bluuebunny/crossref_metadata_2025 huggingface dataset:
Layer-Specific Properties of the Persistent Sodium Current in Sensorimotor Cortex
Authors: Aracri P. , Colombo E. , Mantegazza M. , Scalmani P. , Curia G. , Avanzini G. , Franceschetti S.
Published: February 2006

We evaluated the characteristics of the persistent sodium current ( INaP) in pyramidal neurons of layers II/III and V in slices of rat sensorimotor cortex using whole cell patch-clamp recordings. In both layers, INaPbegan activating around −60 mV and was half-activated at −43 mV. The INaPpeak amplitude and density were significantly higher in layer V. The voltage-dependent INaPsteady-state inactivation occurred at potentials that were significantly more positive in layer V ( V1/2: −42.3 ± 1.1 mV) than in layer II/III ( V1/2: −46.8 ± 1.6 mV). In both layers, a current fraction corresponding to about 25% of the maximal peak amplitude did not inactivate. The time course of INaPinactivation and recovery from inactivation could be fitted with a biexponential function. In layer V pyramidal neurons the faster time constant of development of inactivation had variable values, ranging from 158.0 to 1,133.8 ms, but it was on average significantly slower than that in layer II/III (425.9 ± 80.5 vs. 145.8 ± 18.2 ms). In both layers, INaPdid not completely inactivate even with very long conditioning depolarizations (40 s at −10 mV). Recovery from inactivation was similar in the two layers. Layer V intrinsically bursting and regular spiking nonadapting neurons showed particularly prolonged depolarized plateau potentials when Ca2+and K+currents were blocked and slower early phase of INaPdevelopment of inactivation. The biexponential kinetics characterizing the time-dependent inactivation of INaPin layers II/III and V indicates a complex inactivating process that is incomplete, allowing a residual “persistent” current fraction that does not inactivate. Moreover, our data indicate that INaPhas uneven inactivation properties in pyramidal neurons of different layers of rat sensorimotor cortex. The higher current density, the rightward shifted voltage dependency of inactivation as well the slower kinetics of inactivation characterizing INaPin layer V with respect to layer II/III pyramidal neurons may play a significant role in their ability to fire recurrent action potential bursts, as well in the high susceptibility to generate epileptic events.
Direct Recording of Theta Oscillations in Primate Prefrontal and Anterior Cingulate Cortices
Authors: Tsujimoto Toru , Shimazu Hideki , Isomura Yoshikazu
Published: February 2006

Recent evidence has suggested that theta-frequency (4–7 Hz) oscillations around the human anterior cingulate cortex (ACC) and frontal cortex—that is, frontal midline theta (Fm theta) oscillations—may be involved in attentional processes in the brain. However, little is known about the physiological basis of Fm theta oscillations because invasive study in the human is allowed in only limited cases. In the present study, we developed a monkey model for Fm theta oscillations and located the generators of theta waves using electrodes implanted in various cortical areas. Monkeys were engaged in a self-initiated hand-movement task with a waiting period. The theta power in area 9 (the medial prefrontal cortex) and area 32 (the rostral ACC) was gradually increased from a few seconds before the movement and reached a peak immediately after the movement. When the movement was rewarded, the theta power attained a second peak, whereas it swiftly decreased in the unrewarded trials. Theta oscillations in areas 9 and 32 were coherent and phase locked together. This theta activity may be associated with “executive attention” including self-control, internal timing, and assessment of reward. It is probably a homologue of human Fm theta oscillations, as judged from the similar localization, corresponding frequency, and dependency on attentional processes. The monkey model would be useful for studying executive functions in the frontal cortex.
Guidance of Eye Movements During Visual Conjunction Search: Local and Global Contextual Effects on Target Discriminability
Authors: Shen Kelly , Paré Martin
Published: February 2006

The composition of a visual scene influences the ability of humans to select specific details within that scene for discrimination or foveation with saccadic eye movements. With the goal of establishing an animal model to investigate the neural mechanisms underlying the deployment of visual attention and the guidance of saccades during visual search, we studied the visual behavior of three monkeys while they performed a conjunction (color + form) search task similar to those used in human studies. We found that search performance declined when distractors adjacent to the target shared its color, thereby revealing that color was more discriminable than form in these displays and suggesting that monkeys perceptually grouped stimuli by proximity and similarity. Search performance also varied with the overall composition of the display. Most importantly, saccades were biased toward distractors sharing the target color when there were few of them within the display and away from those distractors when they were numerous. Last, the monkeys initiated saccades with a fixed latency, suggesting that their responses to the display were automatic and that search strategies did not involve attentional resources beyond those recruited for regulating saccades. We conclude that monkeys adapt their visual strategies, largely via bottom-up processes, to both the local and the global context of the search. These findings suggest that the visual behavior of monkeys is guided by strategies similar to those observed in humans.
On the Origin of the Extracellular Action Potential Waveform: A Modeling Study
Authors: Gold Carl , Henze Darrell A. , Koch Christof , Buzsáki György
Published: February 2006

Although extracellular unit recording is typically used for the detection of spike occurrences, it also has the theoretical ability to report about what are typically considered intracellular features of the action potential. We address this theoretical ability by developing a model system that captures features of experimentally recorded simultaneous intracellular and extracellular recordings of CA1 pyramidal neurons. We use the line source approximation method of Holt and Koch to model the extracellular action potential (EAP) voltage resulting from the spiking activity of individual neurons. We compare the simultaneous intracellular and extracellular recordings of CA1 pyramidal neurons recorded in vivo with model predictions for the same cells reconstructed and simulated with compartmental models. The model accurately reproduces both the waveform and the amplitude of the EAPs, although it was difficult to achieve simultaneous good matches on both the intracellular and extracellular waveforms. This suggests that accounting for the EAP waveform provides a considerable constraint on the overall model. The developed model explains how and why the waveform varies with electrode position relative to the recorded cell. Interestingly, each cell's dendritic morphology had very little impact on the EAP waveform. The model also demonstrates that the varied composition of ionic currents in different cells is reflected in the features of the EAP.
Influence of Spatial Information on Responses of Tonically Active Neurons in the Monkey Striatum
Authors: Ravel Sabrina , Sardo Pierangelo , Legallet Eric , Apicella Paul
Published: February 2006

Previous studies have demonstrated that tonically active neurons (TANs) in the primate striatum play an important role in the detection of rewarding events. However, the influence of the spatial features of stimuli or actions required to obtain reward remains unclear. Here, we examined the activity of TANs in the striatum of monkeys trained to make spatially directed movements elicited by visual stimuli presented ipsilaterally or contralaterally to the moving arm. Among 181 neurons responding to the trigger stimulus, 127 (70%) were nonselective for stimulus location and 54 (30%) responded to only one location of the stimulus. Most of the selective responses (63%) occurred when the stimulus was presented contralaterally to the moving arm. To examine whether TAN responses are related to the location of the stimulus or to the direction of the movement, we tested a subset of the trigger-responsive neurons ( n = 44) in a condition that elicited reaching toward or away from the stimulus. By comparing TAN activity between the two conditions, we found that half of the responses can be interpreted as being related to the location of the stimulus, one quarter to the direction of movement, and one quarter to the context in which stimulus–movement combination occurs. These results demonstrate that TANs are not limited to motivational processing, but may play a role in the processing of spatial attributes of stimulus and/or movement as well. These response properties suggest that TANs are involved in the flexible shifting of motor responses during spatially directed behavior.
Nitric Oxide Transiently Converts Synaptic Inhibition to Excitation in Retinal Amacrine Cells
Authors: Hoffpauir Brian , McMains Emily , Gleason Evanna
Published: February 2006

Nitric oxide (NO) is generated by multiple cell types in the vertebrate retina, including amacrine cells. We investigate the role of NO in the modulation of synaptic function using a culture system containing identified retinal amacrine cells. We find that moderate concentrations of NO alter GABAA receptor function to produce an enhancement of the GABA-gated current. Higher concentrations of NO also enhance GABA-gated currents, but this enhancement is primarily due to a substantial positive shift in the reversal potential of the current. Several pieces of evidence, including a similar effect on glycine-gated currents, indicate that the positive shift is due to an increase in cytosolic Cl−. This change in the chloride distribution is especially significant because it can invert the sign of GABA- and glycine-gated voltage responses. Furthermore, current- and voltage-clamp recordings from synaptic pairs of GABAergic amacrine cells demonstrate that NO transiently converts signaling at GABAergic synapses from inhibition to excitation. Persistence of the NO-induced shift in ECl− in the absence of extracellular Cl− indicates that the increase in cytosolic Cl− is due to release of Cl− from an internal store. An NO-dependent release of Cl− from an internal store is also demonstrated for rat hippocampal neurons indicating that this mechanism is not restricted to the avian retina. Thus signaling in the CNS can be fundamentally altered by an NO-dependent mobilization of an internal Cl− store.
Loss of TRPV1-Expressing Sensory Neurons Reduces Spinal μ Opioid Receptors But Paradoxically Potentiates Opioid Analgesia
Authors: Chen Shao-Rui , Pan Hui-Lin
Published: February 2006

Systemic administration of resiniferatoxin (RTX), an ultrapotent capsaicin analogue, removes transient receptor potential vanilloid type 1 (TRPV1)-expressing afferent neurons and impairs thermal but not mechanical nociception in adult animals. In this study, we determined how loss of TRPV1-expressing sensory neurons alters the antinociceptive effect of μ opioids and μ opioid receptors in the spinal cord. The effect of morphine and (d-Ala2,N-Me-Phe4,Gly-ol5)-enkephalin (DAMGO) was measured by testing the paw mechanical withdrawal threshold in rats treated with RTX or vehicle. RTX treatment deleted TRPV1-immunoreactive dorsal root ganglion neurons and nerve terminals in the spinal dorsal horn. Also the μ opioid receptor immunoreactivity was markedly reduced in the superficial dorsal horn of RTX-treated rats. However, RTX treatment did not affect the dorsal horn neurons labeled with both TRPV1- and μ opioid receptor-immunoreactivity. Surprisingly, intrathecal morphine or DAMGO produced a greater increase in the withdrawal threshold in RTX- than in vehicle-treated rats. The duration of the effect of intrathecal morphine and DAMGO in RTX-treated rats was also profoundly increased. Furthermore, the antinociceptive effect of systemic morphine was significantly potentiated in RTX-treated rats. The BMAX(but not KD) of [3H]-DAMGO binding and DAMGO-stimulated [35S]GTPγS activity in the dorsal spinal cord were significantly reduced in the RTX group. This study provides novel information that loss of TRPV1 afferent neurons eliminates presynaptic μ opioid receptors present on TRPV1-expressing afferent neurons but paradoxically potentiates the analgesic effect of μ opioid agonists. Mechano-nociception, transmitted through non-TRPV1 sensory neurons, is subject to potent modulation by μ opioid agonists.
Effects of Sodium Pump Activity on Spontaneous Firing in Neurons of the Rat Suprachiasmatic Nucleus
Authors: Wang Yi-Chi , Huang Rong-Chi
Published: February 2006

Cell-attached and whole cell recording techniques were used to study the effects of electrogenic sodium pump on the excitability of rat suprachiasmatic nucleus (SCN) neurons. Blocking the sodium pump with the cardiac steroid strophanthidin or zero K+ increased the spontaneous firing of SCN neurons to different degrees with different recording modes, whereas turning the sodium pump into a nonselective cation channel with the marine toxin palytoxin invariably increased the spontaneous firing to the point of total blockade. Current-clamp recordings indicated that strophanthidin increased the rate of membrane depolarization and reduced the peak afterhyperpolarization potential (AHP), whereas zero K+ also increased the rate of depolarization, but enhanced the peak AHP. The dual effect of zero K+ was reflected by the biphasic time course of voltage responses to zero K+: an inhibitory phase with enhanced peak AHP and slower firing, followed by a delayed excitatory phase with faster rate of membrane depolarization and faster firing. In the presence of strophanthidin to block the sodium pump, zero K+ consistently decreased firing by enhancing the peak AHP. Repetitive applications of K+-free solution gradually turned the biphasic inhibitory-followed-by-excitatory voltage response into a monophasic inhibitory response in cells recorded with the whole cell (but not the cell-attached) mode, suggesting rundown of sodium pump activity. Taken together, the results suggest that spontaneous firing of SCN neurons is regulated by sodium pump activity as well as the AHP, and that sodium pump activity is modulated by intracellular soluble substances subject to rundown under the whole cell conditions.
Simulating the Delaware Bay Buoyant Outflow: Comparison with Observations
Authors: Whitney Michael M. , Garvine Richard W.
Published: February 2006

Coastal buoyant outflows from rivers and estuaries previously have been studied with field research, laboratory experiments, and numerical models. There is a dire need to evaluate model performance in light of coastal current observations. This research simulates the Delaware Bay outflow and compares results with observations of estuarine and shelf conditions. Observations include an estuarine salinity climatology, a record of freshwater delivery to the shelf, coastal current salinity mappings, and surface drifter data. Simulation efforts focus on spring 1993 and spring 1994, the primary field study period. The simulation is forced with river discharge, winds, and tides; only tidal-averaged results are discussed. Estuarine salinity results are consistent with the observed lateral salinity pattern, vertical structure, and response to river discharge. Salinities within the lower bay agree with observations, but the simulation overestimates the along-estuary salinity gradient. Observed and simulated freshwater delivery exhibit the same amplitude of response to river discharge and winds. The simulation produces a buoyant outflow that is generally consistent with the observed buoyancy signature, width, length, and vertical structure over a variety of river discharge and wind conditions. The simulated coastal current, however, tends to be somewhat shorter and fresher than observed. Simulated surface drifter paths exhibit the observed onshore advection during downwelling winds as well as offshore transport and current reversals during upwelling winds. A statistical evaluation based on shelf salinity mappings indicates that the model reproduces the observed variance and has only a small bias (less than 10% of plume buoyancy signature). The rms error of 1.2 psu is linked to the shorter and fresher nature of the simulated coastal current. Observational comparisons discussed in this paper indicate that the model can simulate many coastal current features and its response to river discharge and wind forcing.
Changes in the CFC Inventories and Formation Rates of Upper Labrador Sea Water, 1997–2001
Authors: Kieke Dagmar , Rhein Monika , Stramma Lothar , Smethie William M. , LeBel Deborah A. , Zenk Walter
Published: February 2006

Chlorofluorocarbon (component CFC-11) and hydrographic data from 1997, 1999, and 2001 are presented to track the large-scale spreading of the Upper Labrador Sea Water (ULSW) in the subpolar gyre of the North Atlantic Ocean. ULSW is CFC rich and comparatively low in salinity. It is located on top of the denser “classical” Labrador Sea Water (LSW), defined in the density range σΘ = 27.68–27.74 kg m−3. It follows spreading pathways similar to LSW and has entered the eastern North Atlantic. Despite data gaps, the CFC-11 inventories of ULSW in the subpolar North Atlantic (40°–65°N) could be estimated within 11%. The inventory increased from 6.0 ± 0.6 million moles in 1997 to 8.1 ± 0.6 million moles in 1999 and to 9.5 ± 0.6 million moles in 2001. CFC-11 inventory estimates were used to determine ULSW formation rates for different periods. For 1970–97, the mean formation rate resulted in 3.2–3.3 Sv (Sv ≡ 106 m3 s−1). To obtain this estimate, 5.0 million moles of CFC-11 located in 1997 in the ULSW in the subtropical/tropical Atlantic were added to the inventory of the subpolar North Atlantic. An estimate of the mean combined ULSW/LSW formation rate for the same period gave 7.6–8.9 Sv. For the years 1998–99, the ULSW formation rate solely based on the subpolar North Atlantic CFC-11 inventories yielded 6.9–9.2 Sv. At this time, the lack of classical LSW formation was almost compensated for by the strongly pronounced ULSW formation. Indications are presented that the convection area needed in 1998–99 to form this amount of ULSW exceeded the available area in the Labrador Sea. The Irminger Sea might be considered as an additional region favoring ULSW formation. In 2000–01, ULSW formation weakened to 3.3–4.7 Sv. Time series of layer thickness based on historical data indicate that there exists considerable variability of ULSW and classical LSW formation on decadal scales.
The Quasi-Nondispersive Regimes of Long Extratropical Baroclinic Rossby Waves over (Slowly Varying) Topography
Authors: Tailleux Rémi
Published: February 2006

Actual energy paths of long, extratropical baroclinic Rossby waves in the ocean are difficult to describe simply because they depend on the meridional-wavenumber-to-zonal-wavenumber ratio τ, a quantity that is difficult to estimate both observationally and theoretically. This paper shows, however, that this dependence is actually weak over any interval in which the zonal phase speed varies approximately linearly with τ, in which case the propagation becomes quasi-nondispersive (QND) and describable at leading order in terms of environmental conditions (i.e., topography and stratification) alone. As an example, the purely topographic case is shown to possess three main kinds of QND ray paths. The first is a topographic regime in which the rays follow approximately the contours f /hαc = a constant (αc is a near constant fixed by the strength of the stratification, f is the Coriolis parameter, and h is the ocean depth). The second and third are, respectively, “fast” and “slow” westward regimes little affected by topography and associated with the first and second bottom-pressure-compensated normal modes studied in previous work by Tailleux and McWilliams. Idealized examples show that actual rays can often be reproduced with reasonable accuracy by replacing the actual dispersion relation by its QND approximation. The topographic regime provides an upper bound (in general a large overestimate) of the maximum latitudinal excursions of actual rays. The method presented in this paper is interesting for enabling an optimal classification of purely azimuthally dispersive wave systems into simpler idealized QND wave regimes, which helps to rationalize previous empirical findings that the ray paths of long Rossby waves in the presence of mean flow and topography often seem to be independent of the wavenumber orientation. Two important side results are to establish that the baroclinic string function regime of Tyler and Käse is only valid over a tiny range of the topographic parameter and that long baroclinic Rossby waves propagating over topography do not obey any two-dimensional potential vorticity conservation principle. Given the importance of the latter principle in geophysical fluid dynamics, the lack of it in this case makes the concept of the QND regimes all the more important, for they are probably the only alternative to provide a simple and economical description of general purely azimuthally dispersive wave systems.
Latitudinal Distribution of Mixing Rate Caused by the M2 Internal Tide
Authors: Tian Jiwei , Zhou Lei , Zhang Xiaoqian
Published: February 2006

Ten years of Ocean Topography Experiment (TOPEX)/Poseidon tidal data and an energy balance relation are used to estimate the mixing rate caused by M2 internal tides in the upper ocean. The results indicate that latitudinal distribution of the mixing rate has a generally symmetrical structure with respect to the equator. The maxima are distributed around 28.9°N and 28.9°S and can be as high as 3.8 × 10−5 m2 s−1 in the Pacific, 5 × 10−5 m2 s−1 in the Atlantic, and 3.7 × 10−5 m2 s−1 in the Indian Oceans. The minimum, which is only 10% of those at 28.9°, is located near the equator. The data imply that midlatitudes are the key regions for internal tide mixing.
Vortices of the Mediterranean Sea: An Altimetric Perspective
Authors: Isern-Fontanet Jordi , García-Ladona Emilio , Font Jordi
Published: February 2006

The presence of coherent vortices makes observed mesoscale fields of the ocean resemble two-dimensional turbulence. Using this analogy, a common definition of a coherent structure has been used to study the statistical properties of Mediterranean Sea vortices observed by satellite altimeters over a 7-yr period. A vortex has been defined as the simply connected region with values of the Okubo–Weiss parameter W < −0.2σW, where σW is the spatial standard deviation of W, and the same sign of vorticity. This definition is shown to be appropriate to detect and characterize, statistically, properties such as size, mean kinetic energy, and amplitude of vortices in the Mediterranean basin from sea level anomaly maps corresponding to the period from October 1992 to October 1999. The distribution of such properties for the Mediterranean vortices suggests a heuristic criterion to extract and select very coherent and long-lived vortices from the whole set of structures identified in altimetric maps. Such coherent vortices appear to be selected for amplitudes greater than 2σW, where the amplitude has been defined in terms of the Okubo–Weiss parameter rather than vorticity, and strongly correspond to those reported from observations with independent data. Systematic locating and tracking of such vortices provide, for the first time, a general picture of their preferential paths in the Mediterranean basin, which are characterized by complex but rather well defined patterns.
Finite-Amplitude Baroclinic Instability of Time-Varying Abyssal Currents
Authors: Ha Seung-Ji , Swaters Gordon E.
Published: February 2006

The weakly nonlinear baroclinic instability characteristics of time-varying grounded abyssal flow on sloping topography with dissipation are described. Specifically, the finite-amplitude evolution of marginally unstable or stable abyssal flow both at and removed from the point of marginal stability (i.e., the minimum shear required for instability) is determined. The equations governing the evolution of time-varying dissipative abyssal flow not at the point of marginal stability are identical to those previously obtained for the Phillips model for zonal flow on a β plane. The stability problem at the point of marginally stability is fully nonlinear at leading order. A wave packet model is introduced to examine the role of dissipation and time variability in the background abyssal current. This model is a generalization of one introduced for the baroclinic instability of zonal flow on a β plane. A spectral decomposition and truncation leads, in the absence of time variability in the background flow and dissipation, to the sine–Gordon solitary wave equation that has grounded abyssal soliton solutions. The modulation characteristics of the soliton are determined when the underlying abyssal current is marginally stable or unstable and possesses time variability and/or dissipation. The theory is illustrated with examples.
The Effect of Localized Mixing on the Ocean Circulation and Time-Dependent Climate Change
Authors: Saenko Oleg A.
Published: February 2006

Observations indicate that intense mixing in the ocean is localized above complex topography and near the boundaries. Model experiments presented here illustrate that accounting for this fact can be important. In particular, it is found that in the case of localized mixing, the rate of overturning circulation is proportional to the net rate of generation of potential energy by the vertical mixing, linked to the net downward heat diffusion, rather than to the value of the mean vertical diffusivity coefficient. Furthermore, it is shown that two climate models, having the same vertical profile of diffusivity but differing in their distribution (horizontally uniform versus topography/boundary intensified) can simulate significantly different meridional oceanic circulations, vertical heat transfers, and responses of simulated climate to atmospheric CO2 increase. This is found for relatively large [O(1.0 cm2 s−1)] horizontal-mean values of vertical diffusivity in the pycnocline. However, in cases of relatively small [O(0.1 cm2 s−1)] mean diffusivity in the pycnocline, the simulated integral quantities such as meridional mass and heat transports do not depend much on the details of the mixing distribution. Even so, it is found that the deep western boundary currents are more localized near the boundaries in the case of topography/boundary-intensified mixing; also, the stratification in the deep ocean is set through the localized regions of intense vertical mixing. In addition, it is shown that reconciling the observed basin-mean values of diffusivity in the abyssal ocean of O(10 cm2 s−1) with realistic stratification can be problematic, unless the regions of enhanced vertical mixing are localized.
Internal Tides in the Southwestern Japan/East Sea
Authors: Park Jae-Hun , Watts D. Randolph
Published: February 2006

This paper investigates the internal tidal energy distribution in the southwestern Japan/East Sea using vertical round-trip travel time (τ) data from 23 pressure-sensor-equipped inverted echo sounders (PIES). The τ records are analyzed by bandpass filtering to separate time-dependent variability of the semidiurnal and diurnal bands. The semidiurnal internal tides exhibit a horizontal beam pattern of high energy, propagating into the open basin. They originate from a restricted portion of the shelf break where the Korea Strait enters the Ulleung Basin. The generation appears to occur at ∼200-m water depth near 35.5°–35.7°N and 130°–131°E, where the slope of bottom topography matches that of the wave characteristics, coinciding with the location where the semidiurnal barotropic cross-slope tidal currents are strongest. Maximum vertical displacement of the thermocline interpreted as a long-wave first baroclinic mode from the measured τ is about 25 m near the generation region. Annual and monthly variations of the propagation patterns and generation energy levels are observed, and these are closely associated with changes in the mesoscale circulation and stratification. Eastward (westward) refraction is observed when a warm (cold) eddy crosses the path of internal tide propagation. Moreover, when the generation region is invaded by cold eddies that spoil the match between shelf break and thermocline depth, the internal tidal energy level decreases by a factor of about 2. A simple geometric optics model is proposed to explain the observed horizontal refraction of the beam of semidiurnal internal tides in which stratification and current shear play essential roles. In contrast, diurnal internal tides are observed to be trapped along the continental slope region around 36°N.
Lagrangian Observations of the Middepth and Deep Velocity Fields of the Northeastern Atlantic Ocean
Authors: Lankhorst Matthias , Zenk Walter
Published: February 2006

The circulation of the northeastern Atlantic Ocean at intermediate depths is characterized by watermass transformation processes that involve Iceland–Scotland Overflow Water (ISOW) from the northeast, Labrador Sea Water (LSW) from the west, and Mediterranean Water from the south. Field observations were carried out with 89 eddy-resolving floats (RAFOS and MARVOR types). The data coverage achieved is remarkably high and enables a comprehensive study of the eastern basins between Iceland and the Azores. The trajectories show typical pathways of the water masses involved and the role that the complex bottom topography plays in defining them. The ISOW paths tend to lean against the slopes of the Reykjanes Ridge and Rockall Plateau. Westward escapes through multiple gaps in the ridge are possible, superimposed on a sustained southward flow in the eastern basin along the Mid-Atlantic Ridge. LSW pathways leading to the eastern basins are subject to high variability in flow direction and eddy activity. In addition to a selection of characteristic trajectories, maps of the horizontal distributions of Lagrangian eddy kinetic energy and integral time scales are presented. These reveal distinct areas of intensified mixing in the Iceland Basin, as well as the sharp contrast between the subpolar and subtropical dynamics. A self-contained eddy detection scheme is applied to obtain statistics on individual eddy properties and their abundance. It is suggested that much of the intensified mixing can be related to cyclonic activity, particularly in the subpolar region.
Adapting Industrial Relations to Serve Knowledge-based Economies
Authors: Kochan Thomas A.
Published: February 2006

The central challenge facing industrial relations today is how to adapt its policies, institutions, practices, and research to serve the needs of the workforce and society in a global, knowledge-based economy. The field of industrial relations rose to prominence in the 20th century because it helped workers and employers adapt to their growing industrial economies. Today, we observe that many of the institutions and policies developed for the industrial era are in decline. A similar transformation of policies, institutions, and practices will be needed to help workers, families, communities, and societies adapt to the requirements of a knowledge-based, global economy. This will require renewed commitment to universal and life-long education and training, broad diffusion of knowledge-based work systems in organizations, more transparency and more direct worker voice in corporate governance structures and processes, flexible labor market policies that support mobility and portability of benefits across jobs and movement in and out of full time work as women and men move through different stages of their careers and family lives, and new institutions for worker voice and representation at work and in society. Given the global nature of economic activity, these reforms cannot be limited to single national systems; they must be part of a broader international consensus and coordinated effort to build transnational systems for managing cross border flows of human capital, jobs, knowledge, and value.
Protected Mobility for Employment and Decent Work: Labour Market Security in a Globalized World
Authors: Auer Peter
Published: February 2006

Recent ILO research found that a cluster of OECD countries that might be called ‘numerically flexible’ does in fact demonstrate good labour market results: employment rates overall and rates for relevant groups (young/female/older) are higher and unemployment is lower than in countries with less numerical flexibility as measured by employment tenure. However, when considering indicators of job quality the picture is mixed, with some countries exhibiting low shares of good quality employment and some others high shares. The discriminating variable seems to be labour market institutions and policies. A conclusion is that if efficiency and equity are sought in labour markets in open economies then institutions and policies for ‘protected mobility’ should exist. Institution building (or transformation of existing institutions) is important on several accounts. Firstly, globalization and technical change transforms employment relations and entail more volatility and less security. Secondly, collective bargaining agendas have to be extended to include labour market policies, as employers’ demands for more adjustment flexibility will increasingly be accompanied by worker representatives’ demands for better security in change. In other words: reduced employment protection has to be compensated by labour market security if decent work is a target. Protected mobility by sound labour market policies might result in real ‘flexicurity’ (adaptability for firms and security for workers) and become a common objective of both sides of industry while also reconfirming an enhanced role for the State.
International Labor Standards, Soft Regulation, and National Government Roles
Authors: Kuruvilla Sarosh , Verma Anil
Published: February 2006

In this article, we briefly describe the different approaches to the regulation of international labor standards, and then argue for a new role for national governments based on soft rather than hard regulation approaches. We argue that this new role shows potential for significantly enhancing progress in international labor standards, since it enables governments to articulate a position without having to deal with the enforcement issues that hard regulation mandates. We justify this new role for governments based on the increasing use of soft regulation in the international arena. Of course, this approach is not without its own problems, but given that existing approaches have all provided imperfect solutions to the problem of improving labor standards globally, re-visiting the role of national governments is in our view, highly important.
Globalization and the Logic of Participation: Unions and the Politics of Coalition Building
Authors: Turner Lowell
Published: February 2006

Global liberalization is driving a ‘logic of participation’, for firms and unions alike. Economic pressures drive managers to innovate across a range of possibilities, from outsourcing and union busting to work reorganization and labor-management partnership. Those same pressures, reflected largely through the strategic choices of employers, also force unions to innovate - from concession bargaining and cooperation to coalition building and international solidarity. Because employers are increasingly tempted by strategies that seek to weaken or marginalize unions, sustained participation for unions arguably requires a new period of activist mobilization.

This article explores one significant component of renewed labor mobilization: union coalition building. Based on a case study of coalition efforts in the United States between the United Steelworkers and the Sierra Club from 1999-2004, concepts and causal linkages are suggested for broader analysis. Research findings presented here indicate the following causal processes at work: union strategies, defining moments and spillover combine to drive coalition building processes that include events, campaigns and institution building - ranging from local to national and global levels. Beyond this US-based case, a framework for cross-national comparative analysis is also suggested.
Mexico’s 2006 Elections
Authors: Béjar Alejandro Álvarez
Published: February 2006

As Mexico approaches its 2006 elections, it is simultaneously experiencing the exhaustion of its neoliberal economic model and a political crisis in which the presidency lacks its historical sources of support, the legislature’s power has been limited by the Supreme Court, and the court itself is increasingly discredited. The system of political parties is also in disarray, with deepening divisions between parties, among the leaders within each party, and in the Instituto Federal Electoral itself. Motivated by these circumstances, as well as by high unemployment, low wages, and privatization of strategic public enterprises, an emerging social force, both urban and rural, has begun to seek electoral outlets for its growing dissatisfaction with neoliberalism. The result is a transitional election combining concerns for public security with variants of populism from the right and left aimed at the political reformulation of neoliberalism.
Migration and Borders
Authors: Ruiz Olivia
Published: February 2006

The principal issues regarding international migration and borders facing the 2006 presidential campaigns include remittances, a guest-worker program, relations with the Mexican immigrant population in the United States, Mexico-United States relations, national security, human rights, and Central American immigration. These issues point to a larger debate concerning the course of social and economic development in Mexico and, more specifically, to the failure of more than 20 years of neoliberal economic policy.
One Triangle, Two Campaigns
Authors: Gilly Adolfo
Published: February 2006

Dispossession, contempt, and exploitation are the triangle upon which the domination of labor by capital has always been based in Mexico. During the twentieth century, peasant armies fought a successful revolution against two of the triangle’s legs, forcing the powerful, through the Constitution of 1917, to return them land and show them respect. Under the presidency of Carlos Salinas de Gortari (1988-1994), however, there was a counterreform, dismantling the agrarian reform and other social rights achieved by the Mexico people during the revolution and after. The Partido de la Revolución Democrática emerged during Salinas’s term to fight this assault. Today, however, it has become a vehicle for the political ambitions of many of the same politicians who surrounded Salinas. Under these circumstances, the Other Campaign proposed by the Ejército Zapatista de Liberación Nacional is the only honest response to the presidential campaign of 2006.
Which PRI Wants to Win the Election?
Authors: Montemayor Carlos
Published: February 2006

Rather than a temporary phase, Mexico’s recurring crisis, beginning in 1982, is part of the painful process of economic restructuring envisioned by the proponents of neoliberalism. Moreover, it reflects an effort to dismantle the state as a factor in the development of the country’s economy. Despite the election of new presidents, the economic model employed in Mexico has remained unchanged.
Violencia Femicida
Authors: Olivera Mercedes
Published: February 2006

An extreme expression of violence and sadism against women in Mexico is the increase in murders of women throughout the country. The causes of this violence are associated with the increase in extreme poverty, unemployment, the disintegration of the peasant economy, and social polarization imposed on the poor by neoliberal policies. Femicide and violence may therefore be considered components of the current structural crisis of the capitalist system.
Building a Future for Rural Mexico
Authors: Barkin David
Published: February 2006

The stereotypes of a backward and stagnant peasantry are challenged by the reality of people constructing their own alternatives of social theory and action. In the face of globalization processes that offer few options for large segments of the population, there are numerous social groups actively working to strengthen their rural communities, to rehabilitate and protect their ecosystems, and to contribute to forging a new type of social pact in which they can enjoy rising living standards while also contributing to an improving quality of life for society as a whole. This alternative vision of rural communities is based on a reexamination of information about these areas, reconsideration of the ways in which the communities govern themselves, react to pressures, and make decisions.
TheDrosophilaformin DAAM regulates the tracheal cuticle pattern through organizing the actin cytoskeleton
Authors: Matusek Tamás , Djiane Alexandre , Jankovics Ferenc , Brunner Damian , Mlodzik Marek , Mihály József
Published: February 2006

Formins are involved in a wide range of cellular processes that require the remodeling of the actin cytoskeleton. Here, we have analyzed a novel Drosophila formin, belonging to the recently described DAAM subfamily. In contrast to previous assumptions, we show that DAAMplays no essential role in planar cell polarity signaling, but it has striking requirements in organizing apical actin cables that define the taenidial fold pattern of the tracheal cuticle. These observations provide evidence the first time that the function of the taenidial organization is to prevent the collapse of the tracheal tubes. Our results indicate that although DAAM is regulated by RhoA, it functions upstream or parallel to the non-receptor tyrosine kinases Src42A and Tec29 to organize the actin cytoskeleton and to determine the cuticle pattern of the Drosophila respiratory system.
C/EBPα is required for lung maturation at birth
Authors: Martis Prithy C. , Whitsett Jeffrey A. , Xu Yan , Perl Anne-Karina T. , Wan Huajing , Ikegami Machiko
Published: February 2006

Epithelial cells lining the peripheral lung synthesize pulmonary surfactant that reduces surface tension at the air-liquid interface. Lack of surfactant lipids and proteins in the lungs causes respiratory distress syndrome, a common cause of morbidity and mortality in preterm infants. We show that C/EBPα plays a crucial role in the maturation of the respiratory epithelium in late gestation, being required for the production of surfactant lipids and proteins necessary for lung function. Deletion of the Cebpa gene in respiratory epithelial cells in fetal mice caused respiratory failure at birth. Structural and biochemical maturation of the lung was delayed. Normal synthesis of surfactant lipids and proteins,including SP-A, SP-B, SP-C, SP-D, ABCA3 (a lamellar body associated protein)and FAS (precursor of fatty acid synthesis) were dependent upon expression of the C/EBPα in respiratory epithelial cells. Deletion of the Cebpa gene caused increased expression of Tgfb2, a growth factor that inhibits lung epithelial cell proliferation and differentiation. Normal expression of C/EBPα required Titf1 and Foxa2,transcription factors that also play an important role in perinatal lung differentiation. C/EBPα participates in a transcriptional network that is required for the regulation of genes mediating perinatal lung maturation and surfactant homeostasis that is necessary for adaptation to air breathing at birth.
Degrade to create: developmental requirements for ubiquitin-mediated proteolysis during earlyC. elegansembryogenesis
Authors: Bowerman Bruce , Kurz Thimo
Published: February 2006

The ubiquitin protein conjugation system tags proteins with the small polypeptide ubiquitin. Most poly-ubiquitinated proteins are recognized and degraded by the proteasome, a large multi-subunit protease. Ubiquitin-dependent protein degradation is used as a regulatory tool for many essential processes, the best studied of which is eukaryotic cell cycle progression. More recently, genetic studies in C. elegans have identified multiple roles for the ubiquitin system in early development, where ubiquitin-dependent protein degradation governs such diverse events as passage through meiosis, cytoskeletal regulation and cell fate determination.
Hand, an evolutionarily conserved bHLH transcription factor required forDrosophilacardiogenesis and hematopoiesis
Authors: Han Zhe , Yi Peng , Li Xiumin , Olson Eric N.
Published: February 2006

The Hand gene family encodes highly conserved basic helix-loop-helix (bHLH)transcription factors that play crucial roles in cardiac and vascular development in vertebrates. In Drosophila, a single Handgene is expressed in the three major cell types that comprise the circulatory system: cardioblasts, pericardial nephrocytes and lymph gland hematopoietic progenitors, but its function has not been determined. Here we show that Drosophila Hand functions as a potent transcriptional activator, and converting it into a repressor blocks heart and lymph gland formation. Disruption of Hand function by homologous recombination also results in profound cardiac defects that include hypoplastic myocardium and a deficiency of pericardial and lymph gland hematopoietic cells, accompanied by cardiac apoptosis. Targeted expression of Hand in the heart completely rescued the lethality of Hand mutants, and cardiac expression of a human HAND gene, or the caspase inhibitor P35,partially rescued the cardiac and lymph gland phenotypes. These findings demonstrate evolutionarily conserved functions of HAND transcription factors in Drosophila and mammalian cardiogenesis, and reveal a previously unrecognized requirement of Hand genes in hematopoiesis.
Determination of cell fate along the anteroposterior axis of theDrosophilaventral midline
Authors: Bossing Torsten , Brand Andrea H.
Published: February 2006

The Drosophila ventral midline has proven to be a useful model for understanding the function of central organizers during neurogenesis. The midline is similar to the vertebrate floor plate, in that it plays an essential role in cell fate determination in the lateral CNS and also, later,in axon pathfinding. Despite the importance of the midline, the specification of midline cell fates is still not well understood. Here, we show that most midline cells are determined not at the precursor cell stage, but as daughter cells. After the precursors divide, a combination of repression by Wingless and activation by Hedgehog induces expression of the proneural gene lethal of scute in the most anterior midline daughter cells of the neighbouring posterior segment. Hedgehog and Lethal of scute activate Engrailed in these anterior cells. Engrailed-positive midline cells develop into ventral unpaired median (VUM) neurons and the median neuroblast (MNB). Engrailed-negative midline cells develop into unpaired median interneurons (UMI), MP1 interneurons and midline glia.
Conversational apprentices: Helping children become competent informants about their own experiences
Authors: Lamb Michael E. , Brown Deirdre A.
Published: February 2006

Alleged victims of child abuse are often the only sources of information about the crimes, and this places them in the role of experts when conversing about their experiences. Despite developmental deficiencies in memory, cognition, communication skills, and social style, researchers have shown that children's informativeness in such conversations is profoundly shaped by the interviewing practices of their adult interlocutors. We review techniques that degrade children's performance as well as those that help children perform to the best of their abilities, and discuss how these findings have important implications for the ways in which children learn to converse and interact with adults, and for their understanding of the roles played by conversations in information exchange. When adult interviewers conduct developmentally appropriate interviews with children, they help children become competent informants about their experiences.