Freshwater Turtle Pseudemys Scripta Research Articles

Microvascularization of the cerebellum in the turtle, Pseudemys scripta elegans (Reptilia). A scanning electron microscope study of microvascular corrosion casts, including stereological measurements.

Cerebellar blood supply and microvascular patterns were studied in 12 freshwater turtles Pseudemys scripta elegans by scanning electron microscopy (SEM) of microvascular corrosion casts and histology. Vascular densities were estimated by point counting methods from casts and thin sections (7 microns). Short A2-arterioles and recurrent branches from A3-arterioles supply the capillary bed of the molecular layer, while V2 and V3 venules drain it. The Purkinje cell layer is supplied by horizontal branches ("parallel arteries") of A4 and A3 arterioles, which capillarize toward the granular and molecular layers. V2, V3 and V4 venules drain the areas supplied by A3 arterioles. The deep granular and subependymal layers are supplied by A4 arterioles, those adjacent to the Purkinje cell layer also by A3 arterioles. The areas supplied by A4 arterioles drain via V4 venules. The granular and Purkinje cell layers taken together have an estimated vascular density of 4.1%, while in the molecular layer this value is 3.3%. Our findings largely confirm published data from Testudo geometrica and Pseudemys scripta elegans with respect to gross supply and drainage. The microvascular patterns are similar to those of the human cerebellar cortex, particularly the basic patterns of intracortical arterioles and venules. The molecular layer, like that in the human brain, has a circulatory bed largely independent of that of the Purkinje cell and granular layers. In contrast to the human brain, a cerebellar pial capillary network is present in the brain of the turtle.

Atrial Natriuretic Factor in the Freshwater Turtle Pseudemys scripta: A Partial Characterization

The presence of natriuretic and vasorelaxant materials in the atria and ventricles of a Chelonian reptile, the freshwater turtle Pseudemys scripta, was verified Crude atrial and ventricular extracts were acutely natriuretic and diuretic when administered to anesthetized rats increasing sodium excretion 23.5 ± 7.9 and 5.11 ± 18 μM Na/10 min/mg extract, respectively. Although atrial extracts were relatively more natriuretic than ventricular extracts, the total natriuretic content of ventricular extracts was approximately twofold greater. Moreover, partially purified atrial extracts were found to relax precontracted isolated rat aortic ring segments and exhibited immunoreactivity to mammalian ANP antisera. Also, the natriuretic and immunoreactive substance was purified further by size exclusion chromatography and a molecular weight of 3-5 kDa was determined. Using the bovine adrenal glomerulosa ANP receptor, this partially purified natriuretic substance displayed an apparent binding affinity similar to that of mammalian ANP. Finally, in order to demonstrate that this reptile is physiologically responsive to ANP, synthetic rat ANP (10 μg/kg) was shown to decrease arterial pressure in conscious turtles from a control value of 37.2 ± 5.2 to 30.3 ± 2.7 mm Hg. These data demonstrate that unlike other non-Chelonian reptiles, both the atria and the ventricles of this Chelonian reptile synthesize and store substantial levels of biologically active ANP-like materials, and further, that ANP is a highly conserved and primitive cardiac hormone.

Chemical regulation of cerebral blood flow in turtles

This study was performed to test the effect of the chemical composition of the blood on cerebral blood flow (CBF) regulation in turtles. The CBF response to increases in arterial PCO2 (PaCO2) (hypercapnia) was measured during normoxia and anoxia in anesthetized freshwater turtles Pseudemys scripta. The radioactive-microsphere technique was used to measure CBF. CBF increased with increases in PaCO2. The sensitivity of the CBF response to hypercapnia (delta CBF/delta PaCO2) was 0.68 ml.min-1.100 g-1. Torr-1 during normoxia. delta CBF/delta PaCO2 increased to 3.44 ml.min-1.100 g-1. Torr-1 during anoxia. The increases in CBF occurred at constant mean arterial blood pressure, which indicates that cerebral vascular resistance decreased. The increased CBF response during asphyxia (hypercapnia-anoxia) could be beneficial for survival during prolonged dives by increasing glucose delivery for brain anaerobic metabolism. In addition, increased CBF could aid in regulating brain acid-base composition by controlling extracellular fluid PCO2.

Salt intake and plasma renin activity in the freshwater turtle

In mammals, a well-documented inverse relationship exists between oral salt intake and plasma renin activity (PRA). We carried out this study to determine if a similar relationship exists in the freshwater turtle Pseudemys scripta. Three groups of turtles ( N = 8 for each group) were fed different amounts of salt dissolved in distilled water (2 cc/kg). The high salt group received 580 mg (10 mEq) NaCl/kg twice per week, the medium salt group received 290 mg (5 mEq) NaCl/kg twice per week, and the low salt (control) group received 2 cc/kg distilled water twice per week with no salt. The animals were weighed weekly and blood was collected by cardiac puncture after 3 and 6 weeks of salt loading and again 3 weeks after termination of the salt loading. PRA and plasma electrolytes (P Na, P K, P Cl) were determined. The low salt (control) group showed no changes in any of the measured variables throughout the 9-week study. At 3 weeks the following mean values were obtained for the control group: P Na, 119.5 ± 7.2 mEq/liter; P K, 5.0 ± 1.0 mEq/liter; P Cl, 74.1 ± 2.6 mEq/liter; PRA, 1.0 ± 0.2 ng/ml/hr. In the medium salt group, no significant changes were seen until 3 weeks after termination of the salt loading when P Na and PRA were elevated to 137.9 ± 3.6 mEq/liter and 1.9 ± 0.2 ng/ml/hr, respectively ( P < 0.05 compared to control). In the high salt group, P Na (136.5 ± 6.5 mEq/liter) was elevated after 3 weeks of salt loading. At 6 weeks, P Na (136.8 ± 4.9 mEq/liter) remained elevated in the high salt group and P Cl (86.3 ± 1.3 mEq/liter) and PRA (1.7 ± 0.2 ng/ml/hr) also increased significantly ( P < 0.05 compared to control in each case). Three weeks after termination of salt loading, P Na (136.8 ± 3.3 mEq/liter), P Cl (88.0 ± 1.6 mEq/liter), and PRA (1.9 ± 0.2 ng/ml/hr) remained elevated ( P < 0.05 in each case) in the high salt group while P K dropped to 3.5 ± 1.6 mEq/liter ( P < 0.05). The results show that after 6 weeks of salt loading sufficient to raise P Na in the turtle, PRA was significantly elevated.

The effects of adrenocorticotropin hormone and angiotensin II on adrenal corticosteroid secretions in the freshwater turtle Pseudemys scripta

This study examined the effects of angiotensin II (ANG II) and mammalian adrenocorticotropin hormone (ACTH) on adrenal corticosteroid secretions in the freshwater turtle, Pseudemys scripta. Synthetic turtle ANG 11 ([Asp 1, Val 5] ANG II) was infused at rates of 1, 10, and 100 ng/kg/min in conscious turtles while monitoring blood pressure (BP). One 60-min saline (0.6%) infusion preceded the ANG II infusions; two followed. Blood samples were collected at 30- and 60-min intervals and the plasma was frozen at −20° until assay. Mammalian ACTH was infused at doses of 0.1 and 1.0 IU/min; the procedures were followed as delineated above. The plasma was assayed for corticosterone, cortisol, and aldosterone utilizing radioimmunoassay techniques. Infusions of exogenous, native ANG II at subpressor and pressor rates elicited dose-dependent increases in BP, which rose from a control mean of 22.6 ± 5.8 mm Hg to a maximum mean value of 38.2 ± 11.0 mm Hg ( P < 0.05 compared to control), and plasma corticosterone concentrations, which rose from a control mean of 6.6 ± 2.8 ng/ml to a maximum mean value of 27.2 ± 2.6 ng/ml ( P < 0.05 compared to control). Furthermore, both BP and corticosterone levels returned toward control levels during the final saline recovery period, suggesting that neither physical stress suffered by the animal nor blood volume changes due to infusions and blood sampling affected these parameters. ACTH failed to alter either BP or corticosterone. Neither ANG II nor ACTH had any effect on plasma cortisol or aldosterone concentrations—which fell below the minimal detection levels for these assays. The results suggest that corticosterone may be a primary mineralocorticoid in P. scripta, and perhaps in reptiles in general.

Localization of a salmon calcitonin-like molecule in one type of ultimobranchial cells in the freshwater turtle Pseudemys scripta

Immunohistochemical methods using affinity adsorbed antibodies raised against the three families of calcitonins (CT) were applied to ultimobranchial (UB) cells in situ to investigate the nature of the Chelonian calcitonin molecule and its distribution in the ultimobranchial bodies of the freshwater turtle, Pseudemys scripta. In this species, the UB glands were present on both sides and consisted of scattered cell clumps between epithelial vesicular structures. The neighboring parathyroid tissue also contained two components, the majority being composed of similar vesicles, with occasional solid cell cords evenly distributed. Calcitonin immunoreactivity was found in the cell clumps of the UB gland and in the cell cords of the associated parathyroid, but not in the epithelial component lining the vesicles or in the amorphous material which sometimes filled the lumen. Turtle calcitonin was exclusively of the salmon type, as determined by the negative results obtained in situ after the use of antibodies raised against human and porcine molecules. The salmon-like calcitonin content of the ultimobranchial area was estimated as 15.2 ng; however, the molecule was undetectable in the circulation. In this work we localize the quantitate a salmon-like CT molecule in one type of ultimobranchial and parathyroid cell of a reptile for the first time.

Renin release in turtles: effects of volume depletion and furosemide administration

To gain insight into the phylogenetic history of mechanisms controlling renin release, we conducted studies in the freshwater turtle Pseudemys scripta. Maneuvers known to stimulate renin release in mammals were evoked in the turtle, and the response was compared with that in mammals. Cumulative hemorrhage (30% blood vol) in anesthetized turtles failed to increase renin even though arterial pressure was reduced to 50% of control. An even more severe hemorrhage (60% blood loss) or hypotension induced by nitroprusside infusion in unanesthetized turtles also failed to evoke an enhanced level of renin. However, under identical experimental conditions, a 15% blood loss in rats increased renin at least fourfold (P less than 0.01). In other studies 48 h of furosemide administration in awake turtles increased renin more than threefold (P less than 0.05) and were accompanied by concomitant reductions in plasma sodium and potassium (P less than 0.05). The general conclusions drawn from these studies is that renin secretion in this primitive vertebrate is similar to that in mammals with respect to renal tubular and electrolyte mechanisms, but unlike all mammals tested these turtles do not possess an intrarenal baroreceptor component in renin control.

Excretion rates of sulfamethoxazole and N4-acetyl-sulfamethoxazole by fresh water turtles Pseudemys scripta elegans.

Sulfamethoxazole and N4-acetylsulfamethoxazole are excreted by fresh water turtles Pseudemys scripta elegans in a biphasic mode, characterized half-lives of 5 and 100 min. Acetylation and deacetylation reactions cannot be detected below a dose of 50 mg/kg. The mass balance of the dose administered is incomplete, only 30 per cent of the dose can be recovered as parent compound and metabolite. The sulfonamides must be mainly excreted by the faeces and may be metabolized in the gastro-intestinal tract.

Characterization of the renin-angiotensin system in the turtle Pseudemys scripta.

Studies were conducted in freshwater turtles Pseudemys scripta to define some characteristics of the renin-angiotensin system in this reptile. Dialyzed acid-treated kidney extract (1 g tissue per ml water) produced a prolonged pressor response in unanesthetized turtles, which was eliminated by boiling the extract or by pretreating the turtle with [Sar1, Ile8]angiotensin II. A rat pressor assay was employed because turtle angiotensin (ANG) was bound poorly by the anti-[Asp1, Ile5, His9]ANG I used in our radioimmunoassay. Kidney extract incubated with homologous plasma (pH 5.5 and 25 degrees C) produced a time-dependent pressor response in rats. The pressor activity of the product was eliminated by dialysis or by pretreating the rats with [Sar1, Ile8]ANG II. The pressor response in anesthetized turtles to ANG I was significantly reduced by captopril, whereas the ANG II response remained unchanged, thus demonstrating the presence of ANG-converting enzyme activity in these animals. We determined the velocity of turtle ANG formation at various dilutions of enzyme (kidney extract) or substrate (plasma). Turtle kidney extract incubated with homologous plasma displayed typical Michaelis-Menten kinetics. Finally we conducted experiments to determine whether a portion of turtle plasma renin exists in an inactive form. Trypsinization caused a slight increase in plasma renin activity (PRA), whereas acidification to pH 3.3 yielded a fourfold increase in PRA.

Angiotensin and norepinephrine effects on isolated vascular strips from a reptile

In order to better understand the vascular effects of angiotensin II (AII) in lower vertebrates, the contractile responses of aortic strips from the freshwater turtle Pseudemys scripta elegans were studied. Circumferential strips from the left aortic arch were suspended in a tissue bath in 25°C reptilian Ringer's solution at pH 7.5. Both [Asn 1,Val 5] AII (10 −9–10 −5 M) and norepinephrine (NE) (10 −8–10 −4 M) produced dose-dependent contractions. The threshold dosage for AII was between 10 −9 and 10 −8 M and for NE between 10 −8 and 10 −7 M. Pretreatment with [Sar 1,Ile 8] AII (10 −6 M) significantly attenuated the response to [Asn 1,Val 5] AII at 10 −5 M and totally blocked the response at lower AII concentrations ( P < 0.01 in each case). The response to AII was unaffected by phentolamine (10 −6 M). Phentolamine abolished the response to NE at concentrations of 10 −6 M or less ( P < 0.01) and attenuated the response by 48% at 10 −5 M ( P < 0.05) and 43% at 10 −4 M ( P < 0.05) NE. The response to NE was unaffected by [Sar 1,Ile 8] AII. The results demonstrate that [Asn 1,Val 5] AII has a direct contractile effect on turtle vasculature and that two functionally distinct vascular receptor populations for AII and NE are present in the turtle. Since phentolamine did not affect the responses to AII, it also appears that angiotensin-evoked norepinephrine release from the sympathetic nerve terminals in the vessel is not involved in the angiotensin-induced contractions in this preparation.

Systemic and renal effects of angiotensin II in the freshwater turtle Pseudemys scripta elegans.

This study examined the renal and systemic effects of angiotensin II (ANG II) in the freshwater turtle, Pseudemys scripta elegans. We infused [Asn1, Val5]ANG II at doses of 1, 10, 100, and 500 ng X kg-1 X min-1 in conscious turtles while monitoring blood pressure, glomerular filtration rate (GFR), urine volume, and plasma and urine electrolytes. Saline (0.6%) was infused for two 1-h control periods at 1 ml X kg-1 X h-1 followed by a 1-h infusion of saline with ANG II added. Saline alone was then infused for either two or three 1-h recovery periods. Control values before ANG II infusion averaged 21 mmHg for blood pressure, 1.8 ml X h-1 for urine volume, and 8.0 ml X kg-1 X h-1 for GFR. At 1 (n = 7) and 10 ng X kg-1 X min-1 (n = 6) ANG II produced no significant changes in blood pressure or renal function. Angiotensin infusion at the higher rates of 100 (n = 6) and 500 ng X kg-1 X min-1 (n = 11) significantly elevated blood pressure during ANG II infusion (29 and 44 mmHg, respectively), while electrolyte excretion remained unchanged. Despite the increased blood pressure, GFR and urine volume tended to decrease. At all infusion rates, plasma electrolytes remained unchanged. The results suggest that ANG II is a potent constrictor of preglomerular vessels in the kidney of the turtle.

Acetylation of sulphamethoxazole by fresh water turtles Pseudemys scripta elegans.

Journal of Veterinary Pharmacology and TherapeuticsVolume 6, Issue 3 p. 237-240 Acetylation of sulphamethoxazole by fresh water turtles Pseudemys scripta elegans TOM B. VREE, Corresponding Author TOM B. VREE *Department of Clinical Pharmacy, Sint Radboud Hospital, University of NijmegenDept. of Clinical Pharmacy, Sint Radboud Hospital, University of Nijmegen, Nijmegen, The NetherlandsSearch for more papers by this authorJEROEN B. VREE, JEROEN B. VREE †Dotulabs, Weezenhof, Nijmegen, The NetherlandsSearch for more papers by this author TOM B. VREE, Corresponding Author TOM B. VREE *Department of Clinical Pharmacy, Sint Radboud Hospital, University of NijmegenDept. of Clinical Pharmacy, Sint Radboud Hospital, University of Nijmegen, Nijmegen, The NetherlandsSearch for more papers by this authorJEROEN B. VREE, JEROEN B. VREE †Dotulabs, Weezenhof, Nijmegen, The NetherlandsSearch for more papers by this author First published: September 1983 https://doi.org/10.1111/j.1365-2885.1983.tb00470.xCitations: 14AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume6, Issue3September 1983Pages 237-240 RelatedInformation

Prolonged diving and recovery in the freshwater turtle, Pseudemys scripta—III. The effect of acidosis on lactate generation and O 2 consumption in brain slices

1. 1. The effect of progressive extracellular acidosis on the rate of lactate generation ( Q lactate) and O 2 consumption ( Q O 2 ) was studied in brain slices obtained from the freshwater turtle Pseudemys scripta elegans. 2. 2. At the nadir pH found in vivo during diving, Q lactate is 60% of the value found at pH 7.5 and at an extracellular pH 6.0, the value is 37% of the value at pH 7.5. These findings suggest that ATP supply derived from glycolysis decreases progressively during prolonged diving and that bioenergetic failure is an important factor during this process. 3. 3. Total brain Q o 2 does not change significantly over a range pH 6.0–7.5, averaging 2.3 ± 0.35μM × 100 g tissue −1 × hr −1. This suggests that the failure to repay the apparent O 2 deficit accrued during prolonged diving is not pH mediated.

Bioelectric potential profiles in the bladder mucosa of the tortoise [formula omitted] Gmelin

In the herbivorous terrestrial tortoise Testudo hermanni hermanni Gmelin, the composition of blood and vesical urine indicates that the urinary bladder plays an essential part in the reabsorption of water and sodium (1, 2). This is also the case in Amphibians (3, 4), and the urinary bladder of the toad is generally assumed to act as a reservoir in the hydromineral metabolism of this species. The urinary bladder of a freshwater turtle Pseudemys scripta as well as the bladder of a terrestrial tortoise, Testudo graeca , have been shown to transport sodium actively (5, 6). Attempts to localize the sodium active transport and to explain the electrical potential difference existing in the toad urinary bladder have been made (7) but all experiments performed in this field are carried out on a complex tissue including different epithelial cells as well as blood vessels and bundles of smooth muscle fibers (9). It is therefore difficult to interpret the results as reflecting solely the activity of the epithelial cells bordering the bladder. The bladder epithelium of Testudo hermanni hermanni Gmelin can be easily isolated from the underlying tissues (9) thus giving a suitable preparation for the study of bioelectric potentials and the localization of the sodium active transport mechanism. This paper deals essentially with the determination of the electrical profile of the epithelium lining the sphincter and the urinary bladder.

Excretion in fresh-water turtle (Pseudemys scripta) and desert tortoise (Gopherus agassi)

Excretion in fresh-water turtle (<i>Pseudemys scripta</i>) and desert tortoise (<i>Gopherus agassi</i>)

Intra- and interspecific differences in phototactic behaviour of freshwater turtles.

AbstractWith fresh water turtles Pseudemys scripta elegans some individuals choose a white compartment and others a black one when tested in identical conditions on a small diving stand. These differences could not be related to weight, sex, adaptation to laboratory conditions, or level of illumination in the starting area. Latencies were very variable but for many individual animals responses made to the black side tended to be quicker than those to the white side. Other species (Pseudemys floridana and Pseudemys scripta ornata) showed a higher level of positive phototaxis and less individual variation. In many animals tested the positive response to the white stimulus became more frequent as testing was extended up to 60 trials. Some cautions are given about the design of experiments on learning in turtles. The role of positive phototaxis in the water-finding abilities of hatchling turtles is discussed. The possible value of the study of the negatively phototactic turtles in elucidating some aspects of their life cycle is suggested, but the present work produced no good evidence that individual variations depended on maturational differences.