bluuebunny/crossref_metadata_2025_split huggingface dataset:
Direct introduction of cloned DNA into the sea urchin zygote nucleus, and fate of injected DNA
Authors: Franks Roberta R. , Hough-Evans Barbara R. , Britten Roy J. , Davidson Eric H. 
Published: April 2021

Abstract
A method is described for microinjection of cloned DNA into the zygote nucleus of Lytechinus variegatus. Eggs of this species are unusually transparent, facilitating visual monitoring of the injection process. The initial fate of injected DNA fragments appears similar to that observed earlier for exogenous DNA injected into unfertilized egg cytoplasm. Thus after end-to-end ligation, it is replicated after a lag of several hours to an extent indicating that it probably participates in most of the later rounds of DNA synthesis undergone by the host cell genomes during cleavage. The different consequences of nuclear versus cytoplasmic injection are evident at advanced larval stages. Larvae descendant from eggs in which exogenous DNA was injected into the nuclei are four times more likely (32 % versus 8 %) to retain this DNA in cell lineages that replicate very extensively during larval growth, i.e. the lineages contributing to the imaginal rudiment, and thus to display greatly enhanced contents of the exogenous DNA. Similarly, 36 % of postmetamorphic juveniles from a nuclear injection sample retained the exogenous DNA sequences, compared to 12 % of juveniles from a cytoplasmic injection sample. However, the number of copies of the exogenous DNA sequences retained per average genome in postmeta-morphic juveniles was usually less than 0·1 (range 0·05–50), and genome blot hybridizations indicate that these sequences are organized as integrated, randomly oriented, end-to-end molecular concatenates. It follows that only a small fraction of the cells of the average juvenile usually retains the exogenous sequences. Thus, even when introduced by nuclear microinjection, the stable incorporation of exogenous DNA in the embryo occurs in a mosaic fashion, although in many recipients the DNA enters a wider range of cell lineages than is typical after cytoplasmic injection. Nuclear injection would probably be the route of choice for studies of exogenous DNA function in the postembryonic larval rudiment.
Temporal and spatial pattern of differences in microtubule behaviour during Drosophila embryogenesis revealed by distribution of a tubulin isoform
Authors: Wolf Nurit , Regan Cathy L. , Fuller Margaret T. 
Published: April 2021

Abstract
Immunofluorescence staining of Drosophila embryos with a monoclonal antibody specific for acetylated α tubulin has revealed that acetylated and nonacetylated a-tubulin isoforms have different patterns of distribution during early development. Acetylated α-tubulin was not detected in either interphase or mitotic spindle microtubules during the rapid early cleavage or syncytial blastoderm divisions. Acetylated α-tubulin was first observed as interphase lengthened at the end of syncytial blastoderm, and at cycle 14 was localized to a ring of structures clustered around the interphase nuclei. These structures probably represent a set of stable microtubules involved in nuclear elongation. Absence of detectable acetylated α-tubulin prior to cellular blastoderm seems to be due to rapid turnover of microtubule arrays rather than to lack of the enzyme required for modification, since acetylated α-tubulin appeared in early embryos when microtubules were stabilized by taxol treatment or anoxia. Because acetylated α-tubulin seems to be characteristic of stable microtubule arrays, the appearance of the antigen at cycle 14 represents a fundamental change in microtubule behaviour in the somatic cells of the embryo. Acetylated α-tubulin was not detected in pole cells during the blastoderm or early gastrula stages, indicating that acetylation of α-tubulin is not merely a consequence of cellularization.
After the onset of gastrulation, interphase microtubule arrays in most cell types contain acetylated α-tubulin. However, cells in mitosis lack antibody staining. The resulting unstained patches reveal the stereotyped spatial pattern of cell division during gastrulation. Although the cells that give rise to the amnioserosa have acetylated α-tubulin in their interphase arrays at early gastrulation, by germ band elongation these large, plastic cells completely lack staining with anti-acetylated α-tubulin. In contrast, differentiated cell types such as neurones, which have arrays of stable axonal microtubules, stain brightly with the specific antibody. Although acetylated and nonacetylated α-tubulin are present in roughly equal amounts by the late stages of embryogenesis, acetylated α-tubulin is partitioned into the pellet during centrifugation of extracts of embryos homogenized at 4°C.
Regulation of neurotransmitter metabolic enzymes and tyrosine hydroxylase mRNA level by nerve growth factor in cultured sympathetic neurones
Authors: Raynaud Brigitte , Faucon-Biguet Nicole , Vidal Simone , Mallet Jacques , Weber Michel J. 
Published: April 2021

Abstract
The survival of new-born rat sympathetic neurones in culture was increased in a dose-dependent manner by 7S nerve growth factor (NGF). NGF also increased, in a parallel manner, the specific activities of tyrosine hydroxylase (TOH) and choline acetyltransferase (CAT). Total acetylcholinesterase (AcChE) activity increased with NGF concentration, although less distinctly than TOH and CAT. However, NGF caused a large induction of the asymmetric A12 form of AcChE, and to a lesser extent of the globular G, and G2 forms, whereas the globular G4 form was little affected. This suggests that NGF differentially regulates the syn-thesis and/or assembly of the various AcChE molecular forms.
The levels of TOH mRNA in neurone cultures grown with increasing NGF concentrations were measured by Northern blot analysis with a rat cDNA probe. To correct for variations in the total mass of RNA per neurone, the filters were rehybridized with an 18S rRNA probe. The level of TOH mRNA, measured by the ratio (TOH: 18S) of the hybridization signals increased 3·4-fold between 92 and 740 ng ml-1 7S NGF. Increases of TOH specific activity of the same order of magnitude were observed in sister cultures. The deficit in the level of mature TOH mRNA at low NGF concentration was not accompanied by a compensatory accumulation in unprocessed TOH transcripts. As TOH induction is insensitive to RNA polymerase inhibitors, we suggest that NGF regulates the maturation of TOH pre-mRNAs, and that the unprocessed transcripts are rapidly degraded. The long-term regulation of TOH by NGF may thus constitute a case of process-versus-discard control, as defined by J. E. Darnell.
Colour pattern regulation after surgery on the wing disks of Precis coenia (Lepidoptera: Nymphalidae)
Authors: Nijhout H. Frederik , Grunert Laura W. 
Published: April 2021

Abstract
Partial ablations were done in situ on the imaginai disks of the hindwing in larvae of Precis coenia at ages between 2 and 9 days prior to pupation. While there was no regeneration of the wing lamina, the cut edge developed normal marginal scales and a marginal colour pattern if the ablation was done more than 3-5 days prior to pupation. The response of elements of the marginal colour pattern to partial ablation of the wing disk indicates that the wing margin has an important role in colour pattern determination and appears to act as a sink for a pattern-inducing signal. While the elements of the marginal colour pattern regulate to the shape and position of the new wing margin, the eyespots changed their shape and size but not their position upon partial ablation of the wing disk. When a cut was positioned near one of the dorsal eyespots, the outer rings of the eyspot opened up so that its central field became contiguous with the new margin. The behaviour of the dorsal eyespots of the hindwing in response to ablation of the wing disk, as well as to other developmental disturbances, appears to be the reverse of those on the forewing and ventral hindwing. We conclude that the central field of a dorsal eyespot and the wing margin share similar controlling properties with respect to pattern, and that both appear to act as sinks or as the inverse of the sources of pattern-inducing signal found in the eye-spots of the forewing.
Sequential activation of butyrylcholinesterase in rostral half somites and acetylcholinesterase in motoneurones and myotomes preceding growth of motor axons
Authors: Layer Paul G. , Alber Regina , Rathjen Fritz G. 
Published: April 2021

Abstract
By applying double-staining procedures that combine cholinesterase histochemistry (acetyl- and butyrylcholinesterase, respectively) as indicators of neuronal and myotomal tissue differentiation on longitudinal sections, together with detection of motor axons with antibodies to G4 antigen, we here describe the spatiotemporal expression of all components of the segmental motor units along the trunk of chicken embryos between stages 16–20.
In particular, BChE expression is spatially elevated on the rostral part of the differentiating somite. About 2–3 somites more rostrally (and thus developmentally later), AChE is expressed almost simultaneously in a nonsegmented fashion in neuronal cell bodies of the ventral horn and in the corresponding dermomyo-tomes. There it is first detectable in a rostromedial sector. With a delay (4—6 somites compared with AChE in motoneurones), motor axons begin to grow exclusively through the BChE-rich sclerotomal space towards the AChE-activated myotome anlage. On motor axons, AChE detection is significantly retarded.
We conclude that the rostrocaudal segmental asymmetry is not restricted to the sclerotomes (which other authors have described before by using different markers), but it extends into the dermomyotome, in which cholinesterases introduce an early subdivision. Hence, the entire process of first myotome differentiation, motor axon growth and establishment of first target contacts are taking place within the rostral half somite. We suggest that both cholinesterases might be involved in processes of motor unit differentiation and fibre guidance.
Abbreviations: AChE, acetylcholinesterase (EC 3.1.1.7); AChR, acetylcholine receptor; BChE, butyryl- or pseudo-, or serumcholinesterase (EC 3.1.1.8); BW 284C51, 1,5-bis(4-allyldimethylammoniumphenyl)pentane-3-one dibromide = specific inhibitor of AChE; ChE, cholinesterase; iso-OMPA, tetraisopropylpyrophosphor-amide = specific inhibitor of BChE; NCC, neural crest cells: PBS, phosphate-buffered saline; TBS, Tris-buffered saline; ATC, acetylthiocholine; BTC, butyrylthiocholine.
Serotonin and morphogenesis : I. Sites of serotonin uptake and -binding protein immunoreactivity in the midgestation mouse embryo
Authors: Lauder J. M. , Tamir H. , Sadler T. W. 
Published: April 2021

Abstract
The possible involvement of the neurotransmitter serotonin (5-HT) in morphogenesis of the craniofacial region in the mouse embryo has been investigated using the method of whole-embryo culture. Day-12 embryos were incubated for 3–4 h in the presence of 5-HT or its precursors L-tryptophan (L-TRP) or 5-hydroxytryptophan (5-HTP), followed by fixation, sectioning and staining with a specific antiserum to 5-HT. Sites of 5-HT immunoreactivity were found in a variety of locations in tissues of the head and neck, which are either epithelia derived from the non-neural ectoderm or are non-neuronal midline brain structures. These sites include the surface epithelia of the head, face, nasal prominences, branchial arches, oral cavity and associated parts of the nasal epithelium, the epithelium covering the eye, parts of the otic vesicle, the epiphysis and roof of the diencephalon. With the exception of the oral cavity, sites of immunoreactivity for serotonin-binding protein were identified in the mesenchyme adjacent to these sites. This mesenchyme consists of ectodermally derived neural crest cells, which are known to receive inductive influences from the epithelia with which they interact during their migration through the craniofacial region. The presence of 5-HT uptake sites in epithelia and adjacent sites of SBP in the underlying mesenchyme raises the possibility that 5-HT might be involved in those epithelial-mesenchymal interactions known to be important for the development of structures in the craniofacial region.
Interspecific micronuclear transplantation inParamecium:nucleogenesis and stomatogenesis in asexual and sexual reproduction
Authors: Chau M. F. , Ng Stephen F. 
Published: April 2021

AbstractThe micronucleus of Paramecium plays an essential role in the development of the oral apparatus in both asexual and sexual cycles. The present study analyses this somatic function of the micronucleus by interspecific transplantation of the micronucleus between two species, P. jenningsi and P. tetraurelia. The two species are similar in nucleogenesis in the sexual cycle, in the dependence of stomatogenesis on the micronucleus and in the pattern of the oral ciliature. P. jenningsi, however, has a longer oral apparatus. Renucleated cell lines were derived from heterospecific transplantation (P. jenningsi amicronucleates implanted with micronuclei of P. tetraurelia), and also from homospecific transplantation (P. jenningsi). Both homo- and heterospecific transplants exhibited abnormal micronuclear propagation during cell division. In the sexual cycle, the heterospecific transplants exhibited more severe micronuclear anomalies, suggesting interspecific incompatibility. On the other hand, the stomatogenic consequences of the two types of transplants in the asexual and sexual cycles were similar. It is concluded that micronuclear functions, in the assembly and normal patterning of the oral ciliature in the sexual cycle, are not species-specific. However, the oral apparatuses developed by the homo- and heterospecific transplants were similar in length, and approaching that of normal P. jenningsi. Hence, even though the micronucleus is necessary for developing normal oral length, the oral length characteristic of a species is determined by species-specific nonmicronuclear factors. The present findings resemble heterospecific dermal–epidermal inductive interactions in multicellular development, with the micronucleus exerting a nonspecies-specific ‘intracellular inductive stimulus’ on the oral anarchic field to promote oral development.
Honeybee morphogenesis: embryonic cell movements that shape the larval body
Authors: Fleig Richard , Sander Klaus 
Published: April 2021

Abstract
Crucial steps in honeybee morphogenesis are characterized by the migration of free epithelial edges while well-defined epithelial cell populations expand or translocate. For each step - dorsal strip invasion, gastrulation, formation of serosa, amnion and midgut - scanning electron microscopy reveals a highly specific syndrome of cell shapes and cell movements at the advancing epithelial edge. Epithelial translocation appears to result from various combinations of ameboid movement, cell flattening, cell rearrangement (intercalation) and cell contraction along the free epithelial edge. The direction of epithelial movements could result essentially from the initial shape and orientation of the edge combined with the cells’ tendency to close vacant spaces by extension and migration. These findings are discussed in relation to morphogenetic movements in other insects and to postembryonic wound healing in insects and amphibians.
The formation of pattern on the wing of the moth,Ephestia kühniella
Authors: Toussaint Neil , French Vernon 
Published: April 2021

AbstractTransverse bands of coloured scales are a common feature of lepidopteran wing patterns and it has been suggested that their positions are specified by a propagated ‘Determination Wave’ (Kühn & von Englehardt), or a ‘Gradient’ of diffusible morphogen (Njjhout). We have assessed these models in an experimental study of the formation of bands in the moth, Ephestia kühniella.The banding pattern can be altered by microcautery of the pupal wing between 1 h and 48 h postpupation (at 20°C) and effects are of two types:Local modifications follow early (1–3 h postpupation) cautery located on or between the presumptive sites of the bands; operations more proximally or distally on the wing have no effect. Patterns consist of a loop deflecting the nearest band medially, around the site of cautery; or an isolated ring of band scales surrounding the operation site, with the two bands in their normal positions. The type of pattern formed depends only on the location of the cautery, with rings following medial cautery (midway between the bands).Global modifications follow a 36–48 h cautery anywhere on the wing surface and they consist of a medial displacement of both bands. The degree of displacement is very variable (with band separation reduced to 33–87 % of that on the contralateral control wing) but this does not depend on location of the cautery. Furthermore, the degree of modification does not depend on the precise age at cautery, as an equivalent range of effects is produced at 36 h, at 42 h and at 48 h.The Determination Wave model is disproved since it explicitly assumes that the different degrees of global modification form a temporal sequence (from severe early to mild late) and they do not. Furthermore, this model cannot explain adequately the formation of loop or ring local modifications.The Gradient model can account for many features of the results, but it does not readily explain the ring local modifications or the effect of (36–48 b) cautery in causing a global change in the banding pattern, independent of the site or precise time of operation.
Proliferation kinetics and cell lineages can be studied in whole mounts and macerates by means of BrdU/anti-BrdU technique
Authors: Plickert G. , Kroiher M. 
Published: April 2021

AbstractS-phase cells in intact animals of the coelenterate species Eirene viridula, Hydractinia echinata, Hydra attenuate, and Hydra magnipapillata incorporate the thymidine analogue bromodeoxyuridine (BrdU) into newly synthesized DNA. BrdU-labelled nuclei divide and cells appear to undergo normal differentiation. Whole-mount preparations and macerated tissues were screened for S-phase cells by means of immunocytochemical detection of BrdU (Gratzner, 1982). It is demonstrated that spatial patterns of DNA replication can be evaluated easily. Cell lineages and pathways of cell migration could be traced.
The aetiology and pathogenesis of craniofacial deformity
Authors: Posw1llo David 
Published: April 2021

ABSTRACT
Craniofacial malformations have been recorded since time immemorial. While observational studies have assisted in the recognition of syndromes, little light has been shed on the causal mechanisms which interfere with craniofacial development. Animal studies in which malformations occur spontaneously or have been induced by teratogenic agents have permitted step-by-step investigation of such common deformities as cleft lip and palate. The role of the ectomesenchymal cells of the neural crest and the possible phenomenon of disorganized spontaneous cell death are described in relation to lip clefts. The factors associated with isolated cleft palate, Pierre Robin syndrome and submucous clefts are described by reference to animal models.
The haemorrhagic accident preceding the onset of craniofacial microsomia is discussed as is the distinctly different phenomenon of disturbance to the migration or differentiation of neural crest cells in the pathogenesis of Treacher Collins syndrome. The more severe anomalies of the calvarium such as plagiocephaly, Crouzon and Apert syndrome still defy explanation, in the absence of an appropriate animal system to study; some thoughts on the likely mechanism of abnormal sutural fusions are discussed.
The role of glucose and pyruvate transport in regulating nutrient utilization by preimplantation mouse embryos
Authors: Gardner D. K. , Leese H. J. 
Published: April 2021

ABSTRACT
Preimplantation mouse embryos utilize pyruvate preferentially during the early cleavage stages before switching to glucose at around the time of compaction. This switch in substrate preference has been studied using a non-invasive ultramicrofluorometric analytical technique on single mouse embryos.
On the basis of transport kinetic studies and inhibition by phloretin, cytochalasin B and sugar analogues, a component of glucose uptake by mouse blastocysts was found to be mediated by facilitated diffusion. The Jmax and Kt of this facilitated component were 3·53 pmol embryo −1 h −1 and 0·14 mm, respectively. At physiological concentrations of glucose, the facilitated component accounts for around 75 % of glucose uptake. Glucose uptake by blastocysts was found to be insensitive to insulin, added at a range of concentrations. There was no evidence for glucose active transport. The carrier-mediated component of glucose entry was detectable from the 2-cell stage onwards.
Pyruvate uptake was also mediated by a carrier throughout development. In the absence of glucose in the incubation medium, the characteristic decline in pyruvate uptake does not occur. The data are consistent with a role for embryonic cell transport in regulating glucose utilization prior to compaction, but do not exclude the involvement of metabolic factors, such as the allosteric regulation of the enzymes hexokinase and phosphofructokinase.
Studies in insect segmentation: from teratology to phenogenetics
Authors: Sander K. 
Published: April 2021

ABSTRACT
Old and new data on the segmentation process in arthropods are considered mainly with reference to the genetical basis of segmentation in Drosophila. Problems discussed are the universality (or otherwise) of parasegmental metamery, homeotic genes in insects other than Drosophila, pair-rule traits in myriapods, various segmentation anomalies related to polar morphogenetic centres, and sequential segment determination in the horseshoe crab. The opening and closing paragraphs address the conceptual and terminological progress from the study of ‘developmental monsters’ to the study of ‘developmental genes’ as a means of analysing segmentation.
Homeotic genes and the control of segment diversity
Authors: Akam Michael , Dawson Iain , Tear Guy 
Published: April 2021

ABSTRACT
Homeotic genes control the diversity of segment development, but the domains of action of homeotic genes do not obviously correspond with the major morphological subdivisions of the insect body. We suggest that this lack of correspondence is misleading, because the spatial domains defined by genetics mask fundamental differences in the roles played by individual genes in different regions. In one or more parasegments, each homeotic gene is expressed ‘metamerically’; that is, it is expressed from blastoderm stages onwards in all or virtually all cells of the parasegment primordium. Elsewhere, the same homeotic gene may be deployed adventitiously, only in subsets of cells and at later stages of development. We argue that the early ‘metameric’ domains of gene expression do correlate with the major morphological subdivisions of the fly. This suggests a relatively direct relationship between the expression of particular homeotic genes and the establishment of the ‘ground plan’ that characterizes segments within each major tagma of the body. This relationship allows us to suggest a scenario for the evolution of homeotic genes in relation to the evolving morphological organization of the arthropod body plan in the insect–myriapod lineage.