bluuebunny/crossref_metadata_2025_split huggingface dataset:
The distribution of glycosaminoglycans in the axial region of the developing chick embryo. I. Histochemical analysis
Authors: Kvist Tage N. , Finnegan Cyril V. 
Published: June 2005

AbstractHistochemical analysis of the developing chick axial region indicated very little sulphated glycosaminoglycan present in early embryonic stages (stage 17) and this appeared to be confined extra‐cellularly to the region of the notochordal sheath. Strongly acidic material was observed in the cytoplasm of cells in all examined axial areas, viz., dermatome, myotome, sclerotome, neural tube and notochord. Weakly acidic anionic glycosaminoglycans were present in the extracellular portion of all axial areas and increased in concentration during development, particularly in the neural tube and the sclerotome. At the same time the concentration of sulphated anionic glycosaminoglycans also increased in the extracellular matrix of all axial areas. By stage 25 the extracellular matrix of the perichordal scleratome appeared to be mostly sulphated polyanions, but elsewhere in the axial tissues the staining for sulphated glycosaminoglycans never approached that intensity demonstrated by the weakly acidic anionic glycosaminoglycans. Testicular hyaluronidase digestion suggested that most of the stainable material was either hyaluronic acid or chondroitin‐4‐sulphate and/or chondroitin‐6‐sulphate (chondroitin sulphate A and C). There was a small amount of strongly acidic (polysulphated) glycosaminoglycan present in the scleratome, neural tube and notochord.
Regeneration of larval urodele limbs containing homoplastic transplants
Authors: Foret John E. 
Published: June 2005

AbstractForelimbs of larval Ambystoma were amputated through the elbow. In many cases the humerus was partially or totally extripated. Homoplastic transplants, previously labeled with tritiated thymidine, were then inserted into the limb stump, which was re‐amputated through the graft.Experiments involving the addition of appendicular or visceral skeletal parts revealed fusion of the implant with the humerus and suggested interactions between skeletal components. The morphology of such regenerates was usually normal. The various skeletal elements exhibited a differential susceptibility to regression, Meckel's cartilage being particularly resistant. As a consequence, the distal blastema was often spatially removed from the proximal shoulder region. Nevertheless, reconstitution of the head of the humerus was always observed. The cellular origin of this portion of the regenerate was probably local connective tissue.Unlike Meckel's cartilage, the humerus released many cells to the accumulation blastema. These labeled cells may have divided at a higher rate than other blastemal cells, suggesting the possibility of tissue‐specific regeneration of cartilage.Transplanted muscle and connective tissue originating from either the jaw region or the limb behaved similarly to each other. Labeled connective tissue cells proximal to the amputation plane began dividing before the blastema was established, therefore the time of onset of cell division may vary according to the tissue involved and its location with respect to the blastema. A distinction between inductive phenomena and cell contributions was also made.
Cell sorting out according to species in aggregates containing mouse and chick embryonic limb mesoblast cells
Authors: Burdick Morton L. 
Published: June 2005

AbstractAggregates were prepared containing mouse and chick embryonic limb mesoblast cells. After 21 to 33 hours in culture, these aggregates showed prominent sorting out of the mouse cells from the chick cells. This sorting out was even more extensive after 46 to 54 hours. This sorting out is contrary to previous reports for mouse‐chick limb aggregates.After three to four days of culture, chondrification became quite prominent within the aggregates. Accompanying this event, the segregation of mouse and chick cells became less extensive within the chondrified zones. This rescrambling seems to be due at least in part to the interpenetration of neighboring chondrifying regions. Such interpenetration would be expected, due to the expansion which occurs within chondrifying areas. This reshuffling is the probable reason why sorting out was not observed in earlier experiments with mouse‐chick limb aggregates. In these earlier studies, the reports were limited to aggregates which had extensive matrix secretion.The finding that mouse and chick limb mesoblast cells sort out from each other, together with recent reports that similar sorting out occurs in mouse‐chick heart ventricle aggregates and in mouse‐chick mesonephric aggregates, invalidates the generalization that cell sorting properties for any one tissue are constant from species to species among warm‐blooded vertebrate embryos.
The role of changes in cell contact behavior in amphibian gastrulation
Authors: Johnson Kurt E. 
Published: June 2005

AbstractFive different methods were used to examine cell contact behavior in normal and interspecific hybrid embryos in an attempt to elucidate the role of cell surface adhesiveness in gastrulation. In normal embryos and viable hybrid embryos, all cells show an increasing tendency to attach to glass in vitro with advancing developmental age. Presumptive mesodermal cells from early gastrulae show a high ability to attach to glass and to reaggregate. The rate of disaggregation of whole embryos shows marked decreases with advancing age from the blastula to late gastrula period. Binary combinations of explanted embryonic germ layer fragments from early gastrulae undergo movements that are reminiscent of portions of gastrulation. At the level of fine structure, cell contacts become increasingly intimate from the blastula to late gastrula period. In hybrid embryos which undergo developmental arrest at the onset of gastrulation, there is a lack of gastrular morphogenetic behavior in some or all portions of the embryo. In those portions of arrested hybrids where some morphogenesis is evident, there is “quasi‐normal” cell contact behavior. Most often, however, there is no recognizable gastrulation and a striking departure from the normal pattern of cell contact behavior. These results show that extent of changes in cell contact behavior and extent of normal gastrulation correlate positively. This suggests that changes in cell surface properties, resulting in the formation of stronger intercellular adhesions, are necessary for the morphogenetic movements of gastrulation.
Melanogenesis in amphibians. III. The buoyant density of oocyte and larval Xenopus laevis melanosomes and the isolation of oocyte melanosomes from the eyes of PTU‐treated larvae
Authors: Eppig John J. 
Published: June 2005

AbstractThe buoyant density of melanosomes isolated from oocytes of Xenopus laevis is about 1.88 g/cm3 while most of the melanosomes synthesized in the larvae have a density of about 1.92 g/cm3. The melanosomes isolated from phenylthiourea‐treated larvae or from their eyes have a density of about 1.88 g/cm3. The oocyte melanin of Xenopus was labelled in vivo by injecting the vitellogenic female with 14C‐DOPA. After these injections, only the melanosomes which band at a density of 1.88 g/cm3, whether from the ovary, normal or PTU‐treated progeny or from the eyes alone of PTU‐treated progeny, were radioactive. It is concluded that the melanosomes found in the eyes of PTU‐treated tadpoles originate in the oocyte.
Development and chromosomal constitution of nuclear‐transplants derived from male germ cells
Authors: Di Berardino Marie A. , Hoffner Nancy 
Published: June 2005

AbstractNuclei of spermatogonial cells derived from juvenile and adult (Rana pipiens) were transplanted singly into enucleated eggs to determine whether germ cell nuclei are developmentally totipotent. Control nuclear transfers from undetermined somatic cells promoted genuine cleavage in 77% of the injected eggs and 54% of the complete blastulae derived from this series developed into normal larvae. In contrast to the control study, eggs transplanted with germ cell nuclei formed genuine blastulae in 13% of the cases, and most of the complete blastulae arrested before completing gastrulation. However, three embryos derived from adult germ cell nuclei did attain advanced stages of organogenesis and one of these developed into an abnormal feeding larva. These individuals are the most advanced nuclear‐transplants obtained so far from nuclei of normal adult cells in vivo. Chromosome analyses performed on a sample of nuclear‐transplants derived from germ cells revealed gross chromosomal abnormalities in all individuals except the larva. It is concluded, that even though germ cell nuclei are genetically totipotent, they, like somatic nuclei, undergo developmental restrictions during their process of cell differentiation, and after transplantation to host eggs, give rise to abnormal nuclear‐transplants accompanied in most cases by karyotypic alterations. The significance of the developmental restrictions observed in germ cell nuclei is interpreted as an expression of chromosomal differentiation.
Regulative development in a spiralian embryo as shown by cell deletion experiments on the acoel, Childia
Authors: Boyer Barbara Conta 
Published: June 2005

AbstractSpiral cleavage and mosaicism are closely associated in the Annelida, Mollusca, and probably the polyclad Turbellaria, but the evolutionary history of these phenomena remains uncertain. The Acoela, the most primitive order of turbellarians, exhibit spiral cleavage but with the formation of duets of micromeres rather than the more typical quartets. The regulative versus mosaic capacities of the acoel, Childia groenlandica, were investigated by deleting various combinations of blastomeres from the two‐cell stage through the third duet. The acoel embryo showed extensive regulative ability since all experiments yielded normal animals except those in which both macromeres were deleted. These abnormal animals were ciliated spheres with a central cavity and indicated that the macromeres are necessary for form and organ differentiation. An inductive interaction between the micromeres and macromeres is suggested. Since mosaicism is probably specialized and a derivative of the indeterminate type of development, the regulative capacity of the acoel embryo suggests that this order lies near the ancestral line of the spiralia and represents an evolutionary stage where the very defined pattern of spiral cleavage is not yet associated with early programming of the cell's fate.
Studies on the uptake of 125 I‐triiodo‐L‐thyronine and 14C‐L‐thyroxine by Mexican axolotl tissues
Authors: Prahlad K. V. , Hollinger T. G. 
Published: June 2005

AbstractVarious Mexican axolotl tissues were collected at different times after a single injection of either 125I‐triiodothyronine (T3) or 14C‐thyroxine (T4) to: (a) 5 day old embryos, (b) 150–170 day old larvae, (c) 1400–1440 day old neotenic adults.Pattern of total radioactivity was similar in gill, tail and body of embryos injected with T3 or T4. In both the body continued to accumulate the label whereas gill and tail tissues showed a minor peak by three to five hours, a drop by 16 hours and an increase by 96 hours and a reduction by 240 hours. However, a hours and an increase by 96 hours and a reduction by 240 hours. However, a TLC fractionation of butanol extracts of tissues mentioned above indicated that T3 concentration reached a maximum at three hours and later continued to drop. A large amount of radioactivity was associated with the solvent front fraction. TLC fractionation of tissues from T4 injected embryos showed that very little of the radioactivity was associated with T4 up to 48 hours after which time there was an increase in T4 fraction. Thus, it is seen that the uptake of labeled T3 and T4 by embryonic tissues showed variations even though the total radioactivity appeared to be similar. Larval and adult axolotls injected with T3 showed that radioactivity reached a peak by 16 hours in the larval gill, skin and tail and continued to decline later. The liver showed a peak at 24 hours and decreased after that time. All of the above mentioned tissues from adult axolotls showed a peak radioactivity at 16 hours and later continued to drop.Thus, it is seen that the pattern of labeled thyroid hormone uptake is different in embryonic and post embryonic axolotl tissues. The implications of these results are discussed.
Studies on limb morphogenesis. V. The expression of eudiplopodia and its experimental modification
Authors: Fraser Robert A. , Abbott Ursula K. 
Published: June 2005

AbstractEmbryos homozygous for the autosomal recessive gene (eu) develop supernumerary distal limb parts on the dorsal surface of wings and legs. These from from ectopic ectodermal thickenings which appear a day or more after the primary ectodermal ridge (AER). In addition, a large proportion of the mutant embryos exhibit twinning or more extensive duplications of primary flight feathers in one or more follicles. The expression of eudiplopodia is variable with the postaxial digits being duplicated most frequently. Morphological abnormalities are confined to the limbs and these result from changes in the mutant ectoderm.The apical ridge regenerates when it is removed from eudiplopod leg buds as late as stage 20 while in normal limbs it fails to regenerate after stage 18. Accessory ridge still froms on eudiplopod limbs at stage 22–23 if ectoderm is removed from the dorsal surface of the limb prior to this time. The results suggest that the development of the accessory ridge is independent of that of the apical ridge. Eudiplopod limb ectoderm can from ridge for several stages after normal ectoderm loses this capacity. This characteristic may be partly suppressed by exposing developing mutant embryos to low incubation temperature in the interval between normal ridge formation and the appearance of accessory ridge.
Studies on limb morphogenesis. VI. Experiments with early stages of the polydactylous mutant eudiplopodia
Authors: Fraser Robert A. , Abbott Ursula K. 
Published: June 2005

AbstractProspective limb mesoderm was transplanted to the flank of twoday host embryos in efforts to study tissue specific effects of the avian polydactylous mutant, eudiplopodia. Initially, normal limb mesoderm was placed in the flank of two‐day scaleless hosts and a scaleless limb resulted, ensuring that the regenerating host ectoderm provided the epithelial covering for the graft limb. Eudiplopod limbs developed from grafts of normal mesoderm to two‐day eudiplopod hosts while the reciprocal combination produced normal limbs. Similar transplants showed that eudiplopod ectoderm may respond to leg mesoderm from both quail and talpid2 embryos and does so typically by forming two ridges. Grafts of normal limb mesoderm to three‐and‐one‐half‐day eudiplopod hosts produced supernumerary limbs in the majority of cases whereas most grafts to normal hosts of similar age produced only a skin covered nodule.It is concluded that the mutant gene extends the time of ectodermal competence for ridge formation and that as a consequence of this specificity the mutant effects are seen only in eudiplopod limb ectoderm.
Conservation of web proteins in the spider, Araneus diadematus
Authors: Peakall David B. 
Published: June 2005

AbstractExperiments placing “cold” spiders on radiocative webs and measuring the specific activity of successive webs shows that silk protein is highly conserved during the web building cycle. This conservation of web protein is not affected by feeding the spider flies or cold amino acids. It is considered that the timing of web eating to web construction is critical to this efficient re‐cycling.
Sorting out in pseudoplasmodia of Dictyostelium discoideum
Authors: Francis David , O'Day Danton H. 
Published: June 2005

AbstractDuring its period of migration the pseudoplasmodium of D. discoideum changes from a homogeneous mass of cells to one in which the cells of the front part stain more darkly with neutral red than those of the rear part. It has been asked whether this color change represents differentiation in situ of two cell type or sorting out of previously differentiated cell types.Experiments are described which (1) show that the transition of the pseudo‐plasmodia from one type to another is long continued process, and (2) show by means of labeling parts of pseudoplasmodia with vital dyes or C14 thymidine, that exchange of cells across the color boundary separating tip and rear parts is continuous during the life of a pseudoplasmodium. From the results it appears that sorting out of cell types is probably a major cause of the color change.When combined with previous work, our results suggest that sorting out and redifferentiation are active together both in maintaining and restoring the normal proportions of cell types in a slug. It may prove useful to compare these processes with the components of regeneration in metazoan organisms.
Aspects of cuticle formation in Drosophila melanogaster
Authors: Mitchell Herschel K. , Weber‐Tracy Ursula M. , Schaar Gertraud 
Published: June 2005

AbstractThe molting process and some aspects of puparium formation in Drosophila melanogaster have been examined by electron microscopy and autoradiography. Results indicate clearly alternate phases of production of enzymes involved in cuticle synthesis and enzymes involved in cuticle degradation, in epithelial cells. The synthesis phase begins about four hours before each molt and appears to continue about three hours after puparium formation. Protein which is involved in cuticle structure appears to remain where deposited. On the other hand, metabolic products of tyrosine that are involved in sclerotization and tanning diffuse outward through the cuticle from their origin in the epithelial cells. Channels or canals for transport of materials from cells toward epicuticle have not been observed in larval or prepupal material.
The metabolism of dietary carnitine in Drosophila melanogaster
Authors: Geer B. W. , Dolph W. W. , Maguire J. A. , Dates R. J. 
Published: June 2005

AbstractDrosophila melanogaster larvae require choline for growth but when fed dl‐carnitine in place of choline, carnitine is decarboxylated to β‐methylcholine and phosphatidyl‐β‐methylcholine is synthesized to replace phosphatidylcholine. Feeding (−)‐carnitine in place of choline results in a moderate deficiency of lecithin‐type phospholipid and a corresponding reduction in growth. The capacity of larvae to employ (+)‐carnitine for phosphatidyl‐β‐methylcholine synthesis and subsequently for growth is very limited. Only 41% as much phosphatidyl‐β‐methylcholine is synthesized by larvae fed 5.7 X 10−4 M (+)‐carnitine as is formed when the same concentration of (−)‐carnitine is fed. This suggests that (−)‐carnitine is the preferred substrate for carnitine decarboxylase, the enzyme that degrades carnitine to form β‐methylcholine. Utilization of carnitine for phospholipid synthesis is clearly dependent upon a choline‐deficient state. The presence of small quantities of choline, either in body tissues or in the diet, inhibits the incorporation of carnitine derivatives into phospholipid. Intact carnitine is needed for maximum larval growth and adult activity, indicating that D. melanogaster larvae synthesize a suboptimal quantity of carnitine. Thus, dietary carnitine supplements in vivo carnitine synthesis for physiological purposes.
The distribution of melanosomes in larvae reared from normal and from pigmentless eggs of Xenopus laevis
Authors: Eppig John J. , Dumont James N. 
Published: June 2005

AbstractThe distribution of pigment granules or melanosomes in tadpoles of Xenopus laevis reared from phenylthiourea (PTU)‐induced pigmentless eggs is compared with the distribution of melanosomes in tadpoles from normal eggs. Some animals from each group were raised in a solution of PTU. It is concluded that melanosomes observed in the central nervous system, liver, epidermis, oral sucker, gut, notochord, and early eye of normal larvae originate in the oocyte. Those in the brain ventricles become engulfed by macrophages. Melanosomes do not appear in these tissues of early tadpoles reared from pigmentless eggs; however, pigment is later synthesized in dermal, meningeal, and peritoneal melanocytes as in the normal larvae. Since the synthesis of new melanin is blocked in embryos reared in PTU, tadpoles derived from pigmentless eggs and reared in PTU are completely devoid of melanosomes.
A biochemical and cytological investigation of differentiation in the interspecific hybrid amphibian embryo Rana pipiens ♀ × Rana sylvatica ♂
Authors: Johnson Kurt E. 
Published: June 2005

AbstractStarch gel electrophoresis, light microscopy, and electron microscopy were used to investigate biochemical and cytological differentiation in the interspecific hybrid amphibian embryo Rana pipiens ♀ × R. sylvatica ♂. Paternal sylvatica lactate dehydrogenase‐B genes (and possibly LDH‐A genes) begin to function in hybrid embryos at the same time as in normal embryos (when normals are Stage 19, heart beat). Paternal sylvatica genes for phosphoglucomutase, NAD‐malate dehydrogenase, and 6‐phosphogluconate dehydrogenase do not begin to function in hybrid embryos before embryonic death, which occurs approximately six days after fertilization. Cytological results show that hybrid embryos form nucleoli and apparently are equipped for protein synthesis. Hybrid cells are capable of differentiating basement membranes, cilia, myofibrils, and other structures which suggest that these lethal hybrids are capable of substantial protein synthesis after “developmental arrest” at the early gastrula stage. These results are discussed in terms of the cessation of normal development at the early gastrula stage in this and other interspecific hybrid amphibian embryos.
Allograft reactivity in chick embryos
Authors: Seto Frank 
Published: June 2005

AbstractKinetic studies with the splenomegaly assay and the in vivo antibody assay of marker allogeneic immunocompetent cells were made to ascertain when in embryonic development the capacity to actively reject foreign cells is manifested by the chick embryo. It was found that (1) the splenomegaly response elicited with equivalent amounts of immunologically competent cells was high in 14‐day embryo hosts but much less in embryo hosts 16‐, and 18‐day of age. Whereas the GVH reaction was effectively reduced in cyclophosphamide‐pretreated 14‐day hosts, no such effect was observed in older hosts; (2) the antibody production by allogeneic immunocytes, as measured with the in vivo assay, was high in 14‐ and 16‐day embryo hosts, but significantly reduced in 18‐day embryo and day‐old chick hosts. In contrast the antibody output remained high in all cyclophosphamide‐pretreated hosts; and (3) the marker immunocytes, cultured in embryo hosts for several days, maintained their antigen‐responsive capacity unimpaired up to the seventeenth day of incubation but showed some loss by the eighteenth day. The experimental findings indicate that the host response during splenomegaly in young embryo hosts is not associated with graft rejection. However, coinciding with the reduction in splenomegaly in older hosts is rejection of donor cells. Alloimmune responsiveness exists as early as the seventeenth‐eighteenth day of chick development.