bluuebunny/crossref_metadata_2025_split huggingface dataset:
Rubrospinal Control of Static and Dynamic Fusimotor Neurones
Authors: Appelberg B. , Jeneskog T. , Johansson H. 
Published: December 2008

AbstractRubrospinal effects on about 60 extracellularly recorded γ‐motoneurones were studied in anesthetized cats. All cells were antidromically identified from various muscle nerves. 23 cells were regarded as dynamic as they were activated from a mesencephalic region previously known to influence selectively muscle spindle dynamic sensitivity. The pattern of rubrospinal influence on static fusimotor neurones to different muscles closely followed that previously demonstrated for α‐motoneurones with predominantly excitation of flexor neurones and excitation or inhibition in equal amounts of extensor cells. Dynamic fusimotor neurones were influenced in a strictly reciprocal manner with excitation of flexor cells and inhibition of extensor cells except for a few neurones which could not be reached from nucleus ruber. Evidence was also obtained indicating that the shortest path from nucleus ruber to static fusimotor neurones involves one interneurone.
Pulsatile Secretion of ACTH, GH, LH and TSH in Man
Authors: Leppäluoto J. , Laisi U. , Lybeck H. , Partanen J. , Ranta T. , Virkkunen P. 
Published: December 2008

AbstractBlood samples were taken every 4 min for 80 min from 5 healthy subjects. Plasma ACTH, GH, LH and TSH were estimated by radioimmunoassays. The mean peak intervals were11, 12, 13 and 14 minutes respectively and mean peak amplitudes were 25 pg, 1.1 ng, 11 ng and 5.3 μU. Mean durations of ascending and descending limbs of the plasma patterns of these hormones were also measured. The timing of the different hormone peaks appeared to be independent.
Non‐Hyperbolic Force‐Velocity Relationship in Single Muscle Fibres1
Authors: Edman K. A. P. , Mulieri L. A. , Scubon‐Mulieri B. 
Published: December 2008

AbstractThe force‐velocity relation has been studied in sixteen single fibres from frog semitendinosus muscle with particular attention to the high‐force portion of the curve. The force‐velocity curve was hyperbolic except for a reversal of curvature near 80 % measured isometric tension (P0). Rectangular hyperbolas fitted (linear, least‐squares method) these data well only when values below 0.78 P0 were considered. Extrapolation of these hyperbolas above 0.78 P0 gave predicted isometric tensions (P*0) which averaged 32±6% above the measured P0 values. Hill's constants (1.84°C) for these hyperbolas were: a/P*0=0.177±0.021, b = 0.329±0.035 M.L./sec, Vmax=1.91±0.074 M.L./sec. The reversal of curvature persisted when force‐velocity data were obtained using: 1 or 60 min response intervals, afterloaded isotonic responses, grid stimulation, electrically induced contractures and bundles of fibres. The reversal of curvature diminished when force‐velocity data were obtained from slightly stretched fibres (about 2.3 μm sarcomere length as compared to 2.1 μm in the control). The results indicate that sarcomere length redistributions probably do not account for the non‐hyperbolic force‐velocity relation. An explanation for the behavior based on the geometry of the contractile filament lattice is discussed.
The Effect of Serotonin and Transcapillary Pressure on the Capillary Permeability in therete mirabileof the Eel (Anguilla vulgarisL.)
Authors: Myhre Kjell , Steen Johan B. , Stray‐Pedersen Sverre 
Published: December 2008

AbstractMeasurements of transcapillary exchange of high‐molecular dextrans, K+ and THO in therete mirabileof eel (Anguilla vulgaris L.) have been made under steady‐state conditions while the transcapillary pressure was varied and pharmaca added to the perfusates. Raising the transcapillary input pressure increased the exchange of dextrans and K+ but lowered that of THO. Histamine and ouabain had no effect on the transcapillary exchange of the test molecules. The highest dose (100 μg/ml) of serotonin reversibly increased the capillary permeability of D‐75 000, K+and THO while the medium dose (50 μg/ml) only raised the transcapillary exchange of K+and THO. The lowest dose (10 μg/ml) had no permeability effect. Our main conclusion is that serotonin reversibly increases the area of the intercellular pores by affecting the capillary wall directly.
Plasma Renin Activity Following Central Infusion of Angiotensin II and Altered CSF Sodium Concentration in the Conscious Goat
Authors: Eriksson Lea , Fyhrquist Frej 
Published: December 2008

AbstractTo study central influences on the renal release of renin, angiotensin II was infused into the lateral cerebral ventricle of conscious hydrated goats. CSF sodium concentration was increased or lowered by similar infusions of hypertonic NaCl or of isotonic fructose solution. Infusion of anglotensin II in doses from 0.5 to 1 μgcaused a drop in plasma renin activity (PRA) and elicited a rise in blood pressure, antidiuresis, natriuresis, and thirst. Intraventricular infusion of hypertonic NaCl also suppressed PRA, induced anti‐diuresis, natriuresis, and an inconsistent rise in blood pressure. Lowering of CSF [Na+] by infusion of isotonic fructose caused a rise in PRA and was followed by a water diuresis in the non‐hydrated animal. The fructose infusions caused some decrease in renal K+excretion but no consistent change in renal Na+excretion. The results indicate that angiotensin II and changes in sodium balance modulate renal renin release alsoviathe central nervous system.
Local Reflex in Microcirculation in Human Cutaneous Tissue
Authors: Henriksen O. , Sejrsen P. 
Published: December 2008

AbstractBlood flow in cutaneous tissue measured by the local133Xenon washout technique decreased about 35 per cent during venous stasis of 40 mmHg in three normal subjects. The response was unaffected by block of the nerve three cm proximally to the labelled area. When the tissue was infiltrated with lidocaine or with phentolamine, blood flow remained constant, indicating that the decrease in blood flow is due to an arteriolar vasoconstrictor response to increase in venous transmural pressure. Local venous stasis elicited a vasoconstrictor response in an adjoining area not affected by the stasis. The response was blocked by lidocaine applied to the side of stasis. In 2 chronically sympathectomized patients, the vasoconstrictor response was abolished in the denervated limbs hut present on the non‐operated side (1 patient with unilateral sympathectomy). The results indicate that the vasoconstrictor response to an increase in venous transmural pressure is due to a local nervous mechanism involving sympathetic adrenergic fibres, most likely a sympathetic axon reflex.
Formation and Action of Prostaglandin Endoperoxides in the Isolated Human Umbilical Artery
Authors: Tuvemo Torsten , Strandberg Kjell , Hamberg Mats , Samuelsson Bengt 
Published: December 2008

AbstractThe effects on the isolated human umbilical artery (HUA) of the recently isolated endoperoxide intermediates in prostaglandin (PG) biosynthesis, PGG2 and PGH2, were studied. Both endoperoxides were potent contractors of the artery strips, the threshold concentrations being 3 (1–4) ng/ml for PGG2 and 1 (1–2) ng/ml for PGH2, as compared with 200 (40–400) ng/ml for PGE2. The hemiacetal derivative of 8‐(1‐hydroxy‐3‐oxopropyl)‐9,12L‐dihydroxy‐5,10‐heptadecadienoic acid (thromboxane B2), a metabolite of PGG2, appeared in the bath medium indicating PG and thromboxane generation in the isolated HUA. The formation of thromboxane B2 was inhibited by indomethacin (8–40 μg/ml) and by eicosa‐5,8,11,14‐tetraynoic acid (ETA) (25 μg/ml). ETA also inhibited the contractile responses to both endoperoxides. The results support the view that local generation of PGs might be involved in the closure of the HUA at birth.
Inhibition by Acidosis of Adenosine 3‘,5’‐Cyclic Monophosphate Accumulation and Lipolysis in Isolated Rat Fat Cells1
Authors: Fredholm Bertil B. , Hjemdahl Paul 
Published: December 2008

AbstractLipolysis and cyclic AMP accumulation were studied in isolated rat fat cells at normal (7.4) and decreased (7.0, 6.6) pH. Acidosis inhibited lipolysis and cyclic AMP accumulation due to NA non‐competetively. Maximal lipolysis (3 μM NA) was inhibited by 25% at pH 7.0 and by 61 % at pH 6.6. Cyclic AMP accumulation 5 min after 3 μM NA was inhibited by 57% at pH 7.0 and by 83% at pH 6.6. Between 10 and 60 minutes of incubation NA‐stimulated lipolysis was linear at pH 7.4, whereas a progressively increasing inhibition was seen at lower pH. The FFA production was inhibited to the same degree as glycerol production by acidosis. The fraction of FFA associated with the cells was the same at all pHs. Thus, we have no evidence that acidosis inhibits lipolysis via accumulation of FFA intracellularly. NA‐induced accumulation of3H‐cAMP from3H‐ATP, endogenously formed by prelabelling the cells with3H‐adenine, was inhibited by acidosis both in the presence and absence of theophylline in the incubation medium (by 48 and 44% respectively at pH 7.0 and by 74 and 68 % at pH 6.6). Cyclic nucleotide phosphodiesterase in homogenates of fat cells was inhibited by decreasing the pH, whether measured at high or low substrate concentrations. Basal adenylyl cyclase activity in a cell membrane fraction from fat cells was affected to a minor degree, while NA‐stimulated activity was inhibited by decreased pH. The response to 3 μM NA at pH 6.6 was inhibited by 43% relative to control. The results show that acidosis inhibits NA‐induced cyclic AMP accumulation by interfering with the formation, rather than the inactivation of the nucleotide. Since NA‐induced lipolysis is a cyclic AMP‐mediated process it is suggested that at least part of the antilipolytic effect of acidosis is due to inhibition of cyclic AMP formation.
Cyclic AMP‐Dependent and Independent Inhibition of Lipolysis by Adenosine and Decreased pH
Authors: Hjemdahl Paul , Fredholm Bertil B. 
Published: December 2008

AbstractNA‐stimulated lipolysis and cAMP formation in isolated rat fat cells is inhibited by acidosis. In the present report we have examined the quantitative relationship between lipolysis and cAMP formation at normal and reduced pH and the possible involvement of adenosine, an endogenous inhibitor of cAMP formation. Adenosine antagonized cAMP accumulation and to a considerably lower degree lipolysis, effects potentiated by acidosis. Theophylline, an antagonist of adenosine effects, stimulated lipolysis and cAMP‐accumulation, and potentiated responses to NA. Adenosine deaminase (ADA) had theophylline‐like effects. Acidosis inhibited lipolysis and cAMP accumulation induced by ADA and theophylline to a larger extent than those induced by NA. It is suggested that adenosine modulates fat cell cAMP production and may contribute to the antilipolytic effect of acidosis. There was a curvilinear relationship between cAMP elevation and glycerol production in fat cell suspensions, which was different at pH 7.4 and at pH 6.6. The amount of cAMP needed for half‐maximal activation of lipolysis increased from 1.3 (pH 7.4) to 3.1 pMol × 10‐5cells (pH 6.6). The maximal glycerol production was reduced from 1 300 to 900 nMol × 10‐5cells. The antilipolytic effect of acidosis is apparently due partly to an inhibition of cAMP formation and partly to inhibition of subsequent step(s) in the activation sequence.
Rubrospinal Effects on Ventral Spinocerebellar Tract Neurones
Authors: Baldissera F. , ten Bruggencate G. 
Published: December 2008

AbstractStimulation of the contralateral red nucleus evoked monosynaptic EPSPs in 14 of 82 ventral spinocerebellar tract neurones. In some of these cells the monosynaptic EPSP was followed by a disynaptic IPSP. The remaining cell population received di‐ or polysynaptic PSPs from the rubrospinal tract, either EPSPs or IPSPs or both. Convergence of the rubrospinal tract onto interneurones of the segmental pathways projecting to VSCT cells was demonstrated. Rubrospinal volleys facilitated disynaptic Ia IPSPs evoked in VSCT neurones from both flexors and extensors, as well as disynaptic Ib IPSPs. Facilitation of the Ia interneurones was disynaptic whereas facilitation of Ib interneurones was monosynaptic. Disynaptic rubrospinal EPSPs and IPSPs were facilitated by volleys in ipsi‐ as well as in contralateral cutaneous and high threshold muscle afferents. The complex pattern of projections from the rubrospinal tract onto VSCT neurones and the related reflex pathways gives further support to the hypothesis that these tract cells convey information on transmission through interneurones of the spinal segmental mechanisms.
Signal Characteristics of EMG at Different Levels of Muscle Tension
Authors: Komi Paavo V. , Viitasalo Jukka H. T. 
Published: December 2008

AbstractElectromyographic activity of m. rectus femoris at submaximal and maximal voluntary contractions was quantified by conventional integration technique and also be a more “qualitative” procedure of automated motor unit averaging and frequency spectrum analysis. By relating the EMG parameters to produced muscle tension it was observed that the integrated EMG increased in a slightly nonlinear fashion with the increase in muscle force. The other EMG variables also showed clear changes as a function of muscle tension. The averaged motor unit potential (AMUP) and its specific parameters (number of spikes, amplitude, rise time and amplitude‐rise time ratio) showed such changes with muscle tension that they may be useful in estimation of the recruitment pattern of the different types of motor units.
Myocardial Blood Flow in the Diving Seal
Authors: Blix Arnoldus Schytte , Kjekshus John K. , Enge Ivar , Bergan Anstein 
Published: December 2008

AbstractGrey seals exhibit a marked drop in heart rate, a slight decrease in ventricular contractility, and an essentially unchanged stroke volume upon diving. In the present study, we have demonstrated that the resulting drop in cardiac output is associated with a 90% reduction of coronary blood flow. Such reduction of myocardial blood flow takes place despite a significant increase in effective coronary driving pressure, and is indicative of a 800% increase in coronary vascular resistance. This means that the circulatory adjustments displayed by the diving seal (i.e. a reduction of the workload on the heart) are so effective that myocardial blood flow can be reduced to 10% of the pre‐dive value without loss of cardiac function and blood pressure. It is suggested that even partial simulation of such a circulatory state might be a successful approach in the treatment of ischemic injuries in the heart of man.
The Nature of the Training Response; Peripheral and Central Adaptations to One‐Legged Exercise
Authors: Saltin B. , Nazar Kristina , Costill D. L. , Stein E. , Jansson Eva , Essén Birgitta , Gollnick P. D. 
Published: December 2008

Abstract13 male subjects were studied and placed in 3 groups. Each group exercised one leg with sprint (S), or endurance (E) training and the other leg oppositely or not at all (NT). Oxygen uptake (Vo2), heart rate and blood lactate were measured for each leg separately and for both legs together during submaximal and maximal bicycle work before and after 4 weeks of training with 4–5 sessions per week. Muscle samples were obtained from the quadriceps muscle and assayed for succinate dehydrogenase (SDH) activity, and stained for myofibrillar AT Pase. In addition eight of the subjects performed after the training two‐legged exercise at 70% Vo2 max for one hour. The measurements included muscle glycogen and lactate concentrations of the two legs as well as the blood flow and the a‐v difference for O2, glucose and lactate.The improvement in Vo2 max, the lowered heart rate and blood lactate response at submaximal work levels were only found when exercising with a trained leg (E or S). Part of the variables studied were markedly more changed with E as compared with S‐training. Although muscle fibre composition did not change a pronounced muscle adaptation took place with the training with enhancement of the SDH activity of the S and E legs while the NT‐leg did not change. Blood flow and oxygen uptake were similar in NT and S–E legs while femoral vein oxygen content was slightly lower in the trained as compared to the NT‐leg. Glycogen utilization was lowest in the trained leg with similar glucose uptake in all legs regardless of training status. Moreover, lactate was only continuously released from the NT‐leg. It is concluded that training induces marked local adaptations which not only affects the metabolic response to exercise but also are of importance eliciting an improved cardiovascular function.
Studies of Cerebral Osmoreceptors in Anesthetized Dogs: The Effect of Intravenous and Intracarotid Infusion of Hyper‐Osmolar Sodium Chloride Solutions during Sustained Water Diuresis
Authors: Bie Peter 
Published: December 2008

AbstractThe function of the suggested hypothalamic osmoreceptors was investigated in dogs during light chloralose anesthesia. The dogs were subjected to an i.v. load of 40 ml/kg b.wt. of a hypo‐osmolar solution of sodium chloride and glucose. This degree of hydration was kept constant by a specially constructed servo system based on the weight of the animal. During water diuresis the renal free water clearance remained essentially constant for several hours (mean about 0.2 ml/kg b.wt.‐min). Renal sodium excretion was low (mean 0.82 μmol/kg b.wt. · min) and decreased continuously throughout the experimental period. I.v. infusion of hyper‐osmolar sodium chloride solution (1.33 mmol/kg b.wt. in 30 min) was followed by prolonged parallel increases in free water clearance and sodium excretion, without any detectable change in the excretion of osmoles and potassium. The renal response to bilateral infusion of hyper‐osmolar NaCl (1.33 mmol/kg b.wt. in 30 min) into the common carotid arteries was identical to the response to i.v. infusion. The estimated increase in the osmolality of the carotid blood was 2.2 %. In seven out of eight experiments intracarotid infusion of NaCl (1.33 mmol/kg b.wt. in 8 min) did not elicit any reduction in free water clearance. On the contrary, an increase was found similar to that obtained after i.v. infusion. The estimated increase in the osmolality of the carotid blood was 8.4%. The present results question the validity of the currently held view that hypothalamic osmoreceptors play an important role in the control of the osmolality of plasma.
Convergence on Interneurones Mediating the Reciprocal Ia Inhibition of Motoneurones III. Effects from supraspinal pathways
Authors: Hultborn H. , Illert M. , Santini M. 
Published: December 2008

AbstractSupraspinal effects were investigated in interneurones identified as mediating the disynaptic reciprocal Ia inhibition of motoneurones (referred to as “Ia inhibitory interneurones”). It was revealed that volleys in the vestibulospinal tract may evoke mono‐ and disynaptic EPSPs in interneurones monosynaptically excited from extensor muscles, i.e. extensor coupled Ia inhibitory interneurones. Flexor coupled interneurones instead received disynaptic inhibition. Volleys in the rubrospinal tract evoked a dominating polysynaptic excitation, usually mixed with inhibition, in flexor as well as extensor coupled interneurones. Disynaptic rubrospinal EPSPs and IPSPs were also revealed. The pyramidal tract also gives rise to a dominating polysynaptic excitation, usually mixed with inhibition, in flexor as well as extensor coupled Ia inhibitory interneurones. Rubrospinal and pyramidal volleys were shown to facilitate transmission in various segmental reflex pathways to the Ia inhibitory interneurones. A detailed comparison reveals a striking parallelism of segmental and supraspinal effects on α‐motoneurones and Ia inhibitory interneurones connected to the same muscles. This considerably strengthens the hypothesis of an “α–γ‐linkage in the reciprocal inhibition”.
Transfer of I125‐Albumin from Blood into Brain and Cerebrospinal Fluid in Newborn and Juvenile Rats
Authors: Amtorp Ole 
Published: December 2008

AbstractHuman fetuses, rabbit fetuses and newborn rats have a relatively high concentration of protein in cerebrospinal fluid (csf) as compared with the adult. The present study was undertaken in an attempt to evaluate whether this high protein concentration in newborn rats is caused by a high permeability of the blood‐brain‐csf barrier to protein or by a low production rate of csf. The results suggest that the high concentration of protein in csf in newborn rats is due to a low rate of production of csf rather than to an increased transfer of protein across the blood‐brain‐csf barrier.
Release of Adenosine‐like Material from Isolated Perfused Dog Adipose Tissue Following Sympathetic Nerve Stimulation and its Inhibition by Adrenergic α‐Receptor Blockade
Authors: Fredholm Bertil B. 
Published: December 2008

AbstractFollowing the intraarterial infusion ofsH‐adenine to isolated perfused canine subcutaneous adipose tissue, its adenine nucleotides are labelled. A continuous release of radioactivity, comprised of non‐nucleotide material, was observed. The rate of this release was markedly enhanced by sympathetic nerve stimulation. The major components of the enhanced release appeared to be inosine and adenosine. Adrenergic α‐receptor blockade (phentolamine or Hydergin®) abolished the enhanced nucleoside release, while glycerol release was enhanced. The release of radioactivity was decreased during mechanical blood flow reduction and enhanced afterwards. However, the magnitude of this enhancement of release after clamp was much less than following nerve stimulation. The results suggest that adenosine or a closely related compound is released from canine subcutaneous adipose tissue by sympathetic nerve stimulation and that the release is related to adrenergic α‐receptor stimulation. Since adenosine is a potent inhibitor of catecholamine induced lipolysis in this tissue the possibility of a regulatory role must be considered.
Effects of Ultraviolet Radiation on Pinocytosis inAmoeba proteus
Authors: Josefsson J.‐O. , Hansson S. E. 
Published: December 2008

AbstractUltraviolet (UV) irradiation (4000–10000 erg × mm‐2) decreased membrane potential and input resistance ofAmoeba proteusand induced formation of pinocytotic channels. Submaximal pinocytosis induced by UV light was additive to pinocytosis induced by K+or Na+and stimulated in the presence of EGTA. It was not inhibited by the presence of La+++or by pretreatment with dibucaine. In these respects and with respect to optimum pH and pCa, UV induced pinocytosis resembled potassium induced pinocytosis. Accumulation of K+in the amoeba membrane after a dose of radiation may explain the similarity between pinocytosis induced by UV light and potassium salts. Ca++present during the period of irradiation inhibited the effect of UV light. Instead Ca++applied after irradiation (1–20 mM) increased channel formation. This effect was stimulated by the presence of local anesthetic drugs. It is suggested that high doses of UV light may induce channel formation by releasing Ca++from the cell membrane into the cell (UV induced pinocytosis). Ca++may be released at the moment of absorption of UV light in the membrane as well as during the period of depolarization which follows irradiation. Low doses of UV light may permit extracellular Ca++to enter the cell and stimulate channel formation (calcium induced pinocytosis). Dithiotreitol (1 mM) applied after irradiation depressed both UV and calcium induced pinocytosis so these may be the result of the same structural change which involves the formation of disulphide bonds in the membrane.