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Biomedical subjects

D R Cohen

Publications and source records attributed to D R Cohen.

At least 37 records · Page 2Linked to original sources
PubMed1996

CRF stimulates expression of multiple fos and jun related genes in the AtT-20 corticotroph cell.

Recent studies have shown that corticotropin releasing factor (CRF) stimulates c-fos gene expression in the AtT-20 corticotroph cell line, and that overexpression of c-Fos results in activation of POMC gene transcription. Since transactivation by c-Fos requires dimerization with a Jun family member to form the active transcription factor AP-1, we have examined the expression of multiple fos and jun related genes and have correlated their expression with AP-1 DNA binding activity in AtT-20 nuclear extracts after stimulation with CRF. Although basal expression of c-fos mRNA was extremely low, it was rapidly and transiently stimulated in AtT-20 cells following administration of either constant or a single pulse of CRF. In contrast, basal expression of c-jun mRNA was slightly higher and underwent little or no change in response to CRF. Specific ribonuclease protection analysis showed that in addition to c-fos, mRNA transcripts encoding fos B and jun B were rapidly stimulated in response to CRF, though levels of induced fos B mRNA were 20-40 times lower than c-fos or jun B, respectively. Gel shift analysis demonstrated that CRF caused a sustained increase in AP-1 DNA binding to both a canonical AP-1 element as well as to the POMC exon-1 AP-1 site. Studies with specific antisera directed against c-Fos revealed that although no c-Fos could be detected in AP-1 complexes in basal cell extracts, c-Fos became a prominent component of AP-1 following CRF stimulation, reaching maximal levels by 4 h. Despite the fact that AP-1 DNA binding activity remained elevated for at least 24 h after CRF, c-Fos was most prominent during the early phase of the response. Similarly, JunB was shown to be a major component of AP-1 DNA binding activity in CRF-stimulated AtT-20 nuclear extracts that persisted for at least 24h after stimulation. Despite the obvious induction of fos B mRNA in response to CRF, FosB protein was not detected in DNA bound AP-1 complexes. These data demonstrate that CRF is a potent stimulus for corticotroph expression of c-fos, jun B and fos B, and suggest that the subsequent increase in AP-1 may play a role in activation of gene expression and/or as a modulator of glucocorticoid receptor function.

Animals↗
PubMed1996

Analysis of the role of Amh and Fra1 in the Sry regulatory pathway.

Sry is the Y-chromosomal gene responsible for initiating the pathway of male development in mammals, presumably by regulating downstream target genes. As a basis for examining the role played by Sry and other candidate sex-determining genes, we have used reverse-transcriptase PCR to produce a precise temporal profile of expression of Sry in the developing gonad. Sry expression first occurs at 10.5 days postcoitum (dpc) and is upregulated to reach a maximum level from 11.25 to 12 dpc. Expression is then steadily downregulated from 12.25 to 13.25 dpc and is completely extinguished by 13.5 dpc. Two genes implicated in sexual development are Amh, encoding anti-müllerian hormone (AMH), and Fra1, encoding Fos-related antigen-1. Expression profiles of Amh and Sry in fetal gonads indicate a possible role for AMH in the downregulation of Sry expression. We show, however, that the timing of Sry downregulation is unaffected in Amh-deficient mice, excluding a role for AMH as a negative regulator of Sry. Further, we have examined the possibility that SRY may activate Fra1 during testis determination by analysing the expression of Fra1 in mouse fetal gonads. Fra1 is not expressed at any stage at or around the critical period of sex determination when Sry transcripts are present, thus excluding a role for Fra1 in sex determination and differentiation.

Animals↗
PubMed1995

Messages from Mid Glamorgan: a multi-programme experiment with marginal analysis.

This paper discusses the issues and problems arising from the first attempt to apply marginal analysis across a full range of health care activities within a UK Health District. Following a brief description of the two stage process undertaken in Mid Glamorgan, the paper focuses on the importance of a conducive environment to a successful application of the approach and to three key issues of group composition, group dynamics and openness/explicitness. The paper also addresses two parts of the Mid Glamorgan process which might be of questionable importance; the need for programme budgets prior to the exercise and the relevance of stage II which attempted to interfere with the expressed priorities identified by the expert groups in stage I. The main message is that marginal analysis works in practice as well as being attractive in theory and that much can be achieved even when only crude data on marginal costs and benefits are available. It is more important that priority setting be addressed within an appropriate framework than with accurate data. Marginal analysis provides such a framework.

Budgets↗
PubMed1994

SRY protein enhances transcription of Fos-related antigen 1 promoter constructs.

In mammals, testis determination is under the control of the chromosome Y-linked SRY gene. Sry is expressed in the fetal mouse just before development of the testis and shows germ-cell-dependent expression in the adult mouse. SRY protein contains a high-mobility-group (HMG)-box DNA-binding domain, and potential target sequences have been identified. The fos-related antigen 1 (fra-1) gene is closely related to the protooncogene c-fos and encodes a component of transcription factor AP-1. Fra-1 is expressed during spermatogenesis, and the promoter of the rat fra-1 gene contains several potential binding sites for members of the HMG-box family of DNA-binding proteins. We demonstrate that purified SRY protein binds strongly to one of the putative fra-1 HMG-box response elements and that SRY enhances the transcription of rat fra-1 promoter constructs in cotransfection experiments. These results suggest that the function of HMG-box transcription factors may be mediated, in part, by activation of members of the AP-1 transcription factor family.

Amino Acid Sequence↗
PubMed1994

The use of an endotracheal ventilation catheter for jet ventilation during a difficult intubation.

This case report describes the use of an endotracheal ventilation catheter (ETVC) to provide prolonged intraoperative jet ventilation, reintubation and the maintenance of tracheal access following extubation. It emphasizes that excellent oxygenation and ventilation can be achieved but such management can be complicated by a pneumothorax even when the risks are minimized. A 43-yr-old man presented for possible pulmonary sleeve resection. Placement of a double lumen endotracheal tube (DLT) by direct laryngoscopy was unsuccessful due to the inability to visualize the glottis. A 7.5 mm endotracheal tube (ETT) was successfully introduced over a fibreoptic bronchoscope (FOB). An ETVC was passed, permitting manually cycled jet ventilation while general intravenous anaesthesia and muscle relaxation were maintained. The ETT was then withdrawn over the ETVC and jet ventilation continued for approximately 90 min, while attempts at placing a DLT over a now malfunctioning FOB continued. These attempts were eventually abandoned and the patient was returned to the post-anaesthesia care unit (PACU) haemodynamically stable. The trachea was extubated over the ETVC, which remained in situ. A pneumothorax was noted on the postoperative chest x-ray. This case illustrates prolonged intraoperative jet injection via a "jet stylet" with satisfactory ventilation and oxygenation but complicated by a pneumothorax. Also it illustrates a strategy for the management of a "difficult extubation."

Adult↗
PubMed1994

Cloning and characterisation of the mouse fra-2 gene.

Transcription factor AP-1 is comprised of multiple protein complexes that include members of a family of genes related to the proto-oncogene c-fos. In this report, we have extended the analysis of one member of this family, fos-related antigen-2 (fra-2), by isolating and characterising genomic and cDNA clones encoding the mouse fra-2 homolog. The overall gene structure (number and positions of introns) was similar to that of both the chicken fra-2 gene and other members of the fos family, and the relative positions of putative enhancers in the 5' regulatory region were well conserved between the mouse and chicken fra-2 genes. High levels of fra-2 mRNA were detected in ovary, stomach, small and large intestine, brain, lung and heart. The mouse Fra-2 protein showed 94% and 87.5% conservation with human and chicken Fra-2, respectively, and mouse Fra-2, like the chicken homolog, induced transformation of chicken embryo fibroblasts. The characterisation of the mouse fra-2 gene provides a basis for analysis of Fra-2 function in the whole animal.

Amino Acid Sequence↗
PubMed1993

Economic implications of smoking cessation therapies: a review of economic appraisals.

There is a paucity of studies on the economics of smoking cessation. Those undertaken have investigated only a narrow range of available interventions, using variable methodologies which make interstudy comparisons problematical. There is a need for more economic appraisal in this area and for greater consistency in the methodologies employed. Growing evidence on the effectiveness of pharmacotherapies has not been matched by evidence of their cost effectiveness, and studies in this area, particularly on transdermal nicotine, are urgently required. Cost-benefit analyses (CBAs) have focused on programmes targeted at pregnant women and indicate that resource savings, mainly from reductions in the number of low birthweight neonates, can exceed the costs of the measures. Efforts to persuade pregnant women to quit thus appear to be highly cost beneficial, but further evidence on the efficiency of measures targeted at other groups or to the general population of smokers is required. Cost-effectiveness analyses (CEAs) suggest that measures targeted at specific groups are more cost effective than those targeted at the general population of smokers, and that the cost effectiveness of such programmes is further improved by providing educational materials that are specific to the targeted groups. Advice on how to maintain abstinence appears to improve the cost effectiveness of help with quitting, and routine advice from physicians to their smoking patients is a cost-effective way of reducing smoking prevalence.

Cost-Benefit Analysis↗
PubMed1993

Transcriptional regulation in the testis: a role for transcription factor AP-1 complexes at various stages of spermatogenesis.

The products of two proto-oncogenes, c-fos and c-jun, have been implicated in signal transduction pathways as regulators of gene expression. Both proto-oncogenes are members of gene families encoding closely related proteins that together make up transcription factor AP-1. The expression of members of this transcription factor has been associated with cellular pathways that result in both mitosis and differentiation. We have been studying the process of spermatogenesis, which is a complex, continual cycle of cell renewal, proliferation and differentiation. Using a seasonal breeder, the European red fox (Vulpes vulpes), as our model, we have examined the expression of five AP-1 family members (c-fos, fra-1, fra-2, c-jun and junB) with a view to elucidating their role in the regulation of spermatogenesis. Unique patterns of expression, falling into three broad categories, were observed for the five genes: (i) continuous expression throughout the spermatogenic cycle (c-fos); (ii) expression only at times corresponding to the onset and shutdown of spermatogenesis (fra-1, fra-2 and c-jun); and (iii) expression only at the onset of the cycle (junB). Furthermore, the proteins were expressed in both premeiotic and post-meiotic cell types, suggesting a role in haploid, as well as diploid, gene expression in this tissue. The data suggest distinct, although not necessarily unrelated, roles for the different components of transcription factor AP-1 in the regulation of spermatogenesis.

Animals↗
PubMed1990

Introducing quality into cost effectiveness.

The objective of this study is to explore the problems which can arise when quality issues are introduced without proper analysis of the nature and objectives of health care. The principles of economics are used to explain why the primary output of health care should be perceived in terms of health gained (or maintained). Cost Effectiveness Analysis (CEA) is concerned with achieving a given output at lowest cost. The problems of measuring and valuing health gains, as well as problems arising when a quality dimension is introduced, are discussed with reference to the Quality Adjusted Life Year (QALY) as a measure of health gain. Quality of service provision is normally achieved at an increased cost per QALY. This need not make high quality services inefficient provided care is taken in use of terms and Cost Benefit Analysis (CBA) is used to highlight the value placed on consumer satisfaction.

Consumer Behavior↗
PubMed1990

Induction of c-fos mRNA expression by afterdischarge in the hippocampus of naive and kindled rats.

Periodic induction of focal electrical seizure [afterdischarge (AD)] is an absolute prerequisite for the development of kindling, an animal model of complex partial epilepsy. Once established, it is a permanent condition. The mechanism(s) that translate ADs, which last tens of seconds, into life-long alterations in the CNS is unclear. Cellular immediate-early genes have been implicated in the conversion of short-term stimuli to long-term alterations in cellular phenotypes by regulating target gene expression. We have investigated the contribution of one such early gene, c-fos, to this process. The relationship between ADs and expression of c-fos gene in the rat hippocampus, a key structure in kindling development, was studied by analysis of mRNA levels. The low constitutive expression of c-fos mRNA in the hippocampus was not altered by kindling. There was an "all-or-none" relationship between induction of c-fos and the duration of AD. The threshold for induction was approximately 30 s of AD. Above-threshold ADs induced c-fos in both naive and kindled animals to the same extent and with identical temporal profiles. Although the expression of c-fos is unchanged with kindling, c-fos may nonetheless contribute to many long-term changes of kindling, both adaptive and epileptogenic.

Animals↗
PubMed1990

Transcriptional activation and repression by Fos are independent functions: the C terminus represses immediate-early gene expression via CArG elements.

The Fos-Jun complex has been shown to activate transcription through the regulatory element known as the AP-1 binding site. We show that Fos down regulates several immediate-early genes (c-fos, Egr-1, and Egr-2) after mitogenic stimulation. Specifically, we demonstrate that the target for this repression is a sequence of the form CC(A/T)6GG, also known as a CArG box. Whereas Fos bound to the AP-1 site through a domain rich in basic amino acids and associated with Jun via a leucine zipper interaction, mutant Fos proteins lacking these structures were still capable of causing repression. Furthermore, Jun neither enhanced nor inhibited down regulation by Fos. Critical residues required for repression are located within the C-terminal 27 amino acids of c-Fos, since v-Fos and C-terminal truncations of c-Fos did not down regulate. In addition, transfer of 180 c-Fos C-terminal amino acids to Jun conferred upon it the ability to repress. Finally, Fra-1, a Fos-related protein which has striking similarity to Fos in its C-terminal 40 amino acids, also down regulated Egr-1 expression. Thus, Fos is a transcriptional regulator that can activate or repress gene expression by way of two separate functional domains that act on distinct regulatory elements.

Animals↗
PubMed1990

Analysis of dimerization and DNA binding functions in Fos and Jun by domain-swapping: involvement of residues outside the leucine zipper/basic region.

The products of two cellular proto-oncogenes c-fos and c-jun form a heterodimeric complex that contribute to the DNA-binding activity referred to as AP-1 (activator protein-1). Two domains have been proposed to be required for heterodimer formation and protein-DNA complex formation. The leucine zipper domain mediated the interaction between the two proteins and a highly basic region immediately N-terminal to the leucine zipper forms a DNA binding domain. To assess the role of these two domains in dimerization and DNA binding and to determine what contribution, if any, is made by residues outside of these regions, we carried out an extensive domain swap analysis. Restriction sites created in the fos and jun cDNAs flanking the basic region and leucine zipper allowed these domains to be swapped between the two proteins either singly or in various combinations with adjacent domains. The chimeric proteins were assayed for their ability to dimerize with each other and to interact with the AP-1 consensus sequence. It was found that two Jun leucine zipper regions could mediate protein dimerization, whereas two Fos leucine zipper regions could not. The dimers formed between two Jun leucine repeats were less stable than those formed between a Fos and a Jun leucine zipper. A conserved His residue seven amino acids C-terminal of the last leucine of the zipper region contributed to the stability of protein-protein interactions. The basic region of both Fos and Jun was found to interact with DNA without the presence of the other, i.e. the combination of two Fos- or two Jun-DNA binding domains could bind to the AP-1 site. However, replacement of the Jun N-terminus with that of Fos resulted in a decrease in DNA binding, indicating that residues outside of the Jun basic region contribute to DNA binding. The results also suggest that the dimerization and DNA binding functions of each protein are not completely independent properties, but that each exerts an influence on the other.

Amino Acid Sequence↗
PubMed1989

The product of a fos-related gene, fra-1, binds cooperatively to the AP-1 site with Jun: transcription factor AP-1 is comprised of multiple protein complexes.

fra-1 encodes a serum-inducible protein (Fra-1) that is antigenically related to Fos. We have characterized Fra-1 expression in serum-stimulated cells using antibodies raised against several regions of this protein. Fra-1, expressed transiently in COS cells or in serum-stimulated rat fibroblasts, undergoes extensive post-translational modification, primarily by phosphorylation of serine residues. It is present in both the nucleus and the cytoplasm and participates in a protein complex with Jun. Using proteins synthesized in reticulocyte lysates, we have shown that Fra-1, like Fos, binds to the AP-1 recognition element cooperatively with Jun. A truncated Fra-1 protein that contains the leucine zipper region but not an adjacent basic amino acid domain, complexes with Jun in vitro but fails to bind AP-1 oligonucleotides. These results demonstrate that Fra-1 contributes to the DNA-binding activity ascribed to transcription factor AP-1.

Animals↗
PubMed1988

Fos-associated protein p39 is the product of the jun proto-oncogene.

The Fos protein complex and several Fos-related antigens (FRA) bind specifically to a sequence element referred to as the HeLa cell activator protein 1 (AP-1) binding site. A combination of structural and immunological comparisons has identified the Fos-associated protein (p39) as the protein product of the jun proto-oncogene (c-Jun). The p39/Jun protein is one of the major polypeptides identified in AP-1 oligonucleotide affinity chromatography extracts of cellular proteins. These preparations of AP-1 also contain Fos and several FRA's. Some of these proteins bind to the AP-1 site directly whereas others, like Fos, appear to bind indirectly via protein-protein interactions. Cell-surface stimulation results in an increase in c-fos and c-jun products. Thus, the products of two protooncogenes (and several related proteins), induced by extracellular stimuli, form a complex that associates with transcriptional control elements containing AP-1 sites, thereby potentially mediating the long-term responses to signals that regulate growth control and development.

Cell Transformation, Neoplastic↗