Transplacental Toxicity and Carcinogenesis Studies in Rats with Hexamethylenetetramine

In a previous paper (Fd Cosmet. Toxicol., 6: 707–715, 1968) it was reported that hexamethylenetetramine (HMT) had no carcinogenic activity in long-term experiments in mice and rats. In the present study, 12 ♀ and 6 ♂ Wistar rats were given 1% HMT in the drinking water starting 2 weeks before mating. The females were kept under treatment during pregnancy and lactation. A similar untreated group of 12 ♀ and 6 ♂ served as control. Twelve treated females and eleven controls became pregnant and gave birth to 124 and 118 babies respectively; no malformations were noted. From these animals, 24 for each sex were continued on the 1% HMT up to the 20th week of age or were kept untreated. The body weight of treated animals was significantly lower than that of controls one, only up to the 9th week of age for the males and up to the 13th week for the females. At the end of the treatment both groups were sacrificed; the weight of organs was identical in the treated and control animals; there were no gross or histological pathology. In a second experiment, rats were given 1% HMT in the drinking water for 3 successive generations, up to the age of 40 weeks in the F1 and F2 groups and of 20 weeks for F3. The three groups were composed of 13 ♂ and 7 ♀, 15 ♂ and 11 ♀, 12 ♂ and 12 ♂, respectively. In addition, a group of 16 ♂ and 16 ♀ descendants of 2% HMT treated parents, were given 2% HMT for 50 weeks. A group of 48 ♂ and 48 ♀ served as untreated controls. All groups were kept under observation for over 2 years of age. No evidence of carcinogenicity was found in any of the HMT-treated groups.

Antioxidative properties of natural polyamines and dimethylsilane analogues

Structural analogues of natural polyamines, which contain a -Si(CH3)2 group in the central carbon chain, have previously been found to be cytotoxic to various tumor cell lines in vitro and to inhibit tumor cell growth in experimentally grafted animals. In the present study, the antioxidative properties of dimethylsilane polyamine analogues were analyzed in comparison with the natural polyamines. Reactivities of these various polyamines against superoxide anions (generated from the hypoxanthine/xanthine oxidase reaction) and peroxyl radicals (produced from the thermal decomposition of water-soluble 2,2'-azo-bis-[2-amidinopropane] hydrochloride) were investigated. The dimethysilane analogues, and more particularly the hexamine derivative, exhibited the highest scavenging efficiency towards these two reactive oxygen species (ROS). Furthermore, analysis of their ability to prevent hydroxyl radical formation and to trap this ROS showed that the efficiency of the hexamine as a metal chelator and hydroxyl radical scavenger is similar to that of spermine. The higher antioxidant efficiency of the dimethylsilane polyamine analogues with respect to spermidine, together with their ability to displace this polyamine, essential for the promotion of cell growth, from its cellular anionic binding sites that are particularly prone to oxidation, could be biologically relevant and contribute to their in vivo cytotoxic effect and anti-tumor activity. Further experiments will be necessary to demonstrate clearly the relationship between their antioxidant properties and their antiproliferative effects.

[Quantitative assessment of the biological activity of chemicals by soil microbial associations]

Quantitative assessment, using three Pseudomonas sp. strains, of the activity of the microbial biocide Soncid 8101 demonstrated that the values of effective sublethal concentrations (L50) differed by 500% (because of individual variations in the sensitivity of the test strains). The spread of parameters of biocidal activity could be narrowed by using a mixture of microorganisms with high, medium, and weak resistance. A method for quantitative assessment of the activity of microbial biocides was proposed, based on the use of natural associations of soil bacteria.

Activation of adriamycin by the pH-dependent formaldehyde-releasing prodrug hexamethylenetetramine

Previous studies have shown that Adriamycin can react with formaldehyde to yield an activated form of Adriamycin that can further react with DNA to yield Adriamycin-DNA adducts. Because hexamethylenetetramine (HMTA) is known to hydrolyze under cellular conditions and release six molecules of formaldehyde in a pH-dependent manner, we examined this clinical agent for its potential as a formaldehyde-releasing prodrug for the activation of Adriamycin. In IMR-32 neuroblastoma cells in culture, increasing levels of HMTA resulted in enhanced levels of Adriamycin-DNA adducts. These adducts were formed in a pH-dependent manner, with 4-fold more detected at pH 6.5 compared with pH 7.4, consistent with the known acid lability of HMTA. The resulting drug-DNA lesion was shown to be cytotoxic, with combined Adriamycin and prodrug treatment resulting in a 3-fold lower IC(50) value compared with that of Adriamycin alone. Given the acidic nature of solid tumors and the preferential release of formaldehyde from HMTA in acidic environments, HMTA therefore has some potential for localized activation of Adriamycin in solid tumors.

[Antimicrobial action of ammonium salts of fused heterocycles containing ortho-nitrogen]

By alkylation of hexamethylenetetramine with halogenated derivatives of ketones, ethers, esters or amides of acids, alkyl- and aralkyl halides the corresponding N-monoalkylated compounds of hexamethylenetetramine were obtained. The quaternization of pyridine nitrogen in 5,6-benzoquinoline, 8-hydroxyquinoline, quinoline, 1,10-phenanthroline molecules with alkyl- or aralkylhalides was carried out. The susceptibility of Gram-positive (Streptococcus agalactiae and Staphylococcus aureus) and Gram-negative (E. coli, Salmonella cholerae suis, Salmonella enteridis Gartneri) microorganisms to synthesized quaternary ammonium salts by disc difussion method has been detected. The bacteriostatic action of 0.5-1% solutions of all compounds was assessed in comparison with benzalkonium chloride. It was shown, that the most effectiveness against all strains is possessed by quaternary hexamethylenetetramine ammonium salts, and especially salts, containing 1-propynyl- or hydroxycarbamoylmethyl radicals. The action of these two compounds against Salmonella and Streptococcus was stronger than the action of benzalkonium chloride. Susceptibility of Pseudomonas aeruginosa to these compounds were detected. It was shown, that 1% solutions of chlorides of N-(1-propynyl) hexamethylenetetramonium and N-(hydroxycarbamoylmethyl) hexamethylenetetrammonium demonstrate the same bacteriostatic action against P. aeruginosa as well as benzalkonium chloride.

Dimethylsilane polyamines: cytostatic compounds with potentials as anticancer drugs. II. Uptake and potential cytotoxic mechanisms

Dimethylsilane tetramines are structural analogues of spermine with a (CH3)2 Si-group incorporated into the central carbon chain. They have potential as anticancer drugs. Their cytotoxic effect was considered to rely mainly on their polyamine antagonist property. In order to obtain new ideas about cellular mechanisms, which are potential targets of the dimethylsilane polyamines, the effects of these compounds on some basic cell functions, such as protein and DNA synthesis, and calmodulin antagonism were studied. In addition, their mode of accumulation in cells was investigated. It became evident that the intracellular accumulation of dimethylsilane polyamines is almost exclusively achieved via the polyamine transport system. However, the exchange of a part of the intracellular natural polyamines against dimethylsilane polyamines has only a small effect on polyamine uptake. Binding to the endoplasmic reticulum and inhibition of protein synthesis are presumably important for the cytotoxic action of bis(11-amino-4,8-diazaundecyl)dimethylsilane, a hexamine, but seem of no importance for the tetramines. Calmodulin antagonism, however, is likely to contribute to their cytotoxic effect.

Polyamine structural effects on the induction and stabilization of liquid crystalline DNA: potential applications to DNA packaging, gene therapy and polyamine therapeutics

DNA undergoes condensation, conformational transitions, aggregation and resolubilization in the presence of polyamines, positively charged organic molecules present in all cells. Under carefully controlled environmental conditions, DNA can also transform to a liquid crystalline state in vitro. We undertook the present work to examine the ability of spermidine, N4-methylspermidine, spermine, N1-acetylspermine and a group of tetramine, pentamine and hexamine analogs of spermine to induce and stabilize liquid crystalline DNA. Liquid crystalline textures were identified under a polarizing microscope. In the absence of polyamines, calf thymus DNA assumed a diffused, planar cholesteric phase with entrapped bubbles when incubated on a glass slide at 37 degrees C. In the presence of spermidine and spermine, the characteristic fingerprint textures of the cholesteric phase, adopting a hexagonal order, were obtained. The helical pitch was 2.5 micro m. The final structures were dendrimeric and crystalline when DNA was treated with spermine homologs and bis(ethyl) derivatives. A cholesteric structure was observed when DNA was treated with a hexamine at 37 degrees C. This structure changed to a hexagonal dendrimer with fluidity on prolonged incubation. These data show a structural specificity effect of polyamines on liquid crystalline phase transitions of DNA and suggest a possible physiological function of natural polyamines.

Comparison of methods for identification of Pneumocystis carinii in bronchoalveolar lavage fluid

Pneumocystis carinii pneumonitis in one of the most common life-threatening opportunistic infections in patients with AIDS. The definitive diagnosis of this infection can be established only by demonstration of the organism in clinical specimens. This study was a comparison of methods that provide easy recognition of the organism which is readily available, simple and can be performed rapidly in laboratory-diagnosis. Bronchoalveolar lavage fluids obtained from 35 AIDS patients suspected of having Pneumocystis carinii pneumonitis were examined by three staining methods for the presence of Pneumocystis carinii. With Giemsa stains, P. carinii could be identified in 18 cases (51.4%). Three developmental stages: "cyst", "sporozoite" and "trophozoite" were seen. The contrast of organisms against host cells was not outstanding in these stains. Toluidine blue O stains provided easy recognition of the organisms, with marked contrast between the cysts and host cells. 21 cases (60%) were positive in these stains, but the intracystic structures and trophozoites could not be identified. It was suggested that the clinical specimen should be stained first with toluidine blue O which is more rapid and permits easy recognition of the cyst clusters. If the sporozoites and trophozoites had to be identified, Giemsa stains can be made. In addition, with the methenamine silver nitrate stains, 21 cases (60%) were positive. They revealed the morphology as seen with toluidine blue O but the cost of material may make it unavailable in many laboratories especially with the budgetary restraints of developing countries.

Antimicrobial activity of four root canal sealers against endodontic pathogens

The antibacterial effects of various types of widely used endodontic sealers have not been compared systematically on facultative or obligate anaerobic endodontic pathogens. The aim of this study was to evaluate the antimicrobial properties of four commonly used endodontic sealers: two epoxy-resin-based sealers (AH26, AH plus), one zinc-oxide eugenol-based sealer (N2), and one calcium hydroxide-based sealer (Sealapex). The testing microbes were four facultative anaerobic species (Streptococcus mutans, Streptococcus sanguis, Escherichia coli, and Staphylococcus aureus) and four obligate anaerobic species (Porphyromonas gingivalis, Porphyromonas endodontalis, Fusobacterium nucleatum, and Prevotella intermedia). The freshly mixed sealers were placed into the prepared wells of agar plates inoculated with the test microorganisms. After varying periods of incubation (2 days for facultative anaerobic species and 7 days for obligate anaerobic species), the zones of growth inhibition were observed and measured. All the sealers were distinctly different from each other in their antimicrobial activity. The sealers showed different inhibitory effects depending on the types and bacterial strains. N2 containing formaldehyde and eugenol proved to be the most effective against the microorganisms. The extreme antimicrobial potency of this root canal sealer must be weighted against its pronounced tissue toxic effect.

A comparison of the effect of three endodontic sealers on adherence of mouse peritoneal macrophages

Leakage of sealer from root canals to periapical tissues during root canal obturation may occur. This study was designed to evaluate the possible effect of three root canal sealers (zinc oxide-eugenol, Grossman, and AH 26) on adherence of mouse macrophages. Macrophages were obtained from the peritoneal cavity of BALB/c mice and suspended in RPMI-1640 medium. Adherence capacity assays were carried out in Eppendorf tubes. Each sealer was tested four times after mixing (immediately, 12 hours, 24 hours, and 48 hours after) and for three period of incubation (10, 20, and 30 minutes) with suspended cells. Cells were counted under the light microscope, and the adherence index was determined. Zinc oxide-eugenol and Grossman sealers killed all macrophages, and the adherence index was considered less than 1 for these sealers. AH 26 reduced the adherence index in all different periods after mixing and incubation times. But in sealer that had mixed 48 hours before the experiment and with 10 minutes of incubation, the adherence index was increased slightly, but the difference was not statistically significant (P < 0.05).

Efficient protection of human bronchial epithelial cells against sulfur and nitrogen mustard cytotoxicity using drug combinations

The aim of this study was to test the efficacy of several candidate molecules against sulfur mustard (SM) and nitrogen mustard (HN2) using a human bronchial-epithelial cell line (16HBE14o-). Candidate molecules were chosen on the basis of the known cytotoxicity mechanisms of mustards or their efficacy previously observed on other cellular models. It included the sulfhydryl-containing molecules N-acetyl-cysteine (NAC) and WR-1065, the nucleophile hexamethylenetetramine (HMT), the energy-level stabilizer niacinamide (NC), the antioxidant dimethylthiourea (DMTU), L-arginine analogues such as L-thiocitrulline (L-TC) and L-nitroarginine methyl ester (L-NAME), and the anti-gelatinase doxycycline (DOX). Their efficacy was determined using 2-(4-[3-iodophenyl)-3-(4-nitrophenyl)-5-(2, 4-disulfophenyl)-2Htetrazolium (WST-1) reduction by viable cells 24 h after initial exposure to 100 microM HN2 or SM. On individual immediate cotreatment, some molecules exhibited selective protection against only one mustard, such as DMTU and WR-1065 against HN2 and DOX against SM, whereas NAC and L-TC were effective against both SM and HN2 cytotoxicity. However, as the level of protection against SM was always weak compared to HN2, several combinations were investigated against SM to improve the protection. The effective combinations (L-TC + DOX, NAC + DOX, NAC + DMTU, NAC + HMT, NC + DOX) combined agents, reducing the bioavailability of the mustard with compounds possibly acting on the consequences of alkylation. One of these combinations, NAC + DOX, appeared to be the most interesting, as these agents are already used in human therapy. It exhibited good efficacy in delayed cotreatment (up to 90 min) against SM.

Effect of various mixing ratios on antibacterial properties and hardness of endodontic sealers

Most chemically cured two-component dental materials, including endodontic sealers, are marketed with mixing instructions but with no strict mixing ratios. The present study evaluated the antibacterial properties and hardness of three endodontic sealers: Roth's cement (RC), CRCS, and AH26, mixed to four controlled consistencies within the range of the manufacturer recommendations. Using Enterococcus faecalis as the test microorganism, antibacterial activity was evaluated by agar diffusion and direct contact test. Surface hardness of sealers with the same consistency was evaluated on week-old specimens by the Knoop Hardness Number tester. In the agar diffusion test, light consistency of RC showed larger zones of inhibition than heavier consistency, whereas no significant differences were found with AH26 or CRCS. In the direct contact test, RC and CRCS exhibited complete inhibition of bacterial growth at all consistencies, whereas AH26 with the heavier consistencies did not inhibit bacterial growth at 24 h samples. The hardness of AH26 and CRCS was significantly lower with lighter consistencies. It is concluded that endodontic sealers possess different antibacterial and physical properties according to their mixing consistencies.

Gutta-percha: a look at the need for sterilization

Many have argued that the prevention of contamination becomes a problem when gutta-percha cones are used to obturate the root canal space. This study evaluated the extent of contamination of commercially available gutta-percha cones taken directly from the manufacturer's box. Results show that if gutta-percha is not intentionally contaminated, there is no need for chemical decontamination before obturation.

Antimicrobial effect of six endodontic sealers: an in vitro evaluation

The aim of this study was to determine the in vitro antimicrobial effect of six endodontic sealers after 2, 20 and 40 days. The sealers studied were Apexit, Endion, AH26, AH-Plus. Procosol and Ketac Endo. The microorganisms used were Candida albicans, Staphylococcus aureus, Streptococcus mutans and Actinomyces israelii. Petri dishes were filled with sterile agar and 0.1-ml wells were prepared and filled with the sealers. The agar plates were stored for 24 h at 37 degrees C. The samples were then removed, immersed in 4.5 ml of culture medium and divided into three groups. The samples in group 1 were stored for 2 days at 37 degrees C whereas the samples of groups 2 and 3 were stored at 4 degrees C for 20 and 40 days respectively. The samples were then removed and discarded, and 0.1 ml of the culture medium was seeded on the agar plates in order to perform colony forming unit counts. Apexit, Endion and AH-Plus produced slight inhibition on Streptococcus mutans at 20 days and on Actinomyces israelii at every time interval. No effect was found on Candida albicans and Staphylococcus aureus. Ketac Endo only produced an antimicrobial effect on Actinomyces israelii at 2 and 40 days. AH26 and Procosol showed antimicrobial effect at 40 days on Candida albicans, at 20 and 40 days on Streptococcus mutans and Staphylococcus aureus, and an effective inhibition on Actinomyces israelii at every time interval. Statistical analysis revealed both sealers and microorganisms to be significant factors affecting results in groups 2 and 3. In conclusion, the sealers evaluated in this study showed different inhibitory effects depending on time span. Overall, sealers containing cugenol and formaldehyde proved to be most effective against the microorganisms at the time intervals studied.

Protection of human upper respiratory tract cell lines against sulphur mustard toxicity by hexamethylenetetramine (HMT)

1. Sulphur mustard ('mustard gas', HD) is a highly toxic chemical warfare agent which affects the skin and respiratory tract. The primary targets of inhaled HD are the epithelia of the upper respiratory tract. Hexamethylenetetramine (HMT) has been shown to protect human lung cells against HD toxicity and has also been shown to be effective in vivo against the chemical warfare agent phosgene. The ability of HMT to protect against the toxicity of HD was investigated in the human upper respiratory tract cell lines BEAS-2B and RPMI 2650. 2. HD was highly toxic to both cell lines, with LC50 values of 15-30 microM. HMT, at a concentration of 10 mM, was shown to protect the cell lines against the toxic effects of 20 microM and 40 microM HD. Results demonstrated that it was necessary for HMT to be in situ at the time of exposure to HD for effective cytoprotection. No protection was seen when cells were treated with HMT following exposure to HD, or where HMT was removed prior to HD exposure. 3. Results suggest that HMT may be effective prophylaxis for exposure to HD by inhalation.

Cytotoxicity of four root canal sealers in permanent 3T3 cells and primary human periodontal ligament fibroblast cultures

OBJECTIVES

The purposes of this study were to determine the cytocompatibility of four endodontic sealers and gutta-percha using various extracts and to compare the cellular injuries resulting from these materials in permanent 3T3 monolayers and primary human periodontal ligament fibroblasts.

STUDY DESIGN

Set specimens from four sealers (AH26, Apexit, Sealapex, N2) as well as gutta-percha were eluted with cell culture medium for 24 hours, 5 days, 5 days, and 24 hours, respectively. Cytotoxic effects due to these extracts were evaluated by determining proliferation of permanent 3T3 cells and primary human periodontal ligament fibroblasts by means of the fluorochrome propidiumiodide.

RESULTS

No statistically significant cellular alterations were induced by gutta-percha and Apexit, whereas various extracts of AH26 and Sealapex caused significant moderate or severe growth inhibition. Severe cellular damage was documented for all extracts of N2, which was statistically significantly different from the other materials in both cell lines (p < 0.05).

CONCLUSIONS

Our results confirm that various root canal sealers constantly segregate substances after being exposed to an aqueous environment for extended periods, possibly causing moderate or severe cytotoxic reactions and possibly contributing to failure.

Presence of methenamine/glutathione mixtures reduces the cytotoxic effect of sulphur mustard on cultured SVK-14 human keratinocytes in vitro

The basal epidermal keratinocytes of the skin are a main target for the vesicating agent, sulphur mustard (SM). A human keratinocyte cell line (SVK-14) has been used to model the effects of SM on the basal epidermal keratinocytes and subsequently to test the efficacy of potential prophylactic compounds in reducing the SM-induced cytotoxicity. The cultures were pretreated with mixtures of methenamine (HMT) and glutathione (GSH) for 1 h prior to exposure to 10 microM SM. The viability of the cultures was then assessed using neutral red (NR) dye uptake and crystal violet DNA staining assays at 24 h intervals post exposure. Pretreatment led to a 1.9 fold increase in culture viability (NR assay) compared to those exposed to SM only, and a 2.3 fold increase in cell number (crystal violet assay). Photomicrography showed that pretreatment preserved the morphology of the cultured cells and maintained their mitotic activity whereas those exposed to SM only show non-proliterative cultures with extensive cellular damage. The results of this study show that it is possible to protect mitotically active cultures from the effects of SM, however the measures must be in place prior to SM exposure.

Protection of A549 cells against the toxic effects of sulphur mustard by hexamethylenetetramine

The A549 cell line was used as a model of the deep lung to study the toxicity and mechanism of action of sulphur mustard (HD), using the neutral red (NR) dye retention and gentian violet (GV) assays as indices of cell viability. It was found that exposure to concentrations in excess of 40 microM HD resulted in a rapid onset of toxicity. Exposure to 1000 microM HD reduced viability in A549 cell cultures to 61% after 2 h (control cultures = 100%), whereas exposure to 40 microM HD did not result in deleterious effects until 26 h at which point viability fell to only 84% (NR assay). Agarose gel electrophoresis of cell cultures exposed to 40 and 1000 microM HD and harvested at 4.5, 19 and 43 h after exposure to HD, indicated that cell death was due to necrosis, despite the observation that at the higher concentration of HD cells displayed many of the features common to cells undergoing apoptotic death. The ability of hexamethylenetetramine (HMT) to protect A549 cells against the effects of an LC50 challenge dose of HD was assessed using the GV and NR assays. It was found that HMT (15 mM) could protect cells against the effects of HD though HMT had to be present at the time of HD challenge. Cultures treated with HD only were 49% viable at 48 h after HD challenge, compared to 101% for protected cultures (NR assay) and 58% and 91% for unprotected and protected cultures respectively using the GV assay. Morphological observations of GV and NR stained cultures confirmed these findings. HMT concentrations of 2.5 to 25 mM were used. Maximal protection against the toxic effects of HD (LC50) was found at 10 to 25 mM HMT. Over this concentration range, HMT did not exert any toxic effects on A549 cells. Pretreatment of A549 cultures with HMT followed by its removal prior to HD challenge had no protective effect. Similarly, treating cultures with HD followed by addition of HMT did not increase the viability of the cultures, even if the HMT was added immediately after HD exposure. HMT was found to protect against the toxic effects of HD, though it must be present at the time of HD challenge. A549 cells were found to be a valuable experimental model for studying the toxicology of HD and other lung damaging agents, and for screening other compounds for potential therapeutic efficacy as a prelude to studies with non-transformed cell culture systems and in vivo models.

Assessment of antibacterial activity of endodontic sealers by a direct contact test

It is recognized that endodontic success depends on bacterial elimination from the root and root canal system. Antibacterial activity of endodontic sealers can improve the success rate of endodontic treatment, provided the physical properties are not compromised. The aim of this study was to evaluate the antimicrobial properties of two endodontic sealers (AH26 and Endoflas) using a direct contact test (DCT) which was designed for this purpose. The DCT is based on measuring the effect of close contact between test bacteria and the tested material on the kinetics of bacterial outgrowth using a temperature controlled microplate spectrophotometer (THERMOmax). For comparison, the agar diffusion test (ADT) was performed for both materials. The results of the DCT showed that Endoflas was a significantly more potent bacterial growth inhibitor than AH26, whereas when assessed with the ADT, AH26 was capable of producing a larger inhibition zone than Endoflas. The DCT, by being quantitative and virtually independent of solubility and diffusion, was found more suitable to assay solid surfaces. The results demonstrated the added value of DCT in the study of the antimicrobial properties of endodontic sealers.

The antimicrobial effect within dentinal tubules of four root canal sealers

The aim of this study was to investigate four root canal sealers--Pulp Canal Sealer EWT, Sealapex, AH26, and Ketac-Endo--for their antibacterial effects within dentinal tubules. Sterile saline served as a control. Sixty-six standardized bovine root specimens were infected with Enterococcus faecalis following smear layer removal. The materials were placed in the lumina, and six specimens from each group were stored for 24 h (48 h for AH26) and 7 days, after which dentin samples were taken from within the lumina using ISO 023 to 035 burs. Powder samples were incubated and the quantity of bacteria present assessed using spectrophotometry. All sealers showed antibacterial activity at 24 h, except Ketac-Endo. The activity of Pulp Canal Sealer EWT was similar at 24 h and 7 days. Sealapex had greater antibacterial effect at 7 days than it did at 24 h. The strongest effects were demonstrated by AH26.

Immunodetection of Pneumocystis carinii in bronchoalveolar lavage specimens compared with methenamine silver stain

Immunodetection of Pneumocystis carinii, based on immunofluorescence and use of a monoclonal antibody specific for an antigen located within the cyst wall and detectable after trypsin digestion only, was compared with a methenamine silver stain in 553 bronchoalveolar lavage specimens from immunosuppressed patients. P. carinii was found by immunofluorescence in 72 (86%) and by silver stain in 68 (81%) of the total of 84 positive samples detected by either or both of these methods.

Zinc as a growth factor for Aspergillus sp. and the antifungal effects of root canal sealants

Noninvasive aspergillosis of the maxillary sinus is frequently associated with extrusion of root canal cements into the sinus, and it has been suggested that zinc oxide-based materials might promote infection because zinc is a growth factor for Aspergillus sp. To investigate this possibility pure zinc oxide-eugenol cement and five other cements were tested for antifungal activity against five strains of Aspergillus fumigatus, one strain of A. niger, and one strain of A. flavus by zone inhibition and by spectrophotometric measurement of growth rates at various zinc concentrations. All cements had antifungal activity. Eugenol-containing materials had the most activity, but this activity was reduced with mixing and setting. No growth enhancement attributable to zinc was detected by either method. To determine whether contaminated materials might introduce spores into the sinus, 63 samples taken from one clinic were cultured. Aspergillus sp. was isolated from two.

Antimicrobial activity of seven root canal sealers. Results of agar diffusion and agar dilution tests

A comparative study of the antimicrobial action of seven root canal sealers: Traitement Spad, Endométhasone, N2 Universal, Diaket-A, AH26 with silver, Tubli Seal, and Sealapex was done with 120 strains of Staphylococcus aureus. Two antimicrobial susceptibility tests were used: the agar dilution test and the agar diffusion test. The Diaket-A and Traitement Spad sealer cements showed the highest efficiency in the dilution test, whereas Diaket-A was in fourth place in the diffusion test, only better than the antimicrobial activity of the Tubli Seal and Sealapex sealers.

Tissue reaction to endodontic materials: methods, criteria, assessment, and observations

The purpose of this study was to develop methods and criteria for the testing of the biocompatibility of endodontic materials. One hundred twenty-one teeth from 12 baboons (Papio anubis) were used to test three sealers: AH26, Kerr pulp canal sealer, and Kloroperka N.O. Gutta-percha cones were used as solid core in all cases. Under disinfected conditions, access preparation was performed, and with working length approximately 1.0 mm short of the foramen, the instrumentation of the root canal was started, using sodium hypochlorite (1%) for irrigation. After the root canals were cleaned and shaped, they were obturated with gutta-percha cones and the sealer, and by lateral condensation technique. Histologic periapical reactions were evaluated at 1, 7, 30, 365, 730, and 1095 days. The methods and criteria used were adequate for ranking of the biocompatibility of the tested materials in the short and long periods. At short observation periods (1 to 7 days) AH26 caused severe reactions, and Kerr pulp canal sealer and Kloroperka N.O., moderate and mild reactions, respectively. At 2- and 3-year observation periods the ranking was AH26, mild; Kerr pulp canal sealer, moderate; and Kloropercha N.O., severe.

Evaluation of antimicrobial activity in vitro of ten root canal sealers on Streptococcus sanguis and Streptococcus mutans

The antimicrobial activity of ten root canal sealers was studied on Streptococcus sanguis and Streptococcus mutans. One hundred plates of trypticase soy agar-sheep red blood cell (10%), each with four distinct 3 mm diameter wells, were divided into two groups of 50 by means of the Lawn technique; one group was inoculated with S. sanguis and the other with S. mutans. Four milligrams of each root canal sealer was placed in each of three wells in 10 plates (five plates of each inoculant); the fourth well was left empty as a control site. Plates were incubated at 37 degrees C and checked after 2, 7, and 14 days. All root canal sealers inhibited growth of both organisms. The inhibitory zones for S. sanguis were larger than inhibitory zones for S. mutans for all tested sealers, except Diaket. Dentinol, Kerr, and Tubliseal had significantly more inhibitory effect on S. sanguis than did other tested sealers (p less than 0.05). Diaket had superior inhibition on S. mutans.

Effects of methenamine on mouse lymphoma cells

Methenamine, (hexamethylenetetramine H) is a well tolerated drug used in the therapy of E. coli or herpes virus induced diseases. It is detectable in blood for many hours. H behaves similarly to salicylic acid, which has been known just as long, and also has a variety of target points independent of each other. In acid pH medium a dissociation of toxic disintegration products is suggested. During the cell cycle the intracellular pH in many cellular compartments shows a wide variation. Caused by the disintegration products H inhibits the proliferation of L 5178 Y cells and decreases the cell volume and size of the nucleus. Thus in the eukaryotic cell H can be therapeutically important and therefore may prove successful not only against bacteria and viruses.

[The characteristics of antibacterial root canal-filling materials]

The filling material of endomethasone Spad, N2, AH26, Diaket, Iod paste which are used in clinics often are evaluated from the point of view of their antibacterial effects to the microorganisms which are isolated from root canals. In the study, streptococcus were defined as the most often producing microorganisms in the canals. It was observed that, on the producing microorganisms, the most effective filling materials were spad and N2, following these were AH26, Diaket the less effective filling materials were endomenthasone and iod paste.

Subcutaneous reactions to implantation of tubes with AH26 and Grossman's sealer

Twenty-seven polyethylene tubes filled with either U of P brand of Grossman's sealer or silver-free AH26 (Dentinol) were implanted in the backs of seven young guinea pigs. Tissue reactions were studied histologically after 2 months and graded for inflammation and thickness of capsule. The surface of AH26 that was slightly convex or flush with the opening of the tube had a significantly thinner capsule than U of P. The latter also caused more inflammation. The more severe subcutaneous tissue reaction to the zinc oxide--eugenol type of sealer was probably due to the instability of the material, which slowly disintegrated in contact with tissue moisture. This process continuously liberated new foreign particles and prevented resolution of inflammation.

Comparison of in vivo antibacterial activity of hydro-alcoholic solutions of hexamidine and of chlorhexidine

Samples of cutaneous flora were obtained from the antecubital fossa of 20 healthy volunteers before and after treatment with hydro-alcoholic solutions of chlorhexidine (CHX) and of hexamidine (HXM). Percentage reductions in bacterial flora were statistically greater (p less than 0.001) after CHX (99 to 100%) than after HXM (about 70 to 90%). Furthermore, CHX had a smaller disturbing effect upon the natural balance of the bacterial population than HXM with a more rapid return towards the initial proportions of the different organisms one hr after treatment.

Immune responses induced by root canal cements containing synthetic polymers

Immunoglobulins G, A, M, and C3 were quantitated by the single radial immunodiffusion technique. The antibody response to AH26, Diaket A, and Tubliseal were also determined by the hemagglutination method using tannized erythrocytes. No increments of Ig and C3 were found by those methods and conditions under which the experiments were conducted.

An in vitro model for testing biocompatibility of endodontic materials to bone

Calvaria from 6-day old mice labelled 4 days previously with 45CaCl2 were divided into test and control halves and each half cultured separately in vitro. Eluents from four endodontic materials, endomethasone, zinc oxide/eugenol, AH26 and gutta-percha were added separately to the culture medium of each test half. After 24 and 48 h culturing periods, the 45CaCl2 in the media and calvaria was measured by a standard liquid scintillation counting technique and a resorption ratio between test and control halves was computed. This ratio, based on cell mediated resorption, was an indication of toxicity of soluble components of each endodontic material. In accordance with the literature, endomethasone was found, with our method, to be the most toxic and gutta-percha the least toxic of the materials tested. This shows that our model can be used to test the toxicity of other biomaterials to bone cells in vitro.

The effects of methenamine-hippurate upon urinary risk factors for renal stone formation

Among the various treatments for renal calcium stone disease, none has been documented to reduce urinary oxalate. Methenamine-hippurate (Hiprex) has been used extensively in the treatment of urinary tract infections and from micropuncture studies in the rat, using para-aminohippurate, it could be expected to reduce the renal secretion of oxalate. A daily dose of 3 g was given orally to 15 healthy subjects for 2 weeks. However, there was no net decrease in the urinary excretion of oxalate, but a risk index based on the urinary content of calcium, magnesium, oxalate, citrate and urine became reduced during treatment. The urinary inhibition of calcium oxalate crystal growth was unaffected. It is concluded that there may be a potential in methenamine-hippurate for the treatment of calcium stone disease, which can only be evaluated, however, by a clinical trial in stone patients.

[Mutagenicity of organic rubber additives]

The DNA-damaging activities of organic rubber additives such as rubber vulcanizing agents, vulcanization accelerators and rubber anti-oxidants were investigated by the rec-assay using spores of Bacillus subtilis strains H 17 and M 45. For metabolic activation, 9,000 X g supernatant solutions of the liver homogenate of Sprague-Dawley male rats previously treated with aroclor 1,254 were used. Spore rec-assays were carried out at the dose of 1 mg/disk, and the ratio of inhibition zones for M 45 to that for H 17 was calculated. Samples showing a ratio of more than 1.2 were judged positive. In order to know the DNA-damaging capacity of positive samples, the dose-response curves were prepared by carrying out the assays at various doses, and minimal inhibition concentration (MIC) for H 17 and M 45 was obtained from these curves by extrapolation. Then indices of DNA damagenicity were calculated through division of the MIC obtained with H 17 by that with M 45. The 0.005 micrograms/disk of mitomycin C and at 4 micrograms/disk of Trp-P1 were used as positive control, and the 50 micrograms/disk of kanamycin as negative control. The results obtained are as follows: Among 20 tested samples, p-quinone dioxime, bis-morpholine disulfide used as rubber vulcanizing agents and hexamethylenetetramine, zinc butylxanthate used as vulcanization accelerators gave positive results. It was considered that the action of hexamethylenetetramine against DNA was due to the electrophilic state of this material. Furthermore, we supposed that DNA-damaging activity of p-quinone dioxime was concerned with free hydroxyl groups of this compound.(ABSTRACT TRUNCATED AT 250 WORDS)

The antibacterial activity of hexamine (methenamine), hexamine hippurate and hexamine mandelate

The antibacterial activity of hexamine and two of its organic acid salts was compared by continuous turbidimetric monitoring of static cultures exposed to the drugs and in an in vitro model of the treatment of bacterial cystitis. At pH 5.5, concentrations of 32 to 125 mg hexamine per 1 caused some inhibition of bacterial growth, but 250 to 500 mg/l were needed to suppress growth overnight. Hexamine hippurate was found to be less active than hexamine itself, whereas hexamine mandelate was as active as the parent compound. The antibacterial effect was not inoculum dependent over the range 10(6) to 10(8) bacteria per ml, but the activity observed in pooled urine was rather less than that found in broth at the same pH. When a dense bacterial culture was exposed to changing concentrations of hexamine compounds in the bladder model, a 1 g dose infused over a 12-hour period suppressed bacterial growth for 16 to 20 hours. No systematic difference was found in the activity of the three hexamine compounds, but a similar effect was achieved by a very much lower concentration of ampicillin.

Antimicrobial susceptibility of Ureaplasma urealyticum

An antimicrobial susceptibility test, a tow-tube broth dilution and disk elution method for Ureaplasma urealyticum, was modified to incorporate some of the standard procedures followed in traditional antimicrobial testing. The susceptibility pattern of the species was reevaluated by determining the effect of various antimicrobial agents on 21 vaginal isolates. All isolates were inhibited by tetracycline congeners (1 to 6 micrograms/ml) and killed by methenamine mandelate (0.6 mg/ml). All but one isolates were inhibited by erythromycin (0.4 to 3 micrograms/ml). Only eight isolates were inhibited by nalidixic acid (1 to 6 micrograms/ml), and seven were inhibited by nitrofurantoin (20 to 60 micrograms/ml), whereas all isolates were resistant to rifampin (1 microgram/ml) and trimethoprim-sulfamethoxazole (5 micrograms/ml). The in vitro technique described can readily be performed on individual patient isolates before the initiation of antimicrobial therapy.

Interfacial tensions in healthy and atherosclerotic rabbit aortae. Higher values and lesion surfaces

Interfacial tensions at the saline/arterial wall interface were determined by measuring contact angles between various test fluid droplets and the walls of rabbit aortae immersed in physiological saline. These contact angles and the interfacial tensions of the test fluid/bathing fluid interface (measured by the Du Noüy ring method) were converted to saline/arterial wall interfacial tensions by applying Neumann's equation of state. Four diseased animals, fed an atherogenic diet for 6-8 weeks and 6 controls formed the experimental group. A significantly higher interfacial tension (P < 0.001), was determined for lesion surfaces in atherosclerotic arteries (0.36 +/- 0.08 (SEM) mM . M-1, n = 13) compared to both the surrounding undisturbed regions (0.035 +/- 0.01 mN . m-1, n = 14) and the intact surface of control vessels (0.060 +/- mN . m-1, n = 48). This increase may reflect a change in the strength of hydrophilic interactions associated with the lesion surface in atherogenesis.