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The high-affinity sigma receptor 1 (σR1) ligand (+)-pentazocine ((+)-PTZ) affords profound retinal neuroprotection in vitro and in vivo by a yet-unknown mechanism. A common feature of retinal disease is Muller cell reactive gliosis, which includes cytokine release. Here, we investigated whether lipopolysaccharide (LPS) stimulates cytokine release by primary mouse Muller cells and whether (+)-PTZ alters release. Using a highly sensitive inflammatory antibody array we observed significant release of macrophage inflammatory proteins (MIP1γ, MIP2, MIP3α) and interleukin-12 (IL12 (p40/p70)) in LPS-treated cells compared to controls, and a significant decrease in secretion upon (+)-PTZ treatment. Muller cells from σR1 knockout mice demonstrated increased MIP1γ, MIP2, MIP3α and IL12 (p40/p70) secretion when exposed to LPS compared to LPS-stimulated WT cells. We investigated whether cytokine secretion was accompanied by cytosolic-to-nuclear NFκB translocation and whether endothelial cell adhesion/migration was altered by released cytokines. Cells exposed to LPS demonstrated increased NFκB nuclear location, which was reduced significantly in (+)-PTZ-treated cells. Media conditioned by LPS-stimulated-Muller cells induced leukocyte-endothelial cell adhesion and endothelial cell migration, which was attenuated by (+)-PTZ treatment. The findings suggest that release of certain inflammatory cytokines by Muller cells can be attenuated by σR1 ligands providing insights into the retinal neuroprotective role of this receptor.

Homocysteine is a non-proteinogenic amino acid that is an intermediate in methionine and cysteine metabolism. Severe elevations in plasma homocysteine (hyperhomocysteinemia) are caused by homozygous mutations in the regulatory enzymes involved in homocysteine metabolism; these enzymes include methionine synthase, methylene tetrahydrofolate reductase, and cystathionine β-synthase.1 Moderate hyperhomocysteinemia occurs more commonly and is caused by heterozygous mutations in these regulatory enzymes or by nutritional deficiencies in the vitamins folate, B12, and B6. Recently, several clinical studies reported a correlation between elevated plasma homocysteine and retinal degenerative disorders, including open-angle glaucoma, maculopathy, and diabetic retinopathy.2–9 Our laboratory has investigated extensively the potential of homocysteine to induce toxicity to the retina using both in vitro and in vivo models.10–13 Our earliest in vivo study documented that intravitreal injection of a high level of homocysteine (200 μM) led to abundant cell death in the ganglion cell layer.13 To specifically analyze the effect of endogenous elevation of homocysteine on the retina, our laboratory recently used a mutant mouse model of hyperhomocysteinemia developed in the laboratory of Nobuyo Maeda.14 The mouse harbors a deletion of the gene encoding cystathionine β-synthase (cbs), an enzyme required for the conversion of homocysteine to cysteine. Using the heterozygous mutant mouse (cbs+/−) as a model of moderate hyperhomocysteinemia (∼4- to 7-fold elevation in plasma homocysteine), we found that ganglion cell viability was decreased by approximately 20%; even greater neuronal death was observed in mice with higher levels of this amino acid.10 These studies described for the first time that endogenous elevation in plasma homocysteine induces ganglion cell loss. To investigate potential mechanisms of homocysteine-induced ganglion cell toxicity, we performed microarray analysis on neural retinas of cbs+/− mice. The expression of numerous genes was altered in these mice; two genes of particular interest whose expression levels were changed in the neural retina of the cbs+/− mouse were opa1 and fis1.10 Opa1 and Fis1 proteins are involved in mitochondrial fission and fusion; Opa1 is a modulator of mitochondrial fusion, and Fis1 is the rate-limiting protein in mitochondrial fission.15 Mitochondria are the primary energy-producing organelles and are dynamic in that they require a balance of fission and fusion processes to function properly.15 Excessive fission results in mitochondrial fragmentation and eventual cellular apoptosis, whereas excessive fusion results in elongated mitochondria and inhibition of adequate energy production. Given that retinal ganglion cells are neurons that are highly active, as evidenced by a high metabolic rate, they are especially sensitive to alterations in mitochondrial dynamics.16,17 Deficiencies in mitochondrial fission and fusion processes have been implicated in the pathogenesis of several neurodegenerative disorders, including glaucoma, a disease characterized specifically by retinal ganglion cell loss.16,18–20 In the present study, we test the hypothesis that elevation in homocysteine impairs the balance of mitochondrial fission and fusion in retinal ganglion cells, resulting in excessive mitochondrial fission and cellular apoptosis.

A 100-W Beale free-piston Stirling engine was powered remotely by a CO2 laser for long periods of time. The engine ran on both continuous-wave and pulse laser input. The working fluid was helium doped with small quantities of sulfur hexafluoride, SF6. The CO2 radiation was absorbed by the vibrational modes of the sulfur hexafluoride, which in turn transferred the energy to the helium to drive the engine. Electrical energy was obtained from a linear alternator attached to the piston of the engine. Engine pressures, volumes, and temperatures were measured to determine engine performance. It was found that the pulse radiation mode was more efficient than the continuous-wave mode. An analysis of the engine heat consumption indicated that heat losses around the cylinder and the window used to transmit the beam into the engine accounted for nearly half the energy input. The overall efficiency, that is, electrical output to laser input, was approximately 0.75%. However, this experiment was not designed for high efficiency but only to demonstrate the concept of a laser-driven engine. Based on this experiment, the engine could be modified to achieve efficiencies of perhaps 25-30%.

The technique of holographic interferometry provides a means for noninvasive measurement of the air density distribution in the flow field in the vicinity of an aerodynamic model. A test of the applicability of this technique was the objective of this investigation. A holographic interferometer was installed in the 2- by 2-Foot Transonic Wind Tunnel at Ames Research Center. Several tests were conducted with this system on two axisymmetric models, one at subsonic and the other at supersonic speeds. Holograms were made of the flow field around the model for several test conditions. These holograms were reconstructed into interferograms in the laboratory. The fringe distribution (a measure of local densities) from a number of interferograms was digitized for subsequent data reduction. A computer program based on the Fourier transform technique was developed to convert the fringe distribution into a three-dimensional distribution of air density around the model. These results will be presented in this paper.