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Biomedical subjects

S Kandaiya

Publications and source records attributed to S Kandaiya.

11 recordsLinked to original sources
PubMed2005

Analysis of film response to electron beams using a laser scanner system developed in the laboratory.

An optical scanner system, which incorporates a He-Ne laser, photodiode detectors, and a platform for placing film, was built in the laboratory. The laser system operates at the green wavelength of 543.5 nm and functions as a scanning densitometer for measurement of optical changes in a film resulting from irradiation . The central axis electron depth dose of selected electron energies 10,12 and 14 MeV were analysed using Kodak X-Omat and Kodak Extended Dose Range (EDR2) films. The Kodak X-Omat film is routinely used for high-energy electron dose distributions in radiation therapy. The electron depth-dose measured with X-Omat film was found to agree well with standard depth-dose curves in water, obtained using an ion chamber. Conversely, the recently introduced Kodak EDR2 showed an energy dependence for electron beams, the percentage depth-dose curve shifting towards the surface for 12 and 14 MeV electron beams compared to that in water.

Journal Article↗
PubMed1996

Modelling of Auger-induced DNA damage by incorporated 125I.

We have analyzed a newly available high resolution and precision repeat of the original Martin and Haseltine experiment which includes the influence of DMSO on the results. The new model includes the production and diffusion of radical species and .OH radical attack on DNA as well as the direct hits. Calculations of single-strand breaks use individual Auger electron along with the tracks of electrons and radical species superimposed on an atomistic model of B-DNA. Comparison of the preliminary calculations with the experiment supports the earlier choice of data for the amount of energy required to produce a single-strand break, i.e. 17.5 eV. In a separate simulation we found that an average of less than two ionizations inducing a single-strand break gave the best fit to experimental data. Direct hits were found to be predominantly occurring at short range while the damage by .OH radicals was mainly of the long-range type.

DNA, Single-Stranded↗
PubMed1992

Measurement of radon/thoron and its daughter nuclides in room air.

Pumping air through a soft tissue which acts as a membrane is a relatively easy and quick method to collect and measure radon/thoron and its daughter nuclides in air. Analysis of the activity of the radionuclides can be calculated using an alpha counter which has been calibrated. In this method the activity of radon/thoron cannot be separated from the activity of radionuclides already present in the aerosol or dust particles.

Air Pollutants, Radioactive↗
PubMed1986

Radioprotection of radiation damage fixed by misonidazole in Chinese hamster cells--a rapid-mix study.

The indirect effect in the fixation of radiation damage by misonidazole was studied using the rapid-mix apparatus. Under rapid-mix conditions it was shown that the time scale of radiosensitization by misonidazole can be resolved into two components [S. Kandaiya et al., in Proceedings of the Seventh Symposium on Microdosimetry (J. Booz et al., Eds.), pp. 1117-1132, 1980; D. W. Whillans and J. W. Hunt, Radiat. Res. 90, 126-141 (1982)]. Dimethyl sulfoxide (DMSO), a known radioprotector, was used as an OH scavenger. The data obtained indicate that approximately 50% of the lesions fixed by misonidazole in each of the two components can be attributed to OH indirect damage produced by indirect means of radiation deposition in the critical target(s).

Animals↗
PubMed1985

Time scale of radiation damage by 2,4-dinitrophenyl-aziridine (CB 1954) in Chinese hamster cells: a rapid-mix study.

A rapid-mix device was used to study the time-scale of radiation sensitization of hypoxic cells by CB 1954, a monofunctional alkylating agent. It has an electron affinity (E1(7)-385 mV) similar to that of misonidazole but its effectiveness as a sensitizer occurs at a five-fold lower concentration under stationary-state conditions. In the rapid-mix study, the enhancement ratio (e.r.) value of 1 mmol dm-3 CB 1954 rapidly rises to 1.75 within 120 ms, with no further rise by 500 ms. The e.r. obtained is lower than that observed under stationary-state conditions for a similar concentration. The data suggests that CB 1954 sensitizes by at least two independent mechanisms.

Aminoimidazole Carboxamide↗
PubMed1980

The interaction of misonidazole with radiation, chemotherapeutic agents, or heat: a preliminary report.

Survival of hypoxic cells exposed to misonidazole at 37 degrees C show an initial lag period after which survival decreases exponentially with time. Hypoxic cells incubated with misonidazole for a time equivalent to that of the lag period on the survival curve show increased sensitivity when subsequently given x-irradiation. This is consistent with previously published observations. In addition, preincubation of hypoxic cells with misonidazole ata 37 degrees C also renders cells more sensitive to subsequent treatments by heat or melphalan, mustine and cis-Pt(II). Preincubation must be in hypoxia for cells to become sensitive to a second insult; preincubation in air does not change cellular sensitivity even when this preexposure is 5 mM misonidazole for 3 days. The potential of exploiting a physiological property of most solid tumors, viz., hypoxia, in order to increase sensitivity of tumor cells to cytotoxic agents is discussed.

Animals↗