Intermediate Stage Of Development Research Articles

CADM1 Expression and Stepwise Downregulation of CD7 Are Closely Associated with Clonal Expansion of HTLV-I–Infected Cells in Adult T-cell Leukemia/Lymphoma

Cell adhesion molecule 1 (CADM1), initially identified as a tumor suppressor gene, has recently been reported to be ectopically expressed in primary adult T-cell leukemia-lymphoma (ATL) cells. We incorporated CADM1 into flow-cytometric analysis to reveal oncogenic mechanisms in human T-cell lymphotrophic virus type I (HTLV-I) infection by purifying cells from the intermediate stages of ATL development. We isolated CADM1- and CD7-expressing peripheral blood mononuclear cells of asymptomatic carriers and ATLs using multicolor flow cytometry. Fluorescence-activated cell sorted (FACS) subpopulations were subjected to clonal expansion and gene expression analysis. HTLV-I-infected cells were efficiently enriched in CADM1(+) subpopulations (D, CADM1(pos)CD7(dim) and N, CADM1(pos)CD7(neg)). Clonally expanding cells were detected exclusively in these subpopulations in asymptomatic carriers with high proviral load, suggesting that the appearance of D and N could be a surrogate marker of progression from asymptomatic carrier to early ATL. Further disease progression was accompanied by an increase in N with a reciprocal decrease in D, indicating clonal evolution from D to N. The gene expression profiles of D and N in asymptomatic carriers showed similarities to those of indolent ATLs, suggesting that these subpopulations represent premalignant cells. This is further supported by the molecular hallmarks of ATL, that is, drastic downregulation of miR-31 and upregulation of abnormal Helios transcripts. The CADM1 versus CD7 plot accurately reflects disease progression in HTLV-I infection, and CADM1(+) cells with downregulated CD7 in asymptomatic carriers have common properties with those in indolent ATLs.

A Refuge for Inorganic Chemistry: Bunsen's Heidelberg Laboratory

Immediately after its opening in 1855, Bunsen's Heidelberg laboratory became iconic as the most modern and best equipped laboratory in Europe. Although comparatively modest in size, the laboratory's progressive equipment made it a role model for new construction projects in Germany and beyond. In retrospect, it represents an intermediate stage of development between early teaching facilities, such as Liebig's laboratory in Giessen, and the new ‘chemistry palaces’ that came into existence with Wöhler's Göttingen laboratory of 1860. As a ‘transition laboratory,’ Bunsen's Heidelberg edifice is of particular historical interest. This paper explores the allocation of spaces to specific procedures and audiences within the laboratory, and the hierarchies and professional rites of passage embedded within it. On this basis, it argues that the laboratory in Heidelberg was tailored to Bunsen's needs in inorganic and physical chemistry and never aimed at a broad-scale representation of chemistry as a whole. On the contrary, it is an example of early specialisation within a chemical laboratory preceding the process of differentiation into chemical sub-disciplines. Finally, it is shown that the relatively small size of this laboratory, and the fact that after ca. 1860 no significant changes were made within the building, are inseparably connected to Bunsen's views on chemistry teaching.

Floral ontogeny in Dipterygeae (Fabaceae) reveals new insights into one of the earliest branching tribes in papilionoid legumes

Flowers of Dipterygeae (Fabaceae, Papilionoideae) exhibit an unusual petaloid calyx. The two adaxial sepals are large and petaloid, and the three abaxial sepals form a three-toothed lobe. The goal of this study was to elucidate the ontogenetic pathways of this peculiar calyx in light of the floral development of the three genera that comprise the tribe. Floral buds of Dipteryx alata, Pterodon pubescens and Taralea oppositifolia were analysed using scanning electron microscopy and light microscopy. The order of bracteole and sepal initiation varies among the species. The androecium is asymmetric. The carpel cleft is positioned to the right or to the left, and is opposite the adaxial antepetalous stamen. The peculiarity of the calyx becomes noticeable in the intermediate stages of floral development. It results from the differential growth of the sepal primordia, in which the abaxial and lateral primordia remain diminutive during floral development, compared with the adaxial ones that enlarge and elongate. Bracteoles, abaxial sepals, petals and anthers are appendiculate, except in T. oppositifolia, in which the appendices were not found in bracteoles or anthers. These appendices comprise secretory canals or cavities. Considering that the ontogenetic pathway for the formation of the petaloid calyx is similar and exclusive for Dipterygeae, it might be a potential synapomorphy for the group, with the presence of secretory canals in the appendices of abaxial and lateral sepals and petals. © 2014 The Linnean Society of London, Botanical Journal of the Linnean Society, 2014, 174, 529–550.

Restricted expression of classic cadherins in the spinal cord of the chicken embryo

Classic cadherins belong to the family of cadherin genes and play important roles in neurogenesis, neuron migration, and axon growth. In the present study, we compared the expression patterns of 10 classic cadherins (Cdh2, Cdh4, Cdh6, Cdh7, Cdh8, Cdh9, Cdh11, Cdh12, Cdh18, and Cdh20) in the developing chicken spinal cord (SP) by in situ hybridization. Our results indicate that each of the investigated cadherins exhibits a spatially restricted and temporally regulated pattern of expression. At early developmental stages (E2.5–E3), Cdh2 is expressed throughout the neuroepithelial layer. Cdh6 is strongly positive in the roof plate and later also in the floor plate. Cdh7, Cdh11, Cdh12, and Cdh20 are expressed in restricted regions of the basal plate of the SP. At intermediate stages of development (E4–E10), specific expression profiles are observed for all investigated cadherins in the differentiating mantle layer along the dorsoventral, mediolateral, and rostrocaudal dimensions. Expression profiles are especially diverse for Cdh2, Cdh4, Cdh8, Cdh11, and Cdh20 in the dorsal horn, while different pools of motor neurons exhibit signal for Cdh6, Cdh7, Cdh8, Cdh9, Cdh12, and Cdh20 in the ventral horn. Interestingly, subpopulations of cells in the dorsal root ganglion express combinations of different cadherins. In the surrounding tissues, such as the boundary cap cells and the notochord, the cadherins are also expressed differentially. The highly regulated spatiotemporal expression patterns of the classic cadherins indicate that these genes potentially play multiple and diverse roles during the development of the SP and its surrounding tissues.

Insights from in situ and environmental TEM on the oriented attachment of α-Fe2O3nanoparticles during α-Fe2O3nanorod formation

Acicular α-Fe2O3 nanorods (NRs), at an intermediate stage of development, were isolated using a snapshot valve-assisted hydrothermal synthesis (HS) technique, for the purpose of complementary in situ transmission electron microscopy (iTEM) and environmental TEM (ETEM) investigations of the effect of local environment on the oriented attachment (OA) of α-Fe2O3 nanoparticles (NPs) during α-Fe2O3 NR growth. Observations of static snapshot HS samples suggested that α-Fe2O3 NPs undergo reorientation following initial attachment, consistent with an intermediate OA stage, prior to ‘envelopment’ with the developing NR to adopt a perfect single crystal. Conversely, the heating of partially developed α-Fe2O3 NRs up to 250 °C, under vacuum, during iTEM, demonstrated the progressive coalescence of loosely packed α-Fe2O3 NPs and the coarsening of α-Fe2O3 NRs, without any direct evidence for an intermediate OA stage. Direct evidence was obtained for the action of an OA mechanism prior to the consumption of α-Fe2O3 NPs at the tips of developing α-Fe2O3 NRs during ETEM investigation, under an He pressure of 5 mbar at 500 °C. However, α-Fe2O3 NPs more strongly attached to the side-walls of developing α-Fe2O3 NRs were more likely to be consumed through a local NP destabilisation and reordering process, in the absence of an OA mechanism. Hence, the emerging ETEM evidence suggests a competition between OA and diffusion processes at the α-Fe2O3 NP coalescence stage of acicular α-Fe2O3 NR crystal development, depending on whether the localised growth conditions facilitate freedom of NP movement.

Increasing Water Use Efficiency in Husk Tomato (<i>Physalis ixocarpa</i> Brot) Production in Tabasco, Mexico with Improved Irrigation Water Management

Husk tomato production technology was developed utilizing plastic sheeting and drip irrigation based on the results of reference evapotranspiration and crop coefficients (Kc) proposed at different phenological stages. The objectives of this study were as follows: 1) to evaluate the effect of plastic sheeting on the yield of husk tomato fruit with drip irrigation based on crop evapotranspiration; 2) to validate the use of drip irrigation technology and plastic sheeting in husk tomato production using demonstration plots; and 3) to determine the profitability and economic viability of the product in the domestic market. The proposed Kc values were 0.25, 0.71 and 0.56 in the initial, intermediate and final stage of crop development, respectively. Irrigation rates ranged from 2.5 to 6 mm·day-1, which was equivalent to an irrigation time of 0.6 to 2.5 hr. Soil moisture tension was monitored with tensiometers at depths of 15 and 30 cm in a loamy eutricfluvisol. The use of plastic sheeting increased husk tomato yield by 56.2% and water productivity by 63.5% under drip irrigation conditions when basing irrigation levels on crop evapotranspiration. Soil matrix potential varied between depths of 15 and 30 cm based on irrigation or rainfall amounts and the use of plastic sheeting with values being higher when the plastic sheeting was used. The husk tomato fruit yield in validation plots was 46 and 54.6 t·ha-1 with water use efficiencies ranging from 16.1 to 19.1 kg·m-3. These results exceeded the national average of 14 t·ha-1 and water use efficiency of 2.54 kg·m-3. With this new technology, a cost benefit ratio of 3.6 is obtained, which represents an economically profitable margin for farmers in the region.

Mineralogy and Characteristics of Soils Developed on Persian Gulf and Oman Sea Basin, Southern Iran

There are relatively few comprehensive documents about the mineralogy of arid regions, and no study has been reported on the characteristics and mineralogical trends of the soils of arid regions in the Hormozgan Province, southern Iran. The objective of this study was to identify the variations in physical, chemical, and mineralogical composition of soils of the region lying between the southern part of Zagros and Persian Gulf to Oman Sea. X-ray diffraction, thin-section studies, and transmission electron microscopy with energy-dispersive X-ray spectroscopy were conducted to determine the relationship between mineral distribution and climate, along with an evaporate environment reflected by a variety of geological structures. On the basis of nature and composition, the soils can be classified into Alluvial soils rich in silt and Desert soils, sandy soils poor in organic carbon in which evaporate Tertiary Formations played an important role on the formation of contemporary minerals. The maximum portions of silt and sand fraction were composed of quartz and alkali-feldspars, whereas calcite and dolomite were elevated in soil samples without acid treatments. The clay mineralogy results revealed that detrital input and inheritance are possibly the main source of kaolinite, smectite, chlorite, and illite, whereas in situ neoformation during the Tertiary shallow saline and alkaline environment could be the dominant cause of palygorskite occurrences in the sedimentary rocks. The chemical composition of clay suspension, determined by electron microprobe analysis, corresponds to that of Mg-rich predominant palygorskite, with a degree of tetrahedral substitution from almost less than 2 to 23%. In conclusion, the soil mineralogy did not vary systematically with depth but showed spatial variations, and the relative influence of mineral distribution in topsoils can be summarized as follows: parent rocks > geomorphological setting > water table position > climate > physiography and soil evolution. The soils, in general, contained moderate to high amounts of weatherable minerals, indicating their early to intermediate stages of development.

FORMATION OF ANTIQUE RHETORIC: CHRONOLOGY OF RHETORICAL METHODS AND STYLES (PLATO, ARISTOTLE)

Purpose of the article: to analyze the basic points of philosophical concepts of rhetoric of Plato and Aristotle, to prove that from Plato the rhetoric in the true sense starts being approved, and Aristotle is an ancestor of real theory of speech of the new genre, the new form, the new purposes and tasks of the description of verbal art. Problem statement: development of the ancient principles of rhetorical style’s creating is reached by efforts of outstanding speakers, each of them were differed not only by the ideological sympathies or antipathies, but also by nature of works, the concepts put in their basis. Two Ancient Greek philosophers: Plato and Aristotle are considered as founders of ancient rhetorical science. Methodology. Author has used system method, methods of content and comparative analysis. Scientific novelty is displayed in the received results from the comparative analysis of two concepts of public speech of Plato and Aristotle from a position of philosophical justification of rhetoric’s rules with orientation on ancient popular declamation practices. Practical value of article consists in development of insufficiently studied object Antique declamation where Plato and Aristotle's two central rhetorical concepts appear as the intermediate stage in development of a declamation discourse of Ancient Greece and, subsequently, and Ancient Rome. Conclusions. The conclusions can be given by the following facts: from Plato the rhetoric in the true sense is approved: true rhetorical art isn’t based only on argument technique, the true rhethor appears as the philosopher. Plato raises the problem of an ambiguity of two opposite rhetorics presented in Gorgias and Phaedrus . Rhetoric as scientific discipline, as the present theory of speech is first considered by Aristotle. The rhetoric is presented as the science speech and about thoughts, about the relation of thinking to the word.

LEGAL INSTITUTIONS, INNOVATION, AND GROWTH

We analyze the relationship between legal institutions, innovation, and growth. We compare a rigid legal system (the law is set before the technological innovation) and a flexible one (the law is set after observing the new technology). The flexible system dominates in terms of welfare, amount of innovation, and output growth at intermediate stages of technological development—periods when legal change is needed. The rigid system is preferable at early stages of technological development, when commitment problems are severe. For mature technologies, the two legal systems are equivalent. We find that rigid legal systems may induce excessive R&D investment.

Twelve tips on how to set up postgraduate training via remote clinical supervision

Doctors-in-training can now be supervised remotely by specialist clinicians using information and communication technology. This provides an intermediate stage of professional development between on-site supervision and independent medical practice. Remote supervision could increase training capacity, particularly in underserved areas and ensure doctors are willing and able to practice where they are needed once qualified.Remotely supervised doctors learn via virtual autonomy in clinical decision making and working at the limits of their abilities. It suits experienced registrars with resilience, insight into their strengths and weaknesses, capacity to self-monitor and correct, and willingness to seek help. These doctors benefit from remote supervisors who facilitate their learning, monitor their well-being, and support them holistically. Educational organisations need to oversee remote placements and match the right registrar, to the right placement with the right supervisor. We outline in our twelve tips how to set up remote supervision in order to maximise the educational benefits and minimise the risks.

The development of managerial skills in MBA programs

PurposeBusiness schools have been under fire for their alleged inefficacy in developing students’ managerial skills in MBA programs. On the basis of extant learning theories, the purpose of this paper is to propose a reconsideration of learning goals and assessment procedures for managerial skill development within MBA education.Design/methodology/approachThe authors review the literatures on stage, experiential, social, and action learning theories to identify pedagogical suggestions for optimal skill development and to highlight the constraints program administrators and teachers face in efforts to advance students’ acquisition of complex managerial skills in MBA classrooms.FindingsConceptually, the authors argue that an emphasis on mastering complex managerial skills – as an expected learning outcome – might be an overly ambitious goal that can lead to neglecting early attainments in skill acquisition and create false impressions of MBA program failure. Furthermore, the authors discuss how MBA programs could consider the use of newer evaluation procedures for evaluating skill development.Originality/valueThe paper calls for greater attention to intermediate stages of managerial skill development for establishing learning goals, the consideration of knowledge structures for assessing the degree of skill development, and a focus on managerial skill development as a life‐long process.

Open Innovation in Portugal

The empirical studies in the area of Open Innovation (OI) reveal that there is a significant bias in favour of countries on the technological frontier. The present study aims to bridge this gap by examining firms in Portugal, a country at an intermediate stage of technological development. Based on 70 innovative firms, we found that whatever perspective of the OI model is considered, firms tend, on average, to share a relatively closed innovation model when compared with firms located in countries where technological development is advanced. About a quarter of the surveyed firms implemented the OI model in their innovation strategy/business, this being much more widely disseminated regarding the absorption of external knowledge/technology, with almost 40% of firms surveyed acknowledging its use in comparison with the perspective of transfer of knowledge/technology to other organisations — less than 10% provide their “surplus technology” to other organisations. This result may indicate a lack of awareness of the economic potential of making internally created technologies available to third parties, albeit this potential might also depend on other circumstances such as technology architecture (the system and interdependence of technologies).

Integrating Quality Improvement Into Continuing Medical Education Activities Within a Community Hospital System

The integration of the Mercy Health System's quality improvement (QI) and continuing medical educational (CME) activities is described. With the implementation of computerized medical data, the opportunities for QI-focused CME are growing. The authors reviewed their regularly scheduled series and special CME programs to assess their impact on quality care processes. Clinical improvements were affected by combining national guidelines and advancements with local clinical data and interactions with physicians within interdisciplinary as well as specialty conferences. Case-based, multidisciplinary conferences lent themselves to this process to a greater extent than didactic conferences. The latter also could lead to QI when the topics were focused on specific quality initiatives that often are part of a national QI initiative. Although the authors consider these efforts to be at an intermediate stage of development, they have observed several QI/patient safety process improvements.

Hall effect sensor based space vector PWM control of permanent magnet synchronous machine

This paper proposes a space vector control of permanent magnet synchronous machine (PMSM) based on Hall effect sensor, which is very useful in practical applications due to the exactly same hardware structures between PMSM and brushless DC (BLDC) machine. This proposed method can be considered as an intermediate stage of development between the general incremental encoder based and sensorless based PMSM control methods. Because the Hall effect sensor is an absolute position sensor with 60-degree resolution, the position initialization process is not needed and the reversal rotation risk can be avoided. To improve resolution the interpolation method implemented by software is employed. Finally the high performance of this proposed method is validated by some experimental results.

Short‐term succession of aquatic plant species richness along ecosystem productivity and dispersal gradients in shallow lakes

AbstractQuestionsThe highest species richness is usually expected at an intermediate stage of development since the last major disturbance event, but some studies have shown that ecosystem productivity and dispersal may modify this pattern, suggesting the need for further studies on the effects of productivity and dispersal on the dynamics of species richness through succession. In this study, we analysed aquatic plant species richness in relation to (1) succession stage, measured as numbers of years since the last disturbance that affected the ecosystems; (2) lake productivity, measured as the chlorophyll a concentration; and (3) connectivity to similar nearby ecosystems, a proxy for the potential input of diaspores.LocationShallow lakes of the Dombes region, France.MethodsEvery 5–7 yr these shallow lakes are emptied and left to dry out for 1 yr. These drought disturbances lead to complete destruction of the submerged aquatic plant communities. Sixty lakes arranged along a gradient of productivity were selected. The probability of diaspore input was considered to increase from upstream to downstream, as lakes are organized in hydrologically connected networks via ditches, through which the downstream lakes receive water from the upstream lakes. For each lake, the aquatic plant species richness (from systematic summer vegetation sampling), time since the last disturbance (last summer drying), productivity (estimated as chlorophyll a concentration) and probability of diaspore input (assessed from position in the network) were recorded.ResultsThe aquatic plant species richness decreased with the time since the last disturbance for all of the lakes, but there was a significant interaction with the chlorophyll a concentration and position of the lake in the network. At the lowest ecosystem productivities, the relationship between successional stage and species richness was hump‐shaped, whereas the species richness decreased with increasing time since the last disturbance when productivity increased. The lake's position in the network did not influence species richness during the first 2 yr after disturbance, but from year 3 and thereafter, lakes connected to high numbers of upstream lakes consistently exhibited decreased richness, contradicting the expected trend of increasing species richness with increasing diaspore inputs.ConclusionsThis study indicates that both ecosystem productivity and connectivity strongly affected the relationship between aquatic plant species richness and succession, and that these factors should be taken into account in further developments of the intermediate disturbance hypothesis.

Resource management performance in Bahrain: a systematic analysis of municipal waste management, secondary material flows and organizational aspects

This paper presents a detailed review of municipal solid waste (MSW) and resource management in Bahrain, using the recently developed UN-Habitat city profile methodology. Performance indicators involve quantitative assessment of waste collection and sweeping, controlled disposal, materials recovery and financial sustainability together with qualitative assessment of user and provider inclusivity and institutional coherence. MSW management performance in Bahrain is compared with data for 20 other cities. The system in Bahrain is at an intermediate stage of development. A waste/material flow diagram allows visualization of the MSW system and quantifies all inputs and outputs, with the vast majority of MSW deposited in a controlled, but not engineered landfill. International comparative analysis shows that recycling and material recovery rates in Bahrain (8% wt. for domestic waste, of which 3% wt. due to informal sector) are generally lower than other cities, whereas waste quantities and generation rates at 1.1 kg capita(-1) day(-1)) are relatively high. The organic fraction (60% wt.) is comparable to that in middle- and low-income cities (50-80% wt.), although on the basis of gross domestic product Bahrain is classified as a high-income city, for which the average is generally less than 30% wt. Inclusivity in waste governance is at a medium stage as not all waste system stakeholders are considered in decision-making. While the system now appears to be financially stable, key pending issues are cost-effectiveness, improving the standards of disposal and deployment of extensive materials recovery/recycling services.

Expression of delta‐protocadherins in the spinal cord of the chicken embryo

Protocadherins constitute the largest subfamily of cadherin genes and are widely expressed in the nervous system. In the present study, we cloned eight members of the delta-protocadherin subfamily of cadherins (Pcdh1, Pcdh7, Pcdh8, Pcdh9, Pcdh10, Pcdh17, Pcdh18, and Pcdh19) from the chicken, and investigated their expression in the developing chicken spinal cord by in situ hybridization. Our results showed that each of the investigated delta-protocadherins exhibits a spatially restricted and temporally regulated pattern of expression. Pcdh1, Pcdh8, Pcdh18, and Pcdh19 are expressed in restricted dorsoventral domains of the neuroepithelial layer at early developmental stages (E2.5–E4). In the differentiating mantle layer, specific expression profiles are observed for all eight delta-protocadherins along the dorsoventral, mediolateral, and rostrocaudal dimensions at intermediate stages of development (E6–E10). Expression profiles are especially diverse in the motor column, where different pools of motor neurons exhibit signal for subsets of delta-protocadherins. In the dorsal root ganglion, subpopulations of cells express combinations of Pcdh1, Pcdh7, Pcdh8, Pcdh9, Pcdh10, and Pcdh17. The ventral boundary cap cells are positive for Pcdh7, Pcdh9, and Pcdh10. Signals for Pcdh8, Pcdh18, and Pcdh19 are found in the meninges. Surrounding tissues, such as the notochord, dermomyotome, and sclerotome also exhibit differential expression patterns. The highly regulated spatiotemporal expression patterns of delta-protocadherins suggest that they have multiple and diverse functions during development of the spinal cord and its surrounding tissues.

Osteoarthritic change is delayed in a Ctsk‐knockout mouse model of osteoarthritis

Several studies have shown that cathepsin K (CTK) is overexpressed in osteoarthritic (OA) cartilage and subchondral bone. However, it has not been well established whether CTK expression is harmful or beneficial. We undertook this study to investigate the direct involvement of CTK in OA development using Ctsk-knockout (Ctsk(-/-)) mice in a joint instability-induced model of OA. We analyzed the natural course of the phenotype of 25-week-old Ctsk(-/-) mice. OA development was evaluated with a modified Mankin histologic score up to 8 weeks after surgery was performed to destabilize the knee in Ctsk(-/-) and Ctsk(+/+) mice. Histologic analysis was used to evaluate expression of CTK, matrix metalloproteinase 13 (MMP-13), ADAMTS-5, and tartrate-resistant acid phosphatase (TRAP) proteins in chondrocytes, synovial cells, and osteoclasts. Bone architecture was analyzed by histomorphometry. Bone mineral content and bone volume were higher in Ctsk(-/-) mice at 25 weeks, whereas OA did not develop spontaneously in either Ctsk(-/-) or Ctsk(+/+) mice. In a model of destabilization-induced OA, OA progression was significantly delayed in Ctsk(-/-) mice. CTK was overexpressed in chondrocytes and synovial cells of knee joints developing OA in Ctsk(+/+) mice. MMP-13 and ADAMTS-5 were less strongly expressed in chondrocytes of Ctsk(-/-) mice, and MMP-13 was less strongly expressed in synovial cells. TRAP-positive osteoclasts were overexpressed in Ctsk(-/-) mice. These results indicate that CTK plays crucial direct roles in the early to intermediate stage of OA development. CTK-positive chondrocytes and synovial cells may be a possible target to prevent disease progression in OA.

In Vitro Selection of a Salt-tolerant Embryogenic Line in Habanero Pepper (Capsicum chinense Jacq.)

The effect of NaCI salinity on growth and development of somatic embryos of Habanero pepper was examined. Addition of 75 and 100 mm NaCI into the medium greatly increased the growth and development of somatic embryos and both of these concentrations favored the proliferation of somatic embryos. However, supplementation of 200 and 300 mm NaCI to the medium showed a negative effect on the growth and development of somatic embryos. Concentration increases of NaCl provoked a significant reduction of the embryos survival rate with the average lethal dose (46%) being registered in the treatment of 100 mm. Furthermore, a lower tolerance to salt stress (NaCl) was observed in deformed somatic embryos. Concentrations of 200 and 300 mm NaCl significantly delayed development in the surviving embryos in both treatments. These embryos remained at the globular stage throughout culture time. At 75 mm NaCl, most of the embryos were observed in the torpedo stage. However, the embryos exposed to 100 mm NaCl were observed mainly in globular and cotiledonar stages. It is quite likely that the transition from one intermediate stage of development to another occurs rapidly. With the exception of the concentration at 300 mm NaCl, salt stress stimulated embryonic germination, particularly at 100 mm NaCl. The content of proline in somatic embryos increased substantially in response to salinization. The results suggest that somatic embryos of C. chinense can tolerate concentrations of NaCl up to 100 mm without their development being affected. Moreover, they have sufficient cellular mechanisms to tolerate salinity at relatively higher levels.

Foxn1 Regulates Lineage Progression in Cortical and Medullary Thymic Epithelial Cells But Is Dispensable for Medullary Sublineage Divergence

The forkhead transcription factor Foxn1 is indispensable for thymus development, but the mechanisms by which it mediates thymic epithelial cell (TEC) development are poorly understood. To examine the cellular and molecular basis of Foxn1 function, we generated a novel and revertible hypomorphic allele of Foxn1. By varying levels of its expression, we identified a number of features of the Foxn1 system. Here we show that Foxn1 is a powerful regulator of TEC differentiation that is required at multiple intermediate stages of TE lineage development in the fetal and adult thymus. We find no evidence for a role for Foxn1 in TEC fate-choice. Rather, we show it is required for stable entry into both the cortical and medullary TEC differentiation programmes and subsequently is needed at increasing dosage for progression through successive differentiation states in both cortical and medullary TEC. We further demonstrate regulation by Foxn1 of a suite of genes with diverse roles in thymus development and/or function, suggesting it acts as a master regulator of the core thymic epithelial programme rather than regulating a particular aspect of TEC biology. Overall, our data establish a genetics-based model of cellular hierarchies in the TE lineage and provide mechanistic insight relating titration of a single transcription factor to control of lineage progression. Our novel revertible hypomorph system may be similarly applied to analyzing other regulators of development.