bluuebunny/crossref_metadata_2025 huggingface dataset:
Ecosystem controls of juvenile pink salmon (Onchorynchus gorbuscha) and Pacific herring (Clupea pallasi) populations in Prince William Sound, Alaska
Authors: Cooney Robert T. , Allen J. R. , Bishop M. A. , Eslinger D. L. , Kline T. , Norcross B. L. , Mcroy C. P. , Milton J. , Olsen J. , Patrick V. , Paul A. J. , Salmon D. , Scheel D. , Thomas G. L. , Vaughan S. L. , Willette T. M.
Published: March 2003

Five years of field, laboratory, and numerical modelling studies demonstrated ecosystem‐level mechanisms influencing the mortality of juvenile pink salmon and Pacific herring. Both species are prey for other fishes, seabirds, and marine mammals in Prince William Sound. We identified critical time‐space linkages between the juvenile stages of pink salmon and herring rearing in shallow‐water nursery areas and seasonally varying ocean state, the availability of appropriate zooplankton forage, and the kinds and numbers of predators. These relationships defined unique habitat dependencies for juveniles whose survivals were strongly linked to growth rates, energy reserves, and seasonal trophic sheltering from predators. We found that juvenile herring were subject to substantial starvation losses during a winter period of plankton diminishment, and that predation on juvenile pink salmon was closely linked to the availability of alternative prey for fish and bird predators. Our collaborative study further revealed that juvenile pink salmon and age‐0 herring exploit very different portions of the annual production cycle. Juvenile pink salmon targeted the cool‐water, early spring plankton bloom dominated by diatoms and large calanoid copepods, whereas young‐of‐the‐year juvenile herring were dependent on warmer conditions occurring later in the postbloom summer and fall when zooplankton was composed of smaller calanoids and a diversity of other taxa. The synopsis of our studies presented in this volume speaks to contemporary issues facing investigators of fish ecosystems, including juvenile fishes, and offers new insight into problems of bottom‐up and top‐down control. In aggregate, our results point to the importance of seeking mechanistic rather than correlative understandings of complex natural systems.
Effect of intracerebroventricular infusion of urocortin on feed and salt intake in parotid fistulated sheep
Authors: SUNAGAWA Katsunori , McKINLEY Michael J. , PURCELL Brett S. , THOMSON Craig , BURNS Peta L.
Published: March 2003

The effect of a new peptide, brain urocortin (UCN), in the central regulation of feed and salt intake in parotid fistulated sheep was investigated through a continuous intracerebroventricular (ICV) infusion of the peptide at a small dose for 48 h. Feed and salt intake on day 1 of UCN infusion were similar to those before infusion. However, feed and salt intake on day 2 during UCN infusion decreased significantly. Water intake on days 1 and 2 during UCN infusion was the same as that before infusion. Saliva secretion from the unilateral parotid gland during UCN infusion was unchanged from that before infusion. On the other hand, urine excretion during UCN infusion increased significantly. The present results suggested that UCN acts directly on the brain mechanisms of sheep to decrease feed and salt intake, but does not alter water intake.
Distribution of immunoreactive von Willebrand factor in the microvascular network of bovine cystic follicles
Authors: ISOBE Naoki , YOSHIMURA Yukinori , NAKAO Toshihiko
Published: March 2003

The present study was undertaken to examine whether the von Willebrand factor (vWF) expression in the follicular microvasculature in the cystic follicles differs from that in the atretic follicles. Paraffin sections of healthy, atretic and cystic follicles were immunostained with rabbit monoclonal antibody to vWF. The vWF‐positive cells were counted in four different regions of a follicle from the apical to the basal side. In all types of follicles, immunoreactions for vWF were observed in the endothelial cells of capillaries as well as veins and arteries in the theca interna and externa. In the theca interna, vWF‐positive areas were significantly lower in the Type A and B cystic follicles compared to advanced and late atretic follicles. In the theca externa, the vWF‐positive blood vessels and vWF‐positive area were significantly smaller in all types of cystic follicles than in the healthy or atretic follicles. From these results, it is suggested that in the cystic follicles the induction of vWF in the follicular microvasculature system is reduced, which may suppress the degeneration of vascular system. Continuation of stability in vasculature may be one of the factors that delays the tissue regression in the cystic follicles, and also contributes to the accumulation of follicular fluid that originates from the serum.
Optimization of selection and mating schemes in closed broiler lines
Authors: NOMURA Tetsuro , YAMAGUCHI Shigeki , MUKAI Fumio , YAMAMOTO Aya
Published: March 2003

Minimum coancestry mating (MC) is a simple mating system to reduce inbreeding in populations, in which matings are allocated so as to minimize the average inbreeding coefficient of progeny. This system was compared with random mating (RM) in simulated broiler lines. The population structure and genetic parameters were determined on the basis of an existing broiler line. Comparison of mating systems was made under two selection methods. The first method (DIS) was based on selection index for achieving desired genetic gains. In the second method (LPS), a combination of the family index and linear programming technique was applied to obtain the desired genetic gains. The selected traits were body weight at 6 weeks of both sexes and age at sexual maturity of hen. Four schemes by all the possible combinations of selection and mating methods (DIS + RM, DIS + MC, LPS + RM and LPS + MC) were compared in terms of genetic gains and inbreeding during 15 generations of selection and mating. The results obtained are summarized as follows: (i) the four schemes produced similar genetic gains averaged over replicates; (ii) the variations of genetic gains under LPS + RM and LPS + MC schemes were much smaller than under DIS + RM and DIS + MC schemes; (iii) irrespective of the selection methods, MC reduced the average inbreeding coefficients to about 80% of RM and; (iv) the inbreeding coefficients of individuals in the schemes with RM were distributed in a wide range, while the inbreeding coefficients in the schemes with MC showed a high uniformity. From these results, the LPS + MC scheme was recommended as a selection and mating strategy in closed broiler lines.
Pedigree analysis of genetic subdivision in a population of Japanese Black cattle
Authors: HONDA Takeshi , NOMURA Tetsuro , YAMAGUCHI Yuki , MUKAI Fumio
Published: March 2003

Twenty‐five subpopulations (i.e. populations of prefectures) of more than 2000 Japanese Black cows younger than or equal to 10 years of age were analyzed to evaluate the genetic relationships in the current population. The total number of cows analyzed was 392 346 and their pedigrees were traced back to 1944 or before. Using the pedigree records, the genetic relationships among the subpopulations were estimated by the two different measurements: (i) the average additive relationship coefficients and (ii) Nei's standard genetic distances. Principal component analysis (PCA) was performed to the matrix of the average additive relationship coefficients, and the factor loadings of subpopulations were plotted on the plane to visualize the genetic configuration of subpopulations. To understand the grouping process of the subpopulations, cluster analysis was applied to the matrix of the Nei's genetic distances, and a dendrogram was constructed. There was a high consistency between the results from PCA and cluster analysis. Eight subpopulations with relatively low migration rates showed their unique genetic compositions, and the other 17 subpopulations with high migration rates formed a single cluster. The major cause of the genetic similarity among the 17 subpopulations was inferred to be the strong genetic influence from one subpopulation (Hyogo prefecture) with prominent characteristics for meat quality.
Effect of administration of acid‐ and bile‐tolerant lactobacilli on pigs intestinal microbial population
Authors: OTSUKA Makoto , MUTO Tomoko , KATSUNUMA Yu , NAKAMURA Yutaka , TAKADA Ryozo , MINATO Hajime
Published: March 2003

The effects of the administration of four Lactobacillus strains as probiotics on the constitution of microbial populations in the intestine of pigs were investigated by using a litter of pigs. The experimental group was fed a diet blended with the freeze‐dried powder containing lactobacilli at a concentration of 0.2% (W/W). After 4 weeks of probiotics administration, the total viable count of anaerobes in the feces was not significantly different between the pigs fed a diet supplemented with probiotics and the pigs given the non‐supplemented diet. However, viable counts of eubacteria were significantly higher (P < 0.01) in the feces of pigs fed a diet supplemented with probiotics than in the pigs given the non‐supplemented diet. Conversely, viable counts of clostridia were significantly lower (P < 0.01) in the feces of pigs fed a diet supplemented with probiotics than the pigs given the non‐supplemented diet. The total volatile fatty acid concentrations in the feces of pigs that were given a diet supplemented with probiotics were significantly lower (P < 0.05) than those given the non‐supplemented diet. Further, the molar proportion of n‐butyric acids in the feces of pigs that were given a diet supplemented with probiotics, was significantly lower (P < 0.05) than those given the non‐supplemented diet.
Reduction of ammonia emission from growing pig rooms by feeding a lower protein diet supplemented with apple pomace
Authors: YAMAMOTO Akemi , UMEMOTO Eiichi , ITOH Minoru , MATSUI Masatoshi , FUJIMURA Nobuo , FURUYA Shu
Published: March 2003

An experiment was conducted to determine the effect of supplementing a reduced crude protein (CP) diet with apple pomace on the ammonia emissions from growing pig rooms. Four pigs (45 kg BW) each were assigned to one of two diets. Each group was housed in a separate room and fed a standard diet (CP 16.6%) or a low CP, amino acid‐supplemented diet (CP 9.1%) containing 23.1% of dried apple pomace for two 7‐day experimental periods. After the completion of the first period, the pigs were switched to the other diet. The daily ammonia emissions, measured for 3 days after a 4‐day adaptation period, were much lower for pigs fed the apple pomace‐supplemented diet than for pigs fed the standard diet (0.47 g/pig vs 7.30 g/pig, respectively). The daily nitrogen intake for the standard diet and the apple pomace‐supplemented diet was 58.1 and 35.5 g/pig, respectively. The pigs fed the apple pomace‐supplemented diet excreted more fecal nitrogen than pigs fed the standard diet (17.5 g/day vs 11.0 g/day, respectively), but urinary nitrogen excretion with the apple pomace‐supplemented diet was estimated to be 2.9 g/day, which was much lower than that for the standard diet (27.0 g/day). The addition of apple pomace to a reduced CP, amino acid‐supplemented diet reduces urinary nitrogen excretion and thereby ammonia emission.
The concept of idiotypic vaccination against factor VIII inhibitors in haemophilia A
Authors: Lacroix‐Desmazes S. , Bayry J. , Misra N. , Kaveri S. V. , Kazatchkine M. D.
Published: March 2003

Summary.  Idiotypic vaccination has proven successful in several animal models and human trials. Here we suggest that the expression of cross‐reactive idiotypes on factor VIII (FVIII) inhibitors of patients with haemophilia A, patients with anti‐FVIII autoimmune disease and natural anti‐FVIII antibodies of healthy individuals, together with the ability of anti‐idiotypic reagents to neutralize anti‐FVIII antibodies, provides a rationale for designing a vaccine strategy aimed at preventing the occurrence of or suppressing inhibitors, based on the induction of protective anti‐idiotypes. Here we discuss the rationale supporting the concept of using idiotypic vaccination to prevent the occurrence of FVIII inhibitors in patients with haemophilia A.
Inhibitor development in correlation to factor VIII genotypes
Authors: Oldenburg J. , El‐Maarri O. , Schwaab R.
Published: March 2003

Summary.  Alloantibodies (inhibitors) against factor VIII (FVIII) develop in 20–30% of patients with severe haemophilia A and render classical FVIII substitution therapy ineffective. Several studies have shown that genetic factors, the type of FVIII gene mutation and immune response genes (e.g. the Major Histocompatibility Complexes), influence the risk of inhibitor formation. In particular, the type of FVIII gene mutation has proven to be a decisive risk factor. Patients with severe molecular gene defects (e.g. large deletions, nonsense mutations, intron‐22 inversion) and no endogenous FVIII synthesis have a 7–10 times higher inhibitor prevalence than patients with milder molecular gene defects (e.g. missense mutations, small deletions, splice site mutations). To date, at least 10 distinct classes of mutations have been shown which have differing risks of associated inhibitor formation. A challenging observation in inhibitor patients is the heterogeneity of the antibody epitopes with respect to their number and their specifity. At least five epitopes in the FVIII molecule have been identified that constitute the targets for antibodies in most inhibitor patients. These epitopes are located in the ar3 region and the A2, A3, C1, C2 domains which correspond to the functional binding sites of the ligands of the FVIII protein. At present, the determinants of the characteristics of these epitopes and the subsequent inhibitor titre are unknown. A relationship of the mutation site and the epitope localization has been shown for some individual patients with mild haemophilia A. However, in severely affected haemophilia A patients, the influence of patient genetics on inhibitor titre and epitope specifity has yet to be elucidated.
Effects of elevated CO2 and vascular plants on evapotranspiration in bog vegetation
Authors: Heijmans Monique M. P. D. , Arp Wim J. , Berendse Frank
Published: March 2003

We determined evapotranspiration in three experiments designed to study the effects of elevated CO2 and increased N deposition on ombrotrophic bog vegetation. Two experiments used peat monoliths with intact bog vegetation in containers, with one experiment outdoors and the other in a greenhouse. A third experiment involved monocultures and mixtures of Sphagnum magellanicum and Eriophorum angustifolium in containers in the same greenhouse. To determine water use of the bog vegetation in July–August for each experiment and each year we measured water inputs and outputs from the containers. We studied the effects of elevated CO2 and N supply on evapotranspiration in relation to vascular plant biomass and exposure of the moss surface (measured as height of the moss surface relative to the container edge).

Elevated CO2 reduced water use of the bog vegetation in all three experiments, but the CO2 effect on evapotranspiration interacted with vascular plant biomass and exposure of the moss surface. Evapotranspiration in the outdoor experiment was largely determined by evaporation from the Sphagnum moss surface (as affected by exposure to wind) and less so by vascular plant transpiration. Nevertheless, elevated CO2 significantly reduced evapotranspiration by 9–10% in the outdoor experiment.

Vascular plants reduced evapotranspiration in the outdoor experiment, but increased water use in the greenhouse experiments. The relation between vascular plant abundance and evapotranspiration appears to depend on wind conditions; suggesting that vascular plants reduce water losses mainly by reducing wind speed at the moss surface.

Sphagnum growth is very sensitive to changes in water level; low water availability can have deleterious effects. As a consequence, reduced evapotranspiration in summer, whether caused by elevated CO2 or by small increases in vascular plant cover, is expected to favour Sphagnum growth in ombrotrophic bog vegetation.
Regulation of alternative splicing of α‐actinin transcript by Bruno‐like proteins
Authors: Suzuki Hitoshi , Jin Yui , Otani Hifumi , Yasuda Kunio , Inoue Kunio
Published: March 2003

Background: The Bruno‐like or CELF proteins, such as mammalian CUGBP1 and Etr‐3, Xenopus EDEN‐BP, and Drosophila Bruno (Bru), are regulators of gene expression at the post‐transcriptional level, and contain three RNA‐recognition motifs (RRMs). It has been shown that mammalian CUGBP1 and Etr‐3 regulate alternative splicing of cardiac troponin T pre‐mRNA via binding to CUG‐triplet repeats.

Results: Using in vitro selection and UV‐crosslinking experiments, we found that zebrafish Bruno‐like proteins bound to repeat elements of uridine and purine (termed UREs). It is known that non‐muscle (NM) and smooth muscle (SM) exons of the rat α‐actinin gene are used in a mutually exclusive manner. Transfection experiments in mammalian cells showed that zebrafish Brul and Etr‐3 induced the muscle‐specific splicing of rat α‐actinin pre‐mRNA via binding to the URE at the branch point upstream of the NM exon. In contrast, zebrafish Etr‐1 promoted skipping of both the NM and SM exons in a manner which was not dependent on URE‐binding.

Conclusions: Our results showed that Bruno‐like proteins bind to UREs and regulate the alternative splicing of α‐actinin pre‐mRNA. Members of the Bruno family play multiple roles in splicing regulation.
Effects of receptor blockade on metabolism and renal actions of vasopressin in conscious dogs
Authors: Grove L. , Christensen P. , Bie P.
Published: March 2003

Vasopressin – but not the V2 receptor agonist [deamino‐cis1,D‐Arg8]‐vasopressin (dDAVP) – may mediate natriuresis in dogs. The present study investigated this phenomenon by use of nonpeptide antagonists to V1a and V2 receptors 1‐{1‐[4‐ (3‐acetylaminopropoxy)benzoyl]‐4‐piperidyl}‐3,4‐dihydro‐2 (1H)‐quinolinone (OPC‐21268) and 5‐dimethylamino‐1‐{4‐ (2‐methylbenzoylamino)‐benzoyl}‐2,3,4,5‐tetrahydro‐1H‐benzazepine (OPC‐31260), respectively) hypothesising that only V1a inhibition would reduce the natriuresis. In conscious dogs vasopressin secretion was suppressed by water loading (2% body weight) and replaced by infusion of vasopressin (50 pg min−1 kg−1) resulting in physiological plasma concentrations (plasma levels of AVP (pAVP) = 2.0 ± 0.1 pg mL−1). In this setting, OPC‐21268 did not change the rate of sodium excretion. OPC‐31260 increased water excretion 12‐fold without significant changes in sodium excretion. Heart rate, mean arterial blood pressure, glomerular filtration rate, and clearance of endogenous Li+ were unchanged. During vasopressin infusion, both antagonists increased pAVP, OPC‐21268 by 20% and OPC‐31260 by 100% (2.0 ± 0.2–4.0 ± 0.3 pg mL−1). In the absence of vasopressin infusion, OPC‐31260 did not increase pAVP. Thus, the increase in pAVP appeared to be due to a decrease in metabolic clearance rate. The results indicate that the present dose of V1a receptor inhibitor OPC‐21268 does not reduce sodium excretion and that both vasopressin antagonists inhibit vasopressin metabolism.
Internal jugular venous spillover of noradrenaline and metabolites and their association with sympathetic nervous activity
Authors: LAMBERT  , KAYE  , THOMPSON  , TURNER  , COX  , VAZ  , JENNINGS  , WALLIN  , ESLER
Published: March 2003

It is recognized that the brain plays a pivotal role in the maintenance of blood pressure and the control of myocardial function. By combining direct sampling of internal jugular venous blood with a noradrenaline isotope dilution method, for examining neuronal transmitter release, and microneurographic nerve recording, we were able to quantify the release of central nervous system noradrenaline and its metabolites and investigate their association with efferent sympathetic nervous outflow in healthy subjects and patients with pure autonomic failure. To further investigate the relationship between brain noradrenaline, sympathetic nervous activity and blood pressure regulation we examined brain catecholamine turnover, based on the internal jugular venous overflow of noradrenaline and its principal central nervous system metabolites, in response to a variety of pharmacological challenges. A substantial increase was seen in brain noradrenaline turnover following trimethaphan, presumably resulting from a compensatory response in sympathoexcitatory forebrain noradrenergic neurones in the face of interruption of sympathetic neural traffic and reduction in arterial blood pressure. In contrast, reduction in central nervous system noradrenaline turnover accompanied the blood pressure fall produced by intravenous clonidine administration, thus representing the blood pressure lowering action of the drug. Following vasodilatation elicited by intravenous adrenaline infusion, brain noradrenaline turnover increased in parallel with elevation in muscle sympathetic nervous activity. While it is difficult to assess the source of the noradrenaline and metabolites determined in our studies, available evidence implicates noradrenergic cell groups of the posterolateral hypothalamus, amygdala, the A5 region and the locus coeruleus as being involved in the regulation of sympathetic outflow and autonomic cardiovascular control.
Regulation of porcine biliary secretion by secretin
Authors: Sætre S. S. , Andersen N. J. , Houe T. , Svendsen P. , Rehfeld J. F. , Olsen O. , Muckadell O. B. Schaffalitzky de
Published: March 2003

The importance of physiological plasma levels of secretin in biliary bicarbonate secretion is not known. However, in anaesthetized pigs the substantial hepatic output of bicarbonate into the duodenum in response to low doses of secretin exceeds pancreatic bicarbonate output. The aim was therefore to study the relationship between duodenal acidification, secretin and hepatic biliary bicarbonate output in the conscious pig. Göttingen minipigs (n = 22) were cholecystectomized and the common bile duct catheterized. The biliary bicarbonate secretion in response to intraduodenal HCl, secretin or pentagastrin given intravenously, and to meal was studied. Intraduodenal HCl infusion, secretin and pentagastrin given intravenously augmented hepatic bicarbonate output and plasma secretin concentrations significantly. The secretin response to acidification was sufficient to explain the subsequent increase in biliary bicarbonate secretion. Hepatic bicarbonate secretion and concentrations of CCK and secretin in plasma increased postprandially. Exclusion of bile salts from the duodenum abolished postprandial increase in bile volume and increased release of CCK in fasting and fed pigs whereas secretin release was diminished. The results demonstrate that hepatic bicarbonate secretion is stimulated by endogenous secretin and therefore may have a physiological role in duodenal neutralization.
Modulation of short latency stretch reflexes during human hopping
Authors: VOIGT  , DYHRE‐POULSEN  , SIMONSEN
Published: March 2003

To gain insight into central and peripheral reflex control mechanisms in moving humans we have investigated short latency stretch reflex activity in m. tricgif surae during two legged hopping. The objectives were: (1) to compare movement induced short latency stretch reflexes in soleus and medial gastrocnemius (MG) muscles, (2) to determine the relationship between the size of these reflexes and the muscle spindle stretch velocities, and (3) to compare the size of the movement induced short latency stretch reflexes and the H‐reflexes simultaneously. Six well‐trained healthy male subjects participated and they hopped at three different work rates. Surface electromyogram (EMG) and H‐reflexes were recorded during hopping. Muscle spindle length changes were estimated as the difference between estimated origin‐to‐insertion length changes and tendon length changes. The important findings were that during hopping: (1) movement induced short latency stretch reflexes were observed consistently in soleus, (2) the EMG amplitude of this stretch reflex was negatively correlated with the estimated peak muscle spindle stretch velocity (rs=−0.52, P < 0.02), and (3) the amplitude of the soleus H‐reflex at touchdown did not change in parallel with the stretch reflex. The negative correlation observed between the stretch reflex and the estimated peak muscle spindle stretch velocity in soleus is opposite to the basic velocity sensitive behaviour of stretch reflexes mechanically elicited during resting conditions. Possible control mechanisms are discussed. Additionally, muscle spindle length changes estimated from changes in the skeletal movements (joint angles) should be inferred cautiously because of tendon compliance, especially at high tendon forces.
Changes in CNTF receptor α expression in rat skeletal muscle during the recovery period after hindlimb suspension
Authors: GUILLET C. , HUCHET‐CADIOU C. , GASCAN H. , LÉOTY C.
Published: March 2003

This study investigated whether modifications in the contractile function of rat muscle after 3 weeks of hindlimb suspension followed by different recovery periods were associated with changes in ciliary neurotrophic factor (CNTF) receptor α. CNTF receptor α was stronger in control extensor digitorum longus (EDL) than soleus. CNTF receptor α was increased in unweighted as compared to control soleus muscle, while no significant changes occurred in EDL muscle. Furthermore, CNTF level was not significantly modified in adult sciatic nerve.
Influence of the sympathetic nervous system on renal function during hypothermia
Authors: BROMAN M. , KÄLLSKOG Ö. , KOPP U. C. , WOLGAST M.
Published: March 2003

Hypothermia increases preglomerular vasoconstriction leading to decreases in renal blood flow (RBF) and glomerular filtration rate (GFR). Since plasma catecholamine concentrations are increased during hypothermia, the present study was performed to determine the role of the renal sympathetic nervous system in the cold‐induced renal vasoconstriction. In Inactin® anaesthetized rats, hypothermia at 28 °C decreased GFR by 50% but failed to alter efferent renal sympathetic nerve activity (ERSNA). Since hypothermia causes shivering which could have influenced the ERSNA recording, Inactin® anaesthetized rats were treated with pethidine or rats were anaesthetized with pentobarbital sodium or Saffan® to eliminate cold‐induced shivering. In these non‐shivering rats, hypothermia produced a reversible decrease in ERSNA in association with a fall in GFR that was of a similar magnitude as in shivering rats. Further studies in Inactin® anaesthetized rats showed that the fall in GFR was unaltered by renal denervation, bilateral adrenalectomy or intrarenal administration of the α1‐adrenoceptor antagonist prazosin. We conclude that cold‐induced renal vasoconstriction is not due to an increase in ERSNA or adrenaline/noradrenaline‐mediated activation of renal α1‐adrenoceptors.
Myocardial interstitial noradrenaline monitoring during occlusion of inferior vena cava in cats
Authors: KITAGAWA  , AKIYAMA  , YAMAZAKI
Published: March 2003

To investigate myocardial interstitial noradrenaline (NA) kinetics during activation of systemic sympathetic nerves, we applied a dialysis technique to the left ventricle of anaesthetised cats and monitored myocardial interstitial NA levels during 6‐min occlusion of the inferior vena cava (IVC). Dialysis probes were implanted in the left ventricular wall, and dialysate NA levels as an index of myocardial interstitial NA levels, were measured with high‐performance liquid chromatographic–electrochemical detection. During IVC occlusion, dialysate NA levels progressively increased from 110 ± 17 pmol L−1 in the control and reached 620 ± 160 pmol L−1 at 4–6 min of IVC occlusion. Local administration of ω‐conotoxin GVIA at 10 μM decreased the control dialysate NA level to 35 ± 0.2 pmol L−1. The IVC occlusion induced increase in dialysate NA was suppressed only at 0–2 min of IVC occlusion. Intravenous injection of ω‐conotoxin GVIA (10 μg kg−1) did not increase the dialysate NA levels during IVC occlusion. Local administration of desipramine at 100 μM increased the control dialysate NA level to 900 ± 73 pmol L−1. The IVC occlusion induced progressive increase in dialysate NA was augmented at 2–6 min of IVC occlusion. These results suggest that the early increase in myocardial interstitial NA levels is mainly caused by neuronal release of NA from cardiac sympathetic nerve terminals, and that extraction from the circulation and neuronal NA uptake contribute to changes in myocardial interstitial NA levels after a delay of several minutes.
Modulation by nitric oxide of gastric acid secretion in toads
Authors: MOLERO  , HERNANDEZ  , LOBO  , CARDENAS  , ROMERO  , CHACIN
Published: March 2003

Nitric oxide (NO) is a novel chemical messenger that mediates a variety of biological actions. This study was undertaken to investigate the effects of NO on parietal cell function. The rate of [3H]arginine conversion to [3H]citrulline, a parameter of NO synthase activity, and NO formation (as NO−2), were inhibited by the NO synthase inhibitor, N G‐nitro‐
L‐arginine methyl ester (
L‐NAME), in a concentration‐dependent manner in the non‐stimulated toad gastric mucosa. This range of concentrations of
L‐NAME provoked stimulation of H+ secretion in a similar fashion, which was blocked by
L‐arginine but not by
D‐arginine. Pre‐treatment with carbachol plus ethylene glycol‐bis(β‐aminoethyl ether)‐N,N,N ′,N ′‐tetra‐acetic acid (EGTA) prevented the effect of
L‐NAME on H+ secretion and drastically reduced NO synthase activity.
L‐arginine had an inhibitory effect on H+ secretion in non‐stimulated and carbachol‐stimulated gastric mucosa, which was reversed by
L‐NAME. Carbachol and pentagastrin, but not histamine, significantly increased NO formation in the toad gastric mucosa. The results suggest that changes in NO synthesis in the gastric mucosa may modulate parietal cell function and that a calcium‐dependent mechanism may be involved.
Fibre‐type specific expression of fast and slow essential myosin light chain mRNAs in trained human skeletal muscles
Authors: JOSTARNDT‐FÖGEN  , PUNTSCHART  , HOPPELER  , BILLETER
Published: March 2003

The fibre‐type specific expression patterns of fast and slow isoforms of essential (alkali) myosin light chains (ELC) was analysed in trained, untrained and pathological human muscles. Biopsies from m. vastus lateralis of moderately trained and untrained persons, as well as highly trained endurance and strength athletes were analysed, by in situ hybridization, for the expression of the `fast' ELC 1f/3f and the `slow' ELC 1sb. We wanted to investigate if changes in the fibre‐type specific ELC mRNA pattern could be used as markers for training adaptation, especially, if the mRNA of the slow ELC 1sb isoform would appear in type IIA fibres as a result of endurance training (Baumann et al. 1987). We found the fast/slow ELC expression patterns in the fibre types to be remarkably stable. Physiological stress, even high training loads, did not affect it. No IIA fibres expressing ELC 1sb mRNA were found. They could be detected, however, in pathological muscle samples, where fast/slow ELC patterns not found in normal muscles were frequent. Our data suggest that in healthy muscles, only a subset of the theoretically possible combinations of myosin heavy and light chain isoforms are expressed at the level of their mRNAs.
Role of tyrosine phosphorylation in excitation–contraction coupling in vascular smooth muscle
Authors: HUGHES  , WIJETUNGE
Published: March 2003

Increasingly it is recognized that tyrosine phosphorylation plays an important part in the regulation of function in differentiated contractile vascular smooth muscle. Tyrosine kinases and phosphatases are present in large amounts in vascular smooth muscle and have been reported to influence a number of processes crucial to contraction, including ion channel gating, calcium homeostasis and sensitization of the contractile process to [Ca2+]i. This review summarizes current understanding regarding the role of tyrosine phosphorylation in excitation–contraction coupling in blood vessels.
Intracellular targeting and protein kinase C in vascular smooth muscle cells: specific effects of different membrane‐bound receptors
Authors: HALLER  , MAASCH  , LINDSCHAU  , BRACHMANN  , BUCHNER  , LUFT
Published: March 2003

Protein kinase C is an important second messenger system, which is translocated from the cytosol to the cell membrane upon cell stimulation. We used confocal microscopy to study the spatial distribution of protein kinase C isoforms after stimulation of cultured vascular smooth muscle cells with different agonists. First, we analysed the effects of angiotensin II and platelet‐derived growth factor (PDGF). Confocal microscopy showed a rapid assembly of PKC α along cytosolic fibres followed by a translocation towards the nucleus with angiotensin II. PDGF engendered a similar, but much slower response; however, a cytoskeletal distribution was not observed. We then investigated the effects of thrombin and bFGF on nuclear translocation. bFGF induced a rapid translocation of the isoform towards the perinuclear region and into the nucleus. bFGF had a similar effect on PKC ɛ. In contrast, thrombin had a smaller effect on nuclear translocation of PKC α and did not influence PKC ɛ, but instead induced a rapid nuclear translocation of PKC ζ. Thus, tyrosine kinase receptor activation via bFGF induces a rapid association of PKC α and ɛ within nuclear structures. Our results show that agonists cause, not only a translocation of protein kinase C isoforms into the cell membrane but also into the cell nucleus. Lastly, we analyzed the nuclear immunoreactivity of the PKC isoforms α, δ,ɛ and ζ in vascular smooth muscle cells during the cell cycle. Resting cells were stimulated with foetal calf serum (FCS, 10%), which translocated PKC α and ɛ to the perinuclear region and into the nucleus, while PKC δ and ζ showed no increase in nuclear immunoreactivity. After 4 h of FCS, the nuclear immunoreactivity for PKC α and ɛ was reduced to or below control values. At 8 h, increased nuclear expression of isoforms α,ɛ and ζ was observed, while isoform δ was not affected. Our results demonstrate a complex spatial and temporal regulation of PKC isoforms in response to vasoactive hormones and growth factors. We suggest that protein kinase C may be important for nuclear signaling and demonstrate that nuclear translocation of PKC isoforms is differentially regulated during the cell cycle.
Effects of endurance training on the size and blood flow of the arterial conductance vessels in humans
Authors: Miyachi M. , Iemitsu M. , Okutsu M. , Onodera S.
Published: March 2003

The aim of the present study was to determine non‐invasively the effects of endurance training on both the size and blood flow of the arterial conductance vessels during exercise by men. Twelve healthy male subjects were assigned to either an exercise‐trained group (ET, n = 7) or a sedentary control group (S, n = 5). The ET group underwent cycle‐endurance training for 8 weeks (80% V˙O2max, 40 min day−1, 5 days week−1). The S group led normal lives during the 8‐week period. Before and after the training period, cross‐sectional areas (CSA) of the ascending and abdominal aorta were measured by echography. Measurements were taken in the semisupine position on a cycle ergometer fitted with a backrest, at rest and during 40, 60 and 80% V˙O2max of exercise. In addition, Doppler ultrasonographic velocity and flow in the ascending aorta were simultaneously measured. The CSA of the ascending and abdominal aorta after training were significantly larger than those before training in the ET group. Although there were no significant differences in the peak and mean velocities in the ascending aorta before and after the training in the ET group, the blood flow in the ascending aorta during exercise after training was significantly larger than that found before training at each relative intensity. There were no significant differences in any of the Doppler echographic parameters in the S group. These findings suggest that the arterial conductance vessels can be morphologically altered in an adaptive response to the endurance training. Furthermore, the dilation of the conductance vessels with endurance training contributes to an increase in blood flow to the exercising muscles without a rise in blood velocity. In other words, the arterial conductance vessels adapt to maintain adequate blood velocity and shear stress.
Renal tubular transport and metabolism of carboxyamidated and glycine‐extended gastrins in pigs
Authors: HANSEN C.PALNÆS , STADIL  , REHFELD
Published: March 2003

Renal handling of postprandial and intravenously administered gastrin was investigated in anaesthetised pigs. The fractional extraction of postprandial carboxyamidated and glycine‐extended gastrin in the kidneys was 0.21 ± 0.01 and 0.16 ± 0.02, but the respective urinary clearance comprised only 0.57 ± 0.03 and 0.44 ± 0.05% of the GFR (P < 0.02). The respective total body clearance of carboxyamidated and glycine‐extended gastrin‐17 (gastrin‐17 and gastrin‐17Gly) during continuous infusion was 22.9 ± 1.5 and 19.6 ± 1.4 mL kg−1 min−1 (NS), and the renal fractional extraction of the peptides was 0.31 ± 0.03 and 0.29 ± 0.05, respectively. The kidneys accounted for 8% of total body clearance of gastrin‐17. Renal filtration rate of gastrin‐17 exceeded renal extraction rate (9.739 ± 0.487 vs. 6.407 ± 0.321 pmol min−1). Urinary clearance of gastrin‐17 and gastrin‐17Gly amounted only 0.91 ± 0.16 and 0.13 ± 0.03%, respectively, of the GFR (P < 0.01), but urinary excretion rate correlated with the filtered amount of the peptides (r = 0.93, P < 0.01). Neither was a renal plasma threshold recorded nor was a Tm value for tubular uptake or degradation of gastrin achieved in spite of supraphysiological plasma levels of the peptides. The results indicate that filtered gastrin is almost completely removed in the renal tubules, primary by metabolism although part of the absorbed peptides may be returned to the circulation in intact form. The process for uptake or metabolism has a high capacity but varies with the molecular form of gastrin.
Neurohumoral responses to a single haemodialysis in chronic renal patients
Authors: UUSIMAA  , HUTTUNEN  , RUSKOAHO  , LINNALUOTO  , IKÄHEIMO
Published: March 2003

The effect of volume reduction on vasoactive substances and their role in estimating dry weight in haemodialysis patients was studied. Plasma atrial natriuretic peptide (ANP), catecholamines, antidiuretic hormone, renin activity and serum aldosterone were measured in 12 patients before and after bicarbonate haemodialysis. Haemodynamical changes were registered and cardiac function and diameter of the inferior vena cava were measured by echocardiography before and after dialysis. Plasma concentration of ANP was significantly reduced by haemodialysis from 209 ± 51 to 69 ± 13 pg mL−1 (n = 12, P < 0.05), whereas concentrations of the other hormones were unchanged. The change in the concentration of ANP did not have significant correlation with weight reduction. The concentration of ANP correlated positively with the diameter of the inferior vena cava (r = 0.70, P < 0.05) after dialysis, but not before dialysis. The concentration of ANP before or after haemodialysis or its change during dialysis did not correlate with any other biochemical parameter. The results show that plasma ANP level is decreased after volume reduction in patients with chronic renal failure, whereas other hormonal systems are unresponsive. However, plasma concentration of ANP seems to have no role in estimating dry weight in chronic haemodialysis patients.
Serial effects of high‐resistance and prolonged endurance training on Na+–K+ pump concentration and enzymatic activities in human vastus lateralis
Authors: GREEN  , DAHLY  , SHOEMAKER  , GOREHAM  , BOMBARDIER  , BALL‐BURNETT
Published: March 2003

The purpose of this study was to compare two contrasting training models, namely high‐resistance training and prolonged submaximal training on the expression of Na+–K+ ATPase and changes in the potential of pathways involved in energy production in human vastus lateralis. The high‐resistance training group (VO2peak = 45.3 ± 1.9 mL kg−1 min−1, mean ± SE, n = 9) performed three sets of six to eight repetitions maximal, each of squats, leg presses and leg extensions, three times per week for 12 weeks, while the prolonged submaximal training group (VO2peak = 44.4 ± 6.6  mL kg−1 min−1, n = 7) cycled 5–6 times per week for 2 h day−1 at 68% VO2peak for 11 weeks. In the HRT group, Na+–K+ ATPase (pmol g−1 wet wt), measured with the 3H‐ouabain binding technique, showed no change from 0 (289 ± 22) to 4 weeks (283 ± 15), increased (P < 0.05) by 16% at 7 weeks and remained stable until 12 weeks (319 ± 19). For prolonged submaximal training, a 22% increase (P < 0.05) was observed from 0 (278 ± 31) until 3 weeks (339 ± 29) with no further changes observed at either 9 weeks (345 ± 25) or 11 weeks (359 ± 34). In contrast to high‐resistance training, where a 15% increase (P < 0.05) was observed, only in the maximal activity of phosphorylase, prolonged submaximal training resulted in increases in malate dehydrogenase, β‐hydroxyl‐CoA dehydrogenase, hexokinase and phosphofructokinase. In contrast to high‐resistance training which failed to result in an increase in VO2peak, prolonged submaximal training increased VO2peak by ≈15%. Only for prolonged exercise training was a relationship observed for VO2peak and Na+–K+‐ATPase (r = 0.59; P < 0.05). Correlations between VO2peak and mitochondrial enzyme activities were not significant (P > 0.05) for either training programme. It is concluded that although both training programmes stimulate an up‐regulation in Na+–K+ ATPase concentration, only the prolonged submaximal training programme enhances the potential for β‐oxidation, oxidative phosphorylation and glucose phosphorylation.
Body composition, resting and running metabolic rates, and net cost of running in rats during starvation
Authors: FUGLEI  , ØRITSLAND
Published: March 2003

Resting metabolic rate decreases during starvation. However, effects of starvation on the cost of running are not clear. The aim of this study was to examine the effects of 5 days starvation on body composition, resting metabolic rates, running metabolic rates, and net cost of running in male rats. Five days starvation resulted in reductions of 70% fat, 8% protein and 12% carbohydrates. Mass−0.75 specific resting metabolic rate was significantly reduced from 3.69 ± 0.27 to 2.73 ± 0.17 W kg−0.75 after 5 days starvation. The reduction in metabolic rate after 5 days starvation was maintained during running, in that running metabolic rate was reduced from 10.65 ± 0.41 to 8.97 ± 0.47 W kg−0.75. The net costs of running were calculated and expressed as the costs of moving 1 kg a distance of 1 m. After 5 days of starvation it was reduced from 31.16 ± 2.03–29.79 ± 1.69 J m−1 kg−1. The reduction however was not significant. The present results therefore suggest that 5 days starvation resulted in a metabolic depression of the resting metabolic rate that was maintained during running. However, the net cost of running remained unchanged, suggesting that the muscle tissues are not significantly involved in the metabolic changes during starvation.
Cardiodepressant mediators are released after myocardial ischaemia: modulation by catecholamines and adenosine
Authors: Stangl  , Harms  , Frank  , Stangl  , Muß  , Buttke  , Baumann  , Felix
Published: March 2003

The interaction of recently characterized cardiodepressant mediators with catecholamines and adenosine after myocardial ischaemia was investigated using a model of sequential perfusion of two isolated guinea‐pig hearts. Sequential perfusion was initiated after 10, 20, and 30 min (group I, II, and III) of global ischaemia in the first heart. At the onset of sequential perfusion LVdP/dtmax and min of Heart II decreased by 46 and 44% in group I, by 28 and 34% in group II, and increased by 60 and 24% in group III. Infusion of the β1‐receptor antagonist metoprolol (2.8 μmol L–1) into Heart II did not modulate contractile changes after 10 min of ischaemia in Heart I, prevented the attenuation of the cardiodepressant effect after 20 min of ischaemia, and completely reversed the positive inotropic effect after 30 min of ischaemia. The A1‐ and A2‐receptor antagonists DPCPX (2 μmol L–1) and DMPX (20 μmol L–1) enhanced the positive inotropic and lusitropic effects in Heart II (LVdP/dtmax +154%, LVdP/dtmin +71%) during sequential perfusion after 30 min of ischaemia in Heart I. It is concluded that the effects of cardiodepressant mediators released after myocardial ischaemia are counteracted by a time‐dependent release of catecholamines. Endogenous cardiac adenosine, in turn, attenuates the modulatory effects of catecholamines.
Hyperoxia does not increase peak muscle oxygen uptake in small muscle group exercise
Authors: Pedersen P.K. , Kiens B. , Saltin B.
Published: March 2003

We examined the influence of hyperoxia on peak oxygen uptake (V˙O2peak) and peripheral gas exchange during exercise with the quadriceps femoris muscle. Young, trained men (n=5) and women (n=3) performed single‐leg knee‐extension exercise at 70% and 100% of maximum while inspiring normal air (NOX) or 60% O2 (HiOX). Blood was sampled from the femoral vein of the exercising limb and from the contralateral artery. In comparison with NOX, hyperoxic arterial O2 tension (PaO2) increased from 13.5 ± 0.3 (x ± SE) to 41.6 ± 0.3 kPa, O2 saturation (SaO2) from 98 ± 0.1 to 100 ± 0.1%, and O2 concentration (CaO2) from 177 ± 4 to 186 ± 4 mL L–1 (all P < 0.01). Peak exercise femoral venous PO2 (PvO2) was also higher in HiOX (3.68 ± 0.06 vs. 3.39 ± 0.7 kPa; P < 0.05), indicating a higher O2 diffusion driving pressure. HiOX femoral venous O2 saturation averaged 36.8 ± 2.0% as opposed to 33.4 ± 1.5% in NOX (P < 0.05) and O2 concentration 63 ± 6 vs. 55 ± 4 mL L–1 (P < 0.05). Peak exercise quadriceps blood flow (Q˙leg), measured by the thermo‐dilution technique, was lower in HiOX than in NOX, 6.4 ± 0.5 vs. 7.3 ± 0.9 L min–1 (P < 0.05); mean arterial blood pressure at inguinal height was similar in NOX and HiOX at 144 and 142 mmHg, respectively. O2 delivery to the limb (Q˙leq times CaO2) was not significantly different in HiOX and NOX. V˙O2peak of the exercising limb averaged 890 mL min–1 in NOX and 801 mL min–1 in HiOX (n.s.) corresponding to 365 and 330 mL min–1 per kg active muscle, respectively. The V˙O2peak‐to‐PvO2 ratio was lower (P < 0.05) in HiOX than in NOX suggesting a lower O2 conductance. We conclude that the similar V˙O2peak values despite higher O2 driving pressure in HiOX indicates a peripheral limitation for V˙O2peak. This may relate to saturation of the rate of O2 turnover in the mitochondria during exercise with a small muscle group but can also be caused by tissue diffusion limitation related to lower O2 conductance.