569 research outputs found
Collective Almost Synchronization in Complex Networks
This work introduces the phenomenon of Collective Almost Synchronization
(CAS), which describes a universal way of how patterns can appear in complex
networks even for small coupling strengths. The CAS phenomenon appears due to
the existence of an approximately constant local mean field and is
characterized by having nodes with trajectories evolving around periodic stable
orbits. Common notion based on statistical knowledge would lead one to
interpret the appearance of a local constant mean field as a consequence of the
fact that the behavior of each node is not correlated to the behaviors of the
others. Contrary to this common notion, we show that various well known weaker
forms of synchronization (almost, time-lag, phase synchronization, and
generalized synchronization) appear as a result of the onset of an almost
constant local mean field. If the memory is formed in a brain by minimising the
coupling strength among neurons and maximising the number of possible patterns,
then the CAS phenomenon is a plausible explanation for it.Comment: 3 figure
Hepatocyte ALOXE3 is induced during adaptive fasting and enhances insulin sensitivity by activating hepatic PPARγ
Prolonged hypothyroidism severely reduces ovarian follicular reserve in adult rats
Background There is substantial evidence both in humans and in animals that a
prolonged reduction in plasma thyroid hormone concentration leads to
reproductive problems, including disturbed folliculogenesis, impaired
ovulation and fertilization rates, miscarriage and pregnancy complications.
The objective of the present study is to examine the consequences of chronic
hypothyroidism, induced in adulthood, for the size of the ovarian follicle
pool. In order to investigate this, adult female rats were provided either a
control or an iodide deficient diet in combination with perchlorate
supplementation to inhibit iodide uptake by the thyroid. Sixteen weeks later
animals were sacrificed. Blood was collected for hormone analyses and ovaries
were evaluated histologically. Results At the time of sacrifice, plasma
thyroid-stimulating hormone concentrations were 20- to 40-fold increased,
thyroxine concentrations were negligible while tri-iothyronin concentrations
were decreased by 40% in the hypothyroid group, confirming that the animals
were hypothyroid. Primordial, primary and preantral follicle numbers were
significantly lower in the hypothyroid ovaries compared to the euthyroid
controls, while a downward trend in antral follicle and corpora lutea numbers
was observed. Surprisingly the percentage of atretic follicles was not
significantly different between the two groups, suggesting that the reduced
preantral and antral follicle numbers were presumably not the consequence of
increased degeneration of these follicle types in the hypothyroid group.
Plasma anti-Müllerian hormone (AMH) levels showed a significant correlation
with the growing follicle population represented by the total ovarian number
of primary, preantral and antral follicles, suggesting that also under
hypothyroid conditions AMH can serve as a surrogate marker to assess the
growing ovarian follicle population. Conclusions The induction of a chronic
hypothyroid condition in adult female rats negatively affects the ovarian
follicular reserve and the size of the growing follicle population, which may
impact fertility
Dual Effect on Adult-Type Leydig Cell and Sertoli Cell Development
Transient neonatal 6-propyl-2-thiouracil (PTU) induced hypothyroidism affects
Leydig and Sertoli cell numbers in the developing testis, resulting in
increased adult testis size. The hypothyroid condition was thought to be
responsible, an assumption questioned by studies showing that uninterrupted
fetal/postnatal hypothyroidism did not affect adult testis size. Here, we
investigated effects of transient hypothyroidism on Leydig and Sertoli cell
development, employing a perinatal iodide-deficient diet in combination with
sodium perchlorate. This hypothyroidism inducing diet was continued until days
1, 7, 14, or 28 postpartum (pp) respectively, when the rats were switched to a
euthyroid diet and followed up to adulthood. Continuous euthyroid and
hypothyroid, and neonatal PTU-treated rats switched to the euthyroid diet at
28 days pp, were included for comparison. No effects on formation of the
adult-type Leydig cell population or on Sertoli cell proliferation and
differentiation were observed when the diet switched at/or before day 14 pp.
However, when the diet was discontinued at day 28 pp, Leydig cell development
was delayed similarly to what was observed in chronic hypothyroid rats.
Surprisingly, Sertoli cell proliferation was 6- to 8-fold increased 2 days
after the diet switch and remained elevated the next days. In adulthood,
Sertoli cell number per seminiferous tubule cross-section and consequently
testis weight was increased in this group. These observations implicate that
increased adult testis size in transiently hypothyroid rats is not caused by
the hypothyroid condition per se, but originates from augmented Sertoli cell
proliferation as a consequence of rapid normalization of thyroid hormone
concentrations
Angptl4 serves as an endogenous inhibitor of intestinal lipid digestion
Dietary triglycerides are hydrolyzed in the small intestine principally by pancreatic lipase. Following uptake by enterocytes and secretion as chylomicrons, dietary lipids are cleared from the bloodstream via lipoprotein lipase. Whereas lipoprotein lipase is inhibited by several proteins including Angiopoietin-like 4 (Angptl4), no endogenous regulator of pancreatic lipase has yet been identified. Here we present evidence that Angptl4 is an endogenous inhibitor of dietary lipid digestion. Angptl4−/− mice were heavier compared to their wild-type counterparts without any difference in food intake, energy expenditure or locomotor activity. However, Angptl4−/− mice showed decreased lipid content in the stools and increased accumulation of dietary triglycerides in the small intestine, which coincided with elevated luminal lipase activity in Angptl4−/− mice. Furthermore, recombinant Angptl4 reduced the activity of pancreatic lipase as well as the lipase activity in human ileostomy output. In conclusion, our data suggest that Angptl4 is an endogenous inhibitor of intestinal lipase activity
Complete genome sequence of Syntrophobacter fumaroxidans strain (MPOB(T)).
Syntrophobacter fumaroxidans strain MPOB(T) is the best-studied species of the genus Syntrophobacter. The species is of interest because of its anaerobic syntrophic lifestyle, its involvement in the conversion of propionate to acetate, H2 and CO2 during the overall degradation of organic matter, and its release of products that serve as substrates for other microorganisms. The strain is able to ferment fumarate in pure culture to CO2 and succinate, and is also able to grow as a sulfate reducer with propionate as an electron donor. This is the first complete genome sequence of a member of the genus Syntrophobacter and a member genus in the family Syntrophobacteraceae. Here we describe the features of this organism, together with the complete genome sequence and annotation. The 4,990,251 bp long genome with its 4,098 protein-coding and 81 RNA genes is a part of the Microbial Genome Program (MGP) and the Genomes to Life (GTL) Program project
Bacteriophage DNA glucosylation impairs target DNA binding by type I and II but not by type V CRISPR-Cas effector complexes
Prokaryotes encode various host defense systems that provide protection against mobile genetic elements. Restriction-modification (R-M) and CRISPR-Cas systems mediate host defense by sequence specific targeting of invasive DNA. T-even bacteriophages employ covalent modifications of nucleobases to avoid binding and therefore cleavage of their DNA by restriction endonucleases. Here, we describe that DNA glucosylation of bacteriophage genomes affects interference of some but not all CRISPR-Cas systems. We show that glucosyl modification of 5-hydroxymethylated cytosines in the DNA of bacteriophage T4 interferes with type I-E and type II-A CRISPR-Cas systems by lowering the affinity of the Cascade and Cas9-crRNA complexes for their target DNA. On the contrary, the type V-A nuclease Cas12a (also known as Cpf1) is not impaired in binding and cleavage of glucosylated target DNA, likely due to a more open structural architecture of the protein. Our results suggest that CRISPR-Cas systems have contributed to the selective pressure on phages to develop more generic solutions to escape sequence specific host defense systems
Substituent effects on the electrochemical, spectroscopic, and structural properties of Fischer mono- and biscarbene complexes of Chromium(0)
A series of ten ferrocenyl, furyl, and thienyl mono- and biscarbene chromium(0) complexes were synthesized and characterized spectroscopically and electrochemically. The single crystal structure of the biscarbene complex [(CO)5Cr═C(OEt)-Fu′-(OEt)C═Cr(CO)5] (4a) was determined: C20H12Cr2O13; triclinic; P1̅; a = 6.2838(5), b = 12.6526(9), c = 29.1888(19) Å, α = 89.575(2), β = 88.030(2), γ = 87.423(2)°; Z = 4. Results from an electrochemical study in CH2Cl2 were mutually consistent with a computational study in showing that the carbene double bond of 1 – 6 is reduced to an anion radical, –Cr–C• at formal reduction potentials < −1.7 V vs FcH/FcH+. The Cr centers are oxidized in two successive one electron transfer steps to Cr(II) via the Cr(I) intermediate. Only Cr(I) oxidation is electrochemically irreversible. Dicationic Cr(II) species formed upon two consecutive one-electron oxidation processes are characterized by a peculiar bonding situation as they are stabilized by genuine CH···Cr agostic interactions. With respect to aryl substituents, carbene redox processes occurred at the lowest potentials for ferrocene derivatives followed by furan complexes. Redox process in the thiophene derivatives occurred at the highest potentials. This result is mutually consistent with a 13C NMR study that showed the Cr═C functionality of furyl complexes were more shielded than thienyl complexes. The NHBu carbene substituent resulted in carbene complexes showing redox processes at substantially lower redox potentials than carbenes having OEt substituents.The National Research Foundation, South Africa (D.I.B., Grant number 76226; J.C.S., Grant number 81829), and the Spanish MICINN and CAM (I.F., Grants CTQ2010-20714-CO2-01/BQU, Consolider-Ingenio 2010, CSD2007-00006, S2009/PPQ-1634).http://pubs.acs.org/journal/inocajhb2013ai201
FXYD2 and Na,K-ATPase Expression in Isolated Human Proximal Tubular Cells: Disturbed Upregulation on Renal Hypomagnesemia?
Autosomal dominant renal hypomagnesemia (OMIM 154020), associated with hypocalciuria, has been linked to a 121G to A mutation in the FXYD2 gene. To gain insight into the molecular mechanisms linking this mutation to the clinical phenotype, we studied isolated proximal tubular cells from urine of a patient and a healthy subject. Cells were immortalized and used to assess the effects of hypertonicity-induced overexpression of FXYD2 on amount, activity and apparent affinities for Na+, K+ and ATP of Na,K-ATPase. Both cell lines expressed mRNA for FXYD2a and FXYD2b, and patient cells contained both the wild-type and mutated codons. FXYD2 protein expression was lower in patient cells and could be increased in both cell lines upon culturing in hyperosmotic medium but to a lesser extent in patient cells. Similarly, hyperosmotic culturing increased Na,K-ATPase protein expression and ATP hydrolyzing activity but, again, to a lesser extent in patient cells. Apparent affinities of Na,K-ATPase for Na+, K+ and ATP did not differ between patient and control cells or after hyperosmotic induction. We conclude that human proximal tubular cells respond to a hyperosmotic challenge with an increase in FXYD2 and Na,K-ATPase protein expression, though to a smaller absolute extent in patient cells
Erythrocyte sedimentation rate as a marker of inflammation and ongoing coagulation in stroke and transient ischaemic attack
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