bluuebunny/crossref_metadata_2025_split huggingface dataset:
Basic features of an extracellular recording method to study secretion of a sympathetic co‐transmitter, presumably ATP
Authors: STJÄRNE L. , STJÄRNE E. 
Published: December 2008

An extracellular recording method is described which permits in suitable model tissues (e. g.guinea‐pig or mouse vas deferens) study of the nerve impulse in sympathetic terminals and the release of transmitter from sites inside or outside the recording electrode. Negative‐ or positive‐going potentials were assumed to reflect the excitatory junction current (EJC) caused by transmitter released inside or outside the electrode, respectively, and hence termed ‘EJCi’ (i for inside) or ‘EJCo’ (o for outside).The EJCo were shown to be Ca2+‐dependent, blocked by addition of tetrodotoxin or guanethidine, resistant to the α1 adrenoceptor blocking agent prazosin but suppressed by desensitization of P2‐purinoceptors by α,β‐methylene ATP, and hence, presumably, are caused by release of ATP as a sympathetic co‐transmitter. The amplitude of the EJCo was voltage‐dependent and increased with the length and frequency of stimulus trains within the range of 1–50 shocks at 0.1–2.5 Hz.In conclusion, combined use of EJCi and EJCo provides a useful tool for physiological and pharmacological analysis of pre‐ and post‐junctional events associated with the secretion of a sympathetic co‐transmitter, presumably ATP.
Evidence for sympathetic regulation of the hydraulic conductance of rat jejunal mucosa in vivo
Authors: HEMLIN M. , SJÖVALL H. 
Published: December 2008

The aim of the study was to test the hypothesis that sympathetic nerve stimulation inhibits jejunal fluid secretion by decreasing the hydraulic conductance (Lp)of the mucosa. Jejunal segments of anaesthetized rats were mounted in a specially constructed chamber which makes it possible to measure net fluid transport together with transmural potential difference or short circuit current in vivo. Lp was estimated by measuring the effects on net fluid transport rate elicited by stepwise changes in luminal pressure. Lp was measured in four groups of animals: (1) under control conditions; (2) after hexamethonium administration, to block intramural secretory neurons; (3) during efferent stimulation of the mesenteric nerves, to activate sympathetic neurons, and (4) during mesenteric nerve stimulation (MNS) after pre‐treatment with phentolamine, an a‐adrenergic antagonist, to block the sympathetic effector mechanism. Lp measured at positive luminal pressures in control animals was approximately 4 μl min‐1 cmH2O‐1 100 cm‐2 serosal surface area. When measured at negative luminal pressures, this value increased approximately threefold. Hexamethonium did not significantly influence Lp. At positive luminal pressures, MNS decreased Lp to a value not significantly different from zero. This effect was abolished by phentolamine. At negative lumina] pressures, MNS decreased Lp by approximately 50% and this effect was partly antagonized by phentolamine. The results suggest that a decrease in mucosal hydraulic conductance may contribute to the antisecretory effect of sympathetic nerve stimulation in vivo.
Total calorimetry and temperature regulation in the nine‐banded armadillo
Authors: MERCER J. B. , HAMMEL H. T. 
Published: December 2008

Cold exposure in the nine‐banded armadillo causes vigorous shivering and a rise in core temperature (Te). The increase in metabolic rate and Te depends upon exposure temperature, but may be as much as six times and 3 °C respectively (Johansen 1961). These findings might indicate an insensitivity to Te, which is puzzling since internal temperature is thought to be the primary and regulated variable. It is suggested that positive feedback may play a role in temperature regulation in these animals. To investigate this problem two series of experiments were performed in the same species. Series 1. Measurements of changes in heat loss (direct calorimetry) and heat production (indirect calorimetry) following transferral from a thermoneutral to a cold environment. The difference between these measurements determines whether heat storage is positive due to the increased core temperature or negative due to reduction in the size of the core with the increased temperature. Series 2. Investigation of core thermosensitivity (body core cooling using colonic thermode) under different environmental conditions.The results of the first series showed that the rise in Te was accompanied by positive heat storage in the body. The second series demonstrated core thermosensitivities similar to those previously reported for a variety of other homeothermic mammals.
Orienting reactions to light tactile stimuli after single and repeated partial spinal cord lesions in the cat
Authors: DANIELSSON I. , NORRSELL U. 
Published: December 2008

Cats which had been trained to remain quietly standing were tested for orienting responses to light tactile stimulation (ORLT) of either hindlimb before and after different single, and subsequently increased, low thoracic spinal cord lesions. The individual lesions covered one dorsal column, and/or the dorsal part of one lateral funiculus, and/or the ventral part of the lateral funiculus, and/or one entire lateral funiculus and/or one or both ventral quadrants.Normal ORLTs were produced from the first post‐operative test after each of the above lesions alone, or in combination with one of the others. Acute and chronic disappearances and/or disturbances of the ORLTs were observed for one hindlimb only after lesions involving at least the dorsal column and the dorsal part of the lateral funiculus of the ipsilateral side, as well as the contralateral lateral funiculus. The amount of disturbance varied with the technique in such a way that the number of operations which had been carried out to cause the actual lesion was inversely correlated to the degree of post‐operative defect.The findings showed that the severity of the tactile symptoms after spinal cord lesions may depend on the speed with which they had developed. The types of lesions causing defects indicated that cats, under normal conditions, may utilize one of the three ascending spinal pathways for orienting reactions to light tactile stimulation. In relation to the peripheral receptive fields, these pathways are the ipsilateral dorsal column and spinocervical pathways, and a pathway of the contralateral lateral funiculus. The possible spinothalamic character of the crossed pathway has yet to be established.
ATP as a sympathetic co‐transmitter in rat vasomotor nerves‐further evidence that individual release sites respond to nerve impulses by intermittent release of single quanta
Authors: ÅRSTRAND P. , STJÄURNE L. 
Published: December 2008

A combination of intra‐ and extracellular recording was used to study neurotransmitter release in sympathetic vasomotor fibres in rat femoral and mesenteric arteries. The results show that neurotransmission in these preparations is similar to that in the ‘short’ sympathetic nerves in guinea‐pig vas deferens and the ‘long’ sympathetic nerves in rat tail artery in the following respects:

The intracellularly recorded excitatory junction potentials (EJPs) and the extracellularly recorded junction currents (EJCs) presumably are caused by ATP secreted as a sympathetic co‐transmitter.
The stimulus‐evoked and spontaneous EJCs share the same brief time‐course, which is similar to that of spontaneous EJPs, but much briefer than that of stimulus‐evoked EJPs.
‘Successful’ nerve impulses appear to release single transmitter quanta.
The probability of activation of individual release sites is low (0.002–0.02).
The low release probability cannot be accounted for by failure of the nerve impulse to invade the terminals.

Moreover, it is also shown that application of tetrodotoxin to the medium within the recording electrode effectively abolishes transmitter secretion in the area enclosed by the tip of the electrode, indicating that the effective length constant for a passively propagating nerve action potential is probably very small and that activation of the release mechanisms in ‘long’ sympathetic nerve fibres seems to require that the varicosities are actively invaded.
Temporal relationship between blood flow changes and release of ions and metabolites from muscles upon single weak contractions
Authors: KIENS B. , SALTIN B. , WALLØSE L. , WESCHE J. 
Published: December 2008

The temporal changes in muscular blood flow and in the release of ions and metabolites have been studied during and after short‐lasting isometric contractionsBlood velocities in the human femoral artery were measured using pulsed bidirectional Doppler ultrasound equipment during single contractions of the quadriceps muscle group. Contractions of 5 s and 30 s duration and at a tension of 10% MVC (maximal voluntary contraction) were investigated. Even the contractions of 5 s duration caused conspicuous post‐contraction increases in femoral arterial flow..The following substances were analysed in the femoral vein during and following the contractions: potassium, lactate, inorganic phosphate, calcium, sodium, oxygen and haemoglobin. Following contractions of 5 s duration, an increase in the venous potassium concentration (by 0.9mM) was found, but there was no change in concentration of any of the other substances analysed. Following contractions of 30 s duration a more marked increase in the venous potassium concentration (by 1.5 mM) was found, and in addition substantial changes in venous lactate concentration and oxygen saturation. There were small but statistically significant changes in the concentrations of inorganic phosphate and calcium, but no change in the sodium concentration.The time‐course and magnitude of the changes in venous potassium concentration fit well with the idea that potassium is important in the initiation and regulation of the functional hyperaemia in contracting muscles.
Vasoactive intestinal peptide (VIP) may reduce the removal rate of cytosolic Ca2+ after transient elevations in clonal rat lactotrophs
Authors: SAND O. , CHEN B. , LI Q. , KARLSEN H. E. , BJØRO T. , HAUG E. 
Published: December 2008

The prolactin‐producing rat anterior pituitary GH4C1 cells possess Ca2+‐activated K channels which are activated by physiological elevations of the cytosolic Ca2+ concentration even at membrane potentials more negative than the normal level of about ‐ 50 mV. Whole‐cell current recordings showed a marked outward tail current following depolarizing voltage steps to o mV from a holding potential close to the normal membrane potential. The half‐time of this tail current was about 1.3 s after a 4‐s depolarization step. The GH4C1 cells also possess voltage‐activated Ca channels, and we conclude that this tail current is a Ca2+‐activated K+ current for the following reasons:(hd) The reversal potential for the tail current was close to thhd K+ equilibrium potential for a range of transmembrane K+ gradients.(2) The tail current was blocked by a Ca2+ antagonist, and the voltage dependence of this current closely mirrored the voltage dependence of the isolated Ca2+ current.The time‐course of the decline of the tail current thus reflects the removal rate of the Ca2+ entering the cytosol through voltage‐dependent Ca channels during the depolarizing voltage step. VIP stimulates prolactin secretion from GH4C1 cells, and this peptide prolonged the half‐time of the tail current by about 47% in 63% of the cells. This indicates that VIP may prolong the transient cytosolic Ca2+ elevations following the action potentials in these cells. Such a mechanism might be an important factor for the control of the cytosolic Ca2+ level, and hence hormone secretion.
Growth hormone‐releasing factor induces a biphasic modulation of K+ permeability in perfused cultured rat somatotrophs
Authors: OHLSSON L. , LINDSTRÖM P. 
Published: December 2008

Ohlsson, L. & Lindström, Phd 1989. Growth hormone‐releasing factor induces a biphasic modulation of K+ permeability in perfused cultured rat somatotrophs. Acta Physiol Scand 137, 237–241. Received 22 May 1989, accepted 16 June 1989. ISSN 0001–6772. Department of Histology and Cell Biology, University of Umeå, Sweden.Growth hormone‐releasing factor (GKF) induced a biphasic response in 86Rb outflow in rat somatotrophs. An early inhibition was observed at all GRF concentrations tested, 1 pm‐10 nm, and this was followed by a later increase. The increase in 86Rb outflow rate came earlier at high GRF concentrations and GRF had a dose‐related effect on the magnitude of the increase. The effects of GRF on 86Kb outflow were observed also in the absence of extracellular calcium. Peak growth hormone release preceded peak 86Rb outflow rate. The timing of the effects of GRF on potassium outflow is consistent with the hypothesis that reduced potassium outflow is involved in somatotroph depolarization leading to increased exocytosis, followed by a later increase in potassium outflow leading to repolarization.,
The cold pressor test: effects on sympathetic nerve activity in human muscle and skin nerve fascicles
Authors: FAGIUS J. , KARHUVAARA S. , SUNDLOF G. 
Published: December 2008

Micro‐electrode multi‐unit recordings of muscle nerve sympathetic activity (MSA) involved in cardiovascular homeostasis or skin nerve sympathetic activity (SSA) involved in thermoregulation were made in the right peroneal nerve of 48 healthy volunteers during performance of the cold pressor test, i.e. immersion of one hand in ice water (zko.5 “C) for I min. Eleven subjects underwent the same procedure on a second MSA recording occasion. As a rule, immersion evoked an increase in MSA, with a gradual decrease on emersion. The response showed a wide range of variation between and within subjects; the intra‐individual difference between first and second immersion on the same recording occasion was up to sevenfold, and from first to second recording up to fivefold. The increase in MSA correlated with the degree of discomfort from the ice water. In nine subjects with a large increase in MSA on ice water immersion, intracutaneous painful electrical stimulation to a level equalling the discomfort from the ice water was added, but it was not accompanied by any change in MSA. The increase in MSA was accompanied by and correlated quite well with an increase in blood pressure. Intra‐arterial blood pressure recordings showed that MSA occurred at pressure levels normally associated with total inhibition of MSA, and that an inverse linear relationship between diastolic blood pressure and MSA at rest was abolished during the ice water immersion. SSA showed no consistent change with ice water immersion.I t is concluded that the cold pressor test is a powerful activator of MSA, i.c. baroreceptor‐governed vasoconstrictor outflow; that MSA contributes to the blood pressure elevation with this manoeuvre; that MSA operates at another blood pressure level during the manoeuvre and that the baroreflex inhibitory level consequently is changed; and that the response is not a reaction to pain only.
The metabolic relation between hypoxanthine and uric acid in man following maximal short‐distance running
Authors: WESTING Y. HELLSTEN , EKBLOM B. , SJÖDIN R. 
Published: December 2008

Hellstn Westing, Y., Ekblom, B. & Sjödin, R. 1989. The metabolic relation between hypoxanthine and uric acid in man following masimal short‐distance running. Acta Physiol Scand 1–37, 341–345. Received 10 March 1989, accepted 24 June 1989. ISSN 0001–0772. Department of Physiology III, Karolinska Institute, and Swedish Defence Research Establishment, Stockholm, Sweden.This study was performed to asscss the metabolic relation between hypoxanthine and uric acid following short‐distance maximal running. Eleven trained males, mean age 22 years (16–31), were instructed to run 800 m in the shortest time possible. Bood samples were collected before warm‐up, before the run, immediately after the run and periodically up to 24 h following the run. Blood lactate was determined after warm‐up, and at 5, 10, and 30 min following the run. Mean Vo2 mas for the subjects was 65.8 (4.7) (SD) ml kg‐1 min‐1 and mean oxygen demand for the running was 118 (8)%, of Vo2 may. Plasma hl‐poxanthine levels rose from 3.3 (1.4) to a peak of 48.2 (19.0)μmol l‐1 at to min following the run and at 180 min had almost returned to pre‐tun levels Plasma uric acid levels rose from a pre‐run value of 267 (34) to a peak value of 131 (87) μmol l‐1 at 45 min following the run. Uric acid concentrations had not returned to normal at 10 h following the run. The hlood lactate level peaked at j min with 13.7 (2.0) mmol l‐1. The results obtained in this study indicate a metabolic relationship between the formation of hypoxanthine and the formation of uric acid. The data also indicate that xanthine osidase is active following short‐distance intensive running.
Calcium dependency of the post‐stimulatory potentiation of the neurogenic response in small mesenteric arteries from the rat
Authors: SJÖRLOM‐WIDFELDT N. , NILSSON H. 
Published: December 2008

We have previously shown that the contraction of small mesenteric arteries in response to nerve stimulation is enhanced by preceding high‐frequency stimulation. We have now investigated the calcium dependency of this post‐stimulatorp potentiation. Small arteries (inner diameter 150–250 μm) from normotensive rats were dissected free from surrounding tissue, and segments were mounted in a myograph where the wall tension was measured at well‐defined circumferences. Nerve stimulation was performed by field stimulation.A single stimulation of the nerve caused a contraction of 2.6 ± 0.25%, of maximal adrenergic response. After a high‐frequency nerve stimulation with 16 Hz and 480 pulses the response to a single nerve stimulation was enhanced 6.6 ± 1.3 times. The potentiation decayed with a time constant of 93.7 ± 20.0 s. The amplitude of the post‐stimulatory potentiation was dependent on the extracellular calcium concentration during the conditioning stimulation. In a solution containing 2.5 mM calcium the single twitch was enhanced 6.6 times while after exposure to reduced calcium (0.5 mm) it was only enhanced twice.The contraction caused by a short burst of high‐frequency nerve stimulation (20 Hz and 10 pulses) was potentiated four times by a conditioning stimulation (16 Hz and 480 pulses), and this potentiation seemed to be independent of the extracellular calcium concentration during the conditioning stimulation.Thus the magnitude of the post‐stimulatory potentiation of single nerve stimulations is linearly related to the extracellular calcium concentration during the conditioning nerve stimulation. For the potentiation of the response to burst stimulation no relation was found between the potentiation and extracellular calcium.
Renal and circulatory effects of medullipin I, as studied in the in‐vivo cross‐circulated isolated kidney and intact Wistar‐Kyoto (WKY) rat
Authors: KARLSTRÖM G. , ARNMAN V. , BERGSTRÖM G. , MUIRHEAD E. E. , RUDENSTAM J. , GÖTHBERG G. 
Published: December 2008

The renal medulla harbours powerful humoral antihypertensive mechanisms, as earlier explored in unclipping experiments on renal hypertensive rats or in normotensive isolated kidneys cross‐circulated at increased perfusion pressures from ‘donor rats’, in which renal function also seemed to be affected. Injection of the renomedullary factor medullipin I (Med I; formerly ANRL) mimics these haemodynamic responses, and Med I seems to be one of the most important mediators of the depressor effects.The present study was performed to analyse further the haemodynamic and, particularly, the renal effects of Med I, using anaesthetized intact WKY rats and constant‐pressure perfused (90 mmHg) isolated WKY kidneys, cross‐circulated by these intact ‘donor’ rats. Mean arterial pressure (MAP), heart rate (HR) and renal function were followed for one 30‐min period before and two 30‐min periods after injection of 1 mg Med I (M; n = 7) or an equal volume of saline as control (C; n = 13).In the intact ‘donor’ WKY, MAP and HR remained largely constant in C during the three periods, being 126 ± 5, 125 ± 5, and 120 ± 5 mmHg, while MAP fell in the M group after Med I, from 121 ± 5 to 107 ± 7 and 107 ± 5 mmHg (P <0.05), and also HR tended to decrease in M. Renal resistance (RR) fell while renal plasma flow (RPF) and glomerular filtration rate (GFR) increased significantly (P < 0.05) after Med I in the M donor rats despite their MAP reduction. However, in the constant‐pressure perfused, cross‐circulated kidneys the RR, RPF and GFR changes were clearly more pronounced (P < 0.01) and also diuresis, natriuresis, osmolar excretion and osmolar clearance increased significantly after Med I (P <0.01). In conclusion, the present results support the view that Med I not only has important and long‐lasting depressor effects but also affects renal function in important ways, inducing vasodilatation and increasing GFR, RPF, diuresis and sodium‐osmolar excretion.
Sex‐linked variation in creatine kinase release, and its dependence on oestradiol, can be demonstrated in an in‐vitro rat skeletal muscle preparation
Authors: AMELINK G. J. , KOOT R. W. , ERICH W. B. M. , VAN GIJN J. , BÄR P. R. 
Published: December 2008

Creatine kinase (CK) release from male and female rat soleus muscles was studied for 4.5 h in vitro, under basal conditions and after electrical stimulation. Basal CK release was greater from male than from female muscles, and CK release from male muscles increased significantly when the muscle tension in the in‐vitro set‐up was increased. CK release after electrical stimulation was also more marked in male soleus muscles. Pretreatment of male rats and ovariectomized female rats with oestradiol for 3 weeks attenuated the enzyme efflux, but ovariectomy 24 h before in females, or oestradiol administration 24 h before in males, did not affect the release of CK in vitro. The data show that sex‐linked differences in CK efflux are still present, under both basal and stimulated conditions, when muscles are isolated from the intact animal, and that hormone treatment of the intact animal affects these properties in the isolated muscle in vitro.(Experiments with rats were performed under supervision of a legally appointed administrator.)
Cardiovascular and endocrine responses to haemorrhage in the pig
Authors: JACOBSEN J. , SØFELT S. , SHEIKH S. , WARBERG J. , SECHER N. H. 
Published: December 2008

Heart rate (HR), mean arterial pressure (MAP), indices of sympathetic and parasympathetic activity (plasma concentrations of adrenaline, noradrenaline and pancreatic polypeptide, PP), vasopressin (VP) and aldosterone (ALDO) were measured in six pigs during continuous bleeding resulting in hypovolaemic shock, from which five survived. Three stages of haemorrhage could be defined.Stage I. Resting MAP was 85 ± 6 mmHg and increased to 96 ± 5 mmHg with a blood loss of 275 (range 250–300) (10 (9–12)% of the estimated blood volume) concomitant with an increase in HR from 105 ± 5 to 113 ± 6 beats min‐1 (P < 0.05).Stage II. After a blood loss of 375 (300–500) ml (15 (13–16)%) MAP fell to 62 ± 9 mmHg and HR to 95 ± 5 beats min‐1 (P < 0.05).Stage III. A blood loss of 1113 (825–1450) ml (44 (30–52)%) resulted in a MAP of 50 ± 4 mmHg and an increase in HR to 206 ± 3 beats min‐1 (P < 0.05). Adrenaline increased from 0.3 ± 0.1 to 0.8 ± 0.3 (stage II) and 3.6 ± 1.1 nmol l‐1 (stage III) (P < 0.05); noradrenaline from 0.4 ± 0.1 to 1.5 ± 0.4 (stage II) and 5.9 ± 1.7 nmol l‐1 (stage III) (P < 0.05); PP from 6.2 ± 1.6 to 13.3 ± 2.3 (stage II) and 20.9 ± 7.8 pmol l‐1 (stage III) (P < 0.05). VP changed only marginally, but ALDO increased from 496 ± 54 to 623 ± 76 pmol l‐1 (stage III) (P < 0.05). The results suggest that a high HR and intense sympathetic activity is seen during severe haemorrhage in the pig while vagal slowing of the heart and moderate hypotension are prominent when bleeding amounts to approximately 15% of the estimated blood volume.