bluuebunny/crossref_metadata_2025_split huggingface dataset:
Concurrent protein synthesis is required for in vivo chitin synthesis in postmolt blue crabs
Authors: Horst Michael N. 
Published: June 2005

AbstractChitin synthesis in crustaceans involves the deposition of a protein‐polysaccha‐ride complex at the apical surface of epithelial cells which secrete the cuticle or exoskeleton. The present study involves an examination of in vivo incorporation of radiolabeled amino acids and amino sugars into the cuticle of postmolt blue crabs, Callinectes sapidus. Rates of incorporation of both 3H leucine and 3H threonine were linear with respect to time of incubation. Incorporation of 3H threonine into the endocuticle was inhibited greater than 90% in the presence of the protein synthesis inhibitor, puromycin. Linear incorporation of 14C glucosamine into the cuticle was also demonstrated; a significant improvement of radiolabeling was achieved by using 14C‐N‐acetylglu‐cosamine as the labeled precursor. Incorporation of 3H‐N‐acetylglucosamine into the cuticle of postmolt blue crabs was inhibited 89% by puromycin, indicating that concurrent protein synthesis is required for the deposition of chitin in the blue crab. Autoradiographic analysis of control vs. puromycin‐treated crabs indicates that puromycin totally blocks labeling of the new endocuticle with 3H glucosamine. These results are consistent with the notion that crustacean chitin is synthesized as a protein‐polysaccharide complex. Analysis of the postmolt and intermolt blue crab cuticle indicates that the exoskeleton contains about 60% protein and 40% chitin. The predominant amino acids are arginine, glutamic acid, alanine, aspartic acid, and threonine.
Either chick embryo dermis or retinoid‐treated mouse dermis can initiate glandular morphogenesis from mammalian epidermal tissue
Authors: Hardy Margaret H. , Dhouailly Danielle , Törmä Hans , Vahlquist Anders 
Published: June 2005

AbstractExcess retinoids can cause developing mouse vibrissa follicles to be transformed into mucous glands in organ culture. The objective was to test the hypothesis that retinoids act in this system by altering morphogenetic properties of the dermis. After inititation by retinoic acid (RA) in organ culture, glands were shown to develop further in embryonic skin grafted to the chick chorioallantoic membrane (CAM). Recombinants of 12.5 day mouse epidermis with untreated or RA‐treated mouse or chick dermis were then grafted to CAM for 7 days. For homospecific recombinants, 13.5 day mouse dermis originated from 11.5 day skin cultured for 2 days, with or without 5.2 μg/ml RA. For heterospecific recombinants, 12 day dermis came from chick embryos, previously injected with 250 μg RA. Glands were absent from the homospecific recombinants including untreated mouse dermis, but appeared in 26% of those with RA‐treated dermis. Among heterospecific recombinants, 75% of those with RA‐treated chick dermis and 29% of those with untreated dermis had glands. Untreated 10–12 day chick skin contained two forms of endogenous vitamin A, retinol (4.5 μg/g protein) and dehydroretinol (3.7 μg/g protein), while 13–14 day mouse skin contained only retinol (1.8 μg/g protein), as shown by high performance liquid chromatography. RA injection increased retinol and dehydroretinol in chick skin, while RA was undetectable. Thus RA can act through mouse dermis to form epithelial glands and through chick dermis to increase the incidence of glands. The glands in recombinants with untreated chick dermis may result from the higher levels of endogenous retinoids in chick skin, compared with mouse skin.
Radioreceptor Assay for growth hormone in coho salmon (Oncorhynchus kisutch) and its application to the study of stunting
Authors: Gray Elisabeth S. , Young Graham , Bern Howard A. 
Published: June 2005

AbstractBinding sites for native chum salmon growth hormone (sGH) in coho salmon (Oncorhynchus kisutch) hepatic membranes were analyzed by radioreceptor assay. Displaceable (specific) binding represented up to 25% of total radiolabeled sGH added. Binding was dependent on buffer pH and membrane protein concentration, and was complete by 24 hours at 15°C. Specific binding was greatest in liver membranes, and was also detected in rr.uscle, ovary, gill, kidney, and brain. Scatchard analyses indicated a single class of hepatic binding sites that were specific for sGH. In stunts, abnormal seawater salmon with elevated plasma GEI levels and inhibited growth, specific binding of sGH to liver membranes was three times lower thiin in normal seawater smolts. The concentration of salmon GH binding sites was decreased in stunt livers by 60%, while their affinity for sGH was unchanged. Down‐regulation of hepatic GH receptors by high plasma GH levels may explain in part the low sGH binding in stunts.
Evidence for phosphorylation/dephosphorylation control of phosphofructokinase from organs of the Anoxia‐Tolerant sea mussel Mytilus edulis
Authors: Michaelidis Basile , Storey Kenneth B. 
Published: June 2005

AbstractThe transition from aerobic to anoxic conditions induced stable modifications of the kinetic and regulatory properties of 6‐phosphofructo‐1‐kinase (PFK) from the posterior adductor muscle and hepatopancreas of the marine bivalve mollusc Mytilus edulis L. Anoxia resulted in a reduction in the maximal activity of PFK, a decrease in affinity for fructose‐6‐P (S0.5 increased by 60% in muscle and twofold in hepatopancreas), reduced effects of activators (AMP, fructose‐2,6‐P2), and reduced inhibition by ATP (I50 increased 2–2.4 fold). Organ‐specific differences in PFK properties were greatest for enzyme activators, with the hepatopancreas enzyme showing much lower Ka values for AMP and fructose‐2,6‐P2 as well as activation by inorganic phosphate (Ka 0.07 mM aerobic, 0.11 mM anoxic). By contrast, the muscle enzyme was not affected by Pi and neither enzyme was inhibited by citrate. To determine if the anoxia‐induced modifications of PFK were due to covalent modification of the enzyme protein, PFK preparations were incubated with ATP + Mg2+ + protein kinase second messengers (cAMP, cGMP, or Ca2+ plus phorbol 12‐myristate 13‐acetate) or with Mg2+ + alkaline phosphatase. Protein kinase action on posterior adductor muscle PFK increased enzyme Vmax, and affinity for fructose‐6‐P. cAMP‐ or cGMP‐stimulated protein kinase had the same action on hepatopancreas PFK; but incubation with stimulators of protein kinase C had the opposite effect on the enzyme. Alkaline phosphatase treatment reversed the effects of in vitro phosphorylation. The data suggest that the glycolytic rate depression (reverse Pasteur effect) that occurs with the transition to anoxia in these facultative anaerobes is facilitated by reversible phosphorylation control over the activity of PFK.
Heterogeneity of purified actin in the electric organ of the electric eel Electrophorus electricus
Authors: AyresSá Lilian , Neto Vivaldo Moura , de Oliveira Mécia M. , Chagas Carlos 
Published: June 2005

AbstractActin extracted from the electric organ and epaxial muscle of the electric eel Electrophorus electricus was characterized by several biochemical techniques. Isoelectric focusing gels revealed two isoforms of actin in the electric organ, in contrast to the unique form of actin present in the epaxial muscle of this eel and the rabbit leg muscle, which were used as controls. Proteolytic digestion and immunoblotting analysis confirmed that these isoforms were composed of actin. When actin from the electric organ was mixed with actin from the epaxial muscle or from rabbit muscle and subjected to isoelectric focusing gel, it was possible to identify an alpha‐actin isoform in the electric organ as well as a more basic actin that migrated in the same manner as cytoplasmic actin or gamma actin from smooth muscle. The data are interpreted in terms of the differentiation of the electric organ of E. electricus.
Vitellogenin purification and development of assay for vitellogenin receptor in oocyte membranes of the tilapia (Oreochromis niloticus, linnaeus 1766)
Authors: Chan S. L. , Tan C. H. , Pang M. K. , Lam T. J. 
Published: June 2005

AbstractAn assay has been successfully developed for vitellogenin receptors in isolated oocyte membranes of the tilapia (Oreochromis niloticus). Vitellogenin produced by estrogen stimulation of the male tilapia was purified by anion‐exchange chromatography on DEAE‐Sephacel and identified by its incorporation of 32P‐orthophosphate and 3H‐leucine in vivo. Only one molecular form of vitellogenin was found to be induced by estrogen treatment. After iodination with Iodogen, the 125I‐vitellogenin was shown to be immunologically similar to the unlabeled protein and was used to develop an assay for vitellogenin receptors. For such assays, the optimal conditions for binding were pH 7.4, 6‐h incubation at 23°C with 7.5 mM Mg2+ and 10 mM Ca2+. The magnitude of the specific binding was dependent on the amount of oocyte membranes and was saturable. The binding shows both tissue and protein specificity: the 125I‐vitellogenin binds specifically to only oocyte membranes and not to those of the brain, muscles, liver, intestine, and testis; its binding was displaceable only by unlabeled vitellogenin and a yolk protein extract. Saturation studies and Scatchard analyses revealed only a single class of binding sites. These studies provide unequivocal evidence that the binding sites for vitellogenin in the tilapia oocytes are specific receptors. The number and affinity (KD) of these receptors increase from the previtellogenic (9.98 × 109/oocyte) to the vitellogenic stage (3.65 × 1012/oocyte), and remained unchanged at the preovulatory stage (3.53 × 1012/oocyte), at which time the affinity of the receptors was also highest (0.3 μM).
Fate of haploid parthenogenetic cells in mouse chimeras during development
Authors: Ito Michihiko , Kaneko‐Ishino Tomoko , Ishino Fumitoshi , Matsuhashi Michio , Yokoyama Minesuke , Katsuki Motoya 
Published: June 2005

AbstractThe developmental capability of haploid parthenogenetic cells was investigated by studies on haploid parthenogenetic ⟷ fertilized mouse chimeras. Two chimeras were born. One female chimera was smaller at birth and grew slower than its littermates. The distribution of haploid‐derived cells in the chimeras was analyzed 11 months after their birth. Cells derived from haploid embryos were found only in the brain, eyes, pigment cells in hair follicles, and spleen, in which they constituted 30%, 20%, 10%, and <5%, respectively, of the cells. The correlation between the parthenogenetic contribution to the brain and growth retardation is discussed. All of the cells examined in these chimeric organs (brain and eyes) contained a diploid amount of DNA, suggesting that diploidization of the haploid parthenogenetic cells occurred during development. Possibly, the haploid state is not sufficient for cell growth, even in chimeras with fertilized embryos.
Expression of the cell adhesion molecules, L‐CAM and N‐CAM during avian scale development
Authors: Shames Rose B. , Jennings Anita G. , Sawyer Roger H. 
Published: June 2005

AbstractTo examine the involvement of cell adhesion molecules in the inductive epithelial‐mesenchymal interactions during avian scale development, a study of the spatiotemporal distribution of L‐CAM and N‐CAM was undertaken. During scutate scale development, L‐CAM and N‐CAM are expressed together in cells of the transient embryonic layers destined to be lost at hatching. The ongoing linkage of the cells of these layers by both CAMs sets them apart, early in development, as unique cell populations. L‐CAM and N‐CAM were also expressed simultaneously at the basal surface of the early germinative cells where signal transduction is presumed to occur. In spite of the differences in cell shape, adhesion, density and proliferative state between populations of epidermal placode and interplacode cells, the expression of L‐CAM and N‐CAM appeared to be uniform and nondiscriminating for these discrete cell lineages. The same pattern of L‐CAM and N‐CAM expression was observed during morphogenesis of reticulate scales that develop without placode formation. While L‐CAM and N‐CAM are present during the early stages of scale development and most likely function in cell adhesion, the data do not support a role for these adhesion molecules in the formation of the morphogenetically critical placode and interplacode cell populations.In both scale types, L‐CAM became predominantly epithelial, and N‐CAM became predominantly dermal as histogenesis occurred. Initially, N‐CAM was concentrated near the basal lamina where it may be involved in the reciprocal epidermal‐dermal interactions required for morphogenesis. However, as development of the scales progressed, N‐CAM disappeared from the tissues. L‐CAM expression continued in the epidermis and was intense on all suprabasal cells undergoing differentiation into either an αstratum or β‐stratum. However, L‐CAM was more prevalent on the basal cells of α‐keratinizing regions than on the basal cells of β‐keratinizing regions.
Fibroblast growth factor and culture in monolayer rescue mesoderm cells destined to die in the developing avian wing
Authors: MacCabe J. A. , Blaylock R. L. , Latimer J. L. , Pharris L. J. 
Published: June 2005

AbstractIn an effort to elucidate control mechanisms for developmentally programmed cell death, conditions were sought that rescue the cells destined to die. Three areas of mesodermal cell death in the chick wing were examined: the posterior necrotic zone (PNZ), the opaque patch (OP), and apical mesoderm. The PNZ and OP are areas of normally programmed cell death, whereas the apical mesoderm undergoes cell death only after the overlying apical ectodermal ridge is excised. Cell death in vitro was quantitated using the chromium‐release assay. While these tissues undergo apparently normal cell death in organ culture, in monolayer culture almost all are rescued. In addition, the cells are rescued by the addition of fibroblast growth factor to organ cultures. Since fibroblast growth factor is present in decreasing amounts in the limb at this stage of development, normal cell death may occur upon withdrawal of growth factor.
Effects of olfactory tract lesions on gonadotropin and milt responses to the female sex pheromone, 17α, 20β‐dihydroxy‐4‐pregnen‐3‐one, in male goldfish
Authors: Dulka Joseph G. , Stacey Norman E. 
Published: June 2005

AbstractFor approximately 10 h before ovulation, female goldfish release the gonadal steroid 17α,20β‐dihydroxy‐4‐pregnen‐one (17,20β‐P) to the water where it functions as a potent sex pheromone that induces in males a rapid (15‐min) increase in blood gonadotropin (GtH) and a subsequent (4–6 h) increase in milt (sperm and seminal fluid) volume. To determine which olfactory pathways mediate responses to pheromonal 17,20β‐P, this study examined the effects of various olfactory tract (OT) lesions on the 17,20β‐P‐induced GtH and milt responses in male goldfish. Males remained intact (INTACT) or received either a sham operation (SHAM), complete bilateral OT section (OTX), or bilateral lesions to the lateral (LOTX) or medial (MOTX) subdivisions of the paired OTs. At both 2 days and 1 week after surgery, one‐half of each treatment group was exposed to either ethanol (control) or water‐borne 17,20β‐P for 1 h and then blood sampled for GtH determination. Milt was stripped and collected from all fish 7–8 h after the exposures had commenced. Exposure to water‐borne 17,20β‐P induced increases in GtH and milt volume in INTACT, SHAM, and LOTX animals but failed to evoke these responses in OTX and MOTX fish. The results indicate that central projections of the medial olfactory tracts constitute a functional neuroanatomical pathway by which pheromonal 17,20β‐P stimulates GtH and milt production in goldfish. In addition, functional and anatomical similarities between this pathway and the mammalian vomeronasal system are discussed.
Potassium dependence for sperm–egg fusion in mice
Authors: Boldt Jeffrey , Casas Adela , Whaley Elizabeth , Creazzo Tony , Lewis Jill B. 
Published: June 2005

AbstractIn this study, we examined the potassium requirements for sperm–egg fusion in mouse. Zona‐free mouse eggs prepared by the method described by Boldt and Wolf were inseminated with capacitated sperm in culture media containing 0‐6 mM extracellular K+, and scored for penetration. Penetration of zona‐free eggs was dependent on extracellular K+, with no penetration observed under K+ ‐free conditions. Media transfer experiments indicated that the lack of penetration observed was due to effects on fusion, and not on postpenetration events such as sperm head decondensation. To analyze whether the K+ effect was attributable to an effect on the sperm (i.e., occurrence of acrosome reactions), sperm were treated with the Ca2+ ionophore A23187 before insemination. Less than 5% of zona‐free eggs were penetrated with ionophore‐treated sperm under K+ ‐free conditions, suggesting that K+ is required for fusion per se. Addition of ionophore to insemination cultures similarly did not overcome the block to fusion observed under K+ ‐free conditions. The potassium channel blockers 4‐aminopyridine (0.1‐5 mM) and tetraethyl ammonium chloride (5–50 mM) had no inhibitory effect on fusion. These data indicate that extracellular K+ is required for sperm‐egg fusion and that this requirement may not involve membrane K+ channels.
Culture medium and protein supplementation influence in vitro fertilization and embryo development in the domestic cat
Authors: Johnston L. A. , Donoghue A. M. , O'brien S. J. , Wildt D. E. 
Published: June 2005

AbstractThe influence of culture medium and protein supplements on in vitro fertilization (IVF) and morula‐to‐blastocyst development in culture was examined in the domestic cat. In Study I, follicular oocytes were fertilized and cultured in 1) modified Krebs Ringer bicarbonate (mKRB); 2) modified Tyrode's solution (TALP) without phosphate or glucose; or 3) Ham's F10. All media contained bovine serum albumin (BSA). Fertilization rates were similar (P>.05) among mKRB (75.0%), TALP (70.6%), and Ham's F10 (80.0%) treatments. Compared to TALP (77.8%), more (P<.05) embryos in Ham's F10 (95.0%) developed to the morula stage; development of mKRB embryos (88.9%) was intermediate and not different (P>.05). Study II evaluated the effects of protein availability and type on IVF and embryo growth. Ham's F10 was supplemented with polyvinylalcohol (PVA, 2 mg/ml), BSA (4 mg/ml), fetal calf serum (FCS, 5%), or estrous cat serum (ECS, 5%) and used to fertilize and culture embryos. Fertilization was enhanced (P<.05) using either FCS (84.0%) or ECS (85.2%) compared to PVA (67.3%). Oocytes exposed to BSA fertilized at a rate (76.1%) similar (P>.05) to other treatments. Embryos exposed to all four treatment groups (PVA, 82.8%; BSA, 82.8%; FCS, 92.9%; or ECS, 97.8%) were equally capable (P>.05) of becoming morulae. However, more FCS‐ or ECS‐supplemented morulae continued to the early blastocyst stage (30.8%, 22.2%, respectively, P<.05) than PVA‐ (10.3%) or BSA‐ (13.8%) exposed morulae. In the domestic cat IVF system, the type of medium and protein supplement used appears to have a greater impact on embryo development in vitro than on fertilization. There also is a morula‐to‐blastocyst developmental block for cat embryos resulting from IVF which is partially circumvented by adding serum to the culture medium. Ham's F10 containing FCS or ECS produces the highest incidence of fertilization (∼85%), and ∼2‐fold more of these embryos develop in culture to blastocysts compared to embryos supplemented with PVA or BSA.
Dependence of body growth on thyroid activity in turtles
Authors: Denver Robert J. , Licht Paul 
Published: June 2005

AbstractWe surgically thyroidectomized (Tx) or sham‐operated hatchling slider turtles—Trachemys (Pseudemys) scripta—and measured their growth (mass and carapace length) for 5 to 7 months. Autopsy at the end of the experiments revealed that up to 30% of the thyroidectomized animals had regenerated thyroid follicles (thyroids had few but enlarged follicles). Therefore, we segregated thyroidectomized turtles a posteriori into two groups: those with observable thyroid tissue at autopsy, greater than 3 ng/ml plasma thyroxine (T4), and normal plasma T4 binding capacity were designated partial Tx (PTx), and others with no observable thyroid tissue, less than 3 ng/ml plasma T4, and low plasma T4 binding capacity were designated Tx. Growth rate was significantly reduced 6–8 weeks after thyroidectomy in the Tx animals; length‐specific growth rate was affected sooner than mass‐specific growth rate. Growth of Tx animals continued to diverge from sham turtles through the end of the experiment; PTx animals did not differ from shams at any time. In a second experiment growth rate was reduced in Tx turtles maintained under both varibale (14L:10D, thermal gradient of 19 to 40°C) and constant (constant light and temperature—30°C) environmental conditions (i.e., reduced growth rate was probably not related to a thermoregulatory dysfunction). However, all animals maintained under the constant conditions stopped growing after 3 months, whereas turtles kept under varibale conditions continued to grow to the end of the experiment (4.5 months). Thyroxine (T4) replacement therapy of long‐term Tx turtles restored growth after 6 weeks.Plasma thyrotropin (TSH) was greatly elevated in Tx turtles (301 ± 48.7 ng/ml) and at low to nondetectable levels in controls (⩾ 1 ng/ml). T4 replacement therapy was effective in reducing TSH levels in Tx turtles. Plasma T4 and TSH concentrations showed the expected inverse relationship. However, although PTx animals had elevated plasma T4 levels that were in the lower range of the sham controls (PTx: 36.6 ± 8.2 vs. 112.7 ± 17.1 ng/ml in sham), their plasma TSH was also significantly elevated (36.5 ± 9.3 ng/ml vs. 0.8 ± 0.2 ng/ml in sham). These results demonstrate the requirement of an intact thyroid gland for normal growth of turtles, and provide the first direct evidence for a role for the thyroid in body growth of a reptile. They also reveal that the set‐point for the feedback between the thyroid and pituitary secretion can be altered by perturbation of thyroid activity.
Identification of epididymal proteins associated with hamster sperm
Authors: Robitaille Gilles , Sullivan Robert , Bleau Gilles 
Published: June 2005

AbstractThe electrophoretic analysis of the proteins that were extracted from immature caput and mature cauda sperm showed evidence of accumulation of several proteins during the epididymal transit of the sperm. An antiserum, raised against detergent‐extracted proteins from mature spermatozoa, immunostained six epididymal proteins with apparent molecular masses of 16, 22.5, 26, 37, 60, and 80 kDa on Western blots of epididymal fluid. Of these proteins, only the 26 kDa protein was significantly immunodetected in proximal caput epididymal fluid. Its biosynthesis by caput epididymis was confirmed by immunoprecipitation of an in vitro translated product of caput poly (A) RNA. The homology of the 26 kDa epididymal protein with the 26 kDa sperm protein was verified by epitope mapping. The other epididymal proteins were found in the fluid of the more distal portions of the organ. Their presence in the epididymal fluid coincided with their detection on the sperm. These epididymal proteins were considered to be sperm‐coating proteins.