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Biomedical subjects

B Zhang

Publications and source records attributed to B Zhang.

At least 631 records · Page 35Linked to original sources
PubMed1991

A mouse DNA repair enzyme (APEX nuclease) having exonuclease and apurinic/apyrimidinic endonuclease activities: purification and characterization.

A mouse repair enzyme having priming activity on bleomycin-damaged DNA for DNA polymerase was purified to apparent homogeneity and characterized. The enzyme extracted from permeabilized mouse ascites sarcoma (SR-C3H/He) cells with 0.2 M potassium phosphate buffer (pH 7.5) was purified by successive chromatographies on phosphocellulose, DEAE-cellulose, phosphocellulose (a second time), Sephadex G-100, single-stranded DNA cellulose and hydroxyapatite. The purified enzyme has an Mr of 34,000 as determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Enzymatical studies indicated that it is a multifunctional enzyme having exonuclease, apurinic/apyrimidinic endonuclease and phosphatase activities, similar to Escherichia coli exonuclease III. This enzyme is tentatively designated as APEX nuclease for apurinic/apyrimidinic endonuclease and exonuclease activities. The amino acid composition, amino-terminal amino acid sequence and an internal amino acid sequence of APEX nuclease are determined.

Amino Acid Sequence↗
PubMed1991

Binding properties of chimeric insulin receptors containing the cysteine-rich domain of either the insulin-like growth factor I receptor or the insulin receptor related receptor.

We constructed and expressed chimeric receptor cDNAs with insulin receptor exon 3 (residues 191-297 of the cysteine-rich region) replaced with either the comparable region of the insulin-like growth factor I receptor (IGF-IR) or the insulin receptor related receptor (IRR). Both chimeric receptors still could bind insulin with as high affinity as the wild-type receptor. In addition, chimeric receptors containing exon 3 of the IGF-IR could also bind with high affinity both IGF-I and IGF-II. In contrast, chimeric receptors containing exon 3 of IRR did not bind either IGF-I, IGF-II, or relaxin. These results indicate that (1) the high affinity of binding of insulin to its receptor can occur in the absence of insulin receptor specific residues encoded by exon 3, the cysteine-rich region; (2) the cysteine-rich region of the IGF-I receptor can confer high-affinity binding to both IGF-I and IGF-II; and 3) the IRR is unlikely to be a receptor for either IGF-I, IGF-II, or relaxin.

Base Sequence↗
PubMed1991

The regulatory role of known tyrosine autophosphorylation sites of the insulin receptor kinase domain. An assessment by replacement with neutral and negatively charged amino acids.

Autophosphorylation of the insulin receptor has been previously documented to activate the phosphotransferase activity of the receptor from 20- to 200-fold. Biochemical studies have correlated activation of the receptor kinase with the autophosphorylation of tyrosines residues 1158, 1162, and 1163. To further assess the role of these 3 tyrosines in the activation process, we have studied the effect of their substitution with either the neutral amino acids phenylalanine or alanine or with the negatively charged amino acids aspartate and glutamate. In several other proteins, it has been shown that substitution of phosphorylated residues with negatively charged amino acids can mimic the phosphorylation state of the protein. In agreement with previous studies, tyrosines at positions 1162 and 1163 were found to be crucial in the kinase activation process. In contrast, mutant receptors with tyrosine 1158 changed to either phenylalanine or aspartate were still activated to the same extent as the wild-type receptor. An increased basal exogenous kinase activity was observed upon replacement of tyrosines 1162 and 1163 with, in increasing order of potency, aspartate = glutamate less than alanine = phenylalanine. These results indicate that phosphorylation of tyrosines 1162/1163 but not 1158 play a critical role in the activation of the receptor kinase and that the mechanism of activation of the receptor kinase by autophosphorylation is more complex than just an introduction of a cluster of negative charges in this region of the receptor. In addition, the finding of an increased basal kinase activity in receptors lacking tyrosines 1162 and 1163 could explain the reported ability of this receptor to mediate certain biological responses.

Amino Acids↗
PubMed1991

Immunogold labelling of the intermediate filament-lamina-nuclear matrix system in HeLa and BHK-21 cells.

Whole-mount, sequentially extracted cells combined with immunogold electron microscopy were developed to demonstrate the intermediate filaments, lamina, and nuclear matrix (IF-L-NM) and to identify their protein components. The IFs of HeLa cells were reacted both with keratin and vimentin monoclonal antibodies; meanwhile, the IF network of BHK-21 cell was reacted only with vimentin monoclonal antibody. The lamina and nuclear matrices of both HeLa and BHK-21 cell were labelled, respectively, with lamin monoclonal antibody-gold complex and 280 Kd nuclear matrix protein monoclonal antibody-gold complex. The monoclonal antibody to keratin could cross-react with the lamina both of HeLa and BHK-21 cells.

Animals↗
PubMed1991

DNA damage by peplomycin and its repair in an in vitro system.

1. DNA damage by peplomycin, an antitumor antibiotic, and its repair by cellular enzymes were studied using pUC18 plasmid DNA. The DNA damage and repair were measured by monitoring the conformational changes of pUC18 DNA. 2. Peplomycin-induced DNA damage was enhanced by addition of ferrous ion and inhibited by deferoxamine, a specific iron chelator, suggesting iron-requirement for the DNA damage. 3. DNA damage by peplomycin was inhibited by superoxide dismutase in both native and heat-inactivated forms, possibly due to non-enzymatic interaction. 4. Peplomycin-induced, single-strand breaks in pUC18 DNA was repaired by incubating with a priming factor (an exonuclease purified from mouse ascites sarcoma cells), DNA polymerase beta, four deoxynucleoside triphosphates, T4 DNA ligase and ATP. The average repair patch size was estimated to be approximately four nucleotide length.

Adenosine Triphosphate↗
PubMed1991

Teenage pregnancy in South Australia, 1986-1988.

Teenage pregnancies accounted for 6.0% of confinements and 24.8% of legal abortions in South Australia in 1986-1988. The teenage pregnancy rate has declined by 28.5% since the early 1970s, associated with a 52.6% decline in the confinement rate. The abortion rate rose in the 1970s but fell slightly in the 1980s; nearly half the teenage pregnancies now end in legal abortion: abortion was a more likely pregnancy outcome for younger teenagers and for teenagers resident in metropolitan areas. Compared with women confined in their twenties, confined teenagers were more likely to be single, primigravid and Aboriginal, to have few antenatal visits and to have a medical or obstetric complication during their pregnancy. They were less likely to have an induction of labour or an elective Caesarean section. They had higher frequencies of preterm deliveries (8.9%) and low birth-weight babies (9.3%). The youngest teenagers had the most risk factors and the worst outcomes. In the small group of Aboriginal teenagers aged 16 years and under, about a third of the babies were low birth-weight or premature and one in 12 babies was a perinatal death. Comparison of singleton pregnancies of teenagers with women in their twenties all of whom were single, Caucasian and primigravid, with 7 or more antenatal visits, showed similarity in outcomes. This suggests that being teenage is not in itself a risk factor. Continued support and extension of teenage counselling and antenatal care services is essential.

Adolescent↗
PubMed1991

Dibutyryl cAMP activates bumetanide-sensitive electrolyte transport in Malpighian tubules.

The effects of dibutyryl adenosine 3',5'-cyclic monophosphate (DBcAMP) and bumetanide (both 10(-4) M) on transepithelial Na+, K+, Cl-, and fluid secretion and on tubule electrophysiology were studied in isolated Malpighian tubules of the yellow fever mosquito Aedes aegypti. Peritubular DBcAMP significantly increased Na+, Cl-, and fluid secretion but decreased K+ secretion. In DBcAMP-stimulated tubules, bumetanide caused Na+, Cl-, and fluid secretion to return to pre-cAMP control rates and K+ secretion to decrease further. Peritubular bumetanide significantly increased Na+ secretion and decreased K+ secretion so that Cl- and fluid secretion did not change. In bumetanide-treated tubules, the secretagogue effects of DBcAMP are blocked. In isolated Malpighian tubules perfused with symmetrical Ringer solution, DBcAMP significantly hyperpolarized the transepithelial voltage (VT) and depolarized the basolateral membrane voltage (Vbl) with no effect on apical membrane voltage (Va). Total transepithelial resistance (RT) and the fractional resistance of the basolateral membrane (fRbl) significantly decreased. Bumetanide also hyperpolarized VT and depolarized Vbl, however without significantly affecting RT and fRbl. Together these results suggest that, in addition to stimulating electroconductive transport, DBcAMP also activates a nonconductive bumetanide-sensitive transport system in Aedes Malpighian tubules.

Aedes↗
PubMed1991

Peplomycin-induced DNA repair synthesis in permeable mouse ascites sarcoma cells.

DNA repair synthesis induced in permeable mouse ascites sarcoma cells by peplomycin, an antitumor antibiotic, was studied. Mouse ascites sarcoma (SR-C3H/He) cells were permeabilized with a low concentration of Triton X-100 in an isotonic condition. Permeable cells were treated with an appropriate concentration of peplomycin to introduce single-strand breaks in permeable cell DNA. DNA repair synthesis in peplomycin-treated permeable cells was measured by incubating the cells with four deoxynucleoside triphosphates in an appropriate buffer system. The DNA repair synthesis was enhanced by ATP and NaCl at near physiological concentrations. More than 90% of DNA synthesis in the present system depended on the peplomycin-treatment. The repair nature of the DNA synthesis was confirmed by a BrdUMP density shift technique. The repair patches were largely completed and ligated in the presence of ATP. Analyses using selective inhibitors for DNA polymerases showed that both DNA polymerase Beta and aphidicolin-sensitive DNA polymerases (DNA polymerase alpha and/or delta) were involved in the repair DNA synthesis.

Animals↗
PubMed1991

[Effects of econazole and clotrimazole on TXB2 and PGE2 production in calcimycin-stimulated neutrophils and arachidonic acid-stimulated platelets].

The effects of econazole and clotrimazole which are used as antifungal agents, on TXB2 and PGE2 production in calcimycin (A-23187)-stimulated rat pleural neutrophils and arachidonic acid (AA)-stimulated washing rabbit platelets were examined by radioimmunoassay. Econazole and clotrimazole 0.05-100 mumol.L-1 inhibited TXB2 production both in rat pleural neutrophils and in rabbit platelets with a dose-dependent manner. The most potent inhibition was found in rabbit platelets. At the concentration of 50 mumol.L-1, econazole and clotrimazole were sufficient to inhibit TXB2 production in rabbit platelets by up to 99% and 98% respectively. Econazole and clotrimazole 0.05-5 mumol.L-1 also increased PGE2 biosynthesis in rabbit platelets. But econazole and clotrimazole 50 mumol.L-1 reduced the PGE2 production in rabbit platelets to 11% and 37% of the amounts of 5 mumol.L-1 econazole and clotrimazole respectively. The results suggest that econazole and clotrimazole at lower concentration may have a selective inhibitory effect on thromboxane synthetase, at higher concentration they also inhibit cyclooxygenase.

Animals↗
PubMed1991

[A clinical operation of acne vulgaris treated with benzoyl peroxide].

This paper describes the treatment of 58 patients with acne, including 30 patients treated with 5% benzoyl peroxide cream and 28 patients treated with 0.025% retinoic acid ointment as control. Improvement could be seen after 4 weeks. The efficacy in the test group was 93.3% and that in the control group was 53.5% (P less than 0.001). The early effect was obtained within one week, and no side effects were seen in the test group. Animal test has shown no side effects, including irritation and sensitive reactions with the skin painted with 10% BPC. The conclusion is that 5% BPC is a treatment of choice for patients with acne vulgaris.

Acne Vulgaris↗
PubMed1991

[A controlled study of clinical therapeutic effects of laser acupuncture for schizophrenia].

A controlled study of clinical therapeutic effects of laser acupuncture was made for 33 patients suffering from schizophrenia. As evaluated by BPRS, CGI, a rating scale for extramidal side effects and chinese clinical assessments for therapeutic effects. Our clinical practise suggests that laser acupuncture was as effective as chlorpromazine in the treatment of schizophrenia.

Acupuncture Points↗
PubMed1991

[Isolation and characteristics of Borrelia burgdorferi from Ixodes persulcatus].

We reported the detailed characteristics of Lyme disease spirochetes (Borrelia burgdorferi), strain H7, isolated from Ixodes persulcatus in Heilongjiang. Cells of strain H7 were 9.8--26.5 microns long and 0.13--0.35 microns wide. There were 1--11 waves with a wavelength of 1.2--3.0 microns and an amplitude of 0.59--1.13 microns. Direction of spires was left. Seven flagella were inserted subterminally at each end of the cell and ends were pointed. 31 degrees C was the optimum cultural temperature in vitro. The major constitutional and antigenic proteins were 21k, 32k and 34k proteins. H7 could react on the patient sera of Xinjiang and Heilongjiang with IFA and western blot. These findings demonstrated that strain H7 belonged to species Borrelia burgdorferi, but was a new "subtype" which differed from the strains isolated from other areas and vectors.

Animals↗
PubMed1991

[Observation on the production of interleukin-1 and interleukin-2 and response to interleukin-2 in patients with schistosomiasis].

The ability of adherent and nonadherent peripheral blood mononuclear cells (PBMC) from forty patients with schistosomiasis to produce IL-1 and IL-2 was studied. The results indicated that ConA-stimulated nonadherent-PBMC from patients exhibited a decreasing ability to produce IL-2 compared with controls (P less than 0.001), and that their ConA-activated blast cells expressed a smaller number of cell surface IL-2 receptor since IL-2 adsorption to the patient cells was lower than that to the normal cells (P less than 0.01). On the other hand, IL-1 production by LpS-stimulated adherent-PBMC from the patients was in agreement with that from the normal controls (P greater than 0.05). From above results, it seems that human organism following infection of Schistosoma japonicum might display a sort of suppressive phenomenon in the production of and the response to IL-2.

Adult↗
PubMed1991

[Percutaneous cholecystolithocenosis. Report of 421 cases].

Modified percutaneous cholecystolithocenosis (PCLC) was performed in 421 cases of gallstones. The advantages of this operation included less traumatic, fast convalescence, few complications, and thorough stone clearing. It was suitable for in operatable elder patients. The procedure was safe, and did not produce any incidental injury to the internal organs. The successful rate was 100%. 122 cases were followed up cholecystographically. Gallstones disappeared in 96.8% of the patients and gallbladder function was improved. Follow-up of 57 cases after extracorporeal shock wave lithotripsy (ESWL) showed that gallstones were broken into small pieces which are feasible to pass through the gallbladder tube.

Adolescent↗