bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pattern regulation during regeneration of limb stumps bearing partial circumferences of flank skin in the newt, Notophthalmus viridescens
Authors: Tank Patrick W. 
Published: June 2005

AbstractThe regenerative ability of limb stumps bearing partial circumferences of flank skin was tested in the newt, Notophthalmus viridescens. Skin dorsal to the lateral line of the flank was removed and used to replace 1/4, 1/2, or 3/4 of the skin of the upper forelimb. Grafts were placed at anterior, posterior, dorsal, or ventral positions relative to the axes of the limb. After 30 days of graft healing the limbs were amputated through the grafts and were permitted to regenerate for 60 days. Limb stumps bearing 1/4 circumference of flank skin regenerated complete limbs in 85% of the experimental cases. After 1/2 circumference of limb skin was replaced, 57% regenerated complete limbs. When 3/4 of the limb skin was replaced by flank skin, 29% regenerated complete limbs. Only 2% of experimental limbs bearing a full circumference of flank skin regenerated complete limbs in an earlier study [Tank, P.W. (1984) J. Exp. Zool., 229:143–153]. The greatest effect on pattern formation was observed when flank skin grafts were placed at the ventral position of the limb stump regardless of graft size. These results are discussed in light of the idea that short‐range cellular interactions between limb cells are essential for pattern formation during limb regeneration.
Putative extraocellar photoreceptors in the outer nerve ring of Polyorchis penicillatus
Authors: Satterlie Richard A. 
Published: June 2005

AbstractPutative sensory cells have been described in the outer nerve ring of the hydrozoan jellyfish Polyorchis penicillatus that resemble ocellar photoreceptors characteristic of this animal group. Each receptor cell bears an apical structure consisting of verticillate lamellae representing evaginations of ciliary membranes (9 + 2 axonemes). Verticils are grouped in clusters of three or more and are distributed throughout the outer nerve ring. Individual lamellae of each verticil are up to 0.2 μM wide and are frequently reflexly folded to form a tightly packed whorl. Multiple axonemes contribute to each verticil. Each receptor cell body contributes a single axon (up to 1.75 μm in diameter) to the neuronal tracts of the outer nerve ring. The structural similarity between the described cells and hydrozoan photoreceptors, and the close agreement between the location of these cells and the localized photoresponse in Polyorchis and related medusae suggest that the putative receptor cells function as photoreceptors.
Effect of hypoxic hypoxia on taurine concentrations in ventricles of mouse hearts
Authors: Eldridge Stuart A. , Hilton Fredrick K. , Hilton Mary A. 
Published: June 2005

AbstractThe effect of hypoxic hypoxia on the concentration of taurine in right ventricles was studied in the hearts of male CF1 mice caged individually and maintained for 16 hr per day in a hypobaric chamber evacuated to an air pressure of 307 mm Hg. After 23 days hearts were excised and right and left ventricles were separated and lyophilized. Hematocrits in chamber animals were 77‐82%, compared to 45–49% for control mice. Mean weights of right ventricles of animals from the chamber were 11.2 ± 0.9, compared to control values of 7.0 ± 0.4, mg dry weight. The mean dry weights of left ventricles in both groups of animals were the same. There were no significant differences in the nmoles taurine per mg dry tissue in either heart chamber, with mean values ± S.E.M. of 124.0 ± 4.6 and 135.0 ± 4.5 in right ventricles and 128.0 ± 4.3 and 110.9 ± 15.3 in left ventricles of experimental and control animals respectively. Thus, hypertrophy which results from hypoxia is not accompanied by increased concentrations of taurine in right ventricles.
Kinetics of cell cycle entry in innervated and denervated forelimb stumps of larval Ambystoma
Authors: Barger Philip M. , Tassava Roy A. 
Published: June 2005

AbstractPulse and continuous labeling with 3H‐thymidine were used to examine the kinetics of cell cycle entry and progression in innervated, regenerating and denervated, nonregenerating limbs of larval axolotls. In innervated limbs the labeling index (LI) increased from a relatively low level after a pulse (30%) to 60% and 80% after 26 and 50 hr, respectively, of continuous labeling, at both preblastema and blastema stages. Thus a considerably larger proliferative fraction was revealed by continuous labeling data than was predicted from pulse labeling data. Much cycling heterogeneity was shown to exist in the blastema cell population, primarily in the G‐1 phase. These results show that many cells of regenerating limbs are transiently quiescent for periods of up to and perhaps longer than 50 hr. The proliferative fraction in denervated limbs on days 4‐6 postamputation was somewhat less than that of innervated limbs but also larger than predicted from pulse labeling data. The data show that most of the dedifferentiated cells enter the proliferative fraction even in the absence of nerves. Most of these initially cycling cells subsequently leave the proliferative fraction; the LI was less than 20% even after 50 hr of continuous labeling on days 8–10 postamputation.
Experimental analysis on the capacity of several larval tissues to promote lens‐forming transformations in the cornea of Xenopus laevis Tadpoles
Authors: Bosco Luigi , Filoni Sergio , Cioni Carla 
Published: June 2005

AbstractFragments of iris ring, spleen, kidney, tail, tail blastema, tentacle, tentacle blastema, and spinal cord were implanted between the outer and the inner cornea in normal eyes of Xenopus laevis tadpoles at stage 50 (according to Nieuwkoop and Faber, '56).Results show that tail blastema, tentacle blastema, and spinal cord can induce varying degrees of lens‐forming transformations in the outer cornea, while the iris ring, spleen, kidney, tail, and tentacle do not produce any significant response from the cornea, thus demonstrating that the lens‐inducing capacity is not widely distributed in the larval tissues of Xenopus.The causes of the different degrees of lens‐inducing capacity in the various larval tissues are discussed.
Electron microscopic observations on sperm entry into eggs of the bitterling during cross‐fertilization
Authors: Ohta Tadayuki 
Published: June 2005

AbstractIn the cross‐fertilization of the two bitterlings Acheilognathus lanceolata (spermatozoa) and Rhodeus ocellatus ocellatus (eggs), the morphology of the gametes and the process of sperm entry were observed using transmission and scanning electron microscopy (TEM and SEM). The spermatozoon (total length, about 30 μm) had a round head (about 1.8 μm), two centrioles, a single large mitochondrion, and a flagellum. The micropyle of the egg did not permit simultaneous passage of two spermatozoa. The chorion was mainly composed of an outer and an inner layer and progressively decreased in thickness away from the vicinity of the micropyle where it was thickest. Filamentous structures were observed in microplicae and microvilli on the egg cortex. After a fertilizing spermatozoon attached to the specialized sperm entry site, it appeared to be incorporated into the egg by membrane fusion. At this time the site swelled and plugged the micropyle. The swollen cytoplasm appeared to be a fertilization cone which did not retract in this fish. With the advance of the cortical change, the egg cytoplasm was detached from the chorion except in the area of and around the sperm entry site. About 20 min after insemination, the egg cytoplasm devoid of cortical alveoli was torn away from the other cytoplasm and adhered to the inside of the chorion. These observations showed that the process of sperm entry in cross‐fertilization was similar to that in homologous fertilization of R. ocellatus.
Extracellular localization of cyclic GMP in the house cricket male accessory reproductive gland and its fate in mating
Authors: Murtaugh Michael P. , Kapoor C. Lal , Denlinger David L. 
Published: June 2005

AbstractThe male accessory reproductive gland (ARG) of the house cricket, Acheta domesticus (L.), contains an exceedingly high concentration of cyclic GMP, about 1,000 pmol/mg protein. Immunofluorescent localization and radioimmunoassay measurements show that cyclic GMP is concentrated in a small number of tubules. It accumulates in the tubule lumina where it is protected from degradation by phosphodiesterases. Cyclic GMP is secreted by the ARG and is incorporated into spermatophores. Over 80% of spermatophore cyclic GMP is found in the handle‐capillary tube, a thin conduit through which sperm pass during transfer to the female. The concentration of cyclic GMP in the insemination fluid is about 20 μM but does not appear to be specifically associated with the sperm. Cyclic GMP enters the female spermatheca during insemination but disappears rapidly. Physiological effects of cyclic GMP on sperm were not observed nor was an effect of cyclic GMP observed on egg laying by mated females. Cyclic AMP was localized on sperm flagella in the spermatophore and in the spermatheca. These studies indicate that cyclic nucleotides have important roles in insect reproduction and that the house cricket is a good model for elucidating these functions.
Cross fertilization in vivo and in vitro between three species of vesper mice, Calomys (Rodentia, Cricetidae)
Authors: Roldan E. R. S. , Vitullo A. D. , Merani M. S. , Von Lawzewitsch I. 
Published: June 2005

AbstractCross fertilization was tested between oocytes of Calomys callidus and spermatozoa from C. callidus, C. musculinus and C. laucha by both in vivo and in vitro insemination. After in vivo and in vitro insemination, respectively, percentages of oocytes fertilized were 68.8 and 46.6 (C. callidus × C. callidus), 20.3 and 12.7 (C. callidus × C. musculinus), 26.7 and 4.3 (C. callidus × C. laucha). Thus, the percentages obtained after in vitro insemination were always lower than those obtained with in vivo insemination. It was found that 23.9% and 44.4% of two‐cell hybrid embryos were present in oviducts 30 hr after in vivo insemination of C. callidus females with C. musculinus or C. laucha spermatozoa, respectively. At a later stage (56 hr postinsemination), development did not progress further, and abnormal embryos were found both at 30 and 56 hr postinsemination, suggesting some kind of cleavage arrest or degeneration of the embryos. We suggest that fertilization is not strictly species‐specific, at least among the species we studied, but that there are some factors that reduce the efficiency of interspecific fertilization.
Developmental mutants isolated from wild‐caught Xenopus laevis by gynogenesis and inbreeding
Authors: Krotoski Danuta M. , Reinschmidt Dana C. , Tompkins Robert 
Published: June 2005

AbstractXenopus laevis obtained from indigenous African populations are a rich source of mutants affecting development. Gynogenesis and inbreeding were used to isolate mutants affecting development from wild‐caught Xenopus laevis females. Fourteen mutants were recovered from eight females tested. One mutant was recovered from each of two females. This load of 1.875 developmental mutants per female is similar to that found in the axolotl (Ambystoma mexicanum), a urodele amphibian, and is only slightly less than the load of mutants with major developmental effects found in Drosophila and man. These results suggest that the anuran amphibian Xenopus laevis, an ancestrally tetraploid species, has undergone extensive diploidization of developmentally important loci and that gynogenesis and inbreeding of wild‐caught animals can provide adequate mutants at diploid loci for developmental genetic studies.
Effects of exposing Drosophila melanogaster parents to ethanol on expression of vestigial in their progeny
Authors: Giesel James T. , Niemann Mark M. 
Published: June 2005

AbstractWhen parental Drosophila melanogaster were chronically exposed at 28°C or 24°C to ethanol during their larval and pupal stages of development, their progeny, produced when parents were 5–16‐day‐old adults, showed modified expression of vestigial alleles in heterozygous and homozygous combinations. Parental alcohol effects were dependent on parental rearing temperature. We conclude that parental environment (alcohol, temperature) causes heritable but transitory changes in progeny phenotype that are elicited by exposure of germ cells to alcohol.
Inverse effects of ethidium bromide on superoxide dismutase and lactate dehydrogenase of Artemia salina embryos
Authors: Bremner Theodore A. , Edwards Kimberly A. 
Published: June 2005

AbstractDevelopment of Artemia salina embryos in the presence of ethidium bromide, an inhibitor of mitochondrial transcription, results in a dose dependent increase in the specific activity of lactate dehydrogenase, and a concomitant decrease in the specific activity of a cyanide‐resistant superoxide dismutase. The inhibition of mitochondrial function by ethidium bromide appears to exert opposite effects on the nuclear cistrons encoding lactate dehydrogenase and superoxide dismutase, and suggests that a common mitochondrial signal may exert diametric effects on nuclear cistrons whose products are characteristic of alternate states of respiration.
Organic matrixlike macromolecules associated with the mineral phase of sea urchin skeletal plates and teeth
Authors: Weiner Stephen 
Published: June 2005

AbstractThe skeletal plates and teeth of the echinoid Paracentrotus lividus contain a heterogeneous assemblage of macromolecules that are not part of the connective tissue, but are presumably intimately associated with the mineral phase. Upon dissolution of the Mg‐calcite mineral phase, some of these molecules are insoluble. The insoluble fractions of the teeth and skeletal plates are quite different, the former being predominantly protein and the latter, primarily some unknown nonproteinaceous material. The soluble constituents are similar in both tissues. These hydrophilic macromolecules have been partially separated and characterized. In both hard parts, two distinct classes of macromolecules are present, as indicated by the amino acid compositions of their protein constituents. These two classes of macromolecules are also present in the shells of a foraminifer and in various mollusks, both of which are formed by the “organic matrix‐mediated” biomineralization process. The locations of these macromolecules in the teeth and skeletal plates are not known, nor whether they form coherent structures. It is therefore premature to conclude that these macromolecules do function as an organic matrix, although the results presented are in agreement with such an interpretation.
Heterogeneity of myofibrillar proteins in lobster fast and slow muscles: Variants of troponin, paramyosin, and myosin light chains comprise four distinct protein assemblages
Authors: Mykles Donald L. 
Published: June 2005

AbstractFast and slow muscles from the claws and abdomen of the American lobster Homarus americanus were examined for adenosine triphosphatase (ATPase) activity and for differences in myofibrillar proteins. Both myosin and actomyosin ATPase were correlated with fiber composition and contractile speed. Four distinct patterns of myofibrillar proteins observed in sodium dodecyl sulfate‐polyacrylamide gels were distinguished by different assemblages of regulatory and contractile protein variants. A total of three species of troponin‐T, five species of troponin‐I, and three species of troponin‐C were observed. Lobster myosins contained two groups of light chains (LC), termed “alpha” and “beta.” There were three α‐LC variants and two β‐LC variants. There were no apparent differences in myosin heavy chain, actin, and tropomyosin. Only paramyosin showed a pattern completely consistent with muscle fiber type: slow fibers contained a species (105 kD) slightly smaller than the principle variant (110 kD) in fast fibers. It is proposed that the type of paramyosin present could provide a biochemical marker to identify the fiber composition of muscles that have not been fully characterized. The diversity of troponin and myosin LC variants suggests that subtle differences in physiological performance exist within the broader categories of fast‐ and slow‐twitch muscles.
Neural fold and neural crest movement in the mexican salamander Ambystoma mexicanum
Authors: Brun Rudolf B. 
Published: June 2005

AbstractIn studies of amphibian neurulation, the terms “neural ridge,” “neural fold,” and “neural crest” are sometimes used as synonyms. This has occasionally led to the misconception that grafting of the neural crest is equivalent to grafting of the neural fold. The neural fold, however, is composed of three parts: the neural crest, prospective neural tube tissue, and epidermis. In order to investigate how these neural fold components move during neurulation, time‐lapse photography, electron microscopy, and grafting were performed. Ambystoma mexicanum embryos were photographed during neurulation at regular intervals. The photographs were analyzed to find the position of those cells at beginning of neurulation that end up on the line of fusion as the neural folds close. Posteriorly, these cells are already on the emerging neural fold. In the anterior neural folds, however, these cells are located in the lateral epidermis. Electron microscopy of the neural folds confirms the presence of epidermis. To follow the movement of the cells differentiating into melanophores (neural crest), neural fold parts were grafted into albino hosts. The crest cells differentiating into melanophores following ectopic grafting are located in the flank of the neural fold that is in contact with the neural plate. In grafts from the outside (distal) flank, no melanophores developed. Semithin sections show that the third part of the neural fold consists of apically constricted cells known to differentiate into neural tissue. Because the neural folds consist of epidermis, neural tissue, and neural crest, neural fold and neural crest cannot be used as synonyms.
An egg envelope component induces the acrosome reaction in sturgeon sperm
Authors: Cherr Gary N. , Clark Jr. Wallis H. 
Published: June 2005

AbstractThe acrosome reaction in Acipenser transmontanus sperm can be induced by a 66,000 dalton glycoprotein that is present in Layer 3 (L3) of the egg envelope and in egg water only following exposure of the eggs to fresh water. When egg water is fractionated on Sepharose CL 6B, the 66,000 dalton glycoprotein‐containing fractions possess acrosome reaction inducing activity. Egg water may be species‐specific in its ability to elicit the acrosome reaction, as demonstrated by the fact that it has no effect on the sperm of Acipenser fulvescens. Egg jelly possesses no acrosome reaction, inducing activity. The major carbohydrate‐containing component of the egg envelope is L3, a layer that contains galactose residues. L3 possesses a 70,000 dalton glycoprotein prior to freshwater exposure and lacks the 66,000 dalton component. If isolated from polyacrylamide gels, the 70,000 dalton glycoprotein elicits acrosome reactions in what appears to be a species specific manner. After freshwater exposure, L3 contains both the 70,000 dalton glycoprotein and the 66,000 dalton glycoprotein that is also present in egg water. The appearance of the 66,000 dalton inducer can be blocked by the incubation of eggs in fresh water containing inhibitors of trypsin activity. Thus, the soluble inducer in egg water may be proteolytically derived from a higher molecular weight complex in the egg envelope.
Placental lactogen secretion in the mouse: In vitro responses and ovarian and hormonal influences
Authors: Soares Michael J. , Talamantes Frank 
Published: June 2005

AbstractIn vivo and in vitro methodologies were utilized to study the regulation of placental lactogen (PL) secretion in the mouse. Chorioallantoic placental explants obtained from midpregnant (day 10 of gestation) C3H/HeN or Swiss Webster mouse conceptuses behaved differently in culture than explants of chorioallantoic placentas obtained later in pregnancy. Midpregnant placental explants maintained or showed an increasing amount of PL output per day for 5–6 days of culture, while gestationally older placental explants demonstrated a progressive decline in PL output per day over the 5–6‐day culture period. On selected days of gestation, bilaterally ovariectomized C3H/HeN or Swiss Webster mice were shown to have significantly higher serum PL concentrations than sham operated mice. Reduction of serum progesterone concentrations by unilateral ovariectomy and/or partial lutectomy had no significant effect on serum PL concentrations. Progesterone significantly reduced PL production by midpregnant placental explants from both C3H/HeN and Swiss Webster mice, whereas 17 β‐estradiol did not significantly affect PL release in vitro. PL production by mouse chorioallantoic placentas has gestational specific characteristics in vitro and is responsive to regulatory influences of the maternal ovaries and progesterone.
Regulation in the neural plate ofXenopus laevisdemonstrated by genetic markers
Authors: Szaro Ben , Ide Charles , Kaye Cynthia , Tompkins Robert 
Published: June 2005

AbstractTo follow the subsequent history of grafted tissue in experiments designed to study regulation and commitment in the amphibian neural plate, previous workers have relied on graft scars, vital dyes applied externally to cells, or xenoplastic grafts. Each of these methods has been criticized on the grounds that they do not indicate unambiguously the origins of individual cells within the operated host. To overcome these difficulties, homoplastic, genetically marked embryonic grafts were taken from the prospective spinal neuroectoderm of triploid and tetraploidXenopus laevisfrogs and transplanted to presumptive eye and prosencephalic regions of the neural plate of diploidX. laevisembryos. Orthotopic presumptive eye grafts also were done. Marked cells were scored in section either by nucleolar number or computerized nuclear size analysis. Of 28 heterotopically grafted embryos that survived to stage 41, when the retina has differentiated, prospective spinal cord neuroectoderm in eight animals gave rise to cell types unique to the eye. The remaining 20 survivors appeared to be mosaic. These results substantiate claims of regulation in the neural plate and extend these observations to the level of individual cell types, a level of resolution not previously obtained in other studies.