bluuebunny/crossref_metadata_2025 huggingface dataset:
Temperature‐induced changes in metabolic and hormonal responses to intensive dynamic exercise
Authors: BLOMSTRAND E. , KAIJSER L. , MARTINSSON A. , BERGH U. , EKBLOM B.
Published: December 2008

Seven male subjects performed intensive cycle exercise to exhaustion at subnormal muscle temperature (Tm, 29 ± 2.8 °C). Exercise at exactly the same rate of exercise and duration (370 ± 34 W, 1.5 ± 0.15 min) was then repeated with normal Tm (35 ± 0.9 °C). During exercise both the arterial (a) and femoral venous (fv) contents of oxygen were significantly higher at subnormal than at normal Tm, because of the higher haemoglobin concentration, but the a‐fv oxygen difference was the same in the two situations. The rate of increase in lactate concentration in both arterial and venous blood during exercise was the same in the two situations. During exercise the plasma concentrations of adrenaline and noradrealine in arterial and venous blood were significantly higher at subnormal than at normal Tm. At rest and after exercise the calf blood flow was significantly reduced at subnormal Tm At the end of exercise the concentrations of glucose‐6‐phosphate and lactate in the muscle were significantly higher at subnormal Tm than in the muscle of normal temperature. These findings suggest that there was a greater increase in glycolysis in the muscle of subnormal temperature during exercise, possibly as a result of impaired work efficiency and/or reduced blood flow in the cold muscle.
Redistribution of glomerular filtration and renal plasma flow in CNS‐induced natriuresis
Authors: SJÖQUIST M. , GÖRANSSON A. , HANSELL P. , ISAKSSON B. , ULFENDAHL H. R.
Published: December 2008

Infusion of hypertonic sodium chloride solution into the third cerebral ventricle results in a marked increase in renal sodium output, indicating an important regulator of extracellular volume homeostasis. The intrarenal events governing the enhanced excretion have not been thoroughly studied previously. In 12 anaesthetized male rats a stainless steel cannula was introduced stereotaxically into the right lateral cerebral ventricle. Urine volume and excretion rates of Na, K, and osmotically active particles were measured during control infusion of artificial cerebrospinal fluid and during stimulation of central mechanisms with 1 M NaCl (520 nl min“1). At the end of the stimulation period, regional renal plasma flow (86 RbCl) and glomerular filtration rate (51 Cr‐EDTA) were measured with single injection techniques. A second group of 12 non‐stimulated rats served as controls. During ICV stimulation, the urine flow rate increased from 1.8 ± 0.1910 6.4 ± 1.01 μl min‐1 (P < 0.001). The urinary concentrations of Na and K increased, leading to a rise in the excretion rates of these ions from 0.12 ± 0.025 to 0.96 ± 0.352 μmol min‐1 (P < 0.001) and 0.40 ± 0.083 to 1.70 ± 0.196 (P < 0.001), respectively. The osmolar excretion rate was 2.9 ± 0.35 μOsm min‐1 before stimulation and 9.6 ± 1.09 higher (P < 0.001) during stimulation. Simultaneously the inner medullary plasma flow rose two‐fold from 0.7 ± 0.06 to 1.4 ± 0.12 μl min_1 mg‐1 tissue (P < 0.008). This increase was accompanied by a significant increase (P < 0.001) in the single nephron glomerular filtration rate (SNGFR) in the inner cortex (to 37 ± 1.4 nl min‐1 g_1 kidney wt) compared with the value in control rats (26 ± 2.7), while SNGFR in the outer cortex remained almost unaltered (24 ± 1.2 compared with 20 ± 2.0 in control rats). In summary, ICV stimulation with hypertonic NaCl solution induced a marked increase in electrolyte excretion. The stimulation affected inner cortical nephrons substantially more than outer cortical ones.
Afferent projections to human tibialis anterior motor units active at various levels of muscle contraction
Authors: ASHBY P. , HILTON‐BROWN P. , STÅLBERG E.
Published: December 2008

The synaptic efficacy of muscle and cutaneous afferents on single tibialis anterior motoneurones in man was derived from changes in the firing probability of single, voluntarily activated, motor units in response to electrical stimulation of peripheral nerves or skin. The motor units were recorded with a Macro EMG electrode. The Macro motor unit potential (Macro MUP) recorded with this electrode reflects the electrical activity of all of the muscle fibres in a single motor unit. The amplitude of the Macro MUP is positively correlated with the recruitment threshold of the unit. Motor units with different Macro MUP amplitudes were examined at approximately the same level of voluntary contraction (less than 20% of maximum). The synaptic efficacy of muscle and cutaneous afferents was similar for units with small and with large Macro MUP amplitudes. Single motor units were examined at several different levels of muscle contraction. There was no consistent change in the facilitation from muscle afferents but there was less facilitation from cutaneous afferents during stronger contractions. This was not simply a consequence of the units faster firing rate. It is concluded that, with increasing voluntary drive to tibialis anterior motoneurones in man, there is a reduction in transmission in the pathways from cutaneous afferents to tibialis anterior motoneurones. There is no evidence that low and high threshold units (judging from their Macro MUP amplitudes) have different afferent connections.
Regional distribution and extracellular levels of amino acids in rat central nervous system
Authors: TOSSMAN U. , JONSSON G. , UNGERSTEDT U.
Published: December 2008

The extracellular levels of aspartate, glutamate, serine, glutamine, glycine, alanine and GABA were studied in vivo with the microdialysis technique in 15 different regions of the rat brain. The effect of high K+ on the overflow of these amino acids was also studied. These results were compared with those from a regional dissection of 17 brain regions in which the tissue content of the same amino acids was determined. The in vivo data showed an unevenly distributed KC1 response of aspartate, glutamate, taurine and GABA, all of which are putative neurotransmitters. It was not possible to predict the response to high K+ from the magnitude of the unstimulated overflow. Glutamine overflow was inversely related to that of glutamate during the high K+ stimulus, which is consistent with glutamine being the main precursor of glutamate. Only for GABA and alanine was overflow proportional to the tissue level in the different regions studied.
Extracellular levels of amino acids in striatum and globus pallidus of 6‐hydroxydopamine‐lesioned rats measured with microdialysis
Authors: TOSSMAN U. , SEGOVIA J. , UNGERSTEDT U.
Published: December 2008

Extracellular aspartate, glutamate, glutamine, taurine and GABA concentrations were measured by microdialysis in the rat striatum and globus pallidus after a unilateral 6‐hydroxydopamine lesion of the dopamine system. The basal and potassium‐evoked overflow of GABA was increased in the ipsilateral striatum, but the evoked overflow was decreased in both contralateral striatum and pallidum. Both basal and evoked overflow of glutamate was increased in ipsilateral striatum. The basal overflow of aspartate was significantly increased in the ipsilateral side. Basal glutamine on the other hand was decreased in the ipsilateral side. Taurine remained unchanged in both regions. These results suggest that dopamine is involved in the regulation of transmission by GABA and glutamate. Since glutamine might be the precursor to glutamate, the change in glutamate might affect the glutamine level. The changed aspartate level has no obvious explanation.
Microdialysis in the study of extracellular levels of amino acids in the rat brain
Authors: TOSSMAN U. , UNGERSTEDT U.
Published: December 2008

Microdialysis has been used forin vivostudies of extracellular amino acids in rat brain. We describe a method where a probe was designed to be implanted vertically. This probe is suitable for regional stereotaxic studies of the rat brain. The dialysis probe was perfused with Ringer's solution and the perfusates were analysed for their amino acid content with a high performance liquid chromatography (HPLC) technique. An orthophthaldialdehyde derivative of the amino acids was formed before the sample was injected onto the column.In vitrostudies of the dialysis probe show that the relative recovery of substances outside the membrane is dependent on perfusion speed and length of dialysing membrane but not on the concentration outside. We were also able to show that the probe was within the blood‐brain barrier (BBB) when implanted into the brain since after intravenous injection of Na99mTcO4, a substance that cannot pass through the intact BBB, it was not possible to recover any isotope from the perfusate. We conclude that microdialysis is a unique method of studying regional neurochemical events within the BBB, for example, changes in putative amino acid neurotransmitters and their metabolites.
Aerobic and anaerobic responses to incremental exercise in a thermoneutral and a hot dry environment
Authors: SMOLANDER J. , KOLARI P. , KORHONEN O. , ILMARINEN R.
Published: December 2008

In an investigation of the effect of acute heat exposure on aerobic and anaerobic metabolism, eight unacclimated men performed two incremental bicycle ergometer tests in random order, once under thermoneutral conditions (25oC) and once in a hot dry (40oC) environment. Oxygen consumption (Vo2) and pulmonary ventilation were measured every minute. Fingertip blood samples were taken at each work level for blood lactate (LA) determination. Compared to the results at 25oC, the meanVo2was significantly (P< 0.01) lower during exercise at 40oC. In the hot dry environment the blood lactate threshold was slightly reduced in four subjects, but neither the average peak nor the post‐exercise blood LA values differed from the findings at 25oC. During the exercise‐heat stress, the ventilatory threshold did not change significantly. The results indicated that, during relatively short‐term incremental exercise in a hot environment, almost adequate muscle metabolism can be maintained.
Relaxant and contractile effects of some amines and prostanoids in myometrial and vascular smooth muscle within the human uteroplacental unit
Authors: MAIGAARD S. , FORMAN A. , ANDERSSON K.‐E.
Published: December 2008

Tissue specimens of human myometrium and placenta were obtained at caesarean section and normal vaginal deliveries. Strips of myometrial tissue, and segments of intramyometrial arteries, chorionic plate arteries and veins, and stem villous arteries were dissected. The preparations were mounted in organ baths, and isometric tension was recorded. In myometrial preparations, prostaglandin F2α(PGF2α), prostaglandin E2(PGE2), noradrenaline (NA) and serotonin (5‐HT) all caused concentration‐related contractions. In vascular preparations, the maximum contractant or relaxant effect,EmaxorImax, and the drug concentrations causing half maximum responses, EC50or ICS0were determined. In intramyometrial arteries no significant differences betweenEmaxor EC50values were found for NA, 5‐HT and PGF2α. TheImaxvalues (relaxation of vessels contracted by vasopressin) ranged prostacyclin (PGI2) > PGF2α= PGE2, and the IC50values PGF2α= PGE2= PGI2(PGF2α< PGI2). Thus, PGF2αshowed dual effects. Only PGI2relaxed placental vessels contracted by PGF2α. In chorionic arteries,Emaxvalues ranged PGE2= PGF2α> 5‐HT > NA, and IC50values 5‐HT < NA = PGF2α= PGE2. In stem villous arteries,Emaxranged PGE2= PGF2α> 5‐HT = NA, and EC505‐HT = NA = PGE2= PGF2α. In chorionic veins the order ofEmaxvalues was PGF2α= PGE2> 5‐HT > NA, and that of the EC50values 5‐HT < NA = PGF2α= PGE2. Smooth muscle tissues from the human uteroplacental unit show individual responses to prostanoids and amines, probably reflecting individual mechanisms for control of contractile activity and blood flow.
Projection of la and lb afferents from forelimb muscles to the C3‐C4 segments of the cat spinal cord
Authors: GORSKA T. , JOHANNISSON T.
Published: December 2008

Group la muscle spindle afferents were activated separately by small stretches applied to the tendons of antibrachial muscles in the forelimb in the cat. Group lb tendon organ afferents were stimulated electrically after a selective increase of the threshold of the la afferents. Recordings of focal synaptic potentials were made in the C3‐C4 segments in the medial part of the base of the dorsal horn. It has been found that both la and lb afferents have monosynaptic connections with neurones in this medial region. Quantitatively, these two groups of afferents produced focal synaptic potentials of approximately the same size. The connections may be to inhibitory interneurones projecting to the C3‐C4 propriospinal neurones, which are known to receive disynaptic IPSPs from group I muscle afferents.
Comparison between pre‐ and postovulatory distributions of oestradiol and progesterone in the brain of the PMSG‐treated rat
Authors: BIXO M. , BÄCKSTRÖM T. , WINBLAD B. , SELSTAM G. , ANDERSSON A.
Published: December 2008

The pre‐ and postovulatory levels of oestradiol and progesterone were measured in seven brain areas, peripheral fat, muscle tissue and blood plasma in 49 immature female rats which had been given an injection of 4IU PMSG (Pregnant Mare Serum Gonadotropin) on the 25th day of life. We observed a uniform decline in oestradiol concentration in all the areas of the postovulatory rat. The highest mean concentrations of oestradiol pre‐and postovulatory were found in the hypothalamus and the striatum (260 ± 26,110 ± 11, 200 ± 39 and 75 ± 13 pg g‐1, respectively). The levels of progesterone showed variable increases in all the areas postovulatory. The highest postovulatory concentration was found in the cerebral cortex (29 $4 2.0 ng g_1) where the increase was six‐fold greater than the increases in any of the other areas compared to preovulatory values. The hypothalamus contained high progesterone levels at both times (3.5 ±0.68 ng g‐1and 27 ± 5.2 ng g‐1) compared to other areas. We conclude that the female rat brain exhibits differences in the distribution of oestradiol and progesterone both pre‐ and postovulatory. Since the levels in different brain areas to a large extent varied independently we suggest different uptake mechanisms and/or different binding capacities in various regions of the rat brain.
Dual capsaicin effects on ureteric motility: low dose inhibition mediated by calcitonin gene‐related peptide and high dose stimulation by tachykinins?
Authors: HUA X.‐Y. , LUNDBERG J. M.
Published: December 2008

The effects of capsaicin, in relation to substance P (SP), neurokinin A (NKA), neuropeptide K (NPK) and calcitonin gene‐related peptide (CGRP) which coexist in local sensory nerves, on the motility of the guinea‐pig ureter were studied in vivo and in vitro. Capsaicin in a low dose (ionmolkg‐1) given i.v. inhibited spontaneous, peristaltic contractions, as revealed by perfusion‐pressure changes of the constantly perfused ureter in vivo. This action was independent of autonomic reflexes and prostaglandin formation. Capsaicin stimulated ureteric motility at higher doses (100 and 500 nmol kg‐1). The dual effects of capsaicin on the ureteric contractility were absent 2 weeks after systemic capsaicin treatment, which depletes sensory neuropeptides. Both NKA and NPK initiated, as well as increased, the magnitude of the peristaltic contractions of the ureter, while SP only caused a minor excitatory effect. The CGRP inhibited spontaneous, as well as NKA‐ and NPK‐induced ureteric peristaltic contractions. In vitro experiments on the ureter revealed that capsaicin (10‐6 M) induced phasic circular muscle contractions in 60% of the experiments. Neurokinin A, NPK and SP consistently increased the contractile activity. The NKA tachyphylaxis inhibited the contractile response to other tachykinins and capsaicin. The SP analogue Spantide (/D‐Arg1, D‐Trp7,9, Leu11/‐SP) inhibited the contractile responses to SP, NKA and NPK. The CGRP also inhibited the NKA‐ and NPK‐induced contractions of the ureter in vitro. In conclusion, capsaicin, which induces the release of mediators from sensory nerves within the ureter, has either stimulatory or inhibitory effects on ureteric smooth muscle, depending on the in vivo dose administered. The inhibitory response at a low capsaicin dose is similar to the effect of CGRP, while the contractile effects at higher doses resemble the response to tachykinins.
Rate of oxidative and glycolytic metabolism in the guinea‐pig oviduct in relation to contractility and hormonal cycle
Authors: LYDRUP M.‐L. , HELLSTRAND P.
Published: December 2008

The rates of oxygen consumption and lactate production in the guinea‐pig oviduct were measured together with registration of contractile activity during three phases of the hormonal cycle. In pro‐oestrus (high oestrogen, low progesterone levels) and oestrus (time of ovulation, high oestrogen and progesterone) the rate of O2 consumption was higher than in dioestrus (low oestrogen, high progesterone). The frequency of spontaneous contractions was higher in oestrus than in the other phases. No significant differences in the proportion of the cross‐sectional area occupied by smooth muscle were found between oviducts in di‐ and pro‐oestrus. Stimulation by phenylephrine caused decreased frequency and increased amplitude of contractions in dioestrus but not in pro‐oestrus, suggesting hormonal modulation of adrenergic mechanisms. The rate of relaxation of high‐K+ contractures was higher in pro‐ than dioestrus. Lactate production and contents of ATP, ADP and phosphocreatine showed no significant variation with hormonal state. The increased rate of oxidative metabolism under oestrogenic dominance could in part reflect changes in ionic transport mechanisms, such as intracellular Ca2+ handling.
NN′‐dicyclohexylcarbodiimide (DCCD) reduces pancreatic NaHCO3 secretion without changing pancreatic tissue ATP levels
Authors: GROTMOL T. , BUANES T. , RÆDER M. G.
Published: December 2008

To study the mechanism responsible for pancreatic NaHCO3 secretion, the inhibitor NN'‐dicyclohexylcarbodiimide (DCCD) was administered to six secretin‐infused, anaesthetized pigs. Pancreatic juice was collected from a catheter in the main pancreatic duct. Secretion rate was measured at several arterial pH values in each animal, both before and after DCCD. 15 (14–30) μmol kg‐1 body wt DCCD, intra‐arterially, reduced pancreatic NaHCO3 secretion from 296 (234–398) to 181 (134–237) μmol min‐1 at arterial pH 7.43 (7.42‐7.47). Similar fractional reductions of secretion occurred at lower arterial pH. Pancreatic tissue ATP concentration, 1.8 (i.4‐2.o)μmol g‐1 wet wt, was not changed by DCCD. DCCD, ≤ 10‐4 mol l‐1, did not change Na,K‐ATPase nor carbonic anhydrase activities in separate in vitro assay systems. It is concluded that DCCD reduced pancreatic NaHCO3 secretion by a mechanism not involving ATP depletion nor inhibition of Na,K‐ATPase nor carbonic anhydrase activities in pancreatic cells. Because DCCD inhibits proton pumps, DCCD may have reduced NaHCO3 secretion through interfering with a proton pump involved in extruding H+ from HCO3‐ secreting cells to interstitial fluid in the pancreas.
Sympatho‐adrenergic inhibition of vagaliy induced gastric motility and gastroduodenal HCO3‐ secretion in the cat
Authors: FÄNDRIKS L.
Published: December 2008

Chloralosed cats were acutely vagotomized and their adrenal glands were ligated. The gastric lumen was perfused with isotonic NaCl and gastric motility was recorded as change in hydrostatic pressure within the perfusion circuit. Gastric secretions of H+ HCO3‐ were calculated from continuous measurements of pH and pCO2 in the perfusate. Mucosal HCO3‐ secretion in the distal duodenum was titrated in situ by pH‐stat equipment. The experiments were divided into three different groups dependent on the state of sympathetic splanchnic nervous supply: (1) intact; (2) cut on a preganglionic level; (3) blocked with the adrenolytic agent guanethidine. Basal levels for gastric motility, gastric H+ HCO3‐ secretions and duodenal HCO3‐ secretion were more or less similar in all groups. Gastric motility, gastric HCO3‐ duodenal HCO3‐ secretory responses to bilateral vagal stimulation were significantly enhanced in splanchnicotom‐ized or guanethidine‐treated animals as compared to controls with intact sympathetic supply. However, no clear differences in gastric H+ secretory responses to vagal stimulation were demonstrated between animals with an intact or disrupted sympathetic innervation. These results suggest a sympatho‐adrenergic inhibitory action on vagaliy induced mucosa‐protective HCO3‐ secretion in the stomach and the duodenum. Furthermore, vagal stimulation in animals with intact splanchnic nerves induced a guanethidine‐resistant delayed increase in duodenal HCO3‐ secretion. The nature of this response was not further analysed.
Secretin potentiates cholinergically induced glucagon secretion in the mouse
Authors: AHRÉN B. , LUNDQUIST I.
Published: December 2008

Glucagon secretion is stimulated by cholinergic activation, and it is known that the polypeptides VIP (vasoactive intestinal polypeptide) and GIP (gastric inhibitory polypeptide) both potentiate this cholinergically induced glucagon secretion. In this study, we investigated whether secretin, which shows structural similarities to both VIP and GIP, affects basal and cholinergically induced glucagon secretion in the mouse. Secretin was injected i.v. to mice at dose levels varying from 0.53 to 17 nmol kg‐1, and plasma samples were taken at 2, 6 and 10 min following injection. It was found that secretin in this wide dose range did not affect basal glucagon concentrations. When the cholinergic agonist carbachol was injected i.v. at 0.16 μmol kg‐1, plasma glucagon levels were elevated; at 2 min at 0.84 ± 0.04 ng ml‐1 compared to 0.31 ± 0.02 ng ml‐1 in controls(P < 0.001). A combination of carbachol and secretin (4.25 nmol kg‐1)enhanced plasma glucagon levels to 1.22 ± 0.07 ng ml‐1. Thus, secretin potentiated carbachol‐induced glucagon secretion by 70% (P < 0.001). Concomitantly, plasma glucose levels were elevated: 10.8 ± 0.4 mmol 1‐1, compared to 9.2 ± 0.4 mmol 1‐1 in controls (P < 0.001). We conclude that secretin, while being without effect on basal glucagon secretion, markedly potentiates cholinergically induced glucagon secretion in the mouse, resulting in increased plasma glucose levels.
Isoflurane effects in rat hippocampal cortex: a quantitative evaluation of different cellular sites of action
Authors: BERG‐JOHNSEN J. , LANGMOEN I. A.
Published: December 2008

In order to evaluate quantitatively the effects of an inhalation anaesthetic on neuronal excitability and on synaptic transmission in the central nervous system, we have examined the action of isoflurane on slices from rat hippocampal cortex. Isoflurane 1.5 % (1.38 % anaesthetize 50 % of tested rats (MAC)) reduced orthodromically evoked activity in pyramidal cells by 62%. This was due to the combined effects on afferent fibres, excitatory synapses and pyramidal cells. The effect on the postsynaptic neurones was almost as strong as the effect on the excitatory synapses: the population spike evoked by a given synaptic current was reduced by 24%, and the field‐EPSP in response to a given afferent fibre volley by 27%. The presynaptic fibre volley was reduced by 17%.
Modifications of the pancreatic β‐cell function after lowering their potassium content
Authors: BERGSTEN P. , RORSMAN F. , HELLMAN B.
Published: December 2008

β‐cell‐rich pancreatic islets from ob/ob‐mice were kept for 3 days in a culture medium and analysed for their content of potassium. In a normal ionic milieu intracellular potassium was calculated as 190–260 mM. Whereas this concentration remained essentially unaffected after lowering extracellular K+to 1.5 mM, further reduction to o. 15 mM depressed islet potassium to 5 % or less of its original value. Irrespective of its medium concentration, potassium in the islets increased when glucose was raised from 1 to 20 mM. Depression of the islet potassium was associated with a rise of intracellular calcium. Despite profound depletion of potassium, the β‐cells maintained their insulin content and could still oxidize glucose at a substantial rate. When potassium was suppressed to 25 % or less of the original content, the β‐cells responded to glucose with a paradoxical inhibition of insulin release. After 3 days of potassium depletion, exposure to a normal ionic milieu neither restored the intracellular content of potassium nor a stimulated insulin secretory response to glucose.
Comparison of the vasodilatory effects of vasoactive intestinal polypeptide (VIP) and peptide‐HI (PHI) in the rabbit and the cat
Authors: NILSSON S. F. E. , MÄEPEA O.
Published: December 2008

In rabbits, intravenous infusion of increasing doses of peptide‐HI (PHI), with direct measurement of the uveal blood flow from a cannulated vortex vein, caused a dose‐dependent decrease in the uveal vascular resistance. The maximal effect, a 50% decrease, was achieved with about 60 pmol kg‐1 min‐1. This is similar to what has previously been reported for vasoactive intestinal polypeptide (VIP). Determination of local blood flows, with radioactive microspheres, showed that i.v. infusion of VIP or PHI (60 pmol kg‐1 min‐1) caused about the same increase in the choroidal blood flow, while the local blood flow in the anterior uvea was unaffected by both peptides. The most marked effect of VIP was observed in glandular tissues, such as the pancreas, submandibular, parotid and thyriod glands. The pancreas was the only one of these tissues in which PHI caused an increased blood flow. In cats, i.v. infusion of VIP (30 pmol kg‐1 min‐1) during 5–7 min caused a markedly increased blood flow in several tissues. The vasodilation in glandular tissues was even more marked than in rabbits; 3–15 times the normal compared with two to five times the normal in rabbits. The chorodial blood flow was however significantly decreased and the local flow in the anterior uvea tended also to be reduced. Intravenous infusion of either a higher dose of VIP (60 pmol kg‐1 min‐1) or of PHI (1800 pmol kg‐1 min‐1) during 2 min had no effect on the uveal vascular resistance. This dose of PHI had only minor effects on local blood flows in other tissues. The results of the present study indicate that porcine VIP is a more potent vasodilator than porcine PHI in most tissues of both the cat and the rabbit, but that there may be exceptions such as the rabbit uvea. The difference in potency may also vary considerably between the species.
The effects of naloxone on behavioural depression due to hypotensive haemorrhage in unanaesthetized spontaneously hypertensive rats
Authors: SKARPHEDINSSON J. O. , THORÉN P.
Published: December 2008

The purpose of the study was to examine the effects of naloxone on signs of cerebral ischaemia during hypotensive haemorrhage in unanaesthetized spontaneously hypertensive rats. Mean arterial blood pressure (MAP), heart rate (HR) and somatosensory evoked potentials (SEP) were recorded. Arousal tests were also performed and the behavioural responses quantified. The SEP alone were a poor indicator of cerebral function in these unanaesthetized rats, because they were markedly influenced by changes in activity and arousal of the animals. Hypotensive haemorrhage resulted in a biphasic tachycardia response, an attenuation of the first SEP component and a reduction of the behavioural response score. Naloxone, 5 mg kg‐1 i.v., induced transient bradycardia and a dramatic improvement in arousal test responses, while SEP were not clearly altered. The MAP was kept constant after naloxone injection by adjustments of bleeding and transfusion. Injection of naloxone in unbled control SHR also induced bradycardia but without any changes in SEP and the behavioural responses. The results indicate that naloxone can have beneficial effects in cerebral ischaemia. Possible mechanisms are discussed.
Effects of anaemia and stepwise‐induced polycythaemia on maximal aerobic power in individuals with high and low haemoglobin concentrations
Authors: CELSING F. , SVEDENHAG J. , PIHLSTEDT P. , BLOM B. EK
Published: December 2008

Increasing the haemoglobin concentration ([Hb]) improves the oxygen transport capacity but it also increases the viscosity of the blood. The influence of changes in [Hb] and viscosity on submaximal exercise capacity and maximal aerobic power was investigated in eight healthy males in varying states of training and with a normal resting [Hb] ([Hb]r), ranging from 123 to 178 g]‐1. The subjects were venesected five times (450 ml per unit) and exercise tests were performed in the anaemic state. After 5–7 weeks, when [Hb] had returned to the ‘normal’ value, a stepwise re‐transfusion of three to five units of blood was performed with exercise tests after each transfusion. The [Hb]r was 137 ± 15 g l‐1 in the anaemic state (A) and 170 ± 16 g l‐1 after the last re‐transfusion (LT). The Vo2max rose from 3.94 ± 0.35 in A to 4.68 ± 0.30 1 min‐1 after LT. Individual regression lines for [Hb] and Vo2max revealed a mean increase in Vo2max of 19 ± 6 ml min‐1 per g l‐1 change in [Hb]. This value did not differ between individuals with high and low normal [Hb]. Furthermore, in intra‐individual comparisons the relationship between [Hb] and Vo2max in high and low individual [Hb] ranges was not found to be statistically different despite a 40% increase in the in vitro viscosity from the anaemic to the polycythaemic state. The average individual correlation (based on five to seven measurements) between [Hb] at rest and after exercise and Vo2max was r= 0.89 (P > 0.01) in the former case and r= 0.92 (P > 0.01) in the latter. The running velocity corresponding to a blood lactate concentration of 4 mM (VHla4.0) increased from 15.3 ± 2.3 in the control state to 15.6±2.3 km h1 after the last transfusion (P > 0.01). A leftward shift of the blood lactate curve, expressed as a percentage of Vo2max, was found. In conclusion, the results obtained indicate a close relationship between Vo2max and [Hb] up to at least 170 g l‐1. Furthermore, both inter‐and intra‐individual comparisons suggest that the influence of viscosity as such on Vo2max does not differ at high and low [Hb] levels.
D‐Arg1, D‐Trp79, Leu11‐substance P (spantide) does not antagonize substance P‐induced hyperexcitability of the nociceptive flexion withdrawal reflex in the rat
Authors: WIESENFELD‐HALLIN Z. , DURANTI R.
Published: December 2008

The effect of D‐Arg‐1, D‐Trp7,9, Leu11‐substance P (SP) (spantide), a putative SP antagonist, on SP‐induced facilitation of the flexion reflex was examined. The drugs were injected intrathecally (i.t.) in decerebrate, spinalized, unanaesthetized rats. Substance P (10 ng) caused an increase in reflex magnitude for about 5 min. Spantide (10 ng and 100 ng) also caused a facilitation of the reflex that was similar to SP. Spantide (10 ng) plus SP (10 ng) also had a similar excitatory effect. One microgramme of spantide totally blocked the flexion reflex, which could not be reversed by SP, L‐glutamate, L‐aspartate or naloxone. It is concluded that spantide does not have an antagonistic effect on SP‐induced changes in spinal reflex excitability. Some of the effects of i.t. spantide observed in behavioural studies may be due to a non‐specific spinai motor block. It is suggested that the flexion reflex in the decerebrate, spinalized rat is a useful physiological model in studies of the effects of algesic and analgesic drugs at spinal level.
Effects of chronic salt loading on plasma atrial natriuretic peptide (ANP) in the spontaneously hypertensive rat
Authors: GRADIN K. , HEDNER J. , HEDNER T. , TOWLE A. C. , PETTERSSON A. , PERSSON B.
Published: December 2008

Plasma concentrations of immunoreactive atrial natriuretic peptide (ANP) was measured in spontaneously hypertensive rats (SHR) during chronic salt loading (1.5% NaCl in drinking water). During the 3‐week experimental period mean arterial blood pressure, heart rate, urinary sodium excretion and body weight was assessed in salt‐loaded as well as in control rats. The sodium excretion was more than lo‐fold increased in the rats on the high salt diet. The plasma ANP concentration was significantly increased only 24h after the start of the high salt intake. Thereafter plasma ANP concentrations were not significantly different from values obtained in control rats. The blood pressure was significantly increased after 3, weeks on the high salt diet. At the end of the 3‐week experimental period the rats were subjected to a 10 and 20% acute volume expansion with homologous whole blood. During this intervention the increase in plasma ANP concentrations was blunted in the high salt rats compared to the control group. It is concluded that during chronic salt loading in SHR there is an initial rise in plasma ANP levels and that other hormonal and neuronal systems are more important in the long term maintenance of fluid and electrolyte balance.
Fast voluntary trunk flexion movements in standing: motor patterns
Authors: ODDSSON L. , THORSTENSSON A.
Published: December 2008

The electromyographical (EMG) activity was studied during voluntary flexion movements of the trunk in erect standing man. The movements were performed at maximal velocity with successively increasing amplitude to cover the whole range of motion. The EMG activity was recorded from agonist‐antagonist pairs of muscles at the ankle, knee, hip and trunk. The angular displacements at the corresponding joints were recorded using a Selspot optoelectronic system. The duration of initiating activity in prime movers (rectus abdominis and rectus femoris) as well as time to onset of activity in muscles braking the primary movement (erector spinae, gluteus maxims and hamstrings) were highly correlated with amplitude, duration, peak velocity and time to peak velocity of the movement (r = 0.59–0.91). The corresponding correlations for peak acceleration and deceleration of the movement were low (r = 0.03–0.38), indicating that acceleration and deceleration of a movement was not coded in the temporal aspects of the EMG. Onset of activity in rectus abdominis and rectus femoris as well as an early appearing burst of activity in vastus lateralis were invariant in relation to start of movement over the whole movement range. In the initial phase of a fast trunk flexion, activity in tibialis anterior appeared successively earlier with increasing movement amplitude. This resulted in a changed order of activation for the muscles from proximal to distal (rectus abdominis first) to distal to proximal (tibialis anterior first). Two different forms of associated postural adjustments are present during a fast trunk flexion, one early fast knee flexion and a later slower angle extension. Prior to knee flexion, no activity was recorded from muscles flexing at the knee implying that some other force must create a flexing torque around the knee. It is suggested that activity in rectus abdominis initiating the primary movement also initiates knee flexion through the upward pulling of pelvis. This would be possible since rectus femoris stabilizes the pelvis in relation to the leg, allowing the force in rectus abdominis to be transmitted below the hip joint and act extending around the ankle joint. However, when tibialis anterior is activated it stabilizes the shank which in turn will cause a knee flexion controlled by a lengthening contraction in vastus lateralis. During the subsequent ankle extension activity appears in lateral gastrocnemius and soleus causing the associated postural adjustment at the ankle. It can be concluded that activation of postural muscles prior to prime mover muscles is not always necessary. The term linked postural adjustments is proposed for the class of associated movements where activation of prime movers causes both the primary movement and the postural adjustment thus minimizing the perturbation of the equilibrium.
Adaptability in frequency and amplitude of leg movements during human locomotion at different speeds
Authors: NILSSON J. , THORSTENSSON A.
Published: December 2008

In this study of human locomotion we investigate to what extent the normal frequency and amplitude of leg movements can be modified voluntarily at different constant velocities, and how these modifications are accomplished in terms of changes in duration and length of the support and swing phases of the stride cycle. Eight healthy male subjects performed walking and running on a motor‐driven treadmill at speeds ranging from 1.0 to 3.0 m s‐1 (walking) and 1.5 to 8.0 m s‐1 (running), respectively. At each speed the subjects walked and ran with: (i) normal stride frequency; (2) the highest possible stride frequency, and (3) the lowest possible stride frequency. Time for foot contact was measured with a special pressure transducer system under the sole of each shoe. At all speeds of walking and running it was possible to either increase or decrease the frequency of leg movements; that is, to decrease or increase stride cycle duration. The range of variation decreased with increasing speed. The mean overall stride frequency range was 0.41 (low frequency walk 1.0 m s‐1)‐3.57 Hz (high‐frequency run 1.5ms‐1). Stride length ranged 0.40 (high frequency walk 1.0 ms‐1)‐5.00 m (low frequency run 6.0 m s‐1). At normal frequency the overall ranges of stride frequency and length were 0.83–1.95 Hz and 1.16–4.101m, respectively. The stride frequency increased with speed in low frequency walking and running (as in normal frequency) and decreased in high frequency, despite the effort to maintain extreme frequencies. Only in high frequency walking could the stride frequency be kept approximately constant. Stride length increased with speed in all situations, except for low frequency running, where a levelling off occurred at approximately 6 m s‐1. A decrease was observed in support duration with speed, except in high frequency running where it was kept approximately constant (0.12–0.145). Support length showed a total range of 0.19–1.62 m. The longest support length was observed in low frequency walking (all speeds). In normal and high frequency support length increased with speed (in normal frequency up to 1. 10–1.20 m in both walk and run). Thus, locomotion over a wide range of constant velocities can be achieved by different combinations of durations and amplitudes of the stride cycle and its different phases. The normal combination represents a compromise allowing for functional adjustments.
Orosomucoid as one of the serum components contributing to normal capillary permselectivity in rat skeletal muscle
Authors: HARALDSSON B. , RIPPE B.
Published: December 2008

The effects of human serum orosomucoid (normal serum concentration 0.7–1.0 g l‐1) on capillary permeability were investigated in 12 isolated maximally vasodilated rat hindquarters perfused with bovine serum albumin (50 g l‐1) in modified Tyrode. Measurements were made of capillary filtration coefficient (CFC), permeability surface area product (PS) for vitamin B12 and isogravimetric clearance of radiolabelled albumin (Cla1b). The results were compared with those obtained using perfusates without addition of orosomucoid (‘albumin group’) or perfusates containing horse serum (‘serum group’). Clearance of albumin was almost four‐fold higher in the albumin than in the serum group, 0.0895 ± 0.0066 (n= 12) and 0.0252 ± 0.016 ml min‐1 per 100 g (n= 18), respectively, while intermediate Cla1b values were obtained with human orosomucoid in the perfusate (> 0. 1 g l‐1), 0.0436 ± 0.0034 ml min‐1 per 100 g) (n= 8). These changes in Cla1b were not accompanied by any differences in CFC or PS. We conclude that orosomucoid is one of the components in serum (besides albumin) needed for the maintenance of normal permselectivity of the capillary walls of rat skeletal muscle. Alternatively, human orosomucoid is structurally related to other substances exerting this ‘serum effect’.
Systemic and centrally mediated angiotensin II effects in the horse
Authors: ANDERSSON B. , AUGUSTINSSON O. , BADEMO E. , JUNKERGÅRD J. , KVART C. , NYMAN G. , WIBERG M.
Published: December 2008

The primary aim of the study was to evaluate the potential value of intravenous (i. v.) infusion of angiotensin II (AII) for phonocardiographic differential diagnosis of equine valvular insufficiency. Ten‐minute AII infusions at 4.5–33 pmol kg‐1 min‐1 induced clear‐cut dose‐dependent rises in systemic arterial blood pressure (aBP), whereas the pulmonary aBP remained largely unaffected. It implies that i. v.infusion of All at about 10 pmol kg‐1 min‐1 could be a valuable tool for the acoustic differentiation between mitral and tricuspid valvular dysfunction in the horse. The infusion at, and above 9 pmol kg‐1 min‐1 caused increased heart rate. This chronotrophic effect was not strictly dose‐dependent and exhibited significant tachyphylaxis. Angiotensin II administration at, or above 9 pmol kg‐1 min‐1 was needed to induce an urge to drink, suggesting that angiotensin‐induced thirst does not appear in the euhydrated horse until the octapeptide reaches supraphysiological blood concentration. Determinations of plasma aldosterone concentration (PA) revealed comparatively high morning control values (269 ± 46 pmol‐1).Three consecutive AII infusions with 10‐min intervals and at increasing dosages caused a cumulative, almost fourfold elevation of PA.The PA pattern indicated that AII‐induced hypersecretion of aldosterone continued for several minutes after the end of the infusions, but also showed that the metabolic clearance of the hormone took precedency of the secretion within 20 min post‐infusion. In two of the horses a fall in PA occurred during a fourth, final infusion, indicating that in these instances the previous AII administration had impoverished the store of aldosterone available for release from the adrenal cortex.
Plasma atrial natriuretic peptide in DOCA‐NaCl‐treated rats
Authors: TIKKANEN T. , TIKKANEN I. , FYHRQUIST F.
Published: December 2008

In order to assess the possible role of atrial natriuretic peptide (ANP) in the development of deoxycorticosterone (DOCA)‐NaCl‐induced hypertension, plasma immunoreactive ANP concentration was compared with sodium balance and blood pressure in NaCl‐ or DOCA‐NaCI‐treated rats. Both NaCl‐and DOCA‐NaCl‐loading increased plasma ANP levels (to 86 ± 8.1 and 105 ± 12 pg ml‐1 respectively; 47±6.7–60±4.6 pg ml‐1 in controls), which were correlated to sodium intake and excretion. In DOCA‐NaCI‐treated rats, the highest ANP levels (105 ± 12 pg ml‐1) were found 4 weeks after the beginning of DOCA‐NaCl treatments. Along with the development of DOCA‐NaCl hypertension in 1‐kidney‐DOCA‐NaCl‐treated rats, however, plasma ANP concentration did not rise further. We conclude that secretion of ANP into the circulation is increased during DOCA‐NaCl treatment. Elevated blood pressure does not stimulate ANP release in DOCA‐NaCI‐treated rats further.
Changes in human cerebral blood flow due to step changes in PAO2 and PACO2
Authors: ELLINGSEN I. , HAUGE A. , NICOLAYSEN G. , THORESEN M. , WALLØE L.
Published: December 2008

The effect of moderate hypoxia on cerebral blood flow (CBF) in man has not been well described, and little is known about the interaction of changes in arterial PO2 and PCO2 as regards CBF.Using a non‐invasive doppler ultrasound method we have measured the instantaneous mean blood velocity (which is proportional to CBF as long as the cross‐section of the vessel is constant) in the carotid artery in four healthy unanaesthe‐ tized subjects. We found in all subjects that a reduction in alveolar PO2 from about 13 to about 8.7 kPa with maintained constant alveolar PCO2 (PACO2) caused CBF to increase gradually over 10 min (half‐time about 4 min) to about 125% of control. The CBF decreased quickly (half‐time about 45s) towards control when alveolar PO2 was reset to 13 kPa. As measured 5 min after a step‐change in PA,O2, the change in CBF was independent of PA, CO2 within the range 3.3–6.7 kPa. An increase in PA, O2 to about 33 kPa reduced CBF only if PA, CO2 was in the hypercapnic range. Unexpectedly we found that the CBF response showed ‘adaptation’ during both maintained increase and decrease in PA, CO2.The CBF started to return towards control level within 10 min after induction of hypo‐ or hypercapnia. We conclude that also moderate hypoxia causes increased CBF in unanaesthetized man within a wide range of PA,CO2.
IGF‐I expression in blood vessels varies with vascular load
Authors: HANSSON H.‐A. , JENNISCHE E. , SKOTTNER A.
Published: December 2008

The present study was designed to investigate if the immunoreactivity of insulin‐like growth factor I (IGF‐I, somatomedin C) in blood vessels was changed in relation to the vascular load in adult rats. Occlusion of the right femoral artery resulted within 24 h in a strongly increased IGF‐I immunoreactivity in the media of the contralateral, left, femoral artery and a significant decrease in the IGF‐I expression in the right femoral artery distal to the occlusion. The increased labelling of the smooth muscle cells persisted for at least 21 days. Inactivity of the right hind limb, secondarily to an ischaemic insult, likewise induced a significant increase in IGF‐I immunoreactivity, within 24 h, in the femoral vessels of the undamaged, contralateral left hind limb. It is concluded that IGF‐I immunoreactivity varies with the dynamic load in the vascular walls. It is proposed that IGF‐I may serve as a parahormone exerting its effect by paracrine and/or autocrine mechanisms, taking part in regulating the structural adaption of blood vessels in response to stress.
A search for a model tissue for studying effects of thiazide diuretics
Authors: ERIKSSON Ö. , WISTRAND P.J.
Published: December 2008

A search was made for a model tissue of NaCl absorption which would be sensitive to inhibition by diuretics of the thiazide type. A lack of such a model through the years has hampered the analysis of the cellular mechanism of action of this important class of drugs. Using the short‐circuit current technique, the urinary bladders of the toadsBufo spinosusandBufo marinus, and the frogRana temporariawere investigated regarding the effects of various thiazides. These bladders have NaCl absorptive properties similar to those of the distal renal tubules, and are claimed to be sensitive to the inhibitory effect of thiazides on sodium transport. The short‐circuit current (SCC), which is representative of the sodium transport across the epithelium, was reduced by cyclopenthiazide and polythiazide, but only at high concentrations (above 0.1 mM).To rule out the possibility that this was an unspecific effect, attempts were made to block the effect by the ‘thiazide blocker’ Ex 4877, but without success. This finding, together with the fact that dose‐response curves were difficult to obtain, would indicate that these epithelia are not suitable for the stated purpose. Preliminary studies were also conducted on the urinary bladder of the plaice,Pleuronectes platessa, which has a different system of NaCl absorption that is claimed to be rapidly and reversibly inhibited by thiazides. Polythiazide, added to both sides of the bladder, had no effect on SCC.