Thermal damage prediction for collagenous tissues part I: a clinically relevant numerical simulation incorporating heating rate dependent denaturation

Subablative thermotherapy is frequently used for the treatment of joint instability related diseases. In this therapy, mechanically deformed collagenous tissues are thermally shrunk and the stability of the tissue is re-established. In this research, the thermal damage fields generated by three different clinical heating modalities (monopolar and bipolar radio frequency and Ho:YAG laser) are compared numerically using finite element analysis. The heating rate dependent denaturation characteristics of collagenous tissues are incorporated into the model using experimental data from in vitro experimentation with rabbit patellar tendons. It is shown that there are significant differences among the thermal damage profiles created by these modalities, explaining the main reason for the discrepancies reported in the literature in terms of the efficacy and safety of each modality. In the complementary paper, the accuracy of the model presented here is verified by in vitro experimentation with a model collagenous tissue and by quantifying the denaturation-induced birefringence change using Optical Coherence Tomography and Magnetic Resonance Imaging.     

Cadmium hyperaccumulation protects Thlaspi caerulescens from leaf feeding damage by thrips (Frankliniella occidentalis)

Metal hyperaccumulation has been proposed as a plant defensive strategy. Here, we investigated whether cadmium (Cd) hyperaccumulation protected Thlaspi caerulescens from leaf feeding damage by thrips (Frankliniella occidentalis). Two ecotypes differing in Cd accumulation, Ganges (high) and Prayon (low), were grown in compost amended with 0-1000 mg Cd kg(-1) in two experiments under glasshouse conditions. F2 and F3 plants from the Prayon x Ganges crosses were grown with 5 mg Cd kg(-1). Plants were naturally colonized by thrips and the leaf feeding damage index (LFDI) was assessed. The LFDI decreased significantly with increasing Cd in both ecotypes, and correlated with shoot Cd concentration in a log-linear fashion. Prayon was more attractive to thrips than Ganges, but the ecotypic difference in the LFDI was largely accounted for by the shoot Cd concentration. In the F2 and F3 plants, the LFDI correlated significantly and negatively with shoot Cd, but not with shoot zinc (Zn) or sulphur (S) concentrations. We conclude that Cd hyperaccumulation deters thrips from feeding on T. caerulescens leaves, which may offer an adaptive benefit to the plant.     

Sulphur fractionation in calcareous soils and bioavailability to plants

Sulphur fractionation and availability to plants are poorly understood in calcareous soils. Sixty-four calcareous soils containing varying amounts of CaCO₃ were collected from ten provinces in China and their S fractions determined. Organic S was the predominant fraction of S, accounting for on average 77% of the soil total S. The amounts of adsorbed sulphate were found to be negligible. 1 M HCl extracted substantially more sulphate than either 0.01 M CaCl₂ or 0.016 M KH₂PO₄, indicating the existence of water-insoluble but acid-soluble sulphate, probably in the form of sulphate co-precipitated with CaCO₃. The concentrations of water-insoluble sulphate correlated positively with the contents of CaCO₃ and accounted for 0.03–40.3% (mean 11.7%) of soil total S. To test the bioavailability of water-insoluble sulphate, a sulphate-CaCO₃ co-precipitate labelled with ³⁵S was prepared and added to a calcareous soil in a pot experiment with either NH₄⁺ or NO₃^– as the N source. In 29 days, wheat plants took up 10.6% and 3.0% of the ³⁵S added to the soil in the NH₄⁺ and NO₃^– treatments, respectively. At the end of the pot experiment, the decrease of water-insoluble, acid-soluble, sulphate was more apparent in the NH₄⁺ than in the NO₃^– treatment. The results indicate that sulphate co-precipitated with CaCO₃ in calcareous soils may become partly available for plant uptake, depending on rhizosphere pH, if the field precipitate is similar to the laboratory prepared sample studied.     

Extracellular matrix protein 1 interacts with the domain III of fibulin-1C and 1D variants through its central tandem repeat 2

Extracellular matrix protein 1 (ECM1), a widely expressed glycoprotein, has been shown to harbor mutations in lipoid proteinosis (LP), an autosomal recessive disorder characterized by profound alterations in the extracellular matrix of connective tissue. The biological function of ECM1 and its role in the pathomechanisms of LP are unknown. Fibulins comprise a family of extracellular matrix components, and the prototype of this family, fibulin-1, is expressed in various connective tissues and plays a role in developmental and pathologic processes. In this study, we demonstrate that ECM1, and specifically the second tandem repeat domain which is alternatively spliced, interacts with the C-terminal segments of fibulins 1C and 1D splice variants which differ in their C-terminal domain III. The interactions were detected by yeast two-hybrid genetic system and confirmed by co-immunoprecipitations. Kinetics of the binding between ECM1 and fibulin-1D, measured by biosensor assay, revealed a K(d) of 5.71 x 10(-8) M, indicating a strong protein-protein interaction. Since distinct splice variants of ECM1 and fibulin-1 have been shown to be co-expressed in tissues affected in LP, we propose that altered ECM1/fibulin-1 interactions may play a role in the pathogenesis of this disease as well as in a number of processes involving the extracellular matrix of connective tissues.     

Expression cloning and periplasmic orientation of the Francisella novicida lipid A 4'-phosphatase LpxF

Francisella tularensis and related intracellular pathogens synthesize lipid A molecules that differ from their Escherichia coli counterparts. Although a functional orthologue of lpxK, the gene encoding the lipid A 4'-kinase, is present in Francisella, no 4'-phosphate moiety is attached to Francisella lipid A. We now demonstrate that a membrane-bound phosphatase present in Francisella novicida U112 selectively removes the 4'-phosphate residue from tetra- and pentaacylated lipid A molecules. A clone that expresses the F. novicida 4'-phosphatase was identified by assaying lysates of E. coli colonies, harboring members of an F. novicida genomic DNA library, for 4'-phosphatase activity. Sequencing of a 2.5-kb F. novicida DNA insert from an active clone located the structural gene for the 4'-phosphatase, designated lpxF. It encodes a protein of 222 amino acid residues with six predicted membrane-spanning segments. Rhizobium leguminosarum and Rhizobium etli contain functional lpxF orthologues, consistent with their lipid A structures. When F. novicida LpxF is expressed in an E. coli LpxM mutant, a strain that synthesizes pentaacylated lipid A, over 90% of the lipid A molecules are dephosphorylated at the 4'-position. Expression of LpxF in wild-type E. coli has no effect, because wild-type hexaacylated lipid A is not a substrate. However, newly synthesized lipid A is not dephosphorylated in LpxM mutants by LpxF when the MsbA flippase is inactivated, indicating that LpxF faces the outer surface of the inner membrane. The availability of the lpxF gene will facilitate re-engineering lipid A structures in diverse bacteria.     

Evidence that complement protein C1q interacts with C-reactive protein through its globular head region

C1q acts as the recognition unit of the first complement component, C1, and binds to immunoglobulins IgG and IgM, as well as to non-Ig ligands, such as C-reactive protein (CRP). IgG and IgM are recognized via the globular head regions of C1q (C1qGR), whereas CRP has been postulated to interact with the collagen-like region (C1qCLR). In the present study, we used a series of nine mAbs to C1q, five directed against C1qGR and four against C1qCLR, to inhibit the interaction of C1q with CRP. The F(ab')(2) of each of the five mAbs directed against C1qGR inhibited binding of C1q to polymerized IgG. These five mAbs also successfully inhibited the interaction of C1q with CRP. Moreover, these five mAbs inhibited C1 activation by CRP as well as by polymerized IgG in vitro. In contrast, none of the four mAbs against C1qCLR inhibited C1q interaction with CRP or IgG, or could reduce activation of complement by CRP or polymerized IgG. These results provide the first evidence that the interaction of C1q with CRP or IgG involves sites located in the C1qGR, whereas sites in the CLR do not seem to be involved in the physiological interaction of C1q with CRP.     

Structure-guided design of peptide-based tryptase inhibitors

Improved peptide-based inhibitors of human beta tryptase were discovered using information gleaned from tripeptide library screening and structure-guided design methods, including fragment screening. Our efforts sought to improve this class of inhibitors by replacing the traditional Lys or Arg P1 element. The optimized compounds display low nanomolar potency against the mast cell target and several hundred-fold selectivity with respect to serine protease off targets. Thus, replacement of Lys/Arg at P1 in a peptide-like scaffold does not need to be accompanied by a loss in target affinity.     

Novel IL10 gene family associations with systemic juvenile idiopathic arthritis

Juvenile idiopathic arthritis (JIA) is the most common cause of chronic childhood disability and encompasses a number of disease subgroups. In this study we have focused on systemic JIA (sJIA), which accounts for approximately 11% of UK JIA cases. This study reports the investigation of three members of the IL10 gene family as candidate susceptibility loci in children with sJIA. DNA from 473 unaffected controls and 172 patients with sJIA was genotyped for a single nucleotide polymorphism (SNP) in IL19 and IL20 and two SNPs in IL10. We examined evidence for association of the four SNPs by single marker and haplotype analysis. Significant differences in allele frequency were observed between cases and controls, for both IL10-1082 (p = 0.031) and IL20-468 (p = 0.028). Furthermore, examination of the haplotypes of IL10-1082 and IL20-468 revealed greater evidence for association (global p = 0.0006). This study demonstrates a significant increased prevalence of the low expressing IL10-1082 genotype in patients with sJIA. In addition, we show a separate association with an IL20 polymorphism, and the IL10-1082A/IL20-468T haplotype. The two marker 'A-T' haplotype confers an odds ratio of 2.24 for sJIA. This positive association suggests an important role for these cytokines in sJIA pathogenesis.