PubMed Health⌕ Search

Biomedical subjects

J M Sneddon

Publications and source records attributed to J M Sneddon.

At least 37 records · Page 2Linked to original sources
PubMed1973

Effect of cations on the blood platelet release reaction.

1. Stimulus-secretion phenomena in blood platelets incubated with trypsin or thrombin have been investigated.2. Secretion occurs in at least two stages: (a) induction, obtained when the platelets are incubated with proteolytic enzymes in the presence of the chelating agent EDTA, and (b) release, which occurs with the subsequent addition of Ca(2+) to the incubation medium.3. Ca(2+) was the only essential divalent cation required for release. Ba(2+) and Mg(2+) inhibited release and Sr(2+) could only partially substitute for Ca(2+).4. Blood platelets exhibited recovery from enzymic perturbation by trypsin or thrombin by a mechanism that was temperature dependent, but did not require the synthesis of new protein.5. The results are discussed in relationship to stimulus-secretion in other cells.

Adenine Nucleotides↗
PubMed1971

Relationship between internal Na + -K + and the accumulation of 14 C-5-hydroxytryptamine by rat platelets.

1. 5-Hydroxytryptamine (5-HT) transport has been investigated in rat blood platelets poisoned with dinitrophenol-sodium fluoride or ouabain.2. The inhibition of transport produced by different concentrations of the metabolic inhibitors has been correlated with changes in the internal Na(+) and K(+) concentrations of the platelets.3. Platelets poisoned in a high K(+) medium maintained a high internal K(+) concentration in the absence of cellular metabolism. When transferred to Krebs solutions containing different concentrations of Na(+) they accumulated 5-HT by a process that was related to the magnitudes of the internal and external Na(+) concentrations.4. The results are consistent with the hypothesis that the spontaneous movement of ions through the platelet membrane is capable of providing, at least in part, the energy requirements for 5-HT transport.

Animals↗
PubMed1971

Effect of mitosis inhibitors on blood platelet microtubules and aggregation.

1. An inhibitory action of the mitosis inhibitors colchicine, colcemid and vinblastine on blood platelet aggregation has been demonstrated.2. The inhibitory action of low concentrations of these drugs was surmountable by increasing the concentration of the aggregating agents adenosine diphosphate (ADP) or thrombin. High concentrations completely inhibited aggregation.3. The presence of a circumferential bundle of microtubules has been demonstrated in rabbit platelets.4. After exposure to aggregating doses of ADP and thrombin the microtubules move to the centre of the cell, ;trapping' the platelet intracellular organelles in a relatively clear cytoplasm.5. Concentrations of the antimitotic agents which reduce platelet aggregation depolymerize the platelet microtubules and prevent the rearrangement of the platelet organelles during aggregation.6. It is suggested that the microtubules are not essential for platelet aggregation but are intimately involved in the movement of intracellular granules. This may be a preliminary stage in the eventual discharge of the granules during the platelet ;release reaction'.

Adenine Nucleotides↗
PubMed1969

Sodium-dependent accumulation of 5-hydroxytryptamine by rat blood platelets.

1. The influence of sodium and potassium on the accumulation of 5-hydroxytryptamine (5-HT) by rat blood platelets was investigated.2. An absolute dependence of 5-HT uptake on the sodium concentration in the medium was found.3. Removal of potassium reduced the uptake by about 60%. High concentrations of potassium inhibited sodium-dependent accumulation.4. The observations have been discussed in terms of a carrier-mediated transport process for 5-HT operating in the platelet membrane.

Animals↗