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PubMed1987

Wavelength discrimination in the turtle Pseudemys scripta elegans.

Wavelength discrimination was measured with two individuals using a behavioral training technique. The delta lambda function has three minima, indicating best discrimination at 400, 510 and at 570 nm (S2) or 600 nm (S1). In the range between 450 and 510 nm the ability to discriminate wavelengths was absent. This can be explained by the filter effect of the colored oil droplets, as indicated by a model computation. Color mixture experiments revealed that the high discrimination ability at 400 nm is based on an ultraviolet sensitive photoreceptor which is the fourth cone type involved in turtles' color vision. Spectral sensitivity in the ultraviolet region (measured for one turtle) is maximal at 370-380 nm.

Animals↗

PubMed1989

Coexistence of NMDA and non-NMDA receptors on turtle horizontal cells revealed using isolated retina preparations.

Effects of glutamate and its agonists on horizontal cells appeared diversely when studied in turtle eyecup preparations. Consistent results were obtained when the isolated retina preparations were used. Not only kainate and quisqualate but also N-methyl-D-aspartate (NMDA) caused a sustained depolarization and light-evoked responses were suppressed for as long as these agonists were superfused. A selective antagonist of NMDA, 2-amino-5-phosphonovalerate (APV), hyperpolarized horizontal cells and reduced their light-evoked responses. These results indicate the coexistence of NMDA and non-NMDA receptors on turtle horizontal cells.

2-Amino-5-phosphonovalerate↗

PubMed1994

Identification of the synaptic pedicles belonging to the different spectral types of photoreceptor in the turtle retina.

In this paper we describe the morphology of the different spectral types of photoreceptor pedicles in the outer plexiform layer (OPL) of the Pseudemys turtle as studied by light (LM) and electron microscopy (EM). Tangential serial thick sections were cut from the oil droplet region to the level where the axons emerge from cell bodies and then serial thin sections through the axons and the entire pedicles were collected and examined. Thus photoreceptor pedicles could be identified by tracing cells from their oil droplets to their synapses in the OPL. Double cone pedicles consisted of closely applied pairs with the principal member's pedicle wrapping around the accessory member's pedicle. Each pedicle was approx. 104 microns 2 in area and contained 12 and 8 synaptic ribbons respectively. Rods comprised 8% of the pedicles in the field, were small (84 microns 2), contained closely packed synaptic vesicles, and on average, 9 long ribbons. Single red and green cone pedicles could not be told apart without following them from their oil droplets, however, both were about the same size (106-127 microns 2) and contained 10-12 ribbons. Blue cone pedicles were small and round (80 microns 2) and arose from short oblique axons giving off from large, greenish, clear oil droplet-containing cell bodies (13% of the cone population). The least common pedicle types (5% of the cone population) were identified tentatively as UV cones because they originated from small, clear oil droplet-containing cell bodies. UV cones had spherical pedicles, elongated in the vertical axis, that arose from extremely long, angled axons. Their very small pedicles (64 microns 2) exhibited characteristic "horns" that projected from the top sides of the pedicle. Both putative UV and blue cone pedicles ended more vitread in the OPL than other pedicles and contained only 5-6 and 8-10 ribbons respectively. Understanding the ultrastructural features that distinguish the different types of photoreceptor pedicle will allow us to begin a study of spectral connections to second order neutrons in the turtle OPL in the future.

Animals↗

PubMed1989

Physical and chemical characterization of macroglobulin from marine turtle eggwhite.

Macroglobulin was purified from the eggwhite of the marine turtle (Caretta caretta Linn.) by gel filtration through Sephadex G-200 and Sepharose 4B. It was characterized by physical techniques including sedimentation velocity, diffusion and viscosity. Its molecular weight (Mr) was determined as 724,000 with four subunits of equal molecular weight. A large amount of water was hydrodynamically associated with the macroglobulin. It inhibited the activities of trypsin and papain and did not cross-react with human alpha 2-macroglobulin. Its amino acid composition was similar to that of human alpha 2-macroglobulin. Results suggest that turtle eggwhite macroglobulin is a homologous but distinct protein from human alpha 2-macroglobulin.

Amino Acids↗

PubMed1986

Recording of spindle afferent discharge during hindlimb movements in spinalized turtles.

The feasibility of spindle afferent recording during naturally or electrically induced hindlimb movements is demonstrated in the case of spinalized, decapitated turtles. Since these recordings are obtained from fine filaments of exposed dorsal roots, it is possible for the experimenter to select the afferents of interest. This feasibility, together with the fact that spinally generated movements are readily exhibited, make the turtle an attractive animal for the study of spinal motor control mechanisms.

Action Potentials↗

PubMed1983

The primary structure of myoglobin from pacific green sea turtle (Chelonia mydas caranigra).

The amino acid sequence of the main component myoglobin from skeletal muscle of Pacific green sea turtle (Chelonia mydas caranigra) has been determined. The globin is 153 residues in length and has a free amino-terminus. The heme-binding and internal residues are as found in mammalian myoglobins. Ten substitutions are observed between this myoglobin and that from map turtle. About 38, 52, 47 and 86 substitutions are noted in comparison with the myoglobins of other reptiles, mammals, birds and fish, respectively. The inferred pattern of structural stabilization and conservation of two loci are typical of tetrapod myoglobin.

Alligators and Crocodiles↗

PubMed1990

Phosphofructokinase from a vertebrate facultative anaerobe: effects of temperature and anoxia on the kinetic parameters of the purified enzyme from turtle white muscle.

The effects of low temperature and anoxia were determined on phosphofructokinase (PFK) purified from white skeletal muscle of the freshwater turtle, Pseudemys scripta. These effects were assayed by comparing PFK kinetic constants measured at a high (20 degrees C) and low (6 degrees C) temperature using enzyme obtained from animals held under normoxic and anoxic conditions. When assayed at 20 degrees C, PFK from anoxic animals had a lower Ka for phosphate, a lower Ka for AMP and showed no inhibition with increasing concentrations of ATP (up to 10 mM) when compared to enzyme from normoxic animals. At 6 degrees C, anoxic enzyme had a higher Km for fructose 6-phosphate and a higher I50 value for citrate with respect to normoxic enzyme. Decreasing temperature also had a differential effect on PFK kinetic parameters depending on the source of the enzyme. When normoxic enzymes were compared at 20 and 6 degrees C, the enzyme measured at 6 degrees C showed a lower Km for ATP and a lower Ka for AMP. Comparison of anoxic enzymes at these two temperatures showed that anoxic PFK at 6 degrees C had a higher Ka for phosphate, a higher Ka for AMP, and a larger Hill coefficient. A comparison of maximal velocities at varying temperature showed that normoxic enzyme (Q10 = 2.22) was more temperature sensitive than the anoxic enzyme (Q10 = 1.80). It is possible to interconvert the normoxic and anoxic forms of PFK by incubating normoxic enzyme with the active subunit of protein kinase, suggesting that the kinetic changes observed during anoxia resulted from enzyme phosphorylation. These data are discussed with respect to the mechanisms underlying white muscle function during diving and hibernation in red-eared turtles.

Adenosine Triphosphate↗

PubMed1995

Effects of pH on calcium transport in turtle bladder.

This study was designed to examine the effect of apical and basolateral (ie, mucosal and serosal) pH on calcium (Ca) transport in turtle bladder, a nonmammalian analog of the distal nephron. Unidirectional Ca45 fluxes were measured when serosal pH was 6.4, 7.4, or 8.4 (mucosal pH, 7.4) in the presence and absence of ouabain. When serosal pH was 8.4, M-->S Ca45 flux increased significantly, and when it was 6.4, M-->S Ca45 flux decreased markedly. Changes in serosal pH did not affect the S-->M Ca45 flux. When 5 x 10(-4) mol/L ouabain was added to inhibit sodium transport, M-->S Ca45 flux, at pH 7.4, was 221.6 +/- 27.4 pmol/mg/h (n = 10), and low pH again inhibited this flux (approximately 50%). Lowering mucosal pH (with serosal pH 7.4) also decreased M-->S Ca45 flux. In stripped bladders, Ca45 uptake increased linearly as medium pH was increased from 4.4 to 8.4. Total tissue Ca concentration did not change when serosal pH was varied, except at the extreme of pH 4.4, where tissue Ca decreased. By contrast, when apical pH was 6.4, tissue Ca rose substantially (approximately 1.5-fold). these results demonstrate that extracellular pH directly affects Ca homeostasis in the turtle bladder. Lowering the pH of either the serosal or mucosal medium directly inhibits apical Ca permeability. This change in Ca permeability is seen in the presence of ouabain. By contrast, alkalization of the serosal medium enhances apical permeability, but this effect is, in some manner, related to sodium transport.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1983

Enzymatic inhibition of lysine transport across rat and turtle small intestine.

Trypsin, Phospholipase-D and Neuraminidase at different concentrations inhibited significantly (P less than 0.001) lysine accumulation in rat intestinal cells, whereas Chymotrypsin did not show any significant effect. Trypsin, Chymotrypsin and Phospholipase-D did not show any significant change in lysine accumulation when incubated with mucosal strips isolated from turtle intestine; however, Neuraminidase caused a significant decrease in lysine uptake by these strips. Unidirectional lysine influx across the rat small intestine was significantly reduced (P less than 0.01) by the presence of Trypsin, Phospholipase-D and Neuraminidase in the preincubation solution, and its influx across the turtle small intestine was significantly inhibited (P less than 0.01) by Neuraminidase only. The cell water content and the cell volume were not altered by preincubating the intestinal tissues with any of the enzymes in both animals.

Animals↗

PubMed1984

The effect of local anesthetics on calcium transport across the rat and turtle small intestine.

Procaine at different concentrations enhanced significantly (P less than 0.01) calcium accumulation in rat intestinal cells, whereas the same concentrations of procaine inhibited significantly (P less than 0.01) calcium uptake by the turtle small intestine. Unidirectional calcium influx across the rat small intestine was significantly enhanced (P less than 0.001) by the presence of procaine in the preincubation medium. However, procaine had no effect on calcium influx across the turtle intestinal cells. The cell water content and the cell volume were not altered by preincubating the intestinal tissues with procaine in both animals.

Anesthetics, Local↗

PubMed1985

Characterization of the testicular binding site for iodinated rat FSH in the turtle, Chrysemys picta.

1. To correlate the morphological observations with the known gonadotropic activity of FSH in the turtle testis, studies of the binding of iodinated FSH were conducted. 2. These demonstrated the presence of gonadotropin-binding sites of high affinity (apparent Kd = 10(-10) M) for [125I]rFSH in turtle testicular membrane preparations. 3. Although these sites did not bind iodinated human LH or avian LH, these hormones, as well as PMSG and FSH, were effective competitive inhibitors of the binding of the radioligand. 4. Binding of the radioligand to the testis was influenced by duration of incubation and temperature. 5. Binding activity was lost after incubation with proteolytic enzymes (trypsin, pronase) but not with DNAase, lipase, collagenase and neuraminidase. 6. The binding exhibited target organ specificity (no binding observed in brain, epididymis, lung, muscle and pancreas). 7. In addition, the number of binding sites varied according to the stage spermatogenesis, being highest when the tubules contained spermatocytes and spermatids, intermediate when the tubules consisted to Sertoli cells and spermatogonia and lowest st spermiation.

Animals↗

PubMed1985

The viability of nearctic freshwater turtles submerged in anoxia and normoxia at 3 and 10 degrees C.

Survival times of temperature-acclimated freshwater turtles submerged in normoxic and anoxic water were determined. Juvenile Chrysemys scripta from Alabama and adult Chrysemys picta bellii from Wisconsin exhibited the maximal survival times of the 10 species and subspecies investigated, both being able to survive at least a half-year of submergence at 3 degrees C in normoxic water. Minimal viability was exhibited by Sternotherus odoratus and Trionyx spiniferus submerged in anoxia at 10 degrees C (5.2 and 2.6 days, respectively). All species lived longer in normoxic water than in anoxic water, attesting to the importance of extrapulmonary gas exchange during submergence at low temperature. While freshwater turtles are often reputed to overwinter buried in mud, which is an anoxic microenvironment, this behaviour seems unlikely for southern Trionyx and Sternotherus, although it may be possible for northern Chrysemys.

Acclimatization↗

PubMed1989

Permeability of the urinary bladder of the turtle, Pseudemys scripta elegans, to ammonia.

1. The permeability of the isolated turtle urinary bladder to ammonia was investigated by varying the ratio of NH3 to NH4+ concentration in the serosal bath and measuring the flux of ammonia into the mucosal bath. 2. The permeability of the turtle bladder to NH3 was in the range of 5.4-6.1 x 10(-3) cm/sec and the permeability of the unstirred layer to NH4+ was in the range of 1.1-2.1 x 10(-5) cm/sec. 3. The flux of ammonia calculated from the permeability of NH3 can account for the decrease in mucosal H+ secretion observed with addition of NH4Cl to the serosal bath.

Ammonia↗

PubMed1989

Turtle urinary bladder epithelial cell line.

1. We compared enzymatic and functional properties of a turtle bladder cell line to those of turtle bladder epithelial cells. Like the original epithelium, the cell line displays carbonic anhydrase activity and acetazolamide inhibits O2 consumption in isolated cells and acidification by cells grown in monolayers. 2. Staining with acridine orange revealed the presence of cytoplasmic orange red vesicles which could be dissipated by NH4Cl or protonophores indicating that these vesicles represent areas of low pH. 3. Addition of ATP to cells permeabilized by digitonin led to reappearance of the red granules suggesting that acidification of the vesicles is mediated by H+-ATPase.

Animals↗

PubMed1996

Adrenergic and cholinergic response of ventricular muscle from the turtle, Trachemys (Pseudemys) scripta.

Muscle strips were dissected from the ventricle of the turtle, Trachemys (Pseudemys) scripta. Individual strips were placed in a muscle bath, set at a resting tension of three grams and electrically paced at 24 min(-1) for a control period of 1 hr. Cumulative dose-response curves were constructed using the adrenergic agonist, epinephrine (Epi) and the cholinergic agonist, metacholine (MCh). The administration of Epi to the muscle bath resulted in a dose-dependent increase in active tension development. The maximum tension developed was 40% above the control values and the concentration producing a half-maximal response (EC50) was 7.5 x 10(-7) M. The positive inotropic effect of Epi was diminished following the administration 1 x 10(-7) M propranolol. This reduced the maximum active tension by over 80% at the highest dose of Epi. In addition, the EC50 was increased to 8.9 x 10(-6) M. The administration of MCh resulted in a dose-dependent decrease in active tension development. The maximum decrease in active tension was 35% below the control values and the EC50 was 2.5 x 10(-6) M. The negative inotropic effect of MCh was diminished by the application of 1 x 10(-6) M atropine, with the EC50 increasing to 2.5 x 10(-4) M. These findings show that the isolated, in vitro turtle ventricle responds to adrenergic and cholinergic agonist. The results of this study support the hypothesis that the ventricular function, in reptiles, is controlled by both subdivisions of the autonomic nervous system.

Acetylcholinesterase↗

PubMed1996

Ca2+ and Cl(-)-dependence of the turtle olfactory response to odorants and forskolin.

In the turtle olfactory system, large responses to odorants appeared after application of cAMP of forskolin at high concentrations to the isolated olfactory receptor neurons or the olfactory epithelium, suggesting that a cAMP-independent pathway greatly contributes to the generation of odor responses. We measured the effects of the mucosal Ca2+ and Cl- concentrations and a Ca(2+)-activated Cl(-)-channel blocker, 4-acetamide-4'-(isothiocyano) stilbene-2,2'-disulphonic acid (SITS), upon olfactory bulbar responses to explore the contribution of the Ca(2+)-activated Cl(-)-channels to cAMP-dependent and independent pathways. Elimination of mucosal Ca2+ by addition of 2 mM EGTA to the stimulating solution partially inhibited the cAMP-independent responses to 0.1 mM citralva but did not affect those to 0.1 mM lilial or 0.1 mM l-carvone. Substitution of mucosal Cl- with gluconate slightly enhanced the total response to 0.1 mM citralva but practically did not affect the responses to other odorants tested. SITS (2 mM) partially inhibited the responses to 50 microM forskolin and 0.1 mM citralva but did not affect the cAMP-independent response to 0.1 mM citralva in Ca(2+)-free Ringer's solution. These results suggested that the Ca(2+)-activated Cl- channels do not contribute to the generation of the cAMP-independent responses, but that they partially contribute to the generation of the cAMP-dependent responses in the turtle.

4-Acetamido-4'-isothiocyanatostilbene-2,2'-disulfo↗

PubMed1989

Pineal 5-methoxytryptophol rhythms in the box turtle: effect of photoperiod and environmental temperature.

The effect of different photoperiods and temperatures on pineal 5-methoxytryptophol (ML) content was investigated in male box turtles, Terrapene carolina triunguis. A rhythm in pineal ML was evident in the long photoperiod (18 h light (L)-6 h dark (D] with high daytime levels of 178 +/- 48 pg/gland (means +/- S.E.M.) which dropped to 38 +/- 6 pg/gland during lights off. In the short photoperiod (8L:16D) no clearcut ML rhythm was observed. Diurnal (10.00-12.00 h) ML concentrations rose linearly (P less than 0.05) with increasing ambient temperatures (5, 15, 20 and 27 degrees C). Day/night differences in ML levels, however, were not significant. Pineal ML in the box turtle thus seems to be modified by the photoperiod and, to a lesser extent, by temperature.

Animals↗

PubMed1989

MK801-induced antagonism of NMDA-preferring excitatory amino acid receptors in horizontal cells of the turtle retina.

Intracellular recordings were made from axon terminals of L-type horizontal cells in the turtle (Pseudemys scripta elegans) retina. Superfusion with Ringer's solution containing 3.0 mM N-methyl-D-aspartate (NMDA) or 0.2 mM kainic acid (KA) induced depolarization and reduction in the hyperpolarizing light responses of horizontal cells, consistent with an agonist effect of these excitatory amino acid (EAA) analogs on postsynaptic receptors. Delivery of 0.1 mM MK801, a selective blocker of NMDA-type EAA receptors, had no apparent effect on membrane potential or photoresponses, nor did it change the KA depolarization. Exposure of the retina to 3.0 mM NMDA following 0.1 mM MK801 always caused hyperpolarization of the horizontal cell and loss of light responses. Because MK801 is specific for NMDA-preferring receptors, we suggest that the reversal of the NMDA response to one of antagonism following MK801 is strong evidence for the presence of NMDA-preferring EAA receptors in turtle horizontal cells.

Animals↗