Joint Report of the First International Comparison Test on Swine Lymphocyte Alloantigens (SLA)

The first international comparison test on swine lymphocyte alloantigens (SLA) was held in Helsinki, Finland in July 1986. The results reported were based on a comparison of 157 alloantisera originating from six laboratories. The antisera were tested against a selected panel of 264 lymphocyte samples belonging to four laboratories. The most common breeds in Europe were chosen for this first comparison test (Landrace and Large White). Eighteen of the 31 previously known specificities were confirmed and a new nomenclature was established.     

Influence of oxygenated sterol compounds on phase transitions in model membranes. A study by differential scanning calorimetry

A marked influence of oxygenated sterol compounds (OSC: 7 alpha-, 7 beta-, and 25-hydroxycholesterol and 7-ketocholestanol) on the reversible gel to liquid-crystalline phase transition behavior of cholesterol-free and cholesterol-containing model membranes is evidenced by high-sensitivity differential scanning calorimetry. Liposomes of dipalmitoylphosphatidylcholine (DPPC) were chosen as model membranes. Each of the investigated OSC exerts an individual influence on the phase transition of DPPC liposomes, which expresses itself in the temperature range, the corresponding enthalpy, and the peak shape of calorimetric curves. The onset temperature of the phase transition is lowered in the following range of effectiveness: 7 beta-hydroxycholesterol greater than 7 alpha-hydroxycholesterol greater than 7-ketocholestanol greater than cholesterol. The mutual presence of cholesterol and of OSC leads to the following order: 7 alpha-hydroxycholesterol approximately equal to 7 beta-hydroxycholesterol greater than 7-ketocholestanol greater than cholesterol (without OSC) greater than 25-hydroxycholesterol. The enthalpy of the phase transition is decreased with increasing content of cholesterol, 7 alpha- or 7 beta-hydroxycholesterol, or 7-ketocholestanol. At a concentration of about 10 mol % of the latter three OSC, the corresponding enthalpy value of the transition is lowered from 9.1 kcal/mol for pure DPPC to about 7.5 kcal/mol, whereas 10 mol % cholesterol lowers the enthalpy value to 7.0 kcal/mol.(ABSTRACT TRUNCATED AT 250 WORDS)     

Isolation of variants of BALB/c 3T3 cells defective in complex ganglioside biosynthesis

In an attempt to clarify the relationship between altered glycosphingolipid metabolism and other aspects of the transformed phenotype, we have isolated variants of BALB/c 3T3 cells (clone A31) which are defective in synthesis of the more complex gangliosides (GM2, GM1 and GD1a). The selection protocol was based on the specificity of cholera toxin for ganglioside GM1, and the ability to lyse cells which bound toxin using anti-toxin and complement. Following treatment of cells with ethane methane sulfonate (EMS), populations resistant to lysis were obtained after 5-6 rounds of selection, despite a low and rather variable killing efficiency (75-95%). Five out of six clones isolated from such populations showed reduced toxin-binding capacity and loss of gangliosides more complex than GM3, as determined by metabolic labelling with [1-14C] palmitate. An identical phenotype was displayed by a variant isolated from a non-mutagenized population of cells. The phenotype remained stable for several months in culture and for over at least 40 cell doublings. Ganglioside nomenclature is according to Svennerholm [24].     

通往风景园林行业的BIM之路——数字化竖向设计教育

随着全球建造业向数字化全面转型,建筑信息模型（BIM)的教学将是未来几年风景园林设计与实施的重要主题。介绍了风景园林专业BIM的教学方法和数字化竖向设计及其应用在BIM场地设计项目中的重要性。数字化竖向设计是实现BIM的途径。风景园林教育必须在其教学中讲解BIM建模方法和过程。     

Experimental silicification of the extremophilic Archaea Pyrococcus abyssi and Methanocaldococcus jannaschii: applications in the search for evidence of life in early Earth and extraterrestrial rocks

Hydrothermal activity was common on the early Earth and associated micro‐organisms would most likely have included thermophilic to hyperthermophilic species. 3.5–3.3 billion‐year‐old, hydrothermally influenced rocks contain silicified microbial mats and colonies that must have been bathed in warm to hot hydrothermal emanations. Could they represent thermophilic or hyperthermophilic micro‐organisms and if so, how were they preserved? We present the results of an experiment to silicify anaerobic, hyperthermophilic micro‐organisms from the Archaea Domain Pyrococcus abyssi and Methanocaldococcus jannaschii, that could have lived on the early Earth. The micro‐organisms were placed in a silica‐saturated medium for periods up to 1 year. Pyrococcus abyssi cells were fossilized but the M. jannaschii cells lysed naturally after the exponential growth phase, apart from a few cells and cell remains, and were not silicified although their extracellular polymeric substances were. In this first simulated fossilization of archaeal strains, our results suggest that differences between species have a strong influence on the potential for different micro‐organisms to be preserved by fossilization and that those found in the fossil record represent probably only a part of the original diversity. Our results have important consequences for biosignatures in hydrothermal or hydrothermally influenced deposits on Earth, as well as on early Mars, as environmental conditions were similar on the young terrestrial planets and traces of early Martian life may have been similarly preserved as silicified microfossils.     

Fruit structure of Amborella trichopoda (Amborellaceae)

The indehiscent fruitlets of the apparently basalmost extant angiosperm, Amborella trichopoda, have a pericarp that is differentiated into five zones, a thin one‐cell‐layered skin (exocarp), a thick fleshy zone of 25–35 cell layers (outer mesocarp), a thick, large‐celled sclerenchymatous zone (unlignified) of 6–18 cell layers (middle mesocarp), a single cell layer with thin‐walled (silicified?) cells (inner mesocarp), and a 2–4‐cell‐layered, small‐celled sclerenchymatous zone (unlignified) derived from the inner epidermis (endocarp). The border between inner and outer mesocarp is not even but the inner mesocarp forms a network of ridges and pits; the ridges support the vascular bundles, which are situated in the outer mesocarp. In accordance with previous observations by Bailey & Swamy, no ethereal oil cells were observed in the pericarp; however, lysigenous cavities as mentioned by these authors are also lacking; they seem to be an artefact caused by re‐expanding dried fruits. The seed coat is not sclerified. The fruitlets of Amborella differ from externally similar fruits or fruitlets in other basal angiosperms, such as Austrobaileyales or Laurales, in their histology. © 2005 The Linnean Society of London, Botanical Journal of the Linnean Society, 2005, 148 , 265–274.     

Cell Wall Solubilization in Pedicel Abscission of Begonia Flower Buds

Effects of metabolic inhibitors and growth regulators on the course of abscission and on the activities of cell wall solubilizing enzymes were studied in pedicel explants of Begonia flower buds. Actinomycin D, chloramphenicol and 2,4-dinitrophenol slightly retarded abscission, whereas cycloheximide exerted a strong inhibition if applied until 10.5 h after explant excision. Indoleacetic acid retarded and ethylene promoted abscission and cell wall solubilization. However, the activities of cell wall solubilizing enzymes did not correspond with the course of abscission. No polygalacturonase and pectic acid and pectin transeliminases could be detected in the abscission zone during abscission, whereas a low pectin methylesterase activity did not change. Endo- and exocellulase activities did not increase until about 10 h after the onset of abscission, indicating that they are the result rather than the cause of abscission.     

Hormonal Regulation of Pedicel Abscission in Begonia Flower Buds

In order to analyse the hormonal regulation of flower bud shedding in Begonia, levels of indoleacetic acid (IAA), abscisic acid (ABA) and ethylene were determined in buds and pedicels. The translocation and metabolism of ¹⁴C-labeled IAA in pedicel segments were also studied. In a monoecious Begonia fuchsioides hybrid, abscising male flower buds contain about 1% of the IAA present in non-abscising female flowers. In a male Begonia davisii hybrid, the seasonal variation in bud drop coincides with changes in the IAA content of the buds, while also the release of IAA from the bud to the pedicel is hampered. Abscission zones of these pedicels always contain abscission promoting ethylene concentrations. The tissue is prevented from responding with abscission by IAA from the flower buds. The buds also contain ABA but without influencing abscission considerably. Pretreatment with ethylene or ABA does not affect IAA transport in pedicel segments. The rate of this transport is 4–6 mm × h^–1:; the capacity increases with the transverse area. In young segments, IAA is decarboxylated and also otherwise metabolized.