Reaction of organocuprate reagents with protected 1,2-anhydro sugars. Stereocontrolled synthesis of 2-deoxy-C-glycosyl compounds

The reaction of protected 1,2-anhydro-α-d-gluco- and β-d-manno-pyranoses with alkyl and phenyl organocuprates afforded the corresponding C-glycosyl compounds in acceptable to high yield. Complete stereocontrol was obtained, leading respectively to the β-d or the α-d anomer. With the perbenzylated manno derivative, deoxygenation at C-2 was achieved in high yield, affording 2-deoxy-α-d-C-glycosyl compounds.     

A microanalytic study of particles transport across the alveoli: role of blood platelets

Following intratracheal injection of particles of colloidal gold (30 nm) in the rat, particles in the blood platelets of the alveolar capillaries can rapidly be observed. The presence of the gold is confirmed by microanalysis. The role of this phenomenon in pulmonary clearance is discussed.     

Ants impact the composition of the aquatic macroinvertebrate communities of a myrmecophytic tank bromeliad

In an inundated Mexican forest, 89 out of 92 myrmecophytic tank bromeliads (Aechmea bracteata) housed an associated ant colony: 13 sheltered Azteca serica, 43 Dolichoderus bispinosus, and 33 Neoponera villosa. Ant presence has a positive impact on the diversity of the aquatic macroinvertebrate communities (n = 30 bromeliads studied). A Principal Component Analysis (PCA) showed that the presence and the species of ant are not correlated to bromeliad size, quantity of water, number of wells, filtered organic matter or incident radiation. The PCA and a generalized linear model showed that the presence of Azteca serica differed from the presence of the other two ant species or no ants in its effects on the aquatic invertebrate community (more predators). Therefore, both ant presence and species of ant affect the composition of the aquatic macroinvertebrate communities in the tanks of A. bracteata, likely due to ant deposition of feces and other waste in these tanks.     

Coronary perfusion and muscle lengthening increase cardiac contraction: different stretch-triggered mechanisms

An increase in coronary perfusion, transversal stretch of the myocardium, increases developed force (F(dev)) (Gregg effect) through activation of stretch-activated ion channels (SACs). Lengthening of the muscle, longitudinal stretch of the myocardium, causes an immediate increase in F(dev) followed by a slow F(dev) increase (Anrep effect). In isometrically contracting perfused papillary muscles of Wistar rats, we investigated whether both effects were based on similar stretch-induced mechanisms by measuring F(dev) and intracellular Ca(2+) concentration ([Ca(2+)](i)) after a muscle length increase from 85% to 95% L(max) (length at which maximal isometric force develops) at low and high coronary perfusion before and after inhibition of SACs with gadolinium (10 micromol/l Gd(3+)). The increase of F(dev) and peak [Ca(2+)](i) by the Gregg effect was of similar magnitude as the Anrep effect (from 3.5 +/- 0.8 to 3.9 +/- 1.2 mN/mm(2) and from 3.0 +/- 0.7% to 3.8 +/- 0.9% normalized [Ca(2+)](i), means +/- SE). SAC blockade completely blunted the increase of F(dev) and peak [Ca(2+)](i) by the Gregg effect; however, it did not affect the Anrep effect. The slow force response, but not the calcium response, was augmented by an increase in coronary perfusion. Therefore, increased coronary perfusion, transversal stretch of the myocardium, and muscle lengthening, longitudinal stretch of the myocardium, increase myocardial contraction in the rat through different stretch-triggered mechanisms.     

Functional analysis of Toxoplasma gondii protease inhibitor 1

We have characterized a Kazal family serine protease inhibitor, Toxoplasma gondii protease inhibitor 1 (TgPI-1), in the obligate intracellular parasite Toxoplasma gondii. TgPI-1 contains four inhibitor domains predicted to inhibit trypsin, chymotrypsin, and elastase. Antibodies against recombinant TgPI-1 detect two polypeptides, of 43 and 41 kDa, designated TgPI-1(43) and TgPI-1(41), in tachyzoites, bradyzoites, and sporozoites. TgPI-1(43) and TgPI-1(41) are secreted constitutively from dense granules into the excreted/secreted antigen fraction as well as the parasitophorous vacuole that T. gondii occupies during intracellular replication. Recombinant TgPI-1 inhibits trypsin, chymotrypsin, pancreatic elastase, and neutrophil elastase. Immunoprecipitation studies with anti-rTgPI-1 antibodies reveal that recombinant TgPI-1 forms a complex with trypsin that is dependent on interactions with the active site of the protease. TgPI-1 is the first anti-trypsin/chymotrypsin inhibitor to be identified in bradyzoites and sporozoites, stages of the parasite that would be exposed to proteolytic enzymes in the digestive tract of the host.     

Toward positional cloning of Vgt1, a QTL controlling the transition from the vegetative to the reproductive phase in maize

Vgt1 (Vegetative to generative transition 1) is a quantitative trait locus (QTL) for flowering time in maize (Zea mays L.). Vgt1 was initially mapped in a ca. 5-cM interval on chromosome bin 8.05, using a set of near-isogenic lines (NILs) in the genetic background of the late dent line N28, with the earliness allele introgressed from the early variety Gaspé Flint. A new large mapping population was produced by crossing N28 and one early NIL with a ca. 6-cM long Gaspé Flint introgression at the Vgt1 region. Using PCR-based assays at markers flanking Vgt1, 69 segmental NILs homozygous for independent crossovers near the QTL were developed. When the NILs were tested in replicated field trials for days to pollen shed (DPS) and plant node number (ND), the QTL followed a Mendelian segregation. Using bulk segregant analysis and AFLP profiling, 17 AFLP markers linked to the QTL region were identified. Statistical analysis indicated a substantial coincidence of the effects of Vgt1 on both DPS and ND. Vgt1 was mapped at ca. 0.3 cM from an AFLP marker. As compared to DPS, the higher heritability of ND allowed for a more accurate assessment of the effects of Vgt1. The feasibility of the positional cloning of Vgt1 is discussed.     

Ephemeral bio-engineers or reef-building polychaetes: how stable are aggregations of the tube worm Lanice conchilega (Pallas, 1766)?

Dense aggregations of tube-worms can stabilize sediments and generate oases for benthic communities that are different and often more diverse and abundant than those of the surroundings. If these features are to qualify as biogenic reefs under nature-conservation legislation such as the EC Habitats Directive, a level of stability and longevity is desirable aside from physical and biological attributes. Lanice conchilega (Pallas, 1766) is widely distributed around the European coast and aggregations of this tube-dwelling polychaete are known to have a positive effect on the biodiversity of associated species in inter- and sub-tidal areas. This increases the value of L. conchilega-rich habitats for higher trophic levels such as birds and fish. However, L. conchilega is currently not recognized as a reef builder primarily due to uncertainty about the stability of their aggregations. We carried out three studies on different spatial and temporal scales to explore a number of properties relating to stability: (1) Individual aggregations of L. conchilega of ～1 m(2) were monitored for up to 1 year, (2) records of L. conchilega from a 258-ha area over a 35-year period were analyzed, (3) the recovery of a population of L. conchilega subjected to disturbances by cultivation of Manila clams (Ruditapes philippinarum) was followed over 3 years. The studies provided evidence about the longevity of L. conchilega aggregations, their resistance to disturbance, their resilience in recovering from negative impact and their large-scale persistence. The results showed that populations of L. conchilega were prone to considerable fluctuation and the stability of aggregations depended on environmental factors and on recruitment. The tube-worms proved to be susceptible to disturbance by cultivation of Manila clams but demonstrated the potential to recover from that impact. The long-term monitoring of a large L. conchilega population in the Bay of Mont Saint Michel (France) indicated that aggregations can persist over many decades with a constant, densely populated core area and an expanding and contracting more thinly populated fringe zone. The stability of aggregations of L. conchilega and the structures they form do not unequivocally fit the currently accepted definition of a reef. However, given L. conchilega's accepted reef-like potential to influence diversity and abundance in benthic communities, we suggest clarifying and expanding the definition of reefs so that species with records of significant persistence in particular areas and which otherwise meet expectations of reefs are included within the definition.     

Thymic nurse cells: morphological study during their isolation from murine thymus

Summary Thymic nurse cells (TNC), which are multicellular complexes composed of epithelial cells and thymocytes, were obtained from C3H-mice thymuses. They were described by means of light and electron microscopy. The morphology of epithelial cells forming isolated TNC compared to that of small tissue fragments obtained by enzymatic digestion revealed that TNC could be derived from all parts of the thymus: cortex, corticomedullary junction and medulla, the cortex being their principal source. This variety of origin, the presence of several epithelial cells inside a single TNC, the presence of non-lymphoid cells, and the various locations of eleaved desmosomes confirmed that their aspect in vitro as round and sealed structures can be considered to be an artifact due to the isolation technique used. Indeed, during this procedure, they are formed by a process of wrapping of the epithelial cytoplasm around the tightly associated thymocytes. All three epithelial cell types: cortical reticular cells, medullary reticular cells, and medullary globular cells can form TNC.A portion of this work was presented at the first Thymus Workshop. Rolduc, Netherlands, April, 1988     

Spectrum of phenylketonuria mutations in Western Europe and North Africa,and their relation to polymorphic DNA haplotypes at the phenylalanine hydroxylase locus

Summary A total of 252 chromosomes from 126 patients with phenylalanine hydroxylase (PAH) deficiencies were analyzed for both mutant genotypes and restriction fragment length polymorphism (RFLP) haplotypes at the PAH locus. The mutant genes studied originated either from Western Europe (116 alleles) or from Mediterranean countries (136 alleles). Only 27% of all mutant alleles were found to carry identified mutations, particularly mutations at codon 252 (2.3%), 261 (7.5%), 280 (6.3%), 408 (3.5%) and at the splice donor site of intron 12 (6.3%). The mutant genotypes were associated with RFLP haplotypes 7, 1, 38, 2 and 3 at the PAH locus respectively. Except for the splice mutation of intron 12, these associations were preferential, but not exclusive, since the other four mutations were found on the background of at least two RFLP haplotypes. These results, together with the observation that 85% of PAH deficient patients are heterozygotes for their mutant genotypes, emphasize the great heterogeneity of PAH deficiencies in Mediterranean countries and hamper systematic DNA testing for carrier status in this population.