bluuebunny/crossref_metadata_2025 huggingface dataset:
A study in the maintenance phase of ischaemic acute renal failure in the rat
Authors: BAYATI A.
Published: December 2008

The fate of the trapped deformed erythrocytes seen in the early recirculation phase after ischaemia and the generation of long Tamm‐Horsfall (TH) cylinders in the renal medulla during the first week after recirculation was studied in rats. In an in‐vitro study the effects of different concentrations of TH protein on the permeability to Na+ of a semipermeable membrane were also investigated. The trapping of erythrocytes was found to be a reflow phenomenon, as there was no increase in the capillary area of the medulla in kidneys subjected to ischaemia but with no recirculation. This area increased to a maximum of 34.6 ± 2.07% 20 min after recirculation and decreased to a normal value of 3.3 ± 0.74% 1 day after the primary ischaemia. The area occupied by cylinders increased to a maximum of 19.2 ± 1.4% 2 days after the primary damage and was as large as 16.7 ± 1.47 % after 1 week. It was also shown that the diffusion half‐time of Na+ ions across a semipermeable membrane increased from 11.4 ± 0.45 min to a maximum of 32.2 ± 2.19 min with a protein concentration of 1 mg ml‐1. It was concluded that the trapping of erythrocytes alone could not explain the decrease in renal function 1 week after the primary damage, but that the blockade of the tubules by the long homogeneous TH cylinders could be responsible for this decrease.
Binding of cholecystokinin and somatostatin to isolated porcine gastric mucosal cells and effects on aminopyrine uptake
Authors: SJÖDIN L. , ENGLUND L. J. , MÅRDH S.
Published: December 2008

Mucosal cells were prepared by enzymatic digestion of porcine gastric mucosa with pronase and collagenase. The resulting cell suspension contained 10–15% parietal cells, which responded to histamine stimulation by an up to 20‐fold increase in [14C]aminopyrine accumulation over control levels. Cholecystokinin‐8 (CCK‐8) evoked a more moderate stimulation of [14C]aminopyrine accumulation, whereas somatostatin inhibited histamine‐stimulated accumulation. Parietal cells were enriched by elutriation and isopycnic centrifugation on density gradients of Percoll. A fraction with 60% parietal cells bound approximately three times more iodinated CCK‐8 than a fraction containing 70% non‐parietal cells. Binding of [125I]BH‐CCK‐8 to preparations containing 30–60% parietal cells was specifically inhibited to about 50% by 10‐9 M unlabelled CCK‐8 but not by bombesin. Cell fractions containing about 30% parietal cells also bound [125I]somatostatin. Unlabelled somatostatin at 10‐9 M inhibited tracer binding by about 50%, while CCK‐8 did not affect somatostatin binding to such a preparation. The results suggest the existence of specific receptors for CCK and somatostatin on porcine parietal cells exerting a regulatory influence on acid secretion.
Muscarinic supersensitivity in the rat urinary bladder after capsaicin pretreatment
Authors: MALMGREN A. , EKBLAD E. , SUNDLER F. , ANDERSSON K.‐E. , ANDERSSON P.O.
Published: December 2008

The effects of capsaicin on urinary bladder function have been investigated in adult rats. Ten days after capsaicin treatment immunocytochemical investigations showed a nearly complete disappearance of substance P (SP) and calcitonin gene‐related peptide (CGRP) in all parts of the bladder. Recordings of micturition patterns and cystometrical investigations in conscious animals revealed no functional effects of capsaicin treatment.

In‐vitro experiments showed that the contractile response to substance P was similar before and after capsaicin treatment and CGRP exerted no contractile effects on the urinary bladder in either group of rats.

The concentration–response curve to carbachol as well as the frequency‐response curve to electrical stimulation were significantly shifted to the left in bladder muscle after capsaicin treatment. However, the maximal responses were similar in control and capsaicin‐treated bladders. In the presence of scopolamine the maximal response to electrical stimulation was clearly lower in bladders subjected to capsaicin treatment than in controls.

In conclusion, depletion of substance P and CGRP in the rat urinary bladder by capsaicin induced no supersensitivity to these peptides. However, the increased sensitivity to carbachol and to electrical stimulation seen after capsaicin treatment indicates the development of a supersensitivity to muscarinic receptor stimulation. Despite this supersensitivity in vitro no functional effects of capsaicin treatment were found in vivo.
Transport of serotonin from the rat jejunal lumen into mesenteric veins in vivo
Authors: LARSSON I. , GRÖNSTAD K. O. , DAHLSTRÖM A. , AHLMAN H.
Published: December 2008

The transport of labelled (hot) and non‐labelled (cold) serotonin (5‐HT) into the mesenteric venous circulation was studied after instillation of test solutions into an isolated jejunal loop of anaesthetized rats. After instillation of [3H]H2O and [14C]5‐HT there was an almost parallel appearance of the isotopes in mesenteric venous blood. After instillation of 5‐HT a marked early increase of the total amounts of cold 5‐HT was observed in mesenteric veins compared with animals instilled with saline only. In a third type of experiment the label was detected in mesenteric venous whole blood after instillation of [3H]5‐HT into the gut lumen. After hydrolysis of blood cells and protein precipitation the samples were fractionated and determined for 5‐HT and metabolites. Only 5‐HT was detected in these fractions. The label was present within 5‐HT peaks in three out of eight animals. The experiments indicate rapid transport of 5‐HT (or metabolites) across the rat jejunal mucosa. These substances may be bound to a binding protein in platelets since the isotope was detected in whole blood but more seldom in supernatants after hydrolysis and precipitation.
Atropine treatment induced cholinergic supersensitivity at receptor and second messenger levels in the rat salivary gland
Authors: WESTLIND‐DANIELSSON A. , MÜLLER R. M. , BARTFAI T.
Published: December 2008

Physiological, biochemical and morphological correlates of chronic treatment of rats with the classical muscarinic antagonist atropine for 14 days (20 mg kg‐1 day‐1 s. c.) were studied in submandibular salivary glands.

The amount of saliva collected from submandibular glands following a single injection of isoproterenol (30 mg kg‐1 i. p.) was significantly larger and had higher protein concentration in rats treated with atropine than in saline‐treated animals. In the glands of atropine‐treated rats a conspicuous increase in the amount of rough endoplasmic reticulum (RER) along with a decrease in the mucous volume was observed in the acinus when examined by light microscopy.

Several biochemical changes were observed in an enriched plasma membrane fraction from the submandibular gland of the atropine‐treated rats: (1) an increase in the number of muscarinic antagonist binding sites (31 ± 3.4%), (2) a decrease in the specific activity of basal adenylate cyclase, (3) a significantly lower Vmax of the adenylate cyclase in the presence of GTP (10 μM) and varying concentrations of Mg2+ (0–22.5 mM) with no apparent change in affinity of the enzyme for Mg2+ but (4) higher magnitude of stimulation in the presence of GTP (100 μM), vasoactive intestinal polypeptide (5 μM), isoproterenol (100 μM), NaF (10 mM) and forskolin (10μM). There was however no change in the density of β‐adrenergic receptors upon atropine treatment.

In tissue slices from the submandibular glands of atropine‐treated rats we found lower basal cAMP levels (decrease 29 ± 6.9%) and no significant change in the phosphatidylinositol breakdown stimulated by carbachol (10‐6 to 10‐4 M).

It appears that chronic blockade of an inhibitory muscarinic input to the adenylate cyclase system is compensated by lowered adenylate cyclase activity. Phosphoinositide metabolism is not subject to the same adaptation, suggesting that cAMP may be the pivotal second messenger in the supersensitive salivary response.
Endothelium‐independent potentiation by neuropeptide Y of vasoconstrictor responses in isolated arteries from rat and rabbit
Authors: GUSTAFSSON H. , NILSSON H.
Published: December 2008

An endothelium‐dependent action of neuropeptide Y (NPY) has been implicated in studies on various vascular beds. In the present study, the requirement of an intact endothelium for NPY‐evoked potentiation of the response to sympathetic nerve stimulation was determined in the small mesenteric arteries of the rat and in the central ear artery of the rabbit. Further, NPY‐mediated inhibition of relaxing influences was determined in small mesenteric arteries of the rat.

Vascular segments were mounted in a double myograph, where one of the two suspended vessels was denuded of endothelium by gently rubbing the intimal surface. Removal of endothelium was verified by en‐face silver staining.

In both species, the response to bursts of transmural field stimulation eliciting 10% of maximal contraction was potentiated 2–4 times in the presence of ionM NPY, whether the endothelium was present or not.

In small mesenteric arteries precontracted with noradrenaline, addition of acetylcholine (1 μM) caused relaxation only in vessels with an intact endothelium. Subsequent addition of ionM NPY enhanced vasoconstriction in both intact and endothelium‐denuded vessels. The endothelium‐independent β‐adrenergic agonist isoprenaline (1 μM) relaxed both intact and denuded small mesenteric arteries, and in both further addition of 10 nM NPY increased the contraction to about the same extent.

The results demonstrate that NPY potentiates the responses to sympathetic field stimulation in small mesenteric arteries from the rat and in central ear artery from rabbit whether the endothelium is present or not. NPY inhibits both endothelium‐dependent and ‐independent relaxations in small mesenteric arteries from rat.
Sympathetic a‐adrenergic control of large‐bore arterial vessels, arterioles and veins, and of capillary pressure and fluid exchange in whole‐organ cat skeletal muscle
Authors: MASPERS M. , BJÖRNBERG J. , GRÄNDE P.‐O. , MELLANDER S.
Published: December 2008

The sympathetic nervous control of the vascular bed of cat gastrocnemius muscle was studied with a new whole‐organ technique which permits simultaneous, continuous and quantitative measurements of capillary pressure (Pc), capillary fluid exchange and resistance reactions in the whole vascular bed and in its three consecutive sections: large‐bore arterial vessels (> 25 μm), arterioles (< 25 μm) and veins. The results demonstrated a distinct neural control of all three consecutive vascular sections, graded in relation to the rate of nerve excitation up to maximum at 16 Hz. Stimulation at high rates, which in the steady state caused an average rise of overall regional resistance from 15.3 to 120 PRU (7.8‐fold increase), thus raised large‐bore arterial vessel resistance from 8.8 to 64 PRU (7.3‐fold increase), arteriolar resistance from 4.5 to 49 PRU (10.9‐fold increase) and venous resistance from 2.0 to 7 PRU (3.5‐fold increase). The rate of resistance development (PRU s‐1) of the sympathetic constrictor response was much higher in the arteriolar than in the other sections, which indicates that the neural control is especially prompt and efficient in the arterioles. A passive component was shown to contribute to the described responses only on the venous side, but in no case by more than 10% of the total sympathetic venous resistance response, which thus is mainly active. Of special functional importance was that the new technique provided information about the adrenergic control ofPc, in absolute figures. From the control value of 19 mmHg, graded sympathetic stimulation caused a graded decline inPc, at maximum constriction by about 7 mmHg. This resulted in marked net transcapillary fluid absorption, in turn increasing plasma volume.
Brain stem auditory‐evoked potentials in different strains of rodents
Authors: CHEN T.‐J. , CHEN S.‐S.
Published: December 2008

This study was conducted to evaluate variations in brain stem auditory‐evoked potentials (BAEPs) among different strains of rodents. BAEPs were recorded by routine procedures from rodents of different strains or species. These included 22 Long‐Evans, 28 Wistar and 28 Sprague‐Dawley rats, and six hamsters. Within the first 10 ms, there were five consistent and reproducible positive waves of BAEPs in each rodent, named I, II, III, IV and V in correspondence with the nomenclature of waves I‐VII in human BAEPs. These BAEPs were also similar to those observed in other vertebrates and in human controls. However, there were variations in waveforms and peak latencies among rodents, even in the rats of the same strain that came from different laboratory centres. At optimal stimulation intensity, usually around 90 dB, the mean latencies of the waves varied as follows: I, 1.23–1.53 ms; II, 1.88–2.28 ms; III, 2.62–2.94 ms; IV, 3.49–3.97 ms; and V, 4.47–5.14 ms. They were significantly different between species, but not in different strains of rats if they came from the same animal centre. The conduction time in the central portion illustrated by interpeak latencies between I and III, III and V, and I and V was dependent on the species (P < 0.05). When recorded in a soundproof incubator, the minimal hearing threshold showed a significant species difference. The animal BAEP model can be employed for evaluating the physiological function or the pathological conditions of the brain stem. The confirmation of BAEP variations among different species or strains will be helpful in deciding which kind of rodents will be appropriate to serve as animal models for the various purposes of BAEP studies.
Amino acid stimulation of Na, K‐ATPase activity in rat proximal tubule after high‐protein diet
Authors: JAKOBSSON B. , LARSSON S. H. , WIESLANDER Å. , APERIA A.
Published: December 2008

Ouabain‐sensitive (OS) O2 consumption was determined in proximal tubular cells from weanling rats fed 21 % (normal‐protein, NP) or 50% (high‐protein, HP) protein diet for 4 days. Butyric acid 10‐3 M was added as a substrate for mitochondrial respiration and the ionophore amphotericin B (10 μ ml‐1) was used to sodium‐load the cells. OS respiration was higher in HP than in NP cells in both DME and amino acid‐free electrolyte solution (ES). Amphotericin B significantly increased OS respiration in both NP and HP cells, implying that the Na‐K pump was activated by increased intracellular Na. In cells incubated in ES, addition of amino acids stimulated OS respiration significantly in HP cells (16.9 ± 1.4 vs 21.2 ± 1.1 nmol min ‐1 mg‐1 protein) and in NP cells (13.9 ± 0.3 vs 14.9 ± 0.6 nmol min‐1 mg‐1 protein). Stimulation was significantly higher in HP cells (26 ± 4%) than in NP cells (7 ± 4%) (P < 0.001). The amino acids did not stimulate ouabain‐insensitive respiration.

The results indicate that an HP diet to weanling rats will increase proximal tubule cell Na, K‐ATPase‐dependent respiration by enhancing Na entry via the Na‐amino acid symports.
Exocrine and endocrine release of kallikrein after reflex‐induced salivary secretion
Authors: BERG T. , JOHANSEN L. , POULSEN K.
Published: December 2008

Exocrine and endocrine release of rat submandibular gland kallikrein has been shown to be low after parasympathetic and β‐adrenergic stimulation but greatly increased after α‐adrenergic stimulation. In the present study, release of glandular kallikrein was investigated under conditions known to give a reflex‐induced salivary gland response.

Heat stress induced a rich flow of saliva originating in the submandibular glands. Salivary kallikrein secretory rate was higher than after parasympathetic stimulation but lower than after sympathetic stimulation (P < 0.005). Only heat stress increased circulating glandular kallikrein (12.7 ± 0.8 ng ml‐1 before heat exposure and 53.3 ± 14.1 ng ml‐1 40 min afterwards, P < 0.005). There were no indications that the endocrine release of kallikrein was due to non‐specific leakage. Atropine abolished heatinduced salivation and endocrine kallikrein secretion, possibly through interference with central pathways (P < 0.05). However, phentolamine did not, which may indicate an as yet unidentified mediator of endogenous kallikrein release. The salivary gland response to acid and ether was comparable to that observed after parasympathetic nerve stimulation and was abolished by atropine (P < 0.005). Stimuli known to influence other salivary gland ductal cells, such as aggression and starvation followed by drinking, also did not increase the plasma concentration of glandular kallikrein. The fact that various conditions which induce salivation did not increase circulating glandular kallikrein, coupled with the fact that kallikrein concentration was the highest in animals that died from heat stress, may suggest that the increase in circulating glandular kallikrein seen after heat stress may be pathological and could contribute to the development of heat shock.
Atrial natriuretic peptide, renin activity, aldosterone, urine volume and electrolytes during a 24‐h sleep‐wake cycle in man
Authors: LEPPÄLUOTO J. , RUSKOAHO H.
Published: December 2008

To investigate the diurnal variation in the plasma atrial natriuretic peptide (ANP) concentrations and its relation to renin activity, aldosterone, urine volume and electrolytes, blood samples from six healthy male subjects were collected and blood pressure and heart rate recorded every 4 h during a 24‐h sleep–wake period. Systolic blood pressure and heart rate were at the lowest during sleep. Plasma ANP, extracted on Sep‐Pak cartridges and measured by radioimmunoassay, had the highest concentration at midnight and lowest at 04.00 h (27 ± 18 vs 16 ± 18 ng I‐1, mean ± SD, P < 0.05 after normalization of the original values). Plasma renin activity and aldosterone were at the highest at 08.00 and 12.00 h, whereafter they both began to decrease (P < 0.001, also normalized). Urinary volume, sodium, potassium and chloride showed highest values (P < 0.05) between 08.00 and 16.00 h.

Plasma ANP levels did not correlate with systolic blood pressure, heart rate, serum or urinary Na or plasma renin or aldosterone (r = 0.1–0.3, P > 0.05). Plasma renin activity correlated with aldosterone and aldosterone with urinary K (r = 0.66 and 0.58 respectively, P < 0.001).

These results suggest that the low plasma ANP levels found in our subjects at 04.00 h may be associated to diminished atrial distension accompanied by the inactivity of the sleep period. In addition, ANP does not appear to affect the secretion of renin and aldosterone in a normal sleep–wake cycle.
Relationship between interdigestive gallbladder emptying, plasma motilin and migrating motor complex in man
Authors: NILSSON B. I. , SVENBERG T. , TOLLSTRÖM T. , HELLSTRÖM P. M. , SAMUELSON K. , SCHNELL P. ‐O.
Published: December 2008

The aim of this study was to elucidate the importance of biliary output for the regulation of migrating motor complex and the release of plasma motilin. Gallbladder emptying was monitored by hepatobiliary scintigraphy, plasma motilin concentration by radioimmunoassay and gastrointestinal motility by a perfused catheter system. During a total recording time of 46 h and 20 min in 16 volunteers, we observed 29 episodes of gallbladder emptying, 27 plasma motilin peaks and 23 activity fronts (phase 3 activity) of the migrating motor complex (MMC). Twelve episodes of gallbladder emptying started in phase I and continued into phase 2 of the MMC. The remaining 17 episodes of gallbladder emptying started in phase 2, and three of these continued into phase 3 of the MMC. Biliary output was associated with a significant rise in plasma motilin concentration, whereas plasma motilin significantly decreased after the activity fronts. These observations may explain the well‐known fluctuations of plasma motilin concentration in the fasted state. Motilin is released into the circulation as a result of biliary output, while the ensuing activity front of the MMC removes this stimulant from the proximal small bowel, resulting in a fall in plasma motilin. In conclusion, we have confirmed a temporal relationship between biliary output into the duodenum and the release of plasma motilin. The observed transition from phase 1 to phase 2 and from phase 2 to phase 3 of the MMC during gallbladder emptying episodes suggests that biliary output stimulates gastrointestinal motility in the fasted state.
Analysis of endothelin‐1‐induced contractions of guinea‐pig trachea, pulmonary veins and different types of pulmonary arteries
Authors: CARDELL L. O. , UDDMAN R. , EDVINSSON L.
Published: December 2008

Endothelin‐I (ET‐I), a peptide produced by the vascular endothelium, has been found to produce strong and persistent contractions of various blood vessels. In the present study, the effects of ET‐I were studied on isolated pulmonary arteries from four different levels (main pulmonary artery, large lobar arteries, small lobar arteries and intrasegmental arteries) of the guinea‐pig. In addition, the effects of ET‐I on pulmonary arteries were compared with those of pulmonary veins and trachea. ET‐I elicited a strong concentration‐dependent contraction of pulmonary arteries, veins and trachea. The effects of ET‐I were more pronounced in pulmonary arteries than in corresponding veins. Significant regional variations within the pulmonary arterial system were disclosed. The tracheal segments showed the same sensitivity and the same degree of relative maximal contraction as the pulmonary veins. Although the cellular mechanisms behind the action of ET still are not clear, our results favour a direct action of ET‐I on the vascular smooth muscle during vasoconstriction. Furthermore, the ET‐I‐induced contraction in guinea‐pig lung seems to be independent of extracellular calcium.
Task specificity in the control of intrinsic trunk muscles in man
Authors: ODDSSON L. , THORSTENSSON A.
Published: December 2008

The human trunk is a complex mechanical system comprised of large and small segments interconnected with several layers of muscles. An accurate control of this system is important during a variety of everyday tasks such as voluntary movements of the trunk, walking and running. This study was designed to investigate the interaction between muscles controlling the pelvis and the trunk during a variety of movements requiring a finely tuned coordination.

Four subjects carried out seven different forms of fast oscillatory movements of the pelvis and trunk in the sagittal and transverse planes. Electromyographical activity (EMG) was recorded with surface electrodes from the abdominal muscles rectus abdominis (RA), obliquus externus (OE), obliquus internus (OI) and erector spinae (ES), from the hip flexor muscle rectus femoris (RF), the hip extensor muscle gluteus maximus (GM) and from the hip extensor/knee flexor muscles of the hamstrings group (HAM). Movements were recorded with an optoelectronic system (Selspot).

The results indicate that during spontaneous flexion‐extension movements of the trunk there was a basic alternating activation between a pure flexor (RF‐RA‐OE‐OI) and an extensor synergy (ES‐GM‐HAM). Different mixed synergies appeared when more specific patterns of coordination of the pelvis and spine were performed. For example, during pelvic tilts in the sagittal plane, RA‐OE‐OI‐GM formed a synergy which was activated reciprocally with ES.

The neural circuitry controlling muscles of the pelvis and trunk is apparently adaptable to a variety of different tasks. Individual muscles were shown to either cause, brake or prevent a movement and to be integrated in several different task‐specific motor synergies. Such a flexibility of the motor system is important for an accurate control of postural equilibrium and coordinative movements of the pelvis and trunk.
The effects of remobilization and exercise on collagen biosynthesis in rat tendon
Authors: KARPAKKA J. , VÄÄNÄNEN K. , VIRTANEN P. , SAVOLAINEN J. , ORAVA S. , TAKALA T. E. S.
Published: December 2008

The activities of prolyl 4‐hydroxylase (PH) and galactosylhydroxylysyl glucosyl‐transferase (GGT), and the concentration of hydroxyproline (Hyp) were measured in the Achilles and tibialis anterior tendons of rats after periods of o, 3, 7 and 14 days remobilization following a 7‐day cast immobilization. PH, GGT and Hyp were also observed in the soleus and tibialis anterior muscles and the Achilles tendon 2, 5 and 10 days after a single bout of exhaustive exercise. During immobilization, the specific activity of PH decreased by 23% (P < 0.05) and 54% (P < 0.01) in the Achilles and tibialis anterior tendons. A less pronounced decrease was observed in GGT activity. During the remobilization experiment the specific activity of PH increased gradually, whereas GGT activity increased rapidly. The GGT activity was 61–66% (P < 0.01) above the control value in the Achilles and tibialis anterior tendons after 3 days, decreasing to the control level after 14 days. Hyp concentration did not change significantly. In the exercise experiment, the specific activity of PH in the soleus muscle increased by 64% (P < 0.05) 2 days after the prolonged exercise and then decreased gradually to the control level. There were no significant changes in PH or GGT activity in the tibialis anterior muscle. The specific activity of PH and GGT and Hyp concentration remained unchanged in the Achilles tendon. The results suggest that, in the tendon, restoring normal cage activity after immobilization results in acceleration of collagen synthesis. The results suggest also that collagen synthesis of the tendon is insensitive, but that of the soleus muscle is sensitive, to an acute increase in physical activity.
Effects of histamine H2‐receptor blockade on the cardiovascular reflex response to lower‐body negative pressure in man
Authors: SJÖVALL H. , JÖNSSON C. , HÄGGENDAL J. , OLBE L.
Published: December 2008

The role of histamine H2‐receptors in cardiovascular control is unknown. In seven healthy volunteers, we studied how histamine H2‐receptor blockade affected the reflex response to hypovolaemia induced by lower‐body negative pressure (LBNP). In placebo‐treated individuals, LBNP down to ‐40 mmHg did not change systolic pressure but increased diastolic pressure, heart rate, forearm vascular resistance, plasma noradrenaline concentration and plasma renin activity. After pretreatment with ranitidine, a specific histamine H2‐receptor antagonist, the diastolic pressure rise no longer sufficed to maintain a constant systolic pressure during LBNP. Ranitidine pretreatment also attenuated the heart rate response and the rise in plasma renin activity induced by LBNP, but did not significantly change the reflex forearm vasoconstriction or the forearm plasma noradrenaline response.

The results suggest that histamine H2‐receptor blockade attenuates the reflex vasoconstrictor response to lower‐body negative pressure. The mechanism behind this effect remains unknown, but the data do not support the idea that the effect is exerted in the skeletal muscle vascular bed.
Cardiovascular and sympathoadrenal responses to mental stress: a study of sensory intake and rejection reactions
Authors: FREYSCHUSS U. , FAGIUS J. , WALLIN B. G. , BOHLIN G. , PERSKI A. , HJEMDAHL P.
Published: December 2008

Cardiovascular, sympathoadrenal and subjective responses to mental stress induced by two mental challenges eliciting sensory intake (word identification test = WIT) and sensory rejection (colour word conflict test = CWT) reactions were studied in 10 healthy males. Pressor responses to these stressors have been proposed to differ haemodynamically. Sympathoadrenal activity was assessed by arterial and femoral venous plasma catecholamine determinations and direct recordings of muscle sympathetic activity in the right peroneal nerve (MSA). Basal measurements differed little from those made during an active relaxation procedure, with the exception of MSA, which decreased. Both stress tasks elicited increases in heart rate, cardiac output, calf blood flow and brachial and pulmonary arterial blood pressures. WIT and CWT elicited qualitatively similar responses, but the amplitudes of the circulatory responses were lower with WIT, which also was rated as a weaker stressor.

MSA increased during CWT, while marginal increases were seen during WIT. Arterial adrenaline showed a transient increase by 0.14 nmol 1‐1 during WIT. During CWT arterial adrenaline increased significantly by 50%. Increases in arterial adrenaline and subjective stress ratings were related to increases in cardiac output and reductions of systemic vascular resistance. Arterial and femoral venous noradrenaline increased during CWT, while changes during WIT were small. MSA and noradrenaline responses did not correlate to local vascular responses in the calf.

Differences in the responses to mental challenges evoking sensory intake or rejection seem to be of a quantitative rather than a qualitative character.
Gastric mucosal electrical potential difference, pH, blood flow, and morphology during hypoxia and selective gastric ischaemia with and without allopurinol pretreatment in anaesthetized dogs
Authors: HØJGAARD L. , BÜLOW J. B. , MADSEN J.
Published: December 2008

Ischaemia has been implicated in the pathogenesis of gastric mucosal disorders. The aim of this investigation was to study the gastric mucosal electrical potential difference (PD), pH, blood flow and morphology during hypoxia, gastric ischaemia, and gastric ischaemia following inhibition of free radical formation with allopurinol. PD and pH were measured simultaneously with an intragastric microelectrode, and the PD values were corrected for the liquid junction potentials created by the intragastric pH variation. Blood flow was measured by the radiolabelled microsphere technique in 18 anaesthetized dogs. Short general hypoxia and short ischaemia caused reversible declines in PD, increases in pH, and no morphological damage. Ischaemia for 1 h caused a significant decline in PD persistent after reperfusion, an increase in pH, and morphological damage. After allopurinol pretreatment, 1 h ischaemia caused a short initial decline in PD, but after reperfusion PD was normalized. Gross morphology was normal, and histology showed only minor damage. The results therefore support the hypothesis that oxygen‐derived free radicals are involved in gastric mucosal injury occurring during ischaemia and reperfusion.
The effect of post‐natal malnutrition on pepsinogen secretion receptors in weanling rats
Authors: YAHAV J. , FRADKIN A. , DIVER‐HABER A. , JONAS A.
Published: December 2008

Post‐natal malnutrition was induced in rats using the expanded litter model. Pepsinogen secretion of isolated gastric glands in response to several secretagogues was measured. Malnourished 19‐day‐old pups showed no response to carbachol, CCK‐8, gastrin, secretin and ionophore A23187 compared to well‐nourished animals, but showed comparable secretion of pepsinogen after stimulation with dibutyryl cAMP (DiBcAMP). Hydrocortisone treatment for 48 h caused increased pepsinogen accumulation and elevated pepsinogen secretory responsiveness to carbachol and secretin of gastric glands isolated from post‐natal malnourished pups. Our results indicate that isolated gastric glands obtained from well‐nourished rats possess two functionally distinct receptors for gastrin and C‐terminal fragment of CCK. Our study supports the concept that in malnourished rats there is a decreased number of binding sites or/and some post‐receptor defects. Pepsinogen release mechanisms remain unaffected.
Isotonic secretion via frog skin glands in vitro. Water secretion is coupled to the secretion of sodium ions
Authors: NIELSEN R.
Published: December 2008

In isolated frog skin at least three different types of cells are engaged in the transepithelial ion and water transport; these are the granular cells, the mitochondriarich cells and the glandular cells. The experiments presented were carried out on isolated frog skin bathed in Cl‐ or NO3 Ringer's solution, where the active transepithelial Na+ uptake via the granular cells was blocked by amiloride. Transepithelial current and water flow were measured. When a negative current was passed across the skins (the skins were clamped at – 100 mV), the current was mainly carried by a net influx of Cl‐ via the mitochondria‐rich cells. The current had no effect on the transepithelial water movement. This finding indicates that there is nearly no coupling between the Cl‐ flux and the movement of water via the mitochondria‐rich cells. Prostaglandin E2 activates the glandular cells of the exocrine glands in the skin. When prostaglandin E2 was added under these experimental conditions (the skins were clamped at – 100 mV, with amiloride in the apical bathing solution, and the glandular secretion of ions was blocked by the use of NO‐3 Ringer's solution), then the transepithelial current became more negative. This change in current was mainly due to an increase in the Na+ efflux via the glands. Thus PGE2 increase the Na+ conductance of the skin glands. Together with this increase in the Na+ efflux a highly significant increase in the water secretion was observed. The water movement (secretion) across the skin was under these conditions coupled to the PGE2‐induced efflux of Na+, and when one Na+ was pulled from the basolateral to the apical solution via this pathway 215 molecules of water followed. This must be due to electro‐osmosis (friction between ions and water) or current‐induced local osmosis.
Effects of hypothalamic paraventricular nucleus lesion on the cold‐stimulated TSH responses to 5‐HT in male rats
Authors: TOIVONEN M. , TUOMAINEN P. , MÄNNISTÖ P. T.
Published: December 2008

The effects of lesion of the hypothalamic paraventricular nuclei (PVNx), the main thyrotrophic area, on the cold‐stimulated thyrotropin (TSH) responses to intracerebroventricular (i. c. v.) 5‐HT were studied in male rats. PVNx significantly attenuated the cold‐stimulated TSH levels, but significantly affected neither hypothalamic thyrotropin‐releasing hormone nor somatostatin content. Serum T3 levels were significantly decreased 8 days after PVNx. Irrespective of the lesion (sham or PVNx), 5‐HT infusion (9 μg per rat) into the posterior third ventricle attenuated markedly the cold‐stimulated TSH levels, whereas infusion into the anterior third ventricle did not. Bilateral 5‐HT infusions (2 μg per side) into the hypothalamic dorsomedial nuclei significantly decreased serum TSH, but bilateral infusions into the posterior hypothalamic nuclei were without effect. Sham‐lesion and PVNx decreased serum prolactin levels without affecting the stimulation of prolactin secretion by i. c. v. 5‐HT. These results suggest that the inhibitory effect of i. c. v. 5‐HT on TSH secretion and its stimulatory action on prolactin secretion are only partially dependent on the PVN.
Role of different serotonergic receptors in the long‐lasting blood pressure depression following muscle stimulation in the spontaneously hypertensive rat
Authors: HOFFMANN P. , CARLSSON S. , SKARPHEDINSSON J. O. , THORÉN P.
Published: December 2008

In a previous study prolonged low‐frequency muscle stimulation in the hind leg of the spontaneously hypertensive rat (SHR) was shown to induce a reduction in blood pressure (about 15 mmHg) that lasted for many hours. We showed in that study that endorphin and serotonin systems were involved.

In the present study drugs with selective affinity for the serotonin (5‐HT) receptors were used to analyse further the involvement of different serotonin systems. In one group of SHR, a prestimulatory dose of metitepine maleate (a 5‐HT1 and 5‐HT2 receptor antagonist) completely abolished the post‐stimulatory depressor response. The long‐lasting depressor response was still present, although less pronounced, after a bolus dose of the 5‐HT2 blocking agent ritanserin (R 55667) at the start of stimulation. The 5‐HT3 receptor antagonist ICS 205–930 did not influence the response at all, nor did the selective 5‐HT1a receptor agonist 8‐OH‐DPAT enhance the depressor response. These results indicate that the reduction in blood pressure after muscle stimulation is mainly mediated by the 5‐HT1 receptor.
Renal hypertension following aortic constriction is abolished by angiotensin II converting enzyme inhibitor, but not by low‐salt diet
Authors: EKLÖF A.‐C. , APERIA A.
Published: December 2008

This study evaluates the role of different sodium intakes and the role of angiotensin II in the development and the maintenance of renovascular hypertension in rats with constriction of the aorta proximal to the renal arteries. The rats were studied 3 weeks after surgery when the hypertension was well established. Glomerular filtration rate was decreased and filtration fraction was increased in rats with proximal aortic constriction. Low and high salt intakes had no effect on glomerular filtration and filtration fraction. Treatment with angiotensin II converting enzyme inhibitor increased the glomerular filtration rate and reduced the filtration fraction in rats with proximal aortic constriction to the same levels as in control rats. Serum levels of angiotensin II were about the same in rats with proximal aortic constriction as in control rats.
The concentration of ouabain binding sites in biopsies of uterine muscle
Authors: EVERTS M. E. , SKAJAA K. , HANSEN K.
Published: December 2008

The concentration of Na, K‐ATPase in biopsies of uterine muscle was determined bymeasurement of [3H]ouabain binding in the presence of vanadate. For this purpose amethod previously described for skeletal muscle (Norgaard et al. 1983) was modified. Biopsies were obtained from uterine muscle from pregnant women (during caesariansection), non‐pregnant women (during hysterectomy) and from adult, non‐pregnantguinea‐pigs and rats.

The ouabain binding site concentration in uterine muscle of the pregnant women averaged 72 ± 2 pmol g‐1wet wt (n= 8), with an apparent dissociation constant (KD) for ouabain of 3 times 10‐9mol 1‐1. The ouabain‐binding capacity in uterine muscle of the non‐pregnant women amounted to 83 ± 9 pmol g‐1wet wt (n = 8). In uterine muscle of the guinea‐pig, two populations of ouabain binding sites were observed: one with a maximum binding capacity of 230 pmol g‐1wet wt and an apparent KDof 1.6 times 10‐6mol 1‐1, and one with a maximum capacity of 62 pmol g‐1wet wt and an apparent KDof 5 times 10‐8mol 1‐1.

Immediate freezing of the biopsies in liquid N2and storage at‐60 °C for up to 6 weeks caused no change in ouabain‐binding capacity. The dry weight/wet weight ratio of the samples from different subjects showed values of around 20±.

It is concluded that the concentration of Na‐K pumps in human uterine muscle can be quantified by [3H]ouabain binding using samples weighing 5–10 mg. The method may provide a useful approach in clinical studies, i.e. analysis of the changes in Na, K‐ATPase concentration that may occur as a basis for disturbances of labour.
Influence of serotonin on total intravascular capacity in the anaesthetized dog
Authors: HEDBERG P. A. , RUTLEN D. L.
Published: December 2008

The influence of serotonin on intravascular volume in the total capacitance circulation has not previously been examined. Thus, blood was drained from the venae cavae to an extracorporeal reservoir and returned to the right atrium at a constant rate so that total intravascular volume changes could be recorded as the inverse of changes in reservoir volume in 31 anaesthetized dogs.

Thus, serotonin causes a biphasic change in total intravascular volume. The initial decrease in intravascular volume is not mediated by a reflex or by 5‐HT1, 5–HT2, or α‐adrenergic receptor stimulation. The late intravascular volume increment appears to be mediated, at least in part, by preganglionic or ganglionic stimulation, which may well be at a 5–HT1receptor. In an animal with an intact circulation, the biphasic volume change might be expected to act via the Starling mechanism to first increase and then decrease cardiac output and thereby enhance the effect of the biphasic total peripheral resistance change on arterial pressure.

Serotonin (588 ± 47 μg) in the left atrium was associated with an initial decrease in intravascular volume of 39 ± 12 ml(P < 0.01) followed by an increase of 129 ± 31 ml (P < 0.01) above control at 20 min. Mean arterial pressure increased from a control of 74 ± 4 mm Hg to 99 ± 7 mmHg (P < 0.01) initially and then decreased to 64 ±5 mm Hg (P < 0.05) at 20 min. Following ganglionic blockade with mecamylamine, serotonin caused only a decrease in intravascular volume, which was 73 ± 12 ml (P < 0.01) at 20 min. 5‐HT2and α‐adrenergic blockade with ketanserin did not attenuate the early decrease in intravascular volume. 5‐Carboxamidotryptamine (82 ± 39 μg), a 5‐HT1agonist, was associated with only an increase in intravascular volume, which was 82 ± 13 ml (P < 0.01) at 20 min and which was abolished after ganglionic blockade.
Influence of angiotensin on total intravascular capacity in the anaesthetized pig
Authors: RUTLEN D. L. , HELGESEN K. G. , CHRISTENSEN G. , VENGEN Ø. A. , ILEBEKK A.
Published: December 2008

The present study examined the influence of angiotensin on total intravascular capacity. In eight anaesthetized pigs, splenectomy, carotid sinus denervation and cervical vagotomy were performed. Blood was drained from the venae cavae to an extracorporeal reservoir and returned to the right atrium at a constant rate so that changes in total intravascular volume could be recorded as the inverse of changes in reservoir volume. Angiotensin administration at 0.2μg kg‐1 min‐1 i.v. for 5 min was associated with a decrease in total intravascular volume of 57 ± 6 ml (P < 0.05) and an increase in aortic pressure from 96 ± 5 to 119 ± 6mmHg (P < 0.05). With subsequent angiotensin administration in five of the animals, the responses were not attenuated. In five of the animals, angiotensin was associated with a decrease in intravascular volume of 72 ± 8 ml (P < 0.05) before abdominal evisceration and 33 ± 13 ml (P < 0.05) after evisceration. These responses were significantly different from each other. In four of these eviscerated animals, angiotensin was associated with a decrease in intravascular volume of 35 ± 17 ml (P < 0.05) before ligation of all four limbs and a decrease of 36 ± 4 ml (P < 0.05) after limb ligation. Thus, angiotensin acts directly to decrease total intravascular volume. The decrease is due to decreases in both splanchnic and extrasplanchnic volume. The extrasplanchnic volume decrement is not due to decreases in skeletal muscle or cutaneous tissue intravascular capacity in the limbs.
Effects of indole‐pyruvic acid on sleep and food intake in the rat
Authors: PICH E. MERLO , SOLFRINI V. , BIAGINI G. , FUXE K. , AGNATI L. F.
Published: December 2008

Indole‐pyruvic acid was studied for its short‐ and long‐term effects on electro‐encephalographic sleep and on food intake in rats implanted with cortical and muscular electrodes. Following a single injection, indole‐pyruvic acid (10–50 mg kg‐1 i.p.) reduced by 16–23 min (range) the latency of the first slow‐wave episode in a dose‐related fashion and produced a significant increase in slow‐wave sleep time (12–40%) in doses of 10–30 mg kg‐1. Rapid eye movement sleep latency and rapid eye movement sleep time were increased (by 23–37 min) and reduced (57–71%) respectively. The effects of indole‐pyruvic acid on slow‐wave sleep time were still present after 3, 7 and 14 days of chronic administration (10 mg kg‐1 day‐1), whereas tolerance to the effect of indole‐pyruvic acid on rapid eye movement sleep was observed. Daily food consumption was reduced (20–28%) by acute administration of indole‐pyruvic acid (15–30 mg kg‐1 i.p.), but tolerance developed after 5 days of repeated injections. These findings are in accordance with previous evidence suggesting that indole‐pyruvic acid effects may be related to the activation of central serotonin neurons, which are involved in the inhibitory control of sleep and food intake.
Secretory effects of 5‐hydroxytryptamine following neonatal sympathectomy in rat parotid gland
Authors: HENRIKSSON R. , SUNDSTRÖM S. , DANIELSSON Å. , HELLSTRÖM S.
Published: December 2008

Unilateral sympathetic denervation of rat parotid glands was performed within 4 h after birth. Nine weeks later the glands were used for in‐vitro studies of amylase secretion, and 86Rb+ was used as a marker for potassium efflux. The non‐denervated contralateral glands served as controls. The tissue concentrations of 5‐hydroxytryptamine and its metabolite 5‐hydroxyindole acetic acid were also measured. 5‐Hydroxytryptamine caused a significant dose‐dependent increase in amylase secretion, which was inhibited by methysergide. There was no difference between controls and denervated glands. 5‐Hydroxytryptamine was without effect on potassium efflux from either denervated or control glands. The sympathectomy caused increased levels of 5‐hydroxytryptamine and 5‐hydroxyindole acetic acid as compared with contralateral controls. The results suggest that 5‐hydroxytryptamine influences the two main secretory processes in rat parotid gland differently. A significant amylase discharge was seen following 5‐hydroxytryptamine stimulation, whereas no effect was seen on 86Rb+ efflux. Although it is also proposed that there are no 5‐hydroxytryptamine‐associated nerves in the superior cervical ganglion innervating parotid tissue, it seems that there is a complex connection between the sympathetic pathway and the serotoninergic system.
Colchicine blocks the effects of secretin on bile duct cell tubulovesicles and plasma membrane geometry and impairs ductular HCO3‐ secretion in the pig
Authors: VEEL T. , BUANES T. , GROTMOL T. , ENGELAND E. , RAEDER M. G.
Published: December 2008

Secretin causes the bile duct cells to secrete HCO3‐. To examine whether the transformation of duct cell ultrastructure that follows secretin stimulation depends on microtubules and is important for ductular HCO3‐ secretion, we examined the effect of colchicine on ductular HCO3‐ secretion and on the morphology of cells lining bile ductules of anaesthetized pigs. Colchicine blocked secretin‐dependent cytoplasmic clearance of tubulovesicles and prevented expansion of the basolateral plasma membrane in duct cells and reduced the ductular HCO3‐ secretory response from 132 ± 25 μmol min‐1 to 97 ± 14 μmol min‐1. In contrast, lumicolchicine did not affect secretin‐dependent tubulovesicle clearance or plasma membrane geometry or ductular HCO3‐ secretion. Accordingly, secretin‐dependent cytoplasmic clearance of tubulovesicles in bile duct cells appears to depend on microtubules and to be important for ductular HCO3‐ secretion.