The periodic loss of metabolically unstable DNA during replication of chromosomal DNA of CHO cells

The fate of ³H-thymidine incorporated into newly synthesized DNA of CHO cells was analyzed by either the estimation of the incorporated radioactivity per cell or sedimentation in alkaline sucrose gradient. Under conditions in which DNA synthesis proceeded continuously, of incorporated radioactivity was periodically lost and regained during a 90 min chase, corresponding to a cyclic change in the sedimentation profiles. When DNA synthesis was inhibited by hydroxyurea no cyclic change of the incorporated radioactivity was observed. The cyclic changes were regarded as the result of an actual metabolic change in³H-labelled DNA probaly joining to one of the newly formed sister strands of DNA and the loss of radioactivity seems to require active continued DNA synthesis.     

Prostaglandin E2 Activates Ca2+ Channels in Bovine Adrenal Chromaffin Cells

We have demonstrated that prostaglandin E2 (PGE2) treatment of bovine adrenal chromaffin cells results in a sustained elevation of intracellular Ca2+ concentration ([Ca2+]i) in these cells. Because the continued elevation of [Ca2+]i was dependent on extracellular Ca2+ concentration, it can be assumed that the PGE2-induced [Ca2+]i increase is due, at least in part, to an opening of membrane Ca2+ channels. In this study, we used electrophysiological methods to examine the mechanism of the PGE2-induced [Ca2+]i increase directly. Puff application of PGE2 to the external medium resulted in a prolonged depolarization in about half of the chromaffin cells examined. In whole-cell voltage-clamp recordings, an increase in inward current was observed over a 6-7 min period following bath application of PGE2 (greater than or equal to 10 microM), even in the absence of external Na+. This inward current was abolished when the recordings were made with the cells in a Ca2(+)-free medium, but it was not inhibited by Mn2+, a blocker of voltage-dependent Ca2+ channels. In cell-attached patch-clamp configuration, PGE2 produced an increase in the opening frequency of inward currents. The reversal potential of the PGE2-induced currents was about +40 mV, which is close to the reversal potential of the Ca2+ channel. The opening frequency was not affected by membrane potential changes. In inside-out patch-clamp configuration, inositol 1,4,5-trisphosphate (2 microM) added to the cytoplasmic side activated the Ca2(+)-channel currents, but PGE2 was ineffective when applied to the cytoplasmic side. These results suggest that PGE2 activates voltage-independent Ca2+ channels in chromaffin cells through a diffusible second messenger, possibly inositol 1,4,5-trisphosphate.     

Chondroitinase-Producing Bacteria in Natural Habitats

A search was undertaken for bacteria which degrade chondroitin sulfate in nature and to find bacteria with a usefully high rate of chondroitinase (ChSase) productivity. First, 253 ChSase-producing bacteria were obtained from aquatic and land environments in Japan by aerobic and anaerobic screening methods. Identification according to Bergey's Manual of Determinative Bacteriology or Bain and Shewan (1968) permitted assignment of the majority of the isolates to seven genera, Aeromonas, Vibrio, Flavobacterium, Beneckea, Proteus, Micrococcus, and Arthrobacter. Next, ChSase productivities of all the isolates were compared with those of two established ChSase-producing stock strains, Proteus vulgaris NCTC 4636 and Flavobacterium heparinum ATCC 13125. As a result, special attention was given to production by a strain of Aeromonas sp. of large quantities of extracellular ChSase-AC. None of the isolates from the current study displayed significant ChSase-ABC productivity. Finally, ChSase-AC was prepared from the culture fluid of the Aeromonas strain by fractional precipitation with ammonium sulfate, chromatography on phospho-cellulose and diethylaminoethyl-cellulose, and gel filtration on Sephadex G-200. It was concluded that the Aeromonas strain may represent a profitable source of the enzyme ChSase-AC.     

The skull evolution of oviraptorosaurian dinosaurs: the role of niche partitioning in diversification

Oviraptorosaurs are bird‐like theropod dinosaurs that thrived in the final pre‐extinction ecosystems during the latest Cretaceous, and the beaked, toothless skulls of derived species are regarded as some of the most peculiar among dinosaurs. Their aberrant morphologies are hypothesized to have been caused by rapid evolution triggered by an ecological/biological driver, but little is known about how their skull shapes and functional abilities diversified. Here, we use quantitative techniques to study oviraptorosaur skull form and mandibular function. We demonstrate that the snout is particularly variable, that mandibular form and upper/lower beak form are significantly correlated with phylogeny, and that there is a strong and significant correlation between mandibular function and mandible/lower beak shape, suggesting a form–function association. The form–function relationship and phylogenetic signals, along with a moderate allometric signal in lower beak form, indicate that similar mechanisms governed beak shape in oviraptorosaurs and extant birds. The two derived oviraptorosaur clades, oviraptorids and caenagnathids, are significantly separated in morphospace and functional space, indicating that they partitioned niches. Oviraptorids coexisting in the same ecosystem are also widely spread in morphological and functional space, suggesting that they finely partitioned feeding niches, whereas caenagnathids exhibit extreme disparity in beak size. The diversity of skull form and function was likely key to the diversification and evolutionary success of oviraptorosaurs in the latest Cretaceous.     

Sulfurimicrobium lacus gen. nov., sp. nov., a sulfur oxidizer isolated from lake water,and review of the family Sulfuricellaceae to show that it is not a later synonym of Gallionellaceae

Archives of Microbiology - A facultatively anaerobic sulfur-oxidizing bacterium, strain skT11T, was isolated from anoxic lake water of a stratified freshwater lake. As electron donor for...     

River to river: First evidence of eel movement between distant rivers via the sea

Environmental Biology of Fishes - Eel movement patterns have been frequently studied to learn about their movements within the fresh- and brackish waters of the same river before their spawning...     

Export of dissolved iron from river catchments in northeast Japan

Landscape and Ecological Engineering - This study investigated the export of dissolved iron (DFe) from river catchments with emphasis on land use and land cover (LULC). The DFe concentrations were...     

Clinical relevance of oncogenic driver mutations identified in endometrial carcinoma

PurposeEndometrial carcinoma (EC) is a clinically heterogeneous disease characterized by a number of different histological subtypes, and its heterogeneity may be involved in the accumulation of multiple genetic alterations. The aim of this work was to investigate the comprehensive mutational profile of EC tumors, and examine the associations between somatic mutations and clinicopathological features or survival in EC patients.MethodsA total of 100 surgical tumors were obtained from EC patients who had previously undergone surgery. Genomic DNA samples extracted from fresh-frozen tissues were analyzed using the Ion AmpliSeq Cancer Hotspot Panel v2 Kit, covering 50 tumor-related genes.ResultsValidated mutations were detected in 91 of the 100 tumors (91%) and identified in eight of the most frequently mutated genes, namely PTEN (57%), PIK3CA (51%), TP53 (30%), KRAS (23%), CTNNB1 (21%), FBFR2 (13%), FBXW7(10%) and RB1 (9%). PTEN mutations were found to associated with young age (< 60), early-stage, endometrioid histology, non-recurrence and better overall survival (OS). CTNNB1 mutations were associated with young age, endometrioid histology and better OS. On the other hands, TP53 mutations were associated with late-stage, non-endometrioid histology, high-grade, recurrence and worse OS. FBWX7 mutations were associated with late-stage, vascular invasion and lymph node metastasis. FGFR2 mutations correlated with deep (≥ 1/2) myometrial invasion.ConclusionOur comprehensive mutational profile will be useful for understanding and evaluating the molecular characteristics of EC tumors, and may lead to the establishment of novel treatment strategies that improve the survival of patients with EC in the future.     

Cyclin D1 overexpression perturbs DNA replication and induces replication-associated DNA double-strand breaks in acquired radioresistant cells

Fractionated radiotherapy (RT) is widely used in cancer treatment, because it preserves normal tissues. However, repopulation of radioresistant tumors during fractionated RT limits the efficacy of RT. We recently demonstrated that a moderate level of long-term fractionated radiation confers acquired radioresistance to tumor cells, which is caused by DNA-PK/AKT/GSK3β-mediated cyclin D1 overexpression. The resulting cyclin D1 overexpression leads to forced progression of the cell cycle to S-phase, concomitant with induction of DNA double-strand breaks (DSBs). In this study, we investigated the molecular mechanisms underlying cyclin D1 overexpression-induced DSBs during DNA replication in acquired radioresistant cells. DNA fiber data demonstrated that replication forks progressed slowly in acquired radioresistant cells compared with corresponding parental cells in HepG2 and HeLa cell lines. Slowly progressing replication forks were also observed in HepG2 and HeLa cells that overexpressed a nondegradable cyclin D1 mutant. We also found that knockdown of Mus81endonuclease, which is responsible for resolving aberrant replication forks, suppressed DSB formation in acquired radioresistant cells. Consequently, Mus81 created DSBs to remove aberrant replication forks in response to replication perturbation triggered by cyclin D1 overexpression. After treating cells with a specific inhibitor for DNA-PK or ATM, apoptosis rates increased in acquired radioresistant cells but not in parental cells by inhibiting the DNA damage response to cyclin D1-mediated DSBs. This suggested that these inhibitors might eradicate acquired radioresistant cells and improve fractionated RT outcomes.