Genomic sequence of the pathogenic and allergenic filamentous fungus Aspergillus fumigatus

Aspergillus fumigatus is exceptional among microorganisms in being both a primary and opportunistic pathogen as well as a major allergen. Its conidia production is prolific, and so human respiratory tract exposure is almost constant. A. fumigatus is isolated from human habitats and vegetable compost heaps. In immunocompromised individuals, the incidence of invasive infection can be as high as 50% and the mortality rate is often about 50% (ref. 2). The interaction of A. fumigatus and other airborne fungi with the immune system is increasingly linked to severe asthma and sinusitis. Although the burden of invasive disease caused by A. fumigatus is substantial, the basic biology of the organism is mostly obscure. Here we show the complete 29.4-megabase genome sequence of the clinical isolate Af293, which consists of eight chromosomes containing 9,926 predicted genes. Microarray analysis revealed temperature-dependent expression of distinct sets of genes, as well as 700 A. fumigatus genes not present or significantly diverged in the closely related sexual species Neosartorya fischeri, many of which may have roles in the pathogenicity phenotype. The Af293 genome sequence provides an unparalleled resource for the future understanding of this remarkable fungus.     

Bicuculline and the depression of medullary reticular neurones by GABA and glycine

Zusammenfassung Der Einfluss von mikroelektrophoretisch verabreichtem Bicucullin auf die hemmende Wirkung von GABA und Glycin wurde an Neuronen der bulbären Formatio reticularis der nichtnarkotisierten, decerebrierten Katze untersucht. Bicucullin verminderte oder blockierte oft in reversibler Weise die durch GABA hervorgerufene Hemmung. An einigen Neuronen wurde jedoch auch die durch Glycin erzeugte Hemmung geringgradig reduziert.     

Identification of D segments of immunoglobulin heavy-chain genes and their rearrangement in T lymphocytes

The finding that the diversity (D) and joining (JH) but not the variable (VH) DNA segments of mouse immunoglobulin heavy-chain genes are joined in the DNA of some cloned cytolytic T cells, led to identification and sequencing of three different D DNA segments. Two segments identified on the embryo DNA carry on both the 5' and 3' sides two sets of characteristic sequences separated by a 12-base pair spacer, which have been implicated as recognition signals for a recombinase. The third segment, identified in a form joined with a JHDNA segment in a T cell, carries the recognition signal on the 5' side. These results support the 12/23-base pair model for somatic generation of immunoglobulin V genes, and rule out the possibility that the cytolytic T cells use assembled VH, D and JH sequences to encode their antigen receptors.     

Pfiesteria shumwayae kills fish by micropredation not exotoxin secretion

Pfiesteria piscicida and P. shumwayae reportedly secrete potent exotoxins thought to cause fish lesion events, acute fish kills and human disease in mid-Atlantic USA estuaries. However, Pfiesteria toxins have never been isolated or characterized. We investigated mechanisms by which P. shumwayae kills fish using three different approaches. Here we show that larval fish bioassays conducted in tissue culture plates fitted with polycarbonate membrane inserts exhibited mortality (100%) only in treatments where fish and dinospores were in physical contact. No mortalities occurred in treatments where the membrane prevented contact between dinospores and fish. Using differential centrifugation and filtration of water from a fish-killing culture, we produced 'dinoflagellate', 'bacteria' and 'cell-free' fractions. Larval fish bioassays of these fractions resulted in mortalities (60-100% in less than 24 h) only in fractions containing live dinospores ('whole water', 'dinoflagellate'), with no mortalities in 'cell-free' or 'bacteria'-enriched fractions. Videomicrography and electron microscopy show dinospores swarming toward and attaching to skin, actively feeding, and rapidly denuding fish of epidermis. We show here that our cultures of actively fish-killing P. shumwayae do not secrete potent exotoxins; rather, fish mortality results from micropredatory feeding.     

Dendrite growth increased by visual activity requires NMDA receptor and Rho GTPases

Previous studies suggest that neuronal activity may guide the development of synaptic connections in the central nervous system through mechanisms involving glutamate receptors and GTPase-dependent modulation of the actin cytoskeleton. Here we demonstrate by in vivo time-lapse imaging of optic tectal cells in Xenopus laevis tadpoles that enhanced visual activity driven by a light stimulus promotes dendritic arbor growth. The stimulus-induced dendritic arbor growth requires glutamate-receptor-mediated synaptic transmission, decreased RhoA activity and increased Rac and Cdc42 activity. The results delineate a role for Rho GTPases in the structural plasticity driven by visual stimulation in vivo.     

Fleas (Siphonaptera) in nests of boles ( Microtus spp.) in montane habitats of three regions of Utah

As a parallel study of a survey of fleas of trapped small mammals in montane southern Utah, we removed 77 adult fleas from 12 of 13 nests of voles ( Microtus longicaudus, M. montanus and M. richardsoni ) collected from montane meadows in the Abajo and La Sal Mountains, the Markagunt Plateau and Pine Valley Mountains, and the Uinta Mountains, May 1991-July 2002. Six species and subspecies of fleas parasitic on Microtus spp. were found, 1-3 species in each nest. Three specimens of the ubiquitous deer mouse ( Peromyscus spp.) flea Aetheca wagneri (Baker) were also found. We collected the following 7 taxa from the locations indicated: Catallagia decipiens Rothschild in 5 nests: Abajo and Pine Valley Mountains and Markagunt Plateau; Hystrichopsylla dippiei truncata Holland in 2 nests: La Sal and Uinta Mountains; H. occidentalis sylvaticus Campos & Stark in 5 nests: Pine Valley Mountains; Peromyscopsylla selenis (Rothschild) in 1 nest: Markagunt Plateau; A. wagneri in 2 nests: Abajo and Pine Valley Mountains; Megabothris abantis (Rothschild) in 5 nests: Abajo and Uinta Mountains and Markagunt Plateau; Malaraeus telchinus (Rothschild) in 2 nests: Abajo and Pine Valley Mountains. One preserved larva was identified as Hystrichopsylla prob. occidentalis sylvaticus , and 2 dead larvae, the only specimens found in nest 13, were identified as probably the same. Kane County is a new record for C. decipiens and P. selenis ; Kane and Summit Counties are new for M. abantis . Nest surveys can generally supplement rather than replace trapped-host surveys. Their main value is in population studies. They are also a source of larvae for morphology and taxonomy research.     

Absence of growth by most receptor-expressing fetal thymocytes in the presence of interleukin-2

The growth of mature T cells is regulated by receptors for interleukin-2 (IL-2) and by IL-2 itself. Binding of antigen to T-cell antigen receptors induces the expression of IL-2 receptors, and binding of IL-2 to these receptors induces transferrin receptor expression and is sufficient to promote the growth of T cells for several days. However, nothing is known about the growth requirements of pre-T cells. We have therefore studied the dividing population of T-cell precursors which carry the Thy-1 surface antigen, but lack surface antigens Ly2 and L3T4; these cells are present in 14-day-old embryonic thymus. If the thymus is removed at this stage and placed in organ culture, all lymphocyte subpopulations normally present in thymuses of adult mice develop in vitro, that is, the nonfunctional Ly2+, L3T4+ population and the functional Ly2+, L3T4- and Ly2-, L3T4+ populations. We now report that, in contrast to their progeny, the early Ly2-, L3T4- cells express large amounts of IL-2 receptors, but most of them do not grow in IL-2-containing media outside the thymus. In contrast to dividing mature T cells, most fetal thymocytes express low amounts of transferrin receptors.