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1.
The mid-Ediacaran Mistaken Point biota of Newfoundland represents the first morphologically complex organisms in the fossil record. At the classic Mistaken Point localities the biota is dominated by the enigmatic group of "fractally" branching organisms called rangeomorphs. One of the few exceptions to the rangeomorph body plan is the fossil Thectardis avalonensis, which has been reconstructed as an upright, open cone with its apex in the sediment. No biological affinity has been suggested for this fossil, but here we show that its body plan is consistent with the hydrodynamics of the sponge water-canal system. Further, given the habitat of Thectardis beneath the photic zone, and the apparent absence of an archenteron, movement, or a fractally designed body plan, we suggest that it is a sponge. The recognition of sponges in the Mistaken Point biota provides some of the earliest body fossil evidence for this group, which must have ranged through the Ediacaran based on biomarkers, molecular clocks, and their position on the metazoan tree of life, in spite of their sparse macroscopic fossil record. Should our interpretation be correct, it would imply that the paleoecology of the Mistaken Point biota was dominated by sponges and rangeomorphs, organisms that are either known or hypothesized to feed in large part on dissolved organic carbon (DOC). The biology of these two clades gives insight into the structure of the Ediacaran ocean, and indicates that a non-uniformitarian mechanism delivered labile DOC to the Mistaken Point seafloor. 相似文献
2.
Zogopoulos G Ha KC Naqib F Moore S Kim H Montpetit A Robidoux F Laflamme P Cotterchio M Greenwood C Scherer SW Zanke B Hudson TJ Bader GD Gallinger S 《Human genetics》2007,122(3-4):345-353
Genomic copy number variation (CNV) is a recently identified form of global genetic variation in the human genome. The Affymetrix
GeneChip 100 and 500 K SNP genotyping platforms were used to perform a large-scale population-based study of CNV frequency.
We constructed a genomic map of 578 CNV regions, covering approximately 220 Mb (7.3%) of the human genome, identifying 183
previously unknown intervals. Copy number changes were observed to occur infrequently (<1%) in the majority (>93%) of these
genomic regions, but encompass hundreds of genes and disease loci. This North American population-based map will be a useful
resource for future genetic studies.
Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users. 相似文献
3.
Importance of hydrogen-bonding interactions involving the side chain of Asp158 in the catalytic mechanism of papain 总被引:1,自引:0,他引:1
R Ménard H E Khouri C Plouffe P Laflamme R Dupras T Vernet D C Tessier D Y Thomas A C Storer 《Biochemistry》1991,30(22):5531-5538
In a previous study, it was shown that replacing Asp158 in papain by Asn had little effect on activity and that the negatively charged carboxylate of Asp158 does not significantly stabilize the active site thiolate-imidazolium ion pair of papain (Ménard et al., 1990). In this paper, we report the kinetic characterization of three more mutants at this position: Asp158Gly, Asp158Ala, and Asp158Glu. From the pH-activity profiles of these and other mutants of papain, it has been possible to develop a model that enables us to dissect out the contribution of the various mutations toward (i) intrinsic activity, (ii) ion pair stability, and (iii) the electrostatic potential at the active site. Results obtained with mutants that place either Gly or Ala at position 158 indicate that the hydrogen bonds involving the side chain of Asp158 in wild-type papain are indirectly important for enzyme activity. When CBZ-Phe-Arg-MCA is used as a substrate, the (kcat/KM)obs values at pH 6.5 are 3650 and 494 M-1 s-1 for Asp158Gly and Asp158Ala, respectively, as compared to 119,000 M-1 s-1 for papain. Results with the Asp158Glu mutant suggest that the side chain of Glu moves closer to the active site and cannot form hydrogen bonds similar to those involving Asp158 in papain. From the four mutations introduced at position 158 in papain, we can conclude that it is not the charge but the hydrogen-bonding interactions involving the side chain of Asp158 that contribute the most to the stabilization of the thiolate-imidazolium ion pair in papain. However, the charge and the hydrogen bonds of Asp158 both contribute to the intrinsic activity of the enzyme. 相似文献
4.
Christian Laflamme Louis Gendron Nathalie Turgeon Geneviève Filion Jim Ho Caroline Duchaine 《Systematic and applied microbiology》2009
Rapid detection of Bacillus spores is a challenging task in food and defense industries. In situ labeling of spores would be advantageous for detection by automated systems based on single-cell analysis. Determination of antibiotic-resistance genes in bacterial spores using in situ labeling has never been developed. Most of the in situ detection schemes employ techniques such as fluorescence in situ hybridization (FISH) that target the naturally amplified ribosomal RNA (rRNA). However, the majority of antibiotic-resistance genes has a plasmidic or chromosomal origin and is present in low copy numbers in the cell. The main challenge in the development of low-target in situ detection in spores is the permeabilization procedure and the signal amplification required for detection. This study presents permeabilization and in situ signal amplification protocols, using Bacillus cereus spores as a model, in order to detect antibiotic-resistance genes. The permeabilization protocol was designed based on the different layers of the Bacillus spore. Catalyzed reporter deposition (CARD)–FISH and in situ polymerase chain reaction (PCR) were used as signal amplification techniques. B. cereus was transformed with the high copy number pC194 and low copy number pMTL500Eres plasmids in order to induce resistance to chloramphenicol and erythromycin, respectively. In addition, a rifampicin-resistant B. cereus strain, conferred by a single-nucleotide polymorphism (SNP) in the chromosome, was used. Using CARD–FISH, only the high copy number plasmid pC194 was detected. On the other hand, in situ PCR gave positive results in all tested instances. This study demonstrated that it was feasible to detect antibiotic-resistance genes in Bacillus spores using in situ techniques. In addition, in situ PCR has been shown to be more sensitive and more applicable than CARD–FISH in detecting low copy targets. 相似文献
5.
Guillaume Laflamme Thierry Tremblay-Boudreault Marc-André Roy Parker Andersen éric Bonneil Kaleem Atchia Pierre Thibault Damien D'Amours Benjamin H. Kwok 《The Journal of biological chemistry》2014,289(40):27418-27431
Structural maintenance of chromosome (SMC) proteins are key organizers of chromosome architecture and are essential for genome integrity. They act by binding to chromatin and connecting distinct parts of chromosomes together. Interestingly, their potential role in providing connections between chromatin and the mitotic spindle has not been explored. Here, we show that yeast SMC proteins bind directly to microtubules and can provide a functional link between microtubules and DNA. We mapped the microtubule-binding region of Smc5 and generated a mutant with impaired microtubule binding activity. This mutant is viable in yeast but exhibited a cold-specific conditional lethality associated with mitotic arrest, aberrant spindle structures, and chromosome segregation defects. In an in vitro reconstitution assay, this Smc5 mutant also showed a compromised ability to protect microtubules from cold-induced depolymerization. Collectively, these findings demonstrate that SMC proteins can bind to and stabilize microtubules and that SMC-microtubule interactions are essential to establish a robust system to maintain genome integrity. 相似文献
6.
Reyes-Moreno C Laflamme J Frenette G Sirard MA Sullivan R 《Molecular reproduction and development》2008,75(3):512-520
Normal epididymal function, such as protein expression and secretion, is primarily regulated by testicular androgens and temperature. However, the role of spermatozoa in this critical process has never been studied. In order to determine whether sperm itself could regulate epididymal function, we have developed a cell culture system of bovine epididymal cells to study the interactions between spermatozoa and the epididymal epithelium. Primary cells from caput, corpus, and cauda epididymal tissues were cultured in the presence of androgens at 32 degrees C (scrotal) and 37 degrees C (abdominal). Newly synthesized proteins were metabolically labeled with (35)S-methionine after sperm co-incubation and the pattern of secreted proteins was analyzed by two-dimensional polyacrylamide gel electrophoresis. Proliferation rate, protein secretion rate and electrophoretic patterns of secreted proteins were evaluated 48 hr post-co-incubation. Incubation at 32 degrees C indicated that spermatozoa stimulation increases the level of protein secretion of cultured cells from all epididymal sections while it slightly decreases proliferation of corpus cells. At 37 degrees C, spermatozoa co-incubation significantly decreases the protein secretion rate of cultured cells from all epididymal sections. Independently of cell incubation temperature, spermatozoa stimulation induces both an increase in the intensity of radiolabeled proteins and the appearance of new secreted proteins of caput cells without affecting the protein pattern of corpus or cauda cells. Incubation at 37 degrees C, however, greatly modifies the pattern of proteins expressed at 32 degrees C by cauda cells. Taken together, these results support the hypothesis that spermatozoa themselves affect epididymal cell function, most importantly for caput epididymides. 相似文献
7.
Dutil S Tessier S Veillette M Laflamme C Mériaux A Leduc A Barbeau J Duchaine C 《Journal of applied microbiology》2006,100(5):955-963
AIMS: To confirm the presence of viable Legionella spp. in dental unit waterlines (DUWL) using fluorescent in situ hybridization (FISH) and compare this method with culture approach and also to validate the utility of an enrichment to increase FISH sensitivity. METHODS AND RESULTS: Water samples from 40 dental units were analysed. Three different techniques for detecting Legionella spp. were compared: (i) culture approach, (ii) direct FISH and (iii) FISH with a previous R2A medium enrichment (R2A/FISH). The FISH detection was confirmed by PCR. The use of the direct FISH does not improve significantly the detection of legionellae when compared with the culture. On the contrary, when R2A/FISH was performed, sensitivity was, respectively, two- and threefold higher than that with the direct FISH and culture approach. Using R2A/FISH, 63% of water samples analysed showed a contamination by legionellae. CONCLUSIONS: Legionellae detection by direct FISH and R2A/FISH in dental unit water is possible but is more rapid and more sensitive (R2A/FISH) than the culture approach. SIGNIFICANCE AND IMPACT OF THE STUDY: R2A/FISH showed that several pathogens present in DUWL are viable but may not be culturable. Unlike PCR, R2A/FISH is designed to detect only metabolically active cells and therefore provides more pertinent information on infectious risk. 相似文献
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