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Biomedical subjects

G Guidi

Publications and source records attributed to G Guidi.

At least 109 records · Page 6Linked to original sources
PubMed1984

Pressure-induced metabolic activation of platelets demonstrated in vitro by determination of malondialdehyde formation.

Platelet rich plasma (PRP) exposed in vitro to 200 mm Hg above atmospheric pressure showed a significant increase in malondialdehyde (MDA) formation compared to PRP at atmospheric pressure. This difference is also evident when platelets are incubated with arachidonic acid. The increase of MDA demonstrates that the increased beta-thromboglobulin and platelet factor 4 in plasma and the shape changes of platelets after pressure stimulation in vitro that were described in a previous paper result from the release reaction. Pressure-induced effects in vivo are discussed.

Blood Platelets↗
PubMed1984

The enzyme glutathione peroxidase in arachidonic acid metabolism of human platelets.

We investigated the possible regulatory role of glutathione peroxidase on thromboxane formation by reducing peroxides in platelets. Experiments carried out in platelet lysates demonstrated that the burst of the arachidonate metabolism was accompanied by a simultaneous burst of hydrogen transfer from glutathione to peroxides, catalyzed by endogenous glutathione peroxidase. The burst of hydrogen transfer was partially inhibited by acetylsalicylate concurrently with the complete inhibition of malondialdehyde formation, thus suggesting that the hydrogen acceptor peroxides were derived in part from the cyclooxygenase pathway. Moreover, increasing glutathione peroxidase activity by adding purified enzyme to the incubation media decreases thromboxane formation. Intact platelets, stimulated with arachidonic acid or thrombin, produced malondialdehyde and thromboxane in amounts roughly inversely related to the endogenous glutathione peroxidase activity. In contrast, no correlation was observed between glutathione peroxidase activity and agonist-induced platelet aggregation. Our experiments suggest that in normal platelets, glutathione peroxidase controls thromboxane formation.

Adult↗
PubMed1983

Chronobiological aspects of phosphohexoseisomerase in monitoring multiple myeloma.

In the field of oncology, the most important aim to date has been the finding of new means to improve the diagnosis and treatment of neoplastic diseases. Chronobiologically we have studied the behavior of phosphohexoseisomerase (PHI) in 11 multiple myeloma patients before treatment and in another group of 11 patients undergoing polychemotherapy treatment. From all patients, under the same standard conditions, 6 venous samples were taken at 4-hour intervals starting at 08.00 h, for a day. PHI serum levels were determined spectrophotometrically. The data obtained were analyzed by 'group mean cosinor' and from this analysis a mesor reduction of more than 50% was noted in subjects after polychemotherapy (M2) correlated with the absence of a circadian rhythm. The data suggest that PHI levels can be related to the characteristics of tumor growth and we feel they can be used as a guide in monitoring multiple myeloma patients.

Aged↗
PubMed1980

Bone marrow percentage of plasma cells in the staging of monoclonal gammopathies.

In the present study, the relationships between percentage of bone marrow plasma cells (BMP%), tumor cell mass, stage, and survival are statistically analyzed in a large number (90) of monoclonal gammopathies (MG). Though BMP% has not been included among the criteria for the staging of multiple myeloma, our results indicate that the above mentioned parameters correlate at highly significant degrees. BMP% is therefore proposed as a new, useful parameter in the staging of MG.

Bone Marrow↗
PubMed1976

Plasma iron and erythrocytic glutathione peroxidase activity. A possible mechanism for oxidative haemolysis in iron deficiency anemia.

The red cell glutathione-peroxidase (GSH-Px) activity of 9 normal subjects is compared with that of 15 cases of iron deficiency anaemia and with 13 cases of heterozygous beta-thalassemia with the same degree of anaemia and hypochromia. 2 cases of sideroblastic anaemia with high serum iron levels were also examined. Enzymatic activity was found to be significantly decreased in iron deficiency anaemia (about 55% of normal range), while it was not affected in heterozygous beta thalassaemia and it was increased in the 2 cases of sideroblastic anaemia. Moreover, GSH-Px activity exhibited a significant correlation with serum iron levels in all the patients studied. The observed modifications in GSH-Px activity are not correlated with erythrocyte ageing because reticulocyte-poor fractions exhibited GSH-Px activity which was not significantly reduced in respect of the reticulocyte-rich ones. These data seem to suggest that iron has a crucial connection with erythrocyte GSH-Px and that the enzyme deficiency may be of some importance in explaining the decreased red cell survival observed in severe iron-deficiency anaemias.

Anemia, Hypochromic↗