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Biomedical subjects

J E FitzGerald

Publications and source records attributed to J E FitzGerald.

10 recordsLinked to original sources
PubMed1998

Postural stability of normal subjects measured by sway magnetometry: pathlength and area for the age range 15 to 64 years.

Fifty-eight subjects with no known vestibular pathology, postural problems or cerebrovascular disease were studied to determine the range of sway values in a normal working-age population. Sway was measured with a magnetometry system, previously shown to be highly successful in distinguishing sway with and without the eyes open in individual subjects. 30 subjects were aged 15-29 years and 28 aged 30-64 years. With the subject standing on a firm base the pathlength and area enclosed by movement of the hips in the horizontal plane were measured over 30 second periods with eyes open and eyes closed. There were no significant differences between the two age ranges. We obtained the following upper limits of normal values for the age range 15 to 64 years: pathlength with eyes open 140 mm, pathlength with eyes closed 200 mm, area with eyes open 150 mm2, and area with eyes closed 300 mm2. The mean and standard deviation of the Romberg coefficient (sway with eyes open/sway with eyes closed) was 0.73 +/- 0.09 for pathlength measurement and 0.70 +/- 0.26 for area measurement.

Adolescent↗
PubMed1997

Identification of non-organic instability by sway magnetometry.

This paper describes the application of sway magnetometry, which objectively measures stability, to assist in the identification of non-organic instability. Three subject groups were studied; 14 normal subjects, 14 subjects with organic dizziness, and 19 subjects assessed as having possible non-organic dizziness before further clinical investigation. Eight of these 19 were subsequently classed as having non-organic dizziness on grounds of their history, clinical examination and standard audio-vestibular investigations. Movement in the horizontal plane at the hips was measured by sway magnetometry in each subject. The absolute and percentage change in path length and area were determined for 15 s before and 15 s after the subject was informed that the test was starting. For absolute path length and area, five out of the eight subjects with non-organic dizziness showed an increase in sway above the upper limit of normal, while only one out of the other 11 subjects in the group showed such an increase (P < 0.02). None of the subjects in the normal or organic group exceeded the upper limit of normal when results were expressed as absolute change in path length or area. Sway magnetometry can provide valuable data to assist the clinician in identification of non-organic dizziness.

Adolescent↗
PubMed1996

Measurement of the vestibulo-ocular reflex by magnetometry during active head movement.

A new method of measuring the vestibulo-ocular reflex (VOR) during active head movements is presented. Subjects sat and attempted to maintain their gaze upon a fixed point whilst turning their heads from side to side in response to an auditory cue, to attain frequencies of head rotation that increased from 1 Hz to 4 Hz during a 24 s period. Head movements were monitored by a small magnetic field detector worn on the subject's forehead and positioned a set distance from a magnetic field transmitter coil. Eye movements were monitored using the corneo-retinal potential. Gain (eye angle/head angle) and phase difference (eye phase-head phase) were calculated to define the VOR. Three repeat measurements were made on 20 normal subjects. Gain decreased significantly (P < 0.0001) with increasing frequency whilst the phase difference remained unchanged. The 95% prediction intervals were narrow for both gain (+/- 0.28) and phase (+/- 11 degrees). These data, together with the speed and ease of performance of the test, suggest that the test can provide valuable information on the performance of the vestibular system.

Adult↗
PubMed1993

Comparison of balance assessment by sway magnetometry and force platforms.

Sway magnetometry, which monitors body movement at the hips, was compared with two commercial force platforms to determine its sensitivity in identifying differences in stability between eyes opened and eyes closed. Sway path length and area were examined. All devices showed an ability to distinguish between stability with eyes opened and eyes closed on repeated testing. The magnetometry system using path length analysis was most sensitive and was able to detect an increase in sway with eyes closed compared with eyes open for individual tests with 97% confidence (mean [+/- SD] path length Romberg Coefficient, .76 +/- .13). Standing on a rubber base caused destabilization of posture. Sway magnetometry is seen as a potentially useful tool in quantification of body sway to aid the clinician in assessment of balance in the dizzy patient.

Adult↗
PubMed1992

An evaluation of commercial water irrigation systems used for caloric testing.

The post-1982 Grant Caloric Test Apparatus, and the Atmos Variotherm were evaluated and compared to BS5724 Part 1 (1989). Quality of construction is satisfactory, but design features may result in failure of tests for which this type of equipment should conform; namely splash, liquid leakage and spillage. For the Variotherm the proximity of the water piping to the electrical parts could result in wetting of the electrical units in the event of a leakage. The large vents in the Grant tanks allow easy access of water to electrical parts in the event of splashing. Both sets of equipment fail BS5724 Part 1 (1989) with respect to labelling. The Grant irrigation nozzle is well designed, but the Variotherm nozzles are not so, as they can accidentally pass down the external auditory meatus causing meatal wall or tympanic membrane damage. Both sets of equipment passed on electrical safety test for Class I Type B equipment. Cut-outs are fitted to prevent heating in the absence of water or over-heating of the water. The 44 degrees C Grant tank cut out after 20 s in the absence of water and at 49 degrees C as the water temperature rose above the operating temperature. The Variotherm heater did not operate in the absence of a water supply. The Variotherm thermal cut-out was not assessed. The force of the water at recommended flow rates using the Variotherm 'standard' metal nozzle was considered to pose a potential hazard of tympanic membrane perforation, and has subsequently been withdrawn by the supplier. The plastic nozzle minimized any such risk. The Variotherm is easier to use due to the well-designed trigger handle for controlling water delivery. Both sets of equipment performed at the correct temperature to within +/- 0.5 degrees C and achieved a flow rate of 250 ml in 30 s.

Caloric Tests↗
PubMed1989

Rheologic studies on middle ear effusions and their mucus glycoproteins.

The properties of pooled thick and thin middle ear effusions, from children with otitis media with effusion, were studied by viscometry. Mucus glycoproteins were responsible for effusion viscosity. Their percentage by weight in thick and thin effusions was 25% and 8.2%, respectively. N-acetylcysteine and 0.2 mol/L of mercaptoethanol caused a 39% viscosity drop in a 5-mg/mL glycoprotein solution, whereas S-carboxymethylcysteine had no effect. Treatment of thick effusions with 0.2 mol/L of mercaptoethanol initially caused a viscosity decrease followed by a gradual increase. Higher reducing agent concentrations (0.5 mol/L) caused a more rapid decrease followed by a rapid increase, presumably by causing nonspecific aggregation of reduced protein molecules. These results suggest that the concentration of and the time that a mucolytic is in the middle ear would be of prime importance in achieving the desired decrease in viscosity.

Acetylcysteine↗
PubMed1987

Characterization of human middle ear mucus glycoprotein in chronic secretory otitis media (CSOM).

Middle ear effusion was obtained from children with chronic secretory otitis media undergoing myringotomy. The effusions contained about 120 mg/ml non-dialysable solids, of which 18-31% was mucus glycoprotein. The purified mucus glycoprotein had a composition characteristic of other mucus glycoproteins. Amino acid analysis of the glycoprotein indicates a protein core consisting of glycosylated regions resistant to proteolysis and non-glycosylated regions susceptible to proteolysis. Analysis of the mucus glycoprotein by gel filtration on Sepharose 2B showed that reduction caused a decrease in hydrodynamic size and proteolysis caused a further decrease. The difference was confirmed by sedimentation coefficient and viscosity measurements. The reduced glycoprotein had an intrinsic viscosity of 0.113 ml/mg and an S0(20) of 15.2S compared to a value of 0.018 ml/mg and 9.6S for the proteolytically digested glycoprotein. These results suggest a model for this middle ear mucus glycoprotein, in which the native glycoprotein is a large molecular mass polymer maintained by disulphide bridges. These disulphide linked glycoprotein units are broken down into smaller units by proteolysis. The mucus glycoprotein could not be purified completely free from low molecular mass components. A glycoprotein, susceptible to proteolysis Mr 28,000-33,000 co-fractionates with the major high molecular mass mucus glycoprotein.

Child↗
PubMed1984

Endogenous beta-galactoside-specific lectins in rabbit tissues.

Soluble beta-galactoside-specific lectins have been detected in many rabbits tissues and are relatively abundant in certain organs. These lectins are apparently identical to the lectin in rabbit bone marrow, which may be involved in inter-erythroblast associations during differentiation, and are very similar in structure and activity to lectins described in a number of species both in adult and embryonic tissues. The rabbit lectin is a monomer with a relative molecular mass of approximately 12 000 and has a low specific activity in the haemagglutination of trypsinized rabbit erythrocytes relative to lectins from other species, which are predominantly dimeric. In addition to the major antigen two minor isoforms of the rabbit galaptin were detected in all tissues. Since these lectins are widely distributed, it seems probable that they are involved in cellular functions that are prominent during development and also maintained in certain differentiated tissues. Experimental evidence currently available suggests that these lectins may be involved in the organization of extracellular matrix components.

Animals↗