Renato M. E. Sabbatini

Possible interaction between the inferior colliculus and the substantia nigra in audiogenic seizures in wistar rats

Male Wistar rats were tested for sensitivity to audiogenic seizures (AS; 110 dB), using an audiogenic severity index (SI). Sensitive (S) animals were subjected to bilateral lesion of the inferior colliculus (IC) and/or the lateral lemniscus (LL). Resistant (R) animals were subjected to bilateral lesions of the IC, unilateral sequential lesions of the substantia nigra reticulata (SN) and/or IC (contralateral to one another), and unilateral thalamic and sham lesions. Bilateral lesions of the IC and LL abolish AS in S rats. Lesion of the SN resulted in more pronounced sensitivity to AS than unilateral lesion of IC, in R rats. When the SN lesion was contralateral to a previous IC lesion, the effect was not only an increase in the SI, but also a reversal of the asymmetry generated by IC lesion. Although the behavioral effects resulting from IC lesions are due to alterations in the primary structures involved in the origin of AS, unilateral SN lesions can alter critical substrates of sensorimotor integration involved in the control and expression of AS.

One-year mortality prognosis in heart failure: a neural network approach based on echocardiographic data.

OBJECTIVES This study sought to assess the usefulness and accuracy of artificial neural networks in the prognosis of 1-year mortality in patients with heart failure. BACKGROUND Artificial neural networks is a computational technique used to represent and process information by means of networks of interconnected processing elements, similar to neurons. They have found applications in medical decision support systems, particularly in prognosis. METHODS Clinical and Doppler-derived echocardiographic data from 95 consecutive patients with diffuse impairment of myocardial contractility were studied. After 1 year, data regarding survival or death were obtained and produced the prognostic variable. The data base was divided randomly into a training data set (47 cases, 8 deaths) and a testing data set (48 cases, 7 deaths). Results of artificial neural network classification were compared with those from linear discriminant analysis, clinical judgment and conventional heuristically based programs. RESULTS The study group included 57 male (47 survivors) and 38 female patients (33 survivors). Linear discriminant analysis was not efficient for separating survivors from nonsurvivors because the accuracy at the ideal cutoff value was only 67.4%, with a sensitivity of 67.5%, positive predictive value of 27.8% and negative predictive value of 91.5%. In contrast, all artificial neural networks were able to predict outcome with an accuracy of 90%, specificity of 93% and sensitivity of 71.4%, for the best artificial neural network. Both clinical judgment and automatic heuristic methods were also inferior in performance. CONCLUSIONS The artificial neural network method has proved to be reliable for implementing quantitative prognosis of mortality in patients with heart failure. Additional studies with larger numbers of patients are required to better assess the usefulness of artificial neural networks.

Neuroethological evaluation of audiogenic seizures in hemidetelencephalated rats.

Wistar-derived male rats were tested for audiogenic seizure (AS) susceptibility, and classified into sensitive (S) and resistant (R) groups. Rats from group R underwent unilateral ablation of the telencephalon, or were detelencephalated (HD), or sham-lesioned, and were tested for audiogenic susceptibility one month and one year after surgery. It was found that previously AS-resistant, HD-operated animals developed generalized tonic-clonic convulsions upon high intensity (110.8 dB) acoustic stimulation, with higher severity and shorter latencies than the susceptible, non-operated control animals. Sham-lesioned R animals maintained their previous resistance to AS. HD-lesioned R animals also presented asymmetric motor patterns, such as gyrating and barrel-rolling behavior, always oriented towards the side contralateral to the lesion. HD-lesioned S animals presented an increase in the severity of seizures, as well as a shortening of the latencies of the running (procursive) and convulsive phases of the seizures. This effect was more marked one year after surgery. Contralateral barrel-rolling behavior was also observed in these animals. The fact that seizure severity increases and latency decreases with time after lesion seems to indicate a role for denervation hypersensitivity and other cerebral plasticity phenomena in explaining the effects of HD lesions on AS. The fundamental neural structures involved appear to be those related to sensorimotor coordinating systems (substantia nigra/pontine-mesencephalic reticular formation and substantia nigra/superior colliculus), the acoustic pathways (inferior colliculus) and their projections to the superior colliculus and reticular formation.

The development and evaluation of a distance learning system in ophthalmology

INTRODUCTION: Web-based e-learning is a teaching tool increasingly used in many medical schools and specialist fields, including ophthalmology. AIMS: this pilot study aimed to develop internet-based course-based clinical cases and to evaluate the effectiveness of this method within a graduate medical education group. METHODS: this was an interventional randomized study. First, a website was built using a distance learning platform. Sixteen first-year ophthalmology residents were then divided into two randomized groups: one experimental group, which was submitted to the intervention (use of the e-learning site) and another control group, which was not submitted to the intervention. The students answered a printed clinical case and their scores were compared. RESULTS: there was no statistically significant difference between the groups. CONCLUSION: We were able to successfully develop the e-learning site and the respective clinical cases. Despite the fact that there was no statistically significant difference between the access and the non access group, the study was a pioneer in our department, since a clinical case online program had never previously been developed.

Lack of Lymph Node Reaction to Subcutaneously Injected Silicone Gel: Histological and Computer Aided Morphometric Study in Rats

The gel of silicone implants may bleed through the elastomeric envelope or may come into contact with the body because of rupture of the implant. We have studied the effects of free silicone gel injected into the subcutaneous space in rats and analysed the morphological features of the axillary and inguinal lymph nodes. Ninety six Wistar rats had 3 cm3 of silicone gel injected into their subcutaneous space and 96 Wistar rats (the control group) had distilled water injected into their subcutaneous space. The animals were killed on days 1,3,7,9,15, 30,60,90,120,180,270, and 365 after the injection. There was no detectable silicone and no damage to the lymph nodes on routine histopathological analysis. Small amounts of silicone that could migrate to lymph nodes could result in hyperplasia. To evaluate this possibility, a morphometric study based on a computer aided system compared the area of lymph node sections between treated and control animals, and showed no difference between treated and control groups. If silicone did migrate, it did not provoke morphological signs or hyperplasia in the lymph nodes.

A multilayered neural network for processing 2D tomographic images in neurosurgery

Summary form only given. A prototype artificial neural network (ANN) which is capable of processing serial sections of the brain obtained from computed-tomography (CT) or magnetic resonance imaging (MRI) tomographs has been designed. The segmented, outlined images, representing internal brain structures, both normal and abnormal, are then used as an input to a 3-D stereotaxic radiosurgery planning software. The algorithm was implemented as a software simulation in a microcomputer, structured as three cascading subnetworks. The ANN performs very well in the overall task of obtaining automatically outlined and segmented brain slices, for the purposes of 3-D reconstruction and surgical planning.<<ETX>>

A Microcomputer Software Laboratory for Teaching Informatics to Medical Students

We report the development of a suite of microcomputer programs, which were used in a regular course on Medical Informatics to medical and nursing undergraduate students as a software resource for demonstrations and hands-on experience with medical applications. The 17 programs have a simple and standard user interface, and cover the following applications: medical records, patient interviewing, risk assessment, coding of medical data, laboratory automation, biological signal and image processing, computer-assisted diagnosis and therapy, medical research and education, and epidemiology. User guidelines and proposed exercises complement the use of these programs in a Medical Informatics course. The results obtained so far were very good: an increase in student awareness of potential benefits and limitations of applications of computers to Medicine; an interest in using the software for their own purposes; and a fostering of personal computer skills and independent learning. Other medical schools are currently adopting our software and course layout, due to its compactness, effectiveness and low cost, particularly for developing countries.