bluuebunny/crossref_metadata_2025_split huggingface dataset:
Lower Body Negative Pressure and Effects of Autonomic Heart Blockade on Cardiovascular Responses
Authors: Bjurstedt H. , Rosenhamer G. , Tydén G. 
Published: December 2008

AbstractHeart rate, arterial pressure and cardiac output were recorded in eight healthy male volunteers during exposure to 80 mmHg of lower body negative pressure (LBNP) in the supine position before and after beta‐adrenergic and combined beta‐adrenergic and parasympathetic blockade of the heart as induced by the i.v. administration of propranolol 0.25 mg/kg b.wt. and atropine 0.04 mg/kg b.wt. After propranolol, heart rate response to LBNP averaged 48 % of that observed without blockade indicating that LBNP‐induced cardioacceleration is of both sympathetic and parasympathetic origin. Tolerance to LBNP was reduced by beta‐adrenergic blockade, since the decrease in mean arterial pressure during LBNP was exaggerated by such blockade. Although the addition of atropine markedly elevated mean arterial pressure and cardiac output in the control situation, tolerance to LBNP was not enhanced by this drug as judged from the arterial pressure response. Post‐LBNP overshoot in mean arterial pressure was strikingly augmented by combined cardiac effector blockade and was in part due to a lingering elevation of total peripheral resistance, cardiac output remaining decreased for more than 110 s after release of LBNP.
The Compliance Curve for the Flow Limiting Segments of the Airway. I. Model Studies
Authors: Pedersen Ole Find , Nielsen Tage Mors 
Published: December 2008

AbstractBy means of a pitot‐static tube airway compliance curves describing the cross‐sectional area (A) as a function of transmural pressure (Ptm) were constructed for several locations in the elastic airway of a mechanical model of the lung. From these curves local relations between elastic recoil pressure of the lung (Pel) and maximal expiratory flow (V̇max) were calculated and compared with the experimentally determined Pel‐V̇max curve for the entire airway, i.e. all parts in series. Theory and experiments showed that the latter was the lower borderline of all the local Pel‐v̇max curves. This means that the maximal flow through the entire airway at a given Pel is determined by the segment of the airway, having the smallest v̇max, just as the maximal strength of a chain is determined by its weakest link. The relation between the critical transmural pressure (Ptm‘) and the corresponding cross‐sectional area (A’) was derived from theexperimental Pel‐V̇max curve. This Ptm‘‐A’ curve had a composed appearance, which was found to reflect parts of the different local Ptm‐A curves and transitions between them because of movement of the flow limiting site within the airway. The Ptm‘‐A’ curve depends on the elastic properties of the flow limiting segment, and the slope of this curve (dA‘/dPtm’) is the compliance of the flow limiting segment. Significant frictional pressure losses upstream from the site of flow limitation caused underestimation of both A‘ and dA’/dPtm“, but downstream pressure losses had no influence on the Ptm‘‐A’ curve.
Effect of the Polyene Antibiotic Filipin on the Permeability of the Inward‐ and the Outward‐facing Membranes of the Isolated Frog Skin (Rana temporaria)
Authors: Nielsen Robert 
Published: December 2008

AbstractThe effect of the polyene antibiotic filipin on the electrical properties and the passive permeability of the cell membranes was investigated. The addition of filipin to the outside bathing solution has the following effects: 1. it results in a drastic reduction in the transepithelial resistance and potential, 2. it causes a 10–20 times increase in the passive transepithelial chloride, sodium and sucrose flux, 3. it results in the formation of an amiloride insensitive sodium pathway in the outward facing membrane, 4. it results in an active outward transport of potassium, 5. it results in a highly significant swelling of all the cells in the epithelium. The addition of filipin to the inside bathing solution has the following effects 1. it results in an activation of the active sodium transport, 2. it causes a slight increase in the passive transepithelial chloride and sodium permeabilities but has no effect on the sucrose permeability, 3. it has no effect on the amiloride inhibition of the short‐circuit current, 4. it has no effect on the volume of the cells in the epithelium. It is suggested that the addition of filipin to the outside bathing solution increases the direct sodium flow from cell to cell in neighbour layers. Furthermore these experiments indicate that the outward facing membrane of the isolated frog skin has a high cholesterol content as compared with the cholesterol content of the inward facing membrane.
Alpha‐Receptor Subsensitivity of Isolated Atria from Rats Following Physical Training or Repeated ACTH‐Injections
Authors: Siltovuori Anneli , Tirri Rauno , Harri Mikko N. E. 
Published: December 2008

AbstractDecreased chronotropic and inotropic sensitivity of isolated atria to phenylephrine but not to isoprenaline was found in rats following repeated physical training by swimming or repeated ACTH‐injections. These changes were induced within a week of subjection of animals to these treatments. It is concluded, that these effects are mediated by increased adrenergic activity which results in this subsensitivity of alpha‐receptors.
The Effect of 6‐Aminonicotinamide Blockade of the Pentose Phosphate Pathway on Catecholamines in the Rat Adrenal Medulla, Superior Cervical Ganglion, Hypothalamus and Synaptosome Fractions
Authors: Jansson S.‐E. , Gripenberg J. , Harkonen M. 
Published: December 2008

AbstractThe effect on tissue catecholamines of blockade of the pentose phosphate pathway with 6‐aminonicotinamide (6‐AN) was studied in the rat. 6‐AN at 35–50 mg kg‐1persistently lowered the adrenaline content in the adrenal gland to less than 10% of control values and caused a 50% loss of noradrenaline, which recovered. When the amine turnover rate was increased by a preceding period of drum stress, 6‐AN also consistently depressed noradrenaline in the gland. 6‐AN was without significant effect on the noradrenaline concentration in heart tissue, hypothalamus and superior cervical ganglion and did not affect the uptake or release of catecholaminesin vitro.The possibility is discussed that 6‐AN interferes with the biosynthesis of catecholamines, when it blocks the pentose phosphate pathway, by decreasing the supply of reducing equivalents in the form of NADPH which are necessary for the tetrahydropteridine cofactors of tyrosine hydroxylase.
Relation between chloride exchange diffusion and a conductive chloride pathway across the isolated skin of the toad (Bufo bufo)
Authors: Kristensen Poul , Larsen Erik Hviid 
Published: December 2008

AbstractSubstitution of chloride in the outside bathing medium of the toad skin with bromide, iodide, nitrate and sulphate leads to a reduction in the apparent exchange diffusion of chloride across this tissue, and also to a reduction of the chloride current recorded during hyperpolarization. A series of inhibitors (thiocyanate, furosemide, phloretin, and acetazolamide) also affects chloride exchange diffusion, hyperpolarization current as well as chloride influx during hyperpolarization. Although in some cases, effects on short circuit current were also observed, none of the effects on chloride transport systems could be explained as secondary effects due to a primary interaction with the sodium transport mechanisms. A correlation was found between the clamping current recorded during hyperpolarization and the efflux of chloride under short circuit conditions with chloride Ringer's on both sides. On the basis of these findings, and the results reported in the previous paper (Hviid Larsen and Kristensen 1977) it is considered probable that the membrane molecules responsible for chloride exchange diffusion under short circuit conditions, are rearranged under the influence of a hyperpolarizing clamping voltage, thereby forming channels allowing charge transferring transport of chloride.
Fall in choline acetyltransferase activity in the ventricles of the rat heart after treatment with a ganglion blocking drug
Authors: Ekström Jörgen 
Published: December 2008

AbstractThe choline acetyltransferase activity was found to be 27% lower in the ventricles of rats which had been given the ganglion blocking drug chlorisondamine than in those of untreated rats. Since the weight of the ventricles were also lower in the treated rats than in the untreated ones, it was wondered whether a change in the muscle mass as such affected the activity of the enzyme: isoprenaline treatment was found to cause the weight to increase markedly, while it left the enzyme activity unchanged. The decrease in enzyme activity observed after the prolonged ganglion blockade is interpreted as being the consequence of a reduced traffic of impulses along the postganglionic parasympathetic nerves of the ventricles. Thus, the results of the present investigation give further support for the idea of a vagal innervation of this part of the heart.
Kidney volume expansion and prostaglandin release by bradykinin. The effect of indomethacin pretreatment
Authors: Olsen Uffe Bang 
Published: December 2008

Abstract100 ng/kg/min bradykinin was infused into the left renal artery in anaesthetized dogs which were loaded with 10% mannitol in saline to produce a diuresis of approximately 1 ml/min. Bradykinin initially increased renal blood flow (70%), kidney volume (20%), subcapsular pressure (85%), urine PG‐excretion (410%), diuresis (80%) and decreased urine osmolarity (20%). Kidney volume, diuresis and urine osmolarity remained equally changed during continuous kinin infusion, while other parameters subsided toward the control levels. When renal blood flow was maintained constant during the infusion of bradykinin, urine PG‐excretion increased (330%), the glomerular filtration decreased (60%) and this was accompanied by decreased kidney volume, diuresis/natriuresis with unchanged urine osmolarity. Indomethacin treatment (2.5 mg/kg i.v.) decreased renal blood flow (35%) and inhibited urine PG‐excretion. Bradykinin after indomethacin showed effects which were very similar to those observed before indomethacin treatment. It is concluded that increased intratubular volume is a main determinant of bradykinin induced increase of whole kidney volume. The accompanying increase of intrarenal pressure does not apparently contribute to the kinin induced PG‐release. The vasodilation by bradykinin seems independent of released prostaglandins. The diuresis/natriuresis and decreased urine osmolarity are probably of hemodynamic origin.
A quantitative study of the insulin release induced by vagal stimulation in anesthetized cats
Authors: Uvnäs‐Wallensten Kerstin , Nilsson Göran 
Published: December 2008

AbstractInsulin was released by vagal stimulation in anesthetized and eviscerated cats. The plasma insulin concentration and blood flow in the portal vein were determined concomitantly and the insulin output was calculated. Stimulation of either the right or the left cervical vagus released the same amount of insulin, whereas bilateral stimulation released twice as much. Following a stimulation that depleted the “vagally‐releasable pool”, a recovery period of 15–20 min was needed before the same maximal output could be obtained again. With shorter interstimulatory periods the amounts of insulin released were reduced. When less than 2–3 000 impulses were applied during a stimulation period, the amount of insulin released per impulse was constant. Atropine (0.2–2 mg/kg) did not reduce the vagally‐induced insulin release.
The effects of cholera toxin on intramural blood flow distribution and capillary hydraulic conductivity in the cat small intestine
Authors: Cedgård Sture , Hallbäck Dan‐Axel , Jodal Mats , Lundgren Ove , Redfors Staffan 
Published: December 2008

AbstractBlood flow distribution to the mucosa‐submucosa and to the muscularis in the cat small intestine was investigated with a85Kr elimination technique before and after exposing the intestinal mucosa for 30 min to cholera enterotoxin. In all experiments the toxin induced an intestinal secretion. Concomitantly, total intestinal blood flow was increased to a level 50 per cent above control 3 h after exposure. This vasodilatation reflected a doubling of mean blood flow in the mucosa‐submucosa while muscularis blood flow remained unchanged. In another series of experiments the effect of cholera toxin on intestinal capillary hydraulic conductivity was investigated by determining the capillary filtration coefficient (CFC). A slight increase in CFC was noted during the 3 h observation period but this was not more pronounced than would have been expected from the concomitant vasodilatation. It is concluded that hemodynamic changes in the intestinal mucosa may be one of the several factors that probably are involved in the pathogenesis of cholera.
Prostaglandin content in blood and lung tissue during alveolar hypoxia
Authors: Wiberg Terje , Vaage Jarle , Bjertnæs Lars , Anton Hauge  , Gautvik Kaare M. 
Published: December 2008

AbstractThe aim of the present work was to investigate whether prostaglandins (PGs) are synthetized and released from isolated blood‐perfused rat and cat lungs secondary to vasoconstriction induced by alveolar hypoxia. The lungs were perfused with autologous blood with constant volume inflow via the pulmonary artery in a recirculating system. They were ventilated with constant volume positive pressure, and acute alveolar hypoxia was induced by ventilation with a gas containing 2% O2. A superfusion bioassay technique was used to measure PG‐like activity in the perfusate from the lungs, the blood being re‐oxygenated before reaching the assay tissues. The oxygenator prevented the perfusate hypoxia induced by ventilation hypoxia to affect the bioassay tissues. The assay tissues were rat stomach strip, rat colon and chick rectum. They were sensitive to calibrating doses of 0.5–1 ng/ml PGE2 and 1–2 ng/ml PGF2α. In another series of experiments PGs of the F‐series were measured in lung tissue from normoxic and hypoxic lungs with radioimmunoassay technique. No increase in PG‐like activity could be detected in the venous effluent by means of bioassay during hypoxia, nor was the lung tissue content of immunoactive PGF increased by hypoxia. The present findings indicate that alveolar hypoxia does not stimulate PG‐synthesis in lungs, refuting that PGs are important mediators of the pulmonary vasoconstrictor response to alveolar hypoxia. It is concluded that PGs play no significant role in producing the pressor response to alveolar hypoxia.
Effect of adenosine, adenosine analogues and drugs inhibiting adenosine inactivation on lipolysis in rat fat cells
Authors: Fredholm Bertil B. 
Published: December 2008

AbstractIt has been suggested that adenosine may be a physiologically important modulator of lipolysis. In the present study it was found that adenosine inhibited lipolysis stimulated by low (0.03 μM) concentrations of noradrenaline (NA). Lipolysis stimulated by higher concentrations (0.3 and 3 μM) of NA was inhibited to a minor degree or not at all. Theophylline (1 mM)‐induced lipolysis was inhibited by adenosine (IC60˜ 10μM). Inhibition of theophylline‐induced lipolysis was tested for several analogues of adenosine. Some N6‐sub‐stituted adenosine analogues and 2‐Cl‐adenosine were more potent inhibitors. Adenine‐nucleotides (ATP, ADP, AMP) were about equipotent with adenosine. Several adenosine analogues, including its breakdown products were considerably less potent or ineffective. None of the analogues tested inhibited the action of adenosine. Dipyridamol, dilazep and papaverine, which inhibit the uptake of adenosine into cells, caused only a slight enhancement of the antilipolytic effect of adenosine. None of the analogues inhibited the effect of adenosine. It is concluded that adenosine can inhibit lipolysis due to low, “physiological” concentrations of noradrenaline and of low concentration of theophylline via an action on a receptor structure on the cell surface which exhibits structural specificity.
Prostaglandin‐mediated inhibition of noradrenaline release: II. Dual mechanism behind its frequency‐dependence
Authors: Wennmalm ÅKe 
Published: December 2008

AbstractSympathetically innervated, isolated rabbit hearts were perfused according to Langendorff and the nerves were stimulated at 2, 5 or 10 Hz by equally long trains of pulses. The outflows of prostaglandin‐like substances (PLS) and of noradrenaline (NA), induced by the nerve stimulations, were followed. The sensitivity of the process of NA release to exogenous PGE1 (2–6 × 10‐8 M) at 2, 5 and 10 Hz was assayed. The outflow of PLS was found to be frequency‐dependent, being greater at 2 Hz than at higher discharge rates, while the outflow of NA was similar at the different frequencies. The inhibitory action of PGE, on the NA release process was more pronounced at 2 than at 10 Hz. It is concluded that the frequency‐dependence of the endogenous PGE‐mediated inhibition of the release of NA from discharging sympathetic nerves is based on 2 independent, frequency‐related mechanisms: a) a higher synthesis rate of PLS/impulse, and b) a more pronounced sensitivity of the process of NA release, at low compared to higher impulse frequencies.
Characteristics of static and dynamic regulatory mechanisms in myogenic microvascular control
Authors: Per‐Olof Grände  , Mellander Stefan 
Published: December 2008

AbstractThe recently described static and dynamic components in myogenic microvascular control (Grände, Lundvall and Mellander 1977) were analysed in this study with regard to their stimulus‐effector characteristics. Total and microvascular resistance responses in the sympathectomized vascular bed of skeletal muscle were analysed during graded changes of vascular transmural pressure (PT) applied at different rates (dPT/dt) in the range from +7.5 to ‐7.5 mmHg/s. The dynamic microvascular resistance responses, developing during the phase of changing PT, were pronounced and distinctly graded in relation to the magnitude of the dPT/dt stimulus, both with regard to amplitude of resistance response and rate of resistance change per unit time (dRmicro/dt). The static responses, revealed in the steady state phase of constant increased PT, were comparatively small and graded in relation to the amplitude of the PT increase. Rate‐sensitivity in microvascular myogenic control was bi‐directional, eliciting excitatory effects (constriction) in response to positive, and inhibitory effects (dilation) in response to negative, values of dPT/dt. The dynamic constrictor response to a given dPT/dt stimulus increased with increasing amplitude of PT and, thereby, increased duration of the dynamic stimulus. This effect might be explained by successive activation of myogenic “receptor units” with different thresholds. The described rate‐sensitivity in the myogenic control system seems to increase its rapidity, stability, and sensitivity and thereby can contribute efficiently to well‐adapted and refined microvascular adjustments.
Anticholeretic effect of substance P in anesthetized dogs
Authors: Holm Inger , Thulin Lars , Hellgren Margareta 
Published: December 2008

AbstractNine anesthetized dogs were provided with acute common duct fistulas after exclusion of the gallbladder. Synthetic Substance P was administered as caval infusions in a dosage of 0.5–20 ng × kg‐1× min‐1, duration 10 min. The output of hepatic bile, sodium and amylase decreased during infusion by 40–52 per cent at the highest doses. After termination of infusion all 3 parameters increased by 19–60 per cent above the basal level. The biliary concentration of sodium was constant, while that of amylase increased during infusion. The responses were dose‐related. The anticholeresis induced by Substance P might be due to inhibition of the canalicular bile fraction, which presumably is mediated by active sodium transport and independent of bile salt excretion.
Maturation of circulating red blood cells in young baltic salmon (Salmo salar L.)
Authors: Härdig Jan 
Published: December 2008

AbstractThe maturation of circulating red blood cells (RBC) in salmon (Salmo salar L.) has been studied. A developmental RBC series of 6 classes based on morphological criteria was proposed. After a single dose of iron (55Fe) given to 5–6 months old salmon the incorporation of radioactivity in maturing RBC was followed by autoradiography on blood smears. The relative distribution of labelled RBC between the 6 classes in specimens taken 15, 20, 41, and 52 days after the injection of iron showed that the RBC matured along the proposed series. The projected area of the RBC increased by 100% during the maturation. This RBC growth was caused by an elongation of the RBC. Thus the ratio between short and long axes of the RBC decreased with maturation and can be used as a measure of the degree of maturation. The uptake of radioactive iron measured as grain count per RBC or per projected area of the RBC increased during the maturation in classes II‐IV. Radioactive iron was not incorporated by mature RBC. The maturation time from class I to class VI was shorter than 41 days. RBC iron bound to non‐haemoglobin proteins as a possible restriction in estimations of the haemoglobin concentrations of developing RBC is discussed.
Effects of pindolol, sotalol and the optical isomers of propranolol on muscle action potentials and depolarization‐secretion coupling in the rat
Authors: Larsen Andreo 
Published: December 2008

AbstractMuscle action potentials and miniature end‐plate potential frequency were studied in different concentrations of pindolol,d‐andl‐propranolol and sotalol using intracellular microelectrode recording from rat phrenic nerve‐diaphragm preparations,d‐andl‐propranolol at concentrations of 10 to 40 mg/1 and pindolol at 20 to 100 mg/1 slowed down the rate of rise, prolonged rise and half‐decay times and reduced the overshoot of the muscle action potentials. Sotalol had similar effects but only at higher concentrations (100 to 200 mg/1). The drugs had no effect on the increase in the miniature end‐plate potential frequency obtained with depolarization by increased extracellular potassium concentration.
Effect of the nonionic detergent Triton X‐100 on sodium permeability of the myelinated nerve fibre ofXenopus laevis
Authors: Brismar Tom , Rydqvist Bo 
Published: December 2008

AbstractThe effect of the nonionic detergent Triton X‐100 (TX‐100) on the Na permeability (PNa) properties of the nodal membrane in myelinated nerve fibres ofXenopus laeviswas analysed with potential clamp technique. Application of TX‐100 caused a rapid initial decrease in PNathat was reversible at wash out as well as a slow irreversible block. Both effects depended on [TX‐100] and duration of exposure. The reversible reduction of PNaat the steady state was 50% at 40–60µM TX‐100. The slope of the Hill plot for the reaction was 1.75 indicating a deviation from a first order reaction. The equilibrium dissociation constant (KD) for n = 1.75 was 0.9 × 10‐7(M1.75). KDcalculated from the rate constants for onset and offset of the reversible reaction (KD= k2/k1) was 1.5 × 10‐7(M1.75). The possibility that the action of TX‐100 involves membrane proteins is discussed.