The architecture of variant surface glycoprotein gene expression sites in Trypanosoma brucei

Trypanosoma brucei evades the immune system by switching between Variant Surface Glycoprotein (VSG) genes. The active VSG gene is transcribed in one of approximately 20 telomeric expression sites (ESs). It has been postulated that ES polymorphism plays a role in host adaptation. To gain more insight into ES architecture, we have determined the complete sequence of Bacterial Artificial Chromosomes (BACs) containing DNA from three ESs and their flanking regions. There was variation in the order and number of ES-associated genes (ESAGs). ESAGs 6 and 7, encoding transferrin receptor subunits, are the only ESAGs with functional copies in every ES that has been sequenced until now. A BAC clone containing the VO2 ES sequences comprised approximately half of a 330 kb 'intermediate' chromosome. The extensive similarity between this intermediate chromosome and the left telomere of T. brucei 927 chromosome I, suggests that this previously uncharacterised intermediate size class of chromosomes could have arisen from breakage of megabase chromosomes. Unexpected conservation of sequences, including pseudogenes, indicates that the multiple ESs could have arisen through a relatively recent amplification of a single ES.     

Tumor antigens and antigen-presenting capacity in breast cancer.

AIMS: Cancer cells frequently express antigens capable of being recognized by the host immune system; however, any resultant immune response is often ineffective. This may be related in part to tumor-induced defects in antigen presentation. We screened for dendritic cell infiltration, tumor MHC II expression and associated lymphocytic reaction in the context of three established breast tumor antigens. METHODS: Forty primary breast tumors were evaluated by immunohistochemical techniques for expression of her2/neu, p53, and MUC1 and MHC class II molecules. Twenty-five samples were further analyzed for p53 mutations by PCR-SSCP analysis and DNA sequencing. The phenotype of tumor-infiltrating inflammatory cells was evaluated using the following markers: CD1a, MHC Class II, CD3, CD45, and CD45RO. RESULTS: Tumors with p53 mutations and overexpression, but not her2/neu or MUC1 overexpressing tumors, more frequently harbored marked CD1a+ dendritic cell infiltrates. An overall correlation between CD1a+ cell infiltrates and HLA class II expression on tumor cells (p = 0.0008) was also observed and these tumors had greater CD45RO+ lymphocytic infiltrates. CONCLUSIONS: In breast cancer, p53 mutations may present a more visible signal to the immune system and hence provide a better target for immunotherapy. Infiltrating CD1a positive cells are associated with a more dense tumor lymphocytic infiltrate and tumor cell expression of MHC II molecules.     

Mitral cell temporal response patterns evoked by odor mixtures in the rat olfactory bulb

Mammals generally have the ability to extract odor information contained in complex mixtures of molecular components. However, odor mixture processing has been studied electrophysiologically only in insects, crustaceans, and fish. As a first step toward a better understanding of this processing in high vertebrates, we studied the representation of odor mixtures in the rat olfactory bulb, i.e., the second-order level of the olfactory pathways. We compared the single-unit responses of mitral cells, the main cells of the olfactory bulb, to pure odors and to their binary mixtures. Eighty-six mitral cells were recorded in anesthetized freely breathing rats stimulated with five odorants and their 10 binary mixtures. The spontaneous activity and the odor-evoked responses were characterized by their temporal distribution of activity along the respiratory cycle, i.e., by cycle-triggered histograms. Ninety percent of the mixtures were found to evoke a response when at least one of their two components evoked a response. Mixture-evoked patterns were analyzed to describe the modalities of the combination of patterns evoked by the two components. In most of the cases, the mixture pattern was closely similar to one of the component patterns. This dominance of a component over the other one was related to the responsiveness of the cell to the individual components of the mixture, to the molecular nature of the stimulus, and to the coarse shape of individual response patterns. This suggests that the components of binary mixtures may be encoded simultaneously by different odor-specific temporal distributions of activity.     

Hepatic hemobilia: Hemorrhage from the intrahepatic biliary tract,a review

Hepatic hemobilia is defined as hemorrhage arising from pathological changes in the intrahepatic biliary tract. The main causes are iatrogenic trauma, cholangitis, tumors, and coagulopathy. The salient features of the hemobilia syndrome are described and their causes explained. The treatment, when necessitated by hemorrhage or clot formation, is either resection of the liver or occlusion of the responsible artery by ligature or embolization. The iatrogenic trauma may be operative, resulting from instrumental lesion of the bile ducts, needle biopsy, transhepatic cholangiography, biliary tract prosthesis, or inlaying hepatic artery catheters. Among the inflammatory etiologies, special attention is given to nematodes in the ducts, the tropical hemobilia. Spontaneous hemobilia may, just as nose bleeds or hematuria, result from treatment with anticoagulants.

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Résumé L'hémobilie d'origine hépatique répond à l'hémorragie qui provient de lésions situées au niveau des voies biliaires intra-hépatiques. Les causes principales en sont le traumatisme, l'angiocholite, les tumeurs et les troubles de la coagulation. Les caracteres saillants de l'hémobilie sont décrits ainsi que ses causes. Le traitement quand il devient nécessaire en raison de l'importance de l'hémorragie ou de la formation de caillots consiste à réséquer une partie du parenchyme hépatique ou à obtenir l'occlusion de la plaie vasculaire par ligature ou par embolisation.Le traumatisme peut être d'origine iatrogène, qu'il soit le fait d'une lésion instrumentale des canaux biliaires hépatiques, d'une biopsie du foie à l'aiguille, de la cholangiographie transhépatique, ou encore de la présence d'une prothèse au niveau des voies biliaires ou d'un cathéter artériel.Parmi les causes inflammatoires une attention spéciale doit être accordée à l'existence de nématodes au niveau des canaux biliaires intra-hépatiques qui sont à l'origine de l'hémobilie tropicale.L'hémobilie spontanée, comme l'épistaxis ou l'hématurie, peut être la conséquence d'un traitement anti-coagulant.ResumenLa hemobilia hepática se define como hemorragia proveniente de alteraciones patológicas en el tracto biliar intrahepatico. Las causas principales son el trauma iatrogénico, la colangitis, los tumores y la coagulopatía. Se describen las características sobresalientes del síndrome de hemobilia y se explican sus causas. El tratamiento, cuando se hace necesario por hemorragia o por formación de coágulos, es la resección del hígado o la oclusión de la arteria responsable por ligadura o por embolización. El trauma iatrogénico puede ser de origen operatorio, como resultado de lesión instrumental de los canales biliares, biopsia por aguja, colangiografía transhepática, prótesis en el tracto biliar y catéteres colocados en la arteria hepática. Entre las etiologías de naturaleza inflamatoria se presta atención especial a la presencia de nemátodos en los canales, la hemobilia tropical. Al igual de lo que ocurre con las epistaxis o las hematurias, la hemobilia espontanea puede ser consecuencia de tratamientos con anticoagulantes.

     

The Potential of Anti-Bullying Efforts to Prevent Academic Failure and Youth Crime. A Case Using the Olweus Bullying Prevention Program (OBPP)

Prevention Science - The effectiveness of bullying prevention programs has led to expectations that these programs could have effects beyond their primary goals. By reducing the number of victims...     

Distinct immunopathological mechanisms of EBV-positive and EBV-negative posttransplant lymphoproliferative disorders

EBV-positive and EBV-negative posttransplant lymphoproliferative disorders (PTLDs) arise in different immunovirological contexts and might have distinct pathophysiologies. To examine this hypothesis, we conducted a multicentric prospective study with 56 EBV-positive and 39 EBV-negative PTLD patients of the K-VIROGREF cohort, recruited at PTLD diagnosis and before treatment (2013–2019), and compared them to PTLD-free Transplant Controls (TC, n = 21). We measured absolute lymphocyte counts (n = 108), analyzed NK- and T cell phenotypes (n = 49 and 94), and performed EBV-specific functional assays (n = 16 and 42) by multiparameter flow cytometry and ELISpot-IFNγ assays (n = 50). EBV-negative PTLD patients, NK cells overexpressed Tim-3; the 2-year progression-free survival (PFS) was poorer in patients with a CD4 lymphopenia (CD4⁺<300 cells/mm³, p <  .001). EBV-positive PTLD patients presented a profound NK-cell lymphopenia (median = 60 cells/mm³) and a high proportion of NK cells expressing PD-1 (vs. TC, p = .029) and apoptosis markers (vs. TC, p < .001). EBV-specific T cells of EBV-positive PTLD patients circulated in low proportions, showed immune exhaustion (p = .013 vs. TC) and poorly recognized the N-terminal portion of EBNA-3A viral protein. Altogether, this broad comparison of EBV-positive and EBV-negative PTLDs highlight distinct patterns of immunopathological mechanisms between these two diseases and provide new clues for immunotherapeutic strategies and PTLD prognosis.     

Untersuchungen über die Ausspritzmethode zur Lokalisation der Mikroelektrodenspitze bei Potentialmessungen am proximalen Konvolut der Rattenniere

Summary In measurements of transtubular potential differences of the rat kidney, reported previously, the electrode tip could be localized by ejection of electrode fluid under microscopic observation. In the proximal tubule it was found in contrast to the distal tubule that all potential differences disappeared irreversibly upon fluid ejection. The present study is concerned with the mechanism underlying this effect.The localization of the puncturing electrode was controlled by a coupling pulse technique. Current pulses were injected into the tubular lumen through a first electrode, and the same tubule was punctured subsequently with a second electrode which measured the potential difference. It was found that in most impalements the puncturing electrode would stop within the tubular wall, although from microscopic inspection it appeared to have reached the tubular lumen. Furthermore, when fluid was ejected from the electrode tip, the electrode abruptly penetrated into the tubular lumen. Simultaneously the potential difference recorded hitherto disappeared. This coincidence suggests that the breakdown of the potential difference merely corresponds to the potential step between cellular compartment and tubular lumen and that it is not caused by a transtubular leak.Conclusive evidence against the development of leaks during fluid ejection was derived from microperfusion experiments. During perfusion of the tubular lumen with choline chloride solution proximal tubules develop a transtubular potential difference significantly different from zero (up to 30 mV, lumen positive). Whether the electrode entered the tubular lumen during the impalement immediately, or whether the penetration was only accomplished by fluid ejection, did not affect the magnitude of the positive potential differences recorded. Hence these experiments constitute proof that the method of fluid ejection permits reliable measurements of transtubular potential differences in the proximal tubule. They confirm our finding that under normal free flow conditions no transtubular potential difference exists across the proximal tubular epithelium of the rat kidney.

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Mit Unterstützung durch die Deutsche Forschungsgemeinschaft.     

Nocardia ignorata, a new agent of human nocardiosis isolated from respiratory specimens in Europe and soil samples from Kuwait

Nocardia ignorata is a recently described species identified on the basis of a single isolate of unknown origin. Here we describe the epidemiological, phenotypic, and phylogenetic characteristics of this new species, based on five new clinical and soil isolates.