bluuebunny/crossref_metadata_2025_split huggingface dataset:
Studies on the mechanism of neurulation in the chick: Microfilament‐mediated changes in cell shape during uplifting of neural folds
Authors: Nagele Robert G. , Lee Hsin‐Yi 
Published: June 2005

AbstractThe organization and properties of microfilaments of developing chick neuroepithelial cells were investigated in an attempt to elucidate the structural basis for the observed changes in cell shape during uplifting of neural folds. Microfilaments in the apical regions of cells are more organized than those along the lateral and basal cell margins and are associated with developing junctions. At the level of the zonula occludens, microfilaments are arranged into a loose meshwork extending just below the luminal surface. At the level of the zonula adherens, microfilaments are organized into several discrete bundles rather than as a single circumferential bundle. The opposite ends of these bundles appear to make contact with the plasma membrane at specialized areas of the junction. Microfilaments in the peripheral cytoplasm of the neck and basal regions form a continuous but sparse meshwork. All of these microfilaments bind heavy meromyosin. The implications of the present findings to the observed changes in cell shape during uplifting of neural folds in the chick is discussed.
Polyamines and diamines in regenerating tissues of the Japanese newt, Triturus (Cynops) pyrrhogaster
Authors: Matsuzaki Shigeru , Inoue Sakae 
Published: June 2005

AbstractNewt forelimb and tail regenerates of various stages were analyzed for their contents of diamines and polyamines, including putrescine, spermidine, spermine, sym‐homospermidine, and cadaverine. All the regenerates were particularly rich in putrescine and spermidine among the amines tested. The putrescine level in forelimb regenerates continued to increase during the bud formation period to reach a maximum at 45 days after amputation (“palette stage” to “medium digit stage”) and then decreased. In tail regenerates, putrescine level doubled within 14 days, reached a peak at 26 days, and then decreased gradually. The spermidine level in forelimb regenerates increased gradually for 45 days after amputation and decreased thereafter, while that in tail regenerates reached a peak at 26 days and remained nearly constant thereafter. The spermine and sym‐homospermidine concentration changed little throughout the experiment. Cadaverine levels were lower in the regenerates of the male newt than in intact tissues.
Production of androgenetic diploid axolotls by suppression of first cleavage
Authors: Gillespie Laura L. , Armstrong John B. 
Published: June 2005

AbstractAndrogenetic diploid axolotls were produced by a combination of ultraviolet inactivation of the egg pronucleus and pressure suppression of the first cleavage division. Although survival was low, this technique will prove to be useful for producing completely homozygous animals in one step.
Isolation of hatching gland cells from the teleost, Oryzias latipes, by centrifugation through percoll
Authors: Yoshizaki Norio , Sackers Rudolf J. , Schoots André F. M. , Denucé J. M. 
Published: June 2005

AbstractHatching gland cells (HGCs) of the teleost, Oryzias latipes, have been isolated. The optimum condition is mechanical dissociation of the buccal tissues in Ca‐free saline containing 15% bovine serum albumin (BSA). The cell suspension is fractionated by centrifugation through 30–33.3% Percoll TM containing 5% BSA. The isolated HGCs are washed in 5% BSA. BSA in the latter two solutions can be omitted when a swing‐out rotor is used. The recovery of total and viable HGCs was about 74% and 45%, respectively. The purity was 75–85%. Cellular integrity was shown by pseudopodial movements of the cultured cells.
Effects of growth hormone and thyroxine on pituitary and testicular function in two types of hereditary dwarf mice
Authors: Doherty P. C. , Bartke A. , Dalterio S. , Shuster L. , Roberson C. 
Published: June 2005

AbstractHereditary dwarf mice are growht hormone (GH)‐ and prolactin (PRL)‐deficient and hypothyroid. Administration of PRL, GH, or thyroxine (T4) can induce fertility inmale dwarf mice. The mechanism of action of PRL appears to involve stimulation of FSH release, increased ability of the testes to bind LH, and increased production of testosterone (T) and spermatozoa. To obtain some information on the action of GH and T4 on the pituitary‐testicular axis in these animals, we have examined spermaogenesis, plasma hormone levels, and testicular T production in vitro in Snell (dw) and Ames (df) dwarf mice treated with GH or T4. Treatment with T4 (2μg/day for 2 weeks; 1μg/day for 4 weeks or 4–6μg 3 ×/wk for 6 weeks) or with GH (125 μg/day for 2 weeks; or 38–150 μg/day for 4 weeks) increased body weight, stimulated spermatogenesis, and increased the weight of the testes and seminal vesicles. Treatment with T4 had no significant effects on plasma hormone levels, while treatment with GH for 2 weeks increased plasma levels of LH, FSH, and T in Ames but not in Snell dwarf mice. The ability of the testes to produce T in vitro in the presence of hCG was not affected by in vivo treatment with GH or T4 in either df or dw dwarf mice. These results indicate that the stimulatory effect of T4 and GH on testicular function of dwarf mice does not involve increased responsiveness to gonadotropins or major chages in gonadotropin release. Comparison of the present results with those obtained earlier with PRL indicates that the ability of PRL to induce fertility in dwarf mice may be a specific action of this hormone on the pituitary‐testicular axis, rather that a result of its inherent somatotropic activity.
DNA synthesis and mitosis in adult newt limbs following amputation and insertion into the body cavity
Authors: Loyd Robert M. , Tassava Roy A. 
Published: June 2005

AbstractExperiments were designed to investigate the roles of injury, nerves, and wound epidermis in regeneration. By immediate insertion of amputated limbs into the body cavity, the wound epidermis was prevented from forming. Through 3 weeks post amputation, these inserted limbs showed lower 3H‐thymidine labeling indices and mitotic indices than control normally regenerating limbs. No blastema formed and regeneration did not occur. When denervation preceded insertion, some labeling with 3H‐thymidine was seen but essentially no mitoses were observed. When insertion of innervated limbs was delayed for 48 hr to allow the wound epidermis to form, regeneration occurred in a normal fashion. These results emphasize the importance of injury, nerves, and wound epidermis in controlling cell cycle events during regeneration.
Frequency of supernumerary limbs following blastemal rotations in the newt
Authors: Stock Gregory B. , Krasner Gary N. , Holder Nigel , Bryant Susan V. 
Published: June 2005

AbstractAn examination has been made of the supernumerary limbs produced as a result of tissue interaction following ipsilateral rotation of blastemas at the stage of early digits. The frequency of supernumerary limb formation peaks sharply at angles of rotation near 180°, where tissues from widely separated circumferential locations are opposed. This behavior is compatible with predictions of the polar coordinate model with positional values clustered in the anteriorventral quadrant of the circumference (French et al., '76; Bryant and Iten, '76).
Cytochemical localization of acid phosphatase in ocelli of the seastar Patiria miniata during recycling of photoreceptoral membranes
Authors: Brandenburger Jean L. , Eakin Richard M. 
Published: June 2005

AbstractThe amount and distribution of the lysosomal enzyme acid phosphatase in ocelli of seastars (Patiria miniata) in a 24‐hour light‐dark cycle were studied by a standard cytochemical technique. The enzyme was found in the Golgi apparatus, GERL, and primary and secondary lysosomes of sensory and pigmented supportive cells. We conclude that photoreceptoral membrane of the sensory microvilli is resorbed inthe day by incorporation into pinocytotic vesicles and saccules and degraded in the late day and at night in the secondary lysosomes. Photoreceptoral membrane of microvilli abscised into the ocellar cavity in the day is probably recycled by phagocytosis and digestion in secondary lysosomes of the supportive cells, and perhaps to a lesser extent in the corneal cells. We speculate that recaptured molecules, including photopigment, are returned, in some unknown way, to the distal ends of the sensory cells where the receptoral microvilli are regenerated in the dark. Pinocytotic vesicles may provide stored membrane.
Neural tube closure defects following in vitro exposure of mouse embryos to xylocaine
Authors: O'shea K. S. , Kaufman M. H. 
Published: June 2005

AbstractEarly somite mouse embryos were exposed in vitro to xylocaine (Lignocaine hydrochloride) to examine its effect on neural tube closure. When embryos were exposed to 2.4 × 10−4 mg/ml xylocaine for the entire 36‐hour culture period, cephalic neural tube closure did not take place. When examined by SEM, the neuroepithelial cells of these embryos were incompletely elevated, and depressions in their lateral surfaces were often observed. TEM observations on the neuroepithelium of similar embryos indicated that the microtubules and apical microfilament bundles were absent.The role of calcium in the maintenance of neuroepithelial cell asymmetry and in the production of these defects is considered.
Genome exclusion in gametogenesis by an interspecific Rana hybrid: Evidence from electrophoresis of individual oocytes
Authors: Uzzell Thomas , Hotz Hansjürg , Berger Leszek 
Published: June 2005

AbstractThe diploid hybridogenetic frog Rana esculenta, an interspecific hybrid of R. ridibunda and R. lessonae, usually transmits its ridibunda genome to progeny: the lessonae genome is lost before gametogenesis is completed. Samples of ovary reveal only ridibunda alleles when examined electrophoretically. Cytological and genetic evidence suggests that the lessonae genome is excluded premeiotically. Since recombination between the parental genomes occurs at a low frequency, such recombination should be detectable by examination of the alleles expressed in individual enlarged oocytes.Examination of electrophoretic markers for four loci from 860 individual oocytes (100 each from eight females, ten each from six females) revealed no evidence of either heterozygosity or recombination, although the eight females for which 100 oocytes were examined were somatically heterozygous 29 times for these loci, so that there were 2,900 possibilities for detecting heterozygosity or recombination in the oocytes.These data abundantly confirm the inactivity of the lessonae genome during vitellogenesis in Rana esculenta. They are consistent with a premeiotic exclusion of the lessonae genome, but do not require it. The lessonae genome may be present although inactive, which may permit occasional crossing over between the lessonae and ridibunda genomes. The exclusion of the lessonae genome possibly is a consequence of its inactivity. Exclusion of the non‐ridibunda genome seems to be under control of loci located in the ridibunda genome. A regulatory endoduplication of the ridibunda genome may be necessary before an orderly meiosis can occur.
Male fertility in a female‐sterile mutant of Drosophila melanogaster
Authors: Trippa G. , Loverre A. , Cicchetti R. 
Published: June 2005

AbstractThe fertility and the fecundity of males homozygous for the recessive female‐sterile factor fs(2)TLM have been investigated. Both for standard mating and for observed mating procedures, there was a more than 35% male sterility. Moreover, in a total fecundity experiment the fertile males (about 70%) were effectively fertile for a shorter time than the control males, and the mean progeny per male was about a third that of the controls.It can thus be concluded that the penetrance of the fs(2)TLM factor is different in the two sexes, being complete in the females and incomplete (0.35) in the males. Furthermore, in the males it shows two different degrees of expressivity: complete sterility and fecundity lowered by about 70%.It is suggested that the resultant sterility of these males is a consequence not merely of altered processes causing testicular abnormalities, but also of independent events directly affecting spermatogenesis.
Mitotic activity in the pseudoapical ridge of the trout pelvic fin bud, Salmo gairdneri
Authors: Geraudie Jacqueline 
Published: June 2005

AbstractA radioautographic study of the pseudoapical epidermal ridge, after tritiated thymidine labelling, shows that basal cells do not incorporate this precursor to DNA synthesis. The results conform with the low mitotic activity of this structure after vinblastine treatment, and point to a special metabolism of these cells, probably associated with their involvement in actinotrichial development.
Ribonucleoside metabolism by mouse oocytes: Metabolic cooperativity between the fully grown oocyte and cumulus cells
Authors: Heller David T. , Schultz Richard M. 
Published: June 2005

AbstractRibonucleoside uptake and metabolism were studied in mouse oocytes arrested at dictyate and metaphase II, with or without attached cumulus cells. Uptake of uridine and guanosine decreased after meiotic maturation, whereas that of adenosine and cytidine remained unaltered. Dictyate oocytes free of cumulus cells (denuded) phosphorylated all of the radiolabeled ribonucleosides. Little radiolabeled ribonucleoside‐5′‐triphosphate was found. This is in contrast to the early mouse embryo, which rapidly converts ribonucleosides to the 5′‐triphosphate (Daentl and Epstein, '71; Clegg and Piko, '77). Following meiotic maturation, the major metabolite present when metaphase II oocytes were cultured with cytidine or uridine was the ribonucleoside, whereas the 5′‐monophosphate was still the major species for oocytes cultured with guanosine or adenosine.Ribonucleoside uptake was increased and the distribution of phosphorylated metabolites was different for cumulus‐enclosed dictyate oocytes compared to their denuded counterparts. This increase in uptake and alteration in metabolite distribution was not observed for cumulus‐enclosed metaphase II oocytes. These results are discussed in terms of gap junction‐mediated metabolic cooperativity between the cumulus cells and the fully grown oocyte and the possible role this type of cell‐to‐cell interaction may serve during oocyte growth.
Erythrocyte metabolism: Kinetic and electrophoretic analyses of pig red cell hexokinase
Authors: Dixon Earl , Wilson B. A. 
Published: June 2005

AbstractThe mature erythrocyte of the pig has been observed to possess the slowest metabolic rate of any mammalian cell type. Previous studies in this laboratory suggested that the hexokinase isolated from these cells was inhibited by glucose in concentrations in excess of 0.2 mM. In the present study, the enzyme was isolated by utilizing DEAE‐Sephadex A‐50, ammonium sulfate precipitation, DEAE‐cellulose (DE‐52), and Sephadex G‐100 gel‐filtration. Studies on the hexokinase isolated from the pig mature erythrocyte by the above procedures revealed two distinct isozymes of hexokinase that do not behave kinetically and electropho retically as those previously found in other mammalian red blood cells. The isozyme isolated from the erythrocyte of the young adult pig (less than six months of age) migrated at a slower electrophoretic rate than the one isolated from the adult pig (more than six months of age). Coupled with the observed difference in electrophoretic mobilities were changes in the apparent Km̂, values as well as Vmax as a function of substrate concentration. In spite of the changes observed in relation to glucose, the apparent Km̂ for Mg‐ATP−2 was not altered during development. Diphosphoglycerate (DPG) was observed to be a “linear‐mixed” inhibitor of both isozymes with respect to Mg‐ATP−2. An experiment designed to determine the type of inhibition by DPG on the type I isozyme isolated from the horse erythrocyte revealed competitive inhibition with the Mg‐ATP−2 site. Free Mg activated both isozymes in low concentrations (< 2.5 mM) but inhibited the enzymatic activity as the concentration was elevated. The data suggest that both the young adult and the adult pig erythrocyte possess two distinct type III isozymes of hexokinase.
Wing buds with three ZPAs
Authors: Iten Laurie E. , Murphy Douglas J. , Javois Lorette C. 
Published: June 2005

AbstractIt has been hypothesized that a diffusible morphogen emanates from the ZPA of the embryonic chick limb and that cells can have their presumptive fate respecified to form more posterior structures when exposed to a higher concentration of morphogen. Attempts to raise the concentration of morphogen by grafting two additional ZPAs into a host wing bud failed. Instead, the greater the positional disparity between the donor and host tissue at the graft sites, the greater the number of extra structures that formed.
Mechanics of tail resorption in triiodothyronine‐induced metamorphosing tadpoles
Authors: Dmytrenko George M. , Kirby Gerald S. 
Published: June 2005

AbstractThe mechanics of tail resorption in triiodothyronine (T3) induced metamorphosing Rana catesbeiana tadpoles was investigated. Premetamorphic (Taylor and Kollros stages 7–11) tadpoles'tails were permanently marked off into three segments with silk suture loops anchored in metameric musculature of the tail. A dose of 3 × 10−10 moles T3/gram of body weight was administered intraperitoneally. Tail length measurements were made daily for 6 days after injection. Significant reductions were observed in total tail length as well as concurrent reductions in proximal, middle and distal tail segment lengths. These data indicate that resorptive activity is not confined to the distal tail tip, but that tissue resorption occurs simultaneously along the entire tail length. The rate of shortening is greatest in the distal segment and least in the proximal segment. Key words: Tail resorption, Metamorphosing, Triiodothyronine, Tadpole.
The cellular origin of the zona pellucida antigen in the human and hamster
Authors: Bousquet D. , Léveillé M. C. , Roberts K. D. , Chapdelaine A. , Bleau G. 
Published: June 2005

AbstractThe origin of the zona pellucida in follicles at different stages of maturation was studied in the hamster and human by indirect immunofluorescence microscopy using a specific anti‐hamster zona pellucida serum. The earliest detection of the zona pellucida material occurred in the ooplasm of oocytes in primordial follicles. In primary follicles, the fluorescence was localized at the periphery of the oocyte. In secondary and in mature follicles a deposition of fluorescent material was visualized on the inner and outer regions of the zona pellucida. Follicular cells, other than the oocyte, failed to exhibit a fluorescent reaction with the antizona pellucida serum. It is concluded that the oocyte is an important source of the antigenic material of the zona pellucida of hamster and human ova.
Adaptation and tolerance of invertebrate nervous systems to osmotic stress
Authors: Prior David J. , Pierce Sidney K. 
Published: June 2005

AbstractBoth the osmotic and ionic concentration changes accompanying a salinity alteration might be expected to have profound effects on neuronal physiology, especially in euryhaline animals. We have examined the effects of salinity change and followed the subsequent adaptation to that change by an invertebrate neuron. The spontaneous activity of the follower cell of the cardiac ganglion of Limulus polyphemus is altered during salinity stress. The membrane potential is depolarized, the burst frequency is altered and the impulse pattern within each burst is disrupted following hypoosmotic stress. With time in the reduced salinity, adaptation occurs and both the membrane potential and the burst pattern return to control levels. Further, all these changes are due to osmotic variation with no detectable ionic component. Coincident with the adaptation of the electrical characteristics of these follower cells is an efflux of intracellular free amino acids which in turn, presumably, is regulating cell volume. Thus, this temporal correlation suggests that the electrical adaptation is dependent upon the cell volume regulatory mechanisms of the neurons.
Adaptation of nitrogen metabolism to hyperosmotic environment in Amphibia
Authors: Balinsky John B. 
Published: June 2005

AbstractA large number of species of Amphibia, both Anura and Urodela, are capable of tolerating a moderately saline environment. Rana cancrivora, Bufo viridis, and Xenopus laevis are among the most euryhaline frogs so far studied. Rana cancrivora can tolerate undiluted seawater. In a saline environment, Amphibia show raised plasma sodium and chloride and raised intracellular potassium and chloride. In the adults, plasma and tissue urea are elevated, especially in the more euryhaline species. Free amino acids contribute negligibly to plasma osmolarity, but are very important in intracellular fluids. By these various means, the osmotic pressure of body fluids is always maintained at a higher level than that of the surroundings. Larval Amphibia, however, do not make urea; Rana cancrivora tadpoles can live in saltwater, but maintain the osmolarity of their body fluids below that of their surroundings.Adaptive responses to hyperosmolar environment include decreased skin sodium transport, greatly reduced urine flow, and release of posterior pituitary hormones. After the initial response, the release of these hormones declines, and urine flow increases. Accumulation of urea occurs slowly, but this substance plays an increasingly important role as adaptation proceeds. Accumulation is due initially to urea retention, and possibly to greater synthesis due to a high concentration of precursors of the urea cycle. In later stages of adaptation, increased urea synthesis is due to elevated levels of urea cycle enzymes, especially those that appear to have been rate‐limiting. Liver glutamate dehydrogenase is also elevated. In animals subjected to pure osmotic stress, in solutions not containing sodium, responses are similar to, but not identical with, those caused by a medium containing sodium chloride.
Cell volume regulation in crustaceans: Relationship between mechanisms for controlling the osmolality of extracellular and intracellular fluids
Authors: Gilles R. , Péqueux A. 
Published: June 2005

AbstractThe control of cell volume in tissues of crustaceans acclimating to salinity changes cannot be ascribed to a single mechanism; it results rather from different processes acting both at the cell level and at the blood level. The mechanisms at work at the cell level are discussed and some possible relations between them and those acting at the blood level are considered. The amino acids leaking out of the cells during cell volume readjustment, following application of hypoosmotic conditions, can be stored in the form of blood proteins. Increased deamination and oxidation of amino acids also occur under such conditions, the products of this increased catabolic activity being used in the gills as counterions for NaCl active uptake.