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Biomedical subjects

J Chang

Publications and source records attributed to J Chang.

At least 379 records · Page 21Linked to original sources
PubMed1993

Potentiation of 2,6-dinitrotoluene genotoxicity in Fischer-344 rats by pretreatment with Aroclor 1254.

Pretreatment of Fischer 344 rats for 5 weeks with Aroclor 1254, a commercial mixture of polychlorinated biphenyls, potentiated the genotoxicity of 2,6-dinitrotoluene (DNT), a component of an industrial chemical used in the production of polyurethane foams. This interaction resulted from Aroclor 1254-mediated bioactivation of DNT to markedly greater levels of the genotoxic metabolites, that were excreted in urine and formed DNA adducts in the liver. A significant increase in the excretion of mutagenic urinary DNT metabolites was observed after the first week of Aroclor 1254 treatment, peaked at week 2 and then declined by nearly 25% at week 4. Nevertheless, by week 5, there was almost a 4-fold increase in the formation of hepatic DNA adducts. Significantly elevated hepatic metabolism and increased beta-glucuronidase in the small intestine and cecum, at 4 weeks, may account for the increased adducts and decreased urinary mutagens. Altered nitroreductase activity, reduced pH, and changes in the microfloral population may also play a role in the effect of Aroclor 1254 on the bioactivation of DNT. Such chemical interactions could be important to predictive risk assessment because the overall cancer risk of the mixture would exceed that determined by the current guidelines for chemical mixtures.

Animals↗
PubMed1993

Molecular analysis of the nerve growth factor inducible ornithine decarboxylase gene in PC12 cells.

In an effort to understand molecular mechanisms by which nerve growth factor (NGF) regulates gene expression, we have isolated a full-length rat cDNA clone encoding ornithine decarboxylase (ODC) and utilized this probe to identify and examine the transcriptionally active, NGF inducible ODC gene in rat PC12 cells. This same gene is also responsive to epidermal growth factor, basic fibroblasts growth factor, and dibutyryl cAMP. Primer extension analysis demonstrates that both basal and NGF induced transcription of the ODC gene utilize the same major transcriptional start site, demonstrating that NGF acts to increase transcriptional activity at the basal start site as opposed to unmasking an alternative, stronger start site. Functional promoter analysis reveals the presence of a constitutive core promoter residing between positions -201 and +390, relative to the start site of transcription. Additional analyses reveal that sequences in the region -7800 to +2257 are insufficient to mediate NGF induced transcriptional activation, demonstrating that at least some of the regulatory sequences necessary for NGF mediated transcriptional induction of the ODC gene must reside at relatively enormous distances from the transcriptional start site. Such a long distance transcriptional regulatory mechanism is unique when compared with other NGF responsive genes that have been similarly analyzed.

Animals↗
PubMed1993

Residual Ph- cells in chronic myeloid leukemia: detection and usefulness.

Bone marrow cells from patients with chronic myeloid leukemia (CML) in in vitro long-term bone marrow culture (LTBMC) show an impaired survival of Philadelphia (Ph) positive cells and, in a proportion of patients, the emergence of Philadelphia negative hemopoiesis. The standard conditions of in vitro cultures provide optimal purging effect. Selected patients can now have autologous bone marrow transplants (ABMT) with in vitro purged cells.

Bone Marrow Transplantation↗
PubMed1993

The immunochemistry of sandwich ELISAs--VI. Greater than 90% of monoclonal and 75% of polyclonal anti-fluorescyl capture antibodies (CAbs) are denatured by passive adsorption.

Quantitative data are presented showing that the method most commonly used to immobilize antibodies in microtiter immunoassays functionally inactivates most of the antibodies. These results were collected using five affinity purified polyclonal antibodies (pAbs) and six monoclonal antibodies (mAbs) specific for fluorescein (FLU) as capture antibodies (CAbs). These CAbs were tested for their ability to capture FLU4.2-BSA after immobilization by passive adsorption, the Protein-Avidin-Biotin-Capture (PABC) system or using previously adsorbed anti-globulins. Results indicate that under optimal conditions, < 10% of monoclonal capture antibody equivalents (CAbeqv) and congruent to 22% of polyclonal CAbeqv remain functional after passive adsorption. Immobilization via the PABC system improved the performance of mAbs by more than five-fold but had less than a two-fold effect on pAbs. Many CAbs immobilized using an anti-globulin retained full activity including the ability to bind two molecules of FLU4.2-BSA/molecule of CAb. The latter result is not necessarily a recommendation for the use of anti-globulin immobilization, since the number of functional CAbeqv per well is not significantly greater than that which can be achieved using passive adsorption.

Adsorption↗
PubMed1993

Bulky DNA-adduct formation induced by Ni(II) in vitro and in vivo as assayed by 32P-postlabeling.

Various small oxidation products (e.g. 8-hydroxydeoxyguanosine) can be induced in DNA by nickel compounds. In this study, the 32P-postlabeling assay was applied to determine whether Ni(II) compounds are able to induce bulky DNA-adduct formation in vitro and in vivo. In vitro studies detected two major and several minor adducts in DNA incubated with NiCl2 and H2O2 at 37 degrees C for 1 h. Formation of the two major adducts increased with incubation time (0-24 h) and NiCl2 concentration (0-800 microM). Adduct levels were greatly reduced by hydroxyl free-radical scavengers, i.e. 0.4 M sodium formate or 0.05 M p-nitrosodimethylaniline, and by a singlet oxygen scavenger, 0.05 M sodium azide. The in vitro effects of NiCl2 on DNA were significantly enhanced by (1) addition of 3 mM ascorbic acid, (2) replacement of H2O with D2O in the reaction, and (3) prior denaturation of DNA. Adduct formation presumably involved a Fenton-type reaction, in which DNA crosslinks may arise by reaction with hydroxyl free radicals and singlet oxygen. For in vivo studies, male 6-8 wk old B6C3F1 mice were used. In untreated mice, several I-compounds (putative indigenous DNA modifications that increase with age) were detected in liver, kidney, and lung. Two of these (spots 1 and 2) were chromatographically identical to the two major spots induced by Ni(II) in vitro. The intensities of spots 1 and 2 in kidney and of some other spots in liver and lung were increased 1 and 2 h after i.p. injection with a single dose of 170 mumols/kg NiAc2. The effects of NiAc2 were reduced or undetectable in the three tissues 24 h after treatment. These observations indicate the capacity of Ni(II) to induce and modulate bulky DNA modifications both in vitro and in vivo.

Animals↗
PubMed1993

Intestinal rotation and fixation abnormalities in heterotaxia: early detection and management.

Intestinal rotation and fixation abnormalities (IRFA) are known to coexist with heterotaxia (defined as an abnormal arrangement of body organs that is different from complete situs solitus or complete situs inversus), but little is known about the incidence of this association or its clinical management. We have reviewed the records of 34 patients diagnosed with heterotaxia during a 12-year period at Yale-New Haven Hospital in order to develop a plan for the early diagnosis of IRFA and to assess the value of preventive treatment in this complicated group of patients. Of the 34 patients with heterotaxia, all except one presented with complex congenital heart disease. The 34 patients were divided into two groups on the basis of their gastrointestinal workup for suspected IRFA. The 28 patients in group A had no upper gastrointestinal (GI) contrast study performed prior to symptoms suggestive of IRFA. Four of these 28 patients (14%) eventually developed complications of IRFA requiring emergency surgery. Group B consisted of six patients seen during the past 5 years with heterotaxia who had upper GI contrast studies while asymptomatic. All six (100%) were shown to have IRFA and subsequently underwent an uncomplicated elective Ladd procedure once their cardiac condition stabilized. This study confirms the high incidence of IRFA in patients with heterotaxia. We propose that evaluating patients with heterotaxia syndrome for IRFA while asymptomatic may prevent the need for emergency abdominal surgery in patients that have major cardiovascular anomalies.

Abnormalities, Multiple↗
PubMed1993

Evaluation of functional analogs of CC-1065 and the duocarmycins incorporating the cross-linking 9a-chloromethyl-1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indol-4-on e (C2BI) alkylation subunit.

The DNA alkylation properties and in vitro cytotoxic activity of a series of analogs of CC-1065 and the duocarmycins incorporating the 9a-chloromethyl-1,2,9,9a-tetrahydrocyclopropa[c]benz[e]indol-4-one (C2BI) alkylation subunit are detailed. The C2BI-based agents have been shown to alkylate DNA within the minor groove in a fashion analogous to CC-1065 or duocarmycin. The stereoelectronically-controlled adenine N3 addition to the least substituted cyclopropane carbon occurs with a selectivity that represents a composite of the two enantiomers of the corresponding CBI-based agents. Additional high affinity alkylation sites were detected which were not prominent alkylation sites for either enantiomer of the CBI-based agents. Such sites may represent induced high affinity alkylation sites resulting from DNA cross-linking following complementary strand alkylation at a high affinity alkylation site and each such site detected proved consistent with predicted models of an adenine-adenine cross-linking event. Further, consistent with this interpretation, the C2BI agents were shown to constitute efficient cross-linking agents with DNA cross-linking being observed at the same concentrations as DNA alkylation. In comparison to the parent CBI-based agents, the C2BI-based agents proved to be approximately 100-10,000x less effective at DNA alkylation and 100-10,000x less potent in cytotoxic assays. This is suggested to be the consequence of a significant steric deceleration of the adenine N3 alkylation reaction attributable to the additional 9a-chloromethyl substituent. Consistent with this interpretation, the noncovalent binding constant of C2BI-CDPI2 for poly[dA]-poly[dA]-poly[dT] proved nearly identical to that of CDPI3 under kinetic binding conditions, and prolonged incubation of C2BI-CDPI2 with poly[dA]-poly[dT] (72 h, 25 degrees C) provided covalent complexes with a helix stabilization comparable to that observed with (+)- or (-)-CPI-CDPI2 indicating that the size of the C2BI subunit inhibits but does not preclude productive DNA alkylation.

Alkylation↗
PubMed1993

HLA class II alleles and susceptibility and resistance to insulin dependent diabetes mellitus in Mexican-American families.

The role of HLA class II alleles in genetic predisposition to insulin dependent diabetes mellitus (IDDM) was examined by PCR/oligonucleotide probe typing of 42 Mexican-American IDDM families derived from Hispanic Caucasians and Native Americans. All high risk haplotypes (HLA-DR3 and DR4) were of European origin while the most strongly protective haplotype (DRB1*1402) was Native American. Of the 16 DR-DQ DR4 haplotypes identified, only those bearing DQB1*0302 conferred risk; the DRB1 allele, however, also markedly influenced IDDM risk. The general pattern of neutral and protective haplotypes indicates that the presence of Asp-57 in the HLA-DQ beta chain does not confer IDDM protection per se and indicates that both DRB1 and DQB1 influence IDDM susceptibility as well as protection.

Alleles↗
PubMed1993

Isolation and properties of a soluble sialidase from the culture fluid of Chinese hamster ovary cells.

A soluble sialidase that can degrade recombinant glycoproteins expressed in Chinese hamster ovary (CHO) cells has been isolated and purified to near homogeneity from the cell culture fluid of this host. Purification of approximately 34,000-fold was carried out using conventional purification techniques including sequential DEAE-Sepharose and S-Sepharose ion-exchange chromatography, followed by hydrophobic interaction chromatography with Phenyl-Toyopearl. Final purification was achieved by heparin-agarose and chromatofocusing chromatography. The minimum molecular weight of the sialidase on SDS-PAGE was approximately 43,000 Da. When the final preparation was examined under non-denaturing conditions, two major (pI = 6.8 and 7.0) and five minor electrophoretic forms with different isoelectric points were identified. The basis for the electrophoretic heterogeneity is not known, but it was not due to carbohydrate diversity since no carbohydrates were detected on the purified protein. The enzyme degraded a variety of sialyl-conjugate substrates, at a pH optimum of 5.9, including intact glycoproteins, oligosaccharides and gangliosides with a 4-fold preference for 2,3- versus 2,6-linked sialic acid residues. With ganglioside substrates, internally linked sialic acid residues were not cleaved by the enzyme. Delineation of this enzyme from the lysosomal and plasma membrane sialidases was made using inhibition studies with C-9 substituted 5-acetamido-2,6-anhydro-3,5-dideoxy-D-glycero-D-galacto-non-2- enonic acid derivatives. The enzyme was identified in several CHO cell lines by immunoblotting using antiserum raised against a synthetic peptide based on amino acid sequence of a fragment derived by trypsin digestion of the purified sialidase.(ABSTRACT TRUNCATED AT 250 WORDS)

Amino Acid Sequence↗
PubMed1993

Human immunodeficiency virus type 1 infection of human placental macrophages in vitro.

Placental macrophages (Hofbauer cells) were isolated and cultured in vitro to investigate their susceptibility to human immunodeficiency virus type 1 (HIV-1) infection. Of adherent cells, 80% expressed CD14, and > 99% were nonspecific esterase-positive. CD4 antigen was expressed at very low levels. CD4 mRNA could be detected in the cells by reverse transcription followed by polymerase chain reaction. The macrophages were infected productively after inoculation with low-passage blood isolates of cell-free HIV-1. Peak virus titers were detected 3-7 days after infection by HIV-1 antigen ELISA and reverse transcriptase assay. Replication of HIV-1 in placental macrophages was less than in blood monocytes. HIV-1 RNA was detected in placental macrophages by in situ hybridization 16 days after infection. Multinucleated giant cells were identified in some cultures, indicative of an HIV-induced cytopathic effect. Thus, placental macrophages can be infected productively with clinical isolates of HIV-1, and such cells may act as a reservoir of virus for transmission to the fetus in utero.

Antigens, CD↗
PubMed1993

Selective brain cooling increases cortical cerebral blood flow in rats.

To evaluate the effect of selective brain cooling on cortical cerebral blood flow, we reduced brain temperature in nitrous oxide anesthetized adult rats using a high speed fan while keeping rectal temperature at 37-38 degrees C. During selective brain cooling, cortical cerebral blood flow, as measured by laser-Doppler flowmetry, increased to 215 +/- 26% (mean +/- SE) of baseline at a cortical brain temperature of 30.9 +/- 0.5 degrees C and a rectal temperature of 37.5 +/- 0.1 degrees C. During rewarming, as brain temperature increased, cortical cerebral blood flow decreased. The cerebral vasodilatory response to hypothermia may explain its protective effects during and after cerebral ischemia.

Animals↗
PubMed1993

Flow cytometric analysis of DNA ploidy in primary non-small cell carcinoma of the lung in Korea.

Flow cytometrically determined nuclear DNA content has been measured on 74 formalin-fixed, paraffin embedded specimens of non-small cell carcinoma of the lung. Of the 60 tumors that were successfully analyzed, 32 (53%) were diploid and 28 (47%) were aneuploid. The mean DNA index of aneuploid tumor was 1.5 +/- 0.25, ranging from 1.1 to 2.0. There was no significant correlation between DNA ploidy and the patient's clinical characteristics, histology of tumor, nodal status or tumor stage. Tumor ploidy was not found as a prognostic determinant in non-small cell carcinoma of the lung in this study.

Adult↗
PubMed1993

A reconstructive surgeon's taste in art: Dr Peter Parker and the Lam Qua oil paintings.

Hidden within the basement archives of Yale University's Historical Medical Library lie the original oil painting collection and personal papers of the first American surgeon to practice in China. The Reverend Dr Peter Parker, a graduate of Yale, established the first American hospital in Guangzhou (formerly Canton) in 1835 and successfully introduced Western surgical techniques including amputation, anesthesia, and reconstructive surgery. In addition to this distinguished career of medical missionary service, Parker commissioned the Chinese artist Lam Qua to paint a fascinating series of portraits depicting patients with extreme tumor growths. In this article, Parker's own journals are examined to reveal both his missionary zeal and his frustrations working in China. Selected examples of the Lam Qua paintings are presented along with Parker's corresponding patient descriptions. These detailed patient reports give insight into the extent of surgical pathology as well as the relative brutality of surgical techniques in the early to mid-1800s. The historical significance of the Peter Parker-Lam Qua collaboration within the context of the Western transformation of Chinese art and medicine is also discussed.

China↗
PubMed1993

Improved long-term stability of blood cocaine in evacuated collection tubes.

A study was undertaken to determine if a relatively minor modification of our existing specimen collection tubes could enhance the long-term stability of blood cocaine. We added cocaine, benzoylecgonine (BE) and ethanol to whole sheep blood in glass tubes that were prepared to contain one of several combinations of preservatives and anticoagulant. On day 1 and at intervals of up to one year, the drugs were measured by gas chromatography-mass spectrometry (cocaine and BE) or headspace gas chromatography (ethanol). Storage of blood containing 200 ng/mL cocaine at 4 degrees C for one year resulted in 100% loss of the drug using our normal 10 mL specimen collection tubes containing 100 mg sodium fluoride and 20 mg potassium oxalate. The substitution of oxalic acid for potassium oxalate reduced this loss to 76% without any significant effect on the benzoylecgonine or ethanol concentrations. Further addition of 10 mg echothiophate iodide, a quaternary ammonium compound, brought the cocaine loss down to 60% of the original concentration by one year. Further work will be required to determine if oxalic acid and/or echothiophate iodide could be used in blood collection vials intended for forensic toxicological purposes without any detrimental effect on other assays.

Animals↗