bluuebunny/crossref_metadata_2025 huggingface dataset:
Autoradiographic patterns of [3H]uridine incorporation during the development of the mollusc, Acmaea scutum
Authors: Karp Gerald C.
Published: April 2021

Autoradiographic experiments on eggs and embryos of the gastropod mollusc, Acmaea scutum, have provided information on the time of initiation of [3H]uridine incorporation into RNA, the relative degree to which different embryonic regions are participating, and the relative rates of incorporation at different times of development. The unfertilized egg does not incorporate exogenous [3H]uridine. After fertilization the first indication of incorporation in the stages examined was at the beginning of the sixth cleavage. There is a marked increase in the level of incorporation during the sixth cleavage which marks the beginning of gastrulation in these embryos. After this stage there is a gradual increase in incorporation per embryo, throughout development to the mid-veliger. Very little indication of significant differences in the level of incorporation among the cells of any embryo was found. The most pronounced exception was the lower activity of the anterior ectodermal cells of the trochophore larva. At later stages the derivatives of these cells were as active as the cells of other regions.
Analyse de la morphogenèse du pied des Oiseaux à l’aide de mélanges cellulaires interspécifiques: I. Etude morphologique
Authors: Pautou Marie-Paule
Published: April 2021

Morphogenesis of the feet of birds, studied in limbs developed from reaggregated heterospecific mesoderm

Experiments were undertaken to determine whether species-specific characters of chick and duck mesodermal leg-bud cells are retained after dissociation and reaggregation in homo-and heterospecific mixtures.

Prospective zeugopod and autopod mesoderm from chick and/or duck leg buds were isolated, dissociated into a cell suspension and pelleted by centrifugation. The reaggregated mesoderm was packed into a leg-bud ectodermal jacket; the recombined leg bud was then grafted on the wing stump of a host embryo. Recombinants whose mesoderm was a homo-specific reaggregate developed into typical chick or duck leg parts according to the specific origin of the mesodermal component; the feet of nearly all these legs lacked an tero-posterior polarity. Recombinants containing heterospecific reaggregates were also capable of forming reasonably organized leg structures.

The foot was not, as a rule, of the specific type expected of the majority component. In a mixture of 75% chick mesoderm cells and 25% duck mesoderm cells, the feet which developed were either of chick type or of composite chick/duck type, where typical chick areas were next to typical or aberrant (steganoid) duck areas. When the ratio was reversed (25% chick, 75% duck), the majority of the feet were again of chick type or of composite chick/duck type, the typical duck phenotype being exceptional. Even in a mixture of 10% chick cells and 90% duck cells, duck-type feet were not obtained. They were all of composite type: half of their interdigital zones were of chick type, the other half were occupied, in most cases, by under-developed, indented webbing or by one or several discrete flaps, and, in a few cases, by normal webbing.

The vast majority of the feet developed from heterospecific mesoderm were characterized by the profusion of the toes, which were not polarized along the a-p axis.
Distribution of the head-activating substance in hydra and its localization in membranous particles in nerve cells
Authors: Schaller H. , Gierer A.
Published: April 2021

The low-molecular-weight substance activating head and bud formation in hydra is shown to occur in the animal as a gradient decreasing from the hypostomal to the basal region. The concentration of head-activating substance increases during head regeneration and during bud initiation.

Most of the low-molecular-weight head-activating substance is present in the animal in a structure-bound form. More than 90% was sedimentable; 70% was recovered in a highly purified fraction consisting of membranous particles of ∽1200 Å diameter. This implies that in the animal only a minor portion of the total activating activity is freely diffusible, i.e. present in the low-molecular-weight form.

The head-activating substance is mainly produced by and/or stored in nerve cells or a subgroup of the nerve cells. Nerve cells were enriched tenfold in a fraction containing most of the head-activating substance in a more than 10 times higher specific activity than in the animal. In addition, it is shown that only the nerve cells are positively correlated with the distribution of head-activating activity both with regard to localization within the animal as to time sequence of appearance during head regeneration and bud formation.
The effect of hydrocortisone on limb regeneration in the bullfrog tadpole, Rana catesbeiana
Authors: Weis Judith S. , Bleier Larry P.
Published: April 2021

Tadpoles of the bullfrog Rana catesbeiana lose the ability to regenerate limbs amputated through the femur at a very early stage in development. Well-differentiated limbs which in other species can regenerate if amputated through the ankle, cannot in this species. Non-regenerating tadpole limbs either show rapid healing of the cut surface by connective tissue with no breakdown of skeletal structures, or the beginning of dedifferentiation in the cartilage. However, the cells of the rudimentary blastema that forms do not undergo proliferation; instead they become separated from the epidermis by the regrowth of the connective tissue layer which acts as a block to regeneration. This condition, termed the critical stage, is reached more often by animals that received injections of hydrocortisone than by control animals. Experimental animals furthermore, produced larger blastemata. No advanced regeneration could be obtained however.
Competence tests of early amphibian gastrula tissue containing nuclei of one species (Rana palustris) and cytoplasm of another (Rana pipiens)
Authors: Hennen Sally
Published: April 2021

Competence tests of tissue from lethal nucleocytoplasmic hybrids consisting of diploid R. palustris nuclei in R. pipiens cytoplasm were carried out by grafting pieces of early gas-trulae to normal R. palustris early gastrula hosts. In the majority of cases, early gastrula ectoderm of the nucleoplasmic hybrids failed to differentiate further than if left in the intact embryo, although the grafts healed nicely and survived for several days. Grafts of the dorsal lip of the blastopore from nucleocytoplasmic hybrids to normal R. palustris hosts induced small secondary embryos with prominent suckers or sucker Anlage, a characteristic of nucleocytoplasmic hybrid development. These results indicate that the abnormal behaviour of the nucleocytoplasmic hybrids is an inherent property of the tissue, in the sense that contact with normal host does not alter its expression. Furthermore, the results with dorsal lip grafts suggest that nucleocytoplasmic hybrid tissue influences the direction in which normal tissue differentiates.
Etude autoradiographique des premiers stades du développement de l’ébauche du membre antérieur chez deux espèces de Chéloniens (Testudo graeca L. et Emys orbicularis L.)
Authors: Vasse J.
Published: April 2021

Autoradiographic study of early stages of the anterior limb-bud in two species of chelonian embryos

Embryos of two chelonian species (Testudo graeca L., Emys orbicularis L.) from 20-somites stage to 34-somites stage, fixed 2–4 h after an injection of tritiated thymidine or uridine or leucine, then emulsion-exposed 12–14 days, showed the following results:

These results are compared with results obtained in other reptiles and chick embryos, in the light of the theories on the role of the somites and of the apical crest in the development of the anterior limb-bud.
Gap junctions and electrotonic coupling in foetal rabbit adrenal cortical cells
Authors: Joseph T. , Slack C. , Gould R. P.
Published: April 2021

In an electron-microscope study of the developing rabbit adrenal gland numerous gap junctions and desmosomes were identified between the cortical cells, particularly in the juxtamedullary cortical tissue. An electrophysiological examination of the cortical cells showed them to be electrotonically coupled. Such couplings were more frequently found in the juxtamedullary cortical tissue than in the outer cortex.
Immunochemical analysis of chick phosvitin
Authors: Carinci P. , Grossi C. E. , Locci P.
Published: April 2021

Phosvitin is a yolk phosphoglycoprotein bound to lipoproteins within the yolk granules. Its absorption and utilization during chick embryogenesis is still unclear.

The presence of phosvitin was investigated by immunodiffusion techniques in the watersoluble fraction (WSF) of the yolk during oocyte maturation and chick development and in the embryonic fluids.

The immunochemical analysis showed that phosvitin consists of two components, one of which is detectable during oocyte maturation, while both are shown in the yolk WSF of the incubated egg. The appearance of the second phosvitin component during incubation is probably dependent on granule dissolution, as suggested by the immunochemical and biochemical determinations on the embryonic fluids.
The Anatomy and Development of Brachypodism in the Mouse
Authors: Grüneberg H. , Lee A. J.
Published: April 2021

The autosomal recessive gene for brachypodism (bp) in the mouse affects the appendicular, but not the axial skeleton. Manus and pes are more severely affected than the rest of the limbs; the girdles are normal. In digits 2–5, the basal and middle phalanges of the normal are replaced by a short and thin element which never ossifies properly; by contrast, the terminal phalanges are normal or nearly so. Up to the 13-day stage, the limbs of brachypods are externally quite normal, but anomalies of the digital blastemata are detectable in the 12-day embryo already, i.e. before the onset of chondrification. In the 14-day embryo, the overall length of metapod + phalanges is still nearly normal; but the basal and middle phalanges of the normal are represented by a single thin element which is absolutely longer whereas the metacarpale (metatarsale) is correspondingly reduced in length and calibre. This situation is subsequently reversed by heterogonie growth as the phalangeal element of brachypods grows very little. The normality of the terminal phalanges is largely due to the fact that, in the mouse, much of the terminal phalanx is formed directly from membrane and not by replacement of its cartilaginous ‘model’ on which it sits like a thimble. Brachypodism is thus due to an abnormality of the limb blastemata which precedes chondrification, but whose nature is unknown. Generally, muscular and tendinous anomalies parallel those of the skeleton.
Early cyclical changes in polyamine synthesis during sea-urchin development
Authors: Manen Carol-Ann , Russell Diane H.
Published: April 2021

The polyamines, putrescine, spermidine, and spermine, undergo dramatic cyclical variation in both synthesis and accumulation during the early cleavage stages of sea-urchin development. Ornithine decarboxylase activity (putrescine synthesis) in developing Strongylocentrotus purpuratus exhibits maxima at and 2 h after fertilization; increases in ornithine decarboxylase activity appear to correspond to the first and second S phases. Putrescine-stimulated S-adenosyl-L-methionine decarboxylase (spermidine synthesis) and spermidine-stimulated S-adenosyl-L-methionine decarboxylase (spermine synthesis) activities reflect rises during prophase-metaphase of the first and second divisions in two species of sea urchins. Cyclical changes in the concentrations of these three amines were evident also. In general, there were drops in the levels of the amines prior to cleavage. These rapid declines in polyamine concentrations may reflect (1) selective degradation or (2) selective secretion.
DNA synthesis inhibition, cytotoxicity and their relationship to teratogenesis following administration of a nicotinamide antagonist, aminothiadiazole, to pregnant rats
Authors: Scott William J. , Ritter Edmond J. , Wilson James G.
Published: April 2021

Four groups of Wistar rats were treated with 100 mg/kg aminothiadiazole (ATD) i.p. on day 12 of gestation. The first group was allowed to proceed to day 20, when they were sacrificed and the teratogenic effects analyzed in the surviving fetuses. A second group was given 100 mg/kg nicotinamide (NAM) i.p. simultaneously or at intervals of 4, 8 or 12 h following ATD. Third and fourth groups corresponded to the first and second except that [3H]thymidine was administered and one uterine horn removed for histological study or analysis of DNA synthesis rates. The following observations were made:

ATD proved teratogenic to 90% of the surviving fetuses, causing one or more malformations of organs such as limbs, tail, palate and heart. Nicotinamide was capable of protecting the embryo against ATD teratogenicity. This effect diminished as the interval between ATD and NAM administration lengthened so that by 12 h little protection remained. ATD produced a severe and prolonged inhibition of DNA synthesis, reaching a low of 12% of control level at 17 h and returning to near normal by 38 h. NAM reversed this inhibition of DNA synthesis in proportion to the length of the interval between ATD and NAM administration. ATD produces severe cytotoxicity especially in the limb buds and neural tube. Based on this and earlier studies the hypothesis is proposed that the time of appearance of maximal cell death plays a major role in determining the degree and pattern of forelimb ectrodactyly.
ATP metabolism in cleavage-staged mouse embryos
Authors: Ginsberg L. , Hillman N.
Published: April 2021

Total ATP, ATP/ADP ratios, the rates of synthesis and turnover of ATP, and the level of cyanide inhibition of ATP synthesis were determined for 2-cell, 4-cell, 8-cell, late-morula and late-blastocyst mouse embryos. The results show that from the 2-cell stage to the late-blastocyst stage there are progressive decreases in total ATP and in the ATP/ADP ratios. These are accompanied by increases in the rates of ATP turnover as well as in the percentage of inhibition of ATP synthesis by cyanide. These data are discussed in relation to results from other metabolic studies on mouse cleavage-staged embryos and from studies describing configurational changes in the ultrastructure of mitochondria at these developmental stages. It is postulated that the mitochondrial ultrastructural changes during cleavage reflect differences in the levels of oxidative phosphorylation during specific metabolic steady states.
Elicitation of lens formation from the ‘ventral iris’ epithelium of the newt by a carcinogen, N-methyl-N′-nitro-N-nitrosoguanidine
Authors: Eguchi Goro , Watanabe Kenji
Published: April 2021

A potent carcinogenic compound, N-methyl-N′-nitro-N-nitrosoguanidine (NG), was administered to the lentectomized eyes of the newt, Triturus pyrrhogaster. Supernumerary lenses were formed from the dorsal iris and even from the ventral iris, which never transforms into lens following simple surgical lentectomy or the grafting of isolated iris pieces into lentectomized eyes. After the administration of NG the pigmented epithelial cells of the ventral iris were induced to gain the competence for transformation into lens cells. The induced competence of the iris epithelial cells was stably maintained for at least 12 months. The secondary regeneration of the lens 45 days or 12 months after the primary lentectomy took place at the same positions of the ventral area of the iris where the primary lens regeneration had been induced by NG.

The effects of NG were also confirmed by implanting isolated pieces of iris treated with NG solution into lentectomized eyes. Five implants out of 42 available experiments on the ventral half of the iris were found to be transformed into lens.
Properties of the primary organization field in the embryo ofXenopus laevisV. Regulation after removal of the head organizer, in normal early gastrulae and in those already possessing a second implanted organizer
Authors: Cooke J.
Published: April 2021

Patterns of individuation occurring in the primary embryonic axis of Xenopus following excision of the organizer region of the early gastrula are described. In some 70 % of cases the information for induction of the complete head is qualitatively restored by the time of cell determination, giving rise to an essentially normal embryo. In some 40 % of cases a second posterior axis of bilaterality is formed, causing development of a secondary anus, tail-fin and spinal cord, and often somites. The probabilities of twinning in the tailfield and of failure to complete apical regulation (= head formation) are largely independent.

After such excision of the head organizer region, a delay of some 3 h in the schedule of visible differentiation in the neurula/tail-bud embryo is commonly incurred, whether or not apical regulation is successful.

When the apex is excised from a host embryo which has already contained for some hours a second apex (= head organizer) as described in an earlier paper, that grafted apex then captures a considerably increased territory in the host material, as seen from the size of the individuation field finally caused by it. Such a shift across host cells, of the boundary between fields of positional information due to two organizers, is not seen under any conditions where these are left intact, or where host excision is carried out soon after implanting the donor organizer.

In discussing the results and reconciling them with earlier observations, it is shown that they strongly suggest the presence of local polar (i.e. vectorial) properties in the presumptive mesoderm, due to signals from restricted regions which have achieved a special apical state. Repolarization of cells by a new organizer is not very rapid, and may spread decrementally from the source. Data on further delays in development, caused by the presence of the second organizer during regulation in the host apex, suggest that one organizer may act directly on cells elsewhere to delay or prevent the restoration of the apical state there.
Induction d’une queue et de parapodes surnuméraires par déviation de l’intestin chez les Nereidae (Annélides Polychètes)
Authors: Boilly B.
Published: April 2021

Supernumerary tail and parapodia induction by deviation of the intestine in nereids (Annelida: Polychaetd)

Localized ablation of the intestine has been performed on normal and grafted specimens of the two polychaetes Nereis pelagica L. and Perinereis cultrifera G. with the following results: In the absence of the intestine, segments are not regenerated but parapodia grow on the plane of section.A segmented tail arises where the intestine is deviated; the regenerate we obtain in this case is of the ‘aneurogenic’ type and without anal cirri and parapodia.These results suggest that caudal regeneration results from the association of different tissues (intestine and the body wall) whereas the nerve cord exerts an influence upon the organization of the regenerate. Likewise the caudal regeneration of parapodia is the consequence of the juxtaposition of a dorsal and a ventral body wall in the presence of the central nervous system.
Teratogenic activity of methadone hydrochloride in mouse and chick embryos
Authors: Jurand A.
Published: April 2021

Teratogenic activity of methadone HCl (Physeptone, Burroughs Wellcome and Co.) was tested on inbred JBT/Jd and outbred Q strain mouse embryos and on chick embryos. 22–24 mg/kg injected subcutaneously on the 9th day of pregnancy caused by the 13th day exencephaly in 56 out of 479 JBT/Jd embryos but after 32 mg/kg only in 1 out of 220 of the Q strain. Some affected JBT/Jd embryos showed also rachischisis in the cervical area.

The second abnormality shown by the embryos of both strains is Z-shaped kinkage of the spinal cord.

In explanted chick embryos cultured in vitro as well as in embryos treated in ovo metha-done causes non-closure of the neural tube with extensive necrosis of the neural plate cells in the cephalic region.

The results of this study indicate that methadone, which is a neutropic drug, has an embryo-toxic activity directed against the developing central nervous system.
Passage of bovine serum albumin from the mother to rabbit blastocysts II. Passage from uterine lumen to blastocyst fluid
Authors: Kulangara Abraham C. , Crutchfield Floy L.
Published: April 2021

Passage of bovine serum albumin (BSA) into unimplanted rabbit blastocysts was studied using intravenous or intrauterine injection of the mother and in vitro cultivation of 5-day blastocysts. BSA concentration in blastocyst fluid was measured using a quantitative radial immunodiffusion method and confirmed by double diffusion in agar.

Intravenous injection of up to 200 mg/kg body weight produced a mean concentration of 106 μg/ml in uterine fluid and the blastocyst fluid was mostly negative. In vitro cultivation with 1–20 mg BSA/ml resulted in appreciable passage which was confirmed by intra-uterine injection. BSA appeared in blastocyst fluid after 2–3 h of exposure. After 24 h, 0·25–2 ·0μg BSA was accumulated. The highest concentration observed in blastocyst fluid was 338 μg/ml and this was about 1·7 % of the surrounding concentration. Combined with previous results on passage from plasma into uterine fluid, it could be calculated that in 24 h the blastocyst fluid acquired about 0· 08 % of the maternal serum concentration of BSA.

The accumulation of BSA by the blastocyst is about half that of rabbit albumin in the same period (5–6 days p.c.), which suggests that the unimplanted blastocyst is capable of discriminating between native and foreign serum albumin.
Parthenogenetic development of mouse embryos in vivo: II. Postimplantation development
Authors: Witkowska Anna
Published: April 2021

CBA-p and CBA-T6T6 females were mated with vasectomized males of A strain and early in the morning the eggs were activated in situ with the electric shock of 30, 40 and 50 V. Females were killed between the 5th and the 10th day of pregnancy and the implantation sites were studied histologically or their content was examined under the dissecting microscope. Of the uterine horns, 43·6% contained at least one implantation and the mean number of implantations per horn was 0·76. Altogether 152 implantations were collected. The implantation rate was twice as high in older females (12 weeks and over) as in young ones (6 –8 weeks). The number of living embryos decreased with every day so that on the 9th and 10th day only 2 out of 86 embryos were alive (2·3%). With one exception all embryos which were alive at the time of examination were retarded in development for approximately 1 day. The most advanced embryo was at the 8-somite stage. Two attempts aimed at increasing the synchrony between the embryos and the uterus at the time of implantation (activation immediately after delayed mating and transfer of 4·5-day embryos to 3·5-day uterus) did not improve the survival of embryos after implantation.
Changes in protein during development of Triturus embryos: I. Contents and syntheses of soluble or basic protein of cell components
Authors: Imoh Hiroshi , Minamidani Tsutomu
Published: April 2021

The present paper reports basic data on DNA content, protein content, and protein synthesis in Triturus pyrrhogaster embryos during development from cleavage to the hatching stage. Except for measurements of DNA and total protein contents, embryos were labeled with sodium carbonate-14C for 10 h and fractionated into embryonic cell components, i.e. cytoplasmic mass, yolk and pigment granules, and nuclei, in a discontinuous density gradient of sucrose. The protein content and the radioactivity incorporated into protein were measured in each fraction. Those fractions combining protein soluble in buffer at pH 8·3 and in 0·25 N-HCl were further studied with polyacrylamide gel electrophoresis.

In the newt embryo, four stages of active DNA increase were observed when cultured at constant temperature; they were gastrula, neurula, late tail-bud, and before-hatching stages. Total protein per embryo decreased from 3 to 2 mg during the development studied. The content of cytoplasmic soluble protein per embryo was low and constant throughout development. Synthesis of the fraction was observed at the earliest stage of development studied though the rate was not high and specific activity of the soluble protein increased during development. Qualitative changes in the newly synthesized protein were observed. With the yolk fraction, synthesis of protein, other than from probable contamination with the cytoplasmic fraction, was not detected and a detailed description was omitted.

Changes were observed at two stages of development in the synthesis of nuclear protein soluble in buffer at pH 8·3, the first at gastrulation and the second at late tail-bud stage. The change at gastrulation seemed to be the start of syntheses of the nuclear soluble proteins, while quantitative enhancement rather than qualitative change was noticed at late tail-bud stage. Most of the nuclear protein soluble in 0·25 N-HCl was histone. The histone content increased in accordance with increase in the DNA content and the rate of DNA accumulation was accompanied by proportionate incorporation of radioactivity into histone. Among histone fractions, unique behaviour of the very lysine-rich histone was observed.

The availability of [14C]sodium carbonate in rough estimations of protein synthesis in embryos and significance of the data obtained have been discussed.
Positional information and pattern regulation in hydra: formation of the foot end
Authors: Hicklin J. , Wolpert L.
Published: April 2021

The time required for foot end formation increases with distance from the foot end. Using lateral grafting it was shown that both the peduncle and basal disc could induce a proximal axis when grafted into the gastric region. The time for foot end determination was shown to be about 4 h at the proximal end of the gastric region and to increase towards the head end. In general the determination of the foot end is similar to that of the head end.
The retinotectal projection from a double-ventral compound eye in Xenopus laevis
Authors: Straznicky K. , Gaze R. M. , Keating M. J.
Published: April 2021

The retinotectal projection was mapped in 22 post-metamorphic Xenopus in which the eye under investigation had been made double-ventral by operation at stage 32. The contralateral retinotectal projection from a double-ventral eye is neither normal nor does it show the type of abnormality predicted from previous work on double-nasal and double-temporal eyes. In the case of double-ventral eyes, the nasal part of the field projection tended to be reduplicated about the horizontal midline and those field positions corresponding to latero-medial rows of electrode positions on the tectum ran ventrodorsally in the field. As the electrode rows on the tectum progressed more caudally, so the corresponding rows of stimulus positions in the field tended to curl in a temporal direction. These observations have been interpreted as indicating that the nasotemporal and dorsoventral polarities of the eye are not irreversibly determined at stage 32 and that the mechanisms generating the nasotemporal and dorsoventral axes of the eye may interact with each other.
The fine structure of the reconstructed neural retina of chick embryos
Authors: Fujisawa H. , Nakamura H. , Chin M.
Published: April 2021

The fine structure of reconstructed neural retina formed from dissociated neural retinal cells of -day-old chick embryos on the chorio-allantoic membrane of chick embryos was examined with the electron microscope.

Three nuclear layers (ganglion cell layer, inner and outer nuclear layers) and two fibrous layers (inner and outer plexiform layers) are found within the reconstructed retina.

Both the outer and the inner limiting membranes of the reconstructed structure are constituted from the processes of differentiated Müller cells.

The ganglion cell layer consists of two types of cell, though a typical ganglion cell with axonal process is not observed. Optic nerve fibres are not formed.

Amacrine cells are recognized within the inner nuclear layer.

Differentiation of the inner segment of the photoreceptor cell occurs, but not of the outer segment.

Synaptic structures are recognized in the inner plexiform layer, but not in the outer plexiform layer.
Influence of extrinsic factors on the development of the bulboventricular loop of the chick embryo
Authors: Del RÍO Jorge Salazar
Published: April 2021

Of several chick culture methods investigated, New’s technique produced the greatest percentage of normal bulboventricular loops.

In embryos with two left cardiogenic areas or with two right cardiogenic areas or with the areas exchanged, the bulboventricular loop develops to the right in the cases in which there is integration. When each of the areas was permitted to be expressed without the other and there was closure of the gut, both areas were expressed according to their intrinsic quality. We believe that in stage 5, the type of loop is not determined.
Genetic and environmental factors determining the morphological maturation of the mouse and its relationship with weight growth
Authors: Garrard G. , Harrison G. A. , Weiner J. S.
Published: April 2021

Data on the morphological development of inbred and F1 hybrid mice reared at 22·8 °C dry bulb, 17·8 °C wet bulb, and 32·2 °C dry bulb, 26·7 °C wet bulb are presented. Animals were weighed at birth, 1 and 2 weeks of age and at each developmental stage. All animals were examined for the freeing of the ear pinnae, eruption of the lower incisor teeth and perforation of the eye membranes and in addition females were examined for the appearance of the first pair of nipples and for perforation of the outer part of the vagina.

Within each environment, but especially at 23 °C, there are genotypically characteristic differences in the ages at maturation of each variable. Though the ages of maturation of the different variables are highly correlated within genotypes, early maturation of one variable is not necessarily associated with the early maturation of others. Reciprocal F1 hybrid differences indicate a maternal effect upon the age of maturation which is more marked at 23 than at 32 °C.

Comparisons of the ages at maturation in the two environments showed that the only character to mature earlier at 23 than at 32 °C was pinna freeing. The most marked influence of the 32 °C environment in advancing development was on the appearance of nipples and on vaginal opening. In almost all cases, animals reared at 32 °C were lighter at the time of maturation than those at 23 °C. Hence when allowance was made for environmental differences in body weight the association between an environment at 32 °C and early development was further enhanced. Those animals that were relatively heavy when weighed at the weekly interval prior to maturation matured earlier than the lighter ones, especially at 23 1C, indicating that morphological maturation was closely related to overall growth.

Both the within, and between, litter variation in the ages and body weights at maturation of a strain tended to be greater in animals exposed to the higher temperature. In bilaterally distributed characters, asymmetrical maturation was more common at 32 than at 23 °C.
The development of the retino-tectal projection in Xenopus laevis: an autoradiographic and degeneration study
Authors: Scott T.M.
Published: April 2021

The development of the retinotectal projection in Xenopus laevis was studied using degeneration and autoradiographic techniques. At stage 47 only the rostral pole of the tectum receives optic fibres. By stage 50 half of the tectum is innervated and by metamorphosis all of the tectum except for narrow caudal and medial strips contains optic fibre terminals.
Micro-disc electrophoresis of soluble proteins in rabbit blastocysts
Authors: Petzoldt Ulrich
Published: April 2021

Soluble proteins were studied in the developing rabbit blastocyst by using a micro-disc electrophoresis technique. The tissues of the blastocyst (in later stages separated into the embryoblastic and trophoblastic parts) were analysed, and their protein patterns were compared with those of uterine secretion and blastocyst fluid.

A protein pattern with more than 20 protein fractions was found in the tissues of the blastocysts. This protein pattern was quite different from those previously reported in uterine secretion or blastocyst fluid. After cleavage and during early phases of development of blastocysts the protein pattern was changing; from the 5th day p.c. it became fairly homogeneous. The protein patterns of the embryonic and trophoblastic parts of the blastocyst tissues were rather similar.

The origin of the proteins in the blastocyst fluid is discussed.
The morphogenetic properties of the node in Clytia johnstoni
Authors: Hale L. J.
Published: April 2021

1.

The experiments show that

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It is concluded that
Origine et evolution des cellules trophoblastiques intra-artérielles, chez le rat: etude autoradiographique
Authors: Legrand C.
Published: April 2021

An autoradiographic study of the origin and development of the intra-arterial trophoblast cells in the rat

The trophoblastic origin of the intra-arterial cells observed in the utero-placental arteries has been demonstrated, in the pregnant rat, by conjoined use of colchicine and tritiated thymidine. The development of these large cells is described. The intra-arterial trophoblast originates from a special placental cell population well segregated from the 10th–11 th day of gestation. Due to their cytophysiological characteristics, these foetal cells belong to the ‘renewing cell population’ described in the adult rat.
La lignée germinale chez les Echinodermes: Origine et évolution des cellules germinales au cours de la régénération de la gonade chez l’étoile de merAsterina gibbosaPenn.
Authors: Huet Michel
Published: April 2021

The germinal Une in Echinodermata: the origin and development of the germinal tissue in the course of gonadal regeneration in the sea-star Asterina Gibbosa Penn

After partial surgical removal of the genital apparatus in an interradial structure, the elements removed regenerate. This regeneration produces a migration of germinal cells from a reserve of gonocytes situated in the aboral sinus. When destroyed by irradiation, the reserve cannot regenerate, though somatic regeneration is still possible. These results seem to indicate that Asterina possesses a germinal line distinct from the somatic line.

The developmental level of the germinal tissue in the regenerated gonad conforms to that of gonads which have followed their normal cycle. This development is not related to the existence of a privileged anatomical place in the genital apparatus.
Effects of Nerve Growth Factor from the venom ofVipera russellion sensory and sympathetic ganglia from the embryonic chick in culture
Authors: Charlwood Katharine A. , Griffith Marjorie J. , Lamont Margaret D. , Vernon C. A. , Wilcock Joan C.
Published: April 2021

Sensory and sympathetic ganglia of embryonic chick were cultured in media in which no growth of fibres occurred, and then transferred to culture conditions favouring the growth of fibres. The effects on fibre outgrowth of having NGF in neither, one or both media were examined quantitatively. It was concluded that the main effect of NGF, under these conditions, is to maintain the viability of the neurons. Subsidiary experiments supporting this view are also reported.
Experimental manipulations of early Drosophila embryos: II. Adult and embryonic defects resulting from the removal of blastoderm cells by pricking
Authors: Bownes Mary , Sang J. H.
Published: April 2021

Cells were removed from three regions (anterior, mid-lateral and posterior) of Drosophila eggs at blastoderm formation, by pricking. Embryonic defects were generally correlated with the site of damage, as is also found with microcautery and with u.v. irradiation. But many structures can develop autonomously, independently of surrounding damage. Most hatching adults were normal, suggesting that there may be mechanisms which permit compensation for cell loss. Malformed or missing adult structures are those expected from the fate map obtained from studies of genetic mosaics.
The anionic binding-sites at the cell surface after tissue dissociation and during the early phases of cell reaggregation
Authors: Caravita Silvia , Zacchei Anna Maria
Published: April 2021

The fixation of dissociated chick embryonic cells in the presence of ruthenium red or alcian blue revealed a remarkable reduction in the binding of these cations to cell surfaces following tryptic digestion at 37 °C, but not after trypsin used at 4 °C or EDTA.

The reconstitution of anionic sites present over the cell plasma membrane was studied in retina, liver and heart cells from embryos of different ages, cultivated according to a method which promotes cell reaggregation. All these cells regenerated ruthenium red-stainability within the first hour of culture. Culturing at 15 °C, substitution of saline for the culture medium or addition of puromycin or of neuraminidase to the culture media did not affect this restitutive process. Neuraminidase and hyaluronidase digestion were not able to alter the ruthenium red-binding, once it was present.

From these data and from the reports available in the literature it has been concluded that the anionic binding-sites cannot be identified with the cell surface coat, and probably not with sialic acids, which require active metabolic processes and a much longer time interval for regeneration. The presence of these sites probably favours the formation of initial cell contacts but is not sufficient for cell reaggregation.
Extent and properties of the regeneration field in the larval legs of cockroaches (Leucophaea maderae):II. Confirmation by transplantation experiments
Authors: Bohn Horst
Published: April 2021

The investigation of the regeneration field of the larval legs of cockroaches (Leucophaea maderae), which commenced in a previous paper with extirpation experiments, has been continued by transplantation experiments. The extirpation experiments showed that there are two regions near the leg which are indispensable for leg regeneration: the basal sclerites, and the membranous region extending behind the leg up to the spiracle of the next segment, called Teg-inducing membrane’ (LIM). The LIM is followed by ‘sclerite-inducing membrane’ (SIM) which, upon contact with sclerites, only allows formation of sclerite structures.

The results of the extirpation experiments have been confirmed by transplantation experiments. When the whole leg including the basal sclerites is removed, no leg regeneration occurs. The regenerative ability can be restored by implantation of part of the basal sclerites (for instance, the trochantin), but leg regeneration takes place only when the implantation area is covered by LIM. When the sclerites are transplanted to a region which is covered by SIM only additional basal sclerites are formed.

Whole sets of basal sclerites have been implanted at different distances behind the uninjured hindleg. Additional legs are regenerated only in the anterior half of the membranous field extending between the hindleg and the first abdominal segment. Thus, there is a distribution of LIM and SIM in the region of the hindleg, similar to that near the midleg.

Whole sets of basal sclerites have been implanted at various sites on the dorsal or ventral surfaces of the abdomen. Legs are formed on both surfaces, but only when the transplanted sclerites contact the intersegmental membranes. This means that the intersegmental membranes of the abdomen also have leg-inducing capacities.

The implantation of a trochantin into a field of LIM is followed by the development of two regenerates -a normal one at the posterior border of the field, and one with reverse anterior-posterior polarity at the anterior border. When the trochantin is transplanted together with the praecoxa in a similar way, only one normal regenerate is formed at the posterior margin of the trochantin. The praecoxa prevents contact of the anterior margin of the trochantin with LIM, and contact of the anterior margin of the praecoxa with LIM does not promote leg regeneration.
Regeneration and growth control in Nereis: III. Separation of wound healing and segment regeneration by experimental endocrine manipulation
Authors: Golding D. W.
Published: April 2021

Loss of posterior segments from immature Nereis is followed by the associated processes of wound healing and segment regeneration. In the absence of a hormone secreted by the brain, wound healing alone ensues. However, proliferation of segments can be initiated by intracoelomic implantation of a living brain (removed from a donor) during the course of wound healing or subsequent to its completion. In this way, wound healing and regenerative growth can be separated experimentally. Wound hormones may have a role in wound healing, but are probably not involved in the initiation of segment regeneration in Nereis. However, developments at the site of the wound which follow loss of posterior segments in the absence of regeneration progressively reduce the regenerative activity which follows subsequent brain implantation. The nature of the changes is unknown. Maintenance in a decerebrate condition also reduces regenerative capacity. This effect is independent of changes at the wound and may be due to accelerated maturation.
Parthenogenetic activation of rhesus monkey follicular oocytesin vitro
Authors: Abramczuk Jan , Stark Richard A. , Konwinski Marian , Solter Davor , Mastroianni Luigi , Koprowski Hilary
Published: April 2021

Rhesus monkey follicular oocytes obtained from gonadotropin-injected animals were treated with hyaluronidase and cultured in Whitten’s medium. Of 74 oocytes beyond germinal vesicle stage, 57 were activated. Twenty-one of the activated oocytes cleaved one to three times. Behavior in culture and the values of relative Feulgen-DNA content in nuclei of six normally cleaved 6-to 10-cell parthenogenones showed that four resulted from the activation of primary oocytes, one from a secondary oocyte, and one from a primary polyploid oocyte. One parthenogenone with four pronuclei, and two with a single pronucleus (without extrusion of the first and second polar bodies in either case) were also observed.
Etude expérimentale sur les premiers stades du développement du membre antérieur chez l’embryon du Chélonien Emys orbicularis L.: détermination en mosaïque et régulation
Authors: Vasse J.
Published: April 2021

Experimental study on the early stages of development of the front limbs of the embryo of the chelonian Emys orbicularis L. : mosaic determination and regulation

Ablation of postotic somites 6– 13 on one side in embryos of Emys orbicularis L. or injury to the adjacent somatopleure at the developmental stage when 15– 21 somite pairs were present, led to arrest of forelimb-bud development in this part of the somatopleure on the operated side. Limb development in the remaining part of prospective somatopleure on the operated side was investigated 5– 11 days after the operation.

When this part of somatopleure was adjacent to cranial somites 6– 9 or 6-10, the development stopped at the start of the apical crest as in Anguis or Scelotes forelimb-buds. A part of somatopleure adjacent to caudal somites 8– 12, 9– 12 or 10– 12 developed into a normal limb with three segments; a part of somatopleure adjacent to 1– 2 somites only, developed into a reduced limb, scarcely swelling.

Each somitic level developed in relation to its initial regional determination dependent on position in the cephalocaudal axis; to its environment (cranial or caudal bud) and to the quantity of somatopleural material in the bud.
Glycosaminoglycan localization and role in maintenance of tissue spaces in the early chick embryo1
Authors: Fisher Marilyn , Solursh Michael
Published: April 2021

Comparison of sections stained with Alcian blue at pH 1·0 or 2·5 demonstrates the distribution of sulfated and non-sulfated glycosaminoglycans in the extracellular matrix of the stage-8 (Hamburger & Hamilton, 1951) chick embryo. Both types of GAG are present in basement membranes throughout the embryo. Treatment of sections with Streptomyces hyaluronidase, reported to be specific for hyaluronic acid, prior to staining with Alcian blue at pH 2·5 reveals that hyaluronate is an important constituent of the extracellular matrix in basement membranes and in intercellular spaces within the mesoderm. Hyaluronate is shown to be the predominant glycosaminoglycan in the matrix of the head mesenchyme. In addition, examination by SEM and light microscopy of embryos after treatment in ovo with hyaluronidase shows that removal of hyaluronate from living embryos results in a dramatic decrease in cell-free spaces and a weakening of the association between mesoderm and ectoderm in the head.
Morphogenèse de l’épiderme imaginai de l’abdomen de Calliphora erythrocephala (Insecte, Diptère)
Authors: Bautz Anne-Marie
Published: April 2021

The morphogenesis of the abdominal epidermis in Calliphora erythrocephala begins by a cellular proliferation which proceeds slowly in larvae and rapidly in pupae. This allows histoblasts to glide and invade the whole abdominal surface.

As soon as the new epidermal sheet has become continuous, differentiation begins. Generalized epidermal cells show an intense activity which leads to the deposition of imaginai cuticle from the 6th day after pupation onwards. After cuticle deposition they darken and become inactive although they remain alive, even after emergence.

Trichogen and tormogen cells are even more active than generalized epidermal cells, especially the trichogen cell in which polyribosomes and microtubules are abundant. The former are possibly involved in microtubule synthesis. After cuticle deposition the trichogen and tormogen cells undergo degeneration. Their nuclei contract, rough endoplasmic reticulum breaks down and cytoplasm breaks up into fragments through infoldings which proliferate from the plasma membrane. Finally only generalized epidermal cells and sensory cells remain alive in the adult.
The influence of the lower beak on the interorbital septum-prenasal process complex in the chick embryo
Authors: Wouterlood F. G. , Pelt W. Van
Published: April 2021

The effect of removal of the lower beak on the development of the interorbital septum-prenasal process (ISPP) complex was studied in chick embryos. In normal development the angle between the ventral contour of the interorbital septum and the long axis of the prenasal process increases. At the same time the angle between the ventral contour of the interorbital septum and the basal plate increases.

After surgical removal of the prospective lower beak at stage 29, the position of the entire ISPP complex was altered in stage-38 embryos and the prenasal process showed elongation. In stage-38 embryos in which the prospective upper beak had been removed at stage 29, Meckel’s cartilage was elongated. It is concluded that straightening of the angle between the ventral contour of the interorbital septum and the long axis of the prenasal process is not influenced by the lower beak, whereas the position of the entire ISPP complex and the size of the prenasal process are under the epigenetic influence of the lower beak. The position and size of Meckel’s cartilage are under the epigenetic influence of the upper beak.