bluuebunny/crossref_metadata_2025_split huggingface dataset:
The role of the visceral yolk sac in mediating protein utilization by rat embryos cultured in vitro
Authors: Freeman Stuart J. , Beck Felix , Lloyd John B. 
Published: April 2021

ABSTRACT
Conceptuses from 9·5-day pregnant rats have been cultured for 48 h in heat-inactivated homologous serum. Embryonic development was normal. The protein contents of embryos and visceral yolk sacs after different periods of culture were recorded.
When 125I-labelled polyvinylpyrrolidone or [3H]dextran were added to the culture serum, radioactivity was accumulated by the yolk sac, but only background levels were detected in the embryo itself. The amount of radioactivity found in the yolk sac varied with the length of the interval before harvesting during which 125I-labelled PVP or [3H]dextran was present.
When formaldehyde-denatured 125I-labelled bovine serum albumin was added to the culture serum, little radioactivity accumulated in the yolk sac and only background levels were found in the embryo. Trichloroacetic acid-soluble radioactivity steadily appeared in the culture serum, however.
When conceptuses were cultured in glucose- and vitamin-supplemented dialysed serum from rats injected 2 h previously with [3H]leucine, radioactivity was found in both embryos and yolk sacs. The amount of radioactivity in these tissues increased with duration of exposure to 3H-labelled serum proteins. After short exposures little of the yolk sac and embryonic radioactivity was acid-insoluble, but this proportion increased with duration of exposure.
These results are interpreted as follows. Intact macromolecules cannot enter the cells of the embryo itself, but are captured by pinocytosis into the cells of the visceral yolk-sac endoderm. Indigestible macromolecules such as 125I-labelled polyvinylpyrrolidone and [3H]- dextran accumulate within the yolk-sac lysosomes, but proteins are digested there by the lysosomal enzymes. The radiolabelled digestion product of 125I-labelled bovine albumin is [125I]iodotyrosine, which cells cannot utilize and so is excreted into the culture serum. The labelled digestion product of the 3H-labelled rat serum proteins is [3H]leucine, which is used for protein synthesis in both embryo and yolk sac.
The experiments provide direct evidence for the long-suspected role of the yolk sac in mediating embryonic nutrition in the period of development prior to the establishment of a functional chorioallantoic placenta.
Size regulation inDictyostelium
Authors: Kopachik Will 
Published: April 2021

ABSTRACTThe division of large aggregate centres into separate slugs was examined in two strains of Dictyostelium discoideum which differ in size. The evidence is consistent with the hypothesis that the size of the slugs is determined by two factors; one is the ability of a tip to inhibit surrounding cells from forming an independent, rival tip; the other is the ability of the surrounding cells to resist being subjected to the inhibition of the newly arisen tip. If the surrounding cells are easily inhibited, then the slugs produced will be large; if they are resistant to inhibition the resulting slugs will be correspondingly small. An assay for tip inhibition was developed which was used to estimate the volume and distance over which inhibition occurs, the time over which it acts and the effect of tip size and cell mass shape on size regulation. The measurements and the results of experiments which showed inhibition across a thin agar layer are consistent with the hypothesis that an inhibitor spreads out from the tip by simple diffusion. In further studies it was found that although inhibition strength varies with the size of the tip, the ability to inhibit was the same in both strains whereas the resistance to inhibition was greater in the smaller strain.
A correlation between the capacity of cavity formation and the subsequent differentiation of teratocarcinoma embryoid body lines
Authors: Uno Kazuko 
Published: April 2021

ABSTRACT
Seven different embryoid body (EB) lines of mouse teratocarcinoma were isolated from a single EB. With regard to each of the lines, a comparison was made of the following developmental properties, including potentiality: (1) cavity formation in a short term intraperitoneal passage, (2) growth in vivo, (3) cardiac muscle differentiation in vitro following intraperitoneal passage and (4) differentiation of solid tumours in vivo. These lines could be divided into three distinct groups with respect to their capacity for cardiac muscle differentiation. It has been shown that a high capacity for cell differentiation in vitro correlates well with the capacity for cavity formation of an EB during the in vivo period. This cavity formation was followed by the appearance of primitive-streak-like structures, from which mesodermal cells were subsequently formed.
Cell migration from the chick olfactory placode: a light and electron microscopic study
Authors: Mendoza A. S. , Breipohl W. , Miragall F. 
Published: April 2021

ABSTRACT
The differentiation of the olfactory placode in the chick has been studied using light and electron microscopy. Special attention was paid to the appearance of neuronal cells within the placodal ectodermal thickening, the migration of cells out of this tissue and the appearance of the first fila olfactoria in the differentiating olfactory mucosa.
Between the third and fifth day of incubation a large number of cells is observed leaving the base of the invaginating olfactory placode, often in contact with thin axon bundles. These cells are characterized by a well-developed Golgi apparatus, a considerable number of mitochondria and dense-core vesicles. The morphology of these migrating cells resembles that of cells observed near the basement membrane within the developing olfactory epithelium and is clearly different from the mesenchymal cells which are filled with poly-ribosomes. At the sixth day of incubation thick axon bundles can be observed within the epithelium and the underlying lamina propria. The possible fate of the migrated epitheloid cells is discussed.
La Région caudale d’une Planaire est-elle capable d’induire la régénération d’un pharynx?
Authors: Sengel Catherine 
Published: April 2021

ABSTRACT
Experiments involving amputation and irradiation have been made on the fresh-water planarians Dugesia lugubris and Polycelis nigra to ascertain the precise roles of head and tail (Fig. 1) in the induction of a pharyngeal zone and of a pharynx. During the normal regeneration of a prepharyngeal cephalic fragment (region I, Fig. 2a), a pharynx regenerates in the original tissues of the fragment at the same time as the caudal blastema appears. During the normal regeneration of a postpharyngeal caudal fragment (region III, Fig. 2b), the pharynx appears in the new tissues of the blastema. The eyes of the regenerated head have by then already appeared. The caudal blastemata of cephalic fragments were cut away every day or every second day. A pharynx appears after a few days in the fragment (Fig. 3a). The cephalic blastemata of caudal fragments were cut away every second day. No pharynx regenerated under these conditions (Fig. 3 b). A zone close to the cut was irradiated with X-rays, which prevents the fragments regenerating for a long time. A pharynx appears in the cephalic fragment long before the regeneration blastema. In the caudal fragments, the pharynx cannot regnerate before the blastema has formed. It appears only after the blastema has differentiated into a head (Fig. 5). The same results have been obtained in another species of planarian, Polycelis nigra. The regeneration of the pharynx is therefore possible in a cephalic fragment, devoid of any blastema. The regeneration of a pharynx is impossible in a tail without cephalic, prepharyngeal or pharyngeal regions.
The Responses of Some Developing Feathers to X-rays
Authors: ’espinasse Paul G. 
Published: April 2021

ABSTRACT
Doses of up to 1,000 r. of X-rays administered to a patch on the back of the neck of Brown Leghorn capons had no permanent effects on either the structure or the colours of the feathers subsequently produced in the patch. A dose of 2,000 r. was followed by a marked and permanent loss of colour, but no recognizable structural abnormalities, beyond a slight reduction in size, in the feathers subsequently produced in the patch. The immediate response of an actively growing feather-germ to a dose of 2,000 r. was closely comparable with its known response to traumatic treatment such as cauterization. It can be understood as an abnormal and local moult. Feathers growing in the patch after a dose of 2,000 r., if they had colour at all, had it mostly at their distal ends. Series of feathers which were white with coloured tips were produced from identified follicles. The irradiation appears to have affected the physiological situation of the feather-germs in such a way as to forbid the melanocytes, though present and potentially functional, to enter the ectoderm in the normal way and to donate pigment. The melanocytes in these abnormal circumstances fail to develop normal processes. The melanin in them is in an abnormal physical state of aggregation. This condition is also to be seen in the non-donating ‘mulberry cells’ and in the coloured elements of some melanomata. This effect is probably due to a change in the ectoderm, but this change must be of a most restricted character since it does not interfere with the capacity of the ectoderm to produce structurally normal feather. Its nature is not yet understood.
Host-transplant Interactions in Biosynthesis of Drosophila Pteridines
Authors: Goldschmidt Elisabeth , Hadorn Ernst 
Published: April 2021

ABSTRACT
The isoxanthopterin deficiency of the mutant sepiaoid is a non-autonomous character. Non-autonomous changes in the level of isoxanthopterin are correlated with changes in three other pteridine fractions. A sepiaoid host is able to normalize the red pigments in implanted eyes of the mutant rosy, but does not repair its isoxanthopterin defect. The reaction of other pteridines to drosopterin formation can thus be separately observed. While isoxanthopterin synthesis may generally be host dependent, its retention in the imago is autonomous. Wild-type eyes maintain their pteridine levels in a white host that excretes its own fluorescent materials. Compression of the testis by numerous eye transplants diminishes its isoxanthopterin storage. The surplus of diffusible precursors leads to increased deposition in host eyes and eye-transplants.
The Effects of the Chelating Agent Ethylenediamine Tetra-acetic Acid on Cell Adhesion in the Slime Mould Dictyostelium discoideum
Authors: Dehaan Robert L. 
Published: April 2021

ABSTRACT
Vegetative myxamoebae and pseudoplasmodia of the slime mould Dictyostelium discoideum were treated with the chelating agent ethylenediamine tetra-acetic acid. The myxamoebae first respond by rounding up, and then by throwing out active, continuously moving, hyaline lobopodia. At high concentrations of EDTA the cells are unable to migrate, although cellular ‘writhing’ continues for hours. At lower concentrations writhing also occurs, but the cells are able to move together into loose heaps. A migratory pseudoplasmodium immersed in 5 mM EDTA begins disaggregating rapidly. Its smooth surface breaks down and individual cells exhibit membrane activity similar to that described above. The cells lose their attachments to one another, and are maintained in a loose pile only by a tenuous matrix in which they appear to be embedded. Mild agitation now easily separates them into single cells and small clumps of cells. The effects noted on both myxamoebae and pseudoplasmodia are reversible by replacing the EDTA with Bonner’s solution. Moreover, preparations treated with EDTA in the presence of equimolar concentrations of calcium chloride are unaffected. How the removal of cations from cells might result in their dissociation from one another is discussed. It is suggested that EDTA may have its effects by (a) dissolving extra-cellular ground substance or sheath material, and (b) producing a state of instability in the cell membrane allowing continuous pseudopodia! activity and distortion of relations between apposed cell surfaces.
Identification of the Type of Blood-cell Responsible for the Graft-versus-Host Reaction in Chicks
Authors: Terasaki P. I. 
Published: April 2021

ABSTRACT
An attempt has been made to identify the cell responsible for the splenic enlargement caused by the injection of adult homologous blood and spleen cell suspensions into embryonic or newborn chicks. Adult chicken blood lymphocytes 99–100 per cent, pure produced marked splenic enlargement when injected intravenously into chick embryos of a different breed or strain. As little as 30,000 lymphocytes could produce a detectable effect. Adult chicken spleen-cells also produced enlargement of the embryonic spleen. Adult monocytes and thymocytes did not cause significant enlargement. Evidence is presented that the development of inflammatory nodules after the local intracutaneous injection of cells from adult homologous donors is, like splenic enlargement, principally the result of a reaction of the grafted cells against the host. Adult blood lymphocytes when injected intracutaneously were shown to cause the production of a nodule in 3–5 days. Monocytes and thymocytes did not cause the formation of these nodules. From these experiments it is concluded that, in chickens, cells of the peripheral blood lymphocyte family are immunologically competent, and are capable of producing an iso-immune reaction against antigens present in their embryonic or juvenile host.
Hair Growth and its Relation to Vascular Supply in Rotated Skin Grafts and Transposed Flaps in the Albino Rat
Authors: Ebling F. J. , Johnson Elizabeth 
Published: April 2021

ABSTRACT
Hair follicles of albino rats were translocated and allowed to develop vascular connexions in new sites. The translocation was achieved either by rotation of skin grafts in the mid-flank before the expected start of the first wave of growth (4 weeks after birth), or by transposition of flaps—in two stages—so that they were never completely cut off from a blood-supply. The first and second waves of hair-growth on the body adjacent to the grafts or flaps continued as in intact rats; the waves of growth moved from ventral to dorsal, and the dorsal hairs were longer than ventral ones. The appearance of hair of the first wave on unrotated control grafts was in retard of that on the body, but passed from ventral to dorsal in the normal way. During the second wave of growth, follicular activity on the graft continued out of phase with that on the body. The first and second waves of hair-growth on rotated grafts were similarly retarded, but began in the dorsal region and passed ventrally. There was no retardation of growth on the transposed flaps. Hairs first appeared on the dorsally transposed ventral skin of the flaps at the same time as on the ventral body, followed by growth on the ventral flap and dorsal body. The length of hair produced on both rotated grafts and transposed flaps was consistent with the origin of the follicles and not in accordance with their new positions. In intact rats it was demonstrated that follicular activity precedes vascularization. Vascularization of follicles in grafts or transposed flaps was always consequent upon follicular activity, even when this was out of phase with the normal waves of hair-growth on the adjacent body. The evidence suggests that follicular activity depends mainly on an inherent rhythm, and that the hyperaemia which accompanies hair-growth is consequent upon an innate demand of the follicles and is not itself the cause of their activity.
The Differentiation Centre Inducing the Development from Larval to Adult Leg in Pieris brassicae (Lepidoptera)
Authors: Kim Chang-Whan 
Published: April 2021

ABSTRACT
It is generally supposed that the imaginal bud of the leg in Lepidoptera, which Bodenstein (1935, 1937) reported to be visible in the second segment during the last larval instar of Vanessa urticae, develops to produce the adult leg by histogenesis.
Study on the participation of neoplastic cells in the development of mouse embryos
Authors: Calef Enrico , Crimi Corrado , Fruscalzo Alberto , Jucker Richard 
Published: April 2021

ABSTRACT
To test the ability of cloned committed erythroleukemic cells to participate in development we have injected Friend leukemia cells (FLC) into C57B1/6 mouse blastocysts together with Friend leukemia virus (FLV) and we have examined the newborn individuals derived from them. Five animals out of 32 born have FLC-derived neoplasia. The incidence of neoplasia is increased as compared with other similar experiments without the virus. In two of the animals with the FLC neoplasia the disease manifestation is an erythroid leukemia similar to the one obtained directly with the virus in normal DBA/2 mice.
The effect of tail skin on the morphology and morphogenesis of limb regenerates in the red-backed salamander, Plethodon cinereus
Authors: Dinsmore Charles E. 
Published: April 2021

ABSTRACT
Tail skin cuffs have been grafted to the upper forelimb of red-backed salamanders in either normal or 180°-rotated dorsoventral orientation. Subsequent amputation through the graft region resulted in arrested regeneration, distally deficient or typical four-digit regenerates. Distribution was not substantially influenced by graft orientation nor were there any supernumerary limbs induced by the axially dislocated tail skin on the limb stumps. Furthermore, regenerates bore no indication of tail-like structures other than large granular skin glands proximally. These data indicate that, unlike limb skin, tail skin is not morphogenetically active in the epimorphic process of limb regeneration. In addition, the species used in this study is a fin-less, round-tailed salamander. It is therefore suggested that the previously reported morphogenetic effects of tail skin on limb regeneration may be related to the presence of tail fins on the species studied.
Mechanism of size regulation in mouse embryo aggregates
Authors: Lewis N. E. , Rossant J. 
Published: April 2021

ABSTRACT
A detailed comparison of the postimplantation development of normal and double-sized mouse embryos, produced by aggregating two 8-cell stage eggs, revealed that size regulation occurred in the double embryos between 5 days, 16 h post coitum (p.c.) and 6 days, 16 h p.c. Size regulation occurred simultaneously in all tissues, suggesting that a single regulatory mechanism may control size in the early embryo. Size regulation appeared to be brought about by alteration in cell cycle length. There was no obvious increase in cell death in the double embryos nor an increase in the non-dividing cell population. However, colcemid treatment revealed a significant difference in mitotic index between double and control embryos over the period of size regulation. Control embryos showed a proliferative burst around 6 days, 8 h p.c. which did not occur in the double embryos. It is not yet clear whether this control of proliferative activity in double embryos is exerted by the embryo itself or by the uterine environment.
Histological analysis also suggested that proamniotic cavity formation, which occurs before size regulation, was dependent on total cell number and not on the number of cell cycles undergone since fertilization. Proamniotic cavity formation was observed to occur at different times but at similar cell numbers in double, control and half embryos.
Comparative Investigations of the Action of Two Nitrogen Mustard Derivatives on the Early Stages of Development of Chick Embryos
Authors: Jurand A. 
Published: April 2021

ABSTRACT
Cytotoxic compounds act by combining with the biochemical constituents of cells. Because of the complexity of living matter, the cytotoxic activity is highly complicated in nature and is therefore far from being thoroughly understood. In order to analyse the cytotoxicity of any chemical compound, many biological variables concerned in determining the mode of action of the compound and its selectivity for any particular range of cells have to be taken into account (Danielli, 1952,1954).
The Growth of the Locust Embryo
Authors: Salzen E. A. 
Published: April 2021

ABSTRACT
Three measures of the growth of the embryo of Locusta migratoria migratorioides (R. & F.) were determined from the third to the twelfth days of development at 30° C. These measures were the dry weight, reduced weight, and number of nuclei. Measurements of the density of the embryo were also made and used with the R.W. to calculate the wet weight. The same measurements of the intact egg were taken throughout development. The growth in dry weight of the locust embryo from the third to twelfth days of development appeared closely comparable with that of vertebrate embryos such as the chick embryo and could be described by the usual double logarithmic relation with growth constants of closely comparable values. Increase in R.W. and wet weight could be similarly described from the third to ninth days after which the rate of increase fell away more rapidly than expected. Increase in nuclear number occurred at a higher rate than any of the other measures up to the ninth day after which no further increase above a total of about two million nuclei could be detected. As in some vertebrate embryos, cell multiplication seemed not to parallel growth in weight. The implications of the differences in rates of increase of these measures were considered. From the third to ninth days the embryo was approximately 90 per cent, water, the density of the dry material may have increased and the dry weight per nucleus decreased rapidly to a constant value. After the ninth day there appeared to be a fall in water content and dry density and an increase in the dry weight/nuclear number ratio. The density of the wet embryo increased steadily after the sixth day. The total loss in dry weight of the egg due to respiration was about 20 per cent., an amount typical of many insect eggs. The eggs increased in weight by about 120 per cent., chiefly during the fourth and fifth days. The percentage water content rose from about 50 per cent, to about 80 per cent. Changes in the density of the eggs reflected perfectly the changes in water content. The R.W. of the eggs was constant except for a rise of about 40 μ g. during the fourth and fifth days. It was suggested that this could be accounted for by the presence in the chorion of about 0 04 /xl. of air which was displaced when water uptake took place after the third day. This would also have accounted for the very small difference in the measured changes in density compared with those calculated from the water intake. A constant R.W. and a large decrease in dry weight imply that the density of the dry material of the eggs must have increased at the same rate as the respiratory loss in dry weight. Combustion of fat might account for this.
Stimulating Action of Tissue Extracts on Regenerative Processes
Authors: Tumanishvili G. D. 
Published: April 2021

ABSTRACT
By means of systematic injections of tissue extracts one may obtain stimulation of regeneration of muscles (in frogs) and liver (in frogs, rabbits, guinea-pigs). Such extracts, however, apparently only influence homologous tissue. The influence of extracts does not show any class specificity. On the con-trary, the stimulation of regeneration of frog muscle and liver is more effectively produced by corresponding extracts of hen tissues than by those of the frog. Aqueous extracts are as active as those obtained with isotonic saline. Heating to 60° C. for 5 minutes inactivates the extract. The analysis of our data and of those published elsewhere leads to the conclusion that the stimulating agent is a water-soluble protein fraction, or that it is some substance (e.g. RNA) forming a rather strong complex with this fraction.