Effects of ammonia exposure on antioxidant function, immune response and NF-κB pathway in Chinese Strip-necked Turtle (Mauremys sinensis).

As one of the main toxic substances in aquaculture water, ammonia causes seriously physiological harm to aquatic animals. In order to investigate the effects of ammonia exposure on the antioxidant defense, immune response, and NF-κB signaling pathway in Chinese Strip-necked Turtle (Mauremys sinensis), we designed two experimental groups (control and 6.45 mM ammonia), and sampled at 6 h, 24 h, 48 h, re 24 h (recover 24 h), and re 48 h. The results showed that the blood ammonia (BA) content was significantly increased when the turtles were subjected to ammonia, and the activities of cholinesterase (CHE) and aspartate aminotransferase (AST) in the serum also showed a significant upward trend. The malondialdehyde (MDA) content continuously increased during ammonia exposure, and more than doubled at 48 h compared with the control group. The activities of superoxide dismutase (SOD), glutathione peroxidase (GSH-PX), catalase (CAT) and their corresponding relative mRNA expression levels in the liver during ammonia exposure were obviously increased when compared to the control group, but most decreased to the normal levels at re 48 h. In addition, the relative mRNA and protein expression levels of NF-E2 related factor 2 (Nrf2) showed similar up-regulation patterns to antioxidase during ammonia exposed periods; whereas kelch-like ECH-binding protein 1 (Keap1), as Nrf2 negative regulator, showed opposite patterns. Moreover, the relative mRNA expression levels of heat shock proteins (HSP70, HSP90) significantly elevated upon the exposure of ammonia. Furthermore, ammonia increased the relative mRNA and protein expression levels of p50 and p65 at different exposed times. The reative mRNA expression levels of immune cytokines (BAFF and IL-6) were upregulated during ammonia exposured time, while there was a decline but did not return to normal levels, in the recovery periods. Taken together, these results indicated that antioxidation, immunity, and NF-κB signaling played a certain protective role for Mauremys sinensis under ammonia exposure. Our results will be helpful to understand the mechanism of aquatic toxicology induced by ammonia in turtles.

Blanding's turtles (Emydoidea blandingii) as a reservoir for Leptospira spp.

Leptospira spp. are re-emerging zoonotic pathogens. Previous research has found that Blanding's turtles (Emydoidea blandingii) experimentally infected with Leptospira interrogans shed leptospires in their urine, suggesting that they could play a role in transmitting pathogen within an aquatic ecosystem. This study investigated whether a population of wild Blanding's turtles known to be exposed to Leptospira spp. actively shed the pathogen under natural conditions. Blood samples were collected for serologic testing and to assess the health of the turtles. Free catch urine was collected for polymerase chain reaction (PCR) testing. All turtles were seropositive for Leptospira spp. and 73.5% (25/34) of the urine samples were PCR positive. All animals appeared clinically healthy and showed no apparent signs of disease. This study confirms that wild Blanding's turtles can actively shed Leptospira spp. in their urine and suggests that they may play a role in the epidemiology of this disease in habitats in which they reside.

Digestive parameters and water turnover of the leopard tortoise.

Leopard tortoises (Stigmochelys pardalis) experience wide fluctuations in environmental conditions and unpredictable availability of food and water within the Nama-Karoo biome. It was hypothesised that tortoises fed two diets differing in preformed water and fibre content would have differing food intake, gut transit rate, assimilation efficiency, faecal and urinary water loss, and urine concentrations. It was predicted that tortoises fed these contrasting diets would attempt to maintain energy and water balance by altering their digestive parameters. Leopard tortoises fed lucerne (Medicago sativa) had a low food intake coupled with long gut transit times, which resulted in the lowest amount of faecal energy and faecal water lost. Tortoises fed tomatoes (Solanum lycopersicum) had higher food intake and faster gut transit times, but more energy and water was lost in the faeces. However, daily energy assimilated and assimilation efficiency were comparable between tortoises fed the two diets. Urine osmolality was significantly different between tortoises on the two diets. Results indicate that leopard tortoises can adjust parameters such as transit rate, food intake, water loss and urine osmolality to maintain body mass, water and energy balance in response to a high fibre, low water content and a low fibre, high water content diet. This study suggests that this digestive flexibility allows leopard tortoises in the wild to take advantage of unpredictable food and water resources.

A double-membrane model for urinary bicarbonate secretion.

To define the transport pathway for HCO-3 secretion (JHCO3) across the apical and basolateral membranes of turtle bladder, we examined the effects of cAMP, isobutylmethylxanthine (IBMX), the Cl- channel blocker 9-anthroic acid (9-AA), and the disulfonic stilbene DIDS (4,4'-diisothiocyanostilbene-2,2'-sulfonic acid) on the electroneutral and electrogenic components of JHCO3. Total JHCO3 was measured by pH stat titration of the mucosal compartment after Na+ absorption and H+ secretion were abolished by ouabain and a delta pH, respectively. Addition of cAMP or IBMX increased total JHCO3 and induced a short-circuit current (ISC), accounting for a large part of JHCO3; net Cl- absorption was reduced. Mucosal 9-AA inhibited the IBMX-induced electrogenic component of JHCO3, whereas mucosal DIDS inhibited the electroneutral component and acetazolamide reduced both. We suggest that HCO-3 is generated within the cell by a Na-independent primary active acid-base transport at the basolateral membrane (H+ extrusion into the serosal compartment). Cellular HCO-3 accumulation drives JHCO3 via a Cl-HCO3 exchanger at the luminal membrane. IBMX and cAMP activate a 9-AA-sensitive anion conductance parallel to the exchanger. The apparent reversal of the transport elements between the two cell membranes (compared with H+-secreting cells) led to an ultrastructural examination of the carbonic anhydrase-rich cells.

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.

Diuretics stimulate H+ secretion in turtle urinary bladder.

The effect of various diuretics on H+ secretion was studied in the isolated short-circuited urinary bladder of the turtle. Mucosal (urinary) chlorothiazide stimulated H+ secretion promptly, from 1.33 +/- 0.24 to 3.03 +/- 0.25 mueq/h (P less than 0.001). The effect was rapidly reversible upon washout of the drug, H+ returning to control levels, 1.37 +/- 0.26 mueq/h (P less than 0.001). Similar effects were observed with mucosal hydrochlorothiazide and mucosal ethacrynic acid/cysteine. Stimulation of H+ secretion occurred in the presence or the absence of exogenous CO2, in the presence or absence of mucosal Na+ and during inhibition of Na+ transport by ouabain. There was no stimulation of H+ secretion by uncomplexed ethacrynic acid or by mucosal furosemide. The nondiuretic sulfonamide, sulfasoxizole, and the nonsulfonamide buffer, borate, had no effect on H+ SECRETION. These observations indicate that the stimulatory effect of diuretics on H+ secretion is not related to active sodium transport, transepithelial electrical potential, or the buffering capacity of the drugs. Since the transepithelial pH gradient at which active H+ secretion was abolished was identical for chlorothiazide-treated tissues (2.68 pH U) as for control tissues (2.65 pH U, NS), the data suggest that the protonmotive force of the H+ pump was unaffected by the diuretic. This observation, plus the rapid onset and reversibility of the drugs, is consistent with an effect on the mucosal membrane to increase H+ conductance (K). The findings raise the possibility that direct enhancement of renal H+ secretion may play a role in the metabolic alkalosis induced by some diuretics.

Bicarbonate ion transport: a mechanism for the acidification of urine in the turtle.

The uricotelic turtle Pseudemys scripta acidifies the urine to a pH as low as 4 in the urinary bladder. Data in this report show that the mechanism of acidification in this bladder is the transport of bicarbonate ion from lumen to serosa, and that the temperature to which the turtles are adapted prior to the in vitro experiment largely determines the direction of the transmural carbon dioxide gradient observed. This temperature effect also serves to reconcile apparently disparate data that were previously reported. A new technique for the direct determination of the partial pressure of carbon dioxide was employed.