Very low-loss passive fiber-to-chip coupling with tapered fibers.

A novel passive fiber-to-chip coupling based on the use of fiber tapers embedded in a guiding structure is proposed. By beam-propagation calculations it is verified that this new coupling method exhibits a very low insertion loss. Major advantages of the proposed method compared with butt coupling are demonstrated by simulation results: first, tolerance requirements for the fibers, e.g., diameter variations and core eccentricity, and for fabrication of the alignment structure are reduced by at least 1 order of magnitude. Second, coupling to waveguides of nearly arbitrary dimensions and refractive indices seems to be possible. Experimental results on thermal drawing of fiber tapers are presented and used as input data for the simulations. A concept for fabrication of the new coupling method with the Lithographic Galvanik Abformung (LIGA) technique is presented.

Inhibition of degranulation of polymorphonuclear leukocytes by angiogenin and its tryptic fragment.

A degranulation inhibiting protein was purified to apparent homogeneity from plasma ultrafiltrates of patients with uremia using gel-permeation chromatography, ion-exchange chromatography, affinity chromatography on blue Sepharose, and ion-exchange chromatography on a Mono S HR 5/5 fast protein liquid chromatography column. The identity of the isolated degranulation inhibiting protein with angiogenin was demonstrated by amino acid sequence determination, immunoblotting, and identical inhibitory activity effects on leukocyte degranulation. At concentrations in the nanomolar range, the protein inhibited spontaneous degranulation of polymorphonuclear leukocytes (PMNL) to 40%. The protein discharge of cells, which were preincubated with nanomolar concentrations of angiogenin and then stimulated with the chemotactic peptide formyl-norleucyl-leucyl-phenylalanyl-norleucyl-tyrosyl-leucine (FNLPNTL), was inhibited by 70%. Cellular functions such as chemotaxis, phagocytosis, and the oxidative respiratory burst were not obviously affected by angiogenin. A polyclonal antibody to human recombinant angiogenin abolished the inhibitory effect of the isolated protein upon PMNL. The same but reduced effect was induced by the disulfide C39-C92 containing tryptic angiogenin fragment L-H-G-G-S-P-W-P-P-C92-Q-Y-R-G-L-T-S-P-C39-K, indicating a new, so far unknown biologically active site of angiogenin which is different from the sites responsible for angiogenic or ribonucleolytic activity. Two synthetic peptides containing residues 83-95, one with S92 instead of C92, revealed the same inhibitory effect on the protein degranulation of PMNL as the entire tryptic fragment.

Effect of immunosuppressive drugs on the release of metalloproteinases from human polymorphonuclear leukocytes.

The concentration of the metalloproteinases type I collagenase and gelatinase was measured in isolated polymorphonuclear leukocytes (PMNLs) of renal transplant recipients treated either with cyclosporin A (CyA) and prednisolone (Pr) (n = 8) or azathioprine (Aza) and Pr (n = 8), and of healthy subjects (n = 12). PMNLs of CyA- and Aza-treated transplant patients displayed markedly higher gelatinase content (2427 +/- 489 and 3284 +/- 357 ng/10(7) cells) than PMNLs of controls (528 +/- 83 ng/10(7) cells). There was also a higher content of type I collagenase in PMNLs (3374 +/- 292 ng/10(7) cells) of Aza-treated patients and significantly elevated levels in PMNLs of patients receiving CyA (3625 +/- 229 ng/10(7) cells) compared with healthy subjects (2878 +/- 151 ng/10(7) cells). In contrast, neutrophil lactoferrin content was lower in transplant patients. Thus, immunosuppressive drugs may reduce the release of leukocyte proteinases, which are known for their deleterious role in proteolytic tissue and matrix breakdown. In vitro, the effects of different immunosuppressive drugs on the release of lactoferrin, collagenase and gelatinase were investigated on FMLPNTL-stimulated PMNLs isolated from healthy subjects. CyA but not Aza or Pr caused inhibition of gelatinase, collagenase and lactoferrin release.