| regulation of extracellular glutamate levels in the long-term anoxic turtle striatum: coordinated activity of glutamate transporters, adenosine, k (atp) (+) channels and gaba. | early in anoxia the mammalian brain experiences an uncontrolled release of glutamate, which combined with the failure of glutamate reuptake mechanisms, leads to massive neurotoxic increases in extracellular glutamate. by contrast, the anoxia tolerant turtle (trachemys scripta) shows no increase in extracellular glutamate levels over many hours of anoxia. during the first hours of anoxia extracellular glutamate levels are maintained by a reduction in glutamate release (mainly due to the inhibitio ... | 2007 | 17629717 |
| adrenal-kidney-gonad complex measurements may not predict gonad-specific changes in gene expression patterns during temperature-dependent sex determination in the red-eared slider turtle (trachemys scripta elegans). | many turtles, including the red-eared slider turtle (trachemys scripta elegans) have temperature-dependent sex determination in which gonadal sex is determined by temperature during the middle third of incubation. the gonad develops as part of a heterogenous tissue complex that comprises the developing adrenal, kidney, and gonad (akg complex). owing to the difficulty in excising the gonad from the adjacent tissues, the akg complex is often used as tissue source in assays examining gene expressio ... | 2007 | 17592622 |
| evidence that a late-emerging population of trunk neural crest cells forms the plastron bones in the turtle trachemys scripta. | the origin of the turtle plastron is not known, but these nine bones have been homologized to the exoskeletal components of the clavicles, the interclavicular bone, and gastralia. earlier evidence from our laboratory showed that the bone-forming cells of the plastron were positive for hnk-1 and pdgfralpha, two markers of the skeletogenic neural crest. this study looks at the embryonic origin of these plastron-forming cells. we show that the hnk-1+ cells are also positive for p75 and foxd3, confi ... | 2017 | 17501750 |
| gonadal expression of sf1 and aromatase during sex determination in the red-eared slider turtle (trachemys scripta), a reptile with temperature-dependent sex determination. | many egg-laying reptiles have temperature-dependent sex determination (tsd), where the offspring sex is determined by incubation temperature during a temperature-sensitive period (tsp) in the middle third of development. the underlying mechanism transducing a temperature cue into an ovary or testis is unknown, but it is known that steroid hormones play an important role. during the tsp, exogenous application of estrogen can override a temperature cue and produce females, while blocking the activ ... | 2007 | 17490415 |
| analgesic efficacy and respiratory effects of butorphanol and morphine in turtles. | to test the hypothesis that butorphanol or morphine induces antinociception with minimal respiratory depression in conscious red-eared slider turtles. | 2007 | 17472564 |
| distribution and characteristics of endogenous digestive enzymes in the red-eared slider turtle, trachemys scripta elegans. | distribution and properties of the main digestive enzymes including protease and amylase, from stomach, pancreas and the anterior, middle and posterior intestine of the adult red-eared slider turtle trachemys scripta elegans were studied at various phs and temperatures. the optimum temperature and ph for protease in stomach, pancreas and the anterior, middle and posterior intestine were 40 degrees c, 2.5; 50 degrees c, 8.0; 50 degrees c, 7.0; 50 degrees c, 8.0; and 50 degrees c, 8.5; respectivel ... | 2007 | 17462929 |
| effect of temperature and prolonged anoxia exposure on electrophysiological properties of the turtle (trachemys scripta) heart. | cardiac activity of the turtle (trachemys scripta) is greatly depressed with cold acclimation and anoxia. we examined what electrophysiological modifications accompany and perhaps facilitate this depression of cardiac activity. turtles were first acclimated to 21 degrees c or 5 degrees c and held under either normoxic or anoxic (6 h at 21 degrees c; 14 days at 5 degrees c) conditions. we then measured cardiac action potentials (aps) using spontaneously contracting whole heart preparations and wh ... | 2007 | 17442785 |
| effects of temperature on anoxic submergence: skeletal buffering, lactate distribution, and glycogen utilization in the turtle, trachemys scripta. | to test the hypothesis that submergence temperature affects the distribution of the lactate load and glycogen utilization during anoxia in turtles, we sampled a variety of tissues after 7 days, 24 h, and 4 h of anoxic submergence at 5, 15, and 25 degrees c, respectively. these anoxic durations were chosen because we found that they produced similar decreases in plasma hco(3)(-) ( approximately 18-22 meq/l). the sampled tissues included ventricle, liver, small intestine, carapace, and the followi ... | 2007 | 17395788 |
| flow cytometric analysis of red-eared slider turtles (trachemys scripta) from tar creek superfund site. | tar creek superfund site (tcsfs) was heavily mined from the 1890s to 1970 and currently is contaminated with lead, zinc, and cadmium. flow cytometry (fcm) was used to measure variation in nuclear dna content of red blood cells collected from trachemys scripta living within tcsfs and reference sites, lake carl blackwell (lcb) and sequoyah national wildlife refuge (snwr). we also used atomic absorption spectrometry to measure pb in blood and carapace and cd in blood samples of turtles from tcsfs a ... | 2007 | 17364238 |
| [reproductive ecology and hunting of the turtle tachemys scropta (testudinata: emydidae) in the "momposine depression", northern colombia]. | we studied the reproductive ecology of the slider turtle. trachemys scripta callirostris, during the reproductive season of the year 2000, in an area of the mompós depression, northern colombia. we examined the number of nests ovoposited in locations with different characteristics, their hatching success rates and the natural causes of egg mortality. we also determined the effects of exploitation of nesting females, in two populations with different levels of harvesting. the results showed that ... | 2004 | 17357421 |
| pharmacokinetics of metronidazole in the red-eared slider turtle (trachemys scripta elegans) after single intracoelomic injection. | | 2007 | 17348904 |
| suppression of reactive oxygen species production enhances neuronal survival in vitro and in vivo in the anoxia-tolerant turtle trachemys scripta. | hypoxia-ischemia with reperfusion is known to cause reactive oxygen species-related damage in mammalian systems, yet, the anoxia tolerant freshwater turtle is able to survive repeated bouts of anoxia/reoxygenation without apparent damage. although the physiology of anoxia tolerance has been much studied, the adaptations that permit survival of reoxygenation stress have been largely ignored. in this study, we examine ros production in the turtle striatum and in primary neuronal cultures, and exam ... | 2007 | 17326763 |
| expression of sox9, mis, and dmrt1 in the gonad of a species with temperature-dependent sex determination. | sex determination in vertebrates, the process of forming an ovary or testis from a bipotential gonad, can be initiated by genetic or environmental factors. elements of the downstream molecular pathways underlying these different sex-determining mechanisms have been evolutionarily conserved. we find the first evidence that sox9 expression is preferentially organized in the testis early in the temperature-sensitive period in a species with temperature-dependent sex determination (trachemys scripta ... | 2007 | 17326219 |
| parasympathetic control of the pupillary light response in the red-eared slider turtle (pseudemys scripta elegans). | we investigated effects of both vecuronium bromide, a nicotinic cholinergic antagonist, and atropine, a muscarinic cholinergic antagonist, on the pupil of the turtle to determine whether responses to light are controlled by parasympathetic innervations acting on the iris. | 2013 | 17324166 |
| effects of extracellular changes on spontaneous heart rate of normoxia- and anoxia-acclimated turtles (trachemys scripta). | heart rate (f(h)) of the anoxia-tolerant freshwater turtle (trachemys scripta) during prolonged anoxia exposure is 2.5- to 5-times lower than the normoxic rate, but whether alterations in blood composition that accompany prolonged anoxia contribute to this bradycardia is unknown. we examined how temperature acclimation, oxygen deprivation, acidosis, hyperkalemia, hypercalcemia and adrenaline affect chronotropy in the turtle myocardium. we monitored spontaneous contraction rates of right-atrial p ... | 2007 | 17234611 |
| immunohistochemical and hodological characterization of calbindin-d28k-containing neurons in the spinal cord of the turtle, pseudemys scripta elegans. | neurons and fibers containing the calcium-binding protein calbindin-d28k (cb) were studied by immunohistochemical techniques in the spinal cord of adult and juvenile turtles, pseudemys scripta elegans. abundant cell bodies and fibers immunoreactive for cb were widely and distinctly distributed throughout the spinal cord. most neurons and fibers were labeled in the superficial dorsal horn, but numerous cells were also located in the intermediate gray and ventral horn. in the dorsal horn, most cb- ... | 2007 | 17203484 |
| lactate uptake by skeletal bone in anoxic turtles, trachemys scripta. | previous studies have shown that freshwater turtle shells can accumulate lactate during periods of anoxic submergence. our objective in this study was to determine lactate uptake in other parts of the turtle's skeleton. we measured lactate concentration of 7 skeletal elements and 4 shell samples of red-eared slider turtles, trachemys scripta, in control animals (n=12) and in animals following submergence for 4-5 days in n(2)-equilibrated water at 10 degrees c (n=8). we also collected blood sampl ... | 2007 | 17188012 |
| effects of ultraviolet radiation on 25-hydroxyvitamin d3 synthesis in red-eared slider turtles (trachemys scripta elegans). | to determine whether there are increased concentrations of 25-hydroxyvitaminn d(3) in red-eared slider turtles (trachemys scripta elegans) after exposure to uv radiation. | 2006 | 17144809 |
| beyond anoxia: the physiology of metabolic downregulation and recovery in the anoxia-tolerant turtle. | the freshwater turtle trachemys scripta is among the most anoxia-tolerant of vertebrates, a true facultative anaerobe able to survive without oxygen for days at room temperature to weeks or months during winter hibernation. our good friend and colleague peter lutz devoted nearly 25 years to the study of the physiology of anoxia tolerance in these and other model organisms, promoting not just the basic science but also the idea that understanding the physiology and molecular mechanisms behind ano ... | 2007 | 17049896 |
| germ cell depletion does not alter the morphogenesis of the fetal testis or ovary in the red-eared slider turtle (trachemys scripta). | in the red-eared slider turtle, trachemys scripta, both prospective male and female gonads contain primitive cord structures at the time when the gonad first forms. primordial germ cells arrive in the gonad and accumulate on the coelomic surface. if testis development is initiated, these cords develop further at the same time that germ cells migrate from the coelomic surface and become sequestered in the interior of the cords. in contrast, in the developing ovary germ cells proliferate in a defi ... | 2007 | 17041961 |
| toxicity of glyphosate as glypro and li700 to red-eared slider (trachemys scripta elegans) embryos and early hatchlings. | more than 8.2 billion ha of cropland, gardens, and forests are treated with the herbicide glyphosate each year. whereas the toxicity of glyphosate and associated adjuvants has been measured in other vertebrates, few, if any, studies have looked at their effects in reptiles. in some instances, management of turtle habitat requires control of successional stages through application of herbicides. adults and juvenile turtles may be exposed directly, whereas embryos may contact the chemicals through ... | 2006 | 17022419 |
| estrogen response system in the reproductive tract of the male turtle: an immunocytochemical study. | portions of the reproductive tract of the male (trachemys scripta) turtle were examined by immunocytochemistry for evidence of the capacity to produce and respond to estrogen hormones (via the expression of p450 aromatase and estrogen receptors). aromatase was detected in both the sertoli and leydig cells of the testis and was expressed at different levels during the spermatogenic cycle, being highest in the quiescent testis and lowest during germ cell meiosis. eralpha was found in the leydig ce ... | 2007 | 16935286 |
| force development at elevated [mg2+]o and [k+]o in myocardium from the freshwater turtle (trachemys scripta) and influence of factors associated with hibernation. | the effects of high [mg(2+)](o) on force development were examined for heart muscle of freshwater turtle. plasma [mg(2+)] during hibernation may increase drastically and like plasma [k(+)] approach values as high as 10 mm. each experiment performed at either 20 or 5 degrees c involved four ventricular preparations of which one pair was exposed to 10, and one to 1 mmmg(2+). one preparation of each pair was furthermore exposed to 10 mm k(+), whereas the other was maintained at 2.5 mm k(+). during ... | 2006 | 16928457 |
| benign ovarian teratoma in a red-eared slider turtle (trachemys scripta elegans). | | 2006 | 16861392 |
| tissue glycogen and extracellular buffering limit the survival of red-eared slider turtles during anoxic submergence at 3 degrees c. | the goal of this study was to identify the factors that limit the survival of the red-eared slider turtle trachemys scripta during long-term anoxic submergence at 3 degrees c. we measured blood acid-base status and tissue lactate and glycogen contents after 13, 29, and 44 d of submergence from ventricle, liver, carapace (lactate only), and four skeletal muscles. we also measured plasma ca(2+), mg(2+), na(+), k(+), cl(-), inorganic phosphate (p(i)), lactate, and glucose. after 44 d, one of the si ... | 2016 | 16826499 |
| quantitative genetics of plastron shape in slider turtles (trachemys scripta). | shape variation is widespread in nature and embodies both a response to and a source for evolution and natural selection. to detect patterns of shape evolution, one must assess the quantitative genetic underpinnings of shape variation as well as the selective environment that the organisms have experienced. here we used geometric morphometrics to assess variation in plastron shell shape in 1314 neonatal slider turtles (trachemys scripta) from 162 clutches of laboratory-incubated eggs from two ne ... | 2006 | 16637501 |
| gene transcription of neuroglobin is upregulated by hypoxia and anoxia in the brain of the anoxia-tolerant turtle trachemys scripta. | neuroglobin is a heme protein expressed in the vertebrate brain in mammals, fishes, and birds. the physiological role of neuroglobin is not completely understood but possibilities include serving as an intracellular oxygen-carrier or oxygen-sensor, as a terminal oxidase to regenerate nad(+) under anaerobic conditions, or involvement in no or ros metabolism. as the vertebrate nervous system is particularly sensitive to hypoxia, an intracellular protein that helps sustain cellular respiration woul ... | 2006 | 16636779 |
| nonadditive interactions between animal and plant diet items in an omnivorous freshwater turtle trachemys scripta. | nonadditive interactions occur when diet items interact with one another such that the net energy or nutrient gain from a mixed diet differs from that predicted by summing the gains from individual diet components. we quantified nonadditive effects between duckweed, lemma valdiviana, and grass shrimp, palaemontes paludosus, in the freshwater turtle trachemys scripta. we fed turtles 100% duckweed, 100% shrimp, and two mixed diets containing 67% duckweed, 33% shrimp and 14% duckweed, 86% shrimp (d ... | 2006 | 16503179 |
| ontogenetic diet shifts and digestive constraints in the omnivorous freshwater turtle trachemys scripta. | many reptiles undergo an ontogenetic diet shift from carnivory to herbivory. in this study, we used the yellow-bellied slider turtle, trachemys scripta, as a model to evaluate whether juvenile turtles are carnivorous because physiological constraints preclude herbivory. we conducted feeding trials in which we fed juvenile and adult turtles a duckweed plant, lemna valdiviana, or a freshwater grass shrimp, palaemontes paludosus, for 5 wk. during the trials, we measured mass-specific intake, digest ... | 2006 | 16380936 |
| housing density and growth in juvenile red-eared turtles. | growth rates in juvenile turtles relate strongly to their health and welfare, both in the wild and in captivity. newly hatched turtles in the wild are subject to such high levels of predation that, in some cases, as few as i % survive their first year of life. juvenile turtles in captivity succumb more quickly to the effects of poor housing conditions and poor diets than do older adults. in both the wild and in captivity, turtles who grow quickly during their first year of life stand a better ch ... | 1999 | 16363952 |
| dmrt1 expression in response to estrogen treatment in a reptile with temperature-dependent sex determination. | dmrt1 has been implicated as an important factor in sex determination in all classes of vertebrates, including reptiles with temperature-dependent sex determination (tsd). specifically, early embryonic expression of dmrt1 appears to be an integral part of normal testicular development in vertebrates. recently, a number of tsd studies have placed dmrt1 expression at the top of a short list of putative temperature-sensitive events for tsd. dmrt1 expression has been shown to be up-regulated at male ... | 2006 | 16217798 |
| metal accumulation in eggs of the red-eared slider (trachemys scripta elegans) in the lower illinois river. | the illinois river is a highly utilized navigable waterway in the us midwest, and has historically been contaminated with metal toxicants from various industrial and municipal pollution sources. little information on metal contamination is available in the lower illinois river, and in particular, in the habitat of the red-eared slider (trachemys scripta elegans) at the southern end of the river near grafton, il. this study was conducted to determine current levels of metal contamination in water ... | 2006 | 16216308 |
| hair bundle heights in the utricle: differences between macular locations and hair cell types. | hair bundle structure is a major determinant of bundle mechanics and thus of a hair cell's ability to encode sound and head movement stimuli. little quantitative information about bundle structure is available for vestibular organs. here we characterize hair bundle heights in the utricle of a turtle, trachemys scripta. we visualized bundles from the side using confocal images of utricular slices. we measured kinocilia and stereocilia heights and array length (distance from tall to short end of b ... | 2006 | 16177175 |
| endothelin-1 causes systemic vasodilatation in anaesthetised turtles (trachemys scripta) through activation of etb-receptors. | the effects of endothelin-1 (et-1) on systemic and pulmonary circulation were investigated in anaesthetised freshwater turtles (trachemys scripta) instrumented with arterial catheters and blood flow probes. bolus intra-arterial injections of et-1 (0.4-400 pmol kg(-1)) caused a dose-dependent systemic vasodilatation that was associated with a decrease in systemic pressure (p(sys)) and a rise in systemic blood flow (q(sys)), causing systemic conductance (g(sys)) to increase. et-1 had no significan ... | 2005 | 16169951 |
| endocrine and behavioral response to a decline in habitat quality: effects of pond drying on the slider turtle, trachemys scripta. | the effect of the simulated drying of a pond on the behavior and corticosterone secretion of trachemys scripta was measured in a field situation. slider turtles were held in experimental and control ponds (12 x 15 m) enclosed with a drift fence integrated with spring-triggered livetraps. the experimental pond water level was dropped 10 cm per day for 8 d, until water was completely drained. slider turtles responded to the draining of the pond by the emigration of the majority (75%) of the experi ... | 2005 | 16161015 |
| spinal cord injury-induced changes in breathing are not due to supraspinal plasticity in turtles (pseudemys scripta). | after occurrence of spinal cord injury, it is not known whether the respiratory rhythm generator undergoes plasticity to compensate for respiratory insufficiency. to test this hypothesis, respiratory variables were measured in adult semiaquatic turtles using a pneumotachograph attached to a breathing chamber on a water-filled tank. turtles breathed room air (2 h) before being challenged with two consecutive 2-h bouts of hypercapnia (2 and 6% co2 or 4 and 8% co2). turtles were spinalized at dorsa ... | 2005 | 16099823 |
| purification and properties of the glutathione s-transferases from the anoxia-tolerant turtle, trachemys scripta elegans. | glutathione s-transferases (gsts) play critical roles in detoxification, response to oxidative stress, regeneration of s-thiolated proteins, and catalysis of reactions in nondetoxification metabolic pathways. liver gsts were purified from the anoxia-tolerant turtle, trachemys scripta elegans. purification separated a homodimeric (subunit relative molecular mass =34 kda) and a heterodimeric (subunit relative molecular mass = 32.6 and 36.8 kda) form of gst. the enzymes were purified 23-69-fold and ... | 2005 | 16008560 |
| androgen receptor in the oviduct of the turtle, trachemys scripta. | circulating androgens reach high concentrations in females of some reptiles and amphibians. we are testing the hypothesis that androgens can act directly in female reptilian reproductive tissues, via the androgen receptor. in this study, we sought to determine if androgen receptors are present in the oviduct of the turtle, trachemys scripta, using radioligand-binding assays and immunological assays. an androgen-binding site was detected in turtle oviductal cytosol and oviductal nuclear extract b ... | 2005 | 15820135 |
| thalamocortical connections in the pond turtle pseudemys scripta elegans. | thalamocortical connections are a neuroanatomical feature shared among vertebrates, although the extent and organization of these connections vary among species. from an evolutionary standpoint, reptiles represent early stages of the pattern of connectivity between the thalamus and cortex, and elucidation of these pathways may help to reveal the biological significance of these projections. the present tract tracing study was performed to examine the organization of thalamocortical projections i ... | 2005 | 15761219 |
| adenosine and atp-sensitive potassium channels modulate dopamine release in the anoxic turtle (trachemys scripta) striatum. | excessive dopamine (da) is known to cause hypoxic/ischemic damage to mammalian brain. the freshwater turtle trachemys scripta, however, maintains basal striatal da levels in anoxia. we investigated da balance during early anoxia when energy status in the turtle brain is compromised. the roles of atp-sensitive potassium (k(atp)) channels and adenosine (ad) receptors were investigated as these factors affect da balance in mammalian neurons. striatal extracellular da was determined by microdialysis ... | 2005 | 15718391 |
| distribution of facial motor neurons in the pond turtle pseudemys scripta elegans. | a tract tracing study was performed to examine the localization of the facial nucleus in the brain stem of the pond turtle, pseudemys scripta elegans. neurobiotin and the fluorescent tracers alexa fluor 488 and 594 were used to retrogradely label neurons of the abducens or facial nerves. the results showed that the facial nucleus has two subnuclei, a medial group and a lateral group. measurements of cell size revealed no significant differences between these populations. double labeling studies ... | 2005 | 15567568 |
| neuronal control of turtle hindlimb motor rhythms. | the turtle, trachemys scripta elegans, uses its hindlimb during the rhythmic motor behaviors of walking, swimming, and scratching. for some tasks, one or more motor strategies or forms may be produced, e.g., forward swimming or backpaddling. this review discusses experiments that reveal characteristics of the spinal neuronal networks producing these motor behaviors. limb-movement studies show shared properties such as rhythmic alternation between hip flexion and hip extension, as well as variabl ... | 2005 | 15452660 |
| structural determination and histochemical localization of ghrelin in the red-eared slider turtle, trachemys scripta elegans. | we purified ghrelin peptide and determined the cdna sequence encoding the precursor protein from the stomach of the red-eared slider turtle, trachemys scripta elegans. the trachemys ghrelin is comprised of 25-amino acids and has the sequence gssflspeyqntqqrkdpkkhtkln. the third serine residue was modified by n-octanoic (c8:0), decanoic (c10:0) or unsaturated decanoic acid (c10:1). the carboxyl-terminal end of the peptide was not amidated, as seen in the ghrelins of other land vertebrates. quanti ... | 2004 | 15242751 |
| differences between stereocilia numbers on type i and type ii vestibular hair cells. | a major outstanding goal of vestibular neuroscience is to understand the distinctive functional roles of type i and type ii hair cells. one important question is whether these two hair cell types differ in bundle structure. to address this, we have developed methods to characterize stereocilia numbers on identified type i and type ii hair cells in the utricle of a turtle, trachemys scripta. our data indicate that type i hair cells, which occur only in the striola, average 95.9 +/-16.73 (sd) ster ... | 2004 | 15201311 |
| endocrine-disrupting compounds and mixtures: unexpected dose-response. | the current study examined the effects on the red-eared slider turtle of extremely low doses of three endocrine-disrupting compounds (edcs)--trans-nonachlor, chlordane, and p,p'-dde-singly and in mixtures. previous studies using the red-eared slider turtle have proven its value as an organism for obtaining information about the effects of endocrine-disrupting compounds. the sex of the turtle, easily manipulated by exposure during embryogenesis, continues to be a marker of effects. when red-eared ... | 2004 | 15106679 |
| morphology of the turtle accessory optic system. | neural signals of the moving visual world are detected by a subclass of retinal ganglion cells that project to the accessory optic system in the vertebrate brainstem. we studied the dendritic morphologies and direction tuning of these brainstem neurons in turtle (pseudemys scripta elegans) to understand their role in visual processing. full-field checkerboard patterns were drifted on the contralateral retina while whole-cell recordings were made in the basal optic nucleus in an intact brainstem ... | 2016 | 15088717 |
| the cardiovascular responses of the freshwater turtle trachemys scripta to warming and cooling. | seven freshwater turtles trachemys scripta were instrumented with flow probes and cannulated for blood pressure measurements. the turtles were warmed from 24 to 34 degrees c, and cooled down to 24 degrees c, with and without atropine. animals exhibited a hysteresis of heart rate and blood flow to both the pulmonary and systemic circulations, which was not cholinergically mediated. blood pressure remained constant during both warming and cooling, while systemic resistance decreased during heating ... | 2004 | 15037641 |
| resistance to disuse atrophy in a turtle hindlimb muscle. | the purpose of this study was to characterize the changes in a turtle hindlimb muscle (external gastrocnemius) after exposure to three conditions of disuse: immobilization, tenotomy, and spinalization. histochemical analysis and measurement of muscle fiber cross-sectional area and weighted cross-sectional area were used to assess the potential conversion of muscle fiber types and changes in fiber size. it was found that unlike its counterpart in mammalian endotherms, the external gastrocnemius m ... | 2004 | 14968256 |
| structure and growth of the utricular macula in the inner ear of the slider turtle trachemys scripta. | in general, postembryonic production of inner ear vestibular hair cells (hcs) is believed to occur in all nonmammalian vertebrates. however, no study on this topic has been published on reptiles and, consequently, it is not known whether this also applies to these vertebrates. therefore, the present study applied stereological methods in order to estimate the total number of hcs in turtles of varying sizes. the findings are that in prehatchlings the utricular macula (um) contains approximately 4 ... | 2003 | 14716509 |
| expression of dmrt1 in a turtle with temperature-dependent sex determination. | there is a variety of sex determining mechanisms among vertebrates. many reptiles possess temperature-dependent sex determination (tsd), in which the incubation temperature of the egg determines the sex of the hatchling. the red-eared slider turtle, trachemys scripta has often been used as a model system for examining the physiology of tsd. in the current study, the expression of dmrt1 was examined during tsd in this turtle. dmrt1 is a putative regulator of sex determination/differentiation and ... | 2003 | 14684999 |
| cardiac output and shunt during voluntary activity at different temperatures in the turtle, trachemys scripta. | red-eared slider turtles (trachemys scripta) were chronically instrumented with blood flow probes for a long-term study of voluntary behavior in an enriched laboratory setting. cardiovascular measures consisting of total cardiac output (q(tot)), pulmonary blood flow (q(pul)), systemic blood flow (q(sys)), net cardiac shunt (q(shunt)), heart rate (hr), and stroke volume (sv) were obtained during spontaneous activity at a constant body temperature (tb=2 degrees c) and at unstable (variable) t(b)'s ... | 2008 | 14671716 |
| alpha-adrenergic regulation of systemic peripheral resistance and blood flow distribution in the turtle trachemys scripta during anoxic submergence at 5 degrees c and 21 degrees c. | anoxic exposure in the anoxia-tolerant freshwater turtle is attended by substantial decreases in heart rate and blood flows, but systemic blood pressure (p(sys)) only decreases marginally due to an increase in systemic peripheral resistance (r(sys)). here, we investigate the role of the alpha-adrenergic system in modulating r(sys) during anoxia at 5 degrees c and 21 degrees c in the turtle trachemys scripta, and also describe how anoxia affects relative systemic blood flow distribution (%.q(sys) ... | 2004 | 14668311 |
| gene transcription of brain voltage-gated potassium channels is reversibly regulated by oxygen supply. | voltage-dependent potassium channels (kv channels) are important determinants of brain electrical activity. hypoxia may be an important modifier, because several voltage-gated k+ channels are reversibly blocked by acute hypoxia and are thought to act as oxygen sensors. here we show, using the anoxia-tolerant turtle brain (trachemys scripta) as a model, that brain kv1 channel transcription is reversibly regulated by oxygen supply. we found that in turtle brains exposed to 4-h anoxia kv1 transcrip ... | 2003 | 14615400 |
| effects of fatigue on the catchlike property in a turtle hindlimb muscle. | the purpose of this report was to test for the possibility that a catchlike, force-enhancing property, attributable to a particular stimulation pattern, could be evoked in non-mammalian turtle muscle, just as it has been shown in mammalian muscle. we tested for the presence of this property in dynamic lengthening and shortening contractions, as well as in the more commonly studied isometric contractions. a second aim was to note the effects of fatigue on the catchlike property, if the latter was ... | 2003 | 14566421 |
| connectivity of the turtle accessory optic system. | recent whole-cell recordings show that there are multiple synaptic inputs to the accessory optic system of the pond turtle pseudemys scripta elegans (the basal optic nucleus, bon), suggesting a complex role in visual processing. the bon outputs have now been investigated using transport of dii, rhodamine-conjugated and biotinylated dextrans. although transport was primarily anterograde, contralateral retinal ganglion cells were labeled retrogradely, confirming that the injection site was a retin ... | 2003 | 14519514 |
| colocalization of wt1 and cell proliferation reveals conserved mechanisms in temperature-dependent sex determination. | during vertebrate development the gonad has two possible fates, the testis or the ovary. the choice between these fates is made by a variety of sex-determining mechanisms, from the sex-determining gene on the y chromosome (sry) in mammals, to nongenetic temperature-dependent systems in many reptiles. despite the differences in the mechanisms at the top of the sex-determining cascade, the resulting morphology and many genes involved in early testis and ovarian development are common to most verte ... | 2003 | 12717730 |
| malignant ovarian teratoma in a red-eared slider (trachemys scripta elegans). | a 7-year-old intact female red-eared slider (trachemys scripta elegans) presented with anorexia of 2-3-weeks duration. coelomic radiographs demonstrated 3 shelled eggs in the right cavity. hormone therapy failed to induce oviposition. exploratory laparotomy revealed 3 calcified eggs in the right oviduct and a large mass obliterating the left ovary. the large, multilobulate mass had scattered, firm, white nodules and weighed 450 g. histopathology revealed a malignant teratoma composed of immature ... | 2003 | 12580303 |
| cloning and expression of aromatase in a turtle with temperature-dependent sex determination. | it has been hypothesized that estrogen production may play a pivotal role in the sex determination of reptiles with temperature-dependent sex determination (tsd). this hypothesis has been furthered by studies that have shown higher aromatase activity in the developing ovaries in some reptiles. however, other studies have not consistently supported this hypothesis. in the current study we addressed this issue by cloning p450 aromatase cdna in the turtle, trachemys scripta, and developing a quanti ... | 2003 | 12568787 |
| cytological evaluation of spermatogenesis and organization of the germinal epithelium in the male slider turtle, trachemys scripta. | the germ cell development in the slider turtle (trachemys scripta) testis was investigated by viewing the histology of the seminiferous epithelium in plastic sections with a light microscope. germ cell morphologies in the slider turtle testis were similar to the morphologies of other vertebrate germ cell types. however, the slider turtle seminiferous epithelium contained germ cells that progress through spermatogenesis in a temporal rather than a spatial pattern, resulting in a single spermatoge ... | 2003 | 12520551 |
| hormone levels in yolk decline throughout development in the red-eared slider turtle (trachemys scripta elegans). | this study investigates the potential effects of maternally derived hormones present in the yolk of reptile eggs. specifically, we ask when are these hormones utilized by developing red-eared slider turtles (trachemys scripta elegans), a species with temperature-dependent sex determination (tsd). eggs were incubated at 27 degrees c, a male-producing temperature, and at 31 degrees c, a female-producing temperature. concentrations of progesterone, testosterone, and 17beta-estradiol were measured a ... | 2002 | 12460601 |
| turtle sex determination assay: mass balance and responses to 2,3,7,8-tetrachlorodibenzo-p-dioxin and 3,3',4,4',5-pentachlorobiphenyl. | polyhalogenated hydrocarbons have been implicated in the anomalous sexual differentiation of mammals and reptiles. here, a temperature-sensitive turtle sex determination assay using the red-eared slider (trachemys scripta elegans) was used to determine the estrogenic or antiestrogenic activity of 2,3,7,8-tetrachlorodibenzo-p-dioxin (tcdd) and 3,3',4,4',5-pentachlorobiphenyl (pcb-126). neither tcdd nor pcb-126 showed a statistically significant difference in the resulting sex ratios (fisher's exa ... | 2002 | 12389929 |
| adrenergic control of the cardiovascular system in the turtle trachemys scripta. | freshwater turtles, trachemys scripta, like all non-crocodilian reptiles, are able to shunt blood between the pulmonary and systemic circulations owing to their undivided ventricle. the prevailing hypothesis is that the ratio of pulmonary and systemic resistances is the primary determinant of cardiac shunting in turtles. in the present study, we have examined the adrenergic influences on vascular resistances in the pulmonary and systemic circulations and the associated effects on cardiac shunts ... | 2002 | 12324543 |
| dacryops in a red-eared slider (chrysemys scripta elegans): case report. | clinical and histologic findings of an orbital lacrimal cyst (dacryops) in a 23-year-old-female red-eared slider (chrysemys scripta elegans) are described. main ophthalmologic findings included unilateral exophthalmus, engorged episcleral vessels, periocular swelling superior to the globe, incomplete lid closure, and reduced ocular motility. based on sonographic and cytologic examination of the tissue, the preliminary diagnosis of an orbital cyst was established. after surgical resection of the ... | 2002 | 12236878 |
| experimental manipulation of steroid concentrations in circulation and in egg yolks of turtles. | steroid hormones in egg yolks are increasingly recognized as an important component of maternal and offspring fitness in oviparous vertebrates. yet, except for in birds, the mechanism by which females allocate these resources is poorly understood. we manipulated systemic levels of hormones in reproductively mature female red-eared slider turtles (trachemys scripta elegans) with silastic implants to test the hypothesis that hormones are allocated to developing follicles as a quantitative function ... | 2002 | 12115919 |
| mechanisms for maintaining extracellular glutamate levels in the anoxic turtle striatum. | the turtle trachemys scripta is one of a limited group of vertebrates that can withstand hours to days without oxygen. one facet of anoxic survival is the turtle's ability to maintain basal extracellular glutamate levels, whereas in most vertebrates, anoxia triggers massive excitotoxic glutamate release. we investigated glutamate release and reuptake in the anoxic turtle and the effects of adenosine and atp-sensitive potassium (k(atp)) channels on glutamate homeostasis. striatal extracellular gl ... | 2002 | 11959671 |
| photoreceptors and visual pigments in the red-eared turtle, trachemys scripta elegans. | absorbance spectra of cone outer segments and oil droplets were recorded microspectrophotometrically in the retina of the red-eared turtle, trachemys scripta elegans. there are four cone visual pigments, with lambda(max) = 617 nm (red sensitive), 515 nm (green sensitive), 458 nm (blue sensitive), and 372 nm (uv-sensitive). the red-sensitive pigment resides in single cones with red or orange oil droplets, and in both members of double cones. the principal member of the double cone contains an ora ... | 2008 | 11925010 |
| the intracardiac shunt as a source of myocardial oxygen in a turtle, trachemys scripta. | the functional significance of many features of the reptilian cardiopulmonary system remains unknown; particularly the importance of cardiac shunts. one hypothesis for a physiological function for shunts is that they play a role in myocardial oxygenation and are therefore important when cardiac work is elevated. in this study we examined cardiac function by monitoring electrocardiograms in red-eared slider turtles (trachemys scripta) with a reduced myocardial oxygen supply. exposing the animals ... | 2002 | 21708712 |
| high-speed vsd imaging of visually evoked cortical waves: decomposition into intra- and intercortical wave motions. | in the pond turtle, pseudemys scripta elegans, visually evoked cortical waves propagate at different velocities within the primary visual area compared with waves that pass into the secondary visual area. in an effort to separate intra- and intercortical wave motions, movies of visually evoked cortical waves recorded by high-speed voltage-sensitive dye (vsd) imaging were subjected to karhunen-loéve (kl) decomposition. this procedure decomposes the vsd movies into a series of basis images that ca ... | 2002 | 11877522 |
| role of steroidogenic factor 1 and aromatase in temperature-dependent sex determination in the red-eared slider turtle. | red-eared slider turtles are genetically bipotential for sex determination. in this species, as in many other reptiles, incubation temperature of the egg determines gonadal sex. at higher incubation temperatures females are produced and increasing temperature appears to increase estrogen production in the embryonic brain. treatment of eggs incubating at a male-producing temperature with exogenous estrogen causes ovaries to form. at a female-biased incubation temperature, prevention of estrogen b ... | 2001 | 11748608 |
| population coding of motion patterns in the early visual system. | using extracellular recordings and computational modeling, we study the responses of a population of turtle (pseudemys scripta elegans) retinal ganglion cells to different motion patterns. the onset of motion of a bright bar is signaled by a rise of the population activity that occurs within less than 100 ms. correspondingly, more complex stimulus movement patterns are reflected by rapid variations of the firing rate of the retinal ganglion cell population. this behavior is reproduced by a compu ... | 2001 | 11730302 |
| bafilomycin a1 at nanomolar concentrations saturably inhibits a portion of turtle bladder acidification current. | an earlier report indicated that acid secretion in turtle urinary bladder is driven by an unusual vacuolar h+-atpase and that the atpase accounts for essentially all acid secreted. these results, however, are difficult to reconcile with the acid transporters currently ascribed to the renal collecting duct. here, we re-examine the effect of bafilomycin a1, an inhibitor of vacuolar (v-type) h+-atpases, on acid secretion by intact isolated bladders from pseudemys scripta turtles. serosal-side bafil ... | 2001 | 11683444 |
| development of an evolutionarily novel structure: fibroblast growth factor expression in the carapacial ridge of turtle embryos. | the turtle shell, an evolutionarily novel structure, contains a bony exoskeleton that includes a dorsal carapace and a ventral plastron. the development of the carapace is dependent on the carapacial ridge (cr), a bulge in the dorsal flank that contains an ectodermal structure analogous to the apical ectodermal ridge (aer) of the developing limb (burke. 1989a. j morphol 199:363-378; burke. 1989b. fortschr zool 35:206-209). although the cr is thought to mediate the initiation and outgrowth of the ... | 2001 | 11598915 |
| embryonic exposure to low-dose pesticides: effects on growth rate in the hatchling red-eared slider turtle. | in the red-eared slider turtle, pesticides can alter expected sex outcomes, a major step in the inferred pathway of sex determination, and hatchling steroid physiology. changes such as these can profoundly affect an organism's fitness. other potential markers for effects on fitness include hatchling mass, hatchling use of maternal stores (residual yolk), and especially early hatchling growth rates. in the current study, red-eared slider turtles were exposed during embryogenesis to one of three c ... | 2001 | 11594703 |
| reductions in systemic oxygen delivery induce a hypometabolic state in the turtle trachemys scripta. | we investigated the effects of vagal reductions in o(2) delivery on oxygen consumption (vo(2)) in the anesthetized freshwater turtle trachemys scripta. specifically, these experiments tested the hypothesis that reductions in arterial oxygen partial pressure (po(2)) and/or systemic oxygen transport (sot) trigger a metabolic downregulation. during electric stimulation of the efferent branch of the sectioned right vagus nerve (rvef), systemic cardiac output decreased 60-70%, systemic po(2) fell by ... | 2001 | 11557639 |
| accumulation and selective maternal transfer of contaminants in the turtle trachemys scripta associated with coal ash deposition. | coal combustion wastes are enriched in a number of potentially toxic compounds and may pose risks to biota exposed to the wastes. slider turtles (trachemys scripta) are common inhabitants of coal ash settling basins in south carolina, usa, where they feed on contaminated prey items and accumulate high levels of potentially toxic compounds in their tissues. furthermore, female sliders sometimes nest in contaminated spill piles and thus may expose embryos to contaminated soils. we examined two pot ... | 2001 | 11525496 |
| ultraviolet colour opponency in the turtle retina. | we have examined the functional architecture of the turtle pseudemys scripta elegans retina with respect to colour processing, extending spectral stimulation into the ultraviolet, which has not been studied previously in the inner retina. we addressed two questions. (i) is it possible to deduce the ultraviolet cone spectral sensitivity function through horizontal cell responses? (ii) is there evidence for tetrachromatic neural mechanisms, i.e. uv/s response opponency? using a constant response m ... | 2001 | 11511668 |
| medetomidine-ketamine anesthesia in red-eared slider turtles (trachemys scripta elegans). | this study evaluated the effects of high and low dosages of medetomidine-ketamine in red-eared slider turtles (trachemys scripta elegans) and the reversibility of the anesthesia with atipamezole. thirty healthy adult turtles were assigned randomly to one of two dosage groups. the lower dosage group received 0.1 mg medetomidine/kg body weight intramuscularly (i.m.) combined with 5 mg ketamine/kg i.m. the higher dosage group received 0.2 mg medetomidine/kg i.m. combined with 10 mg ketamine/kg i.m. ... | 2001 | 11353517 |
| role of gaba(a)-mediated inhibition in controlling the responses of regular spiking cells in turtle visual cortex. | the visual cortex of freshwater turtles contains pyramidal cells, which have a regular spiking (rs) firing pattern, and several categories of aspiny, inhibitory interneurons. the interneurons show diverse firing patterns, including the fast spiking (fs) pattern. postsynaptic potentials (psps) evoked in fs cells by visual stimulation of the retina reach their peak amplitudes as much as 200 ms before psps in rs cells (mancilla et al., 1998). fs cells could, consequently, control the amplitudes of ... | 2013 | 11347819 |
| oxygen binding by single red blood cells from the red-eared turtle trachemys scripta. | oxygen-binding properties of single red blood cells from the red-eared turtle trachemys scripta were measured by microspectrophotometry to describe the variation in oxygen affinity of red blood cells and to gain insight into the distribution of functionally different hemoglobins among red blood cells. methodologically, this study represents the first report on the cell-to-cell variation in oxygen-binding properties based on oxygen-binding curves of single vertebrate red blood cells. the cells di ... | 2001 | 11299255 |
| an immunohistochemical study on the endocrine cells in the alimentary tract of the red-eared slider (trachemys scripta elegans). | the regional distribution and relative frequency of endocrine cells in the alimentary tract of the red-eared slider, trachemys scripta elegans, were investigated by immunohistochemical methods using 10 antisera. most of the immunoreactive cells in the intestine were spherical or spindle-like in shape (open-type cells), while round cells (closed-type cells) were occasionally found in the stomach. these immunoreactive cells were located in the basal portion of the intestine, including the oesophag ... | 2001 | 11284161 |
| estradiol and incubation temperature modulate regulation of steroidogenic factor 1 in the developing gonad of the red-eared slider turtle. | red-eared slider turtles are genetically bipotential for sex determination, with incubation temperature of the egg determining gonadal sex. at higher incubation temperatures, females are produced, possibly due to increased biosynthesis of estrogen. exogenous estrogen causes the formation of ovaries, and prevention of estrogen biosynthesis results in the development of testes. in mammals, steroidogenic factor 1 (sf-1) regulates most genes required for estrogen biosynthesis from cholesterol. in ma ... | 2001 | 11250919 |
| effects of high extracellular [k+] and adrenaline on force development, relaxation and membrane potential in cardiac muscle from freshwater turtle and rainbow trout. | increases in extracellular k(+) concentrations reduced the twitch force amplitude of heart muscle from the freshwater turtle (trachemys scripta elegans) and rainbow trout (oncorhynchus mykiss). adrenaline augmented twitch force amplitude and reduced the relative influence of [k(+)]. in the absence of adrenaline, high [k(+)] had less effect in reducing twitch force in turtle than in trout, whereas the reverse was true in the presence of adrenaline. under anoxic conditions, twitch force was lower ... | 2001 | 11136612 |
| mitogen-activated protein kinases and anoxia tolerance in turtles. | the response of two vertebrate mitogen-activated protein kinase (mapk) family members, the extracellular signal-regulated kinases (erks) and c-jun nh2-terminal kinases (jnks), to anoxia exposure in vivo was examined in organs (liver, heart, kidney, brain, spleen) of the anoxia-tolerant adult turtle, trachemys scripta elegans. erks activities rose during anoxia only in spleen (a 2.8-fold increase). jnk activity showed a significant increase only in liver (4-fold increase) after 5 hr of anoxic sub ... | 2000 | 11110161 |
| the cardiovascular responses of the red-eared slider (trachemys scripta) acclimated to either 22 or 5 degrees c. i. effects of anoxic exposure on in vivo cardiac performance. | the extreme anoxia-tolerance of freshwater turtles under cold conditions is well documented, but little is known about their cardiac performance in such situations. using chronic catheterization techniques, we measured systemic cardiac power output (po(sys)), systemic cardiac output (q(.)(sys)), heart rate (fh), systemic stroke volume (v(s,sys)), systemic resistance (r(sys)) and mean arterial pressure (p(sys)) in red-eared sliders (trachemys scripta). the effects of cold acclimation and anoxic e ... | 2000 | 11076774 |
| the cardiovascular responses of the red-eared slider (trachemys scripta) acclimated to either 22 or 5 degrees c. ii. effects of anoxia on adrenergic and cholinergic control. | cardiovascular control in cold-acclimated freshwater turtles during chronic anoxic exposure is not well understood. we tested the hypothesis that the observed bradycardia in trachemys scripta results from increased cholinergic inhibitory tone and reduced sympathetic activity. cardiovascular status was measured in vivo in turtles acclimated to either 22 degrees c or 5 degrees c and either acutely exposed (6 h) to anoxia at 22 degrees c or chronically exposed (22 days) to anoxia at 5 degrees c. in ... | 2000 | 11076740 |
| aromatase activity during embryogenesis in the brain and adrenal-kidney-gonad of the red-eared slider turtle, a species with temperature-dependent sex determination. | gonadal sex in the red-eared slider turtle is determined by the incubation temperature that the embryo experiences during the mid-trimester of development. high temperatures result in female-biased sex ratios, and low temperatures produce male-biased sex ratios. the physiological equivalent of temperature appears to be a combination of the nature and abundance of steroidogenic enzymes and their products-including estradiol and its precursor, testosterone-and aromatase, the enzyme that converts t ... | 2000 | 10936040 |
| widespread expression of the mrna encoding a novel vitamin d/thyroxine dual binding protein in the turtle trachemys scripta. | vitamin d-binding protein (dbp) is the major transport protein for the vitamin d sterols in a variety of mammalian and avian species. the dbp found in the emydid family of turtles is unique in that it exhibits high-affinity binding of both vitamin d and thyroxine (d/tbp). sequence analysis has revealed that the emydid d/tbp is homologous to mammalian dbp and shares no homology with mammalian thyroxine-binding globulins. northern blot analysis was used to examine the spatial profile of d/tbp tran ... | 2000 | 10890574 |
| kinocilia heights on utricular hair cells. | kinocilium height is a critical determinant of any hair cell's response to head movement, but accurate measurements of kinocilia heights have been difficult to achieve. we have developed a method for measuring kinocilia heights that combines immunochemical staining with three-dimensional morphometry, and we have used this method to measure kinocilia in the utricle of a turtle, pseudemys scripta. our results suggest that kinocilium height varies with position on the utricular epithelium and that ... | 2000 | 10867272 |
| role of nitric oxide in the systemic and pulmonary circulation of anesthetized turtles (trachemys scripta). | in reptiles the influence of local vascular factors on blood flow regulation is vaguely understood. the aim of this study was to investigate the role of nitric oxide (no) on vascular function in anesthetized trachemys scripta. the experimental protocol consisted of serial injections of sodium nitroprusside (snp; 25 microg. kg(-1)), l-arginine (185 mg. kg(-1)) and l-name (50 mg. kg(-1)). snp induced a systemic vasodilation (0.05 to 0.02 kpa. min. kg. ml(-1), p = 0.015), with no change in pulmonar ... | 2000 | 10797320 |
| embryonic treatment with xenobiotics disrupts steroid hormone profiles in hatchling red-eared slider turtles (trachemys scripta elegans). | many compounds in the environment capable of acting as endocrine disruptors have been assayed for their developmental effects on morphogenesis; however, few studies have addressed how such xenobiotics affect physiology. in the current study we examine the effects of three endocrine-disrupting compounds, chlordane, trans-nonachlor, and the polychlorinated biphenyl (pcb) mixture aroclor 1242, on the steroid hormone concentrations of red-eared slider turtle (trachemys scripta elegans) hatchlings tr ... | 2000 | 10753091 |
| identification of the pancreatic endocrine cells of pseudemys scripta elegans by immunogold labeling. | the endocrine pancreatic cells of pseudemys scripta elegans were investigated immunocytochemically by light and electron microscopy. insulin-, somatostatin (sst)-1, sst-28 (1-12)-, salmon (s)sst-25-, glucagon-, pancreatic polypeptide (pp)-, peptide tyrosine tyrosine (pyy)-, and neuropeptide tyrosine (npy)-like immunoreactivities were observed. insulin cells were immunogold labeled with bonito insulin antiserum and secretory granules were characterized by a wide halo and a dense core of varying s ... | 2000 | 10642438 |
| developmental expression of steroidogenic factor 1 in a turtle with temperature-dependent sex determination. | a variety of reptiles possess temperature-dependent sex determination (tsd) in which the incubation temperature of a developing egg determines the gonadal sex. current evidence suggests that temperature signals may be transduced into steroid hormone signals with estrogens directing ovarian differentiation. steroidogenic factor 1 (sf-1) is one component of interest because it regulates the expression of steroidogenic enzymes in mammals and is differentially expressed during development of testis ... | 1999 | 10603272 |
| discordant responses of mitogen-activated protein kinases to anoxia and freezing exposures in hatchling turtles. | the role of two vertebrate mitogen-activated protein kinases (mapks) in mediating responses to in vivo anoxia or freezing exposures was examined in four organs (liver, heart, kidney and brain) of hatchling red-eared turtles, trachemys scripta elegans, which are naturally tolerant of these stresses. the extracellular signal-regulated kinases were not stress-activated except in brain of frozen turtles. the c-jun nh2-terminal kinases (jnks) were transiently activated by anoxia exposure in all four ... | 1999 | 10595322 |
| cardiorespiratory response to progressive hypoxia and hypercapnia in the turtle trachemys scripta | the ventilatory responses of chelonian reptiles to hypoxic and hypercapnic stress have been fairly well described. as turtles are capable of large cardiac shunts, changes in pulmonary perfusion may be an equally viable and potent response to these stressors. to test this hypothesis, conscious unrestrained turtles were unidirectionally ventilated while blood flow in the left pulmonary artery ( q_dot (lpa)) and left aortic arch ( q_dot (lao)) was monitored. turtles were exposed to step changes (2. ... | 1999 | 10539969 |
| morphological changes induced by prolonged darkness in the retinal pigment epithelium of the turtle (pseudemys scripta elegans). | the retinal pigment epithelium of vertebrates was shown to be sensitive to cyclic oscillations of light and darkness. the morphological changes induced by prolonged darkness on the retinal epithelial cells of the freshwater turtle were studied, with particular regard to their localization and to their reversibility if animals are recovered under cyclic light. the eyes were processed for light and electron microscopy and a morphological and morphometric analysis was performed on the specimens. af ... | 2003 | 10575821 |
| identification and expression of gastrin and cholecystokinin mrnas from the turtle, pseudemys scripta: evidence of tissue-specific tyrosyl sulfation(1). | gastrin and cholecystokinin (cck) are related peptide hormones expressed in the brain and gut of vertebrates. in this study, complementary dnas have been characterised from the red-eared slider turtle, pseudemys scripta. the encoded preprocck contains mono and dibasic endoproteolytic processing sites for formation of the previously identified cck-70, cck-40 and cck-8 products, whereas preprogastrin contains two dibasic processing sites for the generation of gastrin-52. alignment of the predicted ... | 1999 | 10561540 |
| effects of exogenous corticosterone on locomotor activity in the red-eared slider turtle, trachemys scripta elegans. | we investigated the effects of exogenous corticosterone on the locomotor activity of captive red-eared slider turtles, trachemys scripta elegans. an increase in plasma corticosterone often increases locomotor activity in mammals and birds, but there are no reported findings for turtles. in this study turtles implanted with corticosterone-filled silastic((r)) implants showed a significant increase in caged locomotor activity when compared to control animals with empty implants. corticosterone-tre ... | 1999 | 10531550 |
| incubation temperature influences sex-steroid levels in juvenile red-eared slider turtles, trachemys scripta, a species with temperature-dependent sex determination. | incubation temperature determines gonadal sex in the red-eared slider turtle, trachemys scripta. however, little is known about the long-term effects of incubation temperature on traits other than gonadal sex in this species. to investigate the hypothesis that incubation temperature (independent of gonadal sex) influences sex steroid levels after hatching, we incubated eggs of the red-eared slider turtle at three temperatures (26, 28.6, and 31 degrees c). we then measured plasma levels of dihydr ... | 1999 | 10529274 |
| hypoxic hypometabolism in the anesthetized turtle, trachemys scripta. | a hypometabolic response during acute exposure to hypoxia has been measured in both endothermic and ectothermic vertebrates. in the turtle, we determined the metabolic response to normocapnic hypoxia and hypercapnic hypoxia. in addition, we tested the hypothesis that hypoxic hypometabolism was a regulated response that did not depend on o(2) availability. metabolic, cardiovascular, and blood gas measurements were collected in anesthetized turtles under two conditions: during normocapnic hypoxia ... | 1999 | 10409253 |
| co2 excretion and postcapillary ph equilibration in blood-perfused turtle lungs | turtles possess a significant postcapillary co2 partial pressure (pco2) disequilibrium between arterial blood and alveolar gas. there are several possible explanations for this blood disequilibrium including a slow rate of erythrocyte physiological anion shift (cl-/hco3- exchange) or inaccessibility of plasma hco3- to red blood cell or pulmonary carbonic anhydrase. the present study characterized the contribution of erythrocyte anion exchange and pulmonary and erythrocyte carbonic anhydrase to c ... | 1999 | 10085269 |