The relationship between plasma vasopressin concentration and urinary excretion during left atrial distension in anaesthetized dogs

The relationship between the changes in plasma vasopressin (AVP) concentration and urinary concentration during left atrial distension has been examined in 12 anaesthetized dogs. Left atrial pressure was increased by 1.2 kPa for 30 min. Plasma AVP concentration (radioimmunoassay) was decreased 5 min after the start of atrial distension and was increased again 5 min after the end of distension. The average decrease was about 50% from a mean of 6.4±2.4 pg · ml^–1 (SE). Urine osmolality decreased more slowly reaching its lowest value in the first 10 min after removal of atrial distension. In contrast sodium excretion increased immediately upon atrial distension. Because of the difference in the time course of the changes in plasma AVP and urine osmolality, plasma AVP was compared with the urine osmolality in samples collected 15 min after the plasma samples. At any plasma AVP concentration there was a wide variation in urine osmolality between dogs, but in any one dog there was clear relationship between plasma AVP and urine osmolality. The results support the view that the diuretic response to left atrial distension is due, at least in part to decreases in plasma AVP concentration. They also show that a stimulus arising from increased left atrial pressure influences the relationship between plasma osmolality and plasma AVP concentration.     

The temporal relationship between intraocular pressure and extraocular muscle activation in cats

The temporal relationship between intraocular pressure and extraocular muscle activation was studied in cats in response to the administration of the depolarizing muscle relaxant, succinylcholine (i.e. bolus doses of 0.1 and 1.0 mg/kg). Simultaneous changes in intraocular pressure, extraocular muscle force, extraocular electromyograms (EMGs), limb muscle EMGs and hindlimb muscle afferent activity were recorded. Increases in intraocular pressure were associated with extraocular muscle activation and had two components: (1) an initial abrupt increase (lasting seconds) which correlated with fasciculations within the extraocular and hindlimb muscles; and (2) a latter more sustained component (minutes) presumably due to tonic muscle activation which correlated with increases in hindlimb muscle afferent activity (e.g. due to sustained activation of bag 1 intrafusal fibers by succinylcholine). In a separate group of animals, in which the extraocular muscles were detached from the right eye bilateral intraocular pressures were measured: depolarization by succinylcholine caused a significant increase in intraocular pressure only for the eye with intact muscles. Thus, increases in intraocular pressure following the administration of succinylcholine are directly related to the changes in extraocular muscle tension which is dependent on both tonic and phasic muscle fiber responses.     

The relationship between body sway and foot pressure in normal man

The relationship between the movement of the centre of foot pressure in the anterio-posterior plane and the rotation which occurs in the same plane at the level of the ankles, hips and shoulders during postural sway was examined in a group of normal human subjects. Expressed as three frequency-dependent functions this relationship consists of both relative magnitude and phase components. The magnitude component indicates that the pressure centre was most sensitive to ankle rotation, less to hip and least sensitive to rotation at the level of the shoulders. The sensitivity of the pressure centre was also a function of the frequency of the rotations and this is evidenced by the presence of several resonant peaks in the relationship. It is suggested that these could be due to body inertia and transmission delays. The resonant peaks became more prominent when the subjects stood with eyes closed. The growth of resonant peaks is taken as a sign of reduced postural stability and on this basis it is argued that a distinction should probably be made between the concepts of the stability and the steadiness of stance.     

The relation between carotid body chemoreceptor discharge, carotid sinus pressure and carotid body venous flow

1. Activity in forty-two single chemoreceptor afferent fibres from the carotid body in thirty-nine cats was measured when the carotid body was naturally and artificially perfused. In nine of these cats, carotid body venous flow was also measured.     

Dynamic relations between right and left atrial pressure shifts induced by catecholamines

Acute experiments on cats showed that injection of catecholamines induced unidirectional shifts in right and left atrial pressure in 70% cases (these shifts were positive in one half of cats and negative in the other half). In 30% cases, the left and right atrial pressures changed in opposite direction: right atrial pressure decreased, while left atrial pressure increased (19%), or vice versa (11%). The pressure changes in the left atrium had greater amplitude and longer duration compared to those in the right atrium.__________This revised version was published online in August 2005 with the addition of the issue titleTranslated from Byulleten’ Eksperimental’noi Biologii i Meditsiny, Vol. 139, No. 1, pp. 4–7, January, 2005     

The relationship between the left atrial volume and the maximum P-wave and P-wave dispersion in patients with congestive heart failure

PURPOSE: A maximum P-wave duration (Pmax) of > or = 110 msec and a P-wave dispersion (PWD) > or = 40 msec are accepted indicators of a disturbance in interatrial conduction and an inhomogeneous propagation of the sinus impulse, respectively. The left atrial (LA) volume has been reported to be strongly associated with a systolic and diastolic dysfunction and is considered to be an index of atrial remodeling. We aimed to investigate the relationship between LA volume and Pmax or PWD in patients with congestive heart failure (CHF). PATIENTS AND METHODS: Sixty-one patients with CHF were enrolled in this study. The study population was classified into four groups: two groups were divided according to the Pmax (> or = 110 msec or < 110 ms), and the other two groups were formed based on the PWD (> or = 40 msec or < 40 msec). The left atrial volume index (LAVi) was measured by three-dimensional (3-D) transthoracic echocardiography. The Pmax and PWD were measured from a 12-lead electrocardiogram. RESULTS: There were significant differences in the ejection fraction (EF), diastolic function, and LAVi between patients with a Pmax > or = 110 ms or a PWD > or = 40 ms and those with a Pmax < 110 ms or a PWD < 40 ms. The LAVi was independently associated with a disturbance in interatrial conduction and an inhomogeneous propagation of the sinus impulse. The LAVi can be used to identify patients with a disturbance in interatrial conduction and an inhomogeneous propagation of the sinus impulse with reasonably good accuracy. CONCLUSION: We concluded that a disturbance in interatrial conduction and an inhomogeneous propagation of the sinus impulse in patients with CHF is associated with an increase in the LA volume and a deleterious systolic and diastolic dysfunction.     

The relationship between resting blood pressure,body mass index and lean body mass index in British children

Background: Elevated blood pressure (BP) in childhood is associated with overweight and obesity. However, lean body mass index (LBMI, cm²/kg) has been suggested as a better means than body mass index (BMI, kg/m²) by which to consider the relations between weight status and health indices in children.

Objective: To assess the relationship between resting BP and weight status in youth whilst considering BMI and LBMI when examining this issue.

Methods and procedures: Height, body mass and resting blood pressure were assessed in 384 boys and 277 girls, aged 11–14 years from Central England.

Results: SBP was significantly lower in ‘normal weight’ children compared to overweight and obese children and in overweight compared to obese children (both p = 0.0001). DBP was significantly lower in ‘normal weight’ children compared to those classified as overweight (p = 0.006). BMI and LBMI were both significant predictors of SBP and DBP (p = 0.0001). However, LBMI was normally distributed, unlike BMI, and was a better predictor of BP than BMI.

Conclusions: Overweight and obesity is associated with higher resting BP in British children. However, when examining the effect of weight status on BP, the researcher should consider use of LBMI over BMI.     

Influence of intravenous saline infusion on the aortic baroreceptor and left atrial B-type receptor activity in dogs

Influence of i.v. saline infusion on aortic arch pressure, left atrial mean pressure, heart rate, and the time-related characteristics of aortic arch baroreceptor and left atrial B-type receptor activities were studied in 20 beagle dogs. Saline infusion induced tachycardia in 10 dogs and bradycardia in 10. Aortic arch and left atrial pressures increased in both HR response groups. The average discharge rate of baroreceptors increased in both HR response groups, while the duration of baroreceptor burst, the number of baroreceptor action potentials/heart cycle and the average burst frequency did not increase significantly in the group that responded with tachycardia but increased significantly in the group that responded with bradycardia. The number of left atrial B-type action potentials/heart cycle, the average discharge rate and average burst frequency increased in both HR response groups. We conclude that the duration of baroreceptor burst, baroreceptor average burst frequency and the number of baroreceptor impulses/cardiac cycle are the important parameters eliciting baroreceptor reflex to i.v. saline infusion.     

不同体质量幼儿纵跳过程中的生物力学特征

背景:超重和肥胖在幼儿中越来越普遍,有研究表明体质量过大会影响幼儿的基本运动能力,但运用生物力学方法进行分析的研究较少,更加缺乏将仿真运用其中分析其运动过程中肌肉用力情况的研究.目的:运用运动生物力学研究方法分析不同体质量的幼儿在纵跳过程中的运动学、动力学以及动作过程中下肢肌肉力值,比较这些数据的差异.方法:在北京某幼...     

The relationship between body weight and estradiol-induced activity

Estradiol-induced activity was found to be of equal magnitude in ovariectomized rats allowed to achieve supranormal body weight and in ovariectomized animals restricted to preoperative weight. The results suggest that estradiol-induced activity is not weight regulatory.     

Renal effects of left atrial distension in dogs with chronic congestive heart failure.

The renal response to left atrial balloon inflation in normal dogs was compared with that in dogs with chronic congestive heart failure (CHF). CHF was induced by the production of an aortocaval fistula below the level of the renal arteries. CHF dogs showed elevated left ventricular end-diastolic pressure, enlarged hearts, a depression of myocardial contractility, pulmonary edema, ascites, and peripheral edema. They also showed significant decreases in urine flow, creatinine clearance, para-aminohippurate clearance, sodium and potassium excretion, fractional sodium excretion, osmolar clearance, arterial blood pressure, and heart rate. Balloon distension of the left atrium evoked a significant increase in urine flow and free-water clearance in the normal group. The reflex nature of this response was indicated by its blockade after bilateral cervical vagotomy. In contrast, the CHF group did not exhibit significant changes in urine flow or free-water clearance during balloon inflation. Plasma antidiuretic hormone (ADH) was significantly elevated in the CHF group; however, balloon distension reduced plasma ADH in both groups of dogs. Plasma renin activity was significantly elevated in the CHF dogs and was not changed by balloon distension in either group of dogs. It is concluded that animals with high-output CHF do not exhibit the atrial-diuretic reflex in spite of their ability to reduce ADH levels by atrial distension.     

The relationship between hostility and blood pressure in children

The relationship between two dimensions of hostility and resting blood pressure was examined in 98 children aged 7 to 10 years. The children completed the expressive and experienced hostility subscales of the Buss-Durkee Hostility Inventory and one week later had blood pressure and obesity levels assessed. Multiple regression analyses and analyses of variance showed that expressive hostility was positively associated with blood pressure, although this relationship became marginally significant when the effects of obesity were controlled. A significant inverse relationship was found between experienced hostility and systolic blood pressure. These results are discussed as they relate to findings in adults on hostility and cardiovascular disease and the relationship between hostility, blood pressure, and obesity.     

The role of left atrial receptors in the regulation of renin release in anesthetized dogs

Experiments were performed on anesthetized dogs to further define the role of left atrial cardiopulmonary receptors in the reflex neural control of renin release. Non-hypotensive arterial hemorrhage produced reversible decreases in left atrial pressure and increases in renin release without significant changes in mean arterial pressure or renal blood flow. When non-hypotensive arterial hemorrhage was performed, while keeping left atrial pressure constant via left atrial balloon inflation, no increase in renin release was observed. These experiments indicate that changes in blood volume unaccompanied by changes in arterial pressure are sensed by left atrial cardiopulmonary receptors, which results in renin release mediated by a neural reflex arc involving in the vagus as the afferent pathway and the renal sympathetic nerves as the efferent pathway.     

The response to distension of the pulmonary vein—left atrial junctions in dogs with spinal section

1. A reflex increase in heart rate in response to pulmonary vein distension was observed in decerebrate dogs. This increase could not be totally abolished by treatment with both propranolol and bretylium tosylate. Only bilateral cervical vagotomy abolished the reflex increase in heart rate.2. A significant increase in heart rate occurred in a total of seventeen spinal dogs during pulmonary vein distension.3. In seven spinal animals in which blood pressure was maintained by the continuous infusion of noradrenaline, the increase in heart rate could be totally prevented by cervical vagotomy.4. The time course of the increase in heart rate observed in the spinal animals was rapid, reaching maximum expression within 10 sec of pulmonary vein distension. Such a time course is dissimilar from that associated with pulmonary vein distension in intact or decerebrate dogs in which maximum increases in heart rate take 1-3 min to develop.5. It is concluded that the reflex tachycardia resulting from pulmonary vein distension may be mediated by both an efferent sympathetic and an efferent vagal pathway, the relative significance of each component being dependent upon the prevailing autonomic drive existent in the animal at any specific time.