bluuebunny/crossref_metadata_2025 huggingface dataset:
Blood pressure and heart rate response to voluntary and non‐voluntary static exercise in man
Authors: HULTMAN ERIC , SJÖHOLM HANS
Published: December 2008

6 healthy men produced static knee extension with one leg for 5 min. In one series of experiments the force was held constant at 20% of the isometric maximum voluntary contraction force. In another series of experiments the same subjects performed the same work non‐voluntarily by direct percutaneous electrical stimulation. Heart rate and blood pressure was continuously recorded. Heart rate increased by 40% and systolic and diastolic blood pressure by 30% and 50% in both kind of experiments. It is concluded that receptors within the muscle has the full capacity to adjust central circulation to the muscle work performed.
Shortening induced deactivation of skinned fibres of frog and mouse striated muscle
Authors: EKELUND M. C. , EDMAN K. A. P.
Published: December 2008

The depressant effect of active shortening, previously established in intact muscle fibres, was studied during calcium induced contractures of chemically skinned fibres from the semitendinosus muscle of Rana temporaria and the psoas muscle of the mouse. The decrease in contractile activity was determined by comparing the rate of force redevelopment (at a given tension level) after a large (test) and a small (control) release step. Under standard experimental conditions (ionic strength: frog 135 mM, mouse 190 mM; Ca2+ 3.0 μM; Mg2+: frog 25 μM, mouse 100 μM; MgATP2‐: frog 1.0 mM, mouse 2.0 mM) active shortening of 0.15 μm per sarcomere (in excess of control release) reduced the contractile activity by approximately 50% of the control in both frog and mouse muscle fibres. Full contractile activity was regained within 4 s during isometric activity after the shortening phase. The depressant effect of shortening was steadily reduced, to almost complete disappearance of the effect, by increasing the free calcium concentration within the range 1.5–12.0 μM. Similarly, an increase in ionic strength from 105 to 235 mM reduced the depressant effect by approximately 40%. In contrast, there was a progressive enhancement of the shortening effect as the magnesium ion concentration was increased from 25 to 590 μM. It is proposed that interaction between the myosin cross‐bridges and the thin filament during sarcomere shortening leads to a decrease in troponin‐calcium binding resulting in a temporary deactivation of the contractile system.
VIP as a mediator of hexamethonium‐sensitive, atropine‐resistant vasodilation in the cat tongue
Authors: LUNDBERG JAN M. , ÄNGGÅRD ANDERS , FAHRENKRUG JAN
Published: December 2008

Electrical stimulation (10 V, 0.2 ms) of the chorda‐lingual nerve caused a biphasic vasodilatory response in the cat tongue with an initial phase which was most marked at low frequencies and a maintained phase which increased with frequency. Simultaneously, there was a VIP release as indicated by a marked increased VIP output from the tongue. VIP output increased with time of stimulation and was most pronounced at high frequencies. Atropine abolished the initial phase of vasodilation at low frequencies as well as reduced this phase at medium frequencies. At high frequency stimulation (15 Hz), the vasodilation was still somewhat reduced by atropine but in contrast to the cat submandibular salivary gland, the duration of the vasodilatory response did not increase after atropine. Furthermore, atropine did not increase VIP output from the tongue during nerve stimulation. Hexamethonium completely abolished VIP release as well as most of the vasodilation upon stimulation of the chorda‐lingual nerve. The remaining vasodilation may be due to antidromic stimulation of unmyelinated trigeminal sensory neurons, since it was present when using high threshold stimulation parameters (10 V, 5 ms). Local intra‐arterial infusion of acetylcholine or VIP caused a marked vasodilation of the tongue. Also substance P infusion induced a vasodilatory response. The response to acetylcholine was atropine sensitive, while the effects of VIP and substance P were atropine‐resistant. Combined infusions of VIP and acetylcholine had an additive effect on vasodilation. In conclusion, the present data suggest that low threshold chorda‐lingual nerve stimulation induced a release of both acetylcholine and VIP from postganglionic neurons in the tongue. The contribution by these two agents in the vasodilatory response may then depend upon time and frequency of stimulation. In contrast to the VIP nerves in the submandibular gland, no evidence suggests that VIP release from vascular nerves in the tongue is affected by atropine. High threshold stimulation also induces antidromic vasodilation possibly mediated via substance P release.
Cross‐innervation of fast and slow‐twitch muscles by motor axons of the sural nerve in the mouse
Authors: TAXT TORFINN
Published: December 2008

The extensor digitorum longus (EDL) or soleus muscles of adult mice were cross‐innervated by the sural nerve (SN) and deprived of their original innervation. The number and sizes of motor units and the location of endplates in these muscles were studied 1.5 to 16 months later. In the EDL muscle, the SN cross‐innervated the original endplates. Very few ectopic endplates were seen, even when the nerve was implanted well outside of the original endplate area. Only 3% of the fibres were polyneuronally innervated. In the soleus muscle, however, the SN formed large numbers of ectopic endplates whether the nerve was implanted in the original endplate zone or outside of it. In addition, 20% of the muscle fibres were polyneuronally innervated. The SN cross‐innervated both EDL and soleus muscles completely. There was no preference for a particular group of the SN motoneurones since all the cross‐innervated muscles were innervated by all SN motor axons and the motor unit sizes of the SN were similar in the cross‐innervated EDL, and soleus muscles. It is concluded that intrinsic properties of a muscle determine the ability to form ectopic synapses. The distribution of the motor unit sizes is determined by the particular pool of motoneurones which innervates the muscle.
Molecular forms of gastrin in canine duodenum after antrectomy
Authors: BRODIN KERSTIN , NILSSON GÖRAN
Published: December 2008

Extracts of the proximal third of the duodenum from 8 antrectomized dogs with the gastrointestinal continuity restored by gastroduodenostomy (n=4) or gastrojejunostomy (n=4) as well as from 4 unoperated controls were subjected to gel chromatography. The eluates were all assayed using two different gastrin antisera, one directed against the COOH‐terminal end of gastrin and the other directed against the NH2‐terminal end of gastrin‐17. The gastrin component pattern was very similar in all antrectomized dogs regardless if they had a gastroduodenostomy or a gastrojejunostomy. Gastrin‐17 was found to dominate while the amount of gastrin‐34 was at most one tenth of that of gastrin‐17. Using the COOH‐terminal directed antiserum approximately 15% (mean value) of the total gastrin‐like immunoreactivity eluted in a peak appearing in the same region as the COOH‐terminal octapeptide of cholecystokinin. In unoperated control dogs the corresponding peak constituted approximately 70% (mean value) of the total gastrin‐like immunoreactivity. In two of the control dogs small amounts of gastrin‐like immunoreactivity appeared at the elution volumes of gastrin‐34 and gastrin‐17. In the duodenal extracts of all dogs gastrin‐like immunoreactivity was found between the elution sites of gastrin‐34 and gastrin‐17. This material probably represents cholecystokinin‐33. The present results show that the increase in duodenal gastrin found after antrectomy, which we have reported previously, is due mainly to an increase in gastrin‐17.
Cardio‐vascular and metabolic alterations caused by hemorrhage in fed and starved rats
Authors: QUIROS G. , WARE J.
Published: December 2008

Non‐starved (fed) and starved rats, sedated with a neurolept analgesic, were subjected to 45 min of hemorrhagic hypotension. The hemorrhage inflicted did not cause hypoxic changes, and left fed and starved animals with the same residual blood volume. Fed animals developed a state of hyperglycemic hyperosmolality and their free fatty acids tended to rise, while these observations were modified among starved animals. After 15 min of hemorrhage the cardiovascular parameters were the same in fed and starved animals, but at 45 min striking differences were observed. In fed animals, cardiac output, stroke volume, skin and muscle flows were substantially higher than starved animal values, while the latter animals had a higher heart rate and peripheral resistance. These effects are attributed to the state of hyperosmolality developed by the fed animals, and can explain the association between nutritional status and survival in hemorrhage.
Description of the structural control systems of ovum transport in the quail oviduct
Authors: ARJAMAA O. , TALO A.
Published: December 2008

Some electronmicroscropic and light microscopic aspects of the quail oviduct have been studied in relation to ovum transport. Previously it has been shown that in this smooth muscle there exist spontaneous coordinated electrical and mechanical activity which suggests a good electrical and mechanical coupling of the muscle cells. The structural basis for this coupling is not known. The majority of muscle cell contacts observed were simple appositions and intermediate junctions. Less numerous were attachments of the interdigitation type. No nexuses or tight junctions were seen. Mechanical stretching or contraction of cells induced with 10‐4M carbachol did not affect the contacts. The fine structure of the muscle cells did not differ from that described for other smooth muscles. Electronmicroscopically the muscle cell bundles could not be distinguished into separate layers, in the light microscope the cell bundles were spirally arranged. Stretching of the oviductal strips to the length to which the ovum stretches the muscular wall during ovum transport caused re‐orientation of the muscle cell bundles. One‐directional stretching turned the axes of the muscle cells and the collagen bundles parallel, while stretching in two direction made the tissue look like a network. The re‐orientation of muscle cell bundles may be of importance in producing forces in the muscular tunic during ovum transport. The nerve supply to the muscle cells was negligible. These and previous results show that structurally the muscular wall of the quail oviduct is a dynamic unity in which the ovum via stretch induces the electrical and mechanical activity throughout the tissue. Innervation may play a minor role in controlling the contractions.
Effect of prostaglandin synthesis inhibitors on basal and carbon dioxide stimulated cerebral blood flow in man
Authors: ERIKSSON S. , HAGENFELDT L. , LAW D. , PATRONO C. , PINCA E. , WENNMALM Å.
Published: December 2008

The effect of acute and chronic administration of three different prostaglandin (PG) synthesis inhibitors–aspirin, indomethacin and naproxen–on the basal and CO2‐stimulated cerebral blood flow (CBF) was studied in healthy subjects, using the N2O wash‐in technique for assessment of CBF. The regional O2 extraction over the brain, the regional production of free fatty acids (FFA)–including the PG precursor arachidonic acid (AA)–and the regional production of two prostacyclin (PGI2) metabolites, were also measured. The efficacy of cyclo‐oxygenase inhibition by these drugs was monitored through AA‐induced platelet aggregation in blood samples taken before and after drug administration. In the basal state there was no detectable release of AA, other FFA or PGI2 metabolites over the brain. Acute administration of aspirin (45 mg/kg) failed to affect CBF, as did chronic administration of this drug (15 mg/kg × 3 daily). Indomethacin (1.5 mg/kg) significantly (p<0.05)reduced CBF after acute administration, but after one week's treatment (0.8 mg/kg × 3 daily) this effect had disappeared. Acute administration of naproxen (4 mg/kg) did not affect O2 extraction over the brain, thus indicating that CBF was unchanged. After chronic administration, naproxen (4 mg/kg × 2 daily) also failed to change CBF. During inhalation of CO2, no release of AA, other FFA or PGI2 metabolites occurred in untreated subjects. In subjects given indomethacin there was a small but significant release of AA during inhalation of CO2. Both acute and chronic administration of aspirin failed to affect the CO2‐induced elevation of CBF, whereas both forms of indomethacin administration significantly reduced this rise. Chronic administration of naproxen did not affect the CO2‐induced increase in CBF. We conclude that in healthy subjects: 1) local PGI2 production does not appear to be involved in the regulation of cerebral blood flow: 2) indomethacin reduces basal and CO2‐stimulated CBF, an effect not shared by the other structurally unrelated cyclo‐oxygenase inhibitors: 3) the mechanism(s) of indomethacin‐induced reduction of CBF does not appear to be related to inhibition of PG‐synthesis and remains to be determined.
Dissociation of training effects on skeletal muscle mitochondrial enzymes and myoglobin in man
Authors: SVEDENHAG JAN , HENRIKSSON JAN , SYLVÉN CHRISTER
Published: December 2008

The effect of endurance training on skeletal muscle myoglobin concentration in man was investigated. 8 healthy sedentary males (20–31 yrs) trained on cycle ergometers 40 min/day, 4 days a week for 8 weeks. The work consisted of continuous exercise at a work load that during the last 5 weeks corresponded to 75% of the pretraining maximal oxygen uptake (VO2 max). The training program resulted in a 7% increase in VO2 max (p<0.01). The activities of the mitochondrial enzymes citrate synthase (CS), succinate dehydrogenase (SDH) and cytochrome c oxidase (Cyt‐c‐ox) in the fluadriceps femoris muscle, as indicators of muscle respiratory capacity, increased by 62–82% (p<0.01). The metabolic adaptation of skeletal muscle was further indicated by a 17% increase in the work load corresponding to a blood lactate concentration of 4 mmol/1, as determined by a progressive exercise test (p<0.05). There was, however, no change in the myoglobin concentration of the thigh muscle with training (‐1%, NS). It is suggested that endurance exercise in man at 75% of the maximal oxygen uptake does not severely tax the functions of myoglobin in skeletal muscle.
Factors contributing to blood pressure elevation during norepinephrine and phenylephrine infusions in dogs
Authors: STOKLAND OLAV , THORVALDSON JØRGEN , ILEBEKK ARNFINN , KIIL FREDRIK
Published: December 2008

To examine the factors contributing to the rise in systemic blood pressure during α‐ and β‐ adrenergic stimulation, phenylephrine, an α‐adrenergic agonist, and norepinephrine, an α‐ and β‐adrenergic agonist, were infused intravenously to anesthetized dogs until mean aortic blood pressure was raised equally by 40–60 mmHg. Changes in preload were estimated by changes in left ventricular end‐diastolic pressure or segment length recorded by an ultrasonic technique. By obstructing the inferior vena cava (IVC), the increase in preload could be reduced to control level during phenylephrine and norepinephrine infusions without altering peripheral resistance (mean aortic blood pressure/cardiac output). Normalization of preload reduced the pressure response by 2/3 during phenylephrine infusion and by 1/4 during norepinephrine infusion. However, after β‐adrenergic blockade by propranolol, normalization of preload reduced the pressure response by 2/3 during both phenylephrine and norepinephrine infusions. Thus, during α‐adrenergic stimulation, the increase in preload is a more important factor than the increase in peripheral resistance. Norepinephrine raised stroke volume by 24±5%. When the increase in stroke volume was prevented by IVC obstruction, the pressure response to norepinephrine was halved. Thus, during norepinephrine infusion the rise in stroke volume caused by β‐adrenergic stimulation is as important as α‐adrenergic stimulation for the pressure response.
Neurogenic modification of the vulnerability of the blood‐brain barrier during acute hypertension in conscious rats
Authors: JOHANSSON BARBRO B. , AUER LUDWIG M.
Published: December 2008

To study the possible influence of sympathetic adrenergic tone on the blood‐brain barrier function during acute hypertension in conscious unrestrained rats with indwelling catheters in the aorta and a jugular vein the blood pressure was increased by noradrenaline, 6‐hydroxydopamine (6‐OHDA) or baclofen. One or 60 min later the rats were sacrificed and the extravasation of125I labelled albumin determined in the brain. After i. v. injection of noradrenaline the baroreceptor reflex will decrease the sympathetic tone whereas the blood pressure increase induced by the other two drugs is accompanied by an increased sympathetic activity. One minute after a corresponding rise in blood pressure the albumin content in the brain was considerably lower in rats given 6‐OHDA than in those given noradrenaline. 60 min after the injection of 6‐OHDA or baclofen the extravasation in the brain did not differ despite a considerably more rapid increase in pressure after 6‐OHDA. Pretreatment with clonidine increased the blood‐brain barrier dysfunction in rats given 6‐OHDA but not in those given baclofen, probably because the slower rise in pressure facilitates myogenic autoregulation. It is concluded that neurogenic influences on vessel tone can modify the response of the blood‐brain barrier during acute hypertension in conscious rats.
Prostaglandin‐mediated inhibition of noradrenaline release
Authors: WENNMALM ÅKE
Published: December 2008

The effect of indomethacin, a prostaglandin (PG) synthesis inhibitor, on some cardiovascular reflexes was studied in healthy subjects. Heart rate (HR) and respiratory sinus arrhythmia (RSA) in the basal state and during carotid stimulation (neck suction), Valsalva ratio, and changes in heart rate and blood pressure (BP) during an orthostatic test were measured before and one hour after administration of indomethacin (1.5 mg/kg). The efficacy of the PG synthesis inhibitor was monitored by analysis of platelet aggregation induced by arachidonic acid. Following indomethacin no change was observed in basal HR. Carotid stimulation depressed the HR and this effect was of the same amplitude before and after indomethacin. The amplitude of RSA was not affected by indomethacin, either in the basal state or during carotid stimulation. The Valsalva ratio and the changes in HR and BP during the orthostatic test were similar before and after the drug. Circulating levels of noradrenaline were unaffected by indomethacin. These data demonstrate that inhibition of PG bioformation in man does not affect major cardiovascular reflexes. Consequently they disfavour the hypothesis that endogenously formed PG would be involved in the normal activity of the afferent, central or efferent pathways for cardiovascular regulation.
Effects of selective α1and α2adrenoceptor active drugs on86Rb+ efflux from pieces of rat parotid gland
Authors: DANIELSSON Å. , SEHLIN J.
Published: December 2008

Minute pieces of rat parotid gland were used in studies of adrenergic regulation of K+ efflux using86Rb+ as a probe for K+. Noradrenaline induced a concentration‐dependent Rb+ efflux, whereas the β1‐selective agonist prenalterol was without effect. On the other hand, the β2‐selective drug, terbutaline, at high concentrations displayed a small enhancement of Rb+ ‐secretion. The selective α1‐adrenoceptor drug, phenylephrine, was as potent as noradrenaline, whereas the α2‐agonist clonidine had only a small effect. The noradrenaline‐induced Rb+‐efflux was effectively inhibited in the presence of prazosin, an α1‐blocker, whereas the α2‐antagonist, yohimbine, was roughly 50 times less potent. The results suggest that catecholamine‐induced K+‐secretion from the rat parotid gland is mediated via activation of post‐synaptic α‐adrenoceptors of the α1‐subtype.
Electrovibration, cutaneous sensation of microampere current
Authors: GRIMNES S.
Published: December 2008

The human threshold of sensation of 50 Hz current has hitherto been considered to be around 1 mA. A new sensing mechanism is reported which lowers the threshold about 3 decades. It is elicited when the skin slides on the current carrying conductor, and the sensation disappears when the skin is wet. The sensation is a feeling of vibration or increased surface roughness. The sensing mechanism has been shown to be due to electrostatic forces in the skin caused by the electric field in a poorly conducting stratum corneum. The mechanism is primarily potential dependent, and the absolute threshold of sensation has been found to be about 1.5 volt or 0.15 μA rms at 50 Hz. In practical daily‐life situations it is shown that 82% of 40 test subjects were able to sense a current of 2 μA rms, 50 Hz.
Hypotaurine transport in mouse brain synaptosomal preparations
Authors: KONTRO PIRJO
Published: December 2008

The transport of hypotaurine, the precursor of the probable neuromodulator taurine, was investigated using mouse brain synaptosomal preparations. Hypotaurine uptake was concentrative, energy‐and sodium‐dependent and strongly inhibited by GABA, l‐DABA (l‐2,4‐diaminobutyric acid) and β‐alanine, suggesting interactions with GABA uptake systems. The uptake consisted of only one saturable transport component both in adult and in 6‐day‐old brain, being more efficient in the latter.
Effects of ischemia on the hepatic cell membrane potential in the rat. Differences between fed and fasted animals
Authors: JENNISCHE EVA
Published: December 2008

The effect of ischemia on the hepatic cell membrane potential (MP) was studied in vivo in fed and fasted rats. Liver ischemia was induced for 1 h by clamping all afferent vessels to the left lateral and medial lobes and was followed by a 3 h period of reflow. The liver content of ATP, glucose, lactate and glycogen was repeatedly measured and related to the MP changes. The initial ATP content was 40% higher and the glycogen content 10 times higher in the fed animals, while the MP was similar in both groups. During the ischemic period the ATP content as well as the MP decreased in a similar manner in both groups of animals. During reflow the ATP content increased to about 50% of the initial value in both groups of animals. The MP was normalized more rapidly in fed animals than in fasted ones, indicating a better capability for recovery after ischemic injury in fed animals.
Rhythmical oscillations in rat testicular microcirculation as recorded by laser Doppler flowmetry
Authors: DAMBER JAN‐ERIK , LINDAHL OLOF , SELSTAM GUNNAR , TENLAND TORSTEN
Published: December 2008

We have earlier reported that local testicular blood flow, recorded by laser Doppler flowmetry, shows large oscillations with a frequency of 5–10 min‐1. In the present study it is proposed that the recorded oscillations represent mainly local microvascular blood flow variations rather than variations in total testicular blood flow or tissue movements. The reasons for this are: (a) Blood flow simultaneously measured at two separate sites showed oscillations with different frequencies, (b) A local subcapsular injection of room‐tempered saline under one probe site eradicated oscillations under that probe but not under another adjacent probe, (c) When the testicular capsule was split open, recordings of blood flow continued to show oscillations, (d) The amplitude of the oscillations was rather large (peak to peak value about 50% of mean flow value). No movements of the testicular surface were seen. A 20 min continuous infusion of 0.4 μg/min noradrenaline did induce a decrease in plasma testosterone concentration, but did not change the mean blood flow. However, the oscillations nearly completely disappeared during the infusion period. The present study also shows that laser Doppler flowmetry is a versatile method and the rat testis provides a suitable organ in the study of the origin and functional importance of these oscillations.
Kinetics of the TTX sensitive Na+ current in the slowly adapting lobster stretch receptor neurone
Authors: GESTRELIUS S. , GRAMPP W. , SJÖLIN L.
Published: December 2008

The kinetics of the TTX sensitive Na+ current (INa) in the slowly adapting lobster stretch receptor neurone were investigated in sub‐and near‐threshold voltage regions using electrophysiological and pharmacological techniques. In dynamic conditions INa was found to display both fast and slow reactions. These were attributed to a fast Hodgkin‐Huxley type of Na activation and inactivation, and a slow type of Na inactivation, respectively. In stationary conditions the voltage dependence of the slow Na inactivation was shifted in a depolarizing direction by increasing, and in a hyperpolarizing direction by decreasing the extracellular Ca++ concentration. From this finding as well as from its kinetic properties the slow Na inactivation was classified as a genuine gating process. The processes of fast Na activation and inactivation were too fast for a dynamic analysis with the recording technique available. An estimate of their stationary voltage dependence could however be obtained in a voltage range from about ‐80 to about ‐50 mV. The experimental findings were used for the formulation of a mathematical description of INa in the present preparation based on constant field and state transition theories.
A new design of double‐barrelled microelectrodes for intracellular pH‐measurement in vivo
Authors: HAGBERG H. , LARSSON S. , HALJAMÄE H.
Published: December 2008

Intracellular pH (pHi) is one important regulator of cellular function. Most determinations of pHi in vivo have been performed by using indirect methods, e. g. CO2/HCO3 or DMO techniques, since no suitable direct method for reliable in vivo measurements have been available. In the present study a new type of double‐barrelled microelectrode for simultaneous in vivo measurements of pHi and membrane potential (Em) is presented. The electrode was constructed on the basis of a combined recessed‐and pencil‐tip design. The tip diameter of the double‐barrelled microelectrode was about 1.5 μm. The response of the pH channel was 55–60 mV/pH unit and the response time was between 30 s and 1 min. In vivo measurements of pHi and Em of rabbit skeletal muscle fibers are presented. A mean pHi of 7.00 (in 8 animals) at a membrane potential of ‐90.3 mV (arterial pH: 7.30, arterial PCO2: 6.39 kPa) was obtained. The new design of pH microelectrode offers some advantages over previously described microelectrodes and is well suited for in vivo measurements.
Intracellular ion control in lobster stretch receptor neurone
Authors: EDMAN Å. , GESTRELIUS S. , GRAMPP W.
Published: December 2008

The control of intracellular ion concentrations by means of passive and active transmembrane ion transports was investigated in the lobster stretch receptor neurone using electrophysiological and pharmacological techniques in combination with recording with ion‐sensitive microelectrodes. In resting conditions [Na+];, [K+]i, and [Cl‐]i were, in both slowly and rapidly adapting cells, found to be in the order of 20, 155, and 50 mM, respectively. In the slowly adapting cell impulse firing at stationary frequencies of 7–10 Hz caused an increase in [Na+]i and a drcrease in [K+]i of 20–30 mM; [Cl‐]i was only little affected, the rise in [Na+]i led to an enhanced Na‐K pump activity noticeable as an increase in pump current production. In stationary conditions the quotient between pump current and Na+ influx increments was about 0.3, which is compatible with a 3:2 Na‐K pumping ratio in the present preparation. From measurements of the pump current activation during stationary firing at maximum tolerable frequencies an estimate was made of the cell's maximum pump current production. The measurements were used in the formulation of a mathematical model of the intracellular ion control in which expressions of active and passive transmembrane ion transports are incorporated into the continuity equation for the ion fluxes involved.
Changes in length and volume of smooth muscle cells of the hypertrophied rat urinary bladder
Authors: EKSTRÖM JÖRGEN , UVELIUS BENGT
Published: December 2008

Rat urinary bladders were denervated by bilateral excision of the pelvic ganglion. After 10 days the hypertrophied bladders were removed, filled with 0.75 ml Krebs solution, fixated and embedded for electron microscopy. Normal bladders filled with the same volume were used as controls. Tangential and transverse sections of longitudinal muscle bundles were cut both for phase contrast and electron microscopy. The profiles of cross‐sectioned cells from control bladders had regular, often almost circular contours, and were rather uniform in size. The cell contours from the denervated bladders were irregular with wrinkled surfaces and the cells varied considerably in size. In tangential sections the cells from denervated bladders had corrugated surfaces in contrast to the control cells. Mean length and volume of the muscle cells were determined morphometrically. Whereas cell volume was larger in denervated (3 800 μm3) than in control bladders (2 200 μ3), cell length was less (226 versus 335 μm). The finding of shorter cells in denervated bladders favour the opinion, brought forward previously (Ekström & Uvelius 1981), that the rightward shift of the active length‐tension curve in denervated bladders is due to an increase in the number of muscle cells that are coupled in series around the bladder circumference.
The pressure equilibrating function of pars flaccida in middle ear mechanics
Authors: HELLSTRÖM STEN , STENFORS LARS‐ERIC
Published: December 2008

In the adult male rat the precise volumes of the middle ear cavity, the lateral attic compartment and a maximally retracted pars flaccida were calculated to 550 μl, 21 μl and 3 μl respectively, using Woods metal. Small intratympanal pressure or volume changes caused the pars flaccida to move in a medial‐lateral direction. As the volume of a maximally retracted or bulging pars flaccida only amounted to about 0.5% of the total middle ear volume and the pars flaccida reacted even at volume changes of 0.1 % of the middle ear, it would seem that the pressure equilibrating capacity of the elastic pars flaccida is negligible. On the other hand the pars flaccida is extremely sensitive to pressure and volume changes in the middle ear and may take part in the pressure equilibrating system as a detector for minute pressure and/or volume changes in the middle ear.
Antroduodenal motor response induced by (Gln4)‐neurotensin in man
Authors: THOR KJELL , RÖKAEUS ÅKE
Published: December 2008

The effect of (Gln4)‐neurotensin on antroduodenal motor activity was investigated in 7 healthy volunteers. Motor activity was monitored by measuring the intraluminal pressure in the antrum and in the proximal and middle part of the duodenum. Intravenous infusion of (Gln4)‐neurotensin (6 pmol × kg‐1 × min‐1) for 20 min significantly increased the number of contractions in the duodenum, from 13.8 ± 1.1 to 33.2 ± 3.0 contractions × 5 min‐1, and changed the motility pattern in the duodenum to irregular pressure waves similar to those seen after the ingestion of food. The contractile activity (amplitude × number of contractions) in the antrum and duodenum changed significantly from 230 ± 29 to 148 ± 39 and from 288 ± 21 to 556 ± 62 mmHg ± 5 min‐1, respectively, despite the fact that the baseline pressure gradient was unchanged. The number of antral contractions migrating to the duodenum was significantly reduced from 3.3 xyp 0.4 to 0.1 ± 0.1 contractions × 5 min‐1 and their velocity was also significantly decreased, from 18.2 ± 1.7 to 11.1 ± 1.7 mm × sec‐1. The concentration of p‐NTLI rose from 39 ± 11 pM to a maximum of 150 ± 14 pM at 20 min; these latter levels are within the range found after a fatty meal. Thus, (Gln4)‐neurotensin changes antroduodenal motility to a pattern seen after a meal. This suggests that neurotensin, or a neurotensin metabolite, may carry the information to the antroduodenal area to decrease the rate of gastric emptying after a fatty meal.
The importance of bile and pancreatic juice for fat‐induced release of neurotensin‐like immunoreactivity (NTLI) from the small intestine of the rat
Authors: RÖKAEUS ÅKE , AL‐SAFFAR AHMAD
Published: December 2008

The aim of the present study in the rat was to localize the gastrointestinal site(s) of NTLI release and to investigate the importance of bile and pancreatic juice for fat‐induced NTLI release. Administration of Intralipid (2 ml) into the stomach and oleic acid (0.5 ml) into the duodenum increased the plasma concentration of NTLI (p‐NTLI). The increase in p‐NTLI levels occurred only when the jejunum and ileum were exposed to Intralipid but not when the exposure was limited to the stomach and duodenum. Exclusion of pancreatic juice significantly reduced the p‐NTLI response and exclusion of both bile and pancreatic juice completely abolished the p‐NTLI response to duodenally‐administered oleic acid. The results indicate that neurotension is released by a direct luminal exposure of the neurotensin containing N‐cells to fatty acids. It seems probable that fatty acids have to be transformed to a micellar form in order to release NTLI
In vivo effect of noradrenaline on the cyclic AMP level in rat corpora lutea
Authors: NORJAVAARA ENSIO , SELSTAM GUNNAR , DAMBER JAN‐ERIK , JOHANSSON BRITT‐MARIE
Published: December 2008

Under in vitro conditions adrenaline and noradrenaline can stimulate the production of cyclic AMP in rat corpora lutea to a similar extent as a maximal dose of LH. The present study was undertaken to compare the effects of noradrenaline and LH under in vivo conditions. Anaesthetized rats bearing 2 days old corpora lutea were either infused intraarterially with noradrenaline (0.4 μg/min) or given a single intraarterial injection of 5 μg LH. The cAMP levels in whole ovaries had increased already after 30 sec of noradrenaline infusion. These levels remained high for a few minutes and, thereafter the effect decreased with time. No effect was seen after 20 min of infusion. Infusion of noradrenaline for 20 min increased cAMP in corpora lutea, but not in non‐luteal tissue. LH was effective both in luteal and non‐luteal tissue. The results show that noradrenaline in vivo can increase the cAMP content only in corpus luteum and within a rather short time period (5 min). This effect is different from that seen with LH which, instead, acts on both corpus luteum and stromal tissue
Muscle sympathetic activity and plasma noradrenaline in normotensive and hypertensive man
Authors: MÖRLIN CLAES , WALLIN B. GUNNAR , ERIKSSON BRITT MARIE
Published: December 2008

Micro‐electrode recordings of muscle sympathetic activity were made in the peroneal nerve of 20 normotensive subjects and 18 patients with essential hypertension resting in the recumbent posture. The level of sympathetic activity was quantitated as bursts/100 heart beats or bursts/min. On another occasion blood was sampled from an antecubital vein and analyzed for plasma noradrenaline using radioenzymatic technique. In both groups the level of sympathetic activity increased with age and taking age into account there was no significant difference in sympathetic activity between normotensive and hypertensive subjects. There was no significant difference in plasma levels of noradrenaline between the groups. Both for normotensive and for hypertensive subjects there was a positive correlation between a subject's level of sympathetic activity and his plasma concentration of noradrenaline, and the regression lines did not differ significantly between the groups. It is suggested (a) that outflow of transmitter from sympathetic terminals in muscles contributes significantly to plasma concentrations of noradrenaline at rest both in normotensive and hypertensive subjects; (b) that neither for muscle sympathetic activcity nor for plasma noradrenaline do the resting levels differ between normotensive and hypertensive subjects
Segmental distribution of vascular resistances during ureteral occlusion: The vasoconstrictive effects of angiotensin and CaCl2 differ from those of catecholamines and renal nerve stimulation
Authors: VIKSE ARILD , HOLDAAS HALLVARD , HARTMANN ANDERS , KIIL FREDRIK
Published: December 2008

Examinations of renal autoregulation and renin release suggest that α‐adrenergic agonists, in contrast to other vasoconstrictors, preferentially constrict the preglomerular arteries. To examine this hypothesis, experiments were performed in anesthetized dogs during ureteral occlusion. At a ureteral pressure (UP) of 100 mmHg the afferent arterioles are dilated and mechanical constriction of the renal artery does not alter intrarenal vascular resistances. Whereas angiotensin and CaCl2 infused into the renal artery reduced renal blood flow (RBF) by 25–30% without reducing UP, renal nerve stimulation reduced RBF and UP in proportion. During angiotensin and catecholamine infusion, measurements of UP and intrarenal venous pressure permitted calculations of preglomerular, efferent vascular and intrarenal venous resistances. Until RBF was reduced by 25%, angiotensin raised both preglomerular and efferent vascular resistances, whereas norepinephrine and the α‐adrenergic agonists, phenylephrine and methoxamine raised preglomerular more than efferent vascular resistance. When RBF was reduced by more than 25%, all vasoconstrictors showed a similar pattern with large increments both in preglomerular and efferent vascular resistances. Conclusions: Humoral and nervous stimulation of α‐adrenergic receptors reduce glomerular capillary pressure by preferentially constricting the preglomerular arteries and may affect renal autoregulation and renin release by reducing the transmural pressure of the afferent arterioles.
The liver‐like anion transport system in the rabbit uvea does not eliminate iodipamide from the eye
Authors: BÁRÁNY E.
Published: December 2008

Iodipamide is known to be actively taken up in vitro by the rabbit iris‐ciliary process preparation. This uptake is partly resistant to high concentrations of hippurate and the resistant part has been called the ‘liver‐like’ system. In vivo iodipamide is eliminated from the rabbit eye after injection into the vitreous by a saturable process. This process is hippurate‐sensitive and no role for any hippurate‐resistant system was found. Two explanations for the discrepancy between the results in vitro and in vivo are offered: (1) Iodipamide may be a less than perfect model substance for physiological compounds that normally are transported by a liver‐like system from the vitreous cavity and the posterior aqueous humour to the blood. (2) Iodipamide is a model for compounds that are taken up by the non‐pigmented epithelium of the ciliary processes by a liver‐like system and transported to the pigmented epithelium for metabolic modification.
Release of gastrin and insulin in response to suckling in lactating dogs
Authors: UVNÄS‐MOBERG KERSTIN , ERIKSSON MAUD
Published: December 2008

The concentration of gastrin and insulin was determined in peripheral blood of 4 lactating dogs during suckling. Suckling induced an immediate rise of gastrin and insulin levels, twofold and threefold, respectively. A peak was reached at ˜5 min after suckling was started, and basal levels were reached again within 15–20 min. The increase in gastrin and insulin levels coincided with the let‐down reflex, i. e.it occurred when the puppies started to obtain milk from their mothers. Sham feeding and feeding induce a vagally mediated increase of gastrin and insulin release in dogs. We suggest that the changes in the gastrin and insulin levels observed by us in the lactating dogs, reflect a similar vagal activation induced by suckling. Possible effects of the suckling induced release of gastrin and insulin on milk ejection and secretion are discussed.
External pressure‐blood flow relations during limb compression in man
Authors: NIELSEN HENRIK VAGN
Published: December 2008

The effect of increased tissue pressure on blood flow in subcutaneous and skeletal muscle tissue was studied in 8 healthy humans resting in horizontal position. Blood flow was measured by the local 133Xe washout technique in the mid‐calf region. Tissue pressure in the depot area was increased by inflating a compression cuff, 50 cm wide (knee to ankle). Blood flow rates were obtained from compressed tissues with normal vasomotor tone, at papaverine‐induced vasoparalysis and during distension of the compressed vessels. The latter was achieved by inflating a proximal (extra) compression cuff on the thigh 10 or 20 mmHg above the pressure level in the more distally placed compression cuff. Increased tissue pressure was a potent stimulus for arteriolar dilatation (autoregulation) in both tissues. The autoregulatory response was to some extent counteracted by an increase in local vascular resistance in the postcapillary section as evidenced by the results of simultaneous venous stasis. Blood flow ceased in vasoparalysed tissues as well as in tissues with normal vasomotor tone, when the compression cuff was inflated to the level of the local diastolic blood pressure. Maintaining external compression at the diastolic blood pressure level, blood flow reappeared in both tissues, when the compressed vessels were distended by adding the proximal (extra) compression. It is concluded, that blood flow cessation in compressed tissues is caused by a widespread arterial‐arteriolar collapse in diastole, as the volume of blood injected during the systolic peak is too small to expand also the distal sections of the precapillary vessels.
Effects of endurance training on alkaline protease activities in rat skeletal muscles
Authors: SALMINEN A. , KOMULAINEN J. , AHOMÄKI E. , KAINULAINEN H. , TAKALA T. , VIHKO V.
Published: December 2008

This study aimed at comparing the effects of running and swimming training protocols and the termination of training on the activities of two proteases with alkaline pH‐optima (alkaline protease and myofibrillar protease) in the tibialis anterior, soleus, and gastrocnemius muscles of male rats. The training on treadmill decreased the activities of alkaline and myofibrillar proteases by approx.10–20% in the muscles studied. The activities of both proteases were unchanged in swimming‐trained rats. Two weeks after the termination of running training the activity of alkaline protease was increased in gastrocnemius muscle but not in the other muscles. Swimming training increased the activity of citrate synthase in all muscles studied but training by running only in the soleus muscle. The running protocol increased the activity of β‐glucuronidase in the tibialis anterior muscle and decreased the activity in the gastrocnemius muscle. The swimming program did not affect β‐glucuronidase activities. These results show diverse effects of running and swimming trainings on alkaline proteolytic activities as well as on mitochondrial and lysosomal marker enzymes.
Comparison of electrical thresholds of intradental nerves and jaw‐opening reflex in the cat
Authors: NÄRHI MATTI , VIRTANEN ANTTI , HIRVONEN TIMO , HUOPANIEMI TIMO
Published: December 2008

In experimental animals the jaw‐opening reflex in response to stimulation of pulp nerves has been used as a nociceptive reflex. However, there seems to be only scanty information about the amount and types of pulp nerve fibres that mediate the reflex. In the present work on 8 anesthetized cats electrical thresholds of single functional pulp nerve units were compared to the thresholds of jaw‐opening reflex. Monopolar cathodal current pulses were applied to each canine tooth. Reflex responses of the digastric muscle were recorded. The inferior alveolar nerve of the left side in 3 cats was exposed for nerve dissection and responses of pulp nerve units coming from the lower left canine tooth were recorded. The mean threshold of the jaw‐opening reflex with 10 ms pulses was 5.9 ± 3.0 (SD) μA.Below or at that level only part of the fast conducting pulp nerve units could be activated. Thresholds of A‐(n=32) and C‐(n=24) fibres were 9.9 ± 5.7 and 37.4 ± 14.5 (SD) μA respectively. Nerves of the periodontal tissues (20 units recorded) were not activated with current pulses of up to 200 μA applied to the tooth. Consequently, at threshold level the jaw‐opening reflex in response to the present type of stimulation is mediated by the fast conducting intradental nerve units.
Time course of segmental reflex changes after chronic spinal cord hemisection in the rat
Authors: MALMSTEN J.
Published: December 2008

In a companion paper (Hultborn & Malmsten 1983a) it was described that, in the cat, direct excitatory reflexes became larger on the side of a chronic spinal hemisection than on the other side. In this paper the time course for change of the size of excitatory reflexes after spinal cord hemisection in the rat is described. Ipsilateral reflexes obtained by stimulation of cut dorsal roots L 4 and L 5 were recorded in the corresponding cut ventral roots. It was found that reflexes became larger on the lesioned (left) side than on the opposite side. For both mono‐and polysynaptic reflexes there was a marked peak in left/right ratio of reflex size at 2 to 6 days post lesion. The ratio then returned to normal but increased again from about 21 days until at least 135 days. In control rats reflexes were larger on the right side, in agreement with findings in the cat.
Effects of prostanoids on isolated feline cerebral arteries
Authors: USKI TORE K. , ANDERSSON KARL‐ERIK
Published: December 2008

The roles of extra‐and intracellular calcium for the contractile effects of PGF2α in the feline basilar artery (BA) were investigated. Comparisons were made with contractions induced by K+ and noradrenaline (NA). Addition of nifedipine to PGF2α‐or K+ (124 mM)‐contracted arteries resulted in an incomplete relaxation, whereas NA‐contracted vessels were completely relaxed. Incubation of the preparations in a calcium‐free medium containing 10‐5 M EGTA for 5–10 min almost abolished contractions induced by K+ and NA. In contrast, 63 % of the response to PGF2α remained after pretreatment of the arteries in a calcium‐free solution for 40 min; PGF2α produced a biphasic contraction in 17 out of 20 preparations consisting of a rapidly developing initial phase followed by a second increase in tension after 1–6 min. The second phase was absent if the EGTA‐concentration was increased to 10‐4 M, or if the arteries were pre‐treated with nifedipine. After incubation of the arteries in a calcium‐free medium for 40–120 min and K+‐depolarization, re‐addition of calcium elicited contractions at lower concentrations in the presence of PGF2α than in controls. The results suggest that PGF2α‐induced contractions in the feline BA are considerably less dependent on extracellular calcium than contractions evoked by K+ or NA. PGF2α appears to be able to release calcium from two cellular stores, and may also promote calcium influx through the cell membrane.