Nucleotide sequence analysis of the lemur beta-globin gene family: evidence for major rate fluctuations in globin polypeptide evolution

Lemur beta-related globin genes have been isolated and sequenced. Orthology of prosimian and human epsilon-, gamma-, and beta-related globin genes was established by dot-matrix analysis. All of these lemur globin genes potentially encode functional beta-related globin polypeptides, though precisely when the gamma-globin gene is expressed remains unknown. The organization of the 18-kb brown lemur beta-globin gene cluster (5' epsilon-gamma-[psi eta-delta]-beta 3') is consistent with its evolution by contraction via unequal crossing-over from the putative ancestral mammalian beta-globin gene cluster (5' epsilon-gamma- eta-delta-beta 3'). The dwarf lemur nonadult globin genes are arranged as in the brown lemur. Similar levels of synonymous (silent) nucleotide substitutions and noncoding DNA sequence differences have accumulated between species in all of these genes, suggesting a uniform rate of noncoding DNA divergence throughout primate beta-globin gene clusters. These differences are comparable with those observed in the nonfunctional psi eta pseudogene and have therefore accumulated at the presumably maximal neutral rate. In contrast, nonsynonymous (replacement) nucleotide substitutions show a significant heterogeneity in distribution for both the same gene in different lineages and different genes in the same lineage. These major fluctuations in replacement but not silent substitution rates cannot be attributed to changes in mutation rate, suggesting that changes in the rate of globin polypeptide evolution in primates is not governed solely by variable mutation rates.      

The physiological basis of seed dormancy in Avena fatua. II. On the involvement of alternative respiration in the stimulation of germination by sodium azide

Chromatography on DEAE-cellulose of an extract from etiolated leaves of sorghum ( Sorghum vulgare Pers. cv. INRA 450), a C₄ plant, gave only one form of phosphoenol pyruvate carboxylase with functional and regulatory properties of a C₃ type plant enzyme. Greening of the leaves resulted in a significant increase in activity. This increase was due to the appearance of a new form of the enzyme, which eluted at lower ionic strength and exhibited new properties. This form was glucose-6-P activated and showed a sigmoidal curve response to the concentration of the substrate phosphoerralpyruvate. These kinetic properties are typical of a C₄ plant enzyme.     

Lipoteichoic acid increases TLR and functional chemokine expression while reducing dentin formation in in vitro differentiated human odontoblasts

Gram-positive bacteria entering the dentinal tissue during the carious process are suspected to influence the immune response in human dental pulp. Odontoblasts situated at the pulp/dentin interface are the first cells encountered by these bacteria and therefore could play a crucial role in this response. In the present study, we found that in vitro-differentiated odontoblasts constitutively expressed the pattern recognition receptor TLR1-6 and 9 genes but not TLR7, 8, and 10. Furthermore, lipoteichoic acid (LTA), a wall component of Gram-positive bacteria, triggered the activation of the odontoblasts. LTA up-regulated the expression of its own receptor TLR2, as well as the production of several chemokines. In particular, an increased amount of CCL2 and CXCL10 was detected in supernatants from LTA-stimulated odontoblasts, and those supernatants augmented the migration of immature dendritic cells in vitro compared with controls. Clinical relevance of these observations came from immunohistochemical analysis showing that CCL2 was expressed in vivo by odontoblasts and blood vessels present under active carious lesions but not in healthy dental pulps. In contrast with this inflammatory response, gene expression of major dentin matrix components (type I collagen, dentin sialophosphoprotein) and TGF-beta1 was sharply down-regulated in odontoblasts by LTA. Taken together, these data suggest that odontoblasts activated through TLR2 by Gram-positive bacteria LTA are able to initiate an innate immune response by secreting chemokines that recruit immature dendritic cells while down-regulating their specialized functions of dentin matrix synthesis and mineralization.     

Sedentary life style of Neotropical sedge wrens promotes song imitation

To what extent has the style of song development among songbirds coevolved with other life history strategies? Among Cistothorus wrens in North America, it seems that sedentary or site-faithful habits of marsh wrens, C. palustris, favour song imitation, but seminomadic habits of sedge wrens, C. platensis, favour song improvisation, whereby each male generates a large but unique song repertoire. In this study, we tested whether more sedentary populations of sedge wrens in the Neotropics would imitate songs. At our primary study site near Cartago, Costa Rica, breeding birds were colour-banded during 1995 and 1996, and follow-up surveys revealed that the birds remained at this site the year round. Extensive tape recording and analysis of songs showed that males had large song repertoires (200-300+ songs), and that many songs were shared among neighbouring males. In addition, males only 27 km distant, at La Pastora, used different songs. Furthermore, matched countersinging, in which two males answer each other with identical song types, was recorded near Brasilia, in Brazil. The sharing of songs among permanent neighbours, microgeographical variation in song, and matched countersinging can be achieved only through song imitation, thus revealing a striking difference in the style of song development among different populations of the sedge wren. In the Neotropics, having predictable neighbours throughout life appears to have favoured song imitation, so that individuals can interact using a common, learned code typical of the local population; among more mobile populations in North America, however, individuals improvise large repertoires of species-typical songs, thereby enabling singing males to communicate with any individual, no matter what the population of origin. Strategies of song development must correlate with life history features, and further surveys are needed to make sense of the great diversity of singing behaviours among songbirds. Copyright 1999 The Association for the Study of Animal Behaviour.     

Screening of nonpolyenic antifungal metabolites produced by clinical isolates of actinomycetes

The purpose of this work was to screen clinical isolates of actinomycetes producing nonpolyenic antifungals. This choice was made to limit the problem of rediscovery of well-known antifungal families, especially polyenic antifungals. One hundred and ten strains were tested, using two diffusion methods and two test media, against three yeast species and three filamentous fungi. Among 54 strains (49%) showing antifungal activity, five strains belonging to the genus Streptomyces were active against all test organisms and appeared promising. These results indicate that clinical and environmental isolates of actinomycetes could be an interesting source of antifungal bioactive substances. The production of nonpolyenic antifungal substances by these five active isolates was investigated using several criteria: antibacterial activity, ergosterol inhibition, and UV-visible spectra of active extracts. One active strain responded to all three selection criteria and produced potentially nonpolyenic antifungal metabolites. This strain was retained for further investigation, in particular, purification, structure elucidation, and mechanism of action of the active product.     

Junonia coenia densovirus-based vectors for stable transgene expression in Sf9 cells: influence of the densovirus sequences on genomic integration

The invertebrate parvovirus Junonia coenia densovirus (JcDNV) shares similarities with terminal hairpins and nonstructural (NS) protein activities of adeno-associated virus (AAV) despite their evolutionary divergence (B. Dumas, M. Jourdan, A. M. Pascaud, and M. Bergoin, Virology, 191:202-222, 1992, and C. Ding, M. Urabe, M. Bergoin, and R. M. Kotin, J. Virol. 76:338-345, 2002). We demonstrate here that persistent transgene expression in insect cells results from stable integration of transfected JcDNV-derived vectors into the host genome. To assess the integrative properties of JcDNV vectors, the green fluorescent protein (GFP) gfp marker gene was fused in frame into the major open reading frame (ORF1) of the viral sequence under the control of the P9 capsid protein promoter. In addition, the influence of the nonstructural proteins on the posttransfection maintenance of the vectors was examined by interruption of one or all three NS ORFs. Following transfection of Sf9 cells with each of the JcDNV constructs, clones showing persistent GFP expression were isolated. Structural analyses revealed that the majority of the JcDNV plasmid sequence was integrated into the genome of the fluorescent clones. Integration was observed whether or not NS proteins were expressed. However, the presence of NS genes in the constructs greatly influenced the number of integrated copies and their distribution in the host genome. Disruption of NS genes expression resulted in integration of head-to-tail concatemers at multiple sites within the genome. Further analyses demonstrated that the cis JcDNV 5' inverted terminal repeat region was the primary site of recombination. Sequence analyses of integration junctions showed rearrangements of both flanking and internal sequences for most integrations. These findings demonstrate that JcDNV vectors integrate into insect cells in a manner similar to AAV plasmids in mammalian cells.     

Juvenile hormone-controlled vitellogenin synthesis in Locusta migratoria fat body: Cytological development

Cytological development in the fat body of adult female Locusta migratoria, related to vitellogenin synthesis, has been studied by light and electron microscopy. In the newly-emerged adult, the cells are filled with lipid droplets, which indent the nucleus, and with fields of glycogen, while ribosomes and endoplasmic reticulum are scarce. Correlated with the onset of vitellogenin synthesis, about day 8 of adult life, the nucleus enlarges, lipid droplets and glycogen decrease, and rough endoplasmic reticulum and Golgi complexes become the most abundant organelles. These changes reflect a conversion of the principal role of the fat body from nutrient storage to the synthesis and secretion of protein. They are prevented by allatectomy, and restored by subsequent treatment with the juvenile hormone analogue, ZR-515. Late in the first gonotrophic cycle, about day 20, dense bodies, vesicle-containing bodies and lysosomes are seen, indicating recycling of cellular materials. Five days after ZR-515 treatment, when protein synthesis has declined, the rough endoplasmic reticulum appears in arrays adjacent to lipid droplets, possibly awaiting reactivation. By the use of ferritin-labelled antivitellin immunoglobulin, vitellogenin has been localized intracellularly in the RER saccules and Golgi vesicles, and extracellularly in channels between the folded plasma membranes, showing sites of accumulation and secretion of this protein.     

Pollination ecology and breeding system of the very narrow coastal endemic Seseli farrenyi (Apiaceae). Effects of population fragmentation

The reproductive biology of Seseli farrenyi (Apiaceae), a very narrow endemic to Cape Creus (Catalonia, Spain), including flowering timing patterns, quantity and quality of pollination services (type and frequency of pollinators, pollen carryover, pollen deposition on stigmas and reproductive success measured as fruit set), and breeding system was studied. Given the decline of population size detected in the last twenty years, we also analyzed the effects of fragmentation on pollination mechanisms. Protandry along with strong synchrony of floral development within umbels and sequential inflorescence emission within individual stalks, produces sexual phase alternation that promotes a strong outcrossing despite its non-specific pollination system and its (at least partial) self-compatibility. This pronounced xenogamy is supported by results of the insect exclusion test, hand-pollination experiments, and high P/O ratio. S. farrenyi flowers received visits from at least 28 species of insects, including wasps, small bees, ants, flies, syrphid flies, beetles and stink bugs, with different pollen carry-overs. Heterospecific pollen on stigmas decreased notably during the season (50% to 2.5%), averaging 12%. In the small population the stigmatic pollen loads and seed set decreased, but there was no effect of pollinator visitation rates. It was more affected by the composition of pollinators and their efficiency. The wind had a considerable effect on the plant. Some conservation measures are proposed.