Shot noise in linear macroscopic resistors.

We report on direct experimental evidence of shot noise in a linear macroscopic resistor. The origin of the shot noise comes from the fluctuation of the total number of charge carriers inside the resistor associated with their diffusive motion under the condition that the dielectric relaxation time becomes longer than the dynamic transit time. The present results show that neither potential barriers nor the absence of inelastic scattering are necessary to observe shot noise in electronic devices.

Prognosis of hibernating myocardium is independent of recovery of function: evidence from a routine based follow-up study.

Revascularization of hibernating segments improves both ventricular function (VF) and survival. In this study, we determined whether this relation is true in a routine based patients population with mildly reduced VF. Two to 6 years after undergoing 201Tl scintigraphy to detect hibernation, 153 patients were interviewed in order to collect medical information. This population was divided into four groups, according to the presence or absence of myocardial hibernation and of revascularization. Age, gender and left ventricular ejection fraction (LVEF) were similar in the four groups. Hard cardiac events (HEs) were noted in 14/33 (41%) patients with uncorrected hibernation, while in the other three groups HEs were recorded in fewer than 3% of patients. Univariate analysis indicated that the presence of hibernation, regardless of its extension, was the highest significant predictor of HEs. Multivariate analysis indicated that hibernation, stress ischaemia, age and absence of revascularization were significant predictors of HEs. These findings were not related to changes in LVEF or to New York Heart Association (NYHA) class during follow-up. In this routine based patient population, with mildly reduced VF, the rate of HEs seems to be related to uncorrected hibernation regardless of its extension. In these patients revascularization of hibernating segments is effective in reducing the risk of HEs while its role in improving VF or NYHA class is negligible.

Cardiac effects of hexarelin in hypopituitary adults.

Growth hormone (GH)-releasing peptides possess specific pituitary, hypothalamic, and myocardial receptors. Seven adult male patients with GH deficiency (GHD) (age, mean+/-S.E.M.: 42.0+/-4.0 year) were studied by equilibrium radionuclide angiocardiography after i.v. administration of hexarelin, a peptide GH secretagogue. Data for these patients were compared with those for nine adult male controls (37.0+/-2.7 year). The GH response to hexarelin was negligible in patients with GHD compared to control subjects (CS) (peak: 1.9+/-0.9 vs. 45.7+/-3.6 microg/l, P<0.001). Basal left ventricular ejection fraction (LVEF) in patients with GHD was lower than that in CS (50+/-1% vs. 63+/-2%, P<0.001). Hexarelin administration increased LVEF both in patients with GHD and in CS (peak: 57+/-2 vs. 70+/-2, respectively, P<0.05 vs. baseline) without changing catecholamine levels, mean blood pressure (MBP), or cardiac output in either group. In conclusion, the acute administration of hexarelin exerts a short-lasting positive inotropic effect in humans, probably GH-independent and mediated by specific myocardial receptors for GH secretagogues.

Myocardial ischaemia in neonates with perinatal asphyxia. Electrocardiographic, echocardiographic and enzymatic correlations.

In asphyxiated neonates, hypoxia is often responsible for myocardial ischaemia. To evaluate cardiac involvement in neonates with respiratory distress, ECG and echocardiographic recordings were performed, and cardiac enzymes determined. These data were related to clinical presentation and patient outcome. Three groups of neonates were studied: 22 healthy newborn infants (group I) with 5 min Apgar scores > 9 and pH > 7.3; 15 neonates with moderate respiratory distress (group II) which had Apgar scores ranging between 7 and 9, and pH between 7.2 and 7.3; and 13 neonates with severe asphyxia, Apgar scores < 7, and pH < 7.2 (group III). The ECGs were evaluated according to the 4-grade classification proposed by Jedeikin et al. [8]. On the echocardiograms, fractional shortening and aortic flow curve parameters were taken into account. Serum creatine kinase (CK), creatine kinase-MB isoenzyme (CK-MB) and lactate dehydrogenase were determined. All of groups I and II survived, but 5 out of 13 in group III died within the 1st week. Grade 3 or 4 ECG changes were observed only in group III patients, while all group II and 3 patients of group I showed grade 2 ECG changes. Fractional shortening, peak aortic velocity and mean acceleration were significantly reduced in group III, whereas the only abnormality found in group II was a reduced fractional shortening. CK, CK-MB, CK-MB/CK ratio and lactate dehydrogenase were all increased in group III, while in group II only CK-MB and the CK-MB/CK ratio were abnormal. Severely asphyxiated newborn infants reflect relevant ischaemic electrocardiographic changes, depressed left ventricular function and marked cardiac enzyme increase. These alterations are far less pronounced in neonates with mild respiratory distress.

Acute cardiovascular and hormonal effects of GH and hexarelin, a synthetic GH-releasing peptide, in humans.

Reduced cardiac mass and performances are present in GH deficiency and are counteracted by rhGH replacement. GH and IGF-I possess specific myocardial receptors and have been reported able to exert an acute inotropic effect. Synthetic GH secretagogues (GHS) possess specific pituitary and hypothalamic but even myocardial receptors. In 7 male volunteers, we studied cardiac performance by radionuclide angiocardiography after iv administration of rhGH or hexarelin (HEX), a peptidyl GHS. The administration of rhGH or HEX increased circulating GH levels to the same extent (AUC: 1594.6+/-88.1 vs 1739.3+/-262.2 microg/l/min for 90 min) while aldosterone and catecholamine levels did not change; HEX, but not rhGH, significantly increased cortisol levels. Left ventricular ejection fraction (LVEF), mean blood pressure (MBP) and heart rate (HR) were unaffected by rhGH (62.4+/-2.1 vs 62.1+/-2.3%, 90.6+/-3.4 vs 92.0+/-2.5 mm Hg, 62.3+/-1.8 vs 66.7+/-2.7 bpm). HEX increased LVEF (70.7+/-3.0 vs 64.0+/-1.5%, p<0.03) without significant changes in MBP and HR (92.8+/-4.7 vs 92.4+/-3.2 mm Hg, 63.1+/-2.1 vs 67.0+/-2.9 bpm). LVEF significantly raised at 15 min, peaked at 30 min and lasted up to 60 min after HEX. These findings suggest that in man, the acute administration of Hexarelin exerts a short-lasting, positive inotropic effect. This effect seems GH-independent and might be mediated by specific GHS myocardial receptors.

Radionuclide angiocardiographic evaluation of the cardiovascular effects of recombinant human IGF-I in normal adults.

OBJECTIVE: IGF-I possesses specific myocardial receptors and is able to promote cardiac remodelling and even inotropic effects in both humans and other animals. In fact, reduced cardiac mass and performance are present in GH deficiency and these alterations are counteracted by recombinant human (rh) GH replacement, restoring IGF-I levels. Recently, the acute administration of 60 microg/kg rhIGF-I has also been reported to be able to improve cardiac performance evaluated by echocardiography or impedance cardiography in normal subjects. The aim of our study was to verify the effects of a subcutaneous low dose of rhIGF-I (20 microg/kg) on cardiac performance in humans. METHODS: In six healthy male adults (mean+/-S. e.m.: 35.7+/-4.3 years of age), the effects of rhIGF-I on left ventricular function evaluated by radionuclide angiocardiography and on circulating IGF-I, GH, insulin, glucose and catecholamines levels were studied. RESULTS: Administration of rhIGF-I increased circulating IGF-I (peak at +150 min vs baseline: 330.2+/- 9.6 vs 199. 7+/-8.7 microg/l, P<0.03) to levels which persisted similarly up to +180min. Neither GH nor catecholamine levels were modified by rhIGF-I administration, while insulin and glucose levels showed a slight but significant decrease. Basal left ventricular ejection fraction (61.8+/-2.0%) significantly increased at +180 min after rhIGF-I (65.3+/-2.7%, P<0.03). No change was recorded in mean blood pressure while a non-significant trend towards a reduction of heart rate was present by +120 min. CONCLUSIONS: These findings indicate that even subcutaneous administration of a low dose of rhIGF-I has acute inotropic effects as evaluated by radionuclide angiocardiography in healthy adults.

Neuroendocrine carcinomas of the lung and role of 111In-DTPA-octreotide scintigraphy: preliminary results.

The authors report their experience on the use of 111In-DTPA-octreotide scintigraphy in the diagnosis of neuroendocrine carcinomas of the lung. The studies were performed both preoperatively, to obtain a correct staging of the tumor, or postoperatively, because of the suspicion of a recurrence or distant metastases. The main findings were: high sensitivity in localizing the tumor and its recurrences or metastases and high predictive value for responsiveness to "cold" octreotide therapy.

Silicon Detector System for High Rate EXAFS Applications.

A multichannel silicon pad detector for EXAFS (Extended X-ray Absorption Fine Structure) applications has been designed and built. The X-ray spectroscopic measurements demonstrate that an adequate energy resolution of 230 eV FWHM (corresponding to 27 rms electrons in silicon) can be achieved reliably at -35 °C. A resolution of 190 eV FWHM (corresponding to 22 rms electrons) has been obtained from individual pads at -35 °C. At room temperature (25 °C) an average energy resolution of 380 eV FWHM is achieved and a resolution of 350 eV FWHM (41 rms electrons) is the best performance. A simple cooling system constituted of Peltier cells is sufficient to reduce the reverse currents of the pads and their related shot noise contribution, in order to achieve resolutions better than 300 eV FWHM which is adequate for the EXAFS applications.