Publications

endogenous yolk steroid hormones in turtles with different sex-determining mechanisms.	maternal transfer of nutrients, including steroid hormones, to embryos during gestation in viviparous amniotes is well known, but the concordant process in oviparous amniotes is poorly understood. recent evidence suggests that steroid hormones are present in freshly laid eggs of archosaurs and that their concentrations may influence offspring phenotypes. this process might be especially important in reptiles with temperature-dependent sex determination (tsd), because embryonic sex determination ...	1998	9707477
chelonacarus elongatus n. gen., n. sp. (acari: cloacaridae) from the cloaca of the green turtle chelonia mydas (cheloniidae).	chelonacarus elongatus n. gen., n. sp. is proposed for a cheyletoid mite (acari: prostigmata) of the family cloacaridae found in the cloacal tissue of the endangered green turtle chelonia mydas linnaeus, 1758 from the atlantic coast of the republic of panama. in females, the new genus is distinguished from other genera of turtle cloacarids by the elongate slender shape of the idiosoma, the shape and pattern of sclerotization of the dorsal shield, and the fused distal ends of apodemes ii. a combi ...	1998	9714221
kinematics of aquatic and terrestrial prey capture in terrapene carolina, with implications for the evolution of feeding in cryptodire turtles.	studies of aquatic prey capture in vertebrates have demonstrated remarkable convergence in kinematics between diverse vertebrate taxa. when feeding in water, most vertebrates employ large-amplitude hyoid depression to expand the oral cavity and suck in water along with the prey. in contrast, vertebrates feeding on land exhibit little or no hyoid depression. in this study we compared the kinematics of terrestrial and aquatic prey capture within one species of turtle, terrapene carolina, in order ...	1998	9658591
environmental occurrence and potential toxicity of planar, mono-, and di-ortho polychlorinated biphenyls in the biota.	four non-ortho-, eight mono-ortho-, and two di-ortho-chlorinated congeners have been determined in fresh water and salt water mussels, fish, snapping turtles, mallard, seals, and in human milk and adipose tissue. the planar pcb congeners are separated from the remainder of pcbs by activated carbon chromatography or hplc on porous graphitic carbon followed by gas chromatography with electron capture detection. pcb toxic equivalency factors (tefs) recommended by who [1] for 3 non-ortho, 8 mono-ort ...	1998	9503581
lead poisoning and intestinal perforations in a snapping turtle (chelydra serpentina) due to fishing gear ingestion.	an adult male snapping turtle (chelydra serpentina) was presented to the tufts wildlife clinic with generalized weakness and limited ability to walk. a fishing hook was lodged in the corner of its mouth, monofilament line trailed from its cloaca, and radiography revealed that the turtle had ingested two additional hooks and a large sinker. the hemogram showed leukocytosis. at exploratory celiotomy, the fishing line was seen to have acted as a linear foreign body and had perforated the intestines ...	1997	9226626
the regulation of tyrosinase gene transcription.	tyrosinase is one of the key enzymes essential for melanogenesis. the control of its activity rests in part at the level of transcriptional regulation. the 5' promoter regions of the human, mouse, chicken, quail, snapping turtle, and frog tyrosinase sequences have been isolated and the mechanisms regulating the activity of these sequences are beginning to be elucidated. this review provides an update on the following aspects of tyrosinase gene regulation: basal promoter elements that determine t ...	1997	9266599
purification and partial amino acid sequences of two distinct albumins from turtle plasma.	two putative albumins, denoted alb-1 (apparent molecular mass of 67 kda) and alb-2 (68 kda), were purified from plasma of the emydid turtle (trachemys scripta). concentrations in serum or plasma were determined by radioimmunoassay using 125i-labeled alb-1. in juvenile turtles (less than 2 years of age), serum concentrations of alb-1 and alb-2 were 2.72 +/- 0.23 mg/ml and 1.68 +/- 0.22 mg/ml, respectively, while concentrations in plasma pooled from adult turtles were 4.2 mg/ml and 2.6 mg/ml, resp ...	1997	9440230
abundant synthesis of transthyretin in the brain, but not in the liver, of turtles.	the binding of thyroxine to proteins in the blood plasma of the turtle, trachemys scripta, was analyzed by incubation with radioactive thyroxine, electrophoresis and autoradiography. albumin and an alpha-globulin were found to bind thyroxine; no thyroxine-binding transthyretin was detected in the prealbumin region. in contrast to blood plasma, a thyroxine-binding prealbumin was observed in medium from t. scripta choroid plexus incubated in vitro. rna was extracted from brain tissue containing ch ...	1997	9253180
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 ...	1997	9523632
seasonal changes in gonadal activity and the effects of stress on reproductive hormones in the common snapping turtle, chelydra serpentina.	the seasonal gonadal cycle (including gonadal histology, sex steroids, and gonadotropins) was studied in freshly captured common snapping turtles, chelydra serpentina, from wisconsin, and the effects of capture stress were evaluated. the ovarian and testicular cycles are shorter than those reported in other freshwater turtles; the cycles commence in mid-may and terminate in early september, immediately after the completion of gonadal growth and maturation. in the female, testosterone (t), 17beta ...	1997	9268617
heart rate during development in the turtle embryo: effect of temperature.	growth and development can occur over a wide range of physical conditions in reptiles. cardiovascular function must be critical to this ability. however, information on cardiovascular function in developing reptiles is lacking. previous work indicated that in reptiles the effects of temperature on growth and metabolism are largely restricted to early development. this study examined whether the previously observed effects of temperature and different perinatal patterns of metabolism observed in ...	1996	8981759
temporal and geographic variation of organochlorine residues in eggs of the common snapping turtle (chelydra serpentina serpentina) (1981-1991) and comparisons to trends in the herring gull (larus argentatus) in the great lakes basin in ontario, canada.	common snapping turtle (chelydra serpentina serpentina) eggs from five sites within the great lakes basin, and from a reference site in north-central ontario were collected during 1981-1991 and analyzed for four organochlorine pesticides, polychlorinated biphenyls (pcbs) including six non-ortho pcbs, polychlorinated dibenzodioxins (pcdds), and polychlorinated dibenzofurans (pcdfs). the pattern of geographic variation was consistent over time in eggs with cootes paradise/ hamilton harbour and lyn ...	1996	8975824
comparative effects of diverse vertebrate gonadotropins on estradiol-17 beta formation in vitro in an immature rat sertoli cell bioassay.	the biopotencies of pituitary gonadotropins (gths) from various vertebrate classes were examined in an in vitro rat sertoli cell bioassay which was previously established for mammalian follicle-stimulating hormones (fshs). potencies of the gonadotropins were determined by incubation of sertoli cells obtained from 10-day-old rats, with increasing doses of gths, which resulted in dose-related and parallel estradiol-17 beta formation converted from added 19-hydroxy-androstenedione. in general, mamm ...	1996	8930616
purification and characterization of plasma vitamin d binding protein from the snapping turtle, chelydra serpentina.	vitamin d binding protein (dbp) was isolated from the plasma of the snapping turtle, chelydra serpentina (mixed sex adult), and compared with the previously characterized dual function binding plasma protein that binds both thyroxine (t4) and vitamin d (tstdbp) in an emydid turtle, trachemys scripta. purification of chelydra serpentina dbp (csdbp) was accomplished by ion exchange chromatography, preparative polyacrylamide gel electrophoresis, and reverse-phase high-performance liquid chromatogra ...	1996	8954770
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 ...	1995	7857807
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 ...	1995	7584861
experimental evidence for the evolutionary significance of temperature-dependent sex determination.	the evolutionary significance of sex-determining mechanisms, particularly temperature-dependent sex determination (tsd) in reptiles, has remained unresolved despite extensive theoretical work. to investigate the evolutionary significance of this unusual sex-determining mechanism, i incubated eggs of the common snapping turtle (chelydra serpentina) at a male-producing temperature (26°c), a female-producing temperature (30°c), and an intermediate temperature that produced both sexes about equally ...	1995	28564861
temperature-dependent sex determination in the snapping turtle: manipulation of the embryonic sex steroid environment.	in 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 ...	1994	7851724
sequence analysis of the zfy and sox genes in the turtle, chelydra serpentina.	we have sequenced regions of the zfy and sox genes in the turtle chelydra serpentina, a reptile with temperature-dependent sex determination. the zfy gene in mammals encodes a transcription factor with multiple zinc fingers that may be involved in spermatogenesis as well as other processes. the turtle homologue, zft, is 92% identical to the zfy gene at the nucleotide and amino acid levels in the region of zinc fingers 7-12. there are several sox genes in the turtle that are only 57-70% identical ...	1994	8025725
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 ...	1994	7931129
the amino acid sequence of iguana (iguana iguana) pancreatic ribonuclease.	the pyrimidine-specific ribonuclease superfamily constitutes a group of homologous proteins so far found only in higher vertebrates. four separate families are found in mammals, which have resulted from gene duplications in mammalian ancestors. to learn more about the evolutionary history of this superfamily, the primary structure and other characteristics of the pancreatic enzyme from iguana (iguana iguana), a herbivorous lizard species belonging to the reptiles, have been determined. the polyp ...	1994	8307028
comparative studies of thyroxine binding proteins in turtle plasma using column chromatography.	thyroxine (t4) binding proteins in turtle plasma were compared with those of various mammalian and nonmammalian (fish, birds) species using gel filtration chromatography (bio-gel). high-affinity t4 binding was observed in all mammals studied, in the chicken, and in one species of turtle, trachemys scripta. this high affinity t4 binding protein (tbp) appears to be the major component of t4 transport in the turtle; selective removal of this tbp greatly diminished binding activity in t. scripta pla ...	1993	8428644
binding affinities of thyroxine-binding proteins in turtle plasma.	binding affinities (ka) for thyroxine (t4) by blood plasma and purified plasma proteins from two turtles, the slider (trachemys scripta) and snapper (chelydra serpentina), were compared with those of a human using equilibrium dialysis. the purified t4 binding protein (tbp) from t. scripta had a high affinity that was lower by about fivefold than that of human tbg (3.2 x 10(9) vs 1.7 x 10(10) m-1). the affinity of t4 binding by tbp was similar to that determined for whole plasma from this species ...	1993	8504925
purification and properties of alligator mississipiensis cytochrome c.	cytochrome c has been purified to homogeneity from alligator liver (alligator mississipiensis) using aluminum sulfate precipitation, cm-cellulose and gel-filtration chromatography, and reverse-phase hplc. the protein exhibited a single band on sodium dodecyl sulfate-polyacrylamide gel electrophoresis with an approximate molecular weight of 12,000 da. oxidized and reduced visible spectra yielded maxima at 408 (tau) nm and 315 (delta), 415 (tau), 520 (beta), and 550 (alpha) nm, respectively, while ...	1993	8384830
environmentally induced variation in body size of turtles hatching in natural nests.	eggs from three snapping turtles (chelydra serpentina) were divided between two natural nests in a factorial experiment assessing the role of the nest environment as a cause for variation in body size and energy reserves of hatchlings at our study site in northcentral nebraska. nest # 1 was located in an unshaded area on the south side of a high sandhill, whereas nest #2 was located in an unshaded area on level ground. eggs in nest #1 increased in mass over the course of incubation, with eggs at ...	1993	28313447
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
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
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
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
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
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
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
development of the turtle carapace: implications for the evolution of a novel bauplan.	the chelonian carapace is composed of the endochondral ribs and vertebrae associated with a specialized dermis. the ribs are found in an aberrant position compared to those of all other tetrapods; they are superficial and dorsal to the limb girdles. this morphological arrangement, which constitutes the unique chelonian bauplan, is examined from a developmental perspective. embryos of chelydra serpentina were studied during stages of carapace development. tissue morphology, autoradiography, and i ...	1989	29865619
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
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
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 ...	1988	3203874
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 ...	1988	3162890
disposition of toxic pcb congeners in snapping turtle eggs: expressed as toxic equivalents of tcdd.		1987	3120832
disposition of low and high environmental concentrations of pcbs in snapping turtle tissues.		1987	3107636
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 ...	1987	3446810
functional mechanisms and histologic composition of the lingual appendage in the alligator snapping turtle, macroclemys temmincki (troost) (testudines: chelydridae).	gross and microscopic examination of the lingual appendages of juvenile and adult alligator snapping turtles, macroclemys temmincki, shows that it is divided into an anterior horn, a body, and a posterior horn. lingual appendages of adults usually are more darkly pigmented than those of juveniles and melanocyte distribution is variable, resulting in a mottled appearance. the musculoskeletal components of the hyoid apparatus, presumably responsible for most of the motion displayed by the appendag ...	1987	29914228
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
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 ...	1986	3734671
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 ...	1986	3940901
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 ...	1986	3803892
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
electron microscopy of golgi-impregnated photoreceptors reveals connections between red and green cones in the turtle retina.	red 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 ...	1985	4031990
the development and homology of the chelonian carpus and tarsus.	the long-standing controversies involving the number and homologies of the elements of the carpus and tarsus of turtles are reviewed from a developmental perspective. the analysis is based on a detailed description of the chondrogenesis of the carpus and tarsus in the species chelydra serpentina and chrysemys picta. the first stage described is the differentiation of a y-shaped chondrogenetic condensation involving the humerus (femur)-radius/ ulna (tibia/fibula). this stage is followed by the ea ...	1985	30005563
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 ...	1985	3857207
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
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 ...	1985	4076178
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 ...	1985	4093878
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 ...	1985	3882411
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 ...	1984	6203781
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 ...	1984	6373420
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 ...	1984	6706002
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, ...	1984	6734872
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.	1984	6488024
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 ...	1984	6533256
polychlorinated biphenyl, mercury, and cadmium concentrations in minnesota snapping turtles.		1983	6404330
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 ...	1983	6308900
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 ...	1983	6310101
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 ...	1983	6183356
marine turtle reception of bone-conducted sound.	an 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 ...	1983	6679547
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 ...	1982	6763329
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 ...	1982	6890707
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.	1981	17760193
purification of thyrotropin from the pituitaries of two turtles: the green sea turtle and the snapping turtle.		1981	7286628
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 ...	1981	7241601
temperature-sensitive periods of sex determination in emydid turtles.	in 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 ...	1981	7338727
determination of temperature sensitive stages for sexual differentiation of the gonads in embryos of the turtle, emys orbicularis.	in order to determine the temperature sensitive stages for sexual differentiation of the gonads in emys orbicularis, eggs of this turtle were shifted at different stages of embryonic development from the male-producing temperature of 25°c to the female-producing temperature of 30°c and reciprocally. based on the series of developmental stages described by yntema ('68) for chelydra serpentina, temperature begins to influence sexual differentiation of emys orbicularis at stage 16, a stage in which ...	1981	30114859
characteristics of growth hormone isolated from sturgeon (acipenser güldenstädti) pituitaries.	gh 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 ...	1981	7449727
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 ...	1980	7381784
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 ...	1980	7217866
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 ...	1980	7452729
water relations of pliable-shelled eggs of common snapping turtles (chelydra serpentina).		1980	7427826
the rate of conversion of [14-(14)c]pregnenolone to [4-(14)c]progesterone by corpora lutea of the snapping turtle, chelydra serpentina.		1980	7419051
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 ...	1980	28309683
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 ...	1980	7230014
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
temperature levels and periods of sex determination during incubation of eggs of chelydra serpentina.	eggs of chelydra serpentina were shifted during incubation between the female producing temperatures of 20°c or 30°c and the male producing temperature of 26°c. in the 20°c and 26°c combination, the stages during which incubation temperature determined sex were stage 14 through stage 16 (stages of normal series, yntema, '68). in the 30°c and 26°c combination, the temperature sensitive stages for sex determination were stage 14 through stage 19. incubation at 26°c throughout this period was neede ...	1979	30205629
mixed rod-cone responses in horizontal cells of snapping turtle retina.		1979	473609
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
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
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
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
[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
effects of incubation temperatures on sexual differentiation in the turtle, chelydra serpentina.	eggs of the common snapping turtle, chelydra serpentina, were incubated at constant temperatures ranging from 20°c to 30°c, at hatching, the oviducts were absent or incomplete in males; the testes were differentiated. in females at hatching, the oviduct was intact hut in some cases the gonad retained bisexual characteristics. three months after hatching, the ovary was differentiated and contained follicles. eggs incubated at 20°c and at 30°c developed into females in 100% of the cases. at 26°c, ...	1976	30257532
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
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
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
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
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
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
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