PMID(sorted ascending)
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
the effect of malnutrition on immunocompetence and whole body resistance to infection in chelydra serpentina. 1979437240
mixed rod-cone responses in horizontal cells of snapping turtle retina. 1979473609
water-vapor conductance of testudinian and crocodilian eggs (class reptilia).flexible-shelled eggs of snapping turtles (chelydra serpentina) have conductances to water vapor that are 55 times higher than predicted for avian eggs of similar size, whereas rigid-shelled eggs of softshell turtles (trionyx spiniferus) and american alligators (alligator mississippiensis) have conductances that are only five times higher than expected for comparable eggs of birds. the differences between empirical and predicted values result from the much higher effective pore areas in reptilia ...1979515558
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
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
observations on haemogregarina balli sp. n. from the common snapping turtle, chelydra serpentina.haemogregarina balli sp. n. is described from the blood and organs of the common snapping turtle chelydra serpentina serpentina and from the gastric and intestinal ceca of the presumed invertebrate hosts, the leeches placobdella parasitica and placobdella ornata. in the peripheral blood of the turtle, male and female gametocytes and immature erythrocytic schizonts are found within erythrocytes. the maturation of erythrocytic schizonts containing 6-8 merozoites is recorded from liver imprints. sc ...1976819649
purification and properties of reptilian and amphibian growth hormones.highly purified growth hormone was isolated from the pituitaries of two reptilian species, the snapping turtle and the sea turtle, and two amphibian species, the bullfrog and the leopard frog. characterization studies were performed with these growth hormones in comparison with mammalian and avian growth hormones. great similarities among these species were found in chromatographic behavior, ve/vo ratios (2.0) on gel filtration, disc electrophoretic patterns, terminal amino acid residues and imm ...1976821743
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
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
electrical properties of the rod syncytium in the retina of the turtle.1. intracellular responses were recorded from rods in isolated eye-cups of the snapping turtle. chelydra serpentina. responses to flashes of small (less than 100 mum diameter) and large (1000 mum diameter) spots of 500 nm light were studied. 2. responses produced by small and large diameter spots which delivered less than 0-3 photons mum-2 had the same shape. the responses produced by large spots were, however, nearly ten times greater in amplitude. the difference in amplitude is termed enhancem ...1976950599
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
[the orbitotemporal region in the cranium of chelydra serpentina linnaeus (chelonia) and lacerta sicula rafinesque (lacertilia)].an analysis of the ontogenesis of the chondrocranium gives the following homologies in the skull of lacerta and chelydra: (see article). it is shown that the extracranial position of the cavum epiptericum in lacerta corresponds to the stage of maximal development of the chondrocranium in chelydra. but further development brings about a dermal sidewall in the orbitotemporal region, b,ilt up by descending parietal flanges which incorporate the epipterygoid. this not only allows the pila antotica t ...19761007875
pituitary growth hormones: further evidence for evolutionary conservatism based on immunochemical studies.immunochemical relatedness of preparations of purified somatotropins (growth hormones) of somatotropins in pituitary extracts from various vertebrate species was investigated by applying an antiserum to a purified somatotropin from a submammalian species, the snapping turtle. with the exception of monkey somatotropin, all mammalian, reptilian, and avian preparations tested showed reactions of identity or near identity by immunodiffusion studies in agar gel. radioimmunoassay employing labeled rat ...19751060111
antileptospiral activity in lower-vertebrate sera.normal serum from the painted turtle (chrysemys picta), the snapping turtle (chelydra serpentina), and the frog (rana pipiens) were found to possess bactericidal activity towards leptospira. leptospires from both the parasitic and biflexa complexes were killed by these sera at high dilutions. this pattern differs from that of mammalian serum, as generally only the biflexa complex leptospires are killed by normal mammalian serum. the activity in c. picta serum was characterized as being complemen ...19751081972
rod-rod interaction in the retina of the turtle.intracellular responses were recorded from rods in isolated eye-cups of the snapping turtle, chelydra serpentina. responses to small and large diameter spots of 500 nm light were studied. 1. the peak amplitudes of responses smaller than approximately 2 mv were directly proportional to irradiance. small spots (less than 100 mum diameter) produced approximately 30 muv/rhodopsin molecule bleached. increasing stimulus diameter to 400-500 mum increased this five to seven times to about 200 muv/rhodop ...19751133789
cones excite rods in the retina of the turtle.the intracellular responses of rods in the retina of the turtle, chelydra serpentina, were studied with brief flashes of monochromatic light. 1. flashes of red or green light applied over an area 25 mum in diameter produce responses with the same shape. with such restricted stimuli, the spectral sensitivity of a rod agrees well with the absorption spectrum of the porphyropsin pigment contained in its outer segment. 2. with stimulating spots more than 500 mum in diameter, dim flashes of red or gr ...19751133790
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
isolation and characterization of follicle-stimulating hormone and luteinizing hormone and its subunits from snapping turtle (chelydra serpentina) pituitaries.highly purified luteinizing hormone and follicle-stimulating hormone have been isolated from extracts of snapping turtle (chelydra serpentina) pituitaries. both hormones are potent in non-mammalian gonadotropin bioassays (1.8 x nih-lh-s1 and 30 x nih-fsh-s1). the materials have been characterized by polyacrylamide gel electrophoresis, amino terminal group analysis, amino acid and carbohydrate content, and, in the case of turtle luteinizing hormone, ultracentrifugation. the luteinizing hormone wa ...19761261497
phylogeny of regulatory regions of vertebrate tyrosinase genes.highly homologous dna elements were found to be shared by the upstream regions of the mouse tyrosinase and tyrosinase related protein (trp-1) genes. several nuclear proteins were shown to bind to both of these upstream regions. shared homologous dna elements were also found in the 5' flanking sequences of japanese quail and snapping turtle tyrosinase genes. shared homologous nucleotide sequences were found to be scattered like an archipelago in the 5' upstream regions of mouse and human tyrosina ...19921292011
report of dysgerminoma in the ovaries of a snapping turtle (chelydra serpentina) with discussion of ovarian neoplasms reported in reptilians and women.a malnourished, captive, young adult (weight-11 kg, carapace length-25 cm), female snapping turtle (chelydra serpentina) was presented for examination and treatment of malnutrition and multiple carapace necroses. because treatment was unsuccessful, the animal was euthanatized and necropsied. the main necropsy observations showed the presence of a 9 cm greyish-white/yellow, soft, fleshy to fatlike mass involving the right ovary near the oviduct opening and multiple similar, pea-to-walnut sized ma ...20041520837
heritable variation for sex ratio under environmental sex determination in the common snapping turtle (chelydra serpentina).the magnitude of quantitative genetic variation for primary sex ratio was measured in families extracted from a natural population of the common snapping turtle (chelydra serpentina), which possesses temperature-dependent sex determination (tsd). eggs were incubated at three temperatures that produced mixed sex ratios. this experimental design provided estimates of the heritability of sex ratio in multiple environments and a test of the hypothesis that genotype x environment (g x e) interactions ...19921592234
alternative leech vectors for frog and turtle trypanosomes.trypanosoma pipientis infections were achieved by exposing laboratory-raised bullfrog tadpoles (rana catesbeiana) to the leech desserobdella picta that had fed on infected frogs. likewise, a laboratory-raised snapping turtle (chelydra serpentina) was infected with trypanosoma chrysemydis following exposure to infected placobdella ornata. transmission of the trypanosomes by these leeches constitutes new vector records for the parasites. the biology of d. picta and p. ornata suggests that they are ...19921597811
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
brain peptide yy receptors: highly conserved characteristics throughout vertebrate evolution.we have shown previously that peptide yy (pyy) receptors are uniquely distributed in various mammalian brains and also have identified the receptor from porcine hippocampal membranes as a protein of 50,000 mol wt. to extend these observations, both the characteristics of pyy-receptor interaction and the structure of the receptor have been examined and compared with those of its sister peptide, neuropeptide y (npy), in the brains of various vertebrates including mammals (human, dog, guinea pig, r ...19911657579
sizing bands on autoradiograms: a study of precision for scoring dna fingerprints.we replicated dna fingerprints of snapping turtles (chelydra serpentina) and hypervariable restriction fragments of red-winged blackbirds (agelaius phoeniceus) to estimate the between-blot and between-lane components of variance in molecular weights of restriction fragments. molecular weight standards were included in every lane, and bands were sized using a sonic digitizer. in both studies, a strong positive correlation was found between band size and coefficient of variation (cv; mean = 0.7%). ...20061674911
the case for a cause-effect linkage between environmental contamination and development in eggs of the common snapping turtle (chelydra s.serpentina) from ontario, canada.concentrations of polychlorinated biphenyls (pcbs), dibenzo-p-dioxins, and dibenzofurans, organochlorine pesticides, and their metabolites were measured in eggs of the common snapping turtle (chelydra s.serpentina) collected from four wetlands on the shorelines of lakes ontario, and erie, and one control location in central ontario, canada. snapping turtle eggs from these sites were also artificially incubated to determine hatching success, and incidence of deformities in embryo and hatchling tu ...19911908525
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
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
temperature dependence of in vitro pituitary, testis, and thyroid secretion in a turtle, pseudemys vitro culture was used to examine the direct actions of temperature at the level of pituitary hormone [luteinizing hormone (lh), thyrotropin (tsh), growth hormone (gh), prolactin (prl)] responses to neuropeptides and two related peripheral endocrine responses [thyroid hormone (t4) and testicular androgen secretion] to pituitary hormones (tsh and gonadotropins) in a turtle, pseudemys scripta. all these responses were fully suppressed at very low temperatures (5-6 degrees) and maximal near the ...19892512196
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
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
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
the effects of cold acclimation on electrocardiogram parameters in five species of turtles.the effects of thermal acclimation at 25 or 5 degrees c on electrical activity in the heart were investigated in pseudemys scripta, terrapene carolina, chrysemys picta marginata, chrysemys picta dorsalis, chelydra serpentina, and sternotherus odoratus. the durations of the qrs complex and p-r, r-t and r-r intervals were found to increase with decreasing body temperature in all animals tested. the amplitudes of the p and t waves and qrs complex were dependent upon both acclimation temperature and ...19872886260
cardiovascular correlates of exercise in snapping turtles, chelydra serpentina.1. heart rate increased with a rise in body temperature (10-30 degrees c) and with induced physical exercise in snapping turtles. 2. maximum heart rate increment occurred at 30 degrees c. 3. standard oxygen pulse did not change with a rise in temperature. 4. oxygen pulse during exercise and oxygen pulse increment were maximal at 10 degrees c and minimal at 20 degrees c. 5. the increase in heart rate with exercise accounted for only 9-22% of the increase in oxygen transport during activity; the r ...20092900107
somitomeres: mesodermal segments of vertebrate embryos.well before the somites form, the paraxial mesoderm of vertebrate embryos is segmented into somitomeres. when newly formed, somitomeres are patterned arrays of mesenchymal cells, arranged into squat, bilaminar discs. the dorsal and ventral faces of these discs are composed of concentric rings of cells. somitomeres are formed along the length of the embryo during gastrulation, and in the segmental plate and tail bud at later stages. they form in strict cranial to caudal order. they appear in bila ...19883077109
disposition of low and high environmental concentrations of pcbs in snapping turtle tissues. 19873107636
disposition of toxic pcb congeners in snapping turtle eggs: expressed as toxic equivalents of tcdd. 19873120832
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
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
cytoplasmic progesterone receptors in uterine tissue of the snapping turtle (chelydra serpentina).a high affinity progesterone-binding component was detected in the cytosol of the uterus of the snapping turtle, chelydra serpentina. density gradient centrifugation indicated that binding of [3h]progesterone and [3h]promegestone (r5020) was to a fraction with a heavier sedimentation coefficient than bovine serum albumin (bsa) appearing as a broader peak in the 6-7 s region; it was not affected by excess cortisol. another binding peak, lighter than bsa and appearing with [3h]r5020 and [3h]proges ...19863734671
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
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
nonmammalian growth hormones have diabetogenic and insulin-like activities.purified ghs isolated from ostrich, sea turtle, snapping turtle, bullfrog, tilapia, and sturgeon were tested for in vivo diabetogenic activity in the hereditarily obese ob/ob mouse and for in vitro insulin-like activity in isolated adipose tissue from hypophysectomized rats. ghs from all species exhibited significant diabetogenic activity, causing fasting hyperglycemia and decreased glucose tolerance when administered at doses of 100 micrograms/day (ostrich, bullfrog, and sturgeon) or 200 microg ...19853882411
comparison of the structure of turtle pancreatic ribonuclease with those of mammalian ribonucleases.there are 33 invariant amino acid positions out of 132 positions in 42 investigated sequences of ribonucleases from a number of mammalian species and a reptile (snapping turtle, chelydra serpentina). these invariant residues are unequally distributed over 3 different parts of the molecule. the lobe of the s-protein part of the molecule, which lacks one disulfide bridge and has two shortened loops in turtle ribonuclease, has the lowest percentage of invariant residues, although the active-site re ...19863940901
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
the amino acid sequence of snapping turtle (chelydra serpentina) ribonuclease.snapping turtle (chelydra serpentina) ribonuclease was isolated from pancreatic tissue. turtle ribonuclease binds much more weakly to the affinity chromatography matrix used than mammalian ribonucleases. the amino acid sequence was determined from overlapping peptides obtained from three different digests. the n-terminal amino acid sequence of the protein determined by others [e. a. barnard, m. s. cohen, m. h. gold j.-k. kim (1972) nature (lond.) 240, 395-398] and homology were used as additiona ...19854076178
the absence of spread of adaptation between rod photoreceptors in turtle retina.adaptation by weak backgrounds and the spatial spread of desensitization between rods was studied in the snapping turtle retina, chelydra serpentina. intracellular membrane potentials were recorded from these photoreceptors in an eyecup preparation. the kinetics and sensitivity of rod responses were changed significantly by large, very dim backgrounds. for the twenty-five most sensitive rods where the dark-adapted flash sensitivity, sdf, was greater than 1.0 mv/rh*, rh* being the number of effec ...19854093878
the graft-versus-host reaction in the snapping turtle chelydra serpentina. 19734148147
separation of two distinct gonadotropins from the pituitary gland of the snapping turtle (chelydra serpentina). 20134544465
lymphoid tissue in the snapping turtle, chelydra serpentina. 19724638093
somatotropic effects of prolactin and growth hormone in juvenile snapping turtles (chelydra serpentina). 19734753356
responses of single rods in the retina of the turtle.1. the responses of rods in the retina of the turtle, chelydra serpentina, have been studied by intracellular recording.2. the identification of rods as the origin of the recorded responses has been confirmed by marking with procion yellow.3. the response to a small spot of light was a hyperpolarization which increased with increasing light intensity. for dim, small diameter stimuli, the shape of the rod response was similar to that of cones but 2x slower and 2x larger in amplitude. the time int ...19734759680
pituitary regulation of appetite and growth in the turtles pseudomys scripta elegans and chelydra serpentina. 19744813415
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
tissue culture analysis of immunological capacity of snapping turtles. 19684877627
skin allograft and xenograft rejection in the snapping turtle, chelydra serpentina. 20164893940
the maturation of the capacity to reject skin allografts and xenografts in the snapping turtle, chelydra serpentina. 19694893941
survival of xenogeneic grafts of embryonic pigment and carapace rudiments in embryos of chelydra serpentina. 19704922223
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
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
survival of embryonic limb bud transplants in snapping turtles. 19715132600
structure and development of the optic tectum of the snapping turtle (chelydra serpentina l.). 19715132820
motility of the turtle embryo, chelydra serpentina (linné).periodic motility of turtle embryos was observed during their incubation periods (60 +/- 5 days). cyclic activity was first observed between days 10 to 14; it increased to a peak level of 50 percent of the standard observation period on day 30 +/- 5, then declined to low levels until hatching activities were initiated. during the first third of the incubation period, motility of the turtles closely resembled that previously described for chick embryos at similar stages of development.19675212408
eimeria chelydrae n. sp. (protozoa: eimeriidae) from the snapping turtle, chelydra serpentina. 19695388988
twinning in the common snapping turtle, chelydra serpentina. 19705461766
extirpation experiments on embryonic rudiments of the carapace of chelydra serpentina. 19705482414
a series of stages in the embryonic development of chelydra serpentina. 19685681661
experimental studies on the columella-capsular interrelationship in the turtle chelydra serpentina. 19655861722
food imprinting in the snapping turtle, chelydra serpentina.three groups of hatchling snapping turtles, totaling 20, were fed either meat, fish, or worms. when they were tested for preference after 12 daily feedings, each preferred the diet to which it was accustomed. after 12 more days of eating a different food, each still preferred its original diet. a form of imprinting may be operative in the feeding behavior of this species.19665908961
primary structure of the cytochrome c from the snapping turtle, chelydra serpentina. 19665968568
depletions in the cervical and thoracolumbar sympathetic system following removal of neural crest from the embryo of chelydra serpentina. 19665969768
naturally abundant basophils in the snapping turtle, chelydra serpentina, possess cytophilic surface antibody with reaginic function.basophils constitute 50 to 63% of the blood leukocytes in chelydra serpentina, the snapping turtle. immunoglobulin (ig) on the surface of the turtle basophil was detected by indirect immunofluorescence by using an igg fraction from rabbit anti-turtle ig serum (ratig) and a fluoresceinated goat anti-rabbit antibody incubated at 4 degrees c. however, when the cells were incubated with ratig at 22 degrees c, the basophil number, as determined by wright's stain and neutral red counts, decreased dram ...19836183356
anti-immunoglobulin induced histamine release from naturally abundant basophils in the snapping turtle, chelydra serpentina.the dose response, temperature sensitivity, time course and calcium dependency of histamine release from snapping turtle basophils treated with rabbit anti-turtle immunoglobulin (ratig) sera was explored. this investigation indicated that the level of histamine release induced by ratig was dependent upon the concentration of ratig with concentrations of 350 mcg/ml inducing optimal release. in addition, release was temperature dependent with release increasing over a temperature range of 10 degre ...19846203781
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
an analysis of transmission from cones to hyperpolarizing bipolar cells in the retina of the turtle.voltage noise was recorded from centre-hyperpolarizing bipolar cells in the retina of the snapping turtle. the identity of the cells was confirmed by intracellular staining. the variance of the voltage fluctuations of the membrane potential present in the dark was suppressed by up to 30-fold by 100 microns diameter light spot stimuli centred on the cell's receptive field. such noise reduction is expected when light hyperpolarizes the photoreceptors and reduces the rate of release of transmitter ...19836310101
surface immunoglobulin on granular and agranular leukocytes in the thymus and spleen of the snapping turtle, chelydra serpentina.spleen and thymus suspensions from the turtle, chelydra serpentina were examined by indirect immunofluorescence and found to contain both agranulocytes and granulocytes positive for surface ig. among the splenic agranulocytes , 50% of the lymphocyte and monocyte population was positive for surface ig. in the thymus only 7% of the thymocytes were positive. ninety-two percent of the granulocytes, composed primarily of basophils and eosinophils, were positive for surface ig in both the thymus and s ...19846373420
polychlorinated biphenyl, mercury, and cadmium concentrations in minnesota snapping turtles. 19836404330
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
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
marine turtle reception of bone-conducted individual each of the marine turtles, caretta caretta and lepidochelys kempi, were stimulated with audiofrequencies delivered directly to the skull. startle responses were observed to underwater stimuli of .25 and .5 kc/s. neural responses to underwater bone-conducted (bc) sound were recorded in another aquatic form, the snapping turtle, chelydridae serpentina. the morphology of the neural response suggested the involvement of the auditory system in bc responsivity. bc hearing appears to be ...19836679547
morphogenesis of the cranial segments and distribution of neural crest in the embryos of the snapping turtle, chelydra serpentina.recent studies of the heads of vertebrates have shown a primitive pattern of segmentation in the mesoderm and neural plate not previously recognized. the role of this pattern in the subsequent distribution of cranial crest and the development of branchial arches and cranial nerves, may resolve century-old arguments about the evolution of vertebrate segmentation. in this study, we examine the early embryonic development of the cranium of a primitive amniote, the snapping turtle, with the sem. we ...19846706002
turtle lymphocyte surface antigens in chelydra serpentina as characterized by rabbit anti-turtle thymocyte sera.spleen and thymus suspensions from the turtle, chelydra serpentina were examined by indirect immunofluorescence with a rabbit anti-turtle thymocyte serum (ratt). after the species-specific antibodies had been absorbed out, the antisera labeled all lymphocytes in the thymus and spleen. the specificity of ratt for thymocytes was greater than the specificity for splenic lymphocytes. the presence of two antigens, one thymus specific, ts, and another shared by both thymocytes and splenic lymphocytes, ...19846734872
the development of segmentation in the cranial region of vertebrate embryos.the purpose of this review is to show how the development of metameric pattern in the mesoderm of vertebrate embryos is related to cranial segmentation. direct visual evidence is presented which shows that the segmental development of several vertebrate embryos is initiated as early as gastrulation. in the paraxial mesoderm of the head, somitomeres, identified in stereo with the sem, accumulate as tandem units. somitomeres remain contiguous in the cranial region, but separate from one another in ...19826763329
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
somite formation in cultured embryos of the snapping turtle. chelydra serpentina.a simple, reliable method for the in vitro cultivation of snapping turtle embryos was demonstrated. this technique was used to study somite formation in explants containing segmental plates. segmental plates formed a full complement of somites whether the neural tube or the neural tube and notochord was present. explanted snapping turtle segmental plates formed an average of 6.6 +/- 1.2 somites. removal of the node region or tail bud from cultured intact embryos led to a cessation of somite form ...19807217866
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
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
purification of thyrotropin from the pituitaries of two turtles: the green sea turtle and the snapping turtle. 19817286628
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
temporal and spatial characteristics of the voltage response of rods in the retina of the snapping turtle.1. in response to strong, large-field flashes the dark-adapted rods of chelydra serpentina gave initial hyperpolarizing responses of 30-40 mv, declining rapidly to plateaus of 10-15 mv which lasted 20 sec or more.2. in the most sensitive cells the flash-sensitivity at 520 nm to a large illuminated area was 3-6 mv per photoisomerization (assuming an effective collecting area of 13.6 mum(2)).3. the initial response to a step of light agreed with that predicted by super-position from the flash resp ...19807381784
the rate of conversion of [14-(14)c]pregnenolone to [4-(14)c]progesterone by corpora lutea of the snapping turtle, chelydra serpentina. 19807419051
water relations of pliable-shelled eggs of common snapping turtles (chelydra serpentina). 19807427826
characteristics of growth hormone isolated from sturgeon (acipenser güldenstädti) was isolated and characterized from pituitaries of a primitive bony fish, sturgeon (acipenser güldenstädti). sturgeon gh was very active in a mammalian gh assay, the rat tibia test. relative to ovine gh (nih-gh-s9), sturgeon gh gave a parallel dose-response slope and had a potency of 0.4. sturgeon gh also showed strong cross-reaction in a snapping turtle gh ria, comparable to that shown by tetrapod ghs and much greater than that of modern bony fish (teleost) gh. these results, predicted by ea ...19817449727
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
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
temperature-dependent sex determination in the snapping turtle: manipulation of the embryonic sex steroid certain reptiles with temperature-dependent sex determination (tsd), estrogens act as a signal for female differentiation. because aromatase produces estrogens from androgens, this enzyme plays a pivotal role in tsd. whether androgens act as the signal for male differentiation in tsd species in not yet clear. we manipulated the hormonal environment in eggs of the common snapping turtle (chelydra serpentina) to determine the effects of an estrogen (estradiol 17-beta), an aromatase inhibitor (f ...19947851724
dermatophilus chelonae sp. nov., isolated from chelonids in australia.three isolates of a previously undescribed dermatophilus sp. obtained from chelonids (two strains obtained from turtles and one strain obtained from a tortoise) were compared with 30 dermatophilus congolensis isolates obtained from australian mammals. the microscopic appearance, the colony morphology, and most biochemical test results for the chelonid isolates were characteristic of the genus dermatophilus. our isolates differed from the mammalian d. congolensis isolates in a number of cultural ...19957857807
molecular mechanisms of tsd in reptiles: a search for the magic bullet.significant progress has been made in understanding mechanisms of genetic sex determination. the zfy gene encodes a zinc finger protein but is not the primary signal in sex determination. the sry gene is the testis determining gene in man, mouse, rabbit, and probably marsupial mouse and wallaby. temperature dependent sex determination probably involves a modification of development of the indifferent gonad due to differential expression of one or more specific dna sequences whose behavior is con ...19947931129
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