Metarhizium robertsii Produces an Extracellular Invertase (MrINV) That Plays a Pivotal Role in Rhizospheric Interactions and Root Colonization

As well as killing pest insects, the rhizosphere competent insect-pathogenic fungus Metarhizium robertsii also boosts plant growth by providing nitrogenous nutrients and increasing resistance to plant pathogens. Plant roots secrete abundant nutrients but little is known about their utilization by Metarhizium spp. and the mechanistic basis of Metarhizium-plant associations. We report here that M. robertsii produces an extracellular invertase (MrInv) on plant roots. Deletion of MrInv (⊿MrInv) reduced M. robertsii growth on sucrose and rhizospheric exudates but increased colonization of Panicum virgatum and Arabidopsis thaliana roots. This could be accounted for by a reduction in carbon catabolite repression in ⊿MrInv increasing production of plant cell wall-degrading depolymerases. A non-rhizosphere competent scarab beetle specialist Metarhizium majus lacks invertase which suggests that rhizospheric competence may be related to the sugar metabolism of different Metarhizium species.     

Identification of a novel coronavirus from a beluga whale by using a panviral microarray

The emergence of viruses such as severe acute respiratory syndrome coronavirus and Nipah virus has underscored the role of animal reservoirs in human disease and the need for reservoir surveillance. Here, we used a panviral DNA microarray to investigate the death of a captive beluga whale in an aquatic park. A highly divergent coronavirus, tentatively named coronavirus SW1, was identified in liver tissue from the deceased whale. Subsequently, the entire genome of SW1 was sequenced, yielding a genome of 31,686 nucleotides. Phylogenetic analysis revealed SW1 to be a novel virus distantly related to but most similar to group III coronaviruses.     

Defining the herpes simplex virus-specific CD8+ T cell repertoire in C57BL/6 mice

HSV type 1 (HSV-1) expresses its genes sequentially as immediate early (α), early (β), leaky late (γ1), and true late (γ2), where viral DNA synthesis is an absolute prerequisite only for γ2 gene expression. The γ1 protein glycoprotein B (gB) contains a strongly immunodominant CD8(+) T cell epitope (gB(498-505)) that is recognized by 50% of both the CD8(+) effector T cells in acutely infected trigeminal ganglia (TG) and the CD8(+) memory T cells in latently infected TG. Of 376 predicted HSV-1 CD8(+) T cell epitopes in C57BL/6 mice, 19 (gB(498-505) and 18 subdominant epitopes) stimulated CD8(+) T cells in the spleens and TG of HSV-1 acutely infected mice. These 19 epitopes identified virtually all CD8(+) T cells in the infected TG that represent all or the vast majority of the HSV-specific CD8(+) TCR repertoire. Only 11 of ～84 HSV-1 proteins are recognized by CD8(+) T cells, and most (～80%) are expressed before viral DNA synthesis. Neither the immunodominance of gB(498-505) nor the dominance hierarchy of the subdominant epitopes is due solely to MHC or TCR affinity. We conclude that the vast majority of CD8(+) T cells in HSV-1 acutely infected TG are HSV specific, that HSV-1 β and γ1 proteins that are expressed before viral DNA synthesis are favored targets of CD8(+) T cells, and that dominance within the TCR repertoire is likely due to the frequency or expansion and survival characteristics of CD8(+) T cell precursors.     

Metabolic and morphologic properties of single muscle fibers in the rat after spaceflight, Cosmos 1887

The adaptation of a slow (soleus, Sol) and a fast (medial gastrocnemius, MG) skeletal muscle to spaceflight was studied in five young male rats. The flight period was 12.5 days and the rats were killed approximately 48 h after returning to 1 g. Five other rats that were housed in cages similar to those used by the flight rats were maintained at 1 g for the same period of time to serve as ground-based controls. Fibers were classified as dark or light staining for myosin adenosine triphosphatase (ATPase). On the average, the fibers in the Sol of the flight rats atrophied twice as much as those in the MG. Further, the fibers located in the deep (close to the bone and having the highest percentage of light ATPase and high oxidative fibers in the muscle cross section) region of the MG atrophied more than the fibers located in the superficial (away from the bone and having the lowest percentage of light ATPase and high oxidative fibers in the muscle cross-section) region of the muscle. Based on quantitative histochemical assays of single muscle fibers, succinate dehydrogenase (SDH) activity per unit volume was unchanged in fibers of the Sol and MG. However, in the Sol, but not the MG, the total amount of SDH activity in a 10-microns-thick section of a fiber decreased significantly in response to spaceflight. Based on population distributions, it appears that the alpha-glycerophosphate dehydrogenase (GPD) activities were elevated in the dark ATPase fibers in the Sol, whereas the light fibers in the Sol and both fiber types in the MG did not appear to change. The ratio of GPD to SDH activities increased in the dark (but not light) fibers of the Sol and was unaffected in the MG. Immunohistochemical analyses indicate that approximately 40% of the fibers in the Sol of flight rats expressed a fast myosin heavy chain compared with 22% in control rats. Further, 31% of the fibers in the Sol of flight rats expressed both fast and slow myosin heavy chains compared with 8% in control rats. Immunohistochemical changes in the MG were minimal. These data suggest that the magnitude and direction of enzymatic activity and cell volume changes are dependent on the muscle, the region of the muscle, and the type of myosin expressed in the fibers. Further, the ability of fibers to maintain normal or even elevated activities per unit volume of some metabolic enzymes is remarkable considering the marked and rapid decrease in fiber volume.     

Anti-myosin heavy chain monoclonal antibodies reveal two IIB (fast) fiber subtypes

Indirect immunofluorescence analysis of different rat skeletal muscles using anti-myosin heavy chain (MHC) monoclonal antibodies (MAb) revealed the presence of two immunologically distinct kinds of fibers within the IIB fibers, histochemically identified by myosin ATPase staining. Some IIB fibers (designated here as IIB1) were unreactive with one anti-fast MHC MAb, whereas they did react with another anti-fast MHC MAb; other IIB fibers (designated here as IIB2) reacted with both anti-fast MAbs. Neither of the two IIB fiber subtypes was significantly reactive with a neonatal MHC MAb. The number of each IIB fiber subtype was age-dependent, at least in the plantaris muscle. IIB1 fibers were observed only in the superficial portion of the plantaris and gastrocnemius muscle. The ratio of IIB1:IIB2 fibers was about the same throughout the extensor digitorum longus and extraocular muscles. Therefore, the two kinds of IIB fibers here observed have a different myosin heavy chain content. On the basis of their specific immunoreactivities, we suggest that IIB1 fibers contain the previously described MHCB. IIB2 fibers contain either a unique new MHC isoform or a mixture of at least two MHC, possibly composed of the MHCB and either the previously described MHCA or a new MHC isoform.     

Ultrastructural studies of alterations induced by microwaves in Toxocara canis eggs: prophylactic interest

The ultrastructure of Toxocara canis eggs is described before and after exposure to microwaves. The morphology of normal eggs is compared to that of eggs from other helminths. Following treatment, the complete disorganization of the surface structure of the shell and the loss of much turgidity of the egg are observed. The destruction of the internal structure is most marked in the center of the egg and is associated with the disappearance of some layers of the shell. In addition, there is substantial damage to the synthesis apparatus (ribosomes, endoplasmic reticulum, lipid cisternae). An explanation based on the specific action of microwaves and micro-overheating is proposed, and the prophylactic use of this technique is considered.     

Cyclooxygenase-2 positively regulates Akt signalling and enhances survival of erythroleukemia cells exposed to anticancer agents

Cyclooxygenase-2 (COX-2) has been found to be highly expressed in many types of cancers and to contribute to tumorigenesis via the inhibition of apoptosis, increased angiogenesis and invasiveness. In hematological malignancies, COX-2 expression was found to correlate with poor patient prognosis. However, the exact role of COX-2 expression in these malignancies, and particularly in erythroleukemias, remains unclear. The aim of this work was to describe and understand the relationships between COX-2 expression and apoptosis rate in erythroleukemia cells after apoptosis induction by several anticancer agents. We used three different erythroleukemia cell lines in which COX-2 expression was modulated by transfection with either COX-2 siRNA or COX-2 cDNA. These cellular models were then treated with apoptosis inducers and apoptosis onset and intensity was followed. Cell signalling was evaluated in unstimulated transfected cells or after apoptosis induction. We found that COX-2 inhibition rendered erythroleukemia cells more sensitive to apoptosis induction and that in cells overexpressing COX-2 apoptosis induction was reduced. We demonstrated that COX-2 inhibition decreased the pro-survival Akt signalling and activated the negative regulator of Akt signalling, phosphatase and tensin homologue deleted on chromosome 10 (PTEN). Conversely, in COX-2 overexpressing cells, Akt signalling was activated and PTEN was inhibited. In these last cells, inhibition of casein kinase 2 or Akt signalling restored sensitivity to apoptotic agents. Our findings highlighted that COX-2 can positively regulate Akt signalling mostly through PTEN inhibition, partly via casein kinase 2 activation, and enhances survival of erythroleukemia cells exposed to anticancer agents.