bluuebunny/crossref_metadata_2025_split huggingface dataset:
Accumulation of Calcium by Retinal outer Segments
Authors: Hemminki Kari 
Published: December 2008

AbstractTwo preparations of bovine photoreceptors, including intact and lysed outer segments, are used to study accumulation of Ca++ in order to differentiate between binding and transport. The two preparations accumulate initially roughly equal amounts of Ca++ in the presence or absence of ATP. In the absence of ATP no further accumulation occurs. With ATP accumulation continues most rapidly in intact outer segments. The addition of a Ca++‐ionophore (A 23187) to assays containing ATP, results in kinetics of uptake similar to those in the absence of ATP. Thus the initial phase of Ca++ accumulation is predominantly due to binding, while that induced by ATP is due to transport. Accumulation of Ca++ by outer segments can be stimulated by preloading them with ATP suggesting that ATP enters the structures and acts intracellularly. Illumination decreases binding of Ca++ to outer segments but does not consistently affect transport. After illumination more Ca++ is retained by intact than lysed outer segments indicating that plasma membrane acts as a barrier to the escape of Ca++. Phospholipids and protein appear to be responsible for Ca++ binding of outer segments as suggested by a reduced binding ability after removal of these constituents. Phosphatidyl ethanolamine is the main phospholipid class of outer segments.
The Postnatal Development of Some Twitch and Fatigue Properties of the Ankle Flexor and Extensor Muscles of the Cat
Authors: Hammarberg C. , Kellerth J‐O. 
Published: December 2008

AbstractThe isometric responses of the medial gastrocnemius (MG), soleus (SOL) and anterior tibial (TA) muscles to single shocks and different modes of repetitive stimulation were studied in kittens of varying postnatal ages and in adult cats. The postnatal decrease in time‐to‐peak and half‐relaxation time of the twitch contractions was similar for the MG and TA muscles and adult values were attained at around 6–7 weeks of age. The SOL muscle displayed a transient decrease in contraction time during the first postnatal weeks, followed later by a slowing towards adult values. The susceptibility to fatigue during iterative stimulation was smallest in the SOL at all ages studied, and usually largest in TA. It changed only little for the MG and SOL postnatally while increasing markedly for the TA up until 6–7 weeks of age. Tetanic contraction resulted in similar depressions in contractile tension of all three muscles in the youngest kittens, but the SOL displayed a greater ability to recover from this depression than the MG and, in particular, the TA muscles. Tetanus resistance increased postnatally and adult responses were attained at 6–7 weeks of age.
Studies on the Central Integration of Excitatory Chemoreceptor Influences and Inhibitory Baroreceptor and Cardiac Receptor Influences
Authors: Wennergren Goran , Little Rod , ÖBerg Bengt 
Published: December 2008

AbstractExperiments were performed on cats to explore the integrated cardiovascular responses when excitatory (chemoreceptor) and inhibitory (baroreceptor or cardiac receptor) influences are simultaneously presented to the medullary cardiovascular areas. At a given sinus pressure in the low or medium pressure range, the systemic blood pressure and the vascular resistance were higher when the chemoreceptors were stimulated, while a high, pulsating sinus pressure, i.e. a strong baroreceptor stimulation, could suppress completely even an intense chemoreceptor activation. Thus, the set point and the gain of the baroreflex were increased by a concomitant chemoreceptor activation. These effects are compatible with a simple, mutual ‘summation’ of excitatory and inhibitory influences on a common population of central vasomotor neurons. The reflex vasodilator effects elicited via vagal cardiac afferents were found to be more effectively suppressed by a concomitant chemoreceptor stimulation than were the baroreceptor effects, provided a primary chemoreceptor response (bradycardia) was at hand, while the heart rate responses were essentially uninfluenced by the prevailing chemoreceptor activity. This chemoreceptor suppression of the reflex vasodilatation from cardiac receptors, which may be of great importance in hypoxic situations, e.g. during a dive, suggests a more complex, neuronal interaction between the two reflex mechanisms in the CNS.
Spread of the Junction Potential in the T‐System in Hagfish Slow Muscle Fibres
Authors: Nicolaysen Kåre 
Published: December 2008

AbstractThe membrane constants of the slow muscle fibres from the Atlantic hagfish were determined by analyzing the responses to sinusoidal currents at different frequencies. The apparent low frequency membrane resistance was 20–50 kΩcm2 and was not significantly altered by replacing external chloride with methyl sulphate. The low frequency capacitance was 2.1–2.4 μF/cm2 and decreased to about 1 μF/cm2 at 100 Hz. A model of the T‐system consisting of a number unbranched T‐tubules was fitted to the impedance locus. About 15 tubules per sarcomere with a length approximately 8 times the fibre radius gave good fit to the observed impedance locus. The electrical characteristics of the T‐system allow an efficient electrotonic spread of the junction potential through the fibre cross‐section.
Skeletal muscle metabolism and ultrastructure in relation to age in sedentary men
Authors: ÖRlander Jan , Kiessling Karl‐Heinz , Larsson Lars , Karlsson Jan , Aniansson Amelie 
Published: December 2008

AbstractIn order to find out if there are age‐related changes in human skeletal muscle metabolism or ultrastructure, biopsy material from 56 sedentary men aged 22–65 years was studied by means of enzyme activity determinations, histochemistry and quantitative electron microscopy. For comparison, a younger (16–18 years) and an older (66–76 years) group were included. These subjects were relatively more active. There was an increase in percentage of slow twitch fibres with age. Mitochondrial volume fraction decreased with age, primarily due to diminished mean mitochondrial volume. In spite of this, no overall decrease in the activities of five enzymes, representative of the major pathways in energy metabolism, was observed. Thus, increased amounts of enzymes per unit mitochondrial volume are implicated. Lipofuscin was more frequently found in the older groups. Correlations were present between fibre type distribution and oxidative enzymes, as well as between different enzymes. It was concluded, that the decrease in maximal oxygen uptake and muscular strength in aging humans probably may not be explained in terms of a deteriorating skeletal muscle energy metabolism.
A note on the single injection residue function method to determine capillary permeability
Authors: Garby Lars , Grønlund Jørgen 
Published: December 2008

AbstractThe assumptions inherent to the single injection residue function method to determine capillary permeability have been made explicit. Furthermore, it is shown that agreement between the deduced wash‐out function of the transmitted molecules of the test substances and that of reference molecules does not constitute proof of the validity of the method.
Plasma catecholamine levels in the coronary sinus, the left renal vein and peripheral vessels in healthy males at rest and during exercise
Authors: Manhem Per , Lecerof Harry , Hokfelt Bernt 
Published: December 2008

AbstractNoradrenaline and adrenaline were determined in blood samples from the brachial vein, the brachial artery, the left renal vein and the femoral vein in 6 healthy males (aged 23–35 y). In 3 of the subjects catecholamines were determined also in blood from the coronary sinus. All samples were taken simultaneously in supine position after 30 min of rest and then in connection with exercise in supine position using a bicycle ergometer, firstly with a work load of 50 W for 9 min and secondly with a work load of 150 W for the same period of time. Under resting conditions the catecholamine levels were about the same at all locations, the mean for noradrenaline being 1.59 nmol/l with a range of 1.30–2.11 nmol/l and for adrenaline 0.46 nmol/l and 0.234.65 nmol/l, respectively. At 50 W the noradrenaline concentration increased significantly in the brachial artery, the left renal vein and the femoral vein, whereas adrenaline increased significantly only in the femoral vein. At 150 W the noradrenaline content increased markedly in all samples, especially in the left renal vein (mean increase 13.02 nmol/l) and the coronary sinus (mean increase 13.06 nmol/l). Adrenaline concentration increased significantly in the brachial artery and the femoral vein. At 150 W the mean net output of noradrenaline as estimated from the calculated flows and actual AV‐differences amounted to 2.25 nrnol/min from the heart and to 0.36 nmol/min from the kidney.
Blood pressure and heart rate response to static exercise in relation to electromyographic activity and force development
Authors: SCHIBYE B. , MITCHELL J. H. , PAYNE F. C. , SALTIN B. 
Published: December 2008

5 healthy men performed static knee extension (90° knee angle) with one leg for 5 min. In one series of experiments the force was held constant at 20% of the isometric maximal voluntary contraction. In the other the initial force development was also 20%, but the smoothed, rectified electromyographic activity, (SREMG) recorded after 5 s of contraction was kept constant. Heart rate (HR), arterial mean blood pressure (MBP) (measured 20 cm proximally to the elbow in a. brachialis), EMG (surface electrodes) from the lateral portion of m. quadriceps femoris, and force were continuously recorded.HR and MBP increased approximately 40% in the force‐constant experiments and approximately 20% in the SREMG‐constant experiments. The greatest increase occurred during the first two minutes of contraction. In the force‐constant experiments SREMG doubled, with the most marked increases occurring during the very early and late parts of the contraction. SREMG correlated with both HR (r=0.85) and MBP (r=0.98). In the SREMG‐constant experiments force declined quickly during the first minute and remained at about 12% MVC thereafter.The observed cardiovascular responses to static contraction can best be explained as the result of the combined action of central and peripheral drives, the central drive being related to the central activity for the recruitment of motor units, and the peripheral drive being mediated through chemoreceptors in the exercising muscles.
Effects of sympathetic stimulation on cerebral and ocular blood flow Modification by hypertension, hypercapnia, acetazolamide, PGI2 and papaverine
Authors: BEAUSANG‐LINDER MARIANNE 
Published: December 2008

The effect of unilateral, electrical stimulatio of the cervical sympathetic chain in rabbits anesthetized with pentobarbital sodium and vasodilated by hypercapnia, acetazolamide, papaverine or PGI2 was investigated to determine to what extent the sympathetic nerves to the brain and the eye cause vasoconstriction and prevent overperfusion in previously vasodilated animals. Evans blue was given as a tracer for protein leakage. Blood flow determinations were made with the labelled microsphere method during normotension and acute arterial hypertension. Hypertension was induced by ligation of the thoracic aorta and in some animals metaraminol or angiotensin was also used. Acetazolamide caused a two to threefold increase in cerebral blood flow (CBF) and hypercapnia resulted in a fivefold increase. CBF was not markedly affected by papaverine or PGI2. In the choroid plexus, the ciliary body and choroid, papaverine and hypercapnia caused significant blood flow increases on the control side. Sympathetic stimulation induced a 12 % blood flow reduction in the brain in normotensive, hypercapnic animals. Marked effects of sympathetic stimulation at normotension were obtained under all conditions in the eye. In the hypertensive state the CBF reduction during sympathetic stimulation was moderate, but highly significant in hypercapnic or papaverine‐treated animals as well as in controls. Leakage of Evans blue was more frequently seen on the nonstimulated side of the brain. In the eye there was leakage only on the control side except in PGI2‐treated animals where 2 rabbits had bilateral leakage.The effect of sympathetic stimulation on the blood flow in the cerebrum and cerebellum in vasodilated animals seems to be small or absent if the blood pressure is normal. In the eye pronounced vasoconstriction occurs under these conditions. In acute arterial hypertension sympathetic stimulation protects both the cerebral and ocular barriers even under conditions of marked vasodilation.
Effect of frequency of growth hormone administration on longitudinal bone growth and body weight in hypophysectomized rats
Authors: JANSSON JOHN‐OLOV , ALBERTSSON‐WIKLAND KERSTIN , EDÉN STAFFAN , THORNGREN KARL‐GÖRAN , ISAKSSON OLLE 
Published: December 2008

JANSSON, J.‐O., ALBERTSSON‐WIKLAND, K., EDÉN, S., THORNGREN, K.‐G. and ISAKSSON, O.: Effect of frequency of growth hormone administration on longitudinal bone growth and body weight in hypophysectomized rats. Acta Physiol Scand 1982, 114:261–265. Received 11 May 1981. ISSN 0001–6772. Department of Physiology, University of Göteborg and Department of Orthopaedic Surgery, University of Lund, Sweden.The effect of frequency of growth hormone (GH) administration on longitudinal bone growth and body weight was studied in hypophysectomized rats. Replacement therapy with 3 different doses of human GH [(hGH) Crescormone®] was started 10–14 days after hypophysectomy and was continued for 5 days. Longitudinal bone growth, as measured by the tetracycline method, and body weight were determined during the injection period. With a daily replacement dose of 128 μg of hGH body weight gain and longitudinal bone growth were significantly higher when the hormone was injected 4 and 8 times per day compared with animals receiving the hormone in one daily injection. When the dose of hGH was 32 or 8 μg per day, longitudinal bone growth and body weight gain were more pronounced in animals receiving the hormone 2 and 4 times per day compared with animals receiving the hormone one or 8 times per day. The results of the present study demonstrate that the frequency of GH administration influence body growth. The findings suggest that the secretory pattern of GH influence the growth rate under in vivo condition.
Hydraulic permeability of the peritubular and glomerular capillary membranes in the rat kidney
Authors: LARSON M. , HERMANSSON K. , WOLGAST M. 
Published: December 2008

The hydraulic conductivity of the peritubular capillary membrane was calculated from I) single nephron fluid reabsorption and 2) net driving force, i. e. from hydrostatic and colloid osmotic pressures in renal interstitium and peritubular capillary blood, as determined by a micropuncture technique and with use of a computer‐based model.Under control conditions the net driving force was estimated to be 15.4 mmHg and the hydraulic conductivity 1.04 nl/(mmHg) per 100 g rat. During extracellular volume expansion with 0.15 M saline, 4% and 10% of body weight, the net driving force decreased to 12.5 mmHg and 6.4 mmHg, respectively, whereas the conductivity increased to 1.85 and 3.14 nl/(min‐mmHg) per 100 g rat. The reduction in net driving force was compensated by an increased hydraulic conductivity. In the glomeruli the net driving force for filtration increased from 14.2 mmHg under control conditions to 21.2 mmHg and 25.3 mmHg during saline expansion 4% and 10%, whereas the corresponding hydraulic conductivity decreased from 1.13 nl/(min‐mmHg) per 100 g rat to 1.03 and 0.80 nl/(min‐mmHg) per 100 g rat during the two expansions. During saline expansion the water permeability of the glomerular capillaries is decreased while that of the peritubular capillaries is increased. These changes in the water permeability will lead to retarded excretion of the excess fluid.
Calcium‐dependent enhancement by carbachol of the VIP‐induced cyclic AMP accumulation in cat submandibular gland
Authors: ENYEDI PETER , FREDHOLM BERTIL B. 
Published: December 2008

The interaction of two coexisting transmitters in the cat submandibular gland has been elucidated by studying effects of VIP and carbachol on cyclic AMP accumulation in isolated acini from the gland. Carbachol was found to potentiate the cyclic AMP increase induced by VIP by an atropine sensitive mechanism. The effect of carbachol on cyclic AMP accumulation was abolished by including EGTA in the incubation medium as was the carbachol mediated potentiation of VIP responses. The calmodulin inhibitor trifluoperazine had a similar, but less marked effect. The effect of carbachol was mimicked by phenylephrine (30 μM) and by the calcium inophore A 23187 (3 μM), and also by ethanol in a concentration reported to enhance membrane fluidity. The phospholipase A2inhibitor, mepacrine, tended to decrease carbachol actions.Our results show that the poteniation of VIP responses in feline submandibular gland is calcium‐dependent. The mechanism could involve a calcium‐calmodulin‐induced stimulation of adenylate cyclase or calcium‐induced change in membrane phospholipid metabolism.
Effects of neuropeptide Y (NPY) on mechanical activity and neurotransmission in the heart, vas deferens and urinary bladder of the guinea‐pig
Authors: LUNDBERG JAN M. , HUA XIAO‐YING , FRANCO‐CERECEDA ANDERS 
Published: December 2008

The effects of preincubation for 10 min with synthetic porcine neuropeptide Y (NPY) on muscle tone and autonomic transmission in the guinea‐pig right atrium, vas deferens, urinary bladder, portal vein and trachea were analysed in vitro. NPY induced a metoprolol‐resistant, long‐lasting, positive inotropic and cronotropic effect per se in the spontaneously beating right atrium. Furthermore, NPY caused a reversible inhibition of both the metoprolol and atropine‐sensitive auricle responses to field stimulation (2 Hz or 4 Hz for 2 s) without affecting the response to exogenous noradrenaline (NA) or acetylcholine (ACh).NPY did not induce any contraction of the vas deferens, but inhibited both the rapid twitch response and the sustained tonic contraction induced by field stimulation. The NPY‐induced inhibition of the tonic contraction was more long‐lasting than that of the twitch response. The tonic contraction was blocked by phentolamine and the twitch response by α‐, β‐methylene ATP tachyphylaxis. NPY did not inhibit the contractile effects of NA, ATP or α‐, β‐methylene ATP. NPY also induced a reversible reduction of the non‐cholinergic, non‐adrenergic contractile response to field stimulation of the urinary bladder. In the portal vein, NPY (up to 5×10–7M) did not inhibit the spontaneous motility or the phentolamine‐sensitive contractile responses to field stimulation and NA. The atropine‐sensitive contraction of the trachea or the non‐adrenergic, non‐cholinergic relaxation induced by field stimulation were not significantly influenced by NPY in doses up to 5×10–7M. In conclusion, the present data show that in the guinea‐pig, NPY exerts positive chronotropic and inotropic effects on the right atrium of the heart. Furthermore, NPY may have presynaptic effects on adrenergic, cholinergic and non‐adrenergic—noncholinergic neurotransmission.
ATP‐induced cation influx in myotubes is additive to cholinergic agonist action
Authors: HÄGGBLAD JOHAN , ERIKSSON HÅKAN , HEILBRONN EDITH 
Published: December 2008

HÄGGBLAD, J., ERIKSSON, H. & HEILBRONN, E. 1985. ATP‐induced cation influx in myotubes is additive to cholinergic agonist action. Acta Physiol Scand125, 389–393. Received 20 March 1985, accepted 1 May 1985. ISSN 0001–6772. Unit of Neurochemistry and Neurotoxicology, University of Stockholm, S‐172–46 Sundbyberg, Sweden.Using biochemical methods, ATP was shown to induce an inward flux of 86Rb into cultured chick myotubes. A biphasic dose‐response curve was observed, the first part of which was saturable and had an EC50 value of approximately 10 μM. β,γ‐imido ATP inhibited the ATP‐induced uptake. ADP, AMP and adenosine were less potent than ATP in producing influx. ATP‐induced influx of 86Rb was found to be additive to carbachol‐induced influx and, in contrast to the latter, not blocked by the nicotinic acetylcholine receptor antagonist α‐bungarotoxin. The results suggest the presence of an ATP recognition‐site on myotubes, triggering ion‐permeation.
Evidence for substance P‐immunoreactive spinal afferents that mediate bronchoconstriction
Authors: SARIA ALOIS , MARTLING CLAES‐ROLAND , DALSGAARD CARL‐JOHAN , LUNDBERG JAN M. 
Published: December 2008

SARM, A., MARTLING, C.‐R., DALSGAARD, C.‐J. & LUNDBERG, J.M. 1985. Evidence for substance P‐immunoreactive spinal afferents that mediate bronchoconstriction. Acta Physiol Scand 125, 407–414. Received 7 March 1985, accepted 30 April 1985. ISSN 0001–6772. Department of Experimental and Clinical Pharmacology, University of Graz, Austria, and Departments of Pharmacology and Anatomy, Karolinska Institutet, and Department of Anaesthesiology, Karolinska Sjukhuset, Stockholm, SwedenThe origin and functional role of capsaicin‐sensitive substance P‐(SP‐) immunoreactive (IR) nerve fibres in the lower airways were studied in the guinea‐pig. Stellatectomy caused a significant reduction of SP‐IR in the lung and pulmonary artery. Immuno‐histochemical analysis, however, did not reveal any clear‐cut change in the number and distribution of SP‐IR fibres in the lung of these animals. After combined stellatectomy plus local capsaicin treatment of the vagal nerves, most SP‐IR nerves disappeared in the lower airways. The bronchoconstriction induced by capsaicin was significantly reduced after stellatectomy and abolished after stellatectomy plus capsaicin pretreatment of the vagal nerves. Ether inhalation caused bronchoconstriction, which was not influenced by stellatectomy but markedly reduced by combined capsaicin treatment of vagal nerves and stellatectomy. Stellate ganglion stimulation in animals that had been chemically sympathectomized by 6‐OH‐dopamine caused bronchoconstriction, which was resistant to cholinergic or adrenergic receptor blockade. This response was absent after systemic capsaicin pretreatment, suggesting that it was due to antidromic stimulation of afferent fibres traversing the stellate ganglion. In conclusion, the present data suggest that the lower airways receive SP‐IR capsaicin‐sensitive C‐fibre afferents of both vagal and spinal origin. These sensory fibres seem to have branches both within the bronchial smooth muscle and around blood vessels.
Effects of calcium and limited proteolysis on membrane‐bound and releasable dopamine β‐hydroxylase in adrenomedullary catecholamine granules
Authors: HELLE K. B. , PIHL K. E. , SERCK‐HANSSEN G. 
Published: December 2008

HELLE, K.B., PIHL, K.E. & SERCK‐HANSSEN, G. 1985. Effects of calcium and limited proteolysis of membrane‐bound and releasable dopamine β‐hydroxylase in adrenomedullary catecholamine granules. Acta Physiol Scand125, 423–427. Received 9 January, accepted 6 May 1985. ISSN 0001–6772. Department of Physiology, University of Bergen, Norway.Bovine chromaffin granules were shown to contain two potent proteolytic systems resulting in limited proteolysis of granule proteins at pH 6.0 in the cold in the presence of inhibitors of serine and thiol proteases. Calcium, whether added during lysis or remaining bound to the lysate protein during dialysis in non‐chelating solutions, enhanced recoveries of total immunoreactive dopamine β‐hydroxylase (14% of total protein) and soluble enzyme (9% of lysate protein) due to degradation of chromogranins. A pepstatin A‐blockable, catepsin D‐like proteolytic system converting membrane‐bound enzyme to its soluble counterpart at pH 6.0 was detected in the granule membrane fraction.