bluuebunny/crossref_metadata_2025_split huggingface dataset:
The aetiology of neurological complications of organic acidaemias—A role for the blood–brain barrier
Authors: Kölker S. , Sauer S. W. , Surtees R. A. H. , Leonard J. V. 
Published: October 2006

SummaryThe blood–brain barrier (BBB) metabolically isolates the central nervous system (CNS) from the circulation and protects it against fluctuations of hydrophilic nutrients in plasma and from intoxication. Recent studies have shown that dicarboxylic acids (DCAs) are transported across the blood–brain barrier at very low rates. In organic acidaemias, neurological complications are common. We hypothesize that, as a result of the very limited efflux, in certain organic acidaemias there is pathological accumulation of DCAs (e.g. glutarate, 3‐hydroxyglutarate, D‐2‐ and L‐2‐hydroxyglutarate, methylmalonate) in the brain secondary to the metabolic block. At high concentrations some of these compounds may become neurotoxic. Treatment should be aimed at preventing the accumulation of these compounds using our understanding of the properties of the BBB.
Differential effects of palmitate and palmitoleate on insulin action and glucose utilization in rat L6 skeletal muscle cells
Authors: Dimopoulos Nikolaos , Watson Maria , Sakamoto Kei , Hundal Harinder S. 
Published: October 2006

An increase in circulating levels of specific NEFAs (non-esterified fatty acids) has been implicated in the pathogenesis of insulin resistance and impaired glucose disposal in skeletal muscle. In particular, elevation of SFAs (saturated fatty acids), such as palmitate, has been correlated with reduced insulin sensitivity, whereas an increase in certain MUFAs and PUFAs (mono- and poly-unsaturated fatty acids respectively) has been suggested to improve glycaemic control, although the underlying mechanisms remain unclear. In the present study, we compare the effects of palmitoleate (a MUFA) and palmitate (a SFA) on insulin action and glucose utilization in rat L6 skeletal muscle cells. Basal glucose uptake was enhanced approx. 2-fold following treatment of cells with palmitoleate. The MUFA-induced increase in glucose transport led to an associated rise in glucose oxidation and glycogen synthesis, which could not be attributed to activation of signalling proteins normally modulated by stimuli such as insulin, nutrients or cell stress. Moreover, although the MUFA-induced increase in glucose uptake was slow in onset, it was not dependent upon protein synthesis, but did, nevertheless, involve an increase in the plasma membrane abundance of GLUT1 and GLUT4. In contrast, palmitate caused a substantial reduction in insulin signalling and insulin-stimulated glucose transport, but was unable to antagonize the increase in transport elicited by palmitoleate. Our findings indicate that SFAs and MUFAs exert distinct effects upon insulin signalling and glucose uptake in L6 muscle cells and suggest that a diet enriched with MUFAs may facilitate uptake and utilization of glucose in normal and insulin-resistant skeletal muscle.
Ascorbate removes key precursors to oxidative damage by cell-free haemoglobin in vitro and in vivo
Authors: Dunne Jacqueline , Caron Alexis , Menu Patrick , Alayash Abdu I. , Buehler Paul W. , Wilson Michael T. , Silaghi-Dumitrescu Radu , Faivre Beatrice , Cooper Chris E. 
Published: October 2006

Haemoglobin initiates free radical chemistry. In particular, the interactions of peroxides with the ferric (met) species of haemoglobin generate two strong oxidants: ferryl iron and a protein-bound free radical. We have studied the endogenous defences to this reactive chemistry in a rabbit model following 20% exchange transfusion with cell-free haemoglobin stabilized in tetrameric form [via cross-linking with bis-(3,5-dibromosalicyl)fumarate]. The transfusate contained 95% oxyhaemoglobin, 5% methaemoglobin and 25 μM free iron. EPR spectroscopy revealed that the free iron in the transfusate was rendered redox inactive by rapid binding to transferrin. Methaemoglobin was reduced to oxyhaemoglobin by a slower process (t1/2=1 h). No globin-bound free radicals were detected in the plasma. These redox defences could be fully attributed to a novel multifunctional role of plasma ascorbate in removing key precursors of oxidative damage. Ascorbate is able to effectively reduce plasma methaemoglobin, ferryl haemoglobin and globin radicals. The ascorbyl free radicals formed are efficiently re-reduced by the erythrocyte membrane-bound reductase (which itself uses intra-erythrocyte ascorbate as an electron donor). As well as relating to the toxicity of haemoglobin-based oxygen carriers, these findings have implications for situations where haem proteins exist outside the protective cell environment, e.g. haemolytic anaemias, subarachnoid haemorrhage, rhabdomyolysis.
The family 42 carbohydrate-binding module of family 54 α-L-arabinofuranosidase specifically binds the arabinofuranose side chain of hemicellulose
Authors: Miyanaga Akimasa , Koseki Takuya , Miwa Yozo , Mese Yuichiro , Nakamura Sachiko , Kuno Atsushi , Hirabayashi Jun , Matsuzawa Hiroshi , Wakagi Takayoshi , Shoun Hirofumi , Fushinobu Shinya 
Published: October 2006

α-L-Arabinofuranosidase catalyses the hydrolysis of the α-1,2-, α-1,3-, and α-1,5-L-arabinofuranosidic bonds in L-arabinose-containing hemicelluloses such as arabinoxylan. AkAbf54 (the glycoside hydrolase family 54 α-L-arabinofuranosidase from Aspergillus kawachii) consists of two domains, a catalytic and an arabinose-binding domain. The latter has been named AkCBM42 [family 42 CBM (carbohydrate-binding module) of AkAbf54] because homologous domains are classified into CBM family 42. In the complex between AkAbf54 and arabinofuranosyl-α-1,2-xylobiose, the arabinose moiety occupies the binding pocket of AkCBM42, whereas the xylobiose moiety is exposed to the solvent. AkCBM42 was found to facilitate the hydrolysis of insoluble arabinoxylan, because mutants at the arabinose binding site exhibited markedly decreased activity. The results of binding assays and affinity gel electrophoresis showed that AkCBM42 interacts with arabinose-substituted, but not with unsubstituted, hemicelluloses. Isothermal titration calorimetry and frontal affinity chromatography analyses showed that the association constant of AkCBM42 with the arabinose moiety is approximately 103 M−1. These results indicate that AkCBM42 binds the non-reducing-end arabinofuranosidic moiety of hemicellulose. To our knowledge, this is the first example of a CBM that can specifically recognize the side-chain monosaccharides of branched hemicelluloses.
Design of immunogens that present the crown of the HIV-1 V3 loop in a conformation competent to generate 447-52D-like antibodies
Authors: Chakraborty Kausik , Durani Venuka , Miranda Edward Roshan , Citron Michael , Liang Xiaoping , Schleif William , Joyce Joseph G. , Varadarajan Raghavan 
Published: October 2006

gp120 is a subunit of the envelope glycoprotein of HIV-1. The third variable loop region of gp120 (V3 loop) contains multiple immunodominant epitopes and is also functionally important for deciding cell-tropism of the virus. 447-52D is a monoclonal antibody that recognizes the conserved tip of the V3 loop in a β-turn conformation. This antibody has previously been shown to neutralize diverse strains of the virus. In an attempt to generate an immunogen competent to generate 447-52D-like antibodies, the known epitope of 447-52D was inserted at three different surface loop locations in the small, stable protein Escherichia coli Trx (thioredoxin). At one of the three locations (between residues 74 and 75), the insertion was tolerated, the resulting protein was stable and soluble, and bound 447-52D with an affinity similar to that of intact gp120. Upon immunization, the V3 peptide-inserted Trx scaffold was able to generate anti-V3 antibodies that could compete out 447-52D binding to gp120. Epitope mapping studies demonstrated that these anti-V3 antibodies recognized the same epitope as 447-52D. Although the 447-52D-type antibodies were estimated to be present at concentrations of 50–400 μg/ml of serum, these were not able to effect neutralization of strains like JRFL and BAL but could neutralize the sensitive MN strain. The data suggest that because of the low accessibility of the V3 loop on primary isolates such as JRFL, it will be difficult to elicit a V3-specific, 447-52D-like antibody response to effectively neutralize such isolates.
Influence of pre-analytical and analytical factors on soluble CD40L measurements
Authors: Varo Nerea , Nuzzo Rebecca , Natal Cristina , Libby Peter , Schönbeck Uwe 
Published: October 2006

The soluble form of CD40L (CD40 ligand), a pro-atherogenic mediator, has emerged as a diagnostic and prognostic marker for cardiovascular events. However, as platelets can shed CD40L upon activation, accurate measurement has proved challenging. The present study addresses the controversy regarding the appropriate specimen and preparation for laboratory evaluation of blood sCD40L (soluble CD40L). Serum and plasma (collected in EDTA, citrate or heparin) were collected from healthy volunteers (n=20), and sCD40L was analysed by ELISA immediately or after one to three freeze–thaw cycles and at different centrifugation speeds. Urine sCD40L levels were measured in subjects with low- and high-plasma sCD40L levels. Serum sCD40L levels (5.45±4.55 ng/ml; P&lt;0.001) were higher than in citrate, EDTA or heparin plasma (1.03±1.07, 1.43±1.03 or 1.80±1.25 ng/ml respectively), with no significant differences between plasma preparations. Increasing g values (200–13000 g), which gradually deplete plasma of platelets, yielded lower sCD40L levels. Repeated freeze–thaw cycles significantly (P&lt;0.05) increased sCD40L concentrations in platelet-rich, but not platelet-depleted, plasma (up to 2.4-fold). Bilirubin and haemoglobin interfered positively, and triacylglycerols (triglycerides) and cholesterol quenched CD40L signalling. No sCD40L was detected in urine samples. In conclusion, serum yields higher sCD40L concentrations than plasma; accurate measurements of sCD40L require exclusion of platelets and avoiding their post-hoc activation. Samples with high concentrations of bilirubin, haemoglobin and/or triacylglycerols should be excluded, as these substances interfere with the assay.
Universal characteristic factors and Furstenberg averages
Authors: Ziegler Tamar 
Published: October 2006

Let

X
=
(

X
0

,

B

,
μ
,
T
)

X=(X^0,\mathcal {B},\mu ,T)

be an ergodic probability measure-preserving system. For a natural number

k
k

we consider the averages

(*)

1
N

∑

n
=
1

N

∏

j
=
1

k

f
j

(

T

a
j

n

x
)

\begin{equation*} \tag {*} \frac {1}{N}\sum _{n=1}^N \prod _{j=1}^k f_j(T^{a_jn}x) \end{equation*}

where

f
j

∈

L

∞

(
μ
)

f_j \in L^{\infty }(\mu )

, and

a
j

a_j

are integers. A factor of

X
X

is characteristic for averaging schemes of length

k
k

(or

k
k

-characteristic) if for any nonzero distinct integers

a
1

,
…
,

a
k

a_1,\ldots ,a_k

, the limiting

L
2

(
μ
)

L^2(\mu )

behavior of the averages in (*) is unaltered if we first project the functions

f
j

f_j

onto the factor. A factor of

X
X

is a

k
k

-universal characteristic factor (

k
k

-u.c.f.) if it is a

k
k

-characteristic factor, and a factor of any

k
k

-characteristic factor. We show that there exists a unique

k
k

-u.c.f., and it has the structure of a

(
k
−
1
)

(k-1)

-step nilsystem, more specifically an inverse limit of

(
k
−
1
)

(k-1)

-step nilflows. Using this we show that the averages in (*) converge in

L
2

(
μ
)

L^2(\mu )

. This provides an alternative proof to the one given by Host and Kra.
A ‘large infrequent disturbance’ in an East African savanna
Authors: Gillson Lindsey 
Published: October 2006

AbstractThere is growing interest in large infrequent disturbances (LIDs), but by definition they occur rarely and long‐term data are needed in order to study their effects and frequency. Palaeoecological records have the potential to provide information on the effects and frequency of LIDs. By comparing recent sedimentary records with known historical data, the effects of LIDs on pollen, charcoal and sedimentary sequences can be assessed. In this study, a LID in East Africa is described, and its representation in the palaeoecological record is explored. Historical records show that there was severe drought and famine in East Africa at the end of the 19th century. Fossil pollen and charcoal records from this period show evidence of a disturbance event that occurred at approximately this time. Statistical comparison of pollen and charcoal data from before, during and after the disturbance event identified it as a LID. The data also suggest that an erosion event occurred part way through the drought, indicating that an environmental threshold was exceeded.
CD80/CD28 co-stimulation in human brucellosis
Authors: Skendros P , Boura P , Kamaria F , Raptopoulou-Gigi M 
Published: October 2006

SummaryDespite treatment, 10–30% of brucellosis patients develop chronic disease, characterized by atypical clinical picture and/or relapses. A defective T helper 1 (Th1) response and a long percentage of CD4+/CD25+ cells have been described in chronic brucellosis patients. CD80/CD28 co-stimulation is critical for an efficient Th1 response and has not been studied previously in human brucellosis. In order to investigate the role of CD80/CD28 co-stimulation, 13 acute brucellosis patients (AB), 22 chronic brucellosis patients (CB, 12/22 relapsing type-CB1 and 10/22 atypical type-CB2), 11 ‘cured’ subjects and 15 healthy volunteers (controls) were studied. The percentage of CD4+/CD28+ T lymphocytes and CD14+/CD80+ monocytes were analysed by flow cytometry both ex vivo and after phytohaemagglutinin (PHA)-stimulation with or without heat-killed Brucella abortus (HkBA). Ex vivo analysis showed no differences between all groups studied. PHA stimulation up-regulated the percentage of CD80+ monocytes in AB compared to ‘cured’ subjects and controls (P &lt; 0·001), although the proportion of CD4+/CD28+ cells did not alter. A higher percentage of CD80+ monocytes was observed in the CB1 subgroup, compared to AB, ‘cured’ subjects and controls (P = 0·042, &lt; 0·001 and &lt; 0·001, respectively). CB2 was characterized by a lower percentage of CD80+ monocytes in comparison to CB1 (P = 0·020). HkBA in PHA cultures down-regulated the percentage of CD80+ monocytes compared to PHA alone in all groups, especially in AB and CB patients (P &lt; 0·001 and P = 0·007, respectively). In conclusion, the diminished percentage of CD4+/CD25+ T cells in CB is not associated with inadequate CD80/CD28 co-stimulation. We speculate that differential frequency of CD80+ monocytes after PHA stimulation could serve as a qualitative parameter of disease status, related to the different clinical forms of chronic brucellosis.
Cokriging particle size fractions of the soil
Authors: Lark R. M. , Bishop T. F. A. 
Published: October 2006

SummaryIt is often necessary to predict the distribution of mineral particles in soil between size fractions, given observations at sample sites. Because the contents in each fraction necessarily sum to 100%, these values constitute a composition, which we may assume is drawn from a random compositional variate. Elements of a D‐component composition are subject to non‐stochastic constraints; they are constrained to lie on a D– 1 dimensional simplex. This means we cannot treat them as realizations of unbounded random variables such as the multivariate Gaussian. For this reason, there are theoretical reasons not to use ordinary cokriging (or ordinary kriging) to map particle size distributions. Despite this, the compositional constraints on data on particle size fractions are not always accounted for by soil scientists.The additive log‐ratio (alr) transform can be used to transform data from a compositional variate into a form that can be treated as a realization of an unbounded random variable. Until now, while soil scientists have made use of the alr transform for the spatial prediction of particle size, there has been concern that the simple back‐transform of the optimal estimate of the alr‐transformed variables does not yield the optimal estimate of the composition. A numerical approximation to the conditional expectation of the composition has been proposed, but we are not aware of examples of its application and it has not been used in soil science.In this paper, we report two case studies in which we predicted clay, silt and sand contents of the soil at test sites by ordinary cokriging of the alr‐transformed data followed by both the direct (biased) back‐transform of the estimates and the unbiased back‐transform. We also computed estimates by ordinary cokriging of the untransformed data (which ignores the compositional constraints on the variables) for comparison.In one of our case studies, the benefit of using the alr transform was apparent, although there was no consistent advantage in using the unbiased back‐transform. In the other case study, there was no consistent advantage in using the alr transform, although the bias of the simple back‐transform was apparent. The differences between these case studies could be explained with respect to the distribution on the simplex of the particle size fractions at the two sites.
Modelling the transformations and sequestration of soil organic matter in two contrasting ecosystems of the Andes
Authors: Pansu M. , Sarmiento L. , Metselaar K. , Hervé D. , Bottner P. 
Published: October 2006

SummaryThe mechanisms linking soil respiration to climate and soil physical properties are important for modelling transformation and sequestration of C and N in the soil. We investigated them by incubating 14C and 15N labelled straw in soils of the dry puna (Bolivian altiplano, semi‐arid shrubland at 3789 m above sea level) and the humid paramo (Venezuelan tropical alpine vegetation at 3400 m). These two ecosystems of the high Andes are comparable in terms of altitude, mean temperature and land use, but are very different regarding organic matter content, rainfall patterns and soil physical properties. Total 14C and 15N, microbial‐biomass 14C and 15N, soil moisture and meteorological data were recorded over 2 years. Daily soil moisture was predicted from a water balance model. The data from the paramo site were used to calibrate MOMOS‐6, a model of organic matter decomposition based on microbial activity and requiring only kinetic constant parameters to describe: (i) inputs to microbial biomass from plant debris and microbial metabolites, and (ii) losses from the biomass by mortality and respiration (respiration coefficient and microbial metabolic quotient qCO2). The simulated qCO2–14C agrees well with qCO2–14C and qCO2 measured at the calibration site and with published data. To apply MOMOS‐6 to the puna site, only the respiration coefficient of the biomass was re‐estimated. The dynamics of 14C and 15N were very different in the two systems. In the puna, the transformation processes stop during the long dry periods, though total annual mineralization is greater than in the paramo. The change in the value of the respiration coefficient enables us to predict that the amount of C and N sequestered in the stable humus is greater in the paramo than in the puna. The data in this paper can be used to estimate values of the respiration coefficient so that MOMOS‐6 can be applied to other systems.
Visualization of root growth in heterogeneously contaminated soil using neutron radiography
Authors: Menon M. , Robinson B. , Oswald S. E. , Kaestner A. , Abbaspour K. C. , Lehmann E. , Schulin R. 
Published: October 2006

SummaryWe used neutron radiography (NR), a non‐invasive and in situ technique, to study living plant roots in soil. Plant roots have a larger water content than their unsaturated surrounding media. As water strongly attenuates a neutron‐beam, NR can identify root structures in detail. We investigated the use of NR to visualize the root growth of lupin in quartz sand and in a loamy sand field soil. Further experiments elucidated the root growth of lupin in the loamy sand heterogeneously contaminated with 10 and 20 mg kg−1 boron (B) and 100 mg kg−1 zinc (Zn). We obtained high‐quality images of root growth dynamics in both media with a resolution range of 110–270 μm. The images with quartz sand revealed fine structures such as proteoid roots that are difficult to locate in situ by other methods without destruction of the soil. Though quartz sand provided excellent visibility of roots, it proved to be a poor medium for growing plants, probably because of its bulk density (1.8 Mg m−3). The images with field soil showed normal root growth with slightly less contrast than the quartz sand. The poorer contrast was due to the greater neutron interaction with soil water and soil organic matter. In the heterogeneously contaminated soil, root growth was significantly reduced in the contaminated part of the soil in all B and Zn treatments. This study shows that NR has potential as a non‐invasive method to investigate root growth over time as well as the response of roots to various abiotic stress factors.
Transit towards floristic homogenization on oceanic islands in the south‐eastern Pacific: comparing pre‐European and current floras
Authors: Castro Sergio A. , Muñoz Mélica , Jaksic Fabian M. 
Published: October 2006

AbstractAim  To quantify the occurrence of processes of homogenization or differentiation in the vascular flora of six oceanic islands.Location  Six islands in the south‐eastern Pacific drawn from the Desventuradas Archipelago, Easter Island and the Juan Fernández Archipelago.Methods  Using published floristic studies, we determined the floristic composition of each island at two different stages: (1) pre‐European colonization and (2) current flora. We compared changes in the number of shared plants and the floristic similarity among islands for each stage.Results  The number of plant species doubled from 263 in pre‐European flora to 531 species currently. Only three native species became extinct, four natives were translocated among the islands and 271 plant species were introduced from outside. The frequency of plant species shared by two or more islands is higher in the post‐European floras than prior to European contact, and the level of floristic similarity between islands increased slightly.Main conclusions  Considering the low naturalization rate of alien plants, the small number of extinctions and the meagre increase in floristic similarity, these islands are undergoing a slow process of floristic homogenization.