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PubMedDate not supplied

[Radiation inactivation of alpha-chymotrypsin in aqueous solutions. Effect of irradiation conditions].

A comparative study was made of inactivation by gamma- and beta-radiation of alpha-chymotrypsin within a wide range of its initial concentrations (from 10(-4) to 10(-7) M). The regularities of gamma- and beta-inactivation are the same, and distinctions, if any, are due to a greater radiation effect of beta-rays on dilute enzyme solutions (less than or equal to 5 X 10(-6) M). The inactivation of alpha-chymotrypsin by radiation proceeds either via primary molecule unfolding followed by degradation of the most accessible and radiosensitive amino acid residues (pH 7.8) or, to a greater extent, via direct disruption of amino acid residues which can probably be random (pH 3.0). Calcium ions stabilize, on the whole, the enzyme molecule upon irradiation.

Amino Acids↗
PubMedDate not supplied

[Role of injuries to the vascular plexus in the development of a radiation lesion of the skin in swine].

A single action of beta-radiation of different energy on the swine skin was studied. The analysis and comparison of clinical and histological features of radiation injury to the mode of the absorbed dose formation associated with the depth of location of the skin structural elements permitted to consider deep vascular plexus of the dermis to be the second critical structure (in addition to basal layer of the epidermis) responsible for the radiation reaction development and for the rate and completeness of repair processes, in particular.

Animals↗
PubMed1985

[A method for partial or whole-body irradiation with fast electrons].

A method for the electron irradiation of the body surface is presented which can easily be applied and standardized. The patient is placed in prone and supine position on the normal irradiation table. Contrary to many other methods, this proceeding is especially comfortable for the patient.

Beta Particles↗
PubMed1985

Late nonstochastic changes in pig skin after beta irradiation.

Late radiation-induced changes in pig skin have been assessed following irradiation with beta-rays from a 22.5- or 15-mm-diameter 90Sr/90Y source and a 19- or 9-mm-diameter 170Tm source. Late damage, in terms of dermal atrophy, was assessed 2 years after irradiation from measurements of dermal thickness in irradiated and normal skin. After 90Sr irradiation maximum atrophy, a dermal thickness of 40-50% of the control value, occurred at a dose of approximately 40 Gy from the 22.5-mm source and approximately 75 Gy from the 15-mm source. In the case of 170Tm the 19- and 9-mm sources produced similar degrees of atrophy at equal doses. Maximum atrophy occurred at approximately 70 Gy, when the dermis was approximately 70% of the thickness of normal skin. Significant late tissue atrophy was seen at doses, from both types of radiation, which only produced minimal erythema in the early reaction. Such late reactions need to be taken into account when revised radiological protection criteria are proposed for skin.

Animals↗
PubMed1985

[Use of electrons above 20 MeV for reduction of radiation exposure].

After many years of clinical application of a 42 MeV betatron, the following indications were found for deep therapy with electrons above 20 MeV: tumors situated in the brain, mediastinum, kidney, liver, bladder, rectum, as well as peripheral tumors situated in different body regions. For eight different cases, the total body exposure and the radiation exposure of some risk organs was calculated for an irradiation with electrons alone, a combination of electrons and photons, an irradiation with 42 MeV X-rays and with Co-60 gamma rays alone. All these calculations were based on a most favorable irradiation technique. The results showed that electrons up to 40 MeV can spare more than 30% of the total body dose; a combination of electrons and photons allows a reduction of the total dose of about 15% as against that of photons alone, which makes possible a better conservation of skin. This total dose reduction corresponds to that achieved by the substitution of ultrahard X-radiation for Co-60 gamma radiation in deep therapy. The radiation exposure of risk organs can often be reduced by the use of electrons, too. Thus electron deep therapy shows to be justified for the mentioned tumor cases. This is also confirmed by clinical experience.

Beta Particles↗
PubMed1985

Difference in DNA strand break by gamma- and beta-irradiations: an in vitro study.

Lambda DNA (125 micrograms/ml in Tris buffer, pH 7.4) was irradiated with 60Co gamma-rays and 3H beta-rays, respectively, and the number of strand breaks was determined by electrophoresis. Number of single-strand breaks increased linearly with radiation dose in both gamma- and beta-radiations and the relative effectiveness (beta/gamma) was found to be 1.82 in N2 and 1.16 in O2. Number of double-strand breaks increased with the square of the radiation dose in gamma-irradiation, but it increased linearly with radiation dose in beta-irradiation. Therefore, the relative effectiveness (beta/gamma) is higher at lower doses. O2 effects was observed by gamma-irradiation but was minimal after beta-irradiation.

Beta Particles↗