Isolation and biological characterization of Legionella pneumophila mutants resistant to aminoglycoside antibotics and their protective action]

Preliminary estimation of virulence in some antibiotic resistant mutants of Legionella pneumophila, Philadelphia 1 in various models of infection revealed its decrease in the mutants resistant to azlocillin, cefotaxime, fluoroquinolone LIB-80, neamine and streptomycin. Detailed investigation of the neamine resistant mutants showed that in relation to streptomycin susceptibility such mutants could be divided into 3 classes: susceptible to streptomycin, resistant to high concentrations of streptomycin and resistant to moderate concentrations of streptomycin. Part of mutants Nea(r)Strr and Nea(r)Strr500 and all mutants Nea(r)Strr100 proved to be less virulent with respect to guinea pigs and chick embryos. The study of the spectinomycin resistant mutants of Legionella spp. did not reveal any changes in the virulence which made it possible to suggest that the influence of the mutations in the ribosomal protein genes determining resistance to streptomycin and neamine on virulence of L. pneumophila was based on the interdependence of the mutant effect on the suppression and the influence on the virulence detected by us in S. flexneri, Y. pseudotuberculosis, L. monocytogenes and F. tularensis. The Legionella mutants Nea(r)Strr100 were characterized by significant protective activity and protected immunized guinea pigs when tested in a model of their aerogenic infection.     

Inhibition of potassium (KATP) channels reduces the short-circuit current response of rat colonic mucosa to acetylcholine

Intestinal secretion depends upon electrogenic chloride transport into the gut lumen, which requires maintenance of an electrically negative cell-membrane voltage. We have investigated whether secretory responses of rat colonic mucosa to acetylcholine were sensitive to inhibition of potassium channels and whether selective inhibition could indicate the nature of the channel involved. Rat colonic mucosa was set up in Ussing chambers, short-circuit current responses obtained to acetylcholine, and the sensitivity of such responses to inhibition of potassium channels was investigated. Non-selective potassium-channel blockade by barium induced concentration-dependent inhibition of responses to acetylcholine. Similar inhibitory effects were obtained using 4-aminopyridine and glibenclamide. 5-Hydroxydecanoate and phentolamine also inhibited the increase in short-circuit current. However, a combination of charybdotoxin plus apamin was without effect. We conclude that a basolateral outward movement of potassium ions is required for the secretory action of acetylcholine on rat colonic mucosa. The potassium channel involved seems to be ATP-dependent and calcium-insensitive.     

Characterization of a human papillomavirus type 16 variant-dependent neutralizing epitope

We have determined that three type-specific and conformationally dependent monoclonal antibodies, H16.E70, H16.U4, and H16.V5, neutralize pseudotype human papillomavirus type 16 (HPV16) virions in vitro. H16.U4 and H16.V5 neutralized pseudotype virions derived from the German HPV16 variant 114K and the Zairian variant Z-1194 with equal efficiency. In contrast, neutralization of Z-1194 pseudotype virions by H16.E70 was two orders of magnitude weaker than neutralization of 114K pseudotype virions. This difference correlated with enzyme-linked immunosorbent assay reactivity of H16.E70 to L1 virus-like particles of the two variants. A substitution at residue 282 of L1 was responsible for this differential reactivity, suggesting that this residue constitutes part of the H16.E70 epitope.     

Byssotoxin A, a secondary metabolite of Byssochlamys fulva

Byssochlamys fulva, isolated from corn, was grown on nutrient-amended shredded wheat medium for 14 days at 25 C. Crude solvent extract from these cultures was toxic to brine shrimp, chicken embryos, and rats. The extract was slightly inhibitory to the germination of of pea seeds, but was nontoxic to ten species of bacteria and one of yeast. One metabolite was isolated, given the trivial name byssotoxin A, and partially characterized chemically and physically.     

Influence of testosterone on some behavioral reactions of male immature rats

A 31-year old woman with acquired immunodeficiency syndrome (AIDS) and a history of lymphoma presented with a 2-week history of severe hyperthyroid symptoms and new-onset neck swelling. On physical examination, she was found to be clinically hyperthyroid, with a markedly enlarged, diffuse, tender goiter. Thyroid function testing confirmed hyperthyroidism. The patient had a rapidly deteriorating clinical course and died within days of her presentation. At autopsy, near-complete replacement of the thyroid gland with anaplastic large cell lymphoma was found, without coexisting infectious or autoimmune processes in the gland. This is the first case report of a patient with AIDS developing symptomatic thyroid involvement by lymphoma, and one of only a few case reports of hyperthyroidism associated with lymphoma in general.