bluuebunny/crossref_metadata_2025 huggingface dataset:
Dynamic exercise in man as influenced by experimental restriction of blood flow in the working muscles
Authors: EIKEN O. , BJURSTEDT H.
Published: December 2008

The effects of reduced muscle perfusion pressure on dynamic exercise performance and cardiovascular and respiratory functions were investigated. Eight subjects were studied during supine cycle ergometry at stepwise increasing workloads until exhaustion with and without the legs exposed to a supra‐atmospheric pressure of 50 mmHg (Leg Positive Pressure, LPP), a novel and convenient means of reducing the perfusion pressure in the working muscles. In the LPP condition exercise performance was reduced by 40% which, judging from assessments of perceived exertion, was due to premature muscle fatigue, indicating local or overall underperfusion of the working muscles. At any given work load, the arterial pressure response was considerably stronger during LPP than in the control condition. LPP also caused greater increases in blood lactate concentration and pulmonary ventilation, the differences from control increasing with the work load. Furthermore, the ventilatory equivalent for O2 at a given work load was markedly higher in the LPP than in the control condition, while exercise‐induced decreases in end‐tidal PCO2 were considerably exaggerated by LPP. The augmented pressor response during flow‐restricted exercise, together with the strong ventilatory response which was out of proportion to overall O2 uptake, suggests increased activation of muscle chemoreflexes by accumulation of metabolic end products, the increased pressor response tending to reduce the local flow error in the working muscles.
Small intestinal fluid absorption in the rat during haemorrhage and its importance for plasma refill
Authors: REDFORS S.
Published: December 2008

Small intestinal net fluid absorption and its importance for plasma volume restitution during a slow, stepwise haemorrhage was studied in rats. A continuous administration of a Krebs–glucose solution into the intestinal lumen increased the tolerated maximal bleeding volume from 31 to 70% of initial total blood volume. The ‘small intestinal’ autotransfusion rate, i.e. the rate of fluid mobilized from the intestinal lumen into the vascular compartment, was calculated to 2.3 ml h‐1 too cm‐2 small intestinal serosal surface. ‘Small intestinal’ autotransfusion is proposed to be an important mechanism in the defence line against hypovolaemia.

Haemorrhage induced a 40% increase in small intestinal net fluid absorption. This increase was abolished after pretreatment with Captopril, an angiotensin‐converting enzyme blocker. Post‐ganglionic denervation of the small intestine reduced, but did not abolish, the stimulatory effect of haemmorrhage on net fluid absorption. These results indicate that both a direct nervous component and the renin‐angiotensin system are of importance for the increase in small intestinal net fluid absorption observed after haemorrhage.
Contrasting effects of two xanthines, theophylline and enprofylline, on the cardio‐respiratory stimulation of infused adenosine in man
Authors: MAXWELL D. L. , FULLER R. W. , CONRADSON T.‐B. , DIXON C. M. S. , ABER V. , HUGHES J. M. B. , BARNES P. J.
Published: December 2008

Six normal male subjects, ages 28–40 years, were studied on separate days during increasing infusions with adenosine, 40–120 μg kg‐1 min‐1, before and during infusions of two xanthine derivatives, theophylline (mean plasma concentration 9 mg 1–1) and enprofylline (mean plasma concentration 3 mg 1–1). The study was double‐blind, randomized, placebo controlled. Cardio‐respiratory variables were measured non‐invasively. Adenosine by itself increased heart rate (P < 0.05), skin temperature (P < 0.05), resting minute ventilation (P < 0.01) and decreased estimated Pa, CO2 (P < 0.01). Compared with placebo enprofylline increased heart rate (P < 0.05) and shifted the heart rate and ventilation dose–response curves of adenosine upwards (P < 0.05 and P < 0.02, respectively). Theophylline did not by itself affect heart rate but significantly (P < 0.05) reduced the heart rate response to adenosine. Compared with placebo theophylline caused a small increase in minute ventilation (P < 0.05) and flattened the dose‐response curves of the effects of adenosine on ventilation (P < 0.01) and Pa, CO2, (P < 0.01). Theophylline also reduced abdominal and chest discomfort caused by adenosine permitting significantly (P < 0.05) higher infusion rates of adenosine. These findings suggest that, with equipotent bronchodilating plasma concentrations, theophylline can inhibit while enprofylline augments some cardio‐respiratory stimulant effects of infused adenosine in man.
Course and mode of action of descending system conveying nucleus raphe magnus induced inhibition of flexion reflex in rats
Authors: JØIRUM E. , SHYU B. C.
Published: December 2008

In lightly anaesthetized rats, the latencies and magnitudes of heat‐evoked withdrawal reflexes from the hindlimb were measured electromyographically. Low‐intensity (20–50 μA) stimulation of the nucleus raphe magnus (NRM) resulted in an inhibition of the flexion reflex (commonly referred to as analgesia) as evidenced by increased latency and decreased amplitude. The effect lasted for several minutes after the stimulation was terminated. Following lesions of the dorsolateral funiculus (DLF) at the neural thoracic levels 7–8, baseline latencies were reduced and the effect of the NRM stimulation was abolished. Lesions of the DLF at lumbar level 1 resulted in unaltered baseline latencies with persistence of the inhibitory effect of NRM stimulation.

The results of the present experiment show that pathways exerting a tonic inhibition of the withdrawal reflex, and mediating the effect of electrical stimulation from the NRM, descend in the DLF at the thoracic level of the spinal cord. At the lumbar level, there is a shift away from the DLF.

The antinociceptive effect of 20 μA NRM stimulation was partly reduced by pretreatment with the serotonin synthesis inhibitor para‐chlorophenylalanine (PCPA) or the opiate naloxone (1 mg kg–1 i.v.). In animals pretreated with PCPA, naloxone (1 mg kg–1 i.v.) completely abolished the analgesic effect of the stimulation. Thus, both serotonergic and opioid systems may be implicated in mediating the analgesia. With 50 μA stimulation the same treatment only partly attenuated the NRM‐induced analgesia, indicating an additional non‐serotonergic and non‐opioid mechanism which requires a higher current intensity for its activation.
Incorporation and distribution of eicosanoid precursor fatty acids in murine fibroblasts in culture
Authors: PUNNONEN K. , PUUSTINEN T. , KOULU L. , JANSÉN C. T.
Published: December 2008

Murine fibroblasts in culture were labelled with either [14C]arachidonic acid, [14C]dihomo‐γ‐linolenic acid or [14C]eicosapentaenoic acid. All these [14C]fatty acids were effectively incorporated into the fibroblasts and the bulk of the radioactivity was recovered in various phospholipids. The major radiolabelled phospholipids were phosphatidylethanolamine, phosphatidylcholine and the phosphatidylinositol + phosphatidylserine fraction. Significant amounts of radiolabel were found also in the triacylglycerols: even as much as 30% of the total of the incorporated dihomo‐γ‐linolenic acid was recovered in the triacylglycerols. The present study suggests that arachidonic acid, dihomo‐γ‐linolenic acid and eicosapentaenoic acid are effectively taken up and esterified into different lipid fractions of murine fibroblasts and that also the triacylglycerols are significantly involved in the incorporation, storage, and release of the eicosanoid precursor fatty acids.
Electrogenic and electroneutral components of the sympathetic effect on fluid absorption in the rat jejunum
Authors: HEMLIN M. , BUTCHER P. , SJÖVALL H.
Published: December 2008

The aim of the study was to test the hypothesis that the sympathetic nerves to the jejunum enhance net fluid absorption rate by inhibiting an electrogenic flux of anions into the lumen. The design of the experiments was based on the observation that the effect of catecholamines on electrogenic transport is abolished by yohimbine, anα2adrenergic antagonist.

Net electrogenic transport in jejunal segments of anaesthetized rats was estimated by measurement of the transepithelial potential difference (PD) and short‐circuit current (SCC). Net fluid absorption rate was quantified by a gravimetric technique. The sympathetic nerves to the segment were stimulated electrically, bothin vitroandin vivo. The effect of sympathetic nerve stimulation on SCC and net fluid transport was determined in the absence and presence of theα‐adrenergic antagonists phentolamine (a non‐selectiveα‐adrenergic antagonist), prazosin (a selectiveα1‐antagonist) and yohimbine (a selectiveα2antagonist).

Sympathetic nerve stimulation decreased PD and SCC and increased net fluid absorption rate. Phentolamine abolished both the electrogenic response and the effect on net fluid absorption rate, without having any significant intrinsic effects on either parameter. Prazosinper semarkedly increased net fluid absorption rate, but did not significantly influence the sympathetic effect on SCC or net fluid absorption rate. Yohimbine abolished the electrogenic effect of sympathetic stimulation, andper seincreased net fluid absorption rate in innervated but not in denervated segments. In innervated segments, the absorption rate during sympathetic nerve stimulation was similar in controls and yohimbine‐treated animals. In denervated segments, yohimbine significantly attenuated the sympathetic response.

The results suggest that the sympathetic nerves enhance fluid absorption rate via effects on both electrogenic and electroneutral epithelial transport. These two components of the sympathetic response seem to be mediated by differentα‐receptor mechanisms.
Enteric nerves mediate the fluid secretory response due to Salmonella typhimurium R5 infection in the rat small intestine
Authors: BRUNSSON I.
Published: December 2008

Eighteen hours after intragastric inoculation Salmonella tyhimurium elicited a net fluid secretion in the jejunum and ileum of rats. The mechanisms behind the secretory response were analysed in vivo. Extrinsic denervation of the experimental intestinal segments had no effect. The nerve‐blocking agents hexamethonium (i.v.) and lidocaine (serosally applied) blocked the secretion but atropine had no effect. It was demonstrated that the bacteria were invasive by culturing from the intestinal wall. The presence of inflammatory reactions was supported by the facts that i.v. indomethacin blocked the secretory response and that there was an increased capillary leakage of albumin‐bound Evans Blue into the interstitium of the intestinal mucosa. There was also a secretory response upon inoculation of the jejunal and ileal segments by cell‐free supernatants of broth where bacteria had been cultured for 24 h and thereafter lysed. This response was, however, blocked by i.v. atropine, which had no effect on the secretion elicited by living bacteria. We could show no presence of E. coli LT, ST or cholera toxin in the cell‐free supernatant by means of ELISA‐tests. We therefore conclude that (1) S. typhimurium R5 invaded the rat jejunal and ileal mucosa, thereby creating an inflammatory response which in turn activated a nerve reflex(es) within the ENS leading to a net fluid secretion; (2) the presence of prostaglandin was needed for activating the reflex(es); (3) the reflex(es) contained a nicotinergic transmission; (4) enterotoxin was of no importance for the secretory response in the model used.
Transient increase in insulin‐like growth factor I immunoreactivity in rat peripheral nerves exposed to vibrations
Authors: HANSSON H.‐A. , DAHLIN L. B. , LÖWENADLER B. , LUNDBORG G. , PALEUS S. , SKOTTNERU A.
Published: December 2008

Hind legs of adult rats were exposed to vibrations (81 Hz; amplitude 0.50 mm peak to peak) for 4 h during two consecutive days. The sciatic, tibial and plantar nerves were isolated and processed for immunohistochemical demonstration of IGF‐I (insulin‐like growth factor I; somatomedin C) immunoreactivity at different time intervals after the vibration exposure.

In sham‐exposed rats the axons in peripheral nerves showed no or faint IGF‐I immunoreactivity while most Schwann cells were negative. Exposure of the hind legs to vibrations induced increased IGF‐I immunoreactivity in the Schwann cells, demonstrable at the end of the exposure period and reaching maximal intensity 2–3 days after vibration exposure. Several distended axons similarly showed increased staining. The IGF‐I immunoreactivity decreased after 7–10 days to almost the level in the control nerves. The most extensive changes were observed in the plantar nerves. The tibial nerves similarly expressed strongly increased IGF‐I immunoreactivity in their Schwann cells. The sciatic nerve showed, however, only slightly to moderately increased staining. Cells in the epineurium of the plantar and, to a limited extent, of the tibial nerves expressed concomitantly increased IGF‐I immunoreactivity. We conclude that the transiently increased IGF‐I immunoreactivity in peripheral nerves reflects reactive changes caused by vibrations and most prominently expressed by the Schwann cells.
Effects of intraruminal loads of saline or water followed by voluntary drinking in the dehydrated lactating goat
Authors: DAHLBORN K. , HOLTENIUS K. , OLSSON K.
Published: December 2008

In five goats water deprivation for 26 h increased plasma osmolality, total plasma protein concentration, and plasma vasopressin (AVP) concentration to higher levels during lactation compared to nonlactation. At the end of the dehydration period intraruminal loads of saline or water (corresponding to 50% of the body weight loss) were given to lactating goats. The saline load decreased the plasma protein concentration below control levels, while plasma osmolality, Na concentration and AVP did not change. After the water load the plasma protein concentration stayed elevated. Plasma osmolality, Na concentration and AVP fell, but remained significantly above control levels. Both plasma renin activity (PRA) and aldosterone (PA) concentration increased after water, but decreased after saline administration. Three hours after the fluid loads the goats were offered water to drink. AVP decreased at the sight of water. After drinking, plasma osmolality, Na and AVP continued to decrease in water loaded animals, and fell also in saline loaded goats. PRA remained elevated, and PA increased in water loaded goats, while these hormones still were depressed in saline loaded goats. Mean renal ‘free water clearance’ became positive after drinking in both groups. It is concluded that the water losses with the milk cause lactating goats to become dehydrated more rapidly than non‐lactating goats during water deprivation. Lowering of the plasma osmolality and Na concentration are more important than restoration of the plasma volume in suppressing the high plasma AVP concentration in the dehydrated lactating goat. The water diuresis, which occurred after voluntary drinking, indicates that the goats had not been able to anticipate their water deficit accurately. In goats, water deprivation causes no stimulation of PRA, but PRA increases in response to both a load of water and to voluntary drinking. The cause of these effects is unclear.
Non‐linearities in response properties of insect visual cells: An analysis in time and frequency domain
Authors: WECKSTRÖM M. , KOUVALAINEN E. , JÄRVILEHTO M.
Published: December 2008

Intracellularly recorded voltage responses of the visual cells of the blowfly (Calliphora erythrocephala) were analysed in the time and frequency domains. The photoreceptors were stimulated with pulse (impulse), sine, sine‐sweep and pseudorandomly (white noise) modulated green light. The blowfly photoreceptor responses, as analysed from the linear transfer functions, seem to arise from a system similar to that of cascaded low‐pass Alters, with a corner frequency at about 63 Hz (SD ± 12 Hz). The system is likely to have at least five poles, including one linear second order term, and a pure delay element. Arising from the non‐linearities a second harmonic can be seen in the power spectra of responses elicited by sine modulated light. This non‐linearity is at least partly explained by the self‐shunting property of the membrane voltage response. Light adaptation increases the non‐linearities in frequencies lower than 20 Hz, as seen in the decrease of the coherence function with the signal‐to‐noise ratio remaining constant. Light adaptation also accelerates the transduction process and it appears in the linear transfer function in a form typical to negative feedback. With low stimulus frequencies it causes a ‘phase lead’‐type non‐linearity. In addition, the sine‐sweep responses show quite different frequency characteristics in respect of depolarization and repolarization. Lateral inhibition between photoreceptor responses recorded from retinular cell axons in the lamina appears as a drop in gain and as an increasing phase‐lag in frequencies from 30 Hz upwards in linear transfer functions. The source of this capacitive‐like coupling can be considered to be in the high resistance barriers compartmentalizing the second optic ganglion into discrete anatomical units.
Effects of pancreatic noradrenaline infusion on basal and stimulated islet hormone secretion in the dog
Authors: AHRÉN BO , JR GERALD J. TABORSK Y.
Published: December 2008

We investigated the direct pancreatic effects of noradrenaline in vivo on the secretion of insulin, glucagon, and somatostatin from the in situ pancreas in halothane‐anaesthetized dogs. Noradrenaline was infused into the superior pancreatic artery at 12 ng min‐1, a rate that did not alter systemic glucose or noradrenaline levels nor heart rate or blood pressure. This pancreatic infusion of noradrenaline did not affect the basal pancreatic output of insulin, yet did markedly inhibit arginine‐stimulated insulin secretion. The acute insulin response (AIR) to an intravenous injection of arginine (2.5 g), which was 4293 ± 1260 μU min l under control conditions, was reduced to 1054 ± 396 μ min‐1 by noradrenaline (P < 0.01). Noradrenaline increased basal pancreatic glucagon output from 321 ± 130 pg min‐1 to 876 ± 309 pg min‐1 after 20 min of infusion (P < 0.05) and the acute glucagon response (AGR) to arginine, being 1033 ± 203 pg min‐1 under control conditions and 1746 ± 249 pg min‐1 during noradrenaline infusion (P < 0.05). The basal output of somatostatin did not change during noradrenaline infusion, but arginine‐stimulated somatostatin secretion was impaired. The acute somatostatin response (ASLIR) to arginine was 473 ± 124 fmol min‐1 under control conditions and was decreased to 140 ± 80 fmol min‐1 by noradrenaline (P < 0.01). We conclude (1) that insulin and somatostatin secretion are regulated similarly by noradrenaline in vivo, (2) that B cell and D cell sensitivity to noradrenaline depends on the degree of secretory stimulation: while basal secretion is not affected, arginine‐stimulated secretion is inhibited, and (3) that both basal‐ and arginine‐stimulated glucagon secretion are stimulated by noradrenaline in vivo.
Substance P receptors in the rat spinal cord: the effect of GTP and of chronic antidepressant treatment
Authors: IVERFELDT KERSTIN , ÖGREN SVEN‐OVE , BARTFAI TAMAS
Published: December 2008

Substance P receptors were examined in crude synaptosomal fraction preparations of the rat spinal cord using [125I]Bolton Hunter Substance P ([125I]BHSP) which binds with an affinity of 0.043 ± 0.015 nM. The concentration of binding sites in the dorsal and in the ventral part was 4.55 ± 0.86 and 2.35 ± 0.35 fmol mg‐1respectively. GTP inhibited the specific binding of [125I]BHSP in a concentration dependent manner, with io‐3mol I‐1GTP yielding 89–90% inhibition and io‐5mol l‐1GTP producing 50% inhibition. This value was similar in dorsal and ventral spinal cord. The effects on SP receptors of chronic treatment with the tricyclic antidepressant imipramine (2 × 10 μmol kg‐1day‐1p.o. 14 days) and the specific5‐I IT (serotonin) uptake blockers alaproclate (2 × 20μmol kg‐1day‐1p.o. 14 days) and zimelidine (2 × 10μmol kg‐1day‐1p.o. 14 days) were examined in the ventral spinal cord, where SP and 5‐IIT coexist in the terminals of descending neurons from the raphe nucleus. Zimelidine treatment was found to cause a significant reduction in the number of substance P binding sites in the rat ventral spinal cord as compared to saline treated controls. These findings are discussed in light of the previous observation (Brodinet al. 1984) that SP levels are significantly elevated after treatment with antidepressant drugs especially with zimelidine, which alters the firing rates of 5‐HT and 5‐HT/SP neurons.
Early postnatal deprivation of active sleep with desipramine or zimeldine impairs later behavioural reactivity to auditory stimuli in rats
Authors: HILAKIVI L. A. , TAIRA T. , HILAKIVI I.
Published: December 2008

To examine the functional significance of early postnatal active sleep for the development of behavioural reactivity to auditory stimuli, rat pups were daily injected i.p. from the 7th to the 18th postnatal days with 5 mg kg‐1 (6.6 mmol 1‐1) desipramine or 25 mg kg‐1 (12.2 mmol 1‐1) zimeldine. Sleep‐wake behaviour was recorded with a static‐charge‐sensitive bed (SCSB) method. Both desipramine and zimeldine suppressed the percentage of active sleep relative to the total recording time throughout the treatment period. In addition, these drugs increased the percentage of quiet state and waking. At the age of 38 days the zimeldine‐treated rats showed more motor activity in the open field than the controls. At the age of 39 and 78 days all rat groups behaved similarly in the open field. Startle measures and motor activation, provoked by auditory stimulation, were determined by the SCSB method when the rats were 4 months of age. Auditory stimuli, consisting of a series of ten clicks, induced a greater number of startles as well as strong movement responses in the control rats than in the desipramine‐ or zimeldine‐treated rats. The number of small movement responses did not differ between the rat groups. These findings indicate that early postnatal active sleep and the monoaminergic systems regulating it may be important for the normal development of neuronal circuitry associated with later reactivity to auditory stimuli.
Gas exchange during high‐frequency ventilation in the pigeon (Columba livia)
Authors: BECH C. , JOHANSEN K. , NICOL S.
Published: December 2008

We studied the effect of high‐frequency ventilation (HFV) on the gas exchange of tracheotomized pigeons. The pigeons were artificially ventilated using a piston pump, which alternately connected the pigeons' airways to a constant‐flow source. Two‐minute periods of HFV were interposed between long periods of normal ventilation. The effect of HFV was assessed by the recorded changes in the PO2, pCo2 and pH of arterial blood and from the changes in the composition of the gas in the interclavicular air sacs. The results showed that HFV can augment gas exchange when the tidal volume (VT) is less than the volume of the anatomical dead space (VD). However, normal arterial gas composition can only be maintained if respiratory frequency is high (> 20 Hz). At the normal panting frequency of pigeons (7.8 Hz), gas exchange can thus only be maintained if tidal volume is approximately 125% of the dead space. When panting the VT must be greater than the VD. This finding agrees with the results of recent work showing flush‐out‐ or compound‐panting in birds: i.e. if, during panting, VT approaches close to the VD, intermittent interruptions, by taking deeper breaths in order to ensure a supply of fresh air to the lungs, are necessary.
Thioredoxin and thioredoxin reductase show function‐related changes in the gastric mucosa: immunohistochemical evidence
Authors: HANSSON H.‐A. , HELANDER H. F. , HOLMGREN A. , ROZELL B.
Published: December 2008

Low levels of thioredoxin and thioredoxin reductase immunoreactivity were demonstrated immunohistochemically in rat gastric epithelial cells. The intensity was influenced by feeding and fasting, the former resulting in diminished reactions. Acute vagotomy, which abolishes basal acid secretion, resulted in a strongly increased thioredoxin immunoreactivity in all gastric epithelial cells. Stimulation of vagotomized rats with pentagastrin and carbachol reduced the levels of thioredoxin and thioredoxin reductase. Atropine and omeprazole (in stimulated, vagotomized rats) completely inhibited acid secretion, but caused different effects on the thioredoxin levels of gastric cells. Atropine restored the thioredoxin immunoreactivity in most gastric epithelial cells to that of the unstimulated, vagotomized controls. Omeprazole, however, did not reverse the effects of stimulation, and, except in the parietal cells, weaker fluorescence was observed. Similar reaction patterns were seen for thioredoxin reductase, although at lower staining intensities. The results demonstrate that thioredoxin and thioredoxin reductase are expressed in resting cells, and to a lower extent in cells with ongoing secretion.
Red‐cell pH in tench. Interacting effects of cellular nucleoside triphosphates, Hb‐oxygenation and extracellular pH
Authors: JENSEN F. B.
Published: December 2008

Experimental adjustments of red‐cell pH (pHi) by varying red‐cell nucleoside triphosphate (NTP) content, blood oxygenation state and extracellular pH (pHe) demonstrated a tight interdependence of these variables in their influence upon pHi The increase in pHi with deoxygenation (ΔpHi (d – o)) is large, but becomes strongly reduced when the NTP content is decreased and when pHe falls. Lowering of red‐cell NTP increases pHe, notably at high pHe but this NTP dependence of pHi (ΔpHi/A(NTP/Hb)) is much smaller in deoxygenated than in oxygenated blood. The pHi dependence of pHi (ΔpHi/ΔpHe) increases upon reduction of red‐cell NTP content and upon deoxygenation. The results are consistent with the view that pHi is governed by Donnan‐like distribution of protons across the red‐cell membrane, and show that a pronounced red‐cell swelling accompanies increases in the distribution ratio [H+]e/[H+]i. The data are interpreted in terms of changes in the red‐cell non‐permeable charge as induced by NTP and its linkage with the haemoglobin proton equilibria.
Noradrenaline as a possible mediator in the renal response to vascular expansion with blood in the cat
Authors: RASMUSSEN S. N. , ANDERSEN J. S. , NIELSEN B. E. , KNIGGE U.
Published: December 2008

In chloralose anaesthetized cats with renal arterial pressure kept constant at 100 mmHg, vascular expansion with precirculated blood, 20 ml kg b.w.‐1, caused significant increments in arterial inflow rates of blood to the deep (ARBFD) and superficial (ARBFS) renal venous drainage area of 35 ± (SE)10 and 19 ± 6%, respectively, and in the excretion rates of water and sodium of 73 ± 24 and 75 ± 28 %, respectively, while GFR remained essentially unchanged. In acutely denervated kidneys the responses to expansion were not significantly different from those of innervated kidneys, which indicated largely humoral mediation. Arterial plasma concentrations of noradrenaline, adrenalin, and vasopressin fell significantly to values of a half to one‐third of pre‐expansion values, while plasma dopamine was not significantly changed by expansion. The response to expansion could be (1) reversed by a ‘substituting’ intraaortic infusion of noradrenaline, and (2) imitated, without volume expansion, by an infusion of an a‐adrenergic blocking agent (phentolamine). It is concluded that the renal response (excretory and vascular) to volume expansion with blood is largely humorally mediated and that circulating noradrenaline may play a causal role in the response.
Transcapillary clearance of albumin in rat skeletal muscle monitored by external detection. Effects of alterations in capillary surface area
Authors: HARALDSSON B. , RIPPE B.
Published: December 2008

The effects of noradrenaline (NA)‐induced vasoconstriction on the transcapillary passage of albumin was evaluated by an external detection technique, allowing repetitive measurements of albumin clearance (Cl) during various conditions (in the same animal). Six isolated rat hindquarters were perfused with serum‐albumin solutions during maximal vasodilation (papaverine 90 μM) AND Cl was determined at different net filtration rates (Jv) induced by elevations of venous pressure. Then, the perfusate was changed to one of similar composition but containing noradrenaline (2–4 μM), AND the procedure of determining Cl vs. Jv was repeated. Tissue accumulation of [99mTc]albumin was expressed in terms of clearance, using the isogravimetric CI of defined muscle samples during maximum vasodilation in separate experiments as reference, the latter being 0.0246 ± 0.0012 ml min ‐1 per 100 g. Noradrenaline caused an increase in vascular resistance from 2 to 14 mmHg min 100 g ml‐1, while the Cl vs. Jv relationship was shifted downwards in a fashion parallel with the control Cl vs. Jv curve. For Jv = o, Cl was 0.0101 ± 0.0014 ml min ‐1 per 100 g during NA challenge. The average reflection coefficient for albumin (σtot) was 0.92 ± 0.01 irrespective of vascular tone. Thus, both albumin clearance and the capillary filtration coefficient (CFC) seem to vary in direct proportion to the capillary surface area available for exchange.
Increase in myoglobin content and decrease in oxidative enzyme activities by leg muscle immobilization in man
Authors: Jansson E. , Sylvén C. , Arvidsson I. , Eriksson E.
Published: December 2008

Biopsies from m. quadriceps femoris from the operated leg of nine patients were taken before, and 6 weeks after, knee surgery. During the whole postoperative period the operated leg was immobilized with the knee in 40–500 of flexion. Myoglobin (MYO) and the enzymes citrate synthase (CS), creatine kinase (CK) and its isozymes MB (CK‐MB) and mitochondrial CK (CK‐MIT), aspartate aminotransferase (ASAT), phospho‐fructokinase (PFK) and lactate dehydrogenase (LD) were determined on the biopsies. Citrate synthase, ASAT, CK, CK‐MB, CK‐MIT and LD activities were decreased (12–30%) after the postoperative leg immobilization period. Phosphofructokinase did not change, while MYO content was increased (16%). In conclusion, a different control of the synthesis of oxidative enzymes and MYO is suggested, as the induced changes following immobilization were in opposite directions. The function of the increased MYO content may be to facilitate the oxygen extraction.
Brain‐gut peptides in sauna‐induced hyperthermia
Authors: JENSSEN T. G. , HAUKLAND H. H. , BURHOL P. G.
Published: December 2008

The release of brain‐gut peptides during sauna bathing was studied in seven women. All'women underwent a 20 min sauna bath. Their sublingual temperature rose from 36.9 ± 0.1 oC to 38.6 ± 0.2 oC (mean ± SEM). A significant increase in circulating plasma vasoactive intestinal polypeptide (VIP) was observed during heat exposure, whereas plasma pancreatic polypeptide (PP), motilin and blood glucose rose and stayed significantly elevated first during the ensuing 60 min (P < 0.05 in all cases). A similar increase in plasma insulin failed to reach statistical significance, whereas the plasma levels of somatostatin and cholecystokinin (CCK) remained unchanged. It is suggested that the plasma VIP levels are related to compensatory mechanisms during heat exposure with vasodilatation and heat loss.
Muscle pathomorphology in m. quadriceps of marathon runners. Early signs of strain disease or functional adaptation?
Authors: SJÖSTRÖM M. , JOHANSSON C. , LORENTZON R.
Published: December 2008

Muscle biopsies were obtained from m. vastus lateralis of five male marathon runners and five sprinters. The athletes performed their last competition at least 2 weeks prior to the investigation. No clinical signs of discomfort or injury were observed in the runners. The biopsy specimens from the sprinters showed an ordinary overall morphology, although fibre sizes varied considerably within and between the individuals. In contrast, in the marathon runners, structural deviations of pathologic value appeared in four out of five subjects. The fibre shapes were irregular, irrespective of fibre type, and internal architectural changes were common. An increased amount of connective tissue was found. A majority of fibres showed one or more central nuclei. A few fibres were flat and there were also evidence of fibre type grouping.

The divergent picture might be an expression of repeated fibre injury with subsequent processes. If so, a peripheral, relative, arterial insufficiency is suggested as a possible aetiology. However, it cannot be ruled out that the deviations express a functional adaptation to the extreme endurance demands.
Serum levels of thyroid and adrenal hormones, testosterone, TSH, LH, GH and prolactin in men after a 2‐h stay in a cold room
Authors: LEPPÄLUOTO J. , KORHONEN I. , HUTTUNEN P. , HASSI J.
Published: December 2008

Twenty healthy male volunteers, dressed in shorts, stayed for 30 min in a room with an ambient temperature of 28°C followed by a stay in a room with a temperature of 10°C for 120 min. The mean skin temperature fell rapidly during the first minutes in the cold but the rectal temperature began to fall as late as at 60 min (o. 1°C) and was 0.4°C lower at the end of the cold exposure than before it. The metabolic rate, and the systolic and diastolic blood pressures, increased, and the pulse rate fell, in the cold. Serum samples were taken before moving to the cold (10°C) room and after the 2‐h stay and assayed for 11 hormones. There were no significant changes in the serum concentration of adrenalin, T3, T4, testosterone, TSH or LH. The serum level of noradrenaline increased from 4.5 to 6.3 nmol L1 (P < 0.01) and those of Cortisol, GH and prolactin fell by 20, 87 and 48% (all P < 0.01). The total serum proteins increased by 11% and free fatty acids by 28%(P < 0.01). Our results show that the short‐term exposure of adult man to low ambient temperature does not have any effect on the pituitary‐thyroid and pituitary‐testis axes and adrenal medulla. The increase of noradrenaline is probably due to general activation of the sympathetic nerves at low temperatures. The decreases in the serum levels of GH and prolactin reflect a true decrease in their secretions and may be mediated by inhibitory hypothalamic mechanisms.
Insulin‐like growth factor I in the pancreas of normal and diabetic adult rats
Authors: HANSSON H.‐A. , EDWALL D. , LÖWENADLER B. , NORSTEDT G. , PALEUS S. , SKOTTNER A.
Published: December 2008

Insulin‐like growth factor I (IGF‐I, somatomedin C) was mapped by immuno‐cytochemistry in the pancreas of normal and experimentally influenced rats. The polyclonal IGF‐I antiserum K 37 was characterized and demonstrated to be specific. In the exocrine pancreas some duct cells showed IGF‐I immunoreactivity, other components being negative.

The three main endocrine cell types in the islets of Langerhans were IGF‐I immunoreactive, most strikingly the D cells. Hypophysectomy resulted in loss of IGF‐I immunoreactivity in all three endocrine cell types, i.e. D, A and B cells, while the levels of somatostatin, glucagon and insulin, respectively, remained unchanged. Starvation seemed to increase and feeding to decrease the IGF‐I immunoreactivity in the B cells. Cysteamine pre‐treatment reduced the normally intense IGF‐I and somatostatin immunoreactivities in the D cells. In rats made diabetic with alloxan or streptozotocin, the B cells were irreversibly damaged and lost both their insulin and IGF‐I immunoreactivities, while the IGF‐I immunoreactivity was increased in A cells; the D cells remained unchanged. The concentrations of IGF‐I mRNA in the pancreas were almost equal in normal and alloxan diabetic rats as were the concentrations of extractable IGF‐I.

We conclude that IGF‐I immunoreactive material can be demonstrated in adult animals in all endocrine islet cells, most prominently in the D cells. The expression of IGF‐I immunoreactivity is in part under pituitary control. In the adult rat only one islet cell type synthesizes IGF‐I immunoreactive material, i.e. the D cells, while, in contrast, the B cells are likely to be a major IGF‐I source in fetal and neonatal islets.
Effects of arterial pH and carbon dioxide on pancreatic exocrine H+/HCO‐3 secretion and secretin‐dependent translocation of cytoplasmic vesicles in pancreatic duct cells
Authors: BUANES T. , GROTMOL T. , LANDSVERK T. , NAFSTAD P. , RÆDER M. G.
Published: December 2008

To elucidate why arterial pH and carbon dioxide (Paco2) modify the pancreatic H+/ HCO‐ 3 secretory response to secretin stimulation, experiments were performed on anaesthetized pigs, recording the effects of arterial pH and Paco2 on exocrine H+/ HCO‐ 3 secretion and on morphology of pancreatic duct cells. Duct cells contained numerous cytoplasmic vesicles at secretory rest. Their number more than doubled during elevation of Paco2 from 5.5 to 11.0 kPa. At arterial pH 7.40, maximal secretin stimulation cleared the cytoplasm of duct cells of more than 90% of the vesicles. At high Paco2, this was accompanied by doubling the basolateral plasma membrane area and a 30% higher secretion rate than at Paco2 5.5 kPa. Lowering arterial pH to 7.0 more than halved the secretin‐induced vesicle clearance of duct‐cell cytoplasm as well as exocrine H+/HCO‐ 3 secretion and abolished the secretin‐dependent basolateral membrane area changes. Supramaximal secretin stimulation did not reverse the inhibitory effect of severe metabolic acidosis on secretion. It is concluded that Paco2 and arterial pH may modify the secretory response to secretin through determining the incorporation of cytoplasmic vesicle material into the basolateral plasma membrane of duct cells.
Human granulopoiesisin vitro‐medium‐dependent growth regulation by a granulocyte‐derived inhibitor
Authors: HELGESTAD J. , BØYUM A. , STORM‐MATHISEN I. , GAUDERNACK G. , LIE S. O.
Published: December 2008

A number of reports have indicated that mature blood granulocytes produce regulators that inhibit proliferation of progenitor cells in the bone marrow. However, this concept of negative feedback of granulopoiesis is still controversial. To examine whether conflicting results may depend upon the experimental set‐up, we have compared colony formation by human bone marrow cells in different growth media. Unmodified McCoy's medium, which in feeder layer cultures supports the formation of large numbers of colonies, was a poor growth medium in cultures supplied with crude or recombinant colony stimulating factor (CSF). The colony formation improved when the medium was supplemented with defined additives. In CMRL 1066 cultures, granulocyte extract (GRE) consistently caused a strong inhibition of colony formation. In contrast, with unmodified McCoy's medium, granulocyte extract enhanced colony formation in a dose‐dependent manner. The enhancing effect of granulocyte extract coincided with low colony numbers in the control cultures. The stimulatory effect of granulocyte extract in McCoy's medium, switched to strong inhibition when thymidine, a component of CMRL 1066 medium, was added. The inhibitory and stimulatory activities were found in the same molecular weight fractions (30–60 kD) after gel filtration. Both modulators in granylocyte extract appeared to be independent of monocytes and T lymphocytes in the bone marrow, as shown by removal of these cells with magnetic microspheres coated with specific monoclonal antibodies. The present work shows that regulation of cell prolifierationin vitrodepends strongly on culture conditions, such as choice of medium. It appears that thymidine acts as co‐factor for the inhibitor in granulocyte extract.
Phosphorylase activity in needle biopsy samples‐factors influencing transformation
Authors: REN J. M. , HULTMAN E.
Published: December 2008

Phosphorylase was determined in biopsy samples frozen immediately or after a delay of 10 s to 6 min. Muscle biopsies were performed at rest without and with propranolol, or adrenalin infusion and after electrical stimulation. The phosphorylase a fraction was 36% (28–44) in resting samples frozen immediately and 12% (12–13)after to s delay and remained at the same level when the freezing was further delayed (up to 6 min). It is suggested that an increase in [Ca2+] in the cytoplasm due to the insertion of the needle in muscle or cutting of tissue membranes may cause transformation of phosphorylase from b to a form, a transformation which is restored when Ca2+ is pumped back during the delay. Also the increased phosphorylase a fraction observed in biopsy samples obtained during adrenalin infusion reverted partially back when freezing was delayed for 10 s and 30 s, respectively. In muscle samples taken during contraction the mole fraction of phosphorylase a decreased from 53 to 12% when freezing was delayed for 10 s. The lowest value of the phosphorylase a mole fraction was observed in resting muscle after β‐blockade when the tissue samples were frozen 10 s after sampling and corresponded to 10% of the total phosphorylase. It is concluded that both muscle sampling and circulating adrenalin will increase phosphorylase a fraction in resting muscle and probably also augment the effect of adrenalin infusion.
Occurrence of an insulin‐like peptide in extracts of human nervous tissue
Authors: UVNAS‐MOBERG K. , POSLONCEC B. , JACOBSSON B. , UVNÄS B.
Published: December 2008

Peripheral nerves of the cat such as the vagal and the sciatic nerves have been shown to contain a peptide with insulin‐like properties. The aim of the present study was to investigate whether insulin‐like immunoreactivity (ILI) can be demonstrated in human nervous tissue collected from autopsy material. Biopsies were taken in connection with autopsy from various peripheral nerves and their content of ILI was investigated. ILI in amounts up to about 12 ng g‐1 was found in about 30% of all biopsies taken from peripheral nerves. The ILI coeluted with a bovine insulin standard in an HPLC system indicating that it corresponds to a peptide identical with or similar to pancreatic insulin. Autopsy specimens taken from the sciatic nerve of individuals with diabetes type II or from individuals without established diabetes contained similar amounts of ILI.
The analgesic effect of peripheral nerve stimulation in various tests of nociception in rats
Authors: E.JØRUM
Published: December 2008

The present study examines analgesic properties of 2 Hz peripheral nerve stimulation in four different tests of nociception: the tail‐flick, hot‐plate, jump‐response and formalin tests. Radial, sciatic and trigeminal nerve stimulation produced decreased response amplitudes to weak electrical foot shocks in the jump‐response test. The fact that all three nerves produced the same effect suggests the involvement of general, non‐segmental mechanisms. The nerve stimulation produced a characteristic after‐effect, lasting several minutes, suggesting the involvement of supraspinal mechanisms. The radial nerve stimulation resulted in the most pronounced reduction in jump responses. Sciatic nerve stimulation also produced analgesia in the formalin test but had no effect on the responsiveness to a brief stimulus at threshold level in the hot‐plate or the tail‐flick tests. It is concluded that analgesia by peripheral nerve stimulation in animals is most readily detected by tests allowing a quantitative evaluation of responses to above‐threshold noxious stimuli and not only measuring reactions occurring at the threshold for nociception.
Neurotropism in nerve regeneration: an immunohistochemical study
Authors: NACHEMSON A. K. , HANSSON H.‐A. , LUNDBORG G.
Published: December 2008

A rectangular pseudomesothelial‐lined chamber was used to elucidate the hypothesis that in adult rats neurotrophic factors are formed after nerve injury and may influence regeneration of peripheral nerves. The proximal end of a cut sciatic nerve was inserted into one corner of the chamber. In one group of animals the distal end of the cut sciatic nerve was implanted in the diagonally opposite corner of the chamber. In another group we just introduced the proximal end of the sciatic nerve; no distal implant was used. The organization, length and direction of the nerve fibres, regenerating from the proximal end of the sciatic nerve, was visualized immunohistochemically with the aid of antibodies against neurofilaments at 2, 3 and 4 weeks after surgery. When a distal sciatic nerve segment was used, nerve fibres regenerating from the proximal cut end of the sciatic nerve showed an organized growth across the chamber, formed bundles and grew into the diagonally implanted nerve piece. If there was no distal implant, the growth of the randomly directed nerve fibres ceased after about two weeks, resulting in formation of a neuroma‐like structure. Increased immunoreactivity of the trophic peptide insulin‐like growth factor I (IGF‐I, somatomedin C) was demonstrated in the regenerating nerve, most evidently in reactive Schwann cells.

It is concluded that a positive neurotropic effect is exerted on growing nerve fibres by injured, reactive peripheral nerve tissue. There could tentatively be a relation between nerve regeneration and local formation of trophic factors.
Measurements of macula densa cell volume changes in isolated and perfused rabbit cortical thick ascending limb. II. Apical and basolateral cell osmotic water permeabilities
Authors: GONZÁLEZ E. , SALOMONSSON M. , MÜLLER‐SUUR C. , PERSSON A. E. G.
Published: December 2008

Cortical thick ascending limbs containing macula densa plaques were dissected and perfused in vitro. Macula densa cell osmotic water permeability of the apical and basolateral membranes were measured by setting up osmotic steps across them in less than 0.1 s and following the ensuing time‐dependent cell volume changes. The results of this study are in accordance with the view that the macula densa cells have a relatively low permeability to water. Apical and basolateral osmotic water permeabilities are 2.4 and 30.4 times 10‐4 cm3 s‐1 osMolar‐1 cm‐2 basement membrane area, respectively. No infoldings were taken into consideration. These water permeabilities were not affected by maximal and supramaximal doses of vasopressin. This paper provides new insight into the physiological behaviour of this small, and almost inaccessible, sensing epithelial disc of cells which improves the understanding of its participation in the juxtaglomerular feedback response.
Colloid osmotic pressure of interstitial fluid in rat subcutis and skeletal muscle: comparison of various wick sampling techniques
Authors: WIIG H. , HEIR S. , AUKLAND K.
Published: December 2008

Interstitual fluid for measurement of colloid osmotic pressure (COP1) was collected from rat subcutis and skeletal muscle with three wick methods; saline‐soaked wicks implanted in vivo, titration with wicks preloaded with serial dilutions of rat plasma implanted postmortem (crossover method) and dry wicks implanted in vivo and post‐mortem. When compared in 12 rats, the mean subcutaneous COP1 of 14.2 and 13.3 mmHg as estimated with the crossover method and dry wick method, respectively, both exceeded the 10.7 mmHg obtained in saline‐soaked wicks implanted for 60 min. Colloid osmotic pressure (COP) in fluid from dry wicks implanted subcutaneously was slightly lower than in plasma 5 min after implantation in vivo, then fell gradually, but remained stable the last 30 min of the 60 min in vivo implantation period and the first 30 min postmortem, when again starting to rise. COP in fluid isolated from dry wicks implanted in muscle post‐mortem approached or even exceeded that of plasma, suggesting leakage of intracellular proteins to wick fluid. Electrophoresis of dry wick fluid from subcutis showed a pattern similar to that of plasma, while protein fractions not present in plasma were observed in muscle wick fluid. For measurement of COP1 we recommend the use of dry wicks implanted post mortem for subcutis and saline‐soaked or dry wicks implanted in vivo for 90–120 min for skeletal muscle.