Porcine malignant hyperthermia susceptibility: halothane-induced increase in cytoplasmic free calcium in lymphocytes

We tested the hypothesis that lymphocytes from swine with susceptibility to malignant hyperthermia (MH) had increased sensitivity to the membrane-perturbing effects of halothane that increase cytoplasmic calcium. Cytoplasmic concentration of ionized calcium in lymphocytes isolated from blood was determined in the presence and absence of halothane for 10 Pietrain x Poland China swine that were susceptible to MH and 20 Yorkshire swine that were resistant to MH. Calcium was determined by dual-emission spectrofluorometry and by measuring the ratio of free to calcium-bound form of the fluorescent calcium dye Indo-1. Mean values for calcium concentrations in lymphocytes from MH-susceptible (MHS) swine were 80% less than control values (40.5 +/- 38.8 and 185.3 +/- 91.6 nmol/L; P less than 0.01). Untreated lymphocytes from MHS swine accumulated calcium at half the rate observed for controls. Exposure to 1 mmol/L halothane resulted in a 3-fold increase of free calcium concentration to 127.9 +/- 81.3 nmol/L in the lymphocytes of MHS swine, but had no significant effect on lymphocytes from control swine (225.0 +/- 91.4; P less than 0.01). Exposure to 2 mmol/L halothane resulted in a 6-fold increase of free calcium concentration to 255.9 +/- 91.4 nmol/L in lymphocytes from MHS swine and a 63% increase in lymphocytes from controls (303.8 +/- 116). The rate of halothane-induced increase in cytosolic calcium was 13 times greater in lymphocytes from MHS swine, compared with controls. These data indicated that the molecular defect that results in halothane-hypersensitivity and is characteristic of muscle of MHS swine also occurs in lymphocytes from MHS swine.     

Atypical bacterial gill disease: a new form of bacterial gill disease affecting intensively reared salmonids

An unusual form of bacterial gill disease (BGD) was identified which affected five species of cultured salmonids from Canada (i.e. rainbow trout, chinook salmon and Atlantic salmon), Norway (i.e. brown trout) and Chile (i.e. coho salmon). All outbreaks occurred at low water temperatures (< 10 °C) and with clinical presentations distinct from classical BGD, which is caused by Flavobacterium branchiophilum. In contrast to classical BGD, fish did not show marked respiratory distress with flaring of the opercula, the animals did not orientate at the surface of the water column near inflow water or at the margins of the tanks, and the feed response of the fish was varied. While mortality was increased, it was not precipitous as in classical BGD. Eight outbreaks were examined in greater detail using histopathology, scanning electron microscopy, bacteriology and immunohistochemistry. Large numbers of small bacterial rods were seen adhering to the lamellar epithelium of affected gills from all outbreaks. Histologically, the lamellar epithelium appeared swollen, often with evidence of single cell degeneration and exfoliation. In more severe instances, the formation of lamellar synechiae was seen, usually associated with sequestration of bacteria between fused lamellae. By contrast with typical BGD, overt epithelial hyperplasia, lamellar fusion and filamental clubbing were not common sequelae to infection; instead, the end result was shortened and somewhat stubby lamellae covered with swollen epithelial cells. The predominant bacterium recovered from affected gills was a small, Gram-negative, motile, fluorescent pigment-producing rod that shared phenotypic characteristics with Pseudomonas fluorescens. Polyclonal antisera prepared against three representative isolates indicated a weak antigenic similarity among them. Immunohistochemistry corroborated this finding, in that the antisera reacted strongly with gill sections containing the homologous bacteria, but not against morphologically similar bacteria in heterologous sections. A Gram-negative, yellow pigmented bacterium (YPB), identified as Flavobacterium psychrophilum, was also recovered, but only from the gills in the Ontario outbreaks. Antiserum prepared against this YPB indicated an antigenic similarity among isolates recovered from the Ontario outbreaks, but immunohistochemistry failed to recognize antigenically related bacteria on the gills of fish from the other outbreaks. Based on the unusual clinical presentation and the histopathological appearance of the gills, in conjunction with the absence of filamentous bacteria associated with and recovered from affected gills, the present authors have called this condition ‘atypical bacterial gill disease’ or ABGD.     

Examination of the origin of increased equine serum alkaline phosphatase concentrations

Serum alkaline phosphatase activity was found to be increased in 32.6% of equine samples analyzed at the Ontario Veterinary College over an 18 month period. An attempt was made using sensitivity to L-phenylalanine and heat to identify the origin of increased serum alkaline phosphatase isoenzymes present in 44 clinical cases. No difference in sensitivity to either procedure was observed for serum alkaline phosphatase from groups of foals and horses representing different clinical problems. Alkaline phosphatase of osseous tissue origin appeared to be the major source of activity for each group of animals reported.