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Biomedical subjects

A Faulkner

Publications and source records attributed to A Faulkner.

At least 19 recordsLinked to original sources

On the relation between time perception and the timing of motor action: evidence for a temporal oscillator controlling the timing of movement.

Studies of time estimation have provided evidence that human time perception is determined by an internal clock containing a temporal oscillator and have also provided estimates of the frequency of this oscillator (Treisman, Faulkner, Naish, & Brogan, 1990; Treisman & Brogan, 1992). These estimates were based on the observation that when the intervals to be estimated are accompanied by auditory clicks that recur at certain critical rates, perturbations in time estimation occur. To test the hypothesis that the mechanisms that underlie the perception of time and those that control the timing of motor performance are similar, analogous experiments were performed on motor timing, with the object of seeing whether evidence for a clock would be obtained and if so whether its properties resemble those of the time perception clock. The prediction was made that perturbations in motor timing would be seen at the same or similar critical auditory click rates. The experiments examined choice reaction time and typing. The results support the hypothesis that a temporal oscillator paces motor performance and that this oscillator is similar to the oscillator underlying time perception. They also provide an estimate of the characteristic frequency of the oscillator.

Adult

Speech pattern hearing aids for the profoundly hearing impaired: speech perception and auditory abilities.

A family of prototype speech pattern hearing aids for the profoundly hearing impaired has been compared to amplification. These aids are designed to extract acoustic speech patterns that convey essential phonetic contrasts, and to match this information to residual receptive abilities. In the first study, the presentation of voice fundamental frequency information from a wearable SiVo (sinusoidal voice) aid was compared to amplification in 11 profoundly deafened adults. Intonation reception was often better, and never worse, with fundamental frequency information. Four subjects scored more highly in audio-visual consonant identification with fundamental frequency information, five performed better with amplified speech, and two performed similarly under these two conditions. Five of the 11 subjects continued use of the SiVo aid after the tests were complete. A second study examined a laboratory prototype compound speech pattern aid, which encoded voice fundamental frequency, amplitude envelope, and the presence of voiceless excitation. In five profoundly deafened adults, performance was better in consonant identification when additional speech patterns were present than with fundamental frequency alone; the main advantage was derived from amplitude information. In both consonant identification and connected discourse tracking, performance with appropriately matched compound speech pattern signals was better than with amplified speech in three subjects, and similar to performance with amplified speech in the other two. In nine subjects, frequency discrimination, gap detection, and frequency selectivity were measured, and were compared to speech receptive abilities with both amplification and fundamental frequency presentation. The subjects who showed the greatest advantage from fundamental frequency presentation showed the greatest average hearing losses, and the least degree of frequency selectivity. Compound speech pattern aids appear to be more effective for some profoundly hearing-impaired listeners than conventional amplifying aids, and may be a valuable alternative to cochlear implants.

Adult

School nurses: constraints and opportunities for the future.

School nurses are all too often the forgotten element of the school health services, lacking in central guidance and with a great variety of duties and functions which have grown up in an ad hoc and unstructured way. At a time when many districts are reviewing their approach to these services in the light of current policy changes, it would be helpful to step back and consider the issues from a historical perspective in order to understand the great variability in the role of school nurses today. Changing management structures demand improved understanding and acceptance of review and evaluation mechanisms, but where basic information is lacking, overall considerations of need and effectiveness may be severely limited.

Forecasting

Changes in the plasma concentration of gastric inhibitory polypeptide and other metabolites in response to feeding in sheep.

Plasma concentrations of gastric inhibitory polypeptide (GIP)-like activity were determined in sheep before and after refeeding following a 48-h fast. Plasma concentrations increased significantly after feeding, from about 250 pg/ml to about 550 pg/ml. Other metabolites in plasma also increased at this time, reflecting the absorption of nutrients from the gastrointestinal tract. Significant increases were observed in the plasma concentrations of acetate, beta-hydroxybutyrate and triacylglycerol. By comparing the time-courses of the changes in concentration of GIP and other metabolites in plasma, possible sites of secretion and secretagogues of GIP in ruminant animals are proposed. The results demonstrate that GIP is secreted in response to nutrient absorption in adult ruminants and that, as in simple-stomached animals, the absorption of long-chain free fatty acids plays an important role in this secretion.

3-Hydroxybutyric Acid

Ocular infections associated with Comamonas acidovorans.

Comamonas acidovorans (Pseudomonas acidovorans) is a ubiquitous gram-negative rod. Although generally considered nonpathogenic, we found C. acidovorans to be associated with six cases of ocular infections. The organism was the only isolate in three cases, whereas an association of other organisms was present in three cases. The multiple resistance patterns of these strains to antibiotic susceptibility testing emphasizes the need for culturing ocular infections. We recommend the identification and susceptibility testing of all ocular gram-negative rod isolates.

Adolescent

Mammary gland blood flow and plasma concentrations of 6-keto-prostaglandin F1 alpha in the goat.

1. Mammary blood flow and concentrations of the stable metabolite of prostacyclin, 6-keto-prostaglandin F1 alpha, in mixed venous and mammary venous blood plasma have been measured in five lactating goats at various times during the day. 2. Natural variation in blood flow was not associated with any local release of 6-keto-prostaglandin F1 alpha into the mammary venous circulation.

6-Ketoprostaglandin F1 alpha

Effect of lactation on gluconeogenesis and ketogenesis in ovine hepatocytes.

1. Rates of glucose synthesis from radioactive precursors and ketogenesis were determined in hepatocytes from control and lactating sheep. 2. Gluconeogenesis from propionate was the same in both groups. Gluconeogenesis from lactate + pyruvate was three-fold higher in hepatocytes from lactating sheep. Palmitate stimulated gluconeogenesis from lactate + pyruvate in both groups. 3. Rates of ketogenesis from palmitate but not butyrate were slightly higher in hepatocytes from lactating sheep. No other differences in the metabolism of palmitate or butyrate were seen in the two groups. Exogenous carnitine stimulated ketogenesis from palmitate. Propionate inhibited ketogenesis from palmitate and butyrate. Lactate + pyruvate also inhibited ketogenesis slightly but stimulated oxidation and esterification. 4. It is concluded that the major changes in glucose and ketone production seen in the lactating ruminant are not the result of long-term changes within the hepatocyte but occur because of the changes in substrate supply to the liver and changes in intracellular concentrations of metabolites.

Animals

Effects of truncated glucagon-like peptide-1 on the responses of starved sheep to glucose.

The effects of i.v. glucagon-like peptide-1-(7-36)amide (GLP-1; 10 micrograms) on starved sheep given an i.v. glucose load (5 g) were studied. Plasma insulin concentrations rose significantly more after glucose administration in fed than in starved sheep. Giving GLP-1 to starved sheep increased the insulin response to the glucose load. The rise in plasma insulin concentrations in starved sheep given GLP-1 was similar to that observed in fed sheep. Plasma glucose concentrations returned to normal values more quickly in the starved sheep given GLP-1 than in starved sheep not given gut hormone. Plasma concentrations of free fatty acid, urea and alpha-amino nitrogen decreased more quickly following glucose administration in starved sheep given GLP-1 than in those not given GLP-1. The data suggest a role for GLP-1 in regulating plasma insulin concentrations and hence metabolism in ruminant animals. The possible role of gut hormones in ruminants is discussed.

Animals

Insulin resistance of hind-limb tissues in vivo in lactating sheep.

1. The effects of varying the plasma insulin concentration by infusion while maintaining euglycaemia by infusion of glucose on nutrient arterio-venous differences across the hind-limb and mammary gland in lactating and non-lactating sheep were investigated. 2. Insulin infusion increased the glucose arterio-venous difference across the hind-limb; this effect of insulin was decreased by lactation, suggesting that lactation induces insulin resistance in skeletal muscle. 3. Lactation increased but insulin infusion decreased the plasma concentrations of acetate, beta-hydroxybutyrate and non-esterified fatty acids. 4. Insulin infusion decreased the arterio-venous differences of acetate and hydroxybutyrate across the hind-limb; this effect of insulin is probably indirect, resulting from the decrease in plasma concentrations of these metabolites. 5. Infusion of insulin had no effect on the glucose arterio-venous difference across the mammary gland, but did decrease the oxygen arterio-venous difference. 6. The results suggest that lactation results in insulin resistance in skeletal muscle, at least with respect to glucose utilization; this should facilitate the preferential utilization of glucose by the mammary gland.

Acetates

Effects of glucagon and alpha- and beta-agonists on glycogenolysis and gluconeogenesis in isolated ovine hepatocytes.

(1) The effects of glucagon, dibutyryl cyclic AMP, vasopressin, phenylephrine, and isoproterenol on glycogenolysis and gluconeogenesis were investigated using isolated ovine hepatocytes. (2) Glycogenolysis was stimulated by all effectors except vasopressin. The response to alpha-agonists was greater than that of beta-agonists in older animals. Stimulation by beta-agonists increased after 30 h primary culture. (3) Gluconeogenesis from propionate or L-lactate plus pyruvate was stimulated to a small extent by dibutyryl cyclic AMP, glucagon and isoproterenol but not by vasopressin or phenylephrine. (4) No effects of lactation were observed. (5) Data are compared to results obtained in other species and the physiological significance of the results in relation to the ruminant is discussed.

Animals

The onset of mammary secretion of medium-chain-length triglyceride fatty acids in the cow milked pre-partum.

Six Friesian cows were milked daily, and arterial and mammary venous blood samples were taken between day 266 of gestation and day 6 after parturition. Samples of blood plasma were analysed for their content of acetate and progesterone, and mammary secretion for potassium, isocitrate, 2-oxoglutarate and triglyceride fatty acids. The onset of secretion of medium-chain triglyceride fatty acids was preceded by, or coincided with, increases of potassium and isocitrate concentration in the secretion. The onset of fatty acid secretion was not accompanied by any change in the gland's extraction of acetate from the circulation, and did not occur at a consistent time relative to parturition or changes in plasma progesterone concentration.

Acetates

The internal clock: evidence for a temporal oscillator underlying time perception with some estimates of its characteristic frequency.

Evidence for the proposition that human time perception is determined by an internal clock is largely indirect. It would strengthen the case for this hypothesis if a model for the internal clock were available from which predictions could be derived and tested, and if the basic parameter of such a model, the frequency at which the clock runs, could be estimated. A model for an internal temporal pacemaker is briefly described and its properties are explored by computer simulation. Results are obtained that provide a basis for predicting that, under appropriate conditions, interference between an imposed rhythm and the frequency of a temporal oscillator may cause perturbations in temporal judgment which are related to the characteristic frequency of that oscillator. Experimental data are reported which appear to demonstrate such an interference pattern. These results allow some estimates of the characteristic frequency of the temporal oscillator to be obtained.

Adult

Metabolic responses to euglycaemic hyperinsulinaemia in lactating and non-lactating sheep in vivo.

Glucose utilization and production and changes in concentrations of plasma metabolites were studied in lactating and non-lactating sheep in response to three levels of insulin infusion whilst maintaining euglycaemia. Glucose utilization and production responded to insulin infusion similarly in both lactating and non-lactating ewes but, as circulating concentrations of insulin were lower in lactating animals, these parameters appeared more sensitive to plasma concentrations of insulin in lactating sheep. Changes in plasma concentrations of glycerol and free fatty acids during lactation indicated reduced sensitivity to insulin in adipose tissue and changes in plasma concentrations of amino acids were also less during lactation, suggesting reduced sensitivity of protein synthesis to insulin. Changes in plasma concentrations of urea and beta-hydroxybutyrate during lactation were similar to those in non-lactating animals, indicating similar insulin sensitivity of hepatic metabolism. It is concluded that during lactation ovine adipose tissue and muscle are more resistant to increased concentrations of insulin but that the sensitivity of the sheep liver is unchanged or increased. The rate of removal of insulin from the circulation was higher in lactating animals.

Animals