bluuebunny/crossref_metadata_2025_split huggingface dataset:
Protein synthesis in lethal nucleocytoplasmic hybrids between the species Pleurodeles waltlii Michahelles and Ambystoma mexicanum shaw (Urodele amphibians) obtained by nuclear grafting
Authors: Aimar C. , Desvaux F. X. , Chalumeau‐Le‐Foulgoc M. Th. 
Published: June 2005

AbstractUsing Polyacrylamide gel electrophoresis, proteins stemming from the nucleus of the donor species in nucleocytoplasmic hybrids were determined. The interspecific lethal nucleocytoplasmic hybrids of Pleurodeles waltlii and Ambystoma mexicanum were studied. The presence of these proteins at the blastula or early gastrula stages attests to the early nuclear control of their synthesis.
Phagocytosis of chloroplasts in Placida dendritica (Gastropoda: Sacoglossa)
Authors: McLean N. 
Published: June 2005

AbstractPhagocytosis of algal chloroplasts by digestive gland cells in the sacoglossan opisthobranch Placida dendritica is described. It is suggested that engulfment of chloroplasts is accomplished by veils of cytoplasm which are derived from elongating microvilli.
Respiratory behaviour of sea‐urchin spermatozoa. I. Effect of pH and egg water on the respiratory rate
Authors: Ohtake Hideki 
Published: June 2005

AbstractEffects of pH and egg water on the respiration of sea‐urchin spermatozoa were polarographically studied in three sea‐urchins and one starfish species. Sea‐urchin sperm respiration is extremely sensitive to change in the pH of the suspending medium over a wide range. In normal‐sea water, the pH of the sperm suspension decreased from 8.02 to 7.62, after four to five minutes' incubation at 18°C. The Respiratory Dilution Effect could be recognized in the same medium. However, when sea water was buffered with HEPES at pH 8.2, the Effect was no longer observed. The diffusate from egg water (jelly coat solution) brought about a striking increase in the respiration when added to moderately respiring spermatozoa in HEPES‐sea water of pH values lower than 7.9. No increase in the respiration was observed when the diffusate was added to vigorously respiring spermatozoa in HEPES‐sea water of pH values higher than 8.2. Sperm motility was also inhibited by acid pH, and this inhibition was reversed by the addition of the diffusate. It does not seem that there is any species‐specificity among three sea‐urchins and one starfish used. The role of the diffusate is discussed in relation to the penetration of spermatozoa through the jelly coat to the egg surface.
The role of calcium in the acrosome reaction: An analysis using ionophore A23187
Authors: Talbot P. , Summers R. G. , Hylander B. L. , Keough E. M. , Franklin L. E. 
Published: June 2005

AbstractThe role of Ca+2 in the acrosome reaction of echinoid and mammalian sperm was investigated using the Ca+2 transporting ionophore A23187. The ionophore induced morphologically normal acrosome reactions in both types of sperm (as assessed by electron microscopic observation of echinoid sperm and phase contrast microscopic observation of mammalian sperm). In echinoids, these reactions were immediate. In the guinea pig and hamster, ionophore significantly decreased the capacitation interval; early reactions were accompanied by activation of motility. Ionophore induced reactions were affected by sperm, ionophore and Ca+2 concentrations. Since both ionophore induced and natural reactions require extracellular Ca+2, it is suggested that an influx of Ca+2 represents the initial step of the acrosome reaction. Under natural conditions, the permeability change which results in Ca+2 influx may be induced in echinoid sperm by egg jelly and may occur in mammalian sperm during capacitation.Ionophore A23187 should prove an experimentally useful drug for further study of the acrosome reaction since its effect on cells is understood, it induces synchronous reactions in a high percentage of sperm, and it conveniently reduces the capacitation interval in mammalian sperm.
Biosynthesis of crustacean lipovitellin. III. The incorporation of labeled amino acids into the purified lipovitellin of the crab Pachygrapsus crassipes
Authors: Lui Chung W. , O'Connor John D. 
Published: June 2005

AbstractElectrophoretically pure subunits were obtained from the lipovitellin (LV) of the intertidal crab, Pachygrapsus crassipes. The molecular weights of these subunits were determined. In addition, it was demonstrated that the ovaries of Pachygrapsus, incubated in vitro, incorporated 3H‐leucine into the two principal subunits of lipovitellin. At the end of a 30 hour incubation the specific activity of each of the principal subunits was approximately 30,000 dpm/mg protein. It is concluded that the ovaries of Pachygrapsus crassipes are capable of synthesizing the proteinaceous yolk found in the mature egg.
Esterase isozyme patterns in developing embryos of Brachydanio rerio (zebra danio), Brachydanio abolineatus (pearl danio), and their hybrids
Authors: Hart Nathan H. , Cook Marie 
Published: June 2005

AbstractThe ontogeny of esterase isozymes in Brachydanio rerio (zebra danio), Brachydanio albolineatus (pearl danio), and hybrids formed by their reciprocal crosses was investigated using polyacrylamide disc electrophoresis. Seven esterase isozymes were identified in each species from the unfertilized egg stage to nine days posthatch. Electrophoretic analysis of qualitative changes in enzyme pattern indicated that some esterases were present at all stages of development while other esterases abruptly appeared at a specific stage of morphological differentiation. The esterases of both species were classified on the basis of differential substrate and inhibitor specificities.In developing hybrids formed by B. rerio eggs inseminated with B. albolineatus sperm, the maternal isozyme pattern persisted until Stage 17 (gastrulation). Embryonic extracts from Stage 17 onward showed a slow‐moving, DFP‐sensitive carboxylesterase of paternal origin. In developing hybrids fromed by B. albolineatus eggs inseminated with B. rerio sperm, a paternal contribution to the esterase pattern was probably present by the end of gastrulation; esterase activity of distinctively paternal origin was present by Stage 22 (retinal pigmentation). The maternal contribution to the total esterase profile appeared to remain high through hatching.Additional evidence for gene activity at gastrulation was obtained in experiments utilizing actinomycin‐D and cycloheximide. Results of exposing embryos of B. rerio to 15μg/ml of actinomycin‐D indicated that transcription of the template RNA coding for cholinesterase occurred during gastrulation or some 20–30 hours prior to the appearance of the isozyme at Stage 22. This template RNA was translated sometime during the 10‐hour interval immediately preceding Stage 22.
Base composition of DNA from some reptiles
Authors: Olmo Ettore , Odierna Gaetano 
Published: June 2005

AbstractThe DNA base composition was studied in 9 reptilian species (4 chelonians, 3 saurians, and 2 ophidians) by the thermal denaturation method. This preliminary investigation has brought to light differences in GC percentages and in the shape of melting curves between chelonian DNA and that from saurians and ophidians.
Involvement of a trypsin‐like activity in sperm penetration of zona‐free mouse ova
Authors: Wolf Don P. 
Published: June 2005

AbstractThe presence of trypsin inhibitors during insemination reduced penetration of zona‐intact and zona‐free mouse ova by capacitated sperm. This inhibition was dependent upon both concentration of inhibitor and sperm. Preincubation of gametes in inhibitors did not markedly influence their subsequent fertility, nor did it alter sperm motility. Trypsin inhibitors may exert an effect on penetration by interfering with the induction of the sperm acrosome reaction or with the process of sperm‐egg fusion.
Tail regeneration in the plethodontid salamander, Plethodon cinereus: Induced autotomy versus surgical amputation
Authors: Dinsmore Charles E. 
Published: June 2005

AbstractRegeneration of the tail in the plethodontid salamander, Plethodon cinereus, occurs following either surgical amputation or induced autotomy. Autotomy may occur along any one of the caudal myosepta which form natural cleavage planes. The distally attached myofibers break away from the myoseptum which then becomes part of the stump surface remaining intact during subsequent regeneration of the distal segments. Under these conditions, therefore, muscle fibers do not normally participate in tail regeneration. If, however, the myofibers of a caudal myotome are interrupted as in mid‐segment amputation, the damaged fibers undergo hyaline degeneration and are largely replaced by connective tissue often as far proximally as the next myoseptum. Other tissues at the amputation surface are concurrently engaged in the epimorphic regeneration of the tail, including myogenesis, though at a slower initial rate than that following autotomy. Muscle cells, therefore, appear not to participate in epimorphic tail regeneration in Plethodon cinereus following either surgical amputation or induced autotomy.
Turnover of cytochrome C in skeletal muscle of green sunfish (Lepomis cyanellus, R.) during thermal acclimation
Authors: Sidell Bruce D. 
Published: June 2005

AbstractThe concentration of cytochrome c in the skeletal muscle of the green sunfish (Lepomis cyanellus) increases with decreasing temperature of acclimation: 1.51 ± 0.09, 1.17 ± 0.03, and 0.98 ± 0.07 nanomnoles per gram wet weight from muscle of animals acclimated to 5°, 15°, and 25°C, respectively.The roles of synthesis and degradation of cytochrome c during thermal acclimation were investigated by measurement of loss of specific radioactivity from cytochrome c and from total mitochondrial heme protein, and by analysis of the rate of change in concentration of cytochrome c. The radioisotope used was 14C‐δ‐aminolevulinic acid, a non‐reutilizable heme precursor.At 25°C, the half‐life of cytochrome c was 7.1 days based on radioactivity measurements and 5.6 days based on change in concentration. Statistical analysis showed no significant difference in half‐lives obtained by the two methods. The half‐life of total mitochondrial heme protein was determined to be 5.7 days on the basis of radioactivity data, under the same conditions. No significant difference was found between the rate of turnover of the heme protein pool from mitochondria and either measurement for cytochrome c at 25°C.At an acclimation temperature of 5°C, the half‐life of cytochrome c from skeletal muscle was 13.7 days based upon changes in concentration. At low acclimation temperature, radioactive label was retained in acid‐soluble form by fish for many days, precluding measurement of half‐life by this technique.Transfer of fish from 25° to 5°C resulted in a rapid decrease of approximately 40% in rates of synthesis of skeletal muscle cytochrome c, and a concomitant decrease in the degradation rate constant for this molecule of approximately 60%. The disproportionality in temperature‐sensitivities of these two processes leads to an approximately 50% net increase in the concentration of cytochrome c during acclimation. In transfer from 5° to 25°C, the converse, rapid readjustments in synthetic and degradative parameters occur, resulting in the observed decrease in cytochrome c content.
Volume regulation by Flounder red blood cells: The role of the membrane potential
Authors: Cala Peter M. 
Published: June 2005

AbstractThe nucleated red blood cells of the Winter Flounder Pseudopleuronectes americanus demonstrate a volume regulatory response subsequent to osmotic perturbation. The net water movements associated with the response are secondary to net inorganic cation flux. The increased net cation fluxes occur in response to increased cation permeability (Pcation). While ionic strength and cell volume do not appear to be the stimulus for the volume regulatory response i.e. increased Pcation, changes in the cell membrane potential (Vm), as calculated from the chloride distribution ratio, do appear to result in increased Pcation. These studies demonstrate that manipulations leading to membrane hyperpolarization result in net loss of cellular K and water. In contrast treatments which depolarize Vm lead to cellular uptake of Na, K, Cl and water.
Correlation of structure and active transport in the teleost nephron
Authors: Trump Benjamin F. , Jones Raymond T. 
Published: June 2005

AbstractIn the present study we have extended our investigations concerning the correlation between ultrastructure and active transport in the isolated flounder nephron. The composition of the fish nephron is defined in ultrastructural terms and its behavior when incubated in vitro under short term and long term culture conditions is described. Using the in vitro system originally described by Forster, a variety of inhibitors and conditions which modify cell structure and function were tested. Ultrastructure was correlated with chlorphenol red dye transport. In general, conditions altering active transport also markedly altered cellular ultrastructure. The principal alterations consisted of membrane changes involving various organelles — most importantly the plasma membrane and the mitochondria. Conditions associated with irreversible cell injury could be rapidly produced by interference either with mitochondrial ATP synthesis or with the integrity of the plasma membrane. Both of these rapidly lead to irreversible events which are preceded by reversible structural changes. Organelle changes progress in a rather well‐defined sequence of reversible and irreversible stages which are defined. One difference between the two types of interactions is the presence of intramitochondrial calcification which does not occur with direct modification of the mitochondrial electron transport system. The concept of utilizing long term explant organ cultures of fish nephrons for environmental studies is introduced.
Interdependence of active Na+ and Cl− transport by the isolated urinary bladder of the teleost, Pseudopleuronectes americanus
Authors: Renfro J. Larry 
Published: June 2005

AbstractThe relationship between transepithelial Na+ and Cl− active transport from the mucosal toward the serosal surface was studied by ion substitution experiments in the isolated, perfused urinary bladder of the winter flounder, Pseudopleuronectes americanus. The tissue behaves as a simple ohmic resistance of about 1000 ohm·cm2 which was not significantly changed by perfusion of the lumen (mucosal surface) with Na‐free or Cl‐free solutions. Transepithelial electrical potential difference and short‐circuit current were reversed (mucosa positive to negative) by Cl‐free perfusion but unaltered by Na‐free medium. Short‐circuit current did not agree with isotopically measured net Na+ and Cl− flux in either control or ion‐substituted medium. Cl‐free perfusion depressed net Na+ flux more than 50% and a similar effect was seen on net Clflux upon Na‐free perfusion. A kinetic analysis of the relationship of Na+ or Clflux to the concentration of Na+ or Cl− in the perfusate in the presence and absence of Cl− or Na+, respectively, indicated that Cl‐free medium acted as a non‐competitive inhibitor of Na+ transport, and the effect of Na‐free medium on Cl− transport could be interpreted similarly. This inter‐dependence of Na+ and Cl− transport was taken as an indication of co‐transport of these two ions. Amiloride (10−4 M) seemed to inhibit a component of Na flux distinct from the Cl‐dependent flux. It had no effect on Cl− transport.
Ouabain inhibition of gill Na‐K‐ATPase: Relationship to active chloride transport
Authors: Silva Patricio , Solomon Richard , Spokes Katherine , Epstein Franklin H. 
Published: June 2005

AbstractOuabain circulating in blood inhibits Na‐K‐ATPase in the gills of seawater eels at a concentration similar to that necessary for inhibition in vitro. By contrast, a much higher concentration is required when ouabain is applied to the exterior of the gill. Inhibition by external ouabain occurs only when the drug gains access to the circulation of the fish, as evidenced by simultaneous inhibition of Na‐K‐ATPase in the kidney. These results suggest that the Na‐K‐ATPase of gill chloride cells faces inward, lining intracytoplasmic tubular channels continuous with the extracellular fluid.Inhibition of gill Na‐K‐ATPase by ouabain in intact salt water eels results in almost complete inhibition of the efflux of both Na+ and Cl−. The efflux of tritiated water was much less reduced, to 60% of normal. Since chloride is actively transported outward across the gill of seawater teleosts, it is suggested that active chloride transport is coupled to Na‐K‐ATPase. A neutral sodium chloride carrier is postulated that is energized by the movement of sodium from extracellular fluid down its electrochemical gradient into the chloride cell.
Renal excretion of chlorphenol red and related organic acids in the intact flounder Pseudopleuronectes americanus
Authors: Mackenzie Duncan D. S. , Maack Thomas , Kinter William B. 
Published: June 2005

AbstractRenal clearance experiments were performed on unanesthetized winter flounder from which bladder urine was collected continuously and caudal vein blood was sampled periodically; renal tissue was also obtained terminally for comparison of test organic acid content in vivo and after incubation in vitro. Urine flow rates and inulin U/P (urine to plasma concentration) ratios were relatively constant for a given fish and averaged 1.0 ml/hr × kg fish and 2.6, respectively. In contrast, U/P ratios for all three test acids cycled from minima of near 100 to maxima of over 1000 roughly every 24 hr when plasma concentrations of unbound acid were below 1 μM; correction of plasma protein binding was required in the case of chlorphenol red, but not PAH or Diodrast. Both in vivo and in vitro the organic acid content of renal tissue was intermediate between plasma and urine concentrations. These results demonstrate that kidneys of intact flounder exhibit the remarkable concentrative capacity for exogenous organic acids previously observed with isolated tubules and suggest that the tubular urine concentration is established in two steps by cell transport first at the peritubular and second at the luminal membrane. The anterior kidney position and the magnitude of maximal PAH and Diodrast clearances, about 1000 ml/hr × kg flounder, are consistent with most of the cardiac output returning to the heart through the renal portal circulation; a regulatory shunt bypassing the peritubular capillaries is proposed to explain cycling of organic acid clearances to minimal values.
Prolactin and substrate stimulation of locomotor activity in adult tiger salamanders (Ambystoma tigrinum)
Authors: Duvall David , Norris David O. 
Published: June 2005

AbstractGroups of adult tiger salamanders were treated with either prolactin or saline and were maintained between behavioral observation on either a moist pea gravel substrate or in water. During 60‐minute observation periods, all animals in a group were placed together in moisture‐gradient apparati, and locomotor activity scores and substrate preferences were recorded and analyzed. Prolactin or saline and substrate type exerted no effects on eventual substrate preference. However, animals in both substrate groups treated with prolactin displayed greater activity than either group treated with saline. The group of salamanders treated with prolactin and held between behavioral observations on moist gravel displayed significantly more activity than animals in any other group. These results suggest that prolactin‐stimulated locomotion represents a behavioral component of a “second metamorphosis” event in tiger salamanders.
Ultrastructural study of concanavalin‐A binding to the surface of preimplantation mouse embryos
Authors: Konwinski Marian , Vorbrodt Andrzej , Solter Davor , Koprowski Hilary 
Published: June 2005

AbstractReceptors for Con‐A were labelled (using the peroxidasediaminobenzidine technique) on the plasma membrane of unfertilized and fertilized mouse eggs, cleavage stage embryos, trophoblast and inner cell mass (ICM) of the blastocyst. Embryos were exposed to Con‐A concentrations of 10 μg/ml, 50 μg/ml, or 1,000 μg/ml and the lowest concentration was observed to be the most suitable for discerning differeces between stages of embryonic development.On the surface of unfertilized and fertilized eggs and 2‐cell embryos, reaction product appeared as a thin, discontinuous layer. The surface of 4‐ and 16‐cell stage embryos had a thicker, continuous, although non‐uniform, layer of the reaction product. On the surface of the cells of the late morula, and on the trophoblastic cells of the blastocyst, clustering of reaction product, was observed. Cells of ICM of intact blastocyst were free of the reaction product, showing that either Con‐A and/or peroxidase cannot penetrate tight junctions between trophoblastic cells. Reaction product in the form of a thin, uniform layer covered the free surface of the cells of the ICM after they had been isolated (using immunosurgery) and exposed to 50 μ/ml of Con‐A.The amount and distribution of Con‐A receptors is discussed, along with their redistribution and mobility in relation to the agglutinability of preimplantation mouse embryos.
The phosphoenol‐pyruvate branchpoint in adult Hymenolepis diminuta (cestoda): A study of pyruvate kinase and phosphoenol‐pyruvate carboxykinase
Authors: Moon T. W. , Mustafa T. , Hulbert W. C. , Podesta R. B. , Mettrick D. F. 
Published: June 2005

AbstractThe properties of pyruvate kinase (PK) and phosphoenol pyruvate carboxykinase (PEP CK), two enzymes that determine the preferrential accumulation of either succinate or lactate as endproducts of carbohydrate metabolism, are described in adult Hymenolepis diminuta. PK activity at Vmax and Km levels of PEP was unaffected by ATP, alanine, FDP4, or H+ ions, but was inhibited by 50% at 6.3 mM L‐lactate and 30 mM HCO3−. The addition of 30 mM HCO3− increased the Km (PEP) by 6‐fold but did not alter the Vmax. The inhibition of PK by HCO3− cannot be explained entirely by an effect of ionic strength, but probably represents a specific modulator‐enzyme interaction. Under similar conditions PEP CK was maximally activated. Although L‐lactate inhibited PEP CK (Ki(lac) = 1.8 mM), this effector may play a minor role in regulation of PEP flux. These results implicate the poise of the HCO3− :CO2 system as a major determiner of endproduct accumulation in H. diminuta.
Is the activated spermatozoon really capacitated?
Authors: Barros Claudio , Berrios Miguel 
Published: June 2005

AbstractA culture medium (7N) consisting only of salts and devoid of any macromolecule was prepared to test its effect upon survival, activation and acrosome reaction of golden hamster spermatozoa. Incubation of spermatozoa in medium 7N allowed a temporal separation of activation and acrosome reaction. Over seventy per cent of spermatozoa were activated after four hours at 37°C while the acrosome reaction remained very low (8%). Activated spermatozoa with intact acrosomes were incubated with zona‐free hamster oocytes at 37°C for one to two hours. When these oocytes were examined with the electron microscope it was found that the spermatozoa were closely bound to the egg plasma membrane, mainly by the plasma membrane overlying the acrosome, but in no instance had the gamete membranes fused. Prolonged incubation resulted in an engulfment of the sperm by the oocyte in a phagocytic manner. The experimental evidence would indicate that an activated spermatozoon is not capacitated since it cannot fertilize oocytes.