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Biomedical subjects

S Dick

Publications and source records attributed to S Dick.

10 recordsLinked to original sources
PubMed2005

Consideration of ergonomic aspects in the development of a new endoscopic navigation system.

During the development of new navigation systems, the ergonomic aspects of the accompanying software are seldom taken into account. The VN system is a navigation system working with real and previously stored neuroendoscopic images. The latter enable the module to execute virtual back movement, e.g. in case of bleeding. Several other modules are offered. The aim of the study was the ergonomic analysis of different modules and their learning curves in cadaveric heads. The endoscope was navigated by the neurosurgeon while another person operated the computer. A total of 128 experiments were performed with two software versions. When the landmark tracking module was used, a real learning curve could be observed. By contrast, testing the measurement module did not produce a learning curve. A significant reduction of the time required by the three modules investigated could be observed with software version 2. The module for virtual back movement works best with a minimum time of 20 s for image storage. During machine-human interactions ergonomic software use is important, especially if operative procedures are performed.

Clinical Competence↗
PubMed2001

Correlation between postoperative 3-[(123)I]iodo-L-alpha-methyltyrosine uptake and survival in patients with gliomas.

UNLABELLED: The aim of this study was to evaluate the prognostic value of SPECT imaging using the amino acid analog 3-[(123)I]iodo-L-alpha-methyltyrosine (IMT) in patients with gliomas. METHODS: One hundred fourteen consecutive patients with newly diagnosed gliomas were examined by IMT SPECT (low-grade glioma, n = 12; anaplastic astrocytoma or oligodendroglioma, n = 46; glioblastoma, n = 56). Seventy-one of these patients had undergone tumor resection 4-6 wk before SPECT imaging (group A). Forty-three patients with unresectable tumors were examined after stereotactic biopsy (group B). IMT uptake at the site of the tumor was assessed visually and quantified relative to a contralateral reference region (IMT uptake ratio). After IMT SPECT, all patients were treated with conformal radiotherapy. The median follow-up time was 27 mo. RESULTS: In group A, focal IMT uptake at the resection site was visible in 52 of 71 patients (73%). Median survival was only 13 mo in these patients, whereas median survival was reached in patients without focal IMT uptake (P = 0.02). Furthermore, the intensity of IMT uptake significantly correlated with survival: patients with an IMT uptake ratio > 1.7 were at a 4.6 times higher risk of death than were patients with a lower IMT uptake (P < 0.001). The IMT uptake ratio remained a significant prognostic factor when age and grading were included in a multivariate model. In contrast, IMT uptake did not correlate with survival in group B (P = 0.95). CONCLUSION: In patients with unresectable high-grade gliomas, IMT uptake appears not to correlate with the biologic aggressiveness of tumor cells. Nevertheless, the clear association between focal IMT uptake after tumor resection and poor survival suggests that IMT is a specific marker for residual tumor tissue. Therefore, IMT SPECT is expected to become a valuable tool for the planning and monitoring of local therapeutic modalities.

Adult↗
PubMed1999

Lysine: N6-hydroxylase: stability and interaction with ligands.

Recombinant lysine:N6-hydroxylase, rIucD, which is isolated as an apoenzyme, requires FAD and NADPH for its catalytic function. rIucD preparations have been found to undergo time-dependent loss in monooxygenase function due to aggregation from the initial tetrameric state to a polytetrameric form(s), a process which is reversible by treatment with thiols. Ligand-induced conformational changes in rIucD were assessed by monitoring its CD spectra, DSC profile, and susceptibility to both endo- as well as exopeptidases. The first two methods indicated the absence of any significant conformational change in rIucD, while the last approach revealed that FAD, and its analog ADP, can protect the protein from the deleterious action of proteases. NADPH was partially effective and L-lysine was ineffective in this regard. Deletion of the C-terminal segment, either by treatment with carboxypeptidase Y or by mutagenesis of iucD, results in the loss of rIucD's monooxygenase activity. These findings demonstrate the crucial role of the C-terminal segment in maintaining rIucD in its native conformation.

Adenosine Diphosphate↗
PubMed1998

Access to primary care for patients with diabetes at an urban public hospital walk-in clinic.

The purpose of this study was to determine the regular source of primary care, the content of care, and barriers to accessing primary care for 218 medically indigent adults with diabetes mellitus. Patients were surveyed at a public hospital walk-in clinic and were queried regarding demographics, regular source of care, and the content of care they received during the preceding year. Seventy percent of the patients were medically uninsured, and 60 percent had household incomes under $10,001. Forty-three percent reported no regular source of care, and 18 percent named an episodic care site as their regular source. Patients with a regular source of primary care had twice as many annual ambulatory visits as those without primary care. Patients with a regular source of primary care reported more diabetic-related services than those without. This patient population is largely poor and uninsured and has difficulty accessing primary care.

Analysis of Variance↗
PubMed1998

Voting with their feet: public hospitals, health reform, and patient choices.

OBJECTIVES: This study identified public hospital patients' preferences under managed care and health reform. METHODS: A cross-sectional survey of 348 ambulatory public hospital patients was conducted. RESULTS: Patients reported a high degree of loyalty to the public hospital given several hypothetical reform scenarios. Those patients who stated they would remain at the hospital increased (from 74.2% to 85.5%) when care elsewhere required copayment for medications and physician visits. CONCLUSIONS: Patients at one public hospital reported a high likelihood of remaining in the public system, and this likelihood increased when copayment for services was required elsewhere.

Adult↗
PubMed1996

Naive human alpha beta T cells respond to membrane-associated components of malaria-infected erythrocytes by proliferation and production of interferon-gamma.

Crude extracts of Plasmodium falciparum schizont-infected erythrocytes (PfSE) induce polyclonal activation of peripheral blood T lymphocytes from naive (malaria unexposed) humans. We demonstrate that the active component of PfSE is membrane bound, soluble in sodium dodecyl sulphate (SDS) and partially heat stable, but distinct from the tumour necrosis factor (TNF)-inducing, exoantigen-like activity of schizont extracts. Malaria pigment induces little or no T-cell activation. The responding cells are predominately CD4+, CD45RO+, T-cell receptor (TCR) alpha beta+. Contrary to previous reports, expansion of the TCR gamma delta+ subset was observed in cells from only one of eight donors. Proliferating cells secrete interferon-gamma (IFN-gamma) and release large amounts of soluble interleukin-2R (sIL-2R) into the culture supernatant but produce no detectable interleukin-4 (IL-4), a phenotype typical of the T-helper (Th)1 subset of CD4+ T cells. We propose that these activated T cells may initiate the inflammatory response to malaria infection in non-immunes and may contribute to the pathology of the disease.

Animals↗
PubMed1977

Hemispheric differences in simple reaction time to auditory stimuli of different frequencies.

To determine whether reaction time varies as a function of tone frequency and/or ear stimulated 27 adult subjects were presented with two two-tone series (1,000 Hz vs 2,500 Hz and 1,500 Hz vs 4,000 Hz) in a simple reaction-time paradigm. The analyses clearly indicated that the higher tone in each series and stimulation to the right ear resulted in significantly shorter reaction times. These results were interpreted as indicating that cerebral asymmetries are apparent in tasks and with stimuli that do not seem to require higher-order inferences regrading the functional organization of the cerebral hemispheres.

Adult↗
PubMedDate not supplied

Positive support.

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Abortion, Spontaneous↗