The structure of the iron complex in metaquohemerythrin

The novel binuclear iron complex in metaquohemerythrin is described. One of the two iron atoms is octahedrally coordinated, the other being penta-coordinate. A number of questions concerning the structure of the metal complex in different forms of this nonheme iron oxygen transport protein have been clarified. The structure of the complex presented here differs from that of metazidohemerythrin in that the Fe atom providing the binding locus for azide ion is five-coordinate with no small molecule ligand bound to it. The coordination polyhedron of this Fe is best described as a trigonal bipyramid.     

Shiny spheres of placozoans (Trichoplax) function in anti-predator defense

Abstract. When individual placozoans, Trichoplax adhaerens , were fed to polyps of the hydroid Podocoryna carnea , the polyps became paralyzed in all 27 trials. In one instance the hydroid polyp died and in five instances a fragment of the placozoan survived. The time to recovery from paralysis varied with the relative size of the polyp and the placozoan. Placozoans were disassociated into separate cells and then reaggregated by centrifugation to produce pellets of tissue lacking the vesicles called shiny spheres, normally abundant in the upper epithelium. We fed pellets of two size classes to the hydroid polyps. When the placozoan pellet was smaller than the hydroid, paralysis was eliminated in nine of ten trials. When the placozoan pellet was comparable in size to the polyp, paralysis occurred but the recovery time was substantially reduced, compared with trials in which polyps were fed intact placozoans possessing shiny spheres. These results support a function of shiny spheres in anti-predator defense.     

The induction of orientational instability and bivalent interlocking at meiosis

The administration of 40° C heat-treatments was found to induce bivalent orientational instability and interlocking at male meiosis in the locust Locusta migratoria. Only the longest members of the complement showed orientational instability and these usually possessed single distally sited chiasmata, with near-maximal intercentromeric distances. An effect on the stability of spindle fibre microtubule association, or attachment to the chromosome, is considered to be a possible explanation of the behaviour found. Bipolar orientation was generally achieved prior to anaphase I so that chromosome segregation was usually normal. Diamphitelic bivalents provided the most common exception to this rule. They sometimes lagged at anaphase, with the separation of half-bivalents and the production of structures indistinguishable from lagging univalents. The bivalent interlocking also involved the longest members of the complement. Most combinations of rod/rod, rod/ring and ring/ring types of interlocking were found. Usually only two bivalents were interlocked in any one cell, although occasionally three were found interlocked. All types appeared to involve an effect on the regulation of chromosome pairing, although at least one of the cells found showed interlocking caused by the metaphase orientational instability. In most cells, interlocked bivalents showed stable orientation and this usually involved the unipolar orientation of each bivalent's two centromeres. Such configurations provide concrete support for the importance of physical tension in the maintenance of metaphase orientational stability. They lead to double non-disjunction at anaphase I. Interlocked bivalents showed normal congression to a mid-equatorial position with no tendency for the re-adjustment of arm ratios to equalise centromere distances from the poles. This behaviour is discussed in relation to spindle fibre dynamics and it is concluded that no hypothesis of congression currently available can satisfactorily explain all that we know of the behaviour of univalents, bivalents, multivalents and interlocked bivalents.     

MIPHENO: data normalization for high throughput metabolite analysis

Background  

High throughput methodologies such as microarrays, mass spectrometry and plate-based small molecule screens are increasingly used to facilitate discoveries from gene function to drug candidate identification. These large-scale experiments are typically carried out over the course of months and years, often without the controls needed to compare directly across the dataset. Few methods are available to facilitate comparisons of high throughput metabolic data generated in batches where explicit in-group controls for normalization are lacking.     

Transmission Genetics of Allorecognition in Hydractinia Symbiolongicarpus (Cnidaria: Hydrozoa)

Allorecognition is ubiquitous, or nearly so, amongst colonial invertebrates. Despite the prominent role that such phenomena have played both in evolutionary theory and in speculations on the origin of the vertebrate immune system, unambiguous data on the transmission genetics of fusibility (i.e., the ability of two individuals to fuse upon tissue contact) is lacking for any metazoan outside of the phylum Chordata. We have developed lines of the hydroid Hydractinia symbiolongicarpus (Phylum Cnidaria) inbred for fusibility and here report results of breeding experiments establishing that fusibility segregates as expected for a single locus with codominantly expressed alleles, with one shared allele producing a fusible phenotype. Surveys of fusibility in field populations and additional breeding experiments indicate the presence of an extensive allele series.     

INTERSPECIFIC INCOMPATIBILITY IN GOSSYPIUM. IV. TEMPERATURE-CONDITIONAL LETHALITY IN HYBRIDS OF G. KLOTZSCHIANUM

A number of interspecific hybrids involving G. klotzschianum are embryo-lethal or seedling-lethal at temperatures considered optimal for cotton culture (26–32 C). At temperatures between 33–37 C, lethal symptoms (cell-necrosis and vascular plugging) for both stages of lethality are greatly ameliorated and at 40 C lethal symptoms are absent and hybrid ontogeny is normal for embryo- and seedling-lethals. Temperature-repressed lethals revert to type within 12–24 h after being returned to a non-repressive temperature regime.     

Dying Cells Protect Survivors from Radiation-Induced Cell Death in Drosophila

We report a phenomenon wherein induction of cell death by a variety of means in wing imaginal discs of Drosophila larvae resulted in the activation of an anti-apoptotic microRNA, bantam. Cells in the vicinity of dying cells also become harder to kill by ionizing radiation (IR)-induced apoptosis. Both ban activation and increased protection from IR required receptor tyrosine kinase Tie, which we identified in a genetic screen for modifiers of ban. tie mutants were hypersensitive to radiation, and radiation sensitivity of tie mutants was rescued by increased ban gene dosage. We propose that dying cells activate ban in surviving cells through Tie to make the latter cells harder to kill, thereby preserving tissues and ensuring organism survival. The protective effect we report differs from classical radiation bystander effect in which neighbors of irradiated cells become more prone to death. The protective effect also differs from the previously described effect of dying cells that results in proliferation of nearby cells in Drosophila larval discs. If conserved in mammals, a phenomenon in which dying cells make the rest harder to kill by IR could have implications for treatments that involve the sequential use of cytotoxic agents and radiation therapy.