Oxypetalum banksii subsp. banksii: a taxon of Asclepiadaceae with an extragynoecial compitum

 The floral morphology of seven Oxypetalum species and, in particular, the spatial relationship between the five stigmatic chambers and two separate ovaries of their flowers with respect to transmission of the pollen tube are studied. In all species, except O. banksii subsp. banksii, floral morphology is similar to that in other Asclepiadeae, and the flowers pollinated with one pollinium develop only one follicle, which means compitum absence. In O. banksii subsp. banksii flowers, the secretory interstaminal tissue lines the inner walls of the stigmatic chambers as in the other species studied, but it also reaches the upper part of the inner surface of the filament tube, where it surrounds the styles, an unprecedented feature for Asclepiadaceae. This tissue secretes nectar and mucilage; the latter acts as transmitting medium for the growth of pollen tubes from pollinia inserted and hydrated in stigmatic chambers (“hyperstigmas”). Mucilage also functions as an extragynoecial compitum: in flowers pollinated with one pollinium both carpels develop into a follicle. Received August 28, 2001; accepted April 9, 2002 Published online: October 14, 2002 Addresses of the authors: Milene Faria Vieira (e-mail: mfvieira@mail.ufv.br), Departamento de Biologia Vegetal, Universidade Federal de Vi?osa, 36571-000, Vi?osa, Minas Gerais, Brazil. George John Shepherd, Departamento de Botanica, Instituto de Biologia, Universidade Estadual de Campinas, C.P. 6109, 13083-970, Campinas, S?o Paulo, Brazil.     

Inhibition of GABA uptake potentiates the effects of exogenous GABA on locust skeletal muscle

Insect skeletal muscle is relatively insensitive to applied GABA, responses are elicited only when relatively high concentrations of GABA are used (greater than 10(-6) M). Pretreatment of the muscle with the GABA uptake inhibitors nipecotic acid, beta-aminobutyric acid or beta-alanine increases the sensitivity of the muscle to GABA by as much as 1000-fold. The evidence suggests the existence of a GABA uptake mechanism in the insect neuromuscular system which could reside in glial cells.     

The cellular location of proteases in Candida albicans

Vacuoles prepared from yeast cells of Candida albicans were enriched in proteinase ycaB (EC 3.4.21.48) but not in aminopeptidase or beta-glucosidase. Proteinase ycaB, assayed in situ, increased 1.5-fold during starvation whereas aminopeptidase activity decreased by 25%. Proteinase ycaB increased a further 1.5-fold during germ-tube formation.     

Anti-IgA-mediated transfusion reactions in Canada.

During a 6-year period (1977 to 1982) blood samples from 152 Canadian patients were referred to the national reference laboratory of the Canadian Red Cross Society because the referring hospitals had not been able to determine the cause of the patients'' severe nonhemolytic transfusion reactions. Twenty-one patients were found to be IgA deficient, and 12 of them had strong class-specific anti-IgA antibodies, which were presumed to have been responsible for the reactions. The spectrum of symptoms that accompanied these violent reactions was documented for 10 of the patients. As a probable minimum, the incidence of anti-IgA-mediated reactions averaged 1.3 per million units of blood or blood products transfused during this period.     

Mapping Soil Properties of Africa at 250 m Resolution: Random Forests Significantly Improve Current Predictions

80% of arable land in Africa has low soil fertility and suffers from physical soil problems. Additionally, significant amounts of nutrients are lost every year due to unsustainable soil management practices. This is partially the result of insufficient use of soil management knowledge. To help bridge the soil information gap in Africa, the Africa Soil Information Service (AfSIS) project was established in 2008. Over the period 2008–2014, the AfSIS project compiled two point data sets: the Africa Soil Profiles (legacy) database and the AfSIS Sentinel Site database. These data sets contain over 28 thousand sampling locations and represent the most comprehensive soil sample data sets of the African continent to date. Utilizing these point data sets in combination with a large number of covariates, we have generated a series of spatial predictions of soil properties relevant to the agricultural management—organic carbon, pH, sand, silt and clay fractions, bulk density, cation-exchange capacity, total nitrogen, exchangeable acidity, Al content and exchangeable bases (Ca, K, Mg, Na). We specifically investigate differences between two predictive approaches: random forests and linear regression. Results of 5-fold cross-validation demonstrate that the random forests algorithm consistently outperforms the linear regression algorithm, with average decreases of 15–75% in Root Mean Squared Error (RMSE) across soil properties and depths. Fitting and running random forests models takes an order of magnitude more time and the modelling success is sensitive to artifacts in the input data, but as long as quality-controlled point data are provided, an increase in soil mapping accuracy can be expected. Results also indicate that globally predicted soil classes (USDA Soil Taxonomy, especially Alfisols and Mollisols) help improve continental scale soil property mapping, and are among the most important predictors. This indicates a promising potential for transferring pedological knowledge from data rich countries to countries with limited soil data.     

Effects of climate change on the delivery of soil‐mediated ecosystem services within the primary sector in temperate ecosystems: a review and New Zealand case study

Future human well‐being under climate change depends on the ongoing delivery of food, fibre and wood from the land‐based primary sector. The ability to deliver these provisioning services depends on soil‐based ecosystem services (e.g. carbon, nutrient and water cycling and storage), yet we lack an in‐depth understanding of the likely response of soil‐based ecosystem services to climate change. We review the current knowledge on this topic for temperate ecosystems, focusing on mechanisms that are likely to underpin differences in climate change responses between four primary sector systems: cropping, intensive grazing, extensive grazing and plantation forestry. We then illustrate how our findings can be applied to assess service delivery under climate change in a specific region, using New Zealand as an example system. Differences in the climate change responses of carbon and nutrient‐related services between systems will largely be driven by whether they are reliant on externally added or internally cycled nutrients, the extent to which plant communities could influence responses, and variation in vulnerability to erosion. The ability of soils to regulate water under climate change will mostly be driven by changes in rainfall, but can be influenced by different primary sector systems' vulnerability to soil water repellency and differences in evapotranspiration rates. These changes in regulating services resulted in different potentials for increased biomass production across systems, with intensively managed systems being the most likely to benefit from climate change. Quantitative prediction of net effects of climate change on soil ecosystem services remains a challenge, in part due to knowledge gaps, but also due to the complex interactions between different aspects of climate change. Despite this challenge, it is critical to gain the information required to make such predictions as robust as possible given the fundamental role of soils in supporting human well‐being.     

Two respiratory enzyme systems in Campylobacter jejuni NCTC 11168 contribute to growth on l‐lactate

Campylobacter jejuni, a major food‐borne intestinal pathogen, preferentially utilizes a few specific amino acids and some organic acids such as pyruvate and l ‐ and d ‐lactate as carbon sources, which may be important for growth in the avian and mammalian gut. Here, we identify the enzymatic basis for C. jejuni growth on l ‐lactate. Despite the presence of an annotated gene for a fermentative lactate dehydrogenase (cj1167), no evidence for lactate excretion could be obtained in C. jejuni NCTC 11168, and inactivation of the cj1167 gene did not affect growth on lactate as carbon source. Instead, l ‐lactate utilization in C. jejuni NCTC 11168 was found to proceed via two novel NAD‐independent l ‐LDHs; a non‐flavin iron–sulfur containing three subunit membrane‐associated enzyme (Cj0075c‐73c), and a flavin and iron–sulfur containing membrane‐associated oxidoreductase (Cj1585c). Both enzymes contribute to growth on l ‐lactate, as single mutants in each system grew as well as wild‐type on this substrate, while a cj0075c cj1585c double mutant showed no l ‐lactate oxidase activity and did not utilize or grow on l ‐lactate; d ‐lactate‐dependent growth was unaffected. Orthologues of Cj0075c‐73c (LldEFG/LutABC) and Cj1585c (Dld‐II) were recently shown to represent two novel families of l ‐ and d ‐lactate oxidases; this is the first report of a bacterium where both enzymes are involved in l ‐lactate utilization only. The cj0075c‐73c genes are located directly downstream of a putative lactate transporter gene (cj0076c, lctP), which was also shown to be specific for l ‐lactate. The avian and mammalian gut environment contains dense populations of obligate anaerobes that excrete lactate; our data indicate that C. jejuni is well equipped to use l ‐ and d ‐lactate as both electron‐donor and carbon source.     

Expression of collier in the premandibular segment of myriapods: support for the traditional Atelocerata concept or a case of convergence?

Background  

A recent study on expression and function of the ortholog of the Drosophila collier (col) gene in various arthropods including insects, crustaceans and chelicerates suggested a de novo function of col in the development of the appendage-less intercalary segment of insects. However, this assumption was made on the background of the now widely-accepted Pancrustacea hypothesis that hexapods represent an in-group of the crustaceans. It was therefore assumed that the expression of col in myriapods would reflect the ancestral state like in crustaceans and chelicerates, i.e. absence from the premandibular/intercalary segment and hence no function in its formation.