Diphtheria pathogenesis in Guinea pig tracheal organ culture

The effects of Mycoplasma mobile 163 K on the ciliary epithelium of tracheal organ cultures

Mycoplasma (M.) mobile 163 K, isolated from the gills of a tench (Tinca tinca L.), was examined for cytotoxic capacities using tracheal organ cultures from gnotobiotic rats and gnotobiotic piglets in pH-controlled experiments (pH 7.2-7.6). The mycoplasmas caused an inhibition of the ciliary activity at incubation temperatures of 20, 25 and 30 degrees C. The strongest cilia stopping effect was observed at an incubation temperature of 25 degrees C, the optimal growth temperature of the mycoplasmas. No ciliostasis occurred at 37 degrees C. The number of the organisms did clearly affect the severity of ciliostasis in the range from 4.0 x 10(4) to 7.7 x 10(8) c.f.u. in rat as well as in porcine tracheal organ cultures. Toxic substances, secreted by the mycoplasmas into the culture medium, could not be detected. In histological investigations cytopathological changes were observed in the epithelial cells, apparent in the destruction and loss of cilia, cytoplasmatic vacuolization, swelling of mitochondria, peripheral orientation of the nuclear chromatin and detachment of epithelial cells from each other and the basal membrane. The final stage of the infection was characterized by complete exfoliation of the epithelial cells and the complete destruction of the multi-layer epithelium. The localization of the mycoplasmas attached to the ciliary epithelium was shown by scanning and transmission electron microscopy.

Analysis of damage to human ciliated nasopharyngeal epithelium by Neisseria meningitidis

We used an in vitro model of human nasopharyngeal tissue in organ culture to evaluate the effects of Neisseria meningitidis on human cilia and ciliary function. Encapsulated, viable meningococci damaged ciliated epithelium of nasopharyngeal organ cultures, whereas Neisseria subflava, a commensal species, did not. Meningococcus-induced ciliary damage was due to loss of ciliated cells to which meningococci were not attached. Damage was seen with piliated and nonpiliated meningococci and did not appear to require the presence of other specific meningococcal surface proteins. Meningococcal viability was a requirement for both ciliary damage and interactions of meningococci with microvilli of nonciliated epithelial cells. That is, filter-sterilized supernatants from meningococcus-infected organ cultures, heat-killed meningococci at high inoculum, and purified meningococcal or gonococcal lipopolysaccharide at concentrations of 100 micrograms/ml did not damage ciliary activity of nasopharyngeal organ cultures. In contrast, meningococcal lipopolysaccharide at 10 micrograms/ml markedly damaged ciliary activity of human fallopian tube organ cultures, suggesting a selective toxicity of lipopolysaccharide for specific human ciliated cells. Damage to nasopharyngeal ciliated epithelium by N. meningitidis may be an important first step in meningococcal colonization of the human nasopharynx, but meningococcal lipopolysaccharide does not appear to be directly responsible for this toxicity.

Effect of in vitro cultivation and Mycoplasma pneumoniae infection on intracellular cyclic AMP levels in hamster tracheal organ cultures

Exogenous cyclic AMP and dibutyryl cyclic AMP decreased the relative ciliary activity values of tracheal organ cultures. In contrast, theophylline and cholera toxin were not ciliostatic. The use of a radioimmunoassay for cyclic AMP indicated that all of the tested substances increased intracellular cyclic AMP levels to some extent (from 3-fold for cholera toxin to almost 40-fold for dibutyryl cyclic AMP). Physical inactivation of explants by either freeze-thaw or heat destroyed all ciliary activity and greatly decreased intracellular cyclic AMP levels. Cyclic AMP levels of explants remained relatively constant during in vitro cultivation. Three strains of Mycoplasma pneumoniae were found to contain extremely low amounts of cyclic AMP. Infection of tracheal explants produced a significant decrease in relative ciliary activity, but only a slight decline in organ-culture cyclic AMP levels.

Surface parasitism by Mycoplasma pneumoniae of respiratory epithelium

Identification of the attachment factor on virulent Mycoplasma pneumoniae organisms which permits surface parasitism of respiratory epithelium was attempted. Brief pretreatment of M. pneumoniae monolayers with protease prevented mycoplasma attachment ot sensitive host cells without reducing viability of the microorganisms. Gel electrophoretic analysis of mycoplasma proteins before and after exposure of intact mycoplasmas to protease revealed the absence of a major protein species (P1) in enzyme-treated preparations while other protein bands with the exception of P2 were virtually unaffected. The absence of P1 correlated with the failure of enzyme-treated mycoplasmas to attach to tracheal explants. P1 regeneration after protease treatment of mycoplasma monolayers was directly associated with reattachment capabilities in M. pneumoniae. Erythromycin inhibited P1 resynthesis, thus preventing resumed attachment activity by mycoplasmas. Lactoperoxidase-catalyzed iodination of intact M. pneumoniae organisms further confirmed that P1 was an external membrane protein and suggested that his surface component was required for the successful membrane-membrane interaction between host and parasite.

Interaction of virulent Mycoplasma pneumoniae with hamster tracheal organ cultures

Exposure of hamster tracheal organ cultures to virulent Mycoplasma pneumoniae leads to alterations in ribonucleic acid (RNA) and protein biosynthesis and metabolism of the respiratory epithelium. An examination of the turnover rates of RNA and protein in infected tracheal organ cultures indicates that the rates of degradation of both prelabeled host cell RNA and protein are similar to those of uninfected controls. Infected tracheal organ cultures shifted to a nonpermissive medium within 24 h after infection and further incubated in the nonpermissive medium for 72 or 96 h behaved as normal uninfected cultures in terms of metabolic precursor uptake. Under these conditions, mycoplasmas remained attached to the respiratory epithelium. Cell membranes prepared from virulent mycoplasmas by several procedures neither attached to nor altered the metabolic activity of tracheal cultures. These data indicate that the intimate contact between virulent mycoplasmas and the respiratory epithelium does not alone account for the subsequent interruption of host cell metabolism but must be accompanied by continued multiplication and biochemical function of attached mycoplasmas.

Alterations in the metabolism of hamster tracheas in organ culture after infection by virulent Mycoplasma pneumoniae

Exposure of hamster tracheal rings in organ culture to virulent Mycoplasma pneumoniae organisms leads to alterations in macromolecular biosynthesis and metabolic activity of the respiratory epithelial cells. Avirulent organisms derived from the same parent strain do not produce these effects. During the course of infection by virulent mycoplasmas, tracheal rings show an initial increase in [14C]galactose uptake followed by a significant decline as infection progresses which is also accompanied by abnormal processing of galactose as evidenced by amounts of 14CO2 released. Parallel decreases in the rate of [3H]orotic acid and [3H]amino acid uptake are observed. Within 24 h after infection of tracheal rings by virulent mycoplasmas, inhibition of host cell ribonucleic acid and protien synthesis is evident. Ribonucleic acid synthesis in infected cells, analyzed by gel electrophoresis, is reduced by 80% at 48 h and is negligible by 96 h. The course of mycoplasma infection can be interrupted or reversed by erythromycin after the initial mycoplasma-host cell interaction since addition of erythromycin 24 h or earlier after infection prevents the onset of abnormal orotic acid uptake. However, 48 h after infection, rescue of host cells by erythromycin cannot occur and cytopathology becomes evident. These data suggest that mediation of host cell injury requires continued protein synthesis by attached mycoplasmas, and the primary effect of mycoplasma infection on tracheal organ culture may be at a transcriptional or translational level.