bluuebunny/crossref_metadata_2025_split huggingface dataset:
Intercalary regeneration around the circumference of the cockroach leg
Authors: French Vernon 
Published: April 2021

ABSTRACT
Epidermal cells from different circumferential positions around the femur of Blabera craniifer can interact to form an intercalary regenerate. Removal of a longitudinal strip of integument (cuticle plus epidermis) from any position around the circumference leads to the cut edges healing, localized growth and intercalary regeneration of the missing section of the circumference, so that the resulting femur is approximately normal in size and pattern of cuticular structures. Grafting a longitudinal strip of femur integument into a different circumferential position on the host femur confronts epidermal cells from different positions along both the inner and outer longitudinal graft/host junctions. In numerous different situations this results in local growth and intercalary regeneration of that section of the circumference normally separating graft and host positions, by the shorter route around the circumference. Confrontation of opposite positions results in the intercalation of either of the intervening half circumferences. In one opposite confrontation, between mid-anterior and mid-posterior, there was also a third result where graft and host healed together, provoking no intercalary regeneration. Grafts made with reversed proximal/distal polarity show that a confrontation between different circumferential positions gives the same result, regardless of the proximal/distal levels involved, hence circumferential position is an independent aspect of position on the femur.
These results strongly suggest that epidermal position is not specified with respect to two transverse axes running through the epidermis and internal tissue of the leg, but that there is a continuous circular sequence of positional values running around the circumference, in the epidermis. This is analogous to but independent of the sequence previously shown by Bohn (1967) and Bullière (1971) to run proximal/distal along a leg segment. Hence epidermal position on the femur is specified in two dimensions and can be represented in terms of the French, Bryant & Bryant (1976) polar co-ordinate model. Interactions along the edges of the strip-grafts conform to the Shortest Intercalation Rule (French et al. 1976).
At the proximal and distal ends of strip-grafts intercalation restores normal sequences of positional values where possible. However, where the graft, together with the intercalary regenerates formed at the longitudinal graft/host junctions and the adjacent host tissue formed a complete sequence of circular values, then a supernumerary distal regenerate was formed, in agreement with the Complete Circle Rule of French et al. (1976).
The problem of generating a continuous circular sequence of positional values by one or more circumferential gradients, is briefly discussed.
‘Transdifferentiation’ of chicken neural retina into lens and pigment epithelium in culture: controlling influences
Authors: Pritchard D. J. , Clayton R. M. , Pomerai D. I. De 
Published: April 2021

ABSTRACTThe in vitro transdifferentiation of chicken embryo neural retina into pigment epithelium and lens cells was investigated under a variety of experimental conditions. Our findings suggest that some aspects of the phenomena are a function of medium composition and volume, whereas others depend upon conditions which develop during culture growth. Before melanin is visible, potential pigment cells are recognized as foci within epithelial sheets which remain in contact with the dish. The final area occupied by colonies of potential pigment cells is directly proportional to bicarbonate concentration. Low total medium volume also favours formation of potential pigment cells. In contrast the extent of cells other than potential pigment cells is not related to bicarbonate and is favoured when the volume of medium is large. Accumulation of melanin within the potential pigment cell colonies is suppressed when cells are crowded together. Lentoid bodies are formed from cells which are distinct from potential pigment cells and arise in crowded situations, in association with multilayering. Another type of structure superficially resembling a lentoid is derived from cell aggregates formed during the initial establishment of cultures. The survival of these ‘aggregate bodies’ is inversely related to bicarbonate concentration. Crystallin content is unrelated to lentoid numbers. The results provide the basis for a new hypothesis concerning cytodifferentiation in this system.
Interaction between inner cell mass and trophectoderm of the mouse blastocyst:I. A study of cellular proliferation
Authors: Copp A. J. 
Published: April 2021

ABSTRACT
Increase in cell number has been compared with mitotic activity in the polar and mural trophectoderm and in the inner cell mass (ICM) of mouse blastocysts. The results indicate that whereas ICM cells divide at a rate which is compatible with the rate of increase of ICM cell number, polar trophectoderm cells divide faster and mural trophectoderm cells slower than can account for their own rates of cell number increase. It is suggested that the ICM induces a high rate of proliferation in the polar trophectoderm and that there is a resulting cell shift from polar to mural regions during blastocyst development. Mural trophectoderm cells close to the ICM divide faster than those farther away, indicating that cells may retain a ‘memory’ of ICM contact for some time after leaving the ICM. There is considerable cell death in the blastocyst, but this is restricted to a short period of time coincident with the appearance of primitive endoderm.
Participation of the cell surfaces in determining the developmental courses in the cellular slime mould Dictyostelium purpureum
Authors: Saito M. , Yanagisawa K. 
Published: April 2021

ABSTRACT
Dictyostelium purpureum S5 and S6, mating type strains, form fruiting-bodies in a mono-clonal culture, but produce macrocysts in a mix culture. The effects of Concanavalin A (Con A) on both fruiting-body formation and macrocyst formation, and changes of Con A-mediated cell agglutinability during development were studied. It was found that Con A inhibits macrocyst formation but not fruiting-body formation, and that macrocyst-forming cells are much more susceptible to Con A agglutination than are fruiting-body-forming cells during the aggregation stages. When fruiting-body-forming cells are treated with either trypsin or α-chymotrypsin, their Con A agglutinability is enhanced to the same extent as that of macrocyst-forming cells. It was also found that when S6 cells are treated with pro-teases they sometimes produce normal macrocysts even in a monoclonal culture.
The results obtained in these experiments showed that the surface properties of fruiting-body-forming cells and macrocyst-forming cells are different, and that the cell surface might play an important role in determining the two developmental courses.
Cell adhesion and chondrogenesis in brachypod mouse limb mesenchyme: fragment fusion studies
Authors: Duke Jackie , Elmer William A. 
Published: April 2021

ABSTRACT
This study is a continuing investigation of the effect of the brachypod mouse mutation on cell interactions and chondrogenesis during early limb development. In this report, cell adhesiveness was assessed in fused fragments of brachypod and normal limb-bud mesenchyme. Examination of the interface of fused distal postaxial limb fragments show brachypod limb mesenchyme to be more adhesive than normal limb mesenchyme. Chondrogenesis within brachypod fragments is delayed and less extensive than in normal fragments. In addition, chondrogenesis within normal fragments is not affected by the juxtaposition of the brachypod fragment, and vice versa.
Regional differences in the morphology and motility of mesodermal cells from the early wing-bud of normal and talpid3 mutant chick embryos
Authors: Bell D. A. , Ede D. A. 
Published: April 2021

ABSTRACT
A method of culturing has been employed to compare the properties of cells migrating from small mesodermal explants taken from different regions of normal and mutant limb-buds at different stages of development. An analysis by time-lapse cinematography of the morphology and mobility of cells migrating from explants defines a distal region within the limb-bud where these properties are distinct from those of cells from more proximal regions. In the normal wing-bud distal cells subjacent to the apical ectodermal ridge possess a characteristic multipolar morphology and translocate slowly in vitro. Cells from more proximal regions tend to be bipolar and translocate more rapidly. Distal and proximal cells also probably differ in their adhesive strengths. In the mutant, talpid3, distal and proximal cells do not differ in the above properties and cells from all regions of the limb-bud are multipolar, translocate slowly and are more adhesive than normal cells. A study of light micrographs and scanning electron micrographs suggests that these regional differences are found in the limb-bud in vivo and are not merely an effect produced by the in vitro culturing system.
Lens regeneration from cornea of larvalXenopus laevisin the presence of the lens
Authors: Reeve Julie G. , Wild Arthur E. 
Published: April 2021

ABSTRACTIn Xenopus laevis tadpoles, wounding of the outer cornea failed to initiate lens regeneration. If both the outer and inner corneas were wounded or if the lens was dislocated, lens regeneration was initiated but failed to continue beyond stage III. However, lensectomy followed by re-implantation of the lens resulted in the regeneration of a fully differentiated lens in several cases, despite the presence of the re-implanted lens. Although some of the regenerates in these eyes were also arrested at stage III, those which attained full lens differentiation, i.e. stage V, developed normally and synthesized crystallins from the onset of stage IV as indicated by a positive immunofluorescence reaction.Histological examination of the dislocated and re-implanted lenses showed the majority of them to be normal in appearance.Cornea transplanted to the posterior chamber of the eye also regenerated a lens in the presence of the re-implanted lens. All these regenerates underwent lens fibre differentiation to give stage-V regenerates.These findings show that lens regeneration from the cornea can occur in the presence of lens. Results are discussed on the basis that contrary to earlier suggestions, an inhibitory lens factor does not exist in vivo, but rather that a factor for the initiation and maintenance of regeneration emanates from the eye cup and upon wounding of the inner cornea is able to reach the inner cell layer of the outer cornea and initiate lens regeneration.
Cell contacts and sorting outin vivo:the behaviour of some embryonic tissues implanted into the developing chick wing
Authors: Tickle C. , Goodman M. , Wolpert L. 
Published: April 2021

ABSTRACTThe interaction of cells from embryonic liver, neural retina and mesonephros with cells from limb-bud mesenchyme has been investigated in vivo by grafting these tissues into the developing chick wing-bud. The implanted cells were in all cases from quail tissue which can be recognized histologically. As embryonic liver and neural tube are tissues that sort externally to limb-bud mesenchyme in mixed aggregates, it would be expected, from a dif-ferential adhesiveness hypothesis, that heterotypic adhesions along the borders of graft and host would be favoured over cell-cell adhesions in the graft. No morphological signs of this were evident: rather the grafted cells maximized like-like contacts. The cells of the grafts, including those from control mesenchyme, did not invade into the wing. The results were the same irrespective of whether the graft was a fragment of tissue or a pellet of reaggre-gated cells. This supports the idea that cells within tissues are not actively moving around and also provides controls for assaying the invasiveness of other cell types, such as malig-nant cells into the wing.
The mechanical role of the cranial base in palatal shelf movement: an experimental re-examination
Authors: Brinkley L. L. , Vickerman M. M. 
Published: April 2021

ABSTRACT
Straightening of a cranial base flexure observed in the midsagittal presphenoid region of mice has been postulated to play a major role in palate closure by providing the internal shelf force for palatal shelf movement. The straightening is thought to take place during the 8 h immediately preceding closure. This mechanical model assumes that straightening of the cranial base flexure is transmitted laterally to the alar regions of the sphenoid and then downward to the palatal shelves. According to this hypothesis, if the flexure did not straighten or the force generated by this form change was not transmitted to the palatal shelves, movement to the horizontal plane should not take place. Physical disruption of the area of the flexure should remove the potential for form change through force transmission. Swiss-Webster mouse fetuses which were 18 or 24 h prior to palate closure were obtained and the heads removed. Tongue and brain were then removed from each head. In the experimental specimens a midsagittal lesion, averaging 407 μm in length and 84 μm in width, extending from the nasal septum through the craniopharyngeal area was made. This lesion ablated the flexure region of the cranial base far in advance of the time straightening is thought to take place. Heads of litter-mates with intact cranial bases served as controls. Specimens with intact and ablated flexures were suspended in a submerged, circulating culture system which was continuously gassed. After 18 h of culture, palatal shelf elevation had occurred in fetuses of both ages whether or not their cranial bases were intact. Palatal shelf elevation in vitro does not require an intact cranial base.
Adenylation and ADP-ribosylation in the mouse 1-cell embryo
Authors: Young R. J. , Sweeney K. 
Published: April 2021

ABSTRACT
The incorporation of [3H]adenosine into cold trichloroacetic acid (TCA) insoluble material by the mouse 1-cell embryo has been studied. Incorporation of label was high immediately after fertilization, then decreased over the next 7 h with the sharpest decline occurring 3-5 h after fertilization. A small maximum was observed at the time of pronuclear DNA synthesis. Actinomycin D at a concentration which inhibited the cleavage of 1-cell embryos by 50 % had little effect on this incorporation, which in the period 1-6 h post-fertilization was shown by autoradiography to be confined to the ooplasm of the newly fertilized ovum. [3H]Adeno-sine and poly ([3H]A) were released from embryo RNA labelled 1-3 h after fertilization with [3H]adenosine by digestion with a mixture of ribonucleases A and Tx. The poly ([3H]A) segments were hydrolysed by alkali to 3’-[3H]AMP and [3H]adenosine ([3H]AMP/[3H]adeno-sine = 5/1), and by snake venom phosphodiesterase to 5’-[3H]AMP but very little [3H]adeno-sine. These results suggest that adenylation of RNA occurs soon after fertilization, that this is a cytoplasmic event, and that most of the newly synthesized poly ([3H]A) segments are joined to pre-existing poly (A) tracts. The unusual polynucleotide, poly (ADP-ribose), identi-fied by its resistance to alkali and the release of 2’-(5”-phosphoribosyl)-5’[3H]AMP on incu-bation with snake venom phosphodiesterase, was also found in the ribonuclease digest.
Duplicated axolotl regenerates
Authors: Wallace H. , Watson A. 
Published: April 2021

ABSTRACT
Three series of palette stage regenerates were prepared by amputating both arms of juvenile axolotls in the mid-forearm, above the elbow, or close to the shoulder. Within each series, excised regenerates were replaced in their original orientation (as a control) or rotated at 90° intervals about the proximodistal axis, or were transplanted to the contralateral arm with identical rotations. Control grafts occasionally caused the formation of a single extra digit. All experimental rotations provoked duplicate or triplicate structures, ranging from accessory digits to extra forearms. Shoulder level grafts were subject to a pronounced correctional derotation and yielded a variable proportion of duplications. Forearm and elbow-level rotations invariably yielded duplications, which therefore result from an axial discrepancy rather than complete axial opposition between graft and host. These results are incompatible with the clockface model of positional information and demand a modification of other current models. The recorded frequency and orientation of duplications suggest that a limb contains at least two polarized transverse axes which cannot be respecified during regeneration. A substantial discrepancy on either axis reduces the normal regulative interaction between graft and host, allowing either of them to regenerate independently.
Post-embryonic determination of the ecdysial line in the cockroach: evidence for pattern regulation in the medio-lateral axis
Authors: Shelton P. M. J. 
Published: April 2021

ABSTRACTBy removing or transplanting sections of the ecdysial line in the cockroach Grompha-dorhinaportentosa, pattern regulation in medio-lateral axis of an insect has been demonstrated. The line can reform after sections have been removed and when epidermal grafts from either side of the midline are grafted with confronting medial edges. The results are explicable in terms of known mechanisms for pattern regulation in insects.
Formation and consequences of cell patterns in preimplantation mouse development
Authors: Graham C. F. , Lehtonen E. 
Published: April 2021

ABSTRACT
The behaviour of groups of cells was studied in culture during preimplantation mouse development. The following observations were made with intact embryos minus the zona pellucida and with embryos whose cells had been dissociated and recombined. The form of the 4-cell embryo was related to the behaviour of the first cell to divide to this stage. The form of the 8-cell embryo depended on contact between the groups of four cells each derived from a single cell at the 2-cell stage. The form of the 16-cell embryo depended on cell movement during and after division from the 8-to the 16-cell stage. These results suggest that the morpho-genetic movements of these early embryonic cells are principally governed by continuous cell interactions after fertilization. The cell surfaces of the embryos were examined with scanning electron microscopy in an attempt to discriminate between the mechanisms which could account for these movements.
The Keratin Defect and Hair-cycle of a New Mutant (Matted) in the House-mouse
Authors: Jarrett A. , Spearman R. I. 
Published: April 2021

ABSTRACT
The gene matted (symbol ma) reported by Searle & Spearman (1957) causes the body-hair of affected mice to be brittle and inflexible; this results in longitudinal splitting and breaking due to friction against the cage and other objects. In the present paper the keratin abnormality of the hair is studied. The defect in matted hairs is compared with that of Naked (N/ +) mice (Grüneberg, 1952), and the hair-cycle in matted mice is described.
The Composition and Origin of the Allantoic Fluid in the Rabbit
Authors: Dickerson J. W. T. , McCance R. A. 
Published: April 2021

ABSTRACT
The allantoic fluid of the rabbit at the 20th day of gestation has been found: (a) to be opalescent; (b) to be hypotonic relative to the maternal serum; (c) to contain higher concentrations of urea and potassium than the maternal serum; and (J) to contain lower concentrations of sodium and chloride. The facts known about this fluid indicate that it may be very largely a product of the foetal mesonephros.
Embryonic Responses to Structurally Related Inhibitors
Authors: Liedke Kathe B. , Engelman Morris , Graff Samuel 
Published: April 2021

ABSTRACT
Seventeen of 27 structurally related compounds which could act as purine or pyrimidine antagonists inhibited embryonic development to different degrees. Several benzotriazoles were found to exert similar effects on embryos, the intensity varying with substituents. Older, more differentiated, stages are more susceptible to the benzotriazoles than are early cleavage stages. Exposure to the benzotriazoles at the blastula stage results in hypomorphic cyclopian development without necrosis. There is always a marked delay in the rate of development. Swelling and loss of cells is found, particularly in neurula and tail-bud stages, and usually is followed by death. These findings suggest that the surface coat is interfered with. All active benzothiadiazoles, benzimidazoles, and quinoxalines have the same effect on the embryo; the intensity of the response varying with substitution. Younger, and particularly cleavage, stages are more susceptible, and resistance increases with age of embryo. Exposed blastula stages are frequently arrested as dwarfed tail-buds showing extensive necrosis, particularly of the nervous system. Rarely is there arrest in neurula stages, or if it occurs, these are abortive neurula-exogastrulae with large yolk-plug, no swelling, and larger-sized cells than is normal for this stage. There is always a selective cellular response: early differentiating and very rapidly dividing cells are most sensitive and become necrotic first, while other cells are enlarged and remain arrested. The type of response is determined by the compound, the degree or intensity of response by the substituted groups. It is greatest if only a single nitro group is substituted in the benzothiadiazoles, benzimidazoles, and benzotriazoles, but not in the quinoxalines in which other substitutions seem to have the same degree of effectiveness. On the other hand, some substituents, amino or diphenyl groups for example, decrease the effectiveness of the quinoxalines and benzimidazoles. No direct correspondence between structure and biological function has been discerned.
Effects of X-rays on nerve-dependent (limb) and nerve-independent (jaw) regeneration in the adult newt, Notophthalmus viridescens
Authors: Wertz Richard L. , Donaldson Donald J. 
Published: April 2021

ABSTRACT
The newt limb requires nerves for successful regeneration, but the jaw appears to be nerve independent. Among the current hypotheses for the regeneration-inhibitory action of X-rays is one proposing inactivation of nerves as the main cause. We decided to test this hypothesis by comparing the irradiation levels necessary for inhibition of limb and jaw regeneration.
Jaws and left front limbs were exposed locally to doses of ionizing X-irradiation ranging from 250 to 2000 R at least 6 weeks prior to amputation of the jaw and both front limbs. After 90 days post-amputation all surviving animals were examined grossly for signs of regeneration. In addition, some of the controls and most of those receiving 250, 500 and 1000 R were processed for histological examination.
All unirradiated limbs and jaws supported regeneration. Those exposed to 250 R also regenerated, but a third of the jaws were hypomorphic. At 500 R and above, neither jaws nor limbs regenerated. Since both systems were affected by similar doses of X-rays, it appears that nerves are not the primary X-ray target in adult newts.
The dynamics of Drosophila melanogaster spermatogenesis in in vitro cultures
Authors: Cross David P. , R David L. Shellenbarge 
Published: April 2021

ABSTRACT
A photographic description of meiosis and spermatogenesis in single sperm cysts of Drosophila melanogaster cultured in vitro is presented. In addition to the utility of this description for the study of spermatogenesis in whole live testes, the culture procedure provides a means for studying the dynamic development of individual sperm cysts from flies carrying male-sterile mutations, as illustrated with X/O males. Several deviations of spermatogenesis in vitro from that in vivo suggest that sperm morphogenesis is not rigidly coordinated.