bluuebunny/crossref_metadata_2025_split huggingface dataset:
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

AbstractThe 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

AbstractThe 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.
The Critical Transmural Pressure of the Airway
Authors: Pedersen Ole Find , Nielsen Tage Mors 
Published: December 2008

AbstractThe 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

AbstractEndogenous 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

Abstract58 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

AbstractThe 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

AbstractAperia, 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

AbstractHolmberg, 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

AbstractNilsson, 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

AbstractElmér, 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

AbstractRidderstråle, 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

AbstractRosell, 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

AbstractNielsen, 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

AbstractThe 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

AbstractEffect 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

AbstractEnergy 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

AbstractThe 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.