Search PubMed⌕ Search

Biomedical subjects

I C Roddie

Publications and source records attributed to I C Roddie.

At least 37 records · Page 2Linked to original sources
PubMed1983

The effects of catecholamines on pumping activity in isolated bovine mesenteric lymphatics.

Bovine mesenteric lymphatics of 8 cm length were cannulated and arranged so that pressure changes produced by spontaneous contractions and accompanying flow could be measured. The mean frequency of spontaneous contractions, although constant for any one vessel, varied between vessels from 0.5 to 5.2 beats/min (mean 2.6, S.D. 1.6, n = 33). Noradrenaline (100 ng/ml.) invariably increased frequency of contractions but flow was increased only in those vessels which had a low resting frequency. In those vessels which had a higher resting frequency, flow was decreased despite the increase in frequency because stroke volume decreased. This may have been due to increased pace-maker activity causing desynchronization of the contractile activity in the vessel wall and thus decreased effectiveness of pumping. High doses (greater than 1 microgram/ml.) of noradrenaline invariably depressed flow. Isoprenaline slowed the frequency of spontaneous contractions and this either had little effect on flow (due to an increased filling time and thus stroke volume) or depressed it, finally abolishing it entirely at higher doses. It is concluded that in suitable dosage (which varies for different vessels) noradrenaline is capable of enhancing flow and this might, at least in part, explain the increase in lymph flow resulting from noradrenaline infusion in living animals.

Animals↗
PubMed1983

The effect of intravenous adrenaline and noradrenaline infusion of peripheral lymph flow in the sheep.

Pressure fluctuations and lymph flow were measured in popliteal, prefemoral and mesenteric efferent lymphatic vessels in conscious sheep. Intravenous adrenaline infusion increased frequency of lymphatic contraction and lymph flow in all three vessels. In the case of the prefemoral vessels flow remained high after the infusion had stopped. Intravenous noradrenaline infusion also increased frequency of contraction and lymph flow in all three vessels but prefemoral flow was depressed after the infusion had stopped. Lymphatic frequency of contraction and lymph flow increased when the animals were started. Anaesthetizing the animals with pentobarbitone did not abolish lymphatic contractions, nor did it prevent the response to adrenaline and noradrenaline infusion. The most obvious interpretation of these results is that adrenaline and noradrenaline act by increasing frequency and force of pumping of lymphatic vessels.

Anesthesia, General↗
PubMed1983

Bradykinin-induced contractions of bovine mesenteric lymphatics.

The mode of action of bradykinin (BK) on bovine mesenteric lymphatics was investigated by recording isometric tensions and action potentials in the isolated longitudinal segments. Addition of BK in concentrations from 10(-10) to 4 X 10(-6) M caused dose-related tonic contractions. BK in a low concentration accelerated the rhythm of action potential discharges in the spontaneously beating preparations and elicited frequent discharges of action potentials and a rapid rise in smooth muscle tone associated with phasic contractions. BK in high concentrations (more than 10(-7) M) caused a further rise of tension in the preparations which had already been depolarized in a high-K solution. The contraction induced by 4 X 10(-9) M-BK in the standard solution was abolished in a Ca-free environment or in the presence of a Ca-antagonist, 10(-4) M-D-600, though more than 50% of the contraction caused by 10(-6) M-BK still remained in both circumstances. In a Ca-free solution containing 1 mM-EGTA (Ca-free standard solution), 10(-6) M-BK caused a slight contraction even after high-K-induced contractions were completely blocked. The contractile response to 10(-6) M-BK in the Ca-free standard solution was augmented after activation of beta-receptors. It is concluded that the BK-induced contractions may be closely related to an increased Ca influx through the membrane and release of membrane-bound and intracellular Ca. The increased uptake of Ca into the BK-sensitive intracellular store may contribute to the relaxing effect of beta-agonist.

Action Potentials↗
PubMed1981

Relaxation of bovine mesenteric lymphatics in response to transmural stimulation.

The responses of isolated quiescent segments of bovine mesenteric lymphatics to 10-s trains of pulses (50 V for 0.3 ms at 2 Hz) administered transmurally have been studied using various drugs. Each train of pulses consistently produced a brief contraction that was completely blocked by tetrodotoxin, alpha-adrenoceptor antagonists, bretylium, and guanethidine. Cocaine potentiated the contractions. Tyramine caused an increase in the basal tone, some spontaneous contractions, and an inhibition of contraction. The contraction was sometimes followed by a relaxation that could be of short duration or long lasting. Both types of relaxation were abolished by tetrodotoxin. Propranolol reduced both types of relaxation, causing more suppression of the short type. Bretylium completely blocked the short type of relaxation and slightly reduced the long-lasting type. Hexamethonium and atropine had no effect on any of the responses. These findings suggest that the contraction resulting from transmural stimulation is due to the action of excitatory postganglionic sympathetic nerves. It is concluded that both types of relaxation occur mainly in response to beta-adrenergic inhibitory stimulation. The possibility of nonadrenergic inhibitory innervation in bovine mesenteric lymphatics is also discussed.

Action Potentials↗
PubMed1980

Nervous modulation of spontaneous contractions in bovine mesenteric lymphatics.

1. Spontaneous isometric contractions were measured in 2 cm segments of bovine mesenteric lymphatics. 2. Field stimulation at 0.25, 1 anf 4 Hz increased the frequency of contraction. 3. Tetrodotoxin 3 x 10(-6) M blocked the response to electrical stimulation. 4. Phenoxybenzamine 3 x 10(-7) M converted the excitatory effect of stimulation to an inhibitory one. 5. Propranolol 3 x 10(-7) M potentiated the excitatory response to stimulation at 1 and 4 Hz. 6. Field stimulation was without effect in the presence of propranolol and phenoxybenzamine together. 7. Cocaine potentiated the response to stimulation at 0.25 and 1 Hz. 8. Atropine 3 x 10(-7) M failed to block the excitatory effect. 9. Field stimulation at 0.5 and 1 Hz increased the frequency of spontaneous contractions and propulsion of fluid by 8 cm cannulated segments of lymphatic. 10. The results suggest that bovine lymphatic vessels have a noradrenergic innervation which is capable of controlling lymph flow.

Animals↗
PubMed1976

Venous distensibility during pregnancy determined by graded venous congestion.

The increase in volume of the human calf and forearm during pregnancy resulting from graded venous congestion has been measured plethysmographically in the raised leg and forearm of 10 recumbent subjects during and after pregnancy. Normal pressure volume curves were determined and the alterations in this curve over the various stages of gestation were presumed to indicate an alteration in the distensibility of the capacity blood vessels. This distensibility was found to increase with the progression of pregnancy in both the forearm and the calf particularly after the thirtieth week of pregnancy. The distensibility, however, appeared to return to below the 10 week gestation level at the eighth postpartum week. The increase in distensibility was greater in the calf than in the forearm although both were significantly increased.

Adult↗
PubMed1976

The effect of transmural pressure on pumping activity in isolated bovine lymphatic vessels.

1. Isolated preparations of bovine mesenteric lymphatics containing about seven valved segments were cannulated and set up in a perfusion system so that, when the preparation was not contracting, the inflow and outflow pressures were exactly equal and there was no flow through the preparation. 2. Transmural pressure was varied by raising or lowering the inflow and outflow pressures simultaneously by the same amount. 3. The isolated vessels showed rhythmic spontaneous activity; it consisted of quick contractions which spread rapidly over the entire preparation, each followed by a rapid relaxation and a diastolic pause. 4. With each contraction, the preparation decreased in both length and diameter and generated an outflow pressure which pumped fluid in the direction determined by the orientation of the values. 5. Raising the transmural pressure in the preparation increased the output of the preparation; this was achieved by an increase in both the frequency and force of the individual contractions. 6. It was concluded that bovine lymphatics could propel fluid by their intrinsic activity at a rate which was related to the degree of distension of their walls.

Animals↗
PubMed1974

The effect of antidiuretic hormone on human sweating.

1. Changes in insensible perspiration and sweating were followed in normal subjects by continuously monitoring total body weight loss in environmental temperatures of 18, 29 and 37 degrees C.2. Pharmacological doses of ADH had no effect on cutaneous water loss at 18 degrees C.3. Pharmacological doses of ADH are capable of increasing the rate of cutaneous water loss in human subjects who are close to or above the thermal sweating threshold.4. Physiological doses of ADH had no effect on cutaneous water loss in either cool or hot environments.5. At normal rates of secretion in the body, ADH probably does not influence human sweat secretion.

Journal Article↗