Removal of naphthalene and phenanthrene using aerobic membrane bioreactor

The removal of polycyclic aromatic hydrocarbons by membrane bioreactor (MBR) under aerobic conditions had been studied using naphthalene (NAP) and phenanthrene (PHE) as model compounds. Three MBRs with submerged ultra-filtration hollow fiber membranes were operated applying different operational conditions during 6.5 months. Complete NAP and PHE removal was obtained applying loads of 7 gNAP kgTSS^?1 day^?1 and 0.5 gPHE kgTSS^?1 day^?1, while the organic loading rate was adjusted to 0.26 kgCOD kgTSS^?1 day^?1, with the biomass concentration being 6000 mgTSS L^?1, the hydraulic retention time (HRT) 8 h and the solids retention time (SRT) 30 days. Load increases, as well as HRT and SRT reductions, affected the NAP and PHE removals. Biodegradation was found to be the major NAP and PHE removal mechanism. There was no NAP accumulation in the biomass. Low PHE quantities remain sorbed in the biomass and the contribution of the sorption in the removal of this compound was estimated to be less than 0.01 %. The volatilization does not contribute to the PHE removal in MBRs, but the contribution of NAP volatilization can reach up to 0.6 % when HRT of 8 h is applied.     

The lepidopteran mitochondrial control region: structure and evolution

For several species of lepidoptera, most of the approximately 350-bp mitochondrial control-region sequences were determined. Six of these species are in one genus, Jalmenus; are closely related; and are believed to have undergone recent rapid speciation. Recent speciation was supported by the observation of low interspecific sequence divergence. Thus, no useful phylogeny could be constructed for the genus. Despite a surprising conservation of control-region length, there was little conservation of primary sequences either among the three lepidopteran genera or between lepidoptera and Drosophila. Analysis of secondary structure indicated only one possible feature in common--inferred stem loops with higher-than-random folding energies-- although the positions of the structures in different species were unrelated to regions of primary sequence similarity. We suggest that the conserved, short length of control regions is related to the observed lack of heteroplasmy in lepidopteran mitochondrial genomes. In addition, determination of flanking sequences for one Jalmenus species indicated (i) only weak support for the available model of insect 12S rRNA structure and (ii) that tRNA translocation is a frequent event in the evolution of insect mitochondrial genomes.      

Glutamine repeats and inherited neurodegenerative diseases: molecular aspects

Several dominantly inherited, late onset, neurodegenerative diseases are due to expansion of CAG repeats, leading to expansion of glutamine repeats in the affected proteins. These proteins are of very different sizes and, with one exception, show no sequence homology to known proteins or to each other; their functions are unknown. In some, the glutamine repeat starts near the N-terminus, in another near the middle and in another near the C-terminus, but regardless of these differences, no disease has been observed in individuals with fewer than 37 repeats, and absence of disease has never been found in those with more than 41 repeats. Protein constructs with more than 41 repeats are toxic to E. coli and to CHO cells in culture, and they elicit ataxia in transgenic mice. These observations argue in favour of a distinct change of structure associated with elongation beyond 37–41 glutamine repeats. The review describes experiments designed to find out what these structures might be and how they could influence the properties of the proteins of which they form part. Poly- -glutamines form pleated sheets of β-strands held together by hydrogen bonds between their amides. Incorporation of glutamine repeats into a small protein of known structure made it associate irreversibly into oligomers. That association took place during the folding of the protein molecules and led to their becoming firmly interlocked by either strand- or domain-swapping. Thermodynamic considerations suggest that elongation of glutamine repeats beyond a certain length may lead to a phase change from random coils to hydrogen-bonded hairpins. Possible mechanisms of expansion of CAG repeats are discussed in the light of looped DNA model structures.     

Development of cell surface saccharides on embryonic pancreatic cells

Using a battery of seven lectin-ferritin conjugates as probes for cell surface glycoconjugates, we have studied the pattern of plasmalemmal differentiation of cells in the embryonic rat pancreas from day 15 in utero to the early postpartum stage. Our results indicate that differentiation of plasmalemmal glycoconjugates on acinar, endocrine, and centroacinar cells is temporally correlated with development and is unique for each cell type, as indicated by lectin-ferritin binding. Specifically, (a) expression of adult cell surface saccharide phenotype can be detected on presumptive acinar cells as early as 15 d in utero, as indicated by soybean agglutinin binding, and precedes development of intracellular organelles characteristic of mature acinar cells; (b) maturation of the plasmalemma of acinar cells is reached after intracellular cytodifferentiation is completed, as indicated by appearance of Con A and fucoselectin binding sites only at day 19 of development; conversely, maturation of the endocrine cell plasmalemma is accompanied by "loss" (masking) of ricinus communis II agglutinin receptors; and (c) binding sites for fucose lectins and for soybean agglutinin are absent on endocrine and centroacinar cells at all stages examined. We conclude that acinar, centroacinar, and endocrine cells develop from a common progenitor cell(s) whose plasmalemmal carbohydrate composition resembles most closely that of the adult centroacinar cell. Finally, appearance of acinar lumina beginning at approximately 17 d in utero is accompanied by differenetiation of apical and basolateral plasmalemmal domains of epithelial cells, as indicated by enhanced binding of several lectin-ferritin conjugates to the apical plasmalemmal, a pattern that persists from this stage through adult life.     

Titanium and iron titanium oxide nanoparticles in antennae of the migratory ant <Emphasis Type="Italic">Pachycondyla marginata</Emphasis>: an alternative magnetic sensor for magnetoreception?

The most accepted hypothesis of magnetoreception for social insects is the ferromagnetic hypothesis which assumes the presence of magnetic material as a sensor coupled to sensitive structures that transmit the geomagnetic field information to the nervous system. As magnetite is the most common magnetic material observed in living beings, it has been suggested as basic constituent of the magnetoreception system. Antennae and head have been pointed as possible magnetosensor organs in social insects as ants, bees and termites. Samples of three antenna joints: head-scape, scape-pedicel and pedicel-third segment joints were embedded in epoxi resin, ultrathin sectioned and analyzed by transmission electron microscopy. Selected area electron diffraction patterns and X-ray energy dispersive spectroscopy were obtained to identify the nanoparticle compound. Besides iron oxides, for the first time, nanoparticles containing titanium have been identified surrounded by tissue in the antennae of ants. Given their dimension and related magnetic characteristics, these nanoparticles are discussed as being part of the magnetosensor system.     

Substitutions at the opening of the Rubisco central solvent channel affect holoenzyme stability and CO2/O2 specificity but not activation by Rubisco activase

Ribulose-1,5-bisphosphate carboxylase/oxygenase (Rubisco) catalyzes the initial step of carbon metabolism in photosynthesis. The holoenzyme comprises eight large subunits, arranged as a tetramer of dimers around a central solvent channel that defines a fourfold axis of symmetry, and eight small subunits, arranged as two tetramers at the poles of the axis. The phylogenetically divergent small-subunit loops between β-strands A and B form the entrance to the solvent channel. In the green alga Chlamydomonas reinhardtii, Ile-58 from each of the four small-subunit βA–βB loops defines the minimal diameter of the channel opening. To understand the role of the central solvent channel in Rubisco function, directed mutagenesis and transformation of Chlamydomonas were employed to replace Ile-58 with Ala, Lys, Glu, Trp, or three Trp residues (I58W3) to close the entrance to the channel. The I58E, I58K, and I58W substitutions caused only small decreases in photosynthetic growth at 25 and 35 °C, whereas I58W3 had a substantial effect at both temperatures. The mutant enzymes had decreased carboxylation rates, but the I58W3 enzyme had decreases in both carboxylation and CO₂/O₂ specificity. The I58E, I58W, and I58W3 enzymes were inactivated at lower temperatures than wild-type Rubisco, and were degraded at slower rates under oxidative stress. However, these mutant enzymes were activated by Rubisco activase at normal rates, indicating that the structural transition required for carboxylation is not affected by altering the solvent channel opening. Structural dynamics alone may not be responsible for these distant effects on the Rubisco active site.     

Further Thymol Derivatives from Ageratina cylindrica

From the leaves of Ageratina cylindrica, in addition to the described [(2S)‐2‐{4‐formyl‐5‐hydroxy‐2‐[(2‐methylpropanoyl)oxy]phenyl}oxiran‐2‐yl]methyl benzoate (cylindrinol A, 8 ), seven new thymol derivatives were isolated and named cylindrinols B – H ( 1 – 7 ). The structures of these compounds were established as (2‐{4‐(hydroxymethyl)‐2‐[(2‐methylpropanoyl)oxy]phenyl}oxiran‐2‐yl)methyl benzoate ( 1 ), (2‐{4‐formyl‐2‐[(2‐methylpropanoyl)oxy]phenyl}oxiran‐2‐yl)methyl benzoate ( 2 ), (2‐{4‐[(acetyloxy)methyl]‐2‐[(2‐methylpropanoyl)oxy]phenyl}oxiran‐2‐yl)methyl benzoate ( 3 ), [2‐(2‐[(2‐methylpropanoyl)oxy]‐4‐{[(2‐methylpropanoyl)oxy]methyl}phenyl)oxiran‐2‐yl]methyl benzoate ( 4 ), [2‐(5‐hydroxy‐2‐[(2‐methylpropanoyl)oxy]‐4‐{[(2‐methylpropanoyl)oxy]methyl}phenyl)oxiran‐2‐yl]methyl benzoate ( 5 ), 2‐{4‐(hydroxymethyl)‐2‐[(2‐methylpropanoyl)oxy]phenyl}prop‐2‐en‐1‐yl benzoate ( 6 ), and 2‐hydroxy‐2‐[2‐hydroxy‐4‐(hydroxymethyl)‐phenyl]‐3‐[(2‐methylpropanoyl)oxy]propyl benzoate ( 7 ), by spectroscopic means. Compounds 1 showed moderate antiprotozoal activity on both protozoa. Compounds 4 and 5 showed selectivity on Giardia lamblia trophozoites. All isolated compounds were less active than two antiprotozoal drugs, metronidazole and emetine, used as positive controls. Compound 5 exhibited a high inhibitory effect on hyperpropulsive movement of the small intestine in rats; its effect was best than loperamide, antidiarrheal drug used as a positive control.     

Expansion and divergence of the GH locus between spider monkey and chimpanzee

Growth hormone (GH) has been previously described as showing distinct evolutionary stories between primates and other mammals. A burst of changes and successive amplification events took place in the primate lineage giving rise to a multigene family in the three Anthropoidea lineages. Polymerase chain reaction (PCR) was used to obtain the genes and the intergenic regions comprising the GH loci of the spider monkey (Ateles geoffroyi), a New-World primate, and of the chimpanzee (Pan troglodytes), an ape. The intergenic sequences of both species were screened by hybridization to detect copies of the Alu family, which have been implicated in the formation of the human GH locus. The GH locus of the spider monkey contains at least six GH-related genes, four of them were cloned. Likewise, five short intergenic sequences of approximately 3 kb were amplified and cloned. On the other hand, in the chimpanzee four new placental lactogen (PL) genes as well as four intergenic regions were amplified. Consequently, in this ape, six genes (two GHs, previously obtained, and four PLs) are clustered, separated by intergenic sequences of different lengths (two short ones of about 5 kb, and at least two long ones between 9 and 13 kb). The presence of Alu sequences within the intergenic regions of both GH loci corroborates the current hypothesis that they acted as a driving force for the locus expansion. GH sequence comparisons reveal that several gene-conversion events might have occurred during the formation of this genome region, which has undergone independent evolution in the three Anthropoidea branches. To establish the GH's evolutionary history may prove to be a difficult task due to these gene-conversion events.