Comparative modeling of the N-terminal domain of the 67kDa laminin-binding protein: implications for putative ribosomal function

Laminin-binding protein/p40 (LBP/p40) precursor appears to be involved in two seemingly unrelated activities-cell adhesion and ribosomal biogenesis. Analysis of primary structure revealed a two-domain organization of the LBP/p40. The N-terminal portion of LBP is similar to the S2 family of prokaryotic ribosomal proteins, while the C-terminus is unique for Metazoa and is involved in extraribosomal functions. To gain insight into putative ribosomal functions of LBP we performed comparative modeling of the N-terminal domain using crystal structures of S2p from Thermus thermophilus. The LBP model assumes an alpha-beta sandwich fold similar to that of S2. Modeling revealed the loss of a significant portion of ribosomal RNA (rRNA) interaction domain, lack of conservation of many residues involved in interactions with rRNA, and a major shift in surface charge distribution (compared to the S2 protein). The overall stability of the fold argues against a proposed transmembrane domain in the central part of the protein. Partial overlap in S2 and laminin-binding domains suggests that ribosomal and surface receptor functions would be mutually exclusive. The possible biological role of LBP/p40 bifunctionality is discussed.     

Resistance to greenbug (Heteroptera: Aphididae) biotype I in Aegilops tauschii synthetic wheats

The greenbug, Schizaphis graminum (Rondani), is a major pest of wheat in North America, reducing U.S. wheat production by 60 to 100 million dollars each year. In this research, 149 wheat lines containing genes from Aegilops tauschii (Coss.) Schmal. were evaluated for resistance to greenbug biotype I. More than 50% of the lines sustained moderate foliar chlorosis from greenbug feeding, and approximately one third of all the lines were highly resistant. All lines with chlorosis scores similar to the resistant control 'Largo' expressed high levels of antibiosis, producing greenbug populations with mean weights ranging from 0.05 to 11.8 mg. There was no significant difference between greenbug weights on these lines and those reared on 'Largo', but the mean weight of individuals reared on the susceptible control 'Thunderbird' was significantly greater than those reared on 'Largo' or any of the test lines. The mean population size of greenbugs produced on plants of each line was significantly correlated with mean greenbug weight. Tolerance was not evident in any of the lines examined, but was unexpectedly apparent in 'Thunderbird' at a level similar to that in the tolerant control cultivar 'Largo'.     

In-hospital resource utilization in coronary angioplasty: the impact of increased coronary stenting rates and antiplatelet therapy

BACKGROUND: The technique of coronary stenting has evolved over recent years, with improved stent technology and effective antiplatelet therapies to prevent stent thrombosis. In Europe, reductions in stent and equipment costs have resulted from increased market competition. The impact of these changes on the in-hospital procedural cost of percutaneous coronary intervention (PCI) in the current clinical setting is not known. METHODS: We compared the initial equipment and pharmaceutical costs of one hundred consecutive, unselected patients undergoing PCI in 1998 to a similar population who underwent PCI in 1994. RESULTS: Similar patient characteristics were noted, yet more complex disease (multivessel, AHA type B2/C lesions) was treated in the 1998 population. The stent utilization rate (83% vs 15%, p < 0.0001) and use of intravenous and/or oral antiplatelet therapy (abciximab, ticlopidine) (64% vs 4%, p < 0.0001) was higher in 1998. Similar angiographic success was achieved in each group with low complication rates. Mean hospital stay was reduced in the 1998 group (2.6 +/- 2.8 vs 4.3 +/- 3.8 days, p < 0.001). Repeat PCI was required more frequently in the 1994 population (26% vs 9%, p < 0.001). Overall there was no significant difference in the mean equipment cost between the two groups ( pound 1551 vs pound 1422, p=ns). CONCLUSION: Despite the widespread use of coronary stenting and antiplatelet therapies there appears to be no difference in current in-hospital equipment costs for PCI compared to 1994. Improved clinical outcomes in the 1998 population imply that stenting is a cost-effective therapy.     

Tyrosine and catecholamine levels in the hemolymph of tobacco hornworm larvae,Manduca sexta,parasitized by the braconid wasp,Cotesia congregata,and in the developing parasitoids

Parasitism of fifth instar Manduca sexta larvae by the gregarious parasitoid Cotesia congregata prevented normal storage of tyrosine in the hemolymph, whereas total tyrosine levels increased over eight times in the hemolymph of unparasitized larvae by day 4. Tyrosine glucoside, the hemolymph storage form of tyrosine and the precursor for pupal cuticle sclerotizing agents, was found only in trace amounts in parasitized larvae at the time of parasitoid emergence, but had increased to over 6 mM in hemolymph of unparasitized larvae. Concentrations of dopamine and N-β-alanyldopamine (NBAD), precursors for melanization and sclerotization of cuticle, respectively, had approximately doubled in the hemolymph of parasitized larvae by the day of parasitoid emergence, but not in unparasitized larvae. Catecholamine biosynthesis may be transiently stimulated for wound-healing, as black melanic pigmentation appeared around the wasp emergence holes in the host integument. C. congregata larvae accumulate tyrosine, dopamine, and NBAD by the time of emergence and cocoon spinning, either by direct uptake or by synthesis from precursors obtained from the host. NBAD increased in parasitoid larvae close to pupation, suggesting it functions as the main precursor for pupal cuticle tanning. Both dopamine and NBAD increased dramatically in pharate adult wasps just before eclosion and N-acetyldopamine (NADA) appeared for the first time. Dopamine was highest in concentration and total amount, and it can serve both as a precursor for black melanic pigmentation of adult wasp cuticle and for synthesis of NADA and NBAD, the precursors for cuticle sclerotization. Arch. Insect Biochem. Physiol. 38:193–201, 1998. © 1998 Wiley-Liss, Inc.     

Cell surface and substrate distribution of the 67-kDa laminin-binding protein determined by using a ligand photoaffinity probe.

BACKGROUND: Peptide 11, a nine-amino acid sequence from the beta1 chain of laminin-1, has been reported to inhibit tumor cell invasion of basement membranes, and to reduce tumor lung colonization (Iwamoto et al.: Science 238:1132-1134, 1987; Landowski et al.: Clin Exp Metastasis 13:357-372, 1995). The peptide is a ligand for the 32/67-kDa laminin-binding protein (LBP); however, the mechanism by which the 67-kDa LBP promotes invasion is unknown. METHODS: We have synthesized a highly specific probe for the 67-kDa LBP by adding a biotinylated residue, and replacing the required tyrosine in peptide 11 with the photoactivatable bezophenone crosslinker, 4-benzoyl-L-phenylalanine. This probe was used to follow the distribution of the 67-kDa LBP by gel electrophoresis, fluorescence-activated cell scanning, and confocal microscopy techniques. RESULTS: A single crosslinked protein, consistent with the high molecular weight form of the LBP, was found on Western blots of membrane detergent extracts from cells treated with the ligand probe. A CHO cell line, manipulated to overexpress the laminin-specific alpha6beta1 integrin, exhibited increased invasiveness, and expressed more cell surface 67-kDa LBP. Membrane-associated 67-kDa LBP was found in the vicinity of focal adhesion plaques and also associated with the matrix substrate. Studies on conditioned medium indicated that the matrix-associated LBP derived from material that was shed from the cells, with more being shed from the more invasive CHO variants. CONCLUSIONS: These results demonstrate the utility of this novel probe in diverse experimental protocols, and suggest that shedding of the 67-kDa LBP may have a role in promoting tumor cell invasion.     

Leukemia Inhibitory Factor Is an Autocrine Survival Factor for Schwann Cells

Abstract: Schwann cells play a major role in promoting nerve survival and regeneration after injury. Their activities include providing neurotrophic factors and increasing the production of extracellular matrix components and cell surface adhesion molecules to promote axon regeneration. Following nerve transection, leukemia inhibitory factor (LIF) is up-regulated by Schwann cells at the injury site. LIF receptors are also up-regulated at the nerve injury site, but their cellular localization and function have not been fully characterized. We demonstrate that Schwann cells express mRNAs for LIF and the LIF receptor components LIF receptor subunit β and glycoprotein 130 in vitro. We also show that although LIF is not required for the genesis of Schwann cells, it can potentiate the survival of differentiated Schwann cells in the context of neuregulin support. Not only does exogenous LIF promote survival under these conditions, but addition of the soluble LIF receptor (LIF binding protein) and anti-LIF antibodies significantly reduced cell survival, suggesting that LIF exerts autocrine effects. These results suggest that Schwann cell survival following nerve injury is potentially modulated by LIF.     

Characterization of gastric mucoproteins isolated by equilibrium density-gradient centrifugation in caesium chloride

1. The mucoprotein from pig gastric mucus has been purified by equilibrium centrifugation in a CsCl gradient. 2. This procedure removes the non-covalently bound protein, which is closely associated with the mucoprotein and not easily removed from it by gel filtration. 3. The purified mucoprotein is separable by gel filtration into a high-molecular-weight mucoprotein A (mol.wt. 2.3×10⁶) and a low-molecular-weight mucoprotein B/C (mol.wt. 1.15×10⁶). 4. These two mucoproteins have the same chemical analysis namely fucose 11.3%, galactose 26%, glucosamine 19.5%, galactosamine 8.3% and protein 13.6%. 5. Mucoprotein A contains 3.1% ester sulphate. 6. These mucoproteins are isolated without enzymic digestion and have a higher protein content than the blood-group-substance mucoproteins from proteolytic digestion of gastric mucus. Detailed amino acid analysis shows that the extra protein in the non-enzymically digested material is composed of amino acids other than serine and threonine. 7. Mucoproteins A and B/C contain respectively 130 and 9 half-cystine residues per molecule of which about 78 and 6 residues are involved in disulphide linkages. 8. Cleavage of these disulphide linkages by mercaptoethanol splits both mucoproteins into four equally sized subunits of mol.wt. 5.2×10⁵ for mucoprotein A and 2.8×10⁴ for mucoprotein B/C. 9. The sole N-terminal amino acid of mucoprotein A is aspartic acid, whereas mucoprotein B/C has several different N-terminal amino acid residues.     

Innovative combination strategy to enhance effect and diminish adverse effects of glucocorticoids: another promise?

In a paper by Zimmermann and colleagues in this issue of Arthritis Research & Therapy, results of extended laboratory research with the drug combination of prednisolone and dipyridamole are reported. There seems to be a boost and extension of the glucocorticoid effect by the combination, without a clear increase of adverse effects, potentially allowing the application of lower dosages. However, laboratory models are not patients and the glucocorticoid mechanisms leading to effects and adverse effects are manifold. The next required step will be to demonstrate the improved therapeutic window in patients in adequate comparative clinical trials, assessing predefined beneficial effects and adverse effects in a standardized way.