bluuebunny/crossref_metadata_2025 huggingface dataset:
Binding of catecholamines to phospholipids isolated from adrenal medullary granules
Authors: LISHAJKO F.
Published: December 2008

The large granules of the adrenal medullary fraction were lysed and subjected to Sepharose 2 B gel filtration. Proteophospholipids (PPL) were isolated from the membrane fraction and used for binding of catecholamines (CA), such as noradrenaline (NA), adrenaline (A) and dopamine (DA). The affinity order was DA ± NA = A. The binding capacity was dependent on amine concentration, pH and ionic strength, and amounted to about 2 and 3.5 μmol per μmol lipid phosphorus in ether and ether‐ethanol, respectively. A Scatchard plot revealed only one type of binding site;Kd= 8.3 mM. The anionic detergent sodium dodesylsulphonate (SDS) moderately increased the uptake of NA and A while cationic detergents like cetyltrimethylammonium bromide (CTAB) and Hyamine 2389 strongly diminished the binding to PPL. The ionic detergent sodium deoxycholate (DOC) and the non‐ionic detergent Triton X‐100 were without significant effect. It is suggested that the dipolar head group of the granule lipids, particularly the lipid phosphate groups, are involved in electrostatic or complex interactions with the CA, either directly, or through water molecules within the lipid polar head group.
Glomerulotubular balance during renal sympathetic stimulation
Authors: HARTMANN A. , LANGBERG H. , HOLDAAS H. , KIIL F.
Published: December 2008

In volume‐expanded dogs receiving ethacrynic acid, a linear relationship, glomerulotubular balance (GTB), applies between the remaining sodium reabsorption and the glomerular filtration rate (GFR) during mechanical aortic constriction. To examine whether GTB applies during sympathetic stimulation, the GFR was progressively reduced by 70–75% in anaesthetized dogs by renal nerve stimulation, intrarenal norepinephrine infusion or by selective stimulation of α‐adrenoceptors by intrarenal methoxamine infusion. Linear relationships (GTB) were obtained (r> 0.9). Reabsorption was not different during the various kinds of sympathetic stimulation, but less than during aortic constriction; the largest difference in NaCl reabsorption at comparable GFR amounted to 10–15% and was obtained 30–40% below control GFR, whereas inhibition of NaHCO3reabsorption was uncertain. To inhibit NaHCO3reabsorption and associated NaCl reabsorption in the proximal tubules, acetazolamide (30 mg kg‐1) was administered instead of ethacrynic acid. No difference in reabsorption was observed at comparable GFR during norepinephrine infusion and mechanical aortic constriction. Hence, GTB applies during sympathetic stimulation. Compared with data obtained during aortic constriction, α‐adrenergic stimulation reduces proximal reabsorption of NaCl and, possibly, NaHCO3and exerts no effect on distal transcellular NaCl reabsorption.
Regional and selective changes in blood flow of the feline small intestine induced by endoluminal serotonin
Authors: GRÖNSTAD K. O. , DAHLSTRÖM A. , JAFFE B. M. , AHLMAN H.
Published: December 2008

A physiological role for endoluminal serotonin (5‐HT) was explored inin vivoexperiments, where feline jejunal segments were endoluminally perfused with saline or a low concentration of 5‐HT. The upper jejunal segment was initially perfused with saline, followed by 5‐HT in saline, and finally perfused with saline alone. The lower jejunal segment served as a control with constant perfusion with saline. The regional blood flow to the small intestine was determined by the microsphere technique. Endoluminal perfusion with 5‐HT caused a selective muscular hyperaemia of the experimental gut segment, which was normalised upon subsequent saline perfusion. The blood flow to the saline perfused control segment was unchanged. This was also the case for control tissues; that is, adjacent small intestinal regions and kidneys. The 5‐HT‐induced muscular hyperaemia was confined to the experimental gut segment and seems to be mediated by a local cholinergic neural mechanism, activated from the mucosa, since the hyperaemic response was prevented by muscarinic blockade or local anaesthesia applied to the luminal surface of the experimental segment. The vascular response does not seem to involve 5‐HT2receptors, since selective blockade of such receptors did not prevent 5‐HT‐induced hyperaemia.
Unilateral denervation of the rat urinary bladder and reinnervation: a predominance for ipsilateral changes
Authors: EKSTRÖM J. , MALMBERG L. , ÖBERG S.
Published: December 2008

Unilateral removal of the pelvic ganglion affected the bladder‐half on the denervated side more profoundly than that on the non‐denervated side. At an early stage (3–7 days) the former was heavier, had a lower choline acetyltransferase activity, developed less tension to nerve stimulation and, in course of time, became more sensitized to methacholinein vitrothan the latter. At a late stage (30–60 days) the nerve‐evoked contractile responses on the denervated side had increased, which was almost wholly attributed to the atropine‐sensitive part of the contraction, but the recovery was not complete. On the non‐denervated side the nerve‐evoked responses were not significantly changed. It was calculated that in the normally innervated bladders 25–30% of the cholinergic nerves of each half were of contralateral origin. The figure was lower (18%) for the nerves mediating the atropine‐resistant response.,
Substances that rapidly augment ionic conductance of endothelium in cerebral venules
Authors: OLESEN S.‐P. , CRONE C.
Published: December 2008

Classical techniques for studying modulations of microvascular permeability have a time resolution of minutes. A newly developed method allows continuous measurement of the electrical resistance of the microvascular membrane in vivo (Olesen & Crone 1983). The technique exploits microelectrodes impaled into the vascular lumen and is based on cable analysis of the vessel. It was applied to venules on the surface of the frog brain to test the effect on microvascular permeability of a wide variety of substances. The following agents increased ionic permeability reversibly within seconds: 5‐hydroxytryptamine, bradykinin, ATP, ADP, AMP, phospholipase A2, arachidonic acid, leukotriene C4, oxygen‐derived free radicals, ionophore A23187, and unbound Evans blue dye. An irreversible permeability increase was induced by protamine sulphate, neuraminidase, trypsin, melittin, and snake venoms from Crotalus durissus terrificus and Bothrops atrox. The following substances were without effect within an administration period of 5 min: histamine, epinephrine, putrescine, angiotensin II, vasoactive intestinal polypeptide (VIP), substance P, neurotensin, vasopressin, adenosine, PGE2, PGF2α, prostacyclin (PGI2), leukotriene B4, albumin, heparin, plant cytokinins, hyaluronidase, thrombin, wasp venom. Variations in pH between 5.1 and 8.6 did not change permeability. Three conclusions are drawn from the observations: (1) the permeability of cerebral microvessels can be modulated by specific agents, (2) the agents induced changes in the endothelium within a few seconds, and (3) the rapid permeability increase induced by inflammatory mediators was less than two‐fold and reversible within minutes.,
Atropine‐antagonized miosis induced in the goat by intravenous infusions of prostaglandin E (PGE1 and PGE2)
Authors: JÓNASSON H. , BASU S.
Published: December 2008

Effects of 30 min intravenous infusions of prostaglandin (PG) E1 (total dosage 0.07 mg kg‐1)) E2 and F2α (total dosage 0.12 mg kg‐1), respectively, were studied concomitant with measurements of renal excretion of PGF metabolites in hyperhydrated goats. None of the PGs induced any rise in rectal temperature. However, the PGEs elicited pronounced, atropine‐antagonized miosis and an inhibition of the water diuresis accompanied by some increase in renal excretion of arginine vasopressin (AVP). These effects were not obtained in response to PGF2α. The PGF2α rapidly induced a conspicuous and long‐lasting increase in the renal excretion of PGF metabolites. The corresponding effect of the PGEs was more delayed, and less than 10% of the increase obtained in response to PGF2α. Nevertheless, the excretion of these metabolites in response to the PGEs was of the same magnitude as that previously observed during endotoxin fever in the goat. It is concluded that endotoxin‐induced miosis and stimulation of AVP secretion previously demonstrated in the goat might well have been secondary to systemic PGE production. However, this does not seem to hold true for endotoxin‐induced fever.,
Capillary permeability in rat hindquarters as determined by estimations of capillary reflection coefficients
Authors: RIPPE B. , HARALDSSON B.
Published: December 2008

Osmotic reflection coefficients (a) for a variety of solutes ranging from NaCl to albumin were determined in perfused maximally vasodilated rat hindquarters employing the osmotic transient method (Vargas & Johnson 1964). Measurements were performed at high flows and using short tubings with small volumes. Intracapillary solute concentrations of the osmotic transients were measured or estimated for solutes of the size of inulin or smaller. The PS for Cr‐EDTA and cyanocobalamine were determined repeatedly in half of the experiments using an on‐line modification of the single injection (indicator diffusion) method (Rippe & Stage 1978) and capillary filtration coefficients (CFC or LpS) were followed in all experiments. The capillary osmotic reflection coefficient was determined to 0.05 for NaCl, to 0.08 for sucose, to 0.39 for inulin, to 0.57 for myoglobin and to 0.87 for albumin. These reflection coefficients were compatible with a small pore radius' of approximately 40 Å (slit width (w) of approximately 50 Å) according to modern hydrodynamic theories for the reflection coefficient and the parallel transcapillary pathway hypothesis. The best fit of the osmotic transient data to current theories for the reflection coefficient occurred if the major portion (86–87%) of hydraulic conductivity (Lp) was accounted for by this paracellular ‘small pore’ (slit) pathway and if 3.0–4.1% of Lp could be ascribed to a transcellular pathway (σ˜˜ 1) while the remaining fraction (10%) of Lp was accounted for by a non‐selective paracellular pathway (σ˜˜ o); that is, by ‘large pores’.
Effects of prostaglandin E1, E2and 16,16‐dimethyl‐E2on gastric mucosal microcirculation and basal acid output in the rat*
Authors: HOLM‐RUTILI L.
Published: December 2008

The effects of prostaglandins E, (PGE1), E2(PGE2) and 16, 16‐dimethyl‐E2(16, 16‐dm‐PGE2) on the gastric mucosal microcirculation and (spontaneous) acid output were studied in anaesthetized rats. The superficial mucosal vessels were monitored on a TV screen using a microscope, TV camera and videorecorder for off‐line analysis of red cell velocities (VRBC) and vessel diameters, from which the blood flow (QRBC) was calculated. The prostaglandins were either applied topically to the solution bathing the exposed mucosa or administered intravenously as a continuous infusion. Topical application of PGE1(0.5 or 5 μgml‐1), PGE2(5 or 50 μg ml‐1) or 16, 16‐dm‐PGE2(0.005, 0.05 or 0.5 μg ml‐1) increasedVRBCdose‐dependently without altering acid output, except for the highest dose of PGE2(50 μg ml‐1) which inhibited acid output. The latter occurred in spite of a seven‐to eight‐fold increase inVRBC. Mucus secretion (evidenced by an impaired resolution of the TV image) also increased during topical application of the prostaglandins especially at higher doses. Intravenous PGE1, PGE2(2.0 μg kg‐1min_1) or 16, 16‐dm‐PGE2(0.02 μg kg‐1min_1) caused an initial and transient (5–10 min) fall in systemic arterial blood pressure and a decrease inVRBCand acid output. Intravenous 16, 16‐dm‐PGE2in a dose which did not affect secretion or systemic arterial blood pressure (0.002 μg kg‐1min‐1) still significantly reducedVRBC. Thus, topically applied PGE1, PGE2or 16, 16‐dm‐PGE2dose‐dependently increaseVRBCwhile intravenous administration of the same prostaglandins reduceVRBC.
Effects of chloride ion substitution on the frequency dependence and α‐autoinhibition of [3H]noradrenaline secretion in guinea‐pig vas deferens
Authors: STJARNE L. , ALBERTS P. , BARTFAI T.
Published: December 2008

Guinea‐pig isolated vas deferens, in which the stores of noradrenaline (NA) had been labelled by preincubation with [3H]NA, was used to study the effects of substitution of chloride with other anions, on transmitter secretion evoked by electrical stimulation of postganglionic sympathetic nerves. Chloride was omitted from the Tyrode's solution and substituted with acetate, nitrate, methylsulphate, sulphate or HEPES. Ail substituents increased both the spontaneous and the stimulus‐evoked fractional secretion of [3H]NA under control conditions. The effect was essentially the same at all frequencies of stimulation (1–8 Hz). In the presence of the at‐adrenoceptor blocker phentolamine, which enhanced the secretion of [3H]NA in all media, the secretion was not further enhanced by chloride substitution. Chloride substitution reduced the depressing effect of exogenous NA on the secretory response. In conclusion, chloride ions may be required for full expression of a‐adrenoceptor‐mediated inhibition of [3H]NA secretion, but do not markedly influence facilitation by increased frequency of stimulation.,
Angiotensin II infusion during β‐adrenergic stimulation by isoproterenol. Effects on hepatic, splenic and cardiac blood volumes and on the magnitude and distribution of cardiac output in the dog
Authors: STOKLAND O. , MOLAUG M. , THORVALDSON J. , ILEBEKK A.
Published: December 2008

The cardiac and peripheral vascular adjustments to angiotensin II (0.1–0.2 μg kg‐1min‐1i.v.) during high β‐adrenergic activity by a continuous isoproterenol infusion (0.2–0.3 μg kg‐1min‐1i.v.) were examined in anaesthetized, atropinized dogs. Hepatic, splenic and left ventricular (LV) volume changes were estimated by an ultrasonic‐technique, and the blood flow distribution was measured by injecting radioactive microspheres and by electromagnetic flowmetry on the caval veins, the hepatic artery and the portal vein. During isoproterenol infusion, angiotensin II increased the systolic LV pressure by 45 ± 3 mmHg and the stroke volume by 17 ± 6 %. Concomitantly, the hepatic and splenic blood volumes declined by 29 ± 4 and 14 ± 6 ml, respectively, and the LV end‐diastolic segment length increased by 3 ± 1 %. The flow through the inferior caval vein increased by 39 ± 9%, whereas the superior vena caval flow remained unchanged. The hepatic arterial flow more than doubled. Thus, at high inotropy by isoproterenol infusion, angiotensin II relocates blood from the liver and the spleen towards the heart. By activating the Frank‐Starling mechanism, cardiac output is increased and conducted through the lower body, especially through the hepatic artery, because of the poor autoregulation of flow through this vessel.,
Generation and transmission of ovine ureteral contractions, with special reference to prostaglandins
Authors: THULESIUS O. , UGAILY‐THULESIUS L. , ANGELO‐KHATTAR M.
Published: December 2008

The pattern of spontaneous rhythmic contractions was studied in isolated preparations from calyx, pelvic, middle and distal parts of the sheep ureter. The frequency of contractions was highest in intrarenal specimens (13.3 ± 0.8 contractions min‐1). The regional difference in contractions is consistent with proximal dominant pacemaker cells. In isolated rings, indomethacin (10‐5 M) inhibited and finally stopped rhythmic motility. After stoppage prostaglandin PGF2α (10‐6‐10 ‐5 M) promptly re‐established contractions in a manner characteristic of each specimen, apparently according to the pre‐existent dominant pacemaker (frequency and pattern). This was demonstrated in a frequency analysis which showed a highly significant correlation of pacemaker frequencies before and after indomethacin. Experiments using dual recordings from both ends of a longitudinal preparation (tandem mode) showed that co‐ordinated contractile waves travelling from one end to the other could be initiated with PGF2α These results have been interpreted to indicate that prostaglandins in ureteral smooth muscle play a predominant role in co‐ordinating intercellular impulse transmission for which gap junctions could be responsible. The presence of such structures, as clearly demonstrated by an ultrastructural study, lends support to this hypothesis.
Effects of blood volume distribution on ventilatory variables at rest and during exercise
Authors: EIKEN O. , LIND F. , BJURSTEDT H.
Published: December 2008

Ventilatory variables and heart rate (HR) were investigated in eight supine subjects during dynamic leg exercise at o and 100 W with and without the lower portion of the body exposed to a pressure of – 50 mmHg (lower body negative pressure, LBNP). Resting values of inspired minute volume (V1), and respiratory drive in terms of mouth occlusion pressure (P01) were unchanged, whereas HR was higher during LBNP than in the control condition. Exercise values for HR in steady state were not affected by LBNP, whereas V1 was 15 and 11% lower and P0.1 was 20 and 11% lower in this condition at the o and 100 W workload levels, respectively. Time courses for Vl at the onset of 100 W exercise were similar with and without exposure to LBNP, indicating that the sudden increase in venous return occurring upon onset of pedalling during LBNP affords no significant stimulus in the initial development of exercise hyperpnoea. That exercise ventilation and P0.1 in steady state were reduced by LBNP suggests diminished humoral and/or locally induced chemical drive due to improved blood flow in exercising muscles resulting in reduced production of muscle metabolites or facilitation of their removal.
Differential effects of angiotensin, vasopressin and oxytocin on various smooth muscle tissues within the human uteroplacental unit
Authors: MAIGAARD S. , FORMAN A. , ANDERSSON K.‐E.
Published: December 2008

Tissue specimens from various parts of the uteroplacental unit were obtained from women undergoing caesarean section, and placental tissue from women with normal deliveries. Strips of myometrial tissue, and segments of intramyometrial arteries were dissfected together with segments of chorionic plate arteries and veins, and stem villous arteries. The preparations were mounted in organ baths, isometric tension recorded, and the responses to angiotensin II, vasopressin, and oxytocin were studied. In myometrial preparations, angiotensin caused a slight, trancient increase in the frequency of spontaneous contractions, but no changes in amplitude. In all vascular preparations angiotensin produced concentration‐related contractions. The responsiveness of the preparations was myometrial artery < villous artery > chorionic plate artery = chorionic plate vein. All responses were transient and tachyphylaxis was pronounced in all tissues. Tachyphylaxis was not influenced by pretreatment with indomethacin. Vasopressin increased transiently frequency and amplitude of contractions in myometrial strips. Myometrial arteries responded with a sustained contraction, as did chorionic plate arteries and veins but the latter vessels were less responsive. Villous arteries did not respond to vasopressin. Oxytocin preferentially stimulated myometrial strips, but also had a weak concentration‐related contractant effect on chorionic plate arteries and veins. Villous arteries did not respond to oxytocin. At a higher concentration, causing a pronounced increase in the frequency and amplitude of contractions of myometrial strips, oxytocin abruptly caused a marked contraction of myometrial arteries. Lower concentrations of the peptide had almost no effects. The results suggest that various smooth muscle tissues of the human uterus and placenta are highly differentiated as regards responses to angiotensin II, vasopressin, and oxytocin. The physiological and possible clinical importance of the present findings deserve further investigation.
Vagal stimulation of duodenal HCO3 ‐secretion in anaesthetized rats
Authors: JÖNSON C. , NYLANDER O. , FLEMSTRÖM G. , FANDRIKS L.
Published: December 2008

The present study was designed to examine the influence of the vagal nerves on mucosa protective duodenal HCO3‐secretion in chloralosed rats. The HCO3‐secretion was measured by in situ titration in a duodenal segment devoid of Brunner glands. Cervical vagotomy lowered duodenal HCO3‐secretion and stimulation of the cut vagal nerves (10 Hz for 15 min) increased this secretion. Both basal and vagally stimulated duodenal HCO3‐secretions were more pronounced in rats with ligated adrenal glands. Atropine did not influence basal duodenal HCO3‐‐secretion, whereas indomethacin and hexametho‐nium lowered basal secretion in vagotomized rats with ligated adrenal glands. Compared with untreated controls, vagally induced secretory responses were unchanged by atropine, 50% smaller in indomethacin treated rats and almost abolished in rats treated with hexamethonium. The study suggests that the vagal nerves exert an excitatory effect on duodenal HCO3‐‐secretion which is mainly mediated via nicotinic, non‐muscarinic transmission, in part dependent on prostaglandin synthesis. Furthermore, the results indicate that the adrenal glands exert an inhibitory action on both the basal and vagally induced mucosa protective HCO3‐‐secretion.
Some cardiovascular and metabolic effects of repeated sauna bathing
Authors: LEPPÄLUOTO J. , TUOMINEN M. , VÄÄNÄNEN A. , KARPAKKA J. , VUOR J.
Published: December 2008

Ten healthy male volunteers were exposed to the dry heat of a Finnish sauna (+ 80 oC) for 1 h twice a day for a period of 7 days. After each exposure rectal temperature rose by 0.8‐1.1 oC and body weight dropped by 0.7‐0.9 kg. The systolic blood pressure recorded 3–5 min after the sauna did not change during the experiments but the diastolic blood pressure decreased by 7–37 mmHg (P < 0.05). The pulse rate rose from 75–80 to 106–116 beats min‐1 (P < 0.05) after the sauna. The increased responses of pulse and temperature adapted to heat exposures so that they were significantly lower after the 3rd day (rectal temperature) or after 6th day (pulse). Metabolic rate increased by 25–33% (P < 0.01) after the first day. Serum total proteins, Hb and Htc were significantly increased on the 1st and 3rd days but not later, although the dehydration in response to sauna was unchanged as judged from the weight losses. Serum K, Na and Fe were significantly decreased on the 3rd and 7th day indicating that special attention should be given to the electrolyte balance in long‐lasting intense heat exposure. No ECG changes were found in recordings taken on the 7th day.
On the occasion of the 20th Anniversary of the Stockholm ‘Amine Group’, November 1985.
Authors: JOHANSSON O.
Published: December 2008

Neuropeptide Y (NPY)‐like immunoreactivity has been found in autonomic nerve terminals and fibres of the normal human dermis by the use of indirect immunohisto‐chemistry. Also a granular immunoreactivity was observed in the basal cells of the epidermis as well as in the cells of the outer root sheath of hair follicles. Thus, NPY should be considered when examining the role of different autonomic neurotransmitter candidates. Furthermore, NPY and norepinephrine may, at this level, serve together as co‐transmitters or co‐modulators of autonomic function. Finally, the immunoreactivity found in cells of the epidermis and the outer root sheath of hair follicles points to other functional effects so far not understood.
Receptor autoradiographical evidence for high densities of 125l‐neuropeptide Y binding sites in the nucleus tractus solitarius of the normal male rat
Authors: HÄRFSTRAND A. , FUXE K. , AGNATI L. F. , BENFENATI F. , GOLDSTEIN M.
Published: December 2008

By means of quantitative receptor autoradiography using 125I‐neuropeptide Y (125I‐NPY) as a radioligand, the distribution of 125I‐NPY binding sites has been evaluated in coronal sections at various rostrocaudal levels of the medulla oblongata of the male rat. High densities of neuropeptide Y (NPY) binding sites were demonstrated in the nucleus tractus solitarius (nTS), in the nucleus paratrigeminalis, in the area postrema, in the medial nuclei of the inferior olive and in the substantia gelatinosa of the caudal part of the spinal trigeminal nucleus. Low densities were present in the dorsal motor nucleus of the vagus (dmnX) and in the hypoglossal nucleus. Other regions of the medulla oblongata showed only a very low density or no specific binding of 125I‐NPY. These results indicate that the central cardiovascular actions of NPY at least in part may be mediated via an action in the nTS, in this way controlling the baroreceptor reflex activity. Neuropeptide Y mechanisms may also play a role in the regulation of other visceral afferents such as those involved in gastrointestinal control (dmnX) and of cerebellar function (inferior olive). Finally, the results indicate that a high density of NPY immunoreactive terminals in some regions of the medulla oblongata is associated with a low density of high affinity 125I‐neuropeptide Y binding sites and vice versa.
A correlation analysis of the regional distribution of central enkephalin and β‐endorphin immunoreactive terminals and of opiate receptors in adult and old male rats. Evidence for the existence of two main types of communication in the central nervous system: the volume transmission and the wiring transmission
Authors: AGNATI L. F. , FUXE K. , ZOLI M. , OZINI I. , TOFFANO G. , FERRAGUTI F.
Published: December 2008

By means of semiquantitative immunocytochemistry and quantitative receptor autoradiography a correlation analysis has been performed on the pre‐ and post‐synaptic features of enkephalin andβ‐endorphin immunoreactive neuron systems of the 3‐ and 24‐month‐old male rat. A parallel disappearance of enkephalin‐ andβ‐endorphin‐like immunoreactivity and of the density of mu and delta opiate receptors is shown during ageing. Furthermore, the lack of an overall correlation between the amount of pre‐ and post‐synaptic components of the enkephalin andβ‐endorphin synapses give evidence for the existence of a volume type of transmission in such systems in the telencephalic, diencephalic and mesencephalic areas analysed.
Contractile effects of noradrenaline and 5‐hydroxytryptamine in human hand veins: a pharmacological receptor characterization
Authors: ARNER M. , HÖGESTÄTT E. D.
Published: December 2008

The postjunctional receptors mediating contractile responses to noradrenaline (NA) and 5‐hydroxytryptamine (5‐HT) were characterized in ring segments of human hand veins by using subtype selective agonists and antagonists. The mechanical characteristics of the preparations were also examined by length‐tension measurements. The length‐active wall tension curve was bell‐shaped and reached a maximum at a length corresponding to a passive distending pressure of approximately 14 mmHg. (–)‐Phenylephrine consistently contracted the veins and was 24 times less potent than (±)‐NA, whereas clonidine produced a contraction in only two out of 11 vessel segments. Neither prazosin nor rauwolscine competitively inhibited the contractile response to NA, and large inter‐individual differences were found in the degree of inhibition produced by the antagonists. However, application of both prazosin and rauwolscine almost abolished the NA‐induced contraction. Ketanserin and methergoline inhibited the contractile response to 5‐HT; the former in an apparently competitive manner with a pA2value of 8.94, whereas the latter substantially reduced the maximum 5‐HT response. It is suggested that NA elicits contraction in human hand veins by acting at a mixed population ofα1and α2‐adrenoreceptors. The contractile response to 5‐HT, on the other hand, appears to be mediated predominantly by 5‐HT2receptors.
Effect of fasting and refeeding on glucose metabolism in rat aorta
Authors: DAHLKVIST H. , ARNQVIST H.
Published: December 2008

The effect of refeeding on accumulation of [14C]glucose carbon, oxidation of [14C]glucose and glycogen concentration in rat aortic intima‐media was studied in rats fasted for 3 days. Accumulation of glucose carbon and glucose oxidation were determined by incubating rat aortain vitrofor 2 h with 5.6 mM14C‐labelled glucose in the medium. Refeeding with standard pellets for 2–4 h augmented [14C]glucose accumulation in rat aorta but had no significant effect on glucose oxidation. The glycogen concentration in rat aorta tended to increase. After refeeding for 16 h both [14C]glucose incorporation and [14C]glucose oxidation were increased in rat aorta. Refeeding with carbohydrate‐rich pellets (92% carbohydrate) for 3 h increased blood glucose more than did protein‐rich (92% protein) pellets, whereas the rise in plasma insulin was about the same. The accumulation of [14C]glucose carbon measured during the subsequentin vitroincubation for 2 h was augmented after refeeding with protein‐rich pellets and slightly reduced after carbohydrate‐rich pellets. Refeeding of diabetic rats for 2 h with standard pellets increased plasma insulin and markedly increased blood glucose but had no effect on aortic [14C]glucose incorporation. Intravenous infusion of glucose in normal rats for 2 h markedly raised blood glucose but did not increase the aortic glucose incorporation. Raising the ambient glucose concentration from 5 to 10 mM during incubation of normal rat aortain vitrofor 2 h slightly decreased the [14C]glucose incorporation determined during a subsequent incubation for 2 h. These results suggest that refeeding with standard pellets augments glucose incorporation and glucose oxidation in rat aorta. This effect may be due to insulin or other factors but is probably not direcdy due to the increase in blood glucose. Furthermore the effect of refeeding is dependent on the composition of the food.
Calcium dependence of histamine‐induced increases in capillary permeability in isolated perfused rat hindquarters
Authors: HARALDSSON B. , ZACKRISSON U. , RIPPE B.
Published: December 2008

Experiments were performed on isolated maximally vasodilated perfused rat hindquarters to evaluate the role of calcium and magnesium for the capillary permeability increase(s) elicited by histamine. Changes in capillary permeability were quantified by determinations of capillary filtration coefficient (CFC) with gravimetric technique, and capillary diffusion capacity (PS) for vitamin B12(MW = 1355) with a single injection indicator dilution technique. During control, vascular resistance was 2.2 PRU100at a flow of 9.4 ml min_1per 100 g, and PS for B12was 3.7 ± 0.1 ml min‐1per 100 g, while CFC was 0.0377 ± 0.0004 ml min‐1mmHg‐1per 100 g. Perfusion with ‘Mg‐free’ solution for 1 h caused a 24% increase in CFC, while neither ‘Ca‐free’ perfusion nor perfusion with verapamil (5 x io‐5m) nor felodipine (1 ± 10‐6m) induced any changes in CFC. Histamine (100–200 μM) caused in all preparations a 150–200 % increase in CFC with only small changes in PS for B12. This histamine effect was absent after 1 h of ‘Ca‐free’ perfusion and was partially blocked after 1 h of perfusion with o. 1 mM calcium, while the calcium antagonists verapamil and felodipine had no effects on the histamine‐induced changes. The results imply that histamine exerts its action on the endothelial cells through a calcium‐dependent process, probably involving low affinity calcium sites but this process could not be inhibited by the calcium antagonists used. Thus, endothelial cell contractility, which probably is responsible for the histamine‐induced increase in capillary permeability, exhibits unique characteristics, differing from those of vascular smooth muscle.
Contractile effects of various vasoactive agents in small rat portal veins and hepatic arteries and the influence of sympathetic denervation on the noradrenaline response
Authors: HÖGESTÄTT E. D. , HAMMARSTRÖM L.‐E. , ANDERSSON K.‐E. , HOLMIN T.
Published: December 2008

Contractile responses were studied in isolated tubal segments of branches of the rat portal vein (Ø≅300μm)and hepatic artery (Ø≅ 200μm).Portal veins were approximately three times more sensitive to noradrenaline (NA) than hepatic arteries. 5‐hydroxytryptamine contracted hepatic arteries concentration‐dependently, whereas it produced only weak and inconsistent contractions in portal veins. Vasopressin effectively contracted hepatic arteries, whereas it had no effect on portal veins. Both vessel types responded to prostaglandin F2αwith contractions, although the drug potency was relatively low (EC50> 10‐5mol I‐1)‐ Histamine and carbachol failed to induce (hepatic arteries) or caused only weak (portal veins) contractions. Microsurgical hepatic hilar denervation reduced the catecholamine content of the parenchyma to ≥ 25% of controls. In both portal veins and hepatic arteries, the denervation procedure increased the NA sensitivity by factors of 3.1 and 2.0, respectively. In non‐denervated livers, cocaine produced a similar increase of the NA sensitivity, whereas the drug had no significant effect in vessels from denervated animals. Thus, there was a marked difference between rat portal veins and hepatic arteries in their responsiveness to several contractile agents. Furthermore, the results of the present study indicate that the adrenergic nerves in both vessel types can be adequately removed by the microsurgical denervation procedure used.
Fast voluntary trunk flexion movements in standing: primary movements and associated postural adjustments
Authors: ODDSSON L. , THORSTENSSON A.
Published: December 2008

Movement patterns were studied during fast voluntary forward flexions of the trunk from an erect standing position. Three healthy subjects performed three series of six consecutive trunk flexions at maximum velocity and with successively increasing amplitude, covering a major part of the range of motion (range for all subjects: 13–970). Angular displacements of the trunk, hip, knee and ankle were measured together with the tilt of the pelvis and the flexion of the spine using a Selspot optoelectronic system. Trunk flexion was the result of a simultaneous forward pelvic tilt and flexion of the spine. For trunk movements up to 550, spine flexion dominated the movement, whereas for larger movements a major part of the amplitude was caused by pelvic tilt. During flexion of the trunk a simultaneous hip flexion and ankle extension was seen. At the knee there was an initial flexion and a subsequent extension. The net amplitude of the knee flexion showed a negative correlation with net trunk flexion amplitude for movements up to 500, whereas for larger amplitudes the correlation was positive. Time from onset of the trunk movement to peak knee flexion showed a weak correlation to net trunk flexion amplitude (r= 0.34) whereas the corresponding correlation was higher for pelvic tilt, spine flexion, hip flexion, ankle extension, and knee extension (r= 0.60‐0.91). Each successive trial during a series of trunk movements was started from an increasing degree of knee flexion. This gradual adaptation was also present when successive trunk flexions were performed with constant movement amplitude. It is concluded that a voluntary trunk flexion movement is a blend of a spine‐form and a pelvic‐form of the task. Equilibrium is maintained through associated postural adjustments at the knee and ankle. A gradual static adaptation of the initial knee angle pre‐tunes the posture for the primary movement. It is suggested that knee flexion is one form of an associated postural adjustment used in the early phase of a fast trunk flexion, and that ankle extension, which is mainly seen later during the movement, is another form, also necessary for the maintainance of equilibrium.
Force and membrane potential during and after fatiguing, continuous high‐frequency stimulation of single Xenopus muscle fibres
Authors: LÄNNERGREN J. , WESTERBLAD H.
Published: December 2008

‘High‐frequency fatigue’ has been studied in isolated, short toe muscle fibres of Xenopus with recordings of tension and membrane potential during the development of fatigue and during recovery. With 70 Hz, continuous stimulation (22.5 oC) tension fell to 20% of the original in 11.6 ±4.9 s. Tension recovery occurred in two phases: an initial, fast phase to 45–80% of the original with fi of about 1 s, and a second, much slower phase. The membrane potential preceding action potentials (Em) fell gradually to about – 50 mV during stimulation and returned to a level of – 66 to – 70 mV with a time‐constant of about 10 ms when the stimulation was stopped. Action potentials towards the end of stimulation were reduced in amplitude, had a slow time‐course, and showed no signs of an early negative after‐potential (EAP). Increasing[K]o to 14 mM (m.p. – 56 to – 52 mV) caused similar changes in action potential configuration, except that an EAP seemed to be present. Those action potentials were associated with potentiated twitch response reaching 70% of original tetanic tension. It is concluded that mechanical fatigue is unlikely to be due to ‘fatigue’ of surface action potentials per se; a more likely mechanism would be impaired t‐tubule function, associated with membrane depolarization (Em becoming more positive) and possibly compounded by ionic changes of the t‐tubule fluid.
Force and membrane potential during and after fatiguing, intermittent tetanic stimulation of single Xenopus muscle fibres
Authors: WESTERBLAD H. , LANNERGREN J.
Published: December 2008

Tension and membrane potential have been measured in isolated, short toe muscle fibres of Xenopus during development of fatigue produced by intermittent, tetanic stimulation (0.5 s long 70 Hz trains repeated at 0.3‐0.8 Hz) and during recovery. Fibres could be divided into three groups on the basis of their fatigue resistance. In the first group (type 1 fibres) tension fell to 40% of the original after about 70 tetani, in the second group (type 2 fibres) after about 300 tetani and in the third group (type 3 fibres) after about 600 tetani. Recovery was slow in type 1 and 2 fibres and faster in type 3. The former also displayed post‐contractile depression (PCD), a 10–40 min period of severely reduced force production, eventually followed by complete recovery. As a result of fatiguing stimulation the membrane potential fell to –70 to – 60 mV. It returned to the pre‐stimulation value more rapidly than did tension. At the time of maximum PCD most fibres had repolarized to at least –75 mV and action potentials of normal configuration could be elicited. The results of the present experiments underline the importance of defining fibre types in studies of fatigue, also in amphibian muscle. Together with the results of a previous study (Lännergren & Westerblad 1986) they also demonstrate that both the decline phase and the recovery phase are markedly different when different modes of fatiguing stimulation are used.
Malate‐aspartate and alpha‐glycerophosphate shuttle enzyme levels in human skeletal muscle: methodological considerations and effect of endurance training
Authors: SCHANTZ P. G. , SJÖBERG B. , SVEDENHAG J.
Published: December 2008

The aim of the present study was to investigate whether the levels of the malateaspartate and alpha‐glycerophosphate shuttle enzymes in human skeletal muscle are affected by endurance training. The approach used was to compare six untrained and six endurance‐trained subjects as well as through performing a longitudinal study of endurance training on eight untrained subjects. Biopsy samples were obtained from the lateral part of the quadriceps femoris muscle. The trained muscles were characterized by higher levels of oxidative enzymes (55%) as well as enhanced capillary supply (30%). In both the cross‐sectional and longitudinal studies, the malateaspartate shuttle enzyme levels were about 50% higher in the trained state (cytoplasmic malate dehydrogenase 36%, mitochondrial malate dehydrogenase 46%, cytoplasmic aspartate aminotransferase 52% and mitochondrial aspartate aminotransferase 48%). Contrary to this, the alphaglycerophosphate shuttle enzyme levels did not differ significantly (cytoplasmic and mitochondrial glycerol‐3‐phosphate dehydrogenase: 10 and ‐4%, respectively). The activity ratios of the enzymes involved in respective shuttle did not differ significantly between the untrained and endurance‐trained states. It is concluded that endurance training may induce increased levels of malate‐aspartate shuttle enzymes in human skeletal muscle while the levels of the alpha‐glycerophosphate shuttle enzymes are not affected. The study also includes results from several methodological experiments.
Rapid regeneration in postischaemic skeletal muscle with undisturbed microcirculation
Authors: JENNISCHE E.
Published: December 2008

The regeneration of skeletal muscle cells was investigated in the extensor digitorum longus muscle (EDL) of rats subjected to hindlimb tourniquet ischaemia preceded by glycogen depletion. In this experimental model a distinct population of ‘white’ muscle cells are preferentially damaged, while there is minor damage to microvessels. A rapid regenerative response occurred after injury. Mitotic figures were obvious in satellite cells of damaged as well as of uninjured muscle cells within 48 h after the ischaemic insult. All debris of injured cells was phagocytized and removed within 72 h and replaced by clusters of myoblasts. Small immature muscle cells could be demonstrated within 96 h after injury. During the entire regeneration process the basic architecture of the muscle was preserved and surviving muscle cells were present among the regenerating ones. Histochemical investigations 3 weeks after injury revealed an increased number of ‘red’ muscle cells in the postischaemic EDL compared to the contralateral undamaged muscle. It is concluded that the described experimental model may be useful for studies on skeletal muscle regeneration.
Pharmacological characterization of the calcium‐insensitive, intermittent acetylcholine release at the rat neuromuscular junction
Authors: TABTI N. , LUPA M. T. , YU S. P. , THESLEFF S.
Published: December 2008

A variety of pharmacologically active compounds was surveyed for effects on the Ca2+‐insensitive miniature end‐plate potentials (slow mepps) induced by botulinum toxin type A (Botx) poisoning in rat muscle. The purpose was to gain insight into the release process responsible for this type of acetylcholine secretion. It was found that caffeine and dibutyryl cyclic adenosine 3′,5′‐monophosphate increased significantly the frequency of slow mepps in Botx‐poisoned muscles, but had no effect on slow mepps in control muscles. Vinblastine and cytochalasin B significantly increased the slow mepp frequency in Botx‐poisoned as well as in normal control muscles. Inhibitors of oxidative metabolism reduced the frequency of slow mepps by 90%, indicating a high energy requirement for this type of release. No agent was found to augment the slow mepp frequency above 1–2 Hz, suggesting that an upper limit exists for this type of packaging and release of acetylcholine.
Histochemical localization of carbonic anhydrase in the pig's exocrine pancreas
Authors: BUANES T. , GROTMOL T. , LANDSVERK T. , RIDDERSTRÅLE Y. , RæDER M. G.
Published: December 2008

Carbonic anhydrase is essential for the pancreatic secretion of NaHCO3. To localize the distribution of carbonic anhydrase in the exocrine gland and, hence, identify the potential cellular source of secreted NaHCO3, histochemical staining of carbonic anhydrase was carried out on pancreatic biopsies obtained from six pigs at both supramaximal intravenous secretin stimulation and at secretory rest. Tissue staining, using Hansson's technique, revealed a strong staining both in membranes and cytoplasm in the duct cells and a weaker cytoplasmic staining in the acinar cells. Staining reaction was abolished by 10‐5 mol I‐1 acetazolamide. Duct cells, accordingly, seem to be responsible for NaHCO3 secretion, while acinar cells appear unlikely to contribute substantially to NaHCO3 secretion.
The effects of tenotomy and overload on the postnatal development of medial gastrocnemius motor units in the cat
Authors: GOLLVIK L. , KELLERTH J.‐O. , ULFHAKE B.
Published: December 2008

Five‐ to 7‐day‐old kittens were subjected to tenotomy of either the medial gastrocnemius muscle (MG) or its synergists within the Achilles tendon. The effects of these operations on the postnatal differentiation of MG motor units were investigated when the cats had reached the adult stage. The MG tenotomy produced a substantial weight loss, while tenotomy of synergists induced only a minor weight gain of the MG muscle. Tenotomy of the MG synergists induced a marked prolongation of motoneuronal AHP durations in the overloaded MG. This prolongation affected equally motoneurones of the S and F types. The twitches of the tenotomized motor unit group showed a relatively slower relaxation than those of the overloaded group. The muscle unit properties of the tenotomized MG muscles showed a less distinct differentiation than those of the overloaded muscles. The basic features of the various motor unit types were, however, normal in both groups, and there was no evidence of a major shift in the proportions of different motor unit types. It is concluded that the postnatal differentiation of all types of MG motor units is largely unaffected by the abnormal situations introduced in the present study.
Circulatory events following spontaneous muscle exercise in normotensive and hypertensive rats
Authors: SHYU B. C. , THORÉN P.
Published: December 2008

In previous studies we have shown that spontaneously hypertensive rats (SHR) develop a running behaviour and, secondary to the running behaviour, develop an endorphin‐mediated analgesic effect. In the present study the role of the central endorphin system in the cardiovascular responses to spontaneous exercise in normotensive Wistar Kyoto rats (WKY) and SHR was investigated. The experimental design allowed us to record mean arterial pressure (MAP) and heart rate (HR) continuously for more than 1 week without interfering with the daily activities of the animals. They were active in running wheels during the dark period (19.00–07.00 h) and the activity was accompanied by a marked rise in HR. In SHR, a clear depression of blood pressure lasting for about for about 50 min was noted following each running period. The MAP during the post‐running depression was 131.4 ± 1.6 mmHg which was significantly lower than the pre‐running control value (145.2 ± 2.3 mmHg, P < 0.01). In contrast, MAP in the post‐running period in WKY was not significantly different from the pre‐running values. In addition, the depression period of SHR had a mean post‐running length of 49.7 ± 3.4 min, which is significantly longer than in the WKYs (37.8 ± 3.5 min, P < 0.05). In control rats, naloxone infusion had no effect on blood pressure but a marked bradycardia was observed. In nine running SHR receiving a naloxone infusion, their MAP during the depression period was not different from the control pressure. Our study indicates that endorphin systems are involved in the regulating of blood pressure and HR during muscle exercise in SHR. These systems trigger the transient depression of blood pressure observed immediately after a running period in the SHR