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Biomedical subjects

A Mansouri

Publications and source records attributed to A Mansouri.

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

Studies on the oxidation of hemoglobin Zurich (beta 63 E7 Arg).

Autoxidation and chemically-induced oxidation of hemoglobin Zurich (beta 63 E7 Arg) have been investigated by electron paramagnetic resonance and optical absorption spectroscopy. The results show that the replacement of the distal histidine of the hemoglobin beta chains by an arginine greatly enhances the susceptibility of the heme-iron to oxidative challenge. Both the kinetics and the products of the oxidation are pH dependent. Thus, at acidic and neutral pH, treatment of the protein with ferricyanide leads to a fast conversion of the oxy-protein to aquo-methemoglobin, which, eventually, is slowly converted to hemichromes. In contrast, the hydroxy-met derivative, formed upon chemical oxidation at high pH, is rapidly converted to hemichromes. The electron paramagnetic resonance features of the ferric derivatives of hemoglobin Zurich are somewhat singular, reflecting the modifications of the heme environment in the distal region of the abnormal chains. However, they can be related to heme complexes having their structural counterparts in oxidation products of hemoglobin A.

Chemical Phenomena↗
PubMed1984

Inhibition of platelet ADP and serotonin release by carbon monoxide and in cigarette smokers.

The release of 14C-serotonin by ADP, epinephrine and arachidonic acid and the release of ADP by kaolin were measured in normal platelets in the presence and absence of carbon monoxide and in smokers' platelets. It is shown that carbon monoxide inhibits significantly the platelet release reaction. This function is also decreased in platelets obtained from heavy cigarette smokers.

Adenosine Diphosphate↗
PubMed1983

The ability of fibrinogens, FI and FII, to support ADP-induced platelet aggregation.

Fibrinogen plays an integral part in ADP-induced platelet aggregation. Controversy exists in regard to the role of the carboxy termini of fibrinogen A alpha chains in this reaction. We have attempted to clarify this problem in view of the availability of a highly purified FII fibrinogen fraction. Kabi fibrinogen or its purified fractions FI, FII and FIII-IV-V were added to washed platelets in the presence of Tyrode-HEPES buffer pH 7.4. Aggregation was initiated by the addition of calcium and ADP. These fibrinogen fractions equally promoted ADP-induced platelet aggregation. The major difference among these fractions is in their A alpha chains. The FI fraction contains intact A alpha chains while FII and FIII-IV-V fractions have one and two partially degraded A alpha chains at the carboxy terminal portion respectively. We conclude that the carboxy terminal portion of the A alpha chain does not play an important role in promoting ADP-induced platelet aggregation.

Adenosine Diphosphate↗
PubMed1983

A new model of subarachnoid hemorrhage in experimental animals with the purpose to examine cerebral vasospasm.

Using 20 rabbits, we tried to establish a new model of experimental subarachnoid hemorrhage (SAH) for examining both acute and chronic cerebral vasospasm. A cranial opening was drilled, and a puncture made on the posterior branch of the middle cerebral artery. A second puncture was made in the superior sagittal sinus for additional withdrawal of subarachnoid blood. The bleeding thus induced resulted in arterial spasm which was studied by using serial electrocorticograms, cerebral blood flow measurement with 133Xe, and videomicroscopy of the small pial vessels at various intervals. After death of the animals, the brains were observed to identify the extention of the bleeding. It was indeed obvious that large amounts of subarachnoid blood clots had accumulated. This investigation showed that the rabbit can be used as a new experimental model of SAH. With a two-puncture method, it is possible to simulate the clinical phenomenon of a ruptured aneurysm, that seems to produce acute and chronic cerebral vasospasm. For the latter, the accumulation of blood clots in the basal surfaces plays an important role. The three methods of observation, videomicroscopy, cerebral blood flow measurements, and electrocorticography appeared to provide useful information in the study of biphasic vasospasm in the rabbit.

Animals↗
PubMed1983

Proacrosin/acrosin activity during spermiohistogenesis of the bull.

Acrosin and its zymogen form, proacrosin, were extracted from early and late spermatids, from ejaculated and epididymal spermatozoa (caput, corpus, and cauda) of the bull. Activity of proacrosin/acrosin and the time course of proacrosin activation were studied. It turned out that proacrosin/acrosin activity is first demonstrable in haploid spermatids, increases during spermiohistogenesis in the testis, and remains nearly constant in epididymal and ejaculated spermatozoa.

Acrosin↗
PubMed1983

Eosinophilic granulocytes as a possible source of vitamin B12-binding protein.

Leucocyte B12 and B12-binding capacity were measured by Simultrac radioassay in eosinophilic granulocytes, neutrophilic granulocytes and leucocytes obtained from patients with chronic granulocytic and lymphocytic leukaemia. It is shown that (a) eosinophils are a possible source of B12-binding protein similar to neutrophils and (b) granulocytes in myeloproliferative disorders and normal neutrophils have similar B12 and B12-binding capacity indicating that increased B12 and B12-binding capacity in myeloproliferative disorders arise from an increase in myeloid cell turnover.

Eosinophilia↗
PubMed1982

Alteration of platelet aggregation by cigarette smoke and carbon monoxide.

Platelet aggregation with epinephrine, adenosine diphosphate and arachidonic acid was studied in the presence of cigarette smoke and carbon monoxide. It is shown that cigarette smoke inhibits the arachidonic acid induced platelet aggregation as well as the second phase of epinephrine induced aggregation. The adenosine diphosphate induced platelet aggregation is not significantly affected by cigarette smoke. Carbon monoxide causes similar alterations in platelet aggregation. These results suggest that cigarette smoke inhibits platelet aggregation. This aggregation inhibition is due to the presence of carbon monoxide.

Carbon Monoxide↗
PubMed1981

The influence of beta-93 sulfhydryl groups, organic phosphate and heme concentration on methemoglobin reduction.

Native and modified methemoglobin (beta-93-SH groups blocked) were reduced by NADH-dependent methemoglobin reductase in the absence and the presence of organic phosphate (inositol hexaphosphate). These experiments were performed with dilute as well as concentrated methemoglobin solutions (physiological heme concentration). It is shown that: (a) in dilute solutions the blockage of beta-93-SH groups lowers the rate of methemoglobin reduction in the absence of organic phosphate but the rates of native and modified methemoglobin reduction are similar in the presence of organic phosphate; (b) at physiological heme concentration the blockage of beta-93-SH groups does not affect the rate of reduction but the organic phosphate stimulates the reduction of both native and modified methemoglobins in a similar fashion, as it does in dilute solutions. It is concluded that, although in dilute solutions the blockage of beta-93-SH groups alters the reduction rate, at physiological heme concentration the presence of free beta-93-SH groups does not have any significant effect on methemoglobin reduction. On the contrary, the organic phosphates do accelerate the rate of reduction at all ranges of heme concentration.

Cystine↗
PubMed1981

Methemoglobin formation and reduction in relation to hemoglobin oxygen affinity.

It is suggested that although the high oxygen affinity hemoglobins (Hb LR) (beta 143(H21)His leads to Gln) with stabilization of R quaternary conformation is not more susceptible to the oxidizing effect of nitrites in vitro, in an in vivo situation where hemoglobin is partly deoxygenated, it might be more susceptible to methemoglobin formation due to higher oxidation and lower reduction rate.

Cytochrome-B(5) Reductase↗
PubMed1981

Hemoglobin autoxidation under high oxygen pressure - effect of inositol hexaphosphate.

Hemoglobin A in 0.05 M bis-tris buffer was autoxidized under various oxygen pressures from 0.21 (oxygen pressure in air) to 8 atmospheres at pHs 6.5 and 8.5. All experiments were carried out without and with 5 molar excess of inositol hexaphosphate/heme at 37 degrees C. It is shown that increasing the oxygen pressure from 0.21 to 1 atmosphere decreases the autoxidation rate to about 80% whereas increasing the oxygen pressure further to 8 atmospheres has a reverse effect. This phenomenon is observed at both acid and alkaline pHs, although it is less marked at the latter pH. The stimulating effect of inositol hexaphosphate on the autoxidation is abolished at high oxygen pressure. It is suggested that moderate elevation of the oxygen pressure above the atmospheric pressure stabilizes further the hemoglobin R conformation which decreases the autoxidation rate. At very high oxygen pressure, the oxidizing potential of oxygen oxidizes the oxyhemoglobin directly in the R conformation. The maximal shift of hemoglobin T in equilibrium with R conformational equilibrium towards R conformation interferes with the binding of inositol hexaphosphate and hence abolishes its effect.

Hemoglobin A↗