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Biomedical subjects

M Magnani

Publications and source records attributed to M Magnani.

At least 271 records · Page 15Linked to original sources
PubMed1979

Decay pattern of rabbit erythrocyte hexokinase in cell aging.

As previously reported, during rabbit red blood cell aging glucose phosphorylating activities show several modifications. In the first period of the red cell life span the predominant form is similar to hexokinase II, while in the mature erythrocyte the predominant glucose phosphorylating activity resembles hexokinase I. In the oldest cells glucose phosphorylating activity has a low affinity (high Km) for glucose. In this paper the modifications of hexokinase in cell aging have been studied in vivo in a young erythrocyte population synchronized by actinomycin D, and in vitro in red cells separated in fractions according to different ages. Since protein synthesis is lacking in the mature red cell, we are inclined to explain the presence of low-affinity hexokinase activity in the oldest erythrocytes as an age-dependent transformation of a primary hexokinase.

Animals↗
PubMed1979

Comparative studies of galactokinase activity on mammal's red blood cells.

1. ATP: D-galactose-1-phosphotransferase activity was measured in human, pig, cow, rabbit, mouse and rat red blood cells. Mean values of galactokinase activity was markedly lower in the human and pig erythrocyte as compared to those of the other species. 2. The permeability to galactose of the red cells studied was always higher than galactose phosphorylation. 3. The affinity constants of galactokinase for galactose ranged from 119 to 291 microM and from 178 to 406 microM for ATPMg2-. 4. The thermostability values of the galactokinase of the species studied were similar. The pH-optimum is pH 7.5 for the human, mouse and rabbit enzyme and pH 8.0 for cow, pig and rat galactokinase.

Animals↗
PubMed1978

Relationship between glucose phosphorylating activities and erythrocyte age.

Glucose phosphorylating activity of human erythrocytes quickly decreases during cell ageing; the electrophoretic pattern suggests that this fast decrease is due mainly to the isozyme II. We have shown that in the young cells only hexokinase I and II are responsible for the glucose phosphorylation, while in the old cells another glucose phosphorylating activity, more evident at high glucose concentration, is also present. The appearance of this activity during cell ageing could be interpreted as a post-translational modification of the native hexokinase.

Erythrocytes↗
PubMed1978

Comparative studies on red blood cell glucose phosphorylating activities of mammals.

1. ATP-D-hexose-6-phosphotransferase activity was measured in red blood cells of man, rabbit, pig and cow. Mean values ranged from 0.60 to 1.06 units/g haemoglobin and no significant difference was obtained with different glucose concentrations. 2. The characteristics of glucose phosphorylating activities in red blood cells of the species studied were similar. 3. Chromatography on DEAE column revealed two different glucose phosphorylating activities in red cells of man, rabbit and pig, and only one in cow red cells. 4. The first hexokinase activity is the predominant form and is saturated with low glucose concentrations; the second is noticeably marked at high glucose concentrations.

Animals↗
PubMed1978

Glucokinase and hexokinase in pig erythrocytes.

We have shown different enzymatic activities responsible for the phosphorylation of glucose in pig erythrocytes. These activities were observed after partial purification from hemolyzed red cells. One of the enzymes involved is the hexokinase which is present in all tissues; the other is similar to hepatic glucokinase. We have determined the kinetic properties of these activities in hemolysates and in partially purified preparations. Their electrophoretic-migration characteristics were studied too.

Animals↗
PubMedDate not supplied

First trimester monitoring of a pregnancy at risk for glucose phosphate isomerase deficiency.

First trimester prenatal diagnosis was offered to the mother of a child affected by severe haemolytic anaemia due to glucose phosphate isomerase (GPI) deficiency. The mutant enzyme was characterized by an increased thermal lability. Both parents had 50 per cent normal red cell GPI activity. We have shown that the homozygous and heterozygous genotypes can be clearly distinguished from each other and controls by combinations of the measurement of enzyme activity and enzyme thermal lability. Examination of trophoblast cells obtained at 9 weeks of gestation led to the diagnosis of a GPI heterozygous fetus. The result was confirmed by analysis on uncultured and cultured amniotic fluid cells sampled at 16 weeks and by red blood cell studies of the healthy newborn. Prenatal diagnosis of GPI deficiency is indicated in families with previous cases resulting in severe haemolysis and mainly with the conservative view of arranging appropriate therapeutic measures for affected fetuses.

Adult↗
PubMedDate not supplied

Identification of blood erythroid markers useful in revealing erythropoietin abuse in athletes.

Recombinant human erythropoietin (rEpo) is being used with increasing frequency by endurance athletes to improve aerobic potential. Although rEpo administration has been banned by the International Olympic Committee, no methods are available to unequivocally detect its abuse in sports. Prompted by these considerations, we evaluated the main hematological and biochemical modifications measured in the blood of 18 volunteers upon rEpo administration. Different rEpo regimens, iron, folic acid, and vitamin B12 administration did not significantly modify the percentage increase in hematocrit. However, a significant decrease in circulating ferritin (fr) and an increase in the soluble transferrin receptor (sTfr) were not found in athletes receiving low (30 IU/kg) doses of rEpo. Thus, an increase in the sTfr/fr ratio cannot be used as an indicator of rEpo abuse, at least when the hormone is administered at low concentrations. In contrast, the amounts of beta-globin mRNA detected by quantitative competitive (RT)-PCR in whole blood samples significantly increased above the threshold levels in all of the treatments investigated. Taken together, these data suggest that hematocrit value, reticulocyte count, soluble transferrin receptor content, and concentration of beta-globin mRNA, when included in a new multiparametric formula, can detect rEpo abuse in 57.5% of the samples examined with a confidence interval of 99.99%. Thus, the method reported in this paper could significantly improve the tests currently available, which in similar experiments allowed the detection of rEpo abuse in only 7.6% of the samples examined.

Adolescent↗
PubMedDate not supplied

Modulation of ICAM-1 expression in ECV304 cells by macrophage-released cytokines.

Transendothelial leukocyte trafficking during inflammation requires the expression of adhesion molecules such as human intercellular adhesion molecule-1 (ICAM-1). ICAM-1 is constitutively expressed on the surface of endothelial cells and its levels increase in response to a variety of inflammatory mediators, including cytokines. Monocyte/macrophage cells play a crucial role in this context because, upon stimulation, they release proinflammatory cytokines which are responsible for the upregulation of adhesion molecules in endothelial cells. In the present study we investigated whether the modulation of macrophage activation and cytokine release is able to modulate ICAM-1 expression in endothelial cells. Dexamethasone was selectively delivered to macrophages by means of a red blood cell-mediated delivery system. Subsequent stimulation of macrophages by lipopolysaccharide (LPS) was found to inhibit NF-kB activation and tumor necrosis factor-alpha (TNF-alpha) release [R. Crinelli, A. Antonelli, M. Bianchi, L. Gentilini, S. Scaramucci, and M. Magnani (2000) Blood Cells Mol. Dis. 26, 211-222]. Incubation with conditioned medium derived from LPS-stimulated macrophages receiving dexamethasone resulted in a 45% inhibition of ICAM-1 mRNA expression in ECV304 cells. In the same experimental system this reduced ICAM-1 expression was paralleled by a reduced NF-kB DNA binding activity and a twofold higher level of IkB(alpha) in the cytosol of endothelial cells. Activation of ICAM-1 expression in ECV304 cells by macrophage-conditioned medium is not due to IFN-gamma stimulation since STAT-1 DNA binding remained unchanged. Furthermore, treatment of the macrophage-conditioned medium with a TNF-alpha-inactivating antibody resulted in the complete abrogation of induced ICAM-1 expression. These results suggest that TNF-alpha is the main cytokine released by LPS-stimulated macrophages able to promote ICAM-1 gene expression in endothelial cells. Modulation of the NF-kB activation pathway in macrophages by targeted delivery of dexamethasone could potentially be used as a therapeutic strategy with which to inhibit the expression of ICAM-1 in endothelial cells.

Anti-Inflammatory Agents↗
PubMedDate not supplied

Role of target and effector cell structures in natural killer-mediated cytotoxicity.

An analysis of target and effector cell structures involved in the in vitro natural killer (NK)-mediated cytotoxicity has been performed. The degree of surface expression of transferrin receptor (TR) was only in part correlated with that of cell lysis. Moreover, the lysis could not be blocked by treating target cells with two anti-TR monoclonal antibodies. Finally, cell lines poorly affected by NK cells express TR only at the cytoplasmic level. As to the effector cells, the integrity of cytoskeleton components (especially microtubules) was found to be essential for the occurrence of cell lysis. In fact, vinblastine, an anti-microtubule agent, was able to significantly reduce the percentage cell lysis. This effect was not due to a selective depletion in NK cells induced by the drug. It is concluded that the mechanisms underlying NK activity are complex and involve both target and effector cell structures.

Cell Line↗
PubMedDate not supplied

The age-dependent metabolic decline of the red blood cell.

The oxidative and non-oxidative utilization of glucose was evaluated in human erythrocytes of different ages, separated by density gradient ultracentrifugation. Young red blood cells are able to metabolize 2.5 times more glucose than old ones; on the other hand, the amount of glucose utilized via the hexose monophosphate shunt does not show any age dependence. Glucose metabolism evaluated during in vivo ageing of a rabbit red cell population shows results very similar to those obtained for human cells. Metabolic stimulation of glucose utilization by high phosphate in both young and old human red cells increases glucose utilization by 40%. In the same way young and old erythrocytes were able to increase the amount of glucose metabolized via the hexose monophosphate shunt when an oxidative stimulus (methylene blue) was introduced. Human erythrocytes of different age possess similar abilities to transport glucose so that an age-dependent defect in glucose transport can be excluded. The ATP content of human and rabbit red blood cells, as a function of cell age, follows the decrease in glucose metabolized via the Embden-Meyerhof pathway. Reduced glutathione, on the other hand, after a small decrease associated with the "maturation" of reticulocytes into red cells, remains constant like the rate of the hexose monophosphate shunt.

Adenosine Triphosphate↗
PubMedDate not supplied

Synovial metastasis of the shoulder detected by arthroscopy as the presenting manifestation of lung adenocarcinoma.

A case in which a post-traumatic shoulder impairment revealed the presence of the joint involvement by a metastatic localization of lung adenocarcinoma is presented. The patient was a 60-year-old white man, a smoker, in apparent healthy condition complaining of pain and stiffness from a 1-year-old traumatic accident to the right shoulder sustained during a tennis match. He had been unsuccessfully treated for 6 months with physical therapy. Because of the negativity of the usual imaging studies, a diagnostic arthroscopy was performed. It revealed the presence of a traumatic rupture of the glenoid labrum and of an atypical gelatinous synovial formation in the medial wall of the joint; it was histologically and immunohistochemically diagnosed as adenocarcinoma, probably originating in the lung or in the gastrointestinal tract. The pulmonary origin of the neoplasm was confirmed by computed tomography. The patient underwent chemotherapy and eventually died with contralateral lung and femur metastases 8 months after the diagnosis. The clinical importance of this rare observation is discussed.

Adenocarcinoma↗