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Biomedical subjects

S M MacDonald

Publications and source records attributed to S M MacDonald.

At least 19 recordsLinked to original sources
PubMed1999

The human recombinant histamine releasing factor: functional evidence that it does not bind to the IgE molecule.

BACKGROUND: We have previously shown that the human recombinant histamine releasing factor (HrHRF) caused histamine release from a subset of basophils from donors with allergy, and this release seemed to be dependent on the presence of a certain type of IgE, termed IgE+. IgE molecules that did not support HrHRF-induced histamine release were termed IgE-. However, subsequently we demonstrated that HrHRF primes anti-IgE-antibody-induced histamine release from all basophils, irrespective of the type of IgE on the cell surface. OBJECTIVE: Because these data suggested that HrHRF does not exert its biologic effects by binding to IgE, but rather that it interacted with a surface receptor on the basophil, we wanted to obtain functional evidence that HrHRF did or did not bind to the IgE molecule. METHODS: The rat basophilic leukemia cell line (RBL-SX38), which has been transfected to express a functional human FcepsilonRI (alpha-, beta-, and gamma-chains of the receptor) in addition to the normal rat FcepsilonRI, was used. The presence of the human FcepsilonRI receptor enables these cells to be sensitized with human IgE. Cells were passively sensitized with 1000 ng/mL human IgE+ or 1000 ng/mL human IgE- for 60 minutes at 37 degrees C. Unsensitized cells served as a control. After the cells were washed, 1 x l0(5) cells were stimulated in the presence of 1 mmol/L Ca2+ with 0.1 microg/mL anti-IgE, 40 microg/mL HrHRF, or 40 microg/mL mouse recombinant HRF (MrHRF), which has 96% homology to HrHRF. RESULTS: Mean anti-IgE-induced histamine release was 33% +/- 15%, and there was no difference between IgE+ sensitization (32% +/- 12%) and IgE- sensitization (34% +/- 18%). However, in contrast to human basophil experiments, neither HrHRF (0% +/- 0%) nor MrHRF (3% +/- 5%) caused histamine release in RBL cells sensitized with IgE+. In addition, priming the transfected RBL-SX38 cells or the parental cell line, RBL-2H3 cells, with HrHRF or MrHRF did not increase anti-IgE-induced histamine release. CONCLUSION: The results indicate that HrHRF does not bind to IgE, either IgE+ or IgE-. Therefore it appears likely that rHRF signals through its own specific receptor, which is not expressed or functional on RBL-SX38 or RBL-2H3 cells, but which seems to be expressed on basophils of atopic and nonatopic donors.

Animals↗
PubMed1999

Pharmacologic regulation of histamine release by the human recombinant histamine-releasing factor.

BACKGROUND: The recently cloned human recombinant IgE-dependent histamine releasing factor (HrHRF) was initially thought to stimulate histamine release from human basophils from a subpopulation of allergic donors by interacting with the IgE molecules on the surface of these cells. Additional data suggest that HrHRF exerts its biologic effects by binding to a distinct cell surface structure and not to IgE. OBJECTIVE: To address the hypothesis that the HrHRF signaling pathway is distinct from the classical high-affinity IgE receptor (FcepsilonRI) pathway, we used pharmacologic agents known to affect basophil histamine release. METHODS: In this report we compared the effect of staurosporine, Bis II, Gö 6976, rottlerin, and pertussis toxin on histamine release from human basophils mediated by the following stimuli: HrHRF, polyclonal human anti-IgE antibody, and antigen, as well as the IgE-independent stimulus, FMLP. RESULTS: None of these modulators, except rottlerin, could differentiate histamine release induced by anti-IgE or antigen from that induced by HrHRF. Rottlerin enhanced HrHRF-mediated histamine release and dose dependently blocked FMLP-mediated release without affecting basophil activation by either anti-IgE or antigen. CONCLUSION: These data suggest a unique signaling pathway for HrHRF and thus strengthen the hypothesis that HrHRF binds to a specific receptor other than IgE.

Acetophenones↗
PubMed1997

Recombinant histamine-releasing factor enhances IgE-dependent IL-4 and IL-13 secretion by human basophils.

Human recombinant histamine-releasing factor (HrHRF) is known to directly stimulate histamine release and IL-4 secretion from basophils of selected atopic donors in a reaction requiring the expression of a particular type of IgE, referred to as IgE+. In this study, HrHRF is shown to affect the IgE-mediated release of IL-4, IL-13, and histamine from basophils not normally releasing to this protein (i.e, those expressing IgE-). Priming with several different concentrations of HrHRF for 15 min enhanced basophil secretion of IL-4 and histamine after 4 h in a dose-dependent fashion following activation with anti-IgE Ab (10 ng/ml). This effect of HrHRF priming also occurred in cultures activated with 1 or 100 ng/ml of anti-IgE Ab. The secretion of IL-13 protein was enhanced similarly by HrHRF priming in cultures stimulated for 16 to 20 h with anti-IgE Ab. There were, however, no apparent changes in the secretion of histamine or cytokine by basophils primed with HrHRF and activated with the IgE-independent secretogogue, FMLP. These findings suggest that HrHRF modifies the response of basophils for IgE-dependent secretion by binding to a specific receptor, broadening the possible role of this protein in chronic allergic inflammation.

Basophils↗
PubMed1997

Regulation of IgE-dependent IL-4 generation by human basophils treated with glucocorticoids.

Glucocorticoids are widely used in the therapeutic intervention of allergic diseases, affecting the function of a variety of proinflammatory cell types that participate in these disorders. These drugs have been shown to inhibit the release of histamine by human basophils, but not by mast cells, in a reaction requiring 8 to 24 h. To address whether the generation of IL-4 by basophils is similarly affected, we investigated the actions of glucocorticoids on the in vitro release of this cytokine induced by anti-IgE Ab or by the human recombinant histamine-releasing factor. The ability of basophils to generate IL-4 was immediately affected, with secretion of this protein being inhibited >50% with <1-h preexposure to steroid. However, the release of histamine in these cultures was inhibited only after 24-h preincubation, suggesting that the mechanisms controlling the release of this mediator differ significantly from those regulating cytokine secretion. A rank order of potency of the steroids tested for inhibition of IL-4 protein was as follows: triamcinolone > dexamethasone > betamethasone > hydrocortisone. The sex steroids, testosterone and estrogen, showed no effect on basophil secretion. Experiments using reverse transcription-PCR indicate that glucocorticoids inhibit IL-4 generation in basophils on the level of transcription. These studies suggest that the success of glucocorticoids in the treatment of allergic conditions is due in part to their ability to inhibit both mediator release and cytokine secretion by basophils.

Antibodies, Monoclonal↗
PubMed1997

End-of-life decision-making: community and medical practitioners' perspectives.

OBJECTIVE: To examine current attitudes and knowledge of the community and medical practitioners in Queensland to end-of-life decisions. DESIGN: Cross-sectional survey by postal questionnaire. PARTICIPANTS: 387 general practitioners and medical specialists and 910 community members from the Queensland electoral roll. MAIN OUTCOME MEASURES: Responses to five questions about end-of-life decision-making, and to legislative changes relating to such decisions. RESULTS: The overall response rate for medical practitioners was 67% and for community members was 53%. 78% of community members (age adjusted) and 54% of doctors thought that a doctor should comply with a patient's request to turn off a life-support system; 68% of doctors through people would still ask to have their life ended even if pain were controlled, compared with 54% of community members; 70% of community members thought the law should be changed to allow active voluntary euthanasia, compared with 33% of doctors; and 65% of community members thought that a doctor should be allowed by law to assist a terminally ill person to die, but only 36% of doctors agreed. 79% of doctors and 75% of community members agreed that people would still ask for assistance to end their lives even if optimal palliative care were freely available. CONCLUSION: Community members supported greater choice and control over end-of-life decisions, while doctors were less supportive of some of the options canvassed. In a climate of community participation in health care decisions, it is important to better understand the basis and meaning of these different views. Further detailed research is recommended.

Adolescent↗
PubMed1997

Self-determination in terminal care. A comparison of GP and community members' responses.

OBJECTIVES: To examine health practitioner and community concerns, priorities and preferred options regarding patient self-determination in terminal care. METHOD: A postal questionnaire was sent to 229 general practitioners in two areas of Queensland (Brisbane and Wide Bay) and to 1100 community members throughout Queensland. Questions covered a range of end of life decision making issues, including where people wish to die, the use of advance directives and proxy decision makers, and possible barriers to such options. RESULTS: GPs and community members held very different opinions on most issues: community members were divided between home, hospital and hospice as a preferred place to die, while GPs strongly favoured home as their preferred place to die. Both groups supported the use of advance directives and proxies, but differed significantly with respect to barriers preventing the use of such options. CONCLUSION: Clarifying differences in perceptions and preferred options between the two groups on end of life decision making should not only improve communication and interactions between GPs and their patients but also allow both groups to become full participants in current policy and practice debates on end of life decisions.

Adult↗
PubMed1996

Career development for women in academic medicine: Multiple interventions in a department of medicine.

OBJECTIVE: To determine the gender-based career obstacles for women in an academic department of medicine and to report the interventions to correct such obstacles (resulting from the evaluation) and the results of these interventions. DESIGN: Intervention study, before-after trial, with assessment of faculty concerns and perceived change through structured, self-administered questionnaires. SETTING: The Department of Medicine, The Johns Hopkins University School of Medicine, Baltimore, Md. PARTICIPANTS: Full-time faculty. INTERVENTIONS: Multifaceted intervention from 1990 through 1995 to correct gender-based career obstacles reported by women faculty, including problem identification, leadership, and education of faculty, and interventions to improve faculty development, mentoring, and rewards and to reduce isolation and structural career impediments. MAIN OUTCOME MEASURES: Retention and promotion of deserving women faculty, salary equity, quality of mentoring, decreased isolation from information and colleagues, integration of women faculty into the scientific community, and decreased manifestations of gender bias. RESULTS: Junior women were retained and promoted, reversing previous experience, with a 550% increase in the number of women at the associate professor rank over 5 years (from 4 in 1990 to 26 in 1995). Interim 3-year follow-up showed a 183% increase in the proportion of women faculty who expected they would still be in academic medicine in 10 years (from 23% [7/30] in 1990 to 65% [30/46] in 1993). One half to two thirds of women faculty reported improvements in timeliness of promotions, manifestations of gender bias, access to information needed for faculty development, isolation, and salary equity. Men also reported improvements in these areas. CONCLUSIONS: The outcomes reported here indicate that it is possible to make substantive improvements in the development of women's careers, that an institutional strategy to this end can be successful in retaining women in academic medicine, and that such interventions are likely to benefit all faculty. Long-term interventions appear essential.

Academic Medical Centers↗
PubMed1996

An immunoglobulin E-dependent recombinant histamine-releasing factor induces interleukin-4 secretion from human basophils.

A novel recombinant histamine-releasing factor (rHFR), which stimulates secretion from a subpopulation of human basophils that express a particular type of immunoglobulin E (IgE) or IgE+, was found to induce interleukin-4 (IL-4) production from cells isolated from these same donors. The secretion of IL-4 protein induced by rHRF significantly correlated with histamine release and the amount of protein generated, and the kinetics were identical to those caused by anti-IgE activation. Furthermore, the ability of rHRF to induce IL-4 protein production from cells not normally responsive to this protein was transferred by passive sensitization with plasma containing IgE+ antibody. That this novel protein stimulates both mediator release and the secretion of IL-4 protein from human basophils suggests a prominent role for this molecule in allergic disease.

Basophils↗
PubMed1996

Comparative ultrastructural morphology of human basophils stimulated to release histamine by anti-IgE, recombinant IgE-dependent histamine-releasing factor, or monocyte chemotactic protein-1.

An ultrastructural analysis of human basophils stimulated with anti-IgE, recombinant histamine-releasing factor (rHRF), or monocyte chemotactic protein-1 (MCP-1) (compared with unstimulated cells) was performed. Partially purified peripheral blood basophils were prepared for electron microscopy at time points known to precede histamine release and at half-maximum histamine release times for each secretagogue. Activation morphologies associated with stimulation included granule-vesicle attachments, piecemeal degranulation, anaphylactic degranulation, and uropod formation. These features were qualitatively similar in the stimulated samples. Quantitative differences were evident, however, when stimulated samples were compared with controls or at different time points after stimulation with a single agent or when individual secretagogues were compared. All stimulated samples differed quantitatively from the control samples. Rank orders for morphologic activation events revealed that the most effective trigger for anaphylactic degranulation was anti-IgE > MCP-1 > rHRF, whereas the most effective trigger for uropod formation was rHRF > anti-IgE > MCP-1. Rank orders for piecemeal degranulation and granule-vesicle attachments were the same: MCP-1 > anti-IgE > rHRF. Important relationships among these anatomic events reveal that the development of motile configurations is not associated with the development of secretion morphologies and that piecemeal degranulation precedes and is inversely related to anaphylactic degranulation in stimulated samples.

Antibodies, Anti-Idiotypic↗
PubMed1996

Lectins do not distinguish between heterogenous IgE molecules as defined by differential activity of an IgE-dependent histamine releasing factor.

It has been suggested that differential histamine-releasing activity of an IgE-dependent histamine-releasing factor (HRF), which has recently been cloned, is related to carbohydrate difference in the IgE molecule. Lectins are able to recognize specific glycoforms and might therefore be useful in characterizing the proposed heterogeneity of IgE molecules. As one test of this hypothesis, we examined the histamine release potency of several well-characterized lectins on basophils passively sensitized with serum containing IgE molecules that support HRF-induced histamine release (IgE+) or serum that does not support release by this stimulus (IgE-). Histamine release was induced by challenging basophils with different concentrations of concanavalin A, Lens culinaris (LcH), and Pisum sativum (PSA). Dose-response curves revealed that LcH caused 30% histamine release at 2 micrograms/ml with IgE+ sensitized cells, whereas the same release with IgE- cells required sixfold higher concentrations. Similar values for PSA showed a sevenfold difference. With concanavalin A, the selectivity was reversed in that it was fourfold more active on IgE- -sensitized cells. Another pair of sera (IgE+ vs IgE-) revealed the same result for concanavalin A, but no difference occurred in LcH and PSA induced release between the IgE+ - and IgE- -sensitized cells. These contrasting findings with different pairs of IgE+ -and IgE- -containing sera indicated that the lectins LcH and PSA are not able to discriminate between IgE+ -and IgE- -sensitized cells as does HRF and therefore cannot be used to further define the proposed heterogeneity of IgE. this conclusion was supported by experiments in which basophil preparations from donors possessing natural sensitivity or insensitivity to HRF (having IgE+ or IgE- on their surface) were examined fro their response to these lectins. No difference was found in the sensitivity of the cells to challenge with LcH or PSA, and the response to concanavalin A was the opposite of that found when passively sensitized cells were used (30% histamine release at 0.9 vs 3.5 micrograms/ml for IgE+ vs IgE- donors, respectively). We conclude that oligosaccharide-specific lectins do not differentiate between HRF-reactive and HRF-nonreactive IgE molecules on basophils.

Basophils↗
PubMed1996

Histamine-releasing factors.

There is increasing evidence that human basophils accumulate at sites of chronic inflammation, and, in particular, in allergic asthma. Investigators have, therefore, become very interested in identifying proteins that activate these cells. Recently, the gene encoding a candidate for this function, a novel molecule, the IgE-dependent histamine-releasing factor, was cloned.

Animals↗
PubMed1995

Molecular identification of an IgE-dependent histamine-releasing factor.

An immunoglobulin E (IgE)-dependent histamine-releasing factor (HRF) produced by lymphocytes of atopic children and present in biological fluids of allergic patients has been identified and purified. Amino-terminal sequencing revealed extensive homology to a mouse protein, p21, and its human homolog, p23. Both recombinant proteins caused histamine release from the human basophils of a subpopulation of donors, and this release was dependent on IgE. Polyclonal antibodies recognized and removed the biological activity of recombinant and native HRF. HRF identifies a heterogeneity of IgE and is believed to play a prominent role in chronic allergic disease processes.

Amino Acid Sequence↗
PubMed1995

Purification of immunoglobulin E (IgE) antibodies from sera with high IgE titers.

A three stage method for the ultrapurification of polyclonal IgE from human serum is reported using anion exchange chromatography followed by monoclonal antibody based positive and negative affinity chromatography. Following dialysis of 25-100 ml of serum (2.3-14 micrograms IgE/ml, n = 4) against 0.05 M Tris pH 8, each specimen was subjected to diethylaminoethyl (DEAE)-cellulose chromatography (serum/matrix = 1/4). IgE was eluted with 0.05 M Tris, 0.05 M NaCl pH 8, yielding an IgE recovery of 61-93%, with removal of approximately 90% of other serum proteins and an IgE purity ([IgE]/[Igs]) of 0.1-1.1%. After adjusting to 0.1 M NaCl and concentrating approximately 30-fold, the eluted IgE was further purified by affinity chromatography using a panel of IUIS/WHO-documented mouse monoclonal anti-human immunoglobulin antibodies (alpha hIg-MAbs). First, the IgE-enriched DEAE-cellulose chromatography fraction was incubated in a batch mode with two alpha hIgE-Fc MAbs (HP6029, HP6061) coupled to CNBr-Sepharose, CL-4B. IgE was eluted with 0.05 M glycine pH 2.8 and immediately neutralized. The IgE recovery was 32-52% and IgE purity was 72-97%. Silver-stained SDS-PAGE and noncompetitive solid-phase two-site immunoenzymetric assays for total human IgA, IgE, IgG and IgM indicated that IgA, IgG and IgM were the only contaminants. Next, the IgE was concentrated 10-30-fold in the presence of 0.1% HSA. One IgE specimen was ultrapurified in a batch mode by negative selection chromatography using three pairs of alpha hIg-MAbs (alpha hIgA: HP6111 + HP6123; alpha hIgG: HP6017 + HP6046; alpha hIgM: HP6081 + HP6083) coupled to CNBr-Sepharose, CL-4B. IgE purity increased from 91% to > 99.9% with approximately 70% recovery of IgE for this step. The ultrapurified IgE antibody was shown to be functionally reactive for allergen and Fc epsilon RI receptors on human basophils. We conclude that alpha hIg-MAbs are powerful tools to facilitate the affinity purification of functionally active human IgE from serum; however, when the analyte is present in low concentration, a carrier protein needs to be added to minimize non-specific loss of the material during this process.

Antibodies, Anti-Idiotypic↗
PubMed1995

Hypercalcemia of malignancy in the palliative care patient: a treatment strategy.

Hypercalcemia of malignancy is most commonly due to the effects of parathyroid hormone-related peptide, which acts as a humoral factor to cause generalized osteoclast-mediated bone resorption and reabsorption of calcium by the kidney tubule, and may also act as a local resorptive factor adjacent to bone metastases. Local resorptive mechanisms are less common causes of malignant hypercalcemia than previously believed. Treatment begins with intravenous fluid rehydration, followed by a furosemide diuresis and the bisphosphonate pamidronate, 60-90 mg, intravenously. Gallium nitrate is an efficacious but inconvenient alternative to pamidronate. Calcitonin combined with pamidronate is a reasonable initial therapy for severe hypercalcemia to hasten normalization of the serum calcium. Steroids should be reserved for hypercalcemia due to tumor production of 1,25 dihydroxyvitamin D, or for steroid-responsive malignancies. Oral or parenteral bisphosphonates can be used to maintain normocalcemia. In addition to improving the morbidity of acute hypercalcemia, bisphosphonate therapy has been shown to reduce bone pain and pathological fractures in patients with bone metastases, and calcitonin also has a potent analgesic effect in these patients. Treatment for hypercalcemia should therefore be considered in the majority of patients in the palliative care setting.

Aged↗
PubMed1994

The assessment of constipation in terminal cancer patients admitted to a palliative care unit: a retrospective review.

Constipation is a frequent and distressing complication in patients with advanced cancer. However, very few studies have reviewed the assessment and management of these patients. The purpose of this study was to review the documentation and assessment and diagnosis of constipation in patients admitted to a Palliative Care Unit, and the correlation between those findings and radiological evidence of stool in the colon. The records of 122 consecutive patients admitted to the Palliative Care Unit, Edmonton General Hospital were reviewed in order to assess the physician's and the nurse's record of symptoms, physical findings, and diagnosis and treatment of constipation. All patients also underwent a flat abdominal radiograph that scored for the presence of stool in the colon (0 = no stool; and 12 = stool occupying all the lumen of the four quadrants of the colon). The radiograph was scored blindly by two different physicians. Of 103 evaluable patients, a rectal exam was reported only in 42. Correlation between the assessment by the two physicians' radiograph score was high (0.78, P nd nurses' diagnosis of constipation, the presence of laxative treatment, the number of days since the last bowel movement, and the source of the admission (hospital vs home) were not associated with higher radiological scores for constipation. Assessment is insufficient in this population at high risk for severe constipation. Radiological examination may be necessary for adequate diagnosis in some patients. More research is needed in this area.

Aged↗
PubMed1994

Proximal muscle weakness in a patient with hepatocellular carcinoma.

Asthenia and generalized weakness are common in cancer patients. There are multiple causes for these symptoms. We describe a case of rapid onset of proximal muscle weakness in a patient with hepatocellular carcinoma. The differential diagnosis of muscle weakness in the palliative care patient is reviewed. The discussion centers on steroid myopathy and its treatment.

Asthenia↗
PubMed1994

Screening with total cholesterol: determining sensitivity and specificity of the National Cholesterol Education Program's guidelines from a population survey.

The objective of the study was to determine the sensitivity and specificity of the National Cholesterol Education Program (NCEP) guidelines in identifying at-risk individuals for hypercholesterolemia, using population-based data from the Manitoba Heart Health Survey (MHHS). The MHHS surveyed a representative sample of adult residents of the province of Manitoba, Canada, aged 18-74 (n = 2792), 2212 of whom underwent complete lipoprotein analyses: total cholesterol (TC), high-density (HDL) and low-density (LDL) lipoprotein cholesterol, and triglycerides (TG) after overnight fasting. Following NCEP criteria for risk categories, 618 individuals could be considered as "at risk" based on their HDL and/or LDL levels. However, if the NCEP algorithms were followed, i.e. initial screen for TC only, and determination of HDL and LDL for selected individuals with borderline and high TC, only 438 of the total "at risk" individuals would have been identified (sensitivity = 71%). 1203 of 1594 individuals with acceptable HDL and LDL levels were not considered "at risk" on screening (specificity = 76%). If "at risk" status was determined solely on LDL criteria, the NCEP guidelines result in a higher sensitivity (94%) and comparable specificity (76%). However, when only HDL criteria were used, the sensitivity and specificity declined to 38% and 63% respectively. Compared to a simulated screening study based on the Lipid Research Clinic data reported by Bush and Riedel (1991) the estimates of sensitivity from the MHHS were high. Current NCEP guidelines appear to balance optimally the sensitivity and specificity for selecting individuals based on TC levels for further complete lipoprotein analysis.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗