Publications

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 ...	1988	3077109
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 ...	2009	2900107
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 ...	1987	2886260
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 ...	1985	2864192
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 ...	1989	2614338
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 ...	1989	2599345
temperature dependence of in vitro pituitary, testis, and thyroid secretion in a turtle, pseudemys scripta.	in 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 ...	1989	2512196
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 ...	1989	2506623
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 ...	1985	2468693
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 ...	1991	1908525
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%). ...	2006	1674911
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 ...	1991	1657579
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 ...	1992	1635020
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 ...	1992	1597811
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 ...	1992	1592234
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 ...	2004	1520837
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 ...	1992	1292011
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 ...	1976	1261497
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 ...	1976	1248046
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 ...	1975	1133790
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 ...	1975	1133789
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 ...	1975	1081972
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 ...	1975	1060111
[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 ...	1976	1007875
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 ...	1976	986460
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 ...	1976	950599
ultrastructural analysis of normal and immunized spleen of the snapping turtle, chelydra serpentina.	in 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 ...	1976	945353
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, ...	1976	945352
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 ...	1976	821743
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 ...	1976	819649
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 ...	1978	730848
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 ...	1977	592191
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 ...	1979	515558
mixed rod-cone responses in horizontal cells of snapping turtle retina.		1979	473609
the effect of malnutrition on immunocompetence and whole body resistance to infection in chelydra serpentina.		1979	437240
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.	1979	429947