SUMMARY1. The mechanism of the enhancement and the deficit of isometric force by slow length changes in frog fast muscle fibres was studied by recording muscle fibre stiffness changes as measured with sinusoidal vibrations (0-51-9 kHz, peak-to-peak amplitude 01 % of slack length, LO).2. When a tetanized fibre was slowly stretched by 5-9 % from sarcomere lengths 2-4-2-6 ,#m, the force rose to a peak during the stretch and then decreased towards a steady level higher than that during the ordinary isometric tetanus at the same sarcomere length.3. The stiffness of the fibre first rose abruptly in response to stretch and then started to decrease linearly while the stretch went on; after the completion of stretch the stiffness decreased towards a steady value which was equal to that during the isometric tetanus at the same sarcomere length, indicating that the enhancement of isometric force is associated with decreased stiffness.4. If a tetanized fibre was slowly released by 4-12% from sarcomere lengths 2-55-2-7 4tm, the steady force attained after the completion of release was lower than that during an isometric tetanus at the same sarcomere length.5. The stiffness of the fibre changed in parallel with the force both during and after the applied release.6. Recordings of the segmental length changes along the fibre with a high-speed video system (200 frames/s) indicated that all segments lengthened in response to the applied stretch.7. The segmental length changes in response to the applied release were markedly non-uniform; the length of a segment located at the centre of the fibre did not change appreciably both during and after the release.8. These results are discussed in terms of cross-bridge performance and structure of the myofilament lattice.

1. The force enhancement during and after stretch (0 15 4um per sarcomere) was studied during fused tetani of single fibres isolated from the anterior tibialis muscle of Rana temporaria (05-3-6°C; sarcomere length, 2-05-2-65 ,um). Changes in length were recorded simultaneously from the fibre as a whole (puller movement) and from marked segments (-0 5 mm in length) of the same fibre.2. The residual force enhancement after stretch (recorded at the end of a long tetanus) was found to be linearly related to the slow component of tension rise during the stretch ramp. 3. The fibres were released to shorten against a very small load at different times after stretch (load clamp). The shortening records derived after a preceding stretch exhibited a larger and steeper initial transient than that recorded in an isometric tetanus without stretch. The excess length change (Ls; nanometres per half-sarcomere) recorded during the initial transient increased with the amplitude of stretch and was linearly related to the force enhancement produced by the stretch (FE; % of maximum tetanic tension) according to the following regression: LS = 0200 FE + 8-65 (P < 0O001). The length changes recorded from the whole fibre agreed well with measurements from individual segments. 4. Slack-test measurements confirmed the existence of a large initial transient phase when the fibre was released to shorten after a preceding stretch. The excess length change determined from the slack tests agreed closely with the values derived from load-clamp recordings. 5. The results support the view that stretching a muscle fibre during tetanus leads to strain of elastic elements and, presumably, to variation of filament overlap due to non-uniform distribution of the length change within the fibre volume. Regions with greater filament overlap are likely to generate the long-lasting extra force referred to as 'residual force enhancement after stretch'. The elastic elements recruited during stretch can be presumed to play an essential part in this process by supporting regions in which the filament overlap has been reduced during the stretch ramp. Recoil of these elastic elements is responsible for the excess length change that is recorded during the initial transient after release as described under point 3.Striated muscle that is subjected to stretch during tetanic activity increases its force above the level attained in an isometric tetanus at the corresponding sarcomere length (e.g.

The pharmaceutical utility of silk fibroin as a possible material for an oral dosage form for elderly patients was investigated. Silk fibroin gel (SFG) was prepared from its aqueous solution. The gel formation was studied as a function of adjusted pH and concentration of silk fibroin (SF). On the basis of Fourier transform infrared spectroscopy of SFG, the transition from the random coil to the beta-structure was observed. The rate of gelation was sufficiently accelerated by the addition of glycerol to the SF aqueous solution. The glycerol content also affected the rate of gelation of the SF solution. Rheological properties of SFG were evaluated using a creep meter. The SF content and/or glycerol content affected the breaking stress of SFG. Moisture desorption from SFG was retarded with an increase in glycerol content. It was found that SFG was able to be prepared at room temperature (20 +/- 5 degrees C), and the SF content and glycerol content affected the formation and physicochemical properties of SFG.

Osteoarthritis (OA) is a potentially disabling disease whose progression is dependent on several risk factors. OA management usually involves the use of non-steroidal anti-inflammatory drugs (NSAIDs) that are the primary pharmacological treatments of choice. However, NSAIDs have often been associated with unwanted side effects. Cyclooxygenase (COX)-2 specific inhibitors, such as celecoxib, have been successfully used as an alternative in the past for OA treatment and have demonstrated fewer side effects. While abundant data are available for the clinical efficacy of drugs used for OA treatment, little is known about the disease-modifying effects of these agents. A previous review published by Zweers et al. (2010) assessed the available literature between 1990 and 2010 on the disease-modifying effects of celecoxib. In the present review, we aimed to update the existing evidence and identify evolving concepts relating to the disease-modifying effects of not just celecoxib, but also other NSAIDs. We conducted a review of the literature published from 2010 to 2016 dealing with the effects, especially disease-modifying effects, of NSAIDs on cartilage, synovium, and bone in OA patients. Our results show that celecoxib was the most commonly used drug in papers that presented data on disease-modifying effects of NSAIDs. Further, these effects appeared to be mediated through the regulation of prostaglandins, cytokines, and direct changes to tissues. Additional studies should be carried out to assess the disease-modifying properties of NSAIDs in greater detail.

SUMMARY1. The change in the ability of frog skeletal muscle fibres to sustain a load was studied during the course of oscillatory length changes or continuous isotonic lengthening following quick increases in load, by applying 'test' load steps and measuring the initial velocity of resulting isotonic motion.2. When quick decreases in load were applied during oscillatory length changes or continuous isotonic lengthening, the fibres were found to shorten against a load above the maximum tension (P0), indicating an increase in load-sustaining ability after quick increases in load.3. If quick increases in load were applied at various times after preceding quick increase in load, the initial velocity of resulting isotonic lengthening decreased with time, also indicating an increase in load-sustaining ability.4. An increase in load-sustaining ability was also observed during the course of rapid isotonic lengthening under a load of 1-6-1-7 P0, in which the fibres lengthened with increasing velocity.5. The increase in load-sustaining ability after quick increases in load was associated with a shift of the force-velocity curve towards higher force values, while no significant change was observed in the maximum shortening velocity at zero load.6. The stiffness of muscle fibres was estimated by measuring quick length changes coincident with load steps. It decreased with decreasing isotonic load below P0, approaching a certain finite value as the load tended to zero. For isotonic loads above P0, the stiffness increased with increasing isotonic load up to 1-6-1'7 P0, when step decreases in load were used for stiffness measurements.7. The mechanism of enhancement of mechanical performance of the fibres after quick increases in load is discussed in relation to the sliding filament/cross bridge hypotheses of muscle contraction.