bluuebunny/crossref_metadata_2025_split huggingface dataset:
A microelectrochemical technique to measure trans‐plasma membrane electron transport in plant tissue and cells in vivo
Authors: Taylor A. R. , Chow R. H. 
Published: March 2003

AbstractA novel electrochemical technique was developed to enable high‐resolution measurements of trans‐plasma membrane reductase activity in vivo in growing plant tissue and single cells. Carbon fibre microelectrodes (CFMEs) with a tip diameter of 5 µm were used for electrochemical mapping of the reduction of the external impermeant electron acceptor ferricyanide along the root tip surface of 4‐d‐old maize seedlings. Ferricyanide reduction was detected in all locations along the first 12 mm of the growing root apex. However, a distinct peak in activity was detected at the proximal end of the elongation zone (1·5–4·5 mm from the apex), where reductase activity was three times greater than in more apical or distal regions. The inhibition of the ferricyanide reduction at all locations along the growing apex, by the vitamin K antagonists warfarin and dicumarol, supports previous data showing that electron transfer by the constitutive trans‐plasma membrane reductase is achieved via a quinone shuttle. We demonstrate that in addition to their utility in whole‐tissue/‐organ studies, CFMEs are sensitive enough to monitor trans‐plasma membrane electron transport in single cells.
Analysis of the O2 dependency in leaf‐level photosynthesis of two Reynoutria japonica populations growing at different altitudes
Authors: Sakata T. , Yokoi Y. 
Published: March 2003

AbstractTo examine the effects of decreased CO2 and O2 partial pressure on leaf‐level photosynthesis in alpine plants at high altitude, we compared the maximal carboxylation efficiency, CE, of Reynoutria japonica Houtt. var. japonica growing in a highland with one growing in a lowland. CE under the native atmospheric conditions (native CE) of the highland population was significantly lower than that of the lowland one. The O2 dependency of CE was significantly less in the highland population than in the lowland. Using theoretical analysis, we explained that O2 dependency of leaf‐level photosynthesis became less as internal conductance (gi) decreased. We also showed that gi and the content of active Rubisco (E) could be estimated from the O2 dependency of leaf‐level photosynthesis. By applying the analysis, a severe limitation of CO2 diffusion in the leaf was estimated in the highland population, whereas almost the same values of E were estimated in both populations. A reasonable explanation for the difference in the native CE is the smaller O2 dependency and photosynthetic capacity caused by a smaller gi in the highland population in addition to the differences in the partial pressures of CO2 and O2.
Differential regional brain growth and rotation of the prenatal human tentorium cerebelli
Authors: Jeffery Nathan 
Published: March 2003

AbstractFolds of dura mater, the falx cerebri and tentorium cerebelli, traverse the vertebrate endocranial cavity and compartmentalize the brain. Previous studies suggest that the tentorial fold has adopted an increasingly important role in supporting the increased load of the cerebrum during human evolution, brought about by encephalization and an adaptation to bipedal posture. Ontogenetic studies of the fetal tentorium suggest that its midline profile rotates inferoposteriorly towards the foramen magnum in response to disproportionate growth of the cerebrum. This study tests the hypothesis that differential growth of the cerebral and cerebellar components of the brain underlies the inferoposterior rotation of the tentorium cerebelli during human fetal development. Brain volumes and tentorial angles were taken from high‐resolution magnetic resonance images of 46 human fetuses ranging from 10 to 29 gestational weeks. Apart from the expected increases of both supratentorial and infratentorial brain volumes with age, the results confirm previous studies showing a significant relative enlargement of the supratentorial volume. Correlated with this enlargement was a rotation of the midline section of the tentorium towards the posterior cranial base. These findings support the concept that increases of supratentorial volume relative to infratentorial volume affect an inferoposterior rotation of the human fetal tentorium cerebelli. These results are discussed in the context of the role played by the tentorium cerebelli during human evolution and underline implications for phylogenetic and ontogenetic models of encephalization.
Age‐specific breeding probability in black brant: effects of population density
Authors: Sedinger James S. , Lindberg Mark S. , Chelgren Nathan D. 
Published: March 2003

SummaryWe estimated age‐specific probability of breeding for black brant (Branta bernicla nigricansLawrence) (hereafter brant) at the Tutakoke River Colony, Alaska, during a series of years in which local breeding density and juvenile mortality both increased. We use these analyses to examine demographic responses to increased population density.Estimates of breeding probability were based on Kendall & Nichols (1995) full‐likelihood modification of Pollock’s (1982) robust design applied to observations of uniquely colour‐banded brant.Breeding probability varied with female age but not across years, indicating lack of response to increased population density. Annual probability of breeding increased from 0·67 ± 0·042 for 2‐year‐old females to 0·90 ± 0·024 for females 5 years old or older.Annual breeding probability of males ≥ 5 years old was 0·78 ± 0·03. Lower breeding probability of males compared to females probably reflects dispersal of males whose mates died.Lower juvenile survival appears to be a general response to increased density in large herbivorous birds and mammals, while changes in adult survival and reproductive investment may be more variable.
Non‐parametric modelling of non‐linear density dependence: a three‐species host–parasitoid system
Authors: Kristoffersen A. B. , Lingjærde O. C. , Stenseth N. CHR. , Shimada M. 
Published: March 2003

Summary

Time‐series data from a twice‐replicated population experiment (consisting of a seed beetle (host), Callosobruchus chinensis, and two parasitoids, Anisopteromalus calandrae and Heterospilus prosopidis) were studied in order to identify and to estimate the density‐dependent structure.
A non‐parametric host–parasitoid model based on the Nicholson–Bailey model, was studied through non‐parametric autoregressive modelling. An additive non‐linear structure was found in the population growth/parasitism rates for all three species.
The analysis suggests that the abundance of A. calandrae only weakly affects its own parasitism rate as well as H. prosopidis parasitism rate.
The analysis also suggests that the net population growth rate of C. chinensis is highly non‐linear, which may be due to disproportionately higher egg mortality at high adult densities.
Non‐linearity was also demonstrated in the parasitism rate of H. prosopidis, which is consistent with assuming that the density‐dependent mutual interference becomes disproportionately higher at high H. prosopidis adult densities.
Effects of season and fire on the diversity of hypogeous fungi consumed by a tropical mycophagous marsupial
Authors: Vernes Karl , Castellano Michael , Johnson Christopher N. 
Published: March 2003

Summary

Despite the importance of fire in many natural systems, knowledge of how fire affects the relationship between hypogeous fungi and mycophagous mammals in fire‐prone environments is limited. Using experimental fires, we examined consumption of hypogeous ectomycorrhizal fruit‐bodies by an endangered tropical mycophagist, the northern bettong Bettongia tropica Wakefield, in north‐eastern Australia.
Fungus was the major dietary component (56%) throughout all seasons, both before and after fire. At least 35 hypogeous taxa were consumed. Number of taxa consumed during different seasons was similar, but was significantly higher on unburnt sites than on burnt sites. Similarly, diversity of taxa per faecal sample was significantly greater on unburnt sites, but also increased irrespective of fire from wet season to dry season.
Cluster and principal component analyses were used to examine patterns in consumption of fungal taxa. The greatest differences in dietary composition were between the period immediately after fire on burnt sites (early wet season) and all other season and treatment combinations. This difference was due to increased consumption of taxa in the fire‐adapted family Mesophelliaceae and reduced consumption of the genus Elaphomyces. Principal component analysis revealed two major gradients in consumption. The first accounted for 32% of total variance and described change in consumption of taxa with season. The second accounted for 24% of total variance and described change in consumption of taxa before and after fire.
Despite taxon‐specific changes in consumption of hypogeous fungi, the body condition of bettongs did not change significantly between seasons or in relation to fire, suggesting that bettongs were never compromised in their optimal fungal intake.
Our data show that the northern bettong has a flexible response to fire and could be best thought of as a fire‐adapted marsupial. We therefore propose a precautionary approach to fire management of bettong habitat; at the present time this would include maintaining the recent fire regime of low to moderately intense fires every 3–4 years.
Growth strategies of a shade‐tolerant tropical tree: the interactive effects of canopy gaps and simulated herbivory
Authors: Blundell Arthur G. , Peart David R. 
Published: March 2003

Summary

We hypothesized that the survival of shade‐tolerant juvenile trees in the understorey depends on allocation strategies that slow their growth but enhance recovery from herbivore damage. In contrast, allocation patterns should maximize height growth in gaps where competitors grow rapidly. We tested the interactive effects of canopy gaps and simulated herbivory (by removing the apical meristem, or 10%, 50% or 90% of tissue from all leaves) on juvenile (< 1 cm diameter at breast height) Shorea quadrinervis Sloot (Dipterocarpaceae), a dominant canopy tree in Borneo.
Damage did not diminish survival over 8 months, except for 90% foliage removal from understorey plants.Height growth in the understorey was negligible in both control and damaged plants. In gaps, height growth was stimulated by removal of either the apical meristem or 10% of leaf tissue; growth was reduced only after 90% foliage removal.
Higher damage levels increased subsequent net leaf loss. Leaf production was much greater, but leaf retention much lower, in gaps than in the understorey. Ninety per cent foliage removal drastically reduced production in gaps and retention in the understorey. After 10% defoliation, height growth was enhanced in gaps despite approximately 30% net leaf loss.
In a separate experiment, juveniles were moved from a shade house to gaps. After 8 months, gap plants had more leaves and more total biomass, but only half the root : shoot ratio of plants left in the shade.
Allocation patterns, together with the survival of understorey plants after all but the highest levels of damage, indicate that root : shoot allocation there tends to reduce the risk of mortality following herbivore or mechanical damage at the expense of growth. In contrast, in gaps, where interference competition for light is high, resource allocation apparently maximizes height growth.The interaction between resource availability and herbivore damage provides the basis for a more synthetic theory of resource allocation and growth strategies than one based on resource availability alone.
Patterns of vegetation change and the recovery potential of degraded areas in a coastal marsh system of the Hudson Bay lowlands
Authors: Handa I. T. , Harmsen R. , Jefferies R. L. 
Published: March 2003

SummaryIn recent decades, foraging by increasing numbers of lesser snow geese has led to loss of vegetation and changes in soil conditions in marshes on the Hudson Bay coast.Changes in species composition were recorded in areas unprotected from goose foraging and in exclosures of varying age (5–15 years) erected in intact swards and on bare sediments where foraging had occurred at La Pérouse Bay, Manitoba.In the supratidal marsh, plants failed to establish naturally in either open or exclosed (15 years) plots in bare areas. In moist intertidal soils, vegetative fragments of the asexual speciesPuccinellia phryganodesreadily established and formed a mat in exclosures (5 years).Changes in species assemblages occurred over 11 years in exclosed and adjacent open plots in intertidal and supratidal marshes. Loss of vegetation cover and species richness, particularly dicotyledonous species, and the reversion of later successional plant assemblages to earlier successional assemblages occurred in open plots. In the absence of foraging, late successional graminoids and willow species replaced early successional graminoids.Late successional grasses of the upper intertidal marsh died when transplanted into degraded soils but still survived after one season in control plots, suggesting that an early successional template is needed for establishment.In the absence of goose foraging, natural re‐vegetation by clonal propagation can occur only where edaphic conditions are suitable. Within exclosures, vegetation changes resemble those in undamaged areas where goose foraging pressure is still moderate. We propose a state and transition model for vegetation change in the system based on succession patterns, alternative vegetation states and geomorphological events.
Differential expression of inflammation‐ and apoptosis‐related genes in spinal cords of a mutant SOD1 transgenic mouse  model of familial amyotrophic lateral sclerosis
Authors: Yoshihara Tsuyoshi , Ishigaki Shinsuke , Yamamoto Masahiko , Liang Yideng ,   Jun, Niwa Ichi , Takeuchi Hideyuki , Doyu Manabu , Sobue Gen 
Published: March 2003

AbstractFamilial amyotrophic lateral sclerosis (FALS)‐linked mutations in copper–zinc superoxide dismutase (SOD1) cause motor neuron death through one or more acquired toxic properties. We analyzed the molecular mechanism underlying motor neuron degeneration in the transgenic mouse model expressing the SOD1 gene with G93A mutation. Using cDNA microarray, the differentially expressed genes were identified in the spinal cords of G93A mice, 30 being elevated and seven decreased. cDNA microarray analysis to monitor gene expression during neurodegeneration revealed an up‐regulation of genes related to an inflammatory process, such as the tumor necrosis factor‐α (TNF‐α) gene, resulting from glial cell activation, together with the change in apoptosis‐related gene expression, such as caspase‐1. The increased expression of the inflammation‐ and apoptosis‐related genes occurred at 11 weeks of age in the presymptomatic stage prior to motor neuron death. These results suggest a mechanism of neurodegeneration that includes an inflammatory response as an important component. Thus, ALS has paralleled other neurodegenerative disorders, such as Alzheimer's and prion diseases, in which the inflammatory process is believed to participate directly in neuronal death.
Evaluation of the protective effect of oestradiol against toxicity induced by 6‐hydroxydopamine and 1‐methyl‐4‐phenylpyridinium ion (MPP+) towards dopaminergic mesencephalic neurones in primary culture
Authors: Callier Sophie , Le Saux Maryvonne , Lhiaubet Anne‐Marie , Paolo Thérèse Di , Rostène William , Pelaprat Didier 
Published: March 2003

AbstractRecent findings suggest that gonadal steroid hormones are neuroprotective and may provide clinical benefits in delaying the development of Parkinson's disease. In this report we investigated the ability of oestradiol to protect mesencephalic dopaminergic neurones cultured in serum‐free or serum‐supplemented medium from toxicity induced by 6‐hydroxydopamine or 1‐methyl‐4‐phenylpyridinium ion (MPP+). The efficiency of both toxins and oestradiol was evaluated by tyrosine hydroxylase (TH) immunocytochemistry, [3H]dopamine ([3H]DA) uptake, length of dopaminergic processes and␣lactate dehydrogenase (LDH) release measurement. In␣cultures grown in serum‐supplemented medium, a 2‐h pre‐treatment with high concentrations (10–100 µm) of 17β‐oestradiol or 17α‐oestradiol, the stereoisomer with weak oestrogenic activity, protected both dopaminergic and non‐dopaminergic neurones from toxicity induced by 6‐hydroxydopamine (6‐OHDA; 40 or 100 µm) and by the high MPP+concentrations (50 µm) necessary to obtain significant neuronal death under those culture conditions. At these concentrations, MPP+was no longer selective for dopaminergic neurones but affected all cells present in the culture. In contrast, the hormonal treatments did not protect against selective degeneration of dopaminergic neurones induced by lower MPP+concentrations (below 10 µm), related to inhibition of complex I of respiratory chain. In cultures grown in serum‐free medium, oestradiol concentrations higher than 1 µminduced neuronal degeneration and no protection against 6‐OHDA or MPP+toxicity was observed at lower concentrations of the steroid. The neuroprotective effects of 17α‐ or 17β‐oestradiol evidenced in this model might be due to the antioxidant properties of these compounds. However, other non‐genomic effects of the steroids cannot be excluded.
Bidirectional changes in synapsin I phosphorylation at MAP kinase‐dependent sites by acute neuronal excitation in vivo
Authors: Yamagata Yoko , Jovanovic Jasmina N. , Czernik Andrew J. , Greengard Paul , Obata Kunihiko 
Published: March 2003

AbstractSynapsin I is a synaptic vesicle‐associated protein which is phosphorylated at multiple sites by various kinases. It has been proposed to play a role in the regulation of neurotransmitter release and the organization of cytoskeletal architecture in the presynaptic terminal. To better understand the physiological regulation of its phosphorylation in vivo, we induced acute, reversible neuronal excitation by electroconvulsive treatment (ECT) in rats, and studied its effects on synapsin I phosphorylation at sites 3, 4/5 and 6 by immunoblot analyses of homogenates from hippocampus and parietal cortex using phospho‐site‐specific antibodies. A decrease in phosphorylation at all sites was observed soon after the electrical stimulation, followed by a large increase in phosphorylation at site 4/5 peaking at 5 min and a moderate increase in phosphorylation at site 6 peaking at 20 min. Systemic injection of SL327, a mitogen‐activated protein kinase (MAPK) kinase inhibitor, prior to ECT, suppressed the increase in phospho‐site 4/5 level, as well as that in MAPK activity, but not that in phospho‐site 6 level. Thus, phosphorylation at site 4/5 of synapsin I has been shown to be regulated by MAPK in vivo.
FKHRL1 and its homologs are new targets of nerve growth factor Trk receptor signaling
Authors: Zheng Wen‐Hua , Kar Satyabrata , Quirion Rémi 
Published: March 2003

AbstractWe report that the Forkhead family of transcription factors, FKHRL1, FKHR and AFX are novel components of neurotrophin receptor signaling. NGF rapidly induced the phosphorylation of FKHRL1 in PC12 cells. This effect is mediated by high‐affinity TrkA receptor as nerve growth factor (NGF) induced the phosphorylation of FKHRL1 only in TrkA expressing cells and not p75‐expressing cells. Additional experiments with various kinase inhibitors, the transient expression of constitutively active and dominant‐negative Akt, and in vitro kinase assay revealed that phosphatidylinositol‐3 (PtdIns3)/Akt kinase mediated the actions of NGF. Similar data were obtained for brain‐derived neurotrophic factor (BDNF), neurotrophin‐3 (NT‐3) and neurotrophin‐4 (NT‐4) in primary cortical cultured neurons. These findings demonstrate for the first time that the phosphorylation of the Forkhead family of transcription factors can be modulated by neurotrophins via Trk receptors and PtdIns3K/Akt kinase (but not MAP or S6p70 kinases) in neuronal and non‐neuronal cells. Moreover, survival assays with the PtdIns3 kinase inhibitor LY294002, active and dominant‐negative forms of Akt indicate that the phosphorylation of FKHRL1 plays a role in neurotrophins‐mediated cell survival.
Influence of solar UV‐B radiation on peatland microbial communities of southern Argentinia
Authors: Searles Peter S. , Kropp Bradley R. , Flint Stephan D. , Caldwell Martyn M. 
Published: March 2003

SUMMARY

Stratospheric ozone depletion occurs over Tierra del Fuego, Argentina, in the austral spring and summer due to the Antarctic ‘ozone hole’ and the general erosion of the ozone layer. Thus, we investigated the responses of microbial communities to manipulations of solar UV‐B radiation.
Results reported here are for field plots receiving either near‐ambient or reduced solar UV‐B using plastic filters in a Sphagnum peatland and a Carex fen during the second and third years of UV‐B manipulations.
The total number of testate amoebae (Protozoa, Rhizopoda) inhabiting the upper centimeter of Sphagnum magellanicum was greater under near‐ambient solar UV‐B than under reduced UV‐B. No response to UV‐B manipulation was apparent for rotifers, nematodes, bacteria, microfungi, and a common microalga (Euglena mutabilis) inhabiting the S. magellanicum. On leaves of small Nothofagus antarctica trees, the ratio of upper: lower leaf‐surface fungal populations for the genus Aureobasidium and for total fungi indicated lower populations on the upper, relative to the lower, surface under near‐ambient solar UV‐B.
When responses to modifications of the solar UV‐B flux were detected, these involved both direct UV‐B inhibition and indirect consequences of UV‐B manipulation.
Noise‐free Determination of Isochromatic Fringe Order by Load Stepping
Authors: Tamrakar D. K. , Ramesh K. 
Published: March 2003

AbstractThe traditional ambiguity in the sign of fractional retardation in certain zones of the model by phase shifting technique has been overcome with the development of load stepping in digital photoelasticity. However, the existing methodology of load stepping introduces several points in the model domain that are subjected to excessive noise. A new methodology has been proposed that combines the merits of load stepping and phase shifting to obtain fractional retardation free of noise and ambiguity over the model domain.
Evaluation of the HemoCue plasma haemoglobin analyser for assessing haemolysis in red cell concentrates during storage
Authors: Cardigan R. , Smith K. 
Published: March 2003

Background and Objectives To evaluate the HemoCue plasma haemoglobin (Hb) analyser for determining supernatant Hb in red cell concentrates (RCC) during storage and compare this to a spectrophotometric method.Materials and Methods Samples from RCC (n = 20) at days 0, 7, 21, 35 and 42 of storage were tested by both methods for supernatant Hb.Results Results are given as median with range. There was a significant correlation (r = 0·97, P < 0·0001), but statistically significant difference between the two methods (0·72 (0·36–2·77) spectrophotometric vs. 0·70 (0·3–2·6) g/l HemoCue). However, the mean bias was negligible at 0·06 g/l. The HemoCue method gave a interassay coefficient of variation of 5·6% at 1·2 g/l and was linear to at least 20 g/l.Conclusion The HemoCue plasma haemoglobin analyser is a simple, rapid, reliable and accurate method for the determination of supernatant Hb in RCC at the end of storage and compares well to established methods for supernatant Hb measurement.