bluuebunny/crossref_metadata_2025_split huggingface dataset:
Morphodynamic hair bundles arising from sensory cell/supporting cell complexes frequency‐tune nematocyst discharge in sea anemones
Authors: Mire‐Thibodeaux Patricia , Watson Glen M. 
Published: June 2005

AbstractDischarge of nematocysts from cnidocytes occurs in response to appropriate chemical and mechanical stimulation. In sea anemone tentacles, activating chemoreceptors for N‐acetylated sugars shifts maximal discharge into vibrating targets to low frequencies corresponding to prey movements and induces hair bundles to elongate by approximately 1–2 μm. Until now, only indirect, correlative evidence linked these two events. Using cytochalasin D, we provide evidence that bundle elongation is necessary for the frequency shift. Moreover, we find that only bundles associated with sensory cell/supporting cell complexes elongate with chemosensitization, and not bundles associated with cnidocyte/supporting cell complexes as was previously thought. Cytochemical labeling of sensory cells, purported to be bipolar neurons connected to the nerve net, suggests that sensory cells may interconnect with each other and with cnidocytes. Taken together, these findings are incompatible with the classical view that cnidocytes are independent effectors of nematocyst discharge and, furthermore, implicate the involvement of morphodynamic neurons in fine‐tuning vibration‐dependent discharge of nematocysts into swimming prey. © 1994 Wiley‐Liss, Inc.
Endogenous ionic currents and voltages in amphibian embryos
Authors: Metcalf M. E. Mourey , Shi Riyi , Borgens Richard B. 
Published: June 2005

AbstractUsing a noninvasive vibrating electrode for the measurement of extracellular current, we show that a polarized ionic current traverses the embryo for many hours in the anuran, perhaps days in the urodele following gastrulation. The voltage driving these ionic currents is an internally positive transepithelial potential (TEP) normally expressed across embryonic integuments. Current is driven out of the lateral walls of the neural folds and the blastopore and enters most of the rest of the embryo's body surface. The magnitude of the TEP is transitorily dependent on external sodium and can be reduced by the embryo's immersion in Na+depleted media or by treatment with 50 μM amiloride. Both treatments fail to chronically reduce externally detected currents, however. The pattern of currents traversing the embryo suggests they would be associated with rostral‐caudal and medial‐lateral gradients of voltage within the embryo. By sampling the distribution of TEPs in axolotl embryos, we provide measurements of the former—an internal, caudally negative, potential gradient beneath the neural plate ectoderm. The magnitude of these endogenous fields is on the order of 10 to 20 mV/mm and is within a range of potential known to affect the shape and migration of a variety of embryonic cell types in vitro. We suggest that endogenous currents and voltages in the vertebrate embryo may provide gross cues for cell movement and emerging developmental pattern. © 1994 Wiley‐Liss, Inc.
Characterization of striped bass growth hormone receptors by disulfide‐bond reduction and cross‐linking studies
Authors: Gray Elisabeth S. , Tsai Robert W. 
Published: June 2005

AbstractGrowth hormone (GH) receptors were analyzed in striped bass (Morone saxatilis) by addition of disulfide‐bond reducing agents to radioreceptor assays and by cross‐linking both striped bass and coho salmon (Oncorhynchus kisutch) crude membrane preparations to radiolabeled hormone. Dithiothreitol (DTT) caused a dose‐dependent increase in specific binding of 125I‐tilapia (Oreochromis mossambicus) GH to striped bass membrane preparations. Maximal enhancement of 3.4‐fold was obtained with 1 mM DTT and 0.03 trypsin inhibitor units/ml of aprotinin. Addition of N‐ethylmaleimide (NEM), which binds covalently to free sulfhydryl groups, decreased specific binding. Scatchard analysis of striped bass membrane preparations indicated a single class of GH receptors. Addition of DTT with aprotinin increased GH‐binding site concentration from 278 to 507 fmol/mg, while the dissociation constant of 0.56 nM remained unchanged. Cross‐linking 125I‐tilapia GH to striped bass hepatic membrane preparations and 125I‐salmon GH to coho salmon membrane preparations yielded two to three specifically labeled proteins on sodium dodecyl sulfate (SDS)‐polyacrylamide gel electrophoresis. Endoglycosidase H treatment was without effect on specifically labeled proteins from either species. Following digestion with N‐glycosidase F, relative molecular weights of specifically labeled 125I‐GH complexes were reduced, suggesting that hepatic GH‐binding proteins in striped bass and salmon are N‐linked glycoproteins. © 1994 Wiley‐Liss, Inc.
Identification of trypsin‐like activity in sturgeon spermatozoa
Authors: Ciereszko Andrzej , Dabrowski Konrad , Lin Feng , Doroshov Serge I. 
Published: June 2005

AbstractWe documented amidase activity in lake sturgeon (Acipenser fulvescens) and white sturgeon (Acipenser transmontanus) spermatozoa. This activity was inhibited by benzamidine and soybean trypsin inhibitor (SBTI), and N‐α‐p‐tosyl‐L‐lysine chloromethyl ketone‐HCl (TLCK), but not by N‐tosyl‐L‐phenylalanine chloromethyl keton (TPCK), indicating the presence of trypsin‐like activity in sturgeon spermatozoa. Higher activity occurred at pH 8.5 and 9.0 than at 8.0. No effect of 10 mM KCl and 100 mM NaCl on trypsin‐like activity was found. Calcium ions inhibited the activity at 10 and 50 mM. Similar activities were documented in neat semen and washed sperm suspension. Presence of trypsin‐like activity corresponds to the presence of acrosomes and acrosome reaction in spermatozoa of these fishes. © 1994 Wiley‐Liss, Inc.
Effect of hexylene glycol‐altered microtubule distributions on cytokinesis and polar lobe formation in fertilized eggs of Ilyanassa obsoleta
Authors: Conrad Abigail H. , Stephens Andy P. , Conrad Gary W. 
Published: June 2005

AbstractSome effects of gravity on early morphogenesis are correlated with microtubule locations within cells. During first cleavage in Ilyanassa obsoleta embryos, a transitory polar lobe constriction forms and then relaxes, allowing the polar lobe to merge with one daughter cell. If the polar lobe is equally divided or removed, morphogenesis is severely disrupted. To examine microtubule locations during early Ilyanassa development, eggs were fixed and stained for polymerized α‐tubulin during first cleavage. The mitotic apparatus assembles at the animal pole. The cleavage furrow forms between the asters, constricting to a stabilized intercellular bridge encircling midbodybound microtubules, whereas the polar lobe constriction forms below and parallel to the spindle, constricting to a transitory intercellular bridge encircling no detectable microtubules. At metaphase an α‐tubulin epitope is distributed throughout the spindle, whereas a β‐tubulin epitope is present predominantly in the asters. Incubation in hexylene glycol, a drug that increases microtubule polymerization, during mitosis causes the polar lobe constriction to tighten around polymerized α‐tubulin and remain stably constricted. If hexylene glycol is removed, α‐tubulin staining disappears from the polar lobe constriction, which relaxes, whereas microtubules remain in the cleavage furrow, which remains constricted. These observations suggest that asymmetric distribution of microtubules affects early Ilyanassa cleavage patterns, and that continued presence of microtubules extending through an intercellular bridge is important for stabilization of the bridge constriction prior to completion of cytokinesis. These data provide the basis for further analysis of the role of microtubules in possible microgravity disruptions of Ilyanassa development. © 1994 Wiley‐Liss, Inc.
Pre‐metatarsal skeletal development in tissue culture at unit‐ and microgravity
Authors: Klement Brenda J. , Spooner Brian S. 
Published: June 2005

AbstractExplant organ culture was used to demonstrate that isolated embryonic mouse pre‐metatarsal mesenchyme is capable of undergoing a series of differentiative and morphogenetic developmental events. Mesenchyme differentiation into chondrocytes, and concurrent morphogenetic patterning of the cartilage tissue, and terminal chondrocyte differentiation with subsequent matrix mineralization show that cultured tissue closely parallels in vivo development. Whole mount alizarin red staining of the cultured tissue demonstrates that the extracellular matrix around the hypertrophied chondrocytes is competent to support mineralization. Intensely stained mineralized bands are similar to those formed in pre‐metatarsals developing in vivo. We have adapted the culture strategy for experimentation in a reduced gravity environment on the Space Shuttle. Spaceflight culture of pre‐metatarsals, which have already initiated chondrogenesis and morphogenetic patterning, results in an increase in cartilage rod size and maintenance of rod shape, compared to controls. Older pre‐metatarsal tissue, already terminally differentiated to hypertrophied cartilage, maintained rod structure and cartilage phenotype during spaceflight culture. © 1994 Wiley‐Liss, Inc.
Polarity and body pattern in ascidian chimeras formed between normal (situs normale viscerum) and reversed (situs inversus viscerum) bodies
Authors: Ishii Teruhisa , Taneda Yasuho , Saito Yasunori 
Published: June 2005

AbstractIn the compound ascidian Polyandrocarpa misakiensis, when two anterior or two posterior body fragments of zooids are fused together at their cut surfaces, a double‐zooid monster is formed. On the other hand, fusion of an anterior fragment and a posterior fragment results in a single‐zooid chimera. In the present study, we tried to make chimeric zooids between normal (situs normale viscerum) and mirror‐image, or reversed (situs inversus viscerum), adult bodies. In order to distinguish between the two partners in a chimera, zooids of two strains that differed in color pattern were used (Ishii et al., [1993] Zool. Sci. 10:977–982). Using normal zooids of the spotless strain and reversed zooids of the white‐spot strain, we formed chimeras using the anterior fragment of a zooid and the posterior fragment in four combinations between these two colormorphs. In all the combinations, chimeras were obtained. Chimeras obtained from the combinations of a normal anterior fragment and a reversed anterior fragment appeared as double‐zooid monsters. Analysis of the body pattern of these chimeras revealed that the polarity of a reversed anterior fragment returned to normal polarity. Chimera derived from a normal posterior fragment and a reversed posterior fragment also resulted in a double‐zooid monster, but the polarity of a reversed posterior fragment did not change. Chimeras obtained from the combination of a normal anterior fragment and a reversed posterior fragment or from the combination of a reversed anterior fragment and a normal posterior fragment exhibited either of two distinct patterns of body regeneration: they became a malformed double‐zooid monster, or a single‐zooid chimera with normal polarity. Thus, in these single‐zooid chimeras, the reversed polarity of the anterior portion became normal. Furthermore, buds that were formed from the anterior portion of these single‐zooid chimeras had normal polarity. © 1994 Wiley‐Liss, Inc.
Influence of ocular and extraocular photoreception on spermatogenesis in Gambusia affinis holbrooki (Teleostei: Poeciliidae)
Authors: de Miguel María P. , Fraile Benito , Sáez Francisco J. , Vicentini Carlos A. , Paniagua Ricardo 
Published: June 2005

AbstractNon‐blinded and blinded male mosquito‐fish (Gambusia affinis holbrooki) were subjected to three different photoperiods (a short photoperiod of 8 hr light daily, a simulated natural photoperiod that was increased from 12.25 to 14.50 hr of light, and a long photoperiod of 16 hr of light) at a constant mild temperature (20°C) during the spermatogenesis period (March–May). Afterwards, the testes were removed and studied by quantitative histological methods, along with the testes from initial and final field controls. Fish exposed to simulated natural or long photoperiod (16L:8D) developed complete spermatogenesis like the final controls. Fish exposed to short photoperiod developed spermatogenesis up to the primary spermatocyte stage. Photoperiodic effects on spermatogenesis were similar in both blinded and intact males subjected to the same photoperiodic conditions. Thus, extraocular photoreception must be involved in photoperiodic effects on reproduction, and the presence of the eyes is not required for spermatogenesis in this species. © 1994 Wiley‐Liss, Inc.
In vivo and in vitro induction of germinal vesicle breakdown in a freshwater bivalve, the zebra mussel Dreissena polymorpha (Pallas)
Authors: Fong Peter P. , Kyozuka Keiichiro , Abdelghani Haitham , Hardege Jörg D. , Ram Jeffrey L. 
Published: June 2005

AbstractOocyte maturation and germinal vesicle breakdown (GVBD) was induced in zebra mussel (Dreissena polymorpha) oocytes by in vivo and in vitro application of serotonin (5‐hydroxytryptamine, 5‐HT), and in vitro application of 8‐hydroxydipropylaminotetralin hydrobromide (8‐OH‐DPAT, a 5‐HT1A receptor agonist). Oocytes initiated GVBD approximately 30 minutes after exposure to 5‐HT (10−3 M) at 23°C, and by 40–50 minutes after exposure, most oocytes lacked a germinal vesicle. An exposure time to 5‐HT as brief as five to ten minutes was required to trigger the maturation process, which terminates in spawning of fertilizable oocytes in nearly all mussels. But, with an exposure time of less than five minutes, spawning was reduced by application of 10−4 M methiothepin (a potent blocker of 5‐HT‐induced spawning in zebra mussels). Thus, the sequence of oocyte maturation events in zebra mussels was determined. Oocytes are arrested at the germinal vesicle stage (prophase I) within the ovary. 5‐HT reinitiates the maturation process, including GVBD and spawning of metaphase I oocytes, which are further arrested until fertilization. To our knowledge this is the first demonstration of oocyte maturation induction by serotonergic ligands in a freshwater bivalve. © 1994 Wiley‐Liss, Inc.
Evidence in support of a role for Ca2+‐activated K+ channels in the hamster sperm acrosome reaction
Authors: Llanos Miguel N. 
Published: June 2005

AbstractThe sperm acrosome reaction (AR) is a crucial step for mammalian fertilization. This work describes experiments to test the effect of the cesium ion (Cs+) and charybdotoxin (ChTX) on the Ca2+ or Na+/K+ ionophores stimulated hamster sperm AR in vitro. Cs+ and ChTX, a polypeptide toxin from the venom of the scorpion Leirus quinquestriatus, are considered blockers of Ca2+‐activated K+ channels in several somatic cells. Both agents inhibited the AR by 55–66%. The inhibition was completely reversed by the Na+/K+ ionophore nigericin, but not by the Ca2+ ionophore A‐23187. Results give evidence in support of a role for Ca2+‐activated K+ channels in K+ influx required for the occurrence of the hamster sperm acrosome reaction. © 1994 Wiley‐Liss, Inc.
Development of rat × mouse hybrid embryos produced by microsurgery
Authors: Waksmundzka Malgorzata 
Published: June 2005

AbstractExperimental production of hybrid embryos between Mus musculus L. and Rattus norvegicus L. was achieved by nuclear transplantation using both ovulated oocytes in metaphase II and pronuclear zygotes. Recipient egg‐cells were of mouse origin in all cases. The developmental potential of hybrids was examined in vivo.Nucleo‐cytoplasmic hybrids resulting from the introduction of rat metaphase II chromosomes into enucleated mouse oocytes, which were subsequently activated, were regularly blocked at the 1‐ or 2‐cell stage. Nuclear (genetic) hybrids produced by transfer of a rat nucleus (in the form of metaphase II chromosomes or a pronucleus) into a nucleated mouse recipient (oocyte or zygote) were capable of development to the 5‐ to 8‐cell stage. Transplantation of rat cytoplasm alone to intact metaphase II oocytes, followed by oocyte activation, generated cytoplasmic hybrids which developed to the morula stage. In control experiments (nuclear transfer between mouse oocytes or zygotes), a high proportion of embryos formed morulae and blastocysts. These results demonstrate that the rat nucleus is incapable of functioning in mouse cytoplasm, that introduction of the rat genome into intact mouse egg‐cells impairs normal development, and that transfer of foreign (rat) cytoplasm into mouse egg‐cells affects preimplantation development of manipulated embryos. © 1994 Wiley‐Liss, Inc.
Secondary circulation of the vascular heat exchangers in skipjack tuna, Katsuwonus pelamis
Authors: Dewar Heidi , Brill Richard W. , Olson Kenneth R. 
Published: June 2005

AbstractVascular corrosion replicas of the counter current heat exchanger microcirculation in skipjack tuna, Katsuwonus pelamis, were examined by scanning electron microscopy. Smallbore (7–10 μm diameter) vessels, with characteristics typical of those associated with the secondary circulation, were abundant in the central and lateral heat exchangers. These vessels arise from the large‐bore (70 μm diameter) retial arterioles and, after a tortuous path, anastomose repeatedly to form 50–200 μm diameter secondary collecting vessels which ultimately exit from either pole of the rete. © 1994 Wiley‐Liss, Inc.
Temperature‐dependent sex determination: A mechanistic approach
Authors: Wibbels Thane , Bull James J. , Crews David 
Published: June 2005

AbstractA variety of sex determination systems exists in reptiles, including temperature‐dependent sex determination (TSD). While the precise physiological basis of TSD is unknown, numerous past studies have provided a general characterization of this phenomenon. The period of thermosensitivity encompasses the middle one third to one half of embryonic development. It has been shown that in several species of reptiles this period starts prior to (histologically defined) gonadal differentiation and extends to a time when sex specific changes are becoming evident in the gonads. During the thermosensitive period, sex determination is sensitive to both the magnitude and duration of a given incubation temperature. Further, the treatment of developing eggs with specific steroid hormones (in particular, estrogens) has been shown to override the effects of male‐producing temperatures and induce female sex determination. This has led to a variety of studies investigating whether the production of estrogens may be naturally involved in TSD. The results from several studies are consistent with the hypothesis that temperature could be affecting endogenous estrogen production by controlling the production of aromatase. However, the results from other studies are not consistent with this hypothesis. Current studies by a variety of research laboratories are now addressing the estrogen hypothesis as well as TSD in general at various physiological and molecular levels. As such, these studies should provide a wealth of data on the physiological basis of TSD. © 1994 Wiley‐Liss, Inc.
Studies on sex determination in the American alligator alligator mississippiensis
Authors: Lance Valentine A. , Bogart Mark H. 
Published: June 2005

AbstractEstradiol‐17β was measured in the plasma and urogenital tissues of male and female alligator embryos. Hormone levels were generally very low and there was no significant differences between the sexes. There were no significant changes in estrogen levels during the period of gonadal differentiation in either sex. Alligator embryos incubated at male producing temperatures were feminized by small doses of estrogen applied to the egg shell. The antiestrogen, tamoxifen, masculinizes turtle and bird embryos, but, paradoxically, feminized alligator embryos at male producing temperatures. The contraceptive steroid, norethindrone, a progestin that is claimed to block estrogen synthesis, is the most potent estrogenic steroid tested on alligator embryos. A single dose of norethindrone applied to the egg shell caused massive hypertrophy of the Müllerian duct and feminized embryos at male producing temperatures. The androgen, dihydrotestosterone, had no detectable effect on male or female embryos at the doses tested. Undifferentiated urogenital tracts of embryos were cultured at 30 and 33°C in the presence of steroids, tamoxifen, or antibodies to steroids. None of the treatments had any effect on tissue differentiation. Tissues survived for up to 6 weeks, but there was no evidence of gonadal differential in vitro. © 1994 Wiley‐Liss, Inc.
Chromosomal and temperature‐dependent sex determination: The search for a conserved mechanism
Authors: Coriat Anne‐Marie , Valleley Elizabeth , Ferguson Mark W. J. , Sharpe Paul T. 
Published: June 2005

AbstractTo test the hypothesis that the same (or similar) genes may be involved in chromosomal sex determination and temperature dependent sex determination we investigated the expression of the mammalian testis determining gene SRY in the American alligator (Alligator mississippiensis), a species with temperature dependent sex. We have cloned Alligator SRY‐related genes (A‐Srys) which constitute three major gene classes with high degrees of sequence homology (45–87%) to mammalian SRY and related genes. Expression analysis and cellular localisation studies using staged embryonic material from male and female incubation temperatures are underway to assess the role of A‐Sry genes in temperature dependent sex determination. © 1994 Wiley‐Liss, Inc.
Growth and differentiation of the secondary palate in a teleostean fish, Oncorhynchus kisutch
Authors: Shah Ravindra M. , Young Alan V. , Feeley Elizabeth J. E. , Donaldson Edward M. 
Published: June 2005

AbstractA study was undertaken to examine the growth and differentiation of secondary palate in a teleostean fish, Oncorhynchus kisutch. The rate, pattern, and time of synthesis of various macromolecules, which play a crucial role during palate development in higher vertebrates were examined in the developing palate of fish. A spurt in DNA synthesis during midmorphogenesis of fish palate appeared to be related to temporal regulation of palate development. RNA synthesis was high during the time of primordial appearance and increased again from day 4 post hatching (PH) to correspond with differentiation of palate. Protein synthesis remained low initially but its trend paralleled that of RNA synthesis after day 4 PH. Glycosaminoglycan synthesis increased initially with the cartilaginous growth and then with the appearance of mucous cells. An increase in collagen synthesis corresponded with the thickening of collagen layer in the basement membrance. Cyclic AMP activity increased initially prior to the increase in DNA synthesis and subsequently remained high indicating its involvement in both growth and differentiation of fish palate. These profiles of synthesis of various macromolecules in teleostean fish differ considerably from that seen in higher vertebrates. On the basis of comparative analysis, it was suggested that the timing of mesenchymal differentiation may be one of the features in determining the characteristics of palate development in different classes of vertebrates. © 1995 Wiley‐Liss, Inc.