bluuebunny/crossref_metadata_2025_split huggingface dataset:
The yolk syncytial layer of Fundulus: Its origin and history and its significance for early embryogenesis
Authors: Trinkaus J. P. 
Published: June 2005

AbstractBecause of its importance in early embryogenesis, the developmental history of the yolk syncytial layer (YSL) of Fundulus has been investigated in detail. As in other teleosts, the Fundulus YSL forms mainly by collapse of certain marginal blastomeres which then merge with the cytoplasm of the yolk cell peripheral to the blastoderm. Nuclei enter the yolk cell from these open blastomeres variably during cleavages 8–11, but most frequently at cleavages 9 and 10. After entry, the first nuclei divide five times and later nuclei divide with them. Thus, nuclei that have invaded at the next cleavage divide four times, etc. When the first YSL nuclei cease dividing, all other YSL nuclei cease dividing with them. These YSL mitoses occur in metachrony. Two or more metachronous waves progress through the YSL cytoplasm at each mitosis. After each nuclear division, the YSL increases in width and its nuclei are quite evenly spaced. After the 5th and last mitosis, when the YSL is at its widest, it contracts in its animal‐vegetal axis. This slow contraction has two major effects: 1) narrowing of the YSL, accompanied by crowding of its nuclei and their disappearance beneath the blastoderm to nucleate the internal YSL; 2) epibolic expansion of the I‐YSL and the blastoderm, followed soon after by other cell movements of gastrulation. This YSL transition, therefore, sets the stage for the onset of gastrulation. It is preceded by increased duration and variability of succeeding mitoses and, in particular, duration of their interphases, a decrease and deceleration in the rate of the last metachronous waves, and, finally, by the complete cessation of mitosis and the entry of YSL nuclei into permanent interphase. © 1993 Wiley‐Liss, Inc.
Relative roles of jelly layers in successful fertilization of Bufo japonicus
Authors: Omata Setsuko 
Published: June 2005

AbstractThe uterine eggs of Bufo japonicus are invested with four jelly layers, J1, J2, J3, and J4, from inner to outer, respectively. When eggs were inseminated with serially diluted sperm suspensions, a higher concentration of sperm was required for successful fertilization of dejellied uterine eggs in solubilized jelly preparation than fertilization of fully jellied uterine eggs. When the eggs taken from different portions of oviduct were inseminated, the eggs invested with J1J2J3 were fertilized as effectively as fully jellied uterine eggs. Those with J1J2 were fertilized at lower frequency but those with J1 and a thin J2 were hardly fertilizable. Eggs artificially invested with J3J4 were less fertilizable than the J1J2 eggs, but addition of J3J4 to J1 and a thin J2 made eggs as fertilizable as the J1J2 eggs. Observations on the sperm penetrating the jelly indicated that these differences in fertilizability were dependent on two variables: an increased number of sperm penetrating into J3 and J4, and an increased rate of acrosome reacted sperm in J1 and J2. © 1993 Wiley‐Liss, Inc.
Isolation and partial characterization of the sperm motility initiation factor from eggs of the pacific herring, Clupea pallasi
Authors: Pillai Muralidharan C. , Shields Tammy S. , Yanagimachi Ryuzo , Cherr Gary N. 
Published: June 2005

AbstractPreviously, we have demonstrated that sperm from the Pacific herring, Clupea pallasi, remain immotile upon spawning into the surrounding medium and initiate motility only upon contact with the micropyle area of the chorion (Yanagimachi et al., '92, Dev. Growth Differ., 34:447–461). In the present study we have purified a chorion‐bound sperm motility initiating factor (SMIF) and have found it to be a 105 kDa glycosylated polypeptide. The isolated factor was highly bioactive, stimulating prolonged motility in >90% of the cells in vitro. The 105 kDa glycoprotein showed affinity for Con A on western blots. Furthermore, in intact eggs, Con A was localized to only the micropyle area, indicating that SMIF is restricted to this region of the chorion. © 1993 Wiley‐Liss, Inc.
Ion transport in the gill epithelium of aquatic crustacea
Authors: Lucu Čedomil 
Published: June 2005

AbstractIn recent years a convincing body of knowledge has been accumulated indicating transport mechanisms for osmolytes in marine and brackish water Crustacea. Cuticle and epithelium cell layers serve as selective communications for the exchange of ions and small organic molecules between crustacean gills and their environment. The following apparent permeability coefficients in the Carcinus posterior gill epithelia was measured: PRb : PNa : PCl = 1.7 : 1.0 : 0.1.In addition to the presence of ouabain sensitive unidirectional Na exchange (Ja…︁>b) located on the basolateral gill surface, there is also located an oppositely‐directed, ouabain‐sensitive Rb (K) unidirectional flux. Basolaterally applied ouabain inhibits NH4 fluxes (Jb…︁>a) and seems to interact with the Na/K exchanger, in which NH4 appears to substitute for K. In isolated perfused posterior gills, amiloride affected sodium fluxes and transbranchial potentials, supporting the possible presence of an Na/H exchanger. A unique electrogenic 2Na/H antiporter present in membrane vesicles of marine invertebrates has been discussed with the aim to integrate the knowledge at the different functional levels.Branchial cell acidification was studied in Carcinus hemilamellae microspectrofluorimetrically using the fluorescent dye BCECF. In the case when hemilamellae were immersed in Na‐free solution, intracellular acidification was not affected by amiloride. In addition, in perfused gill epithelia in DSW (200 mM Na) identical with the bathing solution, acetazolamide‐inhibited acidification of the perfused medium was observed.The effects of the inhibitors on the transbranchial potentials (TBP) and their role in the ion transport mechanisms of the crustacean gills are reported. © 1993 Wiley‐Liss, Inc.
Transport of amino acids by marine invertebrates
Authors: Preston Robert L. 
Published: June 2005

AbstractMarine invertebrates transport amino acids and other organic solutes across their body surfaces. This surface absorption, in some instances, may contribute significantly to the overall nutritional requirements for an organism. Amino acids are accumulated against gradients as high as 106:1 to 107:1 (intracellular:extracellular concentration). The transport mechanism that has been consistently observed to account for this process is Na dependent cotransport. A review of the general characteristics of these transport systems characterized in marine invertebrate epithelia indicates certain common features: Na dependency with coupling coefficients of 2:1 or 3:1 (Na:amino acid translocated), influx coupled to membrane potential, and low intracellular Na activity. Under these conditions Na cotransport can readily account for gradients approaching 107:1. These transport systems may play a role in acquisition of nutrients by marine invertebrates, but it has also been suggested that they may play additional roles in osmoregulation, nutrient conservation, and chemo‐reception. © 1993 Wiley‐Liss, Inc.
Cyclic nucleotide regulation of methyl farnesoate synthesis by the mandibular organ of the lobster, Homarus americanus
Authors: Tsukimura B. , Kamemoto F. I. , Borst D. W. 
Published: June 2005

AbstractMandibular organ (MO) synthesis of methyl farnesoate (MF) is negatively regulated by extracts of the sinus gland, a neuroendocrine organ in the lobster eyestalk. Sinus gland extracts significantly increased cyclic GMP (cGMP) levels in the MO in vitro, but had no effect on cyclic AMP (cAMP) levels. Extracts of two other neuroendocrine tissues, the brain and thoracic ganglion, did not affect either cAMP or cGMP levels. In vitro treatment of MO with 8‐bromo‐cGMP (a cGMP analog) significantly decreased MF synthesis at concentrations of 10−7 M to 10−4M. Higher concentrations of 8‐bromo‐cAMP (10−5M to 10−4M) were required for significant decreases in MF synthesis. Forskolin and IBMX decreased MF synthesis at a concentration of 10−5M, but had no effect at lower concentrations (10−8M to 10−6M). These data suggest that cGMP is a second messenger for the sinus gland factor that inhibits MF synthesis in the MO. © 1993 Wiley‐Liss, Inc.
Regulation of ecdysteroid biosynthesis in crayfish Y‐organs: I. Role of cyclic nucleotides
Authors: Sedlmeier Dietrich , Fenrich Renate 
Published: June 2005

AbstractEcdysteroidogenesis in crustacean Y‐organs is negatively regulated by the so‐called molt‐inhibiting hormone (MIH), which is thought to inhibit the ecdysteroid pathway either directly through phosphorylation of the key enzyme(s) and/or through action on the synthesis of these enzymes. In the present study the role of cyclic nucleotides in the mode of action of MIH in the astacuran Orconectes limosus was investigated. Orconectes Y‐organs were incubated in vitro with sinus gland conditioned medium (SGCM) and cyclic AMP (cAMP) and cyclic GMP (cGMP) levels were measured. A striking increase of cGMP values (4 to 43 pmoles/mg protein) was observed after 2 hours, whereas cAMP levels were unchanged. Using the established in vitro bioassay for the measurement of inhibitory action on ecdysteroid release from Y‐organs (Soumoff and O'Connor, '82) the potential of dBcAMP, dBcGMP, forskolin, and IBMX to diminish this release was demonstrated, suggesting a possible role of both cyclic nucleotides in the mode of action of MIH. The present findings are discussed in view of the effect of MIH‐material on cyclic nucleotide levels in crab Y‐organs (Mattson, '86). © 1993 Wiley‐Liss, Inc.
Regulation of ecdysteroid biosynthesis in crayfish Y‐organs: II. Role of cyclic nucleotide‐dependent protein kinases
Authors: Von Gliscynski Ursula , Sedlmeier Dietrich 
Published: June 2005

AbstractThe ecdysteroid production of the crustacean molting gland, the Y‐organ, is known to be suppressed by the so‐called molt inhibiting hormone (MIH), a neuropeptide from the X‐organ‐sinus gland complex. Cyclic nucleotides appear to be involved in intracellular effects of MIH in Y‐organs. In the crab Cancer antennarius cAMP synthesis seems to be an initial event in MIH action, while in crayfish results indicate a more important role for cGMP in intracellular effects of MIH. To gain a better understanding of the intracellular mechanisms we examined the cAMP‐ and cGMP‐dependent protein kinase (A‐ and G‐kinase) activity in Y‐organs of the crayfish Orconectes limosus at different molting stages induced by eyestalk ablation. The activity ratio of cGMP‐dependent protein kinase was lower for premolt animals (0.51) than for intermolt animals (0.81), indicating a more pronounced activation of G‐kinase in Y‐organs of intermolt animals by endogenous cGMP. Moreover, preincubation of Y‐organs from destalked animals with sinus gland extract reestablished a G‐kinase activity ratio characteristic for intact animals. On the contrary, the activity ratio of A‐kinase did not vary depending on molting stage and was not altered by sinus gland extract. These results strongly suggest that MIH action in Orconectes limosus Y‐organ is mediated by cGMP rather than by cAMP. © 1993 Wiley‐Liss, Inc.
Seasonal conditions determine the manner of skin rejection in reptiles
Authors: Afifi Ahmed , Mohamed El Rashdy , Ridi Rashika El 
Published: June 2005

AbstractDuring summer, 33%, 52%, and 15% of lizards Chalcides ocellatus rejected first set skin allografts (time between day of first sign of rejection and end point), respectively in an acute (11–14 days), subacute (15–20 days), and chronic (21–24 days) manner. Second set grafts were rejected in an acute fashion (8–13 days). Examination of histological samples from grafted areas revealed evident lymphoid cell aggregations in allo‐ but not in autografts. This suggests that graft rejection results from an immunological reaction against allogeneic cells. In the other seasons, all skin allotransplanted lizards rejected the graft in a chronic manner: in 46–132 days during autumn, 31–79 days in winter, and 40–78 days during spring. These data indicate that graft rejection in reptiles is under the control of seasonal conditions. © 1993 Wiley‐Liss, Inc.
Atrophy of nerve and neuropil following limb loss and regeneration in adult snapping shrimps, Alpheus heterochelis
Authors: McTeague J. A. , Govind C. K. 
Published: June 2005

AbstractChanges in the nervous system were examined in adult snapping shrimps Alpheus heterochelis following the removal and regeneration of the minor or pincer cheliped. In order to compensate for differences amongst animals, the regenerated pincer side was compared to the contralat‐eral pristine major or snapper cheliped. In control shrimps with pristine pincer and snapper chelipeds, the number of axons in the nerves at the base of the ganglion on the pincer side constitute 74.4% of the number on the snapper side while the volume of the pincer neuropil constitutes 94.3% of its snapper counterpart. Following the removal of the pincer cheliped and the regeneration of a smaller one at the next molt, the number of axons in the nerves drops to 41.6% and the neuropil volume is reduced to 80.3% of its pristine snapper counterpart. This atrophy of the nerve and neuropil is further exaggerated following the removal of the pincer cheliped over four successive intermolts. On the regenerated pincer side, the number of axons drops to 8.5% and the neuropil volume to 61.4% compared to the pristine snapper side. Thus, loss of almost all of the peripheral sensory axons reduces the neuropil by about one third. The remaining two‐thirds of the neuropil volume is presumably comprised of input from central elements. © 1993 Wiley‐Liss, Inc.
Prolactin and interrenal hormone balance in adult specimens of Xenopus laevis exposed to hyperosmotic stress for up to one week
Authors: Guardabassi Antonietta , Muccioli Giampiero , Andreoletti Gian Emilio , Pattono Paola , Usai Pasquale 
Published: June 2005

AbstractAdult female specimens of Xenopus laevis were exposed to diluted artificial seawa‐ter for up to 1 week. Statistically significant increases were observed in serum levels of aldosterone and corticosterone, concomitant with a drop in levels of prolactin (PRL) receptors in the cell membranes of the epidermis and kidney, which can be taken as an indicator of the levels of circulating PRL. The changes in hormone levels were detected after 1 day, being followed by a gradual restoration of the initial mean levels of these hormones when the exposure to hyperosmotic stress was extended for up to 2 or 7 days. Comparison of the above results with those previously obtained in Xenopus after longer exposure (15 days) to brackish water substantiates the necessity of recording possible initial fluctuations, as well as any changes that occur over the course of longer exposure during which time adaptation to environmental changes are likely to take place. The reverse responses, which may be not independent of one another, in terms of levels of corticoids and PRL in the animals exposed to hyperosmotic stress, are discussed.A survey of the literature suggests that, in Xenopus, as in the case of other less strictly water‐dwelling amphibians, PRL is one of the hormones required for life in fresh water. © 1993 Wiley‐Liss, Inc.
Bilateral eye formation in the eyeless mutant Mexican salamander following unilateral, partial excision of neural fold tissues: A quantitative study
Authors: Brun Rudolf B. 
Published: June 2005

AbstractPrevious results showed that ectopic neural fold grafts, performed unilaterally during neurulation on eyeless mutant axolotl embryos, frequently stimulated eye formation bilaterally. The analysis of the eyeless mutant was expanded in order to obtain quantitative data on the effect of various types of neural fold grafts. While performing these experiments, significant eye formation occurred in controls. Larvae in which neural fold tissues were not grafted but only partially removed at neurula stages formed eyes in some experiments, but not in others. In those cases that eyes did form, partial removal of the posterior neural fold of the prospective ear region stimulated eyes to differentiate more frequently than partial removal of the anterior neural fold of the prospective nose area. In both cases, unilateral neural fold ectomy frequently resulted in bilateral eye formation. There was a positive correlation between the amount of posterior neural fold tissues excised and the frequency of cases in which eyes formed. This increase was roughly 10% if the posterior neural fold excision was performed bilaterally instead of unilaterally.A comparison of eye formation between neural fold excision experiments and ectopic neural fold grafts was performed. There was a statistically significant different between anterior and posterior neural fold operations, but not between grafting and excision experiments. I interpret these results to suggest that there is a signal in the posterior neural fold of the eyeless mutant that prevents eye formation. This signal can be neutralized most efficiently by wounding of the posterior neural folds. In addition, the results provide strong evidence that the effect of wounding propagates from posterior to anterior regions, as well as from one side of the developing neuroepithelium to the other. © 1993 Wiley‐Liss, Inc.
Eggshell formation in Bdelloura candida, an ectoparasitic turbellarian of the horseshoe crab Limulus polyphemus
Authors: Huggins Luke G. , Waite J. Herbert 
Published: June 2005

AbstractThe marine triclad Bdelloura candida (Turbellaria) episodically deposits stalked eggshells onto the gill lamellae of the horseshoe crab Limulus polyphemus. Ultrastructural and biochemical analyses indicate that the eggshells consist of primary inner and secondary outer layers. Protein of the primary layer is rich in glycine, aspartate/asparagine, serine, and 3,4‐dihydroxyphenylalanine (Dopa). In this regard it resembles the eggshell compositions of other members of the phylum Platyhelminthes. The primary layer appears to be derived from precursors produced in the vitelline cells of the flatworm. Each egg‐laying episode consumes all of the precursor‐containing vitel‐line cells. A Dopa‐containing protein, vitelline protein 1 (Vp1), has been isolated from B. candida and resembles the primary eggshell layer in its composition. Vp1 has an apparent molecular weight of 34.4 and an acidic pI. Dopa‐containing proteins are presumed to be directly involved in the cross‐linking reactions that accompany quinone‐tanning. The secondary outer layer of the eggshell may serve to adhere the eggshell to the gill. Its amino acid composition is unlike that of the primary eggshell and nothing is known about its precursors. © 1993 Wiley‐Liss, Inc.
Pheromonal regulation of the mouse estrous cycle by a heterogenotypic male
Authors: Barkley M. , DeLeon D. Delgado , Weste R. 
Published: June 2005

AbstractThe role of male pheromones in estrous cyclicity was studied in mice selected for different reproductive traits. When females are exposed to males of their own strain, estrous cycles are highly regular in females selected for increased embryo survival (line E). In contrast, cycle regularity is reduced by exposure of line E females to males from a strain characterized by irregular estrous cycles (line CN‐). To investigate the inhibition of estrous cyclicity and the role of androgen in this phenomenon, line E females were housed in the olfactory presence of E males and later rehoused with one of the following: intact or castrated males of line E (homogenotypic condition) or line CN‐heterogenotypic condition) or castrated CN‐ males provided with testosterone replacement. A final exposure to homogenotypic (line E) males was provided. Estrous cyclicity was decreased when line E females were rehoused with intact or castrated CN‐ males. Metestrus was prolonged by intact CN‐ males, whereas diestrus was prolonged in the presence of castrated CN‐ males. Androgen treatment did not enable castrated CN‐ males to prolong metestrus. These results demonstrate that: 1) heterogenotypic pheromones inhibit estrous cyclicity in line E; and 2) the inhibitory influence of line CN‐males on line E estrous cyclicity is mediated by factors in addition to or other than testosterone. © 1993 Wiley‐Liss, Inc.
Maintenance of high extracellular pH does not influence cell pH or metabolism in submerged anoxic bullfrogs
Authors: Wasser Jeremy S. , Jackson Donald C. , Chang Susan Y. , Warburton Stephen J. 
Published: June 2005

AbstractWe compared extracellular and intracellular acid‐base states in paralyzed bullfrogs subjected to 4 h of anoxic submergence at 15°C with or without maintenance of extracellular pH at preanoxic levels by bicarbonate infusion. We also assessed anaerobic metabolism under these conditions by measuring tissue lactate and glycogen concentrations in liver, heart, and skeletal muscle. Although bicarbonate infusion resulted in a significantly higher arterial blood pH (pHe) than saline infusion, intracellular pH (pHi) of heart and skeletal muscle, as determined by the DMO equilibration technqiue, were not significantly different after 4 h of anoxia. We were also unable to demonstrate any differences in anaerobic metabolic rate, since both tissue lactate accumulation and glycogen depletion were identical in bicarbonate‐ and saline‐infused frogs in the tissues studied. We conclude that (1) alterations in the extracellular acid‐base state by bicarbonate infusion are not necessarily reflected in the intracellular compartment, perhaps due to powerful intracellular buffering processes, and (2) maintenance of an alkaline extracellular pH during anoxia in bullfrogs does not influence the anaerobic metabolic rate. We could not, however, rule out a possible role for intracellular pH in regulating anaerobic metabolism during anoxia in frogs. © 1993 Wiley‐Liss, Inc.
Effects of cytochalasin B on calcium transport by 1,25(OH)2D3‐ or PTH‐treated chick embryonic yolk sac in vitro and in vivo
Authors: Lee S. Kyeong , Clark Nancy B. 
Published: June 2005

AbstractThe present study was done to elucidate the mechanism(s) by which calcium is taken up or transported across the yolk sac membrane of the embryonic chick. We examined the effect of various inhibitors or experimental conditions on the uptake of calcium in vitro. Treatment with ouabain, verapamil, antimycin A and calcium ionophore A23187; substitution of choline for sodium or potassium in the buffer; or incubation of the tissue at 0°C had no significant effect on calcium uptake by the yolk sac membrane. Dinitrophenol (DNP) and lanthanum chloride (LaCl2) reduced 45Ca uptake from day 6 and 9 embryos by 15% and 30%, respectively. Cytochalasin B decreased the uptake of 45Ca in yolk sac membrane disks of day 6 embryos, but not in older embryos. The effects of cytochalasin B were explored further in embryos pretreated with either 1,25(OH)2D3 or PTH, both of which enhance calcium uptake. Cytochalasin B decreased calcium uptake in 9‐day and 12‐day vitamin D‐treated embryos to about 60% of their hormone‐enhanced level and also decreased PTH‐stimulated 45Ca uptake into yolk sac disks by about 50% in embryos of all age groups tested.We also examined the effect of cytochalasin B on 45Ca transport across the yolk sac membrane in vivo. Cytochalasin B did not affect this transport in control (vehicle‐treated) embryos. However, it significantly decreased the enhanced in vivo 45Ca transport in day‐9 and ‐12 vitamin D‐treated embryos approximately 30% and 45%, respectively. Additionally, cytochalasin B decreased the transport of calcium from yolk to blood by about 40% in PTH‐treated day‐9 embryos. These results indicated that both calcium uptake and transport by hormone‐stimulated yolk sac membranes involves endocytosis but that some other mechanism(s) must also be involved. © 1993 Wiley‐Liss, Inc.