Matrix metalloproteases MMP-2 and MMP-9: are they early biomarkers of bone remodelling and healing after arthroscopic acromioplasty?

Arthroscopic acromioplasty, one of the most frequent procedures in shoulder surgery, can promote tissue healing process by the release of growth/angiogenic factors from the acromion. Matrix metalloproteinases MMP-2 and MMP-9 are involved in such process. The purpose of this study was to measure MMP-2 and MMP-9 levels in the articular fluid and in the peripheral blood of patients undergoing arthroscopic acromioplasty in order to better understand the local involvement of such factors in the healing process after surgical procedures.Concentrations of MMP-2 and MMP-9 in the subacromial space and peripheral blood collected shortly after surgery were determined by ELISA. MMP-2 and MMP-9 concentrations were measured in the subacromial fluid of 23 patients. In subacromial fluid, the levels between MMP-2 and MMP-9 did not reach statistical significance (127.15 ± 45.56 vs 149.41 ± 53.61 pg/ml, respectively, p > 0.05). Peripheral blood levels of MMP-2 (130.75 ± 47.48 pg/ml) were comparable to the subacromial fluid ones (127.15 ± 45.56 pg/ml) whereas MMP-9 level was higher in the subacromial space (149.41 ± 53.61 pg/ml) than in the peripheral blood (67.61 ± 12.62 pg/ml, p < 0.001). This work suggests that the measurement of bone specific MMPs (MMP-2 and MMP-9) can be an useful tool to be monitored in parallel with growth factor levels and other bone turnover markers in order to evaluate the bone remodelling and tissue healing processes. This study suggests that the measurement of bone specific MMPs levels, in particular MMP-9, may evaluate the bone remodelling and healing after arthroscopic shoulder acromioplasty.     

Stability of haematological parameters and its relevance on the athlete's biological passport model

The stability of haematological parameters is crucial to guarantee accurate and reliable data for implementing and interpreting the athlete's biological passport (ABP). In this model, the values of haemoglobin, reticulocytes and out-of-doping period (OFF)-score (Hb-60√Ret) are used to monitor the possible variations of those parameters, and also to compare the thresholds developed by the statistical model for the single athlete on the basis of its personal values and the variance of parameters in the modal group. Nevertheless, a critical review of the current scientific literature dealing with the stability of the haematological parameters included in the ABP programme, and which are used for evaluating the probability of anomalies in the athlete's profile, is currently lacking. In addition, we collected information from published studies, in order to supply a useful, practical and updated review to sports physicians and haematologists. There are some parameters that are highly stable, such as haemoglobin and erythrocytes (red blood cells [RBCs]), whereas others, (e.g. reticulocytes, mean RBC volume and haematocrit) appear less stable. Regardless of the methodology, the stability of haematological parameters is improved by sample refrigeration. The stability of all parameters is highly affected from high storage temperatures, whereas the stability of RBCs and haematocrit is affected by initial freezing followed by refrigeration. Transport and rotation of tubes do not substantially influence any haematological parameter except for reticulocytes. In all the studies we reviewed that used Sysmex instrumentation, which is recommended for ABP measurements, stability was shown for 72 hours at 4 ° C for haemoglobin, RBCs and mean curpuscular haemoglobin concentration (MCHC); up to 48 hours for reticulocytes; and up to 24 hours for haematocrit. In one study, Sysmex instrumentation shows stability extended up to 72 hours at 4 ° C for all the parameters. There are significant differences among methods and instruments: Siemens Advia shows lower stability than Sysmex as regards to reticulocytes. However, the limit of 36 hours from blood collection to analysis as recommended by ABP scientists is reasonable to guarantee analytical quality, when samples are transported at 4 ° C and are accompanied by a certified steadiness of this temperature. There are some parameters that are highly stable, such as haemoglobin and RBCs; whereas others, such as reticulocytes, mean cell volume and haematocrit are more unstable. The stability of haematological parameters might be improved independently from the analytical methodology, by refrigeration of the specimens.     

Characterization of actomyosin bond properties in intact skeletal muscle by force spectroscopy

Force generation and motion in skeletal muscle result from interaction between actin and myosin myofilaments through the cyclical formation and rupture of the actomyosin bonds, the cross-bridges, in the overlap region of the sarcomeres. Actomyosin bond properties were investigated here in single intact muscle fibers by using dynamic force spectroscopy. The force needed to forcibly detach the cross-bridge ensemble in the half-sarcomere (hs) was measured in a range of stretching velocity between 3.4 x 10(3) nm.hs(-1).s(-1) or 3.3 fiber length per second (l(0)s(-1)) and 6.1 x 10(4) nm.hs(-1).s(-1) or 50 l(0).s(-1) during tetanic force development. The rupture force of the actomyosin bond increased linearly with the logarithm of the loading rate, in agreement with previous experiments on noncovalent single bond and with Bell theory [Bell GI (1978) Science 200:618-627]. The analysis permitted calculation of the actomyosin interaction length, x(beta) and the dissociation rate constant for zero external load, k(0). Mean x(beta) was 1.25 nm, a value similar to that reported for single actomyosin bond under rigor condition. Mean k(0) was 20 s(-1), a value about twice as great as that reported in the literature for isometric force relaxation in the same type of muscle fibers. These experiments show, for the first time, that force spectroscopy can be used to reveal the properties of the individual cross-bridge in intact skeletal muscle fibers.     

Gastrointestinal stromal tumors: case reports and review of the literature

The Authors describe four cases of gastrointestinal stromal tumours (GIST) two of them were localized in the stomach, the others in the ileum. GIST are neoplasms of mesenchymal origin which develop inside the wall of the digestive tract. The most frequent site is the stomach, followed by the small bowel; less commonly these tumors can affect the oesophagus, the colon and the rectum. GIST originate from precursors of the interstitial cells of Cajal, which are localized in the gastro-intestinal wall and are involved in the regulation of the peristalsis. The treatment is surgical resection. For advanced disease there is a new interesting treatment based on the imatinib, a tyrosine kinase inhibitor.     

Mechanism of force enhancement during stretching of skeletal muscle fibres investigated by high time-resolved stiffness measurements

Stretching of active muscles leads to a great enhancement of the force developed without increased ATP consumption. The mechanism of force enhancement is still debated and it is not clear if it is due to increased crossbridge strain or to a stretch-induced increase in crossbridge number. The present study, performed on single fibres from tibialis anterior or interosseus muscles of the frog at 5 °C, was aimed at clarifying this point. A striation follower device was used to measure sarcomere length changes. Force was measured during the application of stretches (0.15–3.9 ms duration, 3–7.8 nm per half-sarcomere amplitude) to activated fibres. Small 4 kHz sinusoidal length oscillations, superimposed on the stretches, were used to calculate fibre stiffness with high time resolution. Stiffness increased during the stretch then subsequently decayed, all in parallel with tension. Likewise, during quick releases, stiffness decreased during the release then subsequently recovered in parallel with tension. Comparison of tension and stiffness both during the tetanus rise and also during stretches which doubled tension, imposed on the tetanus rise, indicated that stretch-induced crossbridge recruitment was only about 11 %, suggesting that force enhancement by stretching is mainly due to an increase of individual crossbridge force, whereas crossbridge recruitment plays only a minor role. The accompanying stiffness changes can be explained by non-linearity of myofilament compliance.     

Mechanical properties of intact single fibres from wild-type and MLC/mIgf-1 transgenic mouse muscle

The effects of overexpression of the local form of insulin like growth factor-1 (mIgf-1) on skeletal muscle were investigated by comparing the mechanical properties of single intact fibres from the flexor digitorum brevis of wild-type (WT) and (MLC/mIgf-1) transgenic mice (TG) at 21–24°C. Isolated single fibres were clean enough to measure accurately the sarcomere length. The parameters investigated were: tetanic absolute and specific force, the force–velocity relationship, and the sarcomere length–tension relationship. In addition, we investigated the properties of the “static stiffness”, a non-crossbridge Ca²⁺-dependent increase of fibre stiffness previously found in frog muscle. Both average cross-sectional area and tetanic force almost doubled in TG fibres, so that specific force was the same in both preparation: 312 ± 20 and 344 ± 34 kN m^?2 in WT and TG fibres, respectively. None of the relative force–velocity parameters was altered by Igf-1 overexpression, however, V _max (8–10 l ₀ s^?1) was greater than previously reported in whole muscles. The sarcomere length–tension relationship was the same in TG and WT fibres showing the classical shape with a plateau region between 2.28 and 2.52 μm and a linear descending limb. The static stiffness was present in both WT and TG fibres and showed similar characteristics to that of frog skeletal muscle. In contrast to the other parameters, static stiffness in TG fibres was about 24% smaller than in WT fibres suggesting a possible effect of Igf-1 overexpression on its mechanism.