A low-cost,high-performance pulse generator for ultrasound imaging

The design of a low-cost pulse generator for ultrasound imaging is presented. The pulser can provide 10 kW pulses with less than 0.7 Vpp ringing. Pulses ranging from 10 to 500 ns have been successfully generated     

Photoreduction of Shewanella oneidensis Extracellular Cytochromes by Organic Chromophores and Dye‐Sensitized TiO2

The transfer of photoenergized electrons from extracellular photosensitizers across a bacterial cell envelope to drive intracellular chemical transformations represents an attractive way to harness nature's catalytic machinery for solar‐assisted chemical synthesis. In Shewanella oneidensis MR‐1 (MR‐1), trans‐outer‐membrane electron transfer is performed by the extracellular cytochromes MtrC and OmcA acting together with the outer‐membrane‐spanning porin ? cytochrome complex (MtrAB). Here we demonstrate photoreduction of solutions of MtrC, OmcA, and the MtrCAB complex by soluble photosensitizers: namely, eosin Y, fluorescein, proflavine, flavin, and adenine dinucleotide, as well as by riboflavin and flavin mononucleotide, two compounds secreted by MR‐1. We show photoreduction of MtrC and OmcA adsorbed on Ru^II‐dye‐sensitized TiO₂ nanoparticles and that these protein‐coated particles perform photocatalytic reduction of solutions of MtrC, OmcA, and MtrCAB. These findings provide a framework for informed development of strategies for using the outer‐membrane‐associated cytochromes of MR‐1 for solar‐driven microbial synthesis in natural and engineered bacteria.     

Five days of oral topotecan (Hycamtin), a phase I and pharmacological study in adult patients with solid tumours

Topotecan is a specific inhibitor to topoisomerase I. An oral formulation of topotecan is available with a bioavailability of 32-44% in humans. A phase I and pharmacological study of the oral formulation of topotecan administered daily for 5 days every 21 days was performed in adult patients with solid tumours to determine the maximum tolerated dose (MTD). Adult patients with a WHO performance status < or = 2 adequate haematological, hepatic and renal functions, with malignant solid tumours refractory to standard forms were entered into the study. Pharmacokinetics were performed on days 1 and 4 of the first course using a validated high performance liquid chromatographic assay. 29 patients entered the study, all patients were evaluable for toxicity and response. The doses studied in the 29 patients were 1.2, 1.8, 2.3, 2.7 mg/m2/day and a fixed dose of 4 mg/day without surface area adjustment. A total of 109 courses were given. Dose limiting toxicity (DLT) was reached at a dose of 2.7 mg/m2/day and consisted of CTC (NCI-Common Toxicity Criteria) grade IV granulocytopenia. The regimen was well tolerated. Non-haematological toxicities were mild, including fatigue, anorexia, nausea, vomiting and diarrhoea. A significant correlation was observed between the percentage decrease in white blood cells versus the area under the curve (AUC(t)) of topotecan lactone (R = 0.76 P < 0.01) which was modelled by a sigmoidal Emax function. The correlation coefficient between the absolute topotecan dose administered and the AUC(t) was R = 0.52 (P = 0.04). Pharmacokinetics of the fixed dose of 4 mg/day were comparable to the 2.3 mg/m2/day dose. DLT in this phase I study of five daily doses of oral topotecan every 21 days was granulocytopenia. The recommended dose for phase II studies is 2.3 mg/m2/day or alternatively, a fixed dose of 4 mg/day.     

Spontaneous and ligand-induced trafficking of CXC-chemokine receptor 4

A chimeric protein consisting of CXC-chemokine receptor 4 (CXCR4) and the green fluorescent protein (GFP) was used for studying receptor localization and trafficking in real time in stably transduced HeLa, U-937, CEM, and NIH/3T3 cells. CXCR4-GFP was fully active as a co-receptor in mediating human immunodeficiency virus (HIV) entry. Both CXCR4 and CXCR4-GFP were found to undergo significant spontaneous endocytosis. Only 51.5 +/- 7.8% of receptor molecules were found on the plasma membrane in CD4-positive cells, 43.9 +/- 8.5% were found in CD4-negative HeLa cells, 75.6 +/- 9.7% were found in U-937 cells, 72.5 +/- 7.9 were found in CEM cells, and almost none were found in in NIH/3T3 cells. Stromal cell-derived factor-1alpha induced rapid endocytosis of cell surface receptor molecules. A significant part of CXCR4 was targeted to lysosomes upon binding of the ligands, and recycling of internalized CXCR4 was not efficient. Only about 30% of receptor molecules recycled back to the cell surface in HeLa cells, 5% recycled in U937, and 10% recycled in CEM cells, suggesting that the protective effect of chemokines against HIV infection can be attributed not only to competition for binding but also to depletion of the co-receptor molecules from the cell surface. Envelope glycoprotein gp120 of syncytia-inducing/lymphocyte tropic HIV-1 strains induced rapid internalization of CXCR4 in both CD4-negative and CD4-positive cells, suggesting that gp120 is a high affinity ligand of CXCR4.     

Functional nonequivalence of Drosophila actin isoforms

We show that different Drosophila actin isoforms are not interchangeable. We sequenced the six genes that encode conventional Drosophila actins and found that they specify amino acid replacements in 27 of 376 positions. To test the significance of these changes we used directed mutagenesis to introduce 10 such conversions, independently, into the Act88F flight muscle-specific actin gene. We challenged these variant actins to replace the native protein by transforming germline chromosomes of a Drosophila strain lacking flight muscle actin. Only one of the 10 reproducibly perturbed myofibrillar function, demonstrating that most isoform-specific amino acid replacements are of minor significance. In order to establish the consequences of multiple amino acid replacements, we substituted portions of the Drosophila Act88F actin gene with corresponding regions of genes encoding other isoforms. Only one of five constructs tested engendered normally functioning flight muscles, and the severity of myofibrillar defects correlated with the number of replacements within the chimeric genes. Finally, we completely converted the flight muscle actin-encoding gene to one specifying a nonmuscle isoform, a change entailing a total of 18 amino acid replacements. Transformation of flies with this construct resulted in disruption of flight muscle structure and function. We conclude that actin isoform sequences are not equivalent and that effects of the amino acid replacements, while minor individually, collectively confer unique properties.     

Time-dependent differential changes of immune function in rats exposed to chronic intermittent noise

Noise is a highly relevant environmental and clinical stressor. Compared to most other experimental stressors, noise is a modest activator of neuroendocrine pathways that mimic the situation in human health where neuroendocrine activation by environmental stressors is often absent or difficult to establish. Little is known about the effects of noise exposure on the immune system. In the present work, the effects of a low-intensity chronic intermittent unpredictable noise regimen on various parameters of immune function was studied. Male wistar rats were exposed to a randomized noise protocol (white noise, 85 dB, 2-20 kHz) for 10 h per day, 15 min per h over a total period of 3 weeks. Control animals were exposed to ambient sound only. Immune function was monitored after 24 h, 7 days, and 21 days of noise exposure. Noise induced several significant changes in immune function in a time-dependent differential pattern involving both immunosuppression and immunoenhancement. After 24 h, serum IgM levels were increased and peripheral phagocytic activity was decreased. Splenic lymphocytic proliferation to mitogens was significantly decreased after 7 days, but slightly elevated after 3 weeks. The activity of splenic NK cells was increased significantly after 24 h and 7 days, but suppressed after 3 weeks. These results show that various parameters of immune function are affected differentially over time in a period of chronic mild noise stress, possibly due to sequential activation of different physiological mechanisms.     

Treatment with anti-interleukin-10 monoclonal antibody enhances early resistance to but impairs complete clearance of Listeria monocytogenes infection in mice

Mice that received an anti-interleukin-10 (anti-IL-10) neutralizing monoclonal antibody (MAb) (SXC-1) prior to infection with Listeria monocytogenes initially demonstrated resistance to the infection, as indicated by reduced recovery of L. monocytogenes from their spleens and livers during the first 5 days after challenge. Anti-IL-10 MAb-treated mice then demonstrated reduced resistance during the later stage of infection, as indicated by persistent infection with L. monocytogenes in their livers 11 days after challenge. Aspartate aminotransferase (AST) levels (a measure of liver damage) in the sera of control mice increased between 1 and 5 days after challenge, while anti-IL-10 MAb-treated mice maintained lower AST levels. At 7 days after challenge, AST levels in the sera of control mice decreased as the numbers of organisms declined. In contrast, AST levels increased as the infections persisted in anti-IL-10 MAb-treated mice. The AST levels in serum reflected liver histopathology as anti-IL-10 MAb-treated mice exhibited fewer granulomatous lesions and less necrosis of liver tissue than the control mice during the first 5 days after challenge. Anti-IL-10 MAb treatment altered the expression of inflammatory cytokine mRNAs during L. monocytogenes infection. Control MAb-treated mice exhibited increased expression of tumor necrosis factor alpha and granulocyte-macrophage colony-stimulating factor mRNA in their lives during L. monocytogenes infection, but this increase did not occur in anti-IL-10 MAb-treated mice. Gamma interferon mRNA expression in the livers of the control MAb-treated mice was increased between 1 and 5 days after L. monocytogenes challenge and then decreased at 7 days after challenge. In contrast, gamma interferon mRNA expression in the livers of anti-IL-10 MAb-treated mice was not decreased until 7 days after challenge. These results indicate that endogenous IL-10 has both beneficial and detrimental effects on the host response to L. monocytogenes infection in mice.     

Enhanced cytotoxicity with interleukin-1 alpha and 5-fluorouracil in HCT116 colon cancer cells

Recombinant human interleukin-1 alpha (rIL-1 alpha), at concentrations that were not growth-inhibitory when given alone (100-10,000 U/ml), enhanced the growth inhibition resulting from a 72-h fluorouracil (FUra) exposure in HCT116 colon cancer cells. Median-effect analysis of clonogenic assays indicated that rIL-1 alpha, given 24 h prior to and following a 24-h exposure to FUra, increased lethality in a more than additive fashion. rIL-1 alpha did not appear to significantly affect [3H]-FUra metabolism, total [3H]-FUra-RNA incorporation or RNA retention after drug removal, inhibition of thymidylate synthase, or thymidine triphosphate pool depletion. During continuous exposure to rIL-1 alpha, transient stimulation of RNA and DNA synthesis was observed at 72 h, with a return to normal by 96 h. A 24-h exposure to 10 microM FUra altered the elution profile of newly synthesized DNA as monitored by pH step alkaline elution. An accumulation of lower-MW single-stranded DNA species was noted with FUra compared to control, accompanied by a significantly decreased proportion of DNA retained on the polycarbonate filter: 10% retained vs. 32% for control (P = 0.01). A 48-h exposure to rIL-1 alpha alone did not affect the elution profile of nascent DNA species, nor did it enhance the effects of FUra. Although FUra did not appreciably affect pulse [3H]-uridine incorporation into RNA for the initial 8-24 h of FUra exposure, progressive inhibition of net RNA synthesis was observed thereafter. FUra prevented the stimulatory effect of rIL-1 alpha on RNA synthesis, and net RNA synthesis was significantly inhibited (by 64-79% after 72 and 96 h) with the combination compared to rIL-1 alpha alone. Continuous exposure to 10 microM thymidine did not rescue cells from the lethality of FUra alone or the combination of FUra plus rIL-1 alpha, suggesting that depletion of deoxythymidine triphosphate as a consequence of thymidylate synthase inhibition was not the most important component of FUra toxicity. In contrast, 1 mM uridine provided partial protection against the toxicity of FUra alone or with rIL-1 alpha. Although uridine did not affect FUra metabolism, it decreased FUra-RNA incorporation by 42-60%, presumably as a consequence of the 2-fold expansion of UTP pools. [125I]-rIL-1 alpha binding was nonspecific; with a 24-h exposure, however, internalized [125I]-rIL-1 alpha exceeded cell surface-bound material by 2-fold.(ABSTRACT TRUNCATED AT 250 WORDS)