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Biomedical subjects

Jim Miller

Publications and source records attributed to Jim Miller.

7 recordsLinked to original sources
PubMed2005

LFA-1 co-stimulation inhibits T(h)2 differentiation by down-modulating IL-4 responsiveness.

Initial T cell activation in the context of different co-stimulatory receptors can influence subsequent lineage commitment into T(h) effector cell subtypes. Specifically, CD28 co-stimulation promotes T(h)2 differentiation, whereas leukocyte function-associated antigen-1 (LFA-1) co-stimulation promotes T(h)1 differentiation and inhibits T(h)2 differentiation. In this report, we have addressed the mechanism of LFA-1-mediated inhibition of T(h)2 responses. We show that co-stimulation through LFA-1 does not decrease early IL-4 secretion, but rather induces a loss in IL-4 responsiveness. T cells primed in the context of LFA-1 co-stimulation require a 5-fold increase in the concentration of IL-4 required to drive T(h)2 differentiation, which is not mediated by a loss in IL-4R expression. To determine whether LFA-1 co-stimulation impacts on proximal signaling from the IL-4R, we first identified a kinetic window where we could separate IL-4-driven T(h)2 differentiation from initial T cell priming. T cells were primed for 2 days under different co-stimulation conditions and re-cultured in the presence of IL-4. Subsequent T(h)2 differentiation was absolutely dependent on addition of IL-4. Proximal IL-4R signaling, as evidenced by tyrosine phosphorylation of signal transducer and activator of transcription-6 (STAT6), was not inhibited by initial co-stimulation through LFA-1, yet these T cells still required higher amounts of IL-4 and corresponding higher levels of STAT6 activation to up-regulate GATA-3 and induce T(h)2 differentiation. Thus, LFA-1 co-stimulation appears to interfere with GATA-3 expression downstream of STAT6. These results suggest that LFA-1 co-stimulation functions as a threshold modulator of T(h)2 differentiation, increasing the effective concentration of IL-4 required to drive T(h)2 responses.

Cell Differentiation↗
PubMed2004

Cutting edge: CD28-mediated transcriptional and posttranscriptional regulation of IL-2 expression are controlled through different signaling pathways.

Despite the clear functional importance of CD28 costimulation, the signaling pathways transduced through CD28 have remained controversial. PI3K was identified early as a candidate for CD28 signaling, but conflicting data during the past decade has left the role of PI3K unresolved. In this report, we have resolved this controversy. We show that mutation of the PI3K interaction site in the cytosolic tail of CD28 site disrupts the ability of CD28 to recruit protein kinase C-theta; to the central supramolecular activation cluster (c-SMAC) region of the immunological synapse, promote NF-kappaB nuclear translocation, and enhance IL-2 gene transcription. In contrast, mutation of the PI3K interaction site had no effect on the ability of CD28 to enhance IL-2 mRNA stability. These results suggest that two distinct pathways mediate CD28-induced up-regulation of IL-2 expression, a PI3K-dependent pathway that may function through the immunological synapse to enhance IL-2 transcription and a PI3K-independent pathway that induces IL-2 mRNA stability.

Active Transport, Cell Nucleus↗
PubMed2004

Endoplasmic reticulum-associated degradation-induced dissociation of class II invariant chain complexes containing a glycosylation-deficient form of p41.

The quality control system in the secretory pathway can identify and eliminate misfolded proteins through endoplasmic reticulum-associated degradation (ERAD). ERAD is thought to occur by retrotranslocation through the Sec61 complex into the cytosol and degradation by the proteasome. However, the extent of disassembly of oligomeric proteins and unfolding of polypeptide chains that is required for retrotranslocation is not fully understood. In this report we used a glycosylation mutant of the p41 isoform of invariant chain (Ii) to evaluate the ability of ERAD to discriminate between correctly folded and misfolded subunits in an oligomeric complex. We show that loss of glycosylation at position 239 of p41 does not detectably affect Ii trimerization or association with class II but does result in a defect in endoplasmic reticulum export of Ii that ultimately leads to its degradation via the ERAD pathway. Although class II associated with the mutated form of p41 is initially retained in the endoplasmic reticulum, it is subsequently released and traffics through the Golgi to the plasma membrane. ERAD-mediated degradation of the mutant p41 is dependent on mannose trimming and inhibition of mannosidase I stabilizes Ii. Interestingly, inhibition of mannosidase I also results in prolonged association between the mutant Ii and class II, indicating that complex disassembly and release of class II is linked to mannosidase-dependent ERAD targeting of the misfolded Ii. These results suggest that the ERAD machinery can induce subunit disassembly, specifically targeting misfolded subunits to degradation and sparing properly folded subunits for reassembly and/or export.

Animals↗
PubMed2004

Managing antidepression overdoses.

Depression is a physiological disorder that is medically treated by increasing the bodily amount of one or all of the following neurotransmitters: serotonin, dopamine and norepinephrine. Although there are seven distinct classes of antidepressants, prehospital care professionals should at minimum be able to distinguish the monoamine oxidase inhibitors (MAOIs), tricyclic antidepressants (TCAs), selective serotonin reuptake inhibitors (SSRIs), and newer antidepressants that are none of these. Monoamine oxidase inhibitors have severe, potentially life-threatening interactions with a variety of medications, including the paramedic drug meperidine, as well as with many common foods. An overdose of tricyclic antidepressants can cause lethal cardiac irregularities. Tricyclics are toxic to children in very small doses. A patient who has overdosed on TCAs may be walking and talking when you first arrive, then quickly deteriorate and die before your eyes. The treatment for TCA overdose is sodium bicarbonate; refer to your medical direction for dosages and indications. A common indication of TCA overdose, secondary to the patient's having access to the drugs, is widening of the QRS complex to greater than 0.12 seconds. Serotonin syndrome is often the result of taking a new generation antidepressant, such as an SSRI, while there is still TCA or MAOI in the bloodstream.

Antidepressive Agents↗
PubMed2003

The Initial Health Assessment: an intervention to identify the supportive care needs of cancer patients.

BACKGROUND: The first step in effective supportive care delivery is an assessment of patient needs. The Initial Health Assessment Form (IHA) was developed to aid clinicians in recognition and documentation of a patient's supportive care needs during their first visit to a comprehensive cancer centre. The purpose of this study was to determine the relative effectiveness of this instrument as compared to routine practice. METHODS: A before-after study was performed. Charts of consecutive patients with newly diagnosed cancer attending the Hamilton Regional Cancer Centre were selected randomly. Each chart was reviewed to determine the documentation at the initial patient assessment of 22 supportive care items under eight domains of need: physical, psychological, daily living, social, financial, informational, special needs and personal resources. The pre-intervention evaluation (T1) occurred over a 3-month period followed by the introduction of the IHA into clinical practice. Three months after its introduction, the post-intervention (T2) evaluation took place over the ensuing 3 months. RESULTS: A total of 306 charts were evaluated (153 each in T1 and T2). Patients from the two time periods were comparable with respect to background demographic variables. Introduction of the IHA increased the mean documentation of supportive care needs and resources from 26% in T1 to 49% in T2 ( p=0.001). Significant improvements were found in all domains of need. Despite improvements, documentation of assessment continued to remain low for daily living, social, financial, and informational needs. CONCLUSIONS: The IHA improved documentation of supportive care needs and resources. There is still room for improvement.

Adult↗
PubMed2003

Pelvic trauma.

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Adult↗