The relationship of the heart rate deflection point to the ventilatory threshold in trained cyclists

The purpose of this study was to assess the relationship of the heart rate deflection point (HRDP) to the ventilatory threshold (VT) in trained cyclists. Twenty-one endurance-trained cyclists (mean +/- SD: Vo(2)max = 67.6 +/- 4.7 ml x kg x min(-1)) completed a maximal cycle ergometer test of volitional fatigue using a ramped protocol. Ventilatory variables (Ve, Vo(2), Vco(2)) and power were measured online with averages reported every 20 seconds. Heart rate (HR) was recorded every 20 seconds using a Polar monitor. VT was calculated using the excess CO(2) elimination curve. The first derivative of a logistic growth curve fit to the HR-power data produced the HRDP. No significant differences (p > 0.01) existed between HR values at HRDP (171.7 +/- 9.6 b x min(-1)) and VT (169.8 +/- 9.9 b x min(-1)) or between Vo(2) values at HRDP (53.6 +/- 4.2 ml x kg x min(-1)) and VT (52.2 +/- 4.8 ml x kg x min(-1)). But power values at HRDP (318.7 +/- 30.7 W) were significantly different (p < 0.01) from those at VT (334.8 +/- 36.7 W). There were significant relationships between HRDP and VT for the physiological variables of HR (r = 0.92, p < 0.001), Vo(2) (r = 0.72, p < 0.001), and power (r = 0.77, p < 0.001). These findings indicate that HR and Vo(2) at HRDP are not significantly different from the values at VT in trained cyclists. HR values derived from HRDP may be used to set parameters for training intensity. Variability in the speed/power-HRDP relationship across detrained/trained states may be used to evaluate training programs.     

Binding of CaMKII to the giant muscle protein projectin: stimulation of CaMKII activity by projectin

Projectin is an integral high molecular mass protein of insect flight muscle binding to myosin and paramyosin. Yet, the role of projectin in insect flight muscle is not well understood. In this study we provide evidence for the interaction of projectin with the calcium sensor Ca(2+)/calmodulin-dependent protein kinase II (CaMKII). Two CaMKII variants of 52 and 60 kDa, respectively, of locust flight muscle cells were shown by an anti-CaMKII antibody. Both variants were associated to myofibrils. The 52 kDa variant was also shown abundant in the cytosol. The cytosolic CaMKII variant was co-precipitated in vitro with externally added purified projectin in a dose-dependent manner. To specify the binding properties of CaMKII to projectin we used both purified projectin from the flight muscle of locust and CaMKII from rat forebrain, a naturally rich source of CaMKII. CaMKII is highly conserved even between insects and mammals. The binding of CaMKII to native projectin was demonstrated in vitro by the solid phase enzyme assay, immunoprecipitation, and 'overlay' binding. One mol projectin bound maximally 1.38 +/- 0.02 mol CaMKII in vitro with a K(d) of 3.08 Z+/- 0.09 nM. Application of in vitro autophosphorylated CaMKII revealed a decreased stoichiometry of binding to projectin (0.86 +/- 0.04 mol mol(-1)) accompanied by a lower affinity (K(d) of 5.54 +/- 0.73) compared to non-autophosphorylated CaMKII. Furthermore, the CaMKII phosphotransferase activity was stimulated up to 2-fold by projectin. Even in the presence of calmodulin projectin enhanced the CaMKII activity moderately. Our data suggest that projectin represents a subcellular compartment for CaMKII to achieve its specificity, and activity in insect flight muscle cells.     

Apparatus and mechanism of photosynthetic oxygen evolution: a personal perspective*

This historical minireview describes basic lines of progress in our understanding of the functional pattern of photosynthetic water oxidation and the structure of the Photosystem II core complex. After a short introduction into the state of the art about 35 years ago, results are reviewed that led to identification of the essential cofactors of this process and the kinetics of their reactions. Special emphasis is paid on the flash induced oxygen measurements performed by Pierre Joliot (in Paris, France) and Bessel Kok (Baltimore, MD) and their coworkers that led to the scheme, known as the Kok-cycle. These findings not only unraveled the reaction pattern of oxidation steps leading from water to molecular oxygen but also provided the essential fingerprint as prerequisite for studying individual redox reactions. Starting with the S. Singer and G. Nicolson model of membrane organization, attempts were made to gain information on the structure of the Photsystem II complex that eventually led to the current stage of knowledge based on the recently published X-ray crystal structure of 3.8 A resolution in Berlin (Germany).With respect to the mechanism of water oxidation, the impact of Gerald T. Babcock's hydrogen abstractor model and all the considerations of electron/proton transfer coupling are outlined. According to my own model cosiderations, the protein matrix is not only a 'cofactor holder' but actively participates by fine tuning via hydrogen bond networks, playing most likely an essential role in water substrate coordination and in oxygen-oxygen bond formation as the key step of the overall process.     

Heterogeneity of microvascular endothelial cells isolated from human term placenta and macrovascular umbilical vein endothelial cells

The present study compares some phenotypic and physiologic characteristics of microvascular and macrovascular endothelial cells from within one human organ. To this end microvascular endothelial cells from human full-term placenta (PLEC) were isolated using a new method and compared with macrovascular human umbilical vein endothelial cells (HUVEC) and an SV40-transformed placental venous endothelial cell line (HPEC-A2). PLEC were isolated by enzymatic perfusion of small placental vessels, purified on a density gradient and cultured subsequently. Histological sections of the enzyme-treated vessels showed a selective removal of the endothelial lining in the perfused placental cotyledons. The endothelial identity of the cells was confirmed by staining with the endothelial markers anti-von Willebrand factor, Ulex europaeus lectin and anti-QBEND10. The cells internalized acetylated low-density lipoprotein and did not show immunoreactivity with markers for macrophages, smooth muscle cells and fibroblasts. The spindle-shaped PLEC grew in swirling patterns similar to that described for venous placental endothelial cells. However, scanning electron microscopic examination clearly showed that PLEC remained elongated at the confluent state, in contrast to the more polygonal phenotype of HPEC-A2 and HUVEC that were studied in parallel. The amount of vasoactive substances (endothelin-1,2, thromboxane, angiotensin II, prostacyclin) released into the culture medium and the proliferative response to cytokines was more similar to human dermal microvessels (MIEC) derived from non-fetal tissue than to HUVEC. Potent mitogens such as vascular endothelial growth factors (VEGF121, VEGF165) and basic fibroblast growth factor (FGF-2) induced proliferation of all endothelial cell types. Placental growth factors PIGF-1 and PIGF-2 effectively stimulated cell proliferation on PLEC (142 +/- 7% and 173 +/- 10%) and MIEC (160 +/- 20% and 143 +/- 28%) in contrast to HUVEC (9 +/- 8% and 15 +/- 20%) and HPEC-A2 (15 +/- 7% and 24 +/- 6%) after 48 h incubation time under serum-free conditions. These data support evidence for (1) the microvascular identity of the isolated PLEC described in this study, and (2) the phenotypic and physiologic heterogeneity of micro- and macrovascular endothelial cells within one human organ.     

Intravenous administration of stabilized antisense lipid particles (SALP) leads to activation and expansion of liver natural killer cells

Stabilized antisense lipid particles (SALP) have been developed for the systemic delivery of oligonucleotides. The impact of intravenous SALP administration was measured with respect to activation of natural killer (NK) and NK1.1+ T (NKT) cells in the livers of immunocompetent mice. Treatment with a SALP containing a highly mitogenic oligonucleotide (INX-6295) generated an increase in NK cytolytic activity and cell number within the liver but did not appear to affect the number of hepatic NKT cells or their cytolytic activity. The same results were observed after intravenous administration of the mitogenic oligonucleotide alone. Interestingly, treatment with a SALP containing a weakly mitogenic oligonucleotide (INX-6300) also activated the liver NK cells, whereas the oligonucleotide alone was unable to elicit these effects. The NK stimulatory activity of a SALP containing INX-6300 required both lipid and oligonucleotide components. These results demonstrate that in addition to modifying the pharmacokinetics and biodistribution of intravenously administered oligonucleotides, SALP possess immunostimulatory activity independent of oligonucleotide mitogenicity, which can serve as an adjuvant to antisense therapies for cancer.     

Photoinhibition as a function of the ambient redox potential in Tris-washed PS II membrane fragments

The mode of photoinhibition as a function of the ambient redox potential (E_ambient) in suspensions of Tris-washed PS II membrane fragments has been analyzed by monitoring flash-induced absorption changes at 830 nm. It was found: (a) the detectable initial amplitude, ΔA^total ₈₃₀, as a measure of the capacity to form the `stable' radical pair, P680^+ċ Q^−ċ _A, drastically decreases during a 10 min photoinhibition at E_ambient values below +350 mV; (b) conversely, the normalized extent of the 18 μs relaxation kinetics, ΔA^{18 μ s} ₈₃₀ as a measure of the electron transfer from Y_Z to P680^+ċ becomes highly susceptible to light stress when E_ambient exceeds values of about +350 mV; (c) effects of the ambient redox potentials are highly pronounced during light exposure under anaerobic conditions, while much smaller differences arise under aerobic conditions; (d) the extent of damage does not correlate with the total concentration of K₃[Fe(CN)₆] and K₄[Fe(CN)₆] in the suspension during photoinhibition but rather depends on the E_m-values; (e) qualitatively similar features are observed when the redox buffer system K₃[Fe(CN)₆]/Na₂S₂O₄ is replaced by K₂[IrCl₆]/Na₂S₂O₄; (f) the characteristic E_ambient-dependence of photoinhibition is observed only under anaerobic conditions. The results are discussed with respect to different redox components that might be involved, including brief comments on a possible role of Cyt b559. This revised version was published online in June 2006 with corrections to the Cover Date.     

Individually Adapted Imagery Improves Brain-Computer Interface Performance in End-Users with Disability

Brain-computer interfaces (BCIs) translate oscillatory electroencephalogram (EEG) patterns into action. Different mental activities modulate spontaneous EEG rhythms in various ways. Non-stationarity and inherent variability of EEG signals, however, make reliable recognition of modulated EEG patterns challenging. Able-bodied individuals who use a BCI for the first time achieve - on average - binary classification performance of about 75%. Performance in users with central nervous system (CNS) tissue damage is typically lower. User training generally enhances reliability of EEG pattern generation and thus also robustness of pattern recognition. In this study, we investigated the impact of mental tasks on binary classification performance in BCI users with central nervous system (CNS) tissue damage such as persons with stroke or spinal cord injury (SCI). Motor imagery (MI), that is the kinesthetic imagination of movement (e.g. squeezing a rubber ball with the right hand), is the "gold standard" and mainly used to modulate EEG patterns. Based on our recent results in able-bodied users, we hypothesized that pair-wise combination of "brain-teaser" (e.g. mental subtraction and mental word association) and "dynamic imagery" (e.g. hand and feet MI) tasks significantly increases classification performance of induced EEG patterns in the selected end-user group. Within-day (How stable is the classification within a day?) and between-day (How well does a model trained on day one perform on unseen data of day two?) analysis of variability of mental task pair classification in nine individuals confirmed the hypothesis. We found that the use of the classical MI task pair hand vs. feed leads to significantly lower classification accuracy - in average up to 15% less - in most users with stroke or SCI. User-specific selection of task pairs was again essential to enhance performance. We expect that the gained evidence will significantly contribute to make imagery-based BCI technology become accessible to a larger population of users including individuals with special needs due to CNS damage.     

Implementation of a Surgical Safety Checklist: Interventions to Optimize the Process and Hints to Increase Compliance

BackgroundA surgical safety checklist (SSC) was implemented and routinely evaluated within our hospital. The purpose of this study was to analyze compliance, knowledge of and satisfaction with the SSC to determine further improvements.MethodsThe implementation of the SSC was observed in a pilot unit. After roll-out into each operating theater, compliance with the SSC was routinely measured. To assess subjective and objective knowledge, as well as satisfaction with the SSC implementation, an online survey (N = 891) was performed.ResultsDuring two test runs in a piloting unit, 305 operations were observed, 175 in test run 1 and 130 in test run 2. The SSC was used in 77.1% of all operations in test run 1 and in 99.2% in test run 2. Within used SSCs, completion rates were 36.3% in test run 1 and 1.6% in test run 2. After roll-out, three unannounced audits took place and showed that the SSC was used in 95.3%, 91.9% and 89.9%. Within used SSCs, completion rates decreased from 81.7% to 60.6% and 53.2%. In 2014, 164 (18.4%) operating team members responded to the online survey, 160 of which were included in the analysis. 146 (91.3%) consultants and nursing staff reported to use the SSC regularly in daily routine.ConclusionThese data show that the implementation of new tools such as the adapted WHO SSC needs constant supervision and instruction until it becomes self-evident and accepted. Further efforts, consisting mainly of hands-on leadership and training are necessary.