Microglial cell-mediated anti-Candida activity: temperature, ions, protein kinase C as crucial elements.

An in vitro established microglial cell line, BV-2, constitutively exhibits high levels of anti-Candida activity. To elucidate the cascade of events leading to the accomplishment of such activity, we studied its dependence on temperature and ion availability. The role of protein kinases has also been studied by the specific inhibitors, 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H7) and N-(2-guanidinoethyl)-5-isoquinoline sulfonamide hydrochloride (HA 1004). We found that (a) the BV-2 cell/Candida conjugate formation is a discrete step, temperature-, ion- and protein kinase-independent; (b) the phagocytic event, which is protein kinase-independent, is significantly impaired by temperature decrease and ion deprivation; (c) the fulfillment of anti-Candida effects is strictly dependent upon temperature, ion availability and functional protein kinase. Functional protein kinase C, but not other kinases, is required for the accomplishment of anti-Candida activity, which, in fact, is selectively abrogated by H7 but not HA. Furthermore, protein kinase C activators, such as 12-O-tetradecanoylphorbol 13-acetate (TPA) or 1-oleoyl-2-acetyl glycerol (OAG), consistently potentiate BV-2 cell-mediated anti-Candida activity, the phenomena being dose-dependent. These results indicate that the multistep events leading a microglial cell to express anti-Candida activity can be dissected and differentiated for biochemical and biological demands, the latest along the cascade being the most demanding steps

VERIFICA DI VITALITA' DEI BACILLI TUBERCOLARI IN PREPARATI MICROSCOPICI PER LA COLORAZIONE DI ZIEHL NEELSEN.

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The Ny-Ålesund Aerosol Cloud Experiment (NASCENT): Overview and First Results

The Arctic is warming at more than twice the rate of the global average. This warming is influenced by clouds, which modulate the solar and terrestrial radiative fluxes and, thus, determine the surface energy budget. However, the interactions among clouds, aerosols, and radiative fluxes in the Arctic are still poorly understood. To address these uncertainties, the Ny-Ålesund Aerosol Cloud Experiment (NASCENT) study was conducted from September 2019 to August 2020 in Ny-Ålesund, Svalbard. The campaign’s primary goal was to elucidate the life cycle of aerosols in the Arctic and to determine how they modulate cloud properties throughout the year. In situ and remote sensing observations were taken on the ground at sea level, at a mountaintop station, and with a tethered balloon system. An overview of the meteorological and the main aerosol seasonality encountered during the NASCENT year is introduced, followed by a presentation of first scientific highlights. In particular, we present new findings on aerosol physicochemical and molecular properties. Further, the role of cloud droplet activation and ice crystal nucleation in the formation and persistence of mixed-phase clouds, and the occurrence of secondary ice processes, are discussed and compared to the representation of cloud processes within the regional Weather Research and Forecasting Model. The paper concludes with research questions that are to be addressed in upcoming NASCENT publications

Molecular characterization of occult hepatitis B virus infection in patients with end-stage liver disease in Colombia.

ABSTARCT: Hepatitis B virus (HBV) occult infection (OBI) is a risk factor to be taken into account in transfusion, hemodialysis and organ transplantation. The aim of this study was to identify and characterize at the molecular level OBI cases in patients with end-stage liver disease. METHODS: Sixty-six liver samples were obtained from patients with diagnosis of end-stage liver disease submitted to liver transplantation in Medellin (North West, Colombia). Samples obtained from patients who were negative for the surface antigen of HBV (n = 50) were tested for viral DNA detection by nested PCR for ORFs S, C, and X and confirmed by Southern-Blot. OBI cases were analyzed by sequencing the viral genome to determine the genotype and mutations; additionally, viral genome integration events were examined by the Alu-PCR technique. RESULTS: In five cases out of 50 patients (10%) the criteria for OBI was confirmed. HBV genotype F (subgenotypes F1 and F3), genotype A and genotype D were characterized in liver samples. Three integration events in chromosomes 5q14.1, 16p13 and 20q12 affecting Receptor-type tyrosine-protein phosphatase T, Ras Protein Specific Guanine Nucleotide Releasing Factor 2, and the zinc finger 263 genes were identified in two OBI cases. Sequence analysis of the viral genome of the 5 OBI cases showed several punctual missense and nonsense mutations affecting ORFs S, P, Core and X. CONCLUSIONS: This is the first characterization of OBI in patients with end-stage liver disease in Colombia. The OBI cases were identified in patients with HCV infection or cryptogenic cirrhosis. The integration events (5q14.1, 16p13 and 20q12) described in this study have not been previously reported. Further studies are required to validate the role of mutations and integration events in OBI pathogenesis

Pattern of cytokine gene expression in brains of mice protected by picolinic acid against lethal intracerebral infection with Candida albicans.

Recently, we demonstrated that intracerebral (i.c.) administration of picolinic acid (PLA) confers protection against a lethal local challenge with the opportunistic pathogen Candida albicans. By histopathological studies, we show here that mice receiving PLA treatment survive challenge and no evidence of fungal invasion is found within the brain compartment. In contrast, PLA-untreated mice succumb to infection within 7-10 days and show massive brain colonization with extensive granulomatous reaction. By PCR analysis, we show that, unlike naive brains, PLA-treated brains show transient activation of TNF alpha, IL-1 beta and IL-6 genes. C. albicans infection results in high levels of all cytokine transcripts, the phenomenon being long-lasting in PLA-untreated brains, while gradually declining in PLA-treated brains. The only exception is IL-1 beta, whose levels remain high at the latest time-points tested, also in PLA-treated brains. Finally, IL-1 alpha, constitutively detectable in naive brains, is slightly enhanced by C. albicans challenge, regardless of prior treatment. These findings, together with the knowledge that PLA is a potent co-stimulus for macrophages, suggest the involvement of cytokine circuits, likely of macrophage origin, in anti-Candida resistance established by PLA at the cerebral leve

Differential Host Susceptibility to Intracerebral Infections with Candida albicans and Cryptococcus neoformans

To investigate the immune defense mechanisms employed against fungi in the brain, mice were experimentally infected by intracerebral inoculation of Candida albicans or Cryptococcus neoformans. Parameters such as median survival time and numbers of yeast cells in the brains were assessed for naive and immunomodulated mice. We found that no mice survived either C. albicans or C. neoformans challenge at doses of .106 yeast cells per mouse. However, when the inoculum size was decreased ('105 yeast cells per mouse), C. albicans was no longer lethal (100%S survival), whereas 100 and 70%o of the mice still succumbed to challenge doses of 104 and 103 C. neoformans yeast cells, respectively. Pharmacological manipulation and transfer experiments revealed that the myelomonocytic compartment had a minor role against C. neoformans but was deeply involved in thecontrol of intracerebral C. albicans infection. By counting the number of yeast cells in the brains of naive and immunomodulated animals, we established that, unlike C. albicans, C. neoformans remained essentially in the brain, where massive colonization and damage occurred whether naive or immunomodulated defensemechanisms were employed by the host. Overall, these data suggest that the differential role of the myelomonocytic compartment, together with the diverse tropisms of the two fungi, can explain the different development and outcome of intracerebral C. albicans and C. neoformans infections

Immunology and pathogenesis of infections of the central nervous system(CNS)

The central nervous system (CNS) has long been regarded as an immunologically privileged site for the presence of blood-brain and blood- cerebrospinal fluid barriers. Nevertheless, experimental evidence indicates that, under physiological conditions, minimal amounts of blood-derived immune cells exist within the brain and cooperate with the resident immune elements, such as microglia and astrocyte, to the surveillance of the district. Following microbial invasion, both blood-derived and local effector systems synergize against the pathogen. The timing and entity of such reaction is crucial, allowing the clearance of the pathogen or rather contributing to the extent of sometimes irreversible brain tissue damage