Publications

synergistic role for pituitary growth hormone in the regulation of hepatic estrogen and progesterone receptors and vitellogenesis in female freshwater turtles, chrysemys picta.	previous studies using the freshwater turtle chrysemys picta have demonstrated that estradiol, progesterone (p), testosterone (t), and growth hormone (gh) regulate hepatic vitellogenin synthesis, suggesting a multihormonal regulation of vitellogenesis in the turtle. in this study we further investigated the interaction between estradiol-17beta (e) and growth hormone in the regulation of vitellogenin (vtg) in hypophysectomized post-reproductive female turtles (c. picta). northern blot analysis wa ...	2005	15596068
observations on the leech placobdella ornata feeding from bony tissues of turtles.	the leech placobdella ornata was observed feeding from the blood sinuses of the plastron and carapace bones of chelydra serpentina and chrysemys picta. evidence of successful feeding included blood upwelling from the point of attachment and gastric ceca of the leeches freshly filled with blood after removal. there was an apparent preference for the sulci between scales of the shell.	2004	15562628
effects of hibernation on mitochondrial regulation and metabolic capacities in myocardium of painted turtle (chrysemys picta).	painted turtles hibernating during winter may endure long-term exposure to low temperature and anoxia. these two conditions may affect the aerobic capacity of a tissue and might be of particular importance to the cardiac muscle normally highly reliant on aerobic energy production. the present study addressed how hibernation affects respiratory characteristics of mitochondria in situ and the metabolic pattern of turtle myocardium. painted turtles were acclimated to control (25 degrees c), cold (5 ...	2004	15556383
avenues of extrapulmonary oxygen uptake in western painted turtles (chrysemys picta belli) at 10 degrees c.	the major avenues of extrapulmonary oxygen uptake were determined on submerged western painted turtles (chrysemys picta bellii) at 10 degrees c by selectively blocking one or more potential pathways for exchange. previous work indicated that the skin, the cloaca, and the buccopharyngeal cavity can all contribute significantly in various species of turtles. o(2) uptake was calculated from the rate of fall in water p(o(2)) in a closed chamber. two series of experiments were conducted: in series 1, ...	2004	15528171
bacterial infection and tissue-specific hsp72, -73 and -90 expression in western painted turtles.	heat shock proteins (hsps) are molecular chaperones that assist intracellular folding, assembly and translocation of proteins in prokaryotic and eukaryotic cells. a variety of stresses including hyperthermia, radiation, heavy metals, ischemia, anoxia and reoxygenation have been shown to increase the expression of hsps. likewise, bacterial infection represents a stress for the host cell. in this study, expression of the constitutive (hsp73) and inducible (hsp72) isoforms of hsp70 and hsp90 was mo ...	2004	15450861
geographic variation of the physiological response to overwintering in the painted turtle (chrysemys picta).	we compared the physiological responses of latitudinal pairings of painted turtles submerged in normoxic and anoxic water at 3 degrees c: western painted turtles (chrysemys picta bellii) from wisconsin (wi) versus southern painted turtles (chrysemys picta dorsalis) from louisiana (la), arkansas (ar), and alabama (al), and eastern painted turtles (chrysemys picta picta) from connecticut (ct) versus c. p. picta from georgia (ga). turtles in normoxic water accumulated lactate, with c. p. bellii acc ...	2016	15449233
time-dependent expression of heat shock proteins 70 and 90 in tissues of the anoxic western painted turtle.	expression of the constitutive hsp73, inducible hsp72 and hsp90 was investigated in brain, heart, liver and skeletal muscle of the anoxia-tolerant western painted turtle chrysemys picta bellii in response to 2, 6, 12, 18, 24 and 30 h forced dives and following 1 h recovery from 12, 24 and 30 h forced dives at 17 degrees c. during a dive, expression of all three hsps examined remained at control levels for at least 12 h in all tissues examined except the liver, where hsp72 showed a decrease at 12 ...	2004	15371485
accumulation of lactate by frozen painted turtles (chrysemys picta) and its relationship to freeze tolerance.	hatchling painted turtles (chrysemys picta) survived freezing at -2 degrees c for 4 d, few recovered from freezing lasting 6 d, and none survived being frozen for 8 d. whole-body glucose and lactate were low in animals that had not been subjected to cold and ice but increased precipitously in animals that were frozen for 2 d. both metabolites continued to increase, but at a somewhat lower rate, in animals frozen for 4, 6, or 8 d. the increase in whole-body lactate reflects a reliance by frozen h ...	2013	15295689
excurrent duct system of the male turtle chrysemys picta.	the epididymis and efferent duct system of the turtle chrysemys picta were examined. seminiferous tubules are drained by a series of ducts that form a rete exterior to the tunica albuginea. the rete is located lateral to the testis and consists of anastamosing tubules of varying diameters, lined by a simple epithelium consisting of squamous to cuboidal cells. the rete is highly vascularized. a series of tubules (efferent ductules) connect the rete to the epididymis proper. the efferent ductules ...	2004	15281059
to freeze or not to freeze: adaptations for overwintering by hatchlings of the north american painted turtle.	many physiologists believe that hatchling painted turtles (chrysemys picta) provide a remarkable, and possibly unique, example of 'natural freeze-tolerance' in an amniotic vertebrate. however, the concept of natural freeze-tolerance in neonatal painted turtles is based on results from laboratory studies that were not placed in an appropriate ecological context, so the concept is suspect. indeed, the weight of current evidence indicates that hatchlings overwintering in the field typically withsta ...	2004	15277545
lactate accumulation, glycogen depletion, and shell composition of hatchling turtles during simulated aquatic hibernation.	we submerged hatchling western painted turtles chrysemys picta schneider, snapping turtles chelydra serpentina l. and map turtles graptemys geographica le sueur in normoxic and anoxic water at 3 degrees c. periodically, turtles were removed and whole-body [lactate] and [glycogen] were measured along with relative shell mass, shell water, and shell ash. we analyzed the shell for [na+], [k+], total calcium, total magnesium, pi and total co2. all three species were able to tolerate long-term submer ...	2004	15235017
effects of swimming on metabolic recovery from anoxia in the painted turtle.	anoxic submergence in the western painted turtle results in a severe metabolic acidosis characterized by high plasma lactate and depressed arterial ph, a response similar to that seen in other vertebrates following exhaustive exercise. we tested the hypothesis that 1 or 2 h of aerobic swimming following anoxic submergence would enhance the rate of lactate disappearance from the blood just as sustained aerobic exercise does in mammals and fishes following strenuous exercise. following 2 h of anox ...	2004	15201303
physiological ecology of overwintering in the hatchling painted turtle: multiple-scale variation in response to environmental stress.	we integrated field and laboratory studies in an investigation of water balance, energy use, and mechanisms of cold-hardiness in hatchling painted turtles (chrysemys picta) indigenous to west-central nebraska (chrysemys picta bellii) and northern indiana (chrysemys picta marginata) during the winters of 1999-2000 and 2000-2001. we examined 184 nests, 80 of which provided the hatchlings (n=580) and/or samples of soil used in laboratory analyses. whereas winter 1999-2000 was relatively dry and mil ...	2008	15057719
regulation of hepatic progesterone and estrogen receptors in the female turtle, chrysemys picta: relationship to vitellogenesis.	previous studies using the fresh water turtle chrysemys picta have demonstrated the differential expression of the two progesterone receptor isoforms (pra and prb) in the liver during the turtle seasonal cycle, correlating with er mrna levels and hepatic vitellogenesis. during the inter-vitellogenic periods the ratio of prb:pra favors pra, suggesting that the prb:pra ratio may be important in the regulation of vitellogenesis. based on these and other studies we hypothesize that progesterone may ...	2004	15028527
effect of gonadal steroids on progesterone receptor, estrogen receptor, and vitellogenin expression in male turtles (chrysemys picta).	hepatic vitellogenin (vtg) is a yolk precursor protein sequestered in follicular oocytes as nutrient supply for developing embryos in nonmammalian vertebrates. in prior research studies we have demonstrated that both progesterone (p) and testosterone (t) inhibit estrogen (e)-induced vitellogenesis in the male fresh water turtle (chrysemys picta), and have suggested that these hormones may be involved in multihormonal regulation of vitellogenesis in the female turtle. however, the modes of action ...	2004	14695685
characterization of the testicular binding site for iodinated rat fsh in the turtle, chrysemys picta.	1. to correlate the morphological observations with the known gonadotropic activity of fsh in the turtle testis, studies of the binding of iodinated fsh were conducted. 2. these demonstrated the presence of gonadotropin-binding sites of high affinity (apparent kd = 10(-10) m) for [125i]rfsh in turtle testicular membrane preparations. 3. although these sites did not bind iodinated human lh or avian lh, these hormones, as well as pmsg and fsh, were effective competitive inhibitors of the binding o ...	1985	14577399
probability-learning by the turtle.	tested in a two-choice situation, the painted turtle, chrysemys picta picta, shows random probability-matching in visual problems and in confounded visual-spatial problems, but only maximizing or nonrandom matching (reward-following) in spatial problems. the results are compared with those of analogous experiments on fish, bird, and mammal.	1965	14294140
renewal of intestinal epithelium in the freshwater turtle, chrysemys picta.		1964	14153303
transport of monosaccharides by intestinal segments of the painted turtle, chrysemys picta.		1961	13894354
size and shape variation in the painted turtle. a principal component analysis.		1960	13790416
metabolism of chrysemys picta during fasting and during cold torpor.		1957	13411235
effects of induced cold torpor on blood of chrysemys picta.		1956	13362596
survival and behavior of freshwater turtles after rehabilitation from an oil spill.	an oil spill in february 2000 at the john heinz national wildlife refuge in southeastern pennsylvania affected four species of freshwater turtles including painted turtles (chrysemys picta), snapping turtles (chelydra serpentina), red-eared slider turtles (trachemys scripta), and red-bellied turtles (pseudemys rubriventris). in the summer and fall of 2000, there were no differences in survival, home range, and temperature preference of 16 oil exposed/rehabilitated (oer) turtles, 18 possibly expo ...	2003	12927492
effects of experimental anemia on blood ion and acid-base status of turtles during submergence in aerated water at 3 degrees c.	the importance of blood hemoglobin to aquatic oxygen uptake by turtles (chrysemys picta bellii) submerged in aerated water at 3 degrees c was tested by comparing the responses of anemic turtles (hematocrit approximately 6%) to turtles with normal hematocrits (hematocrit approximately 33%). all turtles were submerged for 42 days and blood samples were collected at 0, 7, 21, 32 and 42 days. blood was analyzed for ph, pco(2), po(2), hematocrit, hemoglobin concentration ([hb]) and plasma was analyze ...	2003	12890549
how rapidly can maternal behavior affecting primary sex ratio evolve in a reptile with environmental sex determination?	theoretical models identify maternal behavior as critical for the maintenance and evolution of sex ratios in organisms with environmental sex determination (esd). maternal choice of nest site is generally thought to respond more rapidly to sex ratio selection than environmental sensitivity of offspring sex (threshold temperatures) in reptiles with temperature-dependent sex determination (tsd, a form of esd). however, knowledge of the evolutionary potential for either of these traits in a field s ...	2003	12858265
testing hypotheses of aging in long-lived painted turtles (chrysemys picta).	for 38 of the past 50 years, painted turtles were studied on the university of michigan's e.s. george reserve in southeastern michigan. we compared age specific body sizes, reproductive traits and survival of painted turtles ranging from 9 to 61 years of age to test contrasting predictions of the relative reproductive rate and senescence hypotheses of aging. indeterminate growth (i.e. continued body growth of adults) was important in increasing reproductive output of older turtles; however, grow ...	2003	12855285
effect of anoxia and pharmacological anoxia on whole-cell nmda receptor currents in cortical neurons from the western painted turtle.	the mammalian brain undergoes rapid cell death during anoxia that is characterized by uncontrolled ca(2+) entry via n-methyl-d-aspartate receptors (nmdars). in contrast, the western painted turtle is extremely anoxia tolerant and maintains close-to-normal [ca(2+)](i) during periods of anoxia lasting from days to months. a plausible mechanism of anoxic survival in turtle neurons is the regulation of nmdars to prevent excitotoxic ca(2+) injury. however, studies using metabolic inhibitors such as c ...	2016	12695985
lipids and lipid-transporting proteins in chrysemys picta: role of gonadal steroids and growth hormone in intact and hypophysectomized turtles.	in the freshwater turtle, the homeostatic control of plasma lipids and lipid-transporting proteins may be coordinately regulated by ovarian steroids and pituitary hormones such as growth hormone (gh). in order to elucidate the role of these hormones in the regulation of vitellogenesis and ovarian growth, we have investigated lipid metabolic changes in normal male and female turtles, and in hypophysectomized females with and without gh injections, in response to combinations of exogenously admini ...	2003	12679094
molecular systematics, phylogeography, and the effects of pleistocene glaciation in the painted turtle (chrysemys picta) complex.	the painted turtle, chrysemys picta, is currently recognized as a continentally distributed polytypic species, ranging across north america from southern canada to extreme northern mexico. we analyzed variation in the rapidly evolving mitochondrial control region (cr) in 241 turtles from 117 localities across this range to examine whether the painted turtle represents a continentally distributed species based on molecular analysis. we found strong support for the novel hypothesis that c. p. dors ...	2003	12643572
osteology and skeletal development of apalone spinifera (reptilia: testudines: trionychidae).	despite considerable attention that other groups of reptiles have received, few descriptions of the development and sequences of chondrification and ossification of the entire skeleton of turtles exist. herein, the adult skeleton of the spiny softshell turtle, apalone spinifera (testudines: trionychidae), is described; this description forms a basis of comparison for the embryonic skeleton and its ontogenesis. descriptions are made on the basis of cleared and double-stained embryos and dry skele ...	2003	12616574
natural freeze-tolerance in hatchling painted turtles?	hatchlings of the north american painted turtle (family emydidae: chrysemys picta) typically spend their first winter of life inside a shallow, subterranean hibernaculum (the natal nest) where life-threatening conditions of ice and cold commonly occur. although a popular opinion holds that neonates exploit a tolerance for freezing to survive the rigors of winter, hatchlings are more likely to withstand exposure to ice and cold by avoiding freezing altogether-and to do so without the benefit of a ...	2003	12547253
morbidity and mortality of reptiles admitted to the wildlife center of virginia, 1991 to 2000.	medical records from 694 reptiles admitted to the wildlife center of virginia (wcv; waynesboro, virginia, usa) from 1991 to 2000 were reviewed to determine causes of morbidity and mortality. eighteen species were represented but the majority of cases were four species; eastern box turtle (terrapene carolina) (66%), eastern painted turtle (chrysemys picta) (11%), common snapping turtle (chelydra serpentina) (10%), and rat snake (elaphe sp.) (6%). there was a significant increase in reptile cases ...	2002	12528435
gap junctions do not underlie changes in whole-cell conductance in anoxic turtle brain.	an acute reduction in cell membrane permeability could provide an effective strategy to prolong anoxic survival. a previous study has shown that in the western painted turtle whole-cell neuronal conductance (g(w)) decreases during anoxia, which may be mediated by the activation of adenosine a(1) receptors and calcium. reduction in g(w) is thought to be the result of ion channel closure, but closure of gap junctions could also be responsible for this phenomenon. in our study, antibody staining of ...	2003	12507621
endogenous and exogenous ice-nucleating agents constrain supercooling in the hatchling painted turtle.	hatchlings of the painted turtle (chrysemys picta) commonly hibernate in their shallow, natal nests. survival at temperatures below the limit of freeze tolerance (approximately -4 degrees c) apparently depends on their ability to remain supercooled, and, whereas previous studies have reported that supercooling capacity improves markedly with cold acclimation, the mechanistic basis for this change is incompletely understood. we report that the crystallization temperature (t(c)) of recently hatche ...	2003	12502768
tissue-specific expression of inducible and constitutive hsp70 isoforms in the western painted turtle.	expression of hsp73 and hsp72 in four tissues of the naturally anoxia-tolerant western painted turtle (chrysemys picta) was investigated in response to a 24 h forced dive and following 1 h recovery. of the tissues examined, brain and liver displayed approximately threefold and sevenfold higher basal hsp73 expression than heart and skeletal muscle. basal hsp72 expression was relatively low in all tissues examined. after the 24 h forced dive and 1 h recovery, hsp73 expression did not differ signif ...	2003	12477900
seasonal changes in hepatic progesterone receptor mrna, estrogen receptor mrna, and vitellogenin mrna in the painted turtle, chrysemys picta.	previous studies using the fresh water turtle chrysemys picta have demonstrated that progesterone (p) inhibits estradiol (e)-induced vitellogenin (vtg) secretion in this species. further, there is evidence for the differential expression of the two p receptor isoforms (pra and prb) in the liver during the turtle seasonal cycle, correlating with hepatic vitellogenesis. in this study we report changes in the hepatic pr mpna, er mrna, and vitellogenin (vtg) mrna transcripts during the reproductive ...	2002	12392693
environmental sex determination in a reptile varies seasonally and with yolk hormones.	most hypotheses that have been put forward in order to explain the persistence of environmental sex determination (esd) in reptiles assume a relatively fixed association of sex with temperature-induced phenotype and no maternal influence on offspring sex. here we demonstrate the association of maternally derived yolk hormone levels with the offspring sex ratio and describe two new aspects of temperature-dependent sex determination (tsd), i.e. seasonal variation in both thermal response and yolk ...	2000	12233772
hibernating without oxygen: physiological adaptations of the painted turtle.	many freshwater turtles in temperate climates may experience winter periods trapped under ice unable to breathe, in anoxic mud, or in water depleted of o(2). to survive, these animals must not only retain function while anoxic, but they must do so for extended periods of time. two general physiological adaptive responses appear to underlie this capacity for long-term survival. the first is a coordinated depression of metabolic processes within the cells, both the glycolytic pathway that produces ...	2002	12231634
yolk hormone levels in the eggs of snapping turtles and painted turtles.	although yolk steroids appear to play important roles in the development, growth, and behavior of some birds, their effects in oviparous reptiles are largely unknown. these investigations were initiated to determine initial levels of steroid hormones in the yolks of eggs from two turtle species. clutches of snapping turtle (chelydra serpentina) and of painted turtle (chrysemys picta) eggs were collected and individual egg yolks were analyzed for estradiol-17beta (e(2)) and testosterone (t) using ...	2002	12161198
progesterone and progesterone receptors in reptiles.	the role of progesterone (p) has been most extensively studied in the female reproductive tissues (ovary, reproductive tract, mammary gland) and in the brain, in which it is an important regulator and modulator in conjunction with estradiol (e). in nonmammalian vertebrate species, less work has been done on p metabolites involved in ovulation. in addition, p induces the expression of egg-white proteins, decreases myometrial contractility, and facilitates processing of eggs, formation of eggshell ...	2002	12161195
maternally derived yolk hormones vary in follicles of the painted turtle, chrysemys picta.	the transfer of hormones from a female to her offspring is known to occur in egg laying vertebrates, and the potential for these early, maternally derived hormones to influence sex determination in reptiles with temperature-dependent sex determination is intriguing. in the present study, we examine variation in the concentrations of progesterone, testosterone, and estradiol among three follicle size classes within a female painted turtle (chrysemys picta) and among females across four periods th ...	2002	12115920
a genetic analogue of 'mark-recapture' methods for estimating population size: an approach based on molecular parentage assessments.	molecular polymorphisms have been used in a variety of ways to estimate both effective and local census population sizes in nature. a related approach for estimating the current size of a breeding population, explored here for the first time, is the use of genetic 'marks' reconstructed for otherwise unknown parents in paternity or maternity analyses of progeny arrays. this method provides interesting similarities and contrasts to traditional mark-recapture methods based on physical tags. to illu ...	2001	11883884
expression of sr-bi (scavenger receptor class b type i) in turtle (chrysemys picta) tissues and other nonmammalian vertebrates.	in this study, the tissue distribution of the expression of an hdl-receptor (sr-bi; scavenger receptor class b type i) was investigated in the turtle using an antiserum to murine sr-bi. several turtle tissues including liver, heart, small intestine, kidney, oviduct, ovary, and testis were shown to express an 82 kda membrane protein. in addition, sr-bi expression in livers of other nonmammalian species such as the chicken, frog, goldfish, shark, and skate is also reported. ovarian sr-bi expressio ...	2002	11857477
complete suppression of protein synthesis during anoxia with no post-anoxia protein synthesis debt in the red-eared slider turtle trachemys scripta elegans.	two previous studies of the effects of anoxia on protein synthesis in anoxia-tolerant turtles (trachemys scripta elegans, chrysemys picta bellii) have generated opposing results. using the flooding-dose method, we measured the rate of protein synthesis following injection and incorporation of a large dose of radiolabelled phenylalanine to resolve the question of whether anoxia results in a downregulation of protein synthesis. after 1 h of anoxia, levels of protein-incorporated radiolabel indicat ...	2001	11815659
3,3',4,4'-tetrachlorobiphenyl oxidation in fish, bird and reptile species: relationship to cytochrome p450 1a inactivation and reactive oxygen production.	previously we showed that the polychlorinated biphenyl 3,3',4,4'-tetrachlorobiphenyl (tcb) caused a release of reactive oxygen species (ros) from cytochrome p450 1a (cyp1a) of the fish scup (stenotomus chrysops), and from rat and human cyp1a1. this was linked to a tcb- and nadph-dependent oxidative inactivation of the enzyme, which in scup and rat was inversely related to the rates of tcb oxidation. we examined the relationship between rates of tcb oxidation, cyp1a inactivation and ros productio ...	2000	11790349
sperm storage in turtles: a male perspective.	the storage and behavior of sperm collected from the epididymis of two emyiid turtles were examined. in chrysemys picta, the weight of the epididymis does not change significantly throughout the year as does the testis. however, in this species, as well as in trachemys scripta, the epididymis contains sperm throughout the entire year. sperm from both species have a relatively low motility and velocity of movement. in c. picta, equally low motilities are observed both in the autumn, shortly after ...	2002	11754033
transmission of haemogregarina balli from painted turtles to snapping turtles through the leech placobdella ornata.	six leeches (placobdella ornata) were allowed to feed on a painted turtle (chrysemys picta marginata) infected with haemogregarina balli and subjected to a period of diapause before being allowed to feed on 2 laboratory-reared snapping turtles (chelydra serpentina). weekly examination of thin blood films revealed infections of the turtles at 130 days postfeeding. these observations provide support for broad host specificity of hemogregarine parasites of chelonians.	2001	11695407
a heme-protein-based oxygen-sensing mechanism controls the expression and suppression of multiple proteins in anoxia-tolerant turtle hepatocytes.	the o2 sensitivity of protein expression was assessed in hepatocytes from the western painted turtle. anoxic cells consistently expressed proteins of 83.0, 70.4, 42.5, 35.3, and 16.1 kda and suppressed proteins of 63.7, 48.2, 36.9, 29.5, and 17.7 kda. except for the 70.4-kda protein, this pattern was absent during aerobic incubation with 2 mm nacn, suggesting a specific requirement for o2. aerobic incubation with co2+ or ni2+ increased expression of the 42.5-, 35.3-, and 16.1-kda protein bands w ...	1995	11607568
vitellogenin induction in painted turtle, chrysemys picta, as a biomarker of exposure to environmental levels of estradiol.	ponds within cattle farms often support turtle and fish populations and are impacted by manure runoff. cattle excrete metabolized (glucuronide-conjugated) hormones in feces and urine into these ponds, and bacteria cleave the glucuronide metabolites to active steroids, which can be stable for several weeks in wastewater. the objectives of this study were to (1) assess levels of xenoestrogens found in ponds near livestock pastures; and (2) assess whether these levels of xenoestrogens induce vitell ...	2001	11551621
cadmium: tissue distribution and binding protein induction in the painted turtle, chrysemys picta.	the freshwater painted turtle, chrysemys picta, was used to investigate (a) the distribution of an injected dose of 109cd in tissues over a period of 192 h (8 days) and (b) the effect of non-isotopic cadmium injection on tissue metal-binding protein levels. cadmium is cleared from the blood with 9% remaining in the circulation at 192 h. 109cd is found in all tissues, but is accumulated preferentially in liver, kidney, pancreas, and gastrointestinal tract. the liver is the primary site of cd accu ...	2001	11544142
seasonal variation in plasma lipids, lipoproteins, apolipoprotein a-i and vitellogenin in the freshwater turtle, chrysemys picta.	an analysis of plasma lipids and lipoprotein fractions was performed over the course of the annual ovarian cycle of the female turtle, chrysemys picta. determinations of total plasma triglycerides, cholesterol, vitellogenin and apolipoprotein a-i (apoa-i) were made. the lipid and protein composition of the lipoprotein fractions [very low density lipoprotein (vldl), low density lipoprotein (ldl), high density lipoprotein (hdl) and very high density lipoprotein (vhdl)] were also observed over the ...	2001	11544071
ultrastructural changes in granulosa cells and plasma steroid levels after administration of luteinizing hormone-releasing hormone in the western painted turtle, chrysemys picta.	in this study we investigated the effects of treatment by luteinizing hormone-releasing hormone (lhrh) on the morphology and steroid release of ovarian tissues in the western painted turtle, (chrysemys picta). in experiment i, four adult female turtles were injected with synthetic mammalian lhrh (i.p., 500 pg/g bodyweight) and four with saline 2-3 weeks prior to ovulation. granulosa cells from lhrh-treated turtles vs controls contained both preovulatory follicles (16-20 mm in diameter) and small ...	2001	11521952
genetic markers substantiate long-term storage and utilization of sperm by female painted turtles.	most studies of genetic parentage in natural populations have been limited to a single breeding season or reproductive episode and, thus, provide only a snapshot of individuals' mating behaviours. female turtles can store viable sperm in their reproductive tracts for as long as several years, but the extent to which this capacity is utilized in nature has remained unknown. here, we employ microsatellite markers to assess genetic paternity in successive clutches of individually marked, free-rangi ...	2001	11488975
effects of temperature and aquatic p(o2) on the physiology and behaviour of apalone ferox and chrysemys picta.	softshell turtles overwinter in the same bodies of water as some emydids, but their reduced shell and increased non-pulmonary gas exchange may contribute to a different mechanism of overwintering. the dynamics of bimodal respiration, diving behaviour and blood acid-base status in apalone ferox and chrysemys picta were investigated under two different temperatures combined with three different aquatic p(o2) levels. both species obtained oxygen through pulmonary and non-pulmonary routes. apalone f ...	2001	11441060
cold-hardiness and evaporative water loss in hatchling turtles.	north american turtles hatch in late summer and spend their first winter either on land or underwater. adaptations for terrestrial overwintering of hatchlings in northern regions, where winter thermal and hydric regimes are harsh, have not been systematically investigated in many species. we measured intrinsic supercooling capacity, resistance to inoculative freezing, and desiccation resistance in hatchlings of terrestrial and aquatic turtles collected from northern (terrapene ornata, chrysemys ...	2008	11436135
physiological responses to supercooling and hypoxia in the hatchling painted turtle, chrysemys picta.	we investigated physiological responses to supercooling in hatchling painted turtles (chrysemys picta) which remain in their natal nests over winter and therefore may become exposed to subzero temperatures. these turtles are freeze tolerant but also must rely on supercooling to survive exposure to the lower temperatures occurring in nests during winter. we compared whole-body concentrations of lactate, glucose, glycerol, and atp in turtles chilled at 0 degrees c, -4 degrees c, or -6 degrees c fo ...	2001	11409631
seasonal change in the capacity for supercooling by neonatal painted turtles.	hatchlings of the north american painted turtle (chrysemys picta) typically spend their first winter of life inside the shallow, subterranean nest where they completed incubation the preceding summer. this facet of their natural history commonly causes neonates in northerly populations to be exposed in mid-winter to ice and cold, which many animals survive by remaining unfrozen and supercooled. we measured the limit of supercooling in samples of turtles taken shortly after hatching and in other ...	2001	11398756
concentrations of steroid hormones in layers and biopsies of chelonian egg yolks.	the actions of circulating hormones, although relatively well understood for adults, are largely unknown for their developing embryos. transfer of maternal hormones to the egg is known to occur in oviparous species, and recently the presence of hormonally heterogeneous yolk layers has been described in two avian species. to investigate the possibility of a similar phenomenon occurring in chelonian species, egg yolk layers were analyzed in the painted turtle (chrysemys picta marginata) and the re ...	2001	11161774
the physiology of hibernation among painted turtles: the midland painted turtle (chrysemys picta marginata).	midland painted turtles from michigan were submerged at 3 degrees c in normoxic and anoxic water. in predive, and in turtles submerged for up to 150 days, plasma po2, pco2, ph, [cl-], [na+], [k+], total mg, total ca, lactate, glucose, and osmolality were measured; hematocrit and mass were determined, and plasma [hco3-] was calculated. anoxic turtles developed a severe metabolic acidosis, accumulating lactate from a predive value of 4.4 mmol/l to a 150-day value of 185 mmol/l, associated with a f ...	2001	11084202
the role of the integument as a barrier to penetration of ice into overwintering hatchlings of the painted turtle (chrysemys picta).	hatchlings of the north american painted turtle (chrysemys picta) spend their first winter of life inside a shallow, subterranean hibernaculum (the natal nest) where they may be exposed for extended periods to ice and cold. hatchlings seemingly survive exposure to such conditions by becoming supercooled (i.e., by remaining unfrozen at temperatures below the equilibrium freezing point for body fluids), so we investigated the role of their integument in preventing ice from penetrating into body co ...	2000	11074582
characteristics of nest soil, but not geographic origin, influence cold hardiness of hatchling painted turtles.	we investigated environmental factors influencing cold hardiness in hatchling painted turtles (chrysemys picta) indigenous to northeastern indiana and the sandhills of west-central nebraska. in both locations, hatchlings overwinter in their natal nests. survival of hatchlings chilled to minimum temperatures between -2.5 and -6.0 degrees c inside explanted natal nests ranged from 30 to 100%. mortality likely was caused by freezing of the turtles that was induced by contact with ice nuclei in the ...	2001	11070346
immunocytochemical localization of glutamate receptor subunits in the brain stem and cerebellum of the turtle chrysemys picta.	the regional distribution of ionotropic (ampa and nmda) and metabotropic (mglur1alpha) glutamate receptor subunits was examined in the brain stem and cerebellum of the pond turtle, chrysemys picta, by using immunocytochemistry and light microscopy. subunit-specific antibodies that recognize nmdar1, glur1, glur4, and mglur1alpha were used to identify immunoreactive nuclei in the brain stem and cerebellum. considerable immunoreactivity in the turtle brain stem and cerebellum was observed with regi ...	2000	11054706
seasonal changes in physiology and development of cold hardiness in the hatchling painted turtle chrysemys picta.	hatchling painted turtles (chrysemys picta) commonly hibernate in shallow, natal nests where winter temperatures may fall below -10 degrees c. although hatchlings are moderately freeze-tolerant, they apparently rely on supercooling to survive exposure to severe cold. we investigated seasonal changes in physiology and in the development of supercooling capacity and resistance to inoculative freezing in hatchling chrysemys picta exposed in the laboratory to temperatures that decreased from 22 to 4 ...	2000	11044384
succinate and alanine as anaerobic end-products in the diving turtle (chrysemys picta bellii).	the western painted turtle is an extremely anoxia-tolerant vertebrate capable of tolerating blood lactate levels of 150-200 mm. since lactate increases to such high levels, other fermentation end-products such as succinate and alanine, which have not been previously measured in this species, might also be expected to increase. therefore, i measured turtle heart, liver, and blood concentrations of lactate, succinate, and alanine following a 28-day anoxic dive at 5 degrees c. succinate and lactate ...	2000	11007183
hepatic changes in the freeze-tolerant turtle chrysemys picta marginata in response to freezing and thawing.	select hepatic changes in the freeze-tolerant hatchling turtle, chrysemys picta marginata, were studied in response to freezing at -2.5 degrees c and thawing. upon freezing, a small, selective increase in the liver weight with no increase in body weight was seen suggestive of an hepatic capacitance response. in all turtles studies, lobular differences in the hepatic content of glycogen were evident: the smaller lobe contained twice as much glycogen as the larger lobe. the response to freezing an ...	2000	10965355
helminth parasites of the western painted turtle, chrysemys picta belli (gray), including neopolystoma elizabethae n. sp. (monogenea: polystomatidae), a parasite of the conjunctival sac.	neopolystoma elizabethae n. sp. is described from the conjunctival sac of the western painted turtle chrysemys picta belli (gray), from the upper peninsula of michigan. this is the first species found in this location from chelonians in north america. the new species differs from all other species of neopolystoma in possessing a circle of 8 genital spines that are recurved and possess a crescent-shaped base. eight additional species of helminths were found in the 5 turtles examined in this study ...	2000	10958462
lactic acid buffering by bone and shell in anoxic softshell and painted turtles.	we tested two hypotheses: first, that the inferior anoxia tolerance of the softshell turtle, apalone spinifera, compared to the western painted turtle, chrysemys picta bellii, is related to its less mineralized shell, and second, that turtle bone, like its shell, stores lactate during prolonged anoxia. lactate concentrations of blood, hindlimb bone, and shell were measured on normoxic apalone and chrysemys and after anoxic submergence at 10 degrees c for 2 and 9 d, respectively. blood and shell ...	2016	10893168
chemical and thermal effects on the viability and motility of spermatozoa from the turtle epididymis.	the viability and motility of spermatozoa harvested from the epididymides of turtles were estimated to elucidate properties that might enable them to be stored over long periods of time. spermatozoa from the painted turtle, chrysemys picta, were analysed and compared with spermatozoa from two other turtles, trachemys scripta and sternotherus odoratus using the cellsoft analysis system for videotaped images. spermatozoa from c. picta and t. scripta, suspended in f-10 medium, showed low motility ( ...	2000	10864839
bone and shell contribution to lactic acid buffering of submerged turtles chrysemys picta bellii at 3 degrees c.	to evaluate shell and bone buffering of lactic acid during acidosis at 3 degrees c, turtles were submerged in anoxic or aerated water and tested at intervals for blood acid-base status and plasma ions and for bone and shell percent water, percent ash, and concentrations of lactate, ca(2+), mg(2+), p(i), na(+), and k(+). after 125 days, plasma lactate concentration rose from 1.6 +/- 0.2 mm (mean +/- se) to 155.2 +/- 10.8 mm in the anoxic group but only to 25.2 +/- 6.4 mm in the aerated group. the ...	2000	10848524
hypoxia-induced silencing of nmda receptors in turtle neurons.	hypoxia-induced suppression of nmda receptors (nmdars) in western painted turtle (chrysemys picta) cortical neurons may be critical for surviving months of anoxic dormancy. we report that nmdars are silenced by at least three different mechanisms operating at different times during anoxia. in pyramidal neurons from cerebrocortex, 1-8 min anoxia suppressed nmdar activity (ca(2+) influx and open probability) by 50-60%. this rapid decrease in receptor activity was controlled by activation of phosph ...	2000	10804192
living without oxygen: lessons from the freshwater turtle.	freshwater turtles, and specifically, painted turtles, chrysemys picta, are the most anoxia-tolerant air-breathing vertebrates. these animals can survive experimental anoxic submergences lasting up to 5 months at 3 degrees c. two general integrative adaptations underlie this remarkable capacity. first is a profound reduction in energy metabolism to approximately 10% of the normoxic rate at the same temperature. this is a coordinated reduction of both atp generating mechanisms and atp consuming p ...	2000	10794959
accumulation of lactate by supercooled hatchlings of the painted turtle (chrysemys picta): implications for overwinter survival.	hatchlings of the north american painted turtle (chrysemys picta) typically spend their first winter of life inside the shallow, subterranean nest where they completed embryogenesis the preceding summer. neonates at northern localities consequently may be exposed during winter to subzero temperatures and frozen soil. hatchlings apparently survive exposure to such conditions by supercooling, but the physiological consequences of this adaptive strategy have not been examined. we measured lactate i ...	2000	10707324
expression of heat shock proteins in turtle and mammal hearts: relationship to anoxia tolerance.	heat shock proteins (hsps) may play a cardioprotective role during hypoxia or ischemia. we hypothesized that cardiac tissue from hypoxia-tolerant animals might have high levels of specific hsps. we measured myocardial hsp60 and hsp72/73 in painted and softshell turtles during normoxia and anoxia (12 h) and after recovery (12 or 24 h). we also measured myocardial hsps in normoxic rats and rabbits. during normoxia, hearts from the most highly anoxia-tolerant species, the painted turtle, expressed ...	2000	10644641
comparison of cortically and subcortically controlled motor systems. ii. distribution of anterogradely labeled terminal boutons on intracellularly filled rubrospinal neurons in rat and turtle.	the present study examined the circuitry of the red nucleus of the sprague-dawley rat and the freshwater pond turtle, chrysemys picta, by using intracellular cell filling combined with anterograde tract tracing. although both species have a well-developed cerebellorubral system, they differ in that the red nucleus of rats receives direct input from the motor areas of the cerebral cortex, whereas turtles do not. however, a direct descending projection from the hypothalamus to the red nucleus of t ...	2000	10578105
the physiology of diving in a north-temperate and three tropical turtle species.	we examined changes in blood gases, plasma ions, and acid-base status during prolonged submergence (6 h) of four aquatic turtle species in aerated water at 20 degrees c. our objective was to determine whether the temperate species, chrysemys picta bellii, exhibits greater tolerance to submergence apnea than the tropical species, pelomedusa subrufa, elseya novaeguineae, and emydura subglobosa. blood was sampled from indwelling arterial catheters for measurements of blood po2, pco2, ph, and hemato ...	1999	10466218
the physiology of hibernation among painted turtles: the eastern painted turtle chrysemys picta picta.	eastern painted turtles (chrysemys picta picta) from connecticut were submerged at 3 degrees c in normoxic and anoxic water to simulate potential respiratory environments within their hibernacula. those in normoxic water could survive submergence for at least 150 d, while those in anoxic water could survive for a maximum of about 125 d. turtles in normoxic water developed a slight metabolic acidosis as plasma lactate accumulated to about 50 mm in 150 d, while anoxic turtles developed a severe la ...	2006	10438685
the effect of isovolemic anaemia on blood o2 affinity and red cell triphosphate concentrations in the painted turtle (chrysemys picta).	the blood oxygen affinity of vertebrates is regulated, in part, through changes in red cell phosphate levels and increased oxygen affinity during reductions in inspired oxygen and is a well-described and common feature. however, during anaemia, when oxygen delivery is compromised by a reduction in blood oxygen carrying capacity, a lowering of blood oxygen affinity will facilitate oxygen unloading in the tissues, while oxygen loading at the gas exchange organ is not impaired. the present study in ...	1999	10356763
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
reversible decreases in atp and pcr concentrations in anoxic turtle brain.	a hallmark of anoxia tolerance in western painted turtles is relative constancy of tissue adenylate concentrations during periods of oxygen limitation. during anoxia heart and brain intracellular compartments become more acidic and cellular energy demands are met by anaerobic glycolysis. because changes in adenylates and ph during anoxic stress could represent important signals triggering metabolic and ion channel down-regulation we measured pcr, atp and intracellular ph in turtle brain sheets t ...	1998	9828395
hatchling painted turtles (chrysemys picta) survive only brief freezing of their bodily fluids.	neonatal painted turtles (chrysemys picta) spend their first winter inside the shallow, subterranean nest cavity where they completed embryogenesis. consequently, hatchlings at high latitudes may be exposed to ice and cold during the winter. this study was undertaken to determine how long hatchlings withstand freezing at temperatures slightly below 0 degree c because tolerance for freezing has been proposed to be the key to survival by overwintering animals. a thermocouple was glued to the carap ...	1998	9787824
soil hydric characteristics and environmental ice nuclei influence supercooling capacity of hatchling painted turtles chrysemys picta.	hatchling painted turtles (chrysemys picta) hibernate in their shallow natal nests where temperatures occasionally fall below -10 c during cold winters. because the thermal limit of freeze tolerance in this species is approximately -4 c, hatchlings rely on supercooling to survive exposure to extreme cold. we investigated the influence of environmental ice nuclei on susceptibility to inoculative freezing in hatchling c. picta indigenous to the sandhills of west-central nebraska. in the absence of ...	1998	9787130
reduction of nmda receptor activity in cerebrocortex of turtles (chrysemys picta) during 6 wk of anoxia.	survival of brain anoxia during months of winter dormancy by the western painted turtle, chrysemys picta, may rely on inactivation of neuronal ion channels. during 2 h of anoxia, ca2+ influx via the n-methyl-d-aspartate (nmda) subtype of glutamate receptor decreases 30-40%, but it is not known if prolonged anoxic dormancy is associated with even more profound downregulation of this important channel. because ionized ca2+ in cerebrospinal fluid (csf) increases five- to sixfold during prolonged an ...	1998	9688964
cytochromes p450 in liver of the turtle chrysemys picta picta and the induction and partial purification of cyp1a-like proteins.	cytochromes p450 (cyp) in hepatic microsomes from the turtle chrysemys picta picta and their response to inducers were examined. freshly caught turtles had one protein (59 kda) detected in western blot with monoclonal antibody 1-12-3 to scup cyp1a. that same band and a second band were detected with polyclonal anti-mouse cyp1a1. polyclonal anti-scup p450b (putative cyp2b) recognized three bands and anti-scup p450a (putative cyp3a), one band. tcb (3,3',4,4'-tetrachlorobiphenyl) at 5 mg kg-1 injec ...	1998	9659368
evidence for a photosensitive region in the caudal mesencephalon of the turtle brain.	using an in vitro brainstem-cerebellum preparation from the turtle chrysemys picta, burst discharge was recorded from the abducens nerve when light was directed on the brainstem. this burst discharge likely represents a neural correlate of the eye-blink reflex. increasing the intensity of the light stimulus reduced the response latency from a duration of many seconds to approximately 1-2 s. no response was recorded when the light source was covered. the response was present when infrared light w ...	1998	9588779
central trigeminal and posterior eighth nerve projections in the turtle chrysemys picta studied in vitro.	recent electrophysiological studies in the turtle chrysemys picta have suggested that a neural correlate of the eye-blink reflex can be evoked in an in vitro brain-stem-cerebellum preparation by electrical rather than natural stimulation of the cranial nerves. discharge recorded in the abducens nerve, which is similar to emg recordings from extraocular muscles during eye retraction, is triggered by a brief electrical stimulus applied to the ipsilateral trigeminal nerve. evidence also suggests th ...	1998	9553692
in vitro tolerance to anoxia and ischemia in isolated hearts from hypoxia sensitive and hypoxia tolerant turtles.	although freshwater turtles as a group are highly anoxia tolerant, dramatic interspecific differences in the degree of anoxia tolerance have been demonstrated in vivo. painted turtles (chrysemys picta bellii) appear to be the most hypoxia-tolerant species thus far studied, while softshelled turtles (trionyx spinifer) are the most hypoxia-sensitive. we have assumed that this dichotomy persists in vitro but have not, until now, directly tested this assumption. we therefore, directly compared the r ...	1997	9505438
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
hypoxia, temperature, and ph/co2 effects on respiratory discharge from a turtle brain stem preparation.	an in vitro brain stem preparation from adult turtles (chrysemys picta) was used to examine the effects of anoxia and increased temperature and ph/co2 on respiration-related motor output. at ph approximately 7.45, hypoglossal (xii) nerve roots produced patterns of rhythmic bursts (peaks) of discharge (o.74 +/- 0.07 peaks/min 10.0 +/- 0.6 s duration) that were quantitatively similar to literature reports of respiratory activity in conscious, vagotomized turtles. respiratory discharge was stable f ...	1998	9475877
dorsal cortex lesions impair habituation in turtles (chrysemys picta).	two experiments investigated habituation in painted turtles (chrysemys picta). in the first, turtles were given lesions of the dorsal cortex or sham lesions and then trained on a restraint. although the sham-lesioned turtles learned to tolerate the restraint, the lesioned animals continued to struggle against it. thus dorsal cortex lesions disrupted habituation to restraint. in order to test habituation to a looming stimulus in a second experiment, all animals were habituated to the restraint be ...	1998	9435970
cold tolerance in hatchling painted turtles (chrysemys picta): supercooling or tolerance for freezing?	we studied tolerance for cold in hatchling painted turtles (chrysemys picta) from lake metigoshe, bottineau county, north dakota, to determine whether neonates in populations near the northern limit of distribution rely on a tolerance for freezing or on a capacity for supercooling to survive their first winter of life. we placed hatchlings individually into artificial hibernacula constructed in jars of damp, loamy sand and then cooled the jars to approximately -0.45 degrees c, which was below th ...	2008	9361141
lactate accumulation in the shell of the turtle chrysemys picta bellii during anoxia at 3°c and 10°c	lactate concentrations were measured in the shell and plasma of the turtle chrysemys picta bellii after 3 months of submergence anoxia at 3°c and during and after 9 days of submergence anoxia at 10°c. liver and skeletal muscle lactate levels were also measured in control and anoxic animals at each temperature. at 3°c, mean shell lactate concentration (n=4) reached 133mmolkg-1shellmass and plasma lactate levels were 144mmoll-1; at 10°c, shell and plasma lactate concentrations (n=5 ...	1997	9320212
effects of anoxia, acidosis and temperature on the contractile properties of turtle cardiac muscle strips.	the responses to anoxia and acidosis of cardiac ventricular muscle strips from the anoxia-tolerant turtle chrysemys picta bellii were investigated at 10 degrees c and 20 degrees c. force-velocity curves were determined by quick isotonic releases at 85% of the time to peak isometric force under control, anoxia, lactate acidosis and anoxic lactate acidosis conditions. the isotonic forces during quick releases spanned 5-95% of the measured isometric force at each conditions. superfusion solution ph ...	1997	9246780
effects of anoxia on intracellular free ca2+ in isolated cardiomyocytes from turtles.	one of the most important negative consequences of hypoxic stress in the mammalian myocardium is a breakdown in intracellular calcium homeostasis. this study examines the effects of anoxic stress on intracellular calcium regulation in isolated ventricular myocytes from a hypoxia tolerant vertebrate, the western painted turtle (chrysemys picta bellii). isolated calcium tolerant cardiomyocytes from turtle hearts were mounted on a glass cover slip that formed the bottom of a sealed, plexiglas perfu ...	1997	9125683
mechanisms of phi recovery from nh4cl-induced acidosis in anoxic isolated turtle heart: a 31p-nmr study.	mechanisms of intracellular ph (phi) recovery from nh4cl-induced acidosis were investigated on isolated perfused hearts of the turtle, chrysemys picta bellii, using 31p nuclear magnetic resonance (nmr) spectroscopy at 20 degrees c. a major goal was to assess the activity of these mechanisms under anoxic conditions. based on calculated buffer capacity and a phi recovery range at 20 degrees c of 6.75-6.95 (normal phi 7.2-7.4), mean h' efflux rate during perfusion with co2-free n-tris(hydroxymethyl ...	1997	9038985
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
identification of central 5-ht and 5-ht1a receptors in the turtle brain (chrysemys picta).	radiologand binding studies were undertaken in the turtle whole brain, cerebellum and raphe using the selective radioligands [3h]5-hydroxytryptamine trifluoroacetate ([3h]5-ht) amd [3h]+/-8-hydroxy-2-(di-n-propylamino) tetralin hydrobromide ([3h]dpat) to identify serotonin (5-ht) receptors and the specific 5-ht1a receptor subtype. scatchard analysis identified a nanomolar affinity binding site for [3h]5-ht (12 nm) in turtle whole brain assays. a low affinity 5-ht1a site (102 nm) was also identif ...	1996	8832643
protamines of reptiles.	we have characterized for the first time the complete primary structure of the main protamine components of the sperm from four reptiles: chrysemys picta (turtle), elaphe obsoleta (snake), anolis carolinensis (lizard), and alligator mississipiensis (crocodilian). these species were chosen to represent one of each of the main phylogenetic branches of this taxonomic group. comparison of these protamine sequences with those already available from other vertebrate groups allows us to define properly ...	1996	8798564
lactate distribution and metabolism during and after anoxia in the turtle, chrysemys picta bellii.	to determine the fate of lactate during and after prolonged anoxia, 14c-labeled lactate was injected into turtles after 2 h of a 6-h submergence at 20 degrees c. 14c activities of plasma and chamber water were tested at intervals during anoxia and also in expired air during 39 h of recovery. partitioning of label in major body compartments [extracellular fluid (ecf), intracellular fluid (icf), and shell] and 14c activity and glycogen in selected tissues (heart, liver, and muscle) were measured a ...	1996	8770142
anoxia and ischemia tolerance in turtle hearts.	it has been known since ancient times that turtle hearts exhibit extraordinary tolerance to anoxia or ischemia. the mechanisms by which they accomplish this remain obscure. the most important adaptation in anoxic turtles is a rapid and dramatic decrease in metabolic rate. nuclear magnetic resonance measurements indicate that painted turtle (chrysemys picta) hearts respond to anoxia with a rapid decrease in phosphocreatine (pcr; to 50% of control) after which pcr remains constant for at least 4 h ...	2016	8728853
radioligand and immunochemical studies of turtle oviduct progesterone and estrogen receptors: correlations with hormone treatment and oviduct contractility.	progesterone (pr) and estrogen (er) receptors were previously identified and characterized in the reproductive tract of the turtle, chrysemys picta, and changes in pr levels were monitored during the seasonal cycle. to understand the hormonal regulation of pr, intact and ovariectomized animals were treated with estradiol, progesterone, and a combination of estradiol and progesterone, and high affinity pr and er levels were determined by radioligand binding studies. ovariectomy significantly decr ...	1996	8713645