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At least 721 records · Page 40Linked to original sources
PubMed2001

Rapid acquisition of entire DNA polymerase gene of a novel herpesvirus from green turtle fibropapilloma by a genomic walking technique.

A 4837-bp sequence of a newfound green turtle herpesvirus (GTHV), implicated in the etiology of green turtle fibropapilloma, was obtained from tumor tissues of a green turtle with fibropapilloma using a genomic walking method based on restriction enzyme digestion, self-ligation and inverse polymerase chain reaction (IPCR). The 4837-bp sequence was 56.23% G/C rich and contained three nonoverlapping open reading frames (ORF). The largest ORF (3507-bp) encoded the DNA polymerase gene (pol gene), which exhibited a high degree of homology at both amino acid and nucleotide levels with the DNA pol genes of human and animal herpesviruses, with a predicted protein of 1169 amino acids and molecular weight of 132.6 kilodaltons. The ATG at 518 to 520 was the first initiation codon in the ORF and was presumed to be the first methionine codon of the pol gene. Phylogenetic analysis, based on the amino acid sequence of the GTHV DNA pol gene and the corresponding regions of other known human and animal herpesviruses, indicated that GTHV belonged to the Alphaherpesvirinae subfamily. The upstream ORF of the pol gene encoded the N-terminal region of the GTHV homologue of the DNA-binding protein gene, whereas the downstream ORF was the C-terminal region of a gene which was homologous to ORFs conserved in human and animal herpesviruses, i.e., herpes simplex virus 1 (HSV1) gene UL31, Epstein-Barr virus (EBV) gene BFLF2, equine herpesvirus 1 (EHV1) gene 29, and alcelaphine herpesvirus 1 (AHV1) hypothetical protein 69 gene. The arrangement of these three genes in GTHV genome was identical to that seen in other alphaherpesviruses. The sequence and location of the DNA pol gene in the GTHV genome should greatly facilitate future studies of the viral life cycle.

Alphaherpesvirinae↗
PubMed2000

Identification of a small, naked virus in tumor-like aggregates in cell lines derived from a green turtle, Chelonia mydas, with fibropapillomas.

Serial cultivation of cell lines derived from lung, testis, periorbital and tumor tissues of a green turtle (Chelonia mydas) with fibropapillomas resulted in the in vitro formation of tumor-like cell aggregates, ranging in size from 0.5 to 2.0 mm in diameter. Successful induction of tumor-like aggregates was achieved in a cell line derived from lung tissue of healthy green turtles, following inoculation with cell-free media from these tumor-bearing cell lines, suggesting the presence of a transmissible agent. Thin-section electron microscopy of the cell aggregates revealed massive collagen deposits and intranuclear naked viral particles, measuring 50+/-5 nm in diameter. These findings, together with the morphological similarity between these tumor-like cell aggregates and the naturally occurring tumor, suggest a possible association between this novel virus and the disease. Further characterization of this small naked virus will clarify its role in etiology of green turtle fibropapilloma, a life-threatening disease of this endangered marine species.

Animals↗
PubMed1999

A new iridovirus isolated from soft-shelled turtle.

A virus was isolated from soft-shelled turtle (Trionyx sinensis) with 'red neck disease' on a farm in Shenzhen, China, the virus multiplied and caused a cytopathogenic effect (CPE) at 15-30 degrees C in CO, FHM, CK and BF-2 cells. The optimum conditions for replication was in CO cells at 25-30 degrees C. The virus was sensitive to chloroform treatment, acid (pH 3) or alkaline (pH 10) conditions and heating at 56 degrees C for 30 min. Treatment with 5-iodo-2-deoxyuridine (IUDR) inhibited viral replication, indicating the presence of a DNA genome. Electron microscopy of infected CO culture fluid revealed spherical particles measuring 120-160 nm in diameter. Observation of ultra-thin sections showed numerous hexagonal viral particles in the cytoplasm and nucleus of cells typical of an iridovirus. This virus was moderately virulent for turtles in infection tests. We suggest that this virus is named soft-shelled turtle iridovirus (STIV).

Animals↗
PubMed2001

Pituitary adenylate cyclase activating polypeptide is highly abundant in the nervous system of anoxia-tolerant turtle, Pseudemys scripta elegans.

The levels of the pituitary adenylate cyclase activating polypeptide (PACAP) were measured in the central nervous system and in peripheral organs of the anoxia-tolerant freshwater turtle, Pseudemys scripta elegans by radioimmunoassay. The concentration of PACAP38 was strikingly high in the central nervous system and lower but considerable immunoreactivity was detected in the peripheral organs. Levels of PACAP38 in the turtle brain exceed those measured in rat and human brain areas by 10-100-fold. Based on these exceptionally high levels of PACAP and the known neuroprotective role of the peptide, it can be suggested that PACAP38 plays a role in the extraordinary resistance of the turtle brain from anoxia-induced neuronal damage.

Animals↗
PubMed1997

Effects of anoxia on intracellular free Ca2+ in isolated cardiomyocytes from turtles.

One of the most important negative consequences of hypoxic stress in the mammalian myocardium is a breakdown in intracellular calcium homeostasis. This study examines the effects of anoxic stress on intracellular calcium regulation in isolated ventricular myocytes from a hypoxia tolerant vertebrate, the western painted turtle (Chrysemys picta bellii). Isolated calcium tolerant cardiomyocytes from turtle hearts were mounted on a glass cover slip that formed the bottom of a sealed, Plexiglas perfusion chamber. Free [Ca2+]i (determined by FURA2 fluorescence) in isolated turtle cardiomyocytes averaged 31.7 +/- 3.2 nM after 30 min of normoxic perfusion (20 degrees C, pHc = 7.77). This value is on the low end of the published range for mammalian cardiomyocytes. Perfusion with anoxic Ringer equilibrated with 3% CO2, resulted in a significant increase in free [Ca2+]i to 941 +/- 494.6 nM after 60 min. Increasing the CO2 in the perfusion solution to 5% or 6% blunted this rise (peak levels after 60 min of anoxia were 420.5 +/- 176.0 nM and 393.8 +/- 132.8 nM, respectively). A further increase to 8% CO2 increased the maximal value for free [Ca2+]i to 610.9 +/- 297.5 nM. In eight cells from the 5% CO2 protocol in which [Ca2+]i was monitored during recovery, reperfusion with normoxic Ringer rapidly lowered intracellular calcium to 92.8 +/- 9.7 nM within 15 min. Anoxia at relatively high extracellular (and hence intracellular) pH results in an increase in free [Ca2+]i comparable in magnitude and time course to that seen in some mammalian cardiomyocyte preparations. Perfusion of anoxic myocytes with Ringer equilibrated with either 5% or 6% CO2 blunted this increase in intracellular calcium, possibly an example of the pH paradox effect. A more severe combination of respiratory acidosis and anoxia (8% CO2) removed this protective effect.

Animals↗
PubMed2000

Succinate and alanine as anaerobic end-products in the diving turtle (Chrysemys picta bellii).

The western painted turtle is an extremely anoxia-tolerant vertebrate capable of tolerating blood lactate levels of 150-200 mM. Since lactate increases to such high levels, other fermentation end-products such as succinate and alanine, which have not been previously measured in this species, might also be expected to increase. Therefore, I measured turtle heart, liver, and blood concentrations of lactate, succinate, and alanine following a 28-day anoxic dive at 5 degrees C. Succinate and lactate concentrations increased significantly in all three compartments while alanine increased significantly in the liver only. Lactate was found to accumulate by a similar amount in all three compartments (66.4-80.5 micromol g or ml(-1) in the blood compartment) and was used as a reference to which alanine and succinate concentrations could be compared. Succinate and alanine levels increased by 2 and 0.9% of lactate in liver, approximately 0.3 and 0.04% of lactate in blood, and 0.6 and 0.07% of lactate in heart, respectively. The contribution of each to the total anoxic heat production was calculated and accounted for an additional 1.5% of the previously measured exothermic gap. I conclude that succinate and alanine concentrations do increase in the anoxic turtle but are minor anaerobic end-products.

Alanine↗
PubMed2001

Lactate dehydrogenase genes of caiman and Chinese soft-shelled turtle, with emphasis on the molecular phylogenetics and evolution of reptiles.

L-Lactate dehydrogenase (LDH) cDNAs encoding for LDH-A(4) (muscle) and LDH-B(4) (heart) isozymes from caiman (Caiman crocodilus apaporiensis) belonging to the order Crocodilia and Chinese soft-shelled turtle (Pelodiscus sinensis) belonging to the order Chelonia were sequenced. The phylogenetic relationships of the newly determined cDNA and their deduced protein sequences, as well as the previously published sequences of vertebrate LDH isozymes, were analyzed by various phylogenetic tree construction methods. These results indicated that Chelonia is indeed more closely related to Crocodilia. The divergent times between caiman and alligator, turtle and soft-shelled turtle, and Chelonia and Crocodilia were estimated to be approximately 36, 100 and 177 million years, respectively.

Alligators and Crocodiles↗
PubMed2001

Escaping senescence: demographic data from the three-toed box turtle (Terrapene carolina triunguis).

Two criteria have been proposed for the demonstration of negligible senescence. These include (1) no increase in age-related mortality and (2) negligible functional impairments with age. Although researchers have suspected turtles to exhibit negligible senescence, this has been largely based on the former rather than the latter criteria for which scant evidence is available. Using a long-term study on a population of three-toed box turtles (Terrapene carolina triunguis) in Cole County, Missouri, I combine known minimum age ranges and reproductive evidence to demonstrate their apparent escape from senescence. During 1998 and 1999, eight females >60 years of age were found gravid. The oldest of these is estimated to be at least 65-74 years of age. Of females >60 years, the mean clutch size and the proportion gravid were greater, although not significantly different, when compared to females <60 years. These findings indicate that the reproductive function in these turtles does not become impaired with age, thus supporting the second criteria for demonstrating negligible senescence.

Aging↗
PubMed2003

A comparative study on the morphology and topography of the ciliary ganglion in midday gerbil (Meriones meridianus) and turtle (Agrionemys horsfieldii).

The morphology and topography of the ciliary ganglia in the midday gerbil and turtle were studied with use of histochemical and histological techniques. The ciliary ganglion of the midday gerbil consisted of two cell agglomerations: the main ganglion and the accessory ganglion. The main ganglion was situated in the orbit and usually closely attached to the nerve for the inferior oblique muscle. The short ciliary nerves arose from the superior end of the main ganglion and reached the orbit. The accessory ciliary ganglion was smaller than the main ganglion. Usually it was attached to short ciliary nerves. The ganglionic neurocytes, 25.97 microm in diameter, were distributed regularly over the entire surface of the main ganglion. They typically had a single clear nucleus. The ciliary ganglion in the turtle formed a characteristic triangular structure on the inferior branch of the oculomotor nerve. The histological examination showed a small number of nerve cells in comparison to the nerve fibres. The neurocytes were placed mainly in the nasal part of ganglion and they had an irregular arrangement. The average diameter of neurons was 23.55 microm. Significant differences in density of ganglionic components in both species were observed. In midday gerbil the cells were densely packed and took up about 80% of a cross-section, while, in the turtle, neurocytes were located mainly in the surface part of ganglion.

Animals↗
PubMed2000

Living without oxygen: lessons from the freshwater turtle.

Freshwater turtles, and specifically, painted turtles, Chrysemys picta, are the most anoxia-tolerant air-breathing vertebrates. These animals can survive experimental anoxic submergences lasting up to 5 months at 3 degrees C. Two general integrative adaptations underlie this remarkable capacity. First is a profound reduction in energy metabolism to approximately 10% of the normoxic rate at the same temperature. This is a coordinated reduction of both ATP generating mechanisms and ATP consuming pathways of the cells. Second is a defense of acid-base state in response to the extreme lactic acidosis that results from anaerobic glycolysis. Central to this defense is an exploitation of buffer reserves within the skeleton and, in particular, the turtle's shell, its most characteristic structure. Carbonates are released from bone and shell to enhance body fluid buffering of lactic acid and lactic acid moves into shell and bone where it is buffered and stored. The combination of slow metabolic rate and a large and responsive mineral reserve are key to this animal's extraordinary anaerobic capacity.

Acid-Base Equilibrium↗
PubMed2000

Respiratory responses to short term hypoxia in the snapping turtle, Chelydra serpentina.

Among vertebrates, turtles are able to tolerate exceptionally low oxygen tensions. We have investigated the compensatory mechanisms that regulate respiration and blood oxygen transport in snapping turtles during short exposure to hypoxia. Snapping turtles started to hyperventilate when oxygen levels dropped below 10% O(2). Total ventilation increased 1.75-fold, essentially related to an increase in respiration frequency. During normoxia, respiration occurred in bouts of four to five breaths, whereas at 5% O(2), the ventilation pattern was more regular with breathing bouts consisting of a single breath. The increase in the heart rate between breaths during hypoxia suggests that a high pulmonary blood flow may be maintained during non-ventilatory periods to improve arterial blood oxygenation. After 4 days of hypoxia at 5% O(2), hematocrit, hemoglobin concentration and multiplicity and intraerythrocytic organic phosphate concentration remained unaltered. Accordingly, oxygen binding curves at constant P(CO(2)) showed no changes in oxygen affinity and cooperativity. However, blood pH increased significantly from 7.50+/-0.05 under normoxia to 7.72+/-0.03 under hypoxia. The respiratory alkalosis will produce a pronounced in vivo left-shift of the blood oxygen dissociation curve due to the large Bohr effect and this is shown to be critical for arterial oxygen saturation.

Adaptation, Physiological↗
PubMed1998

Reversible decreases in ATP and PCr concentrations in anoxic turtle brain.

A hallmark of anoxia tolerance in western painted turtles is relative constancy of tissue adenylate concentrations during periods of oxygen limitation. During anoxia heart and brain intracellular compartments become more acidic and cellular energy demands are met by anaerobic glycolysis. Because changes in adenylates and pH during anoxic stress could represent important signals triggering metabolic and ion channel down-regulation we measured PCr, ATP and intracellular pH in turtle brain sheets throughout a 3-h anoxic-re-oxygenation transition with 31P NMR. Within 30 min of anoxia, PCr levels decrease 40% and remain at this level during anoxia. A different profile is observed for ATP, with a statistically significant decrease of 23% occurring gradually during 110 min of anoxic perfusion. Intracellular pH decreases significantly with the onset of anoxia, from 7.2 to 6.6 within 50 min. Upon re-oxygenation PCr, ATP and intracellular pH recover to pre-anoxic levels within 60 min. This is the first demonstration of a sustained reversible decrease in ATP levels with anoxia in turtle brain. The observed changes in pH and adenylates, and a probable concomitant increase in adenosine, may represent important metabolic signals during anoxia.

Adenosine Triphosphate↗
PubMed2003

Molecular characterization of hemoglobin alpha-D chains from Geochelone carbonaria and Geochelone denticulata land turtles.

In order to help elucidate the evolution of alpha-globins, the complete cDNA and amino acid sequences of Geochelone carbonaria and Geochelone denticulata land turtles alpha-D chains have been described. In G. carbonaria, the cDNA is 539 bp with ATG start codon located at position 46, TGA stop codon at position 469 and AATAAA polyadenylation signal at position 520. In G. denticulata, the cDNA is 536 bp with ATG start codon located at position 46, TGA stop codon at position 469 and AATAAA polyadenylation signal at position 517. Both cDNAs codify 141 amino acid residues, differing from each other in only four amino acid residues. When comparing with human Hb alpha-chain, alterations in important regions can be noted: alpha110 Ala-Gly, alpha114 Pro-Gly, alpha117 Phe-Tyr and alpha122 His-Gln. There is a high homology between the amino acids of these turtles when compared with chicken alpha-D chains, progressively decreasing when compared with human, crocodile, snake, frog and fish alpha-chains. Phylogenetic analysis of alpha-D chains shows that those of turtles are closer to those of birds than to snakes and lizards.

Amino Acid Sequence↗
PubMed2001

Comparison of reproductive parameters in male yellow-blotched map turtles (Graptemys flavimaculata) from a historically contaminated site and a reference site.

From May to September of 1998, we collected monthly plasma samples from male yellow-blotched map turtles captured at two sites in the Pascagoula River drainage, Mississippi. One site (Vancleave) has a documented history of pollution from industrial sources (principally 2,3,7,8-tetrachlorodibenzo-p-dioxin, TCDD). Fish consumption advisories at the Vancleave site were lifted in 1996 and current impacts appear minimal. However, the yellow-blotched map turtle, a federally protected species, continues to decline in numbers. To determine if endocrine disruption could be a factor in the low reproductive rates observed in Vancleave turtles, we examined levels of plasma testosterone (T) and estradiol-17beta (E(2)) from males at this site and a second site (Leaksville), which has no known source of industrial pollution. Plasma was also tested for vitellogenin (VTG), which, in males, can be a biomarker of exposure to estrogenic contaminants. No males had detectable plasma VTG nor did mean monthly E(2) levels differ between sites. However, 10% of males from the historically polluted site were found to have high levels of E(2) (equivalent to levels found in females) and T was significantly lower for males captured at this site for 3 of 5 months. Our data suggest that the current impact of contaminants on reproduction in this population is limited. However, a portion of the population may have been affected developmentally, as represented by differences in reproductive parameters detected between sites.

Animals↗
PubMed1990

Independent eye movements in the turtle.

In order to evaluate the normal eye movements of the turtle, Pseudemys scripta elegans, the positions of each eye were recorded simultaneously using two search-coil contact lenses. Optokinetic nystagmus (OKN) was strikingly unyoked in this animal such that one eye's slow-phase velocity was substantially independent of that of the other eye. On the other hand, the fast-phase motions of both eyes occurred more or less in synchrony. An eye's slow-phase gain is primarily dependent on the direction and velocity of the stimulus to that eye. Using monocular stimuli, the highest mean gain (0.54 +/- 0.047; mean +/- standard error of mean) occurred using temporal-to-nasal movement at 2.5 deg/s. The mean OKN gain for nasal-to-temporal movement was only 0.13 +/- 0.015 at that velocity. Additionally, using the optimal monocular stimulus (temporal-to-nasal stimulation at 2.5 deg/s) only drove the occluded eye to move nasal-to-temporally at 0.085 deg/s, equivalent to a "gain" of only 0.034 +/- 0.011. The binocular OKN gain during rotational stimuli was higher than monocular gain, especially during nasal-to-temporal movement at high velocities. Also the difference in slow-phase eye velocity between the two eyes was smaller during binocular rotational stimuli. In contrast, when each eye simultaneously viewed its temporal-to-nasal stimulus at an equal velocity, two behaviors were observed. Often, OKN alternated between an animal's left eye and right eye. Occasionally, both eyes moved at equal but opposite velocities. These behavioral data provide a quantitative baseline to interpret the properties of the retinal slip information in the turtle's accessory optic system. Those properties are similar to the behavior of the turtle in that both are tuned to direction and velocity independently for each eye (Rosenberg & Ariel, 1990).

Animals↗
PubMedDate not supplied

The action spectra of cone photoreceptors in the turtle (Mauremys caspica) retina.

Cone photoreceptors in the turtle retina are involved in intricate neuronal interactions with other retinal neurons that modify the responses of the cones to photons absorbed in their outer segments. Therefore, the action spectra of cones strongly depend upon the conditions of measurements. This study describes an attempt to derive the action spectra of turtle cones which are the least distorted by neuronal interactions. To achieve this goal, the photoresponses of cones and horizontal cells were recorded from the turtle retina under different conditions of adaptation using different patterns of the stimulating test flashes. The sensitivity action spectra, derived from small-amplitude (<1 mV) photoresponses, were strongly affected by the recording conditions indicating the contributions of multiple neuronal inputs. Action spectra, constructed from large criterion photoresponses, were less distorted by neuronal interactions and better described the spectral properties of the "isolated" cones. The action spectra of the hyperpolarizing inputs to chromaticity-type horizontal cells were derived by stimulating these cells with mixtures of a saturating red light and a monochromatic light of different wavelength and intensity. The action spectra were constructed from the intensity of the addend component needed to "pull down" the depolarizing response to the red component by a fixed criterion. These spectra, measured in red/green and yellow/blue C-type horizontal cells, are suggested to best represent the "isolated" M-cones and S-cones, respectively.

Absorption↗
PubMed1989

Enkephalinergic modulation of the dopamine system in the turtle retina.

One subpopulation of amacrine interneurons in the turtle retina was shown to contain met-enkephalin by means of immunocytochemistry, and another was demonstrated to have a high-affinity uptake system for [3H]-dopamine by means of autoradiography. Although the amacrine soma size, density, and distribution of their neurites in IPL substrata was similar in retinas in which met-enkephalin and dopamine were localized, combined light microscope immunocytochemistry-autoradiography demonstrated that these two neurotransmitter systems did not coexist in the same cells. Because the two amacrine cell subtypes ramify in the same IPL substrata, neuronal interaction between them is possible. Release experiments showed that the potassium-induced release of [3H]-dopamine from the superfused turtle retina was reduced by 40% when enkephalin was added to the superfusate. The inhibition of [3H]-dopamine release could be blocked by the addition of naloxone. The addition of enkephalin had no effect of the potassium-induced release of [3H]-GABA from the superfused retina. These findings suggest that an enkephalinergic modulation of the dopaminergic amacrine cell system exists in the turtle retina.

Animals↗
PubMed1989

Localization of GABA- and GAD-like immunoreactivity in the turtle retina.

gamma-aminobutyric acid (GABA) has been reported to be an important neurotransmitter in the retinas of many species. This immunocytochemical study detailed the localization of antigens resembling GABA and glutamic acid decarboxylase (GAD, an enzyme involved in the synthesis of GABA), in retinal neurons in the turtle, Pseudemys scripta elegans. GABA-like immunoreactivity was present within somata in the inner and outer regions of the inner nuclear layer, within somata in the ganglion cell layer, and in processes in the outer plexiform layer, inner plexiform layer, and ganglion cell axon layer. GAD-like immunoreactivity was found in somata in the inner and outer regions of the inner nuclear layer and in processes in the inner and outer plexiform layers. Cell counts indicated more somata with GABA-like than GAD-like immunoreactivity in the inner nuclear layer. Double-label studies showed that every somata in the inner nuclear layer which had GAD-like immunoreactivity also had GABA-like immunoreactivity, but that many somata had only GABA-like immunoreactivity. The stratification of immunoreactivity within the inner plexiform layer was analyzed using a scanning densitometer. We described the strate within the inner plexiform layer such that S0 represented the inner nuclear layer/inner plexiform layer border and S100 represented the inner plexiform layer/ganglion cell layer border. Analysis of GAD-like labeling yielded seven distinct strata with peak densities at positions S8, S19, S28, S42, S59, S75, and S93. GABA-like labeling provided five distinct strata with peak densities at positions S17, S28, S67, S84, and S95. The strata with peaks of GABA-like immunoreactivity at S17 and S28 were in statistically identical locations to corresponding strata with GAD-like immunoreactivity. The strata with GABA-like immunoreactivity at S67, S84, and S95 did not have statistically identical peaks of correlated GAD-like immunoreactivity, although there were corresponding strata with GAD-like immunoreactivity nearby. Antiserum directed against GABA failed to produce labeled strata at positions corresponding to the strata with GAD-like immunoreactivity at S8 and S42. In summary, our results indicated that the antisera we used, which were directed against GABA and GAD, produced significantly different labeling in the inner nuclear layer, inner plexiform layer, and the ganglion cell body and axon layers of the turtle retina. Until the physiological significance of these differences is resolved, studies employing these markers to investigate the function of GABA in the turtle retina should be interpreted with caution.

Animals↗