bluuebunny/crossref_metadata_2025 huggingface dataset:
A Longitudinal Study of Workspace Design for Knowledge Exploration and Exploitation in the Research and Development Process
Authors: Coradi Annina , Heinzen Mareike , Boutellier Roman
Published: December 2014

In order to leverage organizational learning, scholars have already defined but are still discussing the interpretation of two different learning types, exploration and exploitation. Exploring new frontiers across knowledge domains and maintaining the balance with exploiting the existing knowledge is critical for the prosperity of an organization. The spatial dimension of organizational learning considers that proximity of employees has an influence on their learning activities, but from a rather macro perspective without taking workspace design into account. We account for these issues by examining the impact of workspace design on knowledge exploration and exploitation on the micro level at distinct stages along the value chain (i.e., the research, development and project market team unit) of Novartis, a pharmaceutical company. In a longitudinal study, employees of the three cases have been interviewed and observed over the course of three years, before and after workspace redesign. With the change from a cellular to an open workspace, employees become closer and highly visible to each other, which influences knowledge work. As the cases occurred sequentially in time, design principles were derived. The findings suggest that exploitation is supported by workspace design that leads to high proximity inducing faster feedback cycles and first‐hand information. Exploration, however, is supported by workspace design that leads to high visibility triggering more cross‐functional interactions and thereby the variability of knowledge. The later the stage in the research and development process, the higher the need for balanced learning activities. This balance is well reflected in a ‘multi‐space’ workspace consisting of shared meeting areas, quiet zones, central staircases and integrated laboratories and desk areas.
Extreme weather conditions correspond with localised vegetation death at Cradle Mountain, Tasmania
Authors: Visoiu Micah , Whinam Jennie
Published: December 2014

A chance observation of a drought‐related plant mortality event in early 2014 in a normally wet and cool alpine area was matched with local weather data providing a unique insight into this event. The observed plant death was largely indiscriminate in areas that were topographically predisposed to being susceptible to drought. The weather conditions surrounding this event included 5 weeks with very little rain, an extreme heatwave and subsequent brief periods where warm temperatures and dry air combined to produce highly evaporative conditions. Extreme weather conditions such as this are expected to occur with increasing frequency as a result of climate change. Observing and reporting on real‐world examples of how extreme weather events affect native vegetation is integral to improved climate change risk assessment and to inform future management actions.
African histoplasmosis: the first report of an indigenous case in India
Authors: Ravindran Sheeba , Sobhanakumari Kunjumani , Celine Machiyanickel , Palakkal Seena
Published: December 2014

Objectives

African histoplasmosis, caused by Histoplasma capsulatum var. duboisii, is an invasive fungal infection endemic in Central and West Africa. Cases seen outside Africa are generally imported. We report a disseminated purely cutaneous form of this infection in an otherwise healthy person from Kerala, in southern India.

Methods

A 59‐year‐old farmer presented with asymptomatic, generalized, reddish skin lesions of five months in duration. Dermatologic examination revealed multiple erythematous papules and plaques of varying sizes, predominantly over the trunk and upper limbs. The patient was otherwise in good health. Systemic examination including the pulmonary and musculoskeletal systems revealed no abnormalities.

Results

Skin biopsy was performed from a lesion on the thigh. Histopathologic examination revealed epithelioid and suppurative granulomas in the upper dermis, with lymphocytes, neutrophils, and plenty of giant cells. Fite–Faraco staining for Mycobacterium leprae was negative. Fungus cultured from the specimen was identified as H. capsulatum var. duboisii, the rarer variant of H. capsulatum. The patient was treated with ketoconazole 200 mg/day for four months and attained complete clearance. No relapse has been detected over two years of follow‐up.

Conclusions

To the best of our knowledge, this case represents the first instance of African histoplasmosis to be reported from India. The occurrence of such a rare infection in an immunocompetent individual, who had not travelled elsewhere, raises the possibility of the indigenous existence of H. capsulatum var. duboisii in Kerala. Further studies of the ecology and epidemiology of this rare infection are essential.
Sleep duration and associated factors in a community sample of elderly individuals in Korea
Authors: Kim Won‐Hyoung , Kim Byung‐Soo , Kim Shin‐Kyum , Chang Sung‐Man , Lee Dong‐Woo , Cho Maeng‐Je , Bae Jae‐Nam
Published: December 2014

Background

This study estimates the duration of sleep and its relationships with clinical correlates in a community sample of elderly individuals in Korea.

Methods

A total of 1924 individuals aged 65 and over were interviewed in Korea. Sleep durations were classified into five categories: 5.00 h or less, 6.00 h per day, 7.00 h per day, 8.00 h per day, and 9.00 h or more per day. Sleep disturbance was classified into four sleep complaints: difficulty initiating sleep, difficulty maintaining sleep, early‐morning awakening, and non‐restorative sleep. The Mini‐Mental Status Examination, the Geriatric Depression Scale, and questionnaires about the presence of cardiovascular disease were employed.

Results

The most frequent self‐reported sleep duration was 7.00 h. The mean sleep duration was 6.46 h. Female subjects, subjects between the ages of 75 and 79, and subjects with current depression were associated with sleeping for 6.00 h or less or 9.00 h or more. Subjects who lived alone and those with cardiovascular disease were associated with sleeping for 5.00 h or less. Subjects aged 80 and over, formally educated subjects, current smokers, and subjects with cognitive dysfunction were associated with sleeping for 9.00 h or more. Sleep disturbances according to sleep duration has a U‐shaped distribution. We found that all sleep disturbances were significantly related to sleep durations of 6.00 h or less compared to sleep durations of 7.00 h. We also found that non‐restorative sleep was significantly related to sleep durations of 8.00 h or more compared to sleep durations of 7.00 h.

Conclusion

A relatively high prevalence of short or long sleep duration was identified. Various sociodemographic variables influenced sleep duration. Depression, cognitive dysfunction, and cardiovascular disease were associated with short or long sleep duration. Careful attention should be paid to the health of elderly individuals who are short or long sleepers.
STUDIES IN THE PHYSIOLOGY OF THE NERVOUS SYSTEM. VIII. NEURAL BALANCE AND REFLEX REVERSAL, WITH A NOTE ON PROGRESSION IN THE DECEREBRATE GUINEA‐PIG
Authors: Brown T. Graham
Published: December 2014

1. In the normal guinea‐pig there is sometimes a dilemma of reaction in the act of the hind limb in response to mechanical stimulation of the femoral fold of skin.

2. The reaction is sometimes one of flexion and sometimes one of extension. The determining factor seems to be the assumption of an active posture. If the active posture is flexion the reaction is more likely to be flexion; if it is extension the reaction will most likely be extension.

3. Amongst the methods of procuring these active postures of peculiar interest are passive bendings of the neck.

4. This reversal of reflex action may be obtained after the complete removal of both cerebral hemispheres. It may therefore take place in the absence of cortical disturbing factors.

5. The reversal here described seems to differ in its causation from that described by Sherrington, Magnus, and v. Uexküll. To v. Uexküll's rule of reflex reversal—that the stretching of a muscle increases the likelihood that that muscle will contract in cases where a dilemma of reaction is possible—may be added another rule: a stimulus which may throw into activity either of twin antagonistic centres (and depress the activity of the other) will tend to activate that which at the time is already in a state of relatively raised activity.

6. Besides this transient reversal by means of the assumption of an active posture there is described in this paper a more permanent tilting of the central balance. This is seen after removal of the cortex on one side—as has been described in a previous paper. In general, flexion reactions are made more likely on the side of the cortical lesion, and extension reactions upon the other side. This is seen even more markedly after section of one crus cerebri—when the posture of the body becomes asymmetrical.

7. To explain these phenomena it may be supposed that one cortex, or cerebral hemisphere, exercises opposite influences on the centres situated on different sides of the body. When both hemispheres are removed, or the cortex is removed on both sides, the tilting of the central balance seems to be in the direction of extension on both sides of the body. This phenomenon may be explained by supposing that the cortical, or cerebral, influence of one side more than counterbalances the antagonistic influence from the cortex, or hemisphere, of the other side.

8. In general it may be supposed that the activity and the reflex excitability of a centre—or of a pair of antagonistic centres—go hand in hand, and that they are the resultant of innumerable excitatory and inhibitory influences which continually play upon the centre. This resultant may be termed the “neural balance.” The central balance may be tilted for a time in one direction by the temporary preponderance of one of the influences which play upon it. And it may be permanently upset by a permanent alteration in the value of the influences which compose the balance.
THE EFFECT OF TEMPERATURE ON BLOOD COAGULATION TIME
Authors: Simpson Sutherland , Rasmussen A. T.
Published: December 2014

In the dog variation in the temperature of the blood, before it is withdrawn from the artery, between the limits of 25° C. and 45·1° C., does not appear to affect its coagulation time provided it is kept at a constant (25° C.) temperature afterwards.

Prolonged etherisation does not affect the coagulation time appreciably.

Changes in the temperature of the blood, after it is withdrawn from the body, produce a marked affect on its coagulation time. From 10° C. to about 40° C. the time is shortened as the temperature rises, and beyond this from 40° C. upwards, it is lengthened. At 55° C. or 56° C. the blood does not coagulate at all.
EXPERIMENTAL MODIFICATION OF THE ACCESSORY SEXUAL APPARATUS IN THE HEN
Authors: Greenwood Alan W. , Blyth J. S. S.
Published: December 2014

1. Peculiarities of form and function in the accessory sexual apparatus of a number of experimental pullets, derived from eggs injected with œstrone at an early stage of incubation, are described and discussed.

2. Only one of a group of 6 females laid normal eggs when sexually mature, the remainder producing eggs devoid of shell or lacking both shell and egg membranes. This phenomenon is ascribed to an abnormality of the oviduct.

3. All the experimental birds autopsied possessed two oviducts which showed incomplete development both as regards total length and length of component parts.

4. The total weight of the two ducts approximated that of the single left oviduct in the normal hen.

5. It is suggested that either the œstrone injection to the egg interfered with the normal processes of differentiation of the mullerian duct into the sex duct in the embryo, rendering it incapable of efficient response to the hormone stimulus subsequently supplied by the functional ovary of the individual, or that the normal level of secretion of female hormone by the fowl's ovary is sufficient only for the complete development of a single duct.
THE EFFECT OF REMOVAL OF THE POSTERIOR LOBE OF THE PITUITARY ON THE INHIBITION OF WATER‐DIURESIS BY EMOTIONAL STRESS
Authors: O'Connor W. J. , Verney E. B.
Published: December 2014

1. The inhibition of water‐diuresis by emotional stress in the dog is largely reduced after removal of the posterior lobe of the pituitary body.

2. Consideration is given to the method of assaying the post‐pituitary antidiuretic hormone by intravenous injection during water‐diuresis.

3. Comparison of the post‐pituitary extract equivalent of the emotional inhibition before, with that after, removal of the posterior lobe shows that only about 5 per cent. of the antidiuretic function of the neuro‐hypophysis, as expressed in the inhibition by emotional stress, remains when the posterior lobe has been removed.

4. This residuum of function is apparently adequate to constrain the output of urine within normal limits.

5. The bearing of these results on the neuro‐hypophyseal control of water‐excretion is discussed.

Grateful acknowledgment is made to the Government Grant Committee of the Royal Society for defraying part of the expenses incurred in this work.
THE ANTIDIURETIC ACTION OF MORPHINE: ITS SITE AND MODE OF ACTION IN THE HYPOTHALAMUS OF THE DOG
Authors: Duke H. N. , Pickford M. , Watt J. A.
Published: December 2014

1. Observations made on dogs show that morphine sulphate administered during the course of a water diuresis is antidiuretic, whether it is given intravenously (0·08 mg./ kg.) to the unanæsthetized animal, or injected into the supraoptic nuclei (4‐32 ug.) under chloralose ancesthesia.

2. After section of the supraoptic tracts the injection of morphine sulphate intravenously into the unanæsthetized dog does not cause antidiuresis.

3. The release of adrenaline from the suprarenal medulla is not a factor in the antidiuretic action of morphine.

4. In unanæsthetized dogs into whose supraoptic nuclei DFP has previously been injected, the intravenous administration of morphine sulphate consistently causes an inhibition of the rate of urine flow.

5. Acute tolerance of the antidiuretic response to morphine is not seen on giving two or three small doses in the course of a few hours.

6. Consideration of the results leads to the conclusion that morphine induces antidiuresis by a direct effect on the supraoptic cells, causing the release of the antidiuretic hormone of the posterior lobe of the pituitary. This effect of morphine is unrelated to cholinesterase.
The contribution of the ‘pacemaker’ current (if) to generation of spontaneous activity in rabbit sino‐atrial node myocytes.
Authors: DiFrancesco D
Published: December 2014

1. The contribution to the diastolic depolarization of the hyperpolarization‐activated current, if, relative to other components was investigated in isolated rabbit sino‐atrial (SA) node myocytes. 2. During the diastolic phase the membrane potential depolarized by 0.1096 +/‐ 0.014 V/s, which requires only about 3 pA of inward current in a cell with an average capacity of 30 pF. The problem of which ionic component is responsible for initiating the diastolic depolarization was investigated by analysing the composition and the properties of the net inward current in the diastolic range of voltages. 3. The measured instantaneous ‘background’ current activated during voltage clamp steps from a holding potential of ‐35 mV was outward positive to approximately ‐61 mV, and had a region of negative slope conductance from ‐45 to ‐35 mV. 4. The instantaneous component lost its rectifying behaviour in the presence of Ni2+ (100 microM) and nitrendipine (10 microM). These blockers of Ca(2+)‐dependent currents modified the instantaneous I‐V relation at voltages positive to ‐45 to ‐50 mV, thus implying that Ca2+ currents become important at less negative potentials than ‐50 mV, towards the very end of diastolic depolarization. 5. Possible errors introduced by voltage clamp analysis with the whole‐cell method on the instantaneous current and on if measurement were evaluated. Leakage through the seal resistance caused the instantaneous I‐V relation to be displaced in the inward direction at negative voltages. Correction for the seal leakage moved the reversal potential for the instantaneous current toward the negative direction from ‐61 to approximately ‐66 mV. Thus, no depolarization can be driven by the background current beyond ‐66 mV. 6. During voltage clamp analysis, lack of series‐resistance compensation led to lack of intracellular voltage control, as was apparent using a second pipette on the same cell. This slowed activation of if and led to a 1.5‐ to 2‐fold reduction of if size in the range ‐55 to ‐115 mV. Thus, uncorrected measurements of the instantaneous component and of if may concur to underestimate the role of if in pacemaking. 7. These results lead to the conclusion that in the SA node cells analysed, pacemaker activity is generated with the essential contribution of the hyperpolarization‐activated current, if. Numerical computation of SA node cell activity using an extension of the DiFrancesco‐Noble model shows that the if‐activation hypothesis can account for the presence of spontaneous action potentials and their sensitivity to if changes.
Substrates for muscle glycogen synthesis in recovery from intense exercise in man.
Authors: Bangsbo J , Gollnick P D , Graham T E , Saltin B
Published: December 2014

1. Intramuscular glyconeogenesis from lactate after intense exercise was examined by using the one‐legged knee extension model which enables evaluation of metabolism in a well‐defined muscle group. 2. In seven subjects measurements of leg blood flow and arterial‐venous differences of various substrates were performed in individuals after intense, exhaustive knee extensor exercise lasting 3.0 min. Muscle glycogen and lactate concentrations were determined in the quadriceps muscle immediately after exercise and three times during 1 h of recovery. 3. Muscle glycogen increased from 93.7 +/‐ 6.7 (+/‐ S.E.M.) to 108.8 +/‐ 8.1 mmol (kg wet wt)‐1 during the recovery period. Muscle lactate was 27.1 +/‐ 2.1 mmol (kg wet wt)‐1 at the end of exercise and decreased to 14.5 +/‐ 2.1, 6.7 +/‐ 1.1, and 3.0 +/‐ 0.5 mmol (kg wet wt)‐1 after 3, 10 and 60 min of recovery, respectively. 4. More than two‐thirds of the lactate that accumulated in the muscle during the intense exercise was released into the blood. It was estimated that between 13 and 27% of the lactate could have been converted to glycogen. This corresponded to a glycogen resynthesis rate from lactate of 0.17‐0.34 and 0.002 mmol glucosyl units min‐1 (kg wet wt)‐1 for the first 10 and last 50 min of recovery, respectively. 5. The O2 debt of the leg was 1.5 l of which the resynthesis of ATP, creatine phosphate (CP) and glycogen and reloading of haemoglobin (Hb) and myoglobin (Mb) only could account for one‐third. It is proposed that the elevated oxygen uptake during recovery is linked to the metabolic use of intramuscular triacylglycerol.
Effects of low ionic strength media on passive human red cell monovalent cation transport.
Authors: Bernhardt I , Hall A C , Ellory J C
Published: December 2014

1. The effect of low ionic strength media on the residual, i.e. (ouabain + bumetanide + Ca2+)‐insensitive, K+ influx was characterized in human red blood cells. 2. This K+ flux was enhanced significantly in isotonic solutions of low ionic strength using sucrose to maintain constant osmolarity. This effect was found for fresh red blood cells as well as for stored (bank) red blood cells. However, the absolute magnitude of K+ influx in solutions of low ionic strength was halved for stored red blood cells. 3. Anion replacement of Cl‐ by CH3SO4‐ did not affect residual K+ fluxes, showing that Cl‐ ‐dependent transport pathways (e.g. the KCl co‐transporter) are not involved in the low ionic strength effect. 4. The enhanced K+ influx in low ionic strength media was reversible when the cells were resuspended in a solution of physiological ionic strength. 5. K+ influx measured in light and dense fractions of erythrocytes (separated by centrifugation and corresponding to samples enriched with either ‘young’ or ‘mature’ red cells) showed that the low ionic strength effect does not change markedly with cell age. 6. Low ionic strength media elevated residual, i.e. (ouabain + bumetanide + Ca2+)‐insensitive, influx of both K+ and Na+ by about the same amount. In both cases the flux was linear with concentration in the range investigated (0.25‐10 mM). No significant increase in the uptake of the cations Ca2+ and lysine in low ionic strength solutions could be found. 7. In CH3SO4‐ ‐containing solutions of physiological ionic strength the residual K+ influx was almost independent of cell volume, whereas this flux in CH3SO4‐ ‐containing solutions of low ionic strength declined as cell volume was increased. 8. K+ flux measurements in solutions of different external pH, where NaCl was replaced by sodium gluconate or sodium glucuronate, showed that the reduced ionic strength is of more importance for the enhanced residual K+ influx than the changed transmembrane potential or the changed intracellular pH. However, a small pH dependence could be found, the K+ flux passing through a minimum around pHi 7.3. 9. Hydrostatic pressure enhanced the residual K+ flux in media of low ionic strength synergistically, so that very large fluxes (greater than 10 mmol (1 cells)‐1 h‐1) were obtained at 40 MPa. The apparent activation volumes (delta V*) for the pressure‐sensitive K+ flux were ‐108 and ‐69 ml mol‐1 in low ionic strength or physiological ionic strength solutions respectively.(ABSTRACT TRUNCATED AT 400 WORDS)
Role of the anomalous rectifier in determining membrane potentials of mouse muscle fibres at low extracellular K+.
Authors: Siegenbeek van Heukelom J
Published: December 2014

1. The membrane potential (Vm) of fibres of the extensor digitorum longus (EDL) of the mouse, measured at 35 degrees C and with extracellular potassium concentration (K+o) 5.7 mM, was Vm = ‐76 mV. 2. Lowering K+o below 1 mM could lead to either a hyperpolarizing or a depolarizing response. When Vm was lower than ‐75.5 mV in the control medium, a reduction of K+o to 0.76 mM led to a hyperpolarization of Vm (‐95.0 +/‐ 0.7 mV, n = 40); otherwise a depolarization occurred (Vm = ‐47.2 +/‐ 1.1 mV, n = 21). 3. The difference in Vm responses did not correlate consistently with functional differences in cell types, as cells that originally hyperpolarized, could later depolarize. 4. The observed phenomena could be explained if the properties of the anomalous rectifier, AR (or inward‐going rectifier), are considered to be similar to those observed in cardiac cells. 5. Apparently caesium acted as a competitive inhibitor; when the inhibition was strong enough the non‐linear properties of the AR regeneratively amplified the depolarization to the full‐blown depolarized state (Vm = ‐46.7 +/‐ 1.3 mV, n = 15). 6. Ouabain (10(‐4) M) reduced Vm (to ‐45 +/‐ 3 mV, n = 5) and reduced dramatically the selectivity of the cell membrane for potassium over sodium. These effects could be reversed readily by washing out the ouabain. 7. Adrenaline (2 microM) added to the medium hyperpolarized Vm (delta Vm = ‐4.6 +/‐ 1.4 mV, n = 9) and increased the changes induced by lowered K+o (from ‐14.3 +/‐ 0.5 mV, n = 5 to ‐18.0 +/‐ 0.8 mV, n = 9); the cells that originally depolarized when K+o was lowered could hyperpolarize after adrenaline addition.
Cytosolic pH regulates maxi K+ channels in Necturus gall‐bladder epithelial cells.
Authors: Copello J , Segal Y , Reuss L
Published: December 2014

1. The patch clamp technique was used to study the effects of internal and external pH on the Ca(2+)‐ and voltage‐activated maxi K+ channel present in the apical membrane of Necturus gall‐bladder epithelial cells. 2. When the pH of the solution bathing the cytosolic side of inside‐out patches (pHi) was lowered from 7.9 to 6.9, with internal free Ca2+ concentration ([Ca2+]i) buffered below saturation levels for the channel gating sites, channel open probability (Po) decreased. At saturating Ca2+ concentrations, Po was near 1.0, and unaffected by pHi. The results are consistent with a competitive interaction between Ca2+ and H+ at regulatory binding sites. Kinetic analysis assuming competitive binding yields a Hill coefficient for H+ of 1.3. 3. At sub‐maximal [Ca2+]i, changing the pH of the solution bathing the extracellular surface of the patch (pHo) between 8 and 7, had no effect on maxi K+ channel Po, but lowering pHo to 6 or 5 significantly reduced Po. At saturating [Ca2+]i, Po was independent of pHo. 4. There were no effects of either pHi or pHo on single‐channel conductance. 5. Inasmuch as reductions in either pHo or pHi decrease maxi K+ channel Po, changes in maxi K+ channel activity account in part for the reduction of apical membrane K+ conductance elicited by acidification of the bathing medium. The dominant effect of pH on maxi K+ channels is on the cytosolic surface of the membrane. 6. The change in Po elicited by small changes in [H+]i (delta Po/delta [H+]i) is ‐7.6 microM‐1, compared to delta Po/delta [Ca2+]i = 2.6 microM‐1, both at Vm = ‐30 mV and at physiological intracellular [H+] and [Ca2+]. This implies that [H+]i and [Ca2+]i have opposite effects on channel Po at physiological levels and underlines the importance of pHi in channel gating.
Inactivation of calcium currents in granule cells cultured from mouse cerebellum.
Authors: Slesinger P A , Lansman J B
Published: December 2014

1. Cells dissociated from mouse cerebellum were grown in vitro. Ca2+ channel currents were recorded from granule cells with the patch‐clamp technique under conditions which suppressed currents through Na+ and K+ channels and minimized run‐down of current through Ca2+ channels. 2. A strong depolarizing voltage step from a hyperpolarized holding potential produced inward Ca2+ channel current that decayed exponentially to a non‐zero level. Inward current decayed to approximately 40% of its peak amplitude (range 20‐90%). 3. The inward current increased in amplitude when Ca2+ was replaced with Ba2+ or after raising the concentration of extracellular Ba2+, but the rate of decay of current was unaffected. 4. The current‐voltage (I‐V) relation showed that peak or sustained current increased with voltage pulses more positive than approximately ‐30 mV, reached a maximum amplitude near +20 mV and became progressively smaller with larger depolarizations. 5. The tail currents produced after rapidly repolarizing the membrane potential to ‐70 mV from a positive test pulse decayed along a single exponential time course with a time constant of approximately 0.5 ms. The amplitude of tail current measured at a fixed repolarization potential increased as the pre‐pulse was made more positive and reached a maximum with pre‐pulses more positive than +40 mV. A plot of normalized amplitude of the tail current as a function of the pre‐pulse potential was fitted with a Boltzmann relation with V1/2 = approximately + 8 mV and steepness k = 14 mV. 6. Shifting the holding potential to more positive potentials reduced the amplitude of the Ca2+ channel current elicited by the fixed voltage step and abolished the decay of the inward current. The peak current was normalized to the maximum peak current elicited from a very negative holding potential and plotted as a function of holding potential. The points were fitted with a Boltzmann relation for inactivation with V1/2 = approximately ‐57 mV and steepness k = 14 mV. 7. The onset of inactivation was studied in two‐pulse experiments in which the duration of conditioning pre‐pulse was varied. Increasing the duration of a pre‐pulse to a fixed potential reduced the peak inward current evoked by the second test pulse. Plotting normalized current as a function of pre‐pulse duration showed that inactivation developed along a double exponential time course. Both fast and slow time constants decreased as the pre‐pulse potential was made more positive.(ABSTRACT TRUNCATED AT 400 WORDS)
Differential connections by intracortical axon collaterals among pyramidal tract cells in the cat motor cortex.
Authors: Kang Y , Endo K , Araki T
Published: December 2014

1. Recurrent EPSPs were produced in fast pyramidal tract (PT) cells in the cat motor cortex by stimulation of the medullary pyramid and/or by the glutamate‐induced activity of neighbouring PT cells using the spike‐triggered averaging (spike‐TA) method. 2. In fast PT cells located lateral to the end of the cruciate sulcus, predominantly the motor cortical representation area of the distal forelimb, two components (fast and slow) of recurrent EPSPs were produced by pyramid stimulation. 3. In response to pyramid stimulation, the appearance of the fast and slow components of recurrent EPSPs correlated with the appearance of N1 and N2 field potentials, respectively. 4. The monosynaptic nature of both the fast and slow components of recurrent EPSPs was demonstrated by a double shock test (interstimulus interval less than 5 ms) and high frequency repetitive stimulation (50‐100 Hz). 5. The generation of the fast and slow components of recurrent EPSPs was attributed to the synaptic action of recurrent collaterals of fast and slow PT cells, respectively. 6. The amplitude of the slow component of recurrent EPSPs markedly increased with an increase in the stimulus frequency whereas that of the fast component did not, despite the change in stimulus frequency. 7. Selected spike‐triggered averaging also revealed frequency facilitation of recurrent individual EPSPs produced in fast PT cells by the activity of single slow PT cells. 8. In fast PT cells located in the anterior and posterior lips of the cruciate sulcus, the motor cortical representation area of the proximal limb or trunk, only the slow component of recurrent EPSPs was produced by pyramid stimulation. 9. It is concluded that the pattern of recurrent connections between neighbouring PT cells differs depending on the motor cortical representation area, and that frequency facilitation of recurrent EPSPs is caused mainly by the input from axon collaterals of slow PT cells.
Effects of Mg2+ on basal and beta‐adrenergic‐stimulated delayed rectifier potassium current in frog atrial myocytes.
Authors: Duchatelle‐Gourdon I , Lagrutta A A , Hartzell H C
Published: December 2014

1. The effects of internal Mg2+ ions on the delayed rectifier potassium current (IK) of bull‐frog atrial myocytes were studied using the whole‐cell configuration of the patch‐clamp technique with a perfusable patch electrode. 2. Initial variations in IK amplitude were dependent on [Mg2+]i. With [Mg2+] greater than 1 mM, the amplitude of IK usually decreased after initiating the whole‐cell recording configuration (run‐down); with [Mg2+]i less than 1 mM, IK usually increased (run‐up). Mg2+ blocked IK with an apparent half‐maximal effect of 0.6 mM [Mg2+]i. 3. The basal free [Mg2+]i, indicated by the amplitude of IK before run‐up or run‐down, was estimated from the relationship between [Mg2+]i and IK to be 0.8 mM. 4. The amplitude of both the activation curve and the instantaneous voltage‐current relationship was decreased by increasing [Mg2+]i. Under these conditions, the voltage dependence of IK was not affected. 5. The rate of activation of the current at +40 mV was slowed by increasing [Mg2+]i with little effect on the rate of deactivation at ‐50 mV. This is in contrast to the effects of isoprenaline, which speeded activation and slowed deactivation. 6. Isoprenaline increased IK on average by about 2.5 pA/pF, whether IK had previously run down or not, and regardless of [Mg2+]i. The reversibility of isoprenaline was partially inhibited at [Mg2+]i less than 1 mM. 7. It is concluded that Mg2+ affects IK via several mechanisms that might include a Mg(2+)‐dependent phosphatase.
Total and free myoplasmic calcium during a contraction cycle: x‐ray microanalysis in guinea‐pig ventricular myocytes.
Authors: Wendt‐Gallitelli M F , Isenberg G
Published: December 2014

1. At 36 degrees C and 2 mM [Ca2+]o single guinea‐pig ventricular myocytes were voltage clamped with patch electrodes. With a paired‐pulse protocol applied at 1 Hz, a first pulse to +5 mV was followed by a second pulse to +50 mV. When paired pulsing had potentiated the contraction to the maximum, the cells were shock‐frozen for electron‐probe microanalysis (EPMA). Shock‐freezing was timed at the end of diastole (‐80 mV) or at different times during systole (+5 mV). 2. The same paired‐pulse protocol was applied to another group of myocytes from which contraction and [Ca2+]i was estimated by microfluospectroscopy (50 microM‐Na5‐Indo‐1). Potentiation moderately reduced diastolic sarcomere length from 1.85 to 1.82 microns and increased diastolic [Ca2+]i from about 95 to 180 nM. In potentiated cells, during the first pulse, contraction peaked within 128 +/‐ 25 ms after start of depolarization. [Ca2+]i peaked within 25 ms to 890 +/‐ 220 nM (mean +/‐ S.E.M.) and fell within 100 ms to about 450 nM. 3. Sigma Camyo, the total calcium concentration in the overlapping myofilaments (A‐band), was measured by EPMA in seventeen potentiated myocytes. During diastole, sigma Camyo was 2.6 +/‐ 0.4 mmol (kg dry weight (DW]‐1 which can be converted to 0.65 mM (mmoles per litre myofibrillar space). Since [Ca2+]i was 180 nM, we estimate that 99.97% of total calcium is bound. 4. A time course for systolic sigma Camyo was determined by shock‐freezing thirteen cells at different times after start of depolarization to +5 mV. Sigma Camyo was 5.5 +/‐ 0.3 mmol (kg DW)‐1 (1.4 mM) after 15‐25 ms, 4.6 +/‐ 0.5 mmol (kg DW)‐1 (1.1 mM) after 30‐45 ms, and 3.1 mmol (kg DW)‐1 (0.8 mM) after 60‐120 ms. The fast time course of sigma Camyo suggests that calcium binds to and unbinds from troponin C at a fast rate. Hence, it is the slow kinetics of the cross‐bridges that determines the 130 ms time‐to‐peak shortening. 5. Mitochondria of potentiated cells contained during diastole a total calcium concentration, sigma Camito, of 1.3 +/‐ 0.2 mmol (kg DW)‐1 (0.4 mM). During the initial 15‐25 ms of systole, sigma Camito did not change, however, during 30‐45 ms sigma Camito rose to 3.7 +/‐ 0.5 mmol (kg DW)‐1 (1.2 mM). The data suggest that sigma Camito can follow sigma Camyo with some delay, thereby participating in both slow diastolic and fast systolic changes in total calcium (sigma Ca), at least under the given conditions.(ABSTRACT TRUNCATED AT 400 WORDS)
Persistent pulsatile release of glutamate induced by N‐methyl‐D‐aspartate in neonatal rat hippocampal neurones.
Authors: Cherubini E , Ben‐Ari Y , Ito S , Krnjević K
Published: December 2014

1. Intracellular recordings were made from CA3 hippocampal neurones in vitro, during the first ten days of postnatal life and in adulthood. 2. Repeated (three to six) applications of N‐methyl‐D‐aspartate (NMDA), in the presence of tetrodotoxin (TTX, 1‐3 microM) and K+ channel blockers (tetraethylammonium chloride or bromide (TEA), 10 mM, and Cs+, 2 mM; or 4‐aminopyridine (4‐AP), 30‐50 microM, and Cs+, 2 mM) induced in neonatal but not in adult neurones, periodic inward currents (PICs) which persisted for several hours after the last application of NMDA. 3. PICs which were due to non‐specific cation currents had a frequency of 0.10 +/‐ 0.04 Hz, and an amplitude of 1.1 +/‐ 0.28 nA at holding potentials between ‐40 and ‐50 mV. The amplitude was a linear function of the membrane potential over the range ‐70 to +20 mV. They reversed polarity at 4.1 +/‐ 9.8 mV. 4. K+ channel blockers alone failed to induce PICs. Repeated (three to six) brief applications of high (12 mM) K+ medium also induced PICs. The frequency and amplitude of K(+)‐induced PICs were however considerably reduced by concomitant applications of the NMDA receptor antagonist D,L‐3‐[( +/‐ )‐2‐carboxypiperazin‐4‐yl‐]propyl‐1‐phosphonic acid (CPP, 20 microM). PICs could be induced also by caffeine (1 mM) in the presence of the phosphodiesterase inhibitor 3‐isobutyl‐1‐methyl‐xanthine (IBMX, 200 microM), TTX, TEA and Cs+. 5. Intracellular injection of the calcium chelator 1,2‐bis(2‐aminophenoxy)ethane‐N,N,N',N'‐tetraacetic acid (BAPTA) did not prevent the induction of PICs by NMDA. However PICs were blocked by removal of the external calcium and by the calcium antagonists cobalt (2 mM) and cadmium (50 microM). 6. In spite of blockade of propagated synaptic activity by TTX, PICs were synchronous in a pair of intracellularly recorded cells. They were also synchronous with extracellular spikes recorded by electrodes located into stratum pyramidal or stratum radiatum. 7. Once established, PICs were unaffected by NMDA receptor antagonists D(‐)2‐amino‐5‐phosphonovaleric acid (AP‐5, 50 microM), CPP (20 microM) and the NMDA channel blocker ketamine (10 microM). They were reversibly blocked by the broad spectrum excitatory amino acid antagonist kynurenic acid (1 mM) and by the selective non‐NMDA receptor antagonist 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX, 10 microM). 8. It is concluded that PICs are generated in neonatal neurones by a synchronous, pulsatile release of glutamate from presynaptic nerve terminals, secondary to oscillations in intracellular calcium.
The effect of acidosis on the relationship between Ca2+ and force in isolated ferret cardiac muscle.
Authors: Orchard C H , Hamilton D L , Astles P , McCall E , Jewell B R
Published: December 2014

1. The relationship between force and intracellular [Ca2+] (monitored using the protein aequorin) has been investigated in papillary muscles isolated from ferret hearts, under control conditions (superfusate pH (pHo) 7.3) and during acidosis (pHo 6.8). 2. At pHo 7.3, increasing bathing [Ca2+] from 0.5 mmol l‐1 to 8 mmol l‐1 led to an increase in the size of the intracellular calcium transient. At the lower [Ca2+] this was accompanied by an increase in developed force; however, at the higher bathing [Ca2+] developed force reached a plateau. 3. Acidosis (produced by increasing the [CO2] of the gas with which the muscle superfusate was equilibrated) decreased maximum force and shifted the curve relating peak developed force to peak intracellular [Ca2+] to the right. 4. The mechanisms underlying the apparent decrease in the sensitivity of the contractile proteins to Ca2+ were investigated by applying rapid length changes to papillary muscles at control pHo, during acidosis, and after bathing [Ca2+] had been increased to match force during acidosis to that in control. 5. Acidosis decreased the change in force produced in response to a given length change (i.e. decreased muscle stiffness) but when bathing [Ca2+] was increased during acidosis, muscle stiffness returned to control. 6. Acidosis had no effect on muscle stiffness after the induction of rigor in the muscle (produced by metabolic inhibition). 7. It is suggested that in intact cardiac muscle the major effect of a mild acidosis is to decrease the sensitivity of the contractile proteins to Ca2+, hence decreasing the number of bound cross‐bridges.
Actions of n‐alcohols on nicotinic acetylcholine receptor channels in cultured rat myotubes.
Authors: Murrell R D , Braun M S , Haydon D A
Published: December 2014

1. The actions of the n‐alcohols from pentanol to dodecanol on nicotinic acetylcholine receptor (nAChR) channels were investigated by recording single ACh‐activated channel activity from inside‐out membrane patches isolated from cultured rat myotubes. Alcohols were applied to the cytoplasmic side of the membrane; aqueous concentrations ranged from 11.7 mM‐pentanol to 0.02 mM‐dodecanol. 2. The intermediate‐chain alcohols (pentanol to octanol) caused channel currents to fluctuate between the fully open and closed state level so that openings occurred in bursts interrupted by brief gaps. Closed time distributions were fitted well with two exponential components, the fast component representing the closures within a burst. The number of gaps within a burst was dependent on alcohol concentration whereas gap duration was independent of concentration but increased with increasing chain length of the alcohol up to octanol. 3. Nonanol and decanol reduced the mean duration of bursts of openings but did not cause an increase in the number of short closed intervals within a burst. Beyond decanol there was a decline in the ability of the n‐alcohols to affect channel function. A saturated solution of undecanol (0.07 mM) reduced the mean open time by 33 +/‐ 17%, whereas a saturated solution of dodecanol had no significant effect. 4. The current integral per burst was reduced by all the n‐alcohols between pentanol and undecanol. The IC50S were as follows: hexanol, 0.53 +/‐ 0.14 mM; heptanol, 0.097 +/‐ 0.02 mM; octanol, 0.04 mM and nonanol, 0.16 +/‐ 0.035 mM. 5. The results were analysed in terms of an open channel block model with a long‐lived closed‐blocked state beyond the blocked state. Over the range of concentrations tested this describes the effects of all the n‐alcohols (C5 to C12) on channel gating reasonably well. 6. Blocking rate constants (k+B) for pentanol through to nonanol were calculated to be between 2.8 and 5.7 X 10(6) M‐1 S‐1. These values are based on the assumption that the concentration of the alcohols at their site(s) of action was equal to the aqueous concentration applied to the membrane. 7. Equilibrium dissociation constants (KD), calculated from the blocking and unblocking rate constants (KD = k‐B/k+B), decreased with increasing chain length from 8 mM for pentanol to 0.15 mM for octanol. The standard free energy per methylene group for adsorption to the site of action was calculated to be about ‐3.3 kJ mol‐1.(ABSTRACT TRUNCATED AT 400 WORDS)
The effects of metabolism on Na(+)‐K(+)‐Cl‐ co‐transport in ferret red cells.
Authors: Flatman P W
Published: December 2014

1. The effects of altering metabolism on Na(+)‐K(+)‐Cl‐ co‐transport were studied in ferret red cells. Na(+)‐K(+)‐Cl‐ co‐transport was measured as the bumetanide‐sensitive uptake of 86Rb. 2. Glucose, but not inosine or adenosine, sustained metabolism and maintained cell ATP content ([ATP]i) at the physiological level. [ATP]i could be reduced by prolonged incubation of cells in a substrate‐free medium or more quickly by incubating cells with 2‐deoxyglucose or with a mixture of iodoacetamide and glucose. 3. Na(+)‐K(+)‐Cl‐ co‐transport activity was inhibited when [ATP]i was reduced to below 100 mumol (1 cell)‐1 by starvation or by treatment with 2‐deoxyglucose. However, a unique relationship between [ATP]i and activity could not be found. [ATP]i and the method and time course of ATP depletion all influenced activity. The inhibition of Na(+)‐K(+)‐Cl‐ co‐transport, caused by reducing [ATP]i could be partially reversed by restoring [ATP]i to normal. 4. Increasing the concentration of intracellular ionized magnesium [( Mg2+]i) did not stimulate co‐transport activity in ATP‐depleted cells. This contrasts with the substantial stimulation seen in cells with normal [ATP]i. 5. Vanadate stimulated Na(+)‐K(+)‐Cl‐ co‐transport activity in ATP‐depleted cells but not in cells with normal [ATP]i. Fluoride did not affect activity at any [ATP]i. 6. The effects of some sulphydryl reagents on Na(+)‐K(+)‐Cl‐ co‐transport were also examined. n‐Ethylmaleimide (1 mM) inhibited Na(+)‐K(+)‐Cl‐ co‐transport while it stimulated bumetanide‐resistant potassium transport. Dithiothreitol (1 mM) did not affect activity. Iodoacetamide (6 mM) appeared to reduce the inhibition of cotransport activity seen at low [ATP]i but also greatly increased cell fragility. 7. The data suggest that activity of the Na(+)‐K(+)‐Cl‐ co‐transport system is controlled by a cycle of phosphorylation and dephosphorylation with the phosphorylated form being active. Phosphorylation and transport appear to be almost maximal in ferret red cells with normal [ATP]i. Reduction of [ATP]i may allow changes in phosphatase activity to manifest as changes in transport rate. Differences in the balance between phosphorylation and dephosphorylation may explain tissue‐dependent variations in the response of the system to various stimuli.
Optical determination of impulse conduction velocity during development of embryonic chick cervical vagus nerve bundles.
Authors: Sakai T , Komuro H , Katoh Y , Sasaki H , Momose‐Sato Y , Kamino K
Published: December 2014

1. Employing an optical method for multiple‐site simultaneous recording of electrical activity, we have determined the conduction velocity in cervical vagus nerve bundles isolated from 5‐ to 21‐day‐old chick embryos, and investigated its developmental changes. 2. The preparations were stained with a voltage‐sensitive merocyanine‐rhodanine dye (NK2761), and action potential‐ (impulse‐) related optical signals were elicited by brief stimuli applied to the end of the vagus nerve bundle with a suction electrode. Optical signals were recorded simultaneously from many contiguous regions using a 12 x 12‐element photodiode array. 3. The optical signals spread with small delay from the site of stimulation. From the relationship between the delay and distance from the current‐applying electrode, conduction velocities were estimated in each tested preparation: the conduction velocity was very small and increased monotonically from about 0.1 m s‐1 at 5 days embryonic age to about 0.4 m s‐1 by hatching. The increase in the conduction velocity was closely related to a developmental increase in the diameter of the vagus nerve bundle. 4. In addition, we have examined the spread of electrotonic potentials. The space constant was very small (200‐450 microns) and increased as development proceeded. 5. Compound optical action signals having two distinct components were also recorded. They often appeared to be concentrated in the preparations from 8‐ to 12‐day‐old embryos. The conduction velocity of the second component was slower than that of the first. We suggest that appearance of the second component reflects degeneration of a subset of axons resulting from ‘neural cell death’ during the development of the vagus nerve.
Ca(2+)‐activated K+ channels in rat thymic lymphocytes: activation by concanavalin A.
Authors: Mahaut‐Smith M P , Mason M J
Published: December 2014

1. The role of ion channels in the mitogenic response of rat thymic lymphocytes to concanavalin A (ConA) was studied using single‐channel patch‐clamp recordings and measurements of membrane potential with the fluorescent probe bis‐oxonol. 2. ConA (20 micrograms ml‐1) evoked a rapid membrane hyperpolarization; Indo‐1 measurements indicated a concurrent increase in [Ca2+]i. The hyperpolarization was blocked by cytoplasmic loading with the Ca2+ buffer BAPTA (bis(O‐amino‐phenoxy)ethane‐N,N,N',N'‐tetraacetic acid), or charybdotoxin, a component of scorpion venom known to block K+ channels in lymphocytes. 3. Cell‐attached patch‐clamp recordings showed that both ConA and the Ca2+ ionophore ionomycin activated channels with high selectivity for K+. Two conductance levels were observed ‐6‐7 pS and 17‐18 pS‐measured as inward chord conductance at 60 mV from reversal potential (Erev) with 140 mM‐KCl in the pipette. The current‐voltage relationship for the larger channel displayed inward rectification and channel open probability was weakly dependent upon membrane potential. 4. These experiments provide the first direct evidence for mitogen‐activated Ca(2+)‐gated K+ channels (IK(Ca)) in lymphocytes. This conductance is relatively inactive in unstimulated rat thymocytes but following the intracellular Ca2+ rises induced by ConA, IK(Ca) channels are activated and produce a significant hyperpolarization of the cell potential.