bluuebunny/crossref_metadata_2025 huggingface dataset:
Dietary effects on glycogen and lipoprotein lipase activity in skeletal muscle in man
Authors: JACOBS I. , LITHELL H. , KARLSSON J.
Published: December 2008

The influence of short‐term adaptation to a fat and protein enriched diet (F+P) and a carbohydrate enriched diet (CHO) on skeletal muscle lipoprotein lipase (LPL) activity and muscle glycogen levels was evaluated in 7 males. Muscle biopsies were taken from the m. vastus lateralis after an uncontrolled, mixed diet (M), after a 3 day F+P diet preceded by intense exercise, and after a 3 day CHO diet. After the F+P diet glycogen concentration was 55% that of the M diet while LPL activity increased by 21% (n. s.). After the CHO diet glycogen levels increased by 82% and LPL activity decreased by 55% compared to the M diet (p<0.01). The changes in LPL after the CHO diet were related to the changes in glycogen concentration (r = 0.98, p<0.01). LPL activity in the control situation was directly related to percent slow twitch (ST) muscle fibre type (r = 0.95, p<0.01). The results suggest that the uptake of fat from the circulation may be actively regulated by the muscle as a function of intramuscular substrate availability and that this regulation may be related to muscle fibre type composition.
Blood flow and secretion in the submaxillary gland of the rabbit during stimulation of the autonomic nerves
Authors: GJÖRSTRUP PER
Published: December 2008

The excitation of the chorda‐tympani nerve caused a marked increase in the blood flow through the gland and in secretion of saliva; both fenomena had a threshold frequency of around 0.3 Hz and reached a maximum at around 20 Hz, where a 6‐fold increase in the blood flow and a salivary secretion of at the most 300 μl/min were seen. Sympathetic excitation severely retarded the blood flow, which almost ceased at frequencies as low as 3–5 Hz; mostly single shocks of sympathetic stimulation reduced the blood flow through the gland. An on‐going parasympathetic activation did not alter the effects of sympathetic stimulation on the blood flow and the parasympathetically produced salivary secretion almost stopped. The experiments support previous results, which have suggested electrical excitation of the sympathetic trunk at or above 2 Hz to cause a vasoconstriction which adversely affects the fluid secretion in the rabbit salivary glands.
Morphology and enzymatic capacity in arm and leg muscles in 78–81 year old men and women
Authors: GRIMBY GUNNAR , DANNESKIOLD‐SAMSØE BENTE , HVID KELD , SALTIN BENGT
Published: December 2008

Twelve men and twelve women 78–81 years of age were studied with muscle biopsies from the right vastus lateralis and biceps brachii and with measurements of isometric and isokinetic strength for knee‐extension and isometric strength for elbow‐flexion. Bicycle ergometry with determination of heart rate and oxygen uptake at submaximal (50 W) and “maximal” work loads was also performed. Body cell mass was estimated from measurements of total body potassium. Muscle fibre composition with respect to slow twitch (ST = type I) and fast twitch (FT = type II) fibres did not differ between the sexes and the younger subjects drawn from population studies. The mean fibre areas averaged in vastus lateralis 4.7 and 3.3 μm2× 103 in men and women, respectively. This is less than 10 up to 30% of values found in sedentary younger subjects. The decline dominated in FT fibres, especially FTb fibres. In contrast biceps brachii did not show any matched fibre size reduction. The number of atrophic fibres was high and so was the frequency of “enclosed” fibres and areas with type grouping (ST fibres), indicating denervation—reinnervation. Such abnormalities are rarely seen in younger ages. Correlation analysis showed that only a minor part of the reduction in body cell mass with age could be explained by a reduction in fibre areas and that a reduction with age of the number of muscle fibres of both fibre types must be assumed. Positive correlations were observed between muscle strength and mean fibre and FT fibre areas. Comparing the present findings of skeletal muscle morphology to those in younger age groups, it is apparent that during the 8th decade of life major changes do occur. The measurements of aerobic and anaerobic enzymatic activities and of muscle capillary supply showed that levels comparable to those of younger age groups are maintained. Thus, quantitative rather than qualitative changes may explain the reduction in work performance with age.
Carbohydrate metabolism and concentration profiles of solutes in the canine lumbar intervertebral disc
Authors: HOLM STEN , SELSTAM GUNNAR , NACHEMSON ALF
Published: December 2008

Utilization of glucose and oxygen by the cells as well as concentration profiles of solutes were studied in the canine intervertebral disc. Cell metabolism in this avascular tissue, being predominantly anaerobic, was found to be dependent on oxygen tension (this being especially pronounced in the region of 0.13–0.4 kPa (1–3 mmHg). A high production rate of lactic acid was found in the nucleus pulposus, whereas towards the periphery of the annulus fibrosus this rate gradually decreased. In the centrally located areas of the disc tissue, far away from the blood circulation, the highest concentrations of lactic acid were found. For the normal disc the energy demands seem to be met as even small amounts of oxygen account for a large energy source, whereas the cellular requirements are balanced up predominantly by glucose. In regions with extremely low oxygen tensions large amounts of glucose are consumed, but an additional potential energy pool of glycogen seems to be available.
Giant miniature endplate potentials induced by 4‐aminoquinoline
Authors: MOLGÓ J. , GOMEZ S. , POLAK R. L. , THESLEFF S.
Published: December 2008

In experiments on the isolated extensor digitorum longus muscle of the rat it was shown that 4‐aminoquinoline (125–250 μM) altered the amplitude distribution of spontaneous miniature endplate potentials to include a large portion of giant miniature endplate potentials with slow rise and decay times. Similar, slow‐rising giant miniature endplate potentials were induced by the drug at neuromuscular junctions with regenerating nerve terminals, i. e. in a condition where spontaneous as well as evoked transmitter release is depressed. The appearance of giant miniature endplate potentials was not correlated with inhibition of cholinesterase since neostigmine (3 μM) failed to induce such potentials. Nerve impulse evoked endplate potentials of amplitudes similar to the spontaneous giant miniature endplate potentials had a faster and more uniform rise time. The results suggest that 4‐aminoquinoline, by a direct action on the nerve terminal, causes the release of larger than normal quanta of acetylcholine. Quantitative assays of acetylcholine released before and in the presence of 4‐aminoquinoline gave similar values showin that the amounts of acetylcholine which give rise to the giant miniature potentials contribute little to the total amount of acetylcholine liberated.
Transport of glucose across the blood‐brain barrier: Reevaluation of the accelerative exchange diffusion
Authors: CHRISTENSEN OVE , LUND‐ANDERSEN HENRIK , BETZ A. LORRIS , GILBOE DAVID D.
Published: December 2008

In an earlier study of glucose transport across the blood‐brain barrier it was concluded that the kinetic transport constants increase as the brain glucose concentration increases, a finding that was attributed to accelerative exchange diffusion (Betz et al. 1975). The conclusion, however, relied upon application of a commonly used simplified treatment of tracer extraction data. In this study it is demonstrated that the simplified treatment is applicable only in the case of zero brain glucose concentration, and a more general model for determination of the kinetic constants is developed. Re‐analysis by this model of the data of Betz et al. (1975)—comprising a range of brain glucose concentrations—gave kinetic constants which did not vary significantly over a wide range of brain glucose concentrations. For brain glucose concentrations up to about 12 mmol l‐1, the kinetic constants obtained for glucose transport across the blood‐brain barrier are

Km =6.18±0.38mmol l‐1

Vmax= 1.65±0.06 μmol g‐1 min‐1
Adenosine actions and adenosine receptors after 1 week treatment with caffeine
Authors: FREDHOLM BERTIL B.
Published: December 2008

After one week treatment with caffeine (20 mg/kg i. p.) the number of adenosine receptors, as determined by specific binding of (3H)‐L‐PIA, in rat cerebral cortical membranes was increased by about 25%. Cyclic AMP accumulation induced by adenosine analogues in slices of rat hippocampus was unaffected by caffeine treatment. The inhibition of lipolysis in rat fat cells by 2‐chloro‐adenosine was similarly unaffected. The potency of caffeine as an antagonist of these adenosine‐receptor mediated effects was not altered by caffeine treatment. It is concluded that at least some adenosine receptors are up‐regulated as a consequence of prolonged caffeine treatment, but that the increase in receptor number is not related to changes in at least two effects of adenosine and caffeine.
The effect of renal sympathectomy on blood pressure and plasma renin activity in spontaneously hypertensive and normotensive rats
Authors: SÄYNÄVÄLAMMI P. , VAALASTI A. , PYYKÖNEN M.‐L. , YLITALO P. , VAPAATALO H.
Published: December 2008

Renal denervation delays the development of hypertension in spontaneously hypertensive (SH) rats. The influence of bilateral surgical renal sympathectomy, verified by fluorescence microscopy, on blood pressure and plasma renin activity in SH and normotensive rats (170–180 g before the sympathectomy) was studied. Neither in SH nor in normotensive rats, did the preoperative systolic blood pressure in the renal‐sympathectomized group differ from that in the sham‐operated controls. After the sympathectomy, blood pressure in the SH rats increased in 4 weeks only insignificantly, from 160±3 to 172±6 mmHg, while that in the sham‐operated SH rats rose from 163±5 to 191±5 mmHg. In normotensive rats, blood pressures in both the renal‐sympathectomized and sham‐operated groups remained at the pre‐operative levels. Thirty days after the operations, plasma renin activity or plasma kininogen in the renal‐sympathectomized group did not differ from that in the sham‐operated one either in SH or in normotensive rats. The results suggest that the delay in hypertension development produced by renal sympathectomy in SH rats is not mediated by a reduction in renin secretion.
Increased levels of VIP (vasoactive intestinal polypeptide)‐like immunoreactivity in peripheral venous blood of dogs following injections of apomorphine and bromocriptine. Do dopaminergic agents induce gastric relaxation and hypotension by a release of endogenous VIP?
Authors: UVNÄS‐MOBERG KERSTIN , GOINY MICHEL , POSLONCEC BRANKA , BLOMQUIST LARS
Published: December 2008

Injections of the dopaminergic agonist apomorphine give rise to multiple effects in the gastrointestinal tract such as vomiting (Borison & Wang 1953), relaxation of the stomach (Valenzuela 1976, Lefebvre, Willems & Bogaert 1981), vasodilation in the splanchnic region (Goldberg 1972) as well as a release of gastrin, insulin and somatostatin (Uvnäs‐Wallensten, Lundberg & Efendic 1978, Uvnäs‐Wallensten & Goiny 1981). Some of the effects exerted by dopaminergic agents on the gastrointestinal tract are mimicked by injections of the peptide VIP (vasoactive intestinal polypeptide). VIP occurs in neurons in the gastrointestinal tract (Larsson et al. 1976) and VIP, like the dopaminomimetics, relaxes the stomach and dilates blood vessels in the gastrointestinal tract (Eklund et al. 1979).
Neuronal substance P in the esophagus. Distribution and effects on motor activity
Authors: LEANDER S. , BRODIN E. , HÅKANSON R. , SUNDLER F. , UDDMAN R.
Published: December 2008

Substance P‐immunoreactive nerve fibres were fairly numerous in the lower esophagus of the guinea‐pig and cat but few in the pig. They were particularly numerous in the myenteric and submucosal plexuses but could be detected also in the circular and longitudinal smooth muscle and in the muscularis mucosae. Only in the cat were SP‐immunoreactive cell bodies detected, albeit in low number, in the myenteric plexus. Radioimmunoassay showed that the lower part of the cat esophagus contained approximately 10 times more immunoreactive SP than the upper part and that the muscle layer contained more SP than the mucosa. Motor effects of synthetic SP were studied on segments from circular smooth muscle of cat esophagus. SP contracted the smooth muscle and enhanced the response to electrical stimulation. These effects of SP could be blocked by the specific SP antagonist (d‐Pro,2d‐Trp7,8)‐SP. The contractile response to electrical stimulation could be blocked by the cholinergic muscarinic blocker atropine and the opiate receptor agonist leu‐enkephalin but not by the SP antagonist or by adrenergic blockers. Hence, the results suggest that cholinergic neurons innervate the circular smooth muscle, and that opiate receptor agonists suppress transmission in these neurons. Neuronal SP in the esophagus may serve to enhance the contractile responses of esophageal smooth muscle.
Effects of phenothiazines and dibenzazepines on axonal transport and microtubule assembly in vitro
Authors: EKSTRÖM PER , KANJE MARTIN , EDSTRÖM ANDERS
Published: December 2008

Various phenothiazines (thioridazine, trifluoperazine and chlorpromazine) and dibenzazepines (lofepramine, amitriptyline and desipramine) were studied for effects on fast axonal transport (AXT) in vitro in frog sciatic nerves. AXT, measured as the accumulation of (3H) leucine‐labelled proteins in front of a ligature, was inhibited by more then 50% by all the drugs tested at 0.2 mM concentrations. Thioridazine and lofepramine were the most potent inhibitors. These effects were not due to decreased ganglionic incorporation. Some of the drugs also reduced the levels of high energy phosphates, adenosinetriphosphate (ATP) and creatinephosphate (CrP), but not to an extent which is likely to explain the arrested AXT. The polymerization of purified brain tubulin was inhibited by the phenothiazines but unaffected by the dibenzazepines at concentrations which inhibited AXT. Phenothiazines and dibenzazepines are chemically related and known to have a high affinity for calmodulin. The possibility that these drugs interefere with calmodulin regulated processes of importance for AXT will be discussed.
Influence of amygdala lesions on cardiovascular responses to alerting stimuli, on behaviour and on blood pressure development in spontaneously hypertensive rats
Authors: FOLKOW B. , HALLBÄCK‐NORDLANDER M. , MARTNER J. , NORDBORG C.
Published: December 2008

Spontaneously hypertensive rats (SHR), and often also humans genetically predisposed to hypertension, exhibit cardiovascular hyperreactivity to alerting stimuli, which derives from limbic‐hypothalamic levels and seems important for inducing primary hypertension. It is further known that the limbic amygdala complex normally reinforces emotionally induced defence reactions. The amygdala were therefore bilaterally destroyed in 6 week old SHR, and compared with sham‐operated SHR concerning development of hypertension, cardiovascular reactivity to environmental stimuli and explorative behaviour. When related to controls, the arterial pressure elevation was significantly attenuated in the amygdala‐lesioned SHR, though their pressure was nevertheless raised 40% at 6 months of age. Concerning cardiovascular responsiveness to mild environmental stimuli the groups did not differ; neither concerning explorative behaviour nor in general motor activity. However, the amygdala‐lesioned SHR responded decidedly less than controls to stressful, fear‐inducing stimuli. The amygdala complex may therefore play an important role in aggravating SHR hypertension by reinforcing defence reactions to stressful influences, when such stimuli are at hand. However, according to the present study the amygdala nuclei are not the origin of the centrally determined cardiovascular hyperreactivity, which in SHR seems decisive for inducing hypertension.
Pharmacological characterization of four related substance P antagonist
Authors: BJÖRKROTH ULLA , ROSELL SUNE , XU JIE‐CHENG , FOLKERS KARL
Published: December 2008

The purpose of this pharmacological study was to further characterize 4 related substance P (SP) analogues, namely (D‐Pro2, D‐Phe7, D‐Trp9)‐SP (I), (D‐Pro2, D‐Trp7.9)‐SP (II), (D‐Arg1, D‐Pro2, D‐Phe7, D‐Trp9)‐SP (III) and (D‐Arg1, D‐Pro2, D‐Trp7.9)‐SP (IV). At a concentration of 10‐4 M they were found to have little or no smooth muscle‐contracting effect on the guinea‐pig ileum, analogues I and II having substantially less agonist activity than III and IV. Pretreatment with the analogues inhibited the contractile responses to SP, but not to histamine or acetylcholine. Of the 4 analogues, II was found to be the most potent SP antagonist. The contractile responses to physalaemin and eledoisin were also inhibited by analogue II. The concentration‐response curves for SP were shifted in parallel to higher concentrations in the presence of the analogues. The pA2‐values derived from Schild plots were 4.61 for (I), 5.43 for (II), 4.69 for (III) and 5.11 for (IV). Except for (I) the slopes of the regression lines of the Schild plots were close to unity. The data are consistent with simple competitive antagonism over the concentration ranges investigated. Without being secretagogues per se, the analogues inhibited SP‐stimulated salivary secretion in the rat. Physalaemin‐stimulated secretion was inhibited by analogue II. The inhibitory effect of sequences with D‐Arg1 instead of L‐Arg1 seemed to be of longer duration. Not one of these analogues blocked the blood pressure‐lowering effect of SP, which indicates the existence of more than one type of SP receptor. This study has shown that 4 related SP analogues specifically inhibit the actions of SP and structurally related peptides physalaemin and eledoisin, both in vitro and in vivo. Analogues II‐IV seem to inhibit in a simple competitive manner. (D‐Pro2, D‐Trp7.9)‐SP was the most potent of the 4 SP antagonists.
β2‐adrenergic control of plasma volume in hemorrhage
Authors: HILLMAN JAHN , GUSTAFSSON DAVID , LUNDVALL JAN
Published: December 2008

Hemorrhage is associated with absorption of extravascular fluid from skeletal muscle to blood in order to compensate for the loss of intravascular volume. Our previous studies have shown that this fluid gain is mainly linked to β‐adrenergic microvascular adjustments leading to decrease in capillary hydrostatic pressure and to precapillary ‘sphincter’ mediated increase in the capillary surface area available for fluid exchange. In the present study the importance of β‐adrenergic control of plasma volume in bleeding was confirmed by measurement of changes in plasma volume after graded hemorrhage in animals with intact and blocked vascular β2‐adrenoceptors (i. v. administration of the ‘selective’β2‐blocking agent ICI 118, 551). With intact β2‐adrenoceptors plasma volume was gradually restored after bleeding so that about 50% of the shed plasma volume (about 35% of the shed blood volume) had been compensated for at two hours after exsanguination of 20% as well as 40% of the blood volume. The corresponding figures in animals with blocked β2‐adrenoceptors were only 14% of the shed plasma volume and 8% of the shed blood volume at both degrees of hemorrhage.
Conduction velocities of single pulp nerve fibre units in the cat
Authors: NÄRHI M. , VIRTANEN A. , HUOPANIEMI T. , HIRVONEN T.
Published: December 2008

Most experiments on dental nerves have been made using dentine recording technique and it seems that only the fast conducting myelinated pulpal nerve fibres can be recorded with this technique. However, histological studies have revealed that even 80% of intradental fibres in the cat are unmyelinated. In the present work we studied activation of intradental nerve fibres with monopolar electrical stimulation of the intact mandibular canine tooth crown of the cat. The purpose was to determine the proportion of responding intradental A‐and C‐fibres dissected from the inferior alveolar nerve. In 17 anesthetized cats 350 pulp nerve fibre units were identified and recorded. Conduction time (based on the shortest latency), distance between the stimulation and the recording sites and threshold current for each fibre unit were determined. The mean conduction velocity for all pulp nerve fibres was 9.2 m/s (SD=9.8). The number of C‐fibres (conduction velocity ≤2.0 m/s) was 122 (34.9%) and the number of A‐fibres was 228 (65.1 %). The mean conduction velocities of C‐ and A‐fibres were 1.0 m/s (SD=0.4) and 13.4 m/s (SD=9.4), repectively. The mean threshold current was 22.8 μA (SD=20.1) for the whole group, 40.4 μA (SD=20.7) for C‐fibres and 13.5 μA (SD=11.8) for A‐fibres. Although the function of pulpal C‐fibres is poorly known, it has been suggested that they have a distinct role in mediation of sensations from tooth, particularly in inflammatory processes. Using nerve dissection technique the activity of a considerable part of intradental C‐fibres can be recorded and it seems to be the only available method to study the function of this fibre group.
Release of nucleosides and nucleotides from the rabbit heart by sympathetic nerve stimulation
Authors: FREDHOLM BERTIL B. , HEDQVIST PER , LINDSTRÖM KARIN , WENNMALM MARIANNE
Published: December 2008

The release of endogenous purine compounds from the isolated Langendorff perfused heart during sympathetic nerve stimulation has been studied. The contents of adenosine, inosine, hypoxanthine and AMP in heart muscle and in the perfusate was studied by HPLC. Adenosine or AMP, administered via the perfusate, was rapidly inactivated by the heart. The recovery of adenosine after a single passage was 13 per cent and that of AMP 40 per cent. The recovery of adenosine was increased by inhibitors of adenosine deaminase or nucleoside uptake; that of AMP by inhibition ofecto‐5'‐nucleotidase. The efflux of adenosine and, especially, inosine was increased by sympathetic nerve stimulation in a time‐ and frequency‐dependent manner. Simultaneously the tissue level of the two nucleosides increased. Nerve stimulation did not enhance AMP efflux in the absence of drugs and did not significantly enhance tissue AMP levels. The effect of sympathetic nerve stimulation was mimicked by noradrenaline and was blocked by adrenoceptor blocking agents. The release of adenosine induced by nerve stimulation was enhanced by uptake inhibitors and by an inhibitor of adenosine deaminase. The release of inosine was simultaneously reduced. In the presence of an inhibitor ofecto‐5'‐nucleotidase nerve stimulation induced a significant release of AMP, but no significant alteration in the release of adenosine or inosine was found. It is concluded that sympathetic nerve stimulation leads to release of both adenine nucleotides and adenosine from the perfused rabbit heart. These substances are rapidly catabolized by 5'‐nucleotidase and by uptake followed by deamination, respectively, to form mainly inosine. It is proposed that the release of adenosine may reflect the energy state of the cardiac cells, while the nucleotide release may depend on depolarization.
Na‐independent and Na‐dependent transport of neutral amino acids in the human red blood cell
Authors: ROSENBERG RABEN
Published: December 2008

Experiments performed at 25°C, pH 7.4, confirmed that the human red blood cell possesses both Na‐independent and Na‐dependent transport systems for neutral amino acids. Further evidence for the existence of a major Na‐independent pathway for the large neutral amino acids (L‐leucine, L‐isoleucine, L‐phenylalanine, L‐valine and L‐methionine), designated the ‘L‐system’, was provided from trans‐acceleration experiments of L‐leucine efflux. Transport via the L‐system with respect to kinetics of substrates and stereospecificity was studied. Experiments on inhibition of transport and on kinetics of Na‐dependence of uptake of L‐alanine and glycine were consistent with Na‐dependent amino acid transport being mediated by two different systems, i. e. an ASC‐system for L‐alanine, L‐serine and L‐cysteine and a Gly‐system for glycine transport. When compared with a ‘high capacity/low affinity’ pattern of kinetics of the L‐system, Na‐dependent uptake of L‐alanine and glycine was found to exhibit ‘low capacity/high affinity’ kinetics. The Na‐dependence of L‐alanine uptake conformed to first order interaction, that of glycine uptake to second order. An effect predominantly on the maximum transport capacity (V12) of the saturable Nadependent uptake route of L‐alanine and glycine, respectively, by a 50% reduction of the extracellular Na+ concentration, was suggested.
Bilateral reflex effects on phrenic nerve activity in response to single‐shock vagal stimulation
Authors: BRUCE E. N. , EULER C. VON. , ROMANIUK J. R. , YAMASHIRO S. M.
Published: December 2008

The bilateral reflex actions of vagus nerve afferent signals on phrenic efferent activity have been tested by unilateral graded single shock electrical stimulation. An early excitation (latency 3–5 msec) was more prominent in the phrenic nerve contralateral to the stimulated vagus. Spinal cord hemisection at C3 eliminated both contralateral and ipsilateral responses: thus, both were mediated via descending tracts in the contralateral cord. A bilaterally symmetrical early inhibition (latency 8–12 msec) followed the early excitation. The electrical thresholds for evoking the early responses and the temperature for blocking these responses during graded vagal cooling were closely similar to the threshold and blocking temperature for pulmonary stretch receptor afferents. Higher stimulus strengths evoked a strong, bilaterally similar, late excitation (latency 12–20 msec) followed by a late inhibition. At very high stimulus strengths a third excitation (latency 25–30 msec) could appear. Sometimes these responses were followed by lowered phrenic activity for the remainder of inspiration. Single shock stimulation of the intact vagus nerve or of the peripheral end of the cut recurrent laryngeal nerve provoked. by the contraction of laryngeal muscles, a strong, short latency (12 msec) inhibition of phrenic activity mediated by superior laryngeal nerve afferents. The implications of these results with respect to the reflex pathways of the different responses and their possible integration in the central respiratory control mechanisms are discussed.
Antagonism by (D‐Pro2, D‐Trp7,9)‐substance P of the cerebrovascular dilatation induced by substance P
Authors: EDVINSSON LARS , McCULLOCH JAMES , ROSELL SUNE , UDDMAN ROLF
Published: December 2008

The effects of (D‐Pro2, D‐Trp7,9)‐substance P, a structural analogue of substance P, were examined in two models on cerebrovascular responses to substance P (SP) in cats; in vitro using segments of the middle cerebral artery and in situ by microapplication of the peptides close to pial arterioles. (D‐Pro2, D‐Trp7,9)‐SP in concentrations up to 6.6×10‐6 M was without significant effect upon isolated middle cerebral arteries under normal conditions and in arteries contracted with prostaglandin F2a. SP caused concentration‐dependent relaxations of middle cerebral arteries contracted by prostaglandin F2a (mean ± SE; EC50: 2.0±1.6×10‐9 M). The presence of (D‐Pro2, D‐Trp7,9)‐SP shifted the concentration‐response curve of SP towards higher concentrations without significantly effecting the maximum response of the arteries to SP. A relaxation by 24.2±4.0% (n=6) was obtained in prostaglandin F2a contracted arteries by increasing the potassium concentration with 2 mM in the buffer solution. This response to potassium was unaltered in the presence of 6.6×10‐6 M of (D‐Pro2, D‐Trp7,9)‐SP (25.0±7.1%, n=5). Perivascular microapplication of SP around individual pial arterioles in situ effected dose‐dependent increases in vascular calibre (mean response 14.5±2% with SP, 10‐7 M). The concomitant perivascular administration of (D‐Pro2, D‐Trp7,9)‐SP (6.6×10‐6 M), which alone did not alter the arteriolar calibre, attenuated significantly the cerebrovascular response to SP (mean response 1.5±3.2%). On the basis of the agonist‐antagonist relation found, these observations point to the possibility of a specific SP receptor site in cerebral arteries and arterioles.
The influence of sympathetic nerve activity on axial position of the rabbit incisor tooth
Authors: AARS HARALD
Published: December 2008

Changes in position of the upper front tooth in response to sectioning and subsequent electrical stimulation of the cervical sympathetic nerves were studied in 25 anesthetized rabbits. The position was continuously recorded by an ultrasonic transit time technique. Sectioning of the nerves was found to induce an average tooth extrusion of about 7 μm. Sympathetic nerve stimulation for periods of 20–30 s caused intrusion of the tooth, with about 70% of maximum occurring at 2 Hz stimulations. The intrusive response was reduced by phentolamine. Neither atropine nor propranolol affected the stimulation response, but the latter drug led to marked extrusion of the tooth. In conclusion, the position of the rabbit's front tooth was found to be highly sensitive to alterations in sympathetic nerve activity to the vasculature of the tooth‐supporting tissues.
Factors responsible for the decreased plasma concentration of prealbumin during acute inflammation and fasting in the rat
Authors: FELDING PETER , FEX GÖRAN
Published: December 2008

The concentration of prealbumin in plasma and the elimination from plasma and whole body of intravenously injected 131I‐labelled rat prealbumin were followed in normal rats and rats subjected to fasting or acute inflammation. During fasting and inflammation the concentration of prealbumin decreased to about 50% of the initial value. It was concluded from the radioactive tracer experiments that decreased synthesis was responsible for the decreased intravascular prealbumin mass in the fasting rats. In these rats the plasma volume also decreased. In the rats subjected to inflammation, both a decreased intravascular fraction and a decreased synthetic rate of prealbumin seemed to contribute to the decreased intravascular mass of prealbumin. The total catabolic rate was decreased in these conditions.
Changes in subcutaneous blood flow during locally applied negative pressure to the skin
Authors: SKAGEN K. , HENRIKSEN O.
Published: December 2008

The effect of locally applied subatmospheric pressure on subcutaneous blood flow was studied in 12 healthy subjects. Blood flow was measured on the forearm by the local 133Xe wash‐out technique. Air suction between 10 mmHg and 250 mmHg was applied to the skin. Subatmospheric pressure of 20 mmHg caused only a minor increase of estimated vascular resistance of 9 per cent. Increasing the suction to 40 mmHg caused a pronounced vasoconstriction corresponding to an increase in vascular resistance of about 90%. Further increase in local suction beyond 40 mmHg caused no additional increase in vascular resistance. The vasoconstriction induced by local suction was abolished by local nervous blockade induced by lidocaine in low doses which do not affect myogenic activity of the vascular smooth muscle cells. This finding confirms previous studies that the vasoconstriction mainly is due to a local sympathetic veno‐arteriolar axon reflex mechanism. The results suggest that the dominant part of the vasoconstriction induced by the local axon reflex occurs when vascular transmural pressure increases from 20 mmHg to 40 mmHg.
The effect of duodenal administration of fatty acids, triolein, liquid paraffin and lecithin on plasma neurotensin‐like immunoreactivity (p‐NTLI) in the rat
Authors: THEODORSSON‐NORHEIM ELVAR , ROSELL SUNE
Published: December 2008

The effect of intraduodenal administration of various types of lipids on the concentration of p‐NTLI has been studied on anesthetized rats. Oleic acid, sodium oleate, triolein, linoleic acid, linolenic acid, arachidonic acid, butyric acid, liquid paraffin, phosphatidyl choline (lecithin) and saline were administered. Oleic acid, triolein, linoleic acid and linolenic acid significantly increased the integrated response of p‐NTLI. The maximal concentration of p‐NTLI was reached 40 min after administration of oleic acid. However after instillation of triolein, the maximal concentration was reached at 100 min which was significantly later. The results indicate that the response of p‐NTLI following administration of fat into the duodenum of rats is a specific event caused by fatty acids rather than by lipophilic substances in general. Of the substances tested 18‐carbon fatty acids were the most effective in increasing the concentration of p‐NTLI. Shorter‐ or longer‐chain fatty acids were less effective. The degree of unsaturation, i. e. the presence of one or more double bounds is also of importance. Triglycerides seem to be hydrolysed to fatty acids before they may bring about an increase in the concentration of p‐NTLI. The charge of lipids seems to be critical since the sodium salt of oleic acid had limited effects. Arachidonic acid did not change the integrated response of p‐NTLI indicating that products of cyclooxygenase and lipoxygenase pathways are not involved in the fatty acid induced release of NTLI.
The pharmacological profile of a substance P (SP) antagonist. Evidence for the existence of subpopulations of SP receptors
Authors: ROSELL SUNE , BJÖRKROTH ULLA , XU JIE‐CHENG , FOLKERS KARL
Published: December 2008

The purpose of this study was to evaluate the pharmacological properties of a substance P (SP) analogue [D‐Arg1, D‐Pro2, D‐Trp7,9, Leu11] SP as an SP antagonist. This analogue, blocked the SP‐induced contractions of the isolated guinea‐pig ileum and the rat urinary bladder and it exhibited no spasmogenic activity on these preparations. The affinity constant (pA2) for [D‐Arg1, D‐Pro2, D‐Trp7,9, Leu11]SP versus SP was 6.31 on the guineapig ileum preparation and 5.30 on the rat urinary bladder preparation. The slopes of the regression lines of the Schild plots were close to unity. These data indicate that [D‐Arg1, D‐Pro2, D‐Trp7,9, Leu11]SP blocks SP receptors in a simple competitive manner and suggest that there are at least two subpopulations of SP receptors. The contractions caused by the closely related tachykinins eledoisin and physalaemin were also blocked by the SP analogue. However, the slopes of the regression lines were significantly different from unity. Moreover, when tested on the hamster urinary bladder, which contracts at low concentrations of eledoisin but is rather insensitive to physalaemin and SP, [D‐Arg1, D‐Pro2, D‐Trp7,9, Leu11]SP did not block the contractile actions of eledoisin or of physalaemin and SP. Compared to SP eledoisin and physalaemin may bind to SP receptors in a different manner. Eledoisin also seems to interact with receptors different from the SP receptors.
Mechanical properties of rat cerebral arteries as studied by a sensitive device for recording of mechanical activity in isolated small blood vessels*
Authors: HÖGESTÄTT E. D. , ANDERSSON K. ‐E. , EDVINSSON L.
Published: December 2008

A sensitive device for recording of mechanical activity in isolated small blood vessels with calibres down to 100 μm is described. This equipment was used to examine the mechanical properties of rat cerebral arteries. The ultrastructure of the preparations was investigated by light‐, transmission, and scanning electron‐microscopy. In general the walls of the middle cerebral and basilar arteries consisted of 3 layers of smooth muscle cells, which occupied approximately 80% of the total wall thickness. The present technique preserved the integrity of the vessel wall and caused no observable damage to the smooth muscle or endothelial cells. Neither the basilar nor the middle crebral arteries developed spontaneous phasic contractions under standard conditions. Potassium excess (124 mM) induced a biphasic contractile response characterized by a fast and partly transient increase in tension (phase A), followed by a slowly developing sustained contraction (phase B). The responses to K+were strong, highly reproducible and not influenced by pH changes in the range 6.9‐7.8, making K+‐stimulation suitable for testing of vascular contractility. Length‐tension measurements were performed on relaxed and K+‐activated basilar arteries. The mechanical behaviour of the vessels conformed to a sliding‐filament model of muscular contraction. Using the “Maxwell model” of a muscle, the length at which the contractile element produced maximum active tension was established. The passive wall tension at this length (˜ 1 mN/mm) averaged only about 20% of the total wall tension the arteries were capable of producing when activated by K+. Under isometric conditions the K+‐contracted basilar artery developed a maximum active wall stress of approximately 240 mN/mm2. In the light of the mechanical data obtained from the length‐tension measurements, the optimum resting wall tension for registration of vascular responses is discussed. It appears that the present in vitro system can be of great value in investigations of the smooth muscle function in small blood vessels.
Pharmacological characterization of postjunctional α‐adrenoceptors in isolated feline cerebral and peripheral arteries
Authors: SKÄRBY TOR V. C. , ANDERSSON KARL‐ERIK , EDVINSSON LARS
Published: December 2008

The vascular α‐adrenoceptors in isolated feline cerebral, lingual and mesenteric arteries were characterized and compared. In the middle cerebral artery the relative order of potency for agonists was: clonidine>oxymetazoline>noradrenaline>phenylephrine which indicates that the postjunctional α‐receptor in this vessel is of α2‐type. This view is further supported by the finding that yohimbine, but not prazosin, had a potent, mainly competitive blocking action. In peripheral arteries, clonidine was without effect. In these vessels, the potency difference between phenylephrine and oxymetazoline was more than 40 times less than in cerebral vessels. The pA2‐values for prazosin correlated well with pA2‐values found for the interaction of this drug with α1‐receptors in a variety of other tissues, thus suggesting the occurrence of an α1‐receptor in these arteries. However, the pA2‐values for yohimbine and rauwolscine correlated well with an α2‐receptor, suggesting also the presence of α2‐receptors. Schild plots for prazosin and rauwolscine in lingual arteries displayed slopes significantly lower than unity, which also supports the view of a mixture of α1‐and α2‐receptors in these vessels. However, the Schild plots for the antagonists in mesenteric arteries did not differ significantly from unity, a finding possibly indicating the presence of an α‐receptor unable to differentiate between substances that in other tissues act preferentially on α1‐ or α2‐receptors.
Capillary transport of H2gas generated locally in renal tissue
Authors: KIRKEBØ A. , ØIEN A. H. , AUKLAND K.
Published: December 2008

Previous measurements by microspheres have shown a higher blood flow in outer cortex and a lower blood flow in inner cortex than found by diffusible tracers. During vasodilation microspheres have indicated a disproportionate increase in deep cortical blood flow, whereas diffusible tracer distributions remained unchanged. These discrepancies could possibly be explained by a variable net inward transport of diffusible tracers in postglomerular vessels, the transport existing in control, but disappearing during vasodilation. To test this hypothesis H2gas was produced electrolytically for 1 s at a platinum electrode in midcortex and the resulting gas concentration curve measured polarographically at two electrodes placed above and below the source. Analysis of a mathematical model showed that the ratio of the curve maxima at the two electrodes (Cmo/Cmi) would best reveal a radial net transport. Average Cmo/Cmiat 25 positions in 7 clamped dog kidneys was close to unity, but rose to 1.24 at control flow. During acetylcholine infusion Cmo/Cmirose to 1.68. Local washout rates at the two electrodes increased equally. Calculations indicated a small outwardly directed net transport in control (3×10‐4cm/s), becoming slightly reinforced during vasodilation (5×10‐4cm/s). Thus the control transport direction is opposite to the hypothesis, and the change during vasodilation was estimated to be too small to explain the disparity between diffusible tracer uptake and microsphere distribution in control. H2concentration maximum was obtained earlier under control flow than in the clamped kidney, indicating an increase in apparent D of the gas in tissue from 3×10‐5cm2/s to 5×10‐5cm2/s, probably due to mixing of H2gas in the capillary net work.
The glomerular filtration rate in unrestrained rabbits determined by means of an implanted telemetrical device
Authors: VADSTRUP STEEN , BOJSEN JØRGEN
Published: December 2008

An implanted radio‐telemetrical device, which consists of a Geiger‐Müller detector, a high voltage supply and a FM transmitter, incapsulated in araldite® (weight 130 g) was used to measure the body disappearance rate of 125I‐iothalamate following a single i. v. bolus in unrestrained and undisturbed rabbits. The disappearance curve is practically monoexponential from 10 to 60 minutes after administration of the indicator and the disappearance rate constant (ke) is closely correlated to the “final slope” of the plasma disappearance curve of 125I‐iothalamate (kp) (r=0.99). A linear correlation was also found between ke and GFR measured simultaneously by constant infusion clearance technique, using an indicator not detected by the Geiger‐Müller detector (51Cr‐EDTA) (r=0.98), The ratios between the renal clearances of 125I‐iothalamate, 51Cr‐EDTA and inulin were determined by constant infusion clearance technique in a separate series of experiments since no data were available in the present literature. The results show that GFR can be determined by means of the telemetrical method and in a seriers of experiments in undisturbed rabbits GFR was found to be on average 4.7 ml min‐1, kg‐1 (expressed as inulin clearance). Using the same technique in lightly pentobarbital anesthetized rabbits GFR was on average 3.5 ml. min‐1. kg‐1.
Muscle fibre type distribution, muscle cross‐sectional area and maximal voluntary strength in humans
Authors: SCHANTZ P. , RANDALL‐FOX E. , HUTCHISON W. , TYDÉN A. , ÅSTRAND P. ‐O.
Published: December 2008

The relationship between maximum voluntary concentric strength, muscle fibre type distribution and muscle cross‐sectional areas were examined in 23 subjects (7 female and 11 male phys. ed. students as well as 5 male bodybuilders). Maximal knee and elbow extension as well as elbow flexion torque at the angular velocities 30, 90 and 180 degrees per second was measured. Muscle biopsies were taken from vastus lateralis and m. triceps brachii. The muscle cross‐sectional area of the thigh and upper arm was measured with computed tomography scanning. The maximal torque correlated strongly to the muscle cross‐sectional area times an approximative measure on the lever arm (body height). Maximal tension developed per unit of muscle cross‐sectional area did not correlate significantly with per cent type I fibre area and did not differ between the female and male students or bodybuilders. Neither did the relative decrease in torque with increasing contraction velocity show any significant relationship to the per cent type I fibre area. The total number of muscle fibres was estimated by dividing the muscle cross‐sectional area with the mean fibre area of m. triceps brachii. The number of fibres did not seem to differ between the sexes.
The effect of the time pattern of presynaptic impulses on the transfer of information across an inhibitory synapse
Authors: LIESTØL KNUT
Published: December 2008

The effects of different time patterns in presynaptic spike trains on the transmission of information across an inhibitory synapse is examined in the muscle receptor organs of the crayfish abdomen. With regular input, the system would be strongly affected by phaselocking (Perkel et al. 1964), and it is shown that a similar phenomenon would occur during closedloop inhibitory feedback. The conditions under which different degrees of phaselocking occur is studied in simple models of the system, and the model predictions is compared with experimental observations of pre‐ and postsynaptic spike trains. The results suggest that phaselocking is uncommon during the normal operation of these sense organs, due to the special design of its neuronal elements, which promote irregular time patterns of impulse firing in both receptors and inhibitory neurons.
Acute effects of acetazolamide on cerbral blood flow in man
Authors: HAUGE ANTON , NICOLAYSEN GUNNAR , THORESEN MARIANNE
Published: December 2008

We have followed the time course of the effect of the carbonic anhydrase inhibitor acetazolamide injected i. v. in unanesthetized healthy human beings. The dose administered was 500 mg as a bolus. Cerebral blood flow (CBF) was measured continuously before, during and after the injection, using a pulsed ultrasound doppler system, which measured the instantaneous mean velocity across the lumen of the internal carotid artery, just below its entrance into the skull. Ventilation, heart‐rate, end‐expiratory PCO2‐ arterial PCO2, pH and systemic blood pressure was also measured. We found that acetazolamide caused a rise in CBF which could be detected as early as 2 min after the injection. A maximal average response of 75% increase in CBF was seen after 25 min. The half‐time of the declining phase of the response was 95 min. There were no systematic differences in the CO2reactivities, given as ACBF/ΔPACO2in % of CBF at normocapnia, before and after acetazolamide injection, regardless of the absolute PACO2level. The present dose of the drug caused no change in ventilation, alveolar and arterial PCO2or in arterial blood pH indicating that the carbonic anhydrase was not fully inhibited. Our observations show that acetazolamide nevertheless caused a rapid vasodilation in the brain and over a wide range of PCO2′s. We suggest that this agent has a local vasodilator effect on the cerebral arterioles, unrelated to its specific effects as a carbonic anhydrase inhibitor.
Carbonic anhydrase in the monkey stomach and intestine
Authors: LÖNNERHOLM GUDMAR
Published: December 2008

The distribution of carbonic anhydrase in the stomach and intestine of the cynomolgus monkey (Macaca fascicularis) was studied by the histochemical method of Hansson. In the gastric surface epithelium high enzyme activity was found in the cytoplasm and at the lateral cell borders. The parietal cells in the gastric glands also showed high enzyme activity, while the chief cells were less active. The mucous cells in the pytoric glands and in the Brunner's glands demonstrated a staining pattern similar to that of gastric surface cells. The mucosa of the duodenum and the jejunum was less intensely stained than the gastric mucosa. The enzyme activity was located at the lateral cell borders of the enterocytes, with weak or no cytoplasmic activity. Goblet cells and Paneth cells were unstained. In the ileum a small number of epithelial cells displayed high enzyme activity; their identity is not clear at present. In the cecum and colon large amounts of cytoplasmic carbonic anhydrase were found in the surface epithelium and in the upper part of the glands. Capillaries showing clear enzyme staining were found in the mucosa of all tissues; they were often located close to the surface epithelium and the glands. In the stomach, cecum and colon the distribution of the enzyme in the monkey appears very similar to that reported for other mammalian species, but in the small intestine clear differences exist. The functional role of carbonic anhydrase at the various sites in the gastrointestinal tract is only partly understood.