The role of anaerobic bacteria in acute and chronic mastoiditis

Mastoiditis (M) is the most common intratemporal complication of otitis media. The incidence of M has decreased since the advent of antimicrobial agents. In the last decade, however, there has been a marked increased in the incidence of acute M in several communities, sometimes in association with the growing resistance of pneumococci. Streptococcus pneumoniae, Streptococcus pyogenes, Staphylococcus aureus and Haemophillus influenzae are the most common organisms recovered in acute M. Several recent studies demonstrated the predominance of Pseudomonas aeruginosa in this infection. However, because P. aeruginosa colonizes the ear canal it can contaminate specimens obtained through the non-sterile ear canal. P. aeruginosa, Enterobacteriaceae, S. aureus and anaerobic bacteria are the most common isolates in chronic M. Anaerobes predominate in studies where adequate methods for their isolation are employed. Management of uncomplicated M requires the administration of parenteral antimicrobial therapy and myringotomy with or without tympanostomy tube placement. If no improvement occurs within 48 h, surgical intervention and drainage may be necessary. The procedure generally employed is simple mastoidectomy, and tympanostomy tube placement. Radical mastoidectomy is performed only if there is no improvement after simple mastoidectomy.     

Acute inactivation of MAP1b in growing sympathetic neurons destabilizes axonal microtubules

Microtubule-associated-protein 1b (MAP1b) is abundant in neurons actively extending axons. MAP1b is present on microtubules throughout growing axons, but is preferentially concentrated on microtubule polymer in the distal axon and growth cone. Although MAP1b has been implicated in axon growth and pathfinding, its specific functions are not well understood. Biochemical and transfection studies suggest that MAP1b has microtubule-stabilizing activity, but recent studies with neurons genetically deficient in MAP1b have not confirmed this. We have explored MAP1b functions in growing sympathetic neurons using an acute inactivation approach. Neurons without axons were injected with polyclonal MAP1b antibodies and then stimulated to extend axons. Injected cells were compared to controls in terms of axon growth behavior and several properties of axonal microtubules. The injected antibodies rapidly and quantitatively sequestered MAP1b in the cell body, making it unavailable to perform its normal functions. This immunodepletion of MAP1b had no statistically significant effect on axon growth, the amount of microtubule polymer in the axon, and the relative tyrosinated tubulin content of this polymer, and this was true in sympathetic neurons from rat, wild type mice, and tau knockout mice. Thus, robust axon growth can occur in the absence of MAP1b alone or both MAP1b and tau. However, immunodepletion of MAP1b significantly increased the sensitivity of microtubules in the distal axon and growth cone to nocodazole-induced depolymerization. These results indicate that MAP1b has microtubule-stabilizing activity in growing axons. This stabilizing activity may be required for some axonal functions, but it is not necessary for axon growth.     

<Emphasis Type="Italic">Physcomitrella patens</Emphasis> and <Emphasis Type="Italic">Ceratodon purpureus</Emphasis>, mosses as model organisms in photosynthesis studies

With the discovery of targeted gene replacement, moss biology has been rapidly advancing over the last 10 years. This study demonstrates the usefulness of moss as a model organism for plant photosynthesis research. The two mosses examined in this study, Physcomitrella patens and Ceratodon purpureus, are easily cultured through vegetative propagation. Growth tests were conducted to determine carbon sources suitable for maintaining heterotrophic growth while photosynthesis was blocked. Photosynthetic parameters examined in these plants indicated that the photosynthetic activity of Ceratodon and Physcomitrella is more similar to vascular plants than cyanobacteria or green algae. Ceratodon plants grown heterotrophically appeared etiolated in that the plants were taller and plastids did not differentiate thylakoid membranes. After returning to the light, the plants developed green, photosynthetically active chloroplasts. Furthermore, UV-induced mutagenesis was used to show that photosynthesis-deficient mutant Ceratodon plants could be obtained. After screening approximately 1000 plants, we obtained a number of mutants, which could be arranged into the following categories: high fluorescence, low fluorescence, fast and slow fluorescence quenching, and fast and slow greening. Our results indicate that in vivo biophysical analysis of photosynthetic activity in the mosses can be carried out which makes both mosses useful for photosynthesis studies, and Ceratodon best sustains perturbations in photosynthetic activity.     

Light-modulated exposure of the light-harvesting complex II (LHCII) to protein kinase(s) and state transition in Chlamydomonas reinhardtii xanthophyll mutants

Reversible phosphorylation of chl a/b protein complex II (LHCII), the mobile light-harvesting antenna, regulates its association and energy transfer/dissipation to photosystem (PS) II or I (state transition). Excitation of LHCII induces conformational changes affecting the exposure of the phosphorylation site at the N-terminal domain to protein kinase(s) [Zer, H., et al. (1999) Proc. Natl. Acad. Sci. U.S.A. 96, 8277-8282; Zer, H., et al. (2003) Biochemistry 42, 728-738]. Thus, it was of interest to examine whether the pigment composition of LHCII affects the light-induced modulation of LHCII phosphorylation and state transition. To this end, we have used thylakoids of wild-type Chlamydomonas reinhardtii and xanthophyll deficient mutants npq1, lor1, npq2, npq1 lor1, and npq2 lor1. Phosphorylated protein bands P11, P13, and P17 are considered components of the mobile C. reinhardtii LHCII complex. The protein composition of these bands has been analyzed by mass spectrometry using Qtof-2 with a nanospray attachment. P11 and P13 contain C. reinhardtii light-harvesting chlorophyll a/b binding protein LhcII type I. P17 contains C. reinhardtii LhcII types III and IV. Illumination of isolated thylakoids inhibits the redox-controlled phosphorylation of polypeptide bands P13 and P17 and to a lower extent that of P11. The light-induced inhibition of LHCII phosphorylation and the state transition process are not influenced by extensive differences in the xanthophyll composition of the mutants. Thus, LHCII can be visualized as possessing two functionally distinct, independent domains: (i) the pigment binding transmembrane domain regulating the extent of energy transfer/dissipation and (ii) the surface-exposed phosphorylation site regulating the association of LHCII with PSII or PSI.     

Tau-Like Proteins in the Nervous System of Goldfish

This report describes the presence of a group of tau-like proteins (TLPs) in goldfish central nervous system. The TLPs were immunoreactive with antibodies that recognized the carboxy-terminal domain of mammalian tau, but not with antibodies that recognized the amino-terminus. The TLPs of goldfish exhibited the basic properties of tau proteins including neuronal specificity, structural heterogeneity, heat stability and the ability to co-assemble with tubulin. We propose that TLPs may represent a precursor of tau, that share the microtubule binding domain and the carboxy-terminal domain with mammalian tau proteins. In contrast the amino-terminus of the TLPs is much shorter and may represent a more variable domain of tau proteins.     

ACCLIMATION OF SYNECHOCOCCUS STRAIN WH7803 TO AMBIENT CO2 CONCENTRATION AND TO ELEVATED LIGHT INTENSITY1

A CO₂ concentrating mechanism has been identified in the phycoerythrin-possessing Synechococcus sp. WH7803 and has been observed to be severely inhibited by short exposure to elevated light intensities. A light treatment of 300–2000 μmol quanta·m^?2·s^?1 resulted in a considerable decay in the variable fluorescence of PSII with time, suggesting decreased efficiency of energy transfer from the phycobilisomes, direct damage to the reaction center II, or both. Measurements of the activity of PSII and changes in fluorescence emission spectra during a light treatment of 1000 μmol quanta·m^?2·s^?1 indicated considerable reduction in the energy flow from the phycocyanin to the phycobilisome terminal acceptor and chlorophyll a. Consequently, whereas the maximal photosynthetic rate, at saturating light and Co₂ concentration, was hardly affected by a light treatment of 1000 μmol quanta·m^?2·s^?1 for 2 h, the light intensity required to reach that maximum increased with the duration of the light treatment.     

Protein factors which regulate cell motility

Summary Cell motility (i.e., movement) is an essential component of normal development, inflammation, tissue repair, angiogenesis, and tumor invasion. Various molecules can affect the motility and positioning of mammalian cells, including peptide growth factors, (e.g., EGF, PDGF, TGF-beta), substrate-adhesion molecules (e.g., fibronectin, laminin), cell adhesion molecules (CAMs), and metalloproteinases. Recent studies have demonstrated a group of motility-stimulating proteins which do not appear to fit into any of the above categories. Examples include: 1)scatter factor (SF), a mesenchymal cell-derived protein which causes contiguous sheets of epithelium to separate into individual cells and stimulates the migration of epithelial as well as vascular endothelial cells; 2)autocrine motility factor (AMF), a tumor cell-derived protein which stimulates migration of the producer cells; and 3)migration-stimulating factor (MSF), a protein produced by fetal and cancer patient fibroblasts which stimulates penetration of three-dimensional collagen gels by non-producing adult fibroblasts. SF, AMF, and MSF are soluble and heat labile proteins with Mr of 77, 55, and 70 kd by SDS-PAGE, respectively, and may be members of a new class of cell-specific regulators of motility. Their physiologic functions have not been established, but available data suggest that they may be involved in fetal development and/or tissue repair.