Quantitative and qualitative analysis of stability for 16 serum immunoregulators over 50 freeze-thaw cycles.

OBJECTIVES: To evaluate the reliability of data from the assay of bio-archived specimens, a 50-freeze-thaw-cycle (FTC) degradation study of fresh sera was conducted to test the stability of 16 immunoregulators. METHODS: Twenty de-identified serum specimens were obtained from volunteers at United Health Services-Wilson Memorial Hospital. Specimens were stored at -20°C and underwent daily 1 h thawing and subsequent freezing for each FTC over 50 consecutive days. Immunoregulator concentrations were assessed via enzyme-linked immunosorbent assay (ELISA) in participant samples at 2 FTC (baseline), 25 FTC, and 50 FTC. Specific immunoregulators observed in the study were C-reactive protein (CRP), interleukin (IL)-1α, 4, 6, 8, 10, monocyte chemoattractant protein-1 (MCP-1, CCL2), monocyte chemoattractant protein-2 (MCP-2, CCL8), eotaxin-1, thymus-and-activation-regulated chemokine (TARC, CCL17), regulated on activation normal T-cell expressed and secreted (RANTES, CCL5), growth-regulated oncogene-alpha (GRO-α, CXCL1), small inducible cytokine A1 (I-309, CCL1), interferon-gamma (IFN-γ), interferon-gamma inducible protein-10 (IP-10, CXCL10), and tumor necrosis factor-alpha (TNF-α). RESULTS: Quantitative stability of serum immunoregulators: Serum CRP, IL-8, IL-10, IFN-γ, IP-10, and eotaxin-1 levels appear to be statistically equivalent from baseline to 50 FTC (p ≤ .05). Retention of patterns in serum immunoregulators: patterns across FTC were retained for TARC (age) and CRP, IFN-γ, and MCP-2 (sex). CONCLUSIONS: While the effect of multiple FTC on serum immunoregulator levels may not replicate prolonged freezer storage, the results of this study provide valuable information on the robustness of immunoregulators for research using bio-archived sera.

A neuron-astrocyte transistor-like model for neuromorphic dressed neurons.

Experimental evidences on the role of the synaptic glia as an active partner together with the bold synapse in neuronal signaling and dynamics of neural tissue strongly suggest to investigate on a more realistic neuron-glia model for better understanding human brain processing. Among the glial cells, the astrocytes play a crucial role in the tripartite synapsis, i.e. the dressed neuron. A well-known two-way astrocyte-neuron interaction can be found in the literature, completely revising the purely supportive role for the glia. The aim of this study is to provide a computationally efficient model for neuron-glia interaction. The neuron-glia interactions were simulated by implementing the Li-Rinzel model for an astrocyte and the Izhikevich model for a neuron. Assuming the dressed neuron dynamics similar to the nonlinear input-output characteristics of a bipolar junction transistor, we derived our computationally efficient model. This model may represent the fundamental computational unit for the development of real-time artificial neuron-glia networks opening new perspectives in pattern recognition systems and in brain neurophysiology.

Lidocaine inhibition of the hyperpolarization-activated current (I(f)) in sinoatrial myocytes.

The aim of this study was to provide information on the dose dependence and biophysical details of lidocaine blockade of the hyperpolarization-activated current (I(f)) in the sinoatrial node. Isolated rabbit sinoatrial myocytes were patch-clamped in the whole-cell configuration at 36+/-0.5 degrees C, in the presence of 1 mM Ba2+ and 2 mM Mn2+ to minimize contamination by K+ and Ca2+ currents, respectively. Lidocaine inhibited I(f) dose-dependently with a maximal inhibition of 69.5% at 75 microM and a half-maximal effect at 38.2 microM. Lidocaine reduced the conductance of fully activated I(f), without affecting the current reversal potential; the blocking effect was independent of membrane potential. Voltage dependence of I(f) activation gating was not affected by lidocaine, whose effect was independent of use and rate. Lidocaine did not modify the time course of I(f) activation. At therapeutic concentrations, lidocaine significantly inhibited I(f) by reducing fully activated channel conductance. Lack of voltage and rate dependence of effect differentiates lidocaine from most of other blockers of this current.

Prevalence of antithrombin III deficiency in blood donors selected for personal or familial history of venous thrombosis.

Antithrombin III (ATIII) was measured using a functional assay in 692 (6.7%) out of 10,332 blood donors selected for their personal or familial history of venous thrombosis. Three subjects with low levels of the protein were observed. Thus, the prevalence of ATIII deficiency was of 0.43%, corresponding to a prevalence of 0.03% in the general population. On the basis of family studies and of clinical and laboratory investigations, inherited ATIII deficiency was excluded and reduced levels of the inhibitor were attributed to an impaired liver function, despite normal blood coagulation tests. Therefore, in this study inherited ATIII deficiency cases were not found; however, acquired ATIII deficiency associated with normal clotting tests might represent a rare but definite risk factor for thrombosis.