Temperature-independent silicon subwavelength grating waveguides.

We demonstrate, by experiment and numerical calculations, temperature-independent subwavelength grating waveguides with a periodic composite core composed of alternating regions of silicon and SU-8 polymer. The polymer has a negative thermo-optic (TO) material coefficient that cancels the large positive TO effect of the silicon. Measurements and Bloch mode calculations were carried out over a range of silicon-polymer duty ratios. The lowest measured TO coefficient at a wavelength of 1550 nm is 1.8×10(-6) K(-1); 2 orders of magnitude smaller than a conventional silicon photonic wire waveguide. Calculations predict the possibility of complete cancellation of the silicon waveguide temperature dependence.

Modulation of stretch reflex excitability during quiet human standing.

Stretch reflex excitability was measured during quiet standing by using a bilateral electro-hydraulic actuator to apply perturbations of angular position to the ankle. Subjects were instructed to stand quietly while pulse displacements were applied at random time intervals. Position, torque, gastrocnemius soleus EMG, tibialis anterior EMG, heel position, tibia angle, femur angle, and sacrum angle were measured. Activation level and reflex excitability varied substantially from trial to trial - reflex torque decreased as the background torque level increased; while reflex EMG increased when background torque increased. This behavior is consistent with previous findings in prone subjects. Reflex torque for a given activation level was found to vary with the initial torque derivative. Negative torque derivatives produced greater reflex excitation then their positive counterparts. These findings suggest that reflex excitability in quiet human standing is modulated to optimize balance.

Interleukin-8 stimulates human immunodeficiency virus type 1 replication and is a potential new target for antiretroviral therapy.

Production of the C-X-C chemokines interleukin-8 (IL-8) and growth-regulated oncogene alpha (GRO-alpha) in macrophages is stimulated by exposure to human immunodeficiency virus type 1 (HIV-1). We have demonstrated previously that GRO-alpha then stimulates HIV-1 replication in both T lymphocytes and macrophages. Here we demonstrate that IL-8 also stimulates HIV-1 replication in macrophages and T lymphocytes. We further show that increased levels of IL-8 are present in the lymphoid tissue of patients with AIDS. In addition, we demonstrate that compounds which inhibit the actions of IL-8 and GRO-alpha via their receptors, CXCR1 and CXCR2, also inhibit HIV-1 replication in both T lymphocytes and macrophages, indicating potential therapeutic uses for these compounds in HIV-1 infection and AIDS.

Malaria and pregnancy: placental cytokine expression and its relationship to intrauterine growth retardation.

Malaria infections during pregnancy can lead to the delivery of low-birth-weight infants. In this study, cytokine mRNA was measured in placentas from 23 malaria-infected and 21 uninfected primigravid women who had delivered in Mangochi, Malawi, a region with a high rate of transmission of falciparum malaria. Significantly increased expression of interleukin (IL)-1beta, IL-8, and tumor necrosis factor (TNF)-alpha and decreased expression of IL-6 and transforming growth factor-beta1 were found in malaria-infected compared with uninfected placentas. TNF-alpha and IL-8 were produced by maternally derived hemozoin-laden placental macrophages. Increased TNF-alpha expression was associated with increased placental hemozoin concentrations. Increased TNF-alpha or IL-8 expression in the placenta was associated with intrauterine growth retardation but not with preterm delivery. The results suggest that malaria infections induce a potentially harmful proinflammatory response in the placenta.

HIV-1 rev antisense phosphorothioate oligonucleotide binding to human mononuclear cells is cell type specific and inducible.

A fluorescein-conjugated, antisense phosphorothioate oligonucleotide with specificity for HIV-1 rev sequence (FAM-anti-rev) was investigated for its ability to bind to specific subsets of human peripheral blood mononuclear cells. Oligonucleotide binding by CD4+ and CD8+ T cells, B cells, and monocytes isolated from 15 normal and 15 HIV-infected individuals was evaluated on both nonstimulated mononuclear cells and after 24-hr activation with phytohemagglutinin (PHA). In both normals and HIV-infected individuals, we found a significantly higher percentage of monocytes and B cells binding oligonucleotide in comparison to T cells. Oligonucleotide binding by both T cells and B cells was enhanced by 24-hr PHA stimulation while monocyte uptake was unchanged. In comparison to normal controls, HIV-1-infected patients showed slightly higher percentages of both unstimulated and PHA activated CD4+, CD8+, and CD25+ T cells binding oligonucleotide. The propensity for a high percentage of monocytes, which may act as an HIV-1 reservoir, to bind the anti-rev oligonucleotide and the enhanced binding by T cells in the HIV-1-infected patient samples provides some optimism for potential in vivo therapy of HIV-1 infection using antisense oligonucleotides.