The effect of a combined rehabilitation program on the temporomandibular joint in systemic sclerosis evaluated by ultrasound exam.

PURPOSE: Temporomandibular joint (TMJ) involvement is frequent in Systemic Sclerosis (SSc). Dysfunction and X-ray changes of TMJ were described only in few observational studies. Treatment as well has been seldom considered. Aim of the present study was to evaluate the effects on TMJ of two specifically designed physiotherapy protocols. METHODS: The study group included 26 SSc outpatients (22 females and 4 males with mean age ± SD 59.08 ± 10.31 years). Thirteen patients were randomly assigned to a treatment (protocol 1) including home exercises for TMJ and thirteen to a treatment (protocol 2) including home exercises and a combined procedure. The rehabilitation effects on the TMJ were evaluated by ultrasound examination (UE) in static and dynamic phases. UE was performed in all patients before and at the end of the treatment and after a follow up (8 weeks). RESULTS: Both rehabilitation protocols induced a significant improvement (protocol 1: p < 0.01 and protocol 2: p < 0.005) of mouth opening with a long-lasting effect. Protocol 2 was more effective than protocol 1. A significant increase of bilateral condyle-head temporal bone distance was detected by UE at the end of both treatments. It was maintained at follow-up in patients treated with Protocol 2. CONCLUSIONS: The present investigation shows that a rehabilitation program characterized by home exercises with a combined procedure is useful to recover the function of TMJ. The data also show that UE is helpful in the evaluation of TMJ in SSc and in the assessment of the efficacy of the rehabilitation programs.

Biosecurity measures in European beekeeping.

Emerging pathogens of honey bees represent an important threat to the development of the beekeeping sector. The implementation of biosecurity measures in beekeeping (BMBs) plays an essential role in supporting honey bee health within the beekeeping sector. A group of experts, in collaboration with the BPRACTICES (Grant Agreement No. 696231, European Research Area on Sustainable Animal Production Systems [ERA-Net SusAn]) project partners, has provided the definition of BMBs. Thus, BMBs are all those operational activities implemented to control the risk of introduction and spread of specific honey bee disease agents. In this paper, the BMBs in the European beekeeping context are identified for the most relevant honey bee diseases in Europe: varroosis, American foulbrood (AFB), European foulbrood (EFB), nosemosis and aethinosis. Moreover, BMBs were classified in â€Ëœcategories' adapted to consider productivity and the â€ËœOne Health' approach: human health, honey bee health and protection of the environment. The 84 BMBs described by the panel of experts were ranked according to the priority score attributed. The implementation of BMBs represents an essential step forwards to increase the resilience and sustainability of European beekeeping.

L'émergence de nouveaux agents pathogènes chez les abeilles mellifères représente une menace importante pour le développement du secteur apicole. La mise en oeuvre de mesures de biosécurité en apiculture est déterminante pour préserver la santé des abeilles mellifères dans les élevages. En collaboration avec des partenaires du projet BPRACTICES (convention de subvention n° 696231, programme ERA-Net SusAn [European Research Area on Sustainable Animal Production Systems]), un groupe d'experts a élaboré un cadre définissant ces mesures de biosécurité. Sont définies comme mesures de biosécurité en apiculture toutes les activités opérationnelles mises en oeuvre pour contrôler le risque d'introduction et de propagation d'agents pathogènes affectant spécifiquement les abeilles mellifères. Les auteurs décrivent les mesures de biosécurité applicables, dans le contexte apicole européen, aux maladies les plus importantes en Europe : la varroose, la loque américaine, la loque européenne, la nosémose et l'infestation par Aethina tumida. En outre, les mesures de biosécurité en apiculture ont été regroupées en « catégories ¼ afin de prendre en compte la productivité et l'approche « Une seule santé ¼ : santé humaine, santé des abeilles mellifères et protection de l'environnement. Les 84 mesures de biosécurité en apiculture décrites par le groupe d'experts ont été classées en fonction du niveau de priorité qui leur a été attribué. La mise en oeuvre de ces mesures représente une étape cruciale pour accroître la résilience et la durabilité de l'apiculture européenne.

Los agentes patógenos emergentes que afectan a la abeja melífera suponen una importante amenaza para el desarrollo del sector apícola. La aplicación de medidas de seguridad biológica dentro de este sector cumple una función esencial para proteger la salud de las abejas. En colaboración con asociados en el proyecto BPRACTICES (acuerdo de subvención nº 696231, programa ERA-Net SusAn [Espacio Europeo de Investigación - «Sistemas sostenibles de producción animal¼]), un grupo de expertos definió las «medidas de seguridad biológica en apicultura¼ como todas aquellas acciones realizadas para controlar el riesgo de penetración y propagación de agentes patógenos de la abeja melífera. Los autores, situándose en el contexto de la apicultura europea, exponen las medidas de seguridad biológica que ayudan a controlar las principales enfermedades de la abeja melífera en Europa: varroosis, loque americana, loque europea, nosemosis y aethinosis (infestación por el escarabajo de las colmenas). Por otra parte, estas medidas fueron divididas en diferentes «categorías¼ para poder tener en cuenta las cuestiones de productividad y el enfoque de «Una sola salud¼: salud humana, salud de la abeja melífera y protección del medio ambiente. Las 84 medidas de seguridad biológica en apicultura que describió el cuadro de expertos fueron jerarquizadas en función de una puntuación atribuida por su nivel de prioridad. La aplicación de este tipo de medidas representa un crucial paso adelante para conferir más resiliencia a la apicultura europea y hacerla más sostenible.

The effects of fatigue and oxidation on contractile function of intact muscle fibers and myofibrils isolated from the mouse diaphragm.

The goal of this study was to investigate the effects of repetitive stimulation and the oxidant H2O2 on fatigue of diaphragm intact fibers and in myofibrils measured with different Ca2+ concentrations. Intact fibers were isolated from mice diaphragm, and twitch and tetanic contractions (500 ms duration) were performed at different frequencies of stimulation ranging from 15 Hz to 150 Hz to establish a force-frequency relation before and after a fatigue and recovery protocol, without or after a treatment with H2O2. Fatigue was induced with isometric contractions (500 ms, 40 Hz) evoked every 0.8 seconds, with a total of 625 tetani. After the fatigue, the force recovery was followed by invoking tetanic contractions (500 ms, 40 Hz) every 1 min, with a total duration of 30 min. Individual myofibrils were also isolated from the mouse diaphragm and were tested for isometric contractions before and after treatment with H2O2 and NAC. In a second series of experiments, myofibrils were activated at different pCa (pCa = -log10 [Ca2+]), before and after H2O2 treatment. After 15 minutes of H2O2 treatment, the myofibrillar force was decreased to 54 ± 12% of its control, maximal value, and a result that was reversed by NAC treatment. The force was also decreased after myofibrils were treated with H2O2 and activated in pCa ranging between 4.5 and 5.7. These results suggest that fatigue in diaphragm intact fibers and at the myofibrils level is caused partially by oxidation of the contractile proteins that may be responsible for changing the force in various levels of Ca2+ activation.

Force decline during fatigue is due to both a decrease in the force per individual cross-bridge and the number of cross-bridges.

Fatigue occurring during exercise can be defined as the inability to maintain the initial force or power output. As fatigue becomes pronounced, force and maximum velocity of shortening are greatly reduced and force relaxation is prolonged. In principle, force loss during fatigue can result from a decrease in the number of cross-bridges generating force or a decrease of the individual cross-bridge force or to both mechanisms. The present experiments were made to investigate this point in single fibres or small fibre bundles isolated from flexor digitorum brevis (FDB) of C57BL/6 mice at 22-24◦C. During a series of 105 tetanic contractions, we measured force and fibre stiffness by applying small sinusoidal length oscillations at 2.5 or 4 kHz frequency to the activated preparation and measuring the resulting force changes. Stiffness data were corrected for the influence of compliance in series with the cross-bridge ensemble. The results show that the force decline during the first 20 tetani is due to the reduction of force developed by the individual cross-bridges and thereafter as fatigue becomes more severe, the number of cross-bridges decreases. In spite of the force reduction in the early phase of fatigue, there was an increased rate of tetanic force development and relaxation. In the latter stages of fatigue, the rate of force development and relaxation became slower. Thus, the start of fatigue is characterised by decreased cross-bridge force development and as fatigue becomes more marked, the number of cross-bridges decreases. These findings are discussed in the context of the current hypotheses about fatigue mechanisms.

Cross-bridge properties in single intact frog fibers studied by fast stretches.

Cross-bridges properties were measured under different experimental conditions by applying fast stretches to activated skeletal frog muscle fiber to -forcibly detach the cross-bridge ensemble. This allowed to measure the tension needed to detach the cross-bridges, P(c), and the sarcomere elongation at the rupture force, L(c). These two parameters are expected to be correlated with cross-bridges number (P(c)) and their mean extension (L(c)). Conditions investigated were: tetanus rise and plateau under normal Ringer and Ringer containing different BDM -concentrations, hyper (1.4T) and hypotonic (0.8T) solutions, 5 and 14 degrees C temperature. P(c) was linearly correlated with the tension (P) developed by the fibers under all the conditions examined, however the ratio P(c)/P changed depending on conditions being greater at low temperature and higher tonicity. These results indicate that, (a) P(c) can be used as a measure of attached cross-bridge number and (b) the force developed by the individual cross-bridge increases at high temperature and low tonicity. L(c) was not affected by tension developed, however it changed under different conditions, being greater at low temperature and high tonicity. These findings, suggests, in agreement with P(c) data, that cross-bridge extension is smaller at low temperature and high tonicity. By comparing these data with tetanic tension we concluded that potentiation or depression induced on tetanic force by tonicity or temperature changes are entirely accounted for by changes of the force developed by the individual cross-bridge.

Is the cross-bridge stiffness proportional to tension during muscle fiber activation?

The cross-bridge stiffness can be used to estimate the number of S1 that are bound to actin during contraction, which is a critical parameter for elucidating the fundamental mechanism of the myosin motor. At present, the development of active tension and the increase in muscle stiffness due to S1 binding to actin are thought to be linearly related to the number of cross-bridges formed upon activation. The nonlinearity of total stiffness with respect to active force is thought to arise from the contribution of actin and myosin filament stiffness to total sarcomere elasticity. In this work, we reexamined the relation of total stiffness to tension during activation and during exposure to N-benzyl-p-toluene sulphonamide, an inhibitor of cross-bridge formation. In addition to filament and cross-bridge elasticity, our findings are best accounted for by the inclusion of an extra elasticity in parallel with the cross-bridges, which is formed upon activation but is insensitive to the subsequent level of cross-bridge formation. By analyzing the rupture tension of the muscle (an independent measure of cross-bridge formation) at different levels of activation, we found that this additional elasticity could be explained as the stiffness of a population of no-force-generating cross-bridges. These findings call into question the assumption that active force development can be taken as directly proportional to the cross-bridge number.

Reversal of the myosin power stroke induced by fast stretching of intact skeletal muscle fibers.

Force generation and movement in skeletal muscle result from a cyclical interaction of overlapping myosin and actin filaments that permits the free energy of ATP hydrolysis to be converted into mechanical work. The rapid force recovery that occurs after a step release imposed on a muscle is thought to result from a synchronized tilting of myosin lever arms toward a position of lower free energy (the power stroke). We investigated the power stroke mechanism in intact muscle fibers of Rana esculenta using a fast stretch to detach forcibly cross-bridges. Stretches were applied either with or without a conditioning step release. Cross-bridge rupture tension was not significantly influenced by the release, whereas sarcomere elongation at the rupture point increased immediately after the release and returned to the prerelease condition within 15-20 ms, following a slower time course compared to the recovery of tension. These observations suggest that the rupture force of a bridge is unaltered by a conditioning release, but rupture must first be preceded by a power stroke reversal, which restores the prepower stroke state. The sarcomere extension at the rupture point indicates both the extent of this power stroke reversal and the time course of strained bridge replenishment.

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 degrees 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 Ca(2+)-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 microm 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.

Effect of temperature on cross-bridge properties in intact frog muscle fibers.

It is well known that the force developed by skeletal muscles increases with temperature. Despite the work done on this subject, the mechanism of force potentiation is still debated. Most of the published papers suggest that force enhancement is due to the increase of the individual cross-bridge force. However, reports on skinned fibers and single-molecule experiments suggest that cross-bridge force is temperature independent. The effects of temperature on cross-bridge properties in intact frog fibers were investigated in this study by applying fast stretches at various tension levels (P) on the tetanus rise at 5 degrees C and 14 degrees C to induce cross-bridge detachment. Cross-bridge number was measured from the force (critical force, P(c)) needed to detach the cross-bridge ensemble, and the average cross-bridge strain was calculated from the sarcomere elongation needed to reach P(c) (critical length, L(c)). Our results show that P(c) increased linearly with the force developed at both temperatures, but the P(c)/P ratio was considerably smaller at 14 degrees C. This means that the average force per cross bridge is greater at high temperature. This mechanism accounts for all the tetanic force enhancement. The critical length L(c) was independent of the tension developed at both temperatures but was significantly lower at high temperature suggesting that cross bridges at 14 degrees C are more strained. The increased cross-bridge strain accounts for the greater average force developed.

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.

Effects of the number of actin-bound S1 and axial force on X-ray patterns of intact skeletal muscle.

Effects of the number of actin-bound S1 and of axial tension on x-ray patterns from tetanized, intact skeletal muscle fibers were investigated. The muscle relaxant, BDM, reduced tetanic M3 meridional x-ray reflection intensity (I(M3)), M3 spacing (d(M3)), and the equatorial I(11)/I(10) ratio in a manner consistent with a reduction in the fraction of S1 bound to actin rather than by generation of low-force S1-actin isomers. At complete force suppression, I(M3) was 78% of its relaxed value. BDM distorted dynamic I(M3) responses to sinusoidal length oscillations in a manner consistent with an increased cross-bridge contribution to total sarcomere compliance, rather than a changed S1 lever orientation in BDM. When the number of actin-bound S1 was varied by altering myofilament overlap, tetanic I(M3) at low overlap was similar to that in high [BDM] (79% of relaxed I(M3)). Tetanic d(M3) dependence on active tension in overlap experiments differed from that observed with BDM. At high BDM, tetanic d(M3) approached its relaxed value (14.34 nm), whereas tetanic d(M3) at low overlap was 14.50 nm, close to its value at full overlap (14.56 nm). This difference in tetanic d(M3) behavior was explicable by a nonlinear thick filament compliance which is extended by both active and passive tension.

Crossbridge properties investigated by fast ramp stretching of activated frog muscle fibres.

Very fast ramp stretches at 9.5-33 sarcomere lengths s(-1) (l0 s(-1)) stretching speed, 16-25 nm per half-sarcomere (nm hs(-1)) amplitude were applied to activated intact frog muscle fibres at tetanus plateau, during the tetanus rise, during the isometric phase of relaxation and during isotonic shortening. Stretches produced an almost linear tension increase above the isometric level up to a peak, and fell to a lower value in spite of continued stretching, indicating that the fibre became suddenly very compliant. This suggests that peak tension (critical tension, P(c)) represents the tension at which crossbridges are forcibly detached by the stretch. The ratio of P(c) to the isometric tension at tetanus plateau (P0) was 2.37 +/- 0.12 (S.E.M.). This ratio did not change significantly at lower tension (P) during the tetanus rise but decreased with time during the relaxation and increased with speed during isotonic shortening. At tetanus plateau P(c) occurred when sarcomere elongation attained a critical length (L(c)) of 10.98 +/- 0.13 nm hs(-1), independently of the stretching speed. L(c) remained constant during the tetanus rise but decreased on the relaxation and increased during isotonic shortening. Length-clamp experiments on the relaxation showed that the lower values of P(c)/P ratio and L(c), were both due to the slow sarcomere stretching occurring during this phase. Our data show that P(c) can be used as a measure of crossbridge number, while L(c) is a measure of crossbridge mean extension. Accordingly, for a given tension, crossbridges on the isometric relaxation are fewer than during the rise, develop a greater individual force and have a greater mean extension, while during isotonic shortening crossbridges are in a greater number but develop a smaller individual force and have a smaller extension.

Myosin lever disposition during length oscillations when power stroke tilting is reduced.

M3 reflection intensity (I(M3)) from tetanized, intact skeletal muscle fiber bundles was measured during sinusoidal length oscillations at 2.8 kHz, a frequency at which the myosin motor's power stroke is greatly reduced. I(M3) signals were approximately sinusoidal, but showed a "double peak" distortion previously observed only at lower oscillation frequencies. A tilting lever arm model simulated this distortion, where I(M3) was calculated from the molecular structure of myosin subfragment 1 (S1). Simulations showed an isometric lever arm disposition close to normal to the filament axis at isometric tension, similar to that found using lower oscillation frequencies, where the power stroke contributes more toward total S1 movement. Inclusion of a second detached S1 in each actin-bound myosin dimer increased simulated I(M3) signal amplitude and improved agreement with the experimental data. The best agreement was obtained when detached heads have a fixed orientation, insensitive to length changes, and similar to that of attached heads at tetanus plateau. This configuration also accounts for the variations in relative intensity of the two main peaks of the M3 reflection substructure after a length change. This evidence of an I(M3) signal distortion when power stroke tilting is suppressed, provided that a large enough amplitude of length oscillation is used, is consistent with the tilting lever arm model of the power stroke.

Short- and long-term effects of a dietary yeast beta-glucan (Macrogard) and alginic acid (Ergosan) preparation on immune response in sea bass (Dicentrarchus labrax).

The present study investigated the immunomodulatory activity of Ergosan, an algal extract containing alginic acid, and Macrogard, a yeast extract containing beta-glucans, on innate and specific immunity in sea bass (Dicentrarchus labrax). Four cycles of experimental feeding using normal fish feed formulation (control group) supplemented with Ergosan (0.5%) or Macrogard (0.1%) were performed at 60-day intervals (15 days of treatment+45 days of suspension). Serum complement, lysozyme, total proteins and heat shock protein (HSP) concentrations were measured at 15, 30 and 45 days from the end of the first 15-day feeding cycle (short term) and 45 days after the end of each feeding cycle over a 35-week period (long term). The percentage of B- and T-lymphocytes in peripheral blood leucocytes and gut were measured over long-term trial. Significant elevation (P < 0.05) in serum complement activity occurred in sea bass fed with alginic acid and glucans, at 15 days from the end of first cycle of treatment. Significant elevation (P < 0.05) in serum lysozyme, gill and liver HSP concentration were observed in the same experimental groups at 30 days from the end of treatment, whereas a significant increase (P < 0.05) of complement activity was only observed in fish that received an Ergosan diet. At 45 days from the end of treatment, complement, lysozyme and HSP concentration did not differ among groups. Over the long-term period, no significant differences were observed in innate and specific immune parameters, survival, growth performances and conversion index in treated and control fish. A dramatic decrease of both innate and acquired immune parameters was observed during the winter season in all groups, followed by a partial recovery when water temperature increased. Reduction in complement and lysozyme activities was significatively correlated (p < 0.01) to water temperature variation. The results suggested the potential of alginic acid and beta-glucans to activate some innate immune responses in sea bass, and particularly under conditions of immunodepression related to environmental stress.

Non-cross-bridge calcium-dependent stiffness in frog muscle fibers.

At the end of the force transient elicited by a fast stretch applied to an activated frog muscle fiber, the force settles to a steady level exceeding the isometric level preceding the stretch. We showed previously that this excess of tension, referred to as "static tension," is due to the elongation of some elastic sarcomere structure, outside the cross bridges. The stiffness of this structure, "static stiffness," increased upon stimulation following a time course well distinct from tension and roughly similar to intracellular Ca(2+) concentration. In the experiments reported here, we investigated the possible role of Ca(2+) in static stiffness by comparing static stiffness measurements in the presence of Ca(2+) release inhibitors (D600, Dantrolene, (2)H(2)O) and cross-bridge formation inhibitors [2,3-butanedione monoxime (BDM), hypertonicity]. Both series of agents inhibited tension; however, only D600, Dantrolene, and (2)H(2)O decreased at the same time static stiffness, whereas BDM and hypertonicity left static stiffness unaltered. These results indicate that Ca(2+), in addition to promoting cross-bridge formation, increases the stiffness of an (unidentified) elastic structure of the sarcomere. This stiffness increase may help in maintaining the sarcomere length uniformity under conditions of instability.

Frequency-dependent distortion of meridional intensity changes during sinusoidal length oscillations of activated skeletal muscle.

Bundles of intact, tetanized skeletal muscle fibers from Rana temporaria were subjected to sinusoidal length oscillations in the frequency domain 100 Hz to 3 kHz while measuring force and sarcomere length. Simultaneously, intensity of the third-order x-ray reflection of the axial myosin unit cell (I(M3)) was measured using synchrotron radiation. At oscillation frequencies <1 kHz, I(M3) was distorted during the shortening phase of the sinusoid (i.e., where bundle length was less than rest length). Otherwise, during the stretch phase of oscillations at all frequencies, during the shortening phase of oscillations above 1 kHz, and for bundles in the rigor state, I(M3) was approximately sinusoidal in form. Mean I(M3) during oscillations was reduced by 20% compared to the isometric value, suggesting a possible change in S1 disposition during oscillations. However, the amplitude of length change required to produce distortion (estimated from the phase angle at which distortion was first evident) corresponded to that of a step release sufficient to reach the maximum I(M3), indicating a mean S1 disposition during oscillations close to that during an isometric tetanus. The mechanical properties of the bundle during oscillations were also consistent with an unaltered S1 disposition during oscillations.

Effect of long-term oral administration of an immunostimulant diet on innate immunity in sea bass (Dicentrarchus labrax).

Immunostimulants represent a modern and promising tool in aquaculture, enhancing the resistance of cultured fish to disease and stress. This study investigated the effect of a combination of dietary glucans, alpha-tocopherol and ascorbic acid on the innate immune response of cultured sea bass (Dicentrarchus labrax). After 5 weeks of adaptation on a commercial diet containing 100 p.p.m. ascorbic acid and 200 p.p.m. alpha-tocopherol, sea bass were switched to a diet supplemented with 2% beta-1.3/beta-1.6 glucans and ascorbic acid and alpha-tocopherol at 500 p.p.m. The supplemented diet was given at 2% of body weight per day over a 2-week period, every 3 months. Plasma lysozyme concentration, content and distribution of major plasma proteins and complement activity were measured prior to feeding the supplemented diet and after 40 weeks. Alternative pathways of complement activation and lysozyme activity were both significantly enhanced in fish fed on glucans and elevated doses of vitamins. No significant differences were observed in protein content or in albumin/globulin ratio. Compared to lysozyme activity, which showed marked individual variation, complement-mediated haemolytic activity has been shown to be a more reliable indicator of sea bass immunocompetence. Further studies are in progress to clarify the effect of each dietary component on the innate immune response and disease resistance.

Crossbridge kinetics in single frog muscle fibres in presence of ethylene glycol.

Single fibres isolated from frog muscle were tetanically stimulated at 14 degrees C to produce isometric tetani at a sarcomere length of about 2.16 microm, using a striation follower device to measure the sarcomere length of a selected segment of fibre. Force-velocity data were obtained by applying ramp releases at pre-set velocity at the tetanus plateau. Sarcomere stiffness was measured at isometric plateau and during isotonic shortening by using sinusoidal length changes at 2 kHz frequency and about 1 nm per half sarcomere (hs) peak to peak amplitude. A correction method was used to compensate for the force truncation due to the quick recovery. After data collection, the bathing solution was substituted with Ringer plus ethylene glycol (EG) at 2 M (11.2% v/v). When the fibre was fully equilibrated with the new solution, the measurements were repeated. Ethylene glycol reduced the speed of the tetanus rise and tetanus relaxation without altering the isometric tension, and reduced the maximum shortening velocity by about 20%. During isotonic contraction tension and stiffness at each given shortening velocity were reduced by about the same amount, so that the stiffness/tension ratio remained almost unaltered. Force-velocity and stiffness data in both standard and EG Ringer were analysed in terms of a two state model (Huxley, 1957). The analysis showed that our results can be accounted for by assuming that EG at 2 M concentration reduces all the rate constants for crossbridges interaction by about the same amount.