bluuebunny/crossref_metadata_2025 huggingface dataset:
Growth and differentiation of Tabularía cells in a chemically defined physiological medium
Authors: Burnett Allison L. , Ruffing Faith E. , Zongker June , Necco Anna
Published: April 2021

Although hydroids have proven valuable experimental animals for studies involving polarity and regeneration, they have not been extensively used by chemical embryologists studying control mechanisms in differentiation. Ideally, hydroids should be valuable tools for such a study. Their morpohology is relatively simple since they are diploblastic; their cells achieve a high degree of specialization (cnidoblasts, nerve cells, gland and mucous cells); cell differen-tiation (and morphogenesis) from a reserve stock of interstitial or i-cells is rapid; and many species can be cultured in large numbers under controlled environmental conditions.
The respective roles of mitotic activity and of cell differentiation in Planarian regeneration
Authors: Chandebois Rosine
Published: April 2021

Blastema formation, which is the first step of regeneration in adult Metazoa, is generally considered to be merely an accumulation of undifferentiated cells provided by mitotic activity, which occurs near the wound following amputation. Afterwards, these undifferentiated cells are thought to differentiate rapidly, thus affecting the organization of the regenerate.
Primordial germ cells in normal and transected duck blastoderms
Authors: Rogulska Teresa
Published: April 2021

Suggestive evidence for the extragonadal origin of germ cells in birds was first presented by Swift (1914), who described primordial germ cells in the chick embryo at as early a stage as the primitive streak. According to Swift, primordial germ cells are originally located extra-embryonically in the anterior part of the blastoderm and occupy a crescent-shaped region (‘germinal crescent’) on the boundary between area opaca and area pellucida. Swift also found that primordial germ cells later enter into the blood vessels, circulate together with the blood throughout the whole blastoderm and finally penetrate into the genital ridges, where they become definitive germ cells. Swift’s views have been confirmed in numerous descriptive and experimental investigations. Among the latter, the publications of Willier (1937), Simon (1960) and Dubois (1964a,b, 1965a,b, 1966) merit special attention. Dubois finally proved that the genital ridges exert a strong chemotactic influence on the primordial germ cells.
Auto- und allotypische DifFerenzierungen aus Blastemen der Halterenscheihe von Drosophila melanogaster nach Kultur in vivo
Authors: Gehring W. , Mindek G. , Hadorn E.
Published: April 2021

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 Kultur-medium, in welchem die Blasteme proliferieren, wobei sie jedoch ihren larvalen Dificrenzierungszustand beibehalten. Die Adultdifferenzierung kann durch Rücktransplantation der Blasteme in eine Wirtslarve, mit der das Implantät die Metamorphose durchläuft, vollendet werden. Die imaginalen Strukturen des Integumentes können anschlieβend aus dem Abdomen des metamorpho-sierten Wirtes herausprapariert und untersucht werden.
The influence of the dental papilla on the development of tooth shape in embryonic mouse tooth germs
Authors: Kollar Edward J. , Baird Grace R.
Published: April 2021

Studies of epithelio-mesenchymal interactions during embryonic organogenesis have led to a number of conclusions regarding (he nature of cellular and tissue differentiation (McLoughlin, 1963; Grobstein, 1967). For example, the importance of both the epithelium and the mesenchyme and the dependence of some systems on a limited number of specific mesenchymal tissues have been pointed out (Hilfer, 1968).
Etude expérimentale de la localisation, par rapport au plan d’amputation, de la source des cellules de régénération mésodermiques chez une Annélide Polychète (Syllis arnica Quatrefages)
Authors: Boilly B.
Published: April 2021

Lors d’une étude histologique (Boilly, 1967a,) et ultrastructurale (Boilly, 1968a, b) des premiers stades de l’histogenèse régénératrice chez Syllis arnica Q. (Annélide Polychète), nous avons été conduits à considérer les tissus anciens (épiderme, épithélium pharyngien, épithéliums cœlomiques, épithélium intestinal) du seul segment contigu à la blessure comme étant à l’origine des trois types de cellules régénératrices (ectodermiques, mésodermiques, endodermiques) assurant l’édification du blastème. Une étude expérimentale a d’ailleurs déjà permis de confirmer le rôle histogénétique des épithéliums cœlomiques (Boilly, 1968c, d) et de l’épithélium intestinal (Boilly, 1968e), au cours de la régénération chez cette Annélide. Cependant, bien que nos observations histologiques et ultrastructurales nous conduisent à constater l’absence de migration intersegmentaire de cellules de régénération, elles ne permettent pas de démontrer la validité de cette hypothèse. Néanmoins, elles suggèrent que, parmi ces cellules, seules celles provenant des épithéliums cœlomiques (cellules régénératrices mésodermiques) seraient susceptibles de présenter un phénomène de migration. En effet, les cellules de régénération issues de l’épiderme sont sur place. D’autre part, celles provenant de l’épithélium pharyngien ou de l’épithelium intestinal ne parviennent jusqu’au niveau de section que sous la forme d’un tissu organisé et non sous celle de cellules libres, même si, au départ, les épithéliums dont elles dérivent sont éloignés du plan d’amputation; en outre, ces cellules ne participent à la régénération de leurs structures qu’au sein des tissus dont elles proviennent, sans jamais s’en échapper. Par contre, les tissus à l’origine des blastocytes mésodermiques sont les seuls à ne pas conserver leur intégrité lors de la mise en place du blastème; en conséquence, un déplacement cellulaire plus ou moins important, analogue à celui décrit chez les Oligochètes, peut être envisagé pour cette catégorie de cellules régénératrices.
Une mutation récessive (pd) déterminant la polydactylie chez Xenopus laevis D. (Batraciens anoures)
Authors: Uehlinger Verena
Published: April 2021

Ce travail a été exécuté dans le cadre de l’analyse génétique des noyaux somatiques chez l’anoure Xenopus laevis D. (Fischberg, 1961; Fischberg & Blackler, 1963; Fischberg et al. 1964).
A new teratogenic agent applied to amphibian embryos
Authors: Levengood W. C.
Published: April 2021

It has been demonstrated that the application of the magnetic probe to Drosophila pupae has a pronounced influence on the pattern of morphogenesis (Levengood, 1966). In addition to morphological abnormalities, there was a retardation of development which continued to occur without further treatment in succeeding generations. A theoretical basis for these disturbances has been proposed (Levengood, 1967).
Interkinetic nuclear migration during the early stages of lens formation in the chicken embryo
Authors: Zwaan Johan , Bryan Phillips R. , Pearce Thomas L.
Published: April 2021

The optic vesicle in the chicken embryo, after growing out sufficiently to establish contact with the overlying ectoderm, adheres very firmly to the latter for a period of 12-15 h (McKeehan, 1951). Within the area of adhesion the surface ectoderm is transformed into a lens placode under influence of the developing retina. Little is known about the biochemical changes involved in this tissue transformation. Langman (1959) and Langman & Maisel (1962) found a cytotoxic effect of lens protein antisera and specific a-crystallin antibodies on presumptive lens cells shortly after induction had started but before the first morphological changes characteristic for the lens placode were visible. They concluded that the synthesis of a-crystallin might be a prerequisite for lens placode formation. Recent studies with the fluorescent antibody technique, however, indicate that the first crystallins are not produced until the very end of the contact period (Zwaan & Ikeda, 1965, 1968; Ikeda & Zwaan, 1966). α-Crystallin appears even later, at about 3-5 days of incubation when the formation of primary lens fibers has progressed far enough almost to obliterate the lens cavity (Ikeda & Zwaan, 1967).
Variation of the lumbar vertebrae of mice at two environmental temperatures
Authors: Munro Kathleen M. H. , Barnett S. A.
Published: April 2021

The house mouse, Mus musculus L., usually has twenty-six presacral vertebrae: these consist of seven cervical, thirteen thoracic and six lumbar vertebrae (Weber, 1950; Deol, 1958; Berry & Searle, 1963; Berry, 1964). The twenty-sixth vertebra is, however, sometimes abnormal, especially among laboratory mice: on one or both sides it may be fused with the sacrum. There are then five typical lumbar vertebrae, instead of six. The proportion of such abnormalities in a population is influenced by genotype, diet and unidentified maternal factors (reviewed by Griineberg, 1963). Evidence is given below that a low environmental temperature can also increase the incidence of ‘sacralization of L6’.
Chondrogenesis in chick embryo somites in vitro
Authors: Ellison M. L. , Ambrose E. J. , Easty G. C.
Published: April 2021

During the embryonic development of vertebral cartilages, cells from the somite mesoderm differentiate into chondrocytes around the spinal cord and notochord. Grafting experiments in amphibian and chick embryos have indicated that the spinal cord and notochord have some influence on this differentiation of somite cells to cartilage (Holtzer & Detwiler, 1953; Watterson, Fowler & Fowler, 1954). Further analysis in vitro has established that, under specified culture conditions, cartilage formation from somites is, in fact, dependent on the presence of either spinal cord and/or notochord or their extracts (Grobstein & Parker, 1954; Grobstein & Holtzer, 1955; Strudel, 1962, 1963; Lash, 1963).
The permeability of the hamster placenta to radioactive cadmium
Authors: Ferm Vergil H. , Hanlon David P. , Urban John
Published: April 2021

Studies on the permeability of the mammalian placenta to teratogenic agents during the early critical stages of embryogenesis have been relatively few. Most of these studies have been done in the pregnant rabbit, in which the unusually large size of the blastocyst makes it possible to obtain samples of blastocyst fluid for analysis. Thus, investigations have been done on the permeability of the rabbit blastocyst wall to trypan blue and other teratogenic azo dyes (Ferm, 1956), changes in blastocyst sugar content following maternal administration of insulin (Curry & Ferm, 1962; Lutwak-Mann, 1962) and the effect of thalido-mide and other agents on the implanting rabbit blastocyst (Lutwak-Mann & Hay, 1962; Hay, 1964; Fabro, Smith & Williams, 1965; Keberle et al. 1965; Fabro, Hague & Smith, 1967).
Etude des ribosomes et du glycogène des gastrules de Xenopus laevis par cytochimie ultrastructurale
Authors: Gansen P. Van , Schram A.
Published: April 2021

Les travaux de J. Brachet et de ses collaborateurs sur le rôle des acides nucléiques dans le développement embryonnaire des Amphibiens ont eu pour hypothèses directrices, ces dernières années (Brachet, 1965, 1967a, b, 1968), que les synthèses protéiniques spécifiques des différentes étapes de la morphogénèse se feraient dans le cytoplasme au niveau des polyribosomes. Les RNA messagers de ces organites existeraient dans l’œuf sous des formes stables qui se démasqueraient au moment de la maturation et assureraient les synthèses protéiniques pendant la segmentation; à partir de la gastrulation, ils seraient synthétisés au contact de DNA chromosomiaux déréprimés de façon différentielle par les territoires cytoplasmiques où ils se trouvent. Au gradient ribosomial animal-végétatif de l’œuf indivis se superposerait ainsi dans les gastrules un gradient polysomial dorso-ventral, ce double gradient étant l’équivalent biochimique des gradients morphogénétiques des embryo-logistes. Cette conception s’appuie actuellement sur un très grand nombre d’expériences faites à l’aide de techniques biochimiques et autoradiographiques (Brachet, 1967b).
Observations on the origin of the ‘germinal cytoplasm’ in Xenopus laevis
Authors: Czołowska Renata
Published: April 2021

The early appearance of the ‘germinal cytoplasm’ and its behaviour during the formation of cells which are thought to represent the primordial germ cells have been described in detail for Rana temporaria by Bounoure (1927, 1934, 1939) and Blackler (1958). These observations were extended to Xenopus laevis (Nieuwkoop, 1956; Nieuwkoop & Faber, 1956; Blackler, 1958), Bufo bufo (Blackler, 1958), (Berardino, 1961), Discoglossus pictus (Gipouloux,1962a) and Rana esculenta (Hammer, cited by Blackler, 1965b).
Ontogenetic changes in hemoglobin synthesis of two strains of Chironomus tentans
Authors: English Darrel S.
Published: April 2021

Differentiating cells can be characterized by the number and types of proteins they produce (Markert, 1963). In man and other organisms the diversity of hemoglobins has been correlated with ontogenetic changes which reflect the alterations of gene activity (Ingram, 1963). Furthermore, the types of proteins produced are generally specific for the species.
Fate of primordial germ cells in the transplanted hind gut of mouse embryos
Authors: Ożdżeński Wacław
Published: April 2021

During normal development of the mouse embryo, primordial germ cells (PGCs) differentiate in the root of the allantois and in the hind region of the embryo, then pass to the hind gut and through the mesentery to reach the germinal ridges (Chiquoine, 1954; Bennett, 1956; Mintz & Russell, 1957; Mintz, 1957; Ożdżeński, 1967). The number of PGCs increases greatly during migration (Chiquoine, 1954; Mintz & Russell, 1957). After penetrating into the gonads PGCs continue to divide mitotically for a certain time, then undergo changes which differ in each sex: the meiotic prophase begins in the ovaries (Brambell, 1927; Borum, 1961), gonial divisions are arrested in the testes and the chromatin in the nuclei of the germ cells undergoes characteristic dispersion. The behaviour of germ cells in the male embryos of the mouse is similar to that described by Clermont & Perey (1957) and Beaumont & Mandl (1963) in the rat.
Chemically stimulated differentiation of post-nodal pieces of chick blastoderms
Authors: Chauhan S. P. S. , Rao K. Vasudeva
Published: April 2021

Earlier studies on the role of sulfhydryl (-SH) groups in morphogenesis have indicated that in chick and amphibian embryos, an -SH-containing substance can act as an inducing stimulus in the action of the primary organizer. Thus, blocking -SH groups by chloroacetophenone (CAP) has specific developmental effects and the inducing capacity of the Hensen’s node is affected (Lakshmi, 1962 a, b). Reversal of the effects of -SH block by cysteine indicated that whatever is blocked by the -SH inhibitor is restored by cysteine (Mulherkar, Rao & Joshi, 1965; Mulherkar, Rao, Joshi & Joshi, 1966). It appears, however, that not all -SH-containing substances can reverse the effect of -SH block by CAP. Thus the teratogenic effects of CAP could not be ameliorated by a subsequent treatment with cysteamine, a decarboxylation product of cysteine, while CAP and cysteamine mixed in equimolar proportions had no effect on development (Rao, 1969). Inhibition of developing neural tissue and of inducing capacity of the organizer may be due to block of -SH groups of proteins or of the -SH in free cysteine and/or glutathione in the inducing tissue. Since the effects of -SH block can be reversed effectively by cysteine and not by cysteamine, it is likely that the action of cysteine in reversing the effects of -SH block is not the restoration of -SH groups. On the other hand, it is quite likely that an inducing stimulus can be given by substances of low molecular weight, probably cysteine or reduced glutathione. Waheed & Mulherkar (1967) have shown that postnodal pieces (PNPs) treated with cysteine and reduced glutathione, when used as organizer grafts, can induce neural tissue and that the grafts are neuralized or differentiate into somites. Thus there is good evidence that -SH-containing substances like cysteine and glutathione have the ability to stimulate differentiation of axial structures. In the present investigation an attempt has been made to study the inductive effects of cysteine and glutathione on post-nodal pieces of the chick embryo.
Les caractères de la segmentation et la détermination de la polarité dorsoventrale dans le développement de quelques Spiralia
Authors: Guerrier Par Pierre
Published: April 2021

C’est une particularité du développement des Spiralia que d’établir une liaison stricte entre la distribution des blastomères dès le début de la segmentation et les principales orientations de l’embryon qui sera produit en fin de compte. Dès le stade IV, on peut reconnaître la direction antéropostérieure, le plan dorsoventral de symétrie et le sens dextre ou sénestre de la segmentation.
Les caractères de la segmentation et la détermination de la polarité dorsoventrale dans le développement de quelques Spiralia
Authors: Guerrier Par Pierre
Published: April 2021

La formation de la polarité dorsoventrale chez les Spiralia a été interprétée par plusieurs auteurs comme l’expression d’une structure préformée dans l’œuf indivis. Des études antérieures (Guerrier, 1970) m’ont amené à rejeter cette conception pour le développement de Limax maximus où les éléments essentiels de la symétrisation s’expriment de manière relativement tardive au cours du développement. Cependant, chez d’autres Spiralia, comme Sabellaria alveolata, le caractère inégal des premières divisions rend la position du plan de symétrie apparente dès le début du développement. Je me suis donc proposé d’examiner si cette espèce présente, pour la détermination de sa polarité dorsoventrale, un mécanisme particulier.
Etude histochimique dé la distribution des sialomucines dans l’oviducte et les gangues muqueuses des ovocytes de Rana pipiens. Comportement dans l’eau des différentes gangues
Authors: Pereda Par Jaime
Published: April 2021

Les recherches histochimiques ont révélé chez les amphibiens divers mucopolysaccharides, situés dans l’oviducte à des niveaux bien définis et dont la topographie est très précise dans les gangues gélatineuses qui entourent les ovocytes (Humphries & Hughes, 1959; Humphries, 1966; Humphries & Workman, 1966; Pereda, 1969).
The role of exogenous heart-RNA in development of the chick embryo cultivated in vitro
Authors: Niu M. C. , Mulherkar L.
Published: April 2021

The physiological effect of fresh calf heart-RNA was studied on the explanted chick blastoderm at the definitive streak stage. It was found that heart-RNA interferes with normal development of the central nervous system, especially forebrain, and of the body axis, but not with normal development of the heart. To analyse this effect further, the untreated and RNA-treated fragments of the antero-lateral blastoderm were investigated by intrablastodermal transplant and in vitro. Approximately 50% of the treated grafts transplanted intrablastodermally developed into heart, but none of the controls. In vitro formation of the heart-like structure was found in 45% of the heart-RNA-treated series as opposed to 20% of the PC saline controls and none of the liver-RNA series. When the explants of the presumptive forebrain were treated with heart-RNA and cultured in isolation in vitro, 11% developed into brain vesicle compared with 76% of the controls. It appears, therefore, that heart-RNA has somehow collaborated with the macromolecules responsible for heart formation but interfered with those responsible for the development of the central nervous system.
The reaction of the mouse blastocyst and its zona pellucida to enzymes in vitro
Authors: Bowman Patricia , Mclaren Anne
Published: April 2021

Mouse blastocysts were cultured for 24 h in the presence of various substances at concentrations as high as possible, consistent with blastocyst survival. Lysis of the zona pellucida was produced by trypsin and pronase, but not by hyaluronidase, collagenase, β-glucuroni-dase, ribonuclease, neuraminidase or oestrogen. This suggests that the zona lysin secreted by the mouse uterus at the time of implantation consists of a proteolytic enzyme.
The developmental endocrinology of the spleen in chick embryos: I. The pars distalis
Authors: Betz T. W.
Published: April 2021

Partial decapitation (‘hypophysectomy’) of the chick embryo significantly reduces body growth by 20 days (stage 46—) of incubation as indicated by body weights, 60 % of normal; the lengths of the toe and tibiotarsus, 80 % and 78 % of normal respectively; and liver growth, 47 % of normal, but the gall bladder was not apparently enlarged. It significantly increases spleen growth to 82 % greater than normal, suppresses or retards white pulp differentiation and splenic vasculogenesis but enhances red pulp development.

A single pars distalis gland placed as a chorioallantoic graft into operated embryos prevents the development of these defects except for liver growth which, while improved, is still subnormal. If the number of grafts is increased by one or two there is no change in the amount of influence on growth and development of the chick embryo. This apparent regulation occurs by some unknown mechanism even in the absence of the hypothalamus.

Thus body and liver growth is normally stimulated by the pars distalis but spleen growth and red pulp differentiation are suppressed even though the gland stimulates splenic white pulp histogenesis. The hypothalamus, epiphysis and pars nervosa (removed by partial decapitation) are not apparently involved in the developmental endocrinology of the spleen in chick embryos.
The in vitro effect of the nerve growth factor on chick embryo spinal ganglia—a light-microscopic evaluation
Authors: Weis Peddrick
Published: April 2021

The effect of the nerve growth factor (NGF) on chick embryo spinal ganglia was studied in the hanging-drop bioassay system by comparison with parallel development in vivo.

The well-differentiated ventrolateral neuroblasts, which in vivo increase 1·33 times in size during the culture period, did not increase in size at all in vitro. Only 65–72% survived to the end of the culture period regardless of the NGF concentration.

The less-differentiated mediodorsal (M-D) neuroblasts, which in vivo increase .1-31 times in size during the culture period, were found to increase equally in vitro if sufficient NGF was present. Such a quantity was greater than that which evoked maximum outgrowth of neurites.

Survival of M-D neuroblasts was also related to NGF concentration but did not equal the in vivo condition even at the highest concentration. The hyperchromatic type of degeneration prevented by high NGF concentrations is that which results in vivo from insufficient peripheral field.

From this and other reports it would appear that the response to NGF seen in vitro is due only to the M-D neuroblasts, and that all biochemical and cytological observations which have been reported would therefore represent conditions within those cells only.
Ontogeny of haemoglobin in the royal penguin Eudyptes chrysolophus schlegeli
Authors: Shaughnessy P. D.
Published: April 2021

Haemoglobins of chicks, yearlings and known-age sub-adults of the royal penguin were investigated by starch-gel electrophoresis at pH 8·6.

Two haemoglobin components were observed in yearlings and sub-adults. These were assumed to be the haemoglobins of adults.

Another three haemoglobin components were observed in 3-week-old chicks.

Tn seven out of eight fledging chicks, these chick haemoglobins had disappeared.

The existence of other haemoglobin components in royal penguin embryos is predicted.
A radioautographic analysis of the migration and fate of cells derived from the occipital somites in the chick embryo with specific reference to the development of the hypoglossal musculature
Authors: Hazelton R. D.
Published: April 2021

The migration pattern and fate of cells of the occipital somites and overlying ectoderm have been described for the chick embryo with particular reference to the development of the hypoglossal musculature.

Tritium-labelled thymidine (0·5–10 μCi per egg) was used as a cell-specific marker. Occipital somites (2–5) with overlying ectoderm were transplanted orthotopically from labelled donor embryos to unlabelled host embryos (Hamburger & Hamilton, stage 9–10). The embryos were incubated, for varying lengths of time (24 h–5 days), sacrificed, sectioned and the migration pattern and fate of the labelled cells determined radioautographically.

It appears that the hypoglossal as well as other hypopharyngeal musculature originates from the occipital somites.

The mesodermal migration pattern extended from the occipital somite region in a ventro-posterior direction to the dorsal surface of the pericardial cavity posterior to the expanded portion of the pharynx. At this position a so-called hypoglossal cord formed on each side which ran anteriorly to the level of the second pharyngeal pouch where it turned medially and together with the cord from the other side entered the pharyngeal area of the embryo. This material apparently forms the intrinsic musculature of the tongue. The mesodermal movements are attributed to differential growth movements of the areas concerned as well as to active cell mutiplication and migration.

Selective embryonic neuronal staining was undertaken to study the relationship between the migrating hypoglossal cord and nerve. The cord preceded the nerve in its migration.

There is an occipital somitic contribution to the primitive meninx, to the endothelial walls of developing blood vessels, possibly to microglial cells and to the cartilage surrounding the notocord.

The occipital ectoderm expands dorso-anteriorly and ventro-laterally. Tn the ventro-lateral position as contact is made with the pharyngeal endoderm a placode is formed which contributes cells to the nodose ganglion of the tenth cranial nerve. There is no other contribution of the ectoderm to the underlying tissues.
Studies on the transmission of hypostome inhibition in hydra
Authors: Wilby Owen K. , Webster Gerald
Published: April 2021

The inhibition of hypostome formation in hydra has been investigated using isolation and transplantation techniques.

The transmission of inhibition does not seem to be polarized; a hypostome situated at the proximal end of the digestive zone can inhibit distal regeneration with no change in regeneration polarity. The time required for the proximal hypostome to establish an effective inhibitory ‘field’ is about 4–7 h. The results confirm that inhibition and polarity are quite separate factors.

The transmission of inhibition by a digestive zone is impaired by treating the region with media containing reduced concentrations of Ca2+ and Mg2+. This treatment has no effect on the inhibitory activity of the hypostome, nor on the resistance of the tissue to inhibition.

The effect of divalent cations on the transmission of inhibition does not seem to be due to an effect on cell adhesion. There is an effect on general cell permeability but this is not temporally correlated with the effect on transmission.

It is suggested that transmission of inhibition is dependent upon contact-mediated intercellular communication, possibly involving functional coupling between cells.
Cartilage anomaly (can); a new mutant gene in the mouse
Authors: Johnson D. R. , Wise Jean M.
Published: April 2021

Cartilage anomaly (symbol can) is a recessive gene in the mouse producing achondroplasia. Abnormal mice die at about 10 days after birth. Light microscopy reveals a systemic deficiency in the cartilaginous matrix. Electron microscopy suggests that the collagen of the matrix is normal and that the mucopolysaccharide component is reduced.
The origin and movements of the hepatogenic cells in the chick embryo as determined by radioauto graphic mapping
Authors: Rosenquist Glenn C.
Published: April 2021

The origin of the prehepatic cells was determined by tracing the movements of [3H]thymidine-labelled grafts excised from medium-streak to 4-somite stage chick embryos and transplanted to the epiblast, streak and endoderm-mesoderm layer of similarly staged recipient embryos.

Although exact definition of prehepatic areas was not possible because of the small number of grafts placed at each developmental stage, the study showed in general that at the mediumstreak stage, the prehepatic endoderm cells are in the anterior third of the primitive streak; they shortly begin to migrate anteriorly and laterally into the endoderm layer ventral to the precardiac areas of mesoderm. They are in the yolk-sac endoderm at the 2–4-somite stage, and by the 15–17-somite stage are clustered at the anterior intestinal portal. At the 26-somite to early limb-bud stages, the anterior and posterior liver diverticula have formed from these endoderm cells, and some of the branches of the diverticula may have reached the prehepatic mesenchyme, where the two tissues have begun to form cords and sinuses.

At the medium-streak stage, the prehepatic mesoderm is located slightly more than halfway from the anterior to the posterior end of the primitive streak. From this position it migrates anteriorly and laterally into the lateral plate mesoderm, and from the head-process to the 2–4-somite stage it is situated posterior to the prehepatic endoderm and posterior and lateral to the heart-forming portion of the splanchnic layer. By the 15–17-somite stage the prehepatic mesoderm has reached a position in the splanchnic layer of mesoderm which forms the dorsolateral wall of the sinus venosus. By the 26-somite to early limb-bud stage the hepatic diverticula have joined with the hepatic mesenchyme to form the rudimentary cords and sinuses of the liver.
Tissue-specific mitotic inhibition in the kidneys of embryonic grafts and partially nephrectomized host Xenopus laevis
Authors: Chopra D. P. , Simnett J. D.
Published: April 2021

Immature Xenopus laevis were unilaterally nephrectomized and implanted subcutaneously with stage 38 (prefeeding) larvae.

Rat kidney extract was injected 8 and 16 days after the operation and the mitotic incidence (MI) in the host and implant tissues was measured by the colcemid metaphase arrest technique.

The MI in the kidney of nephrectomized hosts was higher than normal at 8 days but had returned to the control level at 16 days. Injection of kidney extract inhibited mitosis in the host kidney both at 8 and 16 days after partial nephrectomy.

The MI of implant pronephros was higher in nephrectomized than in control hosts both at 8 and 16 days. Injection of kidney extract into nephrectomized hosts inhibited mitosis in the implant pronephros both at 8 and 16 days.

Neither host nephrectomy nor injection of kidney extract had any effect on the MI in the epidermis of the implants.

Unoperated immature Xenopus were injected with rat kidney or liver extracts. Kidney extract inhibited mitosis in the kidney but not in the liver, while liver extract inhibited mitosis in the liver but not in the kidney.

The rate of mitosis in the kidney and liver of normal animals may be controlled by tissuespecific inhibitors of cell division.
Abnormal spermiogenesis in two pink-eyed sterile mutants in the mouse
Authors: Hunt D. M. , Johnson D. R.
Published: April 2021

Abnormal spermiogenesis is described in two neutron-irradiation induced alleles at the pink-eye locus in the mouse. Testicular hypotrophy and abnormal spermateliosis are present, resulting in the formation of giant sperm with abnormal heads and multiple tails. Abnormal sperm-head shape results from abnormal proacrosome formation and multiplication of tail number from a failure in cytokinesis.

The pleiotropic effects of the locus on coat colour, fertility, behaviour and growth are reviewed in conjunction with similar mutants in other rodents: it is suggested that pituitary dysfunction could explain all aspects of the ‘pink-eye’ syndrome.
Laser irradiation of the chick embryo germinal crescent
Authors: Mims Martha Fearon , Mckinnell Robert Gilmore
Published: April 2021

The germinal crescent of head-fold and one-somite-stage chicken embryos was irradiated with multiple pulses of a microbeam ruby laser. Primordial germ cells were not detected in the gonad primordium of six laser-irradiated 5-day embryos; ten laser-irradiated embryos had varying numbers of primordial germ cells. Ten control embryos had gonad primordia populated with many primordial germ cells.
The relationship between cleavage and blastocoel formation in Xenopus laevis
Authors: Kalt Marvin R.
Published: April 2021

Blastocoel formation in Xenopus laevis was investigated by light microscopy using serial sections of epoxy-embedded, staged embryos. The earliest manifestation of the blastocoel in the embryo appeared during the first cleavage as a modification in the animal pole furrow tip. This modification consisted of an expansion of a localized area of the furrow. As the blastocoel became a distinct entity, it remained stationary, while the furrow tip continued to advance inwardly. In contrast, no such furrow cavity was observed in the vegetal pole furrow during its formation. During subsequent cleavages, up to the late morula stage, furrows on opposite sides of any given blastomere had different morphologies. As further divisions occurred, the mode of furrow formation became identical regardless of location in the embryo. It is suggested that the cytokinetic pattern in early amphibian embryos is modified to allow for the formation of the blastocoel. After the blastocoel has formed, the cytokinetic pattern changes to one which is concerned solely with cell division.
A three-dimensional collagen network for cartilage reconstruction
Authors: Moskalewski S. , Kamiński M. , Dukwicz A.
Published: April 2021

To obtain a three-dimensional network which would support cells during culture, cold collagen solution was mixed with cells and converted into a gel at 37 °C. Gelation of collagen did not influence cell viability.

The development of chondrocyte cultures in collagen gels depended on the distance between the cells. Single chondrocytes were surrounded by a mucopolysaccharide ring. The collagen fibres in parts of the cultures with moderate cell density were strongly alcian-blue-positive. Chondrocytes in crowded areas of cultures formed a cartilage matrix. Collagen gel with Ehrlich ascites tumour cells and liver cells remained unchanged after cultivation. Cultures of kidney cells and some chondrocyte cultures shrivelled, owing to partial collagen digestion.

The delicate primary collagen network in some cultures partially transformed to much thicker, long fibres or to distinct capsules around chondrocytes.
Development of division asynchrony and bilateral symmetry in the first quartet of micromeres in eggs of Lymnaea
Authors: Biggelaar J. A. M. van den
Published: April 2021

Experiments were undertaken to investigate the cleavage pattern of eggs of Lymnaea developing into exogastrulae after a treatment for 2 h with 5 × 10−2 M-LiCl at 6 °C at the beginning of second cleavage. It appeared that the 16-cell stage is reached normally, but that in the vegetative cells the following division is considerably retarded. It is assumed that this delay is associated with the suppression of division asynchrony in the first quartet of micromeres, which normally adumbrates bilateral symmetry in the animal hemisphere, and with suppression of gastrulation.
Activités cholinestérasiques dans le foie de Poulet Rôle de l’endoderme dans l’apparition d’activités cholinestérasiques dans la composante mésenchymateuse du tissu hépatique
Authors: Houssaint Par Elisabeth , Douarin Nicole Le
Published: April 2021

Cholinesterases in the chick liver. The role of the endoderm in the appearance of the activity of cholinesterases in the hepatic mesenchyme

The histochemical method of Koelle & Friedenwald (1949), as modified by Gerebtzoff (1953), has been used to investigate the distribution of cholinesterases in the chick embryonic and adult liver. Non-specific cholinesterases and, in a lower proportion acetylcholinesterase, have been detected in the endothelial cells of blood sinusoids of both adult and embryonic hepatic tissue. The hepatocytes do not show any cholinesterase activity.

Cholinesterases appear precociously in the liver mesenchyme, since they already occur in the septum transversum of the 3-day-old chick embryo.

An experimental procedure preventing the invasion of the hepatic mesenchymal Anlage by the endodermic cords has been used. The experimentally isolated hepatic mesenchyme shows an important cholinesterase activity; therefore this activity does not depend on the presence of the hepatocytes.

The grafting of the determined hepatic endodern in the somatopleura of the 3-day-old chick embryo results in the development of hepatic tissue in the body wall. In this experimentally produced liver, cholinesterase activities are present in the endothelial cells which have arisen from somatopleura mesenchymal cells, though normally somatopleural mesenchyme does not possess these enzymes. The role of the endoderm in the appearance of this enzymic activity in the somatopleural mesenchyme is discussed.
Studies on nucleocytoplasmic interactions during early amphibian development
Authors: Brachet J. , Hubert E.
Published: April 2021

The dorsal or the ventral cortex of Xenopus laevis eggs, at the one- or two-cell stage, has been slightly injured with a microneedle; 184 of these eggs have been examined cytologically.

The frequency of early (cleavage) and late (gastrulation, neurulation) abnormalities after dorsal injury was about twice that after ventral injury.

Abnormalities of the mitotic apparatus and of the chromosomes are very frequent during cleavage after slight cortical damage.

At later stages, the previously wounded embryos often display aneuploidy, as shown by cytophotometric measurements of the DNA content of the individual nuclei. Aneuploidy is much more frequent after injury of the dorsal cortex than injury of the ventral cortex.

Autoradiography studies have shown that there is a close correlation between morphogenesis and nuclear RNA synthesis.

The results are discussed in relation to current ideas on the morphogenetic and genetic significance of the grey crescent and its cortex.
Hydrocortisone-increased glycogen deposition and its dependence on tissue interactions in mouse embryonic lung developing in vitro
Authors: Alescio T. , Dani A. M.
Published: April 2021

We have performed experiments showing that the epithelial tree of embryonic rudiments, when cultured in vitro in the presence of hydrocortisone, sharply increases its glycogen content. The distribution of the polysaccharide remains very similar to that observed in the absence of the hormone.

The increased glycogen deposition in response to the hormonal treatment requires the presence of homologous (bronchial) mesenchyme, as shown by the complete inability of the epithelium to accumulate glycogen when experimentally associated with metanephrogenic mesenchyme.

The increased deposition of glycogen in the epithelial tree does not result in an enhanced rate of budding activity.
RNA synthesis at the two-cell stage of mouse development
Authors: Knowland John , Graham Chris
Published: April 2021

This paper describes a method for quantitative extraction of nucleic acids from cultured pre-implantation mouse embryos in a form suitable for electrophoresis, and its application to the analysis of RNA synthesized during early mouse development. The nucleic acids synthesized by early mouse embryos have been identified by the use of RNase, DNase and mild alkaline hydrolysis. No obvious differences in the kinds of RNA synthesized in the blastocyst, trophoblast or embryonic fibroblast were found. At the two-cell stage of mouse development, which is the earliest that can be successfully labelled with radioactive precursors of RNA, all major RNA classes with similar electrophoretic mobilities to the RNA species of adult cells are synthesized, and it is likely that 28 s and 18 s RNA are synthesized at this stage. It is suggested that the onset of rRNA synthesis may not be associated with a particular stage of embryonic development.
Cell lines derived from late embryonic stages of Drosophila melanogaster
Authors: Schneider Imogene
Published: April 2021

The development of three cell lines initiated from the late embryonic stages of Drosophila melanogaster is described. The primary cultures consisted of trypsinized fragments from embryos 20–24 h old. The length of time between primary culture and subsequent subculture varied from 8 months for the first line to 3 weeks for the third. All three lines have been maintained in vitro for more than a year. The characteristics of each line are given and evidence is presented that at least one line is derived from imaginal disc cells. A few comments on insect tissue culture in general are also made.
Regeneration, post-embryonic induction and cellular interaction in the eye of Periplaneta americana
Authors: Hyde Cornelia Anne Tuten
Published: April 2021

The eye grows by the addition of new ommatidia rather than by an increase in size of existing ones. New ommatidia develop as a result of induction of epidermal cells by functional ommatidia. The eye has great regenerative ability, but following removal of the entire eye and the growth zone that surround it regeneration does not occur. Transplanted eye cells or epidermal cells from normal-eyed or from lavender-eyed mutants resulted in the development of normal eye pigmentation in a mutant that lacked any pigmentation in the eye. Only the eye to which the graft had been made developed pigments. The development of pigments was a result of tissue contact, not of a blood-borne factor. When epidermal tissues from the prothorax of normal-eyed roaches were placed above the developing eye of a mutant with no pigment in the eye they were eventually incorporated into the eye as it grew. When these cells became eye cells, normal eye pigments were synthesized. Growth of the eye is by a constant recruitment of epidermal cells that express their own genetic capability when they become eye cells.
DNA synthesis in the preimplantation mouse embryo
Authors: Barlow P. , Owen D. A. J. , Graham Chris
Published: April 2021

Strain PO preimplantation embryos were labelled with [3H]thymidine. The incorporation of the label was studied by autoradiography of air-dried and serially sectioned embryos. DNA amounts were measured with a microdensitometer.

The following observations were made at the 5- to 16-cell stages. All nuclei contained 2C–4C amounts of DNA and all could eventually synthesize DNA. However, after short labelling intervals, unlabelled nuclei were found with 2C and 4C amounts of DNA. We concluded that both the Gx and the G2 phases of the cell cycle were present at this time. Embryos were found in which the S phase of the 4th and the 5th cell cycles post fertilization overlapped. In 12- to 15-cell embryos which contained inside cells it was found that the inside cells were produced by one of the first four 8-cell-stage blastomeres to divide.

The inside cells of 9- to 256-cell embryos had a significantly higher labelling index than the outside cells and the number of inside cells increased faster than the number of outside cells during development. We concluded that the inside cells were dividing faster than the outside cells.

Blastocysts which had developed in vivo or in vitro contained nuclei with greater than 4C amounts of DNA. We concluded that the development of excess DNA amounts does not depend on the maternal environment. These nuclei which contained greater than 4C amounts of DNA were labelled after short exposures to radioactivity. We concluded that it was likely that they were becoming polyploid.
An in vitro study of functions of embryonic membranes in the rat
Authors: Payne G. S. , Deuchar E. M.
Published: April 2021

Ten-day rat embryos have been cultivated in vitro, with different layers of the extra-embryonic membranes removed. The effects of presence or absence of each membrane on the morphology of the embryos, their histodifferentiation and their uptake of leucine into protein have been followed.

Explants with all membranes left intact failed to expand fully and to undergo axial rotation of the embryo, but nevertheless showed highest total protein and highest leucine uptake in biochemical estimations and in autoradiographs.

Explants with outer membranes removed and the visceral yolk sac left intact showed the most normal morphology and expansion of the extraembryonic cavities when compared with embryos removed from the uterus at 11·5 days’ gestation, but they showed less protein and less leucine uptake than the first series.

Explants in which the visceral yolk sac was removed underwent little growth or development and had low total protein values and radioactivity counts. The amnion collapsed and the amniotic cavity disappeared. When the amnion was removed there was a greater incidence of death, as well as little or no development, and lower radioactivity counts than in the first two series.

It is concluded that the outer membranes and the visceral yolk sac play an important role in the transfer of small metabolites to the embryo, as well as in regulating the volume of the extraembryonic fluids.
The isolation and properties of a clonal tissue culture strain of pluripotent mouse teratoma cells
Authors: Evans Martin J.
Published: April 2021

A clonal tissue culture strain of pluripotent cells has been isolated from a transplantable teratoma of inbred strain of mice 129 Sv-S1j CP. This cell strain SIKR when re-inoculated into mice produces teratomas containing at least ten types of tissue. Sub-clones have been isolated and two types distinguished.

(1) ‘C-type’ with a densely-piled in vitro growth. These are tumourigenetic and pluripotent displaying a comparable range of differentiation to the original SIKR.

(2) ‘E-type’ spreading, often epithelioid growth. These grow to a lower density in culture than ‘C-type’. Mostly non-tumourigenetic; in those cases where a tumour has been obtained it did not display multiple differentiations.

The results are interpreted as demonstrating that the culture consists of equivalently pluripotent cells which may become determined and differentiate spontaneously in vitro into slower growing cell types which are continuously overgrown by the culture.
The uptake and transfer of radioactive compounds in axial grafts ofHydra
Authors: Olson J. A.
Published: April 2021

Hydra littoralis and H. attenuata were labelled with 45Ca, 32PO4, or [3H]thymidine, either by exposing them to a medium containing the isotope or by injecting the isotope into their gut cavities. Various portions of labelled and unlabelled hydra were grafted together in diverse combinations, and the rate of transfer of radioactivity to the unlabelled portion was assessed. The relative transfer rates of the isotopes were 32PO4 > 45Ca2+ ⪢ [3H]thymidine. The transfer rates for 32P-labelled compounds and 45Ca were unaffected either by the polarity gradient (from head to foot and vice versa) or by the existence of potentially separate biological fields. Isotopes were not readily transferred between hydra or pieces of hydra which were in apposition but not grafted together. A rapid and sensitive method for the measurement of hydra mass is also described.