摘要:

Cardiac function was studied in spontaneously breathing, adult spontaneously hypertensive rats (SHR) and Wistar‐Kyoto normotensive rats (WKY). By rapid intravenous blood infusion, the relation between left ventricular end‐diastolic pressure (LVEDP) and stroke volume (SV) was determined while the cardiac nervous control was pharmacologically blocked. Since SV is greatly influenced by the level of afterload (mean arterial pressure, MAP), SV was also determined at increased MAP (constriction of abdominal aorta) and at decreased MAP (vasodilation by hydralazine). At low LVEDP levels, a righward shift of the Frank‐Starling relationship was observed in SHR. This rightward shift seems mainly to depend on the increased MAP present in SHR since it was less prominent if MAP was lowered to normotensive levels in SHR. Maximal SV during volume infusion was similar in SHR and WKY, despite a much higher MAP in SHR. When peak SV was instead compared at similar MAP levels for both (either at ‘normotensive’ or ‘hypertensive’ levels) it was always significantly greater in SHR, and was increased largely in proportion to their increased left ventricular weight. This indicates that the left ventricular hypertrophy present in SHR is, at least at this stage, a physiological adaptation of the heart to increase its performance, in order to maintain a normal SV and hence cardiac output, despite an increased arte

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb06991.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The effects of local intraarterial infusions of VIP, acetylcholine (ACh), substance P. iso‐prenaline and bradykinin on submandibular gland blood flow and salivary secretion were studied in cats. It was found that VIP (lo‐14to 10‐‐10mol/min) caused an atropine resistant vasodilation but no salivary secretion. Several hundred fold higher doses of exogenous VIP had to be infused than the amounts of VIP seen in the venous outflow during maximal nerve stimulation at a similar vasodilatory response. ACh infusions (5×10–12to 5×10‐‐8mol/min) caused both a muscarinic vasodilation and salivary secretion. ACh was about 100 times less potent than VIP as a vasodilating agent. Both ACh and VIP induced in high doses a vasodilatory response similar to that seen during parasympathetic nerve stimulation at 15 Hz. ACh by itself did in the present doses, however, only induce about 50–60% of the maximal secretory response. Combined infusions of ACh and VIP, had mostly an additive effect on vasodilation. The salivatory volume response to ACh was potentiated by VIP and to a smaller extent also by isoprenaline. This potentiating effect may be due to a direct effect on secretory elements as well as partly to the additional increase in blood flow. Bradykinin was about 1000 times less potent than VIP as a vasodilating agent. Substance P (10‐‐9mol/min) only caused a weak vasodilation. Since there is evidence that ACh and VIP coexist within the same neurons and are both released upon parasympathetic nervous activation, the present findings suggest that the secretory and vasodilatory responses may be caused by an interaction bet

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb06992.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Radiocardiography was used to measure cardiac output, stroke volume and left ventricular ejection fraction at rest and during muscular exercise in relation with age in 148 healthy subjects (age range: 6–78 years). A clear dependence of these parameters on age was found. The mean annual decrease at rest was 22±9 ml/min/m2for cardiac index, 0.22±0.04 ml/m2for stroke index and 0.0017±0.0003 for left ventricular ejection fraction. Male subjects had significantly (p<0.001) greater cardiac (9±4%) and stroke indices (11±23%) than females. During submaximal exercise cardiac index increased from 3.5±0.7 l/min/m' to 8.1±1.6 l/min/m2in male subjects (mean age: 32 years) and from 3.1±0.4 l/min/m2to 7.2±1.2 l/min/ m2in female subjects (mean age: 29 years). The corresponding increases in stroke index and left ventricular ejection fraction were: from 52±7 ml/m2to 62±9 ml/m2. from 46±7 ml/m2to 51±9 ml/m2and from 0.66±0.08 to 0.79±0.05 and from 0.64±0.10 to 0.72±0.10. In subjects who were 60 years and older the increases of these parameters during exercise were co

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb06993.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The acetylcholine synthesizing (ACh‐s) activity and the binding of the nicotinic ligands3H‐α‐bungarotoxin (α‐Btx) and3H‐d‐tubocurarine (d‐TC) were analysed in rat hind limb muscles 1–32 days after denervation. Muscles of the contralateral leg served as controls. ACh‐s activity was considerably lower in tibialis anterior as compared to the extensor digitorum longus and the peroneus longus muscles. After denervation there was a rapid decrease in ACh‐s activity in parallel to a considerable increase in α‐Btx binding. The binding of d‐TC was essentially unchanged following denervation indicating the special characteristics of the newly formed receptors. ACh‐s activity can be differentiated into one specific (choline acetyltransferase)

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb06994.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

By occluding the descending thoracic aorta, blood transferred from the lower to the upper part of the body increases left ventricular end‐diastolic volume and maintains stroke volume despite a rise in systolic left ventricular pressure (LVP) of about 60 mmHg. Seventy percent of the blood drained stems from the splanchnic circulation. To examine which splanchnic organs contribute to the cardiac effects, selective occlusions were performed during ultrasonic measurements of spleen and liver dimensions and left ventricular myocardial chord length (MCL) in atropinized, open‐chest dogs. Drainage of 15±2 ml from the spleen accounted for 18±4% of the increase in end‐diastolic MCL, whereas liver dimensions remained unaltered. Similar results were obtained during aortic occlusion at high inotropy (isoproterenol infusion). it was ascertained by occlusion of the coeliac and mesenteric arteries that about 50% of the cardiac response to aortic occlusion was due to drainage from the intestines and the aorta. Liver blood volume could be reduced by combined occlusion of the aorta and portal vein or coeliac and mesentenc arteries and was sensitive to changes in pressure in the inferior vena cava, but did not contribute to the cardiac response to aortic oc

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb06995.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Previous results (MacRobbie&Ussing 1961) in combination with published values for cellular chloride concentration and for intracellular potentials show that the chloride concentration in frog skin epithelium cells is higher than predicted for equilibrium with the inside bathing solution. Both the apical and the basolateral membrane of these cells are normally almost tight to chloride, so that the maintenance of the high chloride concentration requires little work. A basolateral permeability to chloride is, however, activated by cell swelling, and the cells lose KCI. It is now shown that the KCI thus lost cannot be regained neither in the absence of sodium in the inside bath nor in the presence of furosemide. The volume regulation reactions are, however, independent of the composition of the outside bath. It is concluded that the recovery of KCI by the epithelium is due to a basolateral co‐transport of NaCl from medium to cells, combined with return of Na to the medium via the Na‐K pump. The co‐transport mechansism thus restores the high chloride concentration of the cells, but seems to be virtually dormant unless the cells have lost chl

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb06996.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

During hypovolemia extravascular fluid is transferred across the capillaries into the circulation in order to restore blood volume. Several studies have shown that this process. which mainly occurs in skeletal muscle, effectively can compensate for the blood loss. The present investigation performed in the cat strongly indicates, however. that this vital compensatory mechanism is inactivated in situations of pronounced hypovolemia leading to hypotension levels of 30–40 mmHg, i.e. when the need for refill of the circulatory system is most in demand. It is suggested that the cessation of fluid transfer from skeletal muscle to blood during marked hypotension is causally linked to the evoked pronounced reduction of blood flow, due partly to the much reduced perfusion pressure and partly to the marked vasoconstriction. Pronounced vasoconstriction in the hemodynamically important vascular bed of skeletal muscle is obviously an essential part of the necessary resistance response evoked in the systemic circulation in order to avoid circulatory collapse already in the early phase of a large blood loss. However, the chances for the organism to survive is minimized if the vasoconstriction leads to impairment of the mechanisms for plasma volume regulatio

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb06997.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

The effect of cervical sympathetic stimulation upon regional blood flows was investigated in albino rabbits during graded hemorrhagic hypotension and mild to moderate hypoxic hypoxia. Regional blood flows were determined using labelled microspheres. Cerebral blood flow (CBF) decreased in response to progressive hypotension and increased considerably during hypoxia (100–200%). Unilateral sympathetic stimulation did not change the ipsilateral cerebral flow responses under either condition. There was a greater tendency to autoregulate down to lower blood pressures in deep than in superficial cerebral structures. During hypoxia cortical gray matter blood flow increased relatively more than did white matter blood flow. Blood flow in different parts of the eye decreased during hypotension and tended to increase during hypoxia. Unilateral sympathetic stimulation reduced tlow rates on the stimulated side (10–50% of control side) under both conditions. The vasoconstrictory effect upon retinal blood flow tended. however, to be less during hypoxia. Dural blood flow showed a poor autoregulation and also no consistent vasodilatory response upon hypoxia. Sympathetic stimulation had a very marked effect. The results suggest that the cervical sympathetic nerves do not have any appreciable effect upon cerebral circulation during profound hypotensive and moderate hypoxic states. Dural and most ocular blood flows seem. however. to be clearly affected by sympathetic stimulation even under these extreme conditi

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb06998.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Unilaterally sympathectomiced rats were exposed to 100 dB Leqfrequency‐modulated noise for I month. Normotensive as well as spontaneously hypertensive animals (with a blood pressure of above 200 mmHg) were investigated. Auditory sensitivity was determined by auditory brainstem responses to 1/3‐octave filtered sine waves in the frequency range 0.8–20.0 kHz. In addition, a morphological analysis was carried out. It was found that the sympathetic innervation to the inner ear of the rat originated in, or passed through the ipsilateral superior cervical ganglion. Sympathectomy did not alter pre‐exposure hearing thresholds nor influence the size of the noise‐induced hearing loss either in 3 or 11 months old hypertensive rats, or in normotensive rats of 11 months. A slightly smaller loss was seen in the sympathectomized side in young normotensive rats. It was concluded that the sympathetic does not exert a protection of the inner ear against functional disturbances in hypertension, neither during basal metabolic condition nor during extreme conditions, i.e. during noxious noise

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb06999.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY

摘要:

Ring preparations of the superficial buccal segment of the human facial vein, taken from extirpated tissue in 12 patients during neck surgery, were studied in vitro. The vein developed a maintained intrinsic myogenic tone in response to passive stretch and was supplied with α‐ as well as β‐adrenoceptors, both of which could be influenced by transmural nerve stimulation (TNS) and noradrenaline. These unusual characteristics for a vein are basically similar to the ones described for the rabbit facial vein by Pegram, Bevan&Bevan (1976). In man there seemed to be an inter‐individual difference with regard to the abundance of ‘innervated’α‐ and β‐adrenoceptors. Facial vein specimens from some subjects thus responded with prompt and pronounced net dilatation to TNS with maximum at 4 Hz and those from others with net constriction with maximum at 16 Hz. The latter showed a reversal into neural β‐adrenergic dilatation after α‐adrenergic blockade. The human external jugular vein was devoid of intrinsic tone and β‐adrenoceptors. It is tentatively proposed that a β‐adrenergic neuro‐effector mechanism in superficial ramifications of the facial vein in man might be involved in

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1982.tb07000.x

出版商:Blackwell Publishing Ltd    

年代:1982

数据来源: WILEY