Chromosome structure and behaviour in Bursaphelenchus xylophilus (Nematoda: Parasitaphelenchidae) germ cells and early embryo

Chromosome structure and behaviour in both meiosis of the germ cells and mitosis of the embryo from fertilisation to the two-cell stage in Bursaphelenchus xylophilus were examined by DAPI staining and three-dimensional reconstruction of serial-section images from confocal laser-scanning microscopy. By this method, each chromosome’s shape and behaviour were clearly visible in early embryogenesis from fertilisation through the formation and fusion of the male and female pronuclei to the first mitotic division. The male pronucleus was bigger than that of the female, although the oocyte is larger and richer in nutrients than the sperm. From the shape of the separating chromosomes at anaphase, the mitotic chromosomes appeared to be polycentric or holocentric rather than monocentric. Each chromosome was clearly distinguishable in the male and female germ cells, pronuclei of the one-cell stage embryo, and the early embryonic nuclei. The haploid number of chromosomes (N) was six (2n = 12), and all chromosomes appeared similar. The chromosome pair containing the ribosomal RNA-coding site was visualised by fluorescence in situ hybridisation. Unlike the sex determination system in Caenorhabditis elegans (XX in hermaphrodite and XO in male), the system for B. xylophilus may consist of an XX female and an XY male

Effect of fungal interactions on the numbers of the pinewood nematode, Bursaphelenchus xylophilus (Nematoda : Aphelenchoididae), carried by the japanese pine sawyer, Monochamus alternatus (Coleoptera : Cerambycidae)

#Monochamus alternatus sortant de blocs de bois préalablement inoculés avec #Ophiostoma minus et ensuite avec #Trichoderma sp. (O + T) transporte un plus grand nombre de #Bursaphelenchus xylophilus (PWN) que ceux sortant de blocs inoculés simultanément avec ces deux champignons (O, T) ou inoculés avec #Trichoderma sp. puis avec #O. minus (T + O). La raison est que : les populations de PWN sont plus élevées dans les blocs O + T que dans ceux des autres traitements, et que le pourcentage de juvéniles de dispersion de 3ème stade, les "dauer" juvéniles et les PWN qui passent réellement dans l'insecte sont plus nombreux dans les blocs O + T. En contraste, le nombre de PWN transportés par l'insecte sortant de blocs inoculés avec #O. minus et #Verticillium sp. est beaucoup moins élevé quelle que soit la séquence d'innoculum parce que les populations de PWN ne s'établissent pas. Il est conclu que les espèces de champignon les plus abondantes dans les pins tués par le dessèchement concourent à déterminer le nombre de PWN transportés par l'insecte sortant du bois. (Résumé d'auteur

PCR-RFLP and sequencing analysis of ribosomal DNA of Bursaphelenchus nematodes related to pine wilt disease

La réaction en chaîne des polymérases/polymorphisme des fragments de restriction (PCR-RFLP) a été utilisée pour séparer des isolats du nématode #Bursaphelenchus. Les isolats de #B. xylophilus examinés provenaient du Japon, des USA, de Chine et du Canada, et ceux de #B. mucronatus du Japon, de Chine et de la France. L'ADN ribosomal contenant le gène 5.8S, les segments de transciption interne 1 et 2, et les segments partiels des gènes 18S et 28S ont été amplifiés par PCR. La digestion des produits amplifiés provenant de chaque isolat à l'aide de douze endonucléases de restriction et l'examen des données en RFLP qui en découlent révèlent, par une analyse en grappe, une séparation significative entre #B. xylophilus et #B. mucronatus. Parmi les isolats de #B. xylophilus examinés, les isolats pathogènes du Japon, ceux de Chine et des USA étaient tous identiques, tandis que les isloats non pathogènes du Japon étaient légèrement distincts et que ceux du Canada formaient une grappe séparée. Parmi les isolats de #B. mucronatus, deux isolats provenant du Japon étaient très semblables ; de même un autre isolat du Japon et un isolat de Chine étaient identiques. Les données provenant des séquences d'ADN montrent 98 différences (substitution nucléotidiques ou séparations) dans les 884 paires de bases examinées chez les isolats de #B. xylophilus et #B. mucronatus. Les données provenant des séquences d'ADN chez #Aphelenchus avenae et #Aphelenchoides fragariae diffèrent non seulement de celles des #Bursaphelenchus mais aussi entre elles. Afin de préciser les relations phylogéniques de ces espèces, les données séquentielles du gène 5.8S provenant de l'ADN ribosomal ont été examinées... (D'après résume d'auteur

Luminal acidification of diverse organelles by V-ATPase in animal cells

Eukaryotic cells contain organelles bounded by a single membrane in the cytoplasm. These organelles have differentiated to carry out various functions in the pathways of endocytosis and exocytosis. Their lumina are acidic, with pH ranging from 4.5 to 6.5. This article describes recent studies on these animal cell organelles focusing on (1) the primary proton pump (vacuolar-type H+-ATPase) and (2) the functions of the organelle luminal acidity. We also discuss similarities and differences between vacuolar-type H+-ATPase and F-type ATPase. Our own studies and interests are emphasized

The Behavioral Role of Males of Platypus Quercivorus Murayama in Their Subsocial Colonies

The behavioral role of male ambrosia beetles, Platypus quercivorus, in subsocial colonies both field and laboratory has been investigated. The entrance tunnels, where the male beetles are staying, are short, with a mean 4 cm long and mostly incline upwards from outside to inside at an angle of around 20º. To examine the role of males, another male or female (as the invader) was placed into a tunnel. When inhabitant males stayed in the tunnel they quickly expelled the invaders, regardless of their sex of the invaders. However, when an inhabitant male was removed an introduced male or female could freely enter the tunnel and was accepted by the inhabitant female. Upon replacing an inhabitant male with an invader male or female and then putting another invader male or female into the tunnel, no rejection occurred, suggesting that invader males and females play no role in guarding the tunnel. Based on the results an inhabitant male seems to have three responsibilities; protection of the gallery from invaders, protection of progeny (larva) from falling down and also keeping the gallery clean from frass. The 20º angle of the entrance tunnel tends to aid both in gallery protection and in frass clearing

Microfluidic model of bubble lodging in microvessel bifurcations

The lodging mechanisms and dynamics of cardiovascular gas bubbles are investigated in microfluidic model bifurcations made of poly(dimethylsiloxane). This work is motivated by gas embolotherapy for the potential treatment of cancer by tumor infarction. The results show that the critical driving pressure below which a bubble will lodge in a bifurcation is significantly less than the driving pressure required to dislodge it. From the results the authors estimate that gas bubbles from embolotherapy can lodge in vessels 20 μm20μm or smaller in diameter, and conclude that bubbles may potentially be used to reduce blood flow to tumor microcirculation.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/87802/2/244103_1.pd

Simple multi-level microchannel fabrication by pseudo-grayscale backside diffused light lithography

Photolithography of multi-level channel features in microfluidics is laborious and/or costly. Grayscale photolithography is mostly used with positive photoresists and conventional front side exposure, but the grayscale masks needed are generally costly and positive photoresists are not commonly used in microfluidic rapid prototyping. Here we introduce a simple and inexpensive alternative that uses pseudo-grayscale (pGS) photomasks in combination with backside diffused light lithography (BDLL) and the commonly used negative photoresist, SU-8. BDLL can produce smooth multi-level channels of gradually changing heights without use of true grayscale masks because of the use of diffused light. Since the exposure is done through a glass slide, the photoresist is cross-linked from the substrate side up enabling well-defined and stable structures to be fabricated from even unspun photoresist layers. In addition to providing unique structures and capabilities, the method is compatible with the "garage microfluidics" concept of creating useful tools at low cost since pGS BDLL can be performed with the use of only hot plates and a UV transilluminator: equipment commonly found in biology labs. Expensive spin coaters or collimated UV aligners are not needed. To demonstrate the applicability of pGS BDLL, a variety of weir-type cell traps were constructed with a single UV exposure to separate cancer cells (MDA-MB-231, 10-15 ??m in size) from red blood cells (RBCs, 2-8 ??m in size) as well as follicle clusters (40-50 ??m in size) from cancer cells (MDA-MB-231, 10-15 ??m in size)close1

Adaptation of anaerobic cultures of Escherichia coliK-12 in response to environmental trimethylamine-N-oxide

Systematic analyses of transcriptional and metabolic changes occurring when Escherichia coliK-12 switches from fermentative growth to anaerobic respiratory growth with trimethylamine-N-oxide (TMAO) as the terminal electron acceptor revealed: (i) the induction of torCAD, but not genes encoding alternative TMAO reductases; (ii) transient expression of frmRAB, encoding formaldehyde dehydrogenase; and (iii) downregulation of copper resistance genes. Simultaneous inference of 167 transcription factor (TF) activities implied that transcriptional re-programming was mediated by 20 TFs, including the transient inactivation of the two-component system ArcBA; a prediction validated by direct measurement of phosphorylated ArcA. Induction of frmRAB, detection of dimethylamine in culture medium and formaldehyde production when cell-free extracts were incubated with TMAO suggested the presence of TMAO demethylase activity. Accordingly, the viability of an frmRAB mutant was compromised upon exposure to TMAO. Downregulation of genes involved in copper resistance could be accounted for by TMAO inhibition of Cu(II) reduction. The simplest interpretation of the data is that during adaptation to the presence of environmental TMAO, anaerobic fermentative cultures of E.coli respond by activating the TorTSR regulatory system with consequent induction of TMAO reductase activity, resulting in net oxidation of menaquinone and inhibition of Cu(II) reduction, responses that are sensed by ArcBA and CusRS respectively

Comparison of the dynamic responses of monopiles and gravity base foundations for offshore wind turbines in sand using centrifuge modelling

Monopiles and gravity base foundations (GBF) are two of the most commonly used offshore foundations for wind turbines. As resonance can cause damage and even failure of wind turbines, understanding the difference between the dynamic responses of monopiles and GBFs under free vibration is important, however there is little experimental data regarding their natural frequency, especially for model tests at correct stress levels. This paper presents the results of novel monopile and GBF tests using a centrifuge to directly determine the natural frequency (fn) of the foundation-soil system. The natural frequencies of wind turbine monopiles and GBFs in centrifuge models were measured during harmonic loading by a piezo-actuator, with the results confirming that soil-structure interaction must be considered to obtain the system natural frequency as the frequency reduces substantially from fixed-base values. These results will contribute to preventing resonance damage in designs for wind-turbine foundations

Bacterial flora and its association with the pine wood nematode (Bursaphelenchus xylophilus)

In recent years a hypothesis was proposed that not pine wood nematode, but its accompanying bacteria is responsible for the symptom development in pine wilt disease. To ascertain this, we investigated the bacterial flora associated with the nematode and its possible roles in the disease by means of molecular biological techniques. As a result, the dominant bacterial species were different from those in past researches and none of them showed a significant pathogenicity against susceptible pine seedlings. On the other hand, one of the dominant species was frequently detected in seedlings inoculated with bacteria- free nematodes and in vector beetle-associated samples, indicating its possible involvement in the disease