Adrenergic innervation of the arteries of different diameters in the human and animal pia mater

The adrenergic nervous plexuses of the pial arteries from 450- to 50 micron in diameter have been studied in dogs, cats and humans from 4 age groups (22-44 years, 55-64 years, 65-74 years and 75-86 years old). It has been found that the decrease in the vessel diameter was accompanied by a marked decline in the absolute number of nervous fibers in the nervous plexuses, however the concentration of the nerve fibers has not revealed any significant differences between human arteries from 450 to 100 micron in diameter and animal arteries from 300 to 80 micron in diameter. The number of varicosities-thickness along the nerve fiber--was the greatest in 200-100 micron human arteries and in 80-60 micron animal arteries. With ageing, the number of varicosities in the adrenergic nervous plexus of human pial vessels decreased faster than in the nerve fibers.     

Mitotic activity of pial microvascular endothelium rat in postnatal ontogenesis

Mitotic activity of endothelium in pial microvessels has been studied with the aid of intra-vessel autoradiography in 4-, 12- and 30-day old rats using these parameters: number of labeled nuclei per vessel or per 100 mcm of its length, or per 1 mm2 endothelial surface area, as well as number of vessels with labeled endothelium cells. The first parameter was independent of vessel diameter. The other parameters had highest value in the pericapillary vessels in all rats. These values decrease with rat age. The highest rate of brain growth was revealed after reaching the greatest mitotic endothelium activity in pial bed.     

Scanning electron microscopy of the vitelline membrane of the hen ovum

Manual removal of the perivitelline layer overlying the animal pole (AP) reveals three morphologically distinct regions of the vitelline membrane (VM). (1) The central germinal region is 600-800 micron in diameter and is densely populated with pleomorphic microvillous projections. (2) The periblastic region, which also exhibits microvillous projections, is 250-550 micron wide and consists of numerous (80-120) lacunae that are 10-60 micron in diameter and up to 20 micron in depth. (3) At the outer periblastic region, the microvillous projections are less numerous. In the vegetal hemisphere, the VM has few projections and occasionally is discontinuous.     

Spatial synchronization of potentials in the frontal zones of the brain during performance of nominative speech in children

Characteristics of spatial-temporal relations of the frontal zones potentials with those of other brain centres were studied in five- to six-year old children during naming of visually presented objects. EEG cross correlation analysis has shown that during visual perception of familiar objects the correlations of frontal areas with the interior pariental area of the left hemisphere are enhanced; the rhythms of the inferior parietal and occipital zones in the left hemisphere precede the potentials in the frontal area, while in the right hemispere synphasic relations are set up between the frontal and occipital zones. Naming the objects by the appropriate word as compared with rest and showing of the object, leads to enhancement of both intra- and interhemispheric correlations between potentials in the frontal zone and the inferior parietal and temporal zones. The frontal lobe rhythms begin to precede the inferior parietal and occipital potentials and form synphasic relations with the temporal and motor zone potentials in the left hemisphere.     

Axial shift of erythrocytes in arteries supplying blood to the cerebral cortex

In experiments with rabbits the widths of the axial flows of erythrocytes and of the parietal plasma layers were assessed in pial arterial ramifications supplying the cerebral cortex after their in vivo and in situ fixation under conditions of control and vasodilatation. A strict proportional relationship was revealed between the width of red cell flows and the diameter of pial arteries of 15-200 microns wide. However, the relative plasma volume in the microvessels below 50 microns in diameter was comparatively greater than in the larger vessels. The obtained results prove the feasibility of assessing the microvessels' diameters in tissues where one can see the red cell flow but the vascular walls are invisible. One of the reasons for the lower hematocrit in smaller blood vessels as compared to the larger ones was also elucidated.     

Pial arteriole dilation during somatosensory stimulation is not mediated by an increase in CSF metabolites

Pial arterioles supplying the hindlimb somatosensory cortex dilate in response to contralateral sciatic nerve stimulation. The mechanism of this pial vasodilation is not well understood. One possibility is that vasoactive metabolites released during brain activation may diffuse to subarachnoid cerebrospinal fluid (CSF) to dilate pial vessels. To test this hypothesis, we implanted closed cranial windows in rats and measured pial arteriolar dilation to sciatic nerve stimulation during constant rate superfusion of the pial surface with artificial CSF. We reason that flushing the pial surface with CSF should quickly dissipate vasoactive substances and prevent these substances from dilating pial arterioles. CSF flow (1 and 1.5 ml/min) significantly reduced pial arteriole dilation induced by 5% CO2 inhalation, but the same flow rates did not affect dilator responses to sciatic nerve stimulation. We conclude that brain-to-CSF diffusion of vasoactive metabolites does not play a significant role in the dilation of pial arterioles during somatosensory activity.     

Ouabain prevents loss of autoregulation in rat pial arterioles caused by reoxygenation after a brief hypoxic episode

Pial arteriolar diameter changes inversely with changes in systemic arterial blood pressure. Such changes are consistent with autoregulatory functions. These responses are reduced by a brief period of hypoxia followed by reoxygenation. By using an open cranial window preparation we assessed the changes in pial arteriolar diameters during blood pressure changes in rats induced by hemorrhage and reinfusion of blood, before and after a brief period of hypoxia. The slopes of the changes in pial arteriolar diameter as a function of mean arterial blood pressure were -0.47 +/- 0.26 micron/mmHg (mean +/- SD; 1 mmHg = 133.3 Pa) before hypoxia and -0.11 +/- 0.23 micron/mmHg after hypoxia in the untreated rats. In ouabain-treated rats, corresponding slopes were -0.42 +/- 0.24 and -0.46 +/- 0.22 micron/mmHg. The observed protective effects of ouabain might be a blockade of the Na-K pump in the sarcolemma of the vascular smooth muscle.     

Interrelations of the cerebral hemispheres in the cat in early stages of ontogeny

Multiple recording of transcallosal responses (TCRs) from different cortex areas has been carried out by means of acute experiments with immobilized and anesthetized kittens at the age of 1 to 30 days after birth. Homotopical TCRs in kittens at the age of 2-15 days appear earlier, are presented wider and reveal features of a greater maturity configuration and of amplitudinal-temporal parameters in association zone (parietal and sensorimotor) in comparison with projection zones (somatosensory, visual and auditory). Interhemispheric interrelations in association cortex of kittens are carried out not only by means of callosal but extracallosal system. In the course of animal developing in the parietal cortex the drain of the surface-positive oscillation moves from V to III layer and the drain of the surface-negative deviation remains at the level of II-III layers. The late component is registered up to the depth of III-IV layers, having the drain in I-II layers. In sensorimotor cortex the surface-negative oscillation has the drain in I-II layers, surface-positive--in III and V--VI layers. The interhemispheric asymmetry emerging from the moment of responses appearance is peculiar to TCRs of projection and association zones. In the first month of the postnatal development the asymmetry of positive and negative TCR oscillation amplitude has an individual character in sensorimotor cortex and a specific one--in parietal. The temporal parameters of TCR in association areas of the left hemisphere cortex are significantly shorter than of the right one. The data given testify to the possibility of interhemispheric interrelation realization and the presence of interhemispheric asymmetry in cat's brain on the early stages of postnatal ontogenesis.     

Evidence for Differing Origins of the Serotonergic Innervation of Major Cerebral Arteries and Small Pial Vessels in the Rat

We have studied the nature and origin of the serotonergic innervation of two distinct anatomical cerebrovascular compartments, namely, small pial vessels and major cerebral arteries, in the rat. To this end, the levels of serotonin [5-hydroxytryptamine (5-HT)] and 5-hydroxyindoleacetic acid (5-HIAA) were measured by HPLC in both cerebrovascular compartments after either bilateral sympathectomy or destruction of the ascending serotonergic pathways, which originate from the raphe nuclei. We first showed that the small pial vessel samples were not contaminated by underlying cortical tissues through the use of an immunohistochemical approach that revealed the glia limitans, the most superficial cortical layer. Superior cervical ganglionectomy caused a marked decrease in noradrenaline concentrations in major cerebral arteries (-77%), although the reduction was less pronounced (-34%) in small pial vessels. Sympathectomy decreased by 33% 5-HT concentrations in the major cerebral arteries but was without effect on 5-HT levels in the small pial vessels. Destruction of the ascending serotonergic pathways (via local administration of 5,7-dihydroxytryptamine into the ventral tegmental area) produced a dramatic fall in 5-HT and 5-HIAA concentrations in both vascular compartments. To establish the authenticity of the serotonergic innervation, the synthesis of 5-HT [as assessed by measuring the accumulation of 5-hydroxytryptophan (5-HTP) after decarboxylase inhibition] was measured in the two vascular beds under control conditions and after destruction of the ascending serotonergic pathways. The rate of accumulation of 5-HTP was higher in the small pial vessels than in major cerebral arteries, an observation that indicates an important de novo synthesis of 5-HT in small pial vessels.(ABSTRACT TRUNCATED AT 250 WORDS)     

Alteration of pial vessel responses to blood pressure changes in rats after hypoxia

Previous studies in newborn lamb have shown impairment of cerebral blood flow autoregulation after hypoxia followed by reoxygenation. The present study was done to see if such a phenomenon existed in the adult rat and if it could be demonstrated at the level of the pial arterioles. Using an open cranial window preparation, we assessed the changes in pial vessel diameter during blood pressure alterations induced by hemorrhage and reinfusion of blood, before and after 30 s of hypoxia, in 15 male Sprague-Dawley rats. Mean diameters of pial arteries in the study group of rats were 128 +/- 54 microns before hypoxia and 141 +/- 61 microns after normoxia following hypoxia. The corresponding diameters in rats serving as time controls were 136 +/- 52 and 138 +/- 52 microns. Slopes of pial vessel diameters as a function of mean arterial blood pressures decreased significantly (p less than 0.05) after hypoxia from -0.86 +/- 0.45 to 0.03 +/- 0.66 (mean +/- SD). In the control rats not subjected to hypoxia, the slopes remained unchanged over a similar time period (-0.60 +/- 0.16 and -0.42 +/- 0.19). The negative slopes indicate that pial vessels dilate during hypotension and constrict during hypertension. Such vascular responses may play a role in autoregulation of cerebral blood flow. We found that a relatively brief period of hypoxia can cause a long-lasting impairment of vascular responses even after restoration of normoxia. These findings are consistent with a previous report of persistent impairment of cerebral blood flow autoregulation after a brief period of hypoxia.     

Elasticity of arterioles and venules in postmortem human lungs

The elasticity and branching order of noncapillary microscopic blood vessels less than 100 microns diam were studied in human lungs obtained 7-30 h postmortem, using a silicone elastomer method that selectively filled pulmonary arterioles or venules. The lungs were inflated to 10 cmH2O pressure and a gradient of transmural vascular pressure of 0-17 cm H2O, from lobe base to apex, was established in the silicone-filled vascular system. Histological materials were obtained after airway fixation by formaldehyde solution and analyzed for vessel diameter in the branching order of 1, 2, and 3, with the smallest noncapillary vessel designated as order 1, in accord with the Strahler system. The change in vessel diameter within a branching order at different levels of transmural pressure is a derived measure of vascular elasticity expressed as compliance coefficient alpha, alpha Values are 0.128, 0.164, and 0.210 micron/cmH2O or 0.682, 0.472, and 0.354%/cmH2O, respectively, of orders 1-3 for arterioles and 0.187, 0.215, and 0.250 micron/cmH2O or 0.992, 0.612, and 0.424%/cmH2O, respectively, of orders 1-3 for venules. The percent is normalized with D0, which is the value of diameter (D) when the transmural pressure is zero. These data are compared with those for the cat where alpha = 0.274 for similar juxta-alveolar vessels.     

Dynamics of the direction of static connections in the electrical activity of the cerebral cortex in the cat

Data have been obtained on three cats for analysis of statistic connections of electrical activity in the visual, parietal and somatosensory cortical zones during development of evoked potentials to photic signal in these areas, and also in periods previous to photic stimulation and on traces of its action. An increase in shown of the influence of activity in the visual area on that of the somatosensory zone in post-stimulus periods and a sharp increase of two-way connections between these areas against the background of a relative equilibrium of direct and backward connections in trace periods.     

As human pial arteries (internal diameter 200-1000 microm) get smaller, their wall thickness and capacity to develop tension relative to their diameter increase.

Pial arteries play a key role in the regulation of human cerebral blood flow. However, many of the features and mechanisms that regulate the tone and diameters of these vessels cannot be studied in situ. One approach is to study in vitro segments of arteries obtained during neurosurgical procedures. The ratios of arterial media thickness to lumen diameter and of the capacity to develop wall force to lumen diameter have important functional consequences and are known to change in disease. Experiments were carried out on pial arteries from normotensive humans to determine the way in which these parameters vary with vessel size. Vessel dimensions--media thickness and lumen diameter were derived from fixed sections using quantitative morphometry. Wall force was measured using a resistance artery myograph. The ratio of media thickness to lumen diameter and of maximum tension developed to lumen diameter both increased as vessel diameter decreased. These ratios do not change over the age range of 15-75 years. These findings show that although in vivo intralumenal pressure falls as human pial arteries become smaller, their media thickness and capacity to develop tone increase.     

Seasonal changes in the adrenergic fibers in the wall of the microvessels of the cheek pouch of the hamster, Mesocricetus auratus

Adrenergic innervation has been investigated by fluorescent histochemical method with glyoxylic acid. Adrenergic fibers were found in summer period on the arterioles with a diameter varying from 100 to 30 micron, their fluorescence being significantly lower than that in the vessels of microcirculatory bed of the mesentery, tongue, femoral muscles of the same animal. No adrenergic fibers were revealed on the arterioles with a smaller diameter, on veins and venules. In winter period, fluorescence is completely absent from all the vessels of the cheek pouch, which may be due to the decrease in the level of catecholamines in the nerves and other tissues during hibernation.     

Ultrastructural localization of the membrane-bound Mg-adenosine triphosphatase activity in rat meninges

The distribution of the membrane-bound magnesium ions-dependent adenosine triphosphatase (Mg-ATPase) activity has been studied ultracytochemically in rat meninges by the method of Wachstein and Meisel (1957). A device specially constructed to avoid preparation artefacts has been used to obtain sections from the parietal region of the head. The meninges display an intense though irregularly distributed ATPase activity marked by depositions of electron-dense reaction product (RP) which is almost absent in the outer and middle dural layers. In the borderline zone between dura mater and the arachnoid the RP deposits are found at the outer surface of the inner dural cells and at the contact sites between these cells and the dural neurothelium. The intercellular cleft(s) between the neurothelium and the outer arachnoidal layer, occupied by an "electron-dense band", remains free of RP. The strongest accumulations of reactions granules are observed on the surface of the leptomeningeal cells of the arachnoidal space. In the contact region between the inner arachnoidal and the outer pial layers the distribution of the RP is similar to the one observed in the interface zone dura mater/arachnoid, while the pial cells themselves are definitely reaction-positive. In all meningeal vessels RP is found at the lumenal and abluminal aspects of the endothelium as well as at the cell membranes of the perivascular cells. These results emphasize the importance of the dural neurothelium for the functions of the blood-cerebrospinal fluid (CSF)-barrier between the dural blood vessels and the CSF.     

Effect of beta-neo-endorphin--an agonist of chi-opiate receptors on the neuronal activity of the cerebral cortex

Experiments on cats were made to examine the neuronal responses (the first zone of the somatosensory cortex and the 5th region of the parietal associative cortex) to microapplications of beta-neo-endorphine (an agonist of kappa-opiate receptors), morphine (an agonist of mu-opiate receptors), leuenkephalin (an agonist of delta-opiate receptors) and beta-endorphine (an agonist of mu, delta, epsilon-opiate receptors). beta-Neo-endorphine and other opioid peptides produced similar depressive changes in spontaneous activity. Naloxone in doses which block the depressive reactions of morphine, leu-enkephalin and beta-endorphine did not remove the depressive reactions of beta-neo-endorphine. Opioid peptides and morphine produced different changes in nociceptive-stimulated neuronal activity in the first zone of the somatosensory cortex and photostimulated neuronal activity in the 5th region of the parietal cortex. It is assumed that the different types of opiate receptors and their endogenous ligands (opioid peptides) play different functional roles in the preparation of the nociceptive and visual information in the cortex.     

Effect of adenosine receptor blockade on pial arteriolar dilation during sciatic nerve stimulation

In the present study, we report the effects of adenosine receptor antagonists on pial vasodilatation during contralateral sciatic nerve stimulation (SNS). The pial circulation was observed through a closed cranial window in alpha-chloralose-anesthetized rats. In artificial cerebrospinal fluid (CSF), SNS resulted in a 30.5 +/- 13.2% increase in pial arteriolar diameter in the hindlimb somatosensory cortex. Systemic administration of the selective adenosine A2A receptor antagonist, 4-(2-[7-amino-2-[2-furyl][3,2,4]triazolol[2,3-a][1,3,5]triazin-5-yl-amino] ethyl)phenol (ZM-241385), significantly (P < 0.05, n = 6) attenuated the SNS-induced vasodilatation. Systemic administration of 8-(p-sulfophenyl)theophylline (8SPT), a nonselective antagonist that is blood-brain barrier (BBB) impermeable, had no effect on vasodilatation to SNS. In contrast, systemic theophylline, which readily penetrates the BBB, nearly abolished the SNS-induced vasodilatation (P < 0.01; n = 7). Topical superfusion of 8SPT significantly (P < 0.01; n = 6) attenuated vasodilatation during SNS. Topical superfusion of 8- cyclopentyl-1,3-dipropylxanthine (DPCPX), a selective adenosine A1 receptor antagonist, significantly potentiated SNS-induced vasodilatation (P < 0.01; n > or = 5). Hypercarbic vasodilatation and somatosensory-evoked potentials were not affected by any of the compounds tested. Our findings suggest that luminal endothelial adenosine receptors are not involved in the arteriolar response to SNS, as demonstrated by a lack of effect with systemic 8SPT. Furthermore, the adenosine A2A receptor subtype appears to be involved in the dilator response to SNS. Finally, the neuromodulatory action of adenosine, via the A1 receptor subtype, significantly influences SNS-induced vasodilatation. Thus the present study provides further evidence for a role of adenosine in the regulation of CBF during somatosensory stimulation.     

Banding of the pulmonary artery in infancy: selection of patients and results of main pulmonary artery banding in the treatment of congenital heart disease.

Patterns of blood flow were examined in the surface vessels of the surgically exposed brain by intracarotid injection of 1% fluorescein and rapid serial photographs timed by a photo-cell signal. Matching colour filters were used for black and white or Ektachrome film.As developed in cats and monkeys, and applied in five patients during craniotomy, the technique gave a picture of flow patterns in the pial and cortical vascular bed, demonstrating “water-shed” areas bordering major arterial territories, laminar flow in veins, and, in particular, the details of filling and clearing in the fine pial vessels, the superficial cortical capillary bed and in the vascular beds of tumours.Since these features are rendered in finer detail and sharper contrast than by standard x-ray angiography, the method affords a new means of more adequately examining the epicerebral circulation in man during craniotomy for a variety of lesions.     

Intercentral interactions in the neocortex of 2-year-old children when exposed to verbal signals

It has been shown by the EEG correlation analysis method that perception by children of the third year of life of signal verbal stimuli consderably increases spatial synchronization of biopotentials as compared with the action of indifferent verbal stimuli. Perception and recognition of words is attended with involvement in the synchronous activity of potentials of the inferior parietal and frontal associative zones and the projection zone of the auditory analyser in the left hemisphere. In addition, children of the indicated age, as compared with a younger age, display an involvement in the sensory analysis of a word of the projection zones of the articulation apparatus, which establish an interconnection with the frontal zones of the dominant hemisphere.     

Temperature evolution in tissues embedded with large blood vessels during photo-thermal heating

During laser-assisted photo-thermal therapy, the temperature of the heated tissue region must rise to the therapeutic value (e.g., 43 °C) for complete ablation of the target cells. Large blood vessels (larger than 500 micron in diameter) at or near the irradiated tissues have a considerable impact on the transient temperature distribution in the tissue. In this study, the cooling effects of large blood vessels on temperature distribution in tissues during laser irradiation are predicted using finite element based simulation. A uniform flow is assumed at the entrance and three-dimensional conjugate heat transfer equations in the tissue region and the blood region are simultaneously solved for different vascular models. A volumetric heat source term based on Beer–Lambert law is introduced into the energy equation to account for laser heating. The heating pattern is taken to depend on the absorption and scattering coefficients of the tissue medium. Experiments are also conducted on tissue mimics in the presence and absence of simulated blood vessels to validate the numerical model. The coupled heat transfer between thermally significant blood vessels and their surrounding tissue for three different tissue-vascular networks are analyzed keeping the laser irradiation constant. A surface temperature map is obtained for different vascular models and for the bare tissue (without blood vessels). The transient temperature distribution is seen to differ according to the nature of the vascular network, blood vessel size, flow rate, laser spot size, laser power and tissue blood perfusion rate. The simulations suggest that the blood flow through large blood vessels in the vicinity of the photothermally heated tissue can lead to inefficient heating of the target.