bluuebunny/crossref_metadata_2025 huggingface dataset:
The effect of propranolol on the serotonin concentration in the portal plasma after vagal nerve stimulation in the cat
Authors: PETTERSSON GÖSTA , AHLMAN HÅKAN , BHARGAVA HEMENDRA N. , DAHLSTRÖM ANNICA , KEWENTER JAN , LARSSON INGER , SIEPLER JOHN K.
Published: December 2008

Efferent cervical vagal nerve stimulation in the cat caused a marked increase of the portal plasma 5‐HT concentration. This increase was more than two‐fold within 15 min of stimulation. After cessation of stimulation portal plasma 5‐HT returned to basal levels within 10 min. Treatment with the β‐adrenoceptor antagonist propranolol, in various doses (0.1–2 mg/kg b.wt.), did not abolish but significantly reduced the response to vagal stimulation, particularly during the final part of the stimulation period. The results confirm the existence of a β‐adrenoceptor‐mediated release of 5‐HT, but also suggest that other mechanisms for 5‐HT release may be involved in the response on vagal nerve stimulation.
Adenosine 3‘, 5’ cyclic monophosphate, calcium and magnesium excretion in ethanol intoxication and hangover
Authors: LINKOLA JAAKKO , FYHRQUIST FREJ , YLIKAHRI REINO
Published: December 2008

Effect of ethanol on adenosine 3′, 5′ cyclic monophosphate (cAMP), calcium (Ca) and magnesium (Mg) excretion was studied in controlled clinical conditions in man. Seven male volunteers served as their own controls. In 5 subjects cAMP excretion was primarily suppressed by ethanol. Ethanol appeared to have a biphasic effect on Ca excretion, an initial stimulation followed by a conservation phase. Mg excretion was stimulated by ethanol in 5 subjects. Subjects having nausea and vomitus and the most severe hangover symptoms had the lowest urinary Ca excretion and the lowest initial cAMP excretion. Ca and Mg metabolism and the susceptibility of the body to the toxic effects of ethanol appeared to be interrelated.
On the nature of basal vascular tone in cat skeletal muscle and its dependence on transmural pressure stimuli
Authors: GRÄNDE PER‐OLOF , BORGSTRÖM PER , MELLANDER STEFAN
Published: December 2008

The aim of the present study was to elucidate in some detail the characteristics of the intrinsic basal vascular tone in the adrenergically blocked skeletal muscle with regard to its extent and site along the vascular bed, its dependence on arterial pressure via static and dynamic transmural pressure stimuli, and its sensitivity to local metabolic influence. Basal tone, which apparently is of myogenic nature, was pronounced in ‘proximal arterial vessels’ (>25 μm i.d.) and in the ‘microvessels’ (<25 μm), but low in ‘large veins’. Its functional characteristics, however, were different in the ‘proximal arterial vessels’ and the ‘microvessels’. Normal basal tone in the ‘microvessels’ thus seemed to be intimately dependent on the arterial blood pressure level and, at least partly, initiated by its static mean pressure distension effect as well as by its dynamic pulse pressure oscillations. It could be virtually abolished by a transmural pressure decrease applied at fast rate (‘strong inhibitory dynamic transmural pressure stimulus’). Basal tone in the ‘proximal arterial vessels’, on the other hand, was little affected by arterial pressure and almost irresponsive to transmural pressure stimuli. Basal tone in the ‘microvessels’ was much more sensitive to metabolic stimuli than that in the ‘proximal arterial vessels’. The present results, viewed in the light of some recent electrophysiological studies on vascular smooth muscle, suggest that smooth muscle in the ‘microvessels’ is mainly of the spike‐generating type, whereas that in the ‘proximal arterial vessels’ seems to be of different nature, possibly of the non‐spike‐generating type.
Olfactory sensitivity to bile acids in salmonid fishes
Authors: DØVING KJELL B. , SELSET ROLF , THOMMESEN GEORG
Published: December 2008

Monopolar DC‐recordings were made simultaneously from two positions on the olfactory bulb of chars (Salmo alpinus L.) and graylings (Thymallus thymallus L.) using bile acids and amino acids as olfactory stimulants. The bile acids induced responses with characteristic spatial differences from those of the amino acids. The distribution of responses to bile acids indicated a neuronal activity in the medial part of the bulb. In contrast, amino acids elicit responses in the lateral part of the bulb. Taurine conjugated bile acids were up to 1 000 times more potent as olfactory stimuli than methionine. The results suggest that olfactory receptors are of two types, one responding to bile acids, the other to amino acids. 3‐α‐hydroxysteroids are released from the fish into the water in quantities that suffice for detection by their olfactory system. The odorant potency of the bile acids, their evolutionary history and variability, together with their renowned adherent properties made them interesting candidates for specific signals in the aquatic environment.
Correlative analysis of microcirculatory and cellular metabolic events in skeletal muscle during hemorrhagic shock
Authors: AMUNDSON BJÖRN , JENNISCHE EVA , HALJAMÄE HENGO
Published: December 2008

Skeletal muscle reactions to hemorrhagic shock were investigated in anesthetized cats (n= 23). The tenuissimus muscle was exposed for vital microscopy and shock was induced by single‐withdrawal of 45% of the blood volume. Muscle microcirculation, energy metabolism and cell membrane potentials were followed over a 2 h period along with blood pressure, hematocrit and blood leukocyte, platelet, glucose, pyruvate and lactate contents. Bleeding usually caused complete cessation of muscle blood flow for 5–20 min, while the animal compensated the blood pressure. Reflex constriction occurred in medium‐sized but not in terminal arterioles. When flow reappeared a marked maldistribution was evident in the capillary bed. Flow remained in 30–50% of the capillaries, permanently or intermittedly. Leukocytes could be found lodged in many arrested capillaries and also adhering to venules in large numbers. Erythrocyte or platelet plugs were not seen in the muscle microvasculature. Glucose and G6‐P contents doubled and lactate increased 5‐fold in muscle tissue during shock. CP was reduced by about 25% while the ATP‐level remained unchanged. Membrane potentials declined 12% in shock and the spread in potentials from adjacent fibers increased.
White blood cell deformability and plugging of skeletal muscle capillaries in hemorrhagic shock
Authors: BAGGE ULF , AMUNDSON BJÖRN , LAURITZEN CLAES
Published: December 2008

The cause of maldistributed capillary perfusion in hemorrhagic shock was investigated in a combined in vivo and in vitro study. The cat tenuissimus muscle was observed by vital microscopy before and after withdrawal of 45% of the blood volume. The induced shock conditions reduced the number of perfused capillaries about 50%. Close examination of the scattered, nonperfused capillaries showed that they remained open and almost invariably contained one or several leukocytes. These cells were usually located at the bulgings of endothelial cell nuclei, and when occasionally dislodged, recirculation immediately occurred. Platelet or erythrocyte aggregates were not seen in the microvasculature in shock. To test whether the trapping of leukocytes reflected an impaired deformability of these cells in shock or was merely a pressure dependent phenomenon, deformability studies were performed on leukocytes in vitro. Central venous blood was drawn before and 2 h after bleeding and leukocytes were separated by sedimentation. The passage‐time of single leukocytes through a glass capillary stenosis at constant driving pressures was used as an index of cell deformability. No qualitative changes in stiffness were found after shock. The distribution of cell passage‐times indicated, however, that the stiffest portion of the leukocyte population was removed from the circulation in shock.
Cardiovascular responses during one‐ and two‐legged exercise in middle‐aged men
Authors: MAGNUSSON G. , KAIJSER L. , ISBERG B. , SALTIN B.
Published: December 2008

Eight healthy and regularly physically active men, 44–69 years old, performed one‐ and two‐legged dynamic knee extension exercise at increasing work intensities, including one leading to exhaustion. Leg blood flow increased linearly in relation to work rate, reaching a peak value of 5.1 ±0.4 1 min‐1. With a mean weight of quadriceps femoris of 2.2 ±0.1 kg, a peak perfusion of 2.3 ±0.11 kg‐1 min‐1 was attained. The maximal leg oxygen uptake was 0.72 ±0.071 min‐1 (0.33 ±0.03 1 kg‐1 min‐1). At submaximal work the elevation in limb oxygen uptake accounted for between 70 and 100% of the rise in pulmonary oxygen uptake. Comparing two‐ with one‐legged knee extension the cardiac output was 1.5 1 min‐1 higher at each work level, reaching 13.7±0.7 and 12.3 ± 1.0, respectively at exhaustion, leaving 3.5 and 7.2 1 min‐1 of blood flow to the remaining body (cardiac output –leg blood flow). The mean arterial pressure was 119 ±5 mmHg at rest and increased to 155 mmHg for both test modes at the maximal work rate. The femoral arterial and venous plasma concentrations of lactate, ammonia and noradrenaline were significantly higher for two‐legged as compared with one‐legged exercise at the maximal load performed. However, the rate of release per leg, for both lactate and ammonia, did not differ between the two test conditions.

It is concluded that physically active middle‐aged men, with a well‐retained muscle mass, can maintain a high skeletal muscle perfusion, similar to that of young males. However, the blood flow is achieved with a higher mean arterial pressure and an elevated sympathetic activity, as reflected by noradrenaline in plasma and spillover from the exercising limb.
An inhibitory effect of veratridine during tetanic stimulation of the rat diaphragm
Authors: RØED A.
Published: December 2008

The membrane ‘labilizer’ veratridine (3.7 ± 10‐6 m) which potentiates the contractions at twitch (0.1 Hz) stimulation due to multiple discharges, inhibited the tetanic contractions (50 Hz in 10 s) and the simultaneously recorded electromyogram in a use‐dependent way, leading to fading of tetanic tension. The effect was equal during indirect and direct stimulation, and could therefore be localized to the excitable sarcolemma. This was confirmed by intracellular recording of action potentials, showing a marked veratridine‐induced fallout of action potentials during continuous 50 Hz stimulation, whereas endplate potentials were unaffected. Accordingly, veratridine probably caused a use‐dependent inhibition of the Na+ channels of the excitable sarcolemma. The tetanic fade was unaffected by K+ depolarization, increased by hyperpolarization in K+‐free solution, and decreased by high Ca2+. All these changes of the ionic concentrations inhibited the twitch potentiating effect of veratridine. Since hyperpolarization and increasing the electric field in the membrane with high Ca,+ had opposite effects on the tetanic fade, the field change was probably not the cause of the antagonism in high Ca2+. Instead, a membrane stabilizing effect of high Ca2+ is suggested, since the neutral local anaesthetic benzocaine (1.5 ± 10‐4 m), which is also a membrane stabilizing drug, had the same effects as high Ca2+ on the veratridine‐induced tetanic fade. The effect of veratrine during tetanic stimulation was partly reversible upon washing. The reversibility was enhanced by high Ca2+ or benzocaine.
Density of L‐type calcium channels in ischaemically preconditioned porcine heart regions
Authors: STOKKE M. , AKSNES G. , LANDE K. , HAGELIN E. M. , BR0RS O.
Published: December 2008

Ischaemic preconditioning by brief ischaemic episodes could be explained by reduced cellular calcium ion (Ca2+) influx, reduced cytosolic Ca2+overload and delayed cell‐injury during subsequent long‐lasting ischaemia. L‐type calcium channels (LCC) regulate sarcolemmal Ca2+influx in myocardial cells. The aim of this study was to investigate if preconditioning was associated with reduced density or altered state of LCC in the preconditioned region of the heart. To test this we compared the density and the dissociation constant of (4‐)‐[3H]isradipine binding to LCC in membranes from preconditioned and control regions of porcine hearts. Eight porcine hearts were regionally preconditioned by two 10‐min occlusions of the mid left anterior descending artery, and each occlusion was followed by 30 min of reperfusion. Biopsies were taken from the preconditioned regions and control regions supplied by the circumflex artery at the end of the last reperfusion, and (+)‐[3H]isradipine binding to membranes made from the biopsies was measured. The differences in density and dissociation constant of (4‐)‐[3H]isradipine binding to LCC in membranes from preconditioned and control regions were not significant. In conclusion, the proposed effect of ischaemic preconditioning to reduce Ca2+influx, does not involve local changes in density or state of LCC that could be detected by (+)‐[3H]isradipine binding.
Cerebello‐thalamo‐cerebral projection from the dentate nucleus onto the frontal eye field in the cat
Authors: OKUDA B.
Published: December 2008

To elucidate the role of the cerebellar dentate nucleus in oculomotor system, we investigated the dentato‐cerebral projection onto the frontal cortex around the fundus of the presylvian sulcus corresponding to a subregion of the frontal eye field (FEF) in the cat. Stimulation of the dentate nucleus induced laminar field potentials consisting of mainly a surface positive‐depth negative wave and a subsequent depth positive wave with or without a surface negative wave in the contralateral FEF. Thalamic relay neurones, identified by collision test, were mainly distributed in the dorsal part of the ventromedial (VM) nucleus. Injection of wheat germ agglutinin conjugated horseradish peroxidase into the thalamic VM nucleus anterogradely labelled afferent terminals in layers I and III of the FEF and retrogradely labelled somata of cerebello‐thalamic neurones in the contralateral dentate nucleus. Both electrophysiological and morphological results consistently revealed cerebello‐thalamo‐cerebral projection onto the FEF which may be implicated in eye‐limb coordination control.
Lactate transport in rat sarcolemmal vesicles and intact skeletal muscle, and after muscle contraction
Authors: McDERMOTT J. C. , BONEN A.
Published: December 2008

To determine whether it was possible to measure lactate transport rates into intact skeletal muscles, the transport of lactate (zero‐trans) was determined in soleus muscle strips incubated in vitro and compared with lactate transport in sarcolemmal vesicles. In addition, the effects of muscle contractility on lactate transport were investigated in electrically‐stimulated soleus muscle strips. In both the intact muscle and the sarcolemmal preparations the rates of transport were saturable, stereospecific, and inhibitable by monocarboxylates (pyruvate, α‐cyano‐4‐hydroxycinnamate) and a protein modifier (A'‐ethylmaleimide; P < 0.05). The anion exchange inhibitor SITS had no effect on lactate uptake (P > 0.05). In both preparations lactate transport followed an inwardly directed proton gradient. Relative comparisons (%) between the preparations indicated a similar slope of increasing transport rates with increasing lactate concentrations and similar responses to a changing pH environment. These characterizations of L‐lactate transport into isolated sarcolemmal vesicles and muscle strips revealed that both preparations yielded similar conclusions regarding the transmembrane movement of L‐lactate. By using this more physiological muscle preparation, contractile activity, induced by electrical stimulation, did not increase lactate uptake in skeletal muscle in the post‐exercise period whereas under similar conditions a marked increase in 2‐deoxy‐D‐glucose uptake occurred (+47%; P < 0.05). These data suggest that the transport of glucose and lactate in contracting muscle is regulated differently. These studies also show that the incubated muscle strip preparation may be useful for studying lactate transport in an intact cell system during physiological experiments.
Discrepant effects of angiotensin II and phenylephrine on plasma volume in conscious goats
Authors: OLSSON K. , HOSSAINI‐HILALI J. , CVEK K.
Published: December 2008

Pressor doses of angiotensin II induced haemodilution in goats despite renal fluid losses. This study was undertaken to determine if this response is dose‐dependent and correlated to the vasoconstrictor action of angiotensin II. Angiotensin II at the doses 0.025, 0.05 and 0.1 fig min‐1 was given intravenously to five goats. Mean arterial blood pressure increased by 3, 10 and 20 mmHg, respectively, and the renal Na excretion rose. The haematocrit decreased by 7, 10, and 9% (percentage of control values) and the plasma protein concentration by 1% (n.s.), 4.5, and 3.5%, respectively. Infusions of phenylephrine (40 fig min‐1; n= 6) caused an equivalent increase of blood pressure and renal Na excretion as angiotensin II (0.1 fig min‐1), but the haematocrit increased by 16% and the plasma protein concentration by 6.5%. Infusions of atrial natriuretic peptide (1 μgmin‐1) alone or together with angiotensin II (0.1 μg min‐1), or phenylephrine were also given (n= 6). Infusions of atrial natriuretic peptide alone did not change blood pressure, but renal Na excretion increased. The haematocrit rose by 10.5% and the plasma protein concentration by 7.6%. Adding atrial natriuretic peptide to the angiotensin II solution attenuated the rise of MAP and counteracted the haemodilution, but did not decrease the natriuresis. Infusions of phenylephrine plus atrial natriuretic peptide caused similar elevations of blood pressure and renal Na excretion as phenylephrine alone. The haematocrit rose by 24% and the plasma protein concentration by 13%. These results show that in the intact conscious goat rapid and marked changes in haematocrit and plasma protein concentration can be provoked by intravenous infusions of vasoactive agents and that these effects are not correlated to changes in arterial blood pressure or renal Na excretion.
Effects of transmural field stimulation in isolated muscle strips from rabbit sphincter of Oddi and duodenum
Authors: ELBRØND H. , TøTTRUP A. , VIRCHENKO S. , FORMAN A.
Published: December 2008

The purpose of the study was to compare the effect of transmural field stimulation (TMS) on isolated smooth muscle strips from rabbit sphincter of Oddi (SO), duodenal circular layer (Dc) and duodenal longitudinal layer (D. The strips were suspended in thermostatically controlled 5‐ml organ baths containing Krebs solution constantly bubbled with 5% COain 02. TMS was delivered through platinum electrodes (140 V, 0.4 ms, 5 s trains, 40 Hz). The TMS responses could be divided in two main responses: (1) contraction initiated after cessation of the stimulus train, preceded by an inhibitory phase during TMS (‘off’); and (2) contraction initiated during TMS (‘duration’). The ‘duration’ response was observed in one out of 20 strips in the SO and Dccompartments, whereas 11 D, strips (55%) showed ‘duration’ responses (P< 0.001). Atropine (10‐6) converted all ‘duration’ responses to an ‘off’ response preceded by an inhibitory phase during TMS and reduced the contractile amplitudes with 40–65%. L‐NNA significantly increased the number of ‘duration’ responses in all types of muscle, and caused a 40% increase in Dj contractile amplitude. Inhibitory responses could not be removed by atropine, propranolol and phentolamine. The results suggest that the intrinsic innervation of SO and duodenal muscle consists of a mixture of excitatory, cholinergic and inhibitory NANC pathways. The latter may utilize, wholly or partly, NO or a related compound as transmitter. A relative dominance of excitatory, cholinergic responses was present in the D:strips, whereas inhibitory responses were dominating in the SO and Dcstrips.
Myosin heavy chain isoforms in single fibres from m. vastus lateralis of sprinters: influence of training
Authors: ANDERSEN J. L. , KLITGAARD H. , SALTIN B.
Published: December 2008

The myosin heavy chain (MHC) composition of single fibres from m. vastus lateralis of a group of male sprint athletes (n= 6) was analysed, before and after a three months period of intensive strength‐ and interval‐training, using a sensitive gel electrophoretic technique. Significant improvements were observed after training in almost all of a series of performance tests. After training the sprinters revealed a decrease in fibres containing only MHC isoform I (52.0 ±3.0% vs. 41.2 ±4.7% (mean±SE) (P < 0.05)) and an increase in the amount of fibres containing only MHC isoform IIA (34.7 ±6.1% vs. 52.3 ±3.6% (P < 0.05)). Fibres showing co‐existence of MHC isoforms IIA and IIB decreased with training (12.9 ± 5.0% vs. 5.1 ±3.1%, (P < 0.05)). Only one out of 1000 fibres analysed contained only MHC isoform IIB. In contrast, a higher amount of type IIB fibres (18.8 ± 3.6% vs. 10.5 ± 3.9%, (P < 0.05)) was observed with myofibrillar ATPase histochemistry. The majority of histochemically determined type IIB fibres of sprinters seems therefore to contain both MHC isoforms IIA and IIB. Sprint‐training appears to induce an increased expression of MHC isoform IIA in skeletal muscles. This seems related to a bi‐directional transformation from both MHC isoforms I and IIB towards MHC isoform IIA.
Relationship between mean arterial pressure and muscle cell phi during forearm ischaemia after sustained handgrip
Authors: NISHIYASU T. , UENO H. , NISHIYASU M. , TAN N. , MORIMOTO K. , MORIMOTO A. , DEGUCHI T. , MURAKAMI N.
Published: December 2008

Recent evidence suggests that there is a close correlation between the physiological responses to muscle chemoreflex and the decrease in intracellular pH during ischaemia after handgrip. This study evaluated whether the relationship is linear or has an apparent threshold. We measured muscle cellular pH through phosphorous nuclear magnetic resonance spectroscopy (31P‐NMR), mean arterial blood pressure (MAP) and heart rate (HR) during ischaemia after sustained handgrip exercise at 50% of maximum voluntary contraction (MVC). Contraction was sustained for 15, 30, 45 and 60s, followed by 2 min of circulatory arrest, respectively. Muscular pH during the ischaemia decreased linearly with increasing contraction time, from the base‐line level of 7.11± 0.03 units (U) to 6.98 ± 0.03, 6.90 ± 0.04, 6.72 ± 0.08 and 6.54 ± 0.06 U after 15‐, 30‐, 45‐ and 60‐s contractions, respectively. The MAP was 86 ± 2 mmHg at rest and did not change during the ischaemia after 15‐ and 30‐s contractions. However, it significantly increased to 95 ±2 and 107 ± 2 mmHg, after 45‐ and 60‐s contractions, respectively. These data indicate that the relationship between MAP and pH is not a single linear relationship, showing one breaking point around the pH of 6.90 units. It suggests that the muscle chemoreflex has a clear threshold around 6.90 units of muscle pH, and below this pH, MAP increased linearly with decreasing muscle cellular pH.
Nitric oxide (NO) in expired air at rest and during exercise
Authors: TROLIN G. , ANDÉN T. , HEDENSTIERNA G.
Published: December 2008

Nitric oxide (NO) was analysed in expired air from 27 healthy human subjects. At rest the NO concentration was 10.5 ± 0.9 ng 1‐1(mean ± SEM) corresponding to 8.6 ± 0.7 parts per billion (ppb). The expired NO concentration did not change when the subjects were switched from breathing NO‐free tank gas to room air which contained 7.7 ng 1‐1NO. Repeated measurements of expired NO with an interval of 1 day showed a mean variation of 2.2 ± 0.7ngl‐1NO. The NO concentration in the first portion in the expired tidal volume (44%) was insignificantly higher than in the latter expired portion, 6.9 ± 1.9 vs. 5.1 ± 1.0 ng 1‐1(n= 5). During moderately heavy exercise on an ergometer bicycle (90 W for women,n= 4, 150 W for men,n= 4) the expired concentration of NO decreased, however because of increased minute ventilation, the expired amount of NO almost doubled (from 111 ± 12 to 209 ± 30 ng min‐1). The source of the expired NO is not clear and both the airways and the pulmonary circulation may contribute.
On the point of action for sympatho‐adrenergic inhibition of duodenal alkaline secretion in the rat
Authors: JÖNSON C. , JOHANSSON B. , FÄNDRIKS L.
Published: December 2008

Experiments were performed on chloralose anaesthetized rats. A duodenal segment was decentralized by means of bilateral vagotomy and splanchnicotomy. The mucosal alkaline secretion by the segment was measured using anin situpH‐stat titration. The duodenal alkaline secretion was raised by about 100% utilizing two different secretagogues; vasoactive intestinal polypeptide (VIP) and prostaglandin E2(PGE2). Direct splanchnic nerve stimulation (10 Hz, 5 min, bilaterally), or exogenous administration of the alpha‐2‐adrenoceptor agonist clonidine (15 μg h‐1kg‐1), inhibited the secretion stimulated by PGE2, but not by VIP. The results suggest that the sympathetic nerves exert their inhibitory effect mainly on enteric secretomotor neurones.
Graded action potentials generated by differentiated human neuroblastoma cells
Authors: JOHANSSON S.
Published: December 2008

Stimulus‐dependent impulses and resting membrane parameters of human SH‐SY5Y neuroblastoma cells, induced to differentiate by retinoic acid, were investigated with tight‐seal recording techniques. Mean resting potential was ‐53 mV, mean input resistance 2.1 GΩ, mean capacitance 14 pF, and mean time constant 30 ms. Rectangular current steps induced clearly stimulus‐dependent impulses, with stronger current steps causing impulses of larger amplitude. The degree of impulse variability differed significantly among different cells. The current thresholds for impulse generation ranged from 35 to 100 pA for 10 ms current steps. With longer current steps, thresholds below 10 pA were recorded. In response to 0.5‐1 s long current steps, most cells generated only a single impulse, but a few cells generated two impulses. When two impulses were generated, the interval between the impulses decreased with increasing stimulus strength. Whole‐cell currents were recorded under voltage‐clamp conditions. Voltage‐activated, tetrodotoxin‐sensitive Na+ currents and ‘delayed rectifier’ K+ currents were recorded. The degree of impulse variability was correlated to the maximum Na+ current density. Cells with large Na+ currents showed little impulse variability, while a marked variability was recorded in cells with intermediate or small Na+ currents. Cells which generated more than one impulse in response to prolonged stimuli belonged to the group with large Na+ currents. Spontaneous impulse‐currents were recorded from cell‐attached membrane patches on intact cells. Also these impulses showed a large variability in amplitude: In each of five cells analysed, the peak‐to‐peak amplitude varied by a factor larger than 1.7.
Cortisone‐induced changes in myosin heavy chain distribution in respiratory and hindlimb muscles
Authors: POLLA B. , BOTTINELLI R. , SANDOLI D. , SARDI C. , REGGIANI C.
Published: December 2008

In this study the effects of administration of cortisone acetate (100 mg kg‐1 body weight subcutaneously for 11 days) on distribution and cross‐sectional area of different fibre types of rat skeletal muscles were investigated. Diaphragm, parasternal intercostal (PI), extensor digitorum longus (EDL) and soleus muscles were examined in cortisone treated animals (CA) in comparison with ad libitum controls (CTRL) and pair‐fed (PF) controls. Four fibre types (I or slow and IIA, IIX, IIB or fast) were identified on the basis of their myosin heavy chain composition using a set of monoclonal antibodies.

In CA rats the reduction of cross‐sectional area was above 30% in IIX fibres of diaphragm, IIB fibres of PI and in all fast fibres of EDL. In all muscles slow fibres were spared from atrophy.

Significant variations in fibre type distribution were found in the muscles of CA rats when compared to CTRL. The percentage of IIB fibres decreased in EDL, PI and diaphragm. This decrease was accompanied by an increase in the percentage of IIA fibres in the same muscles. No changes in the percentage of slow fibres and of fast IIX fibres were observed in EDL, PI and diaphragm of CA rats in comparison with CTRL. In soleus of CA rats the proportion of IIA fibres was lower than in CTRL. In EDL of PF rats atrophy of IIA fibres and changes in fibre type distribution were similar to those observed in CA rats. In diaphragm, PI and soleus of PF rats no significant decrease in fibre cross‐sectional area nor significant changes in fibre distribution were found in comparison with CTRL rats.
The role of volume‐sensitive CI channels in the stimulation of chloride absorption by short‐chain fatty acids in the rat colon
Authors: DIENER M. , PETER A. , SCHARRER E.
Published: December 2008

The short‐chain fatty acids acetate, propionate and butyrate induced a concentration‐dependent decrease in short‐circuit current (Isc) of the rat colonin vitro.The decrease inIsc, being more pronounced in the distal than in the proximal colon, was dependent on the presence of CI‐ions and partly on the presence of HCO‐3. In the distal colon, the fall inIsccould be inhibited by amiloride, indicating that the activity of the Na+/H+exchanger is necessary for the induction of this response. The decrease inIscwas diminished by the CI‐channel blocker, 5‐nitro‐2‐(3‐phenylpropylamino)‐benzoate, and the lipoxygenase inhibitor, nordihydroguaiaretic acid. In contrast, inhibitors of the leukotriene pathway or a CI‐channel blocker did not affect theIscresponse in the proximal colon.

Measurements of unidirectional fluxes revealed that butyrate caused a stimulation of the mucosa to serosa fluxes (Jms) of Na+and CI‐in the distal, but only of jmsNain the proximal colon. Unidirectional Rb+fluxes were not altered. The stimulation of jmsclcorrelated with the degree of metabolism of the short‐chain fatty acid. The increase in jmsclwas most pronounced for butyrate, smaller for acetate and not observed with the poorly metabolizable short‐chain fatty acid, isobutyrate. Consequently, two factors seem to be responsible for the stimulation of CI‐absorption by short‐chain fatty acids in the distal colon: (1) the intracellular production of HCO‐3during the oxidation of short‐chain fatty acids as substrate for the apical Cr/HCO‐3exchanger, and (2) the activation of volume‐sensitive basolateral CI‐channels.
Natriuresis in conscious dogs caused by increased carotid [Na+] during angiotensin II and aldosterone blockade
Authors: EMMELUTH C. , DRUMMER C. , GERZER R. , BIE P.
Published: December 2008

The renal response to a selective increase in the Na+ concentration of the blood perfusing the central nervous system was investigated in conscious dogs treated with the converting enzyme inhibitor enalaprilat and the aldosterone antagonist canrenoate. In split‐infusion experiments the plasma [Na+] of carotid blood was increased (approx. 6 mM) by bilateral infusion of hypertonic NaCl. Concomitantly distilled water was infused into the v. cava making the sum of the infusions isotonic. In control experiments isotonic saline was infused at identical rates into all three catheters. Na+ excretion increased markedly in both series, 103 ± 14 to 678± 84 μmol min‐1 during split‐infusion and 90 ± 14 to 496 ± 74 μmol min‐1 during the isotonic volume expansion. Peak rate of excretion, peak fractional sodium excretion, and cumulative sodium excretion were all significantly higher (P < 0.05) during split‐infusion than during control experiments. Plasma vasopressin increased only during split‐infusion (0.68 ± 0.11 to 2.4 ± 0.8 pg ml‐1) while the increases in plasma atrial natriuretic peptide were similar in the two series. Urinary excretion of urodilatin (ANP95‐126) increased significantly more during split‐infusion (46 ±11 to 152 ±28 fmol min‐1) than during the isotonic volume expansion (45 ± 14 to 84 ± 16 fmol min‐1) (P < 0.05). It is concluded that the natriuretic mechanisms activated by a selective increase in the Na+ concentration of carotid blood and associated with increased excretion of urodilatin cannot be eliminated by blockade of the renin‐angiotensin‐aldosterone system.
Intrinsic cardiac rate regulation in the anaesthetized rabbit
Authors: BOLTER C. P.
Published: December 2008

Intrinsic cardiac regulation, the direct effect of changes in right atrial pressure on heart rate, was examined in rabbits under chloralose/urethane anaesthesia. Autonomic influences on the cardiac pacemaker were eliminated by cervical vagotomy and intravenous propranolol. Right atrial transmural pressure was monitored as the difference between right atrial and pleural pressures. Blood volume expansion (5–15%) increased right atrial transmural pressure and heart rate and produced a sinus arrhythmia associated with respiration‐linked fluctuations in right atrial transmural pressure. The gain of intrinsic cardiac rate regulation was calculated as 0.96 ± 0.24 beats min‐1 mmHg‐1 at a heart rate of 218 ± 6 beats min‐1 (values as the mean± SEM, n= 12). When heart rate was reduced by electrical stimulation of the peripheral end of the right vagus nerve, gain increased to 2.25± 0.57* and 4.61 ± 1.6* beats min‐1 mmHg‐1 at heart rates of 180 ± 4 and 130 ± 4 beats min‐1, respectively (n= 6 and n= 10; *P < 0.05 compared with pre‐stimulation values). During vagally‐induced bradycardia, rapid infusion of blood into the left superior vena cava produced a brief marked cardiac acceleration. We conclude that right atrial pressure has a small direct influence on heart rate, and this is enhanced by background cardiac parasympathetic stimulation.
The role of the adrenal medulla in cardiovascular responses to hypertonic saline in haemorrhaged conscious rats
Authors: ELGJO G. I. , EIDE I. , KNARDAHL S.
Published: December 2008

The aim of this study was to determine if the adrenal medulla plays a role in mediating haemodynamic effects of hypertonic saline (HTS) resuscitation during haemorrhagic hypotension in conscious rats. Wistar‐Kyoto rats were either adrenomedullectomized (ADMX,n =11) or sham‐operated (SHAM,n =10) and implanted with intravascular catheters. Pre‐haemorrhage resting mean arterial pressure (MAP) was lower in the ADMX than in the SHAM group. Haemorrhage was performed by withdrawal of blood through the venous catheter, and a MAP of 50 mmHg was maintained for 1 h by further withdrawal when necessary. Both groups responded to haemorrhage with marked bradycardia. Plasma adrenaline (A) rose 10‐fold in response to hypotension in the SHAM group, while remaining at pre‐haemorrhage levels in the ADMX group, indicating successful adrenal demedullation. Infusion of 2.0 ml kg‐1HTS (NaCl 8.0 mg ml‐1i.v.) produced an immediate increase in MAP and heart rate (HR) in both groups, to pre‐haemorrhage values or higher. Plasma noradrenaline (NA) increased in both groups after HTS, while the high levels of A in the SHAM group slowly returned toward baseline. Plasma glucose and rate of haemodilution was higher in the SHAM group during and after hypotension. The maintenance of MAP above 60 mmHg was less effective in the SHAM group during the first 2 h after HTS, but after 24 h, pre‐haemorrhage MAP was established in both groups. In conclusion, the adrenal medulla does not play a major role in the response to HTS resuscitation.
Increased lymphatic hyaluronan output and preserved hyaluronan content of the rat small intestine in prolonged hypoproteinaemia
Authors: ØSTGAARD G. , REED R. K.
Published: December 2008

Nephrotic syndrome was induced in seven rats by daily aminonucleoside injections. Experiments were performed in anaesthesia 6 or 7 d later when protein loss in urine had reduced serum colloid osmotic pressure (COP) to 8.2 ± 0.9 (SD) mmHg compared with 20.2 ± 2.2 mmHg in controls (P < 0.01). Due to the decreased COP in the nephrotic rats, lymph flow in the main mesenteric lymphatic was 29.5 ± 11.5,;1 min‐1 compared with 4.2 ±2.2.2μl min‐1 in the control rats (P < 0.01). The corresponding hyaluronan concentrations were 3.4 ± 0.9 μg ml‐1 and 12.0 ± 3.5 μg ml‐1, respectively (P < 0.01). Nevertheless lymphatic hyaluronan output was doubled in the nephrotic rats, but this did not affect the hyaluronan content of the small intestine of 192 ± 58μg‐1 dry wt compared with 215±69 μg g‐1 in controls (P ± 0.05). During a 20 min intravenous 0.9% saline infusion of 4 ml 100 g‐l rat, the hyaluronan concentration increased to 18.3 (6.0) μg ml‐1 in mesenteric lymph in controls, whereas the concentration in lymph from the nephrotic rats remained unchanged. Lymphatic output increased, however, in this group as well due to the elevated flow. The amount of hyaluronan cleared daily by the main mesenteric lymphatic in awake rats corresponds to about half the tissue hyaluronan content in the drained area (Østgaard & Reed 1993 b). The unaltered tissue content of hyaluronan in the nephrotic rats must therefore imply an increased production of hyaluronan in response to the increased interstitial washout of hyaluronan induced by the hypoproteinaemia.
Electromyographic responses of the human triceps surae and force tremor during sustained sub‐maximal isometric plantar flexion
Authors: LÖSCHER W. N. , CRESSWELL A. G. , THORSTENSSON A.
Published: December 2008

The objective was to investigate electromyographic activity (EMG) and isometric force tremor (IFT) changes during a sustained sub‐maximal isometric contraction in two muscles acting upon the same joint but differing in muscle fibre composition. Surface and intra‐muscular EMG activity from the gastrocnemius and soleus muscles and IFT were recorded during an exhausting isometric plantar flexion (30% of maximal voluntary contraction). Surface EMG amplitude (RMS) of both gastrocnemius and soleus muscles increased significantly over time. Gastrocnemius EMG RMS increased in a non‐linear fashion while soleus EMG RMS increased linearly. A significant linear decrease of surface EMG mean power frequency (MPF) was observed over time for both muscles. The decrease in gastrocnemius MPF was significantly greater than that for soleus. Intra‐muscular EMG results showed similar trends. Correlations of intramuscular EMG RMS and MPF with time were, however, characterized by lower correlation coefficients than those from the surface EMG. Isometric force tremor RMS significantly increased non‐linearly with duration of contraction, while IFT MPF showed a significant linear decrease with time. Changes in surface EMG RMS were correlated to changes seen in IFT RMS, in particular, for the predominantly fast twitch gastrocnemius muscle. Correlation coefficients of surface EMG MPF and IFT MPF were lower than RMS correlations. The associated changes in IFT and EMG with fatigue indicate alterations in motor unit firing rate, recruitment and synchronization. The muscle specificity of the EMG and IFT changes suggests a coupling to muscle fibre type composition, although differences in the relative force contribution of each muscle could also affect the results.
Effects of glyceryl trinitrate, nitroprusside and nitric oxide on arterial, venous and capillary functions in cat skeletal muscle in vivo
Authors: EKELUND U.
Published: December 2008

The aim of the present study was to analyse quantitatively, on a cat gastrocnemius preparationin vivo, the effects of i.a. or i.v. administered glyceryl trinitrate (GTN), sodium nitroprusside (SNP) or nitric oxide (NO dissolved in saline) on vascular resistance (tone) in the following consecutive vascular sections: Large‐bore arterial resistance vessels (> 25 μm), small arterioles (< 25 μm), and the veins. Effects on hydrostatic capillary pressure(Pcv) and transcapillary fluid exchange were simultaneously recorded. Close‐arterially infused GTN (1–4096μg kg tissue‐1min‐1), SNP (0.5–32 %mUg kg tissue‐1min‐1) and NO (0.14‐0.82 mg kg tissue‐1min‐1) elicited a generalized dose‐dependent dilator response in all three sections, though with a preferential action on the arterial side. Further, these agents caused an increase inPcvand transcapillary fluid filtration. The sites of action along the vascular bed of these exogenous vasodilators differed from that previously established for endogenous EDNO. Infusion of GTN, SNP and NO during EDNO blockade (L‐NAME) could, therefore, not restore the vascular resistance distribution to that prevailing in the initial control state. Myogenic vascular reactivity to standardized transmural pressure stimuli was clearly depressed by GTN and SNP. Intravenously infused GTN (4–512 μg kg body wt‐1min‐1) and SNP (4–64μg kg body wt‐1min‐1) decreased arterial pressure and elicited, via reflex sympathetic activation, a dose‐dependent vasoconstriction in skeletal muscle, a decrease inPcv, and net transcapillary fluid absorption. The constrictor response thus overruled the direct dilator effect of the drugs. The plasma volume expansion known to result from long‐term systematic administration of nitrovasodilators seems in part to be caused by transcapillary fluid absorption in skeletal muscle.
Spectral sensitivities of short‐ and long‐wavelength sensitive cone mechanisms in the frog retina
Authors: KOSKELAINEN A. , HEMILÄ S. , DONNER K.
Published: December 2008

ERG mass photoreceptor responses were recorded across the isolated, aspartate‐perfused retina of the frog, Rana temporaria, in order to determine spectral sensitivities of cones. Cone responses were distinguished from rod responses by their faster kinetics, and responses from different cone types were isolated by selective background adaptation. Our main finding is that of a novel short‐wavelength sensitive cone population peaking at about 431 nm. Further, we find that the sensitivity spectrum of the dominant long‐wavelength sensitive cone population fully accounts for the most common type of photopic ganglion cell spectrum. Both can be described by a nomogram with λmax= 562 nm. This resolves a long‐standing apparent conflict between cone absorbance spectra and ganglion cell sensitivities. Including the 502 nm cones previously described by microspectrophotometry, the frog possesses a collection of cones that could support trichromatic photopic vision.
Rhythmic contractions of isolated, pressurized small arteries from rat
Authors: GUSTAFSSON H. , BÜLOW A. , NILSSON H.
Published: December 2008

The present study was undertaken to examine the influence of transmural pressure on vasomotion and to determine if any such influence was endothelium–dependent. Responses to changes in intravascular pressure of cannulated mesenteric small arteries were investigated under no–flow conditions. Both intact and endothelium–denuded arteries dilated passively when intravascular pressure was increased stepwise from 20 to 140 mmHg. When tone was induced by noradrenaline, pressure increase resulted only in dilatation, independent of endothelium. The sensitivity to noradrenaline was significantly increased in vessels without endothelium, indicating a relaxing influence of the endothelium. Rhythmic contractions in response to noradrenaline occurred in all intact arteries, but were absent when the endothelium was removed. The amplitude of the rhythmic contractions decreased significantly when transmural pressure was elevated. The frequency increased when pressure was elevated from 20 to 80 mmHg and then remained rather constant during further pressure increases. As shown previously in non–pressurized arteries, exogenous cyclic GMP induced oscillations in endothelium–denuded arteries. Pressure–related effects on vasomotion were not dependent on an intact endothelium. Ryanodine, ouabain or verapamil inhibited the rhythmic activity, confirming previous results in non–pressurized arteries.

Thus, changes in transmural pressure can modulate vasomotion, but this effect does not appear to be mediated by the endothelium. Generation of vasomotion may depend on release of Ca2+ from intracellular stores, the activity of the Na+, K+–pump and transmembrane Ca2+ inflow in a pressurized artery as shown previously in these arteries under isometric conditions.
Effects of NIC, receptor antagonists on vasodilation induced by chemical and electrical activation of sensory C–fibre afferents in different organs
Authors: STJÄRNE P. , RINDER J. , DELAY–GOYET P.
Published: December 2008

The effects of the non–peptide NK, receptor antagonists, CP96,345 and RP–67,580, were investigated in a model using anaesthetized pigs. Both the blood flow in the internal maxillary and the bronchial artery (ultrasonic flowmetry) and the superficial blood flow in nasal mucosa and the skin (laser–Doppler flowmetry) were monitored simultaneously. Vasodilation induced by substance P administered i.v. systemically was blocked by pretreatment with CP–96,345, 3 mg kg1 but not by RP–67,580. CP–96,345 had no effects on the vasodilationo induced by calcitonin gene–related peptide or vasoactive intestinal polypeptide. The capsaicin–induced vasodilation in the superficial blood flow of the nasal mucosa and the skin, was reduced after the CP–96,345 pretreatment. The vasodilation induced by capsaicin infusion in the internal maxillary or the bronchial artery was not affected by the CP–96,345 pretreatment. Electrical stimulation of the vagal nerve induced a vasodilation in the bronchial circulation which was not attenuated by pretreatment with CP–96,345.

In the nasal mucosa and the skin NK1 receptors seem to be involved in the vasodilation in the superficial small vessels, due to chemical activation of sensory C–fibre afferents. Furthermore, CP–96,345 is a useful tool in the evaluation of NKX receptor–mediated responses. RP–67,580 which has been shown to have NK1 antagonistic properties in the rat has no such effects in the domestic pig.
Inhibition of SKF 89976–A of the y–aminobutyric acid release from primary neuronal chick cultures
Authors: LEWIN L. , MATTSSON M.–O. , GRAHN B. , SELLSTRÖM Å.
Published: December 2008

Neuronal cultures were made from the 8–d–old embryonic chick telencephalon. The primary culture model was further improved, the medium composition was modified, and the cells grown for 10 d, which allowed the development of relatively differentiated neurones. A superfusion protocol was developed and applied to study the release of [3H]–γ–aminobutyric acid ([3H]GABA). High endogenous activity levels of glutamate decarboxylase (GAD) and of a Ca–dependent potassium stimulated [3H]GABA release were used as criteria for GABAergic differentiation. The influence of the non–substrate inhibitor of GABA transport, SKF 89976–A, on the GABA release, was studied using the primary neuronal culture. The release was found to be inhibited by SKF 89976–A at higher concentrations (= 400 μM).
Role of the endothelium in regulation of vascular functions in two teleosts
Authors: SVERDRUP A. , KRUGER P. G. , HELLE K. B.
Published: December 2008

Functional and structural aspects of the vascular endothelium were studied in major blood vessels from two distantly related species, the Atlantic salmon(S. salar)and the cod (G.morhua.) The ventral aorta (VA) of both teleosts and the dorsal aorta (DA) and the coeliaco mesenteric artery (CMA) of the cod and the salmon respectively were examined for endothelium dependent and independent responses to acetylcholine (ACh), adrenaline (A) and endothelin–1 (ET–1).

In the salmon, endothelial probing resulted in reduced contractile responses to high K+in both VA and CMA while the responses to ACh and A were reduced only in CMA. Indomethacin, but not L–NMMA, enhanced vasoconstrictions to high K+, ACh and A in the unprobed CMA.

In the cod vessels the endothelial probing caused reduced contractile responsestothe two effective vasoconstrictors in both vessels, to high K+and A in VA and to high K+and ET–1 in DA. Both indomethacin and L–NMMA enhanced contractile tension to A in VA, while indomethacin, but not L–NMMA, enhanced the constrictions by high K+in VA and by ET–1 in DA.

These experiments have revealed heterogeneous patterns of endothelial function in blood vessels of two teleosts, reflecting differences in endothelial morphology and in production of potent endothelial derived contracting factors as well as prostanoic and non–prostanoic endothelium–derived dilating factors.