Analog Computer Research

Contains reports on two research projects

Non-hormonal systemic therapy in men with hormone-refractory prostate cancer and metastases: a systematic review from the Cancer Care Ontario Program in Evidence-based Care's Genitourinary Cancer Disease Site Group

BACKGROUND: Prostate cancer that has recurred after local therapy or disseminated distantly is usually treated with androgen deprivation therapy; however, most men will eventually experience disease progression within 12 to 20 months. New data emerging from randomized controlled trials (RCTs) of chemotherapy provided the impetus for a systematic review addressing the following question: which non-hormonal systemic therapies are most beneficial for the treatment of men with hormone-refractory prostate cancer (HRPC) and clinical evidence of metastases? METHODS: A systematic review was performed to identify RCTs or meta-analyses examining first-line non-hormonal systemic (cytotoxic and non-cytotoxic) therapy in patients with HRPC and metastases that reported at least one of the following endpoints: overall survival, disease control, palliative response, quality of life, and toxicity. Excluded were RCTs of second-line hormonal therapies, bisphosphonates or radiopharmaceuticals, or randomized fewer than 50 patients per trial arm. MEDLINE, EMBASE, the Cochrane Library, and the conference proceedings of the American Society of Clinical Oncology were searched for relevant trials. Citations were screened for eligibility by four reviewers and discrepancies were handled by consensus. RESULTS: Of the 80 RCTs identified, 27 met the eligibility criteria. Two recent, large trials reported improved overall survival with docetaxel-based chemotherapy compared to mitoxantrone-prednisone. Improved progression-free survival and rates of palliative and objective response were also observed. Compared with mitoxantrone, docetaxel treatment was associated with more frequent mild toxicities, similar rates of serious toxicities, and better quality of life. More frequent serious toxicities were observed when docetaxel was combined with estramustine. Three trials reported improved time-to-disease progression, palliative response, and/or quality of life with mitoxatrone plus corticosteroid compared with corticosteroid alone. Single trials reported improved disease control with estramustine-vinblastine, vinorelbine-hydrocortisone, and suramin-hydrocortisone compared to controls. Trials of non-cytotoxic agents have reported equivocal results. CONCLUSION: Docetaxel-based chemotherapy modestly improves survival and provides palliation for men with HRPC and metastases. Other than androgen deprivation therapy, this is the only other therapy to have demonstrated improved overall survival in prostate cancer in RCTs. Further investigations to identify more effective therapies for HRPC including the use of systemic therapies earlier in the natural history of prostate cancer are warranted

Gi- and Gs-coupled GPCRs show different modes of G-protein binding.

More than two decades ago, the activation mechanism for the membrane-bound photoreceptor and prototypical G protein-coupled receptor (GPCR) rhodopsin was uncovered. Upon light-induced changes in ligand-receptor interaction, movement of specific transmembrane helices within the receptor opens a crevice at the cytoplasmic surface, allowing for coupling of heterotrimeric guanine nucleotide-binding proteins (G proteins). The general features of this activation mechanism are conserved across the GPCR superfamily. Nevertheless, GPCRs have selectivity for distinct G-protein family members, but the mechanism of selectivity remains elusive. Structures of GPCRs in complex with the stimulatory G protein, Gs, and an accessory nanobody to stabilize the complex have been reported, providing information on the intermolecular interactions. However, to reveal the structural selectivity filters, it will be necessary to determine GPCR-G protein structures involving other G-protein subtypes. In addition, it is important to obtain structures in the absence of a nanobody that may influence the structure. Here, we present a model for a rhodopsin-G protein complex derived from intermolecular distance constraints between the activated receptor and the inhibitory G protein, Gi, using electron paramagnetic resonance spectroscopy and spin-labeling methodologies. Molecular dynamics simulations demonstrated the overall stability of the modeled complex. In the rhodopsin-Gi complex, Gi engages rhodopsin in a manner distinct from previous GPCR-Gs structures, providing insight into specificity determinants

Mechanistic insights into allosteric regulation of the A2A adenosine G protein-coupled receptor by physiological cations.

Cations play key roles in regulating G-protein-coupled receptors (GPCRs), although their mechanisms are poorly understood. Here, 19F NMR is used to delineate the effects of cations on functional states of the adenosine A2A GPCR. While Na+ reinforces an inactive ensemble and a partial-agonist stabilized state, Ca2+ and Mg2+ shift the equilibrium toward active states. Positive allosteric effects of divalent cations are more pronounced with agonist and a G-protein-derived peptide. In cell membranes, divalent cations enhance both the affinity and fraction of the high affinity agonist-bound state. Molecular dynamics simulations suggest high concentrations of divalent cations bridge specific extracellular acidic residues, bringing TM5 and TM6 together at the extracellular surface and allosterically driving open the G-protein-binding cleft as shown by rigidity-transmission allostery theory. An understanding of cation allostery should enable the design of allosteric agents and enhance our understanding of GPCR regulation in the cellular milieu

Miscellaneous Problems

Contains reports on three research projects

Miscellaneous Problems

Contains reports on two research projects

Impact of spinal deformity characteristics on patient-reported outcome measurement information system scores in patients with idiopathic scoliosis undergoing posterior spinal fusion

INTRODUCTION: The impact of posterior spinal fusion (PSF) on physical function and pain and mental health in pediatric patients as quantified by the Patient-Reported Outcomes Measurement Information System (PROMIS), developed by the National Institute of Health, is largely unknown. The purpose of this study is to report the changes of PROMIS scores for upper extremity (UE), pain interference (PI), mobility (MOB), and peer relationships (PR) after PSF in patients with idiopathic scoliosis (IS), compare postoperative changes in PROMIS PI and Scoliosis Research Society-30 pain scores, and evaluate associations between curve characteristics and PROMIS scores. METHODS: A retrospective cohort of 122 patients (\u3c18 years old) who underwent PSF for IS was identified through electronic medical record search. PROMIS scores were obtained preoperatively and 6 weeks, 6 months, 1 years, 2 years, and 3 years postoperatively. RESULTS: The mean age of the cohort was 14.2 ± 1.6 years, and the mean Cobb angle was 62.9 ± 13.8° at surgery. Eighty patients had preoperative PROMIS data. UE and MOB scores were statistically lower at 6 weeks and 6 months postoperatively and returned to baseline with a longer follow-up. PI scores were significantly lower at 1 and 2 years postoperatively. PR was unchanged up to 2 years postoperatively and then showed significant improvement. There was a statistically significant negative relationships between lowest instrumented vertebra and PROMIS UE and MOB scores at 6 weeks and 1 year postoperatively, but not at a longer follow-up. There were no significant differences noted in PI and PR PROMIS scores and lowest instrumented vertebra. PROMIS scores were not statistically associated with the Lenke Classification, number of vertebral levels fused, or percentage coronal correction. DISCUSSION: Changes in PROMIS functional domains (UE and MOB) postoperatively normalize at longer follow-ups. Changes in PI and PR demonstrated improvements over preoperative values at 1 to 2 years postoperatively. Preoperative coronal and sagittal measures, and the percentage correction did not correlate with any PROMIS scores

Stationary density profiles in the Alcator C-mod tokamak

In the absence of an internal particle source, plasma turbulence will impose an intrinsic relationship between an inwards pinch and an outwards diffusion resulting in a stationary density profile. The Alcator C-mod tokamak utilizes RF heating and current drive so that fueling only occurs in the vicinity of the separatrix. Discharges that transition from L-mode to I-mode are seen to maintain a self-similar stationary density profile as measured by Thomson scattering. For discharges with negative magnetic shear, an observed rise of the safety factor in the vicinity of the magnetic axis appears to be accompanied by a decrease of electron density, qualitatively consistent with the theoretical expectations. © 2012 American Institute of Physics.United States. Department of Energy. Office of Fusion Energy Science