Equivalence between hot tensile and creep testing data for Kanthal A1 alloy

Hot tensile and creep tests were carried out on Kanthal A1 alloy in the temperature range from 600 to 800 degrees C. Each of these sets of data were analyzed separately according to their own methodologies, but an attempt was made to find a correlation between them. A new criterion proposed for converting hot tensile data to creep data, makes possible the analysis of the two kinds of results according to usual creep relations like: Norton, Monkman-Grant, Larson-Miller and others. The remarkable compatibility verified between both sets of data by this procedure strongly suggests that hot tensile data can be converted to creep data and vice-versa for Kanthal A1 alloy, as verified previously for other metallic materials.

Central but not systemic inhibition of inducible nitric oxide synthase modulates oxytocin release during endotoxemic shock

Previous studies have shown that immunological challenges as lipopolysaccharide (LPS) administration increases plasma oxytocin (OT) concentration. Nitric oxide (NO), a free radical gas directly related to the immune system has been implicated in the central modulation of neuroendocrine adaptive responses to immunological stress. This study aimed to test the hypothesis that the NO pathway participates in the control of OT release induced by LPS injection. For this purpose, adult male Wistar rats received bolus intravenous (i.v.) injection of LPS, preceded or not by iv. or intracerebroventricular (i.c.v.) injections of aminoguanidine (AG), a selective inducible nitric oxide synthase (iNOS) inhibitor. Rats were decapitated after 2, 4 and 6 h of treatment, for measurement of OT by radioimmunoassay. In a separate set of experiments, mean arterial pressure (MAP) and heart rate (HR) were measured every 15 min over 6 h, using a polygraph. These studies revealed that LPS reduced MAP and increased HR at 4 and 6 h post-injection. LPS significantly increased plasma OT concentration at 2 and 4 h post-injection. Pre-treatment with i.c.v. AG further increased plasma OT concentration and attenuated the LPS-induced decrease in MAP, however, i.v. AG failed to show similar effects. Thus, iNOS pathway may activate a central inhibitory control mechanism that attenuates OT secretion during endotoxemic shock. (C) 2009 Elsevier Inc. All rights reserved.

Role of dexamethasone on vasopressin release during endotoxemic shock

The present study was designed to assess the hypothesis that dexamethasone (DEX) through the control of nitric oxide (NO) synthesis could regulate the release of vasopressin (AVP), which plays an important role in the regulation of arterial pressure and plasma osmolality. Endotoxemic shock was induced by intravenous (i.v.) injection of 1.5 mg/kg lipopolisaccharide (LPS) in male Wistar rats weighing 250-300 g. After LPS administration, a group of animals were treated with DEX (1.0 mg/kg of body weight), whereas saline-injected rats served as controls. The LPS administration induced a significant decrease in mean arterial pressure (MAP) with a concomitant increase in heart rate (HR) (Delta VMAP: -16.1 +/- 4.2 mm Hg; Delta VHR: 47.3 +/- 8.1 bpm). An increase in plasma AVP concentration occurred and was present for 2 h after LPS administration (11.1 +/- 0.9 pg/mL) returning close to basal levels thereafter and remaining unchanged until the end of the experiment. When LPS was combined with i.v. administration of a low dose of DEX, we observed an attenuation in the drop of MAP (Delta VMAP: -2.2 +/- 1.9 mm Hg) and a decrease in NO plasma concentration [NO] after LPS administration (1098.1 +/- 68.1 mu M) compared to [NO] after DEX administration (523.4 +/- 75.2 mu M). However, this attenuation in the drop of MAP was accompanied by a decrease in AVP plasma concentration (3.7 +/- 0.4 pg/mL). These data suggest that AVP does not participate in the recovery of MAP when DEX is administered in this endotoxemic shock model. (C) 2008 Elsevier B.V. All rights reserved.

Evaluation of molar and incisor bite force in indigenous compared with white population in Brazil

The purpose of this study was to deter-mine maximum bite force in molar and incisor regions in young Brazilian indigenous individuals, who have had a natural diet since birth, and compare the sample with white Brazilian individuals. To do this, individuals were paired one-to-one (same weight, height, and Class I facial pattern). A secondary purpose was to elucidate the relation between bite force and gender in both populations. Eighty-two Brazilians took part in this study. Participants were aged between 18 and 28 years and were divided into two groups: 41 Xingu indigenous individuals and 41 white Brazilian individuals, with 28 men and 13 women in each group. The inclusion criteria were: having complete dentition; normal occlusion; no neurological, psychiatric or movement disorders.; no reports of toothaches; having satisfactory periodontal health; absence of large facial skeletal alterations (typical Class II and Class III individuals); and no previous treatments using occlusal splints. To measure maximum bite force, a digital dynamometer model IDDK (Kratos-Equipamentos Industriais Ltda, Cotia, Sao Paulo, Brazil) was used, with a capacity of 1000 N, adapted for oral conditions. Assessments were made in the first molar (right and left) and central incisive regions. Results reveal that mean maximum bite forces in indigenous individuals of the right molar is 421 N, left molar 429 N and incisor region is 194 14 and for white individuals of the right molar is 410 N, left molar 422 N and incisor region is 117 N. Comparing indigenous with white individuals, maximal bite force showed a tendency of being greater in the indigenous group. It was observed that the incisor region showed statistical significance (p < 0.0005) but no significance was observed in the molar region. Moreover, indigenous men showed the highest bite force values. (C) 2007 Elsevier Ltd. All rights reserved.