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Biomedical subjects

C S Hill

Publications and source records attributed to C S Hill.

At least 19 recordsLinked to original sources
PubMed2001

Loss of Smad4 function in pancreatic tumors: C-terminal truncation leads to decreased stability.

At early stages of tumorigenesis, the transforming growth factor-beta (TGF-beta) signaling pathway is thought to have tumor suppressor activity as a result of its ability to arrest the growth of epithelial cells. Smad4 plays a pivotal role in the TGF-beta signaling pathway and has been identified as a tumor suppressor, being mutated or deleted in approximately 50% of pancreatic carcinomas and 15% of colorectal cancers. A nonsense mutation generating a C-terminal truncation of 38 amino acids in the Smad4 protein has been identified in a pancreatic adenocarcinoma (Hahn, S. A., Schutte, M., Hoque, A. T., Moskaluk, C. A., da Costa, L. T., Rozenblum, E., Weinstein, C. L., Fischer, A., Yeo, C. J., Hruban, R. H., and Kern, S. E. (1996) Science 271, 350-353), and here we investigate the functional consequences of this mutation. We demonstrate that the C-terminal truncation prevents Smad4 homomeric complex formation and heteromeric complex formation with activated Smad2. Furthermore, the mutant protein is unable to be recruited to DNA by transcription factors and hence cannot form transcriptionally active DNA-binding complexes. These observations are supported by molecular modeling, which indicates that the truncation removes residues critical for homomeric and heteromeric Smad complex formation. We go on to show that the mutant Smad4 is highly unstable compared with wild type Smad4 and is rapidly degraded through the ubiquitin-proteasome pathway. Consistent with this, we demonstrate that the pancreatic adenocarcinoma harboring this mutated allele, in conjunction with loss of the other allele, expresses no Smad4 protein. Thus we conclude that these tumors completely lack Smad4 activity.

3T3 Cells↗
PubMed2001

pp(macro)-->tt(macro)H: a discovery mode for the Higgs boson at the Fermilab Tevatron.

The production of a standard model Higgs boson in association with a top quark pair at the upcoming high luminosity run ( 15 fb(-1) integrated luminosity) of the Fermilab Tevatron ( square root of s = 2.0 TeV) is revisited. For Higgs masses below 140 GeV we demonstrate that the production cross section times branching ratio for H-->bb macro decays yields a significant number of events and that this mode is competitive with and complementary to the searches using pp(macro) -->WH,ZH associated production. For higher mass Higgs bosons the H-->W(+)W(-) decays are more difficult but have the potential to provide a few spectacular events.

Journal Article↗
PubMed2001

Xenopus Smad3 is specifically expressed in the chordoneural hinge, notochord and in the endocardium of the developing heart.

The Smads are intracellular signalling molecules that transduce signals from receptors for members of the TGF-beta superfamily to the nucleus. We have cloned the Xenopus orthologue of Smad3 (XSmad3). It is 94.6% identical to human Smad3 at the amino acid level. It is expressed as a maternal mRNA which disappears after stage 10.5, but reappears at the early tailbud stages. It is much less abundant than XSmad2 at the early developmental stages. From Stage 27 onwards XSmad3 is expressed with XSmad2 throughout the head region and in the somitic region. Strikingly however, XSmad3 alone is specifically expressed in the chordoneural hinge, the notochord and in the developing heart. Closer analysis reveals that XSmad3 is specifically expressed in the endocardium but not in the myocardium or pericardium. The chordoneural hinge staining persists at least until stage 40 whereas the staining in the endocardium peaks at approximately stage 32/33.

Amino Acid Sequence↗
PubMed2001

TGF-beta signalling pathways in early Xenopus development.

Many different ligands of the TGF-beta superfamily signal in the early Xenopus embryo and are required for the specification and patterning of the three germ layers as well as for gastrulation. Recent advances in the field are helping us understand how ligand activity is regulated both spatially and temporally, the mechanism by which the signals are transduced to the nucleus and how essentially the same signalling pathway can activate completely different sets of genes in different regions of the embryo.

Animals↗
PubMed2001

Molecular diagnostic testing for infectious diseases using TMA technology.

Molecular diagnostic tests based on nucleic acid amplification technologies (NAATs) have become widely established in clinical microbiology laboratories in recent years. The acceptance of these tests has been driven by the development of more accurate and less labor-intensive commercial assay kits by diagnostic manufacturers. Infectious disease diagnostic assays using transcription-mediated amplification (TMA) NAAT have become increasingly popular in many clinical microbiology laboratories. Recent technology developments have improved the performance and simplified the use of the TMA assays. These new technologies have been applied to the development of multiplex TMA tests to improve the testing accuracy for organisms, such as Chlamydia trachomatis and Neisseria gonorrhoeae in clinical microbiology laboratories. TMA tests for HIV-1 and HCV have also led to improvements in blood bank testing which can improve the safety of the public blood supply.

Blood↗
PubMed2000

Raf induces TGFbeta production while blocking its apoptotic but not invasive responses: a mechanism leading to increased malignancy in epithelial cells.

c-Raf-1 is a major effector of Ras proteins, responsible for activation of the ERK MAP kinase pathway and a critical regulator of both normal growth and oncogenic transformation. Using an inducible form of Raf in MDCK cells, we have shown that sustained activation of Raf alone is able to induce the transition from an epithelial to a mesenchymal phenotype. Raf promoted invasive growth in collagen gels, a characteristic of malignant cells; this was dependent on the operation of an autocrine loop involving TGFbeta, whose secretion was induced by Raf. TGFbeta induced growth inhibition and apoptosis in normal MDCK cells: Activation of Raf led to inhibition of the ability of TGFbeta to induce apoptosis but not growth retardation. ERK has been reported previously to inhibit TGFbeta signaling via phosphorylation of the linker region of Smads, which prevents their translocation to the nucleus. However, we found no evidence in this system that ERK can significantly influence the function of Smad2, Smad3, and Smad4 at the level of nuclear translocation, DNA binding, or transcriptional activation. Instead, strong activation of Raf caused a broad protection of these cells from various apoptotic stimuli, allowing them to respond to TGFbeta with increased invasiveness while avoiding cell death. The Raf-MAP kinase pathway thus synergizes with TGFbeta in promoting malignancy but does not directly impair TGFbeta-induced Smad signaling.

Animals↗
PubMed2000

Homeodomain and winged-helix transcription factors recruit activated Smads to distinct promoter elements via a common Smad interaction motif.

We have investigated the regulation of the activin-inducible distal element (DE) of the Xenopus goosecoid promoter. The results show that paired-like homeodomain transcription factors of the Mix family, Mixer and Milk, but not Mix.1, mediate activin/TGF-beta-induced transcription through the DE by interacting with the effector domain of Smad2, thereby recruiting active Smad2/Smad4 complexes to the Mixer/Milk-binding site. We identify a short motif in the carboxyl termini of Mixer and Milk, which is demonstrated to be both necessary and sufficient for interaction with the effector domain of Smad2 and is required for mediating activin/TGF-beta-induced transcription. This motif is not confined to these homeodomain proteins, but is also present in the Smad2-interacting winged-helix proteins Xenopus Fast-1, human Fast-1, and mouse Fast-2. We demonstrate directly that transcription factors of different DNA-binding specificity recruit activated Smads to distinct promoter elements via a common mechanism. These observations, together with the temporal and spatial expression patterns of Mixer and Milk, lead us to propose a model for mesoendoderm formation in Xenopus in which these homeodomain transcription factor/Smad complexes play a role in initiating and maintaining transcription of target genes in response to endogenous activin-like signals.

Activins↗
PubMed2000

The Smad4 activation domain (SAD) is a proline-rich, p300-dependent transcriptional activation domain.

Transforming growth factor-beta (TGF-beta) family members signal through a unique set of intracellular proteins called Smads. Smad4, previously identified as the tumor suppressor DPC4, is functionally distinct among the Smad family, and is required for the assembly and transcriptional activation of diverse, Smad-DNA complexes. We previously identified a 48-amino acid proline-rich regulatory element within the middle linker domain of this molecule, the Smad4 activation domain (SAD), which is essential for mediating these signaling activities. We now characterize the functional activity of the SAD. Mutants lacking the SAD are still able to form complexes with other Smad family members and associated transcription factors, but cannot activate transcription in these complexes. Furthermore, the SAD itself is able to activate transcription in heterologous reporter assays, identifying it as a proline-rich transcriptional activation domain, and indicating that the SAD is both necessary and sufficient to activate Smad-dependent transcriptional responses. We show that transcriptional activation by the SAD is p300-dependent, and demonstrate that this activity is associated with a physical interaction of the SAD with the amino terminus of p300. These data identify a novel function of the middle linker region of Smad4, and define the role of the SAD as an important locus determining the transcriptional activation of the Smad complex.

Amino Acid Sequence↗
PubMed2000

Transforming growth factor beta-independent shuttling of Smad4 between the cytoplasm and nucleus.

Smad4 plays a pivotal role in all transforming growth factor beta (TGF-beta) signaling pathways. Here we describe six widely expressed alternatively spliced variants of human Smad4 with deletions of different exons in the linker, the region of Smad4 that separates the two well-conserved MH1 and MH2 domains. All these Smad4 variants form complexes with activated Smad2 and Smad3 and are incorporated into DNA-binding complexes with the transcription factor Fast-1, regardless of the amount of linker they contain. However, sequences encoded by exons 5 to 7 in the linker are essential for transcriptional activation. Most importantly, our observation that different Smad4 isoforms have different subcellular localizations has led us to the identification of a functional CRM1-dependent nuclear export signal in the Smad4 linker and a constitutively active nuclear localization signal in the N-terminal MH1 domain. In the absence of TGF-beta signaling, we conclude that Smad4 is rapidly and continuously shuttling between the nucleus and the cytoplasm, the distribution of Smad4 between the nucleus and the cytoplasm being dictated by the relative strengths of the nuclear import and export signals. We demonstrate that inhibition of CRM1-mediated nuclear export by treatment of cells with leptomycin B results in endogenous Smad4 accumulating very rapidly in the nucleus. Endogenous Smad2 and Smad3 are completely unaffected by leptomycin B treatment, indicating that the nucleocytoplasmic shuttling is specific for Smad4. We propose that, upon TGF-beta signaling, complex formation between Smad4 and activated Smad2 or -3 leads to nuclear accumulation of Smad4 through inhibition of its nuclear export. We demonstrate that after prolonged TGF-beta signaling Smad2 becomes dephosphorylated and Smad2 and Smad4 accumulate back in the cytoplasm.

Active Transport, Cell Nucleus↗
PubMed2000

Medical students' attitudes toward pain and the use of opioid analgesics: implications for changing medical school curriculum.

BACKGROUND: Barriers to pain management include physicians' lack of knowledge and attitudes. Our aim was to investigate future physicians' knowledge and attitudes toward pain and the use of opioid analgesics. METHODS: We tested a medical school class during their freshman and senior years. Stepwise regression analysis was used to identify the personal traits that predicted opiophobia. RESULTS: The professionalization process of medical training may reinforce negative attitudes. Psychologic characteristics were associated with reluctance to prescribe opioids, and fears of patient addiction and drug regulatory agency sanctions. CONCLUSIONS: Consistent attitudes were found in senior medical students with preferences for certain specialty areas and the practitioners of their future specialties, suggesting a "preselection" effect. Higher scores on reliance on high technology, external locus of control, and intolerance of clinical uncertainty were associated with higher scores on one or more of the three dimensions of opiophobia. Implications for medical education are discussed.

Acute Disease↗
PubMed2000

Physicians' attitudes toward pain and the use of opioid analgesics: results of a survey from the Texas Cancer Pain Initiative.

BACKGROUND: Despite extensive progress in the scientific understanding of pain in humans, serious mismanagement and undermedication in treating acute and chronic pain is a continuing problem. This study was designed to examine the barriers to adequate pain management, especially as they might be associated with community size and medical discipline. METHODS: A 59-item survey was used to measure physicians' attitudes, knowledge, and psychologic factors that contribute to pain management practices. RESULTS: Overall, a significant number of physicians in this survey revealed opiophobia (prejudice against the use of opioid analgesics), displayed lack of knowledge about pain and its treatment, and had negative views about patients with chronic pain. There were significant differences among groups of physicians based on size of geographic practice area and medical discipline. CONCLUSIONS: New educational strategies are needed to overcome these barriers and to improve pain treatment in routine medical practice. The effect of practice milieu must be taken into consideration.

Acute Disease↗
PubMed1999

Xenopus Smad4beta is the co-Smad component of developmentally regulated transcription factor complexes responsible for induction of early mesodermal genes.

Smad4 is defined as the common-mediator Smad (co-Smad) required for transducing signals for all TGF-beta superfamily members. This paper describes two Smad4s in Xenopus: XSmad4alpha, which is probably the Xenopus orthologue of human Smad4, and a distinct family member, XSmad4beta, which differs primarily at the extreme N-terminus and in the linker region. Both XSmad4s act as co-Smads, forming ligand-dependent complexes with receptor-regulated Smads 1 and 2 and synergizing with them to activate transcription of mesodermal genes in Xenopus embryos. The two XSmad4 genes have reciprocal temporal expression patterns in Xenopus embryos and are expressed in varying ratios in adult tissues, suggesting distinct functional roles in vivo. XSmad4beta is the predominant maternal co-Smad and we go on to demonstrate its role in the transcriptional regulation of early mesodermal genes. We have identified two distinct nuclear complexes that bind the activin-responsive element of the Xenopus Mix.2 promoter: one formed in response to high levels of activin signaling and the other activated by endogenous signaling pathways. Using specific antisera we demonstrate the presence of endogenous XSmad4beta and also XSmad2 in both of these complexes, and our data indicate that the DNA-binding components of the complexes are different. Furthermore, we show that the presence of these complexes in the nucleus perfectly correlates with the transcriptional activity of the target gene, Mix.2, and we show that one of the XSmad4beta-containing transcription factor complexes undergoes a developmentally regulated nuclear translocation.

Activins↗
PubMed1999

Growth factors and gene expression: fresh insights from arrays.

Gene array technology allows researchers to evaluate patterns of gene expression at a genome-wide level. Two recent papers have applied this powerful technique to characterize how gene expression is changed in response to growth factors and mitogens. The studies focus on two important questions concerning specificity in signal transduction. First, are the multiple signaling pathways activated by a single growth factor receptor used to activate gene expression, and if so, do these pathways act combinatorially? Second, how does the initial genetic response of a cell to a signal stimulus relate to the patterns of gene expression that determine that cell's ultimate biological response to the stimulus? Hill and Treisman take a critical look at what these array technology studies tell us concerning these questions and discuss technical issues arising from them.

Animals↗
PubMed1999

The Smads.

The Smads are a family of intracellular signalling molecules that act downstream of receptors for the transforming growth factor (TGF)-beta family of ligands. Three classes of Smads have been identified. The receptor-regulated Smads are direct substrates for the type I receptors, which are serine/threonine kinases. Once phosphorylated and activated, these Smads form hetero-oligomeric complexes with a second class of Smad, the common mediator Smads. These Smad complexes translocate to the nucleus, where they are recruited to DNA primarily by site-specific DNA binding transcription factors, and participate in regulating the transcription of target genes. Inhibitory Smads are the third identified class which antagonise the activity of the receptor-regulated Smads. Aberrant TGF-beta signalling has been associated with several human diseases such as cancer and fibrosis. The identification of the Smads as primary transducers of TGF-beta signals raises the possibility that agents directed at modulating Smad activity would have therapeutic applications.

Animals↗
PubMed1998

Radiotherapy residents' knowledge of and attitudes toward management of cancer pain.

PURPOSE: To evaluate the fund of knowledge of and attitudes toward cancer pain management of radiotherapy residents across the nation. METHODS: Radiotherapy (XRT) residents who had completed at least a year of training were surveyed by questionnaire. Residents (n = 10) from a training program who had been given instructional resources in cancer pain management skills were compared with residents from across the nation (n = 61). A validated survey used in national Cancer Pain Initiative Role Model Programs was administered by mail. The survey contained 30 questions that evaluated attitude alone (A), knowledge alone (K), and how attitude affects the application of knowledge (A/K). RESULTS: The residents from the training program scored significantly higher in K (p < 0.005) and A/K (p < 0.04) than did the residents across the nation. No difference in scores evaluating A were detected (p = 0.26). Compared with the baseline knowledge of physicians in practice who had attended a workshop on cancer pain management, the national XRT residents had significantly lower scores in A (p < 0.006) and K (p < 0.001); however, no difference was found in A/K scores. After the workshop, the physicians in practice had significant gains in cancer pain management skills (p < 0.006). When the post-instruction survey was compared with the national XRT resident scores, there were marked differences in A (p < 0.00001), K (p < 0.00001) and A/K (p < 0.01). CONCLUSIONS: XRT residents in the United States are empathetic, but knowledge of cancer pain management is lacking. Instruction in the principles of cancer pain management can make a profound difference in knowledge and attitude. There is a need to recognize cancer pain management as a significant aspect of radiotherapeutic practice.

Attitude of Health Personnel↗