bluuebunny/crossref_metadata_2025_split huggingface dataset:
Possible involvement of arachidonic acid and eicosanoids in metamorphic events in Hydractinia echinata (Coelenterata; hydrozoa)
Authors: Leitz T. , Beck H. , Stephan M. , Lehmann W. D. , De Petrocellis L. , Di Marzo V. 
Published: June 2005

AbstractUpon induction of metamorphosis, larvae of the marine hydroid Hydractinia echinata release [14C]‐arachidonic acid from previously labeled endogenous sources. The lipoxygenase inhibitors nordihydroguaiaretic acid and 5,8,11,14‐eicosatetraynoic acid inhibited metamorphosis induced by Cs+ and 1,2‐sn‐dioctanoylglycerol, whereas the inhibitors of cyclooxygenase, indomethacin, and acetylsalicylic acid were ineffective, suggesting a role for lipoxygenase metabolites of arachidonic acid in induction of metamorphosis. Lipoxygenase products in Hydractinia echinata were isolated and identified by gas chromatography/mass spectrometry. 8‐ and 12‐HETE were the most abundant metabolites. In cytosolic fractions from larvae activity of an arachidonic acid metabolizing enzyme, presumably a lipoxygenase, was found. The metabolic product was identified by 1H‐NMR and chiral phase HPLC as 8(R)‐HETE. Its production was strongly inhibited by NDGA, but not by indomethacin. © 1994 Wiley‐Liss, Inc.
Metabolic depression in land snails: In vitro analysis of protein kinase involvement in pyruvate kinase control in isolated Otala lactea tissues
Authors: Brooks Stephen P. J. , Storey Kenneth B. 
Published: June 2005

AbstractIsolated tissues from the land snail Otala lactea were used to examine the relationship between protein kinase activity and phosphorylation‐induced changes associated with metabolic depression. Hepatopancreas and foot muscle were removed from active and estivating land snails and incubated in vitro under aerobic and anoxic conditions. Pyruvate kinase (PK), cAMP‐dependent protein kinase (PKA), and protein kinase second messenger compounds (cyclic AMP and inositol 1,4,5‐triphosphate) were measured after incubating the tissues for 4 hours. Pyruvate kinase from the hepatopancreas of active snails was phosphorylated during anoxic incubations as indicated by changes in the I50 value for L‐alanine. However, measurements of PKA activity and of cellular cAMP concentrations suggested that PKA activity was lower in these incubated tissues. When foot muscle was used as the tissue source, incubation under anoxic conditions produced no changes in PK activity even though PKA activity was drastically reduced. Analysis of changes in inositol 1,4,5‐triphosphate concentrations after tissue incubation showed that they were not consistent with changes in PK activity in either organ. These results suggest that PKA and Ca2+/phospholipid‐dependent protein kinase C do not phosphorylate PK during anoxia in land snails. The differences between values measured in incubated tissues and those measured in vivo suggest that isolated O. lactea tissues are not a good in vitro model system for studying metabolic changes associated with depressed metabolism. © 1994 Wiley‐Liss, Inc.
Seasonal and daily variations in the plasma gonadotropin II response to a LHRH analog and serotonin in Atlantic croaker (Micropogonias undulatus): Evidence for mediation by 5‐HT2 receptors
Authors: Khan Izhar A. , Thomas Peter 
Published: June 2005

AbstractThe effects of serotonin (5‐hydroxytryptamine; 5‐HT) alone, and in combination with luteinizing hormone‐releasing hormone analog (LHRHa), on plasma levels of maturational gonadotropin (GtH II) in the post‐vitellogenic female and spermiating male Atlantic croaker were investigated during mid‐light, late‐light, mid‐dark, and late‐dark phases of the day‐night (12 hr light: 12 hr dark) cycle. Although LHRHa stimulated GtH II secretion throughout the day‐night cycle, maximal stimulation was observed during the mid‐dark phase. Serotonin significantly potentiated LHRHa‐induced GtH II secretion at all time points tested except during the late‐dark phase. The plasma GtH II response to LHRHa was markedly reduced, and the response to 5‐HT was abolished in regressed Atlantic croaker. Pretreatment of the fish with a 5‐HT2 antagonist, LY 53,857 maleate, almost completely abolished the stimulatory effect of 5‐HT on LHRHa‐induced GtH II secretion, whereas a 5‐HT1 antagonist, methiothepin mesylate, failed to influence the stimulatory effect of 5‐HT on GtH II secretion. In addition, a 5‐HT2 agonist, (±) DOI hydrochloride, potentiated the effect of 5‐HT on basal and LHRHa‐induced GtH II secretion, while a 5‐HT1 agonist, m‐chlorophenylpiperazine dihydrochloride, did not. The results clearly demonstrate timeand season‐dependent stimulatory effects of LHRHa and 5‐HT on plasma GtH II levels in Atlantic croaker. Moreover, the stimulatory effect of 5‐HT appears to be mediated by 5‐HT2 receptors in this species. © 1994 Wiley‐Liss, Inc.
Amphibian cross‐fertilization and polyspermy
Authors: Gómez Marta I. , Cabada Marcelo O. 
Published: June 2005

AbstractA string of oocytes from Bufo arenarum (Ba) was inseminated with spermatozoa from Ba, Leptodactylus chaquensis (Lch), or Bufo paracnemis (Bp). Homologous insemination resulted in monospermic eggs and normal development, while in the case of heterologous fertilization both polyspermy and abnormal development were the rule. Oocytes from Ba inseminated with homologous spermatozoa, when reinseminated 30 sec after the first insemination with heterologous spermatozoa, exhibit a high rate of polyspermy and abnormal development. A lower rate of abnormalities was observed when reinsemination was carried out 60 sec after the first insemination. Normal development and an absence of polyspermy were observed in the case of eggs reinseminated 300 sec after initial insemination. This result indicated that the electrophysiological blockage of fertilization either was not triggered or was ineffective. The establishment of the permanent blockage of polyspermy, either by artificial activation of oocytes or as a result of their incubation with the products of the cortical granules, inhibited penetration of Ba eggs by heterologous sperm. © 1994 Wiley‐Liss, Inc.
Role of P‐450 aromatase in sex determination of the diamondback terrapin, Malaclemys terrapin
Authors: Jeyasuria Pancharatnam , Roosenburg Willem M. , Place Allen R. 
Published: June 2005

AbstractSex determination in the diamondback terrapin, Malaclemys terrapin, is temperature‐dependent. Eggs incubated at 31°C, and above, hatch in approximately 45 days as females. Eggs incubated below 27°C hatch in about 60 days as males. Sex is not reversible after hatching. Nest temperatures in the wild can be as low as 20°C and as high as 37°C with as much as a 10°C diel cycle. The shortest incubation time measured in nature was 56 days and the longest approaching 120 days. Nests in our study site produced predominantly (> 95%) male hatchlings. Treatment of developing embryos with estrogen produces females at male producing temperatures while treatment with fadrozole (a nonsteroidal aromatase inhibitor) induces partial male‐like gonads. Treatment with a steroidal aromatase inhibitor (4‐hydroxyandrostenedione, 4‐OHA) had no effect on sex determination. Both fadrozole and 4‐OHA are potent competitive inhibitors (Ki approximately 40–50 nM) for terrapin in vitro aromatase activity. These findings are consistent with aromatase expression being a key step in sex determination of terrapins. We have cloned a partial single copy P‐450 aromatase from the terrapin using a cDNA library constructed from ovarian mRNA. This partial clone is highly homologous to other vertebrate aromatases. © 1994 Wiley‐Liss, Inc.
Molecular mechanisms of TSD in reptiles: A search for the magic bullet
Authors: Spotila James R. , Spotila Loretta D. , Kaufer Norbert F. 
Published: June 2005

AbstractSignificant progress has been made in understanding mechanisms of genetic sex determination. The ZFY gene encodes a zinc finger protein but is not the primary signal in sex determination. The SRY gene is the testis determining gene in man, mouse, rabbit, and probably marsupial mouse and wallaby. Temperature dependent sex determination probably involves a modification of development of the indifferent gonad due to differential expression of one or more specific DNA sequences whose behavior is controlled by some temperature sensitive process or to differential action of a gene product such as a protein. There are ZFY and SRY‐like genes in reptiles. We cloned and sequenced a portion of the ZFY gene (Zft) from snapping turtle (Chelydra serpentina) that is found in both sexes. We cloned and sequenced portions of SRY‐like genes (Sra for SRY‐related‐autosomal) from snapping turtle. Similar genes are found in alligator (Alligator mississippiensis) and lizards. Cladistic analysis suggests that there are two or three major families of SRY‐like genes in vertebrates in addition to sex specific SRY genes located on the Y chromosome of eutherian and marsupial mammals. When placed on a phylogenetic tree these data indicate that Sras were present in early tetrapods. Sequestering of the SRY gene on the Y chromosome probably happened only once and this may have been the defining moment that set the mammalian line of Therapsid reptiles apart from other reptilian groups. © 1994 Wiley‐Liss, Inc.
Postecdysial cuticle alteration in the blue crab, Callinectes sapidus: Synchronous changes in glycoproteins and mineral nucleation
Authors: Shafer Thomas H. , Roer Robert D. , Midgette‐Luther Carol , Brookins Teresa A. 
Published: June 2005

AbstractIn order to investigate the control of the onset of postecdysial mineralization of the cuticle of the blue crab, Callinectes sapidus Rathbun, EDTA‐soluble proteins and glycoproteins were analyzed at short intervals after ecdysis by SDS‐PAGE. Gels were either stained with silver, blotted to polyvinylidene difluoride membranes and stained with periodic acid/Schiff reagent (PAS), or blotted to nitrocellulose membranes and probed with a variety of lectins [particularly the mannose‐binding lectins concanavalin A(Con A) and Galanthus nivalis agglutinin (GNA)]. Pieces of cuticle were also tested for their ability to nucleate calcite in vitro. A major change occurred in the biochemistry of the cuticle between 1 and 3 hr after ecdysis. This change, which we term the post‐ecdysial cuticle alteration (PECA), involved 1) loss of a major 66 kDa glycoprotein band, 2) decrease in Con A binding by a 79 kDa protein band, 3) complete loss of PAS‐reactivity of both 66 and 79 kDa proteins, 4)gain in Con A affinity of an existing band at 73 kDa, and 5) an increase in the intrinsic ability of cell‐free cuticle pieces to mineralize, as measured by the in vitro calcite crystal nucleation assay. © 1995 Wiley‐Liss, Inc.
Sensitive assay for cholesterol in biological membranes reveals membrane‐specific differences in kinetics of cholesterol oxidase
Authors: Crockett Elizabeth L. , Hazel Jeffrey R. 
Published: June 2005

AbstractQuantification of cholesterol in biological membranes from a variety of sources is an important step toward understanding cholesterol's roles in membranes function. We extend to biological membranes the fluorometric/enzymatic approach (cholesterol oxidase) to measures cholesterol, originally described for whole cells (Heider and Boyett [1978] J. Lipid Res., 19: 514–518; Gamble et al. [1978] J. Lipid Res., 19: 1068–1070) and serum (Huang et al. [1975] Clin Chem., 21: 1605–1608). This method has a detection limit of 0.3 μg cholesterol. As revealed by comparison with high‐performance liquid chromatography, the fluorometric/enzymatic method with biological membranes is accurate (within 4% and 8% for intestinal and hepatic plasma membranes, respectively). The assay may be completed within 3 to 4 hours and requires neither lipid extraction nor chromatographic techniques. Kinetics of the cholesterol oxidase reaction are membrane‐specific, and first‐order rate constants (k) are positively correlated with membrane order. © 1995 Wiley‐Liss, Inc.
Prolactin receptor concentrations in the skin of mink during the winter fur growth cycle
Authors: Rose Jack , Garwood Todd , Jaber Basem 
Published: June 2005

AbstractThe objectives of this study were to determine: 1) if the skin of mink might be a target organ for prolactin (PRL) by establishing if PRL binding sites (receptors) exist in the cell membranes of skin, and 2) if PRL receptor concentrations change during onset and progression of the winter fur growth cycle. Skin was collected on October 6, 1992 for characterization of PRL receptors and from July through December 1992 (N = 3 mink/month) to evaluate possible changes in PRL receptor concentrations during the fur growth cycle. PRL receptors were quantified using125I‐ oPRL in a validated radioreceptor assay. Scatchard analysis of saturation data revealed a single class of high‐affinity (Kd=5.21 × 10−11±. 84M), low capacity (Bmax= 27.03 ± 3.37 fmoles/mg) binding sites. Only oPRL (40% displacement) and to a lesser extent oGH (3% displacement) inhibited the binding of125I‐oPRL to mink skin cell membranes. No inhibition of125I‐oPRL binding to membranes occurred in the presence of a 500‐fold excess of bTSH of oLH, indicating that the receptors were hormone specific. Concentrations of125I‐oPRL receptors during the onset and development of winter fur growth (July through November) exhibited no significant change. However, following completion of the winter fur growth cycle (December 1) PRL receptor concentration was significantly higher than all preceding months. The greater binding observed at that time may reflect a change in tissue sensitivity, in preparation for growth of the summer pelage. These data suggest to us that the skin of mink is a target organ for PRL and are consistent with the hypothesis that part of the affects of PRL on fur growth occur directly at the level of the skin. © 1995 Wiley‐Liss, Inc.
Cytoskeletal organization in clusters of isolated polarized skate hepatocytes: Structural and functional evidence for microtubule‐dependent transcytosis
Authors: Henson John H. , Capuano Stephanie , Nesbitt David , Hager David N. , Nundy Surajit , Miller David S. , Ballatori Nazzareno , Boyer James L. 
Published: June 2005

AbstractIsolated hepatoctes from the marine vertebrate Raja erinacea (the little skate) retain their structural and functional integrity as clusters of cells formed around a single tubular bile canaliculus, and therefore can be used as a model of polarized hepatocytes in situ. In this study we used confocal and conventional epifluorescence microscopy in conjunction with fluorescent markers and immunocytochemistry to examine the structure and function of the cytoskeleton in these cells. Actin filaments in the hepatocyte clusters were found cortically and also concentrated in a pericanalicular array, while microtubules disrupting agent, nocodazole, resulted in the microtubules depolymerizing from the basolateral surfaces towards the apical surface, indicating that the microtubules were oriented with their plus ends at the basolateral surface and their minus ends at the apical surface. Nocodazole was also found to disrupt the ability of clusters to transcytose a fluorescent bile salt derivative into their canalicular lumens. We detected cytoplasmic dynein in skate hepatocyte homogenates by Western blotting using an anti‐dynein intermediate chain anti‐body, and immunofluorescent staining of intact hepatocytes revealed a punctate vesicular pattern. The polarized arrangement of microtubules, the presence of cytoplasmic dynein, and the inhibition of bile salt secretion by nocodozole are consistent with the microtubule cytoskeleton playing a fundamental role in the mediation of transcytosis, endocytosis, and bile excretory function in these hepatocytes. These polarized isolated skate hepatocytes represent an excellent experimental model for the in vitro study of hepatic transport, and allow for important comparative studies aimed at elucidating the evolutionarily conserved nature of various hepatocyte structures amongst the vertebrates. © 1995 Wiley‐Liss, Inc.
Influence of pH and temperature on hemolysis by adult Schistosoma mansoni membranes
Authors: Kasschau Margaret R. , Byam‐Smith Mary P. , Gentry Deborah S. , Watson Fay N. 
Published: June 2005

AbstractMembrane fractions from homogenized adult Schistosoma mansoni are known to lyse host red blood cells (RBC's), Which serve as an important nutrient source for the parasite, In order to learn more about the homolytic process, we investigated the effects of pH and temperature on the steps involved in the hemolytic process. For maximum schistosome induced hemolysis to occur the worm lytic agent must be in the contact with RBCs in a low pH (pH 5.1), high temperature (37°C) environment for a short time (30 min), after which hemolysis occurs at both pH 7.5 and 5.1 At pH 7.5 the hemolytic process is relatively temperature independent and highly concentration dependent. Dose‐response experiments suggest that a multi‐hit process of hemolysis is probably involved. Temperature and dextran experiments suggest that a pore is formed in the RBC membrane at pH 7.5 At pH 5.1 hemolysis is temperature dependent and not very concentration dependent. Dose‐response data suggest that a single‐hit process of hemolysis is utilized at low pH. The hemolytic process at pH 7.5, the pH of the host blood, and pH 5.1, the approximate pH of the worm gut, appears to be very different. © 1995 Wiley‐Liss, Inc.
Comparative study of Msx‐1 expression in early normal and vitamin A‐deficient avian embryos
Authors: Chen Yiping , Kostetskii Igor , Zile Maija H. , Solursh Michael 
Published: June 2005

AbstractHomeobox‐containing genes may play an important role in establishing embryonic patterns during development of vertebrates. Retinoic acid is able to induce expression of Hox genes in cells in culture and to alter expression patterns in the developing vertebrate embryos. Using wholemount in situ hybridization, we have examined and compared the expression patterns of a homeobox‐containing gene, Msx‐1, in early normal and vitamin A‐deficient quail embryos. At gastrulation stage, Msx‐1 is primarily expressed in the posterior half of both normal and vitamin A‐deficient embryos. However, the gene is expressed wider and stronger in the vitamin A‐deficient embryos. At neurulation stages, Msx‐1 is continuously expressed in the posterior region up to Hensen's node and in the edge of the neural fold in both normal and vitamin A‐deficient embryos. Notably, in the vitamin A‐deficient embryos, Msx‐1 is expressed more strongly and is also expressed ectopically in the anterior and precardiac regions. These results provide evidence that endogenous retinoids are involved in the normal expression of Msx‐1 in avian embryo and that the expression of Msx‐1 is downregulated by endogenous and physiological retinoids in vivo during early avian embryogenesis. © 1995 Wiley‐Liss, Inc.
Promotion of differentiation of newt primary spermatocytes into spermatids by mammalian FSH via Sertoli cells
Authors: Ji Zai‐Si , Kubokawa Kaoru , Abé Shin‐Ichi 
Published: June 2005

AbstractOur previous studies showed that mammalian follicle‐stimulating hormone (FSH) promoted the differentiation of primary spermatocytes into elongated spermatids in organ culture of testes fragments from Cynops pyrrhogaster. To elucidate the mechanism of FSH action, in this study the testes in the primary spermatocyte stage were dissociated and fractionated into germ and somatic cells, the latter comprising more than 80% Sertoli cells. Radioreceptor assays showed that FSH bound to somatic cells, very probably Sertoli cells, but not to germ cells. FSH elevated intracellular cyclic AMP levels in somatic but not germ cells.In cultures of cell aggregates somatic cells stimulated the differentiation of primary spermatocytes into round spermatids even in the absence of FSH, but to a greater extent in the presence of FSH. However, in the absence of somatic cells the extent of differentiation was similar, irrespective of the presence of FSH. Luteinizing hormone (LH) had no stimulatory effects. Most, if not all, of the somatic cells adherent to germ cells were Sertoli cells based on the criterion that they contained lipid droplets. This indicates that FSH stimulates the differentiation of primary spermatocytes via Sertoli cells.To examine if direct contact between Sertoli cells and germ cells is required for the promotion of differentiation, Sertoli and germ cells were cultured in two different compartments which were separated by a permeable membrane. Under these conditions Sertoli cells did not promote the differentiation of primary spermatocytes either in the absence or presence of FSH, indicating that direct contact between germ and Sertoli cells is required for Sertoli cells to promote the differentiation of primary spermatocytes. © 1995 Wiley‐Liss, Inc.
Successful production of chimeric honeybee larvae
Authors: Omholt Stig W. , Rishovd Svein , Hagen Arne , Elmholdt Odd , Dalsgard Brita , Fromm Sigurd 
Published: June 2005

AbstractThe honeybee (Apis mellifera) is likely to become the major model system for resolving the genetic basis of advanced perceptual and behavioural abilities of highly social insects because of the high level of knowledge regarding its physiology and social behaviour and its ease of handling. Here we report for the first time genetic transformation of honeybees by the production of chimeric larvae obtained by nuclear transplantation, identified by use of a genetic marker. Two chimeras expressed only the genotype of the donor indicating developmental totipotency of nuclei up to the 11th cleavage mitosis. © 1995 Wiley‐Liss, Inc.
Ontogeny of respiratory function in crustaceans exhibiting either direct or indirect development
Authors: Spicer John I. 
Published: June 2005

AbstractDialysed haemolymph from the planktonic larvae of the Norwegian lobster Nephrops norvegicus possessed a lower O2 affinity than the benthic adult stage at equivalent pH. This difference could be correlated with the ability to maintain O2 uptake during progressive hypoxia; adult individuals showed better developed regulation than the larvae. The intrinsic O2 affinity of both larval and adult haemocyanin (Hc) could be modified by preexposure to chronic hypoxia. In contrast, there were no significant differences noted in either Hc O2 affinity or the ability to regulate O2 uptake during progressive hypoxia between newly hatched and adult individuals of the direct developing amphipod Echinogammarus pirloti. Unlike the case in N. norvegicus preexposure to chronic hypoxia did not result in any change in respiratory performance at the level of the whole animal or in intrinsic Hc O2 affinity. The changes (or absence of them) in these aspects of the respiratory biology of the two species examined are discussed in the context of their ecological requirements. © 1995 Wiley‐Liss, Inc.
Changes in the distribution of fibroblast growth factor in the teleostean testis during spermatogenesis
Authors: Watanabe Akihiko , Onitake Kazuo 
Published: June 2005

AbstractThe distribution of fibroblast growth factor (FGF) in the testes of Salvelinus leucomaenis and Oryzias latipes was investigated by immunofluorescence staining. In S. leucomaenis, spermatogonia were strongly stained in the infantile testis. When human chorionic gonadotrophin (HCG) was injected into individual fish, the uptake of 5‐bromo 2′‐deoxyuridine (BrdU) occurred within a day. At the same time, FGF became undetectable in spermatogonia, but appeared for the first time around the testicular somatic cells. A similar distribution was seen in the mature testes of S. leucomaenis and O. latipes. The positively immunostained area corresponded to the predominant site of the Sertoli cells. This pattern of distribution of FGF suggests that FGF plays an important role in the initiation and progression of spermatogenesis in the teleostean testis. © 1995 Wiley‐Liss, Inc.