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PubMed1976

Effect of inhaling medication vapors from a colds preparation on murine pulmonary bacterial defense systems.

The usefulness of murine pulmonary defense systems as a means for assessing potential toxicity was further confirmed. Recent investigations had indicated that the effects of a chemical agent on mucociliary transport and phagocytic function comprised a sensitive indicator. As one example of such an application, because of the wide usage of proprietary colds preparations containing volatile oils, as well as the use of such oils in various industries, it is important to reassess the potential of such preparations for toxicity when new test systems become available. Mice and rats were exposed to vapors of camphor, menthol, eucalyptol, and turpentine, as contained in a commonly used colds preparation, for 4 and 8 hr prior to challenge with aerosols of radiolabeled Staphylococcus aureus. The exposure system simulated conditions present when the colds preparation is vaporized according to directions for use. Rates of pulmonary bacterial transport and inactivation, as well as of phagocytic ingestion, were determined following exposure to the colds preparation. Each of these rates was unchanged by the treatment. Thus, in this biological system exposure to therapeutic levels of the colds preparation did not impair mucociliary or phagocytic function.

Animals↗
PubMed2006

Antiproliferative activities of parthenolide and golden feverfew extract against three human cancer cell lines.

The medicinal herb feverfew [Tanacetum parthenium (L.) Schultz-Bip.] has long been used as a folk remedy for the treatment of migraine and arthritis. Parthenolide, a sesquiterpene lactone, is considered to be the primary bioactive compound in feverfew having anti-migraine, anti-tumor, and anti-inflammatory properties. In this study we determined, through in vitro bioassays, the inhibitory activity of parthenolide and golden feverfew extract against two human breast cancer cell lines (Hs605T and MCF-7) and one human cervical cancer cell line (SiHa). Feverfew ethanolic extract inhibited the growth of all three types of cancer cells with a half-effective concentration (EC50) of 1.5 mg/mL against Hs605T, 2.1 mg/mL against MCF-7, and 0.6 mg/mL against SiHa. Among the tested constituents of feverfew (i.e., parthenolide, camphor, luteolin, and apigenin), parthenolide showed the highest inhibitory effect with an EC50 against Hs605T, MCF-7, and SiHa of 2.6 microg/mL, 2.8 microg/mL, and 2.7 microg/mL, respectively. Interactions between parthenolide and flavonoids (apigenin and luteolin) in feverfew extract also were investigated to elucidate possible synergistic or antagonistic effects. The results revealed that apigenin and luteolin might have moderate to weak synergistic effects with parthenolide on the inhibition of cancer cell growth of Hs605T, MCF-7, and SiHa.

Anti-Inflammatory Agents, Non-Steroidal↗
PubMed1991

A three-dimensional molecular template for substrates of human cytochrome P450 involved in debrisoquine 4-hydroxylation.

A three-dimensional molecular template has been generated for substrates of human debrisoquine 4-hydroxylase cytochrome P450 (CYP2D6). This template defines the stereochemical requirements for CYP2D6 substrates in terms of the volume occupied and positions of key atoms. The modelling was based on the X-ray crystallographic coordinates of the location of the attacked C5 atom of camphor in relation to the haem in cytochrome P450 cam. Interactive molecular graphics combined with energy calculations were used to identify allowed conformers to superpose known CYP2D6 substrates to yield a molecular template. This model takes into account the site of attack of the known substrates and the requirement for a protonated nitrogen atom to interact with an anion site of the protein. A nitrogen-anion distance of between 2.5 and 4.5 A was allowed for the interaction. The substrates modelled were cardiovascular drugs (debrisoquine, sparteine, guanoxan and perhexiline), beta-adrenergic blocking agents (bufuralol and propranolol), tricyclic anti-depressants (desipramine, amitriptyline and nortriptyline) and other miscellaneous compounds (phenformin, methoxy-amphetamine, codeine and dextromethorphan). The template generated in this manner was then used to determine the likelihood that certain other compounds were substrates for CYP2D6. A carcinogenic protein pyrolysate product, 2-amino-1-methyl-6-phenylimidazo[4,5-b]pyridine (PhIP), did not fit the template and is therefore unlikely to be activated by this enzyme. A potent carcinogen in tobacco smoke, 4-(N-methyl-N-nitrosamino)-1-(3-pyridyl)-1-butanone (NNK), fitted the template but could not be modelled to form a favourable nitrogen-anion interaction. Experimental substrate competition studies also showed that NNK is unlikely to be a CYP2D6 substrate. It was also shown that the widely used drug for treatment of breast cancer, trans-1-(4-beta-dimethylaminoethoxyphenyl)-,2-diphenyl-1-ene (tamoxifen), did not fit the molecular template and is unlikely to be metabolized by CYP2D6. Coordinates of the template are available.

Camphor↗
PubMed1997

Rapid classical conditioning of odor response in a physiological model for olfactory research, the tiger salamander.

In recent years there have been a number of important advances in the understanding of cellular mechanisms related to olfactory function. Hypotheses regarding the complex relationships among odorant structure, physiological activity and behavioral outcome generated by these findings, however, remain largely untested due to a paucity of psychophysical data on stimulus discrimination in the same experimental species. Comparisons between behavioral and physiological responses are essential for elucidating the critical aspects of stimulus coding in sensory systems. We have developed a method for generating psychophysical data in one of the primary model species used in olfactory research, the tiger salamander, Ambystoma tigrinum. These psychophysical experiments are carried out under the same conditions as physiological experiments in our laboratory. Using classical conditioning, individual salamanders are trained over a period of 2-3 h to show skin potential responses to odor and not air. Failure to train using backward pairing demonstrates that the response is not due to sensitization or pseudoconditioning. The conditioned response is mediated by the olfactory pathway, as it is blocked by olfactory nerve section. We show that salamanders detect three odorants that are commonly used stimuli in physiological experiments (butyl alcohol, butyl acetate and amyl acetate), but cannot detect a fourth common experimental odorant, camphor. This method should be a powerful tool for studying olfactory information processing by providing data on discriminability of stimuli used in salamander physiological studies.

Acetates↗
PubMed2001

Adrenodoxin-cytochrome P450scc interaction as revealed by EPR spectroscopy: comparison with the putidaredoxin-cytochrome P450cam system.

The cholesterol side-chain cleavage reaction catalyzed by cytochrome P450scc comprises three consecutive monooxygenase reactions (22R-hydroxylation, 20S-hydroxylation, and C(20)-C(22) bond scission) that produces pregnenolone. The electron equivalents necessary for the oxygen activation are supplied from a 2Fe-2S type ferredoxin, adrenodoxin. We found that 1:1 stoichiometric binding of oxidized adrenodoxin to oxidized cytochrome P450scc complexed with cholesterol or 25-hydroxycholesterol caused shifts of the high-spin EPR signals of the heme moiety at 5 K. Such shifts were not observed for the low-spin EPR signals. Ligation of CO or NO to the reduced heme of cytochrome P450scc complexed with reduced adrenodoxin and various steroid substrates did not cause any change in the axial EPR spectrum of the reduced iron-sulfur center at 77 K. These results are in remarkable contrast to those obtained for the cytochrome P450cam-d-camphor-putidaredoxin ternary complex, suggesting that the mode of cross talk between adrenodoxin and cytochrome P450scc is very different from that in the Pseudomonas system. The difference may be primarily due to the location of the charged amino acid residues of the ferredoxins important for the interaction with the partner cytochrome P450.

Adrenal Cortex↗
PubMed2000

Protein engineering of cytochrome p450(cam) (CYP101) for the oxidation of polycyclic aromatic hydrocarbons.

Mutations of the active site residues F87 and Y96 greatly enhanced the activity of cytochrome P450(cam) (CYP101) from Pseudomonas putida for the oxidation of the polycyclic aromatic hydrocarbons phenanthrene, fluoranthene, pyrene and benzo[a]pyrene. Wild-type P450(cam) had low (<0.01 min(-1)) activity with these substrates. Phenanthrene was oxidized to 1-, 2-, 3- and 4-phenanthrol, while fluoranthene gave mainly 3-fluoranthol. Pyrene was oxidized to 1-pyrenol and then to 1,6- and 1,8-pyrenequinone, with small amounts of 2-pyrenol also formed with the Y96A mutant. Benzo[a]pyrene gave 3-hydroxybenzo[a]pyrene as the major product. The NADH oxidation rate of the mutants with phenanthrene was as high as 374 min(-1), which was 31% of the camphor oxidation rate by wild-type P450(cam), and with fluoranthene the fastest rate was 144 min(-1). The oxidation of phenanthrene and fluoranthene were highly uncoupled, with highest couplings of 1.3 and 3.1%, respectively. The highest coupling efficiency for pyrene oxidation was a reasonable 23%, but the NADH turnover rate was slow. The product distributions varied significantly between mutants, suggesting that substrate binding orientations can be manipulated by protein engineering, and that genetic variants of P450(cam) may be useful for studying the oxidation of polycyclic aromatic hydrocarbons by P450 enzymes.

Amino Acid Substitution↗
PubMed1994

Comparison of the construction of a 3-D model for human thromboxane synthase using P450cam and BM-3 as templates: implications for the substrate binding pocket.

A 3-D model of human thromboxane A2 synthase (TXAS) was constructed using a homology modeling approach based on information from the 2.0 A crystal structure of the hemoprotein domains of cytochrome P450BM-3 and P450cam. P450BM-3 is a bacterial fatty acid monooxygenase resembling eukaryotic microsomal cytochrome P450s in primary structure and function. TXAS shares 26.4% residue identity and 48.4% residue similarity with the P450BM-3 hemoprotein domain. The homology score between TXAS and P450BM-3 is much higher than that between TXAS and P450cam. Alignment between TXAS and the P450BM-3 hemoprotein domain or P450cam was determined through sequence searches. The P450BM-3 or P450cam main-chain coordinates were applied to the TXAS main chain in those segments where the two sequences were well aligned. These segments were linked to one another using a fragment search method, and the side chains were added to produce a 3-D model for TXAS. A TXAS substrate, prostaglandin H2 (PGH2) was docked into the TXAS cavity corresponding to the arachidonic acid binding pocket in P450BM-3 or camphor binding site in P450cam. Regions of the heme and putative PGH2 binding cavities in the TXAS model were identified and analyzed. The segments and residues involved in the active-site pocket of the TXAS model provide reasonable candidates for TXAS protein engineering and inhibitor design. Comparison of the TXAS model based on P450BM-3 with another TXAS model based on the P450cam structure indicated that P450BM-3 is a more suitable template for homology modeling of TXAS.

Amino Acid Sequence↗
PubMed2006

Cytochrome P450 active site plasticity: attenuation of imidazole binding in cytochrome P450(cam) by an L244A mutation.

We have identified a P450(cam) mutation, L244A, that mitigates the affinity for imidazole and substituted imidazoles while maintaining a high affinity for the natural substrate camphor. The P450(cam) L244A crystal structure solved in the absence of any ligand reveals that the I-helix is displaced inwards by over 1 A in response to the cavity created by the change from leucine to alanine. Furthermore, the crystal structures of imidazole-bound P450(cam) and the 1-methylimidazole-bound P450(cam) L244A mutant reveal that the ligands have distinct binding modes in the two proteins. Whereas in wild-type P450(cam) the imidazole coordinates to the iron in an orientation roughly perpendicular to the plane of the heme, in the L244A mutant the rearranged I helix, and specifically residue Val247, forces the imidazole into an orientation almost parallel to the heme that impairs its ability to coordinate to the heme iron. As a result, the imidazole is much more weakly bound to the mutant than it is to the wild-type enzyme. Despite the constriction of the active site by the mutation, previous work with the L244A mutant has shown that it oxidizes larger substrates than the wild-type enzyme. This paradoxical situation, in which a mutation that nominally increases the active site cavity appears to decrease it, suggests that the mutation actually increases the active site maleability, allowing it to better expand to oxidize larger substrates.

Amino Acid Substitution↗
PubMed1992

Cytochrome P450cam: crystallography, oxygen activation, and electron transfer.

Several crystal structures of various substrate and inhibited complexes of the camphor monoxygenase, cytochrome P450cam from Pseudomonas putida, are now available. These structures, together with mutagenesis, biochemical, and biophysical studies, have allowed for a detailed penetration into the problem of how P450s activate molecular oxygen, control stereoselectivity, and transfer electrons. This review will provide a summary of the crystallographic work in light of what these structures have taught us about P450 function.

Amino Acid Sequence↗
PubMed2001

Effect of sodium hypochlorite and five intracanal medications on Candida albicans in root canals.

The aim of this study was to evaluate the effect of 1% sodium hypochlorite and five intracanals medications on Candida albicans harvested inside root canals. The contaminated canals were irrigated with sterile saline solution and then treated as follows: (i) filled with Calen paste (calcium hydroxide/ glycol polyethylene paste); (ii) filled with camphorated paramonochloro phenol (CPMC); (iii) filled with 2% iodine-iodate solution; (iv) filled with tricresol formalin; (v) filled with Calen and CPMC pastes; (vi) irrigation with 1% sodium hypochlorite and filled with no intracanal medication; and (vii) no intracanal medication was used. Canal access and the apical foramen were then sealed with Cavit and the roots were stored in a humid chamber at 37 +/- 1 degree C for 14 days. The canals were reinstrumented and irrigated with sterile saline solution. Sterile paper points were used to transfer the root canal contents to test tubes containing sterile saline solution. Part of the suspension was harvested in Sabouraud dextrose agar with chloramphenicol and incubated at 37 +/- 1 degree C for 48 h. CPMC was effective in 100% of the samples followed in decreasing order of effectiveness by calcium hydroxide with CPMC (70% effective), 1% sodium hypochlorite (70% effective) (p < 0.05), tricresol formalin (60% effective), 2% iodine-iodate solution (50% effective), calcium hydroxide paste (30% effective), and saline + no intracanal medication.

Anti-Infective Agents, Local↗
PubMed2001

Prevention of the ingress of a known virulent bacterium into the root canal system by intracanal medications.

Contamination of the root canal system by persistent, enteric bacteria via leakage through interim restorations has been well documented. This in vitro study evaluated the ability of interappointment medications to prevent contamination of the root canal system by Enterococcus faecalis. Coronally unsealed, medicated tooth roots fixed in a closed system were contaminated daily with a standardized, aerobic, broth culture of E. faecalis. Four medications were evaluated (n = 15): group A, calcium hydroxide/methylcellulose paste; group B, camphorated parachlorophenol/calcium hydroxide paste; group C, 1% chlorhexidine/methylcellulose gel; and group D, calcium hydroxide points. The mean number of days to contamination as indicated by turbidity in the closed system was the following: group A, 37; group B, 46; group C, 16; group D, 5; and a positive control (no medication), 3. A one-way analysis of variance with a Scheffe post hoc test (p = 0.05) detected significant differences in effectiveness with A and B superior to C and D, and C superior to D.

Analysis of Variance↗
PubMed1990

On the bacterial cell cycle: Escherichia coli mutants with altered ploidy.

We describe a scheme for isolation of new classes of mutants in the cell cycle of Escherichia coli. The mutants were selected as resistant to camphor vapors, which results in increased ploidy, and were subsequently screened for an increase in cell density and an increase in the gene dosage of the lac operon. Our mutations are located at four different places in the chromosome; we have named these loci mbr (moth ball resistant). mbrA maps to 68 min on the E. coli chromosome, mbrB to 88.5 min, mbrC to 89.5 min, and mbrD to 90 min. mbrD mutations may be alleles of rpoB (a subunit of RNA polymerase). In addition to the selected or screened phenotypes, most of the mutants fail to grow on rich media or at high temperatures. We have examined the nine mutants under nonpermissive conditions, using several techniques to determine the cause of death. We have also coupled our mutations with lesions in dnaA, which is required for cell-cycle-specific DNA replication, and rnh (the gene for RNase H), which is required for specificity in the DNA initiation reaction, and determined the effects of the double and triple mutants under permissive and nonpermissive conditions. These tests have shown that bacteria mutated at mbrA do not tolerate a null mutation in rnh, indicating that they are dependent on DNA replication initiating at oriC. In contrast, mutations at mbrB, mbrC, and mbrD exhibit their phenotypes independent of oriC initiation of DNA replication, suggesting that the mutations affect factors that influence the DNA/cell ratio regardless of the origin of DNA replication. Based on our results, the mbr mutations appear to have defects in cell-cycle timing and/or defects in chromosomal partitioning.

Camphor↗
PubMed2005

Production and X-ray crystallographic analysis of fully deuterated cytochrome P450cam.

Neutron protein crystallography allows H-atom positions to be located in biological structures at the relatively modest resolution of 1.5-2.0 A. A difficulty of this technique arises from the incoherent scattering from hydrogen, which considerably reduces the signal-to-noise ratio of the data. This can be overcome by preparing fully deuterated samples. Efficient protocols for routine and low-cost production of in vivo deuterium-enriched proteins have been developed. Here, the overexpression and crystallization of highly (>99%) deuterium-enriched cytochrome P450cam for neutron analysis is reported. Cytochrome P450cam from Pseudomonas putida catalyses the hydroxylation of camphor from haem-bound molecular O(2) via a mechanism that is thought to involve a proton-shuttle pathway to the active site. Since H atoms cannot be visualized in available X-ray structures, neutron diffraction is being used to determine the protonation states and water structure at the active site of the enzyme. Analysis of both hydrogenated and perdeuterated P450cam showed no significant changes between the X-ray structures determined at 1.4 and 1.7 A, respectively. This work demonstrates that the fully deuterated protein is highly isomorphous with the native (hydrogenated) protein and is appropriate for neutron protein crystallographic analysis.

Camphor 5-Monooxygenase↗
PubMed1998

An improved procedure for the preparation of X-ray diffraction-quality crystals of cytochrome p450cam.

A procedure for the crystallization of recombinant cytochrome P450cam has been developed which avoids the difficulties inherent in the glass-capillary free-interface diffusion method reported previously. The surface mutation, Cys334-->Ala (C334A), originally designed to prevent dimer formation and thus improve routine handling of the enzyme, facilitates crystallization by the hanging-drop vapour-diffusion technique. Crystals of (C334A)P450cam grow within 48 h and diffract to beyond 1.2 A at 100 K in-house on a Siemens multiwire area detector. Data have been collected from the camphor-bound form to 1.35 A.

Alanine↗
PubMed2004

In vitro evaluation of the effectiveness of irrigants and intracanal medicaments on microorganisms within root canals.

AIM: To evaluate in vitro the effectiveness of sodium hypochlorite (NaOCl), chlorhexidine (CHX) and five intracanal medicaments on microorganisms within root canals. METHODOLOGY: Ninety-six human single-rooted extracted teeth were used. After removing the crowns, canal preparation was completed and the external root surfaces were coated with epoxy resin. Following sterilization, the teeth were contaminated with Candida albicans and Enterococcus faecalis, and were incubated at 37 +/- 1 degrees C for 7 days. The teeth were divided according to the irrigant solution or intracanal medicament: group 1, sterile physiologic solution (SPS) and calcium hydroxide (Ca(OH)2) paste; group 2, SPS and camphorated paramonochlorophenol (CPMC); group 3, SPS and tricresol formalin; group 4, SPS and CaOH2 + CPMC paste; group 5, SPS and PMC furacin; group 6, 2.5% NaOCl without intracanal medication; group 7, 2.0% CHX without intracanal medication and group 8, SPS without intracanal medication (control group). Microbiological samples were collected with sterile paper points, and bacterial growth was determined. The data were submitted to the analysis of variance (anova, P = 0.05). RESULTS: For C. albicans, groups 3 and 8 were statistically less effective than groups 1, 2, 4 and 5 (Kruskal-Wallis (K-W) = 65.241; gl = 7; P = 0.001). For E. faecalis, groups 6 and 8 were statistically less effective than groups 1-4 and 7 (K-W = 61.048; gl = 7; P = 0.001). CONCLUSIONS: Ca(OH)2 + CPMC paste was the most effective intracanal medicament for the elimination of the two microorganisms; 2.0% CHX solution was more effective than 2.5% NaOCl against E. faecalis.

Calcium Hydroxide↗
PubMed1987

The effect of aromatics on inspiratory and expiratory nasal resistance to airflow.

Unilateral inspiratory and expiratory nasal resistance to airflow were measured in 35 subjects using active anterior rhinomanometry. No significant difference was found between inspiratory and expiratory resistance. Inhalation of a mixture of aromatics, camphor, menthol, oil of pine needles and methyl salicylate had no effect on inspiratory or expiratory nasal resistance. Factors influencing inspiratory and expiratory resistance and the actions of aromatics are discussed.

Adult↗
PubMed1992

Microbiological evaluation of the efficacy of chlorhexidine in a sustained-release device for dentine sterilization.

The aim of this in-vitro study was to evaluate the effect of chlorhexidine in solution and in a sustained-release device as an intracanal medication. Hollow cylindrical dentine specimens prepared from bovine incisors were incubated with Streptococcus faecalis for a period of 3 weeks. The intracanal medicaments tested were 0.2% chlorhexidine gluconate solution (CH), chlorhexidine in a sustained-release device (1.2 mg) (SBD), camphorated paramonochlorophenol (CMCP), and a control (no medication). Each medicament was introduced into the lumen of one dentine specimen and incubated for 5 min, 24 h, 48 h or 7 days at 37 degrees C. The bacteriological samples were taken by shaving the dentine inside the lumen with dental burs ranging in size from ISO 023-033. The dentine powder was collected in test-tubes containing growth medium and incubated for 24 h. The optical density of the medium was recorded by means of a spectrophotometer at a wavelength of 540 nm. There was a statistically significant difference between the control group and all the medicaments tested.

Animals↗
PubMed1990

Effect of the tyrosine 96 hydrogen bond on the inactivation of cytochrome P-450cam induced by hydrostatic pressure.

The effects of removal of the tyrosine 96 hydrogen bond on the stability and conformational events of cytochrome P-450cam are presented in this communication. Hydrostatic pressure has been used as a tool to perturbe the structure leading to the formation of cytochrome P-420, an inactivated but soluble and undenatured form of the enzyme. We show that the spin transition of cytochrome P-450cam, which is known to be influenced by hydrostatic pressure, is affected by this single mutation. The free energy of stabilisation of native substrate-free cytochrome P-450cam is not affected by the removal of the tyrosine 96 hydrogen bond via mutagenesis to phenylalanine, whereas the substrate-bound protein shows a difference of 21 kJ/mol. These results, as well as an observed 110 ml/mol difference for the volume of the inactivation reaction between substrate-bound native and mutant proteins, have been interpreted in terms of a more hydrated heme pocket for the site-directed mutant at position 96 compared to the wild-type protein where camphor is tightly bound via the tyrosine 96 hydrogen bond and water excluded from the active site.

Camphor↗