Biomedical subjects

Anil Cherian

Publications and source records attributed to Anil Cherian.

6 recordsLinked to original sources

PubMed2006

The effect of timing of radiotherapy after breast-conserving surgery in patients with positive or close resection margins, young age, and node-negative disease, with long term follow-up.

PURPOSE: The aim of this study was to determine the effect of timing of radiotherapy after conservative breast surgery on local recurrence in women with positive resection margins and young age, treated without systemic therapy. METHODS AND MATERIALS: A total of 568 patients with T1 and T2, N0 breast cancer were treated with breast-conserving surgery and breast irradiation, between January 1, 1985, and December 31, 1992, at the London Regional Cancer Centre. 63 patients (11.1%) had positive/close resection margins (< 2 mm) and 48 patients (8.4%) were age < or = 40 years. For patients with positive resection margins, the time intervals from breast surgery to breast irradiation used for analysis were, 0 to 8 weeks, > 8 to 12 weeks and > 12 weeks. For patients < or = 40 years, the intervals used for analysis were 0 to 8 weeks and > 8 weeks. RESULTS: Median follow up was 11.2 years. For patients < or = 40 years, local recurrence rate at 5 and 10 years was 17.2% and 19.8% respectively. Four patients (17.4%) treated in the 0-week to 8-week interval and 7 patients (28.0%) treated in the > 8 week interval had local recurrences. For patients < or = 40 years with positive resection margins, the local recurrence rate was 25.0%. For patients with positive resection margins, 5-year and 10-year local recurrence rates were as follows: 0 to 8 weeks, 0% and 10.5% respectively; > 8 to 12 weeks, 10.3% and 10.3% respectively; and > 12 weeks, 13.3% and 20.0% respectively. CONCLUSION: Patients < or = 40 years have an increased local recurrence rate which occurs early. Patients with positive resection margins have higher local recurrence rates that become apparent when breast irradiation is delayed.

Adult↗

PubMed2006

Modeling unidimensional categorization in monkeys.

The categorization performance of monkeys on a unidimensional perceptual categorization task was examined with reference to decision bound and exemplar theories of categorization. Three rhesus monkeys were presented with stimuli varying along a single dimension, the displacement of a target light from a fixation point. Left or right saccade responses were probabilistically reinforced according to one of three functions, two of which were nonmonotonic at one end of the stimulus space. The monkeys all showed a monotonic increase in response probability as a function of target light displacement in this region, consistent with decision bound theory. Fits of a single-boundary model (GRT, Ashby & Gott, 1988) and two exemplar models--one using a probabilistic response function (GCM; Nosofsky, 1986), the other using a deterministic response function (DEM; Ashby & Maddox, 1993)--revealed overall support for the decision bound model. The results suggest that monkeys used a perceptual decision boundary to perform the task.

Animals↗

PubMed2005

Eleven-year follow-up results in the delay of breast irradiation after conservative breast surgery in node-negative breast cancer patients.

PURPOSE: This retrospective review was conducted to determine if delay in the start of radiotherapy after conservative breast surgery had any detrimental effect on local recurrence or disease-free survival in node-negative breast cancer patients. METHODS AND MATERIALS: A total of 568 patients with T1 and T2, N0 breast cancer were treated with breast-conserving surgery and breast irradiation, without adjuvant systemic therapy, between January 1, 1985 and December 31, 1992 at the London Regional Cancer Centre. The time intervals from definitive breast surgery to breast irradiation used for analysis were 0 to 8 weeks (201 patients), greater than 8 to 12 weeks (235 patients), greater than 12 to 16 weeks (91 patients), and greater than 16 weeks (41 patients). Kaplan-Meier estimates of time to local-recurrence and disease-free survival rates were calculated. RESULTS: Median follow-up was 11.2 years. Patients in all 4 time intervals were similar in terms of age and pathologic features. No statistically significant difference was seen between the 4 groups in local recurrence or disease-free survival with surgery radiotherapy interval (p = 0.521 and p = 0.222, respectively). The overall local-recurrence rate at 5 and 10 years was 4.6% and 11.3%, respectively. The overall disease-free survival at 5 and 10 years was 79.6% and 67.0%, respectively. CONCLUSION: This retrospective study suggests that delay in the start of breast irradiation of up to 16 weeks from definitive surgery does not increase the risk of recurrence in node-negative breast cancer patients. The certainty of these results is limited by the retrospective nature of this analysis.

Adult↗

PubMed2005

Effects of eye position upon activity of neurons in macaque superior colliculus.

We examined the activity of neurons in the deep layers of the superior colliculus of awake behaving rhesus monkeys during the performance of standard oculomotor tasks as well as during self-guided eye movements made while viewing natural images. The standard tasks were used to characterize the activity of neurons based on established criteria. The natural viewing paradigm enabled the sampling of neuronal activity during saccades and fixations distributed over a wide range of eye positions. Two distinct aspects of eye-movement behavior contributed to the modulation of firing activity in these neurons. The well-established influence of saccade amplitude and direction was strongest and most prevalent surrounding the time of the start of the saccade. However, the activity of these neurons was also affected by the orbital position of the eyes, and this effect was best observed during intervals of fixation. Many neurons were sensitive to both parameters, and the directions of their saccade vector and eye position response fields tended to be aligned. The sample of neurons included visual, build-up, and burst activities, alone or in combination. All of these activity types were included in the subpopulation of neurons with significant eye-position tuning, although position tuning was more common in neurons with build-up or burst activity and less common in neurons with visual activity. The presence of both eye-position as well as saccade-vector signals in the superior colliculus is likely important for its role in the planning and guidance of combined movements of the eyes and head.

Animals↗

PubMed2003

A comparison of macaque behavior and superior colliculus neuronal activity to predictions from models of two-choice decisions.

Recently, models in psychology have been shown capable of accounting for the full range of behavioral data from simple two-choice decision tasks: mean reaction times for correct and error responses, accuracy, and the reaction time distributions for correct and error responses. At the same time, recent data from neural recordings have allowed investigation of the neural systems that implement such decisions. In the experiment presented here, neural recordings were obtained from superior colliculus prelude/buildup cells in two monkeys while they performed a two-choice task that has been used in humans for testing psychological models of the decision process. The best-developed psychological model, the diffusion model, and a competing model, the Poisson counter model, were explicitly fit to the behavioral data. The pattern of activity shown in the prelude/buildup cells, including the point at which response choices were discriminated, was matched by the evidence accumulation process predicted from the diffusion model using the parameters from the fits to the behavioral data but not by the Poisson counter model. These results suggest that prelude/buildup cells in the superior colliculus, or cells in circuits in which the superior colliculus cells participate, implement a diffusion decision process or a variant of the diffusion process.

Action Potentials↗

PubMedDate not supplied

Incidence of neural tube defects in the least-developed area of India: a population-based study.

Hospital-based records from major cities of India, where roughly a quarter of the population resides, identified the frequency of neural tube defects (NTDs) as ranging from 3.9 to 8.8 per 1000 births, but the incidence in rural areas is unknown. We did a population-based door-to-door survey of mothers living in remote clusters of villages in Balrampur District in Uttar Pradesh, a region ranked as the least-developed area in India. The data showed that the incidence of NTDs was 6.57-8.21 per 1000 livebirths, which is among the highest worldwide. India's Ministry of Health needs to produce a strategy to reduce the incidence of such defects.

Female↗