bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of papillary exposure on intrarenal distribution of glomerular filtration rate and of plasma flow
Authors: HANSELL P. , GÖRANSSON A. , SJÖQUIST M. , ULFENDAHL H. R. 
Published: December 2008

Removal of the renal pelvis in order to expose the renal papilla has been shown to cause impairment of the renal concentrating ability by an unknown mechanism. To study this phenomenon, urine osmolality (Uosm), single‐nephron glomerular filtration rate (SNGFR) in outer and inner cortical nephrons and the inner and outer medullary plasma flow were determined. Measurements were performed on groups of rats before (control) and 15, 45 and 90 min after exposure of the left renal papilla. Rats with an intact ureter were studied in parallel to see whether the variables varied within the 90‐min period of the study. In all groups of animals with an exposed papilla, Uosm was lower than in non‐exposed animals. Outer cortical SNGFR in rats with exposed papillae, regardless of time, was not different from that in control rats. Inner cortical SNGFR after 45 and 90 min of exposure did not differ from that in controls, but after 15 min of exposure it was lower than in control animals. Outer and inner medullary plasma flow did not differ between rats with exposed papillae and controls, irrespective of exposure time.In conclusion, papillary exposure results in a permanent decrease in urine osmolality. This impairment of the concentrating ability cannot be attributed to prolonged changes in renal haemodynamics.
Cholinergic‐induced oscillating transepithelial short‐circuit current in cultured human sweat duct cells
Authors: PEDERSEN P. S. 
Published: December 2008

Human sweat duct cells in primary culture were investigated by voltage‐clamp technique. Stimulation with the muscarinic agonist, metacholine (MCh), produced an abrupt transient rise followed by sustained regular oscillations in the transepithelial short‐circuit current (Iscc), which in these cells is carried by a mucosal amiloride‐sensitive Na+ influx, secondary to a Ca2+‐activated, voltage‐dependent, large K+ shunt across the serosal membrane.The time of latency, the initial transient phase, and the sustained oscillating phase of the MCh‐induced Iscc response were demonstrated to be differently affected by changes in temperature, agonist concentration and external Ca2+ supply. From these results a model is proposed for the MCh‐induced signal transduction in cultured sweat duct cells, involving a primary intracellular oscillatory Ca2+ mobilization, activated by IPP, sustained by a temperature‐regulated external Ca2+ supply, and counter‐regulated by cytosolic Ca2+.
Extracellular levels of quinolinic acid are moderately increased in rat neostriatum following severe insulin‐induced hypoglycaemia
Authors: WESTERBERG E. , MAGNUSSON K. , WIELOCH T. , UNGERSTEDT U. , SPECIALE C. , SCHWARCZ R. 
Published: December 2008

Extracellular concentrations of the brain metabolite quinolinic acid, an endogenous excitotoxin, were monitored by microdialysis in rat neostriatum and hippocampus/cortex during and following a 30‐min period of insulin‐induced hypoglycaemia. During hypoglycaemia‐induced isoelectricity, extracellular levels of quinolinic acid in the striatum (basal value, 1.1±0.3pmol per 30‐μl fraction) were elevated 1.7 times as compared to the control period. Thirty to ninety minutes following hypoglycaemia a significant increase in extracellular quinolinic acid to 2.2 times basal level was noted. After 2 h recovery, the beginning of neuronal necrosis was observed in the dorsolateral striatum. Implantation of the dialysis probe did not influence the extent of neuronal damage. No changes in extracellular quinolinic acid levels were observed in the hippocampus/cortex.The data indicate that following a severe hypoglycaemic insult vulnerable striatal cells are exposed to hyperphysiological extracellular quinolinic acid concentrations over an extended period of time. Considering the pronounced susceptibility of rat striatal neurons to the toxin, the small but prolonged elevation in the extracellular levels of quinolinic acid could be of significance for the development of delayed neuronal death in hypoglycaemia.
Adrenal cortex contributes to the regulation of NaCl‐stimulated ANP release in the rat
Authors: ARJAMAA O. , VUOLTEENAHO O. , TASKINEN T. , TUOMINEN M. , LEPPÄLUOTO J. 
Published: December 2008

The present study documents the effects of hypophysectomy and the effects of dexamethasone substitution on the NaCl‐stimulated release and on the basal secretion rates of ANP from the rat atria in vitro. We also measured the concentration of mRNA in the atria after hypophysectomy. Rats (n = 12) were subjected to hypophysectomy by a parapharyngeal approach. One group of rats (n = 6) received dexamethasone 0.2 mg s. c. daily for 4 weeks, while the other group was left unsubstituted. After 4 weeks, the atrial block (n = 10) was excised, placed in an organ bath (field stimulation 4 s‐1, 20 V, I ms; resting tension = 5 mN) and superfused (7 ml min‐1) either with a physiological buffer solution (295 mosmol kg‐1) or with a hyperosmotic NaCl solution (330 mosmol kg‐1). The atria from the hypophysectomized rats did not respond to the stimulus: the concentration of ANP in the I‐min samples of the perfusate was under 100 pg ml‐1. Dexamethasone treatment significantly (P < 0.05) increased the ANP concentration to a maximum of 165 ± 17 (mean ± SEM) pg ml‐1 during the superfusion while the control concentration was 110±19 pg ml‐1. The ANP mRNA/18 S RNA ratios did not differ between the atria of hypophysectomized and control rats.In conclusion, glucocorticoids are required in the stimulus‐induced release of ANP and the impaired release of ANP after hypophysectomy does not depend on an impaired synthesis of ANP.
Multiunit neural responses to strong finger pulp vibration. I. Relationship to age
Authors: SCHMIDT R. F. , WAHREN L. K. , HAGBARTH K.‐E. 
Published: December 2008

The effect of age on mechanoreceptive function in the distal part of the fingers was studied in 12 healthy subjects aged 18–64 years.A recording microelectrode was inserted into a sensory fascicle of the median nerve at the wrist. Multiunit mechanoreceptor activity was recorded from the fascicular field, which is typically restricted to the ulnar or radial half of one finger, corresponding to the innervation zone of one digital nerve. Strong standardized vibration (40 Hz) was applied to the finger pulp, with the amplitude of the vibration pulses high enough to induce maximal neural impulse volleys. With the same microelectrode recording position, maximal neural impulse volleys were also induced by electrical pulses applied to the ventral digital nerve supplying the finger pulp. In each subject, the areas of the mechanically and the electrically induced responses were measured (after integration and averaging) and the ratio of mechanically to electrically induced responses (MR/ER) was determined.The MR/ER ratio decreased with increasing age of the subject. This finding was considered to indicate that it is the peripheral parts of the sensory units, involved in the mechanoelectrical transfer functions, that exhibit the most pronounced degenerative changes during the ageing process. This is in line with previous histological findings of pronounced age‐related degeneration of Meissner corpuscles and other mechanoreceptive end organs in the finger pulps.
Lack of fusimotor modulation in a motor adaptation task in man
Authors: AL‐FALAHE N. A. , NAGAOKA M. , VALLBO Å. B. 
Published: December 2008

Single‐unit activity was recorded from the radial nerve of human subjects along with surface electromyogram, joint angle, velocity, and torque at a metacarpophalangeal joint. Nine afferents from muscle spindles in the extensor digitorum muscles were studied in a motor adaptation task which involved modulations of the long‐latency stretch reflex. While subjects slowly moved one finger, a perturbation which rapidly stretched the parent muscle was applied. The subjects' task was to return their finger as fast as possible. In a series of identical control experiments, electromyographic activity and performance alone were recorded, but not spindle afferents.Subjects improved their performance by a varying degree when the test was repeated. Optimal performance was usually associated with increased electromyographic activity at a latency of about 60 ms, which was interpreted as a long‐latency stretch reflex.The response of the individual spindle afferents to perturbation was uniform in repeated tests regardless of the size of the reflex, e.g. whether it was large or lacking altogether.It was concluded that modulations of the size of the long‐latency stretch reflex in the present motor adaptation task were accounted for by mechanisms other than adjustments of the fusimotor activity, because spindle response to an invariant perturbation remained invariant when the size of the reflex varied substantially.
Stimulus–response properties of the slowly adapting stretch receptor neuron of the crayfish
Authors: RYDQVIST B. , SWERUP C. 
Published: December 2008

The receptor potential and receptor current in response to ramp‐and‐hold extensions were measured in the slowly adapting stretch receptor of the crayfish, using potential clamp technique. The stimulus‐response relationship for the peak amplitude of the receptor current showed a linear behaviour for extensions less than 2% and a nonlinear behaviour for extensions larger than 5%. Using the Stevens power law, R=k(S—So)“, where R is response, S is stimulus, So is threshold stimulus and n the power coefficient, n was found to be 3 for extensions between 5 and 15%. The receptor current saturated at extensions above 20–25% of the zero length of the muscle, resulting in a lower n value. However, the n value is difficult to define in this region due to the saturation.The stimulus‐response relation for the receptor current can be explained by the properties of the stretch‐activated channels for which the open probability is exponentially dependent on the square of the membrane tension, as suggested by recent findings.The receptor potential, using tetrodotoxin, in response to identical ramp‐and‐hold extensions as those used to record current responses showed a more complex time‐course, indicating involvement of potential‐dependent channels, potassium channels being the most probable candidate. This was supported by a mathematical model which takes into account the viscoelastic properties of the receptor muscle, the properties of the stretch‐activated channels and a potential dependent K+ current.
Difference in the actions of calcitonin gene‐related peptide on pig detrusor and vesical arterial smooth muscle
Authors: PERSSON K. , GARCIA‐PASCUAL A. , ANDERSSON K.‐E. 
Published: December 2008

Calcitonin gene‐related peptide has been demonstrated in urinary bladder nerves, and suggested to play a role in local control of bladder motility. In isolated strips of pig detrusor muscle, calcitonin gene‐related peptide did not affect spontaneous contractile activity, or contractions induced by high K+, carbachol, substance P, and electrical field stimulation. In contrast, calcitonin gene‐related peptide elicited a concentration‐dependent and pronounced (78–99%) relaxation of vesical arteries precontracted with endothelin‐1, noradrenaline or prostaglandin F2x. As a vasodilator, CGRP was approximately 50 times more potent than acetylcholine. Removal of the endothelium abolished acetylcholine‐induced relaxation, but did not affect the relaxation produced by calcitonin gene‐related peptide. Pretreatment with methylene blue, glibenclamide or indomethacin had no influence on CGRP's ability to relax the vessels. The inhibitor of NO‐synthesis, NG‐nitro‐L‐arginine, had no effect on the maximum vascular relaxation induced by calcitonin gene‐relate peptide.It is concluded that in the pig, calcitonin gene‐related peptide has no functionally important mechanical effects on isolated detrusor muscle strips, but is a potent dilator of vesical arteries. The vascular effects of the peptide are endothelium‐independent, and seem to be exerted directly on the vascular smooth muscle.
The interaction between cAMP‐dependent and cAMP‐independent mechanisms in mediating the somatostatin inhibition of insulin secretion in isolated rat pancreatic islets
Authors: MALM D. , VONEN B. , BURHOL P. G. , FLORHOLMEN J. 
Published: December 2008

To characterize the intracellular mechanisms by which somatostatin modulates the insulin secretion, studies were performed with isolated rat pancreatic islets at 12 mmol 1‐1 glucose. Somatostatin (0.1–1000 nmol 1‐1) inhibited the glucose‐induced insulin secretion concentration‐dependently. Increasing intracellular cAMP concentration either with dibutyryl‐cAMP (1 mmol 1‐1) or by the adenylate cyclase activator forskolin (20 μmol 1‐1) partly reversed the inhibition by somatostatin (100 nmol l‐1). Neither somatostatin (100 nmol 1‐1) nor dibutyryl‐cAMP (1 mmol 1‐1 were able to affect the low insulin secretion observed in the absence of extracellular Ca2+. To study cAMP‐independent mechanisms of somatostatin, the experiments were performed with and without dibutyryl‐cAMP (1 mmol 1‐1) present. Both somatostatin (100 nmol 1‐1) and the Ca21‐channel blocker verapamil (25 μmol 1‐1) inhibited the insulin secretion both with and without dibutyryl‐cAMP present. An additional inhibition of the insulin secretion was observed when somatostatin was combined with verapamil in the absence, but not in the presence of dibutyryl‐cAMP.We conclude that somatostatin inhibits the glucose‐induced insulin secretion both by cAMP‐dependent mechanism which requires extracellular Cat2+, and by cAMP‐independent/verapamil‐sensitive Ca+2‐channel‐dependent mechanism.
Regional distributions of blood flow and tissue uptake rates of vitamin B12 and albumin within single rabbit skeletal muscles
Authors: IVERSEN P. O. , NICOLAYSEN G. 
Published: December 2008

The mechanism underlying the marked regional variations in blood flow within single skeletal muscles has not been identified. The present investigation was prompted by previous data pointing to a regional distribution of the number of perfused vessels as one possible determinant for the heterogeneous perfusion pattern. We examined this possibility by assessing the regional tissue uptake rates of vitamin B12 and albumin assuming that these are related to the number of perfused vessels. This is the first study that has included simultaneous measurements of regional blood flow and of regional tissue uptake rates of vitamin B12 and albumin within single skeletal muscles in the intact animal.The microsphere method was adopted to measure regional blood flow in 0.25 g muscle regions in awake and in anaesthetized rabbits. Various tracers were used to assess the regional distributions of tissue uptake rates and of vascular and interstitial volumes.Albeit displaying a marked regional heterogeneity, neither the tissue uptake rate of vitamin B12 nor that of albumin were correlated to regional blood flow (P < 0.05) at rest (awake or anaesthetized rabbits) or during exercise hyperaemia (anaesthetized). At rest, but not during exercise, the distributions of regional tissue uptake rates of the two tracers showed a striking bimodal pattern. Vascular and interstitial volumes showed minimal interregional variations.The lack of correlation between regional blood flow and tissue uptake rates and the minute interregional variation in vascular volume, argue against variations in the number of perfused vessels as the explanation for the regional heterogeneity in blood flow.
Lactate transport during differentiation of skeletal muscle cells: evidence for a specific carrier in L6 myotubes
Authors: ABIDA K. EL , DUVALLET A. , THIEULART L. , RIEU M. , BEAUDRY M. 
Published: December 2008

El abida, K., Duvallet, A., Thieulart, L., Rieu, M. & Beaudry, M. 1992. Lactate transport during differentiation of skeletal muscle cells: evidence for a specific carrier in L6 myotubes. Acta Physiol Scand144, 469471. Received 12 June 1991, accepted 8 October 1991. ISSN 0001–6772. Laboratoire de physiologie des adaptations, CIIU Cochin, 24 rue du Faubourg Saint Jacques, 75104 Paris, France.Cellular uptake of lactate involves a carrier in numerous types of mammalian cells. In cultured rat L6 myoblasts, lactate diffuses freely. We show that during myogenesis a carrier appears at the myotube stage.The degree of cellular differentiation was determined by microscopic observation and by measurement of a marker of biochemical differentiation: the increase in specific activity of creatine kinases.
Renal effects of urodilatin and atrial natriuretic peptide in volume expanded conscious dogs
Authors: BESTLE M. H. , BIE P. 
Published: December 2008

The renal effects of urodilatin and atrial natriuretic peptide (ANP) were examined in conscious dogs during acute volume expansion maintained through independent infusions of water and NaCl. Peptide was infused in a step‐up fashion, in 40‐min periods at rates of 2.5, 12.5 and 50.0 ng kg‐1 min‐1 (ANP, urodilatin) or 0.5, 2.5 and 10.0 ng kg‐1 min‐1 (second series of urodilatin). ANP immunoreactivity (ANPir) in plasma was measured with an antibody showing 100% cross‐reactivity with urodilatin.At 50 ng kg‐1 min‐1, ANP increased plasma ANPir some 10‐fold (64 ± 6 pg ml‐1 to 728 ± 82 pg ml‐1) while urodilatin elicited a 25‐fold increase in ANPir (78± 13 pg ml‐1 to 1645 ± 204 pg ml‐1). ANP doubled sodium excretion (61 ± 12 to 124±30 μmol min‐1, P < 0.05) while urodilatin increased sodium excretion to 269 ± 45 μmol min‐1. Both peptides approximately doubled urine flow. Urodilatin at 10 ng kg‐1 min‐1 increased sodium excretion from 57±17μmol min‐1 to 106 ± 25 μmol min‐1, i.e. similar to the response ANP elicited at 50 ng kg‐1 min‐1. In the time control series a significant fall in sodium excretion was observed, despite the continuous replacement of sodium and water.The results demonstrate that in identical, relatively high doses, the changes in sodium excretion, diuresis, heart rate (HR) and arterial pressures elicited by urodilatin are more pronounced than those of ANP. However, such amounts seem to produce plasma concentrations of urodilatin higher than those of ANP. A given small increase in sodium excretion required higher plasma levels of ANP compared to urodilatin. Therefore, for a given modest plasma level, urodilatin is a more potent natriuretic agent than ANP.
Control of shivering and heart rate in incubating bantam hens upon sudden exposure to cold eggs
Authors: TØIEN Ø. 
Published: December 2008

To distinguish shivering released by cooling of the brood patch from shivering released by low core temperature, incubating bantam hens were exposed to water perfused eggs. Responses to a period of egg cooling were compared to the recovery period after egg temperature had been returned to 40 oC, but cloacal temperature (Tb) still was low. At an ambient temperature (Ta) of 23 oC and exposure of the hens to between two and eight eggs cooled to 10–35 oC (series 1), electromyographic (EMG) activity of musculus iliotibialis increased rapidly with an occasional overshoot, and was higher during egg cooling than during recovery. This hysteresis in EMG activity and Tb was weakly correlated to egg temperature and clutch size. Heart rate (HR) showed an almost parallel increased to shivering except that a maximum HR was reached at high shivering intensities. These responses were also present at a Ta of 37 oC when the hens were slightly hyperthermic before exposure to eight eggs at 20 oC (Series 2). At the highest starting Tbs EMG activity increased linearly after a drop in Tb. Shivering in m. pectoralis showed a lower threshold Tb and lower activity than m. iliotibialis during egg cooling, and immediately ceased at the end of egg cooling. Total body thermosensitivity estimated from the recovery periods at low and high Ta was –9.7 and –6.4 W kg‐1oC‐1, respectively.It is concluded that shivering in incubating birds warming cold eggs probably is stimulated both by peripheral and central thermoreceptors. The peripheral component shows phasic properties typical for skin receptors.
Mechanisms behind cyclic changes in duodenal fluid transport in the fasting state
Authors: MELLANDER A. , ABRAHAMSSON H. , SJÖUVALL H. 
Published: December 2008

The relationship between distal duodenal motility, fluid transport and transmural potential difference (PD) was studied in 33 healthy volunteers. Motor activity was registered with a low‐compliance pneumohydraulic system; one pressure channel also served as an intraluminal flowing electrode for registration of transmural PD. Net fluid and bicarbonate transport were measured with a triple lumen perfusion technique.The relation between net fluid transport (NFT) and transmural PD depended on the current phase of the migrating motor complex (MMC). In phase I and early phase II (low motor activity), a significant net fluid absorption was seen when the perfusate contained glucose (30 HIM). If glucose was substituted with mannitol, NFT was not significantly different from zero and transmural PD was slightly lumen positive. In the early part of the MMC cycle (low motor activity), there was a significant correlation between a more lumen negative transmural PD and a higher net fluid absorption in individual experiments (r =–0.65; P < 0.01).In late phase II of the MMC cycle (high motor activity), NFT changed significantly in the secretory direction in both Krebs mannitol and Krebs glucose perfused segments, and the perfusate‐related difference in transport rate was no longer statistically significant. In the Krebs mannitol group, transmural PD became significantly more lumen negative, and there was also a decrease in net bicarbonate absorption as well as a slight acidification of the luminal contents. The relationship between transmural PD and NFT was reversed, i.e. a more lumen negative PD was associated with a higher net fluid secretion in individual experiments (r = 0.82; P < 0.05).The results show that in the fasting state, the distal duodenum alternates between an absorptive and a secretory mode. Fluid secretion is probably generated by activation of an electrogenic secretory process during late phase II of the MMC cycle.