Efeitos da fumaça de cigarro sobre a osteogênese e a resistência mecânica óssea em ratos / Effects of cigarette smoke on osteogenesis and bone mechanical resistance in rats

This paper reports a study of the effects of exposure to cigarette smoke on osteogenesis and the mechanical strength of bone in rats. Twelve male rats were separated into two groups (n=6): CT (control) and CI (cigarette). All the animals had free access to rat chow and water throughout the experiment. Group CI was exposed to the smoke of 6 cigarettes/day for 12 weeks. After 6 weeks of exposure to cigarette smoke, a defect was produced on the parietal bone and dense hydroxyapatite (DHA) ceramic bodies were implanted into cavities made surgically in the tibia of the animals, in each group. After surgery, the CT and CI groups returned to normal experimental conditions and, at the end of 12 weeks, they were euthanized, and their tibiae and parietal bones removed for histological processing, while the femurs were subjected to biomechanical tests in a MTS TestStar II three-point flexion module. Consumption of solid and liquid diet was satisfactory in both groups, all animals gaining weight throughout the experiment. CI animals showed a smaller volume of newly formed bone in the parietal defect (8.l9±0.2) and around the DHA implant in the tibia (33±0.5) than the rats in the CT group (14.4±0.5 and 39±1 respectively). The maximum force needed to break the femur was smaller in CI (119±3.2) than in CT (140±6.5). The results of this study led to the conclusion that exposure to cigarette smoke interfered with osteogenesis in the bone defect and around the DHA implant and reduced the maximum force required to completely break the femur, revealing that bone fragility can be caused by tobacco smoke.

O presente estudo teve como objetivo avaliar os efeitos da exposição à fumaça de cigarro sobre a osteogênese e a resistência mecânica do osso em ratos. Foram utilizados doze ratos machos, divididos em dois grupos (n=6): grupo CT (controle) e grupo CI (cigarro). Durante 12 semanas, os animais do grupo CI foram expostos à fumaça de seis cigarros/dia. Após seis semanas de exposição à fumaça de cigarro, uma falha óssea de 5mm foi produzida no osso parietal e corpos cerâmicos de hidroxiapatita densa (HAD) foram implantados em cavidade produzida cirurgicamente na tíbia dos animais do grupo CI e CT. Após as cirurgias, os animais retornaram aos protocolos experimentais e, ao término de doze semanas de experimentação, foram eutanasiados, as tíbias e os ossos parietais foram coletados para processamento histológico e os fêmures encaminhados para ensaio biomecânico em um módulo MTS TestStar II®. A exposição à fumaça do cigarro não interferiu no ganho de peso dos animais e os consumos de dieta líquida e sólida foram satisfatórios entre os grupos. Os animais do grupo CI apresentaram menor volume de osso neoformado na falha óssea (8,9±0,2) produzida no osso parietal e ao redor do implante de HAD na tíbia (33±0,5). A força máxima necessária para romper o fêmur dos animais foi menor no grupo CI (119±3,2) do que no grupo CT (140±6,5). Com bases nos resultados obtidos no presente trabalho, pôde-se concluir que a exposição à fumaça do cigarro interferiu na osteogênese da falha óssea e ao redor do implante de HAD, diminuiu a força máxima necessária para a ruptura completa dos fêmures e demonstrando a fragilidade óssea causada pelo hábito tabagista.

Mutants with heteroresistance to amphotericin B and fluconazole in Candida

Several studies have reported the occurrence of infections caused by Candida yeasts as well as the increasing prevalence of non albicans species. The aim of the present work is focused on the obtaining of heteroresistance to amphotericin B and fluconazole in Candida species using two distinct methodologies: selection and induction. Resistant samples were obtained by selective pressure using a medium with fluconazole for growth, followed by growth in a medium with amphotericin B. The selective pressure was also created beginning with growth in amphotericin B medium followed by growth in fluconazole medium. Concomitantly, samples were submitted to the induction of resistance through cultivation in increasing concentrations of fluconazole, followed by cultivation in increasing concentrations of amphotericin B. Subsequently, the induction began with amphotericin B followed by fluconazole. Three samples resistant to fluconazole and amphotericin B were obtained, two by induction (C. glabrata and C. tropicalis) and one by selection (C. tropicalis). Both C. tropicalis originated from the same wild sample. After successive transfers for drug free medium, only the sample obtained by selection was able to maintain the resistance phenotype. These results suggest that the phenotype of heteroresitance to fluconazole and amphotericin B can be produced by two methodologies: selection and induction.

Antimicrobial activity of benzophenones and extracts from the fruits of Garcinia brasiliensis.

The pericarp and seeds from fruits of Garcinia brasiliensis were subjected to extraction with hexane and ethanol. The pericarp hexane extract (PHE) and seed ethanol extract (SEE) were purified by silica gel column chromatography, which permitted isolation of the prenylated benzophenones 7-epiclusianone (1) and guttiferone-A (2), respectively. The antimicrobial activity of PHE, SEE, and compounds 1 and 2 were evaluated against Candida albicans, Staphylococcus aureus, Escherichia coli, and Bacillus cereus cultures. The minimum inhibitory concentration and minimum bactericidal concentration were established. The substances presented activity against S. aureus and B. cereus as follows: PHE, 4.0 microg/mL and 2.4 microg/mL; SEE, 10.0 microg/mL and 12.6 microg/mL; 7-epiclusianone, 1.2 microg/mL and 0.6 microg/mL; and guttiferone-A, 2.4 microg/mL and 2.4 microg/mL, respectively. The direct relationship between the lipophilic character of the structure and activity in Gram-positive bacteria was specifically observed. Therefore these extracts and prenylated benzophenones represent an interesting topic for further studies and open possibilities for an alternative control of diseases associated with Gram-positive bacteria.

Mutants with heteroresistance to amphotericin B and fluconazole in Candida.

Several studies have reported the occurrence of infections caused by Candida yeasts as well as the increasing prevalence of non albicans species. The aim of the present work is focused on the obtaining of heteroresistance to amphotericin B and fluconazole in Candida species using two distinct methodologies: selection and induction. Resistant samples were obtained by selective pressure using a medium with fluconazole for growth, followed by growth in a medium with amphotericin B. The selective pressure was also created beginning with growth in amphotericin B medium followed by growth in fluconazole medium. Concomitantly, samples were submitted to the induction of resistance through cultivation in increasing concentrations of fluconazole, followed by cultivation in increasing concentrations of amphotericin B. Subsequently, the induction began with amphotericin B followed by fluconazole. Three samples resistant to fluconazole and amphotericin B were obtained, two by induction (C. glabrata and C. tropicalis) and one by selection (C. tropicalis). Both C. tropicalis originated from the same wild sample. After successive transfers for drug free medium, only the sample obtained by selection was able to maintain the resistance phenotype. These results suggest that the phenotype of heteroresitance to fluconazole and amphotericin B can be produced by two methodologies: selection and induction.

Correlation between CLSI, EUCAST and Etest methodologies for amphotericin B and fluconazole antifungal susceptibility testing of Candida spp. clinical isolates.

This study analyzed the correlation between the results obtained through two microdilution methods: Clinical and Laboratory Standard Institute (CLSI) (M27-A2) and European Committee on Antibiotic Susceptibility Testing (EUCAST) (document E. Dis. 7.1) and an agar base method Etest for determining minimmun inhibitory concentration (MIC) for amphotericin B and fluconazole against 30 clinical isolates of Candida spp. The agreement between Etest, CLSI and EUCAST MICs within +/- 2 log2 dilutions was higher for amphotericin B than for fluconazole However, Pearson correlation demonstrated a greater agreement for fluconazole. The categorical agreement between MICs provided by the Etest/ CLSI and Etest/EUCAST methodologies was high for both amphotericin B (100%) and fluconazole (> or = 96.66%). This study demonstrated the adequacy of Etest method using Mueller Hinton agar to evaluate amphotericin B and fluconazole susceptibility of clinical isolates of Candida spp.

Erythematous candidosis in patients with complete dentures and HIV+/AIDS.

This investigation was designed to evaluate the frequency of erythematous candidosis (EC) and Candida species, proteinase and phospholipase exoenzyme production, and to compare clinical features in patients with complete dentures and HIV+/Acquired Immunodeficiency Disease Syndrome (AIDS). Fifty-one patients were selected from a total of 285 with EC: denture wearers (n = 30) and HIV+/AIDS (n = 21). The yeast prevalence and the production of exoenzymes, such as proteinase and phospholipase by Candida species were evaluated by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) electrophoresis. The frequency of Candida albicans was significantly higher (P < 0.05) in both groups although other yeast species (Candida glabrata, Candida krusei, Candida parapsilosis, Candida guilliermondi and Candida tropicalis) were also found. Candida albicans showed greater levels of proteinase production in the denture wearers, when compared with the HIV+/AIDS group. There was no difference between groups with regard to phospholipase production. The protein bands presented similar molecular weights, showing the presence of proteinases in both groups. It could be concluded that the clinical manifestation of EC may be related to its proteinase production capacity. Combination therapies using proteinase inhibitors play an important role in inhibiting exoenzyme production by Candida species, mainly C. albicans.

Evaluation of the allergenicity of spore and mycelia extracts of Pisolithus tinctorius.

The antigenic and allergenic chemical analysis of spore and mycelia extracts of Pisolithus tinctorius was carried out. The spores were collected from basidiocarps in plantations of Eucalyptus spp and the mycelia from culture in MNM medium. With basis on the fungus growth curve, the mycelia masses were obtained after 10, 20, 30, and 40 days of incubation, which correspond, respectively, to the beginning, middle and end of the log phase, and beginning of the decline phase. The mycelia masses, together with the spores, were submitted to the action of three extractors (Coca, Tris-HCl, and ammonium bicarbonate). The contents of carbohydrates and proteins were determined. The SDS-PAGE electrophoretical analysis revealed separate fractions in these extracts, besides common fractions, in function of cultivation time and extraction methods. The selected extracts for the allergic tests were the ones with the highest number of fractions. The prick-tests were conducted in 374 patients--rural workers, eucalyptus plantation workers, and college students. The positivity to the "prick test" with the antigenic extract of P. tinctorius was, respectively, 3.78%, 28.20% and 6.40%. Most prick-test positive patients (82.75%) also presented symptoms of respiratory allergy (asthma and rhinitis). There was no reactivity difference when the spore and mycelia extracts were employed. The analysis of the positive patients' sera revealed the presence of IgE specific to the P. tinctorius antigens. Since Pisolithus tinctorius is found as mycorrhiza of Eucalyptus spp, and this plant is used in reforestation in most countries, the importance of that fungus should be regarded as a possible cause of respiratory allergies, especially in occupationally exposed workers.