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Biomedical subjects

D R Jones

Publications and source records attributed to D R Jones.

At least 379 records · Page 21Linked to original sources
PubMed1976

Respiratory and cardiovascular interactions in ducks: the effect of lung denervation on the initation of and recovery from some cardiovascular responses to submergence.

Lung denervation in ducks, by sectioning all vagal branches to one lung following mid-cervical vagotomy on the other side, resulted in immediate bradycardia and fall in breathing frequency. Some 3-5 weeks after lung denervation breathing frequency was within the normal range but the lung inflation reflex, present in unilaterally vagotomized sham-operated ducks, was abolished. During 2 min dives there were no significant differences between sham-operated and denervated ducks in heart rate, arterial blood pressure, blood gas tensions and pH(a). However, during recovery from diving heart rate increased more slowly in denervates and breathing rate was significantly below that attained by shams, although tidal volume rose to a maximum increase of 139% to a maximum of 225% of the pre-dive value in denervates in contrast to a maximum increase of 139% of pre-dive in sham-operated ducks. Both sham-operated and denervated ducks exhibited a significant fall in diastolic blood pressure 60 sec after emergence...

Action Potentials↗
PubMed1976

NHS resources: scales of variation.

The dangers inherent in comparing measures of health service provision and usage at high levels of aggregation and of ignoring variations at lower levels are illustrated with particular reference to regional and subregional level in the NHS. Analysis of variance indicates that, for a wide range of variables, there is more variation at the subregional level than regional level.

Health Expenditures↗
PubMed1976

Open-loop respiratory chemosensitivity in chickens and ducks.

In order to study the behavior of the avian respiratory center under open-loop conditions, recordings of respiratory motor discharges were made from an intercostal nerve in a unidirectionally ventilated paralyzed preparation during normoxic hypercapnia, hypoxic normocapnia and asphyxia, and under control conditions. Respiratory motor burst rate (RMBR) in ducks showed a maximum at 40 mmHg Paco2 with depression at higher and lower values, both in the steady state and during rapid transients. RMBR was apparently independent of Paco2 in chickens, and of Pao2 in both species. During asphyxia, RMBR in ducks fell steadily while the number of spikes in each burst did not change. RMBR during asphyxia bore the same relationship to Paco2 as during unidirectional ventilation. Chickens did not respond consistently to asphyxia, but RMBR tended to increase and, in some cases, the number of spikes per burst also increased. Possible mechanisms and functions of the asphyxic respiratory depression observed in ducks are discussed.

Animals↗
PubMed1976

The initiation of diving apnoea in the frog, Rana pipiens.

1. Diving apnoea in Rana pipiens was initiated by submerging the external nares. As the water level was raised above the frog, both buccal and lung pressure increased by an amount corresponding to the water head. During submergence the external nares remained closed, although the apnoeic period was punctuated by ventilation movements which moved gas between the lungs and buccal cavity. 2. Bilateral section of the ophthalmic nerves did not alter the normal pattern of ventilation in air, although it often resulted in the intake of water into the buccal cavity on submergence. Introduction of water into the buccal cavity, either naturally as in denervates or by injection through a catheter in intact frogs, triggered sustained electromyographical activity in some respiratory muscles. 3. Electroneurograms recorded from the cut peripheral end of an ophthalmic nerve showed that receptors in the external narial region were stimulated by movement of a water meniscus across them. Activity could also be recorded in the ophthalmic nerve in response to water flow past the submerged nares. Punctate stimulation of the narial region confirmed that these receptors were mechanosensitive. 4. Bilateral electrical stimulation of the central ends of cut ophthalmic nerves in lightly anaesthetized frogs caused apnoea with a latency of less than 200 ms. The external nares remained closed throughout the period of stimulation although buccal pressure events, resembling underwater ventilation movements, occurred when stimulation was prolonged.

Action Potentials↗
PubMed1976

The control of breathing in birds with particular reference to the initiation and maintenance of diving apnea.

Avian respiratory pacemaker activity is dependent on some form of peripheral input but it may be inhibited by both central and peripheral stimulation. At present the results of central nervous stimulation are difficult to interpret but, aside from cortical influences, diving apnea appears to be maintained, in the face of increasing chemoreceptor input, by noxious stimulation of the upper respiratory tract and depression of the output of medullary respiratory neurons by advancing hypercapnia. If this is so, an obvious problem for future research is what initiates the prompt onset of hyperpnea when the animal surfaces and breathes. It is known that post-dive hyperpnea is little affected by either carotid body or pulmonary denervation, so peripheral chemoreceptors are unlikely to play a major role in this response.

Action Potentials↗
PubMed1975

Venous thromboembolism in infancy and childhood.

A retrospective study of Scottish hospital inpatients aged 15 years or less has revealed, over a 4-year period, 36 cases of venous thrombosis or phlebitis. Of these 10 were considered to have deep venous thrombosis; 2 cases were associated with obvious pulmonary embolism and 2 cases developed chronic venous insufficiency. change in the coding allocations are proposed. There are "high risk" situations in childhood disease in which a diagnosis of venous thromboembolic disease should be considered and investigated.

Adolescent↗
PubMed1975

Central cardiovascular dynamics of ducks.

Blood pressures and flows have been recorded from the heart and arterial arches of ducks in order to present a complete picture of central hemodynamics in an avian species. An attempt has also been made to define the characteristics of the avian central circulation in terms of either "windkessel", or wave-transmission models. Mean arterial pressure (143 plus or minus 2.2 mmHg) and cardiac output (219 plus or minus 7ml/kg per min) were high compared with those of similarly sized mammals, although therewas no evidence of elevated pulmonary pressures, perhaps because of the unusual structure of the avian lung. Only 25% of the total systemic flow was distributed by the aorta, the remainder supplying the wing, flight muscles, and head via the brachiocephalic arteries. The contours of central pressure and flow waves ressembled those recorded inmammal except that significant circulation impedance modulus graphs indicated that resistance to pulsatile flow fell sharply to a minimum of 1/30th the DC value at 9-12 Hz. Flow led pressure at frequencies below 9-12Hz and pressure led flow at higherfrequencies. Impedance modulus in the pulmonary circulation fell to one-half the DC value and remained constant over a wide range of frequencies with pressure and flow being in a phase at all frequencies. Aortic pulse wave velocity varied with position inthe aorta as did the pressure pulse profile: these factors obviously limit the applicability of a windkessel model to the avian circulation.

Animals↗
PubMed1975

Water flow dynamics in the respiratory tract of the carp (Cyprinus carpio L.).

Simultaneous measurements of water velocity in the buccal chamber, and buccal and opercular hydrostatic pressure of carp have revealed surprisingly high water velocities. The high flow velocities mean that, at times, the kinetic energy of flow makes a substantial contribution to the total fluid energy. This suggests that there may be unequal distribution of hydrostatic pressures within the buccal chamber. Anatomical examinations showed that fluid channels in the buccal chamber and gill raker sieve are complex and can be expected to vary spatially and temporally throughout the respiratory cycle. It appears that there is a potential for error in many of the previous analyses of 'gill resistance and energetics of fish breathing based solely on hydrostatic pressure measurements and the simplifying assumption of steady-state conditions.

Animals↗