33 research outputs found
HMG-CoA reductase is regulated by environmental salinity and its activity is essential for halotolerance in halophilic fungi
The activity and level of HMG-CoA reductase (HMGR) were addressed in
halophilic fungi isolated from solar saltpans. Representative fungi belonging
to the orders Dothideales, Eurotiales and Wallemiales have a
specific pattern of HMGR regulation, which differs from salt-sensitive and
moderately salt-tolerant yeasts. In all of the halophilic fungi studied, HMGR
amounts and activities were the lowest at optimal growth salinity and
increased under hyposaline and hypersaline conditions. This profile paralleled
isoprenylation of cellular proteins in H. werneckii. Inhibition of
HMGR in vivo by lovastatin impaired the halotolerant character. HMGR
may thus serve as an important molecular marker of halotolerance
Expression of fatty-acid-modifying enzymes in the halotolerant black yeast Aureobasidium pullulans (de Bary) G. Arnaud under salt stress
AbstractMultiple tolerance to stressful environmental conditions of the black, yeast-like fungus Aureobasidium pullulans is achieved through different adaptations, among which there is the restructuring of the lipid composition of their membranes. Here, we describe three novel genes encoding fatty-acid-modifying enzymes in A. pullulans, along with the levels of their mRNAs under different salinity conditions. High levels of Δ 9−desaturase and Δ12−desaturase mRNAs were seen at high salinities, which were consistent with an increased desaturation of the fatty acids in the cell membranes. Elevated levels of elongase mRNA were also detected. Surprisingly, increases in the levels of these mRNAs were also seen following hypo-osmotic shock, while hyperosmotic shock had exactly the opposite effect, demonstrating that data that are obtained from up-shift and down-shift salinity studies should be interpreted with caution
Re-entrant ferroelectricity in liquid crystals
The ferroelectric (Sm C) -- antiferroelectric (Sm C) -- reentrant
ferroelectric (re Sm C) phase temperature sequence was observed for system
with competing synclinic - anticlinic interactions. The basic properties of
this system are as follows (1) the Sm C phase is metastable in temperature
range of the Sm C stability (2) the double inversions of the helix
handedness at Sm C -- Sm C and Sm C% -- re-Sm C phase
transitions were found (3) the threshold electric field that is necessary to
induce synclinic ordering in the Sm C phase decreases near both Sm
C -- Sm C and Sm C -- re-Sm C phase boundaries, and it has
maximum in the middle of the Sm C stability region. All these properties
are properly described by simple Landau model that accounts for nearest
neighboring layer steric interactions and quadrupolar ordering only.Comment: 10 pages, 5 figures, submitted to PR
Adaptation of extremely halotolerant black yeast Hortaea werneckii to increased osmolarity: a molecular perspective at a glance
Halophilic adaptations have been studied almost exclusively on prokaryotic
microorganisms. Discovery of the black yeast Hortaea werneckii as the
dominant fungal species in hypersaline waters enabled the introduction of a
new model organism to study the mechanisms of salt tolerance in eukaryotes.
Its strategies of cellular osmotic adaptations on the physiological and
molecular level revealed novel, intricate mechanisms to combat fluctuating
salinity. H. werneckii is an extremely halotolerant eukaryotic
microorganism and thus a promising source of transgenes for osmotolerance
improvement of industrially important yeasts, as well as in crops
The peculiarities of cross-correlation between two secondary precursors - radon and magnetic field variations, induced by stress transfer changes
A model of precursor manifestation mechanisms, stimulated by tectonic
activity and some peculiarities of observer strategy, whose main task is the
effective measurement of precursors in the spatial area of their occurrence on
the Earth's daylight, are considered. In particular, the applicability of
Dobrovolsky's approximation is analyzed, when an unperturbed medium
(characterized by the simple shear state) and the area of tectonic activity
(local inhomogeneity caused by the change only of shear modulus) are linearly
elastic, and perturbation, in particular, surface displacement is calculated as
a difference of the solutions of two independent static problems of the theory
of elasticity with the same boundary condition on the surface. Within the
framework of this approximation a formula for the spatial distribution (of
first component) of magnetic field variations caused by piezomagnetic effect in
the case of perturbed regular medium, which is in simple shear state is
derived. Cogent arguments in favor of linear dependence between the radon
spatial distribution and conditional deformation are obtained.
Changes in magnetic field strength and radon concentrations were measured
along a tectonomagnetic profile of the total length of 11 km in the
surroundings of the "Academician Vernadsky" Station on the Antarctic Peninsula
(W 64{\deg}16', S 65{\deg}15'). Results showed a positive correlation between
the annual surface radon concentration and annual changes of magnetic field
relative to a base point, and also the good coincidence with theoretical
calculation.Comment: 27 pages, 11 figures, 3 tables (a substantially revised and extended
edition; v3 -- some analysis of recent publications added
Molecular simulation of chevrons in confined smectic liquid crystals
Chevron structures adopted by confined smectic liquid crystals
are investigated via molecular dynamics simulations of the Gay-Berne
model. The chevrons are formed by quenching nematic films confined
between aligning planar substrates whose easy axes have opposing
azimuthal components. When the substrates are perfectly smooth, the
chevron formed migrates rapidly towards one of the confining walls to
yield a tilted layer structure. However, when substrate roughness is
included, by introducing a small-amplitude modulation to the particle-
substrate interaction well-depth, a symmetric chevron is formed which
remains stable over sufficiently long runtimes for detailed structural
information, such as the relevant order parameters and director orien-
tation, to be determined. For both smooth and rough boundaries, the
smectic order parameter remains non-zero across the entire chevron,
implying that layer identity is maintained across the chevron tip. Also, when the surface-stabilised chevron does eventually revert to a tilted layer structure, it does so via surface slippage, such that layer integrity is maintained throughout the chevron to tilted layer relaxation process.
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Prevalence of H63D, S65C and C282Y hereditary hemochromatosis gene mutations in Slovenian population by an improved high-throughput genotyping assay
<p>Abstract</p> <p>Background</p> <p>Hereditary hemochromatosis (HH) is a common genetic disease characterized by excessive iron overload that leads to multi-organ failure. Although the most prevalent genotype in HH is homozygosity for C282Y mutation of the <it>HFE </it>gene, two additional mutations, H63D and S65C, appear to be associated with a milder form of HH. The aim of this study was to develop a high-throughput assay for <it>HFE </it>mutations screening based on TaqMan technology and to determine the frequencies of <it>HFE </it>mutations in the Slovenian population.</p> <p>Methods</p> <p>Altogether, 1282 randomly selected blood donors from different Slovenian regions and 21 HH patients were analyzed for the presence of <it>HFE </it>mutations by an in-house developed real-time PCR assay based on TaqMan technology using shorter non-interfering fluorescent single nucleotide polymorphism (SNP)-specific MGB probes. The assay was validated by RFLP analysis and DNA sequencing.</p> <p>Results</p> <p>The genotyping assay of the H63D, S65C and C282Y mutations in the <it>HFE </it>gene, based on TaqMan technology proved to be fast, reliable, with a high-throughput capability and 100% concordant with genotypes obtained by RFLP and DNA sequencing. The observed frequency of C282Y homozygotes in the group of HH patients was only 48%, others were of the heterogeneous <it>HFE </it>genotype. Among 1282 blood donors tested, the observed H63D, S65C and C282Y allele frequency were 12.8% (95% confidence interval (CI) 11.5 – 14.2%), 1.8% (95% CI 1.4 – 2.5%) and 3.6% (95% CI 3.0 – 4.5%), respectively. Approximately 33% of the tested subjects had at least one of the three HH mutations, and 1% of them were C282Y homozygotes or compound heterozygotes C282Y/H63D or C282Y/S65C, presenting an increased risk for iron overload disease. A significant variation in H63D allele frequency was observed for one of the Slovenian regions.</p> <p>Conclusion</p> <p>The improved real-time PCR assay for H63D, S65C and C282Y mutations detection is accurate, fast, cost-efficient and ready for routine screening and diagnostic procedures. The genotype frequencies in the Slovenian population agree with those reported for the Central European populations although some deviations where observed in comparison with other populations of Slavic origin. Regional distribution of the mutations should be considered when planning population screening.</p
Structural transitions in surface-stabilized smectic-C cells near the smectic-C–smetic-A phase-transition temperature
This study continues the development of the Landau–de Gennes theory of chevron structure in a surface-stabilized Sm-C liquid crystal cell. In this paper we study in detail the consequences of varying the magnitude of the planar surface anchoring. The strength of the anchoring is found to govern the order of the phases close to the Sm-A–Sm-C phase transition. Depending on the strength of the anchoring, we find two possible transition sequences: (a) Sm-A?bookshelf Sm-C?nonplanar chevron; (b) Sm-A?planar chevron?nonplanar chevron