bluuebunny/crossref_metadata_2025_split huggingface dataset:
Culturein vitrode blastèmes de régénération de Planaires
Authors: Sengel Catherine 
Published: April 2021

ABSTRACTYoung regeneration blastemata of Planarians have been cultivated in vitro on an agar-embryo extract culture medium which is a modification of the organ culture medium devised by Wolff & Haffen. Transverse cuts were made in whole worms and 3 days later the blastemata were isolated on the culture medium, where they survive for 10–15 days. There is no visible growth, but the observations reveal pigment formation by the third day, the appearance of muscles on the fourth or fifth day, and the presence of the eyes and brain by the tenth day. All three types of differentiation have been observed in the cultures of head blastemata, but only pigment and muscles are present in the cultures of tail blastemata. When two or more head blastemata are cultured together they differentiate into a larger head with supplementary eyes. The association of two or more tail blastemata does not result in the differentiation of eyes or brain. The combination of one head blastema with one or two tail blastemata in such cultures gives rise to a small planarian with a pharynx and a gut. The method of culturing regeneration blastemata in vitro reveals that the fate of the blastemata is determined quite early. A head blastema can differentiate cephalic structures, whereas a tail blastema cannot. However, if a head blastema is associated with a tail blastema in culture, then they differentiate into a complete planarian.
L’action inductrice du chordo-mésoblaste au cours de la gastrulation et de la neurulation et les effets de la culturein vitrosur ses manifestations
Authors: Gallera J. 
Published: April 2021

ABSTRACTOne species of Urodele, Trituras alpestris, was used. The inducing capacities of the anterior chordal zone of the archenteron roof were studied in vitro by the ectoblastic ‘sandwich ‘method. The inducing material was taken from different stages of gastrulae and neurulae. The duration of induction (16–24 hours) had been determined by the results of the author’s previous experiments: it was sufficient to provoke a clear reaction in the ectoblast, but too short for the chordomesoblast to exert fully its specific regional inductive capacity.When the period of induction was at an end, the two layers of the ‘sandwich ‘were separated to remove the inductor, and the layers were allowed to develop separately in Holtfreter’s solution. No difference was found in the inductive capacities of the dorsal and ventral surfaces of the archenteron roof.Histological examination of the neural structures produced by the expiants confirmed the results obtained previously in analogous experiments involving transplants to the embryo. The inductive power of the chordomesoblast becomes considerably modified during gastrulation and neurulation. Its feeble power of inducing a forebrain is a more or less delayed acquisition, which only comes into action at the time when the process of neural induction is almost achieved in the embryo. It always possesses, however, a predominant power of inducing deutencephalon and spinal cord. The induction by the chordomesoblast of cerebro-sensory complexes which are exclusively acrencephalic becomes possible only when one dissociates the effects of the two activities manifested by the inductor.A comparison of these results with those of the author’s previous experiments shows that it is easier for the chordomesoblast to induce a forebrain in ectoblast cultivated in vitro than in grafts implanted on the archenteron roof and then transplanted to the ventral surface of another embryo. In the first case, not only are acrencephalic formations much more frequent, but one can obtain them with a younger chordomesoblast. The saline solution of Holtfreter has a feeble acrencephalogenic action on the neural structures which have resulted from an insufficient induction and which are still labile in the direction of their development.The author reviews the conception of neural induction held by Nieuwkoop, and the similar interpretation adopted by Johnen to explain the results of her experiments.
The role of the glycoconjugates in the migration of anuran amphibian germ cells
Authors: Delbos M. , Gipouloux J.-D. , Saidi N. 
Published: April 2021

ABSTRACT
The presence of a large amount of glycoconjugates on the anuran amphibian germ cells was demonstrated using fluorescein isothiocyanate lectins binding specifically to D-galactose and at a lower level, by other lectins binding specifically to N-acetyl-galactosamine. Glycoconjugates including D-galactose were found near the pseudopodial expansions and in the extracellular space, between germ cells and follicular cells. They were also disseminated in the cytoplasm. The injection of PNA lectin (from Arachis hypogea) into the endoderm inhibited the migration of 90% of the germ cells. This inhibition was lectin-concentration dependent. Ultrastructural study of germ cells, the migration of which was inhibited, showed that they were degenerating. These results suggest that glycoconjugates are related to the migratory activity of germ cells.
Intestinal cyto differentiation in vitro of chick stomach endoderm induced by the duodenal mesenchyme
Authors: Ishizuya-Oka Atsuko , Mizuno Takeo 
Published: April 2021

ABSTRACT
The inductive action of duodenal mesenchyme on the cytodifferentiation of stomach endoderm in chick embryos was investigated in vitro with electron microscopy and immunofluorescence. Morphologically undifferentiated endoderm of the stomach of a 4-day embryo could differentiate only into a mucous secretory epithelium when cultured in the absence of mesenchyme. However, when cultivated in recombination with 6-day duodenal mesenchyme, most cells of 4-day stomach endoderm differentiated into intestinal absorptive cells possessing striated border and sucrase, and goblet cells, but not into stomach-type mucous secretory cells. In contrast, when 4-day stomach endoderm was cultured recombined with mesenchyme of embryonic digestive organs other than intestine, none of the stomach endoderm cells differentiated into intestinal epithelial cells. The competence of stomach endoderm for intestinal cytodifferentiation decreased rapidly with development, but remained until relatively later stages in the gizzard region. The present investigation demonstrates that duodenal mesenchyme can induce stomach endoderm, which has acquired the potency for self-differentiation into stomach-type epithelium, to cytodifferentiate into intestinal epithelium.
Regeneration of surgically created mixed-handed axolotl forelimbs: pattern formation in the dorsal—ventral axis
Authors: Holder Nigel , Weekes Charleston 
Published: April 2021

ABSTRACT
The regeneration of surgically created mixed-handed limb stumps is examined in the axolotl. Operations were performed in the lower arm and upper arm regions and grafts were allowed to heal for approximately one month prior to amputation or were amputated immediately. In the lower arm group both anterior and posterior limb halves were inverted, whereas only posterior halves were inverted in the upper arm group. Almost all the limbs regenerated were normal in the anterior-posterior axis, whereas a range of limb types were found when the dorsal-ventral axis was analysed using the metacarpal muscle pattern and epidermal Leydig cell number as positional markers. The carpal and forearm muscle patterns were also analysed in order to assess whether the pattern determined from analysis at the metacarpal level reflected that seen at more proximal levels. The results are discussed in terms of the possible role of cell contribution from the stump to the blastema and the relevance of the study to models of pattern regulation.
Muscle gene activation by induction and the nonrequirement for cell division
Authors: Gurdon J. B. , Fairman S. 
Published: April 2021

ABSTRACT
We are investigating the mechanism by which animal cells of an amphibian blastula are induced to differentiate as muscle after contact with blastula vegetal cells. After briefly summarizing previous work on this system, we have asked whether this response of animal cells to vegetal induction requires cell division. Animal and vegetal parts of a blastula were placed in contact with each other, and the resulting conjugates cultured in medium containing a sufficient concentration of colchicine or cytochalasin B to inhibit cell division. Muscle differentiation, as indicated by cardiac actin gene transcription, is induced when cell division is inhibited, though at a substantially reduced rate. However, cytoskeletal actin gene transcription, which does not depend on induction, is also much reduced under the same inhibitory conditions. We conclude that, although the cell division inhibitors seem to reduce all gene transcription, they have no preferential effect on the response to induction, and therefore that this process does not require cytoplasmic or nuclear division.
The phenotypic interdependence of the musculoskeletal characters of the mandibular arch in mice*
Authors: Kay Elizabeth D. 
Published: April 2021

ABSTRACT
Evidence from studies of craniofacial anomalies and the evolutionary transition from reptiles to mammals suggests that the temporomandibular joint (TMJ), bony zygomatic arch, middle ear ossicles and mandibular muscle pattern may form a correlated suite of characters. To test the degree of phenotypic interdependence among these features, mandibular arch defects were analysed in prenatal mice. Retinoic palmitate was administered to pregnant mice on day 8-7 to produce test foetuses with malformations of the mandibular arch. A rating scale was developed for each of the four characters so that numerical values could be assigned to each phenotype encountered. Control animals were used to establish normal phenotypes for each character which were assigned a value of 1. Data from each test age, 16, 18 and 19 days postconception, were pooled and Spearmann rank correlation coefficients between each of the traits were calculated.
Coefficients (R) range from a high of 0·87, between the TMJ and zygomatic arch, to a low of 0-67 between the zygomatic arch and the mandibular musculature showing highly significant correlations (P&lt; 0·0001) among all characters. Therefore, the data suggest that the musculoskeletal features of the mandibular arch are phenotypically interdependent during development.
The effect of replacing different regions of limb skin with head skin on regeneration in the axolotl
Authors: Wigmore Peter , Holder Nigel 
Published: April 2021

ABSTRACT
Head skin was used to replace different halves of limb skin from the upper and lower arms of axolotls. Replacement of upper arm posterior skin caused the regeneration of a high proportion of single-digit limbs while replacement of dorsal, ventral or anterior skin caused only minor defects to the normal skeletal pattern. When dorsal or ventral skin was replaced, however, regenerates often lacked dorsal or ventral muscle. Results from the lower arm were different in that replacement of any half of limb skin failed to cause defects either in the skeletal or muscular pattern. These results are used in conjunction with previous work (Wigmore & Holder, 1985; Wigmore, 1986) to suggest that posterior skin is essential for regeneration of the anteroposterior axis and dorsal and ventral skin is necessary for the differentiation of the muscle pattern in regenerates from the upper arm. In the lower arm no localized region of skin appears to be essential for regeneration of the normal pattern and the patterning mechanism may have a different spatial organization.
Dynamics of the control of body pattern in the development of Xenopus laevis: IV. Timing and pattern in the development of twinned bodies after reorientation of eggs in gravity
Authors: Cooke Jonathan 
Published: April 2021

ABSTRACT
The mesendodermal anatomy of twinned larval axes is described in relation to the normal single pattern, when twinning has been caused by experimental tilting of eggs before first cleavage. The formation of two origins for gastrulation movements (dorsal lips) and their relatively rapid spread and coalescence to give a circular blastopore, is a predictor of twin formation in individual embryos after treatment. The anatomy of twins where development has been disturbed from the outset in this way is appreciably different from that induced by the later operation of second dorsal lip implantation. It is also variable in a systematic way. The total sizes of cellular allocations to individual notochords and prechordal head patterns are enhanced above normal if they arise relatively close together in the tissue, but significantly reduced if they arise far apart. These and other features of twinned patterns due to precleavage disturbance are discussed in terms of what they might indicate about the physicochemical nature of the body positional system. The results confirm that by a variety of rather simple, nonsurgical manipulations the relative amounts of territory in the egg devoted to different parts of the body can be greatly influenced.
Topographical control of cell behaviour: I. Simple step cues
Authors: Clark P. , Connolly P. , Curtis A. S. G. , Dow J. A. T. , Wilkinson C. D. W. 
Published: April 2021

ABSTRACT
The photolithographic techniques of the microelectronics industry have allowed us to fabricate patterned plastic substrata to investigate contact guidance of animal tissue cells. The reactions of cells to single steps on a substratum were examined using time-lapse videorecording and scanning electron microscopy. BHK cells and chick embryonic neural cell processes exhibited gradual inhibition of crossing steps with a concomitant increase in alignment at steps dependent on increasing step height. Comparison of these cells’ reactions, with those of chick heart fibroblasts and rabbit neutrophils, at a 5 fim step revealed that the influence of topography is also dependent on cell type, the neutrophils being relatively unaffected. The presence of an adhesive difference at a series of steps altered BHK cells’ reactions such that the frequency of crossing was dependent on the direction of approach to a step. Although our data are consistent with Dunn & Heath’s proposal (1976) that the inflexibility of the cytoskeleton of a moving cell’s protrusion is the cellular property determining such reactions to topography, we have found that, on encountering a topographical feature, the response of a cell may be predictable on a probabilistic basis, i.e. the topographical feature reduces the probability of a cell making a successful protrusion and contact in a given direction, that even the largest features tested did not act as absolute barriers to cell locomotion since a small proportion of a population of cells were able to overcome them, and that other guidance cues could significantly alter a cell’s response. Even in situations where it is not the primary cue in directing cell locomotion, topographical control may be an important factor during morphogenesis since it must, at the very least, influence the efficiency of other cues.
Differential deposition of basement membrane components during formation of the caudal neural tube in the mouse embryo
Authors: O’Shea K. Sue 
Published: April 2021

AbstractThe distribution of basement membrane and extra-cellular matrix components laminin, fibronectin, type IV collagen and heparan sulphate proteoglycan was examined during posterior neuropore closure and secondary neurulation in the mouse embryo. During posterior neuropore closure, these components were densely deposited in basement membranes of neuro-epithelium, blood vessels, gut and notochord; although deposition was sparse in the midline of the regressing primitive streak. During secondary neurulation, mesenchymal cells formed an initial aggregate near the dorsal surface, which canalized and merged with the anterior neuroepithelium. With aggregation, fibronectin and heparan sulphate proteoglycan were first detected at the base of a 3- to 4-layer zone of radially organized cells. With formation of a lumen within the aggregate, laminin and type IV collagen were also deposited in the forming basement membrane. During both posterior neuropore closure and secondary neurulation, fibronectin and heparan sulphate proteoglycan were associated with the most caudal portion of the neuroepithelium, the region where newly formed epithelium merges with the consolidated neuroepithelium. In regions of neural crest migration, the deposition of basement membrane components was altered, lacking laminin and type IV collagen, with increased deposition of fibronectin and heparan sulphate proteoglycan.
Developmental and spatial patterns of expression of the mouse homeobox gene,Hox2.1
Authors: Krumlauf Robb , Holland Peter W. H. , Mcvey John H. , Hogan Brigid L. M. 
Published: April 2021

AbstractThe H ox 2.1 gene forms part of a cluster of homeo-box -containing genes on mouse chromosome 11. Analysis of Hox2.1 cDNAs isolated from an -day p.c. mouse embryo library predicts that the gene encodes a 269 amino acid protein (Mr, 29432). This deduced protein contains a homeobox 15 amino acids from the carboxy terminus and is very rich in serine and proline. A second partially conserved region present in several other genes containing homeo-boxes, the hexapeptide De-Phe-Pro-Trp-Met-Arg, is located 12 amino acids upstream of the homeodomain and is encoded by a separate exon. Analysis of Hox 2.1 gene expression reveals a complex and tissue-specific series of RNA transcripts in a broad range of feta] tissues (lung, spinal cord, kidney, gut, spleen, liver and visceral yolk sac). Comparison of the temporal patterns of gene expression during development and in the adult suggests that Hox2.1 is regulated independently in different tissues. Evidence is also presented that transcripts from other loci have extensive homology to the Hox2.1 gene in sequences out-side of the homeobox. In situ hybridization shows that Hox2.1 transcripts are regionally localized in the spinal cord in an apparent anterior–posterior gradient extending from the hind brain. The distribution of RNA also displays a cell-type specificity in the. lung, where mesodermal cells surrounding the branching epithelial cell layer accumulate high levels of Hox2.1 transcripts.
Chemotaxis of Chinese hamster ovary cells expressing the human neutrophil formyl peptide receptor: role of signal transduction molecules and α5β1 integrin
Authors: Miettinen Heini M. , Gripentrog Jeannie M. , Jesaitis Algirdas J. 
Published: April 2021

ABSTRACT
Activation of the N-formyl peptide receptor (FPR) of human neutrophils by ligands such as N-formyl-methionine-leucine-phenylalanine (fMLP) induces mobilization of intracellular calcium, cell adhesion, chemotaxis, superoxide production and degranulation. Chinese hamster ovary (CHO) cells are normally devoid of FPR and unresponsive to fMLP, but when stably transfected with a human FPR cDNA, exhibited some of these same responses. Specifically, stimulation with fMLP resulted in release of intracellular calcium and chemotactic migration toward a gradient of fMLP. As in neutrophils, both processes were inhibited through receptor desensitization by prior exposure to a higher or equal concentration of ligand or by treatment with pertussis toxin. Soluble and membrane-bound fibronectin greatly increased fMLP-induced chemotaxis of CHO cells expressing FPR, but not of wild-type CHO cells, suggesting a role for FPR in activation of integrin function. Evidence for this hypothesis was obtained by demonstrating that CHO cells expressing FPR rapidly increased their adhesion to a fibronectin-coated surface after stimulation with fMLP. Both chemotaxis and adhesion were largely inhibited by RGDS peptide and a function-blocking antibody against α5 integrin. FPR-mediated chemotaxis of the CHO transfectants was partly inhibited by a tyrosine kinase inhibitor, herbimycin A, and blocked by a phosphoinositide 3-kinase inhibitor, wortmannin. These data suggest that stimulation of CHO FPR transfectants with a gradient of fMLP results in phosphoinositide 3-kinase-dependent chemotactic migration, which is enhanced by binding of activated α5β1 to fibronectin. This non-myeloid, non-lymphoid fibroblastic cell line will thus serve as a useful model to investigate additional requirements of signal transduction molecules, adhesion molecules and cytoskeletal elements in FPR-mediated chemotaxis.
Apparent H+ Excretion and CO2 Dynamics Accompanying Carapace Mineralization in the Blue Crab (Callinectes Sapidus) Following Moulting
Authors: Cameron James N. , Wood Chrism M. 
Published: April 2021

ABSTRACT
Just after moulting the blue crab, Callinectes sapidus, is soft and defenceless, but in the following days, a hard calcareous shell is formed for support and protection. The carapace of intermoult (hard) crabs constitutes 27% of the wet weight and 53% of the dry weight, with 14% of the body water contained in a carapace fluid compartment. The pH of the shell fluid compartment is maintained at 0·3 to 0·5 pH units above that of the blood. The mineral portion of the carapace is primarily CaCO3, with minor components of Mg2+ and PO4−3 plus traces of other ions. The formation of a new shell after moulting is accomplished by apparent H+ excretion and Ca2+ uptake at remarkable rates, averaging 12·5 and reaching as high as 21 mequiv kg−1 h−1. Direct bicarbonate uptake from the sea water appears to be an important component of the apparent H+ efflux, since CO2 is deposited in CaCO3 at a rate greater than metabolic production, and the animals show a net CO2 uptake for several days.
A Quantitative Description of Flagellar Movement in Golden Hamster Spermatozoa
Authors: Ishijima Sumio , Mohri Hideo 
Published: April 2021

ABSTRACT
Flagellar movement of golden hamster spermatozoa obtained from the testis and the caput and cauda epididymides was observed by a light microscope while holding them at their heads with a micropipette. Flagellar movement of capacitated spermatozoa and of reactivated spermatozoa demembranated with Triton X-100 was also observed. Testicular and caput epididymal spermatozoa showed weak movement in Tyrode’s solution, whereas cauda epididymal spermatozoa showed vigorous movement. The flagellar bends of the’ cauda epididymal spermatozoa were almost planar. Capacitated spermatozoa moved with waves of a large amplitude. Demembranated spermatozoa reactivated with ATP only had a latent period before the initiation of flagellar movement, and beat at low frequency, whereas demembranated spermatozoa reactivated with both ATP and cAMP began to move immediately at high frequency. Thrust and hydrodynamic power output were calculated using the parameters for the typical waveforms of cauda epididymal spermatozoa before and after capacitation. The possible role of the large amplitude beat in capacitated spermatozoa is discussed. A comparison of the ‘principal’ and ‘reverse’ bends in golden hamster sperm flagella as defined by Woolley (1977) with those in sea urchin sperm flagella suggests that the so-called ‘principal’ bend in golden hamster sperm flagella corresponds to the reverse bend in sea urchin sperm flagella and vice versa.