bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hormone‐induced pigment translocations in amphibian dermal iridophores, in vitro: Changes in cell shape
Authors: Butman Bryan T. , Obika M. , Tchen T. T. , Taylor John D. 
Published: June 2005

AbstractHormone‐induced pigment translocation studies were conducted at both the light and electron microscopic levels on cultured dermal iridophores from the Mexican leaf frog, Pachymedusa dacnicolor. Two distinct types of dermal iridophores were characterized which differed in (1) their in vivo locations, (2) their overall morphologies in vitro, (3) their responses to α‐MSH, ACTH, c‐AMP or theophylline, (4) their physical alterations of light, and (5) certain ultrastructural features. One iridophore (Type I) was found to be physiologically responsive to the above hormones or agents by a reversible retraction of cellular processes and a thickening of the cell body, an event which is inhibited by cytochalasin B. The other iridophore (Type II) appeared to be unresponsive. Type I iridophores contain cube‐like pigmentary organelles, refractosomes, while Type II iridophores contain larger, bar‐shaped refractosomes. In addition, both iridophore types contain 60 and 100 Å microfilaments as well as microtubules. By in large, microfilaments were found within microvilli, beneath and parallel to the plasma membrane and in the perinuclear region. Occasionally, bundles of 100 Å microfilaments were found between layers of refractosomes in Type I iridophores. These results are discussed in relation to hormone‐induced changes in cell shape.
Epigenetic formation of lactate dehydrogenase isozymes in the house mouse, Mus musculus
Authors: Yamamura Ken‐Ichi , Ogita Zen‐Ichi , Markert Clement L. 
Published: June 2005

AbstractThe origin of mouse lactate dehydrogenase (LDH) subbands was investigated by using our miniaturized polyacrylamide gel electrophoretic apparatus. Mouse LDH isozymes are generated by combinations of three types of A subunit, the primary type and two epigenetically modified forms. These are designated A1, A2, and A3 in the order of their electrophoretic mobilities towards the anode. The A1 subunit arises from the covalent binding of molecules of glutathione through disulfide bonds to the original subunit, A3. The A2 subunit arises from the covalent binding of molecules of cysteine through disulfide bonds to the A3 subunit. All isozymes can be explained as tetramers composed of the three kinds of A subunit (A1, A2, or A3) in combination with B subunits to yield a total of 35 isozymes. The kinetic properties of these subbands were also examined. There was no difference between A24 and A34 in the Km for pyruvate and for lactate. Thermostability at 56°C was greater for A34 than for A24. The activities of tetramers at the electrophoretic position of A3B1 and A4 in extracts containing all five isozymes were increased by treatment of the extracts with high concentrations of reduced glutathione or cysteine with the concomitant disappearance or decrease in activity of tetramers at the position of B4 and A3B1. These results suggest that, in the presence of reduced glutathione or cysteine, LDH isozymes containing the B subunit are first dissociated and then the A subunits are preferentially recombined.
Injection of sperm heads into immature rat oocytes
Authors: Thadani Vijay M. 
Published: June 2005

AbstractWhen sperm heads are injected into rat oocytes at the germinal vesicle stage the sperm heads remain intact until the germinal vesicle breaks down. Then they decondense but do not form pronuclei. This observation agrees with the results reported for in vitro fertilization of immature oocytes from rats, mice and hamsters.
Pyruvate kinases of salmon: Purification and comparison with the isozymes from birds and mammals
Authors: Guderley Helga , Cardenas Janet M. 
Published: June 2005

AbstractPyruvate kinase occurs as two major forms in coho salmon; the type M isozyme occurs primarily in muscle and heart, but type K has a more generalized tissue distribution, in parallel with the type K isozyme in other vertebrate systems. In order to assess the evolutionary relationships among the fish, avian, and mammalian isozymes of pyruvate kinase, we have purified the two isozymes from fish, have examined some of their physical properties, and have studied their immunological relationships to theavian and mammalian isozymes. Salmon type K is at least partially inactivated by antibody to bovine type L pyruvate kinase as well as by antibodies produced against chicken, bovine, and salmon type M isozymes. Salmon type M pyruvate kinase, on the other hand, is not significantly cross‐reactive with the bovine type L isozyme, but is at least partially inactivated by antibodies produced against bovine or chicken type M isozymes. Mammalian type L pyruvate kinase is immunologically distinct from either mammalian type K or type M, but salmon type K has some structural features in common with all three mammalian isozymes. Thus, salmon fish type K pyruvate kinase could be similar to a primordial form that was antecedent to the three major differentiated isozymes of higher vertebrates.
In vivo and in vitro studies on the early embryonic lethal tail‐short (Ts) in the mouse
Authors: Paterson Hugh F. 
Published: June 2005

AbstractAn histological study reveals that embryos homozygous for the mutation tail‐short (Ts) become abnormal as morulae, although a small amount of cell division may continue to take place during the following day. Homozygotes can be identified at 3½ days post coitum (p.c.) by several criteria including low cell number, absence of cavitation, and weak cytoplasmic staining with haematoxylin. A similar pattern of developmental arrest is exhibited during culture, although an initial degreeof cavitation occurs more frequently.
Lens formation from pericorneal epidermis in the presence of the old lens in larval Xenopus laevis
Authors: Filoni Sergio , Bosco Luigi , Paglioni Nadia , Cioni Carla 
Published: June 2005

AbstractThe lens‐forming capacity of the pericorneal epidermis of Xenopus laevis larvae at stage 51 has been investigated. The results obtained show that, whether or not the lens is present, the pericorneal epidermis can form a lens when it is in direct contact with the vitreous chamber of the eye. It is concluded that the posterior pole of the lens either does not produce any inhibiting substances or else is unable effectively to remove the factor(s) contained in the vitreous chamber which are responsible for the lens‐forming transformations of the pericorneal epidermis.
Alterations in the levels of stem cells (CFU‐s) and plaque‐forming cells (PFC) in mice during chronic phenylhydrazine‐lnduced hemolytic anemia
Authors: Kozlov V. A. , Zhuravkin I. N. , Coleman R. M. , Rencricca N. J. 
Published: June 2005

AbstractThe levels of splenic and medullary pluripotent stem cells (CFU‐s) and splenic plaque‐forming cells (PFC) to sheep red blood cells (SRBC) were monitored in mice during the course of mild chronic phenylhydrazine (PHZ)‐induced hemolytic anemia. The levels of CFU‐s were significantly depressed in the bone marrow and elevated in the spleen throughout. These changes are most likely due to increased CFU‐s migration from marrow to spleen. In this regard, migration of CFU‐s from limb‐shielded marrow to thespleen of irradiated PHZ‐treated mice was demonstrated. Lastly, the numbers of splenic PFC to SRBC were significantly and constantly depressed throughout the course of hemolytic anemia and enhanced erythropoiesis. Stem cell competition between erythroidand lymphoid lines of differentiation may have contributed to the observed reduced immune response.
Effects of hormones on post‐implantation mouse embryos in vitro. I. Insulin
Authors: Fisher D. L. 
Published: June 2005

AbstractDay 9 mouse embryos were cultured in 50% fetal calf serum and 50% Waymouth's medium supplemented with various amounts of insulin. Unmodified medium contained approximately 25% of the normal adult mouse blood insulin. The addition of 0.1 to 1.0 μg insulin/ml to Waymouth's medium was most beneficial to in vitro development. There was a statistically significant increase in protein synthesis, RNA content, glucose utilization, and heart rate, as well as a significant decrease in pericardial edema. DNA, synthesis was unchanged or slightly decreased. The optimal amount of added insulin (0.05 μg/ml) is much higher than the normal circulating levels in adult mice.
Prolonged survival of skin allografts in mallards
Authors: Mueller Nancy S. 
Published: June 2005

AbstractSkin allografts were exchanged between 25 male and 25 female mallards (Anas platyrhynchos) within 2 days after hatching. Of the 42 ducks that survived and whose grafts healed, 14% rejected rapidly before the grafts became feathered, 20% rejected between 3–6 weeks, and one duck rejected when he was 10 weeks old. Twenty‐seven of the 42 ducks (64%) retained their grafts for at least 5 months. The result demonstrate that, in mallards, neither inbreeding nor any treatment of the host is necessary for prolonged survival of skin allografts made shortly after hatching.
Possible control for tubulin synthesis during early development of an insect
Authors: Jäckle Herbert 
Published: June 2005

AbstractTubulin represents a major protein component synthesized during early embryogenesis of the chironomid midge Smittia spec. Both α‐ and β‐tubulin were identified by immunoprecipitation and subsequent analysis by two‐dimensional gel electrophoresis using purified Drosophila microtubule proteins as a marker. The synthesis of tubulin in Smittia embryos was not localized within regions perpendicular to the longitudinal axis. The messenger RNA for both α‐ and β‐tubulin appeared to be maternal in origin (maternal mRNA). The in vivo ratio of [35S]‐methionine incorporation into α‐tubulin relative to β‐tubulin was 1:2.1, and constant at least until the end of blastoderm stage. In a rabbit reticulocyte lysate, tubulin synthesis was directed by total RNA, poly(A)‐containing RNA, and nonpoly(A)‐containing RNA extracted from eggs immediately after deposition. However, the in vitro ratio of [35S]‐methionine incorporation into α‐ and β‐tubulin was 1:1. The results suggest that tubulin is synthesized in the early embryo using maternal mRNA. Therefore, posttranscriptional rather than transcriptional processess seem to regulate the synthesis of α‐tubulin relative to β‐tubulin.
Comparative extraocular muscle blood flow
Authors: Wilcox Lloyd M. , Keough Ellen M. , Connolly Raymond J. , Hotte Clifford E. 
Published: June 2005

AbstractThis study was designed to quantitatively determine blood flow to the extraocular muscles (EOM) of animals showing a wide range of ocular motility. Blood‐flow values (ml/minute/gm) for EOM in primates (0.25 ± 0.03), dogs (0.33 ± 0.06), sheep (0.12 ± 0.01), and geese (0.12 ± 0.04) were determined using the Reference Sample Method with 15 ± 3 μm 103Ru microspheres and complete cardiovascular monitoring. Mammalian EOM blood flow was significantly higher than that determined for other skeletal muscle; however, EOM blood‐flow values for sheep were significantly lower than those for primates and dogs.No significant blood‐flow differences were found between avian EOM and other skeletal muscle, reflecting the unique avian ocular anatomy. These data indicate that high blood flow is not a general property of EOM and suggest a relationship between functional ocular motility and blood flow.
Transport of exogenous substrate and cell volume regulation in bivalve molluscs
Authors: Crowe John H. 
Published: June 2005

AbstractBased on published values for transport kinetics, it has been suggested that uptake of free amino acids from the environment could not play a significant role in altering the intracellular pool of free amino acids during hypersaline acclimation in euryhaline bivalves. A review of more recent findings indicates that this suggestion requires reexamination. It has also been suggested that extracellular sources of amino acids within the animals could be utilized in altering the intracellular pool. Available data having bearing on that hypothesis are reviewed.
On the timing and activation of glycogen catabolism in fertilized sea urchin eggs
Authors: Baginski Richard M. 
Published: June 2005

AbstractDecreased glycogen radioactivity was followed as an indicator of glycogen utilization following activation of Strongylocentrotus purpuratus eggs. Within 15 minutes of exposure to sperm or ammonia, egg glycogen radioactivity decreased. The level of radioactivity in control (unfertilized) eggs remained relatively constant. These results suggest enhanced egg glycogenolysis is a pH‐sensitive event independent of the “respiratory burst”.
Significance of periodic fluctuations in the haemolymph carbohydrates of Scylla serrata (Forskal) during starvation and repeated injury
Authors: Saravanan T. S. , Ravindranath M. H. 
Published: June 2005

AbstractHaemolymph carbohydrates of S. serrata, including reducing sugars (RS), nonreducing sugars (NRS), and glycogen (free and bound to protein) showed intermittent fluctuations in animals subjected to starvation in combination with injury and exsanguination stress (Group I), whereas in animals subjected to starvation alone (Group II) only RS levels showed such significant periodic fluctuations. The timing of periodic ‘peaks’ in the haemolymph total free sugar (TFS) and RS coincided in both groups of animals. Haemolymph TFS, although declining throughout 33 days of starvation, increased significantly on three different days. Similar patterns were observed in the patterns of reducing sugar. Levels of haemolymph NRS and glycogen were greater throughout the 33 days of starvation in group I than in group II. NRS, glycogen, and protein‐bound polysaccharides (PBS) exhibited significant fluctuations only in Group I animals. The significance of the periodic fluctuations in haemolymph carbohydrates is discussed.
Morphological observations on cleavage of the egg of the medaka, Oryzias latipes, following injection with flagellar microtubules of sea urchin spermatozoa
Authors: Ohta Tadayuki , Iwamatsu Takashi 
Published: June 2005

AbstractMature unfertilized eggs of the medaka, Oryzias latipes, were injected with sperm flagellar microtubules of the sea urchin, Hemicentrotus pulcherrimus, and were observed with reference to the process of early development. Groups of injected eggs, most of which initiated cleavage and developed to morulae, were fixed with Feulgen fixative at 10, 30, 45, 60, 80, and 90 minutes and at 5 hours after injection. Light microscopic observation revealed that by 45 to 60 minutes, the eggs had radially organized astral fibers originating from the periphery of the droplet of injected microtubule suspension. First cleavage then occurred at 80 to 90 minutes. At the morula stage (5 hours), each blastomere always contained an aster‐like structure composed mainly of endoplasmic reticula. These observations confirmed that the injected flagellar microtubules induced aster formation and first cleavage in unfertilized eggs of the fish.
Sperm‐induced cell cycle activities in blastomeres arrested by the cytostatic factor of unfertilized eggs in Rana pipiens
Authors: Shibuya Ellen K. , Masui Yoshio 
Published: June 2005

AbstractSuspensions of lysolecithin‐treated sperm were injected into blastomeres of two‐cell embryos which had been arrested with the extract of unfertilized eggs containing cytostatic factor (CSF). Whereas the CSF‐arrested blastomeres remained unchanged if no sperm were injected, those injected with sperm formed abortive cleavage furrows. The injected sperm exhibited characteristics similar to those associated with sperm injected into activated eggs. These were nuclear decondensation to the pronucleus, DNA synthesis, and late chromosome condensation to the metaphase stage. The activity of CSF‐arrested blastomere cytoplasm to promote meiotic maturation when injected into ovarian oocytes rapidly decreased following sperm injection, but later fluctuated at low levels. It was suggested that the CSF‐arrested blastomeres retained the potential to reinitiate cell cycle activities which could be evoked by sperm injection.
Experimental evidence for effective heterokaryon formation in the ciliate Euplotes crassus
Authors: Miceli Cristina , Luporini Pierangelo 
Published: June 2005

AbstractMorphological mutant doublets of Euplotes crassus containing two nuclear complexes and expressing a definite mating type were conjugated with normal singlets of a complementary mating type. After conjugation a class of clones was obtained each of which consisted of doublets having both a capability to form intraclonal pairs and no restriction in the mating spectrum. Doublets were isolated from this class of clones and were subsequently allowed to split into their component halves (singlets). The two singlet sib‐lines deriving by vegetative growth of a split doublet were tested for mating type and were usually found to be different. Also, different allelic combinations were consistently shown to exist at the mt locus, i. e., the locus determining the mating type. Our data support the hypothesis that these doublets which gave rise to two different singlet sib‐lines should have contained nuclear complexes with different, active mt alleles. Thus these doublets capable of expressing two mating types at the same time can be considered to be effective heterokaryons.
Cyclophosphamide‐induced leukopenia and suppression of limb regeneration in the adult newt, Notophthalmus viridescens
Authors: Schotté Oscar E. , Sicard Raymond E. 
Published: June 2005

AbstractCyclophosphamide (cytoxan), a clinical immunosuppressant, produced a marked, persistent leukopenia (> 40% reduction) in adult newts in contrast to a transient, milder leukopenia accompanying amputations without cytoxan treatments. In addition, cytoxan suppressed the formation of regeneration blastemata initially; however, blastema formation occurred if a second amputation was performed two or more weeks following the cessation of cytoxan treatments. The failure of the leukopenias of these latter cases to be corrected suggests that although a cytoxan‐induced leukopenia is correlated with the absence of forelimb regeneration, this leukopenia is not, of itself, a sufficient condition to inhibit regeneration.
Effect of calcium antagonists on light response of cultured melanophors of Oryzias latipes
Authors: Negishi Sumiko 
Published: June 2005

AbstractDispersion of melanosomes in Oryzias melanophores, induced by illumination, was completely inhibited by the Ca2+ antagonists lanthanum (0.2 mM), verapamil (0.3 mM), and papaverine (0.3 mM), but only slightly inhibited by ruthenium red (4 mM). The inhibitory effect of lanthanum or verapamil depended on the extracellular concentration of calcium ions, suggesting the competition between binding of Ca2+ and binding of lanthanum or verapamil. Theophylline induced full dispersion of melanosomes, even in the presence of the Ca2+ antagonists. This fact suggests that Ca2+ is not specifically required for the dispersion of melanosomes per se but, rather, that calcium ions are required for the transduction of light stimulation into cytoplasm. The Ca2+ antagonists affected neither the dark‐induced aggregation of melanosomes nor the aggregation induced by melanophore concentrating hormone.
Differences in the macromolecular composition of the zona pellucida isolated from pig oocytes, eggs, and zygotes
Authors: Hedrick Jerry L. , Wardrip Nathan J. , Berger Trish 
Published: June 2005

AbstractThe macromolecular differences in the zona pellucida (ZP) isolated from pig oocytes, eggs, and zygotes were investigated using two‐dimensional polyacrylamide gel electrophoresis. The ZP was isolated from individual cells or zygotes using micropipettes, radiolabeled with 125I and analyzed using disulfide bond reducing and nonreducing conditions. The reduced ZP isolated from oocytes was composed of four glycoprotein components. The gel pattern of the ZP isolated from a single oocyte was indistinguishable from that isolated en masse. The ovulated egg ZP contained the four oocyte components plus three additional macromolecules. Relative to the egg ZP, the zygote ZP lacked one component but had three additional smaller macromolecules. We concluded that: 1) the macromolecular differences between the oocyte and egg ZPs are caused by the addition of macromolecules to the ZP as the egg transits the oviduct, 2) the macromolecular differences between the egg and the zygote ZPs reflect hydrolytic processing of ZP glycoproteins probably by enzymes derived from the egg cortical granules, and 3) the microheterogeneity of the pig ZP glycoproteins is due to posttranslational modification and is not due to population genetic variation.
Formation of germ layers and roles of the dorsal lip of the blastopore in normally developing embryos of the newt Cynops pyrrhogaster
Authors: Imoh Hiroshi 
Published: June 2005

AbstractThree‐dimensional relationships between tissues during the formation of germ layers were studied in sections of normally developing embryos of the newt, Cynops pyrrhogaster. In gastrulae, the inner postinvolution layer was not in direct contact with the outer preinvolution layer as a result of the presence of an intervening layer of cells. Only after the formation of the yolk plug, a narrow strip of primitive notochord, which consisted of columnar cells, established a close contact with the central part of the overlaying presumptive neural plate. The primitive notochord was also linked to endoderm at its right and left margins, facing the archenteron. Mesodermal cells other than notochord cells were mesenchymal until the neurula stage, when primitive somites appeared on both sides of the notochord. From a comparison of the relative locations of tissues in embryos at different stages of development, it was shown that the notochord elongates by a remodeling of the mass of the primitive notochord, and that, as the anteriorly directed translocation of the neural area and the invagination of endoderm occur, these processes keep pace with the elongation of the notochord. These observations suggest organizing or guiding roles for the notochord in the formation of germ layers. A role for the dorsal lip of the blastopore as the organizer is discussed in relation to the origin of the notochord.