The relationship between isometric force-time curve characteristics and club head speed in recreational golfers

ABSTRACT: Leary, BK, Statler, J, Hopkins, B, Fitzwater, R, Kesling, T, Lyon, J, Phillips, B, Bryner, RW, Cormie, P, and Haff, GG. The relationship between isometric force-time curve characteristics and club head speed in recreational golfers. J Strength Cond Res 26(10): 2685-2697, 2012-The primary purpose of the present investigation was to examine the relationships between club head speed, isometric midthigh pull performance, and vertical jump performance in a cohort of recreational golfers. Twelve recreational golfers (age, 20.4 ± 1.0 years; weight, 77.0 ± 9.8 kg; height, 177.8 ± 6.3 cm; body fat, 17.1 ± 7.6%; handicap, 14.5 ± 7.3; experience, 8.9 ± 3.6 years) completed 3 testing sessions: (a) familiarization session and body composition measurements; (b) measurement of force-time curves in the isometric midthigh pull, countermovement, and static vertical jump (SJ); and (c) measurement of club head speed. During sessions 1 and 2, subjects performed 5 countermovement jumps, 5 SJ, and 2 isometric midthigh pulls. Isometric peak force was measured at 30, 50, 90, 100, 200, and 250 milliseconds. Rate of force development was measured among 0-30, 0-50, 0-90, 0-100, 0-200, and 0-250 milliseconds. Peak rate of force development was determined as the highest value in a 10-millisecond sampling windows. During session 3, subjects performed 10 maximal golf swings with a driver to measure club head speed; peak and average club head speed were analyzed across the 10 swings. Golf handicap was moderately correlated with average (r = -0.52, p = 0.04) and maximal club head speed (r = -0.45, p = 0.07). Force at 150 milliseconds during the isomeric midthigh pull test was moderately correlated with average (r = 0.46, p = 0.07) and maximal club head speed (r = 0.47, p = 0.06). Moderate correlations were also found between the rate of force development from 0 to 150 milliseconds and average (r = 0.38, p = 0.11) and maximal club head speed (r = 0.36, p = 0.12). The present findings suggest that the ability to exhibit high ground reaction forces in time frames <200 milliseconds are related to high club head speeds.     

YphC and YsxC GTPases assist the maturation of the central protuberance,GTPase associated region and functional core of the 50S ribosomal subunit

YphC and YsxC are GTPases in Bacillus subtilis that facilitate the assembly of the 50S ribosomal subunit, however their roles in this process are still uncharacterized. To explore their function, we used strains in which the only copy of the yphC or ysxC genes were under the control of an inducible promoter. Under depletion conditions, they accumulated incomplete ribosomal subunits that we named 45S_YphC and 44.5S_YsxC particles. Quantitative mass spectrometry analysis and the 5–6 Å resolution cryo-EM maps of the 45S_YphC and 44.5S_YsxC particles revealed that the two GTPases participate in the maturation of the central protuberance, GTPase associated region and key RNA helices in the A, P and E functional sites of the 50S subunit. We observed that YphC and YsxC bind specifically to the two immature particles, suggesting that they represent either on-pathway intermediates or that their structure has not significantly diverged from that of the actual substrate. These results describe the nature of these immature particles, a widely used tool to study the assembly process of the ribosome. They also provide the first insights into the function of YphC and YsxC in 50S subunit assembly and are consistent with this process occurring through multiple parallel pathways, as it has been described for the 30S subunit.     

Nitrogen deposition enhances moss growth,but leads to an overall decline in habitat condition of mountain moss‐sedge heath

Ecosystems are subject to multiple, natural and anthropogenic environmental influences, including nitrogen (N) deposition, land use and climate. Assessment of the relative importance of these influences on biodiversity and ecosystem functioning is crucial for guiding policy and management decisions to mitigate global change; yet, few studies consider multiple drivers. In the UK, ongoing loss of the internationally important arctic/alpine moss‐sedge community, Racomitrium heath, has been linked to elevated N deposition, high grazing pressures and their combination; however, the relative importance of these drivers remains unclear. We used environmental gradients across the habitat's European distribution (UK, Faroes, Norway and Iceland) to investigate the relative impact of N deposition and grazing pressure, as well as climate, on the condition of the dominant moss species, Racomitrium lanuginosum. Key variables including tissue chemistry, growth and cover were measured at 36 sites, and multiple linear regressions were used to examine the relative importance of the drivers across sites. Our results clearly show that regional variation in the condition of R. lanuginosum across Europe is primarily associated with the impacts of N deposition, with climate (air temperature) and grazing pressure playing secondary roles. In contrast to previous experimental studies, we found moss growth to be stimulated by elevated N deposition; this apparent discrepancy may result from the use of artificially high N concentrations in many experiments. Despite increased growth rates, we found that moss mat depth and cover declined in response to N deposition. Our results suggest that this is due to increased decomposition of material in the moss mat, which ultimately leads to loss of moss cover and habitat degradation. This study clearly demonstrates both the key role of N deposition in degradation of Racomitrium heath and the importance of observational studies along natural gradients for testing predictions from experimental studies in the real world.     

The impact of asymptomatic helminth co-infection in patients with newly diagnosed tuberculosis in north-west ethiopia

Background

Areas endemic of helminth infection, tuberculosis (TB) and HIV are to a large extent overlapping. The aim of this study was to assess the impact of asymptomatic helminth infection on the immunological response among TB patients with and without HIV, their house hold contacts and community controls.

Methodology

Consecutive smear positive TB patients (n = 112), their household contacts (n = 71) and community controls (n = 112) were recruited in Gondar town, Ethiopia. Stool microscopy, HIV serology, serum IgE level, eosinophil and CD4 counts were performed and tuberculosis patients were followed up for 3 months after initiation of anti-TB treatment.

Results

Helminth co-infection rate was 29% in TB patients and 21% in both community control and household contacts (p = 0.3) where Ascaris lumbricoides was the most prevalent parasite. In TB patients the seroprevalence of HIV was 47% (53/112). Eosinophilia and elevated IgE level were significantly associated with asymptomatic helminth infection. During TB treatment, the worm infection rate of HIV+/TB patients declined from 31% (10/32) at week 0 to 9% (3/32) at week 2 of TB treatment, whereas HIV−/TB patients showed no change from baseline to week 2, 29% (13/45) vs. 22.2% (10/45). This trend was stable at week 8 and 12 as well.

Conclusion

One third of smear positive TB patients were infected with helminths. Eosinophilia and elevated IgE level correlated with asymptomatic worm infection, indicating an effect on host immunity. The rate of worm infection declined during TB treatment in HIV+/TB co-infected patients whereas no decline was seen in HIV−/TB group.     

The cellular production of hydrogen peroxide

1. The enzyme–substrate complex of yeast cytochrome c peroxidase is used as a sensitive, specific and accurate spectrophotometric H₂O₂ indicator. 2. The cytochrome c peroxidase assay is suitable for use with subcellular fractions from tissue homogenates as well as with pure enzyme systems to measure H₂O₂ generation. 3. Mitochondrial substrates entering the respiratory chain on the substrate side of the antimycin A-sensitive site support the mitochondrial generation of H₂O₂. Succinate, the most effective substrate, yields H₂O₂ at a rate of 0.5nmol/min per mg of protein in state 4. H₂O₂ generation is decreased in the state 4→state 3 transition. 4. In the combined mitochondrial–peroxisomal fraction of rat liver the changes in the mitochondrial generation of H₂O₂ modulated by substrate, ADP and antimycin A are followed by parallel changes in the saturation of the intraperoxisomal catalase intermediate. 5. Peroxisomes supplemented with uric acid generate extraperoxisomal H₂O₂ at a rate (8.6–16.4nmol/min per mg of protein) that corresponds to 42–61% of the rate of uric acid oxidation. Addition of azide increases these H₂O₂ rates by a factor of 1.4–1.7. 6. The concentration of cytosolic uric acid is shown to vary during the isolation of the cellular fractions. 7. Microsomal fractions produce H₂O₂ (up to 1.7nmol/min per mg of protein) at a ratio of 0.71–0.86mol of H₂O₂/mol of NADP⁺ during the oxidation of NADPH. H₂O₂ is also generated (6–25%) during the microsomal oxidation of NADH (0.06–0.025mol of H₂O₂/mol of NAD⁺). 8. Estimation of the rates of production of H₂O₂ under physiological conditions can be made on the basis of the rates with the isolated fractions. The tentative value of 90nmol of H₂O₂/min per g of liver at 22°C serves as a crude approximation to evaluate the biochemical impact of H₂O₂ on cellular metabolism.     

Incorporation von [D-4,5-3H]-Ieucine und [2-14C]-Acetat in die photosynthetischen Pigmente und Chinone von Chlorella pyrenoidosa

Der Metabolismus der photosynthetischen Pigmente und Chinone von Chlorella wurde mit Hilfe von ¹⁴CO₂, [2-¹⁴C]-Acetat und [D-4,5-³H]-Leucin als Vorstufen der Isoprenoidsynthese untersucht. Auch wurde untersucht, ob Leucin als Vorstufe in der Biosynthese der Terpenoide fungiert. Die Verwendung der Doppelmarkierung sollte bestehende Unterschiede in der Regulation und Biosynthese der Isoprenoide der Chloroplasten, Mitochondrien und des Zytoplasmas aufdecken. Neben der Verwendung von Radioisotopen wurde die Inkorporation von Deuterium in die Carotinoide verwendet, um den turnover der Prenyl-Lipide direkt nachzuweisen. In tracer-kinetischen Untersuchungen mit ¹⁴CO₂ konnte gezeigt werden, daß ¹⁴-C-α-Carotin zu ¹⁴C-Lutein und ¹⁴C-ß-Carotin zu ¹⁴C-Zeaxanthin umgesetzt wird. Eine Vorstufenfunktion läßt sich auch für Plastohydrochinon-9 nachweisen, das in Plastochinon-9 umgesetzt wird. Die Markierungskinetik der einzelnen Prenyl-Lipide deutet auf einen schnellen turnover hin. Anhand der ¹⁴C-Inkorporationskinetik wurden Halbwertszeiten im Bereich von 30 min bis 220 min ermittelt, während sich aus den Dekorporationskinetiken Zeiten von 9 bis 113 h ergeben. Prenyl-Lipide wie die Carotine, Chlorophyll a und Plastochinon-9, die einerseits Vorstufenfunktion besitzen, andererseits aber auch direkt an der Photosynthese beteiligt sind, werden schneller umgesetzt als ihre Folgeprodukte. Somit scheint ein direkter Zusammenhang zwischen der Funktion des Prenyl-Lipides im Chloroplasten und seinem Umsatz zu bestehen. Sowohl Acetat wie auch Leucin werden von Chlorella als Vorstufen in der Terpenoidbiosynthese verwendet. Acetat wird aber wesentlich schneller inkorporiert als Leucin, was vielleicht darauf zurückzuführen ist, daß Leucin im Zytoplasma zu Acetat oder Mevalonsäure metabolisiert wird und dann in den Chloroplasten gelangt. Auch im tracer-kinetischen Experiment mit ¹⁴C-Acetat und ³H-Leucin läßt sich eine Vorstufen-Produkt-Beziehung für die Chlorophylle, Carotinoide und Chinone zeigen. Im Vergleich zu den Experimenten mit ¹⁴CO₂ zeigen die tracer-kinetischen Experimente mit ¹⁴C-Acetat und ³H-Leucin, daß die Chloroplasten-Isoprenoide wesentlich langsamer metabolisiert werden und ihre Umsatzraten mehr jenen entsprechen, die aus den ¹⁴C-Dekorporationskinetiken des ¹⁴CO₂-Experimentes resultieren. Es zeigt sich aber auch hier, daß jene Prenyl-Lipide, die direkt an der Photosynthese beteiligt sind, schneller metabolisiert werden. Daß die Chloroplasten-Isoprenoide in autotroph kultivierten Chlorellen einem ständigen turnover unterliegen, läßt sich auch sehr eindrucksvoll mit Hilfe der Deuterium-Inkorporation für die Carotine zeigen. Die aus der Deuterium-Inkorporation erhaltenen Umsätze der Carotine entsprechen in etwa denen, die sich aus ihrer Dekorporationskinetik im tracer-kinetischen Experiment mit [2-¹⁴C]-Acetat und [D-4,5-³H]-Leucin ergeben, zeigen allerdings, daß a-Carotin wesentlich schneller umgesetzt wird als ß-Carotin. Die Untersuchungen wurden durch ein Stipendium der Deutschen Forschungsgemeinschaft im Austausch mit der British Royal Society an K.H.G. unterstützt, wofür wir uns bedanken.     

Mechanism of carbamoyl-phosphate synthetase. Binding of ATP by the rat-liver mitochondrial enzyme.

This paper demonstrates, by pulse-chase techniques, the binding to rat liver mitochondrial carbamoyl phosphate synthetase of the ATP molecule (ATPB) which transfers its gamma-phosphoryl group to carbamoyl phosphate. This bound APTB can react with NH3, HCO-3 and ATP (see below) to produce carbamoyl phosphate before it exchanges with free ATP. Mg2+ and N-acetylglutamate, but not NH3 or HCO-3, are required for this binding; the amount bound depends on the concentration of ATP (Kapp = 10--30 microns ATP) and the amount of enzyme. At saturation at least one ATPB molecule binds per enzyme dimer. Binding of ATPB follows a slow exponential time course (t1/2 8--16 s, 22 degrees C), independent of ATP concentration and little affected by NH3, NCO-3 or by incubation of the enzyme with unlabelled ATP prior to the pulse of [gamma-32P]ATP. Formation of carbamoyl phosphate from traces of NH3 and HCO-3 when the enzyme is incubated with ATP follows the kinetics expected if it were generated from the bound ATPB, indicating that the latter is a precursor of carbamoyl phosphate ('Cbm-P precursor') in the normal enzyme reaction. This indicates that the site for ATPB is usually inaccessible to ATP in solution but becomes accessible when the enzyme undergoes a periodical conformational change. Bound ATP becomes Cbm-P precursor when the enzyme reverts to the inaccessible conformation. Pulse-chase experiments in the absence of NH3 and HCO-3 (less than 0.2 mM) also demonstrate binding of ATPA (the molecule which yields Pi in the normal enzyme reaction), as shown by a 'burst' in 32Pi production. Therefore, (in accordance with our previous findings) both ATPA and ATPB can bind simultaneously to the enzyme and react with NH3 and HCO-3 in the chase solution before they can exchange with free ATP. However, at low ATP concentration (18 micron) in the pulse incubation, only ATPB binds since ATP is required in the chase (see above). Despite the presence of two ATP binding sites, the bifunctional inhibitor adenosine(5')pentaphospho(5')adenosine(Ap5A) fails to inhibit the enzyme significantly. A more detailed modification of the scheme previously published [Rubio, V. & Grisolia, S. (1977) Biochemistry, 16, 321--329] is proposed; it is suggested that ATPB gains access to the active centre when the products leave the enzyme and the active centre is in an accessible configuration. The transformation from accessible to inaccessible configuration appears to be part of the normal enzyme reaction and may represent to conformational change postulated by others from steady-state kinetics. The properties of the intermediates also indicate that hydrolysis of ATPA must be largely responsible for the HCO-3-dependent ATPase activity of the enzyme. The lack of inhibition of the enzyme by Ap5A indicates substantial differences between the Escherichia coli and the rat liver synthetase.     

Oxonol dyes as monitors of membrane potential. Their behavior in photosynthetic bacteria

The responses of oxonol dyes to single and multiple single turnovers of the photosynthetic apparatus of photosynthetic bacteria have been studied, and compared with the responses of the endogenous carotenoid pigments. The absorbance changes of the oxonols can be conveniently measured at 587 nm, because this is an isosbestic point in the ‘light-minus-dark’ difference spectrum of the chromatophores.The oxonols appear to respond to the light-induced ‘energization’ by shifting their absorption maxima. In the presence of K⁺, valinomycin abolished and nigericin enhanced such shifts, suggesting that the dyes respond to the light-induced membrane potential. Since the dyes are anions at neutral pH values, they probably distribute across the membrane in accordance with the potential, which is positive inside the chromatophores. The accumulation of dye, which is indicated by a decrease in the carotenoid bandshift, poises the dye-membrane equilibrium in favor of increased dye binding and this might be the cause of the spectral shift.The dye response has an apparent second-order rate constant of approx. 2 · 10⁶ M^?1 · s^?1 and so is always slower than the carotenoid bandshift. Thus the dyes cannot be used to monitor membrane potential on submillisecond timescales. Nevertheless, on a timescale of seconds the logarithm of the absorbance change at 587 nm is linear with respect to the membrane potential calibrated with the carotenoid bandshift. This suggests that under appropriate conditions the dyes can be used with confidence as indicators of membrane potential in energy-transducing membranes that do not posses intrinsic probes of potential.     

Structural maintenance of chromosomes protein of Bacillus subtilis affects supercoiling in vivo

Structural maintenance of chromosomes (SMC) proteins are found in nearly all organisms. Members of this protein family are involved in chromosome condensation and sister chromatid cohesion. Bacillus subtilis SMC protein (BsSMC) plays a role in chromosome organization and partitioning. To better understand the function of BsSMC, we studied the effects of an smc null mutation on DNA supercoiling in vivo. We found that an smc null mutant was hypersensitive to the DNA gyrase inhibitors coumermycin A1 and norfloxacin. Furthermore, depleting cells of topoisomerase I substantially suppressed the partitioning defect of an smc null mutant. Plasmid DNA isolated from an smc null mutant was more negatively supercoiled than that from wild-type cells. In vivo cross-linking experiments indicated that BsSMC was bound to the plasmid. Our results indicate that BsSMC affects supercoiling in vivo, most likely by constraining positive supercoils, an activity which contributes to chromosome compaction and organization.