Has jarosite dumping at a deepwater site off eastern Tasmania,Australia, had a measurable effect on the midwater zooplankton and micronekton communities?

The biomass, abundance, species diversity and length-frequency distribution of macrozooplankton and micronekton at a deep-ocean dumpsite southeast of Tasmania, Australia, were compared with those of the surrounding water masses. The dumping of jarosite – a waste product of zinc refining that contains trace quantities of heavy metals – began in 1973. The dumpsite, which typically receives 170,000 tonnes of jarosite per annum, is in an oceanographically, and biologically, dynamic area. Depending on season and large-scale oceanographic effects, the dumpsite can be dominated by high-salinity, warm waters of subtropical origin or low-salinity, cool waters of subantarctic origin. The comparisons of the macrozooplankton and micronekton parameters between water masses, and between the two years of the study (1992, 1993), did not show any changes that could be attributed to the jarosite dumping. Micronekton abundance was significantly lower over the dumpsite in 1992; however, this appears to be due to the presence of a warm-core eddy in the region of the dumpsite in that year. Changes in the regional oceanography between years also appear to account for significantly greater micronekton biomass over the dumpsite in 1993.     

Ascites and portal hypertension in three young dogs with non-fibrosing liver disease

Three young dogs were evaluated because of the sudden development of ascites. In each case ascites was referable to non-fibrosing hepatic disease associated with portal hypertension. Obstruction to portal flow was pre-sinusoidal in two cases and post sinusoidal in the other. In all cases ascites developed in the absence of severe hypoalbuminaemia. The ratio of the protein content of ascitic fluid in relation to the protein content of plasma proved useful in differentiating between pre- and post sinusoidal portal hypertension. All three animals died or were euthanased because of the sequelae of portal hypertension.     

SCINTIGRAPHIC EVALUATION OF SKELETAL DISEASE AND ITS APPLICATION TO THE HORSE

Bone scintigraphy is a valuable aid in the evaluation of lameness in horses. This review describes the principles of bone radiolabeling, scanning, and scan interpretation. Examples are used to illustrate how bone imaging can contribute significantly to a diagnosis after equivocal physical examination or radiographic findings.     

Per rectal portal scintigraphy in the diagnosis and management of feline congenital portosystemic shunts

Five cats with a congenital portosystemic shunt (CPSS) were examined using transcolonic portal scintigraphy before and after surgical ligation of the shunting vessel. The mean shunt index before surgery was 52 per cent (range 45 to 61 per cent). Repeat portal scintigraphy, six to eight weeks after surgery, indicated a significant reduction in shunt index (mean 13 per cent, range 5 to 25 per cent) in four cats. In one of these cats a marked reduction in the shunt index, as determined by scintigraphy, preceded normal fasting blood ammonia. In the fifth cat there was no significant change in the shunt index, fasting serum bile acids and blood ammonia six months after surgery, although its clinical signs of hepatic encephalopathy had improved. Portal scintigraphy is useful in the diagnosis of CPSS and enables a quantitative assessment of the effects of surgery and may be a more accurate indicator of the degree of shunting after surgery than blood ammonia and serum bile acids.     

COMPARISON OF THREE METHODS FOR CALCULATING PORTAL BLOOD FLOW VELOCITY IN DOGS USING DUPLEX-DOPPLER ULTRASONOGRAPHY

Measurement of portal blood flow in dogs using duplex-Doppler ultrasonography has potential clinical utility for diagnosis of cirrhosis and portosystemic shunts. Three methods for calculating portal blood flow were compared to identify a consistent method with minimal potential for intraoperator variation. Sixteen unsedated, normal beagles had their mean portal blood flow velocity determined using three methods: method 1 used a small Doppler sample volume positioned over the center of the portal vein and manual selection of data points on the resulting velocity spectra, followed by arithmetic correction of the calculated maximum velocity to mean velocity using the factor 0.57; method 2 used a small centrally-located Doppler sample volume and computed maximum flow determination, again corrected using the factor 0.57; method 3 used a large Doppler sample volume that overlapped the walls of the portal vein followed by computed mean blood flow velocity determination. The calculated mean (SD) portal blood flow velocity was 15.8 (1.8), 15.1 (1.4), and 14.7 (2.5) cm/s using methods 1–3, respectively. There was no significant difference between the results of the three methods; however, method 3 (uniform insonation) was easier to use and produced a higher amplitude Doppler signal and therefore represents a useful alternative to the peak flow methods.     

Radiolabeling of equine platelets in plasma with 111In-(2-mercaptopyridine-N-oxide) and their in vivo survival

A method is presented for the in vitro isolation and radiolabeling of equine platelets with the isotope indium 111 (111In: half-life = 2.8 days, gamma = 173 keV, 89%; 247 keV, 94%). The technique described involves complexing 111In with the lipid-soluble chelating agent, 2-mercaptopyridine-N-oxide (merc), in an aqueous medium. 111In-merc platelet-labeling efficiencies in autologous plasma pretreated with or without ferric citrate reagent were 82 +/- 7% and 24 +/- 12%, respectively. Mean intravascular survivals of 111In-merc-radiolabeled platelets in 8 healthy horses according to simple linear, exponential, mean, weighted-mean residual sum of squares analysis, and multiple-hit model were 5.5 +/- 0.49, 3.5 +/- 0.53, 4.5 +/- 0.18, 4.3 +/- 0.65, and 3.6 +/- 0.97 days, respectively.     

ACQUIRED URETEROVAGINAL FISTULA SECONDARY TO OVARIOHYSTERECTOMY IN A DOG: DIAGNOSIS USING ULTRASOUND-GUIDED NEPHROPYELOCENTESIS AND ANTEGRADE URETEROGRAPHY

A one year old Jack Russel terrier became urinary incontinent one week after elective ovariohysterectomy. Intravenous urography and cystourethrography showed right hydronephrosis but failed to demonstrate the cause of incontinence. Nephropyelocentesis under ultrasound guidance produced exudate and subsequent antegrade ureterography demonstrated a ureterovaginal fistula. Exploratory laparotomy confirmed this diagnosis and indicated that the ureter had been included in a ligature around the vaginal stump. This is an uncommon complication of ovariohysterectomy.