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John D Carter

Publications and source records attributed to John D Carter.

16 recordsLinked to original sources
PubMed2006

Synthesis, characterization, and solution properties of a novel cross-bridged cyclam manganese(IV) complex having two terminal hydroxo ligands.

A novel monomeric tetravalent manganese complex with the cross-bridged cyclam ligand 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane (Me2EBC), [Mn(IV)(Me2EBC)(OH)2](PF6)2, was synthesized by oxidation of Mn(II)(Me2EBC)Cl2 with H2O2 in the presence of NH4PF6)in aqueous solution. The X-ray crystal structure determination of this manganese(IV) compound revealed that it contains two rare terminal hydroxo ligands. EPR studies in dry acetonitrile at 77 K show two broad resonances at g = 1.96 and 3.41, indicating that the manganese(IV) exists as a high-spin d3 species. Resonance Raman (rR) spectra of this manganese(IV) species reveal that the dihydroxy moiety, Mn(IV)(OH)2, is also the dominant species in aqueous solution (pH < 7). pH titration provides two pK(a) values, 6.86(4) and 10.0(1), associated with stepwise removal of the last two oxygen-bound protons from [Mn(IV)(Me2EBC)(OH)2](2+). The cyclic voltammetry of this manganese(IV) complex in dry acetonitrile at 298 K demonstrates two reversible redox processes at +0.756 and -0.696 V (versus SHE) for the Mn4+/Mn3+ and Mn3+/Mn2+ couples, respectively. This manganese(IV) complex is relatively stable in weak acidic aqueous solution but easily degrades in basic solution to manganese(III) derivatives with an 88 +/- 1% yield.

Journal Article↗
PubMed2006

Olefin epoxidation by the hydrogen peroxide adduct of a novel non-heme mangangese(IV) complex: demonstration of oxygen transfer by multiple mechanisms.

Olefin epoxidations are a class of reactions appropriate for the investigation of oxygenation processes in general. Here, we report the catalytic epoxidation of various olefins with a novel, cross-bridged cyclam manganese complex, Mn(Me2EBC)Cl2 (Me2EBC is 4,11-dimethyl-1,4,8,11-tetraazabicyclo[6.6.2]hexadecane), using hydrogen peroxide as the terminal oxidant, in acetone/water (ratio 4:1) as the solvent medium. Catalytic epoxidation studies with this system have disclosed reactions that proceed by a nonradical pathway other than the expected oxygen-rebound mechanism that is characteristic of high-valent, late-transition-metal catalysts. Direct treatment of olefins with freshly synthesized [Mn(IV)(Me2EBC)(OH)2](PF6)2 (pKa = 6.86) in either neutral or basic solution confirms earlier observations that neither the oxo-Mn(IV) nor oxo-Mn(V) species is responsible for olefin epoxidization in this case. Catalytic epoxidation experiments using the 18O labels in an acetone/water (H2(18)O) solvent demonstrate that no 18O from water (H2(18)O) is incorporated into epoxide products even though oxygen exchange was observed between the Mn(IV) species and H2(18)O, which leads to the conclusion that oxygen transfer does not proceed by the well-known oxygen-rebound mechanism. Experiments using labeled dioxygen, (18)O2, and hydrogen peroxide, H2(18)O2, confirm that an oxygen atom is transferred directly from the H2(18)O2 oxidant to the olefin substrate in the predominant pathway. The hydrogen peroxide adduct of this high-oxidation-state manganese complex, Mn(IV)(Me2EBC)(O)(OOH)+, was detected by mass spectra in aqueous solutions prepared from Mn(II)(Me2EBC)Cl2 and excess hydrogen peroxide. A Lewis acid pathway, in which oxygen is transferred to the olefin from that adduct, Mn(IV)(Me2EBC)(O)(OOH)+, is proposed for epoxidation reactions mediated by this novel, non-heme manganese complex. A minor radical pathway is also apparent in these systems.

Journal Article↗
PubMed2006

Prevalence of evaluation and treatment of glucocorticoid-induced osteoporosis in men.

BACKGROUND: Screening and treatment of glucocorticoid- induced osteoporosis in male patients is less than recommended despite available screening and therapies. OBJECTIVES: We determined if men treated with long-term oral glucocorticoid therapy for any reason receive assessment and therapy for the prevention and treatment of glucocorticoid-induced osteoporosis. METHODS: A retrospective computer-generated chart review was performed involving all men given prednisone from January 2002 through July 2002. There were 370 patients evaluated from the James A. Haley Veterans Affairs Hospital, Tampa, Florida, a large teaching hospital for the University of South Florida College of Medicine. Charts were reviewed for bone mineral density testing; dose, duration, and indication of glucocorticoid therapy; age of the patients as of January 2002;continuous or intermittent dosing; history of fracture; bone loss prevention medication use, including bisphosphonate, calcitonin, testosterone replacement therapy, calcium, and vitamin D; and the steroid-prescribing and screening practitioner's specialty and sex. RESULTS: Of the 370 men, 258 used 7.5 mg prednisone or more daily and 295 used glucocorticoids for more than 3 months. Of the 370 men, 163 had a bone mineral density test; 87 were treated with a bisphosphonate. Calcium and vitamin D were given to half of the patients. Of the patients with a normal T-score, 13 of 55 were treated with a bisphosphonate (24%) compared with 24 of 40 (60%) with an osteopenic score and 14 of 21 (67%) with osteoporosis. Of the 46 patients with no score available but indication that it had been ordered or otherwise addressed, 23 patients were treated empirically with a bisphosphonate. Rheumatology screened 75% of their patients, whereas primary care screened 30% of their patients. CONCLUSIONS: Bone mineral density testing was performed or ordered for less than half of the glucocorticoid-treated patients and less than one third were taking bisphosphonate therapy. Further intervention is needed to increase prevention of glucocorticoid-induced osteoporosis and subsequent risk of fracture.

Aged↗
PubMed2006

Tumor necrosis factor-alpha inhibition and VATER association: a causal relationship.

Inflammatory conditions that may require the use of a tumor necrosis factor-a (TNF-a) antagonist often involve women of child-bearing age. TNF-a antagonists are presumed to be safe in pregnancy based on animal data. However, this has never been formally studied in prospective trials involving humans. We describe a patient with psoriasis and psoriatic arthritis who took etanercept 50 mg subcutaneously (SQ) twice weekly throughout her pregnancy. She gave birth to a child with VATER association. Animal and human data exist to suggest a possible causal relationship between the mother's use of etanercept and the child's development of VATER association. We propose that the TNF antagonists, specifically etanercept, be used with caution in pregnant women. Patient registries of women who take TNF-a antagonists during pregnancy also need to be followed to see if there is an increase in the birth defects that are part of VATER association.

Abnormalities, Multiple↗
PubMed2005

Olefin oxygenation by the hydroperoxide adduct of a nonheme manganese(IV) complex: epoxidations by a metallo-peracid produces gentle selective oxidations.

The reactive intermediates and mechanisms of oxygenation of olefins by manganese complexes were investigated by treating olefins with newly synthesized [MnIV(Me2EBC)(OH)2](PF6)2 in the presence and absence of peroxide and by studying its catalytic epoxidation reaction in normal aqueous solution and, individually, with isotopically labeled H218O, 18O2, and H218O2. The manganese oxo species is not the reactive intermediate for the oxygen transfer process mediated by this manganese complex. A novel manganese(IV) peroxide intermediate, MnIV(Me2EBC)(O)(OOH)+, was captured by mass spectrometry and is proposed as the intermediate that oxygenates olefins in this catalytic system.

Journal Article↗
PubMed2004

Doxycycline versus doxycycline and rifampin in undifferentiated spondyloarthropathy, with special reference to chlamydia-induced arthritis. A prospective, randomized 9-month comparison.

OBJECTIVE: Chlamydia is a known trigger of reactive arthritis (ReA). It may also be common cause of undifferentiated spondyloarthropathy (uSpA). Persistent, metabolically active, Chlamydiae have been observed in the synovial tissue of these patients years after their initial exposure. Trials with lymecycline and rifampin have shown benefit in early/acute Chlamydia-induced arthritis. In vitro data suggest that persistent Chlamydia become resistant to chronic monotherapy of tetracyclines or rifampin, whereas no such resistance is noted when rifampin is added to antimicrobials that are active against Chlamydia. Rifampin and doxycycline also show synergistic effect against Chlamydia. In addition, rifampin inhibits chlamydial production of heat shock proteins (HSP). HSP60 plays a key role in the chronic persistent state of Chlamydia. We conducted a prospective, randomized 9-month trial to evaluate the efficacy of doxycycline versus a combination of doxycycline and rifampin in the treatment of uSpA. METHODS: The study enrolled 30 patients with chronic inflammatory arthritis (average disease duration 10 yrs) who fulfilled the European Spondylarthropathy Study Group criteria, with no evidence of inflammatory bowel disease, psoriasis, ankylosing spondylitis, or preceding dysentery. Patients received doxycycline 100 mg po twice daily or a combination of doxycycline 100 mg po twice daily and rifampin 600 mg po daily. They received a 4-question self-questionnaire and a blinded joint examination at each visit. The questions include a visual analog scale (VAS) for their current amount of back pain, duration of morning stiffness, back pain at night, and peripheral joint pain. The blinded joint examination consisted of a swollen joint count (SJC) and a tender joint count (TJC). These 6 variables were assessed at baseline and at 1, 3, 6, and 9 months. Responders were defined as those who improved > or = 20% in at least 4 of the 6 variables at 9 months of therapy. RESULTS: Comparing the doxycycline + rifampin arm (D/R) versus the doxycycline arm (D) at 9 months of therapy, all 6 variables improved more in D/R versus D, 4 of which were statistically significant. The mean VAS (scale of 100) decreased 24.4 points in D/R in contrast to 3 points in D (p < 0.03). Duration of morning stiffness decreased by 1.2 h in D/R, with a slight increase of 0.1 h in D (p < 0.003). The back pain at night and peripheral joint pain both improved in D/R group versus D (not statistically significant). Finally, the SJC and TJC also improved in D/R (-2.1 and -2.5) versus D (-0.4 and -0.6; p = 0.02, p = 0.03, respectively). Eleven of 15 patients in the D/R arm were responders, whereas only 2 of 15 D group patients were considered responders (p < 0.003). CONCLUSION: The combination of doxycycline and rifampin for 9 months seemed to be effective in treatment of chronic uSpA. This is the first study to demonstrate therapeutic benefit with antimicrobials to a chronic inflammatory arthritis possibly secondary to persistent Chlamydia.

Adult↗
PubMed2003

Instabilities in the two-dimensional cubic nonlinear Schrödinger equation.

The two-dimensional cubic nonlinear Schrödinger equation (NLS) can be used as a model of phenomena in physical systems ranging from waves on deep water to pulses in optical fibers. In this paper, we establish that every one-dimensional traveling wave solution of NLS with linear phase is unstable with respect to some infinitesimal perturbation with two-dimensional structure. If the coefficients of the linear dispersion terms have the same sign (elliptic case), then the only unstable perturbations have transverse wavelength longer than a well-defined cutoff. If the coefficients of the linear dispersion terms have opposite signs (hyperbolic case), then there is no such cutoff and as the wavelength decreases, the maximum growth rate approaches a well-defined limit.

Journal Article↗
PubMedDate not supplied

Hypersensitivity vasculitis with leukocytoclastic vasculitis secondary to infliximab.

Infliximab is an antibody to tumor necrosis factor (TNF) that is used in the treatment of Crohn disease and rheumatoid arthritis. This medication neutralizes TNF-alpha by binding to TNF receptors and inhibiting further induction of proinflammatory cytokines. We describe a patient with Crohn disease who developed hypersensitivity vasculitis with biopsy-proven leukocytoclastic vasculitis 9 days after her initial dose of infliximab. To our knowledge, this is the first reported case of infliximab-induced hypersensitivity vasculitis with leukocytoclastic vasculitis that occurred after the first dose of drug. It is important to note that hypersensitivity vasculitis can occur secondary to administration of this drug, even after the initial exposure.

Adult↗