Dimethylsphingosine Research Articles

Sphingosines: antimicrobial barriers of the skin.

Among the factors that control the survival of microorganisms on human stratum corneum are skin lipids, including sphingosines. Because the antibacterial spectrum of sphinganine resembles that of cell wall antibiotics, electron microscopy of sphinganine-treated and untreated S. aureus was performed; the lipid induced multiple lesions of cell wall, membrane evaginations and loss of ribosomes. However, comparisons of minimal inhibitory concentration of sphinganine for coccal forms and L-forms of S. aureus, which lack cell walls, and of the respective dose-related reductions in colony-forming units demonstrated both the susceptibility of L-forms and their superior resistance. Therefore, cell wall lesions are sequelae of a probable membrane reaction. Candida albicans was susceptible to sphinganine, sphingosine, dimethylsphingosine, and to a lesser degree, stearylamine. Liquid assays of these lipids against Trichophyton mentagrophytes, T. tonsurans and Epidermatophyton floccosum established their high susceptibility to sphingosine and stearylamine. Sphinganine was the least effective, perhaps due to the presence of L isomers; T. tonsurans was the most sensitive. These four lipids were found to be fungistatic, preventing germination and retarding thalli. Antifungal efficacy was confirmed in vitro on stratum corneum.

Morphology of heart valves preserved by liquid nitrogen freezing.

As a preliminary to establishing a frozen valve bank for replacement surgery, the possible effects of the proposed freezing and thawing procedure on tissue structure were assessed in 16 human pulmonary valves removed from cadavers at necropsy and nine dog valves obtained fresh. The valves were frozen and stored in liquid nitrogen for intervals ranging from 23 to 380 days. Blocks of tissue cut from the central area of one leaflet, and including some adjacent arterial wall and ventricular myocardium, were obtained both before freezing and after thawing and examined by a large specimen resin embedding technique for light and electron microscopy, with histochemical staining for matrix material. Control and thawed tissue from all valves appeared similar, indicating good preservation irrespective of storage time. Fine structural alterations in the cellular elements correlated with the total interval of autolysis (from death to freezing) rather than the cause of death or other variables and were not uniform in any of the specimens.