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Biomedical subjects

M Alecci

Publications and source records attributed to M Alecci.

31 records · Page 2Linked to original sources
PubMed1996

Continuous-wave NMR imaging of solids.

Current pulsed nuclear magnetic resonance methods of imaging samples such as solids with short spin-spin relaxation times are restricted to use with T2 values longer than approximately 10 microseconds. In the present study a method of imaging ultra-short T2 samples using continuous- wave, swept-field NMR is presented that, in principle, will be able to overcome this restriction. The technique is identical to that used in continuous-wave electron paramagnetic resonance imaging of paramagnetic species and involves irradiating the sample continuously with a radiofrequency excitation in the presence of a strong stationary magnetic field gradient. When the main magnetic field is swept over a suitable range, the variation of the NMR absorption signal with applied magnetic field yields a one-dimensional projection of the object under study along the gradient direction. Two- or three-dimensional image data sets may be reconstructed from projections that are obtained by applying the gradient in different directions. Signal-to-noise ratio can be improved by modulating the magnetic field and employing a lock-in amplifier to recover signal variations at the audio modulation frequency. Preliminary experiments were performed using a 7 Tesla magnet and a 300 MHz continuous-wave radiofrequency bridge with lock-in detection. The apparatus is described and the results of pilot experiments that employed vulcanized rubber samples are presented. The ability of the technique to detect short T2 samples was demonstrated by the presence of a background signal from the Perspex former of the birdcage resonator used for signal reception.

Magnetic Resonance Spectroscopy↗
PubMed1996

Platelet serotonin pathway in menstrual migraine.

In order to understand the possible 5-hydroxytryptamine (5HT) anomalies in migraine, particularly in the period before the headache attack, we compared the levels of 5HT, its stable metabolite 5-hydroxyindoleacetic acid (5HIAA) and platelet monoaminoxidase (MAO) activity in patients with menstrual migraine with those of healthy female controls. In every subject, blood samples were drawn during both follicular and late luteal phases of the menstrual cycle. In controls, platelet 5HT levels remained stable, whereas 5HIAA levels and MAO activity were higher in the luteal than in the follicular phase, suggesting an increased catabolism of 5HT which occurs physiologically just before menses. In menstrual migraine 5HIAA levels and MAO activity showed similar changes with higher values in the luteal than in the follicular phase. The luteal phase values were significantly higher than those of controls. Also, and in contrast to controls, 5HT levels decreased in the luteal phase. These data suggest that 5HT availability is reduced in menstrual migraine, possibly due to an increased catabolism and/or to a reduced synthesis, and hence predisposes patients to migraine attacks.

Adult↗
PubMed1995

Metabolism and menstrual cycle rhythmicity of serotonin in primary headaches.

We investigated the platelet and plasma levels of serotonin and its metabolite, 5-hydroxyindoleacetic acid, in patients suffering from episodic tension-type headache and migraine with and without aura, during a headache-free period. In female subjects, blood samples were drawn during the follicular, ovulatory, and late luteal phases of the menstrual cycle. In tension headache and migraine with aura, the group mean values of serotonin and 5-hydroxyindoleacetic acid in platelets and plasma were significantly increased, but migraine without aura patients' levels were normal. The pattern of menstrual cycle-related fluctuations in platelet serotonin levels were similar in female patients with tension headache and in controls, with a maximum value in the follicular phase. In both migraine groups, in contrast, the peak occurred in the ovulatory phase. The results are discussed in view of whether these aberrations in peripheral markers of the metabolism and menstrual cycle-related rhythmicity of serotonin may reflect similar alterations in the central nervous system.

Adolescent↗
PubMed1994

In vivo electron paramagnetic resonance spectroscopy-imaging in experimental oncology: the hope and the reality.

PURPOSE: Low frequency (280 MHz) electron paramagnetic resonance imaging is a new magnetic resonance technique, still being developed, that can map the in vivo spatial distribution of paramagnetic species such as nitroxide free radicals. The reduction rate of these molecules is affected by oxygen concentration. This paper gives some examples of the use of electron paramagnetic resonance imaging methodology in whole rats in the framework of its possible use in experimental oncology. METHODS AND MATERIALS: The 280 MHz apparatus based on a cylindrical 16 pole magnet was developed and designed specifically for 50-200 g laboratory animals. It generates the main field and the three field gradients required for three-dimensional (3-D) projections. A pyrrolidine nitroxyl (2,2,5,5,-tetramethylpyrrolidine-1-oxyl-3-carboxylic acid) was injected intravenously in rats to provide an electron paramagnetic resonance signal for in vivo measurements. Electron paramagnetic resonance X-band spectrometer was used to monitor pyrrolidine nitroxyl decay in an external blood circuit during normoxia and moderate hypoxia (15% O2). RESULTS AND CONCLUSION: One-dimensional (1-D) transversal and longitudinal mapping of this nitroxide free radical distribution in rat whole body was obtained 7-9 min after injection. In circulating blood, nitroxide half-life decreased significantly during hypoxia. The present sensitivity (10(-4)-10(-5) M), spatial resolution (3-10 mm) and collection time (3-5 min) could be drastically improved by narrow linewidth paramagnetic probes and pulsed techniques.

Animals↗
PubMed1994

Simultaneous 280 MHz EPR imaging of rat organs during nitroxide free radical clearance.

A radio frequency (RF) (280 MHz) electron paramagnetic resonance (EPR) spectroscopy and imaging apparatus has been used to localize a pyrrolidine nitroxide free radical in the rat abdomen and thorax. The nitroxide 2,2.5.5,-tetramethylpyrrolidine-1-oxyl-3- carboxylic acid (PCA) had a whole body monoexponential decay with half-life of 13.3 +/- 0.7 (n = 4), 19.4 +/- 0.2 (n = 3), and 23 +/- 2 (n = 6) min for 1, 2, and 3 mmol/kg PCA, respectively. Up to seven one-dimensional longitudinal projections were collected on six rats in the presence of a 8 mT/m field gradient. With an injection dose of 3 mmol/kg, PCA half-lives were 19 +/- 1, 17 +/- 2, and 22 +/- 2 min (n = 6) in the lower abdomen, in the liver, and in the thorax, respectively. Thorax half-life was significantly longer than liver half-life. Sequential two-dimensional images of PCA distribution in a plane longitudinal to the rat body were obtained from eight spectra in the presence of a gradient of 12 mT/m (acquisition time 5 min; spatial resolution 8 mm). After 7 min, the nitroxide was detectable in the left side of the thorax area, but it was mostly localized in the liver. PCA was more uniformly distributed in the image collected after 17 min.

Animals↗
PubMed1994

Decreased collagen-induced platelet aggregation and increased platelet arginine levels in migraine: a possible link with the NO pathway.

We studied whole blood platelet aggregation induced by collagen, platelet activating factor (PAF) and measured basal platelet L-arginine (L-arg) levels, as an indirect index of the nitric oxide (NO) pathway in migraine. Migraine, both with and without aura groups, showed a reduced aggregation to collagen, but not to PAF, compared with control subjects. Platelet L-arg levels were significantly increased in migraine with aura sufferers, whereas the plasma levels were in the same range in migraineurs and controls. Platelet hyperesponsiveness to collagen stimulation in migraine may be linked to an increased availability of the amino acid precursor and an abnormal NO synthesis.

Adolescent↗
PubMed1994

Platelet secretion from dense and alpha-granules in vitro in migraine with or without aura.

Several studies in vivo indicate platelet activation in migraine, as reflected by increased plasma concentrations of platelet secretory products. In vitro data on platelet secretion are scant, which prompted an investigation into agonist-induced platelet aggregation and secretion in platelets from patients with migraine. Sixty two patients with migraine with aura (MA) and 41 with migraine without aura (MwA) were studied during a headache-free phase, together with 26 healthy controls. Platelet aggregation and secretion in platelet-rich plasma were induced by collagen and platelet activating factor (PAF). Serotonin was measured by high performance liquid chromatography and platelet factor 4 (PF4) with an enzyme immunoassay kit. There were no significant aberrations in platelet aggregation in those with migraine compared with healthy controls. The platelet PF4 secretion induced by PAF (1.0 and 0.1 microM) was increased in MwA (p < 0.05, p < 0.0001) compared with controls, and there was a similar trend in MA (NS, p < 0.01). By contrast, the PF4 secretion induced by collagen (0.5 and 2.0 micrograms/ml) was reduced in MA (p < 0.01 and p < 0.05). Further, the MA group exhibited increased basal intraplatelet serotonin concentrations (p < 0.0001) and increased serotonin secretion induced by both concentrations of collagen (p < 0.0001) and PAF (p < 0.001). The data indicate an abnormal platelet a-granule secretion in those with migraine, and focus attention on PAF as a possible factor contributing to the platelet activation associated with migraine. The increased platelet content and secretion of serotonin was specific to MA, and may reflect different serotonin turnover in the two clinical migraine types.

Adolescent↗
PubMed1993

Increased platelet serotonin content and hypersecretion from dense and alpha-granules in vitro in tension-type headache.

We investigated platelet aggregation and secretion from dense and alpha-granules in vitro in 28 tension-type headache (TH) patients and 26 healthy controls. We also measured basal platelet serotonin levels. Platelet aggregation was normal in TH, but the secretion of serotonin and platelet factor 4 (PF4) was significantly increased in response to 0.5 and 2.0 micrograms/ml collagen and to 1.0 mumol/l PAF. The basal platelet serotonin levels were also higher in patients than in controls. The mechanisms of platelet hypersecretion remain to be determined, but the increased secretion of serotonin is probably in part related to the increased basal levels. The increased platelet serotonin in TH patients may reflect an enhanced serotonin turnover.

Adolescent↗
PubMed1992

Whole rat electron paramagnetic resonance imaging of a nitroxide free radical by a radio frequency (280 MHz) spectrometer.

Low frequency (280 MHz) electron paramagnetic resonance spectroscopy has been used to follow uptake, distribution and reduction of the nitroxyl spin label PCA in the rat. No difference of half life was found in seven rats submitted to three administrations of PCA (11.3 +/- 0.4; 11.0 +/- 0.6 and 11.5 +/- 0.7 min). Transversal two-dimensional images of PCA distribution in the rat body were obtained over 6 min by means of field gradients. PCA was observed in three regions by projections along the longitudinal axis of the rat. PCA accumulation was found in the lower abdomen 12 min after the start of the PCA injection.

Animals↗
PubMed1990

Three-dimensional in vivo ESR imaging in rats.

The first experiment of tridimensional in vivo ESR imaging at 1.2 GHz is described in this paper. The tails of rats weighing 300-350 grams were visualized using 1 cc of a 50 * 10(-3) M solution of nitroxide free radical injected in the caudal vein. In an even distribution of spin label is assumed this would correspond to a final concentration of about 10(-4) M. A reconstruction from projections was used to obtain the images. The apparatus utilizes stationary field gradients. Projections were obtained by sweeping the main field. For 3D reconstructions, the projections were collected along 32 * 8 field gradient orientations. The whole procedure takes approximately 18 minutes.

Animals↗
PubMedDate not supplied

Young Investigator Award presentation at the 13th Annual Meeting of the ESMRMB, September 1996, Prague. A proton-electron double-resonance imaging apparatus with simultaneous multiple electron paramagnetic resonance irradiation at 10 mT.

The detection of free radicals in vivo is very important for the study of many physiologic and pathologic conditions. Free radicals have been implicated in a number of diseases such as ischemia, inflammation, kidney damage, and cancer. Proton-electron double-resonance imaging (PEDRI) allows the indirect detection of free radicals via the Overhauser effect. Nitroxide free radicals used for in vivo PEDRI studies present spectra with two or three lines, but most PEDRI experiments performed to date have used only single-line electron paramagnetic resonance (EPR) irradiation. There is theoretical evidence that simultaneous irradiation of multiple EPR transitions could increase the maximum achievable PEDRI enhancement. From the experimental point of view, this requires the combined use of a suitable multiple-frequency EPR source and a multiple-tuned EPR resonator. A novel radiofrequency (RF) triple-tuned loop-gap resonator for use in PEDRI has recently been developed, and dynamic nuclear polarization (DNP) data were reported. In the present study we describe a new PEDRI apparatus, equipped with a triple-tuned resonator, that is suitable for simultaneous double- or triple-EPR irradiation of nitroxide free radicals. In particular, the details of the EPR hardware used to generate the two or three EPR frequencies are given, and PEDRI images obtained with simultaneous multiple EPR irradiation are shown. Moreover, DNP experimental results showing the increase of the enhancement as a function of the EPR power for single and simultaneous double EPR irradiation are presented. The main goal of this apparatus is to improve the sensitivity and/or to reduce EPR irradiation power in a PEDRI experiment. This is likely to be particularly important in future biologic applications of PEDRI where the applied power must be optimized to reduce sample heating.

Awards and Prizes↗
PubMedDate not supplied

Effect of picotamide and aspirin, combined or alone, on platelet aggregation in patients with cerebral infarction.

After 7 and 90 days of treatment, we studied the effect of picotamide, a thromboxane synthase inhibitor (450 and 900 mg/day), aspirin (150 mg/day), and aspirin plus picotamide (150 and 450 mg/day respectively) on platelet aggregation, evaluated in platelet rich plasma of 48 patients affected by ischemic stroke. Platelet aggregation, induced by collagen (1.0 and 2.0 micrograms/ml) and adenosine diphosphate (1.0 and 10 micrograms/L), was significantly increased in patients in comparison with healthy controls. Aspirin (150 mg/day) reduced collagen-induced platelet aggregation (1.0 microgram/ml) after 7 days of treatment. Picotamide (450 mg/day) reduced platelet aggregation induced by both concentrations of collagen, while the higher dose (900 mg/day) had no significant effect. Aspirin plus picotamide reduced the aggregation induced by 1.0 microgram/ml collagen and by 10 mumol/L adenosine diphosphate after 90 days of therapy. This study has shown that patients during the acute phase of stroke are characterized by an increased in vitro platelet aggregation. Aspirin may be beneficial in the acute phase of the cerebral ischemic event. Picotamide and picotamide plus aspirin could be useful for reducing platelet aggregation in long term treatment.

Acute Disease↗