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D L Alexander

Publications and source records attributed to D L Alexander.

15 recordsLinked to original sources
PubMed1999

Metabolism-based polycyclic aromatic acetylene inhibition of CYP1B1 in 10T1/2 cells potentiates aryl hydrocarbon receptor activity.

We have used polycyclic aromatic hydrocarbon (PAH) alkyne metabolism-based inhibitors to test whether CYP1B1 metabolism is linked to aryl hydrocarbon receptor (AhR) activation in mouse embryo fibroblasts (MEF). 1-ethynylpyrene (1EP) selectively inactivated CYP1B1 dimethylbenzanthracene (DMBA) metabolism in C3H10T1/2 MEFs; whereas 1-(1-propynyl)pyrene (1PP) preferentially inhibited CYP1A1 activity in Hepa-1c1c7 mouse hepatoma cells (Hepa). In each cell type >90% inhibition of DMBA metabolism after 1 h treatment with each inhibitor (0.1 microM) was progressively reversed and then increased to levels seen with 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) induction (fourfold stimulation). It was found that 0.1 microM 1EP and 1PP maximally induce CYP1B1 and CYP1A1 mRNA levels in10T1/2 and Hepa cells, respectively, after 6 h. 1-Ethylpyrene (EtP), which lacks the activatable acetylene moiety, was far less effective as an inhibitor and as an inducer. AhR activation is essential for 1EP induction as evidenced by the use of AhR antagonists and AhR-deficient MEFs and absence of induction following inhibition of DMBA metabolism with carbon monoxide (CO). Inhibition of CYP1B1 was linked to enhanced AhR activation even at early stages prior to significant ligand depletion. 1EP and EtP were similarly effective in stimulating AhR nuclear translocation, though 5-10 times slower compared with TCDD, and produced no significant down-regulation of the AhR. TCDD activated AhR/Arnt complex formation with an oligonucleotide xenobiotic response element far more extensively than 1EP or EtP, even at concentrations of 1EP that increased CYP1B1 mRNA to similar levels. CO did not influence these responses to EtP, event hough CO treatment potentiated EtP induction of CYP1B1 mRNA. These differences suggest a fundamental difference between PAH/AhR and TCDD/AhR complexes where CYP1B1 metabolic activity regulates the potency, rather than the formation of the AhR/Arnt complex.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1999

Cytochrome P450 CYP1B1 determines susceptibility to 7, 12-dimethylbenz[a]anthracene-induced lymphomas.

CYP1B1-null mice, created by targeted gene disruption in embryonic stem cells, were born at the expected frequency from heterozygous matings with no observable phenotype, thus establishing that CYP1B1 is not required for mouse development. CYP1B1 was not detectable in cultured embryonic fibroblast (EF) or in different tissues, such as lung, of the CYP1B1-null mouse treated with the aryl hydrocarbon receptor agonist 2,3,7,8-tetrachlorodibenzo-p-dioxin whereas the equivalent wild-type EF cells express basal and substantial inducible CYP1B1 and lung expresses inducible CYP1B1. CYP1A1 is induced to far higher levels than CYP1B1 in liver, kidney, and lung in wild-type mice and is induced to a similar extent in CYP1B1-null mice. 7,12-dimethylbenz[a]anthracene (DMBA) was toxic in wild-type EFs that express CYP1B1 but not CYP1A1. These cells effectively metabolized DMBA, consistent with CYP1B1 involvement in producing the procarcinogenic 3,4-dihydrodiol as a major metabolite, whereas CYP1B1-null EF showed no significant metabolism and were resistant to DMBA-mediated toxicity. When wild-type mice were administered high levels of DMBA intragastrically, 70% developed highly malignant lymphomas whereas only 7.5% of CYP1B1-null mice had lymphomas. Skin hyperplasia and tumors were also more frequent in wild-type mice. These results establish that CYP1B1, located exclusively at extrahepatic sites, mediates the carcinogenicity of DMBA. Surprisingly, CYP1A1, which has a high rate of DMBA metabolism in vitro, is not sufficient for this carcinogenesis, which demonstrates the importance of extrahepatic P450s in determining susceptibility to chemical carcinogens and validates the search for associations between P450 expression and cancer risk in humans.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1999

Molecular cloning of p67, a lysosomal membrane glycoprotein from Trypanosoma brucei.

We have previously characterized a highly glycosylated membrane protein (p67) in Trypanosoma brucei spp that is apparently targeted to lysosomes in a developmentally regulated manner. Antibody to native p67 identified a partial cDNA clone from a T. b. rhodesiense expression library and RT-PCR was used to complete the sequence of the cDNA. Equal levels of p67 transcript are detected in both procyclic and bloodstream stages of the life cycle. The 2771 nt cDNA contains a 1980 nt orf encoding a 659 amino acid polypeptide (72,567 Da). Hydropathy analysis predicts a Type I membrane topology (N to C): an N-terminal signal sequence, a large hydrophilic lumenal domain with 14 N-glycosylation sites, a trans-membrane domain (19 aa), and a short (24 aa) cytoplasmic domain. Peptide microsequencing of purified p67 identified nine residues identical to the deduced amino acid sequence, confirming the identity of the cDNA and defining the signal sequence cleavage site. Antibody to p67 protein produced in E. coli recognizes the same spectrum of native p67 glycoforms as the antibody used to clone the cDNA. All features of the deduced amino acid sequence are consistent with the known properties of the native protein and suggest a structure similar to mammalian LAMPS. The cytoplasmic domain contains two putative di-leucine targeting motifs similar to those involved in lysosomal targeting in vertebrate cells. Our results suggest that a single p67 polypeptide, or a group of highly related polypeptides, is synthesized in both bloodstream and procyclic trypanosomes and that subsequent post-translational processing and lysosomal targeting is subject to stage-specific regulation.

Amino Acid Sequence↗
PubMed1998

Characterization of the mouse Cyp1B1 gene. Identification of an enhancer region that directs aryl hydrocarbon receptor-mediated constitutive and induced expression.

Transcriptional activation of the Cyp1B1 gene in rodents is stimulated by both polycyclic hydrocarbons and cAMP. The mouse Cyp1B1 gene structure contains three exons, of which the second nucleotide of exon 2 is the translation start site. Primer extension analysis identified a transcription start domain defining an exon 1 of 371 base pairs. The sequence 1.075 kilobases upstream of the transcription start site showed 11 xenobiotic-responsive elements (XRE) (TnGCGTG or GCGTG) that are putative aryl hydrocarbon receptor (AhR)-binding sites and three steroidogenic factor-1 motifs that are associated with cAMP-mediated transcriptional activation of genes. A transiently transfected Cyp1B1-luciferase construct, composed of exon 1 and 1.075 kilobases of 5'-flanking region, was induced by 2,3, 7,8-tetrachlorodibenzo-p-dioxin (TCDD; 10.0 +/- 3.0-fold, n = 6) in C3H10T1/2 cells, which exclusively express Cyp1B1. The 90-base pair basal promoter contains two SP-1 sites, one SF-1 site, and a TATA-like box. TCDD induction and basal expression were dependent on positive regulatory elements present between -1075 and -810. Five XRE motifs localized in the enhancer region were completely conserved between mouse and human CYP1B1 sequences. Similar inductions were seen in Hepa-1 cells, which express Cyp1A1 but not Cyp1B1. However, basal Cyp1B1 promoter activities were 4-10-fold higher in C3H10T1/2 cells providing the enhancer region was present, partially reproducing the in vivo cell-specific expression of Cyp1B1. Gel shift experiments established that TCDD stimulates AhR binding to the downstream XRE in the enhancer region. However, oligonucleotides that encompass two other XREs show a high affinity complex of similar size that is evident even without TCDD treatment and that does not contain either the AhR or AhR nuclear translocator. The fourth XRE is immediately adjacent to an E-box, and this oligonucleotide formed a smaller complex that was dependent on this E-box sequence. Negative regulatory sequences have been located between the promoter and TCDD-responsive enhancer regions. Constitutive expression of the Cyp1B1 gene was lost in AhR-deficient cells and was restored by transfected AhR cDNA. Reporter constructs function in a parallel manner, demonstrating the key role of the AhR in constitutive as well as TCDD-induced expression of Cyp1B1 in mouse embryo fibroblasts.

Animals↗
PubMed1998

Aryl-hydrocarbon receptor is an inhibitory regulator of lipid synthesis and of commitment to adipogenesis.

The aryl-hydrocarbon receptor (AhR) is a ligand-dependent transcription factor that mediates the biological effects of 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD). In mouse embryo fibroblasts, TCDD activates expression of multiple genes, including CYP1B1, the predominant cytochrome P450 expressed in these cells. Here, we analyze constitutive functions of the AhR in primary mouse embryo fibroblasts (MEFs) and spontaneously immortalized MEF cell lines derived from wild-type (WT) C57BL/6 mice and also from congenic mice with a targeted disruption of the AhR gene (AhR-/-). After multiple passages, primary MEFs exhibit spontaneous differentiation, growth cessation and senescence. Eventually, colonies of immortalized MEFs arise to provide clonal lines. The senescent phase occurs much earlier for AhR-/- MEFs, while immortalization is substantially delayed. Comparison of AhR-/- and WT MEFs also indicates that constitutive AhR activity is required for basal expression of CYP1B1 and suppresses lipogenesis in subconfluent cultures. Primary WT and AhR-/- MEFs and the corresponding lines undergo adipogenesis when treated at confluence with the appropriate hormonal inducers. Addition of TCDD before or concurrent with hormonal induction suppressed PPAR gamma mRNA and adipogenesis, as measured by lipid accumulation, glycerol phosphate dehydrogenase activity and stearoyl CoA desaturase type 1 mRNA expression. This effect of TCDD treatment was absent in AhR-/- MEFs, establishing the role of AhR in hormone-induced adipogenesis. Such hormonal activation of confluent MEFs and preadipocytes results in a limited proliferative expansion followed by irreversible growth arrest. TCDD-treated MEFs undergo the mitotic expansion but fail to exit the cell cycle. In AhR-/- MEFs, there is no such effect of TCDD. These findings implicate the AhR as a constitutive inhibitor of triglyceride synthesis, and as an early regulator of adipocyte differentiation. AhR interference with cell-cycle arrest in differentiation may be linked to the increased rate of senescence.

3T3 Cells↗
PubMed1997

Ah receptor regulation of CYP1B1 expression in primary mouse embryo-derived cells.

Cytochrome P4501B1 is highly active in the bioactivation of polycyclic aromatic hydrocarbons (PAHs) to mutagenic metabolites. The C3H mouse embryo fibroblast cell line, C3H10T1/2, and primary mouse embryo fibroblasts (MEFs) express CYP1B1 as the predominant cytochrome P-450 form. This is constitutively expressed and induced by 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD) but also, to a greater extent, by PAH. To establish the role of the aryl hydrocarbon receptor (AhR) in the induction responses to PAH and TCDD in MEFs, we measured CYP1B1 expression in primary MEFs generated from congenic C57b/6 mice that differ only at the AhR locus. These MEF cells express either b-1 or d-type Ah receptors, with high and low affinities for AhR agonists, respectively. Both types of MEFs express constitutive CYP1B1 to a similar extent, as measured by expression of mRNA, protein, and activity (PAH metabolism). Induction of CYP1B1 in responsive b-1 MEFs exhibited a 5-fold lower EC50 for TCDD, as compared with MEFs expressing d-type AhR. This is fully consistent with AhR mediation of the induction. Maximal induction of CYP1B1 by 10(-8) M TCDD was comparable in each MEF type. Very low levels of CYP1A1 mRNA, detected by reverse transcriptase-PCR, show a similar dependence on AhR phenotype in these MEFs. The expression of CYP1B1 was highly dependent upon the passage number of the primary MEF cultures. Paralleling decreased proliferation of these cells after passage 7 are changes in cell morphology, the appearance of increasing numbers of differentiated cell types, and the complete loss of CYP1B1 expression. Colonies of these MEFs, which have escaped senescence, proliferate at much later passages, regain CYP1B1 expression, and exhibit the same AhR-dependent CYP1B1 induction responses, as observed in early-passage MEFs and the C3H10T1/2 cell line. We conclude that CYP1B1 expression, including induction via the AhR, parallels a proliferative state for MEF cells.

9,10-Dimethyl-1,2-benzanthracene↗
PubMed1995

A convenient synthesis of 7 alpha-hydroxycholest-4-en-3-one by the hydroxypropyl-beta-cyclodextrin-facilitated cholesterol oxidase oxidation of 3 beta,7 alpha-cholest-5-ene-3,7-diol.

The initial biosynthetic conversions of cholesterol to the bile acids involve sequential 7 alpha-hydroxylation (catalyzed by cholesterol 7 alpha-hydroxylase) followed by C-3 oxidation and concomitant double bond migration (to a delta 4-configuration, catalyzed by 3 beta-delta 5-C27-steroid oxidoreductase) to provide 7 alpha-hydroxycholest-4-en-3-one. A straightforward, and economical, preparation (on a 0.1 g scale) of this pivotal biosynthetic intermediate has been devised. Reduction of 3 beta-(benzoyloxy)-cholest-5-en-7-one with LiB(sec-butyl)3H provided a 4:1 mixture, respectively, of the 7 alpha- and 7 beta-hydroxy diastereomers, which were separated chromatographically. Solvolytic removal of the C-3 benzoyl group gave 3 beta,7 alpha-cholest-5-ene-3,7-diol. A suspension of the 1:1 (v/v) complex (formed by mutual dissolution in MeOH, followed by evaporation of the solvent) of this diol with hydroxypropyl-beta-cyclodextrin, at a concentration of 1 mg mL-1 (in neutral phosphate buffer), was converted by Brevibacterium sp cholesterol oxidase (0.25 U mg-1 of substrate) and catalase (70 U mg-1 of substrate, to recover O2 from the H2O2 produced by the enzymatic oxidation) to a suspension of 7 alpha-hydroxycholest-4-en-3-one and the hydroxypropyl-beta-cyclodextrin. The yield for the enzymatic conversion was in excess of 90%. A much poorer and less reproducible yield (< 20%) was seen in the absence of the hydroxypropyl-beta-cyclodextrin. Routine extraction of this aqueous suspension, and chromatographic purification (85:15 CHCl3/acetone v/v on silica) of the residue, gave pure 7 alpha-hydroxycholest-4-en-3-one in 68% isolated yield. This route is a significant improvement, in terms of reaction scale and convenience, over the previous procedures for the preparation of this steroid.

2-Hydroxypropyl-beta-cyclodextrin↗
PubMed1994

Mouse cytochrome P-450EF, representative of a new 1B subfamily of cytochrome P-450s. Cloning, sequence determination, and tissue expression.

A novel benz[a]anthracene and 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD)-inducible cytochrome P-450 (P450EF), which is very active in polycyclic aromatic hydrocarbon metabolism, has been purified from C3H10T1/2 mouse embryo fibroblasts (Pottenger, L. H., Christou, M., and Jefcoate, C. R. (1991) Arch. Biochem. Biophys. 286, 488-497). P450EF was shown to be immunologically unrelated to the major known P-450 families. A 4.9-kilobase (kb) cDNA encoding P450EF has been isolated from a lambda ZAP cDNA expression library generated from mRNA of TCDD-induced C3H10T1/2 cells. This cDNA comprises 175-base pair (bp) 5'-noncoding, 1629-bp open reading, and about 3100-bp 3'-noncoding sequence. A SmaI fragment of the 4.9-kb cDNA hybridized to a 5.2-kb mRNA species equally induced by benz[a]anthracene (10 microM) and TCDD (10 nM) in C3H10T1/2 cells, consistent with the involvement of the Ah receptor in this induction process. The deduced amino acid sequence (543 amino acids), the longest of any known cytochrome P-450, exhibits 41 and 38% identity to mouse CYP1A1 and CYP1A2, respectively, and less but substantial similarity (30-33% identity) to many members of the CYP2 family. There are five extended regions of > or = 50% identity to CYP1A1 as follows: (a) 51-118; (b) 199-222; (c) 326-343 (I-helix, O2-binding threonine); (d) 357-430; and (e) 460-487 (heme-binding cysteine). These sequence relationships suggest that P450EF is a member of a new CYP1B subfamily (mouse CYP1B1). Hybridization of mRNA and immunoblot analyses of microsomes both demonstrated beta-naphthoflavone (beta-NF) inducibility of Cyp1b-1 expression in C3H mouse lung, liver, and uterus although at lower levels relative to Cyp1a-1. The mobility of the beta-NF-inducible immunoreactive liver protein was significantly higher than that of the CYP1B1 protein detected in mouse lung, uterus, and C3H10T1/2 cells. Compared with the beta-NF-induced uterus, polycyclic aromatic hydrocarbon-induced uterine fibroblasts exhibited 10-20-fold higher levels of CYP1B1, suggesting that stromal fibroblasts are a major source of the protein.

Amino Acid Sequence↗
PubMed1989

Minority workers: educational models for workers, health providers, and planners.

1. The Labor Occupational Health Program's (LOHP) experience with occupational health problems in minority communities demonstrates that information on a client's past work history and occupational exposures is essential in providing comprehensive health care. Occupational health histories are an excellent tool to utilize in community health. 2. Community clinics and primary health care professionals are integral components in health care delivery services. 3. The occupational health professional has a unique opportunity to provide leadership in educating community health providers about the basics of occupational health.

Agriculture↗
PubMed1989

Chronic lead exposure: a problem for minority workers.

1. Despite regulatory and case identification efforts, lead exposure continues to pose a major health problem for minority workers. 2. Minority workers are overrepresented in lead industries such as lead smelting, lead storage batteries, lead pigment production and pottery. 3. Preliminary data from recently instituted lead registries in California and Texas suggest that minority workers continue to be overexposed to lead. 4. A federal policy that strengthens enforcement of the OSHA lead standard is needed to reduce lead exposure among minority workers.

Environmental Exposure↗
PubMed1989

AIDS and the minority health care worker.

1. Large groups of health care workers, many of whom are among ethnic minorities with potential for occupational exposure to HIV/HBV, are generally underserved in training on prevention of occupational transmission of the viruses. 2. The inadequacy of training for indirect client care personnel appears to be one of the primary reasons for high rates of needlestick injuries and exposure to blood. 3. Training in appropriate infection control techniques can help reduce the uneasiness and fear among health care workers over occupationally-related HIV/HBV transmission.

Acquired Immunodeficiency Syndrome↗
PubMed1986

The synthesis of benzindene prostacyclin analogs as potential antiulcer agents.

Two new diastereomeric benzindene prostacyclin analogs (U-72,382 and U-72,383) related to the potent antiulcer agent U-68,215 have been synthesized. These cyclohexyl ring modified analogs of U-68,215 were prepared to determine how the gastrointestinal and hypotensive endpoints observed for U-68,215 would be affected.

Animals↗
PubMedDate not supplied

Detection and significance of granulocyte alloimmunization in leukocyte transfusion therapy on neutropenic dogs.

Studies were carried out in dogs to detect alloimmunization to granulocytes by indirect immunofluorescence (GIIF) and to determine the significance of cross-matching in selecting donors for immunized recipients. All recipients were rendered neutropenic (less than 500 per microliter) by chemotherapy. Three groups of transfusions were evaluated. Group I consisted of 14 transfusions administered to sensitized dogs that were GIIF-negative with donor cells; Group II, 12 transfusions to the same dogs with GIIF-positive donor cells; Group III, 16 transfusions to nonimmunized control dogs. At 1 hour following transfusion, circulating granulocytes demonstrated increments of 956 +/- 137 per microliter (mean +/- SEM) in Group I dogs compared to 236 +/- 57 per microliter for Group II (p less than 0.001). Group III transfusions yielded increments of 888 +/- 116 per microliter, not significantly different from Group I. GIIF correlated better with transfusion results than granulocyte cytotoxicity or lymphocyte cytotoxicity tests or leukoagglutination cross-matching. Nineteen sera with alloantibodies to granulocytes were produced by random or intrafamilial immunizations with granulocytes. Partial characterization of specificities showed that granulocyte specificities were independent of DLA, and consistent with a genetic system of dominant alleles. It was concluded that a) alloimmunization to granulocytes is detected by the GIIF, b) positive tests predict transfusion effects, and c) a genetic system independent of DLA could be recognized on dog granulocytes.

Agranulocytosis↗
PubMedDate not supplied

School employees: the forgotten municipal workers.

The occupational health and safety issues of public school employees in large urban areas are many and complex. Crumbling school infrastructure and crowded classrooms are associated with inadequate indoor air quality, asbestos exposure, noisy environments, and enhanced transmission of communicable and infectious diseases. Poor ventilation in vocational education classrooms, duplicator rooms, kitchens, and science laboratories may also contribute to hazardous exposures. Ergonomic hazards may be responsible for increasing rates of musculoskeletal disorders. Other work-related illnesses and injuries now documented among school employees include asthma, mesothelioma, asbestos-related lung cancer, violent assault, voice disorders, and depression. Such a diverse industry with many potentially hazardous activities and conditions calls for a comprehensive research and intervention agenda.

Accidents, Occupational↗