bluuebunny/crossref_metadata_2025 huggingface dataset:
Morphogenesis of the silkworm egg
Authors: Legay J. M.
Published: April 2021

Ovarian follicle development, which accompanies morphogenesis of the silkworm egg has three distinct phases: spheric, ellipsoidal and flattened-ellipsoid. Transitions between phases are rapid and form-stability (characterized by length/width ratio) is preserved from the beginning of the ellipsoidal phase. The geometric stability of the follicle-oocyte-ovariole system, the polarity of the egg and the determinism in form changes reveal strikingly coordinated spatial and temporal organization.
Target discrimination in regenerating insect sensory nerve
Authors: Mclean Miriam , Edwards John S.
Published: April 2021

The paired abdominal cerci of the cricket Acheta domesticus are mechanosensory appendages which regenerate readily when amputated during larval life. Their peripherally-located sense cells form axons which project centrally as a purely sensory nerve to the terminal abdominal ganglion.

In an attempt to analyze some of the factors which guide a regenerating sensory nerve to correct central terminations, implants of homologous, supernumerary terminal ganglia were made in cricket larvae and the host cerci amputated. The possibility that implants with multiple nerve stumps might release an attracting substance was considered. Surgical procedures used were (1) implant in posterior abdomen; (2) implant in posterior abdomen, ipsilateral to chronic cereal deprivation; (3) implant in mesothoracic leg socket, adjacent to heterotopically-transplanted regenerated cercus; (4) implant in posterior abdomen, ipsilateral host cereal motor nerve sectioned; (5) implant in posterior abdomen, ipsilateral margin of host terminal ganglion wounded. Results were determined after the adult molt, by con-ventional histology or by cobalt chloride filling of regenerated cereal nerves.

In all procedures except (3) and (4), the regenerated afferent nerve bypassed the implant and terminated in the host terminal ganglion. In (3), the regenerated fibers from cereal grafts bypassed the implant; terminations were not found. In (4), some regenerated cereal axons connected with the implant and the majority terminated in the host ganglion.

It is suggested that regenerating cereal afferents may depend in a facultative way on the cereal motor nerve as a pathway guide but there is as yet no clear evidence for a trophic influence from the central nervous system.
Etude comparative de l’évolution des cellules de planaires d’eau douce Polycelis tenuis (lijima) dans des fragments dissociés en culture in vitro aspects ultrastructuraux, incorporations de leucine et d’uridine tritiée
Authors: Franquinet Raphaël
Published: April 2021

Comparative study of the cells of the freshwater planarian Polycelis tenuis (lijima) using dissociated fragments cultivated in vitro: ultrastructural aspects and incorporation of [3H] leucine and [3H]uridine

Study of planaria cells, which are the result of dissociated fragments cultivated in vitro, allows the evolution of two cell groups to be followed:Differentiated cells, which do not divide, and do not dedifferentiate either, incorporate leucine and uridine at a rate which remains stable for the whole duration of the culture.Undifferentiated cells have a mitotic and incorporation rate of leucine and uridine which varies during the period of culture. After 10 days of culture they demonstrate the characteristics of cells undergoing differentiation.

These results are in agreement with those of other authors who attribute an essential role to undifferentiated cells during the regeneration of the adult planaria.
Role of karyoplasm in the emergence of capacity of egg cytoplasm to induce DNA synthesis in transplanted sperm nuclei
Authors: Skoblina M. N.
Published: April 2021

The behaviour of sperm nuclei was studied both in the cytoplasm of intact toad oocytes undergoing maturation and the cytoplasm of oocytes matured without germinal vesicles. The behaviour of the nuclei of pronase-treated sperm injected in the mature egg cytoplasm was shown to be exactly similar to that of the sperm nucleus after fertilization, i.e. they swelled, synthesized DNA, and divided. No changes in such sperm nuclei could be detected in the cytoplasm of the oocytes matured without germinal vesicles.
The signal from fruiting body and conus tips ofDictyostelium discoideum
Authors: Rubin Jonathan
Published: April 2021

Tips from fruiting bodies and conuses were transplanted into interphase fields of Dictyostelium discoideum amoebae. Progressively increasing concentrations of beef-heart phosphodiesterase added to the fields significantly decreased the chemotactic range of the responding amoebae. The findings suggest that the tip secretes c-AMP. We also find that the chemotactic range is independent of the size of the tip implying that the tip may produce a regulating gradient.
The use of variable lactate/malic dehydrogenase ratios to distinguish between progenitor cells of cartilage and bone in the embryonic chick
Authors: Thorogood P. V. , Hall Brian K.
Published: April 2021

The activities of LDH and MDH have been studied, both in differentiated cartilage and bone from the embryonic chick, and in the pool of mixed osteogenic and chondrogenic stem cells found on the quadratojugal, a membrane bone. In confirmation of the model proposed by Reddi & Huggins (1971) we found that the LDH/MDH ratio was greater than 1 in cartilage and less than 1 in bone. Furthermore we established, for the first time, that ratios occurred in the chondrogenic and osteogenic stem cells, similar to the ratios in their differentiated counterparts. Alterations in LDH/MDH resulted from variations in the level of LDH/μg protein. MDH/μg protein remained constant, even when LDH/MDH was changing. We interpret these results in terms of adaptation of chondrogenic progenitor cells for anaerobic metabolism and anticipate that our model will be applicable to other skeletal systems where stem cells are being studied.
Developmental patterns of rat muscle histochemistry
Authors: Curless Richard G. , Nelson Marilyn B.
Published: April 2021

A developmental progression of histochemical fiber typing is demonstrated in normal rat soleus muscle. By utilizing the acid lability of ATPase, the type II fibers are subdivided into type IIA, IIB and IIC. No IIB fibers are present in the newborn or adult rat soleus. In the 1-day-old animal 90 % of the fibers can be differentiated into type I and II with all of the type II’s demonstrating IIC characteristics. Only type I and IIC fibers are present until 18 days, when poorly differentiated IIA fibers first appear and gradually become the predominant type II fiber at the expense of IIC’s.

Further analysis documents the sequence of disappearance of myotubes from up to 80 % of all fibers in the 1-day-old to less than 1 % between 15 and 18 days. An analysis of the progression of fiber size according to type is presented.
Embryological study of aT/tlocus mutation (tw73) affecting trophectoderm development
Authors: Spiegelman Martha , Artzt Karen , Bennett Dorothea
Published: April 2021

Mouse embryos homozygous for the recessive lethal mutation tw73 show specific defects in trophectoderm shortly after implantation. The trophectoderm and ectoplacental cone fail to form the usual close association with the uterine decidua, and proliferation is markedly reduced. The embryo proper ceases to develop beyond the two-layered stage and degenerates and dies within 5 days of implantation.
Cell junctions in the developing compound eye of the desert locust Schistocercagregaria
Authors: Eley S. , Shelton P. M. J.
Published: April 2021

Intercellular junctions in the developing retina of the locust Schistocerca gregaria have been examined by electron microscopy. Different types of junction appear in a well-defined sequence during development. Five stages of ommatidial development are described. Close junctions and punctate junctions are present throughout development. Gap junctions appear transiently amongst the undifferentiated cells, before clearly defined preommatidia can be distinguished. The subsequent disappearance of gap junctions may be correlated with cell determination. Lanthanum studies confirm these findings.

The later sequential appearance of adhesive junction types is described. These include septate desmosomes and two types of desmosomes. In the fully differentiated ommatidium only two types of junction remain, these are: desmosomes and rhabdomeric junctions.
Comparative analysis of cell distribution in the pigment epithelium and the visual cell layer of chimaeric mice
Authors: Sanyal S. , Zeilmaker G. H.
Published: April 2021

In chimaeras of both rdrdCC⟷++cc and rdrdcc⟷ + +CC combinations two types of distribution were observed. In a majority of the chimaeras both retinal layers were chimaeric; whereas in a few cases the pigment epithelium was chimaeric but the visual cell layer was made of + + cells only. No spatial relation was observed in the distribution of the cells in the two layers. The two eyes of the individuals were nearly always identical with regard to occurrence of chimaerism in the two layers. The findings are discussed in the light of the possible site and mode of expression of the rd gene.
Cell aggregation and sexual differentiation in pairs of aggregation-deficient mutants of Dictyostelium discoideum
Authors: Gerisch G. , Huesgen A.
Published: April 2021

A diffusible aggregation-stimulating factor (ASF) is released from a series of aggregationdeficient mutants. Biochemical markers indicate that these ASF-donor mutants are blocked at a later step of cell differentiation than an ASF-requiring mutant. ASF is able to bridge the initial block of differentiation in the latter mutant, such that development proceeds up to aggregation and even further. ASF is most probably neither identical with cyclic-AMP phosphodiesterase nor with an inhibitor of this enzyme which both are released from donor strains.

In certain combinations of aggregation-deficient mutants, macrocysts, the sexual stages of Dictyostelium, are formed. Also, motile giant cells believed to be zygotes are observed in these mutant combinations. The gamone known to be released from one mating type and to induce macrocysts in the other, is probably not identical with ASF since this factor is produced by mutants derived from either one of both mating types.
Polarity and gradients in lepidopteran wing epidermis: I. Changes in graft polarity, form, and cell density accompanying transpositions and reorientations
Authors: Nardi James B. , Kafatos Fotis C.
Published: April 2021

Lepidopteran wing epidermis has certain advantages for studying the spatial organization of cell populations: ease of accessibility and manipulation, large size, an essentially two dimensional structure, and direct expression by the scale cells of their polarity. Grafting experiments reveal that polarity and density of graft cells as well as overall graft form are functions of a graft’s source and its transplantation site; graft polarity is also determined by the orientation of the graft. The results are consistent with the existence of at least one morphogenetic gradient along the proximo-distal axis of the wing’s upper epidermal layer. Various gradient models that might explain the experimental observations are considered.
Injected nuclei in frog oocytes: RNA synthesis and protein exchange
Authors: Gurdon J. B. , Partington G. A. , Robertis E. M. De
Published: April 2021

Nuclei from HeLa and other mammalian cells have been injected into Xenopus oocytes. The synthesis, uptake, and release of RNA and proteins by injected nuclei have been investigated by autoradiography.

Injected nuclei which undergo enlargement synthesize RNA continuously for up to 28 days. When oocytes are incubated in [3H]uridine or [3H]guanosine, injected nuclei are labelled nearly as strongly as the nucleoli, but much more strongly than the nucleoplasm of the oocyte’s germinal vesicle.

Injected nuclei appear to increase their rate of RNA synthesis during incubation in oocytes. This apparent increase in the rate of RNA synthesis is correlated with nuclear enlargement, as well as with the loss of protein from injected nuclei and with their uptake of histone and nonhistone proteins from oocyte cytoplasm. Injected HeLa nuclei lose most of the previously synthesized RNA from their nucleoplasm, but little if any of the RNA from their remaining nucleoli.
Ultrastructure du nœud sino-atrial de l’embryon de souris aux jeunes stades du développement
Authors: Nanot J. , Douarin G. Le
Published: April 2021

Ultrastructure of the embryonic mouse sinus node at the early stages of development

At early stages of development in the mouse embryo (12-13 days post-coitum) the cells of the sino-atrial node are homogeneous but are different to the atrial myocardic cells at this stage of development or a younger stage (9-10 days post-coitum).

Sino-atrial node cells are small; they have many ribosomes, the myofibrillar material and the Golgi apparatus are poorly developed. Membrane contacts are represented by simple appositions and some fascia adherentes. These cells show many pinocytic invaginations and subsarcolemmic vesicles.

From the 14th day post-coitum the sino-atrial node becomes heterogeneous. ‘Clear cells’ are present in the middle part of the node; they are characterized by their irregular shape and the poor development of their myofibrillar material. ‘Dark cells’ are observed at the periphery of the node and seem related to myocardial type cells described in the sino-atrial node of the late mouse foetuses.

Our observations do not support the existence of a 3rd cellular population, called by some authors: ‘transitional cells’. The problem of the segregation between sino-atrial cells and myocardial cells is discussed.
Fertilization of immature frog eggs: cleavage and development following subsequent activation
Authors: Elinson Richard P.
Published: April 2021

Frog eggs are normally fertilized after reaching metaphase II. When eggs are inseminated prior to that, several sperm enter, but entry does not activate the egg. When such inseminated, immature eggs were maintained until they became mature and then were artificially activated, the eggs began to cleave. The cleavage furrows were irregular and often multiple, but the eggs developed to blastulae or partial blastulae. About 2 → 5% of the eggs developed to tadpoles. Typical asters were not associated with the entering sperm; rather, asters appeared only after activation. The sperm nucleus often formed chromosomes which were attached to small spindles. It is clear that sperm which remain for a time in unactivated egg cytoplasm, retain their ability to promote cleavage and development. Aster formation required not only sperm centrioles but also activated egg cytoplasm.

Sperm which entered either near the equator or in the animal half of mature eggs usually produced normal cleavage furrows. Sperm which entered the animal half of immature eggs produced multiple animal half furrows when the egg was subsequently activated. In contrast, sperm which entered near the equator of immature eggs often failed to induce furrowing on subsequent activation or produced unusual equatorial furrows. The difference in the type of furrow between eggs inseminated in the animal half or at the equator is interpreted as a consequence of dissociating sperm entry from the cortical contraction which occurs on activation.
The pattern of cell division during growth of the blastema of regenerating newt forelimbs
Authors: Smith A. R. , Crawley A. M.
Published: April 2021

Pulse and continuous labelling with tritiated thymidine are used for a quantitative study of cell division rates in regeneration blastemas. Proliferation is initially uniform; later a proximodistal gradient develops in the mesenchyme, with the highest labelling index at the tip, where practically all cells are shown to be dividing. In the ectoderm there appear to be two growth bands, one close to the stump and the other close to the tip. The results are consistent with the progress zone theory, and agree well with the numerical estimates of growth rates used in our previously reported simulation.
The effects of ascorbic acid deficiency on collagen synthesis by mouse molar tooth germs in organ culture
Authors: Schiltz John R. , Rosenbloom Joel , Levenson Gordon E.
Published: April 2021

Second molar tooth germs from 2-day-old Swiss-Webster mice, grown in organ culture for 7 days in ascorbic-acid-deficient medium, synthesized about 65 % as much protein (measured by incorporation of [14C]proline during a 24-h pulse) as did ascorbic-acid-supplemented controls. The newly synthesized proteins from ascorbic-acid-deficient cultures contained only about 7 % of the hydroxyproline content of the controls. Collagenase digestion of the newly synthesized proteins showed that collagen comprised the same fraction of the total protein synthesized under both culture conditions. This result indicates that the ascorbate-deficient cultures made significant quantities of underhydroxylated collagen. Partial characterization of the collagen alpha chains on carboxymethyl cellulose columns showed an αl/α2 ratio of about 5, suggesting that at least two different species of collagen were synthesized. The αl/α2 ratio of the chains recovered from the ascorbate-deficient cultures was also about 5 but the chains were slightly underhydroxylated and the total amount of these chains which could be identified accounted for only a small fraction of the total collagen which was synthesized. A large fraction of the synthesized collagenous protein was found in the culture medium, mostly in the form of lower molecular weight peptides. It is concluded that most of the collagen which is synthesized by ascorbate-deficient tooth-bud cultures is not utilized by the component tissues, but is probably degraded and released into the medium.
Developmental precocity after asynchronous egg transfer in mice
Authors: Marsk Lars
Published: April 2021

Asynchronously transferred ova were found to implant 6-8 h earlier than did non-transferred eggs, indicating that the endometrium was receptive to implantation several hours before the native blastocysts were prepared to implant. This developmental precocity was also preserved on day 14, according to the results of a morphological rating study on day 14. Synchronously transferred ova showed no such developmental precocity. No statistically significant difference in implantation time or development on day 14 was found between the two strains, CBA and A/Jax. The importance of precocious development for planning teratological studies is emphasized.
Effects of prenatal administration of hadacidin, a cancer chemotherapeutic agent, on the development of hamster fetuses
Authors: Shah Ravindra M.
Published: April 2021

A single intraperitoneal injection of 1−2·5 g/kg body weight of hadacidin was teratogenic when administered to pregnant hamsters between days 8 and 11 of gestation. Both the frequency of malformation and resorption were related to the dose and time of hadacidin administration. The drug produced both gross and microscopic malformation in the fetus and impaired its general growth. The malformation involved craniofacial structures, central nervous system, respiratory, digestive and urinary systems, limbs and tail.

Morphologically different types of cleft lip and cleft palate were related to the dose and time of hadacidin treatment. An association was observed between cleft lip, cleft palate and micrognathia on one hand, and between cleft palate and micrognathia on the other. Significance of association between the lip, the palate and the mandibular malformation was discussed and the hypothesis that human cases of Pierre Robin syndrome may result from an environmental assault was supported. It was suggested that the fetal weight and the microscopic analysis should be included in the criteria for the teratological drug safety evaluation procedures.
Partial characterization of ‘primordial germ cell-forming activity’ localized in vegetal pole cytoplasm in anuran eggs
Authors: Wakahara Masami
Published: April 2021

Larvae of Rana chensinensis developed from fertilized eggs which had been subjected to ultraviolet (u.v.) irradiation on their vegetal hemisphere at a dose of 20000 ergs/mm2 within 60 min of fertilization contained no primordial germ cells (PGCs) when examined histologically at the stage when the operculum was complete (8 days after fertilization at 18 °C, stage 25 according to Shumway, 1940). The morphogenetic ability of vegetal pole cytoplasm from non-irradiated eggs to establish the PGCs was tested by injecting some fractions of this cytoplasm into the vegetal hemisphere of u.v.-irradiated eggs. Crude homogenate of the vegetal pole cytoplasm without large yolk platelets was able to restore the PGCs when injected into u.v.-irradiated eggs, but a similar fraction from animal half cytoplasm had no ability to form PGCs. The ‘PGC-forming activity’ demonstrated in the crude homogenate of the vegetal pole cytoplasm was not abolished by dialysis, lyophilization and heating to 90 °C for 10 min. When the homogenate was fractionated by differential centrifugation in 0·25 M sucrose, the ‘PGC-forming activity’ was recovered mainly in the precipitate of 15000 g for 30 min. The precipitate of 7000 g for 10 min had also a little ‘activity’. The possibility was discussed that the ‘PGC-forming activity’ demonstrated in the vegetal pole cytoplasm was associated with the germinal granules in the germ plasm rather than the mitochondria.
Developmental effects of X-irradiation of early Drosophila embryos
Authors: Bownes M. , Sunnell L. A.
Published: April 2021

Drosophila embryos were treated at specific stages during early embryogenesis with various doses of X-irradiation. The lethality at various times during development was established and pattern defects in the adults noted. It was observed that the most sensitive stages of embryogenesis to X-ray-induced lethality were also the stages where most morpho-logical defects were found in the adults which emerged. This suggests that presumptive larval and adult cells are sensitive to X-rays at the same stages of embryogenesis.
A technique for introducing localized long-lasting implants in the chick embryo
Authors: Heaton Marieta B.
Published: April 2021

A technique is described for making chronic, localized implants of drug-impregnated Silastic in early chick embryos. This silicone material has been shown to gradually and uniformly release its impregnated contents under such conditions. Following implantation of pieces of Silastic treated with the metaphase-blocking drugs colchicine and vinblastine into the wing-buds of day chick embryos, 53·75% survived 4-5 days, at which time they were sacrificed. Non-impregnated (control) Silastic was also implanted in a group of embryos. In this group, 90% survived 4-5 days. The antimitotic effects of the drugs were very well localized to implanted wings, which were reduced in size by approximately 55 % at the time of sacrifice (day 8-9 of incubation). In control embryos, the implanted wings were normal in size and general morphology. It is suggested that the technique could have numerous appli-cations for the study of neuroembryology or other aspects of embryogenesis.
Magnesium deficiency in embryos of Xenopus laevis
Authors: Miller John C. , Landesman Richard
Published: April 2021

Embryos of Xenopus laevis reared in media with various low (⩽ 10−5 M) magnesium ion concentrations will exhibit differing degrees of a potentially lethal magnesium starvation syndrome depending on the ion concentration and rearing temperature. The higher the rearing temperature or the lower the magnesium ion content of the medium the more severely the syndrome will be expressed. (Normal development can be expected at temperatures 13-30 °C and magnesium ion concentrations > 10−5 M to 10−2 M.)

The magnesium deficiency syndrome in Xenopus embryos is described in detail and compared with the normal and anucleolate conditions. The deficiency condition becomes manifest after hatching as retarded growth and differentiation with progressive paralysis and edema. At the same time alterations are observed in the pattern of soluble proteins. The use of magnesium ions as a probe for investigating developing systems is discussed.
On Early Cell Migration Processes in the Embryonic Brain
Authors: Bergquist Harry
Published: April 2021

The earliest cell migration starts in the ventral part of the neural tube, especially around the plica encephali ventralis. A survey is given of the processes of successive migrations in different parts of the embryonic brain in different species. The first appearance of the second migration layer is in different parts of the brain in Torpedo and chick, possibly correlated with the differing functional importance of the parts in the two species. Experiments show that the formation of a second migration layer in the thalamus of chick embryos is not dependent on the presence of surrounding brain parts.
Wound Contraction in Relation to Collagen Formation in Scorbutic Guinea-pigs
Authors: Abercrombie M. , Flint M. H. , James D. W.
Published: April 2021

In order to investigate the relation of wound contraction to collagen formation, standard skin wounds were made on two groups of guinea-pigs, one group kept on an ascorbic acid deficient diet, the other on the same diet supplemented with ascorbic acid. Ten days after wounding the amount of collagen in the repair tissue, estimated by the method of Neuman & Logan (1950), was much less in the deficient than in the non-deficient animals. Nevertheless, the amount of wound contraction which had occurred, representing a loss of 30 – 40 per cent, of the original wound area, was not significantly different in the two groups. Large amounts of hydroxyproline were found in the massive scabs commonly developed over the wounds of scorbutic animals. It is suggested that the force that brings about wound contraction may be developed by the connective tissue cells of the repair tissue.
Developmental Interactions in the Development of the Imaginal Muscles of Drosophila
Authors: Shatoury H. H. El
Published: April 2021

The thorax of Drosophila contains two main sets of muscles, the dorsal flight-muscles and a lateral set. Among the latter are the trochanteral depressors of the legs, of which those associated with the second legs are the largest. The development of all these muscles during the pupal period is described and an account is given of the effects of the contraction of the tendons of the longitudinal muscles in producing the curvature of the mesothorax and the formation of the post-notum. The dorsal flight-muscles develop from an interaction between (a) three pairs of larval muscles; (b) mesoderm cells derived from the mesothoracic imaginal buds; (c) cells which migrate from the developing trochanteral depressors of the second leg. It is the latter cells which are responsible for splitting the three larval muscles of each side into six. The fibrillar muscles of the lateral set have a similar origin. The trochanteral depressors are tubular, not fibrillar, in structure. They are formed from mesoderm cells of the leg imaginal buds. If the imaginal bud of a first or third leg is removed from the late larva, not only the leg but also the corresponding trochanteral depressor is missing from the adult. If a second leg bud is removed, the dorsal flight-muscles and the lateral fibrillar muscles on that side also fail to develop. In extreme bithorax phenotypes, in which the metathoracic bud has formed a structure externally resembling a mesothorax, this region does not contain a second set of flight-muscles, although there are sometimes small badly differentiated representations of them. The secondary scutellum is not provided with a post-notum. If the normal mesothoracic bud of one side is extirpated from a larva which is developing the bithorax phenotype, the transformed metathoracic bud may shift forward and fuse with the mesothoracic bud of the opposite side. In some such cases the metathoracic mesoderm, in association with cells from the second trochanteral depressor, has developed into flight-muscles. It is concluded that the migrating cells of the second trochanteral depressor provide a stimulus which is essential for the differentiation of the flight-muscles.
Hormone control in regeneration:effects of somatostatin on appendage regeneration,blood glucose and liver glycogen in Diemictylus viridescens
Authors: Vethamany-Globus S. , Globus M. , Hartford J. A. , Fraser I. , Weber D.
Published: April 2021

In the present communication, synthetic somatostatin, a hypothalamic factor which has a known inhibitory effect on the release of growth hormone, thyroid-stimulating hormone, prolactin, insulin and glucagon in man and other mammals, was found to have an inhibitory effect on limb and tail regeneration in adult Diemictylus viridescens, when the newts were treated with a daily dose of 3·5 or 15 μg/animal for a period of 34 days post-amputation. At the higher dose, the animals exhibited total inhibition of appendage regeneration in a few cases and the remainder showed a considerable delay compared to the controls; none of the experimental animals reached the advanced four-digit stage achieved by the controls. Furthermore, the blood glucose and liver glycogen values in the somatostatin-treated animals were significantly lower than the control values. Mechanisms in the storage, mobilization and utilization of glucose (involving hormones) are discussed in relation to appendage regeneration in the newt and possible controls of regeneration at the level of the hypothalamus are suggested.
Retinal growth in double dorsal and double ventral eyes in Xenopus
Authors: Straznicky K. , Tay D.
Published: April 2021

The growth of normal and surgically produced compound dorsal and ventral retinae in Xenopus laevis has been studied autoradiographically following injections of [3H]thymidine at stages 50 and 58. The animals were sacrificed 3 weeks after metamorphosis. The histogenetic pattern of the dorsal and ventral retinal halves was different at the three time points investigated, i.e. up to stage 50, between stages 50 and 58 and between stage 58 and 3 weeks after metamorphosis. Asymmetrical dorsal retinal growth occurred up to stage 50. From stage 50 onwards the retinal growth tendency reversed so that more ganglion cells were produced along the ventral than the dorsal ciliary margins. The overall preponderance of ventral retinal growth was 32·4% in cell number and 12·4% in retinal length from early embryogenesis to 3 weeks after metamorphosis. The characteristic histogenetic pattern of the dorsal and ventral retinal halves was maintained in an ectopic position in the compound eye, indicating that this particular property of the retinal halves is intrinsically determined.
Variation in Habrobracon juglandis ovariole number: I. Ovariole number increase induced by extended cold shock of fourth-instar larvae
Authors: Grosch Daniel S. , Kratsas Robert G. , Petters Robert M.
Published: April 2021

Variation from zero to five ovarioles in the braconid wasp, Habrobracon juglandis, is reported for dissections of females from laboratory stocks. Four ovarioles (two per ovary) is the standard phenotype for the species. Storage of fourth-instar larvae in a refrigerator resulted in a large proportion of females with an increased number of ovarioles (5–11). A

1-to 2-week cold exposure during the period of ovarian differentiation is required for the maximum effect.
Weight differences in rat embryos prior to sexual differentiation
Authors: Scott William J. , Holson Joseph F.
Published: April 2021

Sex of day-.12 rat embryos was determined using Barr body counts made on spreads of amniotic membranes examined histologically. Embryonic weight, protein content and rate of thymidine incorporation were compared in male and female embryos. Male embryos were found to be heavier and accordingly to contain more protein on absolute but not on per unit weight basis. The rate of thymidine incorporation did not differ in the two sexes. Since gonadogenesis in day-12 rat embryos is rudimentary, with gonadal differentiation of sex not yet apparent, the increased weight suggests that sex-linked genes exist which influence body growth prior to gonadal endocrine activity.
Viability and metabolic activity of homozygous Brachyury (T) embryos
Authors: Yanagisawa K. O. , Fujimoto H.
Published: April 2021

Some features of metabolic activity of homozygous mutants for the Brachyury (T) mutation were studied. The embryos incorporated tritium-labelled thymidine up to about the ‘32-36 somite’ stage. The total amount of protein per embryo increased until the same stage. T/T cells proved viable in vitro over the in utero lethal period. Several cell lines were established from +/+ and T/T embryonic cells.
The effects of thalidomide and two analogues on the regenerating forelimb of the newt
Authors: Bazzoli Allan S. , Manson Jeanne , Scott William J. , Wilson James G.
Published: April 2021

Oral administration (3 mg/day) of thalidomide during the dedifferentiation and early limb-bud stages of newt forelimb regeneration produced a variety of specific limb deformities. Proximal and preaxial skeletal elements were the most severely malformed, e.g., preaxial hemimelia, severe proximal deformities, and preaxial polydactyly.

Likewise, oral, daily doses (3 mg) of the teratogenic analogue, EM12, on days 7 and 8 following bilateral amputation caused the same incidence and type of forelimb abnormalities as did thalidomide. Conversely, the non-teratogenic analogue, EM87, when orally administered (3 mg/day) on days 7 and 8 post-amputation resulted in a low rate of limb deformities, similar in type to those seen in control regenerates.

The type of limb deformities observed in the regenerating newt forelimb following thalidomide treatment nearly mimic those seen in the human and monkey syndromes. Therefore, the newt represents a possible model for investigating some of the problems associated with thalidomide teratogenesis.
Cytological and cytochemical studies of the necrotic area of the bulbus of the chick embryo heart: phagocytosis by developing myocardial cells
Authors: Hurle J. M. , Lafarga M. , Ojeda J. L.
Published: April 2021

The muscular wall of the bulbus cordis of the chick embryo was studied by electron microscopy during H. H. stages 27–31. Results show that the muscle cells of the bulbus undergo necrosis during these stages. The morphology of dead cells in this area is similar to that described in other embryonic myogenic tissues. Although dead myocytes appear acid-phosphatase-negative, lysosomes may well be involved in this necrotic process as there is a significant number of cells with autolytic lesions among the neighbouring healthy muscle cells. The phagocytosis of the cell detritus resulting from the degenerative process appears to be carried out by neighbouring myocytes and by macrophages. The significance of these results is discussed both from the cytological and from the morphogenetic point of view.
Tooth development in the ‘crooked’ mouse
Authors: Sofaer J. A.
Published: April 2021

The semidominant gene ‘crooked’ (Cd) in the mouse produces anomalies of the axial skeleton (resulting in a crooked tail), microphthalmia and dental abnormalities, including small molars with simplified cusp patterns that are equivalent to patterns passed through during normal morphodifferentiation. A series of embryonic litters from Cd/+×Cd/+ matings was used to investigate the embryological basis for the dental abnormalities. Micro-phthalmic embryos were classed as Cd/Cd, and their most normal litter mates were selected as controls (+ /+ or Cd/+). An additional set of control embryos came from the inbred strain CBA/Cam (+/ + ). Serial sagittal sections of the heads of these embryos were examined microscopically, and the maximum anteroposterior diameters of the developing upper and lower first molars were measured. Reduction in the rates of growth and morphodifferentiation of Cd/Cd first molars, relative to those of litter mate controls, was associated with the appearance of an adjacent abnormal proliferation of the dental lamina. Some proliferations in older embryos showed signs of early tooth germ formation, but many were seen to have regressed and no examples of supernumerary teeth have been found in Cd/Cd adults. Small size of Cd/Cd molars may therefore result from competitive inhibition of molar growth by a transient abnormal laminal proliferation, and Cd/Cd cusp patterns from the relatively premature onset of hard tissue formation during normal but retarded sequences of morphodifferentiation.
Changes of organelles associated with the differentiation of epidermal melanocytes in the mouse
Authors: Hirobe Tomohisa , Takeuchi Takuji
Published: April 2021

Electron microscopic observations on normally differentiating and a-MSH (melanocytestimulating hormone)-treated epidermal melanocytes of newborn mouse skin were carried out. The process of melanocyte differentiation from premelanosome-containing melanoblasts was investigated in detail with respect to melanosomes as markers.

Melanoblasts containing unmelanized premelanosomes gradually decreased in number after birth, while the number of melanocytes rapidly increased. The epidermis of a-MSH-treated 3-day-old mice and normal 6-day-old mice contained melanocytes with numerous fully melanized melanosomes, and with no or only a few melanoblasts.

Changes in other organelles in differentiating melanocytes were also noticeable. Golgi apparatus and RER (rough endoplasmic reticulum) decreased in number during the normal or a-MSH-induced differentiation of the epidermal melanocytes, though the number of mitochondria showed no notable change. The number of SER (smooth endoplasmic reticulum) per cell did not change in the cells of newborn mice, while in a-MSH-treated cells the number increased significantly. These results led us to an assumption that Golgi apparatus or RER transforms into other forms of organelles including melanosomes and SER during the differentiation of melanocytes.
Le développement de l’appareil uro-génital après la greffe hétérotopique du mésoblaste latéral chez la neurula du crapaud commun Bufo bufo L. (Amphibien Anoure)
Authors: Gipouloux J.-D. , Hakim J.
Published: April 2021

The development of urogenital organs after lateral mesoblast heterotopic graft in the toad (Bufo bufo) neurula

I.

Distinct inversions of anteroposterior and dorsoventral axis of the lateral plate

Anteroposterior inversion of lateral mesoblast of early toad neurula is followed by differentiation of diverse urogenital blastema, according to the transplant position before the graft. Anteroposterior polarity of lateral mesoderm is thus perfectly determined in young neurula. On the contrary, dorsoventral inversion of lateral mesoblast leads to mesodermic blastema formation according to the transplant position after the graft. Particularly, the dorsal region of the lateral plates displaced to ventral position does not form blastema. On the other hand, the ventral region which shows a dorsal position after the graft develops and produces a typical blastema. Thus, in the young neurula, the dorsoventral polarity is not yet determined in the lateral plate of the mesoblast. Such a result shows also that the ventral and posterior regions of the lateral mesoblast are competent to form blastema. Moreover, factors from dorsal origin and external to lateral mesoblast take part in urogenital organ anlagen formation.
Le devéloppement de l’appareil urogénital après la greffe hétérotopique du mésoblaste latéral chez la neurula du crapaud commun Bufo bufo L. (Amphibien Anoure): IL Inversion simultanée des axes antéro-postérieur et dorso-ventral de la lame latérale
Authors: Hakim Par J. , Gipouloux J.-D.
Published: April 2021

The development of urogenital organs after lateral mesoblast heterotopic graft in the toad (Bufo bufo) neurula. II. Simultaneous inversion of anteroposterior and dorsoventral axis of the lateral plate

Simultaneous inversion of the anteroposterior and dorsoventral axes of the lateral meso-blast in the early toad neurula leads to the total agenesis of the urogenital organs. The experimental results show that the lateral mesoblast is unable to undergo self-differentiation, and that three factors at least are required for the formation of the urogenital blastemata.

The mesoblast must be competent: only the posterior (dorsal, but also ventral) part of the lateral mesoderm is endowed with this competence. It must receive two stimulating influences, from the cordomesoblast on the one hand, and from the dorsocaudal endoblast on the other hand.
Permissive and directive interactions in lens induction
Authors: Karkinen-Jääskeläinen Marketta
Published: April 2021

The interactive events leading to lens formation and the developmental potentialities of the presumptive lens ectoderm were examined in vitro. The presumptive lens ectoderm of both mouse and chick embryos was capable of forming a lens even when isolated from the optic vesicle before the two tissues reach the stage of close association. This lens-forming bias can be released with favourable culture conditions and by various heterotypic mesenchymes. The same permissive, unspecific conditions or heterotypic tissues failed to trigger lens formation in trunk ectoderm. The directive effect of the optic vesicle was demonstrated in experiments where it was grown in contact with the trunk ectoderm. The latter developed distinct lentoid bodies synthesizing lens proteins. The origin of the lentoid was confirmed in interspecies combination of chick and quail tissues. It is concluded that lens formation is governed by a series of interactive events consisting of both directive and permissive influences.
Tissue specificity for incorporation of [3H]thymidine by the 10- to 12-somite mouse embryo: alteration by acute exposure to hydroxyurea
Authors: Miller Sue Ann , Runner Meredith N.
Published: April 2021

Radioautograms from 10- to 12-somite mouse embryos labeled for 30 min in vitro with [3H]thymidine were examined for frequency and intensity of incorporation. Results from ten tissues showed that values ranged from 82% of nuclei with a mean of 16·6 grains for visceral yolk sac to .17% of nuclei labeled with a mean of 4·4 grains for epithelium of the anterior gut tube. Labeling in the ten tissues indicated (1) a tissue-specific spectrum of incorporation of [3H]thymidine, (2) close correlation between frequency and intensity of labeling within a tissue and (3) asymmetrical quantities of incorporation between right and left somatopleure.

Treatment with hydroxyurea in vitro reduced the frequency of labeled nuclei by 85% to 12 % of control values. Mean numbers of grains over treated nuclei, 3·3–4·6 grains, were well above background but were clustered below the low end of the control range. Tissues exposed to hydroxyurea showed (1) labeling of significant numbers of nuclei, (2) inhibition of labeling in selected tissues and (3) equalization of bilateral asymmetry in quantity (frequency and intensity) of incorporation in somatopleure. The selective reduction of thymidine incorporation and equalization of asymmetrical rates of proliferation may constitute mechanisms by which hydroxyurea causes abnormal morphogenesis.
Developmental analysis of the tumorous head mutation in Drosophila melanogaster
Authors: Bournias-Vardiabasis N. , Bownes M.
Published: April 2021

The extent and type of adult transformations in the tumorous head (tuh) mutation of Drosophila melanogaster were studied. The observations indicate homeotic transformations, duplications and deficiencies of eye antennal disc derivatives. Contrary to previous observations there is no transformation of eye to abdomen and the only homeotic transformations identifiable are antenna to leg and rostralhaut to genitalia. Embryonic and post-embryonic lethality was also examined. Specific anterior abnormalities were found in embryos leading to early death. The amount of embryonic lethality was not affected by increased temperature during oogenesis. When analysing the adult phenotype, however, the whole period of oogenesis was sensitive to pulses of increased temperature; the pulses however did not have to be restricted to any particular stage of oogenesis to be effective in increasing tuh penetrance. The increase in the penetrance of the adult transformations is also exhibited when eggs are moved from 25 °C to 29 °C from the 8th to the 12th hour of embryonic development. Experiments indicate that the tuh-3 gene is active before the 8th hour of embryogenesis.
A comparative study of spermiogenesis in wild-type and T:t-bearing mice
Authors: Hillman Nina , Nadijcka Mary
Published: April 2021

The results of a comparative ultrastructural study of spermiogenesis in T/tx, + /tx, +/T, C57BL/6J, BALB/c and randomly breeding Swiss Albino mice are reported. The observations show that aberrant spermiogenesis occurs in males of all strains and genotypes and that the same specific types of abnormal spermatids are found in all of the males examined. No unique morphological defect which could be correlated with the increased transmission frequency of tx-bearing gametes can be found in males heterozygous for the tx allele.
The effects of high hydrostatic pressure on microfilaments and microtubules in Xenopus laevis
Authors: Messier Paul-Emil , Seguin C.
Published: April 2021

Xenopus laevis embryos of stages 14–20 were subjected, for periods of 5–330 min, to hydrostatic pressures ranging from 500 to 10000 psi. The specimens were fixed under corresponding pressures and their neuroepithelium was studied under light and electron microscopy. A pressure of 3000 psi, maintained for as long as 180 min, did not inhibit neurulation though it induced slight deformities of the neuroepithelium. A pressure of 4000 psi, applied for 180 min, disrupted the apical ring of microfilaments and blocked neurulation. The cells lost their dissymmetry. The effect was reversible. Lengthening the duration of treatment to 330 min caused the neuroepithelial cells to loose their microtubules and to become round. This situation was not reversible. Our results indicated that microfilaments are more sensitive than microtubules, that both organelles became increasingly sensitive as the exerted pressure was increased and that microtubules of older embryos exhibited a better resistance. Finally, we showed a correlation between the presence of microfilaments and the constricted state of the cellular apices and a relationship between the presence of microtubules and cell elongation.
The stabilization of morphological field size during slime mold morphogenesis
Authors: Peacock Michael , Soll David R.
Published: April 2021

The relationship between aggregate size and morphological field size has been investigated in the cellular slime mold Dictyostelium discoideum. Evidence is presented that aggregate size and field size exhibit different temperature sensitivities and that an aggregate can be induced to separate into several morphological fields by a decrease in temperature. In addition, evidence is presented that field size is stabilized at a point in time just prior to tip formation.