bluuebunny/crossref_metadata_2025 huggingface dataset:
Changes in the calcium current of rat heart ventricular myocytes during development.
Authors: Cohen N M , Lederer W J
Published: December 2014

1. Calcium current (ICa) was recorded in single rat heart cells at two periods during development: (1) at 2‐7 days post‐partum (neonatal), and (2) at 6‐8 weeks (adult). 2. We measured both transient and steady‐state components of ICa and could describe ICa in terms of the steady‐state activation (d infinity) and inactivation (f infinity) parameters, the channel reversal potential (Echannel) and a relative conductance parameter, gr. 3. In adult single cells, the application of ryanodine (10 microM), an agent known to alter the function of the sarcoplasmic reticulum (SR), abolished contraction rapidly and increased ICa. Ryanodine also produced a 13 mV shift in f infinity towards more positive potentials and altered its slope, while producing a small increase in gr but no effect on d infinity. In neonatal single cells, ryanodine (10 microM) had no significant effect on contraction, ICa, d infinity, f infinity, or gr. Caffeine (10 mM), a less specific agent widely used to investigate sarcoplasmic reticulum function, had actions similar to those of ryanodine. 4. In adult myocytes, when EGTA (10 or 20 mM) or bis(o‐aminophenoxy)ethane‐N,N,N',N'‐tetraacetic acid (BAPTA, 10 mM) were included in the pipette solution, contractions were rapidly abolished, while a small (4 mV) shift of f infinity to more positive potentials was seen. A large additional shift of f infinity was observed when ryanodine (10 microM) was added to the superfusion solution in the continued presence of EGTA or BAPTA. The alterations of ICa in EGTA (or BAPTA) plus ryanodine were the same as those seen in ryanodine alone. In neonatal cells, in contrast, when EGTA or BAPTA were included in the pipette solution we observed only a small effect on f infinity and the application of ryanodine had no effect. 5. Electron micrographs of our preparations show that the dissociated adult cells have sharp sarcolemmal borders, fully developed sarcomeres with T‐tubules and sarcoplasmic reticulum membranes. In contrast, the neonatal cells that we use have few of these intracellular structures. Our observations in these preparations are consistent with the work of others (e.g. Penefsky, 1974; Hirakow & Gotoh, 1975; Ishikawa & Yamada, 1975; Legato, 1975; Hoerter, Mazet & Vassort, 1981). 6. Our data suggest that fully developed sarcoplasmic reticulum in rat heart cells can affect ICa.(ABSTRACT TRUNCATED AT 400 WORDS)
Intracellular pH regulation in cultured mouse oligodendrocytes.
Authors: Kettenmann H , Schlue W R
Published: December 2014

1. Intracellular pH (pHi) and the mechanism of pHi regulation have been investigated in cultured oligodendrocytes from mouse spinal cord using double‐barrelled neutral‐carrier H+‐selective microelectrodes. The distribution of H+ was not in electrochemical equilibrium. The pHi was more alkaline than the pH of the bathing medium (pHo), namely 7.5 at pHo 7.2 at 7.6 at pHo 7.4. 2. Removal of HCO3‐ from the bathing medium reduced the steady‐state pHi by 0.4 units. An increase in extracellular K+ caused, with a delay, an increase in pHi. A decrease in pHo to 6.2 caused an acidification of pHi by 0.5 units. 3. The pHi regulation was studied by applying and subsequently removing NH4+ which resulted in an acidification of the cell. The subsequent recovery of pHi could then be analysed. The recovery from an acidification by 1 pH unit lasted 3‐10 min. In HCO3‐ ‐free solution pHi recovery was slowed. 4. In HCO3‐ ‐free solution pHi recovery was completely blocked when either Na+ was removed or when amiloride was applied indicating an exclusive activation of the Na+‐H+ exchanger. 5. In the presence of HCO3‐, removal of Na+ also completely blocked pHi recovery. When Na+ was readded, pHi recovered. In HCO3‐ ‐containing solution amiloride slightly slowed, but did not block pHi recovery. 6. Removal of Cl‐ or application of SITS, DIDS or furosemide, blockers of Cl‐ ‐coupled transport mechanisms, did not affect the pHi recovery in the presence of HCO3‐. 7. In conclusion, oligodendrocytes possess two mechanisms regulating pHi, a Na+‐H+ exchanger and a Na+‐HCO3‐ co‐transporter while the latter is clearly more potent. It follows that pHi regulation of oligodendrocytes is dependent on the transmembrane Na+ gradient and is strictly separated from regulation of internal Cl‐.
The characteristics and regional distribution of afferent fibres in the chorda tympani of the cat.
Authors: Robinson P P
Published: December 2014

1. Experiments were carried out on the cat's tongue to investigate regional variations in sensitivity to gustatory and thermal stimuli and to determine whether taste buds responding to particular stimuli are unique to specific areas. 2. In ten cats, integrated whole‐nerve activity was recorded from the left chorda tympani during stimulation of the anterior, middle or posterior segments of the tongue. The level of activity produced by gustatory or thermal stimuli increased towards the posterior segment of the tongue but the relative activity evoked by each stimulus was similar for each segment. 3. Recordings were made from 108 single units dissected from the chorda tympani; fifty‐five responded principally to gustatory stimuli, twenty were principally thermosensitive and thirty‐three were purely mechanosensitive. 4. The gustatory units could be subdivided according to the stimuli which evoked the most vigorous discharge; there were sixteen salt units, eighteen acid units, nineteen salt‐acid units and two quinine units. The salt units had a higher level of spontaneous activity than the other groups and the acid units supplied more fungiform papillae with a greater separation between them. 5. The two quinine units were both located near to the mid‐line posteriorly but all other groups of gustatory, thermosensitive and mechanosensitive units were distributed over all regions of the dorsal surface of the tongue and did not have higher discharge rates in specific areas. 6. Individual stimulation of the fungiform papillae supplied by a single unit revealed that similar responses were evoked from each papilla but stimulation of a single papilla supplied by two or more units could evoke a different response in each unit. 7. This study revealed that the relative sensitivity to gustatory and thermal stimuli was similar in each region of the tongue and that taste buds responding to particular stimuli are not confined to specific areas.
Neutral amino acid uptake by the isolated perfused sheep choroid plexus.
Authors: Preston J E , Segal M B , Walley G J , Zlokovic B V
Published: December 2014

1. The uptake of neutral amino acids from the blood into the cells of the choroid plexus was studied by means of the rapid (less than 40 s) single‐circulation paired‐tracer dilution technique in the isolated perfused choroid plexus of the sheep. 2. The study provides the first direct evidence for the carrier‐mediated entry of neutral amino acids from blood into the cells of the choroid plexus. 3. In the terms of Christensen's classification the presence of L‐amino acid carrier systems for large neutral amino acids with bulky side chains has been demonstrated. 4. No measurable uptake of [14C]methyl amino isobutyric acid ([14C]MeAIB) during a single passage through the choroid plexus circulation was demonstrated which indicates the probable absence of a significant ‘A’ transport system. 5. The uptake of small neutral amino acids such as glycine and L‐alanine was shown to be carrier‐mediated. Results suggest that these amino acids are mainly transported by the glycine and ASC carrier systems, respectively. 6. The results suggest that there is a similarity between the transport systems for neutral amino acids on the blood side of both the blood‐brain barrier and blood‐cerebrospinal fluid barrier, the exception being for the presence of a glycine carrier on the blood side of the choroid plexus.
Evidence for the ordered release of rubidium ions occluded within individual protomers of dog kidney Na+,K+‐ATPase.
Authors: Glynn I M , Richards D E
Published: December 2014

1. When magnesium and orthophosphate are added to Na+,K+‐ATPase containing occluded rubidium ions, and suspended in a medium containing free rubidium ions, only 50% of the occluded rubidium is released rapidly. This is because the release of occluded rubidium is ordered, and the replacement (by rubidium ions from the medium) of the first occluded rubidium ions to leave slows the departure of the remaining occluded ions. 2. Since the Na+,K+‐ATPase probably exists in the membrane as a structural dimer, the ordered release might represent either the ordered emptying of the two halves of the dimer, or the ordered release of the two rubidium ions thought to be contained in each promoter. 3. The present experiments were designed to decide between these possibilities by examining the behaviour of Na+,K+‐ATPase in which about half of the protomers had been randomly inactivated by pre‐treatment either with fluorescein isothiocyanate or with alpha‐chymotrypsin. 4. The results show that the release of rubidium ions from each protomer is ordered.
Stimulus‐related potassium changes in the organ of Corti of guinea‐pig.
Authors: Johnstone B M , Patuzzi R , Syka J , Syková E
Published: December 2014

1. Potassium concentration was measured with double‐barrelled K+‐selective microelectrodes within the organ of Corti in the first turn of the guinea‐pig cochlea. 2. Penetration of the electrode from scala tympani through the basilar membrane was accompanied by an increase in K+ resting level from 3.0 mmol/l in perilymph to 3.4 mmol/l in cortilymph (n = 8). K+ resting level was not significantly different in various extracellular regions of the organ of Corti. On penetration of the cuticular plate, the K+ level reached 140 mmol/l simultaneously with the occurrence of a +80 mV endocochlear potential. Impalement of hair cells and supporting cells was accompanied by an increase in K+ level, but intracellular K+ level was not systematically measured. 3. Stimulation with pure tones over the frequency range 500 Hz to 25 kHz produced changes in the K+ level in the organ of Corti. The magnitude of these changes was dependent on stimulus frequency and intensity. At high sound intensities the K+ level in the tunnel of Corti could increase by typically 1 mmol/l, while a maximum increase of 3 mmol/l with respect to the resting level was observed immediately adjacent to inner hair cells. 4. During brief exposures to moderate intensity, pure tone acoustic stimulation (10 s, less than 80 dB SPL (sound pressure level] of frequency 4 kHz or greater the K+ level in the extracellular fluid of the organ of Corti rose monotonically to a steady peak level. On cessation of the stimulus the K+ level fell monotonically with a time constant of about 2 s to a level close to the pre‐stimulus level. In some cases this level was slightly above the pre‐stimulus level. 5. For brief exposures to moderate intensity sound (10 s, less than 80 dB SPL) the extracellular potential in the organ of Corti became more positive. The amplitude of this sound‐evoked change adapted during stimulation to a level approximately one‐fifth of its initial value. Upon cessation of the stimulus the potential fell transiently below its pre‐stimulus level, before recovering to that level. The time constant of these changes was between 2 and 3 s. 6. Iso‐response tuning curves for the sound‐evoked elevation in K+ level in the organ of Corti in animals in good condition were similar to iso‐rate tuning curves for primary afferent fibres reported previously.(ABSTRACT TRUNCATED AT 400 WORDS)
The development of topographical maps and fibre types in toad (Bufo marinus) glutaeus muscle during synapse elimination.
Authors: Bennett M R , Davies A M , Everett A W
Published: December 2014

1. The toad glutaeus muscle consists of two muscle compartments. A study has been made of the topographical distribution of motor units in these compartments, in relation to the fibre types which arise during different stages of development. 2. Monoclonal antibodies to myosin allowed the distribution of fibre types to be determined. In mature muscles (from toads of greater than 30 g body weight) clusters of type 5 (tonic) fibres were found exclusively at the dorsal surface of the muscle, surrounded by a layer of type 3 (slow‐twitch) fibres. A homogeneous layer of type 2 (fast‐twitch red) fibres was found beneath this dorsal rind of slow and tonic fibres. The rest of the muscle, including the ventral surface, consisted of a mosaic of type 1 (fast‐twitch white) and type 2 fibres. 3. Glycogen‐depletion methods, together with the myosin antibodies, allowed the distribution of single motor units and their fibre types to be determined. In mature muscles, axons originating from rostral spinal cord possessed muscle units located in a band extending from the ventral surface to beyond the middle of the muscle; these units consisted of 78% type 1 and 22% type 2 fibres found amongst the mosaic of type 1 and type 2 fibres. Intermediate axons possessed muscle units located primarily in the middle and dorsal half of the muscle. These units consisted mostly of type 2 fibres (29% type 1, 71% type 2) also found amongst the mosaic of type 1 and type 2 fibres. Thus rostral and intermediate units were of mixed fibre type, with type 1 fibres predominating in the former units and type 2 in the latter. Caudal axons possessed muscle units located mostly in the homogeneous layer of type 2 fibres, beneath the dorsal rind of tonic fibres; these units were almost always composed entirely of type 2 fibres. 4. The distribution of single motor units and their fibre types were determined for the caudal axons during development. In juvenile animals (toads of about 10 g body weight) the dorsal rind of tonic and slow fibres, together with the underlying homogeneous layer of type 2 fibres, were still present, but the rest of the muscle to the ventral surface consisted almost entirely of type 1 fibres. Caudal axons innervated the type 2 fibre layer at the dorsal surface as they do in mature animals. 5. The glutaeus in post‐metamorphic toads (0.15 g body weight) had only a small number of tonic and slow‐twitch fibres in the very dorsal layer of cells; the muscle was largely type 1.(ABSTRACT TRUNCATED AT 400 WORDS)
Modulation by intracellular Ca2+ of the hyperpolarization‐activated inward current in rabbit single sino‐atrial node cells.
Authors: Hagiwara N , Irisawa H
Published: December 2014

1. The sensitivity to internal Ca2+ of the hyperpolarization‐activated inward current (Ih or If) in rabbit single sino‐atrial node cells was investigated by the whole‐cell voltage‐clamp method. 2. When the patch pipette contained an internal solution of pCa 10, the amplitude of If decreased by 74.8 +/‐ 3.3% in 10 min (n = 7) after rupture of the patch membrane. When the pipette contained an internal solution of pCa 7, If increased by 43.7 +/‐ 8.7% within 10 min (n = 5). 3. Increase of If by the higher Ca2+ internal solution was confirmed in the same cell using the cell dialysis method. Both If and its tail current were increased at every membrane potential. The amplitude of If increased most markedly between pCa 8 and 7. 4. The reversal potential and kinetics of If were unaffected by the internal Ca2+ concentration. Increase of If by the high internal Ca2+ concentration was sensitively blocked by Cs+. These findings confirm that the increased current is indeed If and not a newly activated If‐like current due to elevation of internal Ca2+. 5. The activation curve of If shifted approximately 13 mV in a positive direction by elevating Ca2+ from pCa 10 to 7 (n = 21), indicating that the voltage dependence of If was modulated by internal Ca2+. 6. beta‐Agonists also modulated If, but the underlying mechanisms of their effects on If differed from those of the internal Ca2+. The former affected the If kinetics rather than its amplitude, whereas the latter acted on the If conductance rather than on its kinetics. 7. The increase in If by the internal Ca2+ was unaffected by protein kinase inhibitor or calmodulin inhibitor, suggesting that the internal Ca2+ directly modulates If. 8. When the patch pipette contained pCa 7 internal solution, the maximum diastolic potential shifted towards a positive potential but the heart rate remained almost constant.
Repetitive firing properties of medial pontine reticular formation neurones of the rat recorded in vitro.
Authors: Gerber U , Greene R W , McCarley R W
Published: December 2014

1. Intracellularly recorded neurones in nucleus reticularis pontis caudalis of the medial pontine reticular formation (mPRF) in the in vitro slice preparation were analysed for repetitive firing properties in response to intracellularly applied constant‐current pulses. 2. Three neuronal classes were defined by this procedure: (1) non‐burst neurones, which had only a non‐burst firing pattern; (2) low‐threshold burst neurones, which had either a low‐threshold burst pattern or a non‐burst pattern; (3) high‐threshold burst neurones, which had either a high‐threshold burst pattern or a non‐burst pattern. 3. Histological characterization of electrophysiologically identified mPRF neurones with carboxyfluorescein showed no definite morphological difference between the first two classes. There was a trend for low‐threshold burst neurones to have larger somata. 4. The low‐threshold burst was generated by a slow calcium‐dependent low‐threshold spike, revealed in the presence of tetrodotoxin. The size of the low‐threshold spike and thus the number of fast action potentials in the low‐threshold burst was controlled by at least five factors including: activation; inactivation; amplitude of low‐threshold conductance available to be activated; delayed outward conductance; and early transient outward conductance. 5. The non‐burst pattern examined in both non‐burst and low‐threshold burst neurones appeared to be controlled primarily by one or more calcium‐dependent potassium conductances sensitive to the removal of calcium and tetraethyl‐ammonium. In the presence of tetrodotoxin (TTX), the addition of antagonists to calcium‐dependent potassium current revealed a slow high‐threshold calcium spike which was distinguished from the low‐threshold spike by its threshold, lack of inactivation (at potentials negative to ‐40 mV) and insensitivity to Mg2+. A long‐duration after‐hyperpolarization (greater than 0.5 s) was not observed in any of these cells. 6. An early transient outward rectification sensitive to 4‐aminopyridine and probably mediated by A‐current was apparent in low‐threshold burst and non‐burst neurones and affected both the low‐threshold burst and non‐burst firing patterns. 7. Alteration of resting membrane potential, such as occurs in vivo during the depolarization associated with desynchronized sleep, may inactivate the low‐threshold spike and the transient outward conductance responsible for the distinctive responses observed from more hyperpolarized membrane potentials and produce a more homogeneous non‐burst response pattern. Membrane potential effects on intrinsic conductances thus may furnish an important mechanism for changes in mPRF neuronal responsivene
Cholecystokinin receptor antagonism by peptidergic and non‐peptidergic agents in rat pancreas.
Authors: Dembinski A , Jaworek J , Konturek P K , Konturek S J , Warzecha Z
Published: December 2014

1. Graded doses of bombesin infused I.V. into conscious rats with chronic pancreatic fistulae induced a dose‐dependent stimulation of protein secretion, similar to that obtained with caerulein. This stimulation does not appear to be mediated by cholecystokinin (CCK) receptors because peptidergic (CR‐1409) and non‐peptidergic (L‐364718) CCK antagonists failed to affect protein secretion at a dose range which caused almost complete suppression of caerulein‐induced pancreatic secretion. 2. Studies in vitro on isolated rat pancreatic acini revealed that caerulein, pentagastrin and bombesin all showed the same efficacy in their ability to stimulate amylase release. In contrast, CCK antagonists competitively inhibited amylase release induced by caerulein and pentagastrin but not by bombesin or urecholine, indicating that the latter two agents act directly on acinar cells via receptors which are separate from those involved in stimulation induced by caerulein and pentagastrin. 3. DNA synthesis, measured by the incorporation of [3H]thymidine into DNA, was significantly stimulated by caerulein, soybean trypsin inhibitor (FOY 305), pentagastrin and by bombesin in a dose‐dependent manner. CCK receptor antagonists prevented stimulation of DNA synthesis induced by caerulein, FOY 305 and pentagastrin but not by bombesin. 4. This study indicates that bombesin strongly stimulates pancreatic enzyme secretion, with an efficacy similar to that of caerulein, and also exerts a potent growth‐promoting action on the pancreas, both effects appearing to be mediated by mechanisms independent of the CCK receptors.
Development of desensitization during repetitive end‐plate activity and single end‐plate currents in frog muscle.
Authors: Giniatullin R A , Khamitov G , Khazipov R , Magazanik L G , Nikolsky E E , Snetkov V A , Vyskocil F
Published: December 2014

1. The amplitudes of end‐plate currents (EPCs) in short trains of fifteen to seventeen EPCs at 10 Hz were depressed in the presence of 10 microM‐proadifen when acetylcholinesterase (AChE) was inhibited. 2. The proadifen‐induced EPC depression was voltage‐dependent and the effect was more pronounced at negative membrane potentials. 3. In the presence of proadifen, the mean amplitude of miniature end‐plate currents (MEPCs) was reduced by 36% 5 s after the EPC train as compared with MEPCs before the train. 4. Without proadifen, but with inhibited AChE, an increase of temperature from 20 to 26 degrees C and elevation of external Ca2+ from 1.8 to 2.5 mM led to EPC amplitude depression in the train, which was also potential‐dependent. 5. After AChE inhibition, proadifen (10 microM) progressively shortened MEPC decay without significant reduction of amplitude up to 40 min of exposition. MEPCs were not affected by proadifen when AChE was active. 6. It is concluded that these postsynaptic effects of proadifen can be explained neither by its action on the resting acetylcholine receptors (AChR) nor on open ion channels but are due to its desensitization‐promoting action.
A novel type of delayed tension reduction observed in rat motor units after intense activity.
Authors: Lännergren J , Larsson L , Westerblad H
Published: December 2014

1. A delayed reduction of tetanic tension during recovery from fatigue, produced by repeated tetanic contractions, has been found in isolated amphibian muscle fibres (Westerblad & Lännergren, 1986). We have now followed the recovery in a mammalian muscle preparation to see if a similar phenomenon may appear also in mammalian muscles. 2. Single motor units of the rat tibialis anterior muscle were fatigued by 200 ms‐80 Hz stimulation trains, initially delivered every 4 s and then at decreasing intervals until tension was depressed to about 30% of the original. 3. After about 10 min of recovery tetanic tension was almost normalized. Tension then decreased in most units to a minimum, which occurred after 30‐100 min of recovery. At this stage tension outputs ranged from 6 to 95% of controls. 4. The EMG amplitude was also followed and like tension it was first almost normalized and then depressed. Generally the EMG depression was bigger than the tension loss; the EMG amplitudes were also somewhat reduced in the units not displaying any clear force reduction. 5. Both tetanic tension and EMG amplitude recovered gradually from the depressed state and values similar to controls were eventually reached. 6. In conclusion, we have found a novel type of delayed tension reduction in mammalian muscle during recovery after fatiguing contractions. The exact cause of this reduction is presently unclear, but an important contribution from impaired excitation‐contraction coupling is highly plausible.
Reduction by general anaesthetics of group Ia excitatory postsynaptic potentials and currents in the cat spinal cord.
Authors: Kullmann D M , Martin R L , Redman S J
Published: December 2014

1. The effects of thiopentone and halothane on excitatory synaptic transmission at group Ia afferent synapses on lumbosacral motoneurones were studied in the anaesthetized or decerebrate cat. 2. Thiopentone (10 mg kg‐1) infused on a background of light pentobarbitone anaesthesia caused a decrease in single‐fibre monosynaptic group Ia excitatory postsynaptic potentials (EPSPs) of between 0 and 24%. A step increase in inspired halothane concentration in the range 0.7‐0.9% produced a decrease in EPSP amplitude of between 0 and 31%. These effects were reversible when the anaesthetic level was reduced. 3. Fluctuation analysis of selected single‐fibre group Ia EPSPs revealed that these effects could be accounted for by a decrease in the probability of occurrence of EPSPs of larger amplitude, and an increase in the probability of occurrence of EPSPs of smaller amplitude. The mean separation between discrete amplitudes was not altered by either anaesthetic agent. 4. EPSPs whose time course indicated a somatic site of origin were voltage clamped to study the effect of the anaesthetics on the time course of the synaptic currents. Neither thiopentone nor halothane produced a consistent effect on the time constant of decay of the current, although they both depressed its peak amplitude. 5. The results are interpreted as indicating a presynaptic site of action of both anaesthetics at the concentrations studied: the probability of release of neurotransmitter is reduced, without any detectable change in the mean duration of the postsynaptic conductance increase. These findings are discussed in relation to the mechanisms of action of anaesthetics on exocytosis and presynaptic inhibition.
Further evidence for the origin of circulating calcitonin gene‐related peptide in the rat.
Authors: Emson P C , Zaidi M
Published: December 2014

1. We have attempted to determine the origin of a potent circulating vasodilator, calcitonin gene‐related peptide (CGRP), by assessing the effects of administration of capsaicin and colchicine, and of thyroidectomy on plasma levels. Plasma CGRP, neurokinin A and calcitonin levels were measured using highly sensitive and specific radioimmunoassays, and the circulating forms of CGRP characterized by size‐exclusion gel and high‐performance liquid chromatography. 2. Seven minutes following the intraperitoneal injection of capsaicin (10 mg/kg body weight) plasma CGRP and neurokinin A levels were found to rise by 15‐ and 4‐fold respectively, while there was no change in circulating calcitonin levels. Chromatography revealed that the immunochemical forms of CGRP released into the circulation by capsaicin were similar to those found in normal plasma, which included a peak co‐eluting with the intact CGRP molecule. 3. Six hours after the intraperitoneal administration of colchicine (10 mg/kg body weight), CGRP was not detectable in the circulation of 40‐day‐old rats and plasma levels were significantly lowered in the group of greater than or equal to 200‐day‐old rats. Chromatography revealed that peaks of circulating immunoreactivity corresponding to monomeric CGRP and its fragments were substantially reduced following colchicine treatment. 4. The magnitude of capsaicin‐evoked elevation of plasma CGRP was only marginally (significant at 0.1 greater than P greater than 0.05) reduced by pre‐treatment with colchicine. 5. Thyroidectomy alone caused a significant reduction of plasma CGRP levels in greater than or equal to 200‐day‐old rats; a greater reduction was observed when thyroidectomy was combined with colchicine administration. However, when 40‐day‐old rats were thyroidectomized, there was an unexplained elevation of plasma CGRP levels. 6. The results suggest that while CGRP is normally released into the circulation from nerve terminals, both in young adult (40‐day‐old) and old (greater than or equal to 200‐day‐old) animals, a thyroidal origin is obvious only in old rats.
Size and remoteness: two relatively independent parameters of dendrites, as studied for spinal motoneurones of the cat.
Authors: Kernell D , Zwaagstra B
Published: December 2014

1. The spatial extent of motoneuronal dendrites was analysed using data from the fifty‐two dendritic trees of four completely reconstructed cat motoneurones that had been labelled with intracellularly injected horseradish peroxidase. The cells belonged to m. triceps surae, and their physiological properties covered much of the known range for this muscle. 2. The percentage of total dendritic area extending beyond a radial somatofugal distance of 750 microns (PA750) was selected as an index of ‘dendritic remoteness’. 3. The value of our standard remoteness index PA750 was well correlated with a number of other possible remoteness measures, such as the percentage of total dendritic area beyond 500 or 1000 microns or the percentage of cumulative dendritic length beyond 750 or 1000 microns. 4. Most of the dendritic parameters could be classified as belonging either to a cluster of remoteness‐related properties or to a cluster of size‐related properties. Remoteness‐related properties were significantly correlated with PA750 but not with stem diameter. Size‐related properties were significantly correlated with stem diameter but not with the remoteness index PA750. The remoteness‐related properties included the mean somatofugal distance to branch points, the mean and maximum distance to terminal ending and, somewhat less distinctly, the mean length of terminal branches. The size‐related properties included the total dendritic area, the cumulative dendritic length, and the total number of branch points and terminal endings. 5. The extent of area expansion at branch points and the overall extent of tapering were not systematically related to differences in remoteness. 6. The relative degree of remoteness was greater for medial than for lateral dendrites. 7. Even in the present limited sample of cells, there were marked and systematic differences between different neurones with respect to the relative remoteness of their dendrites. The slowest and most high‐resistance motoneurone was the one with the most remote dendrites. On the whole there was, however, a considerable degree of independence between the variation in dendritic remoteness and the variation in physiologically determined properties (axonal conduction velocity, input resistance, after‐hyperpolarization). 8. In the discussion it is suggested that differences in dendritic remoteness might lead to a selectivity between the various members of a given motoneurone pool with respect to their reception of topographically distributed systems of synapses. It is proposed that such differences might be of interest in relation to, for instance, the organization of innervation to motoneurones belonging to different task groups within the same muscle.
Physiological mechanisms adopted by chondrocytes in regulating longitudinal bone growth in rats.
Authors: Hunziker E B , Schenk R K
Published: December 2014

1. Chondrocyte activities within growth plate cartilage are the principal determinants of longitudinal bone growth, and it was the aim of this investigation to assess how these cell activities are modulated under various growth rate conditions. Using proximal tibial growth plates from rats of different ages, growth rate was determined by fluorochrome labelling and incident light fluorescence microscopy. Various cellular parameters contributing to longitudinal bone growth were quantified by light microscopic stereology. The size of the proliferating cell population ('growth fraction') was estimated by autoradiography (using [3H]thymidine labelling). 2. A comparison between data for suckling (21‐day‐old) and fast‐growing (35‐day‐old) rats revealed that growth acceleration is achieved almost exclusively by cell‐shape modelling, namely by an increase in final cell height and a decrease in lateral diameter, whereas final cell volume and surface area are slightly reduced. Cell proliferation rate in the longitudinal direction and net matrix production per cell remain unchanged. The physiological increase in linear growth rate thus appears to be based principally upon a controlled structural modulation of the chondrocyte phenotype. On the other hand, a physiological reduction in growth rate (i.e. growth deceleration) effected during the transition from pre‐puberty (35‐day‐old rats) to maturity (80‐day‐old rats) is achieved by simultaneous decreases in several chondrocyte parameters, including cell height (i.e. phenotype modulation), cell volume and proliferation rate (in the longitudinal direction). However, chondrocytes continue to produce matrix at a level comparable to that attained during the period characterized by high growth rates (i.e. at 21 and 35 days). Cartilage matrix thus appears to play a subordinate role in regulating longitudinal bone growth rate. The duration of the hypertrophic cell activity (i.e. phenotype modulation) phase remains constant (at approximately 2 days) under the various growth rate conditions. 3. The findings presented in this study indicate that measurement of bulk parameters such as [35S]sulphate incorporation into matrix components, [3H]thymidine uptake by cells and growth plate height are of limited value as estimators of longitudinal bone growth, since changes in the parameters that these measurements quantify bear little relationship to changes in linear growth rate, and may be useful only as indicators of total growth plate activity.
Adrenoceptor profile of blood vessels in the knee joint of the rabbit.
Authors: Ferrell W R , Khoshbaten A
Published: December 2014

1. An in vitro preparation of the rabbit knee joint, perfused with oxygenated Locke solution, was used to assess the nature of adrenoceptors within articular blood vessels. 2. Dose/response relationships were obtained to intra‐arterial injection of alpha‐ and beta‐adrenoceptor agonists. 3. Adrenaline and noradrenaline produced a similar pattern of increasing constriction of articular vessels with increasing dose of drug. 4. The alpha 1‐agonist, phenylephrine, also produced dose‐dependent constrictor responses, but the alpha 2‐agonist; clonidine, had no effect. The alpha 2‐agonist UK‐14304 did, however, produce modest vasoconstriction which was not greatly altered by the alpha 1‐blocker prazosin. The constrictor effect of noradrenaline was abolished by both the alpha 1,2‐blocker phenoxybenzamine and by prazosin but not by the alpha 2‐blocker rauwalscine. 5. The beta‐adrenoceptor agonist, isoprenaline, had little effect at a dose of 10(‐6) M or lower, but gave rise to a constrictor effect at higher concentrations. This response was blocked by phenoxybenzamine but not by the beta 1,2‐blocker propranolol, suggesting that the constrictor effect was mediated via alpha‐adrenoceptors. 6. The results suggest that alpha 1‐ and alpha 2‐adrenoceptors are present within articular blood vessels, but that beta‐receptors are absent. The effects of noradrenaline appear to be mediated principally via alpha 1‐adrenoceptors.
Calcium currents in rat thalamocortical relay neurones: kinetic properties of the transient, low‐threshold current.
Authors: Coulter D A , Huguenard J R , Prince D A
Published: December 2014

1. Calcium currents were recorded with whole‐cell voltage‐clamp procedures in relay neurones of the rat thalamus which had been acutely isolated by an enzymatic dissociation procedure. 2. Low‐threshold and high‐threshold Ca2+ currents were elicited by depolarizing voltage steps from holding potentials more negative than ‐60 mV. A transient current, analogous to the T‐current in sensory neurones, was activated at low threshold near ‐65 mV and was completely inactivating at command steps up to ‐35 mV. Voltage steps to more depolarized levels activated a high‐threshold current that inactivated slowly and incompletely during a 200 ms step depolarization. 3. The high‐threshold current contained both non‐inactivating and slowly inactivating components which were insensitive and sensitive to holding potential, respectively. 4. A ‘T‐type’ current was prominent in relay neurones, in both absolute terms (350 pA peak current average) and in relation to high‐threshold currents. The average ratio of maximum transient to maximum sustained current was greater than 2. 5. T‐current could be modelled in a manner analogous to that employed for the fast Na+ current underlying action potential generation, using the m3h format. The rate of activation of T‐current was voltage dependent, with a time constant (tau m) varying between 8 and 2 ms at command potentials of ‐60 to ‐10 mV at 23 degrees C. The rate of inactivation was also voltage dependent, and the time constant tau h varied between 50 and 20 ms over the same voltage range. With command potentials more positive than ‐35 mV, the inactivation of Ca2+ current could no longer be fitted by a single exponential. 6. Steady‐state inactivation of T‐current could be well fitted by a Boltzman equation with slope factor of 6.3 and half‐inactivated voltage of ‐83.5 mV. 7. Recovery from inactivation of T‐current was not exponential. The major component of recovery (70‐80% of total) was not very voltage sensitive at potentials more negative than ‐90 mV, with tau r of 251 ms at ‐92 mV and 23 degrees C, compared to 225 ms at ‐112 mV. A smaller, voltage‐sensitive component accounted for the remainder of recovery. 8. All kinetic properties, including rates of activation, inactivation, and recovery from inactivation, as well as the amplitude of T‐current, were temperature sensitive with Q10 (temperature coefficient) values of greater than 2.5.(ABSTRACT TRUNCATED AT 400 WORDS)
Comparative Out-of-Sequence Estimation Techniques for Multi-Sensor Target Tracking
Authors: Mosquera-Lopez Clara , Pack Daniel
Published: December 2014

In this paper, performance comparisons are carried out between two out-of-sequence estimation filtering techniques based on the principles of the Extended Kalman Filter (EKF) and the Sigma-point Kalman filter (SPKF), in a mobile platform tracking application where distributed radars are used to estimate both linear and highly nonlinear movements of an aircraft. Two scenarios were considered: 1) aircraft movements fit a white noise acceleration model; and 2) aircraft movement follows a coordinated turn model with unknown turn rate. In addition, we evaluate the individual performance of the out-of-order filters against the ideal cases obtained by running the EKF and SPKF with reordered measurements in a chronological sequence. Simulation results show that the algorithms used for dealing with out-of-sequence measurements closely resemble the performance of the non-out-of-order filters. In terms of estimation accuracy, the out-of-order algorithm based on the SPKF outperforms the one based on the EKF when a highly nonlinear aircraft movement is observed. For nearly linear systems, there is not a significant difference between the two approaches.
A Multi-Target Tracking Formulation of SVSF With the Joint Probabilistic Data Association Technique
Authors: Attari Mina , Gadsden S. Andrew , Habibi Saeid R.
Published: December 2014

Target tracking scenarios offer an interesting challenge for state and parameter estimation techniques. This paper studies a situation with multiple targets in the presence of clutter. In this paper, the relatively new smooth variable structure filter (SVSF) is combined with the joint probability data association (JPDA) technique. This new method, referred to as the JPDA-SVSF, is applied on a simple multi-target tracking problem for a proof of concept. The results are compared with the popular Kalman filter (KF).
Spatial Vibration Control of Thin Beams Using Multimode Modified Positive Position Feedback
Authors: Omidi Ehsan , Mahmoodi S. Nima
Published: December 2014

Spatial multimode resonant vibration suppression using Modified Positive Position Feedback (MPPF) approach is presented in this paper. Spatial implementation of the MPPF controller considers vibration attenuation in the whole structure, rather than on a limited number of local control points. This approach utilizes spatial norm minimization of H2 and H∞, which considers vibration amplitude of all points on the structure in a model-based design. The designed controller is then evaluated using a clamped-clamped (c-c) and a cantilever beam as the test platforms. According to the numerical simulations and experimental results, spatial MPPF controller using both norm minimization techniques provides a high level of vibration suppression all over the structure, and for all active resonant modes. The MPPF-H∞ controlled system has a smoother response in the frequency domain, which is more preferable when the closed-loop system experiences a frequency sweep disturbance. At exact resonant frequency however, experimental results confirm a better suppression performance using the spatial MPPF-H2 method on different points of both beam structures.
Experimental Study of an Omni-Directional Wind Fluttering Energy Harvester
Authors: Arroyo Emmanuelle , Foong Shaohui , Maréchal Luc , Wood Kristin L.
Published: December 2014

Wind energy harvesters based on fluttering are a valuable and efficient alternative to traditional wind turbines. The optimized drive trains of traditional wind turbines have significantly shorter life expectancy and higher fabrication costs compared to harvesting systems based on fluttering. This article presents an analysis of a novel windbelt type energy harvester designed to harvest low-speed and changing direction winds. This experimental study explores the optimal ribbon tension, length and coil position of the wind-to-vibration converter, to obtain the maximum vibration acceleration.
Estimating Cutting Force Coefficients in High-Speed Low-Radial-Immersion Milling Processes
Authors: Bryan Josiah A. , Fales Roger C.
Published: December 2014

A high-speed milling system is considered, which is prone to chatter vibration, a stability condition dependent on system parameters (e.g., cutting force coefficients). This work is motivated by the need for model parameters which can be used in stability analysis. An Extended Kalman Filter (EKF) is proposed to estimate cutting force coefficients for each tooth in a low-radial-immersion milling process to aid chatter stability prediction. The proposed EKF utilizes tool deflection measurements and no force measurements. The model used in the EKF is found to be observable, a quality required to achieve valid state estimations. Running the EKF with experimental tool deflection measurements produces estimates of cutting force coefficients that result in good correlation between simulation (using the estimated coefficients) and experiment. Such an EKF may help customize chatter stability analysis to any particular tool-workpiece system.
Multiagent Coordination Optimization Based Model Predictive Control Strategy With Application to Balanced Resource Allocation
Authors: Zhang Haopeng , Hui Qing
Published: December 2014

Model predictive control (MPC) is a heuristic control strategy to find a consequence of best controllers during each finite-horizon regarding to certain performance functions of a dynamic system. MPC involves two main operations: estimation and optimization. Due to high complexity of the performance functions, such as, nonlinear, non-convex, large-scale objective functions, the optimization algorithms for MPC must be capable of handling those problems with both computational efficiency and accuracy. Multiagent coordination optimization (MCO) is a recently developed heuristic algorithm by embedding multiagent coordination into swarm intelligence to accelerate the searching process for the optimal solution in the particle swarm optimization (PSO) algorithm. With only some elementary operations, the MCO algorithm can obtain the best solution extremely fast, which is especially necessary to solve the online optimization problems in MPC. Therefore, in this paper, we propose an MCO based MPC strategy to enhance the performance of the MPC controllers when addressing non-convex large-scale nonlinear problems. Moreover, as an application, the network resource balanced allocation problem is numerically illustrated by the MCO based MPC strategy.
Experimental Validation of a Nonlinear Self-Tuning Observer
Authors: Mastory Constantine G. , Chalhoub Nabil G.
Published: December 2014

The present work provides an experimental validation for the robust performance of a nonlinear self-tuning observer in accurately estimating the state variables of a structure with configuration-dependent natural frequencies. The observer design combines the advantages of the variable structure systems theory and the self-tuning fuzzy logic technique. The robustness of the observer enables the use of an imprecise model of the plant while the self-tuning characteristic eliminates the need for the extensive tuning of a fixed rule-based expert fuzzy inference system.

The experimental set-up consists of a spherical robotic manipulator with the protruding portion of the third link from the second link considered to be deformable. The prismatic joint induces considerable variations in the natural frequencies of the flexible element. The observer has been implemented to estimate the generalized coordinates pertaining to the flexible motion of the third link. The experimental results confirm the robustness of the observer in accurately estimating the required state variables of the system in spite of significant modeling imprecision and disturbances.
Geometric PID Control for Almost-Global Stabilization of a Quadrotor With Parameter Error and Constant Disturbances
Authors: Maithripala D. H. S. , Berg Jordan M.
Published: December 2014

Intrinsic controllers are invariant under the coordinates used for their representation. In the case of rigid-body motion in two and three dimensions, the intrinsic approach eliminates problems with singularity or over-parametrization that may occur in specific choices such as Euler angles or quaternions. Intrinsic PD controllers that combine almost-global stabilization with a familiar and intuitive PD design framework have been known for several years. In this paper we show how intrinsic integral action may be added to intrinsic PD control. We apply the result to stabilize the attitude of a quadrotor UAV model, and demonstrate in simulation that performance is significantly improved in the presence of parameter uncertainty and constant disturbance forces. We also consider the effect of bounded, time-varying, disturbances.
Improved Rectifier Circuit With Backward Diodes for Low Power Source Harvesting
Authors: Wu Wei , Lozowski Andy G. , Wang Fengxia
Published: December 2014

Most energy harvesting circuits use a Schottky diode rectifier as the first stage in the power conversion system. Schottky diodes are chosen for their low forward-voltage drop which can be as low as 0.15V. Further improvements toward enabling lower voltage sources may be accomplished by using active rectifiers with MOSFET transistors. However such circuits still require an initial start-up phase in which the source voltage needs to exceed the Schottky barrier voltage. As an alternative we propose using backward diodes to build a rectifier with much smaller barrier voltage compared to the Schottky solution. In the past, backward diodes were used in low-voltage diode detectors and are essentially a variation of tunnel diodes. This paper provides both simulation results and an experimental comparative study of the performance of Schottky and backward diodes. The relationship between optimal load, frequency and internal impedance of the voltage source will be discussed as well.