Effects of intermediate filaments on actin-based motility of Listeria monocytogenes.

How does subcellular architecture influence the intracellular movements of large organelles and macromolecular assemblies? To investigate the effects of mechanical changes in cytoplasmic structure on intracellular motility, we have characterized the actin-based motility of the intracellular bacterial pathogen Listeria monocytogenes in normal mouse fibroblasts and in fibroblasts lacking intermediate filaments. The apparent diffusion coefficient of L. monocytogenes was two-fold greater in vimentin-null fibroblasts than in wild-type fibroblasts, indicating that intermediate filaments significantly restrict the Brownian motion of bacteria. However, the mean speed of L. monocytogenes actin-based motility was statistically identical in vimentin-null and wild-type cells. Thus, environmental drag is not rate limiting for bacterial motility. Analysis of the temporal variations in speed measurements indicated that bacteria in vimentin-null cells displayed larger fluctuations in speed than did trajectories in wild-type cells. Similarly, the presence of the vimentin meshwork influenced the turning behavior of the bacteria; in the vimentin-null cells, bacteria made sharper turns than they did in wild-type cells. Taken together, these results suggest that a network of intermediate filaments constrains bacterial movement and operates over distances of several microns to reduce fluctuations in motile behavior.

Secrets of actin-based motility revealed by a bacterial pathogen.

Actin-based cell motility is a complex process involving a dynamic, self-organizing cellular system. Experimental problems initially limited our understanding of this type of motility, but the use of a model system derived from a bacterial pathogen has led to a breakthrough. Now, all the molecular components necessary for dynamic actin self-organization and motility have been identified, setting the stage for future mechanistic studies.

[Reduction modality of a dietary questionnaire]. / Modalità di riduzione di un questionario alimentare.

The data relative to the average daily intake of 7 nutrients and total energy obtained through the answers to a dietary questionnaire, consisting of 152 items and administered to 200 patients (admitted for acute pathologies) has been analysed. The aim has been to elaborate a questionnaire consisting of a more limited number of items but maintaining a great part of the informative contents from the original questionnaire. For this aim, a multiple regression model with a selection procedure for independent variables, of the stepwise type, has been used, where the dependent variable is the daily average intake of the nutrient and the independent variables are the consumption of each food included in the complete questionnaire (QC). By combining the results of the model with the 7 nutrients and total energy, 3 reduced questionnaires have been produced (QR): the first two are based on the sole criteria of the inter-individual variance of the intake of the nutrient, explained by the consumption of the foods included in the QR, the third by adding the foods that offer an adequate contribution in order to explain the supply of the nutrient under examination. The application potentials of the 3 QRs have been analysed both by evaluating the inter-class correlation coefficient, deduced by an concordance/discordance matrix relative to the quintilis values of the nutrient deduced by the QC and by each QR, and by simulating their use in a case-control study; for this aim, the attenuation of the odds ratio trend and the increase of the sample dimension has been calculated following the use of a QR instead of a complete one.(ABSTRACT TRUNCATED AT 250 WORDS)

Pseudoaccommodation with the 3M diffractive multifocal intraocular lens: a refraction study of 52 subjects.

A refraction study was performed of 52 pseudophakic subjects implanted with a 3M diffractive intraocular lens (IOL). Twenty patients implanted with conventional monofocal IOLs from 3M were used as controls. The refraction for distance and near was determined, corresponding to the refractive (distance vision) and diffractive (near vision) foci. Pseudoaccommodation amplitude was measured relative to the variation of visual acuity as a function of "fogging" obtained with plus and minus lenses over any required spherical cylindrical power. Results showed that the 3M diffractive IOL acted as a bifocal lens in all subjects except those whose IOLs had decentered markedly. The dioptric range allowing good vision for distance and near is much wider with the diffractive IOL than it is with a monofocal IOL. Almost perfect vision, and the satisfaction of the patients, was achieved when the distance refraction was near to emmetropia and astigmatism was minimal. However, hyperopic biometric inaccuracies were less disturbing than myopic inaccuracies.

Prospective study of pupil motility in pseudophakia.

We operated on 148 patients with age-related cataracts using the envelope technique and intraocular lens implantation in the capsular bag. Pupil diameters were measured on the day before surgery and again two months after. In pseudophakic eyes, morphologic examinations revealed 80 intact pupils, 32 pupils with slight changes, and 36 pupils with marked alterations. However, no substantial alterations in pupil diameter were observed. The photopic diameter, which was enlarged by approximately 17%, was the exception. Near pupil reactivity showed a 28% reduction; reactivity to light was decreased by 26%. The abnormalities were more frequent after complicated operations and in older patients, but it was not possible to predict postoperative diameters in individual cases.