bluuebunny/crossref_metadata_2025 huggingface dataset:
Olfaction and gustation in fish: an overview
Authors: HARA T.J.
Published: December 2008

Living in an aquatic environment, often devoid of light but rich in dissolved compounds, fish have highly developed chemosensory and chemical signalling systems. The olfactory and gustatory systems comprise the major chemosensory pathways. Despite considerable variations in structural organization of the peripheral olfactory organ throughout fish species, ultrastructural organization of the olfactory sensory epithelium is extremely consistent. The olfactory receptor cell is a bipolar neurone which is directly exposed to the external environment and sends information to the brain by its own axon (cranial nerve I). Four major classes of chemicals have been identified as specific olfactory stimuli and their stimulatory effectiveness characterized: amino acids, sex steroids, bile acids/salts and prostaglandins. Olfactory signals such as those involved in reproduction and feeding may be processed independently through two distinct subsystems: the lateral and medial olfactory systems. The taste buds constitute the structural basis of the gustatory organ. Taste buds may occur not only in the oropharyngeal cavity, but on the whole body surface. Chemical information detected by specialized epithelial cells, gustatory cells, is transmitted to the central nervous system by cranial nerve VII (facial), IX (glossopharyngeal), and X (vagal). Besides diverse sensitivities and specificities for amino acids, fish gustatory receptors detect various organic acids, nucleotides and bile salts. Putative receptors, molecular mechanisms of transduction and the role played by olfaction and gustation in feeding, reproduction, migration and other fish behaviours are discussed.
Dorsal column inhibition of nociceptive thalamic cells mediated by gamma‐aminobutyric acid mechanisms in the cat
Authors: OLAUSSON B. , XU Z.‐Q. , SHYU B.‐C.
Published: December 2008

Cells in posterior parts of the cat thalamus were investigated. Responses in single units excited by electrical stimulation in the lateral funiculus (LF), the dorsal column nucleus (DCN) or the canine tooth pulp (TP) were analysed. All cells had a spontaneous resting activity which could be increased by extracellular iontophoretic application of DL‐homocysteic acid (DLH) and decreased by gamma‐aminobutyric acid (GABA). No effect on the spontaneous firing rate was observed following iontophoresis of the selective GABA‐antagonists, picrotoxin (GABA‐A receptor antagonist) or saclofen (GABA‐B receptor antagonist). However, the decreased firing following GABA application was partially blocked by picrotoxin but not by saclofen. A phasic inhibition induced by DCN stimulation in nociceptive thalamic cells is indicated since simultaneous administration of picrotoxin increased the evoked response. This type of inhibitory mechanism could not be detected following LF or TP stimulation. The extracellular activity evoked by electrical stimulation of LF or TP was significantly depressed by preceding electrical stimulation in the DCN. This inhibition was reversed by simultaneous administration of picrotoxin, indicating an involvement of GABA‐A receptors. The reversal of the DCN‐induced depression of the late responses following LF stimulation occurred after application of saclofen. It is suggested that this effect is partly mediated via GABA‐B receptors. Results from the present study indicate an interaction in the thalamus between presumed low‐threshold (DCN) and presumed nociceptive afferents (LF and TP) similar to that previously described in the spinal cord.
Intramuscular pressure, torque and swelling for the exercise‐induced sore vastus lateralis muscle
Authors: CRENSHAW A. G. , THORNELL L.‐E. , FRIDÉN J.
Published: December 2008

This study investigated changes in intramuscular fluid pressure (IMP), torque and swelling related to delayed onset muscle soreness (DOMS) of the vastus lateralis muscle. IMP was measured via catheterization in the unstretched (0°, full extension) and stretched (90° of knee flexion) muscle at rest; then IMP and knee extension torque were determined during maximal contractions pre and 2 d after (post) repetitive eccentric activity in one leg for eight male subjects. DOMS of the vastus lateralis muscle was associated with a significant elevation in IMP at rest as indicated by pre (0°: 5.4 mmHg, 90°:80mmHg) and post (0°:8.4mmHg, 90°: 13.2 mmHg) comparisons (P = 0.02). Soreness symptoms were aggravated when the muscle was stretched and this was accompanied by a significantly higher post IMP at 90° vs. 0° (P= 0.01). During maximal contractions, peak torque declined by 15% relative to pre and peak IMP declined by 26%; DOMS symptoms, however, were most severe during this manoeuvre. Biopsies from the sore vastus lateralis muscle revealed significantly larger fibre areas for all fibre types as compared with contralateral controls (P<0.01); however, no differences were detected for extracellular volume percent comparisons. This study shows that DOMS of the vastus lateralis muscle is associated with extensive intracellular swelling and with elevated IMP. In line with previous studies, fibre swelling may be a common subsequence to repetitive eccentric activity; the ability of IMP measurements to detect this swelling at rest and during various manoeuvres for other muscles may depend on compartmental compliance.
Effect of ageing on ultrastructure of slow and fast skeletal muscle tendon in rabbit Achilles tendons
Authors: NAKAGAWA Y. , MAJIMA T. , NAGASHIMA K.
Published: December 2008

This reports presents the changing morphological characteristics of collagen and fibroblasts in the soleus and gastrocnemius muscle tendon of female Japanese white rabbits with ageing. The fibroblasts decreased in number per 37 μm2 with ageing in each group, and their morphology became longer and more slender through ageing. The mean fibril area and diameter of the collagen fibrils of soleus muscle tendon (SMT) and lateral gastrocnemius muscle tendon (GMT) in 8‐ to 10‐month old rabbits were significantly higher than those of 3‐wk‐old rabbits during growth (P < 0.01). The mean area and diameter of collagen fibrils of SMT and GMT decreased during senescence: the values for 4‐ to 5‐yr‐old rabbits were lower than those for 8‐ to 10‐month‐old rabbits, but the difference was not significant. Statistically significant differences in fibril area and diameter between the SMT and GMT were not found during ageing. The number of thick fibrils increased during growth, but decreased in senescence. There were more thin fibrils (30–60 nm) in the 3‐wk‐old rabbits than in the 8‐ to 10‐month old and 4 to 5‐yr‐old groups, and the large‐diameter collagen (300–360 nm) was more abundant in the 8‐ to 10‐month‐old group than in the 3‐wk‐old and 4‐ to 5‐yr‐old groups. Differences in fibril size between slow and fast muscle tendons were not observed during ageing.
Cerebral osmoregulatory reduction of plasma renin concentration in sheep
Authors: McKINLEY M. J. , RUNDGREN M. , COGHLAN J. P.
Published: December 2008

A centrally mediated inhibitory influence of plasma hypertonicity on renin secretion was investigated in conscious, Na‐depleted sheep. Infusions of hypertonic solutions were made into the carotid artery or jugular vein, and the effects on plasma renin concentration (PRC) compared. Intracarotid infusion of 1.65 M NaCl significantly reduced PRC (to 74% of the pre‐infusion value) within 15 min of the commencement of the infusion whereas corresponding intrajugular infusion did not. Intracarotid infusion of 3 M sorbitol for 45 min also reduced PRC (to 64% of the pre‐infusion level) significantly after 15 min of infusion. By contrast, neither intrajugular infusion of 3 M sorbitol, nor intracarotid infusion of isotonic 0.15 M NaCl for 45 min significantly reduced PRC. Intracarotid infusion of hypertonic sorbitol for 45 min did not inhibit PRC in sheep with cerebral lesions of the lamina terminalis. These results show that plasma hypertonicity may have an inhibitory influence on renin secretion. The inhibition is probably mediated by an effect of hypertonicity on the CNS, rather than a direct effect on the kidney.
Lymphatic transport and organ uptake of gelatin and hyaluronan injected into the rat mesentery
Authors: ØSTGAARD G. , HELLEVIK T. , REED R. K. , SMEDSRØD B.
Published: December 2008

The metabolic pathways of denatured collagen (gelatin) and hyaluronan were studied by injecting labelled macromolecules into the mesentery of rats. The label, [125I]tyraminecellobiose is trapped intracellularly after endocytosis, allowing localization of the site of uptake. Mesenteric and thoracic lymph was sampled for 6 h in anaesthetized rats. Separate rats were investigated after an awake period of 6 or 24 h. About 30% of the gelatin remained at the site of injection and of the remaining activity 1.7% was recovered in lymph, 11 yo in the liver and 15% in the kidneys, whereas 3 h after an intravenous injection of gelatin > 70% was recovered in the liver. The change in preferable site of uptake from the liver to the kidney was attributed to local degradation in the mesentery as confirmed by chromatography of tissue extracts and lymph.

Following hyaluronan injection and 6 h lymph sampling approximately 30% was left at the site of injection and of the remaining activity 5.7% was recovered in lymph. After an awake period of 6 or 24 h, 30% was regained in the liver. The recoveries in other organs were negligible and mesenteric lymph nodes seem quantitatively unimportant in the uptake of hyaluronan or gelatin from lymph or blood.

The liver has a central role in intestinal hyaluronan metabolism, while denatured collagen is more prone to local degradation with remote uptake shared between the liver and the kidney.
Daily energy expenditure in free living minke whales
Authors: BLIX A. SCHYTTE , FOLKOW L. P.
Published: December 2008

Six minke whales (BaLaenoptera acutorostrata) were instrumented with VHF‐radio transmitters and four with sonic speed‐depth transmitters off the west coast of northern Norway and Svalbard and followed within view for up to 24 h. During such periods their respiratory rate was continuously recorded and their energy expenditure estimated according to Folkow & Blix (1992) at different swimming speeds and types of activity. We found that cost of swimming is remarkably low in these large animals and that their estimated daily energy expenditure on average only amounts to 80 kJ kg‐1 day‐1.
The effects of long‐term hyperinsulinaemia on insulin sensitivity in rats
Authors: HOLMáNG A. , JENNISCHE E. , BJÖRNTORP P.
Published: December 2008

The effects of long‐term exposure (7 wk) to hyperinsulinaemia on insulin sensitivity were studied in female rats. The rats were made hyperinsulinaemic by implantation of osmotic minipumps that were changed once a week. Elevated adrenergic activity and secretion of glucocorticoids were controlled by another minipump with propranolol and adrenalectomy with corticosterone substitution, respectively. This resulted in hyperinsulinaemia and moderate hypoglycaemia, the latter probably counteracted by overeating and increased glucagon secretion, as indicated by increased body weight and lower liver glycogen contents, respectively. Euglycaemic, hyperinsulinaemic clamp measurements showed a significantly higher glucose disposal rate (P < 0.05) in the hyperinsulinaemic rats 18.8± 1.1 mg kg‐1 min‐1 compared with the control groups 14.6±0.4 and 15.4±0.9 mg kg‐1 min‐1. Insulin stimulation of 2‐deoxyglucose as well as glycogen synthesis was measured in the extensor digitorum longus muscle, the red and white part of the gastrocnemius, the soleus muscle, the liver and in parametrial, retroperitoneal, and inguinal adipose tissue. No differences were found between the groups in the insulin response of the 2‐deoxyglucose uptake. Glycogen synthesis was significantly elevated in all muscles in the insulin treated compared with the control rats but no differences were found in the liver. Capillary density was significantly elevated per unit muscle surface area in the soleus and extensor digitorum longus muscles of the insulin‐exposed rats. These results suggest that long‐term exposure to insulin is followed by increased insulin sensitivity, apparently localized to the insulin regulation of glycogen synthesis in muscles. Muscle capillary density is elevated in parallel.
Effect of branched‐chain amino acid and carbohydrate supplementation on the exercise‐induced change in plasma and muscle concentration of amino acids in human subjects
Authors: BLOMSTRAND E. , ANDERSSON S. , HASSMEN P. , EKBLOM B. , NEWSHOLME E. A.
Published: December 2008

Five male endurance‐trained subjects performed exhaustive exercise on a cycle ergometer at a work rate corresponding to 75% of their Vo2max after reduction of their muscle glycogen stores. During exercise the subjects were given in random order a 6% carbohydrate solution contining 7 g L‐1 of branched‐chain amino acids (BCAA), a 6% CHO solution and flavoured water. The physical performance was lowered in four of the five subjects when they were given flavoured water during exercise as compared with the two conditions when CHO was supplied. No difference in performance was found when the subjects were given CHO+BCAA or only CHO during exercise. When CHO+BCAA was supplied the plasma and muscle (vastus lateralis) concentrations of BCAA increased during exercise by 120 and 35%, respectively. In the other conditions there was no change or a slight decrease in the plama concentrations of BCAA, but the muscle concentrations of BCAA were decreased after exercise. The plasma concentration of glutamine over the whole exercise period and 5 min after exercise was higher when CHO+BCAA were supplied during exercise compared with a supply of CHO alone or water. However, exercise caused no change in the muscle concentration of glutamine, whereas that of glutamate decreased in all three conditions. A supply of CHO+BCAA or CHO alone did not affect the exercise‐induced increase in the plasma and muscle concentration of aromatic amino acids, indicating that neither BCAA nor CHO influenced the net protein degradation during exercise.
Pitfalls in the interpretation of spectral analysis of the heart rate variability during exercise in humans
Authors: CASADEI B. , COCHRANE S. , JOHNSOTON J. , CONWAY J. , SLEIGHT P.
Published: December 2008

The recent use of spectral analysis of the R‐R interval variability to assess the autonomic drive during exercise has produced inconsistent results. The purpose of this study was to assess whether the spectral components of the R‐R interval variability reflect different mechanisms at rest and during exercise.

Autoregressive spectral analysis of the electrocardiographic and breathing signals was performed in 11 healthy young men at rest and during incremental cycle ergometry. The amplitude of respiratory sinus arrhythmia, i.e. the absolute power of the high frequency spectral component, fell at the onset of exercise, consistent with a reduction in cardiac vagal activity. Conversely, the normalized power of the high frequency component, (i.e. the percentage of R‐R interval variance due to the respiratory sinus arrhythmia) increased with increasing work rates. The low frequency spectral component of the R‐R interval variability, which when expressed in normalized units is believed to reflect cardiac sympathetic activity, was no longer detectable in severe exercise when the adrenergic drive is known to be elevated.

In conclusion, autoregressive spectral analysis of the R‐R interval variability does not adequately reflect the autonomic changes that occur during incremental exercise. In particular, the evidence indicates that as the cardiac vagal tone falls with increasing levels of exercise, a greater percentage of the residual power of the high frequency component may be due to non‐neural mechanisms.
Myocardial inositoltrisphosphate is depressed by dibutyryl cAMP. An experimental study in the isolated working rat heart
Authors: MARTINUSSEN H. J. , WALDENSTRÖM A. , RONQUIST G.
Published: December 2008

A possible interrelation between IP3and cAMP was studied in rat myocardium through circumvention of the receptor mediated stimulatory step of adenylyl cyclase by the administration of dibutyryl cAMP (db‐cAMP). Changes in IP3and cyclic nucleotide contents were correlated to changes in contractility after 40 min ofβ‐ andα‐adrenergic stimulation. Rat hearts (n= 23) were perfused with Krebs‐Henseleit buffer in a modified Langendorff apparatus as a working preparation. The hearts were allocated to perfusion as control (n= 6); or with phenylephrine (10‐6mol L‐1,n= 6); (—)‐isoproterenol (10‐6mol L‐1,n= 6); db‐cAMP (2 times 10‐4mol L‐1,n= 5). All hearts were freeze‐clamped after 40 min of perfusion. Phenylephrine produced a slow increase inmaxdP/dtreaching a maximal value after 10 min (P< 0.05); thereafter it decreased, reaching the control level at 30 min. Isoproterenol perfusion resulted in an early (20 s) increase inmaxdP/dt(P< 0.05). Over the next 10 smaxdP/dtdecreased markedly reaching an inflection point at 30 s. Thereafter only a slow increase during the rest of the perfusion was seen. Dibutyryl cAMP increasedmaxdP/dtslowly during the whole perfusion period reaching maximum after 40 min. Cyclic‐AMP was increased by 21% after 40 min of phenylephrine perfusion while the corresponding increases by isoproterenol and db‐cAMP were 131 and 105%, respectively (P< 0.05). Phenlyephrine increased IP3content to the same extent as isoproterenol perfusion (P< 0.05). On the other hand, a decreased IP3content was seen at 40 min of db‐cAMP perfusion. Cyclic‐AMPper sedepressed basal myocardial IP3content in myocardial tissue. Despite normalization of contractility after 40 min of phenylephrine perfusion the IP3content was 27% higher than in control hearts pointing out the unclearness of the relationship between myocardial IP3content and the contractile system.
Renal sodium excretion after oral or intravenous sodium loading in sodium‐deprived normotensive and spontaneously hypertensive rats
Authors: MU J. Y. , HANSSON G. C. , BERGSTRÖM G. , LUNDGREN O.
Published: December 2008

Spontaneously hypertensive rats (SHR) and normotensive Wistar‐Kyoto (WKY) rats that had been on a low sodium diet for 3 days were given 1.5 mmol sodium chloride kg‐1 body weight either orally or intravenously. The rats receiving an oral sodium load showed a greater natriuresis than those receiving the same saline load intravenously. No increase of renal sodium excretion was observed when the rats received a hypertonic mannitol solution orally. The cumulative sodium excretion during the 8 h following oral loading was two to three times larger in SHR than in WKY, whereas no difference between strains could be demonstrated after giving saline intravenously. Furthermore, after switching from normal to low sodium diet the rate of decrease of renal sodium excretion was greater in SHR than in WKY rats. It is proposed that there exists a gastrointestinal sensory mechanism for sodium controlling the renal sodium excretion. Furthermore, it is suggested that the function of this mechanism differs between SHR and WKY.
The effects of hypothermia on renal function and haemodynamics in the rat
Authors: BROMAN M. , KÄLLSKOG Ö.
Published: December 2008

The effects of 1–2 h of hypothermia a t 28d̀C and rewarming on renal function were investigated in anaesthetized rats, using conventional clearance methods and the micropuncture technique. Renal blood flow (RBF) decreased from 7.3 ± 0.51 mL min‐1 at 37.5d̀C (control) to 4.0 ± 0.47 at 28d̀C, with almost complete restoration to 6.9 ± 0.59 mL min‐1 after rewarming. Systemic blood pressure remained essentially unaltered. The RBF reduction seen during hypothermia was due to a 75% increase in vascular resistance, mainly attributable to constriction of the afferent arteriole and increased blood viscosity. This was accompanied by a decline in glomerular capillary pressure from 56.7 ± 0.6 to 46.4 ± 1.3 mmHg, overshooting to 59.0 ± 0.7 mmHg. The glomerular filtration rate (GFR) decreased from 1.1 ± 0.08 to 0.6 ± 0.04 mL min‐l, returning to 1.0 ± 0.07 after rewarming, a pattern also observed for single nephron GFR. This resulted from a decrease in net driving force for glomerular filtration, whereas the filtration coefficient was not affected. Both proximal and distal tubular fluid flow decreased, but fractional reabsorption remained unchanged. In contrast, urine flow increased from 1.8 ± 0.16 to 5.7 ± 1.08 μL min‐1, returning to 2.1 ± 0.18, the increase during hypothermia mainly resulting from a disproportionately reduced fluid reabsorption beyond the mid‐distal tubule.
Sympathetic regulation of fructose secretion in the seminal vesicle of the guinea‐pig
Authors: SJÖSTRAND N. O. , HAMMARSTORÖM M.
Published: December 2008

Fructose secretion of everted guinea‐pig seminal vesicles was studiedin vitro. Carbachol produced dose dependent increase in fructose secretion. The effect was blocked by scopolamine but not by hexamethonium, mecamylamine, tetrodotoxin or previous denervation. High concentrations of acetylcholine also increased fructose secretion. This response was not augmented by physostigmine. Methoxamine reduced secretion. Methoxamine, terbutaline, clonidine and vasoactive intestinal peptide counteracted carbachol. Field stimulation produced increased secretion that was not blocked by autonomic drugs, tetrodotoxin or previous denervation. Stimulation of the hypogastric nerve produced frequency dependent increase in fructose secretion. The effect was blocked by tetrodotoxin and scopolamine but not enhanced by physostigmine. If the hypogastric nerve was stimulated close to the seminal vesicle the response was unaffected by hexamethonium but proximal stimulation was blocked. After chronic proximal denervation of the hypogastric nerve, stimulation close to the seminal vesicle produced enhanced response. Destruction of the peripheral ganglia at the base of the seminal vesicle abolished the response. Sections showed that most secretory nervesenter the organ at its base. Phentolamine or yohimbine but not prazosine or propranolol or guanethidine enhanced the secretory response to distal hypogastric nerve stimulation. Tyramine counteracted the response but after reserpinization it was enhanced by tyramine.

It is concluded that the secretory cells of the guinea‐pig seminal vesicle have a sympathetic secretomotor innervation by short cholinergic neurones with a preganglionic supply via the hypogastric nerve. Inhibitory α1and β2‐adrenoreceptors are present on the cells but neurogenic adrenergic inhibition of the secretion is essentially prejunctional and due to activation of inhibitory α2‐receptors on the secretomotor nerves.
Sympatho‐adrenergic inhibition of basal and acid‐induced changes in duodenal motility, mucosal net fluid and alkaline secretion in the anaesthetized cat
Authors: FÄNDRIKS L. , JÖNSON C. , HAMLET A. , DANIELSEN N. , JOHANSSON B. R.
Published: December 2008

Experiments were performed on chloralose anaesthetized cats. A 2‐cm segment of the proximal duodenum was isolated between two luminally situated balloons and perfused with isotonic saline containing [14C]‐PEG 4000 as a non‐absorbable marker. The perfusate was analysed with regard to alkalinity (back titration) and concentration of marker (liquid scintillation). Net alkalinization and net fluid transport were calculated with conventional equations. Motor activity in the duodenal wall was recorded as changes in volume of the proximal balloon. In presence of sympathetic neural activity (spontaneous or electrically stimulated) basal motor of sympathetic neural activity (spontaneous or electrically stimulated) basal motor activity and mucosal alkaline secretion was and increased minimally in response to luminal HCl (30 mM). Net fluid transport was in an absorptive state and shifted to a small secretion upon the acid‐exposure. Subsequent to bilateral acute splanchnicotomy, or the administration of the adrenolytic guanethidine (3–4 mg kg‐1, i. v.), spontaneous duodenal contractions occurred and the alkaline secretion was increased. Furthermore, both parameters were then markedly stimulated by luminal perfusion with 30 mM HCl. Basal net fluid transport was zero and turned into secretion upon the acid‐exposure. No morphological changes of the duodenal surface epithelium could be detected. The study demonstrates the existence of splanchnic nerve‐mediated, adrenergic inhibition of basal, as well as of acid‐induced duodenal motility, fluid and alkaline secretion.
Interdigestive gastroduodenal manometry in humans. Indication of duodenal phase III as a retroperistaltic pump
Authors: BJÖRNSSON E. S. , ABRAHAMSSON H.
Published: December 2008

To elucidate the specific function of the three phases (I‐III) of the migrating motor complex (MMC) by manometry, detailed analysis of individual pressure waves in the proximal duodenum was performed. Twenty healthy subjects (10 men and 10 women of whom 11 were tube‐naive) underwent computerized manometry for 5 h during fasting followed by 45 min after a meal using an 8‐channel water perfused catheter. Three recording points were in the antrum, three in the proximal duodenum (2 cm apart), one in the distal duodenum and one in the proximal jejunum. In all subjects at least one phase III (median 2) was observed during the 5‐h fasting recording. In the proximal duodenum the mean proportion of retrograde pressure waves, out of all propagating waves, was significantly increased in the last part of phase III (85 ± 9%, mean, SE), compared with early phase III (6 ± 5%), late phase II (5 ± 4%) and the feeding phase (10 ± 5%), irrespective of gender or previous tube‐experience. The median length of the MMCs was 108.5 min. There was no statistically significant difference between men and women or between tube‐naive and tube‐experienced subjects for the duodeno‐jejunal motility indices of phase II and phase III, nor for duration or migration of phase III. The postprandial motility index of the small intestine was increased compared with the interdigestive late phase II, particularly in the jejunum (P < 0.02).

The last part of the duodenal interdigestive phase III in healthy subjects shows the feature of a retroperistaltic pump. This cyclic sequence of retropropagation coincides with the reported rapid alkalinization of the duodenal bulb and the gastric antrum occurring in early antral phase I.
Colchicine induces enhanced intestinal permeability in the rat
Authors: FRADKIN A. , YAHAV J. , DIVER‐HABER A. , ZEMER D. , JONAS A.
Published: December 2008

Intestinal permeability was determined in rats receiving colchicine 0.5 ± 0.15 mg day‐1 in drinking water (30 mg L‐1) for periods up to 23 days. The lactulose/mannitol method was used to determine whole gut permeability before and on days 2, 4, 8, 18 and 23 of colchicine administration. The 8‐h urinary lactulose excretion following the test meal increased significantly in rats receiving colchicine, compared with the pretreatment value. Increased lactulose permeability was present after 2 days and remained stable throughout the experimental period. Mannitol urinary excretion was not changed. Colchicine increases intestinal tight junction permeability by an as yet undetermined mechanism.
Skeletal muscle perfusion in electrically induced dynamic exercise in humans
Authors: KIM C. K. , STRANGE S. , BANGSBO J. , SALTIN B.
Published: December 2008

Leg blood flow, blood pressure and metabolic responses were evaluated in six men during incremental one‐legged dynamic knee extension exercise tests (no load exercise ‐ 40 W); one performed with voluntary contractions (VOL) and one with electrically induced contractions (EMS). Pulmonary oxygen uptake was the same in both exercise modes, but the ventilatory coefficient was 2–5 L per L O2higher in EMS than VOL (P< 0.05). Heart rate and mean arterial pressure were slightly higher with EMS than VOL at all exercise intensities reaching 138 (EMS) and 126 bpm (VOL), as well as 148 (EMS) and 137 mmHg (VOL) at 40 W, respectively (P< 0.05). Leg blood flow, oxygen uptake and conductance were similar in the two exercise modes. At 40 W, mean muscle blood flow was close to 200 (range: 165–220) mL 100 g‐1min‐1, mean peak muscle oxygen uptake reached 230 mL kg‐1min‐1, and mean conductance became as high as around 45 mL min‐1mmHg‐1, and normalized for muscle size and arterial pressure it approached 100 mL min‐1100 g‐1100 mmHg‐1. Lactate and ammonia efflux from the leg were higher with EMS than with VOL and the difference became larger with increasing exercise intensity (P< 0.05). Muscle glucose uptake was the same in each exercise mode. Femoral venous K+concentration increased with exercise intensity and was higher with EMS than with VOL, reaching 5.1 (EMS) and 4.7 mmol L‐1(VOL) at 40 W (P< 0.05). The study demonstrates that electrically induced dynamic exercise is associated with a marked cardiovascular response similar to voluntarily performed exercise and a more pronounced activation of the anaerobic metabolism of the muscle. Furthermore, as the electrically activated muscle group is well defined, the present results confirm that peak muscle blood flow can reach 200–250 mL 100 g‐1min‐1.
Prostaglandins and corticosterone in the oviparous female lizard, Podarcis sicula sicula, during reproduction
Authors: GOBBETTI A. , ZERANI M. , BELLINI‐CARDELLINI L. , BOLELLI G. F.
Published: December 2008

The in vitro effects of prostaglandin F2α (PGE2α) and prostaglandin E2 (PGE2) on corticosterone release by ovarian follicles, corpora lutea (CL), and interrenals were studies in the female lizard, Podarcis sicula sicula, during reproduction. Follicles and CL were divided according to their different development stages: follicles: pre‐vitellogenic, early‐vitellogenic, mid‐vitellogenic and fully‐grown; CL: CL 1 (unshelled eggs in the oviducts), CL2 (shelled eggs in the oviducts), CL3 (eggs laid 6 h previously) and CL4 (eggs laid 48 h previously). Interrenals were divided according to the reproductive stages: pre‐vitellogenesis, vitellogenesis, ovulation, post‐ovulation, and post‐deposition.

PGF2α release was highest in fully‐grown follicles and PGE2 in early‐vitellogenic follicles, corticosterone was highest in pre‐vitellogenic and lowest in early‐vitellogenic follicles. PGE2 decreased corticosterone in pre‐vitellogenic, mid‐vitellogenic and fully‐grown follicles. PGE2α release was highest in CL4, and PGE2 in CL1 and CL2, CL3. In interrenals, PGE2α release was highest and PGE2 lowest during ovulation, corticosterone was highest in CL4. PGF2α increased and PGE2 decreased interrenal corticosterone during vitellogenesis, ovulation, and post‐ovulation. In the plama, PGF2α levels were highest and PGE2 lowest during ovulation, corticosterone was highest during ovulation.

These results suggest that corticosterone, modulated by PGF2α and PGE2α, is implied in the reproductive processes with different roles. In fact this steroid could favour ovulatory and luteolytic processes. In addition the hypothesis of an anti‐vitellogenic role of corticosterone in discussed.
Reduced arterial diameter during static exercise in humans
Authors: OLESEN H. L. , MITCHELL J. H. , FRIEDMAN D. B. , IVERSEN H. K. , SECHER N. H.
Published: December 2008

In eight subjects luminal diameter of the resting limb radial and dorsalis pedis arteries was determined by high‐resolution ultrasound (20 MHz). This measurement was followed during rest and during 2 min of static handgrip or of one‐leg knee extension at 30% of maximal voluntary contraction of another limb. Static exercise increased heart rate and mean arterial pressure, which were largest during one‐leg knee extension. After exercise heart rate and mean arterial pressure returned to the resting level. No changes were recorded in arterial carbon dioxide tension, and the rate of perceived exertion was ˜ 15 units after both types of exercise. The dorsalis pedis arterial diameter was 1.50±0.20 mm (mean and SE) and the radial AD 2.45±0.12 mm. During both types of contractions the luminal diameters decreased ˜ 3.5% within the first 30 s (P< 0.05), and during one‐leg knee extension they continued to decrease to a final exercise value 7.6±1.1% lower than at rest (P < 0.05). Thus, they became smaller than during the handgrip. After exercise resting values were reestablished. When the arterial diameter was expressed in relation to mean arterial pressure for the radial and dorsalis pedis artery was 22±3 and 28±3% lower during handgrip than the relation during rest, respectively. After one‐leg knee extension both arteries reached 30±4% lower values. This study demonstrated arterial constriction in the resting limbs within the first 30 s of static exercise, and continued constriction during one‐leg knee extension. These results support to the hypothesis that central command and/or muscle mechano‐ receptors influence arterial tone, and that the exercise pressor reflex becomes important with the involvement of a large muscle mass.
Prostaglandins reduce hydrochloric acid‐induced increase in duodenal mucosal permeability by a mechanism not related to stimulation of alkaline secretion
Authors: NLANDER O. , ANERSSON H. , WILLANDE E. , SABABI M.
Published: December 2008

The aim was to investigate whether prostaglandins affect HCI‐induced permeability and to elucidate the role of mucosal bicarbonate secretion in protection. Proximal duodenum of anaesthetized rats were perfused with hydrochloric acid and the effect on luminla alkalinization, mucosal permeability and morphology examined in the absence in the presence of prostaglandin E2 and/or indomenthacin. Luminal alkalinzation was determined by back titration of the perfusate and mucosal permeability assessed by measuring the clearance of51 Cr‐labelled ethylenediaminetetraacetat (51Cr]EDTA) from blood‐to‐intestinal lumen. Perfusilon with 100mM HCI for adiministration of PGE2 at a concentration of 10‐6 M ahd no effect whereas 10‐4 M increased alkalinization by 100% but neither concentration affected the HCI‐induced increase in mucosal permeability. PGE2 (10‐4 M), however, improved the ability of the doudenal mucosa to recover form teh HCI‐induced in mucosal permeability. Indomethacin (5 mg kg‐1, i. v.) increased alkalinmization, augmented HCI‐induced mucosal permeability and aggrvated mucosal injury. In anikmals pre‐treated with PGE2 plus indomethacin, the HCI‐induced increase in mucosal permeability were lower and was found between the rate of alkalinization and the HCI‐induced increase imcosal permeability. It is concluded that endogenous prostaglandins reduced the extent of 100 mM HCI‐induced duodenal mucosal damage by la mechanism other than the stimulaiton of alkaline secretion.
Synaptic vesicles and release of transmitters: new insights at the molecular level
Authors: FRIED G.
Published: December 2008

Neurotransmitter release from transmitter storage vesicles is a regulated signalling event that has properties in common with other secretory systems. Biochemical characterization of mammalian synaptic vesicle proteins has recently converged with studies of protein traffic in non‐neuronal cells and the genetic dissection of the yeast secretory pathway to give us a considerable amount of new data. Many new synaptic vesicle proteins have been characterized together with plasma membrane proteins with which they interact, and it appears that many of the participating components may be part of a general machinery for secretion. The new results significantly improve our understanding of the molecular mechanisms governing transmitter release. This review discusses the recent progress in terms of synaptic vesicle components and the proposed mechanisms for exocytosis.
Effect of different xanthines and phosphodiesterase inhibitors on c‐fos expression in rat striatum
Authors: Svenningsson P. , Johansson B. , Fredholm B. B.
Published: December 2008

It has previously been shown that caffeine, in a dose‐dependent manner, increases the expression of the protooncogene c‐fos in the rat brain, predominantly in the caudate‐putamen and tuberculum olfactorium. In this study we examined the effect of related xanthines and of selective phosphodiesterase inhibitors on c‐fos expression. The effect of caffeine (75 mg kg1) was mimicked by 3‐isobutyl‐l‐methyl xanthine (IBMX) (25 mg kg‐1) and theophylline (100 mg kg‐1) but not by 8‐p‐sulfophenyltheophylline (10mgkg1), enprofylline, theobromine or paraxanthine (each at 100mgkg1). Moreover, the cyclic AMP‐selective phosphodiesterase inhibitors rolipram (10 or 20mgkg_1) and SQ 20006 (25 mg kg:) and the cyclic GMP‐selective phosphodiesterase inhibitor zaprinast (10 mg kg‐1) failed to induce c‐fos in striatum, but caused a clear‐cut induction in the overlying cerebral cortex. Thus, c‐fos is induced in rat striatum following adminstration of caffeine and other xanthines that (provided they enter the brain) block adenosine receptors, suggesting an involvement of central adenosine receptors. Inhibition of cyclic nucleotide phosphodiesterase does not appear to play any important role in c‐fos induction by the xanthines.
Sympathetic reinnervation of unilaterally denervated rat lung
Authors: TAKACHI T. , MAEDA M. , SHIRAKUSA T. , HAYASHIDA Y.
Published: December 2008

The effect of unilateral sympathetic denervation and reinnervation of the lung on a variety of circulatory parameters was investigated in urethane‐anaesthetized rats. The left main stem bronchus together with its surrounding nerves was cut and reanastomosed in 40 rats: 12 intact rats served as controls. Final experiments were performed after 0 days to 10 months: the left stellate ganglion was stimulated. The effect was greatest at 20 Hz. Pulmonary arterial pressure increased significantly (P < 0.05) by 10% and pulmonary flow decreased significantly (P < 0.05) by 16% in the control rats; no effect on these parameters was found in acutely denervated rats. The stimulus‐elicited change in pulmonary arterial pressure reappeared 1 week after unilateral hilar stripping and gradually returned during reinnervation. After 10 months, the increase in pressure was significantly (P < 0.05) larger than that of the control by 50%, whereas the noradrenaline content of the reinnervated lung was significantly (P < 0.05) smaller than that of the intact side by 48%. This discrepancy may reflect denervation hypersensitivity of vascular muscle cells. The operations had no effect on systemic circulation: heart rate and systemic arterial pressure increased and aortic blood flow decreased to the same extent in all experimental groups during nerve stimulation. These results suggest that sympathetic reinnervation of the rat lung starts within 1 week but that reinnervation is still incomplete 10 months after unilateral hilar stripping.
Role of glucose metabolism and phosphoinositide hydrolysis in glucose‐induced sensitization/desensitization of insulin secretion from mouse pancreatic islets
Authors: THAMS P. , HANSEN S. E. , CAPITO K. , HEDESKOV C. J.
Published: December 2008

The role of glucose metabolism and phosphoinositide hydrolysis in glucose‐induced sensitization/desensitization of insulin secretion was studied. A change in glucose concentration from 5.5 to 16.7 mM during 22–24 h of pre‐exposure of mouse islets in TCM 199 culture medium (0.26 mM Ca2+) led to sensitization of glucose‐induced insulin secretion. This change in islet responsiveness to glucose was not mediated by increases in glucose utilization ([5‐3H]glucose conversion to 3H20) and glucose oxidation ([U‐14C]glucose oxidation to 14C02). Glucose‐induced sensitization of insulin secretion was associated with an increase in glucose‐induced phosphoinositide hydrolysis, leading to a significant increase in inositol 1‐monophosphate formation, but not in inositol 1,4‐bisphosphate or in inositol 1,4,5‐trisphosphate plus inositol 1,3,4‐trisphosphate formation. Diacylglycerol, which may arise from both phosphoinositide hydrolysis and de novo from glucose metabolism, was, on the other hand, not increased during acute exposure to glucose and not changed after pre‐exposure to glucose. At 16.7 mM glucose in TCM 199 medium, a change in Ca2+ concentration from 0.26 to 1.26 mM led to a reduction in glucose‐induced insulin secretion. This Ca2+‐dependent desensitization of insulin secretion in the presence of glucose was associated with a decrease in glucose‐induced phosphoinositide hydrolysis, but not with a change in glucose metabolism or diacylglycerol accumulation. In conclusion, it is suggested that glucose‐induced sensitization/desensitization of insulin secretion may involve changes in phosphoinositide hydrolysis, but may occur independently of concomitant changes in glucose metabolism or diacylglycerol accumulation.
The effect of change in sympatho‐vagal balance on heart rate and blood pressure variability in the foetal lamb
Authors: METSÄLÄ T. , SIIMES A. , VÄLIMÄKI I.
Published: December 2008

Cardiac and vascular function is mainly under autonomic nervous control within seconds to minutes, although the control is not mature at birth. We studied sympatho‐vagal control of heart rate and blood pressure in chronically catheterized foetal lambs in the last trimester of gestation. Power spectral analysis was used to quantitate the frequency‐specific heart rate variability (HRV) and blood pressure variability. We performed 15 experiments in seven foetal lambs. These preliminary studies showed that parasympathetic blockade by atropine (eight experiments) had no significant effect on the distribution of HRV to different frequencies. Beta‐sympathetic blockade by propranolol (seven experiments) decreased the ratio of low and mid to high frequency (0.025‐0.13 to 0.13‐1.00 Hz) HRV (P= 0.02). The increased high frequency HRV in the absence of a similar increase in blood pressure variability and tracheal pressure variability suggests enhanced baroreflex responsiveness after propranolol administration. The frequency‐specific sympathetic control of HRV in foetal lambs, the change in ratio of low and mid to high frequency HRV, might have clinical implications in estimating the level of foetal sympathetic activation in the follow‐up of high‐risk pregnancies.
Modulation of systolic and diastolic function by endothelin‐1: relation to coronary flow
Authors: OFFSTAD J. , TØNNESSEN T. , KIRKEBØEN K. A. , ILEBEKK A. , DOWNING S. E.
Published: December 2008

Different conclusions have been reached with regard to the effect of endothelin (ET‐1) on cardiac contractility. We examined systolic and diastolic function in response to constant known concentrations of ET‐1 with or without ET‐1 induced reductions in coronary flow (CF). Rat hearts (n= 21) were buffer‐perfused using constant coronary flow (cCF) or constant perfusion pressure (cPP). Left ventricular function was assessed isovolumically. Addition of ET‐1 (10‐9M) in the cCF group caused a gradual increase in PP from 61 ± 2 to 165±6mmHg (mean±SE) (P < 0.01). Within 10 min left ventricular systolic pressure (LVSP) increased from 111 ± 2 to a maximum of 134±4mmHg (P <0.01) and[L\dP/dt]increased from 1640 ± 81 to a maximum of 2020 ± 92 mmHg s“1(P <0.01). After 15 min left ventricular end diastolic pressure (LVEDP), a measure of diastolic stiffness (DS), also increased. With ET‐1 (108M), similar haemodynamic alterations appeared more rapidly. In the cPP group, ET‐1 (10”9M) caused a sharp decrease in CF and LVSP fell from 115 ± 8 to 62±12 mmHg at 10 min (P <0.001). Systolic function remained stable at a reduced level for 1 h. DS did not change. Thus, ET‐1 possesses positive inotropic effects and increases diastolic stiffness. Both effects may be masked by vasoconstriction‐induced ischaemia.
Ovarian levels of epidermal growth factor receptor mRNA in the rat‐a postovulatory decrease
Authors: ASSARSSON B. , NILSSON I. , SELSTAM G.
Published: December 2008

Members of the epidermal growth factor (EGF) family have many different effects on ovarian cells including a strong inhibition of estradiol‐17β production. An increased binding of the EGF family to its receptor is seen at the time of ovulation. The aim of the present study was to measure the mRNA levels of the EGF receptor in the preovulatory follicle and to see if the levels are still high after functional luteolysis.

The mRNA of the EGF receptor was measured in whole ovaries, follicles and corpora lutea. Pregnant mare serum gonadotrophin (PMSG) stimulated rats were used to get denned follicles. To achieve luteolytic corpora lutea on day 11, the adult female pseudopregnant rat model was used. Determination of the EGF receptor mRNA was performed with solution hybridization analysis, using a 768 bp long probe of the human EGF receptor (2318–3085).

A two‐fold increase in the mRNA levels of the EGF receptor was registered between 09.00 and 21.00 h during the proestrus day in the preovulatory follicle. Concurrently, serum estradiol‐17β levels decreased from 420 ± 65 to 79 ± 6 pM. High levels of EGF receptor proteins in the preovulatory follicle were verified by immunohistochemistry. The levels of EGF receptor mRNA was decreasing from 25.4 ± 4.4 fmol mg‐1 in the corpus luteum on day 1 to 7.6 ± 9.9 fmol mg‐1 on day 11. Thus, the high amounts of EGF receptor in the ovary during the late preovulatory period might be involved in the regulation of ovarian estradiol‐17β production.
Release of somatostatin, neurotensin and vasoactive intestinal peptide upon inhibition of gastric acid secretion by duodenal acid and hyperosmolal solutions in the conscious rat
Authors: WALLIN C. , GRUPCEV G. , EMÅS S. , THEODORSSON E. , HELLSTRÖM P. M.
Published: December 2008

The inhibitory effect of duodenal exposure to acid and hyperosmolal solutions on pentagastrin‐stimulated gastric acid secretion was studied in conscious rats equipped with chronic gastric fistula and duodenal Thiry‐Vella loop. The loop was challenged with saline, HCl or hyperosmolal polyethylene glycol. Gastric acid secretion was measured in samples from the gastric fistula. Gut peptide concentrations were measured in duodenal perfusates collected each 30 min, and in plasma samples collected both during stimulated acid secretion alone, and at the end of experiments in combination with luminal challenges of the loops. During pentagastrin‐stimulated gastric acid secretion, luminal perfusion of the duodenal loop with acid caused inhibition of acid secretion (P < 0.001) and a prominent release of somatostatin both to the lumen (P < 0.001) and to the circulation (P < 0.05). Also, neurotensin (P < 0.01) and vasoactive intestinal peptide (P < 0.01) were released to the lumen, but not to the circulation. Upon perfusion of the duodenal loop with hyperosmolal polyethylene glycol, acid secretion was inhibited (P < 0.05) and somatostatin alone was released to the luminal side (P < 0.01). In conclusion, duodenal exposure to acid inhibits pentagastrin‐stimulated gastric acid secretion and releases SOM to the circulation that may directly inhibit acid secretion. Concomitantly, somatostatin (SOM), neurotensin and vasoactive intestinal peptide are released to the lumen. Duodenal exposure to hyperosmolal polyethylene glycol inhibits acid secretion with a luminal release of SOM only. Thus, luminal acid and hyperosmolal solutions inhibit gastric acid secretion by separate mechanisms. After acid or hyperosmolal challenge, the release of SOM to the circulation indicates gastric acid inhibition in an endocrine manner, while a luminal release of gut peptides indicates a local peptide overflow that might be of importance via paracrine regulatory mechanisms in the intact animal.