bluuebunny/crossref_metadata_2025_split huggingface dataset:
Reversible and irreversible effects of retinol upon the phenotypic properties of embryonal carcinoma cells
Authors: Sherman Michael I. , Eglitis Martin A. , THOMAS RICHARD 
Published: April 2021

ABSTRACT
We have generated an embryonal carcinoma cell line, NR1, which is not growth-inhibited in response to retinol. Although the retinol-treated cells undergo morphological change, show reduced levels of the surface antigen SSEA-1 and possess increased surface reactivity with antifibronectin serum, the extent of phenotypic change of NR1 cells in response to retinol is not so great as that following treatment with retinoic acid. Furthermore, unlike cells from lines such as F9, the retinol-promoted morphological alterations appear to be reversible. The increased adherence of NR1 cells to glass coverslips in the presence of retinol suggests that stronger interaction with the substratum is responsible for the observed alteration in appearance of the cells. It is possible that NR1 cells exposed to retinol progress no further than a reversible, early stage of differentiation. Alternatively, retinol-treated cells might express a group of markers normally associated with, or accompanying, an irreversible, differentiated phenotype even though the cells are not, in fact, undergoing differentiation.
The pigmentary system of developing axolotls
Authors: Frost S. K. , Epp L. G. , Robinson S. J. 
Published: April 2021

ABSTRACT
The axanthic mutant in the Mexican axolotl (Ambystoma mexicanum) was analysed with respect to the differentiation of pigment cells. Transmission electron micrographs revealed the presence of melanophores and cells that are described as unpigmented xanthophores in axanthic skin. Iridophores apparently failed to differentiate in axanthic axolotls (a pattern similar to that observed in melanoid axolotls). Chromatographic analyses of skin extracts confirmed that there are no pteridines (xanthophore pigments) in axanthic skin, suggesting that the axanthic gene may affect pteridine biosynthesis at some point early in the biosynthetic pathway. Why iridophores fail to differentiate in these animals is not known, but this, too, may be related to an inability to synthesize pigments properly. Xanthophore and iridophore pigments both presumably derive from purine precursors.
Finally, all axanthic animals were found to be infected by a virus. Electron microscopic results demonstrated the presence of numerous macrophages in the dermis of the skin, occupying positions typical of pigment cells. The virus was localized primarily in macrophages, but was also observed in pigment cells. The virus is, as yet, uncharacterized but is thought to contribute to the low survivability of axanthic adults.
Fate of brachial muscles of the chick embryo innervated by inappropriate nerves: structural, functional and histochemical analyses
Authors: Butler Jane , Cauwenbergs Peter , Cosmos Ethel 
Published: April 2021

ABSTRACT
The extent of interaction between brachial muscles and foreign (thoracic) nerves of the chick embryo was determined during an extended period of development in ovo from the perspectives of innervation pattern, function (motility analyses), muscle growth (quantitative analyses of muscle volume) and fibre-type expression (myosin-ATPase profiles). Results indicated that according to all parameters analysed, initially a compatible union existed between the foreign nerves and their muscle targets. During subsequent stages of development, deterioration of the once compatible relationship emerged, until eventually denervation of muscles, i.e. an actual loss of intramuscular nerve branches, was observed. The process of denervation, which proceeded at a differential rate among individual muscles, however was restricted to brachial muscles derived from the premuscle masses of the wing bud. In contrast, brachial muscles of myotomal origin were spared the fate of wing-bud-derived muscles and maintained a successful union with the foreign nerves.
The generation of cell surface polarity in mouse 8-cell blastomeres: the role of cortical microfilaments analysed using cytochalasin D
Authors: Fleming T. P. , Pickering S. J. , Qasim F. , Maro B. 
Published: April 2021

ABSTRACT
The mechanism by which a surface pole of microvilli is generated in mouse 8-cell blastomeres has been investigated. 4-cell and 8-cell embryos (or cell couplets) were incubated for precise times during their respective cell cycles in medium containing cytochalasin D (CCD) to disrupt the microfilament system. The blastomeres were analysed immediately for the distribution and state of organization of their microvilli, using three morphological techniques. The results indicate that the surface pole, characterized by microvilli containing CCD-resistant core filaments, is not generated by the gradual segregation of stable microvilli to the apical surface. An alternative model is proposed, based upon (a) the stabilization of the apical cytocortex prior to the elongation of apical microvilli and (b) the destabilization of cytocortical elements in contact areas and the shortening and loss of basolateral microvilli.
The timing of compaction: control of a major developmental transition in mouse early embryogenesis
Authors: Levy Jeremy B. , Johnson Martin H. , Goodall Harry , Maro’ Bernard 
Published: April 2021

ABSTRACT
The effect of protein synthesis inhibitors on compaction of the 8-cell mouse embryo has been investigated. The effects observed depended upon the duration and time of drug application and on the features of compaction scored. Continuous application from the late 2-cell or early 4-cell stages allowed cell flattening and surface polarization to occur in most embryos and advanced development of these features in many of them. Cell coupling developed only when drug addition was delayed until the mid 4-cell stage, and cytoplasmic polarization developed only when drug addition was delayed until the late 4-cell stage. We suggest that control over the timing of compaction is achieved at a post-translational level via a global permissive change within the blastomeres of the embryo.
Regeneration from half lower arms in the axolotl
Authors: Wigmore Peter 
Published: April 2021

ABSTRACT
A technique involving grafting of pieces of skin from the head onto the limb in order to isolate halves of the limb is described. This technique was used to isolate posterior, anterior, dorsal and ventral halves of the lower arm. All halves produced regenerates but no part of the limb was able to produce a high proportion of regenerates with a complete pattern of skeletal structures. Posterior half stumps regenerated limbs with a mean digit number of 2·7 and had a normal dorsoventral muscle pattern. Anterior half stumps produced a high proportion of single-digit regenerates and had a mean digit number of 1·3. Dorsal and ventral half stumps regenerated limbs with a mean digit number of 2·8 and 2·3 respectively. Hypomorphic regenerates from dorsal and ventral half stumps often had only dorsal or ventral muscle. These results are in contrast to those from the upper arm (Wigmore & Holder, 1985) where a complete skeletal and muscular pattern regenerated from posterior and dorsal halves and hypomorphic regenerates were obtained from anterior and ventral half limbs.
The clonal model of vertebral column development: a reinvestigation of vertebral shape using Fourier analysis
Authors: O’Higgins P. , Johnson D. R. , McAndrew T. J. 
Published: April 2021

ABSTRACT
Little work has been done on the skeletal system of allophenic mice (chimaeras). In this paper we re-examine the evidence presented for the clonal theory of vertebral development using quantitative methods which take account of variation. We conclude that the clonal theory is either an overly simplistic approximation of the real situation, or that the evidence so far given in its support is unsubstantiated.
Whisker growth induced by implantation of cultured vibrissa dermal papilla cells in the adult rat
Authors: Horne Kenneth A. , Jahoda Colin A. B. , Oliver Roy F. 
Published: April 2021

ABSTRACT
Retention of the capacity to induce the growth of hair by cultured adult rat vibrissa dermal papilla cells has been investigated. Small pellets of serially cultured papilla cells were implanted into the bases of the exposed follicular epidermis of amputated adult rat vibrissa follicles. Amputated follicles that received no cell implants or implants of cultured dorsal skin fibroblasts were used as controls. Over 50 % of follicles implanted with cultured papilla cells in the passage range 1 –3 grew hairs. In contrast none of the follicles that received late passage cells (range 6 –15) produced hairs; and spontaneous regeneration of hair occurred in only 3 % of the control follicles. These results demonstrate that cultured papilla cells of early passage numbers retain their ability to induce hair growth. Histological examination confirmed that the implanted papilla cells interacted with follicular epidermis to organize the development of new, hairproducing bulbs, each containing a discrete dermal papilla. An important observation was that aggregative behaviour leading to papilla formation was only manifested by early passage papilla cell implants. This persisting embryonic characteristic appears to be an essential functional component of papilla cell activity which operates to regulate the profound morphogenetic changes that occur during the hair growth cycle.
The differentiation of mouse gonads in vitro : a light and electron microscopical study
Authors: Mackay Sarah , Smith Robert A. 
Published: April 2021

ABSTRACT
Indifferent urogenital complexes were excised from mouse foetuses assessed by developmental criteria as day 10·5 or 11. After 4 or 6–7 days in culture, complexes were fixed and examined by light and electron microscopy. The effect of culturing sexed complexes in mixed sex groups was investigated. The effect of the presence or absence of foetal calf serum in the culture medium was considered. No evidence of inhibition of one sex by the other was found. Ovaries developed further in cultures than testes.
Factors modulating mouse lens epithelial cell morphology with differentiation and development of a lentoid structure in vitro
Authors: Muggleton-Harris A. L. , Higbee N. 
Published: April 2021

ABSTRACT
The morphological and cellular changes that occur with differentiation and development of a lentoid structure from cultured mouse lens epithelial cells have been found to be dependent on the presence of lens capsule in association with the cells. The development of the ‘lentoid body’ is a multiphase process involving cell replication, synthesis of mucosubstances and a basement collagen membrane, cell aggregation and differentiation. Stage-specific synthesis of lens proteins confirms that the genes regulating normal differentiation in vivo are operating in the in vitro system.
The hydrated collagen gel studies described in this report demonstrate that the cuboidal morphology and apical-basal polarity of the lens epithelial cells are dependent on their relationship with the lens capsule. Following a replicative phase the cells assume a mesenchyme-like morphology and migrate into the gel. Trypsinized cells freed from the lens capsule replicate but form colonies on the surface of the gel. The implications of these results are discussed with respect to previous observations made on normal lens development and the abnormalities associated with the congenital cataractous embryonic lens.
Differentiation and grafting of haemopoietic stem cells from early postimplantation mouse embryos
Authors: Hollands P. 
Published: April 2021

ABSTRACTHaemopoietic stem cells evidently arise in early postimplantation mouse embryos at day 6 of gestation, a day earlier than previously thought (Moore & Metcalf, 1970). Disaggregated embryonic cells were injected into mice given a lethal dose of X-irradiation. The presence of donor haemoglobin (Whitney, 1978) and donor lymphocytic glucose phosphate isomerase (GPI) (Siciliano & Shaw, 1976) to detect donor erythrocytes and lymphocytes, respectively, were monitored by starch gel electrophoresis. The presence of donor cells was also assessed by using donor embryos carrying the T6 marker chromosomes. Decidual cells dissected free of embryos did not colonize any recipients. Disaggregated cells from early mouse embryos first colonized the liver and then repopulated the haemopoietic systems of recipients, producing adult donor haemoglobin within 2–3 days and donor GPI within 3–5 days. 80 % of grafted X-irradiated recipients survived and donor markers were found in each of them. All nongrafted controls died within 14 days of X-irradiation and none of them showed donor markers. Disaggregated embryonic cells could be grafted across major histocompatibility barriers unlike adult bone marrow. Haemopoietic stem cells could not be identified in disaggregated cells from embryos aged less than 6 days gestation.
Dorsal root ganglia grafts stimulate regeneration of denervated urodele forelimbs: timing of graft implantation with respect to denervation
Authors: Tomlinson Bruce L. , Tassava Roy A. 
Published: April 2021

ABSTRACT
Amphibian forelimb regeneration is a nervedependent process; nerves presumably release one or more neurotrophic factors that stimulate blastema cell division. To date several candidate molecules/factors have been shown to stimulate macromolecular synthesis and/or mitosis but sustained cell cycle activity and blastema development have not been achieved. Because dorsal root ganglia (DRG) implants are capable of promoting regeneration of denervated adult newt limbs (Kamrin & Singer, 1959), we have evaluated the DRG stimulation of regeneration in denervated limbs of adult newts and larval axolotls; two alternative timing strategies were tested as a step toward defining bioassay parameters that best reflect neurotrophic activity. The frequency of regeneration in denervated adult newt limbs was compared after providing DRG before or at the time of denervation (to maintain neurotrophic and cell cycle activity) versus DRG implantation at various postdenervation times (to resupply neurotrophic activity and restimulate suppressed cell cycle activity).
The results show that denervated adult newt limbs regenerated most frequently using the maintenance strategy, but as the denervation interval was extended in the restimulation strategy, the frequency of regeneration declined. Larval axolotl limbs responded positively in both maintenance and restimulation DRG-grafting protocols. These results suggest that the efficacy of DRG stimulation of regeneration in adult newts was related to the relative number of blastema cells present at the time of denervation and the proliferative status of the blastema cells; bioassays with denervated adult newt limbs should be designed with these constraints in mind. Because such constraints are not as problematic with the larval axolotl, this species may provide the best opportunity for further defining bioassay parameters related to the neurotrophic stimulation of regeneration.
Homarine (N-methylpicolinic acid) and trigonelline (N-methylnicotinic acid) appear to be involved in pattern control in a marine hydroid
Authors: Berking S. 
Published: April 2021

ABSTRACTA morphogenetically active compound has been isolated from tissue extract of Hydractinia echinata and identified to be N-methylpicolinic acid (homarine). When applied to whole animals, homarine prevents metamorphosis from larval to adult stage and alters the pattern of adult structures. The concentration of homarine in oocytes is about 25 mM. During embryogenesis, metamorphosis and early colony development the overall homarine content does not change. Adult colonies contain a fourfold lower homarine concentration than larvae. The polyp’s head contains twofold more homarine than the gastric region and the stolons. A second, similarly active compound, N-methylnic-otinic acid (trigonelline), has also been identified in Hydractinia tissue at concentrations about one-third that of homarine.Incubation of larvae in 10 to 20 μM-homarine or trigonelline prevents head as well as stolon formation. If the compounds are applied in a pulse during metamorphosis, a large part of the available tissue forms stolons. Since μM concentrations of homarine and trigonelline are morphogenetically active, whereas mM concentrations are present in the tissue it appears that both substances are stored within the tissue.
Reformation of the pattern of neuromuscular connections in the regenerated axolotl hindlimb
Authors: Stephens Nigel , Holder Nigel 
Published: April 2021

ABSTRACT
Retrograde neuronal tracing with horseradish peroxidase (HRP) was used to determine the position in the spinal cord of motor neurone pools innervating muscles in the regenerated axolotl hindlimb. This method allows a detailed analysis of the accuracy of reformation of neuromuscular connections. The results show that regenerated distal limb muscles are reinnervated by motor neurones in the same region of the cord as those that innervate normal control distal limb muscles but that proximal muscles are innervated by a mixture of motor neurones in a normal position and motor neurones in a region of the spinal cord that normally supplies innervation to distal limb muscles. This difference between the reinnervation of proximal and distal limb muscles suggests that axons destined for proximal muscles may not enter distal limb territory during reinnervation of the regenerated limb.
Cytoskeletal and DNA structure abnormalities result from bypass of requirement for the cdc10 start gene in the fission yeast Schizosaccharomyces pombe
Authors: Marks John , Fankhauser Christian , Reymond Alexandre , Simanis Viesturs 
Published: April 2021

ABSTRACT
The cdc10 gene of the fission yeast S. pombe is required for traverse of the start control in late G1 and commitment to the mitotic cell cycle. To increase our understanding of the events which occur at start, a pseudoreversion analysis was undertaken to identify genes whose products may interact with cdc10 or bypass the requirement for it. A single gene, sctl+ (suppressor of cdc ten), has been identified, mutation of which suppresses all conditional alleles and a null allele of cdc10. Bypass of the requirement for cdc10+ function by sctl-1 mutations leads to pleiotropic defects, including microtubule, microfilament and nuclear structural abnormalities. Our data suggest that sct1 encodes a protein that is dependent upon cdc10+ either for its normal function or expression, or is a component of a checkpoint that monitors execution of p85cdc10 function.
A quantitative electron microscopic study of changes in microtubule arrays and wall microfibril orientation during in vitro cotton fiber development
Authors: Seagull Robert W. 
Published: April 2021

ABSTRACT
A quantitative electron microscopic (E/M) study of the changes in microtubule arrays and wall microfibril orientation has been done on in vitro grown cotton fibers. Microtubules change orientation during cotton fiber development. During fiber initiation and early elongation, microtubules have a generally random orientation. Microtubules re-orient into shallow pitched helices as elongation and primary wall deposition continue, and into steeply pitched helices during secondary wall deposition. Accompanying the changes in orientation are increases in microtubule length, number, proximity to the plasmalemma and a decreased variability in orientation of the microtubules. Based on these observations, three pivotal stages in microtubule patterns were identified during fiber development: (1) the transition between fiber initiation and elongation, where microtubules develop a shallow pitched helical orientation; (2) the transition between primary and secondary wall synthesis, where microtubules abruptly shift orientation to a steeply pitched helical pattern; and (3) early in secondary wall synthesis, where there is a four fold increase in microtubule number. Microfibrils exhibit changes in orientation similar to the microtubules; however significant differences were found when the precise orientations of microtubules and microfibrils were compared. During secondary wall synthesis, wall microfibrils exhibit some variability in orientation due to inter-fibril bundling, thus indicating that components of the wall may also influence final microfibril orientation.
The contribution of the extracellular matrix to gravisensing in characean cells
Authors: Wayne Randy , Staves Mark P. , Leopold A. Carl 
Published: April 2021

ABSTRACT
The cell-extracellular matrix junction, which includes the cell wall and the outer surface of the plasma membrane, may be an essential region for the perception of gravity by the internodal cells of Chara corallina. Typically, when an internodal cell is oriented vertically, the downwardly directed cytoplasmic stream travels at a velocity that is 10% faster than that of the upwardly directed stream. However, when the cells are treated with impermeant hydrolytic enzymes that partially digest cellulose or hemicellulose, the cells lose their ability to respond to gravity even though streaming continues. By contrast, enzymes that digest pectins have no effect on the gravity-induced polarity of cytoplasmic streaming. Furthermore, gravisensing Is sensitive to protease treatment; Proteinase K, tbermolysin and collagenase, but not trypsin, "-chymotrypsin or carboxypeptidase B, inhibit gravisensing. These findings indicate that proteins in the cell-extracellular matrix junction may be required for gravisensing. Moreover, the tetrapeptide Arg-Gly-Asp-Ser (RGDS) inhibits gravisensing in a concentration-dependent manner, indicating that the gravireceptor may be an integrin-like protein. The macromolecules necessary for gravisensing have been localized to the cell ends. As a consequence of the exoplasmic site of action of the enzymes and the tetrapeptides, we interpret the results to mean that they are acting on the gravireceptor, although we cannot eliminate the possibility that they are acting on the signal transduction chain. On the whole, our observations indicate that the cell-extracellular matrix junction is a sine qua non for graviperception in statolith-free Chara internodal cells and we suggest that the gravireceptor is located in this region.
The 14 kDa β-galactoside binding lectin in myoblast and myotube cultures: localization by confocal microscopy
Authors: Harrison F. Lynne , Wilson T. J. Greer 
Published: April 2021

ABSTRACT
The endogenous 14 kDa β-galactoside-specific lectin has been localised in myoblasts and myotubes by indirect immunofluorescence using confocal microscopy. The antibodies used in these experiments suggest that in myoblast cultures the lectin is abundant on the cell surface and concentrated at ruffled edges of migrating cells. The quantity and distribution of cell surface lectin is independent of the nature of the substratum and undiminished by brief trypsinisation or lactose-washing of the cell suspension. The lectin is also abundant intracellularly, apparently relatively free in the cytoplasm until the cells approach confluency, when the lectin is concentrated into particular areas of cytoplasm resulting in a ‘patchy’ appearance of stained cells. After fusion to form multinucleate myotubes, intracellular lectin is less abundant and concentrated at the periphery of myotubes, from where lectin appears to be released in vesicles packed with lectin which ‘bud off from the myotube surface. In recolonising cultures, lectin is apparently more abundant and lectin-packed vesicles can also be seen ‘budding off from myoblasts. In differentiated cultures, extracellular lectin is detected both on the myotube surface and in fibrillar arrays of extracellular material.