Is physical activity a trigger factor for subarachnoid hemorrhage?

INTRODUCTION: Subarachnoid hemorrhage (SAH) is a serious pathology, associated with 43% mortality and significant disability. In the absence of relevant guidelines, some teams advocate that patients harboring an unruptured intracranial aneurysm (ICA) abstain from all sports activity, as a prophylactic precaution. The aim of the present study was to evaluate the impact of physical activity as a risk factor for SAH, through a review of the literature. METHOD: A systematic literature review was performed for the period 2000 to 2020 in accordance with the PRISMA guidelines. Prospective and retrospective articles reporting more than 50 patients whose physical activity was associated with onset of SAH were included. The main end-point was prevalence of SAH occurring after physical activity. For comparison purposes, the prevalences of other circumstances were calculated to establish a range of frequency. RESULTS: Physical activity appeared to be quite rarely associated with onset of SAH, with a prevalence of 3%, compared to 30% at rest, 7.3% in association with defecation and 4.5% in association with sexual activity. Age under 60 years, male gender (M/F ratio 1.38) and smoking (67.1%) were associated with onset of SAH during physical activity. CONCLUSION: Physical activity appears to be a rare trigger factor for SAH. These results are in contrast to the idea that physical activity should, as a precaution, be avoided in patients with unruptured ICA. There is at present no scientific evidence of an association with aneurysmal SAH.

Carotid artery vein-pouch bifurcation aneurysm in rats: An experimental model for microneurosurgical training.

BACKGROUND: In the era of endovascular treatment of intracranial aneurysms, surgical clipping is still a relevant treatment method in some cases. However, it has become harder to teach this skill, as the number of surgical cases has decreased over the past years. We therefore decided to use a previously described experimental aneurysm model for surgical training. MATERIAL AND METHODS: We operated on 8 rats and constructed a vein-pouch aneurysm at a surgically created carotid bifurcation. Survivors were kept alive for 1 month and operated on to clip the aneurysm. RESULTS: Only 3 rats had survived at 1 month. All the carotid arteries were permeable. Only 2 aneurysms were circulating at 1 month, as 1 had thrombosed. They were successfully clipped at 1 month. CONCLUSIONS: These preliminary results enabled our junior surgeon to clip two circulating aneurysms, under an operative microscope reproducing surgical conditions. Although the efficacy of the model could be improved, we believe it could be used as a first step in training neurosurgical residents in the basics of aneurysm clipping and microsurgical techniques in a realistic setting.

Comparison of theory and experiment for NAPL dissolution in porous media.

Contamination of groundwater resources by an immiscible organic phase commonly called NAPL (Non Aqueous Phase Liquid) represents a major scientific challenge considering the residence time of such a pollutant. This contamination leads to the formation of NAPL blobs trapped in the soil and impact of this residual saturation cannot be ignored for correct predictions of the contaminant fate. In this paper, we present results of micromodel experiments on the dissolution of pure hydrocarbon phase (toluene). They were conducted for two values of the Péclet number. These experiments provide data for comparison and validation of a two-phase non-equilibrium theoretical model developed by Quintard and Whitaker (1994) using the volume averaging method. The model was directly upscaled from the averaged pore-scale mass balance equations. The effective properties of the macroscopic model were calculated over periodic unit cells designed from images of the experimental flow cell. Comparison of experimental and numerical results shows that the transport model predicts correctly - with no fitting parameters - the main mechanisms of NAPL mass transfer. The study highlights the crucial need of having a fair recovery of pore-scale characteristic lengths to predict the mass transfer coefficient with accuracy.

Identification of a cell population that produces alpha/beta interferon in vitro and in vivo in response to noncytopathic bovine viral diarrhea virus.

In vitro infection of bovine cells of many origins with the cytopathogenic bovine viral diarrhea virus (cpBVDV) results in the induction of alpha/beta interferon (IFN-alpha/beta), whereas noncytopathogenic BVDV (ncpBVDV) isolates have been shown not to induce IFN-alpha/beta in vitro. Similarly, cpBVDV induces IFN-alpha/beta in the early bovine fetus, but ncpBVDV does not. However, acute infection of naive cattle with ncpBVDV results in IFN-alpha/beta production. In this study, we identified and characterized a minor population of cells, present in lymph nodes that produce IFN-alpha in response to ncpBVDV. These cells expressed the myeloid markers CD14, CD11b, and CD172a but did not express CD4 and CD45RB. We also established that these cells produced IFN-alpha in the absence of detectable productive infection.

Regulation of CCR6 chemokine receptor expression and responsiveness to macrophage inflammatory protein-3alpha/CCL20 in human B cells.

The regulation of CCR6 (chemokine receptor 6) expression during B-cell ontogeny and antigen-driven B-cell differentiation was analyzed. None of the CD34(+)Lin(-) hematopoietic stem cell progenitors or the CD34(+)CD19(+) (pro-B) or the CD19(+)CD10(+) (pre-B/immature B cells) B-cell progenitors expressed CCR6. CCR6 is acquired when CD10 is lost and B-cell progeny matures, entering into the surface immunoglobulin D(+) (sIgD(+)) mature B-cell pool. CCR6 is expressed by all bone marrow-, umbilical cord blood-, and peripheral blood-derived naive and/or memory B cells but is absent from germinal center (GC) B cells of secondary lymphoid organs. CCR6 is down-regulated after B-cell antigen receptor triggering and remains absent during differentiation into immunoglobulin-secreting plasma cells, whereas it is reacquired at the stage of post-GC memory B cells. Thus, within the B-cell compartment, CCR6 expression is restricted to functionally mature cells capable of responding to antigen challenge. In transmigration chemotactic assays, macrophage inflammatory protein (MIP)-3alpha/CC chemokine ligand 20 (CCL20) induced vigorous migration of B cells with differential chemotactic preference toward sIgD(-) memory B cells. These data suggest that restricted patterns of CCR6 expression and MIP-3alpha/CCL20 responsiveness are integral parts of the process of B-lineage maturation and antigen-driven B-cell differentiation.

BAFF binds to the tumor necrosis factor receptor-like molecule B cell maturation antigen and is important for maintaining the peripheral B cell population.

The tumor necrosis factor (TNF) family member B cell activating factor (BAFF) binds B cells and enhances B cell receptor-triggered proliferation. We find that B cell maturation antigen (BCMA), a predicted member of the TNF receptor family expressed primarily in mature B cells, is a receptor for BAFF. Although BCMA was previously localized to the Golgi apparatus, BCMA was found to be expressed on the surface of transfected cells and tonsillar B cells. A soluble form of BCMA, which inhibited the binding of BAFF to a B cell line, induced a dramatic decrease in the number of peripheral B cells when administered in vivo. Moreover, culturing splenic cells in the presence of BAFF increased survival of a percentage of the B cells. These results are consistent with a role for BAFF in maintaining homeostasis of the B cell population.

Cutting edge: HIV-1 Tat protein differentially modulates the B cell response of naive, memory, and germinal center B cells.

Critical steps of B cell differentiation occur within lymphoid organs that are also major sites of HIV-1 replication. Because Tat can be released by infected cells, we investigated whether extracellular HIV-1 Tat modulates cell proliferation of B cells at critical stages of their differentiation. Here we show that extracellular Tat inhibited the proliferation of B cell receptor-triggered naive and memory B cells by >80% but had no effect on their CD40 mAb and IL-4-mediated proliferation. In striking contrast, Tat doubled the germinal center B cell proliferation induced by CD40 mAb and IL-4. These effects were dose dependent and required the addition of Tat at the initiation of the culture, suggesting that Tat acts on early stages of cell cycle progression. By its effects on B cell subsets, Tat might directly affect the normal B cell differentiation process in HIV-positive patients and favor the occurrence of AIDS-associated B cell lymphomas.

Antigen receptor engagement selectively induces macrophage inflammatory protein-1 alpha (MIP-1 alpha) and MIP-1 beta chemokine production in human B cells.

We show herein that B cell Ag receptor (BCR) triggering, but not stimulation by CD40 mAb and/or IL-4, rapidly induced the coordinated expression of two closely related T cell chemoattractants, macrophage inflammatory protein-1 beta (MIP-1 beta) and MIP-1 alpha, by human B cells. Naive, memory, and germinal center B cells all produced MIP-1 alpha/beta in response to BCR triggering. In contrast to MIP-1 alpha/beta, IL-8, which is spontaneously produced by germinal center B cells but not by naive and memory B cells, was not regulated by BCR triggering. Culturing follicular dendritic cell-like HK cells with activated B cells did not regulate MIP-1 alpha/beta production, but it did induce production of IL-8 by HK cells. Microchemotaxis assays showed that CD4+CD45RO+ T cells of the effector/helper phenotype actively migrated along a chemotactic gradient formed by BCR-stimulated B cells. This effect was partially blocked by anti-MIP-1 beta and anti-CC chemokine receptor 5 Ab, but not by anti-MIP-1 alpha Ab suggesting that MIP-1 beta plays a major role in this chemoattraction. Since maturation of the B cell response to a peptide Ag is mostly dependent on the availability of T cell help, the ability of Ag-stimulated B cells to recruit T cells via MIP-1 alpha/beta, may represent one possible mechanism enabling cognate interactions between rare in vivo Ag-specific T and B cells.

B cell-driven HIV type 1 expression in T cells: an essential role of CD86 costimulatory molecule.

During HIV-1 infection, HIV-1 is sequestered and actively replicates within lymphoid organs, mainly in areas essential for antigen-specific T-B interactions. We investigated whether cognate T-B interactions not only drive humoral response to HIV-1 but also enhance viral replication. Costimulation of in vitro HIV-1-infected tonsillar T cells with autologous or allogeneic activated B cells increased both viral replication and T cell proliferation. Addition of CD86 MAb to cocultures inhibited most p24 (84 +/- 12%, n = 13) and IL-2 (99 +/- 2%, n = 6) production, decreased T cell proliferation by 46 +/- 15% (n = 13), and decreased TNF-alpha and IFN-gamma production by 67 +/- 17% (n = 6) and 53 +/- 6% (n = 6), respectively. In contrast, CD80 MAb, which strongly inhibited IL-2 production (77 +/- 10%, n = 6), moderately downregulated p24 and TNF-alpha production (29 +/- 21%, n = 13 and 34 +/- 10%, n = 6, respectively) and did not decrease T cell proliferation (8 +/- 10%, n = 13) or IFN-gamma production (14 +/- 13%, n = 6). We thus showed that B cells deliver a potent CD86/CD28 costimulatory signal that induces T cell proliferation and simultaneously enhances HIV-1 replication. CD86+ B cells, mainly localized within the light zone of germinal centers, might thus favor active in situ replication of HIV-1 in response to each new challenge by T-dependent antigens.

CD80 expression is decreased in hyperplastic lymph nodes of HIV+ patients.

A centrofollicular hyperplasia is present within secondary lymphoid organs during all the asymptomatic phase of the HIV disease. Although this hyperplasia has been well characterized by histological studies, the nature of the phenotypic alterations in B cell populations occurring within HIV+ lymphoid organs remains to be established. By immunohistochemistry, we thus investigated whether a particular germinal center (GC) B cell population was increased during HIV-induced hyperplasia and whether any phenotypic change was specific to HIV-1 infection. As compared to normal tonsils (three cases) and HIV- hyperplastic lymph nodes (eight patients), we observed a loss of GC polarization in all HIV+ sections (11 patients), with no more delineation between dark and light zones, as shown by Ki67, CD10, CD77, CD95 and CD86 staining. In contrast to CD86 expression which remained as intensive in HIV+ as in HIV- lymph nodes, CD80 staining was strongly decreased in GC of HIV+ lymph nodes but not in their extrafollicular zones. The loss of CD80 expression from CD19+ B cells was also observed by cytometric analysis of cell suspensions of three HIV+ patients. Although we found no evidence of an increase in a particular GC B cell subset in HIV-1-induced hyperplasia, the strong GC disorganization observed may induce impaired cell-cell interactions and thus participate in the loss of CD80 antigen. In contrast to HIV- situations where CD80 and CD86 was similarly expressed on B cells, the lower level of CD80 expression in HIV+ GC may favor Th2 T cell responses through CD86-CD28 interactions.

[Genetic aspects of infantile autism]. / Aspects génétiques de l'autisme infantile.

The cause of infantile austism is as yet unknown. However, many studies have addressed the possibility of genetic transmission. Although a chromosomal abnormality has been outruled, an increasing number of studies in families and twins have shown that at least some symptoms of infantile autism may be transmitted genetically. However, up till now, transmission modalities and the exact nature of what is transmitted are unsure.

Lateral eye movements during verbal and nonverbal dichotic listening.

A dichotic listening paradigm was used to study the relation of eye movement to cerebral lateralization. The eye movements of right-handed subjects were recorded during verbal and nonverbal dichotic-listening tasks. Subjects given a verbal dichotic-listening task made significantly more rightward than leftward eye movements and showed more accuracy and speed in processing information presented to the right than to the left ear. Subjects given a nonverbal dichotic-listening task made significantly more leftward eye movements and processed better information presented to the left ear. These findings suggest a potentially strong link between the direction of lateral eye movement during dichotic listening tasks and left- and right-ear advantages in performance on such tasks. They also suggest that both eye movement and ear performance may be related to cerebral laterality and when examined in combination both could provide valuable information for the further study of hemispheric specialization.