Perceptual confusions of 16 consonant-vowel (CV) syllables were studied with normal-hearing adults under conditions of auditory-visual presentation at various signal-to-noise (S/N) ratios, as well as under auditory-only and visual-only conditions in quiet. An articulatory feature classification system was used to analyze responses with regard to percentage correct intelligibility and relative information transmission. In the auditory conditions, features of voicing and nasality were least affected by noise, while place of articulation showed the greatest reduction in intelligibility. The auditory-visual confusions indicated that the visual channel in bisensory presentations reduced errors when phonemes differed by place of articulation, with the greatest visual complement occurring at the poorer S/N ratios. Responses from the visual-only condition indicated that the subjects were able to categorize the phonemes into discrete homophenous groups. Part-whole reliability for the visual-only condition was high, indicating that a short form of the test could be used for screening aural-rehabilitation clients. Finally, since the subjects' ability to visually recognize five places of articulation was nearly perfect, it was suggested that emphasis in aural rehabilitation be placed on auditory training or use of contextual cues, rather than on lipreading.

To evaluate the relationship between physical characteristics of the lips during vowel production and vowel lipreading confusions, four female talkers were videotaped producing 15 American English vowels and diphthongs in an /h/-V-/g/ context. Ten normal-hearing adults identified the stimuli through lipreading. Three analyses were performed. First, using confusion matrices for individual and pooled talkers, the stimuli were located in a two-dimensional space using multidimensional scaling. The ten monophthongs revealed a clear lip spreading/rounding dimension and a tongue height dimension, and while diphthongs also showed influence of lip rounding, more variability on the tongue height dimension was apparent. Second, tracings were made of the talkers' lips on a single videotape field representing the maximum opening or constriction for each of the 40 monophthong tokens (ten vowels X four talkers), and six physical measurements of the tokens were derived as descriptors of the vowel nuclei. Third, difference scores and other measures of physical pairwise similarity were used as predictors of two ways of representing the vowel lipreading confusions in a multiple regression paradigm. Results indicated that the physical measures were moderately successful as predictors of vowel perception (accounting for approximately 50% of the variance in the perceptual distance measure), although considerable differences in the strength of the prediction occurred among talkers.

Cell-cell interactions between mature T cells and peripheral blood null cells induce erythropoietin-stimulated differentiation of peripheral blood-derived erythroid progenitors. By the use of complement-fixing cytolytic murine hybridoma and antibody uniquely reactive with mature T lymphocytes, this dependence of immature peripheral blood erythroid burst-forming unit (BFU-E) differentiation upon mature T cells or a T cell conditioned medium is confirmed. By using the same antibody, it is demonstrated that the differentiation of mature bone marrow BFU-E does not require either mature T cells or lymphocyte mitogenic factor. These findings do not preclude the presence in the bone marrow of other cells, perhaps even immature T cells, that influence erythropoietin-dependent erythroid differentiation of mature marrow BFU-E.

Chemically tritiated actin from rabbit skeletal muscle was used to investigate the association of G-actin with the red cell membrane. The tritiated actin was shown to be identical to unmodified actin in its ability to polymerize and to activate heavy meromyosin ATPase. Using sealed and unsealed red cell ghosts we have shown that G-actin binds to the cytoplasmic but not the extracellular membrane surface of ghosts. Inside-out vesicles which have been stripped of endogenous actin and spectrin by low-ionic-strength incubation bind little G-actin. However, when a crude spectrin extract containing primarily spectrin, actin, and band 4.1 is added back to stripped vesicles, subsequent binding of G-actin can be increased up to 40-fold. Further, this crude spectrin extract can compete for and abolish G-actin binding to unsealed ghosts. Actin binding to ghosts increases linearly with added G-actin and requires the presence of magnesium. In addition, actin binding is inhibited by cytochalasin B and DNAase I. Negative staining reveals an abundance of actin filaments formed when G-actin is added to reconstituted inside-out vesicles but none when it is added to unreconstituted vesicles. These observations indicate that added G-actin binds to the red cell membrane via filament formation nucleated by some membrane component at the cytoplasmic surface.

A lipreading screening test consisting of 100 consonant-vowel (CV) syllables was prepared on videotape and presented to subjected with normal hearing and vision. The results of visual consonant confusions revealed nine homophenous categories with high test-retest reliability. Based upon these categories, obtained under ideal viewing conditions, criterion levels of performance were specified in an attempt to determine the need for place of articulation instruction during lipreading training. Examples of confusion patterns from hearing-impaired observers are shown and implications for visual training are presented.