bluuebunny/crossref_metadata_2025 huggingface dataset:
Physiologic Variability of Vascular Access Blood Flow for Hemodialysis
Authors: Válek Martin , Lopot František , Dusilová-Sulková Sylvie , Polakovič Vladimír
Published: September 2008

Aim: To assess the variability of blood flow (QVA) through a native arteriovenous fistula (AVF) in the long-term and to determine the QVA reduction at which an intervention is appropriate. Patients and Methods: The study was performed in a group of 34 chronic hemodialysis patients with no history of a AVF intervention. QVA was measured using the thermodilution method (Blood Thermodilution Monitor, Fresenius). Median follow-up was 41 months and the median number of QVA measurements in each patient was 15. The coefficient of variation (CV) of QVA was calculated for each patient. Results: Mean QVA was 904 ± 334 ml/min. The mean CV was 23.3 ± 11.2%. Conclusion: QVA may fluctuate during a long-term follow-up period. The detection of QVA decrease by 20–25% could be still within physiological limits. Based on the results we recommend to first repeat the measurement at a shorter interval and to refer the patient to a radiologist only when the decreasing trend is confirmed.
When Should Renal Replacement Therapy for Acute Kidney Injury Be Initiated and Discontinued?
Authors: Gibney R.T. Noel , Bagshaw S.M. , Kutsogiannis D.J. , Johnston C.
Published: September 2008

Background: Critically ill patients with acute kidney injury (AKI) are at high risk for death and frequently require initiation of renal replacement therapy (RRT). There is wide variation in clinical practice on the indications for and timing of initiation and discontinuation of RRT. Numerous clinical and biochemical factors (i.e. uremic, metabolic, fluid balance) have been used; however, at present there is no consensus to guide clinicians on the most favorable time to initiate and/or discontinue RRT to optimize patient outcomes. Methods: In this review, we appraise the available clinical studies that have assessed timing of initiation and/or discontinuation of RRT for critically ill patients with AKI. ‘Timing’ of initiation has been variably defined including use of conventional biomarkers (i.e. serum urea and creatinine), urine output, fluid balance, and time relative to intensive care unit admission. Conclusions: Numerous studies consistently point toward a survival benefit to early initiation of RRT; however, there is a paucity of high-quality randomized trials. If early RRT is associated with clinical benefit, it remains uncertain whether this is attributable to more rapid metabolic/uremic control, management of fluid balance or a combination of clinical factors. In addition, timing of RRT initiation is likely context-specific and varies by clinical factors and/or etiology of AKI. There is also little data to accurately distinguish in advance between the injured kidney that will need extracorporeal renal support and one that retains capacity for early recovery. Fewer studies have evaluated the process of weaning of RRT or ideal methods to predict sufficient recovery to avoid re-initiation. Longer duration of RRT support, higher illness severity and lower urine output (independent of diuretic therapy) have all predicted need for re-initiation. Additional investigations on these issues are clearly warranted and urgently needed.
Non-Enzymatic Glycation of Human Fibrillin-1
Authors: Atanasova Milena , Konova Emiliana , Betova Tatiana , Baydanoff Stephan
Published: September 2008

Non-enzymatic glycation of proteins is one of the key mechanisms in the pathogenesis of diabetic complications and may be significant in the age-related changes of tissues. We isolated and investigated the in vitro glycation of human aortic fibrillin-1. Fibrillin-1 was prepared from thoracic aortas of 9 accident victims distributed in three age groups. The purity of isolated fibrillin-1 was proved. It was glycated by incubating with different glucose concentrations in 0.2 M phosphate buffer, pH 7.4, for 30 days, at 37°C. The degree of early products of glycation was measured by two colorimetric methods, i.e. nitroblue tetrazolium and 2-thiobarbituric acid. Advanced glycation end products (AGEs) were determined by fluorescence measurement. The highest level of early products of glycation was found on day 2 after the beginning of incubation for the fibrillin-1 isolated from the youngest group. Fluorescence in the age groups, as an index of advanced glycation, consistently increased between days 6 and 24. The fibrillin-1 isolated from the youngest group had the highest capacity to form fructosamine and AGEs under glycation in vitro. The capacity of glycation of the ‘oldest’ fibrillin did not increase significantly during the incubation. Investigation of the properties of glycated fibrillin-1 will help to understand the importance of this long-lived protein to age-related changes in tissues and for diabetic complications.
Druggable Targets and Targeted Drugs: Enhancing the Development of New Therapeutics
Authors: Billingsley Melvin L.
Published: September 2008

The advent of functional genomics, proteomics, chemi-informatics, and other systems-based scientific approaches have raised expectations of novel targets for drug discovery and design. Similarly, advances in materials sciences and biomolecular chemistries raised the prospects of highly targeted therapeutics that maximize efficacy while minimizing systemic toxicity. In spite of these advances, the gross measure of approvable drug output is declining, with only 17 new chemical entities approved by the FDA in 2007. This is in the face of high levels of R&D expenditures in both public and private sectors, and suggests that new, integrative approaches are needed in order to maximally exploit the rapidly expanding knowledge of potential drug and disease targets. The convergence of novel druggable targets with new chemical entities that can be specifically targeted to disease-causing sites and genes represents one means of creating highly efficacious and specific therapies. The approaches that are needed to facilitate such convergence include merging computational methods, systems biology, and gene-linked categorization of diseases with the use of appropriate drug delivery vehicles.
Forearm Venous Reflex Activity in Normal and Essential Hypertensive Subjects
Authors: Harrison, Jr. L.H , Frohlich E.D.
Published: September 2008

Superficial forearm venous pressures, taken at rest and following rapid arterial occlusion, were measured in 11 normal and 14 essential hypertensive subjects, together with the changes in venous pressure induced by reflexogenic maneuvers (cold, Valsalva, hyperventilation, upright tilt) with the forearm circulation arrested. No significant difference was found in either the resting venous pressures (8.7 ± 0.9 mm Hg and 7.8 ± 0.6 mm Hg, respectively), the occluded venous pressures (20.7 ± 1.7 mm Hg and 19.7 ± 2.2 mm Hg), or the reflex venoconstrictor responses of the two groups (cold: 12.1 ± 2.7 mm Hg and 14.4 ± 2.3 mm Hg; Valsalva: 8.4 ± 2.1 mm Hg and 8.8 ± 1.2 mm Hg; hyperventilation: 7.5 ± 1.8 mm Hg and 6.8 ± 1.1 mm Hg; 50° tilt: 6.7 ± 0.9 mm Hg and 6.6 ± 1.4 mm Hg). It is suggested that, even with normal venous pressure and reflex venomotor reactivity, other venous abnormalities might explain certain hemodynamic changes observed in essential hypertension.
Revascularization of Severe Ischemic Legs
Authors: Bartoš J. , Vančura J. , Teršíp K.
Published: September 2008

This report deals with tibial arteries revascularizations performed on 28 patients since the year 1966 at the 1st Surgical Clinic of the Charles University of Prague, Czechoslovakia. Severeischemic changes with rest pain and necroses were the indications in 22 patients. In all cases a special method was used. It is a combination of semi-closed Thromboendarterectomy with saphenous vein bypass which is led along the vessels in the popliteal fossa to tibial arteries as far as the ankle region. This combination enables successful revascularization also in patients without a suitable saphenous vein.
Multifocal Fibrotic Diathesis
Authors: Verstraete M. , Vandenbroucke J.
Published: September 2008

A superior vena cava syndrome most often results from an intrathoracic tumor; a frequent cause of the inferior vena cava obstruction is a proximal expansion of a thrombophlebitis. When both causes can be excluded and patient survives the initial symptoms for years, a chronic fibrosis in the mediastinum or (and) in the retroperitoneum have to be suspected as locations of a multifocal fibrotic diathesis.
The Significance of Synchronization in Syncardial Massage
Authors: Valtonen E.J. , Lilius H.G.
Published: September 2008

According to the inventor of the syncardon the pressure impulses of the cuff must be synchronized with the heart rhythm of the patient. In the present study ten volunteers were treated according to the original method and without the synchronization with the heart rhythm. The results showed that the syncardial massage was able to effect in the same way when given either with synchronization or without it. The electrocardiographic triggering of the syncardon apparatus, and the synchronization itself, seem to be unnecessary.
Capillary Filtration under Normal and Pathological Conditions
Authors: Thulesius Olav
Published: September 2008

The present study summarizes previous studies about the principle of measuring capillary filtration coefficients in animals and humans. Some observations have been presented as to the technical aspects of measurement and changes of capillary filtration due to muscular exercise, infusion of vasodilating substances and arterial occlusion. The mechanism of altered capillary filtration is discussed.
The Effect of Oedema on the Electric Conductivity of the Subcutaneous Tissue
Authors: Hladovec J. , Přerovský I.
Published: September 2008

The conductivity of subcutaneous tissue was measured in rats with various types of experimental oedema. The measured values depended on the water content in tissues and not on the origin of oedema. The conductivity measurements of the subcutaneous tissue above the ankles were also used in patients with several types of clinical oedema in comparison with a group of normal subjects. The method is simple and well reproducible. It is suitable particularly for the evaluation of changes in oedema development.
Surgical Treatment of Ischemic Heart Disease
Authors: Bartoš J. , Pokorný J. , Petz R. , Vančura J. , Volek V. , Mildeová E.
Published: September 2008

In experimental work on 134 dogs, the authors succeeded in verifying a non-suture end-to-end method of vessel anastomosis for the purpose of heart revascularization. Instead of usual steel tubes, the authors used fibrin tubes which make the method more suitable for clinical use also. This method seems to be more advantageous especially for operation on coronary arteries of very small peripheral diameter and possibly for the treatment of acute infarction, too. Besides, it was proved that the best way to prevent ventricular fibrillation after revascularization is the intermittent and gradual release of the blood flow through the anastomosis. The question of possible diagnosis of an unsuccessfull operation during the postoperative course was also studied. It was found that besides electrocardiographical and coronarographical examinations, the plasma-enzyme level (especially SGOT) may be of some help in solving this question.
Isolated Skeletal Muscle Blood Flow and Volume Changes during Contractile Activity
Authors: Baker Carleton H. , Davis Darrell L.
Published: September 2008

Dog gracilis muscles were removed, enclosed in a plethysmograph and perfused at an inflow pressure of 110 mm Hg. Venous outflow pressure was 3 mm Hg. Circulating blood volumes were measured by the constant infusion technique using RBC-51Cr (9 muscles) or albumin-131I (11 muscles). Volumes were calculated from the infusion and from the washout of the indicator. Skeletal muscle contraction was produced by stimulation of the gracilis nerve stump with supramaximal stimuli at 2-15 Hz for 15-60 sec. Volume changes during and following the stimulations were measured by plethysmography and by changes in total muscle radioactivity. Inflow and outflow were also measured. Changes in interstitial fluid volume were calculated as the difference between total tissue and vascular volume changes. Blood volume increased at all contraction rates. Total tissue volume initially decreased during the contraction period and then returned to control. Extravascular volume decreased markedly during the initial period of contraction and then increased above control, returning to the control level following the end of the stimulation. The tissue pressure markedly increased during the contractions causing fluid movement into the vascular system. Minimal loss of labeled albumin during the period of contraction indicated capillary permeability was not altered.
Lithium Substitution Analysis of Na and K Phases in a Small Artery
Authors: Friedman Sydney M. , Mar Maryette , Nakashima Miyoshi
Published: September 2008

Cell Na in the rat tail artery was measured by replacing all extracellular Na with Li at 2°C. Water was partitioned with 14C-sorbitol as the marker. The binding capacity of the cytoplasm was estimated by ion-exchange after the destruction of cell membranes by alternate freezing and thawing. Cell Na is of the order of 20–25 mEq/kg dry weight and about 2/3 of this may be in free solution with [Na]i in the range of 15 mEq/liter. Cell K is about 220 mEq/kg dry weight and, of this, 30 mEq or more is bound so that [K]i is not greater than 190 mEq/liter. These estimates allow only for the low figure of 30 mEq as the sum of site-bound cell monovalent cations. It is shown, however, that as much as 50-60 mEq may be site-bound or otherwise restricted within the cell. A similar amount, mostly Na+, is site-bound within the paracellular matrix.
Role of Calcium in Different Layers of Vascular Smooth Muscle in Norepinephrine Contraction
Authors: Turlapaty Prasad D.M.V. , Hester Kelly , Carrier, jr. Oliver
Published: September 2008

The role of calcium present in adventitial and media-intimal layers of rabbit aorta in the fast (F-) and the slow (S-) components of norepinephrine (10-5m) contraction was evaluated in this study. An increased sensitivity and decreased maximum tension to response to norepinephrine was observed in adventitia-free aorta as compared to whole aorta. Incubation in calcium-free Ringer solution with or without EDTA decreased the F-component of norepinephrine contraction of the adventitia-free aorta, whereas the F-component of the whole aorta was not affected. The S-component of both preparations was abolished in calcium-free Ringer solution. Norepinephrine increased calcium uptake into whole and adventitia-free aortic strips. An increase in calcium uptake induced by norepinephrine during the F-component of norepinephrine contraction was also observed. 45Ca efflux studies revealed the presence of an exchangeable calcium fraction in the adventitial layer. These data suggest that the F-component of norepinephrine contraction is partially dependent on the extracellular calcium distributed in the adventitial layer of rabbit aorta.
Responsiveness of Isolated Dog Veins to Bradykinin and other Bioactive Peptides: Distribution of Sensitivity to Bradykinin and Possible Correlation with Genesis of the Venous System
Authors: Tsuru Hiromichi , Ishikawa Naohisa , Shigei Tatsuro
Published: September 2008

Contractile responses of isolated dog veins to bradykinin were studied. Responses to norepinephrine were taken as standards. According to their sensitivity to bradykinin, the veins obtained from 14 sites of the venous system were divided into two groups, while all the veins were almost uniform in their sensitivity to norepinephrine. One group has high sensitivity to bradykinin and the other has low sensitivity. The former includes the pulmonary, hepatic, splenic, and portal veins, the anterior vena cava, and the upper and the middle divisions of the posterior vena cava. The latter includes the external jugular, cephalic, azygos, femoral, and saphenous veins, and the lower division of the posterior vena cava. The responses of the renal vein were intermediate. A striking correlation was noted between the distribution of bradykinin sensitivity and the genesis of the venous system. Five bioactive peptides other than bradykinin were also studied. Only angiotensin induced contraction in some preparation, but, as a whole, caerulein, eledoisin-related peptide, oxytocin and vasopressin rarely showed contractile activity.
On the Measurement of Vascular and Respiratory Smooth Muscle Responses in vitro
Authors: Hooker Carol S. , Calkins Patricia J. , Fleisch Jerome H.
Published: September 2008

The action of drugs on circular smooth muscle from rabbit renal artery, renal vein, mesenteric vein, inferior vena cava, guinea pig bronchus, and mouse trachea was studied using an inexpensive modification of the method of Bevan, Nielsen and Ovvman, and Bevan and Osher. Two 30-gauge disposable stainless steel hypodermic needles supported the tissue rings in a standard 10-ml isolated muscle bath. All the blood vessels contracted to norepinephrine, histamine, and KCl. The veins, unlike the renal artery, did not respond maximally to KCl and did not contract at all to serotonin. The guinea pig bronchi contracted to carbachol, histamine, and KCl and relaxed to isoproterenol. The mouse trachea contracted maximally to carbachol, did not contract to histamine, and contracted to 50% of maximum in response to KCl. Thus, standard isolated tissue baths can be inexpensively adapted for the study of relatively small blood vessels and airways (about 1 mm in diameter).
Development of Neuroeffector Mechanisms in the Carotid Artery of the Fetal Lamb
Authors: Su C. , Bevan J.A. , Assali N.S. , Brinkman, III C.R.
Published: September 2008

A survey has been made of mechanisms associated with vascular adrenergic neuroeffector transmission in the lamb fetuses between 53 days and term gestation. The common carotid artery was isolated for studies of enzymic activities, uptake of norepinephrine (NE) and reactivity to vasoactive agents. The extra-neuronal NE uptake, monoamine oxidase and catechol-O-methyltransferase activities were present in the carotid artery of the youngest fetuses. The contractile responses to NE and serotonin and neuronal NE uptake preceded the response to adrenergic nerve stimulation during fetal growth. These results suggest that the mechanisms for adrenergic transmitter inactivation, transmitter action on vascular smooth muscle cells, and neuronal transmitter delivery develop in that sequence.
Vascular Adenylate Cyclase: Role of Age and Guanine Nucleotide Activation
Authors: Cohen Marlene L. , Blume Arthur S. , Berkowitz Barry A.
Published: September 2008

Particulate adenylate cyclase activity was examined in broken cell preparations of rat aorta and mesenteric artery from 3- to 5- and 9- to 13-week-old rats. While basal adenylate cyclase activity of the mesenteric artery was 4-fold greater than aortic enzyme activity, there was no difference in enzyme activity with age. GTP and the GTP analogue, 5’-guanylylimidodiρhosphate [Gpp(NH)p] stimulated adenylate cyclase activity. Stimulation by Gpp(NH)p did not differ with age for either tissue and occurred without a detectable lag. The vasodilators, isoproterenol, 2-chloroadenosine and prostaglandin E1, were ineffective in increasing adenylate cyclase activity, although marked stimulation was demonstrated with both sodium fluoride and Gpp(NH)p. Even in combination with Gpp(NH)p, isoproterenol did not increase particulate adenylate cyclase activity of these blood vessels; however, with intact arteries, isoproterenol (10–7 M) did increase aortic and mesenteric cyclic AMP levels. Isoproterenol increased cyclic AMP levels in rats of both ages, at a time when isoproterenol was less effective in maximally relaxing aortic strips from 9- to 13-week-old rats. These data indicate that diminished aortic relaxation with age is not associated with a reduced ability of vascular relaxants to increase aortic cyclic AMP levels. Furthermore, as a first step in establishing that guanine nucleotides are regulators of vascular adenylate cyclase, both GTP and Gpp(NH)p were found to be potent activators of adenylate cyclase from blood vessels.
Ca++-Binding Properties of Canine Aortic Microsomes: Lack of Effect of c-AMP
Authors: Allen Julius C.
Published: September 2008

Ca++ binding to a microsomal fraction from canine aorta has been studied and compared to Ca++ binding to canine cardiac microsomes. The aortic microsomes bound up to 60 nmoles Ca++/mg protein with a first-order binding rate constant of 0.025 sec–1. The binding rate in 5 sec was about half that of cardiac microsomes, 8 versus 15 nmoles/mg. The Ca++ binding to the aortic microsomes had a pH optimum of 7.4, was inhibited by monovalent cations and showed ATP preference when compared to other nucleotides. The binding was not stimulated by the presence of oxalate. c-AMP stimulated incorporation of 32P into the preparation, but had no effect on Ca++ binding.
Repair in Arterial Tissue
Authors: Christensen Bent Collatz , Tkocz Izabella
Published: September 2008

The effects of various numbers of intravenous toxic doses of noradrenaline observed at various time intervals after the injections were studied by scanning electron microscopy (SEM) and surface light microscopy of silver-stained rabbit thoracic aorta and by transmission light microscopy. Hexagonal endothelium: a conspicuous change was observed by SEM and surface light microscopy, increased with the length of observation time, and to a certain degree with the number of noradrenaline injections; this change occurred coincidently with development of media necroses, intimal thickening, dilatation of the vessel and various gross changes. Silver-binding endothelial cells: a discrete lesion prevailed in experiments based on one injection of noradrenaline and seemed partly independent of time of observation. The nature of these cells and their role in the morphology of noradrenaline lesion remained obscure. Hexagonal endothelium and silver-binding endothelial cells may have a partial common pathogenetic mechanism, but a mutual relationship was improbable.
Magnesium and Vascular Tone and Reactivity
Authors: Altura Burton M. , Altura Bella T.
Published: September 2008

It has been reported that the concentration of extracellular magnesium ions ([Mg++]o) can affect blood flow, blood pressure and vascular reactivity in intact mammals. The present studies, using a variety of rat and rabbit blood vessels, were undertaken to shed further light on the relationship between [Mg++]o, Ca++, tone and vascular responsiveness. [Mg++]o was found to differentially affect a variety of hormone and drug-induced contractions in isolated rat and rabbit arteries as well as isolated perfused rat mesenteric arterioles (15–20 µm i.d.). Progressive elevations in [Mg++]o above physiologic levels will dose-dependently produce progressive, increased inhibition of most contractile substances. These results are not reflections of osmolarity. Withdrawal of [Mg++]o can induce contractions of rat arteries as well as of isolated perfused rat mesenteric arterioles. Using isolated rat portal veins, withdrawal of [Mg++] results in rapid enhancement of the spontaneously evoked mechanical responses and increases in rhythmic contractility; these spontaneously evoked responses are abolished in hypermagnesemic solutions (e.g., 10 mM). The contractile responses observed upon withdrawal of [Mg++]o are dependent upon the [Ca++] and the polarity of the membrane but are not related to inhibition of Na+, K+ ATPase. With rat aortic strips, addition of CaEDTA potentiates contractions induced by Mg++ withdrawal, while EGTA promotes rapid relaxations. Rapid relaxations of contractions induced by Mg++ withdrawal in rat aorta could also be induced by Mn++, Ni++, Co++ and Cd++ but not Sr++. Addition of [Ni++] to portal veins exposed either to a Mg++-free solution, or to a solution containing Mg++, results in dose-dependent, and eventual complete, inhibition of all spontaneous mechanical events. These data suggest that [Mg++]o: (a) plays an important role in regulating membrane permeability to [Ca++]o; (b) probably occupies sites which are exchangeable with membrane-bound Ca in arterial, venous and arteriolar smooth muscle; (c) acts intracellularly as well to compete with Ca for certain divalent cation sites; and (d) may play an important role in regulating arteriolar tone and blood pressure.
Vascular Resistance and Reactivity of the Microcirculation in Hypertension
Authors: Folkow Björn , Hallbäck Margareta , Noresson Eddy
Published: September 2008

This brief review summarizes the author’s current understanding of the circulatory changes in hypertension. Differences in four important regulatory systems are dependent on structural changes: (1) An increase in wall-to-lumen ratio of precapillary resistance vessels is responsible for an increase in vascular reactivity, or ‘structural autoregulation’. (2) A structural change primarily in the preglomerular arteriole causes a resetting of the pressure required for glomerular filtration. This serves a ‘long-tem barostatic function’. (3) Stiffening of the aorta and other pressure-sensing systems contributes to a resetting of baroreceptors bringing about a reset of the ‘short-term barostats’. (4) Left ventricular hypertrophy causes a decrease in compliance, hence tending to decrease stroke volume for a given filling pressure. Functional changes such as increased neurogenic activity may serve as important ‘trigger’ elements in spontaneously hypertensive rats and at least in one important variant of essential hypertension in the human. An example of a functional alteration in vascular smooth muscle is found in that the vascular resistance response in the spontaneously hypertensive rat in low calcium concentration (0.2 mM) is better maintained than in the normotensive control rat, but this alteration seems to be secondary in nature. An experiment is described which permits simultaneous assessment of the responses of capacitance and resistance vessels to nerve stimulation: when the splanchnic nerves are stimulated there is a simultaneous decrease in venous capacity and an increase in resistance in the liver, gastrointestinal tract and kidneys. The decrease in venous capacity is reflected in an increase in stroke volume whereas the increase in regional resistance is evidenced in an incraese in total peripheral resistance. Using this index the spontaneously hypertensive rats had a less efficient capacitance response (possibly due to the decrease in ventricular compliance) and a greater resistance response than did the normotensive control rat. Although both functional and structural changes in the cardiovascular system occur, the rapidly developed structural changes appear to be the major determinant of the differences between normal and hypertensive hemodynamics.
Vasoconstrictor and Dilator Actions of Nicotine and Electrical Transmural Stimulation on Isolated Dog Cerebral Arteries
Authors: Muramatsu Ikunobu , Fujiwara Motohatsu , Osumi Yoshitsugu , Shibata Shoji
Published: September 2008

Effects of nicotine and electrical transmural stimulation on isolated dog cerebral arteries were studied. Nicotine (5 × 10–8–10–4 m) usually evoked a phasic contraction in the basilar artery and a relaxation in the middle cerebral artery. The nicotine-induced contraction and relaxation were abolished by pretreatment with pentolinium (10–5 m) but not by tetrodotoxin (TTX) (10–7 m). Phentolamine (10–6 m) or bretylium (10–5 m) abolished or reversed the nicotine-induced contraction, and partially reduced the nicotine-induced relaxation. Electrical transmural stimulation elicited a phasic contraction in the basilar artery and a relaxation or slight contraction in the middle cerebral artery. The contraction induced by transmural stimulation was abolished by bretylium and TTX, and augmented by phentolmine. The relaxation was not inhibited by bretylium. The uptake of 3H-norepinephrine (3H-NE) by the basilar and middle cerebral arteries was markedly reduced by cocaine (3 × 10–6 m). Nicotine and transmural stimulation increased the tritium efflux from both arteries. The nicotine-induced increase in tritium efflux was inhibited by pentolinium. The increased efflux induced by transmural stimulation was abolished by TTX, attenuated by bretylium, and augmented by phentolamine. These results indicate that nicotine and transmural stimulation cause both vasoconstrictor and vasodilator effects in the dog cerebral arteries and that the vasoconstriction is mediated through an adrenergic mechanism.
Partial Purification of Renal Lysosomal Substances Producing Angionecrosis and Increased Vascular Permeability
Authors: Nakamura Motoomi , Kai Mieko , Kanaide Hideo , Kurozumi Takeshi , Yamamoto Yoriko , Yamamoto Hiromichi , Kato Keitaro
Published: September 2008

The lysosomal contents of hog kidney cortex, which induce angionecrosis and/or an increase of vascular permeability, were obtained by differential centrifugation and osmotic shock treatment, and were purified by various chromatographic techniques and electrophoresis. The material producing an increase in vascular permeability of the rabbit skin was purified 600-fold over the homogenate; however, it showed practically no angionecrotic activity. Another substance producing angionecrosis without pressor activity was partially purified.
Pharmacological in vitro Analysis of Amine-Mediated Vasomotor Functions in the Intracranial and Extracranial Vascular Beds
Authors: Owman C. , Edvinsson L. , Hardebo J.E.
Published: September 2008

The cerebrovascular system (the extra- as well as intracerebral vessels) receives a well-developed innervation by the adrenergic (originating in the superior cervical sympathetic ganglia) and cholinergic nerves. In addition, recent immuno-histochemical studies have shown the presence of vasodilatory peptidergic nerve fibres. There may be an association of cerebral blood vessels also with various aminergic nerve systems of intracerebral origin. Besides the nerves, amine-containing mast cells are often located in close relation to the brain vessels. The specific receptors mediating the contractile and dilatory response of the various vasoactive amines – noradrenaline, dopamine, 5-hydroxytryptamine, histamine, acetylcholine – have been characterized in detail in pharmacological experiments. There is a number of major differences in the reactivity of cerebral vessels as compared to vasomotor functions in the peripheral circulation. The observations and results provide a basis for a better understanding of physiological neurogenic control mechanisms in the cerebral circulation, and they may also have implications for the interpretation of pathophysiological phenomena related to, for example, migraine and the vasospasm following subarachnoid hemorrhage.
Differences in the Response of Three Embryologically Distinct Segments of the Isolated Canine Posterior Vena cava to Vasoactive Substances
Authors: Shigei Tatsuro , Ishikawa Naohisa , Ichikawa Tomohiro , Tsuru Hiromichi
Published: September 2008

The canine posterior vena cava was excised and divided into three embryologically distinct segments: segment A (supradiaphragm), segment B-C (intra-hepatic and that between liver and renal veins), and segment D (infrarenal). Circular and longitudinal strips were cut from each segment, suspended in Krebs bicarbonate solution and isometric tensions were recorded. The responses to six vasoactive agents, as well as transmural neural stimulation were studied. Maximum tension and ED50 were obtained for norepinephrine, epinephrine, acetylcholine, bradykinin, histamine and 5-hydroxytryptamine (5-HT). The responses were not only quantitatively, but qualitatively different among the three segments. Bradykinin constricted the strip:; in A and B-C but not in D. 5-HT (<10–5 m) caused a dose-dependent contraction in A and D through its direct stimulating action, while in C, a contractile response appeared only after administration of a higher dose of 5-HT. This was due to an indirect sympathomimetic action of the agent. Segment B-C, which histologically contained massive longitudinal muscle bundles in the outer layer of the wall, exhibited spontaneous, rhythmic contractions. The existence of a cholinergic excitatory innervation, in addition to adrenergic, was demonstrated in C by transmural neural stimulation.
Atherogenic Mechanisms: Enhancement of Regression of Atheromatous Lesions by Phthalazinol
Authors: Shimamoto Takio
Published: September 2008

Atherosclerosis was produced in rabbits by feeding 1% cholesterol pellets for 15 weeks to 35 male rabbits divided into two equal groups – the placebo control and phthalazinol group – with a comparable serum cholesterol level. The phthalazinol group was given 20 mg/kg of the compound daily. 13 rabbits of both groups were on 15 weeks of the treatment and the remaining 22 rabbits were treated for 30 weeks. The treated group exhibited a statistically significant increased removal of cholesterol from atherosclerotic aortas and improvement in pathological changes. This enhancing effect was more marked in the animals treated for 30 weeks. Such evidence indicates that there are substances capable of enhancing the removal of cholesterol from atheromatous lesions. In light of the pharmacological properties of phthalazinol, the possible role of thromboxane A2 released from platelets adhered and aggregated on atheromatous plaques, in the progression of atherosclerosis is worthy of continued investigation.
High-Energy Phosphate Metabolism of Isolated Coronary Arteries in the Dog
Authors: Takenaka Fumio , Sakanashi Matao , Higuchi Makie
Published: September 2008

The correlation between phosphate metabolism and isometric contraction was investigated in helical strips from dog coronary artery. Adenosine triphosphate (ATP) and creatine phosphate (CP) contents of resting strips did not significantly change during anoxia. ATP content remained unchanged during potassium-contracture under aerobic conditions but was significantly reduced by anoxia. Pre-treatment with iodoacetate resulted in a striking reduction in ATP content with a less marked decrease in CP content. ATP-depleting effect of iodoacetate was reduced slightly by the addition of pyruvate, but contractile response was not restored. It is considered that high-energy phosphates provided by anaerobic glycolysis can meet the energy requirements of resting coronary vessels but are insufficient for maintaining active tension. In resting strips equilibrated for 2 h in oxygenated bath solution, the reactivity to KC1 and anoxia appears to be dependent on the availability of ATP.
Role of Vasa Vasorum in Nourishment of the Aorta
Authors: Heistad Donald D. , Marcus Melvin L.
Published: September 2008

The media of arteries is virtually avascular. Thus, oxygen and nutrients must reach the cells of the media by diffusion from the lumen of the vessel and from adventitial vessels. The thickness of the thoracic aorta of man and dog exceeds the effective diffusion distance of oxygen, but nutrition is supplemented by vasa vasorum which enter into the outer layers of the media. Occlusion of vasa vasorum in dogs produces medial necrosis, which indicates that these vessels are essential for the nourishment of the aorta. Recently the microsphere method has been used to provide the first measurements of blood flow through vasa vasorum. There is substantial flow to the outer layers of media of the thoracic aorta in dogs, with virtually no blood flow in the inner layers. The vessels are very responsive to physiological stimuli: they dilate during infusion of adenosine and constrict during stimulation of sympathetic nerves. During acute increases in arterial pressure, blood flow to the media decreases probably from distortion of vasa vasorum. Vasa vasorum may play a role in disease states. Insufficient blood flow through vasa vasorum may contribute to medial necrosis of the aorta and to aortic atherosclerosis. A role of vasa vasorum in aortic changes in hypertension and other vascular diseases merits further study.
Vasoactive Material Present in the Glomerula Caudalia of the Vervet Monkey
Authors: Wright P.G. , Wormald W.
Published: September 2008

Complex encapsulated neurovascular structures, glomus organs, occur in superficial and deep positions in many species. No direct evidence for their function exists. In skin they may serve thermoregulation but the reason for their structural complexity remains obscure. The concept of a local humoral circulatory control mechanism postulated on the basis of a very high acetylcholine content reported for human glomera coccygia has been investigated in homologous caudal glomus organs in monkey. No acetylcholine was detected. The organs contained 3-4 times the concentration of catecholamine (mainly noradrenaline) found in nearby vessels. Neither structure nor content of vasoactive component gives any support for an endocrine function.
Ultrastructural Features of Mast Cells in Human Omental Veins
Authors: Thureson-Klein Åsa , Stijärne Lennart
Published: September 2008

Mast cells are relatively common in human omental veins where they generally occur in the tunica adventitia and among the peripheral smooth muscle cells of the tunica media. The distance between mast cells and adjacent muscle cells is often as short as 1 µm. The tunica intima does not contain mast cells. With few exceptions the typical mast cells were oval in shape, had numerous slender projections and contained granules (0.3–0.7 µm) with characteristic stacks of lamellae and scrolls. A few elongated cells with processes containing granules filled with dense homogeneous matrix material were also detected and could represent so-called chromaffin mast cells. Noradrenergic axons and terminals identified by their large (85 nm) and small (50 nm) dense-cored vesicles are present in the vicinity of many mast cells which could allow various interactions between the two cell types and their released amines and ATP. Electrical field stimulation which affects the nerve terminals does not change the ultrastructure of the mast cells unless the α-blocking agent phentolamine (7.5 × 10-7 M) is present during the stimulation, when degranulation results.
Isolated Brain Microvessels: Preparation, Morphology, Histamine and Catecholamine Contents
Authors: Head R.J. , Hjelle J.T. , Jarrott B. , Berkowitz B. , Cardinale G. , Spector S.
Published: September 2008

A method for the rapid preparation of parenchymal microvessels from rat, rabbit and bovine brains is described. Light and electron microscopic examination of the isolated microvessels showed the smooth muscle and endothelial cells to be intact and substantially free of neutrophil contamination. The observation of 0.2 to 2.0 µm electron dense granules in the adventitial space associated with some of the isolated arteriolar elements and the identification of histamine in microvessel extracts is suggestive of the presence of mast cells in the microvessel preparations. Age-dependent changes in histamine content and an increased histamine content in microvessels from hypertensive rats were noted. Using a sensitive radioenzymatic assay, the catecholamine (CA) contents of microvessels isolated from cow, rat and rabbit were measured. The total CA contents of all microvessel preparations were small (<0.35 µg g–1) with norepinephrine being the predominant CA present. A large ratio of dopamine to norepinephrine was found in microvessels from rat and bovine brain. The possible origins of the CAs present in the isolated microvessels are discussed.
Effects of Tolbutamide and Glyburide on Glucose and Acetate Incorporation into Aortic Lipids of the Dog
Authors: Yelich Michael R. , Whitney John E.
Published: September 2008

The use of oral hypoglycemic agents to treat adult-onset diabetes has been implicated in an increased incidence of cardiovascular mortality. Since it is likely that altered arterial wall metabolism plays an important role in the atherogenic process and in cardiovascular disease, the primary aim of the present study was to investigate the in vitro effects of two oral hypoglycemic agents (tolbutamide and glyburide) on glucose and acetate incorporation into aortic lipids of the dog. Tolbutamide resulted in a significantly increased incorporation of glucose into total lipids, phospholipids and fatty acids of aorta, but had no apparent effect on acetate incorporation into aortic lipids. In contrast, glyburide significantly decreased glucose incorporation into the total lipid, phospholipid and triglyceride fractions. Acetate incorporation into the triglyceride, free cholesterol, fatty acid and cholesterol ester fractions of aorta also was significantly decreased by glyburide. The data indicate that the oral hypoglycemic agents tolbutamide and glyburide can alter glucose and acetate utilization by arterial tissue. These observations on arterial lipid metabolism provide sufficient justification for further studies directed towards characterizing the effects of oral hypoglycemic agents on the various aspects of arterial wall metabolism.
Prostaglandin-Mediated, Angiotensin-Induced Vasoconstriction in Isolated Cat Arteries
Authors: Trachte George J. , Lefer Allan M.
Published: September 2008

The current study examines the prostaglandin contribution to angiotensin II-induced vasoconstriction in isolated perfused cat arteries. Superior mesenteric arteries were the most sensitive to angiotensin II. Superior mesenteric arteries responded to angiotensin II (25 nM) with a vasoconstriction which increased perfusion pressure 47 mm Hg. Sodium meclofenamate diminished this response to 2 mm Hg, but indomethacin did not significantly attenuate this effect. Angiotensin II (25 nM) produced a 31 mm Hg increase in perfusion pressure in coronary arteries but indomethacin (20 µM) or sodium meclofenamate (75 µM) reduced this response to 11 and 14 mm Hg, respectively (p < 0.05). Hepatic arteries were the least responsive to angiotensin. Also, neither cyclooxygenase inhibitor reduced the angiotensin II response in the common hepatic artery. Angiotensin II, therefore, may require prostaglandin synthesis for part of its vasoconstrictor activity in certain vascular beds, notably the coronary vasculature, but less so in splanchnic arteries.
Pulsatile Distention and Vascular Collagen Synthesis in the Rabbit
Authors: Fischer G.M. , Swain M.L. , Cherian K.
Published: September 2008

In rabbits, collagen synthesis was studied in five different regions of the vascular tree which are subjected to different degrees of pulsatile distention, i.e., cyclic stretching, and mean pressure. The vessels with greatest pulsatile distention had the highest specific activity of hydroxyproline in collagen after incubation with 14C-proline and the inferior vena cava with low pressure and negligible pulsatile distention had the lowest specific activity. The findings suggest a link between mechanical stretching and cellular metabolic function and have significance as to the relationship of pulsatile flow to normal vascular and organ physiology.
Uptake and O-Methylation of Isoprenaline in the Rabbit Ear Artery
Authors: Head Richard J. , De La Lande Ivan S. , Irvine Rodney J. , Johnson Stephen M.
Published: September 2008

Factors which influence uptake and O-methylation of 3Hisoprenaline (3HISO) by isolated segments of the rabbit ear artery were investigated. The tendency of the artery to accumulate unchanged amine was enhanced either when the O-methylation of ISO approached saturation at a high substrate concentration (6 µmol l–1 ISO), or when O-methylation was inhibited. Under these conditions, deoxycorticosterone acetate (DOCA) partially inhibited the accumulation of ISO. DOCA exerted a stronger inhibitory effect on O-methylation, but only at low ISO concentrations (0.2 and 0.8 µmol l–1). The results are interpreted as evidence that (a) O-methylation in the intact artery is a saturable process which serves to limit the accumulation of 3HISO when the bathing concentration of the amine is low, and (b) DOCA exerts its effects by inhibiting extraneuronal uptake into the compartment possessing O-methylating activity. Analysis of the kinetics of efflux of 3HISO suggested that O-methylation was restricted to only one compartment, whereas unchanged ISO was accumulated within at least two compartments in addition to the extracellular compartment. Attention is drawn to a small but significant inhibitory effect of chronic sympathetic denervation on the accumulation, although not the O-methylation of ISO, raising the possibility that there may also be distribution of 3HISO within the sympathetic nerves.
Contractile Responses of Aortic and Portal Vein Strips during the Development of DOCA/Salt Hypertension
Authors: Pang Catherine C.Y. , Sutter Morley C.
Published: September 2008

Vascular smooth muscle strips were examined during the development of hypertension in rats treate.d with deoxycorticosterone acetate (DOCA) plus saline to determine if the changes in the contractile responses precede or succeed the increase in blood pressure. After treatment with DOCA/salt for 1,3 and 4 weeks, aortic and portal vein strips were prepared from control and treated rats for studies of cumulative dose-response relationships to noradrenaline (NA) in Krebs’ solutions containing normal (2.5 mM) or low (0.2 and 0.4 mM) concentrations of Ca. 1 week of treatment did not result in any change in blood pressure or in the stress (force/area) developed by the aortic strips in response to NA in normal or low Ca. 3 weeks of treatment caused a significant increase of pressure and the aortic strips developed a significant decrease of stress in response to NA in normal, but not in low Ca. 4 weeks of treatment resulted in a significant increase of pressure and a significant decrease of stress in response to NA in low, as well as in normal, Ca. In contrast to the aortic strips, there was no change in the force induced by NA in the portal vein strips at any time. Thus, the decrease of contractile response in the aortic strips during treatment with DOCA/salt followed the same time course as the increase of arterial pressure and may be a consequence of high blood pressure.
Hydralazine Prevents Changes in the Contractile Response of Aortic but Not Portal Vein Strips in Hypertensive Rats
Authors: Pang Catherine C.Y. , Sutter Money C.
Published: September 2008

Previous studies showed that aortic strips from rats with either spontaneous (SHR) or DOCA/salt-induced hypertension developed less stress (force/area) in response to noradrenaline (NA) when compared to aortic strips from normotensive rats. Portal vein strips from SHR, but not from DOCA/salt hypertensive rats, developed greater force to NA compared to strips from control rats. We have investigated whether these changes are prevented by hydralazine. Hydralazine was added to the drinking solution (1% NACl) of one group of rats from the first day of treatment with DOCA. In the second group, hydralazine was added to the drinking water of 13-week-old SHR. After 3 weeks of treatment with hydralazine, cumulative dose-response relationships to NA were studied using aortic and portal vein strips from hydralazine-treated and control rats. Hydralazine prevented the increase of arterial pressure and the decrease of stress developed to NA by the aortic strips from both SHR and DOCA/salt rats. It did not prevent the increase of force developed to NA by the portal vein strips from SHR. Thus, reduced contractile response of the aortic strips from hypertensive rats seems to be the result of a high pressure, since both the rise in blood pressure and reduced aortic response are prevented by hydralazine. Increased contractile response of the portal vein strips from SHR appears to be independent of blood pressure.