bluuebunny/crossref_metadata_2025 huggingface dataset:
Intestinal fluid transport in the small intestine of normotensive and spontaneously hypertensive rats: the importance of enteric nerves, chloride and bicarbonate secretion
Authors: TANTISIRA M. H. , SJÖVALL H. , JODAL M. , LUNDGREN O.
Published: December 2008

Fluid transport was studied in periarterially denervated jejunal segments of spontaneously hypertensive rats (SHR) of the Okamoto strain and as a control also in Wistar‐Kyoto rats (WKR). In agreement with the findings of an earlier report a ‘spontaneous’ fluid secretion was observed in SHR whereas the intestinal segments of WKR absorbed fluid. The fluid secretion in SHR was inhibited by tetrodotoxin or lidocaine placed on the serosal surface of the intestinal segment under study. These observations confirm our earlier proposal that secretory nervous pathways in the enteric nervous system evoke the fluid secretion in SHR. In an attempt to analyse the cellular mechanisms that underlie the fluid secretion in SHR the animals were given loop diuretics in doses that evoked diuresis. No effect on intestinal fluid transport was seen in SHR or WKR. Furthermore, to study the importance of bicarbonate transport alkaline secretion was monitored with a pH‐stat technique. In the initial part of the experiments the alkaline secretion in SHR and WKR was similar. In half of the SHR experiments alkaline secretion increased with time. This increase could be completely reversed with hexamethonium and atropine (only tested in three experiments). The time course of the alkaline and fluid secretion in SHR did not coincide, indicating that bicarbonate ion transport was not the major cause of fluid secretion in SHR. In agreement with this conclusion it was observed that acetazolamide (a blocker of carbonic anhydrase) did not influence rate of fluid transport in SHR or WKR. It is concluded that the fluid secretion in denervated intestinal segments of SHR is evoked by secretory pathways in the enteric nervous system. The fluid secretion is not influenced by loop diuretics in doses that cause diuresis. Bicarbonate ion transport seems not to underlie intestinal fluid secretion in SHR.
Cardiovascular and metabolic responses to static contraction in man
Authors: GAFFNEY F. A. , SJØGAARD G. , SALTIN B.
Published: December 2008

There is substantial controversy regarding muscle blood flow and its regulation during static exercises. Major issues include (1) the relationship between developed force and muscle blood flow, (2) the ability of metabolic vasodilation to overcome neurally mediated vasoconstriction, (3) the time course and magnitude of hyperaemic flow following static exercise and (4) blood flow to the contralateral inactive limb. At rest, 15, 25 and 50% maximal voluntary contractions (MVC) femoral venous flow in four healthy young men (LBF; mean±1 SD) was 0.4 ± 0.3, 1.76 ± 0.65, 0.90 ± 0.32 and 1.06 ± 0.59 l min‐1, and mean arterial pressures (MAP) were 104±13, 140±14, 160 ± 17 and 161 ± 11 mmHg. Thus, LBF does not increase proportionally with increasing levels of MVC, despite increased arterial pressure. Further, during both 25 and 50% MVC, which were held to exhaustion, an elevated limb vascular resistance was encountered towards the end of contraction, which suggests that neurally mediated vasoconstrictor activity overrides local vasodilation.

Femoral venous effluent documented perfusion of active muscle during contractions of 15 and 25% MVC, but less so at 50% MVC. Immediately in recovery LBF reached levels of 3–3.5 l min‐1, which corresponded to 150 ml 100 g‐1 min‐1. When both O2 uptake and lactate release during the contractions and in recovery were taken into account, a close correlation between rate of energy turnover and exerted force was found.

When MAP was raised by static contraction of the opposite quadriceps, LBF in the inactive leg increased momentarily. Within 1 min vascular resistance became elevated and the blood flow became reduced.
Muscle carnitine metabolism during incremental dynamic exercise in humans
Authors: SAHLIN K.
Published: December 2008

The changes in muscle content of carnitine and acetylcarnitine have been studied during incremental dynamic exercise. Six subjects exercised for 10 min on an ergometer at 40 and 75% of their maximal oxygen uptake (Vo2 max) and to fatigue at 100% of Vo2 max (about 4 min). Muscle samples were taken from the quadriceps femoris muscle at rest and after exercise. Muscle content of free carnitine was (x̄± SE) 15.9 ± 1.7 mmol kg‐1 d. wt (dry weight) at rest and remained unchanged after exercise at low intensity but decreased to 5.9 ± 0.6 and 4.6 ± 0.5 mmol kg‐1 d. wt after exercise at 75 and 100% of Vo2 max respectively. Acetylcarnine content at rest was 6.9 ± 1.9 mmol kg‐1 d. wt and increased during exercise in correspondence with the decrease in free carnitine. Muscle content of pyruvate and lactate was unchanged after exercise at 40% of Vo2 max but increased at the higher intensities. The parallel increases in acetylcarnitine, pyruvate and lactate indicate that formation of acetylcarnitine is augmented when the availability of glycolytic three‐carbon metabolites is high and is consistent with the idea that acetylcarnitine provides a sink for pyruvate and acetyl CoA. This could be of importance for the maintenance of an adequate level of CoA and thus function of the tricarboxylic acid cycle.
Resetting of the pressure range for blood flow autoregulation in the rat kidney
Authors: HOLM L. , MORSING P. , CASELLAS D. , PERSSON A. E. G.
Published: December 2008

Both a myogenic response and the tubuloglomerular feedback control mechanism seem to be involved in autoregulation of glomerular filtration rate (GFR) and renal blood flow (RBF). Earlier experiments have shown that clamping of renal arterial perfusion pressure, below the autoregulatory range, reduces single‐nephron GFR, and that this low value is maintained during the first 10–15 min after release of the clamp. It was also found that the tubuloglomerular feedback mechanism in the early declamp phase was strongly activated to reduce GFR. These findings can not be easily understood with the current knowledge of autoregulation, but would suggest a resetting of RBF and GFR autoregulation to a new level. To test this, left renal arterial perfusion pressure was reduced from 100 to 60 mmHg during 20 min with and without angiotensin converting enzyme inhibition (0.5 mg i. v. enalapril). Renal blood flow was measured with laser‐Doppler flowmetry. When arterial perfusion pressure was reduced from 100 to 60 mmHg for 20 min, RBF was reduced to 77% of control and remained at this low level during the first minutes of declamp. In this situation there was an autoregulation to a new level. Renal blood flow was then slowly normalized (16.1 min). In the enalapril‐treated animals RBF was only reduced to 85 % during the 20 min of clamping and returned immediately to the control level at declamp. Thus, these experiments demonstrate that if renal blood flow is decreased by reducing the perfusion pressure below the normal autoregulatory range the pressure range for blood flow autoregulation resets to a lower level and that this change is mediated via the renin‐angiotensin system.
Cholecystokinin causes contraction of the pupillary sphincter in monkeys but not in cats, rabbits, rats and guinea‐pigs: antagonism by lorglumide
Authors: BILL A. , ANDERSSON S. E. , ALMEGÅRD B.
Published: December 2008

The effects of intracameral injections of cholecystokinin (CCK) on the pupil size were determined in monkeys, cats, rabbits, rats and guinea‐pigs. In animals under muscarinic cholinergic blockade, CCK caused miosis in monkeys but not in the other species investigated. In monkeys CCK‐8 was more potent than CCK‐33, which was, however, much more potent than non‐sulphated CCK‐8. These observations indicate that peripheral type A receptors mediated the miotic response. The effect of CCK‐8 was not appreciably influenced by pretreatment with indomethacin, 3 mg kg‐1 body wt, indicating that prostaglandins were not involved in the response. Nerve blockade with 0.9 μg tetrodotoxin intracamerally had no clear effect on the dose‐response relationship for CCK‐8. The effect of the peptide thus seems to be directly on receptors on the pupillary sphincter muscle. Pretreatment with lorglumide caused a dose‐dependent rightward shift of the dose–response curve, indicating competitive antagonism.

The results indicate that in monkeys, but not in rabbit, cats, rats and guinea‐pigs, CCK is a potent miotic with a direct effect on the pupillary sphincter mediated by type A CCK receptors on the muscle.
Chromogranin A: osmotically active fragments and their susceptibility to proteolysis during lysis of the bovine chromaffin granules
Authors: HELLE K. B. , REED R. K. , EHRHART M. , AUNIS D. , ANGELETTI R. HOGUE
Published: December 2008

Osmotically active fragments of chromogranin A (Chr A) were studied in lysates from bovine chromaffin granules (CG) disrupted in the presence or absence of inhibitors of endogenous proteolytic activities. The effects of various methods of lysis were examined by micro‐osmometry, PAGE‐SDS electrophoretic techniques and immunoblots with polyclonal anti‐Chr A sera. Osmotically active ‘small’ Chr A fragments (below 30 kDa) were conspicuous in lysates containing cocktails of leupeptin, pepstatin A, pHMB, PMSF and aprotinin. The osmotically inactive native Chr A in the 68–100 kDa range and the osmotically active fragments below 47 kDa were degraded in lysates at neutral or acid pH in the absence of inhibitors. However, degradation of the native Chr A and intermediates below 47 kDa could be prevented by extraction directly from intact CG, notably in cold or boiling distilled water. On the other hand, the main product after large‐scale extraction of CG in 1 M acetic acid (pH 1.9, 100 °C) was a novel, osmotically active fragment (22 kDa), immunostaining only for theN‐terminal sequence (Chr A1–40). The heat‐stable fraction (Mr,n23 kDa) exhibited concentration‐independent colloid osmotic pressures even in the absence of phosphate, a property which may distinguish this N‐terminal‐containing fragment from the larger intermediates, probably containing the pancreastatin sequence, and other regions at the C‐terminal side of the prohormone molecule. The functional roles of these osmotically active intermediates in the processing of Chr A are not yet known.
Renal vasoconstriction induced by arachidonic acid during burn shock in rats
Authors: HAUGAN A. , KIRKEBØ A.
Published: December 2008

Metabolites of arachidonic acid are possible mediators of local renal vasoconstriction in burn shock. The prostanoid precursor arachidonic acid (AA) therefore was infused in the control period and at 1 and 2 h after scalding in anaesthetized rats. To avoid systemic effects, AA was infused at low doses directly into the renal artery through a thin cannula introduced through the aortic wall. After control observations 40% of the body surface was scalded in 80 °C water. Renal arterial blood flow (RBF), measured by an electromagnetic probe, fell to 70% and 58% of the control level at 1 h and 2 h after scalding respectively. Arterial blood pressure was almost maintained. Infusion of AA (5, 15 and 25 nmol) in the renal artery over 15 s caused no effects in the control period, whereas a dose‐dependent decrease in RBF was observed after scalding, and was most pronounced 2 h post‐burn. The highest dose of AA reduced RBF by 37% at I h and by 80% of preinfusion flow at 2 h after scalding. The AA‐induced decrease in RBF was abolished by blocking the thromboxane A2receptors with AH23848. In contrast, inhibition of prostacyclin synthesis or blocking of serotonin S2receptors did not significantly influence the response to AA during shock. Thus, infusion of AA into the renal artery caused a marked reduction of RBF after scalding, at doses that did not induce a change during the control period. The augmented effect of AA infusion maybe due to an increased capacity for synthesis of thromboxane A2(TxA2), and possibly PGH2and PGF2α, after scalding.
Renal function during reperfusion after warm ischaemia in rabbits: an experimental study on the possible protective effects of pretreatment with oxygen radical scavengers or lidoflazine
Authors: HANSSON R. , BRATELL S. , BURIAN P. , BYLUND‐FELLENIUS A. C. , JONSSON O. , LUNDGREN O. , LUNDSTAM S. , PETTERSSON S. , SCHERSTEN T.
Published: December 2008

Survival and renal function were studied after 60 min of renal ischaemia and contralateral nephrectomy in four groups of French loop rabbits. One group served as untreated control animals. The other groups were pretreated with superoxide dismutase (SOD) and catalase, lidoflazine or a buffered albumin solution containing mannitol, L‐methionine and MgCl2. Six out of nine rabbits died during the 14‐day follow‐up period in the untreated control group, while the corresponding figure in each of the three treatment groups was one out of nine. Five of the rabbits that died exhibited azotaemia or hyperpotassaemia that could explain the death, while four died of non‐renal related causes. In the surviving animals, no differences in serum creatinine, potassium and sodium concentration or urinary output of osmoles was observed between the four groups. The increase in serum creatinine of the French loop rabbits observed after 60 min of ischaemia was considerably less pronounced than the corresponding increase observed in New Zealand White rabbits, indicating that the kidneys of the former strain are more tolerant to ischaemia. A cardiomyodepressant factor could be demonstrated in the venous effluent from previously ischaemic kidneys. This release could not be prevented by pretreatment with SOD and catalase.
Villus and crypt electrolyte and fluid transport during intestinal secretion
Authors: SJÖQVIST A. , III R. BEEUWKES
Published: December 2008

The apical parts of jejunal villi of net‐absorbing intestine have been shown to contain sodium chloride concentration gradients which are associated with water absorption (Sjöqvist & Beeuwkes 1989). To determine whether these gradients are different in states of intestinal net secretion, jejunal segments of chloralose‐anaesthetized cats were perfused with modified Krebs–Henseleit solutions while secretion was elicited by cholera toxin or vasoactive intestinal polypeptide (VIP). The segments were then rapidly frozen and freeze‐dried, and sodium and chloride contents of the lamina propria of single villi were measured by X‐ray microanalysis. The apical third of the villus was found to contain a concentration gradient of sodium and chloride when the lumen contained sodium, with no difference between secreting intestine and absorbing control intestine. When the intestine was perfused with hypotonic choline–mannitol solution, no sodium or chloride gradient was found. In this state, treatment of the intestines with secretagogues allowed development of an apical concentration gradient. This demonstrated that the absorptive function of the villus tip was unimpaired during secretion and that secretion from the crypt could supply sufficient electrolyte to allow formation of an apical gradient.
Albumin protects against capsaicin‐ and adenosine‐induced bronchoconstriction and reduces overflow of calcitonin gene‐related peptide from guinea‐pig lung
Authors: KRÖLL F. , KARLSSON J. ‐A. , LUNDBERG J. M. , PERSSON C. G. A.
Published: December 2008

In the guinea‐pig isolated, perfused lung, the effect of albumin on oedema formation and bronchoconstriction as well as on capsaicin‐induced overflow of calcitonin generelated peptide‐like (CGRP‐LI) immunoreactivity has been examined. CGRP was used as an indicator of sensory nerve activation since it is more stable than the tachykinins substance P and neurokinin A. As expected, the lung water content was significantly (P < 0.001) higher in lungs perfused with albumin‐free buffer than when the buffer contained 4.5% albumin. Also, in albumin‐free buffer the baseline airway resistance (RL) was increased and dynamic compliance (CDYN) reduced (P < 0.001). Capsaicin (1 ± 10‐6 M) was about 100 times less potent as a bronchoconstrictor when preincubated with albumin for 45 min, and the associated overflow of CGRP‐LI was inhibited (from 221.0 ± 63.4 fmol to 8 fmol fraction‐1). When CGRP (50–200 pM) was incubated for 60 min with albumin, the recovery of CGRP‐LI was 48% lower (P < 0.01) than in the absence of albumin, corresponding to a loss rate of about 1% min‐1. Catabolism or binding of neuropeptides can therefore hardly explain the diminished bronchoconstrictor potency of capsaicin. Capsaicin was also less effective as a constrictor in isolated bronchi after preincubation with albumin, suggesting that capsaicin itself may be bound or absorbed to this macromolecule. The bronchoconstrictor response to adenosine was also diminished in the presence of albumin. Adenosine was about 1000 times less potent as a bronchoconstrictor if dissolved in albumin 45 min before infusion, but only 10 times less potent when administered as bolus doses to albumin bufferperfused lungs. Metabolism of adenosine may be the reason for the decreased potency of adenosine. The enzymatic activity may have been associated with impurities in the albumin preparation used (bovine serum albumin fraction V is ± 96% pure) or contained in the protein itself. Since the bronchoconstrictor effect of acetylcholine was not reduced in the presence of albumin, it is not likely that albumin affects directly the contractility of the smooth muscle. These data demonstrate the importance of studying the influence of albumin on the in‐vitro actions of pharmacological agents. The absence or presence of albumin products in nutrient buffer solutions may mean dramatic differences in potencies of certain drugs. Furthermore, bolus injections of agents are preferable, and preincubation together with albumin should be avoided.
Effects of diazepam on the carotid sinus baroreflex control of circulation in rabbits
Authors: SAKAMOTO M. , OHSUMI H. , YAMAZAKI T. , OKUMURA F.
Published: December 2008

To examine the effects of diazepam on the carotid sinus baroreflex control of circulation, bilateral carotid occlusion was performed on 14 conscious rabbits with aortic denervation. The responses of mean arterial pressure, heart rate, cardiac output and total peripheral resistance were obtained. The haemodynamic responses to carotid occlusion were evaluated at cumulative doses of 0.5 and 1.0 mg kg‐1of diazepam. The administration of diazepam decreased cardiac output and increased total peripheral resistance significantly, but did not affect the arterial pressure and heart rate. The response of total peripheral resistance to carotid occlusion was significantly increased from 0.118 ± 0.018 (mean ± SE) to 0.154 ± 0.026 mmHg min ml‐1at 1.0 mg kg‐1of diazepam. The heart rate response was attenuated significantly from 41 ± 5 to 24 ± 4 beats min‐1at 1.0 mg kg‐1of diazepam. Diazepam did not alter the response of arterial pressure to carotid occlusion. We suggest that the dissociated effects of diazepam on the reflex control of circulation reflect the dissociated influences of diazepam on the central sympathetic and vagal‐mediated pathways.
Effects of denervation on enzyme‐histochemical and morphometrical properties of the rat soleus muscle in relation to age
Authors: ANSVED T. , LARSSON L.
Published: December 2008

The soleus muscle of young adult (5 months), adult (10–11 months) and old (23 months) male Wistar rats was unilaterally denervated for a period of 3 weeks and studied with regard to enzyme‐histochemical and morphometrical properties. Denervation caused a marked atrophy of all fibres, irrespective of age and enzyme‐histochemical type. Fibres having myofibrillar ATPase staining characteristics intermediate to type I and type IIA fibres increased in number in all age groups and a reduction in the number/proportion of type I fibres was found in adult and old animals. These results indicate that a slow‐to‐fast shift in myofibrillar properties as a consequence of denervation, shown to occur in the soleus muscle of young animals, also takes place in old age. This supports the view that atrophic fibres with intermediate myofibrillar ATPase staining characteristics, and possibly also atrophic IIA fibres, seen in old soleus muscle could be type I fibres which have undergone a transformation in response to the age‐related denervation process.
Permeability of the respiratory tract to different‐sized macromolecules after intratracheal instillation in young and adult rats
Authors: FOLKESSON H. G. , WESTRÖM B. R. , KARLSSON B. W.
Published: December 2008

The markers, bovine IgG (BIgG, mol. wt = 150000 Da) and bovine serum albumin (BSA, mol. wt = 67000 Da) together with I‐deamino‐cysteine‐8‐D‐arginine vasopressin (dDAVP, mol. wt = 1067 Da), were intratracheally instilled into young and adult rats and their passages via the respiratory tract were assessed as immunoreactive marker levels in blood serum.

In the adult rats (100–120 days old) the BSA serum levels peaked 16–24 h after instillation and with a calculated transferred amount (bioavailability) of 4.3 ± 1.7 to 5.6 ± 1.4% of the dose given (five resp. 50 mg kg‐1body wt). BIgG passed via the respiratory tract with a maximum at 16 h, and with a transferred amount of 1.5 ± 0.3%, while dDAVP serum levels peaked at I h and with a transferred amount of 20 ± 4%. For the 30‐day‐old rats, similar passage time curves were obtained as for the adult, but the transferred amount was lower for BIgG (0.7 ± 0.3%), similar for BSA (4.1 ± 1.1%) and higher for dDAVP (45 ± 16%). The serum levels of BSA increased linearly with increasing dose instilled (2.5–200 mg kg‐1body wt), indicating a passive transepithelial transport route.

The results show that macromolecules pass via the respiratory tract into the circulation of the rat in mainly intact forms and in high amounts, compared with passage via the GI tract. There appears to exist an inverse relationship between the molecular weights of instilled molecules and the transferred amount, a relationship affected by the development of the lung.
Renal tissue impedance: responses of the real and imaginary component to experimental variations in medullary electrolytes
Authors: SADOWSKI J. , NIEWIADOMSKI W. , RASMUSSEN S. N.
Published: December 2008

In order to assess the renal corticomedullary electrolyte gradient, electrical impedance (Z) and phase angle (Ø) were measured in the in‐situ kidney of anaesthetized rats. A set of platinum/iridium needle electrodes was used, and the frequency (f) of the measuring current was varied between 0.5 and 50 kHz. Z and its imaginary component (Xc) fell sharply as f increased from 0.5 to 3.5 kHz, and then decreased slowly or stabilized, whereas the real component (R) decreased progressively over the entire f range. Ion concentration in the renal medulla was experimentally lowered by administration of furosemide or hypertonic mannitol or by inducing a haemorrhage, and raised by infusing hypertonic NaC1 solution. Both R and Xc varied inversely with tissue electrolyte concentration. Raising f from 3.5 to 10 and further to 20 kHz did not significantly amplify the changes in Z. Within this frequency range R was not a more sensitive index of tissue electrolyte changes compared with overall Z‐value. The results verify previous empirical data indicating that changes in medullary tissue electrolytes can be dynamically estimated by monitoring tissue impedance.
Plasma catecholamines, corticosterone, glucose and fatty acids concentrations and mean arterial pressure and body temperature in haemorrhagic hypovolaemia, hypothermia and a combination of these in the rabbit
Authors: HANHELA R. , HOLLMEN A. , HUTTUNEN P. , HIRVONEN J.
Published: December 2008

Venous plasma noradrenaline, adrenaline, dopamine, corticosterone, glucose and free fatty acid concentrations were measured in anaesthetized rabbits during hypovolaemia, hypothermia and a combination of these. The anaesthetic used was Hypnorm, which contains fentanyl and fluanisone. In the hypovolaemia group blood was shed via the venous cannula until the mean arterial pressure was 50 mmHg. The rabbits in the hypothermia group were cooled in iced water to a central temperature of 32 °C, and the rabbits in the combined hypovolaemia‐hypothermia group were bled until hypovolaemic and then cooled in iced water to a central temperature of 32 °C. Rewarming was done in dry air at 43 °C.

Bleeding and hypothermia activated the sympathicoadrenal system, causing a rise in the noradrenaline and adrenaline concentrations, as well as a rise in corticosterone. There were no significant differences in plasma noradrenaline and adrenaline values between the groups, whereas hypovolaemia alone also increased the dopamine concentration. In the hypothermia group the amount of corticosterone after cooling and rewarming was higher than in the combined group. Hypothermia and hypovolaemia increased the level of free fatty acids and blood glucose, which in the hypovolaemia group remained higher after volume replacement than in the other groups. Hypothermia in both groups increased the mean arterial pressure.

In conclusion, the results suggest that hypothermia may prevent some harmful effects of hypovolaemia, e.g. by correcting mean arterial pressure, thus preventing the mortality seen in the hypovolaemia group.
Influence of the interval between removal and freezing of muscle samples on muscle fibre size with special reference to sample size and fibre type
Authors: LARSSON L. , SKOGSBERG C. , GÜR H.
Published: December 2008

To study the influences of the interval between removal and freezing of a muscle sample on fibre size, rat hindlimb muscles (soleus and extensor digitorum longus, EDL) were cut into three or five pieces and frozen at different intervals, cross‐sectioned, stained and analysed morphometrically. As in a previous study (Larsson & Skogsberg 1988), a pronounced interval‐dependent change in soleus muscle fibre size was observed, the fibres in soleus muscle samples frozen immediately (within 15 s) being significantly (P < 0.01–0.001) larger than those samples frozen 4 or 10 min after removal. However, the interval‐dependent change was only noted in small muscle samples, i.e. those where the maximum muscle fibre length was 6.5 mm, while samples in which the fibres were approximately twice this length showed no change. In the slow‐twitch soleus, type I fibres predominate, and type II fibres were often too few in one or more cross‐sections in each animal to allow reliable measurements of fibre size. The fast‐twitch EDL was therefore studied, and the results indicated an interval‐dependent change in fibre size which was differentiated according to enzyme‐histochemical type, i.e. there was a significant change in type I and II A fibres but not in type II B. It is concluded that the interval between removal and freezing of small muscle samples, as in percutaneous muscle biopsies in man, is of vital importance for fibre size, and that this interval should be at least 2–4 min.
Glycogen and lactate metabolism during low‐intensity exercise in man
Authors: NORDHEIM K. , VØLLESTAD N. K.
Published: December 2008

The influence of high lactate concentration on glycogen metabolism in active type I and inactive type II fibres was investigated. High muscle lactate concentration (26.7 ± 1.4 mmol kg‐1 wet wt) was achieved by three bouts (2 min duration) of bicycle exercise at 112± Vo2 max. Exercise was continued at 40± Vo2 max for 1 h. Serial venous blood samples and biopsies from the vastus lateralis muscle were taken. Over the first 20 min of this low‐intensity exercise muscle lactate concentration decreased by 22.9 ± 0.7 mmol kg‐1 wet wt, while glycogen remained unchanged in type I fibres and increased by 20 mmol kg‐1 wet wt in type II fibres. During the next 40 min of low‐intensity exercise lactate decreased by 1.6 ± 1.2 mmol kg‐1 wet wt, while glycogen concentration decreased by 21 ± 7 mmol kg‐1 wet wt in type I fibres but remained stable in type II fibres. In a second series of experiments, in which lactate was allowed to disappear before the light exercise was started, no changes in glycogen concentration were seen in type II fibres during the 1 h of 40± Vo2 max exercise, while a continuous reduction in glycogen of 28 ± 8 mmol kg‐1 wet wt was found in type I fibres. The results indicate that in the presence of high lactate levels muscle glycogen was resynthesized in inactive type II muscle fibres, while lactate was oxidized in preference to glycogen in type I fibres.
Cholinergic mechanisms involved in release and effect of prostaglandin E2 in HCI‐stimulated duodenal HCO‐3 secretion in the conscious rat
Authors: SMEDFORS B. , ALY A. , HELLSTRÖM P. M. , JARAMILLO E. , JOHANSSON C.
Published: December 2008

Using a proximal duodenal loop in conscious rats, we investigated interactions between prostaglandin E2 and nicotinic and muscarinic receptor mechanisms previously found to be involved in the duodenal HCO‐3 response to HC1. In previous studies using the same model, a 5‐min perfusion of the duodenal loop with 150 mmol 1‐1 HC1 produced a marked and sustained HCO‐3 response. In the present study, the identical challenge produced a rapid 20‐fold increase in the luminal output of prostaglandin E2 during acid exposure, followed by a sustained more than twofold elevation above the basal level during the 45 min monitored. The prostaglandin synthesis inhibitor indomethacin (4 mg kg‐1 i.p.) suppressed the output of prostaglandin E2 during the HC1 challenge from 131 ± 84 to 15.4 ± 10.0 pmol cm‐1 h‐1, and in the post‐stimulatory period from 17.3 ± 9.1 to 4.4 ± 2.2 pmol cm‐1 h‐1. The nicotinic receptor antagonist hexamethonium (20 mg kg‐1 i.v.) had no effect on the output of prostaglandin E2. The muscarinic receptor antagonist atropine (0.5 mg kg‐1 s.c.) had no effect on the output of prostaglandin E2 during HC1 challenge, but reduced the post‐stimulatory output to 7.7 4PL 4.1 pmol ch‐1 h‐1. Perfusion of the duodenal loop with 0.1 mmol 1‐1 prostaglandin E2 produced a HCO‐3 response that was abolished by hexamethonium (20 mg kg‐1 i.v.), but not affected by atropine (0.5 mg kg‐1 s.c). The results indicate that muscarinic receptor mechanisms are involved in the HCI‐stimulated local formation of prostaglandin E2 and that nicotinic receptor mechanisms are required for the duodenal HCO‐3 secretion stimulated by prostaglandin E2.
How do dogs determine the direction of tracks?
Authors: STEEN J. B. , WILSSON E.
Published: December 2008

Two professional tracking dogs were brought in at right angles to 50‐m‐long tracks to try to identify the clues that the dogs used to determine the direction of the tracks. When the dogs were tested on tracks laid by a walking man, they took the direction that the track‐maker had moved significantly more often than predicted by random choice regardless of whether the person had moved forwards or backwards. When tested on tracks laid by bicycling on grass or asphalt, the choice of direction was not significantly different from random, even though the dogs were always rewarded when making correct choices. When four leather strips were tied to the back tyre of the bicycle before laying the track, the one dog tested took the correct direction significantly more often than predicted by random choice. When the leather strips were smeared with sausage before laying the tracks, the dog took the wrong direction more often than predicted by random choice. However, when rewarded for making correct choices, the dog learned“ to choose the direction in which the bicycle had actually moved. We suggest that our dogs determined the direction of tracks by comparing the scents of consecutive prints and following the prints in the direction of increasing intensity.
Multiunit neural responses to strong finger pulp vibration. II. Comparison with tactile sensory thresholds
Authors: SCHMIDT R. F. , WAHREN L. K.
Published: December 2008

In a companion microneurographic study (Schmidt et al. 1990) maximal multiunit sensory responses to finger pulp vibration were compared with maximal responses evoked by electrical stimulation of the digital nerve. It was found that the MR/ER ratio, i.e. the ratio between the magnitudes of the responses to mechanical and electrical stimulation, decreased with increasing age. The shape of this age‐related decline in the ratio corresponded well with the decrease in the number of Meissner corpuscles found in histological studies.

In the present study the tactile sensory detection thresholds were measured in the same subjects that participated in the companion study and the relationship between these thresholds and the MR/ER ratios was examined. The tactile sensory detection threshold increased with age. A weak negative correlation was found between the threshold and the ratio. However, after compensation for common age‐mediated effects, this negative correlation disappeared. Thus, the results indicate that measurement of tactile sensory detection thresholds and determination of MR/ER ratios may complement each other, giving an indication of different types of derangement of the mechanoreceptive system.
Effects of electrical stimulation on eccentric and concentric torque‐velocity relationships during knee extension in man
Authors: WESTING S. H. , SEGER J. Y. , THORSTENSSON A.
Published: December 2008

The purpose of this study was to examine the effects of electrical stimulation on torque output during knee extension. Nine well‐trained males (19–43 years) performed maximal voluntary, electrically evoked and superimposed eccentric and concentric knee extensions at velocities of 60, 180 and 360 ‘s‐’, plus an isometric test (torque was always recorded at a 60± knee angle). Fifty‐hertz stimulation was applied percutaneously at the maximum tolerated voltage (140–200 V). By superimposing electrical stimulation, eccentric torque could be increased by an average of 21–24% above the voluntary level (P < 0.05). No corresponding differences were observed between superimposed and voluntary torques under isometric or concentric conditions. Electrically evoked torque also exceeded voluntary torque under eccentric conditions (11–12%, P < 0.05), but was less under isometric and concentric conditions (‐ 10 to ‐52%, P < 0.05).

Within the limitations of the study, it was concluded that eccentric knee extension torque under maximal voluntary conditions does not represent the maximal torque‐producing capacity. The action of a neural inhibitory mechanism was proposed as an explanation for this finding. If active, this mechanism may protect against the extreme muscle tension that could otherwise develop under truly maximal eccentric conditions.
Effects of eccentric and concentric muscle actions in resistance training
Authors: COLLIANDER E. B. , TESCH P. A.
Published: December 2008

The adaptive responses to two different resistance training regimens were compared. Healthy males performed five sets of either 12 maximum bilateral concentric (Grp CON; n = 11) or six pairs of maximum bilateral eccentric and concentric (Grp ECCON; n = 11) quadriceps muscle actions three times per week for 12 weeks. Uni‐ and bilateral eccentric and concentric peak torque at various angular velocities, vertical jump height and three‐repetition maximum half‐squat were measured before and after training. Muscle biopsies were obtained from m. vastus lateralis and analysed for fibre type composition and area using histochemical techniques.

In contrast to a control group (n = 7), performing no training, Grps CON and ECCON demonstrated marked increases (P < 0.05) in overall eccentric (19 and 37% respectively) and concentric (15 and 26% respectively) peak torques. Grp ECCON, however, showed greater (P < 0.05) increases in peak torque, vertical jump height and three repetition maximum than Grp CON. The 7% increases in slow‐twitch fibre area in Grps CON and ECCON and in fast‐twitch fibre area in Grp CON were nonsignificant.

This study suggests that increases in peak torque and strength‐related performance parameters were greater following a programme consisting of maximum concentric and eccentric muscle actions than resistance training using concentric muscle actions only. Because increases in muscle fibre areas were small it is also suggested that the increased muscle strength shown subsequent to short‐term accommodated resistance training is mainly due to neural adaptation.
Function, morphology and protein expression of ageing skeletal muscle: a cross‐sectional study of elderly men with different training backgrounds
Authors: KLITGAARD H. , MANTONI M. , SCHIAFFINO S. , AUSONI S. , GORZA L. , LAURENT‐WINTER C. , SCHNOHR P. , SALTIN B.
Published: December 2008

The function and morphology of knee extension/m. vastus lateralis and elbow flexion/m. biceps brachii were studied in young (28 ± 0.1 years,n = 7) and elderly (68 ± 0.5 years,n= 8) sedentary subjects and in elderly swimmers (69 1.9 years,n= 6), runners (70 ± 0.7 years,n= 5) and strength‐trained subjects (68 ± 0.8 years,n= 7). On average, the training groups had, for the 12–17 years before the measurements were taken, performed their training regimen 3 ± 0.1 times a week. Compared with the young subjects, the maximal isometric torque of the sedentary elderly subjects was 44% (P< 0.05) lower in knee extension and 32% (P< 0.05) lower in elbow flexion, and speed of movement was between 20 and 26% (P< 0.05) lower in both knee extension and elbow flexion. The cross‐sectional area of m. quadriceps femoris and the elbow flexors was also 24% (P< 0.05) and 20% lower respectively, and the specific tension was 27% (P< 0.05) lower in m. quadriceps femoris and 14% (P< 0.05) lower in the elbow flexors. A 27% (P< 0.05) higher content of myosin heavy chain type I and a 39% (P< 0.05) higher content of the slow‐type myosin light chain — 2 was observed in m. vastus lateralis of the sedentary elderly subjects as compared with the young subjects. The same tendency was also seen with m. biceps brachii. Since the histochemical fibre‐type distribution was identical and no major co‐expression of type I and type II myosin heavy‐chain isoforms was observed with immunocytochemistry, the increase in slow myosin isoforms with ageing seems mainly related to a larger relative area of type I fibres, induced by a selective atrophy of type II fibre area. An increased content of the β‐isoform of tropomyosin was also demonstrated with ageing. In contrast to the swimmers and runners, the elderly strength‐trained subjects had maximal isometric torques, speed of movements, cross‐sectional areas, specific tensions and a content of myosin and tropomyosin isoforms in both muscles studied identical to those of the young controls. These results seem to suggest that strength training can counteract the age‐related changes in function and morphology of the ageing human skeletal muscle.
Effects of hypertonic NaCl solution on microvascular haemodynamics in normo‐ and hypovolaemia
Authors: BOUSKELA E. , GRAMPP W. , MELLANDER S.
Published: December 2008

The aims of this study were to investigate possible resuscitation effects of a single, 10‐min, 350‐μl intravenous infusion of 7.5% NaCl in hamsters in haemorrhagic shock and to compare the effects of such infusion with an identical one of 0.9% NaCl on the hamster cheek pouch microcirculation during normovolaemia and after acute bleeding to a hypotension level of about 40 mmHg. No significant differences could be detected between the effects of either infusion given to normovolaemic normotensive hamsters. In the animals subjected to haemorrhage, upon bleeding, arterioles larger than 40 μ constricted, arterioles smaller than 40 μ dilated and venular diameter did not change, while blood flow decreased in all vessels. The main differences between the infusions after haemorrhage were a significant increase in mean arterial pressure and arteriolar blood flow, venoconstriction and a tendency for the smaller arterioles to remain more dilated and the larger ones more constricted after the hypertonic infusion. Central nervous and/or reflex excitation of the sympathetic nervous system could account for the constriction of venules and larger arterioles, while a direct effect of hyperosmolarity could explain the dilatation of the smaller arterioles. The study can therefore help to explain some of the mechanisms underlying the reported resuscitation effect of 7.5yo NaCl infusion in animals during severe haemorrhagic hypovolaemia.
Polyamines and long‐term disuse of rat parotid glands
Authors: NILSSON B.‐O. , ROSENGREN E. , EKSTRÖM J.
Published: December 2008

Nilsson, B.‐O., Rosengren, E. & Ekström, J. 1990. Polyamines and long‐term disuse of rat parotid glands. Acta Physiol Scand 140, 105–109. Received 1 February 1990, accepted 7 April 1990. ISSN 0001–6772. Department of Physiology and Biophysics, University of Lund and Department of Pharmacology, University of Gothenburg, Sweden.

A decrease in nerve reflex activation for 7–14 days, induced by a liquid diet, caused the rat parotid gland to lose weight, involving reduction in both cell size and number. In the atrophied glands, the activity of ornithine decarboxylase, the key enzyme in polyamine formation, and the levels of the polyamines putrescine, spermidine and spermine were found to be lowered. The present results are compatible with a role for polyamines in cellular growth.
Increase in plasma sodium enhances natriuresis in response to a sodium load unable to change plasma atrial peptide concentration
Authors: EMMELUTH C. , SCHÜTTEN H. J. , KNIGGE U. , WARBERG J. , BIE P.
Published: December 2008

The influence of plasma sodium concentration in the control of sodium excretion was investigated in conscious, water‐diuretic dogs. NaCl was infused for 60 min as a hypertonic or isotonic solution at a rate of 60 μmol NaCl min‐1kg‐1body wt. Plasma sodium concentration rose only during hypertonic infusion (P< 0.05). Sodium excretion increased markedly with both infusions (hypertonic, from 2.4 ± 0.6 to 105 ± 27μmol min‐1; isotonic, from 3.9 ± 1.3 to 58 ± 17 μmol min‐1). Fractional sodium excretion increased more during hypertonic than during isotonic infusion. Hypertonic infusion decreased diuresis from 3.1 ± 0.5 to 1.3 ± 0.6 ml rnin‐l, while isotonic infusion elicited an increase from 3.9 ± 0.5 to 7.2 ± 0.7 ml min‐1. Plasma renin activity and plasma aldosterone decreased markedly in both series (P< 0.05), the relative changes in the two series being very similar. Central venous pressure increased (2.8 ± 0.7 to 4.5 ± 1.0 mmHg) during isotonic infusion but not significantly during hypertonic infusion. Arterial pressure, heart rate and plasma levels of atrial natriuretic peptide and catecholamines did not change measurably in either series. It is concluded that simultaneous increases in extracellular volume and sodium concentration cause a larger natriuretic response than a change in volume alone, and that a 40–fold increase in sodium excretion may occur without measurable changes in plasma atrial natriuretic peptide concentration.
Role of opioid receptors in the long‐lasting blood pressure depression after electric muscle stimulation in the hind leg of the rat
Authors: HOFFMANN P. , DELLE M. , THORÉN P.
Published: December 2008

In a previous study, electrically induced contractions of the gastrocnemius muscle in conscious spontaneously hypertensive rats were shown to induce a blood pressure reduction of 15–20 mmHg lasting several hours. We showed in that study that endogenous opioid systems were involved.

In this study, drugs with selective affinity for different opioid receptors were used to analyse further the involvement of endogenous opioid systems in the post‐stimulatory drop in blood pressure in spontaneously hypertensive rats. Prestimulatory intra‐cerebroventricular administration of β‐FNA (a preceptor antagonist) did not significantly influence the response at all, nor did a lower intravenous dose of naloxone reverse the post‐stimulatory drop in blood pressure. High‐dose naloxone (15 mg kg‐') increased post‐stimulatory blood pressure by around 10 mmHg. About 50% of the drop thus remained after this treatment. A similar, partial reversal of the decreased blood pressure was seen after intravenous administration of a & receptor antagonist, ICI 154, 129. However, the depressor response was completely reversed by a low intravenous dose of MR 2266 BS (a K‐receptor antagonist).

These results suggest that the reduction in blood pressure after muscle stimulation is mainly mediated by the opioid k‐receptor. A certain involvement of the δ‐receptor is also indicated.
Effects of sympathetic stimulation on C‐fibre response after peripheral nerve compression: an experimental study in the rabbit common peroneal nerve
Authors: SHYU B. C. , DANIELSEN N. , ANDERSSON S. A. , DAHLIN L. B.
Published: December 2008

Non‐myelinated C‐fibre responses during sympathetic trunk stimulation were studied in rabbit common peroneal nerve 2 weeks after the nerve had been subjected to compression at 400 mmHg for 30 min. Our previous studies have demonstrated that during sympathetic trunk stimulation the compound action potential of uninjured somatic C‐fibres is characterized by a reduced amplitude and an increased latency. In the present study, nerve compression changed the C‐fibre response to sympathetic stimulation. Three out of eight nerves reacted to nerve compression by increased C‐fibre compound action potential amplitude in response to sympathetic stimulation. In three other rabbits with compressed nerves the C‐fibre action potential amplitude was unchanged, and in the remaining two rabbits the action potential amplitude was decreased during sympathetic stimulation. The action potential latency increased in all tested compressed C‐fibres. The phenomenon of increased C‐fibre amplitude during sympathetic activation has not been observed in uninjured nerves. As in uninjured nerves, noradrenaline infusion produced an increased C‐fibre action potential amplitude and latency in six animals. Sympathetic stimulation did not affect the A‐fibre response. These results indicate that sympathetic activity influences the conduction properties in C‐fibres of somatic origin and that the response can be changed after a nerve injury. The findings may be of importance for the understanding of pain aggravation in different types of nerve injuries during increased sympathetic activity.
Acute effect of ethanol on the pattern of behavioural specialization of neurons in the limbic cortex of the freely moving rabbit
Authors: ALEXANDROV YU. I. , GRINCHENKO YU. V. , LAUKKA S. , JÄRVILEHTO T. , MAZ V. N. , VETLAJEV I. A. S.
Published: December 2008

Single‐unit activity was studied in the limbic cortex of eight freely moving rabbits in order to find out what kind of changes in the organization of unit activity correlate with behavioural disturbances following an acute administration of ethanol (1 g kg‐1). The rabbits were taught to acquire food by pressing pedals in the experimental cage. Unit activity was recorded during this behaviour in a control experiment and the alcohol experiment took place the next day. The number of behavioural mistakes significantly increased in the alcohol experiments. The pattern of behavioural specialization of the units also differed between the control and alcohol experiments. In the control experiments 55% of units did not show any constant activations in relation to the behavioural phases (non‐involved units), 28% of the units were constantly activated in relation to one or more behavioural phases learned in the cage (e.g. use of pedals; L units) and 17% of units showed activations in relation to the behaviour learned before the teaching of food acquisition (e.g. movements in general; M units). In the alcohol experiments the number of active units decreased by one‐third compared with that found in the control experiments. The relative number of non‐involved units did not change, whereas the relation between L and M units was reversed (11% L units and 34% M units). This was the result of a decrease in the number of active L units, mainly in the upper layers of the cortex. The results indicate that ethanol has a selective depressing effect on cortical neurons with different behavioural specialization, which could explain the behavioural disturbances observed in the alcohol experiments.