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Biomedical subjects

C Baker

Publications and source records attributed to C Baker.

At least 19 recordsLinked to original sources
PubMed2005

Diffusion tensor imaging: possible implications for radiotherapy treatment planning of patients with high-grade glioma.

AIMS: Radiotherapy treatment planning for high-grade gliomas (HGG) is hampered by the inability to image peri-tumoural white-matter infiltration. Diffusion tensor imaging (DTI) is an imaging technique that seems to show white-matter abnormalities resulting from tumour infiltration that cannot be visualised by conventional computed tomography or magnetic resonance imaging (MRI). We propose a new term, the image-based high-risk volume (IHV) for such abnormalities, which are distinct from the gross-tumour volume (GTV). For IHV based on DTI, we use the term IHVDTI. This study assesses the value of DTI for the individualisation of radiotherapy treatment planning for patients with HGG. METHODS: Seven patients with biopsy-proven HGG were included in a theoretical planning exercise, comparing standard planning techniques with individualised plans based on DTI. Standard plans were generated using a 2.5 cm clinical target volume (CTV) margin added to the GTV. For DTI-based plans, the CTV was generated by adding a 1 cm margin to the IHVDTI. Estimates of normal tissue complication probability (NTCP) were calculated and used to estimate the level of dose escalation that could be achieved using the DTI-based plans. RESULTS: The use of DTI resulted in non-uniform margins being added to the GTV to encompass areas at high risk of tumour involvement, but, in six out of seven cases, the IHVDTI was encapsulated by the standard CTV margin. In all cases, DTI could be used to reduce the size of the planning-target volume (PTV) (mean 35%, range 18-46%), resulting in escalated doses (mean 67 Gy, range 64-74 Gy), with NTCP levels that matched the conventional treatment plans. CONCLUSION: DTI can be used to individualise radiotherapy target volumes, and reduction in the CTV permits modest dose escalation without an increase in NTCP. DTI may also be helpful in stratifying patients according to the degree of white-matter infiltration.

Adult↗
PubMed2005

Synthesis and antibacterial properties of silver nanoparticles.

Nanometer sized silver particles were synthesized by inert gas condensation and co-condensation techniques. Both techniques are based on the evaporation of a metal into an inert atmosphere with the subsequent cooling for the nucleation and growth of the nanoparticles. The antibacterial efficiency of the nanoparticles was investigated by introducing the particles into a media containing Escherichia coli. The antibacterial investigations were performed in solution and on petri dishes. The silver nanoparticles were found to exhibit antibacterial effects at low concentrations. The antibacterial properties were related to the total surface area of the nanoparticles. Smaller particles with a larger surface to volume ratio provided a more efficient means for antibacterial activity. The nanoparticles were found to be completely cytotoxic to E. coli for surface concentrations as low as 8 microg of Ag/cm2.

Anti-Bacterial Agents↗
PubMed2004

A prognostic index for operable, node-negative breast cancer.

Clinical data and samples from patients diagnosed, more than 10 years previously, with operable node-negative breast cancer (participants in the Scottish Adjuvant Tamoxifen trial), were revisited. Cases with two distinct categories of outcome were selected; more than 10 years disease-free survival ('good outcome') or distant relapse within 6 years of diagnosis ('poor outcome'). An initial set of cases was analysed for a range of putative prognostic markers and a prognostic index, distinguishing the two outcome categories, was calculated. This index was then validated by testing its predictive power on a second, independent set of cases. A combination of histological grade plus immunochemical staining for BCL-2, p27 and Cyclin D1, generated a useful prognostic index for tamoxifen-treated patients but not for those treated by surgery alone. The value of the index was confirmed in a second set of tamoxifen-treated, early stage breast cancers. Overall, it correctly predicted good and poor outcome in 79 and 74% of cases, respectively (odds ratio 11.0). Other markers assessed added little to prediction of outcome. In the case of molecular assays, sensitivity and reliability were compromised by the age of the tissue specimens and the variability of fixation protocols. In selecting patients for adjuvant systemic chemotherapy, the proposed index improves considerably on current international guidelines and matches the performance reported for 'gene-expression signature' analysis.

Biomarkers, Tumor↗
PubMed2003

Corticotropin-releasing hormone immunoreactivity in human T and B cells and macrophages: colocalization with arginine vasopressin.

Corticotropin-releasing hormone (CRH) and arginine vasopressin (AVP) are expressed in cells of the immune system where they exert immunomodulatory roles, but these neuropeptides are poorly characterized in human immune tissues. The aim of this study was to determine concentrations and distribution of CRH and AVP in nonactivated human peripheral blood mononuclear cells (PBMC). PBMC from normal human subjects were separated into enriched subpopulations of T and B cells and monocytes/macrophages by a magnetic bead/monoclonal antibody technique. CRH and AVP were measured in cell extracts by radioimmunoassay (RIA). CRH-immunoreactivity (ir) ranged 0.24-0.8 fmol/million cells (n = 6 subjects) in T cell extracts, 0.4-2.7 fmol/million cells (n = 4) in B cells and 0.63-2.16 fmol/million cells (n = 4) in macrophages. AVP-ir ranged 0.2-0.95 fmol/million cells in T cell extracts, <0.1-0.8 fmol/million cells in B cells and 0.14-3.19 fmol/million cells in macrophages. Reversed-phase high-performance liquid chromatography (HPLC) of T and B cell extracts revealed a peak of CRH-ir which coeluted with synthetic CRH-41; this peak was not present in macrophages. A second peak of CRH-ir which eluted in a more hydrophobic position was observed in extracts of T and B cells and macrophages. This unidentified form of CRH-ir is the predominant form of CRH-ir in nonactivated human PBMC. This is the first study to demonstrate that CRH-ir and AVP-ir are colocalized within human T cells, B cells and monocytes/macrophages. We have confirmed observations of a variant form of CRH-ir in human PBMC and show that this is the predominant form in macrophages and B cells whereas CRH-ir, which coelutes with CRH(1-41) on HPLC, is present in significant amounts only in T cells. These data also confirm that CRH-ir in human PBMC is not urocortin because the antiserum used in the CRH RIA does not bind to urocortin.

Arginine Vasopressin↗
PubMed2001

Peripheral target contact regulates Ca2+ channels in the cell bodies of bullfrog sympathetic ganglion B-neurons.

Tyrosine-hydroxylase immunohistochemistry demonstrated that a single injection of 120 mg/kg 6-hydroxydopamine (6-OHDA) reversibly disconnected bullfrog sympathetic ganglia from their peripheral targets. This was correlated with a decrease in sympathetic outflow to the eyes and a reversible decrease in pupil diameter. 6-OHDA did not damage the cell bodies of ganglionic neurons. Calcium channel current in ganglionic B-neurons, (measured at -10 mV; holding potential -60 mnV; Ba2+ as charge carrier; IBa) was reduced. It reached a minimum of about 40% of control amplitude 7-14 days after 6-OHDA injection and recovered to 73% of control amplitude after 63 days. 6-OHDA induced loss and recovery of functional sympathetic innervation of peripheral target tissues, as determined by measurement of pupil diameter, occurred at a similar rate. Thus, pupil diameter attained mininum values 7-14 days after 6-OHDA treatment and recovered to 81% of control after 63 days. The properties of Ca2+ channels in sympathetic neurons are, therefore, determined by continuity of contact with peripheral target. 6-OHDA also decreased the peak amplitude and duration of the afterhyperpolarization (a.h.p) that follows the action potential (a.p.). The rate of recovery of a.h.p duration was more rapid than the rate of recovery of peak a.h.p. amplitude. This may reflect known differences in properties of two types of Ca2+-sensitive K currents. IC and IAHP, IC, which is responsible for the peak amplitude of the a.h.p has a low affinity for Ca2+, whereas IAHP, which determines a.h.p. duration, has higher Ca2+ affinity.

Action Potentials↗
PubMed2001

Bexarotene capsules and gel for previously treated patients with cutaneous T-cell lymphoma: results of the Australian patients treated on phase II trials.

Bexarotene (Targretin, LGD1069) is a novel synthetic retinoid analogue that binds selectively to retinoid X receptors. We describe eight previously treated patients who entered phase II international multicentre studies examining the role of bexarotene in cutaneous T-cell lymphoma. Patients received either the oral formulation (n = 7) or the topical gel (n = 1). Of the seven patients who received 300 mg/m2 per day capsules, five (71%) achieved a partial response, with mean time to onset of response of 27 days (range, 20-29) with responses persisting for a mean of 92 days (range, 57-115). The single patient receiving the topical preparation (stage IB) remains in partial response at 31 months. The major toxicity with oral administration was hypertriglyceridaemia requiring therapy. Bexarotene capsules and gel are active and generally well-tolerated agents in patients with cutaneous T-cell lymphoma and studies examining its role in previously untreated patients or as part of combination therapy are warranted.

Administration, Oral↗
PubMed2001

Prevalence and risk factors for hepatitis C virus infection at an urban Veterans Administration medical center.

This study was designed to determine the seroprevalence and risk factors for hepatitis C virus (HCV) infection in veterans. Anti-HCV testing was performed in 1,032 patients and a questionnaire regarding sociodemographic characteristics and potential risk factors was administered. Adjusted prevalence of unique HCV-positive patients using outpatient services was 17.7% (95% confidence interval [CI] 17.2%, 18.2%). The following risk factors were associated with HCV infection: a history of injection drug use (IDU), receipt of blood transfusion prior to 1992, history of tattoo (odds ratio [OR], 2.93; 95% CI, 1.70-5.08), combat job as a medical worker (OR, 2.68; 95% CI, 1.25-5.60), history of incarceration over 48 hours (OR, 2.56; 95% CI, 1.52-4.32), greater than 15 lifetime sexual partners (OR, 1.61; 95% CI, 0.94-2.76) and sexual relations with a prostitute (OR, 0.46; 95% CI, 0.25-0.82). We concluded that HCV is common in veterans. Risk factors independently associated with infection are IDU, prior transfusion, prior tattoo, combat medical work, incarceration, and multiple opposite sex partners. Infection with HCV among veterans is strongly associated with traditional risk factors for infection and less strongly associated with combat-related risk.

Adult↗
PubMed2001

D-penicillamine in systemic sclerosis? Yes!

The use of D-penicillamine in systemic sclerosis (SSc) has been controversial. We have reviewed the major published studies on this drug in SSc with diffuse cutaneous (dc) involvement and summarized our own recent experience in dcSSc patients treated with and without D-penicillamine. We conclude that D-penicillamine favourably alters the natural history of skin involvement in dcSSc, even when used in low dose. Furthermore, recurrence of diffuse skin change after discontinuation of D-penicillamine and improvement in skin thickening after reinitiation of the drug support its effectiveness. We believe that the rheumatologic community should use D-penicillamine in patients with early dcSSc.

Antirheumatic Agents↗
PubMed2001

Sticks and stones: racism as experienced by adolescents in New Brunswick.

The purpose of the study was to describe both the nature of racism as experienced by adolescent self-described victims in the province of New Brunswick and their response to the perceived racist incidents. A qualitative methodology based on the constructivist paradigm was used. In-depth interviews were conducted with non-White adolescent victims of racism and with parents of victims. Although the study was initiated in response to an eruption of publicity about teenage racial violence, the findings indicate that racist incidents were not a new phenomenon for the participants. They described a low-key but long-term problem that had begun when they entered the public school system. Name-calling was by far the most common form of racism identified and it played a part in most of the other incidents described; dismissed as harmless by authority figures, it appeared to have long-term consequences for its targets. The participants' response to racism was found to have three phases: splintered universe, spiralling resistance, and disengagement. The results suggest that nurses working in the field of school health should address issues of racism among children and adolescents.

Adolescent↗
PubMed2000

Sensory processing of water currents by fishes.

Water currents are extremely important in the aquatic environment and play a very significant role in the lives of fishes. Sensory processing of water currents involves a number of sensory modalities including the inner ear, vision, tactile sense and the mechanosensory lateral line. The inner ear will detect whole-body accelerations generated by changes in flow, or by turbulence, whereas visual and tactile inputs will signal translational movement with respect to an external visual or tactile reference frame. The superficial neuromasts of the mechanosensory lateral line detect flow over the surface of the body and have the appropriate anatomical distribution and physiological properties to signal the strength and the direction of flow and, hence, contribute to the detection of regional differences in flow over different parts of the body.

Animals↗
PubMed2000

Undecylenic acid inhibits morphogenesis of Candida albicans.

Resilient liners are frequently used to treat denture stomatitis, a condition often associated with Candida albicans infections. Of 10 liners tested, 2 were found to inhibit the switch from the yeast form to hyphae and a third was found to stimulate this switch. The inhibitor was determined to be undecylenic acid.

Candida albicans↗
PubMed2000

Building a vision for the future: strategic planning in a shared governance nursing organization.

Today's health care delivery environment is marked by extreme turbulence and ever-increasing complexity. Now, more than ever, an organization's strategic plan must do more than outline a business plan. Rather, the strategic plan is a fundamental tool for building and sustaining an organizational vision for the future. The strong, dynamic strategic plan (1) represents a long-range vision for improving organizational performance, (2) provides a model for planning and implementing structures and processes for the management of outcomes, (3) reflects and shapes the organizational culture and customer focus, (4) provides decision support for difficult operational choices made day to day, and (5) integrates and aligns the work of the organization. This article describes the development, implementation, and evaluation of a methodology for strategic planning within a shared governance nursing organization. Built upon the strategic plan of the hospital, the process undertaken by the nursing organization reflects the following commitments: (1) to develop a strategic plan that is meaningful and part of daily work life at all levels of the nursing organization, (2) to make the plan practical and realistic through incremental building, (3) to locate and articulate accountability for each step, and (4) to build in a process for checking progress toward goal achievement and readjusting the plan as necessary.

Decision Making, Organizational↗