Association between knee inflammation and knee pain in patients with knee osteoarthritis: a systematic review.

OBJECTIVE: To systematically review the literature on the relationship between markers of inflammation and pain in patients with knee osteoarthritis (OA). METHODS: We searched MEDLINE, Web of Science and EMBASE databases from inception until June 2021. Eligible articles had to report on the association between inflammation (as measured by effusion, synovitis, baker's cysts, cytokines and C-reactive protein) and pain in patients with radiographic knee OA. Two reviewers independently performed a screening on title and abstracts, data extraction and risk of bias assessment using the Newcastle-Ottawa Scale (NOS). A best evidence synthesis was conducted for each inflammatory sign included in this review. RESULTS: 37 studies were included. Articles reported on the following measures: effusion or synovitis assessed via ultrasound (n = 9) or magnetic resonance imaging (MRI) (n = 17); baker's cyst (n = 3); cytokine concentrations (n = 11); and C-reactive protein levels (n = 4). The strength of the association between inflammation and pain does not exceed the moderate level (i.e., correlation coefficient values ranging from 0.19 to 0.61). Moderate levels of evidence were found for the association between synovitis (measured with ultrasound or contrast enhanced MRI) and pain. The levels of evidence between effusion (assessed via ultrasound), effusion/synovitis (assessed via non-contrast enhanced MRI), Baker's cyst, cytokines, C-reactive protein and pain were conflicting. CONCLUSIONS: Different inflammatory markers are associated with pain but the correlation ranges from weak to moderate, and the quality of evidence from conflicting to moderate. Further research is needed to strengthen the level of evidence and to establish mechanisms.

Fiber taper diameter characterization using forward Brillouin scattering.

We propose a fast and non-destructive method to characterize the absolute diameter and uniformity of micrometer-scale fiber tapers using a pump and probe forward Brillouin scattering setup. The fundamental torsional-radial acoustic mode supported by the wire is excited using a pulsed pump laser and oscillates at a frequency that is inversely proportional to the taper waist diameter. This standing time-varying torsional-radial wave induces polarization modulation on a probe signal, whose spectrum structure reveals the sample diameter and its non-uniformity. By comparing our results with measurements using scanning-electron microscopy, a relative deviation of 1% or less was demonstrated, and diameter non-uniformity of less than 0.5% could be detected.

Brillouin scattering self-cancellation.

The interaction between light and acoustic phonons is strongly modified in sub-wavelength confinement, and has led to the demonstration and control of Brillouin scattering in photonic structures such as nano-scale optical waveguides and cavities. Besides the small optical mode volume, two physical mechanisms come into play simultaneously: a volume effect caused by the strain-induced refractive index perturbation (known as photo-elasticity), and a surface effect caused by the shift of the optical boundaries due to mechanical vibrations. As a result, proper material and structure engineering allows one to control each contribution individually. Here, we experimentally demonstrate the perfect cancellation of Brillouin scattering arising from Rayleigh acoustic waves by engineering a silica nanowire with exactly opposing photo-elastic and moving-boundary effects. This demonstration provides clear experimental evidence that the interplay between the two mechanisms is a promising tool to precisely control the photon-phonon interaction, enhancing or suppressing it.

Novel optical fiber design for low-cost optical interconnects in consumer applications.

We propose a novel fiber design optimized for short-reach interconnects in consumer applications. A detailed analysis of the optical and mechanical properties of this fiber design is presented. Results are presented demonstrating (i) low bend loss and enhanced mechanical reliability in bends as small as 3 mm diameter; (ii) high power budget margin to enable relaxed mechanical tolerances on transmitter, receiver, and expanded-beam connectors for low-cost connectivity; and (iii) high bandwidth capability and system testing results at 10 Gb/s.

Raman-like light scattering from acoustic phonons in photonic crystal fiber.

Raman and Brillouin scattering are normally quite distinct processes that take place when light is resonantly scattered by, respectively, optical and acoustic phonons. We show how few-GHz acoustic phonons acquire many of the same characteristics as optical phonons when they are tightly trapped, transversely and close to modal cut-off, inside the wavelength-scale core of an air-glass photonic crystal fiber (PCF). The result is an optical scattering effect that closely resembles Raman scattering, though at much lower frequencies. We use photoacoustic techniques to probe the effect experimentally and finite element modelling to explain the results. We also show by numerical modelling that the cladding structure supports two phononic band gaps that contribute to the confinement of sound in the core.

Breakdown of cytoskeletal proteins during meiosis of starfish oocytes and proteolysis induced by calpain.

Meiosis reinitiation in starfish oocytes is characterized by Ca(2+) transients in the cytosol and in the nucleus and is accompanied by the disassembly of the nuclear envelope, a process which is likely to be mediated by the cleavage of selected proteins. We have used mass spectrometry analysis (mass profile fingerprinting) on 2D polyacrylamide gels of extracts of oocytes in which meiosis resumption was induced by 1-methyladenine and have identified five proteins that were specifically degraded: alpha-tubulin, lamin B, dynamin, and two kinds of actin. They are all components of the cytoskeleton or associated with it. We then investigated whether calpain, which is activated by the increase in cell Ca(2+), could cleave the same proteins that became degraded under the influence of 1-methyladenine and thus be involved in nuclear membrane breakdown. The investigation was prompted by the finding that microinjection of calpain into the nuclei of prophase arrested oocytes induced meiosis in the absence of 1-methyladenine. Incubation of prophase arrested (disrupted) oocytes with calpain produced a 2D gel protein pattern in which some of the degradation products coincided with those seen in oocytes challenged with 1-methyladenine.

Proteome analysis of heat shock protein expression in Bradyrhizobium japonicum.

A set of 19 heat shock proteins (Hsp) was observed - by subtractive two-dimensional gel electrophoresis - to be induced when Bradyrhizobium japonicum, the nitrogen-fixing root-nodule symbiont of soybean, was temperature up-shifted from 28 degrees C to 43 degrees C. Up-regulated protein spots were excised from multiple two-dimensional gels. The proteins were concentrated using a funnel-gel device before being blotted onto poly(vinylidene difluoride) membranes for digestion with trypsin before MS and tandem MS analysis or for Edman sequence determination. Five proteins in the range 8-20 kDa were identified as the small Hsp (sHsp; HspB, C, D, E and H) and three others showed strong sequence similarity to the sHsp family. Two other low molecular mass proteins corresponded to GroES1 and GroES2, and five novel proteins were found. Four proteins of approximately 60 kDa were identified as GroEL2, GroEL4, and GroEL5 and DnaK. An analysis of the heat shock induction of DnaK, of four of the most strongly induced GroESL proteins and six of the sHsp revealed that the proteins could be placed into four distinct regulatory groups based on the kinetics of protein appearance.

An algorithm for the identification of proteins using peptides with ragged N- or C-termini generated by sequential endo- and exopeptidase digestions.

We have developed an algorithm (MassDynSearch) for identifying proteins using a combination of peptide masses with small associated sequences (tags). Unlike the approach developed by Matthias Mann, 'Tag searching', in which the sequence tags are generated by gas phase fragmentation of peptides in a mass spectrometer, 'Rag Tag' searching uses peptide tags which are generated enzymatically or chemically. The protein is digested either chemically or with an endopeptidase and the resultant mixture is then subjected to partial exopeptidase degradation. The mixture is analyzed by matrix assisted laser desorption and ionization time of flight mass spectrometry and a list of intact peptide masses is generated, each associated with a set of degradation product masses which serve as unique tags. These 'tagged masses' are used as the input to an algorithm we have written, MassDynSearch, which searches protein and DNA databases for proteins which contain similar tagged motifs. The method is simple, rapid and can be fully automated. The main advantage of this approach is that the specificity of the initial digestion is unimportant since multiple peptides with tags are used to search the database. This is especially useful for proteins like membrane, cytoskeletal, and other proteins where specific endopeptidases are less efficient and lower specificity proteases such as chymotrypsin, pepsin, and elastase must be used.

Functional conservation of calreticulin in Euglena gracilis.

Calreticulin is the major high capacity, low affinity Ca2+ binding protein localized within the endoplasmic reticulum. It functions as a reservoir for triggered release of Ca2+ by the endoplasmic reticulum and is thus integral to eukaryotic signal transduction pathways involving Ca2+ as a second messenger. The early branching photosynthetic protist Euglena gracilis is shown to possess calreticulin as its major high capacity Ca2+ binding protein. The protein was purified, microsequenced and cloned. Like its homologues from higher eukaryotes, calreticulin from Euglena possesses a short signal peptide for endoplasmic reticulum import and the C-terminal retention signal KDEL, indicating that these components of the eukaryotic protein routing apparatus were functional in their present form prior to divergence of the euglenozoan lineage. A gene phylogeny for calreticulin and calnexin sequences in the context of eukaryotic homologues indicates i) that these Ca2+ binding endoplasmic reticulum proteins descend from a gene duplication that occurred in the earliest stages of eukaryotic evolution and furthermore ii) that Euglenozoa express the calreticulin protein of the kinetoplastid (trypanosomes and their relatives) lineage, rather than that of the eukaryotic chlorophyte which gave rise to Euglena's plastids. Evidence for conservation of endoplasmic reticulum routing and Ca2+ binding function of calreticulin from Euglena traces the functional history of Ca2+ second messenger signal transduction pathways deep into eukaryotic evolution.

A novel muscle protein located inside the terminal cisternae of the sarcoplasmic reticulum.

An immunofluorescence study of adult rat muscle tissues with a polyclonal antibody against the RGD-directed fibronectin receptor of Friend's erythroleukemia cells (alpha5beta1-integrin) unexpectedly revealed a pattern of intracellular antigen distribution. Western blotting analysis of rat and rabbit membrane fractions indicated that the antibody recognizes a 167-kDa protein expressed both in heart and in skeletal muscle (relative abundance: heart > slow muscle > fast muscle), but not in liver and kidney. The 167-kDa protein did not show altered electrophoretic mobility upon reduction and failed to bind several lectins, including wheat germ agglutinin. A study of its subcellular distribution in rabbit skeletal muscle revealed that the 167-kDa protein is mostly associated with the terminal cisternae of the sarcoplasmic reticulum (SR) and, to a smaller extent, with the sarcolemma, while it is absent in the longitudinal tubules of the SR. The 167-kDa protein is not an integral membrane protein since it can be extracted at pH >/=10. This protein can be proteolytically cleaved only in the presence of detergent, indicating that it resides on the luminal side of the SR. The 167-kDa protein could be resolved from the closely spaced sarcalumenin and histidine-rich protein by column chromatography followed by detergent dialysis and two-dimensional gel electrophoresis. The N terminus and the internal sequences did not match any known sequence in protein and DNA data bases, indicating that the 167-kDa protein is a novel muscle protein selectively localized to the SR. Integrins from rat kidney fibroblasts were not recognized by either (i) a polyclonal antiserum against the purified 167-kDa protein or (ii) the anti-alpha5beta1-integrin antiserum after affinity purification onto the 167-kDa protein. These data indicate that the 167-kDa protein is not immunologically cross-reactive with integrins, despite its reaction with a polyclonal anti-integrin antibody.

Probing protein function using a combination of gene knockout and proteome analysis by mass spectrometry.

Recently the determination of the genome sequences of three procaryotes (Haemophilus influenzae, Methanococcus jannaschii and Mycoplasma genitalium) as well as the first eucaryotic genome (Saccharomyces cerevisiae) were completed. Between 40-60% of the genes were found to code for proteins to which no function could be assigned. We describe an approach which combines proteome analysis (mapping of expressed proteins isolated by two-dimensional polyacrylamide gel electrophoresis to the genome) with genetic manipulations to study the complex pattern of protein regulation occurring in Escherichia coli in response to sulfate starvation. We have previously described the upregulation of eight spots on two-dimensional (2-D) gels in response to sulfate starvation and the assignment of six of these to entries in the E. coli genome sequence (Quadroni et al., Eur. J. Biochem. 1996, 239, 773-781). Here we describe the identification of the remaining two proteins which are encoded in a sulfate-controlled operon in the 21.5' region of the E. coli genome. Upregulated protein spots were cut from multiple 2-D gels collected and run on a modified funnel gel to concentrate the proteins and remove the sodium dodecyl sulfate before digestion. The peptide masses obtained from the digests were used to search the SwissProt database or a six-frame translation of the EMBL DNA database using a peptide mass fingerprinting algorithm. A digest can be reanalyzed after deuterium exchange to obtain a second, orthogonal data set to increase the confidence level of protein identification. The digests of the remaining unidentified proteins were used for peptide fragment generation using either post-source decay in a matrix-assisted laser desorption ionization (MALDI) time-of-flight mass spectrometer or collision-induced dissociation (CID) coupled mass spectrometry (MS/MS) with triple stage quadrupole or ion trap mass spectrometers. The spectra were used as peptide fragment fingerprints to search the SwissProt and EMBL databases.

Subcellular and tissue distribution, partial purification, and sequencing of calmodulin-stimulated Ca2+-transporting ATPases from barley (Hordeum vulgare L.) and tobacco (Nicotiana tabacum).

The subcellular distribution of plasma-membrane-type Ca2+-transporting ATPases was studied in barley leaves (Hordeum vulgare L.). A highly enriched plasma membrane (PM) fraction was analysed for Ca2+ pumps and compared with several inner-membrane preparations, including the tonoplast, the envelope of the chloroplast, and an endoplasmic reticulum (ER)-enriched fraction. The enzymes were identified and characterised with regard to the phosphointermediate formation, their nucleotide specificity and their binding to calmodulin. A Ca2+-transporting ATPase (molecular mass approximately 130 kDa), which showed high specificity for ATP and high affinity for calmodulin, was localised in the PM. A 116-kDa Ca2+-transporting ATPase, probably located in the ER, showed lower nucleotide specificity and weaker affinity for calmodulin. A comparison of the distribution of the pumps in leaves and roots indicated that the ratio of expression of the two enzymes changed in a tissue-specific manner: the PM pump was dominant in leaves, while the inner-membrane pump was expressed at a higher level in the roots. For the purification of calmodulin-binding proteins (Ca2+ pumps), microsomes isolated from tobacco cell cultures were used. Two active Ca2+ pumps were identified, and the one at 116 kDa was partially sequenced.

Cold-Resistant and Cold-Sensitive Maize Lines Differ in the Phosphorylation of the Photosystem II Subunit, CP29.

The effects of low temperature on the relative contributions of the reaction center and the antenna activities to photosystem II (PSII) electron transport were estimated by chlorophyll fluorescence. The inhibition of PSII photochemistry resulted from photo-damage to the reaction center and/or a reduced probability of excitation energy trapping by the reaction center. Although chill treatment did not modify the proportion of the dimeric to monomeric PSII, it destabilized its main light-harvesting complex. Full protection of the reaction center was achieved only in the presence of the phosphorylated PSII subunit, CP29. In a nonphosphorylating genotype the chill treatment led to photoinhibitory damage. The phosphorylation of CP29 modified neither its binding to the PSII core nor its pigment content. Phosphorylated CP29 was isolated by flat-bed isoelectric focusing. Its spectral characteristics indicated a depletion of the chlorophyll spectral forms with the highest excitation transfer efficiency to the reaction center. It is suggested that phosphorylated CP29 performs its regulatory function by an yet undescribed mechanism based on a shift of the equilibrium for the excitation energy toward the antenna.

Binding of cytosolic proteins to myofibrils in ischemic rat hearts.

Myofibrillar proteins (MPs) were extracted from isolated and perfused rat hearts subjected to different periods of ischemia to investigate the occurrence of protein degradation and/or the association of cytosolic proteins with the myofibrillar pellet. A 23-kD band was detected by SDS-PAGE of MPs after 5 minutes of ischemia, with its density gradually increasing to a plateau after 20 minutes. Longer periods of ischemia were associated with the appearance of a 39-kD band. Irrespective of the duration of ischemia, both these bands persisted during reperfusion. A partial proteolytic degradation of troponin T (TnT) and troponin I (TnI) has been claimed to be responsible for the generation of these peptides. However, the N-terminal sequence of the 39-kD band was identical to that of GAPDH, whereas Edman sequencing after pepsin digestion showed that the 23 kD is alpha B-crystallin. The binding of the two cytosolic proteins to myofibrils was confirmed by immunofluorescence analysis on cryosections of ischemic hearts. In vitro studies showed that acidosis was sufficient to induce the binding of alpha B-crystallin, whereas the inhibition of ATP depletion prevented the binding of GAPDH. Thiol oxidation is unlikely to promote GAPDH binding, since perfusion with iodoacetate under aerobic conditions or treatment of homogenates with N-ethylmaleimide or diamide failed to induce GAPDH association with the myofibrils. These changes of the myofibrillar proteins could be considered as intracellular markers of the evolution of the ischemic damage. In addition, the binding of the 23-kD peptide might be involved in alterations of contractility.

Evidence that spinach leaves express calreticulin but not calsequestrin.

The presence of either calreticulin (CR) or calsequestrin (CS-like proteins in spinach (Spinacia oleracea L.) leaves has been previously described. Here we report the purification from spinach leaves of two highly acidic (isoelectric point 5.2) Ca(2+)-binding proteins of 56 and 54 kD by means of DEAE-cellulose chromatography followed by phenyl-Sepharose chromatography in the presence of Zn(2+) (i.e., under experimental conditions that allowed the purification of CR from human liver). On the other hand, we failed to identify any protein sharing with animal CS the ability to bind to phenyl-Sepharose in the absence of Ca(2+). Based on the N-terminal amino acid sequence, the 56- and 54-kD spinach Ca(2+)-binding proteins were identified as two distinct isoforms of CR. Therefore, we conclude that CR, and not CS, is expressed in spinach leaves. The 56-kD spinach CR isoform was found to be glycosylated, as judged by ligand blot techniques with concanavalin A and affinity chromatography with concanavalin A-Sepharose. Furthermore, the 56-kD CR was found to differ from rabbit liver CR in amino acid sequence, peptide mapping after partial digestion with Staphylococcus aureus V8 protease, pH-dependent shift of electrophoretic mobility, and immunological cross-reactivity with an antiserum raised to spinach CR, indicating a low degree of structural homology with animal CRs.

A post-translational modification of the photosystem II subunit CP29 protects maize from cold stress.

The resistance of maize plants to cold stress has been associated with the appearance of a new chlorophyll a/b binding protein in the thylakoid membrane following chilling treatment in the light. The cold-induced protein has been isolated, characterized by amino acid sequencing, and pulse labeled with radioactive precursors, showing that it is the product of post-translational modification by phosphorylation of the minor chlorophyll a/b protein CP29 rather than the product of a cold-regulated gene or an unprocessed CP29 precursor. We show here that the CP29 kinase activity displays unique characteristics differing from previously described thylakoid kinases and is regulated by the redox state of a quinonic site. Finally, we show that maize plants unable to perform phosphorylation have enhanced sensitivity to cold-induced photoinhibition.

The 70 kD component of the heart sarcolemmal Na+/Ca(2+)-exchanger preparation is the C-terminal portion of the protein.

The cardiac sarcolemmal Na+/Ca(2+)-exchanger was expressed in COS-7 cells by the vaccinia virus system as a fusion protein with a poly-His tag at its C-terminus. Extracts of cells expressing the exchanger construct without the His-tag reacted with an antiserum against the C-terminal portion of the main intracellular loop of the exchanger: in agreement with the finding routinely made on heart sarcolemma and on plasma membrane of cells expressing the cardiac exchanger gene, three bands of about 160, 120, and 70 kD were detected in Western blots. All three bands shifted to higher molecular masses when the construct with the His-tag was expressed, indicating that the three proteins had the same C-terminus. Thus, the 70 kD protein, whose nature has always been obscure, appears to be a degradation product of one of the two larger proteins. N-terminal sequencing of partially purified exchanger preparations has identified the cleavage site(s) producing the 70 kD protein in the 257-269 residue region of the exchanger molecule.

Gaussian decomposition of absorption and linear dichroism spectra of outer antenna complexes of photosystem II.

Room temperature and 10 K absorption and linear dichroism spectra of the chlorophyll-protein complexes comprising the outer antenna of PSII (LHCII, CP29, CP26, CP24) have been analyzed in terms of a linear combination of asymmetric Gaussian bands. The results demonstrate the following: (a) The absorption and linear dichroism spectra of each sample can be described by nearly the same set of Gaussian bands at room temperature and 10 K. (b) The relative distributions of the transition moments of the major red-absorbing spectral forms seem to be similar in all four outer antenna chlorophyll-protein complexes at room temperature, with the 684-nm band being oriented closest to the particle plane at room temperature and the 677- and 669-nm bands being tilted at progressively greater angles out of the particle plane. The shorter wavelength transitions seem to be oriented close to the magic angle, but interpretation is complicated in this spectral region due to the low linear dichroism values and by overlap with vibrational bands. (c) The 684-nm band, detected in room temperature absorption and linear dichroism spectra of all complexes, vanishes at 10 K.

Heterogenous lipid distribution among chlorophyll-binding proteins of photosystem II in maize mesophyll chloroplasts.

Photosystem II membrane fractions from dark-adapted mesophyll chloroplasts of maize were solubilized in different concentrations of dodecyl beta-D-maltoside. Chlorophyll-binding proteins from photosystem II were isolated either by ultracentrifugation on a sucrose gradient, or by flat bed isoelectric focusing and identified by gel electrophoresis analysis for their polypeptide composition. Lipid and fatty acid compositions were determined in complexes prepared by both methods and also in purified light-harvesting complex II, in minor chlorophyll a/b binding complexes 29, 26, 24, in photosystem II antennae (chlorophyll-protein complexes 43, 47) and in the photosystem II reaction centers chlorophyll-protein complexes. Comparative analysis of the results suggests that a true heterogeneity exists in the lipid class distribution among the different chlorophyll-protein complexes in this region of the photosynthetic membrane. Photosystem II core fractions prepared either by ultra-centrifugation on a sucrose gradient or by isoelectric focusing were found significantly enriched in monogalactosyldiacylglycerol; fractionation of the photosystem II core in its components showed that it was the chlorophyll-protein complexes 43 and 47 which were mainly responsible for this enrichment. One of them, the chlorophyll-protein complex 47, was found containing monogalactosyldiacylglycerol and having a very high level of saturated fatty acids. The minor chlorophyll a/b binding linkers (chlorophyll-protein complexes 24, 26 and 29) retain a largely higher amount of lipids than all other complexes and especially of highly unsaturated galactolipids. Concerning the main light-harvesting antenna (LHCII), it is demonstrated that phosphatidylglycerol is strongly linked to the complex if it cannot be detached at high detergent concentration, while many galactolipids (which nevertheless represent the major lipid classes) are lost. This main light-harvesting complex has been fractionated into several families by isoelectric focusing showing a marked difference in lipid and polypeptide composition. A spectacular increase in the phosphatidylglycerol content was observed in the fraction migrating near the anode and enriched in a 26-kDa polypeptide; but this result is difficult to interpret in physiological terms as it was shown that phosphatidylglycerol alone, because of its negative charge, also migrates toward the anode in isoelectric focusing.

Distribution of the chlorophyll spectral forms in the chlorophyll-protein complexes of photosystem II antenna.

The chlorophyll-protein complexes that form the antenna system of photosystem II have been purified and analyzed in terms of the commonly observed chlorophyll spectral forms. With the exception of chlorophyll b, which is known to be associated with the complexes comprising the outer antenna (LHCII, CP24, CP26, CP29), the spectral forms occur with similar absorption maxima and are present in rather similar amounts in each of the antenna complexes. On the basis of the published chlorophyll stoichiometries for the complexes in photosystem II antenna, the distribution of the spectral forms in a "reconstituted" antenna has been determined. These data were used to calculate the equilibrium population of excited states within the various chlorophyll-protein complexes within photosystem II. This was compared with the light absorption capacity of each of the complexes in the "reconstituted" antenna. The ratio of these two parameters (excited-state equilibrium distribution/absorption capacity) was determined to be 1.21 for the inner (core) antenna and 0.88 for LHCII. The standard free energy change for exciton transfer from the outer to the inner antenna was calculated to be -0.17 kcal mol-1. It is concluded that the photosystem II antenna is arranged as a very shallow funnel.