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Biomedical subjects

S K Ray

Publications and source records attributed to S K Ray.

At least 55 records · Page 3Linked to original sources
PubMed1994

Clinical use of a concomitant boost technique using a gypsum compensator.

PURPOSE: To develop a clinical procedure to treat field within a field (concomitant boost) portals with a single compensated field. METHODS AND MATERIALS: An ordinary manual cerrobend block former was used to produce styrofoam molds from simulator film data. A special gypsum compound was poured into the molds. The compensator block is independently mounted to the treatment machine via a custom-made compensator holder. RESULTS: Measurements confirm that the inhomogeneous dose distribution has been reliably delivered via this technique. The accuracy of placement of the high dose region is sufficient for clinical use. CONCLUSION: The procedure enables the concomitant boost effect to be easily implemented in the clinic without increasing clinical setup time.

Calcium Sulfate↗
PubMed1993

The utility of SPECT lung perfusion scans in minimizing and assessing the physiologic consequences of thoracic irradiation.

PURPOSE: Three-dimensional single photon emission computed tomography lung perfusion scans (SPECT) provide a unique quantitative 3-dimensional map of the distribution of functioning pulmonary vascular/alveolar subunits, information not provided by other imaging modalities. This report describes our initial experience utilizing these scans to assist in the design of radiation treatment beams and to assess changes in regional lung function following irradiation. METHODS AND MATERIALS: Patients were immobilized and scanned in the treatment position with appropriate fiducial markers. Four millicuries of technetium 99M microaggregated albumin were injected and SPECT images of the lung were generated. Pre-treatment SPECT images were used to help design radiation beams to minimize irradiation of functioning lung. Pre- and post-treatment scans were compared to assess changes in regional function. These changes in function were then correlated with the regional radiation dose. RESULTS: Pre-radiotherapy SPECT scans were obtained in 18 patients (11 with lung cancer). Marked variations in regional function were frequently noted. In patients with primary lung tumors, these variations were not necessarily immediately adjacent to the tumor volume. In general, patients with poor pulmonary function pre-treatment, in whom one would like to spare as much normal lung as possible, had the most non-uniform distribution throughout the lung of functioning vascular/alveolar subunits. In these cases, pre-treatment scans were most useful in designing radiation portals to minimize irradiation of functioning lung. SPECT scans were also used to detect changes in regional lung function secondary to radiotherapy in four patients. With doses in excess of 40 Gy, reductions in regional function were noted 1-6 months following completion of radiotherapy. These reductions were not necessarily accompanied by reductions in conventional pulmonary function tests, which are assessments of whole lung function and may not reflect regional lung injury if the volume affected is small. CONCLUSIONS: SPECT lung scans provide an excellent means of assessing regional lung function, superior to that obtainable with planar images. The functional data provided by the SPECT images is useful in designing "optimal" radiation treatment beams and in assessing the effect of radiotherapy on regional lung functions. Efforts are continuing in our laboratory to develop a dose response curve for regional lung damage using the tools of SPECT scanning and 3-dimensional dose calculations.

Aged↗
PubMed1993

3-dimensional optimization of multiple arcs for stereotactic radiosurgery.

PURPOSE: During linear accelerator-based radiosurgery, the physicians and physicists need to determine which combination of treatment arcs are "best" with regard to target coverage and incidental dose to adjacent structures. This is a complex problem, especially when targets are geometrically close to critical structures. The purpose of this article is to present a method to mathematically determine a set of arcs to produce desired target and normal structure dose distributions in linear accelerator radiosurgery. METHODS AND MATERIALS: Nonlinear least squares regression was used to determine the table angles and gantry angle arc ranges and their associated beam weights appropriate to linear accelerator radiosurgery. RESULTS: Three cases are presented: (a) critical structure close to target volume; (b) target volume too large for the largest collimator to cover the volume with one isocenter and a standard plan; (c) target volume located within one critical structure and close to another critical structure. The optimized treatment plans are all shown to be superior to a defined standard plan. CONCLUSION: The method successfully enables one to determine nonstandard arcs which achieve the desired results. In particular, the method enables one to find clinical treatment solutions, even when the desired results cannot be a priori defined.

Humans↗
PubMed1993

Utilization of maternal services in west Bengal.

A study was conducted in selected blocks of West Bengal to assess the utilization of available maternal health services specially immunization, antenatal care and other services. Coverage with two doses of tetanus toxoid levels varied between 58.6 to 86.7% but it fell far short of Universal Immunization Programme target of 100%. Drop out rates were slightly higher in the rural areas. It was observed that in 5 out of 7 blocks more than 55% of the deliveries were conducted either at hospital or Primary Health Centre by health personnel. However, untrained dais predominated over the trained dais in conducting deliveries in most of the areas. This indicates the poor availability or utilization of the latter.

Female↗
PubMed1992

Identification of a 60-kilodalton Rb-binding protein, RBP60, that allows the Rb-E2F complex to bind DNA.

Several reports have indicated that the product of the retinoblastoma gene (Rb) complexes with the transcription factor E2F. We present evidence that the DNA-binding of the Rb-E2F complex involves another cellular factor. Addition of Rb to purified preparations of E2F does not generate an Rb-E2F complex that can bind DNA, and in fact, we see an inhibition of the DNA-binding ability of E2F. On the other hand, addition of Rb to cruder preparations of E2F results in the formation of an Rb-E2F complex (E2Fr) that can bind DNA and produces a distinct complex in gel retardation assays. We have identified and purified a 60-kDa protein that allows the Rb-E2F complex to bind DNA, and we show that this 60-kDa protein exerts its effect by directly interacting with Rb.

Animals↗
PubMed1990

Interaction of central serotonin and dopamine in the regulation of carbaryl-induced tremor.

Carbaryl (50-200 mg/kg, p.o.) produced dose-dependent tremors and inhibition of striatal AChE activity. A dose-dependent elevation of striatal 5-HT and 5-HIAA levels was also observed with carbaryl but at the higher doses (100-200 mg/kg p.o.). L-Trp or 5-HTP or haloperidol potentiated the carbaryl-induced tremors. Further, 5-HTP or haloperidol, when administered (i) alone, reduced the ED50 value and increased the duration of carbaryl-induced tremors without affecting the maximum tremorogenic response of rats and (ii) together, did not change any of these measures significantly. Atropine (acetylcholine antagonist) completely blocked the tremors produced by carbaryl in the absence or presence of 5-HTP or haloperidol. Methysergide (5-HT antagonist) and bromocriptine (DA agonist) antagonised the potentiating effect of 5-HTP and haloperidol, respectively, on the carbaryl-induced tremors. Furthermore, bromocriptine antagonised the potentiating effect of 5-HTP on the carbaryl-induced tremor but, methysergide failed to achieve this antagonism in presence of haloperidol. These results indicate that carbaryl-induced tremors primarily involve the activation of central cholinoceptors and that the serotonergic potentiation of carbaryl-induced tremors is possibly mediated through the dopaminergic disinhibition of cholinergic neurons.

5-Hydroxytryptophan↗
PubMed1986

Pentylenetetrazol: effect on carbaryl-induced changes of serotonin metabolism in pons-medulla of rat brain.

Oral administration of carbaryl to adult male albino rats produced a dose dependent increase in the steady state level of 5-hydroxytryptamine (5-HT) at 1.00 h in pons-medulla (PM). 5-Hydroxyindole acetic acid (5-HIAA) concentration was significantly elevated only in response to a higher dose of this pesticide under similar conditions. A time course study with carbaryl and pentylenetetrazol (PTZ) showed a characteristic elevation of the steady state level of 5-HT in PM, but the 5-HIAA level was significantly elevated at 0.5 h only after carbaryl treatment. No significant change of the 5-HIAA level was evident after administration of PTZ alone or in combination with carbaryl. Tryptophan concentration was significantly elevated in PM at 0.5 h after carbaryl treatment and at 1.0 h after carbaryl + PTZ treatment. No significant change of tryptophan concentration was evident after the administration of PTZ alone under similar conditions. Measurement of (1) pargyline induced (a) accumulation of 5-HT and (b) depletion of 5-HIAA levels, and (2) probenecid-induced accumulation of 5-HIAA level in presence and absence of carbaryl and revealed that carbaryl accelerated the synthesis as well as the breakdown of 5-HT, whereas PTZ alone or in combination with carbaryl accelerated the synthesis of 5-HT without affecting its catabolism. The potency of this pesticide in elevating the pargyline-induced accumulation of 5-HT is in the order of carbaryl + PTZ greater than PTZ congruent to carbaryl. These results suggest that the carbaryl-induced increase in the synthesis of 5-HT is potentiated, and the turnover is reduced, in PM when PTZ is administered to the carbaryl-intoxicated rats.

Animals↗
PubMed1985

Central cholinergic-dopaminergic interaction in carbaryl-induced tremor.

Acute administration of the anticholinesterase agent carbaryl to rats produced a dose-dependent increase of tremors. The carbaryl-induced tremor was significantly reduced by prior treatment of the rats with either atropine or L-DOPA and was exacerbated by haloperidol. These results suggest the possible involvement of a central cholinergic-dopaminergic interaction in the carbaryl-induced tremor.

Animals↗
PubMed1985

Effect of pentylenetetrazol on carbaryl-induced changes in striatal catecholamines.

Administration of pentylenetetrazol (PTZ) (60 mg/kg, s.c.) to normal or carbaryl (200 mg/kg, p.o.) treated adult male albino rats produced characteristic changes in the steady-state levels of striatal dopamine (DA), noradrenaline (NA) and homovanillic acid (HVA) at different time intervals (0.5, 1.0 and 2.0 hr). The elevation of striatal NA level was found to be more pronounced with PTZ than that produced by carbaryl. Treatment of rats with PTZ alone caused a significant elevation of DA levels only at 2.0 hr without any significant change in the level of HVA at any time interval. Carbaryl which did not have any significant effect on striatal DA level produced an elevation of HVA at 0.5 hr and 1.0 hr in striatum. The simultaneous administration of PTZ and carbaryl, under similar conditions, caused a marked reduction in the level of NA at 0.5 hr and DA at 1.0 hr without any significant effect on (i) both the amine levels at 2.0 hr and (ii) HVA level at any of the time intervals. Measurement of (a) alpha-methyl-p-tyrosine (alpha-MpT) (250 mg/kg, i.p.) induced depletion of striatal DA and NA, (b) FLA-63 (25 mg/kg, i.p.) induced disappearance of NA, (c) pargyline (75 mg/kg, i.p.) induced reduction and probenecid (200 mg/kg, i.p.) induced accumulation of striatal HVA in the presence or absence of PTZ and/or carbaryl revealed that: (1) PTZ or carbaryl alone caused a significant increase in the turnover of striatal DA; (2) the turnover of striatal NA was significantly increased after PTZ treatment but not after carbaryl administration; (3) the simultaneous administration of carbaryl and PTZ, on the other hand, attenuated (a) PTZ- or carbaryl-induced increase in metabolic activity of the striatal dopaminergic system, and (b) the enhanced anabolic activity of striatal noradrenergic system caused by PTZ, but failed to affect the enhanced utilization of striatal NA induced by PTZ alone.

Animals↗
PubMed1984

Effect of pentylenetetrazol on the carbaryl-induced changes of serotonin metabolism in rat-brain hypothalamus.

Carbaryl (200 mg/kg or 400 mg/kg, p.o.) significantly elevated serotonin (5-HT) (57-109%) and 5-hydroxyindoleacetic acid (5-HIAA) (60-78%) levels at 1.0 h in the hypothalamic region of adult male rat brain. Further, administration of carbaryl (200 mg/kg, p.o.) for different time intervals (0.5 h, 1.0 h, and 2.0 h) revealed that both 5-HT and 5-HIAA levels elevated maximally at 0.5 h in hypothalamus. These regional 5-HT and 5-HIAA levels were not significantly affected with pentylenetetrazol (PTZ) at any time after its treatment. But simultaneous administration of carbaryl (200 mg/kg, p.o.) and PTZ (60 mg/kg, s.c.) reduced the carbaryl-induced elevation of both 5-HT and 5-HIAA levels. Measurement of (i) probenecid-induced (200 mg/kg, i.p.) accumulation and (ii) pargyline-induced (75 mg/kg, i.p.) depletion of hypothalamic 5-HIAA level in the absence or presence of carbaryl (200 mg/kg, p.o.) and/or PTZ (60 mg/kg, s.c.) revealed that (a) carbaryl enhanced the synthesis as well as the breakdown of 5-HT, (b) PTZ had no effect on either of these processes of 5-HT, and (c) carbaryl-induced increased catabolism of 5-HT became normal in the presence of PTZ.

Animals↗
PubMed1983

Carbaryl-induced elevation of corticosterone level and cholinergic mechanism.

Administration of a single dose (200 mg/kg, p.o.) of carbaryl to rats produced a significant rise in adrenal and plasma corticosterone levels and an increase of tyrosine alpha-ketoglutarate transaminase activity in the liver cytosol. Synaptosomal acetylcholinesterase activity of the hypothalamic and the striatal regions of rat brain was decreased by carbaryl treatment under similar conditions. Pretreatment (0.5 h) with atropine sulphate (10 mg/kg, i.p.) failed to counteract the carbaryl-induced elevation of adrenal and plasma corticosterone levels and hence the liver tyrosine alpha-ketoglutarate transaminase activity. Present results suggest that the carbaryl-induced rise in the corticosterone level in the adrenal gland and plasma is not due to a cholinergic mechanism.

Adrenal Cortex↗
PubMed1983

A stochastic model of malaria transition rates from longitudinal data: considering the risk of "lost to follow-up".

A model, using stochastic processes, is developed to estimate some epidemiological parameters of malaria in a homogeneous population from longitudinal data. Assessments of transition probabilities from one state of health to the other are made taking "lost to follow-up" as a competing risk. The model is based on the assumptions that individuals are transferred at constant rate between states, and only one transition is possible between two consecutive surveys. It shows a good fit to the observed data; the model is simple to understand and can easily be used if computer facilities are not available.

Epidemiologic Methods↗