Preparation and Optimization of a Cell-free Translation System from Vicia sativa Germ Lacking Ribosome-inactivating Protein Activity

A cell-free translation system from Vicia sativa with high activityfor reading endogenous messengers was prepared. The concentrationsof several of the components were optimized. The system washighly sensitive to cycloheximide, puromycin and fusidic acid,but was completely insensitive to chloramphenicol. The systemlacks apparent free endogenous ribosome-inactivating proteinactivity. It was highly sensitive to several well-known ribosome-inactivatingproteins, which makes it very suitable for studying the effectsand the mechanism of action of these plant toxins. Key words: Translation system, protein synthesis, cell-free extracts, ribosome-inactivating proteins, Vicia sativa     

Spatial and Temporal Variability during Periods of "Recovery" after Mass Bleaching on Western Atlantic Coral Reefs

Western Atlantic coral reefs were differentially affected bya mass bleaching (discoloration) event in 1987. We periodicallyassessed the "appearance" of zooxanthellate organisms betweenDecember 1987 and June 1988 at nine conspicuously affected sitesin the Bahamas, Florida, St. Croix, and Venezuela, using a standardizedpoint-count technique. Three to four months after the localinitiation of the event, the "bleached" state was still presentin one to three of the most abundant reef coral taxa and ina few of the less common species (n = 5 sites). "Recovery" occurredsomewhat faster at shallower depths, at least in the Bahamasand Florida. Scleractinian corals which were "prolonged bleachers"had foliaceous or massive, rather than branching, morphologies."Bleached" points disappeared from the point counts after $6to $8 months. Long-term field data on spatial and temporal variability inthe dynamics of zooxanthellate organisms would help us to understandthe ecological consequences of bleaching. More generally, weneed to distinguish anthropogenic changes in the structure andfunctioning of reef ecosystems from those which occur naturally.Point-count techniques are well suited for collaborative studiesinvolving rapid quantification of coloration states and healthin reef corals.     

Water Retention Capacity in Root Segments Differing in the Degree of Exodermis Development

Water loss from roots back into drying soil is a problem ofpractical importance in plants growing under conditions of verylow substrate water potential, such as dry or saline areas.Root exodermis is relatively impermeable and has been suggestedto play a protective role against water loss. The relative waterretention ability was compared in root segments from exodermal(maize, onion, sunflower, Rhodes grass and sorghum) and non-exodermalspecies (Pisum sativum,Vicia fabaand wheat). Apical and basalsegments from exodermal roots, with different degrees of exodermisdevelopment, were also compared, as were segments from sorghumroots in which the exodermis thickness had been modified bysubjecting the plants to a 30 d water stress treatment. Waterretention was significantly higher in segments from exodermalroots. In each root, water loss was higher in apical than inbasal segments, regardless of the presence of exodermis. Insorghum, prolonged drought treatment increased exodermis thickeningin nodal roots, however, no differences in rates of water losswere observed in segments obtained from control and droughtedplants. Soil sheaths formed around roots of Rhodes grass growingin very dry soil with the epidermis adhering tightly to thesheath. In plants growing in the field, soil sheaths may bemore effective than the exodermis in preventing root water loss.Copyright1999 Annals of Botany Company. Root, exodermis, rhizosheaths, water loss.     

Phylogenetic Study of Organic Anion Transfer from Plasma into the Liver

THE discovery of two intracellular proteins, Y and Z, with the unique property of binding certain organic anions, may help to account for the selective and rapid transfer of bilirubin and various dyes, drugs, steroids and metabolites from plasma into the liver, which is known to occur among mammals^1–3. In the rat, from which they were first isolated³, Y and Z have been shown to possess the following characteristics, (i) They selectively bind organic anions, such as bilirubin, sulphobromophthalein (BSP) and indocyanine green, in vivo and in vitro³, (ii) The principal organic anion binding protein, Y, is present predominantly in the liver^3,4, (iii) The concentration of Y increases after administration of phenobarbital, DDT and other drugs and concomitantly the rate of organic anion transfer into the liver is increased⁵. Furthermore, in the newborn monkey, the concentration of Y and the transfer into the liver of BSP, as measured by plasma disappearance rates, are both low and subsequently increase⁶. We report here the results of a phylogenetic study involving various vertebrates. These results further support the theory that Y and Z are intracellular acceptors which facilitate the transfer of certain organic anions from plasma into the liver.     

DISTRIBUTION AND PRODUCTION OF THREE HYDROBIA SPECIES (GASTROPODA: HYDROBIIDAE) IN A SHALLOW COASTAL LAGOON IN THE BAY OF CADIZ, SPAIN

The abundance, life span, growth and production of the mud snailsHydrobia minoricensis, H. ulvae and H. ventrosa in a semi-naturallagoon system were studied by taking monthly samples at threesites during 1991 and 1992. The most abundant species, H. minoricensisoccurred at mean densities of 12834 to 26264 snails m^–2(10.7 to 25.8g dry weigh m^–2), depending on the site.The least abundant species, H. ulvae, occurred at mean densitiesof 185 to 353 snails m^–2 (3.2 to 2.2g dry weight m^–2).The numerical abundance and biomass of the three Hydrobia specieswere positively related to the biomass of benthic macroalgae(P<0.01). Although H. ulvae egg capsules were recorded throughoutthe year, newly hatched snailsof this species were not observed,in contrast to the other two species. The early spring and summercohorts of H. minoricensis and H. ventrosa seemed to be themost numerous. The average life spans of these two species wereestimated to be about 18 and 13 months respectively. Annualproduction estimates for the whole lagoon system were 29.0 (6.3),5.5 (0.8) and 5.2 (1.0)g dry weight (ash-free dry weight) m^–2yr^–1 for H. minoricensis, H. ulvae and H. ventrosa respectively.The annual P/B ratio was about 2 for H. minoricensis and H.ventrosa. (Received 5 July 1994; accepted 5 October 1994)     

一种间接估计阿根廷城市湿地海狸鼠多度的方法

我们设计了一种利用洞穴大小和空间散布来估计海狸鼠(Myocastor coypus)绝对数量的间接方法,并使用个体移除法对绝对数量的估计进行了检验。利用参数相关和效能检验对这两种方法的方程式斜率差异进行了检验,两者间存在高度正相关(r=0·963 ,P=0·002)。以洞穴大小和空间散布估计海狸鼠数量的方程斜率与1·0没有显著性差异(P=0·05) ,其差异检出效能为93 %。因此,利用洞穴大小和空间散布估计海狸鼠绝对数量的这种间接数量估计方法既不影响动物又不扰乱生境,其结果精确且易于实施。     

Multivariate hierarchical analyses of Early Jurassic Ostracoda assemblages

Palaeobiogeographic patterns of Early Jurassic ostracods from the northern and southern hemispheres (96 sections located in Europe, North Africa, Western Australia and North and South America) based on 243 species-level records document global patterns of distribution that can be compared to those previously published on ostracods from the European Epicontinental Sea and Tethyan and South Panthalassa areas. All described records of ostracods from both hemispheres spanning the Hettangian to Early Toarcian have been compiled and verified, and their patterns of origin and distribution have been interpreted. Jaccard coefficient of similarity was used to asses similarities among European, American and Tethyan ostracod shelf faunas. The numerical analysis shows a progressive longitudinal gradient in provincialism through the Early Jurassic, consistent with the northward drift of Tethyan ostracod faunas towards the European Epicontinental Sea and the southward movement of European taxa into Tethys and Panthalassa oceans. The spread of cosmopolitan species and extinction of endemic species, allied to the disappearance of geographical barriers, warmer climate conditions and rising sea levels can explain the reduction in ostracod diversity and the east-west provincialism throughout the Early Jurassic. Interchange between hemispheres, including bipolar distributions, are recognized from the Sinemurian time, pointing out that for most of the studied period, the climate worldwide was warm and tropical.     

Extreme habitats are not refuges: poeciliids suffer from increased aerial predation risk in sulphidic southern Mexican habitats

Extreme environments are often considered a predation refuge for organisms living in them. In southern Mexico several species of poeciliid fishes are undergoing incipient speciation in a variety of extreme (i.e. permanently dark and/or sulphidic) freshwater systems, and previous research has demonstrated reproductive isolation between populations from sulphidic and adjacent benign habitats. In the present study, we investigated bird predation rates (measured as successful captures per minute) in two sulphidic surface and several benign surface habitats, to test the hypothesis that extreme habitats are predation refuges. We found capture rates to be approximately 20 times higher in sulphidic environments: probably facilitated by extremophile poeciliids spending most of their time at the water surface, where they engage in aquatic surface respiration as a direct response to hypoxia. Even birds that are usually not considered major fish predators regularly engage in fish predation in the toxic habitats of southern Mexico. Our results demonstrate that extreme environments do not necessarily represent a refuge from predation, and we discuss the general importance of predation in driving incipient speciation in these systems. Finally, we hypothesize that natural selection via avian predation may play an important role in maintaining reproductive isolation between divergent poeciliid populations. © 2010 The Linnean Society of London, Biological Journal of the Linnean Society, 2010, 101 , 417–426.     

The stem xylem of Patagonian shrubs operates far from the point of catastrophic dysfunction and is additionally protected from drought‐induced embolism by leaves and roots

Hydraulic architecture was studied in shrub species differing in rooting depth in a cold desert in Southern Argentina. All species exhibited strong hydraulic segmentation between leaves, stems and roots with leaves being the most vulnerable part of the hydraulic pathway. Two types of safety margins describing the degree of conservation of the hydraulic integrity were used: the difference between minimum stem or leaf water potential (Ψ) and the Ψ at which stem or leaf hydraulic function was reduced by 50% (Ψ – Ψ₅₀), and the difference between leaf and stem Ψ₅₀. Leaf Ψ₅₀ – stem Ψ₅₀ increased with decreasing rooting depth. Large diurnal decreases in root‐specific hydraulic conductivity suggested high root vulnerability to embolism across all species. Although stem Ψ₅₀ became more negative with decreasing species‐specific Ψ_soil and minimum stem Ψ, leaf Ψ₅₀ was independent of Ψ and minimum leaf Ψ. Species with embolism‐resistant stems also had higher maximum stem hydraulic conductivity. Safety margins for stems were >2.1 MPa, whereas those for leaves were negative or only slightly positive. Leaves acted as safety valves to protect the integrity of the upstream hydraulic pathway, whereas embolism in lateral roots may help to decouple portions of the plant from the impact of drier soil layers.     

The Tyrosinase Gene in Gorillas and the Albinism of ‘Snowflake’

The sequence of the tyrosinase (Tyr) gene coding tracts has been obtained for the gorilla (Gorilla gorilla gorilla). The five exons of the gene were sequenced in three gorillas and in a normally pigmented human. The tyrosinase gene has been found to be a very conserved locus with a very low substitution rate. Some nucleotide and amino acid differences were found between the gorilla and human tyrosinase coding sequences. One of the gorillas included in the study is the only known case of albinism in a gorilla (‘Snowflake’). Mutations of the TYR gene lead to Oculocutaneous Albinism type 1 (OCA1), the most common type of albinism in humans (OMIM accession number 203100). The TYR gene encodes the tyrosinase enzyme (E.C. 1.14.18.1), whose activity was found to be completely lacking in ‘Snowflake’, indicating that a mutation in the Tyr gene is the likely cause of his albinism. Nonetheless, no nucleotide changes were detected that could account for the lack of Tyr product or tyrosinase activity in Snowflake, and explanations of these findings are discussed.