circulation and blood pressure in the great vessels and heart of the turtle (chelydra serpentina). 195713458464
the effects of electrolytes and sugars on the erythrocytes of the turtle, chelydra serpentina. 194918108892
on chelydra serpentina. 189317832441
control of metabolism and growth in embryonic turtles: a test of the urea hypothesis.we performed two experiments to determine (1) whether the metabolism and growth of embryonic snapping turtles (chelydra serpentina) incubating in wet and dry environments are correlated inversely with the concentration of urea inside their eggs, and (2) whether urea accumulating inside eggs might be the cause of reductions in metabolism and growth by embryos. eggs in the first experiment were incubated in different hydric environments to induce different patterns of net water exchange between th ...19892614338
action of sex steroid hormones on temperature-induced sex determination in the snapping turtle (chelydra serpentina).administration of exogenous estradiol benzoate (eb) or an estrogen agonist, r2858, into eggs of snapping turtles caused all embryos incubated at male-producing temperatures to develop as females, whereas testosterone propionate (tp) caused 42% of the embryos to develop as females. some of the embryos treated with eb, r2858, or tp also had hypertrophied oviducts. neither dihydrotestosterone (dht) nor cholesterol had any apparent effect on the sex determination of embryos incubated at male-produci ...19892599345
factors terminating nonventilatory periods in the turtle, chelydra serpentina.pao2, paco2 and pha were measured via an extracorporeal loop in conscious snapping turtles (chelydra serpentina) breathing air or hypoxic (10, 15% o2), hyperoxic (30% o2), or hypercapnic (2% co2) gases. turtles breathed into an inverted funnel ventilated with the test gas. breathing was recorded with a differential pressure transducer. in all turtles, nonventilatory periods were interrupted by breathing episodes containing multiple breaths. in normoxia, pao2 at the end of nonventilatory periods ...19892506623
the role of arginine vasotocin and prostaglandin f2 alpha on oviposition and luteolysis in the common snapping turtle chelydra serpentina.the administration of arginine vasotocin (avt) to gravid snapping turtles with steroidogenically active corpora lutea and high plasma progesterone concentration (1480 +/- 155 pg/ml) did not trigger oviposition, whereas 12 days after ovulation when luteolysis occurred and plasma progesterone concentration was low (570 +/- 78 pg/ml), treatment with avt caused oviposition. controls with high plasma progesterone concentration (1605 +/- 185 pg/ml) oviposited 15-23 days after ovulation when plasma pro ...19883162890
chemical and electrical synapses between photoreceptors in the retina of the turtle, chelydra serpentina.electron microscopic observation of the distal retina of the turtle, chelydra serpentina, revealed that photoreceptors contact each other by means of a variety of junctions. the synaptic terminals of the primary and accessory members of a double cone invariably make punctate contact with each other distal to the basal surfaces. this type of contact was only rarely seen between the synaptic terminals of single photoreceptors. photoreceptor telodendria which emanate from the basal surface of the s ...19852468693
electron microscopy of golgi-impregnated photoreceptors reveals connections between red and green cones in the turtle and green cones of two turtle species (pseudemys scripta elegans and chelydra serpentina) retina have been stained with golgi procedures and examined by light microscopy of whole-mount tissue and by electron microscopy of serial thin sections. by light microscopy, red and green single cones appear indistinguishable, but double cones can be readily identified. all golgi-stained photoreceptors in turtle retina have a spray of telodendria radiating from their synaptic pedicles. the telodendria ...19854031990
ultrastructural changes in testes of the snapping turtle, chelydra serpentina in relation to plasma testosterone, delta 5-3 beta-hydroxysteroid dehydrogenase, and cholesterol.ultrastructural changes in the testes of the common snapping turtle, chelydra serpentina, were observed throughout the year. plasma testosterone levels were measured and compared with the occurrence of delta 5-3 beta-hydroxysteroid dehydrogenase (3 beta-hsd), cholesterol, and steroidogenic ultrastructural features (smooth endoplasmic reticulum (ser), mitochondria with tubular cristae) in sertoli and leydig cells. the testosterone level is highest in may and october (mating) and relatively low du ...19853857207
development of the ovarian follicles in relation to changes in plasma parameters and 5 delta 3 beta hsd in snapping turtle, chelydra serpentina.follicular development in snapping turtle, chelydra serpentina, was studied in relation to changes in plasma levels of estradiol-17 beta, total protein, calcium, inorganic phosphate and cholesterol. histochemical reaction for 3 beta-hsd in granulosa and theca cells of the follicles is strong during the preovulatory and vitellogenic phases when the follicles attain their maximum size (18-22 mm) and estradiol is at a high level. the reaction for 3 beta-hsd is weal during the postovulatory phase wh ...19852864192
morphological and experimental studies of the somitomeric organization of the segmental plate in snapping turtle embryos.the segmental plate mesoderm of snapping turtle embryos (chelydra serpentina) was examined with stereoscanning electron microscopy imaging. a metameric pattern was detected along the entire length of the segmental plates. this pattern consisted of a tandem sequence of mesodermal units, called somitomeres. each somitomere was oval to cubic in shape and the processes of the constituent mesodermal cells tended to be arranged in concentric rings about the centre of the somitomere. several experiment ...19846533256
resistance of the shell membrane and mineral layer to diffusion of oxygen and water in flexible-shelled eggs of the snapping turtle (chelydra serpentina).at oviposition, flexible eggshells of many turtles have an outer mineral layer and an inner membrane layer of approximately equal thickness. we measured conductances of both layers to h2o and o2 at various levels of eggshell hydration. both the mineral layer of the eggshell and the shell membrane offer significant resistance to diffusion of water vapor and oxygen in eggshells of the snapping turtle, chelydra serpentina. conductance to water vapor increases in both the membrane and mineral layer ...19826890707
possible adaptive value of water exchanges in flexible-shelled eggs of turtles.use of energy reserves by embryos of common snapping turtles (chelydra serpentina) is related to the hydric conditions to which eggs are exposed during incubation and to the net exchanges of water through the eggshells. embryos developing inside eggs with a relatively favorable water balance use more of their energy reserves metabolically and grow larger before hatching than embryos inside eggs with less favorable water exchanges.198117760193
characteristics of gonads and oviducts in hatchlings and young of chelydra serpentina resulting from three incubation temperatures.eggs of chelydra serpentina were incubated at 30 degrees c and 26 degrees c. in addition, incubation was done at 20 degree c during the temperature-sensitive period for sex determination. incubation at 20 degrees c and 30 degrees c resulted in females; incubation at 26 degrees c resulted in males in 99% of the cases. the average gonadal length was less in the males. the average length of the 20 degree c ovaries did not vary significantly from that of the 30 degrees c ovaries. the condition of th ...19817241601
current-voltage relations in the rod photoreceptor network of the turtle retina.1. electrical coupling between rod photoreceptors was studied in the eyecup preparation of the snapping turtle, chelydra serpentina, using intracellular micro-electrodes.2. the spatial profiles of rod responses to a long narrow slit of light were determined. the peak response amplitudes were found to decline exponentially as the slit was moved from the most sensitive position in the receptive field of each rod. the mean length constant was 55.7 mum.3. rods were simultaneously impaled in pairs an ...19807230014
ultrastructural morphology of the shell and shell membrane of eggs of common snapping turtles (chelydra serpentina).common snapping turtles (chelydra serpentina) lay nearly spherical, flexible-shelled eggs having an outer mineral layer composed of calcium carbonate in the aragonite form. the mineral layer is arranged into loosely organized groups of nodular shell units, with numerous spaces (or pores) between adjacent shell units. shell units are structurally complex, consisting of an inner tip that is morphologically distinct from the main body of the shell unit. contained within an intact shell unit at the ...19807452729
water relations of pliable-shelled eggs of common snapping turtles (chelydra serpentina). 19807427826
the rate of conversion of [14-(14)c]pregnenolone to [4-(14)c]progesterone by corpora lutea of the snapping turtle, chelydra serpentina. 19807419051
aerial and aquatic oxygen uptake by freely-diving snapping turtles (chelydra serpentina).aerial oxygen consumption of unrestrained, freely-diving warm-and cold-acclimated snapping turtles, chelydra serpentina, was measured at 10, 20, and 30°c. also, simultaneous determinations of aerial and aquatic oxygen uptake by voluntarilydiving animals were made at 4 and 20°c. the standard rates of aerial oxygen consumption are equivalent in cold-and warm-acclimated animals in water and in cold-acclimated ones in air; these rates are all lower than those of warm-acclimated animals in air. thus ...198028309683
the effect of malnutrition on immunocompetence and whole body resistance to infection in chelydra serpentina. 1979437240
seasonal fluctuations in the plasma concentrations of progesterone and oestradiol-17 beta in the female snapping turtle (chelydra serpentina).plasma concentrations of progesterone and oestradiol-17 beta were determined by radioimmunoassay procedures in the sexually mature female snapping turtle at four different stages of the annual ovarian cycle. the highest level of progesterone in the peripheral plasma was detected during the luteal stage (june), whereas the concentration of oestradiol was highest (280 pg/ml) in may, immediately before ovulation.1979429947
horizontal cells of the turtle retina. ii. analysis of interconnections between photoreceptor cells and horizontal cells by light microscopy.criteria were established whereby the chief and accessory members of double cones, red-, green-, and blue-sensitive single cones, and rods could be distinguished from one another in 1-micrometer sections through the retinas of pseudemys scripta elegans and chelydra serpentina. criteria included the presence of absence of an oil droplet, the size, color, and radial position of the oil droplet, the size and shape of the inner and outer segments, and the shape orientation of the connection between ...1978730848
voltage noise observed in rods of the turtle retina.1. intracellular voltage was recorded from rods in isolated retinae of the snapping turtle, chelydra serpentina. the voltage was observed during darkness or during uniform illumination of a large retinal area. during darkness the voltage fluctuated continuously about a mean level. the spontaneous fluctuation is termed ;noise'. during illumination the amplitude of the noise was reduced.2. the noise observed during darkness could also be reduced by injecting a hyperpolarizing current into the impa ...1977592191
ultrastructural analysis of normal and immunized spleen of the snapping turtle, chelydra the ultrastructural comparison of normal, unimmunized spleens with immunized spleens at key intervals after antigenic stimulation with keyhole limpet hemocyanin (klh), we noted cellular and cytological features which reflect the cellular kinetics of the primary immune response, particularly with respect to plasma cell production. although lymphoblasts and mature plasma cells are present in the white and red pulp, respectively, intermediate stages of the plasma cell line are rarely found in no ...1976945353
changes in spleen histology in response to antigenic stimulation in the snapping turtle, chelydra serpentina.proliferative and migratory changes of lymphoid cells in the spleen were observed in turtles stimulated with klh and maintained at 30 degrees c. small foci of pyroninophilic lymphoblasts were first seen in the white pulp at about day 5. progressive enlargement of these centers continued and peaked by days 8-12. by days 15-20 the white pulp returned to a normal (unimmunized) state, while the number of pyroninophilic cells, primarily plasma cells, increased markedly in the red pulp. at days 22-25, ...1976945352
fine structure of the chromophobe in the pars distalis of the common snapping turtle, chelydra serpentina.chromophobes of the pars distalis in young chelydra serpentina have sparse cytoplasm with no specific granules; however, many cytoplasmic filaments are present. the chromophobes are connected to the other cell types by desmosomes, while different types of junctional specializations occur between adjacent chromophobes. cytoplasmic filaments traverse the cytoplasm in a random manner and terminate on both the junctional complexes and the nuclear envelope. it is proposed that, in addition to providi ...19761248046
purification of thyrotropin from the pituitaries of two turtles: the green sea turtle and the snapping turtle. 19817286628
metabolic rates are elevated and influenced by maternal identity during the early, yolk-dependent, post-hatching period in an estuarine turtle, the diamondback terrapin (malaclemys terrapin).non-genetic maternal effects, operating through a female's physiology or behavior, can influence offspring traits and performance. here we examined potential maternal influences on metabolic rates (mr) of offspring in an estuarine turtle, the diamondback terrapin (malaclemys terrapin). females and their eggs were collected from the field and the eggs incubated in the laboratory for subsequent measurement of mr of females, late-stage embryos, newly-hatched individuals that were nutritionally depe ...201727894885
dynamics of yolk steroid hormones during development in a reptile with temperature-dependent sex determination.many oviparous reptiles exhibit temperature-dependent sex determination (tsd); i.e., the temperature at which the egg is incubated determines the sex of the offspring. in tsd reptiles, yolk steroids not only may influence sex determination, but also may mediate hormonal effects on subsequent growth and behavior, as in some avian species. we investigated changes in the levels of estradiol (e(2)) and testosterone (t) during development in yolks of snapping turtle eggs, examined how incubation temp ...200212161199
hematology and clinical chemistry reference ranges for clinically normal, captive new guinea snapping turtle (elseya novaeguineae) and the effects of temperature, sex, and sample type.median values and confidence intervals for hematology and serum and plasma chemistry parameters were established for 29 male and female healthy new guinea snapping turtles (elseya novaeguineae) held at 24.5 degrees c and 30.0 degrees c. creatine kinase, albumin, potassium, and phosphorus values were significantly higher at 24.5 degrees c than at 30.0 degrees c. glucose, alkaline phosphatase, aspartate transaminase, alanine aminotransferase, total carbon dioxide, and chloride values were signific ...19979523632
lipid provisioning of turtle eggs and hatchlings: total lipid, phospholipid, triacylglycerol and triacylglycerol fatty acids.lipid composition of eggs and hatchlings was studied in painted, snapping and blanding's turtles from western nebraska. the average total lipid proportions of the egg yolk, post-embryonic yolk and hatchling soma dry masses were high in painted turtles (29.80%, 42.16% and 14.18%, respectively) relative to snapping and blanding's turtles (egg yolk < 14%, postembryonic yolk < 17%, hatchling soma < 2%). the proportion of total egg yolk lipid used during development varied among species (painted turt ...19957584861
kinetics of synaptic transmission from photoreceptors to horizontal and bipolar cells in turtle retina.the kinetics of synaptic transfer from photoreceptors to second order neurons have been determined in the retina of the snapping turtle. analysis of the fluctuations resulting from the random release of cone transmitter molecules reveals that the action on postsynaptic channels of the depolarizing bipolar cells is prolonged by approximately 10 times compared to the action on the hyperpolarizing bipolar cells. determination of the cone and rod to horizontal cell impulse response shows that the ki ...19836308900
temperature-sensitive periods of sex determination in emydid many turtles sex differentiation is controlled by the incubation temperature of the embryo, with low temperatures producing males, high temperatures producing females. this study investigates the developmental period of temperature-sensitivity in two species of emydid turtles, using different combinations of incubation at a male-determining temperature (25 degrees c) and at a female-determining temperature (31 degrees c). the sensitive period extends throughout much of the middle third of dev ...19817338727
mixed rod-cone responses in horizontal cells of snapping turtle retina. 1979473609
functional characteristics of lateral interactions between rods in the retina of the snapping turtle.1. intracellular recordings were made of the slow hyperpolarizing light responses of single rods in the retina of the snapping turtle. physiological criteria used to identify rods were verified by intracellular injections of procion yellow. 2. the amplitudes of the responses elicited by fixed intensity flashes increased as the stimulus was enlarged to a diameter of 300 mum. scattered light was found incapable of accounting for this effect, which must result from summative interaction of rods wit ...1976986460
beveling of fine micropipette electrodes by a rapid precision method.a technique has been developed for embedding alumina particles 0.05 micrometer in size in the surface of a polyurethane film laid on glass. this abrasive surface is used for rapid, precise, and reliable beveling of pyrex micropipettes with tip diameters at least as small as 0.1 micrometer. in the snapping turtle retina the beveled electrodes give much better cell penetration and intracellular response stability than unbeveled electrodes of considerably higher proach to this problem.19744841617
evolutionary clock: nonconstancy of rate in different using various methods for comparing polypeptide sequences we find that the evolutionary divergence of rattlesnake cytochrome c from cytochromes c of species in other classes has been more rapid than that of cytochrome c of another reptile, the snapping turtle. this suggests that the evolutionary rate of change of cytochromes c is species-dependent as well as time-dependent.19725065730
distribution of creatine, guanidinoacetate and the enzymes for their biosynthesis in the animal kingdom. implications for phylogeny.1. the distribution of creatine and the creatine-synthesizing enzymes in the animal kingdom has been investigated. creatine was found in tissues of all vertebrates examined, and in various invertebrates from phyla annelida, echinodermata, hemichordata and chordata, subphylum cephalochordata. the activities of the creatine-synthesizing enzymes, arginine-glycine transamidinase and guanidinoacetate methylpherase, were not detected in the hagfish or in any of the invertebrates, including those in wh ...19725010856
survival of embryonic limb bud transplants in snapping turtles. 19715132600
use of intravascular carbon dioxide gas to demonstrate interatrial septal defects. 195813606221
a phylogenetic and biogeographic analysis of the genera of spirorchinae (digenea: spirorchidae) parasitic in freshwater turtles.cladistic analysis of the freshwater genera of spirorchinae (schistosomatoidea: spirorchidae sensu yamaguti, 1971) plus haematotrema stunkard, 1923, and aphanospirorchis platt, 1990, was completed. the spirorchinae were considered monophyletic based on synapomorphies of the esophagus. three lineages, spirhapalum (europe/asia), plasmiorchis+hemiorchis (india), and spirorchis + henotosoma + haematotrema + aphanospirorchis (north america), were identified. nelsen consensus analysis was used as the ...19921635020
sensitive periods during embryogeny for hormonally induced sex determination in turtles.administration of exogenous estradiol between embryonic stages 10 and 19 inclusive caused embryos of snapping turtles (a species which exhibits temperature-dependent sex determination) to develop ovaries rather than testes, while administration of hormone either prior to stage 10 or after stage 22 did not affect the predicted sex ratio of offspring. thus the sensitive period for hormonal effects on gonadal development apparently coincides with the period of normal gonadal differentiation. in lig ...19883203874
spatial spread of adaptation within the cone network of turtle retina.1. the spatial characteristics of adaptation were studied in the red-sensitive cones of the snapping turtle retina using intracellular microelectrodes. light responses elicited with slit-shaped test and adapting stimuli revealed that test response amplitudes and adaptation decline similarly with distance from the impaled cone. the spatial spread of adaptation and the light response cannot be accounted for by scattered light and must therefore result from electrical coupling between cones. 2. the ...19873446810
disposition of toxic pcb congeners in snapping turtle eggs: expressed as toxic equivalents of tcdd. 19873120832
disposition of low and high environmental concentrations of pcbs in snapping turtle tissues. 19873107636
steroid hormones reverse sex in turtles.injection of estradiol benzoate into eggs of snapping turtles and painted turtles caused all embryos to develop as females. a similar but less consistent female-determining effect was associated with injection of testosterone proprionate. both species of turtles have temperature-dependent sex determination in nature, whereby embryos incubated at cool temperatures (25 degrees) develop as males and embryos incubated at warm temperatures (31 degrees) develop as females. exogenous estrogens have bee ...19863803892
chemical synapses between turtle photoreceptors.rod photoreceptors of the snapping turtle retina wer golgi impregnated and studied in the electron microscope. telodendria arising from the synaptic bases ended at rods and cones as lateral or central elements of the ribbon synaptic complex, thus providing clear evidence of chemical synapses between turtle photoreceptors.19846488024
polychlorinated biphenyl, mercury, and cadmium concentrations in minnesota snapping turtles. 19836404330
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