Density and binding characteristics of beta-adrenoceptors in the normal and failing equine myocardium

Beta-adrenoceptors are important regulators of cardiac function and their characteristics are known to change in human and canine diseased myocardium. This study aimed to determine the density and subtypes of beta-adrenoceptors in the normal and failing equine ventricular myocardium. Membrane preparations of the left papillary muscles were incubated with increasing concentrations of the nonselective beta-adrenoceptor antagonist [3H]-CGP12177. Saturable and reversible binding of [3H]-CGP12177 to myocardial membranes was demonstrated with Kd values (+/- s.d.) of 0.49 +/- 0.40 and 0.43 +/- 0.22 nmol/l and Bmax values of 93.4 +/- 20.5 and 110.0 +/- 21.2 and fmol/mg protein for normal (n = 19) and heart failure (n = 10) tissues, respectively. Heart failure had no significant effect on the density of ventricular beta-adrenoceptors. The cardiac beta-adrenoceptors were further characterised by studying displacement of [3H]-CGP12177 (0.6 nmol/l) with the beta1-selective antagonists CGP20712A and the beta2-selective antagonist ICI118.551. In normal ventricular muscle, CGP20712A was 26 times more potent than ICI118.551 (Ki values 30.4 +/- 24.8 and 814.1 +/- 485.2 nmol/l, respectively). In heart failure cases, CGP 20712A curves were monophasic with a Ki value of 45.6 +/- 39.7 nmol/l. ICI 118.551 curves were biphasic in 5 horses where 11-31% of the cardiac beta-adrenoceptors had a high affinity for ICI 118.551. These data suggest that the normal equine ventricular myocardium possesses predominately beta1-adrenoceptors, with no evidence for co-existence of a significant population of beta2-adrenoceptors. The density of beta-adrenoceptors did not appear to change in heart failure, but the appearance of receptors with a high affinity for ICI118.551 may suggest that, in some cases, heart failure increases the expression of beta2-adrenoceptors in equine ventricular myocardium. This study provides an insight into the role of the adrenergic system in heart disease in the horse. Further studies in this area are warranted.     

Evaluation of relationships between weather patterns and prevalence of sorghum ergot in the Texas panhandle

ABSTRACT Sorghum ergot caused by Claviceps africana was observed for the first time in the United States in Southern Texas in 1997. That year there was a widespread ergot epidemic in hybrid seed production fields in the Texas Panhandle. However, occurrence of the disease has been sparse during the past 3 years, easing fears that the hybrid seed industry in the region might be endangered. To determine whether climatic factors were associated with observed variations in prevalence of ergot, weather data (temperature, precipitation, and relative humidity) were collected from seven weather stations in the Texas Panhandle. Sorghum ergot prevalence data for the period 1997 to 2000 were collected from records of seed companies in the Panhandle and related to weather variables. Results showed that, in the southern section of the Panhandle, maximum temperature and precipitation between 1 and 15 August were associated (r(2) = 0.98, P = 0.001 and r(2) = 0.81, P = 0.0193, respectively) with variations in the prevalence of ergot during the 4-year period. In the northern section, only maximum temperature during 16 to 31 July was significantly associated (r(2) = 0.91, P = 0.0111) with disease prevalence. Over all, 1997 was wetter and cooler, during the 1 to 15 August period, than each of the subsequent 3 years. In addition to creating humid conditions for ergot development, precipitation was associated with suppression of maximum temperature, enhancing ergot-favorable temperature conditions. Examination of historic weather data for the region showed that there were many instances in the past where temperature depression was associated with a rise in cumulative precipitation, creating ergot-favorable conditions similar to those in 1997. Cross-spectral analysis was used to determine whether such association is periodic. Weather data from five of the seven locations in the region showed peaks of significant coherency ( alpha< 0.05) at 2 to 4 years and 7 to 10 years or greater, indicating the existence of a periodic cycle in the temperature-precipitation association. The results of the investigation suggested that association of precipitation with temperature depression is a primary factor in development of ergot in the Texas Panhandle, and such association has a periodic cycle.     

Induced systemic protection against tomato late blight elicited by plant growth-promoting rhizobacteria

ABSTRACT Two strains of plant growth-promoting rhizobacteria (PGPR), Bacillus pumilus SE34 and Pseudomonas fluorescens 89B61, elicited systemic protection against late blight on tomato and reduced disease severity by a level equivalent to systemic acquired resistance induced by Phytophthora infestans or induced local resistance by chemical inducer beta-amino butyric acid (BABA) in greenhouse assays. Germination of sporangia and zoospores of P. infestans on leaf surfaces of tomato plants treated with the two PGPR strains, pathogen, and chemical BABA was significantly reduced compared with the noninduced control. Induced protection elicited by PGPR, pathogen, and BABA were examined to determine the signal transduction pathways in three tomato lines: salicylic acid (SA)-hydroxylase transgenic tomato (nahG), ethylene insensitive mutants (Nr/Nr), and jasmonic acid insensitive mutants (def1). Results suggest that induced protection elicited by both bacilli and pseudomonad PGPR strains was SA-independent but ethylene- and jasmonic acid-dependent, whereas systemic acquired resistance elicited by the pathogen and induced local resistance by BABA were SA-dependent. The lack of colonization of tomato leaves by strain 89B61 suggests that the observed induced systemic resistance (ISR) was due to systemic protection by strain 89B61 and not attributable to a direct interaction between pathogen and biological control agent. Although strain SE34 was detected on tomato leaves, ISR mainly accounted for the systemic protection with this strain.     

Mycobacterial neuritis in a cat

A 2-year-old spayed female domestic shorthair cat was referred for evaluation of rapidly progressive lameness of the right hind limb, which was paralyzed. Histologic examination of biopsy specimens revealed pyogranulomatous inflammation affecting the sciatic, common peroneal, and tibial nerves, and slender, beaded, acid-fast bacilli within macrophages, nerve fibers, and degenerate axons. A diagnosis of mycobacterial neuritis was made and the cat was treated with clofazimine and enrofloxacin for extended periods. Treatment was partially effective; the goal of returning normal function to the limb was not achieved, but disease progression was halted and the cat remained a viable pet.     

Ventral midline caesarean section for dystocia secondary to failure to dilate the cervix in three alpacas

Three alpacas that presented with dystocia characterised by failure of the cervix to dilate, underwent caesarean section. Surgery on each animal was performed through a ventral midline incision under general anaesthesia. Two live crias were delivered and one cria was dead at delivery. All three alpacas had retained foetal membranes for a period of 12 h to 4 d and one developed uterine prolapse, which was replaced using sedation and epidural anaesthesia. There were no complications associated with the surgical procedure and all three alpacas went on to have confirmed pregnancies. Caesarean section through a ventral midline incision should be considered an alternative for treatment of difficult dystocias in alpacas.     

Suspected sheep-associated malignant catarrhal fever in a zero-grazed dairy herd in Kenya

An outbreak of a disease characterised by very high mortality occurred in a group of nine calves (1B4 months old) in a zero-grazing unit 2-3 weeks after an introduction of an apparently healthy alien sheep into the calf pen. Five of the six calves which contracted the disease died. The main clinical signs observed were marked depression, persistently high body temperature (40,5-41,5 degrees C), copious mucopurulent nasal and ocular discharges, dyspnoea, bilateral keratoconjunctivitis with corneal opacity, enlargement of the superficial lymph nodes and marked erythema and/or superficial erosions of the buccal mucosae. At necropsy there were lesions in the upper respiratory and digestive tracts, lymph nodes, brain, eyes, liver, kidneys and the urinary bladder.The lesions were histopathologically characterized by fibrinoid vasculitis which was accompanied by lymphocytic infiltration in the parenchyma of the affected tissues. Based on the evidence of contact between the calves and the recently introduced foreign sheep, the characteristic clinical signs and histopathological findings, a diagnosis of sheep-associated malignant catarrhal fever was made.     

Dermoid sinus at the lumbosacral junction in an English springer spaniel

A dermoid sinus was identified in a springer spaniel that presented with hindlimb neurological deficits. The sinus was continuous with the dura mater at the level of the lumbosacral junction. The presence of hair and debris adjacent to neural tissue had elicited a myelitis. A dorsal laminectomy was required to allow complete surgical resection of the sinus. The dog's neurological status improved after treatment and this improvement was maintained over a five-month follow-up period.     

Preliminary clinical observations on the use of piroxicam in the management of rectal tubulopapillary polyps

Rectal tubulopapillary polyps were diagnosed in eight dogs following proctoscopy and mucosal pinch biopsy. Histological examination of the pinch biopsies revealed evidence of malignant transformation in three of the cases. The remaining cases were diagnosed as benign polyps. Inflammatory changes were observed in four cases. Seven dogs were treated with piroxicam suppositories and one with oral piroxicam. All dogs were re-examined after four to six weeks of piroxicam therapy and the extent of haematochezia, tenesmus and faecal mucus production was reduced in all cases. The owners of seven of the dogs considered the improvement in clinical signs to be good or excellent. Cases with and without evidence of inflammation responded equally well. This finding supports the hypothesis that piroxicam has an antineoplastic effect due to apoptosis and alteration in the cell cycle. Medical management with piroxicam may provide a non-invasive treatment option for dogs with rectal polyp formation in which surgical treatment is likely to be associated with complications such as incontinence, infection and wound breakdown, or where the owner declines such treatment.     

Retrospective study of the relationships between age, inflammation and the isolation of bacteria from the lower respiratory tract of thoroughbred horses

A total of 1235 tracheal aspirates taken from 724 thoroughbreds in race training, aged from two to 10 years, were examined cytologically and bacteriologically. An inflammation scoring system on a scale of 0 to 9 was devised to allow the severity of lower airway disease to be assessed from the cytological results. The inflammation scores were closely related to the isolation of bacteria (P<0.001), and the most common bacterial isolates were Streptococcus zooepidemicus, Streptococcus pneumoniae and Pasteurella/Actinobacillus-like species. Lower airway disease was less common in older horses (P = 0.031), and the groups at highest risk were the two- and four-year-olds. Lower airway inflammation was more common in the four-year-olds at National Hunt yards than in the four-year-olds at flat racing yards (P = 0.040, odds ratio = 3.80).