Publications

comparative analysis of fmrfamide-like immunoreactivity in caiman (caiman crocodilus) and turtle (trachemys scripta elegans) brains.	the distribution of fmrfamide (fmrfa)-like peptides in caiman (caiman crocodilus) and turtle (trachemys scripta elegans) brains was studied by immunohistochemistry. in both species, distinct groups of fmrfa-like immunoreactive (ir) perikarya were present in the medial septal nucleus, accumbens nucleus, nucleus of the diagonal band of broca, suprachiasmatic area, lateral hypothalamic area, and periventricular hypothalamic nucleus. a few fmrfa-ir neurons in the hypothalamic area were located in th ...	1999	10639745
staining of the dorsal root primary afferent fibers by anterograde movement of horseradish peroxidase and retrograde labelling of motoneurons and preganglionic autonomic cells in the turtle spinal cord.	the enzyme horseradish peroxidase (hrp) has been applied to the proximal stumps of severed thoracic and lumbar dorsal roots in the turtles pseudemys scripta elegans and testudo hermanni. the results obtained confirm the distribution pattern observed with anterograde degeneration techniques. primary afferent terminal structures, however, could be demonstrated in more detail. commonly, ventral roots were also more or less damaged which resulted in the presence of retrogradely labeled motoneurons a ...	1999	93720
characterization of thyroid hormone 5'-monodeiodinase activity in the turtle (trachemys scripta).	thyroid hormone metabolism by 5'-monodeiodinase enzymes (5'md) was characterized in peripheral tissues of the turtle, trachemys scripta, and compared with activity measured in the rat. based on differences in ph dependence, sensitivity to inhibitors, substrate affinity, and cofactor requirements, at least two types of enzyme activities have been identified in the turtle. a 5'md activity was measured in liver and kidney microsomal fractions that exhibits inhibition by 2n-propyl-6-thiouracil (ptu) ...	1999	10068496
embryonic development of connections in turtle pallium.	we are interested in similarities and conserved mechanisms in early development of the reptilian and mammalian thalamocortical connections. we set out to analyse connectivity in embryonic turtle brains (pseudemys scripta elegans, between stages 17 and 25), by using carbocyanine dye tracing. from the earliest stages studied, labelling from dorsal and ventral thalamus revealed backlabelled cells among developing thalamic fibres within the lateral forebrain bundle and striatum, which had similar mo ...	1999	10464368
warm-blooded isochore structure in nile crocodile and turtle.	the genomes of warm-blooded vertebrates are characterized by a strong heterogeneity in base composition, with gc-rich and gc-poor isochores. the gc content of sequences, especially in third codon positions, is highly correlated with that of the isochore they are embedded in. in amphibian and fish genomes, gc-rich isochores are nearly absent. thus, it has been proposed that the gc increase in a part of mammalian and avian genomes represents an adaptation to homeothermy. to test this selective hyp ...	1999	10555283
developmental synergism of steroidal estrogens in sex determination.	gonadal sex in the red-eared slider turtle, trachemys scripta, is determined by incubation temperature during embryonic development. evidence suggests that temperature determines sex by influencing steroid hormone metabolism and/or sensitivity: steroidogenic enzyme inhibitors or exogenous sex steroid hormones and their man-made analogs override (or enhance) temperature effects on sex determination. specifically, nonaromatizable androgens and aromatase inhibitors induce testis differentiation at ...	1999	9924002
identification of renal podocytes in multiple species: higher vertebrates are vimentin positive/lower vertebrates are desmin positive.	we sought to characterize podocytes in the kidneys of numerous species from amphibians to mammals because of the pivotal function of these cells in renal diseases. for this purpose, intermediate filament (if) proteins of podocytes were examined by immunofluorescence microscopy using antibodies against vimentin, cytokeratins, and desmin. these staining patterns were then compared to those of parietal cells of bowman's capsule and tubular cells of the first portion of the proximal tubule from the ...	1999	10090571
multiplicity of glutamic acid decarboxylases (gad) in vertebrates: molecular phylogeny and evidence for a new gad paralog.	the evolution of chordate glutamic acid decarboxylase (gad; ec 4.1.1.15), a key enzyme in the central nervous system synthesizing the neurotransmitter gamma-amino-butyric acid (gaba) from glutamate, was studied. prior to this study, molecular data of gad had been restricted to mammals, which express two distinct forms, gad65 and gad67. these are the products of separate genes and probably are derived from a common ancestral gad following gene duplication at some point during vertebrate evolution ...	1999	10331265
endogenous yolk steroid hormones in turtles with different sex-determining mechanisms.	maternal transfer of nutrients, including steroid hormones, to embryos during gestation in viviparous amniotes is well known, but the concordant process in oviparous amniotes is poorly understood. recent evidence suggests that steroid hormones are present in freshly laid eggs of archosaurs and that their concentrations may influence offspring phenotypes. this process might be especially important in reptiles with temperature-dependent sex determination (tsd), because embryonic sex determination ...	1998	9707477
fatal trematodiasis in research turtles.	during a 5-year period, 16 freshwater turtles (trachemys scripta elegans and chrysemys picta) that were purchased for research purposes died spontaneously. clinical signs of disease included lethargy, constant swimming, swimming sideways, hemiplegia, and ulcerative lesions on the carapace. at necropsy, subcutaneous edema, hepatic necrosis, pancreatic necrosis, splenic necrosis, and intestinal parasites were identified. histologically, trematode eggs were seen within the liver, brain, spleen, kid ...	1998	10090039
sequence and expression analysis of wt1 and sox9 in the red-eared slider turtle, trachemys scripta.	temperature-dependent sex-determination (tsd) is a phenomenon that has been characterized at the ecological, morphological, and endocrinological levels in some reptilian species. we have begun to investigate tsd at the level of molecular development by cloning, sequencing, and analyzing the expression of two genes, wt1 and sox9, in the red-eared slider turtle trachemys scripta. we obtained almost full-length cdna clones for wt1 and sox9 that were greater than 73% identical to the human homologue ...	1998	9662829
expression of a new rna-splice isoform of wt1 in developing kidney-gonadal complexes of the turtle, trachemys scripta.	wt1 is a tumor suppressor gene encoding a zinc finger dna-binding protein required for normal vertebrate kidney and gonad development. although the sequence and function of this gene has been studied mostly in mammals, comparative analysis in other vertebrates may suggest regions of conservation of function as well as evolution of function. we have initiated a study of this gene in the freshwater turtle, trachemys scripta, a species that demonstrates temperature dependent sex determination. the ...	1998	9787767
cellular bioavailability of natural hormones and environmental contaminants as a function of serum and cytosolic binding factors.	environmental contaminants have been reported to function as hormone mimics in various wildlife species. to investigate a potential mechanism for the interaction of contaminants with the endocrine system, we evaluated the cellular bioavailability of numerous chemicals. hormone binding proteins from oviductal cytosol of the american alligator (alligator mississippiensis) and yellow-bellied turtle (trachemys scripta) were used in competitive binding assays with [3h] 17 beta-estradiol. most of the ...	1998	9460179
nomenclature, filling and angioarchitecture of lymph vessels in organs. scanning electron microscopy of the stomach of the turtle pseudemys scripta elegans using different injection methods.	the gastric lymph vessel network of pseudemys scripta elegans shows all the characteristics of initial lymphatics. a differentiation of initial lymphatics in lymphatic capillaries and precollectors is not possible in the turtle. the scanning electron microscopic examination shows that ultrastructural analysis of initial lymphatics is possible after manual subserous injection of glutaraldehyde or application with the vacuum chamber. in the stomach of the turtle all characteristics of initial lymp ...	1998	9505440
identification and structural characterization of a novel member of the vitamin d binding protein family.	the apparent high degree of homology of a blood protein with a unique dual binding affinity for two distinct hormones, thyroxin (t4) and vitamin d, isolated from a turtle, trachemys scripta (family emydidae) and mammalian vitamin d binding protein (dbp) prompted further interspecific comparison to better understand the structure of functional binding sites. using polymerase-chain reaction (pcr) with primers derived from the putative nucleotide sequences encoding peptides from the degradation of ...	1998	9972311
species recognition of congeneric acanthocephalans in slider turtles by random-amplified polymorphic dna (rapd) markers.	species recognition of acanthocephalans of the genus neoechinorhynchus (hamann, 1892) found in the freshwater turtle trachemys scripta (wied, 1838) has previously been based primarily on female body and egg morphology. observed morphological plasticity within and among species may lead to the misclassification of female specimens and leaves males of different species completely indistinguishable. here, random-amplified polymorphic dna (rapd) analysis was used to genetically characterize samples ...	1998	9714226
uv-sensitive input to horizontal cells in the turtle retina.	microspectrophotometry, electroretinography and behavioural studies have indicated that ultraviolet (uv) light contributes to functional vision in various vertebrate species. based on behavioural evidence, this was also suggested for turtle vision. in order to reveal the interactions underlying detection of uv light in the distal retina, we recorded intracellularly the photoresponses of cones and horizontal cells in retinas of pseudemys scripta elegans and mauremys caspica and calculated the act ...	1998	9751127
effects of lead on behavior, growth, and survival of hatchling slider turtles.	in this study the effects of lead on behavioral development of hatchling slider turtles (trachemys scripta) from the savannah river site, near aiken, sc, were examined. it was of interest to determine whether dose or size affects survival, growth, or behavior. hatchlings from 1995 showed no significant differences in growth, survival, or behavior between control and lead-injected animals at a dose of 0.05 and 0.1 mg/g (n = 10 per group). in 1996, 48 hatchlings were divided into four groups injec ...	1998	9860323
atp-sensitive k+ channel activation provides transient protection to the anoxic turtle brain.	there is wide speculation that atp-sensitive k+ (katp) channels serve a protective function in the mammalian brain, being activated during periods of energy failure. the aim of the present study was to determine if katp channels also have a protective role in the anoxia-tolerant turtle brain. after ouabain administration, rates of change in extracellular k+ were measured in the telencephalon of normoxic and anoxic turtles (trachemys scripta). the rate of k+ efflux was reduced by 50% within 1 h o ...	1998	9843892
n-methyl-d-aspartate-mediated bulbospinal respiratory drive is ph/p(co2)-insensitive in turtle brainstem-spinal cord.	a split-bath in vitro brainstem-spinal cord preparation from adult turtles (pseudemys scripta) was used to test the hypotheses that: (1) bulbospinal respiratory synaptic transmission is mediated, at least in part, by n-methyl-d-aspartate (nmda) glutamatergic receptors, and (2) this transmission is suppressed by low spinal ph (induced by hypercapnea). recordings from intact pectoralis (expiratory) and serratus (inspiratory) nerves showed that the in vitro turtle brainstem-spinal cord preparation ...	1998	9840329
hypoxia elicits an increase in pulmonary vasculature resistance in anaesthetised turtles (trachemys scripta).	in mammals and birds, low oxygen levels in the lungs cause a constriction of the pulmonary vasculature. this response is locally mediated and is considered to be important for local matching of perfusion and ventilation. it is not known whether reptiles respond in a similar fashion. the present study describes the effects of altering lung oxygen levels (at a constant fco2 of 0.03) on systemic and pulmonary blood flows and pressures in anaesthetised (nembumal, 50 mg kg-1) and artificially ventila ...	1998	9817833
temperature-dependent sex determination in the red-eared slider turtle, trachemys scripta.	temperature-dependent sex determination (tsd) in the red-eared slider turtle, trachemys scripta, has been the subject of a variety of past studies. incubation temperature appears to affect sex determination in a dose-dependent fashion. this suggests that temperature could be affecting a dosage-sensitive element in the sex-determination cascade. sex determination in t. scripta is sensitive to estrogen, and data from many studies support the hypothesis that endogenous estrogen production may be in ...	1998	9662828
low extracellular dopamine levels are maintained in the anoxic turtle (trachemys scripta) striatum.	the uncontrolled increase of extracellular dopamine (da) has been implicated in the pathogenesis of hypoxic/ischemic damage in the mammalian brain. but unlike the harmful release of excitatory neurotransmitters such as glutamate and aspartate, which occurs on brain depolarization, excessive extracellular da levels occur even with mild hypoxia in the mammalian brain. the purpose of this study was to determine whether hypoxia/anoxia provokes a similar increase in the anoxic tolerant turtle brain. ...	1998	9663509
comparison of blood viscosity in red-eared sliders (trachemys scripta) adapted to cold and room temperature.	red-eared sliders (trachemys scripta) in their northern range undergo hibernation at temperatures of about 5 degrees c, which may result in a profound bradycardia and a drop in blood pressure leading to very slow blood flows. blood viscosity increases with decreasing temperature and at low shear rates associated with slow blood flows. to investigate the effects of temperature on the blood viscosity of these animals, 20 red-eared sliders were randomly assigned to each of two groups, cold environm ...	1998	9621436
cloning and in situ hybridization analysis of estrogen receptor in the developing gonad of the red-eared slider turtle, a species with temperature-dependent sex determination.	many reptiles exhibit temperature-dependent sex determination where the incubation temperature of the egg determines the gonadal sex of the individual. if exogenous estrogen is administered during the temperature-sensitive period to embryos incubating at a male-producing temperature, the temperature effects can be overridden and females will be produced. inhibiting production of endogenous estrogens at female-biased incubation temperatures results in embryos developing as males rather than femal ...	1998	9572366
morphology of basal optic tract terminals in the turtle, pseudemys scripta elegans.	the morphologies of axon terminals of retinal ganglion cells projecting to the basal optic nucleus (bon) via the basal optic tract (bot) were studied in the red-eared turtle. the bot was visualized on the ventral surface of the brainstem in vitro, and either biotinylated dextran amine was injected extracellularly or neurobiotin was injected into physiologically identified axons during intracellular recordings. up to 16 hours after tracer injection, the brains were fixed, sectioned parasagittally ...	1998	9548549
trace elements in egg contents and egg shells of slider turtles (trachemys scripta) from the savannah river site.	in this paper we examine the levels of trace elements in the egg contents and egg shells of slider turtles (trachemys scripta) from the savannah river site, near aiken, south carolina. trace elements have seldom been examined in the tissues or eggs of reptiles, although some turtles and large snakes occupy a high trophic level. lead, mercury, cadmium, selenium, chromium, and manganese levels were examined in one egg and its egg shell collected from each of 16 females that laid in late may and ju ...	1998	9543509
the effects of dietary vitamin c on growth rates of juvenile slider turtles (trachemys scripta elegans).	seventeen juvenile red-eared slider turtles (trachemys scripta elegans) were separated into two groups: one group received a diet that included vitamin c supplementation, the other group received a similar diet devoid of supplemental vitamin c. overall body mass and carapace length were measured monthly for a period of 1 yr. no significant differences were observed between the growth rates of the two experimental groups, suggesting that dietary vitamin c is not essential for normal growth and de ...	1998	10065850
fine structure of the dorsal lingual epithelium of trachemys scripta elegans (chelonia: emydidae).	turtles are adapted to different environments, such as freshwater, marine, and terrestrial habitats. examination of histological and ultrastructural features of the dorsal lingual epithelium of the red-eared turtle, trachemys scripta elegans, and comparison of the results with those of other turtles should elucidate the relationship between the morphology of tongues as well as the fine structure of lingual epithelia and chelonian feeding mechanisms.	1998	9489772
the effect of the renal portal system on pharmacokinetic parameters in the red-eared slider (trachemys scripta elegans).	the premise that drugs not be injected into the caudal body of reptiles because they will be carried by the renal portal system to the kidneys, where they may be nephrotoxic or rapidly excreted, was tested by comparing the pharmacokinetics of gentamicin (excreted via glomerular filtration in mammals) and carbenicillin (excreted partly via renal tubular secretion in mammals) following injection into the forelimb or hindlimb of red-eared sliders (trachemys scripta elegans). ten sliders received in ...	1997	9523631
the anatomy and perfusion of the renal portal system in the red-eared slider (trachemys scripta elegans).	the anatomy of the renal portal system of the red-eared slider (trachemys scripta elegans) is described, based on dissection of six double latex-injected specimens (three males, three females). the anatomy of these vessels, which had not previously been described in this species, was found not to differ significantly from the fundamental chelonian pattern. fluoroscopic radioangiography revealed that venous blood returning from the hindlimbs flowed predominantly to the liver and bypassed the kidn ...	1997	9523630
corticosterone secretion in response to capture and handling in free-living red-eared slider turtles.	the corticosterone response to capture and handling was measured in free-living red-eared slider turtles, trachemys scripta elegans. to determine the ability of this species to exhibit this endocrine response, slider turtles were bled at the time of removal from hoop nets and again at 30 and 60 min following capture to create plasma profiles of acute corticosterone secretion from individuals. plasma corticosterone concentration increased significantly with handling time. the greatest rise in cor ...	1997	9405119
release of adenosine and atp in the brain of the freshwater turtle (trachemys scripta) during long-term anoxia.	extracellular adenosine and atp levels were monitored by microdialysis in the striatum of the freshwater turtle trachemys scripta during long-term n2 respiration. after an initial rise in extracellular adenosine, a second peak of longer duration and higher in intensity, followed. the frequencies of these adenosine cycles varied considerably between individual turtles, such that the shortest time between the peaks was 80 min and the longest was 300 min (mean 151 min). after about 60 min anoxia, t ...	1997	9374196
the effects of artificial lung inflation on pulmonary blood flow and heart rate in the turtle trachemys scripta.	as for most ectothermic vertebrates, the breathing pattern of turtles is episodic, and pulmonary blood flow (qpul) and heart rate (fh) normally increase several-fold during spontaneous ventilation. while some previous studies suggest that these cardiovascular changes are caused by stimulation of pulmonary stretch receptors (psrs) during ventilation, it has been noted in other studies that blood flows often change prior to the initiation of breathing. given the uncertainty regarding the role of p ...	1997	9366085
on the presence of dendrite bundles in the cerebral cortex of the madagascan lesser hedgehog tenrec and the red-eared pond turtle.	in mammals with a well-differentiated neocortex apical dendrites of pyramidal cells form vertical bundles. little is known about the presence of dendrite bundles in animals with a poorly differentiated cortex. in this paper the presence of dendrite bundles has been investigated in the lesser hedgehog tenrec, echinops telfairi, a basal insectivore with a very low degree of neocorticalization. in a further step the arrangement of dendrites has been analyzed in the cerebral cortex of the red-eared ...	1997	9310312
energy metabolism in liver of anoxia-tolerant turtle species (pseudemys scripta): a model for studying hepatic tolerance to cold hypoxia.	we have studied biochemical markers of energy metabolism and glycolysis by enzyme analyses and 1h nmr spectroscopy in livers of the freshwater turtle, pseudemys scripta, after vascular flush and cold storage. values for hepatic atp content and energy charge remained unchanged for 24 h and showed only small declines between 24 and 48 h of cold hypoxia. lactate and glucose levels increased over the 48-h period, demonstrating, respectively, progressive glycolysis and glycogenolysis. these observati ...	1997	9245506
protein synthesis under conditions of anoxia and changing workload in ventricle strips from turtle heart.	an earlier study determined that protein synthesis in isolated perfused turtle (trachemys [= pseudemys] scripta elegans) hearts was three-fold lower under conditions of anoxia than under conditions of normoxia. however, the earlier study did not attempt to define the role of work in the isolated perfused preparation. in this study, the effects of varying workload, as defined by changing frequency of contraction, and anoxia on protein synthesis were examined. the ventricle strip preparation allow ...	1997	9216073
postnatal neurogenesis in the telencephalon of turtles: evidence for nonradial migration of new neurons from distant proliferative ventricular zones to the olfactory bulbs.	postnatal neurogenesis in the the turtle telencephalon was investigated by using bromodeoxyuridine immunocytochemistry and [3h]thymidine autoradiography. red-eared slider turtles trachemys scripta elegans (cryptodira, emydidae) 2-3 months old were injected with the thymidine analogue 5'-bromodeoxyuridine (brdu) and allowed to survive for 7, 30, 90, and 180 days. results indicate that cells in the walls of the lateral ventricles continue to proliferate postnatally. shortly after brdu treatment (s ...	1997	9263587
glutathione systems and anoxia tolerance in turtles.	effects of anoxic submergence (20 h at 5 degrees c) and subsequent 24 h aerobic recovery on glutathione levels and the activities of glutathione-related enzymes were examined in six tissues of trachemys scripta elegans. anoxia exposure resulted in tissue-specific changes in enzyme maximal activities, the most dramatic being suppression of gamma-glutamyl transpeptidase (gamma-gtpase) activity in anoxic kidney to only 2% of control. anoxia exposure also caused significant decreases in activities o ...	1997	9249553
role for adenosine in channel arrest in the anoxic turtle brain.	the remarkable ability of the turtle brain to survive anoxia is based on its ability to match energy demand flexibly to energy production. earlier studies indicate that reduced ion leakage is an important mechanism for energy conservation during anoxia. we tested the hypothesis that extracellular adenosine plays a role in the reduction of k+ flux (channel arrest) that occurs in the anoxic turtle brain. changes in extracellular k+ concentration ([k+]o in the in situ brain of the turtle trachemys ...	1997	9232005
energy turnover in the normoxic and anoxic turtle heart.	we examined the possibility that the heart of the tuttle chrysemys scripta is an exceptional anaerobic performer, by measuring myocardial power output, lactate output, and estimated atp turnover in perfused heart preparations. over a range of myocardial power outputs at 5 and 15 degrees c we find that turtle hearts perfused with anoxic saline do not show a particularly outstanding ability to produce atp anaerobically. furthermore, at 15 degrees c anoxia reduced the atp turnover rate to 50% of th ...	1997	9185339
effects of inhibition of nitric oxide synthesis and of hypercapnia on blood pressure and brain blood flow in the turtle.	in the mammalian brain, nitric oxide (no) is responsible for a vasodilatory tonus as well as the elevation of cerebral blood flow (cbf) induced by hypercapnia. there have been few comparative studies of cerebral vasoregulation in lower vertebrates. using epi-illumination microscopy in vivo to observe cbf velocity on the brain surface (cerebral cortex), we show that turtles (trachemys scripta) exposed to hypercapnia (inspired pco2 = 4.9 kpa) displayed a 62% increase in cbf velocity, while systemi ...	1997	9076965
shell disease in river cooters (pseudemys concinna) and yellow-bellied turtles (trachemys scripta) in a georgia (usa) lake.	a disfiguring shell disease was detected in river cooters (pseudemys concinna) and yellow-bellied turtles (trachemys scripta) from lake blackshear, georgia (usa). the turtles used were part of a mark-recapture study conducted from september 1991 to june 1993. histologic changes on four turtles included acute segmental necrosis of the epidermis, followed by ulceration, necrosis of the underlying dermis and dermal bone, and exaggerated remodeling of bone. additional findings included visceral infl ...	1997	9027694
surfactant regulates pulmonary fluid balance in reptiles.	reptilian lungs are potentially susceptible to fluid disturbances because they have very high pulmonary fluid filtration rates. in mammals, pulmonary surfactant protects the lung from developing alveolar edema. reptiles also have an order of magnitude more surfactant per square centimeter of respiratory surface area compared with mammals. we investigated the role of reptilian surfactant 1) in the entry of vascularly derived fluid into the alveolar space of the isolated perfused lizard (pogona vi ...	1997	9435656
antioxidant systems and anoxia tolerance in a freshwater turtle trachemys scripta elegans.	the effects of anoxic submergence (20 h at 5 degrees c) and subsequent 24 h aerobic recovery on the antioxidant systems of six organs were examined in freshwater turtles, trachemys scripta elegans. both xanthine oxidase and xanthine dehydrogenase were detected in turtle tissues with xanthine oxidase composing 36-75% of the total activity. turtle organs displayed high constitutive activities of catalase (cat), superoxide dismutase (sod), and alkyl hydroperoxide reductase (ahr). measurements of li ...	1997	9144333
epithelial localization of a reptilian na+/h+ exchanger homologous to nhe-1.	basolateral membranes of turtle (pseudemys scripta) colon epithelial cells exhibit robust na+/h+ exchange activity that can be activated by cell shrinkage and is blocked by amiloride [m. a. post and d. c. dawson. am. j. physiol. 262 cell physiol. 31):c1089-c1094, 1992]. the colonic epithelium actively absorbs na+ and secretes k+ and hco3-, but the role of basolateral na+/h+ exchange, if any, in transepithelial transport is unknown. the current studies were undertaken to identify the gene product ...	1997	9227498
membrane properties and monosynaptic retinal excitation of neurons in the turtle accessory optic system.	using an eye-attached isolated brain stem preparation of a turtle, pseudemys scripta elegans, in conjunction with whole cell patch techniques, we recorded intracellular activity of accessory optic system neurons in the basal optic nucleus (bon). this technique offered long-lasting stable recordings of individual synaptic events. in the reduced preparation (most of the dorsal structures were removed), large spontaneous excitatory synaptic inputs [excitatory postsynaptic potentials (epsps)] were f ...	1997	9307099
31p-nmr determinations of cytosolic phosphodiesters in turtle hearts.	as part of our ongoing research on cardiac hypoxia tolerance we have conducted 31p nuclear magnetic resonance (nmr) studies of isolated, perfused, working hearts from freshwater turtles, animals that are well known for their ability to tolerate prolonged periods of anoxia. a striking feature of turtle heart spectra is an extremely high concentration of nmr visible phosphodiesters (pdes). cardiac spectra from mammals, on the other hand, typically exhibit only a small resonance in the pde region. ...	1997	9505428
abundant synthesis of transthyretin in the brain, but not in the liver, of turtles.	the binding of thyroxine to proteins in the blood plasma of the turtle, trachemys scripta, was analyzed by incubation with radioactive thyroxine, electrophoresis and autoradiography. albumin and an alpha-globulin were found to bind thyroxine; no thyroxine-binding transthyretin was detected in the prealbumin region. in contrast to blood plasma, a thyroxine-binding prealbumin was observed in medium from t. scripta choroid plexus incubated in vitro. rna was extracted from brain tissue containing ch ...	1997	9253180
purification and partial amino acid sequences of two distinct albumins from turtle plasma.	two putative albumins, denoted alb-1 (apparent molecular mass of 67 kda) and alb-2 (68 kda), were purified from plasma of the emydid turtle (trachemys scripta). concentrations in serum or plasma were determined by radioimmunoassay using 125i-labeled alb-1. in juvenile turtles (less than 2 years of age), serum concentrations of alb-1 and alb-2 were 2.72 +/- 0.23 mg/ml and 1.68 +/- 0.22 mg/ml, respectively, while concentrations in plasma pooled from adult turtles were 4.2 mg/ml and 2.6 mg/ml, resp ...	1997	9440230
brain na+/k+-atpase activity in two anoxia tolerant vertebrates: crucian carp and freshwater turtle.	the crucian carp (carassius carassius) and freshwater turtles (trachemys scripta) are among the very few vertebrates that can survive extended periods of anoxia. the major problem for an anoxic brain is energy deficiency. in the brain, the na+/k+-atpase is the single most atp consuming enzyme, being responsible for maintaining ion gradients. we here show that the na+/k+-atpase activity in the turtle brain is reduced by 31% in telencephalon and by 34% in cerebellum after 24 h of anoxia. both chan ...	1997	9389603
synaptic inputs to identified color-coded amacrine and ganglion cells in the turtle retina.	previous studies have proposed models of the specific synaptic circuitry responsible for color processing in the turtle retina. to determine the accuracy of these models of the circuits underlying color opponency in the inner retina of the turtle (pseudemys scripta), we have studied the physiology, morphology, and synaptic connectivity of identified amacrine and ganglion cells. these cells were first characterized electrophysiologically and were then stained with horseradish peroxidase. postembe ...	1997	9416919
anoxia-induced gene expression in turtle heart. upregulation of mitochondrial genes for nadh-ubiquinone oxidoreductase subunit 5 and cytochrome c oxidase subunit 1.	a cdna library constructed from heart of anoxia-exposed adult turtles (trachemys scripta elegans) was differentially screened with 32p-labeled single-stranded cdna probes from heart of control versus anoxic animals to clone genes induced by anoxia stress. four cdna clones, pbtar20, pbtar34, pbtar63 and pbtar914 were obtained and confirmed to be upregulated in response to anoxic submergence (20 h in n2-bubbled water at 7 degrees c). two clones, pbtar20 and pbtar63, were characterized by sequence ...	1996	8898892
purification and characterization of plasma vitamin d binding protein from the snapping turtle, chelydra serpentina.	vitamin d binding protein (dbp) was isolated from the plasma of the snapping turtle, chelydra serpentina (mixed sex adult), and compared with the previously characterized dual function binding plasma protein that binds both thyroxine (t4) and vitamin d (tstdbp) in an emydid turtle, trachemys scripta. purification of chelydra serpentina dbp (csdbp) was accomplished by ion exchange chromatography, preparative polyacrylamide gel electrophoresis, and reverse-phase high-performance liquid chromatogra ...	1996	8954770
motor pool organization of the external gastrocnemius muscle in the turtle, pseudemys (trachemys) scripta elegans.	the spinal cord of the adult turtle, pseudemys (trachemys) scripta elegans, is now considered a promising model for the study of the segmental motor system in the generalized tetrapod. to facilitate such studies we have examined the location, soma geometry, soma size, and number of motoneurons innervating the external gastrocnemius (eg) muscle in this species, as this muscle is ideally suited to the study of interrelations between the neuronal and muscular components of the segmental motor syste ...	1996	8568906
metabolic adaptations supporting anoxia tolerance in reptiles: recent advances.	animal survival during severe hypoxia and/or anoxia is enhanced by a variety of biochemical adaptations including adaptations of fermentative pathways of energy production and, most importantly, the ability to sharply reduce metabolic rate by 5-20 fold and enter a hypometabolic state. the biochemical regulation of metabolic arrest is proving to have common molecular principles that extend across phylogenetic lines and that are conserved in different types of arrested states (not only anaerobiosi ...	1996	8936040
prevalence and histopathology of shell disease in turtles from lake blackshear, georgia.	turtles in lake blackshear, crisp county, georgia (usa) were evaluated for shell disease during intensive trapping efforts on 8 and 9 may 1990. the disease was most prevalent in pseudemys concinna (74%) and trachemys scripta (35%). the degree of necrosis on the carapace was significantly positively correlated with the degree of necrosis on the plastron in t. scripta (rs = 0.50), but not in p. concinna (rs = 0.06). female t. scripta with lesions were significantly larger than females without lesi ...	1996	8722263
atrial natriuretic peptide, bradykinin, and angiotensin ii-like immunoreactivity in the harderian gland of the terrapin pseudemys scripta: response to osmotic stress.	the harderian gland of the terrapin pseudemys scripta has four types of acinar cells. type iv cells are very similar to the salt secreting cells of the salt secretory glands of various marine vertebrates. the presence and localization of the ile5-angiotensin ii, atrial natriuretic peptide, and bradykinin has been investigated by immunohistochemical methods. immunoreactivity is confined to the type iv cells. changes in the environmental salinity resulted in different patterns in the immunoreactiv ...	1996	8986047
effects of prolactin and cortisol on the harderian gland of the terrapin, pseudemys scripta, adapted to different salinities.	the harderian gland (hg) of the terrapin, pseudemys scripta, plays a prominent role in osmoregulation owing to the presence of "salt secreting cells" among the acinar cells of its glandular epithelium. osmotic stress provokes different responses according to salinity. seawater adaptation activates a major structural reorganization. the most striking change is shown by the type i glandular cells and "salt secreting cells." the latter increase in number and change from a unicellular form to multic ...	1996	8808397
analysis of cardiac shunting in the turtle trachemys (pseudemys) scripta: application of the three outflow vessel model.	blood distribution within the ventricle was analysed in acutely prepared turtles trachemys scripta by measuring the oxygen concentration and flow rates of blood in the central vessels. pulmonary (qp) and systemic (qs) blood flow rates were similar when total cardiac output (qtot) was below 40 ml min-1 kg-1. above this value, increments of qtot were directed to the pulmonary circuit, with qs levelling off at approximately 20 ml min-1 kg-1. when qtot was larger than 40 ml min-1 kg-1, the systemic ...	1996	9110953
decreased total ventricular and mitochondrial protein synthesis during extended anoxia in turtle heart.	the turtle heart provides a model system to study the effects of anoxia on protein synthesis without the potentially confounding factor of contractile failure and decreased atp levels. protein synthesis, as measured by 3h-labeled phenylalanine incorporation, was studied under conditions of normoxia and anoxia in isolated perfused turtle [trachemys (= pseudemys) scripta elegans] hearts at 15 degrees c. heart rate, cardiac output, and ventricular pressure development were unaffected by 2 or 3 h of ...	1996	8997367
kainic acid blocks a ttx-sensitive sodium channel in retinal horizontal cells of the turtle (pseudemys scripta elegans).	the aim of this study was to investigate the effects of excitatory amino acids on channels found in horizontal cell membranes using patch-clamp techniques. we unexpectedly found that the excitatory amino acid receptor agonist, kainic acid, reversibly inhibited the transient tetrodotoxin (ttx)-sensitive na+ current in isolated horizontal cell bodies and axons from the retina of the turtle (pseudemys scripta elegans). the effect of kainic acid was antagonized by the glutamate receptor antagonist 6 ...	1996	8981397
liver protein kinase c isozymes: properties and enzyme role in a vertebrate facultative anaerobe.	protein kinase c was purified to homogeneity from liver of the anoxia-tolerant turtle (trachemys scripta elegans). two isozymes were present and were identified as pkc alpha and pkc beta by hydroxylapatite chromatography and cross-reaction with specific antibodies to the mammalian isozymes. kinetic characterization of the isozymes showed that both required phospholipids and ca2+ for activation and both were inhibited by low concentrations of pkc inhibitors. the pkc alpha was activated more stron ...	1996	9022285
the effect of altering pulmonary blood flow on pulmonary gas exchange in the turtle trachemys (pseudemys) scripta.	in resting reptiles, the po2 of pulmonary venous return (plao2; left atrial blood) may be 20 mmhg (1 mmhg = 0.1333 kpa) lower than the po2 of gas in the lung. this level of po2 is considerably higher than that observed in resting mammals and birds and results from ventilation-perfusion (v/q) heterogeneity, pulmonary diffusion limitation and intrapulmonary shunting. however, the relative contribution of each of these factors is unknown. many reptiles, particularly chelonians, exhibit an intermitt ...	1996	8896364
[embryonic mortality and hatching rate of trachemys scripta (testudines: emydidae) eggs artificially grown in a protected natural area].	in the northeast of costa rica, illegal collecting, habitat destruction and heavy predation on adult females, young and eggs of trachemys scripta produced a population decline in recent years. the slider turtle has a high reproductive potential and nests were relocated. between january and march 1991, 179 nests (3220 eggs) were collected from natural areas of caño negro national wildlife refuge, costa rica and relocated for incubation under natural conditions in a protected site. the mean of num ...	1996	9332615
cardiorespiratory synchrony in turtles.	many reptiles, particularly diving species, display characteristic cardiovascular changes associated with lung ventilation (cardiorespiratory synchrony). previous studies on freshwater turtles show that heart rate and pulmonary blood flow rate (qpul) increase two- to fourfold during ventilation compared with breath-holding, and some studies report concomitant decreases in systemic blood flow rate (qsys). the primary aim of this study was to provide a detailed description of cardiorespiratory syn ...	1996	8708580
identification of surface glycoconjugates in the olfactory system of turtle.	lectin binding histochemistry was performed on the olfactory system of pseudemys scripta to investigate the distribution and density of defined carbohydrate terminals on the cell surface glycoproteins of the olfactory receptors and their terminals in the olfactory bulbs. the lectin staining patterns indicate that the receptor cells of the olfactory mucosa are characterized by glycoconjugates containing alpha-d-galactose and n-acetyl-d-glucosamine terminal residues. the vomeronasal receptor cells ...	1996	8828589
the relative effectiveness of estrone, estradiol-17 beta, and estriol in sex reversal 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. sex steroid hormones have been implicated in temperature-dependent sex determination in the red-eared slider turtle, trachemys scripta; nonaromatizable androgens are involved in male sex determination and estrogens and aromatizable androgens in female sex determination. administration of exogenous estradiol-17 beta to eggs incubating at a temperature that normally produces only males can ...	1996	8804562
the mechanism of cardiac shunting in reptiles: a new synthesis.	the mechanism of cardiac shunting in reptiles is controversial. recent evidence suggests that a right-to-left shunt in turtles results primarily from a washout mechanism. the mechanism that accounts for left-to-right (l-r) shunting is unresolved. this study used haemodynamic analysis and digital subtraction angiography to determine the mechanism of l-r cardiac shunting in the turtle trachemys (pseudemys) scripta. animals were instrumented with ultrasonic blood flow probes (transonic systems, inc ...	1996	8691116
temperature and non-aromatizable androgens: a common pathway in male sex determination in a turtle with temperature-dependent sex determination?	this study addressed the hypothesis that, in the red-eared slider turtle, trachemys scripta, non-aromatizable androgens are the physiological equivalent of temperature in determining male development. in the first experiment, eggs were treated in the middle of the temperature-sensitive period with 1.0 or 10.0 micrograms androsterone, 5 alpha-dihydrotestosterone, 3 alpha-androstanediol, or 3 beta-androstanediol, while at an all-male, male-biased, or one of two female-biased incubation temperature ...	1996	8691104
the generation of antibody diversity in the turtle.	the ab response in reptiles has been studied at the protein level, and in turtles some aspects resemble those of cold-blooded vertebrates from other classes. the genetic bases for these features are not clear. the present study is the first on the igh organization and complexity of a reptilian ig gene system. the approach to cloning turtle (pseudemys scripta) sequences is entirely pcr based, and its efficacy is demonstrated by obtaining extensive information on a heretofore unexplored ig gene sy ...	1996	8621916
water compartmentalization and extracellular tortuosity after osmotic changes in cerebellum of trachemys scripta.	1. water compartmentalization in the turtle cerebellum subject to media of different osmolalities was quantified by combining extracellular diffusion analysis with wet weight and dry weight measurements. the diffusion analysis also determined the tortuosity of the extracellular space. 2. isolated cerebella were immersed in normal, oxygenated physiological saline (302 mosmol kg-1), hypotonic saline (238 mosmol kg-1) and a series of hypertonic salines (up to 668 mosmol kg-1). the osmolality was va ...	1996	8734998
protein sequences indicate that turtles branched off from the amniote tree after mammals.	the phylogenetic relationships among the major groups of amniote vertebrates remain a matter of controversy. various alternatives for the position of the turtles have been proposed, branching off either before or after the mammals. to discover the phylogenetic position of turtles in relation to mammals and birds, we have determined cdna sequences for the eye lens proteins alpha a- and alpha b-crystallin of the red-eared slider turtle (trachemys scripta elegans). in addition, databases were searc ...	1996	8662010
multicatalytic proteinase activity in turtle liver: responses to anoxia stress and recovery.	activities of the multicatalytic proteinase complex (mpc) were detected in turtle (trachemys scripta elegans) liver. the ratio of peptidylglutamyl-peptide bond hydrolyzing, trypsin-like, and chymotrypsin-like activities was 6:2.7:1 for the mpc partially purified by sepharose cl-6b gel filtration. molecular mass of the turtle liver enzyme was 940 +/- 46 kd. nondenaturing page revealed a single band containing mpc activity reacting with peptide substrate. in vivo anoxia exposure (20 h submergence ...	1996	8829603
role of nitric oxide in the elevation of cerebral blood flow induced by acetylcholine and anoxia in the turtle.	nitric oxide (no)-dependent regulation of brain blood flow has hitherto not been studied in reptiles. by observing the brain surface (telencephalon) of the freshwater turtle (trachemys scripta) with epiillumination microscopy, we show that topical application of acetylcholine (ach) induces an increase in cbf velocity that can be completely blocked by the no synthase inhibitor n(g)-nitro-l-arginine methyl ester (l-name). the effect of l-name was reversed by l-arginine. also, sodium nitroprusside ...	1996	8594061
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 devel ...	1996	8624904
use of the sensitive anterograde tracer cholera toxin fragment b reveals new details of the central retinal projections in turtles.	previous anterograde degeneration and autoradiographic studies have yielded inconsistent results on the extent and target areas of the central retinal projections in turtles. we used the highly sensitive anterograde and retrograde tracer, cholera toxin b fragment (ctb), to re-examine the central retinal projections in pseudemys scripta elegans. in contrast to the results of the previous anterograde degeneration studies and autoradiographic studies, immunohistochemical detection of ctb-labeled ce ...	1996	8955961
steroid-induced sex determination at incubation temperatures producing mixed sex ratios in a turtle with tsd.	previous studies have shown that exogenous steroid hormones can affect sex determination in reptiles with temperature-dependent sex determination (tsd). these studies have also suggested that the sensitivity of tsd to exogenous steroids may vary with incubation temperature. the majority of these studies, however, have utilized incubation temperatures producing all males or all females in the control groups, rather than temperatures which produced mixed sex ratios in control groups. the goals of ...	1995	8575659
the relative effectiveness of androstenedione, testosterone, and estrone, precursors to estradiol, in sex reversal 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. sex steroid hormones have been implicated in temperature-dependent sex determination in the red-eared slider turtle, trachemys scripta; androgen is involved in male sex determination and estradiol in female sex determination. administration of exogenous estradiol and its agonists to eggs incubating at a male-producing temperature can overcome the effect of temperature and result in all-fe ...	1995	8575652
microvascularization of the pineal gland in the freshwater turtle, pseudemys scripta elegans (reptilia): a scanning electron microscopic study of vascular corrosion casts.	gross supply, microvascular patterns, and drainage routes of the pineal gland and its vascular relations with associated structures (dorsal sac, paraphysis, choroid plexus of the third ventricle) were studied by scanning electron microscopy of microvascular corrosion casts in 10 specimens of the freshwater turtle, pseudemys scripta elegans. light microscopy of tissue sections (one transverse and one longitudinal series) served to attribute cast vascular territories to anatomical structures. the ...	1995	8609602
enzymatic control of glycogenolysis during anoxic submergence in the freshwater turtle trachemys scripta.	freshwater turtles trachemys scripta elegans endure prolonged severe hypoxia, and even complete anoxia, while diving or hibernating underwater. metabolic adaptations supporting survival include the activation of glycogenolysis and glucose output from liver, as well as strong metabolic rate depression. the present study analyzes the enzymes of both the phosphorolytic (glycogen phosphorylase, phosphorylase b kinase, camp-dependent protein kinase) and glucosidic (alpha-glucosidase) pathways of glyc ...	1995	7584617
upregulation of the gabaa/benzodiazepine receptor during anoxia in the freshwater turtle brain.	the freshwater turtle brain survives anoxia by decreasing its energy expenditure. during this anoxic period there is a sustained release of the inhibitory neurotransmitter gamma-aminobutyric acid (gaba). this study investigated whether there was a corresponding change in the binding properties of the gabaa/benzodiazepine (gaba/bdz) receptor. turtles (trachemys scripta) were subjected to a 100% n2 atmosphere for up to 24 h. after exposure, the cerebral cortex was dissected out, and saturation bin ...	1995	7771598
conservation and dynamics of microsatellite loci over 300 million years of marine turtle evolution.	microsatellite loci consisting of (ca)n repetitive arrays were obtained from three species of marine turtle, and primers were designed to test for polymorphism within species and the persistence of microsatellites across species. homologous loci were found in each test of six marine species within two families (cheloniidae and dermochelyidae), as well as in a freshwater species (emydidae, trachemys scripta), which indicates a conservation of flanking sequences spanning approximately 300 million ...	1995	7739385
the slider turtle as an environmental sentinel: multiple tissue assays using flow cytometric analysis.	we used flow cytometry (fcm) to conduct a multiple-tissue assay on slider turtles (trachemys scripta) inhabiting radioactive seepage basins. duplicate samples of blood, heart, spleen and kidney were analysed on two different cytometers (leitz mpv and coulter profile ii), each employing distinct staining protocols (dapi and pi, respectively). both dapi and pi assays of spleen cells demonstrated significantly greater variation in dna content for the basin turtles than for 'control' animals from ne ...	1995	24197546
effects of anoxia on protein phosphatase in turtle organs: purification and properties of protein phosphatase type-1 from turtle liver.	protein phosphatase type 1 (pp-1) was analyzed in organs of the red-eared slider turtle, trachemys scripta elegans, a species capable of long-term anoxia survival. during anoxic submergence at 7 degrees c, pp-1 activity in liver rapidly decreased to 63% of the control value within the first hour and remained suppressed over the subsequent 20 h of anoxia. pp-1 activity was also suppressed in red skeletal muscle during anoxia and dropped transiently (after 1 h) in brain but did not change in heart ...	1995	7864641
electrocardiography in anaesthetised red-eared sliders (trachemys scripta elegans).	electrocardiographic (ecg) values were measured in nine red-eared sliders (trachemys scripta elegans), anaesthetised with either ketamine, ketamine/xylazine or ketamine/midazolam, for the purpose of cardiocentesis. lead ii traces were then recorded through three cutaneous electrodes. the ecg complexes consisted of small upright p waves, larger r waves and no q or s wave deflections, very long qt intervals, small upright t waves, and a short tp interval. no sv waves were recorded. this pattern wa ...	1995	7709064
camp-dependent protein kinase and anoxia survival in turtles: purification and properties of liver pka.	the catalytic subunit of turtle (trachemys scripta elegans) liver cyclic amp-dependent protein kinase (pkac) was purified to homogeneity with a final specific activity of 65,783 pmol phosphate transferred.min-1.mg protein-1. subunit molecular weight was 42-43 kda as determined by sds-page and sephacryl s-300 chromatography. the isolectric point was ph 6.41 +/- 0.02. turtle liver pkac showed highest activity with kemptide as its substrate; activity with other artificial substrates, histone iia an ...	1995	7659081
expression of alpha sm actin in terrestrial ectothermic vertebrates.	alpha-smooth muscle (alpha sm) actin of endothermic vertebrates is selectively recognized by the monoclonal antibody anti-alpha sm-1. immunoreactivity to this antibody has been shown to be localized in the nh2-terminal sequence ac-eeed (chaponnier et al. 1994). among terrestrial ectothermic vertebrates, two amphibian (triturus vulgaris, rana esculenta) and three reptilian species (pseudemys scripta elegans, natrix natrix, podarcis sicula) were screened to investigate if their vascular and viscer ...	1995	7553770
vitellogenin induction by xenobiotic estrogens in the red-eared turtle and african clawed frog.	many environmental pollutants have estrogenic activity in animals. xenobiotic estrogens include many pesticides and industrial chemicals that biocumulate. the impact of these common pollutants on the reproductive success of wildlife may be considerable, particularly in threatened or endangered species. this research examined the use of plasma vitellogenin in males as a biomarker for estrogenic xenobiotics in reptiles and amphibians. adult male turtles (trachemys scripta) and frogs (xenopus laevi ...	1995	7556019
fiber-type composition of hindlimb muscles in the turtle, pseudemys (trachemys) scripta elegans.	a description is provided of the fiber-type composition of several hindlimb muscles of the adult turtle, pseudemys (trachemys) scripta elegans. in addition, cross-section areas of each fiber type and an estimation of the relative (weighted) cross-section area (wcsa) occupied by the different fiber types are also provided. seven muscles were selected for study, based on their suitability for future neurophysiological analysis as components of the segmental motor system, and on their homologies wi ...	1995	7666437
a commentary on the segmental motor system of the turtle: implications for the study of its cellular mechanisms and interactions.	a commentary is provided on the segmental motor system of the turtle pseudemys (trachemys) scripta elegans with an emphasis on neuronal, neuromuscular, and muscular mechanisms that control the development of force under normal, fatiguing, and pathophysiological conditions. for the central neuronal component of the segmental motor system, it has recently been shown that intracellular analysis of the firing properties of motoneurons and interneurons can be undertaken for relatively long periods of ...	1995	7666438
microvascularization of the cerebellum in the turtle, pseudemys scripta elegans (reptilia). a scanning electron microscope study of microvascular corrosion casts, including stereological measurements.	cerebellar blood supply and microvascular patterns were studied in 12 freshwater turtles pseudemys scripta elegans by scanning electron microscopy (sem) of microvascular corrosion casts and histology. vascular densities were estimated by point counting methods from casts and thin sections (7 microns). short a2-arterioles and recurrent branches from a3-arterioles supply the capillary bed of the molecular layer, while v2 and v3 venules drain it. the purkinje cell layer is supplied by horizontal br ...	1995	7726392
estrogen downregulation of albumin and a 170-kda serum protein in the turtle, trachemys scripta.	we examined changes in serum protein composition after estradiol-17 beta treatment of ovariectomized female trachemys scripta, with the objective of identifying proteins that are repressed by estrogen. the experimental protocol was validated by measuring serum estradiol-17 beta levels with a specific radioimmunoassay. control turtle sera contained little or no estradiol-17 beta (mean = 25.8 pg/ml) while estrogen-treated turtle sera had elevated estradiol-17 beta levels (mean = 333.3 pg/ml). estr ...	1995	7789749
the influence of center-surround antagonism on light adaptation in cones in the retina of the turtle.	the influence of center-surround antagonism on light adaptation in cone photoreceptors was investigated by intracellular recording from red-sensitive cones in the retina of the turtle, pseudemys scripta elegans. test flashes of 0.15-mm diameter were applied at the center of background fields of 0.25-mm or 2.2-mm diameter. immediately upon expanding the background from 0.25 to 2.2 mm, the membrane potential depolarized by about 1-4 mv. the test flash response was enhanced if the depolarization wa ...	1995	8924411
insulin-like growth factor-i in the plasma of two reptiles: assay development and validations.	radioimmunoassays (rias) of insulin-like growth factor-i (igf-i) in nonmammals are complicated by two problems: decreased specificity due to heterologous assays and assay interference from igf binding proteins. we have developed and validated an ria for the detection of igf-i in reptilian plasma that circumvents these problems. biochemical validations show parallelism between standard curves, plasma dilutions, and internal standards. further, biological validations indicate that (1) plasma igf-i ...	1995	7781962
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
functional morphologies of retinal ganglion cells in the turtle.	retinal ganglion cells in the turtle, pseudemys scripta elegans, were examined by intracellular recording with a protocol of stationary and moving lights. responses were apportioned among off, on, and on-off categories, and directional selectivity. cells were injected with neurobiotin, then later conjugated with avidin-horseradish peroxidase in standard procedure. morphological analysis of the stained cells included measurements of soma and dendritic field sizes, dendritic stratification, number ...	1994	7890834
complexity and scaling properties of amacrine, ganglion, horizontal, and bipolar cells in the turtle retina.	in the present study we have evaluated the complexity and scaling properties of the morphology of retinal neurons using fractal dimension as a quantitative parameter. we examined a large number of cells from pseudemys scripta and mauremys caspica turtles that had been labeled using golgi-impregnation techniques, intracellular injection of lucifer yellow followed by photooxidation, intracellular injection of rhodamine conjugated horseradish peroxidase, or intracellular injection of lucifer yellow ...	1994	7529776
temperature-dependent sex determination in reptiles: proximate mechanisms, ultimate outcomes, and practical applications.	in many egg-laying reptiles, the incubation temperature of the egg determines the sex of the offspring, a process known as temperature-dependent sex determination (tsd). in tsd sex determination is an "all or none" process and intersexes are rarely formed. how is the external signal of temperature transduced into a genetic signal that determines gonadal sex and channels sexual development? studies with the red-eared slider turtle have focused on the physiological, biochemical, and molecular casc ...	1994	8062460
distribution of glial fibrillary acidic protein-immunopositive structures in the brain of the red-eared freshwater turtle (pseudemys scripta elegans).	the distribution of glial fibrillary acidic protein (gfap)-immunoreactivity is described in serial vibratome sections of the turtle brain. the results are discussed in relation to our previous studies of rat and chicken brains. in the turtle brain, the distribution of gfap-positive elements is rather evenly abundant as compared to that observed in the chicken and rat. the gfap-positive structures are fibers of different length and orientation, but the stellate cells are not gfap-positive. the ba ...	1994	7522421