Validity of procedures involved in ultrasound-based measurement of human plantarflexor tendon elongation on contraction

Ultrasonography is becoming increasingly popular for studying the tensile behaviour of in vivo human tendons through elongation measurements during isometric contraction. For the plantarflexor tendons specifically, which receive much attention due to their functional role in locomotion, elongations are conventionally measured by fixing the scanning probe on the calf. Elongation corrections are also made to account for artifactual ankle rotations during the isometric test, by assuming that these occur round the tibio-talar joint axis, as is the case for passive ankle plantarflexion-dorsiflexion rotations. The present work was set out to examine the validity of these procedures. The displacement of the calcaneum, a skin marker on the calf, and the gastrocnemius myotendinous junction, were measured from rest to maximum isometric voluntary plantarflexion contraction (MVC) in six men by using ultrasound probes mounted on externally fixed points (active test). A passive ankle plantarflexion rotation equal in magnitude to that recorded during MVC was then performed (passive test). In the active test, the calcaneum and the skin marker shifted in the proximo-distal direction by approximately 13 mm. Moreover, the calcaneal displacements in the active and passive tests took place round different rotational axes, as indicated by a calcaneal displacement difference of approximately 10 mm between the two tests. These effects resulted in underestimating by 35% the actual elongation of the gastrocnemius tendon when following the currently suggested procedures. The present results directly invalidate the procedures conventionally followed for assessing the tensile response of the human plantarflexor tendons with ultrasonography.     

Interaction between complementary liposomes: a process leading to multicompartment systems formation

Interaction of complementary liposomes induces a series of processes, involving reorganization of their membrane lipids, which lead to the formation of large aggregates. In several cases these aggregates exhibit multicompartment structures and only primitively mimic, in some aspects at least, the multicompartmental features of cells. Similar multicompartment structures were repeatedly obtained following the interaction of a diversity of complementary liposomal pairs. Thus, a working hypothesis is proposed, according to which, molecular recognition of liposomes induces the formation of multicompartment structures.     

Influence of sequential oligopeptide carriers on the bioactive structure of conjugated epitopes: comparative study of the conformation of a Herpes simplex virus glycoprotein gD-1 epitope in the free and conjugated form, and protein "built-in" crystal structure

Synthetic carriers play an important role in immunogen presentation, due to their ability of inducing improved and specific responses to conjugated epitopes. Their influence on the bioactive conformation of the epitope, though admittedly crucial for relevant in vitro and in vivo applications, is difficult to evaluate, given the usual lack of information on the complex conformational features determined by the nature of the carrier and the mode of ligation. Using the Herpes simplex virus glycoprotein D-1 epitope (Leu(9)-Lys-Nle-Ala-Asp-Pro-Asn-Arg-Phe-Arg-Gly-Lys-Asp-Leu(22)) as a model, we have performed a detailed conformational analysis on the free epitope peptide in solution and on three constructs in which the epitope was conjugated to sequential oligopeptide carriers {Ac-[Lys-Aib-Gly](4)-OH (SOC(4))} (through either a thioether or an amide bond; Ac: acetyl) and polytuftsin oligomers {H-[Thr-Lys-Pro-Lys-Gly](4)-NH(2) (T20)}, (through a thioether bond). The analysis of the epitope conformation in the parent protein, in carrier-conjugated and free form, suggests that the beta-turn structure of the -Asp(13)-Pro-Asn-Arg(16)- segment is highly conserved and independent of the epitope form. However, small conformational variations were observed at the C-terminal part of the epitope, depending on the nature of the carrier.     

Tensile properties of in vivo human tendinous tissue

The biomechanical properties of tendinous structures have traditionally been studied using excised material. Limitations associated with displacement measurements and clamping, and uncertainties as to whether in vitro testing represents physiological function, necessitate developing a method for assessing the mechanical properties of tendinous tissue in the in vivo state. This paper reviews recent results taken with an in vivo and noninvasive protocol using ultrasound as a means of measuring tendon-aponeurosis elongation during tensile loading applied by contraction of the in-series muscle. The results obtained indicate that: (1) the Young's modulus and mechanical hysteresis of in vivo tendons is independent of physiological function and loading, (2) there is a strain variation along the tendon-aponeurosis, and (3) in vivo tendons may exhibit creep. These findings agree with reports from experiments on isolated material and have important biological implications for both the tendon and the in-series muscle. The method described here allows designing longitudinal studies on tendon adaptability, but it also has direct clinical applications.     

Probing protonation/deprotonation of tyrosine residues in cytochrome ba3 oxidase from Thermus thermophilus by time-resolved step-scan Fourier transform infrared spectroscopy

Elucidating the properties of the heme Fe-Cu(B) binuclear center and the dynamics of the protein response in cytochrome c oxidase is crucial to understanding not only the dioxygen activation and bond cleavage by the enzyme but also the events related to the release of the produced water molecules. The time-resolved step-scan FTIR difference spectra show the ν(7a)(CO) of the protonated form of Tyr residues at 1247 cm(-1) and that of the deprotonated form at 1301 cm(-1). By monitoring the intensity changes of the 1247 and 1301 cm(-1) modes as a function of pH, we measured a pK(a) of 7.8 for the observed tyrosine. The FTIR spectral changes associated with the tyrosine do not belong to Tyr-237 but are attributed to the highly conserved in heme-copper oxidases Tyr-136 and/or Tyr-133 residue (Koutsoupakis, K., Stavrakis, S., Pinakoulaki, E., Soulimane, T., and Varotsis, C. (2002) J. Biol. Chem. 277, 32860-32866). The oxygenation of CO by the mixed-valence form of the enzyme revealed the formation of the ～607 nm P (Fe(IV)=O) species in the pH 6-9 range and the return to the oxidized form without the formation of the 580 nm F form. The data indicate that Tyr-237 is not involved in the proton transfer pathway in the oxygenation of CO by the mixed-valence form of the enzyme. The implication of these results with respect to the role of Tyr-136 and Tyr-133 in proton transfer/gating along with heme a(3) ring D propionate-H(2)O-ring A propionate-Asp-372 site to the exit/output proton channel (H(2)O pool) is discussed.     

C(15) Acetogenins from the red alga Laurencia obtusa.

Four C(15) acetogenins, 13-epilaurencienyne (3Z) (1), 13-epipinnatifidenyne (3E) (2), (3E, 6S(*), 7R(*), 9S(*), 10S(*), 12R(*))-9-chloro-13-bromo-6:12-epoxy-7, 10-diacetoxypentadec-3-en-1-yne (3), (3Z, 6S(*), 7R(*), 9S(*), 10S(*), 12R(*))-9-chloro-13-bromo-6:12-epoxy-7, 10-diacetoxypentadec-3-en-1-yne (4), along with the known 13-epilaurencienyne (3E) (5), have been isolated from the organic extract of the red alga Laurencia obtusa, collected in the Aegean Sea, Greece. The structures of the new natural products, as well as their relative stereochemistry, were established by means of spectral data analysis, including 2D NMR spectroscopic experiments. Some of the new metabolites exhibited significant insecticidal activity.     

Hydrolysis by phospholipase D of phospholipids in solution state or adsorbed on a silica matrix

Phospholipases D (PLD) catalyse hydrolysis and transphosphatidylation reactions in phospholipids. In the present study, the hydrolytic activity for cabbage PLD was investigated with five different substrates (dipalmitoylphosphatidylethanolamine (DPPE), dipalmitoylphosphatidylcholine (DPPC), didecanoylphosphatidylcholine (DDPC), 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine and lyso-phosphatidylcholine (lyso-PC)) in solution or adsorbed on a silica matrix. In the specific buffer solutions, where the substrates were proved to form large multilamellar polydisperse aggregates, PLD showed preference for DPPC > DPPE > DDPC > 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine > lyso-PC. When the substrates were adsorbed on the silica matrix, PLD hydrolysed 1-alkyl-2-acetyl-sn-glycero-3-phosphocholine and lyso-PC, DDPC, but not DPPC or DPPE. Theoretical studies of the simplest possible adducts between the phospholipids and the silica matrix were performed. Examination of local geometries of DPPC showed a significant blocking of the P-O-X bond-prone to hydrolysis, which could possibly block the access of PLD. Immobilization of phospholipids could be applied for improving the yield of reactions catalysed by PLD as well as for performing a targeted production of short-chain length phosphatidic acid analogs.     

Acute T3 treatment protects the heart against ischemia-reperfusion injury via TRα1 receptor

We have previously shown that acute thyroid hormone treatment could limit reperfusion injury and increase post-ischemic recovery of function. In the present study, we further explore potential initiating mechanisms of this response. Thus, isolated rat hearts were subjected to 30 min zero-flow global ischemia (I) followed by 60-min reperfusion (R). Reperfusion injury was assessed by post-ischemic recovery of left ventricular developed pressure (LVDP%) and LDH release. T3 at a dose of 60 nM which had no effect on contractile function of non-ischemic myocardium, significantly increased LVDP% [48% (2.9) vs. 30.2% (3.3) for untreated group, P < 0.05] and reduced LDH release [8.3 (0.3) vs. 10 (0.42) for untreated group, P < 0.05] when administered at R. T4 (60 and 400 nM) had no effect on contractile function either in non-ischemic or ischemic myocardium. Administration of debutyl-dronedarone (DBD), a TRα1 antagonist abolished the T3-limiting effect on reperfusion injury: Thus, co-administration of T3 and DBD resulted in significantly lower LVDP%, [23% (4.7) vs. 48% (2.9) for T3 group, P < 0.05] and higher LDH release [9.9 (0.3) vs. 8.3 (0.3), for T3 group, P < 0.05]. In conclusion, acute T3 and not T4 treatment will be able to protect against reperfusion injury. T3 can exert this beneficial effect on ischemic myocardium at a dose that has no effects on non-ischemic myocardium. Acute T3-limiting effect on reperfusion injury is mediated, at least in part, via TRα1 receptor.