bluuebunny/crossref_metadata_2025 huggingface dataset:
Educational silos in nursing education: a critical review of practical nurse education in Canada
Authors: Butcher Diane L , MacKinnon Karen A
Published: December 2014

Changes to practical nurse education (with expanded scopes of practice) align with the increasing need for nurses and assistive personnel in global acute care contexts. A case in point is this critical exploration of Canadian practical nursing literature, undertaken to reveal predominating discourses and relationships to nursing disciplinary knowledge. The objectives of this poststructural critical review were to identify dominant discourses in practical nurse education literature and to analyze these discourses to uncover underlying beliefs, constructed truths, assumptions, ambiguities and sources of knowledge within the discursive landscape. Predominant themes in the discourses surrounding practical nurse education included conversations about the nurse shortage, expanded roles, collaboration, evidence‐based practice, role confusion, cost/efficiency, the history of practical nurse education and employer interests. The complex relationships between practical nursing and the disciplinary landscape of nursing are revealed in the analysis of discourses related to the purpose(s) of practical nurse education, curricula/educational programming, relationships between RN and PN education and the role of nursing knowledge. Power dynamics related to employer needs and interests, as well as educational silos and the nature of women's work, are also revealed within the intersection of various discourses.
Olfactory function in elderly people and patients with Alzheimer's disease
Authors: Hori Yuriko , Matsuda Osamu , Ichikawa Sachiko
Published: December 2014

Background

Olfactory function is an important sensory perception function that helps us detect the smell of spoiled food, dirty clothing, and gas leaks. If ageing and Alzheimer's disease (AD) are accompanied by a decline in olfactory function, this might reduce the ability to sense danger, placing the safety and hygiene of elderly people at risk.

Methods

Subjects in this study included 113 healthy subjects aged 20–89 years and 12 persons with AD aged 62–85 years. The healthy subjects were divided into three groups according to age: young‐adult group (20–43 years), middle‐adult group (45–69 years), and old‐adult group (70–89 years). The Hasegawa Dementia Scale‐Revised score of AD subjects ranged from 15 to 26. We developed and implemented an odour identification ability test and a situational judgement test using an odour stick to examine the impact of ageing and AD on olfactory function from the perspective of sensing danger. To examine the impact of mild AD on the olfactory function, we compared the scores between the AD group and the age‐matched control group.

Results

The scores for the situational judgement and odour identification ability tests were significantly lower in an old‐adult group than in the young‐adult and middle‐adult groups. A significant correlation was found between age and scores for both tests in the control group. The AD group exhibited significantly lower total scores on both tests compared with the age‐matched controls.

Conclusions

These results suggest that ageing and mild AD may reduce the ability to identify odours and judge situations based on odours.
Airport Privatisation in Australia: A Tale of Three Cities
Authors: Aulich Chris
Published: December 2014

This article addresses the performance of three Australian airports since they were privatised by divestment. They represent cases of divestment in a monopoly environment, with ownership arrangements for each airport varying markedly. The performances of the divested airports are considered using both financial and non-financial data. There are significant implications for future divestment policies, including the value of divestment as a policy response of governments in less competitive environments, the use of particular infrastructure investment models, and the nature of the linkage between ownership structure and financial performance.
ON THE ACT OF BLINKING
Authors: Ponder Eric , Kennedy W. P.
Published: December 2014

1. It is shown, by an investigation of the movements of blinking in the normal individual, that the distribution of interblink periods (intervals between successive blinks measured in seconds) is remarkably constant for the individual under constant experimental conditions.

2 The movements are not reflex, and do not depend on the integrity of the second, third, fourth, fifth, or sixth cranial nerves. They are centrally controlled, and dependent on intermittent impulses passing from the region of the basal ganglia.

3. The rate of blinking is closely related to the “mental tension” of the subject at the time, and in all probability the movements constitute a kind of relief mechanism, whereby nervous energy, otherwise unutilised, passes into a highly facilitated path.
THE PHYSIOLOGY OF PREGNANCY IN THE RAT.—I. THE PROLONGATION AND INTERRUPTION OF PREGNANCY
Authors: Hain Annie M.
Published: December 2014

1. The gestation period in the rat can be prolonged by from 4 to 10 days by (a) administration of anterior pituitary tissue; (b) extract of human pregnancy urine; (c) alkaline extract of pituitary; (d) extract containing “purified” growth hormone.

2. Pregnancy is apt to be interrupted when injection of the urine extract is made in the early stages.

3. The evidence adduced suggests that the pregnant condition is not maintained solely by the corpus luteum, and that parturition is not due merely to degeneration of that body.
Soma neurofilament immunoreactivity is related to cell size and fibre conduction velocity in rat primary sensory neurons.
Authors: Lawson S N , Waddell P J
Published: December 2014

1. Intracellular recordings were made in dorsal root ganglia in vitro at 37 degrees C. The L4, L5 and L6 ganglia from 46‐ to 51‐day‐old female Wistar rats were used. In each neuron conduction velocity (CV) was measured and fluorescent dye was injected. Later the intensity of the immunoreactivity to RT97 (a monoclonal antibody to the phosphorylated 200 kDa neurofilament subunit) as well as the cell size (cross‐sectional area at the nuclear level) were measured in the dye‐injected neurons. RT97 was used to distinguish between the L (light, neurofilament‐rich) and the SD (small dark, neurofilament‐poor) neuronal somata. 2. Neurons were classified as C neurons (CV less than 1.3 m/s), C/A delta neurons (1.3‐2 m/s), A delta neurons (2‐12 m/s) or A alpha/beta neurons (greater than 12 m/s). 3. All A‐fibre somata were RT97 positive (L) and all C‐fibre somata were RT97 negative (SD), although in the C/A delta group both positive and negative neurons were seen. Thus, RT97‐negative somata had C (unmyelinated) or C/A delta fibres, while RT97‐positive somata had A (myelinated) or C/A delta fibres. 4. The size distributions of A neurons and C neurons were consistent with their classification as L‐ and SD‐cell neurons respectively. The size distribution of A delta cells was skewed with a peak of small cells and a tail of medium‐sized cells. 5. There was a loose positive correlation between cell size and fibre CV. 6. RT97 intensity was positively correlated with CV if all neurons were considered together, but no correlation was seen within the C, A delta or A alpha/beta CV groups. 7. RT97 intensity was positively correlated with cell size when all neurons were considered together. Although no correlation was seen within the C or the A delta CV groups, a clear positive correlation was seen for A alpha/beta neurons. 8. The relationship of RT97 intensity to cell size was not demonstrably altered by axotomy, time in vitro or the presence of intracellular dye in control experiments. 9. RT97‐negative and ‐positive neurons could be seen in neonatal rat ganglia. Their size distributions resembled, respectively, the SD‐ and L‐neuron populations at this age. RT97 immunoreactivity may therefore be a useful predictor of the cell type and myelinated state which a sensory cell is destined to reach in the adult rat.
Evidence for reflex upper airway dilator muscle activation by sudden negative airway pressure in man.
Authors: Horner R L , Innes J A , Murphy K , Guz A
Published: December 2014

1. To determine if negative upper airway pressure causes reflex pharyngeal dilator muscle activation, we used intra‐oral bipolar surface electrodes to record genioglossus electromyogram (EMG) activity in response to 500 ms duration pressure stimuli of 0, ‐2.5, ‐5, ‐15, ‐25 and ‐35 cm H2O (0‐90% rise time less than 30 ms) in ten normal, conscious, supine subjects. 2. With the subjects relaxed at end‐expiration, stimuli were applied in each of three conditions: (i) glottis open (GO), (ii) glottis closed (GC) and (iii) controls with the mouth and nose closed. 3. Six rectified and integrated EMG responses were bin averaged for each pressure in each experimental condition. Response latency was defined as the time when the EMG activity significantly increased above pre‐stimulus levels. Response magnitude was quantified as the ratio of the EMG activity for 80 ms post‐stimulus to 80 ms prestimulus; data from after the subject's voluntary reaction time (for tongue protrusion) were not analysed. 4. Negative airway pressure activated the genioglossus. The median latency of activation (34 ms) was much faster than the time for voluntary activation (184 ms) indicating a reflex response. 5. Significant activation, compared to 0 cmH2O controls and controls with mouth and nose closed, occurred with pressures of at least ‐5 cm H2O (GC) and ‐15 cm H2O (GO). At ‐25 and ‐35 cm H2O, responses with GO were significantly greater than with GC. 6. The magnitude ('strength') of the responses differed between subjects; these differences were repeatable. 7. We conclude that negative airway pressure causes reflex pharyngeal dilator muscle activation in man. Responses with GC suggest that upper airway receptors can mediate the response but larger responses with GO indicate a contribution from subglottal receptors.
Sensitivity and integration in a visual pathway for circadian entrainment in the hamster (Mesocricetus auratus).
Authors: Nelson D E , Takahashi J S
Published: December 2014

1. Light‐induced phase shifts of the circadian rhythm of wheel‐running activity were used to measure the photic sensitivity of a circadian pacemaker and the visual pathway that conveys light information to it in the golden hamster (Mesocricetus auratus). The sensitivity to stimulus irradiance and duration was assessed by measuring the magnitude of phase‐shift responses to photic stimuli of different irradiance and duration. The visual sensitivity was also measured at three different phases of the circadian rhythm. 2. The stimulus‐response curves measured at different circadian phases suggest that the maximum phase‐shift is the only aspect of visual responsivity to change as a function of the circadian day. The half‐saturation constants (sigma) for the stimulus‐response curves are not significantly different over the three circadian phases tested. The photic sensitivity to irradiance (1/sigma) appears to remain constant over the circadian day. 3. The hamster circadian pacemaker and the photoreceptive system that subserves it are more sensitive to the irradiance of longer‐duration stimuli than to irradiance of briefer stimuli. The system is maximally sensitive to the irradiance of stimuli of 300 s and longer in duration. A quantitative model is presented to explain the changes that occur in the stimulus‐response curves as a function of photic stimulus duration. 4. The threshold for photic stimulation of the hamster circadian pacemaker is also quite high. The threshold irradiance (the minimum irradiance necessary to induce statistically significant responses) is approximately 10(11) photons cm‐2 s‐1 for optimal stimulus durations. This threshold is equivalent to a luminance at the cornea of 0.1 cd m‐2. 5. We also measured the sensitivity of this visual pathway to the total number of photons in a stimulus. This system is maximally sensitive to photons in stimuli between 30 and 3600 s in duration. The maximum quantum efficiency of photic integration occurs in 300 s stimuli. 6. These results suggest that the visual pathways that convey light information to the mammalian circadian pacemaker possess several unique characteristics. These pathways are relatively insensitive to light irradiance and also integrate light inputs over relatively long durations. This visual system, therefore, possesses an optimal sensitivity of ‘tuning’ to total photons delivered in stimuli of several minutes in duration. Together these characteristics may make this visual system unresponsive to environmental ‘noise’ that would interfere with the entrainment of circadian rhythms to light‐dark cycles.
Effect of Ag+ on membrane permeability of perfused Helix pomatia neurons.
Authors: Györi J , Kiss T , Shcherbatko A D , Belan P V , Tepikin A V , Osipenko O N , Salánki J
Published: December 2014

1. Isolated, non‐identified neurons were voltage clamped using the internal perfusion technique. 2. Ions of Ag+ (1‐100 microM) introduced into the bathing solution activated a steady‐state inward current (IAg) in the soma. The effect of Ag+ was reversible when the concentration of Ag+ was less than 75 microM or the time of application was shorter than 10 min. 3. IAg was observed both in the presence and absence of Na+ ions in the extracellular saline. It could also be activated when Cs+ ions were substituted for Na+ ions. 4. The current‐voltage characteristics were linear in the voltage range ‐100 to 0 mV. The reversal potential in control saline was an average of 1.19 +/‐ 5.1 mV. 5. The application of Ag+ ions induces an elevation of intracellular free Ca2+ concentration by 10‐20 times in both Ca(2+)‐containing and Ca(2+)‐free extracellular salines, as revealed by Fura‐2 measurements. 6. Agents that increase the intracellular free Ca2+ concentration ([Ca2+]i), like thymol, caffeine and dinitrophenol, increased the amplitude of IAg. The effect was additive. Ruthenium Red, which blocks the release of Ca2+ from intracellular stores, decreased the Ag+ effect. 7. It is concluded that extracellularly applied Ag+ ions increase the cytoplasmic free Ca2+ concentration, which in turn activates non‐specific cationic channels. 8. Ag+ ions in 1‐10 microM concentration were able to decrease the voltage‐activated Ca2+ current amplitude. This decrease, however, was due to the increase of [Ca2+]i which caused Ca(2+)‐dependent inactivation.
A frequency analysis of neuronal activity in monkey thalamus, motor cortex and electromyograms in wrist oscillations.
Authors: Butler E G , Horne M K , Churchward P R
Published: December 2014

1. Extracellular recordings were made in three monkeys while recording from neurones in the motor cortex (eighty‐four cells), ventro‐posterior lateralis pars caudalis (VPLc, forty‐two cells) and cerebellar thalamus (seventy‐seven cells). 2. This experiment was designed to produce active and reflex movements of varying velocities in order to study the relationship between amplitude of velocity and magnitude of neuronal discharge of thalamic neurones. The active movements were voluntary rapid alternating movements (RAMs) of the wrist and the reflex movements were produced by forcibly oscillating the wrist joint between frequencies of 1 and 7 Hz (forced oscillations). 3. This study was also designed to examine cerebellar influences on a reflex path, namely the transcortical reflex loop. Forced oscillations were predicted to provide circumstances where active damping was required to prevent excessive oscillations in the reflex path. Rapid alternating movements of the wrist were predicted to provide circumstances where oscillations at the natural frequency in that reflex path would support and propagate the movements. 4. Forced oscillations from 1 to 7 Hz produced movements of different velocities. VPLc and cerebellar thalamic neurones discharged in relation to the duration of movement in a particular direction, but their discharge levels were unrelated to the magnitude of the velocity. Motor cortex neurones fired in a pattern which was related to the timing but not the magnitude of the acceleration. 5. In forced oscillations of the wrist the resonant frequency was between 3 and 7 Hz. They may be controlled in part by a transcortical reflex. The cerebellar thalamic neurones did not fire before motor cortex neurones. Therefore, it is unlikely that the cerebello‐thalamo‐cortical pathway is necessary to damp these potentially unstable oscillations by an effect on antagonist‐related cortical neurones. 6. Rapid alternating movements (RAMs) of monkeys' wrists were performed in a stereotyped fashion over a narrow range of frequencies with the greatest displacement in joint angle and peak velocity at the natural frequency of 3‐5 Hz. 7. During the performance of RAMs, neuronal discharge modulated sinusoidally in the VPLc, cerebellar thalamus and motor cortex. There was no relationship between velocity and neuronal discharge of the cerebellar thalamic and motor cortical neurones but there did appear to be a relationship between velocity and VPLc neuronal discharge. 8. The onset of electromyogram (EMG) discharge changed earlier than neuronal discharge in the motor cortex and thalamus during the performance of RAMs.(ABSTRACT TRUNCATED AT 400 WORDS)
Kinetics of open channel block by penicillin of single GABAA receptor channels from mouse spinal cord neurones in culture.
Authors: Twyman R E , Green R M , MacDonald R L
Published: December 2014

1. Reduction by penicillin of single gamma‐aminobutyric acidA (GABAA) receptor currents from somata of mouse spinal cord neurones in culture was investigated using the excised outside‐out patch‐clamp recording technique. 2. GABA (2 microM) alone or with penicillin (100‐5000 microM) applied by pressure ejection from micropipettes evoked inward currents when patches were voltage‐clamped at ‐75 mV in symmetrical chloride solutions. Averaged GABA receptor currents were decreased in the presence of penicillin. 3. GABA receptor currents were recorded with at least two conductance states, a more frequent or main‐conductance state of about 27 pS and a less frequent sub‐conductance state of about 19‐20 pS. The conductances of the two states were unchanged in the presence of penicillin. The kinetic properties of the main‐conductance state were analysed and are summarized below. 4. Penicillin produced a concentration‐dependent reduction of GABA receptor open properties by reduction of average GABA receptor channel open duration and an increase in channel opening frequency. 5. Penicillin shifted frequency histograms of GABA receptor channel open durations to shorter durations in a concentration‐dependent manner. Three exponential functions were required to fit best the frequency histograms of open durations, suggesting that the channel had at least three open states. Penicillin produced a concentration‐dependent reduction in the time constants obtained from the open duration frequency histograms. 6. Frequency histograms of GABA receptor channel closed durations could be fitted with five to seven exponential functions, suggesting that the channel had multiple closed states. In the presence of increased concentration of penicillin, there was a reduction in the relative frequency of brief gaps and the appearance of new closed time constants. 7. With increased penicillin concentration, GABA receptor channel burst frequency was unchanged, burst durations were increased, the number of openings per burst was increased and the per cent time open within a burst was decreased. 8. The results suggested that penicillin produced simple open channel blockade of the GABA receptor channel. However, the experimental results also suggested that the association with and, perhaps, the dissociation of the blocker from its binding site were dependent upon the kinetic state of the open channel. Penicillin had faster association and slower dissociation rates when the channel was in unstable, brief open kinetic state than when the channel was in a more stable, longer open kinetic state. Possible models for penicillin reduction of single GABA receptor currents were simulated by computer and analysed.(ABSTRACT TRUNCATED AT 400 WORDS)
Plasma proteins modify the endothelial cell glycocalyx of frog mesenteric microvessels.
Authors: Adamson R H , Clough G
Published: December 2014

1. We have investigated the interaction of plasma proteins with the endothelial cell using cationized ferritin as a marker of the cell surface glycocalyx. 2. Single microvessels of the frog mesentery were sequentially perfused using glass micropipettes with solutions containing cationized ferritin (CF, 6.7 mg ml‐1) in 0.10 M‐NaCl and then with either frog plasma or bovine serum albumin (BSA; 50 or 10 mg ml‐1), or protein‐free Ringer solution, before suffusion fixation in 2.5% glutaraldehyde. 3. A layer of CF, usually two to four molecules thick, was associated with the luminal endothelial cell surface. In vessels post‐flushed with protein‐free Ringer solution the CF layer was closely adherent to all regions of the luminal endothelium, including the plasma membrane, vesicle diaphragms, coated pits and the entrances to clefts. However, when plasma was present during fixation the CF layer was separated from the cell surface by up to 100 nm over all regions. In vessels post‐flushed with BSA the CF layer was also separated from the membrane but the effect was less striking. 4. The association of cationized ferritin with the endothelial cell surface was assessed quantitatively using electron micrographs of transverse sections (approximately 50 nm thick) of the perfused vessels, and expressed in terms of the depth of the layer of CF associated with the endothelial cell surface, its separation from the plasma membrane of the luminal endothelium, and the concentration of CF in the layer. The mean (+/‐ S.D.) separation in the presence of plasma, 32.3 +/‐ 10.5 nm (n = 12), was significantly greater (P less than 0.01) than that with either protein‐free Ringer solution, 3.0 +/‐ 1.4 nm (n = 9), or BSA in Ringer solution, 8.3 +/‐ 3.0 nm (n = 8). The separation seen with BSA in Ringer was also significantly greater than that measured with a final Ringer solution perfusion (P less than 0.01). The effects of 10 and 50 mg ml‐1 BSA were not different from one another. The total glycocalyx thickness, defined as the sum of the separation layer and depth of CF layer, with plasma present, 56.2 +/‐ 13.7 nm, was twice the value seen with Ringer solution, 28.0 +/‐ 9.1 nm (P less than 0.01), while the total thickness with BSA, 30.9 +/‐ 5.4 nm, was not different from the Ringer solution value.(ABSTRACT TRUNCATED AT 400 WORDS)
Tension transients during steady lengthening of tetanized muscle fibres of the frog.
Authors: Piazzesi G , Francini F , Linari M , Lombardi V
Published: December 2014

1. Steady lengthenings at different velocities (0.02‐1.6 microns/s per half‐sarcomere, temperature 2.5‐5.5 degrees C) were imposed on isolated frog muscle fibres at the plateau of the isometric tetanus (tension T0). When tension during lengthening had attained a steady value (Ti), which varied from about 1.5 to about 2 times T0 depending on lengthening velocity, tension transients were elicited by applying step length changes of different amplitudes. The change in length of a selected segment, close to the end of the fibre connected to the force transducer, was controlled by means of a striation follower. 2. The instantaneous plots of tension versus the length change during the step itself showed that at the high forces developed during steady lengthening, as at the plateau of isometric tetanus, the elasticity of the fibre was almost undamped in the whole range of lengthening velocities used. 3. The tension transient elicited by step length changes imposed in isometric conditions exhibited the characteristic four phases described previously: following the tension change simultaneous with the step (phase 1), there was a quick partial recovery (phase 2, the speed of which increased going from the largest step stretch to the largest step release), a subsequent pause or inversion in recovery (phase 3) and finally a slower approach to the tension before the step (phase 4). 4. In the region of small steps the plot of the extreme tension attained during the step (T1) versus step amplitude appeared more linear during steady lengthening than in isometric conditions and deviated progressively from linearity with increase in the size of step releases. The amount of instantaneous shortening necessary to drop tension to zero (Y0), measured by the abscissa intercept of the straight line drawn through T1 points for small steps, was about 4.1 nm per half‐sarcomere in isometric conditions and 5.4 nm per half‐sarcomere during lengthening at low speed (0.09 microns/s per half‐sarcomere, Ti about 1.6 T0). Taken altogether this indicates, in agreement with previous work, that force enhancement during steady lengthening is due to increase in both number and extension of attached cross‐bridges. During lengthening at high speed (0.8 microns/s per half‐sarcomere), further enhancement in steady force (Ti about 1.9 T0) was accompanied by increase of Y0 to 6.3 nm per half‐sarcomere, indicating that increase in lengthening velocity exclusively produces increase in cross‐bridge extension.(ABSTRACT TRUNCATED AT 400 WORDS)
Role of ATP‐sensitive K+ channels during anoxia: major differences between rat (newborn and adult) and turtle neurons.
Authors: Jiang C , Xia Y , Haddad G G
Published: December 2014

1. It is well known that anoxia induces an increase in extracellular K+. The underlying mechanisms for the increase, however, are not well understood. In the present study, we performed electrophysiological, pharmacological and receptor autoradiographic experiments in an attempt to examine K+ ionic homeostasis during anoxia. Ion‐selective microelectrodes were employed to measure intracellular and extracellular K+ activity from hypoglossal neurons in brain slices. 2. During 3‐4 min anoxia, adult hypoglossal neurons lose a large amount of their intracellular K+ and this contributes in a major way to the 8‐fold increase in extracellular K+. 3. Loss of intracellular K+ from hypoglossal neurons is, to a great extent, due to activation of certain specific K+ channels. Glibenclamide, a potential sulphonylurea ligand and a specific blocker of ATP‐sensitive K+ (KATP) channels, has no effect on K+ homeostasis during oxygenated states, but almost halves the anoxia‐induced increase in extracellular K+ in the adult rat. 4. [3H]glibenclamide autoradiography shows that the hypoglossal nucleus in the adult rat has high sulphonylurea receptor density, a finding that is consistent with our electrophysiological observation. 5. Since we have previously shown that newborn mammals and reptiles are more resistant to O2 deprivation than adult mammals, we performed comparative studies among adult rat, newborn rat and adult turtle. In sharp contrast to the adult rat, extracellular K+ activity in newborn rat and adult turtle brain increases little (10 to 100 times less than the adult rat) and glibenclamide has a small and insignificant effect on K+ efflux in the newborn rat and none in the turtle. Glibenclamide receptor binding sites are much lower in the newborn rat than in the adult rat central nervous system (CNS) and barely detectable in the turtle brain. 6. These results support the hypothesis that in the adult rat, K+ is lost during anoxia from neurons through sulphonylurea receptor or KATP channels in a major way. Generally, however, KATP channels are poorly expressed in the newborn rat and adult turtle CNS and have little role to play during O2 deprivation.
Stretch‐activated non‐selective cation channels in the antiluminal membrane of porcine cerebral capillaries.
Authors: Popp R , Hoyer J , Meyer J , Galla H J , Gögelein H
Published: December 2014

1. Single stretch‐activated (SA) channels have been studied in isolated brain capillary endothelial cells as well as in the antiluminal membrane of intact porcine cerebral capillaries using the patch‐clamp recording technique. 2. The SA channels were found to be cation selective and permeable to Na+, K+, Ba2+ and Ca2+. 3. With monovalent cations in the patch pipette, the channels showed inward rectification in cell‐attached patches with a single‐channel conductance of 37 pS at negative and 24 pS at positive clamp potentials. 4. With either 70 mM‐Ca2+ or Ba2+ in the patch pipette, the current‐voltage relation was linear with slope conductances of 16 and 19 pS, respectively. 5. Mean channel open probability increased with increasing pressure and with depolarizing clamp potentials. 6. Cell swelling induced by hypotonic shock activated the SA channels in cell‐attached experiments. 7. The SA channel may be involved in cell volume or blood flow regulation. The contribution of these channels to the regulation of cerebrospinal salt and water content, especially in brain oedema, is discussed.
Postnatal changes in T‐type calcium current density in rat atrial myocytes.
Authors: Xu X , Best P M
Published: December 2014

1. Postnatal changes in Ca2+ current were studied in voltage clamped atrial myocytes isolated from Sprague‐Dawley rats. T‐ and L‐type Ca2+ currents were identified using standard electrophysiological and pharmacological techniques. Cells were studied from seven groups of male and six groups of female rats ranging in age from 3 to 14 weeks. 2. The density of atrial T‐type Ca2+ current showed significant variation during postnatal development, with a maximum density reached at 4.5‐5 weeks. At this age, T‐current density was 1.44 +/‐ 0.11 pA/pF (n = 23) for cells isolated from male and 1.25 +/‐ 0.09 pA/pF (n = 25) for cells isolated from female animals in bathing solutions containing 2 mM‐Ca2+. T‐current density in atrial cells isolated from younger animals (3.5 weeks postnatal) averaged 1.22 +/‐ 0.06 (n = 18) and 1.00 +/‐ 0.05 pA/pF (n = 22) or 85 and 80% of the maximum seen at 4.5‐5 weeks for male and female rats, respectively. For rats older than 13 weeks, the average T‐current density in atrial cells was 0.50 +/‐ 0.03 (n = 18) and 0.51 +/‐ 0.02 pA/pF (n = 35) or 35 and 41% of the maximum seen at 4.5‐5 weeks for male and female rats, respectively. 3. In contrast to the T‐type current, the density of atrial L‐type Ca2+ current remained unchanged in rats from 3 to 14 weeks old. L‐type current averaged 8.2 +/‐ 0.2 (n = 134) in male and 7.9 +/‐ 0.2 pA/pF (n = 102) in female rats. 4. Fluctuation analysis was used to estimate single T‐channel current levels in 4.5‐ and 7.5‐week‐old male rats. While the T‐current density differed by 70% at these two postnatal ages, no significant difference (P > 0.2) in single channel current was found. Single channel current was 0.12 +/‐ 0.01 pA (n = 9) for cells from 4.5‐week‐old and 0.13 +/‐ 0.01 pA (n = 7) for cells from 7.5‐week‐old rats. Currents were stimulated by test pulses from ‐80 to ‐30 mV at 5 mM‐Ca2+. 5. No postnatal changes were seen in either the kinetics of activation or inactivation of macroscopic T‐current.(ABSTRACT TRUNCATED AT 400 WORDS)
A developmentally regulated blood‐cerebrospinal fluid transfer mechanism for albumin in immature rats.
Authors: Habgood M D , Sedgwick J E , Dziegielewska K M , Saunders N R
Published: December 2014

1. The transfer of albumin between the blood and the cerebrospinal fluid (CSF) has been investigated in neonatal (3 days old) and juvenile (20 days old) rats. At both stages of postnatal development, all of the albumin present in the CSF can be accounted for by transfer from the blood. Thus it is unlikely that in situ synthesis of albumin contributes to the naturally high levels of albumin in CSF in the developing brain. 2. The high concentration of albumin in CSF of the neonatal rat brain cannot be accounted for solely by diffusion from the blood. In the 3‐day‐old rat, only about one quarter of the albumin in CSF enters by diffusion from the blood, whilst the remainder appears to be transported into the CSF by a specific mechanism which can discriminate between different species of albumin. The specific transport component of albumin transfer between the blood and the CSF appears to be developmentally regulated and is not apparent in 20‐day‐old rats. 3. Chemical modification of albumin resulting in either an increase or a decrease in electrophoretic mobility (at pH 7.4), significantly reduces blood‐CSF transfer of albumin in 3‐day‐old rats, but has little effect in the 20‐day‐old rat. Thus overall molecular charge does not appear to be an important feature of the species‐specific blood‐CSF albumin transport mechanism in neonatal rats.
Postural proprioceptive reflexes in standing human subjects: bandwidth of response and transmission characteristics.
Authors: Fitzpatrick R C , Gorman R B , Burke D , Gandevia S C
Published: December 2014

1. This study investigated the reflex control of postural sway during human bipedal stance. The experiments were designed to: (i) find evidence for the operation of 'stretch reflex' pathways during quiet stance, (ii) determine the bandwidth of the reflex response, (iii) describe the reflex transmission characteristics in standing subjects, and (iv) assess the ability of subjects to make a task‐dependent change in the reflex. 2. A continuous random perturbation that did not threaten stability was applied at waist level to nine standing subjects. The effects of the perturbation on ankle torque, ankle movement and soleus electromyographic activity (EMG) were identified by cross‐correlation. The bandwidth of the reflex response and the transmission characteristics of reflexes that respond to ankle movement were identified by spectral analysis. Changes in these reflex responses were investigated when subjects attempted to stand as still as possible, had their eyes closed, or balanced a load equivalent to their own body in a situation in which neither visual nor vestibular reflexes would be activated. 3. When standing, a reflex response coherent with the perturbation was seen in soleus EMG at frequencies up to 5 Hz, with maximal coherence at 1.0‐2.0 Hz. Reflex gain increased with frequency, and there was a frequency‐dependent phase advance of soleus EMG on ankle movement reaching 135 deg at 3 Hz. When attempting to minimize sway, subjects produced a more coherent reflex response and significantly increased reflex gain. 4. The response and transmission characteristics of the lower limb proprioceptive reflex in freely standing subjects were similar to those in subjects balancing a load at the ankle, a situation in which vestibular and visual inputs could not contribute. 5. It is concluded that reflex feedback related to ankle movement contributes significantly to maintaining stance, and that much of the reflex response originates from lower limb mechanoreceptors stimulated by ankle rotation. Although reflex gain may be relatively low during quiet stance it can be increased when necessary to maintain stability.
Action of brief pulses of glutamate on AMPA/kainate receptors in patches from different neurones of rat hippocampal slices.
Authors: Colquhoun D , Jonas P , Sakmann B
Published: December 2014

1. Outside‐out patches were isolated from granule cells of dentate gyrus and pyramidal cells of CA3 and CA1 regions of rat hippocampal slices. Patches were exposed briefly to L‐glutamate using a piezo‐driven double‐barrelled application pipette. 2. Applications of glutamate (1 mM) of 1 ms duration activated patch currents which rose and decayed rapidly. The 20‐80% rise time of these glutamate receptor (GluR)‐mediated currents was usually 0.2‐0.6 ms. At ‐50 mV the peak current varied from 10 to 500 pA in different patches. 3. The peak current‐voltage relation for brief pulses of 1 mM glutamate was virtually linear in normal extracellular solution for patches from the three cell types (‐100 to 60 mV). 4. The permeability of GluR channels activated at the peak to Ca2+, relative to K+, was less than 0.1 for all three cell types (under bi‐ionic conditions with Ca2+ on the extracellular side and K+ on the intracellular side of the membrane). 5. The offset decay time constant of the current following 1 ms pulses of 1 mM glutamate was brief, with mean values of 3.0 +/‐ 0.8, 2.5 +/‐ 0.7, and 2.3 +/‐ 0.7 ms for dentate, CA3 and CA1 cell patches, respectively. Offset time constants were independent of membrane potential and independent of glutamate concentration (200 microM and 1 mM) for the three cell types. 6. Applications of 1 mM glutamate of 100 ms duration showed that glutamate responses desensitized rapidly. The time constants for desensitization were 9.4 +/‐ 2.7, 11.3 +/‐ 2.8, and 9.3 +/‐ 2.8 ms for patches from dentate, CA3 and CA1 cells respectively. Desensitization time constants were only weakly dependent on glutamate concentration (200 microM and 1 mM) for the three cell types. Thus offset time constants are about four times faster than desensitization time constants for both glutamate concentrations. 7. Double pulse application of glutamate indicated that even a 1 ms pulse of 1 mM glutamate causes partial (about 60%) desensitization of GluR channels. The time course of recovery from desensitization was slower in dentate gyrus granule cell patches than in CA3 or CA1 pyramidal cell patches. 8. Desensitization was studied at equilibrium by exposing patches to low glutamate concentrations for at least 15 s before a 1 ms test pulse of 1 mM glutamate.(ABSTRACT TRUNCATED AT 400 WORDS)
Fluctuations in blood flow to acral skin in humans: connection with heart rate and blood pressure variability.
Authors: Lossius K , Eriksen M , Walløe L
Published: December 2014

1. Spontaneous fluctuations in blood flow in arteries supplying acral skin were investigated with Doppler ultrasound in human subjects. Finger blood pressure, heart rate (HR) and cardiac output were measured simultaneously and noninvasively. 2. Synchronous fluctuations in flow were found in arteries supplying the hands and feet. The fluctuations were larger and more rapid than the flow variations which have been demonstrated with other methods. The magnitude of the total flow fluctuations in the hands and feet was estimated to be 5‐10% of cardiac output in resting subjects. This range of flow fluctuations is made possible by spontaneous opening and closing of skin arteriovenous anastomoses (AVAs). 3. The fluctuations in skin blood flow were accompanied by inverse fluctuations in mean blood pressure (MAP). The power spectra of skin vascular conductance and MAP both contained maximum intensity at low frequencies, below 0.15 Hz, with high coherence. 4. The central circulatory events connected with the skin blood flow fluctuations were calculated from the experimental data with the use of transfer function analysis. There was a rise in HR, cardiac output and MAP starting 1‐4 s before a cutaneous vasoconstriction. This indicates that the HR and MAP responses are not only passive effects of changes in peripheral resistance, but are the result of a simultaneous activation of the peripheral vascular and cardiac efferent branches of the autonomic nervous system. The HR and MAP responses are then modified, probably by baroreceptor activation.
Nitric oxide involvement in the peptide VIP‐associated inhibitory junction potential in the guinea‐pig ileum.
Authors: He X D , Goyal R K
Published: December 2014

1. Intracellular membrane potential recordings were made from circular smooth muscle cells of the guinea‐pig ileum in the presence of atropine (1 microM) and nifedipine (0.1 microM) at 30 degrees C. 2. Electrical field stimulation with one or four pulses produced a fast inhibitory junction potential (IJP) which lasted around 1 s. It was abolished by tetrodotoxin (1 microM), apamin (0.3 microM), and alpha, beta‐methylene ATP tachyphylaxis. 3. Nitric oxide synthase inhibitor N‐nitro‐L‐arginine (L‐NNA; 200 microM) had no effect on the resting membrane potential or the fast IJP. 4. Electrical field stimulation in the presence of apamin and substance P desensitization produced a slow IJP which was abolished by tetrodotoxin (1 microM). 5. L‐NNA significantly reduced the amplitude of the slow IJP (P < 0.01). The antagonistic effect of L‐NNA was reversed by L‐arginine but not by D‐arginine. 6. Injections of alpha, beta‐methylene ATP, nitric oxide (NO), and vasoactive intestinal polypeptide (VIP) into the recording chamber caused tetrodotoxin‐resistant hyperpolarizations of the smooth muscle membrane. Substance P desensitization did not modify the amplitudes of the hyperpolarizing response to ATP or NO, but increased the VIP hyperpolarization by 150% (P < 0.01). 7. L‐NNA did not modify the amplitude of hyperpolarization due to ATP or NO; however, it antagonized VIP‐induced hyperpolarization (P < 0.01). 8. These studies show that in the guinea‐pig ileum circular muscle: (a) NO is not involved in the fast IJP which is mediated by ATP; (b) NO is involved in the slow IJP which is mediated by VIP and NO acting in series, and (c) the hyperpolarizing effects of VIP and the slow IJP are normally masked by overlapping depolarization due to concomitant release of substance P by the peptide VIP.
Increase in nitric oxide and cyclic GMP of rat cerebellum by radio frequency burst‐type electromagnetic field radiation.
Authors: Miura M , Takayama K , Okada J
Published: December 2014

1. Using rat cerebellum supernatant, the effects of radio frequency (RF) burst‐type electromagnetic (EM) field radiation on the production of cyclic GMP were examined under various conditions. The radiation was generated by a generator coil, and set at a 10 MHz radiation frequency, a 50% burst time, a 10 kHz burst rate and a 5 V peak‐to‐peak generator voltage. 2. When the cerebellum supernatant was incubated with both exogenous L‐arginine (nitric oxide (NO) donor) and NADPH, and irradiated by an RF burst‐type EM field, the production of cyclic GMP was increased significantly from a level of 21‐22 nmol min‐1 (g tissue)‐1 to 25‐26 nmol min‐1 (g tissue)‐1. By contrast, such an effect was not found when the cerebellum supernatant was irradiated by an RF volley‐type EM field. 3. When neither L‐arginine nor NADPH were added to the cerebellum supernatant, the production of cyclic GMP was lowered to a level of 6 nmol min‐1 (g tissue)‐1 and the radiation effect was not found. When the cerebellum supernatant was chelated with EDTA, the production of cyclic GMP was lowered to a level of 7 nmol min‐1 (g tissue)‐1 and the radiation effect was not found. 4. Incubation with Methylene Blue, a guanylate cyclase inhibitor, lowered the production of cyclic GMP to a level of 10‐12 nmol min‐1 (g tissue)‐1, and the radiation effect did not occur. On incubation with a NO synthase inhibitor, either NG‐methyl‐L‐arginine or N omega‐nitro‐L‐arginine methyl ester, the production of cyclic GMP was lowered to a level of 10‐12 nmol min‐1 (g tissue)‐1 or 5‐9 nmol min‐1 (g tissue)‐1 respectively, and the radiation effect was not observed. 5. Using electrochemical NO probes, the production of NO in the cerebellum supernatant was detected. The concentration of NO increased gradually after the onset of the EM field radiation. The radiation effect persisted, and reached a maximum after the cessation of the radiation. 6. In an in vivo study, the arterioles of the frog web were dilated by the radiation, and this radiation effect was almost completely abolished by the addition of a NO synthase inhibitor. This indicates that radiation activates NO synthase and ultimately induces vasodilatation.
Studies of brain structures involved in diffuse noxious inhibitory controls in the rat: the rostral ventromedial medulla.
Authors: Bouhassira D , Bing Z , Le Bars D
Published: December 2014

1. Previous electrophysiological, pharmacological and anatomical evidence had suggested a possible participation of rostral ventromedial medulla (RVM) in the supraspinal part of the loop underlying diffuse noxious inhibitory controls (DNICs). In order to test this hypothesis, two experimental series were performed during which DNICs were compared in control sham‐operated rats and rats with lesions of the RVM and of an adjacent candidate for such a role, the nucleus gigantocellularis reticularis (Gi). 2. In the first experimental series, lesions were induced, in anaesthetized animals, by injections of quinolinic acid (0.3‐0.8 microliter of a 360 nmol/microliter solution) into the RVM or Gi. In the control animals (n = 10), the vehicle alone (artificial cerebrospinal fluid) was injected. Histological lesion reconstructions were performed after each electrophysiological experiment. Three groups of animals were considered: in the first group (n = 5), the lesion was centered on the RVM, including the two caudal thirds of nucleus raphe magnus (NRM) and adjacent reticular areas; in the second group (n = 5), the lesions extended more rostrally and involved the rostral pole of NRM; in the third group (n = 5), the lesion extended more laterally and dorsally and included nucleus reticularis gigantocellularis pars alpha (GiA), nucleus reticularis paragigantocellularis lateralis (LPGi) and the Gi. In each case, all the neuronal cell bodies within the lesioned area were destroyed. 3. In the second experimental series, electrolytic lesions of the total rostrocaudal extent of the NRM (n = 5) were induced, in anesthetized animals, by passing cathodal current (5 mA, 8 s). In the control animals (n = 5), the electrode was lowered but current was not applied. 4. One week after lesioning, the animals were anaesthetized, paralysed, artificially ventilated and recordings were made from convergent neurones in trigeminal nucleus caudalis. These neurones gave responses due to activation of A and C fibres when percutaneous electrical stimuli were applied to their receptive fields. DNICs were triggered by immersion of each paw in a 50 degrees C water‐bath. Both the general properties of the convergent neurones and the inhibitions of the C fibre‐evoked responses produced by these heterotopic noxious stimuli were compared in the different groups of animals. 5. The sizes of receptive field, spontaneous activities, thresholds for C fibre‐evoked responses and responses to C fibre activation were not different in the control and lesioned animals. The percentage inhibitions of the C fibre‐evoked responses both during and in the 44s following the conditioning periods were also very similar in the different groups of animals.(ABSTRACT TRUNCATED AT 400 WORDS)
Mechanisms of zinc transport into pig small intestine brush‐border membrane vesicles.
Authors: Tacnet F , Lauthier F , Ripoche P
Published: December 2014

1. The purpose of the present work was to examine certain membrane transport mechanisms likely to carry zinc across the brush‐border membrane of pig small intestine, isolated in a vesicular form. 2. In initial velocity conditions, saturation kinetics revealed a great effect of pH on zinc transport: optimal conditions were observed with an intravesicular pH of around 6.6 with or without a H+ gradient; however, this did not allow us to conclude the existence of a neutral exchange between Zn2+ and H+ ions. 3. By measuring 36Cl uptakes, the presence of the Cl(‐)‐HCO3‐ or Cl(‐)‐OH‐antiporter with typical 4,4'‐diisothiocyanatostilbene‐2,2'‐disulphonic acid (DIDS) sensitivity was detected in vesicles; zinc did not alter this anionic exchange activity. A 65Zn time course, performed in conditions identical with those for 36Cl uptake, was DIDS insensitive and was greatly inhibited by an outward OH‐ gradient. This could argue against a transport of zinc as a complex with Cl‐ and HCO3‐ through the anion antiporter. 4. When external Cl‐ and HCO3‐ were replaced by SCN‐, able to form a Zn(SCN)4(2‐) complex, we observed a stimulating effect of outward HCO3‐ gradients on 65Zn uptake but neither DIDS nor diphenylamine‐2‐carboxylate (DPC) inhibited the transport in these conditions. This suggested that the intestinal anion antiporter was not a major route for zinc reabsorption. 5. The tripeptide Gly‐Gly‐His at low concentrations stimulated 65Zn uptake, then inhibited it in a dose‐dependent manner either in the presence of an inward H+ gradient or in the presence of a membrane potential ‘negative inside’ or in both situations. These conditions are necessary for the active transport of the peptide and this strongly suggests that zinc can be transported as a [Gly‐Gly‐His‐Zn] complex, utilizing the peptide carrier system.