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Biomedical subjects

H Peng

Publications and source records attributed to H Peng.

At least 145 records · Page 8Linked to original sources
PubMed1994

Sources of DNA for detecting B cell monoclonality using PCR.

AIMS: To evaluate the polymerase chain reaction (PCR) demonstration of clonal immunoglobulin heavy chain gene rearrangements using routinely prepared, unstained, and stained formalin fixed, paraffin wax embedded tissue samples. METHODS: Extracts from (a) fresh frozen tissue samples, (b) unstained, and (c) haematoxylin and eosin stained formalin fixed, paraffin wax embedded 5 microns tissue sections from 42 cases of low grade B cell lymphoma, all shown to be monoclonal by Southern blot analysis, were analysed using PCR. Two regions of the variable segment of the immunoglobulin heavy chain gene were amplified (framework 2 to joining region [Fr2/JH] and framework 3 to joining region [Fr3/JH]). Twelve samples of reactive lymphoid tissue were studied as controls. Products from each case were directly compared on polyacrylamide gels. RESULTS: Using both primer combinations, monoclonality was detected in 38 of 42 (90%) cases using fresh material, 37 of 42 (88%) using unstained paraffin wax embedded samples, and in 35 of 42 (83%) cases using haematoxylin and eosin stained sections. No false positive results attributable to fixation, processing, or staining were identified, although the efficiency of amplification using the Fr2/JH primers was significantly reduced. CONCLUSIONS: PCR determination of B cell clonality using paraffin wax embedded material is sufficiently sensitive and reliable for use as a routine diagnostic adjunct to conventional morphological and immunocytochemical assessment of lymphoproliferative disease.

Base Sequence↗
PubMed1993

Escherichia coli topoisomerase IV. Purification, characterization, subunit structure, and subunit interactions.

DNA sequence analysis of Escherichia coli parC and parE, encoding the subunits of topoisomerase IV (Topo IV) (Kato, J.-I., Suzuki, H., and Ikeda, H. (1992) J. Biol. Chem. 267, 25676-25684), showed that ParC was 22 amino acids longer on the N terminus and ParE was 29 amino acids longer on the C terminus than reported previously. E. coli strains bearing bacteriophage T7 RNA polymerase-based expression plasmids carrying both intact and truncated parC and parE were used to overproduce the ParC and ParE proteins. Full-length ParC and ParE were required to reconstitute Topo IV activity, whereas the truncated ParC and ParE were inactive. Topo IV activity was supported only by ATP or dATP. The [ATP]1/2 for DNA relaxation was 0.45 mM, almost 25-fold higher than the [ATP]1/2 for decatenation of kinetoplast DNA. Topo IV activity was inhibited by the quinolone and coumarin antibiotics, although the concentrations required for 50% inhibition of activity were 3-30-fold higher than those required to inhibit DNA gyrase. The norfloxacin-induced DNA cleavage patterns of Topo IV and DNA gyrase were distinct but overlapping. The native forms of ParC and ParE were a dimer and a monomer, respectively; whereas the active form of Topo IV was a heterotetramer, ParC2ParE2. The inactivity of the truncated forms of ParC and ParE could be attributed to their failure to form the heterotetramer.

Amino Acid Sequence↗
PubMed1993

Decatenation activity of topoisomerase IV during oriC and pBR322 DNA replication in vitro.

Topoisomerase IV (Topo IV), encoded by parC and parE, is required for partition of the daughter chromosomes in Escherichia coli. This enzyme is likely responsible for decatenating the linked daughter chromosomes after replication. In this report, we have examined the action of Topo IV in both pBR322 and oriC DNA replication reconstituted in vitro with purified proteins. Gyrase fails to decatenate the linked daughter molecules under any condition in the oriC system and at physiological salt concentrations in the pBR322 system, whereas Topo IV stimulates generation of monomer product DNA by 7- to 10-fold. Topo IV-catalyzed decatenation of isolated multiply linked DNA dimers was relatively insensitive to salt; it proceeded at 14% of the maximal rate even in the presence of 800 mM potassium glutamate. In contrast, decatenation in vitro by gyrase was inhibited completely under these conditions. Pulse-chase analysis indicated that Topo IV-catalyzed resolution of linked daughter DNA molecules occurred prior to completion of DNA replication, such that multiply linked daughter molecules did not arise. These results suggest that during DNA replication, gyrase acts primarily to relieve accumulated positive supercoiling and Topo IV acts to segregate the daughter chromosomes.

Bacterial Proteins↗
PubMed1993

Polyamine regulation of Na+/glucose symporter expression in LLC-PK1 cells.

Addition of polyamines or their analogs to newly confluent LLC-PK1 cells resulted in down-regulation of Na(+)-dependent glucose transport (symport) activity. Polyamines prevented the induction of this symporter by the differentiation inducer hexamethylene bisacetamide (HMBA) but did not influence induction by the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX). Partial depletion of endogenous polyamines after addition of alpha-difluoromethylornithine (DFMO) resulted in a 4 to 5-fold increase in symporter expression. Symporter induction by either HMBA or DFMO was inhibited by the protein kinase inhibitor H-7 but H-7 did not affect symporter induction by IBMX. Changes in symporter activity were accompanied by changes in levels of the 75 kD symporter subunit detected by Western blot. Cultures exposed to HMBA exhibited reduced levels of ornithine decarboxylase activity. Our results suggest that induction of symporter expression by HMBA may be mediated in part by its effects on polyamine metabolism, and point to parallel roles of polyamines and cyclic AMP in regulating the expression of this physiologically important renal transport system.

Acetamides↗
PubMed1993

Detection of monoclonality in low-grade B-cell lymphomas using the polymerase chain reaction is dependent on primer selection and lymphoma type.

Detection of B-cell monoclonality using the polymerase chain reaction (PCR) promises the quick and cost-effective separation of monoclonal from polyclonal B-cell disease. However, the efficiency of the method has yet to be fully assessed, particularly with regard to disease type and selection of PCR primers. We have evaluated two approaches based on amplification of the immunoglobulin heavy chain gene using framework 2 (Fr2) and framework 3 (Fr3) region primers. Frozen tissue samples from 94 cases of low-grade B-cell lymphoma were investigated, all of which had previously been shown to be monoclonal by Southern blot analysis. Using a Fr2 primer, we were able to show monoclonality in 85 per cent of cases; with Fr3, 80 per cent of cases; and using both techniques in separate reactions, 90 per cent of cases. Thus, a significant false-negative rate exists with either primer which can be reduced by using both. We also found a difference in the efficiency of detection in different types of lymphoma; only 87 per cent of mucosa-associated lymphomas and centroblastic/centrocytic lymphomas were shown to be monoclonal, whereas all of the other lymphoma types tested were positive using one or both methods. We conclude that PCR detection of B-cell monoclonality allows rapid analysis of tissue samples, including paraffin-processed material. False-negative results which occur in some types of lymphoma can be reduced by the use of two or more primer combinations.

Base Sequence↗
PubMed1993

Epstein-Barr virus (EBV) in enteropathy-associated T-cell lymphoma (EATL).

Using Southern hybridization analysis, we have detected the Epstein-Barr virus (EBV) genome in 36 per cent (4/11) of enteropathy-associated T-cell lymphoma (EATL), a frequency much higher than that seen in nodal T-cell lymphomas in which we were able to show EBV DNA in only 3 per cent (1/30) of the cases examined. Using a terminal fragment probe, monoclonal proliferation of EBV in infected cells was demonstrated in three of the four EBV-positive EATL cases (in one case, insufficient signal prevented the determination of EBV clonality). The EBV genome and an early transcript, EBER1, were identified in tumour cells by in situ hybridization. Expression of latent membrane protein (LMP) was detected in two EBV DNA/RNA-positive EATL cases. In view of the known oncogenic properties of EBV and the putative central role of LMP in EBV-induced cell immortalization, the results of this study suggest that the virus may play an aetiological role in the pathogenesis of EATL.

Blotting, Southern↗
PubMed1993

Abuse of antibiotics in China and its potential interference in determining the etiology of pediatric bacterial diseases.

There is scant information about the etiology and epidemiology of bacterial diseases of infants and children in China because of very little success with bacterial culture. This study describes the severity of abuse of antibiotics among Chinese pediatricians and this abuse's potential interference in determining the etiology of bacterial diseases. According to a survey in Beijing Children's Hospital more than 98% of the patients in the Outpatient Department who were diagnosed with common cold were given antibiotics by physicians. More than one-third of the patients had been taking antibiotics before coming to the hospital. Using a sensitive Staphylococcus aureus assay we found that 70% of blood samples and 43% of cerebrospinal fluid samples from the patients with bacterial meningitis and pneumonia contained antibacterial activity. Bacteria were recovered significantly less often from the samples with antibacterial activity than from those who did not from which antibiotic was not recovered, both in blood (5.3% vs. 12.5%) and in cerebrospinal fluid (2.5% vs. 14.8%). This study indicates that antibiotic abuse is a severe problem in China and that judicious use of antibiotics is urgently needed.

Adolescent↗
PubMed1993

Countercurrent immunoelectrophoresis for diagnosis of acute bacterial pneumonia in Chinese children.

Countercurrent immunoelectrophoresis (CIE) with H. influenzal type b(Hib) and Pneumococci Omni antisera was performed on serum and concentrated urine and pleural fluid samples from 100 patients with acute pneumonia in Beijing Children's Hospital. Thirty-one patients were investigated by bacteriologic techniques (blood culture and pleural fluid culture). CIE was positive in 29/100 (29%) of cases of Hib, 13/100 (13%) of cases for pneumococci. Overall, bacterial causes of pneumonia were diagnosed by CIE in 41/100 (41%) cases. Antigens were detected in 5/90 (5.6%) serum samples, in 36/87 (41.5%) concentrated urine samples, and in 1/2 (50%) samples of pleural fluid. Only one Hib strain was found by pleural fluid culture. The contamination rate of bacterial culture in this group was high (5/31 cases, 16.1%). Therefore, traditional bacteriologic techniques are of very limited value for diagnosing pneumonia in Chinese children. The results showed that bacterial pathogen, especially Hib and Pneumococci, are very common and important causes of pediatric pneumonia in China.

Antigens, Bacterial↗
PubMed1992

nef-naf nexus?

Explore the source record for details and available documents.

Journal Article↗
PubMed1992

Restriction mapping and localization of GL-7-ACA acylase gene.

This paper presents the results about the restriction mapping of recombinant plasmids pMR5 and pMR6 containing GL-7-ACA acylase gene from Pseudomonas sp. 130, gene localization and its expression under the control of different promoters, tet, tac or lac/tac, in Escherichia coli. The analysis of gel electrophoresis of pMR5 cleaved with several kinds of restriction enzymes indicated that there is no sites of EcoRI, HindIII and ClaI but the presence of following sites: one HpaI, two XhoI, three EamHI and four PstI on the cloned gene fragment. The restriction maps of pMR5 and pMR6 were determined by comparative digestion of various endonucleases. The gene of GL-7-ACA acylase was localized on a 3.0kb fragment of B2-B3-HpaI from the studies on a serial subcloning. Expression of subclones pMR9, pMR10 and pMR11 in E. coli was compared. Higher yield of acylase was obtained when the gene fragment was placed downstream of the tac promoter. The expression of Pseudomonas gene in E. coli was also discussed.

Amidohydrolases↗
PubMed1991

[The production of human monoclonal antibodies against Pseudomonas aeruginosa by human-mouse hybridoma technique].

The fusion of peripheral B lymphocytes from human immunized with P. aeruginosa polyvalent vaccine and mouse myeloma cell line SP2/0 was successfully performed. The rate of fusion was 74%(71/96) and the positive rate of antibody was 19.7%. Two hybridoma cell lines (A3 and F8) secreting McAb against P. aeruginosa were obtained after three times cloning by limiting dilution. The human chromosomes together with mouse chromosomes were discovered in karyotype assay of the hybrids. A3 and F8McAbs were human IgG by class determination. These MrcAbs could recognize 43 kd and 36 kd MW specific components of P. aeruginosa antigen by enzyme linked immuno-transfer blot technique.

Animals↗
PubMed1990

[Production and characterization of anti-human hepatocellular carcinoma monoclonal antibodies].

The hepatocellular carcinoma (HCC) cell line, QGY-7703, derived from a Chinese patient, was used to immunize the BALB/c mice. Fifteen hybridomas producing McAb that reacted with QGY-7703 cells were isolated from 858 hybridomas created in three cell fusions. In further studies two McAb, namely, AQGY1 and A-QGY2, were selected which specifically stained HCC cells grown in vitro. The reactivity of these McAb was not removed by the absorption by homogenates of the normal liver, but was by homogenates of HCC cells. A-QGY1 and A-QGY2 also reacted definitely with HCC cells in liver tissues of HCC patients, but neither with other cells in the tissues nor with nontransformed liver tissues of the same patients. Furthermore these two McAb stained the adult or fetal liver tissues, nor all of the other normal or tumor tissues that had been tested. Blocking and absorbing experiments revealed that A-QGY1 and AQGY2 antigens had no immunohomogenicity with antigens such as HBsAg, HBcAg, HBeAg, AFP and CEA. The specificity of these two McAb may be used potentially for the sero diagnosis, histologic identification, radioimmunoimaging and destruction of human hepatocellular carcinoma.

Antibodies, Monoclonal↗
PubMed1990

[The effect of pollen in enhancing tolerance to hypoxia and promoting adaptation to highlands].

Mixed pollen containing four sorts of pollens (Rape, Typhae, Corn, Sunflower) has been proved to have many biology effects. It is capable of increasing body tolerance to acute hypoxia and promoting adaptation to highlands. The experimental study showed that pollen can significantly increase body tolerance to acute hypoxia pollen can also increase the high energy content and normalize the activity of several enzymes which are important to high energy metabolism; regulate the neurotransmitter in 4 parts of the brain and maintain normal activities in the nervous system; increase the secretion of adrenocortical hormone which may favour O2 absorption; increase SOD content in tissues (heart, liver) and hence may prevent super-oxygenation and guard against free radicals, increase PO2 in the brain and arterial blood; decrease oxygen consumption and blood lactic acid concentration; and increase the immunity of animals under normal condition. Pollen has neither acute nor chronic toxicity and causes no allergic reaction. In field study, pollen can also reduce and ameliorate symptoms of acute mountain sickness in human beings.

Adaptation, Physiological↗