摘要:

SUMMARY1. Electromagnetic and Doppler flowmeter methods were compared with the thermodilution technique for the measurement of cardiac output in unanaesthetized rabbits. Cardiac output was varied by haemorrhage and transfusion.2. All three methods give a satisfactory estimate of cardiac output over a wide range of flows. The electromagnetic method is probably the most accurate; errors due to transducer instability, the use of end‐diastolic flow as an index of zero flow, and the failure to detect coronary flow appear negligible.3. The Doppler flowmeter gives a systematic 3–4% overestimate of cardiac output; the error is most probably due to registration of backflow in the aortic root as forward flow.4. The thermodilution technique gives a good estimate of cardiac output at low and normal resting cardiac outputs, but is subject to a small but increasing error as cardiac output rises; the error at high flows is of the order of

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00540.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00541.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. The effects of caffeine, halothane, potassium chloride and procaine have been studied on normal human skeletal musclein vitro.Particular emphasis has been given to the role played by extracellular calcium ions in producing these effects.2. Caffeine produces a concentration‐dependent contracture probably by stimulating the release of calcium ions from the calcium storing membranes of the muscle cell.3. Halothane potentiates the contractures produced by caffeine and potassium chloride probably by facilitating the release of calcium from the storage membranes.4. Potassium chloride produces a contracture only in the presence of caffeine or halothane.5. Procaine inhibits all the contractures studie

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00542.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. A method for assessing the bronchodilator potency of sympathomimetics in anaesthetized cats is described.2. The bronchodilator actions of laevoisoprenaline, rimiterol and salbutamol, administered by cumulative intravenous injection, were assessed against bronchoconstriction produced by an intravenous infusion of serotonin. Rimiterol and salbutamol, by weight, were each about eight times less potent than laevoisoprenaline.3. The method allows the construction of reproducible dose‐response curves. It is relatively quick, and is especially useful when assessing the potencies of long‐acting sympathomimetic bronchodilat

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00543.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. Intraperitoneal administration ofp‐chlorophenylalanine (pCPA: 100–400 mg/kg per day) reduced central serotonin concentrations to 20–50% of control in the rabbit.2. Intraperitoneal administration of a single dose ofpCPA (400 mg/kg) decreased heart rate by 14% for a period of 1–2 days, but did not affect arterial pressure.3. Repeated intraperitoneal administration ofpCPA (100 mg/kg per day) caused a gradual reduction in arterial pressure to about 90% of control values over a 10 day period, but had no consistent effect on heart rate.4. In rabbits that received repeated intraperitoneal injections ofpCPA (100 mg/kg per day), the tachycardia that followed sinoaortic denervation was not as well sustained as in normal rabbits; the development of neurogenic hypertension was unaltered.5. Intracisternal administration ofpCPA was particularly toxic in the rabbit; the maximum doses tolerated did not succeed in lowering central serotonin concentration and had no effect on blood pressure or hea

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00544.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. The ‘steady‐state’ properties of the baroreceptor‐heart rate reflex were studied in twenty‐one renal hypertensive and twenty‐eight normotensive unanaesthetized rabbits. In each animal, intravascular pressures were varied by inflating balloons previously placed around the aorta and inferior vena cava. An average curve relating mean arterial pressure (MAP) to heart period (HP; pulse interval) was constructed for each group.2. The average resting MAP was 134 mmHg (s. e. m. = 5.7) in hypertensive and 91 mmHg (s. e. m. = 4.0) in normotensive rabbits. The mean values for resting HP in the two groups were 254 ms (s. e. m. = 13.4) and 258 ms (s. e. m. = 3.2), respectively. The baroreflex‐dependent heart period range (HPR) between the lower and upper plateau levels of the MAP‐HP curve of hypertensive rabbits was about 80% of the normotensive value. The average gain (change in HP per unit change in MAP) in hypertensives was about 50% of the normotensive value. The threshold pressure for evoking an increase in HP during a rise in MAP, and the median blood pressure (i. e. MAP corresponding to half HPR), were both about 40 mmHg higher in the hypertensive group than in normotensive rabbits.3. The parameter changes in the MAP‐HP curve in renal hypertension are closely similar to those previously observed in patients with essential hypertension of the same severity. The baroreflex changes in essential hypertension are thus probably non‐specific accompaniments of chronic blood

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00545.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. The effects of glucagon andl‐isoprenaline on atrio‐ventricular (A‐V) conduction and sino‐atrial (S‐A) rate were studied in the isolated and cross‐circulated canine A‐V and S‐A node preparations. Drugs were injected intravenously into the donor dog.2.l‐Isoprenaline (0.01–3 nmol/kg) caused a dose‐dependent decrease in the A‐V conduction time and an increase in the S‐A rate. In doses larger than 0.3 nmol/kg, a ventricular ectopic rhythm was provoked in the A‐V node preparation. Dose‐response curves for the changes in A‐V conduction time and the S‐A rate produced byl‐isoprenaline were almost parallel and the responses were maximal with 3 nmol/ kg.3. Glucagon (0.03–3 nmol/kg) also caused a decrease in the A‐V conduction time and an increase in the S‐A rate in a dose‐dependent manner, but unlikel‐isoprenaline, it did not provoke a ventricular ectopic rhythm in the A‐V node preparation even in large doses. The decrease in the A‐V conduction time was maximal with 3 nmol/kg, whereas the increase in the S‐A rate was not more than 50% of the maximum with this dose.4. The durations of the responses to glucagon were increased in a dose‐dependent manner and were far longer than those tol‐isoprenaline in equimolar doses. The positive chronotropic effect of glucagon was less than that ofl‐isoprenaline, not only in the S‐A node preparation, but also in the donor dog.5. The findings suggest that glucagon may serve as a valuable ag

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00546.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. Auditory and visual evoked potentials were recorded in ten young men who were heavy smokers. Recordings were made during periods of tobacco deprivation, normal smoking, and immediately after smoking.2. Tobacco smoking increased the amplitude of the late waves of the visual evoked potentials, but not the auditory evoked potentials which tended to be reduced.3. The above effects were not satisfactorily explained in terms of arousal.

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00547.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY

摘要:

SUMMARY1. Agonistic and antagonistic activities on β‐adrenoreceptors have been assessed for orciprenaline, terbutaline, soterenol and MJ7999–1 using isolated guinea‐pig atrial (β1‐receptor) and tracheal (β2‐receptor) preparations.2. As agonists MJ7999–1 is more selective for β2‐receptors than soterenol because of its increased activity in trachea, whereas terbutaline is more selective for β2‐receptors than orciprenaline because of its decreased activity in atrial preparations.3. Antagonistic activity was assessed from shifts in concentration‐effect curves to (‐)‐isoprenaline.4. MJ7999–1 and soterenol possess competitive β‐receptor blocking actions in atrial (pA2≈6.5) and tracheal (pA2≈6.0) preparations.5. Orciprenaline and terbutaline are relatively selective competitive β‐receptor antagonists, being more potent in atrial (pA2≈6.3) than in tracheal (pA2∼4.9) preparations. In atria non‐competitive antagonistic actions are apparent with these two drugs.6. In rat vas deferens preparations only (‐)‐isoprenaline and soterenol display agonistic actions on α‐receptors. None of the c

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1974.tb00548.x

出版商:Blackwell Publishing Ltd    

年代:1974

数据来源: WILEY