Interdecadal variability and oceanic thermohaline adjustment

Changes in the strength of the thermohaline overturning circulation are associated, by geostrophy, with changes in the east-west pressure difference across an ocean basin. The tropical-polar density contrast and the east-west pressure difference are connected by an adjustment process. In flat-bottomed ocean models the adjustment is associated with viscous, baroclinic Kelvin wave propagation. Weak-high latitude stratification leads to the adjustment having an interdecadal timescale. We reexamine model interdecadal oscillations in the context of the adjustment process, for both constant flux and mixed surface boundary conditions. Under constant surface flux, interdecadal oscillations are associated with the passage of a viscous Kelvin wave around the model domain. Our results suggest the oscillations can be self-sustained by perturbations to the western boundary current arising from the southward boundary wave propagation. Mixed boundary condition oscillations are characterized by the eastward, cross-basin movement of salinity-dominated density anomalies, and the westward return of these anomalies along the northern boundary. We suggest the latter is associated with viscous Kelvin wave propagation. Under both types of boundary conditions, the strength of the thermohaline overturning and the tropical-polar density contrast vary out of phase. We show how the phase relationship is related to the boundary wave propagation. The importance of boundary regions indicates an urgent need to examine the robustness of interdecadal variability in models as the resolution is increased, and as the representation of the coastal, shelf/slope wave guide is improved. (Abriged abstract)Comment: 20 pages, AGU LaTeX, 12 figures included using epsfig, to appear in JGR, complete manuscript also available at ftp://crosby.physics.mun.ca/pub/drew/papers/gp1.ps.g

Quantifying microsatellite mutation rates from intestinal stem cell dynamics in Msh2-deficient murine epithelium

Microsatellite sequences have an enhanced susceptibility to mutation and can act as sentinels indicating elevated mutation rates and increased risk of cancer. The probability of mutant fixation within the intestinal epithelium is dictated by a combination of stem cell dynamics and mutation rate. Here we exploit this relationship to infer microsatellite mutation rates. First a sensitive, multiplexed and quantitative method for detecting somatic changes in microsatellite length was developed that allowed the parallel detection of mutant [CA]n sequences from hundreds of low-input tissue samples at up to 14 loci. The method was applied to colonic crypts in Mus musculus and enabled detection of mutant subclones down to 20% of the cellularity of the crypt (around 50 of 250 cells). By quantifying age-related increases in clone frequencies for multiple loci, microsatellite mutation rates in wild-type and Msh2- deficient epithelium were established. An average 388-fold increase in mutation per mitosis rate was observed in Msh2-deficient epithelium (2.4 x10-2) compared to wild- type epithelium (6.2 x10-5)

Characterization of a heat resistant beta-glucosidase as a new reporter in cells and mice.

BACKGROUND: Reporter genes are widely used in biology and only a limited number are available. We present a new reporter gene for the localization of mammalian cells and transgenic tissues based on detection of the bglA (SYNbglA) gene of Caldocellum saccharolyticum that encodes a thermophilic beta-glucosidase. RESULTS: SYNbglA was generated by introducing codon substitutions to remove CpG motifs as these are associated with gene silencing in mammalian cells. SYNbglA expression can be localized in situ or detected quantitatively in colorimetric assays and can be co-localized with E. coli beta-galactosidase. Further, we have generated a Cre-reporter mouse in which SYNbglA is expressed following recombination to demonstrate the general utility of SYNbglA for in vivo analyses. SYNbglA can be detected in tissue wholemounts and in frozen and wax embedded sections. CONCLUSIONS: SYNbglA will have general applicability to developmental and molecular studies in vitro and in vivo.RIGHTS : This article is licensed under the BioMed Central licence at http://www.biomedcentral.com/about/license which is similar to the 'Creative Commons Attribution Licence'. In brief you may : copy, distribute, and display the work; make derivative works; or make commercial use of the work - under the following conditions: the original author must be given credit; for any reuse or distribution, it must be made clear to others what the license terms of this work are

Side population sorting separates subfractions of cycling and non-cycling intestinal stem cells

Isolation of quiescent intestinal stem cells (ISCs) has remained a challenge.By side population (SP) sorting we show cycling ISCs to be in the upper SP.The lower SP is non-cycling and has markers of the quiescent ISCs.In culture both upper and lower SP cells yield all 4 intestinal lineages.Evidence for a role of lower SP cells in repair of intestinal damage is discussed.We report here that side population (SP) sorting allows for the simultaneous isolation of two intestinal stem cell (ISC) subsets from wild-type (WT) mice which are phenotypically different and represent cycling and non-cycling pools of cells. Following 5-ethynyl-2′-deoxyuridine (EdU) injection, in the upper side population (USP) the percentage of EdU + was 36% showing this fraction to be highly proliferative. In the lower side population (LSP), only 0.4% of cells were EdU +, indicating this fraction to be predominantly non-cycling. Using Lgr5-EGFP mice, we show that Lgr5-EGFPhi cells, representing actively cycling ISCs, are essentially exclusive to the USP. In contrast, using histone 2B-YFP mice, SP analysis revealed YFP label retaining cells (LRCs) in both the USP and the LSP. Correspondingly, evaluation of the SP fractions for mRNA markers by qRT-PCR showed that the USP was enriched in transcripts associated with both quiescent and active ISCs. In contrast, the LSP expressed mRNA markers of quiescent ISCs while being de-enriched for those of the active ISC. Both the USP and LSP are capable of generating enteroids in culture which include the four intestinal lineages. We conclude that sorting of USP and LSP fractions represents a novel isolation of cycling and non-cycling ISCs from WT mice.Figure optionsDownload full-size imageDownload high-quality image (243 K)Download as PowerPoint slid

Drivers of Continued Surface Warming After Cessation of Carbon Emissions

The climate response after cessation of carbon emissions is examined here, exploiting a single equation connecting surface warming to cumulative carbon emissions. The multi-centennial response to an idealized pulse of carbon is considered by diagnosing a 1000 year integration of an Earth system model (GFDL ESM2M) and an ensemble of efficient Earth system model simulations. After emissions cease, surface temperature evolves according to (i) how much of the emitted carbon remains in the atmosphere and (ii) how much of the additional radiative forcing warms the surface rather than the ocean interior. The peak in surface temperature is delayed in time after carbon emissions cease through the decline in ocean heat uptake, which in turn increases the proportion of radiative forcing warming the surface. Eventually, after many centuries, surface temperature declines as the radiative forcing decreases through the excess atmospheric CO2 being taken up by the ocean and land

A90V TDP-43 variant results in the aberrant localization of TDP-43 in vitro

AbstractTAR DNA-binding protein-43 (TDP-43) is a highly conserved, ubiquitously expressed nuclear protein that was recently identified as the disease protein in frontotemporal lobar degeneration with ubiquitin-positive inclusions (FTLD-U) and amyotrophic lateral sclerosis (ALS). Pathogenic TDP-43 gene (TARDBP) mutations have been identified in familial ALS kindreds, and here we report a TARDBP variant (A90V) in a FTLD/ALS patient with a family history of dementia. Significantly, A90V is located between the bipartite nuclear localization signal sequence of TDP-43 and the in vitro expression of TDP-43-A90V led to its sequestration with endogenous TDP-43 as insoluble cytoplasmic aggregates. Thus, A90V may be a genetic risk factor for FTLD/ALS because it predisposes nuclear TDP-43 to redistribute to the cytoplasm and form pathological aggregates

Fixation and Spread of Somatic Mutations in Adult Human Colonic Epithelium.

We investigated the means and timing by which mutations become fixed in the human colonic epithelium by visualizing somatic clones and mathematical inference. Fixation requires two sequential steps. First, one of approximately seven active stem cells residing within each colonic crypt has to be mutated. Second, the mutated stem cell has to replace neighbors to populate the entire crypt in a process that takes several years. Subsequent clonal expansion due to crypt fission is infrequent for neutral mutations (around 0.7% of all crypts undergo fission in a single year). Pro-oncogenic mutations subvert both stem cell replacement to accelerate fixation and clonal expansion by crypt fission to achieve high mutant allele frequencies with age. The benchmarking of these behaviors allows the advantage associated with different gene-specific mutations to be compared irrespective of the cellular mechanisms by which they are conferred

Detection of colorectal dysplasia using fluorescently labelled lectins.

Colorectal cancer screening using conventional colonoscopy lacks molecular information and can miss dysplastic lesions. We tested here the ability of fluorescently labelled lectins to distinguish dysplasia from normal tissue when sprayed on to the luminal surface epithelium of freshly resected colon tissue from the Apc(min) mouse and when applied to fixed human colorectal tissue sections. Wheat germ agglutinin (WGA) showed significantly decreased binding to adenomas in the mouse tissue and in sections of human colon from 47 patients. Changes in WGA binding to the human surface epithelium allowed regions containing normal epithelium (NE) or hyperplastic polyps (HP) to be distinguished from regions containing low-grade dysplasia (LGD), high-grade dysplasia (HGD) or carcinoma (C), with 81% sensitivity, 87% specificity and 93% positive predictive value (PPV). Helix pomatia agglutinin (HGA) distinguished epithelial regions containing NE from regions containing HP, LGD, HGD or C, with 89% sensitivity, 87% specificity and 97% PPV. The decreased binding of WGA and HPA to the luminal surface epithelium in human dysplasia suggests that these lectins may enable more sensitive detection of disease in the clinic using fluorescence colonoscopy.This work was supported by grants from Cancer Research UK (17242, 16465) to KMB.This is the final version of the article. It first appeared from Nature Publishing Group via https://doi.org/10.1038/srep2423

Bone Marrow Cells in Murine Colitis: Multi-Signal Analysis Confirms Pericryptal Myofibroblast Engraftment without Epithelial Involvement

This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credite

Inhibition of WEE1 is effective in TP53- and RAS-mutant metastatic colorectal cancer: a randomized trial (FOCUS4-C) comparing adavosertib (AZD1775) with active monitoring

PURPOSE Outcomes in RAS-mutant metastatic colorectal cancer (mCRC) remain poor and patients have limited therapeutic options. Adavosertib is the first small-molecule inhibitor of WEE1 kinase. We hypothesized that aberrations in DNA replication seen in mCRC with both RAS and TP53 mutations would sensitize tumors to WEE1 inhibition. METHODS Patients with newly diagnosed mCRC were registered into FOCUS4 and tested for TP53 and RAS mutations. Those with both mutations who were stable or responding after 16 weeks of chemotherapy were randomly assigned 2:1 between adavosertib and active monitoring (AM). Adavosertib (250 mg or 300 mg) was taken orally once on days 1-5 and days 8-12 of a 3-week cycle. The primary outcome was progression-free survival (PFS), with a target hazard ratio (HR) of 0.5 and 80% power with a one-sided 0.025 significance level. RESULTS FOCUS4-C was conducted between April 2017 and Mar 2020 during which time 718 patients were registered; 247 (34%) were RAS/TP53-mutant. Sixty-nine patients were randomly assigned from 25 UK hospitals (adavosertib = 44; AM = 25). Adavosertib was associated with a PFS improvement over AM (median 3.61 v 1.87 months; HR = 0.35; 95% CI, 0.18 to 0.68; P = .0022). Overall survival (OS) was not improved with adavosertib versus AM (median 14.0 v 12.8 months; HR = 0.92; 95% CI, 0.44 to 1.94; P = .93). In prespecified subgroup analysis, adavosertib activity was greater in left-sided tumors (HR = 0.24; 95% CI, 0.11 to 0.51), versus right-sided (HR = 1.02; 95% CI, 0.41 to 2.56; interaction P = .043). Adavosertib was well-tolerated; grade 3 toxicities were diarrhea (9%), nausea (5%), and neutropenia (7%). CONCLUSION In this phase II randomized trial, adavosertib improved PFS compared with AM and demonstrates potential as a well-tolerated therapy for RAS/TP53-mutant mCRC. Further testing is required in this sizable population of unmet need