bluuebunny/crossref_metadata_2025_split huggingface dataset:
The distribution of blood flow and glucose uptake within single skeletal muscles in the awake rabbit
Authors: IVERSEN P. O. , NICOLAYSEN G. 
Published: December 2008

We have previously described a substantial regional heterogeneity both in blood flow and in glucose uptake within single skeletal muscles in anaesthetized rabbits. These heterogeneities could be related to effects of anaesthesia. The main goal of the present study was therefore to study regional muscle blood flow and muscle glucose uptake in awake rabbits.We used the microsphere method and the deoxyglucose technique for assessment of regional blood flow and regional glucose uptake respectively. The measurements were performed in 0.25‐g regions from hind leg muscles. Some rabbits were first studied while awake and then during anaesthesia. Others were studied while either awake or anaesthetized.The degree of regional heterogeneity in blood flow and in glucose uptake was similar in awake and anaesthetized rabbits. Both temporal and spatial heterogeneity in blood flow were present. Evidence was found for vasomotion with a cycle time exceeding 45 min in awake rabbits. This perfusion pattern was similar in rabbits in which either the motor or sympathetic vasomotor nerves or both had been blocked.We conclude that regional perfusion and glucose uptake within single muscles are also markedly heterogeneous in awake rabbits. Regional, non‐synchronized fluctuations in blood flow with a long cycle time seem to be an important part of this perfusion heterogeneity.
Occurrence of phospholipase A2 and lysophospholipase in a gastric H, K‐ATPase‐containing membrane fraction, and the formation of lysophosphatidylcholine in stimulated pig parietal cells
Authors: OLAISSON H. , ARVIDSON G. , MA J.‐Y. , MÅRDH S. 
Published: December 2008

A membrane fraction containing ‐ATPase (EC 3.6.1.36) was prepared from pig gastric mucosa and found to contain phospholipase A, (EC 3.1.1.4) and lysophospholipase (EC 3.1.1.5) activities. Washing the membranes decreased their protein content by 25%. Recovery profiles of ‐ATPase, phospholipase A, and lysophospholipase were similar for membranes washed either with water or with 0.15 or 1.5 m KCI. Nearly identical distribution profiles were obtained for the three enzyme activities after centrifugation of washed vesicle membranes on a linear sucrose gradient. The phospholipase A2 activity was stimulated by calcium and increased further in the presence of calmodulin.The amount of cellular radioactively labelled lysophosphatidylcholine was doubled upon cholinergic stimulation of isolated parietal cells prelabelled with [3H]glycerol or 32P1. The liberated lyso(32P]phosphatidylcholine had its acyl chain in the sn‐1 position, which implies an activation of a phospholipase A2. These findings indicate that secretagogues which increase the cytosolic Ca2+ concentration, i.e. acetylcholine, histamine and gastrin, may activate a phospholipase A2 in the parietal cell.
Reversible increase in light scattering during recovery from fatigue in Xenopus muscle fibres
Authors: WESTERBLAD H. , LÄNNERGREN J. 
Published: December 2008

During recovery from fatigue produced by repeated tetanic stimulation, isolated Xenopus muscle fibres often enter a reversible state of severely depressed tension production. This post‐contractile depression has previously been found to be accompanied by an altered light microscopical appearance of fibres (increased light scattering), which suggests some morphological change as the cause of the force reduction. In the present study the relation between tension production and light scattering (measured as optical density) has been studied in more detail. It was found that fibres developing a marked post‐contractile depression exhibited the largest increase in light scattering. When fibres recovered from post‐contractile depression, an increased optical density remained in the central region of fibres, and this region also produced less tension. The tension output of fibres recovering without post‐contractile depression declined markedly when the tonicity of the bathing solution was raised, and this decline was accompanied by increased optical density. However, a close temporal correlation between increased light scattering and tension depression was not always found: in some fibres the time course of changes in light scattering differed from that of the tension depression.In summary, the present results show that reversible structural changes may develop after fatiguing stimulation, and some form of coupling between these changes and the force depression during post‐contractile depression is suggested.
Daily patterns of plasma atrial natriuretic peptide, serum osmolality and haematocirt in the rat
Authors: KANERVO A. , ARJAMAA O. , VUOLTEENAHO O. , LEPPÄLUOTO J. 
Published: December 2008

The present study documents daily rhythms of plasma atrial natriuretic peptide, serum osmolality and haematocrit in the rat. One‐hundred and twenty‐five Sprague‐Dawley rats were used. They were bred under a cycle of 12 h light/12 h dark starting at 07.00 h. Fifty‐three rats were decapitated between 09.00 and 16.00 h (study I) and 72 rats in groups of six were decapitated at 2‐h intervals for a period of 24 h (study II). In study I, plasma atrial natriuretic peptide was 156±11 pg mg‐1 (mean ± SEM). In study II, atrial natriuretic peptide was at a control level from 08.00 to 18.00 h and then began to increase. At 22.00 h, atrial nartriuretic peptide was 420 ± 105 pg ml‐1, which was significantly higher than at 08.00 h (P < 0.05). The serum osmolality was over 300 mosmol kg‐1 during the day. The highest mean osmolalities (315, 317, 312 mosmol kg‐1 were found from 18.00 to 22.00 h. These were significantly different (P < 0.05) from other groups during the day. The haematocrit was highest at 14.00 h (49.5 ± 0.7%) and lowest at 24.00 h (43.6 ± 0.8%) (P < 0.05).In conclusion, we have shown that there are significant daily rhythms of plasma atrial natriuretic peptide, serum osmolality and haematocrit during a 24‐h period and 12 h light/12 h dark cycle in the rat.
Nitric oxide requirement for vasomotor nerve‐induced vasodilation and modulation of resting blood flow in muscle microcirculation
Authors: PERSSON M. G. , WIKLUND N. P. , GUSTAFSSON L. E. 
Published: December 2008

Intravital microscopy of rabbit tenuissimus muscle was used for studies of endogenous nitric oxide as a microvascular regulatorin vivo.Derivatives of were administered in order to modulate the formation of nitric oxide from L‐arginine. Nw‐nitro‐L‐arginine methylester (L‐NAME) (1‐100 mg kg‐1i.v.) dose‐dependently reduced microvascular diameters. A concomitant blood pressure increase and a decrease in heart rate was observed. The blood pressure increase induced by L‐NAME (30 mg kg‐1) was reversed by L‐arginine (1 g kg‐1) but not D‐arginine. Vasodilation in response to topical acetylcholine (0.03‐3 μM) was significantly inhibited by L‐NAME (30 mg kg‐l), whereas vasodilation by sodium nitroprusside (300 nM) was not affected. Vasomotor nerveinduced vasodilatation, induced by stimulation of the tenuissimus nerve after neuromuscular blockade by pancuronium in animals pretreated with guanethidine, was significantly attenuated by L‐NAME, an effect also reversed by L‐arginine. The vasodilatation in response to active contractions of the muscle induced by motor nerve stimulation as well as the vasodilator response elicited by graded perfusion pressure reductions were unaffected by L‐NAME or NG‐monomethyl‐L‐arginine (L‐NMMA, 10‐4M) administered topically.Our results indicate that endogenous nitric oxide formed from L‐arginine is a modulator of microvascular tonein vivo.Furthermore, the results suggest that endogenous nitric oxide is required for vasomotor nerve‐induced vasodilatation, whereas it does not appear to play a role in myogenic vasodilatation or functional hyperaemia in this tissue.
Dual response from human muscle spindles in fast voluntary movements
Authors: AL‐FALAHE N. A. , NAGAOKA M. , VALLBO A. B. 
Published: December 2008

Single‐unit impulses were recorded from the radial nerve of attending human subjects using the microneurography technique. The discharge of muscle spindle afferents from the extensor digitorum muscles was analysed while subjects performed fast lengthening and shortening voluntary movements as well as movements of moderate speed at a single metacarpophalangeal joint. Opposing or assisting loads of moderate size were added in some tests.Fast lengthening movements were, in practically all units, associated with acceleration of spindle discharge. However, the responses were modest and in many primary afferents it was of similar size as their response to small irregularities during slower movements.During shortening movements, most spindle afferents stopped firing altogether, whereas some afferents exhibited a distinct burst of impulses at the onset of active shortening followed by silence during the main part of the movement. This initial shortening responses was sometimes more prominent when the parent muscle worked against an opposing load. It was interpreted as a result of fusimotor drive associated with the building up of force in the contracting muscle.The initial shortening response from the contracting muscle and the stretch response from the antagonist constitute a dual signal, describing accurately the onset of joint movement as seen from the two muscles. It remains to be clarified which role this pattern of afferent responses may have in the design of the current motor output and in the capturing of nature and size of the external load.
Is the humoral renal antihypertensive activity of the spontaneously hypertensive rat (SHR) reset to the high blood pressure?
Authors: Karlström G. , Bergström G. , Folkow B. , Rudenstam J. , Göthberg G. 
Published: December 2008

The kidneys have a humoral antihypertensive system, located in the renal medulla and presumably antagonizing the pro‐hypertensive renin‐angiotensin system. Medullipin I and II and maybe platelet activating factor (PAF), seem to be the mediators of this system, known to be activated after reversal of renovascular hypertension or when the perfusion pressure to a normotensive kidney is suddenly elevated.The present study was undertaken to investigate whether this system is functioning also in the spontaneously hypertensive rat (SHR), and if it is then reset in proportion to the increased mean arterial pressure (MAP). Isolated kidneys from spontaneously hypertensive rats and from Wistar Kyoto rats (WKY) were cross‐perfused in vivo from anaesthetized intact Wistar Kyoto rat ‘donors’. After 30 min of perfusion at 100 mmHg the perfusion pressure to the isolated kidneys were, for 60 min, either kept unaltered at 100 mmHg or, for the Wistar Kyoto rat kidneys, increased to 150–200 mmHg and, for the spontaneously hypertensive rat kidneys, raised to 200 or 250 mmHg.The results show that the humoral antihypertensive system is present also in spontaneously hypertensive rat kidneys, but is here reset upwards to or even beyond the elevated MAP level. Furthermore, all mean arterial pressure reductions caused by high‐pressure perfusion of Wistar Kyoto and spontaneously hypertensive rat kidneys were accompanied by reductions in heart rate (HR) in the ‘donors’, in agreement with previous observations after reversing renal hypertension and after i.v. medullipin I injection.In fact, in spontaneously hypertensive rat kidneys, the ‘incretory’ depressor mechanism appears to be more markedly reset upwards than is the ‘excretory’ depressor mechanism inherent in pressure diuresis with consequent salt‐volume elimination.In conclusion spontaneously hypertensive rats, like Wistar Kyoto rats and Wistar rats, have a humoral antihypertensive system in the kidneys, but it is reset upwards even beyond the elevated mean arterial pressure level in spontaneously hypertensive rats. The combination of a depressor response and reduced heart rate in the ‘donors’ renders further evidence that the medullipins are the principal, though probably not the only, humoral antihypertensive factors released from the cross‐circulated kidneys.
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.
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.
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.
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.
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.