bluuebunny/crossref_metadata_2025_split huggingface dataset:
Vascular Responses to Mechanical Stimulation of the Mucosa of the Cat Colon
Authors: Fasth S. , Hultén L. , Lundgren O. , Nordgren S. 
Published: December 2008

AbstractMechanical stimulation of the mucosa of the proximal colon evoked a hyperemia which also could be elicited when severing the autonomic fibres to the colon. Mechanical stimulation of the distal colon produced a hyperemia which, on the other hand, was abolished by cutting the pelvic nerves. Afferent pelvic nerve stimulation evoked a response similar to that seen when stimulating the distal colon. Adrenergic and cholinergic receptor blockers did not affect the studied colonic vasodilatations. Dihydroergotamine, given in doses abolishing the vascular effects of i.a. injected 5‐hydroxytryptamine, abolished the hyperemia to mechanical stimulation of the proximal colon but not that of the pelvic stimulation. It is concluded that a local nervous vasodilator reflex exists in the proximal colon similar to that earlier demonstrated in the small bowel (Biber et al. 1971) and that the reflex vasodilatation evoked by mechanical stimulation in the distal colon is mediated via the pelvic nerves. Hence, the vascular control differs in the proximal and in the distal parts of the colon.
Reflex Plasma Hyperglycemia and Hyperosmolality Evoked by Unloading of the Carotid Baroreceptors
Authors: Järhult Johannes , Holmberg Jan , Lundvall Jan 
Published: December 2008

AbstractHemorrhage is usually accompanied by a considerable increase in the plasma osmolality and glucose concentration due to an augmented release of glucose from the liver. In the present cat experiments an attempt was made to investigate the possible role of different vascular receptors in mediating this hyperglycemic (hyperosmolar) response. Bilateral vagotomy or stimulation of the carotid chemoreceptors by perfusion of the carotid sinus with venous blood at normal pressure only slightly increased the arterial plasma glucose concentration. On the other hand, when the sinus nerves were cut in the vagotomized animal, thereby simulating complete unloading of the carotid baroreceptors, the arterial plasma glucose concentration rose by about 8 mM/L and the arterial plasma osmolality by about 10 mOsm/kg H2O. Perfusion of the carotid baroreceptors with arterial blood at different levels of hypotension showed that the baroreceptor‐induced hyperglycemia was graded in relation to the pressure level. Regional hypotension of the liver, pancreas, intestine, kidneys or brain did not significantly affect plasma glucose concentration or osmolality. We conclude that the reflex release of glucose from the liver during hemorrhage mainly is initiated from the unloading of arterial baroreceptors.
The Role of Intramural Noradrenaline in the Potassium Induced Contracture of Non‐Estrogenized Smooth Muscle
Authors: Bengtsson Bengt 
Published: December 2008

AbstractThe influence of intramural noradrenaline on potassium induced contractures was studied in isolated preparations of the uterus and the portal vein of the rat. Uterine strips of oophorectomized rats responded with contraction followed by transient relaxation when immersed in a medium containing 127 mM potassium chloride. Reserpinization or blockade of β‐adrenoceptors with propranolol greatly diminished the transient relaxation. In the isolated portal vein, both noradrenaline depletion with reserpine and α‐adrenoceptor blockade (phentolamine) reduced the active tension produced in response to the isotonic potassium solution. These results suggest that intramural noradrenaline plays a significant role in the development of contractures evoked by potassium in the uterus and the portal vein of the rat. In the uterus, the released noradrenaline counteracts the development of active tension, whereas in the portal vein, noradrenaline has a contractile effect which is added to that of potassium. Estrogen treatment reduced (portal vein) or abolished (rat uterus) the contractile effects of intramural noradrenaline. The adrenolytic effect of estrogen is possibly due to reduction in the release of noradrenaline from the sympathetic nerve‐endings.
Effects of Intraventricular 6‐Hydroxydopamine on Cerebrovascular CO2Reactivity in Anesthetized Rats
Authors: Edvinsson Lars , Hardebo Jan Erik , MacKenzie Eric T. 
Published: December 2008

AbstractRegional cerebral blood flow was measured by the14C‐ethanol technique in anesthetized rats before and after intraventricular injection of 6‐hydroxydopamine. This treatment reduced the fluorescence of the central noradrenaline and dopamine nerve terminals, as well as of the perivascular nerve terminals in cerebral vessels. The administration of 6‐hydroxydopamine had no significant effect on cerebral blood flow at normocapnia. The cerebrovascular reactivity to hypercapnia was significantly increased in the 6‐hydroxydopamine treated animals. The results indicate an involvement of central catecholamine pathways in the cerebrovascular reactivity to hypercapnia.
Neuronal and Extraneuronal Outflow of3H‐Noradrenaline Induced by Electrical‐Field Stimulation of an Isolated Blood Vessel
Authors: Schrold Jørgen , Nedergaard Ove A. 
Published: December 2008

AbstractThe adrenergic neuronal selectivity of3H‐outflow elicited by electrical‐field stimulation of rabbit isolated pulmonary artery preloaded with3H‐(‐)‐noradrenaline (3H‐NA) was examined. Following incubation (45 min) of arterial rings at 37°C with3H‐NA (10‐6M) and a 100 min wash‐out period, the sympathetic neurones were stimulated selectively and supramaximally, as regards tension development, with a constant current (250 mA; 300 monophasic pulses; 10 Hz; 0.3 ms). The initial stimulation‐induced3H‐outflow was higher than the subsequent 5 outflows, which remained almost constant (39, 20, 19, 17, 16 and 16 pmol g‐1, respectively).3H‐NA and3H‐O‐methylated plus deaminated metabolites constituted 11% and 74%, respectively, of the total3H‐outflow induced during the initial stimulation period, but 38% and 38%, respectively, during the second stimulation period. Omission of Ca2+in the physiological salt solution reduced the 6 stimulation‐induced outflows to 67, 40, 35, 24, 21 and 21%, respectively, of the untreated preparations. Bretylium (3 × 10‐5M) or tetrodotoxin (10‐6M) reduced the3H‐outflow to approximately the same extent. Stimulation‐induced outflows from artery rings preloaded with3H‐NA in the presence of cocaine (10‐3M) or in the cold (3°C) approximated the Ca2+, bretylium and tetrodotoxin‐insensitive release. These treatments all completely blocked the neurogenic contractile response. When artery rings were preloaded with3H‐NA in the presence of normetanephrine (10‐4M), the stimulation‐induced Ca2+‐insensitive outflows were markedly reduced. The results suggest that the field stimulation‐induced release of3H‐NA is in part of extraneuronal origin.
Experimental Cardiac Hypertrophy and the Synthesis of Poly(A) Containing RNA and of Myocardial Proteins in the Rat: The Effect of Digitoxin Treatment
Authors: Turto Heikki 
Published: December 2008

AbstractThe synthesis of poly(A) containing RNA was increased in heart of non‐digitalized and digitalized rats after aortic constriction, the increase being of the same degree as that of the RNA lacking this sequence. No differences were found, either in the absence or presence of polyuridylic acid, in the incorporation of radioactivity into protein by cardiac ribosomes isolated from animals treated differently. It may be concluded, that after the constriction of the aorta the synthesis of mRNA proceeds at a similar rate as that of the bulk RNA, and that the treatment of the animals with digitoxin does not abolish the stimulus for hypertrophy.
Relationship between Sarcomere Length and Active Force in Rabbit Papillary Muscle1
Authors: Wohlfart B. , Grimm A. F. , Edman K. A. P. 
Published: December 2008

AbstractIsometric peak twitch force (stimulation frequency 0.5/s; 29.5–30.5°C) was correlated with sarcomere length in isolated papillary muscles of the rabbit. Sarcomere length was measured from photographic recordings (1.5 ms exposure time) performed at rest between contractions and at the time of isometric peak twitch force. The sarcomere length at rest was found to be relatively uniform throughout the preparation and to be linearly related to the overall muscle length within the range Lmax‐ 0.85 Lmax. The distribution of sarcomere lengths increased considerably as the muscle went from rest to activity. Studies of surface markers showed different degrees of shortening (or elongation) of individual segments along the length of the preparation. The mean resting sarcomere length at Lmax (the optimum muscle length for force production) was 2.44±0.01 μm (grand mean ± S.E., 7 muscles). The mean active sarcomere length at Lmax was 2.29 ± 0.04 /μm. Active force declined steeply as the muscle length was reduced below Lmax. At a resting sarcomere length of 2.0 μm, active force was approximately 1/3 of the maximum. The observed differences between the length‐tension relationships in myocardium (twitch responses) and skeletal muscle (tetanic contractions) are discussed on the basis of a length dependency of the activation process in cardiac muscle.
Effect of Atropine and SC‐15396 on Stimulated Gastric Acid Secretion in the Atlantic Cod, Gadus morhua
Authors: Holstein Björn 
Published: December 2008

AbstractGastric acid secretion was measured in swimming codfish surgically equipped with a catheter draining the stomach. Gastric acid secretion was stimulated by histamine (5 or 15μg/kg‐h) or by carbachol (5μg/kg‐h). Pretreatment with atropine (1 μmol/kg‐h) completely prevented the acid secretion induced by carbachol, but did not influence the secretion induced by histamine. Atropine had marked effects on the motor functions of the stomach, and seriously reduced the volume draining from the stomach. Infusion of phenol red indicated that the decrease in volume was due to a decrease in recovery of ingested water. SC‐15396, “antigastrin”, significantly depressed acid secretion induced by histamine, and reduced carbachol‐stimulated secretion, although the latter was statistically insignificant. The effects of SC‐15396 is discussed with reference to the absence of receptors for gastrin related to gastric acid secretion in the codfish stomach.
Frequency‐Dependence of3H‐Noradrenaline Secretion from Human Vasoconstrictor Nerves: Modification by Factors Interfering with α‐ or β‐Adrenoceptor or Prostaglandin E2Mediated Control
Authors: Stjärne L. , Brundin J. 
Published: December 2008

AbstractIsolated superfused field stimulated human omental arteries and veins, preincubated with3H‐(‐)‐nor‐adrenaline (NA) were used to study the frequency dependence of NA secretion and of the mechanisms for its local feedback control.3H‐NA secretion per shock was found to be basically a simple hyperbolic function of the stimulation frequency from 1 to 30 Hz, as long as secretion was restricted by prostaglandin E2(PGE2). In the absence of restriction, or during facilitation,3H‐NA secretion per shock reached its maximum at 10 Hz and then declined at 30 Hz, indicating ‘overload’ in some link in the secretory mechanism.3H‐NA secretion was depressed by exogenous NA and by PGE2, and enhanced by isoprenaline, phentolamine and by blockade of PGE2formation. Most of these effects were inversely related to the stimulation frequency. Attempts were made to study interactions between the different control mechanisms and to evaluate possiblein vivoconsequences of disturbance of adrenergic neuroeffector transmission by interference with the local control of the secretory mechanisms.
Effects of Sympathetic Nerve Stimulation in the Presence of a Slow Parasympathetic Secretion in the Parotid and Submaxillary Glands of the Rabbit
Authors: Gjörstrup Per 
Published: December 2008

AbstractSympathetic secretory responses from the parotid and the submaxillary glands of the rabbit were studied; sympathetic excitation occurred either alone or during a slow parasympathetic background secretion, imitating the resting secretion normally present. The fairly rapid sympathetically evoked flow of saliva from the parotid gland was, in the background secretion, further increased and obtained at low frequencies, which at sympathetic stimulation alone were subthreshold. The effects, which could be repeated with sympathomimetic drugs in a pilocarpine induced secretion, were abolished by αand βadrenoceptor blockade in combination. The submaxillary gland gave a very scanty secretion on sympathetic excitation, the effects being mediated via β‐adrenoceptors. The responses were not increased in a background secretion but the main effect of sympathetic activation was to retard the salivary flow. The retardation was attributed to vasoconstriction accompanying sympathetic excitation. Eliminating the vasoconstrictor responses, while retaining the sympathetic secretory effects, did not reveal any increase of the sympathetic salivary responses in the submaxillary gland.
Cardiac Receptors Activated during the Hypothalamic Defence Reaction
Authors: Wennergren Goran , Thorén Peter , Lisander Björn 
Published: December 2008

AbstractThe increases of arterial blood pressure, cardiac inotropy and venous return seen during the hypothalamic defence reaction are likely to lead to concomitant excitation of left ventricular receptors with nonmedullated afferents. The integrated efferent pattern of response resulting from the central interaction between the defence reaction and influences from the mentioned cardiac receptors was recently analyzed. These two, essentially opposing influences on the circulation were then seen to interact in such a way as to produce an optimal cardiovascular response with respect to increases in cardiac output and blood supply to the skeletal muscles. However, direct electrophysiological recordings from nonmedullated cardiac afferents during defence area stimulation have hitherto been lacking. The present experiments, performed on chloralose‐anesthetized cats and utilizing electrophysiological recordings, clearly demonstrate that the left ventricular receptors are activated by the cardiovascular readjustments induced by the defence reaction. Defence area stimulation increased the activity of these receptors, which work within a very narrow, low frequency range, from 1.1 ± 0.3 imp/s to 2.7 ± 0.7 imp/s associated with rises in systolic blood pressure (afterload) and heart rate. Normally such a receptor activation would induce considerable bradycardia and sympathetic inhibition, but particularly the reflex bradycardia is centrally suppressed by a concomitant defence area activation. The marked bradycardia often seen immediately upon interruption of the defence area stimulation is, however, probably to a great extent initiated from the excited ventricular receptors.
Effects of Low Tissue Temperature on Peripheral Vascular Control Mechanisms
Authors: Reite Ola B. , Millard Ronald W. , Johansen Kjell 
Published: December 2008

AbstractInfluence of low temperatures on vascular effects produced by adrenaline, noradrenaline and vasoconstrictor nerve stimulation was studied in the feet of ducks. Observations were made on isolated preparations as well as on intact ducks with one or both feet immersed in ice‐water. Isolated preparations were perfused with physiological solution and information on changes in vascular resistance obtained by direct measurement of flow changes during perfusion at constant pressure or by measuring changes in perfusion pressure during perfusion at constant flow. In intact ducks changes in blood flow were recorded as changes in digital subcutaneous tissue temperature. The study revealed that in the duck foot a relatively large fraction of the resistance to blood flow is found in the arteries of the proximal part of the foot. During cooling of the foot the influence of vasoconstrictor nerve stimulation and low doses of adrenaline and noradrenaline on vascular resistance is gradually lost, and it is negligible at temperatures below 8°C. At these low temperatures the blood vessels stay dilated and blood flow through the web seems to be determined by the digital arterial blood pressure.
Effect of Dehydration on Renal Blood Flow in Dog
Authors: Kirkebø A. , Tyssebotn I. 
Published: December 2008

AbstractThe effect of dehydration on intrarenal blood flow was investigated in 11 dogs, using polarographic determination of H2‐gas desaturation for measuring local blood flow in inner cortex (ICF) and outer cortex (OCF). Dehydration was induced by 48 h water deprivation + 2–300 mg ethacrynic acid (EA) per os the day before the experiment. Compared to a control group (n = 9) ICF was markedly reduced to 2.40 ± 0.47 ml/min×g (control 3.23 ± 0.64) whereas OCF 3.29 ± 0.80 ml/min×g was nearly unchanged (control 3.59±0.85). The ratio OCF/ICF was increased to 1.37 (1.11). Further dehydration by hypertonic peritoneal dialysis for 3 h increased Hct to 60 ± 4 and further reduced OCF and ICF, without significant change of the OCF/ICF‐ratio. At Hct above 55 sudden and intermittent changes in local cortical blood flow were recorded randomly at individual electrode sites, showing ischemic periods lasting for 1 to 60 min. Such flow changes were observed in 13 of 14 expts. and were not accompanied by changes in RBF. It is concluded that moderate dehydration causes a greater reduction of ICF than of OCF. Severe dehydration gives in addition rise to patchy, intermittent ischemia in both cortical layers.
Circulatory Reflex Responses during the Initial Stage of Feline Endotoxin Shock
Authors: Halinen M. O. , Hakumäki M. O. K. , Sarajas H. S. S. 
Published: December 2008

AbstractCardiovascular and autonomic nervous responses to an injection of E. coli endotoxin were followed for up to 15 min. in cats anesthetized with chloralose and given artificial respiration. Within 60 seconds, endotoxin induced a drop of aortic pressure, with simultaneous cardiac acceleration and slight central venous hypertension. There was an associated, almost complete cessation of the aortic arch baroreceptor afferentation. The cardiac sympathetic efferentation increased up to 1.4 times the control level at its maximum. The splenic sympathetic efferentation increased up to 10.6 times the control level at the end of the 15 min period, when the other parameters studied showed a trend to control level. The sympathetic autonomic system seems to be activated through cardiovascular receptors sensing hemodynamic changes touched off by endotoxin‐induced release of vasoactive substances.
Influence of Muscle Length on the Force‐Velocity Relation of K+‐contractures in Smooth Muscle from Rabbit Urinary Bladder
Authors: Uvelius Bengt 
Published: December 2008

AbstractForce‐velocity relations of K+‐contractures of longitudinal smooth muscle from rabbit urinary bladder were studied by isotonic quick release at 37°C. In order to minimize the influence of parallel elasticity the study was limited to the rising part of the length‐tension curve. The force‐velocity data fitted well with Hill's equation. The in situ length of the strip at a bladder volume of 10 ml is called L10. This length is 50% of that at which maximum active tension is developed. At L10 Vmax was 0.29 muscle lengths per second and it was estimated to be 0.36 lengths/s at optimum length. Constant b in Hill's equation had a value of 0.052 L10/s and it was unaffected by length changes over the interval 0.69 L10‐ 1.44 L10. At L10 a/Po was 0.17. In the interval given above, a/Po decreased with increasing length in proportion to the increase in Po, indicating that a was also length independent. According to Hill's equation [V = b(Po ‐ P)/(P + a)], V should increase in proportion to (Po ‐ P) when the muscle length is increased if a and b are constants. Such a linear relation was found at shorter lengths but at lengths close to or at the length for maximum active tension, V increased more than (Po ‐ P). Two possible explanations were considered; firstly that b/(P+a) increased, and secondly that the load on the contractile element could be less than P due to an influence of the considerable tension in the parallel elastic element at these lengths. The series elastic recoil of the active muscle amounted to 3–4% of the muscle length when released to zero tension.
Characteristics of Aortic Baroreceptors with Non‐medullated Afferents Arising from the Aortic Arch of Rabbits with Chronic Renovascular Hypertension
Authors: Jones John V. , Thorén Peter N. 
Published: December 2008

AbstractThe characteristics of 47 non‐medullated and 54 medullated fibres arising from the aortic arches of 6 hypertensive rabbits have been investigated. The threshold for activation of the aortic C‐fibres lay between 78 and 190 (mean 122) mmHg. The threshold for activation of 54 medullated aortic baroreceptors in the same animals was from 70 to 140 (mean 109) mmHg. At the awake mean arterial blood pressure (MABP) of these hypertensive rabbits (143 mmHg) all the medullated fibres were active as were 78% of the C‐fibres. In contrast in a group of normotensive animals 91% of the medullated and only 28% of the non‐medullated fibres were active. Pressure response curves were constructed for 19 C‐fibres and 12 medullated fibres from the hypertensive animals. At a MABP of 110 mmHg the firing in the non‐medullated fibres was 2.0 Hz as compared with 19.0 Hz in the medullated fibres and at the awake MABP mean firing was 9.0 Hz in the non‐medullated fibres and 48.0 Hz in the medullated fibres. The firing at awake MABP was considerably higher in the hypertensives (9.0 Hz) as compared with the normotensives (1.1 Hz). Thus these data indicate that although the aortic C‐fibres are reset in chronic hypertension, they are reset less than the medullated aortic baroreceptors from the same animal. It is suggested that arterial baroreceptor C‐fibres may have an important role in the tonic control of the circulation in hypertension.
Effect of Endurance Training on the Capacity of Red and White Skeletal Muscle of Mouse to Oxidize Carboxyl‐14C‐labelled Palmitate
Authors: Salminen Antero , Vihko Veikko , Pilström Lars 
Published: December 2008

AbstractThree groups of mice were trained for 1, 4 and 5 months according to different running programs on a motor driven treadmill and the fatty acid oxidation capacity (FAO) and the activities of some enzymes of energy metabolism (cytochrome c oxidase, malate dehydrogenase, triosephosphate dehydrogenase, and lactate dehydrogenase) were determined from m. quadriceps femoris (MQF). Endurance training increased the FAO [5‐month training, 4 days/week, 30 min/day 22% (p<0.05); 1‐month training, 7 days/week, 150 min/day 37% (p<0.001); 4‐month training, 5 days/week, 60 min/day 24% (p<0.05)]. The activities of cytochrome c oxidase and malate dehydrogenase increased approx. 30% (p< 0.001) whereas triosephosphate dehydrogenase and lactate dehydrogenase activities were not prominently influenced by training. The predominantly red part of MQF of untrained animals oxidized palmitate four times faster than the predominantly white part. The activities of cytochrome c oxidase and malate dehydrogenase were two times higher showing pronounced FAO in the red part. Endurance training increased the FAO and activities of oxidative enzymes in the red and white parts and in the whole muscle relatively equally resulting in similar differences between the muscle types after training. The absolute increase in the FAO of the red muscle was, however, manyfold when compared in chemical units to the white muscle.