Computational determination of refractive index distribution in the crystalline cones of the compound eye of Antarctic krill (Euphausia superba)

In order to understand how a compound eye channels light to the retina and forms an image, one needs to know the refractive index distribution in the crystalline cones. Direct measurements of the refractive indices require sections of fresh, unfixed tissue and the use of an interference microscope, but frequently neither is available. Using the eye of the Antarctic krill Euphausia superba (the main food of baleen whales) we developed a computational method to predict a likely refractive index distribution non-invasively from sections of fixed material without the need of an interference microscope. We used a computer model of the eye and calculated the most realistic spatial distribution of the refractive index gradient in the crystalline cone that would enable the eye to produce a sharp image on the retina. The animals are known to see well and on the basis of our computations we predict that for the eyes of the adult a maximum refractive index of 1.45-1.50 in the centre of the cone yields a better angular sensitivity and light absorption in a target receptor of the retina than if N(max) were 1.55. In juveniles with a narrower spatial separation between dioptric structures and retina, however, an N(max) of 1.50-1.55 gives a superior result. Our method to determine the most likely refractive index distribution in the cone without the need of fresh material and an interference microscope could be useful in the study of other invertebrate eyes that are known to possess good resolving power, but for a variety of reasons are not suitable for or will not permit direct refractive index measurements of their dioptric tissues to be taken.     

Novel regulation of MHC class II function in B cells

The presence of post-translational regulation of MHC class II (MHC II) under physiological conditions has been demonstrated recently in dendritic cells (DCs) that potently function as antigen-presenting cells (APCs). Here, we report that MARCH-I, an E3 ubiquitin ligase, plays a pivotal role in the post-translational regulation of MHC II in B cells. MARCH-I expression was particularly high in B cells, and the forced expression of MARCH-I induced the ubiquitination of MHC II. In B cells from MARCH-I-deficient mice (MARCH-I KO), the half-life of surface MHC II was prolonged and the ubiquitinated form of MHC II completely disappeared. In addition, MARCH-I-deficient B cells highly expressed exogenous antigen-loaded MHC II on their surface and showed high ability to present exogenous antigens. These results suggest that the function of MHC II in B cells is regulated through ubiquitination by MARCH-I.     

Synergistic contribution of CD14 and HLA loci in the susceptibility to Buerger disease

Buerger disease (BD) is an occulusive vascular disease of unknown etiology. Although cigarette smoking is a well-known risk factor of BD, genetic factors may also play a role in the etiology. Because chronic bacterial infection such as oral periodontitis is suggested to be involved in the pathogenesis of BD, gene polymorphisms involved in the infectious immunity might be associated with BD as the genetic factor(s). We have previously reported that HLA-DRB1*1501 and B54 was associated with BD in Japanese. In this study, polymorphisms in HLA-DPB1, DRB1 and B were analyzed in 131 Japanese BD patients and 227 healthy controls. In addition, we investigated a functional promoter polymorphism, −260 C > T, of CD14 that is a main receptor of bacterial lipopolysaccharide. It was found that the frequencies of CD14 TT genotype [37.4 vs. 24.2%, P = 0.008 OR = 1.87, 95% confidence interval (CI); 1.18, 2.97], DRB1*1501 (34.4 vs. 13.2%, P _c = 4.4 × 10⁻⁵, OR = 3.44, 95%CI; 2.06, 5.73) and DPB1*0501 (79.4 vs. 55.1%, P _c = 4.7 × 10⁻⁵, OR = 3.14, 95%CI; 1.93, 5.11) were significantly higher in the patients than in the controls, demonstrating that at least three genetic markers were associated with BD. Stratification analyses of these associated markers suggested synergistic roles of the genetic factors. Odds ratios ranged from 4.72 to 12.57 in individuals carrying any two of these three markers. These findings suggested that the susceptibility to BD was in part controlled by genes involved in the innate and adaptive immunity.     

Melanin biosynthesis inhibitors from Tarragon Artemisia dracunculus

The EtOH extract of tarragon Artemisia dracunculus, a perennial herb in the family Asteraceae, was found to potently inhibit α-melanocyte-stimulating hormone (α-MSH) induced melanin production in B16 mouse melanoma cells. Bioassay-guided fractionation led to the isolation of two alkamide compounds, isobutyl (1) and piperidiyl (2) amides of undeca-2E,4E-dien-8,10-dynoic acid. The respective EC(50) values for melanin biosynthesis inhibition were 1.8 and 2.3 μg/mL for 1 and 2.     

The role of sphingosine 1-phosphate in migration of osteoclast precursors; an application of intravital two-photon microscopy

Sphingosine-1-phosphate (S1P), a biologically active lysophospholipid that is enriched in blood, controls the trafficking of osteoclast precursors between the circulation and bone marrow cavities via G protein-coupled receptors, S1PRs. While S1PR1 mediates chemoattraction toward S1P in bone marrow, where S1P concentration is low, S1PR2 mediates chemorepulsion in blood, where the S1P concentration is high. The regulation of precursor recruitment may represent a novel therapeutic strategy for controlling osteoclast-dependent bone remodeling. Through intravital multiphoton imaging of bone tissues, we reveal that the bidirectional function of S1P temporospatially regulates the migration of osteoclast precursors within intact bone tissues. Imaging technologies have enabled in situ visualization of the behaviors of several players in intact tissues. In addition, intravital microscopy has the potential to be more widely applied to functional analysis and intervention.     

Multiple translocation of the AVR-Pita effector gene among chromosomes of the rice blast fungus Magnaporthe oryzae and related species

Magnaporthe oryzae is the causal agent of rice blast disease, a devastating problem worldwide. This fungus has caused breakdown of resistance conferred by newly developed commercial cultivars. To address how the rice blast fungus adapts itself to new resistance genes so quickly, we examined chromosomal locations of AVR-Pita, a subtelomeric gene family corresponding to the Pita resistance gene, in various isolates of M. oryzae (including wheat and millet pathogens) and its related species. We found that AVR-Pita (AVR-Pita1 and AVR-Pita2) is highly variable in its genome location, occurring in chromosomes 1, 3, 4, 5, 6, 7, and supernumerary chromosomes, particularly in rice-infecting isolates. When expressed in M. oryzae, most of the AVR-Pita homologs could elicit Pita-mediated resistance, even those from non-rice isolates. AVR-Pita was flanked by a retrotransposon, which presumably contributed to its multiple translocation across the genome. On the other hand, family member AVR-Pita3, which lacks avirulence activity, was stably located on chromosome 7 in a vast majority of isolates. These results suggest that the diversification in genome location of AVR-Pita in the rice isolates is a consequence of recognition by Pita in rice. We propose a model that the multiple translocation of AVR-Pita may be associated with its frequent loss and recovery mediated by its transfer among individuals in asexual populations. This model implies that the high mobility of AVR-Pita is a key mechanism accounting for the rapid adaptation toward Pita. Dynamic adaptation of some fungal plant pathogens may be achieved by deletion and recovery of avirulence genes using a population as a unit of adaptation.     

Development of [Ile40]HTLV‐I protease inhibition assay using novel fluorogenic and chromogenic substrate

HTLV‐I is a debilitating and/or lethal retrovirus that causes HTLV‐I‐associated myelopathy/tropical spastic paraparesis, adult T‐cell leukemia and several inflammatory diseases. HTLV‐I protease is an aspartic retropepsin involved in HTLV‐I replication and its inhibition could treatHTLV‐I infection. A recombinant L40I mutant HTLV‐I protease was designed and obtained from Escherichia coli, self‐processingand purification by ion‐exchange chromatography. The protease was refolded by a one‐step dialysis and recovered activity. The cleavage efficiency of the [Ile⁴⁰]HTLV‐I protease was at least 300 times higher for a fluorescent substratethan that of our previously reported recombinant His‐tagged non‐mutated HTLV‐I protease. In addition, we designed and synthesized a substrate containing a highly fluorescent Mca moiety in the fragment before the scissile bond, and a chromogenic p‐nitrophenylalanine moiety after the scissile bond that greatly amplified spectrometry detection and improved the HTLV‐I protease inhibition potency assay. The HTLV‐I protease inhibition assay with the [Ile⁴⁰]HTLV‐I protease and fluorogenic substrate requires distinctively less protease, substrate, inhibitor and assay time than our previous methods. This means our new assay is more cost‐effective and more time‐efficient while being reproducible and less labor‐intensive. Copyright © 2011 European Peptide Society and John Wiley & Sons, Ltd.