bluuebunny/crossref_metadata_2025 huggingface dataset:
Experiments on the ‘Overgrowth’ Phenomenon in the Brain of Chick Embryos
Authors: Bergquist Harry
Published: April 2021

A pathologic phenomenon consisting of complex folding of the brain-wall has been obtained in living chick embryos after operations upon the rhombencephalon in early stages. The operation consisted of the extirpation of the tip of the notochord and the overlying neuromere. Its results mainly appear in the hemispheres and tectum opticum region, but sometimes also extend to other evaginated brain parts, viz. the optic évaginations, the epiphyseal region, and possibly also the caudal parts of the hypothalamus. The pathologic phenomenon is identical with certain abnormal foldings, described in human embryonic brains by Patten (1952) and called by him ‘overgrowth’. It may be combined with encephaloschisis in the mesencephalic roof.
Recherches sur quelques aspects de l’hétéroploïdie expérimentale chez le Triton Pleurodeles waltlii Michah
Authors: Gallien L.
Published: April 2021

Experimental conditions and methods of rearing which make it possible to obtain heteroploidy in Pleurodeles waltlii are described. A method based on silver impregnation of the tail of young larvae permits the diagnosis of haploidy, diploidy, or triploidy. This method, by outlining the cell borders, makes possible planimetric measurement in any area of the epithelial sheet of the tail skin. The general structural organization of the ectodermal layers is described for the whole of the tail skin, and the alterations and adjustments resulting from an aneuploid make-up are analysed. In aneuploid chimaeras, micro- and macrocells are formed as a result of mitotic anomalies, corresponding respectively to groups of chromosomes lost from the mitotic spindle and to highly polyploid cells. The disappearance of the most atypical cells is followed by movements and reorientations of neighbouring cells producing characteristic rosette formations. Various teratogenic effects of thermal shock to the eggs, compatible with life, are described. Strongly hypomorphic or aneuploid larvae and haploid individuals, which usually have a brief survival, may be reared by means of parabiotic grafting to a normal individual. Amongst triploid males and females, fertile individuals have been obtained.
Recherches sur I’animalisation de l’œuf d’Oursin par les ions Zinc
Authors: Lallier R.
Published: April 2021

La différenciation de l’embryon d’oursin peut être modifiée expérimentalement par des agents chimiques. On peut obtenir ainsi la végétativisation des embryons, c’est à dire l’extension des régions entomésoderrniques, en traitant les œufs par le chlorure de lithium (Herbst, 1893; Lindahl, 1936), L’animalisation ou extension des territoires ectodermiques est provoquée par les ions sulfocyanure (Lindahl, 1936), l’acide iodosobenzoïque (Runnström & Kriszat, 1952) et l’acide thiomalique (Lallier, 1952). Nous avons montré au cours de recherches antérieures que l’animalisation peut être obtenue aisément en traitant les œufs par les ions zinc (Lallier, 1955 a,b) ou par certains dérivés organiques acides (Lallier, 1956, 1957, 1958a). L’animalisation obtenue dans ces conditions est particulièrement forte et homogène.
Embryonic Growth relative to the Vitelline Membrane, and its Role in Determining the Level of Post-operative Abnormalities, as Measured in the Chick
Authors: Silver P. H. S.
Published: April 2021

The changing relationship between a point on the vitelline membrane and the 1st somite or Hensen’s node has been investigated in the chick embryo, between stages of about 6 somites to about 40 somites. A puncture in the V.M. opposite the 1st somite at the six-somite stage lies opposite a point between the 10th—14th somites about 24 hours later, and between the 15th-20th somites about 48 hours later. The anterior intestinal portal maintains its orientation approximately relative to such an opening in normal development. Attention is drawn to the significance of these observations regarding embryos experimented on at an early stage, and which show abnormalities far caudal to the region of operative interference.
Correlation between ventral surface structures and local degeneration of cilia during conjugation inParamecium
Authors: Watanabe Tsuyoshi
Published: April 2021

Correlation between cortical structures, such as the suture lines and the oral apparatus, and local degeneration of cilia during conjugation was investigated using aberrantly shaped cells which were produced by treating normal cells with 2 mM adenine for 24 h. Three types of aberrantly shaped cells were obtained: (1) proters, in which the oral apparatus is located at or near the posterior end of the cell and the preoral suture is much longer than that of a normally shaped cell ; (2) opisthes, in which the oral apparatus is located extremely anteriorly, the preoral suture is very short and bent to the left, and the postoral suture and cytoproct are much longer than those of normally shaped cells; and (3) L-shaped cells, which are cells that have not separated at division and contain two buccal openings. The anterior member of the L-shaped cell (AML) has a long preoral suture and the posterior member of the L-shaped cell (PML) has a long postoral suture and cytoproct. The postoral field of AML and the preoral field of PML are missing. When these cells were mixed with normally shaped cells of the opposite mating type, the mating reaction took place between them. Scanning electron microscopic observation showed that, in all abnormally shaped cells, the degeneration of cilia always occurred along the full length of the preoral suture, regardless of its total length, and along the posterior right field of the buccal vestibulum, regardless of its location in the cell cortex. The localization of the degeneration of cilia, therefore, coincided with the position of the preoral suture and the buccal opening.
Cellular events during early formation of yolk-sac-derived teratomas
Authors: Sobis H. , Hove L. Van , Vandeputte M.
Published: April 2021

A sequential morphological study of the initial cellular events in teratoma induction by displaced visceral yolk sac after foetectomy in rats was undertaken. This study led to the observation that apart from proliferation of cells displaying definite endodermal or mesodermal characteristics, a population of poorly differentiated cells appeared some days after the surgical procedure. It is very likely that these poorly differentiated cells are stem cells from which differentiated structures originate afterwards by a process of redifferentiation. The development of granulation tissue rich in capillaries seems to enhance this process. Similarities and differences with blastema formation are discussed.
Cosegregation of monoclonal antibody reactivity and cell behaviour in the mouse preimplantation embryo
Authors: Randle Beverley J.
Published: April 2021

Expression of an antigen, recognized by a monoclonal antibody raised against PCI 3 embryonal carcinoma, is described in mouse preimplantation embryogenesis. The antigen is found in the cytoplasm of ovulated ova and is first noted on the cell surface of the 1-cell embryo 20 h post-ovulation. Surface labelling of blastomeres is uniform until the 8-cell stage when antigen expression becomes polarized along the radial axis of the embryo. Two major populations of blastomeres are distinguishable on division to the 16-cell morula. Dissociation of morulae in calcium-free medium yields large, polar, antigen-positive cells and small apolar cells with reduced levels of detectable antigen. A third, minor population of small, antigen-negative cells is also found in vivo. Large and small blastomeres differ in their ability to relocate within the embryo when aggregated with intact 16-cell-stage embryos. The small blastomeres of the 16-cell morula contribute significantly to the inner cell mass while the large antigen-positive cells are found only in the trophectoderm.
The effect of cathepsin inhibitor on rat embryos grownin vitro
Authors: Beck Felix , Lowy Adam
Published: April 2021

The addition of leupeptin to New cultures of rat embryos produces growth retardation and abnormalities of embryonic development. The effect is probably due to inhibition of the maternal protein breakdown necessary for embryonic growth. This function is carried out by the visceral layer of the yolk sac which shows distinct morphological changes akin to storage disease when leupeptin is added to the culture medium. We have not found it possible to reverse the effects of leupeptin by addition of amino acids to the culture medium.
Timing of X-chromosome inactivation in postimplantation mouse embryos
Authors: Rastan Sohaila
Published: April 2021

The onset of X-chromosome inactivation was investigated cytologically in postimplantation female mouse embryos of age , and days post-coitum (d.p.c.) and in the isolated epiblasts of 6 d.p.c. embryos before primitive streak formation using a heat/hypotonic technique to reveal the inactive X chromosome by differentially dark staining with Giemsa. The results indicate that X inactivation has taken place in all the cells of the so-called ‘un-differentiated’ epiblast by 6 d.p.c. before primitive streak formation. Further evidence is presented to suggest that X inactivation is complete in all cells of the mouse embryo by d.p.c.
The chromosome complement of single-pronuclear haploid mouse embryos following activation by ethanol treatment
Authors: Kaufman M. H.
Published: April 2021

A technique in which mouse eggs are stimulated to develop parthenogenetically following their brief incubation in 7 % ethanol in PBS is described. Very high rates of activation were achieved, and a detailed analysis presented of the class of parthenogenone which develops a single haploid pronucleus following second polar body extrusion.

As preliminary studies on presumptive haploid morulae indicated that a proportion of the metaphase spreads examined had an aneuploid chromosome constitution, the incidence of aneuploidy at the first cleavage mitosis was investigated. In the control groups the level of aneuploidy was about 1 %, whereas in the ethanol-treated series the incidence ranged from 13·6–18·8%. Additional pre-treatment of ethanol-activated oocytes in low osmolar medium raised the incidence of aneuploidy to 28-3%. Metaphase groups with 18, 19, 21 and 22 chromosomes present were observed in addition to groups with a normal complement of 20 chromosomes. The possible mode of action of ethanol in inducing parthenogenetic activation of mouse oocytes, and a high incidence of aneuploidy, is discussed in relation to previous knowledge of the action of this agent. Preliminary studies using G-banding indicate that the aneuploidy observed appears to arise as a result of non-disjunction which may involve any of the chromosomes of the complement.
Determination of axial polarity in the urodele limb regeneration blastema
Authors: Stocum David L.
Published: April 2021

The state of determination of the anterior-posterior, dorsal-ventral and proximal-distal axes of the undifferentiated limb regeneration blastema was evaluated by heterografting and autografting experiments in which these axes were reversed with respect to the limb stump. Species-specific size differences in skeletal elements were used as markers to trace the origin of regenerate tissues in the heterografting experiments, and differences in the skeletal patterns of hindlimbs and forelimbs were used as markers in the autografting experiments. The resulting primary regenerates fell into two categories, those composed wholly or partly of donor tissues, and those composed entirely of host tissues. Regenerate structures formed from donor tissues always maintained the handedness of origin, while regenerates formed from host tissues always displayed host-side handedness. These results demonstrate that the axes of the blastema are determined from the start of regeneration, and that previous claims of axial lability in reversal experiments are based on an illusion created by resorption of graft tissue, accompanied by regeneration from the host. Reversal of the transverse axes resulted in the formation of supernumerary limbs. Analysis of heterograft cases in which the anterior-posterior axis was reversed showed that 50 % of the supernumeraries were constructed partly of donor blastema tissue whose axial polarity was reversed with respect to the adjacent primary regenerate. The vast majority of the primary regenerates in these cases possessed the normal number of digits. It is thus likely that the reprogrammed donor blastema cells used to construct the supernumeraries are derived by division of a thin band of cells at the edge of the graft adjacent to the supernumerary.
A method for obtaining chimaeric mouse blastocysts with two separate inner cell masses: a preliminary report
Authors: Tarkowski Andrzej K. , Wojewodzka Marie
Published: April 2021

Pairs of zona-free mouse blastocysts aggregated in the presence of inactivated Sendai virus and subsequently cultured in vitro will fuse to form a chimaeric blastocyst with one common blastocoelic cavity. Depending on the relative position of the inner cell masses in the apposed ‘parental’ blastocysts, the resulting chimaeric blastocyst contains either a single inner cell mass (ICM) of dual origin or two discrete ICMs each originating from one embryo. In the present experiments, fusion between the two aggregated blastocysts occurred in 23 % of the pairs and 64 % of these chimaeric blastocysts contained two ICMs. Blastocysts of the latter type could potentially give rise to pairs of embryos which as regards the topography of the foetal membrane would resemble spontaneous identical twins, although they would be genetically dissimilar. Possible applications of the described method are discussed.
Juvenoids cause some insects to form composite cuticles
Authors: Willis Judith H. , Rezaur Rahman , Sehnal Frantisek
Published: April 2021

Metamorphosing insects treated with juvenoids may secrete composite cuticles which combine morphological features of two metamorphic stages within the area secreted by an individual epidermal cell. Characters found combined were pigmentation, tanning, surface sculpturing, and microtrichiae. Neighbouring cells frequently form different types of cuticle. Composite cuticles should not be confused with the more common mosaic cuticles, which are composed of discrete areas with different stage-specific morphology (e.g. some larval patches set in an otherwise normal adult cuticle).

Treatment of last instar nymphs of Pyrrhocoris apterus (Hemiptera) with a juvenoid induced secretion of composite cuticle which combined larval morphological features with imaginal pigmentation. Cells remained susceptible to composite cuticle induction over an extended period prior to the actual initiation of cuticle deposition.

Composite cuticle which contained larval microtrichiae and pupal tanning were induced with juvenoids in the lepidopterans Hyponomeuta malinella, Hyphantria cunea, Spodoptera littoralis, Mamestra brassicae, Pieris brassicae, Aglais urticae, but not in Galleria mellonella. Composite cuticle possessing both pupal and imaginal morphological features was produced with juvenoids in Leptinotarsa decemlineata (Coleoptera). It is suggested that this type of cuticle reveals the secretory capacities of a single epidermal cell when the cellular reprogramming from one developmental stage to the next has been stabilized at an intermediate point by juvenoids.
The pattern of campaniform sensilla on the wing and haltere ofDrosophila melanogasterand several of its homeotic mutants
Authors: Cole Eric S. , Palka John
Published: April 2021

A detailed mapping and description of campaniform sensilla on the wing and haltere of Drosophila melanogaster is provided. Six types of sensilla are distinguished. Similarities in the pattern of their distribution on the dorsal and ventral surfaces of each appendage, as well as between the wing and haltere, are apparent. These data are used to assess the quality of homeotic transformation in several mutants of the bithorax complex in which the halteres are transformed into wings. Flies homozygous for abxbx3pbx produce a complete inventory of wing sensilla on the homeotic appendage. In abx, bx3 and bx3pbx homozygotes the transformation of haltere into wing is incomplete, and each mutant shows characteristic fields of haltere and wing sensilla. It appears that specific regions of the anterior haltere compartment require different combinations of mutant alleles to produce a distinct homeotic transformation. Furthermore, the pbx mutation appears to influence expression of the bx3 mutation within the anterior compartment.
Development of the optic nerve inXenopus laevisIL Gliogenesis, myelination and metamorphic remodelling
Authors: Cima Charles , Grant Philip
Published: April 2021

We studied the time of origin, development and location of glial elements in the developing optic nerve of Xenopus with light and electron microscopy. The first cells acting as a primitive glia are ependymal cells lying dorsal to the chiasmatic optic nerve (CON) at Nieuwkoop & Faber (1956) NF stage 39. Later (stage 47/48), immature astrocyte cell bodies migrate from the periphery of the middle optic nerve (MON) into the central fibre mass along cytoplasmic processes extending from the outer glia limitans. Shortly thereafter, oligodendrocyte cell bodies appear in the centre of the fibre mass and myelination begins, first in the middle of the MON, spreading from the centre distally towards the chiasm and proximally to the retina. In late tadpoles myelinated fibres appear first in the CON then in the retinal optic nerve (RON) increasing markedly in juveniles and adults. Segment-specific patterns of glia and myelination appear during optic nerve development. During metamorphic climax, the optic nerve shortens (Cullen & Webster, 1979), a process involving myelin and axon remodelling primarily in the MON. Neither the profound changes during metamorphosis, nor the processes of gliogenesis and myelination significantly alter the underlying chronotopic ordering in the tadpole nerve. In juvenile and adult optic nerves, however, as myelination and gliogenesis increase, and as more axons mature and grow in diameter, the dorsoventral chronotopic arrangement of axons becomes less apparent.
The patterns of protein synthesis during foetal and neonatal organ development in the mouse are remarkably similar
Authors: Van Blerkom Jonathan , Janzen Richard , Runner Meredith N.
Published: April 2021

The extent to which differential gene expressions can be correlated with organ development was examined at the level of protein synthesis during pre- and postnatal development in the mouse. High resolution, equilibrium, two-dimensional polyacrylamide gel electrophoresis detected, for each of five to ten successive stages for each of seven organ systems, between 850 and 1000 separate newly synthesized proteins. The possibility that the 1000 detectable proteins synthesized at any one time during organ development represent a sampling bias was contra-indicated (a) because a different and larger population of [14C]- amino acid-incorporating protein syntheses gave similar results and (b) because nonequilibrium isoelectricfocusing, electrophoresis, isoelectric points between pH 5·5 and 8·7, confirmed the results from yet a different population of protein syntheses. Within limits of the sampling of protein syntheses, the entire period of organ development examined proceeds with altered expression of small proportion of the total proteins being synthesized. While all protein changes were stage specific, approximately three organ-specific protein syntheses were detected per organ system.

One family of five protein syntheses seen in 16-day foetuses had homologous primary structures and presumably are keratins derived from a single genomic expression. These selected stage-specific protein syntheses examined by electrophoresis of partial proteolytic digests disclosed a programme for post-translational changes in protein syntheses. The current observations indicate that the examined pre- and postnatal organ development of the seven organs occurs in the presence of greater than 99% similarity among proteins synthesized in the same and different organ systems. Functional differentiation during organogenesis, therefore, occurs in the presence of less than 1 % change in qualitative or quantitative switch in protein syntheses. Evidence is presented to indicate that even this remarkably small number of changes in protein syntheses during functional organ differentiation may be derived from an even smaller subset of gene expressions. Collectively, the data suggest that explanatory mechanisms for molecular organogenesis must encompass both selective gene expressions along with post-translational programmed events.
Induction de cartilage in vitro par l’extrait d’otocystes d’embryons de Poulet
Authors: Benoit par Jean A. A.
Published: April 2021

En 1937 De Beer, dans The Development of the Vertebrate Skull, posait le problème suivant: ‘Can extracts of auditory vesicles induce the formation of cartilage in vitro? in vivo?’ (p. 514). Nous pensons avoir trouvé une réponse à la première question: l’extrait d’otocystes induit in vitro la formation de cartilage à partir du mésenchyme otique, chez l’embryon de Poulet.
The Distribution of Sulphur in the Differentiating Visceral Cartilage of Xenopus
Authors: Okada T. S. , Sirlin J. L.
Published: April 2021

The incorporation of sulphate into tissues of Xenopus embryos in various developmental stages was studied by means of autoradiography. Particularly high uptake was demonstrated in the precartilages as well as in the differentiated cartilages. In the earlier stages, when no intercellular matrix has yet been deposited, the tracer is mainly in the cytoplasm of precartilaginous cells, while it is mainly in the matrix and especially in the immediate periphery of the chondrocytes of the differentiated cartilaginous tissue. The movement of tracer stored in the cytoplasm to the intercellular matrix accompanies the histogenesis of cartilage.
Influence of the Supra-oesophageal Ganglion on Posterior Regeneration in Nereis diversicolor
Authors: Clark R. B. , Bonney D. G.
Published: April 2021

Extirpation of the supra-oesophageal ganglion of N. diversicolor before the removal of a number of posterior segments inhibits the formation of new segments. At most, a new pygidium is regenerated. Extirpation of the supra-oesophageal ganglion 3 days after the removal of a number of posterior segments retards but does not inhibit segment-formation. An increase in the quantity of neurosecretory material produced by cells in certain nuclei of the brain of regenerating worms becomes detectable about 12 hours after the posterior segments have been removed. Nereis resembles lumbricid oligochaetes in that the supra-oesophageal ganglion plays an essential role during the initial phases of regeneration, but that once regeneration is initiated, its importance declines.
Aberrant Nerve Fibres in Human Development
Authors: Boyd J. D. , Hughes A. F. W.
Published: April 2021

Attention is drawn to the regular, though transient, presence of aberrant nerve fibres (fibres égarées) in three different regions of human embryos and foetuses. One of these regions is the cartilaginous basisphenoid into which fibres from the abducens nerves pass. The other two regions are the epithelial cord, known as the organ of Chievitz, and, in male specimens, the epithelium of the fused paramesonephric ducts. The possible causes for the atypical behaviour of the aberrant nerve fibres is discussed. It is tentatively suggested that the abducens nerve fibres may be attracted medially by some influence emanating from the cranial end of the notochord. For the aberrant fibres in the uterus masculinas and in Chievitz’s organ the neurotropic attraction is presumed to emanate from the constituent epithelia of the two structures.
Studies on Embryonic Determination of the Harlequin-fly, Chironomus dorsalis : I. Effects of centrifugation and of its Combination with Constriction and Puncturing
Authors: Yajima Hideo
Published: April 2021

By centrifuging, alone or in combination with constricting and puncturing of the egg, the embryonic determination in the harlequin-fly C. dorsalis has been studied. In eggs centrifuged moderately, three zones were distinguished: a centrifugal yolk zone, a centripetal oil zone, and an intermediate zone consisting of cytoplasm with nuclei. The mode of redistribution of the constituents of the centrifuged eggs differs according to the developmental stage at the time of centrifugation and to the centrifugal force. The strata of weakly centrifuged eggs begin to mix with each other immediately after centrifugation. Redistribution of the constituents of strongly centrifuged eggs always occurs in a definite way, even though the redistribution after centrifuging at the nuclear division stage does not take place until later, in the nuclear migration stage, while the cytoplasm of eggs centrifuged during and after nuclear migration begins to migrate as soon as the centrifuge is stopped. By centrifuging the eggs at the nuclear division stage, various types of malformation related to the direction of centrifugation are caused. These malformations are characterized by having duplicated parts. The frequency of occurrence of the malformations increases with increase in the centrifugal force. The structure of the double monsters is further modified by separating a part of the yolk or oil in the centrifuged eggs by strong centrifuging or by constricting, and by removing a part of the cytoplasm from the centrifuged eggs by puncturing. Modification always occurs in the mid-part of the double monster in the form of loss of segments. The number of omitted segments depends on the volume of the separated or the removed part. By applying two successive centrifugations in reverse directions it was found that a causal relationship between the direction of centrifugation before nuclear migration and the resulting malformation type is established at about the nuclear migration stage. From late centrifugation, two other groups of malformations resulted which are different from those obtained by early treatment. Those of the first group, which were caused by centrifuging at the syncytial blastoderm stage, are characterized by having a defect on the centrifugal side and no duplicated parts. Those of the second group were obtained from eggs centrifuged at the cellular blastoderm stage. In the extreme degree of this malformation the cells which reach the final level of differentiation are not organized into an embryo, forming instead small tissue masses. The specific features of the embryonic development of C. dorsalis, particularly thorax development, and the more general problem of the relation of the mode of development of Chironomus to that of other Dipterans, are discussed.
Colour pattern modification by coldshock in Lepidoptera
Authors: Nijhout H. Frederik
Published: April 2021

When young pupae of Vanessa cardui, V. virginiensis and Precis coenia (Lepidoptera: Nymphalidae) are exposed to severe coldshock many develop aberrant adult wing patterns. For each species, a synchronous cohort of experimental animals always develops a broad range of aberrant pattern morphologies but these can always be arranged in a single unbranched morphological series. When such phenotypic series are compared, between species and between wing surfaces within a species (each wing surface usually bears a different colour pattern), many parallel modifications and trends become evident. These parallelisms reveal certain homologies of pattern elements and suggest that a common physiology underlies the development of a considerable diversity of normal and aberrant colour patterns. The case is made that the phenotypic series produced may represent either a series of sequential stages in colour pattern determination or, a series of quantitatively different ‘interpretations’ of an established gradient system. Colour pattern morphoclines reveal which patterns are developmentally ‘adjacent’ to one another and may therefore prove useful in elucidating the evolution of patterns.
The distribution of fibres in the optic tract after contralateral translocation of an eye in Xenopus
Authors: Taylor J. S. H. , Willshaw D. J. , Gaze R. M.
Published: April 2021

In Xenopus embryos of stage 30 the right eye was translocated, without rotation, to a left host orbit. Shortly after metamorphosis the visuotectal projection through the operated eye was mapped electrophysiologically and shown to be normal dorsoventrally but reversed nasotemporally. Labelling of small groups of retinal axons with HRP showed that the fibre trajectories from dorsal and ventral retina were normal, whereas fibres from nasally placed retina had diencephalic pathways and tectal terminations typical of temporal fibres, and fibres from temporally placed retina had diencephalic pathways and tectal terminations typical of nasal fibres. Thus from just beyond the chiasma the fibres had already achieved the major uniaxial rearrangement necessary to establish a normal tract distribution despite the eye translocation. The fibre rearrangement required to permit the formation of a nasotemporally inverted visuotectal projection appears, therefore, to occur not on the tectum or in the optic tract, but either within the nerve or at the chiasma.
The behaviour of growing axons invading developing chick wing buds with dorsoventral or anteroposterior axis reversed
Authors: Stirling R. Victoria , Summerbell Dennis
Published: April 2021

The trajectories of motor axons innervating chick wings reversed about the DV or AP axis before axon invasion were analysed after retrograde filling by HRP injection into biceps or triceps muscles. Chick-quail chimaeras showed that the plane of reversal for flank operations was proximal to the confluence of the 14th, 15th, and 16th spinal roots as they form the plexus. The shoulder reversal plane was distal to the plexus.

In dorsoventral (DV) reversed wings at both shoulder or flank level, the motor axons do not alter their course as they enter the graft. They therefore innervate by passive deployment any target that they encounter. In anteroposterior (AP) reversed wings at both shoulder or flank level, the motor axons clearly corrected their position in the nerve tract after entering the graft and innervated appropriate targets. The innervation of appropriate targets in AP shoulder reversals shows that axons are sensitive to AP mismatch distal to the plexus. Since axons were displaced similar distances from their normal routes in flank DV and AP reversals, the difference in behaviour suggests that they respond to mismatch in the AP but not the DV axis.
Experimental analysis of the role of the ZPA in the development of the wing buds of wingless (ws) mutant embryos
Authors: Wilson D. J. , Hinchliffe J. R.
Published: April 2021

Phenotypically wingless (ws) chick embryos have wing buds characterized by the spreading of mesenchymal cell death in an anterior-to-posterior direction beginning at stage 19. It has been argued that this may reflect the absence of a functional polarizing zone (ZPA). When tested by preaxial grafting into normal wing buds (stages 20 –21), wingless ZPAs (stage 18 –19) had duplicating properties identical with those of normal ZPAs. Equally, normal chick or quail ZPA (stages 20 –22) grafted into the posterior margin of wingless wing buds (stages 18 –20) failed to inhibit the pattern of cell death or to evoke any improvement in their developmental performance. The wingless (ws) condition is not, therefore, due to a ZPA deficiency. Possible explanations are the prior programming for cell death of the wingless mesenchyme, or somitic deficiency, but it appears more likely that the mutant limb mesenchyme fails to transmit or respond to factor(s) produced by the ZPA.
The cell lineage of the muscles of the Drosophila head
Authors: Raghavan K. Vijay , Pinto Ludwin
Published: April 2021

Using a cell marker mutation the cell lineage of the muscles of the Drosophila head are traced out. Three sets of muscles separated by lineage restrictions are observed, even when cells are marked as early as the blastoderm stage. Each set underlies the derivatives of one of the three pairs of imaginal discs which differentiate to form the epidermis of the adult head. Clones of the homoeotic mutation engrailed (enIO) were apparently normal in the muscles of the head. The muscle clone frequency, at the blastoderm stage, in each hemisegment of the fly is similar, indicating an equal partitioning of cells during segmentation.
Cell surface markers to monitor the process of visceral endoderm differentiation from embryonal carcinoma cells: identification of the stage sensitive to high concentration of retinoic acid
Authors: Sato Masahiro , Ozawa Masayuki , Hamada Hiroshi , Kasai Masataka , Tokunaga Tohru , Muramatsu Takashi
Published: April 2021

Two cell surface antigens, brushin and FT-1 were effective in analysis of the process of visceral endoderm differentiation. Brushin was detected on both primitive and visceral endoderm, while FT-1 was detected only on visceral endoderm. When aggregates of N4-1 embryonal carcinoma cells were exposed to 10–8 M-retinoic acid for more than 2 days, external cells differentiated to multilayered and vacuolized visceral endoderm. However, aggregates treated with 10–6M-retinoic acid developed an endoderm layer, which remained one cell thick and was not vacuolized. Cell surface properties of the endoderm cells indicated that the high concentration of retinoic acid inhibited the differentiation pathway at the stage between primitive endoderm cells and visceral endoderm cells. By pulsed exposure to 10–6 M-retinoic acid, the period sensitive to the high concentration of retinoic acid was shown to be around day 4 after the initial exposure to retinoic acid.
Regeneration from isolated half limbs in the upper arm of the axolotl
Authors: Wigmore Peter , Holder Nigel
Published: April 2021

A technique enabling the isolation of half limb stumps using strips of skin from the head is described. Using this technique posterior, anterior, dorsal and ventral halves of the upper arms of axolotls were constructed. All halves produced regenerates and regional differences were shown in the regenerative and regulative abilites of the different halves. Posterior half stumps regenerated limbs with a mean digit number of 3·9 and had a normal dorsoventral muscle pattern. Anterior halves produced hypomorphic limbs with a mean digit number of 1·2 while dorsal and ventral halves produced an average of 3·8 and 2·6 respectively. Regenerates from dorsal half stumps had a normal dorsoventral axis but the majority of those from ventral halves were either double ventral or had little muscle on the dorsal side of the limb.
An analysis of protein synthesis patterns during early embryogenesis of the urodele - Ambystoma mexicanum
Authors: Meuler Debbie Crise , Malacinski George M.
Published: April 2021

Changes in protein synthesis during early Ambystoma mexicanum (axolotl) embryogenesis were monitored using two-dimensional (2-D) polyacrylamide gel electrophoresis. No change in synthesis patterns during progesterone-induced oocyte maturation was detected. In oocytes matured in vivo (unfertilized eggs), however, the synthesis of several oogenetic proteins ceased, only to be resumed later in development. At fertilization, one novel non-oogenetic protein was found. A cleavage-specific protein was also detected.

Dramatic changes in protein synthesis patterns were detected at gastrulation in axolotl embryos. About 10% of the proteins synthesized at earlier stages ceased synthesis at gastrulation. Another 10% of the proteins synthesized during gastrulation were novel. A gastrulation-specific protein was also detected. After gastrulation additional novel nonoogenetic proteins were synthesized for most stages examined. A pronounced increase in the number of novel proteins synthesized was observed at the onset of neurulation and during neural fold fusion. Some of those proteins were specific to dorsal or axial structure tissue (AST) and some were specific to ventral or non-axial structure tissue (NAST).

Actin and tubulin synthesis was also monitored during axolotl development. While the cytoplasmic γ- and β-actins were synthesized at all stages, muscle-specific α-actin synthesis began at the head-process stage (stage 23/25).
Evidence for the role of fibronectin in amphibian gastrulation
Authors: Boucaut J. C. , Darribere T. , Li Shi De , Boulekbache H. , Yamada K. M. , Thiery J. P.
Published: April 2021

In amphibian embryos, fibronectin (FN) assembles as a fibrillar network on the roof of the blastocoel cavity, preceding mesodermal cell migration. Local inversion of the ectoderm to produce a site where no FN is available prevents mesodermal cell migration. Microinjection of monovalent antibodies to FN arrests gastrulation. A complete inhibition of mesodermal cell migration is obtained after microinjection of a synthetic peptide containing the cell binding site sequence of FN. Prevention of interactions between receptors and FN appears to be the primary cause for blockage of gastrulation.
A review of the theories of vertebrate neurulation and their relationship to the mechanics of neural tube birth defects*
Authors: Gordon Richard
Published: April 2021

All of the published theories of neurulation, (some of them forgotten but never disproved), are reviewed for the purpose of assessing just where we are in coming to a satisfactory explanation of this critical step in the formation of the brain and spinal cord, whose occasional failure leads to neural tube birth defects. A new approach to evaluating these theories is introduced, namely finite element analysis, along with a discussion of its promise and present limitations.

‘To think that heredity will build organic beings without mechanical means is a piece of unscientific mysticism’ (His, 1888).
Placental Grafts in Rats
Authors: Payne J. M. , Payne Sylvia
Published: April 2021

Yolk sacs from rat placental membranes taken on the 14th or 15th day of pregnancy grew and differentiated in a remarkable manner when transplanted into the mother’s omentum. A variety of tissues developed within them, including mucus-secreting cysts, epidermoid cysts, cartilage, and bone. The mucus-secreting cysts were surrounded by smooth muscle and closely resembled intes-tine; they probably arose from the endoderm and mesoderm of the yolk sac. The epidermoids could have originated either from amnion remnants included accidentally in the transplant, or from metaplasia of the yolk-sac endoderm. It is obscure whether the cartilage and bone developed from host or graft. Transplants were rarely successful when removed from rats at the 11th or 18th day of gestation.

Similar results were obtained when the hosts were other stock rats, either normal or ovariectomized females or males.

The grafts were well tolerated by the hosts and homograft reactions did not occur. Members of the rat stock used would not tolerate adult skin homografts in the omentum, but transplants of foetal skin and bone grew and differentiated well. It is concluded that the tolerance of yolk-sac membranes is not a charac-teristic peculiar to placental tissue, but is part of a wider phenomenon of toler-ance to foetal tissues in general.
Topography of the Presumptive Rudiments in the Endoderm of the Anuran Neurula
Authors: Tahara Y. , Nakamura O.
Published: April 2021

The topography of the presumptive rudiments of the endodermal organs in the neurula of R. nigromaculata nigromaculata was studied by local vital staining. The results obtained are summarized in Text-fig. 22. The main portion of the fore-gut develops into the pharynx, oesophagus, stomach, and the anterior half of the duodenum. The lateral and ventral walls of the liver diverticulum give rise not only to the liver, but also to the gall-bladder, the bile-duct, and the ventral pancreas. The dorsal pancreas is derived from the dorsal and lateral archenteric walls at the boundary between fore-gut and mid-gut. The yolk mass subjacent to the mid-gut is the material for the small intestine and the posterior half of the duodenum. The whole endoderm originally lining the mid-gut is incorporated into the dorsal wall in consequence of the closure of the archenteron and the perforation of the definitive cavity of the intestine through the yolk mass. The hind-gut mostly forms the rectum; only a small portion at the margin of the blastopore becomes the post-anal gut.
An Immuno-embryological Study on the Chick Lens
Authors: Maisel Harry , Langman Jan
Published: April 2021

The purpose of this experiment was to analyse location and time of appearance of lens proteins during lens development.

Applying the agar-diffusion technique of Ouchterlony the adult lens was found to contain substantial amounts of at least seven soluble antigenic substances, grouped into three main fractions and referred to as Fractions I, II, and III. While Fraction I consists of one antigenic substance, Fraction II contains at least four components and Fraction III usually two components. Fraction I appears to be identical to the protein alpha crystallin (m.w. approximately 1,000,000) as prepared by continuous-flow electrophoresis and tested on homogeneity and identity by ultracentrifugation and paper electrophoresis. It is detected in the epithelial cells of the lens placode before the appearance of any other lens antigens and is thus considered to be the first lens protein to arise during organogenesis. The importance of this protein for lens development is also shown by its presence in the lens of representative species of the vertebrate series and by its presence in iris, retina, and cornea—that is, those tissues which show the capacity to form a lens after removal of the original lens. Fraction II appears to be identical to beta crystallin (m.w. approximately 200,000) and is characterized by at least four closely related antigenic subfractions, which appear at the onset of differentiation and growth of the nuclear lens fibres. As it is localized in the nucleus of the lens, the typical site of con genital cataracts, it is believed to be the main target for teratogenic factors such as German measles virus, which causes a cataract only if acting during differentiation and growth of the nuclear lens fibres. Fraction III appears to be identical to gamma crystallin (m.w. approximately 60,000) and is the last lens antigen to arise during lens development. Its morphological position could not be determined.
The Blood-Vessels of the Developing Spinal Cord of Xenopus laevis
Authors: Sims R. T.
Published: April 2021

The blood-vessels of the developing spinal cord of X. laevis have been studied from stage 45 to stage 66 by the injection technique. Within the substance of the cord the first vessels injected were found at stage 46, and individual vessels were not constant in position or time of appearance. The vascular network is formed by dichotomous branching and joining of vessels. Estimates of the number of vascular segments (i.e. between branches) per mm.3 of spinal cord and the total length of vessel per mm.3 showed that the latter increased during development while the former did not. It is concluded that the vascularity of the spinal cord increases as differentiation of the cord proceeds and is brought about by increasing the average length of the vascular segments.
L’Action de l’irradiation ultraviolette sur le métabolisme des acides nucléiques dans l’embryon de Poulet
Authors: Barbieri par Francisco D.
Published: April 2021

The incorporation of labelled adenine in the neural plate of ultra-violet irradiated chick embryos has been studied. It has been confirmed that small doses of radiation inhibit the closure of the neural folds. The incorporation of adenine increases immediately after radiation and decreases one hour after the treatment. There is a significant increase of the mitotic index during this first hour. In the light of previous results it is possible to attribute the inhibition of closure of the neural folds to some alteration in the metabolism of nucleic acids or proteins.
Investigations of the Germ-plasm in Relation to Nuclear Transplantation
Authors: Berardino Marie A. Di
Published: April 2021

Primordial germ-cells in R. pipiens mid-blastula and early gastrula stages were detected in serial sections, because these cells contained a stainable component, the germ-plasm. Their location was of prime interest in determining whether or not the nuclei of primordial germ-cells had been used in previous transplantation studies (King et al., 1959; Briggs & King, 1960). In the mid-blastula and early gastrula stages the primordial germ-cells were confined to the vegetal hemisphere. The majority of these cells was situated in the upper-third of the vegetal hemisphere. An intracellular displacement of the germ-plasm occurred between mid-blastula and early gastrula stages. The number and location of the primordial germ-cells suggest that only in rare cases could a nucleus from one of these cells have been transplanted in the previous studies, and such cases would probably have been undetectable. What appears most significant is that nuclei derived from cells not containing germ-plasm are capable of giving rise to larvae whose gonads contain numerous auxocytes.
Serologically Active Groups of Amphibian Embryos
Authors: Inoue Kazuko
Published: April 2021

Using the embryos of T. pyrrhogaster, the activity gradients of serologically active surface groups of protein molecules were analysed in buffered saline soluble (S) fractions of early embryonic stages against anti-S-fraction sera. Titrimetric methods were utilized in determination of the relative degree of participation of each group in the antigen-antibody reaction, as evidenced by inhibition of precipitation subsequent to inactivation of specific surface groups. Use was made of the blocking reagents p-chlor omer cur i benzo ate, monoiodoacetamide, cysteine, iodine, tyrosinase, 2,4-dinitrofluorobenzene, phenyl isocyanate, benzoyl chloride, and diazonium compounds in evaluating the reactivity of the sulphydryl, disulphide, phenol, imidazol, and amino groups. In the S-fractions, low activity of SS—SH groups and of the phenol groups is perceptible in the large oocyte; after fertilization the activity of all groups increases rapidly. The curve of SH activity culminates in the blastula; that of SS shows perceptible activity in the morula, wanes in the blastula, and then again rises to a maximum in the early gastrula. The gradient of activity of the phenol groups reaches its peak in the late gastrula stage. The amino and imidazol groups demonstrate maximum activity in the neurula and tail-bud stages of development.
Experiments on the Maternal-Foetal Barrier in the Mouse
Authors: Finegold Milton , Michie Donald
Published: April 2021

Leakage of chromium-labelled erythrocytes from the circulation of pregnant mice into the foetal circulation could not be detected, either following X-irradiation at various dose-levels and gestational stages or in untreated pregnancies. Two exceptions were encountered out of a total of 279 foetuses examined. This was taken as an estimate of the spontaneous incidence of transplacental leakage of maternal erythrocytes and contrasted with the relatively high incidence encountered in the human species.
Experiments on the Maternal-Foetal Barrier in the Mouse: II. A Test for the Transmission of Maternal Serum Albumin into the Foetal Circulation following X-irradiation
Authors: Knobel D. P. , Michie Donald
Published: April 2021

Serum albumin labelled with Evans blue did not pass from the maternal into the foetal circulation in 13 pregnant mice, of which 7 had received 300 r. X-irra-diation at stages ranging from day 13 to day 19, and 6 were untreated. The bearing of this result on studies of placental permeability in other species is considered.
L’Influence de divers mésenchymes sur la différenciation de l’épithélium pulmonaire de l’embryon de Poulet en culture in vitro
Authors: Dameron par Florence
Published: April 2021

Le poumon embryonnaire de Poulet prélevé à 5 jours d’incubation offre l’aspect d’un petit sac mésenchymateux enveloppant un conduit épithélial qui présente deux ou trois dilatations. Les deux ébauches entrent en contact l’une avec l’autre pour édifier l’organe.