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Biomedical subjects

G D Allen

Publications and source records attributed to G D Allen.

At least 37 records · Page 2Linked to original sources
PubMed1989

Unusual phonological behavior and the avoidance of homonymy in children.

Young children sometimes make use of unusual phonological patterns even when they already possess the appropriate sound or a suitable substitute in their phonological systems. In this investigation, we attempted to determine whether in such instances unusual sound changes enable children to avoid potential homonymy with other words in their lexicons. Novel words were presented to children, half serving as potential homonyms, half as unlikely homonyms. The children's acquisition of these words was monitored. For a group of normally developing children, unusual sound changes were found to be more frequent in the words with the potential for homonymy. In contrast, a group of children with specific language impairment showed the same degree of unusual usage for both types of words. The findings suggest that children with specific language impairment are especially limited in their ability to capitalize on the phonetic regularities of the language.

Child, Preschool↗
PubMed1989

The mechanisms of nitrous oxide scavenging devices.

A recent publication discussing the concern with nitrous oxide pollution in dental offices and the methods available to reduce this risk aroused interest in scavenging systems. This is the first in a series of three articles and will explain the mechanisms of the nitrous oxide systems available. The second describes the testing of these systems under ideal conditions and the third will assess their efficiency in various dental offices and the factors which were found to detract from that efficiency.

Air Pollution↗
PubMed1988

Cues for intervocalic /t/ and /d/ in children and adults.

One naturally spoken token of each of the words petal and pedal was computer edited to produce stimuli varying in voice onset time (VOT), silent closure duration, and initial /e/ vowel duration. These stimuli were then played, in the sentence frame "Push the button for the----," to four adult and four 6-year-old listeners who responded by pressing a button associated with a flower (petal) or a bicycle (pedal). Among the findings of interest were the following: (a) VOT was statistically the strongest cue for both listener groups, followed by closure duration and initial vowel duration; (b) VOT was relatively stronger for children than for adults, whereas closure and initial vowel durations were relatively stronger for adults than for children; (c) except for a probable ceiling/floor effect, there were no statistically significant interactions among the three acoustic cues, although there were interactions between those cues and both listener group (adults versus children) and the token for which the stimulus had been derived (petal versus pedal).

Acoustic Stimulation↗
PubMed1986

The disposition of clavulanic acid in man.

Following oral administration of potassium 14C-clavulanate to four human subjects, at least 73% of the radioactive dose was absorbed. The mean absolute bioavailability was 64%. Absorption was rapid with peak plasma concentrations of radioactivity and clavulanic acid (2-6 micrograms/ml) occurring between 45 min and three hours after dosing. Values for the volume of distribution at steady-state and terminal half-life of clavulanic acid in the plasma were 12.01 and 0.8 h respectively. Following intravenous administration of clavulanic acid to the same subjects, the clearance, and volume of distribution at steady-state were 0.21 l/min, and 12.01, respectively. Clavulanic acid was the major radioactive component present in 0-24 h urine following oral dosing (23% of the dose). The two major metabolites were 2,5-dihydro-4-(2-hydroxyethyl)-5-oxo-1H-pyrrole-3-carboxylic acid (15% of the dose) and 1-amino-4-hydroxybutan-2-one (8.8% of the dose). Clavulanic acid and 1-amino-4-hydroxybutan-2-one were the major components in plasma following oral administration (52 and 21% of plasma radioactivity respectively at two hours after dosing). The major route of excretion of radioactivity following oral administration was via the urine (73% of the dose). Most of this radioactivity was excreted in the first 24 h after dosing (68% of the dose). The renal clearance of clavulanic acid was 0.1 l/min. Elimination of radioactivity also occurred via the expired air (17% of the dose) and the faeces (8% of the dose).

Chromatography, Thin Layer↗
PubMed1984

Absorption, metabolism and excretion studies on clavulanic acid in the rat and dog.

At least one third of an oral dose of sodium [G-14C]clavulanate was absorbed by rat and dog. Excretion of radioactivity was rapid in both species. In addition to urinary and faecal excretion of radioactivity, appreciable elimination of 14CO2 occurred, particularly in the rat. This was produced in part by the action of the gut microflora. In the rat, only a small proportion of the radioactive dose was secreted in the bile. The major metabolite in urine was identified as 1-amino-4-hydroxybutan-2-one. Clavulanic acid was also a major component in urine.

Animals↗
PubMed1979

The relationship between nitrous oxide conscious sedation and the hypnotic state.

To evaluate the hypothesis that inhalation of low levels of nitrous oxide-oxygen produces an altered state of consciousness similar to hypnosis, 20 subjects were given three suggestions (analgesia, compulsive behavior, and amnesia) during double-blind administration of either nitrous oxide-oxygen or oxygen. Results suggest that administration of nitrous oxide-oxygen may be of increased clinical usefulness if it is combined with careful use of suggestion.

Anesthesia, Dental↗
PubMed1978

Nitrous oxide pollution levels in oral surgery offices.

Nitrous oxide pollutant levels, surveyed in oral surgery offices in Southern California, were lower than previously reported. These evaluations were related to rebreathed gas samples obtained from the operator and assistants, and appear to correlate well with exposure to nitrous oxide contamination. The lower levels in the hallway were tenfold less than those previously reported. Better air-conditioning in these offices and better airway control could be responsible, in part, for the difference.

Air Pollutants↗
PubMed1977

Timing control accuracy in normal speakers and stutterers.

This study attempted to assess the abilities of 10 normal speakers, five stutterers in therapy, and five stutterers no longer in therapy, to control the time program of repeated utterances. The speech sample comprised repeated sentences, paragraphs, and nursery rhymes, and a finger-tapping task was included as a control. Temporal accuracy was measured. Results suggest that (1) there is a wide range of timing abilities, even among the normal speakers, with considerable overlap between the different groups of speakers; (2) on most of the experimental tasks, normal speakers are more accurate timers than are stutterers; (3) stutterers released from therapy are more accurate timers than are stutterers still in therapy, whenever these groups differ; and (4) subjects' speech timing scores correlate moderately with their tapping scores. These results are discussed in terms of (1) theoretical timing control processes, such as a neural clock for controlling speech segment durations, and a speech motor output buffer, whose capacity may be limited in stutterers, and (2) known effects of rhythmic constraints and respiratory irregularity on fluency.

Female↗
PubMed1977

The efficacy of the laryngeal reflex in conscious sedation.

The Jorgensen technique and nitrous oxide-oxygen sedation were evaluated for the risk of aspiration. Volunteers and patients were studied in the supine, semisupine, and Trendelenburg positions. Aspiration occurred in a single patient under the Jorgensen technique and could be related to the presence of a narcotic in the mixture. The incidence of tracheal soiling was lower than that with other intravenous techniques and could be attributed to the use of the semisupine position or the baseline concept of narcotic dosage in the Jorgensen technique. In the nitrous oxide-oxygen sedation technique, aspiration was not noted. The study suggests that use of a narcotic in an intravenous sedative technique increases the hazard of aspiration.

Adolescent↗
PubMed1976

Human cardiorespiratory and analgesic effects of intravenous diazepam and local anesthesia.

The only clinically detectable cardiovascular changes after intravenous diazepam administration are a moderate fall in systolic blood pressure and a rise in pulse rate. But it will produce significant cardiovascular changes, principally the lowering of total peripheral resistance and stroke volume. The drug has a long history of safety but is not totally innocuous. It is suggested that if diazepam is used in combination with methohexital, consideration should be given to the additive effects on total peripheral resistance.

Analgesics↗
PubMed1976

Cardiorespiratory effects of outpatient anesthesia for oral surgery: trichloroethylene-halothane.

The cardiorespiratory effects of trichloroethylene supplementation of nitrous oxide-oxygen anesthesia, with simultaneous use of halothane at induction as needed, were studied in outpatient oral surgery patients undergoing dental extractions under general anesthesia. The technique produced no deleterious cardiovascular effects that could be attributed to the combined use of these agents. Elevations of blood pressure, stroke volume, and peripheral resistance indicated light anesthesia. The versatility of halothane combined with the absence of nephrotoxic and hepatotoxic breakdown products of trichloroethylene provides a satisfactory technique for outpatient oral surgery. The agents appear pharmacologically complimentary in that halothane lacks analgesic properties and postoperative shivering occurs, while induction with trichloroethylene is slow and tachypnea is a problem.

Adolescent↗