bluuebunny/crossref_metadata_2025 huggingface dataset:
A complex syndrome of left-right axis, central nervous system and axial skeleton defects inZic3mutant mice
Authors: Purandare Smita M. , Ware Stephanie M. , Kwan Kin Ming , Gebbia Marinella , Bassi Maria Teresa , Deng Jian Min , Vogel Hannes , Behringer Richard R. , Belmont John W. , Casey Brett
Published: April 2021

X-linked heterotaxy (HTX1) is a rare developmental disorder characterized by disturbances in embryonic laterality and other midline developmental field defects. HTX1 results from mutations in ZIC3, a member of the GLI transcription factor superfamily. A targeted deletion of the murine Zic3 locus has been created to investigate its function and interactions with other molecular components of the left-right axis pathway. Embryonic lethality is seen in approximately 50% of null mice with an additional 30% lethality in the perinatal period. Null embryos have defects in turning, cardiac development and neural tube closure. Malformations in live born null mice include complex congenital heart defects, pulmonary reversal or isomerism, CNS defects and vertebral/rib anomalies. Investigation of nodal expression in Zic3-deficient mice indicates that, although nodal is initially expressed symmetrically in the node, there is failure to maintain expression and to shift to asymmetric expression. Subsequent nodal and Pitx2 expression in the lateral plate mesoderm in these mice is randomized, indicating that Zic3 acts upstream of these genes in the determination of left-right asymmetry. The phenotype of these mice correctly models the defects found in human HTX1 and indicates an important role for Zic3 in both left-right and axial patterning.
Action of heart and liver RNA on the differentiation of segments of chick blastoderms
Authors: Butros Joseph
Published: April 2021

RNA was prepared from chick embryo hearts and livers respectively by a modified procedure of Kirby. Post-nodal fragments, obtained by transecting definite streak or heard process blastoderms at 0·2 mm. posterior to the primitive pit and trimmed to 1 × 1 mm.2, were cultured for 8 days on a basic medium containing TC 199, whole egg suspension, embryo extract, agar and penicillin. Half of the cultured pieces received one drop of either RNA twice daily; the other pieces were given a drop of the solvent. Heart RNA promoted twitching in localized areas. Differentiation of myoblasts and nerve fibres was enhanced. Liver RNA stimulated the folding of the entoderm layer and modification of the cells to columnar, goblet form. The results are discussed in the fight of current literature on transformation in cells of higher organisms.
A histochemical study of sex inversion produced by estradiol in chick embryos
Authors: Narbaitz Roberto , Teitelman Gladys
Published: April 2021

Forty-five White Leghorn chick embryos were injected on the 4th incubation day with 0·1 mg. estradiol benzoate. Some of them were dissected on the 9th day, their gonads being studied with the digitonine histochemical technique for cholesterol. The rest were dissected either on the 10 th or on the 13th day and used for Δ5-β-hydroxysteroid dehydrogenase histochemical determination. In both groups genetic sex was determined by a chromosome study made on liver cells. The gonads belonging to male embryos contained interstitial cells with cholesterol and enzymatic activity comparable in amount and distribution to those found in normal ovaries. The gonads of female embryos contained apparently normal enzymatic activity but gave negative results with the digitonine technique. Additional experiments were made in order to analyse this fact further. The differentiation, in male embryos, of estrogen-producing cells through the action of estrogens is inferred from our results, and this is explained by supposing that in these cells differentiation is normally inhibited in males by some kind of genetically controlled factor. The action of estradiol would consist in counteracting this inhibition.
Germ-cell transfer and sex ratio in Xenopus laevis
Authors: Blackler A. W.
Published: April 2021

Primordial germ cells have been grafted from one neurula to another in Xenopus laevis by means of the technique of Blackler & Fischberg (1961). A nuclear marker enabled tadpoles derived from graft material to be identified, after surviving animals had been raised to sexual maturity and bred.

The examination of sex ratio in groups of tadpoles has revealed that male gonocytes were sex-reversed in ovaries and vice versa, with eventual production of functional gametes. About half of all transfers made involved grafts between neurulae of unlike sex. It is evident that females of genetic constitution WW are viable in this toad, as well as sperm of constitution W.
The nature of the earliest spontaneous activity of the chick embryo
Authors: Alconero Barbara B.
Published: April 2021

Two types of grafts from 3-day chick embryos were grown on the chorioallantoic membrane of a 9-day-old chick embryo: six isolated somites, 14−20; and six somites 14−20, with adjacent spinal cord. The activity of these noninnervated and innervated grafts was observed during their growth on the membrane. No activity was observed at any time in the fifteen grafts of six somites grafted without spinal cord; but spontaneous twitching could be observed in twenty out of thirty-three grafts which contained sections of the spinal cord. Histological examination confirmed that the twenty active transplants each contained a segment of spinal cord, and large nerve fibers could be traced to the muscle tissue in the grafts. The failure of the other thirteen grafts to show contraction is accounted for either by the absence of well differentiated muscles or by the absence of nerves invading them. The muscle of the non-innervated, inactive pieces showed the same amount of differentiation as that of the innervated active grafts. The activity observed in the innervated muscle tissue shows three different patterns : regular, with a periodicity similar to that of the intact embryo ; irregular and isolated twitches, i.e. less than six twitches in the 10-min. observation period. It is concluded that the spontaneous motility of muscle developing on the chorioallantoic membrane is neurogenic and not myogenic. This finding supports the view that the spontaneous motility observed in vivo is neurogenic from its beginning.
An electrophoretic analysis of proteins of cellular sap in normal and hybrid frog embryos
Authors: Shore Richard E.
Published: April 2021

The degree of abnormality found in amphibian interspecies hybrids varies from one species pair to another, and may also differ between reciprocal matings (Moore, 1955). Although some general ideas exist about the mechanism of arrest and the course of abnormal development, our knowledge is far from complete. One major aspect of development which has received attention only at the gross level is the nature and diversity of those proteins which compose the greater part of the cytoplasmic sap, the ‘soluble’ proteins in the sense of this paper (see below). This paper reports the results of studies on the development of normal (Ranapipiens) and gastrula-arrested hybrid (R. pipiens ♀×R. sylvatica ♁) amphibian embryos.
Cell numbers during cleavage of the zebra fish egg
Authors: Marrable A. W.
Published: April 2021

This paper reports a study of the timing of early cleavage divisions in the zebra fish and of the changes that occur during cleavage in cell size and number.
The development of the spinal cord examined by autoradiography
Authors: Martin Alexander , Langman Jan
Published: April 2021

The wall of a recently closed neural tube is generally considered to consist of three concentric layers. Surrounding the lumen is found the ependymal zone characterized by large pale cells known as the germinal cells of His (1889). These cells are believed to give rise to the neuroblasts and some of the spongioblasts. Soon after formation the neuroblasts move away from the lumen to enter a densely packed nucleated zone referred to as the mantle layer. This layer consisting of spongioblasts and neuroblasts ultimately gives rise to the gray matter of the spinal cord. The outermost layer, known as the marginal layer, contains the fibres of the developing neuroblasts and later forms the white matter.
Action de la vitamine et de l’antivitamine B6 sur le développement de l’embryon de poulet
Authors: Conti par G. , Milio G.
Published: April 2021

Le groupe des vitamines B6 comporte trois substances distinctes: la pyridoxine, qui est un dérivé de la pyridine; la pyridoxamine et le pyridoxal qui dérivent de la pyridoxine. Tous les organismes utilisent le pyridoxal; certains utilisent également la pyridoxine, d’autres la pyridoxamine, d’autres enfin (le rat, par exemple), utilisent les trois substances. Cette constatation a fait penser que la substance réellement active serait le pyridoxal, et que seuls certains organismes pourraient former de la pyridoxine, de la pyridoxamine ou les deux substances. De plus, le pyridoxal, sous forme d’ester phosphorique (pyridoxalphosphate) déploie une action importante comme co-enzyme dans de nombreux complexes enzymatiques actifs dans le métabolisme des acides aminés; parmi ces complexes, il faut citer les transaminases, les aminoacide-décarboxylases, les déshydratases, les désulfhydrases, les racémases, l’histaminase et les tryptophanases.
Action de la vitamine et de l’antivitamine B6 sur le myocarde d’embryon de poulet cultivé in vitro
Authors: Conti par G. , Milio G.
Published: April 2021

Nous avons essayé les effets de la vitamine (PX) et de l’antivitamine B6 (DPX) sur des organes d’embryons de poulet cultivés in vitro; et cela dans le but de voir si l’action inhibitrice de la DPX se manifestait sur la croissance in vitro des organes et si cette action inhibitrice éventuelle pouvait être annulée, ou du moins partiellement empêchée, par l’adjonction simultanée de la vitamine B6 au milieu de culture.
The susceptibility of the offspring of alloxan-diabetic mice to a teratogen
Authors: Takano Kiichi , Tanimura Takashi , Nishimura Hideo
Published: April 2021

Maternal diabetes, or pre-diabetes, has been considered as a possible factor in the aetiology of human congenital malformations by several investigators (De Costa, 1955; Hoet et al., 1960; Hiekkala & Koskenoja, 1961; Nicholson & De Maria, 1963; Pederson et al., 1964; Lenz & Maier, 1964). However, a few authors have reported no increase in the incidence of anomalies among infants of diabetic women (Given et al., 1950; Hall & Tillman, 1951; Rubin & Murphy, 1958). Alloxan-induced maternal diabetes in animals has also been studied, and an increase of stillbirth and foetal macrosomia has usually been recognized (Davis et al., 1947; Lindan & Morgans, 1950; Bartelheimer & Kloos, 1952; Angervall, 1959; Solomon, 1959; Kim et al., 1960; Loveeia/., 1960; Koskenoja 1961). The incidence of malformations, however, was not increased in most cases, the exception being those reported by Ross & Spector (1952), Fujimoto et al. (1958) and Watanabe & Ingalls (1963).
Différenciation des épithéliums du tube digestif in vitro
Authors: Soriano par Luis
Published: April 2021

Nous avons démontré que l’épithelium de l’œsophage de l’embryon de Souris, prélevé à 12 jours de gestation et cultivé in vitro, montre une différenciation accélérée par rapport à celle observée dans le développement normal (Soriano et coll., 1964). Ces résultats ont été obtenus en utilisant une modification de la méthode de Trowell (1954).
The maturation of cortisone-treated embryonic duodenum in vitro. II. The striated border
Authors: Hayes Raymond L.
Published: April 2021

Regulation of the morphological and physiological maturation of embryonic duodenal mucosa by adrenocorticoid hormones has been demonstrated with a variety of techniques. Single injections of cortisone acetate (Moog & Richardson, 1955; Moog & Thomas, 1957); multiple daily administrations of cortisone (Moog & Ford, 1957; Moog, 1959); or in vitro maintenance of duodenal fragments with adrenal steroids (Moog & Nehari, 1954; Moog & Kirsch, 1955) all accelerate morphogenesis and the onset of alkaline phosphatase activity in this tissue.
Obtention expérimentale de Cyclopes parfaits par microchirurgie chez l’embryon de Poulet. Etude histologique
Authors: Schowing par Jean
Published: April 2021

La cyclopie parfaite peut être définie comme une anomalie de développement caractérisée par la présence d’un seul œil situé au milieu de la face, dans la position normalement occupée par le nez.
Experimental studies on the columella-capsular interrelationship in the turtle Chelydra serpentina
Authors: Toerien M. J.
Published: April 2021

The reciprocal effect of two neighbouring structures of different origins on each other during development is of considerable interest to the embryologist. Such a relationship exists between the columella auris and the auditory capsule in the vicinity of the fenestra ovalis. This particular relationship, in addition, embraces an aspect of fundamental importance to the morphologist viz. the possible derivation of part of the columella from the capsule.
Action of rat submaxillary gland extracts on neural tube growth in organ culture
Authors: Adler Ruben , Narbaitz Roberto
Published: April 2021

Organ cultures of portions of chick embryo neural tube together with surrounding tissues, were made in order to test the action of other tissues in nearby culture, and of organ extracts added to the medium. Expiants four somites long, dissected from embryos at Stages 11 to 13 (Hamburger & Hamilton), developed and differentiated normally in vitro. Pieces of limb bud from older embryos, added to the expiants, fused with them and differentiated as usual. The addition of the limb bud pieces did not influence the size of the cultured neural tube. The addition of submaxillary gland extract to the medium produced during the first 6 hours of culture a dorsal opening of the neural tubes and, thereafter, an exuberant and irregular growth of them. Other organ extracts, purified ‘nerve growth factor’ and iodine treated submaxillary gland extract failed to produce the same action. The presence in submaxillary extracts of an active factor independent of ‘nerve growth factor’ and protease activity is deduced from our results.
Effet de la fécondation sur 1’utrastructure du cytoplasme périphérique de l’œuf de Xenopus laevis
Authors: Van Gansen P.
Published: April 2021

Cet article fait suite à celui où nous avons décrit et discuté les modifications provoquées par la maturation dans l’ultrastructure de l’œuf ovarien (Van Gansen, 1966). Nous y avions indiqué dans quelles perspectives ce travail était entrepris (Brachet, 1964, 1965b).
pH-dependence of the inducing activity of lithium ion
Authors: Masui Yoshio
Published: April 2021

Using ectodermal explants isolated from early gastrulae of Triturus pyrrhogaster, the inductive effect of lithium ion was examined at different pH’s and under the influence of neuralizing substances. Treatment with 0·06 M-LiCl brought about the differentiation of axial mesoderm together with neuralization and the production of yolk-laden tissues which sometimes formed gut-like structures. The neuralization and mesodermalization were brought about with minimum frequency by treatment carried out near pH 5·0, but they increased when treatment was carried out at alkaline or acid pH. On the contrary, the production of yolk-laden tissue was brought about with maximum frequency by the treatment near pH 6·0 and decreased as the pH at which the treatment was done was raised or lowered. Treatment with alkaline NaCl solution carried out after the treatment with LiCl solution was found to be effective in enhancement of mesodermalization, but the same treatment carried out before the LiCl treatment had no effect on incidence of mesodermalization. Treatment with LiCl solution containing calcium or magnesium ion which alone have a weak neuralizing action brought about considerable increase of the mesodermalization near neutral pH. On the other hand, zinc and ammonium ions and urea, which act as strong neuralizing agents, had an inhibitory effect or mesodermalization by lithium ion. The results are discussed in relation to the significance of the influence of pH and neuralizing agents on the mesodermalizing effect of lithium ion, and it is suggested that these agents sensitize the mesodermal competence of the ectoderm to the inductive action of the ion, resulting in enhancement of the mesodermalization.
Starch gel electrophoresis of the multiple haemo-globins of small and large larval Chironomus— a developmental haemoglobin sequence in an invertebrate
Authors: Manwell Clyde
Published: April 2021

Small larvae (1-4 mg each) of Chironomus plumosus, whether surveyed in pooled samples or individually, have eight different haemoglobins in the haemolymph. Large larvae (8-11 mg each) of this species have ten different haemoglobins. Seven of the haemoglobins are unchanged throughout larval development. However, small larvae lack two of the major and one of the minor haemoglobins found in all large larvae; furthermore, a unique major haemo-globin of small larvae occurs only in traces in large larvae. The heterogeneity and the ontogenetic differences in Chironomus haemo-globin persist whether the haemoglobin is studied as oxyhaemoglobin, carbon-monoxyhaemoglobin, methaemoglobin or methaemoglobin cyanide, although the electrophoretic mobilities of some of the haemoglobin components are shifted by combination with different ligands and, especially, by oxidation to methaemoglobin. The heterogeneity and the ontogenetic differences are not altered by treatment of the haemoglobin with —SH and —S—S— reagents, nor by conversion of haemoglobin to globin by splitting off the haem with acid-acetone. Electrophoresis of globins prepared from each of the isolated major and minor Chironomus haemoglobins suggests that, in contrast to typical vertebrate haemoglobins, there is only a single polypeptide chain type in each of the multiple Chironomus haemoglobins. However, each of the multiple haemo-globins probably has a unique haemoglobin chain type, suggesting that each Chironomus haemoglobin component is coded from a different gene. Thus the insect Chironomus resembles the human in possessing an onto-genetic haemoglobin sequence involving both constant expression of some haemoglobin genes and modulation of the activity of others. As, in contrast to the human, Chironomus possesses giant chromosomes in many of its tissues, this discovery of an ontogenetic sequence to the major soluble protein present in larval Chironomus presents an attractive system for studying the interrelations between protein phenotype and the nuclear genotype during development.
Congenital eye defects in rats following maternal folic-acid deficiency during pregnancy
Authors: Armstrong R. Christy , Monie I. W.
Published: April 2021

Malformations of fetal rat eyes result from a variety of maternal vitamin deficiencies employed either transiently or continuously during pregnancy. Thus, eye defects have been produced in rat fetuses as a result of maternal deficiencies of vitamin A (Wilson, Jordan & Brent, 1953), pantothenic acid (Lefebvres-Boisselot, 1951; Nelson, Asling & Evans, 1957), niacin (Chamberlain & Nelson, 1963) and pteroylglutamic acid (PGA or folic acid) (Evans, Nelson & Asling, 1951; Nelson, Asling & Evans, 1952; Giroud & Boisselot, 1951; Giroud, Lefebvres & Dupuis, 1952; Giroud, Delmas, Lefebvres & Prost, 1954).

Previous studies on the teratogenic effects of PGA-deficiency on the developing rat eye, although informative, have been concerned mainly with stages after the 15th day of pregnancy (the day of finding sperm in the vagina is considered to be day zero). However, since the eye begins forming between the 9th and 10th days of gestation, it was felt that a study embracing both early and late stages of ocular development in rat embryos from mothers maintained on a PGA-deficient regimen for different lengths of time during gestation would be of more value in understanding the genesis of certain ocular abnormalities. The following account concerns such an investigation and describes the abnormalities en-countered in the visual system.
Etude de 1’origine, de la migration et de la multiplication des cellules germinales chez l’embryon de lapin
Authors: Chretien Par Fr. Ch.
Published: April 2021

La découverte par Waldeyer (1870) des cellules sexuelles ou ‘Ureier’ dans l’épithélium germinatif péritonéal d’embryons de poulet de 3 et 4 jours, ouvrit la voie à toute une série de travaux sur l’origine et la filiation des cellules germinales chez les Vertébrés.
Zellspezifische Determination und Beziehung zwischen Proliferation und Trans-determination in Bein-und Flügelprimordien von Drosophila melanogaster
Authors: Tobler Heinz
Published: April 2021

Cell specific determination and the relationship between proliferation and transdetermination in leg and wing primordio in Drosophila melanogaster
The differentiation of epidermis II. Alternative pathways of differentiation of embryonic chicken epidermis in organ culture
Authors: Dodson J. W.
Published: April 2021

Two series of experiments were made to determine the possible alteration of paths of differentiation of the epidermis from the metatarsal region of 12-day chicken embryos. The epidermis, separated from dermis after Versene treatment of the skin, either was cultivated in isolation for various periods, then recombined with dermis and cultivated further (series 1), or was placed on gels of collagen and grown in culture in the presence of excess of vitamin A (series 2). All explants were examined histologically. When epidermis isolated for 24 h was recombined with dermis, the upper cells degenerated as though still in isolation, but the basal cells, although they had become flattened while isolated, regenerated a viable, keratinizing epidermis; this ability was lost after 30–36 h of isolation. A basement membrane was re-formed against epidermis, following recombination, after isolation for 36–42 h. Thus the basal cells of isolated epidermis can survive for several hours in the absence of a basement membrane; the changes that they undergo are reversible for 24–30 h, but there is then a gradual loss of their potentialities. Epidermis grown on collagen gels on control medium formed a stratum corneum, but in the presence of excess of vitamin A no keratin appeared, the epithelium became thin, and mucous cells developed. The effect resembled that on epidermis of whole skin. The results demonstrate that the effect of the vitamin on the epidermis is direct and is not mediated by the dermis.
The effect of 3-acetylpyridine on the explanted chick embryo
Authors: Buckingham B. J. , Herrmann Heinz
Published: April 2021

A structural analogue of nicotinic acid, 3-acetylpyridine, has been shown to produce morphological and physiological abnormalities in a variety of organisms. The effect of 3-acetylpyridine (AP) on chick embryos has been studied by several investigators using the technique of yolk-sac injection (Ackermann & Taylor, 1948; Zwilling & DeBell, 1950; Landauer, 1957; Herrmann, Clark & Landauer, 1963). Following AP treatment at 96 h of incubation, a reduction in body size, underdevelopment of leg musculature and edema were noted. Teratogenic effects of AP when administered after 24 h of incubation were much more diffuse and included instances of cerebral hernia and muscular hypoplasia (Landauer, 1957). Simultaneous injection of nicotinamide (Ackermann & Taylor, 1948; Landauer, 1957) decreased the incidence and severity of these conditions.
Studies on an embryonic lethal hybrid inDrosophila
Authors: Kinsey Janice D.
Published: April 2021

The problems of nucleocytoplasmic interactions are of central importance in development and genetics. Studies of such interactions may help elucidate the mechanisms of differentiation of cells receiving the same genetic complement. One approach to a study of nucleocytoplasmic interactions is by examination of the development of interspecific hybrids, particularly those in which either syngamy fails to occur, or an abnormal development is produced.
The effect of 2,4-dinitrophenol on the development of early chick embryos
Authors: Bowman Patricia
Published: April 2021

The effect of 2,4-dinitrophenol, an uncoupler of oxidative phosphorylation, has been studied on the chick embryo developing in vitro. 2,4-dinitrophenol in concentrations ranging between 10−4 M and 2 x 10−3 M causes a syndrome of abnormalities, the main features of which are degeneration and sometimes complete absence of neural tissue accompanied by reduction in number of and inhibition of the somites. Heart, notochord and blood islands are unaffected. A comparison is drawn between the effects of 2,4-dinitrophenol and other substances which affect the development of neural tissue and somites in explanted chick embryos.
The control of cell number in the lumbar spinal ganglia during the development ofXenopus laevistadpoles
Authors: Prestige M. C.
Published: April 2021

It is the purpose of this paper to describe the development of the lumbar dorsal root ganglia after amputation of the leg. This operation can be performed at a very early stage before any connexions between the limb and the central nervous system are established. Alternatively, it can be performed at a number of later stages after the limb has been innervated. The extent of interaction can then be investigated for each stage by observing the subsequent development of the ganglia and comparing it with that of normal animals.
Cinemicrographic observations on the trophoblast and zona pellucida of the mouse blastocyst
Authors: Cole R. J.
Published: April 2021

The behaviour of mouse blastocysts during penetration and shedding of the zona pellucida was studied in vitro by time lapse cinemicrography. Blastocysts obtained by super-ovulation were filmed in Waymouth’s medium MB 725/1 in a specially designed disposable plastic chamber with a gas space buffered to maintain 5 % CO 2 in air. Mouse blastocysts undergo cycles of rapid contraction (4–5 min) followed by slower re-expansion (2–3 h), both before and after penetration of the zona. The zona also exhibits slight elasticity unless excessively stretched. The initial penetration of the zona was followed in detail and appears to be the result of specific cellular activity, not non-specific herniation due to increasing blastocoelic pressure. Rotation of the blastocyst was also observed.
Cell proliferation and morphological patterns in the hydroidsTubulariaandHydractinia
Authors: Campbell Richard D.
Published: April 2021

Mitotic figure distributions in the hydroids Tubularia and Hydractinia are related to both the axial and radial morphological organizations of the polyps. Cells divide in all regions of the body except at some extremities, but the abundance of dividing cells varies along the polyp axis. For example, in Hydractinia gonozooids mitotic figures are concentrated in the constricted part of the column, and in the Tubularia hydranth they are most abundant just above the whorl of gonophores. The polyps of both species of hydroids have a similar radial organization. In the distal hydranth portions this is manifested both in the positions of tentacles and in the positions of longitudinal gastrodermal ridges called taeniolae. Taeniolae generally are spaced between tentacles. In Tubularia and in Hydractinia gastrozooids, mitotic digestive cells are radially localized between taeniolae, that is, along the tentacular radii. The taeniolate organization appears to be a fundamental one in view of its wide phyletic distribution and its relation to other morphological and mitotic patterns. The similarity in mitotic patterns among different polyps is consistent with wide homologies existing between the structures of diverse hydroid types.
Recherches sur l’inhibition de la régénération du pharynx chez les planaires
Authors: Ziller-Sengel Par Catherine
Published: April 2021

Des expériences effectuées dans un travail antérieur (Ziller-Sengel, 1967) ont montré qu’il existe dans la région pharyngienne des planaires un facteur autoinhibiteur, capable d’empêcher la formation d’un pharynx si un pharynx est déjà présent. Cette inhibition est due à l’activité d’une substance spécifique diffusible, localisée dans la région pharyngienne. La substance inhibitrice de la formation du pharynx n’est décelée ni dans des extraits de têtes, ni dans des extraits de queues, ni dans des extraits de pharynx. C’est cette substance qui, au cours de la régénération normale du pharynx, empêcherait la formation simultanée de plusieurs pharynx (Wolff, 1962; Wolff, Lender & Ziller-Sengel, 1964; Ziller-Sengel, 1965).
A cell proliferation study of the neural retina in the two-day rat
Authors: Denham S.
Published: April 2021

The development of high resolution autoradiography and the availability of labelled DNA precursors has made possible the detailed analysis of cell proliferation. Such studies are valuable in the investigation both of normal growth and also of the effects of radiation and carcinogens.
Observations on congenital teratology in turkey embryos and its experimental transmission via transplantation
Authors: Tahara Yutaka , Kosin I. L.
Published: April 2021

The embryonic period of the domestic turkey is characterized by a relatively high level of mortality (Kosin & Mun, 1960, 1965). The aim of the investigation reported below was to analyse the significance of certain changes observed in turkey embryos doomed to die because of either congenital or experimentally induced defects.
Tératologie expérimentale chez un Opilion (Arachnide)
Authors: Juberthie Par Christian
Published: April 2021

Dans le grand ensemble des Arthropodes de nombreux morphologistes ont signalé, décrit et figuré un nombre élevé de cas tératologiques. Ces descriptions sont le plus souvent relatives à des cas isolés dont l’étude serait rendue longue et difficile si Balazuc n’avait groupé en des revues critiques les malformations décrites chez les Coléoptères (1948), les Hémiptères (1951), les Orthoptéroïdes (1955), les Hyménoptéroïdes (1958) et les Myriapodes (Balazuc & Schubart, 1962). Il reste, cependant, beaucoup à faire dans cette branche descriptive de la tératologie, et en particulier chez les Opilions où quelques animaux monstrueux seulement ont été décrits, ainsi que je l’ai signalé (Juberthie, 1963a, b).
A radioautographic study of the development of the somite in the chick embryo
Authors: Langman Jan , Nelson George R.
Published: April 2021

Chick embryos ranging in age from 24 to 72 h were treated with 3H-thymidine to examine proliferation, formation and differentiation of the various somite components. The embryos were fixed 1 – 10 h after treatment, sectioned at 4 μ and processed for radioautography. The following observations were made:

Before the formation of the paraxial mesoderm, the DNA-synthesizing mesoderm cells are randomly distributed throughout the tissue. When the paraxial mesoderm cells become arranged in epithelial fashion, DNA synthesis occurs predominantly in the nuclei at the periphery of the epithelium, while the unlabeled nuclei and the mitotic figures are adjacent to the central space. Since 3 h after labeling the mitotic figures are labeled and 5 h later the labeled nuclei are again at the periphery, it is concluded that the nuclei in the walls of the somite undergo interkinetic migration. The cells formed by the ventral and major portion of the medial somite walls are deposited in the central cavity of the somite, where they lose their epithelial shape and become mesenchyme-like. They rarely synthesize DNA. With further increase in the number of the cells in the center of the somite, the ventral and medial walls lose their epithelial continuity and blend with the centrally located cells. Together they form a loosely woven tissue, referred to as the sclerotome. After formation of the sclerotome, the dorsal somite wall, now referred to as the dermatome, is the main source of a layer of cells with pale nuclei and darkly stained nucleoli. This layer, which is directly in contact with the inner surface of the dermatome, is referred to as the myotome. DNA synthesis is never observed in the cells of this layer. After the myotome has extended in a ventro-lateral direction to the coelomic cavity, the dermatome, with the exception of its most dorsal portion, loses its epithelial structure and the cells begin to form the dermis.
The antigenic structure of tumour cells as material for a study of tissue differentiation
Authors: Olenov J. M. , Fel V. JA.
Published: April 2021

In the course of differentiation, in the overwhelming majority of cases, the cell genotype remains unchanged. However, tissue differences are inherited during cell reproduction (histiotypic growth). This means that the effects of determining influences are as a rule totally or almost totally irreversible, and hence only de-differentiation and not de-determination can take place. There is no return to a state from which different ways of development may be chosen.
Fine structure of egg envelopes and the activation changes of cortical alveoli in the river lamprey, Lampetra fluviatilis
Authors: Afzelius Björn A. , Nicander Lennart , Sjödén Inger
Published: April 2021

Most eggs are surrounded by several prominent envelopes which have been given names depending on their origin, structure or chemical composition. As our present knowledge of these envelopes is very fragmentary, the results of attempts to homologize the different layers between different animal groups are still open to debate. The nomenclature in this field is quite confusing.
The relative rates of synthesis of DNA, sRNA and rRNA in the endodermal region and other parts of Xenopus laevis embryos
Authors: Woodland H. R. , Gurdon J. B.
Published: April 2021

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 syn-thesis 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. Any differences between parts of early embryos in respect of nucleic acid synthesis are of further interest, since they are likely to be related to unequally distributed components of the egg cytoplasm. Such a relationship may eventually lead to the identification of cytoplasmic components which regulate the activity of genes during cell differentiation.
Nouvelles recherches expérimentales sur les origines de la lignée reproductrice chez la Grenouille rousse
Authors: Bounoure Louis , Aubry Régine , Huck Marie-Louise
Published: April 2021

Aussi simple, aussi facile à réaliser qu’il soit, aussi clairement qu’il semble parler dans un sens univoque, il n’est point de fait expérimental qui ne prête à controverse au nom de certaines vues théoriques discordantes, ou qui n’appelle des recherches complémentaires, soit quant aux moyens d’en mieux assurer le résultat, soit quant aux conséquences et aux enseignements qui peuvent sortir de sa réalisation imparfaite.
Présentation d’un appareil destiné à faire à de jeunes embryons d’oiseaux de petites injections localisées de substances chimiques
Authors: Ancel P. , Houget J.
Published: April 2021

Les injections de substances chimiques au cours des premiers jours de l’incubation en vue d’obtenir des malformations d’embryons d’oiseaux ont été faites suivant les auteurs dans le blanc, le jaune ou la chambre à air de l’œuf, tandis que d’autres déposaient sur l’embryon une goutte de la solution à étudier. Dans le but de faciliter l’étude de certains problèmes de tératogénèse, nous avons mis au point une autre technique permettant de réaliser des injections localisées à des ébauches embryonnaires déterminées et fait construire un appareil dont nous allons donner la description et le mode de fonctionnement.
The development of teratomas from intratesticular grafts of tubal mouse eggs
Authors: Stevens Leroy C.
Published: April 2021

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 tropho-blast 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 moruiae and blastocysts to the testis, and the morulae never gave rise to embryonic shield derivatives.
Etude expérimentale de la morphogenèse de la cage thoracique chez Fembryon de Poulet: mécanismes et origine du matériel
Authors: Pinot Madeleine
Published: April 2021

An experimental study of the morphogenesis of the thoracic cage of the chick embryo: mechanisms and origins

In the chick embryo, the ribs develop at the level extending from somite 19 to somite 26. According to several investigations, only the dorsal third of the body wall originates from the somitic mesenchyme, whereas more recent works have shown that the whole costal and intercostal material is of somitic origin. In the present paper, the origin of the material that forms the body wall as well as the mechanisms of thoracic morphogenesis have been studied.

The evolution of somites 21-22 to 25, grafted into the coelome of a host embryo under different experimental conditions, and the morphogenesis of the thorax after radiodestruction of the same somitic level at different stages have been examined.

The results have shown that:

The whole costal and intercostal material and the abdominal musculature originate from the somitic mesenchyme, whereas the sternum and the associated pectoral musculature originate from the lateral plate. The morphogenesis of the ribs and the intercostal muscles do not depend upon the lateral plate, nor upon the neural tube and notochord. Ribs and intercostal muscles are formed by a lateral outgrowth of somitic mesenchyme. The morphogenesis of the sternum along with the associated pectoral muscles and the organogenesis of the thoracic dorsal region are completely independent. The lateral outgrowth of the somitic mesenchyme that forms the thoracic ribs and the corresponding intercostal muscles starts antero-posteriorly in embryos which have reached the 22-27 somite stages.
Nucleic acid and protein synthesis and pattern regulation in hydra: I. Regional patterns of synthesis and changes in synthesis during hypostome formation
Authors: Clarkson S. G.
Published: April 2021

Hydra provides a convenient system for the study of the regulation of a linear pattern of organization. Almost any region is capable of being reconstituted into the whole organism and regulation is always polarized, i.e. distal structures (hypostome and tentacles) are formed from distal ends and proximal structures (peduncle and basal disk) from proximal ends.
Ultrastructural changes in the avian vitelline membrane during embryonic development
Authors: Jensen Cynthia
Published: April 2021

The vitelline (yolk) membrane of the avian egg plays a dual role during early embryonic development; it encloses the yolk and provides a substratum for expansion of the embryo (Fig. 1). Expansion appears to be dependent upon the movement of cells at the edge of the blastoderm which is intimately associated with the inner layer of the vitelline membrane (New, 1959; Bellairs, 1963). The blastoderm (embryonic plus extraembryonic cells) has almost covered the entire surface of the yolk by the third and fourth days of incubation, and when this stage has been reached the vitelline membrane ruptures over the embryo and slips toward the vegetal pole.
Methods of transplanting nuclei from single cultured cells to unfertilized frogs’ eggs
Authors: Gurdon J. B. , Laskey R. A.
Published: April 2021

Two methods of transplanting single nuclei from monolayers of cultured cells to unfertilized eggs of Xenopus laevis are described, illustrated, and tested.

The detached-cell method is simpler and quicker to operate and is suitable for homogeneous populations of cells which are easily removed from the substrate on which they are growing. The other, attached-cell, method is technically more elaborate, but is applicable to cells whose properties can be individually determined under the phase-contrast microscope and to cells which are not readily dissociated from other cells or from their substrate.
The dependence of duodenal differentiation in chick embryos on pars distalis hormones
Authors: Bellware F. T. , Betz T. W.
Published: April 2021

Duodenal differentiation in normal chick embryos between 15·75 and 20·5 days of incubation was characterized by the following changes:

The dry weight increases from 4·1 to 12·4 mg. The alkaline phosphatase activity increases from less than 12 to 426 units. The length of the villi increases sixfold. The height of the epithelial cells at the villous tips increases from 12·9 to 25·9 μ. The shape of the mucosal cells changes from low columnar, to cuboidal, to high columnar. The shape of the nuclei progresses from round to ovoid. At first mitotic figures are distributed throughout the epithelium but become restricted to the crypts of Lieberkiihn. Cytoplasmic glycogen appears by day 15·75 and is mobilized by 20·5 days. A mucopolysaccharide at the brush border of the mucosal cells progressively appears at 16-75 days and increases in amount. Alkaline phosphatase activity (Gomori technique) at the brush border appears in low levels at 16-75 days and becomes more intense. Fresh body weights and third toe lengths at 19·75 and 20·5 days of incubation were recorded as indices of body growth. In ‘hypophysectomized’ embryos at 19·75–21·5 days of age: The level of duodenal differentiation approximated that of normal .16·75–17·75 day embryos. In ‘hypophysectomized’ embryos which received a pars distalis chorioallantoic homograft at 9·5 days of incubation the duodena were normal. In ‘hypophysectomized’ embryos with grafts which became atrophic the level of duodenal differentiation was not different from that of untreated ‘hypophysectomized’ embryos. In chick embryos duodenal differentiation depends on pars distalis hormones.
The effect of environmental temperature on the growth of vertebrae in the tail of the mouse
Authors: Noel Janet F. , Wright E. A.
Published: April 2021

C3H mice were bred at 30 °C and 22 °C. At 28 days of age the lengths of the sacral and caudal vertebrae were measured from radiographs and related to the local skin temperature. Growth of the sacral and proximal caudal vertebrae was slightly retarded in the hot environment, but the distal caudal vertebrae showed increased growth which could be quantitatively related to an increase in skin temperature. This suggests that in hot climates the increased growth of peripheral organs of some mammals is due to local increases in tissue temperature.
Melanogenesis in amphibians : II. Electron microscope studies of the normal and PTU-treated pigmented epithelium of developing Notophthalmus viridescens eyes
Authors: Eppig John J.
Published: April 2021

Electron microscopy of 11 -day-old Notophthalmus viridescens retinal pigmented epithelium reveals particulate premelanosomes which are identical to the melanosomes found in the oocyte. These organelles, when found in the pigmented epithelium, are called premelanosomes because they undergo further maturation to form relatively homogeneous, spherical melanosomes. At this stage, oocyte melanosomes found in cells other than melanocytes have not undergone this subsequent maturation.

Elongated melanosomes which develop from fibrillar premelanosomes are also found in the pigmented epithelial cells.

Treatment with phenylthiourea blocks the maturation of both the fibrillar and particulate premelanosomes.
Experimental studies on axial polarity in hydra
Authors: Wilby Owen K. , Webster Gerald
Published: April 2021

There is evidence which suggests that the polarity of regeneration in hydra is determined by axial gradients of some sort. The mechanisms which may be involved in the establishment and maintenance of the gradients have been investigated by studying the reversal of polarity in graft combinations.

Complete polarity reversal can be effected by a grafted hypostome or by a grafted hypostome and peduncle. Partial polarity reversal can be effected by a graft of a peduncle only. Changes in regional properties associated with polarity changes have been investigated using isolation and transplantation techniques.

The experimental results suggest that the axial gradient behaves as a gradient of a substance. Such a gradient could be produced by either (a) simple diffusion of a substance from a source or (b) unidirectional transport of a substance plus back-diffusion. Some of the experimental results are incompatible with mechanism (a). All the experimental results are compatible with mechanism (b).

Some of the problems raised by the interpretation of the axial gradient in terms of a polarized transport model are briefly discussed.
The localization of morphogenetic factors in uncleaved eggs of Dentalium
Authors: Verdonk N. H. , Geilenkirchen W. L. M. , Timmermans L. P. M.
Published: April 2021

The effect of removing parts of unfertilized and fertilized eggs of Dentalium has been studied.

Up to 70 % of the volume of a 1st polar lobe can be removed from the vegetal side of both unfertilized and fertilized eggs, without influencing apical tuft formation. The post-trochal region is reduced. These eggs form a reduced polar lobe at first cleavage.

After removal of more than 70 % of the volume of a 1st polar lobe from the vegetal side of an uncleaved egg, before or after fertilization, no polar lobe is formed and larvae develop without apical tuft or post-trochal region.

The polar lobe area is quantitatively determined in the uncleaved egg, but after fertilization of isolated vegetal fragments regulation occurs and the polar lobe becomes proportional in size to the fragment.

Feulgen-positive granules, present at the vegetal side of the uncleaved egg, can be removed without influencing apical tuft formation. They may be important as determinants for the formation of the post-trochal region or adult structures.
The genetics and development of fused and supernumerary molars in the rice rat
Authors: Sofaer J. A. , Shaw J. H.
Published: April 2021

Analysis of breeding records suggests that the occurrence of fused and supernumerary molars in the rice rat, associated with lower body weight than normal and with reduced fertility, is dependent on a single autosomal recessive gene subject to background modification.

Molar fusion, which is preceded by stripping of the external enamel epithelium from the interdental lamina, may involve the first two molars, or all three molars of the normal series in either jaw.

The supernumerary is a posterior tooth, developing after the three molars of the normal series in either jaw. Supernumerary development usually occurs with fusion of the molars of the normal series, but occasionally a supernumerary may be present in the absence of fusion.

Other examples of association between fusion, subsequent to separation of the external enamel epithelium from the interdental lamina, and supernumerary tooth development are cited. This association suggests that there may be a single common attribute of the dental lamina predisposing to epithelial stripping and to laminal hyperactivity.