Mechanisms of liposomes/water partitioning of (p-methylbenzyl)alkylamines.

PURPOSE: The objective of this study was to compare and interpret the variations in lipophilicity of homologous (p-methylbenzyl)alkylamines (MBAAs) in isotropic (octanol/water) and anisotropic (zwitterionic liposomes/water) system. METHODS: Two experimental approaches were used, namely the pH-metric method to measure lipophilicity parameters in octanol/water and liposomes/water systems, and changes in NMR relaxation rates to validate the former method and to gain additional insights into the mechanisms of liposomes/water partitioning. RESULTS: For long-chain homologues (N-butyl to N-heptyl), the octanol/water and liposomes/water systems mostly expressed hydrophobicity. In contrast, the lipophilicity of the shorter homologues (N-methyl to N-propyl) in the two systems expressed various electrostatic and polar interactions. CONCLUSIONS: The study sheds light on the molecular interactions between zwitterionic liposomes and amphiphilic solutes in neutral and cationic form.

The interrelationship of measures related to vocal function, speech rate, and laryngeal appearance in elderly women.

The purpose of this investigation was to explore the interrelationship of various measures related to vocal function, speech rate, and laryngeal appearance in elderly women. Speakers were 20 women ranging in age from 67 to 86 years. An indirect laryngoscopic examination that included judgments on glottal closure and vocal fold appearance was performed on each speaker. Eight measures related to vocal performance (the production capabilities of the mechanism with regard to pitch range, intensity range, and phonation time) were collected on each speaker. Further, acoustic measures of intensity and fundamental frequency stability were made from sustained vowels, and a reading passage was analyzed for reading rate and intensity level. Factor analysis procedures revealed an association of maximum phonation time with measures of vocal intensity, as well as with pitch range measures. Surprisingly, reading rate was grouped with measures of FO stability as well as with maximum vocal intensity. Although laryngoscopic findings are in general agreement with those reported previously in elderly women (Honjo & Isshiki, 1980), inadequate glottal closure was observed more frequently, and vocal cord edema less frequently, in these women.