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Biomedical subjects

A Camagna

Publications and source records attributed to A Camagna.

At least 37 records · Page 2Linked to original sources
PubMed1988

Mechanisms underlying T-lymphocyte activation: mitogen initiates and IL-2 amplifies the expression of transferrin receptors via intracellular iron level.

Peripheral blood mononuclear cells (PBM) pulsed with lectin (PHA or Con A for 0.25-3 hr) show a low expression of interleukin-2 and transferrin receptors (IL-2Rs, TfRs) and a mild decline of intracellular ferritin level, compared to control cultures grown in continuous presence of mitogen. Interestingly, lectin-pulsed PBM do not release detectable amounts of IL-2 in the medium. Furthermore, expression of TfRs in these lymphocytes is not inhibited by addition of excess anti-IL-2 neutralizing monoclonal antibody, but is significantly inhibited by treatment with iron salts. These observations suggest that mitogen triggers an IL-2-independent expression of TfRs, at least in part via a decrease of intracellular iron level. Addition of either recombinant IL-2 (rIL-2) or an iron chelator (picolinic acid) to lectin-pulsed PBM induces both a marked enhancement of TfR synthesis and a sharp decline of intracellular ferritin level, which are comparable to the corresponding pattern observed in control cultures. Conversely, addition of iron salts fully inhibits the increase of TfR expression induced by rIL-2. These observations strongly suggest that the enhanced TfR synthesis elicited by rIL-2 is mediated by depletion of a regulatory intracellular iron pool. In line with these studies, greater than 99% purified T lymphocytes stimulated by lectin show a low expression of TfRs, which is markedly enhanced by addition of exogenous rIL-2. Altogether, we postulate that: (i) in resting T lymphocytes the gene encoding TfR is apparently in a 'closed' configuration; (ii) even in the absence of IL-2 activity, a mitogen pulse is sufficient to initiate the expression of TfRs, at least in part via a decline of intracellular iron level; and (iii) TfR synthesis is then largely amplified by IL-2, again via a decrease of the size of a regulatory intracellular iron pool.

Cells, Cultured↗
PubMed1988

Activation and proliferation of normal resting human T lymphocytes in serum-free culture: role of IL-4 and IL-6.

Purified human T lymphocytes, completely depleted of accessory cells [i.e. monocytes, large granular lymphocytes (LGL) and B lymphocytes], have been grown in serum-free culture in presence of a mitogenic lectin (phytohaemagglutinin, PHA) and different recombinant cytokines. Only IL-2 and IL-4 induced a marked stimulation of [3H] thymidine ([3H]TdR) uptake, cell proliferation and expression of activation markers [transferrin receptor (TrfR), IL-2R]. The other cytokines (IL-1 alpha, IL-1 beta, IFN-gamma, GM-CSF, TNF-alpha) had no significant effect, except for a moderate, but significant, stimulation of [3H]TdR uptake induced by IL-3. Simultaneous addition of IL-4 and anti-IL-2 neutralizing monoclonal antibodies (mAb) did not modify the effects induced by IL-4 alone. Furthermore, IL-2 was not detected in the supernatant of T cells grown in the presence of PHA and IL-4. Thus, our results indicate that IL-4 acts on T lymphocytes independently of IL-2. We also observed that IL-6 moderately activates DNA synthesis in PHA-stimulated T lymphocytes, but markedly potentiates the proliferative effect of suboptimal amounts of IL-2. In conclusion, the present study suggests that B-cell growth factors, in addition to IL-2, control the proliferation of normal circulating T lymphocytes.

Cells, Cultured↗
PubMed1987

Characterization of differences in insulin receptors from young and old red blood cells.

It has been demonstrated that young RBCs (reticulocytes and early mature erythrocytes) possess more insulin receptors than old RBCs (late mature erythrocytes) but it is not yet known whether insulin receptors on young and old RBCs are regulated similarly. In the present investigation insulin receptors on young and old RBCs have, therefore, been studied in five normal male subjects before and after 2 days dexamethasone ingestion (0.5 mg tablet every 6 h) and, in the same subjects, before and 5 h after ingestion of 75 g glucose. The results obtained clearly demonstrate that dexamethasone increases insulin receptor concentration while glucose ingestion increases both insulin receptor affinity and concentration on young RBCs. By contrast, neither stimuli modify insulin receptors on old RBCs. Studies on RBCs are usually performed on the whole RBC population not taking into account this differential responsiveness of receptors on young versus old RBCs; consequently, this phenomenon might be responsible of the fact that some data reported on RBCs are not in agreement with those reported on monocytes or adipocytes and it should be taken into consideration when using RBCs to evaluate insulin receptor regulation.

Adult↗
PubMed1986

Expression of transferrin receptors in human erythroleukemic lines: regulation in the plateau and exponential phase of growth.

The present study was undertaken in an attempt to elucidate the mechanism(s) underlying transferrin (TRF) receptor expression in human erythroleukemic (K562 and HEL) lines during the exponential and the plateau phase of growth. TRF receptor synthesis is enhanced when stationary cells are subcultured at low density in fresh medium. This rise occurs in either the presence or the absence of serum, which is associated with cell proliferation or quiescence, respectively. In the presence of serum, it is not inhibited by the addition of hydroxyurea (i.e., an agent blocking DNA synthesis). Thus, the receptor synthesis is enhanced not only in subcultures of actively proliferating cells (in the presence of serum), but also in subcultures of quiescent elements (in the absence of serum or upon the addition of serum plus hydroxyurea). Conversely, the ferritin content is markedly decreased when stationary cells are subcultured at low density, in either the presence or the absence of serum. These results suggest that stationary cells subcultured in fresh medium undergo a depletion of their intracellular iron pool, which in turn may represent the stimulus triggering TRF receptor synthesis. This hypothesis is supported by two observations: both the depletion of this pool and the rise in TRF receptor synthesis are more marked in the absence than in the presence of serum; addition of excess exogenous iron fully inhibits the rise of TRF receptor synthesis in cells subcultured with fresh medium and serum.

Blood Physiological Phenomena↗
PubMed1985

[Potentials and limitations of viscometry in hemorheological studies].

The problems of viscometric studies are discussed in depth on the basis of the most recent advances in hemorheology. We present here our contribution to the solution of numerous methodological problems. Particular emphasis was set on the problem of optimization and standardization of viscometric techniques for the study of erythrocyte deformation and aggregation.

Blood Viscosity↗
PubMed1983

Red blood cell age, pyruvate kinase activity, and insulin receptors. Evidence that monocytes and RBCs may behave differently.

Data emerging from insulin receptor studies performed on red blood cells (RBCs) and monocytes from the same subject are not always in agreement; dichotomy might occur since variations in mean RBC age are not taken into account or because insulin receptors on the two cell types behave differently. In the present investigation RBCs from normal male subjects were separated into five populations of different mean age by means of centrifugation of RBCs on a discontinuous gradient of buffered Percoll for 10 min at 1000 X g. Insulin binding varied significantly depending upon the RBC population tested and was closely correlated to the activity of pyruvate kinase (r2 = 0.86), a well-known marker of RBC age. These data suggested that pyruvate kinase assay might be helpful in studies of RBCs. To confirm this hypothesis, RBCs from 10 normal male subjects and 13 male patients with hemolytic anemia were studied; insulin binding was correlated to pyruvate kinase activity. By adjusting insulin binding to 2 X 10(9) RBCs/ml the range of data was abnormally high, but it became acceptable after adjusting insulin binding to pyruvate kinase activity (0.75 U/2 X 10(9) RBCs). The overall data indicated that insulin binding was highly correlated to pyruvate kinase activity (r2 = 0.82) but only slightly to reticulocyte number (r2 = 0.56) since not only reticulocytes but also erythrocytes lose receptors during maturation. Pyruvate kinase activity was measured in RBCs from normal men and from normally menstruating women at the seventh and twenty-fourth days of the cycle; results demonstrated that adjustment of data, according to mean RBC age, broadens dichotomy of monocyte and RBC data.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1983

Circulating anti-insulin receptor antibodies in a patient suffering from lupus nephritis and hypoinsulinemic hypoglycaemia.

A 46-year-old female patient suffering from Lupus Nephritis came to our attention in 1981 for severe recurrent hypoglycaemia; she was obliged to eat every 5-7 hr to maintain glucose values not below 1.3-1.6 mM. All known causes of hypoglycaemia were excluded by performing selective angiography of the pancreas and skull, chest and abdominal computerized tomography, as well as stimulation and suppression tests. Oral glucose tolerance, tolbutamide and intravenous insulin (0.4 U/Kg b.w.) tests demonstrated that the patient was highly insulin resistant; furthermore, studies on the patient's red blood cells suggested that her insulin receptors were completely unable to bind insulin. Studies carried out to reveal the reason for this binding inhibition demonstrated that red blood cells from normal subjects as well as adipocytes from normal rats incubated with the patient's serum did not bind insulin (50% inhibition occurring at about 1:30 serum dilution). Insulin binding inhibitors were found in the fraction of the serum precipitated by ammonium sulphate. The serum cleared of IgG fraction was unable to affect insulin binding. These data demonstrate that the serum from the female patient investigated contained anti-insulin receptor antibodies blocking the binding of insulin to its receptors. Plasmapheresis improved the patient's metabolic status. The clinical picture would suggest that recurrent hypoglycaemia was caused by anti-insulin receptor antibodies acting as insulin on target cells.

Autoantibodies↗
PubMed1982

Factor VII in liver cirrhosis.

Factor VII activity and factor VII cross-reacting material (CRM) in plasma of patients with liver cirrhosis have been studied before and after vitamin K1 parenteral administration. Subjects were divided into two groups according to the absence (group I) or the presence (group II) of the following clinical findings: ascites, portal hypertension, encephalopathy. Factor VII activity and CRM show a statistically significant correlation (p less than 0.001) in all patients. In group II, significantly reduced levels of both activity and CRM were found as compared to the reference and the group I values. No variations were found after vitamin K administration. Different thromboplastins, investigated with respect to their sensitivity for factor VII, acted differently. Patients with normal albumin levels also showed normal levels of factor VII activity and antigen. No correlation was found in group II. The data discussed suggest that in liver cirrhosis with unknown aetiology no immunologically detectable precursor of factor VII is present.

Adult↗
PubMed1981

[In vivo effects of conjugated estrogens on the insulin receptor and on glucose binding in isolated adipocytes of male rats].

Studies have been carried out with labeled substrates on isolated adipocytes of male rats injected with sulpho-conjugated estrogens. Three days treatment did not affect insulin receptor concentration or affinity in the cells. Conversely glucose uptake is reduced in the absence of insulin, or by reduced responsiveness in the presence of it. After ten days treatment, insulin binding impaired on account of reduced receptor concentration, whereas glucose uptake was normal in the absence of insulin, increased at low and decreased at high insulin concentration, on account of both decreased responsiveness and increased sensibility to insulin. Thus it is suggested that estrogens acts on glucose uptake prior to act on the insulin receptor in the adipocytes.

Adipose Tissue↗
PubMed1979

A new abnormal human hemoglobin: Hb Prato (alpha 2 31 (B12) Arg leads to Ser beta 2).

An abnormal human hemoglobin was found in a hemolysate from a 5-year-old healthy child living in Prato (Tuscany, Italy). Strutctural studies demonstrated a previously unreported amino acid substitution, alpha 31 (B12) Arg leads to Ser (this is an alpha 1 beta 1 contact). The new variant has been named Hb Prato. It was unstable in isopropanol and heat-denaturation tests, but has normal functional properties, with respect to whole blood studies. Family studies indicated that the variant had been inherited from the mother, a 39-year-old woman of Sicilian extraction. Hb Prato occurs at 20 and 28% in hemolysates from the boy and woman, respectively.

Adolescent↗
PubMed1977

EPR study of serum ceruloplasmin and iron transferrin in myocardial infarction.

Electron paramagnetic resonance (EPR) analysis of frozen serum from myocardial infarction patients has been conducted. Signal at g=4.3 was found definitively attributable to iron(III)-transferrin complex. Imcrease of serum ceruloplasmin as compared to normal was confirmed, with a concomitant decrease of iron-transferrin content. A mechanism for such correlated variation is hypothesized.

Ceruloplasmin↗
PubMed1974

[A critical analysis of several haematological tests for diagnosis of thalassaemia (author's transl)].

The significance of the haemotological test has been measured on a statistical base. The purpose of such an enquiry is the simplification of diagnosing thalassaemia. A pilot research has been performed on a sample of 25 "normal" and 25 "thalassaemic" cases. The results show that some of the tests are particularly fit to diagnosis. There are reasons to consider best tests, in the order, M.C.Hb., Hb.A2, M.C.V., Hb., Reticolociti, Ht., M.C.Hb.C. By combining such tests one obviously obtains more reliable results. Combination Hb.-Ht. appears a useful test in a large number of cases. The "doubtful" cases can be best treated by adding in a Hb.A2 test or else a G.R. test. In the last case one obtaine Hb./G.R. and Ht./G.R., that is M.C.Hb. and M.C.V.

Erythrocyte Count↗