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Biomedical subjects

A Pyne

Publications and source records attributed to A Pyne.

4 recordsLinked to original sources
PubMed2001

Phase transitions of glycine in frozen aqueous solutions and during freeze-drying.

PURPOSE: To study the solid-state and phase transitions of glycine, (i) in frozen aqueous solutions, and (ii) during freeze-drying. METHODS: X-ray powder diffractometry (XRD) and differential scanning calorimetry (DSC) were used to analyze the frozen systems. In situ freeze-drying in the sample chamber of the diffractometer enabled characterization of phase transitions during freeze-drying. RESULTS: Transitions in frozen systems. Rapid (20 degrees C/min) or slow (2 degrees C/min) cooling of aqueous solutions of glycine (15% w/w) to -70 degrees C resulted in crystallization of beta-glycine. Annealing at -10 degrees C led to an increase in the amount of the crystalline phase. When quench-cooled by immersing in liquid nitrogen, glycine formed an amorphous freeze-concentrate. On heating, crystallization of an unidentified phase of glycine occurred at approximately -65 degrees C which disappeared at approximately -55 degrees C, and the peaks of beta-glycine appeared. Annealing caused a transition of beta- to the -gamma- form. The extent of this conversion was a function of the annealing temperature. Slower cooling rates and annealing in frozen solutions increased the crystalline beta-glycine content in the Iyophile. Freeze-drying of quench-cooled solutions led to the formation of gamma-glycine during primary drying resulting in a lyophile consisting of a mixture of beta- and -gamma-glycine. The primary drying temperature as well as the initial solute concentration significantly influenced the solidstate of freeze-dried glycine only in quench-cooled systems. CONCLUSIONS: The cooling rate, annealing conditions and the primary drying temperature influenced the solid-state composition of freeze-dried glycine.

Calorimetry, Differential Scanning↗
PubMed1988

Antagonism of neuromuscular blockade. The cardiovascular effects in children of the combination of edrophonium and glycopyrronium.

Glycopyrronium 5 or 10 micrograms/kg was administered either simultaneously with, or 1 minute before, edrophonium 1 mg/kg in order to antagonise competitive neuromuscular blockade in 80 children. Both doses of glycopyrronium given before the edrophonium resulted in an initial significant (p less than 0.01) increase in heart rate. Heart rate decreased significantly (p less than 0.01) in all groups after the edrophonium was given, and only glycopyrronium 10 micrograms/kg administered before edrophonium prevented a substantial decrease below baseline. Initial heart rate responses to glycopyrronium or edrophonium are rapid, and measurements at intervals of 30 seconds may be necessary to record these changes.

Child↗
PubMed1984

Age differences in memory for movement.

Two experiments were conducted. The purpose of the first experiment was to determine whether memory deficits for movement occur with age. The 52 subjects for Experiment 1 were placed in four age groups: 18-32; 33-47; 48-62; and 63-77. Tests were administered to determine each subject's ability to encode and recall as many as 12 consecutive linear movement lists. When minimal memory requirements were imposed, there was no significant difference in the ability of the older and younger subjects to immediately recall movements. Older subjects, however, could not recall movements as well as younger subjects when greater memory demands were placed on them. Experiment 2 was conducted to determine why memory impairments occurred in older subjects. Organizational schemes were imposed on the subjects, but age differences were still apparent when greater memory requirements were essential or a larger memory capacity was demanded.

Adolescent↗