bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oxygen dynamics during submergence in the halophytic stem succulentHalosarcia pergranulata
Authors: PEDERSEN O. , VOS H. , COLMER T. D. 
Published: May 2006

ABSTRACTThis study elucidated O2dynamics in shoots and roots of submergedHalosarcia pergranulata(Salicornioideae), a perennial halophytic stem succulent that grows on flood‐prone mudflats of salt lakes. Oxygen within shoots and roots was measured using microelectrodes, for plants when waterlogged or completely submerged, with shoots in light or in darkness, in a controlled environment. Net photosynthesis (PN) when underwater, at a range of dissolved CO2concentrations, was measured by monitoring O2production rates by excised stems. The bulky nature and apparently low volume of gas‐filled spaces of the succulent stems resulted in relatively high radial resistance to gas diffusion. At ambient CO2, quasi‐steady state rates ofPNby excised succulent stems were estimated to be close to zero; nevertheless, in intact plants, underwater photosynthesis provided O2to tissues and led to radial O2loss (ROL) from the roots, at least during the first several hours (the time period measured) after submergence or when light periods followed darkness. The influence of light on tissue O2dynamics was confirmed in an experiment on a submerged plant in a salt lake in south‐western Australia. In the late afternoon, partial pressure of O2(pO2) in the succulent stem was 23.2 kPa (i.e. ∼10% above that in the air), while in the roots, it was 6.2–9.8 kPa. Upon sunset, the pO2in the succulent stems declined within 1 h to below detection, but then showed some fluctuations with the pO2increasing to at most 2.5 kPa during the night. At night, pO2in the roots remained higher than in the succulent stems, especially for a root with the basal portion in the floodwater. At sunrise, the pO2increased in the succulent stems within minutes. In the roots, changes in the pO2lagged behind those in the succulent stems. In summary, photosynthesis in stems of submerged plants increased the pO2in the shoots and roots so that tissues experience diurnal changes in the pO2, but O2from the H2O column also entered submerged plants.
Canine Spinal Cord Neuron and Axon Myelin Sheath Morphometry
Authors: De Francischini Carvalho A. C. , Pacheco M. R. , Baraldi Artoni S. M. , Mateus O. 
Published: May 2006

SummaryThis inedited morphometric study has been developed from healthy canine spinal cord neuron cytoplasm and nucleus, and white matter axonal myelin sheath, from cervical, thoracic and lumbar regions. For the morphometric study, the parameters were area, perimeter, maximum and minimum diameters and roundness for neurons and myelin thickness for axon. For each parameter, 300 neurons were analysed. The results revealed that lumbar neurons had the highest mean values for the analysed parameters, indicating the presence of large neurons in this region, with large axons as a result of myelin thickness, which is proportional to axon calibre. We conclude that these morphometric results can contribute for the establishment of normal patterns, for canine spinal cord cervical, thoracic and lumbar segments.
Quantification by Image Analysis of the Gallus gallus Lung Elastic Fibres from Embryonic to Adult Birds
Authors: De Lurdes Pinto M. , Gonçalves C. , Rodrigues P. , Bairos V. A. 
Published: May 2006

SummaryThe organization of the lung's elastic fibres is amazingly uniform in all vertebrates, with the possible exception of birds, whose pulmonary architecture and air movement are unique. The overall goal of this work was to study and quantify elastic fibre distribution patterns and relative amounts in the parabronchi, during the incubation period until the 42nd day after hatching. Chick embryo lungs were examined on the 14th, 16th, 18th and 20th days of incubation and chick lungs on the 1st, 2nd, 7th, 14th, 35th and 42nd days after hatching. Four animals were used daily, and the observations were randomly performed on both lungs. A morphometric study was carried out focusing on the computerized image analysis of histological sections stained according to a modified Gomori technique. The values obtained for each day result from the observation and processing of 20 images. Complementary studies were performed using transmission electron microscopy, as on the 14th embryonic day the fibres were not visible on light microscopy. The results show that the area occupied by the elastic fibres increases gradually from the 16th day of incubation up till the 7th day after hatching and decreases slowly in the following days of the study. A prominent increase takes place before hatching, which points out to the adequate and essential structural roles played by the elastic fibres in the pulmonary maturation process.
Can low densities of carnivores result in genetic depletion? An investigation within French polecat populations
Authors: Lodé T. 
Published: May 2006

SummaryCarnivores as top predators are commonly found in relatively low densities even in optimal habitats. Despite a lack of empirical studies, it could be suspected that long‐term low density could result in genetic depletion. The genetic structure of European polecatMustela putoriusnatural populations was investigated by allozyme electrophoresis in five distinct areas. Density estimates significantly differed among sites from 0.17 to 0.83 individuals/km2with an average of 0.56 individuals per km2, resulting in a scattered distribution. Genetic structure varied among distinct populations both in number of polymorphic loci and heterozygosity. Polecats from Brittany revealed a very low observed heterozygosity (HO = 0.028) whereas mean heterozygosity reachedHO = 0.072 in Brière. That the lowest heterozygosity levels and highest inbreeding coefficientFISwere significantly associated with the lowest densities suggests that low densities may affect populations of carnivores. Both the loss of polymorphic loci and the reduction in heterozygosity rates suggest a density‐dependent effect and population density can be arguably regarded as a factor affecting genetic diversity in top carnivores.
Molecular Characterization of the Rice Pathogenesis‐related Protein, OsPR‐4b, and Its Antifungal Activity Against Rhizoctonia solani
Authors: Zhu T. , Song F. , Zheng Z. 
Published: May 2006

AbstractWe cloned and identified a new rice pathogenesis‐related (PR)‐4 gene, OsPR‐4b. OsPR‐4b encodes a 151 amino acid protein with a predicted molecular mass of 16.47 kDa and pI of 4.42. The putative OsPR‐4b shows high similarity to PR‐4 type proteins from various plant species and belongs to the Barwin family. Like other PR‐4s from monocot plants, OsPR‐4b contains a conserved Barwin domain and has a signal peptide at its N‐terminus. Recombinant OsPR‐4b protein expressed in Escherichia coli showed antifungal activity in vitro against the sheath blight fungus, Rhizoctonia solani. The results suggest that the OsPR‐4b may play a role in the disease resistance responses of rice against pathogen attacks through its antifungal activity.
Fellow eye of patients with retinal detachment associated with macular hole and bilateral high myopia
Authors: Tsujikawa Akitaka , Kikuchi Masashi , Ishida Kazuhiro , Nonaka Atsushi , Yamashiro Kenji , Kurimoto Yasuo 
Published: May 2006

AbstractPurpose:  To estimate the risk of retinal detachment in the fellow eye of patients with bilateral high myopia who had retinal detachment associated with macular hole (MH‐RD) in one eye.Methods:  The present study examined retrospectively 56 patients with bilateral high myopia who had MH‐RD. To determine the incidence of involvement of the fellow eye, patients who completed a follow up of 12 months or longer were eligible for the current study.Results:  Of 56 patients with MH‐RD due to high myopia, 54 had unilateral detachment at presentation and two had bilateral detachment. Of the 54 highly myopic fellow eyes without retinal detachment at presentation, 37 eyes underwent 12 or more months of documented follow up. Mean follow up after initial surgery to the primary eye was 6.5 ± 4.9 years. During follow up, a macular hole without retinal detachment was noted in one (2.7%) of these 37 eyes. Three other eyes (8.1%) had MH‐RD at 1, 2 and 7 years, respectively, after the initial surgery to the primary eye. At the final visit, 12 eyes (32%) had visual acuity of ≥6/9, whereas 12 eyes (32%) had visual acuity of ≤6/60.Conclusions:  When patients with bilateral high myopia have MH‐RD in one eye, they would be expected to be at increased risk of retinal detachment in the fellow eye.
Notch controls proliferation and differentiation of stem cells in a dose‐dependent manner
Authors: Guentchev Marin , McKay Ronald D. G. 
Published: May 2006

AbstractSelf‐renewal and differentiation of CNS stem cells are regulated by still poorly understood cell–cell interactions. Notch is a well‐known cell surface protein that can promote both cell cycle progression and mitotic arrest but the molecular mechanism controlling these opposite effects is unknown. Here we demonstrate that, in CNS stem cells, the level of active Notch1 determines the cellular response. Specifically, low levels of the active form of Notch1 promote proliferation whereas high levels lead to growth arrest. Here we provide the first evidence that Notch effects on proliferation and differentiation are a function of dose, and propose a hypothesis on how oncogenes may also act as tumor suppressors.
Oxidative modulation of the transient potassium current IA by intracellular arachidonic acid in rat CA1 pyramidal neurons
Authors: Angelova Plamena , Müller Wolfgang 
Published: May 2006

AbstractOxidative stress affects cellular membrane lipids and proteins. Using whole‐cell patch‐clamp recording we demonstrate differential oxidative inhibition of voltage‐gated transient (IA) and delayed rectifier [IK(V)] K+ currents by arachidonic acid (AA) and H2O2 in CA1 neurons in hippocampal slice. We show that intracellular application of 1 pm AA or its non‐metabolizable analog eicosatetraynoic acid (100 pm) reduced IA by ∼42% but did not affect IK(V). AA shifted the voltage dependence of steady‐state inactivation of IA by 12 mV to more negative potentials whereas the rate of inactivation was unchanged. Surprisingly, intracellular glutathione (GSH, 20 mm) enhanced the effect of AA on maximal IA (−62%) and with AA slowed inactivation of IA. The combination of GSH and extracellular ascorbate (0.4 mm) prevented reduction of IA by AA. Intracellular Trolox (a vitamin E analog, 10 µm) reduced IA by 61%and IK(V) by 39%. Like AA, intracellular Trolox caused a 10‐mV left shift of IA steady‐state inactivation but Trolox and AA did not cause a shift when coapplied. Extracellular Trolox (100 µm) had no effects on IA. H2O2 (80 µm) reduced both IA and IK(V) in a GSH‐ and ascorbate‐sensitive manner and slowed the rate of inactivation of IA by a factor of 2. Coapplication of H2O2 with GSH and extracellular ascorbate caused ∼22 mV negative shifts of both steady‐state inactivation and activation. We conclude that AA is extremely potent in affecting IA by oxidative modifications. Antioxidants can augment these effects, probably by catalysis of the underlying reactions between oxidants and IA channel proteins.
The light‐activated signaling pathway in SCN‐projecting rat retinal ganglion cells
Authors: Warren Erin J. , Allen Charles N. , Brown R. Lane , Robinson David W. 
Published: May 2006

AbstractIn mammals, the master circadian clock resides in the suprachiasmatic nuclei (SCN) of the hypothalamus. The period and phase of the circadian pacemaker are calibrated by direct photic input from retinal ganglion cells (RGCs). SCN‐projecting RGCs respond to light in the absence of rod‐ and cone‐driven synaptic input, a property for which they are termed intrinsically photosensitive. In SCN‐projecting RGCs, light activates a nonselective cationic current that displays inward and outward rectification. The goal of the present study was to investigate the identity of the light‐activated ion channel and the intracellular signaling pathway leading to its activation. We considered two candidate channels, cyclic nucleotide‐gated (CNG) channels and transient receptor potential (TRP) channels, which mediate vertebrate and invertebrate phototransduction, respectively. We report that the intrinsic light response relies upon a G‐protein‐dependent process. Although our data indicate that cyclic nucleotides modulate the signaling pathway, CNG channels do not appear to conduct the light‐activated current because (i) cyclic nucleotides in the pipette solution do not activate a conductance or completely block the light response, (ii) CNG channel blockers fail to inhibit the light response, (iii) the effects of internal and external divalent cations are inconsistent with their effects on CNG channels, and (iv) immunohistochemistry reveals no CNG channels in SCN‐projecting RGCs. Finally, we show that the pharmacology of the light‐activated channel resembles that of some TRPC channel family members; the response is blocked by lanthanides and ruthenium red and SK&F 96365, and is enhanced by flufenamic acid and 1‐oleoyl‐2‐acetyl‐sn‐glycerol. Furthermore, immunohistochemical experiments reveal that TRPC6 is expressed in many RGCs, including those that express melanopsin.
NMDA receptors and the differential ischemic vulnerability of hippocampal neurons
Authors: Gee Christine E. , Benquet Pascal , Raineteau Olivier , Rietschin Lotty , Kirbach Sebastian W. , Gerber Urs 
Published: May 2006

AbstractTransient cerebral ischemia causes an inhomogeneous pattern of cell death in the brain. We investigated mechanisms, which may underlie the greater susceptibility of hippocampal CA1 vs. CA3 pyramidal cells to ischemic insult. Using anin vitrooxygen–glucose deprivation (OGD) model of ischemia, we found thatN‐methyl‐d‐aspartate (NMDA) responses were enhanced in the more susceptible CA1 pyramidal cells and transiently depressed in the resistant CA3 pyramidal cells. The long‐lasting potentiation of NMDA responses in CA1 cells was associated with delayed cell death and was prevented by blocking tyrosine kinase‐dependent up‐regulation of NMDA receptor function. In CA3 cells, the energy deprivation‐induced transient depression of NMDA responses was converted to potentiation by blocking protein phosphatase signalling. These results suggest that energy deprivation differentially shifts the intracellular equilibrium between the tyrosine kinase and phosphatase activities that modulate NMDA responses in CA1 and CA3 pyramidal cells. Therapeutic modulation of tyrosine phosphorylation may thus prove beneficial in mitigating ischemia‐induced neuronal death in vulnerable brain areas.
Microbial diversity in alpine tundra wet meadow soil: novel Chloroflexi from a cold, water‐saturated environment
Authors: Costello Elizabeth K. , Schmidt Steven K. 
Published: May 2006

SummaryCold, water‐saturated soils play important biogeochemical roles, yet almost nothing is known about the identity and habitat of microbes active under such conditions. We investigated the year‐round microenvironment of an alpine tundra wet meadow soil in the Colorado Rocky Mountains, focusing on the biogeochemistry and microbial diversity of spring snowmelt – a dynamic time for alpine ecosystems.In situmeasurements revealed spring and autumn periods of long‐term temperature stability near 0°C, and that deeper soil (30 cm) was more stable than surface soil, with more moderate summers and winters, and longer isothermal phases. The soil was saturated and water availability was limited by freezing rather than drying. Analyses of bioavailable redox species showed a shift from Mn reduction to net Fe reduction at 2–3 cm depth, elevated SO42–and decreased soluble Zn at spring snowmelt. Terminal restriction fragment length polymorphism profiles detected a correlated shift in bacterial community composition at the surface to subsurface transition. Bacterial and archaeal small‐subunit rRNA genes were amplified from saturated spring soil DNA pooled along a depth profile. The most remarkable feature of these subsurface‐biased libraries was the high relative abundance of novel, uncultivated Chloroflexi‐related sequences comprising the third largest bacterial division sampled, and representing seven new Chloroflexi subdivisions, thereby dramatically expanding the known diversity of this bacterial division. We suggest that these novel Chloroflexi are active at near −0°C temperatures, under likely anoxic conditions, and utilize geochemical inputs such as sulfide from upslope weathering.
A comparison of stable‐isotope probing of DNA and phospholipid fatty acids to study prokaryotic functional diversity in sulfate‐reducing marine sediment enrichment slurries
Authors: Webster Gordon , Watt Lynsey C. , Rinna Joachim , Fry John C. , Evershed Richard P. , Parkes R. John , Weightman Andrew J. 
Published: May 2006

SummaryMarine sediment slurries enriched for anaerobic, sulfate‐reducing prokaryotic communities utilizing glucose and acetate were used to provide the first comparison between stable‐isotope probing (SIP) of phospholipid fatty acids (PLFA) and DNA (16S rRNA and dsrA genes) biomarkers. Different 13C‐labelled substrates (glucose, acetate and pyruvate) at low concentrations (100 µM) were used over a 7‐day incubation to follow and identify carbon flow into different members of the community. Limited changes in total PLFA and bacterial 16S rRNA gene DGGE profiles over 7 days suggested the presence of a stable bacterial community. A broad range of PLFA were rapidly labelled (within 12 h) in the 13C‐glucose slurry but this changed with time, suggesting the presence of an active glucose‐utilizing population and later development of another population able to utilize glucose metabolites. The identity of the major glucose‐utilizers was unclear as 13C‐enriched PLFA were common (16:0, 16:1, 18:1ω7, highest incorporation) and there was little difference between 12C‐ and 13C‐DNA 16S rRNA gene denaturing gradient gel electrophoresis (DGGE) profiles. Seemingly glucose, a readily utilizable substrate, resulted in widespread incorporation consistent with the higher extent of 13C‐incorporation (∼10 times) into PLFA compared with 13C‐acetate or 13C‐pyruvate. 13C‐PLFA in the 13C‐acetate and 13C‐pyruvate slurries were similar to each other and to those that developed in the 13C‐glucose slurry after 4 days. These were more diagnostic, with branched odd‐chain fatty acids (i15:0, a15:0 and 15:1ω6) possibly indicating the presence of Desulfococcus or Desulfosarcina sulfate‐reducing bacteria (SRB) and sequences related to these SRB were in the 13C‐acetate‐DNA dsrA gene library. The 13C‐acetate‐DNA 16S rRNA gene library also contained sequences closely related to SRB, but these were the acetate‐utilizing Desulfobacter sp., as well as a broad range of uncultured Bacteria. In contrast, analysis of DGGE bands from 13C‐DNA demonstrated that the candidate division JS1 and Firmicutes were actively assimilating 13C‐acetate. Denaturing gradient gel electrophoresis also confirmed the presence of JS1 in the 13C‐DNA from the 13C‐glucose slurry. These results demonstrate that JS1, originally found in deep subsurface sediments, is more widely distributed in marine sediments and provides the first indication of its metabolism; incorporation of acetate and glucose (or glucose metabolites) under anaerobic, sulfate‐reducing conditions. Here we demonstrate that PLFA‐ and DNA‐SIP can be used together in a sedimentary system, with low concentrations of 13C‐substrate and overlapping incubation times (up to 7 days) to provide complementary, although not identical, information on carbon flow and the identity of active members of an anaerobic prokaryotic community.
Risk Preference and Employment Contract Type
Authors: Brown Sarah , Farrell Lisa , Harris Mark N. , Sessions John G. 
Published: May 2006

SummaryWe explore the possibility that a systematic relationship exists between employment within a particular type of contract and risk preference. We exploit a set of proxies for risk preference, whereby some of the proxies capture risk loving behaviour (expenditure on gambling, smoking and alcohol) whereas others capture risk averse behaviour (expenditure on life and contents insurance, and unearned income). The empirical analysis, based on pooled cross-section data from the UK Family Expenditure Survey, 1997–2000, provides evidence of a systematic relationship between employment contract type and risk preference, with, for example, self-employed workers being more or less likely to engage in the consumption of ‘risky’ or financial security products respectively. The results are based on the ordered generalized extreme value model, a relatively infrequently used discrete choice model, which allows for ordering and correlation in the alternatives observed.
QTL Mapping Under Ascertainment
Authors: Peng J. , Siegmund D. 
Published: May 2006

SummaryMapping quantitative trait loci (QTL) using ascertained sibships is discussed. It is shown that under the standard normality assumption of variance components analysis the efficient scores are unchanged by ascertainment, and two different schemes of ascertainment correction suggested in the literature are asymptotically equivalent. The use of conditional maximum likelihood estimators derived under the normality assumption to estimate nuisance parameters is shown to result in only a small loss of power compared to the case of known parameters, even when the distribution of phenotypes is non‐normal and/or the ascertainment criterion is ill defined.
Forms and functions of school refusal behavior in youth: an empirical analysis of absenteeism severity
Authors: Kearney Christopher A. 
Published: May 2006

Background:  School refusal behavior is a particularly nettlesome problem for mental health and education professionals because of its symptom severity and heterogeneity as well as lack of consensus regarding inclusive classification strategies. Alternatively, a functional model of school refusal behavior may provide a particularly useful way of organizing, assessing, and treating this population.Method:  The present study included 222 youths aged 5–17 years (134 males, 88 females) with school refusal behavior and their parents. Participants were assessed at a specialized university‐based clinic for youths with school refusal behavior. Child self‐report and parent‐based measures of forms of behavior related to school refusal as well as functions of school refusal behavior were employed.Results:  Hierarchical regression analysis and structural equation modeling revealed that function was a better determinant of degree of school absenteeism than behavior form.Conclusions:  Assessing the function of school refusal behavior is likely a key factor in the evaluation of this population and may be linked to informed decisions about choice of treatment.