Publications

identification of cholecystokinin from frog and turtle. divergence of cholecystokinin and gastrin occurred before the evolution of amphibia.	cholecystokinins from brain and small intestine of the bullfrog (rana catesbeiana) and red-eared slider turtle (pseudomys scripta) were isolated. the purifications were monitored by an antiserum specific for the common c-terminus of mammalian cholecystokinin and gastrin. the peptide structures were identified by sequence analysis of the intact peptides and proteolytic fragments, mass spectrometry, and amino acid analysis. brain and small intestine of both species contained cholecystokinin-8 and ...	1994	7925386
the relation of the dual thyroxine/vitamin d-binding protein (tbp/dbp) of emydid turtles to vitamin d-binding proteins of other vertebrates.	the relation of a dual binding protein, involved in the transport of both thyroxine (t4) and vitamin d3, in the blood of emydid turtles to blood proteins in other vertebrates was examined immunologically. binding studies with 25-oh-[3h]cholecalciferol (d3) confirmed the presence of a d3-binding protein (dbp) in the plasma of a wide variety of chelonian species representing both major suborders, as well as other species of reptiles, amphibians, birds, and mammals. analysis by polyacrylamide gel e ...	1994	7926631
occurrence and localization of calbindin-d28k in kidney and cerebellum of the slider turtle, trachemys scripta.	since its initial discovery in the avian intestine, calbindin-d28k has been reported to occur in various species and tissues. although calbindin-d28k binds calcium ions in the physiologically relevant range of intracellular calcium, its functional role in the various cell types where it has been localized remains unknown.	1994	8059980
thyroxine-binding protein represents the major vitamin d-binding protein in the plasma of the turtle, trachemys scripta.	structural homology between the high-affinity thyroxine (t4)-binding protein (tbp) in the plasma of the turtle, trachemys scripta, and vitamin d-binding proteins (dbp) of mammals prompted an investigation of plasma vitamin d binding in the turtle. several lines of evidence indicate that the tbp represents the primary binding protein for 25-oh-cholecalciferol (d3) in the turtle plasma. d3-binding protein in whole plasma migrates in the same position as tbp by size-exclusion chromatography and pol ...	1994	8138122
independent eye movements in the turtle.	in order to evaluate the normal eye movements of the turtle, pseudemys scripta elegans, the positions of each eye were recorded simultaneously using two search-coil contact lenses. optokinetic nystagmus (okn) was strikingly unyoked in this animal such that one eye's slow-phase velocity was substantially independent of that of the other eye. on the other hand, the fast-phase motions of both eyes occurred more or less in synchrony. an eye's slow-phase gain is primarily dependent on the direction a ...	1994	2271458
putative aromatase inhibitor induces male sex determination in a female unisexual lizard and in a turtle with temperature-dependent sex determination.	treatment of developing embryos of two diverse species of reptiles with fadrozole (a potent and specific nonsteroidal inhibitor of aromatase activity in mammals) resulted in the induction of male sex determination. in the first experiment, males were produced in an all-female parthenogenic species of lizard (cnemidophorus uniparens). in the second experiment, male sex determination was induced in a turtle (trachemys scripta) with temperature-dependent sex determination. the results support the h ...	1994	8046299
an analysis of the proopiomelanocortin systems in the pituitary of the squamate reptile lacerta galloti.	acid extracts of the pars intermedia of the squamate reptile lacerta galloti were screened for immunoreactive forms of proopiomelanocortin (pomc)-related end products following sephadex g-50 column chromatography. alpha-msh-sized end products were detected with a val-nh2, c-terminal-specific ria, and beta-endorphin-sized end products were detected with a separate c-terminal-directed ria. five peaks of alpha-msh-related immunoreactivity were isolated following fractionation by reversed-phase hplc ...	1994	8194743
effect of anoxia on isolated turtle tissues: is the response to anoxia mediated by protein kinase second messengers?	organ slices from the turtle trachemys scripta elegans were incubated under aerobic and anoxic conditions to examine the effect of protein kinase (prk) second messengers in potentiating the biochemical responses to anoxia exposure. incubating liver slices from aerobic animals under anoxic conditions produced biochemical changes exactly similar to those observed in vivo: phosphofructokinase (pfk) was more sensitive to citrate inhibition and the percentage of glycogen phosphorylase (gp) in the act ...	1994	7696998
role of reductase and aromatase in sex determination in the red-eared slider (trachemys scripta), a turtle with temperature-dependent sex determination.	in many turtles the temperature during the middle of incubation determines the gonadal sex of the hatchling. in the red-eared slider turtle (trachemys scripta), an incubation temperature of 26 degrees c results in all male offspring, whereas an incubation temperature of 31 degrees c results in all female offspring; at temperatures intermediate to these (e.g. 29, 29.2, 29.4 degrees c) a mixed sex ratio is obtained. administration of exogenous oestrogens will overcome the effects of an all-male pr ...	1994	7829992
nitric oxide synthase in the brain of the turtle pseudemys scripta elegans.	the distribution pattern of nitric oxide synthase (nos) was investigated in the brain of the turtle by nadph-diaphorase histochemistry. the specificity of the histochemical staining was tested by immunocytochemical colocalization with an antiserum specific for nos. in the forebrain, neurons staining intensely for nitric oxide synthase were localized in the olfactory tubercle, the basal ganglia complex, the basal amygdaloid nucleus, suprapeduncular nucleus, and the posterior hypothalamic area. ma ...	1994	7529267
time course of anoxia-induced increase in cerebral blood flow rate in turtles: evidence for a role of adenosine.	the exceptional ability of the turtle brain to survive prolonged anoxia makes it a unique model for studying anoxic survival mechanisms. we have used epi-illumination microscopy to record blood flow rate in venules on the cortical surface of turtles (trachemys scripta). during anoxia, blood flow rate increased 1.7 times after 45-75 min, whereupon it fell back, reaching preanoxic values after 115 min of anoxia. topical superfusion with adenosine (50 microm) during normoxia caused a 3.8-fold incre ...	1994	8063883
a tetraethylammonium-insensitive inward rectifier k+ channel in müller cells of the turtle (pseudemys scripta elegans) retina.	ion channels present in isolated glial (müller) cells from the retina of the turtle (pseudemys scripta elegans) were studied with the patch clamp technique. the predominant conductance in these cells was due to an inward rectifying potassium current. the whole-cell conductance of the inward rectifier was 20.2 +/- 1.9 ns (n = 7 cells) in a standard extracellular saline solution (3 mm extracellular potassium). this conductance was dependent on the extracellular potassium concentration, with a 2.88 ...	1994	7807523
regulation of central vascular blood flow in the turtle.	the purpose of this study was to determine the effects of vagal nerve stimulation on the pulmonary and systemic circulations in the turtle pseudemys scripta. the heart rate (hr), systemic vascular resistance (rsys), pulmonary vascular resistance (rpul), total pulmonary blood flow (qpul), and total systemic blood flow (qsys) were measured during electrical stimulation of the vagal efferent and the vagal afferent nerves. vagal efferent nerve stimulation resulted in a bradycardia, increased rsys an ...	1994	8067470
anatomical characterization of retinal ganglion cells that project to the nucleus of the basal optic root in the turtle (pseudemys scripta elegans).	there is little detailed information about retinal ganglion cells which project to specific central targets in the brain. the present study examined retinal ganglion cells projecting to the nucleus of the basal optic root, a major accessory retinal target in the turtle. these ganglion cells were first selectively labeled using retrograde transport of rhodamine injected stereotaxically into the nucleus of the basal optic root. the number and distribution of the retrogradely labeled cells in the r ...	1994	7969940
functional architecture of vestibular primary afferents from the posterior semicircular canal of a turtle, pseudemys (trachemys) scripta elegans.	physiological studies in many vertebrates indicate that vestibular primary afferents are not a homogeneous population. such data raise the question of what structural mechanisms underlie these physiological differences and what functional role is played by afferents of each type. we have begun to answer these questions by characterizing the architecture of 110 afferents innervating the posterior canal of pseudemys scripta. we emphasize their spatial organization because experimental evidence sug ...	1994	7929889
distribution of target cells for 1,25-dihydroxyvitamin d3 in the brain of the yellow bellied turtle trachemys scripta.	five h after injection of tritiated 1,25-dihydroxyvitamin d3 into trachemys scripta, neurons with nuclear concentrations of radioactivity were identified in distinct regions within the central nervous system. coinjection of a 100-fold excess of non-labeled 1,25-dihydroxyvitamin d3 abolished or reduced the specific nuclear binding of tracer. target neurons were present in ventral periventricular brain regions including tuberculum olfactorium, nucleus accumbens, cortex piriformis, primordium hippo ...	1994	8004456
light adaptation and photopigment bleaching in cone photoreceptors in situ in the retina of the turtle.	light adaptation and photopigment bleaching in cone photoreceptors were studied in the intact, superfused retina of the turtle (pseudemys scripta elegans). a new method for measuring changes in the photopigment of cones is described. action spectrum measurements indicate that the signals arise from the red-sensitive cones. measurements of steady-state bleaching are well described by the monomolecular bleaching equation with a half-bleaching constant of about 5.5 log photons sec-1 microns-2. quan ...	1994	8120614
temperature and cerebral blood flow regulation in the freshwater turtle, pseudemys scripta.	chemical regulation of cerebral blood flow (cbf) by co2 has been demonstrated in an ectohermic vertebrate (davies, am. j. physiol. 260: r382, 1991). cerebrovascular sensitivity to co2 (delta cbf/delta paco2), a measure of the vascular reactivity of the cerebral blood vessels to co2, was found to be 0.7 ml.min-1.100 g-1.torr-1 during normoxia and 3.4 during anoxia in the freshwater turtle, pseudemys scripta. in the present study, the effect of body temperature on delta cbf/delta paco2 was studied ...	1994	8059076
glucuronidation of flumequine by the turtle pseudemys scripta elegans.		1994	8196100
glucuronidation of naproxen by the turtle pseudemys scripta elegans.		1994	8196098
mechanical performance of an in situ perfused heart from the turtle chrysemys scripta during normoxia and anoxia at 5 c and 15 c	we developed an in situ perfused turtle (chrysemys scripta) heart preparation to study its intrinsic mechanical properties at 5°c and 15°c using normoxic and anoxic perfusion conditions. the in situ preparation proved durable and stable. at 15°c and a spontaneous heart rate of 23.4 beats min-1, maximum stroke volume was 2.54 ml kg-1 body mass, maximum cardiac output was 62.5 ml min-1 kg-1 and maximum cardiac myocardial power output was 1.50 mw g-1 ventricular mass. there was good agr ...	1994	9317650
vagal regulation of intracardiac shunting in the turtle pseudemys scripta	two principal hypotheses account for intracardiac shunting in reptiles. the 'pressure shunting' hypothesis proposes that there is no fuctional separation between the ventricular cava during systole. the 'washout shunting' hypothesis suggests that the cavum pulmonale is functionally separated from the rest of the ventricle during systole. the purpose of this study was to test the two principal hypotheses in a turtle, pseudemys scripta, after inducing a right-to-left shunt by electrical stimulatio ...	1994	9317438
role of aromatization in testosterone-induced inhibition of luteinizing hormone secretion in female turtles, trachemys scripta.	both 17 beta-estradiol (e2) and testosterone (t) were shown to inhibit in vitro pituitary lh secretion in the turtle trachemys scripta. since t was approximately 500 times less potent than e2, and 5 alpha-dihydrotestosterone was even less active than t, the inhibitory action of t may result from its aromatization to estrogen. we utilized both in vivo and in vitro approaches to elucidate the roles of t and estrogen in the negative feedback of pituitary lh secretion. gonadectomy of adult (vitellog ...	1994	8312438
anoxia induces changes in translatable mrna populations in turtle organs: a possible adaptive strategy for anaerobiosis.	the effects of anoxic submergence (16 h at 15 degrees c) on cellular mrna contents were assessed in five organs of anoxia tolerant turtles trachemys scripta elegans. poly(a)+ rna was extracted from liver, red and white skeletal muscle, kidney and heart of control and anoxic turtles, as well as from heart and kidney of turtles allowed 24 h aerobic recovery (at 15 degrees c) after anoxia exposure. poly(a)+ rna content increased by 30% in white muscle from anoxic turtles relative to control animals ...	1994	7983251
de novo protein synthesis and protein phosphorylation during anoxia and recovery in the red-eared turtle.	changes in de novo protein synthesis and protein phosphorylation were monitored during anoxia and recovery in the red-eared slider trachemys (= pseudemys) scripta elegans. time courses of 35s-radiolabeled methionine incorporation into acid-precipitable material showed an increase up to 5 h postinjection and remained constant after this time. comparison of the total and acid-precipitable 35s label incorporation into tissues from 20-h control, anoxic, and recovering animals showed differences betw ...	1993	8285280
estrogen- and temperature-induced medullary cord regression during gonadal differentiation in a turtle.	gonadal differentiation associated with estrogen-induced female sex determination was examined in a turtle with temperature-dependent sex determination, and was compared to ovarian differentiation at a female-producing temperature. freshly ladi eggs of the red-eared slider, trachemys scripta, were incubated at a male-producing temperature (26 degrees c) and were experimentally manipulated at one of three embryonic stages: stage 15, 17, or 20 (i.e. early, midway, or late in the temperature-sensit ...	1993	8405765
plurality of viual mismatch potentials in a reptile.	abstract studies with auditory stimuli have established in humans that a mismatch potential (mmp) is elicited whenever a deviant stimulus is substituted for a standard stimulus in a train of monotonous standard stimuli presented at rates > 0.25 hz. the mmp in humans is localized in the auditory cortex and is known as mismatch negativily, from its polarity in scalp recordings. it is hypothesized to reflect the operation of sensory memory and to be a necessary component of the auditory orienting r ...	1993	23972152
the orbital glands of the terrapin pseudemys scripta in response to osmotic stress: a light and electron microscope study.	the histochemical and ultrastructural features of both orbital glands--the anterior lacrimal and harderian glands--were compared in the terrapin pseudemys scripta following adaptation either to distilled water or to seawater. seawater adaptation activated the harderian gland and caused a major structural reorganisation. type i cells increased in number, whereas type ii cells became smaller and less numerous. the most striking change was shown by the type iv cells which display the features of a ...	1993	8270473
in vivo gnrh responsiveness of lh secretion in the female turtle, trachemys scripta, in relation to the reproductive stage.	the effects of several forms of gonadotropin-releasing hormone (gnrh) on the in vivo secretion of luteinizing hormone (lh) were investigated in the female turtle trachemys scripta. serial injections of large vitellogenic turtles with 1-2 micrograms (ca. 0.15 micrograms/100 g turtle) of chicken gnrh-i (cgnrh-i) and multiple blood sampling revealed that mature females were unresponsive to gnrh. in contrast, both forms of avian gnrh, cgnrh-i and cgnrh-ii, and an avian gnrh analogue (gnrha) signific ...	1993	8224759
species and tissue distribution of the regulatory protein of glucokinase.	rat liver is known to contain a regulatory protein that inhibits glucokinase (hexokinase iv or d) competitively versus glucose. this inhibition is greatly reinforced by the presence of fructose 6-phosphate and antagonized by fructose 1-phosphate and by kcl. this protein was now measured in various rat tissues and in the livers of various species by the inhibition it exerts on rat liver glucokinase. rat, mouse, rabbit, guinea-pig and pig liver, all of which contain glucokinase, also contained bet ...	1993	8373368
ectoplasmic ("junctional") specializations in sertoli cells of the rooster and turtle: evolutionary implications.	ectoplasmic specializations are complex actin-containing structures found at certain sites of intercellular attachment in sertoli cells. current evidence indicates that these structures are a form of actin-associated adhesion junction. in the turtle (pseudemys scripta) and rooster (gallus domesticus) ectoplasmic specializations are known to occur adjacent to sites of attachment to elongate spermatids and are characterized by a layer of "loosely" cross-linked actin filaments that lies next to the ...	1993	8417627
comparative studies of thyroxine binding proteins in turtle plasma using column chromatography.	thyroxine (t4) binding proteins in turtle plasma were compared with those of various mammalian and nonmammalian (fish, birds) species using gel filtration chromatography (bio-gel). high-affinity t4 binding was observed in all mammals studied, in the chicken, and in one species of turtle, trachemys scripta. this high affinity t4 binding protein (tbp) appears to be the major component of t4 transport in the turtle; selective removal of this tbp greatly diminished binding activity in t. scripta pla ...	1993	8428644
gnrh-induced desensitization of in vitro luteinizing hormone secretion in the turtle, trachemys scripta.	gonadotropin-releasing hormone (gnrh)-induced desensitization of pituitary luteinizing hormone (lh) secretion in female turtles (trachemys scripta) was investigated by in vitro superfusion of whole or hemipituitaries with the endogenous forms of the peptide. in sub-adults, lh secretion was rapidly attenuated (desensitized) by both prolonged and pulsatile treatments of chicken ii gnrh (cii-gnrh), but pulsatile gnrh administration was more effective than prolonged administration in stimulating lh ...	1993	8454169
differential distribution of chicken-i and chicken-ii gnrh in the turtle brain.	chicken-i and chicken-ii gonadotropin-releasing hormone (ci-gnrh and cii-gnrh) were shown to be differentially distributed in the brain of a turtle, trachemys scripta, by hplc and specific radioimmunoassays. the ci-gnrh was most concentrated in the median eminence (me), while cii-gnrh was most concentrated in the caudal brain regions, especially medulla and cerebellum. the ratio of ci- to cii-gnrh in the me of adults was 8:1. age- and sex-related differences in gnrh concentrations were observed ...	1993	8483800
binding affinities of thyroxine-binding proteins in turtle plasma.	binding affinities (ka) for thyroxine (t4) by blood plasma and purified plasma proteins from two turtles, the slider (trachemys scripta) and snapper (chelydra serpentina), were compared with those of a human using equilibrium dialysis. the purified t4 binding protein (tbp) from t. scripta had a high affinity that was lower by about fivefold than that of human tbg (3.2 x 10(9) vs 1.7 x 10(10) m-1). the affinity of t4 binding by tbp was similar to that determined for whole plasma from this species ...	1993	8504925
juvenile turtles for mosquito control in water storage tanks.	juvenile turtles, trachemys scripta, provided highly effective control of mosquito larvae in cement tanks (pilas) where water was stored for household cleaning. when single turtles were introduced to tanks with histories of high mosquito production, nearly all turtles remained in good health and no mosquito larvae survived to the pupal stage. families welcome turtles in their water storage containers in honduras. humane conditions for turtles can be assured by providing small quantities of table ...	1993	7902872
sensitive stages for the effects of temperature on gonadal aromatase activity in embryos of the marine turtle dermochelys coriacea.	many data suggest an involvement of estrogens in gonadal differentiation in reptiles with temperature-dependent sex determination (tsd). however, the site of estrogen synthesis in two species of freshwater turtles is unclear. in emys orbicularis, estrogens were shown to be produced by the gonads, whereas in trachemys scripta, gonadal steroids were not detected. the marine turtle dermochelys coriacea exhibits tsd but in gonadal development, ovarian differentiation is delayed. gonadal aromatase ac ...	1993	8262357
responses to freezing exposure of hatchling turtles trachemys scripta elegans: factors influencing the development of freeze tolerance by reptiles.	hatchling red-eared turtles trachemys (= pseudemys) scripta elegans (wied) from a louisiana population display a significant ability to withstand the freezing of extracellular body fluids. all animals survived at least 2 h of freezing at -2.5 or -4 degrees c. at -2.5 degrees c, survival declined to 50% after 6 h of freezing and no animals recovered after 24 h or longer, when mean ice content reached 54.7 +/- 1.4% of total body water. at -4 degrees c, all turtles recovered from 4 h of freezing ex ...	1992	1634864
actin filaments associated with the basal sertoli cell surface in the alligator and turtle.	we have studied, using electron microscopy, the basal cytoplasm of sertoli cells in the alligator (alligator mississippiensis) and the turtle (pseudemys scripta). filament bundles occur immediately adjacent to the basal plasma membrane. the diameter of these filaments is smaller than that of perinuclear intermediate filaments, but is similar to that of filaments present in peritubular cells. in the alligator, the filament bundles appear to form a branching network over the base of the cell and a ...	1992	18621219
choroid plexus, ependyma and arachnoidea express receptors for vitamin d: differences between "seasonal" and "non-seasonal" breeders.	autoradiographic studies with [3h]1,25-dihydroxyvitamin d3 demonstrated nuclear high affinity binding sites (receptors) in epithelial cells of choroid plexus, ependyma and arachnoid in "seasonal" breeders of various vertebrate phyla, namely xiphophorus helleri, hyla crucifer, xenopus laevis, bufo woodhousei, chrysemys scripta, anolis carolinensis, nerodia sipedon and phodopus sungorus, but vitamin d receptors were undetectable in these tissues in non-seasonal breeders, such as zebra finch, labor ...	1992	1329147
stimulation of in vitro steroidogenesis by pituitary hormones in a turtle (trachemys scripta) within the temperature-sensitive period for sex determination.	to investigate the possible involvement of pituitary hormones in the regulation of steroidogenesis during reptilian sexual differentiation, we tested the ability of gonadotropin (ovine fsh), adrenocorticotropin (porcine acth), and growth hormone (bovine gh) to stimulate in vitro steroidogenesis in embryonic adrenal-kidney-gonad complexes (akgs) of a turtle, trachemys scripta, during and after the temperature-sensitive period for sex determination (tsp). radioimmunoassays were used to measure pro ...	1992	1337278
binding of the benzodiazepine ligand [3h]-ro 15-1788 to membrane preparations of the rabbit and turtle retina.	1. we have studied the binding of [3h]-ro 15-1788 to membrane preparations of the retina of rabbit (lepus cunicula) and turtle (pseudemys scripta elegans). 2. in both species, [3h]-ro 15-1788 binding was maximal at 0 degrees c and decreased with increasing temperature. it was saturable, protein concentration-dependent and specific. flunitrazepam, unlabelled ro 15-1788 and ethyl-beta-carboline were the most effective displacers, whereas ro 5,4864 was ineffective. 3. in both turtle and rabbit reti ...	1992	1354109
diagnostic exercise: high mortality in red-eared slider turtles (pseudemys scripta elegans).		1992	1479815
cerebral anoxia tolerance in turtles: regulation of intracellular calcium and ph.	to investigate mechanisms of cerebral anoxia tolerance, cerebrocortical intracellular calcium ([ca2+]i) and ph (phi) regulation were compared in turtles (trachemys scripta) and laboratory rats. [ca2+]i and phi in living 200 to 300-microns-thick cortical brain slices were measured with the fluorescent indicators fura-2/acetoxymethyl ester (am) and 2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein during exposure to anoxia. within 5 min, [ca2+]i increased to > 1,000 nm in rat brain slices exposed to ...	1992	1481942
measurement of plasma thyroxine binding protein in relation to thyroidal condition in the turtle, trachemys scripta, by radioimmunoassay.	polyclonal (rabbit) antisera were generated against a high-affinity plasma thyroxine (t4) binding protein (tbp) purified from the turtle, trachemys scripta, and used to develop a specific radioimmunoassay (ria). the ria demonstrated the presence of an immunochemically related protein in the plasma of several other species of trachemys and in members of several other genera from the same family, emydidae. plasma from all nonemydids and some emydid genera either showed no competition or nonparalle ...	1992	1563614
identification and purification of a high-affinity thyroxine binding protein that is distinct from albumin and prealbumin in the blood of a turtle, trachemys scripta.	fractionation of plasma proteins in the turtle, trachemys scripta, confirmed the presence of a high-affinity thyroxine (t4) binding protein (tbp) that was distinct from albumin (alb) and prealbumin (pa). the tbp was isolated by adsorption on a t4-affinity column and a high degree of purification was achieved by gel filtration and preparative electrophoresis. analysis by reversed-phase hplc showed a single peak of protein with t4 binding activity. the electrophoretic mobility of the tbp, based on ...	1992	1601251
mechanism of intracardiac shunting in the turtle pseudemys scripta.	two principal hypotheses account for right-left (r-l) intracardiac shunting in reptiles. the "pressure shunting" hypothesis proposes no functional separation between the ventricular cava during systole. the "washout shunting" hypothesis suggests that during systole, the cavum pulmonale (cp) is functionally separate from the rest of the ventricle. the purpose of this study was to test these hypotheses during control, after acetylcholine (ach) administration, after epinephrine (epi) administration ...	1992	1621878
identification of cholecystokinin/gastrin peptides in frog and turtle. evidence that cholecystokinin is phylogenetically older than gastrin.	peptides homologous to mammalian cholecystokinin (cck) and gastrin in brain, antrum, and small intestine of an amphibian (the bullfrog, rana catesbeiana) and a reptile (the turtle, pseudomys scripta) were characterized. all tissues contained peptides reacting with antisera specific for the carboxyamidated c-terminal tetrapeptide common for cck and gastrin. extracts of all tissues, except the turtle antrum, also reacted with an antiserum specific for mammalian sulfated cck, while no extract conta ...	1992	1633800
the orbital glands of the chelonians pseudemys scripta and testudo graeca: comparative histological, histochemical and ultrastructural investigations.	the orbital glands of the chelonians pseudemys scripta and testudo graeca were investigated at the histological, histochemical and ultrastructural levels. four acinar cell types were seen in the harderian gland of p. scripta on the basis of histochemical reactions and ultrastructure. secretory granules were of 2 types, one showing moderate electron density with an electronlucent core, the other being smaller and more osmiophilic with an electron-dense core. in the harderian gland of t. graeca on ...	1992	1452463
vestibular afferents innervating the posterior ampullae in a turtle, pseudemys scripta.		1992	1599219
specificity of steroid hormone-induced sex determination in a turtle.	the specificity of steroid hormone-induced sex determination was investigated in the red-eared slider, trachemys scripta, a turtle with temperature-dependent sex determination. all eggs were incubated at either a female-producing temperature (31 degrees c) or a male-producing temperature (26 degrees c) and received control or experimental treatments at stage 17-18 of embryonic development. a variety of treatments induced female sex determination at the male-producing temperature. oestradiol-17 b ...	1992	1517701
sites of estrogen uptake in embryonic trachemys scripta, a turtle with temperature-dependent sex determination.	female sex determination can be induced in embryonic red-eared slider turtles (trachemys scripta) by exogenous estrogen, as well as by incubation at warm temperature. in the present study, estrogen target areas were identified in embryos before (stage 15), during (stage 18), and after (stage 22) the critical period for sex determination. both hyperfilm and emulsion autoradiography were used to localize tritium accumulation after the injection of radiolabeled 17 beta-estradiol. site-specific trit ...	1992	1617018
effects of temperature and anoxia on regional cerebral blood flow in turtles.	regional cerebral blood flow (cbf) was measured in isoflurane-anesthetized turtles (pseudemys scripta) by the hydrogen clearance method. teflon-coated platinum electrodes (25 microns) were implanted in the olfactory bulbs, midcerebral cortex and cerebellum in eight adult turtles. the electrodes were voltage clamped at +0.30 v relative to a ag-agcl electrode implanted in the dorsal neck muscles. washout kinetics of h2 gas administered via controlled ventilation was used to calculate local blood f ...	1992	1558224
subcellular enzyme binding and the regulation of glycolysis in anoxic turtle brain.	the association of glycolytic enzymes with the particulate fraction of the cell was assessed in the brain of the freshwater turtle, pseudemys scripta elegans, using three different methodologies. each method showed that a large percentage of each of eight enzymes was bound in brain. the effect of environmental anoxia (5 or 20 h submergence in n2-bubbled water at 7 degrees c) on the distribution of enzymes between free and bound states was analyzed. all three techniques showed a significant incre ...	1992	1532698
norepinephrine activates potassium conductance in neurons of the turtle cerebral cortex.	whole-cell voltage and current clamp recordings were obtained from cortical neurons of the pond turtle, pseudemys scripta elegans. norepinephrine (ne) induced an outward current in 50% of pyramidal neurons. this current had a reversal potential of -88.3 +/- 3.2 mv, consistent with a k+ conductance increase, and had a mean amplitude of 18.3 +/- 7.2 pa at -40 mv. the ionic dependence and pharmacological analyses are both consistent with alpha 2 adrenergic receptor stimulation. inhibition of na(+)- ...	1992	1617428
hydroxysteroid dehydrogenase activity associated with sexual differentiation in embryos of the turtle trachemys scripta.	many turtles exhibit temperature-dependent sex determination. we have examined the hypothesis that incubation temperature causes a differential expression of steroidogenic enzymes in embryonic turtles. the activities of three steroidogenic enzymes were studied histochemically in turtle (trachemys scripta) embryos at different developmental stages: sexually undifferentiated (stage 15), differentiating (stage 17), and differentiated (stage 26; i.e., hatchling). steroidogenic enzymes were detected ...	1992	1547311
a "beat-to-beat" interval generator for optokinetic nystagmus.	an analysis of optokinetic responses was used to derive an iterative model that reproduces the duration of nystagmus slow phases and eye position control during optokinetic nystagmus. optokinetic nystagmus was recorded with magnetic search coils from red-eared turtles (pseudemys scripta elegans) during monocular, random dot pattern stimulation at constant velocities ranging from 0.25-63 degrees/s. the beat-to-beat behavior of slow phase durations was consistent with the existence of an underlyin ...	1992	1540673
monoaminergic systems in the brainstem and spinal cord of the turtle pseudemys scripta elegans as revealed by antibodies against serotonin and tyrosine hydroxylase.	with the aim of gaining more insight into the monoaminergic regulation of spinal motor systems in the turtle, we have studied the distribution of 5-ht (5-htir) and tyrosine hydroxylase immunoreactivity (thir) in the brainstem and spinal cord of pseudemys scripta elegans. 5-htir cell bodies were located in the midline in nucleus raphe inferior, nucleus raphe superior, and laterally in nuclei reticularis superior and inferior and nucleus reticularis isthmi. thir cell bodies were located in the com ...	1992	1361496
design and control of the head retractor muscle in a turtle, pseudemys (trachemys) scripta: ii. efferent innervation.	the head retractor muscle (rccq) of pseudemys scripta is a useful model in which to study the mechanisms animals use to vary the force and timing of movement. single fibers in this muscle differ significantly in attachments, length, diameter, taper characteristics, and histochemical properties, suggesting that they may be energetically and architecturally specialized for different roles in head movement. in the present paper, we report the peripheral and central efferent innervation of these div ...	1992	1280283
gabaa, gabab, and benzodiazepine binding sites in the cerebellar cortex of the red-eared turtle (pseudemys scripta).	we used receptor autoradiography to ascertain the distribution of gabaa and gabab binding sites in the cerebellar cortex of the red-eared turtle (pseudemys scripta). gabaa binding sites were found in both molecular and granule cell layers with highest levels in the granule cell layer. gabab binding sites were found at highest level in the molecular layer. benzodiazepine binding sites were found in approximately equal abundance in both layers. little binding of any ligand was seen in the purkinje ...	1992	1334769
barbiturate sensitive components of visual erps in a reptile.	the selective effects of methohexital anesthesia were used to differentiate components of visual event-related brain potentials (erps) in pond turtles (pseudemys scripta). tectal and forebrain omitted stimulus potentials (osps) were found to be particularly sensitive to the barbiturate; they are reversibly abolished while the large early wave of the forebrain flash visual evoked potential (vep; 110-120 ms) is reduced by only 27 +/- 11% and that of the tectal vep (55-65 ms) is increased by 40 +/- ...	1992	1330066
refractive state, contrast sensitivity, and resolution in the freshwater turtle, pseudemys scripta elegans, determined by tectal visual-evoked potentials.	visual-evoked potentials (veps) were recorded from the surface of the optic tectum of the freshwater turtle, pseudemys scripta elegans, in response to phase reversal of square-wave gratings of different spatial frequency and contrast. the refractive state of a group of 12 turtles in air was assessed from veps by placing trial lenses in front of the eye. the group mean refraction did not differ significantly from emmetropia, as compared to 4.8 diopters of hyperopia when refracted retinoscopically ...	1991	1772808
chronology and morphology of temperature-dependent sex determination.	temperature sensitivity and gonadal differentiation were studied in a turtle, trachemys scripta, with temperature-dependent sex determination. sex determination was sensitive to both the duration and magnitude of incubation temperature. temperature exerted an "all or none" effect on the ovarian or testicular nature of most gonads, but affected the length of ovaries in a graded fashion. collectively, the results indicate that sex determination is controlled by the quantitative effect of temperatu ...	1991	1744617
localization of aspartate-like immunoreactivity in the retina of the turtle (pseudemys scripta).	aspartate has been reported to be a putative excitatory neurotransmitter in the retina, but little detailed information is available concerning its anatomical distribution. we used an antiserum directed against an aspartate-albumin conjugate to analyze the anatomy, dendritic stratification, and regional distribution of cell types with aspartate-like immunoreactivity in the turtle retina. the results showed dramatic differences in immunoreactivity in the peripheral versus the central retina. stro ...	1991	1761744
synergism between temperature and estradiol: a common pathway in turtle sex determination?	in many reptiles, the temperature at which the eggs are incubated determines the sex of the hatchlings. administration of estradiol will counteract the masculinizing effects of a male-producing temperature, resulting in female hatchlings. to address whether temperature and estrogen are biologically equivalent, two experiments were conducted with the red-eared slider turtle, trachemys scripta. in the first experiment, varying dosages of estrogen were administered at stage 17 (the middle of the te ...	1991	1791420
novel oxidative pathways of sulphapyridine and sulphadiazine by the turtle pseudemys scripta elegans.	the sulphonamides sulphapyridine and sulphadiazine show novel hydroxy metabolites in the turtle pseudemys scripta elegans. in the excreta of the turtles the monohydroxy metabolites 4-hydroxy- and 5-hydroxysulphapyridine and the dihydroxy metabolite 4,5-dihydroxysulphapyridine were detected. of sulphadiazine only dihydroxy metabolites 4,5- and 4,6-dihydroxysulphadiazine were detected. about 70-90% of the dose of sulphapyridine was recovered, while this figure varied between 48 and 69% for sulphad ...	1991	1776236
measuring the lipid content of live animals using cyclopropane gas.	the cyclopropane technique was validated, and it accurately estimated the lipid mass of six pond turtles (trachemys scripta). this technique provided more accurate estimates of lipid mass and lipid-free mass (by difference) than other nonfatal techniques. this technique was accurate despite the turtles' low lipid contents (0.71-3.5% of body mass), variable water contents (65-74% of body mass), and variable body temperatures (approximately 23-31 degrees c). a computer model of the cyclopropane te ...	1991	1887962
progesterone downregulates progesterone receptor, but not estrogen receptor, in the estrogen-primed oviduct of a turtle (trachemys scripta).	progesterone downregulates nuclear progesterone receptor (rp) and estrogen receptor (re) in the estrogen-primed mammalian uterus and chick oviduct. we sought to determine if this downregulation mechanism is operative in the turtle oviduct. female turtles were primed for 4 days with 17-beta-estradiol, after which progesterone (5 mg) was administered by injection every 24 h. re and rp levels in progesterone-treated and control turtle oviducts were measured by [3h]steroid-binding assays (pyridoxal ...	1991	1916218
o-dealkylation and n4-acetylation of sulpha-2-monomethoxine by the turtle pseudemys scripta elegans.	sulpha-2-monomethoxine is n4-acetylated to an extent of 12% of the dose by pseudemys scripta elegans; 48% is excreted unchanged. no o-dealkylation of the 2-methoxy group takes place.	1991	1949545
estrogen and sex reversal in turtles: a dose-dependent phenomenon.	exogenous estradiol benzoate (eb) or estradiol-17 beta (e2) caused dose-dependent gonadal feminization of slider turtle (trachemys scripta) embryos incubated at a male-producing temperature (26 degrees), suggesting that sex reversal requires a threshold dosage of these hormones. even at dosages resulting in mixtures of males and females, nearly all hatchlings had normal-appearing ovaries or testes. only 7 of 241 hatchlings had gonads that had not differentiated fully into ovaries or testes. thus ...	1991	2055436
chemical regulation of cerebral blood flow in turtles.	this study was performed to test the effect of the chemical composition of the blood on cerebral blood flow (cbf) regulation in turtles. the cbf response to increases in arterial pco2 (paco2) (hypercapnia) was measured during normoxia and anoxia in anesthetized freshwater turtles pseudemys scripta. the radioactive-microsphere technique was used to measure cbf. cbf increased with increases in paco2. the sensitivity of the cbf response to hypercapnia (delta cbf/delta paco2) was 0.68 ml.min-1.100 g ...	1991	1899982
effects of excitatory amino acids and their antagonists on the light response of luminosity and color-opponent horizontal cells in the turtle (pseudemys scripta elegans) retina.	both kainic acid (ka) and n-methyl-d-aspartatic acid (nmda) depolarize luminosity-type horizontal cells (l-type h cells) in normal turtle retina. the presence of both nmda and non-nmda receptors for excitatory amino acids (eaas) on these cells was highlighted by an unusual effect of the noncompetitive nmda-antagonist, mk-801. in retinas that had been exposed to mk-801, the action of nmda was irreversibly altered to one of hyperpolarization, while the depolarizing effect of ka was unaltered. the ...	1991	1675585
search for ion-cyclotron resonance in an na(+)-transport system.	colonic tissue from the turtle (pseudemys scripta) was exposed in a ussing chamber to simultaneously applied static and time-varying magnetic fields. transepithelial differences of potential were monitored as frequency of the ac field was varied continuously or in discrete steps from 3 to 770 hz. density of the dc field was varied from 10 to 220 microt and that of the ac field from 1 to 20 microt. short-circuit currents through tissue were monitored for changes that might have been observed unde ...	1991	2039558
the innervation of the gastrointestinal tract of a chelonian reptile, pseudemys scripta elegans. i. structure and topography of the enteric nerve plexuses using neuron-specific enolase immunohistochemistry.	the general morphological features of the intramural enteric nervous system of a chelonian species, i.e. the red-eared turtle, pseudemys scripta elegans, has been studied in whole-mounts and cryosections by means of neuron-specific enolase immunohistochemistry. a clear visualization of both neuronal cell bodies and nerve fibres allows the recognition of a myenteric plexus as well as a submucous plexus in several gut regions, namely the stomach, midgut and hindgut. the highest innervation density ...	1991	2022490
n2-glucuronidation and n4-acetylation of sulphaphenazole by the turtle pseudemys scripta elegans.	after an oral dose of 100 mg of sulphaphenazole, the turtle pseudemys scripta elegans excretes 27% of the compound unchanged and 3.8% as n4-acetylsulphaphenazole. the expected glucuronide conjugate, sulphaphenazole-n2-glucuronide, is not formed and excreted.	1991	2021055
genetic damage in a population of slider turtles (trachemys scripta) inhabiting a radioactive reservoir.	turtles inhabiting a radioactive reservoir appear to experience genetic damage due to environmental exposure to low concentrations of long-lived radionuclides. total body burdens for the 50 reservoir turtles examined in the survey ranged from 164.7-4679.3 bq for cesium-137 and from 462.6-5098.3 bq for strontium-90. flow cytometric (fcm) assays of red blood cell nuclei demonstrated significantly greater variation in dna content for the reservoir turtles than for turtles from a nearby, non-radioac ...	1991	1996906
ionic influences on the prolonged depolarization of turtle cones in situ.	1. the effects of ion channel blockers and ion substitutions on the prolonged depolarization of cones in the retina of the turtle (pseudemys scripta elegans) were studied by intracellular recording. 2. the results of current injection experiments indicate that the prolonged depolarization is regenerative and accompanied by a reduction in the cone's input resistance. 3. the addition of cobalt (5-10 mm) or the removal of extracellular calcium suppressed the prolonged depolarization. raising extrac ...	1991	1900325
calcitonin gene-related peptide, enkephalin and serotonin coexist in neuroepithelial bodies of the respiratory tract of the red-eared turtle, pseudemys scripta elegans. an immunocytochemical study.	the lungs of the red-eared turtle, pseudemys scripta elegans, have been investigated by light-microscopical immunocytochemistry for serotonin (5-ht) and the neuropeptides calcitonin gene-related peptide (cgrp), enkephalin (enk), bombesin, somatostatin, calcitonin and cholecystokinin. cgrp- or 5-ht-like immunoreactivity (li) was demonstrated in neuroepithelial bodies (nebs) and solitary neuroepithelial endocrine cells lying between the ciliated epithelial cells of the intrapulmonary bronchi, and ...	1991	1856111
calcitonin-gene related peptide is an evolutionarily conserved marker within the amniote thalamo-telencephalic auditory pathway.	the distribution of neurons and fibers containing calcitonin-gene-related peptide (cgrp) was mapped in the thalamo-telencephalic auditory pathways of four amniote species, rats, pigeons (columba livia), caiman (caiman crocodilus), and turtles (pseudemys scripta). in colchicine-treated turtles and pigeons, numerous cgrp+ perikarya were observed in the auditory relay nucleus of the thalamus (n. reuniens of reptiles, and n. ovoidalis of birds). in pigeons, these neurons were most abundant in the ou ...	1991	1765582
isolation, purification and primary structure of insulin from the turtle chrysemys dorbigni.	insulin a and b chains from pancreas of the turtle chrysemys dorbigni have been purified to homogeneity, and their primary structures have been determined. the sequence of the a chain is g-i-v-e-q-c-c-h-n-t-c-s-l-y-q-l-e-n-y-c-n, and that of the b chain is a-a-n-q-h-l-c-g-s-h-l-v-e-a-l-y-l-v-c-g-e-r-g-f-f-y-s-p-k-a. the amino acid sequence of chrysemys insulin is identical to that of another turtle (pseudemys scripta), the chicken, and turkey. when compared with alligator insulin, it has three c ...	1991	1808015
ocular dimensions and schematic eyes of freshwater and sea turtles.	measurements were made of the ocular dimensions from living and frozen eyes of one species of freshwater turtle, pseudemys scripta elegans, and of three species of marine turtles, chelonia mydas, dermochelys cariacea, and eretmochelys imbricata. estimates of refractive error by retinoscopy were also obtained with eyes in air and under water. the results suggest that unaccommodated eyes of all four species are approximately emmetropic in air but strongly hyperopic in water. schematic eyes were ca ...	1991	1772809
excitatory amino acid receptor-mediated transmission in geniculocortical and intracortical pathways within visual cortex.	1. a preparation of turtle (chrysemys picta and pseudemys scripta) brain in which the integrity of the intracortical and geniculocortical pathways in visual cortex are maintained in vitro has been used to differentiate the excitatory amino acid (eaa) receptor subtypes involved in geniculocortical and intracortical synapses. 2. stimulation of the geniculocortical fibers at subcortical loci produces monosynaptic excitatory postsynaptic potentials (epsps) in visual cortical neurons. these epsps are ...	1991	1681038
the innervation of the gastrointestinal tract of a chelonian reptile, pseudemys scripta elegans. ii. distribution of neuropeptides in the myenteric plexus.	the myenteric plexus of the stomach, midgut and hindgut of the red-eared turtle, pseudemys scripta elegans, has been investigated for the occurrence of immunoreactivity to nine neuropeptides. neuropeptide y (npy)-, calcitonin gene-related peptide (cgrp)-, bombesin (bom)- as well as substance p (sp)-like immunoreactivity (li) were found in nerve fibres of all investigated gut regions. from all peptides investigated immunoreactivity for npy was more pronounced. in the stomach npy-li was mainly fou ...	1991	2022491
neurotensin is localized to paracrine cells in the urinary bladder of the turtle, chrysemys picta.	urinary bladder from the painted turtle, chrysemys picta, contains a substantial population of endocrine/paracrine cells scattered through the mucosal epithelium which immunostains using antisera directed toward mammalian neurotensin (nt). radiommunoassay of 0.1 n hcl extracts of chrysemys bladder indicated an immunoreactive nt (int) concentration of 161 +/- 39 pmol/g tissue (n = 9), an amount lower but comparable in magnitude to that found in mucosal scrapings of the intestine (926 +/- 125 pmol ...	1990	2202609
localization of insulin to gastroenteropancreatic cells in the turtle gastrointestinal tract.	insulin has been localized immunocytochemically to open-type gastroenteropancreatic endocrine cells in sections of bouin's-fixed upper, middle, and lower intestine from chrysemys picta, pseudemys scripta scripta, p. scripta elegans, p. floridana, sternotherus odoratus, and trionyx spinifer asper. radioimmunoassay of extracts of mucosal scrapings from chrysemys intestine indicates differential amounts of insulin-like immunoreactivity within the intestine (higher amounts in the lower intestine) an ...	1990	2185121
wavelength-dependent temporal properties of retinal horizontal cells in turtles.	electrical responses of luminosity horizontal cells (l cells) to monochromatic stimuli were analyzed by intracellular recordings in the retinas of the freshwater turtle (pseudemys scripta elegans) and of the sea turtle (chelonia mydas mydas). light intensity, duration, and wavelength were varied to assess temporal effects. for a given intensity of monochromatic light, response amplitude increased with stimulus duration until maximum amplitude occurred at a specific duration. this suprathreshold ...	1990	2271453
lympho-epithelial interactions in the turtle chrysemys scrypta elegans.	the morphological relationships present in the areas of lymphoid infiltration found in the esophagus in chrysemys scripta elegans were studied by the use of light and transmission electron microscopy. these infiltrations are widespread and can be observed in the lamina propria and the covering epithelium. electron microscopy reveals the presence of epithelial cells with differing characteristics at the apex of the lymphoid infiltrations. the introduction of horseradish peroxidase (hrp) into the ...	1990	1695064
modulation of neuropeptide-stimulated pituitary hormone secretion in hatchling turtles.	neuropeptides that have relatively narrow actions on mammalian pituitary secretion may have divergent effects on pituitary hormone secretion in ectothermal vertebrates. in turtles, secretion of both thyrotropin (tsh) and growth hormone (gh) can be stimulated in vitro by thyrotropin-releasing hormone (trh) and by members of corticotropin-releasing hormone (crh) and growth hormone-releasing hormone (ghrh) peptide families. to determine if these neuropeptides share common modes of action, and to st ...	1990	1967241
isolation and structural characterization of insulin, glucagon and somatostatin from the turtle, pseudemys scripta.	the chelonians occupy an important position in phylogeny representing a very early branching from the ancestral reptile stock. hormonal polypeptides in an extract of the pancreas of the red-eared turtle were purified to homogeneity by reversed phase hplc and their primary structures were determined. turtle insulin is identical to chicken insulin. turtle glucagon differs from chicken glucagon by the substitution of a serine by a threonine residue at position 16 and from mammalian glucagon by an a ...	1990	1974347
relation of plasma thyroxine binding to thyroidal activity and determination of thyroxine binding proteins in a turtle, pseudemys scripta.	the ability of plasma to bind thyroxine (t4) was examined in the turtle, pseudemys scripta, in relation to variations in thyroidal state associated with age, sex, environment, and surgical and chemical manipulations. relative plasma binding activity was assessed by use of binding to [125i]t4 on minicolumns of sephadex g-25 (fine). hypothyroidism induced by surgical thyroidectomy (tx) or goitrogen (methimazole) treatment resulted in a marked depression of plasma binding (50- to 100-fold) in juven ...	1990	2127405
salmonella colonization in commercial pet turtles (pseudemys scripta elegans).	an epidemiological survey was conducted on two commercial turtle farms in southern louisiana to determine the reason for an apparent increase in the prevalence of salmonella spp. in turtle hatchlings at the time of pre-export certification examination. pond water was consistently found to be contaminated (6/36 samples) with either salmonella newport, s. arizonae, or s. poona. environmental specimens obtained from eggs and turtle hatcheries (204 specimens) failed to yield salmonella spp. a sample ...	1990	2209735
pet turtles: a continuing international threat to public health.	the occurrence of salmonella spp. in red-eared (pseudemys scripta elegans) turtle eggs imported into canada from louisiana in june to september 1988 was examined. of 28 lots tested, six (21%) lots from three of four exporters harbored salmonellae. salmonella poona and salmonella arizonae were frequently encountered in both fertile eggs and packaging moss. turtles hatched in our laboratory from affected lots of eggs shed salmonella in tank water for up to 11 months. widespread use of gentamicin o ...	1990	2372004
comparative analysis of vasotocin-like immunoreactivity in the brain of the turtle pseudemys scripta elegans and the snake python regius.	the distribution of vasotocin in the brains of the turtle pseudemys scripta elegans and the snake python regius was studied with immunohistochemical methods. in both species, vasotocin-immunoreactive (vti) cells were found in the supraoptic nucleus, the paraventricular nucleus and the bed nucleus of the stria terminalis. no vti cell bodies were seen in the brainstem. vasotocinergic fibers were found in all major brain divisions. intrahypothalamic vti fibers were observed between the supraoptic a ...	1990	2191754
the role of hormone binding in the cold suppression of hormone stimulation of the pituitary, thyroid, and testis of the turtle.	the ability of hormones to bind to their functional receptors on turtle (pseudemys scripta) endocrine target tissues in the cold was tested by treating tissues with secretagogues at low temperatures (5-15 degrees) and then following subsequent target stimulation in the absence of secretagogue at a warm temperature (28 degrees). administration of thyrotropin-releasing hormone (trh), corticotropin-releasing hormone, and growth hormone-releasing hormone to pituitaries at low temperatures (20 degree ...	1990	2289680
effects of synaptic blocking agents on the depolarizing responses of turtle cones evoked by surround illumination.	the effects of synaptic blocking agents on the antagonistic surround of the receptive field of cone photoreceptors were studied by intracellular recording in the retina of the turtle (pseudemys scripta elegans). illumination of a cone's receptive-field surround typically evoked a hybrid depolarizing response composed of two components: (1) the graded synaptic feedback depolarization and (2) the prolonged depolarization, a distinctive, intrinsic response of the cone. the locus of action of synapt ...	1990	2085473
life history and ecology of the slider turtle. j. whitfield gibbons, with contributions by harold w. avery et al. smithsonian institution press, washington, dc, 1990. xiv, 368 pp., illus. $60.		1990	17840206
changes in turtle brain neurotransmitters and related substances during anoxia.	freshwater turtles (pseudemys scripta elegans) were exposed to 0.5-13 h of anoxia at 25 degrees c, whereupon the brain concentrations of 14 amino acid and monoamine neurotransmitters and related substances were measured. monoamines are of particular interest, because their synthesis and (in part) degradation require molecular oxygen. during anoxia, the level of the inhibitory transmitter gamma-aminobutyric acid (gaba) increased (2.3-fold after 13 h) and the level of the excitatory transmitter gl ...	1990	1696793
steroidal modulation of pituitary gonadotropin-releasing hormone responsiveness in young turtles, pseudemys scripta.	steroid-modulated pituitary secretion and glandular content of gonadotropin (gth: lh and fsh) was studied in young slider turtles. injection (ip) of both 17 beta-estradiol (e2) and testosterone (t) reduced pituitary content of both gths and caused significant inhibition of basal lh secretion and gonadotropin-releasing hormone (gnrh)-stimulated lh and fsh secretion measured in vitro. however, gonadectomy did not affect pituitary gth secretion or response in these juveniles, and anti-estrogen and ...	1990	2112103
distribution of [3h]mk-801 binding in the turtle retina: an autoradiographical study.	frozen sections (15 microns) of the turtle (pseudemys scripta elegans) retina were incubated in 1.6 nm [3h]mk-801. autoradiograms were generated using dry autoradiographical techniques. a band of [3h]mk-801 labelling was observed in the outer plexiform layer and cells were occasionally labelled in the inner nuclear and ganglion cell layers. this pattern of labelling was enhanced by preincubation in 1.0 mm glycine but not affected by pre-incubation in 3.0 mm n-methyl-d-aspartate (nmda). we did no ...	1990	2163036
membrane currents of spiking cells isolated from turtle retina.	we examined the membrane properties of spiking neurons isolated from the turtle (pseudemys scripta) retina. the cells were maintained in culture for 1-7 days and were studied with the whole cell patch clamp technique. we utilized cells whose perikaryal diameters were greater than 15 microns since kolb (1982) reported that ganglion cell perikarya in pseudemys retina are 13-25 microns, whereas amacrine perikarya are less than 14 microns in diameter. we identified 5 currents in the studied cells: ( ...	1990	2388180