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Biomedical subjects

A Grossi

Publications and source records attributed to A Grossi.

At least 145 records · Page 8Linked to original sources
PubMed1990

In vivo stimulation of megakaryocytopoiesis by recombinant murine granulocyte-macrophage colony-stimulating factor.

Murine recombinant granulocyte-macrophage colony-stimulating factor (rGM-CSF) was injected in mice, and the effects on bone marrow, splenic megakaryocytes, megakaryocyte precursors (megakaryocyte colony-forming units [CFU-Meg]) were evaluated. In mice injected three times a day for 6 days with 12,000 to 120,000 U rGM-CSF, no significant modification of both platelet levels and mean platelet volume was observed, while there was a twofold increase in blood neutrophils. However, the rate of platelet production, as assessed by the measurement of 75selenomethionine incorporation into blood platelets, was On the contrary, administration of up to 384,000 U rGM-CSF two times a day for 2 days, as for a typical "thrombopoietin assay," failed to modify platelet production. A significant dose-related increase in the number of splenic megakaryocytes occurred in mice receiving 60,000 to 120,000 U rGM-CSF, while a slight increase in the number of bone marrow megakaryocytes was observed in mice injected with 120,000 U rGM-CSF. The proportion of bone marrow megakaryocytes with a size less than 18 microns and greater than 35 microns resulted significantly higher in mice receiving rGM-CSF in comparison with controls; an increase in the percentage of splenic megakaryocytes greater than 35 microns was also observed. A statistically significant increase in the total spleen content of CFU-Meg was observed after administration of 90,000 and 120,000 U rGM-CSF three times a day for 6 days, while no effect on bone marrow CFU-Meg was recorded, irrespective of the dose delivered. Finally, 24 hours after a single intravenous injection of rGM-CSF, there was a significant increase in the proportion of CFU-Meg in S-phase, with the splenic progenitors being more sensitive than bone marrow-derived CFU-Meg. These data indicate that rGM-CSF has in vivo megakaryocyte stimulatory activity, and are consistent with previous in vitro observations. However, an effective stimulation of megakaryocytopoiesis in vivo, bringing about an increase in the levels of blood platelets, may require interaction of rGM-CSF with other cytokines.

Animals↗
PubMed1990

Antibodies to hepatitis C virus in blood donors.

Recently a recombinant polypeptide of hepatitis C virus (HCV) has been developed by the Chiron Corporation in California. This antigen has been used to develop an ELISA test (Ortho Diagnostic Systems for serum anti-HCV antibodies. Preliminary data have shown that this virus is the major cause of NANB hepatitis in the world. We examined differences in anti-HCV prevalence among subgroups of blood donors (total sera examined 639) classified for past or present exposure to HBV or not, and for ALT levels. The anti-HCV prevalence found in regular blood donors with normal ALT levels and no antibody to HBcAg was 1.2%. No significant difference in the anti-HCV prevalence was found among other subgroups of blood donors except that a higher prevalence (10%) was found in a group with both elevated ALT and HBV markers. These preliminary findings suggest that the policy of blood supply should take into account the advent of HCV antibody test.

Blood Donors↗
PubMed1990

Humoral regulation of megakaryocytopoiesis.

If compared to erythroid and granulomacrophage lineages, the knowledge of the regulation of megakaryocytopoiesis has progressed slowly, and only the recent advent of specific clonogenic methods has permitted studies aimed at investigating this aspect of hematopoiesis. The analysis of Mk differentiation and platelet production is still difficult, because methods such as the 75SeM or 35S incorporation are time consuming and their sensitivity is relatively low. A number of laboratories have been able to purify, partially or to homogeneity, fractions stimulating the proliferation and differentiation of megakaryocytes. The biochemical identity between IL-3 and the active fractions found in the C.M. of some cell lines stands for a role of this hemopoietin in the regulation of megakaryocytopoiesis. However, the function of Epo and, above all, of GM-CSF cannot be ruled out, on the basis of experimental works, although only in some clinical trials GM-CSF seems to have been able to modify the platelet number. Hopefully, data on the therapeutic use of rhIL-3, and the sequentiation and identification of a molecule capable of action on the maturative compartment will shed new light on the regulation of megakaryocytopoiesis and the possibility to correct its disorders.

Animals↗
PubMed1990

Lipid peroxidation and lung ultrastructural changes in an experimental model of leukocyte-mediated pulmonary injury.

The aim of this study was to study ultrastructural changes and lipid peroxidation in rabbits lung after massive complement activation and leukocyte aggregation. A prolonged and massive leukocyte activation was induced by intraperitoneal inoculation of zymosan suspected in paraffin. Fifteen animals (group 3) were given 0.6 g/kg of zymosan, 22 animals (group 2) received 1 g/kg, and 11 rabbits (group 1) were treated with paraffin alone and served as controls. An acute mortality rate of 40% was observed in group 3 and of 68% in group 2. Surviving animals were studied for 10 days. In these animals a marked decrease in circulating granulocytes and a progressive decline in arterial PO2 were recorded (PO2 on day 10 in group 2 animals was 51.94 +/- 4.26, p less than 0.01). Microscopic and ultrastructural evaluation revealed sequestration of granulocytes in the pulmonary microvasculature. Studies of lung homogenates demonstrated increased levels of lipid peroxide derivative malondialdehyde (group 2 rabbits, 1624 +/- 638; group 1, 795 +/- 57 pm/mg pt, p less than .001) and decreased levels of the tissue antioxidant alpha-tocopherol. The results of this study are compatible with the hypothesis of leukocyte-mediated injury through production of oxygen radicals.

Animals↗
PubMed1990

Non-parametric analysis of platelet lifespan.

A model-independent and elementary method of analysis of platelet survival is proposed. The method is based on the finding that the mean and standard deviation of the platelet lifespan can be expressed in the terms of the slope at time 0 and the area under the empirical platelet survival curve. The method is tested using Monte-Carlo simulations and then applied to a set of clinical data.

Algorithms↗
PubMed1990

Growth hormone does not inhibit its own secretion during prolonged hypoglycemia in man.

In man, continuous infusion of GH-releasing hormone (GHRH) does not sustain GH secretion, unlike prolonged hypoglycemia. To further evaluate this difference in the stimulation of GH release we measured GH concentrations for 3 h during prolonged insulin-induced hypoglycemia and GHRH-(1-29)NH2 (100 micrograms/h) infusion in normal individuals. We also assessed the GH response to combined and separate administration of insulin and GHRH. Plasma GH levels increased during prolonged hypoglycemia and remained elevated for the third hour (22-24 micrograms/L). GH concentrations increased during GHRH infusion, peaked at 60 min (23.5 micrograms/L), and rapidly declined. Thus, our findings confirmed that prolonged hypoglycemia, unlike GHRH infusion, sustained elevated GH levels and that these high levels did not appear to influence GH secretion from the pituitary. Changes in FFA did not account for the sustained GH secretion. FFA levels initially declined during insulin infusion, but after 3 h of hypoglycemia they returned to near-basal values (basal, 0.1 +/- 0.02 g/L; 180 min, 0.09 +/- 0.02). The maximal GH concentration attained during the combined insulin and GHRH test was significantly higher than that with the insulin tolerance test or GHRH test (insulin plus GHRH, 71.9 +/- 13.5; insulin tolerance test, 34.2 +/- 2.9; P less than 0.025; GHRH test, 27.9 +/- 3.2; P less than 0.02), indicating an additive effect on GH secretion. These data suggest that insulin-induced hypoglycemia stimulates GH secretion through a mechanism partly independent of GHRH. The release from somatostatin inhibition and stimulation through other neuropeptides (e.g. galanin) is suggested as possible causes of hypoglycemia-induced GH secretion.

Adult↗
PubMed1989

A dot assay for the erythropoietin receptor using human recombinant 125I-erythropoietin.

A dot assay was developed for the detection of membrane receptor(s) for erythropoietin (Ep). A relatively homogeneous population of cells bearing the receptor for Ep was generated in the spleen of mice made anemic with phenylhydrazine and crude membrane extracts were prepared from spleen cell suspensions. Aliquots of the membrane extracts were applied to microdishes of nitrocellulose in a volume of 4 microliters. After free reactive sites were blocked, the microdishes were incubated for 2 h at 37 degrees C with 125I-labeled human recombinant Ep (125I-rEp), and nitrocellulose bound radioactivity was determined thereafter. Reproducible curves were obtained, and a significant correlation between bound radioactivity and the amount of membrane proteins applied to the nitrocellulose dishes was found. Specific binding was saturable, reaching a plateau at 2.5 nM. Binding parameters of nitrocellulose-immobilized receptor were not significantly different from the values calculated using intact cells. No appreciable binding of 125I-rEp to control membranes at low Ep-receptor content was observed. Among a panel of growth factors, only unlabeled rEp was able to compete for the binding of 125I-rEp to nitrocellulose-immobilized membrane proteins in a dose-dependent fashion. The technique described herein may be of use in the study of the Ep receptor and as an assay for its purification. Moreover, it may also be of general application in the study of receptor-ligand interactions.

Anemia↗
PubMed1989

Recombinant human erythropoietin has little influence on megakaryocytopoiesis in mice.

The availability of a preparation of recombinant human erythropoietin (rEp) prompted us to investigate the role of Ep in the regulation of megakaryocytopoiesis in mice, using experimental procedures by which the effects on the mitotic and post-mitotic compartment of megakaryocytes could be evaluated separately. In agar cultures of murine bone marrow cells, either serum-depleted or serum-supplemented, rEp (0.1-2 U/ml) did not stimulate megakaryocyte colony formation and when it was added to suboptimal amount of spleen cell-conditioned medium (SCM), it failed to show a significant synergistic activity. On the contrary, rEp increased the number of megakaryocytic colonies developed from splenic precursors in the presence of suboptimal amounts of SCM, although it was unable per se to stimulate colony formation. The effects of rEps on megakaryocyte maturation and platelet production were studied in vivo evaluating the incorporation of 75Se-selenomethionine into platelets, the platelet count and platelet size, and the number of megakaryocyte precursors (small acetylcholinesterase positive cells, sAchE) in the bone marrow of mice injected with 1-8 U of rEp. No modification of these parameters was found in comparison with control mice. On the other hand, rEp increased the number of recognizable splenic megakaryocytes in a dose-dependent fashion. These data suggest that rEp has little influence on megakaryocytopoiesis, at least at the doses we used and which are known to elicit a maximal response of erythropoiesis. However, a subset of megakaryocytes with particular kinetic properties, such as those in the spleen of mice, may be responsive to relatively high doses of rEp. The significance of this observation in the overall regulation of megakaryocytopoiesis remains to be determined.

Animals↗
PubMed1988

6p+ and 9q- in two chromosomally distinct clones occurring in a case of myelodysplastic syndrome evolving to acute nonlymphocytic leukemia.

Different and unrelated chromosome changes were found to occur in a patient with a myelodysplastic syndrome with rapid evolution to acute nonlymphocytic leukemia. A 6p anomaly was found during the chronic phase and a del(9q) characterized the cells in the leukemic phase. Deletions with a breakpoint in 9q31 appeared to be associated with more aggressive disease.

Adult↗
PubMed1988

Early diagnosis of adult respiratory distress syndrome: an experimental model of complement-mediated pulmonary injury.

This article presents an experimental model of pulmonary injury resembling subclinical human adult respiratory distress syndrome (ARDS) mediated by leukocytes. The activation of complement was prolonged by an intraperitoneal injection of a suspension of zymosan in paraffin. The first step in the development of the disease was an accumulation of polymorphonuclear leukocytes in the lungs. No significant changes were observed on chest radiographs or computed tomograms and the pathophysiologic changes were only minimal in spite of the characteristic structural changes. The criteria currently used for the diagnosis of ARDS are not sensitive enough to detect the subclinical phase of the disease.

Animals↗
PubMed1988

Occurrence of haemorrhagic and thrombotic events in myeloproliferative disorders: a retrospective study of 108 patients.

Raised platelet count, impaired platelet function, and high PCV values are all considered risk factors for the haemorrhagic and/or thrombotic events frequently complicating the course of myeloproliferative disorders. Nevertheless, the outcome in young patients is reported as being frequently uncomplicated and, in these cases, treatment could be deferred. We examined retrospectively the occurrence of haemorrhagic and/or thrombotic events at the onset of myeloproliferative disorders in 108 patients and found that 67.4% of patients, with either raised platelet count or isolated high PCV, were symptomatic at the onset and the rate was similar regardless of disease, sex, age, platelet number and PCV values. We were unable to locate a patient group with a lower rate of complications and, in light of the frequency of symptoms, it seems reasonable to attempt a normalization of blood values in every case.

Adult↗
PubMed1988

Serotonin incorporation as a marker of murine megakaryocyte proliferation in liquid cultures.

We have developed a new in vitro method for the quantitation of murine megakaryocyte proliferation that is based on the unique property of megakaryocytes to incorporate and store [14C]serotonin in cytoplasmic dense granules. The specificity of the assay was demonstrated by autoradiography of whole bone marrow cell suspensions, which showed evidence of grain accumulation only in megakaryocytes. Bone marrow cells were cultured in liquid cultures in the presence of a stimulator of megakaryocyte growth before the addition of 2.5 microM [14C]serotonin. The amount of serotonin incorporated in cells was evaluated after 3 h. Radioactivity peaked at days 6 and 7 and remained high until day 10; there was a linear relationship between the incorporation of serotonin and the number of cells plated. A dose-response curve between the incorporation of serotonin and the concentration of pokeweed mitogen spleen-conditioned medium (PWM-SCM) was observed, with inhibitory effects becoming predominant at the highest concentrations. The proliferation of megakaryocyte progenitors was also stimulated by partially purified interleukin 3, whereas both human recombinant erythropoietin and human recombinant granulocyte colony-stimulating factor (rG-CSF) failed to modify the incorporation of serotonin in comparison with unstimulated cultures. Finally, in parallel experiments we observed a significant correlation between the number of megakaryocytic colonies grown in agar and the radioactivity in liquid cultures. The method described herein is reproducible, sensitive, and easy to perform; it should be useful for the study and purification of factors affecting megakaryocyte proliferation.

Animals↗
PubMed1988

Partial purification and biochemical characterization of human plasma thrombopoietin.

A factor that stimulates the incorporation of 75Selenomethionine into the newly formed platelets of recipient mice (thrombopoietin, TPO) has been partially purified from the plasma of thrombocytopenic patients. The activity was precipitated at 60-80% ammonium sulfate saturation and further purified with hydrophobic interaction chromatography. Thrombopoietin was retained by concanavalin-A-Sepharose. Using HPLC size-exclusion chromatography, an approximate molecular weight of 40,000 dalton was calculated. The overall purification factor was about 2,100-fold. TPO was stable in a pH range from 5 to 9 and was heat-sensitive, and the biological activity was destroyed by trypsin treatment and by dithiothreitol. The partially purified molecule did not stimulate the proliferation of megakaryocyte progenitors in vitro and had no effect on the growth of erythroid or granulocyte-macrophage colonies; when administered in-vivo, TPO significantly affected the mean platelet volume and increased the number of small acetylcholinesterase cells in the bone marrow. TPO appears to be specific for the megakaryocytic lineage and active on the postmitotic compartment of megakaryocytes.

Glycoproteins↗
PubMed1987

Megakaryocyte progenitors in the bone marrow and peripheral blood of patients with myeloproliferative diseases.

We studied the behavior in culture of megakaryocyte progenitor cells (CFU-Mk) from peripheral blood (PB) and bone marrow (BM) cells in eight patients with myeloproliferative diseases (MPD). In seven patients we observed megakaryocyte (Mk) colony formation from PB cells, which were generated in the absence of any added stimulator and which did not increase after the addition of a source of Mk-colony stimulating activity (CSA-Mk). The number of BM CFU-Mk was significantly higher in patients than in controls, and in seven out of eight patients the responsiveness to added CSA-Mk was retained. Plasma obtained from six patients did not stimulate normal donors' BM target cells to form Mk colonies. These data demonstrate an expansion of the CFU-Mk pool in MPD patients without increased plasma levels of CSA-Mk, and suggest that PB and BM CFU-Mk of MPD patients might have different kinetic properties.

Bone Marrow Cells↗