bluuebunny/crossref_metadata_2025 huggingface dataset:
On the importance of CSF Na in the regulation of renal sodium excretion and renin release
Authors: LEKSELL L. G. , DENTON D. A. , FEI D. T. W. , McKINLEY M. J. , MÜLLER A. F. , WEISINGER R. S. , YOUNG H.
Published: December 2008

Infusions (20 μl/min) of isotonic (0.27 M) mannitol dissolved in Na‐free artificial cerebrospinal fluid (CSF) were made for 2 h into the lateral cerebral ventricle (IVT) of conscious 68 h dehydrated sheep. The IVT infusion induced a conspicuous drop in renal sodium excretion and marked rise in plasma renin concentration (PRC). The antinatriuretic response to the IVT. infusion was not altered by the intravenous: administration of ADH or the converting enzyme blocker (SQ 14225, Captopril). Surgical bilateral renal denervation did not change the antinatriuretic response while the increase in PRC was extinguished. Samples of CSF were collected prior to, and 15 min after the end of the infusion. These showed a reduction in CSF.[Na], while CSF osmolality remained unchanged. The study supports the view that sodium sensitive receptors close to the cerebral ventricular system participate in the regulation of renal sodium excretion and renin release, it also suggests that renal sodium excretion is affected by an unknown hormonal factor of cerebral origin, while the release of renin seen in response to a reduction in CSF [Na] is mediated by the renal nerves.
Plasma and red cell volumes of microwave irradiated mice tissues
Authors: VIRKKUNEN PEKKA
Published: December 2008

A double isotope technique was applied to the microwave irradiation of mice for reliable measurement of the distribution of red cells and plasma. Microwaves provide a means for rapid cessation of circulation. Hematocrit values of blood in minute tissue samples can be estimated. The red cell and plasma volumes as well as the hematocrit values of the liver, kidney, spleen, intestine, lung and brain tissues of mice are presented. A biological filtration of technetium labelled red cells is necessary for their physiological distribution in circulation.
Output of skeletal muscle contractions A study of isokinetic plantar flexion in athletes
Authors: FUGL‐MEYER AXEL R. , MILD KJELL H. , HÖRNSTEN JAN
Published: December 2008

Maximum torques, total work and mean power of isokinetic plantar flexions were measured with simultaneous registrations. The integrated electromyograms (iEMG) were obtained by surface electrodes from all three heads of the m. triceps surae. The method applied offers possibilities for adequate description of dynamic muscular work which in the case of plantar flexion in trained man declines as a negative exponential function of angular motion velocity. The decline is parallel to that of maximum torques. The summed triceps surae iEMG was inversely proportional to the velocity and direct proportional to time suggesting that structural rather than neural factors determine the relationships between velocity of angular motion and maximum torque/total work of single manoeuves. Moreover, the fact that maximum mean power as well as maximum electrical efficiency were reached at the functional velocity of toe‐off during gait suggests an influence of pragmatic demands on plantar flexion mechanical output.
Evidence for a non‐classical splanchnic neural control of the feline pylorus
Authors: LIDBERG P. , EDIN R. , LUNDBERG J. M. , DAHLSTRÖM A. , KEWENTER J. , AHLMAN H.
Published: December 2008

Electrical stimulation of the divided splanchnic nerves proximal to the celiac ganglion in chloralosed cats induced a dilation of the pylorus in the majority of animals. However, in some cats a pure contractile motor response or a biphasic motor response (contraction followed by dilation) was elicited suggesting that the splanchnic nerves convey excitatory fibres to the pylorus as well. The pyloric and gastric contraction at such stimulation was sensitive to atropine, while the pyloric dilation was not sensitive to cholinergic, adrenergic or ganglionic blocking agents in contrast to the adrenergic gastric dilation. Since the splanchnic nerve and the pyloric wall contain numerous neuropeptides, these substances might be involved in a nonclassical neurotransmission of the splanchnic motor responses of the pylorus.
Oro‐gastro‐intestinal inhibition of hypernatremia‐induced drinking in the goat
Authors: APPELGREN B. , ERIKSSON S. , JÓNASSON H.
Published: December 2008

Reduction of drinking by slow (5 ml/min) administration for 20 min of nearly body‐warm (35°C) and cold (15°C) water into the mouth, the abomasum, or the duodenal bulb was studied in goats made thirsty by the simultaneous i. v. infusion of hypertonic (2 M) NaCl at 2 ml/min. During the control experiments the drinking response to corresponding infusion of 1.7 M NaCl was recorded. This in order to eliminate the possible influence on the results of a postabsorptive thirst inhibition which would occur if the administered water was completely absorbed already during the saline infusion. The entrance of warm water into the mouth or into the abomasum caused about 20%, and into the duodenal bulb about 30% reduction of drinking during the infusion of hypertonic NaCl. The corresponding reduction for cold water was when introduced into the mouth and duodenal bulb about 50% and into the abomasum about 60%. Cold water also considerably delayed the onset of dringing. The inhibition obtained during cold water administration was partially compensated for by increased post‐infusional dringing. As regards the sensory input underlying preabsorptive inhibition of thirst, it is concluded that (regardless of distension, swallowing, and other mechanical factors) the entrance of pure water into various parts of the alimentary tract contributes to reduce the thirst drive. In addition, stimulation of oral, gastric, and duodenal cold receptors obviously diminish the urge to drink considerably.
Effect of diet on muscle glycogen and blood glucose utilization during a short‐term exercise in man
Authors: JANSSON EVA , KAIJSER LENNART
Published: December 2008

7 subjects were studied at rest and during a 6 min submaximal exercise (65% of Vo2, max) on two occasions, the first preceded by a fat rich diet and the second by a carbohydrate rich diet. Oxygen uptake and respiratory exchange ratio (R) were measured at rest and heart rate both at rest and during exercise. Arterial‐femoral venous differences for oxygen, glucose, lactate and β‐hydroxybutyrate and arterial concentrations of free fatty acids were measured at rest and during exercise. Changes in muscle glycogen (in 6 subjects) and lactate concentration were determined by biopsies from m. quadriceps femoris taken before and immediately after exercise. Muscle glycogen decreased less during exercise after the fat than after the carbohydrate diet in 5 of the 6 subjects, whereas blood glucose extraction by the exercising legs did not change with diet. Muscle lactate accumulation and release were smaller after the fat diet. In conclusion, the muscle glycogen utilization during a short‐term exercise appeared to be lower after the fat than after the carbohydrate diet, but not the concomitant blood glucose extraction. These differences between diets were similar to those observed after a more prolonged work at the same load.
Effect of intravenous infusion of hypertonic glucose solutions on pancreatic HCO3 secretion
Authors: RæDER MORTEN , MATHISEN ØYSTEIN
Published: December 2008

To examine why intravenous infusion of hypertonic non‐electrolyte solutions inhibit pancreatic HCO3‐ secretion, the relationship between pancreatic HCO3‐ secretion and plasma pH was examined before and following intravenous infusion of hypertonic glucose to 5 anesthetized, secretin infused (2.7 C.U./kg b. wt. h‐1) pigs. Hyperglycemia (plasma glucose 103±6 mmol/l) did not significantly change plasma pH, NaM+, K+, Cl‐ and HCO3‐ concentrations. Hyperglycemia reduced pancreatic water flux by 48±5% and raised pancreatic juice HCO3‐ concentration by 43±4 mmol/l. Concurrently, HCO3‐ secretion fell by 34±5%. Acidosis, produced through intravenous HC1 infusion and CO2 addition to inspired air, reduced HCO3‐ secretion by 40±6 ±mol/min and 30±5 ±mol/min per 0.1 pH unit reduction in plasma pH before and during hyperglycemia, respectively, and abolished HCO3 secretion at an estimated plasma pH of 6.51 ±0.06 before and a pH of 6.63±0.05 during hyperglycemia. We conclude that hypertonic glucose infusions inhibit pancreatic water flux and cause an increase in pancreatic juice HCO3‐ concentration which may inhibit HCO3‐ secretion through an effect on acid‐base balance in secretory cells.
Modulation of proximal tubular hydraulic conductivity by peritubular capillary oncotic pressure
Authors: ÅGERUP BENGT , PERSSON A. ERIK G.
Published: December 2008

Fluid absorption from the proximal tubular lumen is probably a multifactorial process. Earlier studies from our laboratory have indicated that a transepithelial hydrostatic and oncotic pressure difference may be the driving force for as much as 30% of the reabsorbed fluid. During saline volume expansion proximal tubular reabsorption declines and the present experiments were undertaken to investigate whether this reduction could be caused by changes in the passively driven flux component. The hydraulic conductivity was therefore determined from the reabsorptive rate in split oil droplets with normal and high hydrostatic pressure gradients across the wall, at the same time as the peritubular capillary net‐work was perfused with solutions containing a colloid of high or low concentration. In the reabsorption experiments the split oil droplet radius was measured and in a separate series of experiments the relationship between droplet radius and pressure was determined; this was found to be 7.3 mmHg pressure increase per 1 μm increase in radius. The increase in the rate of reabsorption from the droplets due to increased intraluminal hydrostatic pressure was 1.02±0.13 nl/min/mm tubular length when a solution with a high colloid concentration was perfused through the capillary net‐work, compared with 0.41=0.11 nl/min/mm tubular length when a low colloid containing solution was used for perfusion. The hydraulic conductance in the proximal tubular wall at high colloid perfusion was calculated to be 0.54 nl/min mm mmHg while at a low capillary colloid oncotic pressure it was significantly lower 0.025 nl/min mm mmHg. This drop in hydraulic conductance might be one factor responsible for the decline in fluid absorption in animals exposed to saline volume expansion.
Fasting and diurnal plasma PP, and the effect of fasting and somatostatin on postprandial plasma PP
Authors: JORDE ROLF , BURHOL PER G.
Published: December 2008

6 healthy subjects were studied on 3 separate occasions after ingestion of an ordinary breakfast. Once the meal was given alone, once together with somatostatin infused i.v. (100μg/h) for the first 2 h after start of the meal, and once the meal was preceded by a 34‐h fasting period. The postprandial plasma PP secretion was completely inhibited during the somatostatin infusion, and significantly augmented (p=0.032) after the prolonged fast. During the 34‐h fasting period, the PP levels were almost unaffected. The same group of subjects were also studied during a “normal” day with 4 regular meals. Plasma PP was found to increase shortly after breakfast and did not return to basal levels before early the next morning. The integrated PP secretion during the 24‐h period showed a significant (p<0.003) correlation with the basal levels.
Supersensitivity to substance P and physalaemin in rat salivary glands after denervation or decentralization
Authors: EKSTRÖM JÖRGEN , WAHLESTEDT CLAES
Published: December 2008

Substance P, a putative neurotransmitter in mammals, and physalaemin, present in the skin of an amphibian, are both undecapeptides and belong to the family of tachykinins. The secretory effect of these tachykinins on parotid and submaxillary glands of the rat was examined. Dose‐response curves showed that in the unoperated glands maximal secretory responses were obtained to an intravenous dose of 5–10μg/kg of the tachykinins, that the amount of saliva secreted from the submaxillary gland was twice that from the parotid gland, and that physalaemin was more potent than substance P. Parasympathetic denervation of the parotid gland and decentralization of the submaxillary gland caused a marked sensitization to the tachykinins, as judged by lowered threshold doses for secretion and increased secretory responses to a series of submaximal doses 3 weeks postoperatively. Sensitization was less marked after sympathetic denervation and decentralization; in the parotid gland decentralization caused, in fact, no sensitization while in the submaxillary gland the degree of sensitization was about the same after the two types of operation. The tachykinins acted directly on the gland cells and the effect was not exerted via cholinergic, α‐adrenergic or β‐adrenergic receptors. The pattern of sensitization to the tachykinins, found in the present study, after the different types of operation is similar to that previously found to cholinergic and α‐adrenergic agonists and different from that to a β‐adrenergic agonist. Studies by others have shown that in the rat parotid gland peptidergic receptors share a common intracellular pathway with cholinergic and α‐adrenergic receptors, whereas β‐adrenergic receptors use another pathway. In the present study it is suggested that this intracellular arrangement is of importance for the development of supersensitivity.
The turnover of acetylcholine in ligated sciatic nerves of the rat
Authors: DAHLSTRÖM ANNICA , BÖÖJ SERNEY , LARSSON P.‐A. , McLEAN W. G.
Published: December 2008

The accumulation of acetylcholine (ACh) and choline acetyltransferase (ChAT) and acetylcholinesterase (AChE) activities proximal to a crush on rat sciatic nerves was investigated after superfusion of the nerves in situ with or without inhibitors of ACh synthesis and/or AChE. 9 h after crushing of nerves, the ACh‐content of the 5 mm segment of nerve immediately proximal to the crush was increased from 37±5 to 80±4 pmol (mean ± SE), while ChAT‐activity was increased to 112±10% and AChE‐activity to 198±19% over that in non‐ligated nerves. Superfusion of the nerves for 8 h with Krebs' bicarbonate medium had no effect on enzyme accumulations, but reduced the ACh content to 59±4 pmol. The presence of hemicholinium 3 (HC‐3) (2×10‐5 M) in the superfusion medium reduced the ACh content markedly (to 17±2 pmol), but had no effect on enzyme accumulations at the crush. Adding eserine (10‐5 M) or soman (10‐6 M) to the superfusion medium increased ACh content to 133±8 pmol and 101±8 pmol, respectively, and markedly reduced AChE‐activity; ChAT activity was not effected. Superfusion with a combination of HC‐3 and eserine caused a marked reduction in ACh content compared with eserine alone; the effect was less with soman. The results are consistent with the view that the ACh which accumulates proximal to crush exists in a protective organelle, but that there is a continuous turnover of ACh due to leakage of ACh from the organelle, both during axonal transport and after accumulation.
The effect of antrectomy on the number of gastrinimmunoreactive cells in the canine duodenum
Authors: BRODIN KERSTIN , NILSSON GÖRAN , SUNDLER FRANK
Published: December 2008

The number of gastrin‐immunoreactive cells in the duodenum was assessed by immunohis‐tochemistry in 10 dogs that had been subjected to antrectomy with gastroduodenostomy (Billroth I), in 4 dogs in which an antrectomy with gastrojejunostomy (Billroth II) had been performed and in 4 unoperated controls. Gastrin‐immunoreactive cells were found only in dogs that had been subjected to antrectomy ad modum Billroth I and then only within the first 30 mm of the duodenum, i. e. in the duodenal bulb. The gastrin cells occurred scattered on the villi, in the crypts and within the glands of Brunner. In 3 of the dogs patches of antral‐type mucosa occurred within the first 10 mm of the duodenum. All dogs in which gastrin‐immunoreactive cells were found have in a previous study been shown to have a markedly increased tissue concentration of gastrin in the proximal third of the duodenum compared to unoperated controls. In the dogs subjected to antrectomy ad modum Billroth II in which no cells were observed the level of gastrin in duodenal tissue has been found to be moderately elevated compared to that of control dogs. The results indicate that the increased gastrin concentration in the proximal third of the duodenum following antrectomy ad modum Billroth I corresponds to an increase in the number of gastrin‐immunoreactive cells in the duodenal bulb.
Calcium fractions in seminal plasma and functional properties of human spermatozoa
Authors: ARVER STEFAN , SJÖBERG HANS ERIK
Published: December 2008

The concentration of ionized calcium [Ca++] was reproducibly determined in human seminal plasma with a calcium sensitive electrode (Orion Space Stat 20). Dilution of the seminal plasma gave a linear decrease in free calcium concentration. Freezing and thawning or storage of the seminal plasma under anaerobic conditions did not influence the level of ionized calcium. Storage under aerobic conditions gave a temperature dependent decrease in CA++ which parallelled a spontaneous increase in pH. The mean concentration of ionized calcium (measured after a standardized air exposition) was 0.17 mM±0.05 (SD) (range 0.09–0.29 mM). The Ca++ level was not correlated to the total calcium concentration or to markers for prostatic (zinc) or seminal vesicular (fructose) secretions. There were, however, more motile spermatozoa in semen samples with an ionized calcium level less than the average (0.17 mM) than in semen samples with a higher Ca++ level (53.8%±8.4, N=17 vs 45.0%±12.8, N=15, respectively, p<0.05). The percentage live spermatozoa was also higher (62.4%± 10.4, N=17 vs 50.7%± 14.2, N=15, p<0.01) in the semen samples with a low [Ca++]. Spermatozoa in the low [Ca++] group did also exhibit a better progressive motility than spermatozoa in the high [Ca++] group (p<0.05). It is suggested that the low level of ionized calcium in seminal plasma is of importance for motility of human spermatozoa and that the transfere of spermatozoa from a high Ca++ in the epididymis to the low levels in accessory sex glands secretion might be of significans for activation of spermatozoa upon ejaculation.
Induced hyperosmolality effects on extracellular fluid volume, lymph flow and osmolar equilibrium: studies in the rat
Authors: WARE J. , QUIROS G. , NORBERG K.‐A. , NYLANDER G.
Published: December 2008

The effects of experimentally induced hyperosmolality has been studied in rats. Renal vascular pedicle ligation was performed on all animals to prevent renal clearance of the infused solute, xylose, and allow accurate ECF space determinations with 51Cr EDTA. Small volume hyperosmolar xylose infusions caused parallel elevation of the osmolality of thoracic duct lymph and arterial plasma. A positive correlation was obtained between lymph osmolality and flow alterations. The maximal osmolality elevation of 22 mosmxkg‐1 H2O was associated with an intracellular fluid mobilisation which was equal to 7.1% of the ECF space. The infused and mobilised fluid volumes were distributed unequally between the intra and extra vascular compartments of the ECF.
Characterization of contractions in mechanically and enzymatically isolated myocardial cells from the rat heart ventricles
Authors: TIRRI R. , VORNANEN M. , LEHTO H.
Published: December 2008

Single spontaneously beating myocardial cells were prepared by mechanical or enzymatical isolation. Using a TV camera and videotape recorder, beating parameters were characterized in different buffer solutions in regard to temperature and integrity of sarcolemma, which was tested by ability of cells to exclude a vital stain, Evans blue. The mechanically disaggregated cells were totally permeable to this stain, but about 60% of the enzymatically isolated myocytes were able to exclude the stain. The myocytes prepared in the presence of calcium were most tolerant to physiological concentration of calcium. Contractions were mainly of phasic type where the velocity of contraction wave was very slow (50–330 μm/s). The velocity was not correlated to the beat rate. Temperature dependence of the velocity was positively correlated with the integrity of sarcolemma. Beat rate was inversely related to the integrity of sarcolemma being slowest in calcium tolerant enzymatically isolated cells. Beat rate of calcium sensitive myocytes was higher but unstable and the temperature dependence of the rate was steeply reduced and even reversed during the incubation. Some calcium tolerant myocytes generated occasionally an electric type of contraction which came in bursts and was characterized by synchronous sarcomere shortening without any contraction wave.
Are isolated femoral resistance vessels or tail arteries good models for the hindquarter vasculature of spontaneously hypertensive rats?
Authors: MULVANY M. J. , NILSSON H. , NYBORG N. , MIKKELSEN E.
Published: December 2008

We have investigated the extent to which the properties of small arteries from the hindquarters of spontaneously hypertensive rats (SHRs) are consistent with the characteristics of perfused SHR hindquarter preparations (for which the relaxed vascular resistance, the reactivity and the sensitivity are reported to be increased). We have therefore compared the in vitro morphological and pharmacological properties of a femoral resistance vessel (i. d. ca 200 μm) and of the tail artery (i. d. ca 600 μm) from SHRs with those from control Wistar‐Kyoto rats (WKYs). When relaxed, for any given wall tension, the internal circumference of the SHR resistance vessels was reduced, but that of the SHR tail artery was normal. When activated with 10 μM noradrenaline, the SHR resistance vessels had an increased calcium sensitivity, but the calcium sensitivity of the SHR tail arteries was normal. However, the maximum response of both types of SHR vessels was such that the vessels would have been able to contract against increased transmural pressure. The noradrenaline sensitivity of the SHR resistance vessels was normal but the SHR tail arteries had a decreased sensitivity. The results suggest that the femoral resistance vessel is in general a better model for the hindquarter vasculature than the tail artery.
Potentiation of antidiuretic response to systemic angiotensin II by elevation of CSF NaCI concentration
Authors: APPELGREN B. , ERIKSSON S. , JÓNASSON H. , RUNDGREN M. , ANDERSSON B.
Published: December 2008

The antidiuretic effect of the simultaneous intracerebroventricular (ICV) infusion of 0.24 M NaCl (0.02 ml/min) and intravenous (i. v.) infusion of angiotensin II (12 ng/kg. min) was studied in hydrated goats, and was compared to the antidiuretic effects of the separate infusions. The combined infusions inhibited the water diuresis for 30 min, whereas the separate infusions only reduced the water diuresis by 25% (ICV NaCl) and by 50% (i. v. angiotensin). The combined infusions increased the urine osmolality on the average by 415%. Corresponding increases induced by ICV NaCl and by i. v. angiotensin were 100 and 160%. The results suggest that systemic angiotensin II and elevated CSF NaCl concentration interact and potentiate each other as stimuli for antidiuretic hormone secretion. It is postulated that this synergism may help to preserve body water in hypovolemic conditions associated with hyperactivity of the renal renin‐angiotensin system.
Contribution of local blood flow regulation mechanisms during head‐up tilt in human subcutaneous tissue
Authors: SKAGEN KNUD
Published: December 2008

Local and remote regulation of subcutaneous blood flow in the forearm and leg was studied during head‐up tilt (30°, 457deg; and 70°) in 7 young healthy subjects. Relative blood flow was estimated by the local 133Xe washout technique. Incremental levels of head‐up tilt elicited increasing vascular resistance on arm and leg, respectively. Positive pressure similar to a blood column of the same height was able to prevent a significant part of the vasoconstrictor response on the leg to head‐up tilt. Thus if venous distension is prevented the local veno‐arteriolar reflex is abolished, whereas arteriolar constriction due to centrally elicited reflexes remains unaffected. Subcutaneous blood flow in the extremities are regulated by remote (baroreceptor) as well as local sympathetic reflex mechanisms (veno‐arteriolar reflex); but the relative influence of the local veno‐arteriolar reflex on the increase in total peripheral resistance seems to decrease with increasing tilt angles.
Theophylline‐induced stimulation of sodium transport in frog skin by a mechanism different from the antidiuretic hormone activated pathway
Authors: JOHNSEN ANDERS H. , NIELSEN ROBERT
Published: December 2008

Theophylline (theo) induced a marked increase in the short circuit current (SCC) after maximal stimulation by the antidiuretic hormone, arginine vasotocin (AVT). The stimulation amounted to 20–70% of the AVT‐stimulation. Practically no effect was seen on osmotic water flow after maximal AVT‐stimulation. A concentration dependence of the SCC stimulation was found from 0.04 to 4 mM theo, 16 mM inhibited the SCC. The response to theo was independent of the time of preincubation with AVT. The theo induced increase of SCC was accounted for by active sodium transport. Theo did induce an increase in the cyclic AMP level after stimulation with a maximal concentration of AVT, but so did a supramaximal dose of AVT. This indicates that the mechanism, by which theo stimulated the SCC additional to maximal AVT stimulation, is different from that by which AVT works. This effect of theo may be unrelated to cAMP or it may be explained by differences in cellular specificity of theo and AVT.
A mathematical description of the myogenic response in the microcirculation
Authors: BORGSTRÖM PER , GRÄNDE PER‐OLOF , MELLANDER STEFAN
Published: December 2008

A mathematical model for description of static and dynamic myogenic responses to change of vascular transmural pressure in the arterioles of skeletal muscle was developed for the purpose of elucidating some basic characteristics of the myogenic vascular control system which have proved difficult to reveal by physiological observations alone. The model, which is a refined version of a previous one (Borgström & Grände 1979), is based on a force‐equilibrium in the arteriolar wall, including passive forces related to vascular transmural pressure, wall elasticity, and wall viscosity, an active force related to resting vascular tone, and the active static and dynamic myogenic forces considered to be related to and triggered by wall tension (force) and its rate of change as indicated by our previous results. The effects of biological inertia, of shifts along the length‐tension curve of the smooth muscle, and of pressure induced reactions in the more proximal arterial vessels were taken into account in the present force‐equilibrium equation for the arterioles. Arteriolar wall viscosity was assumed to decrease with increasing rate of wall movement, a behaviour predicted by the model and corroborated by in vitro observations on larger vessels. The model was found capable of faithfully simulating microvascular myogenic responses in cat skeletal muscle in vivo in response to ramp as well as impulse transmural pressure stimuli over the entire biological range from maximum constriction to dilatation. With such characteristics, it can serve as a useful complement to physiological approaches in attempts to define more precisely the mode of operation of the myogenic control system and to reveal inherent complexities of biophysical factors and of interaction of other control mechanisms in microvascular regulation in vivo, as exemplified by presented tests and preliminary results.
An intracellular study of rubrospinal and rubro‐bulbospinal control of lumbar γ‐motoneurones
Authors: APPELBERG B. , HULLIGER M. , JOHANSSON H. , SOJKA P.
Published: December 2008

The actions elicited by electrical stimulation of the rubrospinal path in NR (nucleus ruber), and by stimulation of the rubro‐bulbospinal path in MesADC (mesencephalic area for dynamic control), were studied with intra‐, juxta‐ or extracellular recordings in lumbar γ‐motoneurones of cats anaesthetized with chloralose. The results were obtained during a series of experiments in which reflex effects from muscle, skin and joint afferents were also investigated. 90 cells tested with stimulation both in NR and in MesADC were classified (cf. Appelberg 1981) as dynamic (influenced from MesADC) or static (not influenced). 84 of these γ‐cells responded to stimulation in the red nucleus. The same response pattern was found for dynamic and static γ‐cells. For flexor cells, excitation was by far predominant while equal numbers of extensor cells showed excitatory and inhibitory effects. The shortest route to both static and dynamic γ‐cells was disynaptic. With stimulation of the rubro‐bulbospinal path, excitatory effects were more than twice as frequent as inhibitory effects. No clearcut difference was seen between extensor and flexor cells. The segmental latency for rubro‐bulbospinally mediated excitatory effects could be measured for only one cell, and it is tentatively suggested that the pathway to this dynamic γ‐motoneurone involves one or two interneurones more than in the rubrospinal pathway. Spontaneous activity was significantly more common among the dynamic cells, but the axonal conduction velocities of dynamic and static cells did not differ. The similarities between rubrospinal effects on α‐motoneurones and both classes of γ‐motoneurones indicate that the rubrospinal tract has the ability to coactivate α‐ and γ‐motoneurones (Granit 1955, 1979). The comparison of the properties of the population of γ‐cells classified as dynamic or static showed marked differences strengthening the reliability of the previously introduced classification method.
The needle biopsy technique for fibre type determination in human skeletal muscle–a methodological study
Authors: BLOMSTRAND E. , EKBLOM B.
Published: December 2008

The fibre type composition (type I, IIA and IIB) was determined in repeated needle biopsies from the vastus lateralis muscle of 34 healthy male subjects. Repeated biopsies were taken from one leg (n=20), and from both legs (n=14). The variation between duplicate biopsies was 6.2% and 12.3%, with regard to % type I‐fibres, respectively. Corresponding variation in % type IIA‐fibres was 4.4% and 7.3%, respectively, and in % type IIB‐fibres 5.0% and 7.4%, respectively. The variation in fibre type distribution within a single biopsy was 2.2–3.0% when 200 fibres were classified and counted. Increasing the number of fibres did not reduce the calculated variation to any great extent. A major reduction of the methodological error is obtained when two biopsies are taken from the same site of the muscle. The error in the technique in classifying the type I‐fibres was slight; the classification between the subgroups of type II‐fibres was, however, to some extent subjected to personal estimate. There was no consistent difference in fibre type composition between the right and the left leg.
The effect of stimulating somatic afferents on cholera secretion in the rat small intestine
Authors: CASSUTO JEAN , LARSSON PIA , YAO TAI , JODAL MATS , THOREN PETER , ANDERSSON SVEN , LUNDGREN OVE
Published: December 2008

The effect on rate of cholera secretion in the small bowel of activation of the group III and A delta afferent fibres in the sciatic nerve was studied in rats. Activation of these fibres at 3 Hz for 60 min significantly diminished choleraic secretion from 121 ± 29 to 25 ± 9 μl × min‐1× 100 cm‐2 serosal surface (mean ±SE; n=9). The effect was apparent after the nerve stimulation. Stimulation of the sciatic nerve had no significant effect on choleraic fluid secretion after interrupting the autonomic nerves to the intestine, nor did it significantly alter net fluid transport in non‐choleraic intestine with intact nervous supply. It is proposed that the observations may explain the clinical reports of an effect of acupuncture on cholera secretion.
The effect on intestinal fluid transport of exposing the serosa to hydrochloric acid. A study of mechanisms
Authors: SJÖQVIST ANDERS , CASSUTO JEAN , JODAL MATS , BRUNSSON INGEMAR , LUNDGREN OVE
Published: December 2008

Hydrochloric acid (0.1 M) placed on the serosal surface of a jejunal segment evoked an intestinal secretion (rats) or inhibited a net fluid absorption (cats). In rats it was demonstrated that lidocaine (placed on the serosa of periarterially denervated intestinal segments), hexamethonium (given i. v.; innervated or denervated intestines) and indomethacin (given i. v.; denervated intestines) markedly inhibited the acid induced secretion, while atropine (given i. v.) had no effect. In the cat experiments it was shown that tetrodotoxin (given close i. a. to denervated intestines) returned the rate of net fluid absorption to the control value observed before applying acid. It is concluded that exposing the intestinal serosa to an acid solution evokes a fluid secretion that is nervously mediated. Furthermore, it is proposed that prostaglandins are involved in the induction of the fluid secretion probably via a stimulation of nociceptors. It is also suggested that the results may have pathophysiological implications for some types of paralytic ileus.
The effect of vagal nerve stimulation on net fluid transport in the small intestine of the cat
Authors: SJÖVALL HENRIK , BRUNSSON INGEMAR , JODAL MATS , LUNDGREN OVE
Published: December 2008

The effect of electrical vagal nerve stimulation on intestinal net fluid transport rate was studied in the small intestine of the cat. The splanchnic nerves were severed in all experiments. Absorption was quantified with a new gravimetric technique which made it possible to study fluid transport also during intestinal motility. The stimulation characteristics were varied to activate selectively low threshold fibres or low and high threshold fibres. The observations did not reveal any affects of low threshold stimulation on intestinal fluid transport whereas an inhibition was seen when also the high threshold fibres were stimulated. This inhibitory vagal mechanism could also be elicited after the administration of atropine. Atropine in itself increased “resting” net fluid absorption. The results speak against a role for vagal cholinergic mechanisms in the control of net fluid absorption. There seem, however, to be tonically active intramural cholinergic pathways and noncho‐linergic inhibitory vagal neurons of unknown physiological significance.
Depressant effect of active shortening in the anterior byssus retractor muscle ofMytilus edulis
Authors: EKELUND M. C.
Published: December 2008

The effect of shortening during activity, previously characterized in vertebrate striated muscle, was investigated in the anterior byssus retractor muscle (ABRM) of the molluscMytilus edulis. This muscle is considered to have an essentially myosin‐linked Ca2+‐ regulatory system. Release steps of different amplitude were performed during isometric phasic contraction, and force redevelopment was recorded at a muscle length L1, defined as 90% of the muscle length at which a slight resting tension, approximately 1 mN, appeared in the presence of 2.5 × 10‐5M 5‐HT. Active shortening caused a graded depression of the contractile force without affecting the total duration of the mechanical response. Peak redeveloped force after muscle shortening of 0.06 L1and 0.18 L1was reduced by approximately 1.5% and 7.0%, respectively, of the isometric tension value at L1. The shortening effect was fully reversible, and had a lifetime of approximately 8 to 9 s. The depressant effect of active shortening was augmented at a reduced degree of activation of the muscle. The presence of caffeine and dantrolene and altered tonicity of the extracellular medium (0.9 T‐1.2 T) did not significantly affect the shortening induced depression obtained at maximum phasic activation of the preparation. The nature of the shortening effect is compared to that obtained in vertebrate striated muscle and is discussed on the basis of differences in Ca2+‐regulation of the contractile system in these two muscles.
Immobilization stress‐induced changes in discrete hypothalamic catecholamine levels and turnover, their modulation by nicotine and relationship to neuroendocrine function
Authors: FUXE KJELL , ANDERSSON KURT , ENEROTH PETER , SIEGEL RICHARD A. , AGNATI LUIGI F.
Published: December 2008

Immobilization stress (1 h) induced discrete reductions in noradrenaline (NA) levels in the posterior periventricular hypothalamic region and in the paraventricular hypothalamic nucleus, and a decrease in dopamine (DA) turnover in the medial palisade zone (MPZ) of the median eminence, but failed to induce regional increases of hypothalamic NA turnover. Stress also stimulated the secretion of ACTH, corticosterone and prolactin, while vasopressin, LH and FSH serum levels were unaffected. The stress induced reduction of DA turnover in MPZ may mediate the stress induced increase of prolactin secretion. Nicotine (0.3 mg/kg, s.c., 1 h) did not by itself significantly influence catecholamine (CA) turnover in the various CA nerve terminal systems analyzed in the hypothalamus, but reduced NA levels in the subependymal layer (SEL) of the median eminence. Nicotine administration did not affect the serum levels of any of the hormones evaluated. Nicotine counteracted to a minor degree the immobilization stress‐induced reduction in NA levels, and also the stress‐induced secretion of ACTH, but not of prolactin suggesting the involvement of noradrenergic mechanisms possibly in the paraventricular nucleus in the nicotine modulation of stress induced increases of ACTH secretion. The nicotine‐induced reduction of NA levels in SEL was blocked by stress as well as the tendency for nicotine induced increases of dopamine (DA) turnover in the medial and lateral palisade zones of the median eminence indicating opposing influences of immobilization stress and nicotine on at least some hypothalamic CA systems.
Effects of volatile fatty acids and ketone bodies on lipolysis in isolated adipocytes from Norwegian reindeer (Rangifer tarandus)
Authors: LARSEN TERJE S. , NILSSON NILS ÖSTEN , BLIX ARNOLDUS SCHYTTE
Published: December 2008

The effect of volatile fatty acids (acetate and propionate) and ketone bodies (acetoacetate and DL‐3‐hydroxybutyrate) on adrenaline stimulated lipolysis have been studied in isolated adipocytes from Norwegian reindeer. All four substances caused a strong (63–90%) inhibition of lipolysis, measured as glycerol release, at low concentrations of adrenaline (5 nM). At higher adrenaline concentrations (50 nM) inhibition only took place in the presence of propionate (30% inhibition) or DL‐3‐hydroxybutyrate (43% inhibition). DL‐3‐hydroxybutyrate caused a marked reduction in adrenaline stimulated glycerol release, even at very low concentrations. The effective dose causing 50% inhibition (ED50) was 1.5 mM. It is suggested that both volatile fatty acids and ketone bodies can act as important volatile regulators of lipopolysis in this high arctic ruminant undergoing great seasonal changes in volatile fatty acid and supposedly ketone body production.
Polyamine metabolism in muscles of mice and rats
Authors: PERSSON LO , ROSENGREN ELSA
Published: December 2008

Polyamine biosynthesis in different types of muscle was studied in mice and rats. A sex difference of polyamine biosynthesis in the gastrocnemius of the mouse was demonstrated. Ornithine decarboxylase activity was found to be several‐fold higher in the gastrocnemius of the male mouse than in that of the female. Orchiectomy resulted in a decline of enzyme activity in the gastrocnemius. This effect was reversed by the administration of testosterone. The elevation of ornithine decarboxylase activity in the gastrocnemius by testosterone was reflected in an increased content of the polyamines in the muscle. Muscles of other types, i.e. soleus, heart and urinary bladder were shown to be virtually unresponsive to testosterone treatment. Neither were the muscles of the rat, including gastrocnemius, found to be affected by the androgen.
Adrenergic and pressure‐induced modulation of carotid sinus baroreceptors in rabbit
Authors: YAO T. , THOREN P.
Published: December 2008

The sympathetic control of the carotid sinus baroreceptor activity was studied in rabbits. Stimulation of the cervical sympathetic trunk (10 Hz, 1 ms, 4–12 V) elicited an increase in discharge frequency of the non‐medullated baroreceptor afferents but not of the medullated fibers. An isolated carotid sinus area preparation was used to examine the influence of noradrenaline perfusion on baroreceptor activity. Non‐medullated baroreceptor afferents, but not the medullated afferents, responded to noradrenaline perfusion (10‐6 g/ml) with a significant increase in firing rate. Short‐term resetting of the baroreceptors was also studied with the same preparation. After perfusing the sinus at a hypertensive level for 30 min the pressure‐response curves of both the non‐medullated and the medullated baroreceptor afferents shifted to the right with increased thresholds and decreased maximal discharge frequencies. The extent of the short‐term resetting was greater in non‐medullated afferents than in medullated ones. It is concluded that the carotid sinus baroreceptors with non‐medullated afferents are under the sympathetic control. The physiological significance of this is discussed.
The relationship between urinary prostaglandin excretion rates and urine flow in conscious rats. Evaluation of the radioimmunoassay by gas chromatography‐mass spectrometry
Authors: CHRISTENSEN P. , GRÉEN K. , LEYSSAC P. P.
Published: December 2008

In conscious rats prostaglandin E2‐ and F2a excretion rates increased from about 20 to more than 100 pg/min/g kidney weight as urine flow decreased from about 10 to below 1 μ/min/g kidney weight following 24 h of water deprivation confirming previous data from surgically prepared rats (Leyssac & Christensen 1981 b). There was no difference in this response between rats on a normal sodium diet and severely sodium depleted rats. Additional supply of polyunsaturated fatty acids in the food did not influence the results. Elevated levels of prostaglandin excretion did not correlate with urine osmolality. The reliability of the radioimmunoassays used was documented by comparison with measurements by gas chromatography‐mass spectrometry. The analysis showed that these two methods provide almost identical estimates of urinary PGE2 and PGF2a content. It is concluded that renal prostaglandin production is activated by a negative feedback mechanism as tubular and/or urine flow rate decreases towards subnormal values.
Hydrostatic and oncotic pressures in the interstitium of dehydrated and volume expanded rats
Authors: SELÉN GÖRAN , PERSSON A. ERIK G.
Published: December 2008

The pressures in the renal interstitial space seem to have important influence on the setting of the sensitivity of the tubuloglomerular feedback that controls the glomerular filtration rate (GFR), and on the rate of proximal tubular fluid reabsorption. Measurements were made of interstitial pressure conditions, GFR, renal plasma flow (RPF), urinary excretion of sodium and potassium, and plasma renin activities in dehydrated animals and normopenic controls, before and after saline volume expansion (5% of body weight and hour). Colloid osmotic pressure, estimated from the protein concentration in renal hilar lymph, was 7.5 mmHg in the dehydrated animals (controls 2.8 mmHg) and decreased to 3.1 (controls 1.7 mmHg) after volume expansion. The lymph flow rate was increased in both groups of animals after volume expansion. Interstitial hydrostatic pressure, measured in the subcapsular space, was 2–3 mmHg in dehydrated and control animals and increased to 3–4 mmHg after volume expansion. In dehydrated rats GFR and RPF was reduced to 60% of the control values, but after volume expansion they regained control values. After volume expansion, urinary excretion of fluid and electrolytes increased more in controls than in dehydrated rats. Plasma renin activity was dereased in both groups of rats after volume expansion. Thus, in dehydrated animals there was a high colloid osmotic pressure and a low hydrostatic pressure in the renal interstitium, while after volume expansion the oncotic pressure fell and the hydrostatic pressure rose. The effect of volume expansion was found to be dependent on the preceding volume balance situation in the animal.
Activation of the tubuloglomerular feedback mechanism in dehydrated rats
Authors: SELÉN GÖRAN , MÜLLER‐SUUR ROLAND , PERSSON A. ERIK G.
Published: December 2008

To study the influence of the tubuloglomerular feedback control (TGF) on the regulation of glomerular filtration rate (GFR) during dehydration, micropuncture experiments were performed on surface nephrons of dehydrated rats. Dehydration was achieved by withdrawal of food and water for 24 h. The urine flow rate decreased to 1.5 μl/min (controls 2.9 μl/min) and GFR decreased in these rats to 0.80 ml/min (controls 1.22). TGF was studied by two different micropuncture procedures. With the first technique the changes in proximal stop‐flow pressure in response to changes of the late proximal microperfusion rate were measured. With this technique the perfusion rate necessary to induce a half maximal stop‐flow pressure response, the turning point, was also determined. An increased TGF sensitivity was found in dehydrated rats, as indicated by increased stop‐flow pressure responses (35 versus 26%) and decreased turning points (16 versus 21 nl/min). With the second micropuncture technique the single nephron GFR (SNGFR) was measured at distal and proximal tubular sites, in the same nephron. Distal SNGFR was decreased during dehydration to 32.2 nl/min, versus 42.7 nl/min in controls. A significant difference between paired SNGFR measurements in the same nephron was observed during dehydration, the proximal value being 5.3 nl/min higher than the distal, whereas this difference was not seen in control rats. This finding indicates that activation of the feedback mechanism takes place to reduce SNGFR. It is concluded that the decrease in whole kidney GFR is partly caused by the observed increase in feedback activity. The present results are also in agreement with our earlier hypothesis that the hydrostatic and oncotic pressure conditions within the interstitial space surrounding the macula densa cells modulate the sensitivity of the tubuloglomerular feedback mechanism.
Endurance training reduces the susceptibility of mouse skeletal muscle to lipid peroxidation in vitro
Authors: SALMINEN A. , VIHKO V.
Published: December 2008

Selected estimates of the lipid peroxidative capacity were assayed in the red and white skeletal muscles of control and endurance‐trained mice. Endurance training decreased the lipid peroxidation rate in vitro in both muscle types. The concentration of lipids susceptible to Fe2+‐induced lipid peroxidation was greater in the red than in the white skeletal muscle and increased after endurance training in the red muscle. Endurance training, however, decreased highly significantly the sensitivity of red muscle to in vitro stimulated lipid peroxidation. The activity of catalase and the concentration of vitamin E were considerably higher in the red muscle, whereas the activity of glutathione peroxidase was slightly higher in the white muscle. Endurance training caused no changes in these antioxidants. Endurance training increased the concentrations of reduced and total non‐protein glutathione in the red skeletal muscle but not in the white muscle. The total sulfhydryl group contents were unaffected. Our results suggest that endurance training may increase the resistance of skeletal muscle to injuries caused by lipid peroxidation.