bluuebunny/crossref_metadata_2025_split huggingface dataset:
A comparative study of the mechanisms by which X-irradiation and genetic mutation cause loss of vibrissae in embryo mice
Authors: Jacobson C. M. 
Published: April 2021

ABSTRACT
Both X-irradiation and certain genetic mutations can produce loss of vibrissae in mice. The aim of this investigation was to determine whether disruption occurred at the same point in development and in the same manner. Histological investigation was made of vibrissae during early stages of development. It was found that two periods of epigenetic crisis exist in vibrissa develop-ment, one at the time of site determination and the other at the time of follicle-papilla interaction when development has just been initiated. Irradiation damage acts by disrupting this follicle-papilla interaction. If the contact is broken in the very early stage, the vibrissa will degenerate. If irradia-tion acts a little later, when the cells are less sensitive, the contact is not broken, and the vibrissa follicle cells will recover from the damage and continue to develop. In one mutation studied, the same interaction was destroyed because there was a genetic abnormality in the papilla. This produced the same ultimate effect as did irradiation. In other cases, the mutation acted on the first crisis, affecting the site determination. Here, although the apparent effect was the same as in irradiation, the mechanism differed.
Experimental studies on the role of ‘polar granules’ in the segregation of pole cells in Drosophila melanogaster
Authors: Jazdowska-Zagrodzińska Bożenna 
Published: April 2021

ABSTRACT
When Drosophila eggs are centrifuged at 4250 g posteriorly, anteriorly and laterally, the highest mortality rate was found among the eggs centrifuged posteriorly (46 %) and the smallest among those centrifuged laterally (20 %). The pole plasm is not displaced by centrifugation at 4250 g. Polar granules begin to move when centrifuged at 2700 g for 30 min; complete removal of granules takes place at 4250 g for 10 min. When polar granules are removed from the pole plasm no pole cells are detached from the egg. Polar granules shifted from the pole plasm to other regions do not induce the detachment of any cells similar to pole cells. Both pole plasm and polar granules, in association, are indispensable for pole cell formation in Drosophila melanogaster.
A reinvestigation of some of the tissue movements involved in the formation of the neural tube and the eye/lens system of Triturus alpestris and Xenopus laevis
Authors: Lowery R. S. 
Published: April 2021

ABSTRACT
A scheme of eye/lens development suggested by Chanturishvili is described and compared with the ‘classical’ scheme of Spemann. A cine-micrographic examination of the ectodermal movements involved in neural tube formation in Triturus alpestris and an experimental embryological investigation of the process in Xenopus laevis provided data consistent with the classical scheme and irreconcilable with Chanturishvili’s suggestion that the whole eye/lens system originates as a single continuous anlage within the flat neural plate of Amphibia.
Effects of temperature on reptilian and other cells
Authors: Stephenson N. G. 
Published: April 2021

ABSTRACT
Reptilian cells, whether from adult organs or from entire embryos, may be cultured satisfactorily in Medium 199, to which is added 20 % foetal-calf serum. This medium, used at normal strength, is adequate even for the maintenance and proliferation of kidney and liver cells from an amphibian tadpole, but the performance of cells of lower vertebrates in the medium is inferior to that of mammalian and avian cells. When cultured for periods of at least 2 days, avian cells survive in an apparently normal fashion at higher temperatures (maximal, 45 °C) than reptilian; reptilian cells at higher temperatures than mammalian; and mammalian cells at higher temperatures than amphibian. There is a close correspondence between the lethal high temperatures of embryonic cells of diurnal lizards in culture (42-43 °C) and the known heatdeath temperatures of adult animals. Although inactive and contracted in culture at 3 °C, reptilian, avian and mammalian cells remain viable, often for prolonged periods without change of medium. The optimal temperature for cell culture is in the vicinity of 37·5 °C for reptilian, avian and mammalian cells, and about 31·5 °C for the amphibian cells used. Different types of cells from the same animal may have different temperature ranges. Epithelioid cells, for example, function better at higher temperatures than fibroblasts and in some cases may be shown to have a slightly higher maximal temperature. Dissociated epithelioid cells in culture may adopt a fibroblast-type of morphology, wandering on the glass surface with extended processes, or they may come together with other similar cells to form epithelial sheets. Fibroblasttype cells may contribute to monolayer formation, but do not join with epithelioid cells to form epithelial sheets.
Experimental evidence for the nuclear control of differentiation in Micrasterias
Authors: Selman G. G. 
Published: April 2021

ABSTRACT
After individual cytoplasmic lobes of growing hemicells of Micrasterias were irradiated for 30 or 60 s with a microbeam of ultraviolet light 20 in diameter, the corresponding parts of the fully developed wings were stunted. Tn subsequent divisions the new hemicells were normal. In one case a hemicell, grossly malformed as a result of a 5 min dose of ultraviolet light to the cytoplasm, did not give a completely normal hemicell in the first seven divisions after treatment, although it did so in subsequent divisions. Abnormal development was induced with dinitrophenol. The ultraviolet microbeam irreversibly inactivated the nucleus when applied to it for longer than 5 s. Growth continued after nuclear inactivation but neither thickening of the cell walls nor differentiation took place. After applying the microbeam to the nucleus for 3-4 s, an anuclear type of development was followed by cell-wall thickening without differentiation. Subsequent divisions took place normally. After applying the microbeam to the nucleus for 2 s, partial differentiation took place and subsequent divisions were normal. By allowing hemicells to develop in the presence of actinomycin D at high concentrations for short periods, exactly the same patterns of abnormal development followed by cell recovery were observed as after ultraviolet irradiation of the nucleus. From the experiments, estimates were made of the times of nuclear determinations of lobe-splitting, cell-wall thickening and differentiation. Nuclear determination appeared to take place between 30 and 155 min before the developmental event was observed under the light microscope.
Thyroid growth and its relationship to metamorphosis in Rana temporaria
Authors: Fox Harold 
Published: April 2021

ABSTRACT
Thyroid growth of larvae of Rana temporaria was investigated in relation to specific stages (29-54 inclusive; see Cambar & Marrot, 1954) and events in the metamorphic cycle. Growth is by cellular multiplication and vesicular enlargement, and from stage 41 (16 mm larva) to almost the end of metamorphosis cell volume is constant. Maximum rate of growth in vesicular, tissue and overall volumes occurs between stages 41 and 45 (16 and 28 mm) respectively.
The release of soluble H-2 alloantigens during disaggregation of mouse embryo tissue by a chelating agent
Authors: Edidin Michael 
Published: April 2021

ABSTRACT
Treatment with chelating agents binding divalent cations has been found to effect the dissociation of a variety of tissues of both embryo and adult animals (reviewed in Steinberg, 1958). In the course of dissociation it appears that materials are released from cell surfaces which play a part in their specific adhesion, and which may be shown experimentally to promote selectively the re-aggregation of dissociated cells (Humphreys, 1963; Moscona, 1963). The extracted materials appear to be glycoprotein complexes (Humphreys, 1965), made up of fairly small subunits, estimated to be of 13000-20000 molecular weight (Margoliash et al. 1965). Units of about the same size appear to be the antigenic sites involved in the blocking of sponge cell aggregation by rabbit anti-sponge serum, specific for a given sponge species (MacLennan, 1963). I shall here present evidence that materials of similar molecular weight bearing immunological specificities of the H-2 alloantigen system are released from the tissues of certain mouse embryos during the course of their dissociation by the chelating agent Versene (ethylenediaminetetraacetic acid).
More about the. tabby mouse and about the Lyon hypothesis
Authors: Grüneberg Hans 
Published: April 2021

ABSTRACT
The Lyon hypothesis (L.H.) of dosage compensation of sex-linked genes in mammals postulates that in the female, during embryonic development and at the cellular level, either the paternal or the maternal X-chromosome is inactivated; that this inactivation happens at random; and that it persists in the descendants of the cell in which it has taken place. The genetic evidence hitherto adduced as favouring the L.H. has mainly involved complex situations such as the simultaneous segregation of two sex-linked genes and/or the behaviour of genes in structurally abnormal chromosomes.
By contrast, this paper examines the behaviour of sex-linked genes in mammals (other than man) taken one at a time and in structurally normal X-chromosomes. Criteria are discussed by means of which the validity of the L.H. in such genetically simple situations can be tested. These tests reveal that the behaviour of heterozygotes for three sex-linked genes in the mouse (tabby, striated, brindled) is decisively at variance with the L.H., and the same is probably true for a fourth gene, bent-tail. The remaining sex-linked genes in the mouse give no evidence for or against the L.H. As there is thus clear evidence that in three, and probably in all four instances, both alleles are active as in ordinary autosomal heterozygotes, it is evident that in the mouse there is no inactivation of a whole Jf-chromosome. Indeed, the facts discussed in this paper (including those of one instance each in hamster, cattle and cat) do not suggest that there is any inactivation at all.
Nonetheless there is a suspicion that heterozygotes for sex-linked genes, taken as a group, may include more cases of semi-dominance than occur in autosomal heterozygotes. If this should be substantiated, it would require an explanation.
Limited axial structures in nodeless chick blastoderms
Authors: Butros Joseph 
Published: April 2021

ABSTRACT
Definitive streak to head-fold blastoderms were given two lateral cuts parallel to the streak and a third transverse cut at 0·35 mm posterior to the pit, thus removing a rectangular piece around the node 0·8 × 0·35 mm in area. Upon explantation many of these U-blastoderms developed somites and neural tubes, but notochords were absent. Two types of controls were used: posterior segments of blastoderms produced by transection at 0·35 mm posterior to the pit, and lateral regions of blastoderms explanted from outside the central 0·8 mm zone. These controls did not develop true somites or neural tubes but did form ectodermal invaginations and mesodermal aggregations in the midline. The results are interpreted as manifestations of an increase in the amount of mesoderm and of the space available for morphogenetic movements.
Inductive influence of testosterone upon central sexual maturation in the rat
Authors: Smith W. N. Adams , Peng M. T. 
Published: April 2021

ABSTRACT
The influence of testosterone propionate upon the central sexual maturation of the male rat has been investigated. Male rats castrated on the day of birth and injected with testosterone propionate at 5, 10 or 20 days of age had immature ovarian tissue transplanted to the anterior chamber of one eye when 3 months old. Ovarian grafts in castrate males injected with testosterone at 5 or 10 days of age did not show cyclical activity. Grafts in non-injected castrates or hosts injected with testosterone at 20 days of age showed cyclical activity. The site of action of testosterone is discussed, and it is suggested that it may have an inductive influence upon the sexual maturation of the rat brain.
Induction of the trophoblastic giant-cell transformation after ovariectomy in the mouse
Authors: Dickson A. D. 
Published: April 2021

ABSTRACT
Mice were ovariectomized on the fourth day of gestation and the trophoblastic giant-cell transformation sought in blastocysts recovered from them after progesterone or corn oil had been injected or no treatment given. The giant-cell transformation does not occur in blastocysts of untreated mice. It does take place after progesterone but not after corn oil injection on the fourth day. The transformation does not occur after progesterone on the sixth, seventh and eighth days. Progesterone injection on the fourth day is associated with growth of the blastocyst as a whole and also of its inner cell mass.
A quantitative assessment of mesenchymal contribution to epithelial growth rate in mouse embryonic lung developing in vitro
Authors: Alescio Tommaso , Piperno Emilia Colombo 
Published: April 2021

ABSTRACT
The growth rate of the epithelial tree of mouse embryonic lung cultured in vitro was studied after removal of the right or left part of the rudiment, or after modification of the epithelium/mesenchyme ratio to about one-half of the normal. The epithelial growth rate is enhanced in both experimental conditions well above that of the controls. No satisfactory explanation can be put forward, so far, for the fact that when the total mass of the rudiment is reduced without any change in the ratio of the tissues, the growth rate of the epithelium is enhanced. From the results of the experiments in which the ratio of the two tissues was experimentally changed the conclusion may be suggested that, under the reported conditions of growth in vitro, lung mesenchyme exerts some stimulating influence on the total growth of the epithelium, expressed as total amount of branching, and that this influence is to some extent proportional to the amount of mesenchyme as compared with epithelium.
Etude sur la différenciation in vitro de l’épithélium œsophagien embryonnaire de Souris. Action de la vitamine A et de l’hydrocortisone
Authors: Soriano Luis 
Published: April 2021

ABSTRACT
A study of the differentiation in vitro of the mouse embryonic oesophageal epithelium. The effects of vitamin A and of hydrocortisone
Fragments of embryonic (18 days) oesophagus cultured in standard medium for 8 days achieved a minimum degree of keratinization. Appropriate doses of absolute alcohol administered over the same period enhanced normal keratinization. Vitamin A inhibited keratinization, and differentiation into multistratified epithelium or into a minimally keratinized epithelium took place. The effect of vitamin A depends upon the duration of its administration. Hydrocortisone in concentrations of between 1·1 μg/ml and 10 μg/cc inhibits keratinization in a similar way but with the difference that vacuolated and degenerating cells are found in some of the epithelial cultures. Low concentrations of hydrocortisone (0·5 μg/ml) stimulate keratinization after 9 days of culture. Vitamin A and hydrocortisone in combination appear to be toxic in some cases though they usually together inhibit keratinization in a manner similar to their separate effects. However, there is some evidence of synergistic activity. When explants are treated first with hydrocortisone (0·5 μ g/ml) and later with vitamin A (6·6 i.u./ml) they show predominantly the influence of the vitamin, i.e. inhibition of keratinization. When the reverse treatment occurs, i.e. vitamin A followed by hydrocortisone, most explants show full keratinization.
These results show that it is the last-acting of two opposing influences that is effective in controlling the differentiation of cultured mouse oesophageal epithelium.
Inducing activity in extracts from Xenopus embryos and from isolated dorsal lips
Authors: Deuchar E. M. 
Published: April 2021

ABSTRACT
Tiedemann and his collaborators (Tiedemann, Becker & Tiedemann, 1961) have demonstrated both neural- and mesodermal-inducing activity in extracts from whole gastrulae and neurulae and from ventral gastrula ectoderm of Triturus alpestris. They have also obtained a wide range of inductions from subcellular fractions of 9-day chick embryos (Tiedemann, Kesslring, Becker & Tiedemann, 1962). Microsomal and ribosomal fractions were particularly active. A further finding was that the inducing activity of gastrula ectoderm could be enhanced by phenol treatment (see Tiedemann, 1963, for review). Latterly most of the work has been pursued with chick extracts, and no systematic study of the inducing ability of extracts from different embryonic stages of an amphibian has so far been reported.
Studies on the cell degeneration rate during the differentiation of the epithelium in the uterine cervix and Müllerian vagina of mouse
Authors: Forsberg John-Gunnar 
Published: April 2021

ABSTRACT
Glücksmann (1951) has summarized the results of earlier investigations on cell degeneration processes during normal vertebrate development. To the few investigations on the degeneration in the urogenital region made before the publication of Glücksmann’s paper (1951) can be added Bengmark’s study (1958) on degeneration processes during the separation between the Wolffian duct and the ureteral anlage and Forsberg’s study (1961) on the mechanism of the division of the cloaca. Finally, Forsberg (1963) has given a description of those regions where degeneration can be seen during the development of the vaginal anlage in several species, including man.
Effects of position in the uterus on fetal mortality and on response to trypan blue
Authors: Beck Sidney L. 
Published: April 2021

ABSTRACTIn three strains of mice and an outcross of each to ZRDCT-An, the fetuses occupying the implantation site nearest the common uterus are less likely to survive than the ones nearest the ovary. When dams are treated with trypan blue, mortality in excess of the spontaneous frequency seems greater in the ovarian than in the cervical position. Both the heterogeneity of distribution of spontaneous mortality and the suggestion of treatment-position interaction show the importance of intra-uterine selection upon survival of a developing organism. None of the data are inconsistent with the hypothesis that one mechanism of selection is through variations in blood supply in different regions of the uterus.
Regeneration and growth control inNereis
Authors: Golding D. W. 
Published: April 2021

ABSTRACTThe annelid body, as typified by that of Nereis, consists of a presegmental prostomium, a number of segments, and a postsegmental pygidium. The larval trochosphere is unsegmented. Once proliferation of segments has started, their number increases steadily throughout most of the life of the adrenal, though the rate of proliferation declines (Clark & Clark, 1962). New segments are added posteriorly by proliferation and differentiation of tissue comprising the growth zone, which forms the anterior border of the pygidium. After loss of the pygidium and posterior segments, wound healing is followed by the formation of a new growth zone. Amoebocyte migration (Stephan-Dubois, 1955,1956,1958) and dedifferentiation of cells adjacent to the level of transection (Herlant-Meewis & Nokin, 1962) are important in the early stages of regeneration. Proliferation of segments recommences and they are produced more rapidly than they are in the intact animal, as will be shown later.
Studies on pattern regulation in Hydra
Authors: Webster Gerald 
Published: April 2021

ABSTRACT
The effect of colcemide and puromycin on polarity and regulation in hydra has been investigated at the biological level using isolation and transplantation techniques. Colcemide treatment of hydra from which the hypostome has been removed can bring about an alteration of polarity so that multiple distal structures (hypostome and tentacles) can form on a single animal. Such forms do not arise if the original hypostome is not removed. Treatment with puromycin is much less effective in altering polarity. Transplantation experiments indicate that hypostome formation is inhibited by colcemide treatment but that this substance does not irreversibly affect the determined hypostome or the ‘adult’ hypostome which retain their organizing properties. Puromycin treatment does not inhibit hypostome formation completely since some animals reconstitute tentacles while in puromycin. However, the hypostome which is formed does not possess the normal resistance to absorption following transplantation. This result may indicate that the factors responsible for the organizing properties of the hypostome (i.e. tentacle induction) are distinct from those which control resistance to absorption. Both colcemide and puromycin change certain important properties of the subhypostomal region to those characteristic of more proximal regions. These properties are believed to ‘control’ polarity. The effects of colcemide and puromycin on polarity and regulation are discussed in terms of their effects on a control system which has been previously postulated to account for polarised regulation in hydra. This system involves axial gradients in time for hypostome determination, inhibition of hypostome formation and threshold for inhibition. The experimental results can be explained as a consequence of the direct or indirect action of these substances on the axial gradients.
The correlation of the processes of proliferation and determination in the morphogenesis of iris and ciliary body in rats
Authors: Stroeva O. G. 
Published: April 2021

ABSTRACT
In spite of the fact that causal embryology dealt extensively with the development of the eye in vertebrates, the iris attracted the attention of investigators only as a source of lens restitution in the course of Wolffian regeneration (Reyer, 1954, 1962; Goss, 1965; Scheib, 1965; Yamada, 1966). This is shown by the absence of sections on iris development in recent reviews devoted to the experimental analysis of eye development (Twitty, 1955; Lopashov & Stroeva, 1961 ; Coulombre, 1961, 1965a, b). The present communication reports a study of the development of the neural layers of iris and ciliary body in rat embryos.
Premeiosis and premeiotic DNA synthesis in the left ovary of the female chick embryo
Authors: Callebaut M. 
Published: April 2021

ABSTRACT
Cytological changes occurring during premeiosis in the germ cells of the ovarian cortex of the chick embryo were studied by means of Feulgen staining (specific for DNA).
The evolution of the preleptotene stages of the germ cells after 3H-thymidine pulses was investigated by the combination of pre- and post-autoradiographic observations and photographs.
The germ cells in premeiotic S phase present a particular structure, different from the structure found in germ cells during premitotic S phase. They are the direct precursors of the meiocytes in leptotene stage.