bluuebunny/crossref_metadata_2025 huggingface dataset:
Effects of acute and long‐term atropine treatment on levels, release and response to VIP and PHI in the submandibular gland of cat and rat
Authors: DUNÉR‐ENGSTRÖM M. , LARSSON O. , FREDHOLM B. B. , LUNDBLAD L. , FAHRENKRUG J. , LUNDBERG J. M.
Published: December 2008

We have studied the effects of acute and long‐term treatment of cats and rats with atropine on the levels, release and effects of two peptides, vasoactive intestinal polypeptide (VIP) and peptide histidine isoleucine (PHI), that probably co‐exist with acetylcholine in the parasympathetic nerves supplying the submandibular gland.

Atropine treatment (progressively increasing doses from 2 to 15 mg kg‐1 injected s.c.) for 14 days did not alter the contents of VIP‐ or PHI‐like immunoreactivity (‐IR) in the cat submandibular gland or in three other tissues (nasal mucosa, trachea and tongue). Acute as well as long‐term atropine treatment decreased the vasodilatation following low‐, but not high‐, frequency parasympathetic nerve stimulation. During prolonged stimulation (60 min) there was a decreased vasodilatation response following both acute and long‐term atropine treatment. The overflow of VIP‐IR and PHI‐IR following parasympathetic nerve stimulation was markedly increased by acute, but not by long‐term atropine treatment. The VIP‐ or PHI‐induced stimulation of cyclic AMP (cAMP) accumulation in the cat submandibular gland was not altered after long‐term atropine treatment.

Similarly, treatment of male Sprague‐Dawley rats with atropine (20 mg kg‐1) or imipramine (20 mg kg‐1) for 14 days did not alter the sensitivity to VIP or to PHI of cAMP accumulation in the submandibular gland, nor was there any change in VIP‐IR or PHI‐IR content.

In conclusion, although atropine treatment causes an acute increase in the overflow of VIP and PHI evoked by parasympathetic nerve stimulation, there is no depletion of peptide stores upon long‐term treatment, nor is there any change in the effect of exogenous VIP and PHI on cAMP‐accumulation.
Non‐linearity of skin resistance response to intraneural electrical stimulation of sudomotor nerves
Authors: KUNIMOTO M. , KIRNÖ K. , ELAM M. , KARLSSON T. , WALLIN B. G.
Published: December 2008

Intraneural electrical stimuli (0.3 mA, 0.2 ms) were delivered via a tungsten micro‐electrode inserted into a cutaneous fascicle in the median nerve at the wrist in 16 normal subjects, and the effects on the sweat glands within the innervation zone were recorded as changes of skin resistance. In order to examine the relationship between the skin resistance level and the amplitude of transient resistance responses, trains of high frequency stimulation were used to reduce the skin resistance level and then transient resistance responses were evoked by single stimuli at 0.1 Hz. Regional anaesthesia of the brachial plexus in the axilla eliminated spontaneous sympathetic activity and reflex effects.

At high skin resistance levels response amplitudes to single stimuli were low but they increased successively to a maximum at intermediate levels and then decreased again at low resistance levels. Repeated stimulation sequences evoked qualitatively similar response curves but quantitatively both response amplitudes and skin resistance levels were slightly reduced upon repetition.

We suggest that the changes of response amplitudes are due to variable resistivity of the corneal layer. The shifts of the response curves with repetition of stimulation may result from increased hydration of the corneum.

It is concluded that the variability of response amplitudes to constant stimuli makes the amplitude of a skin resistance response unsuitable as an indicator of the strength of sympathetic sudomotor nerve traffic.
Chemoattractant‐induced firm adhesion of leukocytes to vascular endothelium in vivo is critically dependent on initial leukocyte rolling
Authors: LINDBOM L. , XIE X. , RAUD J. , HEDQVIST P.
Published: December 2008

Leukocyte rolling and firm adhesion at the venular endothelium are two discrete events in the cellular inflammatory response mediated via selectin and integrin adhesion molecules, respectively. The dependency of chemoattractant‐induced firm leukocyte adhesion on the preceding rolling interaction was investigated in rat mesenteric microvessels through use of intravital microscopy. Leukocyte rolling was dose‐dependently inhibited by systemic treatment with the sulphated polysaccharide fucoidin. The firm leukocyte adhesion following stimulation with the chemotactic peptide fMLP was similarly inhibited when fMLP challenge was performed subsequent to inhibition of leukocyte rolling by fucoidin. Thus, based on paired observations in single venules before and after fucoidin treatment, reduced rolling leukocyte flux prior to fMLP challenge was paralleled over a wide range by a proportional decrease in fMLP‐induced leukocyte adhesion. The results demonstrate quantitatively a close relationship between the extent of leukocyte rolling and the magnitude of the subsequent firm adhesion response, and, that an initial rolling interaction is a precondition for firm adhesion to occur at physiological blood flow rates in vivo.
Vasomotion in the rat cerebral microcirculation recorded by laser‐Doppler flowmetry
Authors: MORITA‐TSUZUKI Y. , BOUSKELA E. , HARDEBO J. E.
Published: December 2008

In the present study, changes in frequency and amplitude of the rhythmic variations (vasomotion) in blood flow in the intact cerebral circulation of the rat were investigated using laser‐Doppler flowmetry (LDF) during stepwise decrease in mean arterial blood pressure (MABP) and hyper‐and hypocapnia. Experiments were performed on 12 adult Sprague‐Dawley rats of either sex, anaesthetized with α‐chloralose. The rat's head was fixed on a stereotaxic frame and a small hole was made in the parietal bone but the dura and a thin inner bone layer were kept intact. The microvascular blood flow of the parietal cortex on the right or on both sides was continuously recorded by the laser‐Doppler flowmeter (Periflux PF2B, Perimed, Stockholm, Sweden). The cerebral circulation of the rat exhibited vasomotion in control conditions with a frequency of 8–10 cycles per minute (cpm) and an amplitude of 5–10% of the cerebral blood flow (CBF). No significant changes in CBF could be detected when the MABP was above 60 mmHg, but it decreased significantly when MABP was reduced below 50 mmHg. However, during stepwise pressure reduction the vasomotion frequency decreased progressively while its amplitude showed a reversed U‐shaped curve with a peak at 60–80 mmHg. During hypercapnia, the rhythmical oscillations showed a decrease in both frequency and amplitude, whereas during hypocapnia their frequency did not change but their amplitude increased. These results support the hypothesis that the vasomotion frequency might be dependent of the wall tension and cellular pH while its amplitude could be related to decreased tissue oxygenation.
Changes in muscle sympathetic nerve activity and calf blood flow during combined leg and forearm exercise
Authors: SAITO M. , KAGAYA A. , OGITA F. , SHINOHARA M.
Published: December 2008

In order to examine efferent sympathetic nerve control of the peripheral circulation during exercise, muscle sympathetic nerve activity (MSNA), calf blood flow (CBF), heart rate (HR), blood pressure (BP) and oxygen uptake were measured during combined foot and forearm exercise. An initial period of rhythmic foot exercise (RFE) (60 min‐1at 10% of maximal voluntary contraction (MVC) was followed by the addition of rhythmic handgrip exercise (RFE+OCCL) (60 min at 30% of MVC) and by forearm ischaemia after handgrip exercise while continuing RFE (RFE + OCCL). During RFE, CBF in the working leg, HR and oxygen increased respectively by 560%, 121% and 144% when compared with the control rest period, but MSNA (burst rate) was reduced by 13% (P> 0.05) and BP was unchanged. During RFE+RHG, HR, BP and oxygen uptake were greater than during RFE alone. There was no change in CBF, but a significant increase occurred in calf vascular resistance (CVR) and MSNA increased to 121% of the control level. During RFE + OCCL, MSNA, CVR and BP were all higher than during RFE alone, whereas HR and oxygen uptake decreased slightly, although they remained higher than the control values. The increase in CVR in the working leg and the rise in BP during RFE+RHG or RFE+OCCL might be linked to enhancement of MSNA, which may have been reflexly evoked by input from muscle metabolic receptors in the working forearm.
Tolerance to haemorrhage during vasopressin antagonism and/or captopril treatment in conscious sheep
Authors: ULLMAN J. E. , HJELMQVIST H. , LUNDBERG J. M. , RUNDGREN M.
Published: December 2008

The effect of separate and combined blockade of vasopressin (AVP) V1‐receptors and angiotensin II formation on resistance to a slow venous haemorrhage (0.7 ml kg‐1 min‐1) was studied in six conscious adult sheep by bleeding to the point of an abrupt fall in the mean systemic arterial pressure (MSAP). Intravenous administration of the V1‐receptor antagonist [d(CH2)5Tyr(Me)AVP] (10 μg kg‐1) and/or the angiotensin I converting enzyme inhibitor captopril (20 mg+1 mg h‐1) did not cause any significant haemodynamic changes in the normovolaemic animal. The volume of haemorrhage necessary to induce acute hypotension (MSAP < 50 mmHg) was significantly smaller after AVP blockade alone (13.8±0.7 ml kg‐1; P < 0.01) but not after captopril treatment (14.7±1.6 ml kg‐1; n.s.) compared to control animals receiving no drug treatment (16.8±0.6 ml kg‐1). The combined treatment with the AVP antagonist and captopril caused a further decrease in tolerance to haemorrhage (9.4±1.2 ml kg‐1; P < 0.001).

Blockade of AVP V1‐receptors was associated with an attenuated increase in systemic vascular resistance immediately after the end of haemorrhage, concomitant with an accentuated lowering of the central venous pressure. In contrast, captopril treatment decreased the degree of vasoconstriction mainly during the second half of the post‐haemorrhage observation period of 1 hour.

It is concluded that both AVP and angiotensin II contribute to the maintenance of the MSAP during haemorrhage in conscious sheep. During the spontaneous recovery after hypotensive blood loss, a vasoconstrictor effect of AVP is evident mainly during the initial 15 min, whereas at later stages angiotensin II appears to be of relatively greater importance.
The effects of testosterone on insulin sensitivity in male rats
Authors: HOLMÄNG A. , BJÖRNTORP P.
Published: December 2008

In order to examine the effects of testosterone (T) on insulin sensitivity, male rats were castrated or sham‐operated, and exposed to low or high doses of T to substitute normal or to produce high serum T concentrations. Insulin sensitivity was followed by euglycaemic, hyperinsulinaemic glucose clamp measurements. An index of insulin‐stimulated glucose transport was obtained in the white gastrocnemius (WG), extensor digitorum longus (EDL), red gastrocnemius (RG) and soleus (SOL) muscles after a bolus dose of [2‐3H]deoxyglucose (2‐DOG) when steady state was obtained in the clamp measurements. Glycogen synthesis was followed similarly with [U‐14C]glucose as a labelled precursor after isolation of glycogen in the muscles mentioned, and in the liver. Castration and high T were followed by a marked insulin resistance in the clamp measurements. This was paralleled by a diminished insulin stimulation of glucose incorporation into glycogen down to about 50% of control values, apparently equally pronounced in all muscles but not found in liver glycogen synthesis. 2‐DOG uptake was diminished by castration in the WG and RG muscles but was unaffected by high doses of T. Substitution of castrated rats with a low dose of T, restoring their serum T concentrations to the normal range, completely abolished these perturbations of insulin sensitivity. It is concluded that T is an important regulator of muscular insulin sensitivity, which seems to be highest in a ‘window’ of normal serum T concentrations.
The mediation of increased duodenal alkaline secretion in response to 10 mm HCI in the anaesthetized rat. Support for the involvement of capsaicin‐sensitive nerve elements
Authors: HAMLET A. , JÖNSON C. , FÄNDRIKS L.
Published: December 2008

Experiments were performed on chloralose‐anaesthetized rats. Bicarbonate secretion by the duodenal mucosa was continuously recorded by use of an in situ‐titration technique. Exposing the duodenal segment to 10 mM HCl over 5 min increased the bicarbonate transport by about 65%. This acid‐induced secretory response was resistant to neural decentralization by means of bilateral cervical vagotomy and/or splanchnicotomy. Furthermore, in the decentralized state, serosal application of the local anaesthetic lidocaine or tetrodotoxin (TTX) lowered basal duodenal bicarbonate secretion. Despite the presence of lidocaine or TTX, exposure of the duodenal mucosa to 10 mM HCl induced a net increase in secretion with a magnitude similar to that observed in the control situation with intact nerves. A 5‐min exposure period of the decentralized duodenal segment to capsaicin (1.2 mg ml‐1) raised bicarbonate secretion, a response which also occurred in the presence of lidocaine (serosa). Tachyphylaxis to capsaicin blocked the secretory response to 10 mM HCl and inhibited the response to luminal prostaglandin E2 (1.5 10‐5 M) by 80%.

The present results indicate that luminal exposure to 10 mM HCl activates capsaicinsensitive primary afferents which, locally within the submucosa or epithelium, activate the bicarbonate secretion.
Addition of purified orosomucoid preserves the glomerular permeability for albumin in isolated perfused rat kidneys
Authors: JOHNSSON E. , HARALDSSON B.
Published: December 2008

The serum protein, opsomucoid has been shown to be essential for the maintenance of normal capillary permeability in several different organs, including the kidney. Thus, the clearance of albumin was found to be almost fivefold higher in the absence of orosomucoid in a previous study on isolated rat kidneys, perfused with either of two commercially available human albumin solutions of similar composition, but differing in their content of orosomucoid (0.21 g 1‐‐1 vs. < 0.005 g 1‐‐1), The following experiments were performed in order to verify the hypothesis that this effect on glomerular permselectivity was due to orosomucoid per se and not to other ingredients in the two solutions. Both kidneys of 12 rats were isolated and perfused with identical albumin solutions without orosomucoid, but with the addition of purified orosomucoid (0.25 g 1‐‐1) to one of the kidneys. No significant differences in vascular resistance, urine flow or glomerular filtration rate (GFR), which was found to be 27 ± 2 ml min‐1 100 g‐1, were observed between the two groups of kidneys. The fractional clearance of albumin (θ) was initially similar for both kidneys (0.0022 ± 0.0002). In the absence of orosomucoid, θ gradually increased to 0.0076 ± 0.0013 after 1 h of perfusion compared to 0.0040 ± 0.0006 for the kidneys with orosomucoid added to the perfusate (P < 0.001, n= 12). We conclude that the plasma glycoprotein orosomucoid indeed plays an important role in regulating the dynamic properties of the glomerular capillary wall by reducing the permeability towards macromolecules such as albumin.
Neuropeptide Y and differential sympathetic control of splenic blood flow and capacitance function in the pig and dog
Authors: MODIN A. , PERNOW J. , LUNDRERG J. M.
Published: December 2008

The roles of different mediators in the sympathetic regulation of the pig and dog spleens were investigated using a preparation with intact vascular perfusionin vivo. Sympathetic nerve stimulation caused overflow of neuropeptide Y‐like immunoreactivity (NPY‐LI) and noradrenaline (NA), arterial vasoconstriction, increase in venous blood flow and haematocrit. The dog spleen responded to single impulse stimulation, whereas more prolonged stimulation was required to elicit vascular responses in the pig spleen. Furthermore, the maximal splenic capacitance response was about 10 times larger in the dog than in the pig. After depletion of neuronal NA content by reserpine combined with preganglionic denervation, about 70% of the splenic arterial vasoconstrictor responses in the dog and pig still remained at 5 Hz stimulation. Fifty per cent of the capacitance response evoked by nerve stimulation still remained in the pig while in the dog spleen the capacitance response was virtually abolished after reserpine. The stimulation‐evoked overflow of NPY‐LI in pig spleen was increased several fold after reserpine treatment as compared to controls reaching levels in the venous effluent where exogenous NPY evokes vasoconstriction. In the dog spleen, overflow of NPY‐LI was only observed after reserpine. Administration of NA caused arterial vasoconstriction with an initial increase in venous blood flow while NPY mainly reduced arterial blood flow.

It is concluded that NA is involved in both the splenic arterial vasoconstriction and the capacitance responses while a non‐adrenergic splenic vasoconstriction at least in the pig may be mediated by NPY.
Non‐invasive techniques for assessing carbohydrate flux
Authors: SONKO B. J. , MURGATROYD P. R. , GOLDBERG G. R. , COWARD W. A. , CEESAY S. M. , PRENTICE A. M.
Published: December 2008

A non‐invasive method for studying the dynamics of post‐exercise carbohydrate storage by means of whole‐body calorimetry and 13CO2 breath tests is described. Seven untrained glycogen‐depleted subjects were offered naturally 13C‐labelled high carbohydrate meals (97% by energy) at 30 min intervals for 5 h and asked to consume as much as possible. Mean intake averaged 757 ± 211 (SD) g. Exogenous carbohydrate oxidation over 16 h calculated from gas exchange and isotope ratio measurements averaged 161 ± 45 g, and endogenous carbohydrate oxidation averaged 31 ± 25 g. Net carbohydrate storage, calculated as the difference between amount ingested and oxidized, was 563 g which was more than twice the measured hepatic and muscle carbohydrate oxidized during the depletion phase. After correction for body size the major determinant of glycogen storage was the amount of carbohydrate consumed (r = 0.97, P < 0.001) which in turn was determined by each subject's dietary tolerance. Post‐repletion exercises (12 h after last meal) were used to remobilize freshly stored glycogen. 13CO2 enrichments indicated that a substantial part of the new glycogen was derived from the exogenous carbohydrate provided by the repletion meals.
Effects of exercise training on the biosynthesis of prostacyclin and thromboxane in rats
Authors: CHEN H.‐I. , JEN C. J. , CHANG W.‐C.
Published: December 2008

The effects of exercise training on eicosanoid levels were studied in male Wistar rats. One‐month‐old rats were trained on a drum exerciser at an intensity of around 70% of maximal oxygen consumption for 10 weeks (60 min day‐1, 5 days week‐1) after familiarization. Some animals of the same age did not exercise and served as a control. Two days after training, several blood vessels, including thoracic aortae, inferior vena cavae, external iliac arteries, external iliac veins, common carotid arteries and jugular veins, were excised and incubated for 10 min. Basal release of prostacyclin from these vessels was determined using [125I]radio‐immunoassay (RIA) of 6‐keto‐PGF1α. The levels of plasma prostacyclin and urinary metabolites of prostacyclin and thromboxane were also determined by RIA. Our results showed that trained animals had lower body weight and urine II‐dehydro‐thromboxane B2 levels than the controls (P < 0.001 and P< 0.05, respectively). In contrast, urinary 2,3‐dinor‐6‐keto‐PGF1α level was elevated after training (P< 0.05). Nonetheless, prostacyclin levels in plasma and from various dissected vessel segments, except thoracic aorta, did not change significantly after training. These findings suggest that exercise training may affect endogenous eicosanoid levels by increasing the basal release of prostacyclin and reducing the basal thromboxane level.
Biosynthesis of 12(S)‐hydroxyeicosatetraenoic acid by bovine corneal epithelium
Authors: OLIW E. H.
Published: December 2008

Microsomes of bovine corneal epithelium metabolized [14C]arachidonic acid extensively to [14C]12‐hydroxyeicosatetraenoic acid. The biosynthesis was not stimulated by exogenous NADPH and it could be inhibited by over 90% with two lipoxygenase inhibitors, esculetin and eicosatetraynoic acid. Chiral phase high performance liquid chromatography showed that 12‐HETE consisted of the 125 enantiomer. The results indicate biosynthesis by 12S‐lipoxygenase of bovine corneal epithelium rather than by cytochrome P450.
Increased pressure in venous sinusoids during decongestion of rat nasal rnucosa induced by adrenergic agonists
Authors: KRISTIANSEN A. B. , HEYERAAS K. J. , KIRKEBB A.
Published: December 2008

The haemodynamic effects of sympathetic agonists causing decongestion of the nasal mucosa have been investigated in rats. Access to mucosa was obtained from the dorsal side through a small cavity drilled in the nasal bone. The pressures in the venous sinusoids and in the interstitial fluid of nasal mucosa were recorded by micropuncture technique. The local red cell flux (LDF) was monitored by laser Doppler flowmetry, and the blood volume in the mucosa was measured by radio‐labelled erythrocytes and albumin.

In control rats the tissue blood volume was 0.25 ± 0.03 g (g wet wt)‐1. The interstitial fluid pressure (IFP) was 2.4± 0.6 mmHg and the average blood pressure in venous sinusoids (Ps) was 12.8 ± 2.7 mmHg.

After topical application of noradrenaline (NA) the local blood volume was reduced to 0.12 ± 0.03 g g‐l. P, was increased to 18.0 ± 4.0 mmHg, whereas IFP was maintained and LDF was reduced to 40.4% of control, indicating a greater rise in post than in presinusoid vascular resistance.

Blocking of both α1, and α2,‐receptors by phentolamine caused a rise in mucosa blood volume and in LDF by 16 and 20% of control, respectively. Ps, increased significantly to 15.2 ±3.3 mmHg.

Specific stimulation or blocking of α1,‐receptors by phenylephrine or prazosin induced similar or slightly smaller vascular responses than NA or phentolamine. The effects of the specific α2‐agonist (clonidine) or antagonist (yohimbine) on rat mucosa were small, indicating a domination of the α1,‐receptors.

Thus, application of NA caused a rise in blood pressure in the venous sinusoids of nasal mucosa. As LDF fell simultaneously, the reduced blood volume must be due to an increased tone in the muscular wall of venous sinusoids.
Morning increase in whole blood viscosity: a consequence of a homeostatic nocturnal haemodynamic pattern
Authors: TALAN M. I. , ENGEL B. T.
Published: December 2008

In a series of studies, we have shown that in non‐human primates there is a consistent overnight fall in cardiac output and central venous pressure, and a rise in total peripheral resistance. This haemodynamic pattern is associated with a higher haematocrit level in the morning suggesting that these changes in the circulation are homeostatic adjustments to a nighttime fall in plasma volume. The present study was designed to test the hypothesis that in the morning whole blood viscosity also is higher. Whole blood viscosity was measured at shear rates of 450, 225, 90, 45, and 22.5 s‐l in each of six monkeys, on four occasions, at 2‐week intervals, at 17.00 and 09.00 h the next morning. The average haematocrit was 4.2% higher in the morning than in the previous evening (P < 0.01). Viscosity decreased monotonically at progressively higher shear rates but was always significantly higher in the morning than in the evening (P < 0.01 at all shear rates). When viscosity was adjusted by covarying for haematocrit level, the morning/evening differences became non‐significant. However, the morning/evening differences in linear trend of shear stress as a function of shear rate persisted. These findings add further support to our hypothesis that the nocturnal haemodynamic pattern in non‐human primates is related to a reduction in plasma volume, and they also suggest that the morning rise in haematocrit is a major contributing factor to the elevated viscosity.
Much more potent baroreflex sympathetic control of vascular resistance in the resting human limb than previously believed
Authors: LUNDVALL J. , EDFELDT H.
Published: December 2008

The concept that, in man, the sympathetic control of the resting limb vascular resistance is truly limited and thus strikingly different from animal species, was challenged in the present study. Analyses were performed in healthy male volunteers of reflex forearm vascular resistance changes evoked by lower body negative pressure (LBNP) ranging from low (15 mmHg) to high and barely tolerated (85 mmHg) levels. Graded LBNP was associated with graded increases in resistance. At high 85 mmHg LBNP the responses were pronounced with a rise in forearm resistance to no less than 120 mmHg ml‐1min 100+ ml soft tissue, on average, corresponding to a 377% increase above control. This drastic response seemed entirely neurogenic in origin and calculations, based on the likely assumption that a similar response occurred in all skeletal muscle and skin/(subcutaneous fat), showed that it permitted a marked increment in total systemic vascular resistance because of the fact that these tissues constitute so large a proportion of the body mass. The conclusion was reached that the studied tissues may serve as main targets for powerful homeostatic reflexes. It is also suggested, in contrast to current views, that the high‐pressure arterial rather than the low‐pressure cardio‐pulmonary baroreceptors may be the main mediators of haemodynamically important vasoconstrictor responses.
A search for arteriovenous anastomoses in human skin using ultrasound Doppler
Authors: BERGERSEN T. K.
Published: December 2008

The possible existence of arteriovenous anastomoses (AVAs) in skin regions of the head and thorax has been investigated using the synchronous vasomotion of the AVAs. Simultaneous pairs of blood velocity recordings were made using pulsed, bidirectional Doppler ultrasound. In each pair of registrations, blood velocity was recorded in a reference artery supplying a skin area known to contain AVAs (the radial artery) together with one of four other arteries investigated, i.e. the facial artery, the angular artery, the temporal artery, and the cutaneous branches of the lateral thoracic artery.

The typical large, regular fluctuations in blood velocities caused by synchronous vasomotion in the AVAs in the skin of the hand and fingers were observed invariably in the radial artery. Similar flow variations were found in the angular artery. The fluctuations in this and the radial artery were, in turn, found to be synchronous. However, we have not been able to find the flow patLern characteristic of AVA vasomotion in the temporal artery or in the cutaneous branches of the lateral thoracic artery.

These results show that the skin area of the nose supplied by the angular artery contains AVAs. These AVAs partly may explain the important role of face skin in temperature regulation. These results also support the earlier assumptions that there are no or very few AVAs in the skin areas supplied by the temporal artery and the cutaneous branches of the lateral thoracic artery.
Plasma potassium concentration and Doppler blood flow during and following submaximal handgrip contractions
Authors: JENSEN B. R. , FALLENTIN N. , BYSTRÖM S. , SJØGAARD G.
Published: December 2008

The aim of the present study was to investigate the time‐course of blood velocity in the forearm during and folllowing isometric handgrip contractions and to reveal a possible temporal relationship between the circulatory response and venous effluent potassium concentration ([K]) not only during contractions but also during the post‐exercise recovery period. Contractions of 15% maximal voluntary contraction (MVC) and 30% MVC with and without 3 min of artirial occlusion following the contractions were studied.

All contractions induced a significant increase in venous plasma [K] from an average resting level of 4.0 to 5.0 mM during 15% MVC and 5.8 mM during 30% MVC. Blood velocity increased from a resting level of 0.07 to 0.22 m s‐1 diromg 15% and 30% MVC, respectively. MCC of 30% always elicited a larger blood velocity and [K] response than 15% MVC.

Following the contractions hyperaemia was elicited. Recovery of the local blood velocity was markedly slower than the K recovery, since [K] remained significantly above resting level for only 25 s following 15% MVC and 45 s following 15 and 30% MVC, respectively. Further, a larger hyperaemia following the occlusion was elicited as compared to the contraction without occlusion, in spite of [K] being lower immediately after the occlusion period than immediately after the contraction. Finally, [K] decreased below resting level in the recovery period while the blood velocity remained elebvated. Therefore, the present study showed that the venous plasma [K] is not causally related to the prolonged post‐exercise hyperaemia.

The skin temperature remained unchanged during the contractions, while during the recovery period the skin temperature increased for several minutes. The major part of the temperature increase was likely to be due to conductance of heat from muscles to skin surface as a consequence of muscle hyperaemia.
An age‐related type IIB to IIX myosin heavy chain switching in rat skeletal muscle
Authors: LARSSON L. , BIRAL D. , CAMPIONE M. , SCHIAFFINO S.
Published: December 2008

A novel fast‐twitch motor unit type, called the IIX‐myosin heavy chain (MHC) motor unit, identified by the glycogen depletion technique together with a series of monoclonal antibodies (mAbs) specific for MHCs, has been isolated recently in the rat tibialis anterior muscle. In young animals, this unit has physiological, biochemical and morphometrical properties which separate it from the IIA‐ and IIB‐MHC motor units. In old age, on the other hand, the IIX‐MHC units display physiological, biochemical and morphometrical properties resembling the IIB‐MHC motor units. Based on these results it was proposed that a transition from IIB to IIX motor units occurs during ageing. In an attempt to clarify this point, the MHC composition was identified by 6% SDS‐PAGE and immunoblotting analysis, using specific mAbs antibodies, in the same fast‐twitch tibialis anterior muscles in young (3–6 months, n = 9) and old (20–24 months, n = 16) rats from which the single motor units had been identified previously. The IIX‐MHC comigrates together with the HA‐MHC band in 6% SDS‐PAGE and only two MHC bands are observed in the rat tibialis anterior muscle, i.e. the IIA‐IIX‐and IIB‐MHC bands. A significant increase (P < 0.001) in the average relative amount of the HA‐IIX —MHC was observed in the old (45 ± 17%) as compared to the young (23 ± 4%) animals, accompanied by a corresponding decrease in IIB‐MHC content. It was demonstrated in immunoblotting analysis that only trace amounts of IIA‐MHC were detectable in the IIA‐IIX‐MHC band in both young and old TA muscles, indicating a substantial increase in the IIX‐MHC content in old age. Thus, the present results together with previous observations at the motor unit level strongly support an age‐related motor unit transition from type IIB‐ to IIX‐MHC.
ESR‐measurement of oxygen radicals in vivo after renal ischaemia in the rabbit. Effects of pre‐treatment with superoxide dismutase and heparin
Authors: NILSSON U. A. , HARALDSSON G. , BRATELL S. , SORENSEN V. , AKERLUND S. , PETTERSSON S. , SCHERSTEN T. , JONSSON O.
Published: December 2008

The effects of intracellular and extraceIlular superoxide dismutase and heparin administration on oxygen radical formation after ischaemia in the rabbit kidney were studied. Radicals were measured with ESR and spin trapping. At reperfusion after 60 min of renal ischaemia there was a significant increase in the production of free radicals in the venous effluent from the kidney. Administration of either intracellular superoxide dismutase or extracellular superoxide dismutase before ischaemia and before reperfusion prevented approximately 85 % of the radical formation seen in the untreated control group. Administration of heparin 5 min before recirculation resulted in a 65% decrease in radical production compared to the control group.
Vascular characteristics influence the aortic ultrasound Doppler signal: computer and hydraulic model simulations
Authors: SJÖBERG B. JANEROT , EIDENVALL L. , LOYD D. , WRANNE B. , ASK P.
Published: December 2008

There is an increasing demand for non‐invasive methods for the assessment of left ventricular function. Ultrasound Doppler methods are promising, and the early systolic flow velocity signal immediately distal to the aortic valve has been used clinically for this purpose. However, the signal is influenced not only by left ventricular ejection but also by systemic vascular characteristics. Their relative contribution to the timevelocity signal has not been analysed in depth previously. A theoretical analysis, based on a three‐element Windkessel model, neglecting peripheral outflow in early systole and assuming linear pressure rise, was therefore tested in computer and hydraulic model simulations where peripheral outflow was included. Significant changes in early aortic flow velocity parameters were found when vascular characteristics were altered. As predicted by the theory, with a standardized aortic valve area and aortic pressure change, the simulations confirmed that maximal flow velocity is related to compliance of the aorta and the large arteries, and that maximal acceleration is inversely related to the characteristic impedance of the aorta. Therefore, maximal velocity and acceleration can be used for assessment of left ventricular function only in situations where vascular characteristics can be considered relatively constant or where they can be estimated.
Endurance training increases skeletal muscle lactate transport
Authors: McDERMOTT J. C. , BONEN A.
Published: December 2008

Lactate accumulation in skeletal muscle is reduced after a period of endurance training. Explanations for this phenomena include the increased oxidative capacity of the muscle, a reduction in lactate production, and increased lactate clearance. Muscle membrane transport of lactate can be seen to be a fundamental aspect of such clearance, and transmembrane lactate flux may well be an important aspect of the training response in skeletal muscle. Therefore, the lactate transport capacity in skeletal muscle sarcolemmal membranes in endurance‐trained and sedentary rats was investigated. Training consisted of 6 weeks of progressively increased treadmill exercise. Twenty‐four hours before being killed, both the trained and sedentary animals completed a brief exercise bout. Studies of lactate transport (zero‐trans) were conducted using highly purified sarcolemmal vesicles. When low concentrations of L‐lactate (1 mm) were used a 59.4% increase in lactate transport was observed (P < 0.05). However, when a high concentration of lactate (50 mm) was used no change in lactate transport was found (P > 0.05). Several interpretations are possible for these observations: (1) that there is an alteration in the Km but not the Vmax of the lactate transport system in skeletal muscle membranes; and (2) that specific changes occur in selected isoforms of the lactate transport protein which may co‐exist in muscle.
Changes in K+, Na+ and calcium contents during in vivo stimulation of rat skeletal muscle
Authors: EVERTS M. E. , LøMO T. , CLAUSEN T.
Published: December 2008

The effects of in vivo stimulation via the sciatic nerve on Na+ K+ and calcium contents in slow‐twitch and fast‐twitch muscles were compared. Whereas intermittent stimulation for 24 h at 20 Hz caused only minor changes in soleus (SOL), a considerable loss of K+ (around 24%) and gain of Na+ (around 84%) was observed in extensor digitorum longus (EDL) and tibialis anterior (TA) muscles. These changes could be detected within 0.5 h and a plateau was maintained from 2 to 24 h. Total calcium content increased progressively, reaching values 245 and 382% above the control level in EDL and TA muscle, respectively, after 24 h of 20 Hz stimulation. Whereas the Na+ and K+ content recovered within a few hours, calcium content did not return towards control level until after 48 h of rest. In a pilot study performed with continuous stimulation at 10 Hz, the changes in Na+ and K+ contents in SOL, EDL and TA muscle were comparable to those at 20 Hz. The concentration of the Na+‐K+ pumps was highest in the fast‐twitch EDL and TA muscles and was unaffected by 10 Hz stimulation. It is concluded that a stimulation pattern leading to a rise in intracellular Na+ and a loss of K+ may cause a marked accumulation of calcium. These events seem to be related to insufficient activation of the Na‐K+ pump rather than to variations in the total Na+‐K' pump capacity.
Differential projection of the sural nerve to early and late recruited human tibialis anterior motor units: change of recruitment gain
Authors: NIELSEN J. , KAGAMIHARA Y.
Published: December 2008

The effect of a stimulation of the cutaneous sural nerve [three shocks, 2.5 × perception threshold (PT)] was studied on the tibialis anterior (TA) H‐reflex and single voluntarily activated TA motor units using post‐stimulus time histograms (PSTH). In both cases, when studying only the first recruited motor units, an inhibition with a delay of 10 ms, in relation to the monosynaptic latency of Ia afferents in the common peroneal nerve, was observed. This inhibition had a duration of 10–20 ms.

The inhibition was evoked by low‐threshold cutaneous fibres, since it could be seen at a stimulation strength close to the perception threshold. The central delay of the inhibition was calculated in two subjects to be 1.8 ms and 1.2 ms respectively.

The TA motor units were characterized by their recruitment threshold and minimal firing frequency and the effect of the sural nerve stimulation was subsequently investigated. Early recruited low frequency motor units were found to be inhibited, whereas later recruited motor units with a higher minimal firing frequency were facilitated. Similarly small TA H‐reflexes were inhibited, whereas large reflexes were facilitated.

This difference in the effect of the sural nerve stimulation was not caused by a difference in the descending command, since the same early recruited motor unit was still inhibited when firing at a high frequency and at a high torque level.

Stimulation of the femoral nerve was found to produce a monosynaptic facilitation of the TA H‐reflex and a heteronymous monosynaptic peak in the PSTH of single motor units. A stimulation of the sural nerve increased the size of the reflex facilitation, but had no effect on the size of the monosynaptic peak in the PSTH of the single motor units.

It is concluded that the effect of the sural nerve stimulation on human TA motor units is similar to observations in the cat and that a similar interneuronal system may be responsible. It is furthermore suggested that the sural nerve stimulation increases the recruitment gain of the TA motoneuronal pool.
Vasomotor response of the human face: laser‐Doppler measurements during mild hypo‐ and hyperthermia
Authors: RASCH W. , CABANAC M.
Published: December 2008

The skin of the face is reputed not to vasoconstrict in response to cold stress because the face skin temperature remains steady during hypothermia. The purpose of the present work was to measure the vasomotor response of the human face to whole‐body hypothermia, and to compare it with hyperthermia. Six male subjects were immersed in cold and in warm water to obtain the two conditions. Skin blood flow, evaporation, and skin temperature (Tsk) were recorded in three loci of the face, the forehead, the infra orbital area, and the cheek. Tympanic (Tty) and oesophageal (Toes) temperatures were also recorded during the different thermal states. Normothermic measurements served as control. Blood flow was recorded with a laser‐Doppler flowmeter, evaporation measured with an evaporimeter. Face Tsk remained stable between normo‐, hypo‐, and hyperthermia. Facial blood flow, however, did not follow the same pattern. The facial blood flow remained at minimal vasoconstricted level when the subjects' condition was changed from normo‐ to hypothermia. When the condition changed from hypo‐ to hyperthermia a 3 to 9–fold increase in the blood flow was recorded. From these results it was concluded that a vasoconstriction seems to be the general vasomotor state in the face during normothermia.
Lactation affects pressor, volumetric and natriuretic responses to angiotensin II in goats
Authors: HOSSAINI‐HILALI J. , OLSSON K.
Published: December 2008

Demands on cardiovascular function and fluid turnover increase during lactation and pregnancy in the goat, but the hormonal status is different. This study is aimed at investigating the effects of hypertensive angiotensin II (ANGII) in lactating goats. The results were compared with those of pregnancy and control conditions. ANGII (0.5 pg min‐1) was infused intravenously for 60 min (n = 6). The rise in blood pressure in response to ANGII was attenuated during lactation as in pregnancy (P < 0.001 vs control period). ANGII caused reflex bradycardia. Plasma protein concentration decreased by 7.5% during infusions in lactating goats (pregnancy: 9%; control period: 4.5%). Renal Na excretion increased by 260% (lactation), by 400% (pregnancy; n.s. vs. lactation), and by 800% (control period; P < 0.01 vs. lactation). The glomerular filtration rate was unchanged during ANGII infusions in lactating animals, but increased in the other periods. Effective renal plasma flow decreased. ANGII raised aldosterone from < 34.5 pmol 1‐‐1 to 539 ± 80 pmol l‐1 (lactation) and to 428 ± 41 pmol l‐1 (control; P < 0.05 vs. lactation), and from 72 ± 9 to 651 ± 103 pmol l‐1 (pregnancy; P < 0.01 vs. lactation). Plasma progesterone was undetectable during lactation, but varied from 0 to 17 nmol l‐1 during control conditions and was 16 ± 1 nmol l‐1 during pregnancy. Oestradiol 17β was 181± 22 pmol l‐1 in pregnant goats, and undetectable in lactating animals. In conclusion, lactation affects ANGII‐induced changes in cardiovascular and fluid regulation, but in this period the effects were not related to progesterone or oestradiol 17 β.
An analysis of synaptic transmission to motoneurones in the cat spinal cord using a new selective receptor blocker
Authors: ENGBERG I. , TARNAWA I. , DURAND J. , OUARDOUZ M.
Published: December 2008

We have investigated the role of α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA) receptors on synaptic transmission in vivo between Ia primary afferents and cat spinal motoneurones using a selective non‐N‐methyl‐d‐aspartate (non‐NMDA) receptor antagonist, GYKI 52466.

Both microionophoretic and intravenous application of GYKI 52466 depressed the Ia excitatory post‐synaptic potential (Ia EPSP) in a dose‐dependent manner, without any apparent effect on membrane conductance or resting potential of the motoneurone.

GYKI 52466 reduced selectively α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionate (AMPA)‐ but not N‐methyl‐d‐aspartate (NMDA)‐induced depolarizations.

Our results suggest that a large part of the Ia EPSP is mediated by AMPA receptors. The participation of other excitatory amino‐acid receptors in the Ia EPSP is also discussed.
Effect of diazepam on endocrine and cardiovascular responses to head‐up tilt in humans
Authors: MATZEN S. , SECHER N. H. , KNIGGE U. , BACH F. W. , WARBERG J.
Published: December 2008

Effects of the GABAergic drug diazepam (0.15 mg kg‐1, i.v.) on cardiovascular and endocrine responses to 50± head‐up tilt were evaluated in seven men. During the initial phase of tilt (normotensive phase), increases in heart rate (HR) and total peripheral resistance (TPR) and decreases in cardiac output were unaffected by diazepam. Also the associated increase in plasma noradrenaline did not change, while response in plasma ACTH was diminished and in plasma cortisol abolished by diazepam (F(1, 10) = 6.45; P < 0.03). After 42 ± 4 min of sustained tilt with saline (control) and 47 ± 6 min (n.s.) after diazepam, presyncopal symptoms appeared (hypotensive phase) associated with decreases in HR, MAP, and TPR (P < 0.01). This episode induced a 2–3‐fold increase in plasma ACTH, β‐endorphin, prolactin, cortisol (< 0.01), and a moderate increase in plasma adrenaline (P < 0.05). Diazepam did not significantly change cardiovascular and endocrine responses to the hypotensive phase of tilt. Results indicate that diazepam attenuates the cortisol part of pituitary‐adrenal responses to moderate, but not to severe, central hypovolaemia in humans with no effect on cardiovascular tolerance.
Effect of catecholamines on the ventricular myocyte action potential in raised extracellular potassium
Authors: PATERSON D. J. , ROGERS J. , POWELL T. , BROWN H. F.
Published: December 2008

We describe the relationship between catecholamines and raised extracellular potassium ([K+]o) on action potential parameters and calcium currents in isolated ventricular myocytes of the guinea‐pig and relate these findings to the problem of understanding how the heart is protected from exercise‐induced hyperkalaemia ([K+]a up to 8.5 mm). Action potential duration (APD90), amplitude and upstroke velocity were recorded in stimulated (2Hz) guinea‐pig ventricular myocytes using whole‐cell patch electrode recordings (37 ±C). Cells were superfused with normal K+Tyrode and with raised K+Tyrode in the presence of either noradrenaline, adrenaline or raised calcium. Inward calcium current was measured using voltage clamp. Raised K+(8, 12, 16 mm K+Tyrode) caused a significant (P < 0.01) depolarisation, shortened the APD90 and decreased the action potential amplitude and upstroke velocity. In raised K+Tyrode addition of noradrenaline (0.08–0.1 μm) or adrenaline (0.1–0.2 μm) increased action potential amplitude (P < 0.01), APD90 (P < 0.01) and upstroke velocity (P < 0.01) (measured only in 16 mm K+Tyrode). In 12 mm K+Tyrode raised Ca2+(5–6 mm) increased action potential amplitude (P < 0.05) and shortened APD90 (P < 0.05). Addition of NA (0.08–0.1 μm) increased the inward Ca2+current. All effects were fully reversible. In raised [K+]o increases in catecholamines and [Ca2+]o cause changes in action potential parameters that would be expected to maintain propagation of the cardiac action potential in the whole heart. Thus, in the ventricular myocyte the increase in conductance to Ca2+caused by catecholamines may be one factor that is important in minimising the potentially adverse effects of exercise‐induced hyperkalaemia.