bluuebunny/crossref_metadata_2025 huggingface dataset:
Neurokinin 2 receptor‐mediated activation of protein kinase C modulates capsaicin responses in DRG neurons from adult rats
Authors: Sculptoreanu Adrian , Aura Kullmann F. , De Groat William C.
Published: June 2008

Patch‐clamp techniques and Ca2+ imaging were used to examine the interaction between neurokinins (NK) and the capsaicin (CAPS)‐evoked transient receptor potential vanilloid receptor 1 (TRPV1) responses in rat dorsal root ganglia neurons. Substance P (SP; 0.2–0.5 μm) prevented the reduction of Ca2+ transients (tachyphylaxis) evoked by repeated brief applications of CAPS (0.5 μm). Currents elicited by CAPS were increased in amplitude and desensitized more slowly after administration of SP or a selective NK2 agonist, [Ala8]‐neurokinin A (4–10) (NKA). Neither an NK1‐selective agonist, [Sar9, Met11]‐SP, nor an NK3‐selective agonist, [MePhe7]‐NKB, altered the CAPS currents. The effects of SP on CAPS currents were inhibited by a selective NK2 antagonist, MEN 10,376, but were unaffected by the NK3 antagonist, SB 235,375. Phorbol 12,13‐dibutyrate (PDBu), an activator of protein kinase C (PKC), also increased the amplitude and slowed the desensitization of CAPS responses. Phosphatase inhibitors, decamethrin and α‐naphthyl acid phosphate (NAcPh), also enhanced the currents and slowed desensitization of CAPS currents. Facilitatory effects of SP, NKA and PDBu were reversed by bisindolylmaleimide, a PKC inhibitor, and gradually decreased in magnitude when the agents were administered at increasing intervals after CAPS application. The decrease was partially prevented by prior application of NAcPh. These data suggest that activation of NK2 receptors in afferent neurons leads to PKC‐induced phosphorylation of TRPV1, resulting in sensitization of CAPS‐evoked currents and slower desensitization. Thus, activation of NK2 autoreceptors by NKs released from the peripheral afferent terminals or by mast cells during inflammatory responses may be a mechanism that sensitizes TRPV1 channels and enhances afferent excitability.
fMRI reveals greater within‐ than between‐hemifield integration in the human lateral occipital cortex
Authors: Large Mary‐Ellen , Culham Jody , Kuchinad Anil , Aldcroft Adrian , Vilis Tutis
Published: June 2008

Early visual areas within each hemisphere (V1, V2, V3/VP, V4v) contain distinct representations of the upper and lower quadrants of the contralateral hemifield. As receptive field size increases, the retinotopy in higher‐tier visual areas becomes progressively less distinct. Using functional magnetic resonance imaging (fMRI) to map the visual fields, we found that an intermediate level visual area, the lateral occipital region (LO), contains retinotopic maps with a contralateral bias, but with a combined representation of the upper and lower visual field. Moreover, we used the technique of fMRI adaptation to determine whether neurons in LO code for both the upper and lower contralateral quadrants. We found that even when visual stimulus locations are equivalent across comparisons, the LO was more sensitive to location changes that crossed hemifields than location changes within a hemifield. These results suggested that within high‐tier visual areas the increasing integration of visual field information is a two‐stage process. The upper and lower visual representations are combined first, in LO, then the left and right representations. Furthermore, these results provided evidence for a neural mechanism to explain behavioral findings of greater integration within than between hemifields.
Expertise in dance modulates alpha/beta event‐related desynchronization during action observation
Authors: Orgs Guido , Dombrowski Jan‐Henryk , Heil Martin , Jansen‐Osmann Petra
Published: June 2008

We presented professional dancers and non‐dancers with videos of two movement styles, dance movements and everyday movements. Participants were asked to indicate by a button press to which category a movement belonged. We computed event‐related desynchronization (ERD) in alpha and beta frequency bands between 7.5 and 25 Hz relative to a visual baseline condition. Power in alpha and lower beta frequency bands was significantly reduced if dancers watched dance movements but not if non‐dancers watched dance movements, in particular between 1 and 2 s after movement onset. During observation of everyday movements no such group difference was evident. Thus, ERD in alpha and beta frequency bands was modulated by a participant’s expertise with a certain movement style. The results are discussed in light of a human observation–execution matching system similar to the macaque mirror neuron system and strengthen the idea of a functional relationship between such a system and rhythmical activity in the alpha and beta frequency bands.
On the development of human corticospinal oscillations: age‐related changes in EEG–EMG coherence and cumulant
Authors: James Leon M. , Halliday David M. , Stephens John A. , Farmer Simon F.
Published: June 2008

Changes in coherence and cumulant calculated between electroencephalograph (EEG) recorded from the scalp over primary motor cortex and rectified surface electromyograph (EMG) recorded from the contralateral wrist extensor muscles have been studied during development in humans (48 subjects, age 0–59 years). Using the techniques of EEG–EMG coherence and cumulant analysis and pooled coherence and cumulant analysis we demonstrate that between childhood, adolescence and adulthood there are increases in the prevalence and magnitude of coherence at frequencies between 15 and 35 Hz with corresponding development of a tri‐phasic feature in the EEG–EMG cumulant. The results show for the first time that changes in the cortical ∼20 Hz oscillatory drive to human motoneurone pools take place during motor development.
Selective attention to sound location or pitch studied with event‐related brain potentials and magnetic fields
Authors: Degerman Alexander , Rinne Teemu , Särkkä Anna‐Kaisa , Salmi Juha , Alho Kimmo
Published: June 2008

Event‐related brain potentials (ERPs) and magnetic fields (ERFs) were used to compare brain activity associated with selective attention to sound location or pitch in humans. Sixteen healthy adults participated in the ERP experiment, and 11 adults in the ERF experiment. In different conditions, the participants focused their attention on a designated sound location or pitch, or pictures presented on a screen, in order to detect target sounds or pictures among the attended stimuli. In the Attend Location condition, the location of sounds varied randomly (left or right), while their pitch (high or low) was kept constant. In the Attend Pitch condition, sounds of varying pitch (high or low) were presented at a constant location (left or right). Consistent with previous ERP results, selective attention to either sound feature produced a negative difference (Nd) between ERPs to attended and unattended sounds. In addition, ERPs showed a more posterior scalp distribution for the location‐related Nd than for the pitch‐related Nd, suggesting partially different generators for these Nds. The ERF source analyses found no source distribution differences between the pitch‐related Ndm (the magnetic counterpart of the Nd) and location‐related Ndm in the superior temporal cortex (STC), where the main sources of the Ndm effects are thought to be located. Thus, the ERP scalp distribution differences between the location‐related and pitch‐related Nd effects may have been caused by activity of areas outside the STC, perhaps in the inferior parietal regions.
Impaired GABAergic transmission disrupts normal homeostatic plasticity in rat cortical networks
Authors: Le Roux N. , Amar M. , Moreau A. , Baux G. , Fossier P.
Published: June 2008

In the cortex, homeostatic plasticity appears to be a key process for maintaining neuronal network activity in a functional range. This phenomenon depends on close interactions between excitatory and inhibitory circuits. We previously showed that application of a high frequency of stimulation (HFS) protocol in layer 2/3 induces parallel potentiation of excitatory and inhibitory inputs on layer 5 pyramidal neurons, leading to an unchanged excitation/inhibition (E/I) balance. These coordinated long‐term potentiations of excitation and inhibition correspond to homeostatic plasticity of the neuronal networks. We showed here, on the rat visual cortex, that blockade (with gabazine) or overactivation (with 4,5,6,7‐tetrahydroisoxazolo[5,4‐c]pyridin‐3‐ol) of GABAA receptors enhanced the E/I balance and prevented the potentiation of excitatory and inhibitory inputs after an HFS protocol. These impairements of the GABAergic transmission led to a long‐term depression‐like effect after an HFS protocol. We also observed that the blockade of inhibition reduced excitation (by 60%), and conversely, the blockade of excitation decreased inhibition (by 90%). These results support the idea that inhibitory interneurons are critical for recurrent interactions underlying homeostatic plasticity in cortical networks.
Population coding of song element sequence in the Bengalese finch HVC
Authors: Nishikawa Jun , Okada Masato , Okanoya Kazuo
Published: June 2008

Birdsong is a complex vocalization composed of various song elements organized according to sequential rules. Two alternative views exist that explain the neural representation of song element sequences in the songbird brain. The finding of sequential selective neurons supports the idea that the song element sequence is encoded in a chain of rigid selective neurons. Alternatively, song structure could be encoded in an ensemble of relatively broad selective neurons arranged in a distributed manner. Here we attempted to determine which neural representation actually occurs in the song system by recording neural responses to various stimuli and performing information‐theoretic analysis on the data obtained. We recorded the neural responses to all possible element pairs of stimuli in the Bengalese finch brain nucleus high vocal centre (HVC). Our results showed that each neuron has broad but differential response properties to element sequences beyond the structure of self‐generated song. To quantify the transmitted information by such a broadly tuned neural population, we calculated the time course of mutual information between auditory stimuli and neural activities. Confounded information, which represents the relationship between present and previous elements, increased significantly immediately after stimulus presentation. These results indicate that the song element sequence is encoded in a neural ensemble in the HVC via population coding. These findings give us a new encoding scheme for the song element sequence using a distributed neural representation rather than the chain model of rigid selective neurons.
Dynamic coupling of excitatory and inhibitory responses in the medial nucleus of the trapezoid body
Authors: Tolnai Sandra , Englitz Bernhard , Kopp‐Scheinpflug Cornelia , Dehmel Susanne , Jost Jürgen , Rübsamen Rudolf
Published: June 2008

The neuronal representation of acoustic amplitude modulations is an important prerequisite for understanding the processing of natural sounds. We investigated this representation in the medial nucleus of the trapezoid body (MNTB) of the Mongolian gerbil using sinusoidal amplitude modulations (SAM). Depending on the SAM’s carrier frequency (fC) MNTB cells either increase or decrease their discharge rates, indicating underlying excitatory and inhibitory/suppressive mechanisms. As natural sounds typically are composed of multiple spectral components we investigated how stimuli containing two spectral components are represented in the MNTB, especially when they have opposing effects on the discharge rate. Three conditions were compared: SAM stimuli (1) with rate‐increasing fC, (2) with rate‐increasing fC and an additional unmodulated rate‐decreasing pure tone, and (3) with rate‐decreasing fC and an unmodulated, rate‐increasing pure tone. We found that responses under all three conditions showed comparable strength of phase‐locking. Adding a rate‐decreasing tone to a rate‐increasing SAM increased phase‐locking for modulation frequencies (fAM) of ≤ 600 Hz. A comparison of two possible coding strategies – phase‐locking vs. envelope reproduction – indicates that both strategies are realized to different degrees depending on the fAM. We measured latencies for following modulations in rate‐increasing and rate‐decreasing SAMs using a modified reverse correlation approach. Although latencies varied between 2.5 and 5 ms between cells, a decrease in rate consistently followed an increase in rate with a delay of about 0.2 ms in each cell. These results suggest a temporally precise representation of rate‐increasing and rate‐decreasing stimuli at the level of the MNTB during dynamic stimulation.
N‐ethylmaleimide‐sensitive fusion protein (NSF) is involved in central sensitization in the spinal cord through GluR2 subunit composition switch after inflammation
Authors: Katano Tayo , Furue Hidemasa , Okuda‐Ashitaka Emiko , Tagaya Mitsuo , Watanabe Masahiko , Yoshimura Megumu , Ito Seiji
Published: June 2008

Central sensitization, similar to long‐term potentiation in the hippocampus, refers to the increased synaptic efficacy established in somatosensory neurons in the dorsal horn of the spinal cord following tissue injury or nerve damage. In the course of inflammation, many proteins including glutamate receptors are assumed to be dynamically reorganized in the postsynaptic density (PSD) and involved in persistent pain. Mechanical hyperalgesia induced by intraplantar injection of complete Freund’s adjuvant (CFA) was inhibited at 4 h, but not at 24 h, by indomethacin, an inhibitor of prostanoid synthesis. To elucidate the nature of the molecule(s) involved in the late phase of inflammatory pain, we analysed the PSD fraction prepared from the lumbar spinal cord of rats before and 24 h after CFA injection by conducting two‐dimensional differential gel electrophoresis. N‐ethylmaleimide‐sensitive fusion protein (NSF) was identified as a downregulated protein in the PSD by MALDI‐TOF MS and immunoblotting. Concomitant with the decrease in NSF, GluR2 and GluR3 were decreased and GluR1 was conversely increased in the PSD fraction 24 h after CFA injection. In vivo patch‐clamp recordings of rats 24 h after CFA injection showed that excitatory postsynaptic currents of dorsal horn neurons evoked by pinch stimuli to inflamed skin were inwardly rectified and inhibited by 60% by philanthotoxin‐433, a selective inhibitor of the Ca2+ ‐permeable α‐amino‐3‐hydroxy‐5‐methyl‐4‐isoxazolepropionic acid (AMPA) receptor. These results suggest that peripheral inflammation gives rise to central sensitization in the spinal cord through subunit composition switch of AMPA receptors in the late phase.
Dual modulation of synaptic transmission in the nucleus tractus solitarius by prostaglandin E2 synthesized downstream of IL‐1β
Authors: Marty Vincent , El Hachmane Mickaël , Amédée Thierry
Published: June 2008

The activation of the innate immune system induces the production of blood‐borne proinflammatory cytokines like interleukin‐1β (IL‐1β), which in turn triggers brain‐mediated adaptative responses referred to as sickness behaviour. These responses involve the modulation of neural networks in key regions of the brain. The nucleus tractus solitarius (NTS) of the brainstem is a key nucleus for immune‐to‐brain signalling. It is the main site of termination of vagal afferents and is adjacent to the area postrema, a circumventricular organ allowing blood‐borne action of circulating IL‐1β. Although it is well described that IL‐1β activates cerebral endothelial and glial cells, it is still unknown if and how IL‐1β or downstream‐synthesized molecules impact NTS synaptic function. In this study we report that IL‐1β did not modulate NTS synaptic transmissionper se, whereas prostaglandin E2(PGE2), which is produced downstream of IL‐1β, produced opposite effects on spontaneous and evoked release. On the one hand, PGE2facilitated glutamatergic transmission between local NTS neurons by enhancing the frequency of spontaneous excitatory postsynaptic currents through a presynaptic receptor different from the classical EP1–4 subtypes. On the other hand, PGE2also depressed evoked excitatory input from vagal afferent terminals through presynaptic EP3 receptors coupled to G‐proteins linked to adenylyl cyclase and protein kinase A activity. Our data show that IL‐1β‐induced PGE2can modulate evoked and spontaneous release in the NTS differentially through different mechanisms. These data unravel some molecular mechanisms by which innate immune stimuli could signal to, and be integrated within, the brainstem to produce central adaptative responses.
A novel role for MNTB neuron dendrites in regulating action potential amplitude and cell excitability during repetitive firing
Authors: Leão Richardson N. , Leão Ricardo M. , Da Costa Luciano F. , Rock Levinson S. , Walmsley Bruce
Published: June 2008

Principal cells of the medial nucleus of the trapezoid body (MNTB) are simple round neurons that receive a large excitatory synapse (the calyx of Held) and many small inhibitory synapses on the soma. Strangely, these neurons also possess one or two short tufted dendrites, whose function is unknown. Here we assess the role of these MNTB cell dendrites using patch‐clamp recordings, imaging and immunohistochemistry techniques. Using outside‐out patches and immunohistochemistry, we demonstrate the presence of dendritic Na+ channels. Current‐clamp recordings show that tetrodotoxin applied onto dendrites impairs action potential (AP) firing. Using Na+ imaging, we show that the dendrite may serve to maintain AP amplitudes during high‐frequency firing, as Na+ clearance in dendritic compartments is faster than axonal compartments. Prolonged high‐frequency firing can diminish Na+ gradients in the axon while the dendritic gradient remains closer to resting conditions; therefore, the dendrite can provide additional inward current during prolonged firing. Using electron microscopy, we demonstrate that there are small excitatory synaptic boutons on dendrites. Multi‐compartment MNTB cell simulations show that, with an active dendrite, dendritic excitatory postsynaptic currents (EPSCs) elicit delayed APs compared with calyceal EPSCs. Together with high‐ and low‐threshold voltage‐gated K+ currents, we suggest that the function of the MNTB dendrite is to improve high‐fidelity firing, and our modelling results indicate that an active dendrite could contribute to a ‘dual’ firing mode for MNTB cells (an instantaneous response to calyceal inputs and a delayed response to non‐calyceal dendritic excitatory postsynaptic potentials).
A role for alpha‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid GluR1 phosphorylation in the modulatory effects of appetitive reward cues on goal‐directed behavior
Authors: Crombag Hans S. , Sutton Jeffrey M. , Takamiya Kogo , Holland Peter C. , Gallagher Michela , Huganir Richard L.
Published: June 2008

Alpha‐amino‐3‐hydroxy‐5‐methylisoxazole‐4‐propionic acid (AMPA) receptor regulation has been shown to be critically involved in synaptic plasticity underlying learning and memory. This regulation occurs through trafficking of the receptor and modulation of the receptor’s channel properties, both of which depend on protein phosphorylation. Using homologous recombination (knock‐in) techniques we targeted two phosphorylation sites on the AMPA‐GluR1 receptor: the Ser831 site, phosphorylated by calcium calmodulin‐dependent protein kinase II/protein kinase C, and the Ser845 site, phosphorylated by protein kinase A. Mice with mutations that prevented phosphorylation at one or both of these sites were tested on a single‐outcome Pavlovian‐instrumental transfer task often used to assess the acquisition of incentive motivation by cues for food reinforcement. Mice were separately trained to associate a Pavlovian cue with food and to perform an instrumental lever‐press response to earn that same reward. During a transfer test, the cue was presented while the mice were lever‐pressing under extinction conditions. Whereas wild‐type control mice showed substantial enhancement of lever‐pressing when the cue was presented (i.e. showed Pavlovian‐instrumental transfer), mice with mutations at both of these phosphorylation sites showed no evidence of such transfer. By contrast, mice with either serine site mutated alone showed normal transfer. These results suggest critical roles for GluR1 phosphorylation pathways in a form of incentive learning that can play an important part in regulating normal motivated behavior as well as maladaptive behaviors such as addiction and eating disorders.
Cysteine string protein‐α is essential for the high calcium sensitivity of exocytosis in a vertebrate synapse
Authors: Ruiz R. , Casañas J. J. , Südhof T. C. , Tabares L.
Published: June 2008

Cysteine string protein (CSPα) is a synaptic vesicle protein present in most central and peripheral nervous system synapses. Previous studies demonstrated that the deletion of CSPα results in postnatal sensorial and motor impairment and premature lethality. To understand the participation of CSPα in neural function in vertebrates, we have studied the properties of synaptic transmission of motor terminals in wild‐type and CSPα knockout mice. Our results demonstrate that, in the absence of CSPα, fast Ca2+‐triggered release was not affected at postnatal day (P)14 but was dramatically reduced at P18 and P30 without a change in release kinetics. Although mutant terminals also exhibited a reduction in functional vesicle pool size by P30, further analysis showed that neurotransmission could be ‘rescued’ by high extracellular [Ca2+] or by the presence of a phorbol ester, suggesting that an impairment in the fusion machinery, or in vesicle recycling, was not the primary cause of the dysfunction of this synapse. The specific shift to the right of the Ca2+ dependence of synchronous release, and the lineal dependence of secretion on extracellular [Ca2+] in mutant terminals after P18, suggests that CSPα is indispensable for a normal Ca2+ sensitivity of exocytosis in vertebrate mature synapses.
Environmental enrichment ameliorates a motor coordination deficit in a mouse model of Rett syndrome –Mecp2gene dosage effects and BDNF expression
Authors: Kondo Mari , Gray Laura J. , Pelka Gregory J. , Christodoulou John , Tam Patrick P. L. , Hannan Anthony J.
Published: June 2008

Rett syndrome, commonly associated with mutations of the methyl CpG‐binding protein 2 (MECP2) gene, is characterised by an apparently normal early postnatal development followed by deterioration of acquired cognitive and motor coordination skills in early childhood. To evaluate whether environmental factors may influence the disease outcome of Rett syndrome, we tested the effect of environmental enrichment from 4 weeks of age on the behavioural competence of mutant mice harboring aMecp2 tm1Tam‐null allele. Our findings show that enrichment improves motor coordination in heterozygousMecp2 +/−females but notMecp2 −/ymales. Standard‐housedMecp2 +/−mice had an initial motor coordination deficit on the accelerating rotarod, which improved with training then deteriorated in subsequent weeks. Enrichment resulted in a significant reduction in this coordination deficit inMecp2 +/−mice, returning the performance to wild‐type levels. Brain‐derived neurotrophic factor (BDNF) protein levels were 75 and 85% of wild‐type controls in standard‐housed and environmentally enrichedMecp2 +/−cerebellum, respectively.Mecp2 −/ymice showed identical deficits of cerebellar BDNF (67% of wild‐type controls) irrespective of their housing environment. Our findings demonstrate a positive impact of environmental enrichment in a Rett syndrome model; this impact may be dependent on the existence of one functional copy ofMecp2.
Age‐related changes in dopamine transporters and accumulation of 3‐nitrotyrosine in rhesus monkey midbrain dopamine neurons: Relevance in selective neuronal vulnerability to degeneration
Authors: Kanaan N. M. , Kordower J. H. , Collier T. J.
Published: June 2008

Aging is the strongest risk factor for developing Parkinson’s disease (PD). There is a preferential loss of dopamine (DA) neurons in the ventral tier of the substantia nigra (vtSN) compared to the dorsal tier and ventral tegmental area (VTA) in PD. Examining age‐related and region‐specific differences in DA neurons represents a means of identifying factors potentially involved in vulnerability or resistance to degeneration. Nitrative stress is among the factors potentially underlying DA neuron degeneration. We studied the relationship between 3‐nitrotyrosine (3NT; a marker of nitrative damage) and DA transporters [DA transporter (DAT) and vesicular monoamine transporter‐2 (VMAT)] during aging in DA subregions of rhesus monkeys. The percentage of DA neurons containing 3NT increased significantly only in the vtSN with advancing age, and the vtSN had a greater percentage of 3NT‐positive neurons when compared to the VTA. The relationship between 3NT and DA transporters was determined by measuring fluorescence intensity of 3NT, DAT and VMAT staining. 3NT intensity increased with advancing age in the vtSN. Increased DAT, VMAT and DAT/VMAT ratios were associated with increased 3NT in individual DA neurons. These results suggest nitrative damage accumulates in midbrain DA neurons with advancing age, an effect exacerbated in the vulnerable vtSN. The capacity of a DA neuron to accumulate more cytosolic DA, as inferred from DA transporter expression, is related to accumulation of nitrative damage. These findings are consistent with a role for aging‐related accrual of nitrative damage in the selective vulnerability of vtSN neurons to degeneration in PD.
Enhanced Ras activity preserves dendritic size and extension as well as synaptic contacts of neurons after functional deprivation in synRas mice
Authors: Alpár A. , Naumann N. , Härtig W. , Arendt T. , Gärtner U.
Published: June 2008

The monomeric GTP‐binding protein p21Ras has been repeatedly implicated in neuronal stability and plastic changes of the adult nervous system. Recently, we have shown that expression of constitutively active Ras protein in transgenic synRas mice results in a significant increase in the dendritic size and complexity of differentiated pyramidal neurons as well as in increased synaptic connectivity. In the present study, we examined the organization of the vibrissae‐barrel cortex in synRas mice and the effects of enhanced Ras activity on deprivation‐induced dendritic reorganization after vibrissectomy. The results demonstrate a significant increase in vibrissae‐barrel sizes and proportional spacing between barrels in synRas mice, suggesting that the neuronal target specificity of thalamocortical terminals is preserved. Accordingly, the arrangement of double bouquet cells at the borders of barrel columns ensuring functional distinctness is unchanged. Partial vibrissectomy is followed by significant dendritic regression of corresponding pyramidal neurons in the barrel cortex of wild‐type mice, which, however, could not be observed in synRas mice. The results provide the first evidence for a role of Ras in preserving neuronal structure after functional deprivation in vivo.
The shape of an ecological trade‐off varies with environment
Authors: Jessup Christine M. , Bohannan Brendan J. M.
Published: June 2008

Central to most theories that explain the diversity of life is the concept that organisms face trade‐offs. Theoretical work has shown that the precise shape of a trade‐off relationship affects evolutionary predictions. One common trade‐off is that between competitive ability and resistance to predators, parasitoids, pathogens or herbivores. We used a microbial experimental system to elucidate the shape of the relationship between parasitoid resistance and competitive ability. For each of 86 bacteriophage‐resistant isolates of the bacteriumEscherichia coliB, we measured the degree of resistance to bacteriophage T2 (a viral parasitoid) and relative competitive ability in both the resource environment in which strains were isolated and in two alternate environments. We observed that environmental change can alter trade‐off shape, and that different physiological mechanisms can lead to different trade‐off shapes and different sensitivities to environmental change. These results highlight the important interaction between environment and trade‐off shape in affecting ecological and evolutionary dynamics.
Phylogenetic analysis of Porphyromonas species isolated from the oral cavity of Australian marsupials
Authors: Mikkelsen Deirdre , Milinovich Gabriel J. , Burrell Paul C. , Huynh Sharnan C. , Pettett Lyndall M. , Blackall Linda L. , Trott Darren J. , Bird Philip S.
Published: June 2008

Porphyromonas species are frequently isolated from the oral cavity and are associated with periodontal disease in both animals and humans. Black, pigmented Porphyromonas spp. isolated from the gingival margins of selected wild and captive Australian marsupials with varying degrees of periodontal disease (brushtail possums, koalas and macropods) were compared phylogenetically to Porphyromonas strains from non‐marsupials (bear, wolf, coyote, cats and dogs) and Porphyromonas gingivalis strains from humans using 16S rRNA gene sequence analysis. The results of the phylogenetic analysis identified three distinct groups of strains. A monophyletic P. gingivalis group (Group 1) contained only strains isolated from humans and a Porphyromonas gulae group (Group 2) was divided into three distinct subclades, each containing both marsupial and non‐marsupial strains. Group 3, which contained only marsupial strains, including all six strains isolated from captive koalas, was genetically distinct from P. gulae and may constitute a new Porphyromonas species.
Power output and columbic efficiencies from biofilms of Geobacter sulfurreducens comparable to mixed community microbial fuel cells
Authors: Nevin K. P. , Richter H. , Covalla S. F. , Johnson J. P. , Woodard T. L. , Orloff A. L. , Jia H. , Zhang M. , Lovley D. R.
Published: June 2008

It has been previously noted that mixed communities typically produce more power in microbial fuel cells than pure cultures. If true, this has important implications for the design of microbial fuel cells and for studying the process of electron transfer on anode biofilms. To further evaluate this, Geobacter sulfurreducens was grown with acetate as fuel in a continuous flow ‘ministack’ system in which the carbon cloth anode and cathode were positioned in close proximity, and the cation‐selective membrane surface area was maximized in order to overcome some of the electrochemical limitations that were inherent in fuel cells previously employed for the study of pure cultures. Reducing the size of the anode in order to eliminate cathode limitation resulted in maximum current and power densities per m2 of anode surface of 4.56 A m−2 and 1.88 W m−2 respectively. Electron recovery as current from acetate oxidation was c. 100% when oxygen diffusion into the system was minimized. This performance is comparable to the highest levels previously reported for mixed communities in similar microbial fuel cells and slightly higher than the power output of an anaerobic sludge inoculum in the same ministack system. Minimizing the volume of the anode chamber yielded a volumetric power density of 2.15 kW m−3, which is the highest power density per volume yet reported for a microbial fuel cell. Geobacter sulfurreducens formed relatively uniform biofilms 3–18 μm thick on the carbon cloth anodes. When graphite sticks served as the anode, the current density (3.10 A m−2) was somewhat less than with the carbon cloth anodes, but the biofilms were thicker (c. 50 μm) with a more complex pillar and channel structure. These results suggest that the previously observed disparity in power production in pure and mixed culture microbial fuel cell systems can be attributed more to differences in the fuel cell designs than to any inherent superior capability of mixed cultures to produce more power than pure cultures.
Inverse nickel‐responsive regulation of two urease enzymes in the gastric pathogen Helicobacter mustelae
Authors: Stoof Jeroen , Breijer Simone , Pot Raymond G. J. , van der Neut Daan , Kuipers Ernst J. , Kusters Johannes G. , van Vliet Arnoud H. M.
Published: June 2008

The acidic gastric environment of mammals can be chronically colonized by pathogenic Helicobacter species, which use the nickel‐dependent urea‐degrading enzyme urease to confer acid resistance. Nickel availability in the mammal host is low, being mostly restricted to vegetarian dietary sources, and thus Helicobacter species colonizing carnivores may be subjected to episodes of nickel deficiency and associated acid sensitivity. The aim of this study was to investigate how these Helicobacter species have adapted to the nickel‐restricted diet of their carnivorous host. Three carnivore‐colonizing Helicobacter species express a second functional urea‐degrading urease enzyme (UreA2B2), which functions as adaptation to nickel deficiency. UreA2B2 was not detected in seven other Helicobacter species, and is in Helicobacter mustelae only expressed in nickel‐restricted conditions, and its expression was higher in iron‐rich conditions. In contrast to the standard urease UreAB, UreA2B2 does not require activation by urease or hydrogenase accessory proteins, which mediate nickel incorporation into these enzymes. Activity of either UreAB or UreA2B2 urease allowed survival of a severe acid shock in the presence of urea, demonstrating a functional role for UreA2B2 in acid resistance. Pathogens often express colonization factors which are adapted to their host. The UreA2B2 urease could represent an example of pathogen adaptation to the specifics of the diet of their carnivorous host, rather than to the host itself.
Quantitative microbial faecal source tracking with sampling guided by hydrological catchment dynamics
Authors: Reischer G. H. , Haider J. M. , Sommer R. , Stadler H. , Keiblinger K. M. , Hornek R. , Zerobin W. , Mach R. L. , Farnleitner A. H.
Published: June 2008

The impairment of water quality by faecal pollution is a global public health concern. Microbial source tracking methods help to identify faecal sources but the few recent quantitative microbial source tracking applications disregarded catchment hydrology and pollution dynamics. This quantitative microbial source tracking study, conducted in a large karstic spring catchment potentially influenced by humans and ruminant animals, was based on a tiered sampling approach: a 31‐month water quality monitoring (Monitoring) covering seasonal hydrological dynamics and an investigation of flood events (Events) as periods of the strongest pollution. The detection of a ruminant‐specific and a human‐specific faecal Bacteroidetes marker by quantitative real‐time PCR was complemented by standard microbiological and on‐line hydrological parameters. Both quantitative microbial source tracking markers were detected in spring water during Monitoring and Events, with preponderance of the ruminant‐specific marker. Applying multiparametric analysis of all data allowed linking the ruminant‐specific marker to general faecal pollution indicators, especially during Events. Up to 80% of the variation of faecal indicator levels during Events could be explained by ruminant‐specific marker levels proving the dominance of ruminant faecal sources in the catchment. Furthermore, soil was ruled out as a source of quantitative microbial source tracking markers. This study demonstrates the applicability of quantitative microbial source tracking methods and highlights the prerequisite of considering hydrological catchment dynamics in source tracking study design.
Epibiotic bacteria associated with the recently discovered Yeti crab,Kiwa hirsuta
Authors: Goffredi Shana K. , Jones William J. , Erhlich Hermann , Springer Armin , Vrijenhoek Robert C.
Published: June 2008

The Yeti crab,Kiwa hirsutaMacphersonet al., is the single known species in a recently discovered crab familyKiwaidae(Decapoda:Galatheoidea) from deep‐sea hydrothermal vents. Its chelipeds, walking legs and the ventral surface of its cephalothorax are covered with dense setae that, in turn, are covered with clusters of filamentous bacteria, making the crab appear extraordinarily ‘hairy’. Electron microscopy revealed dense bacterial clusters attached to the chitinous outer layer of the setae. Molecular phylogenetic analyses revealed the setae‐associated bacteria to be dominated by ε‐Proteobacteria(∼56% of the recovered ribotypes), γ‐Proteobacteria(∼25%) andBacteroidetes(∼10%). Fluorescencein situmicroscopy confirmed the attachment of filamentous ε‐Proteobacteriaon setae, but no specialized morphological structures appeared to exist for bacterial attachment. Key enzymes involved in the reductive tricarboxylic acid cycle (ATP‐dependent citrate lyase) and sulfite oxidation or dissimilatory sulfate reduction (bidirectional APS reductase) were detected. Consequently, the potential for carbon fixation and cycling of reduced and oxidized sulfur appear to exist in the dense microflora that grows on the crab's setae.
Excess glycaemic excursions after an oral glucose tolerance test compared with a mixed meal challenge and self‐measured home glucose profiles: is the OGTT a valid predictor of postprandial hyperglycaemia and vice versa?
Authors: Meier J. J. , Baller B. , Menge B. A. , Gallwitz B. , Schmidt W. E. , Nauck M. A.
Published: June 2008

Introduction:  Postprandial hyperglycaemia is often assumed in individuals with high glucose excursions during an oral glucose tolerance test (OGTT), but the relationship between glucose levels during the OGTT and after a mixed meal is yet unclear. We addressed whether (i) glucose concentrations after an oral glucose load are similar to those after a test meal or under daily life conditions and (ii) impaired glucose tolerance (IGT) predicts postprandial hyperglycaemia.

Patients and Methods:  A total of 60 subjects with normal (NGT), IGT or diabetic (DM) glucose tolerance were examined with an OGTT, a mixed meal challenge (3433 kJ) and a self‐determined 10‐point home glucose profile.

Results:  There was a significant correlation between the 120‐min OGTT glucose levels and the glycaemic excursions after the test meal and during everyday conditions. However, glucose excursions during the OGTT exceeded those after the test meal and during everyday conditions by ∼20 and ∼30% respectively. Likewise, insulin and C‐peptide levels rose to higher levels after oral glucose compared with mixed meal ingestion. The mean self‐determined diurnal glucose levels were already 10% higher in subjects with IGT compared with NGT subjects (p < 0.0001).

Conclusions:  Glucose levels reached after an oral glucose challenge and during real life are correlated to some extent, but the absolute levels of glycaemia greatly differ between both conditions. Therefore, ‘postchallenge’ glucose levels measured during an OGTT might be used as a predictor of ‘postprandial hyperglycaemia’, but caution should be taken when both terms are used synonymously. Furthermore, subjects with IGT during an OGTT already exhibit increased postprandial glucose levels under real‐life conditions. This suggests that IGT should already be considered an overt disease condition rather than merely a high‐risk situation.
Glimepiride upregulates eNOS activity and inhibits cytokine‐induced NF‐κB activation through a phosphoinoside 3‐kinase–Akt‐dependent pathway
Authors: Jojima T. , Suzuki K. , Hirama N. , Uchida K. , Hattori Y.
Published: June 2008

Aims: Several studies suggest increased mortality postcoronary angioplasty in patients on sulphonylureas. However, a theoretical reduction in cardiac risk has been suggested with the newer sulphonylurea agents, which differ from the first‐generation agents. In the present study, we investigated whether a third generation of sulphonylurea, glimepiride, might stimulate nitric oxide (NO) production and thereby inhibit cytokine‐induced nuclear factor (NF)‐κB activation in endothelial cells compared with the classical sulphonylurea glibenclamide.

Methods and Results: We demonstrated that glimepiride, but not glibenclamide, induces NO production in human umbilical vein endothelial cells (HUVEC). A significant increase in endothelial NO synthase (eNOS) activity, measured in terms of citrulline production, was observed with glimepiride treatment. Akt phosphorylation followed by phosphorylation of eNOS (Ser1177) was observed with glimepiride treatment in HUVEC. Moreover, two phosphoinoside 3‐kinase inhibitors, wortmannin and LY294002, significantly inhibited glimepiride‐induced NO production. We also demonstrated inhibition of tumour necrosis factor‐alpha (TNFα)‐induced NF‐κB activation in HUVEC treated with glimepiride, which was attenuated by pretreatment with Nω‐nitro‐l‐arginine methyl ester. We also demonstrated a marked increase in p65 in nuclear extracts from untreated HUVEC following stimulation with TNFα, which was dose dependently inhibited by glimepiride, but not by glibenclimide in association with NF‐κB levels.

Conclusion: These data suggest that glimepiride might be a preferable sulphonylurea agent in the setting of type 2 diabetes and vascular disease because it may have protective effects on vascular endothelial cells.
Treatment of Zucker diabetic fatty rats with AVE7688 improves vascular and neural dysfunction
Authors: Oltman C. L. , Davidson E. P. , Coppey L. J. , Kleinschmidt T. L. , Yorek M. A.
Published: June 2008

Aim: Vasopeptidase inhibitors are drugs that inhibit angiotensin‐converting enzyme and neutral endopeptidase (NEP). The latter is a protease that degrades vasoactive peptides and is increased in diabetes. We have previously shown that treating streptozotocin‐induced diabetic rats, an animal model of type 1 diabetes, with AVE7688, a vasopeptidase inhibitor, improves neurovascular and neural function. In this study, we determined the effect of treating Zucker diabetic fatty (ZDF) rats, an animal model of type 2 diabetes, with AVE7688 on vascular and neural function.

Methods: ZDF rats at 12 weeks of age were treated for 12 weeks with AVE7688 (500 mg/kg diet). Afterwards, vascular reactivity of epineurial arterioles of the sciatic nerve and nerve conduction velocity and blood flow was determined.

Results: Vascular and neural function was significantly impaired in ZDF rats compared with age‐matched lean (control) rats. Treating ZDF rats with AVE7688 improved vascular relaxation to acetylcholine and calcitonin gene‐related peptide in epineurial arterioles. Motor and sensory nerve conduction velocity, endoneurial blood flow and thermal nociception end‐points were also improved by treatment compared with untreated ZDF rats. Superoxide and expression of NEP were increased in epineurial arterioles from ZDF rats and attenuated by treatment with AVE7688.

Conclusions: AVE7688 is an effective treatment for microvascular and neural disease in ZDF rats. Thus, vasopeptidase inhibitors may be an effective treatment for diabetic microvascular and neural complication in type 2 diabetes.
Current treatment of non‐alcoholic fatty liver disease
Authors: Ahmed Mohamed H. , Byrne Christopher D.
Published: June 2008

Non‐alcoholic fatty liver disease (NAFLD) is the most common cause of liver disease in Western World and frequently associated with insulin resistance and overweight and occurs often with type 2 diabetes. Interestingly, NAFLD is not only regarded as a hepatic component of the metabolic syndrome but also as an independent risk factor and a marker for increase in cardiovascular disease (CVD). Significantly, NAFLD is associated with an increased risk of all‐cause mortality and predicts future CVD events independent of age, sex, LDL‐cholesterol and features of metabolic syndrome. Although there was initial concern about drug toxicity with NAFLD, increasing evidence suggests that commonly used drugs such as metformin and statins do not cause harm and the thiazolidinediones (TZDs) may even confer a therapeutic benefit in NAFLD. Interestingly, medical and surgical treatments of obesity show potential benefit in treating NAFLD. In this review, we have focused on the safety and therapeutic impact of TZDs, statins, metformins and obesity medications in NAFLD. The potential benefit of bariatric surgery and the role of weight loss per se in treating NAFLD are also discussed.
Changes in the stage and surgical management of renal tumours during 1995–2005: an analysis of the Dutch national histopathology registry
Authors: Kümmerlin Intan P.E.D. , Ten Kate Fiebo J.W. , Wijkstra Hessel , De La Rosette Jean J.M.C.H. , Laguna M. Pilar
Published: June 2008

OBJECTIVE

To evaluate changes in the pathological characteristics, stage of primary renal tumours and their surgical management in the Netherlands during the period 1995–2005.

METHODS

Extracts from the records of all patients who had surgery for primary renal tumours in the Netherlands during the period 1995–2005 were reviewed. Data were collected from PALGA, the nationwide network and archive of histocytopathology. The 2002 Tumour‐Node‐Metastasis and the three‐tier Fuhrman grade were used for staging and grading.

RESULTS

In all there were 12 471 operations for primary renal masses during the study period. The incidence of surgically removed renal cancers increased from 6.2 in 1995 to 7.5 cases per 100 000 inhabitants (P = 0.005) in 2005. The mean (sd, median) age of the patients was 63.3 (11.9, 65.0) years, with a male‐to‐female ratio of 3:2. The mean (sd) tumour size of malignant tumours decreased from 7.3 (3.6) to 6.9 (3.7) cm (P = 0.301). The percentage of benign removed tumours remained relatively stable (P = 0.056), with a mean of 5.4% of all resected tumours. There was an increase of grade 1 tumours; the incidence of T1 tumours increased from 36.6% to 44.2%, and advanced tumours decreased from 46.4% to 33.7%, respectively. The percentage of nephron‐sparing surgery increased from 3.5% in 1995 to 10.1% (P = 0.003) in 2005, mainly in the T1a tumours.

CONCLUSIONS

During the last decade there was an increase in the incidence of surgically treated renal tumours in the Netherlands. Tumours with favourable histopathological characteristics, low stage and grade, accounted for most of this increase. The percentage of surgically removed benign tumours remained stable. The use of nephron‐sparing surgery increased during the last decade, especially in T1a tumours.
The feasibility and safety of high‐intensity focused ultrasound as salvage therapy for recurrent prostate cancer following external beam radiotherapy
Authors: Zacharakis Evangelos , Ahmed Hashim U. , Ishaq Ayesha , Scott Rebecca , Illing Rowland , Freeman Alex , Allen Clare , Emberton Mark
Published: June 2008

OBJECTIVES

To investigate the use of minimally invasive high‐intensity focused ultrasound (HIFU) as a salvage therapy in men with localized prostate cancer recurrence following external beam radiotherapy (EBRT).

PATIENTS AND METHODS

A review of 31 cases treated using the Sonablate® 500 HIFU device, between 1 February 2005 and 15 May 2007, was carried out. All men had presumed organ‐confined, histologically confirmed recurrent prostate adenocarcinoma following EBRT.

RESULTS

The mean (range) age was 65 (57–80) years with a mean preoperative PSA level of 7.73 (0.20–20) ng/mL. The patients were followed for a mean (range) of 7.4 (3–24) months. Side‐effects included stricture or intervention for necrotic tissue in 11 of the 31 patients (36%), urinary tract infection or dysuria syndrome in eight (26%), and urinary incontinence in two (7%). Recto‐urethral fistula occurred in two men, although one was due to patient movement due to inadequate anaesthesia, so the ‘true’ rate is 3%. Half of the patients had PSA levels of <0.2 ng/mL at the last follow‐up. Three patients had metastatic disease whilst another two had only local, histologically confirmed, failure. A further four patients had evidence of biochemical failure only. Overall, 71% had no evidence of disease following salvage HIFU.

CONCLUSIONS

Salvage HIFU is a minimally invasive daycase procedure that can achieve low PSA nadirs and good cancer control in the short term, with comparable morbidity to other forms of salvage treatment. The issue of accurate staging at the time of recurrence is still problematic, as a proportion of these men will harbour microscopic metastases undetected by conventional staging investigations.