Study of Poaceae phenology in a Mediterranean climate. Which species contribute most to airborne pollen counts?

The present study sought to determine which of the common Poaceae species in the study area contribute most to the Poaceae pollen season curve, and to determine the phenological behaviour of the species studied. The different floral phenophases in thirty-three Poaceae species common in and around the city of Córdoba (SW Iberian Peninsula) were checked periodically over the period 2004–2006. Results showed that longer phenological ranges were recorded in the coolest and wettest year, and shorter ranges in the warmest and driest year. Moreover, ranges varied as a function of altitude: populations in lower-lying areas flowered earlier than those at higher altitudes. The results, taken in conjunction with the findings of preliminary research into potential pollen production, showed that probably only four of the Poaceae species studied—Dactylis glomerata, Lolium rigidum, Trisetaria panicea and Vulpia geniculata—were major contributors to the Poaceae airborne pollen curve.     

Lymphocyte subpopulations of regional lymph nodes in human colon and gastric adenocarcinomas

 In order to study the host immune response to tumours, previous knowledge of the cellular composition of regional draining lymph nodes is necessary. Enlarged regional lymph nodes are a common finding in colon and gastric adenocarcinomas. We have studied the cellular composition of normal non-reactive and of regional draining lymph nodes of colon and gastric adenocarcinomas. In normal non-reactive lymph nodes, T lymphocytes (CD2⁺, CD7⁺) constituted the largest fraction of the lymphoreticular cells. These lymphocytes were mainly CD4⁺, and there were more cells expressing the CD45RA isoform of the CD45 antigen than CD45RO. Reactive lymph nodes presented a decreased proportion of CD4⁺ CD45RA⁺ cells and an increased number of B cells. Although most of the T cells in the reactive nodes were CD4⁺ CD45RO⁺, their proportion was similar to that found in normal non-reactive nodes. We studied the presence of the molecules CD28 and CD80 involved in the processes of interaction and activation of T and B lymphocytes. The CD28 molecule was found in all the T lymphocytes, while the CD80 molecule was weakly expressed on the B lymphocyte membrane. Received: 4 January 1996 / Accepted: 28 May 1996     

Biosignatures and Bacterial Diversity in Hydrothermal Deposits of Solfatara Crater,Italy

We have combined mineralogy, organic geochemistry and molecular microbiology to study hydrothermal deposits from Solfatara Crater, a geologically young volcanic formation (～4,000 years old) displaying hot (45–95°C) and acidic (pH 1.7) mud pools and fumaroles. The search for inorganic (mineral) biosignatures revealed the presence of delicate structures, most likely mineralized extracellular polymers (EPSs), and the presence of potential biologically induced minerals: sulfides, sulfates (barite and alunite), elemental sulfur, and iron oxides. Geochemical analyses revealed a low total organic carbon content, 0.13 to 0.53%, displaying δ¹³C values from ?17.09 to ?27.39‰, and total nitrogen contents from 0.03 to 0.12%, which are characteristic of hydrothermal systems and suggest the presence of autotrophic carbon fixation. Lipid biomarker analysis showed the presence of hopanoids and linear alkanes, and the absence of detectable steroids, implying the occurrence of bacteria in our samples. We constructed 16S rRNA gene libraries from the environmental samples. Most environmental sequences obtained were affiliated to the Alpha- and Betaproteobacteria (Hydrogenophilus-like), the Acidobacteria, and to a lesser extent, the Gammaproteobacteria and Actinobacteria. When known, the closest cultivated relatives were often thermophilic or thermotolerant bacteria oxidizing iron, hydrogen, or methane/methanol, suggesting an important microbial contribution to the formation of biominerals.     

Pre-existing glomerular immune complexes induce polymorphonuclear cell recruitment through an Fc receptor-dependent respiratory burst: potential role in the perpetuation of immune nephritis

In immune complex (IC) diseases, FcR are essential molecules facilitating polymorphonuclear cell (PMN) recruitment and effector functions at the IC site. Although FcR-dependent initial tethering and FcR/integrin-dependent PMN accumulation were postulated, their underlying mechanisms remain unclear. We here addressed potential mechanisms involved in PMN recruitment in acute IC glomerulonephritis (nephrotoxic nephritis). Since some renal cells may be recruited from bone marrow (BM) lineages, reconstitution studies with BM chimeras and PMN transfer between wild-type (WT) and FcR-deficient mice (gamma(-/-)) were performed. Severe glomerular damage was induced in WT and W gamma chimeras (BM from WT to irradiated gamma(-/-)), while it was absent in gamma(-/-) and gamma W chimeras (gamma(-/-) BM to WT). Moreover, WT PMN transfer, but not gamma(-/-) PMN, reconstituted the disease in gamma(-/-), indicating that FcR on resident cells is not a prerequisite for PMN recruitment in this disease. Surprisingly, transferred WT PMN were recruited coincidentally with NF-kappa B activation and TNF-alpha overexpression even in glomeruli with preformed IC (nephrotoxic Ab administered 3 days previously), suggesting that PMN can initially be recruited via its own FcR without previous chemoattractant release. Furthermore, H(2)O(2) inhibition by catalase attenuated the acute WT PMN recruitment and the induction of NF-kappa B and TNF-alpha much more than integrin (CD18) blockade, indicating a role for the respiratory burst before integrin-dependent accumulation. In coculture experiments with IC-stimulated PMN and glomeruli, PMN caused acute glomerular TNF-alpha expression predominantly via FcR-mediated H(2)O(2) production. In conclusion, glomerular IC, even preformed, can cause PMN recruitment and injury through PMN FcR-mediated respiratory burst during initial PMN tethering to IC.     

Some common signal transduction events are not necessary for the elicitor-induced accumulation of silymarin in cell cultures of Silybum marianum

A variety of pharmacological effectors of signal transduction pathways were used to investigate the elicitor-activated sequence of cellular responses by which yeast extract (YE) or methyljasmonate (MeJA) enhanced production of silymarin in cell cultures of Silybum marianum. As we recently showed that inhibition of external and internal calcium fluxes significantly increased flavonolignan production in S. marianum cultures, we examined whether calcium mediates signaling events leading to enhancement of silymarin production upon YE or MeJA elicitation. Pre-treatment of cultures with calcium chelators, calcium blockers or intracellular antagonists enhanced the elicitor effect of YE or MeJA. The increase of intracellular-free Ca(2+) level also promoted the elicitor effect, suggesting that an external source of calcium or alterations in internal calcium fluxes were not required for the elicitation to occur. Activation of phosphorylation/dephosphorylation cascades did not appear to mediate the elicitation mechanism; the increase in silymarin induced by elicitation was not suppressed by inhibitors of protein phosphatases or by protein kinase inhibitors. No H(2)O(2) generation was detected at any time after elicitation. Also, diphenyleneiodonium, a potent inhibitor of NAD(P)H-oxidase, did not block silymarin production in elicited cultures. From these results, we conclude that S. marianum cell cultures do not appear to employ conserved signaling components in the transduction of the elicitor signal to downstream responses such as silymarin production.     

Hydrochemistry and microbialites of the alkaline crater lake Alchichica,Mexico

The structure, mineralogy, and accretion processes of the modern and subfossil cyanobacterial microbialites from the alkaline crater lake Alchichica (Puebla, Mexico) were studied, along the lake’s bathymetry and hydrochemistry. The recent lowering of the lake level had exposed microbialitic carbonate mounds and crusts, which emerged up to 2 m above the water surface, while accreting cyanobacterial microbialites were present down to a depth of ~15 m. Morphological and molecular analysis found that the living cyanobacterial mats were composed of diverse filamentous and coccoid cyanobacteria (Nostocales, Chroococcales, Oscillatoriales, and Pleurocapsales). The emerged subfossil microbialites comprised two generations: “white” (domes and crusts composed mainly of hydromagnesite with an admixture of huntite and calcite, ²³⁸U/²³⁰Th age of ~2.8 ka BP), and “brown” (chimneys, columns and laminated crusts composed of aragonite with an admixture of Mg-calcite, ²³⁸U/²³⁰Th age of ~1.1 ka BP). The significant age, structural, mineralogical, and isotopic differences suggest that the two generations were formed in different environmental conditions: the “white” during a dry period, and the “brown” in wet climate associated with high water level and intense inflow of ground water, which lowered the Mg/Ca ratio resulting in formation of aragonite instead of hydromagnesite. The hydromagnesite, replacing the primary aragonite precipitated in the living cyanobacterial biofilm, frequently undergoes silicification, which obliterates both the primary structure of the carbonate and the enclosed remains of cyanobacterial microbiota. This process helps to explain the abundant formation of dolomites and cherts in an allegedly highly alkaline Early Precambrian ocean. Thus, Lake Alchichica represents a modern alkaline environment where biosedimentary structures resembling Precambrian deposits are generated.     

Analysis of a genome fragment of a deep-sea uncultivated Group II euryarchaeote containing 16S rDNA, a spectinomycin-like operon and several energy metabolism genes

We have sequenced and analysed a 39.5 kbp genome fragment of a marine Group II euryarchaeote identified in a metagenomic library of 500 m deep plankton at the Antarctic Polar Front. The clone contains a 16S rRNA gene that is separated from the 23S rRNA gene in the genome. This appears to be a trait shared by Thermoplasmatales and Group II euryarchaeota. This genome fragment exhibits a compact organization, including a few overlapping genes in the canonical spectinomycin-like (spc) operon for ribosomal proteins that is immediately upstream the 16S rDNA. Most open reading frames (ORFs) encoded proteins involved in housekeeping processes and, as expected, exhibited a phylogenetic distribution congruent with that of the 16S rRNA. A considerable number of proteins with predicted transmembrane helices was identified. Among those, two proteins encoded by genes likely forming an operon appear to be part of a membrane terminal electron transport chain. One of these proteins has an unusual domain arrangement including ferredoxin, flavodoxin and one succinate dehydrogenase/fumarate reductase subunit. These proteins probably constitute a new succinate dehydrogenase-like oxidoreductase involved in what could be a novel pathway for energy metabolism in Group II euryarchaeota.     

Comparative analysis of a genome fragment of an uncultivated mesopelagic crenarchaeote reveals multiple horizontal gene transfers

Marine planktonic crenarchaeota have escaped all cultivation attempts to date, all crenarchaeota growing in pure culture so far being hyperthermophiles. Here, we present a comparative genomic analysis of a 16S- plus 23S-rDNA-containing fragment of a crenarchaeote retrieved from an environmental genomic library constructed from picoplankton collected at 500 m depth in the Antarctic Polar Front. The clone DeepAnt-EC39 contained an insert of 33.3 kbp, which was completely sequenced. DeepAnt-EC39 appears to represent a lineage specific to deep-sea waters but widespread geographically, as revealed by the analysis of the 16S-23S-rDNA intergenic spacer region. A comparison with previously sequenced marine crenarchaeotal genomic clones also containing an rrn operon (74A4, 4B7 and Cenarchaeum symbiosum strains A and B) revealed a highly variable structure involving gene rearrangements and insertions/deletions. The surroundings of the rrn operon and the contiguous glutamate-1-semialdehyde aminotransferase gene appear hot spots for recombination. Phylogenetic analyses of all individual predicted proteins revealed the existence of several likely cases of horizontal gene transfer both, between the two archaeal kingdoms and between the two prokaryotic domains. The most frequent horizontal transfers appear to involve genes from mesophilic methanogenic euryarchaeota related to Methanosarcinales. We hypothesise that the acquisition of genes from mesophilic bacteria and euryarchaeota has played a major role in the adaptation of Group I crenarchaeota to life at lower temperatures.