Growth Of Embryonic Tissues Research Articles

Elavl1 is dispensable for appendicular skeletal development.

Elavl1/HuR is a RNA binding protein implicated in multiple developmental processes with pleiotropic roles in RNA life cycle. Loss of Elavl1 is incompatible with life with early embryonic loss of Elavl1 in epiblast cells being lethal with defects in placental branching and embryonic tissue growth. Postnatal global deletion of Elavl1/HuR results in lethality with atrophy in multiple tissues mainly due to loss of progenitor cells. However, roles of Elavl1 specifically during embryonic limb development is not well understood. Here we report that deletion of Elavl1 in limb bud mesenchyme in mouse did not reveal any abnormalities during embryonic development with normal development in pre- and postnatal limb skeleton. Analyses of skeletal patterning, morphogenesis and skeletal maturation including skeletal elements in stylopod, zeugopod and autopod during development did not reveal any significant differences between long bones from control and Elavl1 conditional knockout animals. Our study indicates differential dependency and susceptibility to loss of Elavl1 in different stem cell lineages with its functions being dispensable during limb development.

Embryonic heart rate is affected by yolk androgens and egg laying sequence, and correlates with embryonic tissue growth: A study in rock pigeons

Maternal androgen exposure can have crucial effects on offspring development. Bird eggs are frequently used for studying these effects and virtually all research in this field has focused on post-hatching offspring traits. Yet, much of the yolk, in which the maternal hormones are deposited, is consumed during the embryonic phase. Here, we studied the effects of yolk androgens during this prenatal period. As there is evidence that androgens stimulate post-hatching traits such as increased growth, we measured heart rate throughout incubation as a proxy for prenatal metabolism. Rock pigeons (Columba livia) typically lay 2-egg clutches with yolk androgen levels in second-laid eggs being consistently higher than in first-laid eggs. We investigated whether embryonic heart rate was higher in second- than first-laid eggs. Additionally, we increased yolk androgen levels (testosterone and androstenedione) with the mean difference between those in first- and second-laid eggs, to investigate whether the effects of androgens are egg sequence dependent. As expected, embryonic heart rate predicted body embryo organ- and body mass, and body dimensions, with body mass being significantly higher in second- than first-laid eggs. Androgen treated first-laid eggs increased heart rate to that of second-laid control eggs only temporally, yet it had an overall positive effect on embryo body dimensions but not on tissue mass. Our findings indicate that embryos from different egg laying sequence differed in heart rate and prenatal development outcomes but this can only partially be explained by their difference in maternal androgen levels.

Wider Angle Egg Turning during Incubation Enhances Yolk Utilization and Promotes Goose Embryo Development.

Simple SummaryThe yolk of poultry eggs is the primary source of energy for embryonic development and the only source of lipids for embryonic tissue growth. In our previous studies on improving goose egg hatchability, we demonstrated that a wider 70° egg turning angle significantly increased hatchability and promoted embryonic growth as compared to the traditional 45° or 50° angles. However, the yolk utilization and the associated molecular mechanism, along with improved goose embryonic development, are not clear. In this research, we found that wider-angle egg turning during incubation upregulated the expression of genes related to lipolysis and fat digestion enzymes, as well as genes related to lipid transportation. The upregulation of these genes facilitates the efficient utilization of lipids that are stored in the yolk. We suggest that a wider egg turning angle, 70°, should be used in goose egg incubation to improve hatching performance and gosling quality.We aimed to investigate how wide-angle turning of eggs during incubation affected yolk utilization and the associated molecular mechanism, along with improved goose embryonic development. In total, 1152 eggs (mean weight: 143.33 ± 5.43 g) were divided equally and incubated in two commercial incubators with tray turning angles adjusted differently, to either 50° or 70°. Following incubation under the standard temperature and humidity level, turning eggs by 70° increased embryonic days 22 (E22), embryo mass, gosling weight at hatching, and egg hatchability, but reduced E22 yolk mass compared with those after turning eggs by 50°. Lipidomic analyses of the yolk revealed that egg turning at 70° reduced the concentrations of 17 of 1132 detected total lipids, including diglycerides, triglycerides, and phospholipids. Furthermore, the 70° egg turning upregulated the expression of genes related to lipolysis and fat digestion enzymes, such as lipase, cathepsin B, and prosaposin, as well as apolipoprotein B, apolipoprotein A4, very low-density lipoprotein receptor, low-density lipoprotein receptor-related protein 2, and thrombospondin receptor, which are genes involved in lipid transportation. Thus, a 70° egg turning angle during incubation enhances yolk utilization through the upregulation of lipolysis and fat digestion-related gene expression, thereby promoting embryonic development and improving egg hatchability and gosling quality.

YAP/TAZ functions and their regulation at a glance.

YAP and TAZ proteins are transcriptional coactivators encoded by paralogous genes, which shuttle between the cytoplasm and the nucleus in response to multiple inputs, including the Hippo pathway. In the nucleus, they pair with DNA-binding factors of the TEAD family to regulate gene expression. Nuclear YAP/TAZ promote cell proliferation, organ overgrowth, survival to stress and dedifferentiation of post-mitotic cells into their respective tissue progenitors. YAP/TAZ are required for growth of embryonic tissues, wound healing and organ regeneration, where they are activated by cell-intrinsic and extrinsic cues. Surprisingly, this activity is dispensable in many adult self-renewing tissues, where YAP/TAZ are constantly kept in check. YAP/TAZ lay at the center of a complex regulatory network including cell-autonomous factors but also cell- and tissue-level structural features such as the mechanical properties of the cell microenvironment, the establishment of cell-cell junctions and of basolateral tissue polarity. Enhanced levels and activity of YAP/TAZ are observed in many cancers, where they sustain tumor growth, drug resistance and malignancy. In this Cell Science at a Glance article and the accompanying poster, we review the biological functions of YAP/TAZ and their regulatory mechanisms, and highlight their position at the center of a complex signaling network.

From cancer to rejuvenation: incomplete regeneration as the missing link (Part I: the same origin, different outcomes).

Here, we interpret malignant tissue transformation from the aging point of view, that is, as a result of insufficient cell adaptation to the needs of regeneration/repair and proliferation. A consequence of the aging (senescence) process is gradual loss of self-renewal potential. It limits lifespan and leads to death due to the decline of tissue/organ functions, failure of regulatory mechanisms, disruption of endogenous processes and increased susceptibility to exogenous factors. Recapitulation of the embryonic pathway of self-renewal/rejuvenation in adulthood is epigenetically determined. At the postembryonic stage, in the absence of immune privilege, this recapitulation is transformed into cancer (potency expansion of single structures composing the organism to the detriment of the whole organism or disintegrating growth). We suggest that the process of rebirth occurs in the same way as embryonic tissue growth. Thus, the idea to use the potential of the transformed cells to stop the aging process has been proposed.

Characterizing the timing of yolk testosterone metabolism and the effects of etiocholanolone on development in avian eggs.

Maternal transfer of steroids to eggs can elicit permanent effects on offspring phenotype. Although testosterone was thought to be a key mediator of maternal effects in birds, we now know that vertebrate embryos actively regulate their exposure to maternal testosterone through steroid metabolism, suggesting testosterone metabolites, not testosterone, may elicit the observed phenotypic effects. To address the role steroid metabolism plays in mediating yolk testosterone effects, we used European starling (Sturnus vulgaris) eggs to characterize the timing of testosterone metabolism and determine whether etiocholanolone, a prominent metabolite of testosterone in avian embryos, is capable of affecting early embryonic development. Tritiated testosterone was injected into freshly laid eggs to characterize steroid movement and metabolism during early development. Varying levels of etiocholanolone were also injected into eggs, with incubation for either 3 or 5days, to test whether etiocholanolone influences the early growth of embryonic tissues. The conversion of testosterone to etiocholanolone was initiated within 12 h of injection, but the increase in etiocholanolone was transient, indicating that etiocholanolone is also subject to metabolism, and that exposure to maternal etiocholanolone is limited to a short period during early development. Exogenous etiocholanolone manipulation had no significant effect on the growth rate of the embryos or extra-embryonic membranes early in development. Thus, the conversion of testosterone to etiocholanolone may be an inactivation pathway that buffers the embryo from maternal steroids, with any effects of yolk testosterone resulting from testosterone that escapes metabolism; alternatively, etiocholanolone may influence processes other than growth or take additional time to manifest.

Elastic instability during branchial ectoderm development causes folding of the Chlamydosaurus erectile frill

We study the morphogenesis and evolutionary origin of the spectacular erectile ruff of the frilled dragon (Chlamydosaurus kingii). Our comparative developmental analyses of multiple species suggest that the ancestor of Episquamata reptiles developed a neck fold from the hyoid branchial arch by preventing it to fully fuse with posterior arches. We also show that the Chlamydosaurus embryonic neck fold dramatically enlarges and its anterior surface wrinkles, establishing three convex ridges on each lobe of the frill. We suggest that this robust folding pattern is not due to localised increased growth at the positions of the ridges, but emerges from an elastic instability during homogeneous growth of the frill skin frustrated by its attachment to adjacent tissues. Our physical analog experiments and 3D computational simulations, using realistic embryonic tissue growth, thickness and stiffness values, recapitulate the transition from two to three ridges observed during embryonic development of the dragon's frill.

Nevus Sebaceous Syndrome

Nevus sebaceous (NS) is a hamartomatous disorder of the skin and adjacent tissues characterized by epidermal, follicular, sebaceous, and apocrine gland abnormalities. It occurs in approximately 1 in 1,000 live births. A hyperactivation of Ras pathways has been recently assumed to be the cause of this phenotype. NS lesions may be isolated or coupled with extracutaneous manifestations, mostly of the central nervous, ocular, and skeletal systems, or kidneys; in this case, the term “NS syndrome” is used. Cutaneous distribution of NS usually follows the linear patterns known as “lines of Blaschko,” with lines that do not follow the segmental trajectory of the peripheral sensory nerves but instead reflect the streams or trends of growth of embryonic tissues. Histological characteristics of the lesions appear to be actually more decisive than the clinical evaluation to distinguish between the types of epidermal nevus: the typical NS has both papillated epidermal hyperplasia and a predominance of subjacent abnormal follicular–sebaceous glands.Seizures, mental retardation, and/or cognitive developmental delay are the most common neurologic abnormalities associated with NS and usually are present within the first months of life; eye and skeletal involvement may be present as well.The definitive treatment of NS is full-thickness excision. However, the necessity and timing of excision to prevent possible future malignancy are not clear; lasers and photodynamic therapy are alternatives currently being explored for the treatment of NS, with varying degrees of success.

1 - Growth factors and the regulation of pre- and postnatal growth

Peptide growth factors represent a largely paracrine level of intercellular communication that is basic to the process of life. Growth factors are present in the ovum and are amongst the first products expressed by the embryonic genome. They function as both signals and progression factors for embryonic tissue growth, induction, differentiation, maturation and function. While a widespread tissue expression is demonstrable during fetal development, and in certain postnatal tissues such as the epiphyseal growth plate, growth factor presence in the adult is restricted to tissues sharing rapid cellular turnover such as ovary. However, a transient re-expression of peptide growth factors occurs during adult tissue repair. In addition to mitogenic peptides such as IGFs or EGF, the family of growth factors also includes physiological growth inhibitors such as TGF beta and certain neuropeptides. Insulin is mitogenic in the early embryo and evidence is presented to support a continuation of this role, under defined nutritional conditions, in late gestation. The importance of insulin to pre- and postnatal growth has prompted an expanding literature dealing with the interactions of nutrients, hormones and growth factors during the growth and functional maturation of the islets of Langerhans. While the expression of growth factors in the early embryo is apparently autonomous, some, such as IGFs, become increasingly dependent on nutrient, insulin and GH availability during fetal development and in childhood growth. This has resulted in circulating IGF I and II determinations becoming useful diagnostic markers of endocrine-based growth disorder and nitrogen balance.

Allelopathy due to purine alkaloids in tea seeds during germination

During imbibition of whole tea seeds (6 days) two purine alkaloids, caffeine and theobromine, did not decrease in the seed coats and there was no increase in the seeds. In parallel with and after the breaking of seed coats there was a gradual release of caffeine from coats of germinating seeds. By contrast, when the seed was freed from the outer seed coat and soaked, imbibition of the seed required only 2 days and simultaneously caffeine was released from the inner seed coat. In such seeds, but not in whole seeds, growth of embryonic tissues (roots and shoots) was inhibited after the breaking of the inner seed coats. Nevertheless, caffeine increased more in such roots of the seedlings of decoated seeds than in roots of normal seedlings.

Transplacental effect of methylcobalamin on growth of mouse embryonic kidney tissue in organ culture

This paper gives the results of a study of the transplacental action of methylcobalamin (MC) on growth of embryonic tissues during organ culture. An organ culture of embryonic mouse kidney tissue, sensitive to the transplacental action of biologically active substances, including vitamins and hormones, and also of chemical carcinogens, was used as the experimental model. /sup 3/H-thymidine was added to the nutrient medium before fixation of the explants. The stimulating effect of MC on growth of mouse kidney tissue in the prenatal period as revealed in this investigation, is said by the authors to be an important mechanism modifying the transplacental action of chemical carcinogens.

Energetics of Pacific Herring (Clupea harengus pallasi) Embryos and Larvae Exposed to Low Conentrations of Benzene, a Monoaromatic Component of Crude Oil

Interest in the energetic processes of critical early life stages of Pacific herring (Clupea harengus pallasi) and the potential effects from sublethal exposure to benzene, a monoaromatic component of crude oil, led to a series of experiments which examined metabolism of herring embryos, yolk-sac larvae, and post-yolk-sac larvae. Yolk caloric content was 6,020 cal/g or 1.3 calories per egg. This energy was consumed rapidly during incubation; total yolk absorption occurred 12 days after fertilization. Anabolic rates varied but at no time was there an energy deficit. Oxygen consumption of embryos increased prior to hatching, then a 10-fold rise was seen in newly hatched yolk-sac larvae. Exogenous calories were estimated from ingested rotifers and were less definable than endogenous energy due to variable grazing rates. Sublethal concentrations of benzene caused (a) significantly less embryonic tissue growth, (b) significantly different oxygen consumption in embryos, and (c) significantly greater assimilation in feeding larvae. It is believed activity of larvae played an important role in accounting for increased metabolism of later stages.

Inhibition of growth of embryonic tissues transplanted into syngeneic newborn recipients

Transplants of embryonic skin and teratomas formed after transplantation of minced tissues of embryos at the 18th–20th and 12–14th days of development into newborn syngeneic recipients grew much more slowly than similar grafts transplanted into adult recipients. It is postulated that factors controlling growth of embryonic tissues exist in embryos and newborn animals.

Creation of hyperactive determinant dispatch stations in the caudate nucleus in experimental neuropathological syndromes caused by tetanus toxin

Skin grafts of embryos and teratomas formed after the transplantation of ground tissues of embryos (18-20 day and 12-14-day) to neonatal syngeneic recipients were studied; it appeared that their growth was considerably delayed in comparison with analogous transplants in adult recipients. It is supposed that the organism of embryos and neonates has factors controlling the growth of embryonic tissues.

A system of axioms for mathematical biology

The following six axioms appear to provide an adequate basis for a full and realistic mathematical biology: (1) Any organism is a (topological) union of tissues. (2) Any tissue consists, mathematically speaking, of a finite covering, the neighborhoods of which are the cells of the tissue. Each cell of the tissue has an associated biological action (or actions) that has the mathematical nature of a vector (or tensor) field. (3) A tissue may be regarded topologically as a compact manifold. (4) Biological form and function are mathematically representable as pseudogroups, (5) each of which is characterized by an infinitesimal generator that corresponds to the abstract mathematical formulation of the biological action of the cell. (6) With respect to trophic functions, an organism develops biological structure and function designed to optimize system performance. The first axiom is almost a truism. The second is readily verified by a case-by-case comparison with a standard classification of biological cells. Axioms 1 and 2 together imply the equivalence of the Cell Theory of biology with the principle that the cell constitutes an infinitesimal generator of biological form and function. Axiom 3 follows from the fact that the number of cells in any tissue is necessarily finite. Axioms 4 and 5 are consistent with the primacy of fibrils and filaments in biological structure, the universality of cell nuclei, the presence of “organizing centers” for morphogenesis, and the preservation of particular functions in the face of individual variation. Axiom 5 also expresses the fact that anatomical structures develop out of pre-existing, more primitive ones via small, “differential” changes; in other words, by prolongations of the Lie transformation groups involved. Axiom 6 is essentially a restatement of Rashevsky's principle of adequate design, but applied in its proper sphere, namely, trophic functions. Application of these principles is made to contact induction in embryonic tissue growth and to the phenomena of allometric growth.

Effect of chloromycetin and streptomycin on embryonic tissue growth in in vitro tissue culture.

Effect of chloromycetin and streptomycin on embryonic tissue growth in in vitro tissue culture.

An Improved Method for the Evaluation of Germicidal Substances

In previous papers1, 2 a new method was described for evaluating the efficiency of germicides by testing them for their effect on the growth of living embryonic tissue and on bacteria. A number known as the toxicity-index was determined which was defined as the ratio of the highest dilution of disinfectant that showed no growth of embryonic tissue in 48 hours to the highest dilution required to kill the test-organism in 10 minutes. Theoretically the smaller the index the more nearly perfect the germicide. The present method attempts to control several variables which were not considered in the previous work. These are: (1) performing all tests at 37°C. instead of at 25°C; (2) keeping the time of action of germicide on tissue and bacteria the same, viz., 10 minutes; (3) conducting all tests in the presence of a definite amount of organic matter. Efecct of Gernzicide on Tissue. Chick hearts are removed from 10-12-day-old embryos and minced into fragments about 0.5 mm. in diameter. The fragments are suspended in Tyrode's solution, about 100 pieces per cc. One-half cc. of suspension is pipetted into each of a series of tubes containing 2.5 cc. of a mixture of 3 parts embryonic extract∗ and 1 part defibrinated horse serum. The tubes are placed in a 37°C. waterbath.