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Abstract
The prediction of the biological activity of chemical compounds by means of mathematical models is discussed. Biological activity of chemicals, including their toxicity on man and other biological organisms and systems, involves too complex phenomena to presently be predictable by fundamental models such as ab initio quantum mechanical models or statistical mechanical models. Hence one takes recourse to semi-empirical and empirical models which relate the variation in chemical structure of chemical compounds to the variation in their measured biological activity, e.g. toxicity in one or several test systems. These models are "calibrated" on series of similar compounds with "known" toxicity, the training set. Thereafter the models can--in fortunate cases--be used to predict the toxicity of compounds which are structurally similar to the training set compounds. The formulation and applicability of semi-empirical and empirical models relating chemical structure to biological activity is discussed. Causes and remedies for commonly encountered fallacies are presented.
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2
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Abstract
One of the most serious problems in three-dimensional quantitative structure-activity relationship (3D-QSAR) studies is selection of an alignment rule for molecular super position of the compounds in the data set. In 3D-QSAR analyses of structure-activity data, a reference compound in a defined conformation is chosen, and all structures in the data set are aligned with the reference in a pairwise manner. In subsequent steps, conformation/alignment-dependent descriptors are computed for the compounds and compared to those of the reference. This approach gives much weight to the arbitrarily chosen reference molecule and can introduce a bias in the results. Here an alternative, and more general, approach to molecular alignment is presented that is based on Generalized Procrustes Analysis (GPA). The result is a consensus alignment that uses all molecules in the data set and avoids the bias introduced in the pairwise alignment strategy.
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Affiliation(s)
- P M Kroonenberg
- Department of Education, Leiden University, Wassenaarseweg 52, 2333 AK Leiden, The Netherlands
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3
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Dunn WJ, Koehler M, Stalling DL, Schwartz TR. Relationship between gas chromatographic retention of polychlorinated dibenzofurans and calculated molecular surface area. Anal Chem 2002. [DOI: 10.1021/ac00121a051] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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4
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Dunn WJ, Stalling DL, Schwartz TR, Hogan JW, Petty JD, Johansson E, Wold S. Pattern recognition for classification and determination of polychlorinated biphenyls in environmental samples. Anal Chem 2002. [DOI: 10.1021/ac00272a026] [Citation(s) in RCA: 68] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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5
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Dunn WJ, Nagy PI, Collantes ER. A computer-assisted method for estimation of the partition coefficient. Monte Carlo simulations of the chloroform/water log P for methylamine, methanol, and acetonitrile. J Am Chem Soc 2002. [DOI: 10.1021/ja00021a012] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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Dunn WJ, Söderholm KJ. Comparison of shear and flexural bond strength tests versus failure modes of dentin bonding systems. Am J Dent 2001; 14:297-303. [PMID: 11803994] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Subscribe] [Scholar Register] [Indexed: 02/23/2023]
Abstract
PURPOSE To (1) measure the shear and flexural bond strengths of three different bonding agents that use different application techniques, (2) determine whether the shear and flexural bond tests rank the three materials similarly, and (3) determine whether the fractured surface produced with the flexural test, facilitates studies of failures within the adhesive interphase region. MATERIALS AND METHODS Scotchbond MP (SBMP), Single Bond (SNGB) and Clearfil SE (CLSE) were evaluated. For each material, 16 samples were bonded. Eight of these samples were bonded for shear testing and the other 8 samples for flexural bond strength testing. After the bonding was completed, all samples were stored in water at 37 degrees C for 30 days. Shear bond strength was measured using an orthodontic edge wire loop and flexural strength was measured using a 4-point bending device. The samples used for the flexural test consisted of 3 mm x 3 mm x 20 mm beams in which center a 1 mm thick dentin wafer had been bonded perpendicularly to the length of the beam. An indentation with a microhardness tester was placed at one of the dentin-composite interfaces to serve as an induced flaw. This flaw was placed on the surface in tension during flexural testing. The data were analyzed using ANOVA. Scanning electron microscopy was used to examine each specimen and assign its failure mode. Percent occurrence of failure mode was determined for each material and overall for both test methods. When there was uncertainty regarding failure location, electron dispersive spectroscopy x-ray analysis was used to identify elements present on the fractured surface. RESULTS No significant difference (P > 0.05) in bond strength was observed within each test group, while significant differences (P < 0.05) existed between the two test methods (shear: SBMP = 21.2 +/- 4.0 MPa, SNGB= 24.3 +/- 4.7 MPa, CLSE= 24.6 +/- 4.4 MPa; flexural strength: SBMP= 34.6 +/- 9.3 MPa, SNGB = 31.9 +/- 6.9 MPa, CLSE= 34.3 +/- 4.7 MPa). Shear bond test specimens failed mostly within dentin (54.2%), followed by failures within the adhesive interphase (41.6%), and failures in composite (4.2%). Flexural strength specimens failed mostly within the adhesive interphase (83.3%), followed by failure in composite (16.7%). Bond strengths were similar for all three adhesive systems within each test method group. Failure mode analysis revealed significant differences (P < 0.0001) among the two test methods.
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Affiliation(s)
- W J Dunn
- Dept of Dental Biomaterials, College of Dentistry, University of Florida, Gainesville 32610-0446, USA
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Xu W, Huang LF, Bauer L, Bhargava HN, Dunn WJ. Synthesis and opiate receptor binding properties of 17-methyl-6,7-dehydro-3,14-dihydroxy-4,5alpha-epoxy-6,7:4',5'-pyrimidin omorphinans. Bioorg Med Chem Lett 1999; 9:3375-80. [PMID: 10612602 DOI: 10.1016/s0960-894x(99)00608-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
A class of opioid receptor active derivatives of oxymorphone has been synthesized using a common enaminone intermediate. The derivatives have heterocyclic groups fused to the 6,7-positions of the morphinan system and all were synthesized in high yield. A pyrazolo derivative is an agonist for the mu and delta receptors and an antagonist for the kappa receptor.
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Affiliation(s)
- W Xu
- College of Pharmacy, University of Illinois at Chicago, 60612-7231, USA
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Bhargava HN, Zhao GM, Bian JT, Nan Y, Upadhyaya SP, Xu W, Dunn WJ, Bauer L. Effects of some 7-arylidene and 7-heteroarylidene morphinan-6-ones on the antinociceptive activity of [D-Pen2, D-Pen5]enkephalin and [D-Ala2, Glu4]deltorphin II and on multiple opioid receptors. Peptides 1997; 18:695-701. [PMID: 9213363 DOI: 10.1016/s0196-9781(97)00121-6] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
The in vivo and functional effects of several 7-arylidene and 7-heteroarylidene morphinan-6-ones were determined at the mu-, delta-, and kappa-opioid receptors using the guinea pig brain membranes, guinea pig ileum (GPI), and mouse vas deferens (MVD). In vivo effects included the antagonism by these compounds given subcutaneously on the antinociceptive actions of intracerebroventricularly injected [D-Pen2, D-Pen5]enkephalin (DPDPE) and [D-Ala2, Glu4]deltorphin II (deltorphin II), the highly selective putative delta 1- and delta 2-opioid receptor agonists. Finally, the partition coefficients of these compounds were estimated (CLOGP) and determined experimentally at pH 7.4 in the 1-octanol/water system. Compared with E-7-benzylidenenaltrexone (BNTX), most compounds except for E-7-(4-chlorobenzylidene)naltrexone, were more potent at delta-opioid receptors than at the mu-opioid receptor, whereas, in comparison to the kappa-opioid receptor, the activities of the E-7-arylidene or E-7-heteroarylidene naltrexone derivatives at the delta-receptor were in the following order, where the 7-substituents were: 4-fluorobenzylidene- > benzylidene > 3-pyridylmethylene- > 4-pyridylmethylene- > 1-methyl-2-imidazolylmethylene > 4-chlorobenzylidene. In the MVD preparation, the potencies at the delta-opioid receptor, in comparison to BNTX, were in the following order, where the 7-substituents were: benzylidene = 1-methyl-2-imidazolylmethylene- > 4-fluorobenzylidene- = 3-pyridylmethylene- = 4-pyridylmethylene-. All compounds antagonized delta 1, and delta 2-opioid receptor agonist-induced analgesia. The antagonist potencies at the delta 1-opioid receptor were in the following order, where the 7-substituents were: benzylidene- > 4-chlorobenzylidene- > 4-fluorobenzylidene- > 3-pyridylmethylene- > 1-methyl-2-imidazolymethylene- approximately 4-pyridylmethylene-, whereas at the delta 2-opioid receptor, the order was benzylidene- > 4-chlorobenzylidene- > 4-fluorobenzylidene- > 3-pyridylmethylene- > 1-methyl-2-imidazolymethylene- > 4-pyridylmethylene. In general, all compounds exhibited greater potency at the delta 2- than delta 1-opioid receptor. The computed partition coefficients were, as expected, greater than the apparent log P values, which were determined experimentally. Generally, the lipophilicity values in decreasing order were: 4-chlorobenzylidene- > 4-fluorobenzylidene- > benzylidene > 3-pyridylmethylene- = 4-pyridylmethylene- > 1-methyl-2-imidazolylmethylene-. In general, the benzylidene and 4-pyridylmethylene derivatives, which have medium lipophilicities, were equally effective at the delta 1- and delta 2-receptors; the 3-pyridylmethylene and 1-methyl-2-imidazolylmethylene derivatives had lower lipophilicities and were more selective for the delta 2- than delta 1-receptor; the 4-chlorobenzylidene and 4-fluorobenzylidene derivatives were more lipophilic and had intermediate activity. The plot of pED50 values for the in vivo tests for the delta 1- and delta 2-receptors showed that the two receptors are not independent with respect to this series of compounds.
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Affiliation(s)
- H N Bhargava
- Department of Pharmaceutics and Pharmacodynamics, University of Illinois at Chicago 60612, USA.
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Dunn WJ, Hopfinger AJ, Catana C, Duraiswami C. Solution of the conformation and alignment tensors for the binding of trimethoprim and its analogs to dihydrofolate reductase: 3D-quantitative structure-activity relationship study using molecular shape analysis, 3-way partial least-squares regression, and 3-way factor analysis. J Med Chem 1996; 39:4825-32. [PMID: 8941396 DOI: 10.1021/jm960491r] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Molecular recognition is the basis of rational drug design, and for this reason it has been extensively studied. However, the process by which a ligand recognizes and binds to its receptor is complex and not well understood. For the case in which the geometries (conformation and alignment) of the ligand and receptor are known from X-ray crystal structure data, the problem is simplified. The receptor-bound conformation and alignment of the ligand is assumed, and those of additional ligands are inferred. For the general case in which the geometries of the ligand(s) and receptor are unknown, no general treatment or solution is available and receptor-ligand geometries must be obtained indirectly from structure-activity studies or synthesis and evaluation of rigid analogs. A general treatment for solving for the receptor-bound geometry of a series of ligands is presented here. Using molecular shape analysis, for ligand description, tensor analysis of N-way arrays by partial least-squares (PLS) regression, and 3-way factor analysis, the receptor-bound geometries of trimethoprim and a series of trimethoprim-like dihydrofolate reductase inhibitors are correctly predicted.
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Affiliation(s)
- W J Dunn
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago 60612, USA
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11
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Abstract
PURPOSE The importance of dentofacial attractiveness to the psychosocial well-being of an individual has been well established. Very little information is available regarding dental patient perceptions of a pleasing esthetic image. The purpose of this study was to identify factors distinctive to attractive smiles versus unattractive smiles, as perceived by patients. MATERIALS AND METHODS Standardized format photographs (5 x 7 in, matte finish, at f-32 and 1:2 magnification) of eight male and eight female smiles, framing only lips and teeth, were viewed by 297 subjects. The smiles exhibited differences in symmetry, tooth shade, number of teeth displayed, and height of maxillary lip line, and included both restored and unrestored teeth. Respondents ranked the photographs in order from most to least appealing appearance. Respondents viewed each series of photographs in a similar lighting and time period. A questionnaire identified the respondent's age, sex, race, education, income, and home town. Twenty-five demographic groups were established from the information in the questionnaire. Data were analyzed using stepwise discriminant analysis to determine the combination of smile characteristics that best predicted the ranking. RESULTS The same female smile was chosen as the most attractive by 24 of the 25 demographic groups. This smile is characterized by natural teeth having light shade, high lip line, a large display of teeth, and radiating symmetry. Two female smiles typified by darker shade and asymmetry were rated by all groups as being least attractive. Two male smiles were judged equal as the most pleasing esthetically. Respondents favored those smiles characterized by light shade, a moderate display of teeth, moderate lip line, and a symmetrical arrangement of teeth. One male smile characterized by darker shade was rated as least attractive. CONCLUSIONS In all cases, tooth shade was the most important factor, followed in sequence by unrestored natural teeth and number of teeth displayed. No correlation was found to exist between specific demographic groups and smile variables.
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Affiliation(s)
- W J Dunn
- US An Force, Dental Corps. Howard Air Force Base, Panama, USA
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Abstract
This report describes a new set of amino acid side chain descriptors, the isotropic surface area (ISA), and the electronic charge index (ECI) relevant to peptide quantitative structure--activity relationship (QSAR) studies. These features are derived from optimized three-dimensional structures of the natural and unnatural amino acids. Since the descriptors are derived considering side chain three-dimensional structure, 3D-QSARs result. Using the method of partial least squares, 3D-QSARs of peptide sets were developed. A comparison of the results to those obtained with the principal properties or z-scales shows that the ISA and ECI are comparable for parameterizing the structural variability of the peptide series and represent an interesting alternative.
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Affiliation(s)
- E R Collantes
- Department of Medicinal Chemistry & Pharmacognosy, University of Illinois at Chicago 60612, USA
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Dunn WJ. Consent--is it informed and valid? J Can Dent Assoc 1995; 61:233-4. [PMID: 7773854] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- W J Dunn
- Faculty of dentistry, University of Western Ontario
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Hopfinger AJ, Burke BJ, Dunn WJ. A generalized formalism of three-dimensional quantitative structure-property relationship analysis for flexible molecules using tensor representation. J Med Chem 1994; 37:3768-74. [PMID: 7966136 DOI: 10.1021/jm00048a013] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A general formalism, based upon tensor representation of multidimensional data blocks, is presented to express relationships between dependent properties and independent molecular feature measures. The solutions to these data set problems are three-dimensional quantitative structure-property relationships, 3D-QSPRs. The molecular features are partitioned into the intrinsic molecular shape tensor, the molecular field tensor, a nonshape/field feature tensor, and an experimental feature tensor. The intrinsic molecular shape tensor contains information on the shape of a molecule within the contact surface while the molecular field tensor contains information outside of the contact surface. Molecular features not directly related to molecular shape are put into the nonshape/field tensor. Experimental measures not being used as dependent variables can be considered as independent molecular features in the experimental feature tensor. The 3D-QSPR is realized by constructing the transformation tensor which optimizes the statistical significance between the dependent and independent variables. Use of partial least squares (PLS) regression permits the unfolding of the composite feature tensor and the identification of the optimum transformation tensor. It is pointed out that a variety of fragment, whole-molecule, two-dimensional, and/or three-dimensional features can be placed into a nonshape/field tensor.
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Affiliation(s)
- A J Hopfinger
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago 60612-7231
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Burke BJ, Dunn WJ, Hopfinger AJ. Construction of a molecular shape analysis-three-dimensional quantitative structure-analysis relationship for an analog series of pyridobenzodiazepinone inhibitors of muscarinic 2 and 3 receptors. J Med Chem 1994; 37:3775-88. [PMID: 7966137 DOI: 10.1021/jm00048a014] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
A generalized three-dimensional (3D) quantitative structure-property relationship (QSPR) formalism, based upon molecular shape analysis (MSA), has been applied to an analog series of pyridobenzodiazepinone inhibitors of muscarinic 2 (M2) and 3 (M3) receptors. The fundamental goal of this application is to establish MSA-3D-QSARs (P = A = inhibition activity) that are based upon identifying the active conformations of these flexible analogs. The repetitive use of partial least squares (PLS) analysis permits the construction of the MSA-3D-QSARs. In addition to molecular shape, the identification of the properties of a lipophilic binding site and specific nonallowed steric receptor sites govern the MSA-3D-QSARs. The M2 and M3 QSARs suggest receptor subtype specificity might be realized by targeting upon a specific nonallowed steric receptor site. One conformation, common to both M2 and M3 receptors, emerges as dominant in the optimum MSA-3D-QSARs. However, other similar conformations are also found to yield meaningful MSA-3D-QSARs.
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Affiliation(s)
- B J Burke
- Department of Medicinal Chemistry and Pharmacognosy, College of Pharmacy, University of Illinois at Chicago 60612-7231
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Affiliation(s)
- M M Rasenick
- Department of Physiology, University of Illinois College of Medicine, Chicago 60612
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Stephens RG, Kogon SL, Speechley MR, Dunn WJ. A critical view of the rationale for routine, initial and periodic radiographic surveys. J Can Dent Assoc 1992; 58:825-8, 831-2, 835-7. [PMID: 1393796] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Abstract
Most dentists and dental faculties use an initial radiographic survey for the comprehensive-care patient rather than selective radiography, as recommended by professional organizations and radiation protection agencies. Survey or screening radiography has been justified in the belief that it is an essential health service designed to disclose serious occult disease and that failure to use such films might expose the dentist to successful malpractice litigation. However, incidence data indicate the chance of disclosing tumors, non-inflammatory cysts or other serious bone disease in the asymptomatic patient by screening jaw films is infinitesimal. On this basis, the practice is not justifiable as a public health measure, nor is the dentist who follows published national guidelines for prescription radiography vulnerable to successful litigation.
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Affiliation(s)
- R G Stephens
- Division of Oral Medicine and Radiology, University of Western Ontario, London
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Takács-Novák K, Nagy P, Józan M, Orfi L, Dunn WJ, Szász G. Relationship between partitioning properties and (calculated) molecular surface. SPR investigation of imidazoquinazolone derivatives. Acta Pharm Hung 1992; 62:55-64. [PMID: 1566640] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
Structure-property relationship (SPR) investigations have been carried out for a series of N-bridged compounds synthetized recently as potential antithrombotic agents. The octanol/water partition coefficient and reversed phase HPLC retention (log k') were determined experimentally for ten imidazoquinazolone derivatives. Calculations including total geometry optimization and surface area have been carried out. The isotropic surface area (ISA) of supermolecules were obtained. The good correlations were found between log P, log k' and ISA values, provide simple and reliable means by using a single structural parameter for the log P prediction of polycyclic N-bridged compounds.
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Affiliation(s)
- K Takács-Novák
- Institute of Pharmaceutical Chemistry, Semmelweis University of Medicine, Budapest, Hungary
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Dunn WJ. A new dimension of negligence? J Can Dent Assoc 1991; 57:434. [PMID: 1860084] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Abstract
Due to the demands of time and the high cost of testing compounds for toxicity in test animals, it would be an advantage to be able to estimate the toxic response of chemical agents using theoretical approaches. Predicting whether a compound will be toxic or nontoxic is a classification problem and the methods of studying quantitative structure activity relationships (QSAR) can be used for this purpose [Hansch, C. (1969) Accounts Chem. Res., 2, 232]. It should be recognized, however, that formulating the QSAR problem as one of active vs. inactive makes it different from classical QSAR problems. This requires that methods be applied that can predict the category of a compound to be used, i.e., so-called methods of pattern recognition (Varmuza, K. (1983) J. Chem. Info. Comp. Sci. 23, 6) being required. There are several methods of pattern recognition that can be used with some being more suitable than others. The nature of this unique QSAR problem, the appropriate methods to apply, and some of the pitfalls of applying QSAR techniques to predicting toxicity are discussed.
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Affiliation(s)
- W J Dunn
- Department of Medicinal Chemistry and Pharmacognosy, University of Illinois, Chicago 60612
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Abstract
Primary choroidal malignant melanoma with extension through the overlying retina is a rarely reported entity, and to our knowledge actual seeding of the vitreous has never been reported. The pathologic findings in a 41-year-old woman who presented with a large amelanotic subretinal mass near the optic disc of the right eye are discussed. Fundus examination preoperatively revealed a concentration of discrete, fleshy, oval to round, vitreous bodies of varying size, limited to the area overlying the mass. Histopathology of this tumor revealed a spindle cell posterior choroidal melanoma with marked atrophy of the overlying retina. At the apex, the retina was discontinuous and melanoma cells extended into the overlying vitreous. Some of the cells surrounded asteroid bodies overlying the tumor, altering their clinical appearance. This behavior, while only involving a small fraction of the tumor cells, may imply a more aggressive tumor.
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Affiliation(s)
- W J Dunn
- Department of Ophthalmology, Wilford Hall USAF Medical Center, Lackland Air Force Base, Texas
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Koehler MG, Grigoras S, Dunn WJ. The Relationship Between Chemical Structure and the Logarithm of the Partition Coefficient. ACTA ACUST UNITED AC 1988. [DOI: 10.1002/qsar.19880070306] [Citation(s) in RCA: 29] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Dunn WJ. Court rulings extend statutes of limitation. Ont Dent 1987; 64:14-6. [PMID: 2959891] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
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Stalling DL, Schwartz TR, Dunn WJ, Wold S. Classification of polychlorinated biphenyl residues: isomers vs. homologue concentrations in modeling aroclors and polychlorinated biphenyl residues. Anal Chem 1987; 59:1853-9. [PMID: 3115139 DOI: 10.1021/ac00141a026] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
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Abstract
The logarithm of the partition coefficient (log P) of low-molecular-weight organic compounds is a physicochemical parameter used extensively in structure-biological activity studies to model interactions of the compounds with nonpolar phases in vitro and in vivo. The partition coefficient can be determined between water and a number of nonpolar solvents. The most common nonpolar solvent is 1-octanol, but solvents such as benzene, carbon tetrachloride, and chloroform are frequently used as models for the nonpolar phases. The functional relationship between chemical structure and partitioning is not well-understood. In this paper, partition coefficient data for 50 solutes in six nonpolar solvent systems are analyzed by using principal components analysis. The objective of the work is to explore the relationship between solute structure and partitioning behavior for simple organic compounds. Two structural factors are found to be important, with the isotropic surface area being the most important. The isotropic surface area can be used to estimate log P in some solvents and as an independent variable in quantitative structure-activity relationships (QSAR). This is illustrated by estimating the rate of epidermal diffusion of steroids.
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Dunn WJ. The Association of Canadian Faculties of Dentistry. Twenty years of achievement. J Can Dent Assoc 1987; 53:359-60. [PMID: 3555734] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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27
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Dunn WJ. Specialty certification in Canada. J Can Dent Assoc 1986; 52:765-9. [PMID: 3530402] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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Dunn WJ. The dental profession. A historical review of developments. Re: Licensure and review of current arrangements for testing and licensure. J Can Dent Assoc 1986; 52:402-5. [PMID: 3516342] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
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29
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Abstract
Eight consecutive patients with acquired deviations due to dysthyroid ocular myopathy were injected with botulinum A toxin for relief of their diplopia. Seven patients were acute in the onset of symptoms and one was chronic. All showed improvement in motility and experienced a reduction if not total relief of their symptoms. Six patients required reinjection. Complications were limited to transient ptosis, transient involvement of adjacent muscles and transient but prolonged paralysis that eventually resolved. No systemic complications were noted. We conclude that chemodenervation with botulinum A toxin may have a role in the management of dysthyroid ocular myopathy not amenable to prism treatment and may act as an adjunct to or eliminate the need for surgical correction in some patients.
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Dunn WJ. Third-party coverage and ethical implications in dentistry. Compend Contin Educ Dent (Lawrenceville) 1985; 6:751-2, 754, 756. [PMID: 3866660] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Abstract
Empirical models can be constructed relating the change in toxicity to the change in chemical structure for series of similar compounds or mixtures. The first step is to translate the variation in structure to quantitative numbers. This gives a data table, a data matrix denoted by X, which then is analyzed. The same type of the models can be used to relate the variation of in vivo data to the variation of a battery of in vitro tests. A single data analytical model cannot be applied to a set of compounds of diverse chemical structure. For such data sets, separate models must be developed for each subgroup of compounds. The data analytical problem then partly is one of classification, pattern recognition (PARC). The assumption of structural and biological similarity within each subset of modeled compounds is then essential for empirical models to apply. PARC is often used to classify compounds as active (toxic) or inactive. The data structure is then often asymmetric which puts special demands on the data analysis, making the traditional PARC methods inapplicable. Depending on the desired information from the data analysis and on the type of available data, four levels of PARC can be distinguished: (I) the data X are used to develop rules for classifying future compounds into one of the classes represented in X; (II) same as I, but the possibility of future compounds belonging to "unknown" classes not represented in X is taken into account; (III) same as II, plus the quantitative prediction of one activity variable (here toxicity) in some classes; (IV) same as III, but several quantitative activity (toxicity) variables are predicted.
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Dunn WJ. The Journal. Fifty years of service. J Can Dent Assoc 1985; 51:54-7. [PMID: 3884096] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
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Dunn WJ. The Canada Health Act and its implications for dentistry. J Can Dent Assoc 1984; 50:679-81. [PMID: 6386120] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Dunn WJ. Malpractice--juries no longer barred from the courtroom. Ont Dent 1984; 61:33, 35, 37. [PMID: 6587288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Dunn WJ. Statutes of limitation--without limit. Ont Dent 1984; 61:23-6. [PMID: 6585770] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Dunn WJ, Wold S, Edlund U, Hellberg S, Gasteiger J. Multivariate structure-activity relationships between data from a battery of biological tests and an ensemble of structure descriptors: The PLS method. ACTA ACUST UNITED AC 1984. [DOI: 10.1002/qsar.19840030402] [Citation(s) in RCA: 208] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022]
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Freedman B, Dunn WJ. Informed consent--an attitudinal survey with recommendations. Ont Dent 1984; 61:14-6, 18-20. [PMID: 6583615] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Dunn WJ. British Columbia's Medical Services Act--some disquieting implications. J Can Dent Assoc 1984; 50:63-6. [PMID: 6365287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Abstract
One hundred sixty-eight Angus X Hereford crossbred beef steers were utilized to evaluate the influence of two levels of monensin (0 or 33 ppm) on three levels of dietary protein (9, 11 or 13% on a dry matter basis). The study was divided into a growing phase when steers received ad libitum corn silage and the needed protein supplement to supply the appropriate protein level. The finishing diet consisted of 85% dry corn and 15% corn silage plus a protein supplement to yield an 11% protein diet fed to all steers. Estimates of carcass composition were made at the beginning, at the end of the growing phase and at completion of the study. During the growing phase, growth rate (GR), dry matter intake (DMI) and efficiency of gain (F/G) were all improved (P less than .01) with increasing protein level, while monensin reduced (P less than .01) DMI and improved (P less than .01) F/G, with the greatest improvement coming on the 9% protein diet. The rate of protein deposition was increased (P less than .05) with increasing protein level and was increased (P less than .01) on the 9% protein diet while being reduced on the 13% protein diet when monensin was included in the diet. Previous protein level influenced steer performance during the finishing phase, with the steers previously receiving the 13% protein diet having the poorest GR and F/G while those having received the 11% protein diet having the highest GR.(ABSTRACT TRUNCATED AT 250 WORDS)
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Dunn WJ. Professional self-government - is it justified? Oral Health 1983; 73:13-7. [PMID: 6580590] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
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Dunn WJ. Negligence--the Damoclean sword. Ont Dent 1983; 60:16-23. [PMID: 6587284] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
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Abstract
Twelve 1,4-naphthoquinones have been tested against the ascitic form of sarcoma 180 in Swiss mice. Statistical analysis shows that the most important molecular parameter determining their effectiveness in prolonging the life of mice bearing this tumor is their redox potentials. Although the toxicities of the compounds are also related to the redox potentials in the same way, the therapeutic indexes can be increased by adding substituents of greater lipophilicity. The naphthoquinones differ greatly in antitumor activities and may inhibit the growth of malignant cells by different mechanisms.
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Dunn WJ. Informed consent. J Can Dent Assoc 1983; 49:231-4. [PMID: 6344963] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Dunn WJ. Advertising and the self-regulating professions. J Can Dent Assoc 1983; 49:26-30. [PMID: 6339013] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
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Dunn WJ, Johansson E, Wold S. Nonadditivity of 1-Octanol/Water Partition Coefficients of Disubstituted Benzenes: An Explanation and Its Consideration in Log P Estimation. ACTA ACUST UNITED AC 1983. [DOI: 10.1002/qsar.19830020403] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
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Dunn WJ, Wold S. An assessment of carcinogenicity of N-nitroso compounds by the SIMCA method of pattern recognition. J Chem Inf Comput Sci 1981; 21:8-13. [PMID: 7240353 DOI: 10.1021/ci00029a003] [Citation(s) in RCA: 19] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2023]
Abstract
The ability to predict the toxic responses of potential environmental pollutants on the basis of their physiochemical properties has many advantages. Pattern recognition methods can be used to predict such pharmacological properties. In this report the SIMCA method of pattern recognition is used to predict the carcinogenicity of N-nitroso compounds, and the advantages of this method of pattern recognition in such applications are discussed.
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Dunn WJ, Powers J, Kaddu JB, Njogu AR. 1-(p-Tolyl)-3-acetyl-3-methyltriazene: a compound with activity against African trypanosomiasis. J Pharm Sci 1980; 69:1465-6. [PMID: 7463345 DOI: 10.1002/jps.2600691238] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
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Abstract
In classification studies in which pattern-recognition methods are used to distinguish active compounds from inactive ones, a type of data structure which we call "asymmetric" can be observed. This type of data structure can be quite common and its occurrence can have a profound effect on the classification analysis outcome. The origin of asymmetric data structure and a strategy or obtaining meaningful classification results when it is observed are discussed and illustrated with an example of active and inactive antimalarial quinones.
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Perry TW, Dunn WJ, Peterson RC, Beeson WM, Stob M, Mohler MT. Ammonia-Mineral-Suspension Treated Corn Silage, Protein Levels and Monensin for Growing and Finishing Beef Cattle. J Anim Sci 1979. [DOI: 10.2527/jas1979.484742x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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