bluuebunny/crossref_metadata_2025_split huggingface dataset:
Voltage‐clamp study of the activation currents and fast block to polyspermy in the egg of Xenopus laevis
Authors: Glahn David , Nuccitelli Richard 
Published: May 2003

Voltage‐clamped mature, jelly‐intact Xenopus eggs were used to carefully examine the ionic currents crossing the plasma membrane before, during, and after fertilization. The bulk of the fertilization current was transient, of large amplitude, and reversed at the predicted Cl– reversal potential. However, the large amplitude fertilization current was preceded by a small, step‐like increase in holding current. This small increase in holding current is referred to in this paper as Ion to acknowledge its qualitative similarity to the Ion current previously described in the sea urchin. It was observed in both fertilized and artificially activated eggs, and was found to be unaffected by 10 mm tetra‐ethyl ammonium (TEA), a concentration found to block K+ currents in Rana pipiens. Current–voltage relationships are presented for the large fertilization potential, and show that the fertilization currents have a marked outward rectification and are voltage sensitive. These properties are in contrast to the total lack of rectification and slight voltage sensitivity seen before or after the fertilization currents. The time required for sperm to fertilize the egg was found to be voltage dependent with a relatively more depolarized voltage requiring a longer time for fertilization to occur. The percentage of eggs blocked with varying potential levels was determined and this information was fitted to a modified Boltzmann equation having a midpoint of −9 mV.
Retinoic acid increases the length and volume density of ducts in the rat embryonic pancreas
Authors: Erasmus Carene , Penny Clem , Kramer Beverly 
Published: May 2003

In this study, the role of all‐trans retinoic acid (RA) on the proliferation of rat embryonic pancreas ducts and on the proportion of insulin cells was investigated. All‐trans RA (10−6 m) was added to Ham's F12.ITS serum‐free medium in which 12.5 day rat dorsal pancreatic buds were cultured on Matrigel. Control explants were cultured on Matrigel in Ham's F12.ITS alone or in Ham's F12.ITS containing ethanol (the diluent for RA). After a 7 day culture period, explants were incubated with bromodeoxyuridine (BrdU) for assessment of cell proliferation. Explants were processed for both morphometry and immunocytochemistry. The length density and volume density of the pancreatic ducts were assessed using an image analysis system. Cells positive for insulin, BrdU and glucagon were localized on adjacent serial sections. RA treatment caused a statistically significant increase in the volume density (P < 0.007) and length density (P < 0.008) of the ducts, as well as a 1.2‐fold increase (P < 0.0001) in the proportion of insulin to glucagon cells, compared to both control groups. Few insulin cells were BrdU positive, indicating that cells had a low proliferation rate. The increased proportion of insulin cells may relate to the increased volume density and length density of the ducts in RA‐treated explants. It is suggested that RA stimulated the production of additional progenitor cells and not proliferation of existing insulin cells.
Development and gene expression of nuclear transplants generated by transplantation of cultured cell nuclei into non‐enucleated eggs in the medaka Oryzias latipes†
Authors: Ju Bensheng , Pristyazhnyuk Inna , Ladygina Tatiana , Kinoshita Masato , Ozato Kenjiro , Wakamatsu Yuko 
Published: May 2003

To develop nuclear transplantation techniques for the medaka Oryzias latipes, nuclei of cultured cells from transgenic fish were transplanted into unfertilized eggs of the orange–red variety of O. latipes, without enucleation, in two experimental series. In the first experimental series, fibroblast cells cultured from the adult caudal fin were used as donors, which carried the green fluorescent protein (GFP) gene driven by the promoter of the medaka elongation factor 1α‐A gene. Wild‐type body color was another donor genetic marker used in this experimental series. In the second experimental series, cells cultured from 6‐day‐old embryos were used as donors, which carried the GFP genetic marker driven by the promoter of the medaka β‐actin gene. From more than 1000 eggs transplanted in each experiment, a considerable number of nuclear transplants developed to various embryonic stages showing stage‐ and tissue‐specific expression of the donor genetic markers, although the expression was mosaic in many cases. Three and six of the transplanted eggs in the first and second experimental series (0.3 and 0.5%, respectively) hatched, and the hatchlings expressing the genetic markers survived for up to 3 weeks. The chromosome number varied among cells in a single transplant embryo. The results obtained in these experiments may help future cloning efforts in fish.
Possible involvement of myosin‐X in intercellular adhesion: Importance of serial pleckstrin homology regions for intracellular localization
Authors: Yonezawa Satoshi , Yoshizaki Norio , Sano Mamoru , Hanai Atsuko , Masaki Shigeo , Takizawa Takenori , Kageyama Takashi , Moriyama Akihiko 
Published: May 2003

Subcellular fractionation experiments with mouse hepatocytes, combined with sodium dodecylsulfate (SDS)–polyacrylamide gel electrophoresis (PAGE)–immunoblot analysis using antibodies against two different tail regions of mouse myosin‐X demonstrated a 240 kDa molecular mass to be associated with the plasma membrane‐rich P2 fraction. The basolateral plasma membrane fraction, but not the brush border fraction, isolated from renal cortices also contained the 240 kDa form of myosin‐X. In an attempt to assess relative contributions of possible functional domains in the tail of myosin‐X to localization and function, cDNA corresponding to all three pleckstrin homology (PH) domains and different regions (PH1, 2 and 3, and the two subdomains of PH1: PHS1 and PHS2), as well as the myosin tail homology 4 domain (MyTH4) and the band4.1/ezrin/radixin/moesin‐like domain (FERM) were separately inserted into the pEGFP vector and expressed in cultured COS‐1 cells. As a result, two distinct regions responsible for localization were identified with regard to PH: one covers all three forms that tends to localize to regions of dynamic actin, such as membrane ruffles, lamellipodia and thick cortical actin bundles at the sites of cell–cell adhesion in a Rac‐ and Cdc42‐dependent manner. The other covers PHS1 and PH2 that localizes to filopodia, filopodial puncta and the sites of intercellular adhesion in a Cdc42‐dependent manner. Expression of green fluorescent protein (GFP)‐MyTH4 fusion protein resulted in formation of phalloidin‐positive granules, while GFP‐FERM affected the actin cytoskeletal system in a distinctly different way. Taken altogether, the results lend support to the view that myosin‐X is involved in cell–cell adhesion‐associated signaling‐linked membrane and/or cytoskeleton reorganization.
Nine‐year prospective relationship betweenparental smoking cessation and children's daily smoking
Authors: Bricker JonathanB. , Leroux Brian G. , V.Peterson Arthur , Kealey Kathleen A. , Sarason Irwin G. , Andersen M. Robyn , Marek Patrick M. 
Published: May 2003

ABSTRACTAims  The first prospective investigation of the extent to which parentalsmoking cessation predicts their children's daily smoking.Design  Parental smoking status was assessed when children were aged8/9 years and children's smoking status was assessedat age 17/18 years.Setting  Twenty Washington State school districts in the control groupof the Hutchinson Smoking Prevention Project.Participants and measurements Questionnaire data were gathered on 3012 children (49% femaleand 91% Caucasian) and both of their parents in a cohort witha 95% retention rate.Findings  When both parents quit smoking, children's odds of dailysmoking were reduced by 39% (95% CI = 15%,56%) compared to when both parents were current smokers.Furthermore, when both parents never smoked then children’sodds of daily smoking were reduced by 71% (95% CI = 62%,78%).Conclusions  Parental smoking cessation is associated with reduced risk oftheir children's daily smoking. Parents who quit stillplace children at substantially higher risk compared to parentswho never smoked.
A longitudinal study of the effects of adolescent cannabis use on high school completion
Authors: Lynskey Michael T. , Coffey Carolyn , Degenhardt Louisa , Carlin John B. , Patton George 
Published: May 2003

ABSTRACTObjective  To examine the extent to which weekly cannabis use during mid‐adolescence may increase the risk of early school‐leaving.Setting  A prospective study of a general population sample of adolescents studied from ages 15–21 years in Melbourne, Australia.Method  Computer‐assisted self‐completion questionnaires and telephone interviews conducted in six waves at ages 15–18 and again at age 21 in a sample of 1601 male and female school students.Results  Weekly cannabis use, assessed prospectively, was associated with significantly increased risk of early school‐leaving. This effect remained after adjustment for a range of prospectively assessed covariates including demographic characteristics, other substance use, psychiatric morbidity and antisocial behavior. There was suggestive evidence of an interaction between weekly cannabis use and age with the effects of weekly cannabis use on early school‐leaving being strongest at the youngest ages and diminishing progressively with age.Conclusions  Early regular cannabis use (weekly use at age 15) is associated with increased risk of early school‐leaving. These effects of regular cannabis use may diminish with increasing age and are likely to operate through the social context within which cannabis is used and obtained.
Treatments for spit tobacco use: a quantitative systematicreview
Authors: Ebbert JonO. , Rowland Leah C. , Montori Victor M. , Vickers Kristin S. , Erwin Patricia J. , Dale Lowell C. 
Published: May 2003

ABSTRACTAims  Spit tobacco use is prevalent in the United States and is associatedwith adverse health consequences. Health‐care providers have neitherevidence summaries nor evidence‐based guidelines to assist themin treating patients who use spit tobacco.Design  We completed a systematic review of the literature to determinethe efficacy and safety of pharmacological and behavioral interventionsfor the treatment of spit tobacco use.Findings  We found six randomized controlled trials testing pharmacological interventionsand eight testing behavioral interventions. Using random‐effects meta‐analyses,bupropion sustained‐release (SR) increased point prevalence tobaccoabstinence at 12 weeks [odds ratio (OR) 2.1; 95% confidenceinterval (CI), 1.0–4.2]. Nicotine replacementtherapy with patch or gum increased point prevalence tobacco abstinenceat 6 months (OR 1.3; 95% CI, 1.0–1.6).Behavioral interventions increased long‐term (6 month)point prevalence tobacco abstinence (OR 1.7; 95% CI, 1.1–2.9).Studies including an oral examination followed by feedback to thepatient had the highest treatment effect.Conclusions  Behavioral interventions for ST users are effective for increasing STabstinence rates. Bupropion SR is probably effective and nicotinereplacement therapy may be effective. This evidence from randomizedcontrolled trials provides health‐care professionals with informationnecessary to effectively treat spit tobacco use.
Alexander the Great's relationship with alcohol
Authors: Liappas J. A. , Lascaratos J. , Fafouti S. , Christodoulou G. N. 
Published: May 2003

ABSTRACTAims  This study sought to clarify if Alexander the Great indulged pathologically in alcohol and whether it contributed to his death.Design  The texts of the historians Diodorus of Sicily, Plutarch, Arrian, Curtius Rufus, Athenaeus, Aelian and Justin were studied, with their information concerning wine consumption by Macedonians, and especially Alexander, and were evaluated. The surviving historical texts, all later than Alexander's epoch, are based on a series of contemporary histories and especially on the ‘Royal Journals’, an official diary written in the imperial court.Findings and conclusions  Alexander consumed large quantities of undiluted wine periodically, reaching pathological intoxication. However, the existing data do not provide convincing evidence that Alexander the Great manifested abuse of or dependence on alcohol according to DSM‐IV or ICD‐10 criteria and it seems unlikely that alcohol was involved in his untimely death.
Enhanced growth of sagebrush (Artemisia tridentata) in response to manipulated ecosystem warming
Authors: PERFORS TRACY , HARTE JOHN , ALTER S. ELIZABETH 
Published: May 2003

AbstractGlobal models project impending climate changes that could significantly alter plant species composition in ecosystems. Climate manipulation experiments provide an opportunity to investigate such effects. Here we describe and apply a method for extracting the age‐detrended growth rate of sagebrush (Artemisia tridentata Nutt.) and show that experimental ecosystem warming enhances the growth rate of this shrub. Snowmelt date, not soil temperature or moisture, is demonstrated to be the dominant climate variable controlling the observed effect. Our findings suggest that global climate change will result in increased growth and range expansion of sagebrush near northern or high‐elevation range boundaries in the Western United States.
Effects of N‐fertilisation on CH4 oxidation and production, and consequences for CH4 emissions from microcosms and rice fields
Authors: KRÜGER MARTIN , FRENZEL PETER 
Published: May 2003

AbstractThe world's growing human population causes an increasing demand for food, of which rice is one of the most important sources. In rice production nitrogen is often a limiting factor. As a consequence increasing amounts of fertiliser will have to be applied to maximise yields. There is an ongoing discussion on the possible effects of fertilisation on CH4 emissions. We therefore investigated the effects of N‐fertiliser (urea) on CH4 emission, production and oxidation in rice microcosms and field experiments. In the microcosms, a substantial but short‐lived reduction of CH4 emission was observed after N‐addition to 43‐d‐old rice plants. Methane oxidation increased by 45%, demonstrated with inhibitor measurements and model calculations based on stable carbon isotope data (δ13CH4). A second fertilisation applied to 92‐d‐old plants had no effect on CH4 emission rates.The positive effect of additional N on methanotrophic bacteria was also found in vitro for potential CH4 oxidation rates in soil and root samples from the microcosm and field experiments, indicated by elevated initial oxidation rates and reduced lag‐phases. Fertilisation did not affect methane production in the microcosms. In the field, the effects were diverse: methane production was inhibited in the topsoil, but stimulated instead in the bulk soil. Stimulation occurred probably in the anaerobic food chain at the level of hydrolytic or fermenting bacteria, because acetate, a methanogenic precursor, increased simultaneously.Combining field, microcosm and laboratory experiments we conclude that any agricultural treatment improving the N‐supply to the rice plants will also be favourable for the CH4 oxidising bacteria. However, N‐fertilisation had only a transient influence and was counter‐balanced in the field by an elevated CH4 production. A negative effect of the fertilisation was a transient increase of N2O emissions from the microcosms. However, integrating over the season the global warming potential (GWP) of N2O emitted after fertilisation was still negligible compared to the GWP of emitted CH4.
Soil organic matter biochemistry and potential susceptibility to climatic change across the forest‐tundra ecotone in the Fennoscandian mountains
Authors: SJÖGERSTEN SOFIE , TURNER BENJAMIN L. , MAHIEU NATHALIE , CONDRON LEO M. , WOOKEY PHILIP A. 
Published: May 2003

AbstractWe studied soil organic carbon (C) chemistry at the mountain birch forest‐tundra ecotone in three regions of the Fennoscandian mountain range with comparable vegetation cover but contrasting degrees of continentality and latitude. The aim of the study was to identify functional compound classes and their relationships to decomposition and spatial variation across the ecotone and latitudinal gradient. Solid‐state 13C nuclear magnetic resonance (CPMAS 13C NMR) was used to identify seven functional groups of soil organic C: alkyls, N‐alkyls, O‐alkyls, acetals, aromatics, phenolics and carboxyls. N‐alkyls, O‐alkyls and acetals are generally considered labile substrates for a large number of saprotrophic fungi and bacteria, whilst phenolics and aromatics are mainly decomposed by lignolytic organisms and contribute to the formation of soil organic matter together with aliphatic alkyls and carboxyls. All soils contained a similar proportional distribution of functional groups, although relatively high amounts of N‐alkyls, O‐alkyls and acetals were present in comparison to earlier published studies, suggesting that large amounts of soil C were potentially vulnerable to microbial degradation. Soil organic matter composition was different at the most southerly site (Dovrefjell, Norway), compared with the two more northerly sites (Abisko, Sweden, and Joatka, Norway), with higher concentrations of aromatics and phenolics, as well as pronounced differences in alkyl concentrations between forest and tundra soils. Clear differences between mountain birch forest and tundra heath soil was noted, with generally higher concentrations of labile carbon present in tundra soils. We conclude that, although mesic soils around the forest‐tundra ecotone in Fennoscandia are a potential source of C to the atmosphere in a changing environment, the response is likely to vary between comparable ecosystems in relation to latitude and continentality as well as soil properties especially soil nitrogen content and pH.
Projecting future fire activity in Amazonia
Authors: CARDOSO MANOEL F. , HURTT GEORGE C. , MOORE BERRIEN , NOBRE CARLOS A. , PRINS ELAINE M. 
Published: May 2003

AbstractFires are major disturbances for ecosystems in Amazonia. They affect vegetation succession, alter nutrients and carbon cycling, and modify the composition of the atmosphere. Fires in this region are strongly related to land‐use, land‐cover and climate conditions. Because these factors are all expected to change in the future, it is reasonable to expect that fire activity will also change. Models are needed to quantitatively estimate the magnitude of these potential changes. Here we present a new fire model developed by relating satellite information on fires to corresponding statistics on climate, land‐use and land‐cover. The model is first shown to reproduce the main contemporary large‐scale features of fire patterns in Amazonia. To estimate potential changes in fire activity in the future, we then applied the model to two alternative scenarios of development of the region. We find that in both scenarios, substantial changes in the frequency and spatial patterns of fires are expected unless steps are taken to mitigate fire activity.
Effects of elevated carbon dioxide on green leaf tissue and leaf litter quality in an intact Mojave Desert ecosystem
Authors: BILLINGS SHARON A. , ZITZER STEPHEN F. , WEATHERLY HEATHER , SCHAEFFER SEAN M. , CHARLET T. , ARNONE JOHN A. , EVANS R. D. 
Published: May 2003

AbstractThe effects of elevated carbon dioxide (CO2) on plant litter are critical determinants of ecosystem feedback to changing atmospheric CO2 concentrations. We measured concentrations of nitrogen (N) and carbon (C) and calculated C : N ratios of green leaves of two desert perennial shrubs, and the same quality parameters plus lignin and cellulose content of leaf litter from four shrub species exposed to elevated CO2 (FACE technology; Hendrey & Kimball, 1994) for 3 years in an intact Mojave Desert ecosystem. Shrubs tested were Larrea tridentata, Lycium pallidum, Lycium andersonii and Ambrosia dumosa. We calculated resorption efficiency from green tissue and leaf litter N data and measured lignin and cellulose content in litter in the last year study. Green leaves of L. tridentata grown under elevated CO2 had significantly lower N concentrations and higher C : N ratios than shrubs grown in ambient conditions in 1999 (P < 0.05). Lycium pallidum green leaves grown under elevated CO2 had significantly lower N concentrations and higher C : N ratios than shrubs grown under ambient conditions in 2000 (P < 0.05). There was no CO2 effect on C content of either species. We found no effect of CO2 on N or C content, C : N ratios, or lignin or cellulose concentrations in leaf litter of L. tridentata, L. pallidum, L. andersonii, or A. dumosa. There was no significant effect of CO2 on estimates of shrub resorption efficiency. There was a seasonal effect on green tissue and litter tissue quality for L. tridentata, with lower tissue N content in summer than in spring or winter months. These data suggest that any productivity increases with elevated CO2 in desert ecosystems may not be limited by lower leaf litter quality and that resorption efficiency calculations are best performed on an individual leaf basis.
Carbon sequestration in arid‐land forest
Authors: GRÜNZWEIG J. M. , LIN T. , ROTENBERG E. , SCHWARTZ A. , YAKIR D. 
Published: May 2003

AbstractRising atmospheric CO2 concentrations may lead to increased water availability because the water use efficiency of photosynthesis (WUE) increases with CO2 in most plant species. This should allow the extension of afforestation activities into drier regions. Using eddy flux, physiological and inventory measurements we provide the first quantitative information on such potential from a 35‐year old afforestation system of Aleppo pine (Pinus halepensis Mill.) at the edge of the Negev desert. This 2800 ha arid‐land forest contains 6.5 ± 1.2 kg C m−2, and continues to accumulate 0.13–0.24 kg C m−2 yr−1. The CO2 uptake is highest during the winter, out of phase with most northern hemispheric forest activity. This seasonal offset offers low latitude forests ∼10 ppm higher CO2 concentrations than that available to higher latitude forests during the productive season, in addition to the 30% increase in mean atmospheric CO2 concentrations since the 1850s. Expanding afforestation efforts into drier regions may be significant for C sequestration and associated benefits (restoration of degraded land, reducing runoff, erosion and soil compaction, improving wildlife) because of the large spatial scale of the regions potentially involved (ca. 2 × 109 ha of global shrub‐land and C4 grassland). Quantitative information on forest activities under dry conditions may also become relevant to regions predicted to undergo increasing aridity.
Projected climate change effects on Rocky Mountain and Great Plains birds: generalities of biodiversity consequences
Authors: PETERSON A. TOWNSEND 
Published: May 2003

AbstractClimate change effects on biodiversity are already manifested, and yet no predictive knowledge characterizes the likely nature of these effects. Previous studies suggested an influence of topography on these effects, a possibility tested herein. Bird species with distributions restricted to montane (26 species) and Great Plains (19 species) regions of central and western North America were modeled, and climate change effects on their distributions compared: in general, plains species were more heavily influenced by climate change, with drastic area reductions (mode 35% of distributional area lost under assumption of no dispersal) and dramatic spatial movements (0–400 km shift of range centroid under assumption of no dispersal) of appropriate habitats. These results suggest an important generality regarding climate change effects on biodiversity, and provide useful guidelines for conservation planning.