Spatial and temporal expression of the response regulators ARR22 and ARR24 in Arabidopsis thaliana

ARR22 (At3g04280) is a novel Type A response regulator whose function in Arabidopsis is unknown. RT-PCR analysis has shown that expression of the gene takes place in flowers and developing pods with the tissues accumulating different proportions of splice variants. Spatial analysis of expression, using ARR22::GUS plants as a marker, has revealed that the reporter protein accumulates specifically at the junction between the funiculus and the chalazal tissue. Expression can be up-regulated at this location by wounding the developing seed. A detailed analysis has failed to detect ARR22 expression at any other sites and, to support this assertion, the only evidence for tissue ablation in ARR22::Barnase plants is during seed development, with the consequence that embryo growth is attenuated. Ectopic expression of ARR22, driven by either the CaMV 35S or the pea plastocyanin (PPC) promoters, resulted in the generation of plants exhibiting extremely stunted root and shoot growth. No viable progeny could be isolated from the PPC::ARR22 transgenic lines. An RT-PCR analysis of a recently annotated gene (ARR24-At5g26594), that exhibits 66% amino acid similarity to ARR22, has shown that expression is also predominantly in floral and silique tissues. Examination of ARR24::GUS plants has revealed that the activity of the promoter is primarily restricted to pollen grains indicating that this gene is unlikely to display an overlapping function with ARR22. Analyses of individual KO lines of either ARR22 or ARR24 have failed to identify a mutant phenotype under the growth conditions employed and the double knockout ARR22/ARR24 line is also indistinguishable from wild-type plants. These results are discussed in the light of the proposed role of response regulators in plant growth and development.     

Radiofrequency dosimetry for the Ferris-wheel mouse exposure system

Numerical and experimental methods were employed to assess the individual and collective dosimetry of mice used in a bioassay on the exposure to pulsed radiofrequency energy at 900 MHz in the Ferris-wheel exposure system (Utteridge et al., Radiat. Res. 158, 357-364, 2002). Twin-well calorimetry was employed to measure the whole-body specific absorption rate (SAR) of mice for three body masses (23 g, 32 g and 36 g) to determine the lifetime exposure history of the mice used in the bioassay. Calorimetric measurements showed about 95% exposure efficiency and lifetime average whole-body SARs of 0.21, 0.86, 1.7 and 3.4 W kg(-1) for the four exposure groups. A larger statistical variation in SAR was observed in the smallest mice because they had the largest variation in posture inside the plastic restrainers. Infrared thermography provided SAR distributions over the sagittal plane of mouse cadavers. Thermograms typically showed SAR peaks in the abdomen, neck and head. The peak local SAR at these locations, determined by thermometric measurements, showed peak-to-average SAR ratios below 6:1, with typical values around 3:1. Results indicate that the Ferris wheel fulfills the requirement of providing a robust exposure setup, allowing uniform collective lifetime exposure of mice.     

Use of Pleurotus dryinus for lignocellulolytic enzymes production in submerged fermentation of mandarin peels and tree leaves

It has been shown that the wood-rotting mushroom Pleurotus dryinus IBB 903 is able to effectively produce cellulases, xylanase, laccase, and manganese peroxidase in submerged fermentation of mandarin peels and tree leaves. Gradual increasing of lignocellulosic substrates concentration from 1 to 4–6% enhanced enzyme accumulation in culture liquid. A simple and inexpensive medium containing mandarin peels and yeast extract as sole carbon and nitrogen sources allowed simultaneous production of high levels of both hydrolases and oxidases by P. dryinus IBB 903. Supplementation of this medium by copper and manganese caused earlier and faster accumulation of laccase and manganese peroxidase increasing their yield by 1.5 and 7.5 times, respectively. In addition, by adding manganese to the medium it is possible to regulate the ratio of laccase and MnP in enzyme preparation. The presence of lignocellulosic substrate is the requisite for MnP production by P. dryinus IBB 903 since there was no production of MnP when mushroom has been cultivated in the synthetic medium with different carbon source. Among carbon source tested only utilization of glucose resulted to 21-fold increase of fungus laccase specific activity compared to control medium without carbon source. Carboxymethyl cellulase and xylanase appeared to be inducible enzymes.     

Great apes show highly selective plasma carotenoids and have physiologically high plasma retinyl esters compared to humans

Great apes are the closest living relatives of humans. Physiological similarities between great apes and humans provide clues to identify which biological features in humans are primitive or derived from great apes. Vitamin A (VA) and carotenoid metabolism have been only partially studied in great apes, and comparisons between great apes and humans are not available. We aimed to investigate VA and carotenoid intake and plasma concentrations in great apes living in captivity, and to compare them to healthy humans. Dietary intakes of humans (n = 20) and, among the great apes, chimpanzees (n = 15) and orangutans (n = 5) were calculated. Plasma retinol (ROH), retinol-binding protein (RBP), retinyl esters, and major carotenoids were analyzed. The great ape diet was higher in VA than in humans, due to high intake of provitamin A carotenoids. Plasma ROH concentrations in great apes were similar to those in humans, but retinyl esters were higher in great apes than in humans. Differences in plasma carotenoid concentrations were observed between great apes and humans. Lutein was the main carotenoid in great apes, while beta-carotene was the main carotenoid for humans. RBP concentrations did not differ between great apes and humans. The molar ratio of ROH to RBP was close to 1.0 in both great apes and humans. In conclusion, great apes show homeostatic ROH regulation, with high but physiological retinyl esters circulating in plasma. Furthermore, great apes show great selectivity in their plasmatic carotenoid concentration, which is not explained by dietary intake.     

Evolutionary genomics in Metazoa: the mitochondrial DNA as a model system

One of the most important aspects of mitochondrial (mt) genome evolution in Metazoa is constancy of size and gene content of mtDNA, whose plasticity is maintained through a great variety of gene rearrangements probably mediated by tRNA genes. The trend of mtDNA to maintain the same genetic structure within a phylum (e.g., Chordata) is generally accepted, although more recent reports show that a considerable number of transpositions are observed also between closely related organisms. Base composition of mtDNA is extremely variable. Genome GC content is often low and, when it increases, the two complementary bases distribute asymmetrically, creating, particularly in vertebrates, a negative GC-skew. In mammals, we have found coding strand base composition and average degree of gene conservation to be related to the asymmetric replication mechanism of mtDNA. A quantitative measurement of mtDNA evolutionary rate has revealed that each of the various components has a different evolutionary rate. Non-synonymous rates are gene specific and fall in a range comparable to that of nuclear genes, whereas synonymous rates are about 22-fold higher in mt than in nuclear genes. tRNA genes are among the most conserved but, when compared to their nuclear counterparts, they evolve 100 times faster. Finally, we describe some molecular phylogenetic reconstructions which have produced unexpected outcomes, and might change our vision of the classification of living organisms.     

A synthetic hexapeptide designed to resemble a proteinaceous P-loop nest is shown to bind inorganic phosphate

The hexapeptide Ser-Gly-Ala-Gly-Lys-Thr has been synthesized and characterized. It was designed as a minimal soluble peptide that would be likely to have the phosphate-binding properties observed in the P-loops of proteins that bind the β-phosphate of GTP or ATP. The β-phosphate in such proteins is bound by a combination of the side chain ε-amino group of the lysine residue plus the concavity formed by successive main chain peptide NH groups called a nest, which is favored by the glycines. The hexapeptide is shown to bind HPO(4) (2-) strongly at neutral pH. The affinities of the various ionized species of phosphate and hexapeptide are analyzed, showing that they increase with pH. It is likely the main chain NH groups of the hexapeptide bind phosphate in much the same way as the corresponding P-loop atoms bind the phosphate ligand in proteins. Most proteinaceous P-loops are situated at the N-termini of α-helices, and this observation has frequently been considered a key aspect of these binding sites. Such a hexapeptide in isolation seems unlikely to form an α-helix, an expectation in accord with the CD spectra examined; this suggests that being at the N-terminus of an α-helix is not essential for phosphate binding. An unexpected finding about the hexapeptide-HPO(4) (2-) complex is that the side chain ε-amino group of the lysine occurs in its deprotonated form, which appears to bind HPO(4) (2-) via an N···H-O-P hydrogen bond.     

sAPPα rescues deficits in amyloid precursor protein knockout mice following focal traumatic brain injury

The amyloid precursor protein (APP) is thought to be neuroprotective following traumatic brain injury (TBI), although definitive evidence at moderate to severe levels of injury is lacking. In the current study, we investigated histological and functional outcomes in APP-/- mice compared with APP+/+ mice following a moderate focal injury, and whether administration of sAPPα restored the outcomes in knockout animals back to the wildtype state. Following moderate controlled cortical impact injury, APP-/- mice demonstrated greater impairment in motor and cognitive outcome as determined by the ledged beam and Barnes Maze tests respectively (p < 0.05). This corresponded with the degree of neuronal damage, with APP-/- mice having significantly greater lesion volume (25.0 ± 1.6 vs. 20.3 ± 1.6%, p < 0.01) and hippocampal damage, with less remaining CA neurons (839 ± 245 vs. 1353 ± 142 and 1401 ± 263). This was also associated with an impaired neuroreparative response, with decreased GAP-43 immunoreactivity within the cortex around the lesion edge compared with APP+/+ mice. The deficits observed in the APP-/- mice related to a lack of sAPPα, as treatment with exogenously added sAPPα post-injury improved APP-/- mice histological and functional outcome to the point that they were no longer significantly different to APP+/+ mice (p < 0.05). This study shows that endogenous APP is potentially protective at moderate levels of TBI, and that this neuroprotective activity is related to the presence of sAPPα. Importantly, it indicates that the mechanism of action of exogenously added sAPPα is independent of the presence of endogenous APP.     

Establishing Meal Patterns by Lickometry in the Marmoset Monkey (Callithrix jacchus): Translational Applications From the Bench to the Field and the Clinic

The ability to measure and interpret variables associated with feeding behavior and food intake is essential to a variety of nonhuman primate study modalities. The development of a technique to accurately and efficiently measure food intake and meal patterning in captivity will enhance both the interpretation of foraging behavior in the wild as well as our ability to model clinically relevant human feeding pathologies. In this study, we successfully developed the use of a rodent lickometer system to monitor meal patterning in captive common marmosets. We describe the modifications necessary for this type of instrumentation to be used successfully with marmosets. We define variables of interest that relate to both previous rodent literature and human clinical measures. Finally, we relate our findings to potential translational value for both primate field research and biomedical applications. Am. J. Primatol. 74:901‐914, 2012. © 2012 Wiley Periodicals, Inc.