Barley AGO4 proteins show overlapping functionality with distinct small RNA-binding properties in heterologous complementation

KEY MESSAGE

Barley AGO4 proteins complement expressional changes of epigenetically regulated genes in Arabidopsis ago4-3 mutant and show a distinct affinity for the 5' terminal nucleotide of small RNAs, demonstrating functional conservation and divergence. The function of Argonaute 4 (AGO4) in Arabidopsis thaliana has been extensively characterized; however, its role in monocots, which have large genomes abundantly supplemented with transposable elements (TEs), remains elusive. The study of barley AGO4 proteins can provide insights into the conserved aspects of RNA-directed DNA methylation (RdDM) and could also have further applications in the field of epigenetics or crop improvement. Bioinformatic analysis of RNA sequencing data identified two active AGO4 genes in barley, HvAGO4a and HvAGO4b. These genes function similar to AtAGO4 in an Arabidopsis heterologous complementation system, primarily binding to 24-nucleotide long small RNAs (sRNAs) and triggering methylation at specific target loci. Like AtAGO4, HvAGO4B exhibits a preference for binding sRNAs with 5' adenine residue, while also accepting 5' guanine, uracil, and cytosine residues. In contrast, HvAGO4A selectively binds only sRNAs with a 5' adenine residue. The diverse binding capacity of barley AGO4 proteins is reflected in TE-derived sRNAs and in their varying abundance. Both barley AGO4 proteins effectively restore the levels of extrachromosomal DNA and transcript abundancy of the heat-activated ONSEN retrotransposon to those observed in wild-type Arabidopsis plants. Our study provides insight into the distinct binding specificities and involvement in TE regulation of barley AGO4 proteins in Arabidopsis by heterologous complementation.

Rapid and cost-effective molecular karyotyping in wheat, barley, and their cross-progeny by chromosome-specific multiplex PCR

BACKGROUND

Interspecific hybridisation is a powerful tool for increasing genetic diversity in plant breeding programmes. Hexaploid wheat (Triticum aestivum, 2n = 42) × barley (Hordeum vulgare, 2n = 14) intergeneric hybrids can contribute to the transfer of agronomically useful traits by creating chromosome addition or translocation lines as well as full hybrids. Information on the karyotype of hybrid progenies possessing various combinations of wheat and barley chromosomes is thus essential for the subsequent breeding steps. Since the standard technique of chromosome in situ hybridisation is labour-intensive and requires specific skills. a routine, cost-efficient, and technically less demanding approach is beneficial both for research and breeding.

RESULTS

We developed a Multiplex Polymerase Chain Reaction (MPCR) method to identify individual wheat and barley chromosomes. Chromosome-specific primer pairs were designed based on the whole genome sequences of 'Chinese Spring' wheat and 'Golden Promise' barley as reference cultivars. A pool of potential primers was generated by applying a 20-nucleotide sliding window with consecutive one-nucleotide shifts on the reference genomes. After filtering for optimal primer properties and defined amplicon sizes to produce an ordered ladder-like pattern, the primer pool was manually curated and sorted into four MPCR primer sets for the wheat A, B, and D sub-genomes, and for the barley genome. The designed MPCR primer sets showed high chromosome specificity in silico for the genome sequences of all 18 wheat and barley cultivars tested. The MPCR primers proved experimentally also chromosome-specific for the reference cultivars as well as for 13 additional wheat and four barley genotypes. Analyses of 16 wheat × barley F1 hybrid plants demonstrated that the MPCR primer sets enable the fast and one-step detection of all wheat and barley chromosomes. Finally, the established genotyping system was fully corroborated with the standard genomic in situ hybridisation (GISH) technique.

CONCLUSIONS

Wheat and barley chromosome-specific MPCR offers a fast, labour-friendly, and versatile alternative to molecular cytogenetic detection of individual chromosomes. This method is also suitable for the high-throughput analysis of distinct (sub)genomes, and, in contrast to GISH, can be performed with any tissue type. The designed primer sets proved to be highly chromosome-specific over a wide range of wheat and barley genotypes as well as in wheat × barley hybrids. The described primer design strategy can be extended to many species with precise genome sequence information.

Targeted mutations in the GW2.1 gene modulate grain traits and induce yield loss in barley

Grain Width and Weight 2 (GW2) is an E3-ubiquitin ligase-encoding gene that negatively regulates the size and weight of the grain in cereal species. Therefore, disabling GW2 gene activity was suggested for enhancing crop productivity. We show here that CRISPR/Cas-mediated mutagenesis of the barley GW2.1 homologue results in the development of elongated grains and increased protein content. At the same time, GW2.1 loss of function induces a significant grain yield deficit caused by reduced spike numbers and low grain setting. We also show that the converse effect caused by GW2.1 absence on crop yield and protein content is largely independent of cultivation conditions. These findings indicate that the barley GW2.1 gene is necessary for the optimization between yield and grain traits. Altogether, our data show that the loss of GW2.1 gene activity in barley is associated with pleiotropic effects negatively affecting the development of generative organs and consequently the grain production. Our findings contribute to the better understanding of grain development and the utilisation of GW2.1 control in quantitative and qualitative genetic improvement of barley.

Plasticity of parental CENH3 incorporation into the centromeres in wheat × barley F1 hybrids

Incorporating the centromere-specific histone H3 protein CENH3 into the centromeric nucleosomes is indispensable for accurate centromere function and balanced chromosome segregation in most eukaryotes, including higher plants. In the cell nuclei of interspecific hybrids, divergent centromeric DNAs cohabit and lead the corresponding parental chromosomes through the mitotic and meiotic cell divisions. Depending on the transmission of the parental chromosomes carrying the CENH3-encoding genes, CENH3 proteins from one or both parents may be present in these hybrids. The incorporation of parental CENH3 proteins into the divergent centromeres and their role in the chromosome elimination process in interspecific hybrids is still poorly understood. Here, we produced wheat × barley F1 hybrids that carried different combinations of barley chromosomes with genes encoding for either one (αCENH3) or both barley CENH3 protein variants (α- and βCENH3). We generated specific antibodies distinguishing between the wheat CENH3 proteins and barley αCENH3 and applied them together with FISH probes to detect the precise pattern of parental CENH3 deposition into the wheat and barley centromeric nucleosomes. Analysis of somatic and meiotic nuclei of the wheat × barley hybrids revealed the plasticity of the maternal (wheat) CENH3 proteins to become incorporated into the paternal (barley) centromeric nucleosomes. However, no evidence for paternal CENH3 plasticity was detected in this study. The significance of the unilateral centromere plasticity and possible patterns of CENH3 incorporation into centromeres in interspecific hybrids are discussed.

Development and validation of a sleep questionnaire, SNoRE 3.0, to evaluate sleep in companion dogs

Disturbances in the sleep-wake cycle are a debilitating, yet rather common condition not only in humans, but also in family dogs. While there is an emerging need for easy-to-use tools to document sleep alterations (in order to ultimately treat and/or prevent them), the veterinary tools which yield objective data (e.g. polysomnography, activity monitors) are both labor intensive and expensive. In this study, we developed a modified version of a previously used sleep questionnaire (SNoRE) and determined criterion validity in companion dogs against polysomnography and physical activity monitors (PAMs). Since a negative correlation between sleep time and cognitive performance in senior dogs has been demonstrated, we evaluated the correlation between the SNoRE scores and the Canine Dementia Scale (CADES, which includes a factor concerning sleep). There was a significant correlation between SNoRE 3.0 questionnaire scores and polysomnography data (latency to NREM sleep, ρ = 0.507, p < 0.001) as well as PAMs' data (activity between 1:00 and 3:00 AM, p < 0.05). There was a moderate positive correlation between the SNoRE 3.0 scores and the CADES scores (ρ = 0.625, p < 0.001). Additionally, the questionnaire structure was validated by a confirmatory factor analysis, and it also showed an adequate test-retest reliability. In conclusion the present paper describes a valid and reliable questionnaire tool, that can be used as a cost-effective way to monitor dog sleep in clinical settings.

[Access to health care throughout the country]

The legal basis for describing the regional care situation is based on the adjusted supply rate of the 'demand planning guideline'. However, it provides only limited information about the accessibility of medical care which is crucial for the reality of patients' lives. The aim of this review is to present geographic approaches that spatially measure access to dermatological care in its physical and digital dimension. Here, on the one hand, the classical geographic parameter 'accessibility' is addressed, and on the other hand, data from the Federal Ministry of Transport and Digital Infrastructure (BMVI) on broadband coverage are presented as access parameters of teledermatological applications. In addition to the methodological approach, limitations and potentials in the interpretation of the results, minimum standards are also considered. The access parameters presented here make it possible to investigate spatial disparities and to present them clearly via cartographic representations. While the example of accessibility with a car shows almost area-wide access to the nearest dermatology practice (≤ 30 min), investigations on public transport accessibility reveal rather heterogeneous accessibility. Particularly in the identification of 'dual care gaps', sub-areas with poor physical and digital accessibility, these approaches could support and advance the application of alternative care models. However, the approaches presented here focus on potential accessibility. Further dimensions on actual physician utilisation or availability-also with regard to minimum standards-should be the subject of future research.

[Methods for analysing spatial data : Using the example of skin cancer prevalence in Germany]

BACKGROUND

Studies show a spatial variation in skin cancer frequencies, but the causes have not been fully understood. When analysing spatial patterns and correlations, different approaches need to be considered, as the data have special features due to their spatial structure.

AIM OF THE STUDY

Why the spatial consideration of skin cancer frequencies is important at all, and which methods of analysis are useful is considered in more detail in this article. The article provides an introduction and overview of statistical methods that are important for the spatial analysis of skin cancer frequencies.

MATERIALS AND METHODS

At first it is shown which descriptive methods, such as statistical smoothing, can be applied. Next, spatial cluster and regression analyses will be discussed. Testing for spatial autocorrelation will be considered.

RESULTS

In particular, the spatial dependence of the data on neighbouring regions, which if ignored can lead to biased estimates, is of particular importance in the analysis of spatial data and requires special spatial analysis methods.

DISCUSSION

This article provides an introduction and overview of statistical methods relevant to the spatial analysis of skin cancers.

Regional variations in the use of statutory skin cancer screenings in Germany: population-based spatial multisource analysis

BACKGROUND

Due to the increasing incidence of skin cancer, programmes for the prevention of skin cancer have been developed and implemented in Germany. However, utilization of skin cancer screenings shows marked regional differences. Reasons and predictors of such variations are unclear.

OBJECTIVES

The objective of the study is to identify predictors for regional use of skin cancer screening variations in Germany.

METHODS

Analysis of the population set of ambulatory claims data (2009-2015) of the statutory health insurances (SHI) in Germany (70.2 million people in 2015). Skin cancer screening utilization rate was determined on county level. Descriptive, cluster and multivariate analyses were performed to identify spatial patterns in skin cancer screening utilization.

RESULTS

Overall, 6.5-7.9 million people participated in skin cancer screenings. Utilization rates of people ≥35 years of age were 9.74% (2009) and 10.96% (2015). Marked regional variations were identified between the counties. Dermatologists in Saxony and Westphalia-Lippe as well as general practitioners in Lower Saxony and North Rhine showed particularly high utilization rates. Multiple regression analyses demonstrated e.g. positive associations between the skin cancer screening utilization rates and employees with higher vocational qualifications and shorter travel time by car to the nearest major urban centre.

CONCLUSION

Utilization rates of skin cancer screening vary largely in Germany with specific spatial patterns. Multivariate analyses demonstrate associations with socio-economic and geographical determinants. The results indicate the importance of health policy measures. These should be used in a more targeted manner in the regions in order to increase utilization of skin cancer screening.

Could vectors' fear of predators reduce the spread of plant diseases?

Predators influence the behaviour of prey and by doing so they potentially reduce pathogen transmission by a vector. Arthropod predators have been shown to reduce the consumption of plant biomass by pest herbivores, but their cascading non-consumptive effect on vector insects' feeding behaviour and subsequent pathogen transmission has not been investigated experimentally before. Here we experimentally examined predator-mediated pathogen transmission mechanisms using the plant pathogen Wheat Dwarf Virus that is transmitted by the leafhopper, Psammotettix alienus. We applied in situ hybridization to localize which leaf tissues were infected with transmitted virus DNA in barley host plants, proving that virus occurrence is restricted to phloem tissues. In the presence of the spider predator, Tibellus oblongus, we recorded the within leaf feeding behaviour of the herbivore using electrical penetration graph. The leafhopper altered its feeding behaviour in response to predation risk. Phloem ingestion, the feeding phase when virus acquisition occurs, was delayed and was less frequent. The phase when pathogen inoculation takes place, via the secretion of virus infected vector saliva, was shorter when predator was present. Our study thus provides experimental evidence that predators can potentially limit the spread of plant pathogens solely through influencing the feeding behaviour of vector organisms.

Probing the Interlayer Exciton Physics in a MoS2/MoSe2/MoS2 van der Waals Heterostructure

Stacking atomic monolayers of semiconducting transition metal dichalcogenides (TMDs) has emerged as an effective way to engineer their properties. In principle, the staggered band alignment of TMD heterostructures should result in the formation of interlayer excitons with long lifetimes and robust valley polarization. However, these features have been observed simultaneously only in MoSe₂/WSe₂ heterostructures. Here we report on the observation of long-lived interlayer exciton emission in a MoS₂/MoSe₂/MoS₂ trilayer van der Waals heterostructure. The interlayer nature of the observed transition is confirmed by photoluminescence spectroscopy, as well as by analyzing the temporal, excitation power, and temperature dependence of the interlayer emission peak. The observed complex photoluminescence dynamics suggests the presence of quasi-degenerate momentum-direct and momentum-indirect bandgaps. We show that circularly polarized optical pumping results in long-lived valley polarization of interlayer exciton. Intriguingly, the interlayer exciton photoluminescence has helicity opposite to the excitation. Our results show that through a careful choice of the TMDs forming the van der Waals heterostructure it is possible to control the circular polarization of the interlayer exciton emission.

[Letter to the Editor] Comparison of small RNA next-generation sequencing with and without isolation of small RNA fraction

Address correspondence to Ferenc Marincs, Agricultural Biotechnology Institute, NARIC, Szent-Györgyi Albert u. 4., Gödöllö, Hungary. E-mail: marincs.ferenc@abc.naik.hu.

Polycistronic artificial miRNA-mediated resistance to Wheat dwarf virus in barley is highly efficient at low temperature

Infection of Wheat dwarf virus (WDV) strains on barley results in dwarf disease, imposing severe economic losses on crop production. As the natural resistance resources against this virus are limited, it is imperative to elaborate a biotechnological approach that will provide effective and safe immunity to a wide range of WDV strains. Because vector insect-mediated WDV infection occurs during cool periods in nature, it is important to identify a technology which is effective at lower temperature. In this study, we designed artificial microRNAs (amiRNAs) using a barley miRNA precursor backbone, which target different conservative sequence elements of the WDV strains. Potential amiRNA sequences were selected to minimize the off-target effects and were tested in a transient sensor system in order to select the most effective constructs at low temperature. On the basis of the data obtained, a polycistronic amiRNA precursor construct (VirusBuster171) was built expressing three amiRNAs simultaneously. The construct was transformed into barley under the control of a constitutive promoter. The transgenic lines were kept at 12-15 °C to mimic autumn and spring conditions in which major WDV infection and accumulation take place. We were able to establish a stable barley transgenic line displaying resistance to insect-mediated WDV infection. Our study demonstrates that amiRNA technology can be an efficient tool for the introduction of highly efficient resistance in barley against a DNA virus belonging to the Geminiviridae family, and this resistance is effective at low temperature where the natural insect vector mediates the infection process.

Vacuum ultraviolet excitation luminescence spectroscopy of few-layered MoS2

We report on vacuum ultraviolet (VUV) excited photoluminescence (PL) spectra emitted from a chemical vapor deposited MoS2 few-layered film. The excitation spectrum was recorded by monitoring intensities of PL spectra at ~1.9 eV. A strong wide excitation band peaking at 7 eV was found in the excitation. The PL excitation band is most intensive at liquid helium temperature and completely quenched at 100 K. Through first-principles calculations of photoabsorption in MoS2, the excitation was explicated and attributed to transitions of electrons from p- and d- type states in the valence band to the d- and p-type states in the conduction band. The obtained photon-in/photon-out results clarify the excitation and emission behavior of the low dimensional MoS2 when interacting with the VUV light sources.

Electrochemical Reaction in Single Layer MoS2: Nanopores Opened Atom by Atom

Ultrathin nanopore membranes based on 2D materials have demonstrated ultimate resolution toward DNA sequencing. Among them, molybdenum disulfide (MoS2) shows long-term stability as well as superior sensitivity enabling high throughput performance. The traditional method of fabricating nanopores with nanometer precision is based on the use of focused electron beams in transmission electron microscope (TEM). This nanopore fabrication process is time-consuming, expensive, not scalable, and hard to control below 1 nm. Here, we exploited the electrochemical activity of MoS2 and developed a convenient and scalable method to controllably make nanopores in single-layer MoS2 with subnanometer precision using electrochemical reaction (ECR). The electrochemical reaction on the surface of single-layer MoS2 is initiated at the location of defects or single atom vacancy, followed by the successive removals of individual atoms or unit cells from single-layer MoS2 lattice and finally formation of a nanopore. Step-like features in the ionic current through the growing nanopore provide direct feedback on the nanopore size inferred from a widely used conductance vs pore size model. Furthermore, DNA translocations can be detected in situ when as-fabricated MoS2 nanopores are used. The atomic resolution and accessibility of this approach paves the way for mass production of nanopores in 2D membranes for potential solid-state nanopore sequencing.

Timing and presence of an attachment person affect sensitivity of aggression tests in shelter dogs

Different test series have been developed and used to measure behaviour in shelter dogs in order to reveal individuals not suitable for re-homing due to their aggressive tendencies. However, behavioural tests previously validated on pet dogs seem to have relatively low predictability in the case of shelter dogs. Here, we investigate the potential effects of (1) timing of the behaviour testing and (2) presence of a human companion on dogs' aggressive behaviour. In Study I, shelter dogs (n=25) showed more aggression when tested in a short test series two weeks after they had been placed in the shelter compared to their responses in the same test performed 1-2 days after arrival. In Study II, the occurrence of aggressive behaviour was more probable in pet dogs (n=50) in the presence than in the absence of their passive owner. We conclude that the sensitivity of aggression tests for shelter dogs can be increased by running the test in the presence of a caretaker, and after some period of acclimatisation to the new environment. This methodology could also provide better chances for successful adoption.

Detecting the translocation of DNA through a nanopore using graphene nanoribbons

Solid-state nanopores can act as single-molecule sensors and could potentially be used to rapidly sequence DNA molecules. However, nanopores are typically fabricated in insulating membranes that are as thick as 15 bases, which makes it difficult for the devices to read individual bases. Graphene is only 0.335 nm thick (equivalent to the spacing between two bases in a DNA chain) and could therefore provide a suitable membrane for sequencing applications. Here, we show that a solid-state nanopore can be integrated with a graphene nanoribbon transistor to create a sensor for DNA translocation. As DNA molecules move through the pore, the device can simultaneously measure drops in ionic current and changes in local voltage in the transistor, which can both be used to detect the molecules. We examine the correlation between these two signals and use the ionic current measurements as a real-time control of the graphene-based sensing device.

Abnormal white matter on diffusion tensor imaging in children with new-onset seizures

The aim of this study was to use whole brain quantitative analysis to identify impaired white matter (WM) integrity using diffusion tensor imaging (DTI) in children with new-onset seizures. Thirty-five children with new-onset seizures and normal MRI were recruited. Twelve patients had generalized seizures, and 23 had partial seizures. Thirty-one healthy controls were also recruited. Whole brain fractional anisotropy (FA), apparent diffusion coefficient (ADC), radial diffusivity (RD) and axial diffusivity (AD) maps of patients were compared to controls, corrected for multiple comparisons. There was significantly reduced FA in left postcentral, elevated RD in left posterior cingulum and right external capsule, elevated AD in left middle temporal WM and left thalamus, and reduced AD in left anterior cingulum, left temporal, and right supramarginal WM in patients relative to controls. Patients with partial epilepsy showed elevated RD in bilateral posterior cingulum, increased AD in left middle frontal, reduced AD in left temporal, right parietal and right supramarginal WM. Patients with generalized epilepsy showed increased AD in right cerebellum, and reduced AD in left anterior cingulum and left middle temporal WM. The findings indicate that impaired WM integrity with abnormal myelin and axons is present in children with new-onset seizures.

Visibility of dichalcogenide nanolayers

Dichalcogenides with the common formula MX(2) are layered materials with electrical properties that range from semiconducting to superconducting. Here, we describe optimal imaging conditions for the optical detection of ultrathin, two-dimensional dichalcogenide nanocrystals containing single, double and triple layers of MoS(2), WSe(2) and NbSe(2). A simple optical model is used to calculate the contrast for nanolayers deposited on wafers with varying thicknesses of SiO(2). The model is extended for imaging using the green channel of a video camera. Using AFM and optical imaging we confirm that single layers of MoS(2) and WSe(2) can be detected on 90 and 270 nm SiO(2) using optical means. By measuring contrast under broadband green illumination we are also able to distinguish between nanostructures containing single, double and triple layers of MoS(2) and WSe(2.) We observe and discuss discrepancies in the case of NbSe(2).

Single-layer MoS2 transistors

Two-dimensional materials are attractive for use in next-generation nanoelectronic devices because, compared to one-dimensional materials, it is relatively easy to fabricate complex structures from them. The most widely studied two-dimensional material is graphene, both because of its rich physics and its high mobility. However, pristine graphene does not have a bandgap, a property that is essential for many applications, including transistors. Engineering a graphene bandgap increases fabrication complexity and either reduces mobilities to the level of strained silicon films or requires high voltages. Although single layers of MoS(2) have a large intrinsic bandgap of 1.8 eV (ref. 16), previously reported mobilities in the 0.5-3 cm(2) V(-1) s(-1) range are too low for practical devices. Here, we use a halfnium oxide gate dielectric to demonstrate a room-temperature single-layer MoS(2) mobility of at least 200 cm(2) V(-1) s(-1), similar to that of graphene nanoribbons, and demonstrate transistors with room-temperature current on/off ratios of 1 × 10(8) and ultralow standby power dissipation. Because monolayer MoS(2) has a direct bandgap, it can be used to construct interband tunnel FETs, which offer lower power consumption than classical transistors. Monolayer MoS(2) could also complement graphene in applications that require thin transparent semiconductors, such as optoelectronics and energy harvesting.

Spontaneous pneumomediastinum after kidney transplantation: case report

Spontaneous pneumomediastinum is a rare condition with nonspecific signs and symptoms. A 39-year-old underwent cadaver kidney transplantation. After an uncomplicated operation, progressive dyspnea of unknown origin developed. Findings at chest radiography suggested pneumomediastinum, which was confirmed at computed tomography. Esophageal or tracheal injury was ruled out. The rapidly developing atelectasis of the left lung necessitated urgent bronchoscopy, which revealed occlusion of the left main bronchus. After removal of the occluding mucus plug, the clinical symptoms immediately improved, and the spontaneous pneumomediastinum resolved within 3 days. Asymptomatic increase in airway secretions in patients receiving peritoneal dialysis may result in mucus plug formation during general anesthesia, which can cause spontaneous pneumomediastinum.

Progressive increase of human papillomavirus carriage rates in potentially malignant and malignant oral disorders with increasing malignant potential

INTRODUCTION

We investigated the potential role of human papillomaviruses (HPVs) in potentially malignant oral disorders, oral leukoplakia (OL) and oral lichen planus (OLP), and in oral squamous cell cancer (OSCC) in an Eastern Hungarian population with a high incidence of OSCC.

METHODS

Excised tumor samples (65 OSCC patients) and exfoliated cells from potentially malignant lesions (from 44 and 119 patients with OL and OLP, respectively) as well as from healthy controls (72 individuals) were analysed. OLPs were classified based on clinical appearance, 61 patients had erosive-atrophic lesions (associated with higher malignancy risk, EA-OLP) and 58 had non-erosive non-atrophic lesions (with lower risk of becoming malignant, non-EA-OLP), respectively. Exfoliated cells collected from apparently healthy mucosa accompanied each lesion sample. HPV was detected by MY/GP polymerase chain reaction (PCR) and genotyped by restriction analysis of amplimers. Copy numbers in lesions were determined using real-time PCR. Prevalence rates, copy number distributions, and association with risk factors and diseases were analysed using chi-square test, t-test, and logistic regression, respectively.

RESULTS

We detected HPVs significantly more frequently in lesions than in controls (P < or = 0.001 in all comparisons). HPV prevalence increased gradually with increasing severity of lesions (32.8, 40.9, and 47.7% in OLP, OL, and OSCC, respectively). Copy number distribution patterns roughly corresponded to prevalence rates, but OLP and OL were comparable. HPV prevalence differed significantly between EA-OLP and non-EA-OLP groups (42.6 vs. 22.4%); EA-OLP group showed a prevalence similar to that found in OL.

CONCLUSION

HPVs may be involved in the development or progression of not only OSCC but also of potentially malignant oral lesions.

LCT 13910 C/T polymorphism, serum calcium, and bone mineral density in postmenopausal women

SUMMARY

LCT 13910 CC genotype is associated with lactose intolerance, a condition often resulting in reduced milk intake. Women with the CC genotype were found to have decreased serum calcium and reduced bone mineral density.

INTRODUCTION

The CC genotype of the 13910 C/T polymorphism of the LCT gene is linked to lactose intolerance and low calcium intake.

METHODS

We studied 595 postmenopausal women, including 267 osteoporotic, 200 osteopenic, and 128 healthy subjects. Genotyping, osteodensitometry, and laboratory measurements were carried out.

RESULTS

Frequency of aversion to milk consumption was 20% for CC genotype and 10% for TT + TC genotypes (p = 0.03). The albumin-adjusted serum calcium was 2.325 +/- 0.09 mmol/L for CC genotype and 2.360 +/- 0.16 mmol/L for TT + TC genotypes (p = 0.031). Bone mineral density (BMD; Z score) was lower in the CC than TT + TC genotypes, respectively, at the radius (0.105 +/- 1.42 vs 0.406 +/- 1.32; p = 0.038), at the total hip (-0.471 +/- 1.08 vs -0.170 +/- 1.09; p = 0.041), and at the Ward's triangle (-0.334 +/- 0.87 vs -0.123 +/- 0.82; p = 0.044).

CONCLUSION

LCT 13910 C/T polymorphism is associated with decreased serum calcium level and lower BMD in postmenopausal women.

Temperature-dependent elasticity of microtubules

Central to the biological function of microtubules is their ability to modify their length which occurs by addition and removal of subunits at the ends of the polymer, both in vivo and in vitro. This dynamic behavior is strongly influenced by temperature. Here, we show that the lateral interaction between tubulin subunits forming microtubule is strongly temperature dependent. Microtubules deposited on prefabricated substrates were deformed in an atomic force microscope during imaging, in two different experimental geometries. Microtubules were modeled as anisotropic, with the Young's modulus corresponding to the resistance of protofilaments to stretching and the shear modulus describing the weak interaction between the protofilaments. Measurements involving radial compression of microtubules deposited on flat mica confirm that microtubule elasticity depends on the temperature. Bending measurements performed on microtubules deposited on lithographically fabricated substrates show that this temperature dependence is due to changing shear modulus, implying that the lateral interaction between the protofilaments is strongly determined by the temperature. These measurements are in good agreement with previously reported measurements of the disassembly rate of microtubules, demonstrating that the mechanical and dynamic properties of microtubules are closely related.

Shrinking a carbon nanotube

We report a method to controllably alter the diameter of an individual carbon nanotube. The combination of defect formation via electron irradiation and simultaneous resistive heating and electromigration in vacuum causes the nanotube to continuously transform into a high-quality nanotube of successively smaller diameter, as observed by transmission electron microscopy. The process can be halted at any diameter. Electronic transport measurements performed in situ reveal a striking dependence of conductance on nanotube geometry. As the diameter of the nanotube is reduced to near zero into the carbon chain regime, we observe negative differential resistance.

Interlayer forces and ultralow sliding friction in multiwalled carbon nanotubes

We describe interlayer force measurements during prolonged, cyclic telescoping motion of a multiwalled carbon nanotube. The force acting between the core and the outer casing is modulated by the presence of stable defects and generally exhibits ultralow friction, below the measurement limit of 1.4 x 10(-15) N/atom and total dissipation per cycle lower than 0.4 meV/atom. Defects intentionally introduced in the form of dangling bonds lead to temporary mechanical dissipation, but the innate ability of nanotubes to self heal rapidly optimizes the atomic structure and restores smooth motion.

Catalytically grown carbon nanotubes of small diameter have a high Young's modulus

Experimental studies of carbon nanotubes (CNTs) obtained through different synthesis routes show considerable variability in their mechanical properties. The strongest CNTs obtained so far had a high Young's modulus of 1 TPa but could only be produced in gram scale quantities. The synthesis by catalytic chemical vapor deposition, a method that holds the greatest potential for large-scale production, gives CNTs with a high defect density. This leads to low Young's modulus values below 100 GPa for multiwall CNTs. Here we performed direct measurements of the mechanical properties of catalytically grown CNTs with only a few walls and find a Young's modulus of 1 TPa. This high value is confirmed for CNTs grown under two different growth conditions where the synthesis parameters such as the hydrocarbon source, catalyst material, and the synthesis temperature were varied. The results indicate that the observed difference in the Young's modulus for the catalytically grown CNTs with high and low numbers of walls is probably related to the growth mechanism of CNT.

Oscillation modes of microtubules

Microtubules are long, filamentous protein complexes which play a central role in several cellular physiological processes, such as cell division transport and locomotion. Their mechanical properties are extremely important since they determine the biological function. In a recently published experiment [Phys. Rev. Lett. 89 (2002) 248101], microtubule's Young's and shear moduli were simultaneously measured, proving that they are highly anisotropic. Together with the known structure, this finding opens the way to better understand and predict their mechanical behavior under a particular set of conditions. In the present study, we modeled microtubules by using the finite elements method and analyzed their oscillation modes. The analysis revealed that oscillation modes involving a change in the diameter of the microtubules strongly depend on the shear modulus. In these modes, the correlation times of the movements are just slightly shorter than diffusion times of free molecules surrounding the microtubule. It could be therefore speculated that the matching of the two timescales could play a role in facilitating the interactions between microtubules and MT associated proteins, and between microtubules and tubulins themselves.

Reinforcement of single-walled carbon nanotube bundles by intertube bridging

During their production, single-walled carbon nanotubes form bundles. Owing to the weak van der Waals interaction that holds them together in the bundle, the tubes can easily slide on each other, resulting in a shear modulus comparable to that of graphite. This low shear modulus is also a major obstacle in the fabrication of macroscopic fibres composed of carbon nanotubes. Here, we have introduced stable links between neighbouring carbon nanotubes within bundles, using moderate electron-beam irradiation inside a transmission electron microscope. Concurrent measurements of the mechanical properties using an atomic force microscope show a 30-fold increase of the bending modulus, due to the formation of stable crosslinks that effectively eliminate sliding between the nanotubes. Crosslinks were modelled using first-principles calculations, showing that interstitial carbon atoms formed during irradiation in addition to carboxyl groups, can independently lead to bridge formation between neighbouring nanotubes.

Nanomechanics of microtubules

We have determined the mechanical anisotropy of a single microtubule by simultaneously measuring the Young's and the shear moduli in vitro. This was achieved by elastically deforming the microtubule deposited on a substrate tailored by electron-beam lithography with a tip of an atomic force microscope. The shear modulus is 2 orders of magnitude lower than the Young's, giving rise to a length-dependent flexural rigidity of microtubules. The temperature dependence of the microtubule's bending stiffness in the (5-40) degrees C range shows a strong variation upon cooling coming from the increasing interaction between the protofilaments.

Distribution of Q188R and N314D mutations in the Hungarian galactosemic population

The most common causes of galactosemia are mutations of the gene coding galactose-1-phosphate uridyltransferase. Since genotype may correlate with the outcome of the disease, and probably not all of the naturally occurring disease associated mutations are described, characterization of the genotypes in different galactosemic populations are in progress. So far the most extensively examined mutations are the Q188R and the N314D. The first one is associated with the classical galactosemia producing a severe clinical picture with an early onset in homozygous patients. The N314D mutation is associated with the Duarte phenotype, which means a milder form of the disease with a later onset of the symptoms. We studied these mutations in the whole Hungarian galactosemic population by PCR and restriction analysis. We have found the frequency of the Q188R mutation at 33.3%, and the N314D mutation at 11.1%. These results differ from other published data in any other populations. Since the incidence of the disease is the same in Hungary as in other European countries, our study suggests that it is worth to investigate for other mutations in the Hungarian population, of which frequency should be consequently higher.

Repeated cardiac pacing extends the time during which canine hearts are protected against ischaemia-induced arrhythmias: role of nitric oxide

Right ventricular pacing in lightly anaesthetized dogs (4x5 min periods at a pacing rate of 220 beats/min) protects against the consequences of coronary artery occlusion when this is initiated 24 h after the pacing stimulus. The main purpose of the present experiments was to determine whether repeating the pacing stimulus, at a time when protection from the initial stimulus had faded (48 h), prolonged the protection afforded against ischaemia-induced ventricular arrhythmias and other ischaemic changes (epicardial ST-segment mapping; changes in the degree of electrical inhomogeneity in the ischaemic region). Dogs were paced on two occasions, with a 48 h period between and, at different times (48, 72 and 96 h) after the second pacing stimulus, were re-anaesthetized and subjected to occlusion of the left anterior descending coronary artery. There was a marked reduction in the severity of ischaemia-induced arrhythmias 48 and 72 h after the second pacing stimulus (reduction in occlusion-induced and reperfusion-induced ventricular fibrillation, e.g. at 72 h 0/11 during occlusion and only 3/11 following reperfusion, compared to 7/21 and 10/21 respectively in the controls P<0.05). The protection had disappeared 96 h following the second pacing stimulus. Changes in ST-segment elevation and in the degree of inhomogeneity largely followed these changes in the severity of ventricular arrhythmias. The results suggest the possibility of maintaining protection against life-threatening arrhythmias following coronary occlusion by repeating a preconditioning pacing stimulus. We also demonstrate that this prolonged protection afforded by repeated cardiac pacing is mediated by nitric oxide, since the marked antiarrhythmic effect observed, e.g. 72 h after the second pacing stimulus, was abolished when S-(2-aminoethyl)-isothiourea (AEST), a particularly selective inhibitor of iNOS, had been administered before coronary artery occlusion.

[Incidence of factor V G1681A (Leiden) mutation in samplings from the Hungarian population]

Thromboembolic disorders affect 0.1% of the adult population. Two main groups of the underlying predisposition factors can be identified: environmental factors (e.g. dietary habits, physical activity, surgical interventions, pregnancy etc.) and several genetic predispositions (e.g. inherited anticoagulant defects). After the discovery of the genetic mutation of factor V, called Leiden mutation, it turned out, that this mutation is responsible for the development of resistance to activated protein C in majority of the cases. The importance of the Leiden mutation is further emphasised by population based investigations, which makes it the most frequent thrombosis risk factor known today. In our study we have identified 43 heterozygotes and 3 homozygotes with Leiden mutation in total of 665 samples. The 6.47% heterozigocy is in the range of earlier reports from Europe. The homozygote/heterozygote distribution deviated from the value predicted by the Hardy-Weinberg law.

[Mutation analysis in the CTG-base multiplication in a family with myotonic dystrophy in three generations]

A PCR-based method with a novel silver staining detection was developed for the determination of CTG repeat number in the 3' untranslated region of the MD-PK gene responsible for myotonic dystrophy. Through the investigation of a family with affected members in three generations the application of the method is presented. According to the results, healthy individuals were verified easily, and the repeat number in patients with mild features or with premutation could be determined accurately. In severe clinical forms, e.g. congenital myopathy, the expansion can be deduced only from the lack of amplification, however, this is also helpful if the segregation of familial alleles is known.