bluuebunny/crossref_metadata_2025_split huggingface dataset:
Contact inhibition of cell movement in living embryos of an annual fish, Nothobranchius korthausae: Its role in the switch from persistent to random cell movement
Authors: Lesseps Roland , Hall Marian , Murnane Mary Beth 
Published: June 2005

AbstractThe deep blastomeres of annual fish embryos emigrate from the blastodisc to wander as single cells, during epiboly and early dispersed stages, between the periblast and the enveloping layer cells. Time‐lapse films of the deep blastomere movements were analyzed to determine whether the cells move persistently or randomly and whether or not they show contact inhibition of cell movement. Certain predictions which follow from the random‐walk model (uniform distribution of intersegmental angles, exponential distribution of squared segmental lengths, and a straight‐line plot – passing through the origin – of mean square displacement against time) were tested and, in general, found to apply to these deep blastomeres during dispersed phase 1 but not during epiboly stages. These results indicate that the cells tend to persist in their direction of movement during epiboly, but not during dispersed phase 1, when their movement is random. Upon completion of epiboly, there is a decrease in cell motility, as measured by the augmented diffusion constant, D*, and an increase in the average collision rate. Numerous cases of cell contact between deep blastomeres were observed (297 during epiboly and 167 during dispersed phase 1); in every case one or both cells changed their direction of movement. The role this contact inhibition might play in the persistent movement of epiboly and the random movement of dispersed phase 1 is discussed.
Mitogenic effect of a growth factor derived from myelin on denervated regenerates of newt forelimbs
Authors: Mescher Anthony L. , Gospodarowicz Denis 
Published: June 2005

AbstractFibroblast growth factor injected into denervated early regenerates of adult newt forelimbs promotes mitotic activity in the dedifferentiated mesodermal cells. The effect is dose‐dependent and is not produced with similar doses of cytochrome c, bovine serum albumin, or growth hormone. Epidermal growth factor has a mitogenic effect less than half as great as that of fibroblast growth factor. The results suggest the possibility of a role for myel in‐derived growth factors in blastema formation.
Response of the avian chorionic epithelium to presumptive scale‐forming dermis
Authors: Fisher C. , Sawyer R. H. 
Published: June 2005

AbstractThe isolated chorionic epithelium (CE) from 8‐day chick embryos responds to the inductive influence of anterior shank (scale) dermis (ASD) in different ways depending on the age of the dermis. Eleven‐day dermis induces the fomrmation of barb‐ridges, typical of feathers, yet, very little feather elongation; while 13‐day dermis induces the CE to form normal scale epidermis. Twelve‐day ASD elicits both the formation of barb‐ridges and scales. Thus, the ASD, in association with the overlying scale‐forming epidermis, becomes altered in its inductive ability between 11 and 12 days of development.
Dissolution of rabbit zona by acrosomal extract: Effect of calcium
Authors: Srivastava Prakash N. , Akruk Samir R. , Williams William L. 
Published: June 2005

AbstractThe acrosomal extracts from rabbit spermatozoa were more effective in dissolving the zona pellucida of the rabbit ova in the absence than in the presence of Ca+2. The extracts had high proteolytic activity but low esterolytic activity at alkaline pH in which pH effective zone hydrolysis occurred. The results suggest that acrosomal proteinases in addition to acrosin may be involved in the zona penetration.
Stomatogenesis during sexual and asexual reproduction in an amicronucleate strain of Paramecium caudatum
Authors: Mikami Kazuyuki 
Published: June 2005

AbstractAmicronucleate cells of Paramecium caudatum, whose micronuclei have been artifically removed by micropipetting, are characterized by the appearance of a deciliated area at the posterior part of the buccal opening. These cells form food vacuoles at a slightly lower rate than micronucleate cells. Their mean interfission time is longer than that in micronucleates. The exconjugants of amicronucleate cells can not form food vacuoles and eventually die without fission, though conjugation proceeds normally in them as well as in their micronucleate mate. The oral apparatus of amicronucleate exconjugants seems can be seen through the buccal overture by scanning electron microscope. The results obtained from the cross of micronucleate and amicronucleate strains and from the induction of autogamy in amicronucleate strains suggest that the micronucleus has a primary role in developing the normal oral apparatus after nuclear reorganization.
Effect of thyrotropin releasing factor on body weight of the pond snail Lymnaea stagnalis
Authors: Grimm‐Jørgensen Yvonne 
Published: June 2005

AbstractEarlier studies had demonstrated that in Lymnaea stagnalis thyrotropin releasing factor (TRF) may be the secretory product of the so‐called dark green neurosecretory cells. The dark green cells are believed to serve an osmoregulatory function. If TRF is the secretory product of the dark green cells, it should be capable of controlling the salt and water balance in L. stagnaus. In this study, the effect and fate of synthetic TRF injected in vivo into L. stagnalis was assessed. It was found that TRF caused an increase in the rate of loss of body water which normally occurs after anaesthesia. TRF also increased the loss of body water when it was administered to unanaesthetized animals. The peptide was accumulated and degraded by the tissues of the foot, mantle, and head regions, tissues which are believed to be the targets of the hormone of the dark green cells. Our results support the hypothesis that TRF may be the secretory product of the dark green cells and may be involved in osmoregulation in L. stagnalis.
Abnormal scale morphogenesis: Relationship of polypeptide patterns to action of the scaleless gene
Authors: Mirkes P. E. , Sawyer R. H. 
Published: June 2005

AbstractThe polyacrylamide gradient gel electrophoresis (PAGGE) pattern of polypeptides isolated from normal scuttate scale epidermis of 1‐week‐old chicks was different from that of the anterior shank epidermis from 1‐week‐old scaleless mutant chicks. The PAGGE patterns of polypeptides isolated from normal and scaleless reticulate scale epidermis (from 1‐week‐old chicks) differed by only one band, whereas comparison of mutant's scuttate and reticulate patterns showed three band differences. These data are discussed in relation to the action of the scaleless gene on early morphogenesis of the two types of scales.
Progesterone induction of oocyte maturation in Rana pipiens: Reversibility of cycloheximide inhibition
Authors: Samson Douglas A. , Schuetz Allen W. 
Published: June 2005

AbstractThe reversibility of cycloheximide inhibition of progesteroneinduced oocyte maturation was investigated. Progesterone treated immature oocytes underwent nuclear (germinal vesicle breakdown) and cytoplasmic maturation unless inhibited by incubation in the continuous presence of cycloheximide. However, when previously treated oocytes were simply washed in culture media on the day following the initial treatment, they matured without additional exposure to progesterone. The incidence of germinal vesicle breakdown observed after washing and reincubation was similar to that seen in paired oocytes retreated with progesterone, cycloheximide‐pretreated control oocytes newly treated with progesterone or control oocytes treated only with progesterone on the first day. Oocytes exposed to low concentrations of progesterone matured the following day whereas paired oocytes inhibited by cycloheximide during the first day did not mature at similar low doses following washing on the second day. The time of germinal vesicle breakdown in oocytes previously inhibited with cycloheximide was either slightly delayed or unaltered as compared to that of control oocytes newly treated with progesterone. The results indicate that an initial step of progesterone induced maturation in Rana is reversibly blocked but not detrimentally altered by cycloheximide. The evidence suggests that the effects of cycloheximide may be mediated through effects on the formation and/or autocatalytic production of maturation promoting factor (MPF). The cellular and molecular significance of these data to the process of meiotic arrest and oocyte maturation are discussed.
Acrosome removal induces features analogous to fertilization during mouse sperm fusion with somatic cells
Authors: Široký Jiří , Spurná Věra , Kopečný Václav , Tkadleček Ludvík 
Published: June 2005

AbstractSpontaneous and induced fusion of intact and acrosome removed spermatozoa with mouse fibroblasts (L cells) was studied in vitro.In the experiments with acrosome‐removed spermatozoa some features similar to physiological fertilization were seen during the process of spontaneous heterokaryon (Hk) formation. Even in the initial stage of co‐incubation the treated spermatozoa generally adhered to the surface of somatic cells by the posterior region of the head. The penetration of acrosome‐removed spermatozoa to the cytoplasm of L cells then occurred but was markedly delayed. Penetration of L cells by non‐treated spermatozoa did not occur. The observed triggering of sperm chromation decondensation in the heterokaryon indicates a “true membrane reaction” during the process of fusion of acrosome‐removed spermatozoa and L cells.The degree of sperm head decondensation remained incomplete in all cases detected and only 10−3 Hk contained decondensed chromatin of spermatozoal origin.It is concluded that a true membrane reaction may be induced between spermatozoa and somatic cells, after acrosome destruction by simple physico‐chemical agents, and without “fusogenic” agents.
Nerve dependent macromolecular synthesis in the pectoral fin regenerate of the fish, Fundulus
Authors: Géraudie Jacqueline , Singer Marcus 
Published: June 2005

AbstractTotal resection of the brachial plexus of the regenerating pectoral fin in the fish Fundulus immediately affects protein and DNA synthesis. As in the case of nerve dependent synthesis in urodele limb regeneration, there is at first an outburst in macromolecular synthesis which peaks in the early hours after denervation. Then there is just as rapid a decline to a plateau value about 50–60% of its normal one at 24 to 48 hours after denervation. These data are discussed against the background of previous results from this laboratory on denervated newt limb regenerates.
Interactions between irradiated and unirradiated tissues during supernumerary limb formation in the newt
Authors: Holder Nigel , Bryant Susan V. , Tank Patrick W. 
Published: June 2005

AbstractThe interactions between irradiated and unirradiated blastemas and stumps in the newt forelimb were studied. Irradiated right blstemas at the stage of early digits were grafted to unirradiated left stumps and unirradiated left blastemas were grafted to irradiated right stumps. Grafts were oriented with their anterior‐posterior axes opposed to that of the stumps. Supernumerary limbs ranging in completeness from one to four digits were found to arise predominantly on the anterior or posterior sides of the host limb. The graft developed well when the blastema was unirradiated and had reversed handedness with respect to the stump. Irradiated grafts developed poorly. On occasions, limbs with two supernumerary structures were found. The results are discussed in terms of the origin of the cells which comprise the supernumerary limbs and their bearing on a recently presented model concerned with pattern specification and regulation in epimorphic fields.
DNA polymerase activity in preimplantation mouse embryos
Authors: Kiessling A. A. , Weitlauf H. M. 
Published: June 2005

AbstractDNA polymerase activity was measured in mouse embryos at stages before implantation to determine whether it increases in proportion to the amount of DNA synthesis, as it does in populations of differentiated mammalian cells, or remains constant, as it does in early sea urchin embryos. Total enzyme activity was found to be relatively unchanged following fertilization and in the first few cleavage stages. However, between the 12‐ and 120‐cell (blastocyst) stage, the amount of activity increased by several‐fold. These results indicate that the relationship between amount of DNA polymerase activity and DNA synthesis in mouse embryos exhibits two phases: in the early cleavage phase it is similar to that in sea urchin embryos, whereas, in the blastocyst phase, it is similar to that in differentiated mammalian cells.
Surface contractile activity of the Tubifex egg: Its relationship to the meiotic apparatus functions
Authors: Shimizu Takashi 
Published: June 2005

AbstractThe dependence of surface contractile activity (deformatin movement: DM) on the meiotic process in the fertilized Tubifex egg was examined with colchicine and dinitrophenol (DNP). The normal DM occurred at the time of the formation of the first and second polar bodies, during which the egg shows groove‐forming activity on the surface of the animal hemisphere and the equatorial regions. Grooves invariably appeared first on the equatorial surface, then on the animal hemisphere. A scanning electron microscopic observation revealed that the surface deformation of the animal hemisphere began concurrently with the appearance of proximal constriction of the cytoplasmic bulge for the polar body.DNP of 2.5 × 10−5 M did not disturb the meiotic process but inhibited equatorial grooving. The animal hemisphere grooving in these eggs took place on the same schedule as for normal eggs. The number of microfilaments per unit area of the egg surface apparently decreased after DNP‐ treatment; the organization of microfilaments in the cortical layer was more heavily influenced at the equaorial region than in the animal hemisphere. Colchicine of 4 × 10−3 M destroyed the meiotic apparatus and completely prevented the grooving of the animal hemisphere. The equatorial grooving proceeded normally in these colchicine‐treated eggs. From these results, it is strongly suggested that there are regional differences in the contractile mechanism of the egg surface and that the animal hemisphere grooving is closely related to the presence of the meiotic apparatus while the equatorial grooving is independent of it.
Antibodies against invertebrate actin: Their phylogenetic cross‐reactivity
Authors: Kleve Maurice G. , Fuseler John W. , Clark Wallis H. 
Published: June 2005

AbstractInvertebrate muscle actin was extracted from penaeid shrimp tail muscle and purified by self‐assembly polymerization. Further purification for use as an antigen was accomplished by SDS polyacrylamide gel electrophoresis. Antibodies to highly purified shrimp tail muscle actin were produced in rabbits and were collected as an ammonium sulfate gamma globulin fraction from sera. These antibodies, which cross react with native actin, SDS denatured actin, and formalin fixed actin were successfully used to immunofluorescently label actin in cells. Actin in muscle and non‐muscle cell types from species of five invertebrate phyla and numerous species of vertebrates were labeled with no apparent difference in antibody specificity or sensitivity. These results suggest that the immune identity of the actin molecule is conserved over the span of the phylogenetic tree.
Pineal involvement in the control of circadian rhythmicity in the lake chub, Couesius plumbeus
Authors: Kavaliers Martin 
Published: June 2005

AbstractRemoval of the pineal organ from the lake chub, Couesius plumbeus, had significant effects on circadian locomotor activity. In fish kept in continuous darkness the absolute length of the circadian period was significantly altered; the variability of the period was increased; and ultradian rhythms were eliminated. These findings indicate that the pineal organ is involved in the control of circadian rhythmicity in this teleost fish.
Biochemical studies of the hatching process in sea urchin embryos. I. Effects of protease inhibitors
Authors: Hoshi Motonori , Moriya Tsuneo , Aoyagi Takaaki , Umezawa Hamao 
Published: June 2005

AbstractEffects of 12 protease inhibitors both on the hatching process and on the activity of the hatching enzyme of the sea urchins, Hemicentrotus pulcherrimus and Strongylocentrotus intermedius, were studied. Synthetic inhibitors, N‐tosyl‐L‐phenylalanyl‐chloromethane (often called tosylphenylalanine chloromethylketone; TPCK), N‐α‐tosyl‐L‐lysyl‐chloromethane (often called tosyllysine chloromethylketone; TLCK), p‐nitrophenyl p'‐guanidinobenzoate (NPGB), diphenylcarbamyl chloride (DPCC) and phenylmethane sulfonyl fluoride (PMSF), caused cytolysis of embryos, whereas the microbial inhibitors, chymostatin, leupeptin, antipain, pepstatin, elastatinal and phosphoramidon, and soybean trypsin inhibitor did not. Among them, the inhibitors specific against chymotrypsmsy chymostatin and TPCK, delayed the hatching process and inhibited the hatching enzyme. NPGB also inhibited the enzyme but its effect on the hatching process was uncertain because of its general toxicity to embryos. Esterolytic hydrolysis of N‐acetyl‐L‐tyrosine ethyl ester (ATEE) by a crude preparation of the enzyme was found.The evidence presented suggests that the hatching enzyme of sea urchins is similar to chyrmotrypsin.
Inhibition of desmosome formation in chick cell aggregates
Authors: Overton Jane 
Published: June 2005

AbstractDesmosomes (macula adherens) have been associated with the function of adhesion. Their possible role in aggregation and sorting of chick and mouse epithelial cells has been investigated. Treatment of aggregates with 2–5 μg/ml of actinomycin D which inhibited RNA synthesis also inhibited both desmosome formation and aggregation if administered at the beginning of the aggregation process. In contrast, if the drug was administered at six hours, when the cells had recovered from the process of dissociation, then aggregation over the following six hours appeared normal from observation of living samples. Such aggregates incorporated leucine‐3H at roughly 85% of the control level. A quantitative comparison was made of desmosome formation in aggregates treated with actinomycin D for hours 6–12 and those cultured in normal medium. Desmosome formation was inhibited by the drug, although aggregation could proceed. Combinations of chick corneal and mouse skin cells sorted out in the presence of actinomycin D to the same extent as controls. Thus desmosome formation, which normally occurs during aggregation of the epithelial cells studied here, is not coupled with the aggregation or cell sorting process in these cells of stratified epithelia. When cells were treated with cycloheximide (100 μM) both desmosome formation and the progressive rounding up of aggregates was inhibited.
Evidence for a broadly‐specific, amino acid requiring dehydrogenase at the pyruvate branchpoint in sea anemones
Authors: Ellington W. Ross 
Published: June 2005

AbstractThe tissues of a number of species of sea anemones contain an enzyme(s) capable of oxidizing NADH in the presence of pyruvate and either L‐arginine or L‐alanine. The activities using either amino acid coelute on Sephadex G‐100 and DEAE‐Sephadex −50 columns. In addition, the peak DEAE‐Sephadex fractions utilize other amino acids including glycine, lysine and threonine. The above catalytic activities may be due to a single, broadly‐specific enzyme.
Some peripheral auditory characteristics of the marsupial brush‐tailed possum, Trichosurus vulpecula
Authors: Aitkin L. M. , Gates G. R. , Kenyon C. E. 
Published: June 2005

AbstractSome anatomical and physiological aspects of the peripheral auditory system were examined in anesthetized brush‐tailed possums (Trichosurus vulpecula) and compared with those in the cat. Cochlear microphonic potentials (CM) in response to tones of varying frequency and intensity were recorded at the round window.The cochlea of Trichosurus has a typically mammalian appearance, with three and one‐half turns and a basilar membrane approximately 17 mm in length upon which sit three rows of outer and one of inner hair cells. Three middle ear ossicles, including a delicate stapes of columelliform appearance, are housed in a cavity adjacent to a spongy mass of bone. The latter surrounds the round window and is quite unlike the bullae of many eutherian mammals.Round window recordings revealed that CM potentials of the possum rarely attained magnitudes, for any tone, in excess of 500 μV and were always 10–25 dB less in amplitude than CM of the cat at a given frequency and intensity. The threshold intensities required to elicit a 50 μV CM at frequencies between 0.4 kHz and 10 kHz were smaller for the cat than the possum, but a slightly greater sensitivity was shown by the possum between 0.1 kHz and 0.4 kHz.Peripheral auditory characteristics of the marsupial brush‐tailed possum thus appear to have some features in common, and others at variance, with commonly‐studied placental mammals.
Acute and chronic hypoxia in rats. II. Effect on oxidative phosphorylation and in vitro protein synthesis in liver mitochondria and its subpopulations
Authors: Pickett Cecil B. , Cascarano Joseph 
Published: June 2005

AbstractThe objective of this investigation was to examine liver mitochondrial functions in rats exposed to 0.4 atm for 0, 5 and 27 days. Liver homogenates were fractionated by rate‐zonal centrifugation utilizing iso‐osmotic Ficoll‐sucrose gradients; this eliminates loss of large and small mitochondria and makes possible the separation of mitochondria into subpopulations according to sedimentation coefficient. After pooling all mitochondrial fractions for obtaining composite determinations of the entire population, large diminutions in states 3 and 4 respiration (succinate as substrate) were obtained in day‐5 and day‐27 rats but no changes were evident with regard to ADP:O ratios, respiratory control indices or the capacity for in vitro protein synthesis. By examination of subpopulations of mitochondria, it was found that mitochondria are heterogeneous with regard to ADP:O ratios, respiratory control indices, states 3 and 4 respiration and the capacity for in vitro protein synthesis. The heterogeneity for each of these parameters was altered in day‐5 and day‐27 animals. Although states 3 and 4 respiration were depressed throughout the entire mitochondrial population for day‐5 and day‐27 rats, a subpopulation of mitochondria from day‐27 rats showed respiratory control indices and ADP:O ratios which were higher than any subpopulation of mitochondria of either day‐5 or day‐0 animals.
Interaction between normal and pigment cell populations mutant at the diominant‐spotting (W) and steel(Sl) loci in the mouse
Authors: Mayer Thomas C. 
Published: June 2005

AbstractThrough the use of dermal‐epidermal recombination methods a competition between mouse embryo melanoblasts of the genotype Wν/w C/C, w/w c/c, Sld/sl C/C and sl/sl c/c was established. Control combinations were made between C/C and c/c components. The extent of pigment found in hair of grafts after three weeks growth in mouse testes was used as evidence of an interac‐tion between populations. Normal and albino melanoblasts were found to be similar in viability, whereas melanoblasts of the genotype Wν/w C/C were largely excluded from hair follicles when placed in competition with w/w c/c melanoblasts. No difference in competitive advantage was observed between Sld/sl C/C and sl/sl c/c populations. These results confirm that the W and S1 loci act at different sites. In addition they suggest that Wν/w melanoblasts are marginally viable cells that cannot compete with normal melanoblasts when the populations interact. The Wν/w melanoblast failure can also explain the spotting pattern and pigment dilution characteristic of dominant‐spotting heterozygous mice.