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The acute and subacute toxicity of five biogenic amines-tyramine, spermidine, spermine, putrescine and cadaverine-were examined in Wistar rats. Tyramine and cadaverine had a low acute oral toxicity of more than 2000 mg/kg body weight. Putrescine had an acute oral toxicity of 2000 mg/kg body weight and spermidine and spermine each of 600 mg/kg body weight. All amines investigated caused a dose-related decrease in blood pressure after intravenous administration, except for tyramine, where an increase was found. In 6-wk studies the biogenic amines were administered in the diet to groups of 10 male and 10 female rats. Tyramine and cadaverine were given at levels of 0, 200, 2000 or 10,000 ppm, spermine and putrescine at levels of 0, 200, 2000 or 5000 ppm and spermidine at levels of 0, 20, 200 or 500/1000 ppm in the first study and at levels of 0 or 10,000 ppm in a second study. Spermine was the most toxic. The high dose level showed a great number of changes, such as emaciation, aggressiveness, convulsions and paralysis of the hind legs. Growth, food intake and water intake were considerably decreased. Slight anaemia (males) and changes in plasma clinical chemistry occurred. The relative weights of the thyroid, adrenals, spleen and heart were increased and that of the liver decreased. Impaired kidney function, together with renal histopathological changes and changes in plasma electrolytes and urea, occurred with spermine. Histopathological examinations also revealed decreased glycogen content in the liver, reduction of spermatogenesis, severe depletion of splenic white pulp, acute involution of the thymus and moderate myocardial degeneration in the heart. Myocardial degeneration was also seen in one mid-dose male. Adverse effects were also observed in the top dose groups of all other amines. Decreased body weights associated with diminished food intake were generally seen. Slight increases in packed cell volume, haemoglobin concentration and thrombocytes occurred with cadaverine. With spermidine, decreased plasma creatinine, calcium and inorganic phosphate were observed and decreased potassium levels with cadaverine. The no-observed-adverse-effect level was 2000 ppm (180 mg/kg body weight/day) for tyramine, cadaverine and putrescine, 1000 ppm (83 mg/kg body weight/day) for spermidine and 200 ppm (19 mg/kg body weight/day) for spermine.

Erythritol was orally administered to Wistar rats at dietary levels of 0, 5, and 10% for 4 weeks. Soft stools and diarrhea were observed in male and female animals of the 10% group and in female animals of the 5% group. These symptoms disappeared during the course of the study. Mean body weights of male rats in the high-dose group were significantly lower than those of controls during the course of the study. No such differences were observed in females. Small statistically significant changes in certain hematological, clinical chemistry, and urine parameters were noted in the high-dose group but were judged not to be biologically important. Weights of the cecum were increased relative to those of the controls. No treatment-related histological changes were observed. No ill effects, other than early diarrhea, were observed from erythritol levels at 5 or 10% in the diet. Based on these results, it was concluded that the feeding of erythritol at a dietary level of 10% did not result in toxicologically significant effects.

To identify possible hazards of combined exposure to chemicals with the same target organ, a 24-hr single dose experiment was carried out in which the renal toxicity of mercuric chloride, potassium dichromate, d-limonene and hexachloro-1:3-butadiene administered simultaneously was compared with the nephrotoxicity of the individual compounds, using a total of 11 groups each consisting of five 12-wk-old male Wistar rats. The dose levels used were based on the results of a range-finding study with the individual compounds in the same strain of rats kept under similar experimental conditions, and comprised the 'Minimum-Nephrotoxic-Effect Level' (MNEL) and the 'No-Nephrotoxic-Effect Level' (NNEL) of each of the four compounds alone and in combination. A group of vehicle-treated rats served as controls. At the MNEL of the combination, antagonism of effects was encountered, seen for example as less severely increased activity of gamma-glutamyl transferase in the urine. Synergism of effects was also observed, for example increased severity of renal tubular necrosis, and more markedly increased activity of urinary lysozyme, lactate dehydrogenase, alkaline phosphatase and N-acetyl-beta-glucosaminidase. More importantly, however, at the NNEL of the combination no signs of impaired renal function or renal damage were observed, suggesting absence of both dose additivity and potentiating interaction at the tested subeffective levels of the individual nephrotoxicants.

In a 4-wk oral toxicity study, 4-wk-old male and female Wistar rats were exposed to a combination of arbitrarily chosen chemicals comprising sodium metabisulphite, Mirex, Loperamide, metaldehyde, di-n-octyltin dichloride, stannous chloride, lysinoalanine and potassium nitrite. The dose levels used were based on the 'no-observed-adverse-effect level' (NOAEL) and the 'minimum-observed-adverse-effect level' (MOAEL) of the individual compounds obtained in similar studies with Wistar rats previously performed at TNO-CIVO, and comprised 0 (controls), 1/10 and 1/3 of the NOAEL, the NOAEL and the MOAEL. In comparison with the adverse effects of the individual compounds, both more severe and less severe adverse effects were observed at the MOAEL of the combined compounds, indicating interaction of effects at this exposure level. Slightly decreased haemoglobin content and slightly increased relative kidney weight were the only treatment-related adverse effects seen in the NOAEL group. In the 1/10 and 1/3 NOAEL groups no untoward effects were found that could be related to treatment. The present study clearly demonstrates absence of a simple additive effect, and provides some, but no convincing, evidence for an increased risk from exposure to a combination of chemicals when each chemical is administered at its own individual NOAEL. At lower dose levels no increased risk appears to exist. These generalizations may not be fully justifiable from a purely scientific point of view but are the most important practical lesson learnt from the present study. Chemicals/CAS: Pharmaceutical Preparations

The oral toxicity of gamma-cyclodextrin (gamma-CD) was examined in a 13-week feeding study in which four groups of four male and four female Beagle dogs received gamma-CD in the diet at concentrations of 0 (control), 5, 10, or 20%. No treatment-related changes were noted in behavior or appearance of the dogs and no mortalities occurred. Transient diarrhea occurred in some dogs of the 5 and 10% dose groups and in all dogs of the 20% dose group. However, all dogs remained in good health and gained weight. During the last 6 weeks of the study, the males of the 20% dose group gained less weight, but body weights were not significantly reduced in comparison to controls. Food intakes and food efficiencies were comparable among all groups. No treatment-related differences were observed with respect to ophthalmoscopic examinations, hematological parameters, clinicochemical analyses of the plasma, and semiquantitative urine analyses. Only the urinary pH was slightly below control levels in males of the 20% dose group. No abnormalities were seen at necropsy that could be attributed to treatment. The organ weight data revealed some cecal enlargement in the 10 and 20% dose groups. Relative ovary weights were significantly increased in the 10 and 20% groups but this was probably a result of an unusually low ovary weight in the controls. An increase of relative liver weights in males of the 10 and 20% dose groups also was considered to lack toxicological relevance because it was not associated with changes in plasma liver enzyme levels or histopathological changes. On microscopic examination, no treatment-related effects were observed in any of the various organs and tissues. In conclusion, transient diarrhea, cecal enlargement, and a slightly increased acidity of the urine were the only treatment-related effects reported. These changes are well-known physiological responses to the presence of increased amounts of undigested, fermentable carbohydrates in the lower gut. At the high applied intakes an incomplete digestion of gamma-CD and/or a partial inhibition of pancreatic amylase by gamma-CD could account for these effects. It is concluded that daily gamma-CD consumption of up to 20% in the diet (approximately 7.7 g/kg body wt in male and 8.3 g/kg body wt in female dogs) was tolerated without any toxic effects.

Erythritol is a sugar alcohol (polyol) with potential applications as a low-calorie, bulk sweetener. Ingested erythritol is efficiently absorbed and excreted unchanged via the urine since it is not metabolized systemically by the animal or human body. Erythritol was administered to four groups of 10 male and 10 female Swiss CD-1 mice and four groups of 15 male Wistar Crl:(WI) WU BR rats at dietary levels of 0, 5, 10, or 20% for 90 days. A fifth group of rats received a diet containing 20% erythritol on a time restricted basis (6 hr/day), and a sixth group received a diet containing 20% mannitol for comparison. There were no treatment related mortalities in either mice or rats. Soft stools and occasional diarrhea were observed in rats fed diets with 20% erythritol or mannitol but not in mice. Body weights were slightly yet significantly reduced in rats fed 20% erythritol or mannitol. and in male mice of the 20% dose group. Erythritol intake in the high dose group was approximately 12 g/kg body wt in rats and 44 and 45 g/kg body wt in male and female mice, respectively. Hematological and clinicochemical examinations of blood and plasma did not reveal any treatment related effects. Urine output increased with increasing erythritol dose. In male and female mice of the 20% erythritol group, the creatinine normalized urinary excretion of protein, K-glutamyltransferase (GGT), and electrolytes (Na+, K+, Ca2+, P(i), citrate) was significantly increased while urinary N-acetylglucosaminidase (NAG) remained unchanged. At the 10% level, significantly increased urinary protein (both sexes) and GGT (males only) excretion were seen. In rats, the creatinine-normalized urinary excretion of GGT, NAG, and some electrolytes (Na+, K+, and Ca2+) was increased in some erythritol groups but a clear dose-response relationship was evident only for calcium. On termination of the study, cecal enlargement was seen in rats of the 10 and 20% dose groups and in mice of the 20% dose group. Increased relative and absolute kidney weights were observed in both sexes of mice in the 20% erythritol group, in male mice of the 5 and 10% groups, and in rats of the 10 and 20% erythritol groups. Histopathological examination did not reveal any treatment-related abnormalities in either mice or rats. In conclusion, the ingestion of erythritol for 90 days at dietary levels of up to 20% did not produce signs of toxicity in mice or rats. In particular, the morphological integrity of the kidneys was not adversely affected by the treatment in either species. The increases in urinary excretion of protein, GGT, NAG, and electrolytes were considered to result from extensive osmotic diuresis and a potential overload of the renal excretory system at the high dose levels employed.

The potential toxicity and carcinogenicity of erythritol, a low-calorie sugar substitute, were examined in Wistar Crl:(WI) WU BR rats. Groups of 50 rats of each sex consumed diets with 0, 2, 5, or 10% erythritol, or 10% mannitol, for a period of 104-107 weeks. To each of these main groups, two satellite groups of 20 males each were attached for interim kills after 52 and 78 weeks of treatment. At start of the study, the rats were 5-6 weeks old. The average intakes of erythritol in the 2, 5, and 10% groups were 0.9, 2.2, and 4.6 g/kg body wt/day for males and 1.0, 2.6, and 5.4 g/kg body wt/day for females, respectively. Mannitol intakes were 4.4 and 5.2 g/kg body wt/day in males and females, respectively. All treatments were well tolerated without diarrhea or other side effects. Body weights were significantly below control levels during most of the study in males of the 5% erythritol group and in males and females of the 10% erythritol and 10% mannitol groups. Survival of the animals was not adversely affected by the treatments. Hematological and clinicochemical examinations did not reveal noticeable changes which could be attributed to treatment. Analysis of urine samples collected during five 48-hr periods, from rats of the satellite groups in Weeks 26, 42, 50, and 78 and from rats of the main groups in Week 102, showed that about 60% of ingested erythritol was excreted unchanged. The urine volumes increased with increasing dietary erythritol levels. In line with previous observations on other polyols, erythritol and mannitol ingestion led to an increased excretion of urinary calcium and citrate. The urinary excretions of sodium, potassium, phosphate, N-acetylglucosaminidase (NAG), gamma-glutamyltransferase (GGT), low-molecular-weight protein (LMP), and total protein (TP) were slightly elevated in the 10% erythritol group. Increased GGT and NAG excretions also were seen occasionally at the 5% dose. Significantly increased relative cecum weights were seen in rats of either sex in the 10% mannitol and, somewhat less pronounced, 10% erythritol groups. Some cecal enlargement also was seen in the 5% erythritol group. The relative weight of the kidneys was highest in the 10% erythritol group, the difference from controls reaching statistical significance at interim kills (males) and termination (females). Except for more frequent pelvic nephrocalcinosis in female rats of all erythritol dose groups, the histopathological examinations did not reveal any nonneoplastic, preneoplastic, or neoplastic changes that could be attributed to the ingestion of erythritol. In male and female rats of the 10% mannitol group, pelvic nephrocalcinosis, which in females was associated occasionally with pelvic hyperplasia, was the only remarkable finding. The incidence and progression of nephrosis, which is commonly seen in aging rats of this strain, were not influenced by the treatments. In the absence of morphological alterations in the kidneys or other signs of nephrotoxicity, the increased excretions of NAG, GGT, LMP, and TP are regarded as innocuous, functional sequelae of the renal elimination of erythritol. In conclusion, the toxicological profile of erythritol in rats resembles that of other polyols in several respects. Except for nephrocalcinosis, which is commonly seen in polyol-fed rats, no other treatment-related, morphological changes were observed in the kidneys. Evidence for a tumor-inducing or tumor-promoting effect of erythritol was not seen.

To compare the possible effects of microwave and conventional cooking on a range of common dietary components, mixed human diets containing beef, potatoes and vegetables were fed to groups of 10 male and 10 female Wistar rats for 13 wk. The diet ingredients were cooked by either of the methods in a normal and an abused manner, the latter consisting of the normal treatment followed by two cycles of reheating to approximately 85 degrees C and cooling. The cooked ingredients were freeze-dried, ground and mixed with supplements of vitamins and minerals to meet the rat requirements. An additional control group was fed a cereal-based rodent diet. Criteria to assess toxicity included clinical observations, ophthalmoscopy, growth, food and water intake, haematology, clinical chemistry, urinalysis, organ weights, micronucleated erythrocytes in bone marrow, gross examination at autopsy and microscopic examination of a wide range of organs. The results indicate no adverse effects of the diets cooked by microwave compared with those cooked conventionally.

Enzymatically depolymerized sodium carboxymethylcellulose (CMC-ENZ) is a new functional food ingredient which has a lower molecular weight and viscosity than regular sodium carboxymethylcellulose (CMC). Both compounds are known not to be absorbed to a significant extent, and the human safety of CMC as a thickening agent and stabilizer in food is well established. In the present study, the subchronic oral toxicity of CMC-ENZ was examined and compared with that of CMC in Wistar rats. Seven groups of 20 rats/sex were fed diets with 0 (controls), 2.5, 5 and 10% CMC and 2.5, 5 and 10% CMC-ENZ for a 3-month period. There was only one death that was unrelated to the treatment. Water intake, urine production and urinary sodium excretion increased with increasing doses of CMC and CMC-ENZ due to their sodium content of about 7-8%. The treatment-related occurrence of diarrhoea and caecal enlargement in the mid- and high-dose groups, a slight increase of plasma alkaline phosphatase, and increased urinary calcium and citrate excretions were considered to be generic effects that typically are observed in rodent studies with low digestible carbohydrates. The increased occurrence of nephrocalcinosis and hyperplasia of the urothelial epithelium in some of the treated groups was interpreted as an indirect consequence of a more alkaline urine coupled with an increased calcium excretion. As the frequency and severity of all these changes did not differ between corresponding CMC and CMC-ENZ dose groups, it is concluded that the two products have a similar toxicological profile.

Two acute (4 hr) and one subacute (4 wk) inhalation toxicity studies on germanium dioxide (purity > or = 99%, mean particle size 1.7-2.6 microns) were conducted in young adult Wistar rats. In the acute studies, exposure of two groups of five rats of each sex to maximum attainable concentrations of either 3.10 g amorphous or 1.42 g hexagonal germanium dioxide/m3 for 4 hr was not lethal. In the subacute study, four groups of five rats of each sex were exposed to 0, 16, 72 and 309 mg hexagonal germanium dioxide/m3 for 6 hr/day, 5 days/wk during 4 wk. Two additional groups of 5 rats per sex, exposed either to 0 or to 309 mg/m3, were kept for a 33-day post-exposure period. At the end of the treatment period, changes were observed only in rats of the high concentration group: these changes were decreased body weight gain (both sexes), decreases in haematocrit (females) and thrombocyte count (both sexes), and increases in neutrophil count (both sexes) and white blood cell count (females). On clinical chemistry evaluation, decreased fasting blood glucose (females), decreased total protein concentration (both sexes), increased plasma alanine aminotransferase and aspartate aminotransferase activities (females), increased plasma urea nitrogen (males) and increased plasma bilirubin level (females) were observed. In addition, urinary volume was elevated, and urine density and pH were lowered in both sexes. Relative weights of kidneys, spleen, heart and lungs were higher than in controls. Microscopic examination revealed effects on renal tubular epithelium. Effects on growth, kidneys, and liver were still present at the end of the 33-day recovery period. It was concluded that the 4-hr LC50 value of amorphous germanium dioxide was greater than 3.10 g/m3 and that of the hexagonal form greater than 1.42 g/m3. The no-adverse-effect-level in the 4-wk study using hexagonal germanium dioxide was 72 mg/m3.

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 lifetime (149-wk) oral carcinogenicity study of vinyl chloride monomer (VCM) was carried out. Four groups of Wistar rats were used, each consisting of 100 males and 100 females, except for the high-dose group, which comprised 50 males and 50 females. VCM was administered by incorporating polyvinyl chloride powder with a high content of VCM into the diet. The actual exposure levels of VCM were 0 (control), 0.014, 0.13 and 1.3 mg VCM/kg body weight/day. Detailed histopathological examination was restricted to the liver. In the final stage of the study, the mortality in the high-dose group was slightly higher than in controls. A variety of VCM-related liver lesions was found in the high-dose group. The lesions included increased incidences of liver-cell polymorphism, hepatic cysts, foci of cellular alteration, neoplastic nodules, hepatocellular carcinomas and angiosarcomas. Compared with controls, there were increased incidences of hepatic foci of cellular alteration in females of the mid-dose group and of basophilic foci of hepatocellular alteration in females of both the low- and mid-dose groups. There was no evidence that feeding of VCM affected the incidence of tumours in organs other than the liver. Thus, the present study showed that the feeding of VCM at a level of 1.3 mg/kg body weight/day can induce neoplastic and non-neoplastic changes in the livers of male as well as female rats. The feeding of 0.014 or 0.13 mg VCM/kg body weight/day may result in an increased incidence of (basophilic) foci of cellular alteration in the liver of female rats. It was concluded that 0.13 mg VCM/kg body weight/day is the no-observed-adverse-effect level with respect to the induction of tumours in rats.

Wistar rats were exposed to atmospheres containing 0 (control) or 5000 ppm vinyl chloride monomer (VCM), 7 h/day, 5 days/week, for a period of 52 weeks. After 4, 13, 26 and 52 weeks each time 10 rats/sex/group were killed and subjected to extensive examinations. The present paper deals with growth, mortality, haematology, clinical chemistry and organ weights. Slight growth retardation throughout the experimental period and high mortality in the second half of the study were observed in VCM-exposed animals. Some of the haematological parameters and biochemical blood parameters were slightly influenced by VCM after an experimental period of 52 weeks only. Blood clotting time was generally slightly shorter in VCM-exposed rats than in controls. There were minor indications of increased potassium contents of the blood serum in VCM-exposed animals during the first half of the test period. The kidneys were adversely affected by VCM as appeared from increased blood urea nitrogen levels and relative kidney weights. After 52 weeks increased weights of heart and spleen, and slight signs of anaemia were noticed in VCM-exposed rats. The present study did not produce obviously suitable parameters for early diagnosing 'VCM-disease' in man. Chemicals/CAS: vinyl chloride, 75-01-4; Vinyl Chloride, 75-01-4; Vinyl CompoundsChemicals/CAS: vinyl chloride, 75-01-4; Vinyl Chloride, 75-01-4; Vinyl Compounds

A lifespan oral toxicity of vinyl chloride monomer (VCM) was carried out in Wistar rats, using five groups each of 60-80 males and 60-80 females. VCM was administered by incorporating polyvinyl chloride (PVC) powder with a high VCM content into the diet or by gastric intubation of a 10% VCM solution in soya-bean oil. The VCM doses (actual exposures) were 0 (control), 1.7, 5.0 and 14.1 mg/kg body weight'day provided by diets containing PVC powder, and 300 mg/kg body weight given by stomach tube as a solution of VCM in oil on 5 days/wk. The death rate was higher in all VCM-treated groups than in the controls and increased with increasing VCM doses. The 14/1- and 300-mg/kg treatments were associated with shortened blood-clotting times, slightly increased ??-foetoprotein levels in the blood serum, liver enlargement and an increased haematopoietic activity in the spleen. A variety of neoplastic and non-neoplastic treatment-related liver lesions was found at each of the VCM levels. The changes varied from swollen and irregularly-shaped mitochondria in hepatocytes to hepatocellular carcinomas and hepatic angiosarcomas. The tumour response of the liver appeared to shift from a predominance of angiosarcomas at the highest dose level via a mixture of angiosarcomas and hepato-cellular tumours at the intermediate levels to the exclusive development of hepatocellular tumours at the lowest VCM level. Tumours attributable to VCM exposure and found at other sites included pulmonary angiosarcomas, extrahepatic abdominal angiosarcomas and tumours of the Zymbal glands; these neoplasms occurred at VCM levels of 5.0 mg/kg and above. In addition, there was some evidence that VCM exposure enhanced the development of abdominal mesotheliomas and of adenocarcinomas of the mammary glands. Thus, the present study showed that orally administered VCM is a carcinogen in rats, and that the 'no-observed-adverse-effect level' in rats was lower than 1.7 mg/kg body weight/day under the rigorous conditions of continuous oral VCM exposure resulting from the release of VCM from PVC powder present in the gastro-intestinal tract. Chemicals/CAS: polyvinylchloride, 9002-86-2; vinyl chloride, 75-01-4; Vinyl Chloride, 75-01-4; Vinyl Compounds

Thiodiethyleneglycol-bis-( β -aminocrotonate) (TDGAC) is the major component of certain stabilizers for polyvinyl chloride, which may be used in contact with food. A short-term toxicity study was conducted in young male and female rats, which were fed 0·0 (control), 0·2, 1·0 or 5·0% TDGAC in the diet for 13 wk. Growth and food intake were decreased, and the relative liver and kidney weights were increased at the 5% feeding level in both sexes. The thyroid weight was increased only in females at the 5% level. Haematological values, blood biochemistry and urine examinations were not affected at any dietary level of the test compound. Microscopic examination revealed no abnormality that could be related to the treatment, apart from an increase in the number of active follicles in the thyroid of females at the 5 level. This study established a no-effect level of 1% TDGAC in the diet of rats for 90 days.

Yeast grown on hydrocarbons according to the n-paraffin process of The British Petroleum Company Ltd. was fed to groups of male and female rats at dietary levels of 10, 20 and 30% for 1 yr. Two control diets were used, one being similar to the yeast diet but with soya-bean meal substituted for yeast and the other being the institute's stock diet. The inclusion of the yeast in the diet did not affect mortality, general condition or behaviour, gain in body weight, or food intake. Haematological values and blood biochemistry were not affected by the consumption of the yeast. There was no evidence of impaired kidney function or of changes in urine composition. No effects related to treatment were revealed by the weights of the principal organs nor by extensive gross and microscopie pathological examinations. This investigation indicates, therefore, that yeast grown on pure n-paraffins by the BP process does not induce any deleterious effects when fed to rats at dietary levels up to 30% for 1 yr.

The toxicity of sulphite was studied by feeding rats on diets containing 0–2% sodium metabisulphite (Na2S2O5) for periods up to 2 yr and over three generations. Undue losses of sulphite were reduced by storing the diets at −18°C prior to feeding. Thiamine deficiency due to destruction of this vitamin by sulphite was prevented by drastic enrichment of the diets with thiamine. During storage up to the time of consumption, the losses of sulphite from the diets containing Na2S2O5 at levels of 0·125, 0·25, 0·50, 1·0 and 2·0% averaged 22, 14, 12, 8 and 4·5%, respectively, while the decrease in thiamine was 2·7, 1·7, 8·3, 14·5 and 15·4%, respectively. The feeding of sulphite considerably decreased thiamine levels in the urine and liver, but the addition of 50 ppm thiamine to the diet prevented thiamine deficiency in rats at sulphite levels up to 2%. A level of 2% sulphite caused slight growth retardation in F1- and F2-generation rats both before and after weaning. Occult blood was present in the faeces in groups given 1% sulphite or more. Relative weights of the kidneys were increased by the 2% sulphite level in the F2-generation females only, but this increase was accompanied by neither functional nor histological changes. Pathological examination revealed hyperplastic changes in both the fore- and glandular stomach with levels of 1 and 2% sulphite in each of the three generations. Some slight alterations were found also with 0·5% in the stomach of the F2-generation rats. There was no indication that sulphite had any carcinogenic effect. In studies on high sulphite levels (0–8%) for 10–56 days, diets containing 6% sulphite caused considerable growth depression and reduced food intake and food efficiency. Anaemia occurred at 2% and above, while the leucocyte count was slightly increased at 6%. Splenomegaly accompanied by a pronounced splenic haematopoiesis occurred with levels of 4% and above. In the forestomach, hyperplastic changes were found with 1% sulphite or more, while ulcers and papillomatous elevations occurred with 6 and 8%. In the glandular stomach, hyperplastic glands, haemorrhagic erosions, necrosis and inflammatory changes were observed with 4, 6 and 8% sulphite. The effects of sulphite on growth, food intake, food efficiency, the blood picture, spleen and stomach pathology and the presence of blood in the faeces were reversible. The dietary level of sulphite showing no untoward effect in rats was 0·25 or 0·215% Na2S2O5 (equivalent to 72 mg SO2/kg body weight/day) taking the loss of sulphite from the diet into account.

Formaldehyde was administered in the drinking-water to groups of 70 male and 70 female Wistar rats for up to 24 months. Survivors of subgroups of ten rats/sex/group each were killed after 12 or 18 months. The mean formaldehyde doses administered were 0, 1.2, 15 or 82 mg/kg body weight/day for males, and 0, 1.8, 21 or 109 mg/kg/day for females. There were no adverse effects on general health, survival or haematological or clinical chemistry parameters. Body weight and food intake were decreased in the high-dose group. Liquid intake was decreased by 40% in the high-dose group in both sexes in comparison with the controls. There was a slight temporary increase in the density of urine, whereas there was a tendency towards lower urine production in the high-dose group. The relative kidney weights were increased in the high-dose females. Gross examination at autopsy revealed a raised and thickened limiting ridge of the forestomach in most high-dose rats. In addition, several rats in the high-dose group showed irregular mucosal thickenings in the fore- and/or glandular stomach. Treatment-related histopathological gastric changes seen in most of the animals of the high-dose group included papillary epithelial hyperplasia frequently accompanied by hyperkeratosis and focal ulceration in the forestomach and focal chronic atrophic gastritis, occasionally accompanied by ulceration and/or glandular hyperplasia, in the glandular stomach. A higher incidence and/or degree of renal papillary necrosis occurred in the high-dose rats. From this study it appeared that the 'no-observed-adverse-effect level' of formaldehyde was 15 and 21 mg/kg body weight/day for male and female rats, respectively. Oral administration of formaldehyde at doses of 82 and 109 mg/kg/day to male and female rats, respectively, caused severe damage to the gastric mucosa but did not result in gastric tumours or tumours at other sites. The study did not provide any evidence of carcinogenicity of formaldehyde after oral administration.

A subacute oral toxicity study of acetaldehyde and formaldehyde was carried out in rats. Groups of ten male and ten female 5-wk-old rats received one of the aldehydes in the drinking-water for a period of 4 wk, acetaldehyde being given at dose levels of 25, 125 and 675 mg/kg body weight/day and formaldehyde at dose levels of 5, 25 and 125 mg/kg body weight/day. A group of 20 males and 20 females served as controls and received unsupplemented drinking-water ad lib. An additional group of ten males and ten females was given unsupplemented drinking-water in an amount equal to the amount of liquid consumed by the group given the top dose of formaldehyde. Food and liquid intake were decreased in the groups on the top dose of both acetaldehyde and formaldehyde. Hyperkeratosis of the forestomach, observed only in the top-dose rats, was the only adverse effect of acetaldehyde detected. Effects of formaldehyde, also observed only in the top-dose group, were yellow discoloration of the fur, decreased protein and albumin levels in the blood plasma, thickening of the limiting ridge and hyperkeratosis in the forestomach, and focal gastritis in the glandular stomach. It was concluded that in this study the no-observed-adverse-effect levels of acetaldehyde and formaldehyde were 125 and 25 mg/kg body weight/day, respectively.

Five chemically modified starches, acetylated distarch phosphate, acetylated diamylopectin phosphate, starch acetate, hydroxypropyl distarch glycerol and phosphated distarch phosphate, were fed to rats at dietary levels of 0 (control), 5, 10 and 30% for 2 yr and at one level, 10%, over three generations. In the 2-yr study, no adverse effects were observed on mortality, food intake, haematology, blood biochemistry or urine composition. Each of the modified starches examined, except the phosphated distarch phosphate, slightly reduced body weights at the 30% level and caused distinct caecal enlargement at 10 and 30%, but the microscopic structure of the caecal wall was normal. In comparison with the controls, the males fed the 30% level of any of the modified starches showed a slightly increased degree and incidence of focal hyperplasia of the renal papillary and pelvic epithelium, accompanied by calcified patches in the underlying tissue. The studies did not provide any indication of carcinogenicity. The multigeneration study showed no effect on fertility, on lactation performance or on embryonic or pre-weaning mortality. Extensive microscopic examination of the F3b-generation rats failed to reveal any changes attributable to treatment. It was concluded that the feeding of each of the modified starches at dietary levels up to 30% for 2 yr and at a level of 10% over three generations did not result in any distinct effect of toxicological significance.

A subchronic oral toxicity study with potassium nitrite (KNO 2 ) was carried out in rats. Groups of ten male and ten female 6-wk-old rats received KNO 2 in the drinking-water (tap-water) at levels of 0, 100, 300, 1000 and 3000 mg/litre for a period of 13 wk. The potassium concentration in the nitrite solutions was equalized by adding potassium chloride (KCl) up to the potassium level of the 3000-mg KNO 2 /litre solution. An additional group of ten males and ten females received drinking-water supplemented with KCl only, at an amount resulting in a potassium concentration equivalent to that of the 3000-mg KNO 2 /litre solution. Body weight, food intake and food efficiency were decreased at 3000-mg/litre level in males, while liquid intake was decreased in males given 1000 and 3000 mg/litre and in females given 3000 mg/litre. There was a significant increase in the methaemoglobin concentration in animals given 3000 mg/litre, while slight decreases in red blood cell variables occurred at the 1000- and 3000-mg/litre dose. No impaired renal function was observed in any of the test groups, although the relative weight of the kidneys and the plasma urea nitrogen level was increased at 3000 mg/litre. There was a slight decrease in plasma alkaline phosphatase activity at 3000 mg/litre. A small amount of nitrite was present in the saliva of the rats receiving 3000 mg/litre but there was no evidence of increased mutagenic activity in the urine of these rats. Interestingly, hypertrophy of the adrenal zone glomerulosa was observed in all test groups, the incidence and degree being dose related. It was concluded that in the study reported here the no-effect level is lower than 100 mg KNO 2 /litre in the drinking-water, which is equivalent to a level lower than 10 mg KNO 2 /kg body weight/day.

A chronic feeding study was carried out in mice with two chemically modified potato starches, hydroxypropyl distarch phosphate (HP-starch) and starch acetate (AC-starch), and with lactose and sodium alginate. Each of the materials was fed to a group of 75 male and 75 female mice for 89 wk. The dietary level of the test products was gradually increased until the diets contained (by weight) 55% HP-starch, 55% AC-starch, 55% lactose or 25% alginate. The control diet contained 55% pregelatinized potato starch. Each of the four test materials caused increased water consumption, distinct caecal and colonic enlargement, a slightly increased incidence of intratubular nephrosis and, with the exception of AC-starch, also slightly lower body weights. An increased incidence of gastric trichobezoars was observed in mice fed either the modified starches or lactose. The occurrence of concrements in the renal pelvis along with slight urinary changes, such as increased amounts of amorphous material in the urine and increased urinary Ca content, in mice fed HP-starch, AC-starch or lactose was regarded as an effect of little, if any, toxicological significance. Alginate fed at 25% (w/w) of the diet was nephrotoxic to mice, as shown by extremely high water consumption, high urine production, urinary incontinence, high pH and low specific gravity of the urine, increased level of blood urea nitrogen, increased kidney weights, distension of the renal calyx and the high incidence of dilated distal tubules. Caecal and colonic enlargement and changes in urinalysis were found to be reversible and had completely or largely disappeared within 2-5 wk of the cessation of the treatment in wk 87. The incidence of intratubular calcinosis or of concrements in the pelvic space was not reduced during the recovery period. The study did not provide any evidence of carcinogenicity of the products tested.

Yeast grown on pure n-paraffins was fed at dietary levels of 10, 20 or 30% to groups of 30 male and 30 female rats in a 2-yr study and to groups of ten male and 20 female rats in a reproduction study over three generations. Each study included two control groups, one on feed similar to the yeast diets but with soya-bean meal substituted for the yeast, and the other on the Institute's stock diet. In the 2-yr study, the feeding of the yeast had no adverse effect on mortality, rate of body-weight gain, haematology, urine composition or kidney-function tests. The activities of glutamicoxalacetic transaminase and alkaline phosphatase in the serum of yeast-fed rats were relatively high but within the normal range. The feeding of the yeast did not affect the incidence or severity of histopathological changes nor the type and incidence of tumours. The multigeneration study revealed no effects on fertility, the number of young or the growth and mortality of the young during lactation. In a 90-day study on rats from the third generation, no changes attributable to yeast-feeding were apparent in any of the parameters investigated. It was concluded that the type of yeast examined did not exert a harmful effect in rats at dietary levels up to 30%.

Studies in rats on iocetamic acid show that the LD50 levels of this compound compare favorably with those of a number of other oral cholecystographic agents. Pathologic effects are not found in rats and cats in studies of the subacute toxicity. Incompatibility with an anesthetic or a tranquilizer is not found. The elimination pattern of iocetamic acid in rats and human subjects is different. In rats intestinal excretion is dominating; in human subjects 62% of the dose administered is eliminated in the urine within the first 48 hours. The proportion of iodine recovered from the bile collected in 9 postcholecystectomy patients with biliary fistulas within the first 14 hours after oral administration of iocetamic acid averages 32.3% of the amount of iodine administered; this is enough for good or excellent radiographic findings. No significant changes in the functions of kidney, liver, circulation, or bone marrow are observed in patients after oral administration of routine doses of iocetamic acid. Only the total bilirubin content of plasma increases signficantly within 14 hours; this is a common symptom in oral cholecystography which disappears within 1 week after the administration.

Rats were fed on diets containing 0·0 (control), 0·03, 0·10, 0·30 or 1·00% of various salts or oxides of tin for periods of either 4 or 13 wk. The criteria examined included mortality, body-weight change, diet utilization, measurements of blood, urine and biochemical parameters, organ weights and gross and micropathology. No adverse effects were noted with any levels of stannous sulphide or oleate or of stannous or stannic oxides. Severe growth retardation, decreased food efficiency, slight anaemia and slight histological changes in the liver were observed with 0·3% or more of stannous chloride, orthophosphate, sulphate, oxalate and tartrate. The findings showed a marked difference in toxicity within the range of compounds studied. The signs of anaemia induced by certain cationic tin compounds included distinctly depressed haemoglobin concentrations, slight decreases in red cell counts and haematocrit value and a decreased level of serum iron. Dietary supplements of iron had a markedly protective effect against tin-induced anaemia, whereas a decrease of dietary iron aggravated the condition. These data suggest that some tin compounds may inhibit haematopoiesis, possibly by interfering with the intestinal absorption of iron. The no-effect level of the active tin salts examined was 0·1%, or 22–33 mg tin/kg/day, in a diet containing a liberal amount of iron. The level may be lower on diets marginal in iron.

In order to study the effects of a reduced gain in body weight on organ weight/body weight ratios, a “non-toxic” growth retardation was induced by ad lib. feeding of rats on diets containing high levels of several crude fibre materials (raw potato starch, sawdust, oat-hull feed and cellulose) for 4 or 13 wk. The feeding of cellulose at levels of 45–70% turned out to be a suitable method for the induction of growth retardations ranging from 11 to 58%. Growth retardation had a marked effect on the relative weight of the brain (increased) and the testes (decreased after 4 wk, increased after 13 wk). The relative weights of other organs were only slightly, if at all, affected by retarded growth. It appears, therefore, that in cases of growth reduction, an increase in the relative weights of the liver or the kidneys must be considered to be an effect of the compound. As brain weight is known to be mainly a function of actual age and to alter little with changing body weights, whereas the weights of most of the other organs are more liable to change with body weight, the use of organ weight/brain weight ratios may lead to erroneous conclusions in cases of animals in which growth has been retarded.

A new oral cholecystographic medium called iocetamicacid was submitted to a toxicologic study in rats and dogs. Dosages, which were equivalent to 200 and 1000 mg of the compound per kilogram of body weight per day and were 5 times and 25 times the human routine dose, were administered daily for 3 weeks in order to establish whether the substance exerted an untoward influence on vital organs. In the male rats the thyroid was activated by both doses, but no thyroid activation was demonstrable in dogs. There were no indications of damage of the cells of the liver or kidney. The study showed that iocetamic acid had no special affinity for the kidneys. With the exception of the increased thyroid activity in male rats, no changes were found which could be ascribed to the administration of iocetamic acid.