bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hydrogen peroxide levels in mouse oocytes and early cleavage stage embryos developed in vitro or in vivo
Authors: Nasr-Esfahani Mohammed H. , Aitken John R. , Johnson Martin H. 
Published: April 2021

ABSTRACT
We describe a fluorimetric method for measuring the level of H2O2 in individual mouse oocytes and early embryos. Levels of H2O2 are low but detectable in unfertilized oocytes recovered freshly from the female reproductive tract. The levels in early cleaving embryos (1-cell to 8-cell stages) immediately after recovery from the female tract seem to be slightly higher the later the stage examined. However, when embryos are cultured in vitro from the 1-cell or early 2-cell stage, H2O2 levels rise when the embryos reach the mid-2-cell stage and remain elevated until they enter the early 4-cell stage. No equivalent elevation of H2O2 is seen during the transition from 1-cell to 2-cell or from 4-cell to 8-cell stages. Embryos that are able to develop successfully in vitro, as well as those that show a developmental block at the 2-cell stage on culture in vitro, both show this rise in H2O2 levels after in vitro culture. The relationship between the rise in H2O2 and the ‘2-cell block’ to development is discussed.
Lateral inhibition and the development of the sensory bristles of the adult peripheral nervous system of Drosophila
Authors: Simpson Pat 
Published: April 2021

ABSTRACT
Cells in the neurectoderm of Drosophila face a choice between neural and epidermal fates. On the notum of the adult fly, neural cells differentiate sensory bristles in a precise pattern. Evidence has accumulated that the bristle pattern arises from the spatial distribution of small groups of cells, proneural clusters, from each of which a single bristle will result. One class of genes, which includes the genes of the achaete-scute complex, is responsible for the correct positioning of the proneural clusters. The cells of a proneural cluster constitute an equivalence group, each of them having the potential to become a neural cell. Only one cell, however, will adopt the primary, dominant, neural fate. This cell is selected by means of cellular interactions between the members of the group, since if the dominant cell is removed, one of the remaining, epidermal, cells will switch fates and become neural. The dominant cell therefore prevents the other cells of the group from becoming neural by a phenomenon known as lateral inhibition. They, then, adopt the secondary, epidermal, fate. A second class of genes, including the gene shaggy and the neurogenic genes mediate this process. There is some evidence that a proneural cluster is composed of a small number of cells, suggesting a contact-based mechanism of communication. The molecular nature of the protein products of the neurogenic genes is consistent with this idea.
Patterning of chick brain vesicles as revealed by peanut agglutinin and cholinesterases
Authors: Layer Paul G. , Alber Regina 
Published: April 2021

ABSTRACT
Differentiation of individual rhombomeres of the chicken hindbrain directly follows the emergence of primary brain vesicles. Immediately after the constric tion of the prosencephalon at HH9, a series of vesicles of decreasing size is established almost simultaneously between HH9 and HH10, including mesencephalon, four preotic (R2–R5) and one postotic (R6/R7) rhombo meres. Thereby, the cranial neural tube is ventrally embedded in a mesodermal PNA-binding matrix that particularly accumulates underneath vesicular constric tion sites, as demonstrated for the segregation of the prosencephalon at HH9 and the cerebellar rhombomere R1 from R2 at HH13. The subsequent period of hind brain differentiation is analyzed by cholinesterase (AChE, BChE) and peanut lectin histochemistry, by the BrdU and the neurite-specific G4 antibodies. Preotically, differentiation of two pairs of rhombomeres (R4+R5, R2+R3) starts in R4, immediately followed by R2. The caudal rhombomeres of both pairs are delayed (R5, R3). Then the postotic rhombomere is subdivided, whereby R7 differentiates before R6. Thus, the development in the direct vicinity of the otic vesicle is delayed (R5, R6). R7 is the last rhombomere that is demarcated caudally.
Based on these findings, we postulate two processes that may regulate rhombomere formation in the chicken embryo: (a) an early rostrocaudal wave establishing the major brain vesicles, (b) a superimposed pairwise seg mentation emanating rostrally and caudally from the otic vesicle. The segregation of the cerebellar rhombo mere is a late step.
Abbreviations: AChE, acetylcholinesterase (E.C. 3.1.1.7);
BChE, butyrylcholinesterase (E.C. 3.1.1.8);
BrdU, bromodesoxyuridine;
D, diencephalon;
E, eye stalk;
G4, neurite-specific antigen;
M, mesencephalon;
NP, neuropore;
OV, otic vesicle;
PNA, peanut agglutinin;
P, prosencephalon;
Rl, rhombomere No. 1;
R, rhombencephalon; T, telencephalon.
Development of homogeneous fast and slow motor units in the neonatal mouse soleus muscle
Authors: Fladby Tormod , Jansen Jan K. S. 
Published: April 2021

ABSTRACT
We studied the fiber type composition and contractile properties of mouse soleus motor units at 2 days, 5 days and 2 weeks of age. We used Lucifer Yellow injection to mark muscle fibers belonging to the same motor unit in the two youngest age groups, and the traditional method of glycogen depletion in the oldest. The age groups were chosen because 2 days is at the end of muscle fiber production; 5 days is at the start of synapse elimination in the muscle and 2 weeks is at the end. Muscle fibers were classified as fast (F) or slow (S) on the basis of their myosin heavy chain (MHC) content, as determined by different monoclonal antibodies.
Motor units are already dominated by either F- or S-fibers at 2 days, suggesting an early preferential innervation of the two types of fibers. A substantial part of the remaining refinement of the innervation takes place during the next 3 days, while the total number of terminals in the muscle remains constant. This is most easily explained by an exchange of aberrant for correct synapses during this period. A smaller part of the refinement of the innervation occurs during the sub sequent period of synapse elimination.
Autodifférenciation et induction de cartilage à partir de mésenchyme somitique de Poulet cultivéin vitro
Authors: Strudel par G. 
Published: April 2021

ABSTRACTSelf-differentiation and induction of cartilage from chick somitic mesenchyme cultured in vitroIt has been shown (Strudel & Watterson) that in the absence of inductors (neural tube and notochord) the somitic mesenchyme of the chick embryo does not differentiate in situ into cartilage until after the 27-30 somite stage. In culture, in a medium based upon embryo extract (diluted or undiluted), cartilage only differentiates in mesenchyme taken from embryos of 27 somites. If, on the other hand, the mesenchyme is wrapped in vitelline membrane and cultured in a medium containing undiluted embryo extract it self-differentiates from the 17-somite stage. Differentiation into cartilage can be obtained in mesenchyme taken from younger embryos if extracts of inductors—neural tube and notochord—are added to the culture medium. In these circumstances chondrogenesis may occur in mesenchyme from an embryo of 20 somites when the embryo extract is diluted or from an embryo of 13 somites if it is not. If the somitic mesenchyme from 8 somite embryos is both wrapped in vitelline membrane and cultured in a medium based upon undiluted embryo extract then differentiation of cartilage occurs. These results show that the time-relations of chondrogenesis from chick somitic mesenchyme cultured in vitro varies with the composition of the medium and with the method of culture. These variations make it clear that the capacity of somitic mesenchyme to differentiate into cartilage may exist at very early stages. This early capacity is not revealed unless the somitic mesenchyme is cultured in a very favourable nutritive medium and in the presence of extracts of inducing tissues.
The Early Development of the Otic Vesicle in Staged Human Embryos
Authors: O’Rahilly Ronan 
Published: April 2021

ABSTRACT
The early development of the otic vesicle has been investigated in thirty-six human embryos from stage 9 to stage 18 (3 to 6 post-ovulatory weeks). The otic zone was first distinguished at stage 9 and invagination had commenced in the more advanced specimens of stage 10. The otic pit deepened progressively during stage 11, and certain resemblances to the developing lens were noted. It is believed that contributions from the wall of the otic pit to the vestibulocochlear crest occurred, e.g. at stage 12, but they were not as conspicuous as the corresponding crest migrations from the optic primordium to the sheath of the optic vesicle. The otic pit became closed from the surface at stage 13 to form the otic vesicle, the dorsomedial portion of which became recognizable as the endolymphatic appendage. As in the case of the lens, a part of the basement membrane of the surface ectoderm became invaginated (stages 11 to 13) to form the basement membrane surrounding the otic vesicle. Although their precursors were detectable earlier, the cochlear and the semicircular ducts were clearly defined by the end of stage 18. During the formation of the semicircular ducts, portions of the epithelium lost their identity and their basement membrane disappeared, so that the epithelium merged with the underlying mesoderm, and obliteration of portions of the cavity of the otic vesicle ensued. It has been established previously that the various basement membranes associated with the embryonic eye persist into adulthood. Moreover, it is known that at least certain portions of the adult membranous labyrinth possess a basement membrane, derived presumably from that surrounding the otic vesicle in the embryo. The possible existence of a continuous and intact basement membrane throughout the adult membranous labyrinth, however, seems to require further investigation.
Localization of specific mRNAs in Xenopus embryos by whole-mount in situ hybridization
Authors: Hemmati-Brivanlou Ali , Frank Dale , Bolce Margaret E. , Brown Bob D. , Sive Hazel L. , Harland Richard M. 
Published: April 2021

ABSTRACT
We have adapted a non-radioactive technique to detect localized mRNAs in whole-mount Xenopus embryos. Synthetic antisense RNA transcribed in the presence of digoxygenin-UTP is used as a probe and is detected via an anti-digoxygenin antibody. We show that localized mRNAs can be detected from late gastrula to tadpole stages and that high as well as low abundance RNAs can be detected. The method was tested on muscle actin and α-globin RNAs, whose localization has previously been characterized. In addition, we used the method to determine the distribution of XA-1 RNA, an anterior ectoderm-specific RNA, which we show is expressed in the periphery of the cement gland as well as in the region of the hatching gland. The sequence of an XA-1 cDNA predicts a protein rich in proline and histidine.
Gastric endocrine cells share a clonal origin with other gut cell lineages
Authors: Thompson E. M. , Fleming K. A. , Evans D. J. , Fundele R. , Surani M. A. , Wright N. A. 
Published: April 2021

ABSTRACT
There has been considerable debate about the ontological origin of gut endocrine cells as being either from the neural crest (or primitive epiblast) or from the endodermal stem cell. We have attempted to define the ontological origin of endocrine cells by applying an experimental system that uses a marker to Identify one of the two phenotypes present in chimaeric mice as suggested by Ponder et al. (1985).
This study involved two separate experiments. The first made use of the unique staining properties of Dolichos bifloras agglutinin (DBA), a lectin that binds to the A-acetyl galactosamine sugar residues present on the surface of C57B1 mouse gut, but absent from RoRIII mouse gut, in C57Bl↔Roin mouse chimaeras at the ultrastructural level. A four-stage procedure for staining at the EM level was developed. Although mature villous endocrine cells stained for DBA, immature endocrine cells did not, either in the positive crypts of chimaeric mouse gut or in gut from C57B1 positive controls.
Thus a second marker was chosen. This experiment combined immunocytochemistry (to identify gastric antral gastrin cells chosen as a representative neuro-endocrine cell) with in situ DNA hybridization for the mouse male chromosome repeat sequence PY 353 (to identify XY cells) in XX→XY chimaeric mice. This study showed that the sex chromosomal pattern in the gastrin cells parallels that of other cells in the same gastric gland and therefore are clonal with them. This suggests that gut endocrine cells share a common stem cell with other epithelial cell lineages in the antrum and are endodermally derived.
Primary neurons that express the L2/HNK-1 carbohydrate during early development in the zebrafish
Authors: Metcalfe Walter K. , Myers Paul Z. , Trevarrowf Bill , Basst Michael B. , Kimmel Charles B. 
Published: April 2021

ABSTRACT
In zebrafish, many nerve pathways in both the CNS and periphery are pioneered by a small and relatively simple set of ‘primary’ neurons that arise in the early embryo. We now have used monoclonal antibodies to show that, as they develop, primary neurons of several functional classes express on their surfaces the L2/HNK-1 tetrasac-charide that is associated with a variety of cell surface adhesion molecules. We have studied the early labeling patterns of these neurons, as well as some non-neural cells, and found that the time of onset and intensity of immunolabeling vary specifically according to cell type.
The first neuronal expression is by Rohon-Beard and trigeminal ganglion neurons, both of which are primary sensory neurons that mediate touch sensitivity. These cells express the epitope very strongly on their growth cones and axons, permitting study of their development unobscured by labeling in other cells. Both types initiate axogenesis at the same early time, and appear to be the first neurons in the embryo to do so. Their peripheral neurites display similar branching patterns and have similar distinctive growth cone morphologies. Their central axons grow at the same rate along the same longitudinal fiber pathway, but in opposite directions, and where they meet they appear to fasciculate with one another. The similarities suggest that Rohon-Beard and trigeminal ganglion neurons, despite their different positions, share a common program of early development.
Immunolabeling is also specifically present on a region of the brain surface where the newly arriving trigeminal sensory axons will enter the brain. Further, the trigeminal expression of the antigen persists in growth cones during the time that they contact an individually identified central target neuron, the Mauthner cell, which also expresses the epitope. These findings provide descriptive evidence for possible roles of L2/HNK-1 immunoreactive molecules in axonal growth and synaptogenesis.
Ca2+-activated ATPase of the mouse chorioallantoic placenta: developmental expression, characterization and cytohistochemical localization
Authors: Tuan Rocky S. , Bigioni Neil 
Published: April 2021

ABSTRACTA membrane-associated, Ca2+-activated, Mg2+-dependent ATPase activity has been identified in the mouse chorioallantoic placenta. The enzyme activity is expressed and increases as a function of gestation. Bio-chemical characterization shows that the enzyme is highly specific for Ca2+ and nucleotide triphosphates, with a Km of 0.97 mM [Ca2+] and a Vmax of 1.05 nmol Pt released mg-1 placental protein min-1. The mouse placental Ca2+-ATPase activity has a pl of approximately 6.8, and corresponds to two apparent Mr values of 118 and ISOxlO3, based on Ferguson analysis of non-denaturing electrophoretograms. Enzyme activity is inhibited by phenothiazin (suggesting a calmodulin dependence), vanadate, erythrosin B and quercetin, but not by ouabain or levamisole. Enzyme cytohistochemistry revealed that the Ca2+-ATPase is localized to’polyploid trophoblastic cells of the mouse inner placenta. These results suggest that the enzyme may be a functional component of transplacental calcium transport during mouse embryonic development.
Primordial germ cells in the mouse embryo during gastrulation
Authors: Ginsburg Malka , Snow Michael H. L. , McLaren Anne 
Published: April 2021

ABSTRACT
With the aid of a whole-mount technique, we have detected a small cluster of alkaline phosphatase (ALP)-positive cells in whole mounts of mid-primitive-streakstage embryos, days post coitum (dpc). Within the cluster, about 8 cells contain a small cytoplasmic spot, intensely stained for ALP activity and possibly associated with an active Golgi complex. The cluster lies just posterior to the definitive primitive streak in the extraembryonic mesoderm, separated from the embryo by the amniotic fold. Towards the end of gastrulation, the number of cells containing the ALP-positive spot rises to between 50 and 80. Thereafter the number of cells in the extraembryonic cluster declines, and similar cells start to be seen in the mesoderm of the primitive streak and then in the endoderm. At 8 dpc, about 125 ALP-stained cells are found, mainly in the hindgut endoderm and also at the base of the allantois, their appearance and location at this stage agreeing closely with previous reports on primordial germ cells (PGCs). Embryos from which the cluster area has been removed at the 7-day stage are devoid of PGCs after culture for 48 h, whereas the excised tissue is rich in PGCs. We argue that the cells in the cluster are indeed primordial germ cells, at a stage significantly earlier than any reported previously. This would indicate that the PGC lineage in the mouse is set aside at least as early as 7 dpc, possibly as one of the first ‘mesodermal’ cell types to emerge, and that its differentiation, as expressed by ALP activity, is gradual.
Two alkaline phosphatase genes are expressed during early development in the mouse embryo
Authors: Hahnel Ann C. , Rappolee Daniel A. , Millan Jose Luis , Manes Thomas , Ziomek Carol A. , Theodosiou Nicoleta G. , Werb Zena , Pedersen Roger A. , Schultz Gilbert A. 
Published: April 2021

ABSTRACT
Alkaline phosphatase (AP) activity is stage specific in mouse embryos and may be associated with compaction and separation of trophectoderm from inner cell mass in preimplantation development. We previously sequenced a cDNA and two mouse AP genes that could contribute to the AP activity in embryos. Oligonucleotide primers were constructed from the three sequences and used in the reverse transcription-polymerase chain reaction technique to establish that two of the three AP isozymes are transcribed during preimplantation development. The predominant transcript (E-AP) is from a gene highly homologous to the human tissue-specific APs, but different from the mouse intestinal AP. Tissue non-specific (TN) AP also is transcribed, but there is approximately 10 times less TN-AP than E-AP transcript. The TN-AP isozyme is the predominant transcript of 7 to 14 day embryos and primordial germ cells. A switch in predominance from E-AP to TN-AP must occur during early postimplantation development. This study establishes a framework for experiments to determine the functions of the two isozymes during preimplantation development.
Ontogenetic transition of wound healing pattern in rat skin occurring at the fetal stage
Authors: Ihara Setsunosuke , Motobayashi Yumiko , Nagao Eriko , Kistler Andreas 
Published: April 2021

Abstract
Full-thickness excisional wounds were made in the dorsal skin of rat fetuses at day 16 and day 18 of gestation. A small patch of skin surrounding the open wound was cut out, mounted on a plastic ring and incubated in an organ culture system. In the presence of serum, the open wound in the day-16 fetal skin closed within three days of culture. During the wound-closure process, no new structures were formed in the wound space, and no conspicuous changes were noted in the histological architecture of the surrounding skin during culture, indicating that the wound closure may result from a centripetal movement of the surrounding skin only. In contrast, the size of the open wound in the day- 18 fetal skin remained almost unchanged for one week, but a thin acellular network spread over the wound space within one day of culture. The predominant component of the network was cross-linked fibrin, as disclosed by scanning electron microscopy and sodium dodecylsulfate-polyacrylamide gel electrophoresis followed by immunoblotting. The network served as a scaffold for the ingrowth of fibroblast-like cells. These stage-dependent differences in fetal wound healing were consistent with an in vivo study showing that the day-16 wound was covered with the surrounding skin itself, whereas the day-18 wound was covered with newly formed epidermis and invaded by inflammatory cells. The present investigation strongly indicates the prenatal occurrence of a fetal-to-adult transition in the woundhealing pattern of rat skin.
Expression of a surface epitope on cells that link branches in the tracheal network of Manduca sexta
Authors: Nardi James B. 
Published: April 2021

Abstract
A monoclonal antibody (MAb 2F5) to a cell surface epitope labels a small subpopulation of tracheal epithelial cells in each thoracic and abdominal segment of Manduca. These cells (nodes) represent the sites within the tracheal network at which invaginating tracheal tubes join during embryonic establishment of the tracheal network. Tracheal nodes are also the sites at which tracheal cuticle fractures during each molt. Since tracheal cuticle is shed through each spiracle, a tracheal node lies between each pair of contralateral spiracles within a segment (commissural node) and between each pair of adjacent, ipsilateral spiracles (lateral longitudinal node). MAb 2F5 first labels presumptive nodal cells of tracheal epithelium immediately prior to the linking of epithelial tubes from successive and opposite spiracles. One cell at the tip of each invaginating tracheal branch labels with MAb 2F5. The highly localized expression of the cell surface epitope recognized by MAb 2F5 may be instrumental in the orderly coupling of tracheal branches during embryonic development. On the basis of immunolabeling of Western blots and tissues, MAb 2F5 is believed to recognize Manduca fasciclin II, a member of a class of molecules involved in cell adhesion/recognition.
Concurrent reduction in the sulfation of heparan sulfate and basement membrane assembly in a cell model system
Authors: Brauer Philip R. , Keller Katharyn M. , Keller John M. 
Published: April 2021

Abstract
Basement membranes (BMs) are specialized extracellular matrices that have important roles in cell attachment, migration, growth and differentiation. The murine teratocarcinoma cell line, M1536-B3, has been shown to produce a model BM composed of laminin, entactin and heparan sulfate proteoglycans but lacking collagen. Therefore, M1536-B3 cells are an excellent model system in which to study the role of non-collagenous components in BM assembly. We have used these cells to test for a requirement of mature heparan sulfate (HS) chains in BM assembly. Growth of Ml536-B3 cells in the presence of chlorate, an inhibitor of activated sulfate synthesis, resulted in a dose-dependent decrease in the sulfation of glycosaminoglycans and reduction in the charge density of the isolated HS. The undersulfated HS from chlorate-treated cells had a decreased binding capacity for laminin when compared with control HS. Concurrent with these changes in sulfation, chlorate treatment of M1536-B3 cells resulted in the failure of BM assembly, which was restored upon removal of the chlorate from the growth medium. These results were not due to major alterations in cell attachment, spreading, growth, protein synthesis, or to an inability of the cells to synthesize and secrete laminin. These data suggest that the sulfation of HS and its subsequent ability to interact with other BM components play major roles in the assembly and structure of BMs.