bluuebunny/crossref_metadata_2025 huggingface dataset:
Parallelism between Mechanical and Metabolic Responses to Cholecystokinin and Prostaglandin E2in Extrahepatic Biliary Tract
Authors: Andersson K.‐E. , Andersson R. , Hedner P. , Persson C. G. A.
Published: December 2008

The mechanical effects of the prostaglandins Ei, E2 and F2u were investigatedin vitroin isolated preparations of guinea‐pig gallbladder, cat gallbladder, and cat sphincter of Oddi. The actions of the prostaglandins, and particularly the effects of prostaglandin Ea, proved similar to those of cholecystokinin,i.e.contraction of the gallbladder and relaxation of the sphincter of Oddi were produced; the responses were not influenced by tctrodotoxin or by blockade of adrenoceptors or cholinoceptors. In the anesthetized cat, prostaglandin E2increased the intraluminal gallbladder pressure and decreased the resistance to flow through the sphincter of Oddi. The contractile responses in guinea pig gallbladder after prostaglandin E2were preceded by a decrease in the tissue levels of cyclic AMP and an activation of phosphodiesterase. The relaxation produced by prostaglandin Ea in the cat sphincter of Oddi was associated with an increase in the cyclic AMP content of the tissue, despite an inci'eased phosphodiesterase activity. These metabolic changes were similar to those observed in response to cholecystokinin. The similarities in mechanical and metabolic effects between prostaglandin Ea and cholecystokinin and the possible role of prostaglandin Ea in mediation of the actions of cholecystokinin on the extrahepatic biliary tract are discussed.
Brain Uptake of Lactate, Antipyrine, Water and Ethanol
Authors: Gjedde Albert , Anderson Jan , Eklöf Bo
Published: December 2008

Brain uptake of antipyrine, water and ethanol was studied in rats under normo‐, hypo‐ and hypercapnic conditions. Brain uptake of D‐ and L‐lactate was studied in normal rats. The uptake was determined with the Oldendorf method, using single common carotid arterial injections of a mixture of 14C‐labeled test substance and tritiated reference substance. The results demonstrate that L‐lactate is taken up by the brain in significant amounts. The results also demonstrate marked differences in the uptakes of antipyrine, water and ethanol. The brain uptake of antipyrine is lower, the brain uptake of etnanol higher, than of water. The brain uptake of all 3 substances was shown not to be affected by changes in cerebral blood flow, although a decrease of brain uptake of antipyrine relative to cthanol was observed during hypo‐ and hypercapnia.
Influence of Peritubular Hydrostatic and Oncotic Pressures on Fluid Reabsorption in Proximal Tubules of the Rat Kidney
Authors: ÅGerup Bengt
Published: December 2008

Proximal tubular reabsorption was measured with the split droplet technique under the following conditions. Group I. Star vessel perfusions with ultrafiltrate in the presence of human serum albumin (HSA) and with ultrafiltrate alone. Group 2. Capillary perfusions, under locally high flow rates, with ultrafiltrate in the absence or presence of HSA. Group 3. Subcapsular perfusions with ultrafiltrate of high HSA concentrations but under low hydrostatic pressure and ultrafiltrate of low HSA concentrations but under elevated hydrostatic pressure. In Group I, the presence of HSA increased the reabsorptive rate, whereas ultrafiltrate alone had no provable effect on the reabsorptive rate. In Group 2, a flow dependent decrease of the reabsorptive rate, that was not influenced by the presence of HSA, was observed. Finally, in Group 3, high concentrations of HSA did not alter the reabsorptive rate, whereas elevation of the hydrostatic pressure decreased the reabsorptive rate. The results cannot be explained on the basis of a simple passive mode of action of colloid osmotic and hydrostatic pressure on the reabsorptive rate. The possibility of a direct tubulae capillary transport route is discussed.
Observations of the Early Diuretic Response after Intravenous Administration of Bumetanide and Furosemide in Dogs
Authors: Olsen Uffe Bang
Published: December 2008

A transient natriuretic peak was observed in dogs the third minute after the i.v. administration of the highly active diuretics bumetanide and furosemide. The peak is dependent on the sodium balance such that it is potentiated during positive sodium balance and is not observed in sodium depleted dogs. A relationship exists between the simultaneous occurrence of the peak and abolition of the cortico‐medullary electrolyte gradient.
Atropine Sensitivity of the Rat Urinary Bladder during Nerve Degeneration
Authors: Elmér Mats
Published: December 2008

The pressure response of the rat urinary bladder to electrical stimulation of the pelvic nerve at a low stimulation frequency was found to be almost completely atropine resistant. However, the response to stimulation of the degenerating pelvic nerve 20–30 h after section of the nerve postganglionically using maximal stimulation frequency was totally abolished by atropine or the parasympatholytic agent Hoechst 9980. The responses were not affected by hexamethonium or dihydroergotamine, but were potentiated by eserine. The non‐adrenergic portion of the bladder response to stimulation of the degenerating hypogastric nerves was also abolished by atropine or Hoechst 9980. It is concluded that the transmitter activating the detrusor muscle at stimulation of the pelvic nerve or the non‐adrenergic part of the hypogastric nerve probably is acetylcholine.
Effects on the Ventral Spinocerebellar Tract Neurones from Deiters' Nucleus and the Medial Longitudinal Fascicle in the Cat
Authors: Baldissera F. , Roberts W. J.
Published: December 2008

Effects from the vestibulospinal tract (VST) and from fibres descending in the medial longitudinal fascicle (MLF) on the cells of origin of the ventral spinocerebellar tract (VSCT) have been studied with intracellular recording. Out of 110 VSCT neurones, the VST evoked monosynaptic EPSPs in 27, di‐ or polysynaptic EPSPs in 56 and disynaptic lPSPs in 26. In 93 tested VSCT cells, MLF stimulation evoked monosynaptic EPSPs in 26, monosynaptic IPSPs in 2, di‐ or polysynaptic EPSPs in 25 and disynaptic IPSPs in 21, Convergence of monosynaptic EPSPs from VST and MLF was found in a small proportion of cells whereas the two descending pathways evoked reciprocal effects in another small group of neurones. Convergence of monosynaptic EPSPs from VST or MLF and from group 1 afferents was also modest. In 9 VSCT neurones there was convergence of monosynaptic excitation and disynaptic inhibition from the vestibulospinal tract and the same pattern from MLF was recorded in 9 neurones. The results are discussed in view of the hypothesis that VSCT neurones carry information on the interneuronal transmission in the spinal cord.
In Vitro Uptake of Bile Acids by Choroid Plexus, Kidney Cortex and Anterior Uvea. I. The Iodipamide‐sensitive Transport Systems in the Rabbit
Authors: Bárány Ernst H.
Published: December 2008

Renal cortex, anterior uvea, lateral choroid plexus and terminal ileum accumulate14C‐cholate, glycocholate, deoxycholate and chenodeoxycholate to considerable tissue/medium ratios. Iodipamide partly inhibits accumulation by kidney, uvea and plexus but not ileum. In renal cortex the sensitive part is ˜10, 60 and 90% for dihydroxy acids, cholate and glycocholate respectively. Hippurate depresses uptake in kidney and uvea but hardly in plexus. Simultaneous uptake by renal cortex and uvea of14C‐cholate or glycocholate,125I‐iodipamide and131I‐o‐iodohippurate was studied with unlabelled iodipamide and hippurate as inhibitors. The concentration‐dependence of the inhibition required the assumption of 4 partly overlapping iodipamide‐sensitive transport systems handling the 4 test substances: the hippurate (H‐) system, one moderately (L1) and one very hippurate‐resistant (L2) part of the liverlike L‐system and a fourth system called BS, more evenly inhibitable by iodipamide and hippurate than the others. The L2‐system carries iodipamide but very little bile acids. No iodipamide‐sensitive system clearly specialized for bile acid transport was found. The systems have only moderate affinity for bile acids and probably treat them just as large organic anions. A new mathematical procedure to test the degree of complexity of composite transport systems without kinetic assumptions was used.
Cerebral Blood Flow and Oxygen Consumption in the Rat in Hypoxic Hypoxia
Authors: Jóhannsson Halldór , Siesjö Bo K.
Published: December 2008

In order to measure cerebral blood flow (CBF) and cerebral metabolic rate for oxygen (CMRo2) at pronounced degrees of hypoxic hypoxia the Pao2 of artificially ventilated and normocapnic rats was reduced to between 47 and 22 mm Hg for 15–25 min with subsequent measurements of CBF, using a 133Xenon modification of the Kety and Schmidt technique, and of the arteriovenous difference in oxygen content, the venous blood being obtained from the superior sagittal sinus. When the Pao2 was reduced to minimal values of 22 mm Hg CBF increased 4‐ to 6‐fold, the increase in CBF being unrelated to changes in blood pressure or Paco2. The CMRo2 remained unchanged at all levels of hypoxia. It is concluded that the maintenance of a normal, or near‐normal, cerebral energy state even at extreme degrees of hypoxic hypoxia depends solely on a homeostatic increase in CBF.
Adrenergic and Cholinergic Innervation of the Rat Urinary Bladder
Authors: Alm Per , Elmér Mats
Published: December 2008

The autonomic innervation of the rat urinary bladder was studied using histochemical methods and nerve stimulations. A sparse adrenergic innervation of the detrusor muscle was found. It was supposed to originate from long adrenergic neurones. The trigonum area had a rich supply of adrenergic fibres, probably derived from short adrenergic neurones. A uniformly rich supply of acetylcholine‐esterase (AChE)‐positive nerves was found in the whole bladder. Postganglionic sympathetic denervation caused no detectable change of adrenergic or AChE‐positive nerves in the bladder, while parasympathetic decentralization or denervation produced a total disappearance of adrenergic fibres. The AChE‐positive nerves were appreciably reduced in number after parasympathetic decentralization and not detectable after postganglionic denervation. Neither adrenergic nor AChE‐positive ganglion cells could be demonstrated in the bladder wall. Electrical stimulation of the hypogastric nerves or the pelvic nerves distal to the pelvic ganglia elicited contraction of the detrusor muscle. The responses were not affected by hexamethonium, dihydroergotamine or propranolol but were slightly reduced by guanethidine, reduced to about 40% by atropine and potentiated by eserine. Stimulation of the pelvic nerve proximal to the pelvic ganglion was partially blocked by hexamethonium. It is concluded that the urinary bladder of the rat is supplied by postganglionic adrenergic fibres mainlyviathe pelvic nerves and only to a lesser extentviathe hypogastric nerves. Probably cholinergic fibres pass to the bladder mainlyviathe pelvic nerves but alsoviathe hypogastric nerves, having their cellbodies outside the bladder wall, partly proximal to the pelvic ganglia.
Selective Localization of Histamine to Electron Densen Granules in Antigen‐Challenged Sensitized Rat Mast Cells and to Similar Granules Isolated from Sonicated Mast Cells: An Electron Microscope Autoradiographic Study
Authors: Anderson Per , Uvnäs Börje
Published: December 2008

The subcellular localization of histamine was studied in sensitized rat mast cells following antigen challenge and in granules obtained from sonicated cells, using an electron microscope autoradiographic technique. The mast cells were furnished with labelled histamine by incubation in3H‐histidine. The silver grain distribution (reflecting the localization of radioactive histamine) was highly non‐random. The highest silver grain densities occurred over homogeneous, electron dense (normal) granules and moderately electron dense granules. Swollen, less electron dense (“changed”) granules with a reticular appearance and devoid of a limiting membrane had the lowest density of all subcellular structures studied and were therefore probably almost free of histamine. There was a good correlation between the percentage of electron dense granules, the histamine content and the silver grain density in saline‐washed granule fractions isolated after sonication of mast cells for different times. These results support the hypothesis that histamine release occurs during the sequential exocytosis of storage granules, and during the sonication of mast cells, probably as a cation exchange between the amine, which is ionically bound to the heparin‐protein complex of the granule matrix, and cations from the extracellular fluid. The exchange will occur as soon as the perigranular membrane becomes permeable to water and cations.
Search for an Endogenous Ligand for the Opiate Receptor
Authors: Terenius L. , Wahlström A.
Published: December 2008

It was investigated whether there is an endogenous factor in the brain which binds to the opiate receptor in neural tissue. Extracts from rat brain were processed in different ways; fractions were assayed for ability to inhibit the receptor binding of dihydromorphine. There was no evidence for high‐molecular weight substances or lipid soluble substances with such ability. On the other hand, processing of an acid water extract of brain except the cerebellum (which was negative) yielded an active fraction with receptor blocking activity. This fraction was heat stable, polyionic and had an apparent molecular weight of 1000–1200 dalton. These and other characteristics indicate that it might well be a peptide. The factor inhibited binding to the opiate receptor in synaptic plasma membranes of rat brain and to the receptor of the guineapig ileum although it was less effective on the latter, particularly after long‐term incubation. The interaction between the factor and dihydromorphine was reversible and apparently competitive.
Postnatal Ontogenetic Development of Neurogenic and Myogenic Control in the Rat Portal Vein
Authors: Ljung Bengt , (McMurphy) Dorothy Stage
Published: December 2008

The postnatal ontogenetic development of neuro‐effector control in vascular smooth muscle of the singleunit type has been studied in the rat portal vein. Contractile activity was recorded isometrically in isolated preparations from rats 2–38 days of age and in adults rats. Spontaneous activity, characteristic of the adult portal vein, appeared abruptly during the third postnatal week. Whereas, induced responses to noradrenaline (NA) and acetylcholine (Ach) appeared early during the first week and responses to transmural nerve stimulation occurred at the end of the first week. The appearance of spontaneous activity was accompanied by significant increases in sensitivity to NA (log Ed50) and to transmural nerve stimulation (frequency giving half maximum response), but not to Ach. Also, maximum responses for NA and nerve stimulation relative to Ach responses tended to increase during the first there weeks. It is concluded that the development of a mechanism supporting myogenic propagation as revealed by highly synchronized spontaneous contractions is an important factor for promoting the effectiveness of sympathico‐adrenergic control in this type of vascular smooth muscle.
Levels of Cyclic AMP and Electrical Events during Inhibition of Contractile Activity in Vascular Smooth Muscle
Authors: Ljung Bengt , Isaksson Olle , Johansson Börje
Published: December 2008

The possible relationship between changes in electrical and mechanical activity and in tissue levels of cyclic AMP (cAMP) during relaxation of the myogenically active rat portal vein has been elucidated in response to different inhibitory stimuli. Isoproterenol, 10‐5M, caused an initial pronounced inhibition of spike discharge and contractions followed by a partial recovery over the 15 min exposure period. This inhibitory response was associated with doubling of tissue cAMP after 1 min and a less pronounced increase in later measurements (5 and 15 min). Papaverine, 10‐4M, caused, in contrast, an inhibition of electrical and mechanical activity which developed gradually over the entire 15 min exposure period. The levels of cAMP at 1, 5 and 15 min all exceeded the corresponding values obtained with isoproterenol. The two drugs in combination gave a biphasic inhibitory response associated with a sustained large increase in the level of cAMP. These drug induced inhibitions were thus accompanied by increased levels of cAMP, but the different time courses of the electromechanical responses could not be related to corresponding variations in the content of cAMP. Hyperosmolality (+ 150 mM sucrose) and mechanical vibrations (100 Hz) elicited differentiated inhibitions of smooth muscle activity without changes in tissue cAMP. The mechanical effects elicited by isoproterenol, papaverine and hyperosmolality were accompanied by approximately parallel changes in electrical spike discharge. It is concluded that increased levels of cAMP are not indispensible for vascular smooth muscle relaxation, and that the magnitude of pharmacologically induced inhibitions are not always closely related to the total tissue content of the nucleotide.
Release of Gastrin and Vagal Stimulation in the Cat
Authors: Uvnäs B. , Uvnäs‐Wallensten K. , Nilsson G.
Published: December 2008

Gastrin released by electrical vagal stimulation was measured in the portal blood of eviscerated cats. Blood flow was recorded by a drop chamber technique and the total gastrin output calculated. Basal peripheral gastrin levels averaged 65 pg/ml and basal portal levels 225 pg/ml. On unilateral vagal stimulation with frequencies above 3–4 Hz gastrin release rapidly increased, reaching a peak within 5–10 min. In spite of continued stimulation and independent of frequency, the gastrin levels declined and returned to basal values after a total of 2–3 000 stimuli. A new maximal response could be induced first after a recovery period of 15–30 min. In the same cat stimulation of either the left or the right vagus released equal maximal amounts of gastrin (average 32 000 pg). The maximal gastrin output on vagal stimulation corresponds to less than 1% of the total content of antral gastrin determined with radioimmunoassay.
The Pressure‐Flow Relationship of Different Nephron Populations in the Rat
Authors: Kállskog Ö. , Lindbom L. O. , Ulfendahl H. R. , Wolgast M.
Published: December 2008

The mechanisms behind the autoregulation of the total renal blood flow and the glomerular filtration rate are unclear. In this investigation a modified microsphere technique was applied to measure the blood flow at different depths in the renal cortex during normotensive and hypotensive conditions. No autoregulation was found in the outer cortex while it was well pronounced in the inner one. During similar conditions, glomerular capillary pressure, welling point pressure and intratubular pressure were recorded. By combining these results with the blood flow data, the preglomerular and postglomerula resistances were calculated. It was then found that the preglomerular resistance decreased and the postglomerular resistance increased when the blood pressure was lowered. The results indicate a redistribution of blood flow from the outer parts to the inner parts of the cortex when the blood pressure is decreased. The redistribution of the blood flow might explain the well known linear relationship between the arterial pressure and the urine flow. The single nephron filtration rate of the outermost glomeruli could be calculated and the results seem to indicate a non‐equilibrium at the end of the glomerular capillaries.
Effect of Central Depressants on the Acoustic Middle Ear Reflex in Rabbit: A method for quantitative measurements of drug effect on the CNS
Authors: Borg E. , Møller A. R.
Published: December 2008

The respective effects of pentobarbital‐sodium, enibumal‐sodium, urethane, urethane‐chloralose and lidocaine on the function of the acoustic middle ear reflex in the rabbit were studied. The response of the middle ear muscles was measured by recording changes in both ears' acoustic impedance when the reflex was elicited by applying pure tone stimuli (2000 Hz) to the two ears one at a time. In that way both the crossed and the uncrossed reflexes were studied. All the drugs were found to depress the reflex in such a way that a higher sound intensity was required after administration to achieve the same impedance change as before. The effect of the anesthetics was roughly proportional to their known anesthetic power. Lidocaine produced only a slight depression of the reflex. The crossed reflex showed a greater susceptibility to the general anesthetics than did the uncrossed reflex which suggests a greater complexity of the crossed reflex. Because the method of recording the reflex response does not require any surgery and is equally well applicable in unrestrained rabbits and in humans, it is suggested as a way of testing the effect of drugs on the central nervous system.
Vasomotor Nerve Control of Isolated Arteries and Veins
Authors: Ljung Bengt , Bevan John A. , Pegram Barbara L. , Purdy Ralph E. , Su Mary
Published: December 2008

In order to compare neuro‐effector function in different blood vessels, frequency‐response relationships were determined for the following preparations: 1) Isolated rings of the proximal saphenous, distal saphenous and ear arteries, the parietal branch of the internal iliac vein and the small saphenous vein from the rabbit, 2) spiral strips of the rabbit pulmonary artery and 3) longitudinal preparations of the rat portal vein. In each rabbit tissue only one low (≤4 Hz) and one high (≥8 Hz) transmural nerve stimulation frequency was applied until steady state responses were obtained and these were expressed as a percentage of a maximum response to exogenous noradrenaline (NA) applied in each experiment. The general shape of the frequency‐response curves was similar, but differences in steepness and amplitude of the maximum neurogenic response relative to exogenous NA were found. The steepness of the frequency‐response relationships of the veins tended to be greater than those of the arteries. It appears that factors such as close neuro‐muscular contacts, presence of terminal nerve fibres within the media and the operation of mechanisms for myogenic propagation of activity contribute to the effectiveness of neurogenic vascular control as revealed by frequency‐response curves.In vivo,geometrical factors can greatly augment the hemodynamic significance of the observed differences.
Stimulation of Adrenergic Nerve Fibres to the Urinary Bladder of the Rat
Authors: Elmér Mats
Published: December 2008

The contraction of the rat detrusor muscle caused by electrical stimulation of the hypogastric or pelvic nerves was followed by relaxation when the nerves were stimulated for a short period. The relaxation was more pronounced when the initial contraction was reduced by atropine. It was found to be mediated by adrenergic fibres acting on inhibitory β2‐receptors. Stimulation of the hypogastric or pelvic nerves at high frequencies increased the contractile response probably via adrenergic fibres activating excitatory α‐receptors.
Affinity of Noradrenaline and Dopamine for Neural α‐Receptors Mediating Negative Feedback Control of Noradrenaline Secretion in Human Vasoconstrictor Nerves
Authors: Stjärne Lennart , Brundin Jan
Published: December 2008

Isolated superfused field stimulated biopsy specimens of human peripheral arteries and veins, preincubated with3H‐(‐)‐noradrenaline (NA) to label the neural stores of NA, were used to study the potency of dopamine (DA) and of NA as triggers of α‐adrenoceptor mediated negative feedback control of sympathetic neurotransmitter secretion, evoked by stimulation with trains of 300 shocks at 1 Hz. In this preparation DA was found to be only slightly less potent than NA in depressing both the secretion of3H‐NA, and the contractile response, evoked by nerve stimulation. DA depressed the contraction evoked by exogenous NA as well, but to a very much smaller extent. On the other hand, DA was a very weak agonist on the α‐receptors of the smooth muscle; nearly 1 000 times higher concentrations of DA were required to mimick contractions evoked by exogenous NA. The results show that the neural α‐receptor function involved in control of NA secretion differs considerably from the α‐receptors ofe.g.smooth muscle, with respect to sensitivity to DA. It seems possible that the observed depressing effect of DA on NA secretion may be of pharmacological and clinical interest; it may at least in part explain the vasodilating effect of DA infusions in man.
Intracellular Distribution of Amines Taken up by Rat Mast Cells In Vitro
Authors: Bergendorff Anders
Published: December 2008

Mast cells isolated from rat peritoneal and pleural cavities were incubatedin vitrowith radioactively‐labelled histamine (Hi), 5‐hydroxytryptamine (5‐HT), dopamine (DA), noradrenaline (NA), tyramine (TA), phenylethylamine (PhEA), tryptamine (TrpA), ephedrine (Eph) or amphetamine (Amph). All these amines were taken up by the mast cells. The dose‐response curves for the compound 48/80‐induced release of endogenous Hi and for the various amines taken up by the cells were compared. The release curves for Hi, 5‐HT, DA, NA and TA were found to be similar to that for endogenous Hi, while those for PhEA, TrpA, Eph and Amph were different from that for endogenous Hi. The uptake of Hi, 5‐HT, DA, PhEA, TrpA and Eph into granules in mast cells was studied. Membrane‐bound granules were obtained by sonication of mast cells incubated with the respective amine, followed by differential centrifugation. The amine content of these granules was then measured. Hi, 5‐HT and DA were found to be mainly localized to the granules, while a smaller proportion of the PhEA, TrpA and Eph was found there, the rest being located extragranularly. The present results suggest that, when taken up by rat mast cells, even amines which are not endogenous to the cells are stored in the same way as the endogenous amines Hi and 5‐HT.
The Spread of the Action Potential through the T‐System in Hagfish Twitch Muscle Fibres
Authors: Nicolaysen Kåre
Published: December 2008

The input impedance of twitch muscle fibres of the Atlantic hagfish has been measured with sinusoidal transmembrane currents. The apparent specific membrane resistance and capacitance decreased markedly with frequency, and were relatively independent of fibre diameter. A model of the T‐system based on anatomical observations, was used to predict the input impedance in the normal solution (artificial sea water). The changes in input impedance produced by glycerol treatment, low chloride solution, reduced pH and isotonic solutions with low ionic strength were easily interpreted in terms of the same model. The model predicts severe attenuation of the action potential if conducted electrotonically by the transverse tubules towards the center of the fibre.
N‐Acetyltransferase and Hydroxyindole‐O‐Methyltransferase Activity in Intraocular Pineal Transplants: Diurnal Rhythm as Evidence for a Functional Sympathetic Adrenergic Innervation
Authors: Bäckström Maria , Olson Lars , Seiger ÅKe
Published: December 2008

Immature rat pineal grafts were transplanted bilaterally to the anterior eye chamber of adult male rats. The transplants matured and became sympathetically innervated from the host iris and synthesized 5‐hydroxytryptamine as revealed by fluorescence histochemistry. Transplants were used to investigate whether the newly formed nerve terminals were functional and thus could induce a rhythm in pineal N‐acetyltransferase (NAT) enzyme activity and hydroxyindole‐O‐methyl transferase (HIOMT) enzyme activity. Thein situpineal glands from the recipient animals exhibited NAT and HIOMT levels and diurnal variations of enzyme activities no different from control rats without transplants. Sympathetically innervated transplants showed lower NAT enzyme activity than thein situpineals but did yield a highly significant increase in darkness NAT activity as compared to light NAT activity (20:1). Sympathetically denervated transplants showed a much smaller rise in darkness NAT enzyme activity as compared to light values (1.8:1) but the rhythm was still statistically significant (p < 0.01). Sympathetically innervated transplants had a higher HIOMT activity in darkness than in light (2.7:1). The HIOMT activity of the sympathetically denervated grafts was invariably low. Protein contents of transplants were found to be significantly lower thanin situpineal protein content but failed to show a diurnal variation.
Phenylethanolamine‐N‐methyl Transferase (PNMT) Activity and Catecholamine Content in Chromaffin Tissue and Sympathetic Neurons in the Cod,Gadus morhua1
Authors: Abrahamsson Tommy , Nilsson Stefan
Published: December 2008

The activity of phenylethanolamine‐N‐methyl transferase (PNMT) has been measured in the chromaffin tissue of the head kidney and in the sympathetic neurons of the coeliac ganglion/splanchnic nerve in the cod. The content of adrenaline and noradrenaline in these tissues and in other adrenergically innervated tissues and blood plasma was also determined. Adrenaline dominates over noradrenaline in most sympathetically innervated tissues, in the chromaffin tissue and in blood plasma, but not in the muscularis mucosae of the swimbladder. High PNMT activity was found in the chromaffin tissue in the walls of the posterior cardinal veins, and also in sympathetic neurons. It is concluded that the adrenaline found in the sympathetic nerves may originate from intraneuronal adrenaline synthesis, but also from circulating adrenaline which is taken up and stored.
Adenosine 3‘, 5’‐cyclic Monophosphate in Perfused Rat Hearts Exposed to Isoprenaline and Dopamine
Authors: Osnes Jan‐Bjørn , ØYe Ivar
Published: December 2008

Isoprenaline and dopamine increased cyclic AMP (cAMP) content and contracile activity of isolated perfused rat hearts. The changes of cAMP levels depended on the mode of drug administration. Isoprenaline (4 × 10‐10mol) administered to the perfused heart as a relatively concentrated bolus, caused a substantial, rapid and transient increase of cAMP. Isoprenaline (2 × 10‐10mol and 4 × 10‐10mol) and dopamine (10‐7mol) diluted in 40 ml of perfusate which was continuously recirculated through the heart, caused a gradual increase of cAMP content which approached an apparent steady state. cAMP accumulation occurred at isoprenaline concentrations above 10‐9M and at dopamine concentrations above 10‐6M. Both agents also increased cAMP labelling from14C‐adenine in the perfusate, probably indicating increased cAMP synthesis. Isoprenaline at 2 × 10‐8M and 10‐7M increased labellingmorethan content of cAMP. Isoprenaline and dopamine also increased phosphorylaseaactivity. An association between increased cAMP contents and increased contractile activity was revealed by both the time‐response and the dose‐response curves of hearts exposed to isoprenaline and dopamine. Since both agents stimulate adrenergic β‐receptors in cardiac muscle, the results are concordant with the hypothesis that cAMP is involved as a mediator of the inotropic response to adrenergic β‐stimulation.
Sympathetic Control of Cerebral Blood Flow in Acute Arterial Hypertension
Authors: Bill Anders , Linder Jan
Published: December 2008

The cervical sympathetic chain on one side was stimulated electrically at 10–20 Hz and an acute rise in arterial blood pressure was produced by: intravenous injection of angiotensin, ligation of the thoracic aorta, or ligation of the aorta combined with injection of metaraminol. The blood flow through the cerebrum and the cerebellum was determined by using labelled microspheres. At high blood pressures there was multifocal breakdown of the blood‐brain barrier in the cerebrum as indicated by leakage of Evans blue. The breakdown was restricted to the control side or much more marked on that side than on the stimulated side. Sympathetic stimulation prevented also breakdown of the blood‐aqueous barrier. The blood flow through the cerebrum on the control side was higher than that on the stimulated side in all experiments. Regions with breakdown of the blood‐brain barrier had flow rates which were about 10 times normal values. Cerebellar blood flow was less affected by the hypertension and did not react significantly to sympathetic stimulation. The results indicate that stimulation of the sympathetic nerves to the brain tends to prevent forced dilatation of the arterioles with a resulting regional overperfusion with blood and breakdown of the blood‐brain barrier. It is concluded that one role of the sympathetic nerves supplying the brain is to extend the pressure region with autoregulation in its upper part under conditions of a general increase in sympathetic vasomotor activity.
A Comparison between the Central Effects of Angiotensin II and its Fragments, Des1‐Angiotensin II and Des1, 2‐Angiotensin II
Authors: Eriksson Lea , Fyhrquist F.
Published: December 2008

Angiotensin II is known to act centrally on fluid balance and blood pressure (cf.Severs and Daniels‐Severs 1973). The natural fragment of angiotensin II, 2–8 heptapeptide, so‐called “angiotensin III”, has been found to increase adrenal aldosterone production effectively (Blair‐Westet al.1971), whereas its action on vascular muscle cells is less (cf.Regoli, Park and Rioux 1974).
Influence of phenobarbital on changes in the metabolites of the energy reserve of the cerebral cortex following complete ischemia
Authors: Nordström Carl‐Henrik , Siesjö Bo K.
Published: December 2008

The present study, which concerns the rate of changes in the cerebral cortex concentrations of phosphocreatine (PCr), ATP, ADP, AMP, lactate and pyruvate during complete ischemia, had the objective of finding out whether or not phenobarbital retards depletion of tissue energy reserves during ischemia. Ischemia was induced for periods of 10 s to 10 min in animals maintained on 70% N2O or given 150 mg. kg‐l of phenobarbital. The results showed that the barbiturate anaesthesia delayed utilization of ATP during the first 2 min. However, after 5 min of ischemia PCr and ATP concentrations, as well as the calculated adenylate energy charge, were identical in animals anaesthetized with nitrous oxide and phenobarbital. Thus, phenobarbital induces a very moderate delay in the depletion of cerebral energy reserves that occurs during complete ischemia. The results obtained after 5–20 s of ischemia allowed calculation of energy (˜P) utilization according to Lowry et al (1964). The closed system method gave values for Putilization which were not far from those obtained by CMRo, measurements. However, with normal values for metabolic rate (70% N2O) valid estimates are obtained only with very short ischemic periods (5–10 s) and, with such short periods, the oxygen content of the tissue may introduce an error.
Effect of sympathetic stimulation on the blood brain barrier dysfunction induced by amphetamine and by epileptic seizures
Authors: Johansson Barbro B. , Lund Staffan
Published: December 2008

Stimulation of the sympathetic nerves to the brain is known to make the resistance vessels able to with stand a higher blood pressure,i.e. to prevent blood‐brain harrier (BBB) dysfunction and overpcrfusion in acute hypertension. When hypertension occurs concomitantly with a metabolic vasodilatatione.g. during epileptic seizures and after amphetamine‐administration, protein leakage in the brain is more pronounced than in hypertensionper se. Unilateral stimulation of the cervical sympathetic chain during the administration of amphetamine or bicuculline—the latter a GABA‐receptor blocking substance that induces epileptic activity—attenuated the leakage of Evans blue‐albumin and125IHSA into the brain. Our results thus indicate a prophylactic effect of sympathetic stimulation also when hypertension is combined with a nletabolically induced vasodilatation. The sympathetic nerves may constrict both extracerebral arteries and intracerebral resistance vessels. Unexpectedly the effect on the BBB of unilateral stimulation was to a great extent bi lateral under the present experimental conditions.
Estrogen induced inhibition of3H‐noradrenaline release in the uterus and portal vein of the rat
Authors: Bengtsson Bengt
Published: December 2008

The influence of estrogen treatment on3H‐noradrenaline release, induced by potassium or calcium, was studied in isolated preparations of the uterus and the portal vein of the rat. Uterine strips of oophorectomized rats responded with contraction followed by transient relaxation when immersed in a medium containing 127 mM potassium. The transient relaxation was accompanied by an increased rate of3H‐nor‐adrenaline efflux. When the uterine strips were bathed in calcium‐free potassium solution, addition of calcium (3 mM) evoked an increased outflow of3H‐noradrenaline coinciding with a relaxation phase of the contractile response to calcium. After estrogen treatment of the rats the pattern of response was altered. The uterus then responded to potassium and calcium with sustained contractures and with a relatively small (potassium) or with no (calcium) increase of3H‐noradrenaline efflux. Normetanephrine (5 × 10‐‐5M) did not influence the uptake or release of3H‐noradrenaline in either non‐estrogenized or estrogen treated rats uterus. Calculations, based on the amounts of3H‐noradrenaline released by potassium and on the inhibitory effects of desipramine (10‐‐5M) on neuronal uptake of noradrenaline, suggested that similar amounts of tracer were accumulated in the adrenergic nerves of both non‐estrogenized and estrogen treated preparations. Tyramine (10‐‐4M) had a weaker stirnulatory effect on3H‐noradrenaline release than potassium, and the tyramine induced release was not inhibited by estrogen treatment. Strips of the rat portal vein responded to potassium with an increased rate of3H‐noradrenaline efflux. As in the uterus, estrogen treatment reduced the release of3H‐noradrenaline in response to potassium. The adrenolytic effect of estrogen is possibly due to reduced entry of calcium ions into the nerve terminal.
Vasopressin release induced by hemorrhage in the goat
Authors: Larsson B. , Olsson K. , Fyhrquist F.
Published: December 2008

Effects of moderate hemorrhage were studied in normovolemic and hydrated conscious goats. Plasma arginine vasopressin (AVP) in jugular vein blood did not rise in response to bleeding of 8 and 12 ml/kg b.wt. After a blood loss of 16 ml/kg an abrupt and conspicuous rise in plasma AVP (to > 10 times basic level) was seen in 50% of the experiments, whereas no rise in AVP occurred in the remaining experiments. Bleeding at 20 and 24 ml/kg gave a more consistent AVP response. Hydration did apparently not reduce the AVP‐responsiveness to bleeding. The plasma vasopressin concentration returned to pre‐hemorrhage level about 3 h after bleeding,i.e. before the blood was re‐transfused. A minor, and inconsistent rise in plasma renin activity occurred in response to bleeding. Central venous pressure fell during hemorrhage and stayed depressed until the blood was re‐transfused. Since the depression was of the same order in all experiments, and was still present when plasma AVP had returned to pre‐hemorrhage level, the fall in venous pressure was obviously not the main cause of the AVP‐response. However, the pronounced riseinplasma vasopressin was correlated to a fall in the arterial pressure and to hyperventilation. No urge to drink developed during any of the hemorrhage experiments. It is concluded that the goat does not readily respond to hemorrhage with vasopressin liberation. When it happens, pressor amounts of the hormone are released, and a fall in arterial pressure and/or increased stimulation of respiratory chemoreceptors (hypoxia?) appear(s) to be the ultimate cause(s) of the release. This thirst‐independent regulation of vasopressin secretion is obviously of no importance in day to day control of water balance, but may help to maintain the arterial blood pressure in emergency situations.
Simultaneous measurements of capillary diffusion and filtration exchange during shifts in filtration‐absorption and at graded alterations in the capillary permeability surface area product (PS)
Authors: Rippe Bengt , Kamiya Akira , Folkow Björn
Published: December 2008

The diffusion exchange of Cr‐EDTA, using the single injection indicator diffusion method, was followed simultaneously with estimations of the capillary filtration capacity (CFC) in an “isogravimetric” rat hindquarter preparation during artificial perfusion and maximal dilatation. Measurements were performed at constant flow and during 1) shifts in filtration‐absorbtion, 2) alterations of perfused capillary wall area (graded rarification of capillary network by microsphere injection) and 3) during alterations of permeability (i.a. infusion of histamine). At maximal vasodilatation CFC was 0.037 ± 0.001 ml/min × mmHg × 100 g and PS for Cr‐EDTA 5.67 ± 0.13 ml/min × 100 g. During filtration or absorbtion, Cr‐EDTA transfer from vessels to interstitium changed only slightly but the situation may well be different for solute transfer from interstitium to vessels. Alterations in capillary wall area resulted in proportional changes in PS for Cr‐EDTA while the CFC changes were always relatively smaller. Histamine increased CFC some threefold with a marked increase in protein transfer, while PS for Cr‐EDTA increased only marginally. This hista mine effect could be ascribed mainly to an increase in the number of large pores which, because of their relative paucity, are of little importance for small molecular diffusion exchange but highly important for convective and macromolecular exchange.
Effects of dopaminergic agonists and antagonists on isolated cerebral blood vessels
Authors: Edvinsson L. , Hardebo J. E. , Mcculloch J. , Owman Ch.
Published: December 2008

The vasomotor response of dopamine and dopaminergic agonists was studiedin vitroon middle cerebral arteries from cat and pial arteries from humans. The action of various inhibitors was tested in order to define the receptors involved. A contractile response could be obtained by epinine, apomorphine and dopamine in the mentioned order of potency. The effect was blocked byalpha‐receptor as well as serotonin receptor antagonists. The mode of inhibition suggested that serotonin receptors rather thanalpha‐adrenoceptors mediated the dopamine‐induced contraction. A dose‐dependent dilatation could be evoked by the dopaminergic agonists on actively contracted pial arteries. The relative potency was epinine > dopamine > apomorphine. The order of potency for the agonists, together with blocking experiments (including a parallel shift in the log dose‐response curve induced by bulbocapnine), indicated that the vasodilatation is mediated by specific dopamine receptors.
Human plantar flexion strength and structure
Authors: FUGL‐MEYER AXEL R. , SJÖSTRÖM MICHAEL , WÄHLBY LENNART
Published: December 2008

Plantar flexion strengths were studied in 30 right‐handed males. Static and dynamic maximum plantar flexion torques were recorded, knees fully extended (0°) and in 90° flexion. In five of the subjects the soleus and gastrocnemius muscle structure were studied by light microscopy and enzyme histochemistry. Specimens were obtained by needle biopsy, usually bilaterally. Intraindividual declines of force were found to be a function of angular motion velocity. Static and dynamic torques correlated significantly. Peak torques were significantly greater (mean 15%) at the 0° than at the 90° knee angle and left maximum plantar flexion torques at 0° were greater (mean 10%) than right. Mean morphometric data on the m. soleus suggested right‐left symmetry, which could not be demonstrated for the m. gastrocnemius. Fibres with low stainability for myofibrillar ATPase (Type 1 fibres) had smaller diameters, but constituted the major part of the cross‐sectional areas. In these five non‐athletes no significant correlation between data on plantar flexion strength and morphometric data on triceps surae structure could be demonstrated. On the other hand, strength covariated with calf circumference.
Excess cumulative blood flow and repayment during reactive hyperemia in human cutaneous tissue
Authors: KRISTENSEN JOHANNES K. , HENRIKSEN OLE
Published: December 2008

The influence of duration of vascular occlusion upon the reactive hyperemic response in human cutaneous tissue was studied in 6 subjects. Blood flow in cutaneous tissue was measured dorsally on the distal phalanx of the second finger by the local133Xenon washout technique. Post‐occlusive blood flow, calculated from the steepest part of the133Xenon washout curve just after release of vascular occlusion, reached a maximum value when duration of vascular occlusion was 12 min. However, excess cumulative blood flow, i.e. the integrated blood flow during reactive hyperemia minus integrated pre‐ischemic blood flow for a period corresponding to the duration of the reactive hyperemic response, increased with increasing duration of vascular occlusion from 3 to 24 min. Fractional repayment, i.e. excess cumulative blood flow divided by pre‐ischemic blood flow times duration of vascular occlusion, was not correlated significantly to duration of vascular occlusion. However, there was a significant inverse correlation between fractional repayment and pre‐occlusive blood flow, indicating that, besides metabolic factors, pre‐ischemic blood flow in cutaneous tissue is influenced by other factors, such as heat regulation.
Effects of thyroliberin and 4‐aminopyridine on action potentials and prolactin release and synthesis in rat pituitary cells in culture
Authors: SAND O. , HAUG E. , GAUTVIK K. M.
Published: December 2008

Effects of thyroliberin (TRH) and 4‐aminopyridine (4AP) were studied on prolactin (PRL) secreting rat pituitary tumour cells in culture (GH3cells). Intracellular recordings obtained from the same cell before and during TRH stimulation showed this peptide to increase the spontaneous firing frequency and prolong the Ca2+dependent action potentials. These effects were mimicked by 4 AP, which acts by interfering selectively with voltage dependent ionic channels without affecting resting membrane properties. Optimal doses of TRH and 4AP approximately doubled the release of PRL. In contrast, TRH increased PRL synthesis 1.9‐fold while 4AP had no effect. Increased PRL synthesis is thus not a direct consequence of the hormone release. We conclude that TRH and 4AP both stimulates PRL release via the facilitating effects on the action potentials. TRH has additional intracellular effects which lead to increased synthesis of the hormone. The effects of TRH responsible for stimulation of PRL synthesis are not causally related to the impulse activity of the surface membrane of the cell.
Anaerobic threshold, skeletal muscle enzymes and fiber composition in young female cross‐country skiers
Authors: RUSKO H. , RAHKILA P. , KARVINEN E.
Published: December 2008

Anaerobic threshold (AT) and maximum oxygen uptake (max V̇o2) were determined in 15 young female cross‐country skiers, aged 15–20 years, during incremental bicycle ergo‐meter exercise. Succinate dehydrogenase (SDH), malate dehydrogenase (MDH), citrate synthase (CS) and lactate dehydrogenase (LDH) were analyzed biochemically and percentage of slow twitch fibres (%ST fibres, myosin adenosine triphosphatase staining) histochemically in muscle samples obtained from m. vastus lateralis. Max V̇o2 correlated significantly with anaerobic threshold in ml×kg‐1×min‐1 (mlAT) but when AT was expressed in percent of max V̇o2 (%AT) the correlation was insignificant. Significant correlations were found between %AT and SDH (r=0.63) and between mlAT and CS (r=0.58). Max V̇o2 showed no significant correlations with the enzymes studied or %ST fibres. The results of the study seem to support the hypothesis that anaerobic threshold is related to oxidative capacity of muscle.