Spontaneous thymoma in a juvenile cynomolgus macaque (Macaca fascicularis).

A single, solid, yellow-white thymic mass was found at necropsy of a two-year-old female cynomolgus macaque from a four-week, repeat-dose toxicity and immunogenicity study. Microscopically, the mass was multilobular and well encapsulated, surrounded by a thick connective tissue capsule, and composed of dense sheets of elongate or spindle-shaped cells and large cystic cavities separated by thick connective tissue stroma. Normal thymus was adjacent to the mass, but it was compressed. Within the mass were abundant interspersed Hassall's corpuscles; individual and small clusters of mature, small lymphocytes; scattered eosinophils; large areas of necrosis; focal mineralization; and cholesterol clefts. An interesting feature was the presence of large multinucleated giant cells, which varied widely in size and nuclear number. Immunohistochemical staining for two lymphocyte markers and two structural proteins confirmed the identity of the neoplastic spindle cells and other cellular components. There was no evidence of vascular invasion or metastasis. Features of the thymoma indicated it was a pre-existing condition and not treatment related.

Effect of individual versus group caging on the incidence of pituitary and Leydig cell tumors in F344 rats: proposed mechanism.

Recently, an increase in pituitary tumor (pars distalis adenoma) incidence, and decrease in testicular interstitial cell tumor incidence, has been noted in F344 rats, in 2 year National Toxicology Program dermal and inhalation studies. One of the factors that may have contributed to this correlation is the difference in housing protocols. Rats in inhalation and dermal toxicity studies are singly caged, in contrast to other types of studies in which rats are group-caged, such as dosed-feed, dosed-water, or gavage studies. We propose that stress, related to individual caging, particularly among males, directly impairs testosterone synthesis and produces Leydig cell atrophy which leads to a feedback increase in the synthesis of luteinizing hormone by the anterior pituitary. This is followed by anterior pituitary cell functional hypertrophy, hyperplasia, and eventually neoplasia. It is known that individual caging of male rats produces a stress response associated with increased serum corticosteroids. The testicular interstitial cells (Leydig cells) have specific receptors for the glucocorticoid hormones. The Leydig cell enzyme 11-beta-hydroxysteroid dehydrogenase (11-beta-HSD) inactivates gluococorticoids; however, prolonged stress depletes this enzyme, enabling the gluococorticoids to impair steroidogenesis and eventually to lead to compensatory pituitary proliferations, including neoplasms.

Regenerative hyperplasia is not required for liver tumor induction in female B6C3F1 mice exposed to trihalomethanes.

Chloroform (TCM), a water disinfection by-product, induced liver tumors in female mice when administered by gavage in corn oil but not when given in drinking water at comparable daily doses. Because short-term studies showed that the gavage doses also induced liver toxicity, it has been suggested that the liver tumor response occurs secondary to cytotoxicity and consequent regenerative hyperplasia induced by oxidative metabolism of TCM to the toxic dihalocarbonyl intermediate. This study compares dose-response relationships of gavage-administered chlorinated/brominated trihalomethanes for hepatotoxicity, replicative DNA synthesis, and hepatocarcinogenicity in female B6C3F1 mice. The liver tumor data were obtained from previously published studies. Because bromine is a better leaving group than chlorine, metabolism of bromodichloromethane (BDCM) should produce the same intermediates as would be formed from TCM. Hence, the toxicity and carcinogenicity of BDCM was expected to be qualitatively similar to that of TCM. Dose responses for liver weight, serum sorbitol dehydrogenase and alanine aminotransferase (ALT) activities, hepatocyte degeneration, and hepatocyte labeling index (LI, a measure of replicative DNA synthesis) in female mice were similar following 3 weeks of gavage administration (once per day, 5 days per week) with TCM, BDCM, or chlorodibromomethane (CDBM). Fits of composite data for these trihalomethanes to a Hill equation model revealed sigmoidal dose responses for ALT activity and hepatocyte LI and a nearly linear low-dose response for liver tumor incidence. For this family of chemicals, the mouse liver tumor response was not associated with an elevated hepatocyte LI at doses of approximately 1 mmol/kg or less. High incidences of liver tumors were observed with BDCM and CDBM at doses that had a marginal effect or no effect on the hepatocyte LI. Thus, the carcinogenic effects of trihalomethanes are not simply a consequence of cytotoxicity and regenerative hyperplasia. The possible contributions from other activation pathways, including GSH conjugation and reductive metabolism, need to be considered in assessments of the carcinogenicity of the trihalomethanes.

Dietary restriction reduces insulin-like growth factor I levels, which modulates apoptosis, cell proliferation, and tumor progression in p53-deficient mice.

Diet contributes to over one-third of cancer deaths in the Western world, yet the factors in the diet that influence cancer are not elucidated. A reduction in caloric intake dramatically slows cancer progression in rodents, and this may be a major contribution to dietary effects on cancer. Insulin-like growth factor I (IGF-I) is lowered during dietary restriction (DR) in both humans and rats. Because IGF-I modulates cell proliferation, apoptosis, and tumorigenesis, the mechanisms behind the protective effects of DR may depend on the reduction of this multifaceted growth factor. To test this hypothesis, IGF-I was restored during DR to ascertain if lowering of IGF-I was central to slowing bladder cancer progression during DR. Heterozygous p53-deficient mice received a bladder carcinogen, p-cresidine, to induce preneoplasia. After confirmation of bladder urothelial preneoplasia, the mice were divided into three groups: (a) ad libitum; (b) 20% DR; and (c) 20% DR plus IGF-I (IGF-I/DR). Serum IGF-I was lowered 24% by DR but was completely restored in the IGF-I/DR-treated mice using recombinant IGF-I administered via osmotic minipumps. Although tumor progression was decreased by DR, restoration of IGF-I serum levels in DR-treated mice increased the stage of the cancers. Furthermore, IGF-I modulated tumor progression independent of changes in body weight. Rates of apoptosis in the preneoplastic lesions were 10 times higher in DR-treated mice compared to those in IGF/DR- and ad libitum-treated mice. Administration of IGF-I to DR-treated mice also stimulated cell proliferation 6-fold in hyperplastic foci. In conclusion, DR lowered IGF-I levels, thereby favoring apoptosis over cell proliferation and ultimately slowing tumor progression. This is the first mechanistic study demonstrating that IGF-I supplementation abrogates the protective effect of DR on neoplastic progression.

A 90-day chloroform inhalation study in F-344 rats: profile of toxicity and relevance to cancer studies.

Chloroform acts via a nongenotoxic-cytotoxic mode of action to produce cancer if given in doses and at dose rates sufficiently high to produce organ-specific toxicity. In a recent study, chloroform failed to induce cancer in male or female F-344 rats when administered by inhalation for 2 years at 90 ppm, 5 days/week. The present study was undertaken to define the concentration-response curves for chloroform-induced lesions and regenerative cell proliferation in the F-344 rat when exposed by inhalation and to correlate those patterns of toxicity with the results from the inhalation cancer bioassay. Male and female F-344 rats were exposed to airborne concentrations of 0, 2, 10, 30, 90, or 300 ppm chloroform 6 hr/day, 7 days/week for 4 days or 3, 6, 13 weeks. Additional treatment groups were exposed 5 days/week for 13 weeks or were exposed for 6 weeks and held until Week 13. Bromodeoxyuridine was administered via osmotic pumps implanted 3.5 days prior to necropsy and the labeling index (LI, percentage of nuclei in S-phase) was evaluated immunohistochemically. A full-screen necropsy identified the kidney, liver, and nasal passages as the only target organs. This study confirmed that 300 ppm is extremely toxic and would be inappropriate for longer-term cancer studies. The primary target in the kidney was the epithelial cells of the proximal tubules of the cortex, with significantly elevated increases in the LI at concentrations of 30 ppm and above. However, only a marginal increase in the renal LI in the males was seen after exposures of 90 ppm, 5 days/week. Chloroform induced hepatic lesions in the midzonal and centrilobular regions with increases in the LI throughout the liver, but only at 300 ppm exposures. An additional liver lesion seen only at the highly hepatotoxic concentration of 300 ppm was numerous intestinal crypt-like ducts surrounded by dense connective tissue. Enhanced bone growth and hypercellularity in the lamina propria of the ethmoid turbinates of the nose occurred at the early time points at concentrations of 10 ppm and above. At 90 days there was a generalized atrophy of the ethmoid turbinates at concentrations of 2 ppm and above. Cytolethality and regenerative cell proliferation are necessary but not always sufficient to induce cancer because of tissue, sex, and species differences in susceptibility. A combination of a lack of direct genotoxic activity by chloroform, only a marginal induction of cell proliferation in the male rat kidney, and lower tissue-specific susceptibility in the female rat is apparently responsible for the reported lack of chloroform-induced cancer in a long-term inhalation bioassay with F-344 rats.

A 90-day chloroform inhalation study in female and male B6C3F1 mice: implications for cancer risk assessment.

High doses of chloroform induced liver cancer in male and female B6C3F1 mice when administered by gavage, kidney cancer in male Osborne-Mendel rats when given by gavage or in the drinking water, and kidney cancer in male BDF1 mice when administered by inhalation. The weight of evidence indicates that chloroform is acting through a nongenotoxic-cytotoxic mode of action. The present study was designed to investigate the dose-response relationships for chloroform-induced lesions and regenerative cell proliferation in B6C3F1 mice as the basis for formulation of a biologically based risk assessment for inhaled chloroform. Different groups of female and male B6C3F1 mice were exposed to atmospheric concentrations of 0, 0.3, 2, 10, 30, and 90 ppm chloroform 6 hr/day, 7 days/week for exposure periods of 4 days or 3, 6, or 13 consecutive weeks. Some additional exposure groups were exposed for 5 days/week for 13 weeks or were exposed for 6 weeks and then examined at 13 weeks. Bromodeoxyuridine was administered via osmotic pumps implanted 3.5 days prior to necropsy, and the labeling index (LI, percentage of nuclei in S-phase) was evaluated immunohistochemically from histological sections. Complete necropsy and microscopic evaluation revealed treatment-induced dose- and time-dependent lesions only in the livers and nasal passage of the female and male mice and in the kidneys of the male mice. Large, sustained increases in the liver LI were seen in the 90-ppm groups at all time points. The female mice were most sensitive, with a no-observed-adverse-effect level (NOAEL) for induced hepatic cell proliferation of 10 ppm. The hepatic LI in the 5 days/week groups were about half of those seen in the 7 days/week groups and had returned to the normal baseline in the 6-week recovery groups. Induced renal histologic changes and regenerative cell proliferation were seen in the male mice at 30 and 90 ppm with 7 days/week exposures and also at 10 ppm with the 5 days/week regimen. Nasal lesions were transient and confined to mice exposed to 10, 30, or 90 ppm for 4 days. In a previous cancer bioassay, a gavage dose of 477 mg/kg/day produced a 95% liver tumor incidence in female B6C3F1 mice. This gavage dose is equivalent to a daily 6 hr/day inhalation exposure of approximately 80 ppm, based on the observed induced increases in the LI as an internal dosimeter. The United States Environmental Protection Agency currently uses the linearized multistage model applied to the mouse liver tumor data from the chloroform gavage study to estimate a virtually safe dose (VSD) as a one in a million increased lifetime risk of cancer. The resulting value is an airborne exposure concentration of 0.000008 ppm. Assuming that chloroform-induced female mouse liver cancer is secondary to events associated with necrosis and regenerative cell proliferation, then no increases in liver cancer in female mice would be predicted at the NOAEL of 10 ppm or below based on the results reported here. Applying an uncertainty factor of 1000 yields an estimate of a VSD at 0.01 ppm. This estimate relies on inhalation data and is more consistent with the mode of action of chloroform.

Correlation of regional and nonlinear formaldehyde-induced nasal cancer with proliferating populations of cells.

Formaldehyde induces nonlinear, concentration-related increases in nasal epithelial cell proliferation and squamous cell carcinomas (SCC) in rats. A formaldehyde carcinogenicity study was conducted in which a major end point was correlation of cell proliferation indices with sites of formaldehyde-induced SCC. A poor correlation in certain sites led to incorporation of the number of cells in each site into the correlation. Rats were exposed (6h/day, 5 days/week) to formaldehyde (0, 0.7, 2, 6, 10 or 15 ppm) for up to 24 months with interim sacrifice time points at 3, 6, 12, and 18 mo. A unit length labeling index (ULLI; S-phase nuclei/mm basement membrane) was determined for specific nasal regions in addition to a population-weighted ULLI (PWULLI). The PWULLI was defined as the product of regional ULLI and total number of nasal epithelial cells in the respective site. Nasal SCC sites of origin were mapped. Formaldehyde induced SCC in a highly nonlinear fashion, with no observed effect at the level of 2 ppm, a minimal response at 6 ppm, and a sharp increase at 10 and 15 ppm. The tumor incidence was 1, 22, and 47% at 6, 10 and 15 ppm, respectively. ULLI was significantly (P<0.05) increased at 10 and 15 ppm but not at the lower concentrations. There was a good correlation between PWULLI and regional tumor incidence (R(2) = 0.88), while the correlation of regional SCC with ULLI was relatively poor (R(2) = 0.46). We conclude that target cell population size and sustained increases of cell proliferation in these populations, determined by differences in regional airflow-driven formaldehyde binding to DNA dose to these sites, coupled with the known nonlinear kinetics of formaldehyde binding to DNA, can together account for the nonlinearity and site specificity of formaldehyde-induced nasal SCC in rats.

Application of molecular encapsulation for toxicology studies: comparative toxicity of p-Chloro-alpha, alpha, alpha-trifluorotoluene in alpha-cyclodextrin vehicle versus corn oil vehicle in male and female Fischer 344 rats and B6C3F1 mice.

The application of alpha-cyclodextrin (alpha-CD) as an alternative vehicle for water insoluble and volatile chemicals was investigated in toxicity studies of p-chloro-alpha, alpha, alpha-trifluorotoluene (CTFT). Groups of F344 rats and B6C3F1 mice of each sex were administered CTFT (97% pure) by gavage in either corn oil or alpha-CD aqueous formulations daily for 14 consecutive days. The dose levels used were 10 (mice only), 50, 400, and 1000 mg/kg for corn oil vehicle and 10, 50, and 400 mg/kg (maximum achievable dose at gavage volume of 5 ml/kg) for alpha-CD vehicle. With both vehicles CTFT and alpha 2u-globulin were found to accumulate in the male rat kidney after 14 days of exposure and a dose-related toxic nephropathy was observed at dose of 50 mg/kg or higher. The hepatocellular hypertrophy and cytoplasmic vacuolation of the adrenal cortex which appeared in dosed male and female rats were also found to be independent of vehicle. Clinical pathology findings suggested a mild anemia and cholestasis in rats. With both vehicles no tissue bioaccumulation of CTFT was found in male or female mice. Vehicle-independent hepatocellular hypertrophy and cholestasis were also observed in mice at doses of 400 and 1000 mg/kg. In conclusion, the alpha-CD vehicle does not affect the toxic responses of CTFT in both sexes of both species. The results of the studies suggest that alpha-CD may be an appropriate alternative vehicle for toxicity studies.

Toxicity studies of acetone administered in the drinking water of rodents.

Two- and thirteen-week toxicity studies were conducted using male and female F344/N rats and B6C3F1 mice. Animals were exposed to the following concentrations of acetone in their drinking water: two-week studies 0; 5000; 10,000; 20,000; 50,000; or 100,000 ppm acetone. Thirteen-week rat and female mouse studies 0; 2500; 5000; 10,000; 20,000; or 50,000 ppm acetone. Thirteen week male mice were exposed to 0; 1250; 2500; 5000; 10,000; or 20,000 ppm acetone. Depressed body weight gain was restricted to the 50,000 and 100,000 ppm exposure groups. Male and female mice exposed respectively to 20,000 or 50,000 ppm acetone for 2 weeks developed hepatocellular hypertrophy. This change was not apparent after 13 weeks of exposure although relative and absolute liver weight was increased in high dose female mice. Bone marrow hypoplasia was observed in 5/5 high dose (100,000 ppm) male rats during the 2-week studies. Treatment of male rats for 13 weeks resulted in a variety of mild and subtle hematological changes that often occurred at relatively low levels of exposure (5000 ppm) and resembled those seen during the clinical condition of megaloblastic anemia. Changes characteristic of hypogonadism (depressed sperm motility and cauda epididymal and epididymal weight and elevated incidence of abnormal sperm) were observed in male rats receiving 50,000 ppm acetone for 13 weeks. The incidence and severity of a kidney lesion that is morphologically similar to the spontaneously occurring nephropathy among aging F-344 rats were increased at 20,000 and 50,000 ppm acetone, respectively, in 13-week male rats. In summary, the effects of acetone were either subtle in nature or occurred during very high levels of exposure confirming acetone's low level of toxicity. The daily levels of acetone exposure were often several-fold greater than possibly encountered by humans during the accidental consumption of contaminated groundwater (250 ppm; 5 mg/day) and frequently exceeded maximum levels reported following acute toxic exposures (2,500 mg/kg).

Exercise training and incidence of cerebrovascular lesions in stroke-prone spontaneously hypertensive rats.

To assess the effects of moderate exercise [40-70% maximal oxygen uptake (VO2max)] on resting blood pressures, the presence of cerebrovascular lesions, and the life spans of stroke-prone hypertensive rats, nontrained and trained male and female rats were assigned to two experimental groups. The first (n = 48) were exercise trained after 38 days of age, whereas the second (n = 44) initiated exercise training when the animals were 134 days of age. To facilitate cerebrovascular lesions, the sodium concentrations in the rat chow and in the drinking solutions were increased. Symptoms utilized to denote the presence of cerebrovascular lesions were irritability, hyperresponsiveness, ataxia, lethargy, unwillingness to run, and combinations thereof. All brains were removed immediately after death, fixed, and evaluated grossly and microscopically for lesions. In the study with the younger animals, training was associated with a 7-9% increase in VO2max that was statistically significant only in animals with no histological evidence of cerebrovascular lesions. For the older animals, a significant 5-8% increase in VO2max was noted for animals with or without lesions. After 42 days of training for both groups, resting blood pressures for the trained groups with histological lesions were significantly lower. However, this trend did not continue, and the older trained rats appeared to have strokes earlier and to die sooner than their nontrained controls. Although 83% of the older animals had subjective evidence for a stroke before they died, the percentage of animals with lesions ranged from 42 to 58%, with the trained groups having higher percentages.(ABSTRACT TRUNCATED AT 250 WORDS)

Toxicity studies of intravenous vitamin E in newborn rabbits.

This study was designed to investigate the toxicity of intravenously administered alpha-tocopherol, alpha-tocopheryl acetate, and a polysorbate vehicle similar to that used in a commercial preparation of alpha-tocopheryl acetate intended for intravenous administration. Cesarean-delivered newborn rabbits fed intravenously were administered 100 mg of either alpha-tocopherol or alpha-tocopheryl acetate in a polysorbate vehicle, or the vehicle only, or no treatment for 6 or 7 days. Two intravenous diets were employed which differed in nutritional content and were termed low energy (LE) and high energy (HE). High concentrations of alpha-tocopherol were present in the tissues of all pups that received either treatment with alpha-tocopherol or alpha-tocopheryl acetate in the polysorbate vehicle, irrespective of the nutritional regimen. Pups in all treatment and control groups which received the LE diet had hepatic centrilobular degeneration, necrosis and pigment accumulation, which was attributed to malnutrition. No additional toxicities could be attributed to the vitamin E or polysorbate treatments. Administration of the HE diet eliminated the nutrition-related centrilobular degeneration, and revealed treatment-related liver changes. HE pups treated with alpha-tocopheryl acetate in the polysorbate vehicle had microscopic evidence of mild bile stasis and had elevated serum bilirubin. Minimal lipidosis or fatty change in the liver was observed only in alpha-tocopherol and alpha-tocopheryl acetate-treated pups. Lipidosis in the spleen was moderate in the alpha-tocopherol group and minimal in the alpha-tocopheryl acetate group. Lipidosis also occurred in the adrenal gland primarily in the alpha-tocopheryl acetate group.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepatocytes in the mouse stomach.

Hepatocytes occurred in the stomach as incidental findings in 4 110-112-week-old mice (3 B6C3F1 and 1 Crl:COBS-CD1) sacrificed at termination of 2-yr toxicity/carcinogenicity bioassays of unrelated chemicals. Both sexes, and control and treated animals, were affected. Grossly, 2 mice only had 1.0-5.0 mm, smooth, cream-colored nodules protruding from the glandular stomach mucosa. Histologically, the glandular stomach submucosa and lamina propria adjacent to the limiting ridge, and in one case, the forestomach submucosa had circumscribed accumulations of well-differentiated hepatocytes with abundant eosinophilic cytoplasm and round central nuclei. Adjacent gastric glands sometimes exhibited dilation, epithelial hyperplasia, mineralization and/or microherniation into the submucosa. Ultrastructurally, the hepatocytes were polygonal cells with abundant mitochondria and rough endoplasmic reticulum; intercellular bile canaliculus-like structures exhibiting intraluminal microvilli and bounded by desmosomes were also present. No evidence of hepatocellular carcinoma or primary gastric neoplasms was found. No definitive conclusions concerning cell of origin or pathogenesis of these hepatocytes could be made, but hypotheses include congenital anomaly or post-natal transdifferentiation (metaplasia).

Production and partial characterization of monoclonal antibodies to Pasteurella haemolytica A1 capsular polysaccharide and lipopolysaccharide.

Hybridoma-derived monoclonal antibodies (MAB) against the cell surface antigens of Pasteurella haemolytica serotype 1 were obtained by the fusion of murine myeloma cells (P3 X 63 - Ag 8.653) with splenocytes of BALB/c mice immunized with crude logarithmic growth-phase culture supernatant. Initial screening was performed, using an ELISA, with the same bacterial growth culture supernatant as coating antigens. Further selection was done, using a panel of purified antigens--either capsular polysaccharide or lipopolysaccharide--as the coating antigen in an ELISA, and then performing a leukotoxin-neutralization assay. Two MAB, designated IIB-6 and H-2, reacted specifically with the capsular polysaccharide and the other 3, designated IVG-3, IH-3, and IIC-2, reacted with the lipopolysaccharide. One MAB, designated IH-6, did not react with leukotoxin, capsular polysaccharide, or lipopolysaccharide. The MAB to the capsular polysaccharide (IIB-6 and H-2) were characterized further; both antibodies belonged to the IgM class and were agglutinating. In addition, they promoted neutrophil-mediated opsonophagocytosis and complement-mediated immune bacteriolysis of P haemolytica serotype 1. Results from 3 studies indicated that the MAB IIB-6 and H-2 were specific only to the capsular polysaccharide of serotype 1 of P haemolytica. The MAB to the lipopolysaccharide (IVG-3, IH-3, and IIC-2) were of the IgG1, IgG3, and IgM classes, respectively and were not characterized further. The availability of a MAB identifying a serotype-specific, surface-exposed determinant on the capsule of P haemolytica serotype 1 should facilitate and expand studies concerning the role of the capsular material and lipopolysaccharide in the pathogenicity of P haemolytica infection in cattle.

Development of renal lesions in dogs after 11/12 reduction of renal mass. Influences of dietary protein intake.

Renal failure was induced in 15 normal Beagle dogs by ligation of approximately 5/6 of the renal arteries of the left kidney and contralateral nephrectomy in order to determine how: (a) 11/12 reduction in total renal mass influences urine protein excretion and renal morphology in dogs, and (b) dietary protein intake influences renal function, urine protein excretion, and renal morphology in canine renal failure. Dogs were fed a reduced protein diet for 12 weeks after induction of renal failure, while compensatory renal hypertrophy developed. Renal function was then evaluated and dogs were distributed into 2 groups with approximately equal degrees of renal dysfunction. One group was fed a high protein diet (42% protein) and a second group was fed moderately restricted protein diets (18% protein). After 8 weeks, renal function, magnitude of proteinuria, and renal morphology were re-evaluated. Inulin clearance increased in all dogs fed the 42% protein diet and 3 of 10 dogs fed the 18% protein diets. Proteinuria was significantly greater in dogs fed the high protein diet than dogs fed the reduced protein diets. Compared with previously nephrectomized contralateral control kidneys, glomerular sclerosis and renal interstitial lesions had developed in all dogs, regardless of severity of renal dysfunction or diet fed. Although reduced dietary protein intake did not prevent development of renal lesions, renal lesions were significantly more severe in the 5 dogs fed the 42% protein diet and 3 dogs fed the 18% protein diets in which inulin clearance increased, than in 7 dogs fed the reduced protein diets in which inulin clearance did not increase.

Adaptation of a colorimetric microtitration assay for quantifying Pasteurella haemolytica A1 leukotoxin and antileukotoxin.

A colorimetric microtitration assay was adapted to quantify the cytotoxicity of Pasteurella haemolytica A1 leukotoxin to bovine neutrophils used as target cells. The viability of leukotoxin-treated target cells was detected by use of a tetrazolium dye that living cells reduced to dark blue formazan. The amount of formazan formed (which was quantified by use of an ELISA plate reader) was directly proportional to the number of viable target cells. This assay system also was used to measure leukotoxin-neutralization antibody titers of bovine serum and lung lavage specimens obtained during vaccination experiments. The major advantages of this assay over other methods such as the 51Cr-release and trypan blue-exclusion assays are precision, rapidity, and low cost; it also does not use radioisotopes.

Canine prostatic disease--comparison of ultrasonographic appearance with morphologic and microbiologic findings: 30 cases (1981-1985).

A retrospective analysis was made of 30 cases of canine prostatic disease, with the objective of identifying (via a prepubic approach) the 2-dimensional, gray-scale ultrasonographic appearance most often associated with the various spontaneous prostatic diseases. Ultrasonography was of value in characterizing the parenchymal architecture as normal vs focally hyperechoic and diffusely hyperechoic (associated with chronic inflammation and neoplasia) or focally hypoechoic or anechoic (either accompanied by distant enhancement), which was associated with retention cyst or abscess. Further specificity based only on abnormal echotexture was not possible. Ultrasonography facilitated the differentiation of radiographically identifiable prostatomegaly attributable to abscess or neoplasia from apparent prostatomegaly attributable to paraprostatic cyst. An imaging protocol consisting of distention retrograde urethrocystography and prepubic ultrasonography was recommended, as a distended bladder aided ultrasonographic identification of the prostate gland. In addition, the combination of urethral morphologic features and urethroprostatic reflux appearance complemented the ultrasonographic appearance for differentiation of prostatic abscess from prostatic carcinoma. A classification scheme for spontaneous canine prostatic disease combining germane imaging morphologic features with microscopic and microbiologic findings was proposed.

Canine prostatic disease--comparison of radiographic appearance with morphologic and microbiologic findings: 30 cases (1981-1985).

A retrospective analysis was made of radiographs from 24 clinically normal young adult male Beagles used in previously reported base-line research on the distal male urinary tract. The ventrodorsal and craniocaudal prostate gland dimensions were measured, as visualized on the lateral radiographic view, and expressed as a ratio of the distance between the cranial aspect of the public bone and the sacral promontory. In 17 of these 24 dogs, there was sufficient image clarity to permit confident measurement of prostatic dimensions. From these data, the largest acceptable prostatic dimension, as visualized on the lateral radiographic view, was 70% of the public-promontory distance. A retrospective analysis was made of 30 cases of canine prostatic disease, with the objective of identifying the radiographic (survey and distention retrograde urethrocystogram) appearance most often associated with the various spontaneous prostatic diseases. Prostatomegaly was not specific for the cause of prostatic disease, except if the apparent parenchymal dimensions were greater than or equal to 90% of the public-promontory distance wherein neoplasia, abscess, and paraprostatic cysts (readily differentiated from diffuse intraparenchymal disease by ultrasonography) were the principle considerations. Multifocal, irregularly shaped, parenchymal mineral densities were observed only in dogs with prostatic carcinoma (4/7 cases) or prostatitis (1 case of chronic prostatitis). Narrowing of the prostatic portion of the urethra was observed only in association with abscess, neoplasm, or noninflammatory nonneoplastic disease (possibly benign hypertrophy/hyperplasia), whereas widening of this part of the urethra was not observed.(ABSTRACT TRUNCATED AT 250 WORDS)