Penetration of hydrogen peroxide and degradation rate of different bleaching products

This study's aim was to evaluate the degradation rate of hydrogen peroxide (H2O2) and to quantify its penetration in tooth structure, considering the residence time of bleaching products on the dental enamel. For this study, bovine teeth were randomly divided according to the bleaching product received: Opalescence Xtra Boost 38%, White Gold Office 35%, Whiteness HP Blue 35%, Whiteness HP Maxx 35%, and Lase Peroxide Sensy 35%. To analyze the degradation of H2O2, the titration of bleaching agents with potassium permanganate was used, while the penetration of H2O2 was measured via spectrophotometric analysis of the acetate buffer solution, collected from the artificial pulp chamber. The analyses were performed immediately as well as 15 minutes, 30 minutes, and 45 minutes after product application. The data of degradation rate of H2O2 were submitted to analysis of variance (ANOVA) and Tukey tests, while ANOVA and Fisher tests were used for the quantification of H2O2, at the 5% level. The results showed that all products significantly reduced the concentration of H2O2 activates at the end of 45 minutes. It was also verified that the penetration of H2O2 was enhanced by increasing the residence time of the product on the tooth surface. It was concluded that the bleaching gels retained substantial concentrations of H2O2 after 45 minutes of application, and penetration of H2O2 in the dental structure is time-dependent.

Purification of a beta-galactosidase from cotyledons of Hymenaea courbaril L. (Leguminosae). Enzyme properties and biological function

Beta-galactosidases are enzymes that can be found in most living beings and in the plant kingdom its activity and genes have been detected in several tissues such as ripening fruits, developing leaves and flowers and storage tissues such as cotyledons. In plants, their activities are usually associated with the secondary metabolism or with oligosaccharide or polysaccharide degradation. Polysaccharide specific beta-galactosidases include beta-galactanases, which attack pectic polymers and beta-galactosidases that attack xyloglucans (XG). In the present work we purified an XG-specific beta-galactosidase (named hcbetagal) from cotyledons of developing seedlings of Hymenaea courbaril, a legume tree from the Neotropical region of the world. The enzyme has a molecular weight of 52-62 kDa and was shown to attack specifically xyloglucan oligosaccharides (XGOs) but not the polymer. It has a pH optimum between 3 and 4 and at this pH range the enzyme increases activity linearly up to 50 degrees C. Kinetic studies showed that hcbetagal is inhibited competitively by free galactose (K(i) = 3.7). The biochemical properties of hcbetagal as a whole suggest that it is involved in storage xyloglucan mobilisation during seedling development. Its high specificity towards XGOs, the low pH optimum and the fact that it is inhibited by its product (galactose) suggest that hcbetagal might be one of the biochemical control points in xyloglucan catabolism in vivo. A possible relationship with functional stability of the wall during cell death as cotyledons undergo senescence is discussed.

Hereditary Gingival Fibromatosis: Report of a Five-Generation Family Using Cellular Proliferation Analysis

BACKGROUND

Hereditary gingival fibromatosis (HGF) is an uncommon condition characterized by an accumulation of extracellular matrix resulting in a fibrotic enlargement of the gingiva. The goal of this article is to describe one kindred affected with HGF and discuss the diagnosis, treatment, and control of the disease. The pattern of inheritance, histopathologic characteristics, and proliferative potential of epithelial and mesenchymal cells of HGF are also emphasized.

METHODS

To characterize the pattern of inheritance and the clinical appearance of gingival overgrowth, 117 family members were examined. The recurrence risk was estimated by the use of a genetic analysis program. Immunohistochemistry against the proliferating cell nuclear antigen (PCNA) and pKi-67 was performed to assess cellular proliferation of normal gingiva (NG) and HGF cells.

RESULTS

Examination of the family pedigree demonstrated an autosomal dominant trait of inheritance, and a sibling recurrence risk of 0.085 and an offspring recurrence risk of 0.078, indicating that HGF was a consequence of genetic alteration with low penetrance. Unaffected and affected members transmitted the disease to their offspring. The affected patients showed a generalized but mild gingival overgrowth. Surgical treatment consisted of a combination of gingivectomy and gingivoplasty. Histologic examination showed that the gingival lesions of all patients were quite similar, with increased amounts of collagen fiber bundles in the connective tissue. Immunohistochemistry revealed that the proliferative potential of epithelial cells was significantly higher in the HGF group compared to the NG group, whereas mesenchymal cells from both groups were negative for the proliferative markers.

CONCLUSION

Our data demonstrated that, in the studied family, HGF is transmitted by an autosomal dominant pattern with incomplete disease penetrance, and although the gingival enlargement resulted from an excessive accumulation of collagen fibers, HGF is characterized by an increase in the proliferation rate of epithelial cells.

Effects of long-term pretreatment with isoproterenol on inotropic responsiveness to alpha-adrenoceptor stimulation: study in isolated perfused rat hearts

The effects of chronic pretreatment with isoproterenol (5 mg kg(-1)) daily for 10 days on cardiac alpha-adrenergic responsiveness in Langendorff heart preparations were investigated. Isoproterenol pretreatment caused cardiac hypertrophy (29%) as shown by a significant increase in the ratio of ventricular dry weight to body weight. In preparations from isoproterenol-pretreated rats, both maximum increases in left ventricular systolic pressure and heart rate elicited by isoproterenol (10(-12) to 10(-4) M) were significantly reduced (the isoproterenol concentration producing 50% of the maximum positive inotropic and chronotropic responses was enhanced almost 32- and 4-fold, respectively), while the positive inotropic response to phenylephrine (10(-12) to 10(-4) M) was significantly enhanced (the phenylephrine concentration producing 50% of the maximum positive inotropic effect was reduced almost 100-fold), compared with saline-pretreated rats. In preparations from both groups, phenylephrine infusion induced non-significant changes in heart rate and its positive inotropic response was reduced in the presence of propranolol (10(-7) M) in the perfusion medium. Even under beta-adrenoceptor blockade, the curve for the phenylephrine-induced positive inotropic effect remained shifted upward after isoproterenol pretreatment. Chronic isoproterenol pretreatment induces the expected cardiac beta-adrenoceptor desensitization while simultaneously enhancing the positive inotropic responsiveness to phenylephrine in Langendorff heart preparations. These findings support the hypothesis that cardiac alpha1-adrenoceptor stimulation may contribute to the maintenance of myocardial function under conditions in which beta-adrenoceptor function is compromised.

Comparison of spiramycin and clarithromycin for community-acquired lower respiratory tract infections

This open multicentre study compared the efficacy and tolerability of clarithromycin and spiramycin in the treatment of lower respiratory tract infections in Brazil and Colombia. A total of 125 patients with a clinical and radiological diagnosis of pneumonia, acute bronchitis or exacerbation of chronic bronchitis were randomised to receive oral doses of either clarithromycin (500 mg) or spiramycin (3 MIU) every 12 hours for courses of 5-10 days. Patients were assessed before the start of treatment, and at days 3-4 and days 9-17. Twenty-six (26) patients (16 in the spiramycin group and 10 in the clarithromycin group) reported adverse events, seven of whom withdrew from the trial. Statistical analysis detected no significant differences between efficacy (p = 0.768) or tolerability (p = 0.236) for the two treatment groups. Spiramycin therefore has similar efficacy to clarithromycin in the treatment of community-acquired lower respiratory tract infections.

[The effect of nifedipine on hemodynamics and gas exchange in dogs with experimental acute respiratory insufficiency]

PURPOSE

Evaluate the action of nifedipine, a calcium channel blocking agent, on the hemodynamics and gas exchange experimental acute respiratory failure.

METHODS

Lung injury was provoked in sixteen mongrel dogs with intratracheal instillation of hydrochloric acid (HC1) (0.1N; pH = 2.0; 2.0 ml/kg body weight). As steady state was achieved after HC1 instillation (maintenance of a stable arterial PO2), saline 1 ml (six dogs) or nifedipine (ten dogs) 30 micrograms/kg for body weight were intravenously injected. The hemodynamic variables and gas exchange parameters were analyzed before HC1, after HC1 and 10 and 30 minutes after nifedipine or saline.

RESULTS

The intratracheal instillation of HC1 provoked significant drop of PaO2, of systemic oxygen transport index (ITO2S), and increase of venous admixture (QVA/Q). Nifedipine provoked significant reduction of the mean systemic arterial pressure (Pas), and of the systemic (IRVS) and pulmonary vascular resistance index (IRVP), with significant increase of cardiac (IC) and systolic index (IS), with no changes ot the mean arterial pulmonary (Pap) and capillary pressures (Pcap). After nifedipine there was a significant increase of PaO2, PvO2, and ITO2S, with no significant variations of QVA/Q and alveolar arterial O2 difference (P(A-a)O2).

CONCLUSION

Nifedipine promoted systemic vasodilation, and probably by increasing the venous return and/or by a reflex mechanism, the cardiac output increased, augmenting the ITO2S. The IRVP decreased in the nifedipine group, with no significant alterations of Pap and Pcap, probably consequent to the systemic vasodilation provoked by the drug. The arterial PO2 augmented in the nifedipine group, as a consequence of mixed venous PO2 increase, since no changes occurred in QVA/Q, P(A-a)O2, inspired fraction of O2 and alveolar ventilation.