bluuebunny/crossref_metadata_2025 huggingface dataset:
Slow as Molasses is required for polarized membrane growth and germ cell migration inDrosophila
Authors: Stein Jennifer A. , Broihier Heather Tarczy , Moore Lisa A. , Lehmann Ruth
Published: April 2021

Drosophila germ cell migration is directed by attractive and repulsive guidance cues. We have identified a novel gene, slow as molasses (slam), which is required for germ cell migration. In slam zygotic mutants, germ cells fail to transit off the midgut into the mesoderm. We show that slam is required at this stage in parallel to HMG Coenzyme A reductase, a previously identified germ cell migration gene. Removal of both zygotic and maternal slam results in an earlier defect: a failure to form a cellular blastoderm. Consistent with this phenotype, we found that slam is one of the earliest genes to be transcribed in the embryo, and Slam protein localizes to the growing basal-lateral membrane during blastoderm formation, but Slam is not detected during later stages of embryogenesis. Because slam RNA and protein are expressed earlier than the time when we observe defects in germ cell migration, we propose that Slam is required for the localization of a signal to the basal side of blastoderm cells that is needed later in the posterior midgut to guide germ cells.
A molecular analysis of ascidian metamorphosis reveals activation of an innate immune response
Authors: Davidson Brad , Swalla Billie J.
Published: April 2021

Ascidian metamorphosis represents a powerful model for comparative work on chordate development that has remained largely unexplored. We isolated transcripts differentially expressed during metamorphosis in the ascidian Boltenia villosa by suppressive PCR subtractions of staged larval and juvenile cDNAs. We employed a series of three subtractions to dissect gene expression during metamorphosis. We have isolated 132 different protein coding sequences, and 65 of these transcripts show significant matches to GenBank proteins. Some of these genes have putative functions relevant to key metamorphic events including the differentiation of smooth muscle, blood cells, heart tissue and adult nervous system from larval rudiments. In addition, a significant fraction of the differentially expressed transcripts match identified genes from the innate immune system. Innate immunity confers a rapid response to pathogen-specific molecules and/or compromised self-tissues. The activation of innate immunity genes during metamorphosis may represent the programmed maturation of the adult immune system. In addition, this immune response may be necessary for phagocytosis and re-structuring of larval tissues. An innate immune-related inflammatory response may also underlie two waves of trans-epidermal blood cell migration that occur during the swimming larval period and immediately upon settlement. We characterized these trans-epidermal migrations and discovered that some migratory cells leave the animal entirely through an anterior tunnel in the tunic. We show that these cells are positioned to detect external settlement cues and hypothesize that the innate immune system may also be employed to detect and rapidly respond to environmental settlement cues.
Anterior repression of aDrosophilastripe enhancer requires three position-specific mechanisms
Authors: Andrioli Luiz Paulo Moura , Vasisht Vikram , Theodosopoulou Ekaterina , Oberstein Adam , Small Stephen
Published: April 2021

The striped expression pattern of the pair-rule gene even skipped(eve) is established by five stripe-specific enhancers, each of which responds in a unique way to gradients of positional information in the earlyDrosophila embryo. The enhancer for eve stripe 2(eve 2) is directly activated by the morphogens Bicoid (Bcd) and Hunchback (Hb). As these proteins are distributed throughout the anterior half of the embryo, formation of a single stripe requires that enhancer activation is prevented in all nuclei anterior to the stripe 2 position. The gap genegiant (gt) is involved in a repression mechanism that sets the anterior stripe border, but genetic removal of gt (or deletion of Gt-binding sites) causes stripe expansion only in the anterior subregion that lies adjacent to the stripe border. We identify a well-conserved sequence repeat, (GTTT)4, which is required for repression in a more anterior subregion. This site is bound specifically by Sloppy-paired 1 (Slp1),which is expressed in a gap gene-like anterior domain. Ectopic Slp1 activity is sufficient for repression of stripe 2 of the endogenous eve gene,but is not required, suggesting that it is redundant with other anterior factors. Further genetic analysis suggests that the(GTTT)4-mediated mechanism is independent of the Gt-mediated mechanism that sets the anterior stripe border, and suggests that a third mechanism, downregulation of Bcd activity by Torso, prevents activation near the anterior tip. Thus, three distinct mechanisms are required for anterior repression of a single eve enhancer, each in a specific position. Ectopic Slp1 also represses eve stripes 1 and 3 to varying degrees,and the eve 1 and eve 3+7 enhancers each contain GTTT repeats similar to the site in the eve 2 enhancer. These results suggest a common mechanism for preventing anterior activation of three different eve enhancers.
Pitx2cpatterns anterior myocardium and aortic arch vessels and is required for local cell movement into atrioventricular cushions
Authors: Liu Chengyu , Liu Wei , Palie Jennifer , Lu Mei Fang , Brown Nigel A. , Martin James F.
Published: April 2021

Inactivation of the left-right asymmetry gene Pitx2 has been shown, in mice, to result in right isomerism with associated defects that are similar to that found in humans. We show that the Pitx2c isoform is expressed asymmetrically in a presumptive secondary heart field within the branchial arch and splanchnic mesoderm that contributes to the aortic sac and conotruncal myocardium. Pitx2c was expressed in left aortic sac mesothelium and in left splanchnic and branchial arch mesoderm near the junction of the aortic sac and branchial arch arteries. Mice with an isoform-specific deletion of Pitx2c had defects in asymmetric remodeling of the aortic arch vessels. Fatemapping studies using a Pitx2 cre recombinase knock-in allele showed that daughters ofPitx2-expressing cells populated the right and left ventricles,atrioventricular cushions and valves and pulmonary veins. In Pitx2mutant embryos, descendents of Pitx2-expressing cells failed to contribute to the atrioventricular cushions and valves and the pulmonary vein,resulting in abnormal morphogenesis of these structures. Our data provide functional evidence that the presumptive secondary heart field, derived from branchial arch and splanchnic mesoderm, patterns the forming outflow tract and reveal a role for Pitx2c in aortic arch remodeling. Moreover, our findings suggest that a major function of the Pitx2-mediated left right asymmetry pathway is to pattern the aortic arches, outflow tract and atrioventricular valves and cushions.
Bone morphogenetic proteins negatively control oligodendrocyte precursor specification in the chick spinal cord
Authors: Mekki-Dauriac Soraya , Agius Eric , Kan Paulette , Cochard Philippe
Published: April 2021

In the vertebrate spinal cord, oligodendrocytes originate from a restricted region of the ventral neuroepithelium. This ventral localisation of oligodendrocyte precursors (OLPs) depends on the inductive influence of sonic hedgehog (Shh) secreted by ventral midline cells. We have investigated whether the ventral restriction of OLP specification might also depend on inhibiting signals mediated by bone morphogenetic proteins (BMPs). BMPs invariably and markedly inhibited oligodendrocyte development in ventral neural tissue both in vitro and in vivo. Conversely, in vivo ablation of the dorsal most part of the chick spinal cord or inactivation of BMP signalling using grafts of noggin-producing cells promoted the appearance of neuroepithelial OLPs dorsal to their normal domain of emergence, showing that endogenous BMPs contribute to the inhibition of oligodendrocyte development in the spinal cord. BMPs were able to oppose the Shh-mediated induction of OLPs in spinal cord neuroepithelial explants dissected before oligodendrocyte induction,suggesting that BMPs may repress OLP specification by interfering with Shh signalling in vivo. Strikingly, among the transcription factors involved in OLP specification, BMP treatment strongly inhibited the expression of Olig2 but not of Nkx2.2, suggesting that BMP-mediated inhibition of oligodendrogenesis is controlled through the repression of the former transcription factor. Altogether, our data show that oligodendrogenesis is not only regulated by ventral inductive signals such as Shh, but also by dorsal inhibiting signals including BMP factors. They suggest that the dorsoventral position of OLPs depends on a tightly regulated balance between Shh and BMP activities.
T-brainhomologue (HpTb) is involved in the archenteron induction signals of micromere descendant cells in the sea urchin embryo
Authors: Fuchikami Takuya , Mitsunaga-Nakatsubo Keiko , Amemiya Shonan , Hosomi Toshiya , Watanabe Takashi , Kurokawa Daisuke , Kataoka Miho , Harada Yoshito , Satoh Nori , Kusunoki Shinichiro , Takata Kazuko , Shimotori Taishin , Yamamoto Takashi , Sakamoto Naoaki , Shimada Hiraku , Akasaka Koji
Published: April 2021

Signals from micromere descendants play a crucial role in sea urchin development. In this study, we demonstrate that these micromere descendants express HpTb, a T-brain homolog of Hemicentrotus pulcherrimus. HpTb is expressed transiently from the hatched blastula stage through the mesenchyme blastula stage to the gastrula stage. By a combination of embryo microsurgery and antisense morpholino experiments, we show that HpTb is involved in the production of archenteron induction signals. However, HpTb is not involved in the production of signals responsible for the specification of secondary mesenchyme cells, the initial specification of primary mesenchyme cells, or the specification of endoderm.HpTb expression is controlled by nuclear localization ofβ-catenin, suggesting that HpTb is in a downstream component of the Wnt signaling cascade. We also propose the possibility that HpTbis involved in the cascade responsible for the production of signals required for the spicule formation as well as signals from the vegetal hemisphere required for the differentiation of aboral ectoderm.
The maizedek1gene functions in embryonic pattern formation and cell fate specification
Authors: Becraft Philip W. , Li Kejian , Dey Nrisingha , Asuncion-Crabb Yvonne
Published: April 2021

Mutants in the maize defective kernel1 (dek1) gene are blocked in embryogenesis and the endosperm is chalky and lacks an aleurone layer. Here we show that intermediate alleles result in embryos that lack a shoot axis while weak alleles result in endosperms with mosaic aleurone and deformed plants with epidermal cells that resemble bulliform cells, a specialized epidermal cell type. This indicates that dek1 functions in embryonic pattern formation, cell fate specification and pattern formation in the leaf epidermis, and cell fate specification in the endosperm. Thus, thedek1 gene product appears to control different cellular-developmental processes depending on cellular context. The phenotype of the weakdek1-Dooner allele resembles the crinkly4 (cr4)mutant phenotype. Double mutants between dek1 and cr4 showed elements of epistasis, additivity and synergy, suggesting that the gene products may function in overlapping developmental processes. cr4transcript was detectable in dek1 mutant kernels indicating that DEK1 was not required for Cr4 transcript accumulation. To test whether DEK1 regulated the ligand for the CR4 receptor kinase, a genetic mosaic analysis was performed. The dek1 phenotype appeared to be generally cell-autonomous, leading to the conclusion that it was not likely to produce a diffusible signal molecule, and therefore was not likely to regulate the CR4 ligand.
Sonic hedgehog regulates proliferation and differentiation of mesenchymal cells in the mouse metanephric kidney
Authors: Yu Jing , Carroll Thomas J. , McMahon Andrew P.
Published: April 2021

Signaling by the ureteric bud epithelium is essential for survival,proliferation and differentiation of the metanephric mesenchyme during kidney development. Most studies that have addressed ureteric signaling have focused on the proximal, branching, ureteric epithelium. We demonstrate that sonic hedgehog is expressed in the ureteric epithelium of the distal, non-branching medullary collecting ducts and continues into the epithelium of the ureter— the urinary outflow tract that connects the kidney with the bladder. Upregulation of patched 1, the sonic hedgehog receptor and a downstream target gene of the signaling pathway in the mesenchyme surrounding the distal collecting ducts and the ureter suggests that sonic hedgehog acts as a paracrine signal. In vivo and in vitro analyses demonstrate that sonic hedgehog promotes mesenchymal cell proliferation, regulates the timing of differentiation of smooth muscle progenitor cells, and sets the pattern of mesenchymal differentiation through its dose-dependent inhibition of smooth muscle formation. In addition, we also show that bone morphogenetic protein 4 is a downstream target gene of sonic hedgehog signaling in kidney stroma and ureteral mesenchyme, but does not mediate the effects of sonic hedgehog in the control of mesenchymal proliferation.
R8 development in theDrosophilaeye: a paradigm for neural selection and differentiation
Authors: Frankfort Benjamin J. , Mardon Graeme
Published: April 2021

The Drosophila eye is an outstanding model with which to decipher mechanisms of neural differentiation. Paramount to normal eye development is the organized selection and differentiation of a patterned array of R8 photoreceptors – the founding photoreceptor of each ommatidium that coordinates the incorporation of all other photoreceptors. R8 development is a complex process that requires the integration of transcription factors and signaling pathways, many of which are highly conserved and perform similar functions in other species. This article discusses the developmental control of the four key elements of R8 development: selection, spacing, differentiation and orchestration of later events. New questions that have surfaced because of recent advances in the field are addressed, and the unique characteristics of R8 development are highlighted through comparisons with neural specification in other Drosophila tissues and with ganglion cell development in the mammalian retina.
Subdivision of theDrosophilawing imaginal disc by EGFR-mediated signaling
Authors: Zecca Myriam , Struhl Gary
Published: April 2021

Growth and patterning of the Drosophila wing imaginal disc depends on its subdivision into dorsoventral (DV) compartments and limb (wing) and body wall (notum) primordia. We present evidence that both the DV and wing-notum subdivisions are specified by activation of the Drosophila Epidermal Growth Factor Receptor (EGFR). We show that EGFR signaling is necessary and sufficient to activate apterous (ap) expression, thereby segregating the wing disc into D (ap-ON) and V (ap-OFF) compartments. Similarly, we demonstrate that EGFR signaling directs the expression of Iroquois Complex (Iro-C) genes in prospective notum cells, rendering them distinct from, and immiscible with, neighboring wing cells. However, EGFR signaling acts only early in development to heritably activate ap, whereas it is required persistently during subsequent development to maintain Iro-C gene expression. Hence, as the disc grows, the DV compartment boundary can shift ventrally, beyond the range of the instructive EGFR signal(s), in contrast to the notum-wing boundary, which continues to be defined by EGFR input.
Semaphorin 1a and semaphorin 1b are required for correct epidermal cell positioning and adhesion during morphogenesis inC. elegans
Authors: Ginzburg Val E. , Roy Peter J. , Culotti Joseph G.
Published: April 2021

The semaphorin family comprises secreted and transmembrane proteins involved in axon guidance and cell migration. We have isolated and characterized deletion mutants of C. elegans semaphorin 1a (Ce-sema-1a or smp-1) and semaphorin 1b (Ce-sema-1b or smp-2) genes. Both mutants exhibit defects in epidermal functions. For example, the R1.a-derived ray precursor cells frequently fail to change anterior/posterior positions completely relative to their sister tail lateral epidermal precursor cell R1.p, causing ray 1 to be formed anterior to its normal position next to ray 2. The ray cells, which normally separate from the lateral tail seam cell (SET) at the end of L4 stage, remains connected to the SET cell even in adult mutant males. The ray 1 defects are partially penetrant in each single Ce-sema-1 mutant at 20°C, but are greatly enhanced in Ce-sema-1 double mutants, suggesting that Ce-Sema-1a and Ce-Sema-1b function in parallel to regulate ray 1 position. Both mutants also have defects in other aspects of epidermal functions, including head and tail epidermal morphogenesis and touch cell axon migration, whereas, smp-1 mutants alone have defects in defecation and brood size. A feature of smp-1 mutants that is shared with mutants of mab-20 (which encodes Sema-2a) is the abnormal perdurance of contacts between epidermal cells.
Heparan sulphate proteoglycans and spinal neurulation in the mouse embryo
Authors: Yip George W. , Ferretti Patrizia , Copp Andrew J.
Published: April 2021

Heparan sulphate proteoglycans have been implicated in the binding and presentation of several growth factors to their receptors, thereby regulating cellular growth and differentiation. To investigate the role of heparan sulphate proteoglycans in mouse spinal neurulation, we administered chlorate, a competitive inhibitor of glycosaminoglycan sulphation, to cultured E8.5 embryos. Treated embryos exhibit accelerated posterior neuropore closure, accompanied by suppression of neuroepithelial bending at the median hinge point and accentuated bending at the paired dorsolateral hinge points of the posterior neuropore. These effects appear specific, as they can be prevented by addition of heparan sulphate to the culture medium, whereas heparitinase-treated heparan sulphate and chondroitin sulphate are ineffective. Both N- and O-sulphate groups appear to be necessary for the action of heparan sulphate. In situ hybridisation analysis demonstrates a normal distribution of sonic hedgehog mRNA in chlorate-treated embryos. By contrast, patched 1 transcripts are abnormally abundant in the notochord, and diminished in the overlying neuroepithelium, suggesting that sonic hedgehog signalling from the notochord may be perturbed by inhibition of heparan sulphation. Together, these results demonstrate a regulatory role for heparan sulphate in mouse spinal neurulation.
Inductive patterning of the embryonic brain inDrosophila
Authors: Page Damon T.
Published: April 2021

In vertebrates (deuterostomes), brain patterning depends on signals from adjacent tissues. For example, holoprosencephaly, the most common brain anomaly in humans, results from defects in signaling between the embryonic prechordal plate (consisting of the dorsal foregut endoderm and mesoderm) and the brain. I have examined whether a similar mechanism of brain development occurs in the protostome Drosophila, and find that the foregut and mesoderm act to pattern the fly embryonic brain. When the foregut and mesoderm of Drosophila are ablated, brain patterning is disrupted. The loss of Hedgehog expressed in the foregut appears to mediate this effect, as it does in vertebrates. One mechanism whereby these defects occur is a disruption of normal apoptosis in the brain. These data argue that the last common ancestor of protostomes and deuterostomes had a prototype of the brains present in modern animals, and also suggest that the foregut and mesoderm contributed to the patterning of this ‘proto-brain’. They also argue that the foreguts of protostomes and deuterostomes, which have traditionally been assigned to different germ layers, are actually homologous.
Cerebellar proteoglycans regulate sonic hedgehog responses during development
Authors: Rubin Joshua B. , Choi Yoojin , Segal Rosalind A.
Published: April 2021

Sonic hedgehog promotes proliferation of developing cerebellar granule cells. As sonic hedgehog is expressed in the cerebellum throughout life it is not clear why proliferation occurs only in the early postnatal period and only in the external granule cell layer. We asked whether heparan sulfate proteoglycans might regulate sonic hedgehog-induced proliferation and thereby contribute to the specialized proliferative environment of the external granule cell layer. We identified a conserved sequence within sonic hedgehog that is essential for binding to heparan sulfate proteoglycans, but not for binding to the receptor patched. Sonic hedgehog interactions with heparan sulfate proteoglycans promote maximal proliferation of postnatal day 6 granule cells. By contrast, proliferation of less mature granule cells is not affected by sonic hedgehog-proteoglycan interactions. The importance of proteoglycans for proliferation increases during development in parallel with increasing expression of the glycosyltransferase genes, exostosin 1 and exostosin 2. These data suggest that heparan sulfate proteoglycans, synthesized by exostosins, may be critical determinants of granule cell proliferation.
Novel retinoic acid generating activities in the neural tube and heart identified by conditional rescue ofRaldh2null mutant mice
Authors: Mic Felix A. , Haselbeck Robert J. , Cuenca Arnold E. , Duester Gregg
Published: April 2021

Retinoid control of vertebrate development depends upon tissue-specific metabolism of retinol to retinoic acid (RA). The RA biosynthetic enzyme RALDH2 catalyzes much, but not all, RA production in mouse embryos, as revealed here with Raldh2 null mutants carrying an RA-responsive transgene. Targeted disruption of Raldh2 arrests development at midgestation and eliminates all RA synthesis except that associated with Raldh3 expression in the surface ectoderm of the eye field. Conditional rescue of Raldh2–/– embryos by limited maternal RA administration allows development to proceed and results in the establishment of additional sites of RA synthesis linked to Raldh1 expression in the dorsal retina and to Raldh3 expression in the ventral retina, olfactory pit and urinary tract. Unexpectedly, conditionally rescued Raldh2–/– embryos also possess novel sites of RA synthesis in the neural tube and heart that do not correspond to expression of Raldh1-3. RA synthesis in the mutant neural tube was localized in the spinal cord, posterior hindbrain and portions of the midbrain and forebrain, whereas activity in the mutant heart was localized in the conotruncus and sinus venosa. In the posterior hindbrain, this novel RA-generating activity was expressed during establishment of rhombomeric boundaries. In the spinal cord, the novel activity was localized in the floorplate plus in the intermediate region where retinoid-dependent interneurons develop. These novel RA-generating activities in the neural tube and heart fill gaps in our knowledge of how RA is generated spatiotemporally and may, along with Raldh1 and Raldh3, contribute to rescue of Raldh2–/– embryos by producing RA locally.
Somite necrosis and developmental malformations induced by vitamin A in the golden hamster
Authors: Marin-Padilla Miguel , Ferm Vergil H.
Published: April 2021

A simple method for the induction of developmental malformation in the golden hamster is presented. The teratogenic agent used consists of a single dose of vitamin A. Correlations between the day of gestation at which the vitamin A is administered and the type and percentage of malformations induced are reported. Young embryos obtained from treated mothers on the 8th day of gestation show somite necrosis within 12 hr. of the administration of vitamin A, reaching its maximum at 24 hr. The somite necrosis is considered to be a basic alteration resulting in an abnormal axial mesoderm which then fails to fulfil its function of lodging and protecting the neural tube. The unprotected and exposed neural tissue secondarily degenerates. Somite necrosis is considered to be the primary defect induced by vitamin A causing developmental malformations such as cranioschisis and sacral rachischisis. When somite necrosis occurs before neural tube closure extensive degeneration of the neural tube follows (e.g. cranioschisis). Somite necrosis occurring after closure of neural tube results in only minimal change in the neural tube (e.g. occult sacral rachischisis). Notochordal alterations (hypertrophy and necrosis) are also found in the young hamster embryo after administration of vitamin A to their mother on the 8th day of gestation.
The relationship between oöcyte and follicle in the hen’s ovary as shown by electron microscopy
Authors: Bellairs Ruth
Published: April 2021

In the early stages of oogenesis, the follicle cells contain a ‘complex mass’ of organelles which from its size and position apparently corresponds with the region identified as Golgi body by authors using light microscopy. It contains paired centrioles, radiating tubules, patches of Golgi apparatus and an orderly series of stacks of rough-surfaced endoplasmic reticulum which contain a granular material. It is concluded that these cells are probably secretory. The ‘complex mass’ disappears in the final stages of oogenesis. Using the methyl-green-pyronin test, the follicle cells have been shown to be rich in ribonucleoproteins. Specialized structures termed ‘lining bodies’ are found at irregular intervals at the surfaces of the follicle cells where they abut on to each other or on to the oöcyte. Long processes from the follicle cells indent the surface of the oöcyte, bearing lining bodies with them. Although there is no direct evidence that these lining bodies become engulfed by the oöcyte, nevertheless structures that are found several microns deep within the oöcyte so closely resemble the lining bodies that it seems probable they are derived from them. The available evidence does not support the ideas of Schjeide and his coworkers that the lining bodies give rise to mitochondria. No evidence was found of intercellular bridges between follicle and oöcyte. At first, the follicle and oöcyte membranes lie close together. Gradually, villous-like elevations arise on the oöcyte cell membrane which increase in number and in height. These constitute the zona radiata. Vesicles, containing a granular material, are common in the cortical region of the oöcyte. It is possible that these are formed by pinocytosis, for pinocytoticlike invaginations of the oöcyte cell membrane are visible. These are especially apparent in the zona radiata. The inner layer of the vitelline membrane forms between the follicle and zona radiata, and at first appears to be moulded around projections of the follicle cells. Just before ovulation the cell membrane of the ovum appears to become fragmented into a series of large vacuoles at the cell surface.
Etude au microscope électronique de la réaction corticale: I. La reaction corticale de fécondation chez Paracentrotus et sa chronologie.: II. La réaction corticale de l’oeuf vierge de Sabellaria alveolata
Authors: Pasteels par Jean J.
Published: April 2021

An electron microscope study of the cortical reaction

Paracentrotus lividus

Sabellaria alveolata

General conclusions
Selectivity in regeneration of the oculomotor nerve in the cichlid fish, Astronotus ocellatus
Authors: Sperry R. W. , Arora H. L.
Published: April 2021

It has long been considered a general rule for nerve regeneration that the reinnervation of skeletal muscle is nonselective. Regenerating nerve fibers are supposed to reconnect with one skeletal muscle as readily as another according to studies covering a wide range of vertebrates (Weiss, 1937; Weiss & Taylor, 1944; Weiss & Hoag, 1946; Bernstein & Guth, 1961; Guth, 1961, 1962, 1963). Similarly, in embryogenesis proper functional connexions between nerve centers and particular muscles are supposedly attained, not by selective nerve outgrowth but rather through a process of ‘myotypic modulation’ (Weiss, 1955) that presupposes nonselective peripheral innervation.
Influence de la puromycine sur la morphogenèse et la synthèse des macromolécules chez l’embryon de poulet
Authors: Malpoix Par P. , Limbosch S.
Published: April 2021

L’inhibition des synthèses protéiques par la puromycine confère à cette substance un intérêt particulier pour l’étude précise du mécanisme de la synthèse d’une protéine spécifique au cours de la morphogenèse. Les études déjà effectuées dans notre laboratoire sur les effets de la puromycine chez les œufs de Batraciens et chez Acetabularia (Legros, 1965; Brachet, 1963; Brachet, Denis & De Vitry, 1964), ainsi que sur les racines d’oignons (Bosseler, Six & Simic, 1964) permettent de faire des comparaisons utiles.
The ovary and sexual maturation of the brain
Authors: Smith W. N. Adams
Published: April 2021

Pfeiffer (1935, 1936) reported the induction of constant oestrus in female rats following the transplantation of testes from litter-mate males just after birth and noted that the ovaries of these animals did not contain corpora lutea. These changes remained after removal of the testis transplants. The same effects were obtained by Bradbury (1941) following the administration of multiple doses of testosterone propionate. Barraclough & Leathern (1954) found that a single injection of 1 mg of testosterone propionate at 5 days of age led to permanent sterility in female mice, with no corpus luteum formation in their ovaries. Similar results were obtained in rats by Barraclough (1961) with the administration of a single injection of 1·25 mg of testosterone propionate. This permanent change in ovarian function does not appear to be a direct effect upon the ovary (Bradbury, 1941). The masculinizing influence of testosterone propionate appears to be exerted upon the brain, with only an indirect effect upon the anterior pituitary gland by way of the hypothalamus (Adams Smith & Peng, 1966). The influence of the ovary in sexual differentiation of the central nervous system is not clear. This study was undertaken in an endeavour to determine the pattern of sexual maturation of the brain of the female rat ovariectomized at birth and treated with testosterone propionate at different times during the first three post-natal weeks. Different doses of testosterone were administered to see whether dosage influenced the receptive period of the animal’s brain. The receptive period found in ovariectomized animals would allow a comparison with results obtained by workers who had treated normal females with testosterone, so that an assessment could be made as to whether the presence of the ovary influenced the length of this receptive period. Control procedures were planned to allow an observation of the sexual maturation of the brain of ovariectomized females not subjected to androgen treatment.
The analysis of species specific variations in form and growth pattern in Hydra
Authors: Haynes Julian F.
Published: April 2021

The ability of four different species of Hydra to oxidize succinate has been measured. Each species studied shows a gradient in the activity of succinic dehydrogenase, which appears to be identical to the metabolic gradients described by Child & Hyman. Each species may be recognized by its unique metabolic gradient. The relationship between the growth-regulating system proposed by Burnett for Hydra and the metabolic gradient is discussed. The control of the level of enzyme activity is shown to be by a pair of organismal factors which are also responsible for the maintenance of polarity in Hydra. By using the level of enzymic activity as a measure of the relative amounts of these two factors at any level in the animal, it is possible to explain the differences in form and metabolic gradient of the different species in terms of modifications in the relative amounts of the growth stimulator and inhibitor.
Effects of temperature on tadpole hearts in vitro
Authors: Stephenson Elsie M.
Published: April 2021

Whole hearts of tadpoles of Limnodynastes peroni were cultured successfully in a combined avian-synthetic medium identical with that used for mammalian, avian and reptilian tissues. The extirpated hearts were cultured from 37 to 5°C. Temperature effects on organ viability and function and on cell outgrowth were studied comparatively. Although viability could be maintained for up to 6 days at 37°C, this temperature was ultimately lethal. From 30 to 5°C inclusive total viability or maintenance was the general rule. Rate of heart beat was at first accelerated at 37°C but dropped as moribund conditions developed. For the other temperatures used, though absolute values varied considerably, a more or less constant relative pattern emerged, with the optimal rate at 30°C and successive decreases occurring from 25 to 5°C. Cell migration did not occur at 37 or 5°C. The optimal temperature for outgrowth was 30°C, while progressively slower migration occurred from 25 to 15°C. At 8°C, outgrowth was confined to a few cells in a limited number of cultures. Although these results apply at present to only one species, the establishment of 30°C as an optimal incubation temperature may be important in view of the fact that almost all previous amphibian cultures have been grown at temperatures not exceeding 26°C and often considerably lower.
Reversible effect of chloroacetophenone by sulphydryl groups on morphogenesis of chick embryos
Authors: Mulherkar Leela , Joshi S. S. , Diwan B. A. , Joshi P. N.
Published: April 2021

Chloroacetophenone (CAP), a specific inhibitor of SH groups, applied at 5 × 10−4 M for 15 min at the definitive primitive streak stage of chick embryos causes abnormalities, predominantly in the nervous system. The effects of CAP can be reversed by a subsequent treatment with thiomalic acid (5 × 10−4) or glutathione (1 × 10−5 M). Equimolar concentration of serine (4 × 10−4), which is structurally similar to cysteine except that SH of cysteine is replaced by OH in serine, fails to reverse the effects of CAP. The results of the present work suggest that the reversal of the CAP effects is brought about by SH groups.
Genotype and environment in the determination of minor skeletal variants and body weight in mice
Authors: Howe W. L. , Parsons P. A.
Published: April 2021

Numerous minor skeletal variants have been described in the mouse (Grüneberg, 1963), other small mammals (Berry & Searle, 1963) and in man (Comas, 1960; Brothwell, 1963; Grüneberg, 1963). In genetically heterogeneous material such as man it is very difficult to sort out the factors causing these variants. However, in experimental animals such as the mouse the use of inbred strains and crosses derived from them permits a more detailed understanding of these factors, in particular the relative importance of heredity and environment. Grüneberg (1963) cites numerous references showing very great differences in the percentage incidence of many minor variants in mice between inbred strains and in some cases between hybrids. The conclusion is that much of this variation is genetic in origin. Even so, certain environmental factors have been shown to be of importance, such as maternal age, parity, maternal weight and maternal diet. Some of these environmental factors may be highly correlated, so that large amounts of data may be needed to determine the causative factor. For example, Kalter (1956) found a decrease in the incidence of median cleft palate, induced by injecting primigravid pregnant mice with cortisone, with increasing maternal age. However, from multiple regression analyses, he concluded that maternal weight was the most important factor. Maternal age seemed to play a role only because it is highly correlated with maternal weight (see also Parsons, 1964).
Ploidy,pigment patterns and species specific antigenicity in interspecific nuclear transplantations in newts
Authors: Sládeček F. , Romanovský A.
Published: April 2021

It was shown by Simnett (1964) that in Xenopus laevis skin grafts in adult frogs between members of the same nuclear clone were tolerated in the same way as autografts, but in skin grafts made between individuals belonging to different nuclear clones a homograft rejection occurred. The nucleus is therefore responsible for the synthesis of specific transplantation antigens. It seemed to us useful to investigate the species-specific antigenicity of animals derived from eggs transplanted with foreign nuclei in correlation with their ploidy and with the development of their species-specific pigment patterns, as a proof of functional activity of transplanted nuclei. For this purpose we used two species of Trituras, T. vulgaris and T. alpestris, because of earlier studies carried out in our laboratory on the pigmentation of their hybrids (Romanovský & Štefanová, 1960; Mazáková-Štefanová, 1965) and on their species-specific antigenicity (Romanovský, 1962a, b), in spite of the known difficulties and limitations of nuclear transplantation experiments in these species (Lehman, 1955; Sládeček & Mazáková-Štefanová, 1964, 1965).
A regional change in the rigidity of the cortex of the egg of Rana nigromaculata following extrusion of the second polar body
Authors: Kubota T.
Published: April 2021

Measurements of the consistency of the protoplasm by following the movement of cellular granules under centrifugal force have been made in various materials (e.g. for cytoplasm, Heilbrunn, 1928; Heilbrunn & Wilson, 1948; Allen, 1960; for cortex, Brown, 1934; Wilson, 1951; Zimmerman, Landau & Marsland, 1957). In amphibian eggs such measurements were performed by Konopacka (1908) and Ödquist (1922) on the cytoplasm and by Selman & Waddington (1955) on the cortex. However, since the observations of the latter authors were restricted to dividing eggs, a report on the cortical consistency of uncleaved amphibian eggs determined by the centrifugal method is not available.
L’influence favorable du foie embryonnaire sur l’hématopoïèse in vitro dans la moelle osseuse de l’embryon de poulet
Authors: Salvatorelli Germano
Published: April 2021

Pendant le développement embryonnaire du poulet, on peut noter la succession de différents foyers d’érythropoïèse (Romanoff, 1960; Le Douarin, 1966):

les îlots de Wolff dont l’activité se déroule entre le 1er et 2ème jour d’incubation; le sac vitellin érythropoïétiquement actif du 4ème au 19ème jour d’incubation; le foie et la rate dont la faible activité se déroule entre le 7ème et le lOème jour d’incubation; la moelle osseuse dont l’activité commence au 12ème jour d’incubation et qui deviendra chez l’adulte le seul organe ayant une activité érythropoïétique.
Programming of gastrulation during the second cleavage cycle in Limnaea stagnalis: a study with lithium chloride and actinomycin D
Authors: Geilenkirchen W. L. M.
Published: April 2021

It is well known that treatment with LiCl can cause abnormal embryonic development, but its mode of action is still uncertain (Gustafson, 1954; Geilenkirchen, 1961; Lallier, 1964). It also remains to be shown whether LiCl enters the egg cell at early developmental stages and acts internally, or does not penetrate into the cell and is active only at the outer surface (Elbers, 1959).
Limb development in the polydactylous talpid3 mutant of the fowl
Authors: Hinchliffe J. R. , Ede D. A.
Published: April 2021

Talpid 2 limb development is characterized by excessive elongation of the apical ectodermal ridge (AER). In the forelimb the talpid2 AER is of normal length during stages 22 and 23, but at stage 28 it exceeds the normal by about 65%. In the hindlimb the talpid2 AER is of normal length during stages 22 – 24, but at stage 27 it exceeds the normal by about 20%. Massive cell death is absent from the superficial mesenchyme of both fore and hind talpid2 limbs. Histological and histochemical studies show that areas of dead cell groups rich in acid phosphatase activity are absent in talpid2 from the positions in the superficial limb mesenchyme in which they occur in the normal. This absence of cell death in the limb superficial mesenchyme is thought to account for (a) the abnormal sculpturing of talpid2 limbs, and (b) the excessive elongation of the talpid2 AER, through apical ectodermal maintenance factor (AEMF) being available from areas of mesenchyme normally undergoing necrosis and lacking AEMF. The abnormal talpid2 forelimb skeleton originates in an anomalous pattern of mesenchymal condensation forming the membranous skeleton at stage 26. Talpid2 limb mesenchyme shows an abnormal pattern of alkaline phosphatase distribution beginning at stage 26. The relationship between the abnormal pattern of limb mesenchymal condensation and the absence of massive cell death in the superficial mesenchyme is not understood. Talpid 3 limb development is discussed in relation to other cases where genes affect the pattern of cell death, and in relation to other examples of polydactyly.
Development of blastomeres of mouse eggs isolated at the 4- and 8-cell stage
Authors: Tarkowski Andrzej K. , Wróblewska Joanna
Published: April 2021

Organization of a mammalian egg at the beginning of development has been the subject of several experimental as well as descriptive cytological and cytochemical investigations.
Chromosome changes in embryos treated with various teratogens
Authors: Soukup S. , Takacs E. , Warkany J.
Published: April 2021

Pregnant animals were treated with five chemical teratogens and a teratogenic dietary regime. Embryos were examined for chromosome changes in squash or ‘direct method’ preparations at various times after administration of the teratogen.

Embryos from rats treated with a teratogenic dose of nitrogen mustard or chlorambucil showed a peak of less than 20 % metaphase figures with chromosome abnormalities. Streptonigrin produced less than 10 %. The maximum chromosome abnormalities appeared within 24 h after injection and almost all abnormal metaphase figures disappeared within 48 h after injection.

Other chemical teratogens such as hydroxyurea injected into pregnant rats and thalidomide fed to pregnant rabbits produced no detectable chromosome abnormalities in the embryos. There were also no abnormal metaphase figures detectable in rat embryos after maternal exposure to a riboflavin-deficient diet.
The regeneration of limbs in adult anurans
Authors: Goode Robert P.
Published: April 2021

The regeneration of limbs, after simple amputation, in two families (four genera) of primitive anurans was investigated. All produced hypotypic regenerates of varying size and degree of morphogenesis. Despite certain differences possibly related to phylogenetic affinities, both Discoglossidae and Pipidae regenerated in similar fashion. Regenerates consisted chiefly of well-developed rods of cartilage, surrounded by connective tissue and skin. Muscle regeneration was minimal, resulting in the formation of small striated slips. The role of the stump tissues and their possible relation to the development of the hypotypic regenerate was discussed.
The control of cell number in the lumbar ventral horns during the development of Xenopus laevis tadpoles
Authors: Prestige M. C.
Published: April 2021

The developing limb has been amputated by many workers in several species and in each case the number of surviving motor neurones on the side of the operation was less than normal. This may be observed among the mammals (e.g. Barron, 1945), birds (e.g. Hamburger, 1934), urodeles (e.g. Stultz, 1942), and anurans (e.g. May, 1930). The loss of motor neurones after amputation in adults appears to have been first noticed by Vulpian (1868) and Johnson & Clarke (1868). The early evidence is reviewed by Sherrington (1893) and the later by Piatt (1948). The control that the developing leg has over proliferation, migration, maintenance and degeneration of ventral horn cells has been most completely analysed in the chick, notably by Hamburger (1934, 1939, 1958), Hamburger & Keefe (1944), Bueker (1943, 1944, 1945a), Barron (1946, 1948), Mottet (1952) and Mottet & Barron (1954). Less is known about this in Anura. May (1930, 1933) has recorded that in Discoglossus motor area hyperplasia can be produced by supernumerary limbs, and that the lateral motor horn (ventral horn) can be suppressed by replacement of the limb area with skin grafts. Bueker (1945b) found a frog (Rana) with three functional hind legs on one side; this had a hyperplasia of 22-7% in the ventral horn. Beaudoin (1955) ablated the early limb-bud in Rana pipiens and found a terminal hypoplasia of 82% in the ventral horn. Counts at intermediate stages were interpreted by him as indicating that the operation had delayed differentiation and the normal loss of cells on that side. In Bufo vulgaris, Perri (1956a) removed the hind-limb area at tailbud stages, and found that the ventral horn developed normally up to digit stages, when it regressed. The same happened when the isolated spinal cord was transplanted (Perri, 1956b). Three out of six animals with motile supernumerary limbs had hyperplastic spinal cords on the side of graft; this was not seen in any of the cases with non-motile grafts (Perri, 1957). Supernumerary limbs only became motile when innervated by limb plexus fibres, and never induced formation of new ventral horns in trunk regions. Perri therefore concluded that for the full development of the ventral horn, both regional intrinsic and also extrinsic limb factors were essential, the former necessarily acting before the latter.
Yolk distribution and utililization during early development of a teleost embryo (Brachydanio rerio)
Authors: Thomas Robert J.
Published: April 2021

The work of Oppenheimer (1934, 1936) and Tung (1955, see also Devillers, 1961) suggests that an embryo such as Fundulus, a marine teleost, explanted at early cleavage (two-cell stage) is more dependent upon the amount of periblast yolk included in an explant than is an embryo that is more advanced prior to explanation. In other words, ‘if it (the embryo) is explanted before a so-called critical stage, the blastoderm turns into a hyperblastula (a non-differentiated mass of cells); if it is explanted after that, it undergoes differentiation. The critical stage corresponds to eight blastomeres in Carassius, thirty-two in Fundulus, and a young blastula in Salmo’ (Devillers, 1961, p. 391). The zebrafish, Brachydanio rerio, with a smaller egg than these fish, has not been characterized by explantation. Devillers, in summary, states that ‘these results mean that a substance indispensable for differentiation exists in the yolk sphere’ (p. 392). He continues, ‘On the other hand, how this hypothetical material may reach the blastoderm needs to be explained. The base of the blastoderm is in direct contact with the periblast in the early stages; later on, this syncytium ‘buds’ off blastomeres that add themselves to the embryonic disc’ (p. 397). He then asks the question ‘but then how can one explain that in later stages the syncytium can still impose an orientation on the germ? Are diffusing organizing substances involved?’ (p. 397).
Etude autoradiographique de la synthèse des ADN, ARN et protéines dans l’œsophage embryonnaire de Souris à l’aide de l’actinomycine D
Authors: Soriano Par Luis
Published: April 2021

L’actinomycine D est capable à des doses modérées d’inhiber la synthèse d’ARN dépendant du ADN, et à des doses plus fortes elle peut affecter la synthèse des ARN et protéines cytoplasmiques dans les cellules animales (Goldberg & Rabinovitz, 1962; Caspersson, Farber, Foley & Killander, 1963; Franklin, 1963). D’autre part, ces résultats ont été confirmés en culture de cellules et d’organes par l’utilisation des méthodes autoradiographiques (Wessells, 1964; Yaffe & Feldman, 1964; Yaiïe & Fuchs, 1967).