bluuebunny/crossref_metadata_2025_split huggingface dataset:
The CUP-SHAPED COTYLEDON1 gene of Arabidopsis regulates shoot apical meristem formation
Authors: Takada Shinobu , Hibara Ken-ichiro , Ishida Tetsuya , Tasaka Masao 
Published: April 2021

ABSTRACT
In higher plants, molecular mechanisms regulating shoot apical meristem (SAM) formation and organ separation are largely unknown. The CUC1 (CUP-SHAPED COTYLEDON1) and CUC2 are functionally redundant genes that are involved in these processes. We cloned the CUC1 gene by a map-based approach, and found that it encodes a NAC-domain protein highly homologous to CUC2. CUC1 mRNA was detected in the presumptive SAM during embryogenesis, and at the boundaries between floral organ primordia. Surprisingly, overexpression of CUC1 was sufficient to induce adventitious shoots on the adaxial surface of cotyledons. Expression analyses in the overexpressor and in loss-of-function mutants suggest that CUC1 acts upstream of the SHOOT MERISTEMLESS gene.
Mice doubly deficient for the Polycomb Group genes Mel18 and Bmi1 reveal synergy and requirement for maintenance but not initiation of Hox gene expression
Authors: Akasaka Takeshi , Lohuizen Maarten van , Lugt Nathalie van der , Mizutani-Koseki Yoko , Kanno Masamoto , Taniguchi Masaru , Vidal Miguel , Alkema Mark , Berns Anton , Koseki Haruhiko 
Published: April 2021

ABSTRACT
Polycomb group genes were identified as a conserved group of genes whose products are required in multimeric complexes to maintain spatially restricted expression of Hox cluster genes. Unlike in Drosophila, in mammals Polycomb group (PcG) genes are represented as highly related gene pairs, indicative of duplication during metazoan evolution. Mel18 and Bmi1 are mammalian homologs of Drosophila Posterior sex combs. Mice deficient for Mel18 or Bmi1 exhibit similar posterior transformations of the axial skeleton and display severe immune deficiency, suggesting that their gene products act on overlapping pathways/target genes. However unique phenotypes upon loss of either Mel18 or Bmi1 are also observed. We show using embryos doubly deficient for Mel18 and Bmi1 that Mel18 and Bmi1 act in synergy and in a dose-dependent and cell type-specific manner to repress Hox cluster genes and mediate cell survival of embryos during development. In addition, we demonstrate that Mel18 and Bmi1, although essential for maintenance of the appropriate expression domains of Hox cluster genes, are not required for the initial establishment of Hox gene expression. Furthermore, we show an unexpected requirement for Mel18 and Bmi1 gene products to maintain stable expression of Hox cluster genes in regions caudal to the prospective anterior expression boundaries during subsequent development.
Fgf3 and Fgf8 are required together for formation of the otic placode and vesicle
Authors: Maroon Habib , Walshe Jennifer , Mahmood Radma , Kiefer Paul , Dickson Clive , Mason Ivor 
Published: April 2021

Fgf3 has long been implicated in otic placode induction and early development of the otocyst; however, the results of experiments in mouse and chick embryos to determine its function have proved to be conflicting. In this study, we determined fgf3 expression in relation to otic development in the zebrafish and used antisense morpholino oligonucleotides to inhibit Fgf3 translation. Successful knockdown of Fgf3 protein was demonstrated and this resulted in a reduction of otocyst size together with reduction in expression of early markers of the otic placode.fgf3 is co-expressed with fgf8 in the hindbrain prior to otic induction and, strikingly, when Fgf3 morpholinos were co-injected together with Fgf8 morpholinos, a significant number of embryos failed to form otocysts. These effects were made manifest at early stages of otic development by an absence of early placode markers (pax2.1 and dlx3) but were not accompanied by effects on cell division or death. The temporal requirement for Fgf signalling was established as being between 60% epiboly and tailbud stages using the Fgf receptor inhibitor SU5402. However, the earliest molecular event in induction of the otic territory, pax8 expression, did not require Fgf signalling, indicating an inductive event upstream of signalling by Fgf3 and Fgf8. We propose that Fgf3 and Fgf8 are required together for formation of the otic placode and act during the earliest stages of its induction.
Histopathologic basis of the teratogenic effects of H-1 virus on hamster embryos
Authors: Ferm Vergil H. , Kilham Lawrence 
Published: April 2021

ABSTRACT
Rat virus (RV), an extremely small DNA virus with a diameter of 15 mμ (Dalton, Kilham & Zeigel, 1963), has exhibited a marked ability to proliferate in placental and fetal tissues following intravenous inoculations of pregnant hamsters, the maternal health remaining unaffected. Effects on the fetus, however, have varied with the strains of RV employed. In initial experiments, a strain which had been carried in forty-two passages through suckling hamsters was without apparent effect on hamster fetuses, although present in high titers in both placental and fetal tissues (Ferm & Kilham, 1963). These results encouraged similar studies on other strains of RV, attempting to find some which would proliferate in a similar manner and also induce teratogenic effects. These studies resulted in the finding of the teratogenicity of the H-1 strain of RV (Ferm & Kilham, 1964a). The purpose of the present report is to describe the histopathologic changes, including the numerous intranuclear inclusions, which accompanied fetal infections with H-1 virus and the spectrum of congenital malformations directly induced by viral action. The histopathologic processes found in these embryonic tissues may help to explain the morphogenetic basis of certain congenital malformations.
An immuno-fluorescent study of lens regeneration in larval Xenopus laevis
Authors: Campbell John C. 
Published: April 2021

ABSTRACT
The appearance and localization of lens antigens in lens regenerating from the cornea of larval Xenopus laevis were investigated by the fluorescent antibody technique. The cornea of the normal eye was not stained by the antiserum used, but lens antigens were detected in the cytoplasm of cells of the inner layer of the corneal epithelium overlying the pupillary space within 24 hr. of lens removal. In the cells of the lens vesicle, before fibre formation, the labelling, which was over the cytoplasm, was weak, except for small areas of cells at the posterior margin of the vesicle from which the primary lens fibres are formed. The most intense fluorescence appears over the fibres and is stronger in older fibres, whether primary or secondary. The lens epithelium is always unlabelled. The limitations of the technique are considered and the results are discussed in the light of other immunological data on normally developing and regenerating lens.
Skeletal malformations in the Holtzman rat embryo following the administration of thalidomide
Authors: Dwornik J. J. , Moore K. L. 
Published: April 2021

ABSTRACT
Pregnant Holtzman albino rats were given 25-, 50- or 500-mg. doses of thalidomide intraperitoneally, or by stomach tube, during the time their embryos’ limbs were developing. Except in rare instances, thalidomide had no effect on limb development. In one case, limb malformations closely resembling thalidomide deformities in man and rabbits were observed. The commonest effect of thalidomide on rat development was absent, delayed, or abnormal ossification of the 5th sternebra. The most serious abnormalities observed were maldevelopment, fusion or absence of vertebrae. Other skeletal defects observed occasionally were: ‘scrambled’ sternebrae, abnormal flexion of toes, ‘clubfoot ‘, absence of vertebrae, ribs and tail and supernumerary ribs. In general the 50-mg. dose of thalidomide induced the most serious defects. The method of administration (by stomach tube or by intraperitoneal injection) seemed to make no difference. The critical period during which thalidomide seems to act on the skeletal system in this strain of rat is from the 10th to 12th days of gestation. Some control fetuses had minor skeletal defects suggesting that sodium carboxymethylcellulose may also be a weak teratogen in this strain of rat. The thalidomide-produced vertebral and sternebral defects were not visible during macroscopic examination. Alizarin preparations were needed to demonstrate the defects; this suggests that the above technique should be a part of all investigations aimed at detecting teratogenicity of drugs.
Thalidomide injury to the myocardium of armadillo embryos
Authors: Marin-Padilla Miguel , Benirschke Kurt 
Published: April 2021

ABSTRACT
An injury to the myocardium of armadillo embryos induced by thalidomide when administered to their mothers is reported. The injury consists of focal myocardial necrosis of both atria and ventricles. Myocardial necrosis is more severe and extensive in the youngest embryos (CR 3 mm.). The myocardial damage induced by thalidomide can cause fetal death. Cardiac rupture through an area of artrial necrosis and hemopericardium is reported in one embryo. Also, fetal death can occur from heart failure manifested by cardiomegaly, hepatomegaly and visceral congestion. The significance of myocardial necrosis as a possible cause of later congenital cardiac deformities is discussed.
The embryo-forming potencies of the young chick blastoderm
Authors: Eyal-Giladi Hefzibah , Spratt Nelson T. 
Published: April 2021

ABSTRACT
Very young unincubated chick blastoderms (obtained from winter eggs) are almost equipotential (or totipotential) and under experimental conditions even central fragments can form an embryo in vitro. When a central cut is made in a blastoderm of this age an embryo tends to form along the cut edge and the original embryo-forming centre at the prospective posterior side is suppressed.
In slightly older unincubated chick blastoderms (obtained from summer eggs) and in 4−5 hr. incubated winter eggs the embryo-forming potency is lost from the central part and becomes confined first to the marginal zone and, within it, gradually to its posterior region.
In still older blastoderms, with an expanded hypoblast but prior to streak formation, central fragments of the epiblast with their underlying hypoblast re-acquire the capability to form an embryo.
Inhibition by α-methyl-norvaline of valine and leucine uptake into protein in the chick embryo
Authors: Deuchar E. M. , Dryland A. M. L. 
Published: April 2021

ABSTRACT
α-Methyl-norvaline, an amino acid whose structure resembles both valine and leucine, has been found in certain circumstances to inhibit haemoglobin formation in the area vasculosa of the 48-hr. chick embryo. In the present experiments tracer methods have been used to show that it inhibits the uptake of both valine and leucine into protein of the embryos, and that analogue is itself taken up into protein. There is no evidence in autoradiographs of any differential effect of the analogue on amino acid uptake into blood cells. It had been suggested earlier, however, that the analogue may compete with valine (and possibly also with leucine) for uptake into terminal positions on the peptides ofhaemo-globin. Further experiments will aim at detecting whether, and at what sites, the analogue is taken up into the haemoglobin itself.
Effets du 5-fluoro-uracile et de la 6-m éthylpurine sur le développement de l’œuf de l’oursinParacentrotus lividus
Authors: Lallier par Roger 
Published: April 2021

ABSTRACTLe 5-fluoro-uracile, un analogue de base pyrimidique, interfère avec le métabolisme des acides nucléiques. Le 5-fluoro-uracile inhibe la méthylation au cours de la synthèse de la thymine (Eidinoff et al., 1957; Bosch étal., 1958; Cohen et al., 1958; Harbers et al., 1959). Le 5-fluoro-uracile est incorporé dans l’acide ribonucléique à la place de l’uracile (Bosch et al., 1958; Chaudhuri et al., 1958; Horowitz & Chargaff, 1959). Ce remplacement de base dans l’acide ribonucléique entraîne des modifications de la composition et des propriétés de certaines protéines synthétisées en présence de 5-fluoro-uracile (Naono & Gros, 1960; Hignett, 1964). La synthèse des ribosomes fonctionnels est inhibée par le 5-fluoro-uracile (Kempner & Miller, 1963).
Morphological and autoradiographic studies of cleft palate induced in rat embryos by maternal hypervitaminosis A
Authors: Kochhar Devendra M. , Johnson E. Marshall 
Published: April 2021

ABSTRACT
Oral administration of 60,000 international units of vitamin A acetate to pregnant rats for 3 consecutive days beginning on either day 9 or 10 of pregnancy resulted in more than 80 per cent, of their embryos developing cleft palate. The initiation of palatine shelf movement in normal control embryos was associated with an aggregation of preosteoblastic tissue on the medial aspect of the vertically oriented shelves at the junction of their anterior two-thirds and posterior one-third. Delay in the movement of palatine shelves from the vertical to the horizontal position was not observed in a major percentage of the vitamin A treated embryos. In many vitamin A treated embryos a considerably lesser amount of mesenchymal tissue was contributed by the maxillary processes to form the palatine shelves. A process of heterotopic chondrogenesis was detected within the preosteoblastic tissues of maxillae and palatine shelves as early as day 15 and by day 17 had replaced a major portion of the maxillary bone. On the basis of the methods employed, more S35 was fixed by the tissues of treated embryos than by those of normal controls prior to the time of palatal closure.
Etude d’associations hétérologues de l’uretère et de différents mésenchymes de l’embryon de poulet, par la technique des greffes chorio-allantoïdiennes
Authors: Bishop-Calame par Simone 
Published: April 2021

ABSTRACT
Des recherches récentes effectuées dans de nombreux laboratoires ont permis de mettre en évidence les interactions morphogènes qui s’exercent entre les deux composants, épithélial et mésenchymateux, d’une jeune ébauche en cours de différenciation. Ces travaux, utilisant la technique de digestion partielle par la trypsine qui permet de dissocier une jeune ébauche en ses deux composants (Moscona, 1952), confirment les résultats obtenus par Grobstein (1953,1955)sur les glandes salivaires et le métanephros de l’embryon de souris. Ils établissent les faits suivants :
The effect of high temperature incubation upon the myocardial glycogen in the chick embryo
Authors: Delphia John M. , Elliott John 
Published: April 2021

ABSTRACT
Glycogen accumulation in the myocardium during incubation at 40 ·0°C. has been investigated. Normal temperature incubation (37 · 5° C.) was used for the Control Group. Specimens in Experimental Group I were incubated at 40 ·0°C. during the 3rd through the 6th day of incubation while the specimens in Experimental Group II were incubated continuously at a temperature of 40 ·0°C. The Anthrone method of glycogen determination was employed. The glycogen from the heart was studied in three to thirteen embryos from the Control Group and each Experimental Group for each of the following days of incubation : 6, 8, 10, 11 and 12. The mean per cent, glycogen, standard error and standard deviation from the mean per cent glycogen was determined for each group studied on the days of incubation indicated above. The ‘t’ test for the comparison of two groups was applied. The following results were obtained : There was no significant difference in the per cent, myocardial glycogen in the embryos from the groups at 6 days incubation. The Experimental Group I showed a significant decrease (1 per cent, level of significance) in myocardial glycogen from the Control Group at 11 and 12 days incubation. The myocardial glycogen in Experimental Group II was significantly lower (1 per cent, level of significance) than that of Experimental Group I at 10 days incubation. The application of elevated temperature (40 ·0° C.) sufficient to cause visceral enlargement and coelosomia, whether it is applied during the 3rd through the 6th day of incubation or continuously in the incubation of the chick embryo, results in a significant decrease in the accumulation of myocardial glycogen.
Mesodermal alterations induced by hypervitaminosis A
Authors: Marin-Padilla Miguel 
Published: April 2021

ABSTRACT
The administration of a single dose (20000 u) of vitamin A by gavage to the pregnant hamster is followed almost immediately by changes in the mesoderm of the embryos. These changes appear 6 h after the administration and after 10 h they have reached their maximum severity. The alterations appear first in the cephalic mesoderm, later in the axial non-segmented mesoderm of the body of the embryo and finally in the somitic mesoderm. They consist of shrinkage of the cell cytoplasm, enlargement of the intercellular spaces (fluid accumulation) and reduction of the mitotic rate of mesodermal cells. These alterations precede the cellular necrosis which appeared later in the somites and is considered a secondary change. An analysis of the embryogenesis of the vitamin A induced skeletal malformation based on the changes described is discussed.
Early changes in limb buds of chick embryos after thalidomide treatment
Authors: Jurand A. 
Published: April 2021

ABSTRACT
Since the first observations of hypoplastic and aplastic thalidomide deformities in infants (McBride, 1961; Lenz, 1962), the literature on this subject has grown to many hundreds of communications. Experimental investigations in almost all cases have been undertaken to show whether thalidomide and its metabolites have any teratogenic effects in experimental animals. Numerous review papers are available on this subject, e.g. Giroud, Tuchmann-Duplessis & Mercier-Parot (1962), Somers (1963), and Salzgeber & Wolff (1964).
Les corps multivésiculaires de l’œuf de Barnea candida (Mollusque Bivalve) étudiés au microscope électronique
Authors: Pasteels par Jean J. 
Published: April 2021

ABSTRACT
Multivesicular bodies of the egg o/Barnea candida studied with the electron microscope Fertilized eggs, stained for 5 min with 1/5000 neutral red solution, when examined an hour later (at the stage of the pronuclei) show all the stain con-centrated in vacuoles having a diameter from 4 to 5 μ, crowded around the pronuclei (cf. Pasteels & Mulnard, 1963). After examination with the electron microscope, it appears that these vacuoles are the result of an enlargement of the multivesicular bodies (m.v.b) deriving from the transformation of the yolk platelets. Acid phosphatase activity (after an incubation of 1 h) has been detected in e.m. sections; this activity appears selectively in very limited areas of some yolk platelets, on the m.v.b. and at the top of the cortical microvilli. These observations allow us to confirm the previous hypothesis of Pasteels & Mulnard (1963) : that the a meta-granules are some of the yolk platelets while the β meta-granules are the m.v.b. deriving from those platelets. The pictures of the accumulation of neutral red into the m.v.b. are identical with those which have been published by Robbins, Marcus & Gonatas (1964), who stained Hela cells with acridine orange under the same experimental conditions. The m.v.b. of the egg, although being a transitory phase of the transformation of the yolk, have thus the same properties as the m.v.b. of some non-embryonic cells. It might be concluded that the ‘vacuome’ of Parat (1928) is constituted by the m.v.b. The existence of an acid phosphatase activity on top of the cortical micro-villi permits one to presume that this activity is preliminary to an excretion of some substances from the egg into sea-water.
Les mouvements corticaux de l’œuf de Barnea candida (Mollusque Bivalve) étudiés au microscope électronique
Authors: Pasteels par Jean J. 
Published: April 2021

ABSTRACT
Cortical movements in the egg o/Barnea candida (Mollusca, Lamellibranchiatd) studied with the electron microscope The crenulations of the egg-chorion (‘vitelline membrane’), previously described in Chaetopterus, have been observed occasionally in certain batches of Barnea’, they may be provoked with greater intensity by cold treatment. In both cases the electron microscope demonstrates that these undulating movements are the result of an elongation of the microvilli, occurring in suc-cessive waves. This elongation of the microvilli is autonomous and occurs independently of any undulation of the basal plasmalemma. The tips of the microvilli are firmly embedded in the dense peripheral layer of the chorion, which is, as a result, lifted up and folded by the elongation of the villi. In eggs which have been cold treated before the expulsion of the first polar body, this expulsion is considerably delayed; under these conditions the undula-tions of the chorion may be observed before and during the formation of the polar body, progressing from the animal towards the vegetative pole. Those undulations progressing towards the vegetative pole provoke a translation movement of the chorion which accumulates at the vegetative pole. Through this translation there occurs a tangential disrupture at the base of the microvilli; also, the microvilli-chorion complex is thus lifted from the basal plasmolemma resulting in an ‘elevation of the membrane’, a condition which is pathological for the species (Barnea and Chaetopterus) considered in the present work. The meaning of this cortical activity is discussed. It appears in correlation with physico-chemical changes affecting the entire surface of the egg immediately before the formation of furrows and furrow-like deformations (i.e. polar lobe). In all cases in which the formation of furrows is either abortive (monasters) or considerably delayed (cold shock), this cortical activity is enhanced.
Developmental behaviour of fragments of symmetrical and asymmetrical imaginal discs of Drosophila melanogaster (Diptera)
Authors: Nöthiger Rolf , Schubiger Gerold 
Published: April 2021

ABSTRACT
The developmental behaviour of imaginal discs of Drosophila melanogaster was investigated. The discs were medially halved and transplanted into 55 h old larval hosts to allow a sufficient time for cell proliferation. The different anlagen for the male first leg are asymmetrically distributed on the leg disc. Its median and lateral halves did not differentiate any structures of the complementary half even after intensive growth. The proliferation resulted only in an enlargement or duplication of the already present anlagen. In the symmetrical male genital disc certain anlagen could be eliminated by unilateral local irradiation with UV. This technique allowed the production of asymmetrical discs. After cutting, the non-irradiated half formed a complete and symmetrical genital apparatus. The irradiated half differentiated into a symmetrical apparatus which lacked, however, single elements on both sides. A schematic illustration is given. The results are interpreted to mean that the cell divisions initiated by the fragmentation of the disc always repeat the same state of determination. During a culture period of 3-4 days before metamorphosis a replacement of missing anlagen does not occur. The two terms ‘regeneration’ and ‘regulation’ are discussed with respect to imaginal discs. We have proposed the modified term ‘proliferative regulation’ to describe the special behaviour of imaginal disc fragments. This phenomenon consists of two processes : (1) an intensive cell proliferation whereby the state of determination is conserved; (2) a division of the overgrown blastema into areas of a fixed size (homonomous arealization).