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Biomedical subjects

M Da Prada

Publications and source records attributed to M Da Prada.

At least 163 records · Page 9Linked to original sources
PubMed1972

Lipid composition of membranes of amine-storage organelles.

1. The lipid composition of the membranes from isolated 5-hydroxytryptamine-storage organelles of blood platelets of rabbits and of those from chromaffin granules of bovine adrenal medulla was compared. 2. In contrast with the membranes of the chromaffin granules, those of the 5-hydroxytryptamine organelles did not contain lysophosphatidylcholine (lysolecithin). 3. Both the cholesterol/phospholipid ratio and the relative proportions of phosphatidylethanolamine (kephalin), phosphatidylinositol and phosphatidylserine were about the same in both membranes, whereas phosphatidylcholine (lecithin) and sphingomyelin showed somewhat higher values in the membranes of the 5-hydroxytryptamine organelles. 4. In conclusion, the release of 5-hydroxytryptamine from blood platelets is probably not correlated with the presence of lysophosphatidylcholine in the membranes of the storage organelles and may thus differ from the mechanism of catecholamine release in adrenal medulla.

Adrenal Medulla↗
PubMed1971

Storage of ATP and 5-hydroxytryptamine in blood platelets of guinea-pigs.

1. By density gradient centrifugation of homogenized blood platelets of guinea-pigs, subcellular organelles have been isolated which exhibit much higher concentrations (mumole/mug protein) of ATP than the whole platelets.2. The organelles also store endogenous 5-HT whose concentration is, however, considerably inferior to that of ATP.3. Investigated by electron microscopy most of the isolated organelles look empty and only very few show dense osmiophilic cores indicating the presence of 5-HT. Accordingly the occurrence of dense osmiophilic organelles in the whole platelets is also very rare.4. Exogenous 5-HT taken up by the platelets markedly accumulates in the subcellular fraction containing the organelles storing ATP. Concomitantly, the platelets show a rise in the number of osmiophilic organelles and the frequency of osmiophilic cores in the isolated organelles is increased.5. From these and previous in vitro experiments it is concluded that the so called 5-HT storage organelles of blood platelets primarily store ATP and only subsequently accumulate 5-HT.

Adenosine Triphosphate↗
PubMed1970

Phase separation in solutions of noradrenaline and adenosine triphosphate: influence of bivalent cations and drugs.

1. From aqueous solutions of biogenic amines, such as noradrenaline plus adenosine triphosphate (ATP), a second liquid phase spontaneously separates in the presence of small amounts of bivalent cations such as calcium. This separation is reversible and temperature-dependent; the concentration of amine and ATP in the bottom phase is several times higher than in the supernatant.2. Analytical ultracentrifugation provides evidence that the second phase consists of high molecular weight aggregates of the amine and ATP.3. The separated second phase of the noradrenaline-ATP system dissolves isothermally on addition of tyramine and amphetamine which in vivo are known to liberate biogenic monoamines and which have a low tendency to aggregate with ATP. The apparent molecular weights of noradrenaline-ATP aggregates are decreased by tyramine and amphetamine. Dopamine does not diminish the second phase and it can also form aggregates of high molecular weight with ATP.4. Bivalent cations in high concentrations diminish or abolish the separation of a second phase.5. Small amounts of reserpine affect phase separation.6. It is concluded that the physico-chemical properties of aggregates of biogenic amines with ATP may be of importance for understanding the storage and release of the amines in vivo.

Adenosine Triphosphate↗