Effects of exogenous hexacosanoic acid on biochemical myelin composition in weaning and post-weaning rats.

X-linked Adrenoleukodistrophy (ALD) is characterized by an increase of very long chain fatty acids (VLCFA) in particular of hexacosanoic acid (HA), in tissues and fluids. The biochemical abnormality is due to the dysfunction of peroxisomal degradation of VLCFA. To-date it is unclear if the demyelination which characterizes this disease is the direct consequence of HA accumulation. In order to investigate whether the large amounts of exogenous HA could affect myelin synthesis, 500 micrograms of this fatty acid dissolved in peanut oil were administered daily and by gavage to newborn rats. Since myelin is actively synthesized during early neonatal life and it can be altered by environmental factors including diet, we analyzed lipid and protein composition of myelin after 20, 30 and 60 days of HA administration. Our results show that exogenous HA is incorporated in myelin where it determines biochemical alterations in normal rats having a functioning peroxisomal system. Even though the differences between controls and treated rats are slight, we observed in test rats, a decrease of 2'3'-cyclic nucleotide 3'-phosphohydrolase (CNPase) activity and of myelin basic protein (MBP) content at any time studied. The decrease of glycolipids (GL) was present only after 20 days of treatment. Since these parameters are related to myelin development, our data lead us to think that the myelin of the treated animals is less mature than that of controls.

In-vitro activity of six intracellular antibiotics against Legionella pneumophila strains of human and environmental origin.

The activity of six intracellular antibiotics, doxycycline, erythromycin, clarithromycin, azithromycin, rifampicin and ciprofloxacin, was tested against 60 strains of Legionella pneumophila (21 of human and 39 of environmental origin). MIC50, MIC90, and MBC values were determined by a microdilution method. Inhibitory and bactericidal activity against human and environmental isolates were similar except for rifampicin, which was 100-fold less active for human strains than for environmental strains, particularly in terms of bactericidal activity. Nevertheless, in general, rifampicin was found to be the most active drug. Among the macrolides tested, clarithromycin showed the greatest activity in MIC assays and erythromycin was the least bactericidal. Azithromycin showed higher MICs and MBCs than the two macrolides, and doxycycline was the least active. The most important factors influencing in-vivo activity of antibiotics are discussed. Even if the in-vitro results cannot be fully extrapolated to activity in vivo, these results indicate the susceptibility of L. pneumophila strains in Italy as a basis for treatment of atypical pneumonia that may be due to Legionella spp.