Magnetic field dependence of the circular dichroism in EuTe.

The absorption magnetic circular dichroism in EuTe was investigated as a function of the magnetic field at T = 2 K. In order to describe the optical spectra theoretically, we developed a model that takes into account the magnetic order of the lattice as a function of the magnetic field. The model allows us to calculate the absorption spectrum as a continuous function of the magnetic field intensity. The theory accounts for the strongly dichroic absorption seen at high fields, and for its continuous evolution towards the B = 0 spectrum, which is described by a much weaker and much broader absorption line. The drastic changes observed in the experimental spectra as a function of magnetic field are fully explained by the dependence of the Eu(2+) spin arrangement on the external magnetic field.

Third harmonic generation imaging for fast, label-free pathology of human brain tumors.

In brain tumor surgery, recognition of tumor boundaries is key. However, intraoperative assessment of tumor boundaries by the neurosurgeon is difficult. Therefore, there is an urgent need for tools that provide the neurosurgeon with pathological information during the operation. We show that third harmonic generation (THG) microscopy provides label-free, real-time images of histopathological quality; increased cellularity, nuclear pleomorphism, and rarefaction of neuropil in fresh, unstained human brain tissue could be clearly recognized. We further demonstrate THG images taken with a GRIN objective, as a step toward in situ THG microendoscopy of tumor boundaries. THG imaging is thus a promising tool for optical biopsies.

QTc interval prolongation during infusion with dipyridamole or adenosine.

The aim of our study was to discover whether there was a relationship between the QTc interval prolongation on the standard 12-lead electrocardiogram (ECG) and provoked myocardial ischemia. Since the increase of adenosine plasma levels, obtained either with adenosine or dipyridamole (an adenosine reuptake inhibitor) infusion, has been used to test the coronary artery reserve in patients affected by coronary artery disease, the QTc interval modifications during dipyridamole or adenosine echocardiographic stress test were evaluated. Twenty-five patients admitted to our Institute for evaluation of chest pain of suspected myocardial origin underwent an echocardiographic dipyridamole stress test (0.84 mg/kg over 10 min) after discontinuation of antianginal treatment. Of these patients, 10 underwent an echocardiographic adenosine stress test (scalar doses of 50, 75, 100, 140 micrograms/kg/min) after 48-72 h. The Bazett formula was used to evaluate the QTc interval. After dipyridamole and adenosine administration, a significant prolongation of the QTc interval was observed only in those patients who had positive test results. Our data suggested that QTc interval prolongation during pharmacological stress tests might be considered a marker of myocardial ischemia.

Pharmacological preconditioning of ischemic heart disease by low-dose dipyridamole.

Fourteen patients affected with coronary artery disease underwent two consecutive dipyridamole echocardiographic stress tests, in basal conditions and after repeated low doses of intravenous dipyridamole, following the observation that pulse increases in adenosine plasma levels due to repeated intravenous administration of dipyridamole mimic the mechanism of ischemic preconditioning. Echocardiographic, electrocardiographic, haemodynamic parameters, and adenosine plasma levels were measured. After the second test, six patients were completely negative, and in those eight still positive the onset of dyssynergy was delayed.

Calcium infusion induces myocardial ischaemia in patients with coronary artery disease by a mechanism possibly adenosine mediated.

In the first part of the study five healthy volunteers were submitted to i.v. infusion of 0.2 mM.kg-1 b.w. of calcium gluconate over 20 min. Total calcium (atomic absorption method), ionized calcium (ion-selective electrode method) and adenosine (HPLC technique) were measured at the following times: 0 (basal), 5, 10, 15, 20 (end of infusion), 25, 30, 35, and 50 min. The increase in total and ionized calcium serum levels was associated with a significant increase in adenosine plasma levels (from 207 +/- 41 to 362 +/- 63 nM.l-1, P < 0.001). Since the increase in adenosine plasma levels, obtained either with adenosine or dipyridamole (an adenosine reuptake inhibitor), has been used to test the coronary reserve in coronary artery disease (CAD) patients, in the second part of the study we compared the effects of calcium infusion with dipyridamole in 15 subjects. Pharmacological stress tests were evaluated by monitoring two-dimensional echocardiography and ECG. Ten patients had positive results with both the dipyridamole stress test and the calcium infusion. Our results show that calcium infusion induces an increase in adenosine plasma levels that can elicit a dipyridamole-like coronary steal, thus suggesting the central role of extracellular adenosine in myocardial ischaemia.

[The infusion of calcium gluconate in coronary disease patients induces myocardial ischemia via a possible adenosine-mediated mechanism]. / L'infusione di calcio gluconato in pazienti coronaropatici induce ischemia miocardica attraverso un possibile meccanismo adenosino-mediato.

In the first part of the study 5 control subjects were submitted to iv infusion of 0.2 mM/kg of calcium gluconate in 20 min. Total calcium (atomic absorbtion method), ionized calcium (ion-selective electrode method) and adenosine (HPLC technique) were measured at the following times: 0 (baseline), 5, 10, 15, 20 (end of infusion), 25, 30, 35, and 50 min. The increase of total and ionized calcium serum levels was associated with a significant increase of adenosine plasma levels (from 207 +/- 41 to 362 +/- 63 nM, p < 0.001). Since the increase of adenosine plasma levels, obtained either with adenosine or dipyridamole (an adenosine reuptake inhibitor), has been used to test the coronary reserve in patients with coronary artery disease (CAD), in the second part of the study we compared the effects of calcium infusion with dipyridamole in 15 CAD subjects. Pharmacological stress tests were evaluated by monitoring two-dimensional echocardiography, ECG, heart rate, blood pressure and rate-pressure product. Ten patients were positive both to dipyridamole stress test and to calcium infusion, ad demonstrated by the onset of new areas of transient asynergy in the same myocardial regions. Dipyridamole infusion determined a significant increase in heart rate and rate pressure-product in all patients (both in positive and in negative), whereas calcium induced a slight, not significant decrease of these parameters.(ABSTRACT TRUNCATED AT 250 WORDS)