摘要:

1. Heart rate response to reversible central hypovolaemia can be divided into three stages. In the first stage (corresponding to a reduction of the blood volume by approximately 15%) a modest increase in heart rate (120 beats/ min) is manifest. This stage may proceed into irreversible shock with death from cardiac arrest probably related to the formation of free oxygen radicals.2. Recognition of the vasodepressor–cardioinhibitory reaction to a reduced circulating blood volume is important and suggests the need for immediate treatment with volume expansion in critically ill patie

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1992.tb00411.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARY1. The role of the arterial and cardiac baroreceptors on the arginine vasopressin (AVP) and plasma renin activity (PRA) responses to haemorrhage was studied in conscious rabbits. They were bled at a rate of approximately 3% of their blood volume (BV)/min, both when the autonomic nervous system (ANS) was intact and during ANS blockade, which markedly enhances the AVP response due to the much greater haemodynamic disturbance. Under each condition of ANS function 2×2 factorial analysis was performed, each with four groups of rabbits, including animals with both sets of baroreceptors working, one or other set working and neither set working.2. With intact ANS, haemorrhage had to be terminated at different times in the four groups. This presents problems for factorial analysis due to differences in the relationship between plasma AVP (or PRA) and release rate. A method for overcoming this was developed by extrapolating the BV‐log AVP curves to a common time from the start of bleeding.3. Under both conditions of ANS function the arterial and cardiac baroreceptors together accounted for 90‐95% of the rise in AVP during haemorrhage. With normal ANS function, the rise in AVP was about 70% through cardiac (probably ventricular) baroreceptors (P= 0.01) and about 30% through arterial baroreceptors (P= 0.08). This compares with an earlier study at a rate of bleeding of 1.8% BV/min, where the entire drive came from the cardiac receptors. During ANS blockade, plasma AVP was enhanced approximately five‐fold, which was mostly mediated through the arterial baroreceptors, but the cardiac baroreceptor component was also greater; arterial/cardiac baroreceptor drive was 2/1.4. Baroreflexes played no role in renin release during haemorrhage, but the experiments with ANS blockade suggest that a hormonal factor, which was related to the cardiac innervation, may limit the rise in PRA in the latter part of haemo

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1992.tb00412.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARY1. Triiodothyronine (T3; 1.0 mg/kg per day subcutaneously) was administered to 10 dogs for 14 days; 10 saline‐treated dogs served as controls. T3‐treated dogs showed the expected physiological responses of hyperthyroidism; further, chronotropic responses to isoprenaline in vivo were significantly increased in T3‐treated dogs.2. β‐Adrenoceptor subtype density was measured in membrane preparations by displacement ofl25I‐iodocyanopindolol binding by the selective β2‐adrenoceptor antagonist, ICI 118, 551. T3treatment led to a 93% increase in right atrial β1‐adrenoceptor density and a 141% increase in left ventricular β1‐adrenoceptor density; β2‐adrenoceptor densities in right atrial, left ventricular and lung membranes were unchanged.3. T3‐treatment did not change basal or maximally stimulated adenylate cyclase activities in left ventricular membranes.4. Thus, the cardiovascular changes in experimental hyperthyroidism in dogs were accompanied by an increased chronotropic response in vivo to isoprenaline and an increased β1‐adrenoceptor density in atrial and ventricular membranes. However, there was no corresponding change in basal or maximal responsiveness of adenylate cycla

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1992.tb00413.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARY1. The short‐term (within 30 min periods) and the long‐term (among 30 min periods) variabilities, expressed as variation coefficients, of blood pressure (BP) and heart period (HP) were studied using a computer analysis of BP recordings in freely moving genetically hypertensive (LH), normotensive (LN) and low BP (LL) rats of Lyon strains at ages 5, 9, 21 and 40 weeks. The baroreflex control of HP was estimated with the slope of the linear relationship between systolic BP (SBP) and HP (SBP‐HP slope) computed after phenylephrine and nitroglycerin injections.2. Short‐term variability of BP increased between 5 and 9 weeks of age and then remained stable. Hypertension was accompanied by an increase in both short‐and long‐term variabilities of diastolic BP in adult rats.3. A sharp increase in SBP‐HP slope was observed between 5 and 9 weeks of age in LN rats. SBP‐HP slope of LH rats increased slightly up to 21 weeks but remained lower than that of normotensive controls.4. The weak inverse correlation existing between SBP‐HP slope and BP variability appeared to be mediated by the BP level. In addition, atropine which is known to abolish almost completely the SBP‐HP slope, did not increase BP variability. It is concluded that SBP‐HP slope is not linearly associated with BP variabil

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1992.tb00414.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARY1. The effect of 4 weeks of moderate exercise training on cardiac left ventricular structure and function was examined by repeated echocardiography/ Doppler examination in 10 previously sedentary volunteers participating in a single blind, sedentary phase controlled, cross‐over study.2. Left ventricular internal diastolic diameter increased after 4 weeks of training from 4.98 to 5.11 cm with a further increase to 5.24 cm after 2 weeks of detraining (s.e.d. 0.05 cm, P<0.01). These increases were still significant after adjustment for heart rate which fell from a pretraining average of 67.0‐59.9 beats/min after 4 weeks of training.3. There were no significant changes in systolic diameter or function and left ventricular wall thicknesses were unchanged during training, but were thinned after 2 weeks subsequent detraining.4. The ratio of early to late transmitral filling velocity (E/A ratio) was significantly increased by training. Although E/A ratio was shown to be heart rate sensitive, training effects were still evident after adjustment for heart rate.5. These changes in left ventricular volumes and function may contribute to the cardiovascular reflex changes previously shown to be produced by identical training program

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1992.tb00415.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY

摘要:

SUMMARY1. The effect of disruption to the epithelium of intact porcine bronchi was examined by comparing the responsiveness to agonists applied to the adventitial and luminal surfaces. The development of smooth muscle tone was measured as an increase in pressure in an isovolumic bronchial segment of approximately 2 mm i.d. The reactivity and sensitivity to acetylcholine (ACh) introduced intraluminally was greatly attenuated when compared with adventitial addition.2. Luminal exposure to K+and vanadate (VO3) had little effect compared with strong responses obtained by adventitial application.3. Intraluminal exposure to trypsin, chymotrypsin and elastase (1 mg/mL) selectively augmented both the sensitivity and the reactivity to the luminal addition of ACh, K+and carbachol.4. Mechanical removal of the epithelium produced a 716‐fold increase in sensitivity to ACh introduced luminally but had no effect on ACh applied adventitially.5. The inhibitory effects of luminally introduced isoprenaline on electrical field stimulation responses were also significantly potentiated in segments stripped of epithelium.6. The evidence presented here indicates that the responsiveness of in vitro airways segments is highly influenced by the epithelial layer, which acts most prominently as a barrier inhibiting the penetration of luminally introduced agonist

ISSN:0305-1870    

DOI:10.1111/j.1440-1681.1992.tb00416.x

出版商:Blackwell Publishing Ltd    

年代:1992

数据来源: WILEY