Search PubMed⌕ Search

SEARCH · Search PubMed

Results for “Turtles”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 577 records · Page 32Linked to original sources
PubMed1989

Glycemia and immunohistochemical changes in the endocrine pancreas of the turtle Chrysemys dorbigni treated with streptozotocin.

The diabetogenic action of streptozotocin (SZ) was investigated in the turtle Chrysemys dorbigni after a 1- or 14-day fast. SZ (130 or 250 mg/kg) was injected intravenously, and blood glucose and plasma insulin were measured. Pancreatic endocrine cells were stained immunohistochemically by the immunoperoxidase avidin-biotin-peroxidase complex method. Only 14% of the SZ-treated turtles showed hyperglycemia. Prolonged fasting did not increase the percentage of hyperglycemic animals. In control turtles, insulin (beta)-, glucagon (alpha)- and somatostatin (delta)-immunoreactive cells were detected in increasing order of frequency. The qualitative changes seen in cells from the hyperglycemic SZ-treated turtles were more evident in beta and delta cells.

Animals↗
PubMed1985

Plasma membrane proton-ATPase of a turtle bladder epithelial cell line.

Urinary acidification by the turtle bladder is mediated by a proton ATPase located in the apical membrane. The present study describes a proton ATPase in the plasma membrane of a cell line of turtle bladder epithelial cells. In the presence of ouabain to inhibit Na+,K+-ATPase and in the absence of Ca2+ to inhibit Ca2+-ATPase, we measured ATPase activity of the plasma membranes of the cultured cells. This ATPase was resistant to oligomycin but sensitive to dicyclohexylcarbodiimide, N-ethylmaleimide, and vanadate. In the presence of ATP, the ATPase was capable of acidification as assessed by quenching of acridine orange. Acidification could not be elicited by other nucleotides (GTP, UTP). Acidification was inhibited by dicyclohexylcarbodiimide, N-ethylmaleimide, and vanadate but was not affected by replacement of Na+ by K+. The acidification response was dependent on the presence of chloride, abolished in the presence of gluconate, and inhibited partially by nitrate. Experiments utilizing the voltage-sensitive dye 3,3'-dipropylthiodicarbocyanine iodide showed that the proton ATPase was electrogenic and capable of responding to a favorable electric gradient. In summary, the turtle bladder epithelial cell line has a plasma membrane proton ATPase which is similar to the proton ATPase of turtle bladder epithelium and thus should allow purification and characterization of this enzyme.

Acridine Orange↗
PubMed1985

The co-occurrence of a substance P-like peptide and cholecystokinin-8 in a fiber system of turtle cortex.

Single-label and double-label immunohistochemical techniques were used to demonstrate the coexistence of substance P-like immunoreactivity (SPLI) and cholecystokinin-8-like immunoreactivity (CCK-8-LI) in an extensive fiber system within the telencephalic cortex of turtle. All SPLI-containing fibers and terminals of this system contain CCK-8-LI and vice versa. The fibers of this system course from more medial cortical regions to more lateral ones, originating either from neurons in the more medial cortices or from extracortical neurons, the axons of which ascend the medial wall of the cortex. The precise location of the neurons that give rise to this cortical projection system is uncertain, but a hypothalamic location seems most likely at present. The fibers and terminals of this system are found throughout the entire mediolateral and rostrocaudal extent of the telencephalic cortex of turtle and are largely confined to the cell body layer of the cortex. Fewer SPLI/CCK-8-LI-containing fibers are found in pyriform (olfactory) cortex than in the other cortices. Ultrastructural studies indicate that SPLI/CCK-8-LI-containing terminals make asymmetric synapses on cell bodies or their proximal dendrites. Both SPLI and CCK-8-LI are found in large dense core vesicles in these labeled terminals. Labeled terminals also contained numerous small, round, unlabeled vesicles clustered near synaptic release sites and a number of unlabeled large dense core vesicles. Quantification of the percentage of the large dense core vesicles that were labeled in SP-labeled terminals, in CCK-8-labeled terminals, and in terminals labeled for both SP and CCK-8 provided suggestive evidence that SPLI and CCK-8-LI must be contained within the same large dense core vesicles. Radioimmunoassay indicated that the SP/CCK-8-containing system of turtle cortex contains 0.93 +/- 0.090 pg of SP/microgram of cortical tissue protein and 0.31 +/- 0.11 pg of CCK-8/micrograms of cortical tissue protein. The CCK-8-like material in turtle cortex coelutes with CCK-8-sulfate, using gradient elution high pressure liquid chromatography (HPLC). The SP-like material, although immunologically highly similar to undecapeptide SP (Reiner, A., J. E. Krause, K. T. Keyser, W. D. Eldred, and J. F. McKelvy (1984) J. Comp. Neurol. 226: 50-75), does not coelute with undecapeptide SP using gradient elution HPLC.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1984

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 experiments from a previous study (Packard, 1980b) of snapping turtle segmental plates were repeated, but, instead of culturing the explants and observing the numbers of somites that formed, the explants were fixed immediately for scanning electron microscopy and the number of somitomeres was counted. The segmental plates were found to contain an average of 6.5 +/- 0.7 somitomeres, which is almost identical to the average number of somites formed by such segmental plates when cultured (6.6 +/- 1.2). Furthermore, the number of somitomeres was identical in right and left explants removed from the same embryo, and the number of somitomeres was consistent regardless of the length of the segmental plate. Both of these observations are identical to those made previously for somite formation in culture. This association between numbers of somitomeres and somites strongly suggests that one gives rise to the other. Finally, it was demonstrated that for each somite formed by a segmental plate in culture, the segmental plate contained one less somitomere. This showed in a direct manner that turtle somitomeres become somites. It was concluded that the segmental plate mesoderm of snapping turtle embryos is already segmented, and that the 'segmentation' seen under a dissecting microscope is actually the final stage of somitomere differentiation into an epithelial somite.

Animals↗
PubMed1983

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 a reception mechanism for marine turtles with the skull and shell acting as receiving surfaces. Turtles are capable of receiving the low-frequency spectrum of the natal beach, which may serve as one of the cues in nesting returns.

Animals↗
PubMed1981

Evidence for auditory localization ability in the turtle.

Evidence is presented that the semiaquatic turtle Chrysemys scripta and the terrestrial turtle Terrapene carolina major can detect the direction of a tone within their sensitive area of hearing. It is further suggested that not only can these species respond behaviorally to sound without extensive manipulation but can use limited hearing in a problem-solving situation of maze learning. Adult emydid turtles (5 C. scripta, 3 T. carolina) learned a Y-maze with a 500-c/s signal to an invisible open goal box to avoid bright light. All animals performed above chance levels, but it required over 240 trials on the average to reach 60%-correct performance. Computations suggest that binaural cues used by mammals would not be adequately encoded by the primitive auditory systems of the species studied. It is further suggested that these turtles use bone conduction by coupling their ears to the substrate to hear vibrations in the immediate area. This would appear to be a carryover from the ancient reptile stem stock. The poor middle-ear impedance system relegates air-borne sound processing to be a somewhat insensitive limited low-pass system, depending heavily on monaural cues derived from head scanning. vocal output in these species appears to be spectrally imbalanced with their auditory sensitivity. The role of species-specific vocal signalling is unclear from the present data.

Animals↗
PubMed1980

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 formation after an additional 6.1 +/- 1.8 somites had formed. These results indicate the number of somites the snapping turtle segmental plate will form. Also, the number of somites formed by explanted segmental plates showed only slight variation over a wide range of segmental plate lengths. It was concluded that while snapping turtle segmental plates formed significantly fewer somites than chicken or Japanese quail segmental plates, they were similar to the avian explants in their ability to form a consistent number of somites regardless of the length of the segmental plate.

Animals↗
PubMed1978

[Parasites of fresh water turtles in Tunisia].

A survey work during 1974-75 on the parasites of aquatic turtles of Tunisia, twenty one specimens (9 males and 12 females) were captured in the watercourses of the northern area of Tunisia and dissected in the Institut Pasteur of Tunis. These turtles belong to the species; Clemmys caspica var. leprosa and Emys orbicularis (L. 1758). The following parasites were recovered from these turtles: Trematodes: Polystomoides tunisiensis and Telorchis temimi (Gonzalez and Mishra, 1977) and T. solivagus (Odhner, 1902); Nematodes: Camallanus parvus (Eduardo Caballero, 1939); Spiroxys contortus (Rudolphi, 1819) and Spironoura lambdiensis (Seurat, 1918); Protozoa: Haemogregarina stepanovi (Dan, 1886) and Entamoeba invadens (Geiman and Ratcliff, 1936). Ectoparasites: Placobdella costata (Moquin - Tandom). In addition to these parasites, unidentified nematode larvae were detected on several occasions; in the bile ducts and within the hepatic cysts of the turtles examined. Two trematodes P. tunisiensis and T. temimi are recorded and described for the first time.

Animals↗
PubMed1995

Detection by ELISA of circulating anti-blood fluke (Carettacola, Hapalotrema, and Learedius) immunoglobulins in Hawaiian green turtles (Chelonia mydas).

An enzyme-linked immunosorbent assay (ELISA) is described utilizing the surface glycocalyx crude antigen of adult blood trematodes Learedius learedi, Hapalotrema dorsopora, and Carettacola hawaiiensis, for the detection of circulating antibodies (Ab) in Hawaiian green turtles (Chelonia mydas) naturally infected with the parasites and with or without green turtle fibropapillomatosis (GTFP). A concentration of 10.0 micrograms/ml of antigen was optimal in terms of test specificity and sensitivity. A direct ELISA with anti-reptilian/amphibian phosphatase-labeled IgG identified C. mydas Ab at a dilution of 1/12,800. Utilizing indirect ELISA, it was possible to detect Ab to blood flukes at a dilution of 1/3,200. The gross lesions and histopathology were typical for cardiovascular spirorchidiasis in C. mydas. No significant relationship was found between the size of turtles and the degree of GTFP severity. Forty-seven of 59 (80%) samples, from 5 sites, gave a positive ELISA reaction; 6 of the 47 (13%) specimens gave significantly (P < 0.001) higher absorbance values, with 5 from the same location. All 12 (20%) ELISA-negative turtles originated from 1 site, and the absorbance values of the 41 animals from this location were significantly lower (P < 0.015) when compared with the other 4 sites. The proposed assay is fast, has the feature of visual scoring, and can be used for determination of exposure of C. mydas to the spirorchid trematodes.

Animals↗
PubMed1993

[The phase-dependent response of the heart to vagal stimulation in soft-shelled turtles].

Using cardiac cycle length (A-A interval) as an index, the effect of phase-coupled burst of vagal stimulation on the heart rate were investigated in 27 turtles. The negative chronotropic response depended on timing of the stimulus burst within the cardiac cycle. At first, the A-A interval was lengthened progressively and then showed a rapid decrease. The amplitude (AT) of the mean phase-response curve to right vagal stimulus in turtles treated by propranolol at normal temperature was 1484.10 +/- 213.10 ms. The minimum-to-maximum phase difference of the response curves was 804.00 +/- 210.90 ms. Both the AT and (St-A)max of the response curve varied directly with AA. In contrast, (St-A)min was not influenced by AA. Moreover, it was also found that the tau FR, AT, AA and (St-A)min in hibernant animals were all higher than those in normal ones. However, in three of the six hibernant turtles maximum positive chronotropic response could be elicited at the time when (A-A)min was elicited by vagal stimulation. The results indicated that the phase-dependent response to right vagus in turtles was similar to that in homothermal animals, but significantly different both in the amplitude of the phase-response and the latency of negative chronotropic response. Since the phase-response was abolished by atropine, not by propranolol, it was suggested that the occurrence of phase-response was due to changes of responsiveness of automatic cells to ACh released from the vagus nerve.

Animals↗
PubMed1993

Structural studies on the loggerhead sea turtle (Caretta caretta) myoglobin.

The primary structure of myoglobin from the loggerhead sea turtle (Caretta caretta) has been determined; the protein consists of 153 amino acid residues. The ferric loggerhead sea turtle myoglobin has been crystallized in a form suitable for X-ray structural investigations. The crystals were grown at pH 8.0, in 0.05 M tris/HCl buffer, using 3.2 M ammonium sulfate as precipitating agent, at 4 degrees C, and belong to the orthorhombic space group P2(1)2(1)2(1), with unit cell constants a = 37.2 A, b = 61.1 A, c = 75.2 A (one molecule, 17,000 M(r), in the asymmetric unit). A molecular replacement solution was found for the loggerhead sea turtle myoglobin crystals using sperm whale myoglobin structure as search model. The R-factor value, after molecular replacement, is 0.387, for the data in the 15-3.3 A resolution range. The results here reported are the basis for the first X-ray crystallographic investigation on a reptile myoglobin, and indicate a strong overall structural similarity between the loggerhead sea turtle and mammalian (i.e. sperm whale) myoglobins.

Amino Acid Sequence↗
PubMed1997

Neural circuitry and light responses of the dopamine amacrine cell of the turtle retina.

PURPOSE: To understand the circuitry and electrophysiology of the dopamine cells in the turtle retina. METHODS: Preembedding immunocytochemistry for tyrosine hydroxylase (Toh) was done on vibratome sections of turtle retina. Resultant Toh-immunoreactive (Toh-IR) amacrine cells were then serially thin-sectioned for analysis by electron microscopy (EM). Some sections of Toh-IR cells also were post-embedding immunostained for glycine and GABA content. Intracellular recordings and dye markings were made from the turtle eyecup and slice preparation to determine the light responses of cells called A28, which have the same morphology as Toh-IR amacrine cells. RESULTS: Physiologically A28 cells were L-type (luminosity) and gave sustained depolarizing (ON-center) responses to light pulses. High intensity light pulses produced immediate transients and long depolarizations, lasting beyond the stimulus duration. An after-hyperpolarization and an antagonistic surround could be elicited. EM reconstruction of a Toh-IR cell revealed new circuitry over that described before (Pollard, J. & Eldred, W.D. (1990). J. Neurocytol. 19, 53-66). Bipolar ribbon synapses occurred in all three dendritic tiers. However, amacrine cell inputs dominated numerically (95% amacrine input, 5% bipolar input) many of them in a serial synaptic configuration. GABA+ inputs were seen but not glycine+ inputs. Output from Toh-IR profiles was primarily to large ganglion cell dendrites but also to bipolar cell axons, GABA-IR amacrines, unspecified amacrine cells and other Toh-IR dendrites. CONCLUSIONS: The synaptology of the dopamine cells of the turtle retina suggests that sustained inhibitory amacrine cell pathways, including GABAergic pathways, are chiefly responsible for their response characteristics at low light levels. Conversely, at higher light intensities, transient excitatory amacrine cells probably have influence.

Animals↗
PubMed1997

Simulated hibernation of sea turtles in the laboratory: I. Feeding, breathing frequency, blood pH, and blood gases.

Captive immature green (Chelonia mydas) and Kemp's ridley (Lepidochelys kempi) sea turtles were examined to determine if a hibernation-like state could be induced under controlled conditions. Both species demonstrated that they are able to acclimate to cold temperatures behaviorally. However, the two species appeared to respond differently to decreasing temperature. Whereas the green turtles tolerated the onset of cold water temperatures by reducing swimming activity, the ridleys became very agitated and active as they were exposed to temperatures below 20 degrees C. Nevertheless, both species displayed semi-dormant behavior at temperatures below 15 degrees C, coming to the surface to breathe periodically at intervals of up to three hours. At low temperatures, venous blood pO2 and pCO2 decreased, whereas venous blood pH increased. Feeding also decreased as either species was exposed to cold temperature: greens (at 15 degrees C) and ridleys (at 20 degrees C) decreased food consumption to 50% of control levels, and ceased feeding below 15 degrees C. Thus, these species tolerated temperature drops and the associated hypophagia. They did not exhibit cold-stunning behavior, as has been observed in wild sea turtles exposed to rapid temperature drops, or prolonged periods of hibernation-like dormancy, as has been proposed for wild sea turtles during cold winter months.

Animals↗
PubMed1998

Reconstruction of flexor/extensor alternation during fictive rostral scratching by two-site stimulation in the spinal turtle with a transverse spinal hemisection.

Analyses of fictive scratching motor patterns in the spinal turtle with transverse hemisection provided support for the concept of bilateral shared spinal cord circuitry among neurons responsible for generating left- and right-side rostral, pocket, and caudal fictive scratching. Rhythmic bursts of hip flexor activity, the hip extensor deletion variation of fictive rostral scratching, were elicited by ipsilateral stimulation in the rostral scratch receptive field of a spinal turtle [transection at the segmental border between the second (D2) and third (D3) postcervical spinal segments] with a contralateral transverse hemisection one segment anterior to the hindlimb enlargement (at the D6-D7 segmental border). In addition, other sites were stimulated in this preparation: (1) contralateral sites in a rostral, pocket, or caudal scratch receptive field or (2) ipsilateral sites in a caudal scratch receptive field. A reconstructed fictive rostral scratch motor pattern of rhythmic alternation between hip flexor and hip extensor activation was produced by simultaneous stimulation of one site in the ipsilateral rostral scratch receptive field and another site in one of the other scratch receptive fields. This reconstructed rostral scratch motor pattern resembled the normal rostral scratch motor pattern produced by one-site rostral scratch stimulation of a spinal turtle (D2-D3 transection) with no additional transections. The observation of a reconstructed rostral scratch motor pattern produced by two-site stimulation in the spinal turtle with transverse hemisection supports the concept that hip extensor circuitry activated by stimulation of other scratch receptive fields is shared with circuitry activated by ipsilateral rostral scratch receptive field stimulation.

Animals↗
PubMed1998

Localization of the origin of retinal efferents in the turtle brain and the involvement of nitric oxide synthase.

Previous studies have used selective neurochemical markers or retrograde tracers to localize the cells in the brain giving rise to efferents to the turtle retina. Because of the relative selectivity of the neurochemical markers or the lack of sensitivity of the previously employed retrograde tracers, these studies did not locate all the efferent cell bodies, or they could not describe the anatomy of the efferent cells. In the present study, cholera toxin B was used as a highly sensitive retrograde tracer to investigate the distribution, number, and morphology of the retinal efferent or centrifugal cell system in turtle brain. Previous studies of the turtle retina have indicated that nitric oxide synthase may be found in some retinal efferents. Therefore, we also did colocalization studies of the retrograde tracer with reduced nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase histochemistry to investigate nitric oxide as a possible transmitter used by efferent fibers and to localize these NADPH-diaphorase-positive efferent cell bodies in the turtle brain. We found that each eye received projections from approximately 40 efferent cell bodies that were located primarily in the contralateral midbrain. The majority of efferent cell bodies were centered in the isthmic tegmentum; other efferent cells extended more rostrally into the substantia nigra, and some efferent cells extended more caudally into the nucleus raphes superior. The double-label results showed that 30% of the cholera toxin B-like immunoreactive cells were also positive for NADPH-diaphorase. The location of these double-labeled cells around the locus coeruleus corresponded to the NADPH-diaphorase-positive efferent cells in the avian isthmo-optic field. The localization of NADPH-diaphorase in these efferents indicated that they may use nitric oxide to modulate retinal function.

Animals↗
PubMed1998

Morphologic and cytochemical characteristics of blood cells from Hawaiian green turtles.

OBJECTIVE: To identify and characterize blood cells from free-ranging Hawaiian green turtles, Chelonia mydas. SAMPLE POPULATION: 26 green turtles from Puako on the island of Hawaii and Kaneohe Bay on the island of Oahu. PROCEDURE: Blood was examined, using light and electron microscopy and cytochemical stains that included benzidine peroxidase, chloroacetate esterase, alpha naphthyl butyrate esterase, acid phosphatase, Sudan black B, periodic acid-Schiff, and toluidine blue. RESULTS: 6 types of WBC were identified: lymphocytes, monocytes, thrombocytes, heterophils, basophils, and eosinophils (small and large). Morphologic characteristics of mononuclear cells and most granulocytes were similar to those of cells from other reptiles except that green turtles have both large and small eosinophils. CONCLUSIONS: Our classification of green turtle blood cells clarifies improper nomenclature reported previously and provides a reference for future hematologic studies in this species.

Animals↗
PubMed1999

Effect of tagging marine turtles on nesting behaviour and reproductive success.

We studied green, Chelonia mydas, and loggerhead, Caretta caretta, turtles nesting on the island of Cyprus to determine the effects of flipper tagging on postovipositional behaviour and reproductive success. Tagging was undertaken immediately after oviposition (64 green turtles; 111 loggerheads). On 12 occasions, loggerheads immediately stopped covering the eggs and proceeded directly to the sea. No green turtles abandoned nesting. In all other cases, where sufficient data were collected, the duration of the two postovipositional phases of nesting behaviour (covering and camouflaging) and the speed of descent to the sea did not differ between tagged and untagged turtles. The durations of behaviours also did not differ between females not tagged, tagged once or tagged twice. There was no effect of tagging on the likelihood of hatching or on the hatching success of clutches in either species. Copyright 1999 The Association for the Study of Animal Behaviour.

Journal Article↗
PubMed2001

Characteristics of nest soil, but not geographic origin, influence cold hardiness of hatchling painted turtles.

We investigated environmental factors influencing cold hardiness in hatchling painted turtles (Chrysemys picta) indigenous to northeastern Indiana and the Sandhills of west-central Nebraska. In both locations, hatchlings overwinter in their natal nests. Survival of hatchlings chilled to minimum temperatures between -2.5 and -6.0 degrees C inside explanted natal nests ranged from 30 to 100%. Mortality likely was caused by freezing of the turtles that was induced by contact with ice nuclei in the surrounding soil. Susceptibility to inoculative freezing was strongly influenced by moisture content (7.5-25%, w/w) of the frozen soil in which hatchlings were cooled. When chilled in soil containing 15% moisture, turtles from Indiana resisted inoculative freezing better than hatchlings from Nebraska, but this variation was due to physical characteristics of the soils indigenous to each locale rather than genetic differences between populations. Soil in which the Indiana turtles nested contained relatively higher amounts of clay and organic matter, and bound more moisture, than the loamy sand at the Nebraska site. Soil collected from both locales contained potent ice nuclei that may constrain supercooling of the hatchlings, even in the absence of soil moisture. In addition to temperature and precipitation, local and regional variation in soils is an important determinant of overwintering survival of hatchling C. picta.

Journal Article↗