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Biomedical subjects

C M Young

Publications and source records attributed to C M Young.

At least 55 records · Page 3Linked to original sources
PubMed1982

The relative biological effectiveness of fast neutrons (42MeVd leads to Be) for early and late normal tissue injury in the pig.

Early and late radiation damage has been investigated in a number of normal tissues in the pig after irradiation with single doses of neutrons produced by 42MeV deuterons on beryllium. The results have been compared with data obtained after irradiation with single doses of 250kV X rays. In the skin a low RBE value of approximately 1.2 was obtained for the early (3-9 week) epithelial reaction. For the subsequent dermal vascular response, higher RBE values in the range of 1.35-1.6 were obtained: the RBE decreasing with an increase in the neutron dose. For late skin damage, assessed by the relative reduction in the linear dimensions of an irradiated field, a RBE value of approximately 1.5 was obtained. In the kidney the RBE value, for a neutron dose level (550 cGy) at which renal function was just preserved, was 2.0. A lower value of 1.7 was found for doses resulting in a loss of renal function. The results of 133Xenon clearance studies showed two waves of impaired ventilation function in the irradiated lung. In the acute reaction (3-9 months), at a dose level consistent with just preserving normal ventilation function, the RBE value was less than 1.2. For late lung damage (15-24 months) the RBE value was higher, 1.4. For the rectum, methods are presently only available for assessing acute damage. A RBE of 2.0 was found for neutron doses in the range 350-575 cGy. The RBE values for early endpoints in the skin, lung and gut of the pig are comparable with those published previously for other species, including man. The values for late effects in pig skin and lung were higher than for early damage in those tissues.

Animals↗
PubMed1982

The revascularization of pedicle skin flaps in pigs: a functional and morphologic study.

Functional and morphologic changes occurring during the revascularization of pedicle flaps have been investigated in the skin of pigs. The skin flaps, 16 cm long by 4 cm wide, were based on a row of segmental vessels arising from the internal mammary artery. Comparative measurements were made in flapped and normal skin. The inherent blood supply in the pedicle of the flap was unable to maintain the whole of the flap in a viable state. Flap viability was ascertained at surgery by the use of the intravital dye Disulphine blue. Injections of the dye after surgery gave a less accurate prediction of viability than when dye was injected prior to surgery. Revascularization between the flap and surrounding skin was evident 3 to 4 days postoperatively at the distal, most hypoxic part of the viable flap. The whole flap had a collateral vascular supply 7 to 10 days after surgery. Isotope clearance studies showed that the greatest functional changes occurred in the distal third of the viable flap, where, after initially slowing, the clearance rate became faster than in normal skin (day 5). Potassium extraction studies indicated similar changes. However, an increase in the red-cell volume on day 1 suggested that vascular shunting was occurring. The results of the morphologic studies indicated a correlation between the number of blood vessels per unit area, the thickness of the dermis, and the recorded functional changes. Seven days after surgery, when isotope clearance rates were very rapid, there was a significant increase in the vascular density and dermal thickness.

Animals↗
PubMed1982

The effect of field size on the reaction of pig skin to single doses of X rays.

The importance of the size of the treatment area for the response of the skin to radiation has been studied in the pig. The responses of skin areas of 16 cm3 (4 x 4 cm) and 64 cm2 (16 x 4 cm) were compared after single doses of X rays. In the initial 3-9-week period after irradiation the severity of the erythema reaction, which is associated with epidermal call death, was not influenced by the area of skin irradiated. For the later dermal response (10-16 weeks) a similar result was obtained. The dose required to produce dermal necrosis in 50% of the fields treated (ED50) was approximately 2070 cGy for both field sizes. Additional studies have shown that the ED50 for dermal necrosis was not influenced by the age of animals at the time of irradiation. This was despite considerable differences in the vascular density and blood flow in pig skin with increasing age. The apparent contradiction between the results of this experimental study in the pig, which shows no effect of field size, and currently accepted clinical practice is discussed.

Age Factors↗
PubMed1979

Contraceptive use in Australia.

The purpose of this paper is to trace the pattern of contraceptive use in Australia during the past 50 years, discussing reasons and circumstances related to the changing preference for specific methods, against the background of demographic trends in childbearing and woman's changing role in society. The analysis is based on unique information regarding married couples and young adults in Australia obtained from large-scale demographic surveys carried out in Melbourne during 1971 and 1977 by the Department of Demography at the Australian National University.

Adolescent↗
PubMed1979

Late radiation damage to pig skin.

The severity of skin contraction in a previously delimited treatment field has been used as a measure of late radiation damage to pig skin. Total treatment doses were given as 6, 14, and 30 fractions over 39 days or as 6 fractions over 18 days. Iso-effect curves for severe linear field contraction showed that no simple mathematical formula could be used to calculate safe "tolerance" doses when fractionation regimes were modified. The results do indicate that for a given level of acute damage, late damage was increased by changing from 5 to 2 fractions per week. These findings are similar to those obtained from surveys in man.

Animals↗
PubMed1976

The effects of varied numbers of dose fractions on the tolerance of normal human skin.

The early and late radiation of small areas of normal human skin, included in the treatment of basal cell carcinomata, have been used to evaluate the validity of the fractions exponent of the Ellis NSD equation. Fraction numbers at the lower end of the range used clinically were investigated (3 ,7 and 10 fractions); total doses were calculated using an NSD of 1930 ret with a fractions exponent of 0.22. Time and hence the time exponent was constant (14 days). The patterns of increasing and declining early skin reaction, measured using an arbitrary numerical scoring system, and the proportion of treatment fields reaching skin tolerance were similar for the three treatment groups. The number of treated areas showing late normal tissue damage were also similar. These observations suggest that it is legitimate to apply the NSD hypothesis to treatments involving 3-10 fractions over an interval of 14 days. Of particular interest was the observation that the final cosmetic result and tumour cure was not significantly improved by treatment given as 10 fractions over that obtained with 3 fractions.

Adult↗