bluuebunny/crossref_metadata_2025 huggingface dataset:
Modeling of Radiation Heat Transfer in the Drawing of an Optical Fiber With Multilayer Structure
Authors: Chen Chunming , Jaluria Yogesh
Published: March 2007

A numerical model is developed to study the radiative heat transfer in a furnace for optical fiber drawing with a core-cladding structure in the fiber. The focus is on the effect of the difference in composition and thus the radiation properties in the two regions on radiative transport. The zonal method is applied to calculate the radiative heat transfer within the neck-down region of the preform. The radiative heat transfer between the preform and the furnace is computed by an enclosure analysis. A parallel computational scheme for determining the direct exchange areas is also studied. The radiation model is verified by comparisons with benchmark problems. Numerical results for a pure silica preform, a GeO2-doped silica core with a pure silica cladding preform, and a pure silica core with a B2O3-doped silica cladding preform are presented. Radiation properties for these are obtained from the literatures and a three-band model is developed to represent the values. It is found that radiative heat flux on the surface of the preform is strongly affected by the differences in the absorption coefficient due to doping. However, changes of about 1% in the refractive index have only a small effect on radiative heat transfer. The basic approach is outlined in order to form the basis for simulating optical fiber drawing processes, which typically involve fibers and preforms with a core and a cladding. Furthermore, the approach can apply to estimate the multi-layer fiber drawing, which is of interest in the fabrication of specialty fibers that have been finding uses in a variety of practical applications. The model can be extended to other similar processes, which involve multiple regions with different radiation properties. The main interest in this study is on the approximate representation of radiation properties and on the modeling of the transport process.
Poly(methyl methacrylate) (PMMA) XPS Reference Core Level and Energy Loss Spectra
Authors: Louette Pierre , Bodino Frederic , Pireaux Jean-Jacques
Published: March 2007

XPS measurements of poly(methyl methacrylate) recorded with a SSX-100 spectrometer in standardized experimental conditions are presented: survey scan, high resolution core level spectra as well as the energy loss regions of carbon and oxygen peaks are analyzed. This is part of a contract work aiming to record spectra in the very same conditions of some 40 different polymers.
Poly(p-phenylene ether sulfone) (PES) XPS Reference Core Level and Energy Loss Spectra
Authors: Louette Pierre , Bodino Frederic , Pireaux Jean-Jacques
Published: March 2007

XPS measurements of poly(p-phenylene ether sulfone) recorded with a SSX-100 spectrometer in standardized experimental conditions are presented: survey scan, high resolution core level spectra as well as the energy loss regions of carbon, sulphur and oxygen peaks are analyzed. This is part of a contract work aiming to record spectra in the very same conditions of some 40 different polymers.
Poly(vinyl stearate) XPS Reference Core Level and Energy Loss Spectra
Authors: Louette Pierre , Bodino Frederic , Pireaux Jean-Jacques
Published: March 2007

XPS measurements of poly(vinyl stearate) recorded with a SSX-100 spectrometer in standardized experimental conditions are presented: survey scan, high resolution core level spectra as well as the energy loss regions of carbon and oxygen peaks are analyzed. This is part of a contract work aiming to record spectra in the very same conditions of some 40 different polymers.
Conformationally Controlled Chemistry: Excited-State Dynamics Dictate Ground-State Reaction
Authors: Kim Myung Hwa , Shen Lei , Tao Hongli , Martinez Todd J. , Suits Arthur G.
Published: March 2007

Ion imaging reveals distinct photodissociation dynamics for propanal cations initially prepared in either the cis or gauche conformation, even though these isomers differ only slightly in energy and face a small interconversion barrier. The product kinetic energy distributions for the hydrogen atom elimination channels are bimodal, and the two peaks are readily assigned to propanoyl cation or hydroxyallyl cation coproducts. Ab initio multiple spawning dynamical calculations suggest that distinct ultrafast dynamics in the excited state deposit each conformer in isolated regions of the ground-state potential energy surface, and, from these distinct regions, conformer interconversion does not effectively compete with dissociation.
The Evolutionary Demography of Ecological Change: Linking Trait Variation and Population Growth
Authors: Pelletier Fanie , Clutton-Brock Tim , Pemberton Josephine , Tuljapurkar Shripad , Coulson Tim
Published: March 2007

Population dynamics and evolutionary change are linked by the fundamental biological processes of birth and death. This means that population growth may correlate with the strength of selection, whereas evolutionary change can leave an ecological signature. We decompose population growth in an age-structured population into contributions from variation in a quantitative trait. We report that the distribution of body sizes within a population of Soay sheep can markedly influence population dynamics, accounting for up to one-fifth of observed population growth. Our results suggest that there is substantial opportunity for evolutionary dynamics to leave an ecological signature and visa versa.
Protective Meningococcal Capsular Polysaccharide Epitopes and the Role of O Acetylation
Authors: Fusco Peter C. , Farley Esmé K. , Huang Chun-Hsien , Moore Samuel , Michon Francis
Published: March 2007

Previous studies with group C meningococcal polysaccharide-tetanus toxoid (GCMP-TT) conjugates had suggested that the GCMPO-acetyl group masked the protective epitope for group C meningococci through steric hindrance or altered conformations. For this report, we confirmed this phenomenon and performed comparative studies with group Y meningococcal polysaccharide (GYMP)-TT to determine whether it might extend to other serogroups. The de-O-acetylated (dOA) polysaccharides (PSs) resulted in higher serum bactericidal activities (SBA) towards the O-acetylated (OA) meningococcal strains from the respective serogroups. High-resolution H-nuclear magnetic resonance spectroscopy at 500 MHz and competitive inhibition serum bactericidal assays were used to characterize the nature of the protective epitope. In head-to-head comparisons with OA PSs as SBA inhibitors, the dOA PSs provided 10 to 1,000 times better inhibition for GCMP in human and mouse antisera and 6 to 13 times better inhibition for GYMP in mouse antisera, using OA strains in all assays. In addition, the SBA for OA strains was highly correlated with dOA PS-specific immunoglobulin G (r= 0.72 to 0.98) for both GCMP and GYMP. The results suggest that there may be a generalized role for theO-acetyl group to provide an epitope of misdirected immunogenicity for meningococcal PS capsules, enabling escape from immune surveillance. In addition to greater chemical consistency, the dOA forms of GCMP and GYMP conjugate vaccines endow greater immunologic competence to the PSs, rendering them capable of eliciting higher levels of functional antibodies toward the protective epitopes.
Neisseria
Species Identification Assay for the Confirmation of
Neisseria gonorrhoeae
-Positive Results of the COBAS Amplicor PCR
Authors: Mangold Kathy A. , Regner MaryAnn , Tajuddin Mohammed , Tajuddin Aamair M. , Jennings Lawrence , Du Hongyan , Kaul Karen L.
Published: March 2007

Screening assays for
Neisseria gonorrhoeae
exhibit low positive predictive values, particularly in low-prevalence populations. A new real-time PCR assay that detects and identifies individual
Neisseria
spp. using melt curve analysis was compared to two previously published supplementary assays. NsppID, a 16S rRNA real-time PCR/melt curve assay developed to distinguish
N. gonorrhoeae
from other
Neisseria
spp., was compared to real-time PCR assays targeting genes reportedly specific for
N. gonorrhoeae
, the
cppB
gene and the
porA
pseudogene. A total of 408 clinical specimens (324 female endocervical swabs and 84 male urine or urogenital swab specimens) were screened using the COBAS Amplicor assay for
Chlamydia trachomatis
and
N. gonorrhoeae
(CT/NG) (Roche Diagnostics, Indianapolis, IN) followed by confirmatory testing via real-time PCR. The NsppID assay detected
Neisseria
spp. in 150/181 COBAS-positive specimens (82%), including six dual infections, and identified
N. gonorrhoeae
in 102 (56%) specimens. Sixty-nine of 181 (38%) specimens were positive for
N. gonorrhoeae
by
porA
pseudogene, and 115/181 (64%) were positive for
cppB
. However,
cppB
was also positive in 15% of COBAS-negative specimens, more than either NsppID (4%) or
porA
pseudogene (2%) assays. The
porA
pseudogene assay had the highest specificity for both genders but the lowest sensitivity, especially in female specimens. NsppID had a slightly lower specificity but greater sensitivity and overall accuracy. The least desirable confirmatory assay was
cppB
, due to poor specificity. The NsppID assay is an accurate confirmatory assay for
N. gonorrhoeae
detection. In addition, the NsppID assay can identify the non-
N. gonorrhoeae
species responsible for the majority of false-positive results from the COBAS Amplicor CT/NG assay.
Epstein-Barr Virus (EBV)-Infected Monocytes Facilitate Dissemination of EBV within the Oral Mucosal Epithelium
Authors: Tugizov Sharof , Herrera Rossana , Veluppillai Piri , Greenspan John , Greenspan Deborah , Palefsky Joel M.
Published: March 2007

Epstein-Barr virus (EBV) causes hairy leukoplakia (HL), a benign lesion of oral epithelium that occurs primarily in the setting of human immunodeficiency virus (HIV)-associated immunodeficiency. However, the mechanisms of EBV infection of oral epithelium are poorly understood. Analysis of HL tissues shows a small number of EBV-positive intraepithelial macrophages and dendritic/Langerhans cells. To investigate a role for these cells in spreading EBV to epithelial cells, we used tongue and buccal explants infected ex vivo with EBV. We showed that EBV first infects submucosal CD14+monocytes, which then migrate into the epithelium and spread virus to oral epithelial cells, initiating productive viral infection within the terminally differentiated spinosum and granulosum layers. Incubation of EBV-infected monocytes and oral explants with antibodies to CCR2 receptor and monocyte chemotactic protein 1 prevented entry of monocytes into the epithelium and inhibited EBV infection of keratinocytes. B lymphocytes played little part in the spread of EBV to keratinocytes in our explant model. However, cocultivation of EBV-infected B lymphocytes with uninfected monocytes in vitro showed that EBV may spread from B lymphocytes to monocytes. Circulating EBV-positive monocytes were detected in most HIV-infected individuals, consistent with a model in which EBV may be spread from B lymphocytes to monocytes, which then enter the epithelium and initiate productive viral infection of keratinocytes.
Development of a Cell-Based Assay Probing the Specific Interaction between the Human Immunodeficiency Virus Type 1 Nucleocapsid and Psi RNA In Vivo
Authors: Jang Soo In , Kim Young Ho , Paik Soon Young , You Ji Chang
Published: March 2007

Here, we describe a cell-based in vivo assay that probes the specific interaction between nucleocapsid (NC) protein and Psi (Ψ) RNA, the human immunodeficiency virus (HIV) packaging signal. The results demonstrate for the first time a specific NC-Ψ interaction within living cells. The specificity and applicability of the assay were confirmed by mutational studies of NC and deletion-mapping analyses of Ψ-RNA as well as by testing the in vivo NC-binding effects of NC-aptamer RNAs identified previously in vitro. This assay system would facilitate further detailed studies of the NC-Ψ interaction in vivo and the screening of various anti-HIV molecules targeting NC and the specific interaction.
Importance of Calcium-Binding Site 2 in Simian Virus 40 Infection
Authors: Li Peggy P. , Nguyen Albert P. , Qu Qiumin , Jafri Qumber H. , Aungsumart Saharat , Cheng R. Holland , Kasamatsu Harumi
Published: March 2007

The exposure of molecular signals for simian virus 40 (SV40) cell entry and nuclear entry has been postulated to involve calcium coordination at two sites on the capsid made of Vp1. The role of calcium-binding site 2 in SV40 infection was examined by analyzing four single mutants of site 2, the Glu160Lys, Glu160Arg, Glu157Lys (E157K), and Glu157Arg mutants, and an E157K-E330K combination mutant. The last three mutants were nonviable. All mutants replicated viral DNA normally, and all except the last two produced particles containing all three capsid proteins and viral DNA. The defect of the site 1-site 2 E157K-E330K double mutant implies that at least one of the sites is required for particle assembly in vivo. The nonviable E157K particles, about 10% larger in diameter than the wild type, were able to enter cells but did not lead to T-antigen expression. Cell-internalized E157K DNA effectively coimmunoprecipitated with anti-Vp1 antibody, but little of the DNA did so with anti-Vp3 antibody, and none was detected in anti-importin immunoprecipitate. Yet, a substantial amount of Vp3 was present in anti-Vp1 immune complexes, suggesting that internalized E157K particles are ineffective at exposing Vp3. Our data show that E157K mutant infection is blocked at a stage prior to the interaction of the Vp3 nuclear localization signal with importins, consistent with a role for calcium-binding site 2 in postentry steps leading to the nuclear import of the infecting SV40.
Functional Characterization of the Major and Minor Phosphorylation Sites of the P Protein of Borna Disease Virus
Authors: Schmid Sonja , Mayer Daniel , Schneider Urs , Schwemmle Martin
Published: March 2007

The phosphoprotein P of Borna disease virus (BDV) is an essential cofactor of the viral RNA-dependent RNA polymerase. It is preferentially phosphorylated at serine residues 26 and 28 by protein kinase C ε (PKCε) and, to a lesser extent, at serine residues 70 and 86 by casein kinase II (CKII). To determine whether P phosphorylation is required for viral polymerase activity, we generated P mutants lacking either the PKCε or the CKII phosphate acceptor sites by replacing the corresponding serine residues with alanine (A). Alternatively, these sites were replaced by aspartic acid (D) to mimic phosphorylation. Functional characterization of the various mutants in the BDV minireplicon assay revealed that D substitutions at the CKII sites inhibited the polymerase-supporting activity of P, while A substitutions maintained wild-type activity. Likewise, D substitutions at the PKC sites did not impair the cofactor function of BDV-P, whereas A substitutions at these sites led to increased activity. Interestingly, recombinant viruses could be rescued only when P mutants with modified PKCε sites were used but not when both CKII sites were altered. PKCε mutant viruses showed a reduced capacity to spread in cell culture, while viral RNA and protein expression levels in persistently infected cells were almost normal. Further mutational analyses revealed that substitutions at individual CKII sites were, with the exception of a substitution of A for S86, detrimental for viral rescue. These data demonstrate that, in contrast to other viral P proteins, the cofactor activity of BDV-P is negatively regulated by phosphorylation.
Characterization of Human Immunodeficiency Virus Type 1 Monomeric and Trimeric gp120 Glycoproteins Stabilized in the CD4-Bound State: Antigenicity, Biophysics, and Immunogenicity
Authors: Dey Barna , Pancera Marie , Svehla Krisha , Shu Yuuei , Xiang Shi-Hua , Vainshtein Jeffrey , Li Yuxing , Sodroski Joseph , Kwong Peter D. , Mascola John R. , Wyatt Richard
Published: March 2007

The human immunodeficiency virus type 1 exterior gp120 envelope glycoprotein is highly flexible, and this flexibility may contribute to the inability of monomeric gp120 immunogens to elicit broadly neutralizing antibodies. We previously showed that an S375W modification of a critical interfacial cavity central to the primary receptor binding site, the Phe43 cavity, stabilizes gp120 into the CD4-bound state. However, the immunological effects of this cavity-altering replacement were never tested. Subsequently, we screened other mutations that, along with the S375W alteration, might further stabilize the CD4-bound state. Here, we define a selected second cavity-altering replacement, T257S, and analyze the double mutations in several gp120 envelope glycoprotein contexts. The gp120 glycoproteins with the T257S-plus-S375W double mutation (T257S+S375W) have a superior antigenic profile compared to the originally identified single S375W replacement in terms of enhanced recognition by the broadly neutralizing CD4 binding-site antibody b12. Isothermal titration calorimetry measuring the entropy of the gp120 interaction with CD4 indicated that the double mutant was also stabilized into the CD4-bound state, with increasing relative fixation between core, full-length monomeric, and full-length trimeric versions of gp120. A significant increase in gp120 affinity for CD4 was also observed for the cavity-filling mutants relative to wild-type gp120. The most conformationally constrained T257S+S375W trimeric gp120 proteins were selected for immunogenicity analysis in rabbits and displayed a trend of improvement relative to their wild-type counterparts in terms of eliciting neutralizing antibodies. Together, the results suggest that conformational stabilization may improve the ability of gp120 to elicit neutralizing antibodies.
A petrological and geochemical study of the volcanic rocks of the Crowsnest Formation, southwestern Alberta, and of the Howell Creek suite, British Columbia
Authors: Bowerman Melissa , Christianson Amy , Creaser Robert A , Luth Robert W
Published: March 2007

Alkaline igneous rocks of the Crowsnest Formation in southwestern Alberta and in the Howell Creek area in southeastern British Columbia have been suggested previously to be cogenetic. To test this hypothesis, samples of both suites were characterized petrographically and their major and trace element geochemistry was determined. A subset of the samples was analyzed for whole-rock Sr and Nd isotope geochemistry. The samples of the two suites are latites, trachytes, and phonolites based on the International Union of Geological Sciences (IUGS) total alkalis versus silica (TAS) diagram. Samples from both suites show similar patterns on mantle-normalized trace element diagrams, being enriched relative to mantle values but depleted in the high field-strength elements Nb, Ta, and Ti relative to the large-ion lithophile elements. The chondrite-normalized rare-earth element (REE) patterns for both suites are light REE enriched, with no Eu anomaly and flat heavy REE. The isotope geochemistry of both suites is characterized by low initial 87Sr/86Sr (SrT = 0.704 to 0.706) and low εNdT (–7 to –16). The Howell Creek samples have lower εNdT and higher SrT than do the Crowsnest samples. Based on the intra- and intersuite differences in the isotope geochemistry, we conclude that these samples are not cogenetic, but rather represent samples that have experienced similar evolutionary histories from a heterogeneous source region in the subcontinental lithospheric mantle.
Using Bayesian belief networks in adaptive management
Authors: Nyberg J Brian , Marcot Bruce G , Sulyma Randy
Published: March 2007

Bayesian belief and decision networks are modelling techniques that are well suited to adaptive-management applications, but they appear not to have been widely used in adaptive management to date. Bayesian belief networks (BBNs) can serve many purposes, from illustrating a conceptual understanding of system relations to calculating joint probabilities for decision options and predicting outcomes of management policies. We describe the nature and capabilities of BBNs, discuss their applications to the adaptive-management process, and present a case example of adaptive management of forests and terrestrial lichens in north-central British Columbia. We recommend that those unfamiliar with BBNs should begin by first developing influence diagrams with relatively simple structures that represent the system under management. Such basic models can then be elaborated to include more variables, the mathematical relations among them, and features that allow assessment of the utility of alternative management actions or strategies. Users of BBNs should be aware of several important limitations, including problems in representing feedback and time–dynamic functions. Nevertheless, when properly used, Bayesian networks can benefit most adaptive-management teams by promoting a shared understanding of the system being managed and encouraging the rigorous examination of alternative management policies.
Spatial dynamics of soil moisture and temperature in a black spruce boreal chronosequence
Authors: Bond-Lamberty Ben , Brown Karen M , Goranson Carol , Gower Stith T
Published: March 2007

This study analyzed the spatial dependencies of soil moisture and temperature in a six-stand chronosequence of boreal black spruce (Picea mariana (Mill.) BSP) stands. Spatial variability of soil temperature (TSOIL) was evaluated twice during the growing season using four transects in each stand, employing a cyclic sampling design with measurements spaced 2–92 m apart. Soil moisture (θg) was measured on one occasion. A spherical model was used to analyze the geostatistical correlation structure; θg and TSOIL at the 7- and 21-year-old stands did not exhibit stable ranges or sills. The fits with stable ranges and sills modeled the spatial patterns in the older stands reasonably well, although unexplained variability was high. Calculated ranges varied from 3 to 150 m for these stands, lengths probably related to structural characteristics influential in local-scale energy transfer. Transect-to-transect variability was significant and typically 5%–15% of the mean for TSOIL and 10%–70% for θg. TSOIL and θg were negatively correlated for most stands and depths, with TSOIL dropping 0.5–0.9 °C for every 1% rise in θg. The results reported here provide initial data to assess the spatial variability of TSOIL and θg in a variety of boreal forest stand ages.
Effect of variable-retention harvesting on soil nitrogen availability in boreal mixedwood forests
Authors: Jerabkova Lucie , Prescott Cindy E , Kishchuk Barbara E
Published: March 2007

Clear-cut harvesting of forests may be associated with increased availability and losses of nitrogen (N), and variable-retention (VR) harvesting has been proposed as an environmentally acceptable alternative to clear-cutting. In boreal forests, however, harvesting has often not led to significant increases in N availability and it is thus important to assess whether variable retention practices are necessary and justifiable in such forests with respect to nutrient dynamics. We compared N availability in clear-cut and VR-harvested stands in the boreal mixedwood forest of northwestern Alberta. We measured soil concentrations of nitrate, ammonium, soluble organic N, and microbial N in uncut, 50% and 20% retention, and clearcuts of deciduous-dominated, coniferous-dominated, and mixed stands 4 years after harvesting. There was little apparent effect of harvesting on N availability in all forest types. Nitrate, ammonium, and microbial N concentrations and net N mineralization and nitrification rates were similar in clearcuts and uncut forests and there was no threshold effect of harvesting on N availability. Soluble organic N concentrations were lower in coniferous and mixed clearcuts than in uncut stands on only one occasion. Clear-cut harvesting in itself does not appear to lead to long-lasting increased N availability and losses in boreal mixedwoods. Adoption of VR harvesting in these ecosystems may not be justified on the grounds of reducing changes in N availability when compared with clear-cutting.
Wildfire mitigation strategies affect soil enzyme activity and soil organic carbon in loblolly pine (Pinus taeda) forests
Authors: Boerner R EJ , Waldrop T A , Shelburne V B
Published: March 2007

We quantified the effects of three wildfire hazard reduction treatments (prescribed fire, thinning from below, and the combination of fire and thinning), and passive management (control) on mineral soil organic C, and enzyme activity in loblolly pine (Pinus taeda L.) forests on the Piedmont of South Carolina. Soil organic C was reduced by thinning, either alone or with prescribed fire, and this effect persisted through the fourth post-treatment year. Fire also resulted in reduced soil organic C, but not until several years after treatment. Soil C/N ratio initially increased after fire, either alone or with thinning, but this difference did not persist. The activities of three soil enzymes (acid phosphatase, chitinase, and phenol oxidase) in the upper mineral soil were quantified as measures of microbial activity. During the fourth post-treatment year we observed significant stimulation of all three enzyme systems as a result of thinning or thinning and burning. Although the patterns of variation in acid phosphatase and chitinase activity among treatments were similar during the first and fourth post-treatment years, the first-year treatment effects were not statistically significant. Given the management objective of utilizing these stands for timber production, the increased potential for rapid nutrient turnover offered by thinning gives this approach advantages over prescribed fire; however, management for maximum long-term storage of soil C may be better facilitated by prescribed fire.
NONHOLONOMIC RICCI FLOWS AND RUNNING COSMOLOGICAL CONSTANT I: 4D TAUB-NUT METRICS
Authors: VACARU SERGIU I. , VISINESCU MIHAI
Published: March 2007

In this work we construct and analyze exact solutions describing Ricci flows and nonholonomic deformations of four-dimensional (4D) Taub-NUT space–times. It is outlined a new geometric technique of constructing Ricci flow solutions. Some conceptual issues on space–times provided with generic off-diagonal metrics and associated nonlinear connection structures are analyzed. The limit from gravity/Ricci flow models with nontrivial torsion to configurations with the Levi-Civita connection is allowed in some specific physical circumstances by constraining the class of integral varieties for the Einstein and Ricci flow equations.
THE MASTER EQUATIONS IN THE EUCLIDEAN SCHWARZSCHILD–TANGHERLINI METRIC OF A SMALL STATIC PERTURBATION
Authors: MARTÍNEZ-MORALES JOSÉ L.
Published: March 2007

The master equations in the Euclidean Schwarzschild–Tangherlini space–time of a small static perturbation are studied. For each harmonic mode on the sphere there are two solutions that behave differently at infinity. One solution goes like the power 2-l-n of the radial variable, the other solution goes like the power l. These solutions occur in power series.

The second main statement of the paper is that any eigentensor of the Lichnerowicz operator in a Euclidean Schwarzschild space–time with an eigenvalue different from zero is essentially singular at infinity. Possible applications of the stability of instantons are discussed.

We present the analysis of a small static perturbation of the Euclidean Schwarzschild–Tangherlini metric tensor. The higher order perturbations will appear later. We determine independently the static perturbations of the Schwarzschild quantum black hole in dimension 1+n≥4, where the system of equations is reduced to master equations — ordinary differential equations. The solutions are hypergeometric functions which in some cases can be reduced to polynomials.

In the same Schwarzschild background, we analyze static perturbations of the scalar mode and show that there does not exist any static perturbation that is regular everywhere outside the event horizon and is well-behaved at the spatial infinity. This confirms the uniqueness of the spherically symmetric static empty quantum black hole, within the perturbation framework.

Our strategy for treating the stability problem is also applicable to other symmetric quantum black holes with a nonzero cosmological constant.
Metabotropic Glutamate Receptors in the Lateral Superior Olive Activate TRP-Like Channels: Age- and Experience-Dependent Regulation
Authors: Ene F. Aura , Kalmbach Abigail , Kandler Karl
Published: March 2007

The lateral superior olive (LSO) is the primary auditory nucleus for processing of interaural sound level differences, which is one of the major cues for sound localization. During development, survival and maturation of LSO neurons critically depend on synaptic activity and intracellular calcium signaling. Before hearing onset, glutamatergic synaptic inputs from the cochlear nucleus (CN) to the LSO activate group I metabotropic glutamate receptors (mGluRs), which leads to calcium release from intracellular stores and large calcium influx from the extracellular milieu. Here, we investigated the nature of the mGluR-activated membrane channel that mediates the influx of extracellular calcium. Using Fura-2 calcium imaging in brain stem slices of neonatal and juvenile mice, we found that this calcium channel is blocked by Ni2+, La3+, and 2-aminoethoxydiphenylborane (2-APB), known antagonists of transient receptor potential (TRP) channels. During postnatal development, the contribution of extracellular calcium influx to mGluR-mediated Ca2+responses gradually decreased and was almost abolished by the end of the third postnatal week. Over this period, the contribution of Ca2+release from internal stores remained unchanged. The developmental decrease of TRP-like channel-mediated calcium influx was significantly less in congenitally deaf waltzer mice, suggesting that early auditory experience is necessary for the normal age-dependent downregulation of functional TRP channels.
Defining the Range of Cellular Components, Including Internal Antigens, That Can Serve as Targets of Graft Rejection
Authors: Lampson L. A. , Lampson M. A. , Dunne A. D.
Published: March 2007

The mechanisms underlying rejection of grafted neural tissue are still being defined. Mechanisms relevant to genetically engineered cells are of current interest. To date, attention has focused on major histocompatibility complex (MHC) antigens as targets of graft rejection. Yet even when there is no MHC disparity, as when the patient′s own cells are genetically altered, there is still a potential for graft rejection, directed against the novel antigens. We illustrate this in a rat model.
Noradrenergic Pharmacotherapy, Intracerebral Infusion andAdrenal Transplantation Promote Functional Recovery After Cortical Damage
Authors: Feeney Dennis M. , Weisend Michael P. , Kline Anthony E.
Published: March 2007

The research described in this review briefly
summarizes evidence that short term
pharmacological enhancement of noradrenergic
(NA) synaptic activity, combined with symptom
relevant experience (SRE), promotes functional
recovery of some symptoms of cortical damage
in rat, cat and human beings even when
treatment is initiated from days to weeks after
injury. A summary is provided of the numerous
drugs tested in rodent cortical injury models
which have been proven useful for predicting
beneficial or harmful effects on behavioral
outcome in human stroke. The pattern of drug
effects indicates a central role for NA in
functional recovery. Additionally, studies of the
effects of direct intraventricular infusion of
monoamine neurotransmitters are reviewed and
further support the hypothesized role of NA in
recovery from some symptoms of cortical injury.
The site of NA/SRE interaction to promote
recovery from hemiplegia apparently involves
the cerebellar hemisphere contralateral to the
cortical injury. Microinfusions of NA into the
contra‐ but not ipsilaterai cerebellar hemisphere
dramatically enhance recovery. Furthermore,
like its systemic action, microinfusion of the α1‐
NA receptor antagonist, phenoxybenzamine,
reinstates hemiplegia. A “permanent” symptom
of motor cortex injury in the cat is the complete
loss of tactile placing contralateral to the injury
which does not spontaneously recover for as
long as seven years after ablation. This posturai
reflex is temporarily restored for 8‐12 hours
following amphetamine administration.
However, this permanently lost reflex can be
enduringly restored by transplanting catecholamine secreting adrenal tissue into the
wound cavity. The experiment is reviewed in
detail and involves chromaffin cell autografts
into the frontal cortex ablation wound cavity
producing a restoration of tactile placing for the
7‐10 month duration of the study. This enduring
restoration of tactile placing is considered a
result of the release of catecholamines into the
CNS from the grafted chromaffin cells found, by
histochemical methods, surviving 7‐10 months
after transplant. Lastly, we attribute these
delayed treatment effects to an attenuation of a
diaschisis, or remote functional depression, in
morphologically intact areas anatomically
connected to the area of injury. The widespread
reduction of glycolytic and oxidative
metabolism, produced by focal cortical injury, is
normalized by the same treatment which
alleviates symptoms and is worsened by drugs
which exacerbate deficits. These data support
the hypothesis that providing SRE during a
period of enhanced NA synaptic activity
produces an enduring functional recovery after
cortical injury by attenuating remote functional
depression. This treatment for enhancing
recovery is especially attractive since it is
effective even when begun weeks after cortical
damage.
Effect of Transplanting Suprachiasmatic Nuclei from Donors ofDifferent Ages into Completely SCN Lesioned Hamsters
Authors: Kaufman Claire M. , Menaker Michael
Published: March 2007

The suprachiasmatic nucleus (SCN) is the
primary circadian pacemaker in mammals.
Ralph and colleagues/14/provided recent new
evidence for this by transplanting SCNs between
golden hamsters with different genetically
determined periods and producing circadian
rhythmsof running wheel activity with periods
characteristic of the donor. We have extended
these studies in order to evaluate the age range
of donor tissue that can be used for transplantation.
SCN of hamsters from embryonic day 11
through postnatal day 12 can serve as functional
grafts to restore rhythmicity to arrhythmic SCN
lesioned animals. The time between SCN transplantation
and onset of rhythmicity does not
depend on the age of the donor. The presence of
patches containing vasoactive intestinal peptide
(VIP) immunoreactive cells is a good indicator
of graft success, while its absence is correlated
with a lack of transplant effect. The 18 day span
during which SCN tissue can be harvested for
transplantation should expand the uses to which
this technique can be put. Our results also
suggest that it would be advantageous to
examine the age range of neural tissue that ca’n
be used in other transplantation models.
A Method for Shortening of the Rat Spine and its NeurologicConsequences
Authors: de Medinaceli Luis , Wyatt Richard Jed
Published: March 2007

Large laboratory animals are the usual
choice for complex surgical procedures on the
spine and spinal cord, such as shortening of the
spine. It would, however, be advantageous to be
able to use a small inexpensive mammal like the
rat. We describe a procedure which allows
thoracic spondylectomy (T8‐T9) to be
performed in the rat with a satisfactory survival
rate (69%). Functional consequences of the
procedure on animals with uninjured spinal
cord were monitored over a period of six
months, at which time histologic examination
was performed. There was a good correlation
between operative trauma, consisting of
mechanical injury to the cord assessed from the
surgical notes, and the duration of postoperative
spinal shock. Animals for which the cord
appeared laminated or deformed at the time of
sacrifice tended to show incomplete functional
recovery. Cord cavitation developed, in most
surviving animals (78%) but did not have a
measurable adverse effect on functional
outcome. In the present study, the cord was not
intentionally injured; however, availability of
this procedure may facilitate the future
development of methods to implement recovery
of function following spinal cord injury.
A Method for Studying the Effects of Neurochemicals on Long‐Term Compensation in Unilaterally Labyrinthectomized Rats
Authors: Andersson Lars , Ulfendahl Mats , Tham Richard
Published: March 2007

A new method has been developed to study the influence of drugs and toxicants on longterm recovery of dynamics in the horizontal vestibulo‐ocular reflex of the rat after hemilabyrinthectomy (HL). HL was performed by injecting sodium arsanilate into the middle
ear. The lesion was confirmed by histology. Eye movements elicited by sinusoidal vestibular stimulation, in both light and darkness, were
recorded by a search‐coil technique and then analyzed by a computer program created with virtual instrument soft‐ware, which calculated
the gain of the slow‐phase velocity (SPV) and the saccades para‐meters (frequency, amplitude, and peak velocity) to the lesioned side and to the intact side separately. During the 2‐10 week period after HL, repeated analysis of the spontaneous long‐term recovery of such
parameters revealed a slight but significant reduction of the post‐HL asymmetry between SPV gain to the lesioned side and to the intact side. During the follow‐up period, a post‐HL increase of the phase lead remained unchanged. The reduced number of saccades/min was not
completely restored. To test the usefulness of the experimental model for neurochemical investigation of such adaptation, we administered baclofen and toluene to rats 8–12 wk after hemilabyrinthectomy. Baclofen, a specific
GABAB agonist, immediately restored the symmetry of SPV gain. By contrast, toluene, which has some effects on the central vestibular system that are related to GABAB transmission,
aggravated the asymmetry in both the SPV gain and the number of saccades. We suggest that the experimental model would be useful for studying neurochemical mechanisms in vestibular adaptation processes.
Prenatal Exposure to Ethanol Causes Differential Effects in Nerve Growth Factor and its Receptor in the Basal Forebrain of Preweaning and Adult Rats
Authors: Angelucci Francesco , Cimino Mauro , Balduini Walter , Piltillo Luana , Aloe Luigi
Published: March 2007

In this study we investigated nerve growth factor (NGF) levels in the cortex and hippocampus of the offspring of pregnant female Sprague‐Dawley rats receiving a single intragastric administration of acute ethanol on the 15th day of gestation and compared them
with a control group of rats that received an injection of sucrose. We also examined the distribution of the low‐affinity NGF receptor,
p75NGFR, on NGF‐responsive neurons that are localized in the septum and the nucleus of Meynert, which receive the respective trophic
support from the hippocampus and the cortex. In the ethanol‐treated group, the results show that at post‐natal age 15 days, the NGF septohippocampal pathways were markedly affected. At day 15, the NGF level was significantly higher in the offspring of ethanol‐treated rats.
By day 40, NGF values in both groups decreased to similar levels. At day 60, however, the NGF level in the ethanol‐treated animals decreased to
a significantly lower value than that of the control group, which remained essentially unchanged. In parallel, at day 60 the numbers of
septal cholinergic neurons expressing p75NGFR were also significantly lower in ethanol‐treated rats than in control animals. Because ethanol is known to induce neurological disorders, as well as deficits in cell proliferation and differentiation, the results suggest that one cause of the deleterious effects induced by ethanol is the low availability of NGF during certain stages of postnatal brain development.
The Early Phase of Vascularization in Intraocular Telencephalic Transplants
Authors: Tuba Andrea , Kálmán Mihály
Published: March 2007

The present study focused on the early events of vascularization of intraocular cerebral transplants. Telencephalic pieces of rat embryos (El5) were transplanted into the anterior eye chamber of adult rats in deep ketamine‐xylazine narcosis. At 3‐, 4‐, 5‐, 6‐, or 7‐day postoperative survival periods, the rats were perfused and the transplants, with their iridic beds, were processed into serial, semi‐thin sections, In 3‐ and 4‐day transplants, neither dilated (perfused) nor collapsed blood vessels were found, but tissue defects, without proper wall and filled by non‐nucleated (mature, host) erythrocytes, were seen. On post‐operative day 5, large sinusoids were seen lines by endothel and free of blood cells (as a consequence of perfusion). On days 6 and 7, the usual, although large, blood vessels were found. Our results suggest that the critical period of transplant vascularization is between postoperative days 4 and 5, and that the original vessels of donor tissue degenerate and disappear during the first postoperative days and thus, do not participate directly in transplant vascularization. Our hypothesis is that vascular invasion begins with the opening of host blood vessels into clefts formed by degeneration of graft tissue. For a period, a hemostasis occurs in these blood‐filled lacunae, and then endothel invasion from host vessels forms the proper wall. The transplant vasculature develops from these large sinusoids. The results challenge the role of the pre‐existing donor vessels in transplant vascularization. A possible explanation of such paradoxical results is that the donor tissue must reach a stage of maturation to receive the ingrowing vessels, either host vessels, and the presence of vessels in the donor brain is the sign of this stage of maturation but has no direct role in transplant vascularization
Adaptability and Flexibility of the Human Motor System:Implications for Neurological Rehabilitation
Authors: Mulder Theo , Hochstenbach Jacqueline
Published: March 2007

This article stresses the plasticity of the
adult sensorimotor cortex in response to
various injuries or environmental changes. The
dominant role of sensory input is discussed. A
number of studies are presented that show how
input may lead to learning and change. Learning
is discussed in relation to recovery. It is shown
how concepts from the field of motor control
and learning may be used for improving neurological
rehabilitation. Specific attention is given
to the variability of input, the meaningfulness
of input, and the role of the learning context.
The learning context and the application
context should have essential characteristics in
common, otherwise transfer of learning will be
non‐optimal. It is argued that learning landscapes
are necessary in order to treat patients
in such a way that he learned skills are
transferable to situations outside the hospital.
Experience‐Dependent Color Constancy in Guppies (Poecilia reticulata)
Authors: Intskirveli I. E. , Roinishvili M. O. , Kezeli A. R.
Published: March 2007

We investigated the ability to recognize the color of surfaces in fish (Poecilia reticulata), bred from birth in conditions of artificial light with constant spectral content. The capacity for color constancy significantly deteriorated when compared that to the control group. Further alteration of lighting conditions and transfer into natural daylight conditions restored the suppressed function to its normal level. We suggest that the color constancy function belongs in the visual system‐response functions, the full development of which requires the accumulation of individual visual experience.
Cerebellar Involvement in Clumsiness and OtherDevelopmental Disorders
Authors: Ivry Richard B.
Published: March 2007

Cerebellar abnormalities have been linked to
a number of developmental disorders. Much
evidence is based on the analysis of highresolution
MRI scans. Imaging and behavioral
studies have led researchers to consider
functional contributions of the cerebellum
beyond that associated with motor control. I
review this literature, providing an analysis of
different ways to consider the relation between
cerebellar abnormalities and developmental
disorders. Interestingly, although clumsiness is a
problem of coordination, the contribution of
cerebellar dysfunction to this developmental
problem has received little attention. Select
studies indicate that some clumsy children have
difficulties on tasks requiring precise timing,
similar to that observed in adult patients with
cerebellar lesions. I suggest that the underlying
neural bases of clumsiness are heterogeneous,
with cerebellar dysfunction likely a major
contributor for a subpopulation of such children.
Operant Discriminative Learning and Evidence of SubtelencephalicPlastic Changes After Long‐Term Detelencephalation in Pigeons
Authors: Cerutti S. M. , Diaz-Cintra S. , Cintra L. , Ferrari E. A. M.
Published: March 2007

We analyzed operant discrimination in
detelencephalated pigeons and neuroanatomical
substrates after long‐term detelencephalation.
In Experiment I, experimental pigeons with
massive telencephalic ablation and control
pigeons were conditioned to key peck for food.
Successive discrimination was made under
alternating red (variable‐ratio reinforcement)
and yellow (extinction) lights in one key of the
chamber. These relations were interchanged
during reversal discrimination. The sessions
were run until steady‐state rates were achieved.
Experiment II analyzed the morphology of the
nucleus rotundus and optic tectum in long‐term
detelencephalated and control birds, using a
Klüver‐Barrera staining and image analyzer
system. Detelencephalated birds had more
training sessions for response shaping and
steady‐state behavior (p<0.001), higher red key
peck rates during discrimination (p<0.01), and reversal discrimination indexes around 0.50.
Morphometric analysis revealed a decreased
number of neurons and increased vascularity,
associated with increases in the perimeter
(p<0.001)
in the nucleus rotundus. In the optic
tectum, increases in the perimeter (p<0.05)

associated with disorganization in the layers
arrangement were seen. The data indicate that
telencephalic systems might have an essential
function in reversal operant discrimination
learning. The structural characteristics of subtelencephalic
systems after long‐term detelencephalation
evidence plastic changes that
might be related to functional mechanisms of
learning and neural plasticity in pigeons.
Developmental Coordination Disorder: Is Clumsy Motor Behavior Caused by a Lesion of the Brain at Early Age?
Authors: Hadders-Algra Mijna
Published: March 2007

Children presenting with Developmental
Coordination Disorder or clumsiness often
exhibit signs of minor neurological dysfunction
(MND). The data of the Groningen Perinatal
Project, a long‐term follow‐up project .on the
relations between prenatal and perinatal
adversities and neurological, behavioral, and
cognitive development revealed that two basic
forms of MND can be distinguished: simple and
complex MND. During school age children with
simple MND are characterized by the presence
of one or two dysfunctional clusters of MND, in
adolescence by the presence of choreiform
dyskinesia or hypotonia. Probably the major
sources of origin of simple MND are genetic
constitution and stress during early life. Simple
MND might reflect the lower tail of the normal
distribution of the quality of non‐pathological
brain function. In line with this hypothesis is
the finding that simple MND is associated with
only a moderately increased risk for learning and
behavioral problems. Children with
complex MND present at school age with at
least three dysfunctional clusters of MND, in
adolescence with problems in fine manipulation
or coordination. Perinatal adversities play an
evident etiological role in the development of
complex MND, suggesting that it might be
attributed to a lesion of the brain at early age.
In line with this idea is the finding that complex
MND shows .a strong correlation with attention
and learning problems.