Differential taphonomy of modern brachiopods (San Juan Islands, Washington State): effect of intrinsic factors on damage and community-level abundance

The differences in shell structure and population turnover between organic-poor, impunctate (Hemithiris) and organic-rich, punctate brachiopod (Terebratalia) in a mixed-bottom, siliciclastic setting (San Juan Islands, WA) lead to different taphonomic damage and fidelity with respect to community-level abundance in death assemblages. In comparing shell interiors of similar-sized specimens, Terebratalia is predominantly affected by fibre detachment and shows almost no microbioerosion at the SEM scale; whereas, Hemithiris shows less marked fibre detachment at the SEM scale and is more intensely affected by microbioerosion both at SEM and light microscope (LM) scales. Fibre detachment related to rapid, microbially-induced organic matter decay appears to be the main destructive process acting on Terebratalia. Higher bioerosion levels in Hemithiris at SEM and LM scales are probably related to a combination of a low maceration rate and a preferential settlement by borers. From their vastly different abundances in life assemblages it can be deduced that Terebratalia produces dead shells at a much higher rate than Hemithiris. Therefore, the proportion of altered Terebratalia, relative to Hemithiris, is expected to be decreased due to its higher production of recently dead cohorts. That Terebratalia is also characterized by high damage levels shows that differential population turnover alone is not responsible for the differences in taphonomic damage. This shows that organic-rich and organic-poor shells are characterized by differential post-mortem durability. Although very few Hemithiris are present in the life assemblages, high durability ensures its relative over-representation in death assemblages. Terebratalia is not strongly under-represented in death assemblages, despite its high destruction rate, because of large production of recently dead shells. Even with the biasing effect of differential durability, the good fidelity reported in previous live-dead studies can be enhanced by higher population turnover of numerically dominant taxa, leading to constant input of recently dead shells into death assemblages.     

CO2 enrichment reduces the relative contribution of latex and latex-related hydrocarbons to biomass in Euphorbia lathyris

The hypothesis that plants grown under elevated CO₂ allocate more carbon to the production of latex and C‐rich secondary compounds whereas nutrient addition counteracts this effect was tested. Two similar experiments were conducted in two different experimental facilities. In both facilities seedlings of Euphorbia lathyris were exposed to factorial combinations of two CO₂ concentrations and two levels of nutrient availability for 2 months. The CO₂ treatments and growth conditions differed substantially between these two experiments but treatment responses to elevated CO₂ and fertilizer addition were remarkably similar, underlining the robustness of our findings. Elevated CO₂ increased biomass to a greater extent in fertilized than in unfertilized plants and reduced the leaf biomass fraction by accelerating leaf senescence. Concentrations of non‐structural carbohydrates (NSC) increased in elevated CO₂. However, this apparent carbon surplus did not feed into the whole plant latex pool. The latex harvest per leaf (?25%) and the concentration of latex‐related hydrocarbons (?20%) even decreased under elevated CO₂ (both experiments P < 0.05). Fertilization reduced NSC concentrations (?25%) but neither affected latex yield per leaf nor the concentration of latex‐related hydrocarbons. It is concluded that latex and related hydrocarbons in CO₂‐enriched plants are a negligible sink for excess carbon irrespective of nutrient status and thus, vigour of growth.     

Impact of early applied upper limb stimulation: The EXPLICIT-stroke programme design

Background  

Main claims of the literature are that functional recovery of the paretic upper limb is mainly defined within the first month post stroke and that rehabilitation services should preferably be applied intensively and in a task-oriented way within this particular time window. EXplaining PLastICITy after stroke (acronym EXPLICIT-stroke) aims to explore the underlying mechanisms of post stroke upper limb recovery. Two randomized single blinded trials form the core of the programme, investigating the effects of early modified Constraint-Induced Movement Therapy (modified CIMT) and EMG-triggered Neuro-Muscular Stimulation (EMG-NMS) in patients with respectively a favourable or poor probability for recovery of dexterity.     

Selenium derivatization and crystallization of DNA and RNA oligonucleotides for X-ray crystallography using multiple anomalous dispersion

We report here the solid phase synthesis of RNA and DNA oligonucleotides containing the 2′-selenium functionality for X-ray crystallography using multiwavelength anomalous dispersion. We have synthesized the novel 2′-methylseleno cytidine phosphoramidite and improved the accessibility of the 2′-methylseleno uridine phosphoramidite for the synthesis of many selenium-derivatized DNAs and RNAs in large scales. The yields of coupling these Se-nucleoside phosphoramidites into DNA or RNA oligonucleotides were over 99% when 5-(benzylmercapto)-1H-tetrazole was used as the coupling reagent. The UV melting study of A-form dsDNAs indicated that the 2′-selenium derivatization had no effect on the stability of the duplexes with the 3′-endo sugar pucker. Thus, the stems of functional RNA molecules with the same 3′-endo sugar pucker appear to be the ideal sites for the selenium derivatization with 2′-Se-C and 2′-Se-U. Crystallization of the selenium-derivatized oligonucleotides is also reported here. The results demonstrate that this 2′-selenium functionality is suitable for RNA and A-form DNA derivatization in X-ray crystallography.     

An intronic polymorphism of the hMLH1 gene contributes toward incomplete genetic testing for HNPCC

Hereditary non-polyposis colorectal cancer (HNPCC) is a common hereditary cancer. Genetic testing is complicated by the multiple DNA mismatch repair genes that underlie the disorder. Many suspected HNPCC families have no germ-line mutation identified. We reassessed an unusual family that appeared to have 2 individuals homozygous for a germline mutation within exon 1 of the hMLH1 gene. A few rare individuals with two inherited mutations in one of the mismatch repair genes have been reported and appear to have a distinct clinical appearance. However, there were no clinical features in the family discussed here that were consistent with constitutive lack of hMLH1. Redesigning the intronic primers for exon 1 identified a common polymorphism located within the original intronic primer site. The polymorphism prevented amplification of the wild-type allele, giving the erroneous appearance of homozygous inheritance of the mutated allele. Likewise, common intronic polymorphisms, if located within primer sequences on the chromosome harboring the HNPCC germ-line mutation could restrict amplification to only the wild-type allele, which may contribute significantly to the low success rate of identifying mutations in HNPCC families.     

Growth and reproductive responses to elevated CO2 in wild cereals of the northern Negev of Israel

How might wild relatives of modern cereals have responded to past, and how might they respond to future, atmospheric CO₂ enrichment under competitive situations in a dry, low‐nutrient environment? In order to test this, Aegilops and Hordeum species, common in semiarid annual grasslands of the Middle East, were grown in nine model ecosystems (400 kg each) with a natural matrix of highly diverse Negev vegetation established on native soil shipped to Basel, Switzerland. In a simulated, seasonally variable climate of the northern Negev, communities experienced a full life‐cycle in 280 (preindustrial), 440 (immediate future) and 600 ppm of CO₂ (end of the next century). Neither Aegilops (A. kotschyi and A. peregrina), nor Hordeum spontaneum showed a significant biomass response to CO₂ concentrations exceeding 280 ppm The reproductive output remained unaffected or even declined (A. peregrina) under elevated CO₂. Non‐structural carbohydrates in leaf tissues increased and N concentration decreased with increasing CO₂ concentration. N concentration, germination success and seedling development of newly formed grains were either unchanged or reduced in response to high CO₂ treatment of parent plants. In a separate fertilizer × CO₂ trial with A. kotschyi nested in smaller model communities, we found no effect of P addition, but a 2–3‐fold biomass increase by NPK addition compared to the unfertilized control. A significant stimulation of biomass by CO₂ enrichment (+ 44% between 280 and 600 ppm) was obtained only in the NPK treatment. These data suggest that increased CO₂ concentration had little direct effect on growth and reproduction in these ‘wild cereals’ in the recent past, and the same seems to hold for their future, except if N‐rich fertilizer is added.     

Use of fatty acids for the assessment of zooplankton grazing on bacteria, protozoans and microalgae

1. The distribution of fatty acids in different groups of bacteria, ciliated protozoans and microalgae is reviewed emphasizing specific fatty acids like odd-branched fatty acids and ( n -3) polyunsaturated fatty acids.
2. Odd-branched fatty acids and ( n -6) fatty acids appear to be good indicators of zooplankton grazing on bacteria and ciliates when they are detected in microcrustacean triacylglycerols. We give several examples where these fatty acids may be used as markers. The value of ( n -3) fatty acids in describing zooplankton grazing on phytoplankton seems to be low.     

Allocation of Photosynthate to Individual Tubers of Solanum tuberosum L.: III. RELATIONSHIP BETWEEN GROWTH RATE OF INDIVIDUAL TUBERS, TUBER WEIGHT AND STOLON GROWTH PRIOR TO TUBER INITIATION

Potato plants (Solanum tuberosum L.) were grown in water culture.About 14 d after tuber initiation no significant differenceswere found between apical and basal tuber parts in ¹⁴C-uptakeand partitioning into various fractions from ¹⁴C-labelled photosynthate.Thus, the fresh weight of these tubers could be used as a parameterfor the sink size. The ¹⁴C-content per tuber (sink strength)20 h after ¹⁴CO₂-supply to the foliage was significantly correlatedwith the tuber fresh weight. No correlation was found betweenthe ¹⁴C-concentration of the tuber (sink activity; ct. min^–g^– fr. wt.) and tuber fresh weight. Consequently, tuberfresh weight (sink size) per se must have been a factor whichinfluenced sink strength. Stolon parameters characterizing theirgrowth prior to tuber initiation (e.g. stolon volume) and theircapacity for photosynthate transport (diameter, length) weremeasured at the time of tuber initiation. Significant correlationswere found between these stolon parameters and subsequent growthof individual tubers. Anatomical studies on the proportion ofvarious tissues in the cross sectional area of stolons supportthe idea of a negative relation between growth of individualtubers and transport resistance in the phloem of the stolons.It is concluded that in the initial phase of tuber growth, mainlyfactors outside of the tuber determine its growth rate. In laterstages of tuber growth, when the sink strength increases, thecompeting strength of individual tubers for photosynthate isdominated mainly by factors within the tuber itself, such astheir sink size and sink activity. Key words: Potato tuber, sink size, tuber initiation, transport resistance     

Chromium VI Induced Structural and Ultrastructural Changes in Bush Bean Plants (Phaseolus vulgaris L.)

The effect of a growth reducing chromium VI concentration (9.6x 10^–5M Cr as Na₂CrO₄) on the structure and ultrastructureof different organs of bush bean plants (Phaseolus vulgarisL.) grown on perlite was studied using light, transmission electronand scanning electron microscopy. The structural and ultrastructuralalterations observed were quite different in the various organsanalysed and did not always stay in direct relation to the averageCr content of the whole organ. The primary toxicity effect seemedto be membrane damage, due to the high oxidation power of CrVI. It is suggested that chromium is retained in vacuoles andcell walls of roots, and that the chromium reaching the leavesmay be principally Cr III and present in cell walls. The alterationsobserved in the upper plant parts seemed principally due toindirect Cr effects on the content of essential mineral nutrients. Phaseolus vulgaris L., bush bean, chromium VI toxicity, structure, ultranstructure, light microscopy, transmission electron microscopy, scanning electron microscopy