bluuebunny/crossref_metadata_2025 huggingface dataset:
Ionized calcium influences gastrin stimulated histamine release and acid secretion, but not histamine stimulated acid output in the totally isolated vascularly perfused rat stomach
Authors: SANDVIK A. K. , KOFSTAD J. , HOLST J. J. , WALDUM H. L.
Published: December 2008

When changing from bovine serum albumin to dextran T70 as colloid without adjusting the total calcium concentration in the vascular perfusate of the totally isolated vascularly perfused rat stomach, we noticed a drastic fall in gastrinstimulated acid secretion. In the present study the effect of the two colloids on ionized calcium in the vascular perfusate as well as the effect on acid secretion and vascular histamine release were studied. There was no difference in gastrin‐stimulated acid secretion or vascular histamine release between the two colloids after adjusting the total calcium concentrations so that ionized calcium was similar. Whereas baseline acid secretion showed no marked dependency of ionized calcium within the range tested (0.73–1 54 mmol 1‐1, gastrin‐stimulated acid secretion was highly dependent on ionized calcium being reduced at the higher concentration of Ca2+. Histamine Stimulated acid secretion, on the other hand, was virtually unaffected by the concentration of ionized calcium in the same range. Like gastrin‐stimulated acid secretion, gastrin‐stimulated histamine release was inhibited at higher Ca2+ concentrations. Thus, elevated Ca2+ concentrations seemed to reduce gastrin‐stimulated acid secretion by inhibiting vascular histamine release.
Immunoreactive erythropoietin and erythropoiesis stimulating factor(s) in plasma from hyper‐transfused neonatal and adult mice. Studies with a radioimmunoassay and a cell culture assay for erythropoietin
Authors: SANENGEN T. , CLEMONS G. K. , HALVORSEN S. , WIDNESS J. A.
Published: December 2008

The objective was to study whether the high erythropoietic stimulatory activity found in plasma from neonatal mice during the growth period is erythropoietin (Ep) alone, or Ep in combination with other factors. Plasma from hypertransfused neonatal (20 d) and adult (13–20 weeks) mice were compared with a radioimmunoassay (RIA) and a cell culture assay for Ep. The RIA determines immunoreactive Ep (iEp) while the cell culture assay reflects erythropoiesis stimulating factor(s) (ESF). Compared to control values, hypertransfusion resulting in PCVs of 55% and higher reduced the mean iEp levels in neonatal and adult mice by 82% and 38%, respectively (P < 0.01). There was no detectable difference between the mean iEp levels of hypertransfused neonatal and adult animals (P > 0.3). The parallel ESF data showed a reduction in mean plasma ESF levels by 68% in hypertransfused neonatal and 72% in hypertransfused adult animals (P < 0.001). And notably, in contrast to the iEp data, the mean ESF level found in hypertransfused neonatal mice with PCVs of 55% and higher was significantly above that of hypertransfused adult animals (P < 0.001). No correlation was found between PCV and iEp (r < 0.4, P > 0.1) or ESF (r < 0.2, P > 0.2) in hypertransfused animals. The parallel data from the two Ep assays show that plasma from hypertransfused 20‐d‐old mice contain one or more erythropoietic stimulatory factors not detected by the RIA. It is concluded that part of the high erythropoietic stimulatory activity found in plasma from neonatal mice is due to non‐Ep factors.
The role of adenosine and prostacyclin in coronary flow regulation in healthy man
Authors: EDLUND A. , SOLLEVI A. , WENNMALM Å.
Published: December 2008

Coronary flow regulation in man is incompletely understood. We addressed the hypothesis that endogenous adenosine and prostacyclin (PGI2) affect basal coronary tone and/or the coronary flow response to increased myocardial work. In healthy volunteers coronary sinus flow and cardiac oxygen extraction were measured at rest and during leg exercise (40–50 W), before and after i. v. administration of theophylline (to block adenosine receptors) and oral administration of ibuprofen (to inhibit prostaglandin synthesis). Before drug, the basal coronary flow was 118 ± 23 ml min ‐1 and the cardiac extraction of oxygen 122 ± 3 ml 1‐1. Leg exercise elevated coronary flow by 89 ± 16 ml min′. Theophylline, at a dose blocking the coronary flow response to dipyridamole (an adenosine‐dependent mechanism), induced a moderate increase in myocardial oxygen extraction (by 11%, P < 0.05), but failed to affect either the basal coronary flow (105 ± 16 ml min‐1) or the increase during exercise (88 ± 25 ml min‐1). Ibuprofen inhibited the urinary excretion of PGI2 metabolite by about 90%, but did not affect basal coronary tone or the coronary response to exercise. These data indicate that endogenous adenosine is of limited importance for normal coronary regulation in man, and that PGI2 has no effect.
Metabolic control of large‐bore arterial resistance vessels, arterioles, and veins in cat skeletal muscle during exercise
Authors: BJÖRNBERG J. , MASPERS M. , MELLANDER S.
Published: December 2008

The metabolic control of the vascular bed in cat gastrocnemius muscle during exercise was studied with a new technique (Björnberg et al. 1988) permitting continuous and simultaneous recordings of arteriolar and capillary pressures, and of resistances in the following consecutive vascular section: proximal arterial resistance vessels > 25 μm, arterioles < 25 μm, and on the venous side. The study thereby provided quantitative data for resistance and active intrinsic tone in these vascular segments at rest, during graded exercise vasodilatation, and in the post‐exercise period. Slight activation of the metabolic control system by low‐frequency somatomotor nerve stimulation (light exercise') caused inhibition of intrinsic tone and decreased vascular resistance selectively in the arteriolar section. At increasing workloads, arteriolar resistance was further decreased, but resistance and tone in the proximal arterial resistance vessels and the veins then became clearly reduced as well. This difference in effectiveness of the metabolic control system on the different segments of the vascular bed was expressed quantitatively in terms of a ‘metabolic vasodilator index’. Graded activation of the metabolic control system led to a marked segmental redistribution of intrinsic vascular tone, in turn resulting in an increased pressure drop across the proximal arterial vessels and the veins and a decreased pressure drop over the arterioles. The observed decrease in the pre‐ to post‐capillary resistance ratio caused, at a constant arterial pressure of 100 mmHg, a graded increase in capillary pressure with increasing workloads, at maximum vasodilatation by an average value of 14 mmHg above the resting control value of 15.4 ± 0.6 mmHg. In the post‐exercise period, recovery of vascular tone to control was more rapid in the proximal arterial resistance vessels and the veins than in the arteriolar segment.
An intravital microscopic model for mast cell‐dependent inflammation in the hamster cheek pouch
Authors: RAUD J. , DAHLÉN S.‐E. , SMEDEGÅRD G. , HEDQVIST P.
Published: December 2008

Topical antigen challenge in cheek pouches of immunized hamsters led to an acute inflammatory reaction which was characterized by intravital microscopy. The response consisted of short‐lasting arteriolar spasm, followed by leakage of plasma, vasodilation, and accumulation of leucocytes. Several observations indicated that the reaction was due to mast cell activation. Thus, a very similar inflammatory response was seen after challenge with compound 48/80, and both antigen and compound 48/80 degranulated the numerous mast cells present in the cheek pouch. In addition, fluorescein‐labelled antigen bound specifically to mast cells in cheek pouches of immunized animals, also suggesting the presence of mast cell‐fixed antigen‐specific antibodies, possibly immunoglobulin E. However, although antigen and compound 48/80 caused similar microvascular responses, cross‐desensitization experiments indicated that the two stimuli activated mast cells via different mechanisms.

The histamine antagonist mepyramine, which abolished plasma leakage induced by exogenous histamine, substantially inhibited the increase of microvascular permeability evoked by antigen or compound 48/80, but did not appear to affect the vasospasm and leucocyte accumulation.

It is concluded that the hamster cheek pouch may be a most useful tool for investigation of dynamic microvascular events during allergic mast cell‐dependent inflammation.
Effect of increased α‐adrenergic activity on the blood pressure/cardiac output relationship in dogs
Authors: THORVALDSON J. , ILEBEKK A. , AARS H. , KIIL F.
Published: December 2008

The relationship between mean aortic blood pressure (MAP) and cardiac output (CO) was examined in anaesthetized, open‐chest dogs during variations in pre‐load with and without α‐adrenergic stimulation with phenylephrine. When phenylephrine increased MAP to 200 mmHg, CO fell greatly and could not be increased by volume expansion. Left ventricular ultrasonic measurements and pressure recordings showed that the Frank‐Starling mechanism was maximally activated. During vena cava obstruction CO and MAP fell proportionally. At a lower infusion rate of phenylephrine, MAP increased to 160 mmHg without a great reduction of CO. As in control experiments without phenylephrine infusion, CO could be increased by dextran/saline infusion and lowered about 20% below control by vena cava obstruction with no significant change in MAP; by further caval obstruction CO and MAP fell in proportion. Phenylephrine did not alter the relationship between aortic baroreceptor activity and MAP. The same MAP/CO relationships were obtained before and after bilateral vagotomy and nephrectomy. Caval obstruction and pacing tachycardia resulted in similar MAP/CO relationships despite different effects on left ventricular end‐diastolic pressure. Thus, phenylephrine infusion may raise MAP to 200 mmHg but no cardiac reserve is left. During reduction of CO by caval obstruction, peripheral vascular resistance remains constant despite varying baroreceptor activity. At the lower infusion rate of phenylephrine, raising MAP to 160 mmHg, peripheral vascular resistance is constant at low CO, but at high CO the vasoconstrictive effect of phenylephrine is counteracted by a vasodilatory mechanism which seems to be flow‐dependent.
Intrafascicular multi‐unit recordings from the human infra‐orbital nerve
Authors: NORDIN M. , THOMANDER L.
Published: December 2008

Intrafascicular micro‐electrode recordings were made from the human infra‐orbital nerve close to the infra‐orbital foramen. The fascicular organization was studied and multi‐unit activity from low‐threshold mechanoreceptive afferents was recorded during tactile stimuli, vibration and facial movements. Attempts were also made to record C‐fibre activity.

Innervation zones corresponding to 66 fascicles were mapped with tactile stimuli on facial hairy skin and the red zone of the lip. Most of these fields were located on the upper lip, where they overlapped, indicating a high innervation density. The fields had a median size of 3.8 cm2.

Skin indentation evoked dynamic on‐ and off‐responses and a much less pronounced static discharge. The afferent double‐peaked responses to an oscillating probe applied to the peri‐oral region induced similar grouping of the EMG activity during sustained lip protrusion. Contraction of facial muscles and stretching of the skin evoked on‐ and off‐responses, whereas the static discharge was less pronounced, especially during sustained stretching. The dynamic sensitivity to minor variations in contraction and stretching was high, and during normal facial movements, as in speech, there was a barrage of impulses originating from mechanoreceptors within large facial areas. Functional implications of these sensorimotor interactions are discussed.

Sympathetic C‐fibre activity, frequently seen in recordings from the supra‐orbital nerve, was never encountered in the infra‐orbital nerve recordings, indicating a lack of such fibres. Failure to detect afferent C‐fibre activity could be explained by methodological difficulties.
Some aspects of the communicational and computational organization of the brain
Authors: FUXE K. , AGNATI L.F. , ZOLI M. , BJELKE B. , ZINI I.
Published: December 2008

Some features of the morphofunctional organization of the CNS have been analysed.

Different types of hierarchical organization have been recognized, each of which could deeply affect the circulation (communicational aspect) and elaboration (computational aspect) of information. These two aspects have been discussed on the basis of the existence of two types of electrochemical transmission in the CNS: wiring and volume transmission.

By evaluating the CNS operations at different levels of analysis a ‘computational hierarchical organization’ has been delineated.

This concept is very relevant to the understanding of the ‘computational power’ of the brain (Agnati & Fuxe 1984, Conrad 1985a).In fact, it leads to the distinction between horizontal and vertical elaboration of information.

The hypothesis is introduced that in the vertical elaboration of information a central role may be played by the neuronal membrane. In fact, this structure can not only be influenced by the extra‐ and intracellular signals, but also effectively interconvert the electrical coding into the chemical coding of information. These aspects are discussed in the frame of the possible organization of the membrane into ‘domains’, each domain being a patch of membrane in which pre‐selected molecular movements are possible, resulting in molecular interactions. The movement of a molecule outside its domain is considered energetically unfavourable. The possible formal treatment of this hypothesis is mentioned in Conrad's work (1985b).
Carbachol stimulation of inositol phosphate accumulation in rat submandibular gland fragments is not modified by VIP
Authors: LARSSON O. , FREDHOLM B.B.
Published: December 2008

Formation of inositol phosphates in response to carbachol, phenylephrine and vasoactive intestinal polypeptide (VIP) was studied after labelling with [3H]myo‐inositol in rat submandibular gland fragments. Carbachol enhanced the accumulation of inositol phosphates in a concentration‐dependent manner. This effect was independent of calcium in the incubation medium and totally antagonized by atropine (IC50= approx.1 nM).Phenylephrine also induced an increase in inositol phosphate accumulation, which was totally antagonized by prazosin but not by atropine. Vasoactive intestinal polypeptide, isoproterenol and forskolin, compounds known to enhance the levels of cAMP in rat salivary gland, or addition of dibutyryl‐cAMP (DB‐cAMP) failed to alter basal or carbachol‐evoked accumulation of inositol phosphates.

It is concluded that the formation of inositol phosphates during muscarinic receptor stimulation with carbachol in rat submandibular gland fragments is not affected by adrenoceptor occupation or by cAMP.In particular, addition of VIP, which coexists with acetylcholine, did not alter the muscarinic inositol phosphate response.
Effects of three different cholecystokinin receptor antagonists on basal and stimulated insulin and glucagon secretion in mice
Authors: KARLSSON S. , AHRÉN B.
Published: December 2008

Cholecystokinin (CCK) receptor antagonists may be valuable tools for investigating the physiological role of CCK in islet function. In this study, the effects of the three different CCK receptor antagonists, proglumide, CR 1409 and L‐364, 718, on basal and stimulated insulin and glucagon secretion were investigated in vivo in the mouse. Each of the CCK antagonists was injected intravenously, either alone or together with one of the secretagogues CCK‐8 (5.3 nmol kg‐1), carbachol (0.16 μmol kg‐1) or glucose (2.8 mmol kg‐1).At a low dose level, proglumide (28 μmol kg‐1) inhibited selectively CCK‐8‐induced insulin and glucagon secretion. However, at a higher dose level (280 μmol kg‐1), proglumide inhibited also carbachol‐ and glucose‐induced insulin secretion. Furthermore, proglumide elevated basal plasma levels of both glucagon and glucose. CR 1409 inhibited CCK‐8‐induced insulin secretion at a high (21 μmol kg‐1) but not at a low (0.21 μmol kg‐1) dose level. In contrast, CCK‐8‐induced glucagon secretion was not affected by CR 1409.L‐364, 718 (2.4 μmol kg‐1) inhibited both CCK‐8‐induced insulin and glucagon secretion. In contrast, L‐364, 718 did not affect basal plasma levels of insulin, glucagon or glucose or those levels after stimulation with carbachol or glucose. We conclude that, of these three CCK antagonists, L‐364,718 is the most specific CCK receptor antagonist for studies of both insulin and glucagon secretion in tyhe mouse.
Flow resistance in the feline choledocho‐duodenal sphincter as studied by constant‐pressure and constant‐perfusion techniques
Authors: THUNE A. , JIVEGARD L. , SVANVIK J.
Published: December 2008

During interdigestive periods, there is a resistance to flow in the biliary tract exerted by the sphincter of Oddi, resulting in a pressure gradient between the common bile duct and the duodenum. In this experimental study, this flow resistance was studied with both a constant‐flow and a constant‐perfusion technique in fasted, anaesthetized cats. The flow resistance exerted by the sphincter is higher when it is perfused by a constant flow compared to when the common bile duct pressure is kept constant and the flow varies in response to its muscular activity. It was demonstrated with each method that the flow resistance in the choledocho‐duodenal junction is reduced in response to distension of the biliary tree and gallbladder and also by distension of the duodenum. Cholecystokinin was shown to reduce the flow resistance in the choledocho‐duodenal junction as estimated with either method.
Electrophysiological and mechanical characteristics of isolated hearts from spontaneously hypertensive (SHR) and normotensive (WKY) rats on very high‐ and low‐sodium diets
Authors: VOLKMANN R. , ELY D. , FOLKOW B. , JOHNSSON E. , PETTERSSON A.‐S. , WÅHLANDER H. , FRIBERG P.
Published: December 2008

Electrophysiological, mechanical, dimensional and coronary flow characteristics were studied on papillary strips and on isolated hearts, from spontaneously hypertensive (SHR) and normotensive (WKY) rats respectively, which from 5 to 15 weeks of age had been on either ‘low’ (LNa, 0.5 mmol 100 g‐1 food), control (CNa, 5) ‘high’ (HNa, 50) or ‘very high’ (vHNa, 120) sodium diets. With respect to cardiac electrophysiological characteristics, contractility, and maximal stroke volume capacity only minor, if any, differences were observed between the various Na diet groups, both in WKY and SHR.This is in accordance with our earlier findings concerning vascular smooth muscle, where a largely unchanged sensitivity and responsiveness to, for example, noradrenaline was noted. Further, only to the extent that the various Na diets had also caused changes in average blood pressure levels, adaptations of cardiac and coronary resistance vessel design were observed, in general agreement with our earlier findings in other preparations and experimental designs. The largely unaffected functional characteristics of cardiac as well as vascular effector cells, despite 240‐fold long‐term variations in sodium intake, are in sharp contrast to the marked changes that have been shown to affect the adrenergic nerves, as here chronic low‐Na intakes cause reductions of transmitter release/impulse, and vice versa at high Na intakes. This latter type of change seems to be by far the most important functional deviation affecting cardiovascular control during long‐term alterations of sodium intake, as it can markedly affect both cardiac and vascular influences on haemsodynamics, even though the respective effector functions seem to be surprisingly little influenced directly. Only the modest increase of ‘intrinsic’ heart rate, earlier observed in rats on chronic LNa diets, seemed to be largely independent of the chronically elevated cardiac sympathetic activity in such rats, as it was also seen in one LNa SHR subgroup which had simultaneously been exposed to chronic β1‐receptor blockade.
Renal response to low and high phosphate intake in weanling, adolescent and adult rats
Authors: KARLÉN J.
Published: December 2008

The renal response to low and high phosphate intake was studied in weanling, young and adult rats. Weanling rats were started on experimental diets containing 0.37%, 0.7%, or 1.7% phosphate at 24 days and adult rats at 60 days of age. After 21 days, clearance studies were done in anaesthetized animals. Urine was collected during basal conditions and following a phosphate infusion. Urinary excretion of calcium, phosphate and creatinine, and plasma levels of phosphate and creatinine were determined. Plasma phosphate was slightly higher in the younger rats in all dietary groups but was not influenced by phosphate intake in either age group. Urinary phosphate excretion and fractional phosphate excretion increased significantly in both age groups with increasing phosphate intake. After high phosphate intake, both net and fractional phosphate excretions were significantly higher in younger rats (0.97 ± 0.08 and 0.24 ± 0.06 μcmol min1 100 g‐1, P < 0.01, and 47.5±3.84 and 18.15±5.59%, P < 0.01, respectively).The urinary excretion of calcium related to creatinine was higher in younger rats in all dietary groups with the highest value found after low phosphate intake. During an acute phosphate infusion, fractional phosphate excretion increased significantly in both age groups after normal phosphate intake but remained unchanged after low or high phosphate intake. Plasma phosphate increased significantly only in younger rats with high phosphate intake (2.9±0.18, 3.88±0.43, P < 0.05).It is suggested that hypercalciuria reflects early stages of phosphate depletion and that in young rats stabilized on a high phosphate intake, phosphate retention may occur during an acute phosphate load.
Effects of intravenous calcitonin gene‐related peptide (CGRP) and substance P on the blood–aqueous barrier in the rabbit
Authors: ANDERSSON S.E. , BILL A.
Published: December 2008

The irritation response of the rabbit eye to trigeminal nerve stimulation, which includes a breakdown of the blood–aqueous barrier (BAB), seems to be due to the release of substance P (SP) and calcitonin gene‐related peptide (CGRP). In order to assess the relative importance of these two peptides for the barrier effect, and the role of arachidonic acid metabolites (AAM) in the response, we have studied the effects of intravenous injections of the peptides on the permeability of the blood vessels of the anterior uvea and the BAB using labelled albumins. At a dose of 120 pmol kg‐1 there was marked leakage of labelled albumin into the aqueous humour in animals under pentobarbital anaesthesia. The leakage was enhanced by sympathotomy. In conscious animals 5 pmol kg‐1 CGRP caused enhanced leakage from the blood vessels of the ciliary processes in those pre‐treated with biperiden in order to abolish the cholinergic vasoconstrictor tone in the anterior uvea. 24 and 120 pmol kg‐1 CGRP caused marked leakage of albumin and a breakdown of the epithelial part of the BAB. These effects were not modified by biperiden pre‐treatment, but markedly reduced by pre‐treatment with indomethacin. The protecting effect of indomethacin was lost when biperiden was given as well.

SP did not cause a leakage with 5 nmol kg‐1 and only moderate leakage with 25 nmol kg‐1. This effect was abolished by pre‐treatment with indomethacin but not if indomethacin was combined with biperiden. The results indicate that the effects of CGRP and SP on the blood–aqueous barrier are dependent on the tone of the uveal blood vessels, and suggest that the two neuropeptides tend to release vasodilating AAM. CGRP is likely to play a much greater role than SP in the neurogenic breakdown of the blood–aqueous barrier since the two peptides seem to be released in comparable amounts.
Effect of high pressure on metabolic response to cold in rats
Authors: MARTINI S. , BRUBAKK A.O. , BECH C.
Published: December 2008

The ability of rats to regulate body temperature in a cool helium–oxygen (heliox) atmosphere at high pressure was studied. Thermoregulatory ability in seven awake rats was assessed in a pressure chamber at 1.5, 21 and 41 ATA by monitoring body temperature and oxygen consumption during a gradual reduction of ambient temperature. Body temperature was measured by a radiotelemetry transmitter implanted into the intraperitoneal cavity. The thermal conductance of the rats increased from 0.37 to 0.75 W kg‐1°C‐1 as air was substituted by heliox and increased further to 1.47 and 1.81 W kg‐1°C‐1 as the pressure was increased to 21 and 41 ATA, respectively. At high pressure the rats were able to maintain body temperature until the metabolic rate reached a value of 21.9 ± 2.0 W kg‐1, which corresponds to peak metabolic rate. This occurred at an ambient temperature of approximately 21 °C. Below this ambient temperature the rats did not manage to maintain body temperature. The results show that the thermal effector mechanisms of rats respond adequately to a slowly decreasing ambient temperature in hyperbaric heliox environments.
Kinetic parameters of cytochrome c oxidase in rat skeletal muscle: effect of endurance training
Authors: SOUSSI B. , IDSTRÖM J.‐P. , SCHERSTEN T. , BYLUND‐FELLENIUS A.‐C.
Published: December 2008

The kinetic properties of cytochrome c oxidase (EC 1.9.3.1) in skeletal muscle tissue of sedentary and endurance‐trained rats were studied. The initial velocity of the cytochrome c oxidase reaction was determined polarographically over a large range of cytochrome c concentrations and the maximal velocity (Vmax) and the Michaelis constant (Km) were calculated. The catalytic activity of cytochrome c oxidase in isolated mitochondria was also investigated. The training programme consisted of treadmill running for 2 h a day, 6 days a week, at a speed of 30 m min‐1 and 30° elevation, for 4 weeks.Vmax of cytochrome oxidase with respect to cytochrome c increased significantly from 254 to 310 μmol O2 min‐1 g‐1 protein in response to training (P < 0.001), whereas Km remained unchanged (18.9 and 18.7 μm). The turnover number (TN) increased from 11.1 s‐1 in sedentary rats to 16.6 s‐1 in trained rats (P < 0.001). The results suggest a qualitative change in the enzyme molecule in addition to a true Vmax change of cytochrome c oxidase in response to endurance training.
Arterial PCO2 and pH in man during 3 days' exposure to 2.8 kPa CO2 in the inspired gas
Authors: NICOLAYSEN G. , ELLINGSEN I. , OWE J.O. , MYHRE K.
Published: December 2008

It has not been firmly established how respiration adapts to long‐term CO2 exposure in man. We have therefore exposed five healthy human subjects to 2.8 kPa CO2 in the inspired gas for about 70 h in a chamber with controlled atmospheric conditions at ambient pressure.PCO2 and pH were determined in arterial or arterialized venous blood drawn before, during and after the exposure. One subject was studied twice. We found that PCO2 increased acutely and then increased further within the 5‐ to 24‐h period of exposure to 2.8 kPa CO2. No consistent change was observed during the following 2 days. At the end of exposure the PCO2 was 0.5 kPa above the pre‐exposure level. When the breathing gas was switched back to room air, PCO2 promptly returned to pre‐exposure values. The secondary rise in PCO2 within the first day would correspond to a decrease in alveolar ventilation of about 10% assuming constant production and elimination of CO2. Arterial pH remained slightly below the pre‐exposure level during the entire exposure period. A slight renal compensation resulting in an increase in base excess of about 1 mmol 1‐1 may have occurred in the middle part of the exposure period. We conclude that a significant, but moderate, respiratory adaptation takes place during the first day of exposure to an increased inspired load of CO2
Comparison of tactile discrimination ability of visually deprived and normal monkeys
Authors: CARLSON S. , TANILA H. , LINNANKOSKI I. , PERTOVAARA A. , KEHR A.
Published: December 2008

The tactile discrimination ability of visually deprived and normal monkeys was tested to study whether loss of vision would improve the utilization of the tactual sense. Three normally sighted monkeys and three monkeys that had been deprived of vision during the first year of their life were trained in two tactile discrimination tasks by using a reward system in which the animals received a raisin or half a peanut under a correctly chosen wooden block. Discrimination was based on the gradual roughness or size of various blocks. When the monkeys had learned the tasks to the criterion, discrimination thresholds were determined.

All monkeys improved their performance in both tasks with time, but no statistically significant differences between the performance of the two groups of monkeys were obtained. These results suggest that although the representation of the tactual sense in the cortical association areas has been shown to increase as a result of visual deprivation during the early sensitive period of life, increased representation does not improve the tactual discrimination ability of simple tactual stimuli.
in‐vitro stimulation of the rat epitrochlearis muscle. I. Contractile activity per se affects myofibrillar protein degradation and amino acid metabolism
Authors: NIE Z. T. , LISJÖ S. , KARLSON E. , GOERTZ G. , HENRIKSSON J.
Published: December 2008

The influence of contractile activity on protein degradation and amino acid metabolism in skeletal muscle was investigated by utilizing an in‐vitro electrical stimulation model with the rat epitrochlearis muscle preparation. Graded decreases in contraction force and in the muscle content of ATP and PCr, and increases in lactate were recorded with different rates of stimulation (1 h) and with both isometric twitches and tetanic contractions. 3‐Methylhistidine and phenylalanine were chosen as indicators of myofibrillar and total protein degradation, respectively. The release of 3‐methylhistidine was significantly stimulated by contractile activity, but a significant increase in the total amount of this amino acid (released amount + tissue content) occurred only at the most intense contraction rates. The release rate, tissue content and total amount of phenylalanine were not influenced by the contractions. Glutamate formation was generally inhibited, but its release was increased. Alanine synthesis was increased in moderately and intensely stimulated muscles. Glutamine and glycine were not influenced by the contractions, however. Inhibition of protein synthesis did not significantly influence protein degradation or amino acid release. The data suggest that in the absence of anabolic factors in the medium, myofibrillar protein degradation is increased in heavily activated muscle. This takes place without total protein breakdown being affected.
Effects of growth hormone on skeletal muscle. II. Studies on regeneration and denervation in adult rats
Authors: ULLMAN M. , ALAMEDDINE H. , SKOTTNER A. , OLDFORS A.
Published: December 2008

The effects of human recombinant growth hormone (rhGH) on regenerating skeletal muscle after ischaemic necrosis and on denervated skeletal muscle were studied in normal adult rats. One group of rats was treated with 4 IE rhGH daily by subcutaneous injections, while control rats were injected with saline. The treatment with rhGH resulted in increased levels of insulin‐like growth factor‐I (IGF‐I) in serum.

Ischaemic necrosis was achieved in the extensor digitorum longus (EDL) muscle by cutting the supplying vessels and nerve fascicles at the entrance into the muscle. The wet weight and DNA:protein ratio in the regenerating muscle were determined 2 and 4 weeks after the operation. The weight of the regenerating muscles in the rats treated with rhGH during the period of study was larger than in the control rats, while the DNA:protein ratio did not differ significantly between the groups.

Denervation of the EDL and soleus muscles followed by subsequent reinnervation was obtained by freezing the sciatic nerve with a forceps chilled in liquid nitrogen. Rats treated with rhGH during the period of denervation and reinnervation, i.e. during the 4 weeks after the freezing of the sciatic nerve, revealed increased weight of both the reinnervated and normal muscles compared to corresponding muscles of control rats.

Denervation of the EDL and soleus muscles without subsequent reinnervation was achieved by cutting the sciatic nerve at the level of the thigh. Four weeks after denervation the muscles showed atrophy, mainly affecting type 2 fibres in the EDL muscle and both type 1 and type 2 fibres in the soleus muscle. Both denervated and normal muscles of rats treated with rhGH during the 4 weeks after denervation showed significantly higher weight than the corresponding muscles of control rats.

It is concluded that rhGH administered to normal adult rats results in growth of normal muscle, increased growth of regenerating skeletal muscle after ischaemic necrosis and diminished atrophy of skeletal muscle after denervation.
Motor patterns of a fast voluntary postural task in man: trunk extension in standing
Authors: ODDSSON L.
Published: December 2008

The co‐ordination between muscles controlling the primary movement and associated postural adjustments during fast trunk extension movements was studied in six male subjects. Myoelectrical activity (EMG) was recorded from antagonistic muscle pairs at the trunk, hip, knee and ankle. Horizontal displacements of the upper trunk, hip and knee were recorded with an opto‐electronic system (Selspot).

A backward displacement of the trunk was accompanied by a forward displacement of the hip and knee. In general, the trunk started to move 30 ms before the hip and knee. Muscle activity first appeared in the ankle extensors (soleus/gastrocnemius) up to 150 ms prior to onset of prime mover muscles (trunk extensor, erector spinae; and hip extensors/knee flexors, hamstrings). This pre‐activation was seldom followed by any detectable ankle joint movement. Prime mover muscles were activated simultaneously followed by the hip extensor gluteus maximus. Time to activation of muscles braking the movement (rectus abdominis, rectus femoris and vastus lateralis) was correlated with the amplitude of the primary movement (r = 0.63–0.75, P 0.01). Onset of activity in vastus lateralis was highly correlated with the amplitude of the forward displacement of the knee (r= 0.93, P 0.01). An associated postural adjustment appeared as an ankle flexion accompanied by activity in the ankle flexor tibialis anterior, and often also in the ankle extensors. This co‐activation of antagonistic ankle muscles can under certain conditions have interesting functional implications for the control of posture.
Glucose polymer syrup attenuates prolonged endurance exercise‐induced vasopressin release
Authors: VIINAMÄKI O. , HEINONEN O. J. , KUJALA U. M. , ALÉN M.
Published: December 2008

We investigated the effect of glucose and glucose polymer ingestion on plasma arginine vasopressin (pAVP) levels, on plasma osmolality (p‐osm), and on performance during two prolonged endurance events. The study subjects were 37 Finnish elite endurance athletes, of whom 18 were orienteers and 19 cross‐country skiers. Plasma AVP increased in both combined glucose and glucose polymer groups, but the increase in the glucose polymer group was significantly smaller (P 0.001) than that in the glucose group. A significant change in p‐osm caused a significant change in pAVP and vice versa. Both the orienteers and the skiers on glucose polymer tended to have more success in the competition; the orienteers on glucose polymer ran the last third of the competition significantly faster than those on glucose (P 0.05). It is suggested, in the light of the smaller pAVP response, that after glucose polymer ingestion the physical stress in prolonged endurance exercise is smaller than after ingestion of glucose.
Transfer of DOPA from the sympatho‐adrenal system to the pancreas, liver and kidney via the blood circulation
Authors: ANDÉN N.‐E. , A‐ANDÉN M. GRABOWSK , SCHWIELER J.
Published: December 2008

The concentration of 3,4‐dihydroxyphenylalanine (DOPA) was low in the pancreas, liver, kidney, spleen, salivary glands, heart and adrenal glands of untreated mice, but increased following inhibition of DOPA decarboxylase by 3‐hydroxybenzylhydrazine. The ratio of the accumulation of DOPAtothe concentration of noradrenaline (i.e. the density of sympathetic nerves) was greater in the kidney, liver and, particularly, pancreas than in the other organs studied, suggesting that DOPA occurred outside sympathetic nerves in these organs. The tyrosine hydroxylase inhibitor α‐methyltyrosine almost completely inhibited the accumulation of DOPA in all organs. The DOPA accumulation was enhanced in all organs by the α‐adrenoceptor antagonists phenotolamine and yohimbine. The results indicate that the DOPA was formed in the sympatho‐adrenal system. In the pancreas, liver and kidney, most of the DOPA accumulated might have been formed outside these organs and transferred there via the bloodstream.
The strong contractile effect of the thromboxane receptor agonist U‐46619 in isolated human pulmonary arteries and its competitive antagonism by BM‐13.505
Authors: SJÖBERG T. , STEEN S.
Published: December 2008

Ring segments (1 mm in diameter) of the pulmonary artery obtained from 16 patients undergoing thoracic surgery were mounted in tissue baths. Cumulative concentration‐response curves of some prostanoids and amines were obtained, and Emax and pEC50 values calculated. Noradrenaline, phenylephrine, clonidine and serotonin (5‐HT) showed low intrinsic activities. Prostaglandin F2α (PGF2α) induced strong contractions with an Emax of 126% of the preceding K+ (124 mM)‐induced contraction, but its potency was low (pEC50= 5.70). The thromboxane receptor agonists U‐46619 and U‐44069 induced strong contractions (Emax= 139% and 133% respectively) and were significantly more potent than the other drugs used (pEC50= 8.43 and 8.30 respectively). The thromboxane receptor antagonist BM‐13.505 (10‐8 to 10‐6 M) caused rightward parallel shifts of the U‐46619 concentration‐response curves without reduction of Emax, indicating competitive antagonism.
Hypoxaemia increases the accumulation of inosine monophosphate (IMP) in human skeletal muscle during submaximal exercise
Authors: SAHLIN K. , KATZ A.
Published: December 2008

The effect of hypoxaemia on the muscle content of inosine monophosphate (IMP) during short‐term, low‐intensity exercise has been investigated. Six men cycled twice for 5 min at 120 ± 6 W (mean ± SE), which corresponded to ˜ 50% of their maximal normoxic O2 uptake, breathing air (N) on one occasion and 11% O2 in N2 (H) on the other. Oxygen uptake at the end of the exercise period was similar between treatments. No significant difference was observed between H and N in the muscle metabolite contents at rest. Muscle content of phosphocreatine (PCr) decreased and lactate increased during exercise. Post‐exercise PCr during H was 80% of the value during N (P > 0.05) and post‐exercise muscle lactate was fourfold higher during H than during N (P < 0.001). Post‐exercise muscle content of ADP was significantly higher during H than during N (P < 0.01), while ATP and AMP remained constant under both H and N exercise (P > 0.05 H vs N). IMP was not detectable in pre‐exercise muscle samples (< 0.01 mmol kg‐1 dry wt) but increased during N exercise (0.03 ± 0.01 mmol kg‐1 dry wt, P < 0.05) and even more during H exercise (0.16 ± 0.05 mmol kg‐1 dry wt, P 0.05, H vs N). Post‐exercise IMP was negatively related to PCr (r = ‐0.90) and positively related to lactate (r = 0.88). It is concluded that hypoxaemia results in an enhanced accumulation of IMP during submaximal exercise and that the IMP level is related to the degree of anaerobic energy utilization.
An electrophysiological in‐vivo study on the effects of nerve stimulation, drugs and denervation in the parotid gland of the rat
Authors: THESLEFF P.
Published: December 2008

Electrical stimulation of the sympathetic and parasympathetic nerves to the parotid gland of the rat gave rise to membrane potential changes. Responses were in several cases elicited by single stimuli which did not cause secretion. They were very similar to the ones seen after the administration of noradrenaline or acetylcholine. The peptides substance P (SP) and vasoactive intestinal polypeptide (VIP), in some cells, evoked membrane potential changes. The response was clearly enhanced during concurrent stimulation of the auriculotemporal nerve at a frequency below the secretory threshold. The membrane potential changes always occurred at stimulation frequencies or agonist doses that were lower or the same as those required for secretion. After atropine the cells became less sensitive to both substance P and VIP. Sympathetic or parasympathetic denervation about 2 weeks in advance, to induce supersensitivity, lowered the thresholds for most agonists just like in vitro. Also as in vitro, a greater number of cells responded to SP and VIP in the denervated than in the innervated gland.
Villous sodium gradient associated with volume absorption in the feline intestine: an electron‐microprobe study on freeze‐dried tissue
Authors: SJÖQVIST A. , III R. BEEUWKES
Published: December 2008

Water transport in biological tissue is driven by local osmotic gradients created by accumulation of actively transported ions in tissue compartments. To localize and measure such gradients, jejunal segments from the small intestine of anaesthetized cats were perfused with modified isotonic Krebs‐Henseleit electrolyte solution, and net fluid transport was measured with a volumetric technique. The segments were then rapidly frozen, freeze‐dried, and prepared for X‐ray micro‐analysis of elemental content. Whenever the lumen perfusate contained sodium, the apical third of the villus was found to have a sodium gradient rising to a tip concentration more than twice that at the base of the villus. This sodium gradient was associated with a chloride gradient and fluid absorption. No similar potassium gradient was found. When choline replaced sodium in the intestinal lumen, no gradient of sodium chloride was found and no net fluid absorption occurred. Absorption of fluid was thus apparently coupled to absorption of sodium through creation of a local osmotic gradient in the tip of the intestinal villus.
The effects of various gastrins on intracellular free Ca2+ in isolated pig parietal cells
Authors: CABERO J. L. , REHFELD J. F. , MÅRRDH S.
Published: December 2008

Gastrin 17 (G17) is a potent stimulant of gastric acid secretion in vivo. In this study, the effects of G17 and some related peptides on intracellular free Ca2+ in isolated pig parietal cells were studied. Both G17 and the synthetic peptide pentagastrin increased intracellular free Ca2+ in a dose‐dependent manner over the concentration range 10‐9 to 10‐6 M, suggesting a specific action. The EC50 values were 3 × 10‐8 M for G17 and 8 × 10‐8 M for pentagastrin. The N‐terminal tridecapeptide of G17 [(1–13)617] did not have any effect on intracellular free Ca2+, nor was it able to inhibit the action of G17. A glycine‐extended gastrin [(5–17)617‐Gly)] elicited a small but significant increase in intracellular free Ca2+ although only at 10‐6 M. This increase was approximately 20% of that obtained with a similar concentration of G17. Sequential incubations with (S‐17)G17‐Gly and G17 showed that both peptides increased the intracellular free Ca2+ through the same mechanisms.
Selective thromboxane A2 receptor blockade in experimental exercise‐induced myocardial ischaemia in dogs
Authors: THAULOW E. , GUTH B. D. , SCHULZ R. , JR J. ROSS
Published: December 2008

Thromboxane A2 receptor stimulation induces blood platelet aggregation and vasoconstriction, both potential causes of impaired perfusion of ischaemic myocardium. To study the potential role of thromboxane A2 receptor blockade in exercise‐induced myocardial ischaemia and post‐exercise myocardial dysfunction, nine conscious chronically instrumented dogs with single‐vessel coronary artery stenosis (ameroid constrictor) were studied before, during and after steady‐state treadmill runs which induced regional myocardial ischaemia. Three hours after a control run, the dogs were exercised again after the infusion of a selective thromboxane A2 receptor blocker: BM 13.177 (10 mg kg‐1 i.v.). In the control run, systolic wall thickening (WTh, sonomicrometer) in the post‐stenotic myocardium decreased from 22.1±9.1% at rest to 8.8 ± 5.2% (mean ± SD). Subendocardial blood flow (microspheres) in the ischaemic area decreased from 0.75 ± 0.25 to 0.45 ± 0.27 (ml min‐1 g). The WTh in the ischaemic region remained depressed at 20 min after the run. BM 13.177 reduced peak left ventricular (+) dP/dt (micromanometer) and WTh in both control and post‐stenotic myocardium at rest, during and after the run. WTh in the ischaemic area was reduced to approximately the same levels during running with BM 13.177 (not significantly different from control exercise) and remained depressed for at least 30 min after the run. Regional myocardial blood flow was not affected by BM 13.177. Thus, selective thromboxane A2 receptor blockade with BM 13.177 had a modest negative inotropic effect and did not improve regional function or blood flow in post‐stenotic ischaemic subendocardium.
Aldosterone secretion during acute respiratory acidosis and NH4CI‐induced metabolic acidosis in the goat
Authors: AUGUSTINSSON O. , FORSLID A.
Published: December 2008

Acute respiratory acidosis was induced in goats by inhalation of 6% or 8% CO2 in air for 30 min. The lower CO2 concentration caused a significant rise in plasma Cortisol (PC), but had no appreciable influence upon plasma aldosterone (PA), and did not affect the arterial blood pressure (aBP).

A more pronounced PC response was observed in association with the inhalation of 8% CO2, but also here without concomitant increase in PA. However, the aBP became elevated by about 30% during the CO2 exposure with a simultaneous increase in glomerular filtration rate and a water diuresis, suggesting that the release of arginine vasopressin temporarily became inhibited.

It was confirmed that metabolic acidosis induced by duodenal NH4Cl administration is preceded by a transient rise in PA. Dexamethasone‐induced feedback inhibition of the ACTH secretion blocked the PA response, which possibly reflects NH4 ion stimulation of the ACTH release.

The combined results of the CO2 and NH4Cl experiments seem to justify the conclusion that increases in PA seen in conjunction with acidosis do not reflect a direct hydrogen ion stimulation of the adrenal glomerulosa cells.