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Biomedical subjects

D A Stevens

Publications and source records attributed to D A Stevens.

At least 19 recordsLinked to original sources
PubMed2002

Thyroid status affects number and localization of thyroid hormone receptor expressing mast cells in bone marrow.

Thyroid hormone (T(3)) plays a key role in endochondral ossification. The process relies on the coordinated synthesis and degradation of cartilage matrix and is disrupted in juvenile hypothyroidism, leading to abnormal skeletal development. Mast cells synthesize and store matrix-degrading enzymes. We examined whether thyroid status influences skeletal mast cell distribution in growing rats to determine whether they might modulate the actions of T(3) in bone. Tibiae were collected for histological, histochemical, immunohistochemical, and immunofluorescence analysis. Mast cells were increased throughout the bone marrow in hypothyroid rats compared with euthyroid, thyrotoxic, and hypothyroid-thyroxine replaced animals. Large numbers were present in metaphyseal marrow adjacent to the growth plate in hypothyroid animals and cells were distributed evenly throughout the marrow. Very few mast cells were present in metaphyseal marrow in other groups, but their numbers increased with increasing distance from the growth plate. T(3) receptor alpha1 (TRalpha1) was expressed in the nucleus and cytoplasm of skeletal mast cells, whereas TRalpha2 and TRbeta1 were restricted to the cytoplasm. Localization of TRs was not affected by altered thyroid status. Thus, disrupted endochondral ossification in hypothyroidism may be mediated in part by skeletal mast cells, which express TR proteins and may function as T(3) target cells.

Animals↗
PubMed2001

Defining opportunistic invasive fungal infections in immunocompromised patients with cancer and hematopoietic stem cell transplants: an international consensus.

During the past several decades, there has been a steady increase in the frequency of opportunistic invasive fungal infections (IFIs) in immunocompromised patients. However, there is substantial controversy concerning optimal diagnostic criteria for these IFIs. Therefore, members of the European Organization for Research and Treatment of Cancer/Invasive Fungal Infections Cooperative Group and the National Institute of Allergy and Infectious Diseases Mycoses Study Group formed a consensus committee to develop standard definitions for IFIs for clinical research. On the basis of a review of literature and an international consensus, a set of research-oriented definitions for the IFIs most often seen and studied in immunocompromised patients with cancer is proposed. Three levels of probability are proposed: "proven," "probable," and "possible." The definitions are intended for use in the context of clinical and/or epidemiological research, not for clinical decision making.

Aspergillosis↗
PubMed2001

The impact of culture isolation of Aspergillus species: a hospital-based survey of aspergillosis.

The term "aspergillosis" comprises several categories of infection: invasive aspergillosis; chronic necrotizing aspergillosis; aspergilloma, or fungus ball; and allergic bronchopulmonary aspergillosis. In 24 medical centers, we examined the impact of a culture positive for Aspergillus species on the diagnosis, risk factors, management, and outcome associated with these diseases. Most Aspergillus culture isolates from nonsterile body sites do not represent disease. However, for high-risk patients, such as allogeneic bone marrow transplant recipients (60%), persons with hematologic cancer (50%), and those with signs of neutropenia (60%) or malnutrition (30%), a positive culture result is associated with invasive disease. When such risk factors as human immunodeficiency virus infection (20%), solid-organ transplantation (20%), corticosteroid use (20%), or an underlying pulmonary disease (10%) are associated with a positive culture result, clinical judgment and better diagnostic tests are necessary. The management of invasive aspergillosis remains suboptimal: only 38% of patients are alive 3 months after diagnosis. Chronic necrotizing aspergillosis, aspergilloma, and allergic bronchopulmonary aspergillosis have variable management strategies and better short-term outcomes.

Aspergillosis↗
PubMed2001

Need for alternative trial designs and evaluation strategies for therapeutic studies of invasive mycoses.

Studies of invasive fungal infections have been and remain difficult to implement. Randomized clinical trials of fungal infections are especially slow and expensive to perform because it is difficult to identify eligible patients in a timely fashion, to prove the presence of the fungal infection in an unequivocal fashion, and to evaluate outcome in a convincing fashion. Because of these challenges, licensing decisions for antifungal agents have to date depended heavily on historical control comparisons and secondary advantages of the new agent. Although the availability of newer and potentially more effective agents makes these approaches less desirable, the fundamental difficulties of trials of invasive fungal infections have not changed. Therefore, there is a need for alternative trial designs and evaluation strategies for therapeutic studies of invasive mycoses, and this article summarizes the possible strategies in this area.

Antifungal Agents↗
PubMed2001

The interaction of human monocytes, monocyte-derived macrophages, and polymorphonuclear neutrophils with caspofungin (MK-0991), an echinocandin, for antifungal activity against Aspergillus fumigatus.

The collaboration between human effector cells and caspofungin (MK-0991), a 1,3-beta-D glucan synthase inhibitor, was studied for antifungal activity against Aspergillus fumigatus. Caspofungin was co-cultured for 24h with either human monocytes (Monos), monocyte-derived macrophages (MDM), or polymorphonuclear neutrophils (PMN) against germlings of A. fumigatus and antifungal activity assessed using the XTT metabolic assay. Caspofungin at 0.1 micorg/ml and 0.05 microg/ml or Monos alone against germlings caused significant inhibition. Microscopically this was correlated with less growth and stunted malformed hyphae. The addition of caspofungin at 0.1 microg/ml and 0.05 microg/ml to the monocyte cultures increased antifungal activity. The inhibition of the combination was significantly greater than drug alone (P <.01) and Monos alone (P <.01). MDM against Aspergillus germlings inhibited hyphal growth. The combination of caspofungin at 0.1 microg/ml and 0.05 microg/ml to the macrophage cultures increased antifungal activity. The growth inhibition by the combination was significantly greater than drug alone (P <.01) and MDM alone (P <.01). There was no significant interference with or enhancement of PMNs and caspofungin. These data support the activity of caspofungin against A. fumigatus in vitro, and indicates a cooperative activity with human effector cells. This suggests caspofungin in vivo would have increased efficacy as it combines with host defenses against A. fumigatus.

Anti-Bacterial Agents↗
PubMed2001

Initial isolation of Candida dubliniensis from the Middle East.

Two isolates of Candida dubliniensis were identified from a collection of 30 examined from Israel in a molecular epidemiology study. The 30 isolates were tentatively identified as Candida albicans. The new species, C. dubliniensis, is being reported from new geographic locales. These two isolates, from an Arab and a Druze patient, are the first to be reported from the Middle East.

Adult↗
PubMed2001

Efficacy of interferon-gamma and amphotericin B for the treatment of systemic murine histoplasmosis.

The number of cases of systemic histoplasmosis has increased substantially in recent years, and improved therapy is needed. We examined the efficacy of immunomodulation with interferon (IFN)-gamma alone or in combination with a suboptimal regimen of amphotericin B for the treatment of primary systemic murine histoplasmosis. In the first study, BALB/c mice were infected with Histoplasma capsulatum G217B and treated with 10(5) U of IFN given every other day either preinfection and postinfection or only postinfection, alone or in combination with amphotericin B. IFN alone given subcutaneously (s.c.) postinfection prolonged survival over untreated controls (P < 0.01), whereas intravenous (i.v.) administration was ineffective. All combination regimens and amphotericin B alone significantly prolonged survival (P < 0.0001). The combination regimens of amphotericin B and IFN i.v. (pre- and postinfection) or IFN s.c. (postinfection) reduced the fungal burden in the liver and spleen; the latter regimen had superior efficacy in the spleen (P < 0.05) to either amphotericin B or IFN alone. After infection with a low-challenge inoculum, IFN given s.c. (pre- and postinfection) alone caused a significant reduction in fungal burden in the spleen (P < 0.001). In an acutely lethal model, combination regimens of IFN s.c. or i.v. and amphotericin B again prolonged survival (P < 0.01-0.001), with amphotericin B plus IFN given s.c. (pre- and postinfection) superior to all regimens (P < 0.05-0.01). This regimen also showed enhanced efficacy in causing the reduction of fungal burden in the spleen (P < 0.05). These results indicate that IFN in combination with AmB shows enhanced efficacy in the treatment of systemic histoplasmosis and support the potential utility of IFN as an adjunctive therapy.

Administration, Cutaneous↗
PubMed2001

Effects of granulocyte-macrophage colony stimulating factor (GM-CSF) in vivo on cytokine production and proliferation by spleen cells.

GM-CSF is a potent stimulator of haematopoietic cells as well as some functions of granulocytes and macrophages. GM-CSF has many clinical uses; however, little is known about the effects of GM-CSF treatment in vivo on the responses of tissue lymphocytes in terms of secretion of Th-1 and Th-2 cytokines. We investigated this issue by measuring the responses of spleen cells from mice 24 h after treatment i.p. with saline or rmGM-CSF. GM-CSF at 16.7-50.0 microg/kg significantly increased (P < 0.01) spleen cellularity 2-2.5-fold and enhanced proliferative responses of non-stimulated (no mitogen) as well as concanavalin A (Con A)-stimulated spleen cells. Secretion of IFN-gamma by Con A (2.5 microg/ml)-stimulated spleen cells was significantly (P < 0.01) increased from 1.8 microg/ml by control spleen cells to 5.2 microg/ml by GM-CSF spleen cells. IL-10 production was greater (0.25 microg/ml, P < 0.05) by Con A-stimulated spleen cells from GM-CSF-treated mice compared to control spleen cells (0.06 microg/ml). By contrast, there were no significant differences in IL-4 production by Con A-stimulated spleen cells from the different groups. These results show that GM-CSF treatment increases spleen cellularity and primes lymphocytes for enhanced responses. The enhanced production of Th-1 cytokines by primed lymphocytes may partially explain the beneficial role of in vivo administration of GM-CSF in several clinical situations.

Animals↗
PubMed2001

Overview of host defense mechanisms in systemic mycoses and the basis for immunotherapy.

Host defense against systemic mycoses is multifactoral, depending on innate, as well as acquired, mechanisms. Innate resistance mechanisms include intact physical barriers, host proteins, nonspecific inflammatory responses, hormonal status, sex, and genetic make-up. However, the importance of any 1 factor in resistance to systemic fungal infections can vary depending on the causative agent. Macrophages and neutrophils play a critical role in the stasis or killing of these organisms by using the production of oxygen radicals, cationic proteins, nitric oxide (NO), and peroxides or iron deprivation. Although these cells are often ineffective in killing the organisms innately, activation of macrophages and neutrophils during an acquired immune response by the proinflammatory cytokine interferon-gamma as well as colony-stimulating factors increases the capacity of these cells for killing. A strong Th1 response can provide protective immunity, whereas a Th2 response can result in increased disease severity. The importance of native antibodies in resistance to mycoses remains in question.

Animals↗
PubMed2001

Intrathecal amphotericin in the management of coccidioidal meningitis.

Coccidioidal meningitis is lethal in the absence of treatment. The advent of the azoles has not led to cure, causing many clinicians to revert to intra-cerebrospinal fluid (CSF) amphotericin as part of the treatment regimen, desiring the influence of the latter regimen's ability to clear infection more completely and rapidly. Intra-CSF amphotericin therapy is, however, far more toxic than oral azoles and requires much more clinical management to achieve success and avoid toxicity. This management task increasingly, for insurance reasons or geographic reasons, falls on clinicians unfamiliar with the disease. We delineate our experience in the medical and surgical management of this form of therapy, including procedural details that we have found useful, for the benefit of our colleagues who may wish to use them. As ours is a teaching institution, we have found this material also useful for physicians in training, who are learning about the treatment of these patients.

Amphotericin B↗
PubMed2001

COS-l, a putative two-component histidine kinase of Candida albicans, is an in vivo virulence factor.

The human fungal pathogen, Candida albicans, has three putative histidine kinases showing homology to those of plants, bacteria and other fungi. We have constructed a homozygous deletion strain and a hemizygous reconstituted strain of one of these histidine-kinase-encoding genes, COS-1, in C. albicans. Neither strain showed any growth defect in a number of liquid media nor increased resistance or sensitivity to a number of antifungal drugs. Importantly, we show that the COS-1 homozygous disruption strain had significantly reduced virulence in a systemic murine model of candidosis. Thus, COS-1 appears to be an in vivo virulence factor and may represent a novel target for the development of antifungal drugs.

Animals↗
PubMed2001

Protection of bronchoalveolar macrophages by granulocyte-macrophage colony-stimulating factor against dexamethasone suppression of fungicidal activity for Aspergillus fumigatus conidia.

The objectives of this study were to: (i) see if granulocyte macrophage colony-stimulating factor (GM-CSF) could protect bronchoalveolar macrophages (BAM) against suppression by dexamethasone (DEX) and (ii) test the combined effect of GM-CSF and DEX on lymphocyte responses. Murine BAM killed Aspergillus fumigatus conidia by 33 +/- 4% (mean +/- SD) in a 2.5-h assay, unaffected by GM-CSF treatment. Killing by BAM treated with DEX (10(-7) M) for 48 h in vitro was reduced to 13 +/- 6%; however, if GM-CSF (500 U ml(-1)) was present during DEX treatment of BAM, killing of conidia (33 +/- 2%) by BAM was preserved. By contrast, DEX suppression of lymphocyte responses to concanavalin A was maintained during co-culture with GM-CSF. In sequence treatment experiments, initial treatment of BAM with GM-CSF protected against subsequent treatment with DEX. When macrophages were pretreated with DEX, GM-CSF could reverse suppression even when added subsequently, provided DEX treatment was discontinued. These data suggest that it may be possible to suppress lymphocyte responses with DEX, yet at the same time maintain BAM defenses with GM-CSF against pulmonary infections by conidia of A. fumigatus.

Animals↗
PubMed2001

Efficacy of the partricin derivative SPA-S-753 against systemic murine candidosis.

The polyene partricin compound SPA-S-753 (Societa Prodotti Antibiotici, Milano, Italy) was assessed in a murine model of systemic candidosis. CD-1 mice were infected iv with Candida albicans and treated iv with SPA-S-753 or amphotericin B. All treatment regimens of SPA-S-753 or amphotericin B were equivalent and significantly prolonged survival compared with controls (P < 0.001). Amphotericin B and SPA-S-753 significantly reduced burdens of C. albicans in the spleen and kidneys. Overall, cure rates were similar, amphotericin B at 1 mg/kg cured three and SPA-S-753 at 10 mg/kg cured four mice of infection in both organs. The efficacy of SPA-S-753 is between equivalent and <10-fold as potent as amphotericin B. These results are encouraging and warrant further studies on SPA-S-753.

Amphotericin B↗
PubMed2001

Isolation and characterisation of an anticryptococcal protein in human cerebrospinal fluid.

An earlier study reported that human cerebrospinal fluid (CSF) has fungistatic activity for Cryptococcus neoformans. The present study reports that molecular sieve fractionation of concentrated CSF yielded three protein peaks, one of which (p2) had anticryptococcal activity. On a DEAE-Sephacel anion-exchange column the active molecular sieve peak (p2) gave two peaks that contained anticryptococcal activity. The first (DEAE-1) eluted with 0.1 M NaCl and the second (DEAE-2) eluted with 0.2 M NaCl in buffer. Fungistatic activity of DEAE-1 was reversed by FeCl3. Moreover, FeCl3 reversed inhibition of C. neoformans growth by CSF. In contrast, activity of DEAE-2 was not reversed by FeCl3, indicating that inhibition was produced by an iron-independent mechanism. Immunoblot assays showed that transferrin was present in DEAE-1 but not in DEAE-2, whereas albumin was present in DEAE-2 but not in DEAE-1. On NuPAGE, DEAE-1 protein migrated as a single band corresponding to transferrin and DEAE-2 protein gave a single band corresponding to albumin. In control experiments, human serum albumin subjected to the same isolation protocol acquired anticryptococcal activity similar to that of DEAE-2. Therefore, CSF albumin (DEAE-2) activity was associated with the isolation protocol. These data indicate that transferrin, present in or isolated from CSF, sequesters trace amounts of ferric iron, inhibits growth of C. neoformans and acts as an innate defence mechanism.

Cerebrospinal Fluid↗
PubMed2001

Efficacy of ravuconazole in treatment of mucosal candidosis in SCID mice.

A model of orogastric candidosis in SCID mice, which mimics disease seen in AIDS patients, was used to evaluate ravuconazole in comparison with fluconazole for treatment. Mice were infected orally with Candida albicans and received either no treatment or oral treatment once daily for 12 days with 1, 5, or 25 mg of ravuconazole per kg of body weight per day, 5 or 25 mg of fluconazole per kg per day, or diluent (10% dimethyl sulfoxide in 0.5% carboxymethyl cellulose). The numbers of C. albicans CFU in the esophagus, stomach, small intestine, and cecum on day 25 in mice given no treatment and diluent were equivalent. Both doses of fluconazole significantly reduced numbers of CFU in all four tissues but were equivalent to each other. Ravuconazole showed dose-responsive improvement of clearance of CFU. Ravuconazole at 25 mg/kg was superior in reduction of numbers of CFU in all tissues to controls or 25 mg of fluconazole per kg and to other regimens in at least three tissues. Fluconazole at 25 mg/kg cured no infection in any tissue, whereas 25 mg of ravuconazole/kg cleared infection in all tissues from 50% of mice. Ravuconazole has good efficacy and the potential to cure mucosal candidosis in the absence of a functional immune response.

Administration, Oral↗
PubMed2001

Comparative toxicities and pharmacokinetics of intrathecal lipid (amphotericin B colloidal dispersion) and conventional deoxycholate formulations of amphotericin B in rabbits.

The lipid formulation of amphotericin B, Amphotec (ABCD), has not been used intrathecally. After a single intrathecal dose or after four doses, conventionally formulated deoxycholate amphotericin B (AMB) (Fungizone) resulted in higher levels of amphotericin B in the cerebrospinal fluid of rabbits than did ABCD. Clinically and histologically, ABCD was about threefold less toxic than AMB after a single dose and 3- to 30-fold less toxic after multiple dosing. These data are encouraging for the potential use of ABCD as an intrathecal treatment.

Amphotericin B↗
PubMed2001

Efficacy of recombinant gamma interferon for treatment of systemic cryptococcosis in SCID mice.

We have previously shown that gamma interferon (IFN-gamma) is a useful adjunct to therapy of experimental systemic cryptococcosis in normal mice. To better emulate AIDS patients, SCID mice were infected intravenously with Cryptococcus neoformans. Mice received no therapy, 3 mg of amphotericin B (AmB) per kg of body weight, or 10(5) U of IFN-gamma alone (prophylactically and therapeutically or only therapeutically) or with AmB. In the first experiment, >75% of the mice survived. Therapy with AmB alone was efficacious compared to no therapy in all organs. Both regimens of IFN-gamma alone were efficacious in the brain and lungs, and the combination of AmB and IFN-gamma showed significant synergy in the kidneys. AmB alone cured 40% of mice of infection, whereas the combination regimens cured >50% of the mice and 90% of the brain infections. In a second study, IFN-gamma again proved efficacious alone, and when given with AmB its efficacy was improved. Therapeutic IFN-gamma alone was effective only in the liver compared to no therapy, and the combination regimen, although highly effective, showed no significant synergy. In a third experiment, AmB alone or in combination with IFN-gamma prolonged survival compared to no therapy or IFN-gamma alone. The combination regimen showed significant synergy over AmB alone in the brain, liver, kidneys, and lungs. AmB alone cured no mice of infections in more than two organs, whereas AmB in combination with IFN-gamma cured 55% of infections in three or more organs. These results indicate that IFN-gamma has therapeutic efficacy in severely immunodeficient animals, especially in combination with AmB. Significant synergistic activity was noted in all organs except the spleen. Overall, IFN-gamma has utility as an adjunctive therapy against systemic cryptococcosis in the severely immunocompromised host.

Adjuvants, Immunologic↗