On some computational results for single neurons' activity modeling.

The classical Ornstein-Uhlenbeck diffusion neuronal model is generalized by inclusion of a time-dependent input whose strength exponentially decreases in time. The behavior of the membrane potential is consequently seen to be modeled by a process whose mean and covariance classify, it as Gaussian-Markov. The effect of the input on the neuron's firing characteristics is investigated by comparing the firing probability densities and distributions for such a process with the corresponding ones of the Ornstein-Uhlenbeck model. All numerical results are obtained by implementation of a recently developed computational method.

[Classification of varices with Doppler ultrasonography mapping. Clinical and hemodynamic correlation]. / Classificazione delle varici con mappaggio eco Doppler. Correlazione clinica ed emodinamica.

The authors report their experience concerning the outpatient echo Doppler mapping of peripheral venous circulation in the lower limbs. Out of a total of 240 patients examined, 190 showed monolateral venous insufficiency and 50 bilateral. These results were correlated to the age of the patients and showed that saphenous pathology tended to affect the entire vein in elderly patients, whereas only partial damage was observed in young patients. Varices seemed to appear with the first signs of the insufficiency of collateral veins before signs of saphenous insufficiency became manifest.

On a non-Markov neuronal model and its approximations.

Single neuron's activity modeling is considered with reference to some earlier contributions in which a non-Markov Gaussian process is assumed to describe the time course of the neuron's membrane potential. After re-formulating the problem in a rigorous framework and pinpointing the limits of validity of such a model, the available results on the firing probability density are compared with those obtained by us by means of an ad hoc numerical algorithm implemented for the leaky integrator diffusion firing model and with some data constructed by a simulation procedure of non-Markov Gaussian processes with pre-assigned covariances. Throughout this paper, the notion of 'correlation time' plays a fundamental role for the neuronal coding process modeling.

Composite arterial conduits for a wider arterial myocardial revascularization.

From October 1991 to May 1993, 130 patients were submitted to myocardial revascularization using complex preformed arterial conduits. The age ranged from 29 to 75 years (mean age, 60.1 years); 121 patients were male. One hundred twenty-six patients had double- or triple-vessel disease. The mean ejection fraction was 0.53 (range, 0.22 to 0.79); only 6 patients had an ejection fraction less than 0.35. In 6 cases the procedure was a reoperation. We used 360 arterial conduits, 163 of which as free grafts (3 left internal mammary arteries, 16 right internal mammary arteries, 86 inferior epigastric arteries, 57 radial arteries, and 1 right gastroepiploic artery). One hundred fifty-four free grafts were anastomosed to one or both internal mammary arteries and one to a radial artery. We constructed 136 complex arterial conduits (branched, lengthened, or both). In 6 cases a double arterial system had to be used in a single patient. There was no operative mortality, and no inotropic or mechanical supports were used. The overall mortality rate was 1.5%. Early angiographic controls (between the 7th and 15th postoperative days) demonstrated 100% patency; late angiographic controls (at a mean interval of 9.5 months after operation) documented a mean patency rate ranging from 94.1% of the radial arteries to 100% of the left internal mammary arteries and right gastroepiploic arteries. At a mean follow-up of 7.2 months (range, 1 to 15 months) all patients are alive without recurrence of symptoms.

[Myocardial revascularization with the internal mammary artery. The indications, technics and results]. / La rivascolarizzazione miocardica con arteria mammaria interna. Indicazioni, tecniche e risultati.

This report reviews 218 patients who underwent internal mammary artery (IMA) grafting alone or with vein graft between 1986-1989. Our experience with IMA started with a single attached graft for proximal left anterior descending lesions in young patients affected from stable angina. After that our indications became more extensive. One IMA was utilized in 209 cases, both two IMAs in the remaining 9. Sequential IMA graft was performed in 16 patients and free IMA graft in 8. There were 242 IMA anastomosis and 295 associated vein by-passes. The overall operative mortality was 2.3%. Perioperative complications include myocardial infarction in 3 (1.4%), reoperation for bleeding in 4 (1.8%) and sternal wound complication in 4 (1.8%). These results are comparable to those of patients having only saphenous vein by-pass during the same period. At the follow-up actuarial survival rate at 42 months was 94 1.8% and 90% of these patients were completely asymptomatic. We include that IMA grafting shows low operative risk and provide excellent short term results. Our findings and the high long term patency rate of this conduit encourage us to extend the indication to IMA and to perform those surgical techniques that make possible multiple mammary coronary anastomosis.

[Aneurysms of the abdominal aorta]. / Gli aneurismi dell'aorta addominale.

The authors report 73 cases of abdominal aortic aneurysms with particular emphasis to early and long-term results as well as postoperative complications: 4 patients died at admission, 16 were treated with medical therapy, and 53 underwent surgery. Surgical patients were stratified in two groups: 18 emergency cases (group 1) and 35 elective cases (group 2). Early results showed the highest mortality in group 1 cases presenting with shock. Late results, at the end of the follow up, (6 months-8 years), showed a 56.6% 5-year survival rate, with overlapping survival rates after the immediate postoperative period. The most frequent postoperative complications were thrombosis of prosthesis and lymphorrhea. Survival rates of emergency cases were influenced by early diagnosis and prompt aorta clamping. Before surgery an haemodynamic evaluation of all vascular districts seems necessary in elective cases to prevent complications of atherosclerotic disease.

[Infectious endocarditis. Role of surgical therapy]. / Considerazioni sull'endocardite infettiva. Ruolo della terapia chirurgica.

The problem of infectious endocarditis (IE) is approached through a review of personal experience. The series examined consists of patients, 17 with active and 21 dormant infection. Furthermore 12 in the first group, 18 in the second had natural heart valves, while 5 in group I, 3 in group II had been given artificial ones. After an analysis of the aetiopathogenic, clinical and diagnostic aspects of the condition with emphasis on the fact that Staphylococcus aureus is currently more responsible for infections in natural valves and the epidermidis for acute prosthesis infections which have a higher early and late mortality rate (40% in hospital, 33.3% long-term), the paper discusses the criteria for surgical intervention. In line with opinions expressed in the literature, it is pointed out that, while the patient's haemodynamic status is certainly the main criterion for any decision, other factors such as embolism, impaired conduction, kidney failure and expansion of the infection to contiguous tissues, should not be under-estimated.

[Diagnosis of cerebrovascular diseases. International multicentric study]. / Diagnosi delle malattie cerebrovascolari. Studio policentrico internazionale.

A Polycentric International Study was performed to evaluate the diagnostic methods in patients with cerebrovascular diseases. New tools and new non-invasive methods were proposed by the 15 centers collaborating in this study. The difficulty of defining a standard method to investigate not invasively and invasively these patients still remains.