Biomedical subjects
Publications and source records attributed to R M Harper.
We have developed a new microdrive for fine-wire electrode recording of extracellular neuronal potentials. The new microdrive has advantages of durability of construction as well as enhanced precision and stability of electrode movement, and can be easily assembled with common laboratory tools.
We examined the cardiovascular response to electrical stimulation of the region of the central nucleus of the amygdala during sleep and waking states in the intact cat. Stimulation for 0.5 s produced a profound pressor response in the awake animal. This response was attenuated by quiet sleep and greatly attenuated during REM sleep. The attenuation was present even when the animal aroused from the sleep state in which the stimulus was delivered. The degree of sinus arrhythmia during the bradycardia associated with the hypertensive phase was greater during waking than during quiet sleep. We speculate that REM sleep entails a "functional dissociation" between forebrain and brain stem systems involved in cardiovascular regulation.
The discharge of motor units in the costal and crural regions of the diaphragm was studied in unrestrained cats during defined sleep and waking states. Changes in motor unit recruitment and pattern of activity were observed for different sleep-waking states. During periods of active waking, many motor units were recruited and discrimination of single-unit waveforms was difficult. However, in the transition from active to quiet waking, many diaphragmatic motor units ceased discharging, thus making it possible to discern single-unit waveforms. This cessation of motor unit activity continued during the transition from quiet waking (AW) to quiet sleep (QS) and from QS to rapid eye movement (REM) sleep. In some diaphragmatic motor units, discharge stopped completely during REM sleep and resumed only upon arousal. Thus, it was apparent that the recruitment of diaphragmatic motor units was markedly affected by the sleep-waking state. Changes in the patterns of discharge of diaphragmatic motor units also occurred during different sleep-waking states. Motor unit firing rate was typically slower in QS than AW. The rate of motor unit discharge during REM sleep varied considerably. Autocorrelation histograms demonstrated periodic patterns of motor unit discharge within inspiratory bursts. Intervals of repetitive peaks in the autocorrelation histograms ranged from 40 to 110 ms. These periodic patterns were strongest during AW and REM sleep and generally attenuated during QS. Cross-correlation histograms revealed the presence of synchronous activity between motor units in the diaphragm. This coupling of diaphragmatic motor unit discharge was also attenuated during QS compared with AW and REM sleep. Together, these results demonstrated a marked influence of the sleep-waking state on the neuromotor control of the diaphragm.
The periodic organization of waking, quiet sleep, and active sleep was studied in control infants and siblings of victims of the Sudden Infant Death Syndrome. Spectral estimates of all-night binary state time series recorded at 1 week and 1, 2, 3, 4, and 6 months of age revealed disturbed patterns of sleep states, especially in active sleep, from as early as the first week of life. These disruptions continued until at least 6 months of age. These data support the contention that the temporal patterning of sleep state can be used as an important neurologic marker for development.
Effects of transient hypertension on cardiac rhythm during sleep and waking states in unrestrained cats were investigated. Blood pressure elevation, produced either by phenylephrine injection or by aortic occlusion, was followed by progressive bradycardia in all cats during each sleep-waking state. With phenylephrine, the heart rate response to induced hypertension consisted solely of reflex sinus bradycardia in 67% of the trials, whereas non-sinus cardiac arrhythmias developed during the period of reflex bradycardia in 33% of the trials. In all trials where hypertension was produced by aortic obstruction, non-sinus cardiac arrhythmias occurred. The observed non-sinus rhythms included both atrioventricular junctional and ventricular escape beats. The occurrence of non-sinus arrhythmias after phenylephrine injection was more frequent during sleep states than during waking. Overall, the incidence of escape rhythms varied from a brief burst of non-sinus beats at the onset of bradycardia to repeated trains of non-sinus beats occurring over the span of blood pressure elevation. Respiratory gating of cardiomotor activity was manifested both as respiratory sinus arrhythmia and as inspiratory 'gating' of escape rhythms. Both forms of respiratory gating continued during periods of induced hypertension.
Three types of diaphragmatic muscle fibers were identified histochemically in the sternal, costal, and crural regions of the cat diaphragm. Differences in the proportion of each muscle fiber type were observed between the abdominal and thoracic surfaces of the diaphragm but not among the different regions. A higher percentage of slow-twitch oxidative fibers was noted on the abdominal surface, whereas more fast-twitch fibers (fast-twitch oxidative-glycolytic and fast-twitch glycolytic) were found on the thoracic surface. Differences in muscle architecture were observed between diaphragmatic regions, but not between abdominal and thoracic sides. Overall, muscle fibers were longer in the crural regions, with the longest fibers being found in the crossing-band area of the crura. In the costal regions, fibers were longest in the center and became shorter toward the ventral and dorsal extent of these regions. Fiber lengths were similar throughout the sternal region. In each diaphragmatic region, the length of fibers extended from the origin of the muscle to its insertion. We conclude that functional differences between diaphragmatic regions could be attributed to fiber length and/or orientation, but not to differences in fiber-type composition.
Explore the source record for details and available documents.
We have developed a percutaneous technique for placement of electromyogram electrodes in cat diaphragmatic crura. The technique is convenient and relatively atraumatic. Guided by external landmarks, small gauge hypodermic needles are used to advance electrodes through implant sites within or in contact with the crural portions of the diaphragm. Satisfactory EMG is reliably obtained from both acute and chronic preparations.
Power spectral density measured from central cortical EEG recordings during sleep was compared in two groups of 20 infants each at intervals between 1 week and 6 months of age. One group consisted of siblings of infants who had previously died of the sudden infant death syndrome, as determined by history and autopsy report (sibling group). The second group was made up of age, sex, and socioeconomically matched infants with no familial history of sudden infant death (control group).
To date, various treatment modalities have failed to produce consistent improvement in patients having Behçet's disease. Recent reports in the literature, however, have shown promising results with the use of colchicine. Our patient, an 18-year-old white woman, satisfied the 1977 Istanbul Conference criteria for Behçet's disease by exhibiting ocular inflammation and a five-year history of severe, recurrent oral and vaginal ulcerations. She was treated with 0.6 mg of colchicine orally twice daily, and at the end of two weeks of treatment, the oral lesions had completely resolved, and the vaginal ulcers were reduced in diameter and depth to at least one half. Within one month all oral and vaginal ulcers were completely healed.
The developmental sequence of heart rate and heart rate variability was examined during sleep and waking states in 22 normal infants, and 22 siblings of sudden infant death syndrome (SIDS) victims, using 12-h polygraphic recordings at 1 week and at 1, 2, 3, 4, and 6 months of age. Heart rate was higher in siblings of SIDS victims than in normal infants during quiet sleep over the first 6 months of life and was higher in the waking state at 3 months of age. The sibling group also had lower variability at 1 week during quiet sleep. Gender contributed no significant differences to heart rate, but females at risk for SIDS had lower waking cardiac variability than males.
Twelve-hour, all-night polygraphic recordings were obtained from 25 normal infants at 1 week and 1, 2, 3, 4, and 6 months of age. The objectives of the study were to provide a description of the emerging temporal distribution of quiet sleep (QS), active sleep (AS), and motility, and to describe the maturation of a circadian influence upon heart rates. With increasing age, increased percentages of AS began to cluster toward the end of the night and increased percentages of QS toward the beginning. A circadian influence upon heart rates was observed in AS and indeterminate sleep prior to its existence in QS. At 2 and 3 months of age motility in AS and QS increased linearly during the night.
The discharge of neurons in the nucleus parabrachialis medialis (NPBM) was examined for the presence of high-frequency oscillations (HFOs) by autocorrelation analysis. HFOs were not observed in NPBM activity during any sleep-waking state. In contrast, HFOs were found in the activity of medullary respiratory neurons. It is concluded that the NPBM is not the source of HFOs in the respiratory system.
The normal succession of sleep and waking states through a night is disturbed in infants at risk for the sudden infant death syndrome. Compared with normal infants, siblings of the sudden infant death syndrome victims have longer intervals between active sleep epochs at particular times during the night in the newborn period and a decreased tendency to enter short waking periods at 2 and 3 months of age. The latter finding is interpreted as an increased tendency to remain asleep, or a relative failure to arouse from sleep in infants at risk.
Explore the source record for details and available documents.
Explore the source record for details and available documents.
Explore the source record for details and available documents.