Nonlinear signaling on biological networks: The role of stochasticity and spectral clustering.

Signal transduction within biological cells is governed by networks of interacting proteins. Communication between these proteins is mediated by signaling molecules which bind to receptors and induce stochastic transitions between different conformational states. Signaling is typically a cooperative process which requires the occurrence of multiple binding events so that reaction rates have a nonlinear dependence on the amount of signaling molecule.

Assessing family history of chronic disease in primary care: Prevalence, documentation, and appropriate screening.

Objective: To assess the proportion of primary care patients who report a family history (FH) of type 2 diabetes, coronary artery disease, breast cancer, or colorectal cancer (CRC); assess concordance of FH information derived from the electronic medical record (EMR) compared with patient-completed health questionnaires; and assess whether appropriate screening was informed by risk based solely on FH.

Design: Data from the BETTER (Building on Existing Tools to Improve Chronic Disease Prevention and Screening in Primary Care) trial were used. Patients were mailed questionnaires.

N(2)O(3) enhances the nitrosative potential of IFNgamma-primed macrophages in response to Salmonella.

We show here that the nitric oxide (NO)-detoxifying Hmp flavohemoprotein increases by 3-fold the transcription of the Salmonella pathogenicity island 2 (SPI2) in macrophages expressing a functional inducible NO synthase (iNOS). However, Hmp does not prevent NO-related repression of SPI2 transcription in IFNgamma-primed phagocytes, despite preserving intracellular transcription of sdhA sdhB subunits of Salmonella succinate dehydrogenase within both control and IFNgamma-primed phagocytes. To shed light into the seemingly paradoxical role that Hmp plays in protecting intracellular SPI2 expression in various populations of macrophages, N(2)O(3) was quantified as an indicator of the nitrosative potential of Salmonella-infected phagocytes in different states of activation.

Constitutive acid sphingomyelinase enhances early and late macrophage killing of Salmonella enterica serovar Typhimurium.

We have identified acid sphingomyelinase (ASM) as an important player in the early and late anti-Salmonella activity of macrophages. A functional ASM participated in the killing activity of macrophages against wild-type Salmonella enterica serovar Typhimurium. The role of ASM in early macrophage killing of Salmonella appears to be linked to an active NADPH phagocyte oxidase enzymatic complex, since the flavoprotein inhibitor diphenyleneiodonium not only blocked a productive respiratory burst but also abrogated the survival advantage of Salmonella in macrophages lacking ASM.

Localized reactive oxygen and nitrogen intermediates inhibit escape of Listeria monocytogenes from vacuoles in activated macrophages.

Listeria monocytogenes (Lm) evades being killed after phagocytosis by macrophages by escaping from vacuoles into cytoplasm. Activated macrophages are listericidal, in part because they can retain Lm in vacuoles. This study examined the contribution of reactive oxygen intermediates (ROI) and reactive nitrogen intermediates (RNI) to the inhibition of Lm escape from vacuoles.

Development of genetic circuitry exhibiting toggle switch or oscillatory behavior in Escherichia coli.

Analysis of the system design principles of signaling systems requires model systems where all components and regulatory interactions are known. Components of the Lac and Ntr systems were used to construct genetic circuits that display toggle switch or oscillatory behavior. Both devices contain an "activator module" consisting of a modified glnA promoter with lac operators, driving the expression of the activator, NRI.

Calcium spikes in activated macrophages during Fcgamma receptor-mediated phagocytosis.

Rises in intracellular-free calcium ([Ca(2+)](i)) have been variously associated with Fcgamma receptor (FcR)-mediated phagocytosis in macrophages. We show here that activation of murine bone marrow-derived macrophages increases calcium spiking after FcR ligation. Ratiometric fluorescence microscopy was used to measure [Ca(2+)](i) during phagocytosis of immunoglobulin G (IgG)-opsonized erythrocytes.

pH-dependent regulation of lysosomal calcium in macrophages.

Calcium measurements in acidic vacuolar compartments of living cells are few, primarily because calibration of fluorescent probes for calcium requires knowledge of pH and the pH-dependence of the probe calcium-binding affinities. Here we report pH-corrected measurements of free calcium concentrations in lysosomes of mouse macrophages, using both ratiometric and time-resolved fluorescence microscopy of probes for pH and calcium. Average free calcium concentration in macrophage lysosomes was 4-6x10(-4) M, less than half of the extracellular calcium concentration, but much higher than cytosolic calcium levels.