Generation of chemotactic activity for neutrophils by liver cells metabolizing ethanol

The mechanism of polymorphonuclear leukocyte (PMN) infiltration of the liver in acute alcohol-related liver injury is unknown. We have reported that ethanol metabolism by hepatocytes incubated with moderate concentrations of ethanol (2-50 mM) results in the release into the medium of a chemoattractant for human PMN. This response to ethanol is time- and concentration-dependent with peak activity at 10 mM ethanol. Generation of the factor is specific for hepatocytes and is blocked by inhibiting ethanol metabolism with 4-methylpyrazole. It does not appear to be due to cell death. The activity has been partially characterized: it behaves as a polar lipid, possibly an arachidonic acid metabolite distinct from leukotriene B4. Preliminary studies indicate that a cell-free system derived from liver generates a similar activity. In that system scavengers of oxygen-derived free radicals block production of the factor.     

Loss of endotoxin liberation in Neisseria meningitidis

Four strains of Neisseria meningitidis were studied during serial passage. Upon subcultivation, two of them lost the ability to liberate endotoxin. Ultrastructurally, the two parent endotoxin liberating strains exhibited quantitatively more free cell wall membranes and blebs in the medium than their non-liberating variants. Similarly, the endotoxin-releasing original strains exhibited higher sulfonamide resistance than their variants, and had markedly more sticky cells, which showed pronounced adherence to the surfaces of plastic and heated blood agar.     

Amyloidosis in adrenal glands of hamsters experimentally infected with Leishmania infantum

Thirty 10-week-old hamsters were inoculated intraperitoneally with leishmania infantum amastigotes and were serially killed after 15, 30, 45, 60, 75 and 89-90 days. The adrenal glands of each of them were examined by means of light and electron microscopy. The cortex and medulla of the adrenal gland showed a progressive deposition of amyloid, selectively identified by both optical and ultrastructural techniques. It has been suggested that adrenal amyloidosis during visceral leishmaniasis is directly related to a stimulation of the phagocitary mononuclear system due to the persistence of the antigenic stimulation of the parasite. In addition to these deposits, the presence of inflammatory infiltrates containing lymphocytes, plasmocytes and macrophages with leishmanias confirmed the establishment of leishmaniasis. The deposition of the amyloid fibrils finally leads to the partial destruction of the adrenal parenchyma.     

Airborne Microalgae: Insights,Opportunities, and Challenges

Airborne dispersal of microalgae has largely been a blind spot in environmental biological studies because of their low concentration in the atmosphere and the technical limitations in investigating microalgae from air samples. Recent studies show that airborne microalgae can survive air transportation and interact with the environment, possibly influencing their deposition rates. This minireview presents a summary of these studies and traces the possible route, step by step, from established ecosystems to new habitats through air transportation over a variety of geographic scales. Emission, transportation, deposition, and adaptation to atmospheric stress are discussed, as well as the consequences of their dispersal on health and the environment and state-of-the-art techniques to detect and model airborne microalga dispersal. More-detailed studies on the microalga atmospheric cycle, including, for instance, ice nucleation activity and transport simulations, are crucial for improving our understanding of microalga ecology, identifying microalga interactions with the environment, and preventing unwanted contamination events or invasions.     

Quantification of phagocytosis in human neutrophils by flow cytometry.

Phagocytosis represents a central element of the host response to microbial invasion. We describe a flow cytometric method for measuring the kinetics of phagocytosis of two bacteria by human polymorphonuclear leukocytes (PMNs). Over a 60-min period, isolated human PMNs were exposed to Staphylococcus aureus (rapidly phagocytosed) and Klebsiella pneumoniae (slowly phagocytosed). This method distinguished adherent from ingested bacteria by quenching fluorescein isothiocyanate-labeled extracellular bacteria with ethidium bromide. This further allowed the exclusion of dead, highly permeable, and subsequently bright-red fluorescent PMNs. Our experiments with two different bacteria, various PMN-to-bacteria ratios (1:1, 1:10, 1:100), and different individuals proved that 1) flow cytometric analysis is accurate and useful for characterizing phagocytosis, 2) adherent bacteria can be distinguished from ingested bacteria after quenching with ethidium bromide, and that 3) phagocytosis kinetics of two bacteria with different onsets of phagocytosis can be determined by flow cytometry and the assessment of a score that quantifies phagocytosis.