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Biomedical subjects

I M Young

Publications and source records attributed to I M Young.

At least 37 records · Page 2Linked to original sources
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

Improved reproductive performance from dairy cows treated with dinoprost tromethamine soon after calving.

The first-service conception rate for 74 commercial dairy cows that were given a single injection of dinoprost tromethamine (prostaglandin F(2)alpha THAM) between 14 and 28 d after calving was 56%. For 74 untreated control herdmates the rate was 47%. The average interval from calving to first oestrus was 57 d for treated cows and 70 d for the control group. The difference is significant at the P = 0.017 level. The advantage in the conception rate of treated over control group cows occurred mostly in cows with a blood progesterone concentration of less than 0.5 ng/ml at the time of treatment; this numbered about two-thirds of the cows in the trial. The results support the findings of a previous study.

Journal Article↗
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↗
PubMed1985

The mass spectrometric analysis of the urinary metabolites of melatonin and its deuterated analogues, confirming their identity as N-acetylserotonin and 6-hydroxymelatonin.

In a recent study, we showed that melatonin could be metabolized to N-acetylserotonin and 6-hydroxymelatonin. To confirm this finding rats were administered three different forms of deuterated melatonin intraperitoneally. Their urines were analysed by gas chromatography/mass spectrometry and the results showed, in each case, that the appropriate deuterated (or non-deuterated) metabolite had been formed. From these data it is clear that N-acetylserotonin is a urinary metabolite of melatonin.

Animals↗
PubMed1985

Melatonin is metabolized to N-acetyl serotonin and 6-hydroxymelatonin in man.

To investigate whether melatonin (aMT) can be metabolized to N-acetyl serotonin (NAS), a low dose of deuterated aMT was administered to four normal subjects, and their urine samples were analyzed for the presence of deuterated NAS and deuterated 6-hydroxymelatonin (6-HaMT). In one set of experiments, the urine samples were subjected to column chromatography to separate the glucuronide and sulfate conjugates for independent analysis. In another, an internal standard (NAS-sulfate) was used for quantification and total conjugate analysis. Measurement was by gas chromatography-mass spectrometry, and the molecular ions of deuterated and nondeuterated NAS and 6-HaMT were monitored. Deuterated aMT was metabolized to deuterated NAS and deuterated 6-HaMT. The proportion of NAS was less in the sulfate than in the glucuronide conjugates and, overall, represented 15% of the total. Since demethylation is not a pathway that occurs with other pineal methoxyindoles, even at a much larger dose, it seems to be a significant finding with regard to aMT. Thus, it may be important to elucidate the differential metabolism of aMT at different time points and in different age groups.

Adult↗
PubMed1985

A Bekesy descending-only procedure: effects of attenuation rate and step size, and starting level.

Bekesy fixed-frequency thresholds for pulsed and continuous tones at 1 kc/s yielded by a descending-only technique were compared for suprathreshold starting levels of 38, 58, 78, and 98 db SPL, and attenuation rates of 1, 2, 4, and 8 db/sec with associated attenuation steps of 0.25, 0.5, 1, and 2 db, respectively, with 3 normal-hearing adults. For pulsed tones of 250 msec (duty cycle 50%), thresholds were not significantly affected by attenuation rate/step size or by starting level. However, for continuous tones, increasing attenuation rate/step size yielded better thresholds for a given starting level. Decreasing starting level yielded better thresholds for a given attenuation rate/step size. Thus, deteriorated thresholds were yielded by the slower attenuations/step sizes and by the higher starting levels. These data may be explained as a manifestation of normal adaptation. The similar relative effects found here of attenuation rate/step size and of starting level, as compared to the data of an earlier study (Harbert and Young, 1968) which used the traditional up-down Bekesy method of threshold tracing lend support to the possible future clinical use of a descending-only technique.

Audiometry↗
PubMed1984

Routine induction of farrowing with dinoprost in a commercial sow breeding unit over a year.

Details were recorded on a commercial sow breeding unit where dinoprost was used to induce farrowing in groups of sows every second week. Criteria considered were the interval from injection to start of farrowing, called the induction interval, the time required for farrowing to be completed, called the duration of farrowing, litter size and percentage of piglets born dead. Data were analysed to look for the effect on these of the day of gestation on which the injection was given, the parity status of the sow and the litter size.

Age Factors↗
PubMed1984

Increased conception rate in dairy cows after early post partum administration of prostaglandin F2 alpha THAM.

Commercial dairy cows were given a routine injection of dinoprost tromethamine (prostaglandin F2 alpha THAM) in the early post partum period. The first service conception rate of 64 cows given a single 25 mg injection of dinoprost during the period 14 to 28 days after calving was 68 per cent, that of 64 untreated controls was 43 per cent. The difference was highly significant at the level P = 0.007. In cows with no blood progesterone and with basal progesterone concentrations at the time of treatment, indicating absence of an active corpus luteum, the mean conception rates for 30 treated and 38 control cows were 70 and 44 per cent, respectively, demonstrating that this is not a luteolytic effect. Although that implies a positive myometrial effect, the interval from calving to first service was not shortened in treated cows.

Animals↗
PubMed1984

Pregnant embodiment: subjectivity and alienation.

The pregnant subject has a unique experience of her body. The dichotomy between self and other, self and world, breaks down. She can experience a positive narcissism and sense of process. Some conceptualizations and practices of contemporary medicine, however, can alienate the pregnant subject from this bodily experience.

Body Image↗
PubMed1983

The assessment of a plasma melatonin assay using gas chromatography negative ion chemical ionization mass spectrometry.

It has been shown that negative ion chemical ionization can increase the sensitivity of the mass spectrometric assay of the pineal hormone melatonin. However, it is an exacting assay requiring extensive sample preparation which precludes its use as a general research tool. We have investigated different derivatizing reagents and reaction conditions to demonstrate that a simple negative ion chemical ionization assay can be developed which will measure low picogram or even femtogram levels of the hormone in samples where the data have been ambiguous.

Chemical Phenomena↗