An oral platelet-activating factor antagonist, Ro-24-4736, protects the rat kidney from ischemic injury.

The role of platelet-activating factor (PAF) in ischemic acute renal failure was evaluated by administering an oral PAF antagonist (Ro-24-4736) to rats prior to or after interruption of blood flow to both kidneys for 30 min. In animals treated with the PAF antagonist prior to ischemia, renal function was less impaired and histological abnormalities was less pronounced when compared with postischemic kidneys from vehicle-treated animals. Serum creatinine (mg/ dl) 24 h following renal ischemia was 1.58 +/- 0.17 in the PAF antagonist-treated rats compared with 2.19 +/- 0.15 in rats given placebo (P < 0.01). There was less necrosis in the outer medulla of kidneys of PAF antagonist-treated animals (P < 0.01). Tissue myeloperoxidase activity at 48 and 72 h postischemia was lower in kidneys of PAF antagonist-treated rats (P < 0.05). The PAF antagonist was also protective when administered 30 min but not 2 h following the ischemic insult. The coincident use of anti-intercellular adhesion molecule-1 monoclonal antibody did not confer additional protection over that observed with the oral PAF antagonist alone. These data suggest that PAF contributes to the pathophysiology of renal ischemic injury, perhaps by its effects on leukocyte-endothelial interactions. An orally active PAF antagonist can protect against the development of ischemic acute renal failure.

Tumorigenic activity of fluoranthene, 2-methylfluoranthene and 3-methylfluoranthene in newborn CD-1 mice.

Fluoranthene (FA) is frequently among the more abundant components detected in environmental mixtures of polycyclic aromatic hydrocarbons. Several methylated fluoranthenes, although less prevalent than FA, have also been detected as environmental pollutants. While FA is inactive as a tumorigenic agent on mouse skin, it does induce lung and liver tumors in newborn mice. Among the five isomers of methylfluoranthene, only 2-methylfluoranthene (2-MeFA) and 3-methylfluoranthene (3-MeFA) are active as tumor initiators on mouse skin. A comparative bioassay was performed to determine the relative tumorigenic activity of FA, 2-MeFA and 3-MeFA in newborn CD-1 mice. All three compounds were assayed at doses of 3.46 and 17.3 mumol. The bioassay was terminated when mice were 1 year old. At a dose of 17.3 mumol, FA and 2-MeFA induced a similar incidence of lung tumors (65-96%) in both male and female mice. However, tumor multiplicity in the lung was different between FA and 2-MeFA. At a dose of 17.3 mumol, the multiplicity of lung tumors observed for mice administered 2-MeFA ranged from 3.04 to 3.94 tumors per mouse. In contrast, animals treated with FA developed only an average of 1.12-2.45 tumors per mouse. 3-MeFA did not induce a statistically significant incidence of lung tumors in either male or female mice. All three compounds when administered to newborn mice did induce a significant incidence of liver tumors among male mice. The relative tumorigenic potency observed was FA > or = 2-MeFa >> 3-MeFA. Only 2-MeFA at a dose of 17.3 mumol was tumorigenic in the liver of female mice. These bioassay results are contrasted with prior studies on the in vitro genotoxic activity and metabolic activation pathways of FA, 2-MeFA and 3-MeFA.

A 13-week toxicologic and pathologic evaluation of prolonged cytochromes P450 inhibition by 1-aminobenzotriazole in male rats.

The pharmacologic, toxicologic, and microscopic effects of 100 mg/kg/day of 1-Aminobenzotriazole (ABT), a suicide substrate inhibitor of cytochromes P450, were assessed in male Sprague-Dawley rats over a 13-week period. Hepatic cytochromes P450 levels and resorufin dealkylase activity were decreased to less than 30% of control values beginning at Day 2 and from Day 8 to Day 92. These decreases were not accompanied by overt clinical toxicity, e.g., changes in body weight, food consumption, or clinical appearance, during the study. Hemoglobin, hematocrit, and erythrocyte counts were slightly decreased at 8, 29, and 92 days and were accompanied by increased spleen weights and extramedullary hematopoiesis. Additionally, mean corpuscular hemoglobin concentration, mean corpuscular volume, red cell distribution width, and mean corpuscular hemoglobin were slightly increased at 92 days. Increases in liver weights at 8, 29, and 92 days were accompanied by centrilobular hypertrophy and intracytoplasmic vacuolization consistent with lipid accumulation. Thyroid stimulating hormone (TSH) was slightly elevated and triiodothyronine and thyroxine were slightly decreased at 29 days. TSH was also slightly elevated at 8 and 92 days, and thyroid gland weights were increased at 8, 29, and 92 days with microscopic evidence of hyperplasia and hypertrophy of thyroid gland follicular cells. Increased adrenal weights and hypertrophy of the zona fascicularis of the adrenal gland were observed at 8, 29, and 92 days. Kidney weights were also increased at these assessments. Changes in the thyroid gland, the thyroid hormone profile, and the liver may reflect increased synthesis of microsomal enzymes, an effect that is sometimes difficult to demonstrate directly with suicide substrate inhibitors of cytochromes P450. In general, the effects of daily ABT administration to male rats at a dose that significantly reduces oxidative metabolism over a 13-week period were considered to be well-tolerated under controlled laboratory conditions.

A human tumor necrosis factor (TNF) alpha mutant that binds exclusively to the p55 TNF receptor produces toxicity in the baboon.

A number of recent studies have demonstrated that cellular responses to tumor necrosis factor (TNF) mediated by the p55 and the p75 TNF receptors are distinct. To evaluate the relative in vivo toxicities of wild-type TNF alpha (wtTNF alpha) and a novel p55 TNF selective receptor agonist, healthy, anesthetized baboons (Papio sp.) were infused with a near-lethal dose of either wtTNF alpha or a TNF alpha double mutant (dmTNF alpha) that binds specifically to the p55, but not to the p75, TNF receptor. Both wtTNF alpha and dmTNF alpha produced comparable acute hypotension, tachycardia, increased plasma lactate, and organ dysfunction in Papio. However, administration of wtTNF alpha produced a marked granulocytosis and loss of granulocyte TNF receptors, whereas little if any changes in neutrophil number or cell surface TNF receptor density were seen after dmTNF alpha mutant administration. Infusion of dmTNF alpha resulted in a plasma endogenous TNF alpha response that peaked after 90-120 min. We conclude that selective p55 TNF receptor activation is associated with early hemodynamic changes and the autocrine release of endogenous TNF alpha. Significant systemic toxicity results from p55 TNF receptor activation, but the role of the p75 TNF receptor in systemic TNF toxicity requires further study.

Tumorigenic activity of the 4,5- and 9,10-dihydrodiols of benzo[j]fluoranthene and their syn- and anti-diol epoxides in newborn mice.

Benzo[j]fluoranthene (B[j]F), trans-4,5-dihydro-4,5-dihydroxy-B[j]F, and trans-9,10-dihydro-9,10-dihydroxy-B[j]F were evaluated for tumorigenic activity in newborn CD1 mice. These dihydrodiols were assayed at doses of 1.10 and 0.275 mumol/mouse. B[j]F and the syn- and anti-diol epoxides derived from these dihydrodiols were evaluated at doses of 1.10, 0.275, and 0.110 mumol/mouse (80 mice/group). trans-4,5-Dihydro-4,5-dihydroxy-B[j]F was more potent than trans-9,10-dihydro-9,10-dihydroxy-B-[j]F in inducing pulmonary tumors in both female and male mice. Administration of 1.10 mumol of trans-4,5-dihydro-4,5-dihydroxy-B[j]F resulted in a 90-92% incidence of pulmonary tumors with an average of 3.6 and 4.2 tumors/mouse among female and male mice, respectively. A similar tumorigenic activity was observed for B[j]F in lung. trans-9,10-Dihydro-9,10-dihydroxy-B[j]F was significantly less tumorigenic (P < 0.05), producing a 44 and 64% incidence of pulmonary tumors at a dose of 1.10 mumol with an average of 0.8 and 1.0 tumor/mouse in female and male mice, respectively. A statistically significant (P < 0.001) incidence of hepatic tumors was also produced among male mice administered either B[j]F, trans-4,5-dihydro-4,5-dihydroxy-B[j]F, or trans-9,10-dihydro-9,10-dihydroxy-B[j]F at a dose of 1.10 mumol/mouse. In comparing the tumorigenicity of the diasteromeric diol epoxides derived from both trans-4,5-dihydro-4,5-dihydroxy-B[j]F and trans-9,10-dihydro-9,10-dihydroxy-B[j]F, the anti-diasteromers exhibited greater tumorigenic activity. The most tumorigenic diol epoxide was anti-4,5-dihydroxy-6,6a-epoxy-4,5,6,6a-tetrahydro-B[j]F. At a dose of 0.275 mumol, this diol epoxide induced a 96 and 100% incidence of pulmonary tumors in female and male mice, with an average of 8.6 and 5.0 tumors/mouse, respectively. anti-9,10-Dihydroxy-11,12-epoxy-9,10,11,12-tetrahydro-B[j]F at this dose produced a 56 and 95% incidence of pulmonary tumors in female and male mice with an average of 1.0 and 2.8 tumors/mouse, respectively. syn-4,5-Dihydroxy-6,6a-epoxy-4,5,6,6a-tetrahydro-B[j]F and syn-9,10-dihydroxy-11,12-epoxy-9,10,11,12-tetrahydro-B[j]F at a dose of 0.275 mumol did not induce a significant incidence (P > 0.05) of pulmonary tumors in female or male mice.(ABSTRACT TRUNCATED AT 400 WORDS)

Bioassay of quinoline, 5-fluoroquinoline, carbazole, 9-methylcarbazole and 9-ethylcarbazole in newborn mice.

Quinoline and carbazole are among the more prevalent aza-arenes present as components of environmental pollutants. Both of these aza-arenes are hepatocarcinogenic to mice when administered in the diet. The hepatocarcinogenic potential of quinoline is consistent with its mutagenic activity in Salmonella typhimurium TA100 and potential to induce unscheduled DNA synthesis (UDS) in rat hepatocytes. Structure-activity studies with fluorinated quinolines indicate that the presence of a fluorine atom at the 5-position of quinoline may inhibit detoxification and result in enhanced genotoxic potency. Quinoline and 5-fluoroquinoline were assayed in newborn CD-1 mice at a total dose of 1.75 mumol to establish their relative tumorigenic activity. Liver tumours developed in 60 and 90% of the male newborn mice treated with quinoline and 5-fluoroquinoline, respectively. The majority of liver tumours observed among the quinoline-treated mice were classified as adenomas. In contrast, liver carcinomas developed in most of the male mice treated with 5-fluoroquinoline. Unlike the well established genotoxic potential of quinoline, there is limited evidence for carbazole having either genotoxic or carcinogenic activity. Whereas carbazole is not mutagenic towards several strains of S. typhimurium, both 9-methylcarbazole and 9-ethylcarbazole are active as mutagens in S. typhimurium TA100. Carbazole, 9-methylcarbazole and 9-ethylcarbazole were assayed in primary rat hepatocytes to assess their relative potential to induce UDS in rat hepatocytes; only 9-ethylcarbazole did so. These carbazole derivatives were also assayed in newborn CD-1 mice at a total dose of 1.75 mumol. Neither carbazole nor either of these 9-alkylcarbazoles produced a significant tumorigenic response in this bioassay system.

Subchronic toxicity of benzyl selenocyanate and 1,4-phenylenebis(methylene)selenocyanate in F344 rats.

Chemopreventive agents benzyl selenocyanate (BSC) and 1,4-phenylenebis(methylene)selenocyanate (p-XSC) were fed in NIH-07 diet to male and female F344 rats (4, 2, and 0.5 mg/kg/day for BSC and 20, 10, and 5 mg/kg/day for p-XSC) for 13 weeks. Weight gains were depressed for male and female rats fed 4 and 2 mg/kg/day BSC, females fed 0.5 mg/kg/day BSC, and male rats fed 20 and 10 mg/kg/day p-XSC. At necropsy, no clear treatment-related lesions were noted, but dose-dependent hepatomegaly was observed in both sexes of BSC and p-XSC groups. Plasma transaminases AST and ALT were elevated in the higher dose groups, while hemoglobin, HCT, and RBC were reduced in most BSC and some p-XSC treatment groups. Plasma glucose was reduced in BSC-treated males. Significant histologic findings included moderate to severe hepatic centrilobular hypertrophy with fatty change in all males and females in the 4 mg/kg/day BSC groups and in 9/15 males and 3/15 females in the 2 mg/kg/day BSC groups. Dose-dependent, mild centrilobular hypertrophy with minimal fatty change was observed in the mid- and low-dose BSC groups and in all p-XSC groups. Mild to moderate renal tubular and interstitial nephritis occurred in the 4 mg/kg/day male BSC group. Dietary maximum tolerated dose levels for chemoprevention studies are 0.5 mg/kg/day (3.0 ppm Se) for BSC and 5 mg/kg/day (32.5 ppm Se) for p-XSC, compared to literature values of 2-3 ppm Se for Na2SeO3.

Influence of regional location of the inoculation site and dietary fat on the pathology of MDA-MB-435 human breast cancer cell-derived tumors grown in nude mice.

The effects of inoculation site and dietary fat intake on the growth and metastasis of the MDA-MB-435 human breast cancer cell line were studied in athymic nude mice. The tumor cells, 1 x 10(6), were injected into either a right-sided thoracic or inguinal mammary fat pad (mfp), and 1 week later mice were randomly assigned to a high-fat (HF), 23% corn oil, or a low-fat (LF), 5% corn oil, diet. There were 30 mice in the HF, and 30 in the LF subgroups from each of the two inoculation site groups. The experiment was terminated 15 weeks after the tumor cell inoculations. Within the thoracic mfp-injected group, a HF diet reduced latency, increased growth rate at the primary site, and enhanced metastasis to regional lymph nodes, lungs, and intra-abdominal sites. For mice inoculated into an inguinal mfp, fat intake affected neither primary nor metastatic tumor development and growth; in both subgroups lung metastasis was significantly less than in the HF-fed, thoracic mfp-injected subgroup. The histological features of the lung metastases were consistent with a vascular mode of spread, whereas the extensive intra-abdominal lymph node involvement observed in mice with inguinal mfp tumors was in keeping with lymphatic-borne metastases.

Histopathological and ultrastructural changes in simulated large colonic torsion and reperfusion in ponies.

This investigation examines the histological and ultrastructural lesions of the colonic mucosa during terminal experimental infarction and subsequent reperfusion. Four ponies were anaesthetised and subjected to surgical torsion of the colon. Biopsies were collected at hourly intervals for 3 h, at which point the torsions were corrected. Circulation was re-established for 2 h and the bowel was re-biopsied at hourly intervals. The ponies were killed while under anaesthesia. During the 3 h experimental infarction, the bowel became macroscopically thickened and dark purple. Histologically, the mucosa degenerated from Grade 0 to Grade 3. Ultrastructurally, there was progressive micro-vascular distension with erythrodiapedesis and damage to the interstitial cells. Spaces developed between the bases and sides of the columnar epithelial cells and sloughing followed subsequently. During the 2 h reperfusion interval, the mucosa continued to degenerate rapidly to a Grade 5, and was characterised by extensive interstitial damage, oedema, cellular swelling, necrosis and mitochondrial damage. The results showed that the experimentally infarcted colonic mucosa degenerated sequentially. Following circulatory reestablishment, continued rapid mucosal degeneration characteristic of reperfusion injury occurred. Reperfusion injury is probably responsible, at least in part, for the often poor outcome of infarcted bowel in horses following surgical correction.

Effect of dietary fat on human breast cancer growth and lung metastasis in nude mice.

Results from epidemiological studies have generally indicated an association of dietary saturated animal fats with human breast cancer risk. Some studies, however, have suggested a similar association for some polyunsaturated vegetable fats shown to promote both rodent mammary carcinogenesis and metastasis. This study was performed to evaluate the effects of corn oil on growth and metastasis of MDA-MB-435 human breast cancer cells, which have a propensity for metastasis. Corn oil is rich in the omega-6 fatty acid linoleic acid. Fifty-eight female athymic nude mice (NCr-nu/nu) were fed a high-fat diet (23% wt/wt corn oil; 12% linoleic acid) or a low-fat diet (5% wt/wt corn oil; 2.7% linoleic acid). Seven days after diets were started, tumor cells (1 x 10(6) were injected into a mammary fat pad. The time to appearance of solid tumors and the tumor size were recorded. After 15 weeks, the study was terminated, and autopsies were performed to determine the weight of the primary tumor and the extent of metastasis. The latent interval for tumor appearance in the animals fed the high-fat diet was shorter than that in the low-fat diet group, and the tumor growth rate in the high-fat diet group showed a small but statistically significant increase compared with the low-fat diet group. Primary tumors developed in 27 of the 29 mice on the high-fat diet and in 21 of the 29 on the low-fat diet. Of the mice with palpable primary tumors, 18 of 27 in the high-fat diet group and eight of 21 in the low-fat diet group had macroscopic lung metastases. The extent of metastasis in the high-fat diet group was independent of the primary tumor weight, but only those in the low-fat diet group with primary tumors weighing more than 2 g developed metastases. These results suggest that a high-fat diet rich in omega-6 polyunsaturated fatty acid can enhance metastasis of human breast cancer cells in this mouse model. The findings support the need for further study of the relationship between dietary polyunsaturated fats and breast cancer risk and for experiments to determine the effect on metastasis of only a 50% difference in fat intake--the dietary goal of the proposed clinical trials of low-fat dietary intervention in breast cancer patients.

Disseminated sweat gland adenocarcinoma with acronecrosis in a cat.

Sweat gland adenocarcinomas are uncommon tumors in domestic animals. In this report, a cat with a disseminated sweat gland adenocarcinoma accompanied by acronecrosis is presented. The acronecrosis was characterized by ischemic necrosis and sloughing of the digits in all 4 feet. The neoplasm was characterized by a highly invasive and destructive cell population composed of pleomorphic and anaplastic glandular cells. Metastasis to the heart, lung, lymph nodes, liver and kidney was seen. Within the subcutis of the front feet small neoplastic foci extended to the distal phalanges and sloughed areas. There was also marked thrombosis unassociated with tumor invasion adjacent to areas of digital sloughing. In the rear paws, there was little tumor invasion, and thrombosis at the sloughed sites predominated.

The effects of phenylbutazone on the morphology and prostaglandin concentrations of the pyloric mucosa of the equine stomach.

Phenylbutazone, a nonsteroidal anti-inflammatory drug known to produce gastric ulcers, was administered intravenously (13.46 mg/kg body weight) daily to 12 horses. Horses were euthanatized daily after 24, 48, 72, and 96 hours following the initial injection. Eight untreated horses served as controls. Small multifocal pyloric erosions were seen after 24 hours and then progressed in severity over time. The erosions were characterized by sloughing of the surface epithelium, subepithelial bleb formation, necrosis of the lamina propria, degeneration of the walls of subsurface capillaries, and microthrombosis of the capillaries of the pyloric mucosa. Large numbers of neutrophils with abundant fibrin and cellular debris were present at the erosion sites. Eroded pyloric mucosa and adjacent macroscopically intact mucosa were examined ultrastructurally. In both the macroscopically eroded mucosa and multifocally in the adjacent macroscopically uneroded mucosa, there was cellular swelling of the endothelium, pericytes, and smooth muscle cells of arterioles. In capillaries and post-capillary venules, the endothelium ranged from swollen to lysed and necrotic. Extensive extravasation of erythrocytes and edema were seen. These lesions were not seen in the control horses. Phenylbutazone produces a microvascular injury that is associated with the formation of pyloric erosions in horses. The pyloric mucosa of six horses was assayed for prostacyclin and prostaglandin E2 at 48 and 96 hours following the initial injection. There was no statistically significant difference between prostaglandin concentrations in the mucosa of control and treated horses. It was concluded that there was little correlation between pyloric mucosal prostaglandin concentrations and pyloric erosions after 48 hours.

The effects of phenylbutazone on the intestinal mucosa of the horse: a morphological, ultrastructural and biochemical study.

Phenylbutazone, a non-steroidal anti-inflammatory drug known to produce intestinal erosions, was administered intravenously (13.46 mg/kg bodyweight) to 12 horses which were killed after 24, 48, 72 and 96 h. Eight untreated horses served as controls. Annular erosions in the duodenum and mucosal necrosis in the colon were seen after 48 h which progressed in severity. The erosions were characterised by sloughing of the surface epithelium, subepithelial cleft and bleb formation, necrosis of the lamina propria, degeneration of the walls of subsurface capillaries and microthrombosis. Large numbers of neutrophils with abundant fibrin and cellular debris were present at the erosion sites. Ultrastructurally, there was swelling of the endothelium of capillaries and small vessels, and of pericyte and smooth muscle cytoplasm in arterioles. In capillaries and post capillary venules, the endothelium ranged from swollen to lysed and necrotic. Extensive extravasation of erythrocytes and oedema were seen. These lesions were not seen in the control horses. Phenylbutazone produces a microvascular injury associated with the formation of duodenal and colonic erosions in horses. The duodenal and colonic mucosa were assayed at 48 and 96 h for prostacyclin and PGE2. There was no statistically significant difference between prostaglandin levels in the mucosa of control and treated horses. It was concluded that there was no correlation between mucosal prostaglandin levels and intestinal erosions after 48 h.

Effects of catechol on the induction of tumors in mouse skin by 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrenes.

Catechol (1,2-dihydroxybenzene) is a major phenolic compound present in the co-carcinogenic fraction of cigarette tar. It has been shown to be a potent co-carcinogen with benzo[a]pyrene (BaP) in mouse skin. In this study we have examined the co-carcinogenic and co-initiating activities of catechol with racemic and enantiomeric 7,8-dihydroxy-7,8-dihydrobenzo[a]pyrenes (BaP-7,8-diols) in mouse skin. Similar to enhancement of BaP carcinogenesis, repeated concurrent applications of catechol and (+/-)-BaP-7,8-diol to mouse skin strongly enhanced (+/-)-BaP-7,8-diol tumor multiplicity and tumor incidence, and decreased latency. Co-application of catechol with the racemic or either of the enantiomers of BaP-7,8-diol in a two-stage initiation--promotion protocol increased the tumor initiating activity of racemic BaP-7,8-diol, similar to that of BaP, by approximately 50%, but had no statistically significant effect on the tumor initiating activity of the (+)- or (-)-enantiomers in mouse skin. Thus, catechol is as potent a co-carcinogen with (+/-)-BaP-7,8-diol as it is with BaP. However, as tested here catechol is a weak co-initiator when applied with (+/-)-BaP-7,8-diol or BaP.

Intestinal lymphangiectasia with lipogranulomatous lymphangitis in a dog.

Intestinal lymphangiectasia with lipogranulomatous lymphangitis was diagnosed at necropsy in a 6.5-year-old Maltese dog that had a history of bouts of vomiting, abdominal distention, and diarrhea. The condition was attributed to trauma to the pleural and peritoneal cavities received from bite wounds inflicted one year previously.

Histologic findings in the gastrointestinal tract of horses with colic.

Thirty horses were admitted to the University of Georgia Veterinary Medical Teaching Hospital with colic severe enough to warrant surgery and/or euthanasia. Gastrointestinal tracts of these 30 horses were histologically examined for morphologic changes. The horses were grouped according to cause of the colic (ie, simple obstruction, strangulation obstruction, thromboemboli, and inflammation). Lesions were graded as to severity, and grade scores were correlated with survival or nonsurvival. Mucosal changes developed distal and proximal to the primary lesion site and, although there were some differences between groups, changes characteristic of ischemia were common to all groups. The predictability of lesion grades of 2 or higher for nonsurvivability (90%) indicates that intestinal biopsy may have prognostic value in the postsurgical evaluation and management of equine colic.

Vascular pathology in phenylbutazone intoxicated horses.

Three mature Thoroughbred geldings were given 13.63 mg phenylbutazone/Kg bodyweight intravenously for 3 days and repeated in one horse 4 days later. After 4, 7 and 10 days (double treatment), degeneration of the wall of small veins occurred in all horses. The veins were dilated and/or showed hyalin degeneration. The phlebopathy was interpreted to be paramount in phenylbutazone intoxication. All other manifestations, including erythro- and leukodiapedesis, submucosal edema and ulceration of the gastrointestinal mucosa, phlebothrombosis and significant changes in the hemogram and serum chemistry, were considered secondary to the vein lesions.