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Biomedical subjects

P Howell

Publications and source records attributed to P Howell.

At least 55 records · Page 3Linked to original sources
PubMed1989

Serological and immunological characteristics of maternal anti-Rh(D) antibodies in predicting the severity of haemolytic disease of the newborn.

A number of factors were analyzed for their predictive value in indicating the severity of haemolytic disease of the newborn (HDN) in 72 infants. The factors investigated were: maternal antibody titre in the indirect antiglobulin test, the number of antibody molecules on sensitized standard red cells evaluated by a radiometric antiglobulin test, the IgG subclass specificity and the reactivity in monocyte-monolayer assay (MMA) and in the rosette assays with lymphocytes and granulocytes from healthy individuals. The results of the MMA correlate much better with the severity of HDN than the antibody titre. In clinically unaffected infants the reactivity in the MMA never exceeded 20%, while in the severe/very severe group it was always greater than 20% (in 95% of very severe cases even above 50%). The number of IgG-bound molecules was also shown to closely correlate with the clinical severity and there was a much greater proportion of severe/very severe cases exhibiting combined IgG1 and IgG3 specificity. Of all the evaluations performed the rosette assays with lymphocytes and granulocytes were found to be less useful in predicting the severity of HDN.

Erythroblastosis, Fetal↗
PubMed1989

Jaw movement and bone-conduction in normal listeners and a unilateral hemi-mandibulectomee.

Relative movement between the mandible and skull may compress the auditory meatus and produce an excess sound in the ear canal. To test this, measurements of sound pressure in the ear canal, and movement of the upper and lower jaw are reported on normal subjects and a unilateral hemi-mandibulectomee. On the side the unilateral hemi-mandibulectomee has a jaw and in the subjects with normal jaws, the data confirm that mandible-movement relative to the skull produces sound in the ear canal. The excess sound in the ear canal when the jaw is free to move independently of the skull can be predicted from the relative movement between them.

Bone Conduction↗
PubMed1988

The contribution of the excitatory source to the perception of neutral vowels in stuttered speech.

The vowel in part-word repetitions in stuttered speech often sounds neutralized. In the present article, measurements of the excitatory source made during such episodes of dysfluency are reported. These measurements show that, compared with fluent utterances, the glottal volume velocities are lower in amplitude and shorter in duration and that the energy occurs more towards the low-frequency end of the spectrum. In a first perceptual experiment, the effects of varying the amplitude and duration of the glottal source were assessed. The glottal volume velocity recordings of the /ae/ vowels used in the analyses were employed as driving sources for an articulatory synthesizer so that judgments about the vowel quality could be made. With dysfluent glottal sources (either as spoken or by editing a fluent source so that it was low in amplitude and brief), the vowels sounded more neutralized than with fluent glottal sources (as spoken or by editing a dysfluent source to increase its amplitude and lengthen it). In a second perceptual experiment, synthetic glottal volume velocities were used to verify these findings and to assess the influence of the low-frequency emphasis in the dysfluent speech. This experiment showed that spectral bias and duration both cause stuttered vowels to sound neutralized.

Adult↗
PubMed1988

Assessment of sound in the ear canal caused by movement of the jaw relative to the skull.

To assess whether or not the reduction of threshold to bone-conducted sound on occlusion of the ears (the occlusion effect) is due to compression of the auditory meatus by the jaw, measurements of movement of the skull and mandible and sound in the ear canal are reported from four subjects. The change in bone-conducted sound in the ear canal was also measured when the mandible was moved out and in (presenting more or less of the mandible to compress the auditory meatus) and when vibration was applied directly to the mandible. Sound pressure increased when the jaw was moved out and when vibration was applied to the mandible.

Air Pressure↗
PubMed1986

Segmentation and speech perception in relation to reading skill: a developmental analysis.

The present paper examines the processing of speech by dyslexic readers and compares their performance with that of age-matched (CA) and reading-ability-matched (RA) controls. In Experiment 1, subjects repeated single-syllable stimuli (words and nonwords) presented either in a favorable signal-to-noise ratio or with noise masking. Noise affected all subjects to the same extent. Dyslexic children performed as well as controls when repeating high-frequency words, but they had difficulty relative to CA-controls with low-frequency words and relative to both CA- and RA-controls when repeating nonwords. In Experiments 2 and 3, subjects made auditory lexical decisions about the stimuli presented in Experiment 1. Dyslexics performed less well than CA-controls, gaining similar scores to RA-controls. Thus, their difficulty in repeating low-frequency words could be reinterpreted as a difficulty with nonword repetition. Taken together, these results suggest that dyslexics have difficulty with the nonlexical procedures (including phoneme segmentation) involved in verbal repetition. One consequence is that they take longer to consolidate "new" words; verbal memory and reading processes are also compromised.

Child↗
PubMed1986

Acoustic analysis and perception of vowels in stuttered speech.

In stuttered repetitions of a syllable, the vowel that occurs often sounds like schwa even when schwa is not intended. In this article, acoustic analyses are reported which show that the spectral properties of stuttered vowels are similar to the following fluent vowel, so it would appear that the stutterers are articulating the vowel appropriately. Though spectral properties of the stuttered vowels are normal, others are unusual: The stuttered vowels are low in amplitude and short in duration. In two experiments, the effects of amplitude and duration on perception of these vowels are examined. It is shown that, if the amplitude of stuttered vowels is made normal and their duration is lengthened, they sound more like the intended vowels. These experiments lead to the conclusion that low amplitude and short duration are the factors that cause stuttered vowels to sound like schwa. This differs from the view of certain clinicians and theorists who contend that stutterers actually articulate /schwa/'s when these are heard in stuttered speech. Implications for stuttering therapy are considered.

Acoustic Stimulation↗
PubMed1985

Anorectal function in elderly patients with fecal impaction.

Manometric and other investigations were carried out in 55 elderly patients who had impacted masses of feces in the rectum upon admission to hospital and in 36 elderly age- and sex-matched control subjects. Maximum basal and maximum squeeze sphincter pressures in the patients were similar to those in the elderly controls. Most elderly patients in the impacted group and all control subjects were able to pass a 50-ml balloon from the rectum, although a lower proportion of patients, admitted with impaction, could expel a small solid sphere. In patients the rectum had to be distended with larger volumes than in controls before the presence of the rectal balloon, pain, and the desire to defecate were perceived and before rectal contractions were generated. Rectal pressures, recorded during rectal distention, were lower in the impacted group than in the control group. Finally, anal and perianal sensation was impaired in patients with fecal impaction. These findings are similar to those described in patients with low spinal cord injuries.

Aged↗
PubMed1984

Quantitation of antibody binding to erythrocytes in LISS.

The amount of antibody bound to cells in a low ionic strength solution (LISS) has been quantitated for several antibodies including anti-D, anti-c, anti-Kell, anti-Fya, and anti-Jka. With the exception of the Kell antibodies there was an enhancement of the rate of antibody uptake in LISS. For Rh antibodies the amount bound after a 5-min LISS incubation is comparable to that bound after 45 min in saline. For Kell antibodies a smaller amount was bound in LISS than in saline. The effect of the ratio of serum to cells was also studied, and with several antibodies there was an increase in the amount of antibody bound with a higher serum to cell ratio irrespective of suspending medium. For Kell antibodies this ratio appears to be of greater importance than the ionic strength for antibody detection. A modification to the LISS method to increase the serum to cell ratio is, therefore, presented.

Antigen-Antibody Complex↗
PubMed1983

Preferences for scale structure in melodic sequences.

Most Western music is tonal; that is, pitch organization can largely be described in terms of scales or keys. A considerable amount of research has been conducted on the role played by scale in perceiving notes and melodies. The present article points out a potentially important distinction between scale structure (the set permitted pitch intervals between notes) and mode (the assignment of a special salience or centrality to particular notes within the scale structure). Four experiments are described that investigated the judgment of adult Western listeners for melodies that approximated to scale structure in differing degrees but that were random in other respects. We found that musicians and nonmusicians gave higher ratings of preference and adjudged musicality to melodies containing increased numbers of consecutive notes conforming to scale structure. A significant exception to this rule was the least scalar type of sequence, which received ratings as high as the fully scalar sequences. This exception occurred because subjects identified scale structure not only in groups of contiguous notes but also in groups of discontiguous notes that formed a coherent "stream" as long as the number of notes intervening corresponded to a standard temporal grouping, or meter, such as is commonly found in Western music.

Choice Behavior↗
PubMed1983

A detailed serological study of five anti-Jka sera reacting by the antiglobulin technique.

Detailed serological investigation of five examples of anti-Jka revealed considerable heterogeneity in their characteristics. All the sera were investigated by the antiglobulin technique, with and without complement and by a range of sensitization and testing methods. Three were readily detected in the presence of complement, while two were detectable with anti-IgG, providing a spin test was used. Complement was bound by all and resulted in enhanced reactions, particularly when slide/tile tests were used. The study emphasizes that anti-complement (C3) is an essential component of polyspecific antiglobulin reagents used in cross-matching, enabling the ready detection of these clinically important antibodies.

Antigen-Antibody Reactions↗
PubMed1983

Production and perception of rise time in the voiceless affricate/fricative distinction.

Rise times of voiceless affricates and fricatives were measured when the test material occurred in sentences, in isolated words, and in isolated nonsense syllables. As has been reported previously the rise times of affricates were significantly shorter than those of fricatives. Rise times varied with the type of test material and for all types of material were significantly longer than those reported by L.J. Gerstman [unpublished doctoral dissertation, New York University (1957)]. Differences in the way the previous measurements were made do not appear to explain the discrepancy. Because rise time varies with type of test material, no auditory sensitivity at a single rise time value can be responsible for the perceptual distinction between voiceless affricates and fricatives. This conclusion was also supported by the results of a perceptual experiment in which listeners were asked to label speech or nonspeech stimuli drawn from a continuum varying in rise time. Substantially different estimates of the category boundary were obtained when the range of rise times covered by the stimuli differed.

Computers↗