bluuebunny/crossref_metadata_2025_split huggingface dataset:
Extent and properties of the regeneration field in the larval legs of cockroaches (Leucophaea maderae): I. Extirpation experiments
Authors: Bohn Horst 
Published: April 2021

ABSTRACT
Extirpation experiments have been performed on the larvae of cockroaches (Leucophaea maderae) to determine the extent and properties of the regeneration field of the legs of these insects. The distal segments, including the coxa, may all be removed without loss of regenerative capability; but regenerative capability eventually disappears if more proximal parts are removed. There are two regions adjoining the coxa anteriorly and posteriorly which are both important for leg regeneration. The anterior region consists of the sclerotized basal parts of the leg mainly formed by the trochantin and the praecoxa. The posterior region is an unsclerotized membranous area extending from the posterior border of the coxa to the anterior border of the next segment. This membrane is called ‘leg-inducing membrane’. If only one of these two regions is present, no leg regeneration will occur. The interaction of both parts is necessary to allow the formation of a complete leg. An extra leg with reversed anterior-posterior polarity is formed when the Teg-inducing membrane’ of one segment is brought into contact with the sclerites of the following segment after extirpation of the membranous area which normally separates them. This membranous area, which represents the most anterior part of a segment, is called ‘sclerite-inducing membrane’, for if the basal sclerites or part of them are combined with this membrane only sclerites are formed, either in normal or reversed polarity depending on the experimental conditions.
Morphogenesis of the rudimentary hind-limb of the Glass Snake (Ophisaurus apodus Pallas)
Authors: Rahmanl Tahereh M.-Z. 
Published: April 2021

ABSTRACT
In the legless lizard, Ophisaurus apodus, the hind-limb primordium appears on the caudal extremity of the Wolffian ridge at an early stage in the development of the embryo (4·2 mm long). Three somites each send an extension into this young bud and distribute cells in its mesenchymal mass of cells. An apical epiblastic ridge, appearing as a fold from the exterior, forms on the limb-bud, which at this time is flattened at the distal end. A large vessel and nerves penetrate into the bud which appears normal at this stage. Necrosis then begins, first in the ridge, then in the cells of somitic derivation and finally, when the ridge has almost disappeared, in the mesenchymal cells. The bud which has been growing up till now, starts to regress at this point. It does not, however, disappear completely as it does in the forelimb, but remains as a rod-like appendage on each side of the cloaca. Inside this structure a rudi-mentary skeleton takes shape. The phallic primordium which appears on the ventro-caudal aspect of the hind-limb bud is not involved in this degenerative phenomenon and continues to develop.
The arrest of development may be due to the degeneration of the apical ridge; possibly resulting from a failure of induction by the somites or to an insufficient somitic contribution to the hind-limb bud.
Investigation on the origin of the definitive endoderm in the rat embryo
Authors: Levak-Švajger B. , Švajger A. 
Published: April 2021

ABSTRACT
Single germ layers (or combinations of two of them) were isolated from the primitive streak and the head-fold stage rat embryos and grown for 15 days under the kidney capsule of syngeneic adult animals. The resulting teratomas were examined histologically for the presence of mature tissues, with special emphasis on derivatives of the primitive gut.
Ectoderm isolated together with the initial mesodermal wings at the primitive streak stage gave rise to tissue derivatives of all three definitive germ layers. Derivatives of the primitive gut were regularly present in these grafts. At the head-fold stage, isolated ectoderm (including the region of the primitive streak) differentiated into ectodermal and mesodermal derivatives only.
Endoderm isolated at the primitive streak stage did not develop when grafted and was always completely resorbed. At the head-fold stage, however, definitive endoderm differentiated into derivatives of the primitive gut if grafted together with adjacent mesoderm.
These findings indirectly suggest the migration of prospective endodermal cells from the primitive ectoderm, and therefore a general analogy with the course of events during gastrulation in the chick blastoderm.
Compartmentalization and growth of the Drosophila abdomen
Authors: Lawrence Peter A. , Green Sheila M. , Johnston Paul 
Published: April 2021

ABSTRACT
An analysis of the cell lineage of the adult Drosophila abdomen is reported. Genetically marked clones are produced in the tergites in the embryo and in the sternites and pleura during larval life. The spatial disposition of the segment primordia is also studied in a series of 250 gynandromorphs. We conclude that in the embryo the segments are all separate polyclones soon after blastoderm and these are probably adjacent to each other. Gynandromorph analysis suggests that segments 2-6 develop from similarly sized cell groups but that the first tergite develops from a primordium which is equal to that of two other segments. We suggest that presumptive adult and larval cells are not separated at blastoderm. Our estimate from clonal analysis of the number of larval cells (12) which construct the sternites and pleura is equal to the number observed directly in the ventral nest of histoblasts.
Autonomy of tendon development in the embryonic chick wing
Authors: Kieny Madeleine , Chevallier Alain 
Published: April 2021

ABSTRACT
The aim of this study performed in the embryonic chick wing is to test the ability of the tendons to form and develop in the absence of the muscle bellies.
The experiments were performed on 2-day chick embryos by destroying a portion of the somitic mesoderm by local X-irradiation. The irradiated part included the wing somite level 15-20 and extended three somites (or presumptive somites) in front and two to six presumptive somites in the rear of the wing somite level. The wings of the operated side were examined histologically 3-8 days after the X-irradiation.
The radio-destruction of the somitic mesoderm totally inhibited or severely impaired the development of the forearm muscles. But, despite the absence of the flexor and extensor muscles the differentiation of the distal manus tendons could be observed. This differentiation occurred at the same time and in the same position as in controls. However, these tendons were transient structures. They disappeared within three days after their individuation. Two mechanisms that progressed in proximo-distal direction were involved in their resorption: cellular dislocation and cell death.
We conclude that tendons start to develop autonomously from the muscle bulks, but for their maintenance and further development they require connexion to a muscle belly.
The Effect of Steroid Hormones on the Brown Trout (Salmo trutta L.) during the Period of Gonadal Differentiation
Authors: Ashby K. R. 
Published: April 2021

ABSTRACT
Steroid hormones were administered to trout alevins by adding them to the culture medium in alcoholic solution, the concentration of hormone in the cultures being within the range 50 y to 400 y/1., and that of alcohol, O O5%o to O-3%o. A control culture was maintained in O-5°/oo of alcohol. Oestradiol (50 y and 300 y/I.) and testosterone (60 y/1.) had closely similar effects, which included strong inhibition of the development of germinal tissue except in one male treated with the higher oestradiol concentration, where stimulation occurred posteriorly. There was no evidence of sexual inversion, and vasa deferentia appeared in a normal proportion of individuals. With the partial exception of some males, a large area of the somatopleure in the individuals treated became, as in female breeding trout, a ciliated columnar epithelium resembling the internal epithelium of the gonoducts of other teleosts. The connective tissue of the gonadal area was unusually vascular, and in the body-fluids there were large amounts of deeply chromophil material. The tubules of the pronephros were much enlarged. Those of the mesonephros were increased in diameter and reduced in number in the culture treated with the higher concentration of oestradiol. Both concentrations of oestradiol caused the collapse of the gall-bladder, this being the only obvious difference from the effect of testosterone. There are strong reasons for believing that oestradiol caused enlargement of the cells of the interrenal (‘anterior interrenal’) gland, and some reason to think that in some instances testosterone could also cause their hypertrophy. Progesterone and more particularly desoxycorticosterone acetate inhibited the development of germinal tissue, except in some males treated with the former hormone, where in addition vasa deferentia developed precociously and were much enlarged. Vasa deferentia of a normal size were present in most other individuals lacking oocytes. There was a significant excess of females over males after treatment with DOCA, but the possibility of this being due to a selective mortality cannot be ruled out. There was evidence of such a mortality having occurred in the culture treated with progesterone. Deeply chromophil material was usually present in the body-fluids. Slight sterol-mimetic effects were observed in the controls treated with alcohol. Possible causes are discussed. The results are compared with those obtained from similar experiments in other teleosts and in tetrapods.
Induction by Regions lateral to the Streak in the Chick Embryo
Authors: Mulherkar Leela 
Published: April 2021

ABSTRACT
The discovery of the organization centre of Amphibia by Spemann (1918) opened a new field in the outlook of experimental embryology; but there were several technical difficulties to be overcome in the application of the concept of the organizer to avian embryology. In this connexion the tissue culture technique has several advantages over the earlier methods of in situ sectioning or chorio-allantoic techniques, and it has helped a great deal in the understanding of the processes of development in the chick.
In vitro Culture of the Eye and the Retina of the Mouse and Rat
Authors: Lucas D. R. , Trowell O. A. 
Published: April 2021

ABSTRACT
By means of an organ culture technique previously described, whole eyes of 8-11-day-old mice have been successfully maintained in vitro for 8 days. Isolated retinae from both rats and mice aged 9-14 days have been similarly maintained for 10 days. Isolated retinae survived best in a gas phase of air; 60 per cent, oxygen was toxic. In the whole eye, on the other hand, the retina survived better when pure oxygen was used, doubtless because the outer coats of the eye both consume oxygen and hinder its diffusion to the retina. Isolated rat retinae survived well in an entirely synthetic medium, but mouse retinae did not. Differentiation of the visual cell nuclei proceeded normally in vitro.
Further Observations on the ‘Metaplasia’ of an Amoeba, Naegleria gruberi
Authors: Willmer E. N. 
Published: April 2021

ABSTRACT
The development of flagella by Naegleria gruberi, which occurs when a culture of organisms in the amoeboid form is treated with distilled water, has been shown (Willmer, 1956) to be a phenomenon probably related more to the ionic balance between the organism and its external environment than to the simple movement of water in and out of the cell in response to total osmotic changes. From Text-fig. 1 it may be seen that with respect to the response of the amoeba to different concentrations of the various salts investigated there are for each salt two somewhat critical concentrations. In the case of NaCl solutions in distilled water these turning points occur at about 30 mM. and 1 mM., and in the case of KC1 solutions at about 50 mM. and 6 mM. Above the higher of these concentrations in each case the organisms always assume the amoeboid form, and below the lower they become flagellate at least as frequently as they do in distilled water.
Action of Triethanomelamine (TEM) on Early Stages of Chick Embryos
Authors: Jurand A. 
Published: April 2021

ABSTRACT
Of many closely related compounds investigated recently from the point of view of cytotoxity and tumour-inhibiting properties 2,4,6-tri-(ethyleneimino)-1,3,5-triazine (called also triethanomelamine or TEM) proved to be the most effective substance against the Walker rat carcinoma. First descriptions of this fact were published in 1950 (Buckley et al. and Burchenal et al.). Also in 1950 appeared the publication of the first results of the clinical application of TEM at the First International Cancer Congress (Mueller & Miller). Later on Karnovsky et al. (1951) and Petersen et al. (1951) recommended procedures for parenteral and oral administration of this substance in clinical treatment. Very recently TEM has been introduced in a commercial form for oral and parenteral administration in cases of leukaemia, Hodgkin’s disease, polycythaemia vera, and other neoplastic conditions.
Effects of some Amino-acid and Purine Antagonists on Chick Embryos
Authors: Waddington C. H. , Perry Margaret 
Published: April 2021

ABSTRACT
Several authors have studied the effects on developing embryos of substances which are analogues of naturally occurring amino-acids and purines, and known to act, in other systems, as metabolic inhibitors. It was emphasized by Waddington, Feldman, & Perry (1955) that any particular substance may exhibit very different effects in embryos of different types. They found, for instance, that the purine analogue 8-azaguanine has a very strong action in the chick and a much lesser one in the newt embryo. It is therefore necessary to consider the various classes of embryos separately. In this communication we shall be concerned only with chick embryos.
Experiments on the Diffusibility of the Amphibian Evocator
Authors: Brahma S. K. 
Published: April 2021

ABSTRACTPresumptive neural plate ectoderm of an early gastrula, when separated by a porous membrane (average pore diameters, 4 mμ) from the axial mesoderm, failed to differentiate into neural tube either in Axolotl or in Xenopus. In ectodermal sandwich experiments induction always occurred on the side containing the organizer in Triturus alpestris and was prevented by the interposition of a porous membrane, when the latter had an average pore diameter of 4 mμ or 1· 45 μ. No cytoplasmic connexion across the membrane could be observed. The lack of induction through the membranes might be due either to a total failure of diffusion of an active substance, or to a failure of a diffusing substance to attain a high enough concentration on the other side of the membrane, or the induction may essentially involve cell-to-cell contact. No decision between these alternatives is reached.
The Melanoblast Reservoir Available to a Feather Papilla
Authors: Cock A. G. , Cohen J. 
Published: April 2021

ABSTRACT
In an adult black-red hen which, when a newly hatched chick, had received a homograft of skin from the back of a dominant white chick, active feather papillae have been exchanged between follicles of the neck and the homograft. The distinctive structure of feathers of the two tracts permits reliable identification of feathers growing from these transplanted papillae. Each of six successful transplants from the neck into the homograft has so far produced only black-red feathers (one to three feathers in each case). Five transplants from the homograft into the neck have so far produced from two to five feathers each, with the following sequences of pigmentation types: white— white—white—white—mosaic; black-red—black-red—mosaic—mosaic— mosaic; black-red—white—white—white—black-red; white—white—black—red; white—white. A follicle on the homograft, about 1 cm. in from the edge, and not subjected to any operative interference, has produced three mosaic feathers in succession, each partly pigmented by host-type (black-red) melanocytes. It is concluded (a) that the papilla of a feather follicle contains a reservoir of melanoblasts sufficient to provide the melanocytes of several future feathers; (b) that this reservoir is from time to time augmented by melanoblasts migrating in from the surrounding tissue; and (c) that some of the melanoblasts within a papilla may remain inactive during the growth of one or more feathers, but contribute melanocytes to subsequent feathers. In the vane of each of the seven feathers which are mosaic in respect of their melanocytes, there is a marginal band of intense black where the black-red area adjoins the white. This, it is suggested, may be due to the diffusion of some substance from the white area, and may depend on the fact that the dominant white melanocytes also carried the gene for extended black. Our findings are discussed in relation to previous work on the pigmentation of feathers and hairs.
Factors Affecting Vertebral Variation in Mice
Authors: McLaren Anne , Michie Donald 
Published: April 2021

ABSTRACT
C3H/Bi and C57BL/How inbred strains of mice are known to differ from one another in number of lumbar vertebrae. Reciprocal F1 hybrids between the two strains tend to resemble the maternal strain in this respect. Since the difference between reciprocal hybrids is shown in females as well as in males, it cannot be attributed to sex linkage. Analysis by means of egg transfer has shown that this reciprocal difference in the number of lumbar vertebrae is due to an influence exerted by the mother through the uterine environment, rather than through the cytoplasm of the egg. The number of lumbar vertebrae is not affected by the operation of egg transfer in itself, but only by the specific influence of the host uterine environment. In our material vertebral type is not influenced by the genetic constitution of the other embryos in the uterus, nor by their number. There is no marked dependence of number of lumbar vertebrae upon birth-weight. We conclude that in this instance the uterine environment does not act through promotion or inhibition of overall embryonic growth, but exerts a specific morphogenetic influence upon the unborn young.
Rabbit α-globin messenger RNA translation by the mouse ovum
Authors: Ebert Karl M. , Brinster R. L. 
Published: April 2021

ABSTRACT
Fertilized mouse ova were injected with messenger RNA for rabbit globin. The ova were labelled with [3H]leucine and the synthesized rabbit α-globin measured by immunoprecipitation. Injection of rabbit globin mRNA from 4-0 to 15-8pg/ovum resulted in the synthesis of ∼1200dpm/ovum of a-globin during an 18 h incubation. A concentration of mRNA that was translated below the maximum level of globin synthesis was used to determine translation efficiency. The efficiency of translation was 14·1 molecules of a-globin synthesized/cell/h for each molecule of α-globin mRNA injected. The radioactivity in a-globin was 1 % of the total incorporation in acid-precipitable material. Total incorporation of control and injected ova was not significantly different. This study shows that the fertilized mouse ovum can translate an injected foreign message with essentially the same efficiency as that reported for the Xenopus oocyte but substantially lower than the reticulocyte and that the translational capacity of the mouse fertilized ovum for injected mRNA is limited with little if any spare translational ability.
Stage specificity in the mesenchyme requirement of rodent lung epithelium in vitro : a matter of growth control?
Authors: Lawson Kirstie A. 
Published: April 2021

ABSTRACT
Epithelia from lung rudiments in which secondary bronchial buds are already established (14th and 13th gestational day for rat and mouse respectively) are able to undergo branching morphogenesis and cytodifferentiation in submandibular mesenchyme in vitro, whereas lung epithelium from one day younger foetuses rarely gives a morphogenetic response to submandibular mesenchyme and usually differentiates into primary (non-budding) bronchial epithelium.
The failure of 13-day rat lung epithelium to respond to submandibular mesenchyme can be prevented by peeling off the submandibular mesenchyme from the lung epithelium after days culture and replacing the same mesenchyme, or renewing it with fresh salivary mesenchyme ex vivo. Changes in the epithelial contour are visible by 10 h and buds form within 24 h ; this is followed by branching morphogenesis in more than 66 % of the samples.
The number of cells in S-phase in the epithelium is doubled within 3 to 5 h after the operation and the number of mitotic cells (colchicine block) is increased during an 11 to 19 h period after the operation. Substituting stomach mesenchyme for submandibular mesenchyme after the operation failed to elicit morphogenesis or an increase in the number of S-phase cells in the epithelium.
The proportion of epithelial cells in S-phase in unoperated recombinates does not differ from the proportion in the primary bronchial epithelium (non-budding) of homotypic lung recombinates, whereas the proportion of S-phase cells in operated recombinates approaches that found in the buds of homotypic lung recombinates. The distribution of S-phase cells in visibly responding recombinates 15 to 17 h after operation shows the same heterogeneity as in homotypic lung recombinates, newly formed buds having twice as many cells labelled with [3H]thymidine as the non-budding area.
Cell cycle parameters of intact rat lung growing in vitro were estimated using the labelled mitoses method. Primary bronchial epithelium and bronchial buds both had a total cell cycle time of about 13 h and an S-phase of about 10 h. The growth fraction was 0·54 in the primary bronchus and 0·95 in the buds. It is suggested that, also in the recombinates, differences in the proportion of S-phase cells at any one time in morphogenetically active and inactive areas of the epithelium are due to differences in the growth fraction.
It is concluded that an early event in the morphogenetic response of lung epithelium to submandibular mesenchyme after removing and restoring the mesenchyme is an increase in the size of the population of dividing cells and it is suggested that a high proportion of dividing cells in an epithelial population is a prerequisite for further interaction of epithelium and mesenchyme leading to branching morphogenesis.