Broken flow symmetry explains the dynamics of small particles in deterministic lateral displacement arrays

Deterministic lateral displacement (DLD) is a technique for size fractionation of particles in continuous flow that has shown great potential for biological applications. Several theoretical models have been proposed, but experimental evidence has demonstrated that a rich class of intermediate migration behavior exists, which is not predicted. We present a unified theoretical framework to infer the path of particles in the whole array on the basis of trajectories in a unit cell. This framework explains many of the unexpected particle trajectories reported and can be used to design arrays for even nanoscale particle fractionation. We performed experiments that verify these predictions and used our model to develop a condenser array that achieves full particle separation with a single fluidic input.

Nanoscale lateral displacement arrays for the separation of exosomes and colloids down to 20 nm

Deterministic lateral displacement (DLD) pillar arrays are an efficient technology to sort, separate and enrich micrometre-scale particles, which include parasites, bacteria, blood cells and circulating tumour cells in blood. However, this technology has not been translated to the true nanoscale, where it could function on biocolloids, such as exosomes. Exosomes, a key target of 'liquid biopsies', are secreted by cells and contain nucleic acid and protein information about their originating tissue. One challenge in the study of exosome biology is to sort exosomes by size and surface markers. We use manufacturable silicon processes to produce nanoscale DLD (nano-DLD) arrays of uniform gap sizes ranging from 25 to 235 nm. We show that at low Péclet (Pe) numbers, at which diffusion and deterministic displacement compete, nano-DLD arrays separate particles between 20 to 110 nm based on size with sharp resolution. Further, we demonstrate the size-based displacement of exosomes, and so open up the potential for on-chip sorting and quantification of these important biocolloids.

Ultrafast MR imaging in pediatric neuroradiology

Purpose: To compare the diagnostic information obtained from ultrafast MR imaging with standard MR imaging techniques in pediatric neuroradiology. The goal was to judge whether ultrafast methods can be used to replace standard methods and reduce the need for sedation or general anesthesia as a result of the considerably shorter scan times.

Material and Methods: Our prospective study involved 125 patients. Routine clinical imaging was performed along with two ultrafast methods. Single shot fast spin echo (SSFSE) was used to give T2-weighted images and an echo planar imaging (EPI) sequence to provide a T1-weighted images.

The ultrafast images were presented to an experienced neuroradiologist who was also given the information present on the initial referral card. These reports based on the ultrafast images were then compared with the formal radiologic report made solely on the basis of the standard imaging.

Results: The overall sensitivity and specificity for ultrafast imaging when compared to the reference standard were 78% and 98% with positive and negative predictive values of 98% and 76%. Pathologies characterized by small areas of subtle T2 prolongation were difficult or impossible to see on the ultrafast images but otherwise they provided reliable information.

Conclusions: This paper demonstrates that ultrafast MR imaging can diagnose many pediatric intracranial abnormalities as well as standard methods. Anatomic resolution limits its capacity to define subtle developmental anomalies and contrast resolution limitations of the ultrafast methods reduce the detection of pathology characterized by subtle T2 prolongation.

Restricting feeding to the active phase in middle-aged mice attenuates adverse metabolic effects of a high-fat diet

Time-restricted feeding ameliorates the deleterious effects of a high-fat diet on body weight and metabolism in young adult mice. Because obesity is highly prevalent in the middle-aged population, this study tested the hypothesis that time-restricted feeding alleviates the adverse effects of a high-fat diet in male middle-aged (12months) mice. C57BL6/J mice were fed one of three diets for 21-25weeks: 1) high-fat diet (60% total calories from fat) ad-libitum (HFD-AL), 2) HFD, time-restricted feeding (HFD-TRF), and 3) low-fat diet (10% total calories from fat) ad-libitum (LFD-AL) (n=15 each). HFD-TRF mice only had food access for 8h/day during their active period. HFD-TRF mice gained significantly less weight than HFD-AL mice (~20% vs 55% of initial weight, respectively). Caloric intake differed between these groups only during the first 8weeks and accounted for most but not all of their body weight difference during this time. TRF of a HFD lowered glucose tolerance in terms of incremental area under the curve (iAUC) (p<0.02) to that of LFD-AL mice. TRF of a HFD lowered liver weight (p<0.0001), but not retroperitoneal or epididymal fat pad weight, to that of LFD-AL mice. Neither HFD-AL nor HFD-TRF had any effect on performance in the novel object recognition or object location memory tests. Circulating corticosterone levels either before or after restraint stress were not affected by diet. In conclusion, TRF without caloric restriction is an effective strategy in middle-aged mice for alleviating the negative effects of a HFD on body weight, liver weight, and glucose tolerance.

Thirty years after the Chernobyl accident: What lessons have we learnt?

April 2016 sees the 30(th) anniversary of the accident at the Chernobyl nuclear power plant. As a consequence of the accident populations were relocated in Belarus, Russia and Ukraine and remedial measures were put in place to reduce the entry of contaminants (primarily (134+137)Cs) into the human food chain in a number of countries throughout Europe. Remedial measures are still today in place in a number of countries, and areas of the former Soviet Union remain abandoned. The Chernobyl accident led to a large resurgence in radioecological studies both to aid remediation and to be able to make future predictions on the post-accident situation, but, also in recognition that more knowledge was required to cope with future accidents. In this paper we discuss, what in the authors' opinions, were the advances made in radioecology as a consequence of the Chernobyl accident. The areas we identified as being significantly advanced following Chernobyl were: the importance of semi-natural ecosystems in human dose formation; the characterisation and environmental behaviour of 'hot particles'; the development and application of countermeasures; the "fixation" and long term bioavailability of radiocaesium and; the effects of radiation on plants and animals.

A requirement of serotonergic p38α mitogen-activated protein kinase for peripheral immune system activation of CNS serotonin uptake and serotonin-linked behaviors

Alterations in central serotonin (5-hydroxytryptamine, 5-HT) neurotransmission and peripheral immune activation have been linked to multiple neuropsychiatric disorders, including depression, schizophrenia and autism. The antidepressant-sensitive 5-HT transporter (SERT, SLC6A4), a critical determinant of synaptic 5-HT inactivation, can be regulated by pro-inflammatory cytokine signaling. Systemic innate immune system activation via intraperitoneal lipopolysaccharide (LPS) injection rapidly elevates brain SERT activity and 5-HT clearance. Moreover, the pro-inflammatory cytokine interleukin (IL)-1β rapidly stimulates SERT activity in raphe nerve terminal preparations ex vivo, effects that are attenuated by pharmacological p38 MAPK inhibition. To establish a role of serotonergic p38α MAPK signaling in LPS/IL-1β-induced SERT regulation and attendant behavioral responses, we pursued studies in mice that afford conditional elimination of p38α MAPK in 5-HT neurons (p38α(5HT-)). We found p38α(5HT-) and control (p38α(5HT+)) littermates to be indistinguishable in viability and growth and to express equivalent levels of SERT protein and synaptosomal 5-HT transport activity. Consistent with pharmacological studies, however, IL-1β fails to increase SERT activity in midbrain synaptosomes prepared from p38α(5HT-) animals. Moreover, although LPS elevated plasma corticosterone and central/peripheral pro-inflammatory cytokines in p38α(5HT-) animals, elevations in midbrain SERT activity were absent nor were changes in depressive and anxiety-like behaviors observed. Our studies support an obligate role of p38α MAPK signaling in 5-HT neurons for the translation of immune activation to SERT regulation and 5-HT-modulated behaviors.

Haplosufficient genomic androgen receptor signaling is adequate to protect female mice from induction of polycystic ovary syndrome features by prenatal hyperandrogenization

Polycystic ovary syndrome (PCOS) is associated with reproductive, endocrine, and metabolic abnormalities. Because hyperandrogenism is the most consistent PCOS feature, we used wild-type (WT) and androgen receptor (AR) knockout (ARKO) mice, together with a mouse model of PCOS, to investigate the contribution of genomic AR-mediated actions in the development of PCOS traits. PCOS features were induced by prenatal exposure to dihydrotestosterone (250 μg) or oil vehicle (control) on days 16-18 of gestation in WT, heterozygote, and homozygote ARKO mice. DHT treatment of WT mice induced ovarian cysts (100% vs 0%), disrupted estrous cycles (42% vs 100% cycling), and led to fewer corpora lutea (5.0±0.4 vs 9.8±1.8). However, diestrus serum LH and FSH, and estradiol-induced-negative feedback as well as hypothalamic expression of kisspeptin, neurokinin B, and dynorphin, were unaffected by DHT treatment in WT mice. DHT-treated WT mice exhibited a more than 48% increase in adipocyte area but without changes in body fat. In contrast, heterozygous and homozygous ARKO mice exposed to DHT maintained comparable ovarian (histo)morphology, estrous cycling, and corpora lutea numbers, without any increase in adipocyte size. These findings provide strong evidence that genomic AR signaling is an important mediator in the development of these PCOS traits with a dose dependency that allows even AR haplosufficiency to prevent induction by prenatal androgenization of PCOS features in adult life.

Hydrodynamics of diamond-shaped gradient nanopillar arrays for effective DNA translocation into nanochannels

Effective DNA translocation into nanochannels is critical for advancing genome mapping and future single-molecule DNA sequencing technologies. We present the design and hydrodynamic study of a diamond-shaped gradient pillar array connected to nanochannels for enhancing the success of DNA translocation events. Single-molecule fluorescence imaging is utilized to interrogate the hydrodynamic interactions of the DNA with this unique structure, evaluate key DNA translocation parameters, including speed, extension, and translocation time, and provide a detailed mapping of the translocation events in nanopillar arrays coupled with 10 and 50 μm long channels. Our analysis reveals the important roles of diamond-shaped nanopillars in guiding DNA into as small as 30 nm channels with minimized clogging, stretching DNA to nearly 100% of their dyed contour length, inducing location-specific straddling of DNA at nanopillar interfaces, and modulating DNA speeds by pillar geometries. Importantly, all critical features down to 30 nm wide nanochannels are defined using standard photolithography and fabrication processes, a feat aligned with the requirement of high-volume, low-cost production.

Fixed-gap tunnel junction for reading DNA nucleotides

Previous measurements of the electronic conductance of DNA nucleotides or amino acids have used tunnel junctions in which the gap is mechanically adjusted, such as scanning tunneling microscopes or mechanically controllable break junctions. Fixed-junction devices have, at best, detected the passage of whole DNA molecules without yielding chemical information. Here, we report on a layered tunnel junction in which the tunnel gap is defined by a dielectric layer, deposited by atomic layer deposition. Reactive ion etching is used to drill a hole through the layers so that the tunnel junction can be exposed to molecules in solution. When the metal electrodes are functionalized with recognition molecules that capture DNA nucleotides via hydrogen bonds, the identities of the individual nucleotides are revealed by characteristic features of the fluctuating tunnel current associated with single-molecule binding events.

Carbon nanotube complementary wrap-gate transistors

Among the challenges hindering the integration of carbon nanotube (CNT) transistors in digital technology are the lack of a scalable self-aligned gate and complementary n- and p-type devices. We report CNT transistors with self-aligned gates scaled down to 20 nm in the ideal gate-all-around geometry. Uniformity of the gate wrapping the nanotube channels is confirmed, and the process is shown not to damage the CNTs. Further, both n- and p-type transistors were realized by using the appropriate gate dielectric-HfO2 yielded n-type and Al2O3 yielded p-type-with quantum simulations used to explore the impact of important device parameters on performance. These discoveries not only provide a promising platform for further research into gate-all-around CNT devices but also demonstrate that scalable digital switches with realistic technological potential can be achieved with carbon nanotubes.

Reducing contact resistance in graphene devices through contact area patterning

Performance of graphene electronics is limited by contact resistance associated with the metal-graphene (M-G) interface, where unique transport challenges arise as carriers are injected from a 3D metal into a 2D-graphene sheet. In this work, enhanced carrier injection is experimentally achieved in graphene devices by forming cuts in the graphene within the contact regions. These cuts are oriented normal to the channel and facilitate bonding between the contact metal and carbon atoms at the graphene cut edges, reproducibly maximizing "edge-contacted" injection. Despite the reduction in M-G contact area caused by these cuts, we find that a 32% reduction in contact resistance results in Cu-contacted, two-terminal devices, while a 22% reduction is achieved for top-gated graphene transistors with Pd contacts as compared to conventionally fabricated devices. The crucial role of contact annealing to facilitate this improvement is also elucidated. This simple approach provides a reliable and reproducible means of lowering contact resistance in graphene devices to bolster performance. Importantly, this enhancement requires no additional processing steps.

Proteogenomic analysis of human colon carcinoma cell lines LIM1215, LIM1899, and LIM2405

As part of the genome-wide and chromosome-centric human proteomic project (C-HPP), we have integrated shotgun proteomics approach and a genome-wide transcriptomic approach (RNA-Seq) of a set of human colon cancer cell lines (LIM1215, LIM1899 and LIM2405) that were selected to represent a wide range of pathological states of colorectal cancer. The combination of a standard proteomics approach (1D-gel electrophoresis coupled to LC/ion trap mass spectrometry) and RNA-Seq allowed us to exploit the greater depth of the transcriptomics measurement (∼ 9800 transcripts per cell line) versus the protein observations (∼ 1900 protein identifications per cell line). Conversely, the proteomics data were helpful in identifying both cancer associated proteins with differential expression patterns as well as protein networks and pathways which appear to be deregulated in these cell lines. Examples of potential markers include mortalin, nucleophosmin, ezrin, LASP1, alpha and beta forms of spectrin, exportin, the carcinoembryonic antigen family, EGFR and MET. Interaction analyses identified the large intermediate filament family, the protein folding network and adapter proteins in focal adhesion networks, which included the CDC42 and RHOA signaling pathways that may have potential for identifying phenotypic states representing poorly and moderately differentiated states of CRC, with or without metastases.

The role of kisspeptin and gonadotropin inhibitory hormone in the seasonal regulation of reproduction in sheep

Sheep are seasonal breeders, experiencing an annual period of reproductive quiescence in response to increased photoperiod during the late-winter into spring and renaissance during the late summer. The nonbreeding (anestrous) season is characterized by a reduction in the pulsatile secretion of GnRH from the brain, in part because of an increase in negative feedback activity of estrogen. Neuronal populations in the hypothalamus that produce kisspeptin and gonadotropin-inhibitory hormone (GnIH) appear to be important for the seasonal shift in reproductive activity, and the former are also mandatory for puberty onset. Kisspeptin cells in the arcuate nucleus (ARC) and preoptic area appear to regulate GnRH neurons and transmit sex-steroid feedback signals to these neurons. Moreover, kisspeptin expression in the ARC is markedly up-regulated at the onset of the breeding season, as too are the number of kisspeptin fibers in close apposition to GnRH neurons. The lower levels of kisspeptin seen during the nonbreeding season can be "corrected" by infusion of kisspeptin, which causes ovulation in seasonally acyclic females. The role of GnIH is less clear, but mounting evidence supports a role for this neuropeptide in the inhibitory regulation of both GnRH secretion and gonadotropin release from the pituitary gland. Contrary to kisspeptin, GnIH expression is markedly reduced at the onset of the breeding season. In addition, the number of GnIH fibers in close apposition to GnRH neurons also decreases during this time. Importantly, exogenous GnIH treatment can block both the pulsatile release of LH and the preovulatory LH surge during the breeding season. In summary, it is most likely the integrated function of both these neuropeptide systems that modulate the annual shift in photoperiod to a physiological change in fertility.

Low dose ionizing radiation produces too few reactive oxygen species to directly affect antioxidant concentrations in cells

It has been hypothesized that radiation-induced oxidative stress is the mechanism for a wide range of negative impacts on biota living in radioactively contaminated areas around Chernobyl. The present study tests this hypothesis mechanistically, for the first time, by modelling the impacts of radiolysis products within the cell resulting from radiations (low linear energy transfer β and γ), and dose rates appropriate to current contamination types and densities in the Chernobyl exclusion zone and at Fukushima. At 417 µGy h(-1) (illustrative of the most contaminated areas at Chernobyl), generation of radiolysis products did not significantly impact cellular concentrations of reactive oxygen species, or cellular redox potential. This study does not support the hypothesis that direct oxidizing stress is a mechanism for damage to organisms exposed to chronic radiation at dose rates typical of contaminated environments.

Kisspeptin cells in the ovine arcuate nucleus express prolactin receptor but not melatonin receptor

Melatonin is secreted at night by the pineal gland and governs the reproductive system in seasonal breeders, such as sheep. The mechanism by which melatonin regulates reproduction is not known. The circannual rhythmicity of other factors, including prolactin, is also regulated by photoperiod via changes in melatonin secretion. In sheep, plasma prolactin levels are higher in the nonbreeding season than the breeding season. Kisspeptin, synthesised by neurones in the ovine arcuate nucleus (ARC) and preoptic area, is a key regulator of reproduction through stimulation of gonadotrophin-releasing hormone secretion and its expression in the ARC is reduced during the nonbreeding season. We hypothesised that kisspeptin expression is directly, or indirectly, regulated by melatonin and/or prolactin. We first examined the expression of melatonin receptor (MTNR1A) in kisspeptin (Kiss1 mRNA) neurones in the ARC of ovariectomised (OVX) sheep using double-label in situ hybridisation. MTNR1A mRNA was not expressed by kisspeptin neurones, whereas strong expression was detected in the pars tuberalis. We then examined the expression of the long-form prolactin receptor (PRLR-L) in ARC kisspeptin neurones. In OVX ewes, approximately 60% of kisspeptin neurones expressed PRLR-L mRNA at similar levels in the breeding and nonbreeding seasons. We then aimed to determine whether prolactin treatment during the breeding season regulates kisspeptin expression in the ARC. Continuous central infusion of prolactin (20 μg/h for 7 days) in oestradiol-treated OVX sheep did not alter Kiss1 mRNA expression or luteinising hormone secretion, although it induced substantial phosphorylated signal transducer and activator of transcription 5-immunoreactive nuclei staining in the mediobasal hypothalamus. We conclude that the seasonal change in kisspeptin neurones cannot be regulated directly by melatonin, although it may be a result of changes in prolactin levels. Despite this, kisspeptin expression was unchanged after exogenous prolactin treatment in breeding season ewes.

Changes in water quality of the River Frome (UK) from 1965 to 2009: is phosphorus mitigation finally working?

The water quality of the River Frome, Dorset, southern England, was monitored at weekly intervals from 1965 until 2009. Determinands included phosphorus, nitrogen, silicon, potassium, calcium, sodium, magnesium, pH, alkalinity and temperature. Nitrate-N concentrations increased from an annual average of 2.4 mg l⁻¹ in the mid to late 1960s to 6.0 mg l⁻¹ in 2008-2009, but the rate of increase was beginning to slow. Annual soluble reactive phosphorus (SRP) concentrations increased from 101 μg l⁻¹ in the mid 1960s to a maximum of 190 μg l⁻¹ in 1989. In 2002, there was a step reduction in SRP concentration (average=88 μg l⁻¹ in 2002-2005), with further improvement in 2007-2009 (average=49 μg l⁻¹), due to the introduction of phosphorus stripping at sewage treatment works. Phosphorus and nitrate concentrations showed clear annual cycles, related to the timing of inputs from the catchment, and within-stream bioaccumulation and release. Annual depressions in silicon concentration each spring (due to diatom proliferation) reached a maximum between 1980 and 1991, (the period of maximum SRP concentration) indicating that algal biomass had increased within the river. The timing of these silicon depressions was closely related to temperature. Excess carbon dioxide partial pressures (EpCO₂) of 60 times atmospheric CO₂ were also observed through the winter periods from 1980 to 1992, when phosphorus concentration was greatest, indicating very high respiration rates due to microbial decomposition of this enhanced biomass. Declining phosphorus concentrations since 2002 reduced productivity and algal biomass in the summer, and EpCO₂ through the winter, indicating that sewage treatment improvements had improved riverine ecology. Algal blooms were limited by phosphorus, rather than silicon concentration. The value of long-term water quality data sets is discussed. The data from this monitoring programme are made freely available to the wider science community through the CEH data portal (http://gateway.ceh.ac.uk/).

Abundance and diversity of aquatic macroinvertebrate communities in lakes exposed to Chernobyl-derived ionising radiation

Littoral (lake shore) macroinvertebrate communities were studied in eight natural lakes affected by fallout from the Chernobyl accident. The lakes spanned a range in (137)Cs contamination from 100 to 15500 kBq m(-2) and estimated external dose rates ranged from 0.13 to 30.7 μGy h(-1). General linear models were used to assess whether abundance of individuals, taxon richness, Berger-Parker dominance and Shannon-Wiener diversity varied across the lakes. Step-wise multiple regressions were used to relate variation in total abundance, taxon richness, Berger-Parker dominance, Shannon-Wiener diversity, taxon richness within major groups of macroinvertebrates and abundance of the more common individual taxa to the measured environmental characteristics (conductivity, pH, total hardness and phosphate; lake area, lake maximum depth and total external dose) of the lakes. No evidence was found in this study that the ecological status of lake communities has been influenced by radioactive contamination from the Chernobyl accident. Indeed, the most contaminated lake, Glubokoye, contained the highest richness of aquatic invertebrates. Taxon richness in the eight study lakes varied from 22 (Svyatskoe #7) to 42 (Glubokoye) which spans a range typical for uncontaminated lakes in the region. Since (90)Sr is readily-absorbed by Mollusca, estimated dose rates to this group exceeded those for other invertebrate groups in two lakes (Perstok and Glubokoye). However this study found no association between mollusc diversity or abundance of individual snail species and variation between lakes in the external radiation dose. Indeed Glubokoye, the lake most contaminated by (90)Sr, had the highest richness of freshwater snails per sample (an average of 8.9 taxa per sample).

Transport modulation in Ge/Si core/shell nanowires through controlled synthesis of doped Si shells

Appropriately controlling the properties of the Si shell in Ge/Si core/shell nanowires permits not only passivation of the Ge surface states, but also introduces new interface phenomena, thereby enabling novel nanoelectronics concepts. Here, we report a rational synthesis of Ge/Si core/shell nanowires with doped Si shells. We demonstrate that the morphology and thickness of Si shells can be controlled for different dopant types by tuning the growth parameters during synthesis. We also present distinctly different electrical characteristics that arise from nanowire field-effect transistors fabricated using the synthesized Ge/Si core/shell nanowires with different shell morphologies. Furthermore, a clear transition in the modification of device characteristics is observed for crystalline shell nanowires following removal of the shell using a unique trimming process of successive native oxide formation/etching. Our results demonstrate that the preferred transport path through the nanowire structure can be modulated by appropriately tuning the growth conditions.