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Biomedical subjects

R Walker

Publications and source records attributed to R Walker.

At least 55 records · Page 3Linked to original sources
PubMed2001

Curved saccade trajectories: voluntary and reflexive saccades curve away from irrelevant distractors.

In this study we examined the impact of irrelevant distractors upon trajectories of reflexive and voluntary saccades. Observers made saccades to visual targets above and below fixation as directed by target appearance (reflexive) or by a central directional cue (voluntary) in the presence of an irrelevant distractor stimulus (a cross) whose appearance was simultaneous with target onset. We recorded saccade latency, amplitude and the magnitude of saccade curvature relative to the direct route from the start-to-end of the saccade. Previous studies of saccades curvature have used distractors to provide information about the saccade task and, as a result, have only examined trajectories of voluntary saccades. However, we have shown that both reflexive and voluntary saccades curved away from irrelevant distractors. The effect of irrelevant distractors indicates that observers do not need to attend to distractors in a voluntary fashion for distractors to modify saccade trajectories. Furthermore, it highlights an important parallel in curvature of saccades and reach trajectories, namely that both curve away from irrelevant distractors. The second important observation was that reflexive, as well as voluntary, saccades curved away from distractors. This suggests that curvature is not solely a consequence of voluntary control. These results have been considered within the context of inhibition-based theories of curvature derived from studies of saccade and manual reach trajectories.

Adolescent↗
PubMed2001

The use of mycophenolate mofetil suspension in pediatric renal allograft recipients.

Mycophenolate mofetil (MMF) is widely used to prevent acute rejection in adults after renal, cardiac, and liver transplantation. This study investigated the safety, tolerability, and pharmacokinetics of MMF suspension in pediatric renal allograft recipients. One hundred renal allograft recipients were enrolled into three age groups (33 patients, 3 months to <6 years; 34 patients, 6 to <12 years; 33 patients, 12 to 18 years). Patients received MMF 600 mg/m2 b.i.d. concomitantly with cyclosporine and corticosteroids with or without antilymphocyte antibody induction. One year after transplantation, patient and graft survival (including death) were 98% and 93%, respectively. Twenty-five patients (25%) experienced a biopsy-proven (Banff grade borderline or higher) or presumptive acute rejection within the first 6 months post-transplantation. Analysis of pharmacokinetic parameters for mycophenolic acid (MPA) and mycophenolic acid glucuronide showed no clinically significant differences among the age groups. The dosing regimen of MMF 600 mg/m2 b.i.d. achieved the targeted early post-transplantation MPA 12-h area under concentration-time curve (AUC0-12) of 27.2 microg h per ml. Adverse events had similar frequencies among the age groups (with the exception of diarrhea, leukopenia, sepsis, and anemia, which were more frequent in the <6 years age group) and led to withdrawal of MMF in about 10% of patients. Administration of MMF 600 mg/m2 b.i.d. is effective in prevention of acute rejection, provides predictable pharmacokinetics, and is associated with an acceptable safety profile in pediatric renal transplant recipients.

Adolescent↗
PubMed2001

Association of retinal vessel caliber and visual field defects in glaucoma.

PURPOSE: This study evaluates the asymmetry of peripapillary retinal vessel caliber between inferior and superior hemispheres in eyes with visual field defects predominantly in one hemifield. DESIGN: Observational case series. METHODS: In a retrospective study, 64 eyes of 64 patients with primary open-angle glaucoma who had a marked difference in visual field defects between hemifields and who had no history of diabetes, trauma, or vascular occlusive disease were studied. The diameters of the superior and inferotemporal vessels were measured at the optic disk border with calipers on an enlarged image. RESULTS: In 64 eyes, the average ratio of the superior temporal artery diameter to inferotemporal artery diameter was significantly greater in the eyes with predominantly superior visual field defects as compared with those with inferior defects (1.10 +/- 0.22 vs. 0.92 +/- 0.19, respectively, P =.002, two-tailed t test). This indicates that the arteriole corresponding to the hemifield with the greater visual field defect was narrower than the arteriole in the other hemifield. This relationship was confirmed using chi(2) analysis (P =.002) comparing the proportions of eyes with ratios greater or less than normal vessel caliber ratios (normal ratio = 0.95 from data reported by Jonas and associates to the location of the dominant field defect. No statistically significant relationship was detected between retinal vein diameter and localized visual field defects, as determined by both the unpaired t test and chi(2) analysis. CONCLUSION: In eyes with primary open-angle glaucoma, this study demonstrates a strong association between decreased peripapillary arteriole diameter and visual field defects in the corresponding hemifield. This reflects either an ischemic basis for glaucomatous damage or vascular constriction when there are fewer axons to nourish.

Adult↗
PubMed2001

Changing time in an operating suite.

This study focussed on time as a key resource within a hospital setting. The introduction of casemix-based funding, which changed the ways funds were obtained and distributed within the hospital, was accompanied by large cuts in the funds available to the hospital system. From the introduction of casemix-based funding to the conclusion of this study there was an increase of 20% in the number of cases through the operating suite. The increase was achieved, with a reduced budget, by intensifying work and increasing flexibility in the use of time. This approach to changing the use of time imposed considerable real 'costs' on staff, especially nurses, and created concerns about safety.

Attitude of Health Personnel↗
PubMed2001

The preparation and execution of saccadic eye and goal-directed hand movements in patients with Parkinson's disease.

The oculomotor and manual motor systems were studied in a two-segment movement task in a group of patients with Parkinson's disease and in age matched normal controls. In order to avoid reflexive motor movements the selection of the correct motor sequence was derived from the interpretation of symbolic (coloured) cues. The latencies and dynamics of eye and hand (pointing) movements performed during the first (fixed) movement segment were measured and the planning and execution processes were manipulated by varying the complexity of the second movement segment relative to the first (with regard to direction and amplitude). The results showed that the eye and hand movements made by patients with Parkinson's disease were not impaired in the initiation of the first movement segment. Interestingly, both Parkinson's patients and controls showed increased eye and hand reaction time latencies for the first movement when the second movement was in the direction opposite to the first. This indicates that the complexity of the second movement influences the execution of the first movement, and importantly that complexity affects motor initiation and execution processes in both normal subjects and in patients with Parkinson's disease. The execution of hand movements was found to be impaired in patients with Parkinson's disease as indicated by a reduced peak velocity of manual pointing responses when compared to age matched controls. By contrast, no differences were found in the dynamics of saccadic eye movements. This dissociation is consistent with the notion that the skeletomotor loop passes through the functionally corresponding portions of the basal ganglia independently of the oculomotor loop. Together, these results demonstrate that Parkinson's patients are able to generate multiple non-reflexive eye and hand movements and that the observed (manual) motor deficits are specific to the processes of motor execution.

Aged↗
PubMed2001

Reversible posterior leukoencephalopathy syndrome following CHOP chemotherapy for diffuse large B-cell lymphoma.

A 63-year-old female with stage IE diffuse large B-cell lymphoma developed reversible posterior leukoencephalopathy syndrome (RPLS) following CHOP chemotherapy, with typical clinical and radiological findings. RPLS is a rare neurological syndrome characterised by visual disturbances, seizures, headaches and altered conscious level which has been associated with malignant hypertension, pre-eclampsia and some drugs, including ciclosporin. It has not been previously reported following CHOP chemotherapy. Alternative treatment should be considered for patients who develop this rare complication.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2001

A noninvasive test for vesico-ureteric reflux in children.

OBJECTIVE: To report the development and testing of a device for the noninvasive diagnosis of vesico-ureteric reflux (VUR) which avoids the need for urethral catheterization (currently required to reliably determine the presence of VUR), and which thus avoids the anxiety of parents and patients that causes many families to refuse such evaluation. PATIENTS AND METHODS: Fifty-four children (49 girls and five boys, mean age 7.2 years, range 4-14) previously evaluated as having VUR volunteered to participate; no child was symptomatic at the time of the study. Refluxing units were known to be present by voiding cysto-urethrography (within 1 year, mean 7 months) in 45 and absent in 16. The device developed acquires electronically processed acoustic signals from the child during an observed urination. The signals are then analysed 'off-line' to determine the presence or absence of VUR. The initial preparation for the test included: (i) a full bladder [at least 0.80 x ((2 + age) x 30 mL)] measured by ultrasonography; and (ii) localization of the pelvi-ureteric junction by ultrasonography to accurately place the device's sensors on the child's back. The children were then positioned at a commode after placing the sensors; the recording was started and continued until voiding occurred. The children were tested with the recording and analysis team unaware of the presence and/or degree of VUR. The first 47 studies were single-kidney examinations and the remaining seven included simultaneous monitoring of both kidneys. RESULTS: Sixty-one renal units were assessed and interpretable signals were obtained from 54 (89%). There were seven episodes of 'system failure' when no interpretable data were obtained. One unit with no VUR had a 'reflux' signal; in four kidneys, spontaneous (two) and postsurgical (two) resolution of reflux was predicted by the testing and subsequently verified by cyclic radionuclide cystography. CONCLUSIONS: This noninvasive diagnostic technique detected VUR in 35 of 37 refluxing units and verified no reflux in 16 of 17 units without VUR. Further refinements may allow this technology to be used in all children with suspected VUR.

Adolescent↗
PubMed2001

The potential biocontrol agent Pseudomonas antimicrobica inhibits germination of conidia and outgrowth of Botrytis cinerea.

AIMS: Antifungal metabolites of Pseudomonas antimicrobica have previously been shown to inhibit conidial germination of the grey mould pathogen Botrytis cinerea. In this study, metabolites of the bacterium have been tested at different stages of Botrytis germination to determine their effects on germ tube production and extension. METHODS AND RESULTS: Metabolites were added to conidia that had been pre-incubated for either 120 or 255 min. Pseudomonas antimicrobica inhibited B. cinerea conidial germination and caused a significant reduction in germ tube extension, irrespective of the stage of germination. Abnormal germination and a reduction in the frequency of lateral branching of the germ tubes in the presence of the metabolites were also reported, suggesting interference with normal hyphal development. CONCLUSION: The bacterium can inhibit germination of conidia and extension of germ tubes at different stages of Botrytis development. SIGNIFICANCE AND IMPACT OF THE STUDY: The antagonistic activity of the bacterium has promising implications for its use as a biocontrol agent.

Antifungal Agents↗
PubMed2001

Novel erythropoiesis stimulating protein for treatment of anemia in chronic renal insufficiency.

BACKGROUND: Novel erythropoiesis stimulating protein (NESP) is a glycoprotein with a threefold longer terminal half-life than recombinant human erythropoietin (rHuEPO) in humans. The aim of this study was to determine whether NESP is effective for the treatment of anemia at a reduced dosing frequency relative to rHuEPO in patients with chronic renal failure not yet on dialysis [chronic renal insufficiency (CRI)]. METHODS: This was a multicenter, randomized, open-label study. A total of 166 rHuEPO-naive patients with CRI were randomized in a 3:1 ratio to receive NESP (0.45 microg/kg once weekly) or rHuEPO (50 U/kg twice weekly) administered subcutaneously for up to 24 weeks. Dose adjustments were made as necessary to achieve a hemoglobin response, defined as an increase > or =1.0 g/dL from baseline and a concentration > or = 11.0 g/dL. RESULTS: During the 24-week treatment period, 93% (95% CI, 87 to 97%) of patients receiving NESP and 92% (95% CI, 78 to 98%) of patients receiving rHuEPO achieved a hemoglobin response. The median time to response was seven weeks (range of 3 to 25 weeks) in both groups. After correction of anemia, mean hemoglobin concentrations were maintained within the target range of 11.0 to 13.0 g/dL for the remainder of the 24-week treatment period. The safety profiles of NESP and rHuEPO were similar, and no antibodies were detected to either drug. CONCLUSIONS: These results demonstrate that NESP safely and effectively corrects and maintains hemoglobin concentrations at a reduced dosing frequency relative to rHuEPO in patients with CRI, providing a potential benefit to patients and health care providers.

Aged↗
PubMed2001

The value of transcranial Doppler in predicting cerebral ischaemia during carotid endarterectomy.

OBJECTIVES: transcranial Doppler (TCD) measurement of middle cerebral artery velocity (MCAV) is an indirect method of assessing cerebral blood flow and therefore predicting patients at risk of stroke during carotid endarterectomy (CEA), and may be used to determine the need for shunting. This study evaluates the accuracy of three accepted TCD criteria in predicting the need for a shunt. DESIGN: prospective study. METHODS: one hundred and twenty consecutive CEA were performed under loco/regional anaesthesia. Patients monitored by TCD and Awake neurological examination were included. Shunts were inserted if there was neurological deterioration. Awake patient monitoring was compared with the three TCD criteria. RESULTS: inadequate TCD recordings were obtained in 16 operations (13%). In the remainder (104 cases), 12 developed symptoms of cerebral ischaemia and required a shunt (12%). Comparisons with the three accepted criteria were as follows: (1) m MCAV <30 cm/s had a sensitivity, specificity, PPV and NPV of 92%, 49%, 19%, and 98%, respectively; (2) clamp/pre-clamp ratio <0.6 had a sensitivity, specificity, PPV and NPV of 92%, 75%, 33% and 99%, respectively; (3) greater than 50% reduction in m MCAV had a sensitivity, specificity, PPV and NPV valves of 83%, 77%, 32% and 97%, respectively. CONCLUSIONS: TCD flow velocities are not a reliable method for detecting cerebral ischaemia and therefore determining the need for a shunt in CEA.

Aged↗
PubMed2001

Patient and hospital benefits of local anaesthesia for carotid endarterectomy.

OBJECTIVES: this study reviews and compares carotid endarterectomy (CEA) performed under local anaesthesia (LA) with CEA performed under general anaesthesia (GA) in a single institution. METHODS: data were collected prospectively from 240 CEA procedures. 140 GA CEA procedures are compared to 100 LA CEA procedures in terms of outcome, operative techniques, complications, and length of stay. RESULTS: the groups were similar for age, gender distribution and preoperative risk factors. There were more asymptomatic patients in the LA group. There were no significant differences in death, stroke or death/stroke rate between the two techniques. LA CEA was associated with lower shunt rate (LA 13%, GA 50%, p < 0.001), lower incidence of intraoperative hypotension (LA 8%, GA 40%, p < 0.001), decreased hospital stay (median (IQ); LA 2 (1-2), GA 3 (1-4), and a cost saving of pound235 per CEA procedure. CONCLUSIONS: carotid endarterectomy can be performed safely under local anaesthesia with the advantage that LA CEA enables the surgeon to monitor and selectively shunt patients more accurately. In addition LA CEA is associated with a shorter hospital stay and important cost savings.

Adult↗
PubMed2001

Pregabalin in patients with postoperative dental pain.

Pregabalin is an analogue of the inhibitory neurotransmitter gamma-aminobutyric acid. In preclinical models, it has shown activity as an analgesic agent. A randomized, double-blind, placebo-controlled, parallel-group trial was undertaken to compare pregabalin to placebo and 400 mg of ibuprofen using a dental pain model. Study medication was administered postoperatively to patients who had undergone elective surgery to remove one or two third molars, at least one of which was mandibular and fully or partially impacted in bone. The study was conducted in the UK at a single centre and evaluated pregabalin at doses of 50 and 300 mg. Primary efficacy parameters included pain relief (PR), pain intensity difference (PID), pain relief intensity difference (PRID), time to onset of analgesia, and duration of analgesia. The patient's global impression of the study medication was used as a secondary efficacy parameter. Efficacy data were evaluated for the intent-to-treat (ITT) population, defined as all randomized patients who took study medication. Results showed that there were statistically significant differences in PR, PID, and PRID between the 300-mg pregabalin group and placebo. In addition, the 300-mg pregabalin group had a significantly longer duration of analgesia than the ibuprofen group and had the highest score on the patient global impression of study medication. Adverse events were reported more frequently in the pregabalin 300-mg group. Pregabalin appears to have significant analgesic properties in the third molar extraction model. Further research is needed to confirm these findings.

Adolescent↗
PubMed2001

Comparative study of the activity of total hip arthroplasty patients and normal subjects.

The walking activity of normal subjects and total hip arthroplasty (THA) patients from the Wrightington Hospital for Joint Disease and The General Infirmary at Leeds was assessed by means of electronic pedometers. The principal objectives were to establish the extent to which joint arthroplasty patients recover their activity relative to normal subjects and to establish the number of loading cycles to which prostheses should be subjected in joint simulator studies of implant performance. A further objective was to establish an experimental procedure for the assessment of the role of activity in contributing to the well-known scatter in the measurements of femoral head penetration into acetabular cups in in vivo studies of implant performance. The last-mentioned issue is addressed in another article ([1]). The walking activity of 2 normal subjects of disparate ages was assessed during 1 full year. It was concluded that fair estimates of activity could be achieved by recording pedometer readings during successive 2- to 4-week periods. This approach was adopted in the full assessment of the walking activity of cohorts of normal subjects and THA patients. Linear regression expressions relating the number of steps taken daily and the annual number of loading cycles on each leg to age are presented for normal subjects and THA patients. In all cases, activity declines with age, but it is shown that total joint arthroplasty is not at all restrictive on walking activity-a remarkable testimony to the efficacy of total joint arthroplasty. Attention is drawn, however, to different levels of activity of THA patients recorded in the present United Kingdom study and a similar survey conducted in California.

Activities of Daily Living↗
PubMed2001

First wave PMS pilots: a critical analysis of documentation.

Contracts and interim local evaluation reports for the 14 first wave PMS pilots in Northern and Yorkshire region were analysed by documentary analysis. Both contracts and reports were found to vary considerably in size and scope. Most contracts contained aims and objectives that were too broad or vague to guide project management and they lacked useful milestones. This made it difficult to identify criteria for measuring success. The local evaluation reports were also of variable quality. It is recommended that contracts should be accompanied by a development plan containing specific objectives, timescale and process for implementation as well as an evaluation strategy. The relative importance of different targets should be agreed and specified at the outset, to allow weighting of partial success, where some objectives, but not others, are achieved. Project milestones would be made explicit and measurable in the development plan. More clarity in contracts and evaluation for future pilots is essential.

Continuity of Patient Care↗
PubMed2001

Quantitative cytomorphologic analyses of Papanicolaou-stained smears from oral lichen planus.

OBJECTIVE: To apply quantitative techniques to cytologic smears in order to improve the diagnostic sensitivity of cytology in the detection of malignant change in the oral cavity. STUDY DESIGN: Eighty-two patients with lesions of oral lichen planus were investigated. A total of 247 Papanicolaou-stained buccal smears underwent nuclear and cytoplasmic area measurements using a TV image analyzer. RESULTS: The cytomorphologic results of this study suggest that lesions of oral lichen planus contain smaller cells and nuclei than those observed in clinically normal oral mucosal smears. There was a statistically significant reduction in nuclear area (P < .001) and cytoplasmic area (P < .05) for the oral lichen planus smears. CONCLUSION: The TV image analysis system could provide a valuable method of quantifying cell changes in oral smears collected from oral mucosa as a method of monitoring lesions of oral lichen planus.

Analysis of Variance↗