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Biomedical subjects

R Zhou

Publications and source records attributed to R Zhou.

At least 91 records · Page 5Linked to original sources
PubMed1999

Specification of distinct dopaminergic neural pathways: roles of the Eph family receptor EphB1 and ligand ephrin-B2.

Dopaminergic neurons in the substantia nigra and ventral tegmental area project to the caudate putamen and nucleus accumbens/olfactory tubercle, respectively, constituting mesostriatal and mesolimbic pathways. The molecular signals that confer target specificity of different dopaminergic neurons are not known. We now report that EphB1 and ephrin-B2, a receptor and ligand of the Eph family, are candidate guidance molecules for the development of these distinct pathways. EphB1 and ephrin-B2 are expressed in complementary patterns in the midbrain dopaminergic neurons and their targets, and the ligand specifically inhibits the growth of neurites and induces the cell loss of substantia nigra, but not ventral tegmental, dopaminergic neurons. These studies suggest that the ligand-receptor pair may contribute to the establishment of distinct neural pathways by selectively inhibiting the neurite outgrowth and cell survival of mistargeted neurons. In addition, we show that ephrin-B2 expression is upregulated by cocaine and amphetamine in adult mice, suggesting that ephrin-B2/EphB1 interaction may play a role in drug-induced plasticity in adults as well.

Animals↗
PubMed1999

Mutation spectrum in Salmonella induced by environmental tobacco smoke.

Environmental tobacco smoke (ETS) is a major source of indoor air pollution. Extractable-respirable particulate (ERP) from the ETS-contaminated indoor air (ERP-ETS) was collected from six passenger train cars and one control room. The mutagenicity of ERP-ETS was tested in the Ames/Salmonella test in the presence of male rat liver microsomal fraction S9. The mutation spectrum of ERP-ETS was determined by colony probe hybridization and polymerase chain reaction/DNA sequence analysis in approximately 2,370 His+ revertants. The results indicate that the majority of ERP-ETS-induced mutations were a two-base deletion of GC or CG within the hotspot sequence of CGCGCGCG at the frameshift hisD3052 allele in strain TA98. The ERP-ETS from the control room induced approximately 94.3% such deletions, while the ERP-ETS collected from the passenger cars induced approximately 89.6% such deletions. The ERP-ETS either from the control room or from the passenger cars induced approximately 74% C/G --> A/T transversions, and approximately 23% C/G --> T/A transitions within the primary target CCC at the hisG46 allele in strain TA100.

Air Pollution, Indoor↗
PubMed1999

Topoisomerase II-mediated alterations of K562 drug resistant sublines.

In order to further elucidate the roles of DNA topoisomerase II (topo II) subtypes, alpha and beta, as drug targets in chemotherapy, we have determined the enzyme levels in K562 cells selected for resistance to mitoxantrone (K562/Mxn), daunorubicin (K562/Dnr) and idarubicin (K562/Ida 20 and K562/Ida 60), as well as topo II-DNA complex formation, DNA damage and cytotoxicity, induced by topo II interactive agents, for example etoposide, teniposide, mitoxantrone and amsacrine. As compared to the parental cells, topo IIalpha/beta protein levels in K562/Mxn, K562/Dnr, K562/Ida 20 and 60 lines, measured with Western blot, were 17/67%, 85/88, 24/31% and 10/7% respectively. DNA damage, determined by DNA unwinding technique, induced by teniposide and amsacrine correlated with both topo IIalpha/beta protein levels (r2 = 0.8/0.9, P = 0.03/0.01 and r2 = 0.8/0.9, P = 0.04/0.01, respectively). Topo II-DNA complex formation induced by all studied drugs correlated with topo IIbeta protein levels (r2-range 0.8-0.9, P-range 0.01-0.04), while the correlation with topo IIalpha was weaker. Topo IIalpha/beta protein levels tended to show an inverse correlation with the cytotoxicity of etoposide (r2 = -0.9/-0.7, P = 0.01/0.06). The overall topo II-DNA complex formation correlated with drug-induced DNA damage (r2 = 0.9, P = 0.0001), whilst not with the cytotoxicity. Our findings indicate that both topo II isozymes are the targets of the antitumor agents studied, and of potential clinical relevance for prediction of treatment efficacy. They could play a role in tailored chemotherapy.

Antigens, Neoplasm↗
PubMed1999

Functional magnetic resonance (fMR) imaging of a rat brain tumor model: implications for evaluation of tumor microvasculature and therapeutic response.

Functional MR (fMR) imaging techniques based on blood oxygenation level dependent (BOLD) effects were developed and applied to a rat brain tumor model to evaluate the potential utility of the method for characterizing tumor growth and regression following treatment. Rats bearing 9L brain tumors in situ were imaged during inhalation of room air and after administration of 100% oxygen + acetazolamide (ACZ) injected 15 mg/kg intravenously. Pixel-to-pixel fMR maps of normalized signal intensity change from baseline values were calculated from T2 weighted spin echo (SE) images acquired pre- and post- oxygen + ACZ administration. Resultant fMR maps were then compared to gross histological sections obtained from corresponding anatomical regions. Regions containing viable tumor with increased cellular density and localized foci of necrotic tumor cells consistent with hypoxia were visualized in the fMR images as regions with decreased signal intensities, indicating diminished oxyhemoglobin concentration and blood flow as compared to normal brain. Histological regions having peritumor edema, caused by increased permeability of tumor vasculature, were visualized in the fMR images as areas with markedly increased signal intensities. These results suggest that fMR imaging techniques could be further developed for use as a non-invasive tool to assess changes in tumor oxygenation/hemodynamics, and to evaluate the pharmacologic effect of anti-neoplastic drugs.

Acetazolamide↗
PubMed1999

Solid-phase synthesis of irreversible human rhinovirus 3C protease inhibitors. Part 1: Optimization of tripeptides incorporating N-terminal amides.

The optimization of a series of irreversible human rhinovirus (HRV) 3C protease (3CP) inhibitors is described. These inhibitors are comprised of an L-Leu-L-Phe-L-Gln tripeptide containing an N-terminal amide moiety and a C-terminal ethyl propenoate Michael acceptor. Examination of approximately 500 compounds with varying N-terminal amides utilizing solid-phase synthesis and high-throughput assay techniques is described along with the solution phase preparation of several highly active molecules. A tripeptide Michael acceptor containing an N-terminal amide derived from 5-methylisoxazole-3-carboxylic acid is shown to exhibit potent, irreversible anti-3CP activity (k(obs)/[I] = 260,000 M(-1) s(-1); type-14 3CP) and broad-spectrum antirhinoviral properties (average EC50 = 0.47 microM against four different HRV serotypes).

3C Viral Proteases↗
PubMed1999

Biopharmaceutics of boronated radiosensitizers: liposomal formulation of MnBOPP (manganese chelate of 2,4-(alpha, beta-dihydroxyethyl) deuterioporphyrin IX) and comparative toxicity in mice.

Binary treatment modalities such as photodynamic therapy (PDT) and neutron capture therapy (NCT) combine low-toxicity electromagnetic irradiation with an appropriate radiation sensitizer to enhance selectivity for tumor targets. The porphyrin derivative tetrakiscarborane carboxylate ester of 2,4-(alpha, beta-dihydroxyethyl) deuterioporphyrin IX (BOPP) shows tumor-selective uptake and is active in both treatment modalities. BOPP also chelates paramagnetic ions such as Mn(2+), and therefore its tissue accumulation and selectivity can be detected noninvasively by using magnetic resonance imaging. However, local and systemic toxicity appears elevated for the Mn(2+) chelate (MnBOPP), but is poorly characterized. Here we have developed a liposomal formulation of MnBOPP and compared its toxicity with that of MnBOPP administered to mice in saline. The optimal liposome composition and maximal capacity to accommodate MnBOPP were investigated by differential scanning calorimetry and by encapsulation efficiency. MnBOPP was encapsulated quantitatively at up to 12 mol % (drug:lipid) in liposomes of varying composition, and remained incorporated during extended dialysis. Phase separation of drug- and lipid-rich domains was observed above 12% drug. MnBOPP in buffered saline was lethal to animals at 90 micromol/kg, and caused severe necrosis at the injection site at dose levels of 60 micromol/kg or greater. In contrast, MnBOPP formulated in liposomes was well tolerated at the highest tested dose of 135 micromol/kg, with the elimination of local toxicity.

Animals↗
PubMed1999

Molecular cloning and expression of Galbeta1,3GalNAc alpha2, 3-sialyltransferase from human fetal liver.

Based on the sequences of the highly conserved segments in the previously cloned sialyltransferases, a cDNA encoding Galbeta1, 3GalNAc alpha2,3-sialyltransferase (SIATFL) has been isolated from human fetal liver. Expression analysis of the gene has been performed with various carcinoma cell lines, fetal tissues, fetal and adult liver and both hepatoma and the surrounding tissue from the same liver. The SIATFL gene was expressed poorly in fetal liver and in adult liver, slightly in hepatoma and highly in the surrounding tissue of hepatoma. The cDNA encoding the putative active domain was expressed in COS-1, Escherichia coli, and Pichia pastoris. The recombinant protein expressed in COS-1 could catalyse the transfer of NeuAc from CMP-NeuAc to asialo-fetuin. No enzyme activity was detected with a 32-kDa protein in E. coli and both 32-kDa and 41-kDa proteins in P. pastoris. These results suggested that correct glycosylation of the enzyme might play a key role in its folding that may be directly related to the enzymatic activity.

Amino Acid Sequence↗
PubMed1999

In vitro antiviral activity of AG7088, a potent inhibitor of human rhinovirus 3C protease.

AG7088 is a potent, irreversible inhibitor of human rhinovirus (HRV) 3C protease (inactivation rate constant (k(obs)/[I]) = 1,470,000 +/- 440,000 M(-1) s(-1) for HRV 14) that was discovered by protein structure-based drug design methodologies. In H1-HeLa and MRC-5 cell protection assays, AG7088 inhibited the replication of all HRV serotypes (48 of 48) tested with a mean 50% effective concentration (EC(50)) of 0.023 microM (range, 0.003 to 0.081 microM) and a mean EC(90) of 0.082 microM (range, 0.018 to 0.261 microM) as well as that of related picornaviruses including coxsackieviruses A21 and B3, enterovirus 70, and echovirus 11. No significant reductions in the antiviral activity of AG7088 were observed when assays were performed in the presence of alpha(1)-acid glycoprotein or mucin, proteins present in nasal secretions. The 50% cytotoxic concentration of AG7088 was >1,000 microM, yielding a therapeutic index of >12,346 to >333,333. In a single-cycle, time-of-addition assay, AG7088 demonstrated antiviral activity when added up to 6 h after infection. In contrast, a compound targeting viral attachment and/or uncoating was effective only when added at the initiation of virus infection. Direct inhibition of 3C proteolytic activity in infected cells treated with AG7088 was demonstrated by sodium dodecyl sulfate-polyacrylamide gel electrophoresis analysis of radiolabeled proteins, which showed a dose-dependent accumulation of viral precursor polyproteins and reduction of processed protein products. The broad spectrum of antiviral activity of AG7088, combined with its efficacy even when added late in the virus life cycle, highlights the advantages of 3C protease as a target and suggests that AG7088 will be a promising clinical candidate.

3C Viral Proteases↗
PubMed1999

Enzymatic function of the nor-1 protein in aflatoxin biosynthesis in Aspergillus parasiticus.

The nor-1 gene is involved in aflatoxin biosynthesis in Aspergillus parasiticus and was predicted to encode a norsolorinic acid ketoreductase. Recombinant Nor-1 expressed in Escherichia coli converted the 1' keto group of norsolorinic acid to the 1' hydroxyl group of averantin in crude E. coli cell extracts in the presence of NADPH. The results confirm that Nor-1 functions as a ketoreductase in vitro.

Aflatoxins↗
PubMed1999

Etoposide-induced DNA strand breaks in relation to p-glycoprotein and topoisomerase II protein expression in leukaemic cells from patients with AML and CLL.

Elevated expression of the membrane transporter p-glycoprotein (pgp) and impaired expression of the nuclear enzyme topoisomerase II (topo II) are well-known mechanisms for in vitro acquired drug resistance. The clinical relevance of topo II remains unclear, whereas a relationship between pgp levels and treatment results has been shown in acute myelogenous leukaemia (AML). We have investigated the relationships between the levels of topo II and pgp, and in vitro sensitivity to etoposide in mononuclear blood cells from 24 patients with AML, 16 with chronic lymphocytic leukaemia (CLL) and five healthy blood donors. Following incubation with etoposide, AML cells showed more DNA damage, determined by a DNA unwinding technique, than CLL cells (P = 0.001), whereas there was no difference in cellular etoposide accumulation. Pgp and topo IIbeta levels, determined by Western blot, showed a pronounced variation between patients, but no correlation with induced DNA damage, whereas topo IIalpha protein was undetectable. In the AML group, topo IIbeta expression correlated with pgp expression (rho = 0.7, P = 0.001, n = 24). The topo IIbeta expression was 147.4(+/-74.6)% in the pgp+ AML cells (n = 10), compared to 33.4(+/-27.8)% in pgp- AML cells (n = 14) (P = 0.0001). Our results show a previously unknown coexpression of topo IIbeta and pgp in AML, thereby suggesting that topo IIbeta is a potentially interesting resistance factor in AML.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1999

[Study of transcription and cleavage in vitro of HDV with HBV-specific hammerhead ribozyme].

OBJECTIVE: To study the effect of hepatitis B virus(HBV) specific ribozyme(RZ) and recombinant hepatitis D virus(HDV) inserting hammerhead ribozyme(rHDVRZP and rHDVRZA). METHODS: 831 bp HBV C gene fragment was cloned under the control of T7 promoter, 32P-labeled HBV transcript was incubated with gel-purified RZ, rHDVRZA, rHDVRZP at different temperature and autoradiographed after denaturing gel-electrophoresis. RESULT: These results show that rRZ, rHDVRZA, rHDVRZP were active at 37 degrees C and more so at higher temperatures. CONCLUSION: Recombinant Delt virus could serve as a vector for the delivery of a ribozyme specific for hepatitis B virus cleavage. Our data demonstrate the value of recombinant ribozyme as potential therapeutic agents for treatment of HBV infection. Further study about cleavage in vitro and in vivo will continue.

Cloning, Molecular↗
PubMed1999

[The effects of sera of acute promyelocytic leukemia patients and culture supernates of NB4 cells on normal granulo-macrophage hematopoiesis].

OBJECTIVE: To explore the inhibitory activity of sera from acute promyelocytic leukemia(APL) patients on the growth of granular-macrophage progenitors(CFU-GM) and factors affecting the inhibitory activity. METHODS: Sera of 24 APL patients on the all-trans retinoic acid(ATRA) therapy course were kinetically obtained for cellular culture assay. Meanwhile, granulocyte-colony-stimulating-factor(G-CSF), interferon gamma and tumor necrosis factor(TNF) activities in the patient serum and supernate of NB4 cell culture were detected. RESULTS: Before treatment, there was an inhibitory activity on CFU-GM growth in the sera of APL patients and it was statistically higher than that in remission patients and controls(P < 0.01). As the treatment going on the activity was gradually increased, reached its maximum 3-6 days prior to the peak of white blood cell(WBC) and declined to normal when bone marrow remission was obtained. It was positively correlated with the number of CFU-L and the percentage of promyelocyte in bone marrow, negatively with the number of CFU-GM but not with serum G-CSF and TNF activity. Serum G-CSF level was positively correlated with the number of WBC (P < 0.05). No serum IFN-gamma activity was detected in the sera. CONCLUSIONS: 1. One of the therapeutic mechanisms of ATRA on APL is that ATRA induces APL cell maturation thus reduces the serum inhibitory activity on normal hematopoiesis. 2. The inhibitory activity of APL patient serum on normal hemopoiesis consists of complicated factors.

Antineoplastic Agents↗
PubMed1999

The relationship between the levels of granulocyte colony-stimulating factor and leukocytosis induced by all-trans retinoic acid in acute promyelocytic leukemia.

OBJECTIVE: To explore the mechanism of leukocytosis. METHODS: Enzyme linked immunosorbent assay (ELISA) method was used for detecting levels of serum granulocyte colony-stimulating factor (G-CSF) in 47 cases of acute promyelocytic leukemia (APL) during the treatment with all-trans retinoic acid (ATRA). RESULTS: The peak of increased serum G-CSF level occurred on the 9th day, and WBC number was the highest on the 11th day. After ATRA treatment, both serum G-CSF level and WBC number increased in 68.1% of the cases. In 19.2% of the cases treated, serum G-CSF level was increased but without obvious change in WBC number, and the reverse was true in 12.7% of the cases. CONCLUSION: Serum G-CSF level was statistically correlated to the number of WBC, promyelocytes and its late stage by Spearman's rank-order correlation coefficient.

Adolescent↗
PubMed1999

[Low-tensioned and "b"-like ileocystoplasty].

OBJECTIVE: To perfectly solve the urine-kept and urinary problems of the vesical cancer patients after vesicoectomy. METHODS: We performed low-tensioned and "b"-like ileocystoplasty in 16 patients. RESULTS: After the operation, new vesica urinaria worked well in keeping and emptying urine-urine through the urethra. Residual urine test, chemical test and urography showed that there were no disturbance of body water and electrolyte metetabolism, no reterograde urine in the ureter, no uracratia, and no damage to renal function. CONCLUSIONS: Ileocystoplasty can be used clinically.

Aged↗
PubMed1999

[Determination of nitrite in serum and tissue by oscillopolarography].

A method for determining nitrite in serum and placenta tissue by oscillopolaropgraphy is reported in this paper. Nitrite in 0.10 ml of serum or placenta homogenate reacts with sulfanilmide and N-1 (1-Naphthyl)-ethylendiamindihydrochloride in diluted hydrochloric acid medium to form an azo compound which can produce a sensitive reductive polarographic wave in ammonium alkaline medium. The wave height is directly proportional to the nitrite content, the method has a detection limit of 0.56 microgram/L (corresponding to the nitrite content of 0.61 mumol/L in serum or 0.22 microgram/g), RSD, of 6.1%-7.8% and recoveries of 92.0%-108.0% (mean value 100.6%). The method is sensitive, simple and can determine the nitrite directly without removal of the proteins in the samples.

Humans↗
PubMed1999

[Changes of placental nitric oxide synthase in patients with pregnancy induced hypertension].

The objective of this study was to determine whether the expression of placental endothelial nitric oxide synthase (eNOS) and/or inducible nitric oxide synthase (iNOS) are changed in pregnancy induced hypertension (PIH). The placentas of 32 patients with PIH and 32 normal pregnancies were studied by immunohistochemistry (Avidin-Biotin-Complex method). The results showed there were eNOS and iNOS antigens in placental tissues from PIH and normal pregnancy. They were all localized in placental villi and syncytiotrophoblast cells. The expression of placenta eNOS decreased significantly in patients with PIH as compared with that of normal pregnancy. The expression of placenta eNOS in mild PIH was higher than that of moderate or severe PIH (P < 0.025, P < 0.005, respectively). There was a negative correlation between blood pressure and the expression of eNOS in placenta (P < 0.0005). There was no significant difference between the expression of iNOS in placenta with PIH and that in normal pregnancy. Also, there was no significant difference of the expression of iNOS in placenta between the mild and moderate PIH, or the mild and severe PIH. Furthermore, there was no correlation between blood pressure and the expression of iNOS in placenta with PIH. It is concluded that the decrease of the expression of eNOS in placenta may be associated with the pathogenesis of PIH.

Adult↗
PubMed1999

[Experiment on polyploid induction of Angelica dahurica var. formosana].

Colchicine solution was applied to the primary adventitious buds of Angelica dahurica var. formosana in vitro to induce the polyploid. Compared with non-treated plantlet, the morphology, microhisology, and chromosome number of treated plantlets are varied. It proved that the polyploid induction was effective.

Aneugens↗