Roles for T and NK cells in the innate immune response to Shigella flexneri

Shigella flexneri, an enteroinvasive Gram-negative bacterium, is responsible for the worldwide endemic form of bacillary dysentery. The host response to primary infection is characterized by the induction of an acute inflammation, which is accompanied by polymorphonuclear cell (PMN) infiltration, resulting in massive destruction of the colonic mucosa. However, PMN play a major role in the recovery from primary infection, by restricting the bacterial infection at the intestinal mucosa. In this study, we assessed the roles for T and NK cells in the control of primary S. flexneri infection, using an alymphoid mouse strain (Rag null gamma(c) null) devoid of B, T, and NK cells. Using the mouse pulmonary model of Shigella infection, we showed that alymphoid Rag null gamma(c) null mice were highly susceptible to S. flexneri infection in comparison with wild-type (wt) mice. Whereas PMN recruitment upon infection was similar, macrophage recruitment and production of proinflammatory cytokines were significantly decreased in Rag null gamma(c) null mice compared with wt mice. Upon selective engraftment of Rag null gamma(c) null mice with polyclonal alphabeta T cells, but not with alphabeta T cells from IFN-gamma null , S. flexneri infection could be subsequently controlled. Rag null mice devoid of B and T cells but harboring NK cells could control infection. Local IFN-gamma production by T and NK cells recruited to the lung was demonstrated in S. flexneri-infected wt mice. These data demonstrate that both alphabeta T cells and NK cells contribute to the early control of S. flexneri infection through amplification of an inflammatory response. This cellular lymphocyte redundancy assures IFN-gamma production, which is central to innate immunity against Shigella infection.     

Nitrite as the major source of nitric oxide production by Arabidopsis thaliana in response to Pseudomonas syringae

The origin of nitric oxide (*NO) in plants is unclear and an *NO synthase (NOS)-like enzyme and nitrate reductase (NR) are claimed as potential sources. Here we used wild-type and NR-defective double mutant plants to investigate *NO production in Arabidopsis thaliana in response to Pseudomonas syringae pv maculicola. NOS activity increased substantially in leaves inoculated with P. syringae. However, electron paramagnetic resonance experiments showed a much higher *NO formation that was dependent on nitrite and mitochondrial electron transport rather than on arginine or nitrate. Overall, these results indicate that NOS, NR and a mitochondrial-dependent nitrite-reducing activity cooperate to produce *NO during A. thaliana-P. syringae interaction.     

Initial Enzymatic Steps In The Degradation Of Alpha-Pinene By Pseudomonas Fluorescens Ncimb 11671

The initial steps in the degradation of the bicyclic monoterpene, (-)-alpha-pinene, by a new isolate, Pseudomonas fluorexem NCIMB 11671, are described. Degradation is initiated by an oxygenative attack upon the unsaturated position in the molecule to form the corresponding epoxide, catalysed by a pyridine nucleotide-dependent oxygenase with a narrow substrate specificity. The epoxide undergoes rapid rearrangement and concomitant decyclisation to form a di-unsaturated aldehyde, in which both the cyclobutane and cyclohexane rings of the parent molecule are broken, without the insertion of further oxygen species or the appearance of other intermediate compounds. This represents a new enzymatic mechanism for the disruption of a cyclic ring system.     

Morphological differentiation of the Müller cell: Golgi and electron microscopy study in the chick retina

The sequence of morphological differentiation of Müller cells in the chick retina was investigated in relation to the differentiation of the retinal neurons using the Golgi method. From the beginning of differentiation, the Müller cell develops spurs and lateral processes. Some of these glial processes become transformed into accessory prolongations of the Müller cell. From the 17th or 18th day of incubation, the morphology of the Müller cells is similar to that of the adult retina. On the basis of their inner prolongation, two types of Müller cells were identified. The first type, with diffuse and abundant descending processes, is identical to that described classically. The second type is a cell characterized by sparse and scanty inner ramifications. This report also describes electron microscopic observations of Müller cells and their enwrapping relationship with the axons of the optic nerve fiber layer.     

Interactions of Photobleaching and Inorganic Nutrients in Determining Bacterial Growth on Colored Dissolved Organic Carbon

Abstract Bacteria are key organisms in the processing of dissolved organic carbon (DOC) in aquatic ecosystems. Their growth depends on both organic substrates and inorganic nutrients. The importance of allochthonous DOC, usually highly colored, as bacterial substrate can be modified by photobleaching. In this study, we examined how colored DOC (CDOC) photobleaching, and phosphorus (P) and nitrogen (N) availability, affect bacterial growth. Five experiments were conducted, manipulating nutrients (P and N) and sunlight exposure. In almost every case, nutrient additions had a significant, positive effect on bacterial abundance, production, and growth efficiency. Sunlight exposure (CDOC photobleaching) had a significant, positive effect on bacterial abundance and growth efficiency. We also found a significant, positive interaction between these two factors. Thus, bacterial use of CDOC was accelerated under sunlight exposure and enhanced P and N concentrations. In addition, the accumulation of cells in sunlight treatments was dependent on nutrient availability. More photobleached substrate was converted into bacterial cells in P- and N-enriched treatments. These results suggest nutrient availability may affect the biologically-mediated fate (new biomass vs respiration) of CDOC.     

Cerebellar neurones: Differentiation and modulation of sensitivity to excitotoxic treatment

The neurite outgrowth and adhesion complex (NOAC), isolated from rabbit sera has been dissociated in its major components by reverse-phase chromatography in HPLC by using a C₁₈ column. SDS-PAGE analisys of the active fractions revealed the presence of three major bands of approximately 100, 70 and 50 kDa. Studies on the biological activity of NOAC were carried out on rat cerebellar granule cells. NOAC-cultured cells exhibit a marked resistance to excitotoxic stimuli carried by glutamate.     

Distribution of the molossinus allele of Sry, the testis-determining gene, in wild mice

When the Y chromosome of the laboratory inbred mouse strain C57BL/6 (B6) is replaced by the Y of certain strains of Mus musculus domesticus, testis determination fails and all XY fetuses develop either as hermaphrodites or XY females (XY sex reversal). This suggests the presence of at least two alleles of Sry, the male-determining gene on the Y:M. m. domesticus and B6. The B6 Y chromosome is derived from the Japanese house mouse, M. m. molossinus and therefore carries a molossinus Sry allele. As a first step to determine how the molossinus Sry allele evolved, its distribution pattern was determined in wild mice. The cumulative data of 96 M. musculus samples obtained from 58 geographical locations in Europe, North Africa, and Asia show the molossinus Sry allele is restricted to Japan and the neighboring Asian mainland and confirm that Japanese M. m. molossinus mice were derived in part from a race of M. m. musculus from Korea or Manchuria. Sry polymorphisms, as illustrated by the molossinus Sry allele, can serve as molecular markers for studies on the evolution of wild M. musculus populations and can help determine the role sex determination plays in speciation.      

Chromatin,gene silencing and HIV latency

One of the cellular defenses against virus infection is the silencing of viral gene expression. There is evidence that at least two gene-silencing mechanisms are used against the human immuno-deficiency virus (HIV). Paradoxically, this cellular defense mechanism contributes to viral latency and persistence, and we review here the relationship of viral latency to gene-silencing mechanisms.