Transcriptional networks of knockout cell lines identify functional specificities of H-Ras and N-Ras: significant involvement of N-Ras in biotic and defense responses

We characterized differential gene expression profiles of fibroblast cell lines harboring single or double-homozygous null mutations in H-ras and N-ras. Whereas the expression level of the individual H-, N- and K-ras genes appeared unaffected by the presence or absence of the other ras loci, significant differences were observed between the expression profiles of cells missing N-ras and/or H-ras. Absence of N-ras produced much stronger effects than absence of H-ras over the profile of the cellular transcriptome. N-ras(-/-) and H-ras(-/-) fibroblasts displayed rather antagonistic expression profiles and the transcriptome of H-ras(-/-) cells was significantly closer to that of wild-type fibroblasts than to that of N-ras(-/-) cells. Classifying all differentially expressed genes into functional categories suggested specific roles for H-Ras and N-Ras. It was particularly striking in N-ras(-/-) cells the upregulation of a remarkable number of immunity-related genes, as well as of several loci involved in apoptosis. Reverse-phase protein array assays demonstrated in the same N-ras(-/-) cells the overexpression and nuclear migration of tyrosine phosphorylated signal transducer and activator of transcription 1 (Stat1) which was concomitant with transcriptional activation mediated by interferon-stimulated response elements. Significantly enhanced numbers of apoptotic cells were also detected in cultures of N-ras(-/-) cells. Our data support the notion that different Ras isoforms play functionally distinct cellular roles and indicate that N-Ras is significantly involved in immune modulation/host defense and apoptotic responses.

Unexpected isolation of Bordetella pertussis from a blood culture

Bordetella pertussis was isolated from a culture of blood from a 31-year-old man with Wegener's granulomatosis. The organism was detected with the BACTEC 9240 system after 6 days of incubation and was confirmed as B. pertussis by the Centers for Disease Control and Prevention. To our knowledge, this is the first published report of the recovery of B. pertussis from blood.

Vitreous levels of interleukine-8 and monocyte chemoattractant protein-1 in macular oedema with branch retinal vein occlusion

PURPOSE

To investigate whether interleukine-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) are related with macular oedema in patients with branch retinal vein occlusions (BRVOs).

DESIGN

Retrospective case-control study.

PARTICIPANTS

Nineteen patients who had macular oedema due to BRVO and nine patients with non-ischaemic ocular diseases (control group).

METHODS

Macular oedema was examined by optical coherence tomography. Both venous blood and vitreous samples were obtained at the time of vitreoretinal surgery. IL-8 and MCP-1 levels in vitreous fluid and plasma were determined with enzyme-linked immunosorbent assay kits. Variables were compared with the Mann-Whitney U-test, Wilcoxon's signed-ranked test, and the chi2-test, when appropriate. To examine correlations, Spearman's rank-order correlation coefficients were calculated. Statistical significance was set at P<0.05.

RESULTS

The vitreous fluid levels of IL-8 (median: 63.5 pg/ml) and MCP-1 (median: 1522.4 pg/ml) were significantly higher in the patients with BRVO than in the control group (median: 5.1 and 746.5 pg/ml respectively; P<0.001 and <0.001 respectively). Vitreous IL-8 and MCP-1 were significantly correlated in patients with BRVO (P=0.009).

CONCLUSIONS

Both IL-8 and MCP-1 were elevated in the vitreous fluid of patients with BRVO and macular oedema. Both chemokines may contribute to the pathogenesis of macular oedema in patients with BRVO.

In vitro synthesis of the membrane-bound D-lactate dehydrogenase of Escherichia coli

Synthesis of the membrane-bound, flavin-linked D-lactate dehydrogenase of Escherichia coli has been studied by using a recombinant plasmid containing the dld gene [Young, I. G., Jaworowski, A., & Poulis, M. (1982) Biochemistry (following paper in this issue)]. Expression of the cloned dld gene was achieved either in vivo with transformed minicells or in vitro with a fractionated transcription/translation system. In both instances, a product is observed that is specifically immunoprecipitated by gamma-globulin prepared against the purified enzyme and comigrates with authentic D-lactate dehydrogenase on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Furthermore, the product is catalytically active and binds to membrane vesicles during or after synthesis. Thus, it seems likely that the protein is synthesized in mature form and binds to the membrane without a leader peptide sequence. Interestingly, addition of flavin adenine dinucleotide to the in vitro reaction mixtures causes a 2-fold increase in the synthesis of the enzyme, suggesting that the cofactor plays a regulatory role in the synthesis of the apoprotein. Finally, L factor, a protein involved in regulation of protein elongation, has an inhibitory effect on the expression of the dld gene and a stimulatory effect on the expression of the ndh gene (encoding NADH dehydrogenase).

Establishment of permanent brown adipocyte cell lines achieved by transfection with SV40 large T antigen and ras genes

We established multiple clonal cell lines by transfection of primary rat fetal brown adipocytes (BAT) with constitutive or inducible gene constructs of SV40 large T antigen (SVLTag) alone or in combination with transforming or normal ras genes. While primary BAT cell cultures stop growing and expressing uncoupling protein (UCP) after several passages in culture, our transfected cell lines could be propagated indefinitely and kept properties specific of BAT cells. Interestingly, cells transfected with ras genes alone did not survive as permanent cell lines. In contrast, cells transfected with SVLTag alone or in combination with various ras genes could readily be established as continuous cell lines. BAT cells transfected with SVLTag alone showed fibroblastic, flat morphology and clear contact inhibition of growth. In contrast, cells cotransfected with SVLTag and ras genes were more fusiform and possessed increased proliferative capacity. Thus, cells cotransfected with normal ras reached higher cell density at confluency, while cells cotransfected with transforming ras were clearly refractile, lost contact inhibition of growth, and presented a transformed phenotype. These results are consistent with the notion that ras genes are inefficient at overcoming senescence of primary BAT cells and can only confer improved proliferative ability to cells that have already been immortalized by a cooperating SVLTag gene. RNA analysis showed that most transfected cell lines expressed UCP along with the exogenously transfected genes. This demonstrated that genuine BAT cells, and not other possible contaminating cell lineages, gave rise to our selected cell lines. The variety of cell lines generated may correspond to various stages of progression through BAT development and therefore be useful to characterize signaling pathways and metabolic regulation of this particular tissue.

Oncogenic Ras-induced germinal vesicle breakdown is independent of phosphatidylinositol 3-kinase in Xenopus oocytes

A number of reports have identified phosphatidylinositol 3-kinase as a downstream effector of Ras in various cellular settings, in contrast to others supporting the notion that phosphatidylinositol 3-kinase acts upstream of Ras. Here, we used Xenopus oocytes, a model of Ras-mediated cell cycle progression (G2/M transition) to analyze the contribution of phosphatidylinositol 3-kinase to insulin/Ras-dependent signaling pathways leading to germinal vesicle breakdown and to ascertain whether phosphatidylinositol 3-kinase acts upstream or downstream of Ras in those signaling pathways. We analyzed the process of meiotic maturation induced by progesterone, insulin or micro-injected oncogenic Ras (Lys12) proteins in the presence and absence of specific inhibitors of phosphatidylinositol 3-kinase activity. As expected, the progesterone-induced maturation was independent of phosphatidylinositol 3-kinase since similar rates of germinal vesicle breakdown were produced by the hormone in the presence and absence of wortmannin and LY294002. In contrast, insulin-induced germinal vesicle breakdown was completely blocked by pre-incubation with the inhibitors prior to insulin treatment. Interestingly, similar rates of germinal vesicle breakdown were obtained in Ras (Lys12)-injected oocytes, independently of whether or not they had been pre-treated with phosphatidylinositol 3-kinase inhibitors. The effect of wortmannin or LY294002 on MAPK and Akt activation by progesterone, insulin or Ras was also analyzed. Whereas insulin activated those kinases in a phosphatidylinositol 3-kinase-dependent manner, progesterone and Ras were able to activate those kinases in the absence of phosphatidylinositol 3-kinase activity. Since Ras is a necessary and sufficient downstream component of insulin signaling pathways leading to germinal vesicle breakdown, these observations demonstrate that phosphatidylinositol 3-kinase is not a downstream effector of Ras in insulin/Ras-dependent signaling pathways leading to entry into the M phase in Xenopus oocytes.

Nosema ceranae Winter Control: Study of the Effectiveness of Different Fumagillin Treatments and Consequences on the Strength of Honey Bee (Hymenoptera: Apidae) Colonies

OVERVIEW

In Uruguay, colonies of honey bees moving to Eucalyptus grandis plantation in autumn habitually become infected with the microsporidian Nosema ceranae , a parasite that attacks the digestive system of bees. Beekeepers attributed to N. ceranae depopulation of the colonies that often occurs at the end of the blooming period, and many use the antibiotic fumagillin to reduce the level of infection. The aim of this study was to compare the effectiveness of four different fumagillin treatments and determine how this antibiotic affects the strength of the colonies during the winter season. The colonies treated with fumagillin in July showed less spore load at the end of applications, being the most effective the following treatments: the four applications sprayed over bees of 30 mg of fumagillin in 100 ml of sugar syrup 1:1, and four applications of 90 mg of fumagillin in 250 ml of sugar syrup 1:1 using a feeder. However, 2 month after the treatment applications, the colonies treated with fumagillin were the same size as the untreated colonies. In September, the colonies treated and not treated with fumagillin did not differ in colony strength (adult bee population and brood area) or spores abundance. Our study demonstrates that fumagillin treatment temporarily decreased the spore load of N. ceranae , but this was not reflected in either the size of the colonies or the probability of surviving the winter regardless of the dose or the administration strategy applied. Given the results obtained, we suggest to not perform the pharmacological treatment under the conditions described in the experiment.

RESUMEN

En Uruguay las colonias de abejas melíferas que se trasladan a las forestaciones de Eucalyptus grandis en otoño indefectiblemente se infectan con el microsporido Nosema ceranae , parásito que ataca el sistema digestivo de las abejas. Los apicultores atribuyen a N. ceranae el despoblamiento de las colonias que ocurre con frecuencia al terminar el periodo de floración y muchos emplean el antibiótico fumagilina para reducir el nivel de infección. El objetivo de este estudio fue comparar la eficacia de cuatro tratamientos diferentes con fumagilina y determinar cómo incide en la fortaleza de las colonias durante la invernada. Las colonias tratadas con fumagilina en julio presentaron una menor carga de esporas al terminar las aplicaciones, siendo los tratamientos más eficaces el de 4 aplicaciones mediante asperjado sobre las abejas de 30 mg de fumagilina en 100 ml de jarabe de azúcar 1:1, y el de 4 aplicaciones de 90 mg de fumagilina en 250 ml de jarabe de azúcar 1:1 utilizando un alimentador. Sin embargo, durante el período de experimentación, las colonias tratadas con antibiótico presentaron igual tamaño que las colonias no tratadas. En setiembre, las colonias tratadas y no tratadas con fumagilina no se diferenciaron en la intensidad de infección ni en su tamaño. En las condiciones en que se realizó el estudio, la aplicación de fumagilina disminuyó temporalmente la carga de esporas de N. ceranae pero esto no se reflejó en el tamaño de las colonias ni en la probabilidad de sobrevivir el invierno.

Comparative histopathologic and viral immunohistochemical studies on CeMV infection among Western Mediterranean, Northeast-Central, and Southwestern Atlantic cetaceans

Cetacean morbillivirus (CeMV) is a major natural cause of morbidity and mortality in cetaceans worldwide and results in epidemic and endemic fatalities. The pathogenesis of CeMV has not been fully elucidated, and questions remain regarding tissue tropism and the mechanisms of immunosuppression. We compared the histopathologic and viral immunohistochemical features in molecularly confirmed CeMV-infected Guiana dolphins (Sotalia guianensis) from the Southwestern Atlantic (Brazil) and striped dolphins (Stenella coeruleoalba) and bottlenose dolphins (Tursiops truncatus) from the Northeast-Central Atlantic (Canary Islands, Spain) and the Western Mediterranean Sea (Italy). Major emphasis was placed on the central nervous system (CNS), including neuroanatomical distribution of lesions, and the lymphoid system and lung were also examined. Eleven Guiana dolphins, 13 striped dolphins, and 3 bottlenose dolphins were selected by defined criteria. CeMV infections showed a remarkable neurotropism in striped dolphins and bottlenose dolphins, while this was a rare feature in CeMV-infected Guiana dolphins. Neuroanatomical distribution of lesions in dolphins stranded in the Canary Islands revealed a consistent involvement of the cerebrum, thalamus, and cerebellum, followed by caudal brainstem and spinal cord. In most cases, Guiana dolphins had more severe lung lesions. The lymphoid system was involved in all three species, with consistent lymphoid depletion. Multinucleate giant cells/syncytia and characteristic viral inclusion bodies were variably observed in these organs. Overall, there was widespread lymphohistiocytic, epithelial, and neuronal/neuroglial viral antigen immunolabeling with some individual, host species, and CeMV strain differences. Preexisting and opportunistic infections were common, particularly endoparasitism, followed by bacterial, fungal, and viral infections. These results contribute to understanding CeMV infections in susceptible cetacean hosts in relation to factors such as CeMV strains and geographic locations, thereby establishing the basis for future neuro- and immunopathological comparative investigations.

Treatment of Type II Endoleaks after Endovascular Repair of Abdominal Aortic Aneurysms: Translumbar Puncture and Injection of Thrombin into the Aneurysm Sac

OBJECTIVES

The aim of this article is to report our experience in the use of a new technique for the treatment of type II endoleaks which appear after the endovascular treatment of abdominal aortic aneurysms.

MATERIALS AND METHODS

In three patients with secondary type II endoleaks, we performed a translumbar puncture, introducing a 22-Gauge needle into the aneurysm sac under CT guidance. Once intrasac pressure had been registered, 1000U (2 ml) of human thrombin were slowly injected into the sac.

RESULTS

Complete sealing of the endoleak was achieved in all three patients, confirmed by the lack of contrast filling of the sac in the CT scans performed 5 min and 24 h after the procedure. Initial intrasac pressure was equal to systolic arterial pressure in the three patients. After the procedure, the pressure decreased by 30-40 mmHg. There were no complications during the procedure, which lasted 45-90 min. No endoleak recurrence has been observed in any of the three cases 6 months later.

CONCLUSIONS

We present an alternative method of treating type II endoleaks, which could become the treatment of choice if and when a wider experience confirms our initial good results.

The isoform-specific stretch of hSos1 defines a new Grb2-binding domain

hSos1 isoform II, defined by the presence of a 15 amino acid stretch in its carboxy-terminal region, exhibits higher Grb2 affinity than hSos1 isoform I. In this study, we investigated the cause for this difference and observed that, in addition to the four currently accepted Grb2-binding motifs, a number of additional, putative SH3-minimal binding sites (SH3-MBS) could be identified. The isoform II-specific 15 amino acid stretch contained one of them. Indeed, we demonstrated by site-directed mutagenesis that these SH3-MBS were responsible for the Grb2 interaction, and we found that C-terminal fragments of the two hSos1 isoforms (lacking the four cannonical Grb2-binding motifs, but containing the SH3-minimal binding sites) were able to bind Grb2, with the isoform II fragment showing higher Grb2 affinity than the corresponding isoform I fragment. Furthermore, we provide evidence that C-terminal truncated mutants of either hSos1 isoform, containing only the SH3-minimal binding sites, were able to originate in vivo stable complexes with Grb2. Although, Grb2-binding remains higher in both full-length isoforms, compared to the C-terminal truncated mutants, these mutants were also able to activate Ras, supporting a potential role of this C-terminal region as negative modulator of Sos1 activity. These findings document the existence of a new, functional, SH3-minimal binding site located in the specific stretch of hSos1 isoform II which may be responsible for the increased Grb2 affinity of this isoform in comparison to isoform I, and for the physiological properties differences between both isoforms. Moreover, these SH3-minimal binding sites may be sufficient to attain stable and functional hSosl-Grb2 complexes.

Ab initio studies of Ag-S bond formation during the adsorption of L-cysteine on Ag(111)

Ab initio studies of Ag-S bond formation during the adsorption of L-cysteine on Ag(111) have been performed by combining density functional theory with a quantum mechanical model developed in our group. The adsorbate-silver bond formation has been investigated by analyzing the projected density of states onto the different atoms of the molecule and by charge density difference calculations when the zwitterion radical approaches the surface. The polar character of the bond can be distinguished. For the first time, the coupling constants of the sulfur orbitals with the d and sp bands have been calculated by fitting the density of states. The role of the sp bands in the stabilization of the sulfur-silver bond is analyzed. The differences with the catalysis of hydrogen adsorption are discussed. Copper, gold, and silver are not good catalysts for the adsorption of hydrogen because of the position of the d bands lying too far below the Fermi level. However, the coin metals are excellent for the adsorption of thiols. The reason is that at the equilibrium position the sulfur atom is much farther from the surface than hydrogen, and thus the interactions with the sp bands stabilize its bond to the surface.

Protective role of the HLA–A*02 allele in Portuguese patients with multiple sclerosis

Background

Multiple sclerosis (MS) is associated with human leukocyte antigen (HLA) HLA–DRB1*15. Recent evidence that CD8 T cells are implicated in MS suggests that HLA class I may also contribute. An association of HLA–A*02 and A*03 alleles has been described.

Objectives

We examined the influence of HLA–A*02 and HLA–A*03 in Portuguese patients with MS, independently of HLA–DRB1*15 using a logistic regression model.

Conclusions

DRB1*15 increased the risk of developing MS and HLA–A*02 decreased the risk. A*03 had no effect. To analyze if HLA–A*02 association was independent from DRB1*15, an interaction between these two alleles was introduced in the model; no significant interaction was found.

An epidermal growth factor receptor/ret chimera generates mitogenic and transforming signals: evidence for a ret-specific signaling pathway

A chimeric expression vector which encoded for a molecule encompassing the extracellular domain of the epidermal growth factor (EGF) receptor (EGFR) and the intracellular domain of the ret kinase (EGFR/ret chimera) was generated. Upon ectopic expression in mammalian cells, the EGFR/ret chimera was correctly synthesized and transported to the cell surface, where it was shown capable of binding EGF and transducing an EGF-dependent signal intracellularly. Thus, the EGFR/ret chimera allows us to study the biological effects and biochemical activities of the ret kinase under controlled conditions of activation. Comparative analysis of the growth-promoting activity of the EGFR/ret chimera expressed in fibroblastic or hematopoietic cells revealed a biological phenotype clearly distinguishable from that of the EGFR, indicating that the two kinases couple with mitogenic pathways which are different to some extent. Analysis of biochemical pathways implicated in the transduction of mitogenic signals also evidenced significant differences between the ret kinase and other receptor tyrosine kinases. Thus, the sum of our results indicates the existence of a ret-specific pathway of mitogenic signaling.

Lymphadenitis caused by Aerococcus urinae infection

Aerococcus urinae is rarely reported as a human pathogen. The pathogenesis of this gram-positive coccus is not fully understood. It has been identified as a cause of urinary tract infections but may be associated with severe infections such as endocarditis and septicaemia. This paper presents a case of lymphadenitis caused by A. urinae.