Histopathological studies on the toxicity of ochratoxin A in rats. I. Acute oral toxicity

Traumatic spinal cord lesions in children are infrequent (2 to 5 per cent of all cases admitted to specialised paraplegic centres depending on whether the upper age limit is set at 10 or 15 years). Traffic accidents are responsible for at least 50 per cent of the lesions; playground accidents and various sports add another 35 per cent. A large proportion of the accidents have been found to be related to the child's normal desire for adventure and exploration. The segment most frequently involved in our own series of 18 cases was the cervical and upper thoracic spine. Histopathological studies have shown that splitting of the cartilaginous end-plate in the growth zone of the vertebrae is a common finding. Radiological signs of spinal trauma are less evident than in adults; they may be totally missing. Precise neurological assessment must rely on repeated examination and close clinical observation, especially in the comatous child with a head injury. Spinal cord involvement must be suspected and the child treated as a paraplegic until definite proof of a normal neurological status is available. Due to a highly labile water electrolyte balance in the early post-traumatic stage and considerable fluctuations in plasma volume and temperature regulation, permanent monitoring of the cardiovascular function, body temperature and diuresis is mandatory. In children below the age of 10, deep vein thrombosis and embolism are exceptional (sepsis creates a high-risk situation requiring anticoagulation). In the initial treatment of spinal injury only conservative measures should be considered; there are no indications for laminectomy, nor for spinal fusion. In the tetraplegic child below the age of 6, skull-traction should be avoided and immobilisation of the cervical segment achieved by bilateral padded head-rests.     

Acute oral toxicity of microcystin-LR, a cyanobacterial hepatotoxin, in mice

Microcystin-LR (MCLR) is a hepatotoxic peptide produced by Microcystis aeruginosa, an alga found worldwide in reservoirs for drinking supply; however, acute oral toxicity of purified MCLR remains unknown. Therefore, a single dose of MCLR (more than 95% purity) ranging from 8.0 to 20.0 mg/kg body weight was orally given to female 6-week old BALB/c mice, and lethality and pathological changes were observed. Median lethal dose (LD50) of the orally given MCLR estimated by the up and down method was 10.9 mg/kg, which was 167 times higher than the i.p. LD50 value (65.4 microgram/kg by moving average method). Orally administrated toxin caused primarily hepatocellular injuries with characteristics of hemorrhage and necrosis. In situ end-labeling as well as electron microscopic observation revealed an induction of apoptotic cell death to hepatocytes. These results indicate the lethality of MCLR was much lower in oral dosage than by i.p. administration, but toxic effects are similar. In addition, apoptosis is considered one of major components in MCLR-induced hepatotoxicity.     

Evaluation of the potential carcinogenicity and genetic toxicity to humans of the herbicide acetochlor

Comprehensive toxicological studies of the herbicide acetochlor are presented and discussed. Although it gave a negative profile of responses in the many toxicity tests conducted there were some findings that prompted further investigation. First, although non-mutagenic in the Salmonella assay, acetochlor was clastogenic to mammalian cells treated in vitro. This clastogenic potential was not expressed in vivo in four rodent cytogenetic assays (bone marrow and germ cells). Second, although acetochlor gave a negative response in rat liver UDS assays when tested at the acute MTD, gavage administration of a single, supra-MTD dose (2000 mg/kg) gave a weak positive assay response. This dose-level (2000 mg/kg) was necrotic to the liver, depressed hepatic glutathione levels by up to approximately 80%, altered the metabolism of acetochlor, and was associated with up to 33% lethality. In contrast, reference liver genotoxins such as DMN, DMH and 2AAF were shown to elicit UDS in the absence of such effects, and at approximately 400 x lower dose-levels. Finally, microscopic nasal polypoid adenomas were induced in the rat when acetochlor was administered for two years at the maximum tolerated dose (MTD). The tumours were not life-threatening, they did not metastasize, and no DNA damage was induced in the nasal cells of rats maintained on a diet containing the MTD of acetochlor for either 1 or 18 weeks (comet assay). In order to probe the mechanism of action of these high dose toxicities a series of chemical and genetic toxicity studies was conducted on acetochlor and a range of structural analogues. These revealed the chloroacetyl substructure to be the clastogenic species in vitro. Although relatively inert, this substituent is preferentially reactive to sulphydryl groupings, most evidently, to glutathione (GSH). Similar chemical reactivity and clastogenicity in vitro was observed for two related chemicals bearing a chloroacetyl group, both of which have been defined as non-carcinogens in studies reported by the US.NTP. These collective observations indicate that the source of the clastogenicity of acetochlor in vitro is also the source of its rapid detoxification in the rat in vivo, via reaction with GSH. Metabolic studies of acetochlor are described which reveal the formation of a series of GSH-associated biliary metabolites in the rat that were not produced in the mouse. The metabolism of acetochlor in the rat changes with increasing dose-levels, probably because of depletion of hepatic GSH. It is most likely that a rat-specific metabolite is responsible for the rat nasal tumours observed uniquely at elevated dose-levels. The absence of genetic toxicity to the nasal epithelium of rats exposed acutely or subchronically to acetochlor favours a non-genotoxic mechanism for the induction of these adenomas. The observation of a time- and dose-related increase in S-phase cells in the nasal epithelium is consistent with this conclusion. Despite some confusion caused by the early use of perilethal gavage administrations of acetochlor to rodents, and supra-MTD dietary concentrations in some of the chronic studies, the available MTD data are consistent with acetochlor not posing a genetic or carcinogenic hazard to humans.     

Twenty-six-week oral toxicity study of benzalazine in rats

A 26-week toxicity study by oral gavage administration was performed in Sprague-Dawley rats with benzalazine (2-hydroxy-5-[(4-carboxyphenyl) azo] benzoic acid, CAS 64896-26-0), a new agent for the treatment of ulcerative colitis and Crohn's disease of the large intestine, as a part of a safety evaluation program. Dosages of 0 (control), 300, 900 and 2700 mg/kg b.w./d were selected for this study. Except slight changes in the urinary status (decreased pH value and increased specific gravity) from 900 mg/kg b.w./d p.o. onwards, which were probably substance related, no further intolerance reactions were observed. The urine had a dark-yellow colour which was probably an indication of metabolites of benzalazine or benzalazine itself which were excreted via the urine. Behaviour, external appearance, body weight gain, food and water consumption, haematology, clinical biochemistry, organ weight analysis, macroscopic and microscopic examinations revealed no substance-related influence. Therefore, on the basis of the results obtained, it is concluded that the non-toxic dose level in this study is considered to be 300 mg benzalazine/kg b.w./d p.o. following daily administration for 26 weeks.     

Acute toxicity of ethylene glycol mono-n-butyl ether in the guinea pig

Acute toxicity values, such as oral and percutaneous LD50s, are often used as the basis for classifying chemicals into toxicity categories, and their subsequent regulation. Such values obtained for ethylene glycol mono-n-butyl ether (EGBE; 2-butoxyethanol) in rats and rabbits indicate that it is moderately toxic. However, the cause of death in these acute studies appeared to be secondary to acute intravascular haemolysis, an effect for which guinea pigs and humans are much less sensitive than rats, mice and rabbits. Recently-conducted acute toxicity studies in the guinea pig resulted in an acute oral LD50 of 1400 mg/kg, an acute percutaneous LD50 of greater than 2000 mg/kg, and a 1-hr LC50 greater than 633 ppm. These data are compared with published acute toxicity values, and indicate that the predicted acute toxicity of EGBE in humans, based on data from the guinea pig, would be less than that observed in other animal species. Based in part on the guinea pig data, EBGE is no longer classified as a poisonous substance by either the United Nations or US Department of Transportation.     

Acute mucocutaneous toxicity following high-dose hydroxyurea

Three patients with advanced acute myeloid leukemia were treated with oral high-dose hydroxyurea at a dose of 10 g daily for 8-10 days. Severe acute stomatitis developed in all three patients. In addition, two of the patients developed a peculiar acute cutaneous type of toxicity associated with soreness, violet erythema, and edema of the palms and foot soles followed by intense universal hyperpigmentation of the skin. Apparently, the pronounced acute mucocutaneous toxicity was caused by the sustained high daily dose of hydroxyurea, indicating that myelosuppression may not be the dose-limiting toxicity of this drug.     

Lack of developmental and reproductive toxicity of 2,3,3'',4, 4''-pentachlorobiphenyl (PCB 105) in ring-necked pheasants

BACKGROUND/AIMS: The number connection tests A and B are regarded as sensitive psychometric measures for the assessment of early hepatic encephalopathy. Review of the studies dealing with the diagnostic sensitivity of the number connection tests, however, shows that the scoring of the number connection tests results differs between studies. Most groups define the limits of the normal range by studying small control groups. Others use scores given in the literature without ensuring the comparability of the test versions used. Thus, there is a need for normative data for the number connection test results and for re-evaluation of the sensitivity of the tests using valid scores. METHODS: In this study the number connection tests A and B were administered to 249 healthy volunteers (age: 18 to 76 years) to analyze the influence of age, education and occupation on their results. In addition, the age-corrected normative data were applied to 169 patients with grade 0-I hepatic encephalopathy. The specificity and sensitivity of age-corrected and age-independent normative data of the number connection tests were compared. RESULTS: There was a significant influence of age and education on the number connection test results, but only a negligible effect of occupation. Application of the age-corrected normative data to the test results of the patients with grade I hepatic encephalopathy significantly decreased the sensitivity of the number connection tests for hepatic encephalopathy compared to widely used age-independent normal ranges, but also increased the specificity. CONCLUSION: The use of standardized versions of the number connection tests and age-related normative data is recommended.     

Acute toxicity and pharmacokinetics of dibekacin mice

The LD50 values of dibekacin to mice were determined following three different methods of administration, namely, intravenous constant infusion, intravenous bolus injection, and intramuscular injection. The serum levels of dibekacin were pharmacokinetically analyzed. The differences in LD50 values between the methods of administration were discussed from the viewpoints of pharmacokinetics. 1) The LD50 value following the intravenous constant infusion was higher than that following the intravenous bolus injection and approached the level of that following the intramuscular injection, when the infusion rate of the drug was decreased by increasing the infusion period. 2) The biological half-life of dibekacin in mice was 24--45 min. 3) The volume of distribution increased as its dose increased, and a linear correlation was noted between log Vd and log (dose). 4) The difference among the maximum serum concentrations calculated with dibekacin following the administration of LD50 was small, which coincided with the results of the experiment that the serum concentrations of dibekacin at the death following the administration of LD100 were almost the same regardless of the method of administration.     

Localization of NADPH-d positive cells in the thymus of pheasants and mice

In this case report we discribe clinic, pathology and diagnostic of an avian reovirus-infection in pheasants. The disease was observed 1993 in a flock of game-pheasants in the western part of Turkey. Of a live-stock of 100 animals, 27 were affected most of them being three to five months old. Beside a general disorder, sick pheasants showed signs of shortness of breath as well as greenish, watery diarrhoea and died within a week. The pathologic findings were dominated by an extreme hepatopathia. In addition a fibrinous tracheitis, a catarrhal inflammation of the gut and a perihepatitis fibrinosa could be observed. From organs of affected pheasants a pathogen could be isolated, which was characterized anti-genetically, by physico-chemical properties an by electronmicroscopy as avian reovirus.     

Acute cyanide toxicity caused by apricot kernel ingestion

A 41-year-old woman ingested apricot kernels purchased at a health food store and became weak and dyspneic within 20 minutes. The patient was comatose and hypothermic on presentation but responded promptly to antidotal therapy for cyanide poisoning. She was later treated with a continuous thiosulfate infusion for persistent metabolic acidosis. This is the first reported case of cyanide toxicity from apricot kernel ingestion in the United States since 1979.     

Acute cardiovascular toxicity of thallium (I) ions

The paper deals with: 1. the protein concentration in the perilymph (PL), the serum and the cerebrospinal fluid (CSF), 2. the protein pattern in the PL and 3. histological findings in the middle and inner ear in unilaterally ear-infected guinea pigs. The studies were performed 6 h to 21 days post infectionem (Fig. 1). The pathological changes in the middle ear, which, in most cases, were limited to the infected ear, were initially evaluated under the operating microscope and divided into 4 stages. The analytical and histological results were presented as functions of these stages. As the inflammation intensity increased, the protein concentration in the PL of the infected ears increased to a level exceeding that of the normal value more than ten times (Fig. 2). However, in the serum and in the CSF this concentration remained unchanged. Likewise, no significant protein increase in the PL of the contralateral ears was detectable in most cases. As the inflammation intensity increased, the number of the precipitation lines detectable immunoelectrophoretically increased in the PL of the infected ears (Fig. 3). An increase in the alpha1- and gamma-globulins and a decrease in Albumin was found by electrophoresis on cellulose acetate strips (Tab. 3). The histological findings correlated with initially established inflammatory stages of the middle ear mucous membrane (Tab. 4). As the inflammation intensity increased, the round window, too, was changed pathologically, so that in some cases of purulent otitis media middle ear secretion could enter the cochlea. The protein increase in the PL immediately after the infection is probably due to an increase in the blood vessel permeability in the inner ear.     

Acute pulmonary toxicity of urban particulate matter and ozone

We have investigated the acute lung toxicity of urban particulate matter in interaction with ozone. Rats were exposed for 4 hours to clean air, ozone (0.8 ppm), the urban dust EHC-93 (5 mg/m3 or 50 mg/m3), or ozone in combination with urban dust. The animals were returned to clean air for 32 hours and then injected (intraperitoneally) with [3H]thymidine to label proliferating cells and killed after 90 minutes. The lungs were fixed by inflation, embedded in glycol methacrylate, and processed for light microscopy autoradiography. Cell labeling was low in bronchioles (0.14 +/- 0.04%) and parenchyma (0.13 +/- 0.02%) of air control animals. Inhalation of EHC-93 alone did not induce cell labeling. Ozone alone increased (P < 0.05) cell labeling (bronchioles, 0.42 +/- 0.16%; parenchyma, 0.57 +/- 0.21%), in line with an acute reparative cell proliferation. The effects of ozone were clearly potentiated by co-exposure with either the low (3.31 +/- 0.31%; 0.99 +/- 0.18%) or the high (4.45 +/- 0.51%; 1.47 +/- 0.18%) concentrations of urban dust (ozone X EHC-93, P < 0.05). Cellular changes were most notable in the epithelia of terminal bronchioles and alveolar ducts and did not distribute to the distal parenchyma. Enhanced DNA synthesis indicates that particulate matter from ambient air can exacerbate epithelial lesions in the lungs. This may extend beyond air pollutant interactions, such as to effects of inhaled particles in the lungs of compromised individuals.     

Subacute (4-wk) oral toxicity of a combination of four nephrotoxins in rats: comparison with the toxicity of the individual compounds

In a 4-wk study, 10-wk-old Wistar rats were fed the nephrotoxins hexachloro-1,3-butadiene (HCBD), mercuric chloride, d-limonene and lysinoalanine either alone or in combination. These nephrotoxins damage epithelial cells of the proximal tubules, but by different mechanisms. Each chemical was given alone at a Minimum-Nephrotoxic-Effect Level (MNEL), and at a No-Nephrotoxic-Effect Level (NNEL). The combination was given at the MNEL, the NNEL and one-quarter of the NNEL of the individual chemicals. The individual nephrotoxins caused slight growth depression in males at the MNEL, but not at the NNEL, whereas the combination depressed growth slightly at the NNEL and severely at the MNEL. In females at the MNEL, only HCBD retarded growth; in contrast to the effect in males this was not aggravated by combined treatment. Nephrotoxicity was more severe in males fed the combination than in males given the nephrotoxins alone. The former showed decreased renal concentrating ability and moderate histopathological changes in the kidneys at the MNEL, and a dose-dependent increase in kidney weight and number of epithelial cells in the urine at the NNEL and the MNEL. The males treated with a single agent showed slightly increased kidney weights, and/or slight histopathological changes in the kidneys at the MNEL, and (with d-limonene only) epithelial cells in the urine at the NNEL and MNEL. In females, renal changes induced by the combination were not more severe than those observed with individual compounds. No adverse changes attributable to treatment were observed in rats fed the combination at one-quarter of the NNEL. In the present study, combined exposure to four nephrotoxins at their individual NNEL did not constitute an obviously increased hazard, indicating absence of synergistic interaction, whereas at the MNEL clearly enhanced (renal) toxicity occurred in males, although not in females.     

A 13-week subacute oral toxicity study of pectin digests in rats

A 13-week subacute oral toxicity study of pectin digests was performed in both sexes of F344 rats. Water containing 0, 0.15, 0.5, 1.5 or 5% pectin digests was fed to 10 males and 10 females per group to detect its toxicity. No animals died during the administration period. Body weight gain was suppressed in male of the 5% group compared with the 0% group. Serum biochemistry analysis revealed a significant increase in BUN in male group treated with 5% and increases in CRN in male group treated with 1.5% or more. The weight of liver was significantly increased in female groups treated with 1.5% or more. Histopathologically, no treatment-related damage was observed in any dosed groups. Based on these results, the NOEL of pectin digests for both sexes in F344 rats was considered to be 0.5% in drinking water (male 545, female 657 mg/kg/day).     

Levels of the herbicide glyphosate in well water

The prognostic significance of tumour cell proliferation was investigated in a series of 418 gastric carcinomas using the monoclonal antibody MIB-1. Owing to strong intratumoural heterogeneity of MIB-1 expression three different proliferation indices (PIs) were determined in all carcinomas: (1) PImax in areas of maximal tumour cell proliferation, (2) PIrand in areas randomly distributed over the whole tumour. (3) PIfront in areas exclusively located at the tumour invasion front. There was a strong intertumoral heterogeneity with PImax ranging from 4.9% to 92.2%, PIrand ranging from 3.4% to 81.4% and PIfront ranging from 4.2% to 87.1%. The mean values were 51.3% +/- 19.7 for PImax, 34.2% +/- 18.3 for PIrand and 37.2% +/- 19.5 for PIfront. Whereas no statistically significant correlation could be found between proliferative activity and the clinicopathological parameters depth of invasion, lymph node involvement or grade of tumour differentiation, there was a positive correlation between a high proliferation index at the tumour invasion front (PIfront) and the presence of blood or lymphatic vessel invasion. No significant correlation could be demonstrated between the different proliferation indices and survival, even when different subgroups of patients were analysed separately. The present results suggest that the immunohistochemical evaluation of the proliferation activity has no predictive value for the prognosis of gastric cancer patients or the identification of subgroups of patients who may be at higher risk.