bluuebunny/crossref_metadata_2025_split huggingface dataset:
Cell proliferation in the developing wing-bud of normal andtalpid3 mutant chick embryos
Authors: Ede D. A. , Flint O. P. , Teague P. 
Published: April 2021

ABSTRACTPrevious measurements on mitotic division rate or cell cycle time have been made on samples from a few discrete limb regions or by continuous sampling, but only down a unidimensional limb axis, disregarding morphological discontinuities such as the presence or absence of cartilage. This study presents a new analysis on normal and talpid3 mutant chick embryos, measuring mitotic rate and also cell density through the central proximo-distal axis and at the limb periphery, taking into account the development of cartilage regions. Differentiation of cartilage is correlated with a marked drop in mitotic rate, accounting for a proximo-distal gradient of mitosis in central counts which was not observed at the limb periphery. Talpid3 limbs at an early stage show a central mitotic gradient, but the reverse of that observed in normal limbs.
The early development of haploid and aneuploid parthenogenetic embryos
Authors: Kaufman Matthew H. , Sachs Leo 
Published: April 2021

ABSTRACT
The early development of parthenogenetically activated oocytes has been studied in. C57BL × CBA-T6T6 (F1T6) translocation heterozygote mice and C57BL × CBA-LAC (F1LAC) mice. All F1T6 oocytes had either a quadrivalent or a univalent-trivalent configuration at meiosis I; no such chromosome configurations were observed in the F1LAC oocytes. At ovulation 36·5% of the F1T6 oocytes had 19 or 21 chromosomes, whereas 97% of the F1LAC had the normal haploid chromosome number of 20. After parthenogenetic activation, chromosome counts at metaphase of the first cleavage mitosis were made of the eggs with a single pronucleus following extrusion of the second polar body. These activated eggs had similar frequencies of 19, 20 and 21 chromosomes as had the oocytes at ovulation. The activated 1-cell eggs were transferred to the oviducts of pseudopregnant recipients and the embryos recovered 3 days later. At this stage of development, most of the F1T6 embryos with 19 chromosomes were no longer found, but the frequency of 21-chromosome embryos was similar to the frequency of 21-chromosome oocytes and activated eggs. There was a similar mean number of cells in the embryos with 20 and 21 chromosomes.
The results indicate that nearly all the embryos with 19 chromosomes failed to develop, probably beyond the 2-cell stage, whereas oocytes with 21 chromosomes had a similar development to oocytes with 20 chromosomes up to the morula stage.
Mitotic activity of germ cells during normal development ofXenopus laevistadpoles
Authors: Ijiri Ken-Ichi , Egami Nobuo 
Published: April 2021

ABSTRACTData on the spatio-temporal pattern of germ cell proliferation in Xenopus laevis tadpoles were obtained, tracing the germ cells from the cloacal position forward. This spatial pattern in germ cell distribution and its change during normal development clearly coincided with histological observations of germ gland development. By application of regression lines to the analysis of this complex pattern, an interesting conclusion about the mitotic activity of germ cells was suggested. While the mitotic activity of germ cells before sexual differentiation shows a regional difference along the germ-cell-containing ridge (GCCR), the doubling time of sexually differentiated gonia seems to show a uniform value over the whole GCCR.
Abnormalities in the differentiation and cellular properties of hyperplastic lens epithelium from strains of chickens selected for high growth rate
Authors: Clayton R. M. , Eguchi G. , Truman D. E. S. , Perry M. M. , Jacob J. , Flint O. P. 
Published: April 2021

ABSTRACTSimilar morphological abnormalities of the lens of the eye of two unrelated strains of chicks, both of which had been selected for high growth rate, were found to be associated with epithelial cells showing marked deviations from the normal in cell surface properties, mitotic rate, capacity for differentiation, and in DNA, RNA and protein metabolism. The relationship between these modified properties and the observed morphology is discussed.
Complete preimplantation development in culture of parthenogenetic mouse embryos
Authors: Kaufman Matthew H. , Sachs Leo 
Published: April 2021

ABSTRACTThe present experiments were undertaken to determine whether, in parthenogenesis, heterozygous embryos develop better than homozygous embryos. Such experiments may provide an approach to elucidating whether fertilized embryos develop better than parthenogenetic ones because of heterozygosity, or if the sperm provides another contribution necessary for complete embryonic development. The parthenogenetic embryos studied included uniform haploids after extrusion of the second polar body, mosaic haploids in which each blastomere contained a genetically different haploid nucleus, and heterozygous diploid mouse embryos. Eggs were activated and cultured in a chemically defined medium. About three times as many mosaic haploid or heterozygous diploid eggs developed beyond the 4-cell stage after 98-100 h and to the blastocyst stage after 120 h in culture, than uniform haploid eggs. This indicates that the development of parthenogenetic embryos is probably under genetic control and that there was a better development of the heterozygous embryos. Mosaic haploid embryos showed the same high frequency of development as heterozygous diploids. The results therefore indicate that heterozygosity provided a developmental advantage even when distributed between two genetically different clones of cells in the same embryo.
Effects of formamide on neuroepithelial cells and on interkinetic nuclear migration in the chick embryo
Authors: Messier Paul-Emil 
Published: April 2021

ABSTRACT
Young chick embryos were incubated on media containing formamide at concentrations of 0·1,0·25, 0·31,0·37, 0·43 and 0·5 M. Tn the neuroepithelium of these embryos we found that (1) the 0·1 M concentration had no detectable effect, (2) the 0-25 M concentration only affected mitosis which was blocked in metaphase so that mitotic figures accumulated near the neuro-coele, (3) 0·31 M formamide totally inhibited interkinetic nuclear migration and affected only slightly the cell asymmetry, (4) the 0·37 M concentration considerably reduced the amount of cytoplasmic microtubules and that the cells became round, (5) at 0·43 M formamide, all microtubules had disappeared and all cells were spherical, (6) at 0·5 M formamide all cells were spherical, detached from one another and the epithelium had lost its usual characteristics. Our results on exposure of the cells to low temperature (2 °C) suggest that formamide directly affects microtubules. All the effects observed at concentrations up to 0·43 M formamide are reversible.
A descriptive study of the rate of elongation and differentiation of the skeleton of the developing chick wing
Authors: Summerbell Dennis 
Published: April 2021

ABSTRACTDifferentiation of the wing skeleton is clearly visible in whole mounts from stage 24. It proceeds in proximo-distal and postero-anterior sequence. It is possible to map the part of the limb giving rise to each skeletal element as it appears and subsequently. This enables one to estimate: (a) a rate of elongation curve for each segmental level, (b) the intrinsic rate of change of elongation of the cartilage, (c) a definitive extrapolation back to classical presumptive fate maps, (d) the normal range of variation in the proportion of the limb occupied by the three main segmental levels (stylopod, autopod, zeugopod).
Etude de la mise en place de la patte imaginale deTenebrio molitor: 1. Analyse expérimentale des processus de restauration au cours de la morphogenése
Authors: Huet CL. , Lenoir-Rousseaux J. J. 
Published: April 2021

ABSTRACTAdult leg development of Tenebrio molitor: IExperimental analysis of the restoration process during morphogenesisThe leg of the last instar larva, and especially the pharate pupa, of Tenebrio molitor (Colebptera) shows considerable restoration ability. Restoration refers to the regeneration of leg structures removed during the last larval instar. This process involves only those tissues adjacent to the cut surface. At each level of the leg, amputation before a characteristic time leads to the restoration of a complete leg, but thereafter the new segments formed are hypomorphic or just lobes. After an amputation close to the pupal ecdysis, fragments are obtained, and these incomplete structures show that the restoration process has ceased. Just before the pupal ecdysis the leg is withdrawn from the cuticle, so a very late amputation does not effect the leg tissue and a complete pupal and adult leg is formed.The whole of the larval leg participates in adult leg morphogenesis, and histological techniques demonstrate a great correspondence between larval and adult leg segments. The larval trochanter, however, forms the adult trochanter and the proximal part of the femur. The larval tibia forms the adult tibia plus tarsus, except for the adult claws which develop from the larval tarsal claw.
Cell specific events occurring during development
Authors: Rutherford Charles L. 
Published: April 2021

ABSTRACTUltra-microfluorometric techniques were adapted to follow the time sequence of glycogen degradation during the differentiation of two cell types in Dictyostelium discoideum. Glycogen content, glycogen phosphorylase activity, and inorganic phosphate accumulation were localized in specific cell types during stalk and spore development.Glycogen levels in pre-stalk cells remained constant during the pseudoplasmodium and early culmination stages of development. However, as pre-stalk cells migrated into the position of stalk formation, a cell specific degradation of glycogen was observed. The loss of glycogen from pre-stalk cells was accompanied by an increase in the activity of glycogen phosphorylase. This increase in activity from 0·04 to 0·14 moles/h/kg dry wt. occurred as pre-stalk cells entered the position of stalk formation. An inverse relationship was found between glycogen levels and inorganic phosphate (Pi) levels in the developing stalk. During the process of stalk construction, a gradient of Pi levels occurred from the apex to the base of the developing stalk. Glycogen degradation from pre-spore cells lagged behind that of pre-stalk cells. No change in pre-spore cell glycogen levels was observed until stalk construction was nearly completed. The results emphasize the importance of the physical position of a cell with respect to its composition and fate during development.
Isoenzyme transitions of creatine phosphokinase, aldolase and phosphoglycerate mutase in differentiating mouse cells
Authors: Adamson Eileen D. 
Published: April 2021

ABSTRACTExtracts of embryonic mouse tissues (skeletal, cardiac and smooth muscle, and brain) were analysed by Cellogel electrophoresis, for their isoenzymic distributions of three enzymes, creatine phosphokinase, aldolase and phosphoglycerate mutase. Embryonic tissues from the 12th day to the end of gestation were examined for isoenzyme transitions, and it was found that the adult forms of these enzymes appeared during gestation. Extracts from cloned teratocarcinoma cells were similarly examined in order to determine their degree of bio-chemical differentiation. Undifferentiated embryonal carcinoma cells contained only the early embryonic forms of all three enzymes, while differentiated cells formed in vivo, and in some cases in vitro, started to express the adult types of creatine phosphokinase and aldolase. Thus, biochemical parallels have been demonstrated between developing embryonic tissues and teratocarcinoma cells differentiating in vitro.
Melanoblast-tissue interactions and the development of pigment pattern inXenopuslarvae
Authors: Macmillan Gillian J. 
Published: April 2021

ABSTRACTThe melanophores of larval Xenopus laevis are disparately distributed on the hypomere in that the upper region (UHT) is densely pigmented, the median region (MHT) is moderately pigmented, and the lower region (LHT) is unpigmented. The roles of the melanoblasts and their tissue environment in determining the melanophore pattern was investigated by heterotopic transplantation of hypomeric tissues, culture of neural crest explants in vesicles derived from hypomeric tissues and radioactive marking of neural crest cells.Somite-situated grafts of UHT, MHT and LHT were found to possess melanophore densities similar to those exhibited by such hypomeric tissues when in their normal situation.The number and distribution of trunk melanophores in ‘crestless’ second host larvae bearing grafts of UHT, MHT and LHT transferred from the somites of primary host embryos indicated that (a) many melanoblasts entered all transplants during neural crest migration in the primary host: subsequently, a small number of melanoblasts were lost from transplants of UHT, a greater number from transplants of MHT and almost all from transplants of LHT; (b) almost all melanoblasts migrated out from transplants of MHT and LHT and entered the tissues of the ‘crestless’ host, whereas a considerable number of melanoblasts remained in the transplant when it was formed from UHT.Grafts of UHT placed mid-ventrally in the hypomere failed to exhibit melanophores.Vesicles of (a) UHT + MHT and (b) LHT containing neural crest tissue possessed similar numbers of melanophores. Vesicles of LHT differed from those of UHT 4-MHT in that melanophores were densely aggregated in the implanted neural tissues.Following radioactive marking of neural crest cells labelled nuclei were found on the dorsal ridges of the somites, the surfaces of the neural tube and notochord and in the mesoderm of the upper hypomere and the fin, but were absent from the lateral surfaces of the somites.These results showed that the melanophore pattern in larval Xenopus depended upon melanoblast-tissue interactions, which influenced the migration, rather than the differentiation, proliferation or destruction, of melanoblasts and suggested that tissue selection by migrating melanoblasts enabled these cells to distribute themselves in embryonic tissues in accordance with a hierarchy of melanoblast-tissue affinities.Melanoblast-tissue affinities appeared to be related to the adhesiveness of mesodermal cells: melanoblast extensibility appeared to facilitate exploration of the surrounding tissues.The formation of pigment pattern in larval Xenopus appeared to depend upon the interaction between the melanoblast population pressure and melanoblast-tissue affinities.The present results and those of other workers on amphibian pigmentation were used to construct a model capable of accounting for species-specific differences in larval amphibian pigment patterns, in terms of interactions between species-specific differences in melanoblasttissue affinities and melanoblast population pressure.
Cell death in ovarian chambers ofDrosophila melanogaster
Authors: Giorgi F. , Deri P. 
Published: April 2021

ABSTRACTAn ultrastructural analysis has been made of certain ovarian chambers undergoing abnormal development. The earliest morphological change in these chambers consists of the alteration of the nuclear material which is then followed by engulfment of portions of the nurse cell cytoplasm, including the nuclear fragments, into the overlying follicle cells. The continuation of this process leads to the progressive disappearance of nurse cells with the concomitant formation of huge dense vacuoles in the follicle layer. The morphological features described in the present investigation are similar to those found in other tissues and interpreted as leading to cell death. It is suggested that certain ovarian chambers undergo cell death as a result of the incapability of fürthering their development. The role played by cell death in oogenesis is also discussed on the basis of the current literature.
Evolution of the nucleolar apparatus during oogenesis in Acipenseridae
Authors: Raikova E. V. 
Published: April 2021

ABSTRACTEvolution of the nucleoli has been followed during oogenesis in the Acipenserid fishes, Acipenser ruthenus (the sterlet) and A. güldenstädti (the sturgeon) using light and electron microscopes. In the ovaries of adults, the oogonial nuclei usually have a single nucleolus with an adjacent mass of paranucleolar fibrillar material. The cytoplasm of the oogonia contains two dense bodies peculiar only to gonocytes, one being electron dense and containing RNA and the other being electron-lucent and lacking RNA. Neither is surrounded by membrane. The fine structure of the electron-lucent body is identical to that of the paranucleolar material, while the RNA-containing body structurally resembles the nucleolus. A nuclear origin for both cytoplasmic bodies is likely.Leptotene-stage oocytes usually still have a single nucleolus. During zygotene, it is adjacent to the nuclear envelope and opposite to the chromosomes contracted in synizesis. At pachytene, a ‘cap’ of extrachromosomal chromatin is formed under the nuclear envelope and around the nucleolus. Bivalents also contact this cap. In early diplotene, the primary nucleolus still persists. The material of the cap is dispersed beneath the entire nuclear envelope in the form of granules of extra DNA; each granule then produces a peripheral (secondary) nucleolus. These become typical amphinucleoli with differentially developed granular parts, depending on the age of the nucleolus and the stage of meiosis. Their fibrillar parts always face the nuclear envelope. New peripheral nucleoli continue to form as long as granules of extra DNA persist under the nuclear envelope, i.e. approximately until vitellogenesis.In early vitellogenesis, the peripheral nucleoli become transformed, by re-distribution of their fine structural components, into circular threads trailing towards the centre of the nucleus. The axis of the thread consists of fibres and is coated with granules. In late vitellogenesis, the nucleoli round up and become vacuolized; they are then peripheral again.Proteinaceous RNA-lacking structures which are also produced in the nuclei during oogenesis in the Acipenseridae, are the ‘nuclear bodies’ and. ‘spheres’. The former are adjacent to peripheral nucleoli, the latter form on lampbrush chromosomes. Both are ultra-structurally alike. The loops of lampbrush chromosomes produce also RNP bodies (‘granules’ of Callan & Lloyd, 1960) which are ultrastructurally similar to nucleoli but lack segregation of granules from fibres into spatially distinct parts.The evolution of the nucleolar apparatus during oogenesis in the Acipenseridae closely resembles that in amphibians.
Mechanisms of teratogenesis*
Authors: Saxén Lauri 
Published: April 2021

ABSTRACTIn view of the great number of teratogenic factors known and the vast array of congenital defects, disorders and syndromes, it would probably be a waste of time to search for unifying mechanisms and principles in abnormal development. Instead, therefore, I shall describe a selection of teratogens and their consequences, and try to arrange them in a certain hierarchy based on a simplified model of how they act.
Cleft palate induction in hamster fetuses by glucocorticoid hormones and their synthetic analogues
Authors: Shah Ravindra M. , Kilistoff Alan 
Published: April 2021

ABSTRACT
The effect of prenatal administration of different doses of cortisone, corticosterone, dexamethasone, triamcinolone and prednisolone on the fetus and its palatal development was studied. All the glucocorticoids, except cortisone, produced cleft palate in the fetuses. Both the total frequency and morphologically different types of cleft palate were related to the dose of the teratogen. Triamcinolone appeared to be more potent than other glucocorticoid in inducing cleft palate. An association was noted between fetal growth inhibition, the dose of the teratogen and the frequency and type of cleft palate.
Cell division patterns in the Drosophila head disc : clones on the head cuticle
Authors: Ransom Robert 
Published: April 2021

ABSTRACT
An account of the patterns of clones induced on the head cuticle of Drosophila melanogaster is given. The system was studied using mitotic recombination, induced by X-rays at certain developmental stages. In agreement with the findings of a computer model devised to simulate growth in the head imaginal disc, cuticle clones are found to have a characteristic pattern, sweeping round the central, eye-forming part of the disc. The similarity between model and experiment suggests the validity of the model assumption. It is also shown that cuticle clones are not smaller in the posterior of the head, when induced at the developmental stages studied : this is in contrast to clones in the compound eye, where posterior clones are smaller than anterior ones.
Effects of testosterone implants in pregnant ewes on their female offspring
Authors: Clarke I. J. , Scaramuzzi R. J. , Short R. V. 
Published: April 2021

ABSTRACT
Pregnant ewes were implanted with 1 g testosterone between days 30 –80, 50 –100, 70 –120 or 90 –140 of gestation. Ewes treated between days 30 –80 and 50-100 showed increased aggressive behaviour and clitoral enlargement, whereas this was not seen in the day 70 –120 or 90 –140 groups. Although the implants released similar amounts of testosterone at all stages of gestation, plasma testosterone concentrations were lower in the day 70 –120 and 90 –140 groups. The increased testosterone clearance in late gestation could be a result of increased placental aromatization. Masculinization of the genital tubercle was complete in female lambs in the day 30 –80 group, partial in the day 50 –100 and 70-120 groups, and absent in the day 90-140 group. These results therefore suggest that the ‘critical period’ for masculinization of the external genitalia is between days 40 and 50 of foetal life. In contrast to this anatomical masculinization, one aspect of behavioural masculinization had a later critical period, since female lambs of 30 –80, 50 –100 and 70 –120 day groups adopted male-like urination postures, whereas the day 90 –140 offspring showed the normal female pattern.
Biochemical and cytochemical studies on adenylate cyclase activity in the developing rat submandibular gland: differentiation of the acinar secretory compartment
Authors: Cutler Leslie S. , Rodan Sevgi B. 
Published: April 2021

ABSTRACT
To investigate membrane changes in development of the exocrine cells of the rat submandibular gland (SMG), biochemical and cytochemical studies of adenylate cyclase activity were performed on prenatal and postnatal glands. SMG rudiments and glands were studied from 15 days of gestation up to birth and 1, 2, 3, 4 and 24 weeks after birth. Glands were chemically assayed for adenylate cyclase activity using the procedures of Salomon and coworkers and cytochemically studied using a procedure which was verified biochemically. At .15-16 days of gestation basal adenylate cyclase activity was low and no staining could be observed. Adenylate cyclase activity rose six-fold from the 16th to the 18th day of gestation. Adenylate cyclase staining became evident along the surface of most of the cells of the rudiment at this time. Basal adenylate cyclase activity remained relatively constant from the 18th day of gestation up to 24 weeks of age. However, sequential changes were seen in the cytochemical localization, especially in relation to the apical plasma membrane of the developing secretory cells.