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Biomedical subjects

S F Queener

Publications and source records attributed to S F Queener.

At least 73 records · Page 4Linked to original sources
PubMed1993

2,4-Diaminothieno[2,3-d]pyrimidine analogues of trimetrexate and piritrexim as potential inhibitors of Pneumocystis carinii and Toxoplasma gondii dihydrofolate reductase.

A series of eight previously undescribed 2,4-diaminothieno[2,3-d]pyrimidine analogues of the potent dihydrofolate reductase (DHFR) inhibitors trimetrexate (TMQ) and piritrexim (PTX) were synthesized as potential drugs against Pneumocystis carinii and Toxoplasma gondii, which are major causes of severe opportunistic infections in AIDS patients. 2,4-Diamino-5-methyl-6-(aryl/aralkyl)thieno[2,3-d]pyrimidines with 3,4,5-trimethoxy or 2,5-dimethoxy substitution in the aryl/aralkyl moiety and 2,4-diamino-5-(aryl/aralkyl)thieno[2,3-d]pyrimidines with 2,5-dimethoxy substitution in the aryl/aralkyl moiety were obtained by reaction of the corresponding 2-amino-3-cyanothiophenes with chloroformamidine hydrochloride. The aryl group in the 5,6-disubstituted analogues was either attached directly to the hetero ring or was separated from it by one or two carbons, whereas the aryl group in the 5-monosubstituted analogues was separated from the hetero ring by two or three carbons. 2-Amino-3-cyano-5-methyl-6-(aryl/alkyl)thiophene intermediates for the preparation of the 5,6-disubstituted analogues were prepared from omega-aryl-2-alkylidene-malononitriles and sulfur in the presence of a secondary amine, and 2-amino-3-cyano-4-(aryl/aralkyl)thiophene intermediates for the preparation of the 5-monosubstituted analogues were obtained from omega-aryl-1-chloro-2-alkylidenemalononitriles and sodium hydrosulfide. Synthetic routes to the heretofore unknown ylidenemalononitriles, and the ketone precursors thereof, were developed. The final products were tested in vitro as inhibitors of DHFR from Pneumocystis carinii, Toxoplasma gondii, rat liver, beef liver, and Lactobacillus casei. A selected number of previously known 2,4-diaminothieno[2,3-d]pyrimidines lacking the 3,4,5-trimethoxyphenyl and 2,5-dimethoxyphenyl substitution pattern of TMQ and PTX, respectively, were also tested for comparison. None of the compounds was as potent as TMQ or PTX, and while some of them showed some selectivity in their binding to Pneumocystis carinii and Toxoplasma gondii versus rat liver DHFR, this effect was not deemed large enough to warrant further preclinical evaluation.

Animals↗
PubMed1993

Alcohol-induced inhibition of alveolar macrophage oxidant release in vivo and in vitro.

Alcohol consumption is known to predispose the host to more frequent and severe bacterial infections, suggesting that alcohol compromises the normal immune function of the lung. The pulmonary alveolar macrophage is the resident host defense cell in the lung and forms the first line of defense against invading microorganisms. One of the mechanisms whereby alveolar macrophages kill bacteria is by releasing toxic oxygen radical species, such as superoxide anion and hydrogen peroxide. We hypothesized that chronic alcohol consumption caused alveolar macrophage dysfunction leading to inhibition of oxidant production when stimulated. Our data demonstrate that alveolar macrophages harvested from alcohol-treated rats release significantly lower quantity (p < 0.05) of both superoxide anion and hydrogen peroxide when stimulated with several different types of stimuli including heat-killed Staphylococcus aureus, soluble immune complexes or phorbol myristate acetate. Pair-fed control rats who received isocaloric quantities of maltose dextrin in their diet to compensate for the alcohol were able to produce oxidants in equal quantities when stimulated, to rats who were fed a normal diet. Similar results were noted in vitro experiments when alveolar macrophages harvested from normal rats were incubated in vitro in alcohol-containing media and then stimulated with the aforementioned stimuli. Alveolar macrophages, which had been incubated in alcohol for 4 hr, showed significant decreases in their ability to produce superoxide anion. This defect was noticeable for a period up to 8 hr following removal of alveolar macrophages from the alcohol-containing media.(ABSTRACT TRUNCATED AT 250 WORDS)

Alcoholism↗
PubMed1993

8-aminoquinolines effective against Pneumocystis carinii in vitro and in vivo.

The activities of 25 8-aminoquinolines were compared in tests assessing the ability of the compounds to inhibit the growth of Pneumocystis carinii in culture. Six compounds were effective at or below 0.03 microM: CDRI 80/53, NSC19894, NSC305805, NSC305812, WR182234, and primaquine. Four others were effective at between 0.2 and 0.03 microM: NSC305835, WR225448, WR238605, and WR242511. Fourteen drugs were also tested in a standard model of P. carinii pneumonia in rats at daily doses of 2 mg/kg of body weight in drinking water. CDRI 80/53, NSC305805, NSC305835, and WR225448 were extremely effective in the animal model. The effectiveness of WR238605, WR242511, and primaquine in the rat model has been reported elsewhere (M. S. Bartlett, S. F. Queener, R. R. Tidwell, W. K. Milhouse, J. D. Berman, W. Y. Ellis, and J. W. Smith, Antimicrob. Agents Chemother. 35:277-282, 1991). The length of the alkyl chain separating the nitrogens in the substituent at position 8 of the quinoline ring was a strong determinant of anti-P. carinii activity.

Aminoquinolines↗
PubMed1993

Activity of topoisomerase inhibitors against Pneumocystis carinii in vitro and in an inoculated mouse model.

Five topoisomerase II inhibitors (amsacrine [m-AMSA], two epipodophyllotoxins, and two quinolones) and the alkaloid camptothecin (a topoisomerase I inhibitor) were evaluated to assess their activities against Pneumocystis carinii. In vitro, both etoposide (VP-16) and teniposide (VM-26) at 1 microgram/ml suppressed P. carinii growth. Amsacrine was toxic to P. carinii and to the feeder cells in vitro. Camptothecin suppressed the growth of P. carinii in vitro only at 100 micrograms/ml. Studies in immunosuppressed mice demonstrated the efficacy of teniposide against P. carinii pneumonia, but successful administration of teniposide was schedule dependent with significant toxicity at therapeutic dosages.

Animals↗
PubMed1993

Identification of highly potent and selective inhibitors of Toxoplasma gondii dihydrofolate reductase.

Toxoplasma gondii RH was obtained in high yield from culture in RPMI medium on a line of Chinese hamster ovary cells lacking dihydrofolate reductase activity (ATCC 3952 dhfr-; American Type Culture Collection). Dihydrofolate reductase preparations from harvested organisms had specific activities of 22.9 +/- 2.1 nmol/min/mg. The 50% inhibitory concentrations against reference compounds were 0.014 microM for methotrexate, 0.24 microM for pyrimethamine, 2.7 microM for trimethoprim, and 0.010 microM for trimetrexate. The Km value for NADPH was 11 microM and followed Michaelis-Menten kinetics; the Km for dihydrofolate was ca. 11 microM, but substrate inhibition appeared to occur at high substrate concentrations. Dihydrofolate reductase from T. gondii was used to screen 130 compounds from the National Cancer Institute repository. Thirteen compounds were > 100-fold more potent than pyrimethamine toward T. gondii dihydrofolate reductase; six compounds with various potencies were 8 to 46 times as selective as pyrimethamine for the protozoal form of the enzyme over the mammalian form. Four trimetrexate analogs were more potent than trimetrexate, and two were significantly more selective. Representative compounds were also tested in a culture model of T. gondii employing uracil incorporation as an index of growth. One pyrimethamine analog was as effective as pyrimethamine in inhibiting T. gondii in culture (50% inhibitory concentration, 0.45 microM). Three other compounds were also effective at micromolar concentrations.

Animals↗
PubMed1993

Proliferation of rat Pneumocystis carinii on cells sheeted on microcarrier beads in spinner flasks.

A method of growing rat Pneumocystis carinii with human embryonic lung fibroblasts (HEL-299 cells) sheeted onto microcarrier beads has been developed. This method allows production of large quantities of P. carinii organisms with very little contamination of host cells. A fivefold increase in the numbers of organisms was achieved, as determined by organism count, antigen detection, and DNA quantification. The majority of organisms produced by this method are trophozoites.

Animals↗
PubMed1993

Total cellular fatty acid composition of cultured Pneumocystis carinii.

Oleic acid makes up > 50% of the total fatty acids of Pneumocystis carinii grown on WI-38 cells. Oleic acid levels increased in parallel with increasing trophozoites over 7 days in culture. The fatty acid composition of P. carinii resembles that of certain fungi but differs from those of lung surfactant lipid, host cells, and fetal bovine serum.

Animals↗
PubMed1993

Effects of 8-aminoquinolines on the ultrastructural morphology of Pneumocystis carinii.

Primaquine and other 8-aminoquinolines are effective against Pneumocystis carinii in culture and animal models but the way(s) in which they affect P. carinii are not known. This study used transmission electron microscopy to observe early effects of 8-aminoquinolines on P. carinii grown with human embryonic lung fibroblasts in microcarrier suspension culture. The 8-aminoquinolines evaluated were primaquine and Walter Reed Army Institute for Research (WR) compounds WR6026, WR238605 and WR242511. Samples of P. carinii were taken at 0, 3, 6, 12, 24 and 48 hours from culture flasks containing selected concentrations of the drugs. Time matched samples from a parallel culture without drug served as controls. All the 8-aminoquinolines produced similar morphologic alterations of the internal structure of P. carinii. Initially, dilatation of the nuclear envelopes and membranous arrays arising from the reticular system were observed. Later, more organisms displayed large arrays of smooth membranous material often presenting a concentric membranous pattern. Subsequently, cellular organization was lost resulting in necrosis. At concentrations tested WR242511 appeared to be the most effective, producing alterations in many trophozoites after 6 hours of exposure; WR6026 appeared to be the least effective with some organisms unaffected after 48 hours. The changes observed are consistent with damage to the reticular system of P. carinii, which might be caused by oxidation by the 8-aminoquinolines or their metabolites.

Aminoquinolines↗
PubMed1992

Inoculated mouse model of Pneumocystis carinii infection.

A transtracheally inoculated mouse model of Pneumocystis carinii has been developed using BALB/c mice. The advantage of this strain of mice include that they are widely available, inexpensive, and were not infected with Pneumocystis before inoculation. Inoculated mice that were not treated had a mean infectivity score of 4.1 compared with inoculated mice treated with the effective anti-Pneumocystis drug combination of trimethoprim plus sulfamethoxazole, which had a mean infectivity score of 0.1, an approximately 4 log difference. The inoculated BALB/c mouse provides a model to serve as a valuable addition to rat models currently used, providing a source of organisms from a different host for cross-species comparisons and for studies of drug efficacy for therapy and prophylaxis. The inoculated mouse is especially cost effective and allows testing of compounds in short supply.

Aminoquinolines↗
PubMed1992

Efficacy of intermittent dosage of 8-aminoquinolines for therapy or prophylaxis of Pneumocystis pneumonia in rats.

Experimental 8-aminoquinolines from Walter Reed Army Institute for Research are effective for prophylaxis or therapy of Pneumocystis carinii pneumonia in rat models. In the present study, primaquine, WR6026, and WR238605 were tested in prophylaxis and treatment models of P. carinii pneumonia to compare the effectiveness of continuous versus intermittent dosing. For treatment of P. carinii pneumonia, the drugs showed detectable effects when given once every 4 days (primaquine and WR6026 at doses greater than 8 mg/kg; WR238605 at doses greater than 2 mg/kg). For prophylaxis, WR6026 and WR238605 were effective given alone daily (WR6026 at doses greater than 0.25 mg/kg; WR238605 at doses greater than 0.57 mg/kg). WR6026 and WR238605 at 4 mg/kg given once every 4 days for prophylaxis were as effective as daily trimethoprim-sulfamethoxazole. These studies suggest that higher doses of 8-aminoquinolines administered at appropriate intervals may be as effective as continuous dosing for prophylaxis of P. carinii pneumonia.

Aminoquinolines↗
PubMed1992

Antimicrotubule benzimidazoles inhibit in vitro growth of Pneumocystis carinii.

Nine antimicrotubule benzimidazole derivatives tested in a Pneumocystis carinii culture system with human embryonic lung fibroblast monolayers inhibited organism proliferation. The concentrations of drugs inhibitory in culture ranged from 10 to 0.1 micrograms/ml, with thiabendazole being the least effective (10 micrograms/ml) and parbendazole being the most effective (0.1 microgram/ml). The parent compound, benzimidazole, was inactive at 10 micrograms/ml. Demonstration that this group of compounds has activity against P. carinii provides a new potential target that can be exploited, the microtubules. Also, the variability in the effectiveness of the compounds provides the basis for studies of structure-activity relationships, which were initiated in this study.

Antiprotozoal Agents↗
PubMed1992

An enzyme-linked immunosorbent assay for enumeration of Pneumocystis carinii in vitro and in vivo.

An enzyme-linked immunosorbent assay (ELISA) to quantitate Pneumocystis carinii organisms from culture supernatant and rat lung has been developed. A polyclonal antibody specific to P. carinii was produced in Sprague-Dawley rats by allowing P. carinii-infected animals to recover from infection. This antibody reacted strongly to P. carinii proteins of 50 to 55 kDa and weakly to those of 33 and 116 kDa. The ELISA used this convalescent-phase antibody to quantitate the number of P. carinii organisms in lung homogenates of infected rats and supernatants from infected tissue cultures which were used to screen drugs for P. carinii. The results of the ELISA were compared with those of direct microscopic counting of organisms, and the two methods were highly correlated (r > 0.9). Thus, the ELISA can be used as an alternative method for the quantitation of P. carinii organisms, and it is superior to the conventional microscopic method because it is easier to perform and less labor-intensive.

Animals↗
PubMed1991

8-Aminoquinolines from Walter Reed Army Institute for Research for treatment and prophylaxis of Pneumocystis pneumonia in rat models.

Three 8-aminoquinolines from the Walter Reed Army Institute for Research (WRAIR), WR6026, WR238605, and WR242511, strongly inhibited Pneumocystis carinii growth in vitro at 1 microgram/ml. This activity was similar to that of primaquine. In rat therapy models, the WRAIR compounds affected Pneumocystis pneumonia at doses as low as 0.25 mg/kg (WR242511) or 0.5 mg/kg (WR6026 and WR238605). At these doses, primaquine alone was ineffective as therapy. In a rat prophylaxis model, all three WRAIR 8-aminoquinolines were extremely effective at daily doses of 0.57 mg/kg, showing activity greater than that of primaquine at this dosage and comparable to that of trimethoprim-sulfamethoxazole at 50/250 mg/kg.

Aminoquinolines↗
PubMed1991

In vitro activities of acridone alkaloids against Pneumocystis carinii.

Acridone alkaloids isolated from plants of the family Rutaceae have antiplasmodial activity in rodent models of malaria. Because a variety of antimalarial agents have also been shown to have activity against Pneumocystis carinii, we tested six of these alkaloids in an established culture model for P. carinii. Atalaphillinine and glycobismine A inhibited growth of cultured P. carinii at concentrations of 2.7 and 1.7 microM, respectively. This potency of effect is similar to that of chloroquine (3 microM) but somewhat less than that of primaquine (0.4 microM), which was previously evaluated in the same system.

Acridines↗