bluuebunny/crossref_metadata_2025_split huggingface dataset:
Redifferentiation, cellular elongation and the cell surface during lens regeneration
Authors: Hornsby Sharon , Zalik Sara E. 
Published: April 2021

ABSTRACT
Dorsal irises from normal and lentectomized eyes of the newt Notophthalmus viridescens were cultured in vitro in the presence of colchicine (1·25 × 10−3 to 2·5 × 10−6 M), vinblastine sulfate (4·4 × 10−8) and cytochalasin B (20 μg/ml). Explants were treated for 24 h and implanted into host eyes of previously lentectomized newts. In regenerates treated with colchicine at stages prior to the onset of lens fiber formation, cellular elongation was inhibited or considerably delayed. Cytochalasin B has no effect on lens fiber differentiation when compared with regenerates treated with its solvent, dimethyl sulfoxide. Colchicine-treated regenerates showed no detectable fluorescence when stained with anti-newt lens fluorescent antibodies, suggesting that cells in which cellular elongation was inhibited were unable to synthesize lens specific proteins. Ultrastructural observations of elongating lens regenerate cells showed microtubules present in the cytoplasm parallel to the axis of elongation. Microtubules were not observed in depigmented cells from colchicine-treated regenerates. Characteristic vinblastine-induced microtubule crystals were present in depigmented cells from vinblastine-treated regenerates. Experiments using cell electrophoresis showed that neuraminidase-sensitive groups were detectable at the ionic double layer of cells from implanted regenerates at stages where lens fiber differentiation occurs. Cells from colchicine-treated regenerates showed no significant reduction of their electrophoretic mobility after neuraminidase treatment. This suggests that the appearance of some cell surface components in the redifferentiated cell may also be colchicine sensitive and probably mediated by microtubules.
Recent findings in oogenesis ofDrosophila melanogasterIII. Lysosomes and yolk platelets
Authors: Giorgi F. , Jacob J. 
Published: April 2021

ABSTRACTThe role played by the vitellogenic oocytes of Drosophila melanogaster in relation to the elaboration of material taken from the haemolymph is examined by ultrastructural cytochemistry.As revealed by the Gomori procedure, acid phosphatase occurs widely over the forming yolk platelets of the cortical and central ooplasm. A number of Golgi apparatuses in the cortical ooplasm are also positively stained with lead precipitates.With the proceeding of the ovarian development it becomes progressively more difficult to demonstrate cytochemically the enzyme over the yolk platelets. In stage 9-10 chambers the acid phosphatase is restricted to the so-called associated body, while the rest of the yolk platelet appears devoid of lead deposits.By using a osmium zinc iodide (OZ1) complex as a preferential staining method for the Golgi apparatus, it has been shown that, apart from the apparatus itself, a number of OZI deposits occur over the superficial layer of the forming yolk platelets. When mature yolk plate-lets are formed at later stages, the OZI deposits in the yolk platelets come to be restricted to the cap-like region of the superficial layer which contains the associated body.In vitellogenic oocytes, both the internal lining of the limiting membrane of the forming yolk platelets and the associated body of the mature yolk platelets react positively, to cyto-chemical methods to demonstrate carbohydrates.The present findings are interpreted as indicating the involvement of lysosomal enzymes in the process of maturation of the yolk material. The suggestion is also made that such an involvement is required to accomplish a selective hydrolysis of those blood proteins which have been taken in by vitellogenic oocytes along with yolk precursors.
Further studies on skull growth in achondroplasie (cn) mice
Authors: Brewer A. K. , Johnson D. R. , Moore W. J. 
Published: April 2021

ABSTRACT
The morphology of the basioccipital, basisphenoid and mandibular bones in achondroplasie (cn/cri) mice was compared with that of normal siblings. The two bones of the cranial base were markedly reduced in length but not in width. The percentage reduction in the basisphenoid was twice that in the basioccipital bone and of the same magnitude as that previously observed in the long bones of the limbs. This difference may arise because the basisphenoid, like the long bones, grows in length from two cartilaginous growth sites while the basioccipital grows from one cartilaginous and one periosteal site. The mandible of the cn/cn mice was also reduced in size, although to a lesser extent than were the cranial bones and without the ensuing disproportion. The scale of the mandibular changes suggests that they are largely attributable to regulatory responses to the shortened cranium. The finding that the condylar cartilage of the cnjcn mice is reduced in thickness indicates, however, that the cn gene may have a direct effect on condylar chondrocytes.
Intercellular contacts at the epithelial-mesenchymal interface of the developing rat submandibular gland in vitro
Authors: Cutler Leslie S. 
Published: April 2021

ABSTRACT
An ultrastructural study of the development of the rat submandibular gland (SMG) anlage in vitro was undertaken to determine if epithelial-mesenchymal and epithelial-nerve contacts were integral events in the differentiation of the gland in vitro as they are in vivo. SMG rudiments were removed at the stalk-bulb stage (15 days in utero) and cultured for 6 days on a millipore filter in supplemented McCoy’s 5A media. Rudiments were taken at daily intervals, fixed and processed for electron microscopy. The overall development of the explanted rudiments closely paralleled their maturation in vivo although cultured glands lagged 24-36 h behind their normal counterparts. Direct epithelial-mesenchymal contacts were seen after the morphogenetic patterning of the gland bad been established but prior to functional differentiation of the rudiment. Epithelial-nerve contacts were not seen although healthy axons were seen in the stroma throughout the culture period. The study indicates that epithelial-nerve contacts are probably not required for morphogenesis of cytodifferentiation of the rat SMG. However, direct epithelial-mesenchymal contacts appear to be an integral part of the developmental sequence of the rat SMG.
In vitro chondrogenesis in mouse limb mesenchymal cells; changes in ultrastructure and proteoglycan synthesis
Authors: Royal Patricia D. , Goetinck Paul F. 
Published: April 2021

ABSTRACT
Mouse chondrocytes were allowed to differentiate from 11-day dissociated limb-bud mesenchymal cells cultured at high density. Over a period of 5 days in culture these cells differentiated from a culture containing a population of mesenchymal cells and myoblasts into one containing cartilage nodules. Chondrogenesis, as demonstrated by the sulfated proteoglycans (PGS) synthesized, was monitored quantitatively and qualitatively by molecular sieve chromatography on polyacrylamide and 1 % agarose columns, and by examination of cultures with phase contrast and transmission electron microscopy. Chromatographically, the PGS synthesized could be separated into three fractions (la, lb, and II). In the 24 h cultures a small amount of PGS was synthesized and was predominantly of fraction II. As time in culture elapsed there was, concomitant with chondrogenesis, an increase in PGS synthesis with a preferential increase in peaks la and lb. Peaks la and Ib were shown to have an aggregate-subunit relationship. Fraction la could be dissociated to chromatograph at the Ib position, but the disaggregation was not reversible. Digestion of the various chromato-graphic fractions extracted from the cell layer of the 5-day cultures by chondroitinase ABC and AC revealed that fraction I contained 80 % chondroitin-4-sulfate, 20 % chondroitin-6-sulfate, and negligible amounts of dermatan sulfate, while chondroitinase ABC and AC digestion of fraction II showed 55 % chondroitin-4-sulfate, 0-3-7 % chondroitin-6-sulfate, and 20 % dermatan sulfate. Cytological studies revealed that as nodule development pro-gressed there was a concurrent development of the endoplasmic reticulum and extracellular matrix, and a reduction in mitochondria.
Inhibition of Glyceraldehyde Phosphate Dehydrogenase by Salts other than Lithium Chloride
Authors: Ham Richard G. , Eakin Robert E. 
Published: April 2021

ABSTRACT
Lallier (1954) has shown that 0·4 M lithium chloride strongly inactivates glyceraldehyde phosphate dehydrogenase—a finding which might partially explain some of the developmental changes found in lithium-treated embryos. In an attempt to establish an enzymatic basis for the morphological effects of lithium ion on Hydra which have been observed in this laboratory (Ham & Eakin, 1955), we have repeated the enzyme study with lithium chloride and extended it to include a number of other salts as controls.
Compensation in the Remaining Pronephros of Triturus after Unilateral Pronephrectomy
Authors: Fox H. 
Published: April 2021

ABSTRACT
Larvae of Triturus cristatus survive unilateral pronephrectomy at the early caudal bud stage. The remaining pronephros compensates and in the main the results confirm those of Howland (1921) on Amblystoma punctatum. A comparison between control and operated specimens by an analysis of covariance showed that the pronephros of the pronephrectomized group had significantly higher values for all the measurements made, within the range studied (5·5–7·5 mm. nose to cloaca; 10–17 days after operation). The measurements include the means of: the nuclear population; total cell volume; total lumina volume; overall volume of pronephros; internal surface area of tubules; antero-posterior length of pronephros; volume of individual cell of pronephros. The slopes of the regression lines in the two groups demonstrate that in all measurements except that of individual cell volume, the pronephroi of the operated group grow faster than those of the controls. During development the individual cell volume significantly falls in the control pronephroi, in contrast to the operated group where the mean volume does not significantly change. The duct of the compensating pronephros is expanded in cross-section along its entire length. The duct of the operated side atrophies from the anterior region towards the posterior, becoming a degenerate strand of cells, subsequently losing its lumen throughout its length.
Factors Affecting Vertebral Variation in Mice: 3. Maternal Effects in Reciprocal Crosses
Authors: McLaren Anne , Michie Donald 
Published: April 2021

ABSTRACT
All six possible reciprocal crosses were made between C57BL, C3H/He, and C3H/Bi mice. The last group differs from the other two in having predominantly 5 lumbar vertebrae. The offspring of the C3H/He ♀ ♀ × C57BL ♂ ♂ cross had a lower average number of vertebrae than either parental population. The other crosses gave offspring falling within the range between the parental means. There was a significant difference between reciprocals in the two pairs of inter-strain crosses. The F1 offspring tended towards the vertebral type of the maternal strain. No significant effect was apparent in the inter-substrain cross. The evidence from the reciprocal crosses suggests that, although the C3H/He substrain has since 1930 diverged from the C3H/Bi substrain in the direction of a higher number of lumbar vertebrae, the two substrains continue to show similar maternal effects when crossed with the C57BL strain. Hence the genetic control of maternal influence upon vertebral type can operate independently of the genetic control of vertebral type itself.
Growth and Function in the Foetal Liver
Authors: Dick D. A. T. 
Published: April 2021

ABSTRACT
A method is described for estimating the total population of hepatic cells in the liver of a sheep foetus. Use of this method has shown that during development there is a real decrease in the relative number of hepatic cells in the sheep foetus. The relative number of hepatic cells in the foetus is directly proportional to the specific growth-rate of the foetal body. It is suggested that the relative number of hepatic cells in the foetus is determined by functional requirements, partly to perform normal metabolic processes and partly to maintain growth.
On the Neural Crest of the Lamprey Embryo
Authors: Newth D. R. 
Published: April 2021

ABSTRACT
Those parts of the branchial basket of the ammocoete larva that have chondrified by the time the animal is 7 mm. long are of neural crest origin. Those parts of the trabeculae cranii (anterior parachordals) of the ammocoete that have chondrified by this time are not of neural crest origin, nor do they depend upon the presence of the crest for their normal formation. The factors governing the development of the visceral arch skeleton are, as far as is known, equivalent to those operating in Amphibia. The pre-migratory crest of the branchial region is competent to form cartilage, but not determined to do so. It is probable that the normal development of the visceral arch skeleton is dependent upon the early establishment of contact between branchial ectoderm and endoderm. The cranial neural crest is necessary for the normal development of the ventral arteries of the head. In its absence they are much dilated. It is probable that the walls of these vessels are normally, at least in part, of crest origin. In the absence of the neural crest in the trunk region the dorsal fin of the larva is not formed. Absence of the neural crest leads to absence of the dorsal root ganglia in the trunk and, usually, to a reduction in size of those of the head. The neural crest is a source, if not the only source, of larval melanophores.
Differences in rotation-mediated aggregation between wild-type and homozygous Brachyury (T) cells
Authors: Yanagisawa K. O. , Fujimoto H. 
Published: April 2021

ABSTRACTRotation-mediated aggregation was studied in dissociated cells from 9- and 10-day-old (‘12-40 somite’ stage) mouse embryos homozygous for the Brachyury (T) mutation. Average diameter of the aggregates formed by wild-type cells increased up to the 27-somite stage. In T/T cells, however, a completely different pattern was observed. The disappearance of free cells and the process of aggregate formation were also followed. The possibility that T/T cells have different adhesive properties from +/+ cells is discussed.
Regulation of deficiencies along the proximal distal axis of the chick wing-bud: a quantitative analysis
Authors: Summerbell Dennis 
Published: April 2021

ABSTRACT
The wing-bud shows zero regulation following removal of a whole slice of the proximaldistal axis from stage 22 or later. Prior to this it is possible that it may show some regulation. Some of the apparent regulation may be explained by the way in which the limb grows. The bud never shows perfect size regulation or morphallaxis. The proximal-distal axis of the bud between shoulder and wrist expands uniformly from stage 20.
Waves and periodic events during primitive streak formation in the chick
Authors: Stern Claudio D. , Goodwin Brian C. 
Published: April 2021

ABSTRACT
Morphogenetic movements occurring during formation of the primitive streak in the chick embryo are of a periodic nature, with a mean frequency of one pulse every 2·6 min. The period of the oscillatory movement is shown to be temperature-dependent. The onset of these pulses of movement can be seen as a slow wave starting at the posterior end of the embryo and making its way towards the anterior end. An interpretation of this behaviour is discussed.
On the differentiation of prospective ectoderm to a ciliated cell pattern in embryos ofAmbystoma mexicanum
Authors: Landström Ulf 
Published: April 2021

ABSTRACTThe differentiation of the ectoderm in Ambystoma mexicanum (Harrison stage 26-27) was examined under in vivo and in vitro conditions by scanning electron microscopy under different experimental conditions. About one out of three flank epidermal cells was found to be ciliated in the undisturbed or control embryos. The shape of ciliated cells in the explants from the animal region was only slightly affected. In no case was it possible to find two adjacent ciliated cells, implying that these cells prevent the appearance of cilia in the cells in direct contact. Transformation to ciliated cells is suppressed by hypertonicity but favoured in a hypotonic medium. The differentiation of epidermis is also dependent upon the synthesis of RNA and some kind of sulphated glucosaminoglycan, corroborated by the inhibitory effect of actinomycin and selenate.The differences between the test series and the controls are discussed with regard to factors controlling embryonic epidermal differentiation.
Limb-somite relationship: origin of the limb musculature
Authors: Chevallier Alain , Kieny Madeleine , Mauger Annick 
Published: April 2021

ABSTRACTQuail-to-chick grafting experiments performed during the third day of incubation demonstrate that somites can contribute to limb development. In orthotopic recombinations, migrating cells originating from the grafted unsegmented or segmented somitic mesoderm adjacent to the wing or leg field end up in the musculature respectively of the wing or the leg, where they express exclusively myogenic properties. Thus, in these heterospecific recombinations, the anatomical muscle has a double origin: muscle bulk of somitic origin; tendons and connective tissues of somatopleural origin. Similar features are observed in heterotopic recombinations with (segmented or unsegmented) somitic mesoderm located cranially or caudally to the limb levels.In the reverse chick-to-quail grafting experiments, the somitic participation to the limb mesoderm can also be observed. But it is less regular than that obtained in the quail-to-chick recombinations, and the muscle bulk is made up in various proportions of graft-originated somitic cells and of host somatopleural cells.The possible existence of juxtaposed and interdigitated myogenic and tendinogenic compartments is discussed in view of the dissimilarity between the results of the two kinds of heterospecific recombinations.
The ultrastructure of the mesenchymal element of the palatal shelves of the fetal mouse
Authors: Innes Peter B. 
Published: April 2021

ABSTRACTThe ultrastructure of the mesenchymal element of the palatal shelves of C3H mouse embryos aged 13 days 18 h and 14 days 18 h in utero was studied. At 13 days 18 h the mesenchyme showed a high density of cells. The cells contained a well developed system of rough endoplasmic reticulum and Golgi complex; many were ciliated and multi-vesicular structures were common. By 14 days 18 h, many of the mesenchymal cells contained large numbers of glycogen particles. These cells also possessed long cytoplasmic processes which sometimes were seen to contain many filaments 5–7 nmin diameter. Some of the cells also contained a fine filamentous network just below the plasma membrane. Developing mononuclear and binucleate skeletal muscle cells containing myofibrils were present in the posterior region of the palate, with groups of cells which consisted of typical peripheral neurons and their surrounding satellite cells. Both the muscle and nerve cells were only observed in the 14 day 18 h material. It is suggested that both the myofibrils in the skeletal muscle cells and the filamentous network in the mesenchymal cells may play a role in shelf reorientation.
Growth and sexual differentiation in the gonads of chick and duck embryos
Authors: Gasc Jean-Marie 
Published: April 2021

ABSTRACT
The sex-dependent morphological asymmetry between gonads of bird embryos is generally considered to represent the critical point at which the definitive pattern of sexual differentiation is established. A quantitative study of growth in gonads of chick embryos (6- to 11-day-old) and of duck embryos (7- to 11-day-old) has been carried out in order to clarify in what manner growth of gonads is involved in sexual differentiation. Growth has been estimated by the determination of total protein and DNA content, and of DNA synthesis [3H]Tdr incorporation in vitro).
Increase of protein and DNA content follow different growth curves according to the sex and the laterality of gonads. As early as day 6 (chick) or day 7 (duck) significant differences of protein content exist between gonads: left &gt; right in both sex embryos, and male &gt; female on both sides. Differences in DNA content of gonads are large even at the earliest stages. In the 6-day-old chick embryo both testes contain less DNA than the left ovary and more DNA than the right ovary. In the 7-day-old duck embryo both testes contain the same amount of DNA as the left ovary and twice as much DNA as the right ovary. Consequently, the protein/ DNA ratio has a different value according to the sex of the gonad.
In the 6-day-old chick embryo and in the 7-day-old duck embryo absolute values of DNA synthesis (cpm/gonad) are higher in left gonads than in right gonads, and higher in male than in female gonads. When calculated as a ratio to the protein content (cpm/protein) DNA synthesis is lower in the left ovary than in the three other types of gonads, both in chick and duck embryos. When calculated as a ratio to the DNA content of gonads (cpm/DNA), DNA synthesis is lower in the left ovary than in the three other gonads in the chick, and lower in the left ovary and in testes than in the right ovary in the duck.
The results show that growth of gonads is sex-dependent at a very early stage. The meaning of this sex character is discussed with special reference to the role of steroid hormone secretion.
Temporal and spatial patterns of the synthesis of tissue-specific polypeptides in the preimplantation mouse embryo
Authors: Handyside A. H. , Johnson M. H. 
Published: April 2021

ABSTRACTMouse embryos at different morphological stages in the transition from morula to blastocyst were analysed for the qualitative pattern of their polypeptide synthesis. The first appearance of the individual species of polypeptides specific to trophectoderm or ICM occurred progressively over this developmental period. Populations of inside cells recovered from morulae and early blastocysts synthesized those polypeptides previously shown to be characteristic of ICMs at days, but not those characteristic of trophectoderm.
Scanning electron microscopy of the developing chick anterior corneal epithelium
Authors: Waggoner Phillip R. 
Published: April 2021

ABSTRACT
The anterior corneal epithelium of the developing chick was observed with the scanning electron microscope at various stages of development. In the earlier stages, up to about 15 days of incubation, the cells are characterized by regular polygonal outlines and a proliferation of microvilli on the surface. The microvilli then begin to coalesce and flatten so that the surface is rather smooth by about 19 days of incubation. Just prior to hatching, however, the cells begin to round up and once again become covered by microvilli. The cells then lift off the surface and expose the underlying cells. After hatching, the surface cells lose the synchrony of development that characterized the embryo and are found in various stages of senescence. The cells eventually lose their regular polygonal outlines and the corneal surface takes on a patchwork appearance.
A study of spermatozoan defects in wild-type and T:t-bearing mice
Authors: Hillman Nina , Nadijcka Mary 
Published: April 2021

ABSTRACT
A comparative light and electron microscopic study was done on cauda epididymal spermatozoa from + /tx, T/ +, T/tx, C5TBL/6J, BALB/c and randomly breeding Swiss Albino mice. The results show that all of the males contain abnormal spermatozoa and that all contain the same types of defective gametes. No unique defect was found which can be correlated with the increased transmission frequency of the tx -bearing allele.