bluuebunny/crossref_metadata_2025_split huggingface dataset:
Oogenesis in Xenopus laevis (Daudin) VI. The route of injected tracer transport in the follicle and developing oocyte,
Authors: Dumont J. N. 
Published: June 2005

AbstractIn Xenopus laevis, vitellogenin (the yolk precursor) is synthesized in the liver and transported via the circulatory system to the ovary. In order to reach developing oocytes where it is sequestered, it must exit the circulatory system and traverse several follicular tissue layers including the theca, the follicle cell layer, and the vitelline envelope. This study demonstrates this pathway by means of electron‐opaque tracers, and follows the fate of heterologous macromolecules after their incorporation into the ooplasm. The tracers used were horseradish peroxidase, iron dextran, ferritin, and thorotrast. The bulk of the tracers exit the circulatory system through gaps between adjacent capillary endothelial cells and migrate into the connective tissue theca, where they appear randomly dispersed. All tracers, except thorotrast, penetrate the basement membrane on the distal surface of the follicle cells and pass through channels between adjacent follicle cells into the vitelline envelope and to the surface of developing oocytes, where they are incorporated by endocytosis. Endosomes which contain tracer, and also presumably vitellogenin, fuse to form primordial yolk platelets. During this fusion process an extensive network of smooth‐surfaced tubules arises in the peripheral ooplasm. Endosomes and/or primordial yolk platelets continue to fuse with each other, resulting in the growth of primordial platelets which move deeper into the ooplasm, where they are transformed into yolk platelets with crystalline main bodies. Peroxidase and iron dextran remain in the superficial layer of the platelet, while ferritin is present in both the superficial layer and the crystalline main body.
Quantitative behavioral studies of misdirected responses in skin‐grafted Rana pipiens
Authors: Heidemann Merle Knudson 
Published: June 2005

AbstractThe experiments reported here describe quantitatively wiping responses elicited from three equal body sections of adult Rana pipiens having had one of two types of skin‐graft operations as tadpoles. These experiments assessed the development of abberant wiping responses in individuals and populations of grafted animals. Grafting parameters critical for the development of aberrant wiping responses were also determined. These studies indicated that the phenomenon of “misdirected responses” and the extent of these responses is highly variable among grafted individuals and between different populations of grafted animals. In addition, the development of “misdirected responses” is independent of premetamorphic stimulation and of a critical grafting period. The pro‐portion of “misdirected responses” elicited upon cutaneous stimulation of individuals appears to be stable and predictable after metamorphosis. “Misdirected responses” could be elicited from animals with grafts including over 40% of the trunk skin. Wiping responses and grafting parameters of skin‐grafted R pipiens in other studies are also presented and possible sources of interstudy variation discussed.
Light‐sensitive fish melanophores in culture
Authors: Wakamatsu Yuko 
Published: June 2005

AbstractDermal melanophores in the skin from embryos and young fishes of the black platy fish, Xiphophorus maculatus, were dissociated and cultured in a monolayer. Melanosomes in the melanophores were dispersed in culture. Some of the cultured melanophores directly responded to light by producing reversible melanosome aggregation within a few minutes. A dose‐response relationship was found between light intensity and time required for melanosome aggregation.
The failure of double‐half forelimbs to undergo distal transformation following amputation in the axolotl, Ambystoma mexicanum
Authors: Tank Patrick W. 
Published: June 2005

AbstractAlthough capable of initiating early regenerative responses, axolotl forelimb stumps which are composed of double‐half limb tissues fail to undergo the events that normally lead to the replacement of missing parts. In the present study, the posterior halves of right forelimbs were exchanged with the anterior halves of left forelimbs, or the dorsal halves of right forelimbs were exchanged with the ventral halves of left forelimbs. Forelimbs were amputated through the graft region 30 days after grafting. Limb stumps bearing double‐dorsal, double‐ventral or double‐posterior tissues either produced hypomorphic regenerates or failed to form any externally visible outgrowth. When the limb stump bore double‐anterior tissues, no externally visible structures were formed. Normal and multiple regenerates were never formed by double‐half limbs. These results are discussed in terms of the polar coordinate model and suggest that the regeneration blastema requires a complete circumference of positional values in order to complete distal transformation.
Seasonal effects on osmotic permeability of Rana pipiens in vivo and in vitro
Authors: Parsons Robert H. , Brady Robert , Goddard Bryan , Kernan Donald 
Published: June 2005

AbstractDependence on season of the osmotic water permeability (Lp) of the skin of whole frogs and isolated preparations of frog leg and abdominal skin have been determined. The Lp of frog skin in vivo and in vitro increases during the summer. However, the increase in vivo occurs in April while the increase in vitro does not occur until August. Injection of arginine vasopressin (ADH) into whole frogs in July produces a 200% increase in the osmotic water permeability, while the same injection in March induces only a slight increase. Isolated abdominal skin shows a similar effect upon stimulation by 500 mU/ml of ADH: a large increase in July with a barely detectable effect in March. Isolated leg skin does not show a response to this level of vasopressin either in July or March. The possibility that seasonal changes in the osmotic permeability of whole animals can be attributed to seasonal variations in sensitivity to ADH is discussed.
Mammalian pyruvate kinase hybrid isozymes: Tissue distribution and physiological significance
Authors: Cardenas Janet M. , Dyson Robert D. 
Published: June 2005

AbstractThe purpose of this study was to examine the pyruvate kinase isozymic patterns of a wide variety of tissues from rats and mice, particularly regarding hybrid isozymes. For these studies, we employed longer electrophoresis times than used in most earlier studies in order to improve the resolution of closely spaced bands. The tissue distributions of types K, L, and M pyruvate kinases were found to be approximately the same as those reported earlier for rats and other mammals. In addition, K–M hybrids could be detected in most tissues examined in relative quantities which differed from one tissue to another in the same organism, in corresponding tissues from different species, and within a single tissue during development. Hybrid isozymes containing type L subunits occur in only a few tissues of either the fetus or the adult of either animal.In earlier studies utilizing L–M hybrid isozymes produced in vitro, we showed that the kinetic properties of a given subunit are profoundly affected by the nature of its neighbors within the tetramer (Dyson and Cardenas, ['73] J. Biol. Chem., 248: 8482–8488). Based on these altered kinetic properties, we suggest that there is little need for an organism to suppress completely the gene activity for one subunit type of pyruvate kinase during the synthesis of larger quantities of a second subunit type.
Induced formation of asters and cleavage furrows in oocytes of Xenopus laevis during in vitro maturation
Authors: Heidemann Steven R. , Kirschner Marc W. 
Published: June 2005

AbstractWe have previously reported that injection of purified basal bodies or sperm into unfertilized eggs of Xenopus laevis induced the formation of asters and irregular cleavage furrows. Fully grown oocytes were found to be unable to form asters or cleavage furrows. In this paper we show that the oocyte acquires the ability to form asters upon basal body injection at the time of germinal vesicle breakdown during in vitro maturation. Our evidence indicates that aster formation requires progesterone‐stimulated changes in the oocyte and mixing of cytoplasm and germinal vesicle plasm. The ability of the oocyte to form cleavage furrows arises six to eight hours after germinal vesicle breakdown. We infer that some maturational change in the cell cortex occurs to enable the egg surface to furrow. Experiments on the relationship of aster formation to furrow initiation indicates that asters stimulate furrow formation. However, some furrowing could be induced without aster formation in mature oocytes and unfertilized eggs by an activation stimulus, showing that asters are not essential for cleavage initiation. The significance of these observations are discussed in the light of our current understanding of meiotic maturation, cell cleavage and aster growth.
The possible influence of temporal factors in androgenic responsiveness of urogenital tissue recombinants from wild‐type and androgen‐insensitive (Tfm) Mice
Authors: Cunha Gerald R. , Lung Ben 
Published: June 2005

AbstractTissue recombinants of epithelium and stroma from embryonic and neonatal urogenital rudiments derived from wild‐type and femininized (Tfm/Y) mice were grown as grafts in intact male hosts and analyzed morphologically for androgenic response. When mesenchyme of embryonic wild‐type urogenital sinus (UGS) was associated with epithelium from embryonic wild‐type bladder (B), the epithelium developed into glandular structures resembling prostate. In the reciprocal recombinant (B mesenchyme + UGS epithelium) the response was mixed, half of the recombinants exhibited bladder morphology and half exhibited prostatic‐like morphology.Vaginal‐like histogenesis occurred in UGS recombinants of androgen‐insensitive Tfm/Y mesenchyme and wild‐type epithelium, while prostatic morphology developed in reciprocal recombinants of wild‐type mesenchyme and Tfm/Y epithelium. These observations demonstrate (1) that the presence of wild‐type mesenchyme appears essential for expression of androgen‐dependent morphogenesis during embryonic periods; and (2) that Tfm/Y epithelium is capable of participating in an androgenic response. Conversely, in similar recombinants prepared with neonatal tissues, the presence of wild‐type urogenital stroma may not be required for expression of certain androgen‐dependent phenomena since maintenance of the height and cytodifferentiation of ductus deferens epithelium occurs even when this epithelium is associated with Tfm/Y urogenital stroma. It appears, therefore, that the requirement of urogenital epithelium for wild‐type (androgen sensitive) stroma may vary temporally.
Biochemical and autoradiographic analysis of regeneration in two hydroids
Authors: Samuelson Marlene , Lesh‐Laurie Georgia E. 
Published: June 2005

AbstractPodocoryne carnea and Hydractinia echinata are organisms at a similar taxonomic level with different regenerative abilities. This investigation compared biochemical events following wounding of these organisms, and additionally examined autoradiographically the incorporation of macromolecular precursors into cells in the cut, proximal area of their gastrozooids.Although the non‐regenerating gastrozooids of both organisms incorporated little 3H‐thymidine into cells near the proximal tip, amputation provided a stimulus for cells in this area of both organisms to incorporate greater levels of this precursor. However, the level of stimulation of total incorporation into gastrozooids was substantially greater in Podocoryne. During regeneration, Podocoryne gastrozooids were stimulated to incorporate peak levels of 3H‐uridine into RNA at 6, 15 and 24 hours, whereas Hydractinia gastrozooids exhibited no peak levels of incorporation throughout the 27‐hour post‐wounding period. In the initial nine hours following wounding, Podocoryne gastrozooids were stimulated to much greater levels of incorporation of 3H‐leucine into protein over non‐regenerating gastrozooids than were Hydractinia polyps.Therefore, the results of this biochemical and autoradiographical investigation demonstrated that Podocoryne gastrozooids, which regenerate proximally, had substantially higher levels of stimulation of precursor incorporation into macromolecules during 27 hours following wounding than Hydractinia gastrozooids, which do not regenerate proximally. Additionally, when this level of incorporation was depressed by the use of inhibitors in Podocoryne polyps, they were unable to complete regeneration in the normal manner.
Studies on the regeneration of an entoproct, Barentsia discreta
Authors: Mukai Hideo , Makioka Toshiki 
Published: June 2005

AbstractRegeneration of a colonial entoproct, Barentsia discreta, was studied. In the colony, the stolon is subdivided into alternately arranged fertile and sterile sections by annular septa. The zooid consists of a stalk arising from the fertile section and an apical calyx; the stalk comprises a single “muscular node” at its base and a slender “rod.” In regeneration occurring after partial degeneration of a zooid, the following three types can be distinguished: calyx, rod and zooid regeneration. Double malformations of the calyx were obtained. The double calyx seems to result from calyx regeneration effected without loss of the original calyx. Amputations were made at various levels of the stalk and regeneration both from the cut stump and from the cut piece was observed. The rod can regenerate a calyx both apically and basally. The muscular node can regenerate a calyx apically but can not basally. In every regenerate, the original oral‐anal axis is retained. Continuous contact of calyces with glass slides induced the formation of a muscular node between the calyx and the rod. The stolon can regenerate distally from any site of the fertile or the sterile section, but can not regenerate proximally. Stolons with two serially arranged sterile sections were obtained when amputations were made at the proximal site of the fertile section.
The subcommissural organ of Lacerta s. sicula raf.: Effects of experimental treatments on castrated animals during winter
Authors: D'uva V. , Ciarcia G. , Ciarletta A. , Angelini F. 
Published: June 2005

AbstractThe AA. have studied the effects of testosterone administration and of temperature increase on the subcommissural organ (SCO) of Lacerta s. sicula Raf. castrated during the winter. Testosterone administered to specimens at environment temperature did not cause stimulation of the SCO. It was sufficient to raise the temperature to obtain stimulation. At 28° C the SCO of castrated animals was also stimulated, but after more time and less intensely than in normal animals.
Role of divalent cations in the resumption of meiosis of rat oocytes
Authors: Tsafriri Alexander , Bar‐Ami Shalom 
Published: June 2005

AbstractResumption of meiotic maturation was induced in follicleenclosed rat‐oocytes by treatment with the divalent cationophore A23187 (10−5M). However, the same effect was attained by incubation in Ca++ ‐ deficient medium, even in the presence of EDTA or EGTA (lmM). The stability of the first polar body was increased under Ca++ ‐deficient conditions. Neither the ionophore nor Ca++ ‐deficient medium interfered with the spontaneous maturation of isolated oocytes of the rat. The experiments with cultured follicles suggest that redistribution of divalent cations may participate in the physiological control of meiosis in mammalian oocytes.
Environmental influence on testicular activity in the green frog, Rana esculenta
Authors: Rastogi R. K. , Iela L. , Delrio G. , Di Meglio M. , Russo A. , Chieffi G. 
Published: June 2005

AbstractAdult male Rana esculenta were placed under several combinations of light and temperature in different periods of the year to elucidate the regulation of various testicular phases by environmental factors and to discover the mechanism through which these factors act upon the testis. In nature the quiescence of spermatogenesis in winter is due solely to low temperature. Under controlled experimental conditions a temperature of 4°C, whatever the photoperiod, impairs spermatogenesis at any time of the year. The early spring resurgence of a new wave of spermatogenesis depends upon a gradual rise both in the environmental temperature and the photoperiod. In fact in nature the temperature range favorable for active spermatogenesis is between 12°C, and 25°C with a period of between 10 and 16 hours of light daily. In the laboratory a temperature of ca. 20°C and a period of 12 hours of light daily represent the best combination of these factors for regulating and maintaining active spermatogenesis in any period of the year. Very long (21 hours of light daily) and very short (3 hours of light daily) photoperiods, however, have deleterious effects upon the testis. These effects are manifested mainly in the suppression of primary spermatocytes and successively in a gradual decline in number of secondary spermatocytes and spermatids and appearance of numerous degenerating cell nests. The same occurs when the frogs are treated at very low temperature. Besides this, high temperature stimulates plasma levels of testosterone which does not occur if the animals are kept in the dark. Very low temperature, on the other hand, has the opposite effect.These data suggest that a combination of “critical temperature” and “critical photoperiod” is necessary for regulating and maintaining active spermatogenesis since neither of these factors is effective in the absence of the other. The stimulatory effects of high temperature are due to the increased secretory activity of the pituitary gonadotropin.Furthermore the present results also indicate that the testis of Rana esculenta does not manifest any seasonal change in the degree of its response to thermal and/or photoperiodic regulation i.e., it does not show photo‐ or thermal refractoriness during the year.
The synthesis of melatonin by the trout retina
Authors: Gern William A. , Owens David W. , Ralph Charles L. 
Published: June 2005

AbstractTrout retinae were shown to contain melatonin, which was present in highest (p<.05) concentration during the photophase portion of a light‐dark cycle. Pinealectomy was found not to perturb either the rhythm or the titer of retina melatonin. These results suggest that the trout retina is a melatonin‐synthesizing tissue.
Chloride shift in fish blood
Authors: Cameron James N. 
Published: June 2005

AbstractWhen the physically dissolved CO2 is suddenly increased or decreased in whole blood of red snapper at 24° C, or rainbow trout at 14° C, the plasma Cl− falls or rises with a time constant of 0.35 or 0.40 sec, respectively. The reaction is completely blocked by the carbonic anhydrase inhibitor, acetazolamide. This “chloride shift” provides a rapid dehydration pathway for excretion of the CO2 bound as HCO3. These results would seem to contradict the theory that fish RBC's are impermeable to HCO.
Nerve trophic effects: An in vitro assay for factors involved in regulation of protein synthesis in regenerating amphibian limbs
Authors: Choo Alfred F. , Logan David M. , Rathbone Michel P. 
Published: June 2005

AbstractWe have developed a rapid sensitive test for factors that mimic the trophic effects of nerves by maintaining normal rates of protein synthesis in denervated forelimb blastemata of adult newts (Notophthalmus viridescens). Rates of protein synthesis in secondary blastemata are similar. However, after they are denervated and explanted into organ culture the rates of protein synthesis first increase and later fall below control values. Similar changes occur after denervation in vivo. The alterations in the rates of protein synthesis are prevented by adding to the culture medium aqueous extracts from brains of adult newts or chicken embryos. The active material is either a peptide or a protein.
Detrimental effect of visible light on meiosis of mammalian eggs in vitro
Authors: Hirao Y. , Yanagimachi R. 
Published: June 2005

AbstractShort wavelength visible light (<470–480 nm) emmitted from ordinary light sources is detrimental to unfertilized hamster eggs in that prolonged exposure to the light disturbs the completion of normal meiosis after the eggs are penetrated by spermatozoa. The fluorescent light commonly used in modern laboratories is more harmful than the light from incandescent lamps. In experiments involving the handling of eggs in vitro, minimal exposure to the light or the use of appropriate filters (e.g., red cellophane sheets) is recommended.
Homopolar grafting in Blepharisma japonicum
Authors: Kumazawa H. 
Published: June 2005

AbstractResults of homoplastic grafting in Blepharisma japonicum v. intermedium are described. The parabiotic homopolar fusion complex of two cells either simply splits into two singlets, or undergoes cell division. In the latter case the division results either in two doublets or in two singlets (proters) and a doublet (opisthe). If one or two of the systems of feeding organelles are removed after parabiotic homopolar fusion of two cells, the fusion complex does not split, but undergoes division. If an almost complete set of feeding organelles is lacking, the division of the graft complex usually results either in a singlet proter and a doublet opisthe or in two doublets. If two complete sets of feeding organelles have been excised from the graft complex, division occurs after the regeneration of the missing organelles, most frequently resulting in two doublets. The same operation on the graft complex with two primordium sites placed very close to each other may result in the regeneration of one normal and one reversed peristome, the latter being to the right of the former. The doublet biotypes derived from the graft complexes with or without further experimental changes usually reproduced true to type. The asymmetric doublet with two peristomes less than 180° apart tends to resorb the left peristome, that is, one with a larger left‐hand somatic area than the other. The asymmetric doublet may also form a third peristome on the right side of the original left peristome. The third peristome is usually of reversed asymmetry. That the appearance of the third primordium site might be due to the presence of the original line of fusion of two components of the doublet, and that the tendency of the original primordium sites to reestablish themselves might give rise to the third one, when the original ones fail to be kept away from one another, are discussed.