烟碱对大鼠心电图的影响

烟碱对心率的作用具有阶段性,初期引起心率短暂性减弱,紧接着发生瞬时增加。为进一步确定烟碱对大鼠心脏的作用,对描记烟碱作用后大鼠心电图进行分析,发现烟碱能引起大鼠心电图显示较长的QT间期,增加了PR间期及T波面积,与肾上腺素或去甲肾上腺素引起的QT间期延长相似,且能被M受体阻断剂阿托品所阻断,说明烟碱能够诱导局部释放乙酰胆碱或者作用于部分副交感神经控制的毒蕈碱受体。     

An epidemiological study of myopathies in Warmblood horses

REASON FOR PERFORMING STUDY: There are few detailed reports describing muscular disorders in Warmblood horses. OBJECTIVES: To determine the types of muscular disorders that occur in Warmblood horses, along with presenting clinical signs, associated risk factors and response to diet and exercise recommendations, and to compare these characteristics between horses diagnosed with polysaccharide storage myopathy (PSSM), those diagnosed with a neuromuscular disorder other than PSSM (non-PSSM) and control horses. METHODS: Subject details, muscle biopsy diagnosis and clinical history were compiled for Warmblood horses identified from records of biopsy submissions to the University of Minnesota Neuromuscular Diagnostic Laboratory. A standardised questionnaire was answered by owners at least 6 months after receiving the muscle biopsy report for an affected and a control horse. RESULTS: Polysaccharide storage myopathy (72/132 horses) was the most common myopathy identified followed by recurrent exertional rhabdomyolysis (RER) (7/132), neurogenic or myogenic atrophy (7/132), and nonspecific myopathic changes (14/132). Thirty-two biopsies were normal. Gait abnormality, 'tying-up', Shivers, muscle fasciculations and atrophy were common presenting clinical signs. Forty-five owners completed questionnaires. There were no differences in sex, age, breed, history or management between control, PSSM and non-PSSM horses. Owners that provided the recommended low starch fat supplemented diet and regular daily exercise reported improvement in clinical signs in 68% (19/28) of horses with a biopsy submission and 71% of horses diagnosed with PSSM (15/21). CONCLUSIONS: Muscle biopsy evaluation was a valuable tool to identify a variety of myopathies in Warmblood breeds including PSSM and RER. These myopathies often presented as gait abnormalities or overt exertional rhabdomyolysis and both a low starch fat supplemented diet and regular exercise appeared to be important in their successful management. POTENTIAL RELEVANCE: Warmbloods are affected by a variety of muscle disorders, which, following muscle biopsy diagnosis can be improved through changes in diet and exercise regimes.     

Diagnostic and prognostic utility of surface electrocardiography in cats with left ventricular hypertrophy

Objectives

To assess the ability of electrocardiography (ECG) to predict left ventricular hypertrophy (LVH) in the cat and to investigate the prognostic value of selected ECG variables in cats with LVH.

Atrial natriuretic peptide and cardiac troponin I concentrations in healthy Warmblood horses and in Warmblood horses with mitral regurgitation at rest and after exercise

ObjectiveAtrial natriuretic peptide (ANP) and cardiac troponin I (cTnI) serve as biomarkers for increased cardiac pressure/volume loading and for myocardial stress or damage. The objective was to describe the time course of plasma ANP concentrations (Cp_ANP) and plasma cTnI concentrations (Cp_cTnI) in horses with mitral regurgitation (MR) compared to healthy horses at rest and after exercise, and to describe the relationship of Cp_ANP with cardiac dimensions and intracardiac pressures.Animals15 healthy Warmblood horses and 7 Warmblood horses with MR.MethodsCardiac dimensions at rest were measured using echocardiography. All horses underwent standardized treadmill exercise. Biomarker concentrations and intracardiac pressures were measured at rest and after exercise. Hypotheses were tested using statistical methods. The level of significance was P < 0.05.ResultsHorses with MR showed increased left atrial (LA) and left ventricular (LV) dimensions but similar exercise capacity compared to healthy horses. Pulmonary capillary wedge pressures (PCWP) and Cp_ANP increased with exercise. Horses with MR had higher PCWP and higher Cp_ANP at rest and after exercise compared to healthy horses, with the maximum difference in Cp_ANP reached 10 min after exercise. Cp_ANP was significantly related to PCWP and – although inconsistently and only in healthy horses – to echocardiographic indices of LA and LV size and function. Cp_cTnI was low throughout the study in both groups.ConclusionsCp_ANP is increased in horses with MR and is related to LA pressures and to left heart dimensions. MR is not necessarily associated with exercise intolerance and exercise-induced myocardial stress or damage.     

Diurnal variation and age differences in the biochemical markers of bone turnover in horses

Biochemical markers of bone turnover provide sensitive, rapid, and noninvasive monitoring of bone resorption and formation. Serum concentrations of osteocalcin (OC) reflect rates of bone formation, and urinary concentrations of the pyridinium crosslinks pyridinoline (Pyd) and deoxypyridinoline (Dpd) are specific and sensitive markers of bone resorption. These markers are age-dependent and are used to detect and monitor changes in the rates of bone turnover in a variety of orthopedic diseases in humans and may prove to have similar application in horses. This study examined age differences and diurnal variation in OC, Pyd, and Dpd in eight adult geldings and seven weanling colts. Blood and urine were collected at regular intervals over 24 h. Serum OC and cortisol, and urinary Pyd and Dpd were analyzed. Mean 24-h concentrations of cortisol and all three markers were higher (P<.003) in weanlings than adults. Significant 24-h variation was observed in adult gelding OC, Pyd, and Dpd concentrations (P< .02). Adult OC concentrations were highest between 2400 and 0900; Pyd and Dpd peaked between 0200 and 0800. Similar patterns of bone turnover were observed in weanling values, but they were not significant (P>.17) owing to greater variability between individuals. Cortisol secretion varied (P<.001) over 24 h in both adults and weanlings and, thus, did not seem to be responsible for greater variability in markers of bone turnover between weanlings. These data demonstrate that diurnal rhythms exist for serum OC and urinary Pyd and Dpd in adult horses, as reported in humans, and that sample timing is an important consideration in future equine studies using these markers.     

Diurnal variation of dynamic compliance, resistance and viscous work of breathing in normal horses and horses with lung disorders

Dynamic compliance, airway resistance, viscous work and respiratory frequency were measured at intervals in horses over 12 h periods. Variation, daily averages and circadian patterns were recorded. Examinations were performed on 24 horses. They were divided into three groups: Normal horses, horses with chronic latent bronchitis and horses with manifest chronic obstructive pulmonary disease (COPD). Significant differences were found between the daily averages and the fluctuations when the normal group and the COPD group were compared. In most cases differences between all three groups were significant. A significant circadian rhythm for airway resistance was detected in diseased horses. It was also established that single measurements give an incomplete picture of lung function. As has been established in humans, analysis of fluctuations in respiratory mechanics may be of diagnostic value. The above results should be taken into account particularly in trials with bronchodilators in horses with COPD.     

Genetic correlations between performance traits and radiographic findings in the limbs of German Warmblood riding horses

Results of mare performance tests in the field (MPT-F) of 10,949 mares, mare performance tests at station (MPT-S) of 1,712 mares, and inspections of horses intended for sale at riding horse auctions (AU) of 4,772 horses were used to investigate genetic correlations between corresponding performance traits. Mare performance tests were held in 1995 to 2004 and auction inspections in 1999 to 2004. Scores on a scale from 0 to 10 were given for gaits under rider (walk, trot, canter), rideability (evaluated by judging commission and test rider), free-jumping (ability, style, total), and character. Radiography results of 5,102 Hanoverian Warmblood horses were used to investigate genetic correlations between performance traits and particular radiographic findings. The radiographic findings included osseous fragments in fetlock and hock joints, deforming arthropathy in hock joints, and distinct radiographic findings in the navicular bones, which were analyzed as binary traits, and radiographic appearance of the navicular bones, which was analyzed as a quasi-linear trait. Genetic parameters were estimated multivariately in linear animal models with REML using information on the horses radiographed and their contemporaries (n = 18,609). Heritability of performance traits ranged between 0.14 and 0.61, and heritability of radiographic findings between 0.14 and 0.33. Additive genetic correlations between corresponding performance traits were close to unity for MPT-F and MPT-S, ranged from 0.81 to 0.90 for MPT-F and AU, and were 0.75 to 0.92 for MPT-S and AU. Genetic correlations between performance and radiography results were mostly close to zero. Indications of negative additive genetic correlations were observed for deforming arthropathy in hock joints and canter, rideability evaluated by test rider, jumping traits and character, and osseous fragments in hock joints and character. Selection of horses for radiological health of their limbs will assist further genetic improvement of the performance of young Warm-blood riding horses.     

Circannual variation in plasma adrenocorticotropic hormone concentrations in the UK in normal horses and ponies, and those with pituitary pars intermedia dysfunction

Reasons for performing study: Pituitary pars intermedia dysfunction (PPID) is a common endocrinopathy, frequently diagnosed via plasma adrenocorticotropic hormone (ACTH) concentrations. Seasonal variation in plasma ACTH concentrations has been described in normal horses prompting caution in diagnosing PPID at certain times of the year. The aims of this study were to determine appropriate reference intervals for equine plasma ACTH throughout the year; and to examine the circannual variation of plasma ACTH concentrations in PPID cases. Hypothesis: Plasma ACTH can be used as a test for PPID throughout the year with the use of appropriate reference intervals. Methods: Data for reference interval calculations were obtained from samples collected from inpatients of Liphook Equine Hospital (non‐PPID group, n = 156). Data from PPID cases (n = 941) were obtained from samples submitted to the Liphook Equine Hospital Laboratory from horses with a clinical suspicion of PPID found to have plasma ACTH concentrations greater than our upper reference interval for that time of year. Results: Upper limits for reference interval of plasma ACTH were 29 pg/ml between November and July and 47 pg/ml between August and October. Circannual variation in plasma ACTH occurred in both non‐PPID and PPID horses with the highest ACTH concentrations found between August and October in both groups (P<0.0001). The greatest difference between the 2 populations also occurred between August and October. Conclusions: Plasma ACTH can be used for the diagnosis and monitoring of PPID throughout the year with the use of appropriate reference intervals. These findings demonstrate an increase in pituitary gland secretory activity during the late summer and autumn in both normal and PPID cases.     

Cardiac arrhythmias and electrolyte disturbances in colic horses

Background

Despite increased focus on cardiac arrhythmias in horses, the nature and prevalence is still poorly described. Case reports suggest that arrhythmias occurring secondary to systemic disease are seen more commonly in the clinic than arrhythmias caused by cardiac disease. The aim of this study was to investigate the prevalence of arrhythmias in colic horses referred for hospital treatment. Associations between electrolyte disturbances and arrhythmias were also investigated.The study population consisted of eight control horses and 22 referred colic horses. A Holter electrocardiography (ECG) was recorded during the first 24 hours of admission. The ECG’s were analysed by a software program followed by manual visual inspection. Arrhythmias registered included second degree atrioventricular (AV) blocks, supraventricular premature complexes (SVPCs), and ventricular premature complexes (VPCs). Blood was collected at admission and again between 12 and 24 hours after ECG was applied, and analysed for concentrations of potassium, sodium, ionised calcium, chloride, glucose, and L-lactate.

Results

Heart rate was 37.4 ± 3.7 bpm in the control group, and 51.6 ± 11.8 bpm, in the colic group, which was significantly different (P < 0.0001). AV blocks and SVPCs were found in both groups, however only colic horses showed VPCs. No significant difference between the two groups was found for AV blocks, SVPCs, and VPCs (P = 0.08 - 0.76). The mean levels of potassium, sodium, ionized calcium, and chloride were significantly lower in the colic group compared to the control group at admission. Mean levels of glucose and L-lactate were significantly elevated in the colic group (P < 0.05).

Conclusions

This study describes prevalence of cardiac arrhythmias and electrolytes concentrations in colic horses compared to healthy controls. Although we only observed VPCs in the colic horses, no significant differences between colic horses and controls were found. Despite the colic horses having electrolyte changes at admission no correlation was found between the electrolyte disturbances and cardiac arrhythmias. Although no clear conclusions can be drawn from the present study, the results indicate that relatively mild colic per se is not pro-arrhythmogenic, whereas severe colic probably are more likely to result in ventricular arrhythmia.     

Genetic relations of movement and free-jumping traits with dressage and show-jumping performance in competition of Dutch Warmblood horses

Genetic parameters for traits evaluated at the studbook entry inspection and genetic correlations with dressage and show-jumping performance in competition were estimated. Data comprised 36,649 Warmblood horses that entered the studbook between 1992 and 2002. The genetic analyses were performed using univariate and bivariate animal models. Heritabilities of the studbook entry traits were estimated in the range 0.15–0.40. The movement traits showed moderate to strong mutual genetic correlations, whereas the genetic correlations of movement traits with free-jumping traits were weak to moderate. The free-jumping traits showed strong to very strong mutual genetic correlations.

Competition results of 33,459 horses with performance in dressage and 30,474 horse with performance in show-jumping were linked to the studbook entry data to estimate the genetic relationship with performance in competition. Heritability estimates for dressage and show jumping were 0.14. Genetic correlations of the movement traits with dressage were moderate to strong, and with show-jumping weak to moderate. Genetic correlations of the free-jumping traits with dressage were weak to moderate and unfavourable. The free-jumping traits were genetically strong to very strong correlated to show-jumping. It was concluded that a selection of the traits evaluated at the studbook entry inspection will favourably contribute to estimation of breeding values for sport performance.     

Prevalence of various radiographic manifestations of osteochondrosis and their correlations between and within joints in Dutch Warmblood horses

Reasons for performing study: Osteochondrosis (OC) is the most important orthopaedic developmental disorder in horses and may manifest in several different forms. No detailed study on the prevalence and/or interrelation of these forms is available, even though these data are a prerequisite for conclusive genetic studies. Objectives: To assess the prevalence of the various manifestations of OC as detected radiographically and to evaluate possible relationships between their occurrence within the same joint and between different joints. Methods: The FP (femoropatellar), TC (tarsocrural) and MCP/MTP (metacarpophalangeal/metatarsophalangeal) joints of 811 yearlings selected randomly, descending from 32 representative stallions, were radiographed and scored for the presence and grade of osteochondrotic lesions. Results were compared at the sire, animal, joint and predilection site levels. Results: In the FP joint, the percentage of animals showing normal joint contours in all sites was 60.7%. For the TC joint and the combined MCP/MTP joints, these figures were 68.6 and 64.6%, respectively. For all joints combined, the percentage dropped to 30.5%. Sedation improved detection of OC lesions in the FP joint. There was a high correlation between the right and left joints. The correlation between flattened bone contours and fragments was considerably less. Conclusions: Scoring on a detailed scale is necessary to achieve good insight into the prevalence of OC. Observations on the right and left joints can be combined in further analyses, whereas flattened bone contours and fragments should be evaluated as statistically different disorders. Potential relevance: This study provides insight into the prevalences of various manifestations of OC and their relationships, within and between joints. These results form the basis for detailed quantitative and/or molecular genetic studies that should lead to the establishment of breeding indices and/or genetic marker sets for OC.     

Prevalence of osseous fragments in distal and proximal interphalangeal, metacarpo- and metatarsophalangeal and tarsocrural joints of Hanoverian Warmblood horses

The prevalence of osseous fragments in different limb joints was analysed in 3749 young Warmblood riding horses, which were pre-selected for sale at auction from 1991 to 1998 by the Association of Hanoverian Warmblood Breeders (Verband hannoverscher Warmblutzüchter e.V.) in Verden (Aller), Germany. The evaluation of these horses was based on a standardized radiological examination, including the distal interphalangeal (DIJ), the proximal interphalangeal (PIJ), the metacarpo- and metatarsophalangeal (MC/MTJ) and the tarsocrural joints (TCJ). In 32% of all horses at least one osseous fragment was found on these radiographs. TCJ were affected in 9.6% of the horses and MC/MTJ in 20.7%. The percentage of horses affected in the MTJ was significantly higher (13.7%) than that of horses affected in the MCJ (9.5%). The prevalences of osseous fragments were considerably lower in DIJ (4.5%) and PIJ (0.9%). Osseous fragments only occurred either in DIJ or PIJ or MC/MTJ or TCJ in 87% of the affected horses. Depending on the joint type, osseous fragments were found in analogous joints in the front and the hind limbs in up to 26% of the affected horses, whilst bilateral affection occurred in between 10% and 46% of the horses. Distribution of osseous fragments in the limb joints investigated here did not differ significantly between male and female horses. There was a significant increase in the percentage of horses with osseous fragments in MC/MTJ during the study period. The results of this study indicate the need to act against the high prevalences of osseous fragments in the limb joints of young Warmblood riding horses.     

Animal grouping strategies, sources of variation, and economic factors affecting nutrient balance on dairy farms

Increasing environmental concerns are forcing animal industries to reevaluate current feeding practices and their relationships to nutrient excretion. Previous modeling efforts have used simple budgets of nutrient flows through animals, assuming a constant productivity level. This assumption is not valid if animals are not in a steady state. A response model of dairy cow production to levels of net energy for lactation (NEL) and crude protein (CP) was derived from an abrupt threshold and plateau model of individuals. Monte Carlo techniques were used to simulate populations of cows fed diets of various NEL and CP concentrations, to derive the optimum allocation of NEL and CP, and to estimate how the optimum is affected by herd production potential, prices of inputs, and uncertainty of parameters. The simulation showed that a 25% increase in milk production reduced N excretion per kilogram of milk produced by 8%. Improved knowledge of the biology involved and feed composition can reduce N excretion by an additional 8%. Grouping strategies and number of groups used affect optimum allocation of nutrients. An optimum of six milking groups per production unit was derived from the simulation and would reduce N excretion by 8% compared to herds fed in one group.     

牦牛Q—Tc和Q—Tr值的探讨

对７６头牦牛的Ｑ－Ｔｃ和Ｑ－Ｔｒ值研究表明，牦牛的Ｑ－Ｔｃ值具有年龄差异，成年牦牛，２岁牦牛和１－３月龄牦牛的Ｑ－Ｔｃ值分别为０．３１２，０．３２７和０．３４５。成年牦牛和２岁牦牛的Ｋ常数应定为０．３２ｓ，１－３月龄牦牛应定为０．３４ｓ。