Mechanical behaviour of a prototype orthodontic retraction spring: a numerical-experimental study.

The purpose of this study was to examine the mechanical behaviour of orthodontic delta retraction springs. Twelve titanium-molybdenum (0.016 × 0.022 inch) delta loops were studied. The springs were analysed by means of the finite element (FE) method and experimental tests using a platform transducer. Each spring was activated from 0 to 6 mm. Statistical analysis of the data was carried out by one-way analysis of variance and Games-Howell parametric multiple comparison test for heterogeneous variances. FE analysis revealed that the stress level varied from 277 to 1273 MPa. At 6.1 mm (773 MPa), the springs were still in the elastic range. Force levels varied from 0.1 N (10 g) to 2.2 N (224 g) at 1.4-8.1 mm of activation for the numerical study and from 0.44 N (45 g) at 1 mm to 2.02 N (206 g) at 6 mm of activation in the experimental study. The spring rate was within the levels that are appropriate for clinical use (34 g/mm). Vertical forces (Fy) showed constancy and were of low magnitude. The anterior moment/force ratio from the experimental tests was 14 at 3 mm of activation decreasing to 10.7, 8.7, and 7.2, for 4, 5, and 6 mm of activation, respectively. The springs could be activated up to 7 mm without exceeding the elastic limit.

Fatal pulmonary thromboembolism in gastrectomy intraoperative procedures by gastric adenocarcinoma: case report.

The case of a patient with gastric adenocarcinoma with indication for gastrectomy is reported. The surgery took place without complications. A palliative, subtotal gastrectomy was performed after para-aortic lymph nodes compromised by neoplasm were found, which was confirmed by pathological exam of frozen sections carried out during the intervention. At the end of the gastroenteroanastomosis procedure, the patient began to show intense bradycardia: 38 beats per minute (bpm), arterial hypotension, changes in the electrocardiogram's waveform (upper unlevelling of segment ST), and cardiac arrest. Resuscitation maneuvers were performed with temporary success. Subsequently, the patient had another circulatory breakdown and again was recovered. Finally, the third cardiac arrest proved to be irreversible, and the intra-operative death occurred. Necropsy showed massive pulmonary embolism. The medical literature has recommended heparinization of patients, in an attempt to avoid pulmonary thromboembolism following major surgical interventions. However, in the present case, heparinization would have been insufficient to prevent death. This case indicates that it is necessary to develop preoperative propedeutics for diagnosing the presence of venous thrombi with potential to migrate, causing pulmonary thromboembolism (PTE). If such thrombi could be detected, preventative measures, such as filter installation in the Cava vein could be undertaken.

[Videolaparoscopic appendectomy with linear stapler]. / Apendicectomia videolaparoscópica com auxílio de grampeador linear cortante.

It is presented the experience of 126 cases of acute appendicitis treated by a videolaparoscopic appendectomy using a 12 mm endostapler with 4 lines of staples and a linear cutting device in the middle. It has been used two trocars (5 mm) at the left side and one other (12 mm) trocar at the umbilicus. In the first cases other dispositions were used but this one seemed to be better. Through the left trocars, a dissection is promoted, isolating the appendix, its base and its mesentery, in which a small hole is made, close to the base. Through this hole, it is passed one of the sides of the 12 mm stapler. The device promotes the bilateral stapling and cuts the appendix at its base. The stapler is reloaded with vascular staples and then the mesentery is stapled and cut by the same way. It is a very fast method. Besides, the laparoscopic option gives the opportunity to equally treat appendicitis at unusual positions, to examine other pelvic organs (eventually treating diseases) and to aspirate secretions under direct view, anywhere in the cavity. The specimen is taken out of the cavity inside a plastic bag and we had no case of infection at the trocar sites. Only in 3 cases there were conversion to open surgery, due to difficult dissection and identification of structures, in all of them with very advanced disease and necrosis. It is concluded that this method is fast, safe, easy (although more expensive) and can be utilized routinely, at least in the first approach of the treatment of acute appendicitis.

[Surgical treatment of solitary liver cysts]. / Tratamento cirúrgico do cisto solitário de fígado.

Solitary hepatic cysts an uncommon disease in the past, which incidental diagnosis is increasing with the advent of ultrasound and computed tomography, are nowadays very frequent. Cysts that reach massive proportions often become symptomatic and necessitate surgical intervention. Surgical wide unroofing technique is a simple procedure advocated for the treatment of symptomatic patients. Ten patients with solitary liver cysts were submitted to wide unroofing with good immediate and late results.

Environmental risk factors in endemic pemphigus foliaceus (Fogo selvagem). "The Cooperative Group on Fogo Selvagem Research".

Endemic pemphigus foliaceus or Fogo selvagem (FS) is an epidermal organ-specific autoimmune disease mediated by autoantibodies. Individuals at risk are peasants who live and work on farms located in the interior of certain endemic states of Brazil. This case-control study compares a group of 52 FS patients with 52 patients suffering from other dermatoses admitted and followed at the hospital for pemphigus (Hospital do Penfigo) in the city of Goiania, state of Goias. Patients and controls matched 1:1 by age, sex, and occupation were examined by two dermatologists at the time of admission and asked to respond to a prepared questionnaire. This questionnaire concerned current and past (1 and 5 years) exposure to environmental risk factors. The following risk factors were assessed: black fly bites, presence of rodents at home, exposure to cereal dust, exposure to fumes or dust released by tree and shrub removal, and exposure to insecticides. Relative risks were estimated from tabulated data by the odds ratio and tested for significance by the chi-square test. The 95% confidence interval for the odds ratio was also calculated for each of the risk factors. The only risk factor showing an odds ratio significantly different from one was exposure to simuliidae bites (odds ratio 4.7, p less than 0.001). This study reinforces the hypothesis that chronic exposure to black fly antigens may precipitate IgG4 antibody formation in predisposed individuals. These antibodies in turn may cross-react with epidermal antigens and cause acantholysis and the clinical expression of the disease known as FS.

Logistic analysis of the defense reaction induced by electrical stimulation of the rat mesencephalic tectum.

Subliminal and threshold functions of behavioral output to electrical stimulation of the rat mesencephalic tectum were fitted using the logistic model. The results suggest the existence of isotopic albeit anisotropic freezing and flight mechanisms in the dorsal periaqueductal gray and deep layers of the superior colliculus. Moreover, the marked parallelism of immobility and running threshold functions indicates the probable coupling of these mechanisms through a kind of negative feedback. Finally, the good fitting to the model suggests that the behavioral output to electrical stimulation of these areas follows a logistic function of the logarithm of the stimulus intensity.

Effects of morphine and midazolam on reactivity to peripheral noxious and central aversive stimuli.

Electrical stimulation of the mesencephalic tectum elicits behavioral and autonomic responses similar to those following peripheral noxious stimulation. Benzodiazepine and opioid compounds attenuate escape behavior induced by electrical stimulation of the dorsal periaqueductal gray (PAG) and deep layers of the superior colliculus (SC). The present study determines if microinjections of midazolam and morphine applied to these PAG-SC sites affect both responsiveness to peripheral noxious stimulation and to aversive PAG-SC stimulation. Both aversive brain stimulation or foot-shocks applied at threshold intensities caused running or jumps concomitant with increases in mean arterial blood pressure (MBP) and heart rate (HR). Microinjection of both drugs attenuated the behavioral reaction and increases in MBP and HR induced by mesencephalic tectum stimulation, while attenuating only the increase in heart rate induced by peripheral painful stimulation. These results suggest that the neural substrates of the behavioral and autonomic effects of stimulating the mesencephalic tectum and peripheral nociceptors are different although they may partially overlap.

GABAergic fibers from substantia nigra pars reticulata modulate escape behavior induced by midbrain central gray stimulation.

Electrical stimulation of microinjection of GABA antagonists into the dorsal periaqueductal gray (DPAG) produces escape behavior. In order to determine whether the nigrocollicular gabaergic fibers exert some control over this behavior, rats bearing kainic acid lesion of the substantia nigra pars reticulata were submitted to microinjections of bicuculline or electrical stimulation of the DPAG at the escape threshold. Rats thus treated exhibited a significant decrease in the escape threshold while bicuculline increased the expression of flight behavior. These results suggest an inhibitory control of gabaergic fibers from the substantia nigra pars reticulata on aversive behavior induced by DPAG stimulation.

Gabaergic fibers from substantia nigra para reticulata modulate escape bahavior induced by midbrain central gray stimulation

Eletrical stimulation or microinjection of GABA antagonists into the dorsal periaqueductal gray (DPAG) produces escape behavior. In order to determine whether the nigrocollicular gabaergic fibers exert some control over this behavior, rats bearing kainic acid lesion of the substantia nigra pars reticulata were submitted to microinjections of bicuculline or electrical stimulation of the DPAG at the escape threshold. Rats thus treated exhibited a significant decrease in the escape threshold while bicuculline increased the expression of flight behavior. These results suggest an inhibitory control of gabaergic fibers from the substantia nigra pars reticulata on aversive behavior induced by DPAG stimulation

Independence of aversive and pain mechanisms in the dorsal periaqueductal gray matter of the rat.

Electrical stimulation of the dorsal periaqueductal gray (DPAG) elicits autonomic responses similar to those following peripheral pain stimulation. The present study analyzes the effects of morphine and midazolan applied to the same DPAG site on the autonomic responses induced by both types of stimulation. Both drugs attenuated the increase in heart rate and blood pressure induced by DPAG stimulation while attenuating only the increase in heart rate induced by pain stimulation. These results suggest that the neural substrates of the autonomic expression of the DPAG and pain stimulation are different although they may partially overlap.

Defense reaction induced by microinjections of bicuculline into the inferior colliculus.

Behavioral and autonomic effects of microinjections of bicuculline--a GABA receptor antagonist--into ventral aspects of the inferior colliculus (IC) produced a behavioral activation together with jumps. This activation was similar to escape behavior that has been induced from periventricular structures although it was neither as explosive as that observed from the dorsal periaqueductal gray matter (DPAG) nor as coordinated as that obtained from the medial hypothalamus (MH). In anesthetized rats, microinjection of bicuculline into the IC produced a clear rise in mean arterial blood pressure and in heart rate. These effects reached a maximum after 10 min and subsided within 20 min after injection. GABA receptor blockade in the IC of detelencephalated rats also resulted in escape behavior qualitatively similar to that observed in intact animals. These results suggest that in addition to the central gray and medial hypothalamus, GABA also exerts a tonic inhibitory action on neurons of the IC implicated in the generation or elaboration of aversive responses.

Independence of aversive and pain mechanisms in the dorsal periaqueductal gray matter of the rat

Electrical stimulation of the dorsal periaqueductal gray (DPAG) elicits autonomic responses similar to those following peripheral pain stimulation. The present study analyzes the effects of morphine and midazolan applied to the same DPAG sites on the autonomic responses induced by both types of stimulation. Both drugs attenuated the increase in heart rate and blood pressure induced by DPAG stimulation while attenuating only the increase in heart rat induced by pain stimulation. These results suggest that the neural substrates of the autonomic expression of the DPAG and pain stimulation are different although they may partially overlap