bluuebunny/crossref_metadata_2025 huggingface dataset:
Autoradiographic Studies with 35S‐Sulfate on Somatotrophin and Estrogen Sensitivite Growth Zones in Rat and Mouse Costal Cartilage
Authors: Herbai Georg
Published: December 2008

An autoratliographic study was performed on the regional pattern of incorporation of 35S sulfate in different anatomical regions of costal cartilage in growing mice and rats in uivo and in vitro. Profound regional differences in sulfate incorporation rate have been revealed between the medial or “resting” part of costal cartilage and the “active” growing region of the rib which is located in close association with the osteochondral junction. The regional pattern of sulfation activity showed great similarities in the rib cages of rats and mice. The increased sulfate incorporation activity in the growth region of mouse rib cartilage was also maintained when the rib cage was incubated in vitro with 35S‐sulfate. Hypophysectoniy almost completely abolished, and somatotrophin treatment of hypophysectomized mice with 500 μg GH‐NIH‐S8 for 10 days restored the rate of sulfate uptake to above normal levels in the growth zones of the ribs. A 10 clay treatment with a daily dose of 100 μg estradiol Iienzoate per mouse caused a pronounced fall in the sulfate incorporating activity of the growth region and markedly narrowed the “active” zone of the costal cartilage.
Inhibition of Thromboplastin‐Induced Intravascular Coagulation by Heparin and Trasylol
Authors: Nordström Sam
Published: December 2008

Homologous brain thromboplastin was injected or infused in different ways in dogs, and various coagulation factors were followed for 7 days. Slow infusions of thromboplastin in anesthetized dogs caused changes in platelet count and fibrinogen concentration similar to those usually seen in the postoperative period in man. The heparin co‐factor decreased only slightly, which is contrary to the postoperative reactions in both man and dogs.

The decrease in platelet count and fibrinogen concentration and the rate of thromboemboli after intravenous thromboplastin administration could partly be inhibited, if the dogs were treated prophylactically with Trasylol, and completely inhibited, if they were pretreated with heparin. Trasylol also seemed to exert some slight influence on the antithrombin level in the circulating blood. The in vivo anticoagulant effect of Trasylol might be the result of partial inhibition of more than one reaction in the coagulation process. Compared to heparin Trasylol is a weak anticoagulant.
Contraction Times and Fibre Types in Intact Human Muscle
Authors: Buchthal Fritz , Schmalbruch Henning
Published: December 2008

Twitches were recorded in situ in muscles of normal humans by small transducers connected to a needle in the tendon. The twitches were elicited by stimuli in the endplate zone, the force of the smallest twitches corresponding to the average of one or two motor units. The time to peak contraction was measured of 20–30 bundles of fibres in each muscle examined. The histograms of contraction times agreed with histochemical findings; contraction times longer than 60 msec corresponded to the proportion of fibres rich in mitochondria. Thus, long contraction times predominated in the soleus and gastrocnemius muscles, comprised half the times in the anterior tibia], a third in the brachial biceps (long head) and a few per cent in the brachial triceps muscle (lateral head). Bundles of fibres with short contraction times, those poor in mitochondria had a higher temperature coefficient of the time to peak than bundles with long contraction times. During hypoxia the contraction times shortened. The contraction time of motor units first activated voluntarily lay near the mean of bundles activated electrically. The contraction times of fasciculating fibres were in the range of electrically evoked twitches; the force was about three times that of voluntarily activated units.
Sodium Transport and D.C. Resistance in the Isolated Toad Skin in Relation to Shedding of the Stratum Corneum
Authors: Larsen Erik Hviid
Published: December 2008

It has been assumed that the main resistance to sodium ion movements is located in the superficial layer of the amphibian skin. It is therefore of interest to follow transport function during shedding of the stratum corncum. Shedding of the stratum corneum in the isolated toad skin (Bufo bufo) can be induced by aldosterone treatment of skin from hypophysectornized toads. It is shown that slough formation is followed by an almost three fold increase in short‐circuit current. This increase is accounted for by an increased rate of active sodium transport and is preceded by an increase in passive sodium permeability and a decrease in D.C. resistance. The results are discussed in relation to the functional organization of the skin, and to moulting in vivo.
Effect of Trasylol on Thromboplastin‐Induced Arterial Hypotension
Authors: Nordström Sam
Published: December 2008

The effect on arterial blood pressure of pretreatment with Trasylol was studied in dogs injected i.v. with homologous brain thromboplastin. Trasylol did not consistently inhibit the initial fall in arterial blood pressure, but the return to normal pressure level was faster after administration of the drug. This effect of Trasylol might depend on interference with coagulation processes as well as with release of vasoactive substances.
Effects of Reptilase‐Induced Intravascular Coagulation in Dogs
Authors: Egberg Nils , Nordström Sam
Published: December 2008

The effect of the thrombin‐like enzyme preparation Reptilase, purified from the venom of the snake Bothrops atrox, was studied in dogs injected with 125I‐labelled fibrinogen. Reptilase was capable of inducing intravascular coagulation as shown by the decrease in fibrinogen concentration, but influenced the platelet count only moderately. No bleeding tendency was observed. Pretreatment with heparin did not affect the defibrination process. Secondary activation of the fibrinolytic system was demonstrated by the appearance in plasma and serum of fibrinogen degradation products, studied by radioactivity measurements and immunological methods. Epsilon anunocaproic acid (EACA) and Trasylol could reduce and delay but not completely abolish the secondary fibrinolysis. No thromboemboli were found at autopsy.

In long‐term treatment by daily injections of Reptilase it was possible to keep the fibrinogen concentration at low levels for several weeks without adverse effects. The hemostatic function was maintained undisturbed probably due to the fact that the platelet count was essentially unchanged.
Release and Uptake of Dopamine in Isolated Granules from a Human Carotid Body Tumour
Authors: Lishajko F.
Published: December 2008

Isolated granules from a human carotid body tumour incubated in 130 mM K‐phosphate pH 7.5 release dopamine (DA) with a half time of 23 min at 37° C. Addition of DA 2times10‐5M to the incubation fluid prevents net loss of DA from the granules, owing to reuptake. Further addition of ATP‐Mg2+increases the DA content in the granules about 8 times. This effect is strongly inhibited by reserpine 10‐3M and reduced about 40 per cent by noradrenaline (NA) and adrenaline (A) each in a concentration of 10‐5M.
Testosterone Metabolism by Gastrointestinal Microsomes
Authors: Harri M.‐P. , Hartiala K. , Nienstedt W. , Salmi H. A.
Published: December 2008

In incubation studies with the microsonial fraction of various tissues of the rat, the ability to metabolize testosterone, determined as the decrease in NADPH2 absorbance, was found to be rather high in various gastrointestinal tissues but lower in several non‐gastrointestinal tissues. In one case, some of the numerous metabolites were identified with hepatic, ileal mucosal and heart tissues. All of them apparently produce at least 4‐androstenedione, 5α‐androstanedione, and 17 β‐hydroxy‐5α‐androstan‐3‐one.
Thermogenesis of Brown Adipose Tissue Reflected in Mitochondrial Respiratory Control
Authors: Andersen H. T. , Christiansen E. N. , Grav H. J. , Pedersen J. I.
Published: December 2008

This paper presents data to demonstrate a loosening in the coupling of phosphorylation to respiration in brown adipose tissue mitochondria during cold exposure. This loosening of coupling was accompanied by a significant increase in the respiratory rate. Moreover, the mitochondrial energy conserving mechanism has been shown to recouple when cold exposed animals are returned to thermoneutral surroundings. The degree of coupling of phosphorylation to respiration has been investigated in terms of the P/O ratio and of the respiratory control index. With brown adipose tissue mitochondria, both of these relationships have to be studied independently in order to obtain data relevant to the problem of variations in the energy conserving mechanism since they are differently affected by the in vitro conditions used. Our findings indicate that the non‐shivering thermogenesis of brown adipose tissue is physiologically regulated and perhaps in a more sophisticated way than by simple on‐off control. Guinea‐pigs have been used in the experiments.
Effects of Feeding States on Lipid Radioactivity in Liver, Muscle and Adipose Tissue after Injection of Labelled Glucose in the Rat
Authors: Björntorp P. , Krotkiewski M. , Larsson B. , Somlo‐Szücs Z.
Published: December 2008

0.5 g of glucose/kg b.w. and (U‐14C) glucose was injected i.v. to ad libitum fed, 18 hrs fasting or 48 hrs fasting‐48 hrs refed rats. After 60 min blood glucose had decreased to preinjection values. Recirculation of radioactive metabolites was found in blood in pyruvate‐lactate and to a small extent in glyceride‐glycerol. Rats were sacrificed at this time and radioactivity measured in chloroform: methanol extracts of homogenates from muscle, liver and different adipose tissue regions. Furthermore, radioactivity was measured in fatty acids. Fatty acid radioactivity in different regions was considered to be due to the local synthesis of fatty acids, because no recirculation was discovered at the time of analysis. Liver and adipose tissue fatty acid synthesis was most pronounced in the refed rats. Adipose tissue showed higher fatty acid synthesizing activity than the liver in ad libitum fed, but not in refed rats. Glyceride‐glycerol radioactivity was rather high in muscle. In adipose tissue it was more constant in different feeding states than fatty acid radioactivity was. By additions of measured radioactive metabolites glucose uptake in adipose tissue was roughly estimated to a few per cent of total glucose uptake.
The Effect of Dinitrophenol on Secretory Potentials, Secretion and Potassium Accumulation in the Perfused Cat Submandibular Gland
Authors: Petersen Ole Holger
Published: December 2008

Dinitrophenol strongly depresses salivary secretion and potassium uptake after acetylcholine‐induced potassium loss in the perfused cat submandibular gland. However, transmembrane secretory potentials recorded from the acinar cells after intraarterial injections of acetylcholine change little after introduction of dinitrophenol. This seems to indicate that the secretory potentials are not directly dependent on energy metabolism and that the mechanism of these potential changes may be an increase in ion permeability of the basal acinar cell membrane.
Exchange of Glucose between Plasma, Brain Extracellular Fluid and Cerebral Ventricles in Cats and Effects of Intraventricular Acetazolamide and Insulin
Authors: Brondsted H. E.
Published: December 2008

The ventriculo‐aqueductal perfusion technique was used for a quantitative study of the transport of glucose between the cerebral ventricles and surrounding tissues in cats. The inflow perfusion fluid contained U14C‐D‐glucose and unlabelled D‐glucose. Carrier systems appeared to operate symmetrically. Intraventricular acetazolamide or insulin did not influence the transport of glucose in the brain. At zero net flux of glucose in the system the concentration of glucose in brain extracellular fluid was estimated to be the same as in the ventricles, i.e. about 40 per cent below the concentration in arterial plasma water.
Effect of Hypotonic Mannitol and Saline Load on Diluting Capacity in Man
Authors: Aperia A. , Broberger O. , Feychting H.
Published: December 2008

The effect of hypotonic mannitol and saline loading on the urinary diluting capacity in man has been examined. The further interpretation of the data was built on the assumption that the free water formation is determined by distal tubular Na+ reabsorption. Thus it could be demonstrated that the distal tubular Na+ reabsorption was at first enhanced and later suppressed by progressive increases in the total distal tubular Na+ delivery. No relationship could be demonstrated between distal tubular Na+ reabsorption and urinary Na+ concentration. This was interpreted to mean that the distal tubular Na+ reabsorption was independent of the transtubular Na+ gradient.
Mechanisms Involved in the Cat's Blink Reflex
Authors: Lindquist Chr. , Mårtensson A.
Published: December 2008

Tapping on the cat's facial skin elicits two successive reflex discharges in the orbicularis oculi. The responses have similar thresholds and are most readily evoked from the skin overlying the muscle. Both discharges result also on tapping on a skin flap over the muscle, whereas tapping on the muscle belly is ineffective. Similar responses are elicited on electrical stimulation of low‐threshold trigeminal afferents; the central relay time indicates that the early response is mediated through a polysynaptic reflex arc. Stimulation of high‐threshold afferents in the facial nerve may give a long latency reflex response in the orbicularis oculi and facilitate transmission of a short‐latency reflex response in the same muscle set up by stimulation of trigeminal afferents. Recordings from peripheral filaments provide no evidence for the presence of afferent fibers from muscle spindles or other types of proprioceptors in the facial and trigeminal nerves. A twitch contraction of the orbicularis oculi elicits a high‐amplitude reflex response in the muscle through activation of trigeminal exteroceptive afferents; the possibility is considered that such afferents may serve a proprioceptive function in monitoring the degree of contraction of the facial muscles.
Renal Reabsorption and Metabolic Conversion of Galactose in the Cat
Authors: Rasmussen S. Nybo
Published: December 2008

Extrahepatic elimination of galactose occurs mainly in the kidney. Urinary excretion as well as metabolic conversion may be of significance. At plasma concentrations of galactose between 60 and 1200 mg per liter in cats urine to plasma concentration ratios below one were never observed. At low filtered loads the reabsorption fraction was close to 1.0. At higher loads the reabsorption fraction decreased and seemed to converge towards 0.6. The rate of metabolic conversion of galactose in the kidney — calculated as the RBF times the arterio‐venous concentration difference minus the excretion rate — exceeded considerably the reabsorption rate at low filtered loads. At increasing loads the metabolic rates approached maximum values between 50 and 100 μg per minute and gram kidney weight. The capacity of the kidney for metabolic conversion of galactose appeared (per gram organ weight) to be in the same order of magnitude as that of the liver. Push‐flow experiments indicated that reabsorption of galactose takes place exclusively in the proximal tubular system. When, at low plasma concentrations, the metabolic rate exceeds the reabsorption rate the intracellular concentration of galactose in the tubular wall cells may stay low and this may promote diffusion into the cells and account for the high reabsorption fractions found (conversion reabsorption). At higher concentrations, where the reabsorption rate exceeds the metabolic rate, reabsorption is probably due increasingly to carrier‐facilitated transcellular backdiffusion.
Effects of Increased Liver Metabolism of Nicotine on Its Uptake, Elimination and Toxicity in Mice
Authors: Stålhandske Torbjörn
Published: December 2008

Male albino mice were injected intraperitoneally or intravenously with14C‐labelled nicotine. Both untreated and phenobarbital pretreated mice were used. The concentrations of nicotine and metabolically formed cotinine were determined in the brain, liver and blood 1, 2.5, 5, 10, 20 and 60 min after injection. It was found that phenobarbital pretreated mice exhibited an enhanced liver metabolism of nicotine both in vitro and in vivo. The increased liver metabolism caused a significant decrease of nicotine concentration in the brain only when nicotine was given intraperitoneally. Phenobarbital pretreatment elevated the intraperitoneal LD50value 2–3 times and also increased tolerance to repeated sublethal doses of nicotine. No change in the intravenous LD50value was observed.
Acetylation of P‐Aminohippuric Acid in the Kidney. Renal Clearance of P‐Aminohippuric Acid in the Kidney. Renal Clearance of P‐Aminohippuric Acid and N4‐Acetylated P‐Aminohippuric Acid in Pigs
Authors: Gyrd‐Hansen N. , Rasmussen Folke
Published: December 2008

20 pigs weighing 21–124 kg were used to determine the clearance of PAH, N4‐acetylated PAH and PAHtotal, and for determination of acetylation of PAH and de‐acetylation of N4‐acetylated PAH in the kidney. By examining blood samples taken from a. renalis and v. renalis and urine collected simultaneously, the acetylation and de‐acetylation of PAH and N4‐acetylated PAH in the kidney were determined on 9 pigs. 6 of these acetylated PAH (1.5–10 per cent), while 3 de‐acetylated N4‐acetylated PAH (2–21 per cent). The extraction percentage for PAH and N4‐acetylated PAH were 91 ± 1.4 (S.E.M.) and 84 ± 2.1 respectively. The ratio between clearance of N4‐acetylated PAH and PAH was found to be 1.08 ± 0.07 and between clearance for PAHtotal and PAH 1.01 ± 0.02.
The Relationship between Arylesterase Activity and Growth in Rats
Authors: Augustinsson Klas‐Bertil , Henricson Bengt
Published: December 2008

There was a highly significant negative correlation between blood plasma arylesterase activity and growth rate in male rats when the enzyme activity was determined at younger ages (11–32 days). In females the correlation was only vaguely indicated. A direct or indirect causal relationship between the two parameters is discussed.
Localization of a Microelectrode Tip in Muscle Cell
Authors: Nickels J.
Published: December 2008

A method is described for accurate localisation of a recording glass microelectrode in muscle cell and subsequent histochemical staining of the myoneural junction of the cell with cholinesterase and, finally, for localisation of the recording site itself in an electronmicroscopic picture. Microelectrodes were filled with 1.1 M of K4Fe(CN)6 and 1.5 M of Na2HPO4. With the microelectrode at the recording point, a 1: 1 mixture of 0.1 M of Pb(NO3)2 and 5 per cent acetate‐buffered (pH 5.6) glutaraldehyde was applied to its environment and anions were driven electrophoretically from the microelectrode with a DC of about 2 μA for 5–10 sec. into the muscle cell. The white sediment that originated was turned dark with 1 per cent (NH4)2S. The size of the sediment was 5–20 μ. It was seen clearly under the light microscope. This method did not affect the histochemical stainability of the motor end‐plate. As the sediment contained heavy metals it was visualised also in the electron microscopic picture after further fixation for one hour in buffered glutaraldehyde. The sediment was visible also in the Epon resin block and this helped the trimming of the specimen. The sediment consisted in a normal electron microscopic picture of rough heavy‐metal grains.
Contraction Times of Twitches Evoked by H‐Reflexes
Authors: Buchthal Fritz , Schmalbruch Henning
Published: December 2008

Isometric twitches of the same amplitude were initiated in the human soleus muscle by near threshold H‐reflexes and by stimuli to the efferent nerve (M‐responses) or to the end‐plate zone. The time to peak‐force was longer in reflex than in directly activated twitches: The range was 84 to 130 msec and 52 to 100 msec, respectively (36–37°C).
Circulatory Effects of Interruption and Stimulation of Cardiac Vagal Afferents
Authors: ÖBerg B. , White S.
Published: December 2008

The influence of the rhythmic activity in cardiac vagal afferents on the circulation was analyzed in chloralose‐anesthetized cats by observing the cardiovascular responses to sudden interruption of this activity and to afferent stimulation of the cardiac nerves. The evoked responses were compared with those produced by “unloading” and stimulation of arterial baroreceptors. — Elimination of the impulse traffic in vagal afferents produced a blood pressure rise, a tachycardia and vasoconstrictions in skeletal muscle, intestine and kidney, indicating a tonic restraint of these afferents on the medullary vasomotor centre. The responses were generally moderate in the presence of normally functioning arterial baroreceptors but were pronounced after elimination of “buffering” influences from these receptors. — Comparisons of the inhibitory influences from vagal cardiac afferents and baroreceptor afferents, respectively, on the vasomotor centre indicated that the former were preferentially directed to neurons controlling the efferent discharge to the heart and the renal vessels. There was no evidence for a particularly strong engagement of the capacitance vessels in reflex patterns mediated through cardiac afferents. — Low frequency afferent stimulation of the cardiac nerves generally induced a profound brady‐cardia, which was probably due to stimulation of fibres not normally tonically active.
In Vitro Assay of the Stimulatory Effect of Hypoxic Serum on Cellular Proliferation in the Erythron
Authors: Kivilaakso E.
Published: December 2008

The effect of experimental hypoxia on mitotic homeostasis in the erythron was investigated by means of an in vitro technique. The proliferative responses were measured in terms of 3H‐thymidine incorporation in normal rat bone marrow cells in vitro. Test serum was collected from rats kept in hypoxic conditions. The hypoxic serum caused a significant (22%) stimulation of total incorporation of 3H‐thymidine in the target cells as compared to normal serum. Autoradiographic analysis revealed that this effect was due to an increase in the number of bone marrow cells labelled. The stimulation proved to be tissue‐specific: the number of labelled erythrocyte precursors was increased by 45%, while the effect on the granulocyte population was negligible. Gel filtration of the hypoxic and normal sera on Sephadex G‐200 revealed that the effect was exerted by a stimulatory factor present in the hypoxic serum, there being no substantial difference between the two sera in their contents of the inhibitor, chalone. Elution parameters of the stimulator on Sephadex G‐200 suggested a molecular weight in the region of 60,000–70,000. As judged from the molecular weights, this stimulator and erythro‐poietin may be identical, but the exact relation of the two factors cannot be deduced with certainty on the basis of the data available. The results are discussed.
Inhibitory Control of the Abdominal Stretch Receptors of the Crayfish
Authors: Jansen J. K. S. , Njå A. , Walløe L.
Published: December 2008

By stretch activation of the slowly adapting abdominal stretch receptor of the crayfish, we have found reflex activation of two efferent spikes of different amplitudes in the dorsal nerves of the same and neighbouring segments. The large as well as the small efferent spike inhibit the discharge of the receptor. It is suggested that these two units represent the thick and thin accessory fiber described by Alexandrowicz, as making synaptic contacts with the receptor cell.
The Significance of Age for the Phosphatase Activity of Seminal Fluid
Authors: Wikström Carin
Published: December 2008

Two age groups of rabbits have been compared with respect to the activity of seminal acid phosphatases. The ejaculates of the young (1 year old) rabbits showed about twice as high phosphatase activity as the ejaculates of the older rabbits (3–5 years old). No differences in ejaculate volumes and libido have been observed.
Studies on the Mechanism of Action of Lithium Ions
Authors: Giacobini E. , Stepita‐Klauco M.
Published: December 2008

When the extracellular Na+was replaced by lithium (Li+) the frequency of the impulses elicited by stretching the stretch receptor of crayfish was changed and then inhibited. This effect was not due to the lack of extracellular Na+. Higher firing rate facilitated and low extracellular K+delayed the Li+effect. Ouabain alone (10‐4M) changed the impulse activity in a similar manner to Li+replacement. Ouabain (10‐5M) decreased the rate of recovery during wash‐out after Li+replacement. The Li+‐induced increase in the frequency of the impulse activity was probably the result of a lower intracellular K+concentration, the block of the spike activity being due to the accumulation of Li+in the cell. The Na+pump participated in the recovery of the spike activity after Li+replacement.
Calcium supplementation and thyroid hormone protect against gentamicin‐induced inhibition of proximal tubular Na+, K+‐ATPase activity and other renal functional changes
Authors: FUKUDA Y. , EKLÖF A.‐C. , MALMBORG A.‐S. , APERIA A.
Published: December 2008

Gentamicin can cause proximal tubule necrosis. We have shown that inhibition of PT Na+, K+‐ATPase activity is rapidly induced by gentamicin. We have now investigated whether manipulations known to attenuate the negative effects of gentamicin on renal excretory capacity, i.e. high calcium intake and L‐thyroxine treatment, will also attenuate gentamicin‐induced inhibition of Na+, K+‐ATPase activity and ameliorated signs of proximal tubule damage. Rats were gentamicin‐ or vehicle‐treated for 7 days. Sub‐groups were given 4% calcium (Ca) supplements or L‐thyroxine 20μg 100 g‐1body weight daily. Gentamicin significantly reduced the glomerular filtration rate and increased the urinary excretion of the proximal tubule lysosomal enzyme,N‐acetyl‐β‐d‐glucosaminidase. Gentamicin significantly reduced proximal tubule Na+, K+‐ATPase activity, measured in single permeabilized proximal tubule segments. Sodium excretion was inversely correlated to proximal tubule Na+, K+‐ATPase activity. Both calcium and L‐thyroxine alleviated all gentamicin‐induced side‐effects on renal function as well as on proximal tubule Na+, K+‐ATPase activity. Calcium and L‐thyroxine had no significant effect on renal function. L‐thyroxine, but not calcium, increased proximal tubule Na+, K+‐ATPase activity in control rats. Renal cortical tissue gentamicin concentration was not influenced by calcium but was significantly lowered by L‐thyroxine.

Two procedures which, via different mechanisms, afford protection from gentamicin‐induced changes in renal function also give protection from gentamicin‐induced inhibition of Na+, K+‐ATPase activity. This suggests that loss of integrity of the Na+, K+‐ATPase enzyme contributes to gentamicin‐induced nephrotoxicity.
Calcium‐induced net potassium uptake of pig hearts in vivo
Authors: ELLINGSEN Ø. , AKSNES G. , ILEBEKK A.
Published: December 2008

To determine whether the catecholamine‐induced myocardial potassium uptake could be mimicked by increasing extracellular and intracellular calcium concentrations in vivo, we measured changes in myocardial potassium balance in nine anaesthetized open‐chest pigs with PVC‐valinomycin electrodes in arterial and coronary sinus blood. CaCl2 infusion (200–400 μmol min‐1) into the left coronary artery increased coronary sinus blood calcium concentration from 2.29 (2.19–2.42) to 4.63 (3.76–5.67) mmol I‐1 (median, 95% confidence interval, P= 0.01) indicating a similar increment in myocardial extracellular calcium concentration. The contractility measure LV dP/dt increased 95 (76–147)%, indicating a substantial increment in intracellular calcium concentration. During the CaCl2 infusion coronary sinus potassium concentration declined to a nadir 0.12 (0.09–0.17) mmol l‐1 below baseline (P= 0.008) whereas arterial concentration remained unchanged. Peak myocardial potassium uptake was 18 (7–32) μmol min‐1 100 g‐1 and occurred 150 (110–195) s after start of infusion. The response remained unaltered after adrenoceptor blockade by prazosin and propranolol. Prolonged CaCl2 infusion caused a net myocardial potassium loss which was accompanied by metabolic and haemodynamic indications of myocardial ischaemia. These findings are consistent with enhanced Na‐K pump activity in the intact beating pig heart in response to increased extracellular and intracellular calcium concentrations.
External calcium sensitivity of low sodium contractures in the control and hypertrophied right ventricle of the ferret
Authors: BAUDET S. , NOIREAUD J. , LEOTY C.
Published: December 2008

The existence of possible differences of calcium (Ca2+) fluxes through the sarcolemmal sodium‐calcium (Na+/Ca2+) exchanger during hypertrophy has been tested by comparing the characteristics of the contracture—as an indicator of the intracellular Ca2+ concentration—induced by partial or total withdrawal of external sodium (Na+), in the absence of external potassium, in the right ventricular trabeculae of adult ferret hearts. Pressure‐overload was induced by pulmonary artery clipping and led to an increase of the right ventricular weight of 60%. At an external Ca2+ concentration ([Ca2+]0) of 3 mm, the dependence of the contractures on extracellular sodium concentration ([Na+]0), the rate of tension development, the time course of spontaneous relaxation and the time course for the repriming of the contracture were unchanged by hypertrophy. However, the relationship between [Ca2+]0 and contracture amplitude at various [Na+]0 showed that the apparent affinity of the contracture for [Ca2+]0 was decreased in hypertrophied preparations. Thus, in 0 mM [Na+]0, half‐maximal contracture was induced at a [Ca2+]0 of 0.012 ± 0.016 mm and 0.171 ± 0.021 mM in control (n= 11) and hypertrophy (n= 12) respectively (P < 0.001). Although these data may be indicative of a decreased Ca2+ influx through the Na+/Ca2+ exchanger, it cannot be excluded that intracellular buffering mechanism may also be involved in this differential response to [Na+]0 withdrawal.
Actions of serotonin antagonists on cholera‐toxininduced intestinal fluid secretion
Authors: SJÖQVIST A. , CASSUTO J. , JODAL M. , LUNDGREN O.
Published: December 2008

The effects of several 5‐hydroxytryptamine (5‐HT) receptor antagonists were tested in ratsin vivoon the intestinal fluid secretion evoked by cholera toxin. Five receptor antagonists were used, namely 2‐bromolysergic acid diethylamine (2‐bromo‐LSD), granisetron, ketanserin, methysergide and ondansetron. The drugs were used in doses that inhibited the arterial hypertension and/or bradycardia evoked by 5‐HT given i.v. Granisetron and ondansetron markedly diminished cholera‐toxin‐evoked secretion, whereas ketanserin was without any effect. Methysergide also diminished cholera‐toxininduced fluid secretion particularly when the drug was given as an i.v. infusion. The results are considered in relation to the pathophysiology of cholera secretion and to the current views of receptor subtypes for 5‐HT. It is proposed that the receptor involved is a 5‐HT3receptor, possibly also a receptor of the 5‐HT1type. Results from experiments in which 5‐HT (20 mM) was placed in the intestinal lumen to evoke an intestinal secretion suggest that the 5‐HT3receptor is located in the villus tissue. It was also demonstrated that zimeldine, an inhibitor of presynaptic 5‐HT reuptake, diminished choleraic secretion, an effect that may be ascribed to a 5‐HT tachyphylaxis caused by an accumulation of 5‐HT in a synaptic cleft.
Neuronal plasticity and ageing processes in the frame of the ‘Red Queen Theory’
Authors: AGNATI L. F. , ZOLI M. , BIAGINI G. , FUXE K.
Published: December 2008

On the basis of the morphofunctional evidence obtained in old brains of humans and mammals the present hypothesis has been introduced. This hypothesis states that neuronal plasticity can be used either to compensate for neuronal degeneration or to store new information. Thus, in pathological ageing the marked rate of degeneration has fully exhausted the already reduced plasticity capability of neural networks. In this way marked impairments of memory trace formation take place in pathological ageing conditions such as Alzheimer's disease. The essence of this hypothesis is that a competition for the available plasticity exists between the compensatory responses to ageing‐induced degeneration and the processes necessary for memory trace formation. We have called this hypothesis the ‘Red Queen Theory’, an analogy borrowed from Lewis Carroll's book Through the Looking Glass. Thus, in ageing, processes responsible for plasticity must be forced to run at the highest possible rate to maintain the morphofunctional substrate of the existing networks as well as to allow the formation of new memory traces.
Effect of low glycogen on glycogen synthase in human muscle during and after exercise
Authors: YAN Z. , SPENCER M. K. , KATZ A.
Published: December 2008

Subjects cycled at a work load calculated to elicit 75% of maximal oxygen uptake on two occasions: the first to fatigue (34.5 ± 5.3 min; mean ± SE), and the second at the same workload and for the same duration as the first. Biopsies were obtained from the quadriceps femoris muscle before and immediately after exercise, and 5 min post‐exercise. Before the first experiment, muscle glycogen was lowered by a combination of exercise and diet, and before the second, experiment muscle glycogen was elevated. In the low glycogen condition (LG), muscle glycogen decreased from 169 ± 15 mmol glucosyl units kg‐1dry wt at to rest to 13 ± 6 after exercise. In the high glycogen condition (HG) glycogen decreased from 706 ± 52 at rest to 405 ± 68 after exercise. Glycogen synthase fractional activity (GSF) was always higher during the LG treatment. During exercise in the HG condition, those subjects who cycled for < 35 min (n= 3) had GSF values in muscle which were lower than at rest, whereas those subjects who cycled for > 35 min (n= 4) had values which were similar to or higher than at rest. Thus the change in GSF in muscle during HG was positively related to the exercise duration (r= 0.94; y = 254–17x + 0.3x2; P < 0.001) and negatively related to the glycogen content at the end of exercise (r=–0.82; y= 516–2x + 0.001x2; P < 0.05). During LG exercise GSF remained constant. GSF increased markedly after 5 min post‐exercise in both HG and LG conditions. cAMP dependent protein kinase activity increased similarly during both LG and HG exercise and reverted to the preexercise values 5 min post‐exercise. It is concluded that muscle contraction decreases GSF, but low glycogen levels can attenuate or abolish the decrease in GSF. The rapid increase of GSF during recovery from exercise does not require glycogen depletion during the exercise.
Activation of the Na‐K pump by intracellular Na in rat slow‐ and fast‐twitch muscle
Authors: EVERTS M. E. , CLAUSEN T.
Published: December 2008

Experiments were performed on isolated rat soleus (slow‐twitch) and extensor digitorum longus (EDL) (fast‐twitch) muscle of 4‐week‐old rats. In soleus muscle, electrical simulation at 2 Hz for 5 min increased the ouabain‐suppressible 86Rb+uptake by 138%, without significant changes in intracellular Na+content or Na+/K+ratio. In EDL muscle, the ouabain‐suppressible 86Rb+uptake was stimulated by only 58%, whereas intracellular Na+content and Na+/K+ratio were increased by around 70%. Na+‐loading of the muscles by exposure to K+‐free or K+‐Ca2‐Mg2+‐free buffer stimulated the ouabain‐suppressible 86Rb+uptake in the two muscles to roughly the same extent, but in EDL muscle this was associated with a more than twofold larger increase in Na+/K+ratio. When the Na+influx was increased by exposure to veratridine similar results were obtained. Graded variation in intracellular Na+content was achieved by exposure to monensin. In soleus muscle, a 25% increase in intracellular Na+/K+ratio resulted in a doubling of the ouabain‐suppressible 86Rb+uptake, whereas a doubling of the Na+–K+transport rate in EDL muscle required a 140% increase in Na+/K+ratio. The results indicate that in soleus muscle the Na+/K+pump is much more sensitive to changes in intracellular Na+content than in EDL muscle. This might explain the larger activation of the Na+–K+pump in slow‐twitch muscle during electrical stimulation and might be of significance for the activation of the Na+‐K+pump in vivo during work.
Type A and B monoamine oxidase activities in the human and rat kidney
Authors: FERNANDES M. H. , SOARES‐DA‐SILVA P.
Published: December 2008

The present work has examined the distribution of the two isoforms of monoamine oxidase (MAO), type MAO‐A and MAO‐B, in the cortex and medulla of the human and rat kidney. Homogenates of renal cortex and renal medulla were prepared in 67 mmoles 1‐1phosphate buffer (pH = 7.2) and MAO activity was determined with [3H]5‐hydroxytryptamine ([3H]5HT) and [14C]β‐phenylethylamine ([14C]β‐PEA) as preferential substrates of type A and type B MAO, respectively. KmandVmaxvalues for the two substrates were also calculated. Both MAO‐A and MAO‐B are present in the cortex and the medulla of the human and rat kidneys. In the human kidney, MAO‐A activity was found to be similar in the cortex (Vmax= 142.70±45.05 nmoles mg‐1protein h‐1) and medulla (Vmax= 133.91±35.51 nmoles mg‐1protein h‐1); MAO‐B activity was found to be higher in the cortex (Vmax= 166.19±19.75 nmoles mg1protein h‐1) than in the medulla (Vmax= 92.91±13.22 nmoles mg‐1protein h‐1). In the rat kidney, MAO‐A was also found to be similar in the cortex (Vmax= 62.35±1.74 nmoles mg‐1protein h‐1) and the medulla (Vmax= 59.42±0.97 nmoles mg‐1protein h‐1) and higher than the activity of MAO‐B in the two renal areas (cortex,Vmax= 31.06±1.09 nmoles mg‐1protein h‐1; medulla,Vmax= 14.93±0.97 nmoles mg‐1protein h‐1). No statistically significant differences were found between the Kmvalues towards [3H]5HT and [14C]β‐PEA in the cortex and the medulla of the human and rat kidneys. The results show that in both renal areas, activity of the enzyme is higher in the human kidney than in the rat kidney. Furthermore, in the human kidney, in contrast with the rat kidney, MAO‐B activity closely follows MAO‐A activity.
Effect of atrial natriuretic factor on renal prostaglandin E2release in the anaesthetized dog
Authors: NAESS P. A. , CHRISTENSEN G. , KIRKEBØEN K. A. , KIIL F.
Published: December 2008

Experiments were undertaken in two groups of barbiturate anaesthetized dogs to examine whether atrial natriuretic factor (ANF) exerts an effect on renal release of prostaglandin E2(PGE2). In the first group, intravenous infusion of ANF (50 ng min‐1kg‐1body wt) reduced basal PGE2release from 4.4 ± 0.8 pmol min‐1to 1.8 ± 0.7 pmol min‐1. In the second group, intrarenal infusion of an α‐adrenoceptor agonist, phenylephrine (2.5–6.75 μg min‐1), raised PGE2release from 2.7 ± 0.5 pmol min‐1to 7.5 ± 1.3 pmol min‐1. During continuous α1‐adrenergic stimulation, intravenous infusion of ANF (100 ng min‐1kg‐1body wt) reduced PGE2release to 3.5 ± 1.0 pmol min‐1. These results demonstrate that ANF reduces basal and α1‐adrenergic stimulated renal PGE2release.
In vivo and in vitro studies on the effects of mGnRH on oestradiol‐17β inter‐renal production in the female frog, Rana esculenta, during the post‐reproductive period
Authors: ZERANI M. , GOBBETTI A.
Published: December 2008

Plasma oestradiol‐17β was measured by RIA, in female, Rana esculenta, submitted to hypophysectomy, gonadectomy, or both, and treated with mammalian gonadotropinreleasing hormone (mGnRH), homologous pituitary homogenate, or both, during the post‐reproductive period. In addition, the oestradiol‐17β release was measured in in vitro incubations of ovaries or interrenals treated with mGnRH, pituitary, or both, during the same period.

In vivo and in vitro mGnRH and/or pituitary directly stimulated the production of oestradiol‐17β by the interrenal, but not by ovary, although the stimulatory effects of the pituitary are minor and delayed with respect to those of mGnRH.

These results seem to indicate that mGnRH and pituitary, with probably different mechanisms, stimulate the interrenal to produce high levels of oestradiol which is involved in the post‐reproductive refractoriness.
Atrial natriuretic peptide attenuates pressor but enhances natriuretic responses to angiotensin II in pregnant conscious goats
Authors: OLSSON K. , HOSSAINI‐HILALI J. , ERIKSSONI L.
Published: December 2008

This study was designed to examine the actions of ANP in acute, ANGII‐mediated hypertension during pregnancy. Effects on blood pressure, blood volume, and renal Na and K excretion were evaluated in conscious goats (n= 6). ANP (2 μrg min‐1), ANGII (0.5 μg min‐1), or ANGII + ANP (doses the same as for each peptide alone) was infused intravenously for 60 min. The pressor response to ANGII was reduced in pregnant goats. This reduction was seen in systolic, but not in diastolic pressure. ANP decreased pressure by 5–10 mmHg both in pregnancy and in non‐pregnancy. When ANGII + ANP was infused, blood pressure initially rose as with ANGII but then declined. ANP suppressed only the elevated systolic pressure. Plasma protein concentration and haematocrit was reduced by ANGII but increased by ANP alone or together with ANGII, thereby implying fluid shift into the vasculature by ANGII and opposite movement by ANP. ANGII increased renal Na excretion to 1500 μmol min‐1in non‐pregnancy, but only to half of that in pregnancy. ANP alone caused small natriuresis, but enhanced ANGII‐induced natriuresis to near 3000 μmol min‐1in both non‐pregnant and pregnant goats. In summary, ANP further attenuated the blunted blood‐pressure rise due to ANGII in pregnant goats, and reduced plasma volume, but enhanced renal Na excretion as in non‐pregnant goats. This implies that with the present combination ANP and ANGII caused a near maximal natriuretic response that was not modified by the systemic cardiovascular changes occurring in pregnant goats.
Effects of graded restriction of perfusion on circulation and metabolism in the working leg; quantification of a human ischaemia‐model
Authors: SUNDBERG C. J. , KAIJSER L.
Published: December 2008

An experimental model used with the intention of mimicking the ischaemic condition in patients with arterial obliterative disease was evaluated. The influence of reduced effective perfusion pressure by increased external pressure on leg blood flow and metabolism was determined during exercise in 10 healthy subjects. Catheters were inserted into the right femoral artery and vein and into the left femoral vein. Supine one‐legged (n= 5) or two‐legged (n= 5) cycle exercise was performed with the subject's legs in a pressure chamber. Zero and three different levels of local supra‐atmospheric pressure were applied over the legs: 30, 50 and 60 mmHg. Three submaximal work loads were used: 24, 48 and 72 W/leg. Leg blood flow was measured by the constant‐infusion dye‐dilution technique. Samples were also drawn from the femoral artery and vein for oxygen saturation and lactate determinations and arterial pressure was recorded. Exercise blood flow decreased progressively with increasing chamber pressure (P < 0.001). Exposure to 50 mmHg over the working leg led to a mean reduction of blood flow by 16% and venous oxygen saturation by 12 percentage units (P < 0.05). Lactate release increased with increasing pressure (P < 0.05). In summary, local application of moderate positive external pressure over the working leg reduces blood flow in a ‘dose‐dependent’ manner, and as a consequence, femoral venous oxygen saturation decreases and lactate release increases. Thus, this method makes it possible to induce graded ischaemia in human skeletal muscle during exercise in a controlled fashion.
Force production in voltage‐clamped human atrial muscle
Authors: ARLOCK P. , WOHLFART B. , MÖRNER S. E. J. N. , BRANDT J.
Published: December 2008

Human atrial muscle preparations obtained during open heart surgery were mounted in a sucrose gap. Force and membrane currents were recorded during voltage clamp. After a 20‐s rest, 10 clamps from a holding potential of –40 to 0 mV at 1.0 Hz were given. This was followed by a test clamp (called 1) of a varied duration and amplitude and two more test clamps (called 2 and 3) as during the priming period. Peak force of contraction 1 (Fl) was independent of clamp duration from 2 s to about 100 ms but declined at shorter durations. Peak force of contraction 2 (F2) and 3 (F3) increased with the duration and became potentiated. Increasing the clamp amplitude raised F1 to an optimum value at about + 10 mV and there was a decline at higher voltages. Both F2 and F3 increased at higher amplitudes. A conventional bell‐shaped current‐voltage relation for the second inward current was obtained during clamp 1 with maximum inward current around –10 mV. In control experiments on isolated human myocytes peak current was recorded at somewhat more positive potentials. The relation between F3 and F2 was linear both when duration and amplitude of clamp 1 was varied. The slope of the line, interpreted as a measure of recirculation of activator calcium, was 0.4. It is concluded that force during voltage clamp in human atrial muscle is similarly related to membrane voltage as previously reported for guinea pig and ferret preparations.
Inefficiency of bilateral amygdaloid lesions to reduce the transient motor reactions exhibited by swine during exposure to CO2
Authors: FORSLID A. , HÄGGENDAL J.
Published: December 2008

The aim of the study was to evaluate from the ethical point of view the importance of transient muscular jerks commonly exhibited by swine at an early stage of pre‐slaughter CO2 anaesthesia.

The influence of 5 min restraint upon plasma concentrations of adrenaline (A) and noradrenaline (NA) was studied in swine (n= 6) before and after bilateral lesioning of the amygdaloid region of the brain, as were the motor reactions of the same and three other animals during 1 min exposure to 80% CO2. The A and NA responses to the restraint became almost extinguished after amygdaloid lesioning in three of the animals, were reduced by about 50% in one swine, whereas no reduction was seen in the other two animals investigated. The amygdaloid lesioning did not visibly influence the latency for, and the duration and intensity of the muscular jerks manifested by the swine during the CO2‐exposure.

The results do not favour the possibility that transient motor reactions exhibited by swine during pre‐slaughter CO2‐exposure are manifestations of emotional stress. Instead, the study indirectly supports the idea that the cause of the muscular jerks may be disinhibition of subcortical motor centres being inactivated by the CO2‐anaesthesia somewhat later than neocortical cells normally exerting the inhibition.