Genes for cytochrome P-450 and their regulation

The capacity of the liver microsomal mixed-function oxidase system to metabolize a wide variety of exogenous as well as endogenous compounds reflects the participation of multiple forms of the terminal oxidase, cytochrome P-450, which have different broad, but overlapping, substrate specificities. Several of these isozymes accumulate in the liver after exposure of animals to specific inducing agents. Recent studies employing recombinant DNA techniques to investigate the genetic and evolutionary relatedness of various cytochrome P-450 isozymes as well as the molecular basis for the induction phenomenon are described. The conclusions from these investigations are presented in the context of the substantial body of data obtained from the characterization of specific cytochrome P-450 isozymes and from studies on the induction of specific isozymes or enzymatic activities during development or after treatment of animals with various inducing agents.

Physical symptoms in post-traumatic stress disorder

Physical complaints are recognised accompaniments of Post-Traumatic Stress Disorder (PTSD). This study investigates the reporting of physical complaints in a treatment-naive sample of fire-fighters with and without PTSD. Statistically higher rates of cardiovascular, respiratory, musculoskeletal and neurological symptoms were reported in the PTSD group. Possible explanations are discussed, with an exploration of the contribution of arousal, disordered information processing, dissociation, comorbid diagnoses and premorbid personality. The role of the original stressor and sociocultural issues are explored.

BSAP can repress enhancer activity by targeting PU.1 function

PU.1 and BSAP are transcription factors crucial for proper B-cell development. Absence of PU.1 results in loss of B, T, and myeloid cells, while absence of BSAP results in an early block in B-cell differentiation. Both of these proteins bind to the immunoglobulin kappa chain 3' enhancer, which is developmentally regulated during B-cell differentiation. We find here that BSAP can repress 3' enhancer activity. This repression can occur in plasmacytoma lines or in a non-B-cell line in which the enhancer is activated by addition of the appropriate enhancer binding transcription factors. We show that the transcription factor PU.1 is a target of the BSAP-mediated repression. Although PU.1 and BSAP can physically interact through their respective DNA binding domains, this interaction does not affect DNA binding. When PU.1 function is assayed in isolation on a multimerized PU.1 binding site, BSAP targets a portion of the PU.1 transactivation domain (residues 7 to 30) for repression. The BSAP inhibitory domain (residues 358 to 385) is needed for this repression. Interestingly, the coactivator protein p300 can eliminate this BSAP-mediated repression. We also show that PU.1 can inhibit BSAP transactivation and that this repression requires PU.1 amino acids 7 to 30. Transfection of p300 resulted in only a partial reversal of PU.1-mediated repression of BSAP. When PU.1 function is assayed in the context of the immunoglobulin kappa chain 3' enhancer and associated binding proteins, BSAP represses PU.1 function by a distinct mechanism. This repression does not require the PU.1 transactivation or PEST domains and cannot be reversed by p300 expression. The possible roles of BSAP and PU.1 antagonistic activities in hematopoietic development are discussed.

Gene conversion in a cytochrome P-450 gene family

The mRNAs encoding the two major phenobarbital-inducible forms of cytochrome P-450 of rat liver, P-450b and P-450e, are remarkably similar (98% homologous) in nucleotide sequence, but the distribution of differences within them is not random. While the 5' halves (approximately equal to 1 kilobase) appear to be identical, there are 36 divergent residues in the remaining sequences of the two mRNAs, with 14 differences residing in two short highly divergent segments, which in the P-450e gene are located within exon 7. DNA sequence analysis of portions of a number of P-450b/e-related genes provides strong evidence that at least one of the short divergent segments is the result of a recent gene conversion event between an ancestor to the cytochrome P-450e gene and a related donor P-450 gene of unknown function. The sequence data also suggest that extensive gene conversion has occurred within all the members of this gene family in the region including exons 7 and 8 and the intron between them, with a resultant homogenization of those sequences relative to other portions of the genes. Genomic Southern blotting analysis demonstrates that the presence of an apparent "constant" region in the 5' halves of the P-450b and P-450e mRNAs does not reflect a rearrangement in somatic cells of a germ-line DNA configuration. It is therefore proposed that it, too, is a consequence of a very recent gene conversion event between ancestors of the genes encoding both proteins or of an unequal crossing-over between them. On the basis of these and other data we propose that gene conversion represents an important evolutionary mechanism for the generation of related cytochrome P-450 isozymes in which regions of extraordinary sequence similarity and dissimilarity are intermixed. The gene conversion mechanism would account for some of the overlaps in substrate specificities of distantly related P-450s as well as for substantial differences in catalytic properties between closely related members of the same P-450 protein family.

Enhanced Counseling for Women Undergoing BRCA1/2 Testing: Impact on Subsequent Decision Making About Risk Reduction Behaviors

The authors evaluated the impact of an enhanced counseling intervention, designed to promote well-informed decision making for follow-up risk reduction options for ovarian cancer, among high-risk women undergoing BRCA1/2 testing ( N = 77). Following standard genetic counseling, participants received either an enhanced counseling session—designed to help participants anticipate their reactions to possible test outcomes and plan for postresult consequences—or a general health information control session. One week after disclosure of test results, women in the enhanced counseling group experienced a greater reduction in avoidant ideation, suggesting more complete processing of risk feedback. At the 6-monthfollow-up, intervention respondents reported seeking out more information about prophylactic oophorectomy and were more likely to have actually undergone preventive surgery. The results indicate that the use of enhanced counseling can play an important role in decision making about risk reduction behaviors following BRCA1/2 testing.

Activation of the megakaryocyte-specific gene platelet basic protein (PBP) by the Ets family factor PU.1

Platelet basic protein (PBP) is a chemokine family member that is only found in platelets and their precursors megakaryocytes. The PBP gene is physically linked to the gene for another platelet-specific chemokine, platelet factor 4. While the biological basis of platelet factor 4 expression has been pursued by others, the regulatory features controlling the platelet-specific expression of PBP have not been investigated. In this article, we examined the molecular basis by which this megakaryocyte-specific gene is regulated. Transient expression studies of truncated reporter constructs containing from 4.5 to 0.1 kilobases of the functional PBP gene 5'-flanking region, demonstrated that the proximal 0.1 kilobases of the promoter was sufficient for high levels of expression in human erythroleukemia and CHRF-288 cells, two megakaryocytic cell lines. However, none of these constructs was expressed above background levels in HeLa and 293 cells, two non-megakaryocytic cell lines. Further truncation of this promoter suggested that there was an important regulatory element(s) within a pyrimidine-rich tract. Mobility shift analysis of the pyrimidine-rich tract defined a region between -85 and -64 which bound to a nuclear factor(s). This region contains sequences matching the consensus Ets-binding site from -78 to -75 base pairs. In particular, we noted that this site matched a PU.1 consensus sequence known as a PU box. Mobility shift and supershift studies with nuclear extracts as well as recombinant PU.1 protein and anti-PU.1 antibody further confirmed that PU.1 was the specific Ets family factor that bound to this site. Transient expression assays using reporter constructs which contained point mutations that abrogated PU.1 binding also significantly reduced PBP promoter activity in human erythroleukemia and CHRF cells. In addition, while all reporter gene constructs containing PBP promoters were completely inactive in HeLa cells, transactivation experiments using a PU.1 expression construct demonstrated that exogenous expression of PU.1 could increase reporter gene expression up to 8-fold in these cells. Finally, the role of PU.1 in PBP gene expression was compared between wild-type and PU.1-null embryonic stem (ES) cells that were differentiated in vitro into cells that resembled megakaryocytes both morphologically and immunologically. We found that PBP gene expression in the differentiated PU.1(-/-) null ES cells (as determined by semi-quantitative reverse transcriptase-polymerase chain reaction) was more than four times lower than that in the wild-type ES cells, while other platelet-specific genes were expressed equally or similarly in the two ES cell lines. Previous reports have shown that PU.1 is expressed in several hematopoietic lineages, including megakaryocytes. However, the functional role of PU.1 has only been previously demonstrated in the myeloid and lymphoid lineages. Therefore, our studies are the first to show the biological importance of this nuclear factor in the regulated expression of a megakaryocyte-specific gene.

Isolation and characterization of cDNA clones for cytochromes P-450 immunochemically related to rat hepatic P-450 form PB-1

Rat hepatic cytochrome P-450 PB-1 is a prominent constitutive P-450 form whose levels increase approximately 2-3 fold upon phenobarbital administration. Antibodies raised against this protein recognized two major proteins in immunoblots of rat liver microsomal proteins and precipitated comparable amounts of two electrophoretically separable hepatic mRNA translation products. The levels of the two mRNAs encoding these polypeptides were increased substantially upon phenobarbital administration. The anti-PB-1 antibodies were used to screen a cDNA library, and two distinct cDNA clones, pTF-1 and pTF-2, were isolated. These clones contain inserts of 1227 and 410 base pairs, respectively, and show 80% nucleic acid sequence homology in their region of overlap. The DNA sequences of these clones show 54% sequence homology to the corresponding portions of the mRNA encoding P-450 PB-4, a major phenobarbital-inducible form of rat liver P-450, and can be optimally aligned with the PB-4 sequence without introducing insertions or deletions. The level of hepatic mRNA which hybridizes to clone pTF-2 increases approximately 2-4-fold after phenobarbital treatment, whereas mRNA which hybridizes to pTF-1 does not change in concentration after this treatment. mRNA, which hybridizes to pTF-1, is, however, 4-fold more abundant in livers of female rats than in livers of male rats.(ABSTRACT TRUNCATED AT 250 WORDS)

Differences between treatment seekers in an obese population: medical intervention vs. dietary restriction

This study examined two groups of people who were pursuing treatment for obesity: either medical intervention (a hospital group; N = 20) or support for dietary restriction (a community group; N = 18). This study addressed four questions: (1) Were there differences between the two groups in terms of their psychological distress (as measured by the Symptom Checklist)? (2) Does binge eating moderate psychological distress? (3) Do feelings of ineffectiveness moderate psychological distress? and (4) Which variables best accounted for group membership (i.e., type of treatment sought)? Results suggested that the hospital group was significantly more distressed than the community group. However, there were no differences between the two groups with respect to binge eating or feelings of ineffectiveness. These findings suggest that it is the effects of morbid obesity that are most likely to moderate psychological distress.

Anorexia nervosa following gastric reduction surgery for morbid obesity

Anorexia nervosa and morbid obesity are popularly considered to be opposite ends of the eating disorder spectrum. Research and clinical experience, however, suggest common psychological factors in a subgroup of obese people. This paper details case reports of two subjects who developed anorexia nervosa following gastric reduction surgery for morbid obesity. Clinical profiles, treatment, and outcome are reported. Psychological similarities between morbid obesity and anorexia nervosa in these subjects are explored. Implications for the selection of subjects for gastric reduction surgery and management after surgery are discussed.

A review of dissociation and dissociative disorders

There has been an explosion of activity concerning dissociation and dissociative disorders overseas, but little interest is apparent in Australian psychiatric publications. This article aims to critically examine the current conceptualisation of dissociation and its proposed relevance to the understanding of psychopathology, in order to create discussion about these issues in Australian psychiatry. Multiple personality disorder and post-traumatic stress disorder are critically examined.

Hostility and anger measures in coronary heart disease

Recent research addressing the link between psychological factors and risk of coronary heart disease (CHD) has focused on the areas of hostility and anger and produced sometimes contradictory results. This study makes use of four questionnaire measures of hostility and anger, which were administered to matched groups with and without CHD. Quicker experiences of anger with greater verbal expression best predicted CHD. The difficulties in teasing out the relative contributions of emotional expression, experience and personality using available questionnaires are discussed.

Assignment of 35 single-copy and 17 repetitive sequence DNA probes to human chromosome 3: high-resolution physical mapping of 7 DNA probes by in situ hybridization

Thirty-five single-copy and 17 repetitive sequence DNA probes specific for human chromosome 3 were isolated from human chromosome 3-derived genomic libraries. Seven DNA clones, including three that are polymorphic for BglII or MspI, were mapped by in situ hybridization. Four probes were mapped to 3p subregions and 3 were mapped to 3q subregions. Three of the DNA sequences map to regions overlapping a segment of chromosome 3 (3p14-23) frequently deleted in small cell lung cancer cells. By Southern blot analysis on a deletion hybrid panel, we previously mapped 6 of these probes to three distinct chromosome 3 subregions. Our in situ data support these assignments and more precisely determine the localization of each clone to the following regions: D3S34 (3p14-21), D3S35 (3p21), D3S39 (3p21), D3S40 (3p12-13), D3S37 (3q21-23), and D3S36 (3q21). Clone pL84c, a low repeat sequence clone (approximately 30 copies), was mapped to the 3q21-29 subregion. These DNA clones mapped by in situ hybridization can provide useful landmarks for the ordering and localization of other clones.

Meiotic chromosomal changes and sterility produced by nitrogen mustard and procarbazine in mice

Treatment and survival of reproductive-age patients with chemotherapy raises the question of possible effects on procreative ability. An attempt has been made to establish an animal model system. The anticancer agents nitrogen mustard and procarbazine caused decreased fertility in mice of both sexes and induced meiotic chromosomal abnormalities, at least in the male. Progeny of treated mice showed similar meiotic chromosomal changes. The possibility of similar effects in human beings receiving chemotherapy must be considered.

The association between spouse-reported Type A behaviour pattern and coronary heart disease

This paper describes further validation of the Spouse-Report Type A Behaviour Pattern Questionnaire. In a case controlled study of 61 cardiac patients versus 61 community controls, the questionnaire was found to discriminate statistically between a group of patients with proven coronary heart disease and a group of matched healthy controls on the anger/hostility subscale and total Type A score. No relationship between Type A score and coronary heart disease severity was found. Possible explanations for these findings are examined.

Cocarcinogenesis in vitro using Balb/3T3 cells and aromatic hydrocarbon cocarcinogens

The mouse skin cocarcinogens fluoranthene, pyrene, and undecane were used with the indirect-acting carcinogen, benzo(a)pyrene (BP), and the direct-acting alkylating carcinogen, beta-propiolactone (BPL), in an in vitro transformation assay. Dose response, cytotoxicity, and transformation studies with these compounds were performed with a subclone (A31-1-1) of the Balb/3T3 cell line. Transformation frequencies were found to increase with increasing concentrations of BP used up to 1.0 micrograms/ml or when BPL was used up to 4.0 micrograms/ml. A significant increase (P less than 0.05) in the transformation frequency over that seen with carcinogen alone was observed when cells were exposed to a combination of fluoranthene (4.0 micrograms/ml) and BP (0.063 micrograms/ml) or pyrene (5.0 micrograms/ml) and BP (0.063 micrograms/ml). Thus, the transformation frequency obtained with BP + fluoranthene was 3.8 x 10(-4) compared to 1.2 x 10(-4) when BP was tested alone. Similarly, the transformation frequency using BP + pyrene was 2.8 x 10(-4) vs. 1.2 x 10(-4) when BP was tested alone. Undecane did not exert any cocarcinogenic effect with BP in the dose range tested. In this in vitro assay, no cocarcinogenic effect was observed when BPL was used with any of the above mouse skin cocarcinogens. All cells isolated from transformed foci showed characteristics of transformed cells including anchorage-independent growth.

A cytochrome P-450 multigene family. Characterization of a gene activated by phenobarbital administration

The capacity of the liver microsomal mixed function oxidase system to metabolize a great variety of exogenous as well as endogenous compounds is thought to reflect the participation of multiple forms of the terminal oxidase, cytochrome P-450, which have different broad, but overlapping, substrate specificities. Several of these isozymes accumulate in the liver after exposure of animals to specific inducing agents. In order to approach the questions of the genetic basis for the existence of multiple cytochrome P-450 isozymes and the molecular mechanisms of the induction process, we have used a cloned cDNA for a major phenobarbital-induced form of cytochrome P-450 to identify and characterize thirteen distinct rat genomic clones containing segments of six different genes. Only three clones, representing overlapping segments of a single gene, hybridized to the cloned cDNA or to phenobarbital-induced mRNA under conditions of high stringency. In vitro transcription studies with isolated rat liver nuclei indicated that only this gene, but not the genes represented by the other genomic clones, appears to be markedly activated by phenobarbital treatment of rats. Although there are a small number of differences, DNA sequence analysis of the eight exons of the gene present in these genomic clones indicates that they encode residues 58 to 491 (the COOH terminus) of cytochrome P-450e, a major phenobarbital-induced isozyme. It appears that the other cloned genes may contain only a small region of very strong homology to the cytochrome P-450e gene, a region which includes the exon encoding a tridecapeptide which is also present in two dissimilar forms of rabbit liver cytochrome P-450, one constitutive and one induced by phenobarbital. Southern blotting analysis of rat liver DNA indicates that the rat genome may contain two additional genes which are very closely related to the cytochrome P-450e gene but which we have not yet isolated from the genomic library. One of these genes is likely to encode cytochrome P-450b, the major phenobarbital induced form of cytochrome P-450 whose mRNA is greater than 95% homologous to that encoding cytochrome P-450e.

Chemical cocarcinogenesis with the use of a subclone derived from Balb/3T3 cells with catechol as cocarcinogen

This study was performed for the detection of cocarcinogens by transformation in vitro with the use of a subclone of a Balb/3T3 cell line. Dose response, cytotoxicity, and transformation studies were done with the use of an indirect-acting carcinogen, benzo[a]pyrene (B[a]P), a direct-acting alkylating carcinogen, beta-propiolactone (BPL), and the mouse skin cocarcinogen catechol. The rate of transformation was notably higher in groups treated with B[a]P and catechol or BPL and catechol than in groups treated with either B[a]P or BPL. Catechol alone did not induce any transformation. All the cells isolated from the transformed foci showed characteristics of malignantly transformed cells, such as anchorage-independent growth. Thus chemical cocarcinogenesis was accomplished in vitro similar to that accomplished in in vivo studies reported earlier on mouse skin.