Predominance of a single genotype of Mycobacterium tuberculosis in countries of east Asia

Analysis of the population structure of Mycobacterium tuberculosis strains from the People's Republic of China showed that the vast majority belong to a genetically closely related group. These strains shared the majority of their IS6110 DNA-containing restriction fragments, and also, the DNA polymorphism associated with other repetitive DNA elements, like the polymorphic GC-rich sequence and the direct repeat, was very limited. Because the majority of these strains originated from the province of Beijing, we designated this grouping the "Beijing family" of M. tuberculosis strains. Strains of this family were also found to dominate in neighboring countries such as Mongolia, South Korea, and Thailand, whereas a low prevalence of such strains was observed in countries on other continents. These data indicate that strains of the Beijing family recently expanded from a single ancestor which had a selective advantage. It is speculated that long-term Mycobacterium bovis BCG vaccination may be one of the selective forces implicated in the successful spread of the Beijing genotype.

Stat3-coordinated Lin-28-let-7-HMGA2 and miR-200-ZEB1 circuits initiate and maintain oncostatin M-driven epithelial-mesenchymal transition

Inflammation can act as a crucial mediator of epithelial-to-mesenchymal transition (EMT). In this study, we show that oncostatin M (OSM) is expressed in an autocrine/paracrine fashion in invasive breast carcinoma. OSM stimulation promotes spontaneous lung metastasis of MCF-7 xenografts in nude mice. A conspicuous epigenetic transition was induced by OSM stimulation not only in breast cancer cell lines but also in MCF-7 xenografts in nude mice. The expression of miR-200 and let-7 family members in response to OSM stimulation was downregulated in a signal transducer and activator of transcription factor 3 (Stat3)-dependent manner, resulting in comprehensive alterations of the transcription factors and oncoproteins targeted by these microRNAs. Inhibition of Stat3 activation or the ectopic expression of let-7 and miR-200 effectively reversed the mesenchymal phenotype of breast cancer cells. Stat3 promotes the transcription of Lin-28 by directly binding to the Lin-28 promoter, resulting in the repression of let-7 expression and concomitant upregulation of the let-7 target, high-mobility group A protein 2 (HMGA2). Knock down of HMGA2 significantly impairs OSM-driven EMT. Our data indicate that downregulation of let-7 and miR-200 levels initiates and maintains OSM-induced EMT phenotypes, and HMGA2 acts as a master switch of OSM-induced EMT. These findings highlight the importance of Stat3-coordinated Lin-28B-let-7-HMGA2 and miR-200-ZEB1 circuits in the cytokine-mediated phenotypic reprogramming of breast cancer cells.

MCL1 transgenic mice exhibit a high incidence of B-cell lymphoma manifested as a spectrum of histologic subtypes

Viability-promoting genes such as BCL2 play an important role in human cancer but do not directly cause aggressive tumors. BCL2 transgenic mice develop lymphoma at low frequency, hindering studies of tumorigenesis and its inhibition in the presence of such gene products. MCL1 is a member of the BCL2 family that is highly regulated endogenously and that promotes cell viability and immortalization when introduced exogenously. Mice expressing an MCL1 transgene in hematolymphoid tissues have now been monitored for an extended period and were found to develop lymphoma with long latency and at high probability (more than 85% over 2 years). In most cases, the disease was widely disseminated and of clonal B-cell origin. A variety of histologic subtypes were seen, prominently follicular lymphoma and diffuse large-cell lymphoma. MCL1 thus sets the stage for the development of lymphoma as does BCL2, disease occurring with high probability and recapitulating a spectrum of subtypes as seen in human patients. These findings with the transgene underscore the importance of the normal, highly regulated pattern of MCL1 expression, in addition to providing a model for studying tumorigenesis and its inhibition in the presence of a viability promoting BCL2 family member. (Blood. 2001;97:3902-3909)

Regulation of MCL1 through a serum response factor/Elk-1-mediated mechanism links expression of a viability-promoting member of the BCL2 family to the induction of hematopoietic cell differentiation

Proliferation, differentiation, and apoptosis are tightly regulated during hematopoiesis, allowing amplification along specific lineages while preventing excessive proliferation of immature cells. The MCL1 member of the BCL2 family is up-regulated during the induction of monocytic differentiation (approximately 10-fold with 12-O-tetradecanoylphorbol 13-acetate (TPA)). MCL1 has effects similar to those of BCL2, up-regulation promoting viability, but differs from BCL2 in its rapid inducibility and its pattern of expression. Nuclear factors that regulate MCL1 transcription have now been identified, extending the previous demonstration of signal transduction through mitogen-activated protein kinase. A 162-base pair segment of the human MCL1 5'-flank was found to direct luciferase reporter activity, allowing approximately 10-fold induction with TPA that was suppressible upon inhibition of the extracellular signal-regulated kinase (ERK) pathway. Serum response factor (SRF), Elk-1, and Sp1 bound to cognate sites within this segment, SRF and Elk-1 acting coordinately to affect both basal activity and TPA inducibility, whereas Sp1 affected basal activity only. Thus, the mechanism of the TPA-induced increase in MCL1 expression seen in myelomonocytic cells at early stages of differentiation involves signal transduction through ERKs and transcriptional activation through SRF/Elk-1. This finding provides a parallel to early response genes (e.g. c-FOS and EGR1) that affect maturation commitment in these cells and therefore suggests a means through which enhancement of cell viability may be linked to the induction of differentiation.

Caffeine as a metabolic probe: validation of its use for acetylator phenotyping

The use of two caffeine metabolite ratios for acetylator phenotyping was validated by demonstrating concordance with two sulfamethazine tests in 178 unrelated healthy subjects. The caffeine metabolites used for this purpose were 5-acetylamino-6-amino-3-methyluracil (AAMU), 1-methylxanthine (1X), and 1-methylurate (1U). The ratio AAMU/(AAMU + 1X + 1U), referred to as molar ratio or N-acetyltransferase, was compared with the ratio AAMU/1X. The results indicated that, for screening purposes, the acetylator phenotype can be determined by analysis of a 6-hour urine sample after a cup of coffee or strong tea or a can of caffeine-containing soft drink. The ratio AAMU/1X is the ratio of choice for the study of subjects in whom variability of xanthine oxidase can be neglected; use of the ratio AAMU/(AAMU + 1X + 1U) appears appropriate for special purposes. Gender, ethnic origin, habitual or moderate consumption of coffee, tea, soft drinks, or ethanol, or cigarette smoking have little if any effect on the caffeine tests for acetylator phenotyping.

Inference of gene regulatory networks using S-system: a unified approach

With the increased availability of DNA microarray time-series data, it is possible to discover dynamic gene regulatory networks (GRNs). S-system is a promising model to capture the rich dynamics of GRNs. However, owing to the complexity of the inference problem and limited number of available data comparing to the number of unknown kinetic parameters, S-system can only be applied to a very small GRN with few parameters. This significantly limits its applications. A unified approach to infer GRNs using the S-system model is proposed. In order to discover the structure of large-scale GRNs, a simplified S-system model is proposed that enables fast parameter estimation to determine the major gene interactions. If a detailed S-system model is desirable for a subset of genes, a two-step method is proposed where the range of the parameters will be determined first using genetic programming and recursive least square estimation. Then the mean values of the parameters will be estimated using a multi-dimensional optimisation algorithm. Both the downhill simplex algorithm and modified Powell algorithm are tested for multi-dimensional optimisation. A 50-dimensional synthetic model with 51 parameters for each gene is tested for the applicability of the simplified S-system model. In addition, real measurement data pertaining to yeast protein synthesis are used to demonstrate the effectiveness of the proposed two-step method to identify the detailed interactions among genes in small GRNs.

Retrospective analysis of the Beijing family of Mycobacterium tuberculosis in preserved lung tissues

Direct repeat spoligotyping of 85 paraffin-embedded lung biopsies was used to investigated the occurrence around Beijing of the Beijing family of Mycobacterium tuberculosis. Samples ranged in time from 1956 to 1990. Hybridization patterns were found with 49 (58%) samples, and 45 (92%) produced typical Beijing family patterns extending over the 34-year period.

The stability and fate of a spliced intron from vertebrate cells

Introns constitute most of the length of typical pre-mRNAs in vertebrate cells. Thus, the turnover rate of introns may significantly influence the availability of ribonucleotides and splicing factors for further rounds of transcription and RNA splicing, respectively. Given the importance of intron turnover, it is surprising that there have been no reports on the half-life of introns from higher eukaryotic cells. Here, we determined the stability of IVS1Cbeta1, the first intron from the constant region of the mouse T-cell receptor-beta, (TCR-beta) gene. Using a tetracycline (tet)-regulated promoter, we demonstrate that spliced IVS1Cbeta1 and its pre-mRNA had half-lives of 6.0+/-1.4 min and 3.7+/-1.0 min, respectively. We also examined the half-lives of these transcripts by using actinomycin D (Act.D). Act.D significantly stabilized IVS1Cbeta1 and its pre-mRNA, suggesting that Act.D not only blocks transcription but exerts rapid and direct posttranscriptional effects in the nucleus. We observed that in vivo spliced IVS1Cbeta1 accumulated predominantly as lariat molecules that use a consensus branchpoint nucleotide. The accumulation of IVS1Cbeta1 as a lariat did not result from an intrinsic inability to be debranched, as it could be debranched in vitro, albeit somewhat less efficiently than an adenovirus intron. Subcellular-fractionation and sucrose-gradient analyses showed that most spliced IVS1Cbeta1 lariats cofractionated with pre-mRNA, but not always with mRNA in the nucleus. Some IVS1Cbeta1 also appeared to be selectively exported to the cytoplasm, whereas TCR-beta pre-mRNA remained in the nucleus. This study constitutes the first detailed analysis of the stability and fate of a spliced nuclear intron in vivo.

Thio- and oxoflavopiridols, cyclin-dependent kinase 1-selective inhibitors: synthesis and biological effects

Flavopiridol analogues, thio- and oxoflavopiridols which contain a sulfur (16) or oxygen (18) atom linker between a chromone ring and the hydrophobic side chain, are selective cyclin-dependent kinase 1 (CDK1) inhibitors with an IC(50) of 110 and 130 nM. These analogues were prepared from key intermediate 7 by substituting the ethyl sulfoxide. Enantio pure intermediate piperidone 10 was obtained from the racemic piperidone 8 via a very efficient "dynamic kinetic resolution" in 76% yield. Hydrophobic side chains such as chlorophenyl or tert-butyl produced potent CDK1 inhibitory activity, while hydrophilic side chains such as pyrimidine or aniline caused a severe reduction in CDK inhibitory activity. These analogues are competitive inhibitors with respect to ATP, and therefore activity was dependent upon the CDK subunit without being affected by the cyclin subunit or protein substrate. Thio- and oxoflavopiridols 16 and 18 are not only selective within the CDK family but also discriminated between unrelated serine/threonine and tyrosine protein kinases. CDK1 selective thio- and oxoflavopiridol analogues inhibit the colony-forming ability of multiple human tumor cell lines and possess a unique antiproliferative profile in comparison to flavopiridol.

A spliced intron accumulates as a lariat in the nucleus of T cells

The vast majority of mammalian genes are interrupted by non-coding segments of DNA termed introns. Introns are spliced out of RNA transcripts as lariat structures, and then are typically debranched and rapidly degraded. Here, we described an unusual spliced intron from the constant region of the T cell receptor-beta (TCR-beta) locus that is relatively stable in mammalian cells. This intron, IVS1C beta 1, accumulates as a set of lariat RNA structures with different length tails in the nucleus of T cells. The accumulation of this spliced intron is developmentally regulated during murine thymocyte ontogeny. The property of stability appears to be evolutionarily conserved since the human version of this intron also accumulates in T cells. The stability is selective since other spliced TCR-beta introns do not detectably accumulate in T cells. The unusual stability of this intron does not depend on T cell specific factors since non-T cells transfected with TCR-beta gene constructs also accumulate spliced IVS1C beta 1. The discovery of a mammalian intron that accumulates as a lariat in vivo provides an opportunity to elucidate mechanisms that regulate intron debranching, stability, and nuclear localization.

Quinoxaline N-oxide containing potent angiotensin II receptor antagonists: synthesis, biological properties, and structure-activity relationships

A series of novel quinoxaline heterocycle containing angiotensin II receptor antagonist analogs were prepared. This heterocycle was coupled to the biphenyl moiety via an oxygen atom linker instead of a carbon atom. Many of these analogs exhibit very potent activity and long duration of effect. Interestingly, the N-oxide quinoxaline analog was more potent than the nonoxidized quinoxaline as in the comparison of compounds 5 vs 30. In order to improve oral activity, the carboxylic acid function of these compounds was converted to the double ester. This change did result in an improvement in oral activity as represented by compound 44.

Suberoylanilide hydroxamic acid, a histone deacetylase inhibitor, protects dopaminergic neurons from neurotoxin-induced damage

BACKGROUND AND PURPOSE

Prevention or disease-modifying therapies are critical for the treatment of neurodegenerative disorders such as Alzheimer's disease, Parkinson's disease and Huntington's disease. However, no such intervention is currently available. Growing evidence has demonstrated that administration of histone deacetylase (HDAC) inhibitors ameliorates a wide range of neurologic and psychiatric disorders in experimental models. Suberoylanilide hydroxamic acid (SAHA) was the first HDAC inhibitor approved by the Food and Drug Administration for the sole use of cancer therapy. The purpose of this study was to explore the potential new indications of SAHA for therapy of neurodegenerative diseases in in vitro Parkinson's disease models.

EXPERIMENTAL APPROACH

Mesencephalic neuron-glia cultures and reconstituted cultures were used to investigate neurotrophic and neuroprotective effects of SAHA. We measured toxicity in dopaminergic neurons, using dopamine uptake assay and morphological analysis and expression of neurotrophic substances by enzyme-linked immunosorbent assay and real-time RT PCR.

KEY RESULTS

In mesencephalic neuron-glia cultures, SAHA displayed dose- and time-dependent prolongation of the survival and protection against neurotoxin-induced neuronal death of dopaminergic neurons. Mechanistic studies revealed that the neuroprotective effects of SAHA were mediated in part by promoting release of neurotrophic factors from astroglia through inhibition of histone deacetylation.

CONCLUSION AND IMPLICATIONS

The novel neurotrophic and neuroprotective effects of SAHA demonstrated in this study suggest that further study of this HDAC inhibitor could provide a new therapeutic approach to the treatment of neurodegenerative diseases.

A free-surface capturing method for two fluid flows with moving bodies

A two-fluid solver has been developed for flow problems with both moving solid bodies and free surfaces. The underlying scheme is based on the solution of the incompressible Navier–Stokes equations for a variable density fluid system with a free surface. The cut cell method is used for tracking moving solid boundaries across a stationary background Cartesian grid. The computational domain encompasses fully both fluid regions and the fluid interface is treated as a contact discontinuity in the density field, which is captured automatically without special provision as part of the numerical solution using a time-accurate artificial compressibility method and high resolution Godunov-type scheme. A pressure-splitting algorithm is proposed for the accurate treatment of the normal pressure gradient at the interface in the presence of a gravity term. The Cartesian cut cell technique provides a highly efficient and fully automated process for generating body fitted meshes, which is particularly useful for moving boundary problems. Several test cases have been calculated using the present approach including a moving paddle as a wave generator and the initial stages of entry into still water of rigid wedges. The results compare well with other theoretical results and experimental data. Finally, test cases involving the entry into water and subsequent total immersion of a two-dimensional rigid wedge-shaped body as well as the inverse problem of wedge egress have been calculated to demonstrate the ability of the current method to tackle more general two fluid flows with interface break-up, reconnection, entrapment of one fluid into the other, as well as handling moving bodies of complex geometry.

The role of superoxide anions in the pathogenesis of cerebral vasospasm

BACKGROUND AND PURPOSE

To determine the role of superoxide anions in the pathogenesis of cerebral vasospasm after aneurysmal subarachnoid hemorrhage, we studied the preventive effect of human recombinant copper-zinc superoxide dismutase (h-r SOD) in a rabbit subarachnoid hemorrhage (SAH) model.

METHODS

Forty-five rabbits receiving intracisternal injection of 3 mL autologous nonheparinized blood or 3 mL saline were divided into four groups as follows: (1) saline injected and no treatment (control group, n = 6); (2) blood injected and no treatment (SAH group, n = 20); (3) blood injected and treated by multiple intracisternal injections of 30,000 U of h-r SOD in 0.5 mL saline (SOD group, n = 9); and (4) blood injected and treated by multiple intracisternal injections of 0.5 mL saline (saline group, n = 10). Serial angiograms were performed after the blood injection, and the diameter of the basilar artery was measured. Three animals from the control group and five animals from the SAH and SOD groups each were killed 2 days after SAH, and their basilar arteries were processed for transmission electron microscopic observations.

RESULTS

In the SAH and saline groups, the diameter of the basilar arteries was significantly reduced (28 +/- 14% and 27 +/- 9%, respectively) at 2 days after the blood injection, then recovered to pre-SAH levels until 11 days. In the SOD group, the diameter of the basilar artery was only minimally changed during the follow-up period. Transmission electron microscopy revealed endothelial injury in all basilar arteries in the SAH group, whereas endothelial injury was minimal in the SOD group.

CONCLUSIONS

We determined that h-r SOD prevents the occurrence of vasospasm, possibly as a result of preventing endothelial injury initiated by superoxide anions.

Ex vivo expansion of natural killer cells with high cytotoxicity by K562 cells modified to co-express major histocompatibility complex class I chain-related protein A, 4-1BB ligand, and interleukin-15

A large number of natural killer (NK) cells with high function are expected to generate especially in tumor adoptive immunotherapy. Here K562 cells were genetically modified to co-express major histocompatibility complex class I chain-related protein A (MICA), 4-1BB ligand, and IL-15, called K562-MICA-4-1BBL-IL-15. The modified K562 cells not only promoted activation, proliferation, and survival of NK cells, but also enhanced NK cell cytotoxicity. In long-term culture tests, K562-MICA-4-1BBL-IL-15 cells stimulated NK cell to expand mean 550 folds in 24-day culture and to cover from 14.8% of total peripheral blood monoclonal lymphocytes on day 1 to 86.7% on day 24. Prevalent NK cells after expansion enhanced the ability of killing targets and producing interferon gamma (IFN-γ), and kept high expression of activating receptors. The results indicated that K562-MICA-4-1BBL-IL-15 cells would be developed for expansion of NK cells ex vivo and may have important implications for clinical immunotherapy.

How hard is a colloidal "hard-sphere" interaction?

Poly-12-hydroxystearic acid (PHSA) is widely used as a coating on colloidal spheres to provide a "hard-sphere-type" interaction. These hard spheres have been widely used in fundamental studies of nucleation, crystallization, and glass formation. Most authors describe the interaction as "nearly" hard sphere. In this paper we directly measure this interaction, using layers of PHSA adsorbed onto mica sheets in a surfaces force apparatus. We find that the layers, in appropriate solvents, have no long-range interaction. When the solvent is decahydronaphthalene (decalin), the repulsion rises from zero to the maximum measurable over a distance range of 15-20 nm. The data is converted to equivalent forces between spheres of different diameters, and modeled using a hard core potential. Using zeroth-order perturbation theory and computer simulation, we demonstrate that the equation of state does not deviate from that of a perfect hard-sphere system under any relevant experimental conditions.

Effects of electroacupuncture on gastric migrating myoelectrical complex in dogs

The aim-of this study was to investigate the characteristics of the gastric slow wave during different phases of the migrating myoelectrical complex (MMC) and the effect of electroacupuncture on the MMC. The experiment was performed in eight hound dogs implanted with one pair of bipolar serosal electrodes 2 cm proximal to the pylorus. Gastric myoelectrical activity was recorded for three complete cycles of the MMC in two sessions, one with electroacupuncture at points ST36 and PC6 and the other at sham points. The acupuncture was performed for 30 min in phase I of the second cycle of the MMC. Spectral analysis was performed to compute the frequency and power (amplitude) of the gastric slow wave, whereas blind visual analysis was applied to compute the appearance of spike potentials and the length of each phase of the MMC. It was found that there was a significant difference in the frequency and power of the gastric slow wave during different phases of the MMC (P < 0.05). Phase I was characterized with the highest frequency and lowest power of the gastric slow wave, whereas phase III exhibited the highest power in the slow wave. It was also found that in comparison with the sham points, electroacupuncture at the acupoints increased the number of spike bursts. This increase was not significant during the MMC cycle with electroacupuncture (34.4+/-4.1 vs 27.5+/-2.5%, P > 0.05) but became significant during the cycle after electroacupuncture (39.8+/-3.3% vs 27.5+/-2.5%, P < 0.0005). Similarly, during the MMC cycle after electroacupuncture at the acupoints, there was a significant decrease in the length of phase I (14.8+/-2.2 vs 46.9+/-6.1 min, P < 0.003) and a significant increase in the length of phase II (75.6+/-9.9 vs 30.6+/-4.1 min, P < 0.003) and phase III (25.8+/-0.6 vs 22.1+/-0.7 min, P < 0.003). A similar increase was observed during the MMC cycle with electroacupuncture but was not statistically significant. In conclusion, the gastric slow wave has the highest power during phase III of the MMC, indicating that the antral contraction is characterized not only by the appearance of spikes, but also by the increased power of the slow wave. Electroacupuncture at acupoints of ST36 and PC6 enhances the gastric MMC by reducing the length of phase I and increasing the length of phases II and III.

Role of microglia in inflammation-mediated degeneration of dopaminergic neurons: neuroprotective effect of interleukin 10

Inflammation in the brain has been recognized to play an increasingly important role in the pathogenesis of several neurodegenerative disorders, including Parkinson's disease and Alzheimer's disease. Inflammation-mediated neurodegeneration involves activation of the brain's resident immune cells, the microglia, which produce proinflammatory and neurotoxic factors including cytokines, reactive oxygen species (ROS), nitric oxide, and eicosanoids that directly or indirectly cause neurodegeneration. In this study, we report that IL-10, an immunosuppressive cytokine, reduced the inflammation-mediated degeneration of dopaminergic (DA) neurons through the inhibition of microglial activation. Pretreatment of rat mesencephalic neuronglia cultures with IL-10 significantly attenuated the lipopolysaccharide (LPS) induced DA neuronal degeneration. The neuroprotective effect of IL-10 was attributed to inhibition of LPS-stimulated microglial activation. IL-10 significantly inhibited the microglial production of tumor necrosis factor alpha (TNF-alpha), nitric oxide, ROS and superoxide free radicals after LPS stimulation.

Early organ-specific hemorrhage-induced increases in tissue cytokine content: associated neurohormonal and opioid alterations

Hemorrhage is associated with an impairment in the immune response and with increased concentrations of circulating inflammatory cytokines. The present study determined the time course and localization of alterations in circulating and tissue pro-inflammatory cytokines (TNF-alpha, IL-1-alpha and -beta) in response to fixed-pressure (40 mm Hg) hemorrhage as well as the associated hanges in circulating neurohormonal and opioid mediators. Conscious unrestrained non-heparinized male Sprague-Dawley rats (n = 24) underwent hemorrhage followed by standard resuscitation with lactated Ringer's solution. Animals were sacrificed at three time points; immediately after the hemorrhage period, at completion of resuscitation and 1.5 h after the resuscitation period. Hemorrhage resulted in marked elevations in circulating levels of TNF-alpha, which averaged 860 +/- 201 pg/ml. The levels were similarly elevated following fluid resuscitation (877 +/- 196 pg/ml) and had decreased towards baseline 1.5 h after completion of resuscitation (281 +/- 134 pg/ml). TNF-alpha was not detectable in plasma of time-matched controls. Hemorrhage elevated TNF-alpha content in spleen (25%), lung (55%) and heart (20%), and tissue content remained elevated despite resuscitation. No significant changes in tissue content of TNF-alpha were detected in the liver, kidney or brain. Circulating levels of IL1-alpha and -beta were not detectable in either the time-matched controls or hemorrhaged animals. However, statistically significant elevations in tissue content of IL-1 alpha were observed in heart, spleen, lung, gut and whole brain (15-30%). Tissue content of IL-1 beta did not change in response to hemorrhage and/or fluid resuscitation. Activation of sympathetic outflow, as evidenced by a 3- to 4-fold elevation in circulating epinephrine and norepinephrine levels, was observed immediately after hemorrhage, and was associated with a 5-fold rise in circulating beta-endorphin. These results demonstrate an early increase in tissue cytokine content following hemorrhagic shock, which is associated with elevations in circulating catecholamines and endogenous opioids, consistent with their potential modulatory role in this response.

Neuromancer1 and Neuromancer2 regulate cell fate specification in the developing embryonic CNS of Drosophila melanogaster

T-box genes encode a large family of transcription factors that regulate many developmental processes in vertebrates and invertebrates. In addition to their roles in regulating embryonic heart and epidermal development in Drosophila, we provide evidence that the T-box transcription factors neuromancer1 (nmr1) and neuromancer2 (nmr2) play key roles in embryonic CNS development. We verify that nmr1 and nmr2 function in a partially redundant manner to regulate neuronal cell fate by inhibiting even-skipped (eve) expression in specific cells in the CNS. Consistent with their redundant function, nmr1 and nmr2 exhibit overlapping yet distinct protein expression profiles within the CNS. Of note, nmr2 transcript and protein are expressed in identical patterns of segment polarity stripes, defined sets of neuroblasts, many ganglion mother cells and discrete populations of neurons. However, while we observe nmr1 transcripts in segment polarity stripes and specific neural precursors in early stages of CNS development, we first detect Nmr1 protein in later stages of CNS development where it is restricted to discrete subsets of Nmr2-positive neurons. Expression studies identify nearly all Nmr1/2 co-expressing neurons as interneurons, while a single Eve-positive U/CQ motor neuron weakly co-expresses Nmr2. Lineage studies map a subset of Nmr1/2-positive neurons to neuroblast lineages 2-2, 6-1, and 6-2 while genetic studies reveal that nmr2 collaborates with nkx6 to regulate eve expression in the CNS. Thus, nmr1 and nmr2 appear to act together as members of the combinatorial code of transcription factors that govern neuronal subtype identity in the CNS.

Role of tribochemistry in nanowear of single-crystalline silicon

The effects of counter-surface chemistry, relative humidity, and applied normal load on nanowear of single-crystalline silicon were studied with atomic force microscopy. In the absence of humidity, the silicon surface can resist mechanical wear as long as the contact pressure is lower than the hardness of silicon regardless of the counter-surface chemistry (diamond or SiO(2)) and ambient gas type (vacuum, N(2), O(2), air). In these conditions, the sliding contact region is protruded forming a hillock. However, when the relative humidity is higher than ~7%, the hillock formation is completely suppressed and, instead, tribochemical wear of the silicon surface takes place even at contact pressure much lower than the hardness. The tribochemical wear increases drastically in the relative humidity regime where the adsorbed water layer assumes the "solid-like" structure; further increase of wear is small in higher relative humidity regime where the "liquid-like" water layer is formed. It is also noted that the humidity-induced wear occurs only when the counter-surface is SiO(2); but not with the diamond counter-surface. This implies that the interfacial shear of the water-adsorbed SiO(2) surface with a chemically inert counter-surface is not sufficient to initiate the tribochemical wear; both substrate and counter-surface must be chemically reactive. A phenomenological model is proposed to explain the experimental observations.