This study directly demonstrates that cardiac troponin I (cTnI) is a sensitive, specific, and persistent biomarker in laboratory animals. Histopathological and pathophysiological cardiac changes in dogs, rats and mice correlated with increased serum cTnI with various cardiac inotropic agents, and cardiotoxic drugs and with cardiac arrhythmias, tachycardia, cardiac effusion with dyspnoea, and ageing. A comparison of six immunoassays for cTnI and cardiac troponin T (cTnT) to detect and monitor cardiac injury in a rodent model indicated that enzyme-linked immunosorbent (Life Diagnostics Inc and TriChem Resources Inc, West Chester, Philadelphia, USA) and Immulite (Diagnostic Products Corporation, Llanberis, UK) assays had low sensitivity and less than 1% of the dynamic range of Centaur (Bayer Healthcare Diagnostics, Newbury, UK) cTnI and Elecsys (Roche Diagnostics, Basel, Switzerland) and M8 (Bioveris Europe, Whitney, UK) cTnT assays. In dogs, however, the Immulite assay was effective and correlated with the Centaur. Serum concentrations were highly correlated but 10-fold lower for cTnT compared with cTnI with cardiac injury. Centaur assay also detected cTnI in myocardium from marmosets, swine, cattle, and guinea pigs, indicating it to be candidate cardiac biomarker for these species as well. Purified rat cTnI was 50% more reactive than purified human cTnI in the Centaur assay. In the rat, an age- and gender-dependent variation in serum cTnI was found. Male rats aged six and eight months had a 10-fold greater serum cTnI than age-matched females and three-month-old rats. These increases correlated with minimal histopathological change. Isoproterenol-induced serum cTnI increased up to 760-fold the minimal detectable concentration of 0.07 microg/L, within 4-6 h and decreased with a half-life of 6 h, with an expected return to baseline of 60 h. Severity of histopathological change correlated with serum cTnI during the ongoing injury.

Measurement of blood cTnl levels may be a useful aid in the diagnosis of dogs with suspected heart disease and in indicating the severity of heart failure.

Gonadal steroids exert a powerful regulatory influence upon the functioning of gonadotropin‐releasing hormone (GnRH) neurons despite the apparent absence of gonadal steroid receptors in these cells. By using retrograde‐tracing techniques combined with dual‐labeling immunocytochemistry, we show here that distinct populations of estrogen receptor alpha (ERα)‐containing neurons located in the hypothalamus and caudal brainstem project to the vicinity of the GnRH perikarya located in the rostral preoptic area (rPOA). The strongest estrogen‐receptive afferent projection to this area originated from neurons located in the anteroventral periventricular and medial preoptic nuclei of the preoptic area. Approximately 50% of arcuate nucleus neurons projecting to the rPOA were demonstrated to synthesize either neuropeptide Y or β‐endorphin, but little evidence was found for ERα immunoreactivity in either of these specific subpopulations. Over 80% of all tyrosine hydroxylase‐expressing neurons in the arcuate nucleus expressed ERα, but none projected to the rPOA. In the caudal brainstem, the A1 and A2 norepinephrine neurons comprised nearly all of the retrogradely labeled neurons. However, only the A2 afferents expressed ERα immunoreactivity, whereas the A1 afferents coexpressed neuropeptide Y. These observations, combined with the anterograde labeling data of others, provide neuroanatomical evidence for the existence of specific estrogen‐receptive neuronal cell populations that project to the rPOA and may be involved in the estrogen‐dependent transsynaptic regulation of GnRH neurons in the rat. J. Comp. Neurol. 411:346–358, 1999. © 1999 Wiley‐Liss, Inc.

The perceptions of veterinarians and small animal (SA) clients on what attributes constitute 'a good veterinarian' were examined by a questionnaire survey. The respondents were asked to record how important they considered 20 attributes for a veterinary surgeon to have on a five-point scale from 'not at all important' to 'very important'. In addition, they were asked to list which attributes they considered to be the three most important attributes in a veterinary surgeon; finally, they were asked whether there were any additional attributes that they considered to be highly desirable in a veterinary surgeon. In total, 407 SA clients, 243 SA veterinarians and 61 non-SA veterinarians completed the questionnaire. There were significant differences in the proportion of clients who considered an attribute to be 'very important' compared with SA veterinarians for 12 of the 20 attributes (P<0.005). A larger proportion of clients considered 'confidence', 'knowledge about veterinary medicine and surgery', 'cleanliness', 'good at explaining technical terms', 'patience', 'clear about cost of treatment', 'ability to work in a team', 'honesty', 'politeness', 'decisiveness', 'good with animals' and 'good practical skills' to be 'very important' attributes than the SA veterinarians; a larger proportion of SA veterinarians considered 'good communication skills' to be a 'very important' attribute than the clients.

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