bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical simulations of the seasonal circulation patterns and thermohaline structures of Prince William Sound, Alaska
Authors: Wang Jia , Jin Meibing , Patrick E. Vincent , Allen Jennifer R. , Eslinger David L. , Mooers Christophee N. K. , Cooney R. Ted
Published: March 2003

A three‐dimensional, primitive‐equation ocean circulation model was applied to Prince William Sound, Alaska (3D‐PWS circulation model), under forcing of an ocean tide, freshwater runoff, surface heat flux, Alaska Coastal Current (ACC) throughflow (inflow/outflow), and daily (synoptic), spatially varying winds. The 3D structures and seasonal cycles of the circulation patterns, temperature, salinity (density), and mixed layer are examined. Freshwater runoff significantly contributes to the basin‐scale cyclonic circulation, which was not addressed in the previous simulations. Two typical circulation regimes, cyclonic and anticyclonic, characterize the complex flow patterns that depend on the intensities of the ACC thoughflow, freshwater discharge, and the synoptic wind. The spring (April–May) circulation pattern is characterized by a weak (maximum current 0.1 ms−1) anticyclonic flow in the central Sound, while the autumn (September–October) circulation is dominated by a basin‐scale, cyclonic gyre (maximum current 0.2 ms−1) due to the increase of the ACC throughflow and the maximum freshwater influence. During the summer, the circulation includes the cyclonic and anticyclonic gyres. During the winter, the circulation pattern is controlled by the basin‐scale cyclonic gyre and surface drift driven by the strong north‐easterly (south‐westward) wind forcing. The seasonal cycles of temperature (T) and salinity (S) vs. depth compare well with the observations. The simulated spring and autumn surface circulation patterns compare qualitatively well with the towed ADCP (acoustic Doppler current profilers) flow patterns and dynamic height patterns in the central Sound. An application of this model to zooplankton overwintering is discussed.
Seasonal hydrography and tidal currents of bays and fjords in Prince William Sound, Alaska
Authors: Gay Shelton. M. , Vaughan S. L.
Published: March 2003

Hydrography and tidal circulation are described for two deep fjords (Whale Bay and Eaglek Bay) and two shallow bays (Simpson Bay and Zaikof Bay) used as nursery habitat by juvenile Pacific herring (Clupea pallasi) in Prince William Sound, Alaska from October 1995 to March 1998. The seasonal hydrography varied markedly among the four locations due to the interaction of various factors including local climate, hydrology, advection of allochthonous glacial water, and vertical mixing from winds and tides. The fjords exhibited strong haline stratification in the summer that persisted into winter. In contrast, the bays exhibited brief periods of weak to strong stratification that dissipated early in the autumn. The timing of peak freshwater input also varied among locations depending on the maximum size and elevations of watersheds and the extent of precipitation stored within alpine snow and ice fields. In late winter (March), surface water in the fjords was relatively cold (1–3 °C) and slightly fresh (29–30 psu) in comparison to the bays (3.5–5.5 °C and 31–31.5 psu). The subsurface water (40–80 m) was warmer in the fjords (5–7 °C), whereas the bays exhibited vertically uniform temperature and salinity (T/S) properties. Tidal currents were typically highest near the mouth of most basins (35–150 cm s−1) and exhibited horizontal and vertical shear in the summer and autumn. During these seasons, these flows created baroclinic currents within most basins, anticyclonic eddies at Simpson and Zaikof bays, and inflow of allochthonous glacial water at Whale Bay. Local climate and watershed hydrology of individual bays have a strong influence on water temperatures and haline stratification, which potentially affect production of phytoplankton, zooplankton, and growth and survival of age‐0 herring. Additionally, variability in transport of Gulf of Alaska derived carbon sources into nursery bays is dependent on geographical location and the physical features of each basin, such as maximum depths, presence or absence of sills, and spatial patterns in the winds and currents.
Amoxicillin‐Tetracycline Combinations are Inadequate as Alternative Therapies for Helicobacter pylori Infection
Authors: Perri Francesco , Festa Virginia , Merla Antonio , Quitadamo Michele , Clemente Rocco , Andriulli Angelo
Published: March 2003

Background. Triple therapy with proton pump inhibitors or ranitidine bismuth citrate, clarithromycin and either amoxicillin or nitroimidazole derivatives are the present gold standards for cure of Helicobacter pylori infection. However, primary resistance to either clarithromycin or nitroimidazole derivatives is increasing and alternative therapies are needed.

Aim. To determine the efficacy and safety of three regimens consisting of amoxicillin and tetracycline or doxycycline combined with either lansoprazole or ranitidine bismuth citrate.

Methods. Two hundred and seventy H. pylori infected patients were randomly given one of the following treatments: amoxicillin 1 g twice a day (b.i.d.) plus tetracycline 500 mg four times a day (q.i.d.) with either lansoprazole 30 mg b.i.d. (group LAT) or ranitidine bismuth citrate 400 mg b.i.d. (group RBCAT) for 7 days and amoxicillin 1 g b.i.d. plus doxycycline 100 mg b.i.d. and lansoprazole 30 mg b.i.d. for 14 days (group LAD). Eradication rate was assessed by UBT at 4–6 weeks after therapy.

Results. The three groups (LAT, RBCAT, and LAD) of patients achieved eradication rates of 35% (25–45), 20% (12–29) and 36% (25–46), respectively, on intention‐to‐treat analysis. Patient compliance was optimal and side‐effects minimal in all three groups.

Conclusions. Although the amoxicillin/tetracycline combination is attractive (inexpensive, safe, and with low primary resistance rate), it can not be recommended for H. pylori eradication.
Factors that limit maintenance of recombinant rumen bacterium in sheep rumen
Authors: KOBAYASHI Yasuo , YAMAMOTO Mayu
Published: March 2003

Factors limiting the maintenance of recombinant ruminal bacterium in the rumen were evaluated in vitro, using batch culture prepared from rumen fluid of sheep. Butyrivibrio fibrisolvens expressing a foreign xylanase gene (B. fibrisolvens NO4) was used as a tested recombinant that was selectable on an erythromycin‐containing agar medium. The recombinant tended to reduce its level slowly in the rumen fluid of sheep on a high hay diet, while its initial decrease was more apparent in the rumen fluid of sheep on a high concentrate diet. Incubation with cell‐free ruminal fluid revealed a significant decrease of inoculated recombinant, suggesting the presence of antibacterial factors limiting maintenance of the recombinant. In particular, during the first 12 h of incubation this inhibition was more notable in culture prepared from rumen fluid of sheep given the high concentrate diet. Autoclaving the cell‐free rumen fluid inactivated the inhibition. Numbers of the recombinant for inoculation did not influence the final level of survived recombinant, that is, the initial depression was larger as more recombinant was inoculated. Subculturing with xylan before inoculation and/or direct addition of xylan to the batch culture did not improve survival of the recombinant. From these results it is suggested that the level of survived recombinant is limited to 102–4/mL of in vitro batch culture with restricted energy supply and that initial depression of the recombinant is mainly caused by the heat‐sensitive antibacterial factors not associating with microbial cells in the rumen.
A quantitative study on arginine catabolism by mixed ruminal bacteria, protozoa and their mixture in vitro
Authors: SULTANA Halima , HUSSAIN‐YUSUF Hazizul , TAKAHASHI Toshihiro , MORITA Tetsuo , ONODERA Ryoji
Published: March 2003

The catabolism of arginine (Arg) by mixed rumen bacteria (B), mixed rumen protozoa (P), and their mixture (BP) was quantitatively investigated in an in vitro system in order to confirm the metabolic pathway of Arg and provide basic information for enzymatic and molecular studies as well as an understanding of the quantitative distribution of metabolites. Rumen microbial suspensions (B, P, and BP) collected from fistulated goats were anaerobically incubated with or without 1 mmol/L Arg at 39°C for 12 h. Arg and other related compounds such as citrulline (Cit), ornithine (Orn), proline (Pro) and 5‐aminovaleric acid (5AV) in both supernatant and hydrolyzates of B, P, and BP suspensions were analyzed by HPLC. The metabolic pathways of Arg in mixed rumen bacteria and mixed rumen protozoa were considered to be as follows: rumen bacteria, Arg → Cit → Orn → Pro → 5AV → VFAs + NH3; rumen protozoa, Arg → Cit → Orn → Pro → 5AV. The disappearance of Arg (1 mmol/L) was approximately 52.9 and 88.2% in B, 33.9 and 55.6% in P, and 52.8 and 85.2% in BP during 6 and 12 h incubations, respectively. When expressed in units of ‘per gram (g) of microbial nitrogen (MN)’, the net degradation rate of Arg in BP (50.3 µmol/g MN/h) was approximately 46% lower than that of B during a 12 h incubation period. The presence of protozoa tended to inhibit the production of Orn from Cit and the production of 5AV from Pro which were thought to be rate‐limiting steps of Arg metabolism in rumen microorganisms. As a result, protozoa appeared to have a saving effect on Arg metabolism, that is, protozoa protected Arg from wasteful exhaustion in the rumen.
The influence of fire on carbon distribution and net primary production of borealLarix gmeliniiforests in north‐eastern China
Authors: Wang Chuankuan , Gower Stith T. , Wang Yihong , Zhao Huixun , Yan Ping , Bond‐Lamberty Ben P.
Published: March 2003

The boreal larch forest of Eurasia is a widespread forest ecosystem and plays an important role in the carbon budget of boreal forests. However, few carbon budgets exist for these forests, and the effects of wildfire, the dominant natural disturbance in this region, on carbon budgets are poorly understood. The objective of this study was to quantify the effects of wildfire on carbon distribution and net primary production (NPP) for three major Dahurian larch (Larix gmeliniiRupr.) forest ecosystems in Tahe, Daxing'anling, north‐eastern China:Larix gmelinii–Ledum palustre,Larix gmelinii–grass andLarix gmelinii–Rhododendron dahuricaforests. The experimental design included mature forests (unburned), and lightly and heavily burned forests from the 1.3‐million‐ha 1987 wildfire. We measured carbon distribution and above‐ground NPP, and estimated fine root production from literature values.

Total ecosystem carbon content for the mature forests was greatest forLarix–Ledumforests (251.4 t C ha−1) and smallest forLarix–grass forests (123.8 t C ha−1).Larix–Ledumforests contained the smallest vegetation carbon (13.5%), whileLarix–Rhododendroncontained the largest vegetation carbon (63.1%). Fires tended to transfer carbon from vegetation to detritus and soil. Total NPP did not differ significantly between the lightly burned and unburned stands, and averaged 1.58, 1.29 and 1.01 t C ha−1 year−1forLarix–grass,Larix–RhododendronandLarix–Ledumlightly burned stands, respectively. Above‐ground net primary production (ANPP) of heavily burned stands was 92–95% less than unburned and lightly burned stands. The estimated carbon loss during the 1987 fire showed substantial variability among forest types and fire severity levels. Depending upon the assumptions made about the fraction of the landscape occupied by the three larch forest types, the 1987 conflagration in north‐east China released 2.5 × 107−4.9 × 107t C to the atmosphere. This study illustrates the need to distinguish between the different larch forests for developing general carbon budgets.
The response of soil CO2 flux to changes in atmospheric CO2, nitrogen supply and plant diversity
Authors: Craine Joseph M. , Wedin David A. , Reich Peter B.
Published: March 2003

We measured soil CO2 flux over 19 sampling periods that spanned two growing seasons in a grassland Free Air Carbon dioxide Enrichment (FACE) experiment that factorially manipulated three major anthropogenic global changes: atmospheric carbon dioxide (CO2) concentration, nitrogen (N) supply, and plant species richness. On average, over two growing seasons, elevated atmospheric CO2 and N fertilization increased soil CO2 flux by 0.57 µmol m−2 s−1 (13% increase) and 0.37 µmol m−2 s−1 (8% increase) above average control soil CO2 flux, respectively. Decreases in planted diversity from 16 to 9, 4 and 1 species decreased soil CO2 flux by 0.23, 0.41 and 1.09 µmol m−2 s−1 (5%, 8% and 21% decreases), respectively. There were no statistically significant pairwise interactions among the three treatments. During 19 sampling periods that spanned two growing seasons, elevated atmospheric CO2 increased soil CO2 flux most when soil moisture was low and soils were warm. Effects on soil CO2 flux due to fertilization with N and decreases in diversity were greatest at the times of the year when soils were warm, although there were no significant correlations between these effects and soil moisture. Of the treatments, only the N and diversity treatments were correlated over time; neither were correlated with the CO2 effect. Models of soil CO2 flux will need to incorporate ecosystem CO2 and N availability, as well as ecosystem plant diversity, and incorporate different environmental factors when determining the magnitude of the CO2, N and diversity effects on soil CO2 flux.
The potential effect of high atmospheric CO2on soil fungi–invertebrate interactions
Authors: Frouz Jan , Nováková Alena , Jones T. Hefin
Published: March 2003

Litter mixtures of four meadow plant species,Cardamine hirsuta, Poa annua,Senecio vulgaris, andSpergula arvensis, were produced from laboratory model terrestrial ecosystems maintained at either ambient or enriched (ambient + 200 µmol mol−1) CO2concentrations. The effect of litter source on the oviposition attractivity of fungi to the sciarid flyLycoriella ingenuawas tested for seven fungal species (Absidia glauca,Cladosporium cladosporioides,C. herbarum,Fusarium oxysporum,Penicillium arenicola,P. chrysogenum, andP. janthinellum). For all species, exceptF. oxysporum,oviposition attractivity increased when the fungi were growing on litter derived from CO2‐enriched environments. The relative increase of the oviposition attractiveness of fungi growing on CO2‐enriched litter differed substantially and resulted in a shift in sciarid fly oviposition preference. For example, whenP. chrysogenumandC. herbarumgrew on ambient litter,P. chrysogenumwas more attractive; the opposite was true for mycelia growing on enriched litter. The effect of litter source on the suitability of four fungal species for larval development was also tested. In two species of fungi (A. glaucaandC. herbarum) suitability was significantly higher if growing on CO2‐enriched litter. WithP. chrysogenumthe opposite was true. The consequences of these rarely considered CO2‐induced trophic interactions on ecosystem processes such as nutrient feedback cycles between plants and soil decomposition are considered.
Interaction of PRMT1 with BTG/TOB proteins in cell signalling: molecular analysis and functional aspects
Authors: Berthet Cyril , Guéhenneux Fabienne , Revol Valérie , Samarut Christiane , Lukaszewicz Agnès , Dehay Colette , Dumontet Charles , Magaud Jean‐Pierre , Rouault Jean‐Pierre
Published: March 2003

Background: Several recent reports have connected protein methylation with differentiation. Furthermore, the BTG/TOB proteins have also been implicated in such control. BTG1 and 2 have been shown to interact with PRMT1 (predominant cellular arginine N‐methyltransferase of type I).

Results: First, we have studied the interaction between PRMT1 and the proteins of the BTG/TOB family. We show that boxC, a sequence present only in BTG1 and BTG2, is essential for this association. Using boxC peptide, we have investigated the importance of PRMT1/BTG protein association during type I protein methylation reactions. Finally, we show that the addition of boxC fused to penetratin interferes with the neuronal differentiation of PC12 cells and ES cell‐derived neurones.

Conclusions: Taken together, these results indicate that PRMT1/BTG proteins could play a key role in the arginine methylation‐mediated signalling pathway as well as in neuronal differentiation.
Dual dependence: assessment of dependence upon alcohol and illicit drugs, and the relationship of alcohol dependence among drug misusers to patterns of drinking, illicit drug use and health problems
Authors: Gossop Michael , Marsden John , Stewart Duncan
Published: March 2003

Aims The study investigates severity of alcohol dependence among drug misusers. Specifically, it investigates the inter‐relationship of alcohol and drug dependence and associations with alcohol consumption, drug consumption and substance‐related problems.

Design, setting, participants The sample comprised 735 people seeking treatment for drug misuse problems, who were current (last 90 days) drinkers.

Measurements Data were collected by structured face‐to‐face interviews. Dependence upon illicit drugs and upon alcohol was measured by the Severity of Dependence Scale (SDS).

Findings Three groups of drinkers were identified: non‐alcohol‐dependent drug misusers (63%); low‐dependence (19%); and high‐dependence (18%). Many drug misusers were drinking excessively and alcohol dependence was related to patterns of alcohol and drug consumption. High‐dependence drinkers were more likely to drink extra‐strength beer; they were less frequent users of heroin and crack cocaine but more frequent users of benzodiazepines, amphetamines and cocaine powder; they reported more psychological and physical health problems. The SDS was found to have good reliability and validity as a measure of alcohol dependence. SDS scores for alcohol and drug dependence were unrelated.

Conclusions Alcohol use is an important and under‐rated problem in the treatment of drug misusers. A comprehensive assessment of alcohol use among drug misusers should include separate assessments of alcohol consumption, alcohol‐related problems and severity of alcohol dependence.
Influence of cold shivering on fine motor control in the upper limb
Authors: Meigal A. Y. , Oksa J. , Hohtola E. , Lupandin Y. V. , Rintamäki H.
Published: March 2003

The aim of the investigation was to determine the effects of cold shivering on the accuracy of force output in distal, middle and proximal muscles of the upper limb. Tests of hand grip strength, elbow flexion and shoulder flexion (each done at 10% maximal voluntary contraction for 15 s) were done under three conditions: (1) thermoneutral air (27 °C), a condition of thermal comfort; (2) cold air (10 °C), a condition eliciting an increase in tonic muscle activity; (3) and cold air (10 °C) with a cold drink (8 °C), a condition that causes visible shivering. The averaged (root mean square) electromyogram (AEMG) and mean power frequency (MPF) were measured from proximal, middle and distal arm muscles during the tests and compared. The control of force output was highly effective at thermoneutral condition for all motor tasks. During the cold air condition, all muscles were tonically active but there was no effect on accuracy of test performance. However, AEMG increased ≈20% (P < 0.05) with respect to test performance in thermoneutral condition. During the cold air/cold drink condition, all muscles were shivering to a different extend. AEMG during test performance increased 30–150% in comparison to thermoneutral condition (P < 0.05). In this case, hand grip and elbow flexion were not adversely affected (these tests require middle and distal muscles) by cold shivering. However, the accuracy of performance of shoulder flexion was adversely affected. This is consistent with the fact that proximal muscles are more active during cold shivering.
Skeletal muscle Na+/H+ exchange in rats: pH dependency and the effect of training
Authors: JUEL
Published: March 2003

Skeletal muscle Na+/H+ exchange was studied using giant sarcolemmal vesicles obtained from rat hind limb muscle. Experiments with either the 22Na tracer technique or with the Na+ sensitive fluorescent probe SBFI were conducted to determine the activity of the Na+/H+ exchanger, which was quantified from the amiloride or amiloride derivative 5‐N‐ethyl‐N‐propylamiloride (EIPA) sensitive Na+ influx. At a constant external pH of 7.4 the exchange system was close to half‐activation at an internal pH of 7.2. A further activation was observed at lower internal pH values. The activity of the muscle Na+/H+ exchanger was elevated after 6 weeks of high‐intensity treadmill training. In contrast, the activity of the system was unaffected by endurance training. The enhanced initial rate of amiloride‐sensitive Na+/H+ exchange appears to be involved in the elevated in vivo (dynamical) buffer capacity reported for trained rats and human subjects, indicating that adaptive changes in the exchange system are of importance for pH regulation in association with high‐intensity exercise.
Effect of β‐adrenoceptor stimulation on oxygen consumption and triglyceride/fatty acid cycling after exercise
Authors: BØRSHEIM  , BAHR  , KNARDAHL
Published: March 2003

The purpose of this study was to characterize the effects of prolongedβ‐adrenoceptor stimulation on O2uptake and triglyceride/fatty acid (TG/FA) cycling during rest with and without previous exercise. Eight men performed two exercise (90 min cycling at 56 ± 3 (SD)% of maximal O2uptake, followed by 4.5 h bed rest) and two rest‐control experiments. In one rest and one exercise experiment a bolus dose (5 μg) of theβ‐adrenoceptor agonist isoprenaline was given immediately after exercise, followed by a continuous infusion (20 ng kg–1 min–1), and at the corresponding time in the rest experiment. In the other experiments saline was given instead. The O2uptake increased in the post‐exercise period both with and withoutβ‐stimulation. The total excess post‐exercise oxygen consumption (EPOC) was not different between saline (8.1 ± 1.8 (SE) L) and isoprenaline administration (10.8 ± 1.8 L,P = 0.40). Also, the total accumulated increase in O2uptake for the 4.5 h period after isoprenaline infusion was not different between the rest (12.5 ± 2.0 L) and the exercise experiments (15.2 ± 1.7 L,P = 0.40). The rate of TG/FA cycling increased after both exercise and isoprenaline treatment, but no interaction effect was found. In conclusion, the increases observed in O2uptake and the rate of TG/FA cycling duringβ‐adrenoceptor stimulation were not increased by a previous exercise bout.
Gap junctions in vascular smooth muscle
Authors: BRINK
Published: March 2003

Gap junction channels are the only class of channels which span two closely apposed plasma membranes. There are over a dozen identified subunit proteins or connexins. Three generic types of gap junction channels are possible. They are the homotypic, heterotypic and heteromeric types, each of which has a distinct connexin distribution. The major connexin found in vascular smooth muscle is connexin43. Connexin40 has also been found in vascular smooth muscle. The biosynthesis, trafficking and degradation of connexin43 has only recently been studied but the data reveal some interesting features such as a short half‐life of only 1.5–3.5 h. The gating characteristics of connexin43 reveal mode shifting behaviours which result in prolonged closure of the majority of the gap junction channels. The channel also displays weak voltage dependence and is poorly selective. These features suggest that dynamical regulation of cell‐to‐cell coupling is best designed to reduce cell‐to‐cell coupling, rather than enhance it, by down regulation of channel activity through the biosynthesis, trafficking, degradation pathways and gating via mode shifting.
β‐adrenergic stimulation of cellular K+ uptake in rat distal colon
Authors: AIZMAN  , AIZMAN  , CELSI
Published: March 2003

We recently demonstrated that the ratio between colonic K+ absorptive and K+ secretive pathways was higher in infant than in adult rats. To test the hypothesis that hormones selectively affect these pathways during ontogeny we examined the effect of adrenergic agonists on cellular K+ uptake in distal colon from infant (10‐day‐old) and adult (50‐day‐old) rats. Here we describe that adrenaline (10−5 M) increased total and ouabain‐insensitive 86Rb uptake in both age groups, but it did not affect ouabain‐sensitive 86Rb uptake. This stimulation was more pronounced in adult than in infant rats. The effect of adrenaline was mediated via β‐adrenergic receptors. Incubation in vitro with β‐agonist, isoproterenol, stimulated SCH‐28080‐sensitive, i.e. H+,K+‐ATPase‐dependent, 86Rb uptake in adult but not in infant rats. The threshold dose of β‐agonist was at 10−7 M, and the maximal activation was observed at 10−5 M. In vivo inhibition of β‐adrenergic system with propranolol caused a significant decrease in H+,K+‐ATPase‐dependent 86Rb uptake in infant but not in adult colon. In conclusion, this study suggests that the higher colonic K+ absorption in infant rats may be as a result of a selective β‐adrenergic up‐regulation leading to stimulation of the apical H+,K+‐ATPase.
Regional brain serotonin receptor changes in portacaval shunted rats
Authors: APELQVIST  , BERGQVIST  , LARSSON  , BUGGE  , BENGTSSON
Published: March 2003

The pathogenesis of hepatic encephalopathy is unknown, but metabolic perturbations, including hyperammonaemia and increased brain turnover of serotonin (5‐HT), have been identified. Possible alterations of 5‐HT receptors in the brain have been rudimentarily studied. We therefore investigated the 5‐HT1 A, 5‐HT1 B and 5‐HT2 A receptor density in 18–22 different regions in the brain of portacaval shunted rats by means of radioligand binding with autoradiographical evaluation. The results revealed a decreased 5‐HT1 A receptor binding in seven serotonergic projection areas of the brain, and an increase in the nucleus accumbens, hypothalamus and subiculum. No changes in the raphe nuclei were observed. An increased 5‐HT1 B receptor binding was seen in five brain regions: basal ganglia, olfactorial regions, hippocampus, mid brain and thalamus. However, decreased binding was seen in three regions of cortical areas and hippocampus. The 5‐HT2 A receptor binding site density was essentially unaltered. These findings suggest that perturbations in the central serotonergic neurotransmission may play a functional role in chronic hepatic encephalopathy.
Protein–protein interactions controlling nitric oxide synthases
Authors: Kone
Published: March 2003

Nitric oxide (NO) biosynthesis is tightly regulated by a variety of mechanisms ranging from transcriptional to post‐translational controls. Calmodulin has long been known to be an allosteric modulator of the three major NO synthases (NOS). Recent studies indicate that other proteins directly associate with NOS isoforms and regulate their activity or spatial distribution in the cell. Several proteins residing in or recruited to plasmalemmal caveolae of endothelial cells serve as allosteric regulators of endothelial NOS (eNOS). Caveolins, the resident scaffolding proteins of caveolae, and calmodulin undergo reciprocal Ca2+‐dependent association and dissociation with eNOS in the caveolar membrane that inhibits (caveolins) and activates (calmodulin) eNOS activity. Other caveolar proteins appear to contribute to the eNOS‐membrane complex, including the bradykinin B2 receptor, the angiotensin AT1 receptor, the CAT1 arginine transporter, and Hsp90. Direct interactions of a variety of proteins bearing PDZ domains with the PDZ domain of neuronal NOS (nNOS) have been shown to influence the subcellular distribution and/or activity of the enzyme in brain and muscle. One of these proteins, PSD‐93, co‐localizes with a subpopulation of nNOS in the macula densa. Although considerable emphasis has been placed on transcription as the principal step of regulation for inducible NOS (iNOS), our laboratory has recently defined a regulatory interaction of iNOS with Rho family GTPases. While the role of protein–eNOS interactions in the control of vascular tone has been increasingly clarified, the interactions and regulatory importance of protein association with nNOS and iNOS in the vasculature and kidney remains to be explored.
Blood pressure control in eNOS knock‐out mice: comparison with other species under NO blockade
Authors: Stauss  , Nafz  , Mrowka  , Persson
Published: March 2003

Changes in arterial blood pressure (ABP) lead to changes in vascular shear stress. This mechanical stimulus increases cytosolic Ca2+ in endothelial cells, which in turn activates the endothelial isoform of the nitric oxide synthase. The subsequently formed NO reaches the adjacent vascular smooth muscle cells, where it reduces vascular resistance in order to maintain ABP at its initial level. Thus, NO may play an important role as a physiological blood pressure buffer. Previous data on the importance of eNOS for blood pressure control are reviewed with special emphasis on the fact that endogenous nitric oxide can buffer blood pressure variability (BPV) in dogs, rats and mice. In previous studies where all isoforms of the nitric oxide synthase were blocked pharmacologically, increases in blood pressure and variability were observed. Thus, we set out to clarify which isoform of the nitric oxide synthase is responsible for this BPV controlling effect. Hence, blood pressure control was studied in knock‐out mice lacking specifically the gene for endothelial nitric oxide synthase with their respective wild‐type controls. One day after surgery, under resting conditions, blood pressure was increased by 47 mmHg (P < 0.05), heart rate was lower (−77 beats min−1, P < 0.05), and BPV doubled (P < 0.05). Based on these results, we conclude that chronic blood pressure levels are influenced by eNOS and that there is a blood pressure buffering effect of endogenous nitric oxide which is mediated by the endothelial isoform of the nitric oxide synthase.
Tonometric assessment of jejunal mucosal nitric oxide formation in anaesthetized pigs
Authors: Snygg  , Casselbrant  , Pettersson  , Holm  , Fändriks  , Åneman
Published: March 2003

Nitric oxide (NO) in the gut has attracted increasing interest as a regulatory factor for a wide variety of intestinal functions. This study was performed to evaluate some methodological aspects and jejunal sources for NO synthesis. Bench side evaluations and an animal model using chloralose‐anaesthetized pigs were used. Immunohistochemistry was performed on samples from pig intestine and direct measurements of intestinal NO formation were performed using intraluminal tonometry. Tonometric measurements were quantitatively accurate and with high reproducibility. A substantial NO formation was assessed which was markedly inhibited by luminal administration of the non‐selective NOS inhibitor L‐NAME. Intravenous administration of
L‐NAME also reduced jejunal NO formation but to a lesser extent. Immunohistochemistry revealed staining for the inducible type of NOS in the mucosal surface epithelium whereas endothelial and neuronal subtypes were located in deeper layers of the jejunal wall. The study argues for that the source of jejunal NO production, as measured by intraluminal tonometry, is located in close proximity with the intestinal mucosa. The NOS in this compartment is predominantly of the inducible type.
Forearm vascular and neuroendocrine responses to graded water immersion in humans
Authors: Gabrielsen  , VidebÆk  , Johansen  , Warberg  , Christensen  , Pump  , Norsk
Published: March 2003

The hypothesis that graded expansion of central blood volume by water immersion to the xiphoid process and neck would elicit a graded decrease in forearm vascular resistance was tested. Central venous pressure increased (P < 0.05) by 4.2 ± 0.4 mmHg (mean ± SEM) during xiphoid immersion and by 10.4 ± 0.5 mmHg during neck immersion. Plasma noradrenaline was gradually suppressed (P < 0.05) by 62 ± 8 and 104 ± 11 pg mL–1during xiphoid and neck immersion, respectively, indicating a graded suppression of sympathetic nervous activity. Plasma concentrations of arginine vasopressin were suppressed by 1.5 ± 0.5 pg mL–1(P < 0.05) during xiphoid immersion and by 2.0 ± 0.5 pg mL–1during neck immersion (P < 0.05 vs. xiphoid immersion). Forearm subcutaneous vascular resistance decreased to the same extent by 26 ± 9 and 28 ± 4% (P < 0.05), respectively, during both immersion procedures, whereas forearm skeletal muscle vascular resistance declined only during neck immersion by 27 ± 6% (P < 0.05). In conclusion, graded central blood volume expansion initiated a graded decrease in sympathetic nervous activity and AVP‐release. Changes in forearm subcutaneous vascular resistance, however, were not related to the gradual withdrawal of the sympathetic and neuroendocrine vasoconstrictor activity. Forearm skeletal muscle vasodilatation exhibited a more graded response with a detectable decrease only during immersion to the neck. Therefore, the forearm subcutaneous vasodilator response reaches saturation at a lower degree of central volume expansion than that of forearm skeletal muscle.
Nitric oxide prevents rat duodenal contractions induced by potentially noxious agents
Authors: Hellgren  , Flemström  , Nylander
Published: March 2003

After abdominal surgery, luminal HCl fails to induce duodenal contractions in anaesthetized rats. Elevated tissue levels of nitric oxide (NO) and prostaglandins possibly contribute to this observation. The aim of this study was to compare the effects of luminal capsaicin (1.2 mg mL–1), ethanol (15%) and high partial pressure of CO2 (>250 mmHg) with those of HCl (10 m
M) in anaesthetized rats. Motility (intraluminal pressure), mucosal permeability [blood‐to‐lumen clearance of 51Cr‐EDTA (51Chromium‐labelled ethylenediaminetetraacetate)] and duodenal mucosal bicarbonate secretion (DMBS) were recorded. Three groups of animals were studied: (1) controls, (2) pretreatment with the NO synthase inhibitor N‐nitro‐
L‐arginine‐methyl‐ester (
L‐NAME) and (3) pretreatment with the cyclo‐oxygenase inhibitor indomethacin. Neither capsaicin, ethanol, CO2 nor HCl induced duodenal contractions or affected DMBS in control rats. However,
L‐NAME induced duodenal contractions that were augmented by capsaicin, ethanol and HCl, but not by CO2. Indomethacin also induced contractions that were reversibly diminished by capsaicin and HCl, but not by ethanol or CO2. Significant increases in mucosal permeability occurred during ethanol perfusion in indomethacin‐ and
L‐NAME pretreated rats. In conclusion, NO probably plays a key role in preventing duodenal contractions in response to luminally HCl, capsaicin and ethanol. The HCl‐induced effect on motility appears to be independent of CO2 and is not caused by alteration in mucosal integrity.
A single bout of eccentric exercise increases HSP27 and HSC/HSP70 in human skeletal muscle
Authors: Thompson H. S. , Scordilis S. P. , Clarkson P. M. , Lohrer W. A.
Published: March 2003

Changes in heat shock proteins (HSPs), HSP27 and HSC/HSP70 were characterized in human biceps brachii muscle following damaging high‐force eccentric exercise. Male and female volunteers performed a maximal eccentric resistance exercise with the elbow flexor muscles of the non‐dominant arm known to be sufficient to cause substantial muscle damage. Protein extracts of biopsy tissue samples taken 48 h post‐exercise were immunoblotted for HSC/HSP70 and HSP27. Densitometric analysis demonstrated that these proteins increased significantly (P < 0.01) in the damaged biceps brachii relative to the control arm. The HSC/HSP70 increased 1064% in the exercised sample while HSP27 increased by 234%. Although the literature reports a muscular heat shock response following aerobic, oxidative exercise, this is the first documentation of increases in protein expression of both HSC/HSP70 and HSP27 in human skeletal muscle in response to a single bout of resistance exercise.
Novel modified Ussing chamber for the study of absorption and secretion in human endoscopic biopsies
Authors: Larsen R. , Mertz‐Nielsen A. , Hansen M. B. , Poulsen S. S. , Bindslev N.
Published: March 2003

The aim of this study was to design and evaluate a modified Ussing chamber, that makes use of constant air suction (modified Ussing air suction chamber, MUAS) for fixation of biopsy specimens. Standard size forceps biopsies were taken from the descending part of duodenum from patients undergoing endoscopy. Short circuit current (SCC) and conductance (G) were measured during basal conditions and after addition of different sugars and secretagogues. Histologic examination was performed to determine the degree of tissue damage after study in the chamber. Basal SCC was 54.7 ± 4.3 μA cm–2 and G was 58.7 ± 4.7 mS cm–2 (mean ± SEM, n=48) and steady values of these parameters were observed for at least 2 h. Reproducible and steady responses in SCC were obtained with D‐glucose (SCCmax=172 ± 22.1 μA cm–2; EC50=6.9 ± 0.7 mM, n=5) and D‐galactose (SCCmax=233 ± 55.7 μA cm–2; EC50=9.2 ± 0.7 mM, n=3), and secretory responses with 5‐hydroxytryptamine, 100 μM (ΔSCC= 16.1 ± 3.8 μA cm–2, n=10), histamine, 100 μM (ΔSCC=24.0 ± 4.1 μA cm–2, n=10) and prostaglandin E2, 1 μM (ΔSCC=30.3 ± 5.4 μA cm–2, n=6). Experimental biopsy specimens showed intact surface epithelium by histologic examination and did not differ from controls apart from minor indications of edge damage. No difference in basal electrical parameters and D‐glucose fluxes were found between Helicobacter pylori positive and negative patients. Our data suggests that the MUAS chamber represents a promising alternative approach to measure transport processes in intestinal endoscopic biopsies.
Muscle volume is a major determinant of joint torque in humans
Authors: Fukunaga T. , Miyatani M. , Tachi M. , Kouzaki M. , Kawakami Y. , Kanehisa H.
Published: March 2003

Muscle force (MF) is linearly related to physiological cross‐sectional area (CSA), which is obtained from muscle volume (MV) divided by fibre length. Taking into account the fact that joint torque (TQ) is determined by MF multiplied by the moment arm, the maximal TQ would be a function of MV. This proposition was tested in the present study by investigating the relationship between MV and TQ for elbow flexor (EF) and extensor (EE) muscles of 26 males. The MVs of EF and EE were determined from a series of muscle CSA by magnetic resonance imaging (MRI), and pennation angle (θ) and FL by ultrasonography (US). Maximal isometric TQ was measured at right angle of elbow joint for EF and EE. There was a highly significant correlation between MV and TQ both for EF and EE (r=0.95 and 0.96 respectively) compared with that between muscle CSA and TQ, suggesting the dependence of TQ on MV. Furthermore, prediction equations for MV (MVULT) from muscle thickness (MT) measured by US was developed with reference to MVMRI by the MRI on 26 subjects, and the equations were applied to estimate MV of healthy university students (CON; 160 males) and sports athletes (ATH; 99 males). There were significant linear relationships between MVULT and TQ both for EF (r=0.783) and EE (r=0.695) for all subjects (n=259). The MVULT was significantly higher in ATH (by 32% for EF and 33% for EE, respectively) than in CON. Similarly, significantly greater TQ was observed in ATH (by 35% for EF, 37% for EE, respectively). The θ for EE showed no difference between both groups (17.8° for CON and 17.5° for ATH). On the other hand, the TQ to MV ratio were identical for CON and ATH. The results reveal that the muscle volume of the upper arm is a major determinant of joint torque (TQ), regardless of athletic training.
Effect of pH changes on reactivity of rat mesenteric artery segments at different magnitude of stretch
Authors: Yartsev V. N. , Karachentseva O. V. , Dvoretsky D. P.
Published: March 2003

The reaction to noradrenaline (NA) (10 μM) and electrical field stimulation (EFS) was studied in rat mesenteric artery segments at different magnitude of stretch and the solution pH. Alkaline solution (pH 7.8) potentiated and acidic solution (pH 7.0 or 6.6) inhibited the EFS‐evoked response of segments stretched to values corresponding to arterial pressure of 5–200 mmHg. These pH changes failed to alter resting tension at any magnitude of stretch. Acedic solution of pH 6.6 caused 2‐fold decrease in noradrenaline‐ and 5–15‐fold decrease in the EFS‐evoked response of segments stretched to values corresponding to arterial pressure of 50, 125, and 200 mmHg. In segments pre‐contracted with noradrenaline (10 μM) acidification caused the decrease of the dilation and appearance of the constriction induced by the EFS. The effect of acidosis on the EFS‐evoked response was diminished and the effect on noradrenaline‐evoked response was abolished in the presence of nitric oxide synthase blocker, NG‐nitro‐L‐arginine (100 μM). These results suggest that acidosis effectively impairs reactivity of the rat mesenteric artery in a wide range of its stretch, and the inhibition of the response to noradrenaline occurs completely, while to EFS only partially due to nitric oxide (NO) release, presumably by the endothelium. In addition, it was shown that acidosis is able to act not only as the commonly known dilator agent, but also as an agent potentiating constriction in case of the high noradrenaline‐induced tone.
Effects of nitric oxide donors and inhibitors of nitric oxide signalling on endothelin‐ and serotonin‐induced contractions in human placental arteries
Authors: SAND A. E. , ANDERSSON E. , FRIED G.
Published: March 2003

In order to explore the role of nitric oxide (NO) in the control of fetoplacental vascular tone in normal pregnancy we have examined the effects of NO donors on uteroplacental arteries pre‐contracted with the vasoconstrictor endothelin‐1 (ET‐1) or serotonin (5‐HT). We have furthermore examined the effects of guanylate cyclase inhibitors on the NO‐induced relaxation. Segments of placental arteries (n=102) obtained from 39 placentas immediately after delivery were mounted in organ baths and superfused with Krebs–Ringer solution at 37 °C. The vessel segments were exposed to drugs for various intervals and the tension was recorded isometrically and registered on a polygraph. Cyclic guanosine monophosphate (cGMP) analysis was performed after extraction of vessel segments using a specific radioimmunoassay. The placental artery segments responded to ET‐1 and 5‐HT with a dose‐dependent vasoconstriction. After pre‐contraction with ET‐1 (10–7 M) or 5‐HT (10–6 M), the vessels relaxed in response to the NO donors glyceryltrinitrate (GTN) (10–6 M) and S‐nitroso‐N‐acetyl‐penicillamine (SNAP) (10–5 M). In the presence of the non‐specific guanylate cyclase inhibitor LY 83583 (10–6 M), the vessels responded with a small contraction. In the presence of the soluble guanylate cyclase (sGC) inhibitor 1H[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one (ODQ) the non‐treated vessels responded with a relaxation. 1H[1,2,4]oxadiazolo[4,3‐a]quinoxalin‐1‐one gave no obvious relaxation in pre‐contracted vessels. Addition of 8‐Br‐cGMP, the cell‐permeant analogue of cGMP, with or without pre‐contraction had no effect on the vessels. Cyclic guanosine monophosphate analysis showed that GTN treatment caused an increase in cGMP after 12 min. Our results indicate that NO acts as a vasodilator in placental vessels. The cGMP‐dependent mechanisms may be involved in NO‐induced relaxation but cGMP‐independent mechanisms appear also to be involved.
Fibrinogen induces chemotactic activity in endothelial cells
Authors: Seeger F. H. , Blessing E. , Gu L. , Bornhold R. , Denger S. , Kreuzer J.
Published: March 2003

Chemotaxis of blood monocytes into the vessel wall together with the change of the relative content of the extracellular matrix (ECM) proteins at sites of predilection is an early cellular marker of atherogenesis. To examine the influence of ECM proteins on secretion of chemoattractants by endothelial cells (EC), porcine EC were seeded on gelatin (G), fibronectin (Fn) and fibrinogen (Fg). After 24 h cells seeded on G and Fn showed the histiotypic ‘cobblestone’‐morphology whereas cells seeded on Fg did not. Chemotactic activity for monocytes in supernatants from cells seeded on Fg was more than two‐fold higher compared with G and was independent of soluble Fn or Fg in the supernatant. Quantification of monocyte chemoattracting protein‐1, PDGF‐AB and IL‐8 in EC supernatants showed that Fg led to a significant increase in secretion of all three proteins compared with cells cultured on G.

Preincubation of porcine EC with the tripeptide arginine–glycine–aspartic acid, as inhibitor of binding of Fg to integrin receptors, but not with the control tripeptide arginine–glycine–glutamic acid showed a decrease in chemotactic activity for cells cultured on Fg but not on Fn or G. Inhibition of protein kinase C (PKC) activity in EC by GF109203 resulted in a decrease of fibrinogen‐induced chemotactic activity. Also the tyrosine‐kinase inhibitor herbimycin inhibited fibrinogen mediated secretion of chemokines. The role of the PKC pathway for matrix mediated signal transduction is further corroborated by Fg‐dependent induction of the PKC isoformδ. These data indicate an integrin‐dependent signal transduction pathway leading to induction of chemotactic activity by the ECM protein fibrinogen. This mechanism may contribute to induction of chemokines in early atherosclerotic lesions.
Calcium homeostasis and glucose uptake of murine myotubes exposed to insulin, caffeine and 4‐chloro‐m‐cresol
Authors: Freymond D. , Guignet R. , Lhote P. , Passaquin A.‐C. , Rüegg U. T.
Published: March 2003

The modulation of glucose uptake by cytosolic calcium and the role of insulin on calcium homeostasis in insulin‐target cells are incompletely understood and results are contradictory. To address this issue, we used the C2C12 murine skeletal muscle cell line model and examined the influence of caffeine and 4‐chloro‐m‐cresol, two ryanodine receptor agonists known to mobilize intracellular calcium stores and increase cytosolic free calcium concentration. We followed 45calcium efflux, a validated indicator of cytosolic calcium concentration, and 3‐O‐methyl‐[1–3H]‐d‐glucose uptake in parallel. We also determined if insulin incubation affected 45calcium influx rate. A 30‐min treatment by 1 μm insulin highly significantly increased 45calcium efflux by 8.5% (P = 0.0014), despite a significant reduction of 45Ca2+ influx already measurable after 20 and 30 min of insulin stimulation (−16.6%, P = 0.0119 and −21.3%, P = 0.0047, respectively). Caffeine (1–20 mm) and 4‐chloro‐m‐cresol (0.05–10 mm) concentration‐dependently increased 45calcium efflux, the latter being more potent and efficacious. These agents, in a concentration‐dependent manner, inhibited both basal and, more potently, insulin‐stimulated glucose uptake. This resulted in a negative correlation of glucose uptake and 45calcium efflux (r > 0.95, P < 0.001). This effect was ∼5 times greater for caffeine than for 4‐chloro‐m‐cresol, suggesting a calcium‐independent part of the glucose uptake inhibition by caffeine. In our in vitro model of cultured muscle cells, insulin appears to prevent calcium overload by both stimulating efflux and inhibiting cell storage. This effect, taken together with the observed inhibitory, inverse relationship between 45calcium efflux and glucose uptake, contributes to describing the complex insulin–calcium interplay involved in target cells.