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Biomedical subjects

D Henderson

Publications and source records attributed to D Henderson.

At least 271 records · Page 15Linked to original sources
PubMed1976

Film screening by physician assistants in diagnostic radiology.

Data are presented which indicate that specially selected ART students can be trained to evaluate radiographs as to the presence or absence of significant pathology with an accuracy equivalent to that of experienced staff radiologists. The methods employed in this training program-namely, stressing perceptual recognition of normal and abnormal findings-may be beneficial in the early months of training of diagnostic radiology residents to hasten achievement of an acceptable perceptual performance. Test films, used in this study as an evaluation technique, may also be useful to assess residents' progress.

Clinical Competence↗
PubMed1975

Auditory fatigue: retrocochlear components.

Changes in auditory sensitivity were measured at the VII nerve, cochlear nucleus, and inferior colliculus after a fatiguing sound exposure. Losses in sensitivity progressively increased from peripheral to central auditory sites. The results suggest that there is a retrocochlear component to auditory fatigue when it is induced by low-level sounds of short duration.

Acoustic Stimulation↗
PubMed1975

Combined cleft lip revision, anterior fistula closure and maxillary osteotomy; a one-stage procedure.

The syndrome of defects which characterise the cleft lip and palate patient undergoing secondary surgery is listed, and the traditional system of multiple sequential operations for its correction is challenged. A single stage combined procedure is described which permits the correction of maxillary collapse and hypoplasia to be combined with closure of an anterior palatal fistula and lip revision, together with some improvement of abnormal nasal appearance.

Cleft Lip↗
PubMed1975

Recombination-deficient deletions in bacteriophage lambda and their interaction with chi mutations.

We have isolated a new class of deletion mutants of phage lambda that extend from the prophage attachment site, att, into the gam and cIII genes. In this respect they are similar to certain of the lambda pbio transducing phage, but they differ in having a low burst size and in forming minute plaques. Lytically grown stocks of the deletions contain a variable proportion of phage that produce large plaques. These have been shown to carry an additional point mutation. Similar mutations, called chi, have been described by Lam et al. (1974), who showed that they result in a hot-spot for recombination produced by the host recombination system (Rec). We show that chi mutations can occurat several sites in the lambda genome and produce a Rec-dependent increase in the burst size of the one deletion tested.---In addition to reducing burst size, the one deletion tested reduces synthesis of DNA and emdolysin but increases production of serum blocking protein. A chi mutation partially restores DNA synthesis and endolysin production and reduces serum blocking protein to normal levels. Our results are consistent with the hypothesis put forward by Lam et al., that chi enhances the frequency of Rec-promoted recombination, which provides the only pathway for production of maturable DNAin a red gam infection. The mechanism of the differential effect on protein production is, however, unclear.---Chi mutations are found to occur in DNA other than that of lambda. We show that, as has been suggested elsewhere (McMilin, Stahl and Stahy 1974), the lambda pbio transducing phages carry a chi mutation within the E. coli DNA substitution. A chi mutation also arose in a new substitution of unknown origin isolated in the course of this work.

Chromosome Aberrations↗
PubMed1975

The role of the middle ear in acoustic trauma from impulses.

Exposure to high intensity impulse noise may produce a wide range of audiometric and histological effects in experimental animals. The objective of this study was to assess the changes in the middle ear mechanism after impulse noise exposure and to relate these changes to the audiometric and histological effects. Nine monaural chinchilla were exposed to either 161 or 166 db peak SPL impulses of 1 msec "A" duration, presented at a rate of 1 per minute for 50 minutes. The conductive mechanism of the chinchilla was assessed using standard clinical measures of static and dynamic impedance before and after the noise exposure. Auditory thresholds were measured before and after noise exposure using the average evoked response (AER) technique. At 30 days post-exposure, the animals were sacrificed for histology. Pre-exposure tympanometry showed that: 1. the total mean impedance of the chinchilla ear is considerably lower than that of man; 2. a method related hysterisis effect is present in both the susceptance and conductance tympanograms; and 3. sedation has a significant effect on the total impedance of the ear and on the shape of the tympanograms. After exposure to high level impulse noise: 1. tympanograms become irregular and double peaked, indicating tympanic membrane stress; 2. for the given exposure, 166 db is the impulse intensity needed to rupture consistently the tympanic membrane; and 3. audiometric and histological data correlate with the tympanometric findings and demonstrate a protective effect of a tympanic membrane rupture on the cochlea.

Animals↗