Comparative analysis of three methods to assess viability of mammalian cells in culture

Release of lactate dehydrogenase (LDH) from the cytoplasmic compartment, trypan blue exclusion and methylthiazole tetrazolium (MTT) colorimetric assays were compared with regard to their sensitivity in detecting damage of human cultured epithelial cells induced by sodium fluoride or puromycin. LDH assay did not detect any difference between controls and cells treated with either of the two drugs. Cell monolayers treated with 0.3 sodium fluoride or 10(-2) M puromycin presented higher percentages of cells that took up the trypan blue dye than controls but monolayers treated with lower drug concentrations did not differ from controls. Viability measured by MTT assay was the most sensitive assay, detecting a dose-dependent impairment of cell function after treatment with the two drugs. Moreover, MTT offered major advantages in speed, simplicity and precise quantitation over the other viability assays

Pseudomonas aeruginosa adhesion to normal and injured respiratory mucosa

Human nasal polyps outgrowth culture were used to study the adhesion of Pseudomonas aeruginosa to respiratory cells. By transmission electron microscopy, bacteria associated with ciliated cells were identified trapped at the extremities of cilia, usually as aggregates of several bacterial cells. They were never seen at the interciliary spaces or attached along cilia. Bacteria were also seen to adhere to migrating cells of the periphery of the outgrowth culture. Using a model of repair of wounded respiratory epithelial cells in culture, we observed that the adhesion of P. aeruginosa to migrating cells of the edges of the repairing wounds was significantly higher than the adhesion to non-migrating cells and that adherent bacteria were surrounded by a fibrocnectin-containing fibrillar material The secretion of extracellular matrix components is involved in the process of epithelium repair following injury. To investigate the molecular basis of P. aeruginosa adhesion to migrating cells, bacteria were treated with a fibronectin solution before their incubation with the respiratory cells. P. aeruginosa treatment by fibronectin significantly increased their adhesion to migrating cells. Accordingly, we hypothesize that during cell migration, fibronectin secreted by epithelial cells may favour P. aeruginosa adhesion by establishing a bridge between the bacteria and the epithelial cell receptors. Such a mechanism may represent a critical step for P. aeruginosa infection of healing injured epithelium

Fenomeno de Dienes em Proteus: ausencia de correlacao com a estrutura antigenica e a producao de metabolitos difusiveis. / Dienes phenomenon in Proteus: lack of correlation to antigenic structure and to production of diffusible metabolites

O fenomeno de Dienes consiste na formacao de linha de demarcacao no local de encontro do crescimento invasivo de duas amostras de estirpes diferentes de Proteus, quando se defrontam na superficie de meio solido. O estudo de amostras de P. mirabilis e de P. vulgaris nao revelou correlacao entre estrutura antigenica e a antibiose bacteriana evidenciada pelo teste de Dienes. Tambem nao foi possivel detectar substancias toxicas as quais se pudesse atribuir a inibicao do espraiamento,no confronto de cepas incompativeis

Faringite estreptococica. Aspectos bacteriologicos e sua importancia em saude publica. / Streptococcal pharyngitis. Bacteriological aspects and its importance in public health

O autor apresenta um estudo feito com 198 criancas brasileiras da area do Rio de Janeiro, sobre a incidencia de estreptococos beta hemoliticos em clima tropical.Pretende determinar a frequencia de anginas de etiologia estreptococica entre o grupo etario mais exposto e determinar a taxa de portadores entre criancas sadias, buscando a possivel significacao dos aspectos epidemiologicos documentados