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Aim: Lichens are often regarded as paradigms of mutualistic relationships. However, it is still poorly known how lichen‐forming fungi and their photosynthetic partners interact at a community scale. We explored the structure of fungus‐alga networks of interactions in lichen communities along a latitudinal transect in continental Antarctica. We expect these interactions to be highly specialized and, consequently, networks with low nestedness degree and high modularity. Location: Transantarctic Mountains from 76° S to 85° S (continental Antarctica). Time Period: Present. Major Taxa Studied: Seventy‐seven species of lichen‐forming fungi and their photobionts. Methods: DNA barcoding of photobionts using nrITS data was conducted in 756 lichen specimens from five regions along the Transantarctic Mountains. We built interaction networks for each of the five studied regions and a metaweb for the whole area. We explored the specialization of both partners using the number of partners a species interacts with and the specialization parameter d'. Network architecture parameters such as nestedness, modularity and network specialization parameter H2' were studied in all networks and contrasted through null models. Finally, we measured interaction turnover along the latitudinal transect. Results: We recovered a total of 842 interactions. Differences in specialization between partners were not statistically significant. Fungus‐alga interaction networks showed high specialization and modularity, as well as low connectance and nestedness. Despite the large turnover in interactions occurring among regions, network parameters were not correlated with latitude. Main Conclusions: The interaction networks established between fungi and algae in saxicolous lichen communities in continental Antarctica showed invariant properties along the latitudinal transect. Rewiring is an important driver of interaction turnover along the transect studied. Future work should answer whether the patterns observed in our study are prevalent in other regions with milder climates and in lichen communities on different substrates. [ABSTRACT FROM AUTHOR]

Against a changing climate, the development of evidence‐based and progressive conservation policies depends on robust and quantitative baseline studies to resolve habitat natural variability and rate of change. Despite Antarctica's significant role in global climate regulation, climate trend estimates for continental Antarctica are ambiguous due to sparse long‐term in situ records. Here, we present the longest, spatially explicit survey of Antarctic vegetation by harmonizing historic vegetation mapping with modern remote sensing techniques. In 1961, E. D. Rudolph established a permanent survey plot at Cape Hallett, one of the most botanically diverse areas along the Ross Sea coastline, harboring all known types of non‐vascular Antarctic vegetation. Following a survey in 2004 using ground‐based photography, we conducted the third survey of Rudolph's Plot in 2018 using near‐ground remote sensing and methodologies closely mirroring the two historic surveys to identify long‐term changes and trends. Our results revealed that the vegetation at Cape Hallett remained stable over the past six decades with no evidence of transformation related to a changing climate. Instead, the local vegetation shows strong seasonal phenology, distribution patterns that are driven by water availability, and steady perennial growth of moss. Given that East Antarctica is at the tipping point of drastic change in the near future, with biological change having been reported at certain locations, this record represents a unique and potentially the last opportunity to establish a meaningful biological sentinel that will allow us to track subtle yet impactful environmental change in terrestrial Antarctica in the 21st century. Plain Language Summary: In early 2022, record‐breaking high temperatures were recorded all over Antarctica, sparking concerns about the icy continent's future. Although the effects of climate change have been observed in West Antarctica, much less observation is available for East Antarctica, where almost 90% of the Antarctic ice mass is located. It is now, that East Antarctica is at a tipping point for change, and it is now, that we need to establish progressive conservation measures. What is at stake? The vegetation in East Antarctica is distinct. Any organism that managed to survive here has highly specialized traits, and we only find lichens, mosses, cyanobacteria, and green algae. Especially the mosses are used biological sentinels because they live long and with high specificity. However, because they grow so slowly, any attempt to monitor variation in their fitness has to span decades rather than years or even seasons. This constitutes a key problem when trying to understand the natural dynamics of a functional ecosystem in East Antarctica. By applying machine learning and advanced statistics to modern aerial survey data as well as historic vegetation maps (the oldest in Antarctica, from 56 years ago), we created a unique harmonized data set and gained unique ecological insight. This allows us to establish a biological sentinel for change in East Antarctica, just before it is too late. Key Points: The longest plant cover record in Antarctica revealed Cape Hallett, unlike sites around the Peninsula, unaffected by climate changeAntarctic vegetation shows high plasticity, for which most of the changes can be explained by seasonal variation and water availabilityBy harmonizing historic and modern monitoring methodologies we establish a sustainable biological sentinel for change in East Antarctica [ABSTRACT FROM AUTHOR]

In this synthesis, we assess present research and anticipate future development needs in modeling water quality in watersheds. We first discuss areas of potential improvement in the representation of freshwater systems pertaining to water quality, including representation of environmental interfaces, in‐stream water quality and process interactions, soil health and land management, and (peri‐)urban areas. In addition, we provide insights into the contemporary challenges in the practices of watershed water quality modeling, including quality control of monitoring data, model parameterization and calibration, uncertainty management, scale mismatches, and provisioning of modeling tools. Finally, we make three recommendations to provide a path forward for improving watershed water quality modeling science, infrastructure, and practices. These include building stronger collaborations between experimentalists and modelers, bridging gaps between modelers and stakeholders, and cultivating and applying procedural knowledge to better govern and support water quality modeling processes within organizations. Key Points: We assess four potential improvements in water quality modeling: environmental interfaces, in‐stream processes, soil health, and urban areasChallenges include data quality control, model calibration, uncertainty management, scale mismatches, and model tool provisionModelers need to strengthen connections with experimentalists and stakeholders and cultivate procedural knowledge for modeling processes [ABSTRACT FROM AUTHOR]

This paper studies the impact of trading on government bond prices surrounding the release of macroeconomic news. The results show a significant increase in the informational role of trading following economic announcements, which suggests the release of public information increases the level of information asymmetry in the government bond market. The informational role of trading is greater after announcements with a larger initial price impact, and the relation is associated with the surprise component of the announcement and the precision of the public information. The results provide evidence that government bond order flow reveals fundamental information about riskless rates. [ABSTRACT FROM AUTHOR]

Derivatives valuation and risk management involve heavy use of quantitative models. To develop a quantitative assessment of model risk as it affects the basic option writing strategy that might be followed by a financial institution, we conduct an empirical simulation, with and without hedging, using data from 1976 to 1996. Results indicate that imperfect models and inaccurate volatility forecasts create sizable risk exposure for option writers. We consider to what extent the damage due to model risk can be limited by pricing options using a higher volatility than the best estimate from historical data. [ABSTRACT FROM AUTHOR]

Daily data from interdealer government bond brokers are examined for tax and liquidity effects. We use two approaches to create cash flow matching portfolios of similar securities and look for pricing discrepancies associated with liquidity or tax effects. We also look for the presence of tax and liquidity effects by including a liquidity term when fitting a cubic spline to the after-tax yield curve. We find evidence of tax timing options and liquidity effects. However, the effects are much smaller than previously reported and the effects of liquidity are primarily due to high volume bonds with long maturities. [ABSTRACT FROM AUTHOR]

Summary: Chronosequences at the forefront of retreating glaciers provide information about colonization rates of bare surfaces. In the northern hemisphere, forest development can take centuries, with rates often limited by low nutrient availability. By contrast, in front of the retreating Pia Glacier (Tierra del Fuego, Chile), a Nothofagus forest is in place after only 34 yr of development, while total soil nitrogen (N) increased from near zero to 1.5%, suggesting a strong input of this nutrient.We measured N‐fixation rates, carbon fluxes, leaf N and phosphorus contents and leaf δ15N in the dominant plants, including the herb Gunnera magellanica, which is endosymbiotically associated with a cyanobacterium, in order to investigate the role of N‐fixing and mycorrhizal symbionts in N‐budgets during successional transition.G. magellanica presented some of the highest nitrogenase activities yet reported (potential maximal contribution of 300 kg N ha−1 yr−1). Foliar δ15N results support the framework of a highly efficient N‐uptake and transfer system based on mycorrhizas, with c. 80% of N taken up by the mycorrhizas potentially transferred to the host plant.Our results suggest the symbiosis of G. magellanica with cyanobacteria, and trees and shrubs with mycorrhizas, to be the key processes driving this rapid succession. [ABSTRACT FROM AUTHOR]

Introduction Hemoglobin (Hb) concentration is often measured in global health and nutrition surveys to determine anemia prevalence using a portable hemoglobinometer such as the Hemocue® Hb 201+. More recently, a newer model was released (Hemocue Hb 301) utilizing slightly different methods to measure Hb as compared to the older model. The objective was to measure bias and concordance between Hb concentrations using the Hemocue Hb 301 and Hb 201+ models in a rural field setting. Methods Hemoglobin (Hb) concentration was measured using one finger prick of blood (approximately 10 μL) from 175 Cambodian women (18-49 years) using three Hemocue Hb 201+ and three Hb 301 machines. Bias and concordance were measured and plotted. Results Overall, mean ± SD Hb concentration was 116 ± 13 g/L using the Hb 201+ and 118 ± 12 g/L using the Hb 301; and anemia prevalence (Hb < 120 g/L) was 58% ( n = 102) and 58% ( n = 101), respectively. Overall bias ± SD was 2.0 ± 10.5 g/L and concordance (95% CI) was 0.63 (0.54, 0.72). Despite the 2 g/L bias detected between models, anemia prevalence was very similar in both models. Conclusions The two models measured anemia prevalence comparably in this population of women in rural Cambodia. [ABSTRACT FROM AUTHOR]

Objective: To determine in a group of pregnant women if vitamin D status, based on serum 25-hydroxyvitamin D (25OHD) concentration, was associated with a subsequent risk of pre-eclampsia or adverse pregnancy outcomes.Design: Prospective cohort study.Setting: Vancouver, British Columbia, Canada (49°N).Population: Women attending a specialist antenatal clinic because of clinical or biochemical risk factors for pre-eclampsia (n = 221).Methods: Serum 25OHD concentration measured between 10 and 20 weeks of gestation.Main Outcome Measures: Pre-eclampsia and composite adverse pregnancy outcomes.Results: Of the women, 78% were vitamin D insufficient (25OHD <75 nmol/l) and 53% were vitamin D deficient (25OHD <50 nmol/l). There was no difference in the rates of pre-eclampsia, gestational hypertension, preterm birth or composite adverse pregnancy outcomes by 25OHD concentration.Conclusions: Vitamin D deficiency and insufficiency were common in a group of women at high risk of pre-eclampsia; however, it was not associated with subsequent risk of an adverse pregnancy outcome. [ABSTRACT FROM AUTHOR]

Objective TRIM21 (also known as Ro52) is an autoantigen in rheumatic disease and is predominantly expressed in leucocytes. Overexpression is associated with decreased proliferation, and the TRIM21 gene maps to a tumour suppressor locus. We therefore investigated the expression of TRIM21 in patients with diffuse large B-cell lymphoma ( DLBCL) and its potential usefulness as a prognostic biomarker. Materials and methods TRIM21 expression levels were assessed by immunohistochemistry in lymphoma biopsies from three cohorts of patients with DLBCL: 42 patients with rheumatic disease treated with a cyclophosphamide, vincristine, doxorubicin and prednisone ( CHOP)-like regimen, 76 CHOP-treated and 196 rituximab- CHOP-treated nonrheumatic patients. Expression was correlated with clinical and biomedical parameters. TRIM21 expression was assessed in relation to lymphocyte proliferation by quantitative PCR and correlated with 3H-thymidine incorporation and propidium iodine staining. Results TRIM21 expression levels differed in the lymphomas compared to normal lymphoid tissue, with reduced expression correlating with shorter overall survival in all three cohorts. In the two larger cohorts, progression-free survival was assessed and was also found to correlate with TRIM21 expression. The association was independent of commonly used clinical prognostic scores, lymphoma subtype and several previously reported prognostic biomarkers. In agreement with this clinical observation, we noted an inverse correlation between TRIM21 expression and proliferation of leucocytes in vitro. Conclusions We show that loss of TRIM21 expression is associated with more aggressive lymphoma and increased proliferation, whereas maintenance of TRIM21 expression is associated with better prognosis in patients with DLBCL. Based on our findings, we suggest that TRIM21 should be considered as a novel biomarker for lymphoma characterization and for predicting patient survival. [ABSTRACT FROM AUTHOR]

Patterns of environmental spatial structure lie at the heart of the most fundamental and familiar patterns of diversity on Earth. Antarctica contains some of the strongest environmental gradients on the planet and therefore provides an ideal study ground to test hypotheses on the relevance of environmental variability for biodiversity. To answer the pivotal question, "How does spatial variation in physical and biological environmental properties across the Antarctic drive biodiversity?" we have synthesized current knowledge on environmental variability across terrestrial, freshwater, and marine Antarctic biomes and related this to the observed biotic patterns. The most important physical driver of Antarctic terrestrial communities is the availability of liquid water, itself driven by solar irradiance intensity. Patterns of biota distribution are further strongly influenced by the historical development of any given location or region, and by geographical barriers. In freshwater ecosystems, free water is also crucial, with further important influences from salinity, nutrient availability, oxygenation, and characteristics of ice cover and extent. In the marine biome there does not appear to be one major driving force, with the exception of the oceanographic boundary of the Polar Front. At smaller spatial scales, ice cover, ice scour, and salinity gradients are clearly important determinants of diversity at habitat and community level. Stochastic and extreme events remain an important driving force in all environments, particularly in the context of local extinction and colonization or recolonization, as well as that of temporal environmental variability. Our synthesis demonstrates that the Antarctic continent and surrounding oceans provide an ideal study ground to develop new biogeographical models, including life history and physiological traits, and to address questions regarding biological responses to environmental variability and change. [ABSTRACT FROM AUTHOR]

Traffic simulators are often utilized when researching turfgrass wear tolerance and recovery. However, the availability of a durable traffic simulator capable of producing dynamic force is limited. Therefore, the objectives of this research were to: (i) evaluate a novel traffic simulator with improved durability and capable of producing dynamic force and (ii) evaluate the biophysical effects of the traffic simulator on a native soil turfgrass system. The Baldree traffic simulator is a modified Ryan GA 30 (Jacobsen, A Textron Company, Charlotte, NC) riding aerification unit, equipped with fabricated, spring loaded steel plate feet studded with screw in cleats. The effects of this unit on a 'Tifway' bermudagrass [Cynodon dactylon (L.) Pers. × C. transvaalensis Burtt-Davy] system established on a Tifton loamy sand (fine-loamy, kaolinitic, thermic Plinthic Kandiudults) were evaluated at the Coastal Plains Experiment Station, Tifton, GA. Factors included location (1 and 2) and traffic rate (0, 12, and 24 passes applied over a 6 wk period). Field data included soil bulk density, turf density, and percent green turf cover. An in-ground force plate at the McPhail Equine Performance Center, East Lansing, MI was used to quantify vertical and net shear ground reaction force produced by the Baldree traffic simulator when operated in the forward and backward direction. The Baldree traffic simulator produced more cleat marks per pass than the Brinkman and Cady traffic simulators. At the low traffic rate the Baldree traffic simulator increased soil bulk density, while turf density and percent green turf cover decreased; therefore, the tool can be used to simulate heavy traffic conditions with a minimum number of passes. [ABSTRACT FROM AUTHOR]

Summary Hypolithic microbial communities (i.e. cryptic microbial assemblages found on the undersides of translucent rocks) are major contributors of carbon input into the oligotrophic hyper-arid desert mineral soils of the Eastern Antarctic Dry Valleys. Here we demonstrate, for the first time, that hypolithic microbial communities possess both the genetic capacity for nitrogen fixation (i.e. the presence of nifH genes) and the ability to catalyse acetylene reduction, an accepted proxy for dinitrogen fixation. An estimate of the total contribution of these communities suggests that hypolithic communities are important contributors to fixed nitrogen budgets in Antarctic desert soils. [ABSTRACT FROM AUTHOR]

Field-scale infiltration, soil water, and solute transport models require spatially averaged "effective" soil hydraulic parameters to represent the average flux and storage. The values of these effective parameters vary for different conditions and processes. The objective of this study was to explore some effective parameter sets to describe field- average infiltration and redistribution under different rainfall conditions. We investigated whether an effective field saturated hydraulic conductivity, Ks,eff and correlated hydraulic parameters derived from matching early-stage average ponded infiltration could give reasonable results for infiltration under lower rainfall rates as well as for soil water redistribution. The results of this Effective Parameter Set 1 (EPS-1) were compared with those of two other parameter sets: EPS-2, where the same Ks,effwas combined with other hydraulic parameters that were arithmetic mean values of the component soils in the field; and EPS-3, where all parameters were arithmetic mean values. The RZWQM2 model was used to explore these objectives for five different cases of a heterogeneous field, comparing results from effective properties with weighted mean values of component soils at four different rainfall intensities. The mean absolute error for infiltration generally increased with decreasing rain intensity but were generally least with EPS-1 and greatest with EPS-3. The EPS-1 gave good results for infiltration up to 4 h; however, it gave poor results for the mean soil water content distributions 7 d after infiltration. The EPS-2 gave reasonable results for both cumulative infiltration and soil water redistribution. The study confirms that an optimal EPS must strike a balance between infiltration and redistribution. For infiltration, computing Ks,eff was critical, and this needed to be combined with mean values of water retention parameters for redistribution. [ABSTRACT FROM AUTHOR]

Soil water content is often determined using various permittivity sensors. The Hydra Probe reports both the real (ϵ') and imaginary (ϵ") components of complex permittivity (ϵ*) and estimates electrical conductivity (σ). Previously, a 12-wire probe was used with a vector network analyzer to determines ϵ' and ϵ' and σ' and σ" in undisturbed soil cores. The purpose of this study was to compare results from the Hydra Probe and the 12-wire probe for fluids as well as for soil samples taken from six locations, to better understand the interrelations of ϵ1, ϵ" and σ' from the Hydra Probe. Undisturbed soil cores were collected from an Iowa prairie and adjacent soybean [Glycine max (L.) Merr.] field, an Iowa forest and adjacent soybean field, Idaho burned and unburned sites, Colorado grassland and dryland wheat ( Triticum aestivum L.) sites, Ohio grassed areas, and Texas rangeland and an irrigated field. Because of their density, some of the Texas samples were sieved and repacked. The reported σ' ϵ' and ϵ" values of fluids were compared between the two measurement systems and with theoretical values, Because the theoretical values for soils are not known, the measured values were compared between systems. Both probes showed σ' ϵ' and ϵ" close to the theoretical values for fluids. In soils, we showed that an adjustment was needed in the calculated σ' from the Hydra Probe to account for dielectric relaxation. The soil σ' of the Hydra Probe matched σ' from the 12-wire probe better after the adjustment was made. [ABSTRACT FROM AUTHOR]

Endolithic photosynthetic microorganisms like cyanobacteria and algae are well known from savannas and deserts of the world, the high Arctic, and also Antarctic habitats like the Dry Valleys in the Ross Dependency. These endolithic microbial communities are thought to be at the limits of life with reported ages in the order of thousands of years. Here we report on an extensive chasmoendolithic cyanobacterial community inside granite rocks of Mt. Falconer in the lower Taylor Valley, Dry Valleys. On average, the cyanobacterial community was 4.49 ± 0.95 mm below the rock surface, where it formed a blue-green layer. The community was composed mainly of the cyanobacterium Chroococcidiopsis sp., with occasional Cyanothece cf. aeruginosa (Nägeli) Komárek and Nostoc sp. Mean biomass was 168 ± 44 g carbon · m−2, and the mean chl a content was 24.3 ± 34.2 mg · m−2. In situ chl fluorescence measurements—a relative measure of photosynthetic activity—showed that they were active over long periods each day and also showed activity the next day in the absence of any moisture. Radiocarbon dating gave a relatively young age (175–280 years) for the community. Calculations from microclimate data demonstrated that formation of dew or rime was possible and could frequently activate the cyanobacteria and may explain the younger age of microbial communities at Mt. Falconer compared to older and less active endolithic microorganisms reported earlier from Linnaeus Terrace, a higher altitude region that experiences colder, drier conditions. [ABSTRACT FROM AUTHOR]

This study evaluated the accuracy of pressure plate apparatus for measuring soil water retention at -0.5 and -1.5 MPa matric potential. Samples from 35 contrasting Australian soils were wetted with distilled water and drained on pressure plate apparatus at -0.5 and -1.5 MPa. The soil matric potential of each sample was then determined using a thermocouple psychrometer, and water content was measured. Water content at exactly -0.5 and -1.5 MPa matric potential was determined independently by interpolating between replicates of matric potential-water content data measured using a thermocouple psychrometer. Water content of the soil samples at apparent equilibrium on pressure plates was compared with these "target" water contents. The 35 samples on pressure plates at -1.5 MPa equilibrated, on average, to 0.3% (w/w) wetter than the target water content, with mean matric potential of-i .10 MPa. Fifteen samples were significantly wetter than the target values. Soil samples on pressure plates at -0.5 MPa equilibrated, on average, to 0.2% (w/w) wetter than the target water content, attaining a mean matric potential of -0.48 MPa. Mean error in water content at -1.5 MPa on pressure plates was reduced from >0.5 to <0.1% (w/w) in a subset of 10 samples prone to dispersion by wetting with 0.01 mol L-1 CaCI2. Water contents of samples equilibrated on pressure plates at -1.5 MPa were good estimates of "true" -1.5 MPa water content for the nonswelling soils tested, provided CaCI2 was used to minimize dispersion. Vapor equilibrium measurement methods are recommended for swelling soils. [ABSTRACT FROM AUTHOR]

Objective: Variation in the major histocompatibility complex (MHC) on chromosome 6p21 is known to influence susceptibility to multiple sclerosis with the strongest effect originating from the HLA-DRB1 gene in the class II region. The possibility that other genes in the MHC independently influence susceptibility to multiple sclerosis has been suggested but remains unconfirmed.Methods: Using a combination of microsatellite, single nucleotide polymorphism, and human leukocyte antigen (HLA) typing, we screened the MHC in trio families looking for evidence of residual association above and beyond that attributable to the established DRB1*1501 risk haplotype. We then refined this analysis by extending the genotyping of classical HLA loci into independent cases and control subjects.Results: Screening confirmed the presence of residual association and suggested that this was maximal in the region of the HLA-C gene. Extending analysis of the classical loci confirmed that this residual association is partly due to allelic heterogeneity at the HLA-DRB1 locus, but also reflects an independent effect from the HLA-C gene. Specifically, the HLA-C*05 allele, or a variant in tight linkage disequilibrium with it, appears to exert a protective effect (p = 3.3 x 10(-5)).Interpretation: Variation in the HLA-C gene influences susceptibility to multiple sclerosis independently of any effect attributable to the nearby HLA-DRB1 gene. [ABSTRACT FROM AUTHOR]

The transition to full-time clinical studies holds anxieties for most medical students. While graduate entry medical education has only recently begun in the UK, the parallel undergraduate and graduate entry MBBS courses taught at our school allowed us to study how 2 differently prepared groups perceived this vital time at a comparable stage in their training.An anonymous questionnaire collected demographic data and graded anxiety in 13 statements relating to starting full-time clinical attachments. Two open questions allowed free text comment on the most positive and negative influences perceived during this time. Both a statistical analysis and a qualitative assessment were performed to compare the 2 groups of students.The 2 groups were similar with respect to gender but the graduate entry students were significantly older. The graduate entry students were significantly less anxious about most aspects of the transition period compared to the undergraduates. These course differences remained after adjusting for age and sex. When adjusted for course and age, male students expressed less anxiety. The main positive qualitative statements related to continual clinical and communication skills training in the graduate entry group. The main qualitative concerns in both groups related to‘fitting in’ and perceived lack of factual knowledge.These data support the early introduction of clinical skills teaching, backed up by a fully integrated clinically relevant curriculum with continued assessment, in preparing students and reducing levels of anxiety before they start full-time clinical attachments. These course design differences appear to be more important than any differences in maturity between the 2 groups. [ABSTRACT FROM AUTHOR]

Abstract β-endorphin is an endogenous opioid peptide that has been hypothesized to be involved in the behavioral effects of drugs of abuse including psychostimulants. Using microdialysis, we studied the effect of cocaine on extracellular levels of β-endorphin in the nucleus accumbens, a brain region involved in the reinforcing effects of psychostimulant drugs. Experimenter-delivered cocaine (2 mg/kg, i.v.) increased extracellular β-endorphin immunoreactive levels in the nucleus accumbens, an effect attenuated by 6-hydroxy-dopamine lesions or systemic administration of the D[sub 1]-like receptor antagonist, SCH-23390 (0.25 mg/kg, i.p.). The effect of cocaine on β-endorphin release in the nucleus accumbens was mimicked by a local perfusion of dopamine (5 µ m) and was blocked by coadministration of SCH-23390 (10 µ m). Self-administered cocaine (1 mg/kg/infusion, i.v.) also increased extracellular β-endorphin levels in the nucleus accumbens. In addition, using functional magnetic resonance imaging, we found that cocaine (1 mg/kg, i.v.) increases regional brain activity in the nucleus accumbens and arcuate nucleus. We demonstrate an increase in β-endorphin release in the nucleus accumbens following experimenter-delivered and self-administered cocaine mediated by the local dopaminergic system. These findings suggest that activation of the β-endorphin neurons within the arcuate nucleus–nucleus accumbens pathway may be important in the neurobiological mechanisms underlying the behavioral effects of cocaine. [ABSTRACT FROM AUTHOR]

Members of the plakin family of cytolinker proteins integrate filaments into cellular networks and anchor these networks to the plasma membrane. Their importance is supported by the existence of cell and tissue fragility disorders caused by mutations in certain family members. In this study, the human gene encoding desmoplakin (DSP) was characterized and its structure compared with the related family members: plectin, bullous pemphigoid antigen I (BPAGI). envoplakin (EVPL) and periplakin (PPL). Sequence analysis of genomic clones was carried out in combination with a PCR-based strategy to define intron-exon borders. DSP was mapped using the G84 radiation hybrid mapping panel to the interval between markers D6S296 and AFM043xf2, corresponding to cytogenetic band 6p24. In addition, the murine gene (Dsp) was mapped to mouse chromosome13 by interspecific backeross mapping. DSP encompasses ∼45 kb organized into 24 exons and 23 introns, and the pattern of intron--exon borders bears a striking resemblance to other members of the plakin family. Notable features include the fact that a single large exon encodes the entire C-terminus of each gene. In contrast, the N-termini comprise numerous smaller exons with conservation of many intron -exon borders. Detailed characterization and mapping of these genes will facilitate their further evaluation as targets of genetic disorders and provide insights into the evolutionary relationships among molecules in this emerging gene family. [ABSTRACT FROM AUTHOR]

Photosymbiodemes are lichens which contain a single mycobiont but have cyanobacteria and green algae as primary photobionts in different parts of the thallus. Members of a photosymbiodeme can be found as separate, free-living lichen species. The photosynthesis of the components of two Pseudocyphellaria photosymbiodemes were studied in the natural forest environment in New Zealand. It was found that the green algal component had a large photosynthetic advantage when thallus water contents were low and the thalli were in equilibrium with atmospheric humidity. The cyanobacterial components were at an advantage when thallus water contents were very high. The environment in which photosymbiodemes are found, forest margins in high humidity areas, seems to provide the correct combination of thallus water contents so that neither component has a major advantage. The photosymbiodemes appear to be models, preserved by the special habitat and showing a possible early stage in the evolution before the definite separation of ecologically specialized green algal and cyanobacterial species. [ABSTRACT FROM AUTHOR]

Photosynthetic and stomatal response of loblolly pine (Pinus taeda L.) to water stress were determined for seedlings grown under 4 different nitrogen levels. Photosynthetic rate of well-watered seedlings was linearly related to foliar N. There was no observed N effect on the relative reduction of photosynthesis due to water stress. N did not influence stomatal conductance before or during the water stress period. Therefore, instantaneous water use efficiency of well-watered seedlings was significantly increased with increased N. Significantly reduced internal CO2 concentration (Ci) associated with increased N in well-watered seedlings may be indicative of greater relative stomatal contribution to overall limitation of photosynthesis. Water stress caused an increase in Ci, the slope of the increase being related to N treatment. Stomatal conductance and photosynthesis correlated strongly within each N treatment, and increased N caused an increase in initial slope of the function. Therefore, stomatal control was uncoupled from photosynthetic capacity by N treatment in loblolly pine. These data fail to support the proposition that improved stomatal response to water stress can explain reported gains in water status of nitrogen- fertilized conifers in the field. [ABSTRACT FROM AUTHOR]

Carbon dioxide resistance and water content curves are presented for Pseudocyphellaria amphisticta, P. homoeophylla, P. billardierii, P. colensoi, Sticta latifrons and Peltigera dolichorhiza. In all cases the curves are triphasic with a high resistance at low and high water contents and a low resistance at intermediate water contents. The exact water contents at which these changes in resistance occur, and the rate at which the resistance increases at the higher water contents, appear to be species specific. The depressed NAR often found at higher water contents is shown to be caused in part by the increased resistance since it occurs under conditions where there are no changes in respiratory rate. The increase in resistance at higher water contents is suggested to be a result of water on the lower cortex. [ABSTRACT FROM AUTHOR]

Carbon dioxide. (CO[Sub2]) exchange of Sticta latifrons Rich. was studied using an infrared gas analyzer. Slight differences in the relationship between net photosynthetic rate (NPR) and water content were found when thalli were dried by using air directed solely onto the upper or lower surfaces. Further studies using a simple split chamber which allowed separate analysis of the CO[Sub2] exchange of upper and lower thallus surfaces demonstrated that the vast majority of CO[Sub2] exchanged through the lower surface. The results provide strong circumstantial evidence for the suggestion that cyphellae act as air pores and the possible importance of such pores in the water relations of the species is discussed. [ABSTRACT FROM AUTHOR]

Pseudocyphellaria dissimilis (Nyl.) D. Gall and P. James in litt populations were shown to possess different morphologies. Which correlated with the evaporative demand of their environment. The variations in morphology consisted of increased thallus thickness, mostly from increased medulla thickness, and increased rhizine length in the more exposed population. These changes confer a decreased surface/volume ratio and increased water storage in the form of external water that could be removed by blotting but not shaking. A consequence of these changes was a slower drying down rate. No differences in water loss rate per unit area were found between populations indicating that no morphological modifications exist to decrease water loss. Preliminary work on the acetylene reduction rates of the populations demonstrated a considerable difference in rates between the individual populations' and indicated that acetylene reduction could be another useful indicator of physiological adaptation. [ABSTRACT FROM AUTHOR]

Forty-four species of New Zealand lichens, including 22 species of Pseudocyphellaria and seven of Sticta, were assayed for nitrogenase activity by acetylene reduction. Nitrogen fixation was confirmed by 15N enrichment studies. Ten species, all with green algal phycobionts, showed no detectable nitrogenase activity; the remainder, including all species of Pseudocyphellaria and Sticta, assayed positively. Fixation rates were found to be species specific ranging from 0.2 to 52 nmol g-1 min-1. Nitrogen fixing lichens showed a species specific range of total nitrogen content and all had greater values than non-fixing species. Further analysis of nitrogen fixation in Sticta and Pseudocyphellaria species by plotting a graph of acetylene reduction against nitrogen content showed a highly significant positive relationship; also species of like chemical strain grouped together, and in any one chemical strain lichens with solely blue-green phycobionts possessed higher rates. The possibility exists that these lichens could provide a significant input of nitrogen into some native forests in New Zealand. [ABSTRACT FROM AUTHOR]

Metabolic studies were carried out on two lichen species (Ramalina celastri and Peltigera polydactyla) using ³HHO(g) and 14CO2. Incubations in the presence and absence of light at 100% r.h. resulted in ³H and 14C labelling of a variety of compounds. Tritium fixation during darkness was determined quantitatively as 4.1 and 8.2% of 'light' labelling (for P. polydactyla and R. celastri, respectively), and was localized predominantly in polyols, alanine, glutamic acid, glutamine, aspartic acid and γ-amino butyric acid. Under similar experimental conditions, only trace amounts of 14C were found in sugar alcohols, whereas amino acids were substantially labelled. The dissimilarity between ³H and 14C labelling patterns has led to the conclusion that polyols synthesized in the absence of photosynthesis must be derived from other stored substrates within the thallus. The role of tricarboxylic acid (TCA) cycle-related amino acids in lichen metabolism, and some potential synthetic modes of the unusual amino acid, γ-amino butyric acid, are discussed. [ABSTRACT FROM AUTHOR]

A new radiochemical technique has been applied to a study of anhydrobiotic metabolism in the lichen species, Ramalina celastri (Sprengel) Krog & Swinsc. and Peltigera polydactyla (Neck.) Hoffm. Specimens were incubated in known atmospheric humidities of THO vapour which were found to equilibrate with cellular H2O within 5 days. This method has proved effective in a study of a wide range of in vivo metabolic processes occurring at both high and low cellular water contents. Qualitative and quantitative estimations of the ³H labelling of water soluble cell constituents (amino acids, organic acids, sugars, sugar phosphates, and sugar alcohols), neutral and polar lipids, water soluble macromolecules, and insoluble cell residues have shown that diverse metabolic systems have significantly different levels of resistance to desiccation. Tricarboxylic acid cycle reactions and related amino acid interconversions were shown to be relatively desiccation resistant, whereas Calvin cycle metabolism appeared to be highly sensitive, a conclusion supported by 14CO2 tracer experiments. Conversely, the synthesis of sugar alcohols was found to be active beyond the limit of photosynthetic metabolism. Neither lipid nor macromolecular synthesis was shown to occur to a significant degree in either lichen in the desiccated state. It is proposed that the syntheses of amino adds and sugar alcohols at low cellular saturation levels are important physiological processes. Amino acid synthesis results in the accumulation of an available store of stable intermediates, ready to feed into the T.C.A. cycle by transamination or deamination on rehydration of the lichen. Sugar alcohol metabolism assists in the maintenance of a high sugar alcohol concentration to act as a physiological buffer during extreme dehydration. [ABSTRACT FROM AUTHOR]

The pattern of 14C fixation and release by algae after isolation from lichens was studied using Nostoc from Peltigera canina, Hyalococcus from Dermatocarpon miniatum, Coccomyxa from Peltiger a aphthosa and Trebouxia from Xanthoria aureolo; cultured strains of these algae were also investigated. In all cases, the following changes occur as soon as the algae are isolated: (a) release of fixed 14C to the medium declines sharply; (b) the proportion of released 14C incorporated into simple carbohydrates also falls repidly; and (c) incorporation into ethanol-insoluble material in the cell rises substantially. The direction of these changes is towards the behaviour of cultured algae. It is concluded the lichen algae begin to show substantial changes from their behaviour in symbiosis as soon as they are separated from the fungus. [ABSTRACT FROM AUTHOR]

The gaseous exchange pathways of Sticta latifrons Rich. and Pseudocyphellaria amphisticta Kremp. were examined using both light and scanning electron microscopes. The size and frequency of the pores in the gas exchange structures (cyphellae and pseudocyphellae) and in the medulla were measured and from these CO2 diffusion resistances were calculated. Pseudocyphellae were found to be smaller and more widely spaced than cyphellae, consequently the resistance of the pseudocyphellae, was much greater than that of the cyphellae. Medulla resistances were low in both lichens and are probably unimportant, even at high water contents. No evidence of hyphal swelling was found. Gas exchange structure resistances were more than five-fold greater than medulla resistances. It is suggested that this arrangement of resistances may simultaneously encourage refixation of respired CO2 and maintain a non desiccating environment for the lichen algae. The internal transport resistances calculated in this work approximate experimentally obtained values. [ABSTRACT FROM AUTHOR]

The total resistances to CO2 uptake by Sticta latifrons Rich, and Pseudocyphellaria amphisticta Kremp. were separated into transport and carboxylation components by calculation after transformation of net photosynthesis rate against CO2 concentration curves into a linear form. The use of this technique circumvented the problem of measuring the internal CO2 concentration of the lichen thalli. Both species exhibited an increase in transport resistance at high thallus water contents and an increase in both transport and carboxylation resistances at low water contents. At low and intermediate water contents internal transport resistances were larger than carboxylation resistances when measured at limiting CO2 concentrations. However, at ambient CO2 concentrations carboxylation processes were the dominant factors limiting photosynthesis at all, except the high, water contents. [ABSTRACT FROM AUTHOR]

Programming languages embody two principal forms of conditional statement, the nesting if… then… else… form and the goto form. Sime, Green & Guest (1974) compared these two and a third variety not in common use, nesting with redundancy, and they found that non-programmers learning to write programs based on conditionals obtained best results with this last variety. Their explanation emphasized the need to comprehend a program, and distinguished between two comprehension processes applicable to conditionals: tracing through a program like a computer, and finding how a particular point in a program might be reached. They hypothesized that comprehensibility differences occurred mainly in the second process. The present experiments compared response times of professional programmers in comprehension tasks requiring either the first process (Expt. I) or the second (Expt. II). Much larger differences between the three styles of conditional statements were found in the second task, favouring nesting with redundancy and thus supporting the hypothesis. Implications for research in this area and for programming language design are discussed. [ABSTRACT FROM AUTHOR]

Early-stage lesions of Kaposi's sarcoma (KS) are composed of single-layered, highly flattened cells lining collagen bundles, whereas late-stage lesions contain densely packed, spindle-shaped cells. We examined the progression of KS lesions in oral mucosa and lymph nodes from patients with AIDS, using antibodies specific for blood vascular endothelial cells (Factor VIII-related antigen) and their basement membrane (Type IV collagen and laminin). In addition, the plant lectin Ulex europaeus, which selectively stains blood vessels, was also used. In early-stage KS lesions, fibronectin, laminin and Type IV collagen were co-distributed at the interface between KS cells and collagen bundles; Factor VIII-related antigen and Ulex europaeus lectin staining was present in vascular channels and in the KS cells. However, in late-stage lesions, few if any KS cells stained with antibody to Factor VIII-associated antigen, although endothelial cells lining blood vessels were positive. Strong staining for laminin and Type IV collagen was present in a pericellular pattern throughout the nodular late-stage lesions. Since lymphatic capillary endothelium does not produce basement-membrane-specific macromolecules, these results support the conclusion that KS cells are related to blood vascular endothelium but eventually lose certain endothelium-specific markers as the cells are transformed into the spindle-shaped cell type. [ABSTRACT FROM AUTHOR]

The rain-induced resuspension of bottom sediment in shallow water is measured in a simple laboratory experiment, and found to increase significantly with increasing drop size and rain intensity, and decreasing water depth. [ABSTRACT FROM AUTHOR]

A severe leaf disorder currently affects kiwifruit vines (Actinidia deliciosa var. deliciosa) in New Zealand and a number of other countries. The symptoms, which develop in mid-summer, include interveinal chlorosis, development of necrotic areas on the leaf and eventual leaf death. Field observations strongly indicated the involvement of the root system. The present study investigated the extent to which temperature and oxygen supply at the root influenced the physiology of kiwifruit vines. Maximum root growth occurred at 20 °C. while temperatures in excess of 25 °C reduced growth. Shoot growth was also reduced by root temperatures above 20 °C. No obvious leaf symptoms developed on the vines affected by the high temperatures. Below 20 °C there was a marked reduction in growth with little or no growth occurring at 10 °C. While soil temperature can be expected to influence root growth per se, it would appear unlikely that it directly controls the seasonal pattern of root growth or greatly influences the physiology of the leaf. This study showed kiwifruit vines are not well adapted to tolerate low concentrations of oxygen in their root zone. Growth was substantially reduced when the supply of oxygen to the roots was reduced. The extent of the reduction was proportional to the number of hours per day the vines were without aeration. Root growth was particularly affected. Distinctive leaf symptoms appeared on all oxygen-stressed vines and included the sudden appearance of large necrotic areas on the older leaves, sometimes preceded by an interveinal chlorosis. Measurement of the porosity of the roots indicated that the average air space between the tightly packed cells accounted for 2% or less of the total root volume. There was no obvious change in root porosity with decreasing oxygen supply or difference between the solution grown vines and vines from the field. [ABSTRACT FROM AUTHOR]

The binding characteristics of [3H]-yohimbine on intact human platelets were investigated and compared to those of [3H]-dihydroergocryptine., A significant correlation (r = 0.92, P<0.01, n = 7) was observed between the inhibition of [3H]-yohimbine binding and of noradrenaline-induced platelet aggregation, indicating that [3H]-yohimbine binds to the α2-adrenoreceptor responsible for noradrenaline-induced platelet aggregation., The binding capacity of [3H]-yohimbine in 20 young male volunteers was 39 ± 2.2 fmol/108 platelets (mean ± s.e.m.). This is considerably lower than the binding capacity of [3H]-dihydroergocryptine previously reported., Simultaneous analysis of [3H]-yohimbine and [3H]-dihydroergocryptine binding in 10 subjects showed a significantly lower binding capacity for [3H]-yohimbine (P<0.001, paired t-test). This difference was not present in every subject, and was consistent within individuals on repeated testing., Possible causes of this difference in radioligand binding are discussed. [ABSTRACT FROM AUTHOR]

Seasonal data on leaf conductance (gl for three different apple cultivars grown in four separate orchards with different aged trees was studied between 1979 and 1985. A number of empirical models for predicting leaf conductance from environmental measurements were compared using this data and a general method for adapting such models for the prediction of different data sets is proposed. Although stepwise multiple regression identified relative humidity or vapour pressure as important variables, it frequently did not identify the optimal set of independent variables, which often did not include either of these. There was no advantage in regressing gl against principal components of the environment, rather than against the raw environmental variables. A simple model involving air vapour pressure deficit, air temperature and a hyperbolic function of irradiance was found to explain between 32 and 62% of the variance in gl for the different data sets. Parameters fitted for one data set led to the effective prediction of gl in other years or plots. The model fit could generally be improved significantly by including soil moisture deficit among the independent variables. [ABSTRACT FROM AUTHOR]

Computer programming could be made easier. This paper gives a short account of the authors' empirical studies of programming, showing that very considerable improvements can be obtained both for beginners and for professionals. The improvements are related to, though not wholly dependent on, the new concepts of 'structured programming'; we have found ways to improve both the programming language itself and the procedures used by the programmer. Psychological explanations of the effects are offered and the limitations of present findings are noted. [ABSTRACT FROM AUTHOR]