摘要:

Isometric force and action potentials were recorded in thin atrial strips from guinea‐pigs and rats (32 °C). The restitution of peak force and action potential duration, after a regular contraction, was determined (test interval 0.1–120 s), together with the postextrasystolic potentiation. The mechanical restitution could be described with an exponential function in two phases as: force = A(I–e‐k1t)+B(I–e‐k2t). By increasing the basic stimulation rate in guinea‐pig atria from 0.2 to 2 Hz, the size ofAwas approximately doubled whileBwas only slightly affected. When [Ca2+] was increased from 0.9 to 3.6 mmol I1‐, the size ofAincreased approximately 3.4 times whileBdecreased only slightly. There was a close correlation between steady‐state contractility of the muscle and parameterAbut not parameterB. In a similar fashion postextrasystolic potentiation can be described as: force = Ce‐kt+D. This potentiation was greater in guinea‐pig than in rat hearts. In both species the rate of potentiation decay (k) was usually similar to the rate of the first phase of restitution (k1). It seems reasonable to interpret the parametersAandBas reflections of two separate intracellular compartments

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08554.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The metabolic control of the vascular bed in cat gastrocnemius muscle during exercise was studied with a new technique (Björnberget al. 1988) permitting continuous and simultaneous recordings of arteriolar and capillary pressures, and of resistances in the following consecutive vascular section: proximal arterial resistance vessels>25 μm, arterioles<25 μm, and on the venous side. The study thereby provided quantitative data for resistance and active intrinsic tone in these vascular segments at rest, during graded exercise vasodilatation, and in the post‐exercise period. Slight activation of the metabolic control system by low‐frequency somatomotor nerve stimulation (light exercise') caused inhibition of intrinsic tone and decreased vascular resistance selectively in the arteriolar section. At increasing workloads, arteriolar resistance was further decreased, but resistance and tone in the proximal arterial resistance vessels and the veins then became clearly reduced as well. This difference in effectiveness of the metabolic control system on the different segments of the vascular bed was expressed quantitatively in terms of a ‘metabolic vasodilator index’. Graded activation of the metabolic control system led to a marked segmental redistribution of intrinsic vascular tone, in turn resulting in an increased pressure drop across the proximal arterial vessels and the veins and a decreased pressure drop over the arterioles. The observed decrease in the pre‐ to post‐capillary resistance ratio caused, at a constant arterial pressure of 100 mmHg, a graded increase in capillary pressure with increasing workloads, at maximum vasodilatation by an average value of 14 mmHg above the resting control value of 15.4 ± 0.6 mmHg. In the post‐exercise period, recovery of vascular tone to control was more rapid in the proximal arterial resistance vessels and the veins than in the a

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08555.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Topical antigen challenge in cheek pouches of immunized hamsters led to an acute inflammatory reaction which was characterized by intravital microscopy. The response consisted of short‐lasting arteriolar spasm, followed by leakage of plasma, vasodilation, and accumulation of leucocytes. Several observations indicated that the reaction was due to mast cell activation. Thus, a very similar inflammatory response was seen after challenge with compound 48/80, and both antigen and compound 48/80 degranulated the numerous mast cells present in the cheek pouch. In addition, fluorescein‐labelled antigen bound specifically to mast cells in cheek pouches of immunized animals, also suggesting the presence of mast cell‐fixed antigen‐specific antibodies, possibly immunoglobulin E. However, although antigen and compound 48/80 caused similar microvascular responses, cross‐desensitization experiments indicated that the two stimuli activated mast cells via different mechanisms.The histamine antagonist mepyramine, which abolished plasma leakage induced by exogenous histamine, substantially inhibited the increase of microvascular permeability evoked by antigen or compound 48/80, but did not appear to affect the vasospasm and leucocyte accumulation.It is concluded that the hamster cheek pouch may be a most useful tool for investigation of dynamic microvascular events during allergic mast cell‐dependent i

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08556.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The mechanism by which 12‐o‐tetradecanoylphorbol‐13‐acetate (TPA) desensitizes carbachol mobilization of glucose‐incorporated calcium (Ca2+) was studied in clonal insulin‐releasing cells (RINm5F) using colour indicators and dual wavelength spectrophotometry. The net uptake of Ca2+stimulated by 20 mm glucose reached saturation after 19 ± 2 min when it corresponded to 1.21 ± 0.09 mmol calcium kg‐1protein. Carbachol then induced a release of 0.21 ± 0.03 mmol calcium kg‐1protein. Half of the remaining Ca2+was liberated by antimycin A and the rest with the Ca2+ionophore A‐23187. When 0.1 /μm TPA was added initially, the cells lost 0.29 ± 0.08 mmol calcium kg‐1protein within ro min. The subsequent addition of glucose resulted in a sluggish uptake of only 0.58 ± 0.09 mmol calcium kg‐1protein reaching equilibrium after 35 ± 3 min. Carbachol now failed to induce any Ca2+release. The actions of TPA were essentially unchanged by previous exposure to glucose, removal of Na+from the medium and even when some of the glucose‐incorporated Ca2+had been liberated with carbachol. The results indicate that TPA desensitization of carbachol‐induced mobilization of Ca2+in the RINm5F cells is due to the disappearance of Ca2+from the sensitive pool, an effect which may depend on stimulated extrusion of Ca2+from the

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08557.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The relationship between mean aortic blood pressure (MAP) and cardiac output (CO) was examined in anaesthetized, open‐chest dogs during variations in pre‐load with and without α‐adrenergic stimulation with phenylephrine. When phenylephrine increased MAP to 200 mmHg, CO fell greatly and could not be increased by volume expansion. Left ventricular ultrasonic measurements and pressure recordings showed that the Frank‐Starling mechanism was maximally activated. During vena cava obstruction CO and MAP fell proportionally. At a lower infusion rate of phenylephrine, MAP increased to 160 mmHg without a great reduction of CO. As in control experiments without phenylephrine infusion, CO could be increased by dextran/saline infusion and lowered about 20% below control by vena cava obstruction with no significant change in MAP; by further caval obstruction CO and MAP fell in proportion. Phenylephrine did not alter the relationship between aortic baroreceptor activity and MAP. The same MAP/CO relationships were obtained before and after bilateral vagotomy and nephrectomy. Caval obstruction and pacing tachycardia resulted in similar MAP/CO relationships despite different effects on left ventricular end‐diastolic pressure. Thus, phenylephrine infusion may raise MAP to 200 mmHg but no cardiac reserve is left. During reduction of CO by caval obstruction, peripheral vascular resistance remains constant despite varying baroreceptor activity. At the lower infusion rate of phenylephrine, raising MAP to 160 mmHg, peripheral vascular resistance is constant at low CO, but at high CO the vasoconstrictive effect of phenylephrine is counteracted by a vasodilatory mechanism which seems to be flow

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08558.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

The present study evaluates cardiac function, plasma renin activity (PRA) and left ventricular (I.V) myosin isoenzymes in untreated two‐kidney, one‐clip Goldblatt hypertensive rats (2K1C) and in 2K1C treated with felodipine and metoprolol. Normotensive rats (NCR) and another group of 2K1C, in which the renal artery constriction was removed (UC‐2K1C), were also investigated. Cardiac performance was assessed by means of a working heart perfusion device, allowing also for measurements of myocardial oxygen consumption.Following antihypertensive therapy and unclipping, blood pressure became close to normotensive levels. PRA remained equally elevated in treated and untreated 2K1C, but became practically normalized after unclipping. Relative LV weight in 2K1C increased 74% above that in NCR but in treated 2K1C increased by only 20%. In UC‐2K1C LV hypertrophy became reversed, LV weight/body being about the same as in treated 2K1C. In treated 2K1C, coronary resistance at maximal dilatation was significantly reduced, implying prevention of hypertensive, structural coronary vascular changes, and optimal LV function was improved markedly in the lower range of perfusion pressures compared with untreated 2K1C. When, however, the hearts were challenged at a high pumping resistance (perfusion pressure), I.V function was similar in untreated and treated 2K1C. Myocardial oxygen consumption for given levels of stroke work was significantly lower in treated than in untreated 2K1C. The myosin isoenzyme pattern in the LV of 2K1C was shifted, with significantly higher amounts of VM‐3 than in NCR. This shift was normalized by antihypertensive therapy or by unclipping.In conclusion, antihypertensive therapy with felodipine and metoprolol prevents the development of coronary vascular and left ventricular hypertrophy in 2K1C. This may contribute to enhance cardiac performance at low aortic pressure. The lack of improvement in optimal cardiac performance (at high aortic pressure) implies that the hypertensive stateper se, rather than extent of pressure elevation, cardiac hypertrophy, or changes of LV isoenzymes, determines the reduced cardiac function in renal hypertensive rats (Friberg&Nordb

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08559.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

It is known that transcripts of the calcitonin gene in the thyroid C cells are processed to mRNAs generating precursors for the three peptides, calcitonin, katacalcin, and calcitonin gene‐related peptide (CGRP), and that these peptides are produced and secreted from the C cells. The present study investigated the effects of these three peptides on basal and TSH‐stimulated thyroid hormone secretion in the mouse, according to the McKenzie technique. Mice were pre‐treated with125I and thyroxine. Calcitonin (3 nmol animal‐1) reduced the basal blood radioiodine levels to 72 ± 5% compared to 95 ± 6% in controls (P<0.01). This effect is likely to be renal, since calcitonin significantly increased the renal excretion of a concomitantly injected125I load. In contrast, katacalcin and CGRP were without effect on basal blood radioiodine levels. All three peptides (1 or 3 nmol animal‐1) were without effect on TSH (70μU animal‐1)‐induced increase in blood radioiodine levels. However, when the peptides were given together (either two and two concomitantly, or all three together), the TSH‐induced increase in blood radioiodine levels was inhibited. This inhibition of TSH‐induced thyroid hormone secretion might represent an intrathyroidal regulatory mechanism of the foll

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08560.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Intrafascicular micro‐electrode recordings were made from the human infra‐orbital nerve close to the infra‐orbital foramen. The fascicular organization was studied and multi‐unit activity from low‐threshold mechanoreceptive afferents was recorded during tactile stimuli, vibration and facial movements. Attempts were also made to record C‐fibre activity.Innervation zones corresponding to 66 fascicles were mapped with tactile stimuli on facial hairy skin and the red zone of the lip. Most of these fields were located on the upper lip, where they overlapped, indicating a high innervation density. The fields had a median size of 3.8 cm2.Skin indentation evoked dynamic on‐ and off‐responses and a much less pronounced static discharge. The afferent double‐peaked responses to an oscillating probe applied to the peri‐oral region induced similar grouping of the EMG activity during sustained lip protrusion. Contraction of facial muscles and stretching of the skin evoked on‐ and off‐responses, whereas the static discharge was less pronounced, especially during sustained stretching. The dynamic sensitivity to minor variations in contraction and stretching was high, and during normal facial movements, as in speech, there was a barrage of impulses originating from mechanoreceptors within large facial areas. Functional implications of these sensorimotor interactions are discussed.Sympathetic C‐fibre activity, frequently seen in recordings from the supra‐orbital nerve, was never encountered in the infra‐orbital nerve recordings, indicating a lack of such fibres. Failure to detect afferent C‐fibre activity could be explained

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08561.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

Eighty‐four low‐threshold mechanoreceptive afferents innervating facial hairy skin or the red zone of the lip were recorded with micro‐electrodes from the human infra‐orbital nerve. Based on their responses to skin indentations, the units were classified as slowly or fast‐adapting, with small or large receptive fields. The responses to hair movement, skin stretching and contraction of facial muscles were also studied.Both hairy skin and the red zone were innervated by slowly and by fast‐adapting units. The innervation density was found to be highest at the corner of the mouth and on the upper lip. Slowly adapting units with small fields in hairy skin were most common and included units responding to sustained hair displacement. These units are suggested to have two types of end‐organs, either pilo‐Ruffini endings or Merkel cell‐neurite complexes. The slowly adapting units with large fields were spontaneously active stretch receptors and may have corresponded to Ruffini corpuscles, although the possibility of other, intramuscular, receptors could not be ruled out. Only one afferent possibly innervated a Pacinian corpuscle.Most mechanoreceptors were also activated by skin stretching or contraction of facial muscles. Many of the slowly adapting units with small fields responded to the onset and release of stretch, whereas their discharge in response to sustained stretching adapted more or less completely. Spontaneously active units had the most sustained stretch response. It is concluded that several types of cutaneous mechanoreceptors can operate as sensitive proprioceptors of importance for facial kinaesthesia

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08562.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY

摘要:

It was shown by immunohistochemical methods, using antisera against highly purified carbonic anhydrases CA I, II and III, that CA II and CA III are specifically located in hepatocytes around central veins of adult rat livers. CA II was found in these perivenous hepatocytes of both male and female rats. Its physiological role is probably to facilitate the secretion of bicarbonate ions by these cells into canalicular bile. CA III and CA I were found in the same hepatocytes but only in the livers of male rats. The function of CA I and CA II exclusively in these cells of male rats cannot be simply explained.

ISSN:0001-6772    

DOI:10.1111/j.1748-1716.1989.tb08563.x

出版商:Blackwell Publishing Ltd    

年代:1989

数据来源: WILEY