Binding of human apolipoprotein A-IV to human hepatocellular plasma membranes.

We have investigated the binding of human apolipoprotein A-IV (apo A-IV) to human hepatocellular plasma membranes. Addition of increasing concentrations of radiolabeled apo A-IV to hepatic plasma membranes, in the presence and absence of a 25-fold excess of unlabeled apo A-IV, revealed saturation binding to the membranes with a KD of 154 nM and a binding maximum of 1.6 ng/microgram of membrane protein. The binding was temperature-insensitive, partially calcium-dependent, abolished when apo A-IV was denatured by guanidine hydrochloride or when the membranes were treated with Pronase and decreased when apo A-IV was incorporated into phospholipid/cholesterol proteoliposomes. In displacement studies using purified apolipoproteins and isolated lipoproteins, only unlabeled apo A-IV, apo A-I and high-density lipoproteins effectively competed with radiolabeled apo A-IV for membrane binding sites. We conclude that human apo A-IV exhibits high-affinity binding to isolated human hepatocellular plasma membranes which is saturable, reversible and specific.

Butoxyacetic acid-induced hemolysis of rat red blood cells: effect of external osmolarity and cations.

Hemolysis is the principal toxicity of acute exposure to ethylene glycol monobutyl ether (EGBE) in rats. EGBE itself is not an active hemolytic agent, but its metabolite, butoxyacetic acid (BAA) formed as a result of dehydrogenase activity is a potent hemolysin. Here we address the role of osmolarity and cation composition of the suspending buffers in the mechanism of BAA-induced hemolysis of rat red blood cells in vitro. Rat erythrocytes were protected from BAA-induced cell swelling and hemolysis by the addition of sucrose to the suspending media. Hemolysis and cell swelling were also reduced by replacing external sodium with potassium. When calcium was not present in the suspending medium or when chelated by EGTA, hemolysis was increased after 2 h incubation with 1 mM or 2 mM BAA. Addition of as little as 0.05 mM CaCl(2) reduced hemolysis significantly while the addition of MgCl(2) had no effect. The dose-response relationship between BAA concentration and hemolysis determined in the presence or absence of calcium showed an increased effect of BAA in the absence of calcium. BAA-induced spherocytosis and cell fragmentation were more pronounced in the absence of calcium. The time course of BAA-induced hemolysis in the presence and absence of calcium demonstrated that the effect of calcium is to delay the onset of hemolysis. Increased intracellular calcium as a result of exposure to BAA was verified by atomic absorption spectroscopy. Charybdotoxin, an inhibitor of the calcium activated potassium channel, blocked the protective effect of calcium suggesting that the delay of onset of hemolysis in the presence of calcium is due to potassium loss caused by this channel. We conclude that the mode of action of BAA is to cause a colloid osmotic lysis of the rat red blood cell. Hemolysis requires external sodium and is associated with calcium uptake. Calcium appears to delay the onset of hemolysis. We speculate that: (1) BAA causes sodium and calcium to enter the cell; (2) calcium initially has a protective effect via the calcium activated potassium channel which facilitates the loss of potassium thereby, compensating for the osmotic effect of increased cell sodium; (3) calcium subsequently may have other deleterious effects through activation of proteases and externalization of phosphatidylserine in the exterior leaflet of the membrane.

Indium-111-chloride and three-phase bone scintigraphy: a comparison for imaging experimental osteomyelitis.

To investigate the utility of indium-111-chloride (111In-Cl) imaging in detecting osteomyelitis complicating surgical or fracture sites, the proximal tibia of 11 dogs were experimentally infected with Staphylococcus aureus after creation of a cortical defect. The contralateral limb served as a sham-operated control. Animals were serially imaged by radiography, three-phase technetium-99m-methylene diphosphonate (99mTc-MDP) scintigraphy, and 111In-Cl scintigraphy. There was a significant difference between infected (1.93) and noninfected (1.32) limb's tibia/femur count density ratios on 24-hr (p = 0.0001) and 72-hr (p = 0.0001) 111In-Cl images. A smaller difference was found for 99mTc-MDP bone-phase tibia/femur ratios (p = 0.0199). Using receiver operator characteristic analysis of tibia/femur ratios, a sensitivity of 61%, specificity of 88%, and positive (75%) and negative (79%) predictive values were determined for the 24-hr 111In-Cl images. Indium-111-chloride was superior to 99mTc-MDP in differentiating infected and noninfected operative sites.

Familial immotile-cilia syndrome in English springer spaniel dogs.

A laboratory-maintained colony of English springer spaniel dogs heterozygous for a putative autosomal recessive immotile-cilia syndrome (ICS) has been studied. Matings between dogs thought to be heterozygous for ICS resulted in 22 pups, five (three males and two females) of which were homozygous for ICS. Four of the five ICS-affected dogs had chronic rhinitis and bronchopneumonia. The other dog had a serious nasal discharge and died at 10 days. Four dogs had situs inversus totalis (kartagener syndrome), and the two males of reproductive age were azoospermic. In the two ICS dogs studied for ciliary function, in vivo mucociliary clearance was absent, and in vitro ciliary beat was rarely observed and of low frequency. Scanning and transmission electron microscopy disclosed the same lesions in respiratory cilia from all dogs with ICS, including random orientation and partial outer dynein arm deficiency. Four of five dogs with ICS had dilated lateral ventricles. One female pup with neonatal rhinitis and bronchopneumonia, situs solitus, and dilated lateral ventricles was presumed to be homozygous for ICS, but died without functional or structural confirmation of defective respiratory cilia. An autosomal recessive mode of inheritance for the ciliary defects and respiratory signs of ICS in these dogs is proposed.

Esophagitis due to Pythium insidiosum infection in two dogs.

Chronic esophagitis due to Pythium insidiosum infection caused weight loss, dysphagia, and hypersalivation in 2 dogs from rural Tennessee. Although dog 1 presented for evaluation in December 1984 and dog 2 in October 1992, infection likely occurred during the previous summer by drinking fresh pond water containing zoospores. Hematologic testing revealed eosinophilia and hypergammaglobulinemia in one dog. An etiologic diagnosis was not made until postmortem evaluation when hyphae within necrotic and granulomatous cellular infiltrates in the esophageal wall were identified as P insidiosum by immunoperoxidase staining. Failure to culture the organism from the esophageal wall in dog 2 was attributed to refrigeration of the tissues, since refrigeration decreases the survivability of P insidiosum.

Clinical, cytologic and histopathologic manifestations of protothecosis in two dogs.

Two cases of sudden onset of blindness associated with ocular protothecosis in dogs are reported. Both were adult, spayed female, mixed-breed dogs that lacked the usual clinical signs of systemic infection with Prototheca species. Physical abnormalities at the time of presentation were limited to the affected eyes which had serous discharge, hyperemic conjunctiva, and aqueous flare. The pupillary light reflexes were slow, and the menace reflexes were absent. Both dogs had glaucoma. Results of complete blood counts and serologic titres for antibodies to Blastomyces dermatitidis and Histoplasma capsulatum were within reference intervals. Protothecosis was diagnosed by cytologic analysis of vitreous humor and was confirmed at necropsy. These two cases were unusual because of their presenting signs and prolonged course of disease progression.

Preliminary study of laryngeal sacculectomy in horses, using a neodymium:yttrium aluminum garnet laser technique.

In an attempt to ablate the laryngeal saccule as an alternative method of sacculectomy (conventially done through a laryngotomy incision for laryngeal hemiplegia) a neodymium:yttrium aluminum garnet laser was used transendoscopically in noncontact fashion in 6 horses. The procedure was easy, quick, and labor-saving, with few complications. Endoscopically, the lased sacculectomy site appeared healed at postsurgical day 42. On postsurgical day 42, microscopic examination revealed mucosal remnants under the granulation bed. Laser energy caused thermal damage to tissues adjacent to the lased saccule. Additional work must be done to refine the technique before it can be recommended for clinical applications.

Comparison of effects of cimetidine and omeprazole on mechanically created gastric ulceration and on aspirin-induced gastritis in dogs.

A double-blind study was conducted to compare gastric ulcer healing time in nontreated dogs with that in dogs treated with either cimetidine or omeprazole. Single ulcers were created in the gastric antrum by use of a suction biopsy capsule. Each dog was given 25 mg of aspirin/kg of body weight orally for 20 days after ulcer induction. Five control dogs were given aspirin only (no anti-ulcer medication) during the 20-day study. Six dogs were given cimetidine at dosage of 10 mg/kg orally every 8 hours, and 6 dogs were given omeprazole orally at dosage of 2 mumol/kg (0.7 mg/kg) once daily. All dogs were examined endoscopically on days 5, 10, 15, and 20 and were given a score for the size of the mechanically created ulcer and a score for the degree of aspirin-induced gastritis. All dogs were euthanatized on day 21, and gastric lesions were examined histologically. Significant differences were not evident in ulcer healing scores or degree of aspirin-induced gastritis among treated and nontreated dogs on days 5, 10, 15, and 20. However, aspirin-induced gastritis was less severe in dogs of the omeprazole group than in dogs of the cimetidine or control group on each day observations were made. The effect of omeprazole given once daily was comparable with that of cimetidine given every 8 hours in lessening aspirin-induced gastritis.

Evaluation of anastomoses of small intestine in dogs: crushing versus noncrushing suturing techniques.

Fifteen dogs were used to compare simple interrupted crushing and noncrushing single-layer small intestinal anastomoses. Groups of 5 dogs each were used to evaluate both techniques at 3 postsurgical times--days 4, 21, and 42. There were no significant differences between the 2 techniques at the evaluations. Grossly, there were marked adhesion formations at the 3 evaluation times. Luminal diameters at the anastomotic site indicated there may have been only slightly more stenosis with the noncrushing technique. Bursting pressure studies determined that the anastomotic strengths of the 2 techniques were not measurably different statistically. However, their bursting strengths had greatly increased from day 4 to day 21. There were also significant increases in bursting strengths of jejunal segments caudal to the anastomotic sites from day 4 to day 42. Subjective histopathologic evaluations of anastomotic sites revealed that the types and amounts of inflammation, collagen content, continuity of layers, and severity of peritonitis were not different within each time. It was concluded that both techniques for small intestinal anastomoses in the dog have equal value.

Nonweightbearing lameness secondary to synovial sarcoma in a young dog.

Synovial sarcoma was diagnosed in the right carpus of a 2 1/2-year-old mixed-breed dog. The dog had developed a right forelimb lameness before one year of age. The lameness was progressive for nearly 2 years, resulting in severe disuse atrophy of the right forelimb musculature and pronounced osteopenia. A definitive diagnosis was not made until the dog was referred after 2 years of conservative treatment was ineffectual. Right forelimb amputation was done and the dog survived an additional 15 months. The protracted clinical course before definitive diagnosis underscores the need for aggressive pursuit of a diagnosis when conservative treatment of a lameness is not efficacious.

Solitary osteochondroma of the radius in three horses.

Osteochondroma of the distal portion of the radius was diagnosed in 3 horses with a history of lameness and distention of the common tendon sheath of the superficial and deep digital flexor tendons at the level of the carpal canal. In 2 horses, the exostosis was removed through an incision at the caudal border of the lateral digital extensor muscle above the carpal ligament.

Pleural effusion resulting from malignant hepatoblastoma in a horse.

Pleural effusion, secondary to a metastasis from a malignant hepatoblastoma, was diagnosed in a 3-year-old Appaloosa gelding. Severe hemorrhagic transudate in both pleural cavities resulted in acute onset of labored breathing, tachypnea, tachycardia, and jugular vein pulsation. Results of ultrasonography and radiography of the ventral lung field and cranial portion of the abdomen initially were nondiagnostic, as were results of cytologic examination of peritoneal fluid and tracheal wash specimens. Moderately high serum gamma-glutamyl transferase and alkaline phosphatase activities, despite normal hepatocyte-specific enzyme (sorbital dehydrogenase) activity, were indicative of biliary stasis without hepatocyte destruction. The horse was euthanatized. Necropsy revealed a 47-kg hepatoblastoma, with metastases in the lungs and intestines.

Ultrasonographic diagnosis of renal disease in small animals.

Real-time ultrasonography was found to be useful in the diagnosis of hydronephrosis, renal calculi, and renal neoplasia in the dog and cat. One dog with hydronephorsis, one with renal calculi, and a cat with a renal neoplasm were scanned with a real-time ultrasonic scanner. Abnormal enlargement due to fluid accumulation was determined by ultrasonographic imaging in the case of hydronephrosis. The location and mobility of the renal calculus were observed during ultrasonography. An uneven contour and parenchymal masses in the neoplastic kidney were detected by ultrasonographic imaging of the cat. The findings were confirmed either by radiography or by postmortem examination. Previously, hydronephrosis could be diagnosed only by radiography, especially by excretory urography. Ultrasonography offers a noninvasive method for diagnosis of hydronephrosis. Localization of a urinary calculus at either the proximal end of the ureter or within the renal pelvis may be difficult by radiography. The ability of real-time ultrasonography to detect motion of the calculi within the pelvis offers an improved diagnostic capability to the veterinarian. The inability of radiography to determine the cause of renal enlargement is contrasted with the ability of ultrasonography to detect changes in tissue density that might be compatible with renal neoplasms

Death of an African elephant from probable toxemia attributed to chronic pulpitis.

A 31-year-old captive male African elephant (Loxodonta africana) of 5,000-kg body weight died suddenly in ventral recumbency. Lesions seen at necropsy were bilateral purulent pulpitis and periodontitis of both tusks, serous atrophy of coronary groove fat, Grammocephalus cholangitis, myocardial and skeletal lipofuscinosis, and scattered segmental necrosis in the pectoral muscles. Nonhemolytic streptococci, Corynebacterium sp, Peptostreptococcus anaerobius, Fusobacterium nucleatum, and Bacteroides sp, were recovered from the exudate around one or both tusks. We postulated that the elephant died of hypoxia from prolonged ventral recumbency because of weakness and inability to rise secondary to toxemia from bilateral pulpitis and periodontitis.

Heart failure caused by gossypol poisoning in two dogs.

Two hound-type dogs from the same kennel were admitted in terminal stages of congestive heart failure. An investigation revealed the owner had been feeding the dogs cottonseed meal daily with their kibbled meal. Gossypol toxicosis from feeding this meal caused marked abnormalities in myocardial contractility. Although in severe congestive heart failure, one dog had only minimal dilatation of its heart, as revealed by thoracic radiography. Disseminated intravascular coagulopathy also was diagnosed in this dog. Gossypol is a cumulative toxin; the amount of free gossypol fed was approximately 5.4 to 5.7 mg/kg/day for an unknown duration.

Work intolerance in a horse with thyroid carcinoma.

A thyroid carcinoma was diagnosed in a 14-year-old competitive trail horse with a 3-month history of work intolerance. Abnormal findings included low base-line triiodothyronine (T3) and thyroxine (T4) values, a large thyroid gland and decreased work tolerance. Nuclear medicine scanning revealed displacement of the right thyroid gland by a mass. Needle biopsy of the mass revealed neoplastic changes compatible with thyroid carcinoma. After removing the tumor surgically, T3 and T4 values returned to normal. Subsequently, the horse was able to compete successfully. Horses with work intolerance combined with a large thyroid gland may develop a thyroid carcinoma. In such horses, T3 and T4 values should be determined; if abnormal values are detected, needle biopsy and scintigraphic evaluation should be considered.

Effusive-constrictive pericardial disease secondary to osseous metaplasia of the pericardium in a dog.

Osseous metaplasia of the pericardium causing effusive-constrictive pericardial disease has not, to our knowledge, been reported in dogs. Clinical signs of right-sided congestive heart failure prompted examination of the dog of this report. Documented causes of constrictive pericardial disease in dogs include trauma and actinomycotic, mycobacterial, and fungal infections. These causes were ruled out in this dog. Immune-mediated disorders, as have been reported in people, also were considered unlikely on the basis of test results. It was concluded that this dog had idiopathic osseous metaplasia of the pericardium and pleura. Signs of right-sided congestive heart failure resolved after subtotal pericardiectomy was performed.

Blood volume and erythropoiesis in the rat during spaceflight.

A decreased red blood cell mass (RBCM) and plasma volume (PV) have been consistently found in humans after return from spaceflight. Rats flown on the Spacelab Life Sciences-1 mission were studied to assess changes in RBCM, PV, erythropoiesis, and iron economy. The RBCM and PV increased in both ground control and flight animals as expected for growing rats. However on landing day, both the RBCM and PV, when normalized for body mass, were significantly decreased in the spaceflight animals. During an 8-d postflight observation period, iron incorporation into circulating red blood cells was diminished in the flight animals. During the first 4 d postflight, increases in reticulocyte counts were significantly smaller in the flight than the control animals. Fewer erythropoietin-responsive progenitor cells were recovered from the bone marrow of flight animals after landing than control rats. Serum erythropoietin (EPO) levels were the same in both groups. Thus, rats subjected to a 9-d spaceflight had less increase in RBCM than controls and diminished erythropoiesis during an 8-d post-spaceflight observation period. The rat, like humans, appears to require a smaller blood volume in microgravity.