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J W Cox

Publications and source records attributed to J W Cox.

At least 19 recordsLinked to original sources
PubMed2001

Kinetic analysis of the stepwise formation of a long-range DNA interstrand cross-link by a dinuclear platinum antitumor complex: evidence for aquated intermediates and formation of both kinetically and thermodynamically controlled conformers.

Reported here is a detailed study of the kinetics and mechanism of formation of a 1,4 GG interstrand cross-link by [(trans-PtCl(NH(3))(2))(2)(mu-NH(2)(CH(2))(n)NH(2))](2+) (1,1/t,t (n = 6), 1), the prototype of a novel class of platinum antitumor complexes. The reaction of the self-complementary 12-mer duplex 5'-[d(ATATGTACATAT)(2)] with (15)N-1 has been studied at 298 K, pH 5.4, by [(1)H,(15)N] HSQC 2D NMR spectroscopy. Initial electrostatic interactions with the duplex are observed for 1 and the monoaqua monochloro species (2). Aquation of 1 to yield 2 occurs with a pseudo-first-order rate constant of (4.15 +/- 0.04) x 10(-5) s(-1). 2 then undergoes monofunctional binding to the guanine N7 of the duplex to form 3 (G/Cl) with a rate constant of 0.47 +/- 0.06 M(-(1) s(-1). There is an electrostatic interaction between the unbound [PtN(3)Cl] group of 3 and the duplex, which is consistent with H-bonding interactions observed in the molecular model of the monofunctional (G/Cl) adduct. Closure of 3 to form the 1,4 GG interstrand cross-link (5) most likely proceeds via the aquated (G/H(2)O) intermediate (4) (pseudo-first-order rate constant = (3.62 +/- 0.04) x 10(-5) s(-1)) followed by closure of 4 to form 5 (rate constant = (2.7 +/- 1.5) x 10(-3) s(-1)). When closure is treated as direct from 3 (G/Cl) the rate constant is (3.39 +/- 0.04) x 10(-5) s(-1). Closure is ca. 10-55-fold faster than that found for 1,2 GG intrastrand cross-link formation by the diaqua form of cisplatin. Changes in the (1)H and (15)N shifts of the interstrand cross-link 5 indicate that the initially formed conformer (5(i)) converts irreversibly into other product conformer(s) 5(f). The NMR data for 5(i) are consistent with a molecular model of the 1,4 GG interstrand cross-link on B-form DNA, which shows that the NH(2) protons have no contacts except with solvent. The NMR data for 5(f) show several distinct NH(2) environments indicative of interactions between the NH(2) protons and the DNA. HPLC characterization of the final product showed only one major product peak that was confirmed by ESI-FTICR mass spectroscopy to be a cross-linked adduct of (15)N-1 and the duplex. The potential significance of these findings to the antitumor activity of dinuclear platinum complexes is discussed.

Antineoplastic Agents↗
PubMed1999

DNA modifications by a novel bifunctional trinuclear platinum phase I anticancer agent.

The DNA-binding profile of a novel, trinuclear platinum Phase I clinical agent (BBR3464) is summarized. The structure of BBR3464 is best described as two trans-[PtCl(NH3)2] units linked by a tetra-amine [trans-Pt(NH3)2{H2N(CH2)6NH2}2]2+ unit. The +4 charge of BBR3464, the presence of at least two Pt coordination units capable of binding to DNA, and the consequences of such DNA binding are remarkable departures from the cisplatin structural paradigm. The chemical and biological features argue that the drug should be considered the first clinical representative of an entirely new structural class of DNA-modifying anticancer agents. The high charge on BBR3464 facilitates rapid binding to DNA with a t1/2 of approximately 40 min, significantly faster than the neutral cisplatin. The melting temperature of DNA adducted by BBR3464 increased at low ionic strength but decreased in high salt for the same rb. This unusual behavior is in contrast to that of cisplatin. BBR3464 produces an unwinding angle of 14 degrees in negatively supercoiled pSP73 plasmid DNA, indicative of bifunctional DNA binding. Quantitation of interstrand DNA-DNA cross-linking in plasmid pSP73 DNA linearized by EcoRI indicated approximately 20% of the DNA to be interstrand cross-linked. While this is significantly higher than the value for cisplatin, it is, interestingly, lower than that for dinuclear platinum compounds such as [{trans-PtCl(NH3)2}2H2N(CH2)6NH2]2+ (BBR3005) where interstrand cross-linking efficiency may be as high as 70-90%. Either the presence of charge in the linker backbone or the increased distance between platinating moieties may contribute to this relatively decreased ability of BBR3464 to induce DNA interstrand cross-linking. Fluorescence experiments with ethidium bromide were consistent with the formation of long-range delocalized lesions on DNA produced by BBR3464. The sequence preference for BBR3464 on plasmid DNA was determined to the exact base pair by assaying extension of the polynucleotide by VentR(exo+) DNA polymerase. Strong sequence preference for single dG or d(GG) sites was suggested. The presence of relatively few blocks on DNA in comparison to either cisplatin or BBR3005 was indicative of high sequence selectivity. The following appropriate sequence where stop sites occur was chosen: [sequence: see text] molecular modeling on 1,4 interstrand (G'30 to G33) and 1,5 intrastrand (G33 to G29) cross-links further confirmed the similarity in energy between the two forms of cross-link. Finally, immunochemical analysis confirmed the unique nature of the DNA adducts formed by BBR3464. This analysis showed that antibodies raised to cisplatin-adducted DNA did not recognize DNA modified by BBR3464. In contrast, DNA modified by BBR3464 inhibited the binding of antibodies raised to transplatin-adducted DNA. Thus, the bifunctional binding of BBR3464 contains few similarities to that of cisplatin but may have a subset of adducts recognized as being similar to the transplatinum species. In summary, the results point to a unique profile of DNA binding for BBR3464, strengthening the original hypothesis that modification of DNA binding in manners distinct from that of cisplatin will also lead to a distinct and unique profile of antitumor activity.

Antineoplastic Agents↗
PubMed1999

Effects of feeding virginiamycin and sodium bicarbonate to grazing lactating dairy cows.

The effects of virginiamycin, an agent active against Gram-positive lactic acid-producing bacteria, and NaHCO3 on ruminal and fecal pH, rumen volatile fatty acid proportions, blood metabolites, and milk production and composition were assessed. This study was conducted over 28 d and involved 71 dairy cows that grazed predominantly ryegrass, oats, and clover, and that were fed 10 kg of concentrate pellets/d per head. The pellets contained (per kilogram) no dietary additive, 30 mg of virginiamycin, 20 g of NaHCO3, or 30 mg of virginiamycin and 20 g of NaHCO3 on a DM basis. Ruminal pH tended to be higher in cows fed pellets containing virginiamycin (7.0 vs. 6.9; SED = 0.16). The results of in vitro incubation of ruminal fluid with glucose found the potential for L-lactic acid accumulation in ruminal fluid to be significantly lower in cows fed virginiamycin (15.5 vs. 35.3 mmol/L; SED = 2.98). Cows fed virginiamycin had significantly higher fecal pH (6.72 vs. 6.57; SED = 0.08) and produced more milk (23.94 vs. 23.32 kg/d) and more lactose than those not fed virginiamycin. No effects of NaHCO3 on fecal pH, in vitro potential for L-lactic acid accumulation in ruminal fluid, or milk production were observed, but ruminal pH tended to be higher and ruminal acetate proportion was greater for cows fed NaHCO3. Milk fat and milk protein percentage did not differ significantly as a result of dietary treatment. These data suggest that the inclusion of virginiamycin in the diet will reduce L-lactic acid accumulation in ruminal fluid and increase fecal pH in grazing dairy cattle fed concentrate supplements.

Animal Feed↗
PubMed1996

The social and educational outcome of a cohort of rural children in relation to the racial and socio-economic groupings of their parents.

OBJECTIVE: To evaluate the outcome after a generation of extra health and educational intervention among children whose antenatal and perinatal characteristics appeared influenced by racial origin and socio-economic status. METHODOLOGY: Sixty-five of an original cohort of 103 children born in Cunnamulla, Queensland, 1974-75, remained in the area allowing educational and social outcomes to be assessed: 40 were Aboriginal, 25 were children of unemployed Caucasians and 38 were children of employed Caucasians. The criteria for a successful outcome on leaving school were progression to further education or finding paid employment. RESULTS: Fifty-three of the children who had left school were assessed (the remaining 12 were still at school). Only four of the 30 assessed Aborigines had successful outcomes compared with 10 of the 13 employed Caucasians and three of the 10 unemployed Caucasians. Gender influenced success, with females under-represented such that among the 23 Aboriginal and unemployed Caucasian girls only one had a successful outcome; 13 of these 23 girls were pregnant before finishing secondary education. CONCLUSIONS: The educational and social success of Aborigines is poor compared with the children of employed Caucasians. Outcomes for children of unemployed Caucasians are similar to those of Aborigines, suggesting failure of a range of government and community intervention programmes.

Adolescent↗
PubMed1996

Transcatheter modification of the atrioventricular node in dogs, using radiofrequency energy.

OBJECTIVE: To develop a protocol for reliably inducing atrioventricular (AV) block (ideally first- or second-degree), using radiofrequency energy. DESIGN: An electrosurgical unit was coupled to an ammeter, which was connected to the distal pole of an electrode catheter positioned at the AV node. Control settings had previously been calibrated to the power output in a circuit with a 100-ohm resistance. ANIMALS: 10 clinically normal dogs. PROCEDURE: Transcatheter AV nodal modification was attempted, using progressive power applications of 10 to 20 W for progressive durations of 10 to 30 seconds. Atrioventricular nodal conduction and refractivity were measured before and 20 minutes and 1 month after ablation. Electrocardiograms were monitored throughout the 1-month period. RESULTS: Eight of the 10 dogs developed complete AV block, I developed stable 2:1 AV block, and another had no long-term change in AV nodal conduction. Four dogs attained their maximal degree of AV block in 2 to 5 days. Three of these had no AV nodal conduction changes until 2 to 4 days after ablation. CONCLUSIONS: An electrosurgical unit can be economically modified for radiofrequency transcatheter ablation. Stable, incomplete AV block was rarely induced using this protocol, whereas complete AV block often developed. A major finding was frequent delay between energy delivery to the AV nodal region and induction of AV block. CLINICAL RELEVANCE: Induction of complete AV block using this technique, followed by permanent pacemaker placement, is an effective alternative to long-term antiarrhythmic treatment in animals with chronic atrial arrhythmias. Transcatheter ablation could be used to treat other forms of tachycardia, as it is in human medicine.

Animals↗
PubMed1992

Biochemistry and pharmacology of lipid antioxidants in acute brain and spinal cord injury.

Oxygen radical-mediated lipid peroxidation (LP) has been suggested increasingly to be an important factor in posttraumatic neuronal degeneration. Thus, numerous studies have evaluated the neuroprotective efficacy of pharmacological agents with lipid antioxidant activity in models of spinal cord and brain injury. Intensive pretreatment of animals with the endogenous lipid peroxyl radical scavenger vitamin E (i.e., alpha-tocopherol) has been shown to decrease posttraumatic spinal cord ischemia and to enhance chronic neurological recovery. However, the slow CNS tissue uptake of vitamin E requires chronic dosing, making it an impractical agent for treatment of acute neural injury. The glucocorticoid steroid, methyl-prednisolone (MP), has been shown to possess significant antioxidant efficacy and, when administered to animals or humans in antioxidant doses, improves chronic neurological recovery after spinal cord injury. This activity of MP is independent of the steroid's glucocorticoid receptor-mediated actions, as evidenced by the efficacy of the novel antioxidant 21-aminosteroids, which are devoid of glucocorticoid activity but have greater antioxidant efficacy than MP. One of these, tirilazad mesylate (U-74006F), has been shown to be effective in animal models of brain and spinal cord injury and is currently the subject of phase II clinical trials. Recently, compounds that combine the amino functionality of the 21-amino-steroids with the peroxyl radical scavenging chromanol portion of vitamin E (i.e., 2-methylaminochromans) also have shown promise as neuroprotective agents. The consistent benefit afforded by antioxidant compounds further supports the concept that LP is an important therapeutic target for acute pharmacological neuroprotection.

Animals↗
PubMed1991

Plasma compatibility of injectables: comparison of intravenous U-74006F, a 21-aminosteroid antioxidant, with Dilantin brand of parenteral phenytoin.

The 21-aminosteroid antioxidant U-74006F (1) is being developed as an iv injectable agent for the treatment of human CNS trauma and ischemia. Because of its poor water solubility, the plasma compatibility of the parenteral formulation of 1 was evaluated using three models: (I) static solubility, (II) aggregometric, and (III) dynamic flow. The flow model was designed to mimic an iv infusion into the human antecubital vein, which was assumed to have plasma flow of 10 mL/min. Dilantin (phenytoin), the positive control, produced a precipitate in all three models from a 10% (v/v) mixture with human plasma, which approximates the in vivo ratio when the drug is infused at the recommended rate of 1 mL/min. Approximately 39% of the phenytoin dose in the flow model was retained on a downstream 3-microns filter as crystals. In comparison, the parenteral formulation of 1 produced minimal precipitate in models I and II from 40% mixtures with plasma, but higher percentages produced unstable suspensions with time-dependent precipitation. The percentage of the dose of the parenteral formulation of 1 retained on the filter in the flow model was 0.5% or less at infusion rates as high as 10 mL/min and 3% at 19 mL/min. At the 10-mL/min infusion rate, the mass of 1 retained on the filter per minute was less than 1% of the mass of phenytoin retained at the 1-mL/min infusion rate for Dilantin. The acceptable plasma compatibility of the parenteral formulation of 1 appears to be related to the solubilizing effects of plasma protein binding and pH suppression by the citric acid vehicle.

Antioxidants↗
PubMed1990

Hepatic changes produced by 30-day administration of a novel aminocyclitol antibiotic, trospectomycin sulfate, to laboratory animals.

The studies described here were done to characterize the hepatic response to a new aminocyclitol antibiotic, trospectomycin sulfate, administered intravenously (beagle dog) or subcutaneously (Sprague-Dawley rat) at a variety of dose levels, to investigate reversibility of observed changes, and to document any untoward effects of subchronic trospectomycin sulfate administration. Both species showed significant elevations in serum levels of alanine and aspartate transaminases in higher dose groups. In the dog only, a transient neuromuscular blockade was also observed within higher dose groups. No other functional, morphological, or serum chemical changes were observed. Examination of liver by electron microscopy revealed the presence of cytoplasmic lamellar inclusion bodies, concentrated in the bile canalicular region of the hepatocytes. Occurrence of the lamellar bodies and coincident transaminase increases were found to be reversible upon discontinuance of treatment (studied in the dog). Electron microscopy of acid phosphatase cytochemistry in the rat indicated that most, but not all, of the lamellar bodies contained this enzyme. This observation suggests that they may be derived from the lysosome, or once formed become lysosomal.

Acid Phosphatase↗
PubMed1989

Reversible, hepatic, lysosomal phospholipidosis in rat induced by subchronic daily administration of trospectomycin sulfate.

Trospectomycin sulfate is an experimental aminocyclitol antibiotic which has been shown previously to induce the formation of cytoplasmic lamellar bodies in rat and dog liver in subchronic experiments. The effect of repeated daily administration of trospectomycin sulfate on hepatic phospholipid levels and activities of marker enzymes for subcellular organelles was examined. Rats were treated for 30 or 90 days with 0, 50, or 250 mg/kg/day of trospectomycin sulfate prior to being killed, and another group was dosed for 90 days and then allowed to recover for 79 days prior to sacrifice. Transmission electron microscopy showed the presence of lamellar bodies in hepatocytes in both 50 and 250 mg/kg groups at 90 days but no other apparent changes in cellular morphology. Total phospholipids were increased significantly (1.6-fold) only at 90 days (P less than 0.01) and only in the 250 mg/kg group. Phosphatidylcholine, phosphatidylinositol, and two acidic lysosomal phospholipids, bis(monoacylglycero)phosphate and acylphosphatidylglycerol, accounted for 42, 35, and 21% of the increase in total phospholipids. Changes in the activities of marker enzymes were generally confined to the 250 mg/kg group at 90 days, with the largest and most significant increases being in the lysosomal enzymes acid phosphatase and hexosaminidase (P less than 0.01). Levels of all phospholipids and marker enzymes, with the exception of succinate dehydrogenase, were not significantly different from controls 79 days after cessation of dosing, and lamellar bodies had disappeared. We conclude that repeated trospectomycin sulfate treatment in rat induces a reversible, dose- and time-dependent lysosomal phospholipidosis in liver which is characterized by an increase in lysosomal enzymes and selected anionic phospholipids.

Animals↗
PubMed1988

Irregular retention properties of 21-aminosteroid antioxidants in octylsilane bonded-phase high-performance liquid chromatography.

The retention characteristics of two novel 21-aminosteroid antioxidants, 21-[4-(2,6-di-1-pyrrolidinyl-4-pyrimidinyl)-1-piperazinyl]-16 alpha-methylpregna-1,4,9(11)-triene-3,20-dione dimethanesulfonate (I) and 21-[4-(2,5-di-N-diethylamine-2-pyridinyl)-1-piperazinyl]-16 alpha-methylpregna-1,4,9(11)-triene-3,20-dione hydrochloride (II), in octylsilane bonded-phase high-performance liquid chromatography were examined in detail. Both I and II exhibited irregular retention behaviour which could be explained by the dual retention mechanism model proposed by A. Nahum and Cs. Horváth [J. Chromatogr., 203 (1981) 53]. Unless an amine modifier was added to competitively inhibit association with exposed silanol binding sites, the retention of both compounds in a 70% acetonitrile mobile phase was primarily due to silanophilic interactions. Addition of amine modifiers, lowering the pH, and increasing the sodium ion concentration of the mobile phase all decreased retention times, and modifiers capable of hydrogen bonding diminished peak tailing.

Antioxidants↗
PubMed1988

High-performance liquid chromatographic determination of a 21-aminosteroid antioxidant in plasma.

A novel 21-aminosteroid, 21-[4-(2,6-di-1-pyrrolidinyl-4-pyrimidinyl)-1- piperazinyl]-16 alpha-methylpregna-1,4,9(11)-triene-3,20-dione monomethanesulfonate (I), is under development for the treatment of central nervous system injury in humans. This report describes a reversed-phase high-performance liquid chromatographic (RP-HPLC) method using ultraviolet detection at 254 nm for the determination of I in plasma with low nanogram per milliliter sensitivity. Plasma was deproteinated by mixing with acetonitrile and centrifuging, and I was extracted from the supernatant with disposable bonded-phase columns. The extracts were chromatographed on an octylsilane bonded-phase HPLC column with an acetonitrile-water mobile phase containing triethylammonium acetate, pH5. Quantification was accomplished by peak-height ratio analysis using an analogue of I as the assay internal standard. The method was suitable for the determination of I following a 30 mg/kg intraperitoneal dose in the rat.

Animals↗
PubMed1988

Acute hepatocellular effects of erythromycin, gentamicin, and trospectomycin in the perfused rat liver: lack of correlation between lamellar body induction potency and cytotoxicity.

The formation of multilamellar inclusion bodies in cytoplasm is a generalized cellular response to treatment with a variety of chemical agents. The present study was conducted to determine if a correlation exists between acute lamellar body induction potency and cytotoxicity in the perfused rat liver. Livers were perfused for 3 hrs with various concentrations of erythromycin, gentamicin, sulfate, or trospectomycin sulfate, all of which are known to produce lamellar bodies in the rat in vivo. At the end of the experiments, the livers were perfusion fixed for transmission electron microscopy. Based on the bile flow rate, perfusion rate at constant pressure, and cytoplasmic enzyme release, neither gentamicin nor trospectomycin was hepatotoxic at concentrations up to 1.8 mM, whereas erythromycin was toxic at 0.1 mM. Gentamicin caused no ultrastructural changes compared to controls, but trospectomycin caused the dose-dependent formation of lamellar bodies in hepatocytes without other cytoplasmic alterations. Erythromycin caused cellular degeneration accompanied by an increase in the number of secondary lysosomes, but these lacked lamellated inclusions. It is concluded that hepatic lamellar bodies can be induced in acute ex vivo experiments, but that their formation does not appear to be linked with acute cytotoxicity.

Animals↗
PubMed1988

Pulmonary extraction and pharmacokinetics of prostaglandin E1 during continuous intravenous infusion in patients with adult respiratory distress syndrome.

Prostaglandin E1 (PGE1) is currently being evaluated in clinical trials to determine its usefulness in the treatment of adult respiratory distress syndrome (ARDS). The drug is administered to ARDS patients by continuous intravenous infusion at dosage rates of up to 30 ng/kg/min for 7 days. The present study was conducted to determine the pulmonary extraction efficiency and pharmacokinetics of PGE1 under these conditions. Plasma levels of PGE1 were determined by high performance liquid chromatography in 14 patients who either had ARDS or were considered to be at risk of developing ARDS following trauma or sepsis. Predose plasma levels of PGE1 were below the detection limit of the assay (50 pg/ml). At a dosage rate of 30 ng/kg/min, pulmonary arterial and systemic arterial plasma levels ranged from 265 to 1,009 pg/ml and 50 to 796 pg/ml, respectively. The pulmonary extraction ratio (Ep) of PGE1 varied from 0.11 to 0.90 and was independent of dose but dependent on cardiac output. The data were adequately described by first-order pharmacokinetic equations which assumed that the lung was the only site of PGE1 clearance. Nine of 10 patients with AaPO2/FlO2 below 510 mm Hg had Ep greater than 0.7 and high pulmonary intrinsic clearance for PGE1 (ca. 250 L/min), but all 4 patients with AaPO2/FlO2 above 510 mm Hg had Ep less than 0.6 and low intrinsic clearance (ca. 37 L/min or less). The intrinsic clearance of the lung for PGE1 in ARDS patients therefore appears to decrease abruptly once a threshold of severe respiratory failure is achieved.

Adult↗
PubMed1988

Active specific immunotherapy with an autologous tumor cell vaccine in patients with resected non-small cell lung cancer.

Eighteen postoperative patients with non-small cell lung cancer were actively immunized with a vaccine that included autologous cryopreserved irradiated tumor cells admixed with bacillus Calmette-Guerin. Patients received three weekly intradermal immunizations beginning 1-3 months after surgery (15 patients) or after completion of postoperative radiotherapy (3 patients). There was marked heterogeneity in the relative proportion of tumor cells versus host infiltrating cells within individual vaccines (range of percent tumor cells 7-75%). Five patients exhibited positive delayed cutaneous skin test reactivity (DCR) to autologous irradiated tumor cells prior to immunization, whereas 8 of 13 converted from skin test negative to positive. There were no correlations between DCR reactivity and in vitro lymphoproliferative responses to autologous tumor cells or to clinical outcomes, i.e., freedom from relapse. Possible explanations for the heterogeneity of the lung cancer vaccine and approaches for improving its immunogenicity are discussed.

BCG Vaccine↗