bluuebunny/crossref_metadata_2025 huggingface dataset:
Induction of Plantaricin Production inLactobacillus plantarumNC8 after Coculture with Specific Gram-Positive Bacteria Is Mediated by an Autoinduction Mechanism
Authors: Maldonado Antonio , Jiménez-Díaz Rufino , Ruiz-Barba José Luis
Published: February 2004

Plantaricin NC8 (PLNC8), a coculture-inducible two-peptide bacteriocin fromLactobacillus plantarumNC8, has recently been purified and genetically characterized. Analysis of an 8.1-kb NC8 DNA region downstream of the PLNC8 operon revealed the presence of at least four operons involved in bacteriocin production, showing high homology to the plantaricin cluster inL. plantarumC11. However, we found a three-component regulatory operon involving a quorum-sensing mechanism. Two of these components, the induction factor (PLNC8IF) and the histidine kinase, are novel, while the response regulator is identical to PlnD from C11. Homologous expression ofplNC8IFin NC8 allowed constitutive bacteriocin production. Heterologous expression of this gene inLactococcus lactisMG1363 produced supernatants which promoted bacteriocin production in NC8. Reverse transcription-PCR studies indicated that cocultivation of NC8 with inducing cells promoted transcription of the bacteriocin and regulatory operons in NC8. An identical result was obtained after addition of an external source of PLNC8IF. We propose that the presence of specific bacteria could act as an environmental signal that is able to switch on bacteriocin production inL. plantarumNC8 via a quorum-sensing mechanism mediated by PLNC8IF.
Characterization of Two Methanopterin Biosynthesis Mutants of
Methylobacterium extorquens
AM1 by Use of a Tetrahydromethanopterin Bioassay
Authors: Rasche Madeline E. , Havemann Stephanie A. , Rosenzvaig Mariana
Published: February 2004

An enzymatic assay was developed to measure tetrahydromethanopterin (H
4
MPT) levels in wild-type and mutant cells of
Methylobacterium extorquens
AM1. H
4
MPT was detectable in wild-type cells but not in strains with a mutation of either the
orf4
or the
dmrA
gene, suggesting a role for these two genes in H
4
MPT biosynthesis. The protein encoded by
orf4
catalyzed the reaction of ribofuranosylaminobenzene 5′-phosphate synthase, the first committed step of H
4
MPT biosynthesis. These results provide the first biochemical evidence for H
4
MPT biosynthesis genes in bacteria.
Characterization of Two Kinases Involved in Thiamine Pyrophosphate and Pyridoxal Phosphate Biosynthesis in
Bacillus subtilis
: 4-Amino-5-Hydroxymethyl-2-Methylpyrimidine Kinase and Pyridoxal Kinase
Authors: Park Joo-Heon , Burns Kristin , Kinsland Cynthia , Begley Tadhg P.
Published: February 2004

Two
Bacillus subtilis
genes encoding two proteins (currently annotated ThiD and YjbV) were overexpressed and characterized. YjbV has 4-amino-5-hydroxymethyl-2-methylpyrimidine and 4-amino-5-hydroxymethyl-2-methylpyrimidine pyrophosphate kinase activity and should be reannotated ThiD, and
B. subtilis
ThiD has pyridoxine, pyridoxal, and pyridoxamine kinase activity and should be reannotated PdxK.
VpsT Is a Transcriptional Regulator Required for Expression of
vps
Biosynthesis Genes and the Development of Rugose Colonial Morphology in
Vibrio cholerae
O1 El Tor
Authors: Casper-Lindley Catharina , Yildiz Fitnat H.
Published: February 2004

Vibrio cholerae
switches between smooth and rugose colonial variants. The rugose variant produces more vibrio polysaccharides (VPS
El Tor
) and forms well-developed biofilms. Both phenotypes depend on expression of
vps
biosynthesis genes. We identified a positive transcriptional regulator of
vps
gene expression, VpsT, which is homologous to response regulators of two-component regulatory systems. Disruption of
vpsT
in the rugose variant yields smooth colonies, prevents formation of mature biofilms, and decreases
vps
gene expression. The interaction between VpsT and VpsR, a previously identified positive regulator of
vps
genes, was also investigated.
ARTIFICIAL INTELLIGENCE IN DATABASE SECURITY
Authors: BAI YUN , ZHANG YAN
Published: February 2004

In this paper, we propose a formal approach of Artificial Intelligence (AI) in securing object oriented database systems. We combine the specification of object oriented database with security policies and provide its formal syntax and semantics. The properties in the inheritance of authorizations in object oriented database system and reasoning about authorizations on data objects are also investigated in detail.
HUMAN-CENTERED MULTIAGENT DISTRIBUTED ARCHITECTURE FOR KNOWLEDGE ENGINEERING OF IMAGE PROCESSING APPLICATIONS
Authors: KHOSLA R. , LAI C. , MITSUKURA Y.
Published: February 2004

In this paper we outline a human-centered multilayered multiagent distributed soft computing architecture for providing support to practitioners and problem solvers at four levels, namely, clerical, tool, optimization and task level, respectively. We describe the emergent characteristics of the architecture from a architectural, management and domain perspective. We illustrate the application of these four levels with the help of two image processing applications namely, face detection and annotation, and unstained mammalian cell classification.
CONTENT BASED IMAGE RETRIEVAL USING DISCRETE WAVELET TRANSFORM
Authors: BELKASIM SAEID , HONG XIANYU , BASIR O.
Published: February 2004

Image retrieval plays an important role in a broad spectrum of applications. Contentbased retrieval (CBR) is one of the popular choices in many biomedical and industrial applications. Discrete image transforms have been widely studied and suggested for many image retrieval applications. The Discrete Wavelet Transform (DWT) is one of the most popular transforms recently applied to many image processing applications. The Daubechies wavelet can be used to form the basis for extracting features in retrieving images based on the description of a particular object within the scene. This wavelet is widely used for image compression. In this paper we highlight the common features between compression and retrieval. Several examples are used to test the DWT retrieval system. A comparison between DWT and Discrete Cosine Transform (DCT) is also made. The retrieval system using DWT requires preprocessing and normalization of images, which might slow down the retrieval process. The accuracy of the retrieval using DWT has been significantly improved by incorporating efficient K-Neighbor Nearest Distance (KNND) measure in our system.
DISCOVERY OF CAUSALITY POSSIBILITIES
Authors: MAZLACK LAWRENCE
Published: February 2004

Determining causality has been a tantalizing goal throughout human history. Proper sacrifices to the gods were thought to bring rewards; failure to make suitable observations were thought to lead to disaster. Today, data mining holds the promise of extracting unsuspected information from very large databases. Methods have been developed to build association rules from large data sets. Association rules indicate the strength of association of two or more data attributes. In many ways, the interest in association rules is that they offer the promise (or illusion) of causal, or at least, predictive relationships. However, association rules only calculate a joint probability; they do not express a causal relationship. If causal relationships could be discovered, it would be very useful. Our goal is to explore causality in the data mining context.
RETROGRADE TRACING AND ELECTROPHYSIOLOGICAL FINDINGS OF COLLATERAL SPROUTING AFTER END-TO-SIDE NEURORRHAPHY
Authors: Xiong Ge , Ling Lijun , Nakamura Ryogo , Sugiura Yasuo
Published: February 2004

The aim of this study was to seek more potent evidences of collateral sprouting for both motor and sensory nerve fibres after end-to-side neurorrhaphy using a modified double-labelling retrograde tracing method and to investigate the function of regenerated motor axons with electrophysiological evaluation. Four groups (n=4 for each group) were used: end-to-end coaptation (six months postoperatively), end-to-side coaptation (four months and six months postoperatively) and normal control. Two fluorescent tracers (true blue and diamidino yellow) were applied to the proximal ends of tibial and common peroneal nerves, respectively after four or six months of nerve coaptation. Five days later, we only found single-labelled motor and sensory neurons in the normal and end-to-end coaptation groups, while some dual-labelled neurons can be identified in end-to-side coaptation groups. Four months after surgery, the motor nerve conduction velocity in end-to-side coaptation was significantly slower than in the normal control. But no difference was found in the sixth month. These results suggest that end-to-side neurorrhaphy can induce the functional collateral sprouting of both motor and sensory axons in the peripheral nerve.
A MORPHOLOGICAL STUDY OF THE SCAPHOID USING A MATHEMATICAL TECHNIQUE AND COMPARATIVE STUDY OF THE THREE-DIMENSIONAL MEASUREMENTS OF THE SCAPHOID
Authors: Fukuda Shoji , Ishida Osamu , Kido Mitsuo , Suzumura Fumihiro , Ikuta Yoshikazu
Published: February 2004

To guide reconstruction of scaphoid non-union, we attempted to create full-scale models of the scaphoid by three-dimensional computed tomography (3D CT) of the healthy side. In this study, we obtained 3D scans of 51 cadaveric hands and studied the difference in morphology between genders and between the left and right sides. The major axis length on a fixed plane and Fourier transformation curve were examined. Ten scaphoid images were also obtained with 3D CT before and after removal from the cadaveric hands. Our findings suggest good correlation between models produced using 3D CT images of the scaphoid alone, and this could serve as an accurate model if the magnification is corrected using the regression line. However, the model using 3D CT images of the intact wrist joint has a large margin of error and its use will not be practical.
RECURRENT OSTEOID OSTEOMA OF THE LUNATE: A CASE REPORT AND REVIEW OF THE LITERATURE
Authors: Arora J. , McLauchlan J. , Munro N.
Published: February 2004

Osteoid osteoma is a benign tumour of bone that rarely localises in the carpal bones. Its treatment by curettage and bone grafting is considered to be curative and its recurrence is thought to be rare.

We report a case of an osteoid osteoma of the lunate, which recurred seven years after the initial operation. Recurrent osteoid osteoma of the lunate bone has not been reported in the literature. We present this case report for its atypical presentation and diagnostic difficulty and also to alert the readers of the possibility of an osteoid osteoma as a cause of the chronic unexplained wrist pain in young adults.
BILATERAL SYMMETRICAL GIANT CELL TUMOURS OF THE THUMB
Authors: Dalal S. , Bostock S. H.
Published: February 2004

Giant cell tumours of tendon sheath are common in the hand but multiple lesions are relatively rare. A case report of bilateral symmetrical involvement is presented and discussed.
THE NEGLECTED RUPTURE OF DEEP TRANSVERSE METACARPAL LIGAMENT
Authors: Lee Kwang Suk , Baek Jong Ryoon , Kim Sang Bum
Published: February 2004

The deep transverse metacarpal ligament (DTML) extends in radio-ulnar direction between the palmar plates of the metacarpophalangeal (MCP) joints of the second through fifth finger rays. On the radial aspect of the index and the ulnar aspect of the small fingers, the ligament merges with the collateral ligament of the MCP joints. The ligament has palmar grooves for the flexor tendons at the MCP joints and act as a support for the metacarpal arch. Closed DTML injury is an unusual case, but the physical findings of DTML injury are a decrease in grip strength, deviation of the finger in flexion and pain on the affected site of the hand. We have experienced a case of neglected DTML injury of left third interdigital space in a 23-year-old man.
MINIMAL INVASIVE PERCUTANEOUS HERBERT SCREW FIXATION IN ACUTE UNSTABLE SCAPHOID FRACTURE
Authors: Jeon In-Ho , Oh Chang-Wug , Park Byung-Chul , Ihn Joo-Chul , Kim Poong-Taek
Published: February 2004

The purpose of this study is to document the percutaneous Herbert screw fixation technique with free-hand method to stabilise acute unstable scaphoid fractures and evaluated the clinical results. Thirteen patients with less than 14 day-old fractures were fixed by percutaneous Herbert screw and reviewed retrospectively for a minimum of 24 months (average, 37 months). All were men with an average age of 22 years. According to Herbert's classification, all fractures were classified as of the acute unstable (B2). Fracture union was achieved in all cases at a mean of 9.2 weeks (eight to 12 weeks). Return to work or school ranged from one day to three weeks according to their occupation. This percutaneous fixation technique using Herbert screw is a reliable and effective alternative for acute scaphoid fractures, which enables the patient to use the hand earlier with high satisfaction and minimum complication.
Dependence of Reactive Responses in Human Bimanual Finger Movements on Sensory Feedback and Auditory Cues
Authors: Ohki Yukari , Watanabe Kanae
Published: February 2004

We examined the effects of repetitive experience of feedback events and cue signals on adaptation of bimanual reactive response, both of which can be used to predict load forces on handheld objects. Normal human subjects used bimanual index fingers to hold two plates mounted on separate torque motors. Sensory-driven reactive forces from the fingers were measured during concurrent loading of both plates or isolated loading of the left plate. After repeated experiences of single load conditions, right and left fingers increased normal forces in a coordinated manner during concurrent loading, while the left finger responded almost exclusively during isolated loading of the left plate. However, after switching load conditions from concurrent to isolated load, or vice versa, several trials were needed to adapt to the new condition, as was clearly observed in the dynamic phase of responses from the right finger. Adaptation depends on the number of feedback experiences, and specifically on prediction error, showing intermediate predictions between the two conditions. Thus influences of the previous experiences show similar properties to those observed in self-generated movement, which were reported previously. In addition, auditory cues informing subjects of coming load conditions also partially adapted responses to these conditions. The neuronal center for reactive responses is therefore influenced by both previous experience and cue signals, inducing the appropriate responses for the predicted sensory inputs.
Visuomotor Sensitivity to Visual Information About Surface Orientation
Authors: Knill David C. , Kersten Daniel
Published: February 2004

We measured human visuomotor sensitivity to visual information about three-dimensional surface orientation by analyzing movements made to place an object on a slanted surface. We applied linear discriminant analysis to the kinematics of subjects' movements to surfaces with differing slants (angle away form the fronto-parallel) to derive visuomotor d′s for discriminating surfaces differing in slant by 5°. Subjects' visuomotor sensitivity to information about surface orientation was very high, with discrimination “thresholds” ranging from 2 to 3 degrees. In a first experiment, we found that subjects performed only slightly better using binocular cues alone than monocular texture cues and that they showed only weak evidence for combining the cues when both were available, suggesting that monocular cues can be just as effective in guiding motor behavior in depth as binocular cues. In a second experiment, we measured subjects' perceptual discrimination and visuomotor thresholds in equivalent stimulus conditions to decompose visuomotor sensitivity into perceptual and motor components. Subjects' visuomotor thresholds were found to be slightly greater than their perceptual thresholds for a range of memory delays, from 1 to 3 s. The data were consistent with a model in which perceptual noise increases with increasing delay between stimulus presentation and movement initiation, but motor noise remains constant. This result suggests that visuomotor and perceptual systems rely on the same visual estimates of surface slant for memory delays ranging from 1 to 3 s.
Prefrontal Neuronal Activity Encodes Spatial Target Representations Sequentially Updated After Nonspatial Target-Shift Cues
Authors: Fukushima Tetsuya , Hasegawa Isao , Miyashita Yasushi
Published: February 2004

We examined prefrontal neuronal activity while monkeys performed a sequential target-shift task, in which, after a positional cue indicated the initial saccade target among 8 peripheral positions, the monkeys were required to internally shift the target by one position on every flash of a target-shift cue. The target-shift cue appeared in the center 0 to 3 times within a single trial and was always the same in shape, size, and color. We found selective neuronal activity related to the target position: when the target-shift cue implied the target shift to particular peripheral positions, neurons exhibited early-dominant and late-dominant activity during the following delay period. The early-dominant target-selective activity emerged early in the delay just after the presentation of the target-shift cue, whereas the late-dominant activity gradually built up toward the end of the delay. Because the target-shift cue was not related to any specific target location, the early-dominant target-selective activity could not be a mere visual response to the target-shift cue. We suggest that the early-dominant activity reflects the transitory representation for the saccade target that was triggered by the nonspatial target-shift cue, whereas the late-dominant activity reflects the target representation in the spatial working memory or the preparatory set for the possible impending saccade, being repeatedly updated during sequential target shifts.
Kv1.2-Containing K+Channels Regulate Subthreshold Excitability of Striatal Medium Spiny Neurons
Authors: Shen Weixing , Hernandez-Lopez Salvador , Tkatch Tatiana , Held Joshua E. , Surmeier D. James
Published: February 2004

A slowly inactivating, low-threshold K+current has been implicated in the regulation of state transitions and repetitive activity in striatal medium spiny neurons. However, the molecular identity of the channels underlying this current and their biophysical properties remain to be clearly determined. Because previous work had suggested this current arose from Kv1 family channels, high-affinity toxins for this family were tested for their ability to block whole cell K+currents activated by depolarization of acutely isolated neurons. α-Dendrotoxin, which blocks channels containing Kv1.1, Kv1.2, or Kv1.6 subunits, decreased currents evoked by depolarization. Three other Kv1 family toxins that lack a high affinity for Kv1.2 subunits, r-agitoxin-2, dendrotoxin-K, and r-margatoxin, failed to significantly reduce currents, implicating channels with Kv1.2 subunits. RT-PCR results confirmed the expression of Kv1.2 mRNA in identified medium spiny neurons. Currents attributable to Kv1.2 channels activated rapidly, inactivated slowly, and recovered from inactivation slowly. In the subthreshold range (ca. -60 mV), these currents accounted for as much as 50% of the depolarization-activated K+current. Moreover, their rapid activation and relatively slow deactivation suggested that they contribute to spike afterpotentials regulating repetitive discharge. This inference was confirmed in current-clamp recordings from medium spiny neurons in the slice preparation where Kv1.2 blockade reduced first-spike latency and increased discharge frequency evoked from hyperpolarized membrane potentials resembling the “down-state” found in vivo. These studies establish a clear functional role for somato-dendritic Kv1.2 channels in the regulation of state transitions and repetitive discharge in striatal medium spiny neurons.
Persistent LIP Activity in Memory Antisaccades: Working Memory For a Sensorimotor Transformation
Authors: Zhang Mingsha , Barash Shabtai
Published: February 2004

The lateral intraparietal area (LIP) contains neurons that are active during the memory interval of memory saccades. We call these “persistent neurons.” Here we study the activity of the persistent neurons in memory antisaccades, “motor” (the saccade is made toward the response field, although the response field is not stimulated visually) and “visual” (the response field is stimulated visually, but the movement is away from the field). Most persistent neurons are active during parts of the memory intervals of both visual and motor memory-antisaccades. Typically, these parts significantly overlap each other and together span the entire memory interval. The amplitude of the activity changes systematically during the memory intervals of visual and motor memory antisaccades. These changes are reflected in an antisaccade differential activity, which turns first to the visual direction and then crosses over to the motor direction. Some persistent neurons appear to show the paradoxical activity previously characterized in visual neurons; paradoxical activity accelerates the transition of the neuron's activity from visual to motor. These observations suggest that the persistent neurons reflect working memory for the computation of the antisaccade sensorimotor transformation. Ensembles of persistent neurons with different response fields may make up modules of working memory.
Effect of Experimental Muscle Pain on Motor Unit Firing Rate and Conduction Velocity
Authors: Farina Dario , Arendt-Nielsen Lars , Merletti Roberto , Graven-Nielsen Thomas
Published: February 2004

The aim of this human study was to investigate the relationship between experimentally induced muscle pain intensity (i.e., amount of nociceptive activity) and motor unit (MU) firing decrease and MU conduction velocity (CV). In 12 healthy subjects, nociceptive afferents were stimulated in the right tibialis anterior muscle by three intramuscular injections of hypertonic saline (0.2, 0.5, and 0.9 ml) separated by 140 s. The subjects performed six isometric contractions (20 s long) at 10% of the maximal voluntary contraction during the experimental muscle pain. The same set of six contractions was performed without any infusion before the painful condition on the right leg. The procedure was repeated for the left leg with infusion of isotonic (nonpainful) saline. Intramuscular and surface electromyographic (EMG) signals were collected to assess MU firing rate and CV. The firing rate of the active MUs [range: 7.4-14.8 pulses/s (pps)] did not change significantly in the three control conditions (without infusion for the right and left leg and with infusion of isotonic saline in the left leg). There was, on the contrary, a significant decrease (on average, mean ± SE, 1.03 ± 0.21 pps) of the firing rates during the painful condition. Moreover, MU firing rates were inversely significantly correlated with the subjective scores of pain intensity. Single MU CV was 3.88 ± 0.03 m/s (mean ± SE, over all the MUs) with no statistical difference among any condition, i.e., the injection of hypertonic saline did not alter the muscle fiber membrane properties of the observed MUs. Progressively increased muscle pain intensity causes a gradual decrease of MU firing rates. This decrease is not associated with a change in MU membrane properties, indirectly assessed by CV. This study demonstrates a central inhibitory motor control mechanism with an efficacy correlated to the nociceptive activity.
Optic Flow Signals in Extrastriate Area MST: Comparison of Perceptual and Neuronal Sensitivity
Authors: Heuer Hilary W. , Britten Kenneth H.
Published: February 2004

The medial superior temporal area of extrastriate cortex (MST) contains signals selective for nonuniform patterns of motion often termed “optic flow.” The presence of such tuning, however, does not necessarily imply involvement in perception. To quantify the relationship between these selective neuronal signals and the perception of optic flow, we designed a discrimination task that allowed us to simultaneously record neuronal and behavioral sensitivities to near-threshold optic flow stimuli tailored to MST cells' preferences. In this two-alternative forced-choice task, we controlled the salience of globally opposite patterns (e.g., expansion and contraction) by varying the coherence of the motion. Using these stimuli, we could both relate the sensitivity of neuronal signals in MST to the animal's behavioral sensitivity and also measure trial-by-trial correlation between neuronal signals and behavioral choices. Neurons in MST showed a wide range of sensitivities to these complex motion stimuli. Many neurons had sensitivities equal or superior to the monkey's threshold. On the other hand, trial-by-trial correlation between neuronal discharge and choice (“choice probability”) was weak or nonexistent in our data. Together, these results lead us to conclude that MST contains sufficient information for threshold judgments of optic flow; however, the role of MST activity in optic flow discriminations may be less direct than in other visual motion tasks previously described by other laboratories.
Experimentally Confirmed Mathematical Model for Human Control of a Non-Rigid Object
Authors: Dingwell Jonathan B. , Mah Christopher D. , Mussa-Ivaldi Ferdinando A.
Published: February 2004

Determining the principles used to plan and execute movements is a fundamental question in neuroscience research. When humans reach to a target with their hand, they exhibit stereotypical movements that closely follow an optimally smooth trajectory. Even when faced with various perceptual or mechanical perturbations, subjects readily adapt their motor output to preserve this stereotypical trajectory. When humans manipulate non-rigid objects, however, they must control the movements of the object as well as the hand. Such tasks impose a fundamentally different control problem than that of moving one's arm alone. Here, we developed a mathematical model for transporting a mass-on-a-spring to a target in an optimally smooth way. We demonstrate that the well-known “minimum-jerk” model for smooth reaching movements cannot accomplish this task. Our model extends the concept of smoothness to allow for the control of non-rigid objects. Although our model makes some predictions that are similar to minimum jerk, it predicts distinctly different optimal trajectories in several specific cases. In particular, when the relative speed of the movement becomes fast enough or when the object stiffness becomes small enough, the model predicts that subjects will transition from a uni-phasic hand motion to a bi-phasic hand motion. We directly tested these predictions in human subjects. Our subjects adopted trajectories that were well-predicted by our model, including all of the predicted transitions between uni- and bi-phasic hand motions. These findings suggest that smoothness of motion is a general principle of movement planning that extends beyond the control of hand trajectories.
Effects of Prolactin on Ionic Membrane Conductances in the Human Malignant Astrocytoma Cell Line U87-MG
Authors: Ducret Thomas , Vacher Anne-Marie , Vacher Pierre
Published: February 2004

Prolactin (PRL) is involved in numerous biological processes in peripheral tissues and the brain. Although numerous studies have been conducted to elucidate the signal transduction pathways associated with the PRL receptor, very few have examined the role of ion conductances in PRL actions. We used the patch-clamp technique in “whole cell” configuration and microspectrofluorimetry to investigate the effects of PRL on membrane ion conductances in the U87-MG human malignant astrocytoma cell line, which naturally expresses the PRL receptor. We found that a physiological concentration (4 nM) of PRL exerted a biphasic action on membrane conductances. First, PRL activated a Ca2+-dependent K+current that was sensitive to CTX and TEA. This current depended on PRL-induced Ca2+mobilization, through a JAK2-dependent pathway from a thapsigargin- and 2-APB-sensitive Ca2+pool. Second, PRL also activated an inwardly directed current, mainly due to the stimulation of calcium influx via nickel- and 2-APB-sensitive calcium channels. Both phases resulted in membrane hyperpolarizations, mainly through the activation of Ca2+-dependent K+channels. As shown by combined experiments (electrophysiology and microspectrofluorimetry), the PRL-induced Ca2+influx increased with cell membrane hyperpolarization and conversely decreased with cell membrane depolarization. Thus PRL-induced membrane hyperpolarizations facilitated Ca2+influx through voltage-independent Ca2+channels. Finally, PRL also activated a DIDS-sensitive Cl-current, which may participate in the PRL-induced hyperpolarization. These PRL-induced conductance activations are probably related to the PRL proliferative effect we have already described in U87-MG cells.
Roles of CaMKII, PKA, and PKC in the Induction and Maintenance of LTP of C-Fiber-Evoked Field Potentials in Rat Spinal Dorsal Horn
Authors: Yang Hong-Wei , Hu Xiao-Dong , Zhang Hong-Mei , Xin Wen-Jun , Li Ming-Tao , Zhang Tong , Zhou Li-Jun , Liu Xian-Guo
Published: February 2004

Long-term potentiation (LTP) of C-fiber-evoked field potentials in spinal dorsal horn may be relevant to hyperalgesia, an increased response to noxious stimulation. The mechanism underlying this form of synaptic plasticity is, however, still unclear. Considerable evidence has shown that calcium/calmodulin-dependent protein kinase II (CaMKII), protein kinase A (PKA), and protein kinase C (PKC) are important for LTP in hippocampus. In this study, the roles of these three protein kinases in the induction and maintenance of LTP of C-fiber-evoked field potentials were evaluated by application of specific inhibitors of CaMKII (KN-93 and AIP), PKA (Rp-CPT-cAMPS), and PKC (chelerythrine and Gö 6983) at the recording segments before and after LTP induction in urethane-anesthetized Sprague-Dawley rats. We found both KN-93 and AIP, when applied at 30 min prior to tetanic stimulation, completely blocked LTP induction. At 30 min after LTP induction, KN-93 and AIP reversed LTP completely, and at 60 min after LTP induction, they depressed spinal LTP in most rats tested. Three hours after LTP induction, however, KN-93 or AIP did not affect the spinal LTP. Rp-CPT-cAMPS, chelerythrine, and Gö 6983 blocked the spinal LTP when applied at 30 min before tetanic stimulation and reversed LTP completely at 15 min after LTP induction. In contrast, at 30 min after LTP induction, the drugs never affected the spinal LTP. These results suggest that activation of CaMKII, PKA, and PKC may be crucial for the induction and the early-phase but not for the late-phase maintenance of the spinal LTP.
What the Brain Stem Tells the Frontal Cortex. I. Oculomotor Signals Sent From Superior Colliculus to Frontal Eye Field Via Mediodorsal Thalamus
Authors: Sommer Marc A. , Wurtz Robert H.
Published: February 2004

Neuronal processing in cerebral cortex and signal transmission from cortex to brain stem have been studied extensively, but little is known about the numerous feedback pathways that ascend from brain stem to cortex. In this study, we characterized the signals conveyed through an ascending pathway coursing from the superior colliculus (SC) to the frontal eye field (FEF) via mediodorsal thalamus (MD). Using antidromic and orthodromic stimulation, we identified SC source neurons, MD relay neurons, and FEF recipient neurons of the pathway in Macaca mulatta. The monkeys performed oculomotor tasks, including delayed-saccade tasks, that permitted analysis of signals such as visual activity, delay activity, and presaccadic activity. We found that the SC sends all of these signals into the pathway with no output selectivity, i.e., the signals leaving the SC resembled those found generally within the SC. Visual activity arrived in FEF too late to contribute to short-latency visual responses there, and delay activity was largely filtered out in MD. Presaccadic activity, however, seemed critical because it traveled essentially unchanged from SC to FEF. Signal transmission in the pathway was fast (∼2 ms from SC to FEF) and topographically organized (SC neurons drove MD and FEF neurons having similarly eccentric visual and movement fields). Our analysis of identified neurons in one pathway from brain stem to frontal cortex thus demonstrates that multiple signals are sent from SC to FEF with presaccadic activity being prominent. We hypothesize that a major signal conveyed by the pathway is corollary discharge information about the vector of impending saccades.
What the Brain Stem Tells the Frontal Cortex. II. Role of the SC-MD-FEF Pathway in Corollary Discharge
Authors: Sommer Marc A. , Wurtz Robert H.
Published: February 2004

One way we keep track of our movements is by monitoring corollary discharges or internal copies of movement commands. This study tested a hypothesis that the pathway from superior colliculus (SC) to mediodorsal thalamus (MD) to frontal eye field (FEF) carries a corollary discharge about saccades made into the contralateral visual field. We inactivated the MD relay node with muscimol in monkeys and measured corollary discharge deficits using a double-step task: two sequential saccades were made to the locations of briefly flashed targets. To make second saccades correctly, monkeys had to internally monitor their first saccades; therefore deficits in the corollary discharge representation of first saccades should disrupt second saccades. We found, first, that monkeys seemed to misjudge the amplitudes of their first saccades; this was revealed by systematic shifts in second saccade end points. Thus corollary discharge accuracy was impaired. Second, monkeys were less able to detect trial-by-trial variations in their first saccades; this was revealed by reduced compensatory changes in second saccade angles. Thus corollary discharge precision also was impaired. Both deficits occurred only when first saccades went into the contralateral visual field. Single-saccade generation was unaffected. Additional deficits occurred in reaction time and overall performance, but these were bilateral. We conclude that the SC-MD-FEF pathway conveys a corollary discharge used for coordinating sequential saccades and possibly for stabilizing vision across saccades. This pathway is the first elucidated in what may be a multilevel chain of corollary discharge circuits extending from the extraocular motoneurons up into cerebral cortex.
Enhancement of Potency and Efficacy of NADA by PKC-Mediated Phosphorylation of Vanilloid Receptor
Authors: Premkumar Louis S. , Qi Zhan-Heng , Van Buren Jeremy , Raisinghani Manish
Published: February 2004

The search for an endogenous ligand for the vanilloid receptor (VR or TRPV1) has led to the identification of N-arachidonyl dopamine (NADA). This study investigates the role of protein kinase C (PKC)-mediated phosphorylation on NADA-induced membrane currents in Xenopus oocytes heterologously expressing TRPV1 and in dorsal root ganglion (DRG) neurons. In basal state, current induced by 10 μM NADA is 5-10% of the current induced by 1 μM capsaicin or protons at pH 5. However, PKC activator, phorbol 12,13-dibutyrate (PDBu) strongly potentiated (∼15-fold) the NADA-induced current. Repeated application of NADA at short intervals potentiated its own response approximately fivefold in a PKC-dependent manner. PKC inhibitor, bisindolylmaleimide (BIM, 500 nM), a mutant TRPV1 (S800A/S502A), and maximal activation of PKC abolished the potentiation induced by repeated application of NADA. As a further confirmation that NADA could stimulate PKC, pretreatment with NADA potentiated the response of protons at pH 5 (∼20 fold), which was dramatically reduced in the mutant TRPV1. In DRG neurons, capsaicin (100 nM) induced a ∼15 mV depolarization and initiated a train of action potentials compared with 1 μM NADA that produced a ∼5 mV response. Pretreatment with PDBu induced significantly larger depolarization and potentiated NADA-induced current. Furthermore, exposure of NADA to the intracellular surface of the membrane-induced larger currents suggesting inaccessibility to the intracellular binding site might contribute to its weaker action. These results indicate that NADA is a potent agonist of VR when the receptor is in the PKC-mediated phosphorylation state.
Information Transmission Rates of Cat Retinal Ganglion Cells
Authors: Passaglia Christopher L. , Troy John B.
Published: February 2004

To assess the information encoded in retinal spike trains and how it might be decoded by recipient neurons in the brain, we recorded from individual cat X and Y ganglion cells and visually stimulated them with randomly modulated patterns of various contrast and spatial configuration. For each pattern, we estimated the information rate of the cells using linear or nonlinear algorithms and for some patterns by directly measuring response probability distributions. We show that ganglion cell spike trains contain information from the receptive field center and surround, that the center and surround have similar signaling capacity, that antagonism between the mechanisms reduces information transmission, and that the total information rate is limited. We also show that a linear decoding algorithm can capture all of the information available in retinal spike trains about weak inputs, but it misses a substantial amount about strong inputs. For the strongest stimulus we used, the information rate of the best linear decoder averaged 40-70 bits/s across ganglion cell types, while the directly measured rate was around 20-40 bits/s greater. This implies that under certain stimulus conditions, visual information is encoded in the temporal structure of retinal spike trains and that a nonlinear decoding algorithm is needed to extract the temporally coded information. Using simulated spike trains, we demonstrate that much of the temporal structure may be explained by the threshold for spike generation and is not necessarily indicative of a complex coding scheme.
Na+-H+Exchange Activity in Taste Receptor Cells
Authors: Vinnikova Anna K. , Alam Rammy I. , Malik Shahbaz A. , Ereso Glenn L. , Feldman George M. , McCarty John M. , Knepper Mark A. , Heck Gerard L. , DeSimone John A. , Lyall Vijay
Published: February 2004

mRNA for two Na+-H+-exchanger isoforms 1 and 3 (NHE-1 and NHE-3) was detected by RT-PCR in fungiform and circumvallate taste receptor cells (TRCs). Anti-NHE-1 antibody binding was localized to the basolateral membranes, and the anti-NHE-3 antibody was localized in the apical membranes of fungiform and circumvallate TRCs. In a subset of TRCs, NHE-3 immunoreactivity was also detected in the intracellular compartment. For functional studies, an isolated lingual epithelium containing a single fungiform papilla was mounted with apical and basolateral sides isolated and perfused with nominally CO2/HCO3--free physiological media (pH 7.4). The TRCs were monitored for changes in intracellular pH (pHi) and Na+([Na+]i) using fluorescence ratio imaging. At constant external pH, 1) removal of basolateral Na+reversibly decreased pHiand [Na+]i; 2) HOE642, a specific blocker, and amiloride, a nonspecific blocker of basolateral NHE-1, attenuated the decrease in pHiand [Na+]i; 3) exposure of TRCs to basolateral NH4Cl or sodium acetate pulses induced transient decreases in pHithat recovered spontaneously to baseline; 4) pHirecovery was inhibited by basolateral amiloride, 5-( N-methyl- N-isobutyl)-amiloride (MIA), 5-( N-ethyl- N-isopropyl)-amiloride (EIPA), HOE642, and by Na+removal; 5) HOE642, MIA, EIPA, and amiloride inhibited pHirecovery with Kivalues of 0.23, 0.46, 0.84, and 29 μM, respectively; and 6) a decrease in apical or basolateral pH acidified TRC pHiand inhibited spontaneous pHirecovery. The results indicate the presence of a functional NHE-1 in the basolateral membranes of TRCs. We hypothesize that NHE-1 is involved in sour taste transduction since its activity is modulated during acid stimulation.
From Another Angle: Differences in Cortical Coding Between Fine and Coarse Discrimination of Orientation
Authors: Samonds Jason M. , Bonds A. B.
Published: February 2004

We measured the information available for orientation discrimination from metric distances for 24 cells in area 17 of cats that were paralyzed and anesthetized with Propofol and N2O. The metric distance information confirms fundamental coding differences for discrimination between fine (<10°) and coarse (>10°) orientation differences. The information for discriminating larger orientation differences is contained mainly in the firing rate, with minor enhancements from the coarse (30-70 ms) temporal structure in the firing rate. Both precise spike timing (9.2 ms) and intervals (6.8 ms) sustained over the stimulus presentation provide information for fine discrimination of orientation, where almost no reliable information is provided by the spike count. We compare and confirm the results (using the same data set) to vector distances based on classification theory. The results support a dynamic spiking mechanism where coordinated activity could provide fast and reliable information about detailed angle and/or direction information in the region of the preferred orientation.
Activity in the Hypothalamus, Amygdala, and Cortex Generates Bilateral and Convergent Modulation of Pontine Gustatory Neurons
Authors: Lundy Robert F. , Norgren Ralph
Published: February 2004

Evidence suggests that centrifugal modulation of brain stem gustatory cells might play a role in the elaboration of complex taste-guided behaviors like conditioned taste aversion and sodium appetite. We previously showed that activity in one forebrain area, the central nucleus of the amygdala (CeA), increased the chemical selectivity of taste cells in the parabrachial nucleus (PBN). The present study investigates how activity in 2 other similarly interconnected forebrain sites, the lateral hypothalamus (LH) and gustatory cortex (GC), might influence PBN gustatory processing in rats. The potential convergence of descending inputs from these sites, as well as the CeA, was also evaluated. After anesthesia (35 mg/kg Nembutal ip), 70 PBN gustatory neurons were tested before, during, and after electrical stimulation of these forebrain sites, while responding to 0.3 M sucrose, 0.1 M NaCl, 0.01 M citric acid, and 0.003 M QHCl. Although each forebrain site modulated taste-evoked responses, more PBN neurons were influenced by stimulation of the GC (67%) and CeA (73%) than of the LH (48%). Activation of cortex (71%) and amygdala (85%) most often produced inhibition, whereas inhibition and excitation occurred equally often during hypothalamic stimulation. Of the neurons tested for convergence ( n = 60), 88% were influenced by ≥1 of the 3 sites. Twenty were modulated by stimulation at all 3 sites and another 17 by 2 of the 3 sites. The net effect of centrifugal modulation was to sharpen the across-stimulus response profiles of PBN cells, particular with regard to the NaCl- and citric acid-best cells.
Coupling Between Feline Cerebellum (Fastigial Neurons) and Motoneurons Innervating Hindlimb Muscles
Authors: Matsuyama Kiyoji , Jankowska Elzbieta
Published: February 2004

The aims of the study were twofold: (1) to verify the hypothesis that neurons in the fastigial nucleus excite and inhibit hindlimb α-motoneurons and (2) to determine both the supraspinal and spinal relays of these actions. Axons of fastigial neurons were stimulated at the level of their decussation in the cerebellum, within the hook bundle of Russell, in deeply anesthetized cats with only the right side of the spinal cord intact. The resulting excitatory postsynaptic potentials and inhibitory postsynaptic potentials were analyzed in motoneurons on the left side of the lumbar enlargement. Postsynaptic potentials evoked by the first effective stimulus were induced at latencies <2 ms from descending volleys and <1 ms from interneuronally relayed volleys, indicating a trisynaptic coupling between the fastigial neurons and α-motoneurons, via commissural interneurons on the right side. Cerebellar stimulation facilitated the synaptic actions of both vestibulospinal and reticulospinal tract fibers. However, the study leads to the conclusion that trisynaptic fastigial actions are mediated via vestibulospinal rather than reticulospinal tract fibers [stimulated within the lateral vestibular nucleus (LVN) and the medial longitudinal fascicle (MLF), respectively]. This is indicated firstly by collision between descending volleys induced by cerebellar stimulation and volleys evoked by LVN stimuli but not by MLF stimuli. Second, similar cerebellar actions were evoked before and after a transection of MLF. Mutual facilitation between the fastigial and reticulospinal, as well as between the fastigial and vestibulospinal actions, could be due to the previously reported integration of descending vestibulospinal and reticulospinal commands by spinal commissural interneurons.
Two Distinct Regions of Secondary Somatosensory Cortex in the Rat: Topographical Organization and Multisensory Responses
Authors: Brett-Green Barbara , Paulsen Marcy , Staba Richard J. , Fifková Eva , Barth Daniel S.
Published: February 2004

In rodents, as in other species, regions of secondary somatosensory cortex (SII) may be distinguished from primary cortex (SI) both anatomically and electrophysiologically. However, the number of rodent SII subregions, their somatotopic organization, and their function are poorly understood. The presence of multisensory responsive neurons in some areas of SII suggests that one of its roles may be in the integration of somatosensory information with information from other sensory modalities. In this study, we used auditory, somatosensory, or combined auditory/somatosensory stimuli, and high-resolution epipial-evoked potential maps of rat SII to identify the number of spatially discrete subregions, estimate their somatotopic organization, and delineate regions with multisensory response properties. Maps revealed two distinct subregions within SII, one rostral and the other caudal, which were situated lateral to the posteromedial barrel subfield. Distinct somatotopies were evident at both SII loci, and analysis of evoked responses within both areas indicated multisensory interactions. These data are consistent with the presence of classically defined rostral SII regions and provide functional evidence for a lesser known, but distinct, caudal SII area. Furthermore, evidence for multisensory interactions within SII suggests that both secondary areas may process features specifically associated with multisensory integration in parallel with unimodal processing in primary areas.
Light-Evoked Responses of the Mouse Retinal Pigment Epithelium
Authors: Wu Jiang , Peachey Neal S. , Marmorstein Alan D.
Published: February 2004

In response to light, the retinal pigment epithelium (RPE) generates a series of slow potentials that can be recorded as the c-wave, fast oscillation (FO), and light peak (LP) of the electroretinogram (ERG). As these potentials can be related to specific cellular events, they provide information about RPE function and how that may be altered by disease or experimental manipulation. In the present study we describe a noninvasive means for recording the light-evoked responses of the mouse RPE and use this to define the stimulus-response properties of the major components in three inbred strains of mice (BALBc/ByJ, C57BL/6J, and 129/SvJ) and two mouse mutants that reduce activity in the rod pathway. All of the major ERG components generated by the RPE are readily measured in the mouse. In albino strains (BALBc/ByJ and 129/SvJ) the intensity-response functions for the c-wave, FO, and LP are shifted toward lower intensities in comparison to those for C57BL/6J mice. Each of these components was markedly reduced in mice lacking transducin in which rod phototransduction is interrupted, indicating that they reflect primarily rod photoreceptor activity. All components were observed in no b-wave ( nob) mutant mice, indicating that inner retinal activity does not make a major contribution to these potentials. Further studies of mutant mice will allow us to define the functional consequences of gene manipulation on RPE function and to evaluate specific hypotheses regarding the generation of ERG components.