Effect of titanium dioxide (TiO₂) nanoparticle coating on the detection performance of microfiber knot resonator sensors for relative humidity measurement

In this study, the sensitivity and the linearity of the un-coated and TiO2-coated microfiber knot resonator (MKR) have been analyzed. The MKR is very sensitive to humidity changes since its refractive index is strongly humidity dependent. As a result, shifts occur in the resonance wavelength and there are also changes in output power. The un-coated MKR showed a sensitivity of 1.3 pm/%RH, in terms of the resonance wavelength, and a sensitivity of 0.0626 dB/%RH for the transmitted output power. The sensitivity increased greatly after the deposition of a porous TiO2 nanoparticle coating on the MKR. The TiO2-coated MKR showed an improved sensitivity of 2.5 pm/%RH, with respect to the resonance wavelength, and 0.0836 dB/%RH for the transmitted output power. This MKR sensor has the potential for use in a variety of humidity sensing applications

The Syk Kinase SmTK4 of Schistosoma mansoni Is Involved in the Regulation of Spermatogenesis and Oogenesis

The signal transduction protein SmTK4 from Schistosoma mansoni belongs to the family of Syk kinases. In vertebrates, Syk kinases are known to play specialized roles in signaling pathways in cells of the hematopoietic system. Although Syk kinases were identified in some invertebrates, their role in this group of animals has not yet been elucidated. Since SmTK4 is the first Syk kinase from a parasitic helminth, shown to be predominantly expressed in the testes and ovary of adult worms, we investigated its function. To unravel signaling cascades in which SmTK4 is involved, yeast two-/three-hybrid library screenings were performed with either the tandem SH2-domain, or with the linker region including the tyrosine kinase domain of SmTK4. Besides the Src kinase SmTK3 we identified a new Src kinase (SmTK6) acting upstream of SmTK4 and a MAPK-activating protein, as well as mapmodulin acting downstream. Their identities and colocalization studies pointed to a role of SmTK4 in a signaling cascade regulating the proliferation and/or differentiation of cells in the gonads of schistosomes. To confirm this decisive role we performed biochemical and molecular approaches to knock down SmTK4 combined with a novel protocol for confocal laser scanning microscopy for morphological analyses. Using the Syk kinase-specific inhibitor Piceatannol or by RNAi treatment of adult schistosomes in vitro, corresponding phenotypes were detected in the testes and ovary. In the Xenopus oocyte system it was finally confirmed that Piceatannol suppressed the activity of the catalytic kinase domain of SmTK4. Our findings demonstrate a pivotal role of SmTK4 in gametogenesis, a new function for Syk kinases in eukaryotes

The elegans of spindle assembly

The Caenorhabditis elegans one-cell embryo is a powerful system in which to study microtubule organization because this large cell assembles both meiotic and mitotic spindles within the same cytoplasm over the course of 1 h in a stereotypical manner. The fertilized oocyte assembles two consecutive acentrosomal meiotic spindles that function to reduce the replicated maternal diploid set of chromosomes to a single-copy haploid set. The resulting maternal DNA then unites with the paternal DNA to form a zygotic diploid complement, around which a centrosome-based mitotic spindle forms. The early C. elegans embryo is amenable to live-cell imaging and electron tomography, permitting a detailed structural comparison of the meiotic and mitotic modes of spindle assembly

Genetics of resistance in a non-beta-lactamase-producing gonococcus with relatively high-level penicillin resistance.

A penicillin-resistant (Penr) non-penicillinase-producing Neisseria gonorrhoeae strain responsible for an outbreak affecting 199 persons in Durham, N.C., in 1983 was studied to determine the genetic basis of its unusually high-level (MIC, 2.0 micrograms/ml) Penr. Plasmid screening of the strain revealed no plasmids other than the 2.6-megadalton cryptic plasmid. Penr was found to be partially due to mutations genotypically and phenotypically similar to the previously characterized chromosomal loci penA, mtr, and penB. Resistance loci from the epidemic donor strain were transformed into susceptible recipients FA19 and F62 in a stepwise fashion; the combination of the three loci resulted in moderate levels of penicillin resistance (MIC, 0.5 micrograms/ml), but donor levels of resistance were not obtainable in either recipient, for uncertain reasons. Occurrence of an antibiotic-susceptible (env) mutation in a clinical isolate of the Penr epidemic strain also was documented

Recombination near the antibiotic resistance locus penB results in antigenic variation of gonococcal outer membrane protein I.

In gonococci, the nonspecific antimicrobial resistance locus penB is known to be closely linked to loci designated nmp that alter the Mr and antigenicity of the outer membrane porin protein I (P.I). We report that after selection for the linked donor penB locus, occasional recombinants expressed P.I with some epitopes from each parent. These hybrid P.I antigens were stable on subculture and were transformed at a locus closely linked to penB. The hybrid P.I antigens were detected with monoclonal antibodies in both coagglutination and Western blot assays. The alterations of P.I antigenicity may have resulted from recombination between structural genes for P.I that are closely linked to penB