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Biomedical subjects

D A Stevens

Publications and source records attributed to D A Stevens.

At least 307 records · Page 17Linked to original sources
PubMed1985

Mechanisms in opposite modulation of spleen cell and lymph node cell responses to mitogens following muramyl dipeptide treatment in vivo.

It has been reported that a muramyl dipeptide (MDP) treatment regimen (200 micrograms MDP per mouse, Days -4, -3, -2, and -1) that, given prophylactically, affords protection against several infectious agents also induces lymph node hyperplasia, lymph node cell (LNC) hyperresponsiveness to mitogens, and spleen cell hyporesponsiveness to mitogens. The purpose of the present work was to extend those studies and delineate cellular mechanisms involved in these phenomena. It has been found that hyperresponsiveness of LNC was prolonged (7 days) posttreatment; in contrast, hyporesponsiveness of spleen cells was transient and rebounded by Day 4 posttreatment. Hyperresponsiveness of LNC and hyporesponsiveness of spleen cells actively enhanced and depressed normal lymphoid cell responses, respectively, in cell mixing experiments. Hyporesponsiveness of spleen cells was associated with the plastic-nonadherent, non-B-cell fraction and nylon wool-nonadherent subpopulations. Indomethacin (10(-6) M) did not abrogate hyporesponsiveness of spleen cells. These data suggest that splenic suppressor T cells result from MDP treatment and were responsible for spleen cell hyporesponsiveness. On the other hand, hyperresponsiveness of LNC was associated with the nylon wool-adherent cell subpopulations and a higher percentage of nonspecific esterase-positive cells. Hyporesponsiveness of spleen cells was associated with deficient production of interleukin 2 (IL-2), but not of interleukin 1 (IL-1). In contrast, hyperresponsiveness of LNC was not explained by enhanced IL-1 or IL-2 production.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1985

Antibody response in human nocardiosis: identification of two immunodominant culture-filtrate antigens derived from Nocardia asteroides.

An ammonium sulfate precipitate derived from a culture filtrate of Nocardia asteroides contained 20-30 protein subunits, as identified by gel electrophoresis. Western blot analysis of these proteins (obtained from serum samples from patients with systemic nocardiosis) revealed that all of the 17 samples reacted with a subunit of a protein with an apparent molecular weight of 55,000 and that 11 of the 17 samples reacted with a subunit with a molecular weight of 31,000. In contrast, only two of 25 serum samples obtained from healthy controls or patients hospitalized without nocardial or mycobacterial disease reacted with these subunits. Sera from 21 patients infected with Mycobacterium tuberculosis, a historically troublesome cross-reactive group, failed to react with either the 55,000 or the 31,000 molecular weight subunit. The presence of only two protein subunits that reacted with sera from humans with nocardiosis suggests that these molecules may have use as diagnostic reagents or probes of the immunologic reaction to Nocardia.

Antibodies, Bacterial↗
PubMed1985

A replicator method for the combined determination of minimum inhibitory concentration and minimum bactericidal concentration.

Minimal bactericidal concentrations (MBCs) of nine antimicrobial agents were determined for clinical isolates by a replica plating method. Membranes were placed on the antibiotic-containing plates and the organisms replicated onto the membranes. After 18 h incubation the minimal inhibitory concentrations (MICs) were determined, the membranes were transferred to antibiotic-free plates and incubated a further 18 h and the MBCs determined. MICs and MBCs were also determined in broth. The reproducibility of the 'membrane' method and the agreement of these results for MIC and MBC with the agar and/or broth methods was satisfactory for most antibiotics, within one two-fold dilution. With sulphamethoxazole, trimethoprim and co-trimoxazole the results were less satisfactory, especially with Gram-negative rods, but agreement within two dilutions could be achieved.

Anti-Bacterial Agents↗
PubMed1985

New azole compounds: vibunazole (Bay n7133) and Bay L9139, compared with ketoconazole in the therapy of systemic candidosis and in pharmacokinetic studies, in mice.

Ketoconazole, a new imidazole: Bay L9139, and a new triazole: vibunazole (Bay n7133) were compared in therapy of systemic candidosis. CD-1 male mice were challenged with Candida albicans intravenously (greater than LD80), and treated twice a day, orally, for one month. The isolate of Can. albicans used, and isolates obtained after treatment with the antifungals, were susceptible to all three drugs (MICs less than or equal to 0.5 mg/l). No drug was lethal to uninfected mice in doses of 200 mg/kg/day for one month. With therapy started on the day after infection, all three drugs at 50 or 100 mg/kg/day prolonged survival, compared with controls (P less than 0.05), with ketoconazole slightly superior to the other two drugs, but none did so at 25 mg/kg/day. At 200 mg/kg/day ketoconazole and vibunazole were protective, but L9139 was not, and this suggested synergistic toxicity of L9139 with Can. albicans infection, at this dose. With treatment begun on day 4, ketoconazole prolonged survival (P less than 0.005) at 200 or 100 mg/kg/day compared with controls, but ketoconazole at 10-50 mg/kg/day, and vibunazole and L9139 at 10-200 mg/kg/day were ineffective. Survivors had renal lesions and culture-proven residual infection. Pharmacokinetic studies indicated lower peak vibunazole and 9139 serum concentrations, and reduced area-under-curve (AUC), after 26 days of treatment, as against single dose administration. The relative inefficacy of vibunazole and L9139 appears to be related to unfavourable pharmacokinetic properties with continued administration.

Animals↗
PubMed1985

Activities of the modified polyene N-D-ornithyl amphotericin methyl ester and the azoles ICI 153066, Bay n 7133, and Bay l 9139 compared with those of amphotericin B and ketoconazole in the therapy of experimental blastomycosis.

We studied the efficacy of new experimental antifungal drugs, which represent molecular modifications of present active agents, in a murine model of blastomycosis. Ketoconazole, previously the best azole drug studied and which is protective when administered orally, was superior to a new oral imidazole, Bay l 9139, and a new oral triazole, Bay n 7133. A new oral triazole, ICI 153066, was markedly more effective than ketoconazole and is the only oral drug studied which came close to producing complete sterilization of all visceral infection in all animals treated. Amphotericin B, a polyene given parenterally, was shown to be more efficacious than any drug studied. It completely sterilized the infection. A modified polyene, N-D-ornithyl amphotericin methyl ester, was only slightly less effective on a milligram-per-kilogram basis.

Amphotericin B↗
PubMed1985

Enhanced oxidative burst in immunologically activated but not elicited polymorphonuclear leukocytes correlates with fungicidal activity.

Polymorphonuclear neutrophils (PMN) induced locally in immune mice by intraperitoneal injection of antigen exhibit enhanced fungicidal activity compared with PMN elicited with thioglycolate. The mechanism of the differences in these PMN populations was studied. Sublethal infection was used to produce immunity to Blastomyces dermatitidis. A correlation was sought between the ability of PMN to kill, or not kill, B. dermatitidis and the production of the oxidative burst, as measured by luminol-enhanced chemiluminescence (CL). Although elicited PMN cocultured with Candida albicans produced a burst of CL and were candidacidal, killing did not occur when PMN were cocultured with B. dermatitidis. Lack of killing of B. dermatitidis by elicited PMN correlated with lack of stimulation of a brisk oxidative burst. In contrast to elicited PMN, PMN induced by B. dermatitidis antigen responded to this fungus with a burst of CL and a significant reduction of inoculum CFU (80%). Furthermore, these PMN when cocultured with C. albicans produced an enhanced burst of CL, and killing was enhanced compared with that by elicited PMN, e.g., 86 versus 58%. The CL burst and killing of B. dermatitidis by antigen-induced PMN was abrogated in the presence of catalase, implying a critical role for hydrogen peroxide. Partial but significant depression of CL and killing in the presence of dimethyl sulfoxide, a hydroxyl radical scavenger, identified hydroxyl radical, or its metabolites, as a toxic product(s) responsible for a significant fraction of fungicidal activity. These results indicate that the metabolic activity and microbicidal activity of PMN can be altered (enhanced) at the site of an immunological reaction and thus could constitute an important factor in resistance.

Animals↗
PubMed1985

Recombinant and natural gamma-interferon activation of macrophages in vitro: different dose requirements for induction of killing activity against phagocytizable and nonphagocytizable fungi.

Recombinant murine gamma-interferon (IFN) and supernatants from concanavalin A (ConA)-stimulated spleen cells were tested for their ability to activate resident peritoneal macrophages (M phi) for fungicidal activity. M phi monolayers pulsed overnight with IFN exhibited significantly enhanced fungicidal activity against Candida albicans (44 +/- 12 versus 0.0%) and Blastomyces dermatitidis (34 +/- 1 versus 3 +/- 3%). The effect of IFN was dose dependent; however, less IFN (10 U/ml) was required to activate M phi to kill phagocytizable C. albicans than to kill nonphagocytizable B. dermatitidis (1,000 U/ml). ConA-stimulated spleen cell supernatants were also able to activate M phi for fungicidal activity against both fungi. The capacity of ConA-stimulated spleen cell supernatants to activate M phi for fungicidal activity was neutralized in the presence of antibody to murine IFN. ConA-treated monolayers acquired the ability to kill C. albicans, but not B. dermatitidis, which was shown to be associated with residual (10%) lymphocytes in the monolayers. Lipopolysaccharide (0.001 to 10 micrograms/ml) failed to consistently activate M phi for fungicidal activity. These data show that IFN can exert an immunoregulatory role on M phi defense against these fungal pathogens.

Animals↗
PubMed1985

Comparative antibacterial activities of new beta-lactam antibiotics against Pseudomonas aeruginosa.

In vitro activity of nine new cephalosporins and penicillins was determined against 417 isolates of Pseudomonas aeruginosa. Carbenicillin, ticarcillin, gentamicin, tobramycin and netilmicin were also included in the study. Imipenem showed highest activity. More than 90% of the isolates were susceptible to ticarcillin, piperacillin, azlocillin, cefoperazone, cefsulodin and to tobramycin. 57 isolates included in the study were resistant to gentamicin (MIC greater than 4 mg/l); of these, none were resistant to imipenem, and more than 80% were susceptible to piperacillin, azlocillin, cefoperazone and cefsulodin.

Anti-Bacterial Agents↗
PubMed1985

Study of current and new drugs in a murine model of acute paracoccidioidomycosis.

A new murine model of acute paracoccidioidomycosis, whose features include pulmonary infection with dissemination, was used to study the efficacy of currently available drugs and new agents which might be useful clinically. Two oral imidazole drugs, ketoconazole (KTZ) and Bay l 9139 (l9); two oral triazoles, Bay n 7133 (n7) and ICI 153,066 (ICI); and two polyenes, amphotericin B (AMB) and N-D-ornithyl-amphotericin B methyl ester, were studied. KTZ was superior to n7 and l9, particularly after a less lethal challenge. The polyenes could diminish dissemination, but had only modest effects on the pulmonary infection; AMB appeared slightly more effective. ICI was the most effective drug studied, approximately 5-10 times more potent than KTZ on a milligram/kg body weight basis; it had marked effects on both pulmonary and disseminated disease. These initial applications of the model to therapeutic evaluation suggest sufficient flexibility and utility, with information obtainable after relatively short experiments.

Amphotericin B↗
PubMed1985

Treatment of paracoccidioidomycosis with itraconazole in a murine model.

A new triazole, itraconazole, was studied as oral therapy of paracoccidioidomycosis in a murine model. The Paracoccidioides brasiliensis isolate, susceptible to itraconazole in vitro, was given by intranasal challenge, producing acute pulmonary and disseminated disease. Therapy was given twice daily over 4 weeks, and animals observed over 2 months. The infection was lethal for 70-80% of controls (untreated or polyethylene glycol diluent), whereas all treated animals, given 10-200 mg kg-1 day-1, survived. Itraconazole was ineffective in eradicating lung disease in survivors, though effective in treatment of disseminated sites. Since the highest doses did not give a better response than the lower doses, pharmacokinetic studies were performed. These showed irregular curves and small increases in peak serum concentrations and total area under the serum concentration-time curves, which were not proportional to the dose. This non-linearity appears to be best explained by poor absorption. Itraconazole, from these studies, appears to have promise for the therapy of human paracoccidioidomycosis but possibly with a different formulation.

Animals↗
PubMed1985

Ketoconazole-induced increase in estradiol-testosterone ratio. Probable explanation for gynecomastia.

Ketoconazole, an antifungal drug, causes gynecomastia in some patients. It also inhibits androgen and glucocorticoid synthesis. In four volunteer male subjects, 600-mg doses of ketoconazole depressed serum testosterone concentrations markedly, but serum estradiol to a much lesser degree. The bound and free percentages of both hormones were not significantly altered. The net result was a significant elevation of the estradiol-testosterone ratio, expressed as either total circulating hormone or free hormone. In five male patients receiving long-term high-dose ketoconazole therapy, the testosterone concentrations fell, but the effect on estradiol was variable. In these patients the estradiol-testosterone ratio was persistently increased. Since gynecomastia appears to be the result of an elevated estradiol-testosterone ratio, the selective hormonal effect demonstrated may explain the side effect of gynecomastia after ketoconazole therapy.

Estradiol↗
PubMed1984

Antifungal drug susceptibility testing. A critical review.

The advent of new antifungal drugs provides clinicians with therapeutic options, and it is anticipated requests for fungal susceptibility testing in vitro will increase. Our own laboratory's experience indicates that results can be provided promptly even to distant medical centers. The need in this setting is standardization of procedures, so correlations with in vivo outcome can be made with in vitro results. The variables affecting current testing methods are reviewed. Newer methods of testing are summarized, including our experiences using a spectrophotometer as a tool to assay inhibition. Our understanding of the mechanisms underlying the results with this and classical methods are presented. Several methods were applied to a population survey of Candida albicans isolates, using the drug flucytosine as an example. The results were correlated with in vivo outcome in a mouse model of systemic candidosis. The in vitro results, in general, predicted survival, but exceptions occurred, and it appears the in vitro results provide a relative but not absolute indication of outcome.

Antifungal Agents↗
PubMed1984

Immunological activation of polymorphonuclear neutrophils for fungal killing: studies with murine cells and blastomyces dermatitidis in vitro.

The interaction of elicited murine polymorphonuclear neutrophils (PMN) and the thermally dimorphic fungal pathogen Blastomyces dermatitidis in vitro was studied. The PMN elicited intraperitoneally with thioglycollate, in normal mice or mice immune to B dermatitidis, failed to reduce colony forming units (CFU) of B dermatitidis in the inoculum in a 4-hr in vitro assay, even in the presence of 10% fresh immune serum. In contrast, PMN elicited intraperitoneally in immune mice by injection of nonviable B dermatitidis cells significantly reduced inoculum CFU (60 +/- 5%) under the same conditions. Furthermore, nonviable B dermatitidis intraperitoneally (i.p.) in normal mice or nonviable Candida albicans i.p. in immune mice failed to elicit peritoneal exudate cells that reduced inoculum CFU in this system. These results support the concept that PMN, elicited in a site by means of an immunological reaction, acquired enhanced microbicidal activity. The fungicidal activity of immunologically elicited PMN was shown to be most effective at high effector to target cell ratios (1,000:1), maximal within 2 hr of coculture, and significantly enhanced in the presence of fresh immune serum compared to heat-inactivated immune serum, normal mouse serum, or fetal bovine serum. Such PMN also had significantly enhanced fungicidal activity against C albicans compared to normal PMN. Fungicidal activity was abrogated in the presence of catalase, implicating hydrogen peroxide generation as the killing mechanism in the activated cells.

Animals↗
PubMed1984

The iron-hydrogen peroxide-iodide system is fungicidal: activity against the yeast phase of Blastomyces dermatitidis.

A series of experiments show the potency of a newly described microbicidal system, involving iron, H2O2, and halide, in killing a fungus (Blastomyces dermatitidis). B dermatitidis has previously been shown susceptible to the myeloperoxidase-H2O2-halide system. The present studies show killing of either of two strains in 1 hour if Fe++ at 5 X 10(-5)M, H2O2 at 5 X 10(-5)M and Kl at 5 X 10(-4)M are all present (P less than 0.001). EDTA, a Fe++ chelator, abrogates killing. The mechanism presumably utilizes hydroxyl radical, since an inhibitor, ethanol, also neutralizes the system. The bactericidal and fungicidal system is of great potential importance in vivo.

Antifungal Agents↗
PubMed1984

Effects of oral chemical irritation on taste.

Oral irritation was induced by rinses with capsicum oleoresin and with piperine, constituents of red and black pepper, respectively. The perceived intensities of two concentrations of each of four tastants representing the four classical taste qualities were evaluated after rinsing with these irritants. Comparing taste intensity after rinses with capsicum and after control rinses with emulsifying agents or water, there were significant decrements in taste intensity of citric acid and quinine, and on one concentration of sucrose, but no effect on salt. The effects of piperine were more broad, with significant decrements in perceived intensity relative to emulsion controls for all substances.

Adult↗
PubMed1984

Immunologic responsiveness and safety associated with the Coccidioides immitis spherule vaccine in volunteers of white, black, and Filipino ancestry.

A trial of the killed Coccidioides immitis spherule vaccine was undertaken with 151 healthy skin test negative adult volunteers and controls to evaluate the safety of selected regimens, the induction of humoral and cell-mediated immune responses, and to determine if there were immunogenetic differences in these responses. The vaccine was given as three intra-deltoid doses over 8 weeks. No severe systemic symptoms were noted, although 3% of 3.5 mg doses (but no 1.75 mg doses) were associated with severe local reactions. Half the vaccinees had skin test conversions, which generally persisted greater than or equal to 6 months, two-thirds showed boosting of lymphocyte transformation in vitro, and 16% given three 3.5 mg doses developed antibody. There was an association between degree of local adverse vaccine reaction and immunostimulation, and a trend to immune response in persons of O blood type and with some HLA phenotypes. There was no evidence of deficient response to vaccination in subpopulations known to respond to coccidioidal infection poorly. A regimen of three 1.75 mg doses appears to be safe and without reduced immunogenicity, and there is no evidence dosage modification for certain subpopulations would be necessary in efficacy studies.

Adolescent↗
PubMed1984

Toxic effect of products of oxidative metabolism on the yeast form of Paracoccidioides brasiliensis.

The effectiveness of toxic oxygen metabolites in killing the yeast form of Paracoccidioides brasiliensis (the form that occurs in host tissues) was studied with a fluorescence method in vitro. The two isolates studied were similar in susceptibility and H2O2 alone was lethal with an LD50 of 15-25 mM. The addition of halide (5 X 10(-4) M) augmented the lethality of H2O2 and in that setting H2O2 was c.90% lethal at 5 X 10(-5) M. Killing was most effective in the presence of peroxidase, when only 5 X 10(-6) M H2O2 (a concentration attainable in vivo by phagocytes) was required for a 95% kill. Kinetic studies revealed that toxic concentrations of H2O2 alone or of the H2O2-halide-peroxidase (PPH) system produced significant killing in 1 min; killing was maximal in 15 min. The PPH system was the more rapid in action. The dependence of the PPH killing system on H2O2 was demonstrated by an absence of killing in the presence of catalase. The susceptibility of P. brasiliensis to H2O2 and the PPH system appeared different in some respects from that noted for other dimorphic fungal pathogens. These studies suggest that toxic oxygen metabolites are important in host defence against P. brasiliensis.

Catalase↗