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Jones JP, Norton K. 222-nm ultraviolet light inactivates dried inocula of human rhinovirus and human coronavirus on a glass carrier. J Hosp Infect 2021; 117:190-191. [PMID: 34403769 PMCID: PMC8364420 DOI: 10.1016/j.jhin.2021.08.003] [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] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2021] [Accepted: 08/06/2021] [Indexed: 11/28/2022]
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2
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Affiliation(s)
- J. P. Jones
- Department of Plant Pathology, Agricultural Experiment Station, Louisiana State University, Baton Rouge, Louisiana 70803
| | - G. E. Holcomb
- Department of Plant Pathology, Agricultural Experiment Station, Louisiana State University, Baton Rouge, Louisiana 70803
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3
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Joshi A, Halquist M, Konsoula Z, Liu Y, Jones JP, Heidbreder C, Gerk PM. Improving the oral bioavailability of buprenorphine: an in-vivo proof of concept. J Pharm Pharmacol 2016; 69:23-31. [DOI: 10.1111/jphp.12652] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2016] [Accepted: 09/18/2016] [Indexed: 12/20/2022]
Abstract
Abstract
Objectives
The aim of this study was to improve the oral bioavailability of buprenorphine by inhibiting presystemic metabolism via the oral co-administration of ‘Generally Recognized as Safe’ compounds, thus providing an orally administered drug product with less variability and comparable or higher exposure compared with the sublingual route.
Methods
The present studies were performed in Sprague Dawley rats following either intravenous or oral administration of buprenorphine/naloxone and oral co-administration of ‘Generally Recognized as Safe’ compounds referred to as ‘adjuvants’. Plasma samples were collected up to 22 h postdosing followed by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) analysis.
Key findings
The adjuvants increased Cmax (21 ± 16 ng/ml vs 75 ± 33 ng/ml; 3.6-fold) and AUC(0–22 h) (10.6 ± 8.11 μg min/ml vs 22.9 ± 11.7 μg min/ml; 2.2-fold) values of buprenorphine (control vs adjuvant-treated, respectively). The absolute oral bioavailability of buprenorphine doubled (from 1.24% to 2.68%) in the presence of the adjuvants.
Conclusions
One may suggest that the adjuvant treatment most likely inhibited the presystemic metabolic enzymes, thus decreasing the intestinal ‘first-pass effect’ on buprenorphine. Additional studies are now required to further explore the concept of inhibiting presystemic metabolism of buprenorphine by adjuvants to potentially increase the oral bioavailability of buprenorphine.
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Affiliation(s)
- Anand Joshi
- Department of Pharmaceutics, VCU School of Pharmacy, Richmond, VA, USA
| | - Matthew Halquist
- Department of Pharmaceutics, VCU School of Pharmacy, Richmond, VA, USA
| | | | - Yongzhen Liu
- Global Research & Development, Indivior Inc., Richmond, VA, USA
| | - J P Jones
- Global Research & Development, Indivior Inc., Richmond, VA, USA
| | | | - Phillip M Gerk
- Department of Pharmaceutics, VCU School of Pharmacy, Richmond, VA, USA
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Laffont CM, Gomeni R, Heidbreder C, Jones JP, Nasser AF. Population Pharmacokinetic Modeling After Repeated Administrations of RBP-6000, a New, Subcutaneously Injectable, Long-Acting, Sustained-Release Formulation of Buprenorphine, for the Treatment of Opioid Use Disorder. J Clin Pharmacol 2016; 56:806-15. [PMID: 26479717 DOI: 10.1002/jcph.665] [Citation(s) in RCA: 31] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Revised: 09/30/2015] [Accepted: 10/14/2015] [Indexed: 12/12/2022]
Abstract
RBP-6000 is a novel sustained-release formulation of buprenorphine for the treatment of opioid use disorder, which has been designed for once-monthly (28 days) subcutaneous (SC) injections. A population pharmacokinetic (PK) model was developed to describe the time course of buprenorphine plasma concentrations after repeated SC injections of RBP-6000 at 50 mg, 100 mg, 200 mg, or 300 mg in treatment-seeking opioid-dependent subjects previously on sublingual buprenorphine (Subutex(®) ) treatment. The μ-opioid receptor occupancy was predicted using a previously developed PK/PD Emax model. The results of the population PK analysis jointly with the predicted level of μ-opioid receptor occupancy provided quantitative criteria for clinical dose selection for RBP-6000: the dose of 300 mg every 28 days seems appropriate for immediately achieving an effective exposure after the first SC injection and to maintain effective levels of exposure during chronic treatment. Furthermore, simulations conducted to evaluate the potential impact of a holiday in drug intake indicated that in the unexpected event of a 2-week holiday, levels of μ-opioid receptor occupancy remained consistently above 70% with no significant loss of drug efficacy. This analysis indicated that RBP-6000 has the potential for becoming an effective treatment for opioid-dependent subjects by addressing compliance issues associated with the current once-a-day treatments.
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Affiliation(s)
| | - Roberto Gomeni
- R&D Department, Pharmacometrica, Longcol, La Fouillade, France
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5
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Weidert ER, Schoenborn SO, Cantu-Medellin N, Choughule KV, Jones JP, Kelley EE. Inhibition of xanthine oxidase by the aldehyde oxidase inhibitor raloxifene: implications for identifying molybdopterin nitrite reductases. Nitric Oxide 2014; 37:41-5. [PMID: 24406683 DOI: 10.1016/j.niox.2013.12.010] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2013] [Revised: 12/18/2013] [Accepted: 12/27/2013] [Indexed: 01/10/2023]
Abstract
Sources of nitric oxide alternative to nitric oxide synthases are gaining significant traction as crucial mediators of vessel function under hypoxic inflammatory conditions. For example, capacity to catalyze the one electron reduction of nitrite (NO2-) to ·NO has been reported for hemoglobin, myoglobin and molybdopterin-containing enzymes including xanthine oxidoreductase (XOR) and aldehyde oxidase (AO). For XOR and AO, use of selective inhibition strategies is therefore crucial when attempting to assign relative contributions to nitrite-mediated ·NO formation in cells and tissue. To this end, XOR inhibition has been accomplished with application of classic pyrazolopyrimidine-based inhibitors allo/oxypurinol or the newly FDA-approved XOR-specific inhibitor, Uloric® (febuxostat). Likewise, raloxifene, an estrogen receptor antagonist, has been identified as a potent (Ki=1.0 nM) inhibitor of AO. Herein, we characterize the inhibition kinetics of raloxifene for XOR and describe the resultant effects on inhibiting XO-catalyzed ·NO formation. Exposure of purified XO to raloxifene (PBS, pH 7.4) resulted in a dose-dependent (12.5-100 μM) inhibition of xanthine oxidation to uric acid. Dixon plot analysis revealed a competitive inhibition process with a Ki=13 μM. This inhibitory process was more effective under acidic pH; similar to values encountered under hypoxic/inflammatory conditions. In addition, raloxifene also inhibited anoxic XO-catalyzed reduction of NO2- to NO (EC50=64 μM). In contrast to having no effect on XO-catalyzed uric acid production, the AO inhibitor menadione demonstrated potent inhibition of XO-catalyzed NO2- reduction (EC50=60 nM); somewhat similar to the XO-specific inhibitor, febuxostat (EC50=4 nM). Importantly, febuxostat was found to be a very poor inhibitor of human AO (EC50=613 μM) suggesting its usefulness for validating XO-dependent contributions to NO2- reduction in biological systems. Combined, these data indicate care should be taken when choosing inhibition strategies as well as inhibitor concentrations when assigning relative NO2- reductase activity of AO and XOR.
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Affiliation(s)
- E R Weidert
- University of Pittsburgh School of Medicine, Department of Anesthesiology, United States
| | - S O Schoenborn
- University of Pittsburgh School of Medicine, Department of Anesthesiology, United States
| | - N Cantu-Medellin
- University of Pittsburgh School of Medicine, Department of Anesthesiology, United States; University of Pittsburgh School of Medicine, Vascular Medicine Institute, United States
| | - K V Choughule
- Washington State University, Department of Chemistry, United States
| | - J P Jones
- Washington State University, Department of Chemistry, United States
| | - E E Kelley
- University of Pittsburgh School of Medicine, Department of Anesthesiology, United States; University of Pittsburgh School of Medicine, Vascular Medicine Institute, United States.
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Evangelista EA, Kaspera R, Mokadam NA, Jones JP, Totah RA. Activity, inhibition, and induction of cytochrome P450 2J2 in adult human primary cardiomyocytes. Drug Metab Dispos 2013; 41:2087-94. [PMID: 24021950 DOI: 10.1124/dmd.113.053389] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023] Open
Abstract
Cytochrome P450 2J2 plays a significant role in the epoxidation of arachidonic acid to signaling molecules important in cardiovascular events. CYP2J2 also contributes to drug metabolism and is responsible for the intestinal clearance of ebastine. However, the interaction between arachidonic acid metabolism and drug metabolism in cardiac tissue, the main expression site of CYP2J2, has not been examined. Here we investigate an adult-derived human primary cardiac cell line as a suitable model to study metabolic drug interactions (inhibition and induction) of CYP2J2 in cardiac tissue. The primary human cardiomyocyte cell line demonstrated similar mRNA-expression profiles of P450 enzymes to adult human ventricular tissue. CYP2J2 was the dominant isozyme with minor contributions from CYP2D6 and CYP2E1. Both terfenadine and astemizole oxidation were observed in this cell line, whereas midazolam was not metabolized suggesting lack of CYP3A activity. Compared with recombinant CYP2J2, terfenadine was hydroxylated in cardiomyocytes at a similar K(m) value of 1.5 μM. The V(max) of terfenadine hydroxylation in recombinant enzyme was found to be 29.4 pmol/pmol P450 per minute and in the cells 6.0 pmol/pmol P450 per minute. CYP2J2 activity in the cell line was inhibited by danazol, astemizole, and ketoconazole in submicromolar range, but also by xenobiotics known to cause cardiac adverse effects. Of the 14 compounds tested for CYP2J2 induction, only rosiglitazone increased mRNA expression, by 1.8-fold. This cell model can be a useful in vitro model to investigate the role of CYP2J2-mediated drug metabolism, arachidonic acid metabolism, and their association to drug induced cardiotoxicity.
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Affiliation(s)
- Eric A Evangelista
- Department of Medicinal Chemistry (E.A.E., R.K., J.P.J., R.A.T.) and Division of Cardiothoracic Surgery, University of Washington, Seattle, Washington (N.A.M.)
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Lee CA, Jones JP, Katayama J, Kaspera R, Jiang Y, Freiwald S, Smith E, Walker GS, Totah RA. Identifying a selective substrate and inhibitor pair for the evaluation of CYP2J2 activity. Drug Metab Dispos 2012; 40:943-51. [PMID: 22328583 DOI: 10.1124/dmd.111.043505] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
CYP2J2, an arachidonic acid epoxygenase, is recognized for its role in the first-pass metabolism of astemizole and ebastine. To fully assess the role of CYP2J2 in drug metabolism, a selective substrate and potent specific chemical inhibitor are essential. In this study, we report amiodarone 4-hydoxylation as a specific CYP2J2-catalyzed reaction with no CYP3A4, or other drug-metabolizing enzyme, involvement. Amiodarone 4-hydroxylation enabled the determination of liver relative activity factor and intersystem extrapolation factor for CYP2J2. Amiodarone 4-hydroxylation correlated with astemizole O-demethylation but not with CYP2J2 protein content in a sample of human liver microsomes. To identify a specific CYP2J2 inhibitor, 138 drugs were screened using terfenadine and astemizole as probe substrates with recombinant CYP2J2. Forty-two drugs inhibited CYP2J2 activity by ≥50% at 30 μM, but inhibition was substrate-dependent. Of these, danazol was a potent inhibitor of both hydroxylation of terfenadine (IC(50) = 77 nM) and O-demethylation of astemizole (K(i) = 20 nM), and inhibition was mostly competitive. Danazol inhibited CYP2C9, CYP2C8, and CYP2D6 with IC(50) values of 1.44, 1.95, and 2.74 μM, respectively. Amiodarone or astemizole were included in a seven-probe cocktail for cytochrome P450 (P450) drug-interaction screening potential, and astemizole demonstrated a better profile because it did not appreciably interact with other P450 probes. Thus, danazol, amiodarone, and astemizole will facilitate the ability to determine the metabolic role of CYP2J2 in hepatic and extrahepatic tissues.
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Affiliation(s)
- Caroline A Lee
- Department of Drug Metabolism, Pfizer Global Research, La Jolla, California, USA
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Gallastegui G, Avalos Ramirez A, Elías A, Jones JP, Heitz M. Performance and macrokinetic analysis of biofiltration of toluene and p-xylene mixtures in a conventional biofilter packed with inert material. Bioresour Technol 2011; 102:7657-7665. [PMID: 21715161 DOI: 10.1016/j.biortech.2011.05.054] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/18/2011] [Revised: 05/11/2011] [Accepted: 05/18/2011] [Indexed: 05/31/2023]
Abstract
Interactions of toluene and p-xylene in air treatment biofilters packed with an inert filter media were studied. The effect of the inlet load of toluene, p-xylene and mixtures of both compounds on the biodegradation rate was analyzed in three lab-scale biofilters. A maximum elimination capacity (EC) of 26.5 and 40.3 gCm(-3)h(-1) for an inlet load (IL) of 65.6 and 57.8 gCm(-3)h(-1) was obtained for p-xylene and toluene biofilters, respectively. Inhibition of p-xylene biodegradation by the presence of toluene took place when the mixture was treated, whereas the presence of p-xylene had an enhancing effect on the toluene removal efficiency. Specific growth rates (μ) from 0.019 to 0.068 h(-1) were calculated in the mixed biofilter, where the highest values were similar to mixtures with lower p-xylene levels (IL(p-Xyl) 8.84 ± 0.29 gCm(-3)h(-1)). Michaelis-Menten and Haldane type models were fitted to experimental EC for p-xylene and toluene biofilters, respectively.
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Affiliation(s)
- G Gallastegui
- Department of Chemical and Environmental Engineering, Engineering Faculty, University of the Basque Country, Alda Urquijo s/n, 48013 Bilbao, Spain
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Lee CA, Neul D, Clouser-Roche A, Dalvie D, Wester MR, Jiang Y, Jones JP, Freiwald S, Zientek M, Totah RA. Identification of novel substrates for human cytochrome P450 2J2. Drug Metab Dispos 2009; 38:347-56. [PMID: 19923256 DOI: 10.1124/dmd.109.030270] [Citation(s) in RCA: 98] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Several antihistamine drugs including terfenadine, ebastine, and astemizole have been identified as substrates for CYP2J2. The overall importance of this enzyme in drug metabolism has not been fully explored. In this study, 139 marketed therapeutic agents and compounds were screened as potential CYP2J2 substrates. Eight novel substrates were identified that vary in size and overall topology from relatively rigid structures (amiodarone) to larger complex structures (cyclosporine). The substrates displayed in vitro intrinsic clearance values ranging from 0.06 to 3.98 mul/min/pmol CYP2J2. Substrates identified for CYP2J2 are also metabolized by CYP3A4. Extracted ion chromatograms of metabolites observed for albendazole, amiodarone, astemizole, thioridazine, mesoridazine, and danazol showed marked differences in the regioselectivity of CYP2J2 and CYP3A4. CYP3A4 commonly metabolized compounds at multiple sites, whereas CYP2J2 metabolism was more restrictive and limited, in general, to a single site for large compounds. Although the CYP2J2 active site can accommodate large substrates, it may be more narrow than CYP3A4, limiting metabolism to moieties that can extend closer toward the active heme iron. For albendazole, CYP2J2 forms a unique metabolite compared with CYP3A4. Albendazole and amiodarone were evaluated in various in vitro systems including recombinant CYP2J2 and CYP3A4, pooled human liver microsomes (HLM), and human intestinal microsomes (HIM). The Michaelis-Menten-derived intrinsic clearance of N-desethyl amiodarone was 4.6 greater in HLM than in HIM and 17-fold greater in recombinant CYP3A4 than in recombinant CYP2J2. The resulting data suggest that CYP2J2 may be an unrecognized participant in first-pass metabolism, but its contribution is minor relative to that of CYP3A4.
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Affiliation(s)
- Caroline A Lee
- Pfizer Global Research & Development, 10646 Science Center Dr., San Diego, CA 92121, USA.
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Cabana H, Jones JP, Agathos SN. Elimination of Endocrine Disrupting Chemicals using White Rot Fungi and their Lignin Modifying Enzymes: A Review. Eng Life Sci 2007. [DOI: 10.1002/elsc.200700017] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
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Buhler WG, Langley RL, Luginbuhl RC, Jones JP, Burnette JW. Violations of pesticide use and worker safety regulations in North Carolina. J Agric Saf Health 2007; 13:189-203. [PMID: 17555207 DOI: 10.13031/2013.22619] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [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: 11/11/2022]
Abstract
In North Carolina, responsibility for providing training and enforcing various regulations related to pesticide use and agricultural worker safety rests with three state agencies. This article summarizes an 11-year history of enforcement procedures concerning agricultural pesticide use, the Worker Protection Standard, the Hazard Communication Standard, the Migrant Housing Act of North Carolina, and field sanitation standards. The difficulty of linking specific types of violations with worker safety is discussed.
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Affiliation(s)
- W G Buhler
- Department of Horticultural Science, North Carolina State University, Raleigh, NC 27695-7609, USA.
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Abstract
Freshly lifted seedlings and 21-year-old trees of loblolly pine were wound-inoculated with Leptographium species recovered from the soil and/or roots of trees with loblolly decline symptoms in central Alabama. Seedlings inoculated with L. procerum in the greenhouse produced significantly fewer root initials and a smaller root mass than control seedlings. Vertical lesions produced in seedlings by L. serpens and L. terebrantis were significantly longer than in controls. Lesions produced in mature trees by L. serpens and L. lundbergii were significantly longer than in controls. Of the fungi tested, L. serpens, L. terebrantis, and L. lundbergii were the most aggressive and may pose the greatest threat to loblolly pines.
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Affiliation(s)
| | - J P Jones
- Professor, Department of Plant Pathology and Crop Physiology, Louisiana Agricultural Experiment Station, Louisiana State University Agricultural Center, Baton Rouge 70803
| | - K D Klepzig
- Entomologist, United States Department of Agriculture, United States Forest Service, Southern Research Station, Pineville, LA 71360
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Affiliation(s)
- Meredith B Long
- Department of Surgery, Duke University Medical Center, Box 2601, Durham, North Carolina 27710, USA.
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Karki SB, Dinnocenzo JP, Jones JP, Korzekwa KR. Mechanism of Oxidative Amine Dealkylation of Substituted N,N-Dimethylanilines by Cytochrome P-450: Application of Isotope Effect Profiles. J Am Chem Soc 2002. [DOI: 10.1021/ja00118a001] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.9] [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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Dinnocenzo JP, Karki SB, Jones JP. On isotope effects for the cytochrome P-450 oxidation of substituted N,N-dimethylanilines. J Am Chem Soc 2002. [DOI: 10.1021/ja00069a007] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Xie W, Jones JP, Wong LL, Hill HA. Direct electrochemistry of pentachlorophenol hydroxylase. Chem Commun (Camb) 2001:2370-1. [PMID: 12240080] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/26/2023]
Abstract
The direct electrochemistry of the flavin-containing monooxygenase, pentachlorophenol hydroxylase (PCPH), at an edge plane graphite electrode was observed and a catalytic response, linear with concentration, was found with the substrate pentachlorophenol (PCP).
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Affiliation(s)
- W Xie
- Central Chemistry Laboratory, University of Oxford, South Parks Road, Oxford, UK OX1 3QH
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Christmas P, Jones JP, Patten CJ, Rock DA, Zheng Y, Cheng SM, Weber BM, Carlesso N, Scadden DT, Rettie AE, Soberman RJ. Alternative splicing determines the function of CYP4F3 by switching substrate specificity. J Biol Chem 2001; 276:38166-72. [PMID: 11461919 DOI: 10.1074/jbc.m104818200] [Citation(s) in RCA: 98] [Impact Index Per Article: 4.3] [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: 11/06/2022] Open
Abstract
Diversity of cytochrome P450 function is determined by the expression of multiple genes, many of which have a high degree of identity. We report that the use of alternate exons, each coding for 48 amino acids, generates isoforms of human CYP4F3 that differ in substrate specificity, tissue distribution, and biological function. Both isoforms contain a total of 520 amino acids. CYP4F3A, which incorporates exon 4, inactivates LTB4 by omega-hydroxylation (Km = 0.68 microm) but has low activity for arachidonic acid (Km = 185 microm); it is the only CYP4F isoform expressed in myeloid cells in peripheral blood and bone marrow. CYP4F3B incorporates exon 3 and is selectively expressed in liver and kidney; it is also the predominant CYP4F isoform in trachea and tissues of the gastrointestinal tract. CYP4F3B has a 30-fold higher Km for LTB4 compared with CYP4F3A, but it utilizes arachidonic acid as a substrate for omega-hydroxylation (Km = 22 microm) and generates 20-HETE, an activator of protein kinase C and Ca2+/calmodulin-dependent kinase II. Homology modeling demonstrates that the alternative exon has a position in the molecule which could enable it to contribute to substrate interactions. The results establish that tissue-specific alternative splicing of pre-mRNA can be used as a mechanism for changing substrate specificity and increasing the functional diversity of cytochrome P450 genes.
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Affiliation(s)
- P Christmas
- Center for Immunology and Inflammatory Diseases, Massachusetts General Hospital, Harvard Medical School, Charlestown, Massachusetts 02129, USA.
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Sathyanarayanan PV, Siems WF, Jones JP, Poovaiah BW. Calcium-stimulated autophosphorylation site of plant chimeric calcium/calmodulin-dependent protein kinase. J Biol Chem 2001; 276:32940-7. [PMID: 11399751 DOI: 10.1074/jbc.m009648200] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The existence of two molecular switches regulating plant chimeric Ca(2+)/calmodulin-dependent protein kinase (CCaMK), namely the C-terminal visinin-like domain acting as Ca(2+)-sensitive molecular switch and calmodulin binding domain acting as Ca(2+)-stimulated autophosphorylation-sensitive molecular switch, has been described (Sathyanarayanan, P. V., Cremo, C. R., and Poovaiah, B. W. (2000) J. Biol. Chem. 275, 30417-30422). Here we report the identification of Ca(2+)-stimulated autophosphorylation site of CCaMK by matrix-assisted laser desorption ionization time of flight-mass spectrometry. Thr(267) was confirmed as the Ca(2+)-stimulated autophosphorylation site by post-source decay experiments and by site-directed mutagenesis. The purified T267A mutant form of CCaMK did not show Ca(2+)-stimulated autophosphorylation, autophosphorylation-dependent variable calmodulin affinity, or Ca(2+)/calmodulin stimulation of kinase activity. Sequence comparison of CCaMK from monocotyledonous plant (lily) and dicotyledonous plant (tobacco) suggests that the autophosphorylation site is conserved. This is the first identification of a phosphorylation site specifically responding to activation by second messenger system (Ca(2+) messenger system) in plants. Homology modeling of the kinase and calmodulin binding domain of CCaMK with the crystal structure of calcium/calmodulin-dependent protein kinase 1 suggests that the Ca(2+)-stimulated autophosphorylation site is located on the surface of the kinase and far from the catalytic site. Analysis of Ca(2+)-stimulated autophosphorylation with increasing concentration of CCaMK indicates the possibility that the Ca(2+)-stimulated phosphorylation occurs by an intermolecular mechanism.
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Affiliation(s)
- P V Sathyanarayanan
- Laboratory of Plant Molecular Biology and Physiology, Department of Horticulture,Washington State University, Pullman, Washington 99164, USA
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French KJ, Strickler MD, Rock DA, Rock DA, Bennett GA, Wahlstrom JL, Goldstein BM, Jones JP. Benign synthesis of 2-ethylhexanoic acid by cytochrome P450cam: enzymatic, crystallographic, and theoretical studies. Biochemistry 2001; 40:9532-8. [PMID: 11583152 DOI: 10.1021/bi010063+] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [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: 11/30/2022]
Abstract
This study examines the ability of P450cam to catalyze the formation of 2-ethylhexanoic acid from 2-ethylhexanol relative to its activity on the natural substrate camphor. As is the case for camphor, the P450cam exhibits stereoselectivity for binding (R)- and (S)-2-ethylhexanol. Kinetic studies indicate (R)-2-ethylhexanoic acid is produced 3.5 times as fast as the (S)-enantiomer. In a racemic mixture of 2-ethylhexanol, P450cam produces 50% more (R)-2-ethylhexanoic acid than (S)-2-ethylhexanoic acid. The reason for stereoselective 2-ethylhexanoic acid production is seen in regioselectivity assays, where (R)-2-ethylhexanoic acid comprises 50% of total products while (S)-2-ethylhexanoic acid comprises only 13%. (R)- and (S)-2-ethylhexanol exhibit similar characteristics with respect to the amount of oxygen and reducing equivalents consumed, however, with (S)-2-ethylhexanol turnover producing more water than the (R)-enantiomer. Crystallographic studies of P450cam with (R)- or (S)-2-ethylhexanoic acid suggest that the (R)-enantiomer binds in a more ordered state. These results indicate that wild-type P450cam displays stereoselectivity toward 2-ethylhexanoic acid synthesis, providing a platform for rational active site design.
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Affiliation(s)
- K J French
- Department of Environmental Medicine, University of Rochester School of Medicine and Dentistry, New York 14642, USA
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Ekins S, de Groot MJ, Jones JP. Pharmacophore and three-dimensional quantitative structure activity relationship methods for modeling cytochrome p450 active sites. Drug Metab Dispos 2001; 29:936-44. [PMID: 11408357] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/20/2023] Open
Abstract
Structure activity relationships (SAR), three-dimensional structure activity relationships (3D-QSAR), and pharmacophores represent useful tools in understanding cytochrome P450 (CYP) active sites in the absence of crystal structures for these human enzymes. These approaches have developed over the last 30 years such that they are now being applied in numerous industrial and academic laboratories solely for this purpose. Such computational approaches have helped in understanding substrate and inhibitor binding to the major human CYPs 1A2, 2B6, 2C9, 2D6, 3A4 as well as other CYPs and additionally complement homology models for these enzymes. Similarly, these approaches may assist in our understanding of CYP induction. This review describes in detail the development of pharmacophores and 3D-QSAR techniques, which are now being more widely used for modeling CYPs; the review will also describe how such approaches are likely to further impact our active site knowledge of these omnipresent and important enzymes.
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Affiliation(s)
- S Ekins
- Lilly Research Laboratories, Eli Lilly and Company, Indianapolis, Indiana 46285, USA.
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22
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Abstract
Regioselectivity is used to determine the absolute energetic differences for four different reactions catalyzed by P450. Abstraction of a hydrogen from a benzylic carbon containing a chlorine has a 1.0 kcal/mol lower barrier than abstraction from a simple benzylic carbon, which in turn is 0.4 to 0.9 kcal/mol lower than abstraction from the methyl group of an aromatic ether and 0.1 to 0.6 kcal/mol easier than aromatic hydroxylation. Isotope effects are used to determine if the enzyme-substrate complexes leading to each product, from a given substrate, are in rapid equilibrium. For all enzymes isotopically sensitive branching is observed from the benzylic carbon upon deuterium incorporation at that position to each of the other positions, indicating that each product arises from the same active oxygen species. The energetic differences determined experimentally are accurately reproduced by theoretical hydrogen atom abstractions at both the AM1 semiempirical and DFT levels of theory.
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Affiliation(s)
- L Higgins
- Department of Medicinal Chemistry, University of Washington, Seattle 98195, USA
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23
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Rock D, Rock D, Jones JP. Inexpensive purification of P450 reductase and other proteins using 2',5'-adenosine diphosphate agarose affinity columns. Protein Expr Purif 2001; 22:82-3. [PMID: 11388803 DOI: 10.1006/prep.2001.1385] [Citation(s) in RCA: 14] [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: 11/22/2022]
Abstract
Two reductases, P450 oxidoreductase and P450Bm-3 reductase, were purified on a 2',5'-adenosine diphosphate solid support. Although the efficiency of these columns is well established, the cost of the resin and the eluting material 2'-adenosine can be prohibitive. Herein we show that the less costly 2',3'-adenosine monophosphate is an excellent eluting material.
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Affiliation(s)
- D Rock
- Department of Chemistry, Washington State University, Pullman, WA 99164-4630, USA.
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24
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Laver JH, Hulsey TC, Jones JP, Gautreaux M, Barredo JC, Abboud MR. Assessment of barriers to bone marrow donation by unrelated African-American potential donors. Biol Blood Marrow Transplant 2001; 7:45-8. [PMID: 11215698 DOI: 10.1053/bbmt.2001.v7.pm11215698] [Citation(s) in RCA: 37] [Impact Index Per Article: 1.6] [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: 11/11/2022]
Abstract
African Americans have a lower registration rate for becoming potential bone marrow and stem cell donors. The same attitudes and behaviors are exhibited in regard to solid organ and blood donations, causing a serious under-representation of the African-American population in the donor pool. In our efforts to increase donor availability for African Americans through a project funded by the Medical University of South Carolina, we used a survey to determine the reasons African Americans do not participate as donors for bone marrow. We surveyed 589 African Americans, a great majority of whom were women. Our survey identified major barriers to donation to be the lack of awareness that transplantation can save lives, the cost of donation, and the lack of opportunities to donate. The most effective interventions in increasing donation have been to provide both educational programs preceding marrow drives and the opportunity to donate. Through these efforts, the number of potential African-American donors has increased from 768 (accrued over a period of 12 years) to 1977 in less than 2 years. We conclude that a minority recruitment program targeting African-American volunteers for the National Marrow Donor Program (NMDP) should include an education component addressing the most common barriers before drives.
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Affiliation(s)
- J H Laver
- Department of Pediatrics, Medical University of South Carolina, Charleston, USA
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25
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Jones JP. Concepts of etiology and early pathogenesis of osteonecrosis. Instr Course Lect 2001; 43:499-512. [PMID: 9097180] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Affiliation(s)
- J P Jones
- Diagnostic Osteonecrosis Center and Research Foundation, Kelseyville, California, USA
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26
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Jones JP. Coagulopathies and osteonecrosis. Acta Orthop Belg 2001; 65 Suppl 1:5-8. [PMID: 10084210] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023]
Abstract
Intravascular coagulation of the intraosseous microcirculation (capillaries and venous sinusoids) progressing to generalized venous thrombosis, and less commonly retrograde arterial occlusion, now appears to be the cause of nontraumatic osteonecrosis. However, this coagulopathy is only an intermediary event, which is always activated by some underlying etiologic risk factor(s). Conditions capable of triggering intravascular coagulation include familial thrombophilia (resistance to activated protein C, decreased protein C, protein S, or antithrombin III), hyperlipemia and embolic lipid (alcoholism and hypercortisonism), hypersensitivity reactions (allograft organ rejection, immune complexes, and antiphospholipid antibodies), bacterial endotoxic (Shwartzman) reactions and various viral infections, proteolytic enzymes (pancreatitis), tissue factor release (inflammatory bowel disease, malignancies, neurotrauma, and pregnancy), and other prothrombotic and hypofibrinolytic conditions.
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Affiliation(s)
- J P Jones
- Diagnostic Osteonecrosis Center and Research Foundation, Kelseyville, California 95451, USA
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27
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Jones JP, Behnke AR. Prevention of dysbaric osteonecrosis in compressed-air workers. Clin Orthop Relat Res 2001:118-28. [PMID: 639383] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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28
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Jones JP. Osteonecrosis. Clin Orthop Relat Res 2001:2-4. [PMID: 639390] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Abstract
Polychlorinated benzenes are recalcitrant environmental pollutants primarily because they are resistant to attack by dioxygenases commonly used by micro-organisms for the biodegradation of aromatic compounds. We have investigated the oxidation of polychlorinated benzenes by mutants of the haem mono-oxygenase CYP101 (cytochrome P450(cam)) from Pseudomonas putida with the aim of generating novel systems for their biodegradation. Wild-type CYP101 had low activity for the oxidation of dichlorobenzenes and trichlorobenzenes to the chlorophenols, but no products were detected for the heavily chlorinated benzenes. Increasing the active-site hydrophobicity with the Y96F mutation increased the activity up to 100-fold, and both pentachlorobenzene and hexachlorobenzene were oxidized slowly to pentachlorophenol. Decreasing the space available at the top of the active site with the F87W mutation to force the substrate to be bound closer to the haem resulted in a further 10-fold increase in activity with most substrates. Introducing the F98W mutation, also at the top of the active site, decreased the NADH-turnover rates but increased the coupling efficiencies, and > 90% coupling was observed for 1,3-dichlorobenzene and 1,3,5-trichlorobenzene with the F87W--Y96F--F98W mutant. The V247L mutation generally increased the NADH-turnover rates, and the F87W--Y96F--V247L mutant showed reasonably fast NADH turnover (229 min(-1)) with the highly insoluble pentachlorobenzene without the need for surfactants or organic cosolvents. As all chlorophenols are degraded by micro-organisms, novel biodegradation systems could be constructed in which CYP101 mutants convert the inert polychlorinated benzenes to the phenols, which are then readily degraded by natural pathways.
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Affiliation(s)
- J P Jones
- Department of Chemistry, Inorganic Chemistry Laboratory, University of Oxford, UK
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30
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Rao S, Aoyama R, Schrag M, Trager WF, Rettie A, Jones JP. A refined 3-dimensional QSAR of cytochrome P450 2C9: computational predictions of drug interactions. J Med Chem 2000; 43:2789-96. [PMID: 10956186 DOI: 10.1021/jm000048n] [Citation(s) in RCA: 75] [Impact Index Per Article: 3.1] [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: 11/28/2022]
Abstract
A ligand-based model is reported that predicts the Ki values for cytochrome P450 2C9 (CYP2C9) inhibitors. This CoMFA model was used to predict the affinity of 14 structurally diverse compounds not in the training set and appears to be robust. The mean error of the predictions is 6 microM. The experimentally measured Ki values of the 14 compounds range from 0.1 to 48 microM. Leave-one-out cross-validated partial least-squares gives a q2 value of between 0.6 and 0.8 for the various models which indicates internal consistency. Random assignment of biological data to structure leads to negative q2 values. These models are useful in that they establish a pharmacophore for binding to CYP2C9 that can be tested with site-directed mutagenesis. These models can also be used to screen for potential drug interactions and to design compounds that will not bind to this enzyme with high affinity.
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Affiliation(s)
- S Rao
- Department of Chemistry, Washington State University, Pullman, USA
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31
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Guo H, Karberg M, Long M, Jones JP, Sullenger B, Lambowitz AM. Group II introns designed to insert into therapeutically relevant DNA target sites in human cells. Science 2000; 289:452-7. [PMID: 10903206 DOI: 10.1126/science.289.5478.452] [Citation(s) in RCA: 172] [Impact Index Per Article: 7.2] [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: 11/03/2022]
Abstract
Mobile group II intron RNAs insert directly into DNA target sites and are then reverse-transcribed into genomic DNA by the associated intron-encoded protein. Target site recognition involves modifiable base-pairing interactions between the intron RNA and a >14-nucleotide region of the DNA target site, as well as fixed interactions between the protein and flanking regions. Here, we developed a highly efficient Escherichia coli genetic assay to determine detailed target site recognition rules for the Lactococcus lactis group II intron Ll.LtrB and to select introns that insert into desired target sites. Using human immunodeficiency virus-type 1 (HIV-1) proviral DNA and the human CCR5 gene as examples, we show that group II introns can be retargeted to insert efficiently into virtually any target DNA and that the retargeted introns retain activity in human cells. This work provides the practical basis for potential applications of targeted group II introns in genetic engineering, functional genomics, and gene therapy.
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Affiliation(s)
- H Guo
- Institute for Cellular and Molecular Biology, Department of Chemistry and Biochemistry, and Section of Molecular Genetics and Microbiology, School of Biological Sciences, University of Texas, Austin, TX 78712, USA
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32
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Abstract
Certain fractures and/or dislocations of the femoral head are known to cause arterial injury and result in post-traumatic osteonecrosis. However, the more complex etiology of non-traumatic osteonecrosis is multifactorial and includes chemotherapy, radiotherapy, thermal injuries, and especially coagulopathies, which are now commonly observed in these patients. Intravascular coagulation with fibrin thrombosis begins in the capillaries and sinusoids of the intraosseous microcirculation, and residual venous thrombosis is more likely to occur if there is coexistent hypofibrinolysis. Coagulopathies are intermediary events, which are always activated by some underlying etiologic risk factor(s). Conditions capable of triggering intravascular coagulation include familial thrombophilia (resistance to activated protein C, decreased protein C, protein S, or antithrombin III, and hyperhomocystinemia), hyperlipemia and embolic lipid (alcoholism and hypercortisonism), hypersensitivity reactions (allograft organ rejection, immune complexes, and antiphospholipid antibodies), bacterial endotoxic (Shwartzman) reactions and various viral infections, proteolytic enzymes (pancreatitis), tissue factor release (inflammatory bowel disease, malignancies, neurotrauma, and pregnancy), and other thrombophilic and hypofibrinolytic disorders. Currently known risk factors for non-traumatic osteonecrosis of the femoral head are described briefly in this review article.
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Affiliation(s)
- J P Jones
- Diagnostic Osteonecrosis Center and Research Foundation, Kelseyville, CA 95451, USA
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33
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Lightning LK, Jones JP, Friedberg T, Pritchard MP, Shou M, Rushmore TH, Trager WF. Mechanism-based inactivation of cytochrome P450 3A4 by L-754,394. Biochemistry 2000; 39:4276-87. [PMID: 10757976 DOI: 10.1021/bi992412u] [Citation(s) in RCA: 35] [Impact Index Per Article: 1.5] [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: 11/28/2022]
Abstract
Mechanism-based inactivation of human liver P450 3A4 by L-754,394, a Merck compound synthesized as a potential HIV protease inhibitor, was investigated using recombinant P450 3A4. Enzyme inactivation was characterized by a small partition ratio (3.4 or 4.3 +/- 0.4), i.e., the total number of metabolic events undergone by the inhibitor divided by the number of enzyme inactivating events, lack of reversibility upon extensive dialysis, no decrease in the characteristic 450-nm species relative to control, and covalent modification of the apoprotein. The major and minor products formed during the inactivation of P450 3A4 were the monohydroxylated and the dihydrodiol metabolites of L-754,394, respectively. L-754,394 that had been adducted to P450 3A4 was hydrolyzed under the conditions used for SDS-PAGE, Ni(2+) affinity chromatography, and proteolytic digestion. In addition, the modification was not stable to the acidic conditions of HPLC separation and CNBr digestion. The labile nature of the peptide adduct and the nonstoichiometric binding of the inactivating species to P450 3A4 precluded the direct identification of a covalently modified amino acid residue or the peptide to which it was attached. However, Tricine SDS-PAGE in combination with MALDI-TOF-MS and homology modeling, allowed I257-M317 to be tentatively identified as an active site peptide, while prior knowledge of the stability of N-, O-, and S-linked conjugates of activated furans implicates Glu307 as the active site amino acid that is labeled by L-754, 394.
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Affiliation(s)
- L K Lightning
- Department of Medicinal Chemistry, University of Washington, Box 357610, Seattle, Washington 98195, USA
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34
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Shouval HZ, Goldberg DH, Jones JP, Beckerman M, Cooper LN. Structured long-range connections can provide a scaffold for orientation maps. J Neurosci 2000; 20:1119-28. [PMID: 10648717 PMCID: PMC6774168] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/15/2023] Open
Abstract
In the visual cortex of the cat and ferret, it is established that maturation of orientation selectivity is shaped by experience-dependent plasticity. However, recent experiments indicate that orientation maps are remarkably stable and experience-independent. We present a model to account for these seemingly paradoxical results. In this model, a scaffold consisting of non-isotropic lateral connections is laid down in horizontal circuitry before visual experience. These lateral connections provide an experience-independent framework for the developing orientation maps by inducing a broad orientation tuning bias in the model neurons. Experience-dependent plasticity of the thalamocortical connections sharpens the tuning while the preferred orientation of the neurons remains unchanged. This model is verified by computer simulations in which the scaffolds are generated both artificially and inferred from experimental optical imaging data. The plasticity is modeled by the BCM synaptic plasticity rule, and the input environment consists of natural images. We use this model to provide a possible explanation of the recent observation in which two eyes without common visual experience develop similar orientation maps. Finally, we propose an experiment involving the disruption of lateral connections to distinguish this model from models proposed by others.
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Affiliation(s)
- H Z Shouval
- Departments of Neuroscience and Physics and the Institute for Brain and Neural Systems, Brown University, Providence, Rhode Island 02912, USA.
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35
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Jones JP. A life-cycle approach to ministry with the aging. J Pastoral Care 2000; 53:323-31. [PMID: 10623203 DOI: 10.1177/002234099905300308] [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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
Notes that the demographic predictions of dramatic increase in the number of elderly members of local congregations will change the focus and emphasis in pastoral ministry in the next millennium as the needs of the aging take precedence. Argues for a comprehensive, life-cycle approach to ministries with the aging that integrates theology and the behavioral sciences. Offers examples and practical methods for ministering more effectively to this important and growing population in the local church.
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Affiliation(s)
- J P Jones
- St. Margaret's Episcopal Church, Inverness, FL 34450-4121, USA
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36
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Abstract
False smut, caused by Ustilaginoidea virens (Cooke) Takah., has been occurring in Louisiana rice since at least 1906 (4). A color plate (no. 69) of the disease was published in the Compendium of Rice Diseases published by the American Phytopathological Society (3). The slide for this plate was taken by M. C. Rush in 1976 of rice grown at the Rice Research Station at Crowley, LA. Since that time, the disease has been sporadic and light in Louisiana. In 1997, however, incidence was high. False smut was present on many germ plasms at the Rice Research Station in Crowley and was observed on commercial cultivars in several growers' fields in southwestern Louisiana. Incidence ranged from 1 to 15% of tillers infected with at least two to three spore balls per infected panicle. The disease occurred on both long- and medium-grain cultivars. False smut of rice occurs in the field at the hard dough to mature stages of the crop. A few spikelets in a panicle transform into globose, yellowish green, velvety spore balls that are 2 to 5 cm in diameter and covered by a thin orange membrane. The membrane bursts open and releases powdery dark green spores. The chlamydospores formed in the spore balls are spherical to elliptical, warty, olivaceous, and 3 to 5 × 4 to 6 μm in dimension. Some of the spore balls develop one or more sclerotia, which are the overwintering structure, in the center. False smut has been considered a minor disease of rice that occurs sporadically in Louisiana. The recent discovery of ustilotoxin, a phytotoxin and mycotoxin, produced by this pathogen on diseased tissues suggests that the fungus may be of concern as a contaminant on rice products consumed by livestock and humans (1,2). This increases the need to monitor the incidence of this disease. References: (1) Koiso et al. Ustiloxin: A phytotoxin and a mycotoxin from false smut balls on rice panicles. Tetrahedron Lett. 33:4157, 1992. (2) Koiso et al. Ustiloxins, antimitotic cyclic peptides from false smut balls on rice panicles caused by Ustilaginoidea virens. J. Antibiot. 47:765, 1994. (3) F. N. Lee and P. S. Gunnel. 1992. Compendium of Rice Diseases. The American Phytopathological Society, St. Paul, MN. p. 28. (4) W. A. Orton. 1907. Plant diseases of 1906. Yearbook U.S. Department of Agriculture. U.S. Government Printing Office, Washington, DC, pp. 499-508.
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Affiliation(s)
- M C Rush
- Louisiana State University, Department of Plant Pathology and Crop Physiology, Baton Rouge 70803
| | - A K M Shahjahan
- Louisiana State University, Department of Plant Pathology and Crop Physiology, Baton Rouge 70803
| | - J P Jones
- Louisiana State University, Department of Plant Pathology and Crop Physiology, Baton Rouge 70803
| | - D E Groth
- Rice Research Station, Louisiana State University Agricultural Center, Crowley 70527
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Jones JP, Meck WH, Williams CL, Wilson WA, Swartzwelder HS. Choline availability to the developing rat fetus alters adult hippocampal long-term potentiation. Brain Res Dev Brain Res 1999; 118:159-67. [PMID: 10611515 DOI: 10.1016/s0165-3806(99)00103-0] [Citation(s) in RCA: 104] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Supplementation with choline during pregnancy in rats causes a long-lasting improvement of visuospatial memory of the offspring. To determine if the behavioral effects of choline are related to physiological changes in hippocampus, the effect of perinatal choline supplementation or deficiency on long-term potentiation (LTP) was examined in hippocampal slices of 6-8 and 12-14 month old rats born to dams consuming a control, choline-supplemented, or a choline-free diet during pregnancy. Stimulating and recording electrodes were placed in stratum radiatum of area CA1 to record extracellular population excitatory postsynaptic potentials (pEPSPs). To induce LTP, a theta-like stimulus train was generated. The amplitude of the stimulus pulses was set at either 10% or 50% of the stimulus intensity which had induced the maximal pEPSP slope on the input/output curve. We found that at both ages, a significantly smaller percentage of slices from perinatally choline-deficient rats displayed LTP after 10% stimulus intensity (compared with control and choline-supplemented rats), and a significantly larger percentage of slices from choline-supplemented rats displayed LTP at 50% stimulus intensity (compared with control and choline-deficient rats). Results reveal that alterations in the availability of dietary choline during discrete periods of development lead to changes in hippocampal electrophysiology that last well into adulthood. These changes in LTP threshold may underlie the observed enhancement of visuospatial memory seen after prenatal choline supplementation and point to the importance of choline intake during pregnancy for development of brain and memory function.
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Affiliation(s)
- J P Jones
- Department of Genetics, Duke University, Durham, NC, USA
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38
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He M, Korzekwa KR, Jones JP, Rettie AE, Trager WF. Structural forms of phenprocoumon and warfarin that are metabolized at the active site of CYP2C9. Arch Biochem Biophys 1999; 372:16-28. [PMID: 10562412 DOI: 10.1006/abbi.1999.1468] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.3] [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: 11/22/2022]
Abstract
Possible reasons for the observed differences in metabolic behavior and drug interaction liability between the structurally similar oral anticoagulants warfarin and phenprocoumon were explored. Incubating (S)-phenprocoumon with human liver microsomes and cDNA-expressed CYP2C9 and determining its metabolism both in the absence and presence of the CYP2C9 inhibitor, sulfaphenazole, confirmed that phenprocoumon is a substrate for CYP2C9. Comparing the metabolic behavior of (S)- and (R)-warfarin, (S)- and (R)-phenprocoumon, and fixed structural mimics of the various tautomeric forms [(S)- and (R)-4-methoxyphenprocoumon, (S)- and (R)-2-methoxyphenprocoumon, (S)- and (R)-4-methoxywarfarin, (S)- and (R)-2-methoxywarfarin, and 9(S)- and 9(R)-cyclocoumarol] available to these two drugs with expressed CYP2C9 provides compelling evidence indicating that the ring closed form of (S)-warfarin and the ring opened anionic form of (S)-phenprocoumon are the major and specific structural forms of the two drugs that interact with the active site of CYP2C9. The conclusion that (S)-warfarin and (S)-phenprocoumon interact with CYP2C9 in very different structural states provides a clear basis for the significant differences observed in their metabolic profiles. Moreover, in accord with a previously established CoMFA model these results are consistent with the hypothesis that the active site of CYP2C9 possesses at least two major substrate binding sites, a pi-stacking site for aromatic rings and an ionic binding site for organic anions. An additional electrostatic binding site also appears to contribute to the orientation of coumarin analogs in the CYP2C9 active site by interacting with the C2-carbonyl group of the coumarin nucleus.
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Affiliation(s)
- M He
- Department of Medicinal Chemistry, School of Pharmacy, University of Washington, Seattle 98195, USA
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39
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Abstract
OBJECTIVES To provide non-clinical normative data for the Novaco Anger Scale. To identify the ability of the scale to discriminate between clinical and non-clinical populations. DESIGN Postal survey of individuals from a non-clinical sample. METHOD A non-clinical sample of 212 NHS employees was sent a questionnaire pack, including the Novaco Anger Scale. A clinical sample of 58 outpatient anger-management referrals was identified from a retrospective case-note analysis. RESULTS Descriptive data are presented for both samples. t-score conversions are provided, based on the non-clinical data. Results from a discriminant function analysis demonstrated that the Novaco Anger Scale classified participants as clinical or non-clinical with 94% accuracy. CONCLUSION From this study it appears that the Novaco Anger Scale is able to discriminate between clinical and non-clinical populations. These data offer further support to the validity of the Novaco Anger Scale and its use in clinical assessment.
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Affiliation(s)
- J P Jones
- Clinical Psychology Department, University of Birmingham, UK
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40
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Abstract
R2 elements are non-LTR retrotransposons that insert in the 28S rRNA genes of arthropods. Partial sequence data from many species have previously suggested that these elements have been vertically inherited since the origin of this phylum. Here, we compare the complete sequences of nine R2 elements selected to represent the diversity of arthropods. All of the elements exhibited a uniform structure. Identification of their conserved sequence features, combined with our biochemical studies, allows us to make the following inferences concerning the retrotransposition mechanism of R2. While all R2 elements insert into the identical sequence of the 28S gene, it is only the location of the initial nick in the target DNA that is rigidly conserved across arthropods. Variation at the R2 5' junctions suggests that cleavage of the second strand of the target site is not conserved within or between species. The extreme 5' and 3' ends of the elements themselves are also poorly conserved, consistent with a target primed reverse transcription mechanism for attachment of the 3' end and a template switch model for the attachment of the 5' end. Comparison of the approximately 1,000-aa R2 ORF reveals that it can be divided into three domains. The central 450-aa domain can be folded by homology modeling into a tertiary structure resembling the fingers, palm, and thumb subdomains of retroviral reverse transcriptases. The carboxyl terminal end of the R2 protein appears to be the endonuclease domain, while the amino-terminal end contains zinc finger and c-myb-like DNA-binding motifs.
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Affiliation(s)
- W D Burke
- Department of Biology, University of Rochester, New York 14627-0211, USA
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41
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Henry EC, Kende AS, Rucci G, Totleben MJ, Willey JJ, Dertinger SD, Pollenz RS, Jones JP, Gasiewicz TA. Flavone antagonists bind competitively with 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) to the aryl hydrocarbon receptor but inhibit nuclear uptake and transformation. Mol Pharmacol 1999; 55:716-25. [PMID: 10101030] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/11/2023] Open
Abstract
Previous analyses suggested that potent aryl hydrocarbon receptor (AhR) antagonists were planar, with a lateral electron-rich center. To further define structural requirements and mechanism for antagonism, ten additional flavone derivatives were synthesized. Based on their ability to 1) compete with 2,3,7, 8-tetrachlorodibenzo-p-dioxin (TCDD) for binding to the AhR; 2) inhibit TCDD-elicited binding of AhR to dioxin-responsive elements (DRE) in vitro; and 3) inhibit TCDD-induced transcription of DRE-dependent luciferase in stably transfected hepatoma cells, the most potent flavones contained a 3'-methoxy group and a 4'-substituent having one or more terminal atoms of high electron density (-N3, -NO2, or -NCS). Furthermore, these had low agonist activity as assessed by their inability to elicit AhR. DRE binding or to induce luciferase. Compounds containing bulkier 3' or 4'-substituents, or a 3'-OH group were less potent antagonists, and some were partial agonists. In rat liver cytosol, 3'-methoxy-4'-azido- and 3'-methoxy-4'-nitroflavones bound competitively (with TCDD) to the AhR, indicating that they bind to the TCDD-binding site. When hepatoma cells were exposed to these flavones, AhR complexes were primarily immunoprecipitable from the cytosol and contained 90 kDa heat shock protein. In contrast, AhR in TCDD-treated cells was primarily immunoprecipitated from nuclear extracts and was associated with Arnt but not 90 kDa heat shock protein. Immunocytofluorescence analysis in intact cells further indicated that the potent antagonist inhibited nuclear uptake of AhR and blocked TCDD-dependent down-regulation of AhR. Together, these data indicate that the most potent antagonists bind the AhR with high affinity but cannot initiate receptor transformation and nuclear localization.
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Affiliation(s)
- E C Henry
- Department of Environmental Medicine, University of Rochester, Rochester, New York 14642, USA.
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Haining RL, Jones JP, Henne KR, Fisher MB, Koop DR, Trager WF, Rettie AE. Enzymatic determinants of the substrate specificity of CYP2C9: role of B'-C loop residues in providing the pi-stacking anchor site for warfarin binding. Biochemistry 1999; 38:3285-92. [PMID: 10079071 DOI: 10.1021/bi982161+] [Citation(s) in RCA: 70] [Impact Index Per Article: 2.8] [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: 11/30/2022]
Abstract
Previous modeling efforts have suggested that coumarin ligand binding to CYP2C9 is dictated by electrostatic and pi-stacking interactions with complementary amino acids of the protein. In this study, analysis of a combined CoMFA-homology model for the enzyme identified F110 and F114 as potential hydrophobic, aromatic active-site residues which could pi-stack with the nonmetabolized C-9 phenyl ring of the warfarin enantiomers. To test this hypothesis, we introduced mutations at key residues located in the putative loop region between the B' and C helices of CYP2C9. The F110L, F110Y, V113L, and F114L mutants, but not the F114Y mutant, expressed readily, and the purified proteins were each active in the metabolism of lauric acid. The V113L mutant metabolized neither (R)- nor (S)-warfarin, and the F114L mutant alone displayed altered metabolite profiles for the warfarin enantiomers. Therefore, the effect of the F110L and F114L mutants on the interaction of CYP2C9 with several of its substrates as well as the potent inhibitor sulfaphenazole was chosen for examination in further detail. For each substrate examined, the F110L mutant exhibited modest changes in its kinetic parameters and product profiles. However, the F114L mutant altered the metabolite ratios for the warfarin enantiomers such that significant metabolism occurred for the first time on the putative C-9 phenyl anchor, at the 4'-position of (R)- and (S)-warfarin. In addition, the Vmax for (S)-warfarin 7-hydroxylation decreased 4-fold and the Km was increased 13-fold by the F114L mutation, whereas kinetic parameters for lauric acid metabolism, a substrate which cannot interact with the enzyme by a pi-stacking mechanism, were not markedly affected by this mutation. Finally, the F114L mutant effected a greater than 100-fold increase in the Ki for inhibition of CYP2C9 activity by sulfaphenazole. These data support a role for B'-C helix loop residues F114 and V113 in the hydrophobic binding of warfarin to CYP2C9, and are consistent with pi-stacking to F114 for certain aromatic ligands.
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Affiliation(s)
- R L Haining
- Department of Medicinal Chemistry, University of Washington, Seattle 98195, USA
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Cortright RN, Zheng D, Jones JP, Fluckey JD, DiCarlo SE, Grujic D, Lowell BB, Dohm GL. Regulation of skeletal muscle UCP-2 and UCP-3 gene expression by exercise and denervation. Am J Physiol 1999; 276:E217-21. [PMID: 9886970 DOI: 10.1152/ajpendo.1999.276.1.e217] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
The factors that regulate gene expression of uncoupling proteins 2 and 3 (UCP-2 and UCP-3) in skeletal muscle are poorly understood, but both genes are clearly responsive to the metabolic state of the organism. Therefore, we tested the hypothesis that denervation and acute and/or chronic exercise (factors that profoundly affect metabolism) would alter UCP-2 and UCP-3 gene expression. For the denervation studies, the sciatic nerve of rat and mouse hindlimb was sectioned in one leg while the contralateral limb served as control. Northern blot analysis revealed that denervation was associated with a 331% increase (P < 0.001) in UCP-3 mRNA and a 200% increase (P < 0. 01) in UCP-2 mRNA levels in rat mixed gastrocnemius (MG) muscle. In contrast, denervation caused a 53% decrease (P < 0.001) in UCP-3 and a 63% increase (P < 0.01) in UCP-2 mRNA levels in mouse MG. After acute exercise (2-h treadmill running), rat UCP-3 mRNA levels were elevated (vs. sedentary control) 252% (P < 0.0001) in white gastrocnemius and 63% (P < 0.05) in red gastrocnemius muscles, whereas UCP-2 levels were unaffected. To a lesser extent, elevations in UCP-3 mRNA (22%; P < 0.01) and UCP-2 mRNA (55%; P < 0.01) levels were observed after acute exercise in the mouse MG. There were no changes in either UCP-2 or UCP-3 mRNA levels after chronic exercise (9 wk of wheel running). These results indicate that acute exercise and denervation regulate gene expression of skeletal muscle UCPs.
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Affiliation(s)
- R N Cortright
- Department of Biochemistry, East Carolina University School of Medicine, Greenville, North Carolina 27858-4354, USA
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Koo KH, Jeong ST, Jones JP. Borderline necrosis of the femoral head. Clin Orthop Relat Res 1999:158-65. [PMID: 9973987] [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] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
Abstract
To determine whether the histologic lesions classified by the system of Arlet et al as Type 2 (granular necrosis of fatty marrow) and Type 3 (complete medullary and trabecular necrosis) always progress to Type 4 (complete necrosis with marginal medullary fibrosis and appositional new bone formation), 10 femoral heads (nine patients) were monitored for 4 years using serial magnetic resonance images. These femoral heads had been diagnosed histologically as having either Type 2 (seven hips) or Type 3 (three hips) necrosis on initial core biopsies. On the initial magnetic resonance image, none of the femoral heads showed any focal lesions indicative of osteonecrosis. In all instances, superselective angiography showed interruption of the superior retinacular artery, and the bone marrow pressure was elevated. During a followup period of 48 to 54 months, no patient had a reactive low signal intensity band develop on T1 weightings, as evidence of a reparative process around the necrotic portion of the lesion, or any other findings of osteonecrosis on magnetic resonance images. These findings suggest that some Type 2 and 3 lesions of Arlet et al may not develop an obvious reactive interface of reparative revascularization and thus may not progress to definite and classic Type 4 osteonecrosis. This study supports the hypothesis that there is an ischemic threshold between reversible intraosseous hypoxia (bone marrow edema syndrome) and irreversible intraosseous anoxia (classic bone infarction or osteonecrosis) and suggests that borderline necrosis occurs in the transition zone of this ischemic threshold and is nonprogressive.
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Affiliation(s)
- K H Koo
- Department of Orthopaedic Surgery, Gyeong-Sang National University School of Medicine, Chinju, South Korea
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Halpert JR, Domanski TL, Adali O, Biagini CP, Cosme J, Dierks EA, Johnson EF, Jones JP, Ortiz de Montellano P, Philpot RM, Sibbesen O, Wyatt WK, Zheng Z. Structure-function of cytochromes P450 and flavin-containing monooxygenases: implications for drug metabolism. Drug Metab Dispos 1998; 26:1223-31. [PMID: 9860932] [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] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/09/2023] Open
Abstract
This article is a report on a symposium held at Experimental Biology '98 in San Francisco, California. Recent developments in site-directed mutagenesis, computer-modeling, and mechanistic analysis of cytochromes P450 and flavin-containing monooxygenases are described. A unifying theme is the elaboration of general approaches for understanding and predicting the function of individual forms of these enzymes. A related goal is the production of soluble forms of mammalian cytochromes P450 for X-ray crystallography.
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Affiliation(s)
- J R Halpert
- Department of Pharmacology and Toxicology, College of Pharmacy, University of Arizona, USA.
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Abstract
White leaf streak, caused by Mycovellosiella oryzae (Deighton and Shaw) Deighton (syn. Ramularia oryzae), was found in Louisiana rice. The symptoms closely resemble those of narrow brown leaf spot caused by Cercospora janseana (Racib.) O. Const. (syn. C. oryzae (Miyake)), and it is difficult to distinguish between these two diseases. Initially both produce similar elongated light brown lesions, but later the lesions of white leaf streak become wider with a whitish center and are surrounded by a narrow light brown margin (2,3). The disease was first observed at the Rice Research Station, Crowley, LA, in 1996 on older leaves of the cultivar Lemont at maturity. Leaves containing the unusual lesion types were placed in a moist chamber and incubated at 28°C for 5 days. Abundant conidia were produced and the fungus was isolated on acidified potato dextrose agar (APDA) by single spore isolation and by plating infected tissues after surface sterilization in 40% Clorox for 10 to 15 min. The colonies grew slowly on APDA and were dark gray in color. The conidia formed in branched chains or singly. They were hyaline, cylindrical with tapering ends and a thick hilum; 0 to 3 septate, and 15 to 35 m long (1,3). Pathogenicity tests were conducted in the greenhouse on the Lemont and Cypress rice cultivars by spraying a conidial suspension (103-4 conidia per ml) onto leaf blades at boot stage. Conidia were produced by growing the fungus on PDA for 10 to 14 days. Inoculated plants were placed inside a humid chamber in a greenhouse and maintained for 4 to 5 weeks. Many elongated lesions similar to those observed in the field were produced 3 to 4 weeks after inoculation. Reisolation from these lesions yielded M. oryzae. With the same methods, 45 cultivars and lines were inoculated to determine their reactions to this disease. Most of the cultivars grown in the southern United States were moderately susceptible or susceptible to white leaf streak. Foreign cultivars tested, including BR-7, BR-11, Cica-4, Cica-6, Cica-7. Cica-8, Cica-9, Oryzica llanos, Rax clear, Teqing, and Tetep, were resistant. In 1997, the disease was found prevalent on many cultivars grown at the Rice Research Station, Crowley, LA. As symptoms of both white leaf streak and narrow brown leaf spot were sometimes observed on the same leaf; it is possible that the disease has been present, but not identified as a separate disease because of the similarity of the symptoms of the two diseases. A thorough survey is necessary to determine the extent of its occurrence and further studies are necessary to determine its yield loss potential. At present it appears to be a minor problem for Louisiana rice. White leaf streak has previously been recorded from Papua New Guinea on cultivated Oryza sativa, and from the Solomon Islands, Sabah, Nizeria, and Sierra Leone on cultivated O. glabberima Steudel and on wild perennial rice O. berthii A. Chev. (2). This is the first report of white leaf streak on cultivated rice in the United States. References: (1) F. C. Deighton. Mycol. Pap., CMI 144:1,1979. (2) F. C. Deighton and D. Shaw. Trans. Br. Mycol. Soc. 43: 515, 1960. (3) B. C. Sutton and A. K. M. Shahjahan. Nova Hedwigia 25:197, 1981.
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Affiliation(s)
- A K M Shahjahan
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge 70803
| | - M C Rush
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge 70803
| | - J P Jones
- Department of Plant Pathology and Crop Physiology, Louisiana State University Agricultural Center, Baton Rouge 70803
| | - D E Groth
- Rice Research Station, Crowley, Louisiana State University Agricultural Center, Crowley 70527
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Chandraratna PA, Gallet J, Jones JP, Do Y, Gunawardana R, Narang Y. An investigation of possible effects of high-frequency ultrasound on cellular integrity of cultured fibroblasts. Ultrasound Med Biol 1998; 24:911-914. [PMID: 9740392 DOI: 10.1016/s0301-5629(98)00032-5] [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] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Several investigators have demonstrated the feasibility of imaging at the cellular level using acoustical microscopy. It has also been proposed that acoustical microscopy technology might be adopted for in vivo applications. Before such applications are implemented, it is important to demonstrate that any major deleterious effects are highly unlikely. To this end, we have repeatedly scanned NIH/3T3 mouse fibroblasts in culture using an Olympus UH3 acoustical microscope operating at 600 MHz. No adverse effects were observed even after exposures for 1 h. Spatial peak temporal averaged intensities were estimated to be below 300 mW/cm2.
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Affiliation(s)
- P A Chandraratna
- Division of Cardiology, LA County/USC Medical Center, University of Southern California School of Medicine, Los Angeles 90033, USA
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Abstract
We report the construction of a functional chimera from approximately 50% bacterial (cytosolic) cytochrome P450cam and 50% mammalian (membrane-bound) cytochrome P450 2C9. The chimeric protein shows a reduced CO-difference spectrum absorption at 446 nm, and circular dichroism spectra indicate that the protein is globular. The protein is soluble and catalyzes the oxidation of 4-chlorotoluene using molecular oxygen and reducing equivalents from bacterial putidaredoxin and putidaredoxin reductase. This chimera provides a novel method for addressing structure-function issues and may prove useful in the design of oxidants for benign and stereospecific synthesis, as well as catalysts for bioremediation of polluted areas. Furthermore, these results provide the first evidence that bacterial P450 enzymes and mammalian P450 enzymes are likely to share a common tertiary structure.
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Affiliation(s)
- M Shimoji
- Department of Biochemistry, University of Rochester, New York 14642, USA
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Abstract
In this paper two hypotheses are tested: (i) the active oxygen species is similar in energetics for all cytochrome P450 (CYP) enzymes and (ii) linear free-energy relationships can be used to evaluate the mechanism of the reaction of these enzymes. A series of intramolecular isotope effects were determined and compared for CYPs 1A2, 2B1, 2C9, 2E1, and P450cam. The results indicate that the isotope effects are very similar for each of these isoforms of P450 and that the first hypothesis is likely to be true. Attempts to establish a linear free-energy relationship were only moderately successful: log Vmax = 0.11sigma+p + 1.73; r2 = 0.588. It was determined, through the use of intermolecular isotope effects, that the rates of hydrogen atom abstraction are masked. Thus, the second hypothesis is found to be false. This is likely to be a general result for CYP reactions, and linear free-energy relationships can only be used to determine the mechanism under very special circumstances. In all cases, the rate-limiting step should be evaluated with isotope effect experiments before any mechanistic conclusions can be drawn. If the intermolecular isotope effects are found to be masked, no mechanistic conclusion can be drawn from the linear free-energy relationship study.
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Affiliation(s)
- L Higgins
- Department of Pharmacology and Physiology, University of Rochester, New York 14642, USA
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Bachtold MR, Rinaldi PC, Jones JP, Reines F, Price LR. Focused ultrasound modifications of neural circuit activity in a mammalian brain. Ultrasound Med Biol 1998; 24:557-565. [PMID: 9651965 DOI: 10.1016/s0301-5629(98)00014-3] [Citation(s) in RCA: 57] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
The application of focused, pulsed ultrasound was studied as a method of modifying the activity of a local neural circuit of the mammalian brain. An in vitro hippocampal preparation was used to facilitate delivery, dosimetry and assessment of mechanisms of ultrasound effects. Extracellular evoked potentials were recorded from cell and dendritic layers of the rat hippocampal dentate gyrus. Focused pulses of ultrasound with center frequency of 500 kHz and repetition rate of 200 kHz were studied and found both to enhance and to depress electrically evoked field potentials. The fiber volley and cell population potentials were depressed, whereas the dendritic potential was enhanced. Results suggest a simultaneous mechanical and thermal mechanism of ultrasound in modifying evoked field potentials of dentate local circuits.
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Affiliation(s)
- M R Bachtold
- Department of Radiological Sciences, University of California, Irvine 92697, USA
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