bluuebunny/crossref_metadata_2025_split huggingface dataset:
Diurnal variation of ocular hysteresis in normal subjects: relevance in clinical context
Authors: Laiquzzaman Mohammad , Bhojwani Rajan , Cunliffe Ian , Shah Sunil 
Published: March 2006

AbstractBackground:  This study was conducted to assess the diurnal variation in ocular hysteresis, as measured by the Ocular Response Analyser to establish a relationship between diurnal hysteresis variation and diurnal intraocular pressure (IOP) variation.Methods:  Forty‐two normal eyes of 21 colleagues and staff in a teaching hospital in Birmingham, UK, were recruited. The IOP and hysteresis were measured by the Ocular Response Analyser. The central corneal thickness (CCT) was measured using a hand‐held ultrasonic pachymeter in the mid‐pupillary axis.Results:  The mean ocular hysteresis at 8 am was 12.7 ± 2.3 mmHg, at 11 am was 12.2 ± 2.0 mmHg, at 2 pm was 12.7 ± 2.1 mmHg and at 5 pm was 12.7 ± 1.7 mmHg; the difference between the values at any time of measurement was not statistically significant (P > 0.9, repeated measures). IOP as measured by non‐contact tonometry was 18.4 ± 2.8 mmHg, 17.9 ± 3.3 mmHg, 16.9 ± 3.1 mmHg and 16.8 ± 3.2 mmHg, respectively, for the same time period; the difference between the values in the morning and afternoon was statistically significant (P < 0.0001, repeated measures). The CCT was 548.8 ± 29.5 µm, 547.0 ± 31.4 µm, 548.2 ± 29.6 µm and 548.6 ± 29.4 µm, respectively; the difference between the values was not statistically significant at any time points. Multiple regression analysis showed the relationship between IOP and hysteresis was not statistically significant (P = 0.9).Conclusion:  The ocular hysteresis reading was almost constant throughout the day, whereas the IOP readings showed highest values in the morning with a reducing trend being lowest in the afternoon. The CCT values were almost stable throughout the day. IOP appears to vary independently of a variation in hysteresis or CCT.
GABAA receptor antagonists prevent abnormalities in leptin, insulin and amylin actions on paraventricular hypothalamic neurons of overweight rats
Authors: Davidowa Helga , Ziska Thomas , Plagemann Andreas 
Published: March 2006

AbstractThe hypothalamic regulatory system of body weight which develops in rats during critical periods of early postnatal life seems to express plastic changes depending on nutrition at that time. Adult rats previously exposed to early postnatal overnutrition by raising them in small litters become persistently predisposed to overweight, hyperphagia and hyperleptinaemia. The hypothesis was raised that feeding‐related peptides could be involved through altered effects on neuronal activity of the regulatory systems of such rats. This was studied on brain slices of small‐litter rats and normal‐weight controls between days 60 and 120 of life. Neurons of the medial parvocellular part of the paraventricular nucleus were significantly activated by the adiposity signals leptin, insulin and amylin in controls. This is a kind of negative feedback, because activation of these neurons is known to be followed in vivo by increased energy expenditure. GABAergic mechanisms seem to affect these neuronal responses because the activating effects of insulin and amylin were reduced in the presence of a GABAA receptor antagonist. In overweight small‐litter rats, however, the neuronal responses to the adiposity signals were significantly changed; activating effects were reduced and inhibitory effects increased. By means of blockade of GABAA receptors, significant alterations in the neuronal responses to leptin, insulin and amylin in small‐litter rats were prevented. Responses to the peptides were reversed and now resembled those of controls. In conclusion, changes in neuronal wiring with GABAergic interneurons seem to contribute to a persistently reduced negative feedback of adiposity signals in early postnatally overfed rats.
Transmitter modulation of spike‐evoked calcium transients in arousal related neurons: muscarinic inhibition of SNX‐482‐sensitive calcium influx
Authors: Kohlmeier Kristi A. , Leonard Christopher S. 
Published: March 2006

AbstractNitric oxide synthase (NOS)‐containing cholinergic neurons in the laterodorsal tegmentum (LDT) influence behavioral and motivational states through their projections to the thalamus, ventral tegmental area and a brainstem ‘rapid eye movement (REM)‐induction’ site. Action potential‐evoked intracellular calcium transients dampen excitability and stimulate NO production in these neurons. In this study, we investigated the action of several arousal‐related neurotransmitters and the role of specific calcium channels in these LDT Ca2+‐transients by simultaneous whole‐cell recording and calcium imaging in mouse (P14–P30) brain slices. Carbachol, noradrenaline and adenosine inhibited spike‐evoked Ca2+‐transients, while histamine, t‐ACPD, a metabotropic glutamate receptor agonist, and orexin‐A did not. Carbachol inhibition was blocked by atropine, was insensitive to blockade of G‐protein‐coupled inward rectifier (GIRK) channels and was not inhibited by nifedipine, ω‐conotoxin GVIA or ω‐agatoxin IVA, which block L‐, N‐ and P/Q‐type calcium channels, respectively. In contrast, SNX‐482 (100 nm), a selective antagonist of R‐type calcium channels containing the alpha1E (Cav2.3) subunit, attenuated carbachol inhibition of the somatic spike‐evoked calcium transient. To our knowledge, this is the first demonstration of muscarinic inhibition of native SNX‐482‐sensitive R‐channels. Our findings indicate that muscarinic modulation of these channels plays an important role in the feedback control of cholinergic LDT neurons and that inhibition of spike‐evoked Ca2+‐transients is a common action of neurotransmitters that also activate GIRK channels in these neurons. Because spike‐evoked calcium influx dampens excitability, our findings suggest that these ‘inhibitory’ transmitters could boost firing rate and enhance responsiveness to excitatory inputs during states of high firing, such as waking and REM sleep.
Histone modifications in kainate‐induced status epilepticus
Authors: Sng Judy C. G. , Taniura Hideo , Yoneda Yukio 
Published: March 2006

AbstractTo understand the molecular actions of status epilepticus at the chromatin level, we studied the effects of kainate‐induced status epilepticus on two different histone modifications at amino terminal tails: histone H3 phosphorylation at serine 10 and histone H4 acetylation. In addition to induction of c‐fosand c‐junimmediate early genes (IEGs) expression in mouse hippocampus, we also found the upregulation of acetylation and phosphorylation of histones, coupled with status epilepticus after kainate administration. c‐fosand c‐junmRNA were sequentially induced in response to kainate, in different hippocampal subpopulations, starting from the dentate gyrus (DG) and spreading to the cornus ammonis regions. Immunohistochemical analysis showed that the spatio‐temporal distribution of histone H4 hyperacetylation after kainate treatment was well correlated with the expression of c‐fosand c‐jungenes. Additionally, there was a transient appearance of phosphorylated histone H3 specifically in the DG region. CREB‐binding protein or CBP, a well‐known transcriptional co‐activator with histone acetyltransferase (HAT) activity, was also induced by kainate and its expression pattern well correlated with histone H4 hyperacetylation in the hippocampus. Chromatin immunoprecipitation analysis showed that both histone modifications were associated with c‐fosgene promoter after kainate stimulation, but only histone acetylation with c‐jungene. Pretreatment with curcumin, which has a HAT inhibitory activity specific for CBP/p300, attenuated histone modifications, IEGs expression and also the severity of status epilepticus after kainate treatment. Our findings suggest the involvement of histone modifications induced by kainate not only in IEGs expression but also in the development of epilepsy.
Effect of cortical spreading depression on synaptic transmission of rat hippocampal tissues
Authors: Wernsmann Brigitta , Pape Hans‐Christian , Speckmann Erwin‐Josef , Gorji Ali 
Published: March 2006

AbstractCortical spreading depression (CSD) is believed to be a putative neuronal mechanism underlying migraine aura and subsequent pain. In vitro and ex vivo/in vitro brain slice techniques were used to investigate CSD effects on the field excitatory postsynaptic potentials (fEPSP) and tetanus‐induced long‐term potentiation (LTP) in combined rat hippocampus–cortex slices. Induction of CSD in combined hippocampus–cortex slices in which DC negative deflections did not propagate from neocortex to hippocampus significantly augmented fEPSP amplitude and LTP in the hippocampus. Propagation of CSD to the hippocampus resulted in a transient suppression followed by reinstatement of fEPSP with amplitude of pre‐CSD levels. LTP was inhibited when DC potential shifts were recorded in the hippocampus. Furthermore, CSD was induced in anaesthetized rats and, thereafter, hippocampal tissues were examined in vitro. LTP was significantly enhanced in hippocampal slices obtained from ipsilateral site to the hemisphere in which CSD was evoked. The results indicate the disturbances of hippocampal synaptic transmission triggered by propagation of CSD. This perturbation of hippocampal synaptic transmission induced by CSD may relate to some symptoms occurring during migraine attacks, such as amnesia and hyperactivity.
HIV‐1 gp120 enhances giant depolarizing potentials via chemokine receptor CXCR4 in neonatal rat hippocampus
Authors: Kasyanov Alexander , Tamamura Hirokazu , Fujii Nobutaka , Xiong Huangui 
Published: March 2006

AbstractIn the immature hippocampus, the giant depolarizing potentials (GDPs) are recurrent network‐driven synaptic events generated by γ–aminobutyric acid (GABA), which in neonatal life is depolarizing and excitatory. The GDPs enable a high degree of synchrony in immature neurons and participate in activity‐dependent growth and synapse formation. To understand how human immunodeficiency virus type one (HIV‐1) infection in the immature brain impairs brain growth and development, we studied the effects of HIV‐1 envelope glycoprotein, gp120, a viral toxin shed in abundance by infected cells, on spontaneous occurring GDPs recorded in the CA3 pyramidal cells in neonatal (P2–P6) Sprague–Dawley rat hippocampal slices using whole‐cell patch technique. Bath application of gp120 produced a sustained enhancement of GDP frequency in a concentration‐dependent manner without affecting passive membrane properties, suggesting that the site of action is most likely on neural network, other than on the recorded neurons. The gp120‐induced enhancement of GDPs was blocked by T140, a highly specific antagonist for the chemokine receptor, CXCR4, indicating the involvement of CXCR4 in the gp120‐induced increase of GDPs. Bath application of stromal cell‐derived factor‐1α (SDF‐1α), the only CXCR4 ligand, mimicked the effects of gp120 on GDPs, supporting the engagement of CXCR4 receptors in the gp120‐induced increase of GDP occurrence. Further studies revealed the involvement of protein kinase A/C in the gp120‐induced enhancement of GDPs. These results demonstrate that gp120 enhances GDPs in the neonatal rat hippocampus. This enhancement may cause an excessive increase in intracellular calcium and resultant neuronal injury, leading to retardation of the brain and behavioural development as seen in paediatric AIDS patients.
Localization of nyctalopin in the mammalian retina
Authors: Morgans Catherine W. , Ren Gaoying , Akileswaran Lakshmi 
Published: March 2006

AbstractComplete X‐linked congenital stationary night blindness (CSNB1) is a hereditary visual disease characterized by abnormalities in both the dark‐ and light‐adapted electroretinogram, consistent with a defect in synaptic transmission between photoreceptors and ON‐bipolar cells. The gene responsible for CSNB1, NYX, encodes a novel, leucine‐rich repeat protein, nyctalopin. Consistent with its predicted glycosylphosphatidylinositol linkage, we show that recombinant nyctalopin is targeted to the extracellular cell surface in transfected HEK293 cells. Within the retina, strong nyctalopin immunoreactivity is present in the outer plexiform layer, the site of the photoreceptor to bipolar cell synapses. Double labelling of nyctalopin and known synaptic proteins in the outer plexiform layer indicate that nyctalopin is associated with the ribbon synapses of both rod and cone terminals. In the inner plexiform layer, nyctalopin immunoreactivity is associated with rod bipolar cell terminals. Our findings support a role for nyctalopin in synaptic transmission and/or synapse formation at ribbon synapses in the retina.
Cortical reorganization after brain damage: the oculomotor model
Authors: Nyffeler Thomas , Müri René , Pflugshaupt Tobias , von Wartburg Roman , Hess Christian W. 
Published: March 2006

AbstractRecovery from eye movement deficits after cortical lesions is amazingly rapid and almost complete, which is in sharp contrast to most other neurological deficits of cerebral lesions. The underlying mechanisms of this successful recovery remain uncertain. We had the rare opportunity to examine two patients with recovery from saccade deficits after a lesion restricted to the frontal eye field (FEF) by means of transcranial magnetic stimulation (TMS). The results provide direct evidence that recovery depended on the integrity of the oculomotor regions of the nonlesioned contralesional hemisphere, and that the compensatory network is task‐specific.
Serum‐ and glucocorticoid‐inducible kinase (SGK) is a target of the MAPK/ERK signaling pathway that mediates memory formation in rats
Authors: Lee Ching‐Tien , Tyan Shiaw‐Wei , Ma Yun L. , Tsai Ming‐Chi , Yang Ying C. , Lee Eminy H. Y. 
Published: March 2006

AbstractWe have previously demonstrated that serum‐ and glucocorticoid‐inducible kinase (SGK) plays a causal role in facilitating memory formation of spatial learning in rats, but the SGK signaling pathway involved in spatial memory formation is not known. The mitogen‐activated protein kinase/extracellular signal‐regulated kinase (MAPK/ERK) also plays an important role in memory formation. We therefore examined whether SGK is a downstream target of the MAPK/ERK signaling cascade and whether ERK signaling to SGK mediates spatial memory formation in rats. Results from an in vitro kinase assay revealed that ERK directly phosphorylates SGK at Ser78, but not at Thr256 and Ser422, whereas inhibition of ERK by PD98059 significantly decreased SGK phosphorylation at Ser78, Thr256 and Ser422 following spatial training. Prior administration of PD98059 also antagonized the enhancing effect of 12‐O‐tetradecanoylphorbol‐13‐acetate (TPA), a protein kinase C activator that also causes ERK activation, on SGK phosphorylation and cAMP response element binding protein (CREB) phosphorylation. Moreover, TPA‐induced SGK phosphorylation and CREB phosphorylation was abolished by prior SGKS78A mutant DNA transfection. By contrast, SGKS78A mutant DNA transfection to hippocampal area CA1 did not affect spatial memory formation, whereas SGKT256A mutant DNA transfection to area CA1 significantly impaired spatial memory formation. ERK was known to regulate sgk mRNA expression, but in the present study we have demonstrated that SGK is also a downstream target of the ERK signaling cascade; ERK directly phosphorylates SGK at Ser78 and indirectly activates SGK at Thr256 and Ser422 through unknown intermediate molecules. Furthermore, ERK activation of SGK is involved in spatial memory formation in rats.
Ion currents and spiking properties of identified subtypes of locust octopaminergic dorsal unpaired median neurons
Authors: Heidel E. , Pflüger H.‐J. 
Published: March 2006

AbstractEfferent dorsal unpaired median (DUM) neurons are key elements of an insect neuromodulatory system. In locusts, subpopulations of DUM neurons mediate octopaminergic modulation at specific targets depending on their activity during different behaviours. This study investigates whether in addition to synaptic inputs, activity in DUM neurons depends on intrinsic membrane properties. Intracellular in situ recordings and whole‐cell patch‐clamp recordings from freshly isolated somata characterize somatic voltage signals and the underlying ion currents of individual subtypes of DUM neurons identified beforehand by a vital retrograde tracing technique. Na+, Ca2+, K+ currents and a hyperpolarization‐activated (Ih) current are described in detail for their (in‐)activation properties and subtype‐specific current densities. In addition, a Ca2+‐dependent K+ current is demonstrated by its sensitivity to cadmium and charybdotoxin. This complex current composition determines somatic excitability similar in all subtypes of DUM neurons. Both Na+ and Ca2+ currents generate overshooting somatic action potentials. Repolarizing K+ currents, in particular transient, subthreshold‐activating A‐currents, regulate the firing frequency and cause delayed excitation by shunting depolarizing input. An opposing hyperpolarization‐activated (Ih) current contributes to the resting membrane potential and induces rebound activity after prolonged inhibition phases. A quantitative analysis reveals subtype‐specific differences in current densities with more inhibitory IK but less depolarizing INa and Ih − at least in DUM3 neurons promoting a reliable suppression of their activity as observed during behaviour. In contrast, DUM neurons that are easily activated during behaviour (DUM3,4,5 and DUMETi) express less IK and a pronounced depolarizing Ih promoting excitability.
The infralimbic cortical area commands the behavioral and vegetative arousal during appetitive behavior in the rat
Authors: Valdés José Luis , Maldonado Pedro , Recabarren Mónica , Fuentes Rómulo , Torrealba Fernando 
Published: March 2006

AbstractThe infralimbic cortical area is a good candidate to send processed motivational signals to initiate the arousing and autonomic responses that characterize appetitive behaviors. To test this hypothesis we enticed hungry rats with food while assessing locomotion (as an index of arousal level) and temperature responses, and evaluated Fos immunoreactivity (IR) in the infralimbic area and in subcortical nuclei involved in thermoregulation or arousal. We also recorded from single infralimbic neurons in freely moving rats while enticing them with food. We found that 83% of infralimbic neurons were excited or inhibited by feeding and, in particular, that 33% of infralimbic neurons increased their discharge rate during food enticing. Intact rats showed increased Fos IR in the infralimbic area, as well as in many other cortical areas. The excitotoxic lesion of the infralimbic cortex abolished the arousing and hyperthermic responses observed in intact rats, as well as the expression of Fos IR in the ascending arousal system and subcortical thermoregulatory regions. We conclude that the infralimbic area plays a central role in implementing behavioral arousing and thermal responses during an appetitive behavior.
Patterns in potassium dynamics in forest ecosystems
Authors: Tripler Christopher E. , Kaushal Sujay S. , Likens Gene E. , Todd Walter M. 
Published: March 2006

AbstractThe biotic cycling of potassium (K) in forest systems has been relatively understudied in comparison with nitrogen (N) and phosphorus (P) despite its critical roles in maintaining the nutrition of primary production in forests. We investigated the ecological significance of K in forests from a literature review and data synthesis. We focused on (1) describing patterns of the effects of K availability on aboveground growth and change in foliar tissue of tree species from a variety of forests; and (2) documenting previously unreported relationships between hydrologic losses of K and N in forested watersheds from the Americas. In a review of studies examining tree growth under K manipulations/fertilizations, a high percentage (69% of studies) showed a positive response to increases in K availability in forest soils. In addition, 76% of the tree studies reviewed showed a positive and significant increase in K concentrations in plant tissue after soil K manipulation/fertilization. A meta‐analysis on a subset of the reviewed studies was found to provide further evidence that potassium effects tree growth and increased tissue [K] with an effect size of 0.709 for growth and an overall effect size of 0.56. In our review of watershed studies, we observed that concentrations of K typically decreased during growing seasons in streams draining forested areas in the Temperate Zones and were responsive to vegetation disturbance in both temperate and tropical regions. We found a strong relationship (r2 = 0.42–0.99) between concentrations of K and N (another critical plant nutrient) in stream water, suggesting that similar mechanisms of biotic retention may control the flow of these nutrients. Furthermore, K dynamics appear to be unique among the base cations, e.g. calcium, magnesium, and sodium, because the others do not show similar seasonal patterns to K. We suggest that K may be important to the productivity and sustenance of many forests, and its dynamics and ecological significance warrant further study. We suggest that knowledge about the dynamics of this understudied element is imperative for our understanding patterns and processes in forest ecosystems.
Genetic evidence of frequent long‐distance recruitment in a vertebrate‐dispersed tree
Authors: Hardesty Britta Denise , Hubbell Stephen P. , Bermingham Eldredge 
Published: March 2006

AbstractThe importance of dispersal for the maintenance of biodiversity, while long‐recognized, has remained unresolved. We used molecular markers to measure effective dispersal in a natural population of the vertebrate‐dispersed Neotropical tree, Simarouba amara (Simaroubaceae) by comparing the distances between maternal parents and their offspring and comparing gene movement via seed and pollen in the 50 ha plot of the Barro Colorado Island forest, Central Panama. In all cases (parent‐pair, mother–offspring, father–offspring, sib–sib) distances between related pairs were significantly greater than distances to nearest possible neighbours within each category. Long‐distance seedling establishment was frequent: 74% of assigned seedlings established > 100 m from the maternal parent [mean = 392 ± 234.6 m (SD), range = 9.3–1000.5 m] and pollen‐mediated gene flow was comparable to that of seed [mean = 345.0 ± 157.7 m (SD), range 57.6–739.7 m]. For S. amara we found approximately a 10‐fold difference between distances estimated by inverse modelling and mean seedling recruitment distances (39 m vs. 392 m). Our findings have important implications for future studies in forest demography and regeneration, with most seedlings establishing at distances far exceeding those demonstrated by negative density‐dependent effects.