Mycoplasma haemocanis infection--a kennel disease?

Mycoplasma haemocanis (formerly Haemobartonella canis) is a red blood cell parasite that causes disease mainly in immunosuppressed and splenectomized dogs. Clinical outbreak of the disease resulted in failure of a large experimental project. We aimed to identify whether M. haemocanis has increased prevalence in kennel-raised dogs. In a prospective study, we compared the prevalence of M. haemocanis in whole blood (anti-coagulated by use of EDTA) collected from pet dogs (University of Illinois, Urbana Champaign, Ill.; n = 60) with that in blood from dogs raised in three distinct kennels in western Europe (WE; n = 23), eastern Europe (EE; n = 20), and North America (NA; n = 20). Screening included antibody testing and microscopy of blood smears. The presence of M. haemocanis was identified using a polymerase chain reaction (PCR) assay for specific DNA of the organism. None of the pet dogs (0%) was test positive for M. haemocanis DNA. Mycoplasma haemocanis was found in dogs tested at all of the kennels. Infection rate in the three kennels was 30, 35, and 87%, respectively (all P < 0.001 versus control, chi2-test). Latent infection with M. haemocanis was not a single observation in kennel-raised dogs. Prevalence may be higher than that in a pet dog population. The potential exists for these latent infections to adversely affect or confound research results.     

Tryptophan residues of creatine kinase: a fluorescence study

Spectroscopic studies of rabbit skeletal muscle creatine kinase (CPK) and its complexes with adenosine phosphates have long suggested the occurrence of a tryptophan residue at or near the coenzyme binding sites [K?gi, J. H. R., Li, T.-K., & Vallee, B. L. (1971) Biochemistry 10, 1007-1015; Price, N. C. (1972) FEBS Lett. 24, 21-23]. This conjecture was further supported by nuclear Overhauser effect (NOE) 1H NMR studies indicating through-space interactions between protons of the adenine ring of bound ADP and one or more aromatic side chains of the proteins [Vasák, M., Nagayama, K., Wüthrich, K., Mertens, M. L., & K?gi, J. H. R. (1979) Biochemistry 18, 5050-5055]. Further evidence for a tryptophan residue in the environment of the active site has now been obtained by fluorescence-quenching studies using iodide and acrylamide as external quenchers. Thus, while by the addition of iodide the tryptophan fluorescence of unliganded CPK is reduced to about 75% of the unquenched control, no such effect is manifested upon addition of this quencher to the CPK.ADP and CPK.ATP complexes. Similarly, the relative effectiveness of quenching of the CPK-coenzyme complexes by acrylamide is only about 60% of that measured in the unliganded enzyme. Both these data and the spectral characteristics of the quenched fluorescence suggest that coenzyme binding perturbs a tryptophan residue that is close to the active site and that is partially exposed to the solvent. The differential effectiveness of external quenchers on unliganded and liganded CPK allows the determination of the ligand binding equilibria by fluorescence-quenchability titration.(ABSTRACT TRUNCATED AT 250 WORDS)     

A laser-based method for measuring thermal nociception of cattle

We describe a method for measuring nociception in cattle using a CO(2) laser aimed at the caudal aspect of the metatarsi. In Experiment 1, infrared thermography showed that calves responded by lifting their legs when skin temperatures reached 45-55 degrees C. In Experiment 2a, the validity of the method was tested by comparing the response latencies of 14 calves to two power settings (2.25 W vs. 4.5 W) with each setting being applied six times. We found that both leg-lift latencies and tail-flick latencies were lower at the higher power setting, and the calves were more likely to respond by kicking than by simply moving the leg. The standard deviations between and within calves were smaller at the higher power setting, and the large within-calf variation means that at least three tests were required to obtain reliable measures that could differentiate between calves. In Experiment 2b, application of the laser at a range of power settings (2.0, 3.0, 4.0, 4.5, 5.0 and 5.5 W) on 16 calves showed that response latencies decreased as power increased up to 4.5 W, after which no further change occurred. In Experiment 3, the repeatability of the method was evaluated on nine measures with the high power setting (4.5 W). The coefficient of variation associated with repetition of the measures was 36%. In general, we found little change in response latencies with repeated use of the laser, except that responses on the second test tended to be shorter. Experiment 4 showed that ambient temperatures between 16 degrees C and 27 degrees C did not affect response latencies, but these were longer at temperatures of 7 degrees C. We suggest that the method is a useful way of measuring cattle's sensitivity to nociception as the animals need not be restrained and the distance to the animal need not be closely controlled. However, to obtain accurate, valid and reliable measures it is necessary to use a high power setting (4.5 W) and take at least three consecutive measures of the response latency.