PubMed Health⌕ Search

Biomedical subjects

I M Young

Publications and source records attributed to I M Young.

At least 19 recordsLinked to original sources
PubMed1995

Excimer laser lamellar keratoplasty.

PURPOSE: To evaluate a procedure using the excimer laser to perform lamellar keratoplasty to treat deep corneal scars in the central optical zone. To determine if excimer laser can safely prepare a smooth surface for the host bed and the donor button, assess the interface opacity and evaluate the effects of the ablation on the recipient's endothelial surface with the deeper ablation. METHODS: Nineteen rabbits underwent an excimer laser lamellar keratoplasty in one eye. The rabbits were followed for 9 to 12 weeks until they were sacrificed. RESULTS: Little opacity developed at the graft-host interface and scanning electron microscopy of the endothelial surface showed little difference between the treated and untreated areas or the endothelium of the untreated eyes. CONCLUSIONS: Our results suggest that the use of the excimer laser to treat corneas with deep stromal scars and normal endothelium is feasible. However, we have not proved that this technique will give a better result than conventional lamellar dissection methods.

Animals↗
PubMed1995

Fastpac visual field screening.

In epidemiology, screening for visual field defects has traditionally been expensive, time consuming and laborious. To achieve cost- and time-effective visual field screening, a faster algorithm has been developed for the Humphrey perimeter called Fastpac, which is designed to achieve threshold perimetry in two-thirds the time of the standard algorithm. We compared the Fastpac and conventional full-threshold 24-2 fields obtained in 39 eyes of 36 participants. We divided the participants' fields into normal (14) and glaucomatous (25) visual field groups, and compared the test times, number of questions asked and statistical parameters generated for each field for Fastpac as compared to the standard algorithm. Then we divided the participants' fields into Fastpac and standard fields and again compared the test times, number of questions and statistical parameters. Finally we asked trained observers to judge the fields as being normal or abnormal, in a masked fashion, and found a high degree of agreement between the fields generated by Fastpac and standard. Fastpac offers accurate full-threshold screening in two-thirds the time of the conventional algorithm and would be very useful for large scale prevalence studies in ophthalmic epidemiology.

Adult↗
PubMed1994

Comparison between Fastpac and conventional Humphrey perimetry.

As part of the Melbourne Visual Impairment Project, a substudy was performed to determine the efficacy of the newly released Fastpac program for the Humphrey Field Analyser. A comparison was performed of the Fastpac and conventional full threshold 24-2 fields obtained in 39 eyes of 36 participants. Also a comparison study was performed of the standard and non-standard 80-point screening tests to the standard 24-2 full threshold test in 23 eyes of 23 participants. In the full threshold comparison there was 100% agreement between the two with Fastpac being 32% to 39% faster than standard. In the 80-point screening test comparison, non-standard was no faster than standard. Sensitivities were 17/17 (1.0) for non-standard and 15/18 (0.83) for standard, as compared with the standard 24-2 full threshold test. Fastpac software offers accurate screening and threshold testing in less time than the standard algorithm.

Algorithms↗
PubMed1994

Mechanics of caloric stimulation in a case with a plug in the horizontal semicircular canal.

Horizontal eye movements were recorded by electronystagmography in a subject with a plug of granulation tissue in the unilateral horizontal semicircular canal by the room temperature air caloric stimulation. Stimuli were sequentially presented to both ears with the subject supine and prone, keeping the horizontal canal vertical. Caloric stimuli presented to the unplugged ear resulted in a vestibular nystagmus whose slow phase eye velocity (SPEV) was always directed toward the stimulated side when the subject was supine and toward the opposite side when he was prone. In contrast, calorics presented to the horizontal canal plugged ear showed that SPEV was always directed toward the stimulated side, irrespective of whether the subject was supine or prone. Results were consistent with consensus that the caloric responses noted in the horizontal canal plugged ear reflected horizontal canal afferent activity which may correspond to direct effect of temperature on end organs or afferents. The findings imply that a caloric mechanism exists which is independent of the conventionally accepted one involving concection currents within the canal.

Aged↗
PubMed1992

Non-oral etiologies of oral malodor and altered chemosensation.

A number of non-oral causes for oral malodor have been discussed. Several well documented etiologies for non-oral malodor include renal failure, cirrhosis of the liver, and diabetes mellitus. Each of these conditions has been examined using analytical instrumentation. In addition there appear to be several other metabolic conditions involving enzymatic and transport anomalies (such as trimethylaminuria) which lead to the systemic production of volatile malodors that manifest themselves as halitosis and/or altered chemoreception. Our studies include patients who have been referred to us after being examined by numerous clinical specialists with no identification or relief from their problem. This is due in part to the intermittent nature of many of these problems as well as an apparent lack of knowledge concerning many of these metabolic problems and their relation to oral symptoms.

Acetoin↗
PubMed1990

Time-intensity relations in Békésy audiometry.

Threshold and amplitude measurements were made for fixed frequency Bekesy pure tones on subjects with normal hearing, sensorineural hearing impairment, and functional hearing loss. Following conventional Bekesy audiometry (intensity change 4 dB/sec), -20 dB was added to a signal at the threshold of audibility (bottom of the spike). When sensation was lost at the threshold of inaudibility (top of the spike), +20 dB was added. Adding +/- 20 dB in subjects with normal hearing reduced the amplitude of the spike about 4 dB, corresponding to 1 second, for both pulsed and continuous tones. Adding +/- 40 dB produced essentially similar findings. Adding +/- 20 dB in subjects with sensorineural loss with reduced amplitude of continuous tone tracings also reduced the amplitude approximately 4 dB for pulsed tones, but 3 dB, corresponding to 0.75 seconds, for continuous tones. Abnormal rapid adaptation may account for this reduced amplitude of the spikes. A subject with multiple sclerosis producing excessive abnormal adaptation showed spectacular increased amplitude for continuous tone only when -20 dB was added at bottoms and +20 dB at tops of spikes. An explanation based on slow adaptation is offered. Subjects with functional hearing loss may emphasize either time or intensity in their inappropriate responses when +/- 20 dB is added at tops and/or bottoms of spikes.

Audiometry, Pure-Tone↗
PubMed1989

Dinoprost 14-day oestrus synchronisation schedule for dairy cows.

Oestrus and ovulation were synchronised in 82 lactating Friesian dairy cows with two injections of dinoprost, and the cows were inseminated 72 and 96 hours after the second injection. Twenty-one of the 41 cows (51 per cent) which had a 14-day interval between the dinoprost injections conceived to the inseminations, compared with 18 of the 41 cows (44 per cent) which had an 11-day interval between the injections.

Animals↗
PubMed1989

Decruitment and abnormal auditory adaptation.

1. Factual findings related to decruitment have been presented. 2. Decruitment is considered to be a manifestation of eighth nerve involvement indicating abnormal adaptation. 3. Loudness match as a quick screening test may be applied in cases of suspected abnormal auditory adaptation.

Adaptation, Physiological↗
PubMed1988

Constant pineal output and increasing body mass account for declining melatonin levels during human growth and sexual maturation.

Twenty-four-h urine samples, divided into two fractions representing night- and daytime melatonin production, were collected from 115 healthy individuals between the ages of 3 and 80, of known height and weight, and assayed for 6-hydroxy melatonin sulphate (SaMT), a major urinary metabolite of melatonin, by gas chromatography mass spectrometry. The population was divided for analytical purposes into children (boys aged 3-10.99, girls aged 3-9.59), adolescents (males aged 11-17.99, females aged 9.60-17.99), and adults (men and women over 18). The results showed approximately the same excretion over 24 h in all 3 groups but that the night/day ratio was considerably greater in children and adolescents compared to adults (P less than 0.001). However, when the results were expressed as a function of body weight (BW), body surface area (BSA), or creatinine excretion (CE), nocturnal SaMT was higher in children than in adults (P less than 0.001 for all 3 parameters) or adolescents (BW, P less than 0.001; BSA, P less than 0.002; CE, P less than 0.001) and was higher in adolescents than in adults (BW and BSA, P less than 0.001). Children also excreted more during the day than adults (BW, P less than 0.01; CE, P less than 0.001) or adolescents (BW alpha CE, P less than 0.02). Our results show that pineal output barely changes during childhood and adolescence. However, there is an age related decrease in SaMT excretion/unit body mass which correlates with an age-related increase in body mass. We therefore conclude that the decrease in circulating levels of melatonin during growth and sexual maturation is brought about by an increase in body mass.

Adolescent↗
PubMed1987

Gas chromatographic-mass spectrometric assay for 6-hydroxymelatonin sulfate and 6-hydroxymelatonin glucuronide in urine.

Circulating melatonin is hydroxylated to 6-hydroxymelatonin and excreted in urine as the sulfate and glucuronide conjugates. We extracted these two compounds from urine by using octadecylsilane-bonded silica cartridges to eliminate most of the urea and electrolytes, and silica cartridges to separate the sulfate and glucuronide conjugates. After hydrolyzing the separated conjugates enzymically, we determined the free hydroxymelatonin by gas chromatography-mass spectrometry. Though recoveries were low and variable, we were able to quantify the analyte in the original sample by adding deuterated sulfate and glucuronide conjugates to the urines before extraction.

Arylsulfatases↗
PubMed1986

Factors affecting descending binaural loudness balances as a manifestation of adaptation.

Three trained adults with normal hearing were exposed to a continuous 1-kc/s pure tone in both ears simultaneously at 100 db SPL. In the R ear the tone was attenuated at 1 db/sec until it was inaudible. In the L ear the tone was attenuated at 5 db/sec, and S was asked to adjust the loudness in the L ear by pushing and releasing a hand-switch as in Bekesy audiometry in order to maintain so far as possible a binaural loudness match. At every reduction of 10 db in the R ear (i.e., every 10 sec) the SPL to the L ear was measured from the Bekesy-type tracing which yielded binaural loudness match. While there were inter-subject variations, for all Ss the level of the tone in the L ear (5 db/sec) had to be increased above physical equality for equal loudness, indicating the presence of more rapid adaptation in that ear. The disparity in 2 Ss progressed regularly from near zero after 10 sec to 16-17 db after 1 min. For 1 S, a constant disparity of about 6 db existed throughout the session. Binaural loudness balances by this descending method may be considered a manifestation of normal adaptation, confirming a previous report (Harbert and Young, J. Acoust. Soc. Am., 1968, 43, 752-756) for threshold differences produced by various attenuation rates at various suprathreshold starting levels. An analogous ascending procedure with 1 S yielded results susceptible to the same interpretation.

Acoustic Stimulation↗