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Biomedical subjects

C Signorini

Publications and source records attributed to C Signorini.

At least 19 recordsLinked to original sources
PubMed2001

Identification of Mycobacterium xenopi by gas chromatography.

For the purposes of the following study we cultured 32 strains of Mycobacterium xenopi isolated from clinical specimens and several strains of other slowly growing mycobacteria. The cultures were grown in liquid medium and then analysed--after saponification, methylation, extraction with organic solvent and washing of the organic phase--using a highly sensitive manual gas-liquid chromatographic assay for the determination of secondary alcohol 2-OH-docosanol. The percentage of this compound was compared with that previously measured in strains of Mycobacterium xenopi grown on solid medium. The presence of this specific alcohol was always apparent, even though its quantity was lower than that obtained by growing mycobacteria on solid medium. The absence of interference peaks around the compound was checked by analyzing strains of other slowly growing mycobacteria in the same conditions.

Chromatography, Gas↗
PubMed2000

Protection of erythrocytes against oxidative damage and autologous immunoglobulin G (IgG) binding by iron chelator fluor-benzoil-pyridoxal hydrazone.

Iron is released in a free desferrioxamine-chelatable form when erythrocytes are challenged by an oxidative stress. The release of iron is believed to play an important role in inducing destructive damage (lipid peroxidation and hemolysis) or in producing membrane protein oxidation and generation of senescent cell antigens (SCA). In this report, we further tested the hypothesis that intracellular chelation of iron released under conditions of oxidative stress prevents erythrocyte damage or SCA formation. Fluor-benzoil-pyridoxal hydrazone (FBPH), an iron-chelating molecule of the family of aromatic hydrazones, was prepared by synthesis and used for the above purpose after the capacity of the product to enter cells had been ascertained. GSH-depleted mouse erythrocytes were incubated with the oxidant drug phenylhydrazine in order to produce iron release, lipid peroxidation, and hemolysis. FBPH at a concentration of 200 microM prevented lipid peroxidation and hemolysis in spite of equal values of iron release. FBPH was active even at a lower concentration (100 microM) when the erythrocytes were preincubated with it for 15 min. No preventive effect was seen when FBPH saturated with iron was used. Prolonged aerobic incubation (60 hr) of erythrocytes produced iron release and formation of SCA as determined by autologous immunoglobulin G (IgG) binding. The IgG binding was detected by using an anti-IgG antibody labeled with fluorescein and by examining the cells for fluorescence by confocal microscopy. FBPH prevented SCA formation in a dose-related manner. These results lend further support to the hypothesis that iron release is a key factor in erythrocyte ageing.

Animals↗
PubMed1999

Hemolytic drugs aniline and dapsone induce iron release in erythrocytes and increase the free iron pool in spleen and liver.

Incubation of rat erythrocytes with the hydroxylated metabolites of aniline and dapsone (4-4'-diaminodiphenylsulfone), phenylhydroxylamine and dapsone hydroxylamine, respectively, induced marked release of iron and methemoglobin formation. On the contrary, no release of iron nor methemoglobin formation was seen when the erythrocytes were incubated with the parent compounds (aniline and dapsone). The acute intoxication of rats with aniline or dapsone induced a marked increase in the erythrocyte content of free iron and methemoglobin, indicating that the xenobiotics are effective only after biotransformation to toxic metabolites in vivo. Prolonged administration of aniline or dapsone to rats produced continuous release of iron from erythrocytes. Marked iron overload was seen in the spleen and in the liver Kupffer cells, as detected histochemically. The spleen weight in these subchronically treated animals was significantly increased. The free iron pool was markedly increased in the spleen and to a lower extent in the liver. The possible relationships between iron release in erythrocytes, oxidative damage seen in senescent cells, hemolysis, overwhelmed capacity of spleen and liver to keep iron in storage forms and subsequent increase in low molecular weight, catalitically active iron is discussed.

Aniline Compounds↗
PubMed1999

Iron release in erythrocytes from patients with beta-thalassemia.

Our previous studies have shown that iron is released in a free (desferrioxamine-chelatable) form when erythrocytes undergo oxidative stress (incubation with oxidizing agents or aerobic incubation in buffer for 24-60 h (a model of rapid in vitro ageing)). The release is accompanied by oxidative alterations of membrane proteins as well as by the appearance of senescent antigen, a signal for termination of old erythrocytes. In hemolytic anemias by hereditary hemoglobin alterations an accelerated removal of erythrocytes occurs. An increased susceptibility to oxidative damage has been reported in beta-thalassemic erythrocytes. Therefore we have investigated whether an increased iron level and an increased susceptibility to iron release could be observed in the erythrocytes from patients with beta-thalassemia. Erythrocytes from subjects with thalassemia intermedia showed an extremely higher content (0 time value) of free iron and methemoglobin as compared to controls. An increase, although non-statistically-significant, was seen in erythrocytes from subjects with thalassemia major. Upon aerobic incubation for 24 h the release of iron in beta-thalassemic erythrocytes was by far greater than in controls, with the exception of thalassemia minor. When the individual values for free iron content (0 time) seen in thalassemia major and intermedia were plotted against the corresponding values for HbF, a positive correlation (P < 0.001) was observed. Also, a positive correlation (P < 0.01) was seen between the values for free iron release (24 h incubation) and the values for HbF. These results suggest that the presence of HbF is a condition favourable to iron release. Since in beta-thalassemia the persistance of HbF is related to the lack or deficiency of beta chains and therefore to the excess of alpha chains, the observed correlation between free iron and HbF, is consistent with the hypothesis by others that excess of alpha chains represents a prooxidant factor.

Adult↗
PubMed1999

Gas chromatographic assay of cellular fatty acids and alcohols for the identification of Mycobacterium species.

Ten mycobacterial species obtained from 141 cultures isolated from clinical specimens were studied. The cultures were grown on solid medium and then analysed-after saponification, methylation, extraction with organic solvent and washing of the organic phase--by capillary gas-liquid chromatography for fatty acid and secondary alcohol composition. The absence of secondary alcohols was characteristic of M. genavense, M. tuberculosis and the following Mycobacterium species with specific branched-chain fatty acids allowing their direct identification: M. gordonae, M. kansasii and M. marinum. The presence of secondary alcohols was characteristic of M. avium, M. phlei, M. scrofulaceum, M. terrae and M. xenopi. In the case of M. xenopi direct identification was made possible by the presence of a specific alcohol.

Alcohols↗
PubMed1998

Hypoxia-induced free iron release in the red cells of newborn infants.

Heparinized blood samples were obtained at birth from 164 newborn infants (101 full term; 63 preterm). Intra-erythrocyte free iron concentration and hypoxanthine plasma levels were determined by high-pressure liquid chromatography. Intra-erythrocyte free iron concentration was higher in preterm than in full term babies (p < 0.0001) and adults (p < 0.0001). Statistically significant correlations were observed between intra-erythrocyte free iron concentration and hypoxanthine levels (r = 0.66; p = 0.0001), pH (r = -0.76; p = 0.0001), base excess (r = -0.79; p = 0.0001), and gestational age (r = -0.44; p = 0.0001) in both infant populations. Multiple regression analysis between intra-erythrocyte free iron concentration in cord blood, as an independent variable, and Apgar score at 1 min, pH, base excess, hypoxanthine values, FiO2 needed for resuscitation immediately after delivery, and gestational age, as dependent variables, identified hypoxanthine levels (p = 0.0003; partial F-test = 15.4) as the best single predictor of intra-erythrocyte free iron concentration. In conclusion, hypoxia induces intra-erythrocyte free iron release, and therefore enhances the risk of oxidative injury due to hydroxyl radical generation.

Adult↗
PubMed1997

Protection against oxidative damage of erythrocyte membrane by the flavonoid quercetin and its relation to iron chelating activity.

Incubation of glutathione (GSH) depleted mouse erythrocytes with the oxidants phenylhydrazine, acrolein, divicine and isouramil resulted in the release of free iron and in lipid peroxidation and hemolysis. The addition of the flavonoid quercetin, which chelates iron and penetrates erythrocytes, resulted in remarkable protection against lipid peroxidation and hemolysis. The protection seems to be due to intracellular chelation of iron, since a semi-stoichiometric ratio between released iron and the amount of quercetin necessary to prevent lipid peroxidation and hemolysis was found. Incubation of GSH depleted human erythrocytes with divicine and isouramil did not induce lipid peroxidation and hemolysis in spite of a substantial release of iron. However, divicine and isouramil produced alterations of membrane proteins, such as spectrin and band 3, as well as formation of senescent cell antigen. The addition of quercetin prevented these alterations.

Acrolein↗
PubMed1997

Release of free, redox-active iron in the liver and DNA oxidative damage following phenylhydrazine intoxication.

Following the subchronic intoxication of rats with phenylhydrazine, resulting in marked anemia, reticulocytosis, methemoglobinemia and increased hemocatheresis, the hepatic content of total iron was increased, as was hepatic ferritin and its saturation by iron. A striking increase (approximately 7-fold) was also observed in free iron which appeared to be redox-active. The increase in liver free iron involved the hepatocellular component of the liver. Since DNA is one of the cellular targets of redox active iron, liver DNA from phenylhydrazine-treated rats was analyzed by electrophoresis and found to be markedly fragmented. Experiments with isolated hepatocytes in culture or in suspension challenged with phenylhydrazine or Fe-nitrilotriacetate strongly suggested that the DNA damage was due to reactive iron rather than to the hepatic metabolism of phenylhydrazine. The levels of 8-oxo-7,8-dihydro-2'-deoxyguanosine (8-oxodGuo), a specific marker of oxidative DNA damage, were significantly higher in phenylhydrazine-treated rats as compared to untreated controls. The prolongation of phenylhydrazine treatment over a period of 6 weeks resulted in a persistent damage to DNA and in phenotypic changes such as an increase in hepatocyte gamma-glutamyl transpeptidase (gamma-GT, EC 2.3.2.2) activity. Possible relationships between iron overload, iron release, DNA damage and tumor initiation are discussed.

Animals↗
PubMed1995

Iron release, membrane protein oxidation and erythrocyte ageing.

The aerobic incubation of erythrocytes in phosphate buffer for 24-60 h (a model of rapid in vitro ageing) induced progressive iron release and methemoglobin formation. Membrane proteins showed electrophoretic alterations and increase in carbonyl groups (as documented by IR spectroscopy). None of these phenomena were seen when the erythrocytes were incubated under anaerobic conditions. The membranes from aerobically incubated cells bound a much higher amount of autologous IgG than those from anaerobically incubated ones, suggesting that the aerobic incubation gives rise to the senescent antigen. The addition of ferrozine during the aerobic incubation prevented both the IgG binding and the protein alterations seen in the IR spectra, suggesting an intracellular chelation of the released iron by ferrozine.

Animals↗
PubMed1995

Italian external quality assessment scheme in immunoassay.

This paper deals with the organization, the data processing and some of the results obtained in Italian external quality assessment (EQA) schemes for hormones, tumor markers and hepatitis B markers. The EQA for hormones and tumor markers includes up to sixteen analytes together with the participation, in 1990, of about 250 laboratories. Laboratory results were used to prepare periodic and end-of-period reports. The former includes the results (with the related statistical parameters) obtained by all participants and by laboratories using the same method, as well as the histogram of the data. The end-of-period report contains estimates of imprecision and average bias for all laboratories, for each laboratory and for the more widely employed kits. From 1980 to 1988, laboratory variability improved significantly for TSH, progesterone, estradiol, testosterone, CEA and ferritin, slightly for cortisol, FSH, prolactin and AFP, while there was no improvement for both total T3 and T4. For LH we found an unusually high variability mainly due to systematic differences between kits based on different monoclonal antibodies. About 200 laboratories participated in the EQA for hepatitis B markers (HBsAg and anti-HBs) organized in 1990. For these analytes the periodic reports show the percentage of negative and positive results and the histogram of the responses (absorbance or counts) normalized with respect to the cut off.

Diagnostic Tests, Routine↗
PubMed1995

The quality assurance system in clinical chemistry.

The quality assurance system in clinical chemistry allows for the identification of errors and control actions to correct them. It is well known that laboratory errors can be classified as: pre-analytical, analytical and post-analytical. While pre-analytical and post-analytical errors are very difficult to identify, the analytical variability (both imprecision and inaccuracy) can be monitored with internal quality control (IQC) programs and external quality assessment (EQA) schemes. The purpose of IQC is mainly to verify the stability of laboratory estimates with time and therefore it is essentially a control of imprecision. IQC programs are based on the use of control samples which are analyzed in each analytical series. The easiest method of representing IQC data is by the use of Shewhart's chart, although "cusum" chart and Youden plot are often useful. As for the criteria according to which an analytical series should be accepted or rejected, the use of practical control rules is widely spread in laboratories. Participation in EQA schemes allows the laboratory to have a retrospective estimate of its performance in terms of both imprecision and inaccuracy, if definitive or reference methods are available. In lack of definitive or reference methods, consensus mean or median can be derived from the data obtained by all the participants or, in some cases, by the participants using the same analytical method (e.g. for analytes not yet completely characterized and measured with immunoassays.

Chemistry, Clinical↗
PubMed1994

Iron release, lipid peroxidation, and morphological alterations of erythrocytes exposed to acrolein and phenylhydrazine.

Iron is released in a free [desferrioxamine (DFO)-chelatable] form in mouse erythrocytes incubated with the oxidizing agents acrolein and phenylhydrazine or in erythrocytes drawn from allyl alcohol-intoxicated mice. The release is accompanied by peroxidation of membrane lipids when the cells are depleted of glutathione. Lipid peroxidation is always followed by the lysis of the cells. The release of iron is also accompanied by methemoglobin formation, but the extent of the release does not correlate with the level of methemoglobin production. The addition of DFO to the incubation mixture or the preincubation of the erythrocytes with DFO in millimolar concentrations completely prevents both lipid peroxidation and hemolysis while not significantly changing the level of iron release. Morphological studies carried out with scanning electron microscopy showed a number of alterations in the shape of the incubated erythrocytes, including echinocyte transformation and the appearance of codocyte, stomatocyte, and cnizocyte like forms. These alterations were more prominent with increasing lipid peroxidation and hemolysis, even if occurring in their absence. On the contrary, the appearance of pits and holes was strictly associated with lipid peroxidation and lysis.

1-Propanol↗
PubMed1993

Iron released from an erythrocyte lysate by oxidative stress is diffusible and in redox active form.

The incubation of a ghost-free erythrocyte lysate with the oxidizing agent phenylhydrazine resulted in both methemoglobin formation and release of iron in a desferrioxamine (DFO)-chelatable form. The released iron was diffusible, as shown by a dialysis carried out simultaneously with the incubation. When the dialysate was added to erythrocyte ghosts or to microsomes from liver or brain, lipid peroxidation developed in the membranes, indicating that the diffusible iron was in a redox active form. The addition of ATP to the lysate markedly increased both iron diffusion and lipid peroxidation in the membranes subsequently added to the dialysate. The possible implication of these data in some well known pathologies is discussed.

Adenosine Triphosphate↗
PubMed1992

Iron release and membrane damage in erythrocytes exposed to oxidizing agents, phenylhydrazine, divicine and isouramil.

Mouse erythrocytes were incubated with oxidizing agents, phenylhydrazine, divicine and isouramil. With all the oxidants a rapid release of iron in a desferrioxamine (DFO)-chelatable form was seen and it was accompanied by methaemoglobin formation. If the erythrocytes were depleted of GSH by a short preincubation with diethyl maleate, the release of iron was accompanied by lipid peroxidation and, subsequently, haemolysis. GSH depletion by itself did not induce iron release, methaemoglobin formation, lipid peroxidation or haemolysis. Rather, the fate of the cell in which iron is released depended on the intracellular availability of GSH. In addition, iron release was higher in depleted cells than in native ones, suggesting a role for GSH in preventing iron release when oxidative stress is imposed by the oxidants. Iron release preceded lipid peroxidation. The latter was prevented when the erythrocytes were preloaded with DFO in such a way (preincubation with 10 mM-DFO) that the intracellular concentration was equivalent to that of the released iron, but not when the intracellular DFO was lower (preincubation with 0.1 mM-DFO). Extracellular DFO did not affect lipid peroxidation and haemolysis, suggesting again that the observed events occur intracellularly (intracellular chelation of released iron). The relevance of iron release from iron complexes in the mechanisms of cellular damage induced by oxidative stress is discussed.

Animals↗
PubMed1992

Heart rate variability during the acute phase of myocardial infarction.

BACKGROUND: After acute myocardial infarction (AMI), several abnormalities of the autonomic control to the heart have been described. Heart rate (HR) variability has been used to explore the neural control to the heart. A low HR variability count measured 7-13 days after AMI is significantly related to a poor outcome. Little information is available on HR variability early after AMI and its relation to clinical and hemodynamic data. METHODS AND RESULTS: We studied 54 consecutive patients (42 men and 12 women; mean age, 60.4 +/- 11 years) with evidence of AMI by collecting the 24-hour HR SD from Holter tapes recorded on day 2 or 3. We also measured HR variability in 15 patients with unstable angina and in 35 age-matched normal subjects. HR variability was lower in AMI than in unstable angina patients (57.6 +/- 21.3 versus 92 +/- 19 msec; p less than 0.001) and controls (105 +/- 12 msec; p less than 0.001). Also, HR variability was greater in non-Q-wave than in Q-wave AMI (p less than 0.0001) and in recombinant tissue-type plasminogen activator-treated patients with respect to the rest of the group (p less than 0.02). No difference was found for infarct site. HR variability was significantly related to mean 24-hour HR, peak creatine kinase-MB, and left ventricular ejection fraction (all p less than 0.0001). Patients belonging to Killip class greater than I or who required the use of diuretics or digitalis had lower counts (p less than 0.004, p less than 0.001, and p less than 0.024, respectively). Six patients died within 20 days after admission to the hospital. In these patients, HR variability was lower than in survivors (31.2 +/- 12 versus 60.9 +/- 20 msec; p less than 0.001), and a value less than 50 msec was significantly associated with mortality (p less than 0.025). CONCLUSIONS: HR variability during the early phase of AMI is decreased and is significantly related to clinical and hemodynamic indexes of severity. The causes for the observed changes in HR variability during AMI may be reduced vagal and/or increased sympathetic outflow to the heart. It is suggested that early measurements of HR variability during AMI may offer important clinical information and contribute to the early risk stratification of patients.

Angina, Unstable↗
PubMed1992

Interassay variability of immunometric methods for thyrotropin in an external quality assessment survey: evidence that functional sensitivity is not always adequate for clinical decisions.

We investigated the ability of current immunometric methods for thyrotropin (TSH; thyroid-stimulating hormone) to distinguish between low-normal and subnormal hormone concentrations by using the data from an external quality assessment (EQA) survey in 1990. We computed the interassay (between-run) precision profiles from results from 101 laboratories, which used the five most popular kits in the survey; during the control period (one year) each laboratory assayed 4 EQA pools distributed (as hidden replicates) in five occasions. The interassay CV was relatively low (9-13%) for three pools in the normal TSH range (greater than 0.8 milli-int. unit/L) but markedly higher (30-40%, except for one more precise kit) in the subnormal range (0.2 milli-int. unit/L). We calculated the effect of the between-run variability on the diagnostic accuracy (discrimination between normal and subnormal values) for three representative TSH concentrations: 0.2, 0.4, and 0.5 milli-int. unit/L (0.3 milli-int. unit/L was considered the lower normal limit). The three concentrations were reasonably discriminated (P less than or equal to 5%), and only one kit showed a between-run CV less than 18% at 0.2 milli-int. unit/L. For the other four less-precise kits, only the higher TSH value (0.5 milli-int. unit/L) could be classified with an acceptable diagnostic reliability. With the most precise kit, one can distinguish two TSH concentrations in the 0.3-0.5 milli-int. unit/L range that differ by at least 30%; with the other kits, differences greater than 50-60% are needed for reliable discrimination. Thus many laboratories fail to achieve the functional sensitivity of a second-generation assay, even if they use immunometric methods. TSH assays with a better interassay precision in the low concentration range are needed.

Humans↗