bluuebunny/crossref_metadata_2025_split huggingface dataset:
Experiments on chromosome elimination in the gall midge, Mayetiola destructor
Authors: Bantock C. R. 
Published: April 2021

ABSTRACT
Cleavage in Cecidomyidae (Diptera) is characterized by the elimination of chromosomes from presumptive somatic nuclei. The full chromosome complement is kept by the germ-line nuclei.
The course of cleavage in Mayetiola destructor (Say) is described. After the fourth division two nuclei lie in the posterior polar-plasm and become associated with polar granules, and fourteen nuclei lie in the rest of the cytoplasm. All the nuclei possess about forty chromosomes. During the fifth division the posterior nuclei do not divide and the polar-plasm becomes constricted to form primordial germ cells (pole cells). The remaining fourteen nuclei divide and lose about thirtγ-two chromosomes so that twenty-eight nuclei are formed containing only eight chromosomes. These are the presumptive somatic nuclei. During subsequent divisions the pole cell nuclei retain the full chromosome number; these divisions occur less frequently than those of the somatic nuclei.
Experiments were performed on early embryonic stages to elucidate the properties of the posterior end during the time that chromosome elimination was taking place from the presumptive somatic nuclei. Ultraviolet irradiation, constriction, and centrifugation techniques were used.
The polar granules are concerned with the non-division of the germ-cell nuclei during the fifth division, since if the granules are dispersed by centrifugation, or if nuclei are prevented by constriction from coming into contact with them before the fifth division, all the nuclei divide with chromosome elimination at this division. With each technique it is possible to obtain embryos possessing germ cells with only eight chromosomes in their nuclei.
Individuals possessing germ-line nuclei with only eight chromosomes were allowed to develop to maturity. Abnormalities were confined to the germ cells only and were the same regardless of which technique had been used to produce the deficient germ line. An ovary containing germ-cell nuclei with only eight chromosomes is unable to form both oocytes and nurse cells. A testis containing germ-cell nuclei with only eight chromosomes is unable to form spermatocytes but cells which come to resemble gametes are formed. Experimental males and females are both sterile.
The results are discussed in relation to other experimental work on Cecidomyidae and the following main conclusions are reached: (a) the polar granules are responsible for preventing an irreversible loss of chromosomes from the germ-cell nuclei by preventing the mitosis of these nuclei during the fifth division; (b) the chromosomes normally retained in the germ line are required for gametogenesis, particularly for oogenesis.
The significance of chromosome elimination is discussed.
Study of the development of the internal organs of the double malformations of Chironomus dorsalis by fixed and sectioned materials
Authors: Yajima Hideo 
Published: April 2021

ABSTRACT
The development of the internal structures was investigated by fixed sections of the ‘double cephalon’ and ‘double abdomen’ of Chironomus dorsalis.
The cell proliferation that gives rise to ‘germ Anlage’ or embryonic rudiment begins, in the double cephalon, along the entire convex (ventral) side of the egg and, in the double abdomen, at both ends of the flat (dorsal) side. As a result, a single fused Anlage of the double cephalon appears along the entire convex side of the egg and two germ Anlagen of the double abdomen appear at both ends of the flat side.
During the formation of the germ band, both the posteriormost part of the double cephalon which lies at the middle of the convex side of the egg and the anteriormost part of the double abdomen which is located at the middle of the convex side, fail to differentiate and later degenerate.
In each of the duplicated heads of double cephalon, cephalic segments anterior to the first maxillary segment are formed, but the thoracic and abdominal segments are entirely missing. In each half of the double abdomen, eight abdominal segments posterior to the second abdominal segment are produced and the cephalic and thoracic segments are omitted altogether.
The two pairs of mid-gut rudiment from both halves of the double cephalon are temporarily united but they break apart by the end of the blastokinesis. When the two pairs of mid-gut rudiment from both halves of the double abdomen meet, they remain fused with each other, being surrounded by the visceral mesodermal cells in the normal way, and develop into the mid-gut epithelium.
In the double malformations, the pole cells are contained in only one member of the duplicated structures. The pole cells of the double cephalon develop into the tetra-nucleate state (Hasper’s second step), but they fail to fuse to form the gonad. In the double abdomen, the gonad develops in the one abdomen containing the pole cells and no replacement occurs in the sister abdomen without the pole cells.
The embryonic envelopes of the double cephalon do no’ retract into the interior of the embryo, while they do in the normal way in the double abdomen.
The double cephalon can never hatch but the double abdomen can emerge.
The origin and movement of nephrogenic cells in the chick embryo as determined by radioautographic mapping
Authors: Rosenquist Glenn C. 
Published: April 2021

ABSTRACTThe origin of the presumptive nephrogenic cells in the epiblast of the chick embryo was traced by radioautographic analysis of the movements of tritiated thymidine-labelled grafts excised from medium-streak to 5-somite stage embryos and transplanted to epiblast, streak, and the endoderm-mesoderm layer of similarly staged recipient embryos.The nephrogenic cells originate near the area pellucida margin of the medium-streak-stage embryo, migrate toward the streak, and are invaginated about one-third to one-half the distance from the anterior to the posterior end of the streak, between the definitive-streak and I - to 4-somite stages. Their route into mesoderm is along a relatively narrow pathway between the cells migrating to the paraxial or presomite mesoderm on one side, and those destined for the proximal limbs of the lateral plate on the other.The cells which will form the anterior part of the intermediate mesoderm are the most medially placed cells in epiblast, reach the streak at an earlier stage of development, and are the first nephrogenic cells to migrate into mesoderm. After about the 17- to 19-somite stage, cells from this group which have formed the pronephric cord or duct begin to move posteriorly in relation to the rest of the intermediate mesoderm, toward the future cloaca.The last nephrogenic cells to leave epiblast and enter the streak and mesoderm are those destined for the posterior end of the intermediate mesoderm. This group of cells surrounds the posteriorly migrating pronephric (Wolffian) duct and differentiates into mesonephros.
Morphogenesis and functional differentiation of the rat parotid glandin vivoandin vitro
Authors: Lawson Kirstie A. 
Published: April 2021

ABSTRACTIn comparison with the submandibular and the sublingual glands, the parotid develops slowly in the rat. The foetal rudiment appears a day later than that of the submandibular gland and the formation of adenomeres is slower, leading to a more diffusely branched structure. Cytodifferentiation, in the form of traces of mucopolysaccharide in the tubules and terminal buds, begins at, or just before, birth. There is a transitory increase in mucopolysaccharide production for a few days after birth until the presumptive acinar cells become pyramidal in shape with basal nucleus and granular cytoplasm. Amylase activity of the gland begins to rise between the second and third day after birth and reaches the adult level at weaning. That of the submandibular gland remains at the foetal level.Parotid rudiments were cultivated on a film of agar over a medium of fowl plasma and chick embryo extract. The oxygen in the gas phase of air and 5 % CO2 was increased to 50 % after the first 9 days in vitro. Under these conditions the mass of the rudiments increased tenfold during 18 days cultivation and the initially unbranched rudiment formed adenomeres in which the cytodifferentiation followed the same course as in vivo. The rise in amylase activity of the explants was only slightly delayed compared with that in vivo, suggesting that systemic or environmental factors are not obligatory in the early postnatal development of the rat parotid.
Cell population kinetics of erythroid tissue in the liver of foetal mice
Authors: Tarbutt R. G. , Cole R. J. 
Published: April 2021

ABSTRACT
Measurements have been made of the relative and total numbers of the various types of erythroid cells in the livers of random-bred Swiss foetal mice. It has been shown that the results can be interpreted in terms of two waves of erythropoiesis passing through the liver, one coinciding approximately with the erythropoietin sensitive phase of hepatic erythropoiesis, the other with the insensitive phase.
The mitotic index and thymidine labelling index of early erythroid cells do not change during the period studied, but the labelling index of the late cell types decreases from 30% at 13 days to 15 % at 18 days. This decrease has been interpreted as an increase in the proportion of non-dividing polychromatic erythroblasts.
The cell cycle time of early and late erythroid cells in foetal livers has been determined at 13 and 16 days of age. The cycle time of the early cells is about h at both stages of development, but that of late (polychromatic) erythroblasts decreases from 8 h at 13 days to 5–6 h at 16 days.
It has been shown that the results presented are consistent with the change in the rate of increase of hepatogenic red cells which is observed at about the 15th day of foetal life.
Thymus dysgenesis in nude (nu nu) mice
Authors: Pantelouris E. M. , Hair Janet 
Published: April 2021

ABSTRACT
The thymic rudiment in mice homozygous for the recessive mutation nude (nu) has been compared to the normal at two stages: the 14-to 15-day foetus and the 1-to 2-day-old young. In the former, the normal thymus already comprises two adjacent lobes but in the nude it is represented by a pair of thin strands of tissue, each with a narrow central lumen. In further development these strands become thicker and vesiculated. They progress no further and are found in the 1-to 2-day young as small vestiges that are never populated with lymphoid cells.
The thyroid, parathyroids and mandible of homozygous nude mice are normal, indicating that the complex of structures derived from the third branchial arch is not affected as a whole.
In vitro analysis of the hormonal basis for the sexual dimorphism in the embryonic development of the mouse mammary gland
Authors: Kratochwil Klaus 
Published: April 2021

ABSTRACT
Factors underlying the sexual dimorphism in the embryonic development of mouse mammary glands were analysed in vitro and the following results were obtained: Mammary gland rudiments of 13-day male embryos, explanted immediately before the onset of their regression, were perfectly capable of developing into female-type glands in vitro. Even some of the glands of 14-day male embryos, where the regression process had already begun, recovered after explantation and underwent female-type morphogenesis.Combined explantation of 13-day testes with mammary rudiments of female embryos of 12–14 days gestation resulted in male-type regression of the glands.The addition of testosterone to the culture medium caused a similar regression of explanted (female) mammary-gland rudrudiments. The minimal effective concentration of the hormone was 10−9M, or 0·00029 μg/ml.Cultured mammary rudiments of 15-day female embryos were no longer responsive to the presence of testis explants. They failed to undergo regression and continued their development in vitro.
From these results the following conclusions were drawn: (a) The sexual dimorphism in the embryonic development of mouse mammary glands is caused by their suppression in males and not by their stimulation in female embryos.(b) The androgenic hormones in male foetuses are solely responsible for the regression of the mammary rudiments. They exert their effect directly on the gland without the need for involvement of other endocrine organs.(c) The genetic sex of the gland itself has no influence on its developmental capacities as: (i) glands of male embryos are able to develop in the absence of androgens, and (ii) glands of female embryos undergo typical male-type regression in vitro when exposed to the presence of foetal testes or of testosterone.
Ontogeny of hemoglobin in the house sparrow
Authors: Bush Francis M. , Townsend J. Ives 
Published: April 2021

ABSTRACT
A ‘switchover’ from synthesis of predominantly embryonic hemoglobin to synthesis of predominantly adult hemoglobin occurs during differentiation of the house sparrow. This ‘switchover’ is demonstrated by a change in electrophoretic pattern generally comparable with that of the chicken, slightly different from those of the duck and man, and, perhaps, dissimilar to that of the red-wing blackbird.
Differences in electrophoretic mobility show that 10-day embryos possess one hemoglobin not present in early hatchlings and two hemoglobins not present in adults. Major adult hemoglobin is synthesized by the tenth embryonic day; and minor adult hemoglobin, between the tenth embryonic day and the seventh day after hatching.
The major increase in concentration of hemoglobin occurs between 2 and 11 days after hatching, a time when the two predominant embryonic and two predominant adult hemoglobins are being synthesized. The percentage of packed cells (hematocrit) also increases significantly within this period.
Similarities of peptide maps for the house sparrow and other species, such as the owl, indicate the presence of α-and β-polypeptide chains in adult house sparrow hemoglobin. The shift to hemoglobins with faster anodic mobilities and the presence of a higher concentration of hemoglobin in adults than in early hatchlings suggest that this synthesis is predominantly in the β-chains.
Growth and differentiation of rat egg-cylinders under the kidney capsule
Authors: Škreb N. , Švajger A. , Levak-Švajger B. 
Published: April 2021

ABSTRACTTwo groups of embryonic shields were transferred under the kidney capsule, on days and 9 of normal pregnancy. The first group was without mesoderm and the second one with well-formed mesoderm. Random-bred and inbred Fischer rats were used.Killed and fixed 15 and 30 days after the operation, the grafts looked like teratomata with well-differentiated tissues. Differentiation was the same in embryos explanted at and 9 days, and from the two strains of rat.In order to study the growth potential, transfers within and between each strain of rat were carried out. A difference in weight was found 15 days after the operation among some series. This was not observed 30 days after the transfer. Although the grafts in random-bred rats were larger than in the inbred Fischer strain, factors other than the immunological influence were invoked for the explanation of the initial difference in growth.Long-term grafts were studied only in the inbred strain. Two, 4 and 6 months after the operation all well-differentiated tissues were still present. The amount of growth was very variable within each series, but no graft was found totally resorbed.Only in the largest graft, 6 months after the operation, large masses of cells were found which seemed to be undifferentiated.
Feather morphogenesis and feather pattern in normal andtalpid3mutant chick embryos
Authors: Ede D. A. , Hinchliffe J. R. , Mees H. C. 
Published: April 2021

ABSTRACTA comparative study of feather morphogenesis and the development of feather pattern in normal and talpid3 embryos has been carried out.The development of talpid3 CAM grafts shows that the effect of the gene is autonomous in the skin.The most striking effect of the gene upon feather morphogenesis is the failure of normal feather germ condensations to appear within the dermis. This is reflected in the abnormal distribution of alkaline phosphatase through the dermis.Dermal cells within and between condensations are not orientated in the mutant as they are in normal embryos, probably owing to the same defect in cell behaviour which causes condensation failure in talpid3 precartilage mesenchyme.The role of dermal cell orientation and movement in generating the overall feather pattern is examined in both normal and talpid3 embryos.
The origin and movement of the limb-bud epithelium and mesenchyme in the chick embryo as determined by radioautographic mapping
Authors: Rosenquist Glenn C. 
Published: April 2021

ABSTRACT
The origin of the limb-bud cells was determined by tracing the movements of [3H]thymidine-labelled grafts excised from late medium-streak to 5-somite stage chick embryos and transplanted to the epiblast, streak, and endoderm-mesoderm of similarly staged recipient embryos.
Although exact definition of the prelimb areas was not possible because of the small number of grafts placed at each developmental stage, the study showed in general that at the late medium-streak stage the future limb-bud epithelium is in the epiblast (dorsal) layer near the lateral margin of the area pellucida. It moves medially toward the embryonic axis, just lateral to the premesoderm cells which will be invaginated at the primitive streak. With regression of the streak, the limb-bud epithelium moves relatively anteriorly into a position dorsal to the limb-bud mesoderm, beginning at least as early as the early head-fold stage.
At the definitive-streak stage, the future limb-bud mesoderm is in the epiblast layer about halfway from the streak to the lateral margin of the area pellucida, at a level about halfway between the anterior and posterior ends of the streak. From this position the prelimb mesoderm migrates medially to the streak, and is invaginated into the mesoderm layer at a position about halfway between the anterior and posterior ends of the streak; after the head-process stage, it migrates anteriorly and laterally into the somatic layer of the lateral plate, ventral to the limb-bud epithelium. Mesoderm which will form the anterior limb-bud migrates anterior to mesoderm which will form the posterior limb-bud; mesoderm which will form the ventral portion of each limb-bud migrates posterolateral to mesoderm which will form the dorsal portion of each limb-bud.
Organization of the chick blastoderm edge
Authors: Downie J. Roger , Pegrum Susan M. 
Published: April 2021

ABSTRACT
A band of cells forming the edge of the chick blastoderm, and attached to the vitelline membrane, causes the expansion of the blastoderm in the first few days of incubation by active migration across the vitelline membrane.
The structure and organization of these cells was examined by light microscopy (both on whole mounts and sections) and transmission electron microscopy. The account presented differs markedly from previous descriptions of these cells.
The band of cells at the blastoderm edge is an association, between 90 and 130 μm wide, of flattened, non-dividing cells forming a multilayer; some of these cells, and no other cells of the blastoderm, are attached to the vitelline membrane.
Each attached cell has a thin flattened lamella, centrifugally oriented and underlapping the next cell distally, except (1) the most distal cell, whose lamella is thick and long, though tapering, and is not overlain by other cells; and (2) the most proximal attached cell which has a short centripetally oriented lamella, as well as a centrifugal underlapping one.
The cells of the edge band not attached to the vitelline membrane also have flattened lamellae attached to the cells below; these lamellae are, however, unoriented.
The cells of the edge band all have plentiful cortical filaments and cytoplasmic microtubules. Specialized plaques are involved in the attachment of edge band cells to the vitelline membrane.
The form of this edge structure is compared with the outgrowth edge of a chick yolk sac epiblast explant cultured on vitelline membrane. It seems likely that the way the blastoderm edge cells are organized may explain their prodigious migratory activity.
Effect of erythropoietin on haemoglobin synthesis and haem synthesizing enzymes of mouse foetal liver cells in culture
Authors: Freshney R. I. , Paul John , Conkie David 
Published: April 2021

ABSTRACT
The activities of aminolaevulinate synthetase, aminolaevulinate dehydratase and haem synthetase have been examined in short-term cultures of embryonic mouse liver.
Although synthesis of haemoglobin was induced by erythropoietin in these cultures no increase in activity was detected in any of the three enzymes over 24 h in culture. In each case, however, enzyme activity was higher when erythropoietin was present than in its absence.
The significance of these findings is discussed in relation to control of haemoglobin synthesis and it is concluded that enzyme activity is not rate limiting during induction of haemoglobin synthesis in vitro.
Dependence of tectal neuron differentiation on optic innervation in teleost fish
Authors: Schmatolla Ernest 
Published: April 2021

ABSTRACTThe dependence of optic tectal development, especially differentiation of the stratum griseum periventriculare, on optic innervation is analysed in teleost fish in a comparative anatomical and experimental embryological study.Tectal development of the blind cave fish, Astyanax hubbsi, lacking optic nerves hence having non-innervated tecta, is compared to its river relative, the normal-eyed A. mexicanus. In the embryonic tectum of cave fish there is less white and grey matter, with smaller sized nuclei in the subventricular zone; in the cave adult the tectum is hypoplastic with poorly differentiated neurons in the stratum griseum periventriculare.Extirpation of eye Anlage in river fish embryos produced changes in the tectum comparable to the differences between embryonic tecta of cave and river fish.One-eyed catfish, Ictalurus nebulosus, with a relatively fibre-poor optic nerve from an underdeveloped retina on the eyed side, showed better differentiated cells in the periventricular layer of the innervated side than in the non-innervated side. Periventricular neurons in the tecta of normal catfish were still better differentiated, demonstrating that differentiation of these cells is ‘dosage-dependent’ upon the amount of optic innervation.Embryo zebrafish, Brachydanio rerio, subjected to extirpation of eye Anlage before optic nerve outgrowth, showed the dependence of differentiation of tectal subventricular cells on optic nerve ingrowth as early as the third day of development.Zebrafish raised in the dark compared to those raised in light showed no discernible tectal differences under light microscopy.Lack of differentiation of the neurons in the stratum griseum periventriculare in cave fish, and in eye-extirpated fish, has not been previously emphasized. Differentiation of these neurons appears largely dependent upon interaction with ingrowing optic axons, independent of visual function.
The occurrence of nuclear migration under thiol treatment effective in inhibiting neurulation
Authors: Messier Paul-Emil 
Published: April 2021

ABSTRACTEarly chick embryos were explanted on culture media containing mercaptoethanol and dithiothreitol in concentrations reaching 10−1 M and 10−2 M respectively. Nuclear migration was found to occur normally even under such thiol concentration, which is more than required to inhibit neurulation. Electron miscroscopy revealed that microtubules were not affected in their number and morphology. However, nuclear migration was blocked with 2.5X10−5M colchicine; such treated embryos showed a loss of their microtubules. It is concluded that the two thiols do not act primarily on microtubules when they cause inhibition of neurulation.