Oryzalin-induced chromosome doubling in Rosa and its effect on plant morphology and pollen viability

Shoot tips of the diploid rose Thérèse Bugnet were treated in vitro to oryzalin at concentrations of 5 and 15 microM. Tetraploid shoots were obtained in highest frequencies (40%) after exposure to 5 microM oryzalin for 14 days. Thin (1 mm) nodal sections were treated with 5 microM oryzalin and the highest frequency of tetraploids (66%) was obtained after exposure for only 1 day. The shorter exposure times required to induce chromosome doubling in thin nodal sections is attributed to the more efficient delivery of oryzalin to the meristem. Tetraploids were obtained from four diploid roses and hexaploids from two triploid roses. Chromosome doubling was accompanied by increases in thickness and a darker green colouration of the leaves and, in all diploid to tetraploid and one triploid to hexaploid conversion, the breadth/length ratio of leaflets was significantly increased. Internodes were longer in tetraploids than diploids but significantly shorter in hexaploids than triploids. The number of petals per flower in the tetraploid form of Thérèse Bugnet was double that of the diploid. Significant increases in pollen viability accompanied chromosome doubling of all four diploids and one of the two triploids.

Cytotoxicity of wound dressing materials assessed using cultured skin equivalents

An in vitro system, based on the Bell model of cultured composite skin equivalents, was used to assess the effect of a number of wound dressing materials on DNA synthesis. DNA synthesis was quantified using immunocytohistochemical identification of incorporated bromodeoxy-uridine and the percentage of labelled cells measured, following 7 days' exposure to the dressing material. Differences in labelling index were observed from replica gels covered by different dressing materials and between dressings of the same type of material, but made by different manufacturers.

Time and dose-related changes in the thickness of pig skin after irradiation with single doses of 90Sr/90Y beta-rays

Time-related changes in pig skin thickness have been evaluated using a non-invasive ultrasound technique after exposure to a range of single doses of 90Sr/90Y beta-rays. The reduction in relative skin thickness developed in two distinct phases: the first was between 12 and 20 weeks postirradiation. No further changes were then seen until 52 weeks postirradiation when a second phase of skin thinning was observed. This was complete after 76 weeks and no further changes in relative skin thickness were seen in the maximum follow up period of 129 weeks. The timings of these phases of damage were independent of the radiation dose, however, the severity of both phases of radiation-induced skin thinning were dose related.

Cryopreservation of cultured dermal fibroblast impregnated collagen gels

The survival of cultured dermal fibroblasts was evaluated following manufacture, freezing and disaggregation of fibroblast-impregnated collagen gels. The concentration which gave optimal cell survival was determined for three cryoprotectants (glycerol, dimethyl, sulphoxide (DMSO) and ethanediol) and their efficacy compared. DMSO led to the highest cell viability after freezing and thawing. The effect of rate of freezing was also compared and 0.5 degree C/min (within the range 20 degrees C to -70 degrees C) was found to result in a significant enhancement of cell viability in comparison with freezing at 1.0 degree C/min or rapid freezing.

Dose- and source-size-related changes in the late response of pig skin to irradiation with single doses of beta radiation from sources of differing energy

Late radiation damage to pig skin has been assessed at 104 weeks after exposure to sources of 90Sr/90Y (Emax 2.2 MeV) and 170Tm (Emax 0.9 MeV). Damage was assessed from measurements of dermal thickness in histological sections of irradiated skin and was compared with that of unirradiated skin to establish the relative reduction in dermal thickness. The size of the source varied from 0.1 to 40.0 mm in diameter; this covered the range of source sizes designed to simulate exposure to radioactive "hot" particles (< or = 1.0 mm diameter) up to the lower range of field size that patients may be exposed to in radiotherapy treatments. Radiation doses were measured using an extrapolation chamber with a collecting electrode of 1.1 mm2, and thus the quoted doses represent an average dose over this area. For the larger 90Sr/90Y sources of > or = 5 mm diameter and the larger 170Tm sources of > or = 2 mm diameter there was no evidence, based on levels of damage consistent with a > or = 10, > or = 20, > or = 30, and > or = 40% reduction in relative dermal thickness, for any effect of source size on the ED50 value for each of these specified levels of effect. However, there was a marked effect of beta-particle energy; the skin surface doses associated with the ED50 values (+/- SE) for a > or = 20% reduction in relative dermal thickness were approximately 12 and approximately 40 Gy for 90Sr/90Y and 170Tm, respectively. This difference in skin surface dose for an equivalent level of dermal injury reflects the variation in the depth dose from these two beta-particle emitters. These skin surface doses, for what was considered to be a clinically detectable dermal effect, were below the ED10 for the early skin response of moist desquamation. This supports the selection of late dermal thinning as the effect on which to base dose limits in radiation protection for more generalized larger area skin exposures. In comparison, single exposures to a small area, from sources designed to simulate those from hot particles, reinforced the view that acute ulceration should be the effect on which dose limitation is based. Either the isoeffect doses for a clinically detectable reduction in relative dermal thickness of > or = 20%, following a single exposure to a small area, were higher than the ED10 for acute ulceration or the area of skin showing dermal thinning was so small that it was not considered to be detrimental.

Quantification of radiation-induced epilation in the pig: a biological indicator of radiation dose to the skin

Epilation in the pig has been quantified following single exposures of X-rays in the range 1.0-25.0 Gy. The number of hairs in each field was determined by counting hairs from photographic negatives weekly for 10 weeks following irradiation, and the percentage hair loss was calculated for each individual field from an initial unirradiated control value. Hair loss was dose-dependent for exposures between 1.0 and 15.0 Gy and this response was linearly related to dose. No further increase in hair loss was observed for doses > or = 15.0 Gy, as 20-30% of the hairs remained. It was assumed that these hairs were not actively growing at the time of irradiation and did, therefore, not express damage. The ED50 for the loss of > or = 30% of hairs was 3.8 Gy whilst that for the loss of > or = 50% of hairs was 6.8 Gy and for the loss of > or = 67% of hairs was 12.5 Gy. There was +/- 7% hair loss per Gy exposure for doses between 0.0 and 15.0 Gy. Quantification of hair loss provided a more sensitive assay than the use of visual scoring systems. Hair loss was detectable within 4 weeks of irradiation. The system is simple, non-invasive and appears to have considerable potential for use as a biological dosimeter.

Reduction in the diameter of human hairs following irradiation

A measurable reduction in hair diameter was observed in human hairs following single exposures to gamma-rays, 250 KeV X-rays, 8 MV photons and 10 MV electrons in the range 2.9-14.0 Gy. The data from the different types of radiation were pooled and fitted by linear regression with a slope of 2.34 +/- 0.42% Gy-1. There was approximately 2.4% reduction in hair diameter per Gy exposure. It would appear that the measurement of damage to the matrix cells of growing human hairs exhibits potential for use in biological dosimetry, especially in cases of non-uniform overexposure.

Morphological characteristics of cells derived from plucked human hair in vitro

Cells of various morphologies have been cultured from plucked hairs in vitro. These include keratinocytes, large polygonal cells, large and small spindle-shaped cells and endothelial cells.