Serum anti-Müllerian hormone concentration as a diagnostic tool to identify testicular tissue in canine disorders of sexual development.

Disorders of sexual development (DSD) may have their origin in alterations of the chromosomal, gonadal or phenotypic sex. Affected animals are usually presented because of ambiguous external genitalia, seldom because of reproductive disorders. Anti-Müllerian hormone (AMH) is secreted in the gonads with higher amounts in males than in females and can be used to identify gonadal tissue in sexually normally developed dogs. The aim of this study was to examine the diagnostic potential of serum AMH to identify testicular tissue in 11 dogs with DSD. The diagnostic procedures applied were: determination of the phenotypic sex (n = 11), genital ultrasound (n = 9), determination of the SRY gene (n = 11), karyogram (n = 6), gonadectomy (n = 11), pathohistology of the gonads (n = 10), serum AMH measurement (n = 11). 39 female dogs described in a previous study and 19 male dogs with a normal spermiogram served as controls for the AMH serum concentrations in sexually intact dogs. The 11 dogs with DSD were classified as 7 XY DSD and 4 XX DSD. Presumptive testes were obtained in 10 dogs and 1 dog had an ovotestis combined with a testis. Mean serum AMH values of the dogs with DSD were significantly higher (P < 0.001) than in male and female controls. The upper limit of the AMH test (≥ 23ng/ml) was reached in 6 dogs. High AMH concentrations have been described previously in cryptorchid dogs. 1 dog with a male phenotype and 2 with a female phenotype had AMH values within the range of the male controls, although all of them had cryptorchid testes. A Poodle, in which epididymis were identified but no definitive gonads, had an AMH concentration of the lower limit of the test (≤ 0.01 ng/ml), comparable to previously described castrated dogs. This study indicates that serum AMH levels are a useful diagnostic tool to identify testicular tissue in dogs with DSD and suggests the possible use of AMH to diagnose testicular dysgenesis.

Encephalitozoon cuniculi in rabbits in Germany: prevalence and sensitivity of antibody testing.

The aim of this study was to investigate the prevalence of Encephalitozoon cuniculi antibodies in healthy and diseased rabbits in Germany. Age and gender dependencies were taken into consideration. The sensitivity of the E cuniculi antibody test and its relevance for the diagnosis of E cuniculi infection in rabbits was also examined. A total of 773 healthy and diseased rabbits were tested for E cuniculi antibodies (indirect immune fluorescence antibody test (IFAT) or carbon immunoassay (CIA). No differences between diseased and healthy rabbits were observed with regard to gender, but diseased rabbits were significantly older (P>0.001). Forty-three percent (336/773) of all rabbits were positive for E cuniculi antibodies. Of the diseased rabbits, 48 per cent (266/555) were positive for E cuniculi antibodies. While 96 per cent (91/95) of the rabbits with histopathologically or PCR confirmed encephalitozoonosis were E cuniculi antibody-positive, only 60 per cent (144/241) of the rabbits suspected of E cuniculi infection were antibody-positive. Of the healthy rabbits, 18 per cent (39/218) were positive for E cuniculi antibodies. Diseased rabbits were almost three times more likely to be E cuniculi antibody-positive than healthy ones (P>0.001; relative risk (RR): 2.68; 95% CI 1.99 to 3.61). The sensitivity of the E cuniculi antibody test was 96 per cent.

Proton transfer in bacterial nitric oxide reductase.

The NOR (nitric oxide reductase) from Paracoccus denitrificans catalyses the two-electron reduction of NO to N(2)O (2NO+2H(+)+2e(-)-->N(2)O+H(2)O). The NOR is a divergent member of the superfamily of haem-copper oxidases, oxygen-reducing enzymes which couple the reduction of oxygen with translocation of protons across the membrane. In contrast, reduction of NO catalysed by NOR is non-electrogenic which, since electrons are supplied from the periplasmic side of the membrane, implies that the protons needed for NO reduction are also taken from the periplasm. Thus NOR must contain a proton-transfer pathway leading from the periplasmic side of the membrane into the catalytic site. The proton pathway has not been identified, and the mechanism and timing of proton transfer during NO reduction is unknown. To address these questions, we have studied the reaction between NOR and the chemically less reactive oxidant O(2). When fully reduced NOR reacts with O(2), proton-coupled electron transfer occurs in a reaction that is rate-limited by internal proton transfer from a group with a pK(a) of 6.6. This group is presumably an amino acid residue close to the active site that acts as a proton donor also during NO reduction. The results are discussed in the framework of a structural model that identifies possible candidates for the proton donor as well as for the proton-transfer pathway.