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At least 19 recordsLinked to original sources
PubMed2025

Exploring Hox Genes and Their Temporal Expression in an Embryonic Model of Freshwater Crustaceans.

Hox genes have been investigated in various Arthropod species, resulting in the identification of ten Hox genes, organized in a colinear arrangement within the genome. Among arthropods, crustaceans exhibit a remarkable diversity of body shapes, which are associated with a variety of egg types, embryonic development patterns, and importantly, with the modulation of Hox genes to specify the identity of body segments along the antero-posterior axis of the embryo. Although there are more than 52,000 species of crustaceans described, their genomic resources are relatively limited, making it challenging to employ several molecular tools for studying embryonic development. In this regard, we present a protocol for identifying Hox genes in a freshwater prawn using degenerate primers and transcriptome analysis. This method enables the study of specific functions of Hox genes, thereby contributing to the evolutionary understanding of the diversity of body shapes in crustaceans.

Animals↗
PubMed2026

Maternal redd1 mRNA decline triggers mTORC1 activation during the blastula-gastrula transition in zebrafish embryos.

During early metazoan development, maternal mRNAs and proteins stored in the egg sustain initial cellular functions. After the blastula stage, developmental control shifts to zygotic gene expression, and maternal transcripts are progressively degraded. Although mTORC1 is a central regulator of global mRNA translation and cell growth, its role in controlling maternal mRNA translation prior to gastrulation remains poorly understood. In zebrafish embryos, the mTORC1 inhibitor redd1 is abundantly expressed after fertilization but decreases following the maternal-to-zygotic transition (MZT), inversely correlating with mTORC1 activity. Overexpression of redd1 suppresses mTORC1, impairs gastrulation, and reduces translation of 5'TOP mRNAs and key regulatory genes, underscoring the necessity of relieving mTORC1 inhibition after the blastula stage. To investigate redd1 translation under conditions of low mTORC1 activity, we injected reporter mRNAs containing its 5' and 3' UTRs. The 3'UTR promoted polyadenylation and enhanced translation, while both UTRs enabled efficient reporter expression despite mTORC1 suppression, indicating that redd1 mRNA is translated independently of canonical mTORC1 pathways. Similarly, maternal mRNAs such as nanog, myca, pou5f3, and ccnb1, as well as the early zygotic transcript dharma, are translated through mTORC1-independent mechanisms. Together, these findings reveal a transient phase of mTORC1 suppression in early zebrafish embryos and demonstrate that select maternal and zygotic mRNAs bypass this regulation to ensure proper developmental progression.

Animals↗
PubMed2025

Toxicological Assessment of Melamine-Functionalized Graphene Oxide and Carbon Nanotubes Using Zebrafish Models.

Graphene oxide (GO) and carbon nanotube (CNT)-based nanomaterials have attracted significant interest in various industrial and biomedical applications due to their unique physicochemical properties; however, concerns about their potential toxicity, especially when modified with additives like melamine (M), remain largely unresolved. This study investigates the toxicological effects and underlying mechanisms of graphene oxide-melamine (GO-M) and carbon nanotube-melamine (CNT-M) nanoparticles in zebrafish (Danio rerio) embryos and larvae. To this end, developmental toxicity, phenotypic and behavioral changes, as well as histopathological and immunofluorescence alterations, were evaluated following acute exposure to GO-M and CNT-M nanoparticles at concentrations of 5, 10, and 20 mg/L. Results showed that both nanoparticles delayed larval hatching, particularly at higher concentrations (10 and 20 mg/L). Malformations were observed at 20 mg/L in the GO-M group and at 10 and 20 mg/L in the CNT-M group. Additionally, significant changes in larval length and eye area were observed at all concentrations for both nanoparticles. Behavioral assessments revealed that CNT-M exposure at 10 and 20 mg/L significantly impaired head sensorimotor reflexes, while all concentrations affected tail reflexes. In contrast, GO-M exposure did not significantly alter sensorimotor responses. These findings suggest differential toxic mechanisms and neurobehavioral effects of GO-M and CNT-M nanoparticles during early zebrafish development.

Animals↗
PubMed1986

Stress protein systems of mammalian cells.

Living organisms are known to react to a heat stress by the selective induction in the synthesis of several polypeptides. In this review we list the major stress proteins of mammalian cells that are induced by heat shock and other environments and categorize these proteins into specific subgroups: the major heat shock proteins, the glucose-regulated proteins, and the low-molecular-weight heat shock proteins. Characteristics of the localization and expression of proteins in each of these subgroups are presented. Specifically, the nuclear/nucleolar locale of certain of the major heat shock proteins is considered with respect to their association with RNA and the recovery of cells after a heat exposure. The induction of these major heat shock proteins and the repression of the glucose-regulated proteins as a result of reoxygenation of anoxic cells or by the addition of glucose to glucose-deprived cultures is described. Changes in the expression of these protein systems during embryogenesis and differentiation in mammalian and nonmammalian systems is summarized, and the protective role that some of these proteins appear to play in protecting the animal against the lethal effects of a severe heat treatment and against teratogenesis is critically examined.

Animals↗
PubMed1987

The use of antibodies to gap junction protein to explore the role of gap junctional communication during development.

Antibodies raised against the major 27 kDa protein electrophoretically eluted from isolated gap junctions and affinity purified against the antigen have been used to explore the role of communication through gap junctions in the early amphibian and mouse embryos. In both species, injection of the antibodies into one cell completely blocks both dye transfer and electrical coupling between cells connected by gap junctions. In the amphibian embryo the generation of a communication-incompetent clone of cells leads to patterning defects in the region derived from the antibody-injected cell. In the mouse embryo, blocking cell-to-cell communication leads to decompaction of the communication-incompetent cells. The possible significance of these findings in relation to development in general and to the organization of the first transporting epithelia to appear during development is discussed.

Animals↗
PubMed1988

In vitro analysis of specificity during nerve-muscle synaptogenesis.

The early phase of synapse formation was studied in cultures of Xenopus laevis spinal neurons and myotomal muscle cells. Two early events are described: the pulsatile secretion of acetylcholine from the nerve terminal in response to myocytic or neuronal contacts, and the development of nerve-myocyte adhesion during the first few minutes of contact. The specificity in these early events in synaptogenesis was assessed with respect to the positional and clonal relationships of the neurons and myocytes. Axial position and lineage were determined by injecting embryos with a fluorescent dye, such that dissociated cells could subsequently be identified in culture. We examined the efficacy of spontaneous synaptic currents, and the relative preponderance of growth cone-myocyte associations, for neurite-myocyte pairs of the same or dissimilar origin. Neither of these two assays revealed a dependence on the axial position or the lineage of the cells. Although these studies indicate that early nerve-muscle interactions show little positional or clonal selectivity, myocytes clearly influence the onset of synaptic function.

Acetylcholine↗
PubMedDate not supplied

The freezing of mammalian embryos: perspectives and possibilities.

Since the Ciba Foundation Symposium in 1952 on Mammalian Germ Cells when Dr Audrey Smith reported that 'exposure to very low temperatures is not incompatible with further development of mammalian eggs', much progress has been made on the problem of freezing mammalian embryos. The significant steps leading to this progress are reviewed and an attempt is made to assess the extent of our current knowledge and to relate this to experience gained in other fields of low temperature biology. There is good evidence that certain basic principles concerning cooling and warming rates are applicable to the preservation of all mammalian embryos so far studied, but differences between species and between stages of development within species exist, particularly in their resistance to cooling in temperature ranges above 0 degrees C. Some of these differences are illustrated by reference to experiments with pig embryos. Clearly there are many problems remaining to be solved, but practical applications of techniques for long-term storage of mammalian embryos are already feasible and offer interesting possibilities for future development.

Cryoprotective Agents↗
PubMedDate not supplied

Transport mechanisms in the preimplantation mammalian embryo.

Compaction is associated with major changes in the transport processes in preimplantation embryos. Before this time the processes are homocellular, in which all the component cells exchange materials across their cell membranes with a common environment. After compaction the outer trophoblast cells become organized into a simple, squamous epithelium which is capable of transcellular vectorial transport, that selectively controls the movement of materials into the embryo. Measurements of the intracellular concentrations and membrane permeabilities of Na+, K+ and Cl- in the mouse oocyte and two-cell embryo have demonstrated that they undergo significant changes during this period of development. The development of transcellular transport across the trophectoderm is fundamental in the regionalization of the embryo. These physiological mechanisms are involved in the formation of the blastocoele fluid, and may be dependent on the development of regionally located Na+, K+-ATPase on the juxtacoelic surfaces of the trophoblast cells.

Adenosine Triphosphatases↗
PubMed1975

Localization of tropomyosin in mouse embryo fibroblasts.

Antiserum to chick skeletal muscle tropomyosin was used to localize tropomyosin in mouse embryo fibroblasts by the indirect fluorescein labeled antibody technique. Specific staining was observed cytoplasmic fibers, which extended out into the cell processes. The staining pattern in these cells is similar to that previously described by others for actin. This observation suggests that in fibroblasts tropomyosin, like actin, is localized in fibers in the cytoplasm.

Actins↗
PubMedDate not supplied

Immunogold detection of glycoprotein antigens in sea urchin embryos.

Four developmental stages of sea urchin embryos were labeled with colloidal gold in an attempt to elucidate the intracellular trafficking patterns within the cells that produce the glycoprotein matrix of the embryonic spicule. The primary mesenchyme cells (PMCs) form a syncytium and secrete an organic matrix on which calcium carbonate is laid down to form an endoskeletal spicule. The organic matrix has been isolated and characterized as glycoprotein consisting of four major bands. Polyclonal antibodies to these glycoproteins were used to label embryos from the mesenchyme blastula, early gastrula, late gastrula, and plutei stages of development. The label is concentrated in the Golgi complex and associated vesicles, in secretory vesicles, and in the organic matrix. The density of the labeling increases as development proceeds.

Animals↗
PubMed1989

Reconstitution of endoplasmic reticulum in rapidly dividing cells of early Xenopus embryos.

The cytology of early blastomeres of Xenopus laevis embryos was examined. Particular attention was given to the organization of the nuclear envelope of karyomeres (chromosome vesicles) and the endoplasmic reticulum (ER) at different stages in early cleavage cycles of frog development. Nuclear envelope formation was observed to occur rapidly around individual chromosomes during early anaphase, and karyomeres fused subsequently to yield the final nucleus during telophase. Endoplasmic reticulum in the perinuclear cytoplasm was observed to be vesicular during metaphase and cisternal in form during telophase. Following microinjection of rat liver rough microsomes into early blastomeres, heterologous ER components were identified by electron microscope immunocytochemistry. The foreign ER was observed as large, reconstituted cisternae at stages in the cell cycle when the nuclear envelope was intact. Therefore, transplanted ER maintained the capacity to reconstitute in the cytoplasm of a rapidly dividing cell. In an attempt to better assess ER structure at the metaphase stage of the cell cycle, we next slowed down the division process by treating Xenopus embryos with anti-microtubule agents. Treatment with critical concentrations of colchicine, nocodazole, or vinblastine led to cleavage arrest but not to inhibition of the nuclear cycle. Following such treatment, homologous ER was observed in a vesicular form at all stages of the nuclear cycle. Heterologous ER, however, identified by immunocytochemistry in microinjected cells treated with nocodazole, displayed both vesicular and cisternal forms. We conclude that microinjected ER membranes exhibit cell-cycle-specific behavior, which is different from that of the host cell ER.

Animals↗
PubMed1992

Embryonic expression and functional analysis of a Xenopus activin receptor.

We report the isolation and characterization of a Xenopus activin receptor (XAR1). The amino acid sequence of this protein shows extensive homology with a murine activin receptor. The mRNA is expressed maternally and is ubiquitously distributed during the early stages of embryogenesis. Consistent with a possible role in mesoderm induction and patterning, interference with the normal expression of the receptor by overexpression in the early embryo results in the formation of ectopic dorsal axial structures. During neurulation the XAR1 mRNA is expressed predominantly in the presumptive brain and spinal cord, suggesting an additional function for XAR1 in neurogenesis.

Activin Receptors↗