Embryonic development of Python sebae - I: Staging criteria and macroscopic skeletal morphogenesis of the head and limbs

This study explores the post-ovipositional craniofacial development of the African Rock Python (Python sebae). We first describe a staging system based on external characteristics and next use whole-mount skeletal staining supplemented with Computed tomography (CT) scanning to examine skeletal development. Our results show that python embryos are in early stages of organogenesis at the time of laying, with separate facial prominences and pharyngeal clefts still visible. Limb buds are also visible. By 11 days (stage 3), the chondrocranium is nearly fully formed; however, few intramembranous bones can be detected. One week later (stage 4), many of the intramembranous upper and lower jaw bones are visible but the calvaria are not present. Skeletal elements in the limbs also begin to form. Between stages 4 (day 18) and 7 (day 44), the complete set of intramembranous bones in the jaws and calvaria develops. Hindlimb development does not progress beyond stage 6 (33 days) and remains rudimentary throughout adult life. In contrast to other reptiles, there are two rows of teeth in the upper jaw. The outer tooth row is attached to the maxillary and premaxillary bones, whereas the inner row is attached to the pterygoid and palatine bones. Erupted teeth can be seen in whole-mount stage 10 specimens and are present in an unerupted, mineralized state at stage 7. Micro-CT analysis reveals that all the young membranous bones can be recognized even out of the context of the skull. These data demonstrate intrinsic patterning of the intramembranous bones, even though they form without a cartilaginous template. In addition, intramembranous bone morphology is established prior to muscle function, which can influence bone shape through differential force application. After careful staging, we conclude that python skeletal development occurs slowly enough to observe in good detail the early stages of craniofacial skeletogenesis. Thus, reptilian animal models will offer unique opportunities for understanding the early influences that contribute to perinatal bone shape.     

Asymmetrical growth, differential cell proliferation, and dynamic cell rearrangement underlie epithelial morphogenesis in mouse molar development

During molar development from the cap to bell stage, the morphology of the enamel knots, inner dental epithelium, and epithelial-mesenchymal junction dynamically changes, leading to the formation of multiple cusps. To study the basic histological features of this morphogenetic change, we have investigated the cell arrangement, mitosis, and apoptosis simultaneously in the developing first lower molar of the mouse by means of BrdU injection and immunostaining for P-cadherin, BrdU, and single-stranded DNA. At the typical cap stage, the primary enamel knot shows a characteristic cell arrangement, absence of mitosis, and abundant apoptosis, but also actively dividing cells at its lateral margins. Two secondary enamel knots then appear in the anterior part of the tooth germ. One is completely non-proliferating, whereas the other contains dividing cells, indicating asymmetrical growth of the inner dental epithelium. From this transitional stage to the early bell stage, additional minor BrdU-negative domains appear, and at the same time, the cell arrangement in the inner dental epithelium rapidly changes to show regional differences. Comparisons between the histology and the distribution of BrdU-positive cells have revealed that both the regionally different cell rearrangement and the differential cell proliferation in the enamel knots and inner dental epithelium probably play a significant role in multiple cusp formation.     

Comparison of feto-maternal organ derived stem cells in facets of immunophenotype,proliferation and differentiation

Scientific explorations on feto-maternal organ stem cells revealed its possible applicability in treatment of various diseases. However, establishment of an ideal placental tissue stem cell source in regenerative application is inconclusive and arduous. Hence, this study aims to resolve this tribulation by comparison of mesenchymal stem cells (MSC) from fetal placenta – amniotic membrane (AM-MSC), chorionic plate (CP-MSC) tissue and the maternal placenta-Decidua (D-MSC), thereby facilitating the researchers to determine their pertinent source. The cells were expanded and scrutinized for expression profiling, proliferation and differentiation ability. Remarkable expressions of certain markers in addition to its prospective mesodermal differentiation confirmed their mesenchyme origin. Despite the specified alikeness among these sources, reliable and non-invasive procurement of AM-MSC coupled with its higher growth potency makes it the most constructive stem cell source. However, exhibited similarities demands further investigations on extensive expandability and cytogenetic stability of these sources prior to its therapeutic applicability.     

Embryonic and larval development of the sea anemone Haliplanella lineata from Japan

The development of Haliplanella lineata, following fertilization in the laboratory, was studied by light and electron microscopy. Spawned ova were spherical, magenta in color and about 120–150 µm in diameter. Cleavage was holoblastic and radial. Gastrulation occurred by immigration and invagination. Eighteen hours after fertilization, the embryo became a swimming planula larva with an apical organ and ciliary tuft at the aboral end. In the laboratory, planulae lived for about 2 weeks in the swimming state but in no case was there any settlement by larvae in this study. The structural study of planulae concentrated on the development of the aboral ectoderm, because of the functional significance of its cellular organization in larval settlement.     

Coordination of tooth morphogenesis and neuronal development through tissue interactions: Lessons from mouse models

In addition to being an advantageous model to investigate general molecular mechanisms of organ formation, the tooth is a distinct target organ for peripheral nerve innervation. These nerves are required for the function and protection of the teeth and, as shown in fish, also for their regeneration. This review focuses on recent findings of the local tissue interactions and molecular signaling mechanisms that regulate the early nerve arrival and patterning of mouse mandibular molar tooth sensory innervation.     

FGFR3 regulates brain size by controlling progenitor cell proliferation and apoptosis during embryonic development

Mice with the K644E kinase domain mutation in fibroblast growth factor receptor 3 (Fgfr3) (EIIa;Fgfr3(+/K644E)) exhibited a marked enlargement of the brain. The brain size was increased as early as E11.5, not secondary to the possible effect of Fgfr3 activity in the skeleton. Furthermore, the mutant brains showed a dramatic increase in cortical thickness, a phenotype opposite to that in FGF2 knockout mice. Despite this increased thickness, cortical layer formation was largely unaffected and no cortical folding was observed during embryonic days 11.5-18.5 (E11.5-E18.5). Measurement of cortical thickness revealed an increase of 38.1% in the EIIa;Fgfr3(+/K644E) mice at E14.5 and the advanced appearance of the cortical plate was frequently observed at this stage. Unbiased stereological analysis revealed that the volume of the ventricular zone (VZ) was increased by more than two fold in the EIIa;Fgfr3(+/K644E) mutants at E14.5. A relatively mild increase in progenitor cell proliferation and a profound decrease in developmental apoptosis during E11.5-E14.5 most likely accounts for the dramatic increase in total telecephalic cell number. Taken together, our data suggest a novel function of Fgfr3 in controlling the development of the cortex, by regulating proliferation and apoptosis of cortical progenitors.     

Glucagon-like peptides: regulators of cell proliferation,differentiation, and apoptosis

Peptide hormones are secreted from endocrine cells and neurons and exert their actions through activation of G protein-coupled receptors to regulate a diverse number of physiological systems including control of energy homeostasis, gastrointestinal motility, neuroendocrine circuits, and hormone secretion. The glucagon-like peptides, GLP-1 and GLP-2 are prototype peptide hormones released from gut endocrine cells in response to nutrient ingestion that regulate not only energy absorption and disposal, but also cell proliferation and survival. GLP-1 expands islet mass by stimulating pancreatic beta-cell proliferation and induction of islet neogenesis. GLP-1 also promotes cell differentiation, from exocrine cells or immature islet progenitors, toward a more differentiated beta-cell phenotype. GLP-2 stimulates cell proliferation in the gastrointestinal mucosa, leading to expansion of the normal mucosal epithelium, or attenuation of intestinal injury in experimental models of intestinal disease. Both GLP-1 and GLP-2 exert antiapoptotic actions in vivo, resulting in preservation of beta-cell mass and gut epithelium, respectively. Furthermore, GLP-1 and GLP-2 promote direct resistance to apoptosis in cells expressing GLP-1 or GLP-2 receptors. Moreover, an increasing number of structurally related peptide hormones and neuropeptides exert cytoprotective effects through G protein-coupled receptor activation in diverse cell types. Hence, peptide hormones, as exemplified by GLP-1 and GLP-2, may prove to be useful adjunctive tools for enhancement of cell differentiation, tissue regeneration, and cytoprotection for the treatment of human disease.     

Effect of overexpression of inhibin alpha (1-32) fragment on bovine granulosa cell proliferation, apoptosis, steroidogenesis, and development of co-cultured oocytes

The objective was to determine the effects of an inhibin alpha (1-32) fragment gene on proliferation, apoptosis, and steroidogenesis of bovine granulosa cells (GC) isolated from medium and small follicles (diameter >4-8 and 1-4mm, respectively), and the effect of GC, previously transfected with pEGISI, on oocyte maturation and in vitro embryo development. To enhance expression of the inhibin alpha (1-32) fragment, GC were transfected with pEGISI. Transfection inhibited (P<0.05) GC proliferation (88.8+/-2.1%; mean+/-S.E.M.) compared to the control and EGFP groups (100% and 97.5+/-2.1%) from medium follicles, with no significant effect on GC from small follicles. Apoptosis was higher (P<0.01) in transfected GC than in controls. Transfection increased (P<0.05) estradiol synthesis from both medium and small follicles (0.57+/-0.13 and 0.86+/-0.13 pg/mL vs. 0.19+/-0.05 and 0.35+/-0.09 pg/mL in controls) after culturing for 48 h, with suppression (P<0.05) in transfected GC after 96 h. Transfection reduced (P<0.05) progesterone synthesis in GC from both medium and small follicles (24.5+/-3.4 and 75.4+/-4.6 ng/mL vs. 45.42+/-5.33 and 117.32+/-11.99 ng/mL in controls) after culture for 48 h, with no significant difference after 96 h. Maturation rate of oocytes co-cultured with transfected GC from medium follicles was decreased relative to control (61.5+/-6.8% vs. 71.2+/-5.7%, P<0.05), with no significant effect on embryo development. In conclusion, overexpression of inhibin alpha (1-32) fragment regulated GC development; effects on subsequent oocyte maturation were both time- and stage-dependent.     

Nonmuscle myosin II is required for cell proliferation, cell sheet adhesion and wing hair morphology during wing morphogenesis

Metazoan development involves a myriad of dynamic cellular processes that require cytoskeletal function. Nonmuscle myosin II plays essential roles in embryonic development; however, knowledge of its role in post-embryonic development, even in model organisms such as Drosophila melanogaster, is only recently being revealed. In this study, truncation alleles were generated and enable the conditional perturbation, in a graded fashion, of nonmuscle myosin II function. During wing development they demonstrate novel roles for nonmuscle myosin II, including in adhesion between the dorsal and ventral wing epithelial sheets; in the formation of a single actin-based wing hair from the distal vertex of each cell; in forming unbranched wing hairs; and in the correct positioning of veins and crossveins. Many of these phenotypes overlap with those observed when clonal mosaic analysis was performed in the wing using loss of function alleles. Additional requirements for nonmuscle myosin II are in the correct formation of other actin-based cellular protrusions (microchaetae and macrochaetae). We confirm and extend genetic interaction studies to show that nonmuscle myosin II and an unconventional myosin, encoded by crinkled (ck/MyoVIIA), act antagonistically in multiple processes necessary for wing development. Lastly, we demonstrate that truncation alleles can perturb nonmuscle myosin II function via two distinct mechanisms—by titrating light chains away from endogenous heavy chains or by recruiting endogenous heavy chains into intracellular aggregates. By allowing myosin II function to be perturbed in a controlled manner, these novel tools enable the elucidation of post-embryonic roles for nonmuscle myosin II during targeted stages of fly development.     

Differential regulation of TIMP-1, -2, and -3 mRNA and protein expressions during mouse incisor development

Tissue inhibitors of metalloproteinases (TIMPs) possess multiple functions, in addition to their matrix metalloproteinase (MMP) inhibitory activity. The continuously growing incisor of mouse possesses a stem cell compartment at the apical end of the epithelium (the apical loop) and thus provides an excellent tool to analyze the mechanisms of organogenesis and cytodifferentiation. To understand the functions of TIMPs in tooth development, we have analyzed the gene expression and protein localization of TIMP-1, -2, and -3 during mouse incisor development, from embryonic day 13 (E13) to postnatal day 3 (P3). TIMP-1 was present on the basement membrane during early developmental stages. At P2, TIMP-1 was strongly detected along the apical loop, transiently disappeared from the basement membrane in the cytodifferentiation zone, and later reappeared at the distal end of functional ameloblasts. Expression of TIMP-2 protein was restricted to the outer part of the apical loop throughout the examined stages. At P2, TIMP-2 was present on the basement membrane at the outer part of the apical loop. The dental follicle also expressed Timp-2, and the corresponding protein was abundant within the extracellular matrix. Timp-3 mRNA was highly expressed in the mesenchyme surrounding the apical loop. During matrix formation, Timp-3 was expressed by subodontoblasts, and the protein was detected in this layer and between odontoblasts. Distinct temporal and spatial expression patterns of TIMPs suggest divergent functions of these factors in incisor organogenesis. This work was supported by INSERM, CNRS, ARC, French Ministry of Research (ACI), Japanese Ministry of Education, Culture, Sports, Science, and Technology, and Niigata University Research Projects.     

Dynamics of apoptosis and proliferation in rat thymus and spleen during perinatal development (Ontogenesis)

The levels of spontaneous apoptosis and proliferation of the rat thymic and spleen cells, as well as their regulation by the hypothalamo-hypophysial system were studied during perinatal development. The apoptotic and proliferating cells in the thymus and spleen were assayed using flow cytometry with the DNA-specific dye propidium iodide. The level of apoptosis in the thymus reached 25% on day 18 of embryogenesis (E18) and decreased to 5% thereafter. In the spleen, the level of apoptosis gradually increased from 15 to 37% during the period of E18 to day 30 of postnatal development (P30). The level of proliferating cells in the thymus was 20–25% at all developmental stages studied. In the spleen, it was at a maximum on E18 (32%) and decreased almost twice on E21 (17%). On P7, the amount of proliferating cells again increased to 22% and then gradually decreased to 7% by P30. The surgical ablation of hypothalamus in utero on E18 did not affect cell apoptosis or proliferation in the thymus and spleen. The surgical ablation of both hypothalamus and pituitary led a twofold decrease of the level of apoptosis in the spleen and insignificant increase of the level of proliferation in the thymus. Thus, the numbers of cells in the embryonic thymus is regulated not only by the thymus itself, but also by the hypothalamo-hypophysial system. The programmed cell death in the embryonic spleen appears to be regulated by the hypothalamo-hypophysial system as well.     

Characterization of the effects of butyric acid on cell proliferation, cell cycle distribution and apoptosis

We examined concentration-dependent changes in cell cycle distribution and cell cycle-related proteins induced by butyric acid. Butyric acid enhanced or suppressed the proliferation of Jurkat human T lymphocytes depending on concentration. A low concentration of butyric acid induced a massive increase in the number of cells in S and G2/M phases, whereas a high concentration significantly increased the accumulation of cells in G2/M phase, suppressed the accumulation of cells in G0/G1 and S phases, and induced apoptosis that cell cycle-related protein expression in Jurkat cells treated with high levels of butyric acid caused a marked decrease in cyclin A, cyclin E, cyclin-dependent kinase 2 (CDK2), CDK4 and CDK6 protein levels in G0/G1 and S phases, with apoptosis induction, and a decrease in cyclin B, Cdc25c and p27KIP1 protein levels, as well as an increase in p21CIP1/WAF1 protein level, in the G2/M phase. Taken together, our results indicate that butyric acid has bimodal effects on cell proliferation and survival. The inhibition of cell growth followed by the increase in apoptosis induced by high levels of butyric acid were related to an increase in cell death in G0/G1 and S phases, as well as G2/M arrest of cells. Finally, these results were further substantiated by the expression profile of butyric acid-treated Jurkat cells obtained by means of cDNA array.     

MicroRNA-424-5p enhances chemosensitivity of breast cancer cells to Taxol and regulates cell cycle,apoptosis, and proliferation

Molecular Biology Reports - Combination therapy has been considered as a potential method to overcome the BC chemoresistance. MicroRNAs (miRs) have been suggested as a therapeutic factor in the...     

14-3-3 proteins: key regulators of cell division, signalling and apoptosis

The 14-3-3 proteins constitute a family of conserved proteins present in all eukaryotic organisms so far investigated. These proteins have attracted interest because they are involved in important cellular processes such as signal transduction, cell-cycle control, apoptosis, stress response and malignant transformation and because at least 100 different binding partners for the 14-3-3 proteins have been reported. Although the exact function of 14-3-3 proteins is still unknown, they are known to (1) act as adaptor molecules stimulating protein-protein interactions, (2) regulate the subcellular localisation of proteins and (3) activate or inhibit enzymes. In this review, we discuss the role of the 14-3-3 proteins in three cellular processes: cell cycle control, signal transduction and apoptosis. These processes are regulated by the 14-3-3 proteins at multiple steps. The 14-3-3 proteins have an overall inhibitory effect on cell cycle progression and apoptosis, whereas in signal transduction they may act as stimulatory or inhibitory factors. This article contains supplementary material which may be viewed at the BioEssays website at http://www.interscience.wiley.com/jpages/0265-9247/Suppmat/23/v23_10.936.     

Morphological studies in Zygophyllaceae. II. The floral development and vascular anatomy of Peganum harmala

Floral development and vascular anatomy are investigated in Peganum harmala, emphasizing its unusual androccium with 15 stamens. Sepals arise successively; petals emerge simultaneously with five antesepalous stamens. The five stamen pairs arise in the space between the petals and the antesepalous stamens. The gynoecium arises from three carpel primordia with evidence of two reduced carpels. Placentae are axile and each bears two double rows of ovules. A weakly developed nectary surrounds the base of the ovary. The antepetalous stamen traces diverge from a common supply to petals and sepal laterals, independent of the antesepalous stamen traces. The androecium of Peganum is described as a derived obdiploste-monous form, differing from the complex haplostemonous androecium of Nitraria. “Congenital dédoublement” cannot adequately explain the origin of the paired antepetalous stamens; two stamens can arise either by the splitting of a common primordium or independently, and both ways of inception are best understood as extremes of a gradation. The systematic position of Peganum is discussed in relation to other Zygophyllaceae using a cladistic analysis with Ptelea (Rutaceae) and Quassia (Simaroubaceae) as outgroups. The basal division in the Zygophyllaceae is between Peganum and the rest of the family.     

Response of cassava leaf area expansion to water deficit: cell proliferation, cell expansion and delayed development

BACKGROUND AND AIMS: Cassava (Manihot esculenta) is an important food crop in the tropics that has a high growth rate in optimal conditions, but also performs well in drought-prone climates. The objectives of this work were to determine the effects of water deficit and rewatering on the rate of expansion of leaves at different developmental stages and to evaluate the extent to which decreases in cell proliferation, expansion, and delay in development are responsible for reduced growth. METHODS: Glasshouse-grown cassava plants were subjected to 8 d of water deficit followed by rewatering. Leaves at 15 developmental stages from nearly full size to meristematic were sampled, and epidermal cell size and number were measured on leaves at four developmental stages. KEY RESULTS: Leaf expansion and development were nearly halted during stress but resumed vigorously after rewatering. In advanced-stage leaves (Group 1) in which development was solely by cell expansion, expansion resumed after rewatering, but not sufficiently for cell size to equal that of controls at maturity. In Group 2 (cell proliferation), relative expansion rate and cell proliferation were delayed until rewatering, but then recovered partially, so that loss of leaf area was due to decreased cell numbers per leaf. In Group 3 (early meristematic development) final leaf area was not affected by stress, but development was delayed by 4-6 d. On a plant basis, the proportion of loss of leaf area over 26 d attributed to leaves at each developmental stage was 29, 50 and 21 % in Group 1, 2 and 3, respectively. CONCLUSIONS: Although cell growth processes were sensitive to mild water deficit, they recovered to a large extent, and much of the reduction in leaf area was caused by developmental delay and a reduction in cell division in the youngest, meristematic leaves.     

Role of interferons in the regulation of cell proliferation,differentiation, and development

There now appears to be evidence to support the view that the type I IFNs are naturally produced negative regulators of growth that also modify cell differentiation. Consistent with this, it appears that the ability to produce and respond to IFN is suppressed in early embryonic development when cell proliferation and differentiation are essential. In the later stages of fetal development, IFN production is de-repressed, and cells show increased sensitivity to IFN, which may be important in regulating cell proliferation and/or differentiation processes or the interaction between fetal and maternal tissues. Interestingly, the IFN system can also be suppressed in disease states such as the development of tumours or in the establishment of a (chronic) viral infection. Therefore, understanding the developmental regulation of the IFN system may be important to understanding and controlling the IFN system in disease. More extensive studies of the developmental stage and tissue-specific expression of type I IFNs and their receptors are necessary, as well as more direct in vivo experiments to further elucidate the role of the IFN system in reproduction and development. © 1994 Wiley-Liss, Inc.