bluuebunny/crossref_metadata_2025_split huggingface dataset:
Normal structure and expression of Zfy genes in XY female mice mutant in Tdy
Authors: Gubbay John , Koopman Peter , Collignon Jérôme , Burgoyne Paul , Lovell-Badge Robin 
Published: April 2021

ABSTRACT
Zfy-1 and Zfy-2 are candidate genes for Tdy, the testis determining gene in mice. We have analysed these genes in a line of XY female mice that have been shown to be mutated in Tdy. We have used Southern blot analysis to show that the Zfy genes have not undergone any major structural alterations, and have also demonstrated that both genes are transcribed normally from the mutant Y chromosome (¥) in both adult XY¥ testis and X¥ female embryonic gonads. The fact that these genes show a normal structure and expression pattern in mice with a Y chromosome known to carry a mutation in Tdy and that mutant embryos develop into females despite Zfy-1 expression, strongly supports other recent evi dence that Zfy genes are not directly involved in primary testis determination.
Gonadal sex differentiation in the neonatal marsupial, Monodelphis domestica
Authors: Baker P. J. , Moore H. D. M. , Penfold L. M. , Burgess A. M. C. , Mittwoch U. 
Published: April 2021

ABSTRACT
A quantitative and histological study of the gonads of newborn grey short-tailed opossums, Monodelphis domestica, is described. The pups were karyotyped, and comparisons were made within litters segregating for XX and XY sex chromosomes. A total of four litters including 25 pups were available. On the day of birth, developing testes were significantly larger than the ovaries of litter mates, and testes could be histologically distinguished by the formation of sex cords and a tunica albuginea. The data suggest that in this marsupial species gonadal differentiation may be initiated in utero.
Ammonia promotes accumulation of intracellular cAMP in differentiating amoebae of Dictyostelium discoideum
Authors: Riley Bruce B. , Barclay Stephen L. 
Published: April 2021

ABSTRACT
We used sporogenous mutants of Dictyostelium discoid eum to investigate the mechanism(s) by which exogenous NH4CI and high ambient pH promote spore formation during in vitro differentiation. The level of NH4C1 required to optimize spore formation is correlated inver sely with pH, indicating that NH3 rather than NH4+ is the active species. The spore-promoting activity of high ambient pH (without exogenous NH4CI) was eliminated by the addition of an NH3-scavenging cocktail, sugges ting that high pH promotes spore differentiation by increasing the ratio of NH3:NH4+ secreted into the medium by developing cells. High ammonia levels and high pH stimulated precocious accumulation of intra cellular cAMP in both sporogenous and wild-type cells. In both treatments, peak cAMP levels equaled or exceeded control levels and were maintained for longer periods than in control cells. In contrast, ammonia strongly inhibited accumulation of extracellular Camp without increasing the rate of extracellular cAMP hy drolysis, indicating that ammonia promotes accumu lation of intracellular cAMP by inhibiting cAMP se cretion. These results are consistent with previous observations that factors that raise intracellular cAMP levels increase spore formation. Lowering intracellular cAMP levels with caffeine or progesterone inhibited spore formation, but simultaneous exposure to these drugs and optimal concentrations of NH4CI restored both cAMP accumulation and spore formation to nor mal levels. These data suggest that ammonia, which is a natural Dictyostelium morphogen, favors spore forma tion by promoting accumulation or maintenance of high intracellular cAMP levels.
The Action of Aminopterin on the Explanted Early Chick Embryo
Authors: O’Dell D. S. , McKenzie J. 
Published: April 2021

ABSTRACTOne method of gaining insight into the mechanisms of growth and differentiation is based on the use of defined substances to alter normal development, but analysis of developmental changes so produced may be difficult or impossible if the substances used have an ill-defined biochemical action. The antimetabolites, however, do not have this disadvantage and, among them, folic acid antagonists are especially interesting.
The Embryology of Dacus tryoni 2. Development of Imaginal Discs in the Embryo
Authors: Anderson D. T. 
Published: April 2021

ABSTRACT
The cephalic, wing, haltere, leg and median genital discs of D. tryoni develop in the embryo shortly after dorsal closure and involution of the head. The labial and lateral genital discs first appear in the mid-second larval instar. The wing and haltere discs arise as outgrowths of the ventral meso- and metathoracic discs. The remaining discs arise in the positions generally accorded to them by previous authors. Each pair of discs originates from cells in a definite location in the blastoderm. The relationship between the blastodermal locations of the presumptive discs and the segmental pattern of the larval ectoderm suggests that imaginai disc development in Cyclorrhapha resembles regeneration of a total field by a part.
DNA Synthesis and Nuclear Reproduction during Embryonic Development and Regeneration of Muscle Tissue
Authors: Zhinkin L. N. , Andreeva L. F. 
Published: April 2021

ABSTRACTNuclear reproduction in myosymplasts and myotubes proceeds mitotically. Nuclei synthesizing DNA are found during the development of muscles. The percentage of 3H-thymidine labelled nuclei diminishes with the development of the embryo as mitotic activity decreases. A mitotic cycle in the nuclei of muscle fibres of a 17-day-old rat embryo takes about 20 hr. and the duration of mitosis itself is about 2·5 hr. A comparison of the number of nuclei participating in a mitotic cycle with the mitotic index allows us to suggest that as differentiation proceeds some nuclei provide the synthesis of specialized proteins while others undergo reproduction. During regeneration of muscle fibres, 2 days after operation, a considerable percentage of 3H-thymidine labelled nuclei is found at the ends of cut muscle fibres and, correspondingly, the mitotic index is high. The number of labelled nuclei, as well as that of mitoses, decreases with distance from the wound. Subsequently labelled nuclei move to muscle buds where they only very rarely undergo division. All the facts obtained show that the reproduction of muscle nuclei during embryonic development and during regeneration of muscle fibres in adult animals proceeds in the same manner as in any other cellular tissues where cell reproduction by mitosis is not in doubt.
The Population of Germ Cells in the Developing Female Chick
Authors: Hughes Gillian C. 
Published: April 2021

ABSTRACT
Morphological and cytological changes occurring in the left (functional) ovary of the developing chick were studied by means of both histological and squash preparations. Counts were made of the numbers of oögonia and oöcytes at various stages of meiotic prophase in specimens aged 9 days’ incubation to 1 day after hatching. Neither the mitotic activity of oögonia nor the onset of the successive stages of meiotic prophase are synchronized throughout the ovary. The development of the germ cells is more advanced at the centre than at the extremities of the ovarian cortex. The process of oögenesis ceases at about the time of hatching. Appreciable numbers of oöcytes enter the pre-leptotene phase on the thirteenth day, zygotene and pachytene on the seventeenth, and diplotene on the nineteenth day of incubation. Degeneration of germ cells occurs throughout the developmental period studied. Oögonial mitoses are associated with an increase in the total population of germ cells from about 28,000 at 9 days’ incubation to some 680,000 on the seventeenth day. Subsequently, a high incidence of degenerating germ cells, together with a decline in the number of oögonial mitoses, account for a decrease in the total population between the seventeenth day of incubation and 1 day after hatching, when only about 480,000 oöcytes persist.
The Development of Somites in the Chick Embryo
Authors: Bellairs Ruth 
Published: April 2021

ABSTRACTIn two groups of experiments the so-called ‘somite centres ‘were removed from chick blastoderms. Nevertheless, well-developed somites formed. It is concluded, therefore, that the ‘somite centres’ are not essential for somite formation. The same experiments, and others which are described, also provided evidence that somites can form in the absence of neural tissue. It is concluded, therefore, that neural tissue is not essential for somite formation. Experiments involving extirpation of the node confirmed the now generally accepted findings of various authors that neither the node nor the notochord are essential for the differentiation of somites. It is suggested that the regression movements may play a decisive rôle in influencing somite differentiation.
Behavior of fetal intestinal organ culture explanted onto a collagen substratum
Authors: Altmann G. G. , Quaroni A. 
Published: April 2021

ABSTRACT
A model of organ culture of 18 day old fetal rat intestine (Quaroni, 1985) was modified and characterized in the present work with the purpose of developing an in vitro model for the study of intestinal epithelial cell behaviour. Fragments of this intestine were kept in suspension culture for 7 days and then explanted onto collagen (type I) matrix. Within a day, the fragments became anchored to the substratum and a circular monolayer grew out to about 1 cm diameter.
In the fragments, an outer layer of absorptive epithelial cells came to enclose a stroma, which was polarized into a loose (mesenchymal) and a dense portion. The dense portion contained a mixture of smooth muscle cells and primitive stem-type epithelial cells (‘p-cells’). After explantation, at the contact point with the matrix, the epithelium broke up and the mesenchyme grew into the matrix and anchored the fragment. The epithelial edges now became continuous with the developing monolayer. Radioautography with tritiated thymidine indicated a constant cell renewal in epithelium and monolayer apparently from foci of p-cells, a reserve population of which was seen to be sequestered among the smooth muscle cells. Activated stem cells could differentiate into three mature epithelial phenotypes, each differentiation pathway apparently being determined by the type of underlying stroma. Immunohistochemistry using gold- and fluorescein-labeled monoclonal antibodies indicated that adult differentiation-specific markers (e.g. brush border enzymes) were present in the fragment epithelium but not in the monolayer cells. On the other hand, the monolayer cells could be induced to express some of these markers by contact with mesenchymal cells or by co-culturing with fibroblastic cell lines. Matrigel sub-stratum mixed with collagen (type I) supported the appearance in monolayer of strands positive for amino-peptidase and lactase. The model thus appears to be suitable for the in vitro study of epithelial renewal and differentiation, and it has already provided some results in this respect.
Mammary glands in male marsupials: I. Primordla in neonatal opossumsDidelphis virginlanaandMonodelphls domestica
Authors: Renfree Marilyn B. , Robinson E. S. , Short R. V. , Vandeberg J. L. 
Published: April 2021

ABSTRACTNeonates of the American didelphid marsupials Didelphis virginiana and Monodelphis domestica were sexed by karyotype and histologically examined on the day of birth. Mammary anlagen were found in both sexes of both species, but the neonatal males had less than one-third of the full female complement of mammary glands. Male neonates of both species also had paired scrotal bulges anterior to the genital tubercle but these were never present in females, once again raising the question of whether the pouch and scrotum are homologous structures. Mammary anlagen are not found in male neonates of the Australian marsupial species so far studied, which suggests a dichotomy in the control of some aspects of sexual differentiation in the two marsupial lineages.
Characterization of protein kinase C in early Xenopus embryogenesis
Authors: Otte Arie P. , Kramer Ijsbrand M. , Mannesse Maurice , Lambrechts Caro , Durston Antony J. 
Published: April 2021

ABSTRACT
Recently, we presented evidence that protein kinase C (PKC) is involved in mediating the endogenous signals that induce competent Xenopus ectoderm to differentiate to neural tissue. We report here that PKC is already strongly activated in neural-induced ectoderm from midgastrula embryos and that this activation runs parallel with an increase in the level of inositol phosphates. We further identify several proteins that are phosphorylated, both in natural neural-induced ectoderm and in TPA-treated ectoderm, suggesting that they are phosphorylated through the PKC route. We found no major changes in PKC activity among different pregastrula stages, including the unfertilized egg. However, PKC isolated from animal, ectodermal cells is highly sensitive to Ca2+ and can be activated by low concentrations, (6–25μM) of arachidonic acid, while PKC isolated from vegetal, endodermal cells is more insensitive to Ca2+ and cannot be activated by arachidonic acid. These results suggest that different PKC isozymes are present in animal and vegetal cells.
Morphological and radiochemical evidence for the metabolism of exogenous proteins by the preimplantation sheep blastocyst
Authors: Pullar Duncan , Kronnie Geertruy Te , Peiris I. Dammika , Taverne Nico , Jeacock Marjorie K. , Stroband Henri W. J. , Shepherd David A. L. 
Published: April 2021

ABSTRACT
The ability of the trophoblast of the ovine preimplantation blastocyst to take up and metabolise proteins has been investigated using two experimental approaches, microscopical and radiochemical. The ultrastructure of the expanded blastocyst obtained from 14 and 17 day pregnant ewes was examined. The morphology of tissues maintained in culture for 24 h has been compared with that of fresh tissues. After culture, the cellular morphology of the explants was well preserved. Fresh and 24 h cultured tissues were incubated with horseradish peroxidase and ferritin and these proteins subsequently were found to be localized in coated pits, caveolae and secondary lysosomes of the trophoblast. Comparison of the uptake of [3H]dextran and of 125I-labelled bovine serum albumin indicated that proteins could be taken up by cultured tissue by mechanisms in addition to simple fluid phase endocytosis. During culture of explants of blastocyst with l2SI-labelled bovine serum albumin, a large fraction of the radioactivity taken up by the tissue appeared in the TCA-soluble fraction of the culture medium indicating that cultured trophoblast hydrolysed proteins. That amino acids released from captured protein could be used for protein synthesis by the trophoblast was indicated by the labelling of tissue and medium proteins after culturing explants with β-lactamase labelled with [14C]leucine. A major product (Mr approximately 17X103) present in the medium was likely to have been ovine trophoblast protein-1. It is concluded that, during the expansion of the ovine blastocyst, the trophoblast has the ability to take up proteins, transport them to lysosomes and degrade them to amino acids which are used for protein synthesis. Thus proteins, as well as free amino acids, present in the histotrophe may be an important source of nitrogen for the sheep conceptus in the critical period just prior to implantation.
Spatiotemporal expression of murine carcinoembryonic antigen (CEA) gene family members during mouse embryogenesis
Authors: Huang Jing Qi , Turbide Claire , Daniels Eugene , Jothy Serge , Beauchemin Nicole 
Published: April 2021

ABSTRACT
Carcinoembryonic antigen is a glycosylated protein used as a human tumor marker to assess recurrences of gastrointestinal, breast and lung cancers. This protein is a member of the immunoglobulin supergene family and has been shown to function as a homophilic and heterophilic cell adhesion molecule. We have studied the spatial and temporal expression of two cloned mouse CEA gene family members during development using Northern analyses and in situ hybridization. Transcripts detected by the mouse CEA probes are expressed from 10.5 days post coitum (p.c.) to birth in mouse embryos and fetuses and are present from 16.5 days p.c. to adulthood in intestine and colon as evaluated by Northern analyses. The RNA is also present in many other tissues including meninges, cartilage and bone, blood vessel walls, placenta, dermis, muscle layers of the stomach and intestine and bronchioles of developing mouse embryos and fetuses. This expression pattern is similar to that of proteins of the Transforming Growth Factor β gene family. The role of mouse CEA gene • family members is unclear; however, the localizations of these CEA family members in the mouse embryo and fetus suggest an important functional role during active morphogenesis, a complex process in which cell adhesion molecules are significantly involved.
Pattern formation under the control of the terminal system in the Drosophila embryo
Authors: Casanova Jordi 
Published: April 2021

ABSTRACT
The specification of the most anterior and posterior domains of the Drosophila embryo depends on the activity of the torso protein, a putative tyrosine kinase receptor. Localized torso activity at the poles of the embryo generates graded information that specifies distinct portions of the body. The primary response to the terminal signal in the posterior end of the embryo is likely to be the activation of the gap genes huckebein and tailless. Here I address the question of how the graded maternal signal generates different elements of the pattern at the posterior end of the embryo and what role huckebein and tailless activities may play in this process. These experiments show that distinctly localized activities of huckebein and tailless are responsible for the appropriate expression of other genes known to be under the control of the terminal system. Moreover, they suggest that different elements of the terminal pattern can be specified in response to distinct levels of graded tailless activity.
The pattern of transcription of the neurogenic gene Delta of Drosophila melanogaster
Authors: Haenlin Marc , Kramatschek Bernd , Campos-Ortega José A. 
Published: April 2021

Abstract
The function of the Delta locus of Drosophila melanogaster is required for the correct separation of neural and epidermal cell lineages. We describe here the transcriptional organization of this locus and the spatial pattern of mRNA accumulation during embryogenesis. Delta produces three mRNAs with protein-coding capacity, which differ only at their untranslated 3′ ends and thus encode the same protein; other minor RNAs from the locus are shown not to have any protein-coding capacity and to correspond to introns. No indications were obtained for multiple translational products of the locus. In situ hybridization using digoxigenin-labelled probes confirms that Delta RNA is present at high concentration in all presumptive neurogenic territories of the embryo. Since all the constituent cells of these territories contain Delta RNA, a differential distribution of the protein among the derivatives of the neuroectodermal cells is improbable. Some time after segregation of lineages, Delta RNA reappears in neuroblasts. The possible significance of these observations with respect to the function of the Delta product during lineage segregation is discussed.
Post-transcriptional regulation of ornithine decarboxylase in Xenopus laevis oocytes
Authors: Bassez Therèse , Paris Jeannie , Omilli Francis , Dorel Corine , Osborne H. Beverley 
Published: April 2021

Abstract
The level at which ornithine decarboxylase expression is regulated in growing oocytes has been investigated. Immunoprecipitation of the in vivo labelled proteins showed that ornithine decarboxylase accumulated less rapidly in stage IV oocytes than in previtellogenic stage I+II oocytes. Quantitative Northern analysis showed that ornithine decarboxylase mRNA is abundant in oocytes (about 8×l08 transcripts/cell) and this number does not significantly change during oogenesis. Polysome analysis showed that this mRNA is present in polysomes in stage I+II oocytes but has passed into puromycin-insensitive mRNP particles by stage IV of oogenesis.
Therefore, during the growth phase of oogenesis, ornithine decarboxylase expression is regulated at a translational level. These results are discussed relative to the temporal expression of ornithine decarboxylase and of other proteins whose expression also decreases during oogenesis. In order to perform these experiments, the cDNA (XLODC1) corresponding to Xenopus laevis ornithine decarboxylase mRNA was cloned and sequenced.
Gradients of homeoproteins in developing feather buds
Authors: Chuong Cheng-Ming , Oliver Guillermo , Ting Sheree A. , Jegalian Beatrice G. , Chen Hai Ming , Robertis Eddy M. De 
Published: April 2021

Abstract
Homeoproteins are functionally involved in pattern formation. Recently, homeoproteins have been shown to be distributed in a graded fashion in developing limb buds. Here we examine the expression of homeoproteins in chicken feather development by immunocytochemical localization. We find that XlHbox 1 antigen is present in cell nuclei and is distributed in a gradient in the mesoderm of developing feather buds, with strongest expression in the anterior-proximal region. The gradient is most obvious in feather buds from the mid-trunk level. Feather buds from the scapular level express very high levels of XlHbox 1 and feather buds from the caudal region express no XlHbox 1, suggesting that a broad gradient along the body axis is superimposed on a smaller gradient within each individual feather bud. Feather ectoderm also expresses XlHbox 1 antigen but without an obvious graded pattern. Another homeoprotein, Hox 5.2, is also expressed in developing feather buds in a graded way, and its distribution pattern is partially complementary to that of XlHbox 1. These observations suggest that homeoproteins may be involved in setting up the anteroposterior polarity of cell fields at different levels, first for the body axis, then for the limb axis and finally for the feather axis.
Organotypic arrangement of mouse embryonic lung cells on a basement membrane extract: involvement of laminin
Authors: Schuger Lucia , O’shea K. Sue , Nelson Bradley B. , Varani James 
Published: April 2021

Abstract
The behavior of embryonic murine lung cells on a basement membrane extract (Matrigel) was investigated. Single cell suspensions generated by trypsinization of lungs removed from day 12 embryos were plated on Matrigel and cultured for up to one week. The basement membrane extract was used as a gel, and as a wet or dried him. In all of these instances, organotypic arrangement of the embryonic lung cells was observed. This process consisted of cell aggregation, sorting, polarization and formation of a tridimensional organization resembling embryonic lung. The maximal degree of organotypic development was obtained by using a thick gel; minimal reorganization was observed using a dried Flim. A rabbit polyclonal serum to laminin inhibited organotypic pattern formation while normal rabbit serum did not. Culture of lung cells on laminin gels promoted epithelial cyst formation but poor mesenchymal organization. By studying the behavior of epithelial and/or mesenchymal enriched cell populations on Matrigel, it was concluded that organotypic pattern formation on Matrigel required the presence of both cell populations. Cultivation of dissociated lung cells on a gel consisting of a mixture of collagens type I and III (Vitrogen-100) produced only cell aggregation. Cultivation of lung cells on a thin film of Vitrogen-100 or on uncoated tissue culture plastic produced monolayers of mesenchymal cells alone. Cultivation of lung cells in suspension also failed to induce organotypic arrangement even at maximal cell densities. The present study strongly supports a role for the basement membrane in the organotypic rearrangement of embryonic lung cells and subsequent in vitro cyst formation and budding of the reestablished epithelium. This, in turn, reinforces the concept of the basement membrane as a major regulator of organogenesis.