Evaluation of strontium 90 irradiation in treatment of cutaneous mast cell tumors in cats: 35 cases (1992-2002)

OBJECTIVE: To determine the efficacy of strontium 90 beta irradiation in the management of cutaneous mast cell tumors (CMCTs) in cats. STUDY DESIGN: Retrospective case series. ANIMALS: 35 client-owned cats with CMCTs. PROCEDURE: Medical records of cats with CMCTs in which tumors were radiated by use of a strontium 90 ophthalmic applicator from 1992 to 2002 were reviewed. Cats were included if CMCT was diagnosed, there were no other sites of MCT involvement at the time of treatment, and records contained adequate follow-up information to permit retrospective assessment of local tumor control. RESULTS: 54 tumors in 35 cats were treated with a median dose of 135 Gy of strontium 90 beta irradiation, resulting in local tumor control in 53 of 54 (98%) tumors with a median follow-up time of 783 days after treatment. Median survival time was 1,075 days. Adverse effects of treatment appeared to be infrequent and of mild severity. CONCLUSIONS AND CLINICAL RELEVANCE: Results indicated that strontium 90 beta irradiation resulted in long-term tumor control and should be considered an effective alternative to surgical resection in management of CMCTs in cats.     

Optimization of conditions for in vitro production of radical oxygen species and expression of tissue factor by canine mononuclear cells and granulocytes for use in high-throughput assays

The purpose of this study was to optimize conditions for high throughput measurement of radical oxygen species (ROS) production and expression of tissue factor, also termed procoagulant activity, by canine leukocytes. Granulocytes and mononuclear cells were separated by density gradient centrifugation from peripheral blood collected on several occasions from three healthy large breed dogs. To determine optimal conditions for ROS production, granulocytes were incubated for 1 or 3h in PBG (PBS containing 0.5% BSA and 5mM glucose) or RPMI containing 10% fetal bovine serum (FBS); lipopolysaccharide (LPS), zymosan, peptidoglycan (PGN) and phorbol myristate acetate (PMA) were used as stimuli. ROS was assessed by conversion of the nonfluorescent dye dihydrorhodamine 123 to fluorescent rhodamine 123 by radical species released into the media. To identify optimal conditions for expression of tissue factor, mononuclear cells were incubated for 5h in RPMI containing different concentrations of heat-inactivated FBS (HI-FBS), and LPS, zymosan, PGN or PMA as stimuli. Expression of tissue factor was determined using a one-stage recalcification assay performed in an automated nephelometric coagulation analyzer. Neither LPS nor zymosan increased ROS production by granulocytes incubated in PBG media. In contrast, granulocytes incubated in RPMI had dose-dependent increases in ROS production in response to zymosan and PGN. ROS production was significantly increased by incubation with concentrations of LPS of 0.01microg/ml or greater, and by zymosan concentrations of 0.1microg/ml or greater. ROS production in response to incubation with PMA was significantly increased starting at 10(-7)M, and was significantly greater for cells incubated in RPMI than cells incubated in PBG. LPS-, zymosan- and PGN-stimulated procoagulant activity increased in a dose-dependent manner, whereas PMA-stimulated procoagulant activity peaked at 10(-7)M. Increasing concentrations of HI-FBS significantly increased LPS-, zymosan- and PGN-induced procoagulant activity of mononuclear cells. Results obtained in this study indicate production of ROS by canine granulocytes is optimal when these cells are incubated for 3h in RPMI with LPS (0.1microg/ml), zymosan (10 microg/ml), PGN (10 microg/ml), and PMA (10(-7)M). Furthermore, canine mononuclear cells express procoagulant activity in response to LPS, zymosan, PGN, and PMA, and responses to LPS, zymosan and PGN are enhanced by the addition of HI-FBS. These findings suggest that HI-FBS retains important serum proteins that facilitate interactions between each of these bacterial or yeast derived products and the mononuclear cells. Consequently, future studies regarding the regulation of procoagulant activity by canine mononuclear cells should be performed in the presence of HI-FBS. Both assays utilized in this study allow high throughput of samples, and therefore are appropriate choices for rapid screening of conditions and/or therapeutic interventions affecting the canine inflammatory system.     

Septicaemia secondary to infection by Corynebacterium macginleyi in an Indian python (Python molurus)

A seven-year-old female Indian python (Python molurus) weighing about 35kg was euthanased after several clinical episodes of stomatitis, pneumonia, ophthalmitis and dystocia over a period of four years. The animal had been maintained in a terrarium in a circus truck at an adequate temperature. During shows, however, the snake was considered to be exposed to stressful conditions for several hours at a time at low temperatures and with noise and bright lights. A post-mortem examination indicated ulcerative stomatitis, osteomyelitis, severe pneumonia and numerous granulomata and multifocal necrosis in stomach and spleen. Corynebacterium macginleyi was isolated in pure culture from the ulcerative stomatitis, and mixed with Stenotrophomonas maltophilia from the lungs and spleen. The findings indicated that the snake had died from a septicaemic process caused by C. macginleyi, probably originating from the stomatitis. The role of S. maltophilia as a secondary agent is discussed. The stress of the circus show and poor husbandry may have predisposed the animal to infection and septicaemia. This is the first report of C. macginleyi causing disease in a snake.     

Non-invasive assessment of growth, gender and time of day related changes of respiratory pattern in healthy cats by use of barometric whole body plethysmography

The objective of this study was to establish a reference base for respiratory variables (respiratory rate [R(R)], inspiratory and expiratory time [T(i) and T(e)], peak inspiratory and expiratory pseudoflow [PIF and PEF], tidal volume [V(T)], minute ventilation [V(E)] and enhanced pause [Penh]) of healthy cats by use of barometric whole body plethysmography (BWBP). Eighteen healthy European cats (10 male, 8 female) were studied from the age of 3 to 13 months in order to assess growth- and gender-related changes of BWBP variables. Chest radiographs and bronchoalveolar lavage cytology were performed to confirm pulmonary health status. Diurnal changes were investigated every 2 h over a period of 24 h when the cats were adult. V(T), V(E), PIF and PEF significantly increased during somatic growth and were higher in males than in females, whereas R(R), T(i), T(e), T(e)/T(i) ratio, PEF/PIF ratio and Penh remained unchanged and were not affected by gender. When measured over 24 h, Penh, T(e) and T(i) were significantly increased in the early morning hours (04:00 h), whereas R(R), PIF and PEF were decreased at that time. This study provides reference values of BWBP variables for healthy male and female cats and indicates when circadian changes might be observed.     

Na(+), K(+)-ATPase content in skeletal muscle of dogs with pituitary-dependent hyperadrenocorticism

Several hormones regulate Na⁺, K⁺-ATPase content in the muscle cell membrane, which is essential for maintaining muscle cell excitability. Chronic glucocorticoid excess is associated with muscle weakness and reduced endurance. We hypothesized that chronic glucocorticoid excess affects Na⁺, K⁺-ATPase content in canine skeletal muscle, and contributes to reduced endurance and muscle weakness associated with pituitary-dependent hyperadrenocorticism (PDH) in dogs. Therefore, Na⁺, K⁺-ATPase content in skeletal muscle was evaluated before and after hypophysectomy and hormone replacement (cortisone and l-thyroxin) in dogs with PDH (n = 13), and in healthy controls (n = 6). In addition, baseline and exercise-induced changes in plasma electrolyte concentrations and acid–base balance were evaluated before and after hypophysectomy in dogs with PDH. Na⁺, K⁺-ATPase content of gluteal muscle in dogs with PDH was significantly lower than in control dogs (201 ± 13 pmol/g versus 260 ± 8 pmol/g wet weight; P < 0.01). Similar differences were found in palatine muscle. After hypophysectomy and on hormone replacement, Na⁺, K⁺-ATPase was increased (234 ± 7 pmol/g wet weight). Both plasma pH and base excess in dogs with PDH (7.44 ± 0.01; 1.7 ± 0.6 mmol/l, respectively) were significantly higher (P < 0.05) than after hypophysectomy and hormone replacement (7.41 ± 0.01; −0.2 ± 0.4 mmol/l, respectively). Exercise induced respiratory alkalosis, but did not result in hyperkalemia in dogs with PDH. In conclusion, chronic glucocorticoid excess in dogs with PDH is associated with decreased Na⁺, K⁺-ATPase content in skeletal muscle. This may contribute to reduce endurance in canine PDH, although dogs with PDH did not exhibit exercise-induced hyperkalemia. Na⁺, K⁺-ATPase content normalized to values statistically not different from healthy controls after hypophysectomy and hormone replacement.     

The effect of breed, stage of lactation and parity on sheep milk fat CLA content under the same feeding practices

The cis-9, trans-11 C_18:2 (CLA) content in milk fat of four pure sheep breeds (Awassi, Lacaune, Friesland and Chios) was examined. All sheep were kept indoors all year round under the same feeding practices, without any grazing at all. Sheep nutrition was based on alfalfa hay and concentrates. A total of 237 individual milk samples were collected at three sampling times (December, January and March) from sheep of different parity and different days in milk, for CLA determination. The results showed that: (a) there was a large variation in milk fat CLA content among individuals consuming the same diet, (b) the CLA content of milk fat was lower in Friesland breed, compared to the other three breeds but without any significant difference among the four sheep breeds, (c) the CLA content of milk fat was not affected by ewes parity or days in milk, (d) there was a negative but not significant correlation between milk fat and CLA concentration, (e) the CLA content of milk fat was not correlated with milk yield. In conclusion, no others factors, such as breed, parity, days in milk, etc., can affect CLA content in milk fat, which means that the dietary ones remain the sovereign factors explaining the highest proportion of CLA content variability in sheep milk fat.     

SEASONAL AVAILABILITY OF NEMATODE LARVAE ON PASTURES GRAZED BY CATTLE IN NEW SOUTH WALES

Trends in the numbers of infective nematode larvae on pasture plots contaminated by cattle at different seasons of the year were defined in 3 different climatic regions. The main nematodes were Ostertagia ostertagi, Trichostrongylus spp, Haemonchus spp and Cooperia spp.
On the North Coast of New South Wales with a sub-tropical climate, the numbers of infective larvae of all 4 nematodes rose rapidly to peak levels soon after each seasonal period of contamination began, then fell quickly within a few months. On the Central Coast of New South Wales, the trends were similar to those on the North Coast, except that the larvae persisted on the pasture for a much longer time. On the Northern Tablelands of New South Wales, where temperatures were much colder than on the coast, larval development was slower and major peaks of larval availability did not occur until early spring. These different seasonal trends in each region were considered to be related to the climatic differences between the regions.
On pastures which were contaminated continuously, larval numbers reached maximum levels in mid-winter on the Central Coast and in early spring on the Northern Tablelands. It was concluded that the majority of these larvae were derived from the contamination of pastures in autumn and winter. Subsequently in summer, a rapid dying out of larvae was observed in all the regions, probably due to the effect of hotter weather.
The studies suggest that a reduction in the contamination of pasture with nematode eggs in autumn and winter could result in pastures carrying fewer larvae and thus form the basis of effective worm control programs for cattle.     

Direct and indirect lymphocyte participation in the immunity and immunopathology of tropical canine pancytopenia—A review

Erlichia canis, a rickettsial pathogen which infects monocytes, induces generalized lymphocyte activation. Activated T lymphocytes differentiate into effector cells capable of destroying infected and uninfected monocytes and platelets. Activated B lymphocytes differentiate into plasma cells associated with plasmocytosis, hypergammaglobulinemia with high levels of specific antibody and a platelet migration inhibition factor. These effector mechanisms, aimed at parasite destruction, contribute to the pathogenesis of acute tropical canine pancytopenia and do not completely eliminate the etiologic agent. A carrier state of ‘infection-immunity’ exists between the immunocompetent host and virulent parasite. E. canis has evolved mechanisms of ‘tolerant-symbiosis’ with hostile macrophages and other effector cells in the immune host.