bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolation and characterization of flightless mutants in Drosophila melanogaster
Authors: Koana Takao , Hotta Yoshiki 
Published: April 2021

ABSTRACT
Since animal behaviour is executed through neuronal circuits including sensory receptors and muscle, genes vital for their development and differentiation must be found among mutants having behavioural anomaly. After mutagenesis with ethyl methanesulphonate (EMS), we screened for X-linked flightless mutants of Drosophila melanogaster by using a column-type flight tester. Approximately 104 individuals were screened and 21 mutant genes were isolated. Chromosomal mapping and complementation experiments revealed that they belong to 15 cistrons randomly located on X chromosome, three cistrons having more than two alleles. Two of the isolated mutants (fltO2 and fltH, which are recessive both behaviourally and morphologically) were analysed with the mosaic fate mapping technique, and both were found to have their primary foci in mesodermal region of blastoderm, suggesting that the genes exert their primary effect in indirect flight muscle.
Electronmicroscopic studies on the muscles from four alleles of the fltO2 cistron revealed an abnormality in myofibrillar arrangement. A possible deficit within Z-band components is discussed in relation to wings-up B mutants. The indirect flight muscle of flltH was also examined, and it was found that sarcomere length and diameter of myofibrils were abnormal. It was postulated that a possible factor which controls size of myofibrils is defective in this mutant. These examples indicate the advantage of combining ultrastructural examination with genetic mosaic mapping technique.
Ultrastructural analysis of preimplantation lethal yellow(Ay/Ay)mouse embryos
Authors: Cizadlo Gerald R. , Granholm Nels H. 
Published: April 2021

ABSTRACTEmbryos recovered at 62 and 80 h post coitum from reproductive tracts of yellow (Ay/a) and black (a/a) female mice mated to Ay/a males were examined ultrastructurally to define the developmental defect of lethal Ay homozygotes.No abnormalities were observed in five embryos from control matings (♀ a/a × ♂ Ay/a). Of 24 morulae and blastocysts from Ay/a × Ay/a matings, six were observed to possess some morphological aberration. Two of the six abnormal embryos were morulae and contained isolated blastomeres which had developmental features typical of younger embryos; remaining cells of these embryos were normal. The third, an early blastocyst, contained a degenerating trophoblast cell; other cells of this embryo were also abnormal but not in an advanced stage of degeneration. The fourth abnormal embryo (late cleavage stage) was in an advanced stage of degeneration affectingall blastomeres. Finally, the remaining two abnormal morulae had a unique nucleolar morphology and an unusual abundance of intra-cisternal A particles.Presumably, one or more of the six abnormal embryos from Ay/a × Ay/a matings were Ay homozygotes. However, no single ultrastructural alteration characteristic of Ay/AV embryos was found.
The paths and destinations of the induced ipsilateral retinal projection in goldfish
Authors: Easter Stephen S. , Schmidt John T. , Leber Steven M. 
Published: April 2021

ABSTRACT
Adult goldfish had one tectal lobe removed surgically, and several months later, the eye contralateral to the missing tectum was injected with radioactive proline. Radioautographs of the brains were studied to trace the paths and termination sites of the optic fibers.
The optic tract decussated at the chiasm, as normally, but then ran caudally in a large neuroma on the tectum-less side of the brain. Substantial numbers of fibers left this neuroma to enter two or more of five commissures, through which they recrossed the midline. These commissures: transverse, minor, horizontal, posterior and ansate, ordinarily contain few or no optic fibers. All are normally linked with the tectum. Negligible numbers of aberrant optic fibers recrossed the midline elsewhere. On the intact side of the brain, ipsilateral to the injected eye, the optic fibers innervated some or all of the nuclei and areas normally served by contralateral retinal fibers. An earlier behavioral study of these same fish had shown that some of them made reversed optokinetic nystagmus in response to stripe movement seen by the eye projecting ipsilaterally; others failed to respond to stimuli through this eye. In all the reversed responders, a caudal group of retinal projection sites was labeled ipsilaterally. This included the basal optic nucleus and the caudal portions of nucleus dorsolateralis thalami and area pretectalis. In the non-responders, these targets were not labeled ipsilaterally. Together, these results suggest that one or more of these three sites is or are responsible for optokinetic nystagmus in normal goldfish.
Isolation and development of the inner cell mass after exposure of mouse embryos to calcium ionophore A23187
Authors: Surani M. Azim H. , Torchiana David , Barton Sheila C. 
Published: April 2021

ABSTRACT
Compacted morulae and blastocysts were obtained from CBA, BALB/c and CFLP strains of mice. The embryos were incubated in medium containing 2 × 10−5 M or 2 × 10−6 M ionophore A 23187. With 2 × 10−6 M ionophore, morulae survived for up to 12 h showing slight decompaction. Normal development resumed when the morulae were explanted to fresh medium. There was no detectable effect on blastocysts. With 2 × 10−5 M ionophore, morulae survived for about 20 min and then extensive cell death occurred after this time. With blastocysts however, selective lysis of trophectoderm cells occurred after approximately 30 min following their swelling and vesiculation but the inner cell mass cells (ICM) remained apparently intact and viable. Nearly 80 % of the early blastocysts obtained 87 h post-ovulation and all of the late blastocysts used after 12 h in culture (99 h blastocysts) showed this response. Individual fluid accumulating cells were detected in a few isolated ICMs after their overnight culture in vitro, especially in those obtained from early blastocysts, but the majority of the ICMs did not have these cells. All aggregates of three to five ICMs, except one which reformed into a blastocyst, developed as embryoid bodies after 2 days in culture and these survived for up to 10 days; in some cases they developed into cystic embryoid bodies or attached to the culture dish displaying a variety of cell types. The development of the isolated ICMs in vivo was judged to be normal after their transfer to intact host blasto-cysts as these developed as chimaeric embryos to term.
Anatomical mapping of retino-tectal connections in developing and metamorphosed Xenopus: evidence for changing connections
Authors: Longley Alison 
Published: April 2021

ABSTRACT
Neural connections between the eye and optic tectum in Xenopus laevis were anatomically traced by observing the tectal location of Wallerian degeneration after discrete retinal lesion. These retinotectal connections were mapped in post metamorphic frogs and tadpoles at stage 51, the stage at which retinal axons have grown into about the rostral one-half of the tectum. The course of the experimental degeneration was the same in frogs and tadpoles, but degeneration proceeded faster in the younger animals.
In the frogs, connections were ordered, with nasal retina mapping to the caudal part of the tectum and temporal retina mapping to the rostral tectum. In the tadpoles, within the innervated area at the rostral tectum, the retino-tectal connections were generally organized as in the adults, with the temporal retina mapping to the rostral part of the innervated tectum and nasal retina mapping primarily to the caudal part. But a portion of the nasal fibers consistently mapped to the far rostral tectum as well. Electron microscopic observations showed degenerating synaptic terminals at both rostral and caudal portions of the innervated tectum after lesion of just the nasal retina. Degeneration was not seen in control animals. These results indicate that some fibers (particularly from nasal retina) may shift their terminals caudally on the tectum to match tectal growth and produce the adult pattern of connections. If there is such connection readjustment, the ‘aberrant’ connections from nasal retina in tadpoles may be an indication of this process.
Serum-dependent avian skin differentiation in vitro: time sequence of induced events
Authors: Carinci P. , Stabellini G. , Becchetti E. 
Published: April 2021

ABSTRACT
Information concerning the developmental mechanisms involved in skin differentiation have been mainly derived from in vitro experiments. We have previously observed that 6-day chick embryonic thigh skin keratinizes in vitro in chicken serum-containing medium, but does not do so in chick embryo extract-containing medium. This system seems adequate in many respects for investigating the mutual regulative relationship between epithelium and mesenchyme (so called epithelio-mesenchymal interactions).
We have therefore attempted better to define the time course of differentiative events and their dependence upon the time of serum administration.
Skin explants have been sequentially supplemented with differentiation-stimulating or non-stimulating nutrient, removed at different intervals and examined by histological and histochemical procedures.
Different epithelial and mesenchymal behaviour results according to serum supplementation time. Serum administered in the first 48 h of in vitro maintenance is unable to stimulate either the subsequent epidermal keratinization or the correlated changes in dermal histochemical pattern. On the other hand, serum-containing medium induces keratinization and changes in dermal intercellular composition (glycoproteins accumulate to a greater extent than glycosoaminoglycans, as does hyaluronic acid relative to chondroitin sulphuric acids), if added for only the second two days. In the last 48 h, serum may promote epidermal keratinization provided that in vitro incubation has been prolonged.
Administration of actinomycin D with serum in the second 48 h prevents epidermal keratinization and modifies dermal histochemical reactivity, but is ineffective if added in the last 48 h.
The above findings demonstrate that serum factor(s) stimulating epidermal differentiation act(s) on skin explants in the central incubation period and that correlatively mesenchyme acquires a characteristic histochemical pattern, supporting the possibility that the effect of serum may be mediated by changes in the composition of dermal ground substance.
The presence of F9 antigen on the surface of mouse embryonic cells until day 8 of embryogenesis
Authors: Buc-Caron M. H. , Condamine H. , Jacob F. 
Published: April 2021

ABSTRACTThe fate of F9, a surface antigen common to embryonal carcinoma cells and cleavage embryos, as well as to male germ line cells has been studied in post-implantation mouse embryos. The antigen is readily detected on the surface of 7-day and 8-day, but not on 9-day embryonic cells, using anti-F9 serum absorption experiments and indirect immunofluorescence staining. In addition, it is shown that an anti-F9 serum absorbed with 8-day (but not with 9-day) embryonic cells does not react with cleavage embryos (morulae). It is concluded that the antigenic determinants, which are recognized on the surface of morulae by the anti-F9 serum, persist until day 8 of embryogenesis, but are not detected on day 9, either due to their absence, masking or quantitative reduction.
Colchicine induces multiple axis formation and stalk cell differentiation inDictyostelium discoideum
Authors: O’day Danton H. , Durston Antony J. 
Published: April 2021

ABSTRACTColchicine is shown to have several effects on the development of the pseudoplasmodia of the cellular slime mould Dictyostelium discoideum At concentrations of 0·01 M and above culmination was prevented, while differentiation of cells into stalk cells occurred at the rear of cell masses. Essentially all cells transformed into stalk cells when slugs were left on colchicine agar for a long time. At concentrations of 0·01 M normal slug architecture was maintained while above 0·025 M pseudoplasmodia reorganized into multiple mounds. Each of these mounds developed an apparently normal discrete tip which was devoid of prespore cells as shown by immunofluorescent staining. The same effects were observed in growing cultures and in regulating slugs treated with colchicine. The data are consistent with the ideas that microtubules are involved in the maintenance of slug architecture and in the differentiation of stalk cells. The modes by which these intracellular structures may operate in these functions are discussed.
Facial development in the mouse; a comparison between normal and mutant (amputated) mouse embryos
Authors: Flint O. P. , Ede D. A. 
Published: April 2021

ABSTRACT
This work extends previous investigations into cell interactions involved in specific morphogenetic events during the development of normal and mutant (amputated) mouse embryos. In the mutant mesenchyme, cells tend to clump together and form far more extensive areas of cell contact than are found in normal mesenchyme. This is confirmed for mutant facial mesenchyme. Facial outgrowth in the mutant is retarded. The first stages of this abnormality can be seen in the naso-frontal region at 10·5 days after conception. Neither the quantity of cells contributing to naso-frontal outgrowth nor cell proliferation in the naso-frontal region differ from normal in the mutant, and these factors can be eliminated as causes of the anomaly. Instead, cell clumping and increased areas of contact in the mutant arrest the normal expansion of the naso-frontal mesenchyme which presumably occurs as a result of increased secretion of intercellular matrix material between 9·5 and 10·5 days of development. The importance of this early expansion phase for facial development has not previously been recognized.
Patterns of cellular proliferation during thyroid organogenesis
Authors: Smuts Marybeth S. , Hilfer S. Robert , Searls Robert L. 
Published: April 2021

ABSTRACT
The changes in rate and location of cellular proliferation were analyzed to determine if localized areas of cell division were influencing shape changes in the chick thyroid. Pulse labeling with tritiated thymidine indicates that the gland’s labeling index declines throughout its development. Initially, the thyroid placode has a lower labeling index than the neighboring pharyngeal epithelium. An evaluation of the positions of pulse-labeled cells reveals that the evaginating thyroid grows by annexing cells from the pharyngeal epithelium. The older evaginated regions of the gland exhibit the lowest labeling indices. The newly acquired regions still maintain higher labeling indices.
A study of digit fusion in the mouse embryo
Authors: Maconnachie Elaine 
Published: April 2021

ABSTRACTDuring the embryonic development of the mouse limb separation of the digits is followed by their union. This is a true, though temporary, epithelial fusion, a fused layer of epidermal cells remaining intact until separation takes place after birth. The periderm cells in the line of fusion are displaced to the dorsal or ventral surface of the foot. On the dorsal surface-these displaced cells form a prominent interdigital ridge of elongated, intertwined cells which remains until the periderm is shed. During the fusion of the eyelids, and also of the pinnae to the scalp, a similar ridge of periderm cells is formed.
The influence of local environment on the organization of mesenchyme cells
Authors: Fisher Marilyn , Solursh Michael 
Published: April 2021

ABSTRACTLimb, somite, and neural crest mesenchyme from quail embryos were implanted orthotopically and heterotopically into chick hosts to ascertain the relative importance of the local environment on mesenchyme migration. It was found that mesenchyme behavior is strongly influenced by the environment. Normally non-migratory, limb mesenchyme is capable of spreading like sclerotome when placed in the somite region. A somite placed in the limb acquires an appearance typical of limb mesenchyme. Neural crest placed in the limb migrates only along the co-implanted neural tube or axons growing out from it. The orthotopic transplantations showed that quail mesenchyme behaves normally in chick embryos. Furthermore, it was observed in the orthotopic transplants that there was no intermingling of quail and chick cells even at the edge of the graft. This result indicates that cells within mesenchyme are normally not locomotory; rather, the mesenchyme ‘migrates’ by spreading and expansion of the tissue as a unit in response to local influences.
Experimentelle Beiträge zu einer Analyse der spezifischen Induktionsleistung heterogener Induktoren
Authors: Engländer von Hans , Johnen Anna Gisela 
Published: April 2021

ABSTRACT
With the use of the ‘Einsteck’ method the specific inducing abilities of several tissues of the guinea-pig were tested. Competent ectoderm of early gas-trulae of Triturus vulgaris and T. helveticus served as reacting material. After treatment with alcohol for a short period kidney (renal cortex) and parotid gland showed a deuterencephalic-spinocaudal, liver and heart-muscle an archencephalic inductive effect. Increasing the duration of alcohol treatment (up to 20 days) changed the inducing abilities of kidney and parotid from deuterencephalic-spinocaudal to archencephalic-deuterencephalic. The same effect appeared after prolonged semi-starvation (3–4 weeks) of the donor animals. The archencephalic inductive effect of the liver and heart-muscle was not changed either by prolonged alcohol treatment of the implants or by starvation of the donor animals (only liver was tested). No dependence of inducing ability on age of donor animals was found. These results permit the conclusion that there are two different modes of reaction in the competent ectoderm produced by the underlying action system. It seems that each inducing system contains the archencephalic component which can be dominated by deuterencephalic-spinocaudal inducing factors. If the latter should disappear through any change of the inducing material, e.g. a denaturation caused by alcohol treatment, archencephalic differentiation tenden-cies appear in every case. The fact that induced structures of the deuterencephalic-spinocaudal com-plex decreased in number either as a consequence of alcohol treatment of the implants or through starvation of the donor animals indicates the importance of a degradation or decrease of proteins in the inductive material. The experiments do not support the assumption that the ribonucleic acids are of decisive impor-tance in the realization of the archencephalic complex.
The Action of Testosterone and Oestradiol on the Sebaceous Glands and Epidermis of the Rat
Authors: Ebling F. J. 
Published: April 2021

ABSTRACT
A method is described for estimating the mean volume and mean number of sebaceous glands per unit area from sections of skin. The enlargement of the sebaceous glands which resulted from the implantation of testosterone in spayed rats aged 25 weeks was shown to be due to increases in both cell proliferation and cell volume; at the same time cell loss appeared to have been accelerated. The effect of oestradiol, which reduced the volume of the sebaceous glands, appeared to be due mainly to an acceleration of cell breakdown rather than to an inhibition of cell proliferation; cell size was not affected. When both hormones were administered simultaneously the identity of their individual effects appeared to be maintained, although the size of the resulting glands was not significantly different from normal. Oestradiol reduced the thickness of the epidermis (stratum germinativum plus stratum granulosum) in spayed rats without altering the incidence of mitoses, but testosterone had no significant effect.
Development of the Intestinal Tract during the Larval Period of Drosophila
Authors: Shatoury H. H. El , Waddington C. H. 
Published: April 2021

ABSTRACT
A few hours before the end of the second larval instar the first pair of lymph glands hypertrophies, then releases cells into the haemocoele. This is quickly followed by the growth of the primordia of the more posterior pairs of lymph glands. The cellular contents of the first pair of glands then disintegrates nearly completely and the glands are regenerated from small primordia lying at their posterior end. A similar but less well-marked process takes place at the end of the first larval instar. At the time of the hypertrophy of the first pair of lymph glands in the second larval instar (and to a lesser extent also in the first instar) the main epithelium of the mid-gut hypertrophies, giving off a large number of lumps of cytoplasm, mostly without nuclei, into the lumen of the gut which becomes temporarily filled up with them. When the more posterior lymph glands develop this hypertrophy ceases, the cytoplasmic masses cytolyse and are largely resorbed by the mid-gut epithelium. Rather similar processes of hypertrophy occur in the imaginal rudiment at the anterior end of each salivary gland and in the imaginal rudiment of the hind-gut which lies just caudal to the entrance of the Malpighian tubules. Lying beneath the main epithelium of the mid-gut in the newly hatched larva are scattered small cells referred to as basement cells. It seems likely that these are derived from the lymph glands during the end of the embryonic period. Towards the end of the second larval instar the basement cells are joined by further lymph-gland cells. During the third larval instar these multiply, forming small imaginal primordia each consisting of a nest of deeply basophilic cells, the more peripheral cells throwing out long processes which extend round and enclose the others. Towards the end of the third larval instar, when the lymph gland hexagons become melanized and degenerate, the basement cells also suffer degeneration though not melanization. At the time of puparium formation the central cells of the imaginal primordia proliferate to form the wall of the imaginal mid-gut. The peripheral cells of the imaginal primordia are thrown off into the gut-lumen where they form a continuous layer around the degenerating main larval epithelium.