bluuebunny/crossref_metadata_2025_split huggingface dataset:
Development of the secretory capacity of the chick embryo adrenal glands
Authors: Pedernera Enrique A. 
Published: April 2021

ABSTRACT
The secretory capacity of the chick embryo adrenal was investigated at different stages of its development employing a sensitive bioassay for corticosteroids based upon the modifications produced in vitro by these hormones on the height of the chick embryo duodenal mucosa.
The adrenal gland cultivated in contact with explants of duodenum and stimulated with increasing doses of ACTH exhibited a mucosal response similar to that produced by corticosterone, both in the slope of the bioassay dose-response curve and in the histological pattern.
It has been found that the chick embryo adrenal glands can secrete corticoids from the 5th day onwards by adding ACTH to the culture medium. The basal (unstimulated) secretory capacity of the gland (registered from the 8th day on) is significantly correlated with the total protein content of the adrenals in the different stages of development studied.
The maximal secretory capacity of the gland (measured with the dose of ACTH which produces the maximal response) increases steadily up to the 10th day.
The rate of increase of corticosteroid secretion due to ACTH is a constant within the interval of development investigated.
Hop-sterile, a mutant gene affecting sperm tail development in the mouse
Authors: Johnson D. R. , Hunt D. M. 
Published: April 2021

ABSTRACT
Hop-sterile (hop) is a new mutation in the mouse, the effects of which include complete male sterility, a ‘hopping’ gait and preaxial polydactyly of all feet. Ultrastructural studies of spermiogenesis show that sperm tails are absent or highly modified. Second meiotic division is frequently abnormal or incomplete, often with four centrioles per cell. These centrioles usually fail to form flagella and sperm tail development is arrested.
Influence of the RNA content on oogenesis in the bobbed mutants of Drosophila melanogaster
Authors: Mohan Jag 
Published: April 2021

ABSTRACT
Developing egg chambers of Drosophila melanogaster (wild-type and bobbed mutants) have been examined for their nucleic acid content by cytophotometric methods. No differences were observed in the total DNA and RNA content of the egg chambers at all stages between the bobbed mutants and the wild type. It is shown that the process of oogenesis in bobbed females is prolonged, and that this prolongation occurs at all the stages of oocyte development. Since the ovaries of the bobbed females synthesize less rRNA per unit time, it is likely that this prolongation allows the egg chambers of the bobbed females to normalize their RNA content. When they achieve a given RNA content, they proceed to the next stage of development.
La formation des somites chez l’embryon d’oiseau: étude expérimentale
Authors: Lanot Par R. 
Published: April 2021

ABSTRACT
Somitogenesis in the avian embryo: an experimental study
The determinism of somitogenesis has been studied.
A complete segmental plate can form somites even when isolated from cord, neural tube and somites. Somites are always formed if the segmental plate remains in continuity with the somites which have just formed.
When the segmental plate is separated from the axis and deprived of its apical end, it undergoes no differentiation or differentiates incompletely. In the latter case the quality of differentiation decreases in a cephalo-caudal direction.
When the segmental plate, without its apical end, is left in contact with neural tissue or chorda, it forms somites normally.
The growth of the segmental plate is reduced whenever it has been isolated from neural tube and chorda altogether.
Behind its apical end the segmental plate can regulate excesses as well as deficiencies.
It appears, then, that the intersomitic fissures are determined at the apical ends of the segmental plates, but not behind them.
This determination is progressively established backwards. It can be transmitted by the last differentiated as well as the differentiating somites. However, the neural tube, and possibly the cord, play the leading role in this process, for the intersomitic clefts are fixed at their proper place in connexion with them.
An electrosurgical technique for the production of localized tissue ablations in the early chick embryo
Authors: Jordan R. K. 
Published: April 2021

ABSTRACT
The passage of low-frequency alternating current was found superior to other methods considered for the production of small, discrete, electrolytic ablations in young chick embryos.
Active electrodes of tungsten metal less than 5 μm in diameter were prepared by controlled electrolytic corrosion. These gave reproducible, discrete foci of destruction of the required size, with currents less than 2 mA. The identification of destroyed tissue areas was immediately apparent under the operating microscope and confirmed histologically. Preliminary studies on bilateral extirpation of the ultimobranchial primordia show the absence of the ultimo-branchial bodies 6 days after destruction of the primordia at 96 h of incubation.
Ultrastructure of diploid and haploid cells of Xenopus laevis larvae
Authors: Fox H. , Hamilton Louie 
Published: April 2021

ABSTRACT
A study was made of tissues of diploid and haploid Xenopus laevis larvae by electron microscopy. The comparison of the two types of larvae was both quantitative and qualitative. Haploid cells contain fewer similarly sized mitochondria and/or cilia (compared with the diploid), commensurate with their smaller cell size. Cellular differentiation is retarded in haploids and the degree of retardation is reflected in the retention of cellular lipid and yolk. It is suggested that the failure to differentiate adequately is an important component in the development of the haploid syndrome.
A biochemical and ultrastructural study of RNA in yolk platelets of Xenopus gastrulae
Authors: Kelley Robert O. , Nakai George S. , Guganig Marlene E. 
Published: April 2021

ABSTRACT
Yolk platelets from Xenopus gastrulae were isolated in a sucrose-polyvinyl pyrrolidone medium, washed, centrifuged four times, and portions of each pellet were prepared for electron microscopy.
Electron microscopy revealed isolated platelets to be free of cytoplasmic contamination with progressive disruption of the superficial layer after each washing.
Each washing and the final pellet were extracted with phenol and precipitated with ethanol.
Orcinol analysis indicated that 50–60 μg of RNA were present in yolk platelets isolated from 1000 gastrulae.
Autoradiography of yolk platelets from cells incubated in [5-3H]uridine revealed label in superficial and main body components after treatment with DNase but not after incubation in RNase.
Acrylamide-gel electrophoresis suggests that yolk platelet RNA is of both high and low molecular weight.
The effect of early thymectomy on histogenesis of the lymphoid organs in Xenopus laevis
Authors: Manning Margaret J. 
Published: April 2021

ABSTRACT
The role of the thymus in the ontogenetic development of the lymphoid system of the clawed toad, Xenopus laevis, was investigated by removing the organ at stage 49 of Nieuwkoop & Faber (1967), a stage when small lymphocytes are present in the thymus but have not yet appeared in the peripheral lymphoid organs.
Complete thymectomy, confirmed histologically, was achieved in nine larvae killed at stage 56 and in 23 larvae killed at stage 59.
The spleen was smaller in thymectomized larvae than in sham-thymectomized controls in the series killed at stage 56, but the difference was no longer significant at stage 59. In both series, thymectomized larvae showed a fall in the number of extra-follicular lymphocytes and an increase in the reticulo-myeloid elements of the splenic red pulp.
The pharyngeal ventral cavity bodies were moderately or severely depleted of lymphocytes.
In other areas, histogenesis proceeded normally in the absence of the thymus. In the splenic white pulp, the follicles, which comprised immature cells of the lymphoblast type at the time of thymectomy, developed their normal complement of lymphocytes. All larvae grew and developed at the normal rate.
Transmission and spread of embryonic induction
Authors: Nordling Stig , Miettinen Heikki , Wartiovaara Jorma , Saxén Lauri 
Published: April 2021

ABSTRACT
The question of whether inductive tissue interactions involve factors transmitted by long-range diffusion was investigated. In transfilter experiments with spinal cord as the inductor and metanephric mesenchyme as the responding tissue it was established that interposition of a second TA Millipore filter (pore size 0·8 μm, thickness 25 μm) prolongs the induction time by about 12 h. The prolongation of the induction time was concluded to be due to the time taken by the inductor to pass through the second filter. It was also demonstrated that metanephric mesenchyme partially lost its competence if precultivation lasted more than 12 h. This explains why 100% induction never was achieved in the double-filter experiments.
In order to rule out the possibility that the filters, owing to their inhomogeneous structure and negative surface charge, seriously restricted diffusion, the diffusion of several substances through the filter was measured under conditions as closely similar as possible to those in the transfilter experiments. Although there was some restriction of diffusion, the calculated diffusion constants were of the same order of magnitude as those reported in the literature, indicating that the filter is no major obstacle.
Calculations based on four different hypotheses that the inductor is transmitted by diffusion, indicate that diffusion can hardly explain the long transmission time.
Tentacular and oral-disc regeneration in the sea anemone, Aiptasia diaphana
Authors: Singer Irwin I. 
Published: April 2021

ABSTRACT
Autoradiography with [3H]thymidine and electron microscopy were used to determine (a) the patterns of cellular division exhibited by intact anemones, (b) if measurable increases in cellular proliferation accompany oral-disc regeneration, (c) whether interstitial cells are present in Aiptasia, and (d) if these cells could be responsible for the latter proliferative patterns.
An oral-aboral gradient in cellular proliferation was exhibited by the epidermis of uncut anemones, with the highest levels in the tentacles.
Wound healing did not require cell proliferation and did not immediately stimulate cellular division which was associated with subsequent morphogenetic events.
Indices of presumptive oral-disc [3H]thymidine uptake into nuclei increased tenfold with the outgrowth of the new tentacles. This increase occurred in the epidermis, while only small amounts of gastrodermal proliferation were detected, it is hypothesized that the epidermis contributes new cells to the expanding gastrodermis during tentacle budding.
Most of the [3H]thymidine-labeled nuclei were localized in the basal portions of the epidermis of intact anemones and 1-to 2-day-old regenerates; very few gastrodermal nuclei accumulated the label.
Nests of interstitial cells and transforming interstitial cells were localized in the exact epidermal regions where nuclear labeling took place, suggesting that the proliferative patterns of intact and regenerating Aiptasia are a function of their interstitial cell distribution.
Timing of the phases of the cell cycle with tritiated thymidine and Feulgen cytophotometry during the period of synchronous division in Lymnaea
Authors: van den Biggelaar J. A. M. 
Published: April 2021

ABSTRACT
The duration of the phases of the cell cycle during the 1–, the 2– and the 4–cell stage of the Lymnaea egg were determined with [3H]thymidine and with Feulgen cytophotometry. The M, S and G2 phases occupy 48, 27 and 25% of the first three cell cycles. A G1 phase cannot be observed. Only from the 4-cell stage was [3H]thymidine readily incorporated into DNA. The theory that an increase in respiration during the S phase of the 4-cell stage is connected with the energy requirements of DNA synthesis is discussed.
Timing of the phases of the cell cycle during the period of asynchronous division up to the 49-cell stage in Lymnaea
Authors: van den Biggelaar J. A. M. 
Published: April 2021

ABSTRACT
The duration of the phases of the cell cycle (M-G1-S-G2) has been determined from the 8-up to the 49-cell stage in eggs of Lymnaea, using autoradiography and cytophotometry of Feulgen-stained nuclei. Division asynchrony of corresponding cells in different quadrants is primarily caused by unequal lengthening of the G2 phases. In general it appeared that in the vegetative cells lengthening of the cell cycles is chiefly due to an extension of the G2 phases, whereas in the cells of the animal half the duration of both the S and the G2 phases are extended. DNA synthesis is not blocked in cells which stop dividing and start to differentiate. A conspicuous lengthening of the cell cycles is observed in the 16- and 24-cell embryo; this is accompanied with the reappearance of distinct nucleoli. Supporting evidence has been obtained for the assumption that bilateral symmetry at the animal pole of the embryo is induced by cells from the vegetative hemisphere, presumably by the macromere 3D, during the 24-cell stage.
Forelimb regeneration in hypophysectomized adult Diemictylus viridescens following organ culture and autoplastic implantation of the adenohypophysis
Authors: Liversage Richard A. , Liivamagi Luna 
Published: April 2021

ABSTRACT
After autografting an organ-cultured anterior pituitary gland, maintained in culture for up to 27 days, into the tail or lower jaw of an hypophysectomized adult Diemictylus viridescens, the animals recovered and survived readily until fixation at 102 days (129 days post-hypophysectomy) and normal bilateral limb regeneration occurred. Also, restoration of normal skin colour, muscle tone, eating habits and behaviour was identical to control regenerate cases. In the sham control cases, a muscle fragment from the dismembered portion of the amputated left forelimb was placed in organ culture one day after hypophysectomy and then autografted into the host tail 7 days later. The majority of animals lived only up to 28 days post-hypophysectomy; they acquired the gross characteristics of adult hypophy-sectomized newts; and bilateral forelimb regeneration was thwarted. Newts that were hypophysectomized only, showed no gross signs of limb regeneration and died within 28 days.
Organ culture and autoplastic implantation of the adenohypophysis permitted a study of the inhibition and then the concurrent restoration (left forelimb = old amputee) and initiation (right forelimb) of regenerative activity as well as normal advanced limb regeneration.
Sur le comportement des mastocytes chez le rat en conditions d’hypo- et d’hypervitaminose A
Authors: Spreca Par A. , Modis L. , Conti G. 
Published: April 2021

ABSTRACT
The behaviour of rat mast cells under conditions of high and low vitamin A
The authors have studied the mast cells in normal rats and in rats under hypo- and hyper-vitaminosis A. The main results of their studies are: (a) in the skin (dermis), in the case of A hypervitaminosis, there is a significant rise in the number of the mastocytes with swelling and dcgranulation; (b) in lung and bone marrow, the number of mastocytes is increased under hypovitaminosis A and there is also blood congestion and lipomatosis of bone marrow.
The authors give an interpretation of their results.
Mise en evidence d’un facteur tissulaire intervenant au cours de la morphogenèse du système trachéen chez les insectes diptères
Authors: Pihan Par Jean-Claude 
Published: April 2021

ABSTRACT

Demonstration of a ‘tissue factor’ acting in the morphogenesis of the tracheal system in the dip ter an insects
In an attempt to examine the factors acting during the morphogenesis of the tracheal system in the Diptera (Calliphoridae), various experiments were performed in larvae and pupae so as to modify the relations between the organs and their tracheal supply.
The results are as follows :
The retinotectal projections after uncrossing the optic chiasma in Xenopus with one compound eye
Authors: Straznicky K. , Gaze R. M. , Keating M. J. 
Published: April 2021

ABSTRACT
The nature of the retinotectal projection from a compound (NN or TT) eye in Xenopus raises certain problems concerning the mode of formation of connexions between the eye and the tectum. Each half of the compound eye appears to spread its connexions across the entire extent of the (apparently normal) contralateral tectum. This could indicate a certain plasticity in the way in which optic fibres can connect with the tectum. Alternatively, it is conceivable that each (similar) half of the compound eye is only able to innervate its corresponding half-tectum; in which case the uninnervated half-tectum could remain undeveloped and the innervated half-tectum could overgrow to resemble a normal tectum. This mechanism would preserve the idea of a rigidly fixed cell-to-cell specificity between retina and tectum.
In an attempt to distinguish between these two mechanisms (spreading or overgrown half-tectum) we have given each of a series of Xenopus embryos at stage 32 one compound eye (NN or TT). Then, shortly after metamorphosis, we uncrossed the optic chiasma and 6 months later recorded the retinotectal projections from each eye to the tecta. Thus by connecting up the normal eye to the suspect tectum, and the compound eye to the normal tectum, we used the normal side in each case to provide an indication of the degree of abnormality with which the other side was connected.
The results showed that a compound eye (NN or TT), connected to a normal tectum, gave a typical reduplicated map across the entire tectum, whereas the normal eye, when connected to the tectum which was previously innervated by the compound eye, gave an approximately normal projection across the whole of that tectum.
These results lead us to conclude that, in the Xenopus visual system, no strict cell-to-cell type specificity exists; rather, what is preserved throughout these experimental manoeuvres is the polarity and extent of the projection.
Histological features of neural induction in Xenopus laevis
Authors: Tarin D. 
Published: April 2021

ABSTRACT
It was first established by grafting experiments that neural induction occurs in Xenopus laevis and that it is the mesoderm in the dorsal lip of the blastopore which normally exercises this function. The subsequent histological work provided the following information:
At stage mesodermal invagination was already well under way, in advance of the formation of the archenteric cavity. This confirms the earlier observations of Nieuwkoop & Florschutz (1950).
The first evidence of neural induction, thickening of the mid-dorsal ectoderm combined with the development of an inner tier of columnar cells, occurred at stage .
By stage .12 there was generalized thickening of the dorsal ectoderm and between stage and 13 the brain and spinal cord regions of the neural plate became distinguishable.
The dorsal mesoderm segregated into notochord rudiment and two lateral masses at stage 13 and the latter further subdivided into paraxial mesoderm and lateral plates by stage 14.
The margins of the neural plate were clearly distinguished from presumptive epidermis by stage 15 and the median neural groove was also well marked.
In the next two stages the folding of the neural plate in the line of this groove proceeded rapidly. The dorsoventral enlargement of the somites and the relative shrinkage of the noto-chord were considered to contribute to the mechanism of neurulation.
Regionalization of the brain into prosencephalon, mesencephalon and rhombencephalon was in progress at stages 18 and 19.
These results indicate that induction consists of an initial activation of dorsal ectoderm (generalized thickening) followed by gradual transformation of the neural plate to form the different parts of the central nervous system (regionalization).
Intercellular metachromatic material was noted in various parts of the embryo. This was most plentiful between stage and stage 13 and thereafter gradually decreased. It was the only feature which persisted long enough to represent a possible inductive agent.
At all stages the archenteron was lined with a continuous layer of endoderm. This indicates that the mode of formation of the gastro-intestinal tube in Xenopus is different to that in urodeles. It further implies that the mesoderm is not present on the blastular surface prior to gastrulation but lies in deeper layers.
Reproduction of Dugesia tigrina under short-day and long-day conditions at different temperatures
Authors: Vowinckel C. , Marsden J. R. 
Published: April 2021

ABSTRACT
Five successive generations of asexually derived populations of D. tigrina and their sexually derived parental population were reared under each of six combinations of 20, 23 and 26 °C with 12 and 16 h of daylight. Asexual and sexual reproduction were recorded for each population.
Peaks of asexual reproduction occurred increasingly earlier in consecutive generations to finally disappear or occur later again.
Peaks of sexual reproduction likewise occurred increasingly earlier in consecutive generations to be retarded again or disappear in later generations. Retardation occurs in earlier generations under short-day conditions than under long-day conditions.
All generations later than the third, asexually derived, were sterile.
The implications of these results are discussed and it is suggested that the time of cocoon deposition of all asexually derived offsprings is determined regardless of intervening generations during early development of the sexually derived parent. Attention is drawn to the similarity between the suggested mechanism and environmental control of aphid reproduction.
Synthesis of nuclear and cytoplasmic proteins in the early development of fishes and echinoderms
Authors: Krigsgaber Maya R. , Kostomarova Alla A. , Terekhova Tamara A. , Burakova Tatiana A. 
Published: April 2021

ABSTRACT
Synthesis of nuclear and cytoplasmic proteins was studied biochemically and autoradio-graphically in early loach (Misgurnus fossilis) and sea-urchin (Strongylocentrotus nudus) embryos.
After incubation with [14C]amino acids for 5–120 min the ratio of the specific activities of nuclear, mitochondrial and 12000g supernatant proteins was shown to be equal approxi-mately to 6:1:2 in loach embryos and to 8:4:3 in sea-urchin embryos independently of the duration of labelling.
After incubation with [3H]amino acids the number of silver grains per unit section was on the average 2·4 times higher for nuclei than it was for cytoplasm at mid-blastula and mid-gastrula stages. At the mid-gastrula the vegeto-animal gradient of protein synthesis was found.
A higher level of the synthesis of nuclear proteins as compared with that of cytoplasmic proteins appears to be related to an increase in the nuclear volume and the nucleo-cytoplasmic ratio during the early development of the loach and sea-urchin embryos.
Embryological effects of a minute deficiency in linkage group II of the mouse
Authors: Dunn G. R. 
Published: April 2021

ABSTRACT
A minute deficiency in linkage group II of the mouse, involving the short-ear locus and at least one other functional unit, was found to be lethal by day 8 after coitus when homozygous. The earliest time at which mutants could be detected was 7 days 16 h after coitus. Histologically, the mutant embryos showed overgrowth of ectoderm and trophoblastic giant cells. The mesoderm was almost entirely lacking and the mutant embryos were smaller than their normal litter-mates.
It was concluded that the mutant was first expressed morphologically late on day 7 after coitus and that its primary effect was to stimulate growth of extra-embryonic ectoderm.