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Biomedical subjects

S J Stewart

Publications and source records attributed to S J Stewart.

At least 19 recordsLinked to original sources
PubMed2001

Personality and psychopathology profiles of veterans' wives: measuring distress using the MMPI-2.

The present study compared personality and psychopathology profiles of veterans' wives against married women in the MMPI-2 restandardization sample. Differences in levels of distress and pathology were analyzed using the validity, clinical, and content scales of the MMPI-2. As expected, veterans' wives, when compared to restandardization wives, reported higher levels of psychopathology and distress, with symptoms such as depression, social maladjustment, and other negative, internal symptomatic behaviors. Findings are discussed in terms of the need for additional research examining this "at-risk" population.

Adult↗
PubMed2001

Multiparameter data acquisition and analysis of leukocytes by flow cytometry.

Each laboratory has to establish its own experience base and standard operating procedures. The intent of this discussion has been to illustrate the procedures that will lead to good flow cytometry data acquisition and analysis and to illustrate problematic areas. The most important rule of all is to recognize when there is a problem and find the correct solution. It is hoped the information provided herein will be of help in the recognition process.

Antibodies↗
PubMed2001

HLA class I antigen cell surface expression is preserved on acute myeloid leukemia blasts at diagnosis and at relapse.

Human leukocyte antigens (HLA) class I molecules restrict the interaction between cytotoxic T cells and target cells. Abnormalities in HLA class I antigen expression and/or function may provide tumor cells with a mechanism for escaping immune surveillance and resisting T cell-based immunotherapies. The potential for applying T cell-based immunotherapy in the treatment of acute myeloid leukemia (AML) has stimulated interest in analyzing HLA class I antigen expression on leukemic blasts in this disease. Little information is available in the literature. We have analyzed HLA class I antigen expression on bone marrow samples from 25 newly diagnosed AML patients by indirect immunofluorescence staining with monoclonal antibodies. Five of these patients were also studied at relapse. Leukemic blasts were resolved from normal lymphocytes by staining with antiCD45 antibody; CD45 expression is dim on leukemia cells, but bright on lymphocytes. HLA class I antigen expression was higher on leukemic blasts than on autologous lymphocytes in all but one case. Moreover, there was no significant change in HLA class I antigen expression at relapse. These results suggest that abnormalities in HLA class I antigens are infrequent in AML and should not represent a major obstacle to the application of T cell-based immunotherapies in this disease.

Acute Disease↗
PubMed2001

First-line Herceptin monotherapy in metastatic breast cancer.

The pivotal phase II and III Herceptin trials proved the efficacy and safety of second- or third-line single-agent Herceptin and first-line Herceptin in combination with chemotherapy, respectively. In the current trial, 114 patients were randomized to one of two dose groups of first-line Herceptin monotherapy: standard dose of 4 mg/ kg initial dose followed by 2 mg/kg intravenous (i.v.) weekly; or high dose of 8 mg/kg initial dose followed by 4 mg/kg i.v. weekly. The regimen was generally well tolerated. A similar incidence of adverse events was demonstrated in the two dose groups with the possible exception of acute infusion-related events such as fever and chills as well as rash and dyspnea, which appear to be more prevalent in the higher dose group. The overall response rate was 26% and response rates were similar between the two dose groups (24% for the standard Herceptin dose group and 28% for the high Herceptin dose group). Subgroup analysis determined a higher response rate in IHC 3+ patients (35%) and FISH-positive patients (41%). When women with stable disease for > or =6 months were included with responders, the clinical benefit rate in IHC 3+ patients was 47%. Median survival was 24.4 months, which is comparable with the survival rate seen in the pivotal phase III combination trial (25 months). Therefore, single-agent Herceptin is an important new option for the first-line treatment of HER2-positive metastatic breast cancer patients.

Antibodies, Monoclonal↗
PubMed2001

First-line, single-agent Herceptin(trastuzumab) in metastatic breast cancer: a preliminary report.

Following confirmation of the appropriate dosage, safety and potential efficacy of Herceptin(trastuzumab) in small-scale phase I and II trials involving patients with refractory disease, a large trial was conducted in 222 patients with breast cancer who had relapsed after one or two chemotherapy regimens for their metastatic disease. The results showed a positive and durable overall response rate (15% according to a response evaluation committee (REC) assessment) using trastuzumab monotherapy (initial dose 4 mg/kg intravenously (i.v.) followed by 2 mg/kg i.v. weekly). In another recently completed phase II trial, 113 patients were randomised to two dose levels (initial dose of 4 mg/kg i.v. dose followed by 2 mg/kg i.v. weekly, or initial dose of 8 mg/kg followed by 4 mg/kg i.v. weekly) of single-agent trastuzumab as first-line therapy for metastatic disease. The preliminary overall response rate was 23% based on investigator assessment, and tolerability was excellent as in previous trials; efficacy was similar in both dose groups, but the side-effects tended to be more frequent in the higher dose group. The preferred dosage is therefore the same as that currently recommended, i.e. an initial dose of 4 mg/kg i.v. followed by 2 mg/kg weekly i.v. until disease progression.

Adult↗
PubMed1999

Four color compensation.

Four-color immunophenotyping can now be routinely performed using either a single laser or dual laser flow cytometer. When a single laser instrument is used, the fluorochromes evaluated are usually FITC, PE, PE-TR and PE-CY5 (or PerCP). For two-laser excitation APC is generally used in place of PE-TR. Since each tandem dye construct contains PE, three of the four detectors are affected and compensation can be problematic. In this report we show that each tandem conjugated antibody, whether different batches from the same supplier or conjugates from different suppliers all require unique compensation. This inconsistency results in erroneous data, negates the use of single labeled particles as a method for providing adequate compensation and requires dual and triple labeled cells of known pattern to verify compensation. It is also shown that improper compensation can reduce or eliminate completely the detection of fluorescence emission from PECY5 conjugated antibodies. These problems are caused by a variation in energy transfer between PE and either TR or CY5 because the chemistry involved in preparation and conjugation to antibodies is not sufficiently controlled to produce reagents with uniform compensation requirements. The variation in tandem dye compensation can be addressed by either using the same tandem conjugated antibody, by using the same second step tandem reagent to an appropriate first step antibody or by using software compensation. The latter provides an easy solution because a unique compensation matrix can be produced for each antibody tandem conjugate.

Antibodies↗
PubMed1996

CD11b+CD28-CD4+ human T cells: activation requirements and association with HLA-DR alleles.

Engagement of CD28 induces a major costimulatory pathway required by many CD4+ T cells in addition to activation via the TCR. In the absence of signals provided by CD28, ligation of the TCR alone can induce anergy or apoptosis in CD28+ cells. However, we report here characterization of a distinct subset of CD4+ T cells that are CD28-. Three autoreactive CD4+ human T cell clones that could be activated to produce IL-2 and proliferate by anti-CD3 alone were found to lack expression of CD28. CD28- clones that were activated with anti-CD3 alone were not anergic to restimulation via CD3. The presence of CD28-CD4+ T cells was verified in peripheral blood, and their frequency ranged from 0% to >22% of CD4+ T cells in different individuals. The percentage of CD28-CD4+ T cells in the peripheral blood of 57 individuals was significantly correlated with specific class II MHC alleles. Persons with HLA-DRB1*0401 and DR1 alleles had significantly higher numbers of CD28- T cells, while individuals with HLA-DR2(15) had significantly fewer CD28-CD4+ T cells than the mean. Like the CD28- clones, CD28-CD4+ T cells isolated from peripheral blood proliferated upon CD3 cross-linking in the absence of costimulation. The finding that CD28-CD4+ T cells resist induction of anergy following engagement of the TCR in the absence of conventional costimulation demonstrates one mechanism by which autoreactive T cells can escape processes that censor self-reactivity. The MHC associations observed suggest a relationship with autoimmunity and loss of self-tolerance.

Alleles↗
PubMed1994

p185c-erbB-2 signal enhances cisplatin-induced cytotoxicity in human breast carcinoma cells: association between an oncogenic receptor tyrosine kinase and drug-induced DNA repair.

The c-erbB-2 (HER-2/neu) protooncogene encodes an M(r) 185,000 transmembrane glycoprotein with intrinsic tyrosine kinase activity. Agonistic antibodies against p185c-erbB-2 enhance the cytotoxic effect of the DNA alkylator, cisplatin, against c-erbB-2-overexpressing human carcinoma cells (Hancock et al., Cancer Res., 51:4575-4580, 1991). We have studied the possible association between receptor signal transduction and cisplatin-mediated cytotoxicity utilizing the SKBR-3 human breast cancer cell line and the anti-p185 TAb 250 IgG1. TAb 250 induced tyrosine phosphorylation of p185 and the receptor substrate phospholipase C-gamma 1, as well as rapid association of these molecules in vivo. Simultaneously with phosphorylation, phospholipase C-gamma 1 catalytic activity measured in a [3H]phosphatidylinositol-4,5-bisphosphate hydrolysis assay was increased 61 +/- 12% above control. Preincubation of SKBR-3 cells with the tyrosine kinase inhibitor tyrphostin 50864-2 abrogated the enhancement of drug-mediated cell kill induced by TAb 250. The supraadditive drug/antibody effect was not seen in SKBR-3 cells with TAb 263, an anti-p185 IgG1 that does not induce receptor signaling or with TAb 250 in MDA-468 breast cancer cells which do not overexpress c-erbB-2. In addition, transforming growth factor-alpha increased cisplatin-induced cytotoxicity against NIH 3T3 cells overexpressing an epidermal growth factor receptor/c-erbB-2 chimera. Cellular uptake or efflux of [195mPt]cisplatin by SKBR-3 cells was not altered by TAb 250. Finally, simultaneous treatment of SKBR-3 cells with TAb 250 and cisplatin increased cisplatin/DNA intrastrand adduct formation and delayed the rate of adduct decay. Taken together these data support a direct association between p185c-erbB-2 signal transduction and inhibition of cisplatin-induced DNA repair.

Antibodies, Monoclonal↗
PubMed1994

Multiparameter analysis of leukocytes by flow cytometry.

The flow cytometry described can be performed using a single laser. Each laboratory has to establish its own experience base and standard operating procedures. The intent of this discussion has been to illustrate the procedures that will lead to good flow cytometry data acquisition and analysis and to illustrate problematic areas. The most important rule of all is to recognize when there is a problem. It is hoped the information provided herein will be of help in the recognition process.

Cell Death↗
PubMed1993

Activation of phospholipase D following perturbation of the human T lymphocyte antigen receptor/CD3 complex is dependent upon protein kinase C.

Perturbation of the T lymphocyte antigen receptor/CD3 complex or phorbol ester stimulation leads to activation of phospholipase D in the Jurkat T lymphocyte cell line. These observations suggested that phospholipase D activation might result from activation of protein kinase C. In other systems, phospholipase D activity has been shown to be under G-protein or protein kinase C control. Studies detailed here demonstrate that commonly used inhibitors of protein kinase C had unrelated, diverse effects on phospholipase D activity in T lymphocytes. However, protein kinase C down-regulation resulting from prolonged cellular exposure to phorbol esters led to abrogation of anti-CD3-stimulated phospholipase D activation. The results presented underline the complexity of studies employing inhibitors of protein kinase C, suggest interesting approaches to isolation of phospholipase D dependent signalling pathways, confirm that T cell antigen receptor-linked activation of phospholipase D is dependent upon protein kinase C activity and suggest that distant events of T lymphocyte activation are dependent upon the establishment of a positive feedback loop involving protein kinase C and phospholipase D which would result in the prolonged activation of protein kinase C required for certain lymphokine production.

1-(5-Isoquinolinesulfonyl)-2-Methylpiperazine↗
PubMed1993

Expression of the major outer membrane protein of Chlamydia trachomatis in Escherichia coli.

The major outer membrane protein (MOMP) of Chlamydia trachomatis was expressed in Escherichia coli. To assess whether it assembled into a conformationally correct structure at the cell surface, we characterized the recombinant MOMP (rMOMP) by Western immunoblot analysis, indirect immunofluorescence, and immunoprecipitation with monoclonal antibodies (MAbs) that recognize contiguous and conformational MOMP epitopes. Western blot analysis showed that most of the rMOMP comigrated with authentic monomer MOMP, indicating that its signal peptide was recognized and cleaved by E. coli. The rMOMP could not be detected on the cell surface of viable or formalin-killed E. coli organisms by indirect immunofluorescence staining with a MAb specific for a MOMP contiguous epitope. In contrast, the same MAb readily stained rMOMP-expressing E. coli cells that had been permeabilized by methanol fixation. A MAb that recognizes a conformational MOMP epitope and reacted strongly with formalin- or methanol-fixed elementary bodies failed to stain formalin- or methanol-fixed E. coli expressing rMOMP. Moreover, this MAb did not immunoprecipitate rMOMP from expressing E. coli cells even though it precipitated the authentic protein from lysates of C. trachomatis elementary bodies. Therefore we concluded that rMOMP was not localized to the E. coli cell surface and was not recognizable by a conformation-dependent antibody. These results indicate that rMOMP expressed by E. coli is unlikely to serve as an accurate model of MOMP structure and function. They also question the utility of rMOMP as a source of immunogen for eliciting neutralizing antibodies against conformational antigenic sites of the protein.

Antibodies, Bacterial↗
PubMed1992

Phytochrome Levels in Light-Grown Avena Change in Response to End-of-Day Irradiations.

The effect of 15-minute end-of-day irradiations on photoreversible phytochrome levels in light-grown oat (Avena sativa L., cv Garry) seedlings was investigated. Oat seedlings were grown in a cycle of 8 hours of natural daylight and 16 hours of complete darkness, from sowing until harvest at day 10. The level of extractable, photoreversible phytochrome per unit fresh weight was 60% higher after end-of-day far-red irradiation than after either end-of-day red irradiation or end-of-day far-red followed by end-of-day red. Seedlings irradiated with end-of-day far-red also exhibited a small but significant increase in shoot height and fresh weight per seedling. Extracts of seedlings given each of these end-of-day treatments were analyzed by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, electroblotted, and immunostained with monoclonal antibodies specific to different phytochromes. Regardless of end-of-day light treatment, phytochrome that is abundant in etiolated tissue was below the limit of detection, indicating that one or more of the phytochromes predominating in green tissue changes in abundance.

Journal Article↗