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Biomedical subjects

D R Cooper

Publications and source records attributed to D R Cooper.

118 records · Page 7Linked to original sources
PubMed1968

The effect of gamma-irradiation on soluble collagen.

1. A study was made of the effect of gamma-irradiation on the sub-unit composition, as well as the conformational changes taking place in cooled solutions of thermally denatured neutral-salt-soluble and acid-soluble collagen. 2. The increase in negative rotation and viscosity at 15 degrees for irradiated and thermally denatured collagen solutions becomes less as the irradiation dose is increased. 3. The initial effect of gamma-irradiation is the depolymerization of the dimers found in both neutral-salt-soluble and acid-soluble collagen. 4. The principal effect of gamma-irradiation up to 10 Mrads is the fission of peptide bonds, yielding crystalline irradiation-resistant portions of the molecule incapable of associating to the native structure. 5. The effects of gamma-irradiation on both neutral-salt-soluble and acid-soluble collagen are very similar and bear a close resemblance to the effects induced by ultraviolet irradiation.

Acids↗
PubMed1967

The effect of ultraviolet irradiation on acid-soluble collagen.

1. A study has been made of the effect of ultraviolet irradiation on the conformational changes taking place in cooled solutions of thermally denatured acid-soluble calf-skin collagen. 2. The increase in negative rotation and viscosity at 15 degrees for irradiated and thermally denatured collagen solutions becomes less as the irradiation dose is increased. 3. The principal effect of ultraviolet irradiation is the fission of the primary collagen chains, eventually yielding chain lengths incapable of stabilizing a helical structure. 4. The effects of ultraviolet irradiation on acid-soluble collagen may be closely correlated with similar effects on neutral salt-soluble collagen.

Journal Article↗
PubMed1966

The effect of ultraviolet irradiation on collagen-fold formation.

1. A study has been made of the effect of ultraviolet irradiation, in the presence of air and nitrogen, on the conformational changes taking place in cooled solutions of gelatin prepared from thermally denatured neutral-salt-soluble collagen. 2. The increase in negative rotation and viscosity at 15 degrees for irradiated and thermally denatured solutions of collagen becomes less as the irradiation time is increased. 3. The principal effect of ultraviolet irradiation is the fission of the primary collagen peptide chains, eventually yielding chain lengths incapable of stabilizing a helical structure. 4. Irradiation in both air and nitrogen results in a loss of tyrosine, histidine and phenylalanine, with more denaturation occurring in the presence of nitrogen.

Chemical Phenomena↗
PubMed1965

The effect of ultraviolet irradiation on soluble collagen.

1. The effect of ultraviolet irradiation on acid-soluble and neutral-salt-soluble calf-skin collagen was studied by chromatography, gel filtration, amino acid analysis and sedimentation of the sub-units, and the reaction kinetics of degradation were obtained from viscosity and optical rotation measurements. 2. It was demonstrated that, whereas the structure of neutral-salt-soluble calf-skin collagen may be represented by the formula (alpha(1))(2)alpha(2), the acid-soluble extract has the formula alpha(1).(alpha(2))(2). The acid-soluble collagen is also unusual in containing a large amount of a component that could be beta(22). 3. Ultraviolet irradiation causes the progressive degradation of the collagen molecule into smaller molecular fragments that subsequently lose their helical nature. The rate constants show that the denaturation of soluble collagens by ultraviolet irradiation is much slower, under the conditions used, than denaturation by heat or enzymes.

Journal Article↗
PubMedDate not supplied

Cerebral microvessels in Alzheimer's have reduced protein kinase C activity.

Protein kinase C (PKC) is an important intracellular signalling enzyme. Numerous studies have suggested that alterations in this enzyme occur in aging and dementia. The objective of this study was to examine PKC in the cerebral microcirculation in aging and Alzheimer's disease. PKC activity, amount, and isoform distribution were analyzed in microvessels from adult and aged rodents as well as from Alzheimer patients and nondemented elderly controls. PKC activity was lower in Alzheimer vessels than in vessels from control brains, despite the presence of similar levels of PKC enzyme. In contrast, both activity and enzyme levels in young and aged rats were comparable. The beta-isoform was present in both rat and human microvessels and there were no age- or disease-related alterations. The loss in activity in cerebromicrovascular PKC in Alzheimer's suggest that perturbations in phosphorylation signalling cascades may exist at the Alzheimer blood-brain barrier.

Aged↗