Torque-EMG-velocity relationship in female workers with chronic neck muscle pain

The present study investigated the effect of chronic neck muscle pain (defined as trapezius myalgia) on neck/shoulder muscle function during concentric, eccentric and static contraction. Forty-two female office workers with trapezius myalgia (MYA) and 20 healthy matched controls (CON) participated. Isokinetic (-60, 60 and 180 degrees s(-1)) and static maximal voluntary shoulder abductions were performed in a Biodex dynamometer, and electromyography (EMG) obtained in the trapezius and deltoideus muscles. Muscle thickness in the trapezius was measured with ultrasound. Pain and perceived exertion were registered before and after the dynamometer test. The main findings were that shoulder abduction torque (at -60 and 60 degrees s(-1)) and trapezius EMG amplitude (at -60, 0 and 60 degrees s(-1)) were significantly lower in MYA compared with CON (p<0.001-0.05). Deltoideus EMG and trapezius muscle thickness were not significantly different between the groups. While perceived exertion increased in both groups in response to the test (p<0.0001), pain increased in MYA only (p<0.0001). In conclusion, having trapezius myalgia was associated with decreased strength capacity and lowered activity of the painful trapezius muscle. The most consistent differences-in terms of both torque and EMG-were found during slow concentric and eccentric contractions. Activity of the synergistic pain free deltoideus muscle was not significantly lower, indicating specific inhibitory feedback of the painful trapezius muscle only. Parallel increase in pain and perceived exertion among MYA were observed in response to the maximal contractions, emphasizing that heavy physical exertion provokes pain increase only in conditions of myalgia.     

Mobilisation of stored calcium in the neck region of human sperm--a mechanism for regulation of flagellar activity

Calcium signalling plays a pivotal role in sperm physiology, being intimately involved in the regulation of acrosome reaction, chemotaxis and hyperactivation. Here we describe briefly the mechanisms of calcium regulation in somatic cells and the ways in which these mechanisms have been adapted to function in mature spermatozoa. We then consider recent data from this and other laboratories on the responses of sperm to three compounds: progesterone and nitric oxide (both products of the cumulus oophorus) and 4-aminopyridine. All of these compounds induce calcium signals in the posterior sperm head and neck region and, when applied at appropriate concentrations, modify flagellar activity, causing asymmetric bending of the proximal flagellum. We argue that these effects reflect a common mode of action, mobilisation of calcium stored in the sperm neck region. Finally we consider the nature of calcium signalling pathways in sperm. We suggest that this highly specialised and extremely polarised cell, though working with the same calcium signalling 'tools' as those of somatic cells, employs them to generate unusually 'hard-wired' calcium signals that do not act to integrate stimuli. 'Leakage' between these calcium signalling pathways will generate inappropriate responses, compromising functioning of the cell.     

Deuterium isotope effect of proton pumping in cytochrome c oxidase

In mitochondria and many aerobic bacteria cytochrome c oxidase is the terminal enzyme of the respiratory chain where it catalyses the reduction of oxygen to water. The free energy released in this process is used to translocate (pump) protons across the membrane such that each electron transfer to the catalytic site is accompanied by proton pumping. To investigate the mechanism of electron-proton coupling in cytochrome c oxidase we have studied the pH-dependence of the kinetic deuterium isotope effect of specific reaction steps associated with proton transfer in wild-type and structural variants of cytochrome c oxidases in which amino-acid residues in proton-transfer pathways have been modified. In addition, we have solved the structure of one of these mutant enzymes, where a key component of the proton-transfer machinery, Glu286, was modified to an Asp. The results indicate that the P3-->F3 transition rate is determined by a direct proton-transfer event to the catalytic site. In contrast, the rate of the F3-->O4 transition, which involves simultaneous electron transfer to the catalytic site and is characteristic of any transition during CytcO turnover, is determined by two events with similar rates and different kinetic isotope effects. These reaction steps involve transfer of protons, that are pumped, via a segment of the protein including Glu286 and Arg481.     

Changes in the decomposer community when converting spruce monocultures to mixed spruce/beech stands

The impact of the admixture of beech in spruce monocultures on structure and function of the decomposer community was studies in the Ore mountains (Saxony, Germany) on Dystric Cambisols between 2000 and 2002. The study sites represented four stages of forest conversion from a mature spruce stand to a mature spruce/beech stand. There, the functional profile of the nematodes, enchytraeids, lumbricids, and dipterans was analysed on the basis of ecological guilds, and their metabolic equivalences were calculated to characterize the decomposition potential of the invertebrate decomposer community. Because of the acidic parent soil the coenoses at all study sites were dominated by the enchytraeids with increasing importance of lumbricids and dipterans in progress of forest conversion. Gradual changes with rising coverage of beech culminated in intense differences of entire biomasses and metabolic equivalences between the mature stands, indicating a higher decomposition potential of the invertebrate decomposer community by the admixture of beeches in spruce forests. The quality of the beech litter is likely to be the important factors for these changes. To prove this assumption further investigations of the saprovore food chain are necessary, taking microbial parameters into account.     

Effects of Ca- and Na-lignosulfonate on starch gelatinization and network formation

The interaction of lignosulfonates with starches was examined by microscopy and viscosity measurements. 8% starch dispersions with Ca- or Na-lignosulfonate, or with only Ca²⁺ or Na⁺, were heated to 97 °C and cooled to 50 °C in a Brabender Viscograph, the gelatinization was followed by light microscopy and image analysis, and the gel network formed after cooling to 4 °C was studied under the transmission electron microscope.

The lignosulfonates (2%) delayed the initial granule swelling in all starches (native maize, waxy maize and waxy barley). The presence of ions enhanced amylose leakage resulting in lower peak viscosity. The viscosity during cooling increased more with Ca-LS than with Na-LS. With a low lignosulfonate concentration the network formed after cooling was homogeneous with fine strands. With Na-lignosulfonate, as well as with Na⁺, the network connectivity deteriorated and spherical aggregates formed. Ca-lignosulfonate induced a network with thick strands, but with Ca²⁺ the strands became thinner.     

Microbially induced sedimentary structures indicating climatological, Hydrological and depositional conditions within recent and pleistocene coastal facies zones (Southern Tunisia)

Summary Extensive tidal areas of the Recent coast of southern Tunisia are overgrown by microbial mats. Different mat types of which each are dominated by distinct and well adapted cyanobacterial species develop. Ecological response of the mat-forming microorganisms to climatological hydrological and sedimentological factors produce characteristic sedimentary structures (=microbially induced sedimentary structures). A suecession of Pleistocene rocks crops out near the lagoon El Bibane, southern Tunisia. The stratigraphic section comprises structures that we regard as fossil equivalents to those microbially induced structures we observe in the Recent coastal area. Preservation of the structures is result of lithification of the microbial mats. This we conclude from fossil filaments of cyanobacteria visible within the rock matrix. The Recent microbially induced sedimentary structures indicate facies zones within the modern tidal environment. Comparison of the Recent structures with the fossil analogues recorded in the stratigraphic section aids to identify the same distinct facies zones within the Pleistocene coastal environment also. Erosion by water currents forms step-like cliffs, and the microbial mat is undermined and ripped off piece by piece. shallows within the supratidal area are overgrown by copious microbial mats comprising structures like biolaminites and—varvites, as well as polygons of cracks. The features originate from effects triggered by seasonal variations of climate. Tufts and reticulate pattern of bulges indicate supernatant water films covering the mat surfaces. Morphologically higher parts of the Recent tidal area are overgrown by single-layered mats forming petees, induced by microbial mat growth and evaporitive pumping. The study demonstrates that microbially induced sedimentary structures can be used to reconstruct small-scaled facies zones within coastal environments. The also include hints on paleoclimatological, hydrological and sedimentological conditions.     

Physiological regulation of plant-atmosphere ammonia exchange

Plants have a compensation point for NH₃ which ranges from 0.1 to 20 nmol mol^-1, and may be several-fold higher or lower than naturally occurring atmospheric NH₃ concentrations. This implies that NH₃ fluxes over vegetated surfaces are bi-directional and that ammonia exchange with the atmosphere in many cases contributes significantly to the nitrogen economy of vegetation. Physiological regulation of plant–atmosphere NH₃ fluxes is mediated via processes involved in nitrogen uptake, transport and metabolism. A rapid turnover of NH₃ ⁺ in plant leaves leads to the establishment of a finite NH₃ ⁺ concentration in the leaf apoplastic solution. This concentration determines, together with that of H⁺, the size of the NH₃ compensation point. Barley and oilseed rape plants with access to NH₃ ⁺ in the root medium have higher apoplastic NH₃ ⁺ concentrations than plants absorbing NO₃ ^-. Furthermore, the apoplastic NH₃ ⁺ concentration increases with the external NH₃ ⁺ concentration. Inhibition of GS leads to a rapid and substantial increase in apoplastic NH₃ ⁺ and barley mutants with reduced GS activity have higher apoplastic NH₃ ⁺ than wild-type plants. Increasing rates of photorespiration do not affect the steady-state NH₃ ⁺ or H⁺ concentration in tissue or apoplast of oilseed rape, indicating that the NH₃ ⁺ produced is assimilated efficiently. Nevertheless, NH₃ emission increases due to a temperature-mediated displacement of the chemical equilibrium between gaseous and aqueous NH₃ in the apoplast. Sugarbeet plants grown with NO₃ ^- seem to be temporarily C-limited in the light due to a repression of respiration. As a consequence, the activity of chloroplastic GS declines during the day causing a major part of NH₃ ⁺ liberated in photorespiration to be assimilated during darkness when 2-oxoglutarate is supplied in high rates by respiration. This revised version was published online in June 2006 with corrections to the Cover Date.     

Effect of pre-treatment with ethanolamine on the response of Helianthus annuus L. to salt stress

The accumulation of compatible solutes is one of the strategies that plants have developed to tolerate salt stress. Proline and betaine are the main metabolites that accumulate in various species of higher plants in response to salt stress. In Helianthus annuus L., pre-treatment of seeds with ethanolamine led to enhanced seedling tolerance to conditions of saline stress during germination, as evidenced by the greater growth of pretreated seedlings (EAS group) versus untreated seedlings (S group), evaluated through such parameters as length, water and chlorophyll content. During the germination period, a considerable increase was observed in proline levels (up to 300%) in seedlings subjected to saline stress, whereas in the EAS group, the proline increment was much smaller (20%). Starting from the fourth day of germination, betaine levels in seedlings pretreated with ethanolamine and then with water (EAW group) and in EAS showed a significant increase versus C (control) and S seedlings, possibly because such a precursor promotes betaine biosynthesis. This could be responsible for the enhanced growth observed in EAS versus S seedlings, as well as for preventing the decrease in chlorophyll content in the EAS group. The accumulation of betaine seems to correlate with the greater tolerance of these seedlings against stress induced by sodium chloride.