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Biomedical subjects

M W Vasey

Publications and source records attributed to M W Vasey.

9 recordsLinked to original sources
PubMed1990

Neuroendocrine and gastric myoelectrical responses to illusory self-motion in humans.

We compared gastric myoelectrical activity and endogenous neuroendocrine responses in subjects with and without motion sickness elicited by illusory self-motion or vection. Rotating a drum with black and white vertical stripes around seated stationary subjects (n = 22) produced vection. Gastric myoelectrical activity was recorded with cutaneous electrodes. Thirteen subjects developed gastric dysrhythmias [4- to 9-cycles/min (cpm) signals] and motion sickness during vection, whereas nine subjects maintained normal 3-cpm gastric rhythms and remained symptom free. Base-line plasma cortisol and beta-endorphin levels were significantly greater (P less than 0.01) in the subjects who would develop gastric dysrhythmias and nausea compared with the subjects who would not develop motion sickness. Norepinephrine levels increased in the nauseated group immediately after vection ceased (354.6 +/- 41.1 pg/ml) compared with the symptom-free subjects (223.1 +/- 22.8 pg/ml, P less than 0.05). Epinephrine increased significantly (P less than 0.05) after vection only in the nauseated subjects, whereas dopamine levels were not altered by vection in either group. We conclude that 1) anticipatory increases in plasma cortisol and beta-endorphin occurred in subjects who would develop nausea and gastric tachyarrhythmias during vection; 2) endogenous epinephrine and norepinephrine were increased in subjects who had vection-induced nausea and gastric dysrhythmias; and 3) vection stimulates brain-gut interactions, resulting in gastric tachyarrhythmias and complex neuroendocrine responses in subjects with motion sickness.

Adult↗
PubMed1989

Sham feeding. Cephalic-vagal influences on gastric myoelectric activity.

The effects of sham feeding on gastric motility of human subjects have not previously been studied. The amplitude of 3-cpm electrogastrogram (EGG) waves increases after the ingestion of food. We hypothesized that sham feeding would stimulate a similar, but briefer gastric myoelectric response. Healthy human subjects chewed and expectorated a hot dog on a roll and later ate a second hot dog. EGGs were continuously recorded before, during, and after sham feeding and eating. The results of experiment I (N = 27) showed that the hand-scored amplitude of the 3-cpm waves increased significantly (P less than 0.01) during sham feeding. Two minutes after sham feeding, the mean amplitude of 3-cpm EGG waves returned to baseline level. The increase in EGG amplitude during eating was also significant (P less than 0.01), and remained increased for approximately 30 min after ingestion. The procedure used in experiment II (N = 20) was similar to experiment I, but EGGs were computer analyzed and power, ie, spectral intensities, at 3 cpm were obtained. The increase in power at 3 cpm during sham feeding and during eating was significant (P less than 0.05 and P less than 0.02, respectively). Similar to experiment I, the duration of increase in power at 3 cpm was brief during sham feeding compared to the postprandial increase. Four vagotomized subjects failed to show an increase in power at 3 cpm in response to sham feeding. We conclude: (1) The cephalic-vagal stimulation of sham feeding increases briefly the amplitude and power of 3-cpm gastric myoelectric activity in healthy subjects but not vagotomized patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

Motion sickness and gastric myoelectric activity as a function of speed of rotation of a circular vection drum.

Motion sickness symptoms and electrogastrograms (EGGs) were obtained from 60 healthy subjects while they viewed an optokinetic drum rotated at one of four speeds: 15, 30, 60 or 90 degrees.s-1. All subjects experienced vection, illusory self-motion. Motion sickness symptoms increased as drum speed increased up to 60 degrees.s-1; i.e., symptoms decreased at 90 degrees.s-1. Power, spectral intensity, of the EGG at the tachygastria frequencies (4-9 cpm) was calculated at each drum rotation speed since previous studies have shown a close correspondence between development of tachygastrias and motion sickness symptoms. Power at 4-9 cpm increased as a function of drum speed up to 60 degrees.s-1 and then decreased at 90 degrees.s-1. Power at 4-9 cpm and 60 degrees.s-1 was significantly greater than at 15 degrees.s-1. The correlation between the motion sickness symptoms and the power at 4-9 cpm was significant. Thus, drum rotation speed influenced the spectral power of the EGG at 4-9 cpm, tachygastria, and the intensity of motion sickness symptoms.

Adult↗
PubMed1989

Adaptation to vection-induced symptoms of motion sickness.

The visual-vestibular-proprioceptive sensory mismatch of vection provokes motion sickness in approximately 60% of healthy subjects. Approximately 60% of astronauts experience motion sickness in microgravity where vestibular/otolith function is altered. The purpose of this study was to determine the extent to which symptoms of motion sickness and tachygastria, an abnormal 4-9 cpm rhythm of the stomach, decrease or adapt during three repeated exposures to a rotating circular vection drum. Subjects sat in the drum for 45 min: 15 min baseline, 15 min drum rotation at 60 degrees.s-1, and 15 min recovery. Gastric myoelectric activity was continuously recorded with the electrogastrogram (EGG). Symptom reports were obtained during rotation. In Experiment I, 10 subjects were exposed to the drum 3 times with intersession intervals of 4-24 d. They failed to show adaptation based on subjective reports and all showed tachygastria. In Experiment II, 14 new subjects were exposed to the drum 3 times with intersession intervals of 48 h. The group experienced a reduction in symptoms and tachygastria with repeated exposure to the drum. Thus, symptomatic and physiological improvement occurred after training in subjects susceptible to vection-induced motion sickness. Preflight adaptation to visual-vestibular sensory mismatch may reduce motion sickness experienced in the environment of microgravity.

Adaptation, Physiological↗
PubMed1989

Gastric emptying and gastric myoelectrical activity in patients with diabetic gastroparesis: effect of long-term domperidone treatment.

We measured gastric emptying and gastric myoelectrical activity with solid-phase gastric-emptying tests and cutaneously recorded electrogastrograms (EGGs), respectively, in six insulin-dependent diabetic patients with nausea and vomiting who did not respond to standard treatments. Baseline solid phase gastric emptying was markedly delayed (78 +/- 8% retained at 120 min) and EGG recordings revealed gastric dysrhythmias; tachygastria (4-9 cpm signals) in one patient, 1- to 2-cpm waves in two patients, and flatline patterns in three patients. No patient had a normal 3-cpm EGG pattern. After 6 months of domperidone treatment, mean upper gastrointestinal symptoms scores decreased from 17.8 to 3.7 (p less than 0.01), and normal 3-cpm EGG frequencies were recorded from each of the six patients. The mean percentage of meal retained at 120 min decreased but did not improve significantly. Thus, establishment of normal 3-cpm gastric myoelectric activity and resolution of dysrhythmias, not normalization of emptying rates, was associated with improvement in upper gastrointestinal symptoms in these diabetic patients.

Adult↗
PubMed1983

Controlled smoking for chronic smokers: an extension and replication.

Nine long-term cigarette smokers participated in a seven session controlled smoking program. Employing a multiple baseline across behaviors design, the program focused on making sequential reductions in nicotine content of the cigarette brand smoked, percent of each cigarette smoked and, finally, number of cigarettes smoked per day. Self-monitoring records indicated that subjects were successful in making reductions in each of the three target behaviors and that the timing of these changes closely followed the initiation of treatment for each specific behavior. The magnitude of change was greatest for nicotine content (49% reduction) and somewhat less for number of cigarettes (28% reduction) and amount smoked (24% reduction). Carbon monoxide levels were also reduced and these reductions, as well as the smoking behavior changes, were generally maintained at a 6-month follow-up. This study provides a systematic replication of an earlier study and illustrates the usefulness of single subject designs for studying cigarette smoking. It is concluded that controlled smoking can be achieved by chronic smokers without significant relapse or compensation for at least six months following treatment. Limitations of the study and directions for future research are also discussed.

Adult↗