Isocitrate dehydrogenase 1 R132C mutation occurs exclusively in microsatellite stable colorectal cancers with the CpG island methylator phenotype

The CpG Island Methylator Phenotype (CIMP) is fundamental to an important subset of colorectal cancer; however, its cause is unknown. CIMP is associated with microsatellite instability but is also found in BRAF mutant microsatellite stable cancers that are associated with poor prognosis. The isocitrate dehydrogenase 1 (IDH1) gene causes CIMP in glioma due to an activating mutation that produces the 2-hydroxyglutarate oncometabolite. We therefore examined IDH1 alteration as a potential cause of CIMP in colorectal cancer. The IDH1 mutational hotspot was screened in 86 CIMP-positive and 80 CIMP-negative cancers. The entire coding sequence was examined in 81 CIMP-positive colorectal cancers. Forty-seven cancers varying by CIMP-status and IDH1 mutation status were examined using Illumina 450K DNA methylation microarrays. The R132C IDH1 mutation was detected in 4/166 cancers. All IDH1 mutations were in CIMP cancers that were BRAF mutant and microsatellite stable (4/45, 8.9%). Unsupervised hierarchical cluster analysis identified an IDH1 mutation-like methylation signature in approximately half of the CIMP-positive cancers. IDH1 mutation appears to cause CIMP in a small proportion of BRAF mutant, microsatellite stable colorectal cancers. This study provides a precedent that a single gene mutation may cause CIMP in colorectal cancer, and that this will be associated with a specific epigenetic signature and clinicopathological features.     

Homozygous mutation of MTPAP causes cellular radiosensitivity and persistent DNA double-strand breaks

The study of rare human syndromes characterized by radiosensitivity has been instrumental in identifying novel proteins and pathways involved in DNA damage responses to ionizing radiation. In the present study, a mutation in mitochondrial poly-A-polymerase (MTPAP), not previously recognized for its role in the DNA damage response, was identified by exome sequencing and subsequently associated with cellular radiosensitivity. Cell lines derived from two patients with the homozygous MTPAP missense mutation were radiosensitive, and this radiosensitivity could be abrogated by transfection of wild-type mtPAP cDNA into mtPAP-deficient cell lines. Further analysis of the cellular phenotype revealed delayed DNA repair, increased levels of DNA double-strand breaks, increased reactive oxygen species (ROS), and increased cell death after irradiation (IR). Pre-IR treatment of cells with the potent anti-oxidants, α-lipoic acid and n-acetylcysteine, was sufficient to abrogate the DNA repair and clonogenic survival defects. Our results firmly establish that mutation of the MTPAP gene results in a cellular phenotype of increased DNA damage, reduced repair kinetics, increased cell death by apoptosis, and reduced clonogenic survival after exposure to ionizing radiation, suggesting a pathogenesis that involves the disruption of ROS homeostasis.     

Characterisation of Structures in Salivary Secretion Film Formation. An Experimental Study with Atomic Force Microscopy

The purpose of the present study was to characterise the structure dynamics of pure salivary secretions retained on controlled surfaces with different surface energies in the early stage of salivary film formation. Germanium prisms prepared to have either low surface energy or medium surface energy were incubated in fresh secretions of either human parotid saliva (HPS) or human submandibular/sublingual saliva (HSMSLS) for 15, 90, and 180 min. After controlled rinsing with distilled water, the surfaces were air dried and thereafter imaged with atomic force microscopy (AFM). The amount of adsorbed material and the size of the structures detected increased with increased saliva exposure time. The film thicknesses varied from 10 to 150 nm, and both HPS and HSMSLS films contained structures with diameters varying from 40 nm to 2 μm. Some of these were clustered into special formations. The HPS films exhibited a more granular morphology than the HSMSLS films. Furthermore, branched lines were detected on the low surface energy germanium prisms incubated in saliva. The results indicate that exposure time, surface energy, and type of salivary secretion all are factors affecting the adsorption characteristics of salivary films.     

Migratory behaviour of post-smolt Atlantic salmon during initial stages of seaward migration

The movements of 24 hatchery-reared Atlantic salmon Salmo salar smolts, with miniature acoustic transmitters (pingers) implanted surgically, were determined after release in the coastal waters of Passamaquoddy Bay (mean tide range 6 m), New Brunswick, Canada, to describe the first stages of seaward migration. Automated pinger detection at fixed sites, and pinger location and tracking by boat were used. Post-smolts left the release area rapidly, and the majority moved to open waters of the bay within several tidal cycles. Initially, post-smolts moved with a seaward orientation on ebb tides and held positions on flood tides. Their movements into open waters were diurnal, and the timing corresponded with the state of the tide during which they moved through a narrow channel. Post-smolts moved preferentially through this passageway with the aid of the tidal stream. Successful movements out through the channel occurred during ebb tides and any movements back in were during flood tides. Ground speed of fish moving through the channel was 4·2 body lengths s⁻¹ and faster than the tidal stream velocities in the channel. The relative velocity of fish swimming through the channel was 2 body lengths s⁻¹. Post-smolt movement was indicative of active, directed swimming with a reliance on ebb-tide transport for migration through a coastal area with strong tidal currents. Some post-smolts moved seaward directly with no apparent period of acclimation for the transfer to the marine environment, whereas others delayed their departure. These differences in behaviour were probably related to asynchrony in smolting when fish were released.     

Tricarboxylic Acid Cycle Enzymes and Morphogenesis in Blastocladiella emersonii

During exponential growth, ordinary colorless (OC) plants of Blastocladiella emersonii consumed little glucose and produced no lactic acid. Similarly, resistant sporangial (RS) plants did not utilize glucose or produce lactic acid during the first 24 hr of exponential growth. During the next 24 hr of RS development, glucose was consumed with the concomitant production of lactic acid which was then reutilized. Lactic acid gradually accumulated again at maturity. Enzyme studies on cell-free extracts indicated the presence of all tricarboxylic cycle enzymes except α-ketoglutarate dehydrogenase at all stages of development of both RS and OC plants. Included among the enzymes detected were an adenosine monophosphate-stimulated, nicotinamide adenine dinucleotide-isocitric dehydrogenase, and citrate-condensing enzyme. When measured on a per plant basis, tricarboxylic cycle enzyme levels increased during the exponential growth of both kinds of plants. Only after the bicarbonate ceased to have effect on RS plant morphogenesis was there a decrease in the levels of the tricarboxylic cycle enzymes when measured on a per plant basis. Specific activity measurements indicated some differences in the differential rates of synthesis among the enzymes studied previous to 36 hr. Preliminary studies utilizing short periods of ¹⁴C-bicarbonate fixation in young RS plants indicated that during the first 4 min most of the label was located in aspartic acid. These results are discussed in terms of previous results and particularly Cantino's hypothesis concerning the relationship between bicarbonate induction and tricarboxylic-cycle enzymes in the morphogenesis of B. emersonii.     

Method for the Selective Enumeration of Blue-Green Bacteria in Water

A membrane filter method for the selective enumeration of blue-green bacteria has been developed which, on the basis of studies with laboratory cultures and field tests, has proved to be both practical and reproducible. The filters are incubated under specified conditions of temperature and illumination on a mineral salts agar medium supplemented with yeast extract and containing cycloheximide to eliminate eukaryotic contaminants.     

ConA的抗着床效应

本文用凝集素为探针,探索糖复合物在胚泡着床中的作用,报道了与甘露糖苷有专一结合的伴刀豆凝集素(ConA)有明显的抗小鼠胚泡着床作用。妊娠4d的小鼠,每只子宫角中注入Con A 25μg,22只子宫角中只有4只子宫角有胚泡着床,着床率为18.2％,与生理盐水对照组的着床率87.5％相比有明显差异。将相同剂量的Con A先与0.4mol/L α-甲基-D-甘露糖苷温育1—2h后再注入子宫,20只子宫角中有15只子宫角有胚泡着床,着床率提高到75％。用辣根过氧化物酶直接标记法证明,着床前子宫内膜细胞表面有Con A受体存在,并随着妊娠天数而增加,尤其是间质细胞,发情期时时为阴性反应,到着床期蜕膜细胞膜表面呈现出大量Con A受体。提示精复合物在着床中的重要作用。与甘露糖苷同样专一结合的,但寡糖结构专一性与Con A不同的豌豆凝集素注入子宫则无抗着床效应,着床率为85.7％。由此可以推测,N-连接的包含二个未被取代的或只在C-2位被取代的α-甘露糖苷的寡糖参于胚泡与子宫内膜相互作用的着床过程。     

Chemicals,birth defects and stillbirths in New Brunswick: associations with agricultural activity.

We describe a series of investigations that were conducted in support of the Task Force on Chemicals in the Environment and Human Reproductive Problems in New Brunswick. Geographic and temporal analyses and case-control studies, with the use of vital statistics, hospital records, the Canadian Congenital Anomalies Surveillance System and chemical databases, revealed no association between pesticides used in forestry and reproductive problems. Evidence of an association between the potential exposure to agricultural chemicals and three major anomalies combined as well as spina bifida without hydrocephalus was found. More plausible was an association between stillbirths and such exposure during the second trimester of pregnancy. This finding, along with the cyclic patterns of stillbirth in the agricultural Saint John River basin and the somewhat higher stillbirth rates in New Brunswick than in adjacent provinces or in Canada as a whole, suggests that further attention should focus on possible associations between agricultural activity and stillbirths.