Mechanisms of cell death induced by hexabromocyclododecane (HBCD) involves apoptosis,autophagy, and ER stress

Hexabromocyclododecane (HBCD), was a widely utilized brominated flame retardant, commonly found in a wide range of household products. The pervasiveness of HBCD has identified the presence of this chemical in foods and in human tissues. Therefore, HBCD has been identified as a chemical of concern. The aim was to investigate the degree of cytotoxicity of HBCD in a range of cell lines derived from different tissues, (including hematopoietic, nerve, liver, and kidney-derived cells) with a view of determining any differential cell type effects. In addition, this study also investigated the mechanism(s) by which HBCD could cause cell death. The results showed that HCBD was considerably more toxic to leukocyte-derived (RBL2H3) and neuronal-derived (SHSY-5Y) cells with LC₅₀ values of 1.5 and 6.1 µM, respectively, compared to cells derived from liver (HepG2) and kidney (Cos-7), which had LC₅₀ values of 28.5 and 17.5 µM, respectively. A detailed investigation of the mechanism(s) of cell death showed that HBCD caused, at least in part, Ca²⁺-dependent cell death, caspase-activated apoptosis, and autophagy, but there was little evidence for either necrosis or necroptosis occurring. Furthermore, it was shown that HBCD can also induce the ER stress response which is a known trigger of both apoptosis and autophagy and therefore this could be one of the crucial events by which cell death is initiated. As each of these cell death mechanisms was investigated in at least two different cell lines and no differences were identified, it is likely that the mode of action is not cell-type specific.     

Integration of mitogenomic and morphological data disentangles the systematics of Pollenia and establishes a revised phylogenetic hypothesis for the Polleniidae

The Polleniidae (Diptera) are a family of flies best known for species of the genus Pollenia, which overwinter inside human dwellings. Previously divided across the Calliphoridae, Tachinidae and Rhinophoridae, the polleniid genera have only recently been united. Several studies have utilized molecular data to analyse polleniid phylogenetic relationships, although all have suffered from low taxon sampling or insufficient phylogenetic signal in molecular markers. To alleviate these problems, we utilized two automated organellar genome extraction software, GetOrganelle and MitoFinder, to assemble mitogenomes from genome skimming data from 22 representatives of the polleniid genera: Dexopollenia, Melanodexia, Morinia, Pollenia and Xanthotryxus. From these analyses, we provide 14 new mitogenomes for the Polleniidae and perform phylogenetic analyses of 13 protein-coding mitochondrial genes using both maximum likelihood and Bayesian inference. Subfamilial phylogenetic relationships within the Polleniidae are interrogated and Pollenia is found to form a monophyletic clade sister to Melanodexia, Morinia and Dexopollenia, providing no evidence for the synonymisation of any of these genera. Our topology conflicts with previous morphology-based cladistic interpretations, with the amentaria, griseotomentosa, semicinerea and viatica species-groups resolving as non-monophyletic. We provide support for our topology through analysis of adult morphology and male and female terminalia, while identifying new diagnostic characters for some of the clades of the Pollenia. To test the validity of the current diagnostic morphology in the Polleniidae, newly assembled cytochrome C oxidase subunit 1 (COI) data are combined with a polleniid COI barcode reference library and analysed using the species delimitation software ASAP. COI barcodes support the current morphologically defined species within the Pollenia.     

An investigation of the reaction kinetics of luciferase and the effect of ionizing radiation on the reaction rate

The bioluminescence produced by luciferase, a firefly enzyme, requires three substrates: luciferin, ATP and oxygen. We find that ionizing radiation, in the form of a proton beam from a cyclotron, will eliminate dissolved oxygen prior to any damage to other substrates or to the protein. The dose constant for removal of oxygen is 70 ± 20 Gy, a much smaller dose than required to cause damage to protein. Removal of oxygen, which is initially in excess, leads to a sigmoidal response of bioluminescence to radiation dose, consistent with a Michaelis–Menten relationship to substrate concentration. When excess oxygen is exhausted, the response becomes exponential. Following the irradiation, bioluminescence recovers due to a slow leak of oxygen into the solution. This may also explain previous observations on the response of bioluminescent bacteria to radiation. We have studied the dependence of the reaction rate on enzyme and substrate concentration and propose a model for the reaction pathway consistent with this data. The light output from unirradiated samples decreases significantly with time due to product inhibition. We observe that this inhibition rate changes dramatically immediately after a sample is exposed to the beam. This sudden change of the inhibition rate is unexplained but shows that enzyme regulatory function responds to ionizing radiation at a dose level less than 0.6 Gy.     

Early Host Cell Targets of Yersinia pestis during Primary Pneumonic Plague

Inhalation of Yersinia pestis causes primary pneumonic plague, a highly lethal syndrome with mortality rates approaching 100%. Pneumonic plague progression is biphasic, with an initial pre-inflammatory phase facilitating bacterial growth in the absence of host inflammation, followed by a pro-inflammatory phase marked by extensive neutrophil influx, an inflammatory cytokine storm, and severe tissue destruction. Using a FRET-based probe to quantitate injection of effector proteins by the Y. pestis type III secretion system, we show that these bacteria target alveolar macrophages early during infection of mice, followed by a switch in host cell preference to neutrophils. We also demonstrate that neutrophil influx is unable to limit bacterial growth in the lung and is ultimately responsible for the severe inflammation during the lethal pro-inflammatory phase.     

A role for the Drosophila neurogenic genes in mesoderm differentiation

The neurogenic genes of Drosophila have long been known to regulate cell fate decisions in the developing ectoderm. In this paper we show that these genes also control mesoderm development. Embryonic cells that express the muscle-specific gene nautilus are overproduced in each of seven neurogenic mutants (Notch, Delta, Enhancer of split, big brain, mastermind, neuralized, and almondex), at the apparent expense of neighboring, nonexpressing mesodermal cells. The mesodermal defect does not appear to be a simple consequence of associated neural hypertrophy, suggesting that the neurogenic genes may function similarly and independently in establishing cell fates in both ectoderm and mesoderm. Altered patterns of beta 3-tubulin and myosin heavy chain gene expression in the mutants indicate a role for the neurogenic genes in development of most visceral and somatic muscles. We propose that the signal produced by the neurogenic genes is a general one, effective in both ectoderm and mesoderm.     

Tissue expression of the vesicle protein pantophysin

The cell-type restricted expression of cytoplasmic microvesicle membrane protein isoforms may be a consequence of the functional adaptation of these vesicles to the execution of specialized processes in cells of different specialization. To characterize the expression of the vesicle protein pantophysin, an isoform of the synaptic vesicle proteins synaptophysin and synaptoporin, we have prepared and characterized antibodies useful for the immunological detection of pantophysin in vitro and in situ. Using these reagents, we show by immunoblot analyses that pantophysin expression is not homogeneous but differs significantly between various bovine tissues. Furthermore, these differences are not exactly paralleled by the expression of other vesicle proteins of the SCAMP (secretory carrier-associated membrane protein) and VAMP (vesicle-associated membrane protein) types that have previously been localized to pantophysin vesicles in cultured cells. By immunofluorescence microscopy, pantophysin expression is seen predominantly in non-neuroendocrine cells with pronounced membrane traffic. Pantophysin staining codistributes with SCAMP and VAMP immunoreactivities in most instances but differs in some. Remarkably, pantophysin staining in liver is restricted to cells surrounding sinusoids and is not detectable in hepatocytes, similar to that of the SCAMP and VAMP isoforms as detected by our reagents in tissue sections.