bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intracellular calcium and Na+‐Ca2+ exchange current in isolated toad pacemaker cells
Authors: Ju Yue‐Kun , Allen David G. 
Published: September 2010

Single pacemaker cells were isolated from the sinus venosus of cane toad (Bufo marinus) in order to study the mechanisms involved in the spontaneous firing rate of action potentials. Intracellular calcium concentration ([Ca2+]i) was measured with indo‐1 to determine whether [Ca2+]i influenced firing rate. A rapid transient rise of [Ca2+]i was recorded together with each spontaneous action potential. [Ca2+]i at the peak of systole was 655 ± 64 nM and the minimum at the end of diastole was 195 ± 15 nM.
Reduction of extracellular Ca2+ concentration from 2 to 0.5 mM caused a reduction in both systolic and diastolic [Ca2+]i and the spontaneous firing rate also gradually declined.
Application of the acetoxymethyl (AM) ester of BAPTA (10 μM), in order to increase intracellular calcium buffering, caused a decline in systolic and diastolic [Ca2+]i. The firing rate declined progressively until the cells stopped firing after 10‐15 min. At the time that firing ceased, the diastolic [Ca2+]i had declined by 141 ± 38 nM.
In the presence of ryanodine (2 μM), which interferes with Ca2+ release from the sarcoplasmic reticulum, the systolic and diastolic [Ca2+]i both declined and the firing rate decreased until the cells stopped firing. At quiescence diastolic [Ca2+]i had declined by 93 ± 20 nM.
Exposure of the cells to Na+‐free solution caused a rise in [Ca2+]i which exceeded the systolic level after 4.8 ± 0.3 s. This rise is consistent with Ca2+ entry on a Na+‐Ca2+ exchanger.
Rapid application of caffeine (10‐20 mM) to cells clamped at ‐60 mV caused a rapid increase in [Ca2+]i which then spontaneously declined. An inward current with a similar time course to that of [Ca2+]i was also generated. Application of Ni2+ (5 mM) or 2,4‐dichlorobenzamil (25 μM) reduced the amplitude of the inward current produced by caffeine by 96 ± 1 % and 74 ± 10 %, respectively. In a Na+‐free solution the caffeine‐induced current was reduced by 93 ± 7 %.
Under a variety of circumstances the diastolic [Ca2+]i showed a close association with pacemaker firing rate. The existence of a Na+‐Ca2+ exchanger and its estimated contribution to inward current during the pacemaker potential suggest that the Na+‐Ca2+ exchange current makes a contribution to pacemaker activity.
The effect of length on the relationship between tension and intracellular [Ca2+] in intact frog skeletal muscle fibres
Authors: Claflin Dennis R. , Morgan David L. , Julian Fred J. 
Published: September 2010

The relationship between tension and intracellular calcium concentration ([Ca2+]i) in intact frog skeletal muscle fibres was determined at two fibre lengths, corresponding to mean sarcomere lengths (SL) of 2.2 and 2.9 μm. Tension and [Ca2+]i were recorded during the slow decline of tension following stimulation in the presence of cyclopiazonic acid (CPA), a sarcoplasmic reticulum Ca2+‐uptake pump inhibitor. [Ca2+]i was estimated by injecting the K+ salt form of the fluorescent dye fura‐2 into the fibres. Experimental temperature was 3.0 °C.
At a SL of 2.2 μm, where thick and thin filaments fully overlap, the [Ca2+]i corresponding to 50 % tension generation ([Ca2+]50) was 1.09 ± 0.02 μM (mean ± s.e.m., n= 61 contractions). At a SL of 2.9 μm, where overlap is approximately 50 %, the [Ca2+]50 was significantly lower, 0.69 ± 0.02 μM (n= 22 contractions). This is in agreement with previous results from skinned fibres.
The relationship between tension and [Ca2+]i was very steep, as reported previously from experiments at a SL of 2.2 μm in which the membrane permeant acetoxymethyl ester form of fura‐2 was used. The fall in tension from 90 to 10 % occurred in 0.12 ± 0.01 pCa units (mean ± s.e.m., n= 61) for a SL of 2.2 μm and 0.17 ± 0.01 pCa units (n= 22) for a SL of 2.9 μm, corresponding to Hill coefficients of 15.4 and 10.9, respectively.
We conclude that the increase in sensitivity of tension to [Ca2+] that occurs in skinned skeletal muscle fibres upon stretch also occurs in intact fibres, that the steepness of the relation between tension and [Ca2+]i in intact fibres reported previously cannot be attributed to the use of the acetoxymethyl ester form of fura‐2 to report [Ca2+]i, and that the steepness decreases as myofilament overlap decreases.
Cytoskeletal targeting of calponin in differentiated, contractile smooth muscle cells of the ferret
Authors: Parker Christopher A. , Takahashi Katsuhito , Tang Jay X. , Tao Terence , Morgan Kathleen G. 
Published: September 2010

Biochemical and quantitative image analysis methods were used to investigate the anatomical basis for the previously described agonist‐induced redistribution of calponin.
At 140 nm resolution, the quantitative distribution of calponin in resting cells was statistically indistinguishable from that of filament bundles containing α‐smooth muscle actin and myosin, but was significantly different from that of filaments containing β‐non‐muscle actin. Conversely, in stimulated cells, the distribution of calponin was not significantly different from that of β‐actin filaments in the subplasmalemmal cell cortex but was significantly different from the distribution of α‐actin‐ and myosin‐containing filamentous bundles.
The distribution of calponin significantly differed from that of the intermediate filament proteins vimentin and desmin as well as that of the dense body protein α‐actinin either by ratio analysis of the subcellular distribution or by colocalization analysis.
The imaging results, although limited to 140 nm spatial resolution, suggested the hypothesis that the agonist‐induced redistribution involves the binding of calponin to isoform‐specific actin filaments. This hypothesis was tested by quantifying the relative affinity of calponin for purified α‐ and β‐actin. Light scattering measurements showed that calponin induces bundle formation with β‐actin more readily than α‐actin, indicating that calponin may be preferentially sequestered by β‐actin under appropriate conditions.
These results are consistent with a model whereby agonist activation decreases calponin's binding to filaments, but the tighter binding to β‐actin filaments results in a spatial redistribution of calponin to the submembranous cortex.
Spatio‐temporal receptive fields in carp retinal horizontal cells
Authors: Umino Osamu , Ushio Tomomi 
Published: September 2010

The dynamics of the receptive fields of retinal horizontal cells were examined by applying a spatio‐temporal modulated light signal to the retina.
The spatio‐temporal receptive fields of both cone‐ and rod‐driven horizontal cells, estimated through cross‐correlation between the modulated light signal and the cells’ responses, showed their receptive fields (the space‐dependent component) to be reduced in size with time.
In cone‐driven horizontal cells, the reduction in receptive field size was initially small but then rapidly became prominent with time. The time to peak of the time‐dependent component of spatio‐temporal receptive fields did not depend on the distance from the centre.
Application of a small amount of Co2+, an agent blocking the cone‐driven horizontal cells’ feedback action on cones, or GABA, resulted in a reversal of the time‐dependent shrinkage of receptive fields to time‐dependent expansion.
In rod‐driven horizontal cells, the receptive field shrinkage was slow. The time to peak of the time‐dependent component decreased with the distance from the centre.
Image processing experiments examining the response pattern in the horizontal cell layer (neural image) to a moving square of light showed smudging of the neural image when the time‐dependent receptive field expansion was present, while there was essentially no smudging under conditions of receptive field shrinkage.
Role of spinal premotoneurones in mediating corticospinal input to forearm motoneurones in man
Authors: Pauvert V. , Pierrot‐Deseilligny E. , Rothwell J. C. 
Published: September 2010

Evidence was sought to support the suggestion that corticospinal input can be relayed to motoneurones (MNs) via a population of interneurones (premotoneurones) in the cervical cord, and that this pathway operates in parallel with the direct monosynaptic pathway.
Single motor units were recorded in forearm muscles and post‐stimulus time histograms (PSTHs) of their firing pattern were constructed during voluntary activation. Weak transcranial magnetic stimulation of the contralateral motor cortex was used to produce a small facilitation in the PSTH. We then examined how the size of this peak was affected by low threshold electrical stimulation of either the homonymous muscle nerve or the musculo‐cutaneous nerve at various interstimulus intervals (ISIs).
Homonymous nerve stimulation had the following characteristics: (a) the cortical peak was facilitated when stimuli were timed so that both inputs arrived simultaneously at the MN; (b) the amount of facilitation was only slightly greater than the sum of the effects of each stimulus given alone; and (c) facilitation affected even the earliest bins of the cortically evoked peak. These three features are consistent with a monosynaptic input onto the MN from both sources.
Stimulation of the musculo‐cutaneous nerve (which has no monosynaptic connections with forearm MNs) had no effect at similar timings. It (a) produced facilitation only at longer intervals corresponding to an extra central delay of 4‐6 ms; (b) always gave a significantly larger facilitation than expected from the algebraic sum of the effects of each stimulus given alone; and (c) never affected the earliest bins of the cortical peak. These features are compatible with interaction of peripheral and cortical inputs at a population of premotoneurones.
These results confirm the suggestion that premotoneurones mediate part of the cortical command to MNs innervating forearm muscles.
Excitation is followed by an inhibition which may almost completely suppress the cortical peak. It is suggested that cortical and musculo‐cutaneous volleys also converge onto inhibitory interneurones projecting to the premotoneuronal pool.
Detection of movements of the human forearm during and after co‐contractions of muscles acting at the elbow joint
Authors: Wise A. K. , Gregory J. E. , Proske U. 
Published: September 2010

We report here observations on the effects of muscle contraction history on thresholds for the detection of movements at the elbow joint of human subjects. Detection thresholds were measured in the direction of flexion or extension to movements of the relaxed forearm at a speed of 0.2 deg s−1 with the elbow at 90 deg.
As reported previously, thresholds for movements in the direction of extension were lower than in the direction of flexion after a conditioning co‐contraction of elbow muscles with the arm flexed by 30 deg from its mid‐position (hold‐short). After a co‐contraction with the arm held extended by 30 deg (hold‐long), thresholds were lower in the direction of flexion.
Here we have made two additional observations. Thresholds for movements of the passive forearm after a co‐contraction at the 90 deg test position (hold‐test) were low, both in the direction of flexion and extension. Secondly, when thresholds were measured while subjects were carrying out a co‐contraction of forearm muscles (15‐20 % maximum voluntary contraction), thresholds were much higher.
It is concluded that muscle contraction history is an important factor to consider when making measurements of movement thresholds at the relaxed elbow joint. It is speculated that during an active contraction increases in muscle spindle discharges evoked by fusimotor activity lead to the rise in movement detection threshold.
SOME EFFECTS OF SPINAL CORD LESIONS ON EXPERIENCED EMOTIONAL FEELINGS
Authors: Hohmann George W. 
Published: September 2010

ABSTRACTIn structured interviews, 26 adult males with spinal cord lesions at varying levels were asked to compare certain of their emotional feelings before and after injury. The investigator, himself a paraplegic, knew all subjects well. The major findings follow.

Significant decreases in experienced feelings of anger, sexual excitement, fear, and an over‐all estimate of change were found.
A significant increase in feelings of sentimentality was reported.
Although spinal cord lesions decrease some emotional feelings, overt emotional behavior may continue to be displayed.
Support was offered for the belief that disruption of the autonomic nervous system and its afferent return causes notable changes in experienced emotional feelings. A trend was noted which suggests that the more extensive the disruption, the greater the decrease in some emotional feelings.
AFFECT, VERBALIZATION, AND DIRECTIONAL FRACTIONATION OF AUTONOMIC RESPONSES
Authors: Campos Joseph J. , Johnson Harold J. 
Published: September 2010

ABSTRACTAn experiment was designed to evaluate the effects of pleasantness and un‐pleasantness and instructions to verbalize on directional fractionation of autonomic response. Degrees of pleasant and unpleasant stimulation were presented to Ss under two verbalization instruction conditions. Something like directional fractionation was found for the very unpleasant no‐verbalization condition only, but the pattern disappeared upon the addition of a later‐verbalization requirement. More generally, it was found without exception that conditions of no verbalization are accompanied by cardiac deceleration, regardless of degree or of quality of affect, while later verbalization conditions produce cardiac acceleration, again regardless of degree or quality of affect. The authors conclude that verbalization instructions are important for determining the degree and direction of cardiac activation.
CONDITIONING OF THE ELECTRODERMAL ORIENTING RESPONSE
Authors: Gale Elliot N. , Stern John A. 
Published: September 2010

ABSTRACTThe present study demonstrates that the orienting response (OR) to the conditional stimulus can be conditioned with a delayed differential conditioning paradigm. Controls utilized were two “sensitization” and one backward‐trace differential conditioning group. Conditioned ORs, conditioned anticipatory responses, and conditioned responses at latency of unconditioned response in the absence of the unconditioned stimulus were all demonstrated. In the backward conditioning group the amplitude of the OR to the tone preceded by shock was lower than that found for any other group. Refractoriness of the peripheral components of the electrodermal response (EDR) are invoked to account for this finding.
Concomitant Heart Rate and Eyeblink Pavlovian Conditioning in Human Subjects as a Function of Interstimulus Interval
Authors: Prescott Louisa , Durkin Martin , Furchtgott Ernest , Powell D.A. 
Published: September 2010

ABSTRACTPavlovian heart rate and eyeblink conditioning were simultaneously assessed in human subjects. Tone durations of 0.6, 1.1, and 2.1 s were employed in separate groups of subjects as the conditioned stimulus. A 100‐ms corneal airpuff, which served as the unconditioned stimulus, overlapped the last 100 ms of the tone in each group, thus producing interstimulus intervals of 0.5, 1.0, and 2.0 s. Other groups of pseudoconditioning subjects received explicitly unpaired tone and airpuff presentations of identical durations but in a pseudorandom sequence so that they never occurred together. The best eyeblink conditioning was observed in the group with the .5‐s interstimulus interval, although the 1.0‐s group also demonstrated some evidence of eyeblink conditioning. The group with the 2.0‐s interstimulus interval showed a lower overall rate of conditioned response occurrence and the highest rate of pseudoconditioned responding. The conditioned heart rate response in all three conditioning groups consisted of cardiac decelerations, but tone‐evoked cardiac accelerations were observed in the pseudoconditioning groups. The magnitude of the cardiac deceleration was comparable in all three conditioning groups.
Cardiac Autonomic Mechanisms Associated with Borderline Hypertension under Varying Behavioral Demands: Evidence for Attenuated Parasympathetic Tone but Not for Enhanced Beta‐Adrenergic Activity
Authors: Grossman Paul , Brinkman Annemiek , De Vries Johan 
Published: September 2010

ABSTRACTElevated blood pressure in psychophysiological studies of borderline hypertension is frequently attributed to the effects of increased sympathetic tone, and with few exceptions, the potential parasympathetic contributions have not been considered. Furthermore, of the investigations that have addressed vagal influences upon blood pressure, most have employed invasive pharmacological assessment of parasympathetic tone.In this study, cardiac parasympathetic and beta‐adrenergic influences in borderline hypertension were evaluated noninvasively employing respiratory sinus arrhythmia as a vagal index and pree‐jection period as a sympathetic index of cardiac functioning. Subjects were 30 borderline hypertensive and 23 normotensive males (age range, 24–45 years). The ECG, blood pressure, impedance cardiography, and respiration were measured during two baselines (initial and post‐task), a memory‐comparison reaction time task, the cold pressor, and CO2‐rebreathing.Results indicated tonic differences between groups in all cardiovascular variables across tasks, with the exception of pre‐ejection period, which showed no group effects at all. Hypertensives additionally manifested somewhat heightened systolic blood pressure reactivity and attenuated cardiac parasympathetic responsivity to specific tasks.Our findings provide no support for an exaggerated cardiac beta‐adrenergic tonic level or reactivity in borderline hypertensives. On the other hand, the consistently lower magnitude of respiratory sinus arrhythmia in our hypertensives suggests that reduced parasympathetic control may be involved in the pathophysiology of hypertension.
Analysis of Pattern‐Reversal Visual Evoked‐Potential Topography: Replicability in Normal Subjects and Comparisons with Alzheimer's Disease
Authors: Pollock Vicki E. , Cliff Norman 
Published: September 2010

ABSTRACTThis paper reports two studies using multivariate analysis to aid the interpretation of crosscoherence of multiple electrode sites in evoked potential responses. In the first study, the replicability of principal components and multidimensional scaling was evaluated by applying both methods to pattern‐reversal visual evoked potentials recorded from 28 scalp sites in two subgroups of sex‐ and age‐matched healthy subjects, and then comparing the results. Four dimensions replicated in the two initial multidimensional scaling solutions and appeared to reflect differences in: 1) anterior versus posterior scalp areas, 2) laterality, 3) separation of frontal and occipital sites from other scalp regions, and 4) proximal versus distal placements. The initial principal components did not match well in the two groups, but rotation to congruence improved their replicability and ultimately yielded axes similar to those of the multidimensional scaling dimensions. In the second study, Alzheimer's disease and sex‐ and age‐matched control subjects were evaluated. The four axes identified were the same as those described above, but after the solutions were rotated to align them, the group differences appeared negligible. Examination of the components and dimensions from both studies showed some consistent departures from being merely reflectors of site location, and the apparently visual dimension appeared clearly in all four groups. Judged on the basis of initial interpretability and replicability of the solutions, the results suggest that multidimensional scaling, with appropriate transformation, may provide an effective tool for analyzing pattern‐reversal visual evoked‐potential topography.
The association between lithium carbonate and smooth pursuit eye tracking among first‐episode patients with psychotic affective disorders
Authors: GOODING DIANE C. , IACONO WILLIAM G. , KATSANIS JOANNA , BEISER MORTON , GROVE WILLIAM M. 
Published: September 2010

AbstractThe association between treatment with lithium carbonate and smooth pursuit eye tracking performance was investigated in first‐episode patients with psychotic affective disorders. The horizontal pursuit performance of patients with major depression and bipolar disorder who were receiving lithium carbonate was contrasted with that of patients not receiving lithium carbonate. In addition, the accuracy and quality of pursuit eye tracking was examined in bipolar patients whose lithium status changed from the time of initial testing to the time of retest 10 months later. For the combined group of depressed and bipolar patients, treatment with lithium carbonate was not associated with worse pursuit performance. Bipolar disordered patients on lithium did not differ in tracking proficiency from those not on lithium; bipolar patients whose lithium status changed from intake to retest also did not display a significant change in pursuit performance.
Effects of response conflict on pain‐evoked medial prefrontal cortex activity
Authors: Dowman Robert , Glebus Geoffery , Shinners Lindsay 
Published: September 2010

AbstractExperimental studies of pain may introduce a response conflict, where the subject must inhibit an escape response and make a pain‐rating response. Several lines of evidence have shown that the medial prefrontal cortex is activated by painful stimuli and by response conflict. It is not clear, however, to what extent pain‐evoked medial prefrontal cortex activation reflects response conflict. We examined this question using the Simon task. The participants identified pain threshold and moderately painful target stimuli presented to the left or right sural nerves using their left or right hands. Response conflict occurred when the response was made with the hand contralateral to the target stimulus. The results suggest that pain‐evoked medial prefrontal cortex activity occurring 70 to 190 ms poststimulus, as estimated from the sural nerve somatosensory evoked potential, is not involved in response conflict.
How competent are consumers? The case of the energy sector in France
Authors: Bonnemaizon Audrey , Batat Wided 
Published: September 2010

AbstractThis paper discussed the notion of value co‐creation and the concept of customer competence as suggested by this notion. This led us to consider the competent customer as a social construction related to managerial representations. In order to examine this issue, a longitudinal exploratory research based on participant observation and in‐depth interviews with employees of a French energy supplier was conducted to explore whether customers are perceived as competent or incompetent market actors. The data analysis revealed four categories illustrating customers' profiles coping with the new situation of the ‘Utility X’ group in the energy sector. ‘Utility X’ employees define their customers according to four profiles: myopic, ignorant, uncreative and organizer of company resources. Even if the marketing studies that share the Service‐Dominant Logic point‐of‐view suggest that the customer would be competent at all times, our findings showed that customer competencies are in fact socially constructed and emerge partially from managerial representations. Therefore, the adoption by companies of a marketing philosophy (‘market with’ philosophy), in which the customer and supply chain partners are collaborators in the entire marketing process, seems only possible if they recognize customers' competencies and identify situations when customers do not activate their competencies or do not have the resources that enable them to develop their competencies.