The blood microcirculatory bed of the small intestine, liver and pancreas after resection of the stomach and small intestine

As demonstrate the experiments performed on dogs and rats, after surgical intervention to the stomach and small intestine, other organs of the digestive system experience an increased functional loading, that results in noticeable changes in the intraorganic blood vessels and the blood microcirculatory bed organs. The course of the compensatory processes occurs with a definite regularity--as stages. The first stage is characterized with a predominance of the pathological reactions over the compensatory ones, in the second stage certain compensatory possibilities of the organism are noted. In the third stage the compensatory-adaptive reactions prevail over the pathological processes in the blood vessels and blood microcirculatory bed.     

Function of mature coronary collateral vessels and cardiac performance in the exercising dog

Formation of extensive collateral vessels after chronic constriction of a coronary artery in dogs can provide for similar increases in blood flow to native and collateralized regions of myocardium during exertion. Previous investigations have not compared myocardial blood flow and cardiac functional responses during exercise in constricted and nonconstricted (sham) animals. Thus we evaluated left ventricular performance and myocardial blood flow at rest and during mild, moderate, and severe exertion in sham-operated dogs and in dogs 2-3 mo after placement of an Ameroid occluder around the proximal left circumflex artery. Changes in double product, maximal left ventricular dP/dt, and pressure-work index were similar in both groups for each level of exertion. Despite similar increases in estimated myocardial O2 demand and similar diastolic perfusion pressures, average transmural myocardial blood flow increased less in the constrictor animals, particularly during severe exercise (2.74 +/- 0.22 vs. 1.45 +/- 0.29 ml X min-1 X g-1). The smaller increases in blood flow occurred equally in native and collateralized regions as well as in the papillary muscles and boundary areas between the native and collateralized regions. The differences in flow in the native and collateralized regions were uniform across the wall of the myocardium. We also observed smaller increases in stroke volume and cardiac output in the constrictor group, disparities which increased with increasing exertion (stroke volume, severe exercise = 0.92 +/- 0.13 vs. 0.53 +/- 0.09 ml/kg). We postulate that myocardial active hyperemia is limited either because the coronary vessels remaining after chronic circumflex occlusion cannot dilate sufficiently or that there is inappropriate active vasoconstriction during severe exertion.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of phenylephrine and isoproterenol on mesenteric blood flow in experimental posthaemorrhagic hypotension

In previous reports it was found that in mesenteric blood vessels exist profound alpha-adrenergic, and less profound beta-adrenergic receptors. Our experiments were done on 20 mongrel dogs, both sexes, weighing 6.5-22.5 kg, age from 1-2 years, which were divided into 2 groups: experimental (14 dogs) and control (6 dogs). Experimental group of animals passed through the posthemorrhagic hypotension (180 min. at 5.3 kPa). Aim of investigation was to clarify mesenteric vascular reactivity changes during posthemorrhagic hypotension. In order to reach this goal, phenylephrine and isoproterenol were injected alternatively in one hour intervals through cannulated superior mesenteric artery first proximal branch. Our results indicate that mesenteric blood flow responses to those drugs changed quantitatively, but never ceased. It is apparent from our experiments that those quantitative changes are due to beta 2 adrenoceptors changes during the posthemorrhagic hypotension.     

生物血管异种移植的初步研究

目的为了寻求一种新的小口径血管代用品,建立异种移植的动物实验模型,以观察异种移植物的安全性、可靠性、通畅性及组织学改变。方法共采用17只杂种雌性犬,实验组10只,植入经环氧化物处理的猪血管移植物;对照组7只,植入人造血管。手术方法为右侧股动静脉瘘。术后通过超声和血管造影方法来观察移植血管的通畅性,并在术后3月将移植物取出,进行病理学检查,观察移植前后移植物的组织学改变。结果术后第一周、二周行Doppler超声检查结果,两组动静脉瘘均通畅,2周内血管通畅率为100%。术后3个月动脉造影检查后,生物血管组(PG)通畅5只,通畅率62.5%,e-PTFE组通畅4只,通畅率66.7%。两组数据统计学处理,差异无显著性(P>0.05)。术后3月对移植物取材,进行光镜及扫描电镜病理学检查,通畅的生物血管吻合口无狭窄,吻合部位有新的内膜覆盖,周围组织无钙化,有新生的内皮细胞覆盖。结论经环氧化物处理的猪的血管移植物(PG)生物血管作为异种移植物,生物相容性好,具有一定的可行性。     

The effect of catecholamines on blood circulation in the liver

In acute experiments on dogs under nembutal anaesthesia the pressure and blood flow in the vessels supplying the liver have been recorded simultaneously with registration of the hepatic blood content changes. Catecholamines injected into liver vessels have been found to change significantly the liver circulation: adrenaline and noradrenaline evoke the constriction of intrahepatic vessels and decrease the blood content in the liver, realising through the alpha-adrenoreceptors activation, isadrin causes a weak vasodilatation by the activation of beta-adrenoreceptors. A selective inactivation of isadrin in the liver is shown. The density of alpha-adrenoreceptors distribution in the intrahepatic vessels is large enough and apparently some times exceeds the density of beta-adrenoreceptors. In 1/3 of dogs the beta-adrenoreceptors in the liver vascular bed are absent at all or present in arterial bed only.     

Systemic circulatory reaction in the initial period of Cannon's traumatic shock

In experiments on dogs it was shown that on the basis of the dynamics of circulatory parameters it is possible to divide the erectile phase of traumatic shock into two periods. The first period, similar to "defence reactions" in dangerous situations and under the action of potent non-specific stimuli, is characterized by an increased blood inflow to the myocardium, rise in the cardiac output and reduction of the tonus in peripheral vessels. The second period is characterized by the beginning of decompensation of the cardiovascular system. It is completed by the development of the torpid phase of shock.     

Characteristics of the microcirculation and blood rheology in arterial and venous forms of mesenteric vascular occlusion

The functional properties of microcirculation and rheology of blood were studied in dogs subjected to arterial and venous occlusion of mesenteric vessels (cranial mesenteric artery and cranial mesenteric vein). It was found that a local alterations of microvascular bed of intestinal wall are quite different in case of arterial or venous occlusion. The degree of hemorheological and microvascular deviations is higher in case of acute venous thrombosis than during the acute occlusion of cranial mesenteric artery.     

Proceedings: The effects of hypothalamic and reflexogenic hypertension on renal and femoral circulation.

In anaesthetized dogs, electrical stimulation of the median posterior hypothalamus provoked hypertension accompanied by a decrease of renal blood flow and an increase of femoral blood flow. Similar hypothalamic reactions occurred after bilateral cervical vagotomy or after atropine, 2 mg/kg i.v. During reflexogenic hypertension induced by bilateral carotid occlusion in bivagotomized dogs, the renal and femoral blood flows were not significantly modified. The decrease of the renal blood flow and the increase of the femoral blood flow, during hypothalamic stimulation were greatly reduced or reversed after R 28935 equals erythro-1-(1--e12-(1,4-benzodioxan-2-yl)-2-OH-Et]-4-piperidyl)-2-benzimidaxolinone, 80 mug/kg i.v., but not after clonidine, 5 mug/kg i.v.     

Combination of microangiography and histochemistry

Summary The enzyme histochemical staining properties of microangiographed tissues were studied with special reference to the contrast filled blood vessels. Colouring of the contrast substance occours when the histochemical methods used involve ammonium sulphide treatment. This may disturb the histochemical reactions of the blood vessels themselves, but in the rest of the tissue all reactions remain undisturbed.     

Effects of alpha -adrenergic blockade during acute anemia

Studies were carried out in seven anesthetized paralyzed dogs to examine the importance of alpha -adrenergic tone in the cardiovascular responses during acute anemia. Data were obtained 1) at normal hematocrit (Hct), 2) during anemia produced by isovolemic hemodilution with dextran (Hct, 13-15%), 3) during anemia after alpha -blockade (alpha -bl) with phenoxybenzamine (3 mg/kg), and 4) following volume expansion during anemia with a red blood cell dextran solution. Cardiac output (QT), limb and total body oxygen uptake (VO2), and limb blood flow (QL) were determined. Both QT and QL increased during anemia (P less than 0.01), whereas limb resistance (RL) and total peripheral resistance (TPR) were decreased (P less than 0.01). No further change in either RL or TPR occurred with alpha -blockade anemia, but both QT and QL decreased (P less than 0.01). Whole-body VO2 increased during anemia and then declined with alpha -bl and anemia. Following volume expansion during anemia with alpha -bl, QT, QL, and whole-body VO2 increased. We conclude that alpha -adrenergic sympathetic tone to capacitance vessels is essential for the cardiac output increased during anemia, but has little or no effect on resistance vessels and hence distribution of peripheral blood flow.     

The persisting capability for vasodilatation in duct-occluded canine pancreatic segments

The effect of duct-obliteration and duct-obliteration induced fibrosis on the capability for vasodilatation of the pancreatic vasculature was investigated in dogs. It was demonstrated that the increase of basal blood flow through left pancreatic segments, induced by intra-arterial injection of papaverin, remained unchanged during 6 months after duct-obliteration. It is concluded that impairment of endocrine function of duct-obliterated segmental pancreatic grafts cannot be readily explained by a functional impairment of the pancreatic vessels.     

Role of tracheal and bronchial circulation in respiratory heat exchange

Due to their anatomic configuration, the vessels supplying the central airways may be ideally suited for regulation of respiratory heat loss. We have measured blood flow to the trachea, bronchi, and lung parenchyma in 10 anesthetized supine open-chest dogs. They were hyperventilated (frequency, 40; tidal volume 30-35 ml/kg) for 30 min or 1) warm humidified air, 2) cold (-20 degrees C dry air, and 3) warm humidified air. End-tidal CO2 was kept constant by adding CO2 to the inspired ventilator line. Five minutes before the end of each period of hyperventilation, measurements of vascular pressures (pulmonary arterial, left atrial, and systemic), cardiac output (CO), arterial blood gases, and inspired, expired, and tracheal gas temperatures were made. Then, using a modification of the reference flow technique, 113Sn-, 153Gd-, and 103Ru-labeled microspheres were injected into the left atrium to make separate measurements of airway blood flow at each intervention. After the last measurements had been made, the dogs were killed and the lungs, including the trachea, were excised. Blood flow to the trachea, bronchi, and lung parenchyma was calculated. Results showed that there was no change in parenchymal blood flow, but there was an increase in tracheal and bronchial blood flow in all dogs (P less than 0.01) from 4.48 +/- 0.69 ml/min (0.22 +/- 0.01% CO) during warm air hyperventilation to 7.06 +/- 0.97 ml/min (0.37 +/- 0.05% CO) during cold air hyperventilation.     

Ventilatory changes of pulmonary capillary blood volume assessed by arterial density

By use of an improved density measuring system, we found that the gravimetric density of arterial blood of dogs fluctuates at the same frequency as the spontaneous or mechanical ventilation. Similar density fluctuations were observed in the blood leaving isolated, perfused lobes of dogs that were ventilated cyclicly. Employing an analysis that balanced the erythrocyte and plasma flows through distensible capillaries containing blood with a tube hematocrit lower than the hematocrit in large blood vessels, we derived a relationship to estimate from the density fluctuation the change in pulmonary capillary blood volume (Vc). For mechanical ventilation, the maximum change in density over one ventilation cycle increased from 0.084 +/- 0.01 to 0.47 +/- 0.05 (SE) g/l as the frequency decreased from 29 to 6 cycles/min. These density changes were estimated to be the result of an 1-16% change in Vc. A larger tidal volume for the mechanical ventilation led to a larger density fluctuation. The maximum density change of spontaneous respiration of 6 cycles/min was one-sixth of the mechanical case, indicating a much smaller change in Vc during spontaneous respiration. When the airway flow resistance was increased for spontaneous respiration, larger density fluctuations were observed.     

Responsiveness of microcirculation and local cold vasodilation to capsaicin in the intact and chronically denervated canine tongue

Lingual blood flow and its distribution were determined at rest and in response to local cooling of the tongue (32 degrees C) in 6 anaesthetized, paralyzed and artificially ventilated dogs before and after two intraarterial (i.a.) injections of capsaicin (2.5 mg) at an interval of about 40 min. In 3 dogs, the same protocol was performed after degeneration of the chorda-lingual and glossopharyngeal nerves due to prior transection. In general the first i.a. injection of capsaicin resulted in a marked and the second injection in a smaller decrease of lingual blood flow. Local cooling of the tongue induced significant increases in lingual blood flow before as well as after capsaicin treatment, regardless of whether sensory innervation was intact or degenerated. In both the untreated and capsaicin treated dogs the increase in lingual blood flow during local cooling of the tongue was solely due to an increase in blood flow through the arteriovenous anastomoses, while blood flow through the capillaries of the mucosa and muscles even decreased. The findings suggest that capsaicin-induced vasoconstriction of the tongue vessels is due to a direct effect on vascular receptors. It is further suggested that cold vasodilatation of the canine tongue is not mediated by axon collaterals releasing substance P. Direct thermal effects on the intramural ganglia and the postganglionic vasomotor efferents innervating the AVAs, or on AVAs basal tone itself are suggested as the underlying mechanism.     

Lymphatic and blood vessels of the liver in acute and chronic cholecystitis]

Changes in lymph and blood vessels were studied in 110 dogs with acute and chronic cholecystitis. It was established that in the period of development of acute inflammatory processes in the gall bladder the monolayer network of hepatic capillaries was changed into bi-layer, took place the formation of plane networks at the side of the lobule and lacunary dilatations in the site of fusion of lymph capillaries, dilatation and deformation of lymph capillaries and vessels. Under conditions of chronic cholecystitis fibrosis and sclerosis of the portal tracts were accompanied by intensive growth (and reduction - in parallel) of lymph capillaries. Thick small-looped network was observed to develop around false lobules during development of cyrrhosis. A conclusion is made that early cholecystectomy is necessary in cases of inflammatory diseases of the gallbladder.     

Reaction of the blood forming system of the dogs to acute radiation exposure (by the SRC-Institute of biophysics data bank)

At present time in the SRC--Institute of Biophysics the data bank containing the information on the reactions of 431 dogs to radiation exposure in a wide range of doses has been created. By the results of 4299 blood tests reporting a leukocyte content, including 2509 tests reporting a blood formula, the individual peculiarity of the peripheral blood reaction in dogs were analyzed. Dose dependencies for the reaction of blood-forming system to radiation exposure to doses in the range from 1.0 to 7.0 Gy were obtained. In comparison with the similar data for humans, the neutrophil content in peripheral blood decreased approximately 1.5-2.0 times faster in dogs than in men, resulting in earlier recovery.     

Role of the hypothalamus in regulating liver circulation

In acute experiments on nembutal anesthetized dogs stimulation of anterior hypothalamus elicited changes in the hepatic artery blood flow, which followed those of arterial pressure; the vascular resistance remaining unchanged. The stimulation of medial and posterior hypothalamus led to decrease in flow and increase in the resistance of the hepatic artery. In most cases of hypothalamic stimulation the portal blood flow diminished, portal pressure and vascular resistance increased. The opposite reactions were observed during stimulation of sympathoinhibitory area, paraventricular and lateral hypothalamic nuclei. The conclusion is made that the hypothalamus participates in integrative and differential control of the hepatic circulation.     

Role of endothelin in alpha-adrenoceptor coronary vasoconstriction

It has been proposed that alpha-adrenoceptor vasoconstriction in coronary resistance vessels results not from alpha-adrenoceptors on coronary smooth muscle but from alpha-adrenoceptors on cardiac myocytes that stimulate endothelin (ET) release. The present experiments tested the hypothesis that the alpha-adrenoceptor-mediated coronary vasoconstriction that normally occurs during exercise is due to endothelin. In conscious dogs (n = 10), the endothelin ET(A)/ET(B) receptor antagonist tezosentan (1 mg/kg iv) increased coronary venous oxygen tension at rest but not during treadmill exercise. This result indicates that basal endothelin levels produce a coronary vasoconstriction at rest that is not observed during the coronary vasodilation during exercise. In contrast, the alpha-adrenoceptor antagonist phentolamine increased coronary venous oxygen tension during exercise but not at rest. The difference between the endothelin blockade and alpha-adrenoceptor blockade results indicates that alpha-adrenoceptor coronary vasoconstriction during exercise is not due to endothelin. However, in anesthetized dogs, bolus intracoronary injections of the alpha-adrenoceptor agonist phenylephrine produced reductions in coronary blood flow that were partially antagonized by endothelin receptor blockade with tezosentan. These results are best explained if alpha-adrenoceptor-induced endothelin release requires high pharmacological concentrations of catecholamines that are not reached during exercise.     

Training dogs with help of the shock collar: short and long term behavioural effects

Behavioural effects of the use of a shock collar during guard dog training of German shepherd dogs were studied. Direct reactions of 32 dogs to 107 shocks showed reactions (lowering of body posture, high pitched yelps, barks and squeals, avoidance, redirection aggression, tongue flicking) that suggest stress or fear and pain. Most of these immediate reactions lasted only a fraction of a second. The behaviour of 16 dogs that had received shocks in the recent past (S-dogs) was compared with the behaviour of 15 control dogs that had received similar training but never had received shocks (C-dogs) in order to investigate possible effects of a longer duration. Only training sessions were used in which no shocks were delivered and the behaviour of the dogs (position of body, tail and ears, and stress-, pain- and aggression-related behaviours) was recorded in a way that enabled comparison between the groups. During free walking on the training grounds S-dogs showed a lower ear posture and more stress-related behaviours than C-dogs. During obedience training and during manwork (i.e. excercises with a would-be criminal) the same differences were found. Even a comparison between the behaviour of C-dogs with that of S-dogs during free walking and obedience exercises in a park showed similar differences. Differences between the two groups of dogs existed in spite of the fact that C-dogs also were trained in a fairly harsh way. A comparison between the behaviour during free walking with that during obedience exercises and manwork, showed that during training more stress signals were shown and ear positions were lower. The conclusions, therefore are, that being trained is stressful, that receiving shocks is a painful experience to dogs, and that the S-dogs evidently have learned that the presence of their owner (or his commands) announces reception of shocks, even outside of the normal training context. This suggests that the welfare of these shocked dogs is at stake, at least in the presence of their owner.     

Differing effects of vasopressin on regional cerebral blood flow of dogs following intracisternal vs. intra-arterial administration

We investigated the differential effect of the intracisternal and intraarterial administration of vasopressin on the regional cerebral blood flow (rCBF) in the parietal cortex of dogs. Regional CBF, velocity and blood volume were assayed by laser flowmetry. The intracisternal injection of 1 nmol vasopressin significantly increased the rCBF and velocity, without affecting blood volume. However, the intravertebral arterial injection of 1 nmol vasopressin significantly decreased the rCBF and velocity. This discrepancy can be explained by a difference in the affected vasculature; large blood vessels in the subarachnoid space vs. whole cerebral vascular system. The intracisternal and intraarterial injection of the nitric oxide inhibitor N^G-monomethyl-L-arginine reduced the rCBF from the base line, and significantly suppressed the rCBF elevation induced by vasopressin. The effect of vasopressin may be considered as the summation of the increased flow from the dilated large vessels via the release of nitric oxide from the endothelium, and of the decreased flow from the contracted small vessels.