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111.
The phylogenetic position of Rhopalura ophiocomae (Orthonectida) based on 18S ribosomal DNA sequence analysis 总被引:2,自引:0,他引:2
Hanelt B; Van Schyndel D; Adema CM; Lewis LA; Loker ES 《Molecular biology and evolution》1996,13(9):1187-1191
The Orthonectida is a small, poorly known phylum of parasites of marine
invertebrates. Their phylogenetic placement is obscure; they have been
considered to be multicellular protozoans, primitive animals at a
"mesozoan" grade of organization, or secondarily simplified flatworm- like
organisms. The best known species in the phylum, Rhopalura ophiocomae, was
collected on San Juan Island, Wash. and a complete 18S rDNA sequence was
obtained. Using the models of minimum evolution and parsimony, phylogenetic
analyses were undertaken and the results lend support to the following
hypotheses about orthonectids: (1) orthonectids are more closely aligned
with triploblastic metazoan taxa than with the protist or diploblastic
metazoan taxa considered in this analysis; (2) orthonectids are not derived
members of the phylum Platyhelminthes; and (3) orthonectids and rhombozoans
are not each other's closest relatives, thus casting further doubt on the
validity of the phylum Mesozoa previously used to encompass both groups.
相似文献
112.
Although invertebrate drift is an important ecological process in lotic ecosystems, very little is known about it in Kenyan rivers. The primary aim of this study was to investigate the effect of driftnet mesh size and exposure duration on drift density in 2017. Drift samples were dominated by Chironomidae, Baetidae, Simuliidae, Caenidae and Culicidae. The 100 µm mesh driftnet had the highest mean invertebrate density, followed by the 250 µm and 500 µm nets. Invertebrate drift densities decreased with increased exposure time. This study demonstrates that sampler mesh size and exposure time should be taken into account when characterising invertebrate drift in streams. Future studies should consider sampling different biotopes and during different seasons. 相似文献
113.
Transposable elements induce spontaneous mutations, promote genome
rearrangements, regulate gene expression, and participate in the horizontal
spread of genes encoding traits such as antibiotic resistance among
bacterial genera too distantly related to undergo homologous recombination.
Here we review the bacterial transposon Tn5 and focus on those aspects of
its functional organization and transposition which provide insights into
how it and other elements may have arisen, proliferated, and evolved.
相似文献
114.
Peter Serrano Eugenia L Friedman Jana Kenney Stephen M Taubenfeld Joshua M Zimmerman John Hanna Cristina Alberini Ann E Kelley Stephen Maren Jerry W Rudy Jerry C. P Yin Todd C Sacktor André A Fenton 《PLoS biology》2008,6(12)
How long-term memories are stored is a fundamental question in neuroscience. The first molecular mechanism for long-term memory storage in the brain was recently identified as the persistent action of protein kinase Mzeta (PKMζ), an autonomously active atypical protein kinase C (PKC) isoform critical for the maintenance of long-term potentiation (LTP). PKMζ maintains aversively conditioned associations, but what general form of information the kinase encodes in the brain is unknown. We first confirmed the specificity of the action of zeta inhibitory peptide (ZIP) by disrupting long-term memory for active place avoidance with chelerythrine, a second inhibitor of PKMζ activity. We then examined, using ZIP, the effect of PKMζ inhibition in dorsal hippocampus (DH) and basolateral amygdala (BLA) on retention of 1-d-old information acquired in the radial arm maze, water maze, inhibitory avoidance, and contextual and cued fear conditioning paradigms. In the DH, PKMζ inhibition selectively disrupted retention of information for spatial reference, but not spatial working memory in the radial arm maze, and precise, but not coarse spatial information in the water maze. Thus retention of accurate spatial, but not procedural and contextual information required PKMζ activity. Similarly, PKMζ inhibition in the hippocampus did not affect contextual information after fear conditioning. In contrast, PKMζ inhibition in the BLA impaired retention of classical conditioned stimulus–unconditioned stimulus (CS-US) associations for both contextual and auditory fear, as well as instrumentally conditioned inhibitory avoidance. PKMζ inhibition had no effect on postshock freezing, indicating fear expression mediated by the BLA remained intact. Thus, persistent PKMζ activity is a general mechanism for both appetitively and aversively motivated retention of specific, accurate learned information, but is not required for processing contextual, imprecise, or procedural information. 相似文献
115.
A mathematical approach was developed to model and optimize selection on multiple known quantitative trait loci (QTL) and polygenic estimated breeding values in order to maximize a weighted sum of responses to selection over multiple generations. The model allows for linkage between QTL with multiple alleles and arbitrary genetic effects, including dominance, epistasis, and gametic imprinting. Gametic phase disequilibrium between the QTL and between the QTL and polygenes is modeled but polygenic variance is assumed constant. Breeding programs with discrete generations, differential selection of males and females and random mating of selected parents are modeled. Polygenic EBV obtained from best linear unbiased prediction models can be accommodated. The problem was formulated as a multiple-stage optimal control problem and an iterative approach was developed for its solution. The method can be used to develop and evaluate optimal strategies for selection on multiple QTL for a wide range of situations and genetic models. 相似文献
116.
Eric A Gaucher Logan G Graddy Tang Li Rosalia CM Simmen Frank A Simmen David R Schreiber David A Liberles Christine M Janis Steven A Benner 《BMC biology》2004,2(1):19
Background
Joining a model for the molecular evolution of a protein family to the paleontological and geological records (geobiology), and then to the chemical structures of substrates, products, and protein folds, is emerging as a broad strategy for generating hypotheses concerning function in a post-genomic world. This strategy expands systems biology to a planetary context, necessary for a notion of fitness to underlie (as it must) any discussion of function within a biomolecular system. 相似文献117.
Sebastian A Baldauf Theo CM Bakker Fabian Herder Harald Kullmann Timo Thünken 《BMC evolutionary biology》2010,10(1):301
Background
Studies addressing the adaptive significance of female ornamentation have gained ground recently. However, the expression of female ornaments in relation to body size, known as trait allometry, still remains unexplored. Here, we investigated the allometry of a conspicuous female ornament in Pelvicachromis taeniatus, a biparental cichlid that shows mutual mate choice and ornamentation. Females feature an eye-catching pelvic fin greatly differing from that of males. 相似文献118.
A mathematical approach to optimize selection on multiple quantitative trait loci (QTL) and an estimate of residual polygenic effects was applied to selection on two linked or unlinked additive QTL. Strategies to maximize total or cumulative discounted response over ten generations were compared to standard QTL selection on the sum of breeding values for the QTL and an estimated breeding value for polygenes, and to phenotypic selection. Optimal selection resulted in greater response to selection than standard QTL or phenotypic selection. Tight linkage between the QTL (recombination rate 0.05) resulted in a slightly lower response for standard QTL and phenotypic selection but in a greater response for optimal selection. Optimal selection capitalized on linkage by emphasizing selection on favorable haplotypes. When the objective was to maximize total response after ten generations and QTL were unlinked, optimal selection increased QTL frequencies to fixation in a near linear manner. When starting frequencies were equal for the two QTL, equal emphasis was given to each QTL, regardless of the difference in effects of the QTL and regardless of the linkage, but the emphasis given to each of the two QTL was not additive. These results demonstrate the ability of optimal selection to capitalize on information on the complex genetic basis of quantitative traits that is forthcoming. 相似文献
119.
120.
Marije B Overdijk Sandra Verploegen Marijn B?gels Marjolein van Egmond Jeroen J Lammerts van Bueren Tuna Mutis Richard WJ Groen Esther Breij Anton CM Martens Wim K Bleeker Paul WHI Parren 《MABS-AUSTIN》2015,7(2):311-320
Daratumumab (DARA) is a human CD38-specific IgG1 antibody that is in clinical development for the treatment of multiple myeloma (MM). The potential for IgG1 antibodies to induce macrophage-mediated phagocytosis, in combination with the known presence of macrophages in the tumor microenvironment in MM and other hematological tumors, led us to investigate the contribution of antibody-dependent, macrophage-mediated phagocytosis to DARA''s mechanism of action. Live cell imaging revealed that DARA efficiently induced macrophage-mediated phagocytosis, in which individual macrophages rapidly and sequentially engulfed multiple tumor cells. DARA-dependent phagocytosis by mouse and human macrophages was also observed in an in vitro flow cytometry assay, using a range of MM and Burkitt''s lymphoma cell lines. Phagocytosis contributed to DARA''s anti-tumor activity in vivo, in both a subcutaneous and an intravenous leukemic xenograft mouse model. Finally, DARA was shown to induce macrophage-mediated phagocytosis of MM cells isolated from 11 of 12 MM patients that showed variable levels of CD38 expression. In summary, we demonstrate that phagocytosis is a fast, potent and clinically relevant mechanism of action that may contribute to the therapeutic activity of DARA in multiple myeloma and potentially other hematological tumors. 相似文献