bluuebunny/crossref_metadata_2025 huggingface dataset:
Expression of the β‐glucosidase genePgβglu‐1underpins natural resistance of white spruce against spruce budworm
Authors: Mageroy Melissa H. , Parent Geneviève , Germanos Gaby , Giguère Isabelle , Delvas Nathalie , Maaroufi Halim , Bauce Éric , Bohlmann Joerg , Mackay John J.
Published: January 2015

Periodic outbreaks of spruce budworm (SBW) affect large areas of ecologically and economically important conifer forests in North America, causing tree mortality and reduced forest productivity. Host resistance againstSBWhas been linked to growth phenology and the chemical composition of foliage, but the underlying molecular mechanisms and population variation are largely unknown. Using a genomics approach, we discovered a β‐glucosidase gene,Pgβglu‐1, whose expression levels and function underpin natural resistance toSBWin mature white spruce (Picea glauca) trees. In phenotypically resistant trees,Pgβglu‐1transcripts were up to 1000 times more abundant than in non‐resistant trees and were highly enriched in foliage. The encoded PgβGLU‐1 enzyme catalysed the cleavage of acetophenone sugar conjugates to release the aglycons piceol and pungenol. These aglycons were previously shown to be active againstSBW. Levels ofPgβglu‐1transcripts and biologically active acetophenone aglycons were substantially different between resistant and non‐resistant trees over time, were positively correlated with each other and were highly variable in a natural white spruce population. These results suggest that expression ofPgβglu‐1and accumulation of acetophenone aglycons is a constitutive defence mechanism in white spruce. The progeny of resistant trees had higherPgβglu‐1gene expression than non‐resistant progeny, indicating that the trait is heritable. With reported increases in the intensity ofSBWoutbreaks, influenced by climate, variation ofPgβglu‐1transcript expression, PgβGLU‐1 enzyme activity and acetophenone accumulation may serve as resistance markers to better predict impacts ofSBWin both managed and wild spruce populations.
Classic myrosinase‐dependent degradation of indole glucosinolate attenuates fumonisin B1‐induced programmed cell death in Arabidopsis
Authors: Zhao Yanting , Wang Jiansheng , Liu Yuanyuan , Miao Huiying , Cai Congxi , Shao Zhiyong , Guo Rongfang , Sun Bo , Jia Chengguo , Zhang Liping , Gigolashvili Tamara , Wang Qiaomei
Published: January 2015

The mycotoxin fumonisin B1 (FB1) causes the accumulation of reactive oxygen species (ROS) which then leads to programmed cell death (PCD) in Arabidopsis. In the process of studying FB1‐induced biosynthesis of glucosinolates, we found that indole glucosinolate (IGS) is involved in attenuating FB1‐induced PCD. Treatment with FB1 elevates the expression of genes related to the biosynthesis of camalexin and IGS. Mutants deficient in aliphatic glucosinolate (AGS) or camalexin biosynthesis display similar lesions to Col‐0 upon FB1 infiltration; however, the cyp79B2 cyp79B3 double mutant, which lacks induction of both IGS and camalexin, displays more severe lesions. Based on the fact that the classic myrosinase β‐thioglucoside glucohydrolase (TGG)‐deficient double mutant tgg1 tgg2, rather than atypical myrosinase‐deficient mutant pen2‐2, is more sensitive to FB1 than Col‐0, and the elevated expression of TGG1, but not of PEN2, correlates with the decrease in IGS, we conclude that TGG‐dependent IGS hydrolysis is involved in FB1‐induced PCD. Indole‐3‐acetonitrile (IAN) and indole‐3‐carbinol (I3C), the common derivatives of IGS, were used in feeding experiments, and this rescued the severe cell death phenotype, which is associated with reduced accumulation of ROS as well as increased activity of antioxidant enzymes and ROS‐scavenging ability. Despite the involvement of indole‐3‐acetic acid (IAA) in restricting FB1‐induced PCD, feeding of IAN and I3C attenuated FB1‐induced PCD in the IAA receptor mutant tir1‐1 just as in Col‐0. Taken together, our results indicate that TGG‐catalyzed breakdown products of IGS decrease the accumulation of ROS by their antioxidant behavior, and attenuate FB1 induced PCD in an IAA‐independent way.
Agrobacterium T‐DNA integration into the plant genome can occur without the activity of key non‐homologous end‐joining proteins
Authors: Park So‐Yon , Vaghchhipawala Zarir , Vasudevan Balaji , Lee Lan‐Ying , Shen Yunjia , Singer Kamy , Waterworth Wanda M. , Zhang Zhanyuan J. , West Christopher E. , Mysore Kirankumar S. , Gelvin Stanton B.
Published: January 2015

Non‐homologous end joining (NHEJ) is the major model proposed for Agrobacterium T‐DNA integration into the plant genome. In animal cells, several proteins, including KU70, KU80, ARTEMIS, DNA‐PKcs, DNA ligase IV (LIG4), Ataxia telangiectasia mutated (ATM), and ATM‐ and Rad3‐related (ATR), play an important role in ‘classical’ (c)NHEJ. Other proteins, including histone H1 (HON1), XRCC1, and PARP1, participate in a ‘backup’ (b)NHEJ process. We examined transient and stable transformation frequencies of Arabidopsis thaliana roots mutant for numerous NHEJ and other related genes. Mutants of KU70, KU80, and the plant‐specific DNA LIGASE VI (LIG6) showed increased stable transformation susceptibility. However, these mutants showed transient transformation susceptibility similar to that of wild‐type plants, suggesting enhanced T‐DNA integration in these mutants. These results were confirmed using a promoter‐trap transformation vector that requires T‐DNA integration into the plant genome to activate a promoterless gusA (uidA) gene, by virus‐induced gene silencing (VIGS) of Nicotiana benthamiana NHEJ genes, and by biochemical assays for T‐DNA integration. No alteration in transient or stable transformation frequencies was detected with atm, atr, lig4, xrcc1, or parp1 mutants. However, mutation of parp1 caused high levels of T‐DNA integration and transgene methylation. A double mutant (ku80/parp1), knocking out components of both NHEJ pathways, did not show any decrease in stable transformation or T‐DNA integration. Thus, T‐DNA integration does not require known NHEJ proteins, suggesting an alternative route for integration.
Seed germination of the invasive species Piper aduncum as influenced by high temperature and water stress
Authors: Wen B , Xue P , Zhang N , Yan Q , Ji M
Published: January 2015

Piper aduncum is a common woody weed throughout the tropics and a successful invader in many areas. As this species most often dominates roadsides and forest margins, and these habitats frequently experience extreme changes in temperature and water availability, it is important to understand how the seeds adapt to these stresses. This study investigated the effect of high temperatures and water stress, continuous, periodic or transient, on P. aduncum seed germination before or after imbibition. It was found that P. aduncum seeds exhibited only intermediate tolerance and did not germinate at temperatures above 35°C or water potentials below −0.6 MPa. However, this species is well adapted to local conditions, with fruit ripening in the rainy season, seed desiccation tolerance to eRH 8%, rapid germination under wet conditions, higher temperature tolerance than the maximum ground temperature, germination of most seeds after 60 h continuous heat treatment or daily periodic heat treatments up to 5 h at 40°C and insensitivity to 12 h heat treatment at 40°C during the whole germination process. The intermediate tolerance to high temperature and water stress of P. aduncum, in combination with local environmental conditions in Xishuangbanna, makes P. aduncum an intermediate invader in this area.
Evidence for a functional vasodilatatory role for hydrogen sulphide in the human cutaneous microvasculature
Authors: Kutz Jessica L. , Greaney Jody L. , Santhanam Lakshmi , Alexander Lacy M.
Published: January 2015

Key points

Hydrogen sulphide (H2S) is vasoprotective, attenuates inflammation and modulates blood pressure in animal models; however, its specific mechanistic role in the human vasculature remains unclear.

In the present study, we report the novel finding that the enzymes responsible for endogenous H2S production, cystathionine‐γ‐lyase and 3‐mercaptopyruvate sulphurtransferase, are expressed in the human cutaneous circulation.

Functionally, we show that H2S‐induced cutaneous vasodilatation is mediated, in part, by tetraethylammonium‐sensitive calcium‐dependent potassium channels and not by ATP‐sensitive potassium channels. In addition, nitric oxide and cyclo‐oxygenase‐derived byproducts are required for full expression of exogenous H2S‐mediated cutaneous vasodilatation.

Future investigations of the potential role for H2S with respect to modulating vascular function in humans may have important clinical implications for understanding the mechanisms underlying vascular dysfunction characteristic of multiple cardiovascular pathologies.

The present study aimed to identify the presence of cystathionine‐γ‐lyase (CSE) and 3‐mercaptopyruvate sulphurtransferase (3‐MST), which endogenously produce hydrogen sulphide (H2S), and to functionally examine the mechanisms of H2S‐induced vasodilatation in the human cutaneous microcirculation. CSE and 3‐MST were quantified in forearm skin samples from 5 healthy adults (24 ± 3 years) using western blot analysis. For functional studies, microdialysis fibres were placed in the forearm skin of 12 healthy adults (25 ± 3 years) for graded infusions (0.01–100 mm) of sodium sulphide (Na2S) and sodium hydrogen sulphide (NaHS). To define the mechanisms mediating H2S‐induced vasodilatation, microdialysis fibres were perfused with Ringer solution (control), a ATP‐sensitive potassium channel (KATP) inhibitor, an intermediate calcium‐dependent potassium channel (KCa) inhibitor, a non‐specific KCa channel inhibitor or triple blockade. To determine the interaction of H2S‐mediated vasodilatation with nitric oxide (NO) and cyclo‐oxygenase (COX) signalling pathways, microdialysis fibres were perfused with Ringer solution (control), a non‐specific NO synthase inhibitor, a non‐selective COX inhibitor or combined inhibition during perfusion of increasing doses of Na2S. CSE and 3‐MST were expressed in all skin samples. Na2S and NaHS elicited dose‐dependent vasodilatation. Non‐specific KCa channel inhibition and triple blockade blunted Na2S‐induced vasodilatation (P < 0.05), whereas KATP and intermediate KCa channel inhibition had no effect (P > 0.05). Separate and combined inhibition of NO and COX attenuated H2S‐induced vasodilatation (all P < 0.05). CSE and 3‐MST are expressed in the human microvasculature. Exogenous H2S elicits cutaneous vasodilatation mediated by KCa channels and has a functional interaction with both NO and COX vasodilatatory signalling pathways.
Anomalies of disparity detection in the human visual system.
Authors: Jones R
Published: January 2015

1. Oculomotor and psychophysical depth responses were investigated in thirty individuals by use of briefly exposed disparities in the range from 0‐6 to 4‐6 degrees (1‐8 centrads). 2. The results substantiate a previous finding which reported the common occurrence of specific types of stereoanomalies within a sample from the normal population. However, arguments are presented to suggest that these forms of stereoanomalies are limited to coarse stereopsis and spare mechanisms concerned with fine disparity, high resolution stereopsis. 3. A relatively high proportion of individuals were found to manifest deficiencies of vergence eye movement under these stimulus conditions. These vergence‐anomalies are characterized by a marked reduction, or absence, of neither convergent or divergent eye movements to briefly exposed stimuli. 4. The vergence‐anomaly is not detrimental under normal seeing conditions since it can be present in persons with adequate binocular vision and normal fine stereopsis. 5. The presence of vergence‐anomaly was always associated with the occurrence of stereoanomaly; however, the converse was not true. 6. The results are taken as evidence to show how disparity information is organized prior to its influence upon the processes of coarse stereopsis and vergence initiation.
Responses of intradental nerves to electrical and thermal stimulation of teeth in dogs.
Authors: Matthews B
Published: January 2015

1. Experiments were carried out to investigate the mechanism whereby thermal stimul excite nerves to produce pain from teeth. 2. Recordings have been made from single fibres dissected from the inferior dental nerve in dogs during thermal stimulation of the lower canine tooth. 3. In preliminary experiments, no units were found with thresholds close to the thresholds for pain in man (45 and 27 degrees C) and subsequently test stimuli of 55 degrees C, applied for up to 15 sec, and 0‐5 degrees C were used. 4. Of 117 fibres tested, forty‐three responded to cooling but not to heating and nine responded to heating but not to cooling. 5. By applying thermal stimuli direct to the saphenous nerve in cats, it was shown that these responses might have been due to direct excitation of nerves and not to stimulation of specialized receptors. 6. Some units responded to electrical stimulation of the tooth pulp with a latency which decreased abruptly at a critical intensity as the stimulus was increased above threshold. Evidence was obtained which suggested that this was due to branching of the fibres.
Ballistic contractions in man: characteristic recruitment pattern of single motor units of the tibialis anterior muscle.
Authors: Desmedt J E , Godaux E
Published: January 2015

1. Single motor units were recorded with highly selective electrodes from intact tibialis anterior muscle in the adult man. A detailed parametric analysis was made of the discharge patterns during voluntary isometric contractions of different peak forces carried out at various rates of force development. 2. During the smooth tracking of a ramp force, the different motor units recorded from a given muscle site were recruited in a consistant order, each unit becoming active when the muscle developed a certain level of force. The threshold of some of the units in such slow ramp contractions exceeded 8 kg. By contrast, in brisk ballistic contractions reaching a peak force of 12 kg in less than 0‐15 sec, the same motor units discharged in a transient burst which largely preceded the muscle force production. 3. In slow tracking ramp contractions, the instantaneous frequency of single motor units was initially rather low (5‐15/sec) and it increased as the ramp force augmented. By contrast, in (strong) ballistic contractions, the same units discharged at an unusually high instantaneous frequency (60‐120/sec) early in the burst and the firing frequency decreased thereafter. Such hitherto unknown pattern appears characteristic of ballistic contractions and it was not found in even fast tracking ramp contractions achieving 12 kg in only 0‐4 sec. 4. The potentials of the different motor units activated are rather crowded at intervals of a few msec in the early burst of a strong ballistic contraction and observations on the rank activation of the different motor units do not provide reliable data for the analysis of the recruitment order of units in ballistic contractions. 5. A new method is described for estimating ballistic force threshold of single motor units. When a large series of brisk ballistic contractions with peak forces ranging from 0‐05 to 12 kg was carried out any given motor unit only became active when the ballistic peak force exceeded a certain reproducible value. A detailed analysis of the recruitment order based on these ballistic force thresholds showed it to be virtually identical to the recruitment order of the same units in slow tracking ramp contractions (correlation=0‐95). 6. Ballistic contractions are graded in force both by the recruitment of additional motor units in stronger contractions, and by an increase in their rate of firing. These gradation mechanisms are discussed.
Regenerative amacrine cell depolarization and formation of on‐off ganglion cell response.
Authors: Werblin F S
Published: January 2015

1. Recordings from amacrine and ganglion cells in the mudpuppy retina suggest mechanisms whereby the relatively slow, sustained light responses measured in bipolar cells are converted to rapid, brief, transient activity in the on‐off ganglion cells. 2. Double‐barrel electrodes were used to control the membrane potential under voltage clamp. The clamp revealed synaptic currents, but eliminated the otherwise obvious spike activity elicited by steps of illumination in both amacrine and ganglion cells, suggesting that the spikes are initiated near the somata. 3. The synaptic current in the on‐off ganglion cells was biphasic: a brief inward (depolarizing) membrane current preceded a transient outward (hyperpolarizing) membrane current by about 20 msec. Each component could be isolated by polarizing the membrane to a level near the reversal potential for the other. Each was apparently due to a transient conductance increase of sawtooth shape with a 40 msec time to peak and a decay longer than 400 msec. 4. Synaptic membrane current in amacrine cells was monophasic and inward (depolarizing) of similar sawtooth shape at all potential levels. It was apparently mediated by a conductance increase to ions with a reversal potential more positive than the dark level. 5. When amacrine cells were depolarized in the dark under voltage clamp, a large transient inward membrane current with threshold within 4 mV of the dark level was generated. This regenerative event is capable of boosting a small, 4 mV e.p.s.p. to more than 30 mV in a few milliseconds, thereby generating the leading edge of a rapid sawtooth response. 6. The results suggest that the rapid transient on‐off activity in ganglion cells is mediated by opposing sawtooth shaped synaptic currents with different latencies. It is inferred that each of these antagonistic imputs is generated by a regenerative depolarization in amacrine cells which then form synaptic inputs to the ganglion cells.
Identification of amacrine and ganglion cells in the carp retina.
Authors: Murakami M , Shimoda Y
Published: January 2015

1. Amacrine and ganglion cells in the carp retina were identified from such criteria as photoresponses, intracellular dye staining, responses to optic nerve stimulation and behaviour to a synapse blocking agent. 2. Responses of ganglion cells were accompanied by spike discharges., either facilitated or suppressed by photic stimulation. The cells were also invaded by antidromic impulses, which survived after chemical synapses had been blocked by application of atomized CoCl2 solution. In subsequent histology of the Procion‐stained neurones, the cell bodies were found in the ganglion cell layer and the axons were often traced. 3. Amacrine cells were subdivided into two types. The first type gave rise to transient depolarizations at both on‐ and offsets of spot and annulus illuminations, usually being associated with spike discharges of which the amplitudes varied in different cells. In histology, the cell bodies of this type were situated in the inner nuclear layer and dendrites ramified in two or more discrete sublayers of the inner plexiform layer (the stratified amacrine cell of Cajal). 4. The second type of amacrine cells produced sustained responses during illumination, being associated with no spike but with small oscillatory wavelets. The cell bodies were situated in the inner nuclear layer and the dendrites ramified in a single sublayer of the inner plexiform layer (the monolayered amacrine cell). 5. An attempt was made to see the effect of activation of centrifugal fibres on amacrine cells, but almost all of about 200 cells examined did not respond to optic nerve stimulation. Only two cells produced, with long latency, a small post‐synaptic depolarization which disappeared after chemical synapses in the retina had been blocked. It is considered that the physiological role of the centrifugal system is insignificant in the carp retina.
Characterization of metachronal wave of beating cilia on frog's palate epithelium in tissue culture.
Authors: Eshel D , Priel Z
Published: January 2015

1. A method is suggested to measure phase versus distance between beating cilia by means of a photoelectric device. A statistical method interpreting the results thus obtained is discussed. 2. It was found that: (a) an average phase exists between beating cilia, (b) despite strong fluctuations in phase on a short time scale, the average phase was kept constant over periods of 8 h, (c) the ciliary frequency and the length of the metachronal wave can be measured simultaneously. 3. The average phase differences are linearly dependent on distance. 4. The effective range of synchronization between cilia is of the order of 10 micron indicating that it occurs within one cell. 5. During the cycle of ciliary beating there are periods where coupling is stronger.
Modulation of the vagal drive to the intramural cholinergic and non‐cholinergic neurones in the ferret stomach by baclofen.
Authors: Andrews P L , Bingham S , Wood K L
Published: January 2015

1. In the urethane‐anaesthetized ferret vagotomy (cervical and abdominal) and hexamethonium both produced an increase in gastric corpus pressure after treatment with atropine and guanethidine, section of the greater splanchnic nerves and adrenalectomy. 2. The pressure increase was due to an interruption of a tonic vagal drive to the intramural non‐adrenergic, non‐cholinergic inhibitory neurones. 3. The GABAB receptor agonist baclofen (8 mg/kg s.c.) produced an increase in gastric pressure and enhanced the amplitude of the rhythmic contractions. Baclofen was without effect in vagotomized animals. 4. In the presence of atropine, guanethidine, adrenalectomy and section of the greater splanchnic nerves, baclofen produced only a slight enhancement of rhythmic contractions but the large increase in gastric pressure was still present. Under the above conditions the effects of baclofen on the whole stomach were virtually identical to those observed in the corpus region alone. 5. Baclofen was without effect on the magnitude of the corpus relaxation produced by the submaximal vagal efferent stimulation in the presence of atropine. 6. These results demonstrate that the GABAB agonist baclofen, probably acting at a central site, enhanced rhythmic gastric activity by increasing the vagal drive to the intramural cholinergic neurones. Simultaneously gastric pressure was increased primarily by a reduction in the tonic vagal drive to the intramural non‐adrenergic, non‐cholinergic inhibitory neurones in the corpus region. The results of both the baclofen and vagotomy studies further demonstrate the importance of the vagal innervation of the non‐adrenergic, non‐cholinergic inhibitory neurones in the regulation of gastric pressure.
Response characteristics of pulmocutaneous arterial baroreceptors in the toad, Bufo marinus.
Authors: Van Vliet B N , West N H
Published: January 2015

1. Response characteristics of baroreceptors with receptive fields in the pulmocutaneous artery (p.c.a.) were determined in pithed toads by applying pressure steps, ramps, sine waves, and volume infusions into the vascularly isolated and perfused p.c.a. 2. The baroreceptors exhibited phasic and tonic discharge thresholds (30.3 +/‐ 2.3 and 36.2 +/‐ 2.8 mmHg respectively) which were above mean arterial pressure values reported for conscious undisturbed toads. They are comparable, in this respect, to non‐myelinated mammalian arterial baroreceptors. 3. The maximum‐phasic and minimum‐adapted discharge frequencies of the p.c.a. baroreceptors were low (30 and 2‐3 spikes s‐1, respectively), but resembled those reported for mammalian non‐myelinated baroreceptors when an adjustment was made for the difference in the temperature of mammalian and amphibian preparations. 4. The sensitivity of the baroreceptor discharge frequency to pressure (delta F/delta P) was estimated from pressure‐step and pressure‐ramp stimuli. Both estimates were greater than those reported for mammalian systemic arterial baroreceptors after the values were normalized to the maximum discharge frequency of the receptors. delta F/delta P and saturation discharge frequency values estimated from ramp stimuli increased with the dP/dt of pressure ramps. 5. The diameter of the p.c.a. was measured by sonomicrometry in toads anaesthetized with urethane. The diameter pulsation was 7.7 +/‐ 0.3% of the mean diameter (3.5 +/‐ 0.1 mm) at a mean pulse pressure of 22 +/‐ 1 mmHg, and Peterson's pressure‐strain modulus was calculated to be 4.0 X 10(5) +/‐ 0.3 X 10(5) dyn cm‐2, which suggests that the p.c.a. is highly compliant, and in this respect is comparable to the pulmonary artery, but not to systemic arteries, in mammals. Baroreceptor discharge began near the point of peak dynamic compliance (dV/dP) and continued as dV/dP decreased. Increasing the rate of infusion reduced the peak dV/dP, but increased the baroreceptor discharge frequency. 6. The response to sinusoidal oscillating pressure stimuli was distorted by rectification. Increasing the frequency of sinusoidal stimulation over the range 0.05‐1.0 cycles s‐1 reduced the number of spikes per cycle, but increased the mean discharge frequency.
Transmural calcium fluxes and role of mucins as cellular calcium‐transport vehicles in chicken trachea in vitro.
Authors: Kent P W , Mian N
Published: January 2015

1. Transmural Ca2+ fluxes in tracheal tissue under physiological [Ca2+] conditions and the effect of altered serosal and luminal [Ca2+] on Ca2+ movements were investigated using chicken tracheal preparations in vitro. 2. In the presence of physiological [Ca2+] (1.8 mM), there was unidirectional Ca2+ flux with a small but steady uptake of Ca2+ from the serosal side into the submucosa followed by Ca2+ transport into the mucosa and then Ca2+ efflux into the tracheal lumen. The Ca2+ uptake by the tracheal tissue was via a diffusion process. There was no evidence of Ca2+ uptake via slow Ca2+ channels or Na+‐Ca2+ exchange pathways. On the other hand, Ca2+ uptake from the lumen into the mucosa and Ca2+ efflux from the submucosa into the serosal side were almost negligible. 3. High serosal [Ca2+] (18.0 mM) and/or low luminal [Ca2+] (0.18 mM) increased significantly both Ca2+ uptake by the tissue from its serosal side and Ca2+ efflux into the lumen. Directional Ca2+ effect appeared to increase Ca2+ uptake via a diffusion process. 4. Transport of Ca2+ from the mucosa into the lumen comprised efflux of both filterable and mucin‐bound forms of Ca2+. Under physiological [Ca2+] conditions, whilst initial efflux rates of both filterable and mucin‐bound Ca2+ were almost equal, the net efflux of Ca2+ in mucin‐bound form after 10 min was about 33% higher than that of filterable Ca2+. Similarly, the increase in Ca2+ efflux as a result of high serosal [Ca2+] involved a significant increase in the efflux of mucin‐bound Ca2+ only, whereas the increased Ca2+ efflux as a result of low luminal [Ca2+] involved a significant increase in efflux of both filterable and mucin‐bound Ca2+. 5. The transport of Ca2+ from the mucosa into the lumen in the form of mucin‐bound Ca2+ appeared to play a significant role in the regulation of Ca2+ efflux from the tissue under increased Ca2+ influx or efflux conditions resulting from interventions with serosal and luminal [Ca2+]. 6. A concurrent stimulation of secretion of unique low molecular weight sulphate‐rich components and high molecular weight mucin complexes with increased Ca2+ influx into and efflux from the tracheal tissue in response to high serosal and low luminal [Ca2+] allude to a plausible role of these secretory macromolecular mucin complexes as cellular Ca2+ transport vehicles.
Specificity of synaptic regeneration in the spinal cord of the larval sea lamprey.
Authors: Mackler S A , Selzer M E
Published: January 2015

1. Pairs of central neurones in large larval sea lampreys were impaled with micro‐electrodes and studied for synaptic connexions in both unoperated control animals and animals which had recovered from complete spinal transection. Two identified classes of neurones served as post‐synaptic targets: giant interneurones (g.i.s) and lateral cells (l.c.s). Several identified neurone types were tested as potential sources of presynaptic input. 2. When synaptic potentials had short, fixed latencies they also persisted during activation of the presynaptic cell at 3.3‐33.3 Hz and were not eliminated after addition of lamprey saline containing high (20 mM) Ca2+. These presumably represented monosynaptic connexions. Variable‐latency responses were eliminated by faster rates of stimulation of the presynaptic cell and were mediated via polysynaptic pathways. 3. In control animals, g.i.s received monosynaptic input from more caudal g.i.s in fourteen of thirty‐two tested cell pairs. These excitatory post‐synaptic potentials (e.p.s.p.s) were composite electrochemical responses. The amplitudes of the earlier electrical component averaged 1.66 +/‐ 0.24 mV (mean +/‐ S.E. of mean) and the amplitude of the later chemical component averaged 0.79 +/‐ 0.05 mV. 4. In operated larvae, eight of forty‐seven g.i.‐g.i. pairs separated by the transection scar were connected by monosynaptic composite e.p.s.p.s. In these pairs the electrical component averaged 0.84 +/‐ 0.17 mV (P less than 0.05 vs. control) and the chemical component averaged 1.56 +/‐ 0.40 mV. The average conduction velocity between these cells was less than that in control g.i.‐g.i. pairs (0.93 +/‐ 0.11 vs. 1.61 +/‐ 0.25 m/s; P less than 0.01). 5. The l.c.s showed monosynaptic e.p.s.p.s after activation of a subset of the bulbar Müller neurones (B2‐4) in seven of twelve pairs. In behaviourally recovered larvae three of twenty‐two similar pairs separated by the transection scar were also connected via monosynaptic e.p.s.p.s. The average conduction velocity between these experimental neurones was also less than that in control bulbar‐l.c. pairs (1.03 +/‐ 0.03 vs. 1.58 +/‐ 0.09 m/s; P less than 0.001). 6. Several types of neurones were either infrequently linked or never connected to g.i.s or to l.c.s in control larvae. In animals which had recovered from a spinal transection, no synaptic connexions were found from such neurones on to g.i.s or l.c.s respectively, in 124 tested cell pairs. In addition, dorsal cells (intraspinal primary sensory neurones) received no synaptic input upon stimulation of the spinal cord before or after transection.(ABSTRACT TRUNCATED AT 400 WORDS)
Contributions of inhibitory mechanisms to the shift responses of X and Y cells in the cat lateral geniculate nucleus.
Authors: Eysel U T , Pape H C , Van Schayck R
Published: January 2015

1. Adult cats were anaesthetized with a mixture of halothane, nitrous oxide and oxygen to record from single neurones of the dorsal lateral geniculate nucleus (d.l.g.n.) with five‐barrel glass micro‐electrodes. Periphery effects (shift effects) were elicited by large‐field phase‐reversing gratings presented in the visual field outside the conventional receptive field area. 2. A range of transient excitatory responses was found in X and Y cells. Y cells had phasic shift effects with significantly higher amplitudes and shorter durations (mean 52 impulses/s, 135 ms) than those observed in the tonic shift effects of X cells (mean 24 impulses/s, 169 ms). All Y cells and most X cells responded to stimulation of remote retinal regions. About 7% of the X cells displayed no shift effect. 3. Micro‐ionophoresis of the gamma‐aminobutyric acid (GABA) antagonist bicuculline, acetylcholine (ACh) and L‐glutamate specifically influenced the shift effects of X and Y cells. 4. During continuous application of the GABA antagonist bicuculline the differences in maximal response rates and amplitudes of X and Y cells were eliminated. The maintained activity raised predominantly in X cells and the early peak rates increased more in X‐ than in Y‐cell shift effects, leading to equal average peak rates of 100 and response amplitudes of about 85 impulses/s in both cell classes. The characteristic time courses of X‐ and Y‐cell responses were not affected. 5. Micro‐ionophoretic application of ACh caused a combination of excitatory and disinhibitory effects. Maintained activity as well as early parts of stimulus‐evoked responses were similarly raised in X and Y cells. In addition, the Y‐cell shift effects became less phasic by elevation of the late response part. Sodium pentobarbitone, used to block ACh excitation, suppressed the ACh‐induced effects in the early phase of the X‐ and Y‐cell shift effects and the increase of maintained activity in Y‐cells, while the effect on the late part of Y‐cell responses persisted. Elevation of background activity partially remained in X cells, and the X‐cell responses became tonically prolonged at the same time. 6. L‐Glutamate increased the activity of X and Y cells without changing the characteristic shift‐effect properties of both cell classes. 7. It is concluded that different short‐ and long‐lasting inhibitory mechanisms shape the responses of d.l.g.n. neurones to stimulation outside the conventional receptive field.(ABSTRACT TRUNCATED AT 400 WORDS)
Effects of repetitive activity on developed force and intracellular sodium in isolated sheep and dog Purkinje fibres.
Authors: Boyett M R , Hart G , Levi A J , Roberts A
Published: January 2015

1. When cardiac muscle is stimulated after a rest there is a gradual increase in force development over several minutes. The origin of this 'force staircase' was investigated in experiments on sheep and dog Purkinje fibres. Particular attention was paid to the possible role of changes in the intracellular Na+ activity (aNAi). 2. The first line of evidence for a role for aiNa came from a comparison of sheep and dog Purkinje fibres generating action potentials: after a change in the stimulus rate the slow changes of both aNai and force were monophasic in sheep but biphasic in dog preparations. 3. In the remaining experiments changes in aNai and force in sheep preparations were measured during 4 min trains of voltage‐clamp pulses at a frequency of 2.5 Hz. 4. A number of these voltage‐clamp experiments also indicated that changes in aNai are involved. Depending on the preparation and the duration of the pulses aNai rose or fell during a train‐a rise in aNai was always associated with a gradual rise in force, whereas a fall in aNai was usually accompanied by a gradual fall in force. The addition of tetrodotoxin (TTX) or the use of a low holding potential reduced the progressive rises of both aNai and force, whereas the inclusion of a 10 mV hyperpolarization between pulses potentiated the progressive rises of both. 5. The effect of TTX on the staircase was more marked the longer the pulses during the train; this possibly indicates that the effect of aNai on the force staircase is complex and is more marked with longer pulses. 6. A rise in aNai was shown not to be the only factor underlying the progressive increase in force, because in many preparations a gradual rise in force occurred in spite of no change or even a fall of aNai. 7. It is concluded that an increase in aNai is involved in the slow increase in force during the staircase accompanying a train of action potentials, and that other factors are also involved; various possibilities are discussed.
A fast motile response in guinea‐pig outer hair cells: the cellular basis of the cochlear amplifier.
Authors: Ashmore J F
Published: January 2015

1. Outer hair cells from the cochlea of the guinea‐pig were isolated and their motile properties studied in short‐term culture by the whole‐cell variant of the patch recording technique. 2. Cells elongated and shortened when subjected to voltage steps. Cells from both high‐ and low‐frequency regions of the cochlea responded with an elongation when hyperpolarized and a shortening when depolarized. The longitudinal motion of the cell was measured by a differential photosensor capable of responding to motion frequencies 0‐40 kHz. 3. Under voltage clamp the length change of the cell was graded with command voltage over a range +/‐ 2 microns (approximately 4% of the length) for cells from the apical turns of the cochlea. The mean sensitivity of the movement was 2.11 nm/pA injected current, or 19.8 nm/mV membrane polarization. 4. The kinetics of the cell length change during a voltage step were measured. Stimulated at their basal end, cells from the apical (low‐frequency) cochlear turns responded with a latency of between 120 and 255 microseconds. The cells thereafter elongated exponentially by a process which could be characterized by three time constants, one with value 240 microseconds, and a second in the range 1.3‐2.8 ms. A third time constant with a value 20‐40 ms characterized a slower component which may represent osmotic changes. 5. Consistent with the linearity shown to voltage steps, sinusoidal stimulation of the cell generated movements which could be measured at frequencies above 1 kHz. The phase of the movement relative to the stimulus continued to grow with frequency, suggesting the presence of an absolute delay in the response of about 200 microseconds. 6. The electrically stimulated movements were insensitive to the ionic composition of the cell, manipulated by dialysis from the patch pipette. The responses occurred when the major cation was K+ or Na+ in the pipette. Loading the cell with ATP‐free solutions or calcium buffers did not inhibit the response. 7. It is concluded that interaction between actin and myosin, although present in the cell, is unlikely to account for the cell motility. Instead, it is proposed that outer hair cell motility is associated with structures in the cell cortex. The implications for cochlear mechanics of such force generation in outer hair cells are discussed.
Intracellular studies of the electrophysiological properties of cultured intracardiac neurones of the guinea‐pig.
Authors: Allen T G , Burnstock G
Published: January 2015

1. The electrophysiological properties of intracardiac neurones cultured from ganglia within the atria and interatrial septum of the new‐born guinea‐pig heart were studied using intracellular micro‐electrodes. 2. Three types of neurones with resting membrane potentials in the range ‐45 to ‐76 mV were detected. The first type, AHs cells, had high (15‐28 mV) firing thresholds, pronounced slow post‐spike after‐hyperpolarizations and fired only once to prolonged intrasomal current injection. The second type, AHm cells, were similar to AHs cells, except that they could fire short bursts of spikes (100‐400 ms) at the onset of current injection. The third type, M cells, had low firing thresholds (10‐15 mV), no slow after‐hyperpolarizations and produced non‐adapting trains of action potentials in response to depolarizing current injection. 3. The generation of action potentials in M cells was prevented by tetrodotoxin (TTX; 0.3 microM), whereas in AHs and AHm cells action potentials displayed a channel blockade using solutions containing the divalent cations cadmium, cobalt or manganese (0.02‐1 mM). 4. The post‐spike after‐hyperpolarization in AHs and AHm cells was abolished by the removal of extracellular calcium, shortened in solutions containing the calcium entry blockers CdCl2, MnSO4 and CoCl2 (0.02‐1 mM) and prolonged by the addition of calcium (5.0 mM), tetraethylammonium (1‐3 mM), 4‐aminopyridine (1‐3 mM), cyanide (10 microM) or caffeine (100 microM) to the perfusate. 5. The reversal potential of the post‐spike after‐hyperpolarization was ‐89.1 mV. This value changed by 62.9 mV for a 10‐fold increase in extracellular potassium concentration. 6. The peak conductance change during the post‐spike after‐hyperpolarization (gK,Ca), was largely independent of membrane potential between ‐50 and ‐110 mV. The peak increase in gK,Ca and the duration of the after‐hyperpolarization increased with the number of spikes preceding it. 7. It is concluded that calcium entry during the action potential is responsible for the activation of an outward potassium current in the two types of AH cells; the roles played by intracellular calcium extrusion as well as sequestration mechanisms in the generation of the response are discussed.
Somatic and visceral inputs to the thoracic spinal cord of the cat: marginal zone (lamina I) of the dorsal horn.
Authors: Cervero F , Tattersall J E
Published: January 2015

1. Single‐unit electrical activity has been recorded from fifty‐five neurones whose recording sites were located in or immediately adjacent to the marginal zone (lamina I) of the lower thoracic spinal cord (T8‐T12) of anaesthetized or decerebrate cats. Their responses to stimulation of somatic and visceral afferent fibres and the sizes of their cutaneous receptive fields have been analysed and compared with the responses and receptive fields of neurones recorded throughout the spinal grey matter. 2. Neurones were classified according to their responses to innocuous stimulation of their somatic receptive fields (i.e. brushing and stroking) or to noxious stimulation (i.e. pinching, squeezing and/or heating above 45 degrees C). 52% of all the neurones recorded in lamina I were driven exclusively by noxious stimulation of the skin (nocireceptive); 33% were driven by both noxious and innocuous stimulation of the skin (multireceptive) and 15% were driven exclusively by innocuous stimulation of the skin (mechanoreceptive). 3. Visceral afferent inputs to these neurones were tested by supramaximal electrical stimulation of the ipsilateral splanchnic nerve (15 V, 0.2 ms, 0.3 Hz). Two types of neurone were distinguished according to their responses to visceral stimulation: (i) somatic neurones, driven only by stimulation of somatic afferent fibres and (ii) viscero‐somatic neurones, driven by stimulation of somatic and visceral afferent fibres. Of the neurones recorded in lamina I, 33% were somatic and 67% were viscero‐somatic. This proportion was very similar to the percentages of somatic and viscero‐somatic neurones recorded throughout the grey matter (37 and 63%, respectively). 4. Viscero‐somatic neurones in lamina I had somatic receptive field properties similar to those of viscero‐somatic neurones of the entire spinal cord. Half of them were multireceptive, 39% were nocireceptive and 11% were mechanoreceptive. However, somatic neurones in lamina I had receptive field properties different from those of somatic neurones from other laminae: no multireceptive somatic neurones were recorded in lamina I; the vast majority (78%) were nocireceptive and 22% were mechanoreceptive. 5. The majority of somatic and viscero‐somatic neurones in lamina I had small somatic receptive fields but, even in this group of cells, viscero‐somatic neurones had larger receptive fields than somatic cells. 6. Ascending axonal projections in both dorsolateral funiculi and in the contralateral ventrolateral quadrant were tested in eighteen lamina I neurones. Only one neurone was found to project to the cervical cord.(ABSTRACT TRUNCATED AT 400 WORDS)
Intracellular sodium‐calcium dissociation in early contractile failure in hypoxic ferret papillary muscles.
Authors: Guarnieri T
Published: January 2015

1. Intracellular sodium activity (aNai) and intracellular calcium activity (aCai) were measured in isolated quiescent right‐ventricular ferret muscle: aNai = 9.8 +/‐ 2.2 mM and aCai = 71 +/‐ 19 nM. 2. When the muscles were exposed to 10(‐5) M‐ouabain, aNai increased to 20.4 +/‐ 3.1 mM while aCai increased to 260 +/‐ 99 nM. Twitch tension approximately doubled. 3. During prolonged hypoxia with glucose in the perfusate, aNai and twitch tension were unchanged. 4. During prolonged hypoxia with sucrose (substrate free) in the perfusate aNai increased to 18.9 +/‐ 3.1 mM, but aCai did not change. Twitch tension declined by 50%. 5. The addition of 10(‐5) M‐ouabain to the substrate‐free hypoxic perfusate caused aNai to increase to 31.6 +/‐ 2.8 mM and aCai to increase to 150 +/‐ 35 nM. Twitch tension was unchanged. 6. These data indicate that only during prolonged substrate‐free hypoxia does aNai increase. Despite the increase in aNai, no change in aCai is seen, unless the sodium‐potassium pump is concomitantly inhibited. The lack of rise of aCai is consistent with inhibition of the sodium‐calcium exchange, although other avenues of calcium exchange cannot be excluded.
Quantitative analysis of laryngeal mechanosensitivity in the cat and rabbit.
Authors: Davis P J , Nail B S
Published: January 2015

1. Single afferent fibres in the internal branch of the superior laryngeal nerve which responded to light touch or gentle probing of discrete areas of the exposed epithelium of the opened larynx were identified in anaesthetized, paralysed cats (148 fibres) and rabbits (58 fibres). 2. A quantitative examination of the sensitivity of these laryngeal mechanoreceptors to both static (step indentations) and dynamic (vibratory) forms of mechanical stimulation was undertaken using a servo‐controlled mechanical stimulator. 3. In both species two predominant classes of mechanoreceptors were observed (Boushey, Richardson, Widdicombe & Wise, 1974). One class was distinguished by a regular and continuous pattern of activity at a frequency of 10‐70 Hz (tonic fibres, sixty‐six in cat, thirty‐five in rabbit). The other class was silent or (more rarely) irregularly active at a very low frequency (silent fibres, eighty‐two in cat, twenty‐three in rabbit). 4. The location of the receptive fields was determined by manual probing. Inter‐species and regional variations in receptive field location were observed for the two fibre groups. 5. Conduction velocity was measured for twenty‐one tonic and seven silent fibres in the rabbit by a pre‐triggered averaging technique. The results obtained (tonic: range 10.8‐30.0, mean +/‐ S.E. of mean 21.4 +/‐ 1.2 m/s; silent: 14.8‐28.6, 20.4 +/‐ 1.8 m/s) were characteristic of group III afferent fibres but were not significantly different for the two classes. 6. Both classes of receptor showed a response at the onset of a step indentation of the region of the mucosa that corresponded to their receptive field. Subsequent to this brief initial response the behaviour of the two classes diverged markedly. Tonic fibres were invariably slowly adapting whereas most (forty‐four out of fifty‐five in cat; twenty‐two out of twenty‐three in rabbit) silent fibres were rapidly adapting, at least for smaller indentation amplitudes. 7. Receptors of both classes were readily entrained to discharge at the same frequency as the probe stimulator (1:1 entrainment) when this was made to vibrate upon the receptive area for test periods of 0.5 or 1.0 s. Tuning curves were constructed of the minimum amplitudes required to elicit 1:1 entrainment throughout an entire test period at various frequencies. 8. Individual fibres in the two classes could be entrained at frequencies up to 400 Hz or more at sensitive (e.g. less than 100 microns) vibratory amplitudes. However, all fibres were less sensitive at these higher frequencies than at some lower point on the frequency scale.(ABSTRACT TRUNCATED AT 400 WORDS)
Influence of depolarizing pulse duration on the time course of transmitter release in lobster.
Authors: Parnas H , Parnas I
Published: January 2015

1. Experiments have been made at lobster neuromuscular synapses to study synaptic delays and in particular the phenomenon known as 'latency shift'. Earlier work had suggested that synaptic delay becomes prolonged when pulses of long duration are applied to presynaptic terminals. 2. By observing single quanta, prolonged depolarizing pulses at low and moderate amplitudes have been shown to shift the peak of the synaptic delay histogram. There is however no increase in the minimal delay. 3. The apparent differences between these and earlier results have been shown to depend on differences in experimental procedures. In particular, in the present study equal numbers of pulses are applied at the various pulse durations and the number of quanta that had been released is presented.