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Biomedical subjects

M A Trevisan

Publications and source records attributed to M A Trevisan.

At least 19 recordsLinked to original sources
PubMed2006

Respiratory patterns in oscine birds during normal respiration and song production.

In this work we study the generation of respiratory patterns by oscine birds. We present a model capable of generating realistic respiratory patterns, during normal respiration and song production. The model accounts for the interaction between neural nuclei and air sac dynamics. We performed experiments in vivo in order to test the predictions of the model, measuring air sac pressure during song and normal respiration in canaries (Serinus canaria).

Air Sacs↗
PubMed2005

Simple neural substrate predicts complex rhythmic structure in duetting birds.

Horneros (Furnarius Rufus) are South American birds well known for their oven-looking nests and their ability to sing in couples. Previous work has analyzed the rhythmic organization of the duets, unveiling a mathematical structure behind the songs. In this work we analyze in detail an extended database of duets. The rhythms of the songs are compatible with the dynamics presented by a wide class of dynamical systems: forced excitable systems. Compatible with this nonlinear rule, we build a biologically inspired model for how the neural and the anatomical elements may interact to produce the observed rhythmic patterns. This model allows us to synthesize songs presenting the acoustic and rhythmic features observed in real songs. We also make testable predictions in order to support our hypothesis.

Action Potentials↗
PubMed2005

Dynamics of learning in coupled oscillators tutored with delayed reinforcements.

In this work we analyze the solutions of a simple system of coupled phase oscillators in which the connectivity is learned dynamically. The model is inspired by the process of learning of birdsongs by oscine birds. An oscillator acts as the generator of a basic rhythm and drives slave oscillators which are responsible for different motor actions. The driving signal arrives at each driven oscillator through two different pathways. One of them is a direct pathway. The other one is a reinforcement pathway, through which the signal arrives delayed. The coupling coefficients between the driving oscillator and the slave ones evolve in time following a Hebbian-like rule. We discuss the conditions under which a driven oscillator is capable of learning to lock to the driver. The resulting phase difference and connectivity are a function of the delay of the reinforcement. Around some specific delays, the system is capable of generating dramatic changes in the phase difference between the driver and the driven systems. We discuss the dynamical mechanism responsible for this effect and possible applications of this learning scheme.

Animals↗
PubMed1999

Alteration of the follicular basement membrane in non-obese diabetic mice with spontaneous autoimmune thyroiditis.

The follicular basement membrane (FBM) prevents thyroglobulin from escaping to the peri-follicular space, where it can act as an antigen to induce experimental thyroiditis. Laminin, a component of the FBM, is responsible for directing cell migration and stimulates greater adhesion of activated T lymphocytes. Our purpose was to study the expression of laminin in the thyroid of NOD mice, which have a propensity for autoimmune diseases, including thyroiditis. Thirty NOD mice between 3 and 42 weeks old were studied. Eight had thyroiditis and 22 showed no inflammatory infiltration. An immunohistochemical examination using the streptavidin-biotin-peroxidase technique was conducted on paraffin-embedded tissue sections, with a polyclonal antilaminin antibody. Antigen retrieval was achieved through pepsin digestion and microwave irradiation in citrate buffer. Staining for laminin was restricted to the basement membrane. In thyroids with no infiltration, laminin was shown as a fine, continuous brown line in the basement membrane. In 6 out of the 8 cases of thyroiditis, clearcut interruption and destruction of the FBM was observed, particularly when the follicles were located in lymphocyte infiltrated areas or when there was fibrosis. There were significant alterations in the pattern of the FBM with extensive areas of discontinuity in the distribution of laminin. Such discontinuities could facilitate antigen exposure, especially thyroglobulin, which may contribute to autoimmune thyroiditis in NOD mice.

Animals↗
PubMed1992

Capsular contracture and silicone gel: experimental study.

Wistar rats were used to study the effects, if any, of membrane thickness and implant volume of a silicone gel prosthesis on the development of fibrous capsule contraction. A total of 30 miniprosthesis with three different membrane thicknesses and two different volumes were implanted in the subcutaneous space of five animals. One hundred eighty days later the fibrous capsule was resected and histologically analyzed. Different grades of thickness were observed. The statistical analysis of the data indicates that the thickness of the prosthesis' membrane and the implant's volume did not impact significantly on the grade of fibrosis.

Animals↗
PubMed1989

[Focusing the administrative exercise within the whole of nursing functions].

Within the hospital context, the nurse cannot avoid the administrative function, even though this is a controversial issue in Brazilian nursing. To focus on the problem, in the present study we set out to identify the set of functions of nurses working on the admission floors and to determine the distribution of administrative functions according to their bureaucratic and non-bureaucratic characteristics. The data were collected at four admission units by intermittent observation of work performed by nurses in 1985. The following set of functions were identified: administration (62.5%), patient assistance (19.2%), teaching and research (3.8%), functions that could be delegated to others (6.8%) and personal (7.6%). The administrative functions were classified into bureaucratic and non-bureaucratic with a respective distribution of 77% and 23%. The study indicates that the administrative function is one of the elements defining the nurse's profile, even though the authors believe that this function should be better oriented.

Brazil↗
PubMed1976

South American blastomycosis of the ureter.

A case of disseminated South American blastomycosis with unilateral involvement of the ureter and hydronephrosis is described; it is the third such case to be reported.

Blastomycosis↗
PubMed1975

Jejunal biopsies in protein-calorie malnutrition and intestinal parasitic infestation in Brazil.

Jejunal biopsies were performed in 71 subjects, who were classified into three groups as follows: Forty-one patients, on a poor diet, without clinical signs of malnutrition, with and without parasitic infestation; nineteen patients with severe protein-calorie malnutrition, with and without parasitic infestation; control group, ten medical students and one of the authors on a normal diet and without parasitic infestation. The dissecting microscope appearance showed mild alteration of the intestinal villi of Group A patients with parasitic infestation and severe alteration on Group B patients, especially those with parasitism. On histological examination, only the total mucosal thickness showed statistically significant differences between the Group B (severe protein malnutrition) and the other groups.

Adolescent↗
PubMedDate not supplied

[Cytopathological test performed during colonoscopy in the diagnosis of colorectal stenosis].

The etiological diagnosis for the colorectal strictures can be very difficult. With the colonoscopy, it was possible to obtain samples with direct vision of the lesion. Consequently, the cytologic efficiency improved, with similar or even better results than histopathology. In the present study (107 patients) it was used the cytopathology performed during colonoscopy. After a specimen was obtained, it was smeared on glass slide, fixed in 95% alcohol, stained by HE, and examined microscopically, with conclusions during the procedure. The results were compared and further correlated to the histopathology of surgical specimen or based on clinical follow-up in those case not submitted to operation. The results showed a striking degree of correlation between both exams. For the cytopathology there were no inconclusive results, false-negative were less frequent than with histopathology, and only one case of false-positive (rectal villus adenoma) was observed. Considering the type, localization and perviousness of the lesion, similar conclusions were drawn, and did not affect the results, except that there were more false-negatives in both exams when the lesions were impervious. The cytopathological and histopathological studies were both highly sensitive and specific for the diagnosis of carcinoma. In conclusion, cytopathology performed during colonoscopy is safe and efficient in the study of colorectal strictures, which contributes to improve the orientation of these patients.

Adult↗
PubMedDate not supplied

[Chronic gastritis associated to Helicobacter pylori in patients with non-ulcerating dyspepsia and with duodenal ulcer].

PURPOSE: Prevalence of chronic gastritis and infection of the gastric mucosa by Helicobacter pylori in patients with non-ulcerating dyspepsia and duodenal ulcer. TYPE OF STUDY, SITE, PATIENTS: A prospective study was made of 48 consecutive patients with non-ulcerating dyspepsia of the dismotility type (NUD), and 13 consecutive patients with duodenal ulcer in activity (DU), selected from the gastroenterology outpatient clinic of the Clinical Hospital of the State University of Campinas (Unicamp). INTERVENTIONS: Eight endoscopic biopsies (4 of the body and 4 of the gastric antrum) were performed on each of the patients to identify H. pylori, using three tests: urease, gram and histopathological examination. MEASUREMENTS AND RESULTS: Of the 48 patients with NUD, urease test was positive in 89.6% in the antrum and in 81.2% in the body; gram test was positive in 81.2% in the antrum and in 77.1% in the body; and H. pylori was identified in the histopathological examination in 79.2% in the antrum and in 70.8% in the gastric body. At least one of the three tests applied was positive in the mucosa of the gastric antrum in all 48 patients with NUD. In all 13 patients with DU, the three tests were positive in the gastric antrum, all of them with chronic gastritis of the antrum in the histopathological examination. Chronic gastritis of the gastric body with presence of H. pylori in the histopathological examination was found in 10 out of 13 patients. The urease test was positive in the mucosa of the gastric body in all DU cases. CONCLUSIONS: The authors believed that the high prevalence of the tests used to identify H. pylori in patients with NUD can be explained by the selected group of patients, which belong to the low socio-economic class. The presence of H. pylori in the gastric mucosa of all patients with DU agrees with studies already published.

Adult↗
PubMedDate not supplied

[Nursing research in Brazil].

Starting from an exposition of the concept of production of knowledge in nursing, the evolution of research is reported on the basis of organized meetings and of analyses by research nurses who devote themselves to the question. The present status of investigation is presented, and the perspectives of development of nursing research in Brazil are outlined.

Brazil↗
PubMedDate not supplied

[Criteria for cytological diagnosis of colorectal mucosa].

A detailed description of cytological alterations of the colorectal mucosa in ten different conditions is given. It was based in the study of 150 smears obtained by colonoscopy in cases of inflammatory diseases (80), obstructive lesions (50) and polyps (20). In our hands this procedure proved to be highly reliable, giving a conclusion within a few minutes during colonoscopy.

Biopsy↗