Showing papers in "Development in 1968"

Changes in somatic cell nuclei inserted into growing and maturing amphibian oocytes.

Abstract: When somatic cell nuclei are injected into enucleated unfertilized eggs they very soon cease RNA synthesis (Gurdon & Brown, 1965; Gurdon. 1967 a ), and commence DNA synthesis (Graham, Arms & Gurdon, 1966). By means of such experiments it has been shown (i) that components of living egg cytoplasm can substantially change the nature of nuclear activity, (ii) that nuclear activity is altered in such a way as to conform to that of the host egg cell, and (iii) that these effects are obtained with the nuclei of adult as well as embryonic cells. The experiments to be reported here were designed to find out whether the same generalizations apply to nuclei inserted into cells other than eggs, and whether they are true of changes in nuclear activity other than the repression of RNA synthesis and the induction of DNA synthesis. For this purpose growing and maturing amphibian oocytes have been used.

The development of teratomas from intratesticular grafts of tubal mouse eggs

Abstract: Grafts of cleaving tubal ova from non-inbred mice to ectopic sites usually result in growths composed of extra-embryonic but not embryonic tissues (Fawcett, Wisloki & Waldo, 1947; Fawcett, 1950; Jones, 1951; Whitten 1958; Kirby, 1960, 1962a; Billington, 1965; and others). Runner (1947) grafted tubal mouse ova to the anterior chamber of the eye and one developed the three primary germ layers and then regressed, probably because the host and donor were histo-incompatible. This is the only report of an ectopically grafted pre-uterine egg that developed intra-embryonic derivatives. Kirby (1962b, 1965) grafted oviducal segmenting mouse eggs to the kidney and obtained only trophoblast and extra-embryonic membranes. He concluded that a ‘uterine factor’ is necessary for the development of intra-embryonic structures from mouse eggs. Kirby (1965) and Billington (1965) grafted morulae and blastocysts to the testis, and the morulae never gave rise to embryonic shield derivatives.

The relative rates of synthesis of DNA, sRNA and rRNA in the endodermal region and other parts of Xenopus laevis embryos

Abstract: The onset and rates of synthesis of the major classes of nucleic acids have been extensively studied during the development of whole frog embryos (reviews by Brown, 1965; Gurdon, 1967 a ). Such information is of interest because nucleic acids are the immediate products of genes, and their rates of synthesis therefore provide a direct measure of changes in gene activity. To date nucleic acid synthesis in parts of frog embryos has been analysed mainly by methods which do not distinguish different classes of RNA (e.g. Bachvarova & Davidson, 1966; Flickinger, Miyagi, Moser & Rollins, 1967). Since embryos consist of many different cell types, it is important to know to what extent the pattern of nucleic acid synthesis observed in the whole embryo is true for its individual regions, and in particular for one differentiating cell type.

The role of neurohumors in early embryogenesis. II. Acetylcholine and catecholamine content in developing embryos of sea urchin.

Abstract: In a previous paper (Buznikov, Chudakova & Zvezdina, 1964) it has been reported that serotonin (5-hydroxytryptamine, 5-HT) may be involved in early embryogenesis in various groups of animals. This conclusion was confirmed by Baker9s recent publication (Baker, 1965) concerning 5-HT synthesis in Xenopus laevis embryos. Some other low molecular weight substances, neurohumors or related compounds, are known to be synthesized in fertilized eggs as well. Acetylcholine (ACh) synthesis in sea-urchin eggs and embryos was demonstrated by Numanoi (1953, 1955, 1959, 1961). It seems possible that ACh can be synthesized in fertilized insect eggs as well (Morley & Schachter, 1963; Schachter, 1964). The synthesis of another neurohumor, dopamine (DA), in early insect embryos seems to be indisputable (Furneaux & McFarlane, 1965). However, in most cases changes in the level of neurohumors with age have not been studied. In the present paper data concerning the change of concentration with age of ACh and catecholamines (adrenaline (A) and noradrenaline (NA)) in early sea-urchin embryos will be presented.

Glandular metaplasia of hair follicles and other responses to vitamin A excess in cultures of rodent skin.

Abstract: The demonstration of mucous metaplasia in chicken embryonic epidermis exposed to an excess of vitamin A (Fell & Mellanby, 1953) stimulated many further investigations (reviewed by Fell, 1964; Fell & Rinaldini, 1965; Dingle & Lucy, 1965), leading to new insights into control of differentiation and function at the cellular level. The object of the present experiments was to study the effects of excess vitamin A on another keratin-producing system, the developing hair follicle, in organotypic cultures. Hairs and their follicles have received little attention from other investigators of vitamin A effects in vitro , although Fell & Mellanby (1953) referred to ‘evidence of an inhibitory effect on hair formation’ in some preliminary experiments with mouse embryonic skin, and New (1963) reported that ‘usually the development of hair follicles was suppressed’ in cultures of embryonic skin from the rat and mouse, both in the presence and absence of excess vitamin A.

Observations on CBA-p-CBA-T6T6 mouse chimeras.

Abstract: A considerable amount of information bearing upon mouse chimeras obtained experimentally by fusion of cleaving eggs has already been accumulated (Tarkowski, 1961, 1963, 1964 a , b , 1965; Mintz, 1962 a , b , 1964 a , b , 1965 a , b 1967). Direct and indisputable proofs of the chimerism of the individuals produced were obtained by establishing that two types of pigment cells were present in the outer layer of the retina (Tarkowski, 1963, 1964 a ) and in the coat (Mintz, 1965 a , b , 1967). The cell composition of other organs and tissues has not as yet been investigated. True hermaphroditism in some of the animals obtained was also accepted as an indirect proof of chimerism (Tarkowski, 1961, 1963, 1964 b ; Mintz, 1965 b ) but the postulate of these individuals being six-chromosome chimeras has not as yet been directly confirmed by karyological research.

Cell adhesion and movement in relation to the developing limb pattern in normal and talpid3 mutant chick embryos

Abstract: Descriptive studies of the talpid 3 chick embryonic lethal mutant ( ta 3 / ta 3 ) have suggested that the multiple effects produced by this gene are of mesodermal origin, and that they arise from defective mesenchymal cell movement and condensation (Ede & Kelly, 1964 a , b ). It may be argued that condensation in vivo is comparable to cell reaggregation of dissociated cells in vitro , and that defects in the former are likely to be reflected in the latter. In this case it should be possible to obtain experimental verification of this effect of the gene at the cellular level, using the quantitative methods for assessing aggregation developed by Moscona (1961 a , b ) and Curtis & Greaves (1965). The experiments reported here show a clear genetic effect upon cell adhesion in the wing-bud mesenchyme of the talpid 3 mutant. The wing-bud was chosen because it was hoped to establish a connexion between the effect of the gene at the cellular level and its dramatic effect on limb morphogenesis.

A radioautographic study of the development of the somite in the chick embryo.

Abstract: Considerable difference of opinion exists about the origin of the various components of the somite. According to Williams (1910), Hamilton (1952) and Boyd (1960), the cells of the myotome originate in the dorso-medial angle of the somite wall and migrate beneath the dermatome in ventro-lateral direction. A group of older investigators (Remak, 1855; His, 1888; Bardeen, 1900) state, however, that the myotome cells originate not only in the dorso-medial angle but also along the total length of the dorsal somite wall, formed by the dermatome. Similarly, in birds whether the myotome extends in ventro-lateral direction by growth and migration of existing cells (Engert, 1900; Williams, 1910) or by differentiation of locally found mesoderm cells into myoblasts (Straus & Rawles, 1953) remains even at present a controversial issue.

Changes in the rate of cell divisions in the course of early development of diploid and haploid loach embryos

Abstract: The period of development preceding gastrulation can be divided into two stages. The first is characterized by rapid synchronous cell division. True interphase, which is characterized by the fusion of karyomers and the occurrence of a nucleolus, is absent at this stage. During the second stage the rate of cell division decreases and divisions are asynchronous. The process of cell division is antagonistic to genetic activity of nuclei, as nuclear synthesis of m-RNA appears to cease during mitosis. Consequently, one can suggest that the increase of the length of interphase is necessary for the onset of morphogenetic nuclear function, which ensures gastrulation and subsequent development (Neyfakh, 1959). The present investigation was designed first to determine exactly the time of the appearance of the changes in the rate of cell division and to compare it with the time of onset of morphogenetic nuclear function.

Mise en évidence du rôle inducteur de l'encéphale dans l'ostéogenèse du crâne embryonnaire du poulet

Abstract: Nos experiences d9excision des differents territoires encephaliques (Schowing, 1959, 1961, 1967) mettent en evidence l9importance du role des structures nerveuses dans la differentiation du squelette cranien. Le mecanisme de cette action inductrice, ainsi que la nature de l9inducteur, est mal connu. Nous avons tente de confirmer le role inducteur de l9encephale par des experiences in vitro . Strudel (1959, 1962) a obtenu du cartilage a partir de somites d9embryons de poulet cultives sur le milieu standard de Wolff & Haffen (1952) contenant un extrait de tube nerveux, tandis que Benoit (1960), greffant un fragment de tube nerveux a la place de la placode otique, a observe l9apparition d9un cartilage surnumeraire dans le mesenchyme de l9oreille. Il semble done qu9il existe un facteur inducteur de la chondrogenese dans le tube nerveux. De meme, existe-t-il un facteur de l9osteogenese dans l9encephale embryonnaire? Ce facteur inducteur est-il specifique, comme son homologue chondrogene?

La colonisation des ébauches gonadiques par les cellules germinales de l'embryon de Poulet, en culture in vitro

Abstract: Chez les Vertebres, la segregation de la lignee germinate s9effectue des les stades les plus precoces du developpement. Les cellules germinales primordiales (CGP) apparaissent toujours hors des gonades et se trouvent souvent localisees dans des territoires bien delimites, plus ou moins eloignes des ebauches gonadiques presomptives. La destinee des gonocytes etant liee de facon irreductible a leur installation dans les ebauches genitales, ces cellules entreprennent, a chaque generation, une migration qui les conduit infailliblement aux epitheliums germinatifs. Les nombreux travaux consacres a ce sujet ont permis de distinguer deux modes de migration: — la migration interstitielle qui intervient lorsque les CGP sont situees posterieurement, a proximite des ebauches gonadiques; — la migration vasculaire qui entre en jeu des que les CGP se trouvent eloignees des epitheliums germinatifs. La migration interstitielle s9effectue par des deplacements actifs des CGP qui progressent grâce a leurs mouvements amœboides.

Relationship of epithelial growth to mitotic rate in mouse embryonic lung developing in vitro

Abstract: In an earlier paper (Alescio, 1965) we studied the in vitro growth rate of the epithelial tree of mouse embryonic lung, using as a criterion for growth the increase of the epithelial surface, due to budding activity, as measured on the living cultures. We showed that X-irradiation brings about a dose-dependent growth inhibition (Alescio, 1966). Two experimental situations able to increase the growth rate (budding activity) of the epithelial tree in a highly reproducible way were identified: (1) reduction of the total mass of the rudiment, and (2) increase of the amount of mesenchyme relative to epithelium (Colombo Piperno, 1966; Alescio & Colombo Piperno, 1967). The results led us to conclude that under the reported conditions of growth in vitro : (1) the pulmonary rudiments are able to undergo some kind of ‘compensatory growth’ when their total mass is reduced; (2) the quantity of bronchial mesenchyme controls the epithelial growth (expressed as total amount of branching), so that when more mesenchyme is present an increased rate of epithelial growth follows.

The effect of removing the polar lobe in centrifuged eggs of Dentalium

Abstract: Classical evidence for the existence of morphogenetic substances was provided by experiments with spiralian eggs possessing a polar lobe: Ilyanassa (Crampton, 1896; Clement, 1952, 1956, 1962); Dentalium (Wilson, 1904); Chaetopterus (Tyler, 1930); Sabellaria (Hatt, 1932; Novikoff, 1938); and Mytilus (Rattenbury & Berg, 1954). Eggs from which the polar lobe had been removed developed into embryos with specific abnormalities. In Dentalium, after removal of the polar lobe at the trefoil stage, a trochophore larva is formed without post-trochal region and apical tuft. Removal of the polar lobe at second cleavage causes a larva without post-trochal region, but with an apical tuft. Wilson concluded that specific cytoplasmic materials essential to the formation of the apical tuft are contained in the first but no longer in the second polar lobe. Centrifuging the uncleaved egg just before first cleavage will disturb the normal distribution of substances. The morphogenetic substance for the apical tuft may be also displaced, so that at the formation of the first polar lobe this substance is not only present in the lobe, but also in the blastomeres. The object of the present investigation was to study the effect of removing the first polar lobe in eggs centrifuged immediately before the beginning of first cleavage. MATERIAL AND METHODS All experiments were carried out at the Caribbean Marine Biological Institute at Curacao (Neth. Ant.) with the local species Dentalium antillarum, which is abundant in inner Piscadera Bay. The animals could be obtained easily by collecting the superficial bottom material at a depth of 3-4 m. The material was sieved on the spot and the animals were picked out in the laboratory. They could be kept alive for weeks in small glass aquaria with a bottom of sand and in running sea-water. Mature animals are j- 1 in. in length with a translucent shell, through which the gonads can be observed under a dissecting microscope. In the ovary the 1 Author's address: Zoological Laboratory, Janskerkhof 3, Utrecht, The Netherlands.

The role of acid phosphatase in the fusion of the secondary palate.

Abstract: Complete closure of the secondary palate must progress through two consecutive events: the converging movement of the palatal shelves and their subsequent fusion at the line of contact. Each step is indispensable in normal palatal development since, theoretically, a palatal cleft might be the consequence of a failure of either. Until recently, the mechanisms of shelf movement received most attention (Peter, 1924; Lazarro, 1940; Walker & Fraser, 1956; Larsson, 1960). However, recent investigations have focused on the subsequent step, properly referred to as fusion. These studies, based on organ culture methods (Pourtois, 1966) and electron microscopy (Mato, Aikawa & Katahira, 1966; Farbman, 1967; Smiley & Dixon, 1967), have emphasized the complexity of the fusion process. This process may be viewed as a sequence of four interdependent events: (1) differentiation of the cell layers at the edge of the shelves resulting in the formation of a ‘zone of stickiness’ (Pourtois, 1968); (2) fusion of these differentiated epithelial cells leading to the formation of a laminated wall of epithelium between the shelves; (3) rupture of that partition permitting contact between the elements of the mesenchyme from either side; and (4) finally, degeneration of the epithelial remains of the seam marking the completion of the fusion process.

Analysis of the development of the nervous system of the zebrafish, Brachydanio rerio: I. The normal morphology and development of the spinal cord and ganglia of the zebrafish

Abstract: In teleost fishes, unlike many other vertebrates, the spinal cord originates as a solid structure, the neural keel, which subsequently hollows out. Unlike vertebrates in which the neural tube is formed from neural folds, and where the neural crest arises from wedge-shaped masses of tissue connecting the neural tube to the general ectoderm, teleosts do not possess a clear morphological neural crest. Initially, the dorsal surface of the keel is broadly attached to the ectoderm as described by Shepard (1961). As the neural primordia become larger and more discrete, the region of attachment narrows, and cells become loose (the ‘loose crest stage’). These cells represent the neural crest. Subsequently they begin to migrate and to differentiate into the various derivatives of neural crest. Both sensory and sympathetic neurons arise from neural crest. At the time of their migration the cells are not morphologically distinguishable.

Albumen absorption during chick embryogenesis.

Abstract: In birds albumen represents a substantial part of the reserve material for their embryological development (Romanoff & Romanoff, 1949). In Gallus gallus albumen proteins form 50 % of non-incubated egg protein content (Romanoff & Romanoff, 1949). During incubation such material is absorbed and utilized, to a great extent, for the synthesis of embryonal proteins (Fiske & Boyden, 1926; Rupe & Farmer, 1955). It is not yet well understood how these processes (albumen absorption and utilization for the energetic and nutritional needs of the embryo) take place. The present available data indicate that the amount of albumen solids begins to diminish starting from 11 to 12 days of incubation (Romanoff & Romanoff, 1933; Rupe & Farmer, 1955). From 13 to 14 days, after the seroamniotic connexion perforates, the protein content of the amniotic fluid shows a marked increase because of the passage of albumen (Needham, 1931; Romanoff, 1960).

Influence inductrice de l'encéphale embryonnaire sur le développement du crâne chez le poulet: II. Influence de l'excision de la chorde et des territoires encéphaliques moyen et postérieur sur le développement cranien

Abstract: L9iraportance des resultats que nous avons obtenus par l9excision des territoires encephaliques embryonnaires anterieurs (Schowing, 1968) nous permet d9evaluer le role preponderant qu9ils jouent dans l9organogenese de la tete. Les roles respectifs du mesencephale et du rhombencephale dans les courbures de la tete sont connus depuis les travaux de Waddington (1937). Le territoire mesencephalique est le plus petit de tous les territoires de l9encephale embryonnaire âge de moins de 40 h. A partir de ce stade, il croit brusquement et augmente plus de volume que les autres parties encephaliques. Dans le meme temps, le rhombencephale croit en longueur, et principalement du cote dorsal. Cela determine l9apparition de la flexion aigue, qui semble en correlation aveo l9evolution du mesencephale d9une part, et la croissance de la partie dorsale du rhombencephale d9autre part (Huber, 1957). Independamment de ce role purement mecanique, le mesencephale et le rhombencephale ont-ils une influence sur la differentiation du squelette cranien?

A time-lapse photographic study of chick embryos exposed to teratogenic doses of hypoxia

Abstract: Continuous, long-term observations of amniote embryos have always been difficult. Special culture techniques for young avian and mammalian embryos have been developed (New, 1967) and these have helped to visualize the early stages of development. But studies of normal and abnormal development during the major period of organogenesis have been made largely by tedious indirect methods, such as the examination of a series of embryos preserved at different time intervals. Transitory responses to toxic stimuli have been particularly difficult to detect in this manner. To observe the visible initial effects of teratogenic agents, a photographic time-lapse study of chick embryos in their natural, in ovo , state was initiated. This report compares the changes in normal and hypoxia-treated embryos during the third day of development. Of the many agents which produce abnormal development, oxygen deficiency is one of the better known, since (1) it is readily induced in the laboratory by a variety of means, and (2) it is generally considered to be a significantcause of spontaneously occurring anomalies (Rubsaamen, 1952; Ingalls, 1952).

Cytonucleoproteins in cleaving eggs of Xenopus Iœvis

Abstract: The cytoplasm of unfertilized eggs of Xenopus lœvis induces DNA synthesis in a high proportion of adult and embryonic nuclei introduced into it (Graham, Arms & Gurdon, 1966). This induction of DNA synthesis is not due merely to the fact that the egg cytoplasm supplies precursors of DNA synthesis which might be absent from the nuclei, since adult liver nuclei, at least, of those nuclei which are induced to synthesize DNA after their injection into eggs, do not do so if incubated in vitro with DNA precursors (Arms, 1968). One of the waysin which the cytoplasm of unfertilized eggs might induce DNA synthesis is by supplying other molecules, such as various enzymes, to the introduced nuclei. There are an increasing number of reports describing the transfer of proteins from cytoplasm to nucleus (Zetterberg, 1966) or from one nucleus to another in a binucleate cell (Byers, Platt & Goldstein, 1963; Goldstein, 1964).

The inductors of differentiation of prefollicular tissue and the follicular epithelium in ovarioles of Pyrrhocoris apterus (Heteroptera)

Abstract: Differentiation of the tissues of the telotrophic ovarioles from the embryonic primordium occurs gradually throughout larval development of bugs. All tissues are established already at the beginning of the last larval stage as observed by Wick & Bonhag (1955) in Oncopeltus fasciatus . During the last instar, when the corpora allata are morphogenetically inactive, the synthetic activity of the cells of first ovarian nutritive system, the trophocytes, takes place. The nutrients released by trophocytes at the final emergence activate the oocytes, starting previtellogenesis (Masner, 1966). The function of this nutritive system is known to be independent of any humoral control (Wigglesworth, 1936, and others). Food intake seems to be the only inductor of trophocyte growth. The developing oocyte grows into the prefollicular syncytium. The surrounding tissue starts to organize into a unilayered epithelium. The renewal of corpus allatum activity and the release of the juvenile hormone (JH) is necessary for further vitellogenesis.

An electron-microscope study of centrioles in differentiating motor neuroblasts

Abstract: Mature neurons with centrioles were first described at the end of the nineteenth century and have been observed in many animals (see Cajal, 1911; Ariens Kappers, Huber & Crosby, 1936). As mitosis rarely, if ever, occurs after morphological differentiation of the neuroblast begins, the function of the centrioles in nerve cells posed a problem which has yet to be resolved. Held (1909) described centrosomes in differentiating neuroblasts as being associated with the ‘fibrillogenous zone’, which suggests a role for the centriole in the differentiation of neurofibrils. Recently, electron-microscopic observations have refocused attention on the possibility of morphological and functional association between the centrioles of nerve cells and the fibrillar elements, especially neurotubules, which appear to be similar in fine structure to microtubules of other types of cells and to spindle tubules of the mitotic apparatus.

Teratological studies with sulphonamides and their implications.

Abstract: It is one of the principal aims of teratological research to trace the manner in which particular chemical compounds give rise to abnormal phenotypes by interfering with well-defined metabolic events. Problems that seemed to lend themselves to investigations of this nature arose with the discovery that malformations can be produced by sulphonamides, which in clinical practice are or have been used as inhibitors of carbonic anhydrase and the activity of which was considered to be quite specific in that respect. We had earlier reported on the effects which one such compound has on developing chicken embryos and shall now describe results obtained with three further sulphonamides. We shall then attempt to discuss the meaning of these and related data in terms of general teratological problems. Lay ton & Hallesy (1965) were the first to observe that acetazolamide (2-acetylamino-l,3,4-thiadiazole-5-sulphonamide), when given orally to pregnant rats or mice, was responsible, among the newborn young, for a certain incidence of peculiar and interesting abnormalities of the forelimbs.

Ultrastructure et cytochimie ultrastructurale de la vésicule germinative et du cytoplasme périnucléaire de l'oocyte mûr de Xenopus laevis

Abstract: Les oocytes et les œufs de Batraciens constituent, depuis longtemps, un material de choix pour les embryologistes. Au cours de ces dernieres annees, les phenomenes initiaux du developpement embryonnaire ont ete etudies avec toute la precision que permettent les techniques biochimiques et cytochimiques actuelles. En particulier, l9etude de la maturation des oocytes de Batraciens a ete reprise par plusieurs auteurs depuis que ce phenomene peut etre obtenu in vitro (Dettlaff, Nikitina & Stroeva, 1964; Dettlaff, 1966; Brachet, 1965 a , b , 1967; Smith, Ecker & Subtelny, 1966). Brachet a mis en evidence l9apparition, au cours de la maturation, de grains Feulgen-positifs distincts des chromosomes, dans le sue nucleaire de Rana , de Xenopus et de Bufo ainsi que dans le cytoplasme perinucleaire des oocytes de Bufo . Ces grains se rassemblent dans le cytoplasme cortical, puis ils disparaissent (Brachet, 1965 a ).

A cytological study of Mauthner's cells in Xenopus laevis and Rana temporaria during metamorphosis

Abstract: This paper discusses cytological changes which occur during anuran metamorphosis in a pair of large hind-brain neurones, the Mauthner cells or M-cells which, in many teleosts and amphibians, innervate the tail musculature via ventral horn cells. The M-cells of fishes, urodeles and anuran larvae are unusually large neurones of particular interest, and according to Stefanelli (1951) they constitute a ‘true functional system of nervous activity’. The value of a cytological study is enhanced by the fact that amphibian M-cells have not yet been extensively analysed biochemically (Deuchar, 1966). In teleosts, the abundant synapses, apparently of a special kind, that terminate on M-cells have been studied by Bodian (1937), Furshpan & Furukawa (1962), Furukawa & Furshpan (1963), Furshpan (1964), Furukawa (1966), Robertson (1963), and Robertson, Bodenheimer & Stage (1963) and have been discussed by Eccles (1964).

Analysis of the development of the nervous system of the zebrafish, Brachydanio rerio II. The effect of nerve growth factor and its antiserum on the nervous system of the zebrafish

Abstract: Bueker (1948), investigating the effects of implanted tumors on the development of the nervous system of the chick embryo, found that sarcoma 180 caused enlargement (hypertrophy and hyperplasia) of the spinal ganglia in the segments adjacent to it. The motor columns, however, were not enlarged. He suggested that the sarcoma provided a selective periphery with mechanical and histochemical properties which favored sensory innervation. Subsequently other mouse sarcomas were found to have similar effects. Levi-Montalcini & Hamburger (1951) found that the sarcoma stimulated growth of the sympathetic ganglia to a greater extent than the spinal ganglia. Similar results were obtained when the tumor was grafted on to the chorioallantoic membrane, where the tumor and embryo share circulation but establish no direct contact, so it was hypothesized that a humoral factor from the tumor was responsible for the enlargement of the ganglia (Levi-Montalcini & Hamburger, 1953).

Tératologie expérimentale chez un Opilion (Arachnide)

Abstract: Dans le grand ensemble des Arthropodes de nombreux morphologistes ont signale, decrit et figure un nombre eleve de cas teratologiques. Ces descriptions sont le plus souvent relatives a des cas isoles dont l'etude serait rendue longue et difficile si Balazuc n'avait groupe en des revues critiques les malformations decrites chez les Coleopteres (1948), les Hemipteres (1951), les Orthopteroides (1955), les Hymenopteroides (1958) et les Myriapodes (Balazuc & Schubart, 1962). II reste, cependant, beaucoup a faire dans cette branche descriptive de la teratologie, et en particulier chez les Opilions ou quelques animaux monstmeux seulement ont ete decrits, ainsi que je leai signale (Juberthie, 1963 a , b ). L'etude des stades successifs du developpement des malformations ou teratogenie, branche de la teratologie fondee par Dareste (1891), accuse un retard certain chez les Arthropodes par rapport aux Vertebres; elle est, en effet, inexistante chez les Myriapodes, et la plupart des groupes d'Insectes.

Influence inductrice de l'encéphale embryonnaire sur le développement du crâne chez le Poulet I. Influence de l'excision des territoires nerveux antérieurs sur le développement cranien

Abstract: Nous nous proposons d9etudier les correlations pouvant exister entre l9encephale et la boite cranienne chez l9embryon de Poulet. Il s9agit de rechercher le pouvoir inducteur des differents territoires nerveux de la tete embryonnaire sur la differentiation et le developpement du crâne. Strudel a etudie le developpement correlatif du tube nerveux et de la colonne vertebrate chez le Poulet (1953 a , b , 1955). Il a demontre que l9absence de tube medullaire entraine la disparition de l9are neural des vertebres tandis qu9une partie du corps vertebral se developpe autour de la chorde dorsale. Le tube nerveux peut done etre considere comme l9inducteur de la region dorsale des vertebres. De mime, l9excision de la chorde seule entraine la disparition des corps vertebraux, tandis que les neurarcuaux se developpent normalement. La chorde apparait done comme l9inductrice des corps vertebraux.

Auto- und allotypische Differenzierungen aus Blastemen der Halterenscheibe von Drosophila melanogaster nach Kultur in vivo

Abstract: Von unserer Arbeitsgruppe wurden verschiedene Imaginalscheiben von Drosophila im Abdomen weiblicher Fliegen kultiviert (siehe Arbeiten von Hadorn und Mitarbeitern). Die Hamolymphe des Adultwirtes dient als Kulturmedium, in welchem die Blasteme proliferieren, wobei sie jedoch ihren larvalen Differenzierungszustand beibehalten. Die Adultdifferenzierung kann durch Rucktransplantation der Blasteme in eine Wirtslarve, mit der das Implantat die Metamorphose durchlauft, vollendet werden. Die imaginalen Strukturen des Integumentes konnen anschliesend aus dem Abdomen des metamorphosierten Wirtes herausprapariert und untersucht werden. Die Imaginalscheiben der verpuppungsreifen Larve, die als Ausgangsmaterial fur unsere Kulturen dienen, stellen Mosaike von Organanlagen dar, in denen die Zellen mindestens arealspezifisch determiniert sind. Wahrend der Proliferation im Adultwirt entstehen Mehrfachbildungen der kultivierten Primordien. Es werden aber nicht nur zusatzliche Organe gebildet, die der prospektiven Bedeutung der betreffenden Scheibe entsprechen ( autotypische Differenzierungen ), sondern auch Organe, die normalerweise aus anderen Imaginalscheiben hervorgehen und deshalb als allotypisch bezeichnet werden (Hadorn, 1965 a ).

Natural and synthetic materials with insect hormone activity. IV. Specific female sterility effects produced by a juvenile hormone analogue.

Abstract: The juvenile hormone of insects is known to inhibit the process of insect metamorphosis. It is also known to stimulate ovarian growth in adult females of some species. It has been found recently that some substances with juvenile hormone activity also influence embryonic development. In the bug Pyrrhocoris apterus such substances, which prevent imaginal differentiation in metamorphosis, also affect the differentiation process of embryos at a certain stage of egg development (Slama & Williams, 1966). This has been confirmed with other juvenile hormone analogues on embryonic development of silkworm eggs (Riddiford & Williams, 1967) and grasshoppers (Novak, 1967). According to the above observations eggs treated with the substances show abnormal development of the embryos, which may pass successfully through the early stages of embryogenesis but are unable to complete differentiation. Usually the embryos do not develop beyond the stage of blastokinesis and die within the egg shells.

Studies on the DNA of Xenopus laevis oocytes.

Abstract: The existence of substantial amounts of deoxyribonucleic acid (DNA) in the cytoplasm of amphibian eggs is no longer a matter of discussion (review, Brachet, 1957). However, their intracellular distribution, role and origin remain controversial. According to Dawid (1965, 1966), the bulk of the egg cytoplasmic DNA in Xenopus is of mitochondrial origin. His method of phenol extraction isolates only high molecular weight DNA. On the other hand, Baltus & Brachet (1962) found that 65% of the DNA of Pleurodeles eggs sediments at low centrifugal speed and suggested that this nucleic acid is localized in the yolk platelets. This conclusion was based on chemical estimations of the total DNA present in the egg; they found values about 10 times higher than those presented by Dawid (1966). Brachet & Ficq (1965) confirmed that, in ovaries of Pleurodeles labelled with 14 C-actinomycin, either in vivo or on histological sections, most of the radioactivity detected by autoradiography is concentrated in the yolk.