, indicating that Ras signaling provides only a partial signal for double-positive thymocyte differentiation.

Animals↗
PubMed1997

Expression cloning of a novel farnesylated protein, RDJ2, encoding a DnaJ protein homologue.

The CAAX farnesyltransferase is a heterodimeric enzyme that attaches a farnesyl group to a single cysteine in cellular proteins which terminate in the sequence CAAX, where C is cysteine, A is an aliphatic amino acid, and X is most often methionine or serine. Substrates include the p21ras proteins, nuclear lamins, and a series of retinal proteins. To date, a limited number of substrates for the farnesyltransferase have been identified, predominantly by demonstration of the attachment of a farnesyl group to previously identified cDNA clones which encode proteins containing an appropriate carboxyl-terminal tetrapeptide. We describe here the use of a cDNA fusion protein expression library, together with enzymatic in vitro [3H]farnesyl radiolabeling, as a means of identifying novel farnesylated proteins. One candidate cDNA was fully cloned and found to be a homologue of the Escherichia coli heat shock gene dnaJ. The predicted amino acid sequence of this protein was found to terminate with the tetrapeptide Cys-Ala-His-Gln, which conforms to the consensus sequence for recognition by farnesyltransferase, and was shown to undergo in vivo farnesylation. This farnesylated protein, designated RDJ2 (rat DnaJ homologue 2), is a novel and ubiquitously expressed DnaJ homologue and is the newest member of the subfamily of DnaJ-related proteins which are posttranslationally modified by protein farnesylation.

Alkyl and Aryl Transferases↗
PubMed1997

Kinetic characterization of the human retinoblastoma protein bipartite nuclear localization sequence (NLS) in vivo and in vitro. A comparison with the SV40 large T-antigen NLS.

The retinoblastoma (RB) tumor suppressor is a nuclear phosphoprotein important for cell growth control and able to bind specifically to viral oncoproteins such as the SV40 large tumor antigen (T-ag). Human RB possesses a bipartite nuclear localization sequence (NLS) consisting of two clusters of basic amino acids within amino acids 860-877, also present in mouse and Xenopus homologs, which resembles that of nucleoplasmin. The T-ag NLS represents a different type of NLS, consisting of only one stretch of basic amino acids. To compare the nuclear import kinetics conferred by the bipartite NLS of RB to those conferred by the T-ag NLS, we used beta-galactosidase fusion proteins containing the NLSs of either RB or T-ag. The RB NLS was able to target beta-galactosidase to the nucleus both in vivo (in microinjected cells of the HTC rat hepatoma line) and in vitro (in mechanically perforated HTC cells). Mutational substitution of the proximal basic residues of the NLS abolished nuclear targeting activity, confirming its bipartite character. Nuclear accumulation of the RB fusion protein was half-maximal within about 8 min in vivo, maximal levels being between 3-4-fold those in the cytoplasm, which was less than 50% of the maximal levels attained by the T-ag fusion protein, while the initial rate of nuclear import of the RB protein was also less than half that of T-ag. Nuclear import conferred by both NLSs in vitro was dependent on cytosol and ATP and inhibited by the nonhydrolyzable GTP analog GTPgammaS. Using an ELISA-based binding assay, we determined that the RB bipartite NLS had severely reduced affinity, compared with the T-ag NLS, for the high affinity heterodimeric NLS-binding protein complex importin 58/97, this difference presumably representing the basis of the reduced maximal nuclear accumulation and import rate in vivo. The results support the hypothesis that the affinity of NLS recognition by NLS-binding proteins is critical in determining the kinetics of nuclear protein import.

Adenosine Triphosphate↗
PubMed1997

Characterization and mutational studies of equine infectious anemia virus dUTPase.

The macrophage tropic lentivirus, equine infectious anemia virus (EIAV), encodes a dUTPase in the pol gene that is required for efficient replication in macrophages. Two naturally occurring variants of the enzyme were expressed as recombinant proteins in Escherichia coli; metal chelate affinity chromatography was used to purify histidine-tagged recombinant enzymes to greater than 80% homogeneity in a single chromatographic step. Biochemical and enzymatic analyses of these preparations suggest that this method yields dUTPase that is suitable for detailed mutational analysis. Specific activities of preparations ranged from 4 x 10(3) to 5 x 10(4) units/mg. Recombinant EIAV dUTPase was highly specific for dUTP with a Km in the range of 3 to 8 microM. The enzyme was sensitive to inhibition by dUDP with little inhibition by other nucleotides or the reaction products, dUMP and PPi. The subunit organization of recombinant EIAV dUTPase was probed by gel filtration, glycerol gradient centrifugation, and chemical cross-linking, and is a trimer. We have begun mutational analyses by targeting a conserved domain present at the carboxyl terminus of all dUTPases that shares high homology to the phosphate binding loops (P-loops) of a number of ATP- and GTP-binding phosphatases. The P-loop-like motif of dUTPases is glycine rich but lacks the invariant lysine found in authentic P-loops. Deletion of this motif leads to loss of dUTPase activity; a series of point mutations that have been shown to inactivate authentic P-loops also abolish EIAV dUTPase activity.

Amino Acid Sequence↗
PubMed1997

Induction of the early growth response (Egr) family of transcription factors during thymic selection.

There is little known about the regulation of gene expression during TCR-mediated differentiation of immature CD4+8+ (double positive) thymocytes into mature T cells. Using the DPK CD4+8+ thymocyte precursor cell line, we demonstrate that the early growth response-1 gene (Erg-1), encoding a zinc finger transcription factor, is rapidly upregulated after TCR stimulation. We also report that Egr-1 is expressed by a subset of normal double positive thymocytes in the thymic cortex, as well by a majority of medullary single positive thymocytes. Expression of Egr-1 is dramatically reduced in the thymus of major histocompatibility complex knockout mice, but can be induced by anti-CD3 antibody stimulation of isolated thymocytes from these animals. These and other data suggest that high level expression of Egr-1 in the thymus is a consequence of selection. A similar pattern of expression is found for family members Egr-2 and Egr-3. Using the DPK cell line, we also demonstrate that expression of Egr-1, 2, and 3 is dependent upon ras activation, as is the initiation of differentiation to a single positive cell. In contrast, the calcineurin inhibitor cyclosporin A, which inhibits DPK cell differentiation as well as positive selection, inhibits expression of Egr-2 and Egr-3, but not Egr-1. The identification of the Egr family in this context represents the first report of a link between the two known signaling pathways involved in positive selection and downstream transcriptional regulators.

Animals↗
PubMed1997

Reciprocal expression of the Eph receptor Cek5 and its ligand(s) in the early retina.

Recent evidence suggests that Eph receptor tyrosine kinases and their ligands provide positional information in the developing visual system. We previously found that the Eph receptor Cek5 is more highly expressed in the ventral than dorsal chicken embryonic retina. We now report the identification of a chicken ligand for Cek5 (cCek5-L) that is 75% identical to the ligand LERK2. In situ hybridization experiments do not reveal a dorsoventral gradient of cCek5-L transcripts in the optic tectum at Embryonic Day 8, suggesting that this ligand is not involved in guiding Cek5-expressing axons in the tectum. Surprisingly, it is in the retina that high levels of cCek5-L mRNA are present. In the early retina, cCek5-L is more highly expressed in the dorsal than the ventral aspect. Similarly, a Cek5 Ig chimera labels dorsal but not ventral retina, indicating that even if several Cek5 ligands are present, their overall distribution is complementary to that of Cek5. Hence, Cek5 and cCek5-L may both contribute to define anatomical compartments within the early retina. In contrast, in the 11-day embryonic retina the distributions of Cek5 and its ligand(s) show considerable overlap, suggesting changing functions as development progresses. In dissociated cultures of dorsal or ventral retinal cells seeded on plates coated with either receptor or ligand Ig chimeras, the interaction between Cek5 and its ligand(s) or cCek5-L and its receptor(s) is sufficient to mediate cell adhesion and allows neurite outgrowth.

Amino Acid Sequence↗
PubMed1997

[Research of a screening strategy for high prokaryotic expression clone].

The low expression in E. coli can be often explained by the beginning sequence that causes low translational initiation. A simple selection procedure is then used to enrich those sequences from the bank that lead to high levels of translation. The selection procedure is based on the use of a translationally coupled tetracycline resistance gene. The basic steps are as follows: (1) Construction of selection vector pBV223; (2) Screening high expression clones through different tetracycline concentrations. Several clones have been selected in 60 microg/ml concentration of tetracycline. So this system will provide an important way in preparation of some cytokines which have a low expression level in E. coli but have significant economic value.

Escherichia coli↗
PubMed1997

[Molecular characterization of genetic defects in hemophilia in Shanghai].

OBJECTIVE: To detect gene mutations in hemophilia A in Shanghai. METHODS: PCR, denaturing gradient gel electrophoresis (DGGE) and DNA sequencing were used. Fifty Chinese cases of hemophilia A without intron 22 inversion, including 24 severe, 9 moderate and 17 mild cases, were screened. Genomic DNA was amplified using GC-clamped primers covering all the exons and flanking intron regions, excluding the middle portion of extron 14 encoding the B domain, but including the thrombin cleavage sites at AA740 and 1689. The amplified GC-clamped PCR fragments were then electrophoresed on DGGE. The abnormal bands were sequenced. RESULTS: Eleven different mutations were identified, including 5 nonsense mutations, 5 missense mutations and one small deletion. Among them, 3 mutations, 466Lys (AAG)-Thr (ACG), 719Tyr (TAC)-Stop (TAG) and 312Ile (ATC)-xxC have not been reported before. CONCLUSION: Apart from intron 22 inversion, most gene mutations in hemophilia A were point mutations resulted from single base substitution. Generally the genetic defects correspond to the clinical manifestations.

Asian People↗
PubMed1997

[Study on the recognition and evolutionary genetics of the courtship song of species in Drosphila nasuta species subgroup].

The subgroup of Drosophila nasuta consists of 14 species, subspecies and taxa. It has a wide distribution in area of Indo-Pacific Ocean. The courtship song of species in nasuta subgroup is recorded for the first time in the paper. Some parameters of temporal pattern of pulse song were measured: the inter burst interval (IBI), the interpulse interval (IPI), the length of a pulse train (PTL), the number of pulses in a train (PN), the length of a pulse (PL) and the length of a cycle (CL). Computer analysis techniques were used to make spectral analysis of sine song. A three-dimensional power spectra of the sound was made. In this subgroup, the male of D. pulauna and Taxon-F didn't produce any sound signals during courtship, suggesting that the visual stimuli play an important role in mating process. By analysing the courtship sound signals of other species, subspecies and taxa, the sounds produced by courting male could be described as pulse song or as sine song. By studying the sounds of intra- or interspecific F1 hybrids we have found that the parameters of the temporal pattern of pulse song, for example, the mean value of IPI is controlled by X-linked and autosomal polygene and the sine song frequency is predisposed to the maternity. The phylogenetic tree of the subgroup is constructed based on the temporal pattern of the pulse sounds in different species, subspecies and taxa. The relationship within the members of the Drosophila nasuta subgroup is discussed.

Animals↗
PubMed1995

Elevated levels of syndecan-1 expression confer potent serum-dependent growth in human 293T cells.

Syndecan-1 is the best studied integral membrane proteoglycan and functions to modulate epithelial cell attachment and physiology. Extracellularly, syndecan-1 binds both growth factors and extracellular matrix components, and intracellularly, its cytoplasmic portion interacts with cytoskeletal components. To investigate the possible role of syndecan-1 in epithelial cell transformation that is characterized by alteration in extracellular matrix interactions and cytoskeleton architecture, we established stable transfectants of syndecan-1 in a highly transformed human renal epithelial line expressing two viral oncogenes, adenovirus E1a and SV40 large T antigen (293T cell line). Expression of syndecan-1 core protein and appropriate posttranslational attachment of glycosaminoglycan chains was confirmed by enzymatic digestion and Western blot analysis. Overexpresser cells grew at a significantly faster rate than the vector-transfected control cells in serum-rich media but showed a proliferative disadvantage in serum-reduced media. In addition to this serum dependency, syndecan-1 overexpression caused a partial reversal of the transformed phenotype with the expressing clones becoming more anchorage dependent and less motile than the vector-transfected counterparts. Surprisingly, the overexpressers were more tumorigenic when injected s.c. into nude mice. These results indicate that syndecan-1 expression plays a role in the control of cell proliferation and suggest that serum-dependent growth may be the more reflective of tumorigenicity in nude mice.

Animals↗
PubMed1995

Role of B61, the ligand for the Eck receptor tyrosine kinase, in TNF-alpha-induced angiogenesis.

B61, a cytokine-inducible endothelial gene product, is the ligand for the Eck receptor protein tyrosine kinase (RPTK). Expression of a B61-immunoglobulin chimera showed that B61 could act as an angiogenic factor in vivo and a chemoattractant for endothelial cells in vitro. The Eck RPTK was activated by tumor necrosis factor-alpha (TNF-alpha) through induction of B61, and an antibody to B61 attenuated angiogenesis induced by TNF-alpha but not by basic fibroblast growth factor. This finding suggests the existence of an autocrine or paracrine loop involving activation of the Eck RPTK by its inducible ligand B61 after an inflammatory stimulus, the net effect of which would be to promote angiogenesis, a hallmark of chronic inflammation.

Animals↗