bluuebunny/crossref_metadata_2025 huggingface dataset:
Migrant mobilization between political institutions and citizenship regimes: A comparison of France and Switzerland
Authors: Giugni Marco , Passy Florence
Published: January 2004

Abstract.This article focuses on the political claims made by immigrants and ethnic minorities in France and Switzerland. We look at cross‐national variations in the overall presence of immigrants and ethnic minorities in the national public space, and the forms and content of their claims. Following a political opportunity approach, we argue that claim‐making is affected both by institutional opportunities and by national models of citizenship. The civic‐assimilationist conception of citizenship in France gives migrants greater legitimacy to intervene in the national public space. Furthermore, the inclusive definition of ‘membership in the national community’ favors claims pertaining to minority integration politics. However, the pressure toward assimilation to the republican norms and values tends to provoke claims for the recognition of ethnic and cultural difference. Finally, closed institutional opportunities push migrants’ mobilization to become more radical, but at the same time the more inclusive model of citizenship favors a moderate action repertoire of migrants. Conversely, the ethnic‐assimilationist view in Switzerland leads migrants to stress homeland‐related claims. When they do address the policy field of ethnic relations, immigration and citizenship, they focus on issues pertaining to the entry and stay in the host society. Finally, the forms of action are more moderate due to the more open institutional context, but at the same time the action repertoire of migrants is moderated by the more exclusive model of citizenship. Our article is an attempt to specify the concept of ‘political opportunity structure’, and to combine institutional and cultural factors in explaining claim‐making by immigrants and ethnic minorities. We confront our arguments with data from a comparative project on the mobilization on ethnic relations, citizenship and immigration.
Detection of Specific IgE Antibodies to Nafamostat Mesilate as an Indication of Possible Adverse Effects of Leukocytapheresis using Nafamostat Mesilate as Anticoagulant
Authors: Nagase Kazuko , Fukunaga Ken , Ohnishi Kunio , Kusaka Takeshi , Matoba Yoshika , Sawada Koji
Published: January 2004

Abstract: The aim was to determine whether adverse effects of leukocytapheresis (LCAP) are related to nafamostat mesilate (NM) as an anticoagulant. Anti‐NM IgE were detected in inflammatory bowel disease (IBD) patients who were administrated LCAP in our institute. Forty‐nine patients (ulcerative colitis (UC)/Crohn's disease (CD): 30/19) were evaluated. Anti‐NM IgE was measured by the ELISA method. Total IgE level and eosinophil count was tested concurrently. We retrospectively checked the presence of allergic symptoms and medications used concurrently with LCAP. Anti‐NM IgE were present in six symptomatic patients (6/49; 12.2%) whose adverse effects were highly suspected to be from NM. However, 21 patients showed anti NM IgE‐negative, in spite of the fact that their adverse effects were also highly suspected to be from NM. Through the detection of anti‐NM IgE alone we could not estimate the relevance of NM  as  an  anticoagulant  to  the  adverse  effects  of  LCAP.
Morphometric assessment of nuclei in Bowen's disease and bowenoid papulosis
Authors: Yu Dong‐Soo , Kim Gina , Song Hae‐Jun , Oh Chil‐Hwan
Published: January 2004

Background: Occasionally, Bowen's disease and bowenoid papulosis cannot be distinguished in microscopic finding. Their clinical presentations are quite different from one another. The purpose of this study was to evaluate the histological differences in Bowen's disease and bowenoid papulosis, by comparing the size and shape of nuclei, using image analysis system.

Methods: We performed morphometric assessment on 13 specimens of Bowen's disease and eight specimens of bowenoid papulosis using an image analysis system, and the following parameters were calculated, such as nuclear contour index (NCI), irregularities of nucleus (IN), form factor (form AR) and circulatory factor (form PE).

Results: For NCI, there were significant differences between the Bowen's disease and bowenoid papulosis, and IN also shows significant differences between these two dis‐eases, showing that Bowen's disease has more corrugated or indented nucleus contour than bowenoid papulosis. In the parameter of form PE, there were significant differences between the two diseases, indicating that Bowen's disease has more oval‐shaped nuclei than bowenoid papulosis. There were no significant differences in form factor between Bowen's disease and bowenoid pupulosis.

Conclusions: Significant differences were found in the morphometric evaluation between Bowen's disease and bowenoid papulosis. The nuclei were larger, more oval and more irregular margins in Bowen's disease than bowenoid papulosis.
In vivo quantitative analysis of the effect of hydration (immersion and Vaseline treatment) in skin layers using high‐resolution MRI and magnetisation transfer contrast*
Authors: Mirrashed Fakhereh , Sharp Jonathan C.
Published: January 2004

Background/aims: Many claims are made as to the efficacy of topical preparations in moisturising the skin, yet most of these claims cannot be substantiated by scientific study for the skin layers beneath the stratum corneum, and yield no information on the remainder of the epidermis and dermis. This argues for an in vivo quantitative method for measuring the effect of water loading extended to various layers of the skin.

Methods: Detailed high‐resolution in vivo MRI studies of hydration and dehydration of finger pad skin layers were conducted on one normal subject using two moisturisation methods (topical white soft paraffin (Vaseline) and water immersion). The dehydration study was carried out immediately following removal from prolonged skin moisturisation. Inter‐individual variability for skin hydration (group study) was studied in seven healthy volunteers at 0 and 7 h hydration with Vaseline. Location dependence in skin hydration was investigated on the same subject by looking into the hydration of forearm and finger pad skin. System stability and measurement reproducibility was verified through a detailed phantom study.

Results: Images of normal and hydrated human skin were obtained in vivo at voxel dimensions of 50 μm×150 μm×1000 μm. The effect of hydration and dehydration as a function of exposure to moisturiser (i.e. water and Vaseline) on the image signal intensity, observed T1, and interaction of free and bound water in specific tissues were identified and correlated with existing physiological knowledge. Swelling of stratum corneum due to hydration was expressed as an in vivo model of tissue hydration.

Conclusion: Results of the dehydration study showed that the changes due to the previous hydration of the skin are reversible for all skin layers. For both moisturisation methods (i.e. Vaseline and skin bathing), the effects of hydration and dehydration on the skin were similar. The trends of the MRI parameters for finger pad and arm skin were similar. The group study showed low inter‐subject variability of hydration on stratum corneum and epidermis.
Real‐time spatial compound ultrasound imaging of skin
Authors: Wortsman Ximena C. , Holm Elisabeth A. , Wulf Hans C. , Jemec Gregor B. E.
Published: January 2004

Purpose:  The aim of our study was to evaluate the potential of real‐time spatial compound imaging (RTSCI) in dermatology.

Materials and methods:  An ATL 5000 SonoCT equipped with compact linear 15–7 MHz and linear 12–5 MHz transducers was obtained for skin visualization in a group of dermatological patients with various skin diseases.

Results:  Thirty‐four people participated: 21 patients with various skin diseases and 13 persons with normal skin. The mean age was 43.4 years. For many diseases, RTSCI gave useful information about the lesional structure, thickness and relationship with surrounding structures.

Conclusion: RTSCI allows objective, accurate, noninvasive and easy measurements of several parameters of skin morphology. It is useful in clinical trials, for evaluation of the effects of therapy, for preoperative evaluation of dermatological lesions, and enables visualization of subclinical and deep lesions, giving physicians the possibility of starting treatment before disease intensity increases. However, even such highly advanced ultrasound cannot completely substitute the clinical dermatological approach and the occasional need for histological diagnosis. This new method may, however, become an important adjunct method for the study of skin lesions.
Assessment of pigmented skin lesions in terms of blood perfusion estimates
Authors: Ilias M. A. , Wårdell K. , Stücker M. , Anderson C. , Salerud E. G.
Published: January 2004

Background/aims: Cutaneous malignant melanoma is a disease of increasing clinical and economical importance. The prognosis is good with early diagnosis. The chief differential diagnosis is benign melanocytic naevus, a common lesion in Caucasians. Attempts have been made to use bioengineering techniques to aid in the initial diagnosis. The present study proposes a method of extracting possibly discriminative blood perfusion properties in pigmented skin lesions by combining information on the lesions' blood perfusion with optical or visual information of their spatial extent.

Methods: A total of 46 blood perfusion measurements were performed on 22 pigmented skin lesions, the ultimate diagnosis of which was three histologically proven malignant melanomas, four histologically proven benign naevi and fifteen naevi assessed by two specialist dermatologists as being benign. Laser Doppler perfusion imaging gave two different types of two‐dimensional data sets (64×64 pixels), one representing the total backscattered light intensity at each measurement point (TLI image) and the second corresponding to perfusion values. The boundaries of each examined lesion were derived from the TLI image employing greyscale thresholding, thus resulting in an estimated region of interest (ROI) approximating the optical extent of the lesion. The ROI was superimposed on the perfusion image and extraction of perfusion features was then performed.

Results: The processing of the TLI images was successful in delineating the lesions' boundaries. The first hypothesis that the mean perfusion quotients in MM and benign naevi are equal could not be rejected at the chosen 5% level of significance. The second hypothesis that the mean percent‐age of elevated perfusion values (image pixels) within the ROI shows no difference between MM and benign naevi could be rejected at a 5% level of significance.

Conclusions: This study has presented a method of extracting blood perfusion parameters of pigmented skin lesions by combining blood perfusion information with information on the lesion's optical extent. The proposed method of presenting data could prove to be a useful discriminative adjunct in the assessment of pigmented skin lesions.
Correlation between laser Doppler perfusion imaging and visual scoring of patch test sites in subjects with experimentally induced allergic and irritant contact reactions
Authors: Goon Anthony Teik‐Jin , Leow Yung‐Hian , Chan Yiong‐Huak , Goh Chee‐Leok
Published: January 2004

Purpose: To compare laser Doppler perfusion imaging (LDPI) measurements in experimentally induced allergic contact reactions and irritant contact reactions. The degree of correlation between visual scores and LDPI measurements was also studied.

Methods: Fifteen patients with known contact allergy to nickel or fragrance were patch tested with nickel sulfate 5% pet., fragrance mix 8% pet., sodium lauryl sulfate (SLS) 0.5% pet., SLS 1.0% pet. and two empty control chambers. Visual readings and LDPI measurements were taken at 0, 48 and 96 h.

Results: There was a positive correlation between visual scores and LDPI measurement in the nickel sulfate and fragrance mix patch test sites. However, no correlation between visual scores and LDPI measurements was seen in the SLS 0.5% and SLS 1.0% patch test sites. There was no significant difference (P=0.125) in LDPI measurements between contact‐allergic reactions and contact‐irritant reactions.

Conclusion: LDPI correlates with visual scoring in contact‐allergic reactions, but not in irritant reactions. LDPI is not useful in distinguishing between allergic and irritant reactions.
Post‐spike distance‐to‐threshold trajectories of neurones in monkey motor cortex
Authors: Wetmore Daniel Z. , Baker Stuart N.
Published: January 2004

A recently developed method permits calculation of the post‐spike distance‐to‐threshold trajectory from an extracellularly recorded spontaneous spike train, using a transform of the interspike interval histogram. We applied this method to 61 single neurones recorded from the primary motor cortex of an awake behaving monkey; 39 cells were antidromically identified as pyramidal tract neurones (PTNs). The cells fell into three categories. Fifty‐three trajectories (37 from PTNs) had statistically significant peaks 10–60 ms after the preceding spike. Six neurones (2 PTNs) had non‐peaked trajectories which rose exponentially towards threshold. Two cells (both unidentified) had trajectories which declined monotonically away from threshold with increasing post‐spike latency. The peaked trajectories were unlikely simply to be an artefact of changing firing rate, which potentially can invalidate this method. Firstly, computer simulations confirmed that the method could accurately re‐create both exponential and peaked trajectories, even in the presence of the same rate modulation as seen experimentally. Secondly, the responses of eight cells to weak single pulse intracortical microstimulation (20 μA) through a nearby electrode were measured. For each cell, including representatives of all three trajectory shapes, the modulation of response probability with post‐spike latency was consistent with the trajectory computed from the spontaneous discharge. We also demonstrated that cells showed a peaked trajectory during periods with either high or low spontaneous network oscillations, so that the peaks were likely to be generated in part by single cell properties rather than exclusively by network activity. We conclude that many single neurones in motor cortex have an increased probability of firing a spike around 30 ms after the previous action potential. This could act to enhance synchronized oscillatory discharge among populations of cells at functionally relevant frequencies.
Intrinsic cellular currents and the temporal precision of EPSP–action potential coupling in CA1 pyramidal cells
Authors: Axmacher Nikolai , Miles Richard
Published: January 2004

We examined relations between cellular currents activated near firing threshold and the initiation of action potentials by excitatory postsynaptic potentials (EPSPs) in CA1 pyramidal cells in vitro. Small voltage steps elicited sequences of inward–outward currents at hyperpolarized potentials, but evoked largely inward currents at near threshold potentials. Similarly small EPSP‐like waveforms initiated largely inward currents while larger stimuli evoked sequences of inward followed by outward currents. Shorter rise times of EPSP‐like waveforms accentuated a transient component of inward currents. Voltage clamp data were consistent with the voltage dependence of current clamp responses to injection of EPSP shaped waveforms. Small events were prolonged at subthreshold potentials and could elicit action potentials at long latencies while responses to larger EPSP waveforms showed less voltage dependence and tended to induce spikes at shorter, less variable latencies. The precision of action potentials initiated by white noise depended also on stimulus amplitude. High variance stimuli induced firing with high precision, while the timing of spikes induced by lower variance signals was more variable between trials. In voltage clamp records, high variance noise commands induced sequences of inward followed by outward currents, while lower variance versions of the same commands elicited purely inward currents. These data suggest that larger synaptic stimuli recruit outward as well as inward currents. The resulting inward–outward current sequences enhance the temporal precision of EPSP–spike coupling. Thus, CA1 pyramidal cells initiate action potentials with different temporal precision, depending on stimulus properties.
Membrane cholesterol modulates dihydropyridine receptor function in mice fetal skeletal muscle cells
Authors: Pouvreau Sandrine , Berthier Christine , Blaineau Sylvie , Amsellem Jacqueline , Coronado Roberto , Strube Caroline
Published: January 2004

Caveolae and transverse (T‐) tubules are membrane structures enriched in cholesterol and glycosphingolipids. They play an important role in receptor signalling and myogenesis. The T‐system is also highly enriched in dihydropyridine receptors (DHPRs), which control excitation–contraction (E–C) coupling. Recent results have shown that a depletion of membrane cholesterol alters caveolae and T‐tubules, yet detailed functional studies of DHPR expression are lacking. Here we studied electrophysiological and morphological effects of methyl‐β‐cyclodextrin (MβCD), a cholesterol‐sequestering drug, on freshly isolated fetal skeletal muscle cells. Exposure of fetal myofibres to 1–3 mm MβCD for 1 h at 37°C led to a significant reduction in caveolae and T‐tubule areas and to a decrease in cell membrane electrical capacitance. In whole‐cell voltage‐clamp experiments, the L‐type Ca2+ current amplitude was significantly reduced, and its voltage dependence was shifted ∼15 mV towards more positive potentials. Activation and inactivation kinetics were slower in treated cells than in control cells and stimulation by a saturating concentration of Bay K 8644 was enhanced. In addition, intramembrane charge movement and Ca2+ transients evoked by a depolarization were reduced without a shift of the midpoint, indicating a weakening of E–C coupling. In contrast, T‐type Ca2+ current was not affected by MβCD treatment. Most of the L‐type Ca2+ conductance reduction and E–C coupling weakening could be explained by a decrease of the number of DHPRs due to the disruption of caveolae and T‐tubules. However, the effects on L‐type channel gating kinetics suggest that membrane cholesterol content modulates DHPR function. Moreover, the significant shift of the voltage dependence of L‐type current without any change in the voltage dependence of charge movement and Ca2+ transients suggests that cholesterol differentially regulates the two functions of the DHPR.
Modulation of excitation–contraction coupling by isoproterenol in cardiomyocytes with controlled SR Ca2+ load and Ca2+ current trigger
Authors: Ginsburg Kenneth S. , Bers Donald M.
Published: January 2004

Cardiac Ca2+ transients are enhanced by cAMP‐dependent protein kinase (PKA). However, PKA‐dependent modulation of ryanodine receptor (RyR) function in intact cells is difficult to measure, because PKA simultaneously increases Ca2+ current (ICa), SR Ca2+ uptake and SR Ca2+ loading (which independently increase SR Ca2+ release). We measured ICa and SR Ca2+ release ± 1 μm isoproterenol (ISO; isoprenaline) in voltage‐clamped ventricular myocytes of rabbits and transgenic mice (expressing only non‐phosphorylatable phospholamban). This mouse model helps control for any effect of ISO‐enhanced SR uptake on observed release, but the two species produced essentially identical results. SR Ca2+ load and ICa were adjusted by conditioning. We thus evaluated PKA effects on SR Ca2+ release at constant SR Ca2+ load and ICa trigger (with constant unitary ICa). The amount of SR Ca2+ release increased as a function of either ICa or SR Ca2+ load, but ISO did not alter the relationships (measured as gain or fractional release). This was true over a wide range of SR Ca2+ load and ICa. However, the maximal rate of SR Ca2+ release was ∼50% faster with ISO (at most loads and ICa levels). We conclude that the isolated effect of PKA on SR Ca2+ release is an increase in maximal rate of release and faster turn‐off of release (such that integrated SR Ca2+ release is unchanged). The increased amount of SR Ca2+ release normally seen with ISO depends primarily on increased ICa trigger and SR Ca2+ load, whereas faster release kinetics may be the main result of RyR phosphorylation.
Exercise and nitric oxide prevent bubble formation: a novel approach to the prevention of decompression sickness?
Authors: Wisløff Ulrik , Richardson Russell S. , Brubakk Alf O.
Published: January 2004

Nitrogen dissolves in the blood during dives, but comes out of solution if divers return to normal pressure too rapidly. Nitrogen bubbles cause a range of effects from skin rashes to seizures, coma and death. It is believed that these bubbles form from bubble precursors (gas nuclei). Recently we have shown that a single bout of exercise 20 h, but not 48 h, before a simulated dive prevents bubble formation and protects rats from severe decompression sickness (DCS) and death. Furthermore, we demonstrated that administration of Nω‐nitro‐l‐arginine methyl ester, a non‐selective inhibitor of NO synthase (NOS), turns a dive from safe to unsafe in sedentary but not exercised rats. Therefore based upon previous data an attractive hypothesis is that it may be possible to use either exercise or NO‐releasing agents before a dive to inhibit bubble formation and thus protect against DCS. Consequently, the aims of the present study were to determine whether protection against bubble formation in ‘diving’ rats was provided by (1) chronic and acute administration of a NO‐releasing agent and (2) exercise less than 20 h prior to the dive. NO given for 5 days and then 20h prior to a dive to 700 kPa lasting 45 min breathing air significantly reduced bubble formation and prevented death. The same effect was seen if NO was given only 30 min before the dive. Exercise 20h before a dive surpressed bubble formation and prevented death, with no effect at any other time (48, 10, 5 and 0.5h prior to the dive). Pre‐dive activities have not been considered to influence the growth of bubbles and thus the risk of serious DCS. The present novel findings of a protective effect against bubble formation and death by appropriately timed exercise and an NO‐releasing agent may form the basis of a new approach to preventing serious decompression sickness.
βL–βM loop in the C‐terminal domain of G protein‐activated inwardly rectifying K+ channels is important for Gβγ subunit activation
Authors: Finley Melissa , Arrabit Christine , Fowler Catherine , Suen Ka Fai , Slesinger Paul A.
Published: January 2004

The activity of G protein‐activated inwardly rectifying K+ channels (GIRK or Kir3) is important for regulating membrane excitability in neuronal, cardiac and endocrine cells. Although Gβγ subunits are known to bind the N‐ and C‐termini of GIRK channels, the mechanism underlying Gβγ activation of GIRK is not well understood. Here, we used chimeras and point mutants constructed from GIRK2 and IRK1, a G protein‐insensitive inward rectifier, to determine the region within GIRK2 important for Gβγ binding and activation. An analysis of mutant channels expressed in Xenopus oocytes revealed two amino acid substitutions in the C‐terminal domain of GIRK2, GIRK2L344E and GIRK2G347H, that exhibited decreased carbachol‐activated currents but significantly enhanced basal currents with coexpression of Gβγ subunits. Combining the two mutations (GIRK2EH) led to a more severe reduction in carbachol‐activated and Gβγ‐stimulated currents. Ethanol‐activated currents were normal, however, suggesting that G protein‐independent gating was unaffected by the mutations. Both GIRK2L344E and GIRK2EH also showed reduced carbachol activation and normal ethanol activation when expressed in HEK‐293T cells. Using epitope‐tagged channels expressed in HEK‐293T cells, immunocytochemistry showed that Gβγ‐impaired mutants were expressed on the plasma membrane, although to varying extents, and could not account completely for the reduced Gβγ activation. In vitro Gβγ binding assays revealed an ∼60% decrease in Gβγ binding to the C‐terminal domain of GIRK2L344E but no statistical change with GIRK2EH or GIRK2G347H, though both mutants exhibited Gβγ‐impaired activation. Together, these results suggest that L344, and to a lesser extent, G347 play an important functional role in Gβγ activation of GIRK2 channels. Based on the 1.8 Å structure of GIRK1 cytoplasmic domains, L344 and G347 are positioned in the βL–βM loop, which is situated away from the pore and near the N‐terminal domain. The results are discussed in terms of a model for activation in which Gβγ alters the interaction between the βL–βM loop and the N‐terminal domain.
Opioid receptor stimulation suppresses the adrenal medulla hypoxic response in sheep by actions on Ca2+ and K+ channels
Authors: Keating Damien J. , Rychkov Grigori Y. , Adams Michael B. , Holgert Hans , McMillen I. Caroline , Roberts Michael L.
Published: January 2004

Before the preganglionic regulation of the adrenal medulla is established, hypoxia acts directly on the chromaffin cells to evoke the secretion of catecholamines. This direct action of hypoxia is suppressed by the gradual development of the preganglionic innervation and we have proposed that opioid peptides released from the adrenal splanchnic nerves may be responsible for this suppression. The effects of the specific opioid agonists DPDPE (δ‐agonist), U‐62066 (κ‐agonist) and DALDA (μ‐agonist) on the hypoxia‐evoked response were investigated in both a whole‐gland preparation and in isolated adrenal chromaffin cells using amperometry, whole‐cell patch clamping and measurement of cytosolic [Ca2+]. The combined application of μ‐ and κ‐type agonists abolished the hypoxia‐evoked catecholamine secretion from whole perfused adrenal gland. In isolated chromaffin cells, μ‐ and κ‐opioid agonists reduced the rise in [Ca2+]i that results from exposure to hypoxia. Both agonists decreased the voltage‐dependent Ca2+ current in these cells. The μ‐agonist increased the conductance through SK‐type K+ channels and this action offset the decrease in K+ conductance produced by exposure to hypoxia. The κ‐type agonist decreased the conductance through an action on BK‐type K+ channels, a class of channels that are not involved in initiating the direct response to hypoxia. These data suggest that opioids, through their action on SK channels and voltage‐dependent Ca2+ channels, may be responsible for the nerve‐induced suppression of the hypoxic response of adrenal chromaffin cells and that these effects of endogenous opioids are mediated via μ‐ and κ‐type receptors.
Five basic muscle activation patterns account for muscle activity during human locomotion
Authors: Ivanenko Y. P. , Poppele R. E. , Lacquaniti F.
Published: January 2004

An electromyographic (EMG) activity pattern for individual muscles in the gait cycle exhibits a great deal of intersubject, intermuscle and context‐dependent variability. Here we examined the issue of common underlying patterns by applying factor analysis to the set of EMG records obtained at different walking speeds and gravitational loads. To this end healthy subjects were asked to walk on a treadmill at speeds of 1, 2, 3 and 5kmh−1 as well as when 35–95% of the body weight was supported using a harness. We recorded from 12–16 ipsilateral leg and trunk muscles using both surface and intramuscular recording and determined the average, normalized EMG of each record for 10–15 consecutive step cycles. We identified five basic underlying factors or component waveforms that can account for about 90% of the total waveform variance across different muscles during normal gait. Furthermore, while activation patterns of individual muscles could vary dramatically with speed and gravitational load, both the limb kinematics and the basic EMG components displayed only limited changes. Thus, we found a systematic phase shift of all five factors with speed in the same direction as the shift in the onset of the swing phase. This tendency for the factors to be timed according to the lift‐off event supports the idea that the origin of the gait cycle generation is the propulsion rather than heel strike event. The basic invariance of the factors with walking speed and with body weight unloading implies that a few oscillating circuits drive the active muscles to produce the locomotion kinematics. A flexible and dynamic distribution of these basic components to the muscles may result from various descending and proprioceptive signals that depend on the kinematic and kinetic demands of the movements.
Phasic negative intrathoracic pressures enhance the vascular responses to stimulation of pulmonary arterial baroreceptors in closed‐chest anaesthetized dogs
Authors: Moore Jonathan P. , Hainsworth Roger , Drinkhill Mark J.
Published: January 2004

We investigated whether the reflex responses to stimulation of pulmonary arterial baroreceptors were altered by intrathoracic pressure changes similar to those encountered during normal breathing. Dogs were anaesthetized with α‐chloralose, a cardiopulmonary bypass was established, and the pulmonary trunk and its main branches as far as the first lobar arteries were vascularly isolated and perfused with venous blood. The chest was closed following connection to the perfusion circuit and pressures distending the aortic arch, carotid sinus and coronary artery baroreceptors were controlled. Changes in the descending aortic (systemic) perfusion pressure (SPP; flow constant) were used to assess changes in systemic vascular resistance. Values of SPP were plotted against mean pulmonary arterial pressure (PAP) and sigmoid functions applied. From these curves we derived the threshold pressures (corresponding to 5% of the overall response of SPP), the maximum slopes (equivalent to peak gain) and the corresponding PAP (equivalent to ‘set point’). Stimulus–response curves were compared between data obtained with intrathoracic pressure at atmospheric and with a phasic intrathoracic pressure ranging from atmospheric to around −10 mmHg (18 cycles min−1). Results were obtained from seven dogs and are given as means ±s.e.m.Compared to the values obtained when intrathoracic pressure was at atmospheric, the phasic intrathoracic pressure decreased the pulmonary arterial threshold pressure in five dogs; average change from 28.4 ± 5.9 to 19.3 ± 5.9 mmHg (P> 0.05). The inflexion pressure was significantly reduced from 37.8 ± 4.8 to 27.4 ± 4.0 mmHg (P <0.03), but the slopes of the curves were not consistently changed. These results have shown that a phasic intrathoracic pressure, which simulates respiratory oscillations, displaces the stimulus–response curve of the pulmonary arterial baroreceptors to lower pressures so that it lies within a physiological range of pressures.
The effect of mitochondrial inhibitors on membrane currents in isolated neonatal rat carotid body type I cells
Authors: Wyatt C. N. , Buckler K. J.
Published: January 2004

Inhibitors of mitochondrial energy metabolism have long been known to be potent stimulants of the carotid body, yet their mechanism of action remains obscure. We have therefore investigated the effects of rotenone, myxothiazol, antimycin A, cyanide (CN−) and oligomycin on isolated carotid body type I cells. All five compounds caused a rapid rise in intracellular Ca2+, which was inhibited on removal of extracellular Ca2+. Under current clamp conditions rotenone and CN− caused a rapid membrane depolarization and elevation of [Ca2+]i. Voltage clamping cells to −70 mV substantially attenuated this rise in [Ca2+]i. Rotenone, cyanide, myxothiazol and oligomycin significantly inhibited resting background K+ currents. Thus rotenone, myxothiazol, cyanide and oligomycin mimic the effects of hypoxia in that they all inhibit background K+ current leading to membrane depolarization and voltage‐gated calcium entry. Hypoxia, however, failed to have any additional effect upon membrane currents in the presence of CN− or rotenone or the mitochondrial uncoupler p‐trifluoromethoxyphenyl hydrazone (FCCP). Thus not only do mitochondrial inhibitors mimic the effects of hypoxia, but they also abolish oxygen sensitivity. These observations suggest that there is a close link between oxygen sensing and mitochondrial function in type I cells. Mechanisms that could account for this link and the actions of mitochondrial inhibitors are discussed.
Influence of endogenous nitric oxide on sympathetic vasoconstriction in normoxia, acute and chronic systemic hypoxia in the rat
Authors: Coney Andrew M. , Bishay Mark , Marshall Janice M.
Published: January 2004

We studied the role of nitric oxide (NO) in blunting sympathetically evoked muscle vasoconstriction during acute and chronic systemic hypoxia. Experiments were performed on anaesthetized normoxic (N) and chronically hypoxic (CH) rats that had been acclimated to 12% O2 for 3–4 weeks. The lumbar sympathetic chain was stimulated for 1 min with bursts at 20 or 40 Hz and continuously at 2 Hz. In N rats, acute hypoxia (breathing 8% O2) reduced baseline femoral vascular resistance (FVR) and depressed increases in FVR evoked by all three patterns of stimulation, but infusion of the NO donor sodium nitroprusside (SNP), so as to similarly reduce baseline FVR, did not affect sympathetically evoked responses. Blockade of NO synthase (NOS) with l‐NAME increased baseline FVR and facilitated the sympathetically evoked increases in FVR, but when baseline FVR was restored by SNP infusion, these evoked responses were restored. Acute hypoxia after l‐NAME still reduced baseline FVR and depressed evoked responses. In CH rats breathing 12% O2, baseline FVR was lower than in N rats breathing air, but l‐NAME had qualitatively similar effects on baseline FVR and sympathetically evoked increases in FVR. SNP similarly restored baseline FVR and evoked responses. Inhibition of neuronal NOS or inducible NOS did not affect baselines, or evoked responses. We propose that in N and CH rats sympathetically evoked muscle vasoconstriction is modulated by tonically released NO, but not depressed by additional NO released on sympathetic activation. The present results suggest that hypoxia‐induced blunting of sympathetic vasoconstriction in skeletal muscle is not mediated by NO.
Regulation of Kv4.3 voltage‐dependent gating kinetics by KChIP2 isoforms
Authors: Patel Sangita P. , Parai Rajarshi , Parai Rita , Campbell Donald L.
Published: January 2004

We conducted a kinetic analysis of the voltage dependence of macroscopic inactivation (τfast, τslow), closed‐state inactivation (τclosed,inact), recovery (τrec), activation (τact), and deactivation (τdeact) of Kv4.3 channels expressed alone in Xenopus oocytes and in the presence of the calcium‐binding ancillary subunits KChIP2b and KChIP2d. We demonstrate that for all expression conditions, τrec, τclosed,inact and τfast are components of closed‐state inactivation transitions. The values of τclosed,inact and τfast monotonically merge from −30 to −20 mV while the values of τclosed,inact and τrec approach each other from −60 to −50 mV. These data generate classic bell‐shaped time‐constant–potential curves. With the KChIPs, these curves are distinct from that of Kv4.3 expressed alone due to acceleration of τrec and slowing of τclosed,inact and τfast. Only at depolarized potentials where channels open is τslow detectable suggesting that it represents an open‐state inactivation mechanism. With increasing depolarization, KChIPs favour this open‐state inactivation mechanism, supported by the observation of larger transient reopening currents upon membrane hyperpolarization compared to Kv4.3 expressed alone. We propose a Kv4.3 gating model wherein KChIP2 isoforms accelerate recovery, slow closed‐state inactivation, and promote open‐state inactivation. This model supports the observations that with KChIPs, closed‐state inactivation transitions are [Ca2+]i‐independent, while open‐state inactivation is [Ca2+]i‐dependent. The selective KChIP‐ and Ca2+‐dependent modulation of Kv4.3 inactivation mechanisms predicted by this model provides a basis for dynamic modulation of the native cardiac transient outward current by intracellular Ca2+ fluxes during the action potential.
Voltage‐activated Ca2+ channels and their role in the endocrine function of the pituitary gland in newborn and adult mice
Authors: Sedej Simon , Tsujimoto Tetsuhiro , Zorec Robert , Rupnik Marjan
Published: January 2004

We have prepared fresh pituitary gland slices from adult and, for the first time, from newborn mice to assess modulation of secretory activity via voltage‐activated Ca2+ channels (VACCs). Currents through VACCs and membrane capacitance have been measured with the whole‐cell patch‐clamp technique. Melanotrophs in newborns were significantly larger than in adults. In both newborn and adult melanotrophs activation of VACCs triggered exocytosis. All pharmacologically isolated VACC types contributed equally to the secretory activity. However, the relative proportion of VACCs differed between newborns and adults. In newborn cells L‐type channels dominated and, in addition, an exclusive expression of a toxin‐resistant R‐type‐like current was found. The expression of L‐type VACCs was up‐regulated by the increased oestrogen levels observed in females, and was even more emphasized in the cells of pregnant females and oestrogen‐treated adult male mice. We suggest a general mechanism modulating endocrine secretion in the presence of oestrogen and particularly higher sensitivity to treatments with L‐type channel blockers during high oestrogen physiological states.
Functional and structural conservation of CBS domains from CLC chloride channels
Authors: Estévez Raúl , Pusch Michael , Ferrer‐Costa Carles , Orozco Modesto , Jentsch Thomas J.
Published: January 2004

All eukaryotic CLC Cl− channel subunits possess a long cytoplasmic carboxy‐terminus that contains two so‐called CBS (cystathionine β‐synthase) domains. These domains are found in various unrelated proteins from all phylae. The crystal structure of the CBS domains of inosine monophosphate dehydrogenase (IMPDH) is known, but it is not known whether this structure is conserved in CLC channels. Working primarily with ClC‐1, we used deletion scanning mutagenesis, coimmunoprecipitation and electrophysiology to demonstrate that its CBS domains interact. The replacement of CBS domains of ClC‐1 with the corresponding CBS domains from other CLC channels and even human IMPDH yielded functional channels, indicating a high degree of structural conservation. Based on a homology model of the pair of CBS domains of CLC channels, we identified some residues that, when mutated, affected the common gate which acts on both pores of the dimeric channel. Thus, we propose that the structure of CBS domains from CLC channels is highly conserved and that they play a functional role in the common gate.
Extracellular signal‐regulated kinase activation and endothelin‐1 production in human endothelial cells exposed to vibration
Authors: White Charles R. , Haidekker Mark A. , Stevens Hazel Y. , Frangos John A.
Published: January 2004

Hand–arm vibration syndrome is a vascular disease of occupational origin and a form of secondary Raynaud's phenomenon. Chronic exposure to hand‐held vibrating tools may cause endothelial injury. This study investigates the biomechanical forces involved in the transduction of fluid vibration in the endothelium. Human endothelial cells were exposed to direct vibration and rapid low‐volume fluid oscillation. Rapid low‐volume fluid oscillation was used to simulate the effects of vibration by generating defined temporal gradients in fluid shear stress across an endothelial monolayer. Extracellular signal‐regulated kinase (ERK1/2) phosphorylation and endothelin‐1 (ET‐1) release were monitored as specific biochemical markers for temporal gradients and endothelial response, respectively. Both vibrational methods were found to phosphorylate ERK1/2 in a similar pattern. At a fixed frequency of fluid oscillation where the duration of each pulse cycle remained constant, ERK1/2 phosphorylation increased with the increasing magnitude of the applied temporal gradient. However, when the frequency of flow oscillation was increased (thus decreasing the duration of each pulse cycle), ERK1/2 phosphorylation was attenuated across all temporal gradient flow profiles. Fluid oscillation significantly stimulated ET‐1 release compared to steady flow, and endothelin‐1 was also attenuated with the increase in oscillation frequency. Taken together, these results show that both the absolute magnitude of the temporal gradient and the frequency/duration of each pulse cycle play a role in the biomechanical transduction of fluid vibrational forces in endothelial cells. Furthermore, this study reports for the first time a link between the ERK1/2 signal transduction pathway and transmission of vibrational forces in the endothelium.
Differential effects of turbidity on prey consumption of piscivorous and planktivorous fish
Authors: De Robertis Alex , Ryer Clifford H , Veloza Adriana , Brodeur Richard D
Published: January 2004

Contrast degradation theory predicts that increased turbidity decreases the visibility of objects that are visible at longer distances more than that of objects that are visible at short distances. Consequently, turbidity should disproportionately decrease feeding rates by piscivorous fish, which feed on larger and more visible prey than particle-feeding planktivorous fish. We tested this prediction in a series of laboratory feeding experiments, the results of which indicated that prey consumption by two species of planktivorous fish (juvenile chum salmon (Oncorhynchus keta) and walleye pollock (Theragra chalcogramma)) is much less sensitive to elevated turbidity than piscivorous feeding by sablefish (Anoplopoma fimbria). Planktivorous feeding in the turbidity range tested (0–40 nephelometric turbidity units (NTU)) was reduced at high light intensity, but not at low light intensity. Comparatively low (5–10 NTU) turbidity decreased both the rate at which sablefish pursued prey and the probability of successful prey capture. These results suggest that turbid environments may be advantageous for planktivorous fish because they will be less vulnerable to predation by piscivores, but will not experience a substantial decrease in their ability to capture zooplankton prey.
Cladoceran body length and Secchi disk transparency in northeastern U.S. lakes
Authors: Stemberger Richard S , Miller Eric K
Published: January 2004

Mean cladoceran body length of 59 northeastern U.S. lakes was estimated from functional groups that broadly define taxonomic, body size, and grazing potential. Multiple regression of body length, color, and chlorophyll a or total phosphorus against Secchi disk transparency explained 72% and 83% of the variation across lakes, respectively. Analysis that included body length, color, and particulate carbon, a proxy for light backscattering and absorption by suspended organic particles, explained 85% of the variance in transparency. Body length was as important a predictor of water clarity as chemical factors. Furthermore, body length was significantly correlated to temporal variation in transparency within lakes. Because cladocerans primarily filter organic particles in size ranges having high light attenuation efficiencies, body length was consistently more strongly correlated to transparency than to chlorophyll a. Monitoring cladoceran body length should help to distinguish changes in lake transparency due to nutrient loading from changes that reflect fish population size structure and predation intensity on zooplankton. This simple size index can greatly increase the interpretative value of Secchi transparency observations to lake managers.
Spread of hybridization between native westslope cutthroat trout, Oncorhynchus clarki lewisi, and nonnative rainbow trout, Oncorhynchus mykiss
Authors: Hitt Nathaniel P , Frissell Christopher A , Muhlfeld Clint C , Allendorf Fred W
Published: January 2004

We examined spatial and temporal patterns of hybridization between native westslope cutthroat trout, Oncorhynchus clarki lewisi, and nonnative rainbow trout, O. mykiss, in streams of the Flathead River system in Montana, U.S.A. We detected hybridization in 24 of 42 sites sampled from 1998 to 2001. We found new Oncorhynchus mykiss introgression in seven of 11 sample populations that were determined to be nonhybridized in 1984. Patterns of spatial autocorrelation and linkage disequilibrium indicated that hybridization is spreading among sites and is advancing primarily via post-F1 hybrids. Although hybridized populations were distributed widely throughout the study area, the genetic contribution from O. mykiss decreased with increasing upstream distance from the Flathead River mainstem, suggesting that O. mykiss introgression is spreading in an upstream direction. The spread of hybridization may be constrained more by demographic than by environmental factors, given that (i) hybridized populations generally encompassed the range of environmental variability in nonhybridized populations, and (ii) hybridization status was more strongly associated with neighborhood statistics than measured environmental gradients.
Testing a model of drift-feeding using three-dimensional videography of wild brown trout, Salmo trutta, in a New Zealand river
Authors: Hughes Nicholas F , Hayes John W , Shearer Karen A , Young Roger G
Published: January 2004

We tested the assumptions and predictions of a foraging model for drift-feeding fish. We used three-dimensional videography to describe the foraging behavior of brown trout, Salmo trutta, mapped water depth and velocity in their foraging area, sampled invertebrate drift to determine length class specific drift densities, and captured trout to determine the size composition of their diet. The model overestimated the fish's prey capture rate and gross energy intake rate by a factor of two. Most of this error resulted from the fact that prey detection probabilities within the fish's foraging area averaged only half the expected value. This was the result of a rapid decrease in capture probability with increasing lateral distance from the fish's focal point. Some of the model's assumptions were accurate: equations for predicting reaction distance and minimum prey size supported reliable predictions of the shape and size of the fish's foraging area and the size composition of the diet. Other assumptions were incorrect: fish detected prey within the predicted reaction volume, not on its upstream surface as expected, fish intercepted prey more slowly than the expected maximum sustainable swimming speed, and fish captured about two-thirds of their prey downstream of their focal point, rather than upstream.
Determining long-term water quality change in the presence of climate variability: Lake Tahoe (U.S.A.)
Authors: Jassby Alan D , Reuter John E , Goldman Charles R
Published: January 2004

We developed a time series model of Secchi depth for Lake Tahoe incorporating a mechanistic understanding of interannual variability with sufficient simplicity to allow data-based parameter estimation. Secchi depth is still occasionally over 40 m at Lake Tahoe, but mean annual Secchi depth has declined nearly 10 m since 1967, prompting a large-scale restoration program. Year-to-year variability is extremely high, obscuring restoration actions and compliance with water quality standards. The model focused on Secchi depth during summer, when the lake is least transparent and most heavily used. Interannual variability for the summer season is driven largely by precipitation differences. The model offers a means for determining compliance with water quality standards when precipitation anomalies may persist for years. As demonstrated by means of an ex-post forecast, increasing Secchi depths during 1999–2001 were simply climate-driven and do not represent a recovery of the lake. The long-term trend for summer is most likely due to the accumulation of allochthonous mineral suspensoids.