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R W Grady

Publications and source records attributed to R W Grady.

At least 37 records · Page 2Linked to original sources
PubMed1996

Trophozoite elimination in a rat model of Pneumocystis carinii pneumonia by clinically achievable plasma deferoxamine concentrations.

In a rat model of Pneumocystis carinii pneumonia, a 3-week infusion of deferoxamine producing concentrations in plasma of > or = 1.5 micrograms m-1 eliminated the trophozoite life cycle stage. Since this concentration is well below that routinely achieved in patients treated for iron overload, deferoxamine has promise as a therapy for AIDS-associated P.carinii pneumonia.

Animals↗
PubMed1995

Competition between inhibitors of the trypanosome alternative oxidase (TAO) and reduced coenzyme Q9.

The trypanosome alternative oxidase (TAO) is an attractive target for chemotherapy for the diseases caused by African trypanosomes because there is no equivalent enzyme in mammalian hosts. Many inhibitors of this enzyme have been described, but there have been no data on the mechanism of inhibition. In the present study, reduced 2,3-dimethoxy-5-methyl-6-decyl-1,4-benzoquinone (decyl-CoQ-H2) was used as a substitute for the natural substrate CoQ9-H2 to allow direct measurements of the TAO in crude mitochondrial preparations from Trypanosoma brucei brucei. A Km value of 3.8 microM was obtained for this substrate. The following five compounds that have alkyl side chains from 1 to 4 carbons and belong to three classes of inhibitors showed a competitive inhibition pattern with respect to decyl-CoQ-H: p-methoxybenzhydroxamic acid, p-ethoxybenzhydroxamic acid,p-n-butyloxybenzhydroxamic acid, methyl 3,4-dihydroxybenzoate and N-n-butyl-3,4-dihydroxybenzamide. The following four compounds belonging to the same chemical classes but having alkyl side chains from 10 to 12 carbons showed uncompetitive inhibition patterns: p-n-dodecyloxybenzhydroxamic acid, n-decyl 3,4-dihydroxybenzoate, n-dodecyl 3,4-dihydroxybenzoate, and N-n-decyl-3,4-dihydroxybenzamide. Clearly, the first group of inhibitors compete with CoQ-H2 for the active site of the TAO. We propose that the uncompetitive patterns produced by the second group of inhibitors are due to the greater lipophilicity of these compounds and the resulting change in the interaction of the inhibitors and the membrane containing the TAO, thus affecting the local concentration of the inhibitors at the active site.

Animals↗
PubMed1995

NF-kappa B transcription factor activation by hydrogen peroxide can be decreased by 2,3-dihydroxybenzoic acid and its ethyl ester derivative.

Reactive oxygen species like hydrogen peroxide (H2O2) have been shown to serve as messengers in the induction of NF-kappa B and, hence, in the activation and replication of human immunodeficiency virus type 1 (HIV-1) in human cells. Several antioxidant compounds and iron chelators have been shown to interfere with both NF-kappa B and HIV-1 activation under oxidative stress. Because 2,3-dihydroxybenzoic acid (DHB) and its ethyl ester derivative (DHB-EE) are potent oral iron chelators, we started to investigate their effects on monocytes treated with increasing H2O2 concentrations. These two compounds exert important protective effects against the cytotoxic effect of H2O2 as 300 microM DHB or DHB-EE increased cell survival from 30 to 85%. The treatment of monocytes with increasing amounts of H2O2 (from 0 to 3 mM) leads to the nuclear induction of NF-kappa B which is dose dependently inhibited by both DHB and DHB-EE. Addition of ferric ions to DHB only partially restores the NF-kappa B induction by H2O2, while this effect is almost completely restored by ferric ion addition to DHB-EE. Using spin trapping coupled to electron spin resonance, we have demonstrated that DHB and, to a lesser extent, DHB-EE trapped hydroxyl radicals produced by H2O2 photolysis. These data demonstrate that small aromatic molecules harboring both iron-chelating and antioxidant properties like DHB and DHB-EE can effectively interfere with the deleterious effects of H2O2 in monocytes where iron overload can be observed in HIV-1-infected patients.

Base Sequence↗
PubMed1995

Response of rat model of Pneumocystis carinii pneumonia to continuous infusion of deferoxamine.

The iron-chelating drug deferoxamine mesylate (DFO) is active against Pneumocystis carinii in vitro and in rat and mouse models of P. carinii pneumonia. Because DFO has a short half-life, daily divided or continuous dosage was expected to improve the dose response, as is the case with DFO treatment of malaria. Therefore, results of single daily intraperitoneal injections were compared with results of an evenly divided four-times-daily dosage and the efficacy of delivery with implanted infusion pumps. The highest bolus dosage (1,000 mg kg-1 of body weight day-1) was as effective as the standard combination of trimethoprim with sulfamethoxazole. Unexpectedly, very little improvement was observed with the divided or continuous dosage, and several mechanisms that could account for this are discussed.

Animals↗
PubMed1995

Clinically achievable plasma deferoxamine concentrations are therapeutic in a rat model of Pneumocystis carinii pneumonia.

The iron-chelating drug deferoxamine (DFO) has been shown to be active in animal models of Pneumocystis carinii pneumonia (PCP), with effective daily intraperitoneal bolus dosages being 400 and 1,000 mg of DFO mesylate kg of body weight-1 in mouse and rat models, respectively. Continuous infusion produced a moderately improved response in a rat model. The data reported here demonstrate that the response achieved by continuous infusion of 195 and 335 mg of DFO mesylate kg-1 day-1 in the rat model is associated with mean concentrations in plasma of 1.3 and 2.5 micrograms of DFO ml-1 and mean concentrations in lung tissue of 4.9 and 6.0 micrograms of DFO g of lung tissue-1, respectively. Since current clinical use of DFO mesylate for the treatment of iron overload produces higher concentrations in the plasma of patients, DFO may prove to be a useful anti-PCP treatment. The 2.4- to 3.8-fold higher DFO concentration observed in lung tissue compared with that observed in plasma may be important in the response of PCP to DFO.

Animals↗
PubMed1995

Patterns of metastatic spread in prepubertal yolk sac tumor of the testis.

Of the 212 patients with yolk sac tumors of the testis registered in the prepubertal testis tumor registry of the American Academy of Pediatrics, Section on Urology, we report on 33 who presented with metastatic disease. Metastases occurred to the retroperitoneum alone in 9 cases, sites consistent with hematogenous spread of disease alone in 13, sites consistent with lymphatic and hematogenous spread in 6, and sites not clearly documented in the registry in 5. These findings, which show a hematogenous predilection in the spread of metastases, suggest that retroperitoneal lymph node dissection has no routine role in the treatment of the child who presents with yolk sac tumor of the testis.

Child↗
PubMed1995

Chelation therapy in beta-thalassemia: the benefits and limitations of desferrioxamine.

In summary, long-term studies of DFO therapy in multiply-transfused patients with beta-thalassemia major have clearly shown it to be generally safe and effective. Appropriate use of DFO can remove excess iron, prevent iron-induced organ damage, and improve survival in thalassemia patients. Patients who begin treatment at a young age can be protected from the lethal complications of iron overload for at least two decades, but chelation therapy may not always prevent or ameliorate late growth failure and/or delayed or absent puberty. Those with iron damage to the heart and possibly other organs may experience stability or improvement in function with intense chelation. High-dose intravenous DFO produces a rapid decrease in hepatic iron content and improved cardiac function but can also cause severe toxicity, as can normal doses in patients with a low iron burden. Continuing studies of DFO are necessary to help further define its long-term efficacy and toxicity. In particular, significant attention should be paid to new strategies aimed at fostering improved compliance with its use.

Adolescent↗
PubMed1994

Results from a phase I clinical trial of HBED.

In summary, it has been shown that orally administered HBED causes enhanced excretion of iron in all of the thalassemia major patients studied and that both urinary and stool iron are increased in the process. Increasing the dose from 40 to 80 mg/kg divided t.i.d. caused iron balance to increase from 38% to 50%. While this is significantly less than that expected based on our preclinical studies in animals, the potential usefulness of this chelator has been demonstrated. Efforts to increase its oral bioavailability are now in progress. Lending further support to the effort is the fact that no evidence of toxicity has been observed in the studies performed to date and that negative iron balance was achieved in the one thalassemia intermedia patient studied. The results also reinforce the conclusion that DFO causes the excretion of substantially more iron than would be predicted by an assessment of serum ferritin levels or past compliance with chelation therapy. In patients with thalassemia major, serum ferritin levels relate more to tissue damage than to body iron load. Effective chelation therapy can diminish the former much faster than it can remove storage iron. Hence, in cases of iron overload, aggressive chelation therapy should not be tapered off until a significant reduction in iron excretion can be demonstrated. Routine measurements of urinary iron excretion should now be considered essential in the management of beta-thalassemia. Finally, two more patients with thalassemia intermedia will be studied in an effort to substantiate that net negative iron balance can be achieved in this subgroup of patients. We also plan to study several transfused patients in whom the dose of HBED will be increased to 120 mg/kg divided t.i.d. While the chances of achieving net negative iron balance in these patients seems remote, we hope to further demonstrate the safety of this drug with an eye toward the development of an effective prodrug.

Adolescent↗
PubMed1993

N-n-alkyl-3,4-dihydroxybenzamides as inhibitors of the trypanosome alternative oxidase: activity in vitro and in vivo.

On the basis of our previous demonstration of the high inhibitory activity of a series of p-n-alkyloxybenzhydroxamic acids and n-alkyl esters of 3,4-dihydroxybenzoic acid against the trypanosome alternative oxidase in a cell-free mitochondrial preparation of Trypanosoma brucei brucei, we synthesized a series of N-n-alkyl-3,4-dihydroxybenzamides for evaluation as inhibitors of this enzyme. This class of compounds was selected with the expectation of their having similar inhibitory activity to but greater solubility than the esters and hydroxamic acids noted above and greater resistance to serum hydrolases in vivo. We predicted that such properties would allow an inhibitor of the trypanosome alternative oxidase to be coadministered with glycerol as a means of providing treatment for infections by African trypanosomes. As expected, such benzamides were both more soluble and more stable, some being more active against the target enzyme than the corresponding ester. One, N-n-butyl-3,4-dihydroxybenzamide, was selected for evaluation in vivo against T. brucei brucei. When combined with glycerol, this benzamide was found to be curative. A regimen wherein 450 mg of N-n-butyl-3,4-dihydroxybenzamide per kg and 15 g of glycerol per kg were given hourly in three divided doses cured 17 of 19 mice with established T. brucei brucei infections. This combination is more active in vivo than any other designed to block simultaneously both the unique respiratory electron transport system and the anaerobic glycolytic pathways of these pathogenic protozoa.

Animals↗
PubMed1992

Origin and fate of iron mobilized by the 3-hydroxypyridin-4-one oral chelators: studies in hypertransfused rats by selective radioiron probes of reticuloendothelial and hepatocellular iron stores.

The mechanism of in vivo iron chelation by 3-hydroxypyridin-4-ones (CP compounds) was studied in hypertransfused rats in which the major storage iron pools in hepatocytes and in the reticuloendothelial (RE) system have been labeled by selective radioiron probes. Both dimethyl-3-hydroxypyridin-4-one (CP 20 or L1) and diethyl-3-hydroxypyridine-4-one (CP 94) have an identical and very high (log beta 3 36) binding constant and selective affinity to iron(III), but the lipid solubility of CP 94 is considerably higher than that of CP 20. Both chelators induced an increase in the fecal excretion of hepatocellular iron with no effect on urinary excretion. In contrast, about one third to one half of the iron mobilized from RE cells was excreted in the urine. The chelating efficiency of CP 20 was comparable with that of deferoxamine (DF), whereas CP 94 was up to eight times more effective than DF. Unlike DF, which had no effect by the oral route, the oral and parenteral effectiveness of both CP compounds was identical. These findings indicate that: (1) lipid solubility is an important determinant of in vivo chelating efficiency; (2) urinary iron excretion induced by the CP compounds is derived from RE cells; (3) part of the iron mobilized from RE cells and all of the iron derived from hepatocytes is excreted through the bile; and (4) contrary to previous observations in cell cultures, there is no in vivo evidence for a diminishing chelating efficiency at the lowest doses used.

Animals↗
PubMed1991

Mitochondrial development in Trypanosoma brucei brucei transitional bloodstream forms.

Intermediate and short stumpy bloodstream forms of Trypanosoma brucei brucei are transitional stages in the differentiation of mammal-infective long slender bloodstream forms into the procyclic forms found in the midgut of the tsetse vector. Although the mitochondria of the proliferative long slender forms do not accumulate rhodamine 123, the mitochondria of the transitional forms attain this ability thus revealing the development of an electromotive force (EMF) across the inner mitochondrial membrane. The EMF is inhibited by 2,4-dinitrophenol, rotenone and salicylhydroxamic acid but not by antimycin A or cyanide. Consequently, NADH dehydrogenase, site I of oxidative phosphorylation, is the source of the EMF and the plant-like trypanosome alternative oxidase (TAO) supports the electron flow serving as the terminal oxidase of the chain. Although the TAO is present in the long slender forms as well, it serves only as the terminal oxidase for electrons from glycerol-3-phosphate dehydrogenase. The data presented here, combined with older data, lead to the conclusion that the mitochondria of transitional intermediate and short stumpy forms likely produce ATP. This putative production is either by F1F0 ATPase driven by the complex I proton pump or by mitochondrial substrate level phosphorylation, or most likely by both. These conclusions contrast with the previously held dogma that all bloodstream form mitochondria are incapable of ATP production.

2,4-Dinitrophenol↗
PubMed1990

Iron storage disease in parents and sibs of infants with neonatal hemochromatosis: 30-year follow-up.

Neonatal hemochromatosis (NH), an uncommon and generally fatal disorder of infancy, is defined by hepatic disease of antenatal onset, generally manifest at birth, and by stainable iron in a tissue distribution like that seen in heritable adult-onset hemochromatosis (HH). It is not known if parents and sibs of infants with NH are at risk of iron storage disease in later life. We provide 30-year follow-up for iron overload of a family in which 6 of 9 children died in utero or early in the neonatal period. Four of the 6 came to autopsy, where severe liver disease was found; in 3 of the 4, autopsy material could be reviewed. These 3 children had NH. Studies 30 years later did not identify HH or other iron storage disease in the parents or surviving sibs. These findings suggest that first-degree relatives of persons with NH are not necessarily at increased risk of iron storage disease in later life.

Aging↗
PubMed1990

Deferoxamine and eflornithine (DL-alpha-difluoromethylornithine) in a rat model of Pneumocystis carinii pneumonia.

The iron chelator deferoxamine and the polyamine biosynthesis inhibitor eflornithine (DL-alpha-difluoromethylornithine) were examined for anti-Pneumocystis carinii activity in the rat model of P. carinii pneumonia. The activity of deferoxamine at 250, 500, and 1,000 mg/kg given intraperitoneally provides evidence that iron chelation is a promising novel approach to P. carinii chemotherapy. Results with eflornithine at 2, 3, and 4% in drinking water confirm and extend previously reported activity in the rat model.

Animals↗