Biomedical subjects

G Zhao

Publications and source records attributed to G Zhao.

At least 163 records · Page 9Linked to original sources

PubMed1998

Effects of megakaryocyte growth and development factor on survival and retroviral transduction of T lymphoid progenitor cells.

Murine retroviral vectors have the potential to mediate stable gene transfer into hematopoietic progenitor cells. A known drawback to the use of these vectors is that transduction can only take place in cells actively progressing through the cell cycle. Thrombopoietin, the c-mpl ligand, is known to support division of hematopoietic precursors of primitive origin. Polyethylene glycol (PEG)-conjugated recombinant human megakaryocyte growth and development factor (MGDF) is a polypeptide related to thrombopoietin that stimulates megakaryocyte production. To investigate whether MGDF would also induce stem cell division and support retroviral transduction of CD34+ cells, we compared the effects of MGDF, stem cell factor (SCF), interleukin-3 (IL-3), and IL-6, alone or in combination, using amphotropic and vesicular stomatitis virus (VSV-G) pseudotyped murine retroviral vectors. Similar transduction efficiency was observed when CD34+ cells were transduced in the presence of SCF and MGDF as compared to SCF, IL-3, and IL-6. Using the SCID-hu mouse model of thymopoiesis, we investigated whether CD34+ cells transduced in the presence of these cytokines could reconstitute irradiated thymic implants, and whether vector sequences were present in mature thymocytes. At early timepoints, no significant differences were observed on engraftment of donor progenitors incubated with each cytokine combination. However, a significant difference in the percentage of donor derived CD4+/CD8+ immature thymocytes was observed 9 weeks after implantation of CD34+ cells exposed to the combination of SCF and MGDF as compared to SCF, IL-3, and IL-6 (p = 0.04), indicating that MGDF/SCF better supported the survival of thymocyte precursor cells. Approximately 4% of thymocytes in both cytokine groups harbored vector sequences. These studies provide evidence that MGDF and SCF in combination can mediate transduction of hematopoietic progenitors capable of contributing to long-term thymopoiesis. These results may have important applications for the implementation of gene therapy strategies in disorders affecting the T lymphoid system.

Animals↗

PubMed1998

Effects of long-acting angiotensin-converting enzyme inhibitor, imidapril, on the lower limit of cerebral blood flow autoregulation in hypertensive rats.

The objective of the present study was to examine the effects of a long-acting angiotensin converting enzyme inhibitor, imidapril ((4S)-1-methyl-3-¿(2S)-2-[N-(1S)-1-ethoxycarbonyl-3-phenylpropyl) amino] propionyl¿-2-oxoimidazolidine-4-carboxylic acid hydrochloride), for 7 days on the cerebral blood flow autoregulatory response to hypotension in hypertensive rats. We measured the cerebral blood flow at rest and during hemorrhagic hypotension, using laser-Doppler flowmetry. At the same time, the absolute baseline cerebral blood flow values in the parietal cortex were quantified with the hydrogen clearance method. After administration of imidapril at a dose of 5 mg/kg/day for 7 days, the resting value of mean arterial blood pressure was significantly decreased by 25 mm Hg (P < 0.001), cerebral vascular resistance was lowered by 14.4% (P < 0.05) and the lower limit of cerebral blood flow autoregulation was shifted to a lower level, 106+/-11 mm Hg (mean +/- S.D.), from 137+/-8 mm Hg in the control group (P < 0.001), while resting cerebral blood flow remained unchanged. The present results demonstrated that imidapril preserves cerebral blood flow and significantly shifts the lower limit of cerebral autoregulation towards lower blood pressure levels.

Adenosine Triphosphate↗

PubMed1998

Overproduction and purification of glutaryl 7-amino cephalosporanic acid acylase.

The gene encoding glutaryl 7-amino cephalosporanic acid acylase (GL-7ACA acylase) from Pseudomonas sp. 130 has been cloned and expressed in Escherichia coli using a high-level expression system. The specific activity of the acylase in the crude extract of cells in this system is approximately 10 times that in the previous one. The overproduced enzyme can be easily isolated within 3 days to a purity of over 90% by a simple and inexpensive two-step preparative chromatographic method with an overall yield of nearly 50%. The deletion of the signal peptide and mutation in the alpha-subunit of the acylase have little influence on its posttranslational processing and its kinetic parameters.

Amidohydrolases↗

PubMed1998

Expression, purification, and characterization of recombinant Escherichia coli pyridoxine 5'-phosphate oxidase.

A previously cloned pdxH gene from Escherichia coli coding for pyridoxine 5'-phosphate oxidase was transferred to a pET22b vector and expressed in E. coli HMS174(DE3) cells. The soluble overexpressed enzyme was rapidly purified in high yield using two chromatography columns with an overall purification of about 2.8-fold. The purified enzyme contained tightly bound FMN. The enzyme exhibited the same spectral properties and similar kinetic constants to those previously reported by G. Zhao and M. E.Winkler (J. Bacteriol. 177, 883, 1995), but differed from the properties reported by other investigators. A rapid procedure was developed for preparing apoPNP Ox in high yield. Both the holo- and apoenzymes were homodimers. The molar absorbtivity coefficient for the protein was determined for the fully active apoPNP Ox from is amino acid composition. Using this value and the spectral properties of the bound FMN it was shown by three different methods that the dimeric enzyme contains two molecules of bound FMN per dimer and not one FMN as previously reported.

Base Sequence↗

PubMed1998

Improved accuracy and precision of gas chromatography/mass spectrometry measurements for metabolic tracers.

The use of stable-isotope tracer methodology to study substrate metabolic kinetics requires accurate measurement of the tracer to tracee ratio (TTR), often by gas chromatography/mass spectrometry (GC/MS). Many approaches for measurement of the TTR by GC/MS do not use standards of known isotopic enrichment to control for variability in instrument response. In addition, most GC/MS applications exhibit some degree of concentration dependency whereby the measured ion abundance ratio varies with the quantity of sample analyzed, thereby placing a limitation on the accuracy of isotopic enrichment standard curves unless the quantities of standards and samples analyzed are closely matched. We document the degree to which day-to-day variability can affect the instrument response for several GC/MS analyses of metabolic tracers when isotopic enrichment standards are not used to control for variable instrument response. Furthermore, we report a new approach that incorporates concentration dependencies within a standard curve to improve the accuracy and precision of TTR measurements over a range of sample quantities analyzed. The new approach was applied to plasma samples obtained from experimental protocols performed in human subjects with three commonly used tracers: 2H2-palmitate, 15N2-urea, and 13C-leucine. Variability in the day-to-day instrument response was 84% and 26% for 2H2-palmitate and 15N2-urea, respectively; in addition, up to 10% variability due to concentration dependency was noted for these applications. The new approach virtually eliminated these sources of variability. After controlling for concentration dependency, a threefold reduction in the standard error was noted when the enrichment of 13C-leucine measured by electron-impact (EI) ionization GC/MS was correlated against negative chemical ionization (NCI) GC/MS. These data demonstrate that our new approach decreases the errors in TTR determination caused by variations in instrument response and concentration dependency. This approach is generically applicable, and can improve the accuracy and precision of TTR determinations for most GC/MS analyses.

Adolescent↗

PubMed1998

Dinuclear palladium(II) complexes containing two monofunctional [Pd(en)(pyridine)Cl]+ units bridged by Se or S. Synthesis, characterization, cytotoxicity and kinetic studies of DNA-binding.

Two novel dinuclear palladium(II) complexes, ¿[Pd(en)Cl]2(bpse)¿(NO3)2 (1) and ¿[Pd(en)Cl]2 (bpsu)¿(NO3)2 (2), (where en is ethylenediamine; bpse is bis(3-methyl-4-pyridyl) selenide; bpsu is bis(3-methyl-4-pyridyl) sulfide) have been synthesized. The complexes have been characterized by elemental analysis, IR, 1H NMR, and 13C NMR. They have been assayed for antitumor activity in vitro against the mice leukemia L1210 and the human coloadenocarcinoma HCT8 cell lines. The results show that compound 1 has a lower I.D.50 value against the two cancer cell lines as compared to compound 2; the compounds also shows a lower I.D.50 value than cisplatin against the HCT8 cell line, but a higher I.D.50 value than cisplatin against the L1210 cell line. Binding studies indicate that compound 1 possibly interacts with DNA by a nonintercalative mode. Kinetics of binding of the two compounds to DNA are firstly studied using ethidium bromide as a fluorescence probe with stopped-flow spectrophotometer under pseudo-first-order condition. The stronger binding of two steps in the process of the compounds interacting with DNA are observed, and the Kobs and Ea of binding of the two steps (where Kobs is the observed pseudo-first-order rate constant, Ea is the observed energy of activation) are obtained.

Animals↗

PubMed1998

Palladium(II) complexes with N,N'-dialkyl-1,10-phenanthroline-2,9-dimathanamine: synthesis, characterization and cytotoxic activity.

Five new tetradentate ligands and their corresponding palladium complexes, [Pd(L)]Cl2 (L = N,N'-dimethyl-1,10-phenanthroline-2,9-dimathanamine, N,N'-diethyl-1,10-phenanthroline-2,9-dimathanamine, N,N'-dipropyl-1,10-phenanthroline-2,9-dimathanamine, N,N'-ditert-butyl-1,10-phenanthroline-2,9-dimathanamine, N,N'-dicyclohexyl-1,10-phenanthroline-2,9-dimathanamine) have been synthesized. The ligands and their complexes have been characterized by elemental analysis, IR, and 1H NMR. The complexes have been assayed for antitumor activity in vitro against the mouse leukemia L1210 and the mouse liver carcinoma Bel7402 cell lines. The results showed that the activities of these complexes are significantly dependent on the nature of the alkyl groups on the coordinated amine moieties, and three of these palladium complexes showed lower ID50 values against the two cell lines than cisplatin.

Animals↗

PubMed1998

Ethnic differences in red blood cell sodium/lithium countertransport and metabolic correlates of hypertension: an international collaborative study.

Arterial hypertension is frequently associated with metabolic abnormalities. An abnormal activity of the erythrocyte sodium/lithium countertransport (Na/Li CT), an ion transport system under strong genetic control, is also found in people with hypertension and concomitant metabolic abnormalities. However, little information exists with regard to these clinical associations in different racial groups. The aim of this international collaborative study was to investigate Na/Li CT and the metabolic correlates of hypertension in two comparable samples of normotensive and hypertensive populations in the cities of Naples, Italy, and Shanghai, China, using identical, carefully standardized techniques. Blood pressure, anthropometric and metabolic variables, Na/Li CT, and 24-h urinary Na and K excretion were measured in untreated essential hypertensive (HPT) and normotensive (NT) individuals selected by age (35-60 years), body mass index (BMI; < 30 kg/m2), and blood pressure (BP; HPT, DBP > or = 95 mm Hg; NT, DBP < 90 mm Hg). The analysis of variance with adjustment for age was used to compare the groups. In the Neapolitan population, hypertensive individuals had higher serum triglyceride (P < .05) and uric acid levels (P < .001) than the normotensive group and also had a reduced glucose tolerance (P < .01) and an enhanced insulin response to the oral glucose tolerance test (OGTT) (P < .05). No such differences were seen between normotensive and hypertensive Chinese participants. The Neapolitan population (both NT and HPT) had a higher BMI (P < .01) than their Chinese peers. In the comparison of hypertensive patients in Shanghai and in Naples, the Neapolitans were heavier (P < .001), had a lower HDL/total cholesterol ratio (P < .01), an elevated fasting blood glucose (P < .05), and also a higher glucose (P < .001) and insulin response (P < .001) to OGTT. By contrast, they showed a significantly lower urinary Na/K ratio (P < .001). Na/Li CT was significantly increased in HPT both in Naples (286 +/- 24 v 224 +/- 13 micromol/L RBC x h; P < .05, M +/- SE) and in Shanghai (388 +/- 45 v 265 +/- 30 micromol/L RBC x h; P < .05). Furthermore, Na/Li CT was significantly and inversely associated with HDL cholesterol both in the Neapolitan (P < .01) and in the Chinese (P < .05) population, whereas it was directly correlated with serum triglyceride (P < .001) and serum uric acid (P = .001) only in the Neapolitan population. These results indicate that essential hypertension is associated with a higher prevalence of obesity, impaired glucose tolerance, and hyperinsulinemia in Naples than in Shanghai; and Na/Li CT is linked to both high blood pressure and metabolic abnormalities in the Italian sample, whereas it is an isolated marker of hypertension in the Chinese sample.

Adult↗

PubMed1998

Multiple parameters for the comprehensive evaluation of the susceptibility of Escherichia coli to the silver ion.

The susceptibility of Escherichia coli B to the antibacterial activity of silver ions was measured in terms of the initial inhibitory concentration, complete inhibitory concentration, postagent effect for bacteriostatic susceptibility, minimum bactericidal concentration, maximum tolerant concentration, and log killing time for bactericidal activity. At a concentration of 9.45 microM and an inoculum size of 10(4-5) CFU ml-1, silver caused growth delay of E. coli; at a concentration of 18.90 microM, silver completely inhibited bacterial growth. Prolonged postagent effects ranged between 1.5 and 12 h at 0.75 x the initial inhibitory concentration, 1.0 x the initial inhibitory concentration, and 1.5 x the initial inhibitory concentration of the silver ion. One log-unit of viable bacterial population size was lost every 30 min at the minimum bactericidal concentration of the silver ion. Silver tolerance was determined as 20 times the initial inhibitory concentration with 48 h of exposure. This study presents an evaluative model as a reference for the quantitative analysis of the susceptibility of bacteria to silver ions.

Anti-Infective Agents, Local↗

PubMed1998

Involvement of the gapA- and epd (gapB)-encoded dehydrogenases in pyridoxal 5'-phosphate coenzyme biosynthesis in Escherichia coli K-12.

We show that epd (gapB) mutants lacking an erythrose 4-phosphate (E4P) dehydrogenase are impaired for growth on some media and contain less pyridoxal 5'-phosphate (PLP) and pyridoxamine 5'-phosphate (PMP) than their epd+ parent. In contrast to a previous report, we found that gapA epd double mutants lacking the glyceraldehyde 3-phosphate and E4P dehydrogenases are auxotrophic for pyridoxine. These results implicate the GapA and Epd dehydrogenases in de novo PLP and PMP coenzyme biosynthesis.

Aldehyde Oxidoreductases↗

PubMed1998

CsA-sensitive purine-box transcriptional regulator in bronchial epithelial cells contains NF45, NF90, and Ku.

Human bronchial epithelial (HBE) cells express interleukin (IL)-2 [Y. Aoki, D. Qiu, A. Uyei, and P. N. Kao. Am. J. Physiol. 272 (Lung Cell. Mol. Physiol. 16): L276-L286, 1997]. 16HBE-transformed cells contain constitutive and inducible nuclear DNA-binding activity for the purine-box/nuclear factor (NF) of activated T cell (NFAT) target DNA sequence in the human IL-2 enhancer. Transcriptional activation through the purine-box DNA sequence requires stimulation with phorbol 12-myristate 13-acetate + ionomycin, and this activation is inhibited by cyclosporin A. Immunohistochemical staining of 16HBE cells demonstrates nuclear expression of the purine-box DNA-binding proteins NF45 and NF90 and no expression of NFATp or NFATc. NF90 and NF45 associate with the DNA-dependent protein kinase catalytic subunit and the DNA-targeting subunits Ku80 and Ku70 (N. S. Ting, P. N. Kao, D. W. Chan, L. G. Lintott, and S. P. Lees-Miller. J. Biol. Chem. 273: 2136-2145, 1998). Antibodies to Ku potently inhibit the purine-box DNA-binding complex. The purine-box transcriptional regulator in 16HBE cells likely comprises NF45, NF90, Ku80, Ku70, and the DNA-dependent protein kinase catalytic subunit.

Antigens, Nuclear↗

PubMed1998

ATP-independent membrane depolarization with ischemia in the oxygen-ventilated isolated rat lung.

We hypothesize that lung ischemic injury is related to cessation of flow leading to endothelial cell membrane depolarization and activation of oxidant-generating systems. Cell membrane potential was assessed in isolated, oxygen ventilated, Krebs-Ringer bicarbonate buffer-dextran-perfused rat lungs by lung surface fluorescence after infusion of bis-oxonol or 5,5',6,6'-tetrachloro-1, 1',3,3'-tetraethylbenzimidazolyl-carbocyanine iodide (JC-1), voltage-sensitive dyes. Surface fluorometry showed increased bis-oxonol fluorescence (34.7 +/- 3.3% above baseline) and decreased JC-1 fluorescence (24.5 +/- 4.5% below baseline) with ischemia, compatible with membrane depolarization. Fluorescence change was initiated within 1-2 min of the onset of ischemia and was rapidly reversible with reperfusion. Fluorescence changes varied with perfusion flow rate; maximal increase occurred with the transition from 1.8 ml/min to zero flow. Elevation of static intravascular pressure resulted in only a minor increase of bis-oxonol fluorescence. In situ subpleural fluorescence microscopy showed that endothelial cells are the major site of the increased bis-oxonol fluorescence signal with ischemia. These results indicate that endothelial cell membrane depolarization represents an early event with lung ischemia. Since the adenosine triphosphate content of lung was unchanged with ischemia in the O2-ventilated lungs, we postulate that membrane depolarization results from elimination of shear stress, possibly via inactivation of flow-sensitive K+-channels.

Adenosine Triphosphate↗

PubMed1998

A conserved role for L1 as a transmembrane link between neuronal adhesion and membrane cytoskeleton assembly.

The L1-family of cell adhesion molecules is involved in many important aspects of nervous system development. Mutations in the human L1-CAM gene cause a complicated array of neurological phenotypes; however, the molecular basis of these effects cannot be explained by a simple loss of adhesive function. Human L1-CAM and its Drosophila homolog neuroglian are rather divergent in sequence, with the highest degree of amino acid sequence conservation between segments of their cytoplasmic domains. In an attempt to elucidate the fundamental functions shared between these distantly related members of the L1-family, we demonstrate here that the extracellular domains of mammalian L1-CAMs and Drosophila neuroglian are both able to induce the aggregation of transfected Drosophila S2 cells in vitro. To a limited degree they even interact with each other in cell adhesion and neurite outgrowth assays. The cytoplasmic domains of human L1-CAM and neuroglian are both able to interact with the Drosophila homolog of the cytoskeletal linker protein ankyrin. Moreover the recruitment of ankyrin to cell-cell contacts is completely dependent on L1-mediated cell adhesion. These findings support a model of L1 function in which the phenotypes of human L1-CAM mutations results from a disruption of the link between the extracellular environment and the neuronal cytoskeleton.

Animals↗

PubMed1998

[Histological evaluation of collagen-hydroxyapatite composite as osseous implants in the repair of mandibular defect].

To observe the collagen-hydroxylaptite composite in the repair of bone defect, ten minipigs were chosen to make a mandibular dafect measuring 2 cm in diameter and the composite was implanted, while the use of autogenous bone graft and the blank wese served as control. On the 4, 8, 12, 24 and 48 weeks after the operation, the animals were sacrificed and the samples were examined under light microscope. The result showed that: no infection or necrosis occurred. The composite coalesced with host bone and the outcome was similar to that of the autogenous bone graft. No foreign body giant cells or vacuum left from osteonecrosis was observed. It was suggested that the composite had the advantage of abundant supply, easy to handle and no harm. The biocompatibility was good and might be hopeful as a bone substitute.

Animals↗

PubMed1998

Effect of histidine on myocardial mitochondria and platelet aggregation during thrombotic cerebral ischemia in rats.

AIM: To study the effect of histidine on cerebral thrombosis and possible mechanism. METHODS: Cerebral-cardiac stroke was produced by photochemically induced thrombotic cerebral ischemia in rats. RESULTS: Platelet aggregation in whole blood increased markedly, peak heights at 4 and 24 h were (5.1 +/- 0.5) omega and (4.3 +/- 0.5) omega, respectively. Heart mitochondria volume (V), volume density (Vv), surface density (Nm), and surface density of outer membrane (Sv1) increased (8.2 +/- 5.5, 0.59 +/- 0.16, 0.11 +/- 0.03, and 0.22 +/- 0.05, respectively, P < 0.01), but numerical density (Nv), specific surface of inner membrane (delta 2) and of the cristae (delta 3) decreased (0.07 +/- 0.02, 2.8 +/- 0.8, and 2.4 +/- 0.7, respectively, P < 0.01) after cerebral thrombosis. The myocardial histopathologic characteristics were different from those of ischemic necrosis and myocardial damage caused by ischemic reperfusion. In rat treated with histidine after photochemical reaction, platelet aggregation decreased markedly [(2.93 +/- 1.08) omega, P < 0.01], reversible change often went with parameters related to the inner mitochondrial membrane but not the outer mitochondrial membrane. CONCLUSION: Histidine depressed platelet aggregation and reduced myocardial mitochondrial damage resulted from cerebral ischemia.

Animals↗

PubMed1998

[The flow cytometric analysis of activated platelets of severed finger by severe injury before and after replantation].

To investigate the significance of activated platelet levels before and after surgical operation in patients with severed finger by severe injury, the P-selectin (CD62p) positive platelet percent in peripheral blood was studied in 32 patients before and after operation by flow cytometric immunology. At the second and third day after operation, seventeen patients, which in a high positive platelet percent, were measured again after anticoagulation treatment with a large dose of urokinase etc. The results were that the levels of CD62p positive platelet in peripheral blood before and after operation were significantly higher than that of the normal group (P < 0.01). The CD62p positive platelet percent was increased not much more in the anti-coagulation patients than in the normal ones (P > 0.05). There were a few vascular crisis observed. This study suggested that severed fingers by a crushing or wringing injury enhance the platelet activity and resulted in hypercoagulation, thus anti-coagulation measures should be taken to avoid possible thrombosis and improve the survival rate of replantation. CD62p was one of the sensitive indices of activated platelet, which could be used in calculating hypercoagulation accurately.

Adolescent↗

PubMed1998

[Prevalence of premenstrual syndrome in reproductive women and its influential factors].

OBJECTIVE: To investigate the prevalence of premenstrual syndrome and its influential factors in reproductive women. METHOD: A questionnaire was used in 454 reproductive women aged 15-49 in Beijing. RESULTS: The prevalence of premenstrual syndrome in these women was 30.4%, among which 61.6% was mild, 34.1% moderate, and 4.3% severe. The order of frequency of the symptoms occurring in premenstrual syndrome was irritation, depression, anxiety, diarrhea, lack of concentration and hypersomnia. Women with higher cultural level, greater stress in life (work or study), dysmenorrhea, dislike menstruation and those with depression symptom had a higher incidence than those with lower cultural level, no stress in life, no dysmenorrhea, no dislike toward menstruation and no depression symptom (P < 0.05). CONCLUSIONS: Premenstrual syndrome is a common disease in reproductive women. Clinical doctors should pay attention and adopt comprehensive measures in order to reduce its incidence and improve the quality of life especially for women with high risk factors.

Adolescent↗

PubMed1998

[An analysis of antenatal psychological status and its related factors].

OBJECTIVE: To provide basis for antenatal psychological counselling by investigating psychological status and related factors of parturients. METHODS: Analysing psychological status of 100 primigravida by self-made questionnaires. Symptom checklist go (Scl-go), HAMD and HAMA. RESULTS: Single-factor analysis showed: six factors, that were social behavior, mood controlling, history of abortion, relation with parents, psychological preparation for delivery and family roles, are correlated with psychological status of pregnant women. Multi-factor analysis indicated: 3 factors i.e. relation with parents, psychological preparation for delivery and social behavior were positively correlated with psychological status of parturients. CONCLUSIONS: Relation with parents, preparation for delivery and social behavior are the most important factors to influence antenatal psychological status and useful references for antenatal psychological counselling.

Adult↗