Dynamic discrete model of flashing light effect in photosynthesis of microalgae

For a photobioreactor for mass-culturing microalgae, it is known that flashing light effect enhances the efficiency of photosynthesis. A dynamic model for photosynthesis was developed to elucidate this effect. A particular feature of the model is that discrete RuBP particles circulate in the Calvin cycle and their speeds in the cycle are determined by the amount of ATP generated in the photon reception process. This can realise the light saturation under continuous light and the flashing light effect under fluctuating illumination. Laboratory experiments were conducted to obtain model parameters by curve-fitting for Chaetoceros calcitrans. The present model demonstrates the light flashing effect moderately well and elucidates its mechanism reasonably.     

Effect of pH and salts on the binding of free amino acids to the corn protein zein studied by thin-layer chromatography

Summary. The interaction of free amino acids with the corn protein zein was studied by thin-layer chromatography carried out on cellulose layers covered with zein and the effect of pH and salts on the strength of interaction was elucidated. Only the binding of Arg, His, Lys, Orn and Trp to zein was verified, other amino acids were not retained. Retention of Arg, His, Lys and Orn decreased linearly with increasing concentration of salts the mobile phase indicating the hydrophilic character of amino acid–zein interaction. Both alkaline and acidic pH influenced the strength of binding. Principal component analysis indicated the different character of the influence of pH and salts on the interaction. The results suggest that these amino acid residues may account for the binding of other peptides and proteins to zein.     

ICOS costimulates invariant NKT cell activation

It has been reported that costimulatory molecules, CD80/86-CD28 and CD154-CD40, critically contribute to activation of CD1d-restricted invariant NKT (iNKT) cells. Here we have demonstrated that ICOS, a new member of the CD28 family, plays a substantial role in iNKT cell activation. iNKT cells constitutively expressed ICOS as well as CD28 independently, and ICOS expression was further up-regulated 2-3 days after alpha-galactosylceramide (alpha-GalCer) treatment. Blockade of ICOS-mediated costimulation by administration of anti-ICOS ligand (B7RP-1) mAb or by ICOS gene knockout substantially inhibited alpha-GalCer-induced IFN-gamma and IL-4 production, cytotoxic activity, and anti-metastatic effect. Moreover, blockade of both B7RP-1-ICOS and CD80/86-CD28 interactions mostly abolished the alpha-GalCer-induced immune responses. These findings indicate that iNKT cell activation is regulated by CD28 and IOCS independently.     

Membrane-Induced Structure of Scyliorhinin I: A Dual NK1/NK2 Agonist

Scyliorhinin I, a linear decapeptide, is the only known tachykinin that shows high affinity for both NK-1 and NK-2 binding sites and low affinity for NK-3 binding sites. As a first step to understand the structure-activity relationship, we report the membrane-induced structure of scyliorhinin I with the aid of circular dichroism and 2D-(1)H NMR spectroscopy. Sequence specific resonance assignments of protons have been made from correlation spectroscopy (TOCSY, DQF-COSY) and NOESY spectroscopy. The interproton distance constraints and dihedral angle constraints have been utilized to generate a family of structures using DYANA. The superimposition of 20 final structures has been reported with backbone pairwise root mean-square deviation of 0.38 +/- 0.19 A. The results show that scyliorhinin I exists in a random coil state in aqueous environments, whereas helical conformation is induced toward the C-terminal region of the peptide (D4-M10) in the presence of dodecyl phosphocholine micelles. Analysis of NMR data is suggestive of the presence of a 3(10)-helix that is in equilibrium with an alpha-helix in this region from residue 4 to 10. An extended highly flexible N-terminus of scyliorhinin I displays some degree of order and a possible turn structure. Observed conformational features have been compared with respect to that of substance P and neurokinin A, which are endogenous agonists of NK-1 and NK-2 receptors, respectively.     

Maternal Effect by Stem Females in <Emphasis Type="Italic">Brachionus plicatilis</Emphasis>: Effect of Starvation on Mixis Induction in Offspring

We examined whether starvation during the initial period of life in stem females affected reproductive characteristics of the offspring. Starvation treatment had different effects on rotifers hatched from resting eggs and those hatched from amictic eggs. When stem females experienced starvation after hatching, this induced a higher percentage of mixis in their offspring. When the same starvation treatment was applied to rotifers hatched from amictic eggs, there was no effect on the induction of mixis. It is probable that stem females hatched from resting eggs have specific features that are vulnerable to unfavorable environmental conditions, and that these features can be inherited by their offspring through the maternal cytoplasm.     

Electronic structures of highly symmetrical compounds of f elements: XXXIX. Do more covalent europium(III) compounds exhibit an anti-nephelauxetic behavior?

By comparing the nephelauxetic ratios β of a number of molecular Pr^III compounds, and the Slater parameters F² (or Racah parameters E¹) of molecular Nd^III and selected Sm^III compounds, presumably more covalent types of Eu^III compounds could be identified. Powdered [Eu{N(SiMe₃)₂}₃] (1), “[Eu{OC(tBu)₃}₃]” (“3”) and [Eu(η⁵-C₅H₅)₃(CNC₆H₁₁)] (5) were resynthesized following usual procedures. The absorption transitions ⁷F₀ → ⁵D₀ of an oriented single crystal of 1, a glassy frozen solution of 1 dissolved in a mixture of 2-MeTHF/THF (ratio 3:1) ([Eu{N(SiMe₃)₂}₃(THF)], (2)), of “3” dissolved in 2-MeTHF ([Eu{OC(tBu)₃}₃(MeTHF)], (4)), and of 5 dissolved in a mixture of the inert solvents methylcyclohexane/toluene (ratio 1:1), were measured at room and low temperatures (90 K). The energy differences of this transition for compounds 1, 2, 4 and 5 are larger than those of [Eu(H₂O)₉]³⁺ or even gaseous Eu³⁺, indicating quasi “anti-nephelauxetic” effects. Crystal field calculations, however, reveal that lower Slater parameters F² (or Racah parameters E¹) have to be used than those of [Eu(H₂O)₉]³⁺ in order to reproduce the experimental energy differences between ⁷F₀ and ⁵D₀, thus indicating the expected nephelauxetic effects of more covalent Eu^III compounds.     

Is more choice always desirable? Evidence and arguments from leks,food selection,and environmental enrichment

Recent studies on humans show that too much choice can make subjects less likely to choose any item. I consider general adaptive and non‐adaptive explanations of why such choice aversion, or its converse, might occur in animals. There are three questions: is more choice always preferred, does it ever lead to less consumption (or a lower probability of consumption), and may it result in worse items being selected? A preference for choice is one of the main explanations for lek formation and I draw attention to previously unrecognised parallels with models of human shopping behaviour. There is indeed evidence of female preference for larger leks, although much of the observational data are open to other interpretations. Unfortunately nobody has looked for choice aversion where it is most to be expected, in leks larger than normally occur. Evidence that too much choice of males confuses females is strongest in acoustically advertising frogs, but the widespread decrease of mating skew in larger leks might also have this explanation. A model reanalyses data on skew in black grouse Tetrao tetrix and suggests that considering only a random subset of a large lek may increase the chances of selecting the better males: larger leks are more likely to include better males, but these are less likely to be selected. These opposing effects may lead to an optimum lek size, but only with a sufficient decline in choice accuracy with size. With food choice, very few studies have avoided confounding choice with food quality, by manipulating only flavour. The widespread phenomena of stimulus‐specific satiety and novelty seeking imply that monotonous diets are aversive, but no studies test whether animals choose sites where they know food diversity to be greater. Operant experiments that demonstrate mild preferences for free choice concern choice about the means to get food rather than the food itself. In some insect species even moderate choice of diet can be deleterious, and studies on search images and the confusion effect may be evidence of this in vertebrates. Environmental enrichment of captive animals often relies on increasing the options available, but it need not be the choice itself that is beneficial. I consider briefly further areas in biology where choice preference or aversion are potentially important.     

Inflow of seeds through the forest edge: evidence from seed bank and vegetation patterns

To determine the influence of the proximity of a forest edge on seed bank composition and diversity, we performed a seed bank sampling at ancient deciduous forests bordering intensive arable fields. Also vegetation patterns were taken into account. We hypothised that forest edges may facilitate the entrance of diaspores of invasive species into the forest and the successive incorporation of these species in the forest seed bank. We noticed a substantial influence of the proximity of an edge on seed bank composition at as well the forested side of the edge as the field side. The forest edge zone was limited to 3 m into the forest and the field edge zone extended 3m into the field. The seed bank samples of field and forest edge are characterised by a higher species diversity and seed density and a higher similarity between seed bank and vegetation, compared to field or forest samples. The forest edges contains fewer pioneer species in comparison with the forest interior and more competitive species and species of edges and clearings compared with field and forest samples. The seed longevity index increases towards the forest interior. We can conclude from our data that the forest and edge seed bank are composed by both seeds from recent dispersal processes and local seed set and by seeds originating from past vegetation on the site. Near the edge, actual seed input seems of primal importance. Further towards the forest interior seed input decreases and long-living seeds of past vegetation become more important. Ancient forest edges thus act as a barrier for seeds of species of the surrounding arable field.     

Genetic evidence for a maternal effect locus controlling genomic imprinting and growth

Crosses between two species of deer mouse (Peromyscus) yield dramatic parent-of-origin effects. Female P. maniculatus (BW) crossed with male P. polionotus (PO) produce animals smaller than either parent. PO females crossed with BW males yield lethal overgrowth that has been associated with loss-of-imprinting (LOI). Previously, we mapped two loci influencing fetal growth. These two loci, however, do not account for the LOI, nor for the dysmorphic phenotypes. Here we report that maternal genetic background strongly influences the LOI. Analyses of crosses wherein maternal genetic background is varied suggest that this effect is likely due to the action of a small number of loci. We have termed these putative loci Meil. Estimation of Meil loci number was confounded by skewed allelic ratios in the intercross line employed. We show that the Meil loci are not identical to any of the DNA methyltransferases shown to be involved in regulation of genomic imprinting.     

Effect of humidity on the disintegrant property of α-cellulose,Part II: A technical note

Conclusion  The summary is that the high humidity impaired the disintegrant property of α-cellulose in all 3 tablets tested. Tablets of aspirin, which is the more hygroscopic drug, were also more sensitive to the humidity effect, while tablets of chloroquine phosphate, which is a water-soluble drug, were the least sensitive to the humidity effect. The results permit the conclusion that moisture uptake with subsequent gelling of the α-cellulose is the mechanism of impairment of its disintegrant property. The tablets would not normally be stored under an RH as high as 100%, nevertheless, the results of the accelerated stability study have underscored the need to protect tablets containing α-cellulose as disintegrant from moisture. Published: August 10, 2005