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Biomedical subjects

D J Murphy

Publications and source records attributed to D J Murphy.

At least 199 records · Page 11Linked to original sources
PubMed1981

A comparison of the in vitro binding of alpha-tocopherol to microsomes of lung, liver, heart and brain of the rat.

The in vitro binding of alpha-tocopherol to microsomes of lung, liver, heart and brain of the rat was studied with the insoluble tocopherol ligand presented as a complex with bovine serum albumin. Under these conditions, all microsomes showed nonsaturable binding of alpha-tocopherol and the amount bound to microsomes was linearly proportional to the concentration of albumin-complexed tocopherol. Increasing the amount of alpha-tocopherol bound to microsomes in this manner reduced the extent of lipid peroxidation induced by added ferrous iron. The apparent affinities of the microsomes for alpha-tocopherol, as indicated by the amount bound at a given concentration of albumin-complexed tocopherol, decreased in the order brain greater than liver approximately equal to heart greater than lung. The differences in affinity did not correlate with total fatty acid content (r = -0.39), total unsaturated fatty acid content (r = -0.26), or with the content of fatty acids containing two or more double bonds (r = -0.01). A high positive correlation was found with the content of fatty acids containing three or more double bonds (r = +0.96). Since lung microsomes contain approx. 6-times the tocopherol levels of liver and brain and about twice that of heart microsomes, these results show that the in vivo levels of microsomal tocopherol do not reflect microsomal affinity for this biological antioxidant.

Animals↗
PubMed1981

The lack of a phospholipid-exchange-protein activity in soluble fractions of Spinacia oleracea leaves.

When 14C-labelled liposomes prepared from Spinacia oleracea leaf lipids or 14C-labelled microsomal fraction ('microsomes') prepared from Spinacia oleracea leaf protoplasts were incubated with unlabelled intact chloroplasts, there was a considerable transfer of label to the chloroplasts. This transfer occurred in the absence of added protein, but was stimulated by soluble protein fractions from Spinacia oleracea leaves. The stimulation was heat-stable and decreased after dialysis of the protein fractions. Salt solutions, containing no protein, stimulated lipid transfer proportionally to their conductivity. In all cases, the lipid transfer was not protein-dependent, but rather resulted from the fusion of 14C- and 3H-labelled liposomes or microsomes with chloroplasts. It is proposed that this photosynthetic tissue contains no detectable lipid-exchange activity between liposomes, microsomes and chloroplasts and that lipid transfer between these organelles is achieved by non-protein-dependent means.

Biological Transport↗
PubMed1981

Wing buds with three ZPAs.

It has been hypothesized that a diffusible morphogen emanates from the ZPA of the embryonic chick limb and that cells can have their presumptive fate respecified to form more posterior structures when exposed to a higher concentration of morphogen. Attempts to raise the concentration of morphogen by grafting two additional ZPAs into a host wing bud failed. Instead, the greater the positional disparity between the donor and host tissue at the graft sites, the greater the number of extra structures that formed.

Animals↗
PubMed1981

Photosynthesis of Lipids from CO(2) in Spinacia oleracea.

Young expanding spinach leaves exposed to (14)CO(2) under physiological conditions for up to 20 minutes assimilated CO(2) into lipids at a mean rate of 7.6 micromoles per milligram chlorophyll per hour following a lag period of 5 minutes. Label entered into all parts of the lipid molecule and only 28% of the (14)C fixed into lipids was found in the fatty acid moieties, i.e. fatty acids were synthesized from CO(2)in vivo at a mean rate of 2.1 micromoles per milligram chlorophyll per hour. Intact spinach chloroplasts isolated from these leaves incorporated H(14)CO(3) into fatty acids at a maximal rate of 0.6 micromole per milligram chlorophyll per hour, but were unable to synthesize either the polar moieties of their lipids or polyunsaturated fatty acids. Since isolated chloroplasts will only synthesize fatty acids at rates similar to the one obtained with intact leaves in vivo if acetate is used as a precursor, it is suggested that acetate derived from leaf mitochondria is the physiological fatty acid precursor.

Journal Article↗
PubMed1980

Polyunsaturated Fatty Acid Biosynthesis in Cotyledons from Germinating and Developing Cucumis sativus L. Seedlings.

Etiolated Cucumis sativus L. cotyledons preferentially catabolized exogenous [1-(14)C]oleic acid and [1-(14)C]linoleic acid with relatively little incorporation into complex lipids or desaturation of the (14)C-labeled fatty acids. Following a 16-hour exposure to light, the greening cotyledons efficiently desaturated the exogenous (14)C-labeled fatty acids. A small amount of oleate desaturation to linoleate was observed in etiolated tissue, but hardly any linoleate desaturation to alpha-linolenate was detected. Both oleate and linoleate desaturation showed diurnal variations with maxima at the end of light periods and minima at the end of dark periods. Illumination of etiolated tissue by flashing light, as opposed to continuous light, failed to stimulate either chlorophyll or alpha-linolenic acid biosynthesis, and both processes could be halted or reversed by 10 micrograms per milliliter cycloheximide. Production of polyunsaturated fatty acids from [1-(14)C]acetate, [1-(14)C]oleic acid, and [1-(14)C]linoleic acid, by greening cucumber cotyledons, was markedly affected by tissue integrity with finely chopped cotyledons having very little capacity for their synthesis and intact seedlings showing the highest rates.

Journal Article↗
PubMed1980

In Vivo Pathway of Oleate and Linoleate Desaturation in Developing Cotyledons of Cucumis sativus L. Seedlings.

Exogenous [1-(14)C]oleic acid and [1-(14)C]linoleic acid were taken up and esterified to complex lipids by greening cucumber (Cucumis sativus L.) cotyledons. Both (14)C-labeled fatty acids were initially esterified to phosphatidylcholine prior to eventual accumulation in triacylglycerols and galactolipids. Kinetic data suggest that esterification occurs prior to desaturation and that phosphatidylcholine is the initial site of both [(14)C]-oleate and [1-(14)C]linoleate esterification and of [1-(14)C]oleate desaturation to [1-(14)C]linoleate. [1-(14)C]Linoleic acid was esterified more rapidly than [(14)C]oleic acid and its desaturation product, [1-(14)C]alpha-linolenate, occurred mainly on monogalactosyl diacylglycerol, although some was also observed on the other major acyl lipids, including phosphatidylcholine.

Journal Article↗