Search PubMed⌕ Search

Biomedical subjects

M J Rieder

Publications and source records attributed to M J Rieder.

At least 19 recordsLinked to original sources
PubMed2001

Inhibition of cytokine production and cytokine-stimulated T-cell activation by FK506 (tacrolimus)1.

Insofar as it exerted its immunosuppressive effect by inhibiting cytokine expression, we assessed the effect of FK506 (Tacrolimus) on cytokine-stimulated T-cell activation. Human T cells, treated with FK506, or controls were stimulated with the mitogens PHA + PMA, Con A, and the "CD3-bypass" stimulation regimen, PMA + ionomycin. T-cell proliferation was quantitated by measuring the uptake of tritiated thymidine, and mRNA expression was assessed by RT-PCR. FK506, in a concentration-dependent fashion, inhibited T-cell proliferation and steady-state mRNA expression of IL-2 and IL-7; half-maximal suppression was obtained at 10(-7) to 5 x 10(-8) M. We tested whether FK506 antiproliferative effect could be overcome with exogenously reconstituted rIL-2 and/or rIL-7. Neither rIL-2 nor rlL-7, individually in conjunction with suboptimal concentrations of PHA or Con A, or in combination without any costimulus, was capable of abrogating FK506 antiproliferative effect, indicating that FK506 also acted by inhibiting cytokine-stimulated T-cell activation. To confirm this, T cells were treated with FK506 and stimulated by rIL-2 and rIL-7, individually in conjunction with suboptimal concentration of PHA and Con A. In addition, T cells were stimulated with rIL-2 and rIL-7 without any costimuli. FK506 inhibited T-cell activation stimulated by rIL-2 and by rIL-7, individually and in combination. This confirms that, in exerting its antiproliferative effect, FK506 acts at two levels, by inhibiting cytokine availability and by suppressing cytokine effect on target cells, and explains the beneficial effect of FK506 in attenuating ongoing immune responses.

Carcinogens↗
PubMed2000

Localization of a small genomic region associated with elevated ACE.

Defining the relationship between multiple polymorphisms in a small genomic region and an underlying quantitative trait locus (QTL) represents a major challenge in human genetics. Pedigree analyses have shown that angiotensin I-converting enzyme (ACE) levels are influenced by a QTL located within or close to the ACE gene and most likely resides in the 3' region of this locus. We genotyped seven polymorphisms spanning 13 kb in the 3' end of ACE in 159 Afro-Caribbean subjects to evaluate the linkage disequilibrium between these sites and to narrow the genomic region associated with an elevated ACE level using a cladistic analysis. The linkage disequilibrium measurement D' and a haplotype tree revealed three distinct haplotype segments, presumably because of recombination. The value of the linkage disequilibrium parameter p(excess) was highest for site 22982, which is located in the middle segment. A series of nested, cladistic analyses confirmed that the other two regions are unlikely to be the ACE-linked QTL and that the variant resides in the middle region. Analyses of the same polymorphisms in 98 unrelated Europeans in the Monitoring Trends and Determinants in Cardiovascular Diseases (MONICA) study resulted in fewer haplotypes than were observed among the Afro-Caribbean subjects, suggesting that populations with greater genetic diversity may be especially informative for fine-scale mapping.

Black People↗
PubMed2000

Compliance with prescription filling in the pediatric emergency department.

OBJECTIVES: To determine the rate of compliance with filling of prescriptions written in a pediatric emergency department and to examine the reasons for not filling the prescriptions. DESIGN: Compliance with filling prescriptions was determined using a follow-up standardized telephone questionnaire, designed so that it was not obvious that assessing prescription filling was the major reason for the study. Compliance herein was defined as having the prescription filled on the same or next day of the pediatric emergency department visit. SETTING: Pediatric emergency department of a tertiary care hospital. SUBJECTS: Pediatric patients discharged home with a drug prescription. MAIN OUTCOME MEASURE: The proportion of prescriptions written in the pediatric emergency department that were filled on either the same or next day as determined by telephone follow-up. This outcome is expressed as a proportion with 95% confidence interval. RESULTS: Follow-up was completed in 1014 (83%) of the 1222 children, aged 4.5 +/- 4.2 (mean +/- SD) years. Compliance with prescription filling was 92.7% (940/1014). Parental reasons for not filling the prescription included medication unnecessary (27%), financial (6.8%), and not enough time (6.8%). Dissatisfaction with the explanation of the medical problem, instructions for treatment, and instructions for follow-up treatment were significantly associated with noncompliance by univariable logistic regression (P<.05). CONCLUSION: The rate of prescription nonfilling in children seen in a pediatric emergency department is at least 7%, although lower than that in adults in a similar setting.

Child, Preschool↗
PubMed2000

Palatability of oral antibiotics among children in an urban primary care center.

OBJECTIVE: To evaluate the palatability of antimicrobial agents effective against beta-lactamase-producing bacteria in American children. DESIGN: In a taste test of 4 antimicrobial agents, azithromycin (cherry flavored), cefprozil (bubble gum flavored), cefixime (strawberry flavored), and amoxicillin-clavulanic acid (banana flavored) were compared. SETTING: An urban inner-city primary care clinic. SUBJECTS: A volunteer sample of 30 healthy children (aged 5-8 years). INTERVENTION: Palatability was determined using a single-blind taste test of 4 flavored antimicrobial agents. The 4 antimicrobial agents used were azithromycin, cefprozil, cefixime, and amoxicillin-clavulanic acid. MAIN OUTCOME MEASURES: After each antimicrobial test dose, subjects rated the taste on a 10-cm visual analog scale incorporating a facial hedonic scale. Preference assessments for the best-tasting and worst-tasting agent were also conducted. RESULTS: Of the 20 children who expressed a preference, significantly more children (9 [45%], P<.05) selected the cefixime preparation as the best-tasting formulation compared with the other preparations. The cefixime preparation was also significantly the least likely to be selected as the worst-tasting preparation (2 [10%], P<.05). There were no significant differences between the other 3 preparations with respect to being selected as either the best or worst tasting. The mean (+/- SD) visual analog scale score for cefixime was highest (8.53 [2.49]) compared with the scores for azithromycin (6.78 [3.45]), cefprozil (6.26 [4.04]), and amoxicillin-clavulanic acid (6.24 [4.01]). CONCLUSION: The cefixime preparation was most commonly rated as best tasting by children.

Administration, Oral↗
PubMed2000

Hypertension and single nucleotide polymorphisms.

Hypertension is a common, complex disease phenotype that has been intensively studied to identify susceptibility loci in humans. Candidate genes continue to be uncovered via genetic analysis in model organisms through linkage analysis with families and/or sib-pairs and through association studies using sequence variants in genes that play a role in key pathways regulating blood pressure in humans, such as the renin-angiotensin system (RAS). Recent studies exploring the sequence diversity in human candidate genes suggest that the distribution and organization of single nucleotide polymorphisms (SNPs) within and among human populations is complex. Issues related to the use of SNPs in analyzing the genetic determinants of hypertension are illustrated using recent studies on the angiotensin-converting enzyme (ACE).

Angiotensin-Converting Enzyme Inhibitors↗
PubMed2000

Multiple antibiotic sensitivity syndrome in children.

BACKGROUND: Multiple antibiotic sensitivity syndrome with adverse drug reactions to multiple classes of antibiotics has been described in adults but is not well characterized in children. PATIENTS AND METHODS: Charts of children referred to the adverse drug reaction clinic at the Children's Hospital of Western Ontario, London, Ontario, with adverse drug reactions to multiple antibiotics were reviewed to determine the number of patients with adverse drug reactions to multiple classes of antibiotics and the clinical characteristics of the adverse events. RESULTS: The records of 97 children who were selected as possible candidates for multiple antibiotic sensitivity were studied. These records constituted 11% of referrals to a highly specialized adverse drug reaction clinic, suggesting that in usual clinical practice, this entity, if it does indeed constitute a distinct clinical entity, is quite uncommon. Age at time of the first adverse drug reaction was 26.1+/-26.3 (mean +/- SD) months. Among the 97 children, adverse reactions to five classes of antibiotic were noted in 3.1%, to four in 10.3%, to three in 47. 4% and to two in 39.2%. Most children (85.6%) experienced an adverse reaction to a penicillin, while 71.1% reacted to a cephalosporin, 80. 4% to a sulphonamide and 35.1% to a macrolide. Clinical presentations of the adverse reactions included urticaria or pruritus, other rash, serum sickness-like reaction, angioedema or anaphylaxis, erythema multiforme or Stevens-Johnson syndrome. CONCLUSIONS: There are children who have what appears to be immunologically mediated adverse drug reactions to antibiotics of multiple classes. These reactions, which most commonly manifest as urticaria or other rashes, follow drug use patterns. It remains to be defined whether this is a distinct clinical syndrome or a manifestation of a more fundamental problem in dealing with xenobiotics in the setting of infection. Further work on the immunological and/or biochemical determinants of the multiple antibiotic sensitivity syndrome (MASS) is needed to understand the pathophysiology and determinants of MASS and whether MASS constitutes a distinct clinical entity.

Anti-Bacterial Agents↗
PubMed1999

The cytotoxicity of clozapine metabolites: implications for predicting clozapine-induced agranulocytosis.

BACKGROUND: Therapy of schizophrenia with clozapine is associated with the unpredictable development of severe neutropenia and agranulocytosis in 1% to 2% of patients. The mechanism of this effect is unknown but may involve reactive products of clozapine generated by either hepatic metabolism or oxidation by the peroxidase-peroxide system of activated neutrophils. METHODS: Involvement of reactive metabolites was tested with in vitro cytotoxicity assays with use of peripheral blood mononuclear cells isolated from 3 groups of subjects: normal control subjects, patients with schizophrenia who tolerated clozapine therapy (control patients), and patients with schizophrenia in whom agranulocytosis developed while taking clozapine (patients with agranulocytosis). Cell viability was determined after incubations with clozapine and rat liver microsomes or clozapine and horseradish peroxidase-peroxide (HRP-H2O2). RESULTS: In microsomal incubations, clozapine significantly increased the cell death in all groups: control subjects (8.8%+/-1.6%), control patients (7.4%+/-0.4%), and patients with agranulocytosis (9.1%+/-1.5%). However, differences between mean values were not statistically significant. In similar incubations with HRP-H2O2, clozapine significantly increased toxicity (P < .05) in cells from patients with agranulocytosis (22%+/-4.6%) compared with those from normal control subjects (7.7%+/-4.1%) or control patients (6.5%+/-4.4%). CONCLUSIONS: These results suggest that both generating systems metabolized clozapine to toxic products. Some products may play a role in clozapine-induced agranulocytosis. Of diagnostic relevance is the observation the HRP-H2O2 produces significantly greater toxicity in cells from patients with agranulocytosis than in cells from control patients. Although the exact mechanism(s) of drug activation in vivo remains unclear, the bioactivation of clozapine by HRP-H2O2 may be a useful in vitro tool for predicting which patients are at risk for agranulocytosis before initiation of therapy.

Agranulocytosis↗
PubMed1999

An alternate mechanism of glucocorticoid anti-proliferative effect: promotion of a Th2 cytokine-secreting profile.

Glucocorticoids (GCs) are used as immunosuppressive and anti-inflammatory agents in organ transplantation and in treating autoimmune diseases and inflammatory disorders and they exert their effects by several mechanisms, the most significant of which is inhibition of cytokine production and action. Recent reports suggested that GCs inhibit cytokine expression indirectly through promotion of a T helper cell type 2 (Th2) cytokine-secreting profile, thereby resulting in preferential blockade of pro-inflammatory monokine and T helper cell type 1 (Th1) cytokine expression. The target of GCs appeared to be monocytes macrophages, whereby altered regulation of interleukin (IL)-1/IL-1 receptor antagonist (IL-1ra), coupled with profound blockade of IL-12 synthesis and inhibition of interferon (IFN)-gamma-induced major histocompatibility complex (MHC) class II expression, lead to a preferential cognate stimulation of Th2 cells at the expense of Th1 cells. It is possible that this may have involved the expansion of a Th2-cell pool or, in addition, frank stimulation of uncommitted naive CD4 + T cells toward the Th2 lineage. In addition, GCs may have blocked Th1 cytokine expression, thereby inhibiting ongoing Th1 cytokine secretion, and consequently provided for the unimpeded production of Th2 cytokines. Collectively, this indicates that, in exerting their anti-proliferative effects, GCs act indirectly by altering Th1/Th2 cytokine balance, blocking the (pro-inflammatory) Th1 program and favoring the (anti-inflammatory) Th2 program.

Anti-Inflammatory Agents↗
PubMed1999

Sequence variation in the human angiotensin converting enzyme.

Angiotensin converting enzyme (encoded by the gene DCP1, also known as ACE) catalyses the conversion of angiotensin I to the physiologically active peptide angiotensin II, which controls fluid-electrolyte balance and systemic blood pressure. Because of its key function in the renin-angiotensin system, many association studies have been performed with DCP1. Nearly all studies have associated the presence (insertion, I) or absence (deletion, D) of a 287-bp Alu repeat element in intron 16 with the levels of circulating enzyme or cardiovascular pathophysiologies. Many epidemiological studies suggest that the DCP1*D allele confers increased susceptibility to cardiovascular disease; however, other reports have found no such association or even a beneficial effect. We present here the complete genomic sequence of DCP1 from 11 individuals, representing the longest contiguous scan (24 kb) for sequence variation in human DNA. We identified 78 varying sites in 22 chromosomes that resolved into 13 distinct haplotypes. Of the variant sites, 17 were in absolute linkage disequilibrium with the commonly typed Alu insertion/deletion polymorphism, producing two distinct and distantly related clades. We also identified a major subdivision in the Alu deletion clade that enables further analysis of the traits associated with this gene. The diversity uncovered in DCP1 is comparable to that described for other regions in the human genome. The highly correlated structure in DCP1 raises important issues for the determination of functional DNA variants within genes and genetic studies in humans based on marker association.

Alu Elements↗
PubMed1999

Cytotoxicity of sulfonamide reactive metabolites: apoptosis and selective toxicity of CD8(+) cells by the hydroxylamine of sulfamethoxazole.

Treatment with sulfonamide antibiotics in HIV-infected patients is associated with a high incidence (> 40%) of adverse drug events, including severe hypersensitivity reactions. Sulfonamide reactive metabolites have been implicated in the pathogenesis of these adverse reactions. Sulfamethoxazole hydroxylamine (SMX-HA) induces lymphocyte toxicity and suppression of proliferation in vitro; the mechanism(s) of these immunomodulatory effects remain unknown. We investigated the cytotoxicity of SMX-HA via apoptosis on human peripheral blood mononuclear cells and purified cell subpopulations in vitro. CD19(+), CD4(+), and CD8(+) cells were isolated from human peripheral blood by positive selection of cell surface molecules by magnetic bead separation. SMX-HA induced significant CD8(+) cell death (67 +/- 7%) at 100 microM SMX-HA, with only minimal CD4(+) cell death (8 +/- 4%). No significant subpopulation toxicity was shown when incubated with parent drug (SMX). Flow cytometry measuring phosphatidylserine externalization 24 h after treatment with 100 microM and 400 microM SMX-HA revealed 14.1 +/- 0.7% and 25. 6 +/- 4.2% annexin-positive cells, respectively, compared to 3.7 +/- 1.2% in control PBMCs treated with 400 microM SMX. Internucleosomal DNA fragmentation was observed in quiescent and stimulated PBMCs 48 h after incubation with SMX-HA. Our data show that CD8(+) cells are highly susceptible to the toxic effects of SMX-HA through enhanced cell death by apoptosis.

Apoptosis↗
PubMed1999

Selection of treatment of cefaclor-associated urticarial, serum sickness-like reactions and erythema multiforme by emergency pediatricians: lack of a uniform standard of care.

BACKGROUND: Serum sickness-like reactions (SSLR) and erythema multiforme are common adverse effects of cefaclor therapy and can be associated with significant morbidity. No standardized evidence-based protocol for the optimal treatment of drug-induced SSLR exists. OBJECTIVES: To define the standard of care used by physicians treating adverse reactions associated with cefaclor. METHODS: A retrospective review of the medical records of children discharged from a pediatric emergency room with a diagnosis of adverse events to cefaclor was conducted. Charts of patients were reviewed to determine which therapy was prescribed. RESULTS: During the study period, 74 cases of adverse events attributed to cefaclor presented to the emergency department. SSLR were the most common pattern of adverse events seen (31 cases, 42%), followed by urticarial reactions (26 cases, 35%) and erythema multiforme (17 cases, 23%). An antihistamine was the treatment most often prescribed (88%) for erythema multiforme. Significantly more children with SSLR than with erythema multiforme or urticaria were treated with prednisone, either alone or in combination (P<0.05). CONCLUSIONS: The treatment most often prescribed for serious cefaclor-associated erythema multiforme was an antihistamine. In the case of SSLR, an antihistamine and prednisone were most commonly used. Prospective randomized, controlled trials are needed to define the role of various therapeutic agents and to determine the optimal therapy for SSLR and other serious adverse drug reactions.

Cefaclor↗
PubMed1998

Automating the identification of DNA variations using quality-based fluorescence re-sequencing: analysis of the human mitochondrial genome.

Diagnostic re-sequencing plays a central role in medical and evolutionary genetics. In this report we describe a process that applies fluorescence-based re-sequencing and an integrated set of analysis tools to automate and simplify the identification of DNA variations using the human mitochondrial genome as a model system. Two programs used in genome sequence analysis (Phred, a base-caller, and Phrap, a sequence assembler) are applied to assess the quality of each base call across the sequence. Potential DNA variants are automatically identified and 'tagged' by comparing the assembled sequence with a reference sequence. We also show that employing the Consed program to display a set of highly annotated reference sequences greatly simplifies data analysis by providing a visual database containing information on the location of the PCR primers, coding and regulatory sequences and previously known DNA variants. Among the 12 genomes sequenced 378 variants including 29 new variants were identified along with two heteroplasmic sites, automatically detected by the PolyPhred program. Overall we document the ease and speed of performing high quality and accurate fluorescence-based re-sequencing on long tracts of DNA as well as the application of new approaches to automatically find and view DNA variants among these sequences.

Base Sequence↗
PubMed1998

Serum sickness-like reaction to cefaclor: lack of in vitro cross-reactivity with loracarbef.

OBJECTIVES: A lymphocyte-based in vitro rechallenge technique was used to examine the potential for cross-reactivity between loracarbef and cefaclor in children who had had adverse reactions to cefaclor. STUDY DESIGN: The study cohort included 10 patients (2.2 +/- 1.1 years old) with a serum sickness-like reaction to cefaclor, five patients (4.1 +/- 4.6 years old) with immediate-type hypersensitivity reactions to the drug, and five patients (1.5 +/- 0.9 years old) who had a delayed hypersensitivity reaction to cefaclor without joint involvement (i.e., not a serum sickness-like reaction). Peripheral blood mononuclear cells were isolated from each patient and were exposed to cefaclor, loracarbef, and the metabolites of each generated with phenobarbital-induced murine hepatic microsomes. RESULTS: Among patients with cefaclor-associated serum sickness-like reactions, lymphocyte killing (expressed as percentage cell kill above baseline) in the presence of cefaclor metabolites (83.6% +/- 42.2%) was significantly (p < 0.02) higher than that observed among the patients with either immediate-type (1.1% +/- 2.4%) or delayed hypersensitivity (0%) reactions. In contrast, loracarbef did not produce significant in vitro cytotoxicity among any of the patient subgroups. Our in vitro evidence was supported at therapeutic rechallenge with loracarbef among three children with cefaclor-associated serum sickness-like reactions who tolerated a full course of therapy without adverse reactions. CONCLUSION: The metabolite-mediated cytotoxicity associated with cefaclor among patients who had had serum sickness-like reactions after therapeutic administration of the drug was not shared with loracarbef. The extent to which the apparent lack of in vitro cross-reactivity between cefaclor and loracarbef may be predictive of clinical cross-reactivity is not known.

Cefaclor↗