[A six-month intraperitoneal repeated dose toxicity study of tazobactam/piperacillin and tazobactam in rats].

Tazobactam (TAZ) is a newly developed beta-lactamase inhibitor. Tazobactam/Piperacillin (TAZ/PIPC) is a formulation consisting of TAZ and PIPC in a ratio of 1:4. A six-month intraperitoneal repeated dose toxicity study of TAZ/PIPC and TAZ including a one-month recovery period were carried out using male and female rats. The doses were 200, 400 and 800 mg/kg/day for TAZ/PIPC, and 40, 80 and 160 mg/kg/day for TAZ. The results were as follows. 1. No test article-related deaths occurred during the study period. No effect on clinical finding of survival rats was evident. 2. There was no dose-related increases of food consumption in both the males and females given TAZ/PIPC and PIPC. Slight reductions in body weight gain occurred in males given 800 mg/kg/day of TAZ/PIPC. 3. Decreases in erythrocyte, hemoglobin and hematocrit, and increases in reticulocytes were seen only at study termination in the group given 800 mg/kg/day of TAZ/PIPC. Increases in reticulocytes were seen only at study termination in the females given 80 or 160 mg/kg/day of TAZ. 4. A decrease in triglyceride levels was observed in the males given 800 mg/kg/day of TAZ/PIPC or 160 mg/kg/day of TAZ. 5. The ophthalmoscopic examination or urinalysis show no test article-related changes. 6. Enlarged ceca in all groups of animals given TAZ/PIPC and in the females given 160 mg/kg/day of TAZ were observed. 7. An increase of relative organ weight in liver was noted in the males and females given 800 mg/kg/day of TAZ/PIPC, in the males given 80 or 160 mg/kg/day of TAZ and in the females given 160 mg/kg/day of TAZ. 8. In the hepatocytes, accumulation of PAS-positive materials which was identified histochemically and ultrastructurally as glycogen, was present in the males given 800 mg/kg/day of TAZ/PIPC and in the males given 80 or 160 mg/kg/day of TAZ. 9. After a one-month recovery period, the changes of liver had generally disappeared, suggesting that they were reversible. 10. From the histopathological changes of liver, the no-toxic dose level in both the males and females was 400 mg/kg/day and 40 mg/kg/day for TAZ/PIPC and TAZ, respectively.

A neurotoxicity assessment of high flash aromatic naphtha.

Catalytic reforming is a refining process that converts naphthenes to aromatics by dehydrogenation to make higher octane gasoline blending components. A portion of this wide-boiling range hydrocarbon stream can be separated by distillation and used for other purposes. One such application is a mixture of predominantly 9-carbon aromatic molecules (C9 Aromatics, primarily isomers of ethyltoluene and trimethylbenzene), which is removed and used as a solvent also known as High Flash Aromatic Naphtha (HFAN). A program was initiated to assess the toxicological properties of HFAN since there may be human exposure, especially in the workplace. The current study was conducted to assess the potential for neurotoxicity in the rat. Adult male Sprague-Dawley rats of approximately 300 grams body weight, in groups of twenty, were exposed by inhalation to HFAN for 90 days at concentrations of 0, 100, 500, and 1500 ppm. During this period the animals were tested monthly for motor activity and in a functional observation battery. After three months of exposure, for 6 hours/day, 5 days/week, 10 animals/group/sex were sacrificed and selected nervous system tissue was examined histopathologically. No signs of neurotoxicity were seen in any of the evaluated parameters, nor was there evidence of pathologic changes in any of the examined tissues.

Effect of lanthanum chloride on established atherosclerosis in the cholesterol-fed rabbit. Mitral valve as a site for assessment of treatment effects.

The ability of lanthanum chloride (LaCl3) to retard the progression of established atherosclerosis was investigated in cholesterol-fed rabbits. Rabbits were initially maintained on a high-fat plus cholesterol-supplemented diet for 10 weeks to induce lesions and were then changed to a low-fat diet or a low-fat diet supplemented with LaCl3 for an additional 24 weeks to permit their serum cholesterol levels to normalize. LaCl3 did not affect the rate at which serum cholesterol levels returned to normal. The dose of LaCl3 was approximately 30 mg/kg body weight/day. In comparison with controls, LaCl3-treated rabbits exhibited histologically less severe coronary artery and mitral valve atherosclerosis. Lesion severity in the carotid arteries was unaffected by LaCl3 treatment. Although statistically significant, the salutary effects of LaCl3 were relatively small. The data support the hypothesis that calcium antagonists can retard the progression of established atherosclerotic lesions. The data also illustrate the value of the mitral valve as a site to assess treatment effects on monocyte/macrophages in vivo.

Male reproductive assessment of the rubber accelerator N-oxydiethylene thiocarbamyl-N-oxydiethylene sulfenamide in rats.

The rubber accelerator N-oxydiethylene thiocarbamyl-N-oxydiethylene sulfenamide (OTOS) was evaluated to determine its potential to cause reproductive effects. No evidence of a compound-related effect on mating, fertility, gestation length, number of implants or live births, pup growth, and survival was observed using Sprague-Dawley rats. Furthermore, light and electron microscopy of the testes from the high-dose males failed to reveal any morphological changes compared to the controls. Groups of 12 male Sprague-Dawley rats were continuously administered diets containing 0, 60, 200, or 600 ppm OTOS for 12 weeks. Following 56 days of exposure, the males were subsequently cohoused nightly with two females for a maximum of 21 days. During this mating period, males continued to receive control and OTOS-containing diets; however, feeders were removed for nightly cohabitation. Although a 4 to 8% reduction in body weight was observed in the 600 ppm animals, statistical significance was reached only at the end of the first week of treatment. In the 60 and 200 ppm males body weights generally were slightly elevated compared to the control, with the 60 ppm body weights showing statistically significant differences during Weeks 5 to 7 of exposure.

Absence of hydrocarbon-induced nephropathy in rats exposed subchronically to volatile hydrocarbon mixtures pertinent to gasoline.

Ninety-day inhalation studies were conducted on 50:50 weight percent (wt %) mixtures of n-butane:n-pentane and isobutane:isopentane, respectively, and on a distillation cut boiling below 145 degrees F of a reference unleaded gasoline blend to assess the nephrotoxicity of these volatile mixtures. The mixtures of butanes and pentanes were selected because these four hydrocarbons are the most prevalent components of gasoline vapors encountered under typical occupational exposures. The 0-145 degrees F gasoline distillation fraction was tested because it reasonably approximates the composition of gasoline vapors measured under occupational settings. Male and female F-344 rats were exposed to 2 levels of each mixture, 6 hours per day, 5 days per week, for 13 weeks. The target concentrations for the butane:pentane mixtures were 4500 and 1000 parts per million (ppm), while 5200 and 1200 ppm were set for the gasoline distillation fraction. An interim sacrifice was conducted after 28 days. The rats were not significantly affected by the exposures, and there was no evidence of hydrocarbon-induced nephropathy in either sex at the termination of each study. However, at the 28-day interim sacrifice period for both butane:pentane mixtures, mild, transient treatment-related but not exposure-related kidney effects were observed in the male rats. These perturbations were absent at the interim sacrifice period for the gasoline distillation fraction.

Failure of carbon disulfide and levothyroxine to modify the cardiovascular response of rabbits to a high-cholesterol diet.

Exposure of rabbits for 12 weeks to 300 ppm carbon disulfide (CS2) for 6 h/day, 5 days/week, or to 25 mg/day of thiourea or 2% cholesterol in the diet, or to any combination thereof caused a significant reduction in the concentration of serum thyroxine (T4). The reduction of the concentration of serum T4 in rabbits by the treatments was completely offset by the inclusion of 0.1 mg/day of sodium levothyroxine in the diet. Ingestion of feed containing 2% cholesterol significantly increased the degree of atherosclerosis present in the aortic arch and significantly increased the oil red O positive lipid present in the heart and the aorta, with the aortic arch being the most severely affected. The response of the aorta and the heart to the 2% cholesterol diet was not significantly modified by concurrent exposure to CS2 by inhalation or by treatment with thiourea, a metabolite of CS2. We found no evidence that the development of cardiovascular lesions induced by a 2% cholesterol diet in rabbits was mediated by a mechanism involving a component of hypothyroidism.

Pulmonary changes resulting from subchronic exposure to cadmium chloride aerosol.

Fischer-344 rats were exposed to 0.0, 0.3, 1.0, or 2.0 mg Cd/m3 as CdCl2 aerosol for 6 h/d, 5 d/wk, for 62 exposure days. Exposure to 2.0 mg Cd/m3 resulted in rapid weight loss, and all of the animals died within the first 45 exposure days. As a group, female rats survived significantly longer than the males. Exposure to Cd resulted in dose-dependent increases in lung weight. The increased weight was the result of additional tissue mass rather than edema. Both connective-tissue components, elastin and collagen, were significantly increased in the 1.0-mg/m3 group when these components were expressed on the basis of dry weight. Dose-dependent changes at the terminal bronchioles consisted of hyperplasia and flattening of type II cells, inflammation, and the proliferation of fibroblasts. Exposure to Cd also resulted in the development of intralymphatic microgranulomas in the perivascular and peribronchiolar lymphoid tissues.

Hydrocarbon nephropathy in male rats: identification of the nephrotoxic components of unleaded gasoline.

Previous subchronic and/or chronic inhalation studies of unleaded gasoline and a variety of petroleum naphthas, solvents, and distillates have shown that these complex materials are capable of inducing a distinctive nephropathy which appears limited to male rats. Therefore a series of gavage screening studies using male F-344 rats was conducted on components of gasoline to more clearly identify the major contributors to this nephrotoxicity. The dosing regimen consisted of 20 doses administered once daily, 5 days per wk for 4 wk. Tested were 15 pure hydrocarbon compounds typically found in unleaded gasoline boiling range, 4 naphtha streams representative of those commonly used to blend gasolines and 3 distillation fractions covering the less volatile portions of gasoline. The results revealed that the alkane (paraffin) components were primarily responsible for the nephrotoxic activity seen in unleaded gasoline, with a positive structure-activity response relating the degree of alkane branching to the potency of the nephrotoxic response. In addition, the nephrotoxic activity observed with the naphtha streams and distillation fraction correlated well with the proportion of branched alkanes contained in each.

Kidney structural changes in rats following inhalation exposure to C10-C11 isoparaffinic solvent.

Kidney tissues from Fischer 344 rats exposed by inhalation to either 5.48, 1.83, or 0.0 g/m3 of C10-C11 isoparaffinic solvent vapor for 5, 20 and 40 days (6 h/day, 5 days/week), followed by a 4-week recovery period, were examined by light microscopy (LM) and electron microscopy (EM). At the LM level, an increased incidence of protein droplets was found in the cytoplasm of renal tubular epithelial cells of the exposed male rats relative to controls. Other renal changes observed by LM in the exposed male rats included foci of regenerative epithelium and tubular dilatation with intratubular protein occurring between the inner and outer stripe of the medulla. By EM, the protein droplets were electron dense, angular, crystalline-like structures which were surrounded by acid phosphatase positive reaction product corresponding to remnants of membrane-bound phagolysosomes. After 20 and 40 days of exposure there was focal loss of the brush border, with degeneration and sloughing of necrotic cells. Following a 4-week recovery period reversal of the exposure-related tubular changes was indicated by EM. The kidney changes observed in male rats following exposure to light hydrocarbons have not been observed in female rats or other species and may be unique to the male rat.

Carcinogenic and toxicologic effects of inhaled ethylene oxide and propylene oxide in F344 rats.

The chronic inhalation toxicity and carcinogenicity of ethylene oxide (EO) and propylene oxide (PO) were evaluated in a 2-year inhalation bioassay. Five groups of male weanling Fischer 344 rats, 80 per group, were exposed at 0 ppm (shared control; filtered air), 50 ppm EO, 100 ppm EO, 100 ppm PO, or 300 ppm PO (7 hr/day, 5 days/week) for 104 weeks. Body weights from rats exposed to EO and PO at all exposure concentrations were significantly reduced compared to controls. A statistically significant increase in mortality was observed in all groups of exposed rats compared to controls. Skeletal muscle atrophy in the absence of any sciatic nerve neuropathology was found in rats exposed at 100 ppm EO and 300 ppm PO. Statistically significant associations between EO exposure and an increased incidence of the following rat neoplasms were observed: mononuclear cell leukemia, peritoneal mesothelioma, and mixed cell brain glioma. Among rats exposed to PO there was a dose-dependent increase in the incidence of complex epithelial hyperplasia in the nasal passages, and two adenomas were detected in the nasal passages of rats exposed at 300 ppm PO. The incidence of adrenal pheochromocytomas was elevated in both PO exposure groups, but not in a dose-related manner. All rat groups were affected by an outbreak of Mycoplasma pulmonis infection which occurred about 16 months into the study. This infection alone and in combination with the epoxide exposures affected the survival of rats in this study, and influenced the development of the proliferative lesions in the nasal mucosa of the PO-exposed rats. No treatment-related changes in any clinical chemistry or urinalysis indices were detected. PO exposure did not increase the incidence of the three neoplasms associated with EO exposure; however, adrenal pheochromocytomas and proliferative lesions of the nasal cavity were increased in rats exposed to PO.

Neoplasms and pigmentation of thyroid glands in F344 rats exposed to 2,4-diaminoanisole sulfate, a hair dye component.

2,4-Diaminoanisole sulfate was fed at dietary levels of 0.12% (low dose) or 0.5% (high dose) to groups of 50 male and 50 female inbred F344 rats for 78 weeks. By 107 weeks after the initial exposure, 58% of the male rats and 42% of the female rats administered the high dose had thyroid neoplasms, whereas only 7--8% of the controls developed them. Follicular cell carcinomas were the primary type of neoplasm induced. None of the controls had these tumors. The carcinomas, which were papillary, cystic, or solid, were highly invasive but did not metastasize. A brown pigment was present as granules primarily in thyroid follicular cells in all exposed rats. The amount of pigment as determined by an image-analyzing computer revealed that the cross-sectional area occupied by the pigment granules and the optical density of the granules were dose related.

The effects in rats and guinea pigs from six months exposures to sulfuric acid mist, ozone, and their combination.

Rats and guinea pigs were exposed to 0.5 ppm ozone, 10 mg/m3 sulfuric acid mist, or their combination for 6 hrs/day, 5 days/week for six months. Exposure-related microscopic alterations were seen in the lungs of guinea pigs exposed to ozone alone or in combination with sulfuric acid mist. No other microscopic lesions were present in either rats or guinea pigs. No biologically meaningful synergistic effects were noted in animals exposed to the combination of ozone and sulfuric mist.

Respiratory tract lesions in guinea pigs exposed to sulfuric acid mist.

Guinea pigs were exposed inhalation chambers to 25 mg/m3 sulfuric acid mist 6 h/d for 2 d, and the acute respiratory effects were correlated by light and electron microscopy. This concentration of acid was selected since lower concentrations result in only slight effects while higher concentrations result in death. By light microscopy, the most prominent pulmonary lesion at 48 h was segmental alveolar hemorrhage and edema accompanied by proliferation of alveolar macrophages and type 2 pneumocytes. The segmental distribution of the pulmonary lesion was reaffirmed by scanning electron microscopy, while transmission electron microscopy showed injury to the distal airways and changes in the vascular endothelium.

Effects in rats and guinea pigs of six-month exposures to sulfuric acid mist, ozone, and their combination.

Rats and guinea pigs were exposed to 0.5 ppm O3, 10 mg/m3 sulfuric acid (H2SO4) mist, or their combination for 6 h/d, 5 d/wk for 6 mo. Microscopic alterations were seen in the lungs of guinea pigs exposed to O3 alone or in combination with H2SO4 mist. No other microscopic lesions were present in either rats or guinea pigs. No biologically meaningful synergistic effects were noted in animals exposed to the combination of O3 and H2SO4 mist.

Six month inhalation exposures of rats and guinea pigs to aluminum chlorhydrate.

Groups of rats and guinea pigs were exposed, by inhalation, to 0.25, 2.5, and 25 mg/m3 of aluminum chlorhydrate (ACH) for six months to study the effects of a common component of antiperspirants. Similar groups of animals of both species exposed to clean air served as controls. The ACH was generated as a particulate dust using a Wright dust feed mechanism. After six months of exposure, animals were sacrificed. Decreases in body weight were seen in rats exposed to 25 mg/m3 of ACH. Marked increases in lung weights and significant increases in lung to body weight ratios were seen in rats and guinea pigs exposed to 25 mg/m3 of ACH. The lungs of all rats and guinea pigs showed significant dose-related increases in aluminum accumulation when exposed to either 0.25, 2.5, or 25 mg/m3 of ACH. The lungs of all rats and guinea pigs exposed to either 2.5 or 25 mg/m3 of ACH contained exposure-related granulomatous reactions characterized by giant vacuoled macrophages containing basophilic material in association with eosinophilic cellular debris.

Effects in rats and guinea pigs of short-term exposures to sulfuric acid mist, ozone, and their combination.

Ozone and the oxides of sulfur are common environmental pollutants. The acute pulmonary lesions caused by ozone and sulfuric acid mist in rats and guinea pigs have been characterized. Rats are not affected by sulfuric acid mist in concentrations up to 100 mg/m3 except for reduced body weight at the higher doses. A true alveolitis develops in guinea pigs exposed to more than 20 mg/m3 sulfuric acid mist. The ozone lesion is primarily confined to the terminal bronchioles and proximal alveoli. In combination studies with up to 2 ppm ozone and up to 10 mg/m3 sulfuric acid mist, the pulmonary lesion and lung/body weight data were essentially the same as in exposure to ozone alone, and the number of statistically significant synergistic effects in rats and guinea pigs was about what one would expect to observe by chance alone.

Fibrous plaques in the aortas of adult female rhesus monkeys (Macaca mulatta).

Lesions in the abdominal aorta were found in 36 of 40 mature female rhesus monkeys given various oral contraceptive steroids and in 8 of 10 monkeys of a non-treated control group. The lesions consisted of proliferation of subendothelial smooth muscle cells and collagen, often with fragmentation of the internal elastic lamina, forming a plaque. These occurred also, in order of descending frequency, in thoracic aorta, aortic arch, femoral and iliac arteries, and the carotid and pulmonary arteries. They appear statistically unrelated to steroid treatment and lack correlation with body weight and blood cholesterol levels.

PIP: The effects of oral contraceptive (OC) steroids on fibrous plaques in the aorta were studied in 50 adult female rhesus monkeys. Mestranol with or without norethindrone was administered in 1 or 10 times the human dose cyclically for 7 menstrual cycles. Blood was obtained throughout the study for cholesterol determinations and the animals were sacrificed at the end of 7 cycles for gross and microscopic tissue examinations. 36 of 40 monkeys given OCs and 8 of 10 controls revealed lesions in the abdominal aorta. Proliferation of subendothelial smooth muscle cells and collagen, often with fragmentation of internal elastic lamina, forming a plaque, was revealed in the lesions. The lesions also occurred in descending frequency in thoracic aorta, aortic arch, femoral and iliac arteries and the carotid and pulmonary arteries. There was a tendency for serum cholesterol to increase with body weight but the lesions appeared to be unrelated to steroid treatment and appeared to lack correlation with body weight and cholesterol levels.