Radiation Biophysics – Services

BIO– DOSIMETRY

Blood samples from workers implicated in potential over exposures to ionising radiation are routinely referred to the radiobiology laboratory to establish evidence for cellular radiation damage. The Directorate, Radiation Control of the National Dept. of Health, usually requests these investigations but individuals, their physicians and company managers can also ask for it. For this, the micronuclei frequency in binucleated T-lymphocytes are numerated following a 3 day in vitro cell culture process – see picture. The data is used to calculate the dose absorbed where applicable. Results are most useful to identify erroneous TLD readings or to confirm over-exposures. It is particularly helpful to evaluate possible radiological consequences in the proper perspective. This service has also been instrumental in identifying serious over-exposures (> 1000 mSv) in a few industrial radiation workers.

 micronuclei

Micronuclei in a binucleated T-lymphocyte of a workers accidentally exposed to ionizing radiation.

In a most useful application of molecular radiobiological methodologies, the potential hazard of routine whole-body X-ray examinations – applied as a method of security checks of diamond mineworkers – has been investigated. As the standard micronuclei test is insensitive to distinguish between micronuclei induced by very low levels of radiation and that as part of the background count in a specific worker, fluorescent in-situ hybridisation (FISH) signals from a pan-centromeric DNA probe have been used. The latter indicate micronuclei not induce by radiation. It was shown that centromeric negative micronuclei frequencies lymphocytes for X-irradiated workers were the similar to that of a control group. The work was conducted in collaboration with Prof Vral, University of Gent, Belgium.

 fish

Fluorescent In-Situ Hybridisation (FISH) signals from a pan-centromeric DNA probe.

MICRONUCLEI TEST:

Should a micronuclei test be required for a radiation worker of any other individual – please do the following:
1. Contact Dr J Slabbert by phone (021 843 – 1000 / 082 325 0816) to establish if Bio-monitoring is applicable to the incident in question.
2. In the event that blood samples need to be send to iThemba LABS it should reach the laboratory within 24 hours of being taken. To avoid complications and delays, sample delivery must be arranged in advance with laboratory staff. For this call 021 843 –1227. Keep in mind that micronuclei tests are performed on isolated white blood cells that needs to be cultured over 3 days. As such, the collection and transport of whole-blood samples need to be done as follows.
3. Whole-blood samples are best collected in duplicate in purple cap (EDTA) tubes, packaged without ice in a padded envelope and send by courier the same day or over-night to: iThemba LABS, Old Faure Rd, Faure, Cape Town. Inform the laboratory by phone before sample collection and confirm the sending of samples once collected by a courier service.

Results will be made available as soon as possible to the individual and or responsible person.

CHEMICAL – DOSIMETRY

INDUSTRIAL RADIATION
Chemical dosimetry measurements in the hundreds of gray range are performed on a regular basis in support of Industrial Radiation activities – e.g. the sterile insect technique (SIT) developed at the irradiation facility of ARC-Infruitec Stellenbosch. This to help with studies conducted by Hendrik and Marsheille Hofmeyr – Citrus Research International (Citrusdal) and IAEA fellows Dr Stephanie Bloem and Dr James Carpenter from the United States Dept. of Agriculture. – USDA-ARS Crop Protection and Management Research Unit (Tifton Georgia) and Tallahassee, Florida.

Chemical dosimeters are suitable for sending by post and should it be required contact the laboratory at 021-8431227 or jps@tlabs.ac.za.

A post-graduate student using fluorescent microscopy to analyze cell nuclear damage in human lymphocytes following exposure to ionizing radiation.

Following the labeling of 123-I to an organic molecule, the cellular damage of Auger electrons are followed by in vitro procedures carried out under sterile conditions.

The results of all experiments with neutrons, protons or other special particle radiation types are frequently compared to that observed when the same cells are exposed to Co-60 gamma rays.

 

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