bluuebunny/crossref_metadata_2025_split huggingface dataset:
Expression of Drosophila epidermal growth factor receptor homologue in mitotic cell populations
Authors: Kammermeyer K. L. , Wadsworth Samuel C. 
Published: April 2021

ABSTRACT
Expression of the Drosophila homologue (DER) of the human epidermal growth factor (EGF) receptor has been studied during development by RNA blot hybridizations and in situ hybridizations. One of the hypothetical functions of the protein encoded by this gene is mitotic signal transduction and, therefore, we have searched for evidence of its expression in mitotic cell populations. Increased DER transcript levels were detected in virtually all cells in cellular blastoderm embryos, indicative of the onset of transcription of the gene at this stage of development. These transcripts persist at least until the formation of the ventral furrow at the beginning of gastrulation. Expression of DER has been investigated in populations of nondividing cells, imaginal cells and nervous tissue in third instar larvae. By RNA blot hybridizations, we have shown that imaginal discs contain the bulk of the DER transcripts present in the whole third instar larvae. This result has been confirmed by in situ hybridizations. All imaginal discs, representing dividing cells, contain DER transcripts while salivary glands, representing nondividing cells, do not. Within the central nervous system, hybridization of the DER probe is confined to small clusters of cells in the brain cortex. During oogenesis, cell division programs are highly ordered temporally and spatially. Follicle cells express high levels of DER RNA during their mitotic phase of growth but lose these transcripts as they cease division. Nurse cells also express DER transcripts at lower levels even though they are not dividing. However, nurse cell transcripts represent stored maternal RNA species destined for use during preblastoderm embryonic development. These results indicate that the DER gene is expressed in mitotic cell populations during several stages of development and is not expressed in certain populations of nonmitotic cells.
Genetics of cell and axon migrations in Caenorhabditis elegans
Authors: Hedgecock Edward M. , Culotti Joseph G. , Hall David H. , Stern Brian D. 
Published: April 2021

ABSTRACT
The Caenorhabditis elegans epidermis comprises 78 cells which cover the external surface of the embryo as a single cell layer. These cells secrete the cuticle from their exterior faces and support the body wall muscles and most of the nervous system on their interior faces. The epidermal cells arise by autonomous embryonic cell lineages but show regulative interactions after their assembly into an epithelium. It is believed that the various epidermal cells express different kinds or amounts of surface molecules that govern their mutual assembly and also guide the attachments and migrations of the underlying body muscles and neurones. The first muscles and neurones may in turn express new surface molecules that refine later cell movements. Mutations in some 30 known genes disrupt the movements of cells or axons along the body wall.
In vitro analysis of glucose metabolism and embryonic growth in postimplantation rat embryos
Authors: Ellington S. K. L. 
Published: April 2021

ABSTRACT
The glucose metabolism and embryonic development of rat embryos during organogenesis was studied using embryo culture. Glucose uptake and embryonic growth and differentiation of 10·5-day explants (embryos + membranes) were limited by the decreasing glucose concentration, but not the increasing concentration of metabolites, in the culture media during the second 24 h of a 48 h culture. No such limitations were found on the embryonic development of 9–5-day explants during a 48 h culture although glucose uptake was slightly reduced at very low concentrations of glucose. From the head-fold stage to the 25-somite stage of development, glucose uptake was characteristic of the stage of development of the embryo and not the time it had been in culture.
Embryonic growth of 9·5-day explants was similar to that previously observed in vivo. Glucose uptake by 9·5-day explants was dependent on the surface area of the yolk sac and was independent of the glucose concentration in the culture media (within the range of 9·4 to 2·5 mM). The proportion of glucose converted to lactate was 100 % during the first 42 h of culture then fell to about 50 % during the final 6 h. The protein contents of both the extraembryonic membranes and the embryo were dependent on the glucose uptake.
The monoclonal antibody 69A1 recognizes an epitope found on neurones with axons that fasciculate but not on those with non-fasciculating processes
Authors: Pigott R. , Davies A. M. 
Published: April 2021

ABSTRACT
We have previously reported that the cell-type distribution and pattern of expression of the surface antigen recognized by the monoclonal antibody 69A1, suggests that it may be involved during the period of nerve fibre outgrowth and the formation of fibre bundles in the rat (Pigott & Kelly, 1986). In this current study, we have examined the expression of the epitope recognized by antibody 69A1 in regions of the rat central nervous system in which it is possible to distinguish between neurones with axons that fasciculate to form clearly defined fibre tracts and neurones with non-fasciculating processes. We have also examined antibody 69Al labelling in several regions of the peripheral nervous system. We report that the 69A1 epitope is expressed on neurones with axons that fasciculate but is not found on neurones with short, non-fasciculating axons or on neurones without a morphologically identifiable axon. The antigen 69Al has been purified and shown to be immunochemically closely related or identical to the LI antigen.
Computer-assisted analysis of hyaluronate distribution during morphogenesis of the mouse secondary palate
Authors: Brinkley Linda L. , Morris-Wiman Joyce 
Published: April 2021

ABSTRACT
Hyaluronate mediated extracellular matrix swelling has been hypothesized to play a major role in reorientation of the secondary palatal shelves. A computer-assisted method utilizing image registration and subtraction was used to visualize the distribution of hyaluronate (HA) during morphogenesis of the secondary palate. Patterns of HA distribution in anterior, posterior and presumptive soft palate were examined in the secondary palatal shelves of CD-I mouse fetuses that were 30, 24 and 18 h prior to, and at the time of, shelf reorientation. Adjacent serial sections were taken from each shelf region of three to six specimens from a minimum of three litters for each gestational age. One section was incubated in buffer as a control, the other digested with Streptomyces hyaluronidase to specifically remove HA. Both sections were stained with Alcian blue to visualize the extracellular matrix and counterstained with nuclear fast red to visualize cells. Two different videoimages were then digitized for each tissue section, one using wavelengths of light that were at or near the maximum absorbance of the matrix stain, the other using wavelengths that were at the maximum absorbance of the cellular stain. Thus, a matrix image and a cell image of both control and digested sections were produced. Next, the cell image was subtracted from its respective matrix image, resulting in a control matrix-only image and a digested (HA-removed) matrix-only image. These images were mathematically warped to one another, if necessary, and registered with one another. The digested image was then subtracted from the control image. The resultant difference picture displayed the pattern and relative intensities of HA distribution across the tissue section. Prior to and during shelf reorientation, unique region-specific patterns of HA distribution and relative intensity were identified which became homogeneous after reorientation. Presumptive soft palate shows the most extensive and intense patterns of HA distribution, followed by the posterior region. The anterior region has the most sparse pattern of the three regions examined. The results are consistent with the hypothesized role of HA in shelf reorientation.
Effects of chlorcyclizine-induced glycosaminoglycan alterations on patterns of hyaluronate distribution during morphogenesis of the mouse secondary palate
Authors: Brinkley Linda L. , Morris-Wiman Joyce 
Published: April 2021

ABSTRACT
Chlorcyclizine (CHLR) enhances the degradation of hyaluronate (HA) into smaller molecular weight pieces with no effect on its synthesis. Administration of CHLR to pregnant CD-I mice on gestational days 10·5, 11·5 and 12·5 results in 100 % cleft palate in the fetuses. The caudal two thirds of the palatal shelves are reduced in size and unable to reorient in vitro, while anterior shelf regions are relatively unaffected. Alcian blue staining combined with specific enzymic digestion was used to identify HA in sections of CHLR-treated shelves. With the aid of computer-assisted image subtraction the patterns of HA distribution across the tissue section were objectively identified. Anterior, posterior and presumptive soft palatal shelf regions were examined at gestational days 13·25, 13·5, 13·75 and 14·5. Acquisition of a normal pattern of HA distribution was delayed by about 24 h, as compared to untreated specimens in all three shelf regions. The posterior and soft regions, comprising the caudal two thirds of the shelf, also showed pronounced shape change. These regions only displayed normal curvature of the nasal surface when a normal pattern of HA distribution was attained. These results suggest that, for the caudal two thirds of the palatal shelf, normal shape and the ability to remodel are linked to the molecular configuration of HA and to a specific pattern of HA distribution.
Spreading of microinjected horseradish peroxidase to nondescendant cells in embryos of Patella (Mollusca, Gastropoda)
Authors: Kühtreiber Wiel M. , Serras Florenci , Biggelaar Jo A. M. van den 
Published: April 2021

ABSTRACT
We have injected horseradish peroxidase (HRP) and fluorescein-isothiocyanate dextran (FD) into cells and into the blastocoelic cavity of Patella vulgata embryos, before and during the interval between 5th and 6th cleavage, in which the mesodermal stem cell is determined by means of interactions between the central 3D macromere and the contacting animal micromeres.
Intracellular injections of HRP at different stages showed that, whereas before this contact phase no spreading of label was observed, a clear intercellular transfer of HRP was found after the contact was established. Control experiments showed that it was HRP in its intact, high molecular weight form that was transferred in the living embryo.
Injections of HRP into the blastocoelic cavity gave essentially the same results. In these cases, the HRP was taken up by the cells from contact stage onwards. When FD was injected into the blastocoelic cavity, no uptake was observed, not even after prolonged presence of FD in it. However, when HRP and FD were mixed, both were taken up, starting at contact stage. Differences in labelling pattern of HRP, as compared with FD, and a shift of the FD fluorescence after uptake, suggest that receptor-mediated endocytosis is involved. The possible morphogenetic significance of the transfer mechanism is discussed.
Trans-regulatory functions in the Abdominal-B gene of the bithorax complex
Authors: Casanova Jordi , White Robert A. H. 
Published: April 2021

ABSTRACT
We have investigated the functional organization of the Abdominal-B gene in the bithorax complex using the expression of the Ultrabithorax gene as an assay for Abdominal-B trans-regulatory functions. Using Polycomb mutants to relax the normal spatial control of Ultrabithorax expression, we have examined the effects of Abdominal-B mutations on the expression of Ultrabithorax protein products in parasegment 14. The results support the hypothesis that the Abdominal-B gene contains two trans-regulatory functions: the m element active in parasegments 10–13 and the r element acting exclusively in parasegment 14.
Chromosomal continuity in the abdominal region of the bithorax complex of Drosophila is not essential for its contribution to metameric identity
Authors: Tiong S. Y. K. , Whittle J. R. S. , Gribbin M. C. 
Published: April 2021

ABSTRACT
We have examined the developmental consequences for larval and imaginal segmental cuticular structure of a chromosomal translocation involving a breakpoint in the abdominal region of the bithorax complex (BX-C). This complex makes an essential contribution to the development of metameric differences in part of the thorax and in all abdominal segments. The breakpoint is proximal to the most distal (iab-7) homeobox, and results in the translocation to the Y chromosome of the Ultrabithorax (Ubx) and abdominal-A (abd-A) domains. The genotype deficient for the distal part of the complex shows normal function for Ubx and abd-A but has a phenotype typical for severe Abd-B mutations. Conversely, the distal fragment retains a segment identity function which must represent a contribution from Abd-B in parasegments 13 and 14; the latter metamere is wild type, indicating that it does not require the contribution of Ubx or abd-A.
We also constructed a genotype comprising the proximal fragment of this translocation together with an overlapping distal fragment of the BX-C derived from Df(3R)Ubx109. It therefore contained all sequences of the BX-C though in the abdominal region the abd-A and Abd-B domains were not adjacent to each other in the chromosome. This genotype was phenotypically normal and demonstrates that DNA sequences in the abd-A and Abd-B regions do not require cis-arrangement for their activity.
Homoeobox gene Hox-1.5 expression in mouse embryos: earliest detection by in situ hybridization is during gastrulation
Authors: Gaunt Stephen J. 
Published: April 2021

ABSTRACT
We showed earlier (Gaunt, Miller, Powell & Duboule, 1986) that the mouse homoeobox gene Hox-1.5 is expressed in posterior ectoderm and mesoderm of and -day embryos, and in the -day nervous system posterior to a discrete boundary within the hindbrain. In further in situ hybridization experiments, it is now shown that restriction of Hox-1.5 expression to the posterior regions of the embryo can be detected at stages of development between and days. During this period, the intensity of transcription in presomitic and somitic mesoderm declines rélative to that in the overlying neural ectoderm, and the transcription boundary within the presumptive hindbrain region sharpens. Hox-1.5 expression posterior to the hindbrain boundary is detected in the and -day embryo, but this is no longer found in newborn mice. Embryos of ages and days showed no evidence of Hox-1.5 transcripts. It is concluded that embryos undergoing gastrulation (at days) are the earliest stage at which Hox-1.5 transcripts can be detected by the in situ hybridization technique. In discussion, it is shown how this lies within the period of development during which tissues become determined along the anteroposterior axis of the mouse. Since there may be anterior-to-posterior variation in the time of determination along the body axis, it is suggested that homoeobox genes expressed more posteriorly, such as Hox-3 (Awgulewitsch et al. 1986), might start expression at times later in development.
Prenatal fate of parthenogenetic cells in mouse aggregation chimaeras
Authors: Nagy A. , Páldi A. , Dezso L. , Varga L. , Magyar A. 
Published: April 2021

ABSTRACT
Parthenogenetically activated BCF1 and fertilized BALB/c embryos were aggregated to form chimaeras. The fate of the parthenogenetic component was followed in the conceptus during the second half of gestation. The results indicate an early strong selection against parthenogenetic cells in the extra-embryonal part, which is presumably complete by term, and a weaker selective process in the embryo. During early development, parthenogenetic cells have nearly normal developmental potency in the embryo, which allows their balanced contribution in the chimaeras on day 12. Later, this contribution declines significantly resulting in an unbalanced relation to the advantage of the fertilized counterpart. From the results, we suggest that gametic imprinting may play a role not only in the key steps of preimplantation and early postimplantation development, but later in cell and tissue differentiation.
Hierarchy of the genetic interactions that specify the anteroposterior segmentation pattern of the Drosophila embryo as monitored by caudal protein expression
Authors: Mlodzik Marek , Gehring Walter J. 
Published: April 2021

ABSTRACT
The establishment of the body pattern of Drosophila along the anteroposterior axis requires the coordinated functions of at least three classes of genes. First, the maternally active ccordinate genes define the polarity of the embryo and act as primary determinants; second, the segmentation genes divide the developing embryo into the correct number of segments and third, the segments become specified by the homeotic selector genes. We have examined the effects of mutations in the genes of the first two classes on the spatial distribution of the protein product(s) of the caudal (cad) gene, which in wild type shows a graded distribution along the anteroposterior axis during the syncytial blastoderm stage, whereas its persistent zygotic expression is confined to the telson region (the posterior terminal structures). Mutations in maternal genes that specify the spatial coordinates of the egg and the future embryo change the gradient distribution of cad according to the alterations of the fate map which they produce. A second group of maternally expressed genes, the gap genes of the ‘grandchilless-knirps’ group, which are considered to represent posterior activities, do not have any effect on the cad gradient. The same is true for the zygotic segmentation genes that are active after fertilization. However, the same class of zygotic genes partly affects the zygotic cad expression in the telson. Therefore, the two phases of cad expression represent different levels within the genetic hierarchy. The cad protein gradient seems to form in response to the primary maternal determinants independent of the segmentation genes, whereas the latter influence zygotic cad expression in the telson region which corresponds to a homeotic selector gene function.
Directional cues for growing axons forming the retinotectal projection
Authors: Gierer Alfred 
Published: April 2021

ABSTRACT
In the formation of projections that map one area of the nervous system onto another, guidance of axonal growth cones by directional cues encoded in target tissues is well established by observations on misrouted fibres, though other mechanisms contribute to the precision of connectivity patterns. General physical principles indicate that, if there is directional guidance of normally as well as misrouted axons, leading them toward their appropriate target positions, the inference for a role of graded distributions of molecules is a strong one. As explained in this paper, curving, meandering, branching and shifting connections are fully consistent with a crucial role of directional cues encoded by graded molecular distributions. A model is proposed according to which slight directional cues are strongly enhanced within the axonal growth cone; if the proximal part of the growth cone is activated indicating that the growth cone points in an entirely wrong direction, then a discontinuous directional change such as branching is elicited. Pathways are corrected in this way, and near the appropriate target position the terminal arbour is formed because from there all routes point towards less optimal positions, leading to multiple branching.
Developmental regulation of two microtubule-associated proteins (MAP2 and MAP5) in the embryonic avian retina
Authors: Tucker R. P. , Matus A. I. 
Published: April 2021

ABSTRACT
Previous studies with the mammalian brain have shown that the expression of a number of neuronal microtubule-associated proteins (MAPs) is developmentally regulated. For example, the low-molecular-weight form of MAP2 (MAP2c) is abundant in neonatal rat brains and is less abundant in adults. Similarly, MAP5 levels decrease during postnatal development. Using monoclonal antibodies, we have followed the time of first appearance, cellular distribution, and molecular form of MAP2 and MAP5 during the morphogenesis of the quail retina. MAP2 first appears in ganglion cell bodies and in the axons of the optic fibre layer (OFL) at embryonic day 4 (E4). Anti-MAP2 staining remains restricted to these sites until E10, when staining appears in the inner plexi-form layer (IPL). At E14, one day before hatching, anti-MAP2 staining is found in three broad laminae in the IPL, as well as in photosensitive cells. MAP5 is present in ganglion cell axons from the onset of neurite elongation at E3 and is limited to the OFL until E10. The intensity of anti-MAP5 staining in the OFL and optic nerve decreases after E7, which corresponds with a decrease in the number of actively growing ganglion cell axons. By E14, anti-MAP5 stains five layers in the IPL that correspond with layers of amacrine cell process arborizations. Western blots of E10 brain microtubule proteins show that MAPI is represented by both a 260×103Mr protein and a 60–65 × 103Mr protein; the latter is much more abundant. Anti-MAP5 recognizes a 320×103Mr brain microtubule protein in both the quail and the rat. We conclude that the cellular distribution, developmental regulation and molecular forms of MAP2 and MAP5 are similar in the rat and quail, suggesting that these molecules have conserved and hence fundamental roles in the growth and differentiation of neuronal processes.
Instability of the anteroposterior axis in spontaneous double abdomen (sda), a genetic variant of Chironomus samoensis (Diptera, Chironomidae)
Authors: Kuhn Kristen L. , Percy Jean , Laurel Myrtha , Kalthoff Klaus 
Published: April 2021

ABSTRACT
We have isolated a laboratory strain of Chironomus samoensis in which determination of the anteroposterior egg polarity is disturbed. Most conspicuous is the spontaneous formation of ‘double abdomen’ embryos where head and thorax are replaced by a mirror image of the abdomen. Such double abdomens are found in about half of the egg clusters in this strain, which we call the spontaneous double abdomen (sda) strain as opposed to the normal (N) strain. Also observed in the sda strain, although less frequently, are ‘double cephalon’ embryos showing a mirrorimage duplication of cephalic segments in the absence of thorax and abdomen. Moreover, embryos from the sda strain tend to form cells at the anterior pole resembling the pole cells at the posterior pole. Reciprocal crossings between the sda and the N strain indicate that the sda trait is inherited maternally. Spontaneous double abdomen formation is correlated with signs of disturbed egg architecture, including extruded yolk and detached cells. Double cephalons can also be generated by centrifuging embryos from the N strain, whereas centrifugation of sda embryos produces mostly double abdomens. Double abdomen formation can be induced experimentally by anterior u.v. irradiation of embryos from either strain. The sda trait and u.v. irradiation act in a synergistic fashion. The data suggest that the sda trait may be caused by one or more genomic mutations interfering indirectly with the activity of anterior determinants, i.e. cytoplasmic RNP particles necessary for the development of anterior segments. The sda defects may be ascribed to alterations in cytoskeletal components involved in anchoring anterior determinants and segregating them into anterior blastoderm cells.