Long-term cellular and regional specificity of the photoreceptor toxin, iodoacetic acid (IAA), in the rabbit retina

This study investigated the anatomical consequences of a photoreceptor toxin, iodoacetic acid (IAA), in the rabbit retina. Retinae were examined 2 weeks, 1, 3, and 6 months after systemic IAA injection. The retinae were processed using standard histological methods to assess the gross morphology and topographical distribution of damage, and by immunohistochemistry to examine specific cell populations in the retina. Degeneration was restricted to the photoreceptors and was most common in the ventral retina and visual streak. In damaged regions, the outer nuclear layer was reduced in thickness or eliminated entirely, with a concomitant loss of immunoreactivity for rhodopsin. However, the magnitude of the effect varied between animals with the same IAA dose and survival time, suggesting individual differences in the bioavailability of the toxin. In all eyes, the inner retina remained intact, as judged by the thickness of the inner nuclear layer, and by the pattern of immunoreactivity for protein kinase C-alpha (rod bipolar cells) and calbindin D-28 (horizontal cells). Müller cell stalks became immunoreactive for glial fibrillary acidic protein (GFAP) even in IAA-treated retinae that had no signs of cell loss, indicating a response of the retina to the toxin. However, no marked hypertrophy or proliferation of Müller cells was observed with either GFAP or vimentin immunohistochemistry. Thus the selective, long lasting damage to the photoreceptors produced by this toxin did not lead to a reorganization of the surviving cells, at least with survival as long as 6 months, in contrast to the remodeling of the inner retina that is observed in inherited retinal degenerations such as retinitis pigmentosa and retinal injuries such as retinal detachment.

Correlation between Accurate Electron Density and Linear Optical Properties in Amino Acid Derivatives: L-Histidinium Hydrogen Oxalate

The accurate electron density and linear optical properties of L-histidinium hydrogen oxalate are discussed. Two high-resolution single crystal X-ray diffraction experiments were performed and compared with density functional calculations in the solid state as well as in the gas phase. The crystal packing and the hydrogen bond network are accurately investigated using topological analysis based on quantum theory of atoms in molecules, Hirshfeld surface analysis, and electrostatic potential mapping. The refractive indices are computed from couple perturbed Kohn-Sham calculations and measured experimentally. Moreover, distributed atomic polarizabilities are used to analyze the origin of the linear susceptibility in the crystal, in order to separate molecular and intermolecular causes. The optical properties are also correlated with the electron density distribution. This compound also offers the possibility to test the electron density building block approach for material science and different refinement schemes for accurate positions and displacement parameters of hydrogen atoms, in the absence of neutron diffraction data.

High affinity amino acid transporters specifically expressed in xylem parenchyma and developing seeds of Arabidopsis

Arabidopsis amino acid transporters (AAPs) show individual temporal and spatial expression patterns. A new amino acid transporter, AAP8 was isolated by reverse transcription-PCR. Growth and transport assays in comparison to AAP1-5 characterize AAP8 and AAP6 as high affinity amino acid transport systems from Arabidopsis. Histochemical promoter-beta-glucuronidase (GUS) studies identified AAP6 expression in xylem parenchyma, cells requiring high affinity transport due to the low amino acid concentration in xylem sap. AAP6 may thus function in uptake of amino acids from xylem. Histochemical analysis of AAP8 revealed stage-dependent expression in siliques and developing seeds. Thus AAP8 is probably responsible for import of organic nitrogen into developing seeds. The only missing transporter of the family AAP7 was nonfunctional in yeast with respect to amino acid transport, and expression was not detectable. Therefore, AAP6 and -8 are the only members of the family able to transport aspartate with physiologically relevant affinity. AAP1, -6 and -8 are the closest AAP paralogs. Although AAP1 and AAP8 originate from a duplicated region on chromosome I, biochemical properties and expression pattern diverged. Overlapping substrate specificities paired with individual properties and expression patterns point to specific functions of each of the AAP genes in nitrogen distribution rather than to mere redundancy.

Identification, quantification, spatiotemporal distribution and genetic variation of major latex secondary metabolites in the common dandelion (Taraxacum officinale agg.)

The secondary metabolites in the roots, leaves and flowers of the common dandelion (Taraxacum officinale agg.) have been studied in detail. However, little is known about the specific constituents of the plant’s highly specialized laticifer cells. Using a combination of liquid and gas chromatography, mass spectrometry and nuclear magnetic resonance spectrometry, we identified and quantified the major secondary metabolites in the latex of different organs across different growth stages in three genotypes, and tested the activity of the metabolites against the generalist root herbivore Diabrotica balteata. We found that common dandelion latex is dominated by three classes of secondary metabolites: phenolic inositol esters (PIEs), triterpene acetates (TritAc) and the sesquiterpene lactone taraxinic acid β-d-glucopyranosyl ester (TA-G). Purification and absolute quantification revealed concentrations in the upper mg g−1 range for all compound classes with up to 6% PIEs, 5% TritAc and 7% TA-G per gram latex fresh weight. Contrary to typical secondary metabolite patterns, concentrations of all three classes increased with plant age. The highest concentrations were measured in the main root. PIE profiles differed both quantitatively and qualitatively between plant genotypes, whereas TritAc and TA-G differed only quantitatively. Metabolite concentrations were positively correlated within and between the different compound classes, indicating tight biosynthetic co-regulation. Latex metabolite extracts strongly repelled D. balteata larvae, suggesting that the latex constituents are biologically active.

Antibiotic Susceptibility and Sequence Type Distribution of Ureaplasma Species Isolated from Genital Samples in Switzerland.

Antibiotic resistance in Ureaplasma urealyticum/Ureaplasma parvum and Mycoplasma hominis is an issue of increasing importance. However, data regarding the susceptibility and, more importantly, the clonality of these organisms are limited. We analyzed 140 genital samples obtained in Bern, Switzerland, in 2014. Identification and antimicrobial susceptibility tests were performed by using the Mycoplasma IST 2 kit and sequencing of 16S rRNA genes. MICs for ciprofloxacin and azithromycin were obtained in broth microdilution assays. Clonality was analyzed with PCR-based subtyping and multilocus sequence typing (MLST), whereas quinolone resistance and macrolide resistance were studied by sequencing gyrA, gyrB, parC, and parE genes, as well as 23S rRNA genes and genes encoding L4/L22 ribosomal proteins. A total of 103 samples were confirmed as positive for U. urealyticum/U. parvum, whereas 21 were positive for both U. urealyticum/U. parvum and M. hominis. According to the IST 2 kit, the rates of nonsusceptibility were highest for ciprofloxacin (19.4%) and ofloxacin (9.7%), whereas low rates were observed for clarithromycin (4.9%), erythromycin (1.9%), and azithromycin (1%). However, inconsistent results between microdilution and IST 2 kit assays were recorded. Various sequence types (STs) observed previously in China (ST1, ST2, ST4, ST9, ST22, and ST47), as well as eight novel lineages, were detected. Only some quinolone-resistant isolates had amino acid substitutions in ParC (Ser83Leu in U. parvum of serovar 6) and ParE (Val417Thr in U. parvum of serovar 1 and the novel Thr417Val substitution in U. urealyticum). Isolates with mutations in 23S rRNA or substitutions in L4/L22 were not detected. This is the first study analyzing the susceptibility of U. urealyticum/U. parvum isolates in Switzerland and the clonality outside China. Resistance rates were low compared to those in other countries. We hypothesize that some hyperepidemic STs spread worldwide via sexual intercourse. Large combined microbiological and clinical studies should address this important issue.

Distribution and variability of deformed wing virus of honeybees (Apis mellifera) in the Middle East and North Africa.

Three hundred eleven honeybee samples from twelve countries in the Middle East and North Africa (MENA) (Jordan, Lebanon, Syria, Iraq, Egypt, Libya, Tunisia, Algeria, Morocco, Yemen, Palestine and Sudan) were analyzed for the presence of deformed wing virus (DWV). The prevalence of DWV throughout the MENA region was pervasive, but variable. The highest prevalence was found in Lebanon and Syria, with prevalence dropping in Palestine, Jordan and Egypt before increasing slightly moving westwards to Algeria and Morocco Phylogenetic analysis of a 194 nucleotide section of the DWV Lp gene did not identify any significant phylogenetic resolution among the samples, although the sequences did show consistent regional clustering, including an interesting geographic gradient from Morocco through North Africa to Jordan and Syria. The sequences revealed several clear variability hotspots in the deduced amino acid sequence, that furthermore showed some patterns of regional identity. Furthermore, the sequence variants from the Middle East and North Africa appear more numerous and diverse than those from Europe. This article is protected by copyright. All rights reserved.