2,618 research outputs found
Rigid motions: action-angles, relative cohomology and polynomials with roots on the unit circle
Revisiting canonical integration of the classical solid near a uniform
rotation, canonical action angle coordinates, hyperbolic and elliptic, are
constructed in terms of various power series with coefficients which are
polynomials in a variable depending on the inertia moments. Normal forms
are derived via the analysis of a relative cohomology problem and shown to be
obtainable without the use of ellitptic integrals (unlike the derivation of the
action-angles). Results and conjectures also emerge about the properties of the
above polynomials and the location of their roots. In particular a class of
polynomials with all roots on the unit circle arises.Comment: 26 pages, 1 figur
Beef meat promotion of dimethylhydrazine-induced colorectal carcinogenesis biomarkers is suppressed by dietary calcium
Red meat consumption is associated with increased risk of colorectal cancer. We have previously shown that haemin, Hb and red meat promote carcinogen-induced preneoplastic lesions: aberrant crypt foci (ACF) and mucin-depleted foci (MDF) in rats. We have also shown that dietary calcium, antioxidant mix and olive oil inhibit haemin-induced ACF promotion, and normalize faecal lipoperoxides and cytotoxicity. Here we tested if these strategies are effective also against red meat promotion in dimethylhydrazine-induced rats. Three diets with 60% beef meat were supplemented with calcium phosphate (33 g/kg), antioxidant agents (rutin and butylated hydroxyanisole, 0•05% each) and olive oil (5 %). ACF, MDF, faecal water cytotoxicity, thiobarbituric acid reactive substances (TBARS) and urinary 1,4-dihydroxynonane mercapturic acid (DHN-MA) were measured. Beef meat diet increased the number of ACF (þ30 %) and MDF (þ100 %) (P,0•001), which confirms our previous findings. Promotion was associated with increased faecal water TBARs ( £ 4) and cytotoxicity ( £ 2), and urinary DHN-MA excretion ( £ 15). Calcium fully inhibited beef meat-induced ACF and MDF promotion, and normalized faecal TBARS and cytotoxicity, but did not reduce urinary DHN-MA. Unexpectedly, high-calcium control diet-fed rats had more MDF and ACF in the colon than low-calcium control diet-fed rats. Antioxidant mix and olive oil did not normalize beef meat promotion nor biochemical factors. The results confirm that haem causes promotion of colon carcinogenesis by red meat. They suggest that calcium can reduce colorectal cancer risk in meat-eaters. The results support the concept that toxicity associated with the excess of a useful nutrient may be prevented by another nutrient
Phosphorylation by the stress-activated MAPK Slt2 down-regulates the yeast TOR complex 2
Saccharomyces cerevisiae target of rapamycin (TOR) complex 2 (TORC2) is an
essential regulator of plasma membrane lipid and protein homeostasis. How TORC2
activity is modulated in response to changes in the status of the cell envelope
is unclear. Here we document that TORC2 subunit Avo2 is a direct target of
Slt2, the mitogen-activated protein kinase (MAPK) of the cell wall integrity
pathway. Activation of Slt2 by overexpression of a constitutively active allele
of an upstream Slt2 activator (Pkc1) or by auxin-induced degradation of a
negative Slt2 regulator (Sln1) caused hyperphosphorylation of Avo2 at its MAPK
phosphoacceptor sites in a Slt2-dependent manner and diminished TORC2-mediated
phosphorylation of its major downstream effector, protein kinase Ypk1. Deletion
of Avo2 or expression of a phosphomimetic Avo2 allele rendered cells sensitive
to two stresses (myriocin treatment and elevated exogenous acetic acid) that
the cell requires Ypk1 activation by TORC2 to survive. Thus, Avo2 is necessary
for optimal TORC2 activity, and Slt2-mediated phosphorylation of Avo2
down-regulates TORC2 signaling. Compared with wild-type Avo2, phosphomimetic
Avo2 shows significant displacement from the plasma membrane, suggesting that
Slt2 inhibits TORC2 by promoting Avo2 dissociation. Our findings are the first
demonstration that TORC2 function is regulated by MAPK-mediated
phosphorylation.Comment: This work was supported by National Institutes of Health (NIH)
Predoctoral Traineeship GM07232 and a University of California at Berkeley
MacArthur and Lakhan-Pal Graduate Fellowship to K.L.L., Erwin Schroedinger
Fellowship J3787-B21 from the Austrian Science Fund to AE-A, Marie
Sklodowska-Curie Action H2020-MSCA-IF-2016 InsiliCardio, GA 75083 to CMA, and
NIH R01 research grant GM21841 to J
Meat processing and colon carcinogenesis: Cooked, nitrite-treated and oxidized high-heme cured meat promotes mucin depleted foci in rats
Processed meat intake is associated with colorectal cancer risk, but no experimental study supports the epidemiologic evidence. To study the effect of meat processing on carcinogenesis promotion, we first did a 14-day study with 16 models of cured meat. Studied factors, in a 2 × 2 × 2 × 2 design, were muscle color (a proxy for heme level), processing temperature, added nitrite, and packaging. Fischer 344 rats were fed these 16 diets, and we evaluated fecal and urinary fat oxidation and cytotoxicity, three biomarkers of heme-induced carcinogenesis promotion. A principal component analysis allowed for selection of four cured meats for inclusion into a promotion study. These selected diets were given for 100 days to rats pretreated with 1,2-dimethylhydrazine. Colons were scored for preneoplastic lesions: aberrant crypt foci (ACF) and mucin-depleted foci (MDF). Cured meat diets significantly increased the number of ACF/colon compared with a no-meat control diet (P = 0.002). Only the cooked nitrite-treated and oxidized high heme meat significantly increased the fecal level of apparent total N-nitroso compounds (ATNC) and the number of MDF per colon compared with the no-meat control diet (P < 0.05). This nitrite-treated and oxidized cured meat specifically increased the MDF number compared with similar non nitrite-treated meat (P = 0.03) and with similar non oxidized meat (P = 0.004). Thus, a model cured meat, similar to ham stored aerobically, increased the number of preneoplastic lesions, which suggests colon carcinogenesis promotion. Nitrite treatment and oxidation increased this promoting effect, which was linked with increased fecal ATNC level. This study could lead to process modifications to make non promoting processed meat
Aspiration of biological viscoelastic drops
Spherical cellular aggregates are in vitro systems to study the physical and
biophysical properties of tissues. We present a novel approach to characterize
the mechanical properties of cellular aggregates using micropipette aspiration
technique. We observe an aspiration in two distinct regimes, a fast elastic
deformation followed by a viscous flow. We develop a model based on this
viscoelastic behavior to deduce the surface tension, viscosity, and elastic
modulus. A major result is the increase of the surface tension with the applied
force, interpreted as an effect of cellular mechanosensing.Comment: 4 pages, 4 figures
- …