Successive Developmental Stages Research Articles

Acquiring the cardinal knowledge of number words: A conceptual replication

Understanding the way in which counting represent numerosities was shown to be a long-lasting process. As shown in the Give-a-number task, acquiring the meanings of verbal number words goes through successive developmental stages in which children first learn the cardinal meanings of small number words one at a time before generalizing the cardinal principle they have induced from the first three number words to all number words within their counting range. This acquisition would take about a year, and would be completed by the age of 3 ½ years. The aim of the present study was to provide a conceptual replication of the developmental sequence described in Wynn’s study nearly 30 years ago using the Give-a-number task. A first cross-sectional study was conducted on 213 Belgian children aged between 39 and 74 months using the Give-a-number task to examine the developmental pattern and the influence of age on this acquisition. The time span of acquisition was examined in a second study in which 34 children were tested five times every months between the age of 36 to 52 months. Results showed that acquiring the cardinal meanings of number words spread out over a protracted period, far more extended than assumed by Wynn. Furthermore, children do not generalize all-at-once to large number words, the cardinal knowledge they learned on small number words. Rather, number words were found to be learned one at a time in a really progressive manner. Results were discussed with regard to their implications for the existing theories and in relation with other tasks assessing the acquisition of verbal number symbols.

Multiplicity of alliance learning in the entrepreneurial process: strategies of early-stage biotech firms

Entrepreneurial firms depend on knowledge variety and the ability to manage alliance-network learning for knowledge acquisition, which are both challenging. Some studies argue reliance on one key alliance partner is more effective for entrepreneurial firms with limited resources as it is less demanding than collaborations with multiple ones, while others demonstrate that alliances with different organizations significantly benefit them. Firm strategies and mechanisms of the alliance-network learning with multiple partners remain unclear, and illuminating this puzzle is relevant for understanding small and young firms creating innovations. Focusing on the early stages of human health biotech firms in Canada, this paper examines how they use the alliance-network to identify learning opportunities and pursue knowledge accumulation over their successive developmental stages. Adopting the multiple case study method and analyzing the focal firms’ collaborations and learning outcomes, this research advances a processual model of multiplicity of learning. The model identifies firm-specific strategies combining a variety of knowledge building mechanisms and multiple partners guided by organizational goals to innovate. The study contributes to the intersection of entrepreneurial development and alliance learning literatures with a novel view of early-stage firm learning strategies, and offers insights to entrepreneurs, small firms, and policymakers for innovation.

Identification of Cell Surface Molecules That Determine the Macrophage Activation Threshold Associated With an Early Stage of Malignant Transformation.

The ability of immune cells to sense changes associated with malignant transformation as early as possible is likely to be important for the successful outcome of cancer immunosurveillance. In this process, the immune system faces a trade-off between elimination of cells harboring premalignant or malignant changes, and autoimmune pathologies. We hypothesized that the immune system has therefore evolved a threshold for the stage of transformation from normal to fully malignant cells that first provides a threat (danger) signal requiring a response. We co-cultured human macrophages with a unique set of genetically related human cell lines that recapitulate successive stages in breast cancer development: MCF10A (immortalized, normal); MCFNeoT (benign hyperplasia); MCFT1 (atypical hyperplasia); MCFCA1 (invasive cancer). Using cytokines-based assays, we found that macrophages were inert towards MCF10A and MCFNeoT but were strongly activated by MCFT1 and MCFCA1 to produce inflammatory cytokines, placing the threshold for recognition between two premalignant stages, the earlier stage MCFNeoT and the more advanced MCFT1. The cytokine activation threshold paralleled the threshold for enhanced phagocytosis. Using proteomic and transcriptomic approaches, we identified surface molecules, some of which are well-known tumor-associated antigens, that were absent or expressed at low levels in MCF10A and MCFNeoT but turned on or over-expressed in MCFT1 and MCFCA1. Adding antibodies specific for two of these molecules, Annexin-A1 and CEACAM1, inhibited macrophage activation, supporting their role as cancer “danger signals” recognized by macrophages.

Metabolomic Analysis on the Petal of 'Chen Xi' Rose with Light-Induced Color Changes.

Flower color is one of the most prominent traits of rose flowers and determines their ornamental value. The color of the “Chen Xi” rose can change from yellow to red during flower blooming. In the present study, the flavonoid metabolites were investigated by the UPLC-ESI-MS/MS from the petals of four successive flower development stages under natural conditions. In total, 176 flavonoid components, including 49 flavones, 59 flavonols, 12 flavanones, 3 isoflavones, 12 anthocyanins, and 41 proanthocyanidins were identified, with some of them being detected for the first time in this study. Additionally, there were 56 compounds that showed differences among comparison groups, mainly being enriched in pathways of isoflavone, flavonoid, flavone, flavonol, phenylpropanoids, and anthocyanin. Among them, it is anthocyanins that allow the rose flower to turn red when exposed to sunlight. To verify this result, compounds from rose petal with shading treatment (S2D) was also detected but could be clearly separated from the four samples under light by clustering and principal component analyses (PCA). Consistent with low anthocyanins accumulation, the flower with shading could not turn red. Moreover, it provides a foundation for further research on the light-induced color modification of flower.

Investigating the impact of land surface characteristics on monsoon dynamics with idealized model simulations and theories

AbstractMonsoons emerge over a range of land surface conditions and exhibit varying physical characteristics over the seasonal cycle, from onset to withdrawal. Systematically varying the moisture and albedo parameters over land in an idealized modeling framework allows one to analyze the physics underlying the successive stages of monsoon development. To this end we implement an isolated South American continent with reduced heat capacity but no topography in an idealized moist general circulation model. Irrespective of the local moisture availability, the seasonal cycles of precipitation and circulation over the South American monsoon sector are distinctly monsoonal with the default surface albedo. The dry land case (zero evaporation) is characterized by a shallow overturning circulation with vigorous lower-tropospheric ascent, transporting water vapor from the ocean. By contrast, with bucket hydrology or unlimited land moisture the monsoon features deep moist convection that penetrates the upper troposphere. A series of land albedo perturbation experiments indicates that the monsoon strengthens with the net column energy flux and the near-surface moist static energy with all land moisture conditions. When the land-ocean thermal contrast is strong enough, inertial instability alone is sufficient for producing a shallow but vigorous circulation and converging a large amount of moisture from the ocean even in the absence of land moisture. Once the land is sufficiently moist, convective instability takes hold and the shallow circulation deepens. These results have implications for monsoon onset and intensification, and may elucidate the seasonal variations in how surface warming impacts tropical precipitation over land.

Unexpected contribution of fibroblasts to muscle lineage as a mechanism for limb muscle patterning

Positional information driving limb muscle patterning is contained in connective tissue fibroblasts but not in myogenic cells. Limb muscles originate from somites, while connective tissues originate from lateral plate mesoderm. With cell and genetic lineage tracing we challenge this model and identify an unexpected contribution of lateral plate-derived fibroblasts to the myogenic lineage, preferentially at the myotendinous junction. Analysis of single-cell RNA-sequencing data from whole limbs at successive developmental stages identifies a population displaying a dual muscle and connective tissue signature. BMP signalling is active in this dual population and at the tendon/muscle interface. In vivo and in vitro gain- and loss-of-function experiments show that BMP signalling regulates a fibroblast-to-myoblast conversion. These results suggest a scenario in which BMP signalling converts a subset of lateral plate mesoderm-derived cells to a myogenic fate in order to create a boundary of fibroblast-derived myonuclei at the myotendinous junction that controls limb muscle patterning.

Integrative analysis of transcriptome and proteome revealed nectary and nectar traits in the plant-pollinator interaction of Nitraria tangutorum Bobrov

BackgroundNitraria tangutorum is an important desert shrub that shows resistance to drought, salt and wind erosion stresses. It is a central ecological species in its area. Here, we have studied how N. tangutorum has adapted to achieve a successful reproduction strategy.ResultsWe found that N. tangutorum is mainly pollinated by insects of the Hymenoptera, Diptera and Coleoptera orders. Nitraria tangutorum has very small flowers, with the nectary composed of secretive epidermal cells from which nectar is secreted, located within the inner petals. In addition, analyzing the transcriptome of four successive flower developmental stages revealed that mainly differentially expressed genes associated with flower and nectary development, nectar biosynthesis and secretion, flavonoid biosynthesis, plant hormone signal transduction and plant-pathogen interaction show dynamic expression. From the nectar, we could identify seven important proteins, of which the L-ascorbate oxidase protein was first found in plant nectar. Based on the physiological functions of these proteins, we predict that floral nectar proteins of N. tangutorum play an important role in defending against microbial infestation and scavenging active oxygen.ConclusionsThis study revealed that N. tangutorum is an insect-pollinated plant and its nectary is composed of secretive epidermal cells that specialized into secretive trichomes. We identified a large number of differentially expressed genes controlling flower and nectary development, nectar biosynthesis and secretion, flavonoid biosynthesis, plant hormone signal transduction and plant-pathogen interaction. We suggest that proteins present in N. tangutorum nectar may have both an antibacterial and oxygen scavenging effect. These results provide a scientific basis for exploring how the reproductive system of N. tangutorum and other arid-desert plants functions.

Species of the genus Epilobium (Onagraceae) in plant communities in Ukraine

To assess the coenotic peculiarities of species of the genus Epilobium (Onagraceae), in particular their coenotic amplitudes in the syntaxa of vegetation of Ukraine, 986 relevés from literature sources were analyzed. The names of syntaxa are provided in accordance with the Prodromus of the vegetation of Ukraine. Species of the genus Epilobium are widely represented in many plant communities and participate in the formation of natural, semi-natural and ruderal coenoses, where they are often diagnostic or characteristic species of associations, alliances, orders and classes of vegetation, or only present in their floristic composition. Epilobium species are present in 28 classes, which is evidence of their broad coenotic amplitudes and representation in different vegetation types: wetland, grassland, halophytic, forest, shrubs, chasmophytic, alpine, and anthropogenic (synanthropic). The widest coenotic amplitudes were revealed in such species as: E. hirsutum, E. palustre, E. angustifolium, E. parviflorum, E. tetragonum, E. montanum, E. alsinifolium, and E. collinum. According to the range of coenotic amplitude, all species can be subdivided into three groups: hemistenotopic, which occur within one class (E. adenocaulon, E. dodonaei, E. lamyi, E. nutans), hemi-eurytopic (within two or three classes) – E. alpestre, E. roseum, and eurytopic (within more than three classes) – E. alsinifolium, E. angustifolium, E. collinum, E. hirsutum, E. montanum, E. palustre, E. parviflorum, E. tetragonum. As for participation of species in the coenosis, the vast majority of them are assectators, and only a small portion can be temporary edificators (in some groups, at certain successive stages of vegetation development: E. angustifolium). Plants of Epilobium species can reproduce rapidly, both vegetatively and by seeds, which promotes their active colonization of new habitats. However, they usually do not tolerate increased shading and coenotic competition with other plant species, so their strategy is mainly ruderal.

Cambrian reefs in the lower Poleta Formation: a new occurrence of a thick archaeocyathan reef near Gold Point, Nevada, USA

The lower member of the Poleta Formation is well known for its abundant archaeocyaths, including an exceptionally preserved reef at Stewart’s Mill in Nevada. Large archaeocyath-bearing reefs are relatively uncommon, with most occurring as small nearshore patch reefs. Here, we describe a new 70 m-thick archaeocyath reef from the lower Poleta Formation, herein referred to as the Gold Point Reef, located near the townsite of Gold Point, Nevada. In spite of broad similarities with the Stewart’s Mill exposure, the Gold Point Reef shows an interplay between shoal and reef development over the ~ 70 m exposure that differs from what is observed at Stewart’s Mill. This reef also preserves a small shelly fauna in its uppermost 10 m, dominated by Hyolithellus. Three successive ecological stages of reef development are observed here: the pioneer stage characterized by a single rare frame-building species; the diversification stage involving about nine species of both frame-building and mud-sticking archaeocyaths; and the final foundering stage represented by one to two species of archaeocyaths and facies indicating reef demise, including abundant grainstone/packstone shoals and a silicified upper bed with a settlement of hyolitheminthes. During the apex of reef development here, there are large modular archaeocyaths, which were able to produce thick secondary skeletal tissue for a firm attachment; these archaeocyaths were capable of building large reefs in a variety of settings. Additionally, the carbon isotope profile recorded in the Gold Point Reef shows similarities to nearby exposures of the equivalent lower Poleta Formation, with the exception of a small negative downturn at the top of the reef that is not found in other locations. Combined with the documentation of facies changes over short lateral distances, the isotope data suggest that archaeocyathan reefs may have been time-transgressive across the shelf during deposition of the lower Poleta. Additionally, our work suggests that both here and globally, the specific biotic assemblage reflected the local influences of the environment on reef development, creating highly variable coeval paleocommunities even within a restricted area.

Obtaining Oviparous Grass Snake, Natrix natrix (Serpentes, Colubridae), embryos at Early Developmental Stages by Caesarean Section

There is a specific feature in the developmental biology of oviparous snakes: embryos in the eggs, which were just laid, have already undergone significant development. This fact makes it significantly complicated to obtain data on organs’ development at early stages of embryogenesis. In addition, the fertilization time and the duration of snake pregnancy in the wild are unknown. In order to obtain the embryos of an oviparous grass snake Natrix natrix (Linnaeus, 1758) at successive developmental stages with minimal harm to gravid females we used caesarean section. The past known experience of performing caesarean section in snakes and anesthesia in reptiles were used. All the embryos were taken from the upper oviduct of a female simultaneously; in this way we eliminated the influence of medications on embryos’ development. The described method is valuable when it is necessary to obtain snake embryos and to preserve the life of the female and, possibly,its reproductive ability.

The Spatiotemporal Expression Patterns of Mechanical-Stress Related Regulatory Proteins in Mouse Molar Development

In order to better understand the role of mechanical stress in early tooth development, we examined the spatiotemporal expression patterns of mechanical-stress related regulatory protein (actin filament, or F-actin), non-muscle myosin ⅡB (NMⅡB) and vinculin at different stages of tooth development in mice. Mouse first mandible molars were used as the research model. Immunofluorescence staining was performed to detect the expression patterns of F-actin, NMⅡB and Vinculin, the key molecules constituting the chemical mechanical system, at bud, cap, early bell and late bell stages of tooth. F-actin, NMⅡB and vinculin were all expressed in the tooth epithelium in an extensive or a limited way at different stages of tooth development, while F-actin was also expressed steadily in the mesenchymal cells. The quantitative analysis of fluorescence intensity showed that F-actin and NMⅡB exhibited significantly increase in the early stage of tooth development, but then dropped to their basal levels at the end of the late bell stage and the early bell stage respectively, with the differences of expression changes between successive developmental stages showing statistically significance ( P<0.05). Vinculin expression, however, remained at a relatively constant level except for the late bell stage when vinculin expression was slightly elevated compared to that of the early bell stage ( P<0.05). The findings suggest that mechanical stress is involved in early tooth development. F-actin may have an important role in dispersing and transmitting mechanical stress while NMⅡB may participate in tooth epithelial invagination and cusps formation. The findings also suggest that vinculin can respond to the mechanical stimuli and its interaction with cell adhesion molecules may play a role in tooth development. The mechanism of how actomyosin and cell adhesion interact with each other in regulating tooth development still needs further investigation.

Determination of Spontaneous Ignition Behaviour of Calcium Stearate Dust Accumulation

The self-ignition of combustible dusts depends on their chemical composition, on the properties of the substances in the composition, on the granulometry and geometry of the mass of the material and, last but not least, on the ambient temperature. Self-ignition is a complex process that takes place in three successive or simultaneous stages of development. These stages influence each other and are the following: self-heating, evaporation of moisture, and self-ignition itself. The underlying cause of self-heating (or possibly self-ignition) is that molecules on the surface of combustible dust particles are subjected to exothermic reactions with oxygen in the air transported in the free volume between particles, even at normal temperatures. Any amount of heat released will then cause an increase in temperature in the reactive dust-air system, thus accelerating the reaction of other dust molecules with oxygen. Calcium stearate is a carboxylate of calcium, classified as a calcium soap. It is a component of some lubricants, surfactants, as well as many foodstuffs. Due to its large utilization, it was considered important to analyze the flammability properties at bulk depositing to ensure proper safety regulations to avoid unwanted events such as fires or explosions. This paper aims to describe/present the self-ignition behaviour of combustible dust as a function of volume by evaporation tests under constant temperature conditions. The obtained results showed the maximum quantity that can be stored in bulk and the time until an ignition could take place, so that protective measures can be taken to avoid incidents (fires, explosions).

Androecium anatomy of Isertia laevis, a polysporangiate species of Rubiaceae

In this study, we performed an anatomical analysis of the polysporangiate anthers and the development of pollen in Isertia laevis (Rubiaceae) with the aim to elucidate the internal structure of these atypical anthers. For this purpose, flowers in successive stages of development were dissected and the anthers were processed for conventional anatomical analysis. The material was examined using light microscopy and scanning electron microscopy. The present study shows that the anthers of Isertia laevis have two thecae divided into multiple microsporangia. This division is due to the presence of transverse and longitudinal septa formed of parenchyma and idioblasts with crystals. The septa appear together with the microsporangia and remain in the mature anther, even developing fibrous thickening. As the anther matures, the idioblasts in the septa accumulate crystals until they break, facilitating the separation of the septa from the outer wall of the theca, and thus apparently assisting the process of dehiscence. The mature anther opens through the longitudinal dehiscence of each theca. In addition to the anatomy of the anther, the development and morphology of the pollen, and the presence of orbicules are described. The structure of the anthers of I. laevis is discussed with other polysporangiate species in the Rubiaceae and angiosperms.

Ontogenetic and static allometry in the skull and cranial units of nine-banded armadillos (Cingulata: Dasypodidae:Dasypus novemcinctus)

AbstractA large part of extant and past mammalian morphological diversity is related to variation in size through allometric effects. Previous studies suggested that craniofacial allometry is the dominant pattern underlying mammalian skull shape variation, but cranial allometries were rarely characterized within cranial units such as individual bones. Here, we used 3D geometric morphometric methods to study allometric patterns of the whole skull (global) and of cranial units (local) in a postnatal developmental series of nine-banded armadillos (Dasypus novemcinctus ssp.). Analyses were conducted at the ontogenetic and static levels, and for successive developmental stages. Our results support craniofacial allometry as the global pattern along with more local allometric trends, such as the relative posterior elongation of the infraorbital canal, the tooth row reduction on the maxillary, and the marked development of nuchal crests on the supraoccipital with increasing skull size. Our study also reports allometric proportions of shape variation varying substantially among cranial units and across ontogenetic stages. The multi-scale approach advocated here allowed unveiling previously unnoticed allometric variations, indicating an untapped complexity of cranial allometric patterns to further explain mammalian morphological evolution.

A proteomic analysis of grain yield-related traits in wheat.

Grain yield, which is mainly contributed by tillering capacity as well as kernel number and weight, is the most important trait to plant breeders and agronomists. Label-free quantitative proteomics was used to analyse yield-contributing organs in wheat. These were leaf sample, tiller initiation, spike initiation, ovary and three successive kernel development stages at 5, 10 and 15 days after anthesis (DAA). We identified 3182 proteins across all samples. The largest number was obtained for spike initiation (1673), while the smallest was kernel sample at 15 DAA (709). Of the 3182 proteins, 296 of them were common to all seven organs. Organ-specific proteins ranged from 148 in ovary to 561 in spike initiation. When relative protein abundances were compared to that of leaf sample, 347 and 519 proteins were identified as differentially abundant in tiller initiation and spike initiation, respectively. When compared with ovary, 81, 35 and 96 proteins were identified as differentially abundant in kernels sampled at 5, 10 and 15 DAA, respectively. Our study indicated that two Argonaute proteins were solely expressed in spike initiation. Of the four expansin proteins detected, three of them were mainly expressed during the first 10 days of kernel development after anthesis. We also detected cell wall invertases and sucrose and starch synthases mainly during the kernel development period. The manipulation of these proteins could lead to increases in tillers, kernels per spike or final grain weight, and is worth exploring in future studies.

Dissection of the incidence and severity of purple spot physiological disorder in loquat fruit through a physiological and molecular approach

Loquat (Eriobotrya japonica) fruit marketability is affected by the incidence and severity of purple spot (PS), a pre-harvest physiological disorder showing an evident skin discoloration with depressed surface. Despite its impact in limiting the cultivation and economic potential of loquat, the etiology of this disorder is still poorly understood. To this end, our study aimed to investigate and disclose possible mechanisms underlying PS development. The intensity and severity of PS in three loquat cultivars (‘Morphitiki’, ‘Karantoki’ and ‘Obusa’) was phenotypically monitored during successive on-tree fruit developmental stages. ‘Obusa’ fruits harvested at commercial maturity stage showed the highest incidence of purple spot (58.6%), while ‘Morphitiki’ fruits did not show any symptoms. ‘Karantoki’ fruits demonstrated an intermediate response, with 31.3% of the fruit being affected. Thereafter, fruits with 30–50% PS severity were selected and used for further analysis; peel tissue was removed from both symptomatic and asymptomatic tissue of the same fruit for all examined cultivars. ‘Karantoki’ fruit with PS were characterized by the highest accumulation of total soluble sugars, sucrose, glucose and fructose contents, while the concentration of these primary metabolites was the lowest in asymptomatic fruit of ‘Obusa’, exception made for the sucrose. The incidence of PS was also transcriptionally investigated by assessing the mRNA profile of important genes involved in polyphenolic (PAL1, PAL2 and PPO1) and carbohydrate (CWI2, CWI3, SPS1, SPS2, NI2, NI3, SuSy, HXK, FRK and VI) pathway. The enhanced expression levels of CWI3 and VI genes in symptomatic fruit of the highly susceptible cultivar ‘Obusa’ highlight a cultivar-specific type of response. Notably, SuSy registered significantly suppressed levels in symptomatic tissue of both ‘Obusa’ and ‘Karantoki’. To what extent PPO is associated with PS incidence and whether the etiology of the disorder can be assigned to an oxidative process triggered and coordinated by its action need to be further elucidated. The aforementioned genes are suggested to be further examined as potential markers towards a more sophisticated and informed characterization of purple spot detection in loquat fruit.

The Secret, A Hidden-Found Process

Abstract Following the secret’s customs, encountering it in the myriad manifestations of psychic life and relational domino effect, the current work separates the secret from the act of secretiveness and from trauma, with which the former often confused. The fact that it is intrinsically linked to truth, as it is hidden information waiting to be found, defines the secret as a process involved in working with information-about-self and the self: it is a joy to be hidden and a disaster not to be discovered. This hidden – found process that accompanies us our whole life is transformed according to the biological and psychological stages one must go through. Thus, the secret is interpreted differently, passing through successive stages of development. From the archaic game of “hide-and-seek”, through the primitive scene of “peeping through the keyhole” and discovering the secret of one’s own genitals, continuing with the type of secret offered by a relationship of friendship in latency, reaching the desecretisation and de-sacralisation of adolescence, the secret is an “act of secrecy” that requires an interior architecture as well as borders between the internal and external universe. Otherwise, the “act of secrecy” fails and turns into secretiveness, a failure of the hidden - found process, because either nothing can be hidden (as in paranoid mechanisms) or everything must be hidden (as in trauma mechanisms).

Evidence for Overlapping and Distinct Biological Activities and Transcriptional Targets Triggered by Fibroblast Growth Factor Receptor 2b Signaling between Mid- and Early Pseudoglandular Stages of Mouse Lung Development.

Branching morphogenesis is the basic developmental mode common to organs such as the lungs that undergo a process of ramification from a rudimentary tree. However, the precise molecular and cellular bases underlying the formation of branching organs are still unclear. As inactivation of fibroblast growth factor receptor 2b (Fgfr2b) signaling during early development leads to lung agenesis, thereby preventing the analysis of this pathway at later developmental stages, we used transgenic mice to induce expression of a soluble form of Fgfr2b to inactivate Fgfr2b ligands at embryonic day (E) 14.5, corresponding to the mid-pseudoglandular stage of lung development. We identified an Fgfr2b signaling signature comprised of 46 genes enriched in the epithelium, some of which were common to, but most of them distinct from, the previously identified Fgfr2b signaling signature at E12.5. Our results indicate that Fgfr2b signaling at E14.5 controls mostly proliferation and alveolar type 2 cell (AT2) differentiation. In addition, inhibition of Fgfr2b signaling at E14.5 leads to morphological and cellular impairment at E18.5, with defective alveolar lineage formation. Further studies will have to be conducted to elucidate the role of Fgfr2b signaling at successive stages (canalicular/saccular/alveolar) of lung development as well as during homeostasis and regeneration and repair after injury.

3D Anatomy of the Developing Heart: Understanding Ventricular Septation.

Understanding how the four-chambered mammalian heart is formed from a simple, looped tube remains challenging, notwithstanding the descriptive accounts left by generations of cardiac anatomists. Much of the difficulty lies in attempting to visualize an intricate series of morphological transformations through the restrictive lens of two-dimensional images derived from histology. Modern imaging methods offer a way to overcome this limitation by providing comprehensive and high-resolution image sets of the developing heart. We have used one such method, high-resolution episcopic microscopy (HREM), to obtain virtual three-dimensional (3D) models of successive stages in mouse heart development. Taking advantage of the ability afforded by 3D modeling to view each heart in any orientation or erosion plane, we provide an illustrated account of how the mouse heart divides into left and right ventricular chambers, and how each acquires its own distinct outflow vessel.

High Angular Resolution Diffusion MRI Reveals Conserved and Deviant Programs in the Paths that Guide Human Cortical Circuitry.

Diffusion magnetic resonance (MR) tractography represents a novel opportunity to investigate conserved and deviant developmental programs between humans and other species such as mice. To that end, we acquired high angular resolution diffusion MR scans of mice [embryonic day (E) 10.5 to postnatal week 4] and human brains [gestational week (GW) 17-30] at successive stages of fetal development to investigate potential evolutionary changes in radial organization and emerging pathways between humans and mice. We compare radial glial development as well as commissural development (e.g., corpus callosum), primarily because our findings can be integrated with previous work. We also compare corpus callosal growth trajectories across primates (i.e., humans and rhesus macaques) and rodents (i.e., mice). One major finding is that the developing cortex of humans is predominated by pathways likely associated with a radial glial organization at GW 17-20, which is not as evident in age-matched mice (E 16.5, 17.5). Another finding is that, early in development, the corpus callosum follows a similar developmental timetable in primates (i.e., macaques and humans) as in mice. However, the corpus callosum grows for an extended period of time in primates compared with rodents. Taken together, these findings highlight deviant developmental programs underlying the emergence of cortical pathways in the human brain.