Microcirculation in the upper trapezius muscle during varying levels of static contraction,fatigue and recovery in healthy women —a study using percutaneous laser-Doppler flowmetry and surface electromyography

Summary Microcirculation in the upper portion of the trapezius muscle was measured percutaneously by continuous laser-Doppler flowmetry (LDF) during two 10-min series of alternating 1-min periods of static contraction and rest determined electromyographically (EMG). Stepwise increased contraction was induced by keeping the arms straight and elevated at 30, 60, 90 and 135°, which was repeated with a 1-kg load carried in each hand. Thereafter, fatigue and recovery were recorded while the subject kept her arms straight and elevated at 45° carrying the 1-kg hand load as long as possible, followed by rest with arms hanging and no load. A group of 16 healthy women of different ages was studied. Signal processing was done on line using a 386 SX computer. The LDF- and root-mean-square (rms) EMG signals were normalized. Spectrum analyses of EMG mean power frequency (MPF) and median spectrum frequency were performed. The rms-EMG increased significantly with an increase in the calculated shoulder torque (r=0.75). Accumulated local fatigue was indicated by a decrease in MPF with increased shoulder angle and added load (r = –0.54). Blood flow increased with increased shoulder angle (r=0.82, with hand loadr=0.62) and with increased shoulder torque (r=0.72), and also showed a significant increase with increased EMG activity (r=0.74). The LDF showed a negative correlation to MPF (r= –0.67), with increased values when MPF was lowered. During the endurance test, a moderate increase of LDF occurred which reached its maximum during the 1st min of recovery. Then, a slow return to the base level was recorded. The ability to increase the flow in the microcirculation with increasing muscle load was not diminished with age.     

Analogue simulator of e.e.g. signals based on spectral components

A model describing the spectral properties of e.e.g signals by a set of parameters has previously been introduced. It leads to a decomposition of the spectrum into one or more spectral components. The described e.e.g.-signal simulator is based on such a decomposition into one delta, and three rhythmic components called theta, alpha and beta denoting the location of the resonance peaks. Each component is generated separately with a noise generator and a spectral shaping filter. Care is taken to make the noise generator have a flat spectrum down to zero frequency. The spectral shaping filters are of an active type with a configuration that allows easy adjustment of poles and zeros. The use of the equipment is demonstrated by simulating five different e.e.g. signals first by analysing the e.e.g., and then by setting the simulator to produce an identical spectrum.     

Optimal heparin surface concentration and antithrombin binding capacity as evaluated with human non-anticoagulated blood in vitro

Contact between blood and a biomaterial surface takes place in many applications and is known to activate the coagulation and complement systems. Heparin surface coatings have been shown to reduce blood activation upon contact with artificial surfaces. To establish the optimal heparin surface concentration, blood was incubated in a tubing loop model at 37 degrees C. The tubing was coated with different surface concentrations of heparin and rotated at three different velocities. We demonstrate that the blood compatibility of a surface with regard to coagulation, complement, and platelet activation can be improved by increasing the heparin surface concentration in the 6-12 pmol antithrombin/cm2 concentration interval. The binding of factor H is not influenced by the increased heparin surface concentration, suggesting that this factor is not the primary regulator of complement on heparin surfaces. In addition, the heparin coating has no effect on the complement activation that occurs on gas surfaces in extracorporeal circuits.     

Neuropeptide Y- and alpha-adrenergic receptors in pig spleen: localization, binding characteristics, cyclic AMP effects and functional responses in control and denervated animals

The localization of neuropeptide Y binding sites in the pig spleen, as revealed by [125I]Bolton-Hunter-labelled porcine neuropeptide Y and alpha 1-adrenergic receptor binding sites, as revealed by [125I](2-beta/4-hydroxy-phenyl/-ethylaminomethyl)-tetralone as radioligand, was compared with the distribution of neuropeptide Y and noradrenaline nerves, the latter revealed by tyrosine hydroxylase and dopamine-beta-hydroxylase, using immunohistochemistry. A large degree of codistribution was obtained between [125I]neuropeptide Y and alpha 1-binding sites in the capsule, trabeculae, blood vessels and the red pulp of the spleen. Neuropeptide Y and tyrosine hydroxylase as well as dopamine-beta-hydroxylase-positive nerves were identical in the spleen and had a similar gross distribution pattern as the [125I]neuropeptide Y and alpha 1 binding sites. In functional studies using the isolated blood-perfused spleen from pentobarbital-anaesthetized pigs, neuropeptide Y, noradrenaline and the alpha 1-selective agonist phenylephrine contracted the capsule and induced vasoconstriction in the spleen in vivo. However, the selective alpha 2-adrenoceptor agonists clonidine and azepexole had no effects on blood flow or perfusion pressure, suggesting that postjunctional alpha-receptors were of the alpha 1 type. Neuropeptide Y inhibited the forskolin-evoked, cyclic adenosine monophosphate formation in vitro. The [125I]neuropeptide Y binding, with an equilibrium-dissociation constant of 503 +/- 73 pM and a maximal number of specific binding sites of 23 +/- 3 fmol/mg protein, the neuropeptide Y-induced perfusion-pressure increase in vivo and the inhibition of forskolin-evoked cyclic adenosine monophosphate formation in vitro were dependent on the amidation of the C-terminal portion of the peptide molecule. Furthermore, the effects of neuropeptide Y were not changed by alpha- and beta-adrenoceptor blockade using prazosin and propranolol. Two weeks after postganglionic denervation the neuropeptide Y and the noradrenaline contents of the pig spleen were reduced by 97% and 99%, respectively. These changes were associated with a selective supersensitivity for the noradrenaline-induced perfusion-pressure increase in vivo compared with the effect of neuropeptide Y. However, a similar potentiation of the noradrenaline effect was induced by the monoamine-uptake blocker desipramine in the absence of denervation, and there was no change in the functional response to phenylephrine after denervation.(ABSTRACT TRUNCATED AT 400 WORDS)     

Anxiolytic effects of intra-amygdaloid injection of the D1 antagonist SCH23390 in the rat

The intercalated islands are intra-amigdaloid clusters of D1 receptor rich GABAergic neurons, which control impulse traffic between the basolateral complex and the central nucleus of the amygdala. As dopaminergic transmission within the amygdala may play a role in anxiety, the effect of the D1 antagonist SCH23390 microinjected mainly close to the rostral intercalated islands in rats was studied, using the White and Black Box test. SCH23390 reduced anxiety by an increase in the latency of the first entry into the black compartment and by an increase in the total time spent in the white compartment of the White and Black Box test, while there was no significant modification of locomotion. It is suggested that blockade of D1 receptors in the rostral intercalated islands may reduce anxiety through a reduction of GABA-mediated dishinibition of the central amygdaloid nucleus.     

Coagulation and complement activation

The purpose of this investigation was to assess the effect of heparin coating of a new stent construction (Stent Graft, Jomed Implantate GmbH, Germany) on platelet and coagulation activity. METHODS: Stent grafts with an ePTFE membrane interfoliated between two stents were deployed in tubings to form Chandler loops. Fresh human blood with a low concentration of heparin was rotated for 1 h, then collected and used for measurements of platelet number, thrombin-antithrombin complex (TAT), CD11b, C3a and C5b-9. There were five study groups: Group 1, conventional unmodified stents (n = 8); Group 2, untreated stent grafts (n = 8); Group 3, heparin-coated stents and untreated membrane (n = 7); Group 4, heparin-coated stents and membrane (n = 8); Group 5, heparin-coated PVC tubings with no stents (n = 8). RESULTS: There was a significant drop in platelet count, increase in TAT-values and CD11b expression in Groups 1-3 but not in Group 4 compared to Group 5. Examination by scanning electron microscopy revealed extensive activation on non-modified stents but almost no deposition of thrombotic material on heparin-modified stent grafts. CONCLUSIONS: With unmodified stents and membrane there were signs of significant activation of platelets and coagulation. In contrast, the heparin-coated stent graft induced much less alterations, indicating improved blood compatibility.     

Efficiency of cross presentation of vaccinia virus-derived antigens by human dendritic cells.

Dendritic cells (DC) utilize at least two pathways to process viral antigens onto MHC class I molecules. The conventional endogenous route is used to acquire antigens from both infectious and non-replicating virions. Exogenous pathways are used by DC to acquire and "cross-present" antigens derived from virus-infected donor cells that by themselves lack the ability to activate T cells directly. We analyzed the role of this pathway for antigens derived from vaccinia, a virus which inhibits DC maturation and causes extensive apoptosis of infected cells, yet is highly immunogenic. Using recombinant vaccinia virus encoding the influenza matrix protein as model vector, DC were shown to cross-present vaccinia-derived antigens from both apoptotic and necrotic infected cells to antigen-specific CD8(+) T cells. Efficient cross presentation required uptake of dead cells by immature DC and exposure to maturation stimuli, especially CD40 ligand. The responding CD8(+) T cells secreted IL-2 and IFN-gamma, proliferated and developed into cytotoxic effectors. Quantification of the cross presentation of vaccinia-derived antigens showed this pathway to be highly efficient, corresponding to a peptide pulse of 10-100 nM. While monocytes also phagocytosed apoptotic and necrotic cells, they were far less efficient at cross-presenting vaccinia-derived antigens to CD8(+) T cells. The ability of DC to cross-present vaccinia-derived antigens from infected apoptotic cells or necrotic cell lysates, bypasses the deleterious effects of direct infection of DC and provides one explanation for this pathogen's immunogenicity.     

Exposure to Organic Dust Causes Activation of Human Plasma Complement Factors C3 and B and the Synthesis of Factor C3 by Lung Epithelial Cells <Emphasis Type="Italic">In Vitro</Emphasis>

Exposure in swine confinement buildings induces an intense airway inflammation. Twenty-two volunteers, of whom eleven wore a half-mask, were exposed for 3 hr in a swine barn. Blood samples were drawn before and after exposure. The ratio C3b/totalC3 in plasma decreased from 6.8 to 5.0% (p = 0.02) without mask and from 6.6 to 5.9% (p = 0.01) with mask (p = 0.67 between groups). The ratio Bb/totalB decreased from 14.5 to 13.5% (p < 0.01) without and 14.6–13.3% (p = 0.09) with mask (p = 0.25 between groups). Epithelial cells (A549) incubated up to 24 hr with 0.1 mg/mL dust suspensions were analysed for C3, IL-6 and IL-8 secretion. Cumulative C3 synthesis of dust stimulated cell cultures was 43,000 pg/mL compared to 25,000 pg/mL in unstimulated cells. Cumulative dust-induced IL-6 and IL-8 secretion was 200 and 3000 pg/mL, respectively and below detection in unstimulated cells.The activation of complement in vivo and induced C3 synthesis by epithelial cells suggests a role of complement in the airway reaction to organic dust exposure.     

Desensitization of acetylcholine induced inositol 1,4,5-trisphosphate formation in neuroblastoma SH-SY5Y cells following repetitive acetylcholine stimulations

In this study, the desensitization of acetylcholine-induced inositol 1,4,5-trisphosphate [I(1,4,5)P₃] formation, upon short-time prestimulations, was investigated in cultures of human neuroblastoma SH-SY5Y cells. Four repeated stimulations for 10 seconds with 10 μM acetylcholine were necessary to induce a desensitization of the I(1,4,5)P₃ formation. The desensitization was observed 4 hours after the initiation of repetitive stimulations. The same effect was obtained by a single prestimulation with 1 mM acetylcholine. Preincubation of the cells with phorbol 12-myristate 13-acetate (PMA) markedly down-regulated the acetylcholine-induced I(1,4,5)P₃ formation. However, the protein kinase C (PKC) inhibitors H7 and staurosporine did not influence the desensitization induced by four repeated stimulations with 20 μM acetylcholine. These results indicate that the signal transduction can be desensitized following repeated stimulations with sub-maximal concentrations of receptor agonist and although activation of PKC can induce the same down-regulation, PKC is most likely not involved in the desensitization induced by repetitive acetylcholine-stimulations.