bluuebunny/crossref_metadata_2025 huggingface dataset:
Preparation of cells from pig gastric mucosa
Authors: MÅRDH SVEN , NORBERG LAGE , LJUNGSTRÖM MAGNUS , HUMBLE LENA , BORG THOMAS , CARLSSON CHARLOTTE
Published: December 2008

Cells were isolated from pig gastric mucosa by a combination of mechanical and enzymatic treatment. Isopycnic centrifugation on linear density gradients of Percoll provided a simple and rapid procedure for obtaining highly enriched parietal cells and chief cells. Their densities were 1.06 and 1.10 g/ml, respectively. Isolated mucosal cells attached to Petri dishes coated with fibronectin or collagen. Both parietal cells and chief cells adhered more readily to fibronectin than collagen. Mucosal cells and cells from the Percoll gradients were maintained for up to one week as primary cell cultures. The ability of free parietal cells to produce acid was tested by the14C‐aminopyrine accumulation technique. Maximal accumulation was 2.5 pmol aminopyrine per 104parietal cells after incubation for 45 min at 10‐4M histamine. The EC50for histamine was 5times10‐6M.The accumulation of aminopyrine at 10‐6M carbachol and 10‐7M pentagastrin were for both secretagogues about 0.9 pmol per 104parietal cells.
The effect of a converting enzyme inhibitor on autoregulation and intrarenal distribution of glomerular filtration in the rat
Authors: GÖRANSSON ANN , SJÖQUIST MATS
Published: December 2008

The role of the renin‐angiotensin system in the autoregulation and distribution of the single nephron glomerular filtration rate (SNGFR) in anaesthetized, normotensive rats was investigated. SNGFR in outer cortical (OC) and inner cortical (IC) nephrons of the left kidney were measured with a modified Hanssen technique at three levels of renal arterial pressure (RAP): (1) at a spontaneous arterial pressure; (2) at a value within the autoregulatory limit, 100 mmHg; and (3) at the lower limit of the autoregulatory range, 70 mmHg. This was done in control rats and in rats given a continuous i.v. infusion of the converting enzyme inhibitor (CEI) captopril (3 mg · h‐1· kg‐1BW). In control rats there was complete autoregulation of SNGFR in both OC and IC nephrons when RAP was reduced to 100 mmHg. Further reduction to 70 mmHg elicited different responses among the cortical layers, associated with a decrease in SNGFR. A fractional redistribution of glomerular filtration rate towards IC nephrons was evident. Administration of CEI at spontaneous RAP increased SNGFR in IC nephrons compared with values in control rats, but did not notably alter SNGFR in OC nephrons. Reduction of RAP to 100 mmHg during CEI infusion caused SNGFR to decrease below control values in both OC and IC nephrons, and the autoregulation as found in control rats was impaired. When RAP was lowered to 70 mmHg during CEI administration there was a progressive decrease in SNGFR in all cortical layers, although absolute changes were much greater in IC nephrons than in OC nephrons. This resulted in a fractional redistribution of SNGFR towards OC nephrons, opposite to that seen in control rats when the pressure was reduced. These results show that the autoregulation and distribution of SNGFR are dependent on the renin‐angiotensin system and that IC nephrons are more affected by inhibition of converting enzyme than OC nephrons.
Effects of Ca2+ on force‐velocity characteristics of normal and hypertrophic smooth muscle of the rat portal vein
Authors: ARNER ANDERS , MALMQVIST ULF , UVELIUS BENGT
Published: December 2008

Portal hypertension was induced in rats by partial ligation of the hepatic branches of the portal vein. After 5 days of hypertension the portal veins were taken out and mounted for isometric and quick‐release experiments. Portal veins from sham‐operated normal rats served as controls. The ligated veins had an increased cross‐sectional area, indicating smooth‐muscle hypertrophy. Although the absolute magnitude of active force of these veins was increased, the active force per cross‐sectional area was decreased, indicating an alteration in the properties of the contractile system. No difference in the Ca2+ concentration‐response relations to K+‐activated intact control and hypertrophic veins was found. In chemically skinned preparations, devoid of functional plasma membranes, the hypertrophic veins had similar Ca2+ sensitivity (in the presence of 1 μM calmodulin) but a lower force per cross‐sectional area. Force‐velocity relations were determined in K+‐activated intact preparations. In control veins a reduction in extracellular Ca2+ was associated with a significant reduction in both isometric force and maximal shortening velocity (V max). In hypertrophic veins the decreased isometric force at maximal activation was associated with a low V max. A comparison between hypertrophic and submaximally stimulated control vessels showed corresponding V max and isometric force values. We conclude that the low isometric force of hypertrophic veins is associated with a lower rate of cross‐bridge turnover. This could be an effect of alterations in the activation mechanisms or in the intrinsic properties of the contractile system itself.
Early effects of denervation on isometric and isotonic contractile properties of rat skeletal muscles
Authors: GUNDERSEN KRISTIAN
Published: December 2008

The contractile properties of the fast‐twitch m. extensor digitorum longus (EDL) and the slow‐twitch m. soleus were examined after 5 days of denervation. An increase in twitch time to peak, twitch half relaxation time and twitch/tetanus ratio was observed. The EDL also showed a moderate decrease in maximal isotonic shortening velocity, which is taken as an indication that the contractile proteins are affected. A fatigue test showed that the EDL became less fatigable and the soleus less fatigue resistant after denervation.
Some effects of the calcium promotor BAY K 8644 on feline cerebral arteries
Authors: USKI TORE K. , ANDERSSON KARL‐ERIK
Published: December 2008

The proposed calcium promotor BAY K 8644 contracted feline basilar arteries partially depolarized by iommol‐1‐1 potassium in a concentration‐dependent manner (EC50 value: (2.1 ± 1.2) × 10‐9 mol l‐1). The concentration‐response curve for prostaglandin (PG) F2α was displaced to the left after pretreatment with BAY K 8644. PGF2α induced a biphasic contraction in calcium‐free medium as has been described previously. The second PGF2α‐induced contraction phase in calcium‐free medium was abolished by pretreatment with nifedipine or diltiazem. BAY K 8644 restored the second phase in arteries pretreated with nifedipine, but not in vessels pretreated with diltiazem. The findings suggest that BAY K 8644 acts as a promotor of calcium‐influx, probably by interaction with the ‘dihydropyridine receptor’ in the cell membrane, and also provide support for the view that PGF2α releases membrane‐bound calcium.
Free and forced diving in ducks: habituation of the initial dive response
Authors: GABRIELSEN G. W.
Published: December 2008

Response habituation in pekin ducks was observed during a study of the early phase of the dive response. This is interpreted as the orienting response and strongly suggests higher CNS influence in the initial phase of the forced immersion heart rate response. Repeated forced dives (20–30 s) of restrained ducks were performed with 40 s recovery period between dives. During the first dives, the ducks' heart rates fell 69% (272 ± 8 to 83 ± 32 beatsmin‐1, x̄± SE) of pre‐dive values. The extent of this bradycardia decreased progressively as the dives were repeated. After 60 dives, the heart rates dropped by only 29% (248 ± 3 to 177 ± 25 beats min‐1 for pre‐dive value). Voluntary diving of the ducks, lasting 5–20 s, caused no diving bradycardia. They showed breathing tachycardia which caused a 25% increase in heart rates above diving level (160 ± 5 to 200 ± 12 beats min‐1).
Functional β1‐ and β2‐adrenoceptors in the human myocardium
Authors: ASK J. A. , STENE‐LARSEN G. , HELLE K. B. , RESCH F.
Published: December 2008

Functional β‐adrenoceptor populations in the human heart were studiedin vitroin electrically‐paced strips of the right auricular and ventricular myocardium. The relative potency of selected agonists in producing inotropic responses (Tmax,T′max) in the presence of blockers for neuronal and extraneuronal uptakes was found to be as follows: isoprenaline > noradrenaline = adrenaline = salbutamol > dobutamine. Prenalterol had a negative inotropic effect in these preparations. The selective β1‐(practoloI) and β2‐(H 35/25) blockers reduced inotropic responses to adrenaline (Tmax,T′max) and noradrenaline (T′max) in the auricular strips. These results indicate the participation of β2‐adrenoceptors in inotropic responses in the human auricular and ventricular myocardium. For comparison, inotropic responses of electrically‐paced rat myocardium to β‐adrenergic agonists in the presence of blockers for neuronal and extraneuronal uptakes were likewise studied. The relative potencies forTmaxwere: noradrenaline = adrenaline > prenalterol > dobutamine = salbutamol. Given the high relative potency of salbutamol in the human myocardial strips (analogous to that previous shown in the β2‐dominated atria of the frog and trout) and the low relative potency of salbutamol in the rat tissue, these findings indicate a greater population of functionally active β2‐adrenoceptors in the human than in the rat myocardium.
A comparison of two methods to measure the recovery of nerve fibre excitability
Authors: BORG J. , TEGNER R.
Published: December 2008

A methodological study was performed on single myelinated dorsal root fibres of rats. The recovery of excitability following a conditioning electrical stimulus delivered through the same electrode as the test stimulus and following a conditioning propagated nerve impulse were compared. Using low test stimulus strength, the recovery time permitting a propagated test impulse was 2.31 ± 0.72 ms (mean ± SD) after a conditioning electrical stimulus and 1.96 ± 0.78 ms after a conditioning propagated impulse (P < 0.001). The difference and its significance for clinical refractory period measurements are discussed.
Characterization of pre‐ and post‐junctional adenosine receptors in guinea‐pig ileum
Authors: GUSTAFSSON LARS E. , WIKLUND N. PETER , LUNDIN JAN , HEDQVIST PER
Published: December 2008

The receptors involved in adenosine‐induced modulation of cholinergic neuroeffector transmission in guinea‐pig ileum were explored by means of the non‐selective stable analogue, 2‐chloroadenosine and analogues with preference for A, receptors, L‐N6‐phenylisopropyladenosine (L‐PIA), AND A2 receptors, 5′‐N‐ethylcarboxamideadenosine (NECA) and D‐N6‐phenylisopropyladenosine (D‐PIA). 2‐chloroadenosine, L‐PIA AND NECA were equipotent in inhibiting contractile responses to nerve stimulation, whereas D‐PIA exerted a similar activity only in high concentrations. The release of acetylcholine induced by nerve stimulation was inhibited to a similar degree by NECA, L‐PIA AND D‐PIA. The phosphodiesterase inhibitor, ZK 62.711, and the activator of adenylate cyclase, forskolin, enhanced the inhibitory effect of NECA, but not that of L‐PIA, on contractile responses to nerve stimulation. Only NECA inhibited contractions induced by direct muscle stimulation and ZK 62.711 enhanced this inhibition. It is concluded that adenosine inhibits the neuroeffector transmission in guinea‐pig ileum mainly by a prejunctional, cAMP‐independent, mechanism, involving A, receptors and a supplementary activation of post‐junctional A2 receptors. In addition there may be a prejunctional inhibitory effect of high agonist concentrations, exerted via A2 receptors and influenced by the prevailing levels of cAMP.
Some aspects of thermoregulation in newborn reindeer calves (Rangifer tarandus tarandus)
Authors: MARKUSSEN K. A. , ROGNMO A. , BLIX A. S.
Published: December 2008

At birth reindeer calves often are exposed to sub‐zero ambient temperatures (Ta) sometimes even combined with wind and precipitation. The resting metabolism was measured in three different age groups (1, 7 and 14 days old) at Ta's of –20, –5, 10 and 20oC. Resting metabolism in the thermoneutral zone decreased from 5.1 W‐kg‐1 at day 1 and 7 to 4.8 W‐kg‐1 at day 14. At day 1 apparent lower critical temperature (TIc) was 11oC, while at day 7 it was 7.7oC and at day 14 73oC, but total body conductance continued to decrease below apparent TIc. At Ta of – 5 and – 20oC total body conductance was: 0.77 and 0.72 W‐oC‐1 at day 1, 0.98 and 0.92 WoC‐1 at day 7, r.08 and 0.91 WoC‐1 at day 14, respectively. Thermal conductance of pelt samples from the trunk was determined in vitro at different combinations of windspeed, Ta and wetness. The conductance of dry fur increased from 5.9 to 11.8 W‐m‐2‐oC‐1 at a windspeed of o and 10 m s‐1, respectively, as compared to 28.7 Wm‐2oC‐1 when wetted without wind. Newborn reindeer calves seem to be heavily dependant on non‐shivering thermogenesis in brown adipose tissue for their cold defence since deep body temperature in a calf subjected to propranolol infusion when exposed to a Ta of – 25oC in combination with a 10 m s‐1 windspeed increased its cooling rate five times.
Renal tubular accumulation of organic substances: a new in vivo method which differentiates between luminal and peritubular uptake
Authors: MILTON A. , ODLIND B.
Published: December 2008

Using a modification of the Sperber technique we studied cellular uptake of organic substances in the kidney. A test substance was mixed with an extracellular marker (ethylenediaminetetraacetate or inulin), both radiolabelled with an activity ratio close to 1, and injected into the renal portal system on one side via a leg vein. The animals were killed 1–10 min after injection and the radioactivity in different organs determined. Results showed significantly higher ipsilateral (injection) to contralateral (control) kidney ratios (substance to marker) at 1 min after injection for125I‐Na‐o‐iodohippurate (125I‐Hipp;P< 0.001),14C‐tetraethylammonium bromide (14C‐TEA;P< 0.001),3H‐dihydromorphine (3H‐DHM;P< 0.01), and125I‐iothalamate (P< 0.01), with a progressive decrease in injection kidney ratios for125I‐Hipp and14C‐TEA when death occurred after a longer period. Inhibition of renal tubular transport with novobiocin or mepiperphenidol markedly reduced 1‐ and 4‐min injection kidney ratios for125I‐Hipp and14C‐TEA, respectively. When death occurred after a longer period, ratios in both kidneys increased significantly for125I‐iothalamate. A good correlation was found between peak cellular accumulation in the kidney and excretion efficiency of test substances. Thus, the results indicate (1) that125I‐Hipp,125I‐iothalamate,14C‐TEA, and3H‐DHM were accumulated from the peritubular side of the nephron through the transport systems for organic acids and bases, respectively, and (2) that125I‐iothalamate also showed luminal uptake. In conclusion, this newin vivotechnique is simple and well suited for studying renal tubular accumulation of organic substances and offers the advantage of being able to distinguish luminal from peritubular uptake.
The effect of crown ethers on ionic currents in myelinated nerve fibres from Xenopus laevis
Authors: KRISTBJARNARSON H. , ÅRHEM P.
Published: December 2008

The effect of several crown ethers on the currents at the node of Ranvier was studied. At differing potencies they caused a time‐ and potential‐dependent inactivation of potassium permeability and a time‐ and potential‐independent decrease in sodium permeability. The relative effect on potassium and sodium systems varied and was not directly related to their ionophoric properties. A computer analysis indicated that the induced inactivation was dependent on the normal potassium activation mechanism.
Hypoxic pulmonary vasoconstriction in isolated rat lungs perfused with perfluorocarbon emulsion
Authors: LINDGREN L. , MARSHALL CAROL , MARSHALL B. E.
Published: December 2008

Eight rat lungs were perfused in an in vitro circuit with a blood‐PS solution and then with a perfluorocarbon emulsion (perfluorotributylamine, FC‐43). With perfusion flow constant, the hypoxic pulmonary vasoconstrictor (HPV) response was measured as changes in pulmonary artery pressure when F1 o2 was changed to 0.1, 0.06, 0.04, 0.03, 0.02 and zero with Fl co2 of 0.05. The hypoxic response to an F1 o2 of 0.03, with the blood‐PSS perfusate, was an increase from baseline pressure of 93.5 ± 18% and, with the perfluorocarbon perfusate was 67.5 ±18%; these values were not significantly different (P± 0.2). A stimulus‐response relationship was obtained with the FC‐43 perfusate by plotting the response as a percentage of the maximum response (R%max) against the logarithm of the alveolar oxygen tension. The equation for the linear portion of the response was R%max= 257.9‐140.2 X log (10) PA, o2 and r = 0.78. The PA o2 corresponding to half of the maximum response (ED50) was 30.4 mmHg. The present study demonstrated that HPV is maintained in isolated rat lungs perfused with an FC‐43 emulsion. The stimulus‐response relationship as well as the ED50 with the FC‐43 is similar to earlier results with blood perfusate. Lung oedema was not found after perfusion with the FC‐43 emulsion.
Rates of synthesis of prealbumin and retinol‐binding protein during acute inflammation in the rat
Authors: FELDING PETER , FEX GÖRAN
Published: December 2008

The rates of synthesis of prealbumin (PA), retinol‐binding protein (RBP), and other plasma proteins were measured in primary monolayer cultures of rat hepatocytes isolated from normal rats and from rats 18 h after induction of an inflammatory reaction by subcutaneous injection of croton oil. The inflammatory pattern of protein synthesis seemed to persist in the isolated hepatocytes for 1–2 days. This pattern included significantly decreased rates of synthesis of PA. The rate of synthesis of RBP was probably also decreased, but significantly less than the rate of PA synthesis. The results support the idea that it is mainly the decreased rate of PA synthesis which is responsible for the decreased plasma concentration of PA, and its ligands RBP and retinol during inflammation.
Renal polyamine metabolism in rats with renovascular hypertension
Authors: UVELIUS BENGT , ROSENGREN ELSA
Published: December 2008

A standardized stenosis was induced by applying a silver clip around the left renal artery in male rats. This resulted in arterial hypertension within 10 days (as determined by increase in heart weight). Ornithine decarboxylase (ODC) activity was determined in the right (untouched) kidney, the left kidney, and the adrenal glands 1 day, 10 days, and 3 months after the operation. There was no difference in ODC activity in the right kidney of the operated animals when compared with matched controls. In the left kidney (with artery stenosis), ODC activity decreased to 40% after 1 day. A partial recovery was seen after 10 days (ODC activity 70% of normal), and after 3 months ODC activity had normalized. Removal of the clip 1 day prior to killing induced in the 3‐month group a more than two‐fold increase in ODC activity in the previously clipped kidney; ODC activity in the contralateral kidney was not affected. Only minor changes in ODC activity occurred in the adrenal glands following the operation. Contents of putrescine and spermidine were increased in the left (stenotic) kidney, and after clip removal, also in the right (untouched) kidney. Our observations thus indicate that alterations in renal blood flow are rapidly followed by changes in ODC activity. Contents of putrescine, spermidine and spermine seemed to a great extent to be independent of the ODC activity.
Role of different calcium pools in the contraction of respiratory smooth muscle
Authors: BENGTSSON BENGT , KHAN A. RAUF , WEIBER RIKARD
Published: December 2008

Contractions were evoked in isolated strips of rat trachea by potassium and acetylcholine (ACh) respectively. Extracellular calcium (Ca) was removed by EGTA and Ca influx was inhibited by diethylstilboestrol (DES). Contractions evoked by potassium were completely inhibited in the presence of EGTA or DES. ACh‐induced contractions were rapidly abolished by EGTA whereas DES did not completely block these responses when a high concentration of ACh (10‐4M) was used. Repeated activation by ACh in the presence of DES displayed two different phases of the contractile response; one initial brief contraction that decreased only slowly in the presence of DES, and a second phase with sustained contraction that was more readily depressed by DES. It is suggested that the smooth muscle in rat trachea is activated by Ca originating both intra‐ and extracellularly. As EGTA almost immediately blocked even the initial contractile response, the intracellular store is apparently located in or very close to the plasma membrane.
Autoradiographic changes of3H‐α‐bungarotoxin binding in rat hind limb muscles after a cryoinjury of the sciatic nerve and in acrylamide intoxication
Authors: ASKMARK H. , GILLBERG P.‐G. , LILJEBORG A. , AQUILONIUS S.‐M.
Published: December 2008

The morphological distribution of acetylcholine receptors in rat tibialis anterior and soleus muscles after a cryoinjury of the sciatic nerve was studied byin vitroautoradiography with3H‐α‐bungarotoxin (3H‐α‐Btx). Tibialis anterior from rats intoxicated with acrylamide was also investigated by this technique. A computer system was used for densitometry and colour coding of the autoradiographs. In normal muscle,3H‐α‐Btx binding was observed only at the motor endplates. From the second day after the nerve lesion the area of binding spread from the motor endplate region towards the muscle‐tendon regions and on the 16th day almost all parts of the muscles showed increased binding. The binding had begun to decrease in the middle parts of the muscles on the 20th day and on the 30th day binding was observed only in the motor endplate area. Tibialis anterior from rats intoxicated with acrylamide (total dose 1100 mg·kg‐1) showed3H‐α‐Btx binding over the entire muscle.
Stimulus‐secretion coupling of parathyroid hormone release: studies of45Ca and86Rb fluxes
Authors: WALLFELT CHRIS , LARSSON ROLF , JOHANSSON HANS , RASTAD JONAS , ÅKERSTRÖM GÖRAN , LJUNGHALL SVERKER , GYLFE ERIK
Published: December 2008

Pieces of rat parathyroid glands were used to study fluxes of45Ca and86Rb. The uptake of45Ca increased with the extracellular Ca2+concentration up to at least 5 mM. A rise of extracellular Ca2+had dual effects on45Ca efflux in terms of an initial stimulation and a subsequent inhibition. However, K+depolarization neither affected the uptake nor the efflux of45Ca indicating a lack of voltage‐dependent Ca2+channels. The depolarization obtained with exposure to Ca2+cannot be attributed to a decreased K+permeability, since the86Rb concentrating ability diminished and the efflux of the isotope increased when parathyroid pieces were exposed to a raised Ca2+concentration. A stimulation of86Rb efflux by the Ca2+ionophore A‐23187 indicated that the parathyroid cells possess a K+permeability activated by cytoplasmic Ca2+. It is suggested that Ca2+fluxes through channels sensitive to activation by Ca2+are important both for the membrane potential and the cytoplasmic Ca2+activity.
Adenosine analogues stimulate cyclic AMP formation in rabbit cerebral microvessels via adenosine A2‐receptors
Authors: LI YING‐OU , FREDHOLM BERTIL B.
Published: December 2008

This study has examined the accumulation of cyclic AMP in microvessels from rabbit and feline cerebral cortex induced by a series of adenosine analogues to determine the type of receptor involved. The conversion of tritium labelled adenine nucleotides to [3H]cylic AMP was determined in [3H]adenine labelled microvessels in the presence of an inhibitor of cyclic AMP hydrolysis, rolipram (30 μM). In microvessels from both cats and rabbits two adenosine analogues, N‐5'‐ethylcarboxamido adenosine (NECA) and L (S)‐phenylisopropyladenosine (PIA), stimulated cyclic AMP accumulation. The response was larger and more reproducible in rabbits than in cats. In rabbit cerebral microvessels the order of potency as stimulator of cyclic AMP accumulation was NECA > 2‐chloroadenosine > L‐PIA > cyclohexyladenosine (CHA) > D‐PIA. This order of potency defines the receptor involved as being of the A2subtype. Although the maximal response to CHA appeared to be lower than that to NECA, CHA did not inhibit the response to NECA, suggesting that it is not a classical partial agonist. In the presence of the adenylate cyclase stimulating compound forskolin (1 μM) NECA was more active than in its absence (close to 30‐fold increase in EC50) and also produced a maximal effect six times higher. The maximal responses to PIA and CHA increased proportionally in the presence of forskolin. These results show that rabbit cerebral microvessels possess adenosine receptors of the A2subtype capable of stimulating the formation of cyclic AMP. The functional significance of such receptors is not known, but may be related to regulation of vascular permeability.
Neuropeptide Y and sympathetic control of heart contractility and coronary vascular tone
Authors: FRANCO‐CERECEDA ANDERS , LUNDBERG JAN M. , DAHLÖF CARL
Published: December 2008

The effects of neuropeptide Y (NPY) on contractility of the spontaneously beating guinea‐pig atrium and transmural nerve stimulation (TNS)‐induced efflux of tritium‐noradrenaline (3H‐NA) were studiedin vitro.NPY induced a moderate positive chronotropic and inotropic atrial response, which was resistant to metoprolol. TNS at 2 Hz for 2 s caused an increase in rate and contractile force. These effects were significantly reduced by NPY. NPY also reduced the TNS induced (2 Hz for 20 s), fractional [3H]NA release by 40% without affecting the contractile response. The contractile effects of exogenous NA on the guinea‐pig atrium were not affected by NPY. NPY caused a long‐lasting increase in coronary perfusion pressure, and also, in high doses, an inhibition of ventricular contractility in the isolated, perfused guinea‐pig heart. The perfusion pressure increase to NPY, which most likely reflects coronary vasoconstriction, was resistant to α and β‐adrenoceptor blockade but sensitive to the calcium antagonist nifedipine. A 50% reduction of the vascular NPY response occurred at 10‐9m nifedipine, which did not influence cardiac contractilityper seor the contractile effects of NA. NPY did not modify the increase in ventricular contractility induced by NA. Noradrenaline did not influence coronary perfusion pressure after β‐blockade. Since NPY is present together with NA in cardiac nerves, it may be suggested that NPY is involved in the regulation of NA release as well as the sympathetic control of atrial contractility and coronary blood flow.
Differences in contractile activation between human myometrium and intramyometrial arteries
Authors: MAIGAARD SVEND , FORMAN AXEL , ANDERSSON KARL‐ERIK
Published: December 2008

Small intramyometrial arteries and pieces of adjacent myometrial tissue were obtained from 25 non‐pregnant women undergoing hysterectomy. Vascular and myometrial preparations were dissected, mounted in organ baths and isometric tension was recorded. Myometrial strips, but no vascular preparation, developed spontaneous contractile activity. Noradrenaline (NA) and vasopressin (VP) contracted both vessels and myometrium. Prostaglandin F2α(PGF2α) contracted the myometrial tissue, but had only a minor effect on the vessels. Removal of extracellular calcium almost abolished the myometrial responses to high K+(124 mm)‐solution, PGF2α, NA and VP. The vascular responses remaining after this treatment were 18% (K+), 34% (NA) and 25% (VP) of control contractions induced by high K+(124 mm). Nifedipine potently depressed myometrial contractions induced by NA and VP, but was less active against the vascular responses to these agents. In preparations exposed to calcium‐free medium, nifedipine (10‐7m) almost abolished myometrial contractions induced by calcium in the presence of K+(124 mm), NA or VP. It also effectively depressed vascular responses to calcium in the presence of K+, but was less active if NA and VP were present. It is suggested that PGF2αhas almost no contractant effect on intramyometrial arteries, and that the activation process in these vessels is much less dependent on extracellular calcium than that of the myometrium.
Cholinergic and adrenergic neural control of smooth muscle function in the non‐pregnant rat uterine cervix
Authors: STJERNQUIST M. , OWMAN CH.
Published: December 2008

The isolated circular smooth muscle of the uterine cervix from spayed rats was investigatedin vitro.One group of animals was treated with oestrogen. Preparations from these rats showed no spontaneous contractile activity, but responded with contractions to electrical field stimulation. The contractions were blocked by approximately 85% with atropine, scopolamine and tetrodotoxin, but were unaffected by the adrenergic antagonists propranolol, phenoxybenzamine, and yohimbine. This neurogenic effect was potentiated by neostigmine. Noradrenaline inhibited the nerve‐induced contractions and also lowered resting tension in a concentration‐dependent way. The latter effect of noradrenaline was inhibited by propranolol. The indirect effects of noradrenaline on the electrically induced contractions were also inhibited by propranolol, but potentiated with phenoxybenzamine and, to a less extent, yohimbine. Nerve‐induced relaxation was never observed. Acetylcholine contracted the smooth muscle by an effect that was counteracted by atropine. A second group of spayed rats was not given any steroid treatment. The cervix preparations from these animals showed spontaneous activity, which was uninfluenced by atropine, propranolol, phenoxybenzamine, yohimbine, and tetrodotoxin. Noradrenaline inhibited the spontaneous activity. This noradrenergic effect was counteracted by propranolol and potentiated by phenobenzamine. Acetylcholine increased the smooth‐muscle tone by an atropine‐sensitive action. The results suggest the presence of a cholinergic motor inneveration on the non‐pregnant rat uterine cervix. The cervix also receives an adrenergic innervation, which may act both post‐junctionally (lowering resting tension and inhibiting spontaneous activity) and prejunctionally (modulating the cholinergic nerves) viabeta‐adrenergic as well asalpha‐adrenergic receptors.
Pharmacological analysis of the mechanism of action for colonic contraction induced by neurotensin, substance P and methionine‐enkephalin
Authors: HELLSTRÖM PER M.
Published: December 2008

Infusion of neurotensin, substance P and methionine‐enkephalin induces colonic contraction in the cat. The present study was performed to investigate the effect of various pharmacological blocking agents on colonic contraction evoked by these peptides infused by the i.a. or i.v. route. The contractions caused by infusions of neurotensin were blocked by tetrodotoxin (1 μg kg‐1i.a.), hexamethionium (10 mg kg‐1i.v.), atropine(o.1 mg kg‐1i.v.) or somatostatin (100 pmol min‐1i.a.), but not by haloperidol, methysergide, mepyramine, cimetidine or naloxone. The contractile effect of substance P on the colon was abolished by the substance P receptor antagonist (D‐Arg1, D‐Pro2, D‐Trp7,9, Leu11)‐substance P (70 nmol min‐1i.a.). No other blockers used, such as tetrodotoxin, hexamethonium, atropine, mepyramine, cimetidine, methysergide, naloxone or somatostatin inhibited the response to substance P. Methionine‐enkephalin produced a colonic contraction that was completely blocked by naloxone (1 mg kg‐1i.a.). Both atropine (0.1 mg kg‐1i.v.) and somatostatin (100 pmol min‐1i.a.) reduced the contractile response. However, tetrodotoxin, hexamethonium, mepyramine, cimetidine and methysergide did not affect the response to methionine‐enkephalin. All adrenergic blockers tested, that is, guanethidine, propranolol and phentolamine, increased the contractile responses to the peptides. The results indicate that the colonic contraction induced by neurotensin is mediated via nervous cholinergic pathways. Substance P induces colonic contraction, probably by a direct effect on smooth muscle substance P receptors. Methionine‐enkephalin induces colonic contraction which could be blocked by naloxone. However, a cholinergic or peptidergic link may also be involved in the response to methionine‐enkephalin.
Somatostatin induced apnoea: prevention by central and peripheral administration of the opiate receptor blocking agent naloxone
Authors: HARFSTRAND ANDERS , FUXE KJELL , KALIA MADHU , AGNATI LUIGI F.
Published: December 2008

Somatostatin (SRIF) (6 nmol) given intracisternally (i.c.) into the a‐chloralose anaesthetized rat has recently been shown to cause apnoea with a latency of 5–10 minutes (Kalia et al 1984a). The apnoea produced by SRIF is very rapid, irreversable and leads to the death of the animal. In view of the existence of SRIF nerve cell bodies and terminals in medullary respiratory nuclei such as the ventral and ventrolateral subnuclei of the nucleus of the tractus solitarius (nTS) (Kalia et al 1984b, Johanson et al 1984), we have proposed the existence of somatostatinergic mechanisms in the respiratory nuclei of the medulla oblongata involved in mediating apnoeic conditions (Kalia et al 1984a). In the present study, we have analysed whether the SRIF induced apnoea could be counteracted by a previous i.e. administration of the highly selective a2‐adreno‐receptor blocking agent RX 781094 (2‐(2‐(i,4 benzodioxanyl))2‐imi‐dazoline HC1) (Doxey et al 1983), or an opiate receptor blocking agent such as naloxone. Thus, both a2‐adrenoreceptor agonists and opiates induce respiratory depression, and opiates in high doses cause apnoea (Bolme et al 1974, Hassen et al 1982, Sitsen et al 1982). In addition, catecholamine (CA) and enkephalin immuno‐reactive nerve terminal networks exist in high densities within the nucleus tractus solitarius (nTS) of the medulla oblongata and may therefore interact with somatostatin nerve terminals in regulation of respiratory activity (Kalia et al 1984b).
Dual inhibitory actions of somatostatin on isolated gastric glands
Authors: NYLANDER OLOF , BERGQVIST ELISABET , ÖBRINK KARL JOHAN
Published: December 2008

The growth hormone release‐inhibiting hormone or somatostatin is a potent inhibitor of gastric acid secretion. In the present paper these inhibiting properties were tested on isolated gastric glands from rabbit fundic mucosae, prepared as according to Berglindh & ÖBRINK (1976). Parietal cell activity was measured as [14C]aminopyrine (AP) accumulation and O2‐consumption. Glandular histamine release was determined after condensation with o‐phthalaldehyde and measured fluorometrically. In the gastric glands there are two possible main processes that can be inhibited, namely (1) the release of histamine from some endocrine cells and (2) the activity of the parietal cell itself. It was found that somatostatin acted on both mechanisms. Basal histamine release was, however, not affected by somatostatin while the release induced by pentagastrin (Pg) at a concentration of 3 times 10‐9M, or acetylcholine (10‐5M) was dose‐dependently (10‐12to 10‐6M) inhibited by this peptide. Maximal inhibition, which was about 70%, occurred at a dose of 10‐8M somatostatin. Somatostatin also depressed parietal cell activity induced by histamine (10‐6to 10‐4M), isobutyl‐methyl‐xanthine (IMX, 10‐5to 10‐4M) or the combination of IMX (10‐5M) and Pg (3 times 10‐9M) Basal parietal cell activity was, however, unaffected. The IMX (10‐4M) induced parietal cell activity in cimetidine‐treated (10‐4M) glands was also depressed by somatostatin, which indicates an action directly on the parietal cell not mediated via H2‐receptors. The dual inhibitory actions of somatostatin are probably not mediated via stimulation of prostaglandin synthesis since indomethacin (3 times 10‐6M) did not diminish its effects.
Inhibition of [3H] glutamate release from rat hippocam pal slices by L‐phenylisopropyladenosine
Authors: FASTBOM JOHAN , FREDHOLM BERTIL B.
Published: December 2008

Hippocampal slices were labelled with [H]glutamate. Evoked release, which was calcium‐dependent and inhibited by tetrodotoxin, could be reduced concentration‐dependently by L‐PIA. The effect of L‐PIA was blocked by 10 µM 8‐phenyltheophylline. The results indicate that there are adenosine receptors modulating the efflux of glutamate in field stimulated hippocampal slices.
Histamine: the sole mediator of pentagastrin‐stimulated acid secretion
Authors: EKBLAD E. B. MARGARETA
Published: December 2008

Isolated frog gastric mucosa was used to study the effect of pentagastrin on histamine release and acid secretion. The release of histamine precedes that of acid secretion. The delay time and time of peak acid secretion occur later than during histamine stimulation. Short exposure (pulse) results in transient increases in both acid secretion and histamine release rates, while longer exposure (step) results in prolonged increases in both variables. Dose‐response curves for pentagastrin pulses show that both the total amount of histamine released and the total amount of acid secreted are saturable processes, paralleling each other. Thus, the total amount of acid secreted is a function of histamine (released) exposure (Mmin‐1) in the extracellular space. Repeated exposure will give multiple responses only if the time elapsed between the stimuli is long enough. The magnitude of the responses depends on the length of time intervals between the stimuli and the concentration of the stimuli. Simultaneously administered pulses of histamine and pentagastrin result in merely additive amount of acid being secreted. From these observations I conclude that pentagastrin‐induced acid secretion can be understood solely in terms of its effect on histamine release and that depletion of histamine stores is responsible for the observed refractoriness.
Facilitation of hippocampal long‐lasting potentiation by GABA antagonists
Authors: WIGSTRÖM H. , GUSTAFSSON B.
Published: December 2008

Long‐lasting potentiation (LLP) of synaptic transmission in the CAi region of the hippocampal slice preparation has been examined. The effects of reduced postsynaptic inhibition given by application of y‐aminobutyric acid (GABA) antagonists (mainly picrotoxin) on the generation of LLP were investigated. It was first demonstrated that picrotoxin had little effect on excitatory synaptic transmission itself as judged by the rising phase of the field EPSP. Moreover, there were largely no actions on short‐lasting synaptic effects such as paired pulse facilitation and frequency potentiation. On the other hand, following drug application, much fewer afferent volleys were needed to generate a given amount of LLP. Long‐lasting potentiation could be produced by trains containing as few as 2–5 impulses, trains that normally give rise to only short‐lasting effects. There was no apparent difference in the maximal amount of LLP that could be produced for a given input, suggesting that the GABA antagonists do not operate by enhancing the capacity for LLP production but by facilitating its induction. As in normal solution, the LLP in the presence of the drugs was confined to the tetanized pathway. Tetanization in the treated slices was associated with enhanced somatic firing as well as an increase of the negative extracellular potential recorded in the dendritic layer. It is proposed that part of this increased negativity represents current through synaptically opened A‐methyl‐D‐aspartate (NMDA) receptor channels. Furthermore, it is suggested that the facilitated induction of LLP in the presence of GABA antagonists is related to a facilitated activation of these NMDA receptor channels which is secondary to the higher levels of dendritic depolarization attained during tetanization under conditions of reduced postsynaptic inhibition.
Release of an insulin‐like peptide from perfused extirpated cat legs in response to electrical stimulation of the sciatic and brachial nerves and to administration of ACh, bombesin, oxytocin and glibenclamide
Authors: POSLONCEC B. , UVNÄS‐MOBERG K. , HAGERMAN M. , CASTENNSSON S. , UVNÄS B.
Published: December 2008

The vascular system of extirpated cat legs was perfused with Tyrode's solution and insulin‐like immunoreactivity (ILI) levels were determined in the perfusate with radioimmunoassay. During unstimulated conditions perfusate levels of ILI were almost undetectable. However, in response to electrical stimulation of the sciatic or brachial nerves (within a wide range of stimuli 5–40 V, 2–20 Hz and 0.2–40 ms) 1–20 ng of ILI was recorded in the perfusate. Blockers of cholinergic and adrenergic transmissions added to the perfusate did not influence the output of the ILI induced by nerve stimulation. Furthermore, after administration of acetylcholine (ACh) (0.1 and 10 μg kg‐1)t oxytocin (0.5 and 5 IU kg‐1)i glibenclamide (25 and 100 μg kg‐1) and bombesin (100 and 500 μg kg‐1) to the cat leg preparation, ILI appeared in the perfusate in amounts similar to those induced by electrical stimulation of the nerves. When subjected to high‐performance liquid chromatography (HPLC) the insulin‐like peptide detected in the cat leg perfusate following nervous stimulation, or administration of oxytocin and glibenclamide, co‐eluted with a bovine insulin standard. We have previously shown that some peripheral nerves of the cat, such as the sciatic, brachial and vagal nerves, contain an insulin‐like peptide with HPLC characteristics similar to the bovine insulin standard. It is therefore possible that the insulin‐like peptide released from the isolated cat leg preparation by the above‐mentioned stimuli derives from this nervous pool of insulin. Alternatively, the insulin‐like peptide emanates from the striatal muscles innervated by the sciatic and brachial nerves, since also muscles have been shown to contain an insulinlike peptide.
On the transmission of sacral parasympathetic nervous influence on distal colonic and rectal motility in the cat
Authors: HEDLUND H. , FÄNDRIKS L. , DELBRO D. , FASTH S.
Published: December 2008

Experiments were performed on cats anaesthetized with chloralose and treated with adrenoceptor blocking agents. Distal colonic and rectal motility were selectively recorded by a volumetric method. The effects of muscarinic and ganglionic nicotine receptor blockade on motor responses induced by graded efferent electrical pelvic nerve stimulation (PNS) were studied. Stimulation at low current strength evoked contractions in both the colon and the rectum, which were sensitive to atropine and to hexamethonium. High intensity stimulation elicited distal colonic contractions resistant to both atropine and hexamethonium. Similar excitatory responses to high strength PNS were also observed in the rectum, though not in all experiments. Stimulation at intermediate intensities evoked distal colonic and rectal relaxations which were resistant to atropine but blocked by hexamethonium. The results indicate that PNS influences colonic and rectal motility by activation of at least three discrete non‐adrenergic nervous pathways: (1) low‐threshold excitatory fibres involving nicotinic and muscarinic transmission, (2) high‐threshold excitatory fibres with a non‐muscarinic, non‐nicotinic transmission mechanism, (3) inhibitory fibres with an intermediate stimulus intensity threshold, exerting their effect by a non‐muscarinic mechanism involving a nicotinic step.
Interaction between prejunctional α2‐receptors and neuronal transmitter reuptake in small mesenteric arteries from the rat
Authors: NILSSON HOLGER , SJÖBLOM NINA , FOLKOW BJÖRN
Published: December 2008

The role of the prejunctional α2‐receptors for the response to vaso‐constrictor nerve stimulation has been examined before and after inhibition of neuronal transmitter reuptake in mesenteric resistance vessels from the rat. Small arteries (diameter about 200 μm) feeding the jejunum were mounted in a myograph for recording of their isometric wall tension during transmural field stimulation of the intramural nerves. Blockade of prejunctional α2‐receptors with 0.01 μm idazoxan (RX 781094) caused a marginal potentiation of the neurogenic response when neuronal reuptake was left intact. Also, inhibition of reuptake alone with 3 μm cocaine had little effect on the response. However, when both α2‐receptors and reuptake had been inhibited, a strong enhancement of the neurogenic vasoconstriction was observed. Similar findings were made when yohimbine and LU 3–010 instead were used for α2‐blockade and reuptake inhibition, respectively. The results thus indicate that in these resistance arteries the effector response is normally influenced by the combined activity of α2‐receptors and uptake, and that failure of one mechanism increases the activity of the other, so as to maintain a largely constant effector response.
Modelling of intestinal permeability in man to polyethylene glycols (PEG 400 and PEG 1000)
Authors: SUNDQVIST TOMMY , MAGNUSSON KARL‐ERIC
Published: December 2008

The intestinal permeability barrier was evaluated in four healthy individuals by the 6 h urinary recovery of a mixture of different‐sized polyethylene glycols (PEG 400 and PEG 1000) after a liquid meal of probe molecules. The mixture of PEGs contained around 25 different PEG polymers, ranging from about 194 to 1294 dalton in size. Three models were employed to get a condensed formulation of the intestinal barrier, namely a filter function, describing exclusion of molecules due to the molecular weight, and two expressions for ultrafiltration through a pore due to the Stoke‐Einstein radius. A factor reflecting unrestricted passage of probe molecules in the size‐range used was also included in the mathematical expressions. It was found that a filter function showing half‐maximum exclusion at 589–956 daltons (Da) PEG and a pore function yielding a pore‐size of 8.0–8.5 Å. equally well described the intestinal barrier in the four subjects. The results are discussed in relation to structures of the intestinal epithelium that may restrict the passage of molecules.
Functional development of the visual system in normal and protein deprived rats. Ill: Recordings from adult optic nerve in vitro
Authors: SJÖSTRÖM A. , CONRADI N. G. , GUSTAFSSON B. , WIGSTRÖM H.
Published: December 2008

SJÖSTRÖM, A., CONRADI, N.G., GUSTAFSSON, B. & WIGSTROM, H. 1985. Functional development of the visual system in normal and protein deprived rats. III: Recordings from adult optic nerve in vitro. Acta Physiol Scand, 125, 353–358. Received 8 March 1985, accepted 20 April 1985. ISSN 0001–6772. Departments of Physiology and Pathology, University of Goteborg, Sweden.

A persistent increase in the latencies of the visual evoked response recorded from the cortical surface of protein deprived adult rats was described recently (SJÖSTRÖM et al. 1984). The morphological correlate to this alteration is unknown. Previous studies on malnourished rats have shown a reduction of axonal diameters and in the number of myelin lamellae in relation to axonal circumference, and hence the possibility of a decrease in fibre conduction velocity must be considered. In parallel study, we have established that changes in diameters and myelination of optic nerve fibres similar to those previously reported in malnourished rats are present in adult protein deprived (PD) rats (Conradi el al. 1985). In the present paper, recordings of optic nerves in vitro from adult normal (C) and protein deprived (PD) rats are described. The compound action potentials were very similar in the two groups. Three positive peaks were easily defined probably corresponding to three functional groups of optic nerve fibers. No significant differences in amplitudes or conduction velocities for the three peaks were found between the C and PD rats. It is concluded that the increased latencies of the evoked response are not caused by a decrease in conduction velocity.