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Biomedical subjects

R Gray

Publications and source records attributed to R Gray.

At least 91 records · Page 5Linked to original sources
PubMed2000

Severe normal tissue complication correlates with increased in vitro fibroblast radiosensitivity in radical prostate radiotherapy: a case report.

The radiation responses of fibroblasts taken from four patients undergoing radiotherapy for prostate cancer were evaluated in vitro. One patient exhibited a severe normal tissue late reaction after radiotherapy, and the fibroblasts from this patient also showed increased radiosensitivity. The other three patients exhibited a normal clinical response, and their fibroblast response in vitro was also considered normal when compared with previously published data from our laboratory. When cells were allowed to repair potentially lethal damage (PLDR), the differences between cell lines were reduced; therefore, a deficiency in PLDR did not cause the differences in radiosensitivity. Fractionated radiation resulted in elevated survival due to repair of sublethal damage (SLDR), and the differences in radiosensitivity were increased. In addition, the survival curves displayed an upward bending nature, indicative of an adaptive response. Thus, adaptive response and ability to modify it may play an important role in fractionated radiotherapy. Int. J. Cancer (Radiat. Oncol. Invest.) 90, 336-342 (2000).

Aged↗
PubMed2000

Oral temazepam.

Explore the source record for details and available documents.

Anti-Anxiety Agents↗
PubMed2000

Control of sexually transmitted diseases for HIV-1 prevention: understanding the implications of the Mwanza and Rakai trials.

Two randomised controlled trials of sexually transmitted disease (STD) treatment for the prevention of HIV-1 Infection, in Mwanza, Tanzania, and Rakai, Uganda, unexpectedly produced contrasting results. A decrease in population HIV-1 incidence was associated with improved STD case management in Mwanza, but was not associated with STD mass treatment in Rakai. Some reductions in curable STDs were seen in both studies. These trials tested different interventions in different HIV-1 epidemic settings and used different evaluation methods; the divergent results may be complementary rather than contradictory. Possible explanations include: differences in stage of the HIV-1 epidemic, which can influence exposure to HIV-1 and the distribution of viral load in the infected population; potential differences in the prevalence of Incurable STDs (such as genital herpes); perhaps greater Importance of symptomatic than symptomless STDs for HIV-1 transmission; and possibly greater effectiveness of continuously available services than of intermittent mass treatment to control rapid STD reinfection. Implications of the trials for policy and future research agenda are discussed.

Adolescent↗
PubMed2000

Simulated self-motion alters perceived time to collision.

Many authors have assumed that motor actions required for collision avoidance and for collision achievement (for example, in driving a car or hitting a ball) are guided by monitoring the time to collision (TTC), and that this is done on the basis of moment-to-moment values of the optical variable tau [1] [2] [3]. This assumption has also motivated the search for single neurons that fire when tau is a certain value [4] [5] [6] [7] [8]. Almost all of the laboratory studies and all the animal experiments were restricted to the case of stationary observer and moving object. On the face of it, this would seem reasonable. Even though humans and other animals routinely perform visually guided actions that require the TTC of an approaching object to be estimated while the observer is moving, tau provides an accurate estimate of TTC regardless of whether the approach is produced by self-motion, object-motion or a combination of both. One might therefore expect that judgements of TTC would be independent of self-motion. We report here, however, that simulated selfmotion using a peripheral flow field substantially altered estimates of TTC for an approaching object, even though the peripheral flow field did not affect the value of tau for the approaching object. This finding points to long range interactions between collision-sensitive visual neurons and neural mechanisms for processing self-motion.

Depth Perception↗
PubMed2000

Enhanced in vitro radiosensitivity of skin fibroblasts in two patients developing brain necrosis following AVM radiosurgery: a new risk factor with potential for a predictive assay.

PURPOSE: Radiosurgery is an effective treatment for arteriovenous malformations (AVM) with a low risk of developing brain necrosis. Models have been developed to predict the risk of complications. We postulated that genetic differences in radiosensitivity may also be a risk factor. METHODS AND MATERIALS: Fibroblast cultures were established from skin biopsies in two AVM patients developing radiation necrosis. The results of clonogenic survival assays were compared to a parallel study with two groups of cancer patients treated with radiation: 1) patients without late side effects; 2) patients experiencing severe late sequelae. RESULTS: The survival fraction at 2 Gy (SF2) of the 2 AVM patients was 0.17 (0.14-0.19) and 0.18 (0.14-0.22). The SF2's of the cancer patients ranged between 0.25-0.38 (mean = 0.31) for the control group, and between 0. 10-0.20 (mean = 0.17) for the hypersensitive group. The SF2's of the AVM patients who developed brain necrosis were comparable to that of the hypersensitive group (p = 0.85) but significantly lower than the control group (p = 0.05). CONCLUSION: The two patients who developed radiation necrosis demonstrate increased fibroblast radiosensitivity. The SF2 of skin fibroblasts may potentially be used as a predictive assay to detect patients at risk for brain necrosis.

Adult↗
PubMed2000

Effects of growth hormone treatment on very-low density lipoprotein apolipoprotein B100 turnover in adult hypopituitarism.

Adult hypopituitarism is associated with hyperlipidemia, mainly due to an increase of very-low-density lipoprotein (VLDL) and low-density lipoprotein (LDL) levels. Recent studies have shown that such patients exhibit increased hepatic secretion of VLDL apolipoprotein B100 (VLDL apo B100). To examine the effects of growth hormone (GH) replacement on VLDL apo B100 turnover, 13 GH-deficient hypopituitary patients (8 women and 5 men; aged 47 +/- 3 years, mean +/- SEM; body mass index [BMI], 30 +/- 2 kg/m2) entered a double-blind placebo-controlled study for 6 months (GH 0.125 IU/kg/wk for 4 weeks, and then 0.25 IU/kg/wk). GH was subsequently used in all patients for a further 6 months. A 6-hour [1-13C] leucine infusion was administered at baseline and at 6 months. The secretion rate of VLDL apo B100 was derived by kinetic analysis following quantitation of isotopic enrichment by gas chromatography/mass spectrometry. The GH-treated group (6 patients) demonstrated a similar fractional secretion rate (FSR) for VLDL apo B100 at 0 and 6 months. The pool size and absolute secretion rate (ASR) also were unaffected significantly by GH therapy. No significant changes were observed in the placebo group (7 patients). Treatment with GH for 6 months caused an increase in the high-density lipoprotein (HDL) cholesterol concentration (13 patients, 1.27 +/- 0.13 v 1.16 +/- 0.10 mmol/L, respectively, P = .05), whereas total cholesterol and triglyceride concentrations did not change. Nonesterified fatty acids (NEFAs) increased during GH therapy (471 +/- 43 micromol/L at 6 months v 349 +/- 49 micromol/L at baseline, P < .0005). The data suggest that GH does not affect VLDL apo B100 turnover in a significant way.

Adult↗
PubMed2000

Attentional modulation of motion-in-depth processing.

I used a novel effect of adaptation to a moving stimulus to investigate the role of attention in the processing of motion-in-depth (MID). Following adaptation to expansion, the time required to detect an expanding target in the same location as the adaptation target was significantly longer than following viewing of a constant-sized target. Conversely, following adaptation to contraction, detection times (DTs) for an expanding target were significantly shorter than for a constant-sized adaptation target. Changes in DTs following adaptation to contraction were substantially larger than those following adaptation to expansion. Attentional modulation of MID processing was examined by adding an alphanumeric discrimination task that distracted the observer's attention away from the location of the adaptation target. I compared the magnitude of DT effects while (a) observers passively fixated the alphanumeric sequence (single task condition) and (b) observers performed the discrimination task (dual task condition). DT effects were significantly smaller in the dual task condition than in the single task condition indicating that MID processing is modulated by attention.

Adaptation, Physiological↗
PubMed2000

Accuracy of estimating time to collision using only monocular information in unilaterally enucleated observers and monocularly viewing normal controls.

Since individuals who have lost an eye in early life rely on monocular information, one asked if they would better estimate the time to collision (TTC) with an approaching object based on the monocular cue [(&theta;/(d&theta;/dt), i.e. tau] than a control group using only monocular information. Estimates of TTC were measured with a simulated approaching textured object using a staircase procedure. Seven adult observers who were unilaterally enucleated at an early age were compared with 18 normally sighted control observers who viewed the stimuli monocularly. Consistent with previous findings, the majority of the controls (13/18) underestimated TTC. Three enucleated observers had larger estimation errors than the 95% confidence interval of the mean of the control group. One enucleated observer was unable to give reliable results. These results suggest that unilaterally enucleated observers cannot estimate TTC more accurately (and may even be worse) than normal controls when estimates are based on monocular information alone. Further, the majority (83%) of enucleated observers were influenced by perceived distance information derived from the object's initial size when estimating TTC with an approaching object. The use of this other optical variable could account for their reduction in performance. It was suggested that in every day life enucleated individuals make use of as many optical variables as possible to partially compensate for the lack of binocularity.

Adaptation, Physiological↗
PubMed2000

Estimating the time to collision with a rotating nonspherical object.

We measured the precision (i.e. Weber fraction) and the accuracy with which the time to collision (TTC) with a simulated approaching object is estimated. We simulated a rigid spherical object and a rigid nonspherical object (an oblate spheroid whose longer axis was vertical). We used the following viewing conditions: that the available information about TTC was only monocular (M), only binocular (B) and monocular plus binocular (M and B). In addition to the approaching SPHERE condition, we used the following three simulation conditions for the oblate spheroid: (2) a slow rotation through 90 degrees (SIDE-END); (3) a slow rotation through 90 degrees (END-SIDE); (4) several complete rapid rotations (RROT). Weber fractions for discriminating TTC were similar for all 12 combinations of viewing and simulation conditions. When only monocular information was available, perceived TTC was longer in the M/SIDE-END condition than in the M/SPHERE condition, and shorter in the M/END-SIDE condition than in the M/SPHERE condition. As well, observers were strongly influenced by task-irrelevent variables in the M/SIDE-END condition so that they could not properly perform the task. The addition of binocular information considerably improved the accuracy of estimating TTC in simulation conditions SPHERE, END-SIDE and RROT, and allowed reliably accurate estimations to be made in the SIDE-END simulation condition. We suggest that, when binocular information is combined with monocular information about TTC, the two kinds of information are weighted roughly equally when the approaching object is a rigid sphere, but the binocular information is weighted more heavily when the approaching object is nonspherical and rotating.

Adult↗
PubMed2000

Adjuvant chemotherapy with 5-fluorouracil, L-folinic acid and levamisole for patients with colorectal cancer: non-randomised comparison of weekly versus four-weekly schedules--less pain, same gain. QUASAR Colorectal Cancer Study Group.

BACKGROUND: QUASAR is a large trial of adjuvant chemotherapy for colorectal cancer in which clinicians could choose to deliver a standard adjuvant cytotoxic chemotherapy regimen, 5-fluorouracil (5-FU) and L-folinic acid (L-FA), in either a once-weekly or a four-weekly schedule. We report results of a non-randomised comparison between these schedules with respect to survival, recurrence and differential toxicity. PATIENTS AND METHODS: In a factorial (2 x 2) trial design, QUASAR compared high-dose (175 mg) versus low-dose (25 mg) L-FA and levamisole versus placebo. The dose of 5-FU was fixed at 370 mg/m2 and although the recommended schedule was i.v. bolus delivery, daily for 5 days repeated four-weekly for 6 months, a significant proportion of randomising clinicians were constrained to deliver once-weekly 5-FU-L-FA for 30 weeks. RESULTS: Four thousand nine hundred twenty-seven patients were entered into QUASAR between May 1994 and October 1997, eighteen hundred twenty-nine of whom have recurred and sixteen hundred eighty-nine died. Similar numbers 2370 vs. 2559 were treated with the once-weekly and four-weekly schedules and the demographic features of the 2 groups were well balanced: stage C, 73.3% once-weekly vs. 71.0% four-weekly; colon, 68.0% vs. 68.3%; high-dose FA, 50.1% vs. 49.9%; levamisole, 49.3% vs. 49.3%; females, 40.2% vs. 41.7%; median age (years) 62 vs. 61. The risk of recurrence and survival were similar regardless of schedule: three-year survival was 70.6% once-weekly vs. 71.0% four-weekly; three-year recurrence risk was 35.6% once-weekly vs. 35.5% four-weekly; But, the once-weekly regimen was much less toxic: number of patients for whom toxicity was reported (once-weekly: four-weekly), stomatitis, 37 vs. 337; diarrhoea, 260 vs. 440; neutropenia, 20 vs. 153. CONCLUSIONS: The once-weekly regimen is much less toxic than and, apparently, about as effective as the four-weekly schedule. This suggests that the toxicity of 5-FU-L-FA adjuvant chemotherapy could be reduced substantially by weekly scheduling without compromising efficacy. Alternatively, efficacy might be enhanced with equal toxicity by more dose-intense weekly FU-L-FA regimens. However, this conclusion from a non-randomised comparison needs confirmation in prospective randomised studies.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed2000

Risky driving behavior: a consequence of motion adaptation for visually guided motor action.

The authors examined the effect of adaptation to expansion on overtaking maneuvers in a driving simulator. Following driving on a straight empty road for 5 min, drivers initiated overtaking substantially later (220-510 ms) than comparable maneuvers made following viewing a static scene or following 5 min of curve driving. Following adaptation to contraction (produced by driving backward), observers initiated overtaking significantly sooner. The removal of the road texture significantly reduced the size of the adaptation effect. The authors propose that these changes in overtaking behavior are due to misestimation of the time headway produced by local adaptation of looming detectors that signal motion-in-depth for objects near the focus of expansion. This adaptation effect may increase the risk of rear-end collisions during highway driving.

Adaptation, Psychological↗
PubMed2000

What can we do about acute extrapyramidal symptoms?

Antipsychotic drugs are the most effective treatment for psychotic disorders such as schizophrenia. However, they are known to cause a range of side-effects including acute extrapyramidal symptoms (EPS) that are both distressing and disabling. Mental health nurses play a critical role in both the detection and the management of these symptoms. A review of the literature was conducted to identify strategies for managing acute EPS. Despite a widely held belief that EPS are associated with noncompliance with medication, the data to support this hypothesis are weak. Although akathisia may negatively affect the treatment outcome, there was little evidence to suggest that parkinsonism or dystonia do. Whilst the use of anticholinergic medication may be helpful in treating acute parkinsonism and dystonia they were associated with their own side-effects and the benefit of long-term prophylactic treatment is doubtful. The literature suggests that logical prescribing and rapid detection and management of acute EPS will result in a substantial reduction in the incidence of these disabling side-effects.

Antipsychotic Agents↗
PubMed2000

Traumatic priapism: an unusual cycling injury.

A case is reported of a 35 year old man who sustained an injury to the perineum in a cycling accident which resulted in a traumatic priapism. After confirmation of the diagnosis by Doppler sonography and angiography, therapeutic selective arterial embolisation was followed by successful detumescence of the penis and subsequent return of normal erectile function. It is suggested that percutaneous embolisation of the lacerated cavernosal artery is a safe and effective minimally invasive treatment for this uncommon condition.

Adult↗
PubMed2000

Hypnopompic hallucinations with donepezil.

A case of hypnopompic hallucinations associated with donepezil is described. Electroencephalogram (EEG) and sleep EEG changes are common in Alzheimers Disease and acetylcholinesterase inhibitor drugs can affect rapid eye movement sleep and alertness. The importance of assessing sleep in patients treated with these drugs is discussed.

Alzheimer Disease↗