Search PubMed⌕ Search

Biomedical subjects

Y Zhao

Publications and source records attributed to Y Zhao.

At least 847 records · Page 47Linked to original sources
PubMed1996

[Screening for the new formulation of 25% ascorbic acid injection and studies on its stability].

Two optimum new formulation of 25% ascobic Acid injection were selected by screening with the method of orthogomal design. To estimate the stability of these new formulations, samples were subjected to accelerated stability test at elevated temperatures. The rats of coloration and variation in the concentration of the new formulation under anaerobic degradation were studied. Experimental results indicate that the rule of coloration of ascorbic acid injection may be represented by the following regression equation T = T(o)-kt2 where To is the initial transmittance of the injection, T denotes the transmittance at time t, and k denotes the regression coefficient. The variation in the concentration of the two new formulations under amaerobic degradation was found to proceed in the pseudo-zero order reaction. The discoloration and content of ascorbic acid for two injections were predicted by accelerated stability test with the classical isothermal method and one-point method respectively. The discoloration shelf-life was about 39 months for R I and 36 months for R II, the content shelf-life about 40 months for R I and 38 months for R II respectively.

Animals↗
PubMed1996

[Traffic multiple trauma patient with head injuries: a study of 146 cases].

146 cases of traffic multiple trauma associated with head injuries were studied. There was a significant difference in the ratio of associated injuries in various parts of the body. The three most encountered parts were chest, shoulder and leg. Death were mainly due to severe head injury, chest injury and shock. Atypical ushing syndrome was due to severe blood loss, even intracranial hypertension existed. The blood pressure decreased rapidly after operation. Since comatous patients were unable to provide chief complaint, misdiagnosis occurred during emergency stage.

Accidents, Traffic↗
PubMed1996

[The role of human leukocyte antigen in susceptibility and clinical manifestations of sarcoidosis].

To investigate the association of human leukocyte antigen (HLA) with susceptibility and clinical manifestations of sarcoidosis. Fifty-five patients with sarcoidosis were studied by using allele group specific polymerase chain reaction technique (PCR). Our data show that: (1) the gene frequency of HLA-DR5 is significantly increased in patients with sarcoidosis, but that of HLA-DR7 decreased. (2) Gene frequencies of HLA-DR9 and HLA-DR5 are relatively increased in male patients and in patients with stage I and stage IIa, respectively. The results suggest that HLA-DR gene might contribute to the susceptibility as well as to the difference of clinical manifestations in sarcoidosis.

Adult↗
PubMed1996

Genetic polymorphism of 4'-hydroxylation of S-mephenytoin in 148 Chinese of Han nationality.

AIM: To study genetic polymorphism of S-mephenytoin (S-Mep) 4'-hydroxylation in the Chinese population of Han nationality. METHODS: The lg metabolic ratio (MR) and lg hydroxylation index (HI) in the urine (0-12 h) after oral administration with 100 mg of racemic Mep tablet were determined by HPLC method in 148 consangeously unrelated native Chinese subjects and 21 individuals of 5 families. RESULTS: The lg MR and lg HI showed a bimodal distribution with an antimode of -1.00 and 1.50, respectively. The occurrence of poor metabolizers (PM) was 13.5% in the population. The pedigree analysis in 5 families indicated that deficient S-Mep hydroxylation was an autosomal recessive trait. CONCLUSIONS: The occurrence of PM for S-Mep 4-hydroxylation in Chinese was higher than that of the Caucasians, and both genetic modes were of autosomal recessive trait.

Adult↗
PubMed1995

Catalytic function of the conserved hydroxyl group in the protein tyrosine phosphatase signature motif.

Burst kinetics is observed with the Yersinia protein tyrosine phosphatase (PTPase). This provides direct kinetic evidence for a phosphoenzyme mechanism and suggests that the breakdown of the phosphoenzyme intermediate is the rate-limiting step. Burst kinetics is a powerful tool for mechanistic studies of PTPase catalysis since functional roles of active site residues can be evaluated by studying their effects on the individual elementary steps associated with the formation and the breakdown of the intermediate. In order to investigate the role of Thr410, a conserved residue that is present in the PTPase signature motif, this residue was altered by site-directed mutagenesis to serine and alanine. The effects of these mutations, as observed in both steady-state and pre-steady-state kinetic experiments with p-nitrophenyl phosphate (pNPP) as a substrate, demonstrated that the hydroxyl group of Thr410 is directly involved in catalysis. The hydroxyl group at residue 410 plays an important role in facilitating the breakdown of the phosphoenzyme intermediate.

Amino Acid Sequence↗
PubMed1995

Diversity of the pyruvate dehydrogenase kinase gene family in humans.

Recent evidence from this laboratory indicates that at least two isoenzymic forms of pyruvate dehydrogenase kinase (PDK1 and PDK2) may be involved in the regulation of enzymatic activity of mammalian pyruvate dehydrogenase complex by phosphorylation (Popov, K.M., Kedishvili, N.Y., Zhao, Y., Gudi, R., and Harris, R.A. (1994) J. Biol. Chem. 269, 29720-29724). The present study was undertaken to further explore the diversity of the pyruvate dehydrogenase kinase gene family. Here we report the deduced amino acid sequences of three isoenzymic forms of PDK found in humans. In terms of their primary structures, two isoenzymes identified in humans correspond to rat PDK1 and PDK2, whereas a third gene (PDK3) encodes for a new isoenzyme that shares 68% and 67% of amino acid identities with PDK1 and PDK2, respectively. PDK3 cDNA expressed in Eschierichia coli directs the synthesis of a polypeptide with a molecular mass of approximately 45,000 Da that possesses catalytic activity toward kinase-depleted pyruvate dehydrogenase. PDK3 appears to have the highest specific activity among the three isoenzymes tested as recombinant proteins. Tissue distribution of all three isoenzymes of human PDK was characterized by Northern blot analysis. The highest amount of PDK2 mRNA was found in heart and skeletal muscle, the lowest amount in placenta and lung. Brain, kidney, pancreas, and liver expressed an intermediate amount of PDK2 (brain > kidney = pancreas > liver). The tissue distribution of PDK1 mRNA differs markedly from PDK2. The message for PDK1 was expressed predominantly in heart with only modest levels of expression in other tissues (skeletal muscle > liver > pancreas > brain > placenta = lung > kidney). In contrast to PDk1 and PDK2, which are expressed in all tissues tested, the message for PDK3 was found almost exclusively in heart and skeletal muscle, indicating that PDK3 may serve specialized functions characteristic of muscle tissues. In all tissues tested thus far, the level of expression of PDK2 mRNA was essentially higher than that of PDK1 and PDK3, consistent with the idea that PDK2 is a major isoenzyme responsible for regulation of pyruvate dehydrogenase in human tissues.

Amino Acid Sequence↗
PubMed1995

Expression and function of bicarbonate/chloride exchangers in the preimplantation mouse embryo.

Bicarbonate/chloride (HCO3-/Cl-) exchangers regulate intracellular pH in the alkaline range. Previously, it has been shown that mouse embryos at the two-cell stage exhibit this activity, but that the otherwise ubiquitous mechanisms for regulating intracellular pH in the acid-to-neutral range are undetectable. We have examined mouse embryos during preimplantation development (one-cell zygote through blastocyst) to determine whether HCO3-/Cl- exchange activity exists at all stages, whether it is necessary for preimplantation development, and whether messenger RNAs from the known HCO3-/Cl- exchanger genes are expressed. We have found that all stages of preimplantation embryo have detectable HCO3-/Cl- exchange activity. In addition, inhibition of this activity with the stilbene anion exchange inhibitor DIDS (4,4'-diisothiocyanostilbene-2,2'-disulfonic acid) disrupts intracellular pH homeostasis and markedly inhibits embryo development from the two-cell stage to blastocysts in culture under conditions of moderately high external pH. Finally, mRNA encoding two members of the band 3-related AE anion exchanger gene family are expressed in preimplantation embryos.

4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid↗
PubMed1995

Cleavage of DNA by N-phosphoryl histidine.

DNA cleavage by N-(O,O-diisopropyl)phosphoryl histidine(DIPP-His) is investigated by a submarine agarose electrophoresis technique. It was found that DIPP-His could cleave supercoiled DNAs and lambda DNA without the participation of divalent metal ions, while the histidine itself and N-(O,O-diisopropyl)phosphoryl alanine had no such function. Supercoiled pUC8 and pBR322 DNAs are cleaved to linear DNA and eventually fragments; lambda DNA is cleaved directly to fragments. Two mechanistic pathways are proposed for the cleavage reaction.

Bacteriophage lambda↗
PubMed1995

Divergent functional roles for p90rsk kinase domains.

A unique and highly conserved structural feature of approximately 90-kDa ribosomal S6 kinase (p90rsk or RSK) is the presence of two non-identical kinase domains. To explore the mechanism of RSK activation, a cloned human RSK cDNA (RSK3) was used to generate and characterize several site-directed RSK mutants; K91A (N-Lys, NH2-terminal ATP-binding mutant), K444A (C-Lys, COOH-terminal ATP-binding mutant), N/C-Lys (double ATP-binding mutant) T570A (C-Thr, mutant of the putative MAPK phosphorylation site in subdomain VIII of the C-domain), S218A (N-Ser, mutant of the corresponding NH2-terminal residue). Epitope-tagged RSKs were expressed in transfected COS cells followed by immunoprecipitation with or without prior in vivo epidermal growth factor stimulation. Kinase activity (S6 peptide) of N/C-Lys and N-Lys was ablated (and partially impaired with N-Ser). In contrast, both C-Lys and C-Thr retained high levels of kinase activity and were capable of responding to stimulation. C-Lys also retained partial kinase activity toward other substrates (c-Fos, S40 ribosomes, protein phosphatase 1 G-subunit, histones, and Leu-Arg-Arg-Ala-Ser-Leu-Gly (Kemptide)) whereas N-Lys did not. The isolated NH2-and COOH-terminal domains were also expressed; the C-domain was inactive, whereas the N-domain retained partial activity. Relative to wild-type, both N-Lys and C-Lys (as well as N-Ser and C-Thr) underwent partial in vitro autophosphorylation that was further stimulated by EGF protein tyrosine phosphatase. We conclude that 1) the NH2-terminal RSK kinase domain mediates substrate phosphorylation; 2) both domains contribute to autophosphorylation; 3) the putative MAPK phosphorylation site is not required for growth factor-stimulated autophosphorylation or kinase activation.

Amino Acid Sequence↗
PubMed1995

Characterization of the regulatory function of the ICP22 protein of equine herpesvirus type 1.

The IR4 gene (inverted repeat gene 4) of equine herpesvirus type 1 (EHV-), the homolog of the herpes simplex virus type 1 ICP22 gene, is differentially expressed as a 1.4-kb early transcript and a 1.7-kb late transcript that encode a series of proteins that migrate between 42 to 47 kDa, localize to the nucleus of EHV-1-infected cells, and become packaged within EHV-1 virions (V. R. Holden, G. B. Caughman, Y. Zhao, R. N. Harty, and D. J. O'Callaghan, J. Virol. 68, 4329-4340, 1994). To assess the role of the IR4 protein in EHV-1 gene regulation, an IR4 expression vector was cotransfected with EHV-1 chimeric promoter-CAT reporter constructs and EHV-1 effector plasmids to determine the effects of the IR4 protein on the expression of immediate-early (IE), early, and late promoters. These studies revealed that the IR4 protein: (i) minimally trans-activates EHV-1 promoters, (ii) acts synergistically with the UL3 (ICP27) gene product to trans-activate the IE promoter, (iii) does not interfere with the trans-repression of the IE promoter by the IE protein, (iv) enhances transactivation of early promoters by the IE protein, (v) enhances the transactivation of both early and late promoters by the IE and UL3 proteins, and (vi) interacts synergistically with the IE protein to trans-activate the heterologous HSV-1 ICP4 promoter. These data suggest that the IR4 gene product plays a significant role in EHV-1 gene regulation.

Cell Line↗
PubMed1995

Aromatase P450 gene expression in human adipose tissue. Role of a Jak/STAT pathway in regulation of the adipose-specific promoter.

In the present report we describe a heretofore unrecognized role for a Jak/STAT signaling pathway, namely the stimulation of expression of the aromatase P450 (CYP19) gene, and hence of estrogen biosynthesis, in human adipose tissue. Expression of this gene in adipose tissue as well as in adipose stromal cells maintained in the presence of serum and glucocorticoids is regulated by a distal TATA-less promoter, I.4, which contains a glucocorticoid response element, an Sp1 binding site, and an interferon-gamma activation site (GAS) element. The stimulatory action of serum (in the presence of dexamethasone) can be replaced by interleukin (IL)-11, leukemia inhibitory factor, and oncostatin-M, as well as by IL-6, providing the IL-6 soluble receptor is also present. Stimulation of the cells by these factors led to rapid phosphorylation of Jak1, but not Jak2 or Jak3, on tyrosine residues. STAT3 but not STAT1 was also phosphorylated and bound to the GAS element in the I.4 promoter region. When regions of this promoter were fused upstream of the chloramphenicol acetyltransferase reporter gene and transfected into the cells, mutagenesis or deletion of the GAS element led to complete loss of reporter gene expression. Since adipose tissue is the major site of estrogen biosynthesis in men and in postmenopausal women, this pathway involving a Jak/STAT signaling mechanism acting together with glucocorticoids and Sp1 appears to be the principal means whereby estrogen biosynthesis is regulated in the elderly.

Adipose Tissue↗
PubMed1995

Assessment of stress gene mRNAs (HSP-27, 60 and 70) in obstructed rabbit urinary bladder using a semi-quantitative RT-PCR method.

Stress proteins (HSPs) participate in the cellular response to various stresses including hyperthermia, hypoxia and injury. A previous work using northern blot analysis demonstrated increased expression of stress protein 70 (HSP-70) in rabbit bladder tissue subjected to partial outlet obstruction. In order to determine if the increased expression was specific for HSP-70 or, alternatively, indicated a generalized stress protein response, a modified quantitative RT-PCR technique was used to quantitate HSP mRNAs (HSP-27, 60, and 70) in normal and obstructed rabbit urinary bladder tissues. The results show the following: 1) The modified semi-quantitative RT-PCR is a sensitive and reproducible technique for detecting mRNA in bladder tissue. 2) Constitutive levels of HSP-27, HSP-60, and HSP-70 mRNAs were detected in control bladder tissues; the relative signal intensity was highest for HSP-70 and lowest for HSP-27. 3) A transient increase in HSP mRNAs was observed after obstruction; the mRNAs of HSP-27, 60 and 70 increased 4.3-, 5.6-, and 2.4-fold, respectively, at 24 h following obstruction, then gradually returned to control levels by the end of one week post-obstruction and remained stable up to 14 days post-obstruction. These data indicate that the modified quantitative RT-PCR is a useful technique for detecting mRNA in bladder tissue; the stress response which occurs in rabbit urinary bladder tissue following partial outlet obstruction is a general phenomenon.

Animals↗
PubMed1995

Correction of chromosomal instability and sensitivity to diverse mutagens by a cloned cDNA of the XRCC3 DNA repair gene.

The mutagen-sensitive CHO line irs1SF was previously isolated on the basis of hypersensitivity to ionizing radiation and was found to be chromosomally unstable as well as cross-sensitive to diverse kinds of DNA-damaging agents. The analysis of somatic cell hybrids formed between irs1SF and human lymphocytes implicated a human gene (defined as XRCC3; x-ray repair cross-complementing), which partially restored mitomycin C resistance to the mutant. A functional cDNA that confers mitomycin C resistance was transferred to irs1SF cells by transforming them with an expression cDNA library and obtaining primary and secondary transformants. Functional cDNA clones were recovered from a cosmid library prepared from a secondary transformant. Transformants also showed partial correction of sensitivity to cisplatin and gamma-rays, efficient correction of chromosomal instability, and substantially improved plating efficiency and growth rate. The XRCC3 cDNA insert is approximately 2.5 kb and detects an approximately 3.0-kb mRNA on Northern blots. The cDNA was mapped by fluorescence in situ hybridization to human chromosome 14q32.3, which was consistent with the chromosome concordance data of two independent hybrid clone panels.

Animals↗
PubMed1995

Regions of the JAK2 tyrosine kinase required for coupling to the growth hormone receptor.

Growth hormone (GH) treatment of cells promotes activation of JAK2, a GH receptor (GHR)-associated tyrosine kinase. We now explore JAK2 regions required for GHR-induced signaling. Wild-type (WT) JAK2 and JAK2 molecules with deletions of the amino terminus (JAK2ATD), carboxyl terminus (JAK2CTD), or kinase-like domain (JAK2PKD) were each transiently coexpressed in COS-7 cells with the rabbit GHR. The following responses were assayed: GH-induced transactivation of a luciferase reporter governed by a c-fos enhancer element; GH-induced shift in the molecular mass of a cotransfected epitope-tagged extracellular signal-regulated kinase molecule; and GH-induced antiphosphotyrosine immunoprecipitability of the transfected JAK2 form. In each assay, WTJAK2 and JAK2PKD allowed GH-induced signaling, whereas JAK2ATD and JAK2CTD did not. Anti-GHR serum coimmunoprecipitated WTJAK2, JAK2PKD, and JAK2CTD, but not JAK2ATD. Finally, a chimera in which the JAK2 kinase domain replaced the GHR cytoplasmic domain signaled GH-induced transactivation. We conclude: 1) kinase-like domain deletion eliminates neither physical nor functional interaction between JAK2 and the GHR; 2) kinase domain deletion eliminates functional but not physical coupling of JAK2 to the GHR; 3) interaction with the GHR appears dependent on the NH2-terminal one-fifth of JAK2; and 4) a GH-responsive signaling unit can include as little as the GHR external and transmembrane domains and the JAK2 kinase domain.

Amino Acid Sequence↗
PubMed1995

Deletion and site-directed mutagenesis of EF-hand domain of phospholipase C-delta 1: effects on its activity.

In order to elucidate a role of a putative EF-hand motif (144-172) in phospholipase C-delta 1 (PLC-delta 1), deletion and point mutation of the enzyme were performed and the mutated cDNAs were expressed in CHO cells and E. coli AD202 strain. Deletion of amino acid residues of 141-236 or 173-236 resulted in abolition of PLC activity. However, the decreased PLC activity to 15-20% by deletion of the EF-hand motif (144-172) was still Ca(2+)-dependent. Furthermore, mutants, in which conserved Asp153, Asp157, Glu164 or all these acidic amino acids in the EF-hand motif were replaced with alanine residues, showed nearly the same PLC activity and Ca(2+)-dependency as those of wild-type. These results suggest that the region containing the EF-hand motif may not play a role in regulation of Ca(2+)-sensitivity of PLC-delta 1, but is important for its activity.

Alanine↗
PubMed1995

Calcineurin activation protects T cells from glucocorticoid-induced apoptosis.

In T cell hybridomas, TCR/CD3 complex-mediated stimulation induces apoptosis but inhibits that induced by glucocorticoids. A combination of ionomycin (IM), a calcium ionophore, and PMA, a protein kinase C activator, mimics the effects of the TCR/CD3-mediated stimulation. Glucocorticoid-induced apoptosis is, however, markedly inhibited by IM alone, and less markedly by PMA alone. The immunosuppressant FK506 canceled the inhibition by IM but not that by PMA. As calcineurin (CN) is one of the target molecules of FK506, we examined whether CN activation might have an anti-apoptotic effect. BOG8, a T cell hybridoma, was stably transfected with a mutant CN catalytic subunit with Ca2+/calmodulin-independent, constitutive but FK506-sensitive phosphatase activity. The transfectant clones were fairly resistant to glucocorticoid-induced death. Their resistance, however, was hardly affected by FK506 when added simultaneously with glucocorticoid, but was lost after a prolonged preincubation with FK506. In the parent BOG8 cells, FK506 failed to cancel the inhibitory effect of IM on glucocorticoid-induced death when the addition of FK506 was delayed for 1 h or more. These results suggest that CN activation is required for the resistance only as an early event. The transfectant clones produced IL-2 but failed to undergo apoptosis upon stimulation with PMA alone, whereas apoptosis was induced by a combination of IM and PMA. These results suggest that activation-induced cell death may require a higher level of CN activity than IL-2 production or may require another Ca(2+)-dependent pathway.

Animals↗
PubMed1995

The amino-terminal portion of the JAK2 protein kinase is necessary for binding and phosphorylation of the granulocyte-macrophage colony-stimulating factor receptor beta c chain.

The binding of granulocyte-macrophage colony stimulating factor (GM-CSF) to its receptor stimulates JAK2 protein kinase activation, protein phosphorylation, and JAK2 association with the beta c chain of the GM-CSF receptor. To better understand how different domains of the JAK2 function to regulate association and phosphorylation of the beta c receptor, the minimal portion of the beta c receptor necessary for JAK2 binding has been determined. Using glutathione S-transferase (GST) fusion proteins expressing different portions of the membrane-proximal domain of the beta c chain, we demonstrate that JAK2 binds to amino acids 458-495, but showed little binding to fusion proteins containing amino acids 483-559, 483-530, or 458-484. The GST-beta c 458-495 bound equally well to the wild type (WT) JAK2, a carboxyl-terminal deletion of JAK2 removing the protein kinase domain (amino acids 1000-1129), and a deletion of the kinase-like domain (amino acids 523-746). However, an amino-terminal JAK2 deletion (amino acids 2-239) markedly reduced binding to this GST-beta c. Far Western blotting demonstrated that a GST fusion protein containing amino acids 1-294 of JAK2, but not fusion proteins containing amino acids 295-522, 523-746, or 747-1127, bound GST-beta c 458-559. When the JAK2 WT and deletions were transiently expressed along with the alpha and beta c subunits of the GM-CSF receptor and the cells were treated with GM-CSF, the following results were obtained: 1) WT JAK2 phosphorylated the beta c subunit in a GM-CSF-dependent manner, 2) the kinase-like domain deletion phosphorylated the beta c subunit, and 3) both the kinase domain deletion and the amino-terminal deletion failed to stimulate phosphorylation of the beta c subunit. Therefore, phosphorylation of the beta c subunit requires the binding of JAK2 through its amino terminus.

Binding Sites↗