bluuebunny/crossref_metadata_2025 huggingface dataset:
The role of sarcoplasmic reticulum in endothelium‐dependent and endothelium‐independent rhythmic contractions in the rabbit mesenteric artery
Authors: OMOTE M. , MIZUSAWA H.
Published: December 2008

Upon stimulation with phenylephrine, the rabbit mesenteric artery displays endo‐thelium‐dependent and endothelium‐independent rhythmic contractions in the absence and the presence of ryanodine, respectively. For examination of the involvement of the sarcoplasmic reticulum (SR) in these two types of rhythmic contractions, the mesenteric ring was suspended in an organ chamber for isometric tension recordings. Phenylephrine induced endothelium‐dependent rhythmic contractions (EDRC), which were converted to endothelium‐independent rhythmic contractions (EIRC) by the subsequent addition of ryanodine. Cyclopiazonic acid (CPA) also induced EIRC in the artery contracted with phenylephrine. The nifedipine‐treated artery displayed neither EDRC upon phenylephrine stimulation nor EIRC by the addition of ryanodine or CPA; however, these agents relaxed the arteries. Phenylephrine induced EDRC in the artery treated with the K+channel antagonist sparteine, but these rhythmic contractions were converted to a sustained contraction by ryanodine and CPA without producing relaxation of the artery. Ryanodine and CPA inhibited both phenylephrine‐induced Ca2+release from the SR and Ca2+sequestration, without affecting Ca2+influx across the plasmalemma, evaluated by monitoring agonist‐induced contractions. These findings indicate that: (1) the EDRC may be attributed to Ca2+release from the SR, which may be charged by Ca2+influx via the voltage‐dependent Ca2+channel; and (2) the EIRC may arise from functional impairment of the SR and by the subsequent increase in the K+efflux, presumably via the Ca2+‐activated K+channel.
Evidence for an adrenergic innervation of the adrenal cortical blood vessels in rats
Authors: CARLSSON S. , JÓNSDÓTTIR I. H. , SKARPHEDINSSON J. O. , THORÉN P.
Published: December 2008

The aim of this study was to investigate the blood flow in the adrenal cortex of the rat. Relative changes in the adrenal cortical blood flow were continuously measured by Laser Doppler flowmetry in 33 chloralose‐anaesthetized artificially ventilated rats during electrical stimulation (1 ms, 5 V) of the left great splanchnic nerve (LGSN), which conveys both pre‐ and post‐ganglionic nerve fibres to the adrenal gland. Laser Doppler flux (LDF) was decreased and regional resistance (RR) was increased by augmenting nerve stimulation at increasingly higher frequencies (2, 4, 8, 20 and 40 Hz). The decrease in LDF, when compared to pre‐drug stimulations at 4 Hz was partially or totally inhibited by the adrenergic blocking agents trimethaphan (TRIM), guanethidine (GUA) and aj‐blockade with prazosin (PRAZ). Furthermore, both the decrease in LDF and the increase in RR were either completely or partially blocked by stimulation at 40 Hz after TRIM‐treatment and GUA‐treatment. It is concluded that die adrenal cortex in die rat is innervated by post‐ganglionic adrenergic nerve fibres, which are involved in the regulation of blood flow in the adrenal cortex.
Dopamine and vasoactive intestinal peptide stimulate cyclic adenosine‐3,5 ‐monophosphate formation in isolated rat villus and crypt duodenocytes
Authors: SÄFSTEN B. , FLEMSTRÖM G.
Published: December 2008

Secretion of bicarbonate increases the pH at the duodenal mucosal surface, a process which contributes to the protection against acid/pepsin injury. Previously, we have shown that dopaminergic compounds stimulate the duodenal bicarbonate secretionin situ, in the anaesthetized rat, through an action on peripheral dopamine D1 receptors. In order to study the possible involvement of cyclic adenosine‐3′,5′‐monophosphate (cAMP) as an intracellular mediator in enterocytes isolated from rat duodenum, cells were collected by a combination of enzyme treatment and calcium chelation. Two major cell fractions, one mainly from villi and the other mainly of crypt origin, were studied. In the villus cell fraction, the activity of alkaline phosphatase was 1.6 ± 0.2μmol mg protein‐1min‐1and that of sucrase 98.8± 16.4 nmol mg protein‐1min‐1. In the crypt fraction, activities were 0.7 ± 0.1 and 28± 10.5, respectively. Effects of dopamine, two selective dopamine receptor agonists and vasoactive intestinal peptide (VIP) on intracellular accumulation of cAMP were examined by radioimmunoassay (RIA).

In the crypt cell fraction, VIP (10‐7M) caused an increase in cAMP which was maximal after 5 min (78 ± 28% above control,P <0.01). In the villus cell fraction, maximal responses to VIP (60 ± 24% above control,P <0.05), did not occur until after 60 min of incubation. In contrast, there were no significant differences between villi and crypt enterocytes in respect to effects of dopamine, the dopamine Dl‐receptor agonist SKF‐38393 and the D2‐receptor agonist quinpirole. Dopamine (10‐5M), as well as SKF‐38393 (10‐5M), increased (P <0.05) cAMP accumulation with a maximal response after 5–15 min of incubation. Quinpirole (10‐5M), decreased (P <0.05) cAMP accumulation in both crypt and villi cell fractions.

The results suggest that cAMP is involved as a messenger in dopamine D1 receptor‐mediated stimulation of duodenal ulceroprotective alkaline secretion. The time course of cAMP accumulation induced by the potent duodenal secretagogue VIP is different in crypt and villus cells.
The effects of oestrogen and progesterone on insulin sensitivity in female rats
Authors: KUMAGAI S. , HOLMÄNG A. , BJÖRNTORP P.
Published: December 2008

The effects of 17‐β‐oestradiol (E2) and progesterone (P) on insulin sensitivity were determined in oophorectomized (OVX) rats by the euglycaemic hyperinsulinaemic clamp technique combined with measurements of insulin‐stimulated 2‐deoxy‐D‐glucose (2‐DOG) transport and glycogen synthesis in white and red parts of the gastrocnemius, the extensor digitorum longus and soleus muscles as well as in the liver (only glycogen synthesis). OVX was followed by insulin resistance in the clamp measurements. This was paralleled by a decreased insulin‐stimulated content of 2‐DOG in muscles, an index of glucose transport. Glycogen synthesis in muscle was also decreased, although to less extent. E2, alone or in combination with P, restored this to values of intact controls, while P alone was followed by insulin resistance. Liver glycogen synthesis was also decreased by OVX but this required combination of E2 and P to be fully restored.

It was concluded that particularly E2 plays an important role in the maintenance of normal insulin sensitivity while P alone seems to be followed by insulin resistance, both effects apparently mainly by regulation of glucose uptake in muscle. E2± P may be of importance for maintenance of normal glycogen synthesis in the liver.
Altering the blood‐brain barrier in the rat by intracarotid infusion of polycations: a comparison between protamine, poly‐L‐lysine and poly‐L‐arginine
Authors: WESTERGREN I. , B. JOHANSSON B.
Published: December 2008

To evaluate the role of surface charge for the blood‐brain barrier permeability, the albumin content was determined in the cerebrospinal fluid and in the brain 1 h after intracarotid infusion of protamine sulphate, a natural polycationic protein with a high content of arginine (mol. wt 4000–4400), poly‐L‐arginine (mol. wt 11600) or poly‐L‐lysine (mol. wt 10200).

Five milligrams (4 ± 10‐4 mmol) poly‐L‐arginine increased the albumin content in the brain IS times more than S mg (5 ± 10‐4 mmol) poly‐L‐lysine (P < 0.001) and 3.5 times more than 5 mg (1 times 10‐3 mmol) protamine (P < 0.001); the difference between protamine and poly‐L‐lysine was also significant (P < 0.05). After 0.5 mg (4 ± 10‐4 mmol) poly‐L‐arginine the albumin extravasation was still higher than after 5 mg protamine (P < 0.01) and 5 mg poly‐L‐lysine (P < 0.001). Cisternal albumin increased from control values 0.08 mg ml‐1 to 0.30, 0.46 and 1.21 mg ml‐1 in rats given 5 mg poly‐L‐lysine, protamine and poly‐L‐arginine, respectively (P < 0.01 for difference between arginine and the other two substances).

The higher mol. wt and positive charge of poly‐L‐arginine may at least in part explain the more pronounced albumin leakage after arginine than after protamine. However, the difference between poly‐L‐arginine and poly‐L‐lysine suggests that other factors, possibly related to the guanidino groups, contribute to the blood‐brain barrier opening by poly‐L‐arginine.
Effect of ethanol on hippocampal neurons depends on their behavioural specialization
Authors: ALEXANDROV Yu. I. , GRINCHENKO Yu. V. , LAUKKA S. , JÄRVILEHTO T. , MAZ V. N. , KORPUSOVA A. V.
Published: December 2008

Acute effect of ethanol on hippocampal neurons was studied during food acquisition behaviour in seven rabbits. The rabbits were taught to acquire food from a feeder by pressing a pedal on the same side of the cage. The behaviourally specialized units (L units related to newly learned behaviour and M units related to behaviour formed before learning, e.g. certain movements) were comparable with the ‘plac’ (projectional pyramidal and granular cells) and ‘displac’ (non‐pyramidal interneurons) units of the current classification. The same direction of ethanol effects was found as for the limbic cortex; the number of certain kinds of L units decreased and that of M units increased but there was no significant change in the relative number of L and M units as a whole. The background frequency of L units decreased, but the frequency within activations increased. The results confirm our earlier findings on the most marked depressive effect of ethanol on L units and show that it is the behavioural specialization, not the morphological unit type, which is a major determinant of the ethanol influence.
The antinociceptive effect of non‐noxious sensory stimulation is mediated partly through oxytocinergic mechanisms
Authors: UVNäS‐MOBERG K. , BRUZELIUS G. , ALSTER P. , LUNDEBERG T.
Published: December 2008

The objective of the present study was to investigate whether oxytocinergic mechanisms may contribute to the antinociceptive effect of non‐noxious, sensory stimulation.

To test this hypothesis, oxytocin levels in plasma and cerebrospinal fluid (CSF) were measured in control rats as well as in rats exposed for 30 min to electro‐acupuncture (2 Hz), thermal stimulation (40 oC) or vibration (100 Hz). All modes of stimulation induced significant elevations of oxytocin levels in plasma and/or in CSF, 30 or 90 min after the end of stimulation. Secondly, the antinociceptive effects of these treatments were investigated in the tail‐flick test with and without prior administration of the oxytocin antagonist l‐deamino‐2‐D‐Tyr‐(OEt)‐4‐Thr‐8‐Orn‐oxytocin (1 mg kg‐1 i.p.). All three modes of stimulation caused a significant delay of the tail‐flick latency to the same degree as that caused by injection of oxytocin 1 mg kg‐1 i.p. (electro‐acupuncture P < 0.01, thermal stimulation and vibration P < 0.05). In all cases, the delay was reversed by administration of the oxytocin antagonist (1 rngkg‐1 i.p.). These findings suggest that analgesic effects induced by non‐noxious sensory stimulation may, in part, be mediated through activation of oxytocinergic mechanisms.
In‐vivo glucose uptake and glucose transporter proteins GLUT1 and GLUT3 in brain tissue from streptozotocin‐diabetic rats
Authors: KAINULAINEN H. , SCHÜRMANN A. , VILJA P. , JOOST H. G.
Published: December 2008

The effects of streptozotocin‐induced diabetes (13 weeks) on the in‐vivo glucose uptake and on the protein levels of glucose transporters in rat brain were studied and compared with those in cardiac muscle. Diabetes reduced the uptake of 2‐[3H]deoxyglucose into lobus frontalis by 70%. However, uptake rates corrected for the 4‐fold increase in serum glucose (glucose metabolic index, GMI) were essentially unaltered. The levels of glucose transporter proteins GLUT1 and GLUT3 in crude membranes from brain as assessed by immunoblotting were unaffected by diabetes, whereas GMI and levels of glucose transporters GLUT1 and GLUT4 in heart were reduced by 80 and 65%, respectively. Thus, glucose uptake and levels of glucose transporters in brain, unlike that in insulin sensitive tissues, are normal in long‐term hypo‐insulinaemia.
The exercise pressor response to sustained handgrip does not augment blood flow in the contracting forearm skeletal muscle
Authors: HANSEN J. , JACOBSEN T. N. , AMTORP O.
Published: December 2008

Previous studies have advanced the concept that during sustained handgrip (SHG) reflex increases in blood pressure are able to partially offset increases in tissue pressure and thus effectively maintain increases in muscle blood flow during mild to moderate levels of sustained handgrip. However, this concept is based upon measurements of blood flow to the entire forearm. The aim of this study was to evaluate this concept by simultaneously measuring time‐dependent changes in systemic arterial pressure and blood flow in an active muscle during the actual period of exercise. To accomplish this aim, we measured133Xenon washout from the extensor carpi radialis longus muscle over 3 min of SHG at 15, 30 and 45% of maximal voluntary contraction (MVC). During sustained handgrip at 15% MVC, muscle blood flow increased more than 20 fold from rest to exercise (P < 0.05), even though mean arterial pressure increased by only 12 ± 4 mmHg. This large exercise‐induced hyperaemia was abolished during SHG at both 30 and 45% MVC, despite large and progressive increases in mean arterial pressure of 29 ± 3 and 54 ± 5 mmHg, respectively. We conclude that at levels of handgrip above 15% MVC blood pressure ceases to be an important determinant of blood flow in the active skeletal muscle. Importantly, the increases in forearm blood flow that have been reported previously with such levels of static handgrip do not appear to be directed to the most active muscle.
In vivo effects of local and systemic phencyclidine on the extracellular levels of catecholamines and transmitter amino acids in the dorsolateral striatum of anaesthetized rats
Authors: LILLRANK S. M. , O'CONNOR W. T. , SARANSAARI P. , UNGERSTEDT U.
Published: December 2008

The dose‐dependent effects of systemically and locally administered phencyclidine (PCP) on the extracellular levels of dopamine, dihydroxyphenylacetate (DOPAC), homovanillate (HVA), 5‐hydroxyindolacetate (5‐HIAA), γ‐aminobutyrate (GABA), glutamate and aspartate in the dorsolateral striatum of anaesthetized rats were studied byin vivomicrodialysis. Both local (1, 5, 50 and 100 µM) and systemic (2 and 10 mg kg‐1i.p.) PCP caused a dose‐dependent increase in the extracellular levels of dopamine. The lowest PCP doses caused only a moderate but long‐lasting increase in the extracellular levels of dopamine, while the highest PCP doses caused a massive but transient increase followed by a rebound decrease. The low doses of both systemic and local PCP tended to increase the levels of DOPAC, while those of HVA were not changed. The extracellular levels of 5‐HIAA were increased only by the lowest (1 µM) locally administered dose of PCP. GABA levels were increased when PCP was administered locally at two doses. None of the treatments affected the extracellular levels of glutamate and aspartate. The results show that the effects of local and systemic PCP administration are dissimilar on the extracellular levels of 5‐HIAA and GABA and thus provide new information on the neurochemical effects of PCP.
Mechanical and electrophysiological effects of milrinone on the force‐frequency relationship in mammalian myocardium
Authors: MÖRNER S. E. J. N. , ARLOCK P.
Published: December 2008

Isometric force, action potential and current‐voltage relation were studied in guinea‐pig and ferret papillary muscles. Milrinone (1 μu) increased peak twitch force by 40 + 4%, reduced time to peak tension (TPT) by 12.1 ± 3% (n= 6,P< 0.01) and reduced time to half relaxation by 17.3 ± 4.1 % (n= 6,P< 0.01). The effect of milrinone was potentiated by rolipram, a RI‐PDE inhibitor which in itself had no inotropic effect. After the addition of rolipram peak isometric force was increased by 104 + 8% (n= 6,P< 0.001), TPT was further reduced whereas time to half relaxation was slightly increased after the addition of rolipram. Action potential duration at 75% repolarization was decreased by 11 + 5 ms (n= 6,P< 0.05). Milrinone also potentiated the second inward current (Ist) by 21 + 3.2% (n= 6,P< 0.01). Peak twitch force in response to a test stimulus after an interval, i.e. mechanical restitution was increased at all intervals. The onset of restitution was faster and time to full restitution also shortened. Maximum postextrasystolic potentiation was greater in the presence of milrinone, whereas relative potentiation was smaller in presence of milrinone (46 ± 7%) than in control (74 ± 7%). The recirculation fraction of activator calcium was enhanced by milrinone from 0.35 ± 0.04 to 0.48 ± 0.07. The results support the view that the positive inotropic effect of milrinone is due to a greater inflow of calcium during the action potential and a more efficient intracellular calcium handling. In addition, the effect on mechanical restitution would suggest a more direct action on sarcoplasmic reticulum calcium handling.
Dynamic changes of myocardial inositoltrisphosphate and cyclic nucleotides: relationship to contractile response in the perfused working rat heart after adrenergic and muscarinic agonist stimulation
Authors: MARTINUSSEN H. J. , WALDENSTRÖM A. , RONQJJIST G.
Published: December 2008

Initial and late effects by adrenergic and muscarinic agonists on inositol (1,4,5) trisphosphate (IP3) and cyclic nucleotide levels were determined and correlated to mechanical response in perfused rat hearts. Forty‐three rat hearts were perfused with Krebs‐Henseleit buffer in a modified Langendorff apparatus as a working preparation. The hearts were perfused as controls (n= 11), or with noradrenaline (10‐6mol 1‐1) (n= 21), or with carbachol (3 × 10‐7mol 1‐1) (n= 11) added to the perfusion buffer. The hearts were frozen at 20 s, 30 s and 40 min after addition of noradrenaline and at 20 s and 40 min after addition of carbachol, and after 5 and 45 min of control perfusion. cAMP and cGMP were determined by radioligand methods and IP3by a combined fast performance liquid chromatography (FPLC) ‐ isotachophoretic method. cAMP increased by 36% within 20 s followed by a decrease (22%) during the 10 s following noradrenaline addition. After 40 min cAMP regained its value near that of 20 s. Noradrenaline perfusion did not influence IP3levels during the first 30 s although the value at 40 min was significantly higher (59%). IP3increased (42%) after 20 s of carbachol perfusion followed by a 25 % decrease at 40 min.

Sustained stimulation of β‐receptors (after 40 min in our model) resulted in a repeated increase in cAMP only, without an increase in contractility. Muscarinic receptor stimulation resulted in an early increase in IP3content without a change in mechanical function whereas a‐adrenergic stimulation resulted in only a late increase in IP3content of isolated whole hearts still without any alteration in contractility.
The effect of exercise on the contractile properties of single skinned fast‐ and slow‐twitch skeletal muscle fibres from the adult rat
Authors: LYNCH G. S. , WILLIAMS D. A.
Published: December 2008

The effects of long‐term endurance exercise on the contractile properties of single skinned muscle fibres from adult rats, were investigated. Adult (4‐month‐old) male rats were subjected to a 16‐week, high‐intensity endurance swimming programme, where animals carried a load (corresponding to 2% of body wt), during all 2‐h training sessions. At the conclusion of the training period, muscle fibres isolated from the extensor digitorum longus (EDL), and soleus (SOL), could be classified into distinct classes or fibre types on the basis of their Ca2+‐ and Sr2+‐activated contractile characteristics. The fast‐twitch EDL comprised two fibre populations, while the slow‐twitch SOL was found to be composed of three distinct fibre types. Endurance swimming modified the contractile characteristics of fibres from both the EDL and SOL, but exerted greater influence on those of the SOL. This was illustrated by significant increases in the sensitivity to Ca2+ and Sr2+, and a lower threshold for contraction by these activating ions, in the exercised group. Not one of the total of 272 fibres sampled, exhibited mixed fast‐ and slow‐twitch contractile characteristics, often associated with exercise‐induced fibre type transformations. Thus, high‐intensity endurance swimming induced changes in some single muscle fibre contractile properties of adult rats, but did not cause major changes in fibre type distribution.
Rhythmic contractions in isolated small arteries of rat: role of K+channels and the Na+, K+‐pump
Authors: GUSTAFSSON H. , NILSSON H.
Published: December 2008

Small mesenteric arteries from Wistar rats display rhythmic tension oscillations, associated with oscillations in membrane potential, when stimulated with noradrenaline. The purpose of this study was to investigate the role of potassium conductance and Na+, K+‐pump activity in the generation of these oscillations. The effect on the rhythmic contractions of several agents, interacting with K+channels, was studied. Application of apamin, pinacidil or glibenclamide did not affect the rhythmic activity. Tetraethylam‐monium (TEA) increased the frequency of the rhythmic contractions, while application of 4‐aminopyridine (4‐AP) increased the amplitude by approximately 50%, with no changes in frequency. Ba2+, on the other hand, impaired the rhythmic contractions or converted them to irregular oscillations in the presence of functional endothelium, but did not affect oscillations in endothelium‐denuded vessels. Ouabain or exposure to K+‐free solution, procedures known to inhibit the Na+, K+‐pump, abolished the rhythmic contractions. This effect was immediate, suggesting that it was due to elimination of the electrogenic action of the Na+, K+‐ATPase, rather than to a change in intracellular ion concentrations. Exposure to an extracellular potassium concentration of more than 20 mM also inhibited the oscillation activity. The results suggest that the oscillations are not caused by, but may be modulated by, variations in potassium conductance. The Na+, K+‐pump seems to play an important role in the generation of rhythmic contractions in these vessels.
Effects of long‐term portal hypertension on structure, active force and content of contractile and structural proteins in smooth muscle of the rat portal vein
Authors: MALMQVIST U.
Published: December 2008

Growth of the smooth muscle cells in the rat portal vein was induced by a partial ligation of the vessel. The ligation caused an increase in the transmural pressure and segments of the portal vein were investigated 6 weeks after the ligation. The spontaneous contractile activity of the ligated veins was similar to that of the control veins. In the ligated vessels the active force at optimal length for force development was doubled, 22.8 ± 1.3 compared with 12.5 ± 1.4 mN for the controls. The cross‐sectional area of the media in the ligated veins, determined on transverse sections, increased from the control value of 0.10 + 0.01 to 0.19 ±0.01 mm2. Electron microscopy revealed that the mean cross‐sectional area of the smooth muscle cells in the ligated portal vein was doubled (controls: 6.4 ± 0.6, hypertrophic: 13.6±1.8μm2). This suggests hypertrophy of the smooth muscle cells in the vessel wall as the cause for the increase in cross‐sectional area of the ligated veins. An increase in the number of intermediate filaments was observed in the hypertrophied smooth muscle. The relative contents of contractile (myosin and actin) and structural (desmin and vimentin) proteins were determined with SDS‐polyacrylamide gel electrophoresis. The actin/myosin and vimentin/actin ratios were unaltered by hypertrophy. The hypertrophied veins showed an increase in the desmin/actin ratio (control: 0.20 ± 0.01, hypertrophied: 0.27 ± 0.03). The increased amounts of desmin correlates with the increased number of intermediate filaments observed by electron microscopy. The mechanical and biochemical data indicate a net synthesis of contractile proteins that occurs in proportion to the increase in cell mass.
Quantification of tissue damage in the feline small intestine during ischaemia‐reperfusion: the importance of free radicals
Authors: WEIXIONG H. , ÁNEMAN A. , NILSSON U. , LUNDGREN O.
Published: December 2008

Intestinal ischaemia is accompanied by characteristic mucosal lesions, which can be graded according to a six‐grade system proposed by Chiu et al. (1970). This report describes a continuous grading system which makes it possible to quantify the intestinal damage in connection with ischaemia‐reperfusion. The present morphometric method is based on quantitative histological analysis of intestinal biopsies performed on 200 histological sections from 44 cat experiments. Radical formation was quantified by infusing close i.a. a spin trap, OXANOH, which produces a secondary stable radical, OXANO‐, after reacting with radicals in the tissue. OXANO‐ concentration was determined in venous blood samples with electron spin resonance. We demonstrate a highly significant correlation between the grading system of Chiu et al. (1970) and the morphometric analysis of this study. The tissue damage was located exclusively in the intestinal villi. Comparing the mucosal damage that occurs during 60 min of intestinal ischaemia (superior mesenteric artery pressure 15–25 mmHg) with that seen during the first 30 min reperfusion this study shows that the villus damage occurring during ischaemia is at least twice as large as the aggravation seen upon reperfusion. Furthermore, the authors demonstrate a significant correlation between rate of radical formation and villus tissue damage particularly during the first 30 min after ischaemia. It is concluded that the proposed quantitative morphological method represents a non‐discrete grading system for evaluating tissue damage in connection with ischaemia‐reperfusion in the small intestine. The ischaemia itself inflicted a more severe damage to the intestine than reperfusion. A significant correlation between damage and radical formation was demonstrated during the reperfusion. However, the results suggest that factors other than radical formation are of importance in explaining the tissue damage upon reperfusion. The nature of these factors is presently unknown.
Characteristics of renal sympathetic nerve activity in experimental congestive heart failure in the rat
Authors: FENG Q; P. , CARLSSON S. , THORÉN P. , HEDNER T.
Published: December 2008

Recently emerging evidence has indicated that efferent renal sympathetic nerve activity (RSNA) is increased in congestive heart failure (CHF). In the present study the cyclic activity of the renal nerve in the normal and CHF rat was studied. An ischaemic myocardial lesion resulting in CHF was induced by left coronary artery ligation. Sham‐operated rats subjected to thoracotomy served as normal controls. Renal sympathetic nerve activity was recorded under chloralose anaesthesia. The neural cycle activity was significantly higher in CHF (47 ±3%) compared with sham‐operated rats (34 + 3%,P< 0.005). Baroreceptor control of RSNA was significantly attenuated in CHF compared with normal control rats (P< 0.005). In response to noxious thermal stimulation by 48oC water immersion of the tail tip, the increase of RSNA was significantly higher in CHF compared with sham‐operated rats. A stepwise 15% blood volume expansion over 5 min which induced no alterations of blood pressure or heart rate (HR) resulted in a gradual decrease of RSNA in control rats by approximately 25% at the end of the volume expansion procedure. In CHF rats however, there was no significant change in RSNA during volume expansion. It is concluded that in CHF rats: (1) efferent RSNA is increased; (2) baroreceptor control of RSNA is decreased; (3) RSNA in response to cutaneous thermal noxious stimulation is exaggerated; and (4) RSNA inhibition by cardiopulmonary receptors is blunted.
Endothelium dependence of prostanoid‐induced relaxation in human hand veins
Authors: ARNER M. , USKI T. , HÖGESTÄTT E. D.
Published: December 2008

The endothelium dependence of prostanoid‐induced relaxation was examined in human isolated hand veins precontracted by endothelin. Indomethacin (10‐6mol l‐1) and the thromboxane A2‐receptor antagonist BM 13.505 (10‐6mol l‐1) were present throughout. The endothelium was removed by insufflating carbogen through the vessel lumen. Prostaglandin (PG) F2α, PGE1PGE2, and prostacyclin (PGI2) elicited concentration‐dependent relaxant effects. Removal of the endothelium reduced the relaxation induced by PGE2αand PGE2, but not that elicited by PGE1and PGI2. The order of potency was PGE2≅ PGE1≅ PGI2≅ PGF2αregardless of the presence or absence of endothelium. The relaxation elicited by an acidified solution of NaNO2(generating nitric oxide) was almost identical in intact and endothelium‐denuded vein segments. The results are compatible with the existence of two prostanoid receptor populations mediating relaxation: (1) one located on the smooth muscle cells and; (2) another present on the endothelium or possibly on the smooth muscle and modulated by the endothelium. The latter receptor appears to be activated by PGF2αand PGE2, but not by PGE1and PGI2.
Wall mechanics of the rat bladder. II. Hydrodynamic studies in the frequency domain
Authors: ANDERSSON S. , KRONSTRÖM A. , HENTSCHEL J.
Published: December 2008

The hydrodynamic properties of the urinary bladder in rat were examined by means of very small periodic changes in volume at different frequencies. The elastance increased with increasing frequency of volume changes, indicating the presence of viscoelastic elements. When the bladder was only moderately distended the influence of viscosity was minor. We consider that the rat bladder examined by this technique is an ideal experimental model for assessment ofzn zwoeffects of pharamacological agents on bladder wall tonus. For example, cholinergic treatment showed a 100% increase in elastance and atropine inhibited this effect completely within 3 min.
Central haemodynamics during morphine abstinence in anaesthetized rats
Authors: DELLE M. , THORÉN P. , RICKSTEN S.‐E.
Published: December 2008

Central haemodynamics were studied in one group of morphine‐dependent rats, and in a non‐dependent control group. before and after administration of repeated bolus doses of naloxone. Dependence was induced by s.c. morphine pellet implantations. Mean arterial pressure (MAP), heart rate (HR), cardiac output (CO) and mean transit time (MTT) were measured in the conscious state, after induction of chloralose anaesthesia and after the administration of naloxone (0.005, 0.05, 0.5 and5 mg kg 1 i.v.). Total peripheral resistance (TPR), stroke volume (SV) and central blood volume (CBV) were subsequently calculated. The haemodynamic variables did not differ significantly in the conscious state, except for a lower SV, when compared with the non‐dependent control group. However, in response to anaesthesia the dependent rats exhibited a greater fall in MAP, mainly due to a TPR decrease. Naloxone elicited a marked increase in MAP in the morphine‐dependent group, which was mainly caused by an increase in TPR. Naloxone induced no significant change compared with the control group in CO and CBV, while SV increased concomitantly with a lowered HR after naloxone in the morphine‐dependent group. These results suggest that the withdrawal hypertension during morphine abstinence was mainly explained by an increase in TPR, reflecting an augmented tone of the resistance vessels. The minor changes in CBV indicate that the tone of the venous capacitance vessels was largely unaffected by naloxone‐induced morphine abstinence.
Effects of dynamic leg exercise on subcutaneous blood flow rate in the lower limb of man
Authors: NIELSEN H. V. , STABERG B. , NIELSEN K. , SEJRSEN P.
Published: December 2008

Subcutaneous blood flow (SBF) was studied simultaneously in the upper arm at heart level and in the lower limb during positional changes and during leg exercise in seven healthy males. SBF was estimated by local clearance of ‘“Xenon registered by portable cadmium telluride detectors. Venous pressure was recorded directly on dorsum on the foot. Changinr the position from supine to head‐up tilt, SBF decreased by 43 % (P < 0.01) at the arm level, 40% at the thigh (P < 0.01), 47% at the calf (P < 0.01) and decreased by 51 % at the ankle level (P < 0.01). Performing 20 heel‐raisings per min in nearly erect posture, SBF increased by 96% at the thigh (P < 0.01), 25% at the calf (P > 0.1) and increased by 18% at the ankle level (P > 0.1). At 40 heel‐raisings per min SBF increased by 99% at the thigh (P < 0.0 1), 121 % at the calf (P < 0.0 1), but only 44% at the ankle level (P > 0.1). During leg exercise subcutaneous vascular resistance was significantly increased at arm and ankle levels. In contrast, a vasodilatory response was noticed at the thigh and calf levels and seemed associated with a decrease in local venous pressure to below the trigger level of the sympathetic veno‐arteriolar reflex mechanism. In conclusion, SBF in the lower limb of man was increased during exercise. The increase in SBF could only partly be ascribed to the concomitant increase in perfusion pressure. The local blood flow response seemed modified by changes in sympathetic nervous activity and metabolic rate.
The plasma membrane calcium ATPase (PMCA) of neurones is electroneutral and exchanges 2 H+ for each Ca2+ or Ba2+ ion extruded
Authors: Thomas Roger C.
Published: December 2008

The coupling between Ca2+ extrusion and H+ uptake by the ubiquitous plasma membrane calcium ATPase (PMCA) has not been measured in any neurone. I have investigated this with Ca2+‐ and pH‐sensitive microelectrodes in large voltage‐clamped snail neurones, which have no Na+–Ca2+ exchangers. The recovery of [Ca2+]i and surface pH after a brief depolarization or Ca2+ injection was not slowed by hyperpolarization to −90 mV from a holding potential of −50 mV, consistent with a 1 Ca2+ : 2 H+ coupling ratio. Since Ca2+ injections proved difficult to quantify, and Ca2+ currents through channels were obscured by K+ currents, Ba2+ was used as a substitute. When the cell was bathed in Ca2+‐free Ba2+ Ringer solution, the K+ currents were blocked and large inward currents were revealed on depolarization. The Ca2+‐sensitive microelectrodes were sensitive to intracellular Ba2+ as well as Ca2+. With equal depolarizations Ba2+ entry appeared larger than Ca2+ entry and generated similar but slower pH changes. Ba2+ extrusion was insensitive to hyperpolarization, blocked by eosin or high pH, and about 5 times slower than Ca2+ extrusion. The ratio of the pH change caused by the extrusion of unit charge of Ba2+ influx to that caused by unit charge of H+ injection was 0.85 ± 0.08 (s.e.m., n= 8), corresponding to a Ba2+ : H+ ratio of 1 : 1.7. Both this ratio and the electroneutrality of the PMCA suggest that the Ca2+ : H+ ratio is 1 : 2, ensuring that after a Ca2+ influx [Ca2+]i recovery is not influenced by the membrane potential and maximizes the conversion of Ca2+ influxes into possible pH signals.
Dissociation of E‐cadherin and β‐catenin in a mouse model of total parenteral nutrition: a mechanism for the loss of epithelial cell proliferation and villus atrophy
Authors: Feng Yongjia , Sun Xiaoyi , Yang Hua , Teitelbaum Daniel H.
Published: December 2008

Total parenteral nutrition (TPN) leads a loss of epithelial barrier function, decline in epithelial cell (EC) proliferation, and decreased expression of E‐cadherin. As a large portion of intracellular β‐catenin is tightly associated with E‐cadherin, we hypothesized that the loss of E‐cadherin would result in a redistribution of intracellular β‐catenin, and could be a contributing mechanism for this TPN‐associated loss of EC proliferation. An assessment of small bowel epithelium was performed in mice given either enteral nutrition (Control) or intravenous nutrition (TPN). TPN significantly down‐regulated E‐cadherin and β‐catenin expression, and resulted in a loss of a colocalization of these factors. TPN also up‐regulated phosphorylated (p)‐β‐catenin (Ser31/33,Thr41) and down‐regulated (p)‐β‐catenin(Ser552) expression. To further address mechanisms driving this, we observed a significant decrease in the abundance of p‐AKT and p‐GSK3β expression, and an associated decline in tcf‐4 transcription factors (cyclin D1, c‐myc and Axin2), as well as a loss of EC proliferation by 7 days. To address whether the mechanism driving these changes was the absence of nutritional factors, glutamine was added to the TPN solution. This resulted in a partial restoration of β‐catenin expression and EC proliferation, suggesting that an alteration in nutrient delivery may affect many of these changes. Based on these findings, the loss of EC proliferation with TPN may well be due to a loss of total β‐catenin, as well as a concomintant change in the differential expression of β‐catenin phosphorylation sites, and a reduction in β‐catenin mediated tcf‐4 transcription. This potential pathway may well explain many of the findings of mucosal atrophy associated with TPN.
Microneurographic assessment of C‐fibre function in aged healthy subjects
Authors: Namer B. , Barta B. , Ørstavik K. , Schmidt R. , Carr R. , Schmelz M. , Handwerker H. O.
Published: December 2008

Physiological changes in the nervous system occur with ageing. Both a decline of function and a decrease in the number of C‐fibres in the skin have been reported for healthy aged subjects. With the use of microneurographic recordings from single C‐fibres in humans we have compared the sensory and axonal properties of these neurones in young and aged healthy subjects. A total of 146 C‐fibres were recorded from the common peroneal nerve in young subjects (mean age 24.7 years) and 230 C‐fibres were recorded in aged subjects (mean age 56.2 years). In aged subjects, changes were found in the composition of the C‐fibre population and in sensory and axonal properties. The relative incidence of afferent to efferent C‐fibres was relatively constant independent of the age of subjects. The ratio of mechano‐responsive to mechano‐insensitive nociceptors was approximately 8 : 2 in the young controls while in aged subjects it was 7 : 3. In aged subjects 13% of the fibres showed atypical discharge characteristics, while this was not observed in young subjects. Spontaneous activity, sensitization and loss of sensory function were found regularly. Changes in functions of the conductile membrane were also observed in fibres from aged subjects. The degree of activity‐dependent conduction velocity slowing in response to high frequency stimulation (2 Hz) was more pronounced, while the normalization of conduction velocity subsequent to high frequency stimulation was protracted. We found that both sensitization and desensitization or degeneration of afferent C‐fibres occur with age, but are still rare compared to patients with neuropathy. The changes in the axonal properties of C‐fibres in aged subjects are compatible with hypoexcitability of the fibres. These findings are important for the understanding and differential diagnoses regarding pathological processes and normal ageing.
Laminin acts via focal adhesion kinase/phosphatidylinositol‐3′ kinase/protein kinase B to down‐regulate β1‐adrenergic receptor signalling in cat atrial myocytes
Authors: Wang Y. G. , Ji X. , Pabbidi M. , Samarel A. M. , Lipsius S. L.
Published: December 2008

We previously reported that short‐term (2 h) plating of cat atrial myocytes on the extracellular matrix protein, laminin (LMN) decreases adenylate cyclase activity and β1‐adrenergic receptor (β1‐AR) stimulation of L‐type Ca2+current (ICa,L). The present study sought to determine whether LMN‐mediated down‐regulation of β1signalling is due to down‐regulation of adenylate cyclase and to gain insight into the signalling mechanisms responsible. β1‐AR stimulation was achieved by 0.01 μmisoproterenol (isoprenaline) plus 0.1 μmICI 118551, a selective β2‐AR antagonist. Atrial myocytes were plated for at least 2 h on uncoated cover‐slips (−LMN) or cover‐slips coated with LMN (+LMN). As previously reported, β1‐AR stimulation ofICa,Lwas significantly smaller in +LMN compared to −LMN atrial myocytes. In −LMN myocytes, 10 μmLY294002 (LY), a specific inhibitor of PI‐(3)K, had no effect on β1‐AR stimulation ofICa,L. In +LMN myocytes, however, LY significantly increased β1‐AR stimulation ofICa,L. Western blots revealed that compared with −LMN myocytes, +LMN myocytes showed a significant increase in Akt phosphorylation at Ser‐473, which was prevented by LY. In another approach, +LMN myocytes were infected (multiplicity of infection (MOI), 100; 24 h) with replication‐defective adenoviruses (Adv) expressing dominant‐negative inhibitors of focal adhesion kinase (FAK) (Adv‐FRNK or Adv‐Y397F‐FAK) or Akt (Adv‐dnAkt). Compared with control cells infected with Adv‐β‐galactosidase, cells infected with Adv‐FRNK, Adv‐Y397F‐FAK or Adv‐dnAkt each exhibited a significantly greater β1‐AR stimulation ofICa,L. In −LMN myocytes LY had no effect on forskolin (FSK)‐stimulatedICa,L. However, in +LMN myocytes LY significantly increased FSK‐stimulatedICa,L. Similar results were obtained in +LMN atrial myocytes infected with Adv‐FRNK. We conclude that LMN binding to β1‐integrin receptors acts via FAK/PI‐(3)K/Akt to inhibit adenylate cyclase activity and thereby down‐regulates β1‐AR‐mediated stimulation ofICa,L. These findings provide new insight into the cellular mechanisms by which the extracellular matrix can modulate atrial β‐AR signalling.
Amplified respiratory–sympathetic coupling in the spontaneously hypertensive rat: does it contribute to hypertension?
Authors: Simms Annabel E. , Paton Julian F. R. , Pickering Anthony E. , Allen Andrew M.
Published: December 2008

Sympathetic nerve activity (SNA) is elevated in established hypertension. We tested the hypothesis that SNA is elevated in neonate and juvenile spontaneously hypertensive (SH) rats prior to the development of hypertension, and that this may be due to augmented respiratory–sympathetic coupling. Using the working heart–brainstem preparation, perfusion pressure, phrenic nerve activity and thoracic (T8) SNA were recorded in male SH rats and normotensive Wistar–Kyoto (WKY) rats at three ages: neonates (postnatal day 9–16), 3 weeks old and 5 weeks old. Perfusion pressure was higher in SH rats at all ages reflecting higher vascular resistance. The amplitude of respiratory‐related bursts of SNA was greater in SH rats at all ages (P< 0.05). This was reflected in larger Traube–Hering pressure waves in SH rats (1.4 ± 0.8versus9.8 ± 1.5 mmHg WKYversusSH rat, 5 weeks old,n= 5 per group,P< 0.01). Recovery from hypocapnic‐induced apnoea and reinstatement of Traube–Hering waves produced a significantly greater increase in perfusion pressure in SH rats (P< 0.05). Differences in respiratory–sympathetic coupling in the SH rat were not secondary to changes in central or peripheral chemoreflex sensitivity, nor were they related to altered arterial baroreflex function. We have shown that increased SNA is already present in SH rats in early postnatal life as revealed by augmented respiratory modulation of SNA. This is reflected in an increased magnitude of Traube–Hering waves resulting in elevated perfusion pressure in the SH rat. We suggest that the amplified respiratory‐related bursts of SNA seen in the neonate and juvenile SH rat may be causal in the development of their hypertension.
Effect of DNase and Antibiotics on Biofilm Characteristics
Authors: Tetz George V. , Artemenko Natalia K. , Tetz Victor V.
Published: December 2008

The role of extracellular DNA in the maintenance of biofilms formed by gram-positive and gram-negative bacteria was studied. This study evaluated all the bacterial strains that were tested for the presence of extracellular DNA with an average size of 30 kb in the matrix. Our results indicate changes in community biomass, architecture, morphology, and the numbers of CFU in the presence of DNase. This effect seems to be common to biofilms established by various unrelated gram-positive and gram-negative bacteria. The cleavage of extracellular DNA leads to the formation of an altered biofilm that permits the increased penetration of antibiotics. Thus, the addition of DNase enhances the effect of antibiotics, resulting in decreased biofilm biomass and numbers of CFU.
Efficacy of the Novel Diamidine Compound 2,5-Bis(4-Amidinophenyl)- Furan-Bis-
O
-Methlylamidoxime (Pafuramidine, DB289) against
Trypanosoma brucei rhodesiense
Infection in Vervet Monkeys after Oral Administration
Authors: Mdachi R. E. , Thuita J. K. , Kagira J. M. , Ngotho J. M. , Murilla G. A. , Ndung'u J. M. , Tidwell R. R. , Hall J. E. , Brun R.
Published: December 2008

Owing to the lack of oral drugs for human African trypanosomiasis, patients have to be hospitalized for 10 to 30 days to facilitate treatment with parenterally administered medicines. The efficacy of a novel orally administered prodrug, 2,5-bis(4-amidinophenyl)-furan-bis-
O
-methlylamidoxime (pafuramidine, DB289), was tested in the vervet monkey (
Chlorocebus
[
Cercopithecus
]
aethiops
) model of sleeping sickness. Five groups of three animals each were infected intravenously with 10
4
Trypanosoma brucei rhodesiense
KETRI 2537 cells. On the seventh day postinfection (p.i.) in an early-stage infection, animals in groups 1, 2, and 3 were treated orally with pafuramidine at dose rates of 1, 3, or 10 mg/kg of body weight, respectively, for five consecutive days. The animals in groups 4 and 5 were treated with 10 mg/kg for 10 consecutive days starting on the 14th day p.i. (group 4) or on the 28th day p.i. (group 5), when these animals were in the late stage of the disease. In the groups treated in the early stage, 10 mg/kg of pafuramidine completely cured all three monkeys, whereas lower doses of 3 mg/kg and 1 mg/kg cured only one of three and zero of three monkeys, respectively. Treatment of late-stage infections resulted in cure rates of one of three (group 4) and zero of three (group 5) monkeys. These studies demonstrated that pafuramidine was orally active in monkeys with early-stage
T. brucei rhodesiense
infections at dose rates above 3 mg/kg for 5 days. It was also evident that the drug attained only minimal efficacy against late-stage infections, indicating the limited ability of the molecule to cross the blood-brain barrier. This study has shown that oral diamidines have potential for the treatment of early-stage sleeping sickness.
Postantibiotic Effect of Tigecycline against 14 Gram-Positive Organisms
Authors: Pankuch G. A. , Appelbaum P. C.
Published: December 2008

The in vitro postantibiotic effects (PAEs), postantibiotic sub-MIC effects (PA-SMEs), and sub-MIC effects of tigecycline were determined for 14 gram-positive and gram-negative organisms. The pneumococcal, staphylococcal, and enterococcal PAEs were 1.9 to 5.1, 2.9 to 5.7, and 3.9 to 6.1 h, respectively, and those for
Haemophilus influenzae
,
Escherichia coli
,
Klebsiella pneumoniae
,
Enterobacter cloacae
, and
Acinetobacter baumannii
were 1.1 to 5.0, 1.9 to 2.1, 1.7 to 1.8, 1.0 to 1.7, and 0.7 to 3 h, respectively. The PA-SMEs (four times the MIC) ranged from 6.7 to >11 h for gram-positive organisms and from 2.3 to >11.3 h for gram-negative organisms.