Methyl isobutyl ketone (MIBK) induction of alpha2u-globulin nephropathy in male, but not female rats.

Male F-344 rats were administered corn oil (vehicle control), d-limonene (positive control, 300mg/kg), or MIBK (1000mg/kg) and female F-344 rats corn oil (vehicle control) or MIBK for 10 consecutive days by oral gavage. Approximately 24h after the final dose the kidneys were excised and the left kidney prepared and evaluated for histological changes including protein (hyaline) droplet accumulation, immunohistochemical staining for alpha2u-globulin (alpha2u), and proliferating cell nuclear antigen (PCNA) to quantitate renal cell proliferation. The right kidney was prepared for quantitation of total protein and alpha2u using an ELISA. MIBK elicited an increase in protein droplets, accumulation of alpha2u, and renal cell proliferation in male, but not female rats, responses characteristic of alpha2u-mediated nephropathy. MIBK produced identical histopathological changes in the male rat kidney when compared to d-limonene, an acknowledged inducer of alpha2u-nephropathy except that the grade of severity tended to be slightly lower with MIBK. MIBK did not induce any effects in female rats. Therefore, renal histopathology, along with the other measures of alpha2u accumulation, provides additional weight of evidence to support the inclusion of MIBK in the category of chemicals exerting renal effects through a alpha2u-nephropathy-mediated mode-of-action.

Cytotoxic and oncogenic activities of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)-ethane and metabolites to mouse embryo cells in culture.

The cytotoxic and oncogenic activities of 1,1,1-trichloro-2,2-bis(p-chlorophenyl)ethane (DDT), and its metabolites 1,1-dichloro-2,2-bis(p-chlorophenyl)ethane (DDD), 1,1-dichloro-2,2-bis(p-chlorophenyl)ethylene (DDE), and bis(p-chlorophenyl)acetic acid, were studies at various equimolar concentrations in an in vitro mouse embryo cell culture system that was malignantly transformable. DDD was the most active compound in producing transformation, whereas DDT and DDE showed slight activity. However, none of the transformed foci had the typical malignantly transformed morphology produced by 7,12-dimethylben[a]anthracene and did not produce tumors when inoculated into syngeneic mice.

Metabolism of the pancreatic carcinogen N-nitroso-bis(2-oxopropyl)amine after oral and intraperitoneal administration to Syrian golden hamsters.

The levels of N-nitroso-bis(2-oxopropyl)amine (BOP) and its metabolites in the urine, blood, bile, and pancreatic juice were compared after ip and oral administration of BOP to Syrian golden hamsters to explain the differing organotropic tumor spectra resulting from treatment by these two routes. The levels of BOP and its metabolites N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP) and N-nitroso-bis(2-hydroxypropyl)amine in the urine, blood, bile, and pancreatic juice were generally less after oral administration than after ip administration. The results suggested that HPOP may be a proximate pancreatic carcinogen in hamsters administered BOP, inasmuch as it was the major metabolite in the blood and pancreatic juice after ip administration. However, the results did not indicate a mechanism for the increased incidence of bile duct tumors that after oral administration of BOP.

Metabolism of the pancreatic carcinogens N-nitroso-bis(2-oxopropyl)amine and N-nitroso-bis(2-hydroxypropyl)amine in the Syrian hamster.

Metabolisms of the potent pancreatic carcinogens N-nitroso-bis(2-oxopropyl)amine (BOP) and N-nitroso-bis(2-hydroxypropyl)amine (BHP) were studied in male Syrian hamsters. BHP and a new metabolite, N-nitroso-(2-hydroxypropyl)(2-oxopropyl)amine (HPOP), were detected in the urine of hamsters administered BOP and BHP. The rates of HPOP formation from BOP and BHP were determined by the measurement of blood and urine levels at various times after each compound was administered: HPOP was formed readily from BOP, but slowly from BHP. This may explain the different organotropic spectra and carcinogenic potencies of BOP and BHP.

Metabolism and mutagenicity of N-nitroso-2-methoxy-2,6-dimethylmorpholine in hamsters.

N-Nitroso-2-methoxy-2,6-dimethylmorpholine (MeNDMM) was derived from the cyclic form of N-nitroso-(2-hydroxypropyl)(2-oxopropyl)amine (HPOP), a proposed proximate pancreatic carcinogen for the hamster. MeNDMM was metabolized in vivo by noninbred Syrian golden hamsters to HPOP, which was excreted in urine. In vitro metabolism produced HPOP by cytochrome P450-mediated oxidative demethylation. MeNDMM and HPOP were similarly mutagenic in the Ames Salmonella typhimurium assay, in which hamster liver preparations were used for metabolic activation. MeNDMM, due to its metabolism to HPOP, is probably also a pancreatic carcinogen in the hamster.

Carcinogenicity of N-nitrosobis(2-hydroxypropyl)amine and N-nitrosobis(2-oxopropyl)amine in MRC rats.

Weekly sc injections of equitoxic doses of N-nitrosobis(2-hydroxypropyl)amine (BHP) and N-nitrosobis(2-oxopropyl)amine (BOP) to Wister-derived MRC rats induced tumors. The incidence, latency, multiplicity, morphologic type, and distribution of these tumors varied according to the compound given. The esophagus was the main target organ for BHP (100%), followed by the respiratory tract (87%), pharynx (80%), colon and liver (each 73%), kidneys (20%), thyroid gland (20%), and urinary bladder and urethra (each 7%). BOP was ineffective in the esophagus and pharynx but induced a higher incidence of tumors in the kidneys (27%), thyroid gland (60%), urinary bladder (33%), and urethra (73%) and fewer neoplasms in the respiratory tract (20%), colon (67%), and liver (53%). In addition, BOP caused a few, apparently primary, prostate squamous cell carcinomas. The results are compared with results of BHP treatment in Sprague-Dawley rats and with results of BHP and BOP treatment in Syrian golden hamsters.

Metabolism of three radiolabeled pancreatic carcinogenic nitrosamines in hamsters and rats.

The in vivo metabolism and disposition of three radiolabeled N-nitrosamines which are carcinogenic for the pancreas of the hamster but not the rat have been examined. N-[1-14C]Nitrosobis(2-oxopropyl)amine (BOP), N-[1-14C]nitrosobis(2-hydroxypropyl)amine (BHP), and their suggested proximate pancreatic carcinogenic metabolite N-[1-14C]nitroso-(2-hydroxypropyl)(2-oxopropyl)amine (HPOP) were metabolized and exhaled as 14CO2 to various extents somewhat proportional to their carcinogenic potency. More than 50% of the dose of BOP and HPOP was exhaled as 14CO2, whereas 26% of BHP was excreted this way, and 40% of BHP was excreted unchanged in the urine. Administered BOP was excreted to a small extent in the urine of both species as HPOP and BHP. No other nitrosamine metabolites were detected in urine. HPOP and BHP were detected in the pancreatic juice and bile of both species after administration of BOP and BHP. The results suggest that pancreatic ductular carcinogenesis in the hamster as a result of exposure to BOP is not due to secretion of carcinogenic metabolities in the pancreatic juice or reflux of bile containing nitrosamine metabolites into the ducts. Carcinogen metabolic activation appears to be by an oxidative pathway.

N-nitroso-bis(2-acetoxypropyl)amine as a further pancreatic carcinogen in Syrian golden hamsters.

N-Nitroso-bis(2-acetoxypropyl)amine, a possible beta metabolite of N-nitroso-di-n-propylamine, was shown to be a potent carcinogen in the Syrian golden hamster. After a single s.c. treatment, the pancreas was the most affected organ, followed by the liver, respiratory tract, and kidneys. However, repeated application resulted in a higher incidence of neoplasms of the respiratory tract than of the pancreas and kidneys. The effect of N-nitroso-bis(2-acetoxypropyl)amine on toxicity, target tissues, and carcinogenicity was similar to that of N-nitroso-bis(2-hydroxypropyl)amine. The assumption that these two compounds may have similar metabolic pathways was confirmed; N-nitroso-bis(2-acetoxypropyl)amine was readily deesterified to N-nitroso-bis(2-hydroxypropyl)amine in vivo and in vitro.

Mutagenic activities of oxidized derivatives of N-nitrosodipropylamine in the liver cell-mediated and Salmonella typhimurium assays.

The mutagenic activity of N-nitrosobis(2-oxopropyl)amine (BOP), N-nitroso(2-hydroxypropyl) (2-oxopropyl)amine (HPOP), N-nitrosobis(2-hydroxypropyl)amine (BHP), N-nitrosomethyl-2-oxopropylamine (MOP), and N-nitrosomethyl-2-hydroxypropylamine (MHP) was examined in the Ames liquid incubation assay, using hamster liver homogenate for metabolic activation, and in the hamster liver cell-mediated V79 cell assay. At similar concentrations, the cell-mediated assay showed a greater mutagenic response over background to these nitrosamines than did the bacterial assay. Also, the relative mutagenic potency in the cell-mediated assay (MOP > MHP > BOP > HPOP > BHP) correlated better than that in the Ames assay (HPOP > MHP greater than or equal to BOP = BHP = MOP) with overall carcinogenic potency in the hamster (MOP > BOP > HPOP > BHP). The liver cell-mediated assay may be an important adjunct to the battery of short-term tests for carcinogenicity prescreening.

Carcinogenicity of N-nitrosomethyl(2-oxopropyl)amine in Syrian hamsters.

7-Methylguanine was found in hydrolysates of liver and pancreas DNA from Syrian golden hamsters given a single dose of N-[1-14C]nitrosobis(2-oxopropyl)amine (BOP). This led us to examine the carcinogenicity of a potential methylating metabolite of BOP, N-nitrosomethyl(2-oxopropyl)amine (MOP). MOP was found to be a potent pancreatic carcinogen by either single or weekly s.c. injections. A single MOP treatment (25 mg/kg body weight) induced ductular adenomas and/or adenocarcinomas in 80% of the hamsters. A higher incidence of these neoplasms was found in 93% and 87% of animals receiving, respectively, 3.5 and 1.75 mg MOP per kg body weight weekly for life. However, the lower dose (0.87 mg/kg body weight) was less effective, resulting in a 33% tumor incidence. Compared with the known potent pancreatic carcinogen BOP, MOP seemed to have a greater affinity for the pancreas since considerably lower doses were required to induce similar incidences of equivalent pancreatic tumors. Like BOP, MOP caused tumors of the liver (7 to 100% incidence), kidneys (7 to 80% incidence), and vascular system (7 to 27% incidence). However, in contrast to BOP, which was noncarcinogenic to the upper respiratory tract, MOP-treated animals developed a high incidence of nasal cavity tumors (40% after a single treatment and 27 to 100% after weekly injections). The mutagenesis studies using hamster liver cell-mediated V79 cells confirmed the stronger effect of MOP compared to BOP. The assumption that MOP might be a proximate carcinogenic metabolite of BOP could not be substantiated by our methods for determining the in vivo and in vitro metabolites of BOP.

Carcinogenic effect of N-nitroso(2-hydroxypropyl)(2-oxopropyl)amine, a postulated proximate pancreatic carcinogen in Syrian hamsters.

N-Nitroso(2-hydroxypropyl)(2-oxopropyl)amine (HPOP) proved to be a potent carcinogen in Syrian golden hamsters. The compound is an in vivo metabolite of N-nitrosobis(2-hydroxypropyl)amine, N-nitrosobis(2-oxopropyl)amine (BOP), and N-nitroso-2,6-dimethylmorpholine and a postulated proximate pancreatic carcinogen in hamsters. As with BOP, HPOP induced a higher incidence of pancreatic ductular adenocarcinomas than did N-nitrosobis(2-hydroxypropyl)amine and N-nitroso-2,6-dimethylmorpholine, and these neoplasms showed a great tendency for invasion and metastasis. Also, HPOP induced tumors of the forestomach, liver, gallbladder, kidneys, and vagina (as did BOP). However, HPOP [unlike BOP, but like N-nitrosobis(2-hydroxypropyl)amine and N-nitroso-2,6-dimethylmorpholine] led to tumor development in the nasal cavity, larynx, trachea, intestine, Harderian gland, lips, and flank organ. The possible mechanisms of HPOP carcinogenicity are discussed.

The effect of mediastinal irradiation on cardiac function of patients treated during childhood and adolescence for Hodgkin's disease.

To determine the frequency of cardiac dysfunction in patients treated during childhood or adolescence with mediastinal irradiation for Hodgkin's disease (HD), 28 patients underwent cardiac evaluation 19 to 182 months (median, 90 months) after the completion of radiation therapy. No patient had symptoms of cardiac disease. All were normotensive. All patients had a normal cardiothoracic ratio. There were no abnormalities of voltage or rhythm in the ECGs. The left ventricular end diastolic volume was increased in 19.2% of patients, none of whom had evidence of impaired left ventricular function. The left ventricular ejection fraction (LVEF) was increased in 15.3% of patients. No patient had a decreased LVEF. Pericardial thickening was demonstrated on echocardiograms from 12 of 28 patients (42.9%). Thickening was more frequent among those patients observed for 72 or more months (47.1%; eight of 17) than among those with shorter periods of follow-up (36.4%; four of 11). This study demonstrates that cardiac dysfunction is an infrequent sequela of mediastinal irradiation following treatment using an equally weighted, anterior-posterior technique. Longitudinal study of these patients will be necessary to determine the clinical significance and evolution of the occult pericardial thickening that was identified.

Clinical experience of scoring criteria for Familial Hypercholesterolaemia (FH) genetic testing in Wales.

BACKGROUND/OBJECTIVE: Familial Hypercholesterolaemia (FH) is caused by mutations in genes of the Low Density Lipoprotein (LDL) receptor pathway. A definitive diagnosis of FH can be made by the demonstration of a pathogenic mutation. The Wales FH service has developed scoring criteria to guide selection of patients for DNA testing, for those referred to clinics with hypercholesterolaemia. The criteria are based on a modification of the Dutch Lipid Clinic scoring criteria and utilise a combination of lipid values, physical signs, personal and family history of premature cardiovascular disease. They are intended to provide clinical guidance and enable resources to be targeted in a cost effective manner. METHODS: 623 patients who presented to lipid clinics across Wales had DNA testing following application of these criteria. RESULTS: The proportion of patients with a pathogenic mutation ranged from 4% in those scoring 5 or less up to 85% in those scoring 15 or more. LDL-cholesterol was the strongest discriminatory factor. Scores gained from physical signs, family history, coronary heart disease, and triglycerides also showed a gradient in mutation pick-up rate according to the score. CONCLUSION: These criteria provide a useful tool to guide selection of patients for DNA testing when applied by health professionals who have clinical experience of FH.

Rapid elimination of quinidine in pediatric patients.

The oral absorption and elimination of quinidine in pediatric patients was studied. Single oral doses of quinidine sulfate were administered to 13 patients ranging in age from 4 to 22 years of age. Serum quinidine concentration reached a peak within 30 minutes to two hours after drug administration. The serum half-life of quinidine varied from 2.5 to 6.7 hours and was, on the average, shorter than the reported estimates for adult volunteers and cardiac patients (means ranging from 4.9 to 7.3 hours). Hence more frequent dosing or the use of slow-release preparations may be necessary in some pediatric patients in order to avoid excessive fluctuation in serum drug concentrations over a dosage interval. The oral dose clearance of quinidine (ie, oral dose divided by the area under the serum concentration time curve) varied over a threefold range, from 0.151 to 0.570 liter/hr/kg, and was found to correlate inversely with age (r = .80). In comparison with mean clearance estimates that have been reported for normal adult volunteers (0.293 +/- 0.078 liter/hr/kg), children less than 12 years of age (0.461 +/- 0.117 liter/hr/kg) were found to have significantly higher clearances, whereas no difference was observed between older children (0.287 +/- 0.101 liter/hr/kg) and adults. Inasmuch as the average steady-state serum drug concentration for a given daily maintenance dose is directly related to clearance rate, children less than 12 years of age may require a higher dosage of quinidine on a per kilogram of body weight basis. Proper selection of quinidine dosage, careful adjustment of dosage according to age, and regular monitoring of drug response and serum drug concentration are essential steps to a rational management of quinidine therapy in children.

Two-dimensional echocardiographic recognition of the right aortic arch.

A mirror-image right aortic arch (RAA) is frequently associated with congenital heart disease. The chest roentgenogram with or without contrast remains the noninvasive diagnostic method of choice. While 2-dimensional (2-D) echocardiography has been used to elucidate the left aortic arch (LAA), detailed description of the technique for RAA has not been reported. This study was pursued to delineate the 2-D echocardiographic approach to the patient with RAA. Twenty-seven patients in this study had LAA (Group A) and 27 had RAA (Group B). The 2-D echocardiographic examinations concentrated on the standard suprasternal long-axis (SSNL), parasternal long and short axes, and the subcostal abdominal short-axis views. When the SSNL failed to demonstrate LAA, an alternate position for RAA was utilized. The SSNL correctly identified the LAA in all Group A patients, but in Group B it located only the ascending aorta. This simulated an interrupted aortic arch anomaly. Transducer realignment to position 2 confirmed RAA in all Group B patients. In the parasternal axes, the left descending aorta was detected posterior to the atrioventricular groove or the left ventricle in every Group A patient but in no Group B patient. The descending aorta was found to the left of the spine on the abdominal short-axis view in both groups. The 2-D echocardiographic technique proposed for RAA is simple, rapid, and definitive. It should be pursued whenever LAA cannot be demonstrated, especially in children suspected of having a congenital heart defect. Anticipation of RAA can expedite chest and cardiovascular surgery.

A further pancreatic carcinogen in Syrian golden hamsters: N-nitroso-bis(2-acetoxypropyl)amine.

Weekly subcutaneous injection of N-nitroso-bis(2-acetoxypropyl)amine (BAP) for 20 weeks to Syrian golden hamsters induced pancreatic neoplasms in 50% of the animals, as early as 15 weeks from the start of treatment. The carcinogenic potency and organotropic spectrum of BAP were similar to those of N-nitroso-bis(2-hydroxypropyl)amine (BHP). Metabolism studies indicated that BAP was readily converted in vivo to BHP and that BHP was also the major urinary metabolite.

Methylation of hamster DNA by the carcinogen N-nitroso-bis (2-oxopropyl)amine.

The alkylation of hamster liver, lung and pancreas DNA by [1-14C]- and [2,3-14C]N-nitrosobis (2-oxopropyl) amine (BOP) has been examined. The specific activity of pancreas DNA after [2,3-14C]BOP administration was only 2% of that when [1-14C]BOP was given. 7-Methylguanine, but not O-6-methylguanine, was found in hydrolysates of liver and pancreas DNA. Nearly equal amount of alkylation were produced in the liver when [1-14C]- and [2,3-14C]BOP were given. At least one-half of the radioactivity in the liver was associated with N-alkylated purines, whereas only 20% was in this form in the pancreas.

The Williams syndrome: evidence for possible autosomal dominant inheritance.

We recently evaluated a mother and son with the Williams syndrome. Documentation of the clinical phenotype in two generations of this family suggests that some cases of the Williams syndrome are autosomal dominantly inherited. Recognition of the heritable nature of the Williams syndrome should prompt careful clinical evaluation of other at-risk relatives in order to provide accurate recurrence risk counseling.

Long-term results after excision of fixed subaortic stenosis.

Forty-nine patients underwent surgical excision of fixed subaortic stenosis (discrete fibrous ring and tunnel) between 1968 and 1984 and were followed up for 1 to 16 years (5.8 +/- 4). Twenty-six patients (Group I) had isolated subaortic stenosis and 23 (Group II) had subaortic stenosis and associated cardiac defects. Discrete fibrous ring was present in 46 and tunnel type of obstruction in three patients. For the discrete ring, excision alone was done in 32 patients (four recurrences) and excision with myotomy in 17 (three recurrences). In Group I, there were no operative deaths and one late death from a noncardiac cause. In Group II, one early and two late deaths occurred. The actuarial survival rate for 10 years is 88%. Reoperations were performed in 10 patients, seven for recurrence and three for aortic valve replacement for preexisting aortic regurgitation that had progressed since the primary operation. Cardioplegia was used in 28 patients (one recurrence) and was not used in 21 patients (six recurrences). An operative residual gradient of less than 15 mm Hg was achieved in 25 of 28 patients in whom cardioplegia was used compared to 12 of 21 patients in whom cardioplegia was not used (p = 0.017). These results indicate that complete excision of the ring with the aid of cardioplegia has significantly reduced the recurrence rate of subaortic stenosis (p = 0.033), elimination of the residual gradient at the initial operation has been a significant factor in reducing the recurrence rate (p = 0.017), and addition of myotomy in this series has not altered the outcome.

Closed transventricular pulmonary valvotomy in infants.

In an effort to reassess the efficacy of closed transventricular valvotomy in infants with severe pulmonary stenosis, we reviewed 24 consecutive patients who underwent closed transventricular valvotomy. The age range was 1 day to 11 months (median 53 days), with 10 patients under 1 month and 21 under 6 months of age. The weight range was 2.6 to 9.4 kg (median 4.1 kg). The long-term results were assessed by comparing the postoperative to the preoperative clinical and hemodynamic data. The 20 survivors were followed up for 3 to 133 months (median 54 months). All were asymptomatic upon the last follow-up visit, and their electrocardiograms and chest x-ray films were normal or improved. In 12 patients who had cardiac catheterization 7 to 85 months (median 50 months) after operation, the range for the right ventricular-to-left ventricular, or systemic arterial, peak systolic pressure ratio (RV:LV) was 0.97 to 1.7 preoperatively (mean 1.31) and 0.22 to 0.94 postoperatively (mean 0.42) (p less than 0.001). In order to assess the significance of the RV size for the surgical survival, we measured the preoperative RV end-diastolic volume (RVEDV) in 17 patients. Twelve patients had a normal or enlarged RV and all survived the operation, whereas two of the five patients with an RVEDV more than 2 SD below the normal mean (RVEDV less than 23 ml/m2) died postoperatively (p = 0.075). We conclude that closed transventricular valvotomy can be done successfully in infants with severe pulmonary stenosis and an RV which is not small. The risk of cardiopulmonary bypass is avoided and good long-term results can be obtained. We also present evidence that a small RV (RVEDV less than 23 ml/m2) is a potentially important predictor of the surgical risk.