bluuebunny/crossref_metadata_2025 huggingface dataset:
Prostaglandin Mediated Inhibition of Noradrenaline Release at Different Nerve Impulse Frequencies
Authors: Junstad Marianne , Wennmalm ÅKF.
Published: December 2008

The isolated perfused, sympathetically innervated rabbit heart was stimulated for 6 min at 2 or 10 Hz and the outflow of noradrenaline was monitored by assay of the perfusate from the organ during nerve stimulation. Continuous nerve stimulation caused a decline in the outflow of noradrenaline, which was more pronounced at the higher nerve stimulation frequency. When 5, 8, 11, 14‐eicosa tetranyoic acid, a compound known to inhibit prostaglandin synthesis in this preparation, was infused during nerve stimulation at 2 Hz, the relative outflow of noradrenaline was increased by about 90, while at 10 Hz no significant influence on the outflow of noradrenaline was observed. The outflow of endogenous prostaglandins was slightly more than doubled when the stimulation frequency was increased from 2 to 10 Hz. Simultaneously the sensitivity to exogenous prostaglandin E2 of the chronotropic response to nerve stimulation was decreased. The absence of endogenous inhibition of transmitter release at 10 Hz seems to be the result of both a decreased sensitivity of the noradrenaline release process to prostaglandins and an insufficient increase at this frequency in the amount of prostaglandin available to inhibit this process. The experiments show, that the prostaglandin mediated inhibition of the process of release of the sympathetic transmitter is more efficient at lower, more “physiological”, nerve impulse frequencies.
Rate Limiting Factors in Sympathetic Neurotransmitter Secretion
Authors: Stjärne Lennart
Published: December 2008

Isolated superfused field stimulated preparations of guinea‐pig vas deferens, in which the neural stores of noradrenaline (NA) had been labelled by preincubation with tritium‐marked (‐)‐NA, were used to study the factors regulating the amount of NA secreted from the nerves, per applied shock. The results indicate that ‘stimulation secretion coupling’ in this tissue is subject to 2 different kinds of facilitation, one independent and one dependent on nerve stimulation frequency. Kinetic analysis of the calcium dependence of transmitter secretion, after removal of α‐adrenoceptor mediated negative feedback control, suggests that there is a definite upper limit to the amount of transmitter which can be secreted, per pulse, from each ‘secretory area’ of the nerves. The low Q10 value of this apparent Vmax suggests that the rate limiting factor is non‐enzymatic in nature. It is proposed that the ultimately rate limiting factor in NA secretion may rather be the number of vesicles in each potential ‘secretory area’ which are in a suitable position within the nerve for active participation in the secretion of transmitter.
The Release of Prostaglandin‐Like Substances during Platelet Aggregation and Pulmonary Microembolism
Authors: Vaage J. , Piper Priscilla J.
Published: December 2008

During pulmonary microembolism subsequent to induced platelet aggregation in vivo, a pressor response is elicited in the lungs due to the release of vasoactive substances. During the perfusion of isolated cat lungs with whole blood, platelet aggregation induced by collagen released prostaglandin‐like substances (PG‐LS), and a rabbit aorta contracting substance (RCS) as measured by continuous bioassay of the venous effluent. This release occurred in parallel to the pulmonary pressor response. The same amount of PG‐LS and RCS was released when the lungs were replaced by a blood filter to trap platelet aggregates. Apparently PG‐LS and RCS are released from platelets during their aggregation. As E‐ and F‐type PGs are rapidly inactivated in the pulmonary circulation, there must either be an equal generation of PGs in the lungs themselves, or rather, the release of PGs from platelets must occur distal to the inactivation mechanism without any additional PG‐release from the lungs. The exact role of PGs in the lung responses to intravascular platelet aggregation is not clear.
Airway Effects of Slow Reacting Substance, Prostaglandin F2αand Histamine in the Guinea‐Pig
Authors: Strandberg Kjell , Hedqvist Per
Published: December 2008

SRS, PGF2α, and histamine were administered intravenously or as aerosols to artificially ventilated guineapigs in order to assess their capacity to affect tracheal insufflation pressure measured by means of Konzett‐Rössler technique. Independently of route of administration all three compounds increased tracheal insufflation pressure, SRS being the most potent one. Bilateral cervical vagotomy did not alter the effect. Relative to histamine SRS and PGF2αwere considerably more active by aerosol administration than by intravenous injection. The aerosols had little or no effect on systemic blood pressure. On intravenous injection, histamine decreased and SRS adn PGF2αincreased arterial blood pressure in a dose‐dependent fashion. The airway effects of histamine were correlated to those on blood pressure whereas with SRS and PGF2αthis was not seen when the blood pressure effects were marked. Preadministration of adrenaline or isoprenaline as aerosols antagonized the increase in insufflation pressure, but not the effects on blood pressure, produced by intravenously injected histamine of PGF2α.

It is concluded that SRS, PGF2αand histamine on intravenous or aerosol administration increase tracheal insufflation pressure in the guinea‐pig mainly by an action on airway tone. The data emphasize that SRS is a potent bronchoconstricting agent, possibly of pathophysiological significance in guinea‐pig anaphylaxis.
Reflex Inhibition of the Slowly Adapting Stretch Receptors in the Intact Abdomen of the Crayfish
Authors: Njå A. , Walløe L.
Published: December 2008

The reflex inhibition of abdominal stretch receptors in crayfish was studied by controlled passive flexion of individual abdominal joints. The results are very similar to those obtained by electrical or mechanical stimulation of individual stretch receptors in immobilized abdomens. Reflex effects from posterior to anterior abdominal segments are somewhat stronger than in the opposite direction. Flexion of one abdominal joint excites the stretch receptors of that joint and inhibits the stretch receptors in neighbouring abdominal segments. Without reflex inhibition flexion of one abdominal joint excites the stretch receptors in several abdominal segments.
Plasma Renin Activity and in vitro Synthesis of Aldosterone by the Adrenal Glands of Rats with Spontaneous, Renal, or Pinealectomy‐Induced Hypertension
Authors: Karppanen Heikki , Lahovaara Salme , Männistö Pekka , Vappatalo Heikki
Published: December 2008

In the present study a comparison was made on the role of the renin‐aldosterone system in rats with various forms of experimental hypertension (pinealectomy‐induced, renal and spontaneous). The plasma sodium and potassium concentrations as well as renin activity were measured. The in vitro production of aldosterone by quartered adrenal glands of these rats was also determined. 5 weeks after the operations the blood pressure of the pinealectomized and renal operated rats was significantly increased. The plasma sodium concentration did not differ in various groups, but that of potassium was decreased in the renal hypertensive animals. The plasma renin activity of the pinealectomized rats was elevated while in other forms of hypertension it was at the control level. The basal aldosterone production by the adrenal quarters was equal in all the groups. ACTH, dibutyryl cyclic adenosine‐3′,5′‐monophosphate (DBA) and 5HT stimulated the aldosterone production. The responses to ACTH and DBA were greater in the adrenals of renal hypertensive rats than in the other forms of hypertension or in the controls. We suggest that the renin‐aldosterone system is of importance in the maintenance of renal hypertension, while in pinealectomy‐induced hypertension elevated plasma renin activity reflects an increased sympathetic activity which probably is the main cause of hypertension in these animals.
Prostaglandin Endoperoxides IX. Characterization of Rabbit Aorta Contracting Substance (RCS) from Guinea Pig Lung and Human Platelets
Authors: Svensson Jan , Hamberg Mats , Samuelsson Bengt
Published: December 2008

Material causing contraction of the isolated rabbit aorta (rabbit aorta contracting substance, RCS) was released from guinea pig lung following perfusion with arachidonic acid and from human blood platelets after addition of thrombin to induce aggregation. Prostaglandin endoperoxides (prostaglandins G2 and/or H2) were found both in the perfusate of guinea pig lung (1–3 ng/ml) and in the medium collected after platelet aggregation (13–37 ng/ml). The contractile response of the isolated rabbit aorta to the pure prostaglandins G2 and H2, was also determined. These data combined with the quantitative analyses of the endoperoxides released from the lungs and platelets showed that only a minor part of the rabbit aorta contracting activity was due to the prostaglandin endoperoxides. The major part of the activity consisted of very unstable material. The half life of this material was about 30 s at 37d̀ whereas at this temperature the prostaglandin endoperoxides had a half life of about 5 min.
Consequences of Myocardial Structural Adaptation on Left Ventricular Compliance and the Frank‐Starling Relationship in Spontaneously Hypertensive Rats
Authors: Hallbäck Margareta , Isaksson Olle , Noresson Eddy
Published: December 2008

The Frank‐Starling relationship of hearts from adult spontaneously hypertensive rats (SHR, Okamoto 1969), representing the established phase of hypertension, and of young SHR, representing the initial phase of hypertension, was investigated by using the isoloated working heart preparation. In the “normal” diastolic pressure range (5 to 10 cm H2O), the left ventricle of both SHR groups displayed significantly reduced stroke volumes compared with hearts of normotensive controls (NCR); the degree of reduction being proportional to the left ventricular hypertophy. This is suggested to be due to a reduced left ventricular diastolic compliance in SHR, as indicated by direct measurements of ventricular wall thickness and end‐diastolic volumes in arrested hearts exposed to different end‐diastolic filling pressures. Such a progressive shift of the Frank‐Starling relationship to the right with duration of hypertension could, in combination with the gradual development of “Structural autoregulation” of the precapillary resistance vessels, constitute dominating factors in shifting the hemodynamic situation in labile hypetension into that characterizing the established, or “fixed”, State of hypertension.
Effect of Temperature on Optical Density of Rabbit Blood in Dye Dilution Studies
Authors: M.Anderson Naomi , Creasy Robert K. , de Swiet Michael , Kahanpää Kari V.
Published: December 2008

The optical density of rabbit blood increased on cooling. This increase was additive to the deflection produced by indocyanine green at all concentrations measured. If calibration curves were not corrected for any increasy in optical density produced by cooling the blood, an error (minimum 11%) was introduced in the estimation of cardiac output. The effect of temperature was investigated with three different densitometers. Its wave‐length dependence did not follow the absorption spectrum of oxyhemoglobin.
The Effeect of Restricted Convection‐Diffusion on Bolus Concentration along an Exchange Vessel
Authors: ÅBerg Bo
Published: December 2008

If a sudden rise in solute concentration travels through a capillary system, a diffusible neutral solute passes the walls of the exchange vessels. If then the rate of passage depends on a chemical potential gradient (diffusion) and a hydrodynamical potential gradient (diffusion) and a hydrodynamical potential gradient (convection) and is sterically restricted (restricted convection‐diffusion), water and low molecular weight solvents leave the filtering part of the capillary at a higher rate than the solute, causing a relative increase in its concentration. This phenomenon and the effect of an increasing pore size along the capillary is investigated in a model for an impermeable solute and two diffusible solutes, corresponding to glucose and raffinose. It is shown that in the model, the concentration fall along the capillary tends to become rectilinear.
Enzyme Activities and Muscle Strength after “Sprint Training” in Man
Authors: Thorstensson A. , Sjödin B. , Karlsson J.
Published: December 2008

Sprint type strength training was performed 3–4 times a week for 8 healthy male students (16–18 yrs). The training was carried out on a treadmill at high speed and with high inclination. Muscle biopsies were obtained from vastus lateralis before and after the training period for histochemical classification of slow and fast twitch muscle fibres and for biochemical determination of metabolites and enzyme activities. Muscle fibre type distribution was unchanged. whereas fibre area indicated an increase for both fibre types in 3 subjects after training. The muscle enzyme activities of Mg2+ stimulated ATPase, myokinase and creatine phosphokinase increased 30, 20, and 36 percent, pespectively. Muscle concentration of ATP and creatine phosphate (CP) did not change with training. Sargent's jump increased with on average 4 cm (from 47 to 51 cm), maximal voluntary contraction (MVC) with 19 kp (from 165 to 184 kp), andurance at 50 percent of MVC with 9 s (from 47 to 56 s), respectively. After training all subjects showed a gain in body weight (mean 1.4 kg) and in thigh circumference (mean 1.5 cm) indicating a larger leg muscle volume and consequently also an increase in total ATP and CP.
Reduction of the Tone of the Isolated Human Umbilical Artery by Indomethacin, Eicosa‐5, 8, 11, 14‐Tetraynoic Acid and Polyphloretin Phosphate
Authors: Strandberg Kjell , Tuvemo Torsten
Published: December 2008

The effects of 2 prostaglandin synthetase inhibitors, indomethacin and eicoa‐5, 8, 11, 14‐terraynoic acid (ETA) and of the prostaglandin antagonist, polyphloretin phosphate (PPP), on the tone of the isolated human umbilical artery and on the responses of this preparation to 5‐hydroxytryptamine (5‐HT) and prostaglandin F2α (PGF2α) were investigated. Indomethacin (8μg/ml), ETA (5 μg/ml) or PPP (40 μ/ml) reduced the tone of human umbilical arteries but had no influence on the responses to 5‐HT. In these concentrations ETA and PPP but not indomethacin antagonized the action of PGF2α. When the concentration of indomethacin or PPP was increased 5‐fold both 5‐HT‐ and PGF2α‐induced contractios were antagonized indicating a non‐specific inhibition at these concentration levels. A 10‐fold increase in the concentration of ETA had no antagonizing action on 5‐HT‐induced contractions suggesting a more selective inhibition of the PGF2α action than displayed by the other compounds. The effects on the tone of the human umbilical artery of the compounds studied might reflect inhibition of prostaglandin biosynthesis and/or antagonism of prostaglandins contributes to the maintenance of tone of the isolated human umbilical artery.
Effects on Gastric Motility from the Cerebellar Fastigial Nucleus
Authors: Lisander Björn , Martner Jan
Published: December 2008

In acute experiments on chloralosed cats gastric motility, blood pressure and heart rate were investigated for influences exerted by the fastigial nucleus. Besides pressor responses, fastigial stimulation could produce either gastric excitation or relaxation and the background of these responses was analysed by selective nerve sectioning and administration of suitable autonomic blocking agents. Suppression of prevailing gastric motility was found to be mediated mainly by increased discharge in adrenergic nerve fibres but also by adrenal catecholamine release.–Gastric excitation could be induced in three different ways, first via increased activity in vagal cholinergic fibres, second, by fastigial suppression of the vago‐vagal non‐adrenergic relaxatory reflex. In addition, when laparotomy or other noxious abdominal stimuli had induced inhibitory gastric reflexes, the consequent sympathetic discharge could be suppressed by fastigial stimulation resulting in enhanced gastric motility.–The importance of background activity in the various nervous pathways for the fastigially induced gastric responses is discussed.
The Capillary Permeability of the rete mirabile of the Eel, Anguilla vulgaris L.
Authors: Stray‐Pedersen Sverre , Steen Johan B.
Published: December 2008

Direct measurements of transcapillary exchange during steady‐state conditions have been performed in the rete mirabile of the eel. The capillaries were found to be more than 30 times as permeable to THO (PTHO= 33.2 × 10‐5 cm sec‐1), ethanol and antipyrine than to K+. The mutual relationship of the permeabilities for K+, Na+, urea and sucrose were similar to that between the corresponding free diffusion coefficients in water. The permeability characteristics did not change when the perfusate contained metabolic inhibitors. Addition of 1 mM/1 of albumin lead to a significant transcapillary osmotic flow. NaCl, urea and sucrose, however, did not cause osmotic flow. Based on the quantitative values for permeability and volume flow the capillary pores should be about 1300 Å and have a frequency of 1.3 × 106 per cm2 of the capillary surface, occupying an area of about 0.1% of the total area. The results obtained in the present investigation raise questions as to the validity of the Pappenheimer single‐pore theory for transcapillary transport as well as to the fine structure of the capillary pores. As an alternative to Pappen‐heimer's theory a multi‐pathway model is proposed in order to explain transcapillary transport.
Synthesis of Catecholamines in the Eye after Local Injection of3H‐Precursors
Authors: Rentzhog Leif
Published: December 2008

The possibility that adrenaline may be synthesized locally in the eye was investigated in the rabbit and vervet monkey. L‐tyrosine‐3,5‐3H, L‐tyrosine (side‐chain‐2,3‐3H) or L‐3,4–dihydroxyphenylalanine (3H(G)) was injected into the anterior chamber or the vitreous. The animals were killed after 1/2 h up to 7 days in the tyrosine experiments and after 1 up to 24 h in the DOPA experiments. The synthesis of3H‐adrenaline,3H‐noradrenaline and3H‐dopamine was measured with a modified version of a double isotope technique for determination of catecholamines. No3H‐adrenaline was found. An attempt to stimulate the phenylethanolamine‐N‐methyltransferase activity with a glucocorticoid and to inhibit the metabolism of catecholamines with a monoaminoxidase inhibitor also failed to demonstrate3H‐adrenaline synthesis.3H‐noradrenaline was found in all experiments when3H‐DOPA had been given. The amounts were about 10 times higher after injection into the anterior chamber than after injection into the vitreous.3H‐dopamine was found in all except a few experiments after3H‐DOPA injection. The highest amounts were found after injection into the vitreous. In experiments with3H‐tyrosine we were unable to demonstrate any catecholamine synthesis. This prompts the question of whether tyrosine‐hydroxylase may be absent in the eves of certain animal species.
Renal Handling of Human β2‐Microglobulin in the Rat: The Importance of Sham‐Operation
Authors: Ravnskov Uffe , Karátson András
Published: December 2008

The plasma disappearance rates of human β2‐microglobulin and (hydroxy‐methyl‐C14)‐inulin was measured in unoperated, sham‐operated, ureter‐ligated and nephrectomised rats. Judging from the C14–activity curves in ureter‐ligated and nephrectomised rats a substantial glomerular filtration continued after obstruction of the urine flow. Almost 90% of the injected protein had disappeared from plasma 120 min after injection into nephrectomised rats indicating a considerable extra‐renal elimination and invalidating attempts to evaluate different renal mechanisms of elimination before and after ureter‐ligation. Sham‐operation induced an increase of the plasma disappearance of both β2‐microglobulin and inulin. The latter phenomenon may explain earlier findings of similarity between the disappearance curves of low molecular weight proteins in unoperated and ureter‐ligated animals and stresses the importance of using sham‐operated animals as controls.
Cardiovascular Responses to Changes in Carotid Sinus Transmural Pressure in Man
Authors: Bjurstedt H. , Rosenhamer G. , Tydén G.
Published: December 2008

To study the relative importance of cardiac and peripheral effector mechanisms in the carotid sinus baroreflex in man cardiovascular responses to equal changes of the carotid sinus transmural pressure (Ptm) in either direction of the normal were recorded and compared in eight physically well‐trained young male volunteers. In both the supine and the 70d̀ head‐up position, a decrease in Ptm produced a more potent reflex response of the systemic arterial pressure than did a similar increase in Ptm. Whereas the arterial pressure response to increased Ptm was due solely to a reduction in vascular resistance, a significant increase in cardiac output contributed to the more potent pressor response to a decrease in Ptm and thus to the predominantly antihypotensive properties that characterize the carotid sinus baroreceptor control system in man. However, since combined beta‐adrenergic and parasympathetic blockade abolished the effect of reduced Ptm on cardiac output without greatly impairing the blood pressure response, it is concluded that adjustments in cardiac output are not of critical importance in the buffering function of the carotid sinus baroreceptors. Autonomic cardiac blockade exaggerated the fall in cardiac output on head‐up tilt, the arterial pressure remaining unaffected due to a compensatory increase in systemic vascular resistance.
Effect of Cold Exposure on Free Water Reabsorption in Hydropenic Man
Authors: Wallenberg L. R.
Published: December 2008

With clearance technique, changes in tubular reabsorption of solute free water(TH2Oc), were studied in a group of 9 healthy hydropenic volunteers during a cold stress of 1 h at + 15°C.

Increases were found in(TcH20)and in fractional excretion of sodium and osmoles during cold.

Since(TCH2O)was used as an index of sodium reabsorption in the ascending limb of Henle's loop, the findings indicated that under the conditions used in this study, the concentrating ability of the kidney was not negatively influenced by cold, despite a significant increase in arterial pressure.

It is suggested that the reabsorption by the ascending limb of the loop was increased secondary to a reduced proximal tubular reabsorption of sodium.
Differential Effects of Temperature on Activity of LDH from Seal and Sheep Skin
Authors: Blix Arnoldus Schytte , Messelt Edvard B. , Grav Hans J.
Published: December 2008

The homeothermic seal possesses a heterothermic skin, while the skin of the sheep behaves as a truly homeothermic tissue. A new method for skin homogenization is described. The effect of temperature on the catalytic behaviour of seal and sheep skin LDH has been investigated by fluorimetric activity measurements, with results presented as Arrhenius plots. The seal skin enzyme had ten times higher activity at low temperatures as compared to the sheep skin. The mechanisms responsible for this different behaviour are discussed.
Effect of Spinal Sympathetic Blockade upon Local Regulation of Blood Flow in Subcutaneous Tissue
Authors: Henriksen O. , Alsner T.
Published: December 2008

The influence of spinal sympathetic blockade upon local regulation of blood flow in subcutaneous adipose tissue was investigated in six subjects. The effect of changes in orthostatic pressure on blood flow in subcutaneous tissue in the crus and distal forearm was measured before and after sympathetic blockade obtained by epidural anesthesia in 4 subjects and by a bilateral sympathectomy in 2 patients suffering from manual hyperhidrosis. Blood flow in subcutaneous tissue measured by133Xe washout technique decreased by about 40 per cent when the limb was lowered, and remained constant during 30 cm elevation. This was found both before and after the blockade, though in one of the patients, the orthostatic decrease in blood flow was less pronounced 24 h after sympathectomy. Hence central sympathetic reflexes do not alter local orthostatic changes of blood flow in subcutaneous tissue. These changes therefore are most likely due to local mechanisms.
Recovery of ADH Activity in the Urine of Goats under Normal and Stimulated Conditions
Authors: Lishajko F. , Anderson B.
Published: December 2008

The hydrated goat was used for bioassays of, antidiuretic hormone (ADH) activity recovered by resin column separation from the urine of other animals of the same species. A methodological innovation in the separation procedure was ethanol purification of the column before elution. In this manner substances which sometimes obscured the bioassays were eliminated without loss of ADH activity. With the bioassay method employed, it was possible to determine to the nearest 0.5 of a mU the ADH activity of unknown samples, provided they contained between 0–5 mU of ADH. When arginine vasopressin was infused intravenously into hydrated animals, slightly more than 10% of its antidiuretic activity was recovered in the urine. In the water replete goat the ADH activity found in the urine was of the order of 1 mU per hr urine secretion, indicating a neurohypophyseal ADH release of approximately 5 μU/kg min. After 48 h of dehydration in an environmental temperature of 20°C the renal ADH excretion increased to about 8 mU/h, suggesting an 8‐fold increase of ADH secretion over basic, water replete secretion of ADH. ADH secretion of the same high order was induced in hydrated animals by the infusion of angiotensin II together with hypertonic NaCl into the lateral cerebral ventricle.
Imitation of Glucagon Effects on Splanchnic Hemodynamics and Liver Function by N6, 2′‐O‐Dibutyryl 3′,5′‐Cyclic AMP (DBcAMP) in Cats
Authors: Krarup Niels , Larsen Anker Jens , Munck Anders
Published: December 2008

Fasting cats anesthetized with chloralose were used for the experiments. DBcAMP infused at a rate of 340 nmol/kg/min increased the gastrointestinal and intrahepatic portal conductances whereas the hepatic arterial conductance was decreased. The hemodynamic responses to portal and systemic venous administration of DBcAMP were identical. In half of the experiments DBcAMP increased the splanchnic ethanol elimination rate and oxygen consumption and in all experiments there was a decrease in the plasma clearance and extraction ratio of Indocyanine Green. No change in bile flow was observed. DBcAMP infused at a rate of 85 nmol/kg/min was without significant effects on either splanchnic hemodynamics or liver metabolism. DBcAMP infused at a rate of 850 nmol/kg/min accentuated the decrease in hepatic arterial conductance but was found to decrease the splanchnic ethanol elimination rate and oxygen consumption. Infusion of cAMP, AMP and adenosine at a rate of 340 nmol/kg/min were without measurable effects. Based on these results it is concluded that like the metabolic effects also the vascular effects of glucagon are caused by stimulation of specific glucagon receptors which results in an intracellular release of cAMP.
Accumulation of Calcium by Retinal outer Segments
Authors: Hemminki Kari
Published: December 2008

Two 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

The 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

Experiments 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

The 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

In 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

The 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

Noradrenaline 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.
Performance of the hypertrophied left ventricle in spontaneously hypertensive rat. Effects of changes in preload and afterload
Authors: NORESSON EDDY , RICKSTEN SVEN‐ERIK , HALLBÄCK‐NORDLANDER MARGARETA , THORÉN PETER
Published: December 2008

Isolated hearts from adult spontaneously hypertensive rats (SHR; Okamoto 1969), with established hypertension, were investigated in an antegrade perfusion apparatus where preload and afterload could be varied independently. Frank‐Starling curves were constructed at constant afterloads ranging from 50 mmHg to 150 mmHg. As earlier reported, the SHR hearts exhibited a rightward shift of their Frank‐Starling relationships compared to those from the normotensive control hearts, though visible only at afterloads up to about 100 mmHg. At higher afterloads the SHR hearts performed significantly better then the NCR ones as their maximal stroke volume was significantly greater compared to that of controls. Thus, left ventricular hypertrophy obviously increases the work capacity of the heart, though at the cost of an altered Frank‐Starling relation dependent on the reduced diastolic compliance. For such reasons the myocardial hypertrophy in established SHR hypertension must be considered a physiologic adaptation and not a degenerative phenomenon, though naturally degenerative processes may later become superimposed.
Skeletal muscle metabolism, morphology and function in sedentary smokers and nonsmokers
Authors: ÖRLANDER JAN , KIESSLING KARL‐HEINZ , LARSSON LARS
Published: December 2008

Smokers and nonsmokers of a homogeneous population of sedentary men have been compared with respect to skeletal muscle (vastus lateralis) morphological, metabolic and functional characteristics. The percentage type I fibres was lower and that of type IIB fibres higher in the smokers. Fibre areas were almost equal in the two groups. Muscle oxidative capacity was lowered in the smokers, as judged from decreased mitochondrial enzyme activities and a lowered fibrillar space mitochondrial volume fraction. Isometric and dynamic strengths were lower in the smokers, except at the highest velocity of movement studied. Dynamic strengths expressed in relation to isometric strength were similar at all velocities except the highest, where the smokers were relatively stronger. Muscular endurance, measured in short‐term isometric and dynamic tests, was not different. It is suggested that the lowered muscle oxidative capacity and strength in the smokers may be partly a consequence of the different fibre type distribution. A possibly lower physical activity level, and tobacco smoke constituents (e.g. carbon monoxide) may also be instrumental. It is not clear whether the different fibre type distribution in the smokers is an effect of smoking per se, or if background factors are responsible.
The effect of α‐aminoisobuturic acid and 2,4‐diaminobuturic acid on mouse blastocyst outgrowth in vitro
Authors: NÆSLUND GRELS , LINDQVIST INGER , RONQUIST GUNNAR , NILSON B. OVE
Published: December 2008

Blastocysts recovered from mice in a state of delay of implantation were incubated for 10 h with either α‐aminoisobuturic acid (AIB) or 2,4‐diaminobuturic acid (DAB), two non‐metabolizable amino acids. The incubation medium was composed so as to maintain growth arrest of the inactive, delayed blastocysts in vitro. The blastocysts were then transferred to a complete outgrowth medium without the two non‐metabolizable amino acids to test the capacity for trophoblast outgrowth. AIB, which displays saturation kinetics, was harmless to the blastocysts even at a high concentration, while DAB at a low concentration irreversibly damaged the trophoblast cells and prevented outgrowth, probably due to nonsaturation kinetics resulting in a high intracellular accumulation. The harmful effect of DAB could be abolished by concomitant incubation with l‐alanine and l‐methionine, which compete with DAB for the same transport system, while the d‐forms of the same amino acids had little or no effect. The results suggest the presence of transport System A in mouse blastocysts growth arrested in vitro, indicating an operative carrier mechanism already during delay of implantation.
Importance of sodium and glucose for the establishment of a villous tissue hyperosmolality by the intestinal countercurrent multiplier
Authors: HALLBÄCK DAN‐AXEL , JODAL MATS , LUNDGREN OVE
Published: December 2008

The intestinal countercurrent multiplier has earlier been shown to create an increased tissue osmolality in the villi (Jodal et al. 1978). In the present paper the importance of varying the luminal contents on the creation of the villous hyperosmolality was investigated using the cryoscopic technique described by Jodal et al. (1978). The perfusion solutions used contained 0, 25 or 147 mmol Na/1 and were either provided with mannitol or glucose (30 mmol/1). It was demonstrated that sodium was of particular importance for the establishment of the villous hyperosmolality while glucose only contributed significantly at low luminal sodium concentrations. It is therefore proposed that glucose only in the absence of sodium in the luminal perfusate may effectively participate in the generation of the villous tissue hyperosmolality via the countercurrent multiplication mechanism.
Release of prostaglandin‐like substances during elevations of left atrial pressure in the cat
Authors: WIBERG T. , VAAGE J. , SCOTT E.
Published: December 2008

The purpose of the present work was to measure prostaglandin (PG)‐like activity in arterial blood during acute pulmonary hypertension. Anesthetized cats with the chest opened and given positive pressure ventilation were used. A balloon in the left atrium was inflated to elevate hydrostatic vascular pressure in the lungs. Blood was pumped (10 ml/min) from a carotid artery to superfuse 3 smooth muscle tissues: rat stomach strip, rat colon and chick rectum: the blood was then returned to the jugular vein by gravity. The assay tissues were pretreated with antagonists against catecholamines, histamine, serotonin and acetylcholine during the experiments. They were sensitive to calibrating doses of 2 ng/ml of PGF2α and 1 ng/ml of PGE2. 18 periods with elevated left atrial pressure (Pla) (21–49 mmHg), lasting 2–26 min, were applied in 9 cats. This manoevre usually also caused systemic hypotension. 14 of these Pla elevations were accompanied by increased arterial PG‐like activity, which rapidly subsided when the pressure was released or when indomethacin (2 mg/kg, n= 4) was given i.v. In 3 additional experiments it was found that pulmonary degradation of PGs was unaffected during Pla elevation. I.v. infusion of angiotensin II contracted the tissues in a pattern different from that caused by pressure elevations and the PG calibrations, and these contractions were not affected by indomethacin. This indicates that the assay tissue contractions cannot be caused by angiotensin II which alone does not increase PG‐like activity in arterial blood. Consequently, acute pulmonary vascular hypertension appears to stimulate PG synthesis and release in lungs of intact cats.
Effects of acute hypotension and hypertension on serum TSH concentrations in male rats
Authors: MÄNNISTÖ P. T. , KOKKONEN J. , RANTA T.
Published: December 2008

The effect of acute hypertension and hypotension on serum TSH concentration was studied in anesthetized male rats. I.v. infusions (10 and 30 min) of Na‐nitroprusside and dihydralazine induced a profound hypotension, and angiotensin amide and noradrenaline increased blood pressure, but none of the treatments significantly modified serum TSH concentrations. Also clonidine and noradrenaline, when given i.p., caused hypertension, but again the increase of serum TSH levels was not consistent. When the whole material was analysed, there was a scarcely significant correlation between the change of blood pressure and the change of serum TSH level. It is inferred that the drugs affecting TSH secretion, do not exert their action solely by changing the blood pressure.
Morphometry of myocardial apex in endurance‐trained mice of different ages
Authors: KAINULAINEN HEIKKI , PILSTRÖM LARS , VIHKO VEIKKO
Published: December 2008

Mitochondrial volume density, surface density of the outer mitochondrial membrane, the mean number and size of mitochondria, and the mean surface density of crista membranes together with the volume densities of myofibrils and sarcoplasmic space were morpho‐metrically analyzed in cardiac muscle of two groups of sedentary control mice aged 3 and 7 months, and in two groups of mice trained either 1 month rather intensely or 4 months moderately. Of the calculated mitochondrial variables only the surface density of the outer mitochondrial membrane differed between the older controls and the older trained animals, the density being slightly smaller in the trained group. The myofibrillar volume density of the older controls was smaller than that of the younger controls, while the sarcoplasmic volume density was larger. The latter difference, possibly a function of age, was also observed in the trained groups. The results suggest that at a certain steady state level of exercise‐induced cardiac muscle hypertrophy the muscle cells of trained mice do not differ markedly in ultrastructural properties from those of sedentary controls.
Villous tissue osmolality and intestinal transport of water and electrolytes
Authors: HALLBÄCK DAN‐AXEL , JODAL MATS , SJÖQVIST ANDERS , LUNDGREN OVE
Published: December 2008

The villous tissue hyperosmolality created by the intestinal countercurrent multiplier has been proposed to be of importance for fluid transport across the intestinal epithelium in vivo. This study was performed to test this hypothesis. Net transport of fluid and electrolytes (sodium, potassium and chloride), as well as unidirectional fluxes of water and sodium were determined in the small intestine of the cat. The villous osmolality was altered by varying the composition of sodium and glucose in the isotonic solutions perfusing the intestinal lumen. Net transport of fluid was correlated to tissue osmolality mainly due to an increase of the unidirectional flux of water from lumen to tissue with augmented tissue osmolality. The results are thus consistent with the view that the intestinal countercurrent multiplier is of essential importance for net water transport. A correlation was found between net water and net sodium intestinal transport. A similar correlation was also demonstrated between net sodium and net chloride absorption rates in the jejunum while in the ileum net loss of sodium into the intestinal lumen was not accompanied by any corresponding loss of chloride ions. This observation suggests the presence of a sodium independent transport mechanism for chloride in the ileum but not in the jejunum.