Detection of total- and partial-body irradiation in a monkey model: a comparative study of chromosomal aberration, micronucleus and premature chromosome condensation assays

PURPOSE

To investigate the efficacy of three cytogenetic methods (dicentrics, micronuclei (MN) and premature chromosome condensation (PCC) analysis) for assessment of the unirradiated fraction and the persistence of damage after total-body (TB) and partial-body (PB) irradiation of rhesus monkeys (Macaca mulatta).

MATERIALS AND METHODS

Animals were exposed to X-rays (5 Gy), either TB or PB, with about 6% of marrow cells shielded. Blood samples were collected at different times after exposure, i.e. 1, 3 and 7 days, and cultures were set up for the different cytogenetic endpoints. In addition, blood count analysis was performed before and after irradiation.

RESULTS

Blood count analysis was not suitable for discriminating between TB and PB exposure. By using Poisson or overdispersion distribution as the basis, it was not possible to distinguish TB from PB irradiation when dicentric chromosomes and MN were analysed. PCC analysis, in contrast, showed a Poisson distribution after TB exposure and overdispersion after PB exposure. Using the PCC assay, reliable dose estimates could be obtained up to 7 days after irradiation.

CONCLUSIONS

For dicentrics and MN, shielding of 6% of bone marrow cells was found to be too small to estimate the unirradiated fraction accurately. The PCC technique was useful for dose assessment and the inhomogeneous exposure of 6% was detected within a short period of time after exposure.

Relative contributions of intracortical and thalamo-cortical processes in the generation of alpha rhythms, revealed by partial coherence analysis

The thalamo-cortical relationships of alpha rhythms have been analysed in dogs using partial coherence function analysis. The objective was to clarify how far the large intracortical coherence commonly recorded between different cortical sites could depend on a common thalamic site. It was found that the alpha rhythms of the LGN influenced only moderately the coherence between cortical alpha rhythms whereas that of the pulvinar had much more influence, at least in relation to some cortical areas. Significant phase shifts between thalamus and cortex were also measured. The results demonstrate that there are thalamo-cortical and cortico-cortical components which interact in the generation of cortical alpha rhythms.