bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evidence that glucokinase regulatory protein is expressed  and interacts with glucokinase in rat brain
Authors: Alvarez Elvira , Roncero Isabel , Chowen Julie A. , Vázquez Patricia , Blázquez Enrique 
Published: March 2003

AbstractOur previous description of functional glucokinase isoforms in the rat brain has opened new questions concerning the presence of glucokinase regulatory protein in the brain and the functional role of its interactions with glucokinase. In this study, we found glucokinase regulatory protein mRNA in rat brain, pancreatic islets and liver. In addition, we found two other variant splicing isoforms, both identified in hypothalamus, pancreatic islets and liver. In situ hybridization studies revealed the presence of glucokinase regulatory protein mRNA, the highest number of positive cells being found in the paraventricular nucleus of the hypothalamus. Glucokinase regulatory protein gene expression gave rise to a protein of 69 kDa mainly in nuclear and soluble cell fractions. Glutathione S‐transferase protein fused either to rat liver or human pancreatic islet glucokinase were able to precipitate glucokinase regulatory protein from liver or hypothalamic extracts in the presence of fructose‐6‐phosphate, the amount of protein co‐precipitated being decreased with fructose‐1‐phosphate. These findings suggest that the presence of glucokinase and glucokinase regulatory protein in the rat brain would facilitate the adaptation of this organ to fluctuations in blood glucose concentrations, and both proteins may participate in glucose‐sensing and metabolic regulation in the central nervous system.
Characterization of an N‐terminal secreted domain  of the type‐1 human metabotropic glutamate receptor  produced by a mammalian cell line
Authors: Selkirk Julie V. , Challiss R. A. John , Rhodes Andrew , McIlhinney R. A. Jeffrey 
Published: March 2003

AbstractA Chinese hamster ovary cell line has been established which secretes the N‐terminal domain of human mGlu1 receptor. The secreted protein has been modified to contain a C‐terminal hexa‐histidine tag and can be purified by metal‐chelate chromatography to yield a protein with an apparent molecular weight of 130 kDa. Following treatment with dithiothreitol the apparent molecular weight is reduced to 75 kDa showing that the protein is a disulphide‐bonded dimer. N‐terminal protein sequencing of both the reduced and unreduced forms of the protein yielded identical sequences, confirming that they were derived from the same protein, and identifying the site of signal‐peptide cleavage of the receptor as residue 32 in the predicted amino acid sequence. Endoglycosidase treatment of the secreted and intracellular forms of the protein showed that the latter was present as an endoglycosidase H‐sensitive dimer, indicating that dimerization is taking place in the endoplasmic reticulum. Characterization of the binding of [3H]quisqualic acid showed that the protein was secreted at levels of up to 2.4 pmol/mL and the secreted protein has a Kd of 5.6 ± 1.8 nm compared with 10 ± 1 nm for baby hamster kidney (BHK)‐mGlu1α receptor‐expressing cell membranes. The secreted protein maintained a pharmacological profile similar to that of the native receptor and the binding of glutamate and quisqualate were unaffected by changes in Ca2+ concentration.
Modulation of the GABAA‐gated chloride channel  by reactive oxygen species
Authors: Sah Renu , Galeffi Francesca , Ahrens Rebecca , Jordan Gwendolyn , Schwartz‐Bloom Rochelle D. 
Published: March 2003

AbstractThe accumulation of reactive oxygen species during cellular injury leads to oxidative stress. This can have profound effects on ionic homeostasis and neuronal transmission. γ‐Aminobutyric acid (GABA) neurotransmission is sensitive to reactive oxygen species, but most studies have indicated that this is due to alterations in GABA release. Here, we determined whether reactive oxygen species can alter GABAA receptor‐gated Cl– channels in the adult hippocampus. First, we measured the effects of hydrogen peroxide on intracellular Cl– using UV laser scanning confocal microscopy and the Cl–‐sensitive probe, 6‐methoxy‐N‐ethylquinolium iodide (MEQ). Superfusion of adult rat hippocampal slices with hydrogen peroxide for 10 min decreased MEQ fluorescence (elevation in [Cl–]i) significantly in area CA1 pyramidal cell soma. Alterations in [Cl–]i were prevented by the vitamin E analog Trolox, an antioxidant that scavenges free radicals. After exposure of slices to hydrogen peroxide, the ability of the GABA agonist muscimol to increase [Cl–]i was attenuated. To determine if GABAA receptors were sensitive to oxidative insults, the effect of hydrogen peroxide on the binding of [35S]t‐butylbicyclophosphorothionate (TBPS) to GABA‐gated Cl– channels was measured using receptor autoradiography and homogenate binding assays. Hydrogen peroxide inhibited [35S]TBPS binding in a regionally selective manner, with the greatest inhibition in cerebral cortex, hippocampus and striatum, areas␣vulnerable to oxidative stress. Similarly, xanthine and xanthine oxidase, which generate superoxide radicals, reduced [35S]TBPS binding in these regions. The effect of hydrogen peroxide on [35S]TBPS binding was non‐competitive and was prevented by Trolox and the iron chelator, deferoxamine. We conclude that reactive oxygen species may compromise GABAA‐mediated neuronal inhibition via interaction with pre and postsynaptic sites. A reduction in GABAA‐gated Cl– channel function during periods of oxidative stress may contribute to the development of neuronal damage.
Hydrocortisone decreases retinal endothelial cell water and solute flux coincident with increased content and decreased phosphorylation of occludin
Authors: Antonetti David A. , Wolpert Ellen B. , DeMaio Lucas , Harhaj Nicole S. , Scaduto Russell C. 
Published: March 2003

AbstractCorticosteroids provide an effective treatment to reduce edema for conditions in which the blood–brain or blood–retinal barrier is compromised. However, little is known about the mechanism by which these hormones affect endothelial cell function. We hypothesized that hydrocortisone would reduce transport of water and solutes across bovine retinal endothelial cell (BREC) monolayers coincident with changes to the tight junction protein occludin. Treatment of BREC with 103 nm hydrocortisone for two days significantly decreased water and solute transport across cell monolayers. Immunoblot analysis of occludin extracted in SDS or urea based buffers revealed a 1.65‐ or 2.57‐fold increase in content, respectively. A similar two‐fold increase in occludin mRNA was observed by real‐time PCR. Immunocytochemistry revealed hydrocortisone dramatically increased both occludin and ZO‐1 staining at the cell border. Additionally, 4 h of hydrocortisone treatment significantly reduced occludin phosphorylation. To our knowledge, this is the first example of a regulated decrease in occludin phosphorylation associated with increased barrier properties. In conclusion, hydrocortisone directly affects retinal endothelial cell barrier properties coincident with changes in occludin content, phosphorylation and tight junction assembly. Localized hydrocortisone therapy may be developed as a treatment option for patients suffering from retinal edema due to diabetes.
Expression of human β‐secretase in the mouse brain increases the steady‐state level of β‐amyloid
Authors: Bodendorf Ursula , Danner Simone , Fischer Frauke , Stefani Muriel , Sturchler‐Pierrat Christine , Wiederhold Karl‐Heinz , Staufenbiel Matthias , Paganetti Paolo 
Published: March 2003

Abstractβ‐Site APP‐cleaving enzyme (BACE) initiates the processing of the amyloid precursor protein (APP) leading to the generation of β‐amyloid, the main component of Alzheimer's disease senile plaques. BACE (Asp2, memapsin 2) is a type I transmembrane aspartyl protease and is responsible for the β‐secretase cleavage of APP producing different endoproteolytic fragments referred to as the carboxy‐terminal C99, C89 and the soluble ectodomain sAPPβ. Here we describe two transgenic mouse lines expressing human BACE in the brain. Overexpression of BACE augments the amyloidogenic processing of APP as demonstrated by decreased levels of full‐length APP and increased levels of C99 and C89 in vivo. In mice expressing huBACE in addition to human APP wild‐type or carrying the Swedish mutation, the induction of APP processing characterized by elevated C99, C89 and sAPPβ, results in increased brain levels of β‐amyloid peptides Aβ40 and Aβ42 at steady‐state.
Promotion of neuronal cell adhesion by members of the IgLON family occurs in the absence of either support or modification of neurite outgrowth
Authors: McNamee Christine J. , Reed James E. , Howard Mark R. , Lodge Anthony P. , Moss Diana J. 
Published: March 2003

AbstractThe IgLONs are a family of glycosyl phosphatidyl inositol‐linked cell adhesion molecules which are thought to modify neurite outgrowth and may play a role in cell–cell recognition. The family consists of LAMP, OBCAM, neurotrimin/CEPU‐1 and neurotractin/kilon. In this paper we report the effect of recombinant LAMP, CEPU‐1 and OBCAM, and transfected cell lines expressing these molecules, on the adhesion and outgrowth of dorsal root ganglion (DRG) and sympathetic neurones. CHO cells transfected with cDNA for CEPU‐1 adhered to a recombinant CEPU‐1‐Fc substrate. However, DRG or sympathetic neurones only adhered to CEPU‐1‐Fc when presented on protein A. Although DRG and sympathetic neurones express IgLONs on their surface, both types of neurones exhibited differential adhesion to CEPU‐1‐Fc, LAMP‐Fc and OBCAM‐Fc. Neither DRG nor sympathetic neurones extended neurites on a protein A/IgLON‐Fc substrate and overexpression of CEPU‐1‐GFP in DRG neurones also failed to stimulate neurite outgrowth on an IgLON‐Fc substrate. DRG neurones adhered to and extended neurites equally on transfected and non‐transfected cell lines and the recombinant proteins did not modulate the outgrowth of neurones on laminin. In contrast to previous reports we suggest that IgLONs may not have a primary role in axon guidance but may be more important for cell–cell adhesion and recognition.
Arbuscular mycorrhizal colonization increases with host density in a heathland community
Authors: Genney David R. , Hartley Sue H. , Alexander Ian J. 
Published: March 2003

Summary

The relationship is examined here between Nardus stricta root length colonized (RLC) by arbuscular mycorrhizal (AM) fungi (% RLC) and vegetation composition in a heathland community.
Two approaches were taken: a field survey of AM colonization of Nardus at two contrasting locations (Glen Clunie and Glen Shee, UK) in relation to vegetation composition; and an 11‐month bioassay of AM inoculum potential in Calluna vulgaris and Nardus swards using uncolonized Nardus transplants.
In the field survey, % RLC of Nardus was positively related to Nardus density. This relationship was strongest in Glen Clunie, probably because overall colonization levels were lower at the more fertile Glen Shee site. In the bioassay, Nardus transplants within Calluna swards developed little or no AM colonization, whereas those within Nardus swards had a mean RLC of 23%.
This is the first report that degree of AM colonization is related to host density in the field. Isolated Nardus plants in Calluna swards might be disadvantaged compared with Nardus plants in Nardus swards because of lower of AM colonization.
Substrate‐derived CO2 is important in the development of Sphagnum spp.
Authors: Smolders A. J. P. , Tomassen H. B. M. , Pijnappel H. W. , Lamers L. P. M. , Roelofs J. G. M. 
Published: March 2003

Summary

The effects of different CO2 concentrations in the acrotelm pore water on the development of Sphagnum magellanicum monoliths grown in wet conditions in the laboratory are reported here.
Decomposition processes result in much higher CO2 concentrations in bog acrotelms than atmospheric concentrations. We therefore hypothesized that this substrate‐derived carbon provides an important carbon source for Sphagnum.
S. magellanicum hummocks developed only when CO2 concentrations in the acrotelm water were high. Plants in the low CO2 treatment appeared to be carbon‐limited; they had increased nutrient concentrations and decreased ratios of carbon to other nutrients. Chlorophyll concentrations were much higher in these plants, probably allowing them to harvest more CO2, but the allocation of carbon to structural tissues was lower, resulting in weak stems that were unable to remain upright. As a result of carbon‐limitation, net biomass and height increases of the monoliths were much lower in the low CO2 treatment.
Results indicate that, at least in wet conditions, atmospheric CO2 alone is not sufficient to enable S. magellanicum to develop its normal vertical growth pattern. We conclude that the role of substrate‐derived CO2 as a carbon source for Sphagna is underestimated and requires reconsideration.
Ectomycorrhizas increase apoplastic water transport and root hydraulic conductivity in Ulmus americana seedlings
Authors: Muhsin T. M. , Zwiazek J. J. 
Published: March 2003

Summary

The extent to which water channel transport is responsible for the observed increases in root water flow of ectomycorrhizal plants is reported here.
To examine the contribution of water channel transport to root hydraulic conductance, temperatures in the range 4–20°C and mercuric chloride (HgCl2) were used to study the kinetics of water transport in ectomycorrhizal and nonmycorrhizal roots of American elm (Ulmus americana) seedlings.
Hydraulic conductance declined with decreasing temperatures in both mycorrhizal and nonmycorrhizal seedlings. However, hydraulic conductance and conductivity were higher in the mycorrhizal than the nonmycorrhizal roots at all temperatures studied. Mercuric chloride had a relatively greater impact on root hydraulic conductance in nonmycorrhizal than mycorrhizal roots and activation energy for root hydraulic conductance was significantly higher in mycorrhizal than nonmycorrhizal plants.
The results suggest that ectomycorrhizal hyphae increase hydraulic conductance of roots by decreasing water flow resistance of the apoplast rather than by water channel‐mediated transport. The high rates of hydraulic conductance at low root temperatures might be important to plants growing in cold soils and under other challenging environmental conditions that inhibit metabolism and limit water transport.
Phosphorus and the regulation of nodulation in the actinorhizal symbiosis between Discaria trinervis (Rhamnaceae) and Frankia BCU110501
Authors: Valverde Claudio , Ferrari Alejandro , Gabriel Wall Luis 
Published: March 2003

Summary

After nitrogen (N), phosphorus (P) is the nutrient that most limits plant productivity. The role of P on growth and root nodulation was studied in the actinorhizal symbiosis between Discaria trinervis and Frankia, an intercellular infected N2–fixing association.
Growth, nodulation and nutrient content (N and P) were analysed in symbiotic plants receiving different supplies of P in nutrient solutions. The relative requirement of P for nodulation was analysed in P‐deficient plants.
Nodule initiation was less impaired than general plant growth by low P. However, low P impaired nodule growth to a greater extent than plant growth. The proportion of nodule biomass, although not the number of nodules per plant, was stimulated by P supply. Autoregulation of nodulation was not affected by P. Use of N was limited by availability of P. Reserves of P in seeds were enough for the seedling to establish nodules. However nodule (and plant) growth was limited in the absence of exogenous P.
It is possible that P interacts with the feedback control of nodule growth that is associated with the plant demand for N. Leaf N : P ratio is negatively correlated with the proportion of nodule tissue.
Epicormic strand structure in Angophora, Eucalyptus and Lophostemon (Myrtaceae) – implications for fire resistance and recovery
Authors: Burrows G. E. 
Published: March 2003

Summary

Epicormic bud producing structures in the eucalypts, a large group of woody plants of considerable ecological, horticultural and silvicultural importance, are described here.
The outer portion of epicormic strands excised from the bark of large diameter stems of 18 Eucalyptus species, two Angophora species and Lophostemon confertus was examined anatomically in semithin sections.
In the inner bark each eucalypt strand usually possessed 5–12 radially orientated strips of tissue of meristematic appearance. The meristem strips were c. 30–50 µm high, 70–110 µm wide and 2000–10 000 µm long, with a lacuna above the meristem surface. Few buds or bud primordia were associated with the strands and the strands appeared to have a reduced regenerative potential in the outer bark.
In most angiosperm trees dormant epicormic buds are present in the outer bark, a position where they could be killed by fire. By contrast, in eucalypts the greatest epicormic bud initiation potential is at the level of the vascular cambium, which is protected by the maximum bark thickness. This might explain the pronounced ability of eucalypts to produce bole and branch epicormic shoots after moderate to intense fire.
Antigenemia at 10 years after diethylcarbamazine treatment of asymptomatic microfilaraemic individuals: marginal conversion to infection‐free state
Authors: Beuria M. K. , Bal M. S. , Mandal N. N. , Das M. K. 
Published: March 2003

SummaryA group of asymptomatic microfilaraemic individuals (n = 44, 29 males, 15 females) living in a Wuchereria bancrofti endemic region of Orissa, India, was treated with a standard regimen of diethylcarbamazine (12 days, 6 mg/kg) in 1990. The incidence of microfilaraemia and antigenemia (Og4C3) was determined after a gap of 10 years in 2000. Nineteen individuals reacquired microfilariae (43·2%, 11 males, eight females), five males developed hydrocele, two females became acute filarial patients and 18 subjects (13 males, five females) were asymptomatic amicrofilaraemics. Filarial antigen was detected in 36 individuals (81·2%, 27 male, nine female) comprising microfilaraemics, amicrofilaraemics and diseased. Only eight individuals (18·2%, two males, six females) remained antigen free.
H2O in metamorphism and unexpected behaviour in the preservation of metamorphic mineral assemblages
Authors: Guiraud M. , Powell R. , Rebay G. 
Published: March 2003

AbstractThe preservation of mineral assemblages that were fluid‐present during their prograde history is primarily related to the consumption of the fluid by growth of more hydrous minerals as the retrograde history begins. The range of behaviour relating to the preservation of mineral assemblages is examined using calculated phase diagrams for fluid‐saturated conditions, contoured for the H2O content of the mineral assemblage. At equilibrium, as a mineral assemblage crosses contours of decreasing H2O content along a pressure–temperature path, it dehydrates, the fluid being lost from the rock. If the assemblage crosses contours of increasing H2O content, the mineral assemblage starts to rehydrate using any fluid on its grain boundaries. When the rock has consumed its fluid, the resulting mineral assemblage is that preserved in the rock. Conditions relating to the preservation of mineral assemblages are discussed, and examples of the consequences of different pressure–temperature paths on preservation in a metapelitic and a metabasic rock composition are considered on phase diagrams calculated with thermocalc.
Chromium and manganese zoning in pelitic garnet and kyanite: Spiral, overprint, and oscillatory (?) zoning patterns and the role of growth rate
Authors: Yang P. , Rivers T. 
Published: March 2003

AbstractX‐ray composition maps and quantitative analyses for Mn, Ca and Cr have been made for six pelitic and calc‐pelitic garnet crystals and Al, Fe and Cr analyses maps have been made for two kyanite crystals, from lower and mid/upper amphibolite facies rocks from the Grenville Province of western Labrador, using an electron microprobe analyser and a laser ablation ICP‐MS. Garnet with spiral (‘snowball’) internal fabrics (Si) has spiral zoning in major elements, implying that growth was concentrated in discrete regions of the crystal at any one time (spiral zoning). Cr zoning is parallel to Si in low amphibolite facies garnet with both straight and spiral internal fabrics, indicating that the garnet overprinted a fabric defined by Cr‐rich (mica±chlorite±epidote) and Cr‐poor (quartz±plagioclase) layers during growth (overprint zoning) and that Cr was effectively immobile. In contrast, in mid/upper amphibolite facies garnet porphyroblasts lacking Si, Cr zoning is concentric, implying that Cr diffusion occurred. Cr zoning in kyanite porphyroblasts appears superficially similar to oscillatory zoning, with up to three or four annuli of Cr enrichment and/or depletion present in a single grain. However, the variable width, continuity, Cr concentration and local bifurcation of individual annuli suggest that an origin by overprint zoning may be more likely. The results of this study explain previously observed nonsystematic Cr zoning in garnet and irregular partitioning of Cr between coexisting metamorphic mineral pairs. In addition, this study points to the important role of crystal growth rate in determining the presence or absence of inclusions and the type of zoning exhibited by both major and trace elements. During fast growth, inclusions are preferentially incorporated into the growing porphyroblast and slow diffusing elements such as Cr are effectively immobile, whereas during slow growth, inclusions are not generally included in the porphyroblast and Cr zoning is concentric.