bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects from the Vestibulospinal Tract on Transmission from Primary Afferents to Ventral Spino‐cerebellar Tract Neurones
Authors: Baldissera F. , Roberts W. J.
Published: December 2008

Convergence of vestibulospinal and segmental effects onto spinal interneurones which project to the ventral spino‐cerebellar tract (VSCT) neurones has been studied by intracellular recording in VSCT cells. The disynaptic Ia IPSPs evoked in a group of VSCT neurones from the quadriceps nerve are monosynaptically facilitated by the vestibulospinal tract while there was no facilitation of Ia IPSP evoked from a flexor nerve. These results support the view that Ia inhibition to VSCT cells and motoneurones is mediated by common interneurones. The disynaptic inhibition evoked in other VSCT cells from the vestibulospinal tract is facilitated by volleys in the contralateral flexor reflex afferents (FRA) or bilaterally from the FRA. It is postulated that these actions are mediated by collaterals of the interneurones responsible for the analogous effects in motoneurones. Findings are reported suggesting that the monosynaptic vestibulospinal EPSP in VSCT cells in most cases is collateral to the excitatory input to the last order interneurones of reflex pathways from the FRA to motoneurones and only exceptionally to the corresponding input to Ia inhibitory interneurones. In many VSCT cells the vestibulospinal tract evoked disynaptic EPSPs which are facilitated from the FRA; the functional significance of this actions is uncertain. The results are consistent with the hypothesis that VSCT neurones signal information on interneuronal transmission to motoneurones.
Modification of the Gastric Secretory Response to Sham Feeding by Acidification of the Antrum and the Duodenum in Dogs
Authors: Sjödin Lars
Published: December 2008

The effect of closure of a gastric cannula on the acid response to sham feeding was studied in Pavlov‐pouch dogs with intact antro‐duodenal regions as well as in antrectomized dogs with gastroduodenostomies. In the latter dogs, the sham feeding response was augmented by infusions of low doses of exogenous gastrin. The acid output after sham feeding in intact dogs was reduced on average by 59% by closure of the gastric cannula. In antrectomized dogs receiving a back‐ground stimulation with gastrin, the response to ham feeding was not inhibited by closure of the cannula. The results suggest that the observed hypersecretory response to sham feeding after diversion of gastric acid from antrum and duodenum is mainly due to inactivation of antral inhibitory mechanisms. The pepsin secretion following sham feeding was not consistently changed by closure of the gastric cannula.
Effects on Renal Water and Sodium Excretion of Infusions of either Iso‐Osmolar Saline or a Hypo‐Osmolar Solution of Non‐Electrolytes
Authors: Bie Peter
Published: December 2008

The effects of iso‐osmolar and hypo‐osmolar volume expansion on renal water and sodium excretion were studied in dogs during light chloralose anesthesia. Saline or a hypo‐osmolar solution of glucose and urea was given i.v. (20 ml/kg b.wt. in 60 min). From the start of this infusion the combined weight of the hydration infusate and the dog was maintained constant by a servo system, which controlled the rate of infusion of a hypo‐osmolar solution. Consequently the degree of hydration increased linearly during the infusion period after which it remained constant throughout the experiment. No increase in free water clearance was seen after iso‐osmolar volume expansion. The rate of excretion of sodium increased considerably. Hypo‐osmolar volume expansion provoked a water diuresis during which the rate of excretion of sodium fell to less than 0.1 μmol/kg b.wt. min. It is concluded that under the present circumstances infusion of iso‐osmolar saline is not associated with a decrease in the rate of secretion of vasopressin.
Effect of Strength Training on Enzyme Activities and Fibre Characteristics in Human Skeletal Muscle
Authors: Thorstensson Alf , Hultén Bodil , Döbeln Wilhelm von , Karlsson Jan
Published: December 2008

Progressive strength training was performed 3 times a week for 8 weeks by 14 healthy male students (19–31 yrs). The training program consisted mainly of dynamic exercises for the leg extensors with maximal or close to maximal loads. The training caused significant improvements in dynamic and isometric strength. One repetition maximum in squats increased with 67%, Sargent jump with 22%, and maximal voluntary isometric contraction (MVC) with 13 %, respectively. Body weight and leg muscle circumferences remained unchanged after training, whereas total body potassium, lean body mass and calculated total muscle mass increased, suggesting a change in body composition with training. Muscle biopsies were obtained from vastus lateralis for fibre analyses and determination of enzyme activities. There were no changes in muscle fibre composition or fibre area with training. The activities of Mg2+ stimulated ATPase, creatine phosphokinase and phosphofructokinase remained unchanged, whereas myokinase activity was increased after training (from 1.41 to 1.52 moles × 10‐4× g‐1× min‐1, p > 0.05). After training significant correlations (p > 0.01) were demonstrated between Mg2+ stimulated ATPase activity and % fast twitch fibres (% FT) (r = 0.67), as well as between myokinase activity and % FT (r=0.86).
Mitochondrial Cytochrome Concentrations in Rat Heart and Liver as a Consequence of Different Hypoxic Periods
Authors: Kinnula Vuokko L.
Published: December 2008

Rat heart and liver cytochrome concentrations were determined after three hypoxic conditions (atmospheric pressure 50.5 kPa, 40.8 kPa and 38.0 kPa) lasting one week and two weeks. The heart showed clear hypertrophy which was 38% in most severe hypoxia (38 kPa, 2 weeks). A small decline in the liver weight to body weight ratio was observed, this decrease being 21% in the most severe case. During the hypoxic periods the mitochondrial cytochrome concentration decreased. This phenomenon was more obvious when the degree of hypoxia was increased and more pronounced after 2 weeks than one week. The heart and liver showed quite similar patterns in this respect. In most severe hypoxia the decreases in the liver were 29% for cytochrome aa3, 30% for cytochrome b, 20% for cytochrome c and 15% for cytochrome c1, with the concentrations expressed on mitochondrial protein basis. The corresponding values in the heart were 31%, 43%, 28% and 22%. It can be concluded that in mammals the mitochondrial cytochrome content probably varies according to the amount of oxygen available.
A Computer Program for an Open Two Compartment System Distinguishing Three Models
Authors: Cederblad G. , Floderus A. , Karlsson K. E.
Published: December 2008

A digital computer program is described for the estimation of parameters in an open two compartment system distinguishing 3 models. The mathematical function to be fitted to a given set of experimental data is given initial estimates for the parameters of the function. The program uses an iterative procedure to adjust the parameters until the sum of squares of residuals has converged to a minimum. Assuming that a given substance is introduced into compartment 1, the function can be fitted to the set of experimental data of that compartment. A set of experimental data from compartment 2 can also be included in the minimizing function. Two optional weighting functions are presented. From the constants of the two‐exponential functions the physiological parameters of the three models are determined. Experimental observations of compartment 1 only allow for calculation of physiological parameters of two of the models.
Effects of Colchicine and Vinblastine on Axonal Transport of Choline Acetyltransferase in Rat Sciatic Nerve1
Authors: Dziegielewska K. M. , Saunders N. R. , Evans C. A. N. , Skacel P. O. , Häggendal C. J. , Heiwall P.‐O. , Dahlström A. B.
Published: December 2008

The effects of colchicine (0.5–10‐2 M) and vinblastine (10‐2‐10‐5 M) upon axonal transport of choline acetyltransferase (CAT) and on nerve impulse conduction have been investigated in the rat sciatic nerve. High concentrations of colchicine (0.5 M) and vinblastine (10‐2 M) blocked completely both axonal transport of CAT and impulse conduction. 10‐3 M vinblastine did not affect impulse conduction until 20–22 h after injection, but this concentration of vinblastine did block CAT transport; 5 × 10‐5 and 10‐4 M vinblastine blocked CAT transport but not impulse conduction. 10‐2 M and 10‐1 M colchicine were without effect on impulse conduction, but did produce substantial, although incomplete, block of CAT transport. The results are discussed in relation to the possible involvement of microtubules in transport of CAT.
Isometric and Isotonic Length‐Tension Relations and Variations in Cell Length in Longitudinal Smooth Muscle from Rabbit Urinary Bladder
Authors: Uvelius Bengt
Published: December 2008

Isometric and isotonic length‐tension relations of longitudinal smooth muscle from rabbit urinary bladder were studied together with muscle cell length and tissue structure as revealed histologically. In vivo strip length at a bladder volume of 10 ml is referred to as L10. The smooth muscle was relaxed by Ca2+‐free solution and contracted by K+‐high solution with different Ca2+‐concentrations. Maximal active force, 12.5±0.4 N/cm2 (S.E., n ‐ 11), for whole strips was attained at a length of 206±4% (S.E., n 5) of L10. Passive tension at this length was about 15% of total tension. After correction for amount of connective tissue, maximal active tension of pure muscle bundles was 19 N/cm2. Up to about 165% of L10 isometric and isotonic length‐tension relations were identical; if the muscle was stretched beyond this, it failed to shorten isotonically to the same length as when contracting from a shorter starting length. This decreased shortening capacity was reversible if the muscle was shortened passively. The extent of shortening against zero load was dependent on degree of activation suggesting an internal resistance to shortening. A linear relationship was found between bladder radius and muscle cell length, indicating that no slippage occurs between the cells when the bladder is filled. Mean cell diameter in the nuclear region at L10 was 7.2±0.2 μm (S.D., n = 10). Mean maximal active tension per cell was calculated to be 2.3·10‐6 N and occurred at a cell length of 655 μm.
Cardiac Receptors in Ducks — A Link between Vasoconstriction and Bradycardia during Diving
Authors: Blix Arnoldus Schytte , Wennergren Göran , Folkow Björn
Published: December 2008

It has been demonstrated that cardiac receptors, most likely of the left ventricular type, are present also in the duck's heart. These receptors and their reflex responses (i.e. bradycardia and hypotension) could be blocked by intrapericardial administration of lidocaine. Initially, such receptor blockade did not affect efferent vagal control of heart rate, as revealed by undiminished bradycardia in response to a standardized vagal stimulation. After cardiac receptor blockade, however, the duck's normal bradycardia response to head immersion was greatly reduced. The cardiovascular response to submersion was now instead characterized by a marked rise in arterial pressure, with superimposed bouts of intensified bradycardia and pressure reduction, evidently induced reflexly from the arterial baroreceptors. Meanwhile, the bradycardia response to standardized efferent vagal stimulation was still the same as before intrapericardial lidocaine injection. These results suggest that the marked rise in cardiac filling pressure following the intense chemo‐receptor‐induced constriction of both resistance and capacitance vessels, activates ventricular stretch receptors signalling in vagal afferents. Apparently, the activation of these receptors contributes crucially to the bradycardia and reduction of cardiac output, which balance off the greatly increased peripheral resistance in the diving duck.
Blood Flow Changes in the Submaxillary Gland of the Rat on Parasympathetic and Sympathetic Nerve Stimulation
Authors: Thulin Anders
Published: December 2008

Blood flow and secretion from the submaxillary gland of the rat was recorded. Stimulation of the chordalingual nerve evoked vasodilatation which was little, if at all, decreased after administration of atropine. The secretion evoked on parasympathetic nerve stimulation was greatly reduced but not totally abolished by parasympatholytic agents. Stimulation of the cervical sympathetic trunk evoked secretion, which was mediated both via α. and β‐adrenoceptors and vasoconstriction which was abolished by dihydroergotamine, and thus seemed to be mediated via α‐adrenergic receptors. After α‐adrenoceptor blockade vasodilatation was seen on sympathetic nerve stimulation. This was abolished by the β‐adrenoceptor blocking agent propranolol.
Excitability Changes of the Inspiratory ‘Off‐switch’ Mechanism Tested by Electrical Stimulation in Nucleus Parabrachialis in the Cat
Authors: Euler Curt von , Trippenbach Teresa
Published: December 2008

The time course of the excitability of the inspiratory ‘off‐switch’ mechanism with and without phasic vagal stretch receptor feedback has been studied in cats under light pentobarbitone anesthesia by electrical stimulation in the rostral pons using brief tetanic stimulation (300 Hz for 0.2 s). The threshold strength required just to elicit inspiratory ‘off‐switch’ was high early in inspiration and fell steeply with time. The threshold curves were steeper with than without phasic vagal feedback, and the difference reflects the phasic vagal contribution to the excitability of the inspiratory ‘off‐switch’ mechanism. In the absence of phasic vagal feedback the time course of this threshold curve usually corresponded closely to that of the ‘integrated’ phrenic activity at all PCO2 levels and body temperatures tested indicating that the ‘integrated’ phrenic activity can be used as an index of the centrally generated inspiratory activity. In response to a rise in PCO2 both the rate of change of the excitability of the inspiratory ‘off‐switch’ mechanism and its initial threshold level was increased. Changes in body temperature caused no change in the initial threshold but produced marked changes in the rate of rise of the ‘off‐switch’ excitability. Following an ‘augmented breath’ the inspiratory ‘off‐switch’ threshold was markedly reduced.
Active Transport of3H‐Bretylium in the Rat Vas Deferens in vitro
Authors: Ross Svante B. , Kelder Diana
Published: December 2008

The uptake and efflux of3H‐bretylium in slices of the rat vas deferens were examined. The uptake of bretylium was temperature, Na+and Cl‐dependent, sensitive to 6‐hydroxydopamine but insensitive to reserpine. The uptake was inhibited by desipramine, (+)‐amphetamine, imipramine methiodide and cocaine, whereas the local anaesthetics millicaine and lidocaine were poor inhibitors. The spontaneous efflux was very slow at 0°C and slow at 37°. Desipramine accelerated the efflux probably by inhibiting the re‐uptake of bretylium. (+)‐Amphetamine, low external Na+, high external K+and ouabain caused a pronounced increase in the efflux at 37°C but was almost without effect at 0°C. The efflux evoked by (+)‐amphetamine, low Na+and ouabain was inhibited by desipramine, imipramine methiodide and cocaine, whereas millicaine and lidocaine had very poor effects. The increase of bretylium efflux by hypertonic K+was only slightly inhibited by desipramine and partially antagonized by omission of Ca2+in the medium. The results obtained indicate that bretylium was taken up in noradrenergic neurones by the noradrenaline transport mechanism and that the efflux of bretylium produced by (+)‐amphetamine, low external Na+, low external Cl‐and by ouabain occurred by the same transport mechanism as the uptake but now working in the outward direction whereas the efflux induced by high K+seemed to occur mainly with another mechanism.
Potentiation of Anaphylactic Histamine Release from Isolated Rat Pleural Mast Cells by Rat Serum Phospholipids
Authors: Sydbom A. , Uvnäs B.
Published: December 2008

Isolation of sensitized rat mast cells by density gradient centrifugation in Ficoll decreases the histamine release obtained when they are subsequently exposed to antigen. The histamine release from such isolated cells is potentiated by the addition of 2 % boiled rat serum. This potentiation is dose‐dependent and has a temperature optimum of about 25°C. The potentiating activity was localized to the serum phospholipid fraction. Of the pure phospholipids studied (LPC, PC, PE, PI, PS and SM) only phosphatidylserine and lysophosphatidylcholine were found to potentiate the histamine release. The mechanism behind this potentiation is discussed and it is suggested that the potentiation by phosphatidylserine and lysophosphatidylcholine is due to a requirement of these phospholipids for the ion exchange (Na+, K+and Ca++) or the adenylcyclase activity essential for the histamine release process.
Gustatory Effects of Miraculin, Monellin and Thaumatin in the Saguinus Midas Tamarin Monkey Studied with Electrophysiological and Behavioural Techniques
Authors: Hellekant G. , Glaser D. , Brouwer J. N. , Wel H. van der
Published: December 2008

A comparative electrophysiological and behavioural study has been made in 17 closely related monkeys of the new world species, Saguinus midas tamarin. The electrical activity in the chorda tympani proper nerve of two of the monkeys was recorded during the application to the tongues of 0.02% monellin and thaumatin, 0.5 % miraculin and stimuli representing the four taste qualities. It was observed that monellin and thaumatin gave no or little response and that miraculin enhanced the response to the sour stimulus, but not that to any other taste quality. Behavioural studies were then made with a two‐bottle preference test in 15 monkeys. It was found that the animals did not discriminate or discriminated poorly between water and thaumatin or monellin. After miraculin they changed their strong rejection of 0.02 M citric acid, in a choice between water and acid, into a strong preference for the acid. These results show a close relation between the electrophysiological and the behavioural data.
Autonomic Nerve Control of the Swimbladder of the Goldsinny Wrasse,Ctenolabrus rupestris
Authors: Fänge Ragnar , Holmgren Susanne , Nilsson Stefan
Published: December 2008

The autonomic nerve control of the swimbladder of the goldsinny wrasse has been studied by experiments with isolated strips from the muscularis mucosae, drug effects on gas secretionin vivo, fluorescent histochemistry and quantitative analysis of catecholamine content. Vagotomy, atropine and mecamylamine significantly inhibited induced gas secretion, suggesting a cholinergic vagal secretory innervation of the gas gland. The anterior part of the mucosa (secretory part) is contracted by acetylcholine and α‐adrenoceptor agonists. These responses are competitively antagonized by atropine and phentolamine or yohimbine respectively. The posterior (resorbent) part of the mucosa is contracted by acetylcholine, but β‐adrenoceptor agonists relax the acetylcholine‐precontracted preparations. These responses are competitively blocked by atropine and propranolol respectively. The pA2‐values from all experiments with antagonists are well comparable with values obtained for the same drugs in other teleost or mammalian tissues. Tyramine, 5‐hydroxytryptamine or phenylephrine had mixed effects on the posterior part. This effect is at least in part due to release of nervously stored catecholamines. Fluorescent histochemistry revealed a strong innervation by both smooth and varicose adrenergic fibres in all parts of the swimbladder, noradrenaline being the dominant catecholamine. Yellow fluorescent cells, which may contain 5‐hydroxytryptamine, were also seen in the swimbladder mucosa. No conclusive evidence for a cholinergic innervation of the muscularis mucosae was obtained.
The Influence of Temperature on the Time Course of the Mechanical Activity in Rabbit Papillary Muscle
Authors: Mattiazzi Alicia R. , Nilsson E.
Published: December 2008

The influence of temperature on the time course of the mechanical activity was investigated in isolated papillary muscles of the rabbit. By using the “damped release” technique activity curves were determined in terms of velocity of shortening of the contractile unit at a constant length. At any of the temperatures studied, the time course of the mechanical activity exhibited a slow onset and did not form a distinct plateau. At low contraction frequencies and normal (2 mM) calcium concentration lowering the temperature from 32.5 to 26.5°C did not markedly affect the rate of development of the activity but increased the peak amplitude and the total duration of the activity as well as the time from the stimulus to 90 % of the maximum. It also resultedi n a slower decay phase. At higher contraction frequencies and/or increased calcium concentration the rate of development of the activity was reduced by decreasing the temperature from 32.5°C to 26.57deg;C., whereas the maximal activity reached similar levels at the two temperatures. It is concluded that an alteration in temperature affects several different steps in myocardial excitation‐contraction coupling, the net change in maximum amplitude of the mechanical activity being influenced by both extracellular calcium concentration and contraction frequency.
Influence of pH and pCO2on Alpha‐Receptor Mediated Contraction in Brain Vessels
Authors: Edvinsson Lars , Sercombe Richard
Published: December 2008

The response of isolated brain vessels to various pH levels or carbon dioxide tensions was analyzed. Reduction of the pH induced a slight relaxation of the vessel, whereas an increase in the pH produced a slight contraction. These effects were markedly exaggerated when the alpha‐adrenergic receptors in the vascular wall were activated by noradrenaline. During these conditions the contractile response to noradrenaline was reduced by about 40 per cent at a pH of 7.01, while, on the other hand, the response was enhanced 3‐fold at a pH of 7.80. Variations in carbon dioxide tension of the buffer solution between 16 mmHg and 64 mmHg produced no consistent change, provided the pH remained constant. The results indicate that an interaction between the perivascular pH and the adrenergic alpha‐receptor mediated contraction in brain vessels may occur.
Negligible Role of CSF Cations other than Na+ in the Central Regulation of ADH Release
Authors: Eriksson Lea
Published: December 2008

Previous experiments in the goat (cf. Andersson 1971) have suggested that a sodium sensitive receptor system near the third cerebral ventricle participates in the regulation of antidiuretic hormone (ADH) secretion. Further support for this concept has been obtained by infusions of pure saccharide solutions into the cerebrospinal fluid (CSF) of the lateral and third cerebral ventricles (Eriksson 1974). It was found that such infusions, which obviously reduce CSF [Na+], induce water diuresis in non‐hydrated goats. However, it could not be excluded whether reduced CSF concentration of ions other than Na+ might be of importance for the observed inhibition of ADH release. The results of the present study seem to exclude this possibility.
The Critical Transmural Pressure of the Airway
Authors: Pedersen Ole Find , Nielsen Tage Mors
Published: December 2008

The critical transmural pressure (Ptm.) is defined as the transmural pressure of the airway at the site where and when flow is limited during a forced expiration. According to the presented theory, the maximal expiratory flow (V̇max) can be calculated from the relation between Ptm. and the corresponding cross‐sectional area of the airway (A.). By means of a pitot‐static tube, Ptm‐A curves were constructed for several locations in the elastic airway of a mechanical model. From these curves local V̇max was calculated at different values of Ptm and compared with actual flow, i.e. measured V̇max for the entire airway. In the downstream part of the airway, the actual flow equalled calculated V̇max at most Ptm values. The site of flow limitation, being the most upstream point where actual flow equals calculated local V̇max could therefore be located. Theory and experiments showed positive as well as negative Ptm. not influenced by change in upstream or downstream resistance. Flow limitation could therefore be initiated at distending as well as compressing pressures across the wall of the airway. V̇ was regarded as a function of Ptm and the elastic recoil pressure of the lung (Pel). Measured and calculated iso‐Pel, Ptm‐V̇ curves agreed well with one major exception: when Ptm < Ptm measured curves were distorted due to a concomitant downstream compression of the collapsible airway.
Biosynthesis of Acetylcholine in Different Brain Regions in vivo Following Alternative Methods of Sacrifice by Microwave Irradiation
Authors: Nordberg Agneta , Sundwall Anders
Published: December 2008

Endogenous acetylcholine and biotransformation of tritium‐labelled choline (3H‐CH) were studied in mouse brain regions following different methods of sacrifice, viz. dislocation of the spine (7 min until enzymes inactivated), whole body microwave irradiation (7 s) and irradiation of the head (0.25 s). The brain temperature was measured in different locations 10 to 60 s after irradiation. The slope of the temperature time curves indicated a brain temperature of about 85–90°C at the termination of exposure to both types of irradiation. Acetylcholinesterase (AChE) and choline acetyltransferase (CAT) were practically completely inactivated when measured one to two min after sacrifice.

For turnover studies, mice were killed 1, 5, 10 or 20 min after i.v. injection of 15 nmol of 3H‐Ch. The brains were dissected into 6 regions, extracted and analysed. No significant difference (except in cortex) in the amount of endogenous ACh was found when whole body irradiation was used in comparison to dislocation of the spine. However, the amount of 3H‐acetylcholine CH‐ACh) was much higher in the stri‐atum, hippocampus and cortex, in particular. With the shorter inactivation time (head irradiation) endogenous ACh was markedly increased in the striatum, cortex, medulla, oblongata and midbrain. However, there was no further increase in the radioactive ACh. The difference regarding the post‐mortem sensitivity of endogenous and radioactive ACh does not seem to have been due to methodological artifacts but rather suggests that they are handled differently by the brain tissue. Plots of the specific radioactivity (SA) of Ch and ACh us. time indicated fairly distinct precursor‐product relationship in the different regions, when the animals were sacrificed by irradiation of the head.
A Further Contribution to the Question of Trophic and Hormonal Influences on the Noradrenaline Content of the Male Reproductive Tract: Effect of Combined Androgen and Estrogen Treatment of Prepuberally Castrated Rats
Authors: Kvist Ulrik , Sjöstrand Nils O.
Published: December 2008

58 days old, prepuherally castrated, male rats were treated with estrogen, testosterone or a combination of both hormones for 18 days. The total noradrenaline (NA)‐content of the male accessory glands was increased by the hormone treatments. This increase was smallest in the estrogen treated group and largest in the group treated with both estrogen and testosterone. The NA‐concentration, however, followed the reversed picturei.e. it was largest in untreated castrated rats and smallest in the rats receiving both estrogen and testosterone. Neither treatment brought the NA‐amount up to the level of uncastrated controls of the same age although the weights of the secondary sex glands of rats receiving both estrogen and testosterone exceeded those of uncastrated controls. Similar, but less definite changes were observed in vas deferens and cauda epididymidis. It is concluded that a developing target area exerts some trophic influence on the adrenergic neurons innervating it. However, the trophic influence exerted by the effector organ an the nerves is not of the kind, that the innervation density and NA‐concentration of the organ always are maintained at a constant level.
Influence of Acetate on Glucose Metabolism in the Perfused Hind‐Quarter of the Rat
Authors: Karlsson N. , Fellenius E. , Kiesslin K.‐H.
Published: December 2008

The metabolism of U‐14C‐glucose and U‐14C‐acetate and the interaction between the two substrates in the perfused hind‐quarter of the rat was studied. 5 % of glucose taken up was oxidized to CO., accounting for 15 % of total oxygen consumption. Glucose was mainly incorporated into glycogen, while incorporation into lipids was negligible. Acetate did not significantly alter glucose uptake, 14C‐glucose oxidation or the incorporation of 14C‐glucose into glycogen and lipids. 45% of acetate taken up was oxidized to CO2 accounting for 20–25 % of total oxygen consumption. Insulin did not affect acetate uptake but increased %‐acetate oxidation. Oxygen consumption was slightly increased by simultaneous oxidation of glucose and acetate and in this situation the tissue content of high‐energy phosphate compounds was slightly elevated. It is concluded that only minor effects by acetate on glucose metabolism in the perfused skeletal muscle were found. The insignificant effects compared to previously reported studies on heart tissue (Neely and Morgan 1974) can be explained by differences in acetate metabolism between the two tissues.
Effect of Arterial Blood Pressure Reduction on Renal Hemodynamics in the Developing Lamb
Authors: Aperia Anita , Herin Peter
Published: December 2008

Aperia, A. and P. Herin. Effect of arterial blood pressure reduction on renal hernodynamics in the developing lamb. Acta physiol. scand. 1976. 98. 387–394.

The relationship between pressure and flow in the kidney has been examined in 2–9 and 31–48 day old lambs. Renal blood flow (RBF), determined by the microsphere technique, and glomerular filtration rate (GFR) were first studied under control conditions. The abdominal aorta was then constricted above the renal arteries until the pressure ranged between 60 and 70 mmHg, i.e. just below the normal auto‐regulatory range, and the hemodynamic recordings were repeated. During control conditions the arterial pressure was lower in the younger (93 mmHg) than in the older lambs (107 mmHg). During aortic constriction total RBF and GFR were reduced. In both age groups GFR was reduced out of proportion to RBF. The sodium excretion fell around 60% in both age groups. The fall in perfusion pressure resulted in a more pronounced blood flow reduction to the outer than to the inner cortical glomerular capillaries. This pressure‐induced blood flow redistribution was found in both age groups. The consequences of the pronounced effect of reducing the perfusion pressure to 60–65 mmHg for the young lambs with their basally low arterial blood pressure are discussed.
Tissue Hyperosmolality as a Causal Factor in Vasodilatation Following Sympathetic Stimulation of the Submandibular Gland
Authors: Holmberc Jan , Lundvall Jan
Published: December 2008

Holmberg, J. and J. Lundvall. Tissue hyperosmolality as a causal factor in vasodilatation following sympathetic stimulation of the submandibular gland. Acta physiol. scand. 1976. 98. W06.

In a previous investigation, parasympathetic activation of the submandibular gland in the cat was found to cause a considerable increase of regional tissue osmolality, the degree of which was related to the evoked functional hyperernia; intra‐arterial hypertonic infusion to the resting gland producing tissue hyperosmolality of similar magnitudes caused graded and marked dilatations (Lundvall and Holmberg 1974). It was concluded that hyperosmolality contributes significantly to the functional hyperemia response. In the present study evidence is presented to indicate that tissue hyperosmolality is a mediator of the dilatation associated with sympathetic activation as well. An increase of tissue hyperosmolality, as traced in the venous effluent, was found at all frequencies of sympathetic stimulation (2–16 Hz). At high stimulation rates it sometimes exceeded the resting control level by more than 20 m Osm/kg HO. There was a direct relation between the degree of venous hyperosmolality and the hyperemia response observed immediately after cessation of stimulation. Comparison of the dilator effects evoked by sympathetic stimulation and by hypertonic infusion to the resting gland indicated that tissue hyperosmolality is an important causal factor for the nerve induced dilatation, especially at low and moderate stimulation rates.
Contraction of Glycerol Extracted Fibres of Smooth Muscle by Acetylcholine and Imidazole in the Presence of a Ca‐binding Microsomal Fraction from Rabbit Colon
Authors: Nilsson Karin , Djärv Lars , Anderson Rolf G. G.
Published: December 2008

Nilsson, K., L. Djärv and R. G. G. Andersson. Contraction of glycerol extracted fibres of smooth muscle by acetylcholine and imidazole in the presence of a Ca‐binding microsomal fraction from rabbit colon. Acta physiol. scand. 1976. 98. 407–411.

Microsomal and mitochondrial fractions were isolated from rabbit colon muscle homogenate by differential centrifugation. The calcium content of these fractions were rather similar. The microsomes were divided into subfractions by gradient centrifugation and tested on glycerol treated colon muscle. Acetylcholine and imidazole elicited an EGTA‐sensitive contraction of glycerinated colon muscles in the presence of microsomal subfractions and Mg‐ATP. The glycerinated colon muscle constitute a rapid system for qualitative drug tests on Ca‐metabolism in subcellular fractions of smooth muscle.
Responses of the Denervated Rat Urinary Bladder to Alfa Adrenoceptor Stimulation
Authors: Elmér Mats
Published: December 2008

Elmér, M.Responses of the denervated rat urinary bladder to alfa adrenoceptor stimulation. Acta physiol. scand. 1976.98. 440–444.

The contractile responses of the rat detrusor muscle to noradrenaline were increased 2–3 weeks after partial denervation but had returned to control values 6–9 weeks after the denervation, probably because of reinnervation of denervated muscle cells. 6–9 weeks after partial denervation the excitatory cr‐adreno‐ceptor mediated response to stimulation of the remaining intact nerves was predominant, masking the subsequent inhibitory β‐receptor response, which at this time was seen only after α‐receptor blockade. The possibility of an outgrowth of adrenergic fibres activating a‐receptors in muscle cells normally not innervated by adrenergic nerves is discussed.
Intracellular Localization of Carbonic Anhydrase in the Frog Nephron
Authors: Ridderstråle Yvonne
Published: December 2008

Ridderstråle, Y. Intracellular localization of carbonic anhydrase in the frog nephron. Acta physiol. scand. 1976. 98. 465–469.

The intracellular distribution of carbonic anhydrase has been studied in the frog nephron by a histochemical method. The study of the detailed intracellular localization was possible by sectioning tissue embedded in plastic (Sorwall, JB‐4), before staining essentially according to Hansson. This procedure preserves the intracellular structure well and the resolution is high. For light microscopy sections from 1 to 10 pn were used. For electron microscopy 0.25 pn thick sections were stained and examined in the electron micro scope using an accelerating voltage of 100 kV. The highest concentrations of the enzyme seem to be localized to the cell membranes or their immediate neighbourhood. A faint cytoplasmic staining may sometimes be observed. In distal tubule cells the apical part of the cell membrane was heavily stained. Weaker staining was found at the lateral membranes and their infoldings and to some extent the basal parts of the cell membrane. In the canaliculi cells only the lateral and basal parts of the membranes were stained. This latter localization is similar to that in the parietal cells of the mammalian stomach.
Cardiovascular and Metabolic Actions of Neurotensin and (Gln4)‐Neurotensin
Authors: Rosell Sune , Burcher Elizabeth , Chang Ding , Folkers Karl
Published: December 2008

Rosell, S., E. Burcher, D. Chang and K. Folkers. Cardiovascular and metabolic actions of neurotensin and (Gln4)‐neurotensin. Acta physiol. scand. 1976. 98. 484–491.

The actions of the tridecapeptides neurotensin and (Gln4)‐neurotensin have been studied on the heart and on the blood flow in subcutaneous adipose tissue, skin and small intestine of anesthetized dogs. In addition, their possible actions have been investigated on blood glucose concentration and lipolysis in subcutaneous adipose tissue. The two peptides were found to he approximately equipotent. Intravenous infusion of 20–120 ng × kg % min produced slight hypotension, an initial vasodilatation in the small intestine and a delayed vasoconstriction in denervated subcutaneous adipose tissue and to a lesser extent in the skin and small intestine. At this infusion rate, neurotensin and (Gln4)‐neurotensin did not elicit vasodilatation in the skin or adipose tissue and had no effect on heart rate. The delayed vasoconstriction in adipose tissue was not inhibited by local cr‐receptor blockade. Both neurotensin and (Gln4)‐neurotensin increased glucose concentration in the upper dose range. No effects on lipolysis were observed, either in vivo or in vitro. These experiments show that neurotensin and (Gln4)‐neurotensin have both vasodilator and vasoconstrictor actions in the peripheral vasculature but seem to be without cardiac actions. They also increase blood glucose concentration. It remains to be shown whether these actions are direct or whether some are indirectly mediated.
Temperature Regulation during Exercise in Water and Air
Authors: Nielsen B. , Davies C. T. M.
Published: December 2008

Nielsen, B. and C. T. M. Davies. Temperature regulation during exercise in water and air. Acta physiol. scand. 1976. 98. 500–508.

Four healthy subjects were studied during exercise in water, using a swimming flume, and in air, on a stationary bicycle ergometer at mean skin temperatures of 30 and 33°C, respectively. Measurements included rectal (T), esophageal (T), and mean skin (T) temperatures, metabolic energy liberation (M) and total heat production (H), maximal aerobic power output (Vo max). cardiac frequency and calculated peripheral tissue heat conductance (K). The results showed that for a given M and T, T and T were about 0.4°C lower and the K values were consistently higher in swimming than in bicycling. The intersubject variability in T and T was reduced by considering relative (expressed as %Vomax) rather than absolute work load, but the differences in the body temperatures between the two types of exercise remained. It was concluded that during exercise in water where the capacity for heat dissipation is increased, the body core temperature (T) is maintained at a lower level due to the higher forced convective and conductive heat transfer from the skin in water. This reduces the heat storage at the beginning of exercise compared with conditions in air. The lower T‐ T gradient for a given H in swimming, which results in higher K values implies a greater skin circulation than during cycling in air.
Effect of Urea on Some Electrophysiological Properties of the Frog Muscle Cell Membrane
Authors: Boëthius J. , Rydqvist B.
Published: December 2008

The effect of urea on the electrophysiological properties of the frog muscle cell membrane was studied with intracellular microelectrodes, together with an analysis of the electrolyte composition of the muscle. The different parameters were measured and evaluated after soaking the muscle for 60 min at urea concentrations up to 2.25 M. The resting membrane potential was markedly decreased above 1.50 M and fell to about ‐50mV at 2.25 M. The specific membrane resistance (Rm) was almost unaffected at concentrations of 0.75 M and 1.50 M but was reduced after 60 min in 2.25 M to very low values indicating a leaky membrane. The maximum rate of rise of the action potential (Rm) was unaffected up to 0.50 M but was reduced to about 50% of control value at 0.75 M. Between 0.75 M and 1.25 M it was constant and at higher concentrations reduced to almost zero. The reduction of VA at the lower concentrations was not accompanied by changes in neither the resting membrane potential nor Rm. It is proposed that urea perturbs protein systems concerned with the generation of the muscle action potential without affecting the passive electrical properties of the muscle membrane. The electrolyte analysis revealed an increase in intracellular Na+ and K+ concentrations, mainly due to loss of intracellular water.
Denervation Stimulation of α‐Aminoisobutyric Acid Uptake by the Diaphragm in Developing Rats
Authors: Mamatas S. C. , Oja S. S.
Published: December 2008

Effect of denervation on accumulation of a‐aminoisobutyric acid (AIB) by the diaphragm was studied in 11‐, 21‐, 31‐, and 51‐day‐old rats. In both innervated and denervated diaphragms the accumulation steadily decreased with age. Denervation significantly enhanced accumulation at all ages, the relative increment being greater in older animals owing to the lower basal accumulation ratio for AIB. The denervation‐induced stimulation was partially abolished by dactinomycin administration. The drug obviously inhibits the formation of new carrier sites at plasma membranes for AIB transport.
Oxygen Consumption and Lactate Production of the Rat Portal Vein in Relation to its Contractile Activity
Authors: Hellstrand Per
Published: December 2008

Energy turnover in the isolated rat portal vein was investigated by measurement of oxygen consumption (Jo2) and lactate production (JLA) under simultaneous recording of mechanical activity. In spontaneous activity under aerobic conditions and at optimal muscle length Jo2 and JLA were 0.55 and 0.62/μmol/min g. respectively, corresponding to an ATP‐production of 4.3 μmol/min g. When muscle length was changed, an approximately linear relation was found between energy turnover and mean isometric tension. The tension‐independent part of ATP‐production was 3.0 μmol/min g. In Ca2+‐free solution the metabolic rate was 20 % lower still. Jo2 was nearly equal in isometric contractions and in afterloaded isotonic contractions from the same initial muscle length. During a maximal tonic contracture in K+‐depolarized portal vein Jo2 increased to about twice that in spontaneous activity. Changes in contracture force by variations in muscle length or in [Ca2+]0 were associated with identical linear relations between Jo2 and active tension. This relation was less steep than the corresponding relation for spontaneous activity. The anaerobic lactate production of the portal vein was 2.7 times the aerobic level. The accelerated glycolysis did not compensate for eliminated oxidative metabolism. Under substrate‐free aerobic conditions no lactate was produced by the muscle and compared to the control situation Jo2 declined more than could be accounted for by reduced mechanical aevtivity alone. The metabolic turnover rate in relation to isometric tension is high in the rat portal vein compared to that of tonic vascular smooth muscle from larger vessels. This correlates with differences in dynamic mechanical properties. At comparable tension levels in the portal vein, the rate of cross‐bridge turnover may be higher in spontaneous phasic activity than in sustained contracture.
The Poor Reactivity of Retinal Vessels to Systemic Administration of Vasoactive Agents in Pentobarbital Anesthetized Rats
Authors: Ylitalo Pauli , Ertama Pertti , Ertama Liisa
Published: December 2008

The responsiveness of retinal vasculature to i.v. administration of several potent vasoactive agents was studied in pentobarbital anesthetized rats by taking fundus photographs. Since cerebral vasculature has been claimed to react in a similar manner but less liably than retinal vessels to some vasoactive substances, the findings were applied to the problem of reactivity of brain vessels. Sublethal doses of noradrenaline, adrenaline, 5‐hydroxytryptamine, angiotensin amide and arginine or lysine vasopressin caused no marked acute (2 min) vasoconstriction in retinal vessels. Nor did any of these agents or bradykinin elicit vasodilatation. The late vasoconstriction (2 min) found in succumbing animals was most likely unspecific, since it did not occur until severe toxic symptoms appeared. The findings support the concept that intracerebral vessels are quite resistant to the direct action of many vasoactive agents given i.v.
Changes in Motor Unit Activity and Metabolism in Human Skeletal Muscle during and after Repeated Eccentric and Concentric Contractions
Authors: Komi Paavo V. , Viitasalo Jukka T.
Published: December 2008

This study was designed to investigate electromyographic (EMG), muscle glycogen and blood lactate changes in quadriceps muscle group during repeated 40 maximal eccentric and concentric contractions, and to follow the recovery in EMG, muscle glycogen and serum creatine kinase values during a 4 day period following the work test. The subjects were normal males and the test order (eccentric or concentric) was randomly selected. The results indicated first, that the EMG parameters (IEMG, AMUP), muscle glycogen and blood lactate changed in a similar manner during the both fatigue loads. Despite the high tension work no selective depletion of glycogen could be observed in the slow or fast twitch muscle fibres in either type of work. The restoring of muscle glycogen occurred in a similar manner after the both fatigue loads, and no significant differences were present between eccentric and concentric works in the serum creatine kinase levels for a 2 days period. The eccentric work was associated with muscle soreness, which was strongest during the second day after the termination of the work test. The recovery of the EMG parameters were also delayed in eccentric fatigue. After concentric fatigue EMG‐activity returned to normal values within 2 days.
Dissociation of Preovulatory Maturational Events in Rat Oocytes and Cumuli in the Presence of Dibutyryl Cyclic AMP
Authors: Hillensjö Torbjörn
Published: December 2008

Mammalian oocytes enter the first meiotic division during pre‐natal life. Shortly thereafter the oocytes become arrested at the diplotene (dictyate) stage of the first meiotic division and they remain arrested until just prior to ovulation. The ovulatory LH‐surge leads to resumption of meiosis and the oocytes of preovulatory follicles undergo nuclear progression from dictyate to metaphase II (oocyte maturation). Although it is generally agreed that LH is responsible for the resumption of meiosis, the cellular mechanism for this hormonal effect remains to be elucidated. The immature oocyte in the follicle is surrounded by specialized granulosa cells comprising the cumulus oophorus. Morphological (Zamboni 1970) as well as biochemical (Biggers et al. 1967, Gwatkin and Andersen 1976) evidences suggest a role of the cumulus cells in the regulation of both oocyte growth and maturation. Following the ovulatory LH‐surge the cumulus surrounding the maturing oocyte is radically changed into a dispersed structure of cells embedded in a mucopolysaccharide matrix (e.g. Austin 1961). In a recent report isolated preovulatory follicles of PMSG‐injected immature rats were studied in an incubation system with chemically defined medium (Hillensjöet al. 1976). When LH was added to the medium the follicle‐enclosed oocyte resumed meiosis and the cumulus was transformed into a dispersed structure which was sensitive to hyaluronidase. The aim of this study was to see whether dibutyryl cyclic AMP (dbcAMP) would mimic the effects of LH on the follicle‐enclosed oocyte itself and on the cumulus oophorus.