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Biomedical subjects

R Harding

Publications and source records attributed to R Harding.

At least 181 records · Page 10Linked to original sources
PubMed1981

Oesophageal and diaphragmatic activity during sucking in lambs.

1. Buccal, pharyngeal, oesophageal and diaphragmatic movements during swallowing of saliva and sucking from a bottle were studied in lambs by recording electromyograms (e.m.g.s) from the mylohyoid, thyrohyoid and thyroarytenoid muscles, cervical and caudal thoracic oesophagus and vertebral and costal regions of the diaphragm. Buccal and pleural pressure recordings were also made.2. Swallows of saliva characteristically involved contraction of the mylohyoid followed sequentially by contraction of the thyrohyoid, cervical, and finally, caudal thoracic oesophagus.3. Sucking (indicated by the mylohyoid e.m.g.s and buccal pressure) was initially at rates up to 6 sec(-1), sustained at up to 4 sec(-1) for 30-45 sec and, once established, accompanied by swallows in a 1:1 association with sucking.4. Respiration ceased during the pharyngeal phase of swallowing. At the time the primary contraction (of swallowing) involved the caudal thoracic oesophagus vertebral fibres of the diaphragm forming the hiatus oesophageus became quiescent, although costal fibres continued to contribute to inspiration.5. During sucking, respiration was shallow and rapid, with diaphragm contractions sandwiched between swallows.6. Towards the end of an episode of sucking, contractions of the diaphragm became more intense and occurred in groups with pressure changes corresponding to both individual contractions and the grouped activity.7. Primary oesophageal contractions occurred only after single swallows or at the end of a series of swallows.8. During periods when sucking and swallowing were frequent, short episodes of oesophageal contraction occurred, each being between thyrohyoid contractions.9. Recording from contiguous sites of the caudal thoracic oesophagus confirmed a caudally progressive character of those short contractions of the oesophagus observed during sucking.10. Factors contributing to these changes in oesophageal activity and consequences of altered diaphragmatic activity in sucking have been discussed.

Animals↗
PubMed1981

The effect of brief episodes of diminished uterine blood flow on breathing movements, sleep states and heart rate in fetal sheep.

Responses to brief episodes of occlusion of the middle uterine artery were examined in six fetal sheep in utero between 122 and 140 days of gestation. Continuous recordings were made of fetal breathing movements, electro-cortical (ECoG) and electro-ocular (EOG) activity, arterial pressure and heart rate. Five minutes of unilateral or bilateral arterial occlusion caused fetal hypoxaemia while changes in mean arterial PCO2 and pH were not statistically significant. Occlusions usually led to a cessation of rapid eye movements (REM) and respiratory activity (86% of trials), to the appearance of high-voltage slow waves in the ECoG (84% of trials) and to a fall in heat rate of more than 10% (81% of trials). With the exception of the changes in heart rate, these responses resemble those which frequently occur during non-labour contractions of the uterus. We conclude that the cessation of fetal breathing movements and rapid eye movements and the onset of slow waves in the ECoG seen in association with uterine contractions may be due to the mild hypoxaemia which accompanies them.

Animals↗
PubMed1980

THe relationship between myometrial activity and sleep state and breathing in fetal sheep throughout the last third of gestation.

Between 106 and 144 days' gestation, periods of uterine electromyographic (EMG) activity and associated increases in uterine tone (contractures) were accompanied by a change in fetal ocular activity in 294 (63%) of 467 cases. In 260 (88.4%) of the changes, there was a switch fromm the active to nonactive state. The incidence of this change was significantly greater (p < 0.01) than the switch from the nonactive to the active state. The fetal electrocorticogram changed state in 34 (74%) of 46 contractures, the change being from low-amplitude to high-amplitude activity in 28 (82%) of the cases. This difference was significant (p < 0.01). Fetal breathing movements (FBM), as indicated by activity of the posterior cricoarytenoid muscle, changed in 134 (55%) of 243 contractures, the change being from active to the quiescent state in 115 (85%) of contractures. Diaphragmatic activity changed in 11 (61%) of 183 contractures, with a change from activity to quiescence occurring in 100 instances (90%). Changes in tracheal pressure were associated with an altered state of FBM in 190 (61%) of 314 contractures, and the change was from the presence of FBM to absence of them in 178 (94%) of the changes. In all three of these indicators of FBM, the change from breathing activity to quiescence was statistically significant (p < 0.01).

Animals↗
PubMed1980

Respiratory function of the larynx in developing sheep and the influence of sleep state.

The activities of laryngeal abductor and adductor muscles were recorded in conjunction with other respiratory muscles in unanaesthetized chronically monitored foetal, newborn and adult sheep. In foetuses, rhythmical breathing movements occurred in the presence of rapid eye movements and a low voltage electrocorticogram (REM state) and were accompanied by phasic laryngeal abduction; adductor muscles and intercostals were largely inactive. During the foetal non-REM state laryngeal adductor muscles were tonically active at a low level, but the glottis remained open. Deep inspiratory efforts which occurred at low frequency in this behavioural state were not accompanied by abductor activity and resembled inspiratory efforts associated with regurgitation in ruminants. After birth, expiratory adductive activity of the larynx was also maximal during non-REM sleep and negligible during REM sleep. Active laryngeal adduction was accompanied by delayed expiratory airflow, prolonged TE and reduced respiratory frequency. Adduction of the larynx is dependent on behavioural state and appears to be the principal means of regulating TE in sheep, particularly during early post-natal development.

Action Potentials↗
PubMed1979

Consulting to children in crisis.

Although community consultation is common for psychiatrists, such activity is usually carried out on an elective rather than emergency basis. In a world troubled by community disaster situations--children are often at risk. Psychiatrists, through the use of skillful crisis consultation, can be of great help to these young people. This report describes the effort of a mental health consultation team to meet the needs of a large population of children under acute stress.

Acculturation↗
PubMed1979

Studies on the control of respiration and behaviour during development in ewe-reared lambs.

Radiotelemetric recordings have been made in a series of newborn lambs with implanted electrodes and transducers and an external back-pack transmitter. Cardiac, respiratory and behavioural data have been gathered. These data have been analysed firstly with respect to age. The cardiac and respiratory data have then been related to both sleep state and age. An unexpected rise in both heart and respiratory rates was found after birth and marked differences were obvious in respiratory control in REM and non-REM sleep states.

Animals↗
PubMed1978

Liquid-sensitive laryngeal receptors in the developing sheep, cat and monkey.

1. Action potentials were recorded from single afferent units of the superior laryngeal nerves in neonatal and adult sheep, cats and monkeys when liquids were passed over the laryngeal mucosa. 2. Two types of mucosal receptors, sensitive to water but not to isotonic saline, were found in each species from birth. The most common type of unit responded after a short latency (less than 1 sec), discharged maximally in the first 1-3 sec and became inactive when the stimulus was withdrawn. The other type responded only after several seconds, the discharges gradually increasing in frequency and continuing after removal of the stimulus. 3. Reproducible responses were elicited by tactile stimulation of the laryngeal mucosa over the receptive field of each of the long-latency units. Fewer than 50% of the short-latency units were excited, the remainder responding only unreproducibly to firm pressure. 4. Short-latency, but not long-latency, units responded to milks, gastric contents, saliva and isotonic solutions of sugars. 5. The responses of long-latency units to water were often modified by, but rarely dependent on, reflexly evoked activity in laryngeal muscles. 6. The conduction velocities of afferent fibres of water sensitive units ranged from 22 to 49 m/sec, and differed little from those of water-insensitive laryngeal mechanoreceptors. 7. Histological examination of the laryngeal mucosa showed that taste buds were present in lambs from birth whereas they developed post-natally in kittens and monkeys. The evidence suggests that taste buds were not associated with water-sensitive units.

Action Potentials↗