bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of halothane on the transducer and potential activated currents of the crustacean stretch receptor
Authors: SWERUP C. , RYDQVIST B.
Published: December 2008

SWERUP, C. & RYDQVIST, B. 1985. Effects of halothane on the transducer and potential activated currents of the crustacean stretch receptor.Acta Physiol Scand125, 359–368. Received 20 February 1985, accepted 20 April 1985. ISSN 0001–6772. Department of Physiology II, Karolinska Institute, Stockholm, Sweden.

Halothane was applied to the stretch receptor neuron of the crayfish (Astacus astacus) and the effects on the transducer properties and the potential activated currents were studied with potential clamp technique using two microelectrodes. Exposure to halothane reduced the frequency of action potentials during stretch. This was shown to be due to effects both on the action potential generating currents and the transducer current. Halothane partially blocked the TTX sensitive fast inward current in a dose‐dependent manner (Apparent KD= 3 mM). Halothane also reduced the outward current produced by a positive potential step. Both the fast and the slow component were affected, although the fast outward current seemed to be most sensitive. There was little or no change in the currents resulting from negative potential steps. The peak of the receptor potential and the receptor current were very little affected by halothane. The amplitude of the static phase of the receptor potential was reduced to a greater degree than the static phase of the receptor current (cells treated with TTX). A change in reversal potential of about –13 mV was observed for the peak and the static phase of the receptor current in four cells indicating an increased cord conductance for the transducer channel.
Dual effects of adenosine and adenosine analogues on motor activity of the human fallopian tube
Authors: SAMUELSON ULF E. , WIKLUND N. PETER , GUSTAFSSON LARS E.
Published: December 2008

SAMUELSON, U.E, WIKLUND, N.P. & GUSTAFSSON, L.E. 1985. Dual effects of adenosine and adenosine analogues on motor activity of the human fallopian tube. Acta Physiol Scand125, 369–376. Received 24 January 1985, accepted 20 April 1985. ISSN 0001–6772. Department of Physiology, Karolinska Institute, and National Institute of Environmental Medicine, Stockholm, Sweden.

Effects of adenosine and adenosine analogues on spontaneous contractility of the human fallopian tube during different phases of the menstrual cycle were studied. In isthmic preparations, a stimulatory effect by L‐N6‐phenylisopropyladenosine (L‐PIA), with preference for adenosine A1‐receptors, was seen mainly during the proliferative phase. In ampullary preparations, stimulation by L‐PIA was seen both in the secretory and proliferative phases. Adenosine and 2‐chloroadenosine exerted similar stimulatory effects. 5′‐N‐ethylcarboxamide‐adenosine (NECA), with selectivity for adenosine A2‐receptors, or D‐PIA never showed a stimulatory effect. At concentrations above those needed for stimulation, adenosine, 2‐chloroadenosine and L‐PIA inhibited spontaneous contractions, in common with NECA and D‐PIA. Here, NECA was more potent than L‐PIA. The D‐PIA and L‐PIA were equipotent. The inhibition was seen during the whole menstrual cycle. The competitive adenosine antagonist 8‐j>‐sulphophenyltheophylline (PSOT) reversibly antagonized the stimulatory and inhibitory effects elicited by adenosine and the analogues. The PSøT alone could exert a stimulatory or an inhibitory action on spontaneous contractility. We suggest that adenosine can modulate contractile activity in the human fallopian tube via stimulatory A1 ‐ and inhibitory A2 ‐ receptors. These receptors are located on the smooth muscle cells, and might act via cAMP. The relative receptor dominance may be influenced by cyclic hormonal changes.
Mechanism of hypergastrinaemia after nephrectomy in the rat
Authors: EKELUND M. , MUNSHID H. A. EL , HÅKANSON R. , REHFELD J. F.
Published: December 2008

EKELUND, M., EL MUNSHID, H.A., HÅKANSON, R. & REHFELD, J.F. 1985. Mechanism of hypergastrinaemia after nephrectomy in the rat. Acta Physiol Scand 125, 383–388. Received 17 September 1984, accepted 1 May 1985. ISSN 0001–6772. Departments of Pharmacology and Surgery, University of Lund, Lund, Sweden, and Department of Clinical Chemistry, Rigshospitalet, Copenhagen, Denmark.

Bilateral nephrectomy in the rat is followed by hypergastrinaemia and by activation of gastric histidine decarboxylase. The enzyme activity is thought to reflect the concentration of circulating gastrin. While there is general agreement that post‐nephrectomy hypergastrinaemia is primarily the result of loss of renal elimination of gastrin, it remained to be determined whether gastrin secretion could be stimulated in the hypergastrinaemic state and whether it contributed to the hypergastrinaemia. Histamine, but not pentagastrin, is known to evoke gastric acid secretion in the nephrectomized rat, and histamine, but not pentagastrin, was found to lower the serum gastrin level and the gastric histidine decarboxylase activity, indicating that after nephrectomy gastrin was still secreted and that the secretion could be suppressed by increased acid output. The importance of gastrin secretion for post‐nephrectomy hypergastrinaemia was assessed further by investigating the effect of nephrectomy on the serum gastrin concentration in rats previously subjected to operations that had either reduced (e.g. antrectomy) or raised (e.g. antrum exclusion) the serum gastrin concentration. Post‐nephrectomy serum gastrin levels co‐varied with the levels before nephrectomy. Thus, the capacity to secrete gastrin was not abolished by nephrectomy. Finally, nephrectomy greatly affected the linear correlation between the serum gastrin concentration and the gastric histidine decarboxylase activity in a manner suggesting the operation of a gastrin‐independent factor capable of activating the enzyme.
Acute continuous exposure to cigarette smoke produces discrete changes in cholecystokinin and substance P levels in the hypothalamus and preoptic area of the male rat
Authors: FUXE KJELL , SIEGEL RICHARD A. , ANDERSSON KURT , ENEROTH PETER , MASCAGNI FRANCO , AGNATI LUIGI F.
Published: December 2008

FUXE, K., SIEGEL, R.A., ANDERSON, K., ENEROTH, P., MASCAGNI, F. & AGNATI, L.F. 1985. Acute continuous exposure to cigarette smoke produces discrete changes in cholecystokinin and substance P levels in the hypothalamus and preoptic area of the male rat. Acta Physiol Scand 125, 437–443. Received 8 January 1985, accepted 7 May 1985, TSSN 0001–6772. Department of Histology, Karolinska Institute, Stockholm, Sweden, Research and Development Laboratory, Department of Obstetrics and Gynaecology, Karolinska Hospital, Stockholm, Sweden, Deutsches Primaten Zentrum, Gottingen, FRG, and Department of Human Physiology, University of Modena, Italy.

By means of a Walton Horizontal Smoking Machine, male rats were exposed to the smoke from 1–4 cigarettes burned in a continuous fashion. Cholecystokinin (CCK) and substance P levels (determined by means of radio‐immunoassay) were measured in discrete hypothalamic and preoptic regions. Acute continuous exposure to cigarette smoke induced increases in CCK levels in the paraventricular hypothalamic region as well as decreases in CCK levels in the median eminence. Furthermore, this treatment resulted in decreased CCK and substance P levels in the medial preoptic region. The results have been interpreted to indicate that CCK and substance P containing neuronal systems can be regulated by cholinergic nicotine‐like receptors.
Determinants of pulmonary blood volume. Effects of acute changes in airway pressure
Authors: THORVALDSON JØRGEN , ILEBEKK ARNFINN , KIIL FREDRIK
Published: December 2008

THORVALDSON, J., ILEBEKK, A. & KIIL, F. 1985. Determinants of pulmonary blood volume. Effects of acute changes in airway pressure. Acta Physiol Scand 1985, 125, 471–479. Received 2 November 1984, accepted 10 May 1985. ISSN 0001–6772. Institute for Experimental Medical Research, University of Oslo, Ullevaal Hospital, Norway.

To examine the effects of airway pressure (AWP) on pulmonary blood volume (PBV) at various pulmonary vascular pressures and flows, experiments were performed in anaesthetized, open‐chest dogs. The AWP was raised by elevating end‐expiratory pressure, and PBV was calculated as the product of electromagnetic aortic flow and pulmonary mean transit time for ascorbate (polarographic method). When AWP was raised from 3 to 13 mmHg, changing lung conditions from zone 3 [left atrial pressure (LAP) higher than AWP] to zone 2 (AWP higher than LAP), PBV decreased by 14.5 7plusmn; 6.2%. When LAP was raised above 7 mmHg at constant pulmonary arterial pressure (PAP), PBV increased under zone 2 but not under zone 3 conditions. During blood volume expansion to LAP 15 mmHg, PBV rose by 30–50% and became equal at AWP of 4 and 14 mmHg, whereas the pulmonary vascular resistance remained 40% higher at high AWP. These data suggest that PAP, LAP and AWP regulate PBV by acting on compliant vessels surrounding the alveoli. Under zone 2 conditions with collapsed aveolar capillaries, elevation of LAP results in re‐expansion of the alveolar capillaries, and PBV is restored without a rise in PAP. Under zone 3 conditions, a rise in LAP cannot increase PBV without raising PAP, explaining why PBV remains constant when PAP is kept constant.
Rotational behaviour elicited by intracerebral injections of apomorphine and pergolide in 6‐hydroxy‐dopamine‐lesioned rats. I: Comparison between systemic and intrastriatal injections
Authors: HERRERA‐MARSCHITZ MARIO , FORSTER CHRISTINE , UNGERSTEDT URBAN
Published: December 2008

HERRERA‐MARSCHITZ, M., FORSTER, C. AND UNGERSTEDT, U. 1985. Rotational behaviour elicited by intracerebral injections of apomorphine and pergolide in 6‐hydroxy‐dopamine‐lesioned rats. I. Comparison between systemic and intrastriatal injections.Acta Physiol Scand1985, 125, 519–527. Received 12 March 1985, accepted 22 May 1985. 0001–6772. Department of Pharmacology, Karolinska institutet, S‐104 01 Stockholm, Sweden.

Rotational behaviour in unilaterally 6‐hydroxy‐dopamine‐denervated rats has been attributed to stimulation of dopamine receptors on striatal as well as limbic areas. In the present study the rotational behaviour elicited by local intrastriatal injections of apomorphine or pergolide was compared to the rotation elicited by systemic injections of the drugs. We found that intrastriatal injections induced rotational behaviour almost identical to the behaviour occurring after systemic treatment. Furthermore, studies of the spread of [3H]apomorphine in brain tissue showed that at the peak of rotation the radioactivity was confined within the limits of the striatum. Non‐significant amounts of radioactivity was found in the nucleus accumbens. On the basis of these data we conclude that rotational behaviour elicited by systemic injections of apomorphine or pergolide originates from stimulation of striatal sites. The difference in rotational patterns elicited by these drugs is more likely to relate to differences in receptor stimulation within the striatum than differences in, for example, relative distribution between limbic and striatal areas.
Rotational behaviour elicited by intracerebral injections of apomorphine and pergolide in 6‐hydroxy‐dopamine‐lesioned rats. II: The striatum of the rat is heterogeneously organized for rotational behaviour
Authors: HERRERA‐MARSCHITZ MARIO , FORSTER CHRISTINE , UNGERSTEDT URBAN
Published: December 2008

HERRERA‐MARSCHITZ, M., FORSTER, C. & UNGERSTEDT, U. 1985. Rotational behaviour elicited by intracerebral injections of apomorphine and pergolide in 6‐hydroxy‐dopamine‐lesioned rats. II: The striatum of the rat is hetergeneously organized for rotational behaviour.Acta Physiol Scand125, 529–535. Received 12 March 1985, accepted 22 May 1985. ISSN 0001–6772. Department of Pharmacology, Karolinska institutet, S‐104 01 Stockholm, Sweden.

The present study compares the role of the nucleus accumbens and the striatum, as well as various regions of the striatum, in the ability of intracerebral injections of the dopamine agonists apomorphine and pergolide to elicit rotational behaviour in 6‐hydroxy‐dopamine‐lesioned rats. We found that apomorphine and pergolide elicit rotational behaviour when injected into the denervated striatum, but not when injected into the ipsilateral nucleus accumbens. The striatum seems heterogeneously organized as regards rotational behaviour since maximal‐apomorphine rotation was elicited from the corpus of the striatum as compared to the effects produced by injections into the head and the tail of the striatum. This topographical distribution is similar to the distribution of dopamine‐stimulated cyclic AMP. The pergolide response is more evenly distributed in the striatum. It is suggested that the difference in the topographical distribution of the ability of apomorphine and pergolide to elicit rotational behaviour reflects a regional distribution of dopamine receptors in the striatum of the rat.
Effect of explosive type strength training on isometric force‐ and relaxation‐time, electromyographic and muscle fibre characteristics of leg extensor muscles
Authors: HÄKKUKINEN K. , KOMI P. V. , ALÉN M.
Published: December 2008

.HÄKKUKINEN, K., KOMI, P.V. & ALÉN, M. 1985. Effect of explosive type strength training on isometric force‐ and relaxation‐time, electromyographic and muscle fibre characteristics of leg extensor muscles. Acta Physiol Scand 125, 587–600. Received 26 January 1985, accepted 9 May 1985. ISSN 0001–6772. Department of Biology of Physical Activity and Department of Health Sciences, University of Jyväskylä, Finland.

To investigate the influence of explosive type strength training on isometric force‐ and relaxation‐time and on electromyographic and muscle fibre characteristics of human skeletal muscle, 10 male subjects went through progressive training which included primarily jumping exercises without extra load and with light extra weights three times a week for 24 weeks. Specific training‐induced changes in force‐time curve were observed and demonstrated by great (P < 0.05–0.001) improvements in parameters of fast force production and by a minor (P< 0.05) increase in maximal force. The continuous increases in fast force production during the entire training were accompanied by and correlated with the increases (P < 0.05) in average IEMG‐time curve and with the increase (P < 0.05) in the FT:ST muscle fibre area ratio. The percentage of FT fibres of the muscle correlated (P < 0.05) with the improvement of average force‐time curve during the training. The increase in maximal force was accompanied by significant (P < 0.05) increases in maximum IEMGs of the trained muscles. However, the hypertrophic changes, as judged from the anthropometric and muscle fibre area data, were only slight during the training. It can be concluded that in training for fast force production considerable neural and selective muscular adaptations may occur to explain the improvement in performance, but that genetic factors may determine the ultimate potential of the trainability of this aspect of the neuromuscular performance.
Changes in renal sympathetic outflow during hypotensive haemorrhage in rats
Authors: SKOOG P. , MÅNSSON J. , THORÉN P.
Published: December 2008

SKOOG, P., MÅNSSON, J. & THORÉN, P. 1985. Changes in renal sympathetic outflow during hypotensive haemorrhage in rats.Acta Physiol Scand125, 655–660. Received 11 February 1985, accepted 13 June 1985. ISSN 0001–6772. Department of Physiology, University of Göteborg, Sweden.

The goal of this study was to investigate changes in renal sympathetic outflow during hypotensive haemorrhage. Normotensive Wistar‐Kyoto rats were anaesthetized with chloralose (50 mg kg‐1) and bled to an arterial blood pressure of 50 mmHg for 30 min. Changes in heart rate (HR) and renal nerve activity (RNA) were registered. The hypotensive haemorrhage induced a short‐lasting sympathetic excitation that was followed within 5–10 min by a powerful sympathetic inhibition and bradycardia. The average maximal decrease in sympathetic activity was 65% and the maximal decrease in heart rate was 45 beats min‐1. There was a close correlation between changes in heart rate and renal sympathetic activity.

The marked depressor response was due at least in part to activation of vagal afferents because the depressor responses were acutely reversed by bilateral cervical vagotomy.

As cardiac afferents are known to be activated by prostaglandins and bradykinins, and these agents are released by myocardial ischaemia, haemorrhage was repeated after use of indomethacin and aprotinin (a protein inhibitor decreasing bradykinin formation), and a marked sympathetic inhibition could still be elicited upon haemorrhage. We therefore suggest that the likely mechanism for activation of the vagal afferents is a squeezing of the myocardium when the heart has to contract around an almost empty chamber. In conclusion, this study demonstrated that hypotensive haemorrhage triggers profound inhibition of RNA in rats and that this sympathoinhibition is mediated primarily by mechanically sensitive cardiac vagal afferents.
Vasoconstrictor effect of high FFA/albumin ratios in adipose tissuein vivo
Authors: BÜLOW JENS , MADSEN JOOP , ASTRUP ARNE , CHRISTENSEN NIELS J.
Published: December 2008

BÜLOW, J., MADSEN, ASTRUP, A. & CHRISTENSEN, N.J. 1985. Vasoconstrictor effect of high FFA/albumin ratios in adipose tissuein vivo. Acta Physiol Scand125, 661–667. Received 7 December 1984, accepted 17 June 1985. ISSN 0001–6772. Department of Clinical Physiology/Nuclear Medicine, Institute of Medical Physiology C, Copenhagen, Department of Internal Medicine and Endocrinology, Herlev, Denmark.

Subcutaneous or perirenal adipose tissue blood flow was measured with the133Xe‐washout technique before and after intravenous injection or infusion of Intralipid* in six anesthetized, otherwise intact mongrel dogs. In four anesthetized mongrel puppies adipose tissue blood flow was measured with the radioactive microsphere method in seven different adipose tissue depots before a bolus injection of Intralipid and at the time after the injection when the thermogenic effect of the Intralipid was maximal. The results showed that the vascular resistance increased in all the examined adipose depots in adult as well as in young dogs after this treatment. The administration of Intralipid did notper seinduce the vasoconstriction. The vasoconstriction took place simultaneously with increasing FFA/albumin molar ratios. The results support our previous findings in perfused fat pads that high molar FFA/albumin ratios increase vascular resistance in adipose tissue and they give further support to our suggestion that this vasoconstriction may be a link in a negative‐feedback mechanism regulating FFA‐mobilization in relation to FFA utilization.
Distribution of ouabain‐binding sites along the dog nephron
Authors: SEJERSTED OLE M. , NICOLAYSEN ANNE , MONCLAIR TOM , NICOLAYSEN GUNNAR
Published: December 2008

SEJERSTED, O.M., NICOLAYSEN, A., MONCLAIR, T. & NICOLAYSEN, G, 1985. Distribution of ouabain‐binding sites along the dog nephron. Acta Physiol Scand 125, 699–710. Received 2 May 1985, accepted 9 July 1985. ISSN 0001–6772. Institute of Muscle Physiology; University of Oslo, Institute for Experimental Medical Research, Ullevaal Hospital and Institute of Physiology, Oslo, Norway.

To quantify the relative amount of ouabain bound to different segments of the nephron after in vivo injection of the drug, an autoradiographic (ARG) study was carried out. After intrarenal injection of [3H]ouabain (120 nmol kg‐1 body wt, 0.9–1.2 Ci mol‐1) to intact kidneys of three anaesthetized dogs, 69–89% of renal Na, K‐ ATPase activity was inhibited. Sodium reabsorption decreased by 21–54%. Sections for ARG were obtained from tissue slices frozen in liquid Freon, freeze‐dried and embedded in resin. Almost no loss of activity occurred during processing and background activity was negligible after 23–36 days' exposure. The density of [3H]ouabain grains per μ2 of tubular walls was 3.8 times higher over medullary ascending limbs of Henle's loop (MAL) and distal cortical tubules (DT) as compared to proximal tubules (PT). In terms of tubular length, the grain density of MAL exceeded that of PT by merely 35% since the cross‐sectional area of the MAL was only 25% of that of PT. In DT, grain density in terms of tubular length was lower than in PT by 10%. Based on previous estimate of the absolute ouabain‐binding capacity in MAL of 60 fmol mm‐1 tubule, the ouabain‐binding capacity in PT and DT would equal 45 and 40 fmol mm‐1, respectively. From composite microphotographs, the relative volume of PT was estimated to be 42% of the total renal volume. This means that 47% of the total renal ouabain‐binding sites are localized to PT, whereas MAL and DT together contain 51 %.
Regional distribution of α‐adrenoceptor subtypes in the female rabbit urethra
Authors: LARSSON BENGT , SJÖGREN CHRISTER , ANDERSSON KARL‐ERIK
Published: December 2008

The aim of the present investigation was to study the regional distribution of α‐adrenoceptor subtypes in the female rabbit bladder base and urethra, using radioligand binding and mechanical activity studies. The binding studies performed on membranes prepared from the bladder base, and the proximal and distal part of the urethra, revealed that the number of α1‐adrenoceptors did not significantly differ between the three regions, whereas the number of α2‐adrenoceptors increased distally. The mechanical activity studies showed that noradrenaline and clonidine, but not phenylephrine, were more potent in the distal than the proximal part of the urethra. It is suggested that in the female rabbit urethra the lower EC50‐value found for noradrenaline and clonidine in the distal as compared to the proximal part of the urethra, at least in part, is attributable to a higher number of postjunctional α2‐adrenoceptors in the distal than in the proximal urethra.
Carbonic anhydrase isoenzymes in the rat kidney. Effects of chronic acetazolamide treatment
Authors: LÖNNERHOLM GUDMAR , WISTRAND PER J. , BÁRÁNY ERNST
Published: December 2008

Biochemical, immunocytochemical and histochemical methods were used to study the effect of chronic acetazolamide treatment on carbonic anhydrase (CA) isoenzymes in the rat kidney. Male inbred rats (Lew/Mol) were treated with 15 mg kg‐1day‐1acetazolamide s.c. by Alzet® minipump during 2–9 weeks; some animals had a drug‐free period of 1–4 weeks before being killed. The renal content of CA II was higher in the acetazolamide‐treated rats than in the controls, 178 ±10 vs 144±4.8 μg enzyme protein g‐1tissue (mean ± SE). The distribution of CA isoenzymes did not change during or after chronic acetazolamide treatment. Thus, only CA II was detected in the kidney tubules by immunofluorescence using specific antisera against CA I, CA II and CA III. All animals showed a similar staining pattern, with intense cytoplasmic CA II staining in intercalated cells of collecting ducts, moderate staining in descending thin limbs of Henle, and weak cytoplasmic staining in proximal tubules and chief cells of collecting ducts. All animals also showed histochemical staining of cell membranes in proximal and distal tubules and thick limbs of Henle, suggesting the presence of a membrane‐bound isoenzyme (CA IV). The only difference noted by histochemistry and immunocytochemistry was that the intercalated cells appeared bulkier and protruded more markedly into the tubular lumen in treated than in untreated animals. The functional importance of this finding is unclear. The observed changes in CA cannot alone explain why the effect of acetazolamide, in causing loss of bicarbonate and sodium, is self‐limited on continued administration.
Changes in the probability of firing of motor units following electrical stimulation in human limb muscles
Authors: TARKKA I. M.
Published: December 2008

Changes in the probability of motor unit firing was studied in ten different muscles (six muscles in the upper extremity and four muscles in the lower extremity) of eleven healthy human subjects. The responses were elicited by the electrical stimulation of cutaneous or mixed nerves during weak voluntary contraction of the muscle studied, and were recorded by averaging the rectified surface electromyogram. In eight of the ten muscles, well‐detectable, short and long latency excitatory phases were observed. The most constant and well‐identified excitatory responses were observed in the first interosseus dorsalis muscle in the hand, and in the extensor digitorum brevis muscle in the foot. These two distal muscles seem to be the most useful muscles for routine determination of the short and long latency responses to cutaneous stimulation.
Chloride transport inhibition by various types of ‘loop’ diuretics in fish opercular epithelium
Authors: ERIKSSON ORJAN , WISTRAND PER J.
Published: December 2008

Isolated opercular epithelia of killitish (Fundulus heteroclitus), mounted in an Ussing chamber, were used to study the effects of various diuretics on chloride transport, measured as short‐circuit current (SCC). The acidic ‘loop’ diuretics, ethacrynic acid and azosemide, and the basic ‘loop’ diuretics, muzolimine and MK 447, reduced SCC and exhibited similar dose–effect curves, with EC50s for SCC of 64, 17, > 500 and 224 μm, respectively. The alkaline diuretic tizolemide (HOE 740) and thep‐COOH‐analogue of sulphanilamide were inactive, suggesting that the chloruretic effects of these agents are of a thiazide type. The method can thus discriminate between the effects of loop and thiazide types of diuretics, but not between those of structurally highly different ‘loop’ diuretics of an acidic and basic nature. Monomethylation of the S02NH, group of bumetanide had no effect on the activity of this agent whereas dimethylation reduced it fourfold. The (–)enantiomers of the ‘loop’ diuretics indacrinone and ozolinone were four and > 100 times more active, respectively, than the (+)forms. These results are in accordance with those obtained for the same drugs in the mammalian kidney, and point to the presence of a highly specific binding site for these diuretics. Attempts were also made to explore the prerequisites for binding of the loop diuretic to the active site. Pretreatment of the opercular epithelium with an alpha‐L‐fucose‐binding lectin did not prevent the inhibitory actions of furosemide and indacrinone. Probenecid and (+)ozolinone, both of which block organic anion transport, did not prevent the effects of bumetanide and (–)ozolinone.
Reduced platelet MAO activity during pregnancy
Authors: WAHLUND L.‐O. , SÄÄF J. , ENEROTH‐GRIMFORS E. , NILSSON B. A. , BEVEGÅRD S.
Published: December 2008

The kinetics and thermolability of platelet MAO were studied in twenty‐three women during and after pregnancy. The maximal velocity of the enzyme (Vmax) was significantly reduced during pregnancy, whereas the apparent, Michaelis constant (Km) was unaltered. The initial velocity of the enzyme (v0) was significantly lowered during the pregnant period compared to after delivery. However, when the enzyme activity was determined in the presence of autologous plasma, no significant difference in deaminating activity between the two occasions could be detected. This was caused by a significantly increased activating capacity of the plasma collected during the pregnant period, expressed as the ratio of MAO activity determined in the presence and absence of plasma. Moreover, pregnant women showed an increased thermal stability of the platelet MAO compared to non‐pregnant women.
The effect of calcium‐blockers nicardipine, darodipine, PN‐200‐110 and nifedipine on insulin release from isolated rat pancreatic islets
Authors: AL‐MAHMOOD HUSSAIN A. , EL‐KHATIM MOHAMMED S. , GUMAA KHALID A. , THULESIUS OLAV
Published: December 2008

The effect of the calcium‐blockers nicardipine, darodipine, PN‐200‐no on insulin release from pancreatic islets was studied using nifedipine as a reference compound. All drugs at a concentration of 10‐6M significantly inhibited insulin release in response to both low (5.5 HIM) AND high (22 mM) glucose. The present observations support previous reports that calcium blockers of the dihydropyridine series are effective inhibitors of glucose‐induced insulin release.
Effects of naloxone on dental pain threshold following muscle exercise and low frequency transcutaneous nerve stimulation: a comparative study in man
Authors: OLAUSSON B. , ERIKSSON E. , ELLMARKER L. , RYDENHAG B. , SHYU B.‐C. , ANDERSSON S. A.
Published: December 2008

Previous studies have shown that muscle exercise and low frequency transcutaneous nerve stimulation (TNS) give rise to an analgesic effect in humans and animals. Endorphin has been proposed to mediate this analgesia. In this investigation, the effect of muscle exercise and low frequency TNS, on dental pain thresholds was studied and the possible involvement of endorphinergic mechanisms was investigated using naloxone as an antagonist. Dental pain thresholds were measured in 11 volunteers following leg or arm exercise and after low frequency TNS of the hands or face. After exercise (20 min) or stimulation (30 min) either 0.8 mg naloxone (2 ml) or saline (2 ml) was injected i.v. in a double‐blind fashion. Pain thresholds were measured repetitively before and after exercise or stimulation. Both leg and arm exercise increased pain threshold. Stimulation of the hands also increased pain threshold, but less than arm exercise. A marked increase in pain threshold was seen after face stimulation. These changes in pain threshold were unaffected following injections of either naloxone or saline, except for an early and short‐lasting reduction when naloxone was injected following arm exercise. The increases in pain threshold following muscle exercise and after low frequency TNS, showed similarities suggesting that a common mechanism might be involved. The pain threshold increase after arm exercise could only be partially mediated by endorphinergic mechanisms.
Ionic transport in individual renal epithelial cells from adult and young rats
Authors: LARSSON L. , APERIA A. , LECHENE C.
Published: December 2008

Renal epithelial cells were isolated from the outermost superficial cortex of adult and young rats. The cells, likely of proximal origin, were plated on silicon pieces, and cultured during 1–3 days. Intracellular content and concentrations of K, Na, CI, and P, and the kinetics of change in intracellular content, after inhibition of Na‐K ATPase by incubation with ouabain or in K‐free medium, were measured in individual cells in small populations using electron probe analysis. In control medium, concentrations in mM were approximately: K, 130; Na, 15; CI, 28; P, 140. After 6 h inhibition of Na‐K ATPase, cells exchanged all K for Na, and the intracellular Na concentration increased to 139 mM in K‐free medium. The CI concentration increased at most to 46 mM. The sum of intracellular K + Na + CI did not increase more than 25 % after 24 h incubation in K‐free medium. There were no differences in intracellular K, Na, and CI for adult and young rat cells in similar conditions. The half‐times of K efflux and Na influx after inhibition of Na‐K ATPase measured in adult rat were approximately 16–20 min. In the absence of serum, in K‐free medium, the half‐times of K efflux and Na influx in young rat cells were approximately 30 min, significantly higher than the half‐time in the presence of serum, and with ouabain, being approximately 13 min. Histograms of distributions of K and Na content showed that the cells behaved as a single functional population. Ouabain Kj was estimated to be 10‐4 M. After 24 h preincubation in K‐free medium, when returned in 5 mM K‐containing medium, adult rat cells recovered rapidly normal intracellular K and Na concentrations. Using this approach, expression of the kinetics ionic transport properties of renal epithelial cells during development, and the hormonal influences on terminal differentiation may be studied.
Testicular microcirculation in the rat studied by videophotometric capillaroscopy, fluorescence microscopy and laser Doppler flowmetry
Authors: DAMBER JAN‐ERIK , BERGH ANDERS , FAGRELL BENGT , LINDAHL OLOF , ROOTH PÅL
Published: December 2008

Testicular capillary blood flow was studied in rats using laser Doppler flowmetry, in vivo fluorescence microscopy and videophotometric capillaroscopy. All the methods revealed rhythmical oscillations in testicular microcirculation with a periodicity of 4–10 c.p.m. In arterioles, capillaries and small post‐capillary vessels, periods of continuous blood flow alternated with periods of no or very low flow. No visible leakage of dextran‐150 was observed from the testicular blood vessels. Four, 8 and 16 h after an s.c. injection of 200 IU hCG the blood flow was continuous and there was leakage of dextran‐150 from the microvessels to the interstitial tissue. Twenty‐four and 32 h after hCG the blood flow pattern was again rhythmical, and at 32 h there was no leakage of dextran‐150. This suggests that hCG induces changes in blood flow and transvascular fluid exchange in the testis, perhaps by altering smooth muscle activity at the arteriolar‐level.
Milk‐feeding maintains the prochymosin production in cells of bovine abomasal mucosa
Authors: ANDRÉN ANDERS , BJÖRCK LENNART
Published: December 2008

The effect of milk‐feeding on the development of prochymosin‐producing cells in bovine abomasal mucosa was studied using immunochemical methods. As long as the calf was fed milk both mucous neck, and chief cells in the gastric glands, were immunoreactive for prochymosin, the precursor form of a specific milk‐clotting enzyme. After weaning, the prochymosin immunoreactivity in chief cells in the lower base of the gastric gland declined and finally disappeared. Mucous neck cells and chief cells in the upper base of the gland, however, continued to be immunoreactive for prochymosin. All these cell types contained pepsinogen immunoreactivity both before and after weaning. Exposure to milk components thus seem to be of importance for the production of prochymosin in the abomasal mucosa. The present findings suggest that dietary components influence the cell differentiation in the gastrointestinal mucosa.
Effects of alpha‐adrenoceptor agonists and antagonists on duodenal surface epithelial HCO3‐secretion in the ratin vivo
Authors: NYLANDER O. , FLEMSTRÖM G.
Published: December 2008

In anesthetized rats a 12 mm segment of duodenum, distal to the Brunner's gland area and devoid of pancreatic and bile secretions, was cannulatedin situ.Secretion of HCO3‐by the surface epithelium was measured by continuous titration at luminal pH 7.40. Noradrenaline at doses of 25–200 μg kg‐1h‐1had no (net) effect on duodenal HCO3‐secretion while the non‐selective α‐adrenoceptor antagonist phentolamine (20–1000 μg kg‐1intravenously) dose‐dependently increased secretion. The phentolamine‐induced rise in alkaline secretion was partially inhibited by noradrenaline but this effect was transient and was followed by an increase in secretion in spite of continuous infusion of noradrenaline. The α1,‐adrenoceptor agonist, phenylephrine (100 and 500 μg kg‐1h‐1) stimulated HCO3‐secretion in a dose‐dependent manner and this response was abolished by the α1‐adrenoceptor antagonist prazosin (0.5 mg kg‐1) while the β‐adrenoceptor antagonist propranolol (1 mg kg‐1) was without effect. Basal secretion, as well as secretion stimulated by phentolamine and/or phenylephrine, was inhibited by the α2‐adrenoceptor agonist clonidine (0.75‐15.0 μg kg‐1). The results thus strongly suggest that a,‐adrenoceptor stimulation increases while α2‐adrenoceptor stimulation decreases duodenal surface epithelial HCO3‐‐secretion. This might explain the absence of a net effect of noradrenaline.
Serotonin receptor involvement in the avoidance learning deficit caused byp‐chloroamphetamine‐induced serotonin release
Authors: ÖGREN SVEN OVE
Published: December 2008

The receptor involvement in thep‐chloroamphetamine (PCA, 2.5 mg kg‐1) induced impairment of active avoidance acquisition was examined in the male rat. The avoidance deficit was blocked at low doses by serotonergic (5‐HT)‐receptor blocking agents but not by α‐adrenergic‐, β‐adrenergic‐, opiate‐, muscarinic‐ or dopamine D2‐receptor antagonists. The potency of the 5‐HT antagonists to block the PCA‐ induced deficit correlated with their affinity in displacing [3H]ketanserin but not [3H]5‐HT binding in the frontal cortex. The potencies of the 5‐HT antagonists to block the action of PCA could not be related to their action on muscarinic‐, histaminergic H1‐ or dopaminergic D2‐receptor bindingin vitro.It is concluded that the avoidance learning deficit caused by PCA‐induced 5‐HT release is related to activation of 5‐HT receptors in the frontal cortex having the characteristics of a 5‐HT2receptor.
Flow distribution between the endocrine and exocrine parts of the isolated rat pancreas during perfusion in vitro with different glucose concentrations
Authors: JANSSON L.
Published: December 2008

Previous studies in our laboratory have indicated that pancreatic islet blood flow is stimulated by glucose. In an attempt to evaluate to what extent intrapancreatic control mechanisms are involved in the glucose modulation of islet blood flow the distribution of flow between the endocrine and exocrine parts of the rat pancreas during perfusion in vitro with different glucose concentrations have now been studied. For this purpose pancreatic glands from 29 rats were perfused at a flow rate of 1.5 ml min‐1 for 95 min with low (2.8 mm) or high (16.7 mm) glucose‐containing media. Maintenance of vascular reactivity of this preparation in spite of a marked exocrine oedema was confirmed by administration to the perfusion medium of adrenaline, which immediately raised the perfusion pressure. Insulin concentrations in the effluent media were measured to correlate rates of insulin release to changes in islet flow and to assess the functional viability of the preparation. In each experiment non‐radioactive microspheres with a diameter of 10 μ were injected into the perfusion medium at one of four time‐points: 15, 30, 35 or 80 min after the beginning of the perfusion. Two of these injections (15 and 80 min) took place during perfusion with the low‐glucose media and the remaining two during perfusion with high‐glucose medium. The microspheres were counted separately in the endocrine and exocrine parts of the pancreas. The results showed that all preparations had a biphasic insulin response to glucose. The distribution of microspheres within the pancreas was found to be homogeneous with approximately 6% of the injected spheres present in the islets irrespective of the glucose concentration in the perfusion medium at the time of the microsphere injection. This corresponds to an islet perfusion of about 90 μ1 min‐1 which is similar to our previous findings in vivo. Moreover, the lack of effect of glucose on the distribution of flow between the endocrine and exocrine parts supports the view that extrapancreatic, rather than local, factors are involved in the regulation of islet blood flow after glucose administration.
Continuous monitoring of potassium efflux from rat parotid gland fragments by potassium selective electrodes
Authors: DUNÉR‐ENGSTRÖM M. , LARSSON O. , FREDHOLM B. B.
Published: December 2008

The concentration of potassium ions in a superfusate of rat parotid gland fragment was continuously monitored by potassium selective electrodes to assess the rate of potassium secretion by the gland. The potassium concentration determined from the electrode readings agreed well with values obtained by atomic absorption (r = 0.99). The detection limit for changes in potassium concentration was approximated to 50 μ K+. When medium was recirculated over the gland fragments it was possible to detect even small changes in the rate of potassium efflux. Thus, increases in potassium secretion following administration of substance P (SP) down to 0.1 nM and carbacholine 10 nM was registered. When the buffer medium was passed only once over the gland fragments it was possible to reproducibly study the time course of potassium secretion. However, with this system higher doses of secretagogues were required for detection of potassium efflux, since the potassium secernated was diluted by the perifused buffer. Following SP (0.01 or 0.1 μ) or carbacholine (1 or 10 μ) a peak of potassium secretion was registered during the first 8–10 min, which was followed by a steady low rate. The metabolic state of the gland fragments, as determined by the ratio of adenine nucleotides, was similar to that foundin vivoeven after an experiment of several hours' duration. However, the viable part of the glandular tissue, calculated as the content of adenine nucleotides per mg protein, was decreased to approximately 30% compared to the intact glandin situ.The present results indicate that the potassium efflux from parotid gland fragments may be continuously monitored by means of potassium electrodes placed in contact with buffer that is superfused over the glandular tissue.
Renal handling and effects of [3H]digoxin and interactions with quinidine in the avian kidney
Authors: MILTON A. , ODLIND B. , DENCKER L.
Published: December 2008

Renal handling and effects of tritium digoxin and interactions with quinidine in the avian kidney were studied using a modified Sperber technique. Results showed that tritium digoxin was extracted at the peritubular side of the nephron in a process competitively inhibited by increasing amounts of unlabelled digoxin. Light microscope autoradiography showed distinct concentrations of silver grains only over distal tubules in the injected kidney. Inhibition of the proximal tubular transport systems for organic anions and cations, respectively, did not change extraction. Addition of quinidine to the injection solution up to an estimated concentration of 1.4 10‐5M in systemic blood significantly lowered 1 min peritubular extraction of tritium digoxin. However, when the amount of quinidine was further increased, extraction of tritium digoxin augmented significantly. Tritium recovery in urine after renal portal bolus injection of tritiated and unlabelled digoxin already showed a distinct ipsilateral peak 2 min after injection with an equally distinct peak of ipsilateral sodium excretion appearing 1 min later. When quinidine was added to the bolus ipsilateral tritium recovery in urine (0–7 min) was halved, with the true tubular excretion fraction (TTEF) lowered by two‐thirds, but without changes in the magnitude of ipsilateral natriuresis. Contralateral natriuresis increased more than four‐fold with quinidine in the bolus in spite of unchanged tritium recovery in the urine. Thus, our results show tritium digoxin to be extracted from peritubular blood through a specific process probably localized to the distal nephron of the avian kidney. High levels of quinidine augments peritubular extraction of tritium digoxin, lowers tritium excretion into urine and prolongs the pharmacologic action of digoxin on the Na+/K+ATPase.
Trifluoperazine stimulated sodium transport by increased prostaglandin E2synthesis in isolated frog skin (Rana esculenta)
Authors: BJERREGAARD H. F. , NIELSEN R.
Published: December 2008

Addition of trifluoperazine (TFP)* to the inside bathing solution of the isolated frog skin resulted in a biphasic increase in the short‐circuit current (SCC). The Na+‐flux measurements showed that the TFP‐induced increase of SCC was accounted for by active sodium transport. The intracellular voltage in short circuited skins changed after addition of TFP (100 μM) from a control value of –80.9 ± 0.8 to – 66.2 ± 1.0 mV (n= 8). This depolarization indicates that TFP acts by increasing the Na+‐permeability of the apical membrane. The biphasic increase in SCC is due to different mechanisms. The primary activation could be abolished by the calcium ionophore A23187, whereas the secondary activation could be abolished by the prostaglandin synthesis inhibitor indomethacin, PGE2or A23187. Stimulation of the SCC by TFP and theophylline or antidiuretic hormone (AVT) was additive. Furthermore, TFP did not increase the cAMP level of isolated epithelia or theophylline‐stimulated epithelia. These results indicate that the TFP‐induced change in the Na+‐permeability was not due to an enhanced cAMP level. The TFP simulated SCC requires Ca2+in the inside bathing solution. Addition of TFP resulted in an increase in prostaglandin E2release to the inside bathing solution from a control value of 0.31 ± 0.04 to 5.4 ± 1.4 pmol PGE2h‐1cm‐2(n= 8). It is suggested that TFP induces a Ca2+‐dependent PGE2synthesis, leading to an increase in the intracellular PGE2concentration which might increase the Na+‐permeability of the apical membrane.
Bradykinin‐induced atropine‐sensitive gastric contractions. Activation of an intramural axon reflex?
Authors: DELBRO D. , LISANDER B. , ANDERSSON S. A.
Published: December 2008

Gastric motor responses, recorded as volume changes of an intragastric balloon, were induced by the close i.a. administration of bradykinin (0.75‐4 μg) in chloralose‐anaesthetized cats. The animals were vagotomized and the adrenals were ligated at the outset of the experiments. Prior to autonomic blocking agents bradykinin elicited relaxatory or biphasic motor responses. Following nicotinic ganglionic receptor blockade bradykinin caused predominantly gastriccontractions.Such excitatory responses were antagonized by 80–100% by atropine, suggesting a dominant neurogenic component. An hypothesis is put forward that the observed gastric contractions result from a bradykinin‐induced activation of anaxon reflex arrangementconfined to thin sensory nerve fibres which, by substance P release from intramural collaterals, excite postganglionic cholinergic motor neurones.
Comparison of PGE2, 6‐keto PGF1αand renin release from dog kidneys
Authors: BUGGE J. F. , VIKSE A. , DAHL E. , SLØRDAHL S. H. , KIIL F.
Published: December 2008

Several renal cell types synthesize prostaglandin E2(PGE2) and prostacyclin (PGI2). To examine whether the release of these prostaglandins varies in proportion, prostaglandin synthesis was stimulated in anaesthetized dogs by renal arterial constriction, ureteral occlusion, intrarenal angiotensin II infusion and infusion of arachidonic acid, the precursor of PG synthesis. PGI2was measured as its stable hydrolysed product, 6‐keto PGF1α. The two former procedures raised PGE2release to 13 ± 2 pmol min‐1, 6‐keto PGF1αrelease to 5 ± 2 pmol min‐1and renin release to 23 ± 5 μg AI min‐1, Angiotensin II infusion, reducing the renal blood flow by 30%, increased PGE2and 6‐keto PGF1αrelease only half as much as ureteral and renal arterial constriction, and exerted no significant effect on renin release. By increasing the infusion rate of angiotensin II up to 10 times, the renal blood flow remained unaltered in four dogs and fell to 50% of control in two dogs, but PGE2and 6‐keto PGF1αrelease did not increase further in any of the experiments. Arachidonic acid, infused at 40 and 160 μg kg‐1min‐1, increased prostaglandin release in proportion to the infusion rate. At the highest infusion rate, PGE2release averaged 166± 37 pmol min‐1and 6‐keto PGF1αrelease 98 ± 28 pmol min‐1. All procedures increased PGE2and 6‐keto PGF1αrelease in a fixed proportion of about 2.5:1, whereas renin release increased only during autoregulatory vasodilation.