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Biomedical subjects

G J McKee

Publications and source records attributed to G J McKee.

10 recordsLinked to original sources
PubMed2001

Effect of bolus consistency on swallowing--does altering consistency help?

The influence of food bolus consistency on the pharyngeal wave during swallowing was investigated using a four-sensor manometry probe in 22 healthy volunteers. Pharyngeal pressures were recorded for 5 ml boluses of water, pudding and buttered bread via a manometry probe placed transnasally. The distal sensor was sited within the upper oesophageal sphincter (UOS); the three proximal sensors were then located 2, 4 and 6 cm above the UOS. The amplitude and timing of the swallow waveforms for pudding and buttered bread were recorded and compared with those for water. Increased bolus viscosity led to increased amplitude of the bolus wave and clearing contraction within the pharynx. In the UOS, increased bolus viscosity was associated with a larger pressure nadir (sub-atmospheric pressure) on opening and intra bolus pressure during transit. Bolus consistency also influenced the coordination of the swallow response with delayed pharyngeal clearance. The putative relevance of these findings to dietary modification for patients with neurological and neuromuscular dysphagia is discussed.

Adult↗
PubMed1999

Morphological assessment of the soft palate in habitual snoring using image analysis.

OBJECTIVES: Define differences in palatal and uvular dimensions between habitual snorers and healthy nonsnoring control subjects. Document the changes in palatal configuration after different types of palatoplasty. STUDY DESIGN: A prospective controlled clinical study was performed analyzing video recordings of the soft palate and oropharynx of 251 subjects (121 habitual snorers, 79 patients after laser-assisted uvulopalatoplasty ([LAUP], and 51 healthy volunteers). METHODS: The recordings were captured using a rigid endoscope with a reference measure applied to the soft palate and a mark at the junction of the soft and hard palate. Four parameters were studied in the captured pictures after correction for the distortion deformity in fiberoptic endoscopic images: 1) length of soft palate, 2) length of uvula, 3) width of uvula, and 4) distance between posterior pillars. RESULTS: Analysis showed that habitual snorers, compared with healthy volunteers have significantly increased soft palate length (P = .00001), increased uvula length (P = .0002) and width (P = .00001), and narrowed oropharyngeal isthmus (distance between the posterior pillars) (P = .04). In patients studied after LAUP, the length of the soft palate is significantly shorter (P = .00001) than in the preoperative cohort, and the oropharyngeal isthmus is significantly narrower (P = .00001). Moreover, this latter distance is significantly narrower (P = .00001) when compared with healthy volunteers. CONCLUSIONS: Habitual snorers have a long soft palate, a long wide uvula, and a narrowed oropharyngeal isthmus. LAUP shortens and tightens the elongated palate and causes a further reduction in the space between the posterior pillars.

Adult↗
PubMed1998

Does age or sex affect pharyngeal swallowing?

The influence of age and gender on the pharyngeal pressure wave during swallowing was investigated in 73 healthy volunteers using a four-sensor manometry probe. The distal sensor was placed within the upper oesophageal sphincter (UOS) and three proximal sensors were located in the pharynx 2, 4 and 6 cm above the UOS. Twenty-nine variables describing the amplitude and timing of the swallow waveforms for a 5 ml water bolus were recorded from the pharynx and the UOS. Analysis of the results indicated that aging was associated with slowing of the swallow response in the pharynx, impaired opening of the UOS and a marked reduction in resting UOS tone.

Adult↗
PubMed1994

Nasal airflow after septorhinoplasty.

The changes in nasal function which occur after septorhinoplasty for obstruction were investigated by anterior rhinomanometry in 15 subjects. Objective and subjective measures of outcome were compared. Anterior rhinomanometry was performed after nasal decongestion. These data were mathematically transformed to determine the amount of airflow asymmetry through the nostrils and the stiffness of the nasal valve. The results suggested that the presence of gross airflow asymmetry (> +/- 80%) in patients prior to surgery was a bad prognostic indicator for post-operative satisfaction with the airway. Patient satisfaction with function and cosmetic appearance post-operatively was correlated with the presence of symmetrical nasal airflow. Nasal valve stiffness did not seem to be affected by septorhinoplasty.

Adult↗
PubMed1992

An investigation of normally hearing subjects with tinnitus.

The hearing sensitivity and psychological profile of 18 young subjects with tinnitus and normal hearing were investigated by pure-tone and high-frequency audiometry, notched-noise tests, auditory-brainstem responses, evoked otoacoustic emissions and Crown-Crisp experiential index. Psychoacoustical and brainstem tests were comparable to those of 19 normally hearing subjects without tinnitus. Otoacoustic emissions were worse in ears of tinnitus subjects. Neurotic personality traits were stronger in the tinnitus subjects. These traits may be secondary to otological dysfunction, or may contribute to complaint behaviour.

Adult↗
PubMed1991

The effects of type 1 diabetes mellitus and of tobacco smoke on dissipation of catecholamines in pulmonary endothelial cells--a non-neuronal site of uptake1.

The effects of Type 1 diabetes mellitus and of exposure to mainstream cigarette smoke on noradrenaline (NA) uptake and its subsequent metabolism by catechol-O-methyltransferase (COMT) and monoamine oxidase (MAO) in the perfused lungs of rats were examined. In diabetic (streptozotocin-treated) rats, there was an increase in the metabolic clearance of NA in the lungs, and this appeared to be due to the observed increase in NA uptake. During acute exposure of rat lungs to cigarette smoke, there was again an increase in the metabolic clearance of NA, and this was not due to any increase in the activity of either COMT or MAO, but we have not yet investigated whether it is due to an increase in NA uptake. After prolonged exposure of rats to cigarette smoke (daily for 3 months), NA uptake in the lungs was increased, but there was no change in the activity of either COMT or MAO. The results suggest that increased pulmonary clearance may reduce the elevated plasma catecholamine levels that have been described both in patients with Type 1 diabetes mellitus and in cigarette smokers.

Animals↗
PubMed1989

Role and results of cortical mastoidectomy and endolymphatic sac surgery in Menière's disease.

It is almost impossible to establish the natural history of Menière's disease and, by the same token, it is difficult to confirm the efficacy of endolymphatic sac surgery. The authors doubt the logic of sac operations. Only two controlled trials of sac surgery have been found and both cast doubt upon its value. There do not appear to be any controlled trials indicating that it works. In 14 cases of incapacitating Menière's disease, where vestibular nerve section was indicated, cortical mastoidectomy was offered and accepted in the expectation that two-thirds might be spared the more major procedure. In the event, the vertigo was controlled in eight out of 14 (57 per cent), the remaining six (43 per cent) requiring more major surgery. A surgical model illustrates that, of themselves, these results are essentially meaningless in assessing the efficacy of cortical mastoidectomy in Menière's disease. Until all cases in a community are considered and followed-up, we shall be in doubt about the value of sac surgery and most other treatments of Menière's disease.

Endolymphatic Sac↗
PubMed1989

Tympanosclerosis: a scanning electron microscopic study.

Twelve specimens of tympanosclerosis were examined. Six were immediately fixed in 3% glutaraldehyde and 6 were obtained from the departmental collection of specimens in wax blocks which had previously been examined by light microscopy. Seven specimens were demineralized. The material was examined macroscopically, by light microscopy and by scanning electron microscopy to a magnification of x25,000. The microstructure of tympanosclerosis is an irregular three-dimensional collagen lattice, enclosing distinct, spherical, mineralized aggregates, housed in lacunar-like spaces. This lattice is continuous with the plaque surface which is an envelope, probably of proteinaceous material. The spherical calcified aggregates were absent from the demineralized specimens. There was no structural difference in the scanning electron microscopic appearances of specimens processed conventionally in 3% glutaraldehyde and those previously embedded in wax.

Adult↗
PubMed1984

The effects of mesencephalic neural crest cell extirpation on the development of chicken embryos.

The mesencephalic neural crest cells of Hamburger-Hamilton Stage 9-Stage 11 chick embryos were surgically extirpated unilaterally in 148 embryos and bilaterally in 8 embryos. Sham operations were performed unilaterally on 16 control embryos and bilaterally on one control embryo. Embryos were fixed at various time intervals after operation, studied macroscopically, and by light and scanning electron microscopy, and their development compared with that of 47 normal embryos. The extirpated mesencephalic region was repopulated by crest cells within 6-8 hours after operation. These 'new' crest cells migrated from adjacent neuraxial levels (principally the metencephalon and prosencephalon) along the basement membrane of the neural tube and the regenerating ectoderm. At prosencephalic and metencephalic levels, both intrinsic hyperplasia of migrating cells and prolonged migration of crest cells from the dorsomedian part of the neural tube contributed the additional cells required to repopulate the mesencephalic region. Morphogenesis and differentiation of all crest cell derivatives were normal and craniofacial malformations were absent. Thus the neural crest and neural tube can compensate for an extensive regional loss, premigratory crest cells are neither regionally patterned nor determined (as prosencephalic and metencephalic cells give rise to normal mesencephalic derivatives) and regional failure of crest cell formation is an unlikely facial pathogenetic mechanism. Previous workers who observed facial malformations following crest cell extirpations performed the latter by removing the lips of the neural tube which not only removed the crest cells but also the compensatory mechanism. Cervical scoliosis was observed in extirpated embryos but not in controls. The pathogenesis of this scoliosis may be related to the process of compensation, which could disturb the sequential differentiation of the neural tube and so disorganise the mechanisms of normal axial flexion. These observations may be relevant to the pathogenesis of some forms of congenital and infantile idiopathic scoliosis; such scoliosis in man is frequently present in neurofibromatosis--a neural crest lesion.

Animals↗