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Biomedical subjects

S Greenwood

Publications and source records attributed to S Greenwood.

14 recordsLinked to original sources
PubMed1999

Progression of the morphogenetic furrow in the Drosophila eye: the roles of Hedgehog, Decapentaplegic and the Raf pathway.

During Drosophila eye development, Hedgehog (Hh) protein secreted by maturing photoreceptors directs a wave of differentiation that sweeps anteriorly across the retinal primordium. The crest of this wave is marked by the morphogenetic furrow, a visible indentation that demarcates the boundary between developing photoreceptors located posteriorly and undifferentiated cells located anteriorly. Here, we present evidence that Hh controls progression of the furrow by inducing the expression of two downstream signals. The first signal, Decapentaplegic (Dpp), acts at long range on undifferentiated cells anterior to the furrow, causing them to enter a 'pre-proneural' state marked by upregulated expression of the transcription factor Hairy. Acquisition of the pre-proneural state appears essential for all prospective retinal cells to enter the proneural pathway and differentiate as photoreceptors. The second signal, presently unknown, acts at short range and is transduced via activation of the Serine-Threonine kinase Raf. Activation of Raf is both necessary and sufficient to cause pre-proneural cells to become proneural, a transition marked by downregulation of Hairy and upregulation of the proneural activator, Atonal (Ato), which initiates differentiation of the R8 photoreceptor. The R8 photoreceptor then organizes the recruitment of the remaining photoreceptors (R1-R7) through additional rounds of Raf activation in neighboring pre-proneural cells. Finally, we show that Dpp signaling is not essential for establishing either the pre-proneural or proneural states, or for progression of the furrow. Instead, Dpp signaling appears to increase the rate of furrow progression by accelerating the transition to the pre-proneural state. In the abnormal situation in which Dpp signaling is blocked, Hh signaling can induce undifferentiated cells to become pre-proneural but does so less efficiently than Dpp, resulting in a retarded rate of furrow progression and the formation of a rudimentary eye.

Animals↗
PubMed1997

Managing deliberate self-harm: the A & E perspective.

This paper reports on a retrospective survey of the Accident and Emergency (A & E) treatment of patients who have deliberately harmed themselves. Reasons for self-harm are identified, and current management in A & E is discussed. Suggestions are made for providing these patients with high-quality holistic care instead of treating only their physical injuries.

Emergency Service, Hospital↗
PubMed1997

Different levels of Ras activity can specify distinct transcriptional and morphological consequences in early Drosophila embryos.

The terminal portions of the Drosophila body pattern are specified by the localized activity of the receptor tyrosine kinase Torso (Tor) at each pole of the early embryo. Tor activity elicits the transcription of two 'gap' genes, tailless (tll) and huckebein (hkb), in overlapping but distinct domains by stimulating the Ras signal transduction pathway. Here, we show that quantitative variations in the level of Ras activity can specify qualitatively distinct transcriptional and morphological responses. Low levels of Ras activity at the posterior pole direct tll but not hkb transcription; higher levels drive transcription of both genes. Correspondingly, low levels of Ras activity specify a limited subset of posterior terminal structures, whereas higher levels specify a larger subset. However, we also show that the response to Ras activity is not uniform along the body. Instead, levels of Ras activity which suffice to drive tll and hkb transcription at the posterior pole fail to drive their expression in more central portions of the body, apparently due to repression by other gap gene products. We conclude that tll and hkb transcription, as well as the terminal structures, are specified by two inputs: a gradient of Ras activity which emanates from the pole, and the opposing influence of more centrally deployed gap genes which repress the response to Ras.

Animals↗
PubMed1994

An oncogenic form of human raf can specify terminal body pattern in Drosophila.

Terminal portions of the Drosophila body pattern are specified by an extracellular ligand generated at each end of the early syncytial embryo. This ligand triggers the localized transcription of two gap segmentation genes, tailles (tll) and huckebein (hkb) through a signal transduction cascade involving the receptor tyrosine kinase torso (tor) and homologues of ras, raf, and mek (map kinae kinase). In contrast to the ligand, these signal transducing components are expressed ubiquitously. Here, we show that a constitutively active form of human raf1 protein can trigger tll and hkb transcription in Drosophila embryos and specify elements of the terminal body pattern. This result indicates a strong functional conservation between Drosophila and mammalian raf proteins and argues that the localized activity of Drosophila raf (D-raf) normally carries spatial information specifying the end portions of the body.

Animals↗
PubMed1994

A randomized study of telephone contact following completion of radiotherapy.

The hypothesis tested was that routine contact by telephone might significantly improve the adequacy of support for patients during the potentially stressful period between completing radiotherapy and the first follow-up visit. The study was a randomized controlled trial in which 100 patients were allocated either to telephone contact (intervention arm) or usual care (control arm). Adequacy of support was assessed by a questionnaire administered at the first follow-up visit. There were no significant differences in the perceived adequacy of support between the two arms. Of the 72 patients who completed questionnaires, 76% of those in the intervention arm versus 61% in the control arm rated their support after radiotherapy as 'extremely adequate'. The 95% confidence interval (CI) for this 15% rate difference was -6- +36. Analysis by intention to treat showed a rate difference of only 4% (95% CI -17-(+)25) in favour of intervention. We conclude that, given the limited resources currently available, it is not possible to justify a policy of routine contact by telephone for all patients completing radiotherapy.

Adult↗
PubMed1992

Solitary true cyst of the pancreas in an adult.

A 35-yr-old woman was presented to the hospital because of nausea 20-30 min after eating, associated with weight loss. A CT scan revealed a cystic lesion in the neck of the pancreas. At operation, a 3-cm diameter cyst was excised from the pancreas. Endoscopic retrograde pancreatography (ERP) was used intraoperatively to identify the transected pancreatic duct, after which a Roux-Y pancreaticojejunostomy was performed. Histologically, the cyst proved to be unilocular and was lined with cuboidal epithelium. The natural history of this lesion is unknown as only four previous case reports of unilocular true cysts in adults have been reported in the English literature. These are reviewed.

Adult↗
PubMed1989

Body Recall.

Explore the source record for details and available documents.

Aged↗
PubMed1983

Survey of men and women residents entering United States obstetrics and gynecology programs in 1981.

In July 1981, questionnaires were distributed to 1,128 residents entering the field of obstetrics and gynecology throughout the United States; 546 (48%) were returned and evaluated, 229 from women (42%) and 317 from men (58%). Factors that related to the choice of the specialty showed a universal interest in the birthing process and the surgical aspects of the specialty, with a large majority also interested in health education, endocrinology, primary care of young people, and achievement of a greater understanding of sexuality. Private partnership practice was favored by most of the respondents. Men attributed a greater importance to income than did women, who were more interested in a salaried practice and less irregularity of hours. Women tended to be more liberal on questions that were related to controversial medical and ethical issues in the field of obstetrics and gynecology. Role models, half of whom were teachers, were equally common to men and women (66%).

Adult↗