bluuebunny/crossref_metadata_2025 huggingface dataset:
A Drosophila gene expressed in the embryonic CNS shares one conserved domain with the mammalian GAP-43
Authors: Ng Shi-Chung , Perkins Lizabeth A. , Conboy Gary , Perrimon Norbert , Fishman Mark C.
Published: April 2021

By cross hybridization with the mammalian growth-related protein, GAP-43, we have isolated several Drosophila cDNAs and genomic sequences. These sequences correspond to a single copy gene that encodes two developmentally regulated transcripts 2·4 and 2·0 kb in length. The predicted protein sequence from the cDNAs contains a stretch of 20 amino acids closely related to the mammalian GAP-43 protein. These residues are also highly conserved in a cDNA isolated from the nematode C. elegans. Prior to dorsal closure, expression of the Drosophila gene is observed in non-neuronal tissues, especially in the mesectoderm and presumptive epidermis, both in a metameric pattern. After dorsal closure, expression becomes restricted to sets of cells that are segmentally reiterated along the periphery of the nervous system. These cells appear to include at least one specific set of glia that may establish scaffolding for the development of the longitudinal neuropile.
Expression of the proto-oncogene fos (c-fos) by preimplantation blastocysts of the pig
Authors: Whyte A. , Stewart H. J.
Published: April 2021

Blastocyst material was obtained from 25 pigs during the period 10 to 33 days post coitum, and fixed thin sections of tissue were hybridized in situ to sense and antisense fos RNA probes synthesized using the expression vector Bluescribe M13+. Indirect immunofluorescence using antisera to a synthetic peptide fragment of c-fos was used to confirm the tissue distribution of oncogene-encoded proteins, which were shown by immunoprecipitation to have Mrs of 55 000 and 40 000, which are the known Mrs of the fos gene product and an associated nucleoprotein, respectively. Northern and slot blots were used to assess the distribution of c-fos mRNA and the size of the fos transcript was found to be 2·3kbases.

C-fos was expressed in trophectoderm from blastocysts early in pregnancy but declined with increasing blastocyst development so that it was virtually absent by day 19 of gestation. High levels of fos proto-oncogene expression were, however, retained in the allantoic membranes up to at least day 19 of pregnancy. The expression of the fos protein could be prolonged in trophectodermal cells in monolayer culture by addition of conditioned medium from blastocysts cultured for 2 h, suggesting the presence of a growth-factor-like substance.
Cloning and characterization of a myoblast cell surface antigen defined by 24.1 D5 monoclonal antibody
Authors: Gower Hilary J. , Moore Stephen E. , Dickson George , Elsom VICKI L. , Nayak Ramesh , Walsh Frank S.
Published: April 2021

Monoclonal antibody 24.1D5 reacts specifically with an epitope expressed on the cell surface of mononucleate myoblasts in primary cultures of human skeletal muscle cells, but not with either multinucleate myotubes or fibroblasts. Polypeptides of 60 and 100×103Mr,. were identified by immunoblotting with the McAb. Human muscle cDNAs encoding the 24.1D5 epitope were used to study further the structure and expression of 24.1D5 during skeletal muscle development. Two mRNA species of 3·0 and 2·5 kb were identified in primary cultures of human skeletal muscle and in mouse muscle cell lines.

The levels of both transcripts decreased during myotube formation in vitro and were similarly decreased during myogenesis in the mouse embryo. 24.1D5 mRNAs were expressed by multipotential cells and myoblast derivatives of the mouse embryonic cell line C3H, suggesting that 24.1D5 is expressed at an early stage during skeletal muscle development.
Pre-existing neuronal pathways in the developing optic lobes of Drosophila
Authors: Tix Simone , Minden Jonathan S. , Technau Gerhard M.
Published: April 2021

We have identified a set of larval neurones in the developing adult optic lobes of Drosophila by selectively labelling cells that have undergone only a few mitoses.

A cluster of three cells is located in each of the optic lobes near the insertion site of the optic stalk. Their axons fasciculate with fibres of the larval optic nerve, the Bolwig’s nerve, and then form part of the posterior optic tract. These cells are likely to be first order inter neurones of the larval visual system. Unlike the Bolwig’s nerve, they persist into the adult stage. The possibility of a pioneering function of the larval visual system during formation of the adult optic lobe neuropil is discussed.
Ectodermal inhibition of cartilage differentiation in micromass culture of chick limb bud mesenchyme in relation to gene expression and cell shape
Authors: Gregg B. C. , Rowe A. , Brickell P. M. , Wolpert L.
Published: April 2021

Ectoderm inhibits the formation of cartilage by chick wing bud mesenchyme in micromass culture. This suggests that the pattern of cartilage formation in the limb bud may result from a restriction of cartilage cell differentiation to the limb bud core as cells leave the progress zone. We have used in situ hybridization to investigate whether ectodermal inhibition in micromass culture occurs at the level of gene transcription. We found that ectoderm completely inhibited the accumulation of cartilage-specific type II collagen transcripts in the mesenchyme cells, whilst the level of type I collagen transcripts was unaffected. Morphometric analysis of electron micrographs revealed that inhibition of chondrogenesis in micromass culture was not preceded by cell flattening. In fact, a rounded cell shape was found not to be a prerequisite for cartilage cell differentiation in micromass.
Tissue specific O-linked glycosylation of the neural cell adhesion molecule (N-CAM)
Authors: Walsh Frank S. , Parekh Raj B. , Moore Stephen E. , Dickson George , Barton C. Howard , Gower Hilary J. , Dwek Raymond A. , Rademacher Thomas W.
Published: April 2021

We have shown previously that the predominant N-CAM isoform in skeletal muscle myotubes contains as a result of alternative splicing a novel domain (MSD1) in its extracellular region. Here we show that this region represents a site for O-linked carbohydrate attachment. The lipid tailed N-CAM in myotubes was found to bind peanut lectin while the transmembrane isoform from myoblasts lacking MSD1 did not. In addition, N-CAM from a variety of neural sources failed to bind the lectin. Analysis of 3T3 fibroblasts transfected with various N-CAM cDNAs, showed that peanut lectin binding was correlated specifically with the expression of the MSD1 region. The oligosaccharides isolated from a purified preparation of myotube N-CAM were shown to contain an O-linked oligosaccharide whose core structure was a sialylated version of Galβ1→3GalNac which is the structure recognized specifically by peanut lectin. These data provide the first evidence for the expression of O-linked carbohydrate on any N-CAM isoform and more specifically target this oligosaccharide to the MSD1 region of myotube N-CAM.
Expression of laminin and of a laminin-related antigen during early development of Drosophila melanogaster
Authors: Garzino Véronique , Berenger Hélène , Pradel Jacques
Published: April 2021

This paper reports the characterization of two immunologically related proteins that may be involved in cell adhesion during Drosophila development. These proteins, laminin chain A and a 240K component, share the epitope recognized by monoclonal antibody RD3 (Mab RD3). The two antigens show different developmental expression profiles. Laminin is detected only from 6 to 8 h of development onwards; its concentration increases during embryogenesis to reach steady-state value in larvae, pupae and adult flies. By contrast, the 240K antigen, not found in oocytes, is present before blastoderm stages; its concentration increases during gastrulation, decreases at the end of organogenesis and the antigen is no longer detected in third instar larvae. Light and electron microscope immunolocalization in imaginal discs indicates that laminin is distributed apically in the lumen and basally in the basal membrane that surrounds the nonevaginated disc. During morphogenesis laminin is detected at the basal side of the evaginating part of the disc epithelium. Immunolocalization on paraffin sections of early embryos suggests that the 240K antigen is related to (1) cell formation and polarization in association with cytoskeleton components, (2) establishment of cell—extracellular substratum interactions during the blastoderm cell sheet organization and (3) basement membrane deposition during embryonic germ cell layer segregation. This 240K protein is poorly or not glycosylated, is resistant to chondroitinase ABC and collagenase and appears therefore as a new extracellular component that might be specifically involved in early processes of morphogenesis.
Induction of functional cytodifferentiation in the epithelium of tissue recombinants : II. Instructive induction of Wolffian duct epithelia by neonatal seminal vesicle mesenchyme*
Authors: Higgins Stephen J. , Young Peter , Cunha Gerald R.
Published: April 2021

When grown as renal grafts in adult male hosts, the upper (cranial), middle and lower (caudal) portions of fetal mouse and rat Wolffian ducts developed into epididymis, epididymis plus ductus deferens, and seminal vesicle, respectively. In heterotypic tissue recombinants, the epithelia from upper and middle Wolffian ducts were instructively induced to undergo seminal vesicle morphogenesis by neonatal seminal vesicle mesenchyme. Functional cytodifferentiation was examined in these recombinants using antibodies against major androgen-dependent, seminal vesicle-specific secretory proteins. The instructively induced Wolffian duct epithelia synthesized normal amounts of all of the secretory proteins characteristic of mature seminal vesicles, as judged by immunocytochemistry on tissue sections and gel electrophoresis plus immunoblotting of secretions extracted from the recombinants. In heterospecific recombinants composed of rat and mouse tissues, the seminal vesicle proteins induced were specific for the species that had provided the epithelium. This showed that the seminal vesicle epithelium in the recombinants was derived from instructively induced Wolffian duct epithelium and not from epithelial contamination of the mesenchymal inductor. Upper Wolffian duct epithelium, instructively induced to undergo seminal vesicle morphogenesis, did not express epididymis-specific secretory proteins, showing that its normal development had been simultaneously repressed.
Cytoplasmic regulation of translation during llyanassa embryogenesis
Authors: Collier J. R.
Published: April 2021

Two-dimensional electrophoresis of labeled proteins and hybridization of mRNAs with specific gene probes was used to demonstrate changes in protein synthesis, and the cytoplasmic control of actin maternal mRNAs during the early development of llyanassa.

The isolated polar lobe was used as a nucleus-free egg fragment to study the regulation of translation. It was shown that actin mRNAs are present in the unfertilized egg and are therefore maternal in origin, are inactive during early cleavage, and are translated in normal, lobeless, actinomycin D-treated blastulae and in isolated polar lobes that have been aged for 24 h. Thus, the activation of actin mRNAs is controlled by cytoplasmic factors that function independently of cleavage and nuclear activity. I suggest that the running of a cytoplasmic clock determines when maternal mRNAs are activated, and that this clock is made and set running during oogenesis.

Changes in protein synthesis that occurred during early cleavage were shown to also involve the diminution of some early cleavage proteins, and it was suggested that this diminution is controlled by cytoplasmic factors localized in the blastomeres of the lobeless egg but absent from the polar lobe.
Expression of microinjected hsp 70/CAT and hsp 30/CAT chimeric genes in developing Xenopus laevis embryos
Authors: Krone Patrick H. , Heikkila John J.
Published: April 2021

The expression of microinjected chimeric genes containing Drosophila hsp 70 and Xenopus hsp 70 and hsp 30 promoters linked to the reporter gene coding for bacterial chloramphenicol acetyltransferase (CAT) was examined during early development of Xenopus laevis. Heat-inducible expression of fusion genes containing either the Drosophila hsp 70 promoter (1100 bp) or the Xenopus hsp 70 promoter (750 bp) was first detectable after the midblastula stage of development. This coincides with the embryonic stage at which the endogenous hsp 70 gene is first heat-inducible. A Xenopus hsp 30/CAT fusion gene containing 350 bp of promoter sequences was also heat-inducible after the midblastula stage unlike the endogenous hsp 30 genes which were not heat-inducible until the early tailbud stage (stage 23– 24). Sequences that are present within either the coding or 3’ region of the hsp 30 clone do not cause the microinjected hsp 30 gene to be developmentally regulated in a normal manner. Additionally, microinjected hsp 30 gene sequences have no effect on the developmental regulation of endogenous hsp 30 genes which continue to be activated at the tailbud stage of development. Our data suggest, that an inhibitory system, which may control the expression of the endogenous hsp 30 gene during development, does not regulate the expression of the injected hsp 30 gene.
Cyclic AMP regulation of P0 glycoprotein and myelin basic protein gene expression in semi-differentiated peripheral neurinoma cell line D6P2T
Authors: Gandelman Kuan-Yun , Pfeiffer S. E. , Carson John H.
Published: April 2021

We have analyzed the effects of cAMP-elevating drugs (dibutyryl cAMP, forskolin, and isobutyl methylxan-thine) on growth properties and myelin-specific gene expression in the peripheral neurinoma cell line D6P2T. The steady-state levels of RNA and Polypeptide for the two major PNS myelin proteins, P0 glycoprotein (P0) and myelin basic protein (MBP), were measured by Northern blotting and immunoblotting, respectively. The levels of the two RNAs in individual cells were examined by in situ hybridization. The transcriptional activities of the P0 and MBP genes were analyzed by nuclear run-off experiments. Treatment with cAMP-elevating agents caused cell aggregation and dose-dependent increase in growth control. Expression of P0 RNA was constitutive in untreated cells and was repressed at high doses. Expression of MBP RNA was induced at low doses and repressed at higher doses. For both MBP and P0 the effects on gene expression were first detected after a lag of approximately 6h, were manifested in all cells and were mediated, at least in part, at the transcriptional level. The level of P0 Polypeptide was proportional to the level of P0 RNA, but MBP Polypeptide was not detectable even under conditions where MBP RNA was induced. The results with this clonal model suggest that cAMP plays a pivotal role in regulation of growth and gene expression during Schwann cell differentiation.
Analysis of specific mRNA destabilization during Dictyostelium developments
Authors: Mangiarotti G. , Bulfone S. , Giorda R. , Morandini P. , Ceccarelli A. , Hames B. D.
Published: April 2021

A number of specific mRNAs are destabilized upon disaggregation of developing Dictyostelium discoideum cells. Analysis of a family of cloned genes indicates that only prespore-enriched mRNAs are affected; constitutive mRNAs that are expressed throughout development and mRNAs that accumulate preferentially in prestalk cells are stable under these conditions. The decay of sensitive prespore mRNAs can be halted by allowing the cells to reaggregate, indicating that destabilization occurs by the progressive selection of individual molecules rather than on all members of an mRNA subpopulation at the time of disaggregation. Individual molecules of the sensitive mRNA species remain engaged in protein synthesis in the disaggregated cells until selected. Destabilization of sensitive mRNAs is induced by cell dissociation even in the presence of concentrations of nogalamycin that inhibit RNA synthesis. The reported prevention of disaggregation-induced mRNA decay by actinomycin D and daunomycin is therefore probably a secondary effect unrelated to the inhibition of transcription.
Amounts and modulation of actin mRNAs in mouse oocytes and embryos
Authors: Bachvarova Rosemary , Cohen Emily M. , Leon Victor De , Tokunaga Katsuo , Sakiyama Shigeru , Paynton Barbara V.
Published: April 2021

In order to measure the content of β- and γ-actin mRNA in mouse oocytes and ovulated eggs, Northern and slot blots were hybridized to complementary RNA probes transcribed from mouse isotype-specific cDNA sequences. The blots included samples of isotype-specific sense strand RNA standards prepared from the same cDNA sequences. Total actin mRNA content was estimated to be 40 fg per preovulatory full-grown oocyte or egg, consisting of one-third β-actin mRNA and two-thirds γ-actin mRNA. Ninety per cent of the actin mRNA is on polysomes in full-grown oocytes. The per cent of actin mRNA in polysomal mRNA is similar to the per cent of actin in newly synthesized proteins.

Measurements on other developmental stages showed that, in mid-growth-phase oocytes, each actin mRNA reaches a level twofold higher than in full-grown oocytes. Thereafter, all modulations of the two isotypic mRNAs occur in parallel; that is, they are maintained at constant levels during the late growth phase (oocytes from females 8−14 days old); gradually degraded in oocytes that have completed their rapid growth phase (oocytes from females 15−18 days old), in maturing oocytes, and in 1- and 2-cell embryos; and deadenylated after about 7 h of progression into meiotic maturation.
Retinoic acid application to chick wing buds leads to a dose-dependent reorganization of the apical ectodermal ridge that is mediated by the mesenchyme
Authors: Tickle C. , Crawley A. , Farrar J.
Published: April 2021

Local application of retinoic acid to wing buds of chick embryos leads to dose- and position-dependent changes in the pattern of cellular differentiation. Early effects of retinoid treatment on the apical ectodermal ridge coor- dinate pattern changes and morphogenesis. The length of the apical ridge increases when additional digits will form but decreases when digits are lost. These changes in length can be understood in terms of a threshold response to the local retinoid concentration that results in either disappearance or maintenance of the ridge (Lee & Tickle, J. Embryol. exp. Morph. 90, 139-169 (1985)). Here, we have analysed the mechanisms involved in ridge disappearance by locally applying retinoic acid to the apex of stage 20 chick wing buds. With this treat- ment regime, low doses give duplicated digit patterns and higher doses truncations. The height of the apical ridge is progressively reduced with increasing doses of retinoid and the time course of ridge flattening indicates that the height of the ridge is correlated with bud outgrowth. With high doses of retinoic acid, the typical ridge, a pseudostratified epithelium in which the colum- nar cells are tightly packed, disappears and the epi- thelium at the tip of the bud consists of loosely packed cuboidal cells. Shortly after treatment, there is a de- crease in the number of gap junctions between ridge cells. This early change in cell contacts suggests that gap junctions may be involved in maintaining epithelial morphology. When treated epithelium is recombined with untreated mesenchyme, an apical ridge is re- established and distal structures can be generated. In contrast, when treated mesenchyme is recombined with the epithelium from normal buds, only proximal struc- tures are formed. Therefore, retinoids can lead to a reorganization of the apical ectodermal ridge which is mediated and maintained by the mesenchyme.
Expression of transforming growth factor β2 RNA during murine embryogenesis
Authors: Pelton Ron W. , Nomura Shintaro , Moses HAROLD L. , Hogan BRIGID L. M.
Published: April 2021

We have studied the temporal and spatial expression of transforming growth factor β2 (TGF/β2) RNA in mouse embryos from 10·5 days post coitum (p.c.) to 3 days post partum (p.p.) by in situ hybridization analysis. TGFβ2 RNA is expressed in a variety of tissues including bone, cartilage, tendon, gut, blood vessels, skin and fetal placenta, and is in general found in the mesenchymal component of these tissues. The expression of TGF/12 RNA changes during development in a manner consistent with a role for the gene product in mediating mesenchymal-epithelial interactions.
Expression of multiple heparin-binding growth factor species by murine embryonal carcinoma and embryonic stem cells
Authors: Heath John K. , Paterno Gary D. , Lindon A. Catherine , Edwards Dylan R.
Published: April 2021

Culture medium conditioned by P19 embryonal carcinoma (EC) cells contains potent mitogenic activity which is markedly potentiated when the medium is conditioned in the presence of heparin. Fractionation of P19 medium conditioned in the presence of heparin reveals the existence of two biochemically distinct growth factor species both of which exhibit high affinity for immobilised heparin and significant activity as amphibian mesoderm-inducing agents. One of the species is recovered as a single polypeptide of apparent Mr = 15 000. This molecule is immunologically related to the protein product of the human K-FGF proto-oncogene. Transcripts derived from the murine K-FGF gene are also expressed by both differentiated and undifferentiated EC cells and embryonic stem cells. The second heparin-binding growth factor is recovered as a complex of four polypeptides, the largest of which has an apparent Mr = 17 000. This agent is immunologically and biochemically distinct from both acidic and basic fibroblast growth factor as well as K-FGF, and represents the predominant mitogenic activity in EC-cell-conditioned medium.
Insulin-like growth factor II may play a local role in the regulation of ocular size
Authors: Cuthbertson R. A. , Beck F. , Senior P. V. , Haralambidis J. , Penschow J. D. , Coghlan J. P.
Published: April 2021

The ultimate size and shape of the eye has a profound influence on its refraction and function. However, the role of growth factors in normal ocular development is poorly understood. Insulin-like growth factors IGF-I and -II have major effects on cell growth and differentiation in tissue culture. Recently their importance for in vivo development has been studied; IGF-II is predominant prenatally, with a probable local role in the differentiation of some mesodermally derived tissues. Ocular development and size is partially dictated by the condensation of the outer collagenous scleral coat (the ‘white’) of the eye from orbital mesoderm. We investigated IGF-II expression and IGF-II receptor distribution during normal ocular development in the mouse fetus using in situ hybridization and immunohistochemistry.

IGF-II mRNA was expressed by the loose mesenchmal orbital tissue as it differentiated to form the sclera, but not in the compact mature sclera or cornea, or in the ectodermally derived retina or skin. IGF-II gene expression was seen in the orbit at E14, reached a peak just before parturition and then declined to background levels after birth. Similarly, type 2 IGF receptors were shown with immunohistochemistry to be present on developing scleral cells and to be modulated in parallel with IGF-II mRNA expression.

We suggest the IGF-II expression by differentiating cells that compact to form the collagenous ocular coat plays a local role in determining the ultimate shape and size of the developing eye.
Microtubule distribution reveals superficial metameric patterns in the early Drosophila embryo
Authors: Callaini Giuliano
Published: April 2021

Microtubule distribution was examined in whole mounts of Drosophila embryos from the cellularization of the syncytial blastoderm (stage 6) to the completion of the gastrulation (stage 7) by fluorescence microscopy. During ventral furrow formation, the fluorescence of tubulin network was not uniform, but disposed in zebra stripes.

Antibodies against α-tubulin showed 14 alternating pairs of darker and brighter transverse areas. The possible significance of this pattern is discussed.
P-element-mediated enhancer detection applied to the study of oogenesis in Drosophila*
Authors: Grossniklaus Ueli , Bellen Hugo J. , Wilson Clive , Gehring Walter J.
Published: April 2021

We have stained the ovaries of nearly 600 different Drosophila strains carrying single copies of a P-element enhancer detector. This transposon detects neighbouring genomic transcriptional regulatory sequences by means of a β-galactosidase reporter gene. Numerous strains are stained in specific cells and at specific stages of oogenesis and provide useful ovarian markers for cell types that in some cases have not previously been recognized by morphological criteria. Since recent data have suggested that a substantial number of the regulatory elements detected by enhancer detection control neighbouring genes, we discuss the implications of our results concerning ovarian gene expression patterns in Drosophila. We have also identified a small number of insertion-linked recessive mutants that are sterile or lead to ovarian defects. We observe a strong correlation with specific germ line staining patterns in these strains, suggesting that certain patterns are more likely to be associated with female sterile genes than others. On the basis of our results, we suggest new strategies, which are not primarily based on the generation of mutants, to screen for and isolate female sterile genes.
Expression of engrailed during segmentation in grasshopper and crayfish
Authors: Patel Nipam H. , Kornberg Thomas B. , Goodman Corey S.
Published: April 2021

We have used a monoclonal antibody that recognizes engrailed proteins to compare the process of segmentation in grasshopper, crayfish, and Drosophila. Drosophila embryos rapidly generate metameres during an embryonic stage characterized by the absence of cell division. In contrast, many other arthropod embryos, such as those of more primitive insects and crustaceans, generate metameres gradually and sequentially, as cell proliferation causes caudal elongation. In all three organisms, the pattern of engrailed expression at the segmented germ band stage is similar, and the parasegments are the first metameres to form. Nevertheless, the way in which the engrailed pattern is generated differs and reflects the differences in how these organisms generate their metameres. These differences call into question what role homologues of the Drosophila pairrule segmentation genes might play in other arthropods that generate metameres sequentially.
Analysis of the testes of H-Y negative XOSxrb mice suggests that the spermatogenesis gene (Spy) acts during the differentiation of the A spermatogonia
Authors: Sutcliffe Maxine J. , Burgoyne Paul S.
Published: April 2021

H-Y antigen negative XOSxrb mice, like their H-Y positive XOSxra counterparts, have testes; but, in contrast to XOSxra males, XOSxrb testes almost totally lack meiotic and postmeiotic stages of spermatogenesis. The quantitative analysis of the testes of XOSxrb males and their XY±Sxrb sibs, described in. the present study, identified two distinct steps in this spermatogenic failure. First, there was a reduction in mitotic activity among T2 prospermatogonia, so that approximately half the normal number of T2 prospermatogonia were produced. Second, there was a dramatic decrease in the number of A3 and A4 spermatogonia and no Intermediate or B spermatogonia. These reductions were also largely due to decreased mitotic activity, there being a shortage of A1 and A2 spermatogonial divisions and no divisions among A3 or A4 spermatogonia. Mitotic activity among the T2 prospermatogonia and the undifferentiated A spermatogonia was normal. This means that the spermatogonial stem cells, which are a subset of the undifferentiated A spermatogonia, are unaffected in XOSxrb mice. Sxrb is now known to have arisen by deletion of DNA from Sxra. It is clear from the present findings that a gene (or genes) present in the deleted DNA plays a major role in the survival and proliferation of the differentiating A spermatogonia.
The effects of ectoteloblast ablation in the earthworm embryo
Authors: Storey Kate G.
Published: April 2021

The effects of ablating individual earthworm embryo ectoteloblasts were studied in terms of the morphology of the ventral nerve cord (VNC) and a discrete population of histochemically identified cells normally present in each segment of the worm. The activity of ectoderm cells in the vicinity of the ablated teloblast was assessed by observing the pattern of cells undergoing DNA synthesis for up to 72 h after an ablation. While examination of the morphology of the VNC in whole mounts suggests that a reconstitutive process is elicited by ectoteloblast ablation, this is not borne out in sections and at the level of individual, histochemically identified cells, which up to the hatchling stage appeared to be missing following ablation of particular ectoteloblasts. A proliferative response to ablation by the ectoderm cells in the vicinity of the ablated teloblast, however, suggests that some reconstitutive process(es) operate in this annelid, even if they do not result in a completely normal nerve cord at the hatchling stage.
Control of cell type proportions by a secreted factor in Dictyostelium discoideum
Authors: Inouye Kei
Published: April 2021

It has been shown that, in Dictyostelium discoideum, conversion of prestalk cells to prespore cells in suspension cultures is inhibited by coexisting prespore cells. To examine whether the inhibition of conversion requires direct cell contact or is mediated by substances secreted by the cells, prestalk cells and prespore cells were incubated in shaken suspension, separated from each other by a dialysis membrane, and conversion of the prestalk cells to prespore cells scored after 24 h. Pre-stalk-to-prespore conversion was significantly inhibited if the density of the prespore cells was sufficiently high. In contrast, prestalk cells had little influence on prestalk-to-prespore conversion. Media conditioned by prespore cells, but not by prestalk cells, also inhibited the conversion of prestalk cells. Adenosine, propionate, diethylstilboestrol and differentiation inducing factor (DIF), all of which are known to influence the prestalk/ prespore differentiation, were examined for their effects on prestalk-to-prespore conversion. Among these, all except adenosine significantly inhibited the conversion. Based on these results, possible mechanisms for maintenance of the constant cell-type ratio in D. discoideum slugs were discussed.
Cell-specific metallothionein gene expression in mouse decidua and placentae
Authors: De Swapan K. , McMaster Michael T. , Dey Sudhansu K. , Andrews Glen K.
Published: April 2021

Oligodeoxyribonucleotide excess solution hybridization, Northern blot and in situ hybridization were used to analyze metallothionein gene expression in mouse decidua and placentae during gestation. Metallothionein (MT) -I and -H mRNA levels were constitutively elevated, 11- and 13-fold, respectively, relative to the adult liver, in the deciduum (D8), and decreased coordinately about 6-fold during the period of development when the deciduum is replaced by the developing placenta (DIO-16). Coincident with this decline, levels of MT mRNA increased dramatically in the visceral yolk sac endoderm. In situ hybridization established that MT-I mRNA was present at low levels in the uterine luminal epithelium (D4), but was elevated at the site of embryo implantation exclusively in the primary decidual zone by D5, and then in the secondary decidual zone (D6-8). Although low levels of MT mRNA were detected in total placental RNA, in situ hybridization revealed constitutively high levels in the outer placental spongiotrophoblasts. Analysis of pulse-labeled proteins from decidua and placentae established that these tissues are active in the synthesis of MT. The constitutively high levels of MT mRNA in decidua were only slightly elevated following injection of cadmium (Cd) and/or zinc (Zn), whereas in placentae they increased several-fold. MT mRNA levels were equally high in decidua and experimentally induced deciduomata (D8) which establishes that decidual MT gene expression is not dependent on the presence of the embryo or some embryo-derived factor. Although the functional role of MT during development is speculative, these results establish the concept that, from the time of implantation to late in gestation, the mouse embryo is surrounded by cells, interposed between the maternal and embryonic environments, which actively express the MT genes. This suggests that MT plays an important role in the establishment and maintenance of normal pregnancy.
XIF3, a Xenopus peripherin gene, requires an inductive signal for enhanced expression in anterior neural tissue
Authors: Sharpe C. R. , Pluck A. , Gurdon J. B.
Published: April 2021

A full-length cDNA clone for the Xenopus intermediate filament gene XIF3 has been isolated. It is very similar in sequence to the rat intermediate filament cDNA clone 73 that is thought to encode the neuronal intermediate filament protein ‘peripherin’. By analysing dissected embryos, we show that XIF3 is expressed predominantly in anterior and dorsal structures and most strongly in the brain of the tailbud (stage 26) embryo. In situ hybridization shows XIF3 transcripts to be localized in neural tissue and especially in regions that most probably correspond to the motor neurones of the neural tube and to some cranial nerve ganglia.

New XIF3 transcripts are first found at the start of gastrulation at a low level throughout the ectoderm and are not localized to the presumptive neurectoderm. Expression subsequently increases by about 10-fold in neural tissue, and requires an interaction of the mesoderm with overlying ectoderm. Because new transcripts are found predominantly in neural tissue of the head, this response can be used as a marker of anterior neural induction.
Restoration of pole-cell-forming ability to u.v.-irradiated Drosophila embryos by injection of mitochondrial IrRNA
Authors: Kobayashi Satoru , Okada Masukichi
Published: April 2021

Screening a cDNA library generated from poly(A)+RNA of Drosophila cleavage embryos, we selected a cDNA clone (pDE20.6). The cDNA hybridized specifically with a poly(A)+RNA that is capable of restoring embryos from u.v.-caused inability of pole cell formation. The RNA hybrid-selected by pDE20.6 was also able to induce pole cells in the anterior region of embryos, if it was coinjected with u.v.-irradiated polar plasm, although the RNA or irradiated polar plasm alone was not effective. Pole cells thus formed in the anterior or in the u.v.-irradiated posterior region were identified by polar granules and nuclear bodies, morphological markers for normal pole cells. Furthermore, the RNA-induced pole cells were able to migrate into gonadal rudiments. The nucleotide sequence of pDE20.6 cDNA insert was highly homologous with the mitochondrial large rRNA (IrRNA) gene, but not with any nuclear DNA sequences. Using pDE20.6 as a primer, a full-length cDNA of mitochondrial IrRNA was generated and cloned. The RNA transcribed in vitro from the cDNA was able to restore pole cell formation. The cDNA hybridized only with a 1.5 kb poly(A)+RNA on a Northern blot. The 1.5 kb RNA sedimented more with the post-mitochondrial (P3) fraction than with the mitochondrial (P2) fraction, while the majority of transcripts from another mitochondrial gene was detected in the P2 fraction.
Neural control of the sequence of expression of myosin heavy chain isoforms in foetal mammalian muscles
Authors: Harris A. John , Fitzsimons Robin B. , McEwan John C.
Published: April 2021

The expression of myosin isoforms was studied during development of calf muscles in foetal and neonatal rats, using monoclonal antibodies against slow, embryonic and neonatal isoforms of myosin heavy chain (MHC). Primary myotubes had appeared in all prospective rat calf muscles by embryonic day 16 (E16). On both E16 and E17, primary myotubes in all muscles with the exception of soleus stained for slow, embryonic and neonatal MHC isoforms; soleus did not express neonatal MHC. In earlier stages of muscle formation staining for the neonatal isoform was absent or faint. Secondary myotubes were present in all muscles by E18, and these stained for both embryonic and neonatal MHCs, but not slow. In mixed muscles, primary myotubes destined to differentiate into fast muscle fibres began to lose expression of slow MHC, and primary myotubes destined to become slow muscle fibres began to lose expression of neonatal MHC. This pattern was further accentuated by E19, when many primary myotubes stained for only one of these two Isoforms. Chronic paralysis or denervation from E15 or earlier did not disrupt the normal sequence of maturation of primary myotubes up until E18, but secondary myotubes did not form. By E19, however, most primary myotubes in aneural or paralyzed tibialis anterior muscles had lost expression of slow MHC and expressed only embryonic and neonatal MHCs. Similar changes occurred in other muscles, except for soleus which never expressed neonatal MHC, as in controls. Paralysis or denervation commencing later than E15 did not have these effects, even though it was initiated well before the period of change in expression of MHC isoforms. In this case, some secondary myotubes appeared in treated muscles. Paralysis initiated on E15, followed by recovery 2 days later so that animals were motile during the period of change in expression of MHC isoforms, was as effective as full paralysis. These experiments define a critical period (E15–17) during which foetuses must be active if slow muscle fibres are to differentiate during E19–20. We suggest that changes in expression of MHC isoforms in primary myotubes depend on different populations of myoblasts fusing with the myotubes, and that the normal sequence of appearance of these myoblasts has a stage-dependent reliance on active innervation of foetal muscles. A critical period of nerve-dependence for these myoblasts occurs several days before their actions can be noted.
Unidirectional displacement of cells in fibrillar matrices
Authors: Boocock C. A.
Published: April 2021

It has long been recognised that the alignment of fibrils of an extracellular matrix can guide cell displacement along an axis. However, bidirectional guidance alone is insufficient to explain the directed translocation of cell populations in an embryo. Evidence is presented here that matrix fibrils can also be arranged to confer a unidirectional bias on cell displacement.

When chick heart fibroblasts were cultured between two collagen matrices pretreated by shearing, the dis-placements of these cells were biased in the direction opposite to that of pre-shear. A possible explanation is that cells detect the directional arrangement of fibrils linked to a rigid surface. Results of a second experiment suggested that cells can indeed respond directionally to the linkage of fibrils to rigid surfaces. Cells spreading on the surface of matrices were aligned perpendicular to the edge of a rigid body embedded just beneath the surface. For cells close to this body, the effect of linkage was able to override guidance as the more important orienting cue.

‘DESMOTAXIS’ is suggested as a suitable name for the unidirectional movement of cells in response to the arrangement of fibrils relative to a rigid, anchoring surface. In the embryo, several factors could generate such arrangements of extracellular matrices around relatively solid structures. These possibilities are discussed with reference to directed cell migrations in vivo.
Inducing factors and the control of mesodermal pattern in Xenopus laevis
Authors: Smith J. C. , Cooke J. , Green J. B. A. , Howes G. , Symes K.
Published: April 2021

The mesoderm of Xenopus laevis and other amphibia is formed through an inductive interaction during which cells of the vegetal hemisphere act on cells of the animal hemisphere. Two groups of factors mimic the effects of the vegetal hemisphere. One group consists of members of the fibroblast growth factor (FGF) family, while the other is related to transforming growth factor type β (TGF-β). In this paper we discuss the evidence that the FGF family represents ‘ventral’ mesoderm-inducing signals, and the TGF-β family ‘dorsal’ signals. The evidence includes a discussion of the cell types formed in response to each type of factor, the fact that only XTC-MIF (a member of the TGF-β family) and not bFGF can induce animal pole ectoderm to become Spemann’s organizer, and an analysis of the timing of the gastrulation movements induced by the factors.
Morphogen hunting in Dictyostelium
Authors: Kay Robert R. , Berks Mary , Traynor David
Published: April 2021

A highly regulative pattern of prestalk and prespore tissue is formed during Dictyostelium development, starting from separate amoebae. Potential morphogens controlling this process have been hunted biochemically, using bioassays to monitor activity. All those discovered to date are low MW diffusible compounds: cAMP, adenosine, NH3 and DIFs 1-3. The DIFs are assayed by their ability to induce isolated amoebae to differentiate into stalk cells and have been identified as a family of chlorinated phenyl alkanones.

The diversification of amoebae into prestalk and prespore cells seems to be brought about by cAMP and DIF-1. cAMP is necessary for both pathways of differentiation but DIF-1 specifically induces the differentiation of prestalk cells while suppressing that of prespores.

When DIF-1 is added to intact slugs, it causes a substantial enlargement of the prestalk tissue at physiological concentrations in the time previously shown to be required for pattern regulation.

DIF-1 is a dynamic molecule and we have found that it is metabolized along a pathway involving at least 8 compounds. Metabolism is developmentally regulated and may be important in producing DIF gradients or other effector molecules from DIF.

Although we almost certainly have some of the central actors, it is difficult to formulate a satisfactory theory of pattern formation in Dictyostelium at the moment. We suspect that at least one important actor is missing.
Genes from two intermoult puffs in Drosophila virilis polytene chromosomes are differentially transcribed during larval development
Authors: Kress Horst , Lucka Lothar , Swida Ulrike , Thüroff Eduardo , Klemm Uwe
Published: April 2021

Genes from two Drosophila virilis intermoult puffs were isolated by microcloning. From puff 16A on the X-chromosome a 2.9 kb DNA fragment was obtained, which hybridizes with three transcripts. Two of them represent the mRNAs for larval glue proteins. They are found in different abundancies in third larval instar salivary glands, but also in minor amounts in midgut and in fat body. In puff 55E on chromosome III two genes were identified. They are transcribed exclusively in salivary glands during all three larval instars. Therefore, their products must be related to another glandspecific function, which is sustained throughout larval fife.
Early expression of desmosomal components during kidney tubule morphogenesis in human and murine embryos
Authors: Garrod D. R. , Fleming S.
Published: April 2021

Developing kidneys of human and murine fetuses have been stained with monoclonal antibodies to desmosomal proteins 1 and 2 (desmoplakins) (dp 1&2), desmosomal glycoprotein 1 (desmoglein) and a polyclonal antiserum to desmosomal glycoproteins 2 and 3 (desmocollins). All three antibodies stain the mesenchymal condensates that represent the first stage in kidney tubule development, indicating that desmosomal antigens are expressed very early in tubule morphogenesis. Desmosomal antigens are continuously expressed throughout the developing tubule being concentrated at the apical and basal regions of the lateral membranes of cells. Staining is also present in both visceral and parietal membranes of the developing Bowman’s capsule. In the mature tubule, desmosomal staining becomes restricted to a discontinuous apico-lateral ring around the cells. Staining is completely lost from the visceral membrane of the mature Bowman’s capsule (the podocytes) but persists in the parietal membrane.

At the condensate stage, staining for dpl&2 is much more intense than staining for simple epithelial keratin.

Electron microscopy showed the presence of small (ca 0.1 μm) punctate junctions in the developing tubule. These may be immature desmosomes. No fully mature desmosomes such as are present in mature kidney were found.

The results suggest that desmosomal proteins and glycoproteins are involved in the early development of adhesive contacts between cells of the kidney tubule. The changing pattern of antigen expression, the loss of desmosomal staining from the podocytes and the immaturity of junctions suggest that desmosomal adhesion is labile during tubule morphogenesis, perhaps in order to facilitate changes of cell-cell contact.
Expression of Abdominal-B homeoproteins in Drosophila embryos
Authors: Delorenzi Mauro , Bienz Mariann
Published: April 2021

The Abdominal-B (Abd-B) gene determines development of the posteriormost segments in Drosophila. Genetic and molecular analysis suggested that it consists of two genetically separable functions that are conferred by two related homeoproteins termed m and r. We have raised an antiserum against Abd-B protein to describe the patterns of Abd-B protein expression during embryonic development. The pattern of r protein expression, as deduced by analysis of Abd-B mutants, is restricted to psl4 and 15 in all germ layers and observes a parasegmental boundary at its anterior margin of expression. In contrast, the pattern of m protein expression is unusual as its level in the ectoderm increases from ps10 to ps13 in parasegmental steps. Its anterior margin of expression is highly dynamic shifting anteriorly across more than 3 parasegments during midembryonic development. Evidently, the control mechanisms of m and r protein expression are considerably different. Moreover, an antibody-positive Abd-B mutant suggests that these differ, in the case of m protein expression, to some extent in individual germ layers.
Developmental expression of antioxidant enzymes in guinea pig lung and liver
Authors: Rickett Guy M. W. , Kelly Frank J.
Published: April 2021

Antioxidant enzyme activities, superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GSH-Px) and total glutathione concentration were determined in guinea pig lung and liver over the final period of gestation (days 50–68) and at several ages post-partum. Pulmonary antioxidant capacity increased markedly over the final days of gestation, individual changes ranging from 29% (glutathione) to 198% (GSH-Px). Liver antioxidant capacity was always 4-fold to 10-fold greater than that of the lung and exhibited very similar developmental profiles to those observed in the lung. From day 60 gestation to term (68 days), activity of the liver antioxidants increased, ranging from 246 % (CAT) to 610 % (glutathione). A number of antioxidants in both lung and liver exhibited either immediate pre- or postbirth decreases in activity. These falls could not be attributed to the way in which the results were expressed: i.e. they were similar, expressed per unit DNA, per unit protein, or per g wet wt. Following birth, liver antioxidant capacity increased such that the highest enzyme activities or glutathione concentration were recorded at 66 days post-partum. In lung, only Mn-SOD and glutathione exhibited higher levels at 66 days postpartum than at birth.

In combination, these results of pulmonary and hepatic antioxidant enzyme activity indicate that the lung is not unique in acquiring increased antioxidant protection in the final period of gestation. They also suggest that a tissue’s antioxidant requirement is dictated more by metabolic rate (hence free radical production) than incident partial pressure of oxygen.