The use of survival analysis techniques in evaluating the effect of long-term tacrine (cognex®) treatment on nursing home placement and mortality in patients with

Survival analysis techniques using Cox proportional hazards regressions with time-dependent covariates, life table survival plots, and Kaplan-Meier estimates were used to evaluate the effect of long-term tacrine hydrochloride (Cognex^®) treatment on nursing home placement (NHP) and mortality in patients with Alzheimer's disease. Patients with probable Alzheimer's disease (NINCDS criteria) who were randomized in a 30-week double-blind, placebo-controlled, parallel-group, high-dose study of tacrine (1) were subsequently allowed to receive long-term, open-label treatment during which they could receive doses up to 160 mg/day. Using last tacrine dose the analyses demonstrated a dose-response relationship where patients on higher tacrine doses were less likely to enter a nursing home or die than patients on lower doses. The Cox proportional hazards regression approach with time-dependent covariates is also compared to logistic regression which looks only at the crude proportions of patients having the event. Since logistic regression does not allow for the use of time-dependent covariates

it provides somewhat less conservative estimates of the magnitude of the treatment effect.     

Nonporous polyurethane membranes as islet immunoisolation matrices--biocompatibility studies

Novel elastomeric nonporous polyurethane membranes were synthesised with differing hard segment contents for evaluation as possible islet encapsulation matrices. Physico-chemical properties of these membranes were reported earlier by authors and have been found suitable for immunoisolation. In the present study, membranes were evaluated for their in vitro biocompatibility. Membranes T1, T4, T5 and T6 did not show toxicity in direct cell contact study towards L929 fibroblasts. However, T2 and T3 were found cytotoxic and were excluded from further testing. NIH3T3 cells when exposed to leach out products of T4, T5 and T6 showed no cytotoxicity, while T1 decreased cellular viability as confirmed by MTT assay. T4 and T5 alone were seen to be compatible with mouse islets while T6 was incompatible to the mouse islets. Digital image analysis (DIA) studies showed intact morphology of islets cultured on the T4 and T5 with viability (88.4 and 91% respectively) comparable to islets on tissue culture polystyrene (TCPS) control. Islets on T4 and T5 also retained their functionality, as judged by insulin secretion in response to in vitro glucose challenge (16.0 mM). These studies point out the crucial role of surface free energy and hydrophilicity in deciding compatibility of polyurethane membranes with islets of Langerhans. Studies indicate that polyurethane membranes T4 and T5 could be potential candidates for islet immunoisolation.     

Reduced global longitudinal and radial strain with normal left ventricular ejection fraction late after effective repair of aortic coarctation: a CMR feature tracking study

We sought to determine whether global and regional left ventricular (LV) strain parameters were altered in repaired coarctation of the aorta (COA) with normal LV ejection fraction (EF) when compared with healthy adult controls, and whether such alterations were related to LV hypertrophy (LVH). We identified 81 patients after COA repair (31 female, age 25 ± 8.5 years) with inclusion criteria at follow-up CMR of: age ≥13 years, time post-repair ≥10 years, no aortic valve disease, LV-EF >50 %). LV deformation indices derived using CMR-feature tracking and volumetric EF were compared between COA patients and normal controls (n = 20, 10 female, age 37 ± 7 years), and between COA with versus without LVH. In repaired COA versus controls, LV-EF (%) was 62 ± 7.2 versus 58 ± 3.0 (p = 0.01), and LV mass (g/m²) 66 ± 16.8 versus 57.7 ± 6.0 (p = 0.0001). LV global longitudinal strain (GLS) was decreased to ?17.0 ± 4.7 % in COA (?20 ± 5 % in controls, p = 0.02), and global radial strain (GRS) reduced to 40 ± 15 % (50 ± 12.4 % in controls, p = 0.003). The global circumferential strain (GCS) was preserved in COA at ?23 ± 4.7 % (?24.6 ± 2.4 % in controls, p = 0.14). Regionally, LS decrease was marked in the basal segments (septal, p = 0.005, lateral, p = 0.013). In COA with LVH (n = 45, mass 76.3 ± 12.8 g/m²) versus without LVH (n = 36, mass 52.2 ± 10 g/m²), GLS was more markedly decreased (?15.7 ± 4.8 vs. ?18.5 ± 4.2 %, p = 0.016, but GRS and GCS were similar (p = 0.49 and 0.27). In post-repair COA with normal LV-EF, GLS and GRS are reduced whilst GCS is preserved. GLS reduction is more pronounced in the presence of LVH. GLS may qualify as indicator of early LV dysfunction.     

Valdecoxib does not impair platelet function

The platelet effects of a supratherapeutic dose of the new cyclooxygenase (COX)-2 specific inhibitor, valdecoxib (40 mg twice a day), naproxen 500 mg twice a day, diclofenac 75 mg twice a day, and placebo were compared in 62 healthy adult subjects in this 7(1/2) day single-center, randomized, placebo-controlled trial. Platelet aggregation responses (to arachidonate [AA], collagen, and adenosine diphosphate [ADP]), bleeding time, and serum thromboxane B(2) (TxB(2)) concentrations were measured at baseline and at regular intervals on days 1 and 8. Valdecoxib had no effect on platelet function. Naproxen and diclofenac significantly reduced the platelet aggregation response to AA and to a lesser extent collagen and ADP at most assessments compared with placebo. Naproxen significantly lowered serum TxB(2) levels. In contrast to standard doses of 2 nonsteroidal antiinflammatory drugs (NSAIDs), a supratherapeutic valdecoxib dosage does not impair platelet function (COX-1). Valdecoxib may be a safer analgesic option than conventional NSAIDs in patients for whom bleeding complications are a concern. (Am J Emerg Med 2002;20:275-281.     

Differential regulation of IL-13 and IL-4 production by human CD8+ and CD4+ Th0, Th1 and Th2 T cell clones and EBV-transformed B cells

In the present study, the requirements and characteristics forthe production of IL-13 by human T cells, T cell clones andB cells were determined and compared with those of IL-4. IL-13was produced by human CD4⁺ and CD8⁺ T lymphocyte subsets isolatedfrom peripheral blood mononuclear cells and by CD4⁺ and CD8⁺T cell clones. CD4⁺ T cell clones belonging to T_h0, T_h1-likeand T_h2-like subsets produced IL-13 following antigen-specificor polyclonal activation. In addition, EBV-transformed B celllines expressed IL-13 mRNA and produced small amounts of IL-13protein. Expression of IL-13 mRNA and production of IL-13 proteinby peripheral blood T cells and T cell clones was induced rapidlyand was relatively long lasting, whereas IL-4 production bythese cells was transient In addition, IL-13 mRNA expressionwas induced by modes of activation that failed to induce IL-4mRNA expression. IL-13 shares many biological activities withIL-4 which Is compatible with the notion that the IL-13 andIL-4 receptors share a common component required for signaltransduction. However, IL-13 lacks the T cell-activating propertiesof IL-4. Here we have shown that this is related to the factthat T cells fall to bind radiolabeled IL-13 and do not expressthe IL-13-speclflc receptor component Taken together, theseresults indicate that the differences In expression and biologicalactivities of IL-4 and IL-13 on T cells may have consequencesfor the relative roles of these cytokines In the immune response.     

The A427 anchorage-independence assay as a screening tool to identify potential chemopreventive agents

An in vitro model for screening potential chemopreventive agents using inhibition of anchorage-independent growth of a human lung tumor cell line, A427, is described. A427 cells were selected for the model development, as they are known to be tumorigenic in animals, can grow in soft agarose, and their growth can be inhibited by a well-known chemopreventive agent, 13-cis-retinoic acid. Cells are plated on agarose, allowed to develop colonies for 28 days, the stained colonies are enumerated, and the inhibition of spontaneous colony formation measured. A cytotoxicity test is used concurrently with anchorage independent assay for measuring the relative survival of cells to ensure that any observed inhibition of anchorage independent growth is due to the biological activity of the chemopreventive agents, as it uses human cells as substrates rendering the efficacy data feasible for direct extrapolation to humans.     

Identification of chemopreventive agents by screening for induction of glutathione-S-transferase as a biomarker

For selection and identification of potential chemopreventive agents, a biochemical assay using induction of a phase II enzyme, glutathione-S-transferase (GST) in a liver cell culture is described. A normal human liver cell line (Chang liver cells) was selected as the candidate cell line for induction of GST (liver tissues are abundant in GST) by a known chemopreventive agent, oltipraz. Exponentially growing cells plated for 24 hours are exposed to various doses of a chemopreventive agent for an additional 24 hours, homogenized by sonication, and the homogenate is assayed for GST in a modified microplate enzyme assay using CDNB (1-chloro-2,4-dinitrobenzene) as a substrate. A concurrent protein assay is performed to determine the specific enzyme activity. As the assay is modified from a spectrophotometric assay to a microplate assay, it is reliable, sensitive and fast, a significant number of test agents can be screened in a short time.