In a coordinated research programme sponsored by the International Atomic Energy Agency, the frequencies of chromosomal aberrations induced in peripheral blood lymphocytes (in vitro) by 250 kV X-rays at low doses (0.4, 1, 2, 3, 5, 10 and 30 rad) were determined. Blood from 2 donors was used to conduct one master experiment at these dose levels. The culture time used was 48 h and all samples including the controls were processed according to a standard protocol. The coded slides were scored by investigators from 10 participating laboratories. The main results are the following: (1) the frequencies of all types of chromosome aberrations at 0.4 rad are significantly lower than the control values; (2) there is no increase in the frequencies of dicentrics up to 2 rad and in those of terminal deletions up to 5 rad; (3) the mean frequencies of all aberrations considered together are not significantly different from one another at 1, 2 and 3 rad (P = 0.05); and (4) over the entire dose range the dose-effect relationship is clearly non-linear. A fit of these data to a linear quadratic model (E(D) = c + alpha D + beta D2) showed that the observed total aberration frequencies at doses 1, 2, 3 and 5 rad are below the curve defined by the model. The deviations can be explained by an altered kinetics of aberration production at very low doses probably due to DNA repair mechanisms operating these cells.

Adult↗

PubMedDate not supplied

Relation between number of hemopoietic stem cells in newborn mice and their radiosensitivity.

Fractionation of a radiation exposure causes greater damage in newborn mice than a single application since it induces radioresistant foetal hemopoietic stem cells to differentiate prematurely to more radiosensitive adult ones. In the present investigation, it was studied whether other agents that give rise to extensive stem cell destruction also lead to such a change in radiosensitivity. Indeed, treatment with cytostatic drugs which reduces the number of spleen colony forming units (CFU-s) and total cells also diminished the D0 value of the surviving cells 3 days later. Adriamycin was most effective in causing damage to hemopoietic stem cells and in inducing micronuclei in bone marrow; it also had the most marked action on the D0 of the surviving stem cells.

Aging↗

PubMedDate not supplied

[Relation between the cytogenetic effect and the dose of radiation and chemical mutagenic exposure of somatic cells in vivo: effect of the duration of exposure and cell selection].

Dose-response relationships obtained in vivo in mammalian cells or in vitro when studying structural chromosome aberrations in somatic cells may be used for monitoring human populations exposed to mutagenic agents. While the method appears of interest for biological dosimetry on people exposed to relatively high doses of ionizing radiation, its value for persons professionally exposed to chemicals is, however, limited.

Animals↗

PubMedDate not supplied

Chromosome number adjustment in the Landschütz mouse ascites cancer.

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Animals↗

PubMedDate not supplied

Complications of anterior spinal surgery in children.

The purpose of this study was to document the medical and surgical complications of anterior spine surgery in children and to identify risk factors for complications. A retrospective chart review was conducted of 599 anterior procedures (24 anterior only, 300 staged anterior/posterior, 175 combined anterior/posterior procedures) performed between 1967 and 1991. Major complications occurred in 7.5% of procedures and minor complications in 33%. Risk factors for major complications were age > 14 years, male gender, kyphotic curve type, curve sizes > 100 degrees, vital capacity < 40% of predicted, and use of thoracotomy. Risk factors for minor complications were age > 14 years, curves > 100 degrees, vital capacity < 40% of predicted, and use of a staged procedure. Multivariate analyses of risk factors identified age > 14 years and curves > 100 degrees as the most significant risk factors for major complications and age > 14 years for minor complications. We concluded that anterior spinal surgery can be performed in children with an acceptable level of risk and that referral for surgery before 14 years of age and before the curve size progresses will significantly reduce the risk of complications.

Adolescent↗