bluuebunny/crossref_metadata_2025_split huggingface dataset:
Induction of triploidy in the mouse by cytochalasin B
Authors: Niemierko Anna 
Published: April 2021

ABSTRACT
Mouse eggs fertilized in vivo were treated with cytochalasin B in vitro (5 µg/ml of culture medium) at the moment of extrusion of the second polar body (2·5, 3·0, 3·5 h after copulation). Cytochalasin B inhibits cytokinesis of the second maturation division, so that triploid digynic eggs are formed in over 50% of treated eggs.
Triploid eggs were transplanted to the oviducts of recipients. On the 4th and 5th day of development 41·7% of transplanted eggs were recovered. All embryos recovered on the 4th day were morulae, while on the 5th day blastocysts predominated. Recovered embryos were studied for cell number and ploidy. Twenty-three of 27 embryos with analysable metaphase plates were triploid and four were diploid (the latter were found in females into which both triploid and control diploid eggs were transplanted).
Sex chromosome constitution was determined in seven cases: four triploids were XX Y and three were XXX.
Preliminary observations showed that triploid embryos obtained by the use of cytochalasin B can implant and survive at least to the 9th day.
Neuroectodermal origin of avian hypothalamo-hypophyseal complex: the role of the ventral neural ridge
Authors: Takor T. Takor , Pearse A. G. E. 
Published: April 2021

ABSTRACT
Embryonic discs from White Leghorn chick embryos (presomite to 12-somite stages) were examined in serial transverse and longitudinal sections. Later stages, up to 21 days, were also examined. The following observations were made: Lateral folding rather than head folding is the mechanism by which the avian embryo is delimited. The process takes place at two terminal points, one cephalic the other caudal.Thickening of the ventral ectoderm around the tip of the presumptive anterior neuropore, beginning at the 4-somite stage, subsequently extends the dorsal neural ridge to form a ventral neural ridge.The cephalic portion of the ventral neural ridge, extending from anterior neuropore to optic chiasma, is mainly incorporated into the alar plates of the diencephalon.The caudal portion, extending from optic chiasma to the stomodeum, gives rise to Rathke’s pouch and thus to the adenohypophysis.
We conclude that the latter is to be regarded as of neuroectodermal rather than ectodermal (stomodeal) origin, and that some or all of the neuroendocrine nuclei of the hypothalamus are similarly derived from the neuroectoderm of the neural ridge.
The hypothalamo-hypophyseal complex is thus to be regarded as a single rather than a composite entity.
Iron incorporation and haemoglobin synthesis in erythropoietic cells during the ontogenesis of the mouse
Authors: Schalekamp M. , Harrison P. R. , Paul J. 
Published: April 2021

ABSTRACTIron incorporation (59Fe) into erythropoietic cells from adult and foetal (11-to 15-day) peripheral blood and from foetal (12-to 15-day) livers has been investigated. Ion-exchange chromatography of haemolysates from such cells revealed two groups of 59Fe-containing proteins. The first group (X-fraction) was eluted from CMC-columns in the void volume and was highest in lysates of immature erythropoietic cells. This fraction contained a radiolabelled haemprotein of high molecular weight as well as other S9Fe-containing proteins. The haemprotein does not appear to be related to haemoglobin.The second group consisted of haemoglobins. One major (A1) and two minor (A2 and A3) haemoglobins were found in adult peripheral blood. In foetal liver lysates two major (F1 and A1) and two minor (F2 and A3) haemoglobins were present. The relative proportion of the major haemoglobins changed during development. Haemoglobin F1 was highest in the more mature livers. F1 proved to be different from A1 by chromatographic behaviour, in polypeptide chain composition and in fingerprints. A unique foetal polypeptide chain, intermediate in electrophoretic behaviour between the adult α-and β-chain, was identified. In young foetal peripheral blood (11-day), in which 95 % of the cells are of yolk-sac origin, one major (E1), two intermediate (E2 and E3) and one minor (F1) haemoglobin were demonstrable. Haemolysates of the peripheral blood of older embryos contain haemoglobins from erythroid cells of both yolk-sac and foetal liver origin. The haemoglobin pattern of such lysates is explicable in terms of the decreasing amount of embryonic haemoglobins (E1, E2 and E3) and the increasing amount of foetal haemoglobins (F1 and A1). Since A1 and E1 are the most prominent haemoglobins of livers from young embryos and yolk-sac erythrocytes respectively, and since they are very similar in chromatographic behaviour, foetal peripheral blood at all stages contains one dominant haemoglobin peak in the A1-E1 region. Most authors have neglected the relatively slight elevation of the foetal haemoglobin peak (F1) in front of A1-E1, the more because the F1-A1 region has been suspected sometimes to contain artificial haemoglobin components (Riggs, 1965). This probably explains why no foetal haemoglobin (F1) has been reported previously in the peripheral blood of foetal mice.
The ultrastructure of the polar lobe of Crepidula fornicata (Gastropoda, Prosobranchia)
Authors: Dohmen M. R. , Lok D. 
Published: April 2021

ABSTRACT
Some novel structural features of the polar lobe of the egg of Crepidula are described. The significance of two kinds of aggregate is discussed in relation to the morphogenetic factors present in polar lobes generally. Surface configurations of the polar lobe are also described.
Embryogenesis of an insect nervous system:I. A map of the thoracic and abdominal neuroblasts inLocusta migratoria
Authors: Bate C. M. 
Published: April 2021

ABSTRACTMaps of the thoracic and abdominal neuroblasts have been prepared by reconstruction from serial sections of timed Locusta migratoria embryos. The maps are bilaterally symmetrical, periodic and consistent for embryos of the same age, with a fundamental arrangement of 7 rows of 4-10 cells plus 1 median neuroblast per segment. A map of 60+1 cells is repeated in each of the three thoracic segments, with an additional median cell developing late at the anterior end of the prothorax. The arrangement in the abdomen is similar, with 56+ 1 cells per segment. Neuroblasts differentiate and subsequently degenerate in an antero-posterior sequence, but construction of the thoracic ganglia involves a delayed degeneration of part of the original set in these segments. The maps show that the neuroblasts are as reliable in their number and arrangement as the adult cells they produce. The number of neuroblasts used in constructing the relatively complex thoracic ganglia is similar to that which produces the simpler abdominal ganglia. Some motorneurons have the same parent neuroblast. The maps are intended as a first step in an analysis of the relation between the progeny of different neuroblasts and the family of neurons which each neuroblast produces.
The formation of the gonadal ridge in Xenopus laevis: I. A light and transmission electron microscope study
Authors: Wylie C. C. , Heasman J. 
Published: April 2021

ABSTRACT
In Xenopus laevis tadpoles, between stages 44 and 49 (Nieuwkoop & Faber, 1956), the primordial germ cells (PGCs) migrate from the dorsal mesentery of the gut to the site of the presumptive gonadal ridge. This paper describes the process at the light- and electronmicroscope levels. The PGCs in the mesentery, which at first are very large and yolk-laden, seem to lie entirely within the cellular matrix of the mesentery, although this is not obvious in light micrographs. Where the PGCs bulge out into the coelomic cavity, they stretch the somatic cell covering to a thin, cytoplasmic layer. The somatic cells of the mesentery are held together around them at this stage by well-differentiated desmosomes. At this, and subsequent stages, the PGCs have cytoplasmic processes, roughly the size of microvilli, which are irregularly distributed over their surfaces, and which are inserted between surrounding somatic cells. Whether these processes play any role in locomotion or exploration of the substrate is uncertain.
As the PGCs move laterally from the root of the mesentery to the presumptive gonadal ridge, the coelomic lining cells which cover them, initially with a very thin squamous layer, differentiate to form the cuboidal cells of the germinal epithelium. Several interesting ultrastructural features of these cells, and the PGCs, are described, particularly in the light of their surface interaction.
In the light of the morphological data presented here, particularly of the cell surfaces involved, we conclude that both active locomotion by the PGCs and passive movement by the morphogenetic movements of the cells around them contribute to the establishment of the early gonadal ridge.
Embryological evidence for a possible polyphyletic origin of the recent amphibians1
Authors: Nieuwkoop P. D. , Sutasurya Lien A. 
Published: April 2021

ABSTRACT
The markedly different mode of mesoderm formation in anuran and urodelan amphibians (which is related to the early double-layered nature of the anuran blastula wall in contrast to its single-layered nature in the urodeles), but particularly the fundamentally different place and mode of origin of the primordial germ cells in the two groups of amphibians, strongly pleads in favour of a very ancient bifurcation in the phylogenetic history of the two groups, even suggesting a polyphyletic origin from different ancestral fishes.
The teratogenic effects of hydrocortisone on palatal development in the hamster
Authors: Shah Ravindra M. , Travill Anthony A. 
Published: April 2021

ABSTRACTThe effect of different doses of hydrocortisone, administered at various times during gestation, on the fetal hamster and its palatal development was studied. Both the frequency of cleft palate and that of resorption depended upon the dose of hydrocortisone and the time of its administration. Two peaks in the incidence of cleft palate were observed, which appeared to be due to inhibition of different events.Incidence of morphologically different types of cleft palate was related to the doses and gestational time of hydrocortisone treatment. A close association was observed between the frequency of cleft palate and fetal growth retardation and between the latter and the dose and time of drug administration. It was suggested that maternal physiology and the placental barrier may play a crucial role in cleft palate induction.
Regeneration of amputated limb-buds in early rat embryos
Authors: Deuchar Elizabeth M. 
Published: April 2021

ABSTRACTRat embryos, dissected from the uterus at -days’ gestation, have been used to study the regenerative powers of the embryonic limb. One forelimb-bud of each embryo was amputated, via an incision in the membranes. Embryos were subsequently grown in roller-bottle cultures for 44 h, then examined histologically. Twenty-nine out of 32 healthy embryos had formed limb-bud regenerates, 14 of which were of normal size and shape. Eight of them had a normal apical ectodermal ridge. It is concluded that at this stage of development there is sufficient versatility in the embryonic cells for a limb rudiment to be replaced by adjacent mesenchyme and epidermal cells. The implications of this finding are discussed in connexion with previous studies on the regeneration of appendages in vertebrate embryos.
Effect of dorsal and ventral limb ectoderm on the development of the limb of the embryonic chick
Authors: Searls Robert L. 
Published: April 2021

ABSTRACTLimb ectoderm plus a small amount of subjacent mesoderm obtained from the dorsal or the ventral surface of each of the four limbs of the chick embryo were grafted to the dorsal surface of the right wing in either reversed or normal orientation. The host wings developed an abnormal humerus in all cases except when the graft was obtained from the dorsal surface of the right wing and was in normal orientation. However, the nature of the abnormalities varied with the source of the graft and with the orientation of the graft. It is unlikely that the abnormalities were related solely to the small amount of mesoderm grafted since previous experiments have demonstrated that the mesoderm would regulate. Flank ectoderm plus a small amount of flank mesoderm did not cause limb abnormalities when grafted in the same manner.
Postnatal cytochemical development of muscle fibers in segmental tail muscles of the rat
Authors: Ovalle W. K. 
Published: April 2021

ABSTRACTPostnatal development of extrafusal and intrafusal muscle fibers was examined histo-chemically in segmental tail muscles of the rat. At birth all fibers show a strong reaction for myosin ATPase, uniformity in diameter, and homogeneity in staining intensity. During the first postnatal week, the muscle fibers undergo gradual hypertrophy and hyperplasia but they all maintain the same intense homogeneous staining pattern for the enzyme. By day 9, further differentiation of the muscle fibers results in the formation of a second intrafusal fiber type while the extrafusal fibers are still relatively homogeneous. Finally, two kinds of extrafusal fiber and a third type of intrafusal fiber can be distinguished by day 21. This histochemical fiber pattern is essentially maintained in the adult.These findings show that fiber type development in rat tail muscles lags behind the usual time course of myogenesis known to occur in more rostral regions of the animal. It also indicates that histochemical differentiation of intrafusal fibers in these muscles does not parallel that which occurs in extrafusal fibers. It is likely that arrival and initial contact of sensory nerve terminals on developing intrafusal fibers at day 7 directly influences their relatively early histochemical heterogeneity.
A histological study of embryonic death caused by heterozygosity for the T26H reciprocal mouse translocation
Authors: Boer P. De , Maar P. H. M. D. De 
Published: April 2021

ABSTRACTMale mice, heterozygous for the T26H reciprocal translocation, were mated to normal females. A systematic histological study at day 6 and day 8 of pregnancy, covering altogether 303 implantation chambers, yielded the following results: the average number of decidual reactions per female was 8 ·91, the average number of morphologically normal embryos at day 6 was 4 ·61 and at day 8, 4 ·25. No significant embryonic loss occurred between day 8 and the end of pregnancy. Most (89 ·0 %) of the embryonic loss due to genetically unbalanced (deficiencies combined with duplications) progeny occurs between the moment of the induction of a decidual reaction and day 6, i.e. in ±1 ·5 days. When the genetically unbalanced embryos were grouped in three classes according to the size of their deficiencies, the numbers and types of the aberrant histological pictures found could be reconciled with the expectations of the three classes, based on cytological analysis. According to this, embryos with the smallest deficiencies take just over 2 days before all have died. Embryos with mediumsized deficiencies take ±1 ·5 days, and the group with the largest deficiencies take just over 1 day. At day 6, 8 ·8 % of the implantation chambers had an intact epithelium whereas at day 8, this had dropped to 1 ·3 %. This is consistent with the view that erosion of the uterine epithelium at the site of implantation is an autonomous process, but helped by the phagocytic action of the trophoblast cells.
The use of ‘normal’ and ‘transformed’ gynandromorphs in mapping the primordial germ cells and the gonadal mesoderm inDrosophila
Authors: Gehring W. J. , Wieschaus E. , Holliger M. 
Published: April 2021

ABSTRACTThe primordial germ cells and the gonadal mesoderm were mapped in the Drosophila embryo by analyzing the patterns of mosaicism in ‘normal’ and ‘transformed’ gynandromorphs. Relative to the adult cuticular markers the germ cells map as the posterior most structure, which coincides with their known location in the blastoderm embryo. These data support the hypothesis that the gynandromorph map reflects the real position of the pri-mordia in the embryo. Since after the blastoderm stage the primordial germ cells migrate anteriorly these data also indicate that the map in fact corresponds to the blastoderm stage and not to a later stage of development. The genital disc maps as a single median primordium anterior and ventral to the germ cells, the gonadal mesoderm is located anterior to the genital disc and also forms a single median primordium on the ventral side of the embryo. The primordia for the genital disc and the gonadal mesoderm are unusually large in size, which presumably reflects some indeterminacy of the cell lineage leading to an ‘expansion’ of the map.
La morphogenèse du pied de l’embryon de poulet étudiée à l’aide de malformations provoquées par le vert Janus
Authors: Pautou Marie-Paule 
Published: April 2021

ABSTRACTMorphogenesis of the chick embryo foot as studied by Janus green B-induced malformationsJanus green was injected into the amniotic sac of 6 ·5-day-old chick embryos at a single dose of 8 ·5 or 15 μg; the dye causes respectively 55 and 82 % malformations of the feet. Toes are affected by partial or total soft tissue syndactyly, hypophalangy and infrequently by hyperphalangy. Lateral toes are more severely and more frequently affected by syndactyly and hypophalangy than medium ones. Hyperphalangy is found exclusively in toes I and II and causes the formation of one excess phalanx at most. Syndactylous toes are joined by an overdeveloped digital membrane. Hypophalangic toes have a truncated (non-pointed) distal tip. Two phalanges are lacking at most.These malformations are due to two distinct phases of the Janus green action. The first one, which is early and fast, inhibits interdigital programmed cell death, causing in term the non-regression of the interdigital membranes and thus syndactyly. The second one, which is late and slow, blocks the apical growth; this leads to hypophalangy.
Distortion of patches of retinal degeneration in chimaeric mice
Authors: West J. D. 
Published: April 2021

ABSTRACT
Estimation of the proportion of degenerate retina in rd/rd and + / + (or + /rd) chimaeras, using a linear analysis of histological sections, suggests a considerable preponderance of the normal phenotype, while analyses based on the area of the surviving tissue suggest that the proportion of each component is similar to that in other tissues. This argues against the validity of the linear analyses used by other authors. It is suggested that cell movement occurs in the outer nuclear layer, following the degeneration of the rd/rd population, and results in a distortion of the original patches of normal cells.
Effect of ascorbic acid deficiency on mouse second molar tooth germs cultivatedin vitro
Authors: Levenson Gordon E. 
Published: April 2021

ABSTRACTMandibular second molar tooth germs from two-day old mice were cultured in vitro, on millipore membranes, for periods of up to 20 days in liquid medium with or without added ascorbic acid. Tooth germs grown in ascorbate medium were characterized by relatively normal growth, differentiation, morphology and histology. Cuspation patterns were maintained. The epithelial root sheath continued to grow along the millipore membrane.Tooth germs cultured in ascorbate-deficient medium manifested a consistent and striking failure in maintenance of differentiated odontoblastic and ameloblastic tissue with arrest of predentin synthesis, severe structural collapse and reduction in size. Cuspation patterns were lost in scorbutic molars, with sinking of surface layers into pulpal tissue and flattening of the entire organ. This resulted in a lack of recognizable morphology and in severe disorganization of tissues. Only growing areas of the root sheath with associated proliferation of pre-ameloblasts and pre-odontoblasts and adjacent pulpal tissue remained normal and refractory to ascorbate deficiency. Odontoblastic as well as ameloblastic layers were disrupted and cells were dedifferentiated. Newly differentiated odontoblasts became highly vacuolated when they became polarized and started to secrete extracellular matrix.
Biosynthesis of DNA, RNA and proteins by mouse embryos cultured in the presence of a teratogenic dose of chlorambucil
Authors: Sadler T. W. , Kochhar D. M. 
Published: April 2021

ABSTRACTThe effect of chlorambucil on the rates of DNA, RNA, and protein synthesis in mouse embryos was investigated using a system of whole embryo culture. Embryos were isolated on the 11th day of gestation (33 ± 3 somites) and grown in culture media for periods of 4–8 h. Reichert’s membrane and most of the placental tissue was removed leaving only the amnion and visceral yolk-sac surrounding the embryo. In the presence of teratogenic doses of chlora-bucil (15 μg/ml) the rate of DNA synthesis was significantly decreased at 4 and 8 h. RNA and protein synthesis were not inhibited at either of these times. A trend toward decreasing rates of protein synthesis at some time beyond 8 h was noted, but not tested.
The developmental analysis of an embryonic lethal (c6H) in the mouse
Authors: Lewis Susan E. , Turchin Howard A. , Gluecksohn-Waelsch Salome 
Published: April 2021

ABSTRACTA development study of the effects of the c611 allele at the albino locus has identified the c6H homozygote as an early postimplantation lethal. Homozygous c6H embryos can first be recognized at days of gestation by abnormalities of the ectopiacental cone and parietal endoderm. At days, mutant embryos appear severely retarded with obvious abnormalities in all germ layers. All c6H homozygotes are dead and resorbed by 8 days of development. It is proposed that the mutation interferes with the normal differentiation of the parietal endoderm, ectoplacental cone and extra-embryonic ectoderm of the egg cylinder.
Scanning electron microscopy of lithium-induced exogastrulae of Xenopus laevis
Authors: Smith J. L. , Osborn J. C. , Stanisstreet M. 
Published: April 2021

ABSTRACT
Lithium-induced exogastrulae are abnormal embryos which fail to complete gastrulation and do not form normal neural structures. Scanning electron microscopy has been used to compare the surface structure of the ectoderm cells of exogastrulae with that of the ectoderm cells of normal embryos and has shown that the appearance of ciliated cells is delayed in exogastrulae. In addition, the surface structure of endoderm cells, which remain exposed in these embryos, has been studied.
Morphological changes associated with the growth cycle of vibrissal follicles in the rat
Authors: Young R. D. , Oliver R. F. 
Published: April 2021

ABSTRACT
Morphological changes which occur in the growth cycle of the rat vibrissal follicle during the transitional period between consecutive anagen phases are described. In contrast with pelage hair follicles, there is no shortening of the follicle, no formation of a papilla ‘rest’ and no close synchrony between club differentiation and follicle regression. Telogen is therefore considered to occur after loss of the matrix of the hair bulb and maximal diminution of the dermal papilla to a small aggregation of cells. These differences are discussed in relation to current nomenclature of the hair cycle and the function of the vibrissal follicle.