Hydrogen peroxide decomposition in the oral cavity.

PURPOSE: To determine the clearance of hydrogen peroxide from the oral cavity of infants (3-4 yrs of age), juveniles (7-12 yrs of age), adults (35-66 yrs of age), and adults with impaired salivary flow (34-71 yrs of age). MATERIALS AND METHODS: In all subjects, the amount of H2O2 present in the oral cavity was assessed following a 1-min brushing period with an experimental dentifrice formulated with 3% hydrogen peroxide for up to 9 mins postbrushing. In addition, the oral clearance of 3% hydrogen peroxide delivered in an experimental dentifrice formulated with 5% baking soda was determined in a control population of adults and adult subjects with impaired salivary flow. RESULTS: Most of the hydrogen peroxide decomposed during brushing, with less than 30% of the prebrushing dose of hydrogen peroxide remaining in the oral cavity after 1 min of brushing. No differences between infants, juveniles, and adults were seen in levels of hydrogen peroxide recovered from the oral cavity after tooth brushing. When a mixture of hydrogen peroxide and baking soda was used for brushing, less than 5% of the hydrogen peroxide was recovered from the oral cavity after 1 min of brushing. In conclusion, clearance of hydrogen peroxide from the oral cavity was very rapid in children, adults, and adults with impaired salivary flow. Decomposition of hydrogen peroxide was enhanced approximately six-fold in adults by the presence of baking soda in the dentifrice. No substantial amount of hydrogen peroxide survived beyond the brushing period, and very little material would be present to interact with soft tissues in the oral cavity after expectorating any remaining dentifrice containing hydrogen peroxide.

Hydrogen peroxide: a review of its use in dentistry.

Several dentifrices that contain hydrogen peroxide are currently being marketed. The increased use of bleaching agents containing (or generating) H2O2 prompted this review of the safety of H2O2 when used in oral hygiene. Daily exposure to the low levels of H2O2 present in dentifrices is much lower than that of bleaching agents that contain or produce high levels of H2O2 for an extended period of time. Hydrogen peroxide has been used in dentistry alone or in combination with salts for over 70 years. Studies in which 3% H2O2 or less were used daily for up to 6 years showed occasional transitory irritant effects only in a small number of subjects with preexisting ulceration, or when high levels of salt solutions were concurrently administered. In contrast, bleaching agents that employ or generate high levels of H2O2 or organic peroxides can produce localized oral toxicity following sustained exposure if mishandled. Potential health concerns related to prolonged hydrogen peroxide use have been raised, based on animal studies. From a single study using the hamster cheek pouch model, 30% H2O2 was referred to as a cocarcinogen in the oral mucosa. This (and later) studies have shown that at 3% or less, no cocarcinogenic activity or adverse effects were observed in the hamster cheek pouch following lengthy exposure to H2O2. In patients, prolonged use of hydrogen peroxide decreased plaque and gingivitis indices. However, therapeutic delivery of H2O2 to prevent periodontal disease required mechanical access to subgingival pockets. Furthermore, wound healing following gingival surgery was enhanced due to the antimicrobial effects of topically administered hydrogen peroxide. For most subjects, beneficial effects were seen with H2O2 levels above 1%.

A simplified method to quantify isoflavones in commercial soybean diets and human urine after legume consumption.

Reliable and economical quantification of micronutrients in diets and human is a critical component of successful epidemiological studies to establish relationships between dietary constituents and chronic disease. Legumes are one of the major dietary components consumed by populations worldwide. Consumption of legumes is thought to play a major role in lowering breast and prostate cancer risk. In this study, a simplified method that uses solid-phase extraction and gas chromatography was developed to measure isoflavones at levels down to 10 micrograms/5ml. With the use of this method, 12.5 g miso (a soybean paste), 12 ounces Isomil, and 12 ounces soymilk had daidzin/daidzein levels of 2, 5, and 12.4 mg, respectively, and genistin/genistein levels of 3, 6.5, and 13.7 mg, respectively. In these products, most of the isoflavones were present as glucosides. With the same method, urinary levels of isoflavones in six 15-17-year-old subjects were determined after soymilk ingestion. Each subject was placed on unrestricted nonsoya diets, and three 12-ounce portions of soymilk were given at 12-h intervals. Males excreted 15.02 +/- 2.74 (SD) mg of daidzein glucuronides/sulfates [mean recovery, 40.4 +/- 7.4% (SD)] by 24 h after the third soymilk ingestion, whereas females excreted 25.56 +/- 5.10 mg (68.7 +/- 13.7%) of daidzein conjugates, which was more than males (P = 0.02). Males and females excreted 7.73 +/- 1.95 mg and 9.11 +/- 0.84 mg of genistein glucuronides/sulfates (20% recovery of genistin intake), respectively, in the urine. Most of the isoflavones were excreted within 24 h after ingestion.(ABSTRACT TRUNCATED AT 250 WORDS)

Hepsulfam distribution in blood, plasma and cerebrospinal fluid of baboons.

The alkylating agent Hepsulfam (Sulfamic acid 1,7-heptanediyl ester, NSC 329680) was developed as a more hydrophilic analog of busulfan. The objective of this study was to determine partitioning of hepsulfam between blood, plasma, and cerebrospinal fluid (CSF) in two female baboons following intravenous administration. Hepsulfam was administered at 11 mg/kg, and blood and CSF levels were determined by gas chromatography with electron capture detection. Blood levels were fairly constant between animals (17-25 and 20-23 micrograms/ml) for six hours after administration, following peak levels of 43 and 33 micrograms/ml, respectively, for the two animals. Peak plasma levels of 35 and 36 micrograms/ml were achieved, and initial plasma half-lives in baboons were similar to those seen in other species, with a t1/2 alpha of 1 h. The plasma terminal half life of 0.2 h, estimated from limited sampling times, was shorter in baboons than in mice, dogs, or humans. Baboon CSF levels decreased from 1.7 to 0.3 micrograms/ml during 6 h post infusion, and peak concentrations in CSF lagged behind plasma levels. CSF/plasma ratios ranged from 0.33 to 0.62 in one animal, whereas ratios of 0.2-0.25 were maintained in the other animal during the same period. Results from this study indicate hepsulfam will enter the CSF following intravenous administration, and the CSF/plasma ratios are lower than those obtained following oral busulfan administration.

Altered time course of urinary daidzein and genistein excretion during chronic soya diet in healthy male subjects.

Soybean consumption is associated with reduced rates of prostate and other cancers, possibly due in part to the presence of isoflavones. The metabolism and disposition of these soya-derived phytoestrogens after chronic soya exposure were studied on a metabolic unit in six healthy males (21-35 yrs of age) who consumed an unrestricted hospital diet and a 12-oz portion of soymilk with each meal for one month. The daily isoflavone intake was about 100 mg of daidzein (mostly as diadzin) and about 100 of mg of genistein (mostly as genistin). At two-week intervals, excretion of isoflavones in urine was studied, during which time the subjects consumed a constant basal diet for three to four days, ingested the full daily 36-oz portion of soymilk within 30 minutes each day for one to two days, and collected urine continuously. The urinary recovery of ingested diadzin plus daidzein (46.9 +/- 15.2%, mean +/- SD) and genistin plus genistein (14.6 +/- 9.2%) did not change with prolonged soya ingestion. The absorption half-lives (t1/2) for daidzein and genistein and the appearance t1/2 for equol (1 subject) were initially 1.5 +/- 0.4, 1.9 +/- 0.6, and 2.2 hours, respectively, and 2.5 +/- 1.1 (p = 0.06 compared with baseline) 1.4 +/- 0.9 (p = 0.03) compared with baseline), and 4.2 hours, respectively, during one month of soymilk ingestion. The excretion t1/2 for daidzein, genistein, and equol were initially 2.9 +/- 0.5, 3.8 +/- 0.7, and 5.2 hours, respectively, and 3.9 +/- 1.2 (p - 0.03), 5.5 +/- 1.6 (p = 0.02), and 9.7 hours, respectively, during one month of soymilk ingestion. These results indicate that chronic soya exposure did not induce significant changes in the metabolic pathways of isoflavones but altered the time courses of daidzein and genistein excretion. Thus chronic exposure to soya might prolong the tissue exposure to the presumed biologically active free and unconjugated forms of these isoflavones and thereby enhance their oncoprotective effects.

In vitro cytotoxicity of hepsulfam against human tumor cell lines and primary human tumor colony forming units.

Hepsulfam (sulfamic acid 1,7-heptanediyl ester, NSC 329680) is an alkylating agent currently in Phase I clinical trials. Hepsulfam was developed as an analog of busulfan, an alkylating agent that is used to treat patients with chronic myelogenous leukemia and for marrow ablation prior to bone marrow transplantation. The objective of this study was to identify the spectrum of human tumor cells that were sensitive to hepsulfam. The following three cytotoxicity assays were employed to evaluate the in vitro cytotoxic potential of hepsulfam: 1) primary human tumors were exposed to three levels of hepsulfam for a one hour or continuous exposure, and growth in soft agar was determined; 2) human non-tumor cells and tumor cell lines were compared in an assay that measured the conversion of 14C-glucose to 14CO2 as an index of viability; and 3) the toxicity of hepsulfam to hematopoietic progenitor cells was determined in a progenitor cell colony forming assay. Cytotoxicity was not observed for human tumor cells following one hour hepsulfam exposures; in contrast, marked dose-dependent cytotoxicity was observed with continuous exposures. In human tumor cell lines, the cytotoxicity of hepsulfam was compared directly with busulfan at equimolar concentrations. Hepsulfam was more cytotoxic than busulfan in all cell lines tested. Cytotoxic activity was seen in lung, melanoma, kidney, breast, colon, ovary and brain tumor cells. These results, along with the information obtained from Phase I trials, will facilitate selection of patients who could receive this agent in Phase II efficacy trials.

Mutagenic activity of the 4,5- and 9,10-dihydrodiols of benzo[j]fluoranthene and their syn- and anti-dihydrodiol epoxides in Salmonella typhimurium.

The objective of this study was to determine the relative mutagenic activities of the major dihydrodiol metabolites of benzo[j]fluoranthene (B[j]F) and their corresponding syn- and anti-dihydrodiol epoxides. Salmonella typhimurium tester strains TA97a, TA98, and TA100 were used to evaluate the mutagenic potencies of the parent hydrocarbon and these suspect proximate and ultimate mutagenic metabolites. B[j]F and the trans-dihydrodiol metabolites were active only in the presence of an external metabolic activation system (S9) with the exception of the B[j]F-4,5-diol, which was weakly active in TA98 and TA100 in the absence of S9. The B[j]F-4,5-diol was more mutagenic than the B[j]F-9,10-diol in tester strains TA98 and TA100, whereas the opposite effect was observed in TA97a. In the absence of S9, the anti-B[j]F-4,5-diol epoxide was more mutagenic than the syn-B[j]F-4,5-diol epoxide and the syn- and anti-B[j]F-9,10-diol epoxides in tester strains TA97a and TA100. The exceptional mutagenic potency of the anti-B[j]F-4,5-diol epoxide in TA100 resembles that observed by epoxides located within a fjord, or by the anti-diol epoxides of bay region methylated polycyclic aromatic hydrocarbons. In contrast, the mutagenicity of the pseudo bay region dihydrodiol epoxides arising from the B[j]F-9,10-diol more closely resembles that observed with the classical bay region dihydrodiol epoxides of chrysene. In summary, both dihydrodiol metabolites of B[j]F are mutagenic in S. typhimurium, and the relative potency varies among the tester strains. The highest mutagenic response was achieved in tester strain TA100, which detects base-pair substitutions. The most potent direct-acting dihydrodiol epoxide in this tester strain was the anti-B[j]F-4,5-diol epoxide, which agrees with the results of mouse skin painting studies that indicate that the B[j]F-4,5-diol is more tumorigenic that the parent hydrocarbon or the B[j]F-9,10-diol. A covalent DNA adduct formed between the anti-B[j]F-4,5-diol epoxide and deoxyguanosine was the major species of DNA adduct formed in S. typhimurium. This adduct corresponds to the major DNA adduct formed in mouse skin following application B[j]F.

Effect of fluorine substitution on benzo[j]fluoranthene genotoxicity.

The metabolism and mutagenic activity of 4-fluorobenzo[j]fluoranthene (4F-B[j]F) and 10-fluorobenzo[j]fluoranthene (10F-B[j]F) were evaluated and compared with benzo[j]fluoranthene (B[j]F) using an identical rat liver homogenate preparation. Previous studies have shown that the major genotoxic metabolites of B[j]F are the 4,5- and 9,10-dihydrodiol. The 9,10-dihydrodiol was the principal metabolite formed in the case of 4F-B[j]F, while the 4,5-dihydrodiol was the principal metabolite formed in the metabolism of 10F-B[j]F. Studies on the relative genotoxicity of these fluorinated derivatives were performed to indirectly determine the possible contribution of the 4,5- and 9,10-dihydrodiol in the activation of B[j]F to a genotoxic agent. In the presence of microsomal activation, both of these fluorinated derivatives of B[j]F were more mutagenic in S. typhimurium TA97a, TA98 and TA100 than B[j]F. However, differences in mutagenic potency were observed between 4F- and 10F-B[j]F. 10F-B[j]F had similar mutagenic potency to 4F-B[j]F in TA97a and TA98 at doses associated with the linear portion of the dose response curve. However, a slightly higher mutagenic response was observed with 10F-B[j]F in TA98 at doses above 5 nmol. In contrast, 4F-B[j]F was more active than 10F-B[j]F as a mutagen in TA100. The tumor-initiating activity of these analogs on mouse skin was assessed at doses of 2.0, 1.0 and 0.3 mumol. Skin irritation was observed with the fluorinated B[j]F derivatives at doses above 0.3 mumol. At a dose of 0.3 mumol, 4F-B[j]F exhibited tumorigenic activity which was similar to B[j]F. In contrast, 10F-B[j]F was less active than B[j]F at all three doses assayed. Both fluorinated derivatives of B[j]F formed higher levels of DNA adducts in vivo in mouse skin than B[j]F. A modified 32P-postlabeling method was required to detect fast migrating B[j]F:DNA adducts that went undetected in previous studies. The level of DNA adducts formed from 4F-B[j]F was considerably greater than the levels observed with 10F-B[j]F. This is consistent with the greater mutagenic activity in S. typhimurium TA100 and tumor-initiating activity exhibited by 4F-B[j]F. These studies suggest that fluorine substitution may significantly alter the intrinsic genotoxicity of the 4,5- and 9,10-dihydrodiol of B[j]F. These data also imply that B[j]F may be primarily activated via the formation of the 9,10-dihydrodiol metabolite. This pathway of activation is inconsistent with our previous studies which indicate that the 4,5-dihydrodiol is the most important pathway of activation.(ABSTRACT TRUNCATED AT 400 WORDS)

Cytotoxicity evaluation of a new radiopaque resin additive--triphenyl bismuth.

Triphenyl bismuth (Ph3Bi) is a promising new additive for making biomedical resins visible on x-ray images. We evaluated the cytotoxicity of Ph3Bi, both alone and as a component of a denture resin, as an initial step in determining its biocompatibility. These experimental materials were compared with several types of dental materials that are in current clinical use (PMMA denture acrylic resin, two photo-cured sealants, and two glass-ionomer cements). Human embryonic lung fibroblast tissue cultures (WI-38 cells) were exposed to 24-hour aqueous extracts of the materials. Changes in cell growth, cell viability, and the visual appearance of cells were used for the assessment of toxic response. Only a slight degree of cytotoxicity was observed for Ph3Bi, both alone and in combination with self-cured PMMA. All clinical materials showed a higher level of cytotoxicity than did Ph3Bi. The sealants and cements exhibited the most cytotoxicity and PMMA acrylic the least. The cytotoxicity of PMMA was elevated slightly by inclusion of Ph3Bi, probably due to decreased monomer conversion. When stored in water, the already low levels of cytotoxicity of both PMMA and PMMA with added Ph3Bi were reduced even further. From these results, we can predict a high level of safety for Ph3Bi as a radiopaque additive for biomedical resins. Any toxicity associated with Ph3Bi-containing resins can be reduced or avoided by prior extraction. Alternatively, curing conditions can be selected that would drive the polymerization reaction to a higher level of conversion.

A phase I clinical and pharmacokinetic trial of hepsulfam.

Hepsulfam (1,7-heptanediol-bis-sulfamate) is one of a series of bis-sulfamate acid esters that was synthesized in an attempt to improve the antitumor efficacy of busulfan. Hepsulfam has shown broad antineoplastic activity in preclinical studies. This Phase I trial evaluated hepsulfam given as a single i.v. dose every 21-35 days. Twenty-nine patients with refractory solid tumors participated in this study. Twenty-six of these patients had had either prior chemotherapy or radiation therapy. Fifty-two courses of treatment were given at doses ranging from 30 to 360 mg/m2/day. The dose limiting toxicity was prolonged thrombocytopenia and granulocytopenia. This toxicity was cumulative with Grade 3 or 4 thrombocytopenia occurring in 3 of 15, 4 of 9, and 2 of 2 patients in the first, second, and third courses of greater than or equal to 210 mg/m2, respectively. This toxicity was noted in patients with less than or equal to 1 prior chemotherapeutic regimen, as well as in patients with greater than 1 prior chemotherapeutic regimens. Nonhematological toxicities included Grade 1 or 2 nausea and vomiting and fatigue. There was no evidence of pulmonary toxicity. Plasma levels of hepsulfam were quantified by gas chromatography in 12 patients. The plasma and blood half-lives were 15.9 +/- 4.6 and 90 +/- 13 h, respectively. No objective tumor responses were seen. We conclude that the maximally tolerated dose when hepsulfam is given as a single dose every 35 days is 210 mg/m2, but that there is significant risk of cumulative hematological toxicity at this level.

Thyroid hormone levels and cigarette smoking in baboons.

Using a primate animal model, two studies were undertaken to examine the effects of cigarette smoking on thyroid hormone levels. In study 1, mean total triiodothyronine (total T3) and mean total thyroxine (total T4) levels were measured in two groups of baboons (Papio cynocephalus) who were taught to smoke cigarettes using operant conditioning techniques. The smokers were divided into established and naive smokers according to pack-years of exposure. A control group of never-smoker baboons was included for comparison. Blood sampling was done after long-term cigarette consumption and again 1 week after cigarette deprivation. In the naive smoker group, mean total T3 concentrations were reduced below control group values (P less than 0.05). After cigarette deprivation for 1 week, mean total T3 values returned to normal. No significant differences in total T4 levels were observed in either group. In study 2, we assessed some other indices of thyroid function. The same groups of baboons were divided into good and poor smokers by plasma cotinine and blood carboxyhemoglobin (% COHb) levels during 28 weeks of cigarette smoking activity. Immediate fluctuations and reductions in total T3 levels were observed that were not accompanied by reductions in total T4. The animals were then cigarette deprived for 1 week and blood samples were obtained every other day during this period. Significant increases in total T3 concentrations were observed in poor smokers immediately after cessation. Both groups also exhibited significant reductions (P less than 0.05) in T3 uptake and free T4 index (FT4I) when compared to control group values. These data suggest that poor smokers are more susceptible to thyroid hormone level shifts than more established smokers, since the established smokers become habituated to the compounds contained in cigarette smoke through repeated exposure.

In vitro cytotoxicity of chrysotile asbestos to human pulmonary alveolar macrophages is decreased by organosilane coating and surfactant.

Human pulmonary alveolar macrophages were used to quantitate the cytotoxic effect of surface-altered chrysotile asbestos. Little difference was observed in mortality between chrysotile asbestos that was surface-treated to a 42% extent by a hydrophobic organosilane or untreated chrysotile. Little or no effect on mortality was observed when human pulmonary alveolar macrophages were cultured with untreated chrysotile or acid-leached asbestos in the presence of 10 mM dipalmitoyl lecithin. However, when human pulmonary alveolar macrophages were cultured with a hydrophobically-treated (to a 42% or 95% extent) chrysotile asbestos in the presence of 10 mM dipalmitoyl lecithin, a statistically significant decrease in mortality was observed compared to untreated chrysotile. No mutagenic activity was observed when V79 cells were cultured with acid-leached, or 42% hydrophobically-treated chrysotile asbestos, even when human pulmonary alveolar macrophages were included as an activation source. The 95% hydrophobically-treated and acid-leached chrysotile also exhibited decreased binding of benzo[a]pyrene compared to untreated chrysotile asbestos.

Pharmacokinetics of N'-nitrosonornicotine and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone in laboratory animals.

The pharmacokinetics of N'-nitrosonornicotine (NNN) and 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK) in the Syrian golden hamster, the CD-1 mouse, and the baboon were compared to the pharmacokinetics in the Fischer rat. The formation and biological half-life of 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanol (NNAL), the major metabolite of NNK, was also studied in these animal species. The biological half-life of NNN in these 4 animal species ranged from 0.24 h to 3.06 h, that of NNK from 0.21 h to 0.43 h and NNAL from 0.48 h to 2.9 h. The pharmacokinetic data obtained in the baboon suggest that treatment with NNN and NNK causes an enzyme induction which accelerates the rate of elimination of these compounds.

Enhancement of the mutagenicity of carcinogenic arylamines by ethinyl estradiol.

Ethinyl estradiol, the estrogenic component of oral contraceptives, has been shown to enhance the mutagenicity of 2-aminofluorene, 2-acetylaminofluorene, N-hydroxy-2-acetylaminofluorene, and N-acetoxy-2-acetylaminofluorene with strain TA 98 of Salmonella typhimurium and various rat liver activating systems. The magnitude of the enhancement of mutation produced by ethinyl estradiol is dependent upon: the type of mixed-function oxidase inducer of the liver activating system; the structure and concentration of the arylamine; the concentration of ethinyl estradiol; and metabolism of ethinyl estradiol to its catechol, 2-hydroxyethinyl estradiol, by the activating system. Moxestrol, a biologically potent estrogenic derivative of ethinyl estradiol which is not metabolized effectively to its catechol by the mixed-function oxidases, does not enhance the mutagenicity of the above arylamines and related compounds. Both 2-hydroxyethinyl estradiol and 2-hydroxymoxestrol enhance the mutagenicity of 2-aminofluorene and 2-acetylaminofluorene. Neither the estrogens nor their catechols are mutagenic by themselves in this system. In the presence of ethinyl estradiol, a marked inhibition of ring hydroxylation of 2-acetylaminofluorene was demonstrated. Since ring hydroxylation is a well established detoxification pathway of arylamine and arylamide metabolism, the enhancement of mutagenicity by ethinyl estradiol may be the result of a net increase in N-hydroxylation of arylamines and arylamides.

Analysis of urinary mutagens produced by cigarette-smoking baboons.

Urine concentrates from 17 cigarette-smoking baboons and 12 sham puffers were analyzed for mutagenic activity in S. typhimurium tester strain TA1538. Both the proportion of animals exhibiting measurable mutagenic activity in urine and the mean level of mutagenic activity present were significantly greater in cigarette smoking baboons (P less than 0.05). Mutagenic activity in the urine of male and female cigarette-smoking baboons was not significantly different. Age and smoking history did not, but mean blood carboxyhemoglobin did, correlate with mutagenic activity of the urine concentrate from individual animals. Fractionation of the urine concentrates on silicic acid separated the concentrate into fractions that were more active in TA100 and others that were more active in TA1538. Further fractionation was accomplished by HPLC.

Selenium and glutathione peroxidase levels in patients with epidermoid carcinoma of the oral cavity and oropharynx.

Selenium ingestion may inhibit carcinogenesis. Epidemiologic studies have shown that age-adjusted death rates for cancer at most head and neck sites are lower in states where the soil and forage crops contain higher levels of selenium. The mode of action is incompletely understood, but may be mediated through an increase in the activity of the selenium dependent, antioxidant enzyme glutathione peroxidase (GSH-Px). The authors studied blood selenium levels and blood and tissue GSH-Px activities in 50 patients with untreated cancer of the oral cavity and oropharynx. Mean erythrocyte selenium and glutathione peroxidase were significantly depressed when compared to age-matched controls. Mean plasma selenium, on the other hand, was significantly elevated in the cancer patient group. Data from subsets within the cancer patient group were also discussed. GSH-Px activity did not differ in tumor and adjacent normal tissue. The concept of chemoprevention of carcinogenesis with inhibitory chemical compounds is particularly apropos to head and neck cancer control. Further work is indicated to determine if ingestion of supplemental selenium corrects the abnormalities identified here, and what affect, if any, this would have on the development and behavior of squamous cell cancers in the upper aerodigestive tract.