bluuebunny/crossref_metadata_2025 huggingface dataset:
Passive avoidance conditioning and unitary activity in the basolateral amygdaloid nucleus of the rat
Authors: Yajeya J. , Patino A. , Riolobos A. S. , Criado J. M. , De La Fuente A.
Published: December 2008

Single unit activity was recorded in the basolateral nucleus of amygdala in rats in a passive avoidance test. Simultaneously, visual control of exploratory behaviour was carried out. Prior to establishing the conditioning, the mean frequency of the unit discharge was 14 Hz (SD = 9) and 1 minute after conditioning this unit activity decreased to values close to zero; later on (24 and 48 hours), a progressive recovery of the discharge was observed. Behavioural changes were also detected. The long term recovery of unit activity follows the time course of the extinction process. The possible significance of these findings is discussed in relation to some of the functional roles of this nucleus.
Beta2‐adrenergic attenuation of capillary pressure autoregulation during hemorrhagic hypo tension, a mechanism promoting transcapillary fluid absorption in skeletal muscle
Authors: MASPERS M. , BJÖRNBERG J.
Published: December 2008

The aim of this study was to evaluate a possible humoral β2‐adrenergic effect on the capillary pressure autoregulation capacity in cat skeletal muscle during bleeding. For this purpose capillary pressure autoregulation in response to graded decrease in arterial pressure was studied in sympathectomized muscle in the control state, and during haemorrhagic hypovolaemia in the presence and absence of selective β2‐adrenoceptor blockade (ICI 118,551). The study was performed with a technique that permits continuous recordings of average capillary pressure in absolute terms and of the regional pre‐ and postcapillary vascular resistance, from which the pre‐ to post capillary resistance ratio could be determined. In the pre‐haemorrhagic control state, an experimental decrease in arterial pressure from 100 to 50 mmHg caused a fall of capillary pressure from 17.6 by only 1.7 mmHg (ΔPA/ΔPc= 29), demonstrating an efficient capillary pressure autoregulation. This autoregulation was accomplished by a decrease in pre‐ to post capillary resistance ratio in turn being a result of active precapillary dilatation and a passive increase in post capillary vascular resistance. Haemorrhageper se, via a humoral α‐adrenergic preferentially precapillary vaso‐constriction, caused a decrease in capillary pressure to 16.8 mmHg at arterial pressure 100 mmHg. A superimposed decrease in arterial pressure to 50 mmHg resulted in a capillary pressure fall by 3.7 mmHg (ΔPA/ΔPe=14), indicating impaired autoregulation capacity. This attenuation to a great extent could be ascribed to adrenaline‐induced B2‐adrenoceptor stimulation, since β2‐blockade restored the Δ arterial pressure/capillary pressure ratio to 20. Low‐dose isoprenaline infusion in the control state similarly caused marked impairment of capillary pressure autoregulation. The β2‐adrenergic attenuation of capillary pressure autoregulation appears to be a beneficial effect in haemorrhagic hypotension, since it lowers capillary pressure passively in relation to the arterial pressure fall, thereby reinforcing the a‐adrenergic active capillary pressure decrease, leading to more effective transcapillary fluid absorption and, hence, improved replenishment of plasma volume.
Effects of cervical sympathetic nerve stimulation and neuropeptide Y (NPY) on cranial blood flow in the cat
Authors: GRANSTAM E. , NILSSON S. F. E.
Published: December 2008

Effects of cervical sympathetic nerve stimulation (SNS) at 10 Hz and intravenous infusion of neuropeptide Y (NPY), 10 and 100 pmol×kg body wt‐1×min‐1 for 5 min, on regional blood flow in the cat were investigated with radioactive microspheres.

Sympathetic nerve stimulation caused significant reductions in blood flows in the facial tissues including the eye. Alpha‐adrenoceptor blockade with phenoxybenzamine and combined beta‐ and alpha‐adrenoceptor blockade with propranolol and phenoxybenzamine abolished the effects of sympathetic nerve stimulation in most facial tissues except in the tongue, upper eyelid and masseter muscle.

In most cranial tissues, neuropeptide Y reduced regional blood flow and increased vascular resistance. No effect of neuropeptide Y on vascular resistance was observed in the choroid.

In the present study, evidence for a non‐adrenergic component in sympathetic vasoconstriction was found in the tongue, upper eyelid and masseter muscle but not in the majority of feline facial tissues. Neuropeptide Y was a potent vasoconstrictor in many cranial tissues, while in parts of the area, the effects of neuropeptide Y were less pronounced.
A comparison of laser Doppler flowmetry with the radiolabelled microsphere reference flow technique to measure tracheal blood flow in dogs
Authors: GODDEN D. J. , BAILE E. M. , PARÉ P. D.
Published: December 2008

Measurements of tracheal wall blood flow were made in anaesthetized, ventilated dogs during resting ventilatory conditions, during application of positive end‐expiratory pressure (PEEP) and during eucapnic hyperventilation of dry air, using laser Doppler flowmetry and the radiolabelled microsphere reference flow technique. Six regions of the trachea were studied in each dog, and the average laser Doppler flowmetry measurement derived from 12 sites within each region was compared with the reference flow measurement, obtained using 15 micron diameter microspheres labelled with 113Sn, 103Ru, 141Ce or 151Gd. Under each set of ventilatory conditions, there was a weak, but significant, correlation between laser Doppler flowmetry and reference flow values (baseline r = 0.44, hyperventilation r = 0.44, and PEEP r= 0.74). Average laser‐Doppler flowmetry and reference flow values showed a similar reduction from baseline during application of PEEP. The mean (SD) change from baseline, expressed as a percentage, was ‐63 (15)% for laser‐Doppler flowmetry values, and ‐63 (21)% for reference flow values. However, there was no correlation between the magnitude of change measured in individual regions using the two techniques. During hyperventilation, laser Doppler flowmetry measurements showed variable changes from baseline, and the mean change was ‐12 (45)%, which was not significantly different from zero. Reference flow values increased during hyperventilation, the mean change being 87 (77)%. The results indicate that laser Doppler flowmetry and reference flow measurements of airway wall blood flow are not directly comparable.
Effects of selective phosphodiesterase inhibitors on isolated coronary, lung and renal arteries from man and rat
Authors: LINDGREN S. , ANDERSSON K.‐E.
Published: December 2008

The relaxant effects of some isozyme‐selective phosphodiesterase inhibitors were evaluated in isolated human and rat coronary, lung and renal arteries. Milrinone and OPC 3911, inhibitors of a cGMP‐inhibited cAMP phosphodiesterase (cGI‐PDE), were shown to have distinct vasodilator actions. These agents were less potent as relaxants in rat lung and renal arteries than in the corresponding human tissues. OPC 3911, the more potent cGMP‐inhibited cAMP phosphodiesterase inhibitor, was found to be the more potent vasorelaxant. Rolipram, a selective inhibitor of a cGMP‐noninhibited cAMP phosphodiesterase, had small effects on coronary and lung arteries, but produced a slightly more pronounced relaxation of renal arteries from both man and rat. In human preparations contracted by 30 mm K+, milrinone and OPC 3911 had similar relaxant profiles, and were as potent in coronary as in renal arteries. These results do not support the notion that milrinone has reduced effects on renal vessels in man and show that there may be species differences in vascular responsiveness to cGMP‐inhibited cAMP phosphodiesterase inhibitors.
Cardiac cell membrane repolarization is required for onset of mechanical restitution in papillary muscle
Authors: ARLOCK P. , NOBLE M. I. M. , WOHLFART B.
Published: December 2008

In 10 voltage clamped ferret papillary muscles at 37°C (single sucrose gap), the duration of resting (diastolic, holding) potential was varied in order to define the mechanical restitution process. Following a period of steady state voltage clamp depolarizations to + 20 mV, a single test depolarization clamp of 200 or 500 ms duration was introduced. Then, the following period at resting (holding) potential was varied. All the mechanical restitution curves for the 500 ms clamps were delayed by 300 ms compared with the 200 ms clamps. When mechanical restitution was plotted as the relationship between contractile force and test electrical diastolic interval, all processes started from zero interval (i.e. the time of repolarization). Variation of diastolic holding potential between — 70 mV and — 40 mV did not affect the starting time, but the final force values at full restitution were approached faster and were higher for — 70 mV than for — 40 mV. There was an inverse relationship between force and second inward current during mechanical restitution after an initial phase of restitution of current. Mechanical restitution is postulated to be due to passage of contractile calcium with time from an uptake to a release compartment within the sarcoplasmic reticulum. Thus the rise of contractile force with increasing test cycle duration should have been independent of whether a 200 or 500 ms depolarization was used. In order to accommodate the discrepancy, we postulate either that (1) sarcoplasmic reticulum calcium release channels require sarcolemmal repolarization to begin to be reactivated or (2) that trigger calcium (calcium induced calcium release from the sarcoplasmic reticulum) is derived from the sarcolemma.
Cigarette smoke‐induced changes in guinea‐pig airway responsiveness to histamine and citric acid
Authors: KARLSSON J.‐A. , ZACKRISSON C. , SJÖLIN C. , FORSBERG K.
Published: December 2008

The effect of 50 min cigarette smoke exposure on airway responsiveness to the bronchoconstrictor and tussive effects of histamine and citric acid has been examined in guinea‐pigs. Intravenous histamine increased intratracheal pressure (ITP) in anaesthetized guinea‐pigs and the dose‐response curve was significantly (P < 0.05) steeper in cigarette smoke‐ than in air‐exposed animals. ED50 values were 11.4 nmolkg‐1 (7.416.8, 95% confidence interval) and 42.5 nmol kg‐1 (28.8–61.4, 95% confidence interval), respectively (P < 0.05) in smoke‐ and air‐exposed guinea‐pigs indicating an enhanced reactivity. However, the sensitivity to intravenous histamine was not changed by the cigarette smoke exposure, and the maximum increase in intratracheal pressure was the same as in control animals (air: 247 ± 21%, n = 4; smoke: 223 ± 18%, n = 7). The cigarette smoke‐induced hyperresponsiveness to intravenous histamine was not altered by pretreatment with nebulized lidocaine (0.20 M), ipratropium bromide (0.30 Mm) or cromoglycate (0.06 M), suggesting that a neural reflex is unlikely to be involved in the development of hyperresponsiveness.

Conscious, smoke‐exposed guinea‐pigs had a significantly (P < 0.001) reduced responsiveness to citric acid (0.40 M) and cigarette smoke. Both cough and bronchoconstriction were suppressed for about 1 h, but unchanged 24 h after exposure. The hyporesponsiveness to citric acid was inhibited by atropine (1.4 μmol kg‐1 i.p.) and may therefore, at least in part, be due to increased airway secretions.

The present data demonstrate that inhalation of cigarette smoke may alter guinea‐pig airway responsiveness to tussive and bronchoconstrictor stimuli. The lack of effect of selected drugs, which interferes with local and central nervous system‐mediated airway reflexes, suggests that a neural reflex may not be involved in the development of airways hyperresponsiveness.
Neurokinin A in the parotid and submandibular glands of the rat: immunohistochemical localization and effect on protein and peroxidase secretion
Authors: VIRTA E. , KANGAS S. , TOLONEN R. , SCHULTZ T. , SALO A. , UUSITALO H.
Published: December 2008

An indirect immunofluorescence technique was used to study the distribution of neurokinin A immunoreactive (NKA‐IR) nerve fibres in submandibular and parotid glands of the rat. The functional role of neurokinin A on protein and peroxidase secretion in these glands was evaluated by using in vitro methods. In the parotid gland neurokinin A immunoreactive fibres were mainly distributed around the secretory acini, but some were also in evidence around the stromal blood vessels and ducts. The number of the neurokinin A immunoreactive nerve fibres was lower in the submandibular gland than in the parotid gland. They were mainly distributed around the secretory acini and stromal blood vessels and ducts. In vitro, neurokinin A significantly stimulated the release of total amount of released proteins and peroxidase from parotid gland fragments, while in the submandibular gland only the release of peroxidase was increased. By using SDS polyacrylamide gel electrophoresis (SDS‐PAGE) specific changes were found in the release of proteins after neurokinin A stimulation. The results of the present study demonstrate that neurokinin A immunoreactive nerve fibres are present in the rat parotid and submandibular glands. Their localization around the secretory elements of the glands and the effect of neurokinin A in vitro experiments indicates that neurokinin A might have a significant role in the regulation of salivary secretion.
A calmodulin inhibitor with high specificity, compound 48/80, inhibits axonal transport in frog nerves without disruption of axonal microtubules
Authors: EKSTRÖM P. A. R. , WALLIN M. , KANJE M. , EDSTRÖM A.
Published: December 2008

The calmodulin inhibitor compound 48/80 has previously been shown to arrest axonal transport in vitro in the regenerating frog sciatic nerve. The inhibition was limited to the outgrowth region of nerves, which had been allowed to regenerate in vivo for 6 days after a crush lesion, before they were incubated with or without drugs in vitro overnight. The effects of compound 48/80 on the regenerating nerve were further investigated. A concentration of compound 48/80 (50 μg ml‐1), which effectively inhibits axonal transport, did not cause observable changes of the microtubules of regenerating axons in the outgrowth region as judged by electron microscopy. Furthermore, it was shown that also a lower concentration (25 μg ml‐1) inhibited axonal transport. As a measure of possible metabolic effects, the level of ATP was assessed in the regenerating nerve after exposure to compound 48/80. Compound 48/80 at 25 μg ml‐1 did not change the level of ATP in the nerve. The assembly of bovine brain microtubule proteins in a cell‐free system was unaffected by 25 μg ml‐1 of compound 48/80 and slightly inhibited by 50 μg ml‐1. At higher concentrations (> 100 μg ml‐1) assembly of microtubules appeared stimulated, and microtubule spirals as well as closely aligned microtubules could be seen. These effects appeared to be unrelated to the transport effects. The present results indicate that compound 48/80 arrests axonal transport via mechanisms other than destruction of axonal microtubules or interference with the energy metabolism. It is possible that these mechanisms involve inhibition of calmodulin‐regulated events essential to the transport.
Low ambient temperature increases baroreflex‐governed sympathetic outflow to muscle vessels in humans
Authors: FAGIUS J. , KAY R.
Published: December 2008

Microelectrode multi‐unit recordings of muscle nerve sympathetic activity, primarily involved in blood pressure regulation, were made from the right peroneal nerve in 10 healthy subjects during exposure to cold inside a box used for hypothermic surgery. Blood pressure was monitored by an automatic cuff applied to the left arm. Heart activity (ECG) and the temperature inside the box were monitored.

Muscle nerve sympathetic activity outflow and blood pressure were stable during 15 minutes initial rest at 22.7 ± 0.3 °C (mean ± SEM). All subjects increased muscle nerve sympathetic activity and blood pressure with lowering of ambient temperature. The box temperature was 10.5 ± 0.3 °C at the end of the cooling period. With rewarming the changes in muscle nerve sympathetic activity and blood pressure were reversed. Mean outflows of muscle nerve sympathetic activity during initial rest, final phase of cooling period, and post‐rewarming were 20.3 ± 2.7, 26.6 ± 3.2 and 20.2 ± 2.8 burst min‐1 respectively. Systolic blood pressure during the same periods was 118 ± 3, 131±4 and 120±4 mmHg, respectively, whereas corresponding values for diastolic blood pressure were 73±2, 82 ± 2 and 75 ± 2 mmHg (P < 0.001 for all variables; (ANOVA).

It is concluded that muscle nerve sympathetic activity, while not regarded as being involved in body temperature regulation, is under the influence of ambient temperature and contributes to blood pressure elevation in a cold environment. The increase in muscle nerve sympathetic activity may play a role in body temperature regulation by preserving heat within the central core or by inducing heat production by small muscles in the vessel walls, the latter possibility being in agreement with recent observations suggesting that smooth muscles in limb vasculature may contribute to thermogenesis.
Blood pressure control in arterial‐ and cardiopulmonary receptor denervated dogs
Authors: PERSSON P. B. , EHMKE H. , KIRCHHEIM H. R.
Published: December 2008

The mechanisms influencing arterial blood pressure and heart rate were studied in conscious foxhounds after chronic sino‐aortic and cardiopulmonary denervation (N= 6). In previous investigations it was shown, that this denervation produces hypertension and tachycardia, which is confirmed by the present study: Mean arterial blood pressure increased from 101 ± 3 to 123 ± 6 mmHg (P < 0.05), and heart rate rose from 85 ± 6 to 124 ± 5 beats min‐l (P < 0.001). The variability of mean arterial blood pressure, but not that of heart rate increased (from 6 ± 1 to 22 ± 2 mmHg (P < 0.001)). The administration of the a‐adrenergic blocker prazosin reduced both mean arterial blood pressure (‐33 ± 8 mmHg, P < 0.01) and its variability (‐ 12 ± 1 mmHg, P < 0.01), thus suggesting an α‐adrenergic mediated hypertension. β‐blockade by propranolol blunted the heart rate increase (‐ 24 ± 5 beats min‐1 P < 0.05). Although plasma renin activity increased in the denervated dogs, converting enzyme inhibition had little effect on mean arterial blood pressure and heart rate. In conclusion, chronic sino‐aortic and cardiopulmonary denervation enhances the α and β‐adrenergic component of car diovascular control in a different fashion. While the α‐adrenergic component induces fluctuations around an elevated arterial blood pressure level, the β‐adrenergic tone to the heart increases without any significant increase in variability.
Intracellular cytosolic free calcium concentration in the macula densa and in ascending limb cells at different luminal concentrations of sodium chloride and with added furosemide
Authors: SALOMONSSON M. , GONZALEZ E. , WESTERLUND P. , PERSSON A. E. G.
Published: December 2008

The juxtaglomerular apparatus fulfils several important regulatory functions in the kidney, such as tubuloglomerular feedback (TGF) control and control of renin release. The macula densa (MD) cells sense the fluid load by perceiving the distal NaCl concentration via a Na‐K‐2Cl cotransport system in the luminal cell membrane. It has been proposed that macula densa cell activation may involve changes in intracellular cytosolic free calcium concentration ([Ca2+]1), as one link in the chain of events activating TGF or releasing renin. We therefore investigated the changes in the intracellular calcium concentrations with fura‐2, using a video system, in macula densa cells, and compared them with the changes in the corresponding concentrations in the ascending limb of the loop of Henle (c‐TAL). The results show that our technique for analysing intracellular cystolic free calcium in isolated perfused tubules is valid for this purpose, and the Kd value obtained was similar to that found by Grynkiewicz et al. (1985). The intracellular cystolic free calcium concentration was about 90 nM both in the macula densa and c‐TAL cells, and the macula densa cell intracellular cystolic free calcium concentration increased by about 20 nM when the tubular lumen was perfused with Na and C1 at low concentrations. No significant changes were noted when furosemide was added to the perfusion solutions. We consider it hardly likely that this small change in intracellular cystolic free calcium concentration can be entirely responsible for full activation of renin release or full inactivation of the TGF control mechanism. It would seem that the signal transmission from the macula densa cells could occur by other routes than through activation of intracellular cytosolic free calcium concentration.
On the mechanisms of the basal alkaline secretion in the rat ileumin vivo
Authors: TANTISIRA M. H. , JODAL M. , LUNDGREN O.
Published: December 2008

Basal alkaline secretion of the denervated rat ileum was monitored by a pH‐stat method. Changes of transepithelial electrical potential difference (PD) were also continuously registered. In other experiments net fluid transport was measured with a gravimetric method. The importance of the enteric nervous system for the recorded variables was investigated by giving i.v. hexamethonium, neuropeptide Y (NPY) or methionine‐enkephalin or by stimulating electrically the mesenteric nerves surrounding the superior mesenteric artery. Alkaline secretion was inhibited by about 20% by mesenteric nerve stimulation or by neuropeptide Y (NPY) or met‐enkephalin i.v. A somewhat greater inhibition (∼ 30%) of transepithelial electrical potential difference was elicited by the mesenteric nerve stimulation and NPY whereas met‐enkephalin did not cause any transepithelial electrical potential difference change. Net fluid absorption was markedly diminished (by ∼ 65–75%) by met‐enkephalin but not by NPY. The cellular mechanisms underlying alkaline secretion were investigated by means of amiloride, SITS and acetazolamide. The basal alkaline secretion and transepithelial electrical potential difference were not influenced by 10‐3M or 10‐4SITS. In contrast 10‐3m amiloride caused a significant increase of alkaline secretion but not of transepithelial electrical potential difference. A 35% reduction in the alkaline secretion but not transepithelial electrical potential difference was observed after acetazolamide had been given intravenously. A similar decrease was observed after giving hexamethonium. We conclude: (1) Enteric nerves are of comparatively small importance in controlling the ileal alkaline secretion recorded during basal conditions; (2) About 35% of the basal ileal alkaline secretion is carbonic anhydrase dependent. This mechanism is not influenced by nicotinic receptor blockade; (3) Under the present experimental conditions there may be an alkaline secretion which is concealed by a simultaneously operating Na+/H+exchanger and; (4) No consistent quantitative correlation exists between alkaline secretion, transepithelial electrical potential difference and net fluid transport in the denervated rat ileum.
Comparative studies of the venous resistance and capacitance functions and their sympathetic regulation in skeletal muscle
Authors: BJÖRNBERG J. , MASPERS M.
Published: December 2008

The relation between the capacitance response (regional blood volume mobilization) and the venous resistance response, i.e. the two main functions of the venous system, was investigated during graded sympathetic nerve excitation in cat gastrocnemius muscle under well defined experimental conditions. The neural capacitance response was also compared with the total regional vascular resistance response and its precapillary resistance component. A reliable distinction between precapillary and postcapillary resistance reactions was made possible by a whole‐organ technique permitting continuous recordings of hydrostatic capillary pressure. In the control state, in which a transcapillary fluid equilibrium prevailed, total regional vascular resistance response, precapillary resistance component and venous resistance response averaged 16.6, 14.5 and 2.1 PRU. respectively and total regional blood volume was calculated to comprise 1.0 ml 100 g tissue‐. Graded sympathetic activation, causing graded increments in total regional vascular resistance response, precapillary resistance component and venous resistance response by maximum values of 96, 88 and 8 PRU respectively, were associated with graded decrease in total regional blood volume, at maximum by an average value of 0.57 ml 100 g tissue‐1. The relations between regional blood volume mobilization on the one hand, and total regional vascular resistance response, precapillary resistance component and venous resistance response on the other, were all non‐linear, implying that the sympathetic volume decrease per unit resistance increase was greater for small than large resistance increases. The experimentally established relation between regional blood volume mobilization and total regional vascular resistance response agreed quite well with theoretical data calculated from the simple assumption that both capacitance and resistance responses are the consequences of changes of vascular radius, the capacitance response, though, only to the second, and the resistance response to the fourth, power of the radius change. The distribution of the total adrenergic capacitance response between the pre‐ and postcapillary compartments was further estimated by a theoretical analysis. The relative contribution of the sympathetic capacitance response and the sympathetic transcapillary fluid absorption response to functional circulatory filling was also defined, providing some aspects of short‐ and long‐term volume control and its importance for arterial blood pressure regulation.
Effects of airway luminal concentration of albumin on histamine‐induced mucosal exudation of radio‐iodine labelled albumin
Authors: GREIFF L. , ERJEFÄLT I. , PIPKORN U. , PERSSON C. G. A.
Published: December 2008

In an in vivo study of guinea‐pig airway barriers we have examined the effects of the luminal concentration of albumin on exudation (outward) and absorption (inward) permeabilities to radio‐iodine labelled albumin. Previously validated techniques for superfusion of solutes onto the tracheobronchial mucosal surface and for subsequent tracheal lavage were employed. [1251]albumin was administered intravenously as plasma tracer and [131I]albumin was superfused topically as absorption tracer. Histamine (5.0nmol) was superfused onto the mucosal surface together with the absorption tracer and in the presence of different albumin concentrations (0.3, 3.0 and 30 mg ml‐1). The experiment was terminated 10 minutes after the tracheal mucosal superfusion and samples of plasma and tracheal lavage fluid were collected. The mucosal exudation response was calculated from the detection of [1251]albumin in the airway lumen. The absorption ability of the mucosa was determined by the detection of [1311]albumin in circulating plasma. Histamine induced a significant mucosal exudation of [1251]albumin. This effect was unaffected by the level of albumin on the mucosal surface. There was a small but significant absorption of [1311]albumin in the presence of 0.3 and 3.0 mg ml‐1 of albumin in the luminal liquid. An albumin concentration of 30 mg ml‐ markedly increased the rate of absorption of [1311]albumin. However, the absorption rate was not affected by the histamine‐induced mucosal exudation process at any level of luminal albumin. The present data further demonstrates that plasma exudation and mucosal absorption are independent processes. The data are in keeping with the view that an increased subepithelial hydrostatic pressure moves the plasma exudate across the mucosa as a distinct outward process.
Adaptive response of ileal mucosa to malnutrition in the rat: role of polyamines
Authors: JONAS A. , DIVER‐HABER A. , YAHAV J.
Published: December 2008

Mucosal disaccharidases and ornithine decarboxylase activities were measured in malnourished, preweaning (19 days), post weaning (24 days) and young adult (37 days) rats. Malnutrition resulted in decreased body weight, intestinal weight, DNA and protein content. Mucosal Prot/DNA ratios were elevated in the ileal segments of the 24 and 37 day rats. Preweaned malnourished rats had significantly enhanced lactase specific activity in both jejunal and ileal segments. Adult malnourished rats showed enhanced jejunal lactase and sucrase activities which were not accompanied by elevated ornithine decarboxylase values. Mucosal sucrase and ornithine decarboxylase specific activities were significantly elevated in the ileal segment of the 24 and 37 day old malnourished rats. Studies of adult rats showed that these increased specific activities were located in the mature enterocytes at the villus tip, and persisted during a 24 h diurnal cycle. DFMO administration for 4 days completely inhibited mucosal ornithine decarboxylase and abolished the rise of ileal sucrase activity. We concluded that the intestinal response to reduced food intake is age related and differs in the jejunum and ileum: ornithine decarboxylase and polyamines are involved in ileal adaptation to malnutrition in postweaned and adult rats.
Electromyography and morphology during regeneration of muscle injury in rats
Authors: HURME T. , LEHTO M. , FALCK B. , TAINIO H. , KALIMO H.
Published: December 2008

Healing of the partially ruptured rat gastrocnemius muscle was studied correlating electromyographical findings with morphological changes. Fibrillation potentials and positive sharp waves were seen both proximal and distal to the injury 7 days after the injury and disappeared in the proximal part by day 14 and in the distal part by day 21. Late components of motor action potential were observed from day 14 onwards. Denervation was mainly myogenic, i.e. caused either by rupture of myofibres, whence the abjunctional stump lost its contact with the neuromuscular junction on the adjunctional stump, or by necrosis of the segment of the ruptured myofibre lying underneath the neuromuscular junction. Lesser extent of denervation was neurogenic, i.e. caused by damage to intramuscular nerve fibres. The reinnervation occurs either by regeneration of the necrotized myofibres, by regeneration of the severed nerves, or by collateral innervation of new neuromuscular junctions in the abjunctional stumps. The present study indicates that electromyography may be useful in the diagnosis and follow‐up of skeletal muscle injuries.
In vivo analysis of intracellular thallium‐201 accumulation in skeletal muscle of the rat
Authors: BRISMAR T.
Published: December 2008

The specific accumulation of the K+‐analogue TI+(201Tl+) in muscle after intramuscular injection was analysed by gamma spectrometry in vivo of rat hamstring muscles. A mixture (0.1ml) of 201Tl+ (thallous+ chloride‐) and 99mTc‐pertechnetate‐ (Na+ pertechnetate‐) was given, by which 99mTc‐pertechnetate‐ served as a reference substance with negligible intracellular accumulation. After 30 min 8.9 ± 5.8% of injected 99mTc‐pertechnetate‐ remained in the muscle and 49+10% of 201Tl+ (±SD, n = 18). The difference between 201Tl+ and 99mTc‐pertechnetate‐ at 30 min was taken as a measure of the intracellular 201Tl+ accumulation, which was 40% of the initial amount of 201TI+. The half‐time of the calculated intracellular 201TI+ accumulation was 4.9+1.9 min. In the presence of ouabain (1.0 mM in the injectate) the intracellular 201Tl+ accumulation was 25+10% (n = 7), that is ouabain decreased the intracellular 201Tl+ accumulation by 38% (P = 0.0035). Non‐radioactive TI+ (1.0 mM TI‐acetate in the injectate) inhibited the uptake by 35% (P= 0.0013). Ouabain did not significantly affect the half‐time for the Tl+ uptake. An increase in [K+] of the injectate from 0 to 5 mM had no significant effect. Insulin (0.2 units in the injectate) had no effect.

It is concluded that the specific TI+‐accumulating properties of muscle fibres can be studied with the present in vivo technique, which can provide information about the Na‐K‐ATPase activity and the membrane potential of muscle fibres.
Effects of selective adrenergic agonists and antagonists on gastric tone in the rat
Authors: BOJÖ L. , NELLGÅRD P. , CASSUTO J.
Published: December 2008

The aim of the present in vivo study was to investigate in anaesthetized rats, the effects of selective adrenergic agonists and antagonists on basal gastric tone and phasic contractions by the use of a volumetric method. L‐phenylephrine, an alpha‐1 agonist, induced hypertension, bradycardia and a significant gastric relaxation. Clonidine, an alpha‐2 agonist, caused hypotension, bradycardia and a significant gastric contraction and a reduction of the amplitude of phasic contractions. Salbutamol, a beta‐2 agonist, induced a dose‐dependent tachycardia and a significant inhibition of gastric tone whereas prenalterol, a beta‐1 agonist, induced tachycardia without any significant influence on gastric basal tone. Yohimbine, an alpha‐2 blocker, significantly decreased gastric basal tone and reversed the inhibition of phasic contractions induced by clonidine. Prazocine, a selective alpha‐1 blocker, and propranolol, a non‐selective beta‐blocker, had no significant influence on gastric basal tone or phasic contractions.

It is concluded that sympathetic inhibition of basal gastric tone in the rat is mediated by alpha‐1 and beta‐2 adrenergic receptors. Activation of alpha‐2 adrenergic receptors significantly increased basal gastric tone and reduced the amplitude of phasic contractions. A blockade of alpha‐2 receptors significantly decreased basal gastric tone and restored the amplitude of phasic contractions.
Adenosine modulation of neuroeffector transmission in guinea‐pig uterine smooth muscle
Authors: WIKLUND N. P. , SAMUELSON U. E. , HAMMARSTRÖM M.
Published: December 2008

Effects of adenosine and adenosine analogues on neuroeffector transmission in separate layers of the guinea‐pig uterine smooth muscle during different phases of the oestrus cycle were studied. Adenosine (ADO), N6‐[(R)‐1‐methyl‐2‐phenylethylj‐adenosine (R‐PIA) and 5‐N‐ethylcarboxamideadenosine (NECA) enhanced spontaneous contractile activity as well as contractile responses to nerve stimulation or direct muscle stimulation in the longitudinal and circular muscle layers both at the time of ovulation and implantation. The agonist potency order was R‐PIA NECA > ADO. Furthermore, in the circular muscle layer inhibitory effects were seen at time of implantation and the agonist potency for this inhibitory effect was NECA > R‐PIA ADO. 8‐p‐sulphophenyltheophylline (8‐PSØT) antagonized both the stimulatory and inhibitory effects of the purines and 8‐p‐sulphophenyltheophylline applied to untreated preparations inhibited nerve‐induced contractile activity. NECA inhibited stimulation‐induced release of3H in preparations incubated with [3H Jnoradrenaline. We suggest that adenosine and its analogues can modulate adrenergic neuroeffector transmission in guinea‐pig uterine smooth muscle via action at postjunctional receptors stimulating contractile activity and prejunctional receptors inhibiting transmitter release. In the circular muscle layer postjunctional receptors inhibiting contractile activity were evident at time of implantation. Furthermore, endogenous purines exerting a stimulatory action on the neuroeffector transmission were likely formed during the present experimental conditions.
Characterization of 51Cr‐EDTA as a marker of duodenal mucosal permeability
Authors: NYLANDER O. , SABABÍ M. , BARK J.
Published: December 2008

Proximal duodenum was perfused with various solutions and mucosal permeability assessed by measuring the clearance of 51Cr labelled ethylenediaminetetra‐acetate (EDTA) from blood‐to‐intestinal lumen in anaesthetized rats. Net flux of fluid was determined by measurement of effluent weight changes. Perfusion of duodenum with 50 mm NaCl significantly increased fluid absorption but had no effect on EDTA clearance. EDTA clearance was unaffected by perfusion with 400 mM or 800 mM mannitol. Perfusion with 400 mM NaCl induced a sustained fluid secretion and a small but irregular increase (40%) in EDTA clearance. A significant 3.6‐fold increase in clearance was obtained in response to perfusion of duodenum with deionized water. Similarly, perfusion with either 20 mM HCl or 50 mm ethyleneglycol‐bis‐(β‐aminoethylether)‐N,N'‐tetraacetic acid (EGTA) significantly increased the EDTA clearance 3.3‐fold and 2‐fold respectively. Perfusion with a hypotonic HCl‐solution (10 mm HCl+40 mm NaCl) increased fluid absorption and the EDTA clearance. It is concluded that no positive linear relationship exists between luminal osmolality and 51Cr‐EDTA movement across the mucosa. It is postulated that high luminal acidity or extreme hypotonicity increase the EDTA clearance by widening of and/or disruption of intercellular junctional structure.
Influence of eccentric actions on skeletal muscle adaptations to resistance training
Authors: HATHER B. M. , TESCH P. A. , BUCHANAN P. , DUDLEY G. A.
Published: December 2008

Three different training regimens were performed to study the influence of eccentric muscle actions on skeletal muscle adaptive responses to heavy resistance exercise. Middle‐aged males performed the leg press and leg extension exercises two days each week. The resistance was selected to induce failure within six to twelve repetitions of each set. Group CON/ECC (n= 8) performed coupled concentric and eccentric actions while group CON (n= 8) used concentric actions only. They did four or five sets of each exercise. Group CON/CON (n= 10) performed twice as many sets with only concentric actions. Eight subjects did not train and served as controls. Tissue samples were obtained from m. vastus lateralis using the biopsy technique before and after 19 weeks of training, and after four weeks of detraining. Histochemical analyses were performed to assess fibre type composition, fibre area and capillarization. Training increased (P < 0.05) Type IIA and decreased (P < 0.05) Type IIB fibre percentage. Only group CON/ECC increased Type I area (14%, P < 0.05). Type II area increased (P < 0.05) 32 and 27%, respectively, in groups CON/ECC and CON/CON, but not in group CON. Mean fibre area increased (P < 0.05) 25 and 20% in groups CON/ECC and CON/CON, respectively. Capillaries per fibre increased (P < 0.05) equally for Type I and Type II fibres. Capillaries per fibre area for both fibre types, however, increased (P <0.05) only in groups CON and CON/CON. The changes in fibre type composition and capillary frequency were manifest after detraining. At this time only group CON/ECC showed mean fibre hypertrophy, while capillary density was elevated in groups CON/CON and CON. This study suggests that optimal muscle hypertrophy in response to resistance exercise is not attained unless eccentric muscle actions are performed. The data also show that heavy resistance exercise may produce muscle fibre transformation and capillary neoformation.
Regulation of G protein mRNA levels by thyroliberin, vasoactive intestinal peptide and somatostatin in prolactin‐producing rat pituitary adenoma cells
Authors: PAULSSEN E. J. , PAULSSEN R. H. , HAUGEN T. B. , GAUTVIK K. M. , GORDELADZE J. O.
Published: December 2008

We have investigated the regulation of mRNA levels of alpha‐ and beta‐subunits of guanine nucleotide‐binding regulatory proteins (G proteins) by peptide hormones in prolactin producing rat pituitary adenoma cells (GH3 cells) in culture. The cells were treated with thyroliberin (1 μm), vasoactive intestinal peptide (1 μm) or somatostatin (10 μM) for 6 to 48 hours. Thyroliberin and vasoactive intestinal peptide increased the levels of Gsα Goα, Gi‐2α, Gi‐3α, Gxα, Gβ36 and Gβ35 mRNAs. The effect of vasoactive intestinal peptide was however earlier and more pronounced. Gi‐2α mRNA levels showed the quantitatively largest alterations. Somatostatin upregulated Gsα and downregulated Goα and Gi‐2 mRNAs. G protein mRNAs for Gi‐2α and Goα were increased by exposure of the cells to a medium devoid of serum. We conclude that G protein mRNA levels are subjected to alterations by hormones that act through the corresponding G proteins in the regulation of prolactin synthesis and secretion.
Segmental aortic wall stiffness from intravascular ultrasound at normal and subnormal aortic pressure in pigs
Authors: SLØRDAHL S. A. , PIENE H. , LINKER D. T. , VIK A.
Published: December 2008

Segmental aortic wall stiffness was calculated from intravascular ultrasound images and intravascular pressures in six pigs at normal and subnormal aortic pressures (21 sequences of pressures and areas before and after boli of intravenous nitroglycerin). The wall stiffness was expressed as the pressure–strain elastic modulus (Ep). The Ep was calculated from the formula: Ep=ΔPRΔR‐1 (P, pressure; R, radius) in two different ways. First from maximal and minimal values of pressure and area. Second as the slope of linear regression line of ΔPR as a function of ΔR from 29 simultaneous recorded pressures and images. The average Ep value for all sequences in the different segments was 0.58 ± 0.55 105 Pa (Method 1) and 0.50 ± 0.40 105 Pa (Method 2). Ep increased with the distance from the heart at normal aortic pressures. At subnormal aortic pressures after intravenous nitroglycerin this relationship was not so evident. At subnormal aortic pressures the calculated Ep values were significantly reduced in the lower half of the abdominal aorta. The phase lag, i. e. hysteresis, between pressure and diameter was demonstrated. Our study shows the applicability of intravascular ultrasound as a tool to evaluate arterial wall stiffness.
A note on the errors of using venous congestion in intact rats for determinations of microvascular permeability
Authors: HARALDSSON B. , JOHNSSON E. , RIPPE B.
Published: December 2008

The established ideas of transcapillary exchange have recently been challenged based on studies in intact rats. In vivo measurements of net fluid flux and albumin clearance in muscle (and skin) have given estimates of the reflection coefficient (s̀) for albumin of 0.98–0.99 compared to the s̀ value of 0.90 obtained by most other techniques. This discrepancy has vast consequences for the understanding of the transcapillary passage of macromolecules. A s̀ for albumin near unity implies that there is virtually no coupling between protein and fluid transfer as induced by, for example, increases in vascular hydrostatic pressures. However, there are several assumptions inherent in the seemingly straight‐forward experiments on intact rats, and in the present study we tested the hypothesis that occlusion of the femoral vein by ligation induces only moderate and transient increments of venous pressure (Pv).

During control conditions Pv was 6.3 mmHg and pressure increased to 12.8 mmHg immediately following venous occlusion. However, Pv declined with time and after 30 minutes of occlusion the capillary hydrostatic pressure was only increased by 3.0 mmHg. Calculations of the capillary filtration coefficient gave completely unrealistic values, close to those of maximally vasodilated skeletal muscle.

The findings suggest that data obtained from intact rats, albeit important and interesting, should be evaluated with great care due to possible experimental errors in the in vivo approaches. In particular, the technique of estimating s̀ for albumin in intact rats must be subjected to modifications before allowing any reliable conclusions. The multiple pathway model of microvascular permeability, where large pores significantly contribute to capillary wall selectivity, still seems to offer the best description of the exchange characteristics of continuous capillary walls.
Upper and lower bounds on capillary permeability ratios of Cr‐EDTA to cyanocobalamine in rat hindquarters
Authors: HARALDSSON B. , RIPPE B.
Published: December 2008

The single injection indicator dilution technique, often used for assessing capillary permeability, was employed for estimations of the equivalent pore radius of skeletal muscle microvessels according to the theory of restricted diffusion. There are, however, certain important sources of error that must be considered in order to allow conclusions regarding the degree of restricted diffusion. In this study, we have recalculated previously published data in order to minimize the effect of heterogeneity of the second kind, i. e. a transit‐time dependence of the fractional extraction values. The method used makes it possible to calculate reliable intervals of confidence for the permeability surface area products, and hence for the permeability surface area product‐ratios (and equivalent pore radius), taking into account the maximal theoretical impact of back diffusion on measured extraction data.

After correction for transit‐time dependent effects of heterogeneity, the permeability surface area product‐ratio of Cr‐EDTA to cyanocobalamine (vit. B12) from 48 measurements in eight rats was found to have a theoretical ‘upper bound’ of 2.63±0.06 and a lower bound of 2.10±0.07, corresponding to an equivalent pore radius of 60 to 109 Å. This minimum pore radius estimate was even further reduced by corrections for plasma flow dependent reductions in overall extraction fraction (heterogeneity of the first kind) to 45 Å, whereas the upper bound on pore radius was reduced to 60 Å. These data strongly support the presence of marked restricted diffusion of small solutes in the maximally vasodilated rat hindquarter microvasculature.
Effect of arm‐cranking on leg blood flow and noradrenaline spillover during leg exercise in man
Authors: RICHTER E. A. , KIENS B. , HARGREAVES M. , KJÆR M.
Published: December 2008

Controversy exists whether recruitment of a large muscle mass in dynamic exercise may outstrip the pumping capacity of the heart and require neurogenic vasoconstriction in exercising muscle to prevent a fall in arterial blood pressure. To elucidate this question, seven healthy young men cycled for 70 minutes at a work load of 5540%VO2max. At 30 to 50 minutes, arm cranking was added and total work load increased to (mean ± SE) 82 ± 4% of Vo2max. During leg exercise, leg blood flow average 6.15 4.511 minutes‐1, mean arterial blood pressure 137 ± 4 mmHg and leg conductance 42.3 ± 2.2 ml minutes‐1 mmHg‐1. When arm cranking was added to leg cycling, leg blood flow did not change significantly, mean arterial blood pressure increased transiently to 147 ± 5 mmHg and leg vascular conductance decreased transiently to 33.5 ± 3.1 ml minutes‐1 mmHg‐1. Furthermore, arm cranking doubled leg noradrenaline spillover. When arm cranking was discontinued and leg cycling continued, leg blood flow was unchanged but mean arterial blood pressure decreased to values significantly below those measured in the first leg exercise period. Furthermore, leg vascular conductance increased transiently, and noradrenaline spillover decreased towards values measured during the first leg exercise period. It is concluded that addition of arm cranking to leg cycling increases leg noradrenaline spillover and decreases leg vascular conductance but leg blood flow remains unchanged because of a simultaneous increase in mean arterial blood pressure. The decrease in leg vascular conductance observed when arm cranking increased mean arterial blood pressure could be regarded more as a measure to prevent overperfusion than a measure to maintain arterial blood pressure.