Anaerobic accumulation of amino acids in rice roots: role of the glutamine synthetase/glutamate synthase cycle

Summary. Accumulation of amino acids was studied in rice roots of 3-day-old seedlings subjected for 48 h to anaerobic conditions. Alanine and Gaba were the main amino acids accumulated under anoxia. Their synthesis was strongly inhibited by MSX and AZA, inhibitors of glutamine synthetase and glutamate synthase. These activities increased after 8 h of anaerobic treatment and, by immunoprecipitation of ³⁵S-labeled proteins, it was shown that glutamine synthetase and ferredoxin-dependent glutamate synthase were synthesized during the treatment. These findings indicate that the glutamine synthetase/glutamate synthase cycle play an important role in anaerobic amino acid accumulation. Received April 5, 1999     

Genotoxicity testing of chloramphenicol in rodent and human cells

The results of this work, carried out to extend the limited information at present available on the genotoxic potential of chloramphenicol (CAP), indicate that in millimolar concentrations this antibacterial agent produced a minimal amount of DNA fragmentation in both V79 cells and metabolically competent rat hepatocytes. Moreover, a level of DNA-repair synthesis indicative of a weak but positive response was detected in primary cultures of liver cells obtained from 2 of 3 human donors, and a borderline degree of repair was present in those prepared from rats. The promutagenic character of CAP-induced DNA lesions was confirmed by a low but significant increase in the frequency of 6-thioguanine-resistant clones of V79 cells, which, however, was absent when the exposure was done in the presence of co-cultured rat hepatocytes. Finally, oral administration to rats of 1/2 LD50 CAP did not increase the incidence of either micronucleated polychromatic erythrocytes or micronucleated hepatocytes. Taken as a whole these findings suggest that CAP should be considered a compound intrinsically capable of producing a very weak genotoxic effect, but only at concentrations about 25 times higher than those occurring in patients treated with maximal therapeutic dosages.     

Complete genome sequence of Bacteroides helcogenes type strain (P 36-108)

Bacteroides helcogenes Benno et al. 1983 is of interest because of its isolated phylogenetic location and, although it has been found in pig feces and is known to be pathogenic for pigs, occurrence of this bacterium is rare and it does not cause significant damage in intensive animal husbandry. The genome of B. helcogenes P 36-108(T) is already the fifth completed and published type strain genome from the genus Bacteroides in the family Bacteroidaceae. The 3,998,906 bp long genome with its 3,353 protein-coding and 83 RNA genes consists of one circular chromosome and is a part of the Genomic Encyclopedia of Bacteria and Archaea project.     

Culturable aerobic bacteria from the upstream region of a karst water rivulet

The composition of 681 aerobic and heterotrophic strains that were isolated on two different media was assessed at four sampling points along a ~300 m stretch of a karst water rivulet. Based on partial sequence analysis of 16S rRNA genes, members of 35 genera were identified; however, only a few species dominated as their representatives were repeatedly isolated at different sampling sites. Determination of the phylum affiliation showed that the isolates included members of Bacteriodetes (especially the genus Flavobacterium) and Proteobacteria (mainly Pseudomonas and Stenotrophomonas). MALDI-TOF analysis and/or similarities of partial sequences of flavobacterial strains resulted in the generation of almost complete 16S rRNA gene sequences for 100 isolates, about 60 of which may represent novel phylospecies. The number as well as the intra-phylum distribution of the isolates changed with distance from the discharge site. While phylogenetically restricted at the spring, diversity increased at downstream sampling sites.     

Immune Regulatory Neural Stem/Precursor Cells Protect from Central Nervous System Autoimmunity by Restraining Dendritic Cell Function

Background

The systemic injection of neural stem/precursor cells (NPCs) provides remarkable amelioration of the clinico-pathological features of experimental autoimmune encephalomyelitis (EAE). This is dependent on the capacity of transplanted NPCs to engage concurrent mechanisms of action within specific microenvironments in vivo. Among a wide range of therapeutic actions alternative to cell replacement, neuroprotective and immune modulatory capacities of transplanted NPCs have been described. However, lacking is a detailed understanding of the mechanisms by which NPCs exert their therapeutic plasticity. This study was designed to identify the first candidate that exemplifies and sustains the immune modulatory capacity of transplanted NPCs.

Methodology/Principal Findings

To achieve the exclusive targeting of the peripheral immune system, SJL mice with PLP-induced EAE were injected subcutaneously with NPCs and the treatment commenced prior to disease onset. NPC-injected EAE mice showed significant clinical improvement, as compared to controls. Exogenous NPCs lacking the expression of major neural antigens were reliably (and for long-term) found at the level of draining lymph nodes, while establishing sophisticated anatomical interactions with lymph node cells. Importantly, injected NPCs were never found in organs other than lymph nodes, including the brain and the spinal cord. Draining lymph nodes from transplanted mice showed focal up-regulation of major developmental stem cell regulators, such as BMP-4, Noggin and Sonic hedgehog. In lymph nodes, injected NPCs hampered the activation of myeloid dendritic cells (DCs) and steadily restrained the expansion of antigen-specific encephalitogenic T cells. Both ex vivo and in vitro experiments identified a novel highly NPC-specific–BMP-4-dependent–mechanism hindering the DC maturation.

Conclusion/Significance

The study described herein, identifies the first member of the TGF β/BMP family of stem cell regulators as a novel tolerogenic factor released by NPCs. Full exploitation of this pathway as an efficient tool for vaccination therapy in autoimmune inflammatory conditions is underway.     

Comparison of micronuclei frequencies in mono-, bi- and poly-nucleated lymphocytes from subjects of a residential suburb and subjects living near a metallurgical plant

Spontaneous baseline frequencies of micronuclei in mono-, bi- and poly-nucleated lymphocytes were analyzed, using the cytokinesis-block technique, in 103 subjects living in a residential suburb (Genova-Nervi), and in 203 subjects living in an urban industrialized area near a metallurgical plant and a coke factory (Genova-Cornigliano). Statistical analysis showed that the average frequency of micronucleated binucleated lymphocytes (MnBNL) was significantly higher (1.42-fold) in donors of Nervi than in donors of Cornigliano living in a contaminated environment. In contrast, the average frequency of micronucleated polynucleated lymphocytes (MnPNL) was significantly higher (1.66-fold) in donors of Cornigliano than in donors of Nervi. The existence in the whole population examined of a positive correlation between frequency of MnBNL and frequency of MnPNL and the absence of a positive correlation between frequency of bi- and poly-nucleated lymphocytes and frequency of MnPNL suggest that the formation of MnPNL is a consequence of genetic damage and not of mitotic errors arising during the division of bi- and poly-nucleated cells. In agreement with previous findings the frequency of MnBNL increased with age and was significantly higher in females than in males; unexpectedly it was higher in non-smokers/non-drinkers than in smokers/drinkers.     

Microsporidiosis in a Daphnia pulex population

The impact of parasitism by Thelohania sp., an intracellular microsporidian, on Daphnia pulex inhabiting a vernal pond was studied for three years. Three issues were considered: the distribution of parasites among hosts, the effect of parasites on individuals, and the impact of parasitism on population growth. Each year, Thelohania infected members of at least half of the generations of Daphnia produced in the pond. When the frequency of infection was low, parasites were found only in large adults. As infection frequency increased, parasitism spread downward through host size classes. However, parasites were rarely found in juveniles. Parasitism reduced clutch size drastically, increased mortality to a variable extent, had little impact on egg size or on per instar growth and none on molt frequency. Interaction with other stresses, such as food limitation, exacerbated some of these effects. Parasitism reduced instantaneous birth rate much more than it elevated instantaneous death rate. Population growth was reduced significantly but it is unlikely that Thelohania alone regulates the growth of this Daphnia population.