Parameters of cerebral blood flow of 7- to 11-year-old children living in northern European Russia

Doppler sonography and rheoencephalography were used to study cerebral hemodynamics of young schoolchildren in the village of Klimovskoe (Konosha raion, Arkhangel’sk oblast, Russia). Mean linear blood flow velocities (LBVs) in the major cerebral vessels did not differ significantly from the velocities measured in age-matched children living in St. Petersburg. The index of resistivity was lower in the residents of the North than in their counterparts in St. Petersburg, which suggests a decreased tone of resistive vessels of the children living in the North. Asymmetry of the LBVs through the homonymous cerebral arteries of the left and right hemispheres was found in 67% of children examined. Asymmetry of the LBVs in the anterior, middle, and posterior cerebral and vertebral arteries (VAs) was correlated with a malformed posture (such as scoliosis or a slouch). In most children examined, sideward head rotation was accompanied by compression of VAs at the level of the C ₁ and C ₂ cervical vertebrae; in 71% of them, this condition could be regarded as a hemodynamically significant stenosis. In all children, a decreased LBV observed in one of the VAs was completely compensated by an increased LBV in its contralateral counterpart. Doppler sonographic signs of dystonic VAs and/or asymmetrical LBVs in the VAs were found in 79% of children examined. These children can be supposed to have latent disorders of blood flow in the VA basins caused by vertebral influences (related to irritation of the periarterial nervous plexus or cervical autonomic plexuses). The schoolchildren living in the North exhibited a lower reactivity of their cerebral vessels to hypo-and hypercapnia than their counterparts living in the central parts of the Russian Federation or in St. Petersburg. Regional differences were found in the sensitivity of cerebral vessels to hypocapnia. The volume of blood in the basins of the internal carotid arteries determined in a hypocapnic test was decreased; it was increased in the basins of VAs. This fact can be interpreted as a regional redistribution of the cerebral circulation caused by extreme environmental factors stimulating vital regulatory sites of the brainstem.     

Gas bubbles in the circulation of divers after ascending excursions from 300 to 250 msw

The occurrence of intravascular bubbles in arteries and veins has been studied using pulsed Doppler ultrasound in six subjects who performed two ascending excursions each from 300 to 250 meters of seawater (msw) during a heliox saturation dive. Following decompression, high-intensity reflections could be observed not only in the venous system but also in the arteries, most notably in the carotid artery. Intravascular bubbles were more numerous during the first ascent than during the second. The arterial bubbles most probably come from the venous side of the circulation, indicating that the pulmonary filter is not as effective as previously thought during saturation diving.     

Dependence of constrictor and dilator humoral responses of arteries and veins in the small intestine on calcium ions entering vascular myocytes

Verapamyl administered to the intestine circulation in the dose evoking no shifts in the arterial and venous resistance or in the vascular capacity, decreased 2- or 3-fold both the constrictor and dilatory responses of the arterial vessels. Against the background of Verapamyl, noradrenaline and isoproterenol did not practically change either capacity or resistance in the veins. Responses of veins to angiotensin II increased 10-fold and more, whereas they were absent after administration of atropine into the intestine circulation. Constrictor and dilatory responses of veins need to a greater extent than the arteries penetration of external calcium ions to their myocytes.     

Spare alpha adrenoceptors in the peripheral circulation: excitation-contraction coupling

Postsynaptic alpha adrenoceptors in arteries and veins represent a mixed population of alpha 1 and alpha 2 adrenoceptors, with both subtypes mediating vasoconstriction. In the peripheral arterial circulation, postsynaptic vascular alpha 1 adrenoceptors are found in the adrenergic neuroeffector junction, whereas postsynaptic vascular alpha 2 adrenoceptors are located extrajunctionally. In the venous circulation, it appears that alpha 2 adrenoceptors may be predominantly junctional, whereas alpha 1 adrenoceptors may be predominantly extrajunctional. In general, alpha 1 adrenoceptors play a more important functional role in arteries than in veins, with the converse being true for postsynaptic vascular alpha 2 adrenoceptors. The relationship between alpha-adrenoceptor occupancy and vasoconstrictor response is more favorable for postsynaptic vascular alpha 1 adrenoceptors than for alpha 2 adrenoceptors in both arteries and veins, and there is evidence for a receptor reserve in alpha 1 adrenoceptors in both the arterial and venous circulation. No reserve in postsynaptic vascular alpha 2 adrenoceptors is seen in the arterial circulation, but in isolated venous preparations, a reserve in alpha 2 adrenoceptors has been observed. It has been suggested that spare alpha 2 adrenoceptors found in veins, but not arteries, may be responsible, at least in part, for the exaggerated alpha 2-adrenoceptor-mediated response of veins relative to arteries.     

Alterations of calf venous and arterial compliance following acclimation to heat administered at a fixed daily time in humans

We investigated the effects of heat acclimation on venous and arterial compliance in humans. Four male and four female volunteers were exposed to an ambient temperature of 40°C and relative humidity of 40% for 4 h (1330–1730 hours) per day for 9–10 consecutive days. The calf venous compliance (CV) was estimated using venous occlusion plethysmography with a mercury-in-silastic strain gauge placed around the right calf at its maximum girth. The compliance of the small (CSA) and large (CLA) arteries were assessed by reflective and capacitance compliance by analyzing the radial artery blood pressure waveforms, basing on the use of a modified Windkessel model. The calf CV, CSA, CLA, systolic and diastolic blood pressures, heart rate and core temperature were determined twice a day, 0930–1100 hours (AM test) and 1500–1630 hours (PM test), in both heat-acclimated and non-heat-acclimated (control) conditions. Heat acclimation appeared to decrease blood pressures, heart rate and significantly lowered core temperature only in the PM test. In the control condition, the calf CV was not affected by the time of day and the CSA was significantly depressed in the PM test. After acclimation to heat, the calf CV significantly increased and the CSA did not decrease in the PM test. The results presented suggest that repeated heat exposure in humans, for 4 h at a fixed time daily, increases the calf CV and the CSA particularly during the period when the subjects were previously exposed to heat.     

Hemodynamic changes evaluated by Doppler ultrasonographic technology in the ovaries and uterus of dairy cattle after the puerperium

The present detailed study aimed to establish for the first time the ovarian and uterine hemodynamic change in dairy cows after the end of the puerperal period to investigate a possible association between Doppler indices and volume of blood flow. Twenty cows weighing 500–600 kg (mean 400 ± 50 kg) and 4–5 years of age (mean 3.2 ± 0.5 years) categorized into two main groups (true anestrum, with corpus luteum, n = 10) and (normal cyclic, n = 10), The period of examination started from day 39 till day 70 after calving with day after day routinely examination by b-mode and Doppler performed on both ovaries with ovarian arteries (OA) and uterus with uterine arteries (MUA) in the ipsilateral (ipsi) and contralateral (contra) side to ovulation, in addition to a thickness in horns and body was measured. Estradiol and progesterone were also measured. Results showed that both Doppler indices in the OA and MUA ipsi and contra had a positive (P ≤ 0.001) correlation with contra Doppler indices, but revealed a negative (P ≤ 0.05) correlation with ipsi and contra Doppler velocities, blood flow rate and volume in anestrum cows. Both ovarian and uterine ipsi indices showed an increase (P ≤ 0.05) in the anestrum cows, and both PSV and EDV of both arteries ipsilateral showed (P ≤ 0.05) a decrease in the anestrum cows, the ipsi and contra ovarian and uterine colored % were lower in anestrum group than the normal group. Estradiol (P ≤ 0.05) decreased in anestrum cows than the normal, while progesterone increased in the anestrum group. Conclusion, although uterine and ovarian morphology were changed in anestrum cows, the vascular system of the ovary as well as uterus underwent much more marked vascular changes, the most significant being that of blood flow velocities and volume.     

Plasticity of endothelial cells during arterial-venous differentiation in the avian embryo

Remodeling of the primary vascular system of the embryo into arteries and veins has long been thought to depend largely on the influence of hemodynamic forces. This view was recently challenged by the discovery of several molecules specifically expressed by arterial or venous endothelial cells. We here analysed the expression of neuropilin-1 and TIE2, two transmembrane receptors known to play a role in vascular development. In birds, neuropilin-1 was expressed by arterial endothelium and wall cells, but absent from veins. TIE2 was strongly expressed in embryonic veins, but only weakly transcribed in most arteries. To examine whether endothelial cells are committed to an arterial or venous fate once they express these specific receptors, we constructed quail-chick chimeras. The dorsal aorta, carotid artery and the cardinal and jugular veins were isolated together with the vessel wall from quail embryos between embryonic day 2 to 15 and grafted into the coelom of chick hosts. Until embryonic day 7, all grafts yielded endothelial cells that colonized both host arteries and veins. After embryonic day 7, endothelial plasticity was progressively lost and from embryonic day 11 grafts of arteries yielded endothelial cells that colonized only chick arteries and rarely reached the host veins, while grafts of jugular veins colonized mainly host veins. When isolated from the vessel wall, quail aortic endothelial cells from embryonic day 11 embryos were able to colonize both host arteries and veins. Our results show that despite the expression of arterial or venous markers the endothelium remains plastic with regard to arterial-venous differentiation until late in embryonic development and point to a role for the vessel wall in endothelial plasticity and vessel identity.     

Leg blood flow during slow head-down tilt with and without leg venous congestion

The effects of slow changes in body position on leg blood flow (LBF) were studied in nine healthy male subjects. Using a tilt table, sitting volunteers were tilted about 60° backwards to a supine position within 40 s. To modify the venous filling in the legs, the tilt manoeuvre was repeated with congestion of the leg veins induced by two thigh cuffs inflated to a subdiastolic pressure of 60 mmHg. Doppler measurements in the femoral artery were used to estimate LBF. Additional Doppler measurements at the aortic root in five of the subjects were taken for the determination of cardiac output. The LBF was influenced by body position. In the control experiment it increased from 500 ml · min⁻¹ in the upright to 780 ml · min^–1 after 15 min in the supine position. A mean maximal value of 950 ml · min⁻¹ was observed 20 s after the tilt. Heart rate remained almost constant during the tilt phase, whereas stroke volume increased from 90 ml to 120 ml and it remained at that level after the cessation of the tilt. Congestion of the leg veins had no significant effect on heart rate, stroke volume and mean blood pressure. However, it increased vascular resistance of the leg during and after the tilt. After 15 min in the tilted position LBF amounted to 600 ml · min⁻¹. The results suggest that the filling of the leg veins is inversely related to leg blood flow. The most likely mechanism underlying this observation is a local effect of venous filling on vasomotor tone. Accepted: 20 May 1998     

Effect of ageing on the murine venous circulation

The effect of ageing on the morphology of veins, venous valves and arteries was investigated in male wild-type mice using an adapted procedure with injection of a silicone polymer Microfil^? that preserves morphology of the vasculature. Throughout the hind limb the arterial, but not the venous, lumen area and wall thickness were significantly greater in 24-month as compared to 10-week-old C57BL/6 mice. Venous valves were most frequently located at the sapheno-femoral vein junction in the lower extremities, and appeared thicker at the base supported by structurally intact collagen fibers, and thinner towards the proximal end of the valve leaflet, with less organized collagen. Overall, valves were less supported by structurally intact collagen at 24 months as compared to 10 weeks. Endothelial expression of CD31, endothelial protein C receptor or von Willebrand factor (VWF) was not affected by age, while thrombomodulin expression was lower in aged versus young arteries. At both ages, expression of VWF was lower at venous valves versus veins. Evaluation of the blood coagulation profile revealed that aged mice had shortened prothrombin time, elevated plasma levels of factor (F)VII, FVIII and VWF and increased neutrophil and platelet counts. Thus, our data indicate that in mice with ageing, venous valves become more fragile, in association with a procoagulant and inflammatory blood phenotype. Taken together, we found that the procoagulant state in ageing, is accompanied by mild vascular changes.     

Adrenoceptor function in the bovine pulmonary circulation

The bovine pulmonary vascular response to alpha- and beta-agonists was studied using an awake intact calf model. Pulmonary arterial pressure, pulmonary arterial wedge pressure, left atrial pressure, systemic arterial pressure, and cardiac output were measured in response to 3 min infusions of isoproterenol (beta-agonist; 0.12, 0.24, 0.48, 0.9, and 1.8 micrograms X kg-1 X min-1) and phenylephrine (alpha-agonist, 0.15, 0.30, 0.60, 1.15, and 2.30 micrograms X kg-1 X min-1). Phenylephrine caused an increase in vascular resistance in the pulmonary arterial and venous compartments. The slope of the resistance in response to phenylephrine was greater in the pulmonary arterial than pulmonary venous circulation. Isoproterenol resulted in a dose-dependent decrease in vascular resistance in the pulmonary arteries and veins. The vascular resistance was decreased to the same level in the pulmonary arteries and veins although the arteries showed a greater percent change. In addition, isoproterenol infusion resulted in a transient decrease in arterial pH and increase in values for packed cell volume and haemoglobin.     

Anatomy of the veins of the head in the domestic fowl

The anatomy of the cephalic venous system in the fowl was studied in 19 specimens by means of latex-injected preparations and by dissection. The brain sinuses converge dorsally upon the large cervical sinus and vertebral veins. Dorso-ventral communication is provided by the occipital veins posteriorly, while the ophthalmic system unites both dorsal and ventral sinuses and the temporal rete with the extracranial veins anteriorly. The jugular veins are formed from the superficial branches of the facial veins and serve mainly as outlets for extracranial blood. They are united at the base of the head by a prominent transverse anastomosis which slopes caudally towards the larger, right jugular. As in mammals, the carotid veins envelop the internal carotid arteries and anteriorly form a bulbous sinus cavernosus around the inter-carotid anastomosis.     

Lipid peroxidation rate and the antioxidant protection system during a three-day dry immersion experiment

The content of lipid peroxidation products (diene conjugates, malondialdehyde, Schiff bases) and antioxidant defense system indices (the main lipid antioxidant tocopherol and the level of general antioxidant activity) were measured in the blood serum of five male volunteers aged 25?C40 years in a three-day dry immersion experiment. During the immersion test, no deviations of indices from the background values were found. An increase in the tocopherol concentration within 2 h after the beginning of the experiment was the only exception. A significant increase in the concentration of lipid peroxidation products, particularly, diene conjugates, was observed 2 h after immersion completion during the reconditioning period. However, the tocopherol content was significantly lower than the background values. It is concluded that the subjects?? adaptation to simulated microgravity conditions displays no pronounced stress component, whereas bringing back to normal vital functions after exposure to immersion induces a pronounced stress reaction illustrated by a significant increase in the lipid peroxidation product levels against a background of a decrease in the functional activity of the antioxidant defense system.     

The effect of selective umbilical embolization on the common umbilical artery pulsatility index and umbilical vascular resistance in fetal sheep.

In eight anaesthesized fetal sheep (gestational age 112-127 days; term 147 days), embolization of the umbilical placental circulation was performed in order to evaluate the response of the umbilical artery pulsatility index to an exclusive increase in umbilical vascular resistance. Measurements were performed using a 20 MHz pulsed Doppler transducer and an electromagnetic flow meter mounted on the common umbilical artery and catheters at the aortic trifurcation and in one of the umbilical veins. Umbilical vascular resistance was calculated according the Poiseuille equation as the ratio of aortic to umbilical venous pressure gradient and umbilical blood flow. Microspheres were administered at 15-min intervals through a catheter in one of the cotyledonary arteries, until fetal heart rate had decreased beneath 100 beats/min or had become arrhythmic. The period of examination per fetus varied between 60 and 120 min, after which cardiac decompensation occurred. During this period, umbilical perfusion pressure increased from 20.3 +/- 4.9 to 28.1 +/- 4.7 mmHg (SD; P less than 0.01), umbilical blood flow (ml/min) decreased from 342 +/- 127 to 115 +/- 99 mmHg (SD; P less than 0.01), umbilical vascular resistance increased from 0.065 +/- 0.022 to 0.342 +/- 0.150 mmHg.min/ml (P less than 0.01) and common umbilical artery pulsatility index increased from 0.97 +/- 0.23 to 4.03 +/- 1.69 (P less than 0.01). Fetal heart rate did not change significantly (168 +/- 33 prior to cardiac decompensation versus 178 +/- 19 beats/min at baseline condition). The linear correlation between common umbilical artery pulsatility index and umbilical vascular resistance varied between 0.83 and 0.99 and the average correlation was 0.93 (P less than 0.01).(ABSTRACT TRUNCATED AT 250 WORDS)     

Venous responses to hypoxemia in the fetal lamb

The factors regulating umbilical venous return and its distribution between the ductus venosus and liver are poorly understood. This study was designed to determine where the major changes in resistance to umbilical venous return occur in response to fetal hypoxemia. In eight chronically-instrumented fetal lambs, during control and hypoxemic periods, we measured pressure in the descending aorta, extra-abdominal umbilical vein, portal sinus, and inferior vena cava; we also measured blood flow using radionuclide-labeled microspheres. During the control period, the umbilical arteries and placental vasculature accounted for 82% of total resistance to umbilical-placental blood flow, the umbilical veins for 11%, and the ductus venosus and liver for 7%. Hypoxemia increased resistance in the umbilical veins more than twofold, but did not affect resistance in the umbilical arteries or placenta. Although combined liver/ductus venosus resistance did not change, hepatic vascular resistance increased, and ductus venosus resistance decreased. We conclude that the major increase in resistance to umbilical venous return in response to hypoxemia resides in the umbilical veins. This increased resistance may improve maternal-fetal blood gas exchange by increasing the fetal surface area in the placenta.     

Structural–functional characteristics of brachiocephalic vessels in hypertensive patients under changed atmospheric pressure

The ultrasonic location technique was used to measure the intima-media thickness (IMT) as well as the internal systolic diameter of and the linear blood velocity (LBV) in the cervical arteries in subjects with initial stages of hypertension. Correlation analysis elicited a temporal contingency between these parameters and daily average values of atmospheric pressure. Thus, the common carotid artery IMT tended to increase on high-pressure days. In addition, diameters of the common and internal carotid arteries and vertebral artery were narrowed and, consequently, LBV in these vessels increased. This relationship is more evident in men than women and in elderly subjects than young. These results are suggestive of a vasoconstrictive effect of high atmospheric pressure on these arteries. The relationship is not universal, as it is nonlinear for the diameter of the internal carotid artery and inverse for the external one. This implies different sensitivity of arteries to the factor under study and possible blood redistribution in the arterial tree depending on external pressure. The relationship was observed equally on the day of investigation and previous days, which points to its temporal stability.     

Microvasculature of the mouse eye: Scanning electron microscopy of vascular corrosion casts

Purpose

For drug safety assessment, ophthalmic fundus examination is of diagnostic importance in experimental animals. Interim blood samples are usually collected from the orbital venous sinus in the mouse. This report characterizes the angioarchitecture of the mouse eye.

Methods

In 10 mice, the microvasculature of the eyes of was investigated using scanning electron micrographs of corrosion casts.

Results

The mouse eye was characterized as having a rich vasculature with many thick retinal arteries and a well-developed orbital venous sinus. The eye receives its primary blood supply from the external ophthalmic artery, which is divided into three branches: the central retinal artery, as well as the medial and lateral long posterior ciliary arteries. The central retinal artery is divided into 8-9 radiating retinal arteries. The mouse has an orbital venous sinus around the orbit rather than a well-developed orbital venous plexus in the retrobulbar space as is in the rat. The orbital venous sinus is formed by the episcleral veins, the ophthalmic vein, the superior palpebral vein, inferior palpebral vein and numerous anastomotic veins among these veins.

Conclusions

The mouse ocular vasculature is quite similar to that of rats. It is recommended that the best location for insertion of a capillary tube for collecting blood is in the lateral canthus around the eye where the sinus is larger and is most readily accessible. Functional significance of the vascular patterns of the eye is discussed.     

Functional Organization of the Teleost Gill

The circulation of the gills has been studied in the perch, trout and eel combining the conventional histological methods and casting techniques. The existence of two blood pathways in each gill arch was confirmed. 1 — An arterio-arterial pathway assuming the respiratory function. It includes the afferent branchial artery and in each primary lamella the afferent primary artery, the secondary lamellae capillaries and the primary and branchial efferent arteries. 2 — An arterio-venous pathway arising from both the branchial artery, in the gill arch, and the primary arteries in each primary lamella. This pathway includes the central venous sinus of the primary lamella, several small veins and is finally connected with the branchial veins. 3 — The lack of connections between afferent primary arteries and cvs in the trout and the perch makes impossible a direct blood flow from the afferent to the efferent artery (shunt). In the eel connections between cvs and both afferent and efferent arteries do not mean that a shunt is operating according to the pressure gradient.     

Diameter of the Main Arteries of the Lower Extremities after a Bicycle Ergometer Test

The linear blood flow velocity and the diameter of main arteries of the lower extremities were measured before and after a 30-min bicycle ergometer exercise in 18- to 22-year-old healthy male volunteers not involved in professional sports (controls), as well as in highly qualified wrestlers and track-and-field athletes. In comparison to the control group, the track-and-field athletes have wider arteries, whereas the wrestlers have stronger muscles. The arteries become wider during the first minutes after the bicycle ergometer exercise, which is accompanied by a decrease in the linear velocity of the blood flow. The athletes, especially the track-and-field athletes, have a shorter transitional period. The arterial blood flow in an extremity shows a 20% increase in the first minutes after the test; the shortest recovery period for this parameter was found in the track-and-field athletes.     

Functional activity of the liver under the conditions of immersion and effects of countermeasures

Ultrasound investigations (USI) of the liver, organs and vessels of the gastroduodenal area, as well as blood biochemistry, were performed in two groups of male volunteers on the 4th day of their stay in the conditions of “dry” immersion with and without the application of countermeasures, including the support load imitator (SLI) or high-frequency electromyostimulation. Using ¹³С-methacetin breath test (¹³C-MBT), two other groups were investigated for the effect of immersion on the detoxification activity and metabolic capacity of the liver and the efficacy of SLI. The performed USIs have identified deceleration in the hepatic venous flow and the signs of plethora in the abdominal venous system. Elevated blood levels were detected in pepsinogen, pancreatic amylase, bilirubin total, due to its unconjugated fraction, insulin, and C-peptide. The ¹³C-MBT has shown a slowdown in the rate of ¹³C-methacetin inactivation and a reduction in the hepatic metabolic capacity. The application of countermeasures during the immersion has not affected the ultrasound patterns of the hemodynamic rearrangement in both the liver and the abdomen. High frequency electromyostimulation during the immersion has neutralized the changes in all biochemical indicators except C-peptide, while the application of SLI has led to the restoration of only pepsinogen and amylase to the initial values. In addition, the use of SLI during the immersion counteracted the reduction in the ¹³C-methacetin inactivation rate and did not substantially affect the reduction in the metabolic capacity of the liver.