Compliance characteristics of the hind-limb arterial system of normal and hypertensive rabbits

Pressure transients resulting from square-wave changes in abdominal aortic blood flow rate were used to derive effective arterial compliance and peripheral resistance of the hind-limb circulation of anaesthetized rabbits. The model for deriving these parameters proved applicable if step changes in flow were kept less than 35% of mean flow. Under resting conditions, the effective hind-limb arterial compliance of normal rabbits averaged 3.46 X 10(-3) mL/mmHg (1 mmHg = 133.322 Pa). Hind-limb arterial compliance decreased with increasing pressure at low arterial pressures, but unlike compliance of isolated arterial segments, compliance did not vary at and above normal resting pressures. Baroreflex destimulation (bilateral carotid artery occlusion) caused an increase in effective hind-limb vascular resistance at 48.4% and a decrease of arterial compliance of 50.7%, so that the constant for flow-induced arterial pressure changes (resistance times compliance) was largely unchanged. Similarly, the arterial time constant for rabbits with chronic hypertension was similar to that for controls because threefold increases in hind-limb vascular resistance were offset by decreases in compliance. Reflex-induced decreases in arterial compliance are probably mediated by sympathetic nerves, whereas decreases associated with hypertension are related to wall hypertrophy in conjunction with increased vasomotor tone. Arterial compliance decreased with increasing pressure in hypertensive animals, but this effect was less pronounced than in normotensive rabbits.     

Baroreflexes originated in vertebral artery zones upon peripheral vein tonus, systemic arterial blood pressure, and external respiration

The investigation was intended to study the role ofbaroreceptors ofhemodynamically isolated zone of vertebral arteries in regulation of peripheral veins tonus, arterial pressure and external respiration. Pressure decrease in this vascular reflexogenic zone led to reflex responses of increase in femoral vein tonus, elevation of blood pressure level and stimulation of external respiration. The opposite reflex responses of cardio-respiratory functional system to initial pressure activation of vertebral arteries baroreceptors are observed. Basing on generalization of our own findings and similar physiological and morphological researches of other authors, it is established that afferentation from the vertebral artery zone is a reflexogenic factor of somatic muscles' veins tonus regulation. These reflexes of capacity vessels tonic activity changes are part of cardio-respiratory responses of maintaining the tissue gaseous exchange.     

Cellular composition of different zones in the rat and rabbit hepatic lobule under normal and experimental conditions

Different types of hepatocytes (with caryopycnosis and caryolysis, at the state of mitosis, with amitotic nuclear strangulation and with two nuclei) were counted in the central, middle and peripheral zones of the hepatic lobule in rats subjected to an acute aminosin intoxication, and in rabbits after compressing soft tissues of the extremities. Time of observation--1--90 days in the rats and 10 h--20 days in the rabbits. In the zones of the hepatic lobule with the greatest degree of damage, the number of cells with caryopycnosis and caryolysis, as well as the number of hepatocytes with amitotic nuclear strangulation and binucleated cells were especially great. Mitotic activity of the hepatic cells was about 0.49% in the rats and 0.07% in the rabbits. Regardless the place of the damage in the hepatic lobule in all the zones, there was a definite correlation between the amount of cellular forms reflecting the demage and destruction of hepatocytes and their restoration, the same as observed in certain zones of the intact hepatic lobule.     

Orchiectomy upregulates rabbit prostate peripheral benzodiazepine receptors.

The effect of orchiectomy on peripheral benzodiazepine receptors (PBZr) in the rabbit prostate was studied. The mean PBZr density in the mitochondrial fraction isolated from prostates of intact (non castrated) rabbits was 4066 fmol/mg protein which following castration increased to 7236 fmol/mg protein (p less than 0.005). The apparent dissociation constant (KD) of prostatic PBZr was higher in castrated rabbits (4.2 nM) than in intact animals (2.7 nM). These data suggest a role of androgen in the regulation of prostatic PBZr.     

Effect of adenosine on hemodynamic changes during the development of neurogenic myocardial lesions

The influence of adenosine on hemodynamic changes induced by electrostimulation of reflexogenic zone of aorta was studied in this article. It was shown that 3-hour electrostimulation increased the total peripheral resistance and decreased cardiac output and aortic pressure. Intravenous infusion of adenosine during electrostimulation led to the normalization of main indices of hemodynamics.     

Pulmonary haemodynamics during nasal apnoea in rabbits.

Changes in pulmonary haemodynamics, produced during stimulation of the nasal mucosa with xylol fumes, were found in experiments on anaesthetized rabbits. In spontaneously breathing animals, a decrease in the mean blood pressure in the pulmonary artery and an increase in the mean blood pressure in the left atrium occurred in addition to apnoea and bradycardia. Pulmonary vascular resistance fell significantly, whereas systemic vascular resistance rose. Changes in the pulmonary circulation during nasal stimulation in spontaneously breathing rabbits did not differ significantly from changes in artifically ventilated animals.     

Sinoaortic denervation abolishes pressure resetting for daily physical activity in rabbits

It has been speculated that if baroafferent signals are only related to the negative feedback control of arterial pressure (AP), then physical activity would increase the range of AP fluctuation in baroafferent-denervated animals. Mean AP (MAP), heart rate (HR), and cardiac output (CO) were measured for 24 h in free-moving conscious rabbits. On the basis of hydrostatic pressure and electromyogram, MAP data taken during periods of physical activity and rest were selected from the overall 24-h MAP data and then converted into histograms. During physical activity, the mode of MAP histogram increased in intact rabbits and was unchanged in sinoaortic-denervated (SAD) rabbits. Movement increased the mode of total peripheral resistance (TPR) but did not significantly change CO in intact rabbits. Conversely in SAD rabbits, movement slightly decreased TPR and slightly increased CO. These findings indicate that arterial baroafferent signals are required to shift MAP to a higher pressure level by an increase in TPR but not in CO during a moving phase. These results suggest that baroafferent signals may not only minimize the fluctuating range of MAP through negative feedback control but also be involved in actively resetting MAP toward a higher pressure level during daily physical activity.     

The role of peripheral chemoreceptors in the rapid response of the pulmonary vasculature of the late gestation sheep fetus to changes in PaO2.

The effect of removing the input from the peripheral arterial chemoreceptors on pulmonary vascular responses to changes in PaO2 was examined in late gestation fetal sheep. Blood flow in the left pulmonary artery and driving pressure across the pulmonary vascular bed were monitored in chronically prepared fetal sheep at 126-129 days gestation. Five fetuses had carotid sinus and vagus nerves sectioned bilaterally and four were left intact. In normoxia (PaO2 ca. 23 mmHg) pulmonary vascular resistance was slightly greater and pulmonary blood flow reduced in the denervated group relative to the intact group but these differences were not significant. When made hypoxic (PaO2 ca. 14 mmHg), pulmonary blood flow fell and pulmonary vascular resistance increased in all fetuses. However, in the intact fetuses these changes were significantly more rapid. In all fetuses the vasoconstriction was prolonged after their return to normoxia. When made hyperoxic (PaO2 ca. 27 mmHg), pulmonary blood flow increased by a similar amount in all fetuses. We conclude that in the term fetus the peripheral chemoreceptors play no appreciable role in the maintenance of the high pulmonary vascular resistance in normoxia, or the fall in resistance produced by a rise in PaO2. The chemoreceptors do however initiate the rapid phase of pulmonary vasoconstriction in hypoxia.     

The effect of laser puncture on the functional indices of the mammalian body

Biologically active points (acupuncture points) and reflexogenic zones of Wistar rats of different age were exposed to He-Ne laser radiation with the subsequent control of acetylcholine esterase activity, electric parameters of skeletal muscles and heart, and physical activity. Laser puncture was shown to increase the sympathetic nervous system tonus which was manifested by the decreased acetylcholine esterase activity and increased heart rate. Laser puncture stimulated the growth of membrane potential and increased considerably the performance capability of animals, particularly of three-month-olds.     

Effect of pulsatile flow on microvascular resistance in adult rabbit lungs.

We have determined the effect of pulsatile flow on segmental vascular resistance in lungs from 29 adult rabbits. In group I (n = 4), II (n = 8), and III (n = 8) lungs were isolated. In group IV (n = 9) rabbits were anesthetized, their chests were opened, and lungs were studied in vivo. Group I and II lungs had steady-flow perfusion: group I with intact vasotonus and group II with papaverine treatment. Group III lungs (papaverine treated) were perfused for two consecutive 45-min periods with steady and pulsatile flow. In all isolated lungs and in lungs of five anesthetized rabbits, we measured pressures in subpleural 20- to 50-microns-diam arterioles and venules by use of the micropipette servo-nulling method. Measurement of distribution of blood flow in lungs of four anesthetized rabbits by use of radiolabeled microspheres revealed no abnormality of blood flow to the micropunctured lobe. We found that total and segmental vascular resistances were similar in group I and II lungs, with microvessels representing 55% of total resistance. In group III lungs, total resistance was 30% lower during pulsatile flow than during steady flow because of a lower microvascular resistance. Lungs in vivo (group IV) had a significantly lower total vascular resistance than isolated lungs and had a low fractional resistance in microvessels (approximately 28%). We conclude that, in isolated perfused adult rabbit lungs, vascular resistance is very high, particularly in the microvascular segment, and that pulsatile flow decreases microvascular resistance.     

Pregnancy alters hemodynamic responses to hemorrhage in conscious rabbits

Pregnant animals are less able to maintain mean arterial pressure (MAP) during hemorrhage compared with nonpregnant animals, but the hemodynamic basis of this difference is unknown. The hypothesis that pregnancy attenuates responses of cardiac output, as well as total peripheral resistance (TPR) and femoral conductance, to hemorrhage was tested in conscious rabbits in both the pregnant and nonpregnant state (n = 10). During continuous slow blood loss (2% of the initial blood volume per minute), MAP was maintained initially in both groups. However, MAP then abruptly decreased to <45 mmHg in all animals after a smaller percentage of the initial blood volume was removed in pregnant compared with nonpregnant rabbits (43.6 +/- 1.7%, nonpregnant; 29.6 +/- 2.2%, pregnant; P < 0.005). The more rapid transition to hypotension exhibited by pregnant rabbits was associated with greater initial falls in cardiac output (-56 +/- 10 ml/min, nonpregnant; -216 +/- 33 ml/min, pregnant; P < 0.005) and stroke volume (0.8 +/- 0.1 ml/beat, nonpregnant; -1.3 +/- 0.1 ml/beat, pregnant; P < 0.05). In addition, the increase in TPR as a function of the decrease in cardiac output was markedly attenuated (P < 0.0001) during pregnancy. Whereas femoral conductance decreased in nonpregnant rabbits, it did not change significantly in pregnant animals. In conclusion, the lesser ability of conscious pregnant rabbits to maintain MAP during hemorrhage is due largely to a greater decrease in cardiac output but also to inadequate reflex increases in TPR, possibly in part in the femoral vascular bed.     

兔肾性高血压时的动脉压力感受器反射

14只雄性家兔在双肾缩扎术后12周,经氨基甲酸乙酯静脉麻醉,分别在缓冲神经完整、切断两侧减压神经或切断两侧窦神经后静注新福林或硝普钠升降血压以改变动脉压力感受器活动,观察其心率、后肢血管阻力和肾交感神经活动的反射性变化,并与正常血压兔的反射效应相比较。主要结果如下:(1) 动物双肾动脉缩扎后12周,平均动脉血压(131±9mmHg)较正常动物血压(95±10mmHg)有显著升高(P<0.001);(2) 缓冲神经完整时,新福林和硝普钠升降血压诱发的心率反射性变化与正常血压动物相比显著减弱(P<0.001),而后肢血管阻力和肾交感神经活动的反射性调节无明显改变,表明肾性高血压动物的心率反射性调节与外周循环的反射性调节机能不相平行;而由股动脉内直接注射新福林或硝普钠时,股动脉灌流压的增减幅度与正常血压动物相比并无明显差异;(3) 切断两侧减压神经或切断两侧窦神经后,在正常动物仅使反射性心率调节作用减弱,而后肢血管阻力和肾交感神经活动的反射性调节无明显改变;但在高血压动物,除心率的反射性调节进一步减弱外,新福林和硝普钠升降血压时后肢血管阻力和肾交感神经活动的反射性调节效应也显著地减弱(P<0.001),提示肾性高血压时动脉压力感受器反射的潜在调节能力降低。由此似表明,肾性高血压时动脉压力感受器反射     

Responses of sensorimotor and visual cortical neurons to light in rabbits with a hidden focus of excitation in the CNS (defensive dominanta)

In the sensorimotor cortex of rabbits with a hidden focus of excitation in the CNS, the firing rate of neurons that responded to light was significantly lower (p = 0.01) than the firing rate of neurons that did not respond to light. The same phenomenon was observed in the visual cortex of intact rabbits. Both in intact rabbits and animals with the hidden focus of excitation, 36% of neurons in the sensorimotor responded to a nonspecific for them light stimulation. In the sensorimotor cortex of rabbits with the hidden focus of excitation, more (p = 0.01) neurons responded to light with the latency lower that 100 ms and less (p = 0.02) neurons responded to light with the latency from 200 to 300 ms as compared to intact animals. In the visual cortex of rabbits with the hidden excitation focus, less (p = 0.01) neurons responded to light stimulation with the latency from 50 to 100 ms as compared to intact rabbits.     

Therapeutic effectiveness of gamma-globulin on experimental burns

Experiments on rabbits were made to examine excretory-absorption liver function and the blood kallikrein-kinin system after thermal burn and treatment with gamma-globulin immune to burn skin toxin. Immunotherapy leads to a more rapid and effective recovery of the functional indicators in the burnt animals than in burns without or with the treatment by nonimmune preparations. It was demonstrated that specific detoxification plays an important role in multiple modality treatment of burn disease.     

Pressor responsiveness in renal prehypertensive rabbits with a denervated kidney

Norepinephrine was infused iv at several doses into four groups of conscious rabbits (six per group), and the pressor responses were recorded. The groups were 3-day sham-operated rabbits; 3-day, two-kidney rabbits with unilateral renal artery stenosis (RAS); 3-day, two-kidney rabbits with unilateral renal denervation; and 3-day, two-kidney rabbits with unilateral renal denervation plus RAS of the denervated kidney. The rabbits with RAS of an innervated kidney and those with RAS of a denervated kidney had the same pressor responses to norepinephrine, which were greater than the pressor responses in the sham-operated rabbits or in the rabbits with a denervated kidney but without RAS. Four additional groups of similarly prepared rabbits were infused with norepinephrine at 800 ng/min/kg body wt, and mean arterial pressure and cardiac output were determined before and during norepinephrine infusion. The rabbits with RAS of an innervated or of a denervated kidney had greater increases in total peripheral resistance as well as in mean arterial pressure during norepinephrine infusion than did the two groups of rabbits without RAS. This indicated that the rabbits with RAS also had increased vascular responses to norepinephrine. The concentration of norepinephrine in six denervated kidneys was extremely low as compared to that of six innervated kidneys. Because renal denervation did not diminish pressor and vascular hyperresponsiveness in 3-day RAS rabbits, the signal that originates in the kidney following RAS and that results ultimately in pressor and vascular hyperresponsiveness is not mediated by renal nerves.     

The vascular morphometry of some brain stem parts

With the view of following the vascular system of the cerebral trunk, there have been simultaneously injected coloured tracers combined with radio-opaque substances and radio-isotopes (32P, 22Ca) by intravital perfusion to 130 animals (dogs, rabbits and rats). The macro- and microscopical vasculature of the human brain stem was studied on 30 specimens of adults and children. The angioarchitecture of the diverse parts and sectors of the brain stem was studied as a whole in tetraline transparentised preparations and on histological section in comparison with the microradiographies and to incorporation of radioisotopes. A particular attention has been given to the irrigation of hypoglossal nuclei, the bulbar oliva, and the pontopeduncular region, all being zones with multiple sources of vascularization. The vascular morphometry has been macro- and microscopically performed, the data being worked out mathematically-statistically by computing some hemodynamical indices in order to estimate the circulation in different zones of the brain stem.     

Role of the hypothalamus in inhibiting the hypophysis-adrenal cortex system through the feedback mechanism

Chronic experiments were made on intact rabbits and rabbits with destroyed paraventricular and ventromedial nuclei of the hypothalamus to explore the hydrocortisone-induced inhibition of the stressor response of the pituitary-adrenocortical system. Intravenous injection of hydrocortisone in a dose of 100 micrograms/kg 5 minutes before immobilization stress led to inhibition of corticosteroid elevation induced by immobilization of the animals. Inhibition of the stressor reaction was maximal in intact animals, less in rabbits with destroyed ventromedial nuclei, and further less in animals with destroyed paraventricular nuclei. The paraventricular and ventromedial nuclei of the hypothalamus are necessary for inhibition of the pituitary-adrenocortical system by the feedback mechanisms.     

Involvement of pharyngeal muscles in compensatory responses of the respiration system to inspiration resistance load]

The present study was undertaken to test the hypothesis that recruitment of upper airway muscles in loaded breathing is a result of integration of peripheral chemoreceptor and pulmonary mechanoreceptor afferents. Experiments were performed in spontaneously breathing tracheostomized anesthetized rabbits. It had been studied the effects of inspiratory resistive loading to EMG activity of genioglossus muscle. In the intact rabbits the peak value and duration of inspiratory activity of genioglossus increased in loading. Imposition of resistive load in vagotomized animals did not evoke alteration in inspiratory activity of genioglossus in the first loaded breath. Hyperoxia decreased the response of genioglossus muscle to inspiratory loading and vagatomy. We conclude that hypoxic stimulation of peripheral chemoreceptors and decrease in volume-related afferent activity from pulmonary stretch receptors are major mechanisms of the upper airway muscle recruiment in inspiratory resistive loading.     

Composition and histotopography of receptors in antagonist muscles of the radial area of the human forearm

The m. extensor carpi radialis longus and m. flexor carpi in newborns are richly saturated in terminal sensitive apparatuses and are presented as peculiar reflexogenic zones. Quantity and topography of receptors in these zones are similar. Nevertheless, functionally different muscle areas (both in the extensor and flexor) are not equally supplied with the receptory apparatuses.     

The adrenergic mechanisms are involved in the pulmonary hemodynamics changes following experimental myocardial ischemia in rabbits

In acute experiments in anesthetized rabbits the changes of the pulmonary hemodynamics following myocardial ischemia in the region of the descendent left coronary artery were studied in control animals and after the blockade of alpha-adrenoreceptors by phentolamine or N-cholinoreceptors of autonomic ganglia by hexamethonium. Following myocardial ischemia in control animals the pulmonary artery pressure and flow decreased, the pulmonary vascular resistance was elevated not significantly, the cardiac output decreased more than pulmonary artery flow. Following myocardial ischemia after the blockade of alpha-adrenoreceptors the pulmonary artery flow and cardiac output decreased in the same level and the pulmonary vascular resistance was decreased. In these conditions the pulmonary artery pressure decreased more than in control animals, meanwhile the pulmonary artery flow was decreased in the same level as in the last case. Following myocardial ischemia after the blockade of N-cholinoreceptors the pulmonary hemodynamics changes were the same as they were following myocardial ischemia in the control rabbits, the cardiac output decreased more than pulmonary artery flow. The disbalance of the cardiac output and pulmonary artery flow changes in the case of myocardial ischemia was caused by the pulmonary vessel reactions following activations of the humoral adrenergic mechanisms.