bluuebunny/crossref_metadata_2025_split huggingface dataset:
Relation of apical dendritic spikes to output decision in CA1 pyramidal cells during synchronous activation: a computational study
Authors: Ibarz José M. , Makarova Ioulia , Herreras Oscar 
Published: March 2006

AbstractRecent studies on the initiation and propagation of dendritic spikes have modified the classical view of postsynaptic integration. Earlier we reported that subthreshold currents and spikes recruited by synaptic currents play a critical role in defining outputs following synchronous activation. Experimental factors strongly condition these currents due to their nonlinear behaviour. Hence, we have performed a detailed parametric study in a CA1 pyramidal cell model to explore how different variables interact and initiate dendritic spiking, and how they influence cell output. The input pattern, the relative excitability of axon and dendrites, the presence/modulation of voltage‐dependent channels, and inhibition were cross analysed. Subthreshold currents and spikes on synaptically excited branches fired spikes in other branches to jointly produce different modalities of apical shaft spiking with a variable impact on cell output. Synchronous activation initiated a varying number and temporal scatter of firing branches that produced in the apical shaft‐soma axis nonpropagating spikes, pseudosaltatory or continuous forward conduction, or backpropagation. As few as 6–10 local spikes within a time window of 2 ms ensure cell output. However, the activation mode varied extremely when two or more variables were cross‐analysed, becoming rather unpredictable when all the variables were considered. Spatially clustered inputs and upper modulation of dendritic Na+ or Ca2+ electrogenesis favour apical decision. In contrast, inhibition biased the output decision toward the axon and switched between dendritic firing modes. We propose that dendrites can discriminate input patterns and decide immediate cell output depending on the particular state of a variety of endogenous parameters.
Secondary somatosensory cortex is important for the sensory‐discriminative dimension of pain: a functional MRI study
Authors: Maihöfner Christian , Herzner Barbara , Otto Handwerker Hermann 
Published: March 2006

AbstractA complex cortical network is believed to encode the multidimensionality of the human pain experience. In the present study, we used functional magnetic resonance imaging (fMRI) to examine whether the brain's processing of noxious stimuli differs with different psychophysical properties. Painful mechanical impact and heat stimulations of equal stimulus intensity were applied to the forearm of 14 subjects in a randomized order. Concomitantly, subjects had to evaluate the corresponding sensory‐discriminative and affective‐motivational pain dimensions. fMRI revealed an increased activation of bilateral secondary somatosensory cortices (S2) during mechanical impact pain compared with heat pain. Activations in S2 were significantly correlated with scores for the sensory‐discriminative component during mechanical impact pain. By contrast, corresponding scores for the affective‐motivational pain dimension did not differ between both conditions. In summary, we conclude that S2 plays an important role in the sensory‐discriminative dimension of pain.
Lesions of tuberomammillary nuclei induce differential polydipsic and hyperphagic effects
Authors: Mahía J. , Puerto A. 
Published: March 2006

AbstractThis study aimed to examine the function of the tuberomammillary complex in water and food intake of Wistar rats. The results show that lesions restricted to tuberomammillary subnuclei: caudal ventral tuberomammillary nucleus (E1), rostral ventral tuberomammillary nucleus (E2), medial ventral tuberomammillary nucleus (E3) or medial dorsal tuberomammillary nucleus (E4), induce a strong and persistent polydipsia with specific characteristics for each nucleus. Interestingly, the distribution of tuberomammillary hyperdipsia throughout the day was similar to that in non‐lesioned animals, in contrast to the lack of rhythmicity observed in rats with anodic lesion to median eminence. This polydipsia appears to be independent of food intake, as food deprivation for 22 h did not significantly reduce the water intake. Finally, lesions in ventral tuberomammillary nuclei E1 and E2 induce hyperphagia, confirming a possible role for the tuberomammillary complex in food intake. This increase in food intake is not observed after lesions in medial subnuclei E3 and E4. These results are interpreted in terms of the hypothalamic systems involved in the consumption of both food and water.
The preoptic hypothalamus and basal forebrain play opposing roles in the descending modulation of sleep and wakefulness in infant rats
Authors: Mohns Ethan J. , Karlsson Karl Æ. , Blumberg Mark S. 
Published: March 2006

AbstractRecent findings in infant rats suggest that the preoptic area (POA) and/or basal forebrain (BF) contribute to developmental changes in sleep and wake organization between postnatal day 2 (P2) and P9. To examine the contributions of these forebrain areas to sleep and wakefulness, separate lesions of the POA or BF, or combined lesions (POA + BF), were performed at P9, and precollicular transections were performed at P2. In addition, modafinil, a drug of unknown mechanism of action the effects of which on sleep and wakefulness have been hypothesized to result from inhibition of POA activity, was administered at P2 and P9. Finally, extracellular neuronal activity was recorded from the POA and BF. POA lesions decreased sleep bout durations and increased wake bout durations. BF lesions inhibited sleep bout durations to a lesser extent, while leaving wake bout durations unaffected. POA + BF lesions produced a combination of these effects, resulting in short bouts of sleep and wakefulness similar to those of transected P8 rats. Even at P2, transections decreased sleep bout durations. The finding, however, that the sleep‐inhibiting and wake‐promoting effects of modafinil were more potent at P9 than at P2 suggests increasing sleep–wake modulation by the POA between these two ages. Finally, neuronal recordings confirmed the presence of state‐dependent neurons within the infant POA and BF. We propose that the POA, in addition to promoting sleep, inhibits wakefulness via direct and indirect inhibitory connections with wake‐promoting neurons in the BF, and that this inhibitory influence increases across early development.
Nucleus accumbens neurons encode Pavlovian approach behaviors: evidence from an autoshaping paradigm
Authors: Day Jeremy J. , Wheeler Robert A. , Roitman Mitchell F. , Carelli Regina M. 
Published: March 2006

AbstractEnvironmental stimuli predictive of appetitive events can elicit Pavlovian approach responses that enhance an organism's ability to track and secure natural rewards, but may also contribute to the compulsive nature of drug addiction. Here, we examined the activity of individual nucleus accumbens (NAc) neurons during an autoshaping paradigm. One conditioned stimulus (CS+, a retractable lever presented for 10 s) was immediately followed by the delivery of a 45‐mg sucrose pellet to a food receptacle, while another stimulus (CS–, a separate retractable lever presented for 10 s) was never followed by sucrose. Approach responses directed at the CS+ and CS– were recorded as lever presses and had no experimental consequence. Rats (n = 9) selectively approached the CS+ on more than 80% of trials and were surgically prepared for electrophysiological recording. Of 76 NAc neurons, 57 cells (75%) exhibited increases and/or decreases in firing rate (i.e. termed ‘phasically active’) during the CS+ presentation and corresponding approach response. Forty‐seven percent of phasically active cells (27 out of 57) were characterized by time‐locked but transient increases in cell firing, while 53% (30 out of 57) showed a significant reduction in firing for the duration of the CS+. In contrast, the same excitatory subpopulation exhibited smaller increases in activity relative to CS– onset, while the inhibitory subpopulation showed no change in firing during the CS– period. The magnitude and prevalence of cue‐related neural responses reported here indicates that the NAc encodes biologically significant, repetitive approach responses that may model the compulsive nature of drug addiction in humans.
State‐dependent regulation of sensory‐motor transmission: role of muscarinic receptors in sensory‐motor integration in the crayfish walking system
Authors: Le Bon‐Jego Morgane , Masante‐Roca Ingwild , Cattaert Daniel 
Published: March 2006

AbstractThe aim of this study was to investigate a potential mechanism for state‐dependent regulation of sensory‐motor transmission from sensory afferents of a proprioceptor to motoneurons (MNs) in the walking system of the crayfish. This study was performed using an in vitro preparation of thoracic ganglia including motor nerves and the proprioceptor that codes movements of the second joint (coxo‐basal chordotonal organ − CBCO) of the leg. Application of movements to the CBCO elicits resistance reflex responses intracellularly recorded from Dep MNs. This reflex response is enhanced when Dep MNs are depolarized either spontaneously or by current injection. This enhancement is abolished in the presence of scopolamine (an antagonist of muscarinic acetylcholine receptors). Using pharmacology, we demonstrate that the monosynaptic connection from CBCO sensory neurons to the Dep MNs includes both nicotinic and muscarinic components. In addition, the shape of monosynaptic excitatory postsynaptic potentials (EPSPs) depends on the membrane potential: at a subthreshold depolarizing membrane potential, the time constant of the falling phase of the EPSPs is significantly increased compared with its value at resting potential. This change is suppressed in the presence of scopolamine, indicating that the muscarinic component may contribute to the activation of the Dep MN pool by sensory activity. This state‐dependent amplification of the sensory input may be important for increasing the strength of sensory feedback at times when central activation of the Dep MNs is very strong (e.g. during walking).
Enhanced novelty‐induced activity, reduced anxiety, delayed resynchronization to daylight reversal and weaker muscle strength in tenascin‐C‐deficient mice
Authors: Morellini Fabio , Schachner Melitta 
Published: March 2006

AbstractTenascin‐C (TNC) is an extracellular matrix protein with multiple and important functions during development and in the adult. We here present a study on the behaviour of TNC‐deficient (knockout, KO) mice. Longitudinal experiments including tests for circadian activity, exploration, state and trait anxiety, motor coordination and cognition were performed. KO mice showed increased reactivity to explore a novel environment and decreased anxiety. Spontaneous circadian activity was unaffected, but KO mice showed delayed resynchronization to daylight reversal. TNC deficiency caused weaker muscle strength, whereas gait, coordination and motor learning were unaltered. Short‐ and long‐term memory in the fear conditioning task and working memory in the spontaneous alternation test were normal in KO mice. KO mice showed impaired memory recall in the step‐down, but not in the step‐through, passive avoidance task. Ethological observation of mice behaviour and principal component analyses indicated that the higher novelty‐ and stress‐induced active responses of KO mice account for their poorer performance in passive avoidance tasks, whereas cognitive abilities are unaltered. The present study extends and corrects previous results, and is an example of how an ethological approach allows a precise description and interpretation of the behavioural alterations of mutant mice.
Distinct kinds of novelty processing differentially increase extracellular dopamine in different brain regions
Authors: De Leonibus Elvira , Verheij Michel M. M. , Mele Andrea , Cools Alexander 
Published: March 2006

AbstractBehaviourally relevant novel stimuli are known to activate the mesocorticolimbic dopaminergic (DAergic) system. In this study we tested the reactivity of this system in response to distinct kinds of novelty processing. Using the in vivo microdialysis technique, we measured extracellular amounts of dopamine (DA) in different DAergic terminal regions during a social learning task in rats. In the first session (40 min) rats were exposed to two never previously encountered juveniles (i.e. unconditional novelty). Afterwards, the animals were divided into three groups: Control group was not exposed to any other stimulus; Discrimination group was exposed to one familiar and one new juvenile (i.e. novel stimulus discrimination); and Recognition group was re‐exposed to the two familiar juveniles (i.e. familiarity recognition). In both the medial prefrontal cortex and the nucleus accumbens shell DA increased in response to the first presentation of the juveniles, showing that both structures are involved in processing unconditional social novelty. During the novel stimulus discrimination, we found no change in the prefrontal cortex, although DA increased in the accumbal shell in comparison with the group exposed to two familiar juveniles, showing that the shell is also involved in processing novel social stimulus discrimination. None of the stimuli presented affected DA in the accumbal core. This study provided the original evidence that DA in the various terminal regions is differentially coupled to distinct aspects of novelty processing.
Transcranial fluorescence imaging of auditory cortical plasticity regulated by acoustic environments in mice
Authors: Takahashi Kuniyuki , Hishida Ryuichi , Kubota Yamato , Kudoh Masaharu , Takahashi Sugata , Shibuki Katsuei 
Published: March 2006

AbstractFunctional brain imaging using endogenous fluorescence of mitochondrial flavoprotein is useful for investigating mouse cortical activities via the intact skull, which is thin and sufficiently transparent in mice. We applied this method to investigate auditory cortical plasticity regulated by acoustic environments. Normal mice of the C57BL/6 strain, reared in various acoustic environments for at least 4 weeks after birth, were anaesthetized with urethane (1.7 g/kg, i.p.). Auditory cortical images of endogenous green fluorescence in blue light were recorded by a cooled CCD camera via the intact skull. Cortical responses elicited by tonal stimuli (5, 10 and 20 kHz) exhibited mirror‐symmetrical tonotopic maps in the primary auditory cortex (AI) and anterior auditory field (AAF). Depression of auditory cortical responses regarding response duration was observed in sound‐deprived mice compared with naïve mice reared in a normal acoustic environment. When mice were exposed to an environmental tonal stimulus at 10 kHz for more than 4 weeks after birth, the cortical responses were potentiated in a frequency‐specific manner in respect to peak amplitude of the responses in AI, but not for the size of the responsive areas. Changes in AAF were less clear than those in AI. To determine the modified synapses by acoustic environments, neural responses in cortical slices were investigated with endogenous fluorescence imaging. The vertical thickness of responsive areas after supragranular electrical stimulation was significantly reduced in the slices obtained from sound‐deprived mice. These results suggest that acoustic environments regulate the development of vertical intracortical circuits in the mouse auditory cortex.
Effects of species diversity on disease risk
Authors: Keesing F. , Holt R. D. , Ostfeld R. S. 
Published: March 2006

AbstractThe transmission of infectious diseases is an inherently ecological process involving interactions among at least two, and often many, species. Not surprisingly, then, the species diversity of ecological communities can potentially affect the prevalence of infectious diseases. Although a number of studies have now identified effects of diversity on disease prevalence, the mechanisms underlying these effects remain unclear in many cases. Starting with simple epidemiological models, we describe a suite of mechanisms through which diversity could increase or decrease disease risk, and illustrate the potential applicability of these mechanisms for both vector‐borne and non‐vector‐borne diseases, and for both specialist and generalist pathogens. We review examples of how these mechanisms may operate in specific disease systems. Because the effects of diversity on multi‐host disease systems have been the subject of much recent research and controversy, we describe several recent efforts to delineate under what general conditions host diversity should increase or decrease disease prevalence, and illustrate these with examples. Both models and literature reviews suggest that high host diversity is more likely to decrease than increase disease risk. Reduced disease risk with increasing host diversity is especially likely when pathogen transmission is frequency‐dependent, and when pathogen transmission is greater within species than between species, particularly when the most competent hosts are also relatively abundant and widespread. We conclude by identifying focal areas for future research, including (1) describing patterns of change in disease risk with changing diversity; (2) identifying the mechanisms responsible for observed changes in risk; (3) clarifying additional mechanisms in a wider range of epidemiological models; and (4) experimentally manipulating disease systems to assess the impact of proposed mechanisms.
A double mutant of Pseudomonas putida JLR11 deficient in the synthesis of the nitroreductase PnrA and assimilatory nitrite reductase NasB is impaired for growth on 2,4,6‐trinitrotoluene (TNT)
Authors: Caballero Antonio , Ramos Juan L. 
Published: March 2006

Summary Pseudomonas putida JLR11 can grow on 2,4,6‐trinitrotoluene (TNT) as the sole nitrogen source. We created nasB (nitrite reductase), pnrA (nitroaromatic reductase) and pnrA nasB mutants and tested their growth with TNT as the sole N source. The nasB and pnrA mutants grew at a reduced rate on TNT, whereas the double nasB pnrA mutant did not. This suggests that P. putida JLR11 carries out multiple enzymatic attacks on TNT‐releasing nitrite and/or ammonium. The PnrA nitroreductase plays a key role in the reduction of TNT to 2,6‐dinitro‐4‐hydroxylaminotoluene and the subsequent release of ammonium for growth.
Endoglucanase‐producing fungi isolated from Cape Evans historic expedition hut on Ross Island, Antarctica
Authors: Duncan Shona M. , Farrell Roberta L. , Thwaites Joanne M. , Held Benjamin W. , Arenz Brett E. , Jurgens Joel A. , Blanchette Robert A. 
Published: March 2006

SummaryEarly explorers of Antarctica’s Heroic Era erected wooden buildings and brought large quantities of supplies to survive in Antarctica. The introduction of wood and other organic materials provided nutrient sources for fungi that were indigenous to Antarctica or were brought in with the materials and adapted to the harsh conditions. Seventy‐two isolates of filamentous fungi were cultured on selective media from interior structural wood of the Cape Evans historic hut and 27 of these screened positive for the ability to degrade carboxymethyl cellulose (CMC). Four non‐CMC‐degrading isolates were added to a group of 14 CMC‐degrading isolates for further study, and endo‐1, 4‐β‐glucanase activity was demonstrated in the extracellular supernatant from all of these 18 isolates when grown at 4°C, and also when they were grown at 15°C. Isolates of Penicillium roquefortii and Cadophora malorum showed preference for growth at 15°C rather than 25°C or 4°C indicating psychrotrophic characteristics. These results demonstrate that cellulolytic filamentous fungi found in Antarctica are capable of growth at cold temperatures and possess the ability to produce extracellular endo‐1, 4‐β‐glucanase when cultured at cold and temperate temperatures.
Technological and geographical knowledge spillover in the German empire 1877–1918
Authors: STREB JOCHEN , BATEN JÖRG , YIN SHUXI 
Published: March 2006

SUMMARYWe use a newly developed data set of 39,343 high‐value patents granted between 1877 and 1918 to demonstrate that technological progress during German industrialization occurred in at least four different technological waves. We distinguish the railway wave (1877–86), the dye wave (1887–96), the chemical wave (1897–1902), and the wave of electrical engineering (1903–18). Evidence is presented that inter‐industry knowledge spillovers between technologically, economically, and geographically related industries were a major source for innovative activities during German industrialization. We also show that technological change affected the geographical distribution of innovative regions. Using an index of technologically revealed comparative advantage we find that regions that increased their innovativeness during the waves of technological progress revealed special strength in technological clusters like electrical engineering, mechanical engineering, or chemicals.
Error estimation of the fractal dimension measurements of cranial sutures
Authors: Górski Andrzej Z. , Skrzat Janusz 
Published: March 2006

AbstractThe fractal exponents used to quantify the complexity of cranial sutures were computed for 17 coronal and 17 sagittal sutures of adults from different populations, using the box‐counting algorithm. This paper discusses the main sources of error for the fractal exponents, and gives the error estimates. We then compare our results with those obtained by other authors. We suggest that the usual error estimates implied by the standard deviation for the regression line are too low. We emphasize the crucial role played by the choice of regression line in the log–log plot. For the coronal and sagittal sutures we found mean fractal dimensions of 1.48 and 1.56, respectively. Our values are close to the value for Brownian random walk.
The immune tissues of the endangered red‐tailed phascogale (Phascogale calura)
Authors: Old J. M. , Carman R. L. , Fry G. , Deane E. M. 
Published: March 2006

AbstractThe lymphoid tissues of the red‐tailed phascogale (Phascogale calura) were examined using histological and immunohistochemical techniques. The distribution of immune cells in the tissue beds was documented using antibodies to surface markers CD3 and an MHC Class II antigen (equivalent to HLA DRII). Spleen, gut‐associated lymphoid tissues (GALT), lung, bronchus‐associated lymphoid tissue (BALT) and liver were examined. The spleen had defined areas of red and white pulp, with follicles containing tingible‐bodied macrophages. Anti‐CD3 and anti‐HLA DRII antibodies revealed the presence of T cells in areas of white pulp and around the peri‐arterial lymphatic sheaths. GALT and BALT were detected and appeared as scattered areas of lymphocytes in the tissues beds. This is the first study to report on the lymphoid tissues of this endangered species of marsupial and the first report of the capacity of anti‐human antibodies to a surface MHC molecule to react with Dasyurid cells.