The effects of Strongylus vulgaris parasitism on eosinophil distribution and accumulation in equine large intestinal mucosa

REASONS FOR PERFORMING STUDY

Eosinophilic granulocytes have been associated with parasite or immune-mediated diseases, but their functions in other disease processes remain unclear. Cause and timing of eosinophil migration into the equine gastrointestinal mucosa are also unknown.

OBJECTIVE

To determine the effects of intestinal parasitism on eosinophils in equine large intestinal mucosa.

METHODS

Large intestinal mucosal samples were collected from horses and ponies (n = 16) from the general veterinary hospital population, ponies (n = 3) raised in a parasite-free environment, ponies experimentally infected with 500 infective Strongylus vulgaris larvae and treated with a proprietary anthelmintic drug (n = 14), and a similar group of ponies (n = 7) that received no anthelmintic treatment. Total eosinophil counts and eosinophil distribution in the mucosa were determined by histological examination. A mixed model analysis was performed and appropriate Bonferroni adjusted P values used for each family of comparisons. P<0.05 was considered significant.

RESULTS

There was no difference in large intestinal mucosal eosinophil counts and eosinophil distribution between ponies infected with S. vulgaris and those raised in a parasite-free environment. Experimental infection with S. vulgaris, with or without subsequent anthelmintic treatment, did not change eosinophil counts, and counts were similar to those for horses from the general population.

CONCLUSIONS

Migration of eosinophils to the equine large intestinal mucosa appears to be independent of exposure to parasites. Large intestinal mucosal eosinophils may have more functions in addition to their role in defence against parasites.

The cloning and expression of matrix metalloproteinase-2 and tissue inhibitor of matrix metalloproteinase 2 in normal canine lymph nodes and in canine lymphoma

Matrix metalloproteinase-2 (MMP-2) and its inhibitor, tissue inhibitor of matrix metalloproteinase 2 (TIMP2), are known to be important in cancer. The purposes of this study were to determine the cDNA sequence of canine MMP-2 and to investigate the expression patterns of MMP-2 and TIMP2 in normal canine lymph nodes and spontaneously arising canine lymphomas. We cloned and sequenced a PCR product containing most (1901 base pairs) of the coding sequence of canine MMP-2 that translates into a 623 amino acid protein. The cDNA and deduced amino acid sequences are highly homologous to those of other mammalian species. Canine MMP-2 and TIMP2 mRNAs were detectable in the majority of normal lymph node and lymphomatous samples evaluated. No statistical difference was identified when comparing the expression of either gene with regard to normal versus neoplastic nodes, nodal versus extranodal lymphoma, lymphoma grade, or B versus T cell immunophenotype.

Evaluation of the safety and bioactivity of purified and semi-purified glucoraphanin

The anti-carcinogenic effects of broccoli have been attributed to sulforaphane, the hydrolysis product of glucoraphanin (GRP). Here we determined if purified GRP, in the absence of the plant-derived hydrolyzing enzyme myrosinase, could affect pulmonary and hepatic ethoxyresorufin O-deethylase (EROD) and/or NAD(P)H-quinone oxidoreductase 1 (NQO1) activity. Male F344 rats were administered semi-synthetic, semi-purified or purified GRP (240 mg/kg: 550 micromol/kg rat daily for 4 days) by gavage. Hepatic and pulmonary NQO1 activity increased ( approximately 20%), but not EROD. Varying doses of semi-purified GRP (30, 60, or 120 mg/kg rat daily for 4 days) again caused no change in EROD activity, although a dose-dependent increase in NQO1 was seen. Urinary excretion of mercapturic acids showed no difference between preparations, and recovery increased with decreasing dose. Histopathologic examination revealed no abnormal tissues other than cecum, where inflammation was dose dependent; mild at 120 mg/kg and severe at 240 mg/kg, a greatly supra-physiological dose. We conclude that GRP 30-60 mg/kg p.o. is safe and effectively enhances NQO1 in all tissues evaluated.

Luminal nutrients exacerbate intestinal hypoxia in the hypoperfused jejunum

BACKGROUND

Provision of enteral nutrients shortly after traumatic injury has become the preferred method of nutrition support provided to patients. However, traumatic shock results in splanchnic hypoperfusion, which may cause persistent intestinal hypoxia. This study tested the hypothesis that delivery of enteral nutrients to the hypoperfused jejunum increases oxidative demand beyond that available, thereby exacerbating intestinal hypoxia.

METHODS

Wistar-Furth rats (186+/-4 g; n = 24) were randomized to receive intestinal hypoxia (superior mesenteric artery occlusion) or serve as normoxic controls (sham laparotomy). Within the jejunum of each rat, 4 6-cm loops were randomized to receive luminal perfusions with 1 of 4 substrates: mannitol (an osmotic control); glucose (undergoes active transport via the sodium-glucose co-transporter [SGLT-1] and is metabolized); 3-o-methylglucose (3-o-mg; uses SGLT-1 but is not metabolized); or fructose (does not use SGLT-1 but is metabolized). After in situ perfusions, jejunal tissue was removed for analysis of nutrient transport and barrier function in modified Ussing chambers. Tissue homogenate was used to determine concentration of ATP, lactate, pyruvate, and protein. Also, jejunal tissue was stained with hematoxylin and eosin for qualitative analysis of ischemia and necrosis.

RESULTS

Transmural resistance was lower (p < .001) in the hypoxia groups, irrespective of substrate, indicating increased mucosal permeability. When compared with the normoxic controls, glucose transport was impaired (p < .001) in the hypoxic groups; however, glutamine transport was unaffected. The degree of intestinal hypoxia, assessed by jejunal lactate concentration, was higher (p < .001) in the glucose and fructose groups, than the control mannitol and 3-o-mg groups.

CONCLUSIONS

The observation that 3-o-mg did not differ from the mannitol control indicates that SGLT-1 activation alone does not exacerbate hypoxia. Rather, these results indicate that provision of metabolizable nutrients to the hypoperfused intestine exacerbate hypoxia and potentially lead to intestinal ischemia. Although early enteral nutrition is an important intervention after trauma, care must be taken to ensure intestinal perfusion is adequate to allow for nutrient metabolism and prevent further compromise.

Immunohistochemical detection of betaine-homocysteine S-methyltransferase in human, pig, and rat liver and kidney

Betaine-homocysteine S-methyltransferase (BHMT) has been shown to be expressed at high levels in the livers of all vertebrate species tested. It has also been shown to be abundant in primate and pig kidney but notably very low in rat kidney and essentially absent from the other major organs of monogastric animals. We recently showed by enzyme activity and Western analysis that pig kidney BHMT was only expressed in the cortex and was absent from the medulla. Using immunohistochemical detection, we report here that in human, pig, and rat kidney, BHMT is expressed in the proximal tubules of the cortex. Immunohistochemical staining for BHMT in human, pig, and rat liver indicate high expression in hepatocytes. The staining patterns are consistent with cytosolic expression in both organs.

Rapid isolation and purification of 1-cyano-2-hydroxy-3-butene (crambene) from Crambe abyssinica seed meal using immiscible solvent extraction and high-performance liquid chromatography

1-Cyano-2-hydroxy-3-butene (crambene) is a nitrile found in cruciferous vegetables that causes significant upregulation of quinone reductase and glutathione S-transferases in vivo and in vitro, making it a likely candidate as a cancer chemopreventive compound. To investigate further the putative anticarcinogenic mechanisms of crambene, a compound of the highest possible purity is vital. Therefore, a rapid and effective method of purification of crambene is necessary to continue studies of its beneficial health effects. A rapid method to isolate and purify natural crambene from either Crambe abyssinica (crambe) seed or commercially processed crambe seed meal was developed using immiscible solvent extraction followed by high-performance liquid chromatography. Use of this methodology eliminated the need for time-consuming and relatively inefficient column chromatography, improved extraction efficiency, and resulted in higher purity than previously used methodologies. Elimination of trace amounts of fatty acid residues, unachievable with previous methodologies, also was accomplished.

Preparative HPLC method for the purification of sulforaphane and sulforaphane nitrile from Brassica oleracea

An extraction and preparative HPLC method has been devised to simultaneously purify sulforaphane and sulforaphane nitrile from the seed of Brassica oleracea var. italica cv. Brigadier. The seed was defatted with hexane, dried, and hydrolyzed in deionized water (1:9) for 8 h. The hydrolyzed seed meal was salted and extracted with methylene chloride. The dried residue was redissolved in a 5% acetonitrile solution and washed with excess hexane to remove nonpolar contaminants. The aqueous phase was filtered through a 0.22-microm cellulose filter and separated by HPLC using a Waters Prep Nova-Pak HR C-18 reverse-phase column. Refractive index was used to detect sulforaphane nitrile, and absorbance at 254 nm was used to detect sulforaphane. Peak identification was confirmed using gas chromatography and electron-impact mass spectrometry. Each kilogram of extracted seed yielded approximately 4.8 g of sulforaphane and 3.8 g of sulforaphane nitrile. Standard curves were developed using the purified compounds to allow quantification of sulforaphane and sulforaphane nitrile in broccoli tissue using a rapid GC method. The methodology was used to compare sulforaphane and sulforaphane nitrile content of autolyzed samples of several broccoli varieties.

Xenobiotic metabolism, oxidant stress and chronic pancreatitis. Focus on glutathione

Chronic pancreatitis, although relatively rare in the Western World, is common in certain tropical zones where staple crops such as cassava are rich in cyanogenic glycosides. This paper reviews the evidence for a cyanide connection, with reference to experimental studies using another plant nitrile, crambene; and then examines the hypothesis that chronic pancreatitis represents a manifestation of uncoordinated detoxification reactions between pancreatic cytochrome P450 mono-oxygenases and phase II conjugating enzymes, resulting in the irreversible consumption of glutathione in the acinar cell. The conclusion is that the central role of disrupted pancreatic glutathione status, as a result of 'xenobiotic stress', in the evolution of chronic pancreatitis cannot be overestimated. This position contrasts with that in acute pancreatitis, in which glutathione depletion has a pivotal role too, but occurs as a result of 'stress' from reactive oxygen species.

Carotene, tocopherol, and ascorbate contents in subspecies of Brassica oleracea

Cruciferous vegetables contain high levels of vitamins that can act as antioxidants, compounds that may protect against several degenerative diseases. The edible portions of 50 broccoli and 13 cabbage, kale, cauliflower, and Brussels sprouts accessions were assayed to determine variation in alpha-carotene, beta-carotene, alpha-tocopherol, gamma-tocopherol, and ascorbate contents within and between subspecies of Brassica oleracea. Ascorbate content was estimated in fresh samples using HPLC. Tissues for carotene and tocopherol analysis were lyophilized prior to extraction. Carotene and tocopherol concentrations were simultaneously measured using a reverse phase HPLC system. Results indicate that there is substantial variation both within and between subspecies. Kale had the highest levels of vitamins, followed by broccoli and Brussels sprouts with intermediate levels and then by cabbage and cauliflower, with comparatively low concentrations. Variability in vitamin content among the broccoli accessions suggests that potential health benefits that accrue with consumption are genotype dependent.

Variation of glucosinolates in vegetable crops of Brassica oleracea

Glucosinolates were evaluated in 5 groups and 65 accessions of Brassica oleracea (50 broccoli, 4 Brussels sprouts, 6 cabbage, 3 cauliflower, and 2 kale) grown under uniform cultural conditions. Glucosinolates and their concentrations varied among the different groups and within each group. The predominant glucosinolates in broccoli were 4-methylsulfinylbutyl glucosinolate (glucoraphanin), 3-butenyl glucosinolate (gluconapin), and 3-indolylmethyl glucosinoate (glucobrassicin). Glucoraphanin concentration in broccoli ranged from 0.8 micromol g(-1) DW in EV6-1 to 21.7 micromol g(-1) DW in Brigadier. Concentrations of the other glucosinolates in broccoli varied similarly over a wide range. In Brussels sprouts, cabbage, cauliflower, and kale, the predominant glucosinolates were sinigrin (8.9, 7.8, 9.3, and 10.4 micromol g(-1) DW, respectively) and glucobrassicin (3.2, 0.9, 1.3, and 1.2 micromol g(-1) DW, respectively). Brussels sprouts also had significant amounts of gluconapin (6.9 micromol g(-1) DW). Wide variations in glucosinolate content among genotypes suggest differences in their health-promoting properties and the opportunity for enhancement of their levels through genetic manipulation.

Inhibition of TPA-induced tumor promotion in CD-1 mouse epidermis by a polyphenolic fraction from grape seeds

The anti-tumor promoting activity of a polyphenolic fraction from grape seeds (GSP) was examined in CD-1 mouse skin epidermis. Specifically, the ability of this fraction to inhibit 12-O-tetradecanoylphorbol-13-acetate (TPA)-induced tumor promotion and two markers of promotion in mouse skin, ornithine decarboxylase (ODC) and myeloperoxidase (MPO) activities, was evaluated. Pretreatment of mouse skin with 5, 10, 20 and 30 mg of GSP resulted in a dose-dependent reduction in TPA-induced epidermal ODC activity of 27, 37, 48 and 70%, respectively, compared to controls. In addition, pretreatment of mouse skin with 1, 5, 10 and 20 mg of GSP resulted in a significant 43, 39, 54 and 73% inhibition of MPO activity, respectively, compared to controls. In 7,12-dimethylbenz[a]anthracene (DMBA)-initiated CD-1 mice, biweekly treatment of mouse skin with 5, 10, and 20 mg of GSP 20 min prior to TPA application resulted in a 30, 40, and 60% inhibition of final skin tumor incidence, respectively, compared to controls. In addition, the final number of tumors per mouse in the 5, 10 and 20 mg GSP-treated animals was decreased 63, 51, and 94%, respectively, compared to controls. These studies indicate that GSP possesses anti-tumor promoting activity when applied to CD-1 mouse skin prior to treatment with TPA. The mechanism of this tumor inhibition is due, in part, to a GSP-associated inhibition of TPA-induced epidermal ODC and MPO activities. Thus, GSP warrants further evaluation as a skin cancer chemopreventative agent.

Cutaneous antimicrobial preparation prior to intravenous catheterization in healthy dogs: clinical, microbiological, and histopathological evaluation

The purpose of this study was to determine the effects of a one-minute chlorhexidine gluconate skin preparation protocol prior to cephalic vein catheterization. Twenty-three healthy beagle dogs had one leg aseptically prepared and the opposite leg served as a control. Twenty-six- and 77-hour time groups were studied. Chlorhexidine-treated legs had significantly lower cutaneous bacterial counts than the control legs prior to catheter insertion and prior to catheter withdrawal for both time groups. Control legs developed significantly more dermatitis than the treated legs after 77 h. A one-minute preparation with 4% chlorhexidine gluconate was an effective method for sustained reduction of cutaneous bacterial counts at peripheral intravenous catheter insertion points in dogs. Increased cutaneous bacterial counts were associated with significantly more microscopic dermatitis in untreated legs after 77 h of catheterization.

Characterization of rat pancreatic glutathione S-transferases by chromatofocusing, reverse-phase high-performance liquid chromatography, and immunohistochemistry

The cytosolic glutathione S-transferases (GSTs) are a family of phase II detoxifying isoenzymes that catalyze the interaction of the tripeptide thiol glutathione (GSH) with a wide variety of reactive and often toxic or carcinogenic electrophilic substrates. Pancreatic GSTs, however, have only been partially characterized. In this study, pancreatic cytosolic GSTs from male Fisher 344 rats were semipurified by affinity chromatography and then analyzed for isoenzyme content by chromatofocusing (fast protein liquid chromatography) and for subunit content by sodium dodecyl sulfate-polyacrylamide gel electrophoresis and reverse-phase high-performance liquid chromatography. In addition, polyclonal rabbit antisera were produced against homodimeric isoenzymes purified from rat liver and kidney, including the alpha class isoenzymes 1-1 and 2-2, the mu class isoenzyme 4-4, and the pi class isoenzyme 7-7. These antisera were used in immunohistochemical (IHC) studies of the distribution of the pancreatic GSTs. A range of 0.5-1.6% of the total protein in rat pancreatic cytosol was found to be GST protein. The most abundant subunits present were the pi subunit 7 and mu subunits 3 and 4. Using modified methodology, smaller amounts of the alpha subunit 2 and the mu subunit 6 were detected, whereas very small amounts of the alpha subunits 1 and 8 were present. The IHC demonstrated that the GSTs were in large part limited to the duct system of the exocrine pancreas, with positive staining of endothelial cells and stroma observed for the alpha and mu subunits. Isoenzymes containing the alpha subunit 2 were preferentially expressed in centroacinar cells and small ductules, whereas those containing the mu subunit 4 and the pi subunit 7 were more prevalent within larger ductules and ducts. The lumens of the largest ducts also contained the two subunits 4 and 7. It is concluded that the acinar cells of the exocrine pancreas may lack the protection against electrophilic toxic and carcinogenic agents provided by the ductular system by GSTs.

Induction of apoptosis in pancreatic acinar cells reduces the severity of acute pancreatitis

1-Cyano-2-hydroxy-3-butene (CHB) has been reported to cause cell death in rat pancreatic acini. In this report, we describe the time-dependent effects of CHB on mouse acinar cell apoptosis and the effects of CHB-induced acinar cell apoptosis on the severity of secretagogue-induced acute pancreatitis in mice. CHB administration to mice resulted in a time-dependent increase in pancreatic apoptosis, which was maximal 12 hours after CHB administration. The severity of pancreatitis was significantly reduced by prior CHB administration and maximal protection was observed when the caerulein injections were started 12 hours after CHB administration. These observations indicate that induction of apoptosis can reduce the severity of pancreatitis and they suggest that induction of pancreatic acinar cell apoptosis may be beneficial in the clinical management of acute pancreatitis.

Induction of rat pancreatic glutathione S-transferase and quinone reductase activities by a mixture of glucosinolate breakdown derivatives found in Brussels sprouts

The chemoprotective effects of cruciferous vegetables against cancer has been linked to the induction of detoxification enzymes, including the phase II enzymes, glutathione S-transferases (GST) and quinone reductase (QR). Four glucosinolate breakdown products found in Brussels sprouts and previously shown individually to affect detoxification enzymes--(1-cyano-2-hydroxy-3-butene (Crambene), indole-3-carbinol (I3C), phenylethyl isothiocyanate (PEITC) and 1-isothiocyanato-3-(methylsulfinyl)-propane (IBN) were administered to male F344 rats by oesophageal intubation for 7 days both as a mixture and individually to assess the effect of these compounds on GST and QR activity in the pancreas, an organ previously shown to be affected by cruciferous diets. The doses of each compound in the mixture (50 mg Crambene/kg, 56 mg I3C/kg, 0.1 mg PEITC/kg and 38 mg IBN/kg) were chosen to represent the relative proportions of the parent glucosinolate for each compound in Brussels sprouts and shown to be below the toxic threshold for all the compounds. In rats receiving the mixture, pancreatic QR and GST activities were elevated 31- and 1.7-fold, respectively, while glutathione (GSH) was elevated threefold. On an individual basis, Crambene alone caused a 21-fold elevation of QR and 1.5-fold elevation of GST activities, while pancreatic GSH was elevated by both Crambene and PEITC 2.6- and twofold, respectively. No other significant effects of individual components were found. When the mixture was administered at 60% of the original dose, pancreatic QR and GST activities were elevated 12- and 1.4-fold, respectively, and pancreatic GSH was elevated 1.5-fold. At 20% of the original dose, pancreatic GSH was unaffected and QR and GST activities were elevated 2.7- and 1.3-fold, respectively. The results of these studies suggest that a diet rich in cruciferous vegetables may produce phase 11 enzyme induction in the pancreas, and that Crambene may be the most active component.

The cruciferous nitrile, crambene, induces rat hepatic and pancreatic glutathione S-transferases

Indoles and isothiocyanates found in cruciferous vegetables have been implicated as chemopreventive agents against carcinogenesis. The bioactivities of chemically related cruciferous nitriles, including 1-cyano-2-hydroxy-3-butene (crambene), however, have not been thoroughly evaluated. Crambene causes a prolonged elevation of rat hepatic and pancreatic glutathione and induces the GSH S-transferases (GSTs). Because elevated GST activity against the model substrate chlorodinitrobenzene does not reflect individual isoenzyme induction, quantitative HPLC evaluation of specific GST subunits is necessary to fully assess the range of GST isoenzymes induced by crambene. Accordingly, male Fischer 344 rats were given, via esophageal intubation, either 100 (Experiment 1) or 50 mg crambene/kg body wt (Experiment 2) once daily for 7 days. GSTs were extracted from hepatic cytosol by affinity chromatography, and the individual subunits that comprise the various isoenzymes were quantified by reverse-phase HPLC to gain an estimate of induction. In addition, pancreatic GST subunits were assessed in the low-dose experiment. In parallel with increased GST activity, crambene caused a generalized induction of GST subunits in both liver and pancreas, but the pattern of subunit induction was tissue dependent. In the liver, alpha subunits 1 and 2 and the mu subunit 3 were induced approximately 2-fold, while the mu subunit 4 was induced only 1.5-fold. In the pancreas, the alpha subunit 2 was induced to a much larger extent (2.6-fold) than the other subunits (from no induction to 1.6 fold). These results suggests that crambene-mediated GST induction mechanisms vary from tissue to tissue. Potential chemoprevention provided by crambene against GST-metabolized carcinogens or toxins may differ between liver and pancreas because of differences in the degree and pattern of induction.

A comparison of the individual and collective effects of four glucosinolate breakdown products from brussels sprouts on induction of detoxification enzymes

Four glucosinolate derivatives were evaluated individually and as a mixture for their effects on hepatic P4501A (CYP1A), glutathione S-transferase (GST), quinone reductase (QR), glutathione reductase (G-Rd), and GSH levels. Doses of the derivatives were chosen to represent their relative abundance in Brussels sprouts. Adult male F344 rats received either corn oil (vehicle); one of the agents: indole-3-carbinol (I3C, 56 mg/kg), iberin (38 mg/kg), phenylethylisothiocyanate (PEITC, 0.1 mg/kg), or cyanohydroxybutene (crambene, 50 mg/kg); or all of the agents at the doses shown (as a mixture) given by gavage daily for 7 days. The mixture and I3C caused an 11- and 9.4-fold induction of CYP1A, respectively. Crambene and I3C each caused a 1.4-fold increase in GST, while the mixture caused a 2.5-fold increase. Crambene and I3C caused a 2.5- and 1.9-fold increase in QR, respectively. The mixture caused a 6.2-fold increase. Crambene, PEITC, and the mixture caused a 1.8-, 1.6-, and 2.0-fold increase in hepatic GSH levels, respectively. Crambene, I3C, iberin, and the mixture caused 1.3-, 1.4-, 1.2-, and 1.7-fold increases in G-Rd, respectively. In a second study the mixture was given at 60 and 20% of the original dose. CYP 1A, QR, G-Rd, and GST elevations were dose-dependent; GSH levels were not elevated. It is concluded that I3C and crambene are responsible for the majority of enzyme increases seen. A synergistic effect of I3C and crambene was evident on induction of GST and QR, but not on GSH, G-Rd, or P4501A.

Differential effect of cyanohydroxybutene on glutathione synthesis in liver and pancreas of male rats

1-Cyano-2-hydroxy-3-butene (CHB), an aliphatic nitrile found in cruciferous vegetables, causes a two- and sevenfold elevation in reduced glutathione (GSH) in rat liver and pancreas, respectively, after oral administration of 200 mg/kg. While this dose is also associated with pancreatotoxicity, a single 100 mg/kg dose or multiple lesser doses show the same effect, although somewhat reduced in magnitude, with no concomitant toxicity. In an attempt to identify the mechanism of this increase, we investigated the effect of CHB on GSH synthesis by examining the effect of buthionine sulfoximine (BSO), an inhibitor of GSH synthesis, on CHB-induced GSH elevation. Male Fischer 344 rats received 3 mmol BSO/kg ip 24 and 34 hr following CHB or corn oil. The CHB-mediated elevation in hepatic and pancreatic GSH was eradicated by BSO, suggesting that increased synthesis was responsible. The rate-limiting step in synthesis is gamma-glutamyl cysteine synthetase (GCS); the limiting substrate is cysteine. Therefore, CHB effects on GCS activity and hepatic and pancreatic cysteine equivalents were investigated. When rats were treated by gavage with CHB (100 mg/kg), hepatic GCS mRNA concentrations were increased 24 hr after treatment and hepatic cysteine equivalents were significantly elevated 4 hr following CHB. No significant elevation in hepatic GCS activity was observed, however, even 24 hr following CHB. Pancreatic cysteine equivalents were elevated at both 4 and 8 hr after CHB treatment. However, there was no detectable GCS mRNA or activity in pancreas, in either control or treated animals. Furthermore, CHB had no direct effect on the activity of GCS purified from kidney, regardless of whether GSH was present or absent. These results suggest that the mechanism of CHB-mediated induction of GSH may involve early increases in GSH precursors as well as a later increase in GCS mRNA. The mechanism of GSH elevation identified in these studies may hold therapeutic or prophylactic implications.

Effects of 1-isothiocyanato-3-(methylsulfinyl)-propane on xenobiotic metabolizing enzymes in rats

The glucosinolate hydrolysis product 1-isothiocyanato-3-(methylsulfinyl)-propane (IMSP), also known as iberin, is consumed in the average human (US) diet at approximately 1 mumol/kg/day. The chemoprotective effects observed with the consumption of cruciferous vegetables may be due to the presence of specific glucosinolate hydrolysis products either within the crucifers, or formed after ingestion of the crucifers. The mechanism of chemoprotection may be through selective induction of components of Phase II xenobiotic metabolizing enzymes. The influence of repeated administration of low concentrations of IMSP by gavage on components of Phase I and Phase II xenobiotic metabolizing systems was examined in the liver and small intestine of male Fischer 344 rats. Doses of 1, 10 and 100 mumol IMSP/kg, administered by gavage for 7 days, did not alter weight gain, or hepatic and renal weights, relative to body weight, and did not cause any histological lesions. Intestinal glutathione S-transferase (GST) activity and NAD(P)H:quinone reductase (QR) activities were significantly elevated to 3.1 and 8.1 times control values, respectively, at the 100 mumol/kg dose only. The administration of IMSP at 1, 10 or 100 mumol/kg had no significant effect on hepatic Phase I enzymes activities (cytochrome P-450 concentrations, ethoxycoumarin O-deethylase [ECD] and aminopyrine N-demethylase [AND] activities) or Phase II enzyme activities (GST, QR and UDP-glucuronosyltransferase [UDP-GT] activities towards 1-naphthol or 4-hydroxybiphenyl), at any of the doses tested and no effect on intestinal enzyme activities at doses below 100 mumol IMSP/kg. It is concluded that IMSP does not have a significant influence on induction of the Phase I or Phase II xenobiotic metabolizing enzymes in rats when tested at doses approximating those found in the human diet.

Histological and serum biochemical effects of 1-isothiocyanato-3- (methylsulphinyl)-propane in the F344 rat

1-Isothiocyanato-3-(methylsulphinyl)-propane (IMSP or iberin) is one of the major glucosinolate hydrolysis products found in cruciferous vegetables. The toxicity of IMSP after oral administration is unknown. This study examined the histological lesions and serum biochemical alterations resulting from intragastric administration of IMSP to male Fischer F344 rats. Rats were administered IMSP in corn oil by gavage at concentrations of 0.1, 0.3, 0.6, 1.0 and 2.0 mmol/kg body weight. Rats were anaesthetized and exsanguinated, and perfusion fixed at 4, 24 and 72 hr after dosing. IMSP caused a dose-dependent decrease in body weight for the first 24 hr after dosing. Multifocal haemorrhages and erosions of the mucosal portion of the stomach were grossly and histologically evident after 4 hr in rats dosed with more than 0.3 mmol IMSP/kg body weight, with severity increasing with dose. Mucosal lesions resolved by 72 hr in all but the 2 mmol/kg group. No significant lesions were observed in the liver or kidney. No physiologically significant haematocrit, electrolyte, blood urea nitrogen, creatinine or serum enzyme activity changes were observed. Urine collected after a dose of 1 mmol IMSP/kg body weight accounted for 1% of the IMSP, demonstrating that the compound was absorbed from the gastro-intestinal tract.

Differential effects of cyanohydroxybutene and selenium on normal and neoplastic canine mammary cells in vitro

The in vitro responses of canine mammary tumor (CMT-13) cells and normal canine mammary (NCM) cells to 1-cyano-2-hydroxy-3-butene (CHB), a naturally occurring nitrile in cruciferous plants, and selenium (Se) were investigated. CHB at 10 and 20 mM inhibited growth and viability of CMT-13 and NCM cells, respectively. This differential sensitivity was associated with a decreased ability of CMT-13 cells to increase intracellular glutathione (GSH) in comparison to NCM cells. Exposure of both cell types to 3.2 microM Se as sodium selenite alone had no effects, but addition of 3.2 microM Se 24 h after exposure to non-toxic doses of CHB resulted in a substantial decrease in growth of CMT cells, while NCM cells remained unaffected. The synergy noted between CHB and Se in inhibiting growth and viability of neoplastic mammary cells at levels not toxic to normal mammary cells is promising initial evidence that CHB could have a role in chemoprotection or chemotherapy.

In vitro metabolism of cyanohydroxybutene: formation of a glutathione-S-transferase catalyzed product

The pancreatotoxin cyanohydroxybutene (CHB) causes a significant and prolonged elevation in glutathione (GSH) in liver and pancreas (Wallig and Jeffery, 1990). Here we report that urinary thiols also increase. This suggests that CHB may react with GSH, either directly or following phase I oxidation, to form an adduct, which is further metabolized to the corresponding mercapturic acid for urinary excretion. Metabolism of CHB by hepatic mixed function oxidase and cytosolic alcohol dehydrogenase enzymes was evaluated by monitoring microsomal NADPH consumption and alcohol dehydrogenase-dependent NADH generation, respectively. There was no apparent increase in the rate of microsomal NADPH consumption or alcohol dehydrogenase-dependent NADH generation in the presence of CHB. To evaluate in vitro formation of a glutathione-S-transferase (GST) catalyzed adduct, [3H-glycyl]-GSH and [14C-cyano]-CHB were incubated at 37 degrees C for 1 h, with or without GST. Dinitrophenol derivatization and high performance liquid chromatographic (HPLC) analysis (Farris & Reed, 1987) revealed no double-labeled peaks, suggesting that no stable conjugate was formed. However a tritiated product, not present in control samples, and with an identical retention time to cysteinyl-glycine (cys-gly) was formed. In addition, the product has a fast atom bombardment mass-spectrum consistent with cys-gly. These results suggest that while CHB may not undergo phase I oxidation, in the presence of CHB, GSH may break down to form cys-gly. A mechanism for CHB-dependent breakdown of GSH to cys-gly is proposed, and the pharmacological implications of this finding are discussed.

Separation of the toxic and glutathione-enhancing effects of the naturally occurring nitrile, cyanohydroxybutene

Cyanohydroxybutene (CHB) is reported to be hepatotoxic in male Fischer 344 rats at an oral dose of 300 mg/kg and, while no longer hepatotoxic, pancreatotoxic at 200 mg/kg. In addition, the 200 mg/kg dose causes a persistent elevation in hepatic and pancreatic glutathione (GSH). This study was conducted to determine if smaller doses of CHB could cause GSH elevation in the absence of toxicity. A single oral dose of 100 mg/kg or multiple lower doses (50 mg/kg daily for 3 days or 30 mg/kg for 6 days) caused a significant and persistent increase in pancreatic GSH, although hepatic levels were unchanged. Ten milligrams per kilogram, even daily for 24 days, was without effect on hepatic or pancreatic GSH. Neither a single oral dose of 100 mg/kg nor multiple lower doses were associated with toxicity. However, when either 100 or 50 mg/kg were administered intravenously, pancreatic apoptosis was observed. In animals dosed with 100 mg/kg iv, mixed histiocytic and suppurative inflammation and frank pancreatic necrosis also developed and were associated with elevated plasma lipase and amylase. The animals receiving CHB intravenously also exhibited elevated GSH levels in both pancreas and liver. This study shows that oral doses between 30 and 100 mg CHB/kg can be used to elevate GSH levels without any pancreatotoxicity. However, a single 50 mg CHB/kg dose given intravenously causes apoptosis, while 100 mg/kg causes severe pancreatotoxicity with necrosis.

Lymphosarcoma causing acquired obstructive hydrocephalus in a dog

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Postnatal selenium repletion protects lungs of neonatal rats from hyperoxia

We reported previously that Se-adequate neonatal rat pups born to Se-adequate dams were resistant to lung damage by hyperoxia. To assess whether early postnatal Se repletion could also protect developing pups reared under hyperoxia, female Sprague-Dawley rats (n = 20) were bred and fed a Se-deficient (0.04 microgram/g) diet during pregnancy. On d 1 postpartum, dams were divided into two groups and fed either a Se-deficient diet or a Se-repleted (0.5 microgram/g) diet. On d 4 postpartum, litters in each group were randomly assigned to either air or high oxygen (greater than 95% O2) environments. Histologic evaluation of lungs from d-8 pups indicated that Se repletion significantly reduced the incidence of lung lesions caused by hyperoxia. Selenium-repleted pups also had significantly greater lung volumes and internal surface areas. The 7-d period of Se repletion resulted in significantly elevated maternal milk Se concentrations compared with a Se-deficient group, which was reflected in the pups by elevated plasma and hepatic Se concentrations and Se-dependent glutathione peroxidase (SeGPx) activities. Pulmonary glutathione concentration and SeGPx activity in pups were affected by oxygen exposure only, not by Se nutrition. Therefore, early postnatal Se repletion can protect the developing lung from oxygen-induced injury, a protection that is not entirely due to the effects of Se on pulmonary SeGPx activity and glutathione concentration.

Tracheal collapse in a Holstein heifer

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Efficacy of ivermectin chewable tablets and two new ivermectin tablet formulations against Dirofilaria immitis larvae in dogs

One hundred four heartworm-free Beagles less than 1 year old were studied to determine the efficacy of ivermectin chewable tablets and of 2 other ivermectin tablet formulations against heartworm larvae. At 30 days after SC inoculation of dogs with infective Dirofilaria immitis larvae, all ivermectin formulations were given orally at dosage of 6 micrograms/kg of body weight. The ivermectin chewable tablets also were given orally at dosage of 2 and 6 micrograms/kg at 30 and 45 days, respectively, after injection of larvae. Replicates of 6 or 8 dogs in each study were formed on the basis of gender and body weight and, within replicates, were randomly allocated to treatment groups. At 30 days after injection of larvae, the additional dogs (in replicates of 8) were assigned to the control group and to the group given ivermectin chewable tablets at dosage of 6 micrograms/kg. All dogs were housed individually. Necropsy was performed approximately 5 or 6 months after larvae were administered. In both trials, all control dogs had heartworms at necropsy (University of Illinois--geometric mean, 35.0; Florida--geometric mean, 26.1). In both trials, the ivermectin chewable tablet (6 micrograms/kg) and both tablet formulations (6 micrograms/kg) given at 30 days after larval injection, and the chewable formulation (6 micrograms/kg) given at 45 days after larval injection were 100% effective (P less than 0.01) in preventing development of induced infection with D immitis.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of selenium nutrition in the development of neonatal rat lung

Our study was designed to assess the role of selenium (Se) in development of neonatal lungs under conditions of normoxia and hyperoxia. Thirty-six female Sprague Dawley rats were bred and fed a Se-deficient (0.03 ppm Se) or a Se-adequate (0.5 ppm Se) diet during pregnancy and lactation. At d 2 postpartum, 24 litters were randomly assigned to either high oxygen (greater than 95%) or air and were cross-fostered for 4 d. Lung weight was significantly enhanced in Se-adequate pups and was not related to high oxygen or air exposure of either the pups or dams. Two types of histologic lesions were observed in the lungs of the pups: septal attenuation and interstitial inflammation. When reared in oxygen, all (17 of 17) Se-deficient pups had lesions. In contrast, only 60% (9 of 15) of Se-adequate pups were affected (p less than 0.01). Lung lesions also were more severe in Se-deficient pups. Se-deficient pups also displayed a significant degree of septal attenuation when reared in air. Se-dependent glutathione peroxidase activity in the pup lung was significantly elevated in response to hyperoxia and was unrelated to Se nutriture. No differences in activities of lung superoxide dismutase, catalase, and glutathione s-transferase were noted between Se-deficient and Se-adequate pups reared in air or high oxygen environments. These data indicate that Se has an important role in the development of neonatal lungs, a role that is even more pronounced during conditions of hyperoxia. The protective role of Se in developing lung tissue cannot be completely explained by enhanced glutathione peroxidase activity.

Ethanol consumption and DMBA-induced mammary carcinogenesis in rats

In this study, we report that chronic ethanol intake at 20% of calories can enhance the initiation stage and at 15% of calories can enhance the promotion stage of 7,12-dimethylbenz[a]anthracene (DMBA)-induced mammary tumorigenesis in female Sprague-Dawley rats. Ethanol consumption at 20% of calories by female rats from 25 to 53 days of age was associated with a significant increase in terminal end bud (TEB) structures and a significant decrease in alveolar bud structures of the normal mammary gland. In addition to changes in mammary gland morphology, ethanol consumption at 20% of calories also was associated with a significant increase in incorporation of [3H]thymidine into mammary DNA and a significant increase in the DNA-labeling index of mammary TEB. Therefore, specific ethanol intakes can enhance DMBA-induced mammary tumorigenesis. The enhancement of the initiation stage partly may be explained by alterations in the structural development of the normal rat mammary gland that increase susceptibility to chemically induced mammary tumorigenesis.

Enhancement of pancreatic and hepatic glutathione levels in rats during cyanohydroxybutene intoxication

1-Cyano-2-hydroxy-3-butene (CHB), a cruciferous plant product, is hepatotoxic, pancreatotoxic, and elevates glutathione (GSH) in liver and pancreas. Whether GSH elevation is preceded by a depletion related to toxic insult, or whether toxicity and GSH elevation are unrelated, is not known. To evaluate the temporal relationship between toxicity and GSH levels, male Fisher 344 rats (6/group) were given CHB (200 mg/kg po) and killed up to 96 hr after dosing. At death, histological and ultrastructural evaluations and GSH/GSSG determinations were performed on liver and pancreas. In pancreas, dilatation of the cisternae of the rough endoplasmic reticulum (RER) was evident from 2 hr, becoming progressively more severe 4 and 6 hr after CHB. Frank apoptosis and loss of zymogen granules was evident by 6 hr, becoming widespread by 12 hr. Recovery had commenced by 72 hr, and 50% of treated rats had normal pancreata by 96 hr. No hepatic lesions were observed at this dose. Pancreatic GSH was depressed below 20% at 2 and 4 hr, rose to a maximum of 540% by 12 hr, and remained elevated in treated rats throughout the study (275% at 96 hr). Hepatic GSH only fell to 50%, rose to 150-180%, and returned to normal by 96 hr. While this pattern of depletion and rebound following exposure to hepatotoxins is common, the exaggerated and persistent elevation of pancreatic GSH is unprecedented.

The relationship of vehicle to target organ toxicology induced by the naturally occurring nitrile 1-cyano-2-hydroxy-3-butene

The effects of gavage vehicle on the acute toxicity of the naturally occurring nitrile 1-cyano-2-hydroxy-3-butene (CHB) were investigated by oral administration of 200 mg/kg body wt/day CHB to male CDF (F-344/Crl BR) rats for 2 days. The vehicles studied here were distilled water, 5% aqueous Tween 20, and corn oil. Liver, kidney, and pancreas were examined histologically and the differences in lesion incidence and severity were assessed. The effects of gavage vehicle on nitrile-induced elevations of daily urinary thiocyanate excretion and tissue glutathione concentrations were also assessed. The pancreatotoxicity of CHB was present regardless of vehicle and consisted of apoptosis of pancreatic acinar cells, infiltration of pancreatic lobules by macrophages, and acinar atrophy and disorganization. CHB in water alone was associated with the least pancreatotoxic effect, whereas the aqueous Tween vehicle was associated with more severe CHB-induced pancreatic lesions. CHB-induced elevations of tissue nonprotein thiol and glutathione concentrations occurred in all treatment groups, but the values were elevated significantly less in the pancreata of CHB/Tween-treated rats than in those of rats given CHB in water or corn oil. By contrast, the greatest elevation in daily urinary thiocyanate excretion occurred in rats given CHB in aqueous Tween, indicating increased biotransformation of CHB to cyanide when Tween 20 was used as a vehicle. These results illustrate the difficulty of identifying suitable vehicles for administration of lipophilic compounds in toxicology studies.

Comparative toxicities of the naturally occurring nitrile 1-cyano-3,4-epithiobutane and the synthetic nitrile n-valeronitrile in rats: differences in target organs, metabolism and toxic mechanisms

Toxic but sublethal oral doses of 125 mg/kg (1.1 mmol/kg) of the cruciferous nitrile, 1-cyano-3,4-epithiobutane (CEB), or 175 mg/kg (2.1 mmol/kg) of its synthetic saturated analogue, n-valeronitrile (VN), were given by gavage to male CDF (F-344/CrlBr) rats once daily for 1, 2 or 3 days, in order to compare target tissues and to observe structure-activity relationships between the nitriles. CEB-induced changes included degeneration and necrosis of the pars recta of the renal proximal tubules, ulceration and necrosis in the forestomach, a mild increase (4.5-fold) in daily urinary thiocyanate (SCN-) excretion (only in rats treated for 3 days) and 1.5- to 2.4-fold increases in hepatic and pancreatic non-protein thiol (RSH) concentrations (in all CEB-treated groups). In VN-treated rats, there were no consistent histological changes but 95- to 170-fold increases in daily urinary SCN- excretion, delayed clinical signs of cyanide toxicity and minimal effects on tissue RSH concentrations. These results indicate different toxic mechanisms for VN and CEB. The nephrotoxic effects of CEB were very similar to those of 1-cyano-2-hydroxy-3,4-epithiobutane, suggesting a role for the epithio group in the nephrotoxicity of these nitriles. The relatively low SCN- excretion in CEB-treated rats also suggested that cyanide played only a minimal role in CEB toxicity, while the high SCN- excretion, clinical signs of cyanide poisoning and lack of histological changes imply a greater role for metabolically-derived cyanide in VN toxicity. The enhancement of tissue RSH by CEB treatment with indications of enhanced tissue glutathione concentrations suggested the involvement of glutathione in the detoxication of CEB and/or its reactive metabolites.

Selective pancreato-toxicity in the rat induced by the naturally occurring plant nitrile 1-cyano-2-hydroxy-3-butene

The acute toxicity of 1-cyano-2-hydroxy-3-butene (CHB), a nitrile derived from many cruciferous plants, was investigated. Young male CDF (F-344/CrlBr) rats were treated by gavage once daily with 200 mg (2.1 mmol) CHB/kg body weight for 0-4 days and killed 24 hr after the final dose. Lesions were confined to the exocrine pancreas and characterized by individual acinar cell death, inflammation and acinar atrophy and disorganization. Ultrastructural alterations included dilation of cisternae of the acinar cell endoplasmic reticulum, acinar cell death resembling apoptosis, macrophage phagocytosis of acinar cell debris and regenerative changes in remaining acinar cells. Pancreatic, hepatic and renal non-protein thiol concentrations were elevated, suggesting an enhancement of tissue glutathione concentrations and an alteration in glutathione metabolism. Urinary thiocyanate (SCN-) excretion was modestly elevated, indicating some in vivo cyanide release from this nitrile. The results of this study indicate that CHB is a selective pancreatotoxin, inducing changes consistent with apoptosis. CHB is also a possible inducer of tissue glutathione in the liver and kidneys as well as in the pancreas, even at toxic doses.