bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experimental infection of Atlantic halibut, Hippoglossus hippoglossus L., yolk‐sac larvae with infectious pancreatic necrosis virus: detection of virus by immunohistochemistry and in situ hybridization
Authors: Biering E , Bergh Ø 
Published: April 2006

AbstractThree different concentrations (107, 105 and 103 TCID50 ml‐1) of infectious pancreatic necrosis virus (IPNV) serotype Sp isolated from Atlantic halibut, Hippoglossus hippoglossus L., were used to bath‐challenge Atlantic halibut yolk‐sac larvae. The larvae challenged with 107 TCID50 ml‐1 suffered significantly higher cumulative mortality than the other challenged groups and the control group, and affected individuals displayed necrosis of the intestine, liver and kidney. In larvae from the groups challenged with 107 and 105 TCID50 ml‐1, IPNV was detected by immunohistochemistry and in situ RNA/DNA hybridization in the intestine, liver and kidney. In addition, some individuals stained IPNV‐positive in the heart and eye/brain region. Detection by in situ hybridization did not appear to be more sensitive than immunohistochemistry. However, background staining was virtually absent in comparison with immunohistochemistry, and the staining seemed to be more distinctly localized to the cytoplasm of infected cells. The results show that farmed halibut yolk‐sac larvae can be infected by IPNV immediately after hatching, with resulting high mortality. As the larvae are not immunologically mature at this stage of development, vaccination is not recommended.
Prostaglandin E2 Receptors in the Chicken Spinal Cord:
Authors: Pralong E. , Vesin M.‐F. , Droz B. 
Published: April 2006

AbstractHigh and low affinity binding sites for PGE2 were localized at the cellular level by means of radioautography. Two types of radioautographic reactions were observed in cryostat sections incubated with 0.6 nM [3H]PGE2: (i) a diffuse reaction scattered over the neuropil; (ii) a stronger reaction over the perikarya of some motoneurons. However, not all the motoneurons were equally labelled; the density of silver grains increased 12 times from poorly labelled to highly labelled cells. After incubation with an excess of unlabelled PGE2 the labelling was drastically reduced over motoneurons and the neuropil, so that the specific binding corresponded to 90 and 85% respectively of the total binding. Two facts indicated that the motoneurons possessed mainly high affinity binding sites which could be saturated by PGE2 concentrations in the nanomolar range: (i) a five‐fold increase of [3H]PGE2 concentration (from 0.6 to 3 nM) produced only a 1.5 times increase in the density of silver grains over the perikarya; (ii) incubation in presence of 14 nM unlabelled PGE2 induced a drastic reduction of 0.6 nM [3H]PGE2 binding to the motoneurons. The presence of high affinity binding sites in motoneurons suggests that PGE2 could act as a modulator of spinal reflexes.
Spatial Organization of the Maculo‐Ocular Reflex of the Rat: Responses During Off‐Vertical Axis Rotation
Authors: Hess B. J. M. , Dieringer N. 
Published: April 2006

AbstractPigmented, head restrained rats were rotated on a turntable about a tilted axis (off‐vertical axis rotation; OVAR) in darkness. Evoked eye movements in the horizontal, vertical and torsional planes were recorded simultaneously with a dual search coil in a magnetic field, horizontal response components of both eyes were recorded with a coil on either eye. OVAR resulted in a persisting horizontal, unidirectional ocular nystagmus, compensatory in direction for the rotation of head in space. Superimposed upon this nystagmus were slower cyclic responses of the eye in the vertical and torsional movement planes, that were tightly phase locked with changing head positions in space: ocular depression/elevation with right ear up/down and ocular intorsion/extorsion with nose up/down. Simultaneous recordings of horizontal response components from both eyes revealed phase and gain differences between the horizontal movement components of both eyes, that resulted in a cyclic modulation of the vergence angle. Convergence of the lines of sight during nose up and divergence during nose down, adequate compensatory responses in light for changes in the viewing distance, were actually observed in darkness. Thus the utricular maculo‐ocular reflex takes part of the visual consequences of a translational gaze shift into account. It reduces expected retinal disparities by appropriate and rapid vertical, torsional and vergence response components in the same way as canal‐ocular reflexes ‘compensate’ for direction and velocity of expected retinal image slip during head rotation.
Phorbol Ester Interferes with [3H]Norepinephrine Accumulation into Monolayers of PC 12 Cells by Stimulating the Release of Endogenous Norepinephrine
Authors: Tas Piet W. L. , Schömig Edgar , Koschel Klaus 
Published: April 2006

AbstractIn this study we have observed an inhibition of the [3H]norepinephrine ([3H]NE) accumulation into rat phaeochromocytoma PC 12 cells by phorbol 12‐myristate 13‐acetate (PMA), whereas a biologically inactive phorbol ester was without effect. The inhibition was no longer observed when the PC 12 cells were preincubated with 10 μM reserpine, which inhibits the uptake of norepinephrine into the storage vesicles. This suggested a role of the intact vesicles in the inhibitory phenomenon. Subsequently we could show that PMA increased the efflux of [3H]NE from PC 12 cells in a dose dependent manner. It seemed likely, therefore, that the increased release of endogenous norepinephrine from PC 12 cells by the phorbol ester competed with exogenous [3H]NE for uptake by the plasma membrane NE (uptake1) carrier into the cells. Two observations were in agreement with such a model: (i) an increase in the external NE concentration decreased the effect of PMA on the [3H]NE uptake; and (ii) desensitization of the protein kinase C by long term treatment of the PC 12 cells with phorbol ester abolished the PMA effect on both [3H]NE efflux and [3H]NE uptake.
Quantification and Comparison of Cell Properties in Cat's Striate Cortex Determined by Different Types of Stimuli
Authors: Wörgötter Florentin , Gründel O. , Eysel U. Th. 
Published: April 2006

AbstractDirection and orientation tuning elicited by moving bars, flashing bars and a moving noise field were compared in cells in area 17 of the cat. Fourier analysis of tuning curves (SDO‐analysis) was applied to quantify the general sensitivity (S) to visual stimulation, tuning strength to direction(D) and orientation (O), as well as the preferred direction (PD) and orientation (PO). Results from SDO‐analysis were compared with the commonly used direction index and half‐width‐at‐half‐height orientational tuning parameter and it is demonstrated that the commonly used parameters can be replaced and are superseded by the results from SDO‐analysis. The comparison of the responses elicited by the different types of stimuli showed that a linear correlation between D (or O) components was mainly found in simple cells, while in most cases no correlation was obtained for complex cells. Since several of the simple cells also showed no linear relationship, a direct mutual prediction of the S, D and O components can only be achieved for ∼50% of the cortical cells applying commonly used stimulus types. The general responsiveness (S) shows that flashing bar stimuli are at least as effective as moving bars, whereas moving noise stimulates cortical cells more weakly. A moving bar tends to increase the orientation tuning (O) in most cells and with a moving noise stimulus predominantly the directional tuning (D) of complex cells is strongly enhanced. In conclusion, Fourier analysis of tuning curves (SDO‐analysis) provides a valuable and simple tool for the quantification of direction and orientation specificity. Motion enhances the cortical response specificity which indicates the involvement of facilitation or inhibition exclusively induced by movement.
Receptive Fields of Neurons in the Owl's Auditory Brainstem Change Dynamically
Authors: Wagner Hermann 
Published: April 2006

AbstractBinaural neurons in the barn owl's auditory brainstem have spatial receptive fields. It is shown here that both the frequency tuning of these neurons and their tuning to interaural time difference (ITD), the prime cue for azimuthal sound localization, improves with time after stimulus onset, a process I shall term ‘dynamic sharpening’. Thus, the receptive fields of these neurons also have a temporal dimension. Data were collected in four hierarchically ordered nuclei concerned with the computation of ITD: the nucleus ventralis lemnisci lateralis, pars anterior (VLVa), and three subnuclei in the inferior colliculus. Dynamic sharpening in the frequency tuning curves is evident from a dynamic reduction of tuning width. When stimulated with a tone, the response of all neurons varies in a cyclic manner with ITD. The ITDs at the response peaks differ by one period of the stimulus tone. The responses with noise stimulation are similar to the responses with tonal stimulation in all but the hierarchically highest nucleus, the external nucleus of the inferior colliculus. In this nucleus are found neurons that, if stimulated with noise, respond maximally only to one ITD while the responses at the other peaks are suppressed. This sidepeak suppression is a dynamic process. Dynamic sharpening of ITD tuning is also evident from a dynamic reduction of the tuning width around each of the response peaks. The proportion of neurons showing dynamic sharpening of ITD tuning is the same in all collicular subnuclei, but is lower in VLVa. Therefore, a major component of dynamic sharpening of ITD tuning occurs at the first station of the inferior colliculus. Lateral inhibition is one of the mechanisms underlying dynamic sharpening. Part of the inhibition may be mediated by GABA (Fujita and Konishi, 1988). The function of dynamic sharpening of ITD tuning may be to increase the fine representation of auditory space in single neurons.
Schwann Cells Secrete a PDGF‐like Factor: Evidence for an Autocrine Growth Mechanism involving PDGF
Authors: Eccleston P. A. , Collarini E. J. , Jessen K. R. , Mirsky R. , Richardson W. D. 
Published: April 2006

AbstractWe have investigated the influence of platelet‐derived growth factor (PDGF) in peripheral nervous system gliogenesis using two types of Schwann cell cultures. Short‐term Schwann cell cultures grow very slowly, but when maintained in culture for several months the division rate of some cells increases, and cell lines can be established. We show that Schwann cells in both short‐ and long‐term culture possess PDGF receptors and synthesize DNA in response to PDGF. Competitive binding experiments show that Schwann cells express mainly PDGF β‐receptors and respond better to PDGF‐BB than to PDGF‐AA. Conditioned media from short‐and long‐term Schwann cell cultures contain PDGF‐like mitogenic activity, and anti‐PDGF immunoglobin partially inhibits DNA synthesis in long‐term Schwann cell cultures. Antibody neutralization experiments and Northern blot analyses both indicate that the predominant PDGF isoform in these cultures is PDGF‐BB. PDGF‐like activity is also detected in extracts of rat sciatic nerve. Taken together, these results suggest that PDGF‐BB may stimulate Schwann cell proliferation in an autocrine manner during normal development.
Bicuculline‐ and Phaclofen‐Resistant Hyperpolarizations Evoked by Glutamate Applications to Stratum Lacunosum‐Moleculare in CA1 Pyramidal Cells of the Rat Hippocampus In Vitro
Authors: Williams Sylvain , Lacaille Jean‐Claude 
Published: April 2006

AbstractIn the hippocampus, different types of interneurons may mediate distinct gamma‐aminobutyric acid (GABA) responses, i.e. the early and late inhibitory postsynaptic potentials (IPSPs). To verify this hypothesis, intracellular recordings were obtained from CA1 pyramidal cells (n= 63) in rat hippocampal slices. Glutamate (1 mM) was locally ejected in stratum lacunosum‐moleculare to activate interneurons in this region. Glutamate‐evoked hyperpolarizing responses were characterized in pyramidal cells and compared to the early IPSP and the late IPSP elicited by stratum radiatum electrical stimulation. Several characteristics were similar for the glutamate‐evoked IPSPs and late IPSPs: their amplitude was small (−3.4 versus −4.9 mV, respectively), each was associated with a small conductance increase (5.0 versus 9.3 nS, respectively), their peak latency was slow (124.4 versus 129.8 ms, respectively) and in the majority of cells, each displayed little response reversal. However, the equilibrium potential of the glutamate IPSP (−76.5 mV) was similar to that of the early IPSP (−73.8 mV). Perfusion with a low Ca2+ (0.5 mM)/high Mg2+ (8 mM) medium or with tetrodotoxin (1 μM), which blocked synaptic transmission, also reduced the glutamate IPSP. Therefore the glutamate IPSP may be mediated indirectly by inhibitory interneurons. The GABAA antagonist bicuculline (10 μM), or picrotoxin (10–20 μM), blocked the early IPSP, but not the glutamate IPSP. The GABAB antagonist phaclofen (1 mM) attenuated the late IPSP, but did not affect the glutamate IPSP. The results of these experiments suggest that glutamate stimulation of interneurons in stratum lacunosum‐moleculare evokes a slow IPSP different from the GABA‐mediated early and late IPSPs in CA1 pyramidal cells of the hippocampus.
Comparison of Effects of Various Types of NA and 5‐HT Agonists on Transmission from Group II Muscle Afferents in the Cat
Authors: Bras H. , Jankowska E. , Noga B. , Skoog B. 
Published: April 2006

AbstractA number of noradrenaline and serotonin agonists were tested to investigate which of them replicate the depressive actions of monoamines on transmission from group II muscle afferents in the cat spinal cord. The agonists were applied ionophoretically at the two sites at which maximal monosynaptic focal field potentials are evoked from group II afferents—in the intermediate zone and the dorsal horn of the 4th and 5th lumbar segments. Their effects were estimated from changes in the amplitude of the field potentials. The compounds tested fell into three categories according to the site at which they depressed transmission from group II afferents: one category with highly selective actions in the intermediate zone, a second category with similarly selective actions in the dorsal horn, and a third category with non‐selective actions. Drugs in the first category included three noradrenaline agonists (tizanidine, B‐HT 933 and clonidine), included in the second were five serotonin agonists (8‐OH‐DPAT, 5‐methoxytryptamine, α‐methyl serotonin, DOI and 2‐methyl‐serotonin), and in the third two noradrenaline agonists (phenylephrine and isoproterenol) and two serotonin agonists (RU 24969 and 5‐carboxamidotryptamine). Field potentials evoked by group I afferents remained unaffected by all but one compound (8‐OH‐DPAT). Effects of one noradrenaline agonist and one serotonin agonist (tizanidine and 5‐methoxytryptamine) were also tested on responses of single extracellularly recorded neurons. Tizanidine depressed responses induced by stimulation of group II afferents in intermediate zone interneurons, but not in dorsal horn neurons, while 5‐methoxytryptamine depressed activation of the latter. Tizanidine had no effect on responses evoked by group I afferents, either in intermediate zone interneurons or in the dorsal spino‐cerebellar tract neurons of Clarke's column. It is hypothesized that noradrenaline and serotonin released by descending monoaminergic neurons differ in the potency with which they depress transmission from group II afferents to different functional types of neuron. The results suggest that this depression may involve different membrane receptors at different locations, primarily α2 adrenoceptors in the intermediate zone/ventral horn and 5‐HT‐1A serotonin receptors in the dorsal horn.
Synaptic Connections of Different Strength Between Wind‐sensitive Hairs and an Identified Projection Interneuron in the Locust
Authors: Pflüger H.‐J. , Burrows M. 
Published: April 2006

AbstractAn identified intersegmental interneuron in Locusta and Schistocerca, with its cell body in the fourth abdominal ganglion and an axon which projects to the brain is excited by mechanosensory inputs from receptors on the head and neck. The organization of its receptive field, the types of sensory receptors which contribute to it and the patterns and strengths of the afferent connections were investigated by intracellular recording from the axon of the interneuron close to a spike‐initiating site in the prothoracic ganglion. The receptive field of the interneuron consists of a small patch of hairs on the head ipsilateral to the axon, and from hairs on two regions of the prosternum (a cuticular structure on the ventral surface of the prothoracic segment), first an ipsilateral, lateral region and second a medial but contralateral region. Hairs on the pronotum (dorsal neck) also contribute but were not investigated here. Each spike in the afferent from a hair with a filiform appearance and with a pigmented base on the prosternum consistently evokes an EPSP in the interneuron. These have a short and constant latency, indicating that the connection is probably direct. The head hairs also appear to make direct connections with the interneuron in the prothoracic ganglion, so that the spike‐initiating site here can integrate signals evoked by wind on the head and on the prosternum. Stiff tactile hairs on the prosternum do not connect with the interneuron. The EPSPs evoked by the long filiform hairs are consistently larger than those produced by the short filiform hairs and a single spike in some of the afferents from the long filiform hairs can evoke a spike in the interneuron. The effectiveness of an afferent is therefore correlated with the length of the filiform hair it innervates. The hairs with the most powerful effects are always the longest and occur in the same position on every locust. The shape of the receptive field and the different strengths of connections are apparent even in early larval instars. The axonal branches of the interneuron are restricted to the same side of the ganglion as the axon itself. Afferents from filiform hairs on the medial region of the prosternum project contralaterally, and those from the lateral region project ipsilaterally. Afferents from some of the head hairs project ipsilaterally directly to the prothoracic ganglion. The terminals of all these afferents overlap with the branches of the interneuron. By contrast, the afferents of tactile hairs which do not connect, project to different regions of neuropile. The connections ensure that the high sensitivity of the filiform hairs is maintained at the first stage in the central processing and suggest a role for this interneuron in supplying information about small changes in air currents that may be of use in controlling steering manoeuvres during flight.
Characterization and Function of Spinal Excitatory Interneurons with Commissural Projections in Xenopus laevis embryos
Authors: Roberts Alan , Sillar Keith T. 
Published: April 2006

AbstractThe multipolar somata of dorsolateral commissural (dlc) interneurons (Roberts and Clarke, 1982) lie in a superficial dorsolateral position in the spinal cord of Xenopus laevis embryos. By applying horseradish peroxidase to one‐half of the 100 μm diameter spinal cord, these neurons have been backfilled. Their dendritic branching pattern, commissural axonal projection and distribution near the time of hatching is described. Using Lucifer yellow‐filled microelectrodes a population of sensory interneurons with dlc morphology has been identified. They have multipolar somata in a dorsolateral superficial position, obliquely projecting dendrites and a ventral commissural axon. They receive presumed monosynaptic excitation in response to electrical stimulation of sensory neurites in the skin on the same side as the soma. During fictive swimming activity in curarized embryos the die interneurons are rhythmically inhibited in time with ventral root discharge on the same side. Die interneurons can fire multiple impulses and can turn on fictive swimming when stimulated by intracellular current injection. Skin stimulation is followed by excitatory postsynaptic potentials (EPSPs) in contralateral ventral rhythmic neurons. These EPSPs are reduced by the application of NMDA receptor antagonist. We conclude that dlc interneurons are excited by primary skin afferent Rohon ‐ Beard neurons, carry sensory information across the spinal cord to excite neurons on the opposite side by release of an excitatory amino acid transmitter and participate in reflexes and in the initiation of swimming.
Spontaneous Saccades and Gaze‐Holding Ability in the Pigmented Rat. I. Effects of Inferior Olive Lesion
Authors: Strata P. , Chelazzi L. , Ghirardi M. , Rossi F. , Tempia F. 
Published: April 2006

AbstractWe have studied the effects of lesion of the inferior olive on the spontaneous eye movements performed both in the light and dark in head restrained pigmented rats. The inferior olive lesion was made at least 1 month before study with 3‐acetylpyridine and eye movements were recorded through a phase detection search coil apparatus. Following lesion, the spontaneous saccades performed in the dark present a postsaccadic drift which is made up of two components characterized by their different time courses, the first one being fast and the second one slow. The latter component is due to the leakage of the neural integrator and the former is mainly the consequence of a mismatch between the phasic and the tonic component of the ocular movement. In the light only the first component is present and then the eye maintains a steady position. After the lesion the saccades in the dark present a time constant of the slow component of the postsaccadic drift which is significantly reduced to −600–900 ms from a value of 1600–4000 ms of the intact rats. This means that the integrity of the inferior olive is necessary to keep the time constant of the neural integrator within the physiological range. In the light, the amplitude of the postsaccadic drift depends on two factors. First, there is a mismatch between the phasic and the tonic components of the ocular movement, which are due to the pulse and the step of innervation of the extraocular muscles respectively. Different types of analysis have shown that the gain of the pulse to step transformation is about 0.77 at all saccadic amplitudes and eccentricities. Second, there is an increased leakiness of the neural integrator. Such a contribution increases linearly as a function of the eccentricity with a slope of 0.21. The main sequence of the saccades is not appreciably affected by the olivary lesion. Thus, the consequence of the inferior olive lesion may be interpreted as a general disruption of the integration process which, in physiological conditions, generates a proper and sustained oculomotor signal. More generally, it may be viewed as a loss of coordination between phasic and tonic motor commands.