Integrins regulate the intracellular distribution of eukaryotic initiation factor 4E in platelets. A checkpoint for translational control

Recent evidence from our laboratory demonstrates that platelets synthesize numerous proteins in a signal-dependent fashion (Pabla, R., Weyrich, A. S., Dixon, D. A., Bray, P. F., McIntyre, T. M., Prescott, S. M., and Zimmerman, G. A. (1999) J. Cell Biol. 144, 175-184; Weyrich, A. S., Dixon, D. A., Pabla, R., Elstad, M. R., McIntyre, T. M., Prescott, S. M., and Zimmerman, G. A. (1998) Proc. Natl. Acad. Sci. U. S. A. 95, 5556-5561). Protein synthesis in platelets is controlled at the translational level; however, the mechanisms of regulation are not known. Here we demonstrate that translation initiation factors are redistributed to mRNA-rich areas in aggregated platelets, an event that induces protein synthesis. Interrogation of cDNA arrays revealed that platelet-derived mRNAs are primarily associated with the cytoskeletal core. In contrast, eukaryotic initiation factor 4E (eIF4E), the essential mRNA cap-binding protein that controls global translation rates, is localized in the membrane skeleton and soluble fraction of platelets, physically separated from most mRNAs. Platelet activation redistributes eIF4E to the cytoskeleton and increases interactions of eIF4E with mRNA cap structures. Redistribution of eIF4E to the mRNA-rich cytoskeleton coincides with a marked increase in protein synthesis, a process that is blocked when intracellular actin is disrupted. Additional studies demonstrated that beta(3) integrins are the primary membrane receptor that distributes eIF4E within the cell. These results imply that integrins link receptor-mediated pathways with mRNA-rich cytoskeletal domains and thereby modulate the organization of intracellular translational complexes. They also indicate that the functional status of eIF4E is regulated by its intracellular distribution.

Chordomas: pathological features; ploidy and silver nucleolar organizing region analysis. A study of 36 cases

Chordomas are slow growing malignant neoplasms with a prolonged clinical course which do not usually metastasize. They are histologically benign, locally invasive and often recur following resection. Survival has been shown to vary widely and prognostic indicators have been difficult to identify. Cellularity, mitotic activity and cellular pleomorphism have not been found to have prognostic significance. Thirty-six cases of clival, cervico-thoracic and sacral chordomas were evaluated utilizing four variables as possible predictors of survival: (1) silver nucleolar organizing region (AgNOR), (2) ploidy, (3) fibrosis, and (4) inflammatory response. AgNOR areas in approximately 200 cells per case were calculated and summed. DNA ploidy was obtained in 23 of the cases by analyzing deparaffinized Feulgen-stained tissue. Fibrosis and inflammation were evaluated by hematoxylin and eosin and by trichrome stains. Clinical follow-up was available in the 36 cases with survival ranging from 0.5 to 159 months. A statistical analysis employing the Cox-Proportional Hazards model disclosed no significant correlation between AgNOR area and clinical outcome (P > 0.05). The variables, fibrosis, and inflammation, did not demonstrate prognostic significance (P > 0.05). Ploidy demonstrated a statistical trend for prognostic significance (P = 0.077). It is apparent that three of the four parameters studied do not independently affect survival. Although AgNOR has proved useful in the study of other neoplasms such as those of breast, prostate and bladder, it is not of significant importance in predicting the behaviour of chordomas. Ploidy, on the other hand, may be of value in predicting clinical outcome in chordomas and may be a useful marker in the evaluation of the aggressive biological behavior of these neoplasms.

Quantitative computer-assisted image analysis of suction biopsy in pediatric gastroesophageal reflux

Gastroesophageal reflux is a disorder with well-characterized histopathological features in the adult, but the incidence and pathogenesis of epithelial injury in children are poorly understood. Esophageal suction biopsies from 80 infants exhibiting symptoms of reflux were studied by computer-assisted image analysis and the results compared to routine histological scoring. The histological features evaluated were the number of intraepithelial lymphocytes and eosinophils, papillary height, interpapillary basal cell height, and a novel measure "integrated basal cell height." We quantitatively evaluated these histological criteria by computer-assisted image analysis and compared these results to four subjective grades of esophagitis: low, mild, moderate and high. In this report we now describe this quantitative histopathologic method for the evaluation of pediatric esophageal biopsies. Utilizing this method we demonstrate that both inter- and intra-observer variability were sufficiently low to stratify the mucosal changes reliably into at least four categories. The reliability of this objective analytic technique will permit studies into the disease progression and regression in pediatric reflux esophagitis.

Influence of amplification on the discrimination of dichotic consonant-vowel syllables in a population with sensorineural hearing loss

This study was designed to investigate the premise that the long-term use of monaural amplification influences dichotic listening conditions in a population with sensorineural hearing losses. 30 subjects with moderate, bilateral sensorineural hearing losses and 10 normally-hearing adults were chosen for this study. 20 of the subjects with sensorineural hearing loss had worn amplification successfully for at least 1 year prior to testing. 10 of these subjects had worn amplification only on the right ear while the remaining 10 had worn amplification only on the left ear. All subjects received 60 monaural and dichotic consonant-vowel (CV) nonsense syllables presented at equal loudness levels using the most comfortable level (MCL) as the loudness criteria. While monaural scores revealed nonsignificant differences between ears for all subjects, using percentage of error, dichotic results produced a right-ear advantage for the right-ear-aided, unaided and normally-hearing subjects. A significant left-ear advantage was seen for the left-ear-aided subjects. Results of this study suggest that amplification introduces selective listening effects which alter reported dichotic test scores.

Newborn high-risk hearing screening by maternal questionnaire

State-wide, high-risk hearing screening is made possible in Utah through the use of a questionnaire designed for maternal response during hospitalization. The mothers of those determined high risk are sent a follow-up questionnaire when the infant is 6 to 8 months of age, and a determination is made for audiological testing on the basis of her response. Questionnaires (26352) were received on 50,700 live births, of which 4,591 (17.4%) were categorized high risk. Of the high-risk infants, 181 (3.9%) were determined at risk after follow-up, and 54 (20.8%) of these were found hearing impaired. Questionnaire item analysis is presented. Concerns regarding response validity and low return rate are discussed as is the pilot use of the birth certificate as the initial screening device.

Admittance tympanometry in otosclerotic ears

Twenty-eight surgically confirmed otosclerotic ears were evaluated to determine whether tympanometric admittance measurements could differentiate otosclerosis from a normal population. Subjects were tympanometrically measured at test conditions B220, B660, G220 and G660 Hz. When comparing mean curve peak amplitude to normative standards, 20 ears showed significantly low admittance tympanograms. Further investigation revealed no significant differences in curve width or pressure of the curve peak. Of the remaining eight otosclerotic ears, all produced diphasic "W"-notched tympanometric configurations. Diagnostic implications and physiological hypothesis are discussed.