Evidence and expert consensus based German guidelines for the use of repetitive transcranial magnetic stimulation in depression

INTRODUCTION

Non-invasive brain stimulation techniques such as repetitive transcranial magnetic stimulation (rTMS) offer a promising alternative to psychotherapeutic and pharmacological treatments for depression. This paper aims to present a practical guide for its clinical implementation based on evidence from the literature as well as on the experience of a group of leading German experts in the field.

METHODS

The current evidence base for the use of rTMS in depression was examined via review of the literature. From the evidence and from clinical experience, recommendations for the use of rTMS in clinical practice were derived. All members of the of the German Society for Brain Stimulation in Psychiatry and all members of the sections Clinical Brain Stimulation and Experimental Brain Stimulation of the German Society for Psychiatry, Psychotherapy, Psychosomatics and Mental Health were invited to participate in a poll on whether they consent with the recommendations.

FINDINGS

Among rTMS experts, a high consensus rate could be identified for clinical practice concerning the setting and the technical parameters of rTMS treatment in depression, indications and contra-indications, the relation of rTMS to other antidepressive treatment modalities and the frequency and management of side effects.

Improved EGFR mutation detection using combined exosomal RNA and circulating tumor DNA in NSCLC patient plasma

Background

A major limitation of circulating tumor DNA (ctDNA) for somatic mutation detection has been the low level of ctDNA found in a subset of cancer patients. We investigated whether using a combined isolation of exosomal RNA (exoRNA) and cell-free DNA (cfDNA) could improve blood-based liquid biopsy for EGFR mutation detection in non-small-cell lung cancer (NSCLC) patients.

Patients and methods

Matched pretreatment tumor and plasma were collected from 84 patients enrolled in TIGER-X (NCT01526928), a phase 1/2 study of rociletinib in mutant EGFR NSCLC patients. The combined isolated exoRNA and cfDNA (exoNA) was analyzed blinded for mutations using a targeted next-generation sequencing panel (EXO1000) and compared with existing data from the same samples using analysis of ctDNA by BEAMing.

Results

For exoNA, the sensitivity was 98% for detection of activating EGFR mutations and 90% for EGFR T790M. The corresponding sensitivities for ctDNA by BEAMing were 82% for activating mutations and 84% for T790M. In a subgroup of patients with intrathoracic metastatic disease (M0/M1a; n = 21), the sensitivity increased from 26% to 74% for activating mutations (P = 0.003) and from 19% to 31% for T790M (P = 0.5) when using exoNA for detection.

Conclusions

Combining exoRNA and ctDNA increased the sensitivity for EGFR mutation detection in plasma, with the largest improvement seen in the subgroup of M0/M1a disease patients known to have low levels of ctDNA and poses challenges for mutation detection on ctDNA alone.

Clinical Trials

NCT01526928.

Cooperative functions of the two F-BAR proteins Cip4 and Nostrin in the regulation of E-cadherin in epithelial morphogenesis

F-BAR proteins are prime candidates to regulate membrane curvature and dynamics during different developmental processes. Here, we analyzed nostrin, a so-far-unknown Drosophila melanogaster F-BAR protein related to Cip4. Genetic analyses revealed a strong synergism between nostrin and cip4 functions.Whereas single mutant flies are viable and fertile, combined loss of nostrin and cip4 results in reduced viability and fertility. Double mutant escaper flies show enhanced wing polarization defects and females exhibit strong egg chamber encapsulation defects. Live imaging analysis suggests that the observed phenotypes are caused by an impaired turnover of E-cadherin at the membrane. Simultaneous knockdown of Cip4 and Nostrin strongly increases the formation of tubular E-cadherin vesicles at adherens junctions. Cip4 and Nostrin localize at distinct membrane subdomains. Both proteins prefer similar membrane curvatures but seem to form distinct membrane coats and do not heterooligomerize. Our data suggest an important synergistic function of both F-BAR proteins in membrane dynamics. We propose a cooperative recruitment model, in which Cip4 initially promotes membrane invagination and early-actin-based endosomal motility, and Nostrin makes contacts with microtubules through the kinesin Khc-73 for trafficking of recycling endosomes.

Fat2 acts through the WAVE regulatory complex to drive collective cell migration during tissue rotation

The atypical cadherin Fat2 binds the WAVE regulatory complex (WRC) and acts with receptor tyrosine phosphatase Dlar through the WRC to control collective cell migration during Drosophila oogenesis.

Directional cell movements during morphogenesis require the coordinated interplay between membrane receptors and the actin cytoskeleton. The WAVE regulatory complex (WRC) is a conserved actin regulator. Here, we found that the atypical cadherin Fat2 recruits the WRC to basal membranes of tricellular contacts where a new type of planar-polarized whip-like actin protrusion is formed. Loss of either Fat2 function or its interaction with the WRC disrupts tricellular protrusions and results in the formation of nonpolarized filopodia. We provide further evidence for a molecular network in which the receptor tyrosine phosphatase Dlar interacts with the WRC to couple the extracellular matrix, the membrane, and the actin cytoskeleton during egg elongation. Our data uncover a mechanism by which polarity information can be transduced from a membrane receptor to a key actin regulator to control collective follicle cell migration during egg elongation. 4D-live imaging of rotating MCF10A mammary acini further suggests an evolutionary conserved mechanism driving rotational motions in epithelial morphogenesis.

WHAMY is a novel actin polymerase promoting myoblast fusion, macrophage cell motility and sensory organ development in Drosophila

Wiskott-Aldrich syndrome proteins (WASPs) are nucleation-promoting factors (NPF) that differentially control the Arp2/3 complex. In Drosophila, three different family members, SCAR (also known as WAVE), WASP and WASH (also known as CG13176), have been analyzed so far. Here, we characterized WHAMY, the fourth Drosophila WASP family member. whamy originated from a wasp gene duplication and underwent a sub-neofunctionalization. Unlike WASP, we found that WHAMY specifically interacted with activated Rac1 through its two CRIB domains, which were sufficient for targeting WHAMY to lamellipodial and filopodial tips. Biochemical analyses showed that WHAMY promoted exceptionally fast actin filament elongation, although it did not activate the Arp2/3 complex. Loss- and gain-of-function studies revealed an important function of WHAMY in membrane protrusions and cell migration in macrophages. Genetic data further implied synergistic functions between WHAMY and WASP during morphogenesis. Double mutants were late-embryonic lethal and showed severe defects in myoblast fusion. Trans-heterozygous mutant animals showed strongly increased defects in sensory cell fate specification. Thus, WHAMY is a novel actin polymerase with an initial partitioning of ancestral WASP functions in development and subsequent acquisition of a new function in cell motility during evolution.

The CellBorderTracker, a novel tool to quantitatively analyze spatiotemporal endothelial junction dynamics at the subcellular level

Endothelial junctions are dynamic structures organized by multi-protein complexes that control monolayer integrity, homeostasis, inflammation, cell migration and angiogenesis. Newly developed methods for both the genetic manipulation of endothelium and microscopy permit time-lapse recordings of fluorescent proteins over long periods of time. Quantitative data analyses require automated methods. We developed a software package, the CellBorderTracker, allowing quantitative analysis of fluorescent-tagged cell junction protein dynamics in time-lapse sequences. The CellBorderTracker consists of the CellBorderExtractor that segments cells and identifies cell boundaries and mapping tools for data extraction. The tool is illustrated by analyzing fluorescent-tagged VE-cadherin the backbone of adherence junctions in endothelium. VE-cadherin displays high dynamics that is forced by junction-associated intermittent lamellipodia (JAIL) that are actin driven and WASP/ARP2/3 complex controlled. The manual segmentation and the automatic one agree to 90 %, a value that indicates high reliability. Based on segmentations, different maps were generated allowing more detailed data extraction. This includes the quantification of protein distribution pattern, the generation of regions of interest, junction displacements, cell shape changes, migration velocities and the visualization of junction dynamics over many hours. Furthermore, we demonstrate an advanced kymograph, the J-kymograph that steadily follows irregular cell junction dynamics in time-lapse sequences for individual junctions at the subcellular level. By using the CellBorderTracker, we demonstrate that VE-cadherin dynamics is quickly arrested upon thrombin stimulation, a phenomenon that was largely due to transient inhibition of JAIL and display a very heterogeneous subcellular and divers VE-cadherin dynamics during intercellular gap formation and resealing.

Multiple Periodicities in the Circadian System of Unicellular Algae

Three periodicities in the circadian range are observed when measuring circadian parameters of unicellular organisms in long running experiments (more than 15 days). This is demonstrated for different organisms (Chlamydomonas, Euglena, Chlorella) and different parameters (auto­ kinesis, extracellular pH, CO2- and O2-partial pressure). Having excluded analytical and experimental artefacts (i.e. filter leakage and subpopulation effects), the multiple periodicities have to be interpreted in a physiological model. The three periodicities always exhibit two common features: The locations of the side peaks are symmetrical to the middle peak and their energy contribution is always the same. We therefore favour the model of multiplicative coupling between the circadian oscillator and a low frequency oscillator modulating the amplitude of the circadian rhythm. Since the low frequency rhythm is not correlated to any exogenously running periodicity of the experimental surroundings, it is considered as generated by an endogenous oscillator. This shows the existence of different biological long time oscillators in one single cell and contradicts the so-called master-clock hypothesis stating that one cell has only one clock related oscillator.

System Analysis of the Circadian Rhythm of Euglena gracilis, I. Linearities and Non-Linearities in the Response to Temperature Signals

The approach of control theory is used to describe the structure of the circadian system of Euglena gracilis. As a first step we discriminate linear and non linear properties of the dynamics.

The cellular motility as measured via long time records of sedimentation parameters in cultures is defined as the system output; sinusoidal temperature signals are used as input. By means of non stationary signal processing procedures we estimate gain and phase of the output signal. The problem of defining an appropiate gain of a cell suspension with an undefinite number of cells is solved by using the superimposition of two different input signals and by keeping one of them fixed as a reference signal.

Linear properties are shown with a linear frequency transfer and with the validity of the superposition principle at least within distinct regions of amplitude and frequency. Non linear properties are the signal distortion, the restriction of linear amplification to a distinct range of input temperature and the ambiguity of phase coupling near the circadian eigenfrequency.

The apparent lack of a limit of entrainment -an unexpected linear property - is explained by the masking effect of thermokinesis. A model is proposed describing the simultaneous control of motility by thermokinesis and the circadian system. On the base of that model further experiments are outlined.

System Analysis of the Circadian Rhythm of Euglena gracilis, II: Masking Effects and Mutual Interactions of Light and Temperature Responses

Motility of Euglena gracilis shows free running circadian rhythms. The circadian system is sensitive to light and temperature signals, but it is always masked by direct responses of motility to light (photokinesis) and temperature (thermokinesis). By means of a compartimental model which defines the interrelations between the pathways of thermokinesis, photokinesis and the circadian system a unifying view of effects of temperature and light input signals is outlined. According to the model, and using double sine input signals the dynamics of thermokinesis is described by a differential amplifier with constant gain.

Although thermokinesis heavily masks circadian responses to temperature signals, the limited range of circadian entrainment is indirectly demonstrated by a limited reappearance of free running circadian oscillations after stopping the temperature program. Free running circadian oscillations do reappear only after pretreatment with temperature periods near the circadian eigenperiod.

A white mutant lacking photosynthesis is used to investigate the role of photosynthesis in the signal processing. Although light synchronizes the circadian rhythms of the white mutant if applied as single input, it does not affect the motility if applied together with temperature inputs near the circadian eigenperiod. These results indicate frequency dependent mutual interactions between the model compartments.

The WAVE regulatory complex links diverse receptors to the actin cytoskeleton

The WAVE regulatory complex (WRC) controls actin cytoskeletal dynamics throughout the cell by stimulating the actin-nucleating activity of the Arp2/3 complex at distinct membrane sites. However, the factors that recruit the WRC to specific locations remain poorly understood. Here, we have identified a large family of potential WRC ligands, consisting of ∼120 diverse membrane proteins, including protocadherins, ROBOs, netrin receptors, neuroligins, GPCRs, and channels. Structural, biochemical, and cellular studies reveal that a sequence motif that defines these ligands binds to a highly conserved interaction surface of the WRC formed by the Sra and Abi subunits. Mutating this binding surface in flies resulted in defects in actin cytoskeletal organization and egg morphology during oogenesis, leading to female sterility. Our findings directly link diverse membrane proteins to the WRC and actin cytoskeleton and have broad physiological and pathological ramifications in metazoans.

European Society of Cardiology--XXIII congress. New and established therapies

The annual European Society of Cardiology XXIII Congress was an internationally represented meeting, focusing on the latest developments in cardiac pharmaceutical research and clinical applications. Poster and oral presentations displayed the importance of clinical trials for safety and efficacy of current drugs mainly acting on blocking of signaling pathways in the hyperactivated failing heart or prevention and reversion of vessel occlusions. Additionally, several new drug classes were introduced and tested in small-scale studies. In addition to improved surgical methods discussed at the congress, new classes of minimally invasive treatments were reported, including gene therapy and cell transplantation techniques which could provide additional future cure for cardiac patients.

Residential magnetic fields as a risk factor for childhood acute leukaemia: results from a German population-based case-control study

Our objective was to investigate whether exposure to residential power-frequency (50 Hz) magnetic fields above 0.2 microT increases a child's risk of leukaemia and to confirm or reject a finding from a previous German study on this topic, which reported increased leukaemia risk with exposure to stronger magnetic fields during the night. A population-based case-control study was used, covering the whole of the former West Germany. Residential magnetic fields were measured over 24 hr for 514 children with acute leukaemia identified by the German Childhood Cancer Registry and 1,301 control children taken from population registration files. Magnetic fields above 0.2 microT were relatively rare in Germany (only 1.5% of the study population). Childhood leukaemia and 24 hr median magnetic fields were only weakly related (OR = 1.55, 95% CI 0.65-3.67). A significant association was seen between childhood leukaemia and magnetic field exposure during the night (OR = 3.21, 95% CI 1.33-7.80). A dose-response-relationship was observed after combining the data of all German studies on magnetic fields and childhood leukaemia. The evidence for an association between childhood leukaemia and magnetic field exposure in our study comes from a measure of exposure during the night. Despite the large size of our study, the results are based on small numbers of exposed children. If the observed association stands, the effect on a population level in Germany would be small.

Childhood acute leukaemia and residential 16.7 Hz magnetic fields in Germany

We observed a moderate but statistically non-significant association between magnetic fields (MF) and childhood leukaemia. This is the first such study to cover residential exposure to 16.7 Hz (railway frequency) MF though based on few exposed subjects. Our study does not exclude a small excess risk, but the attributable risk must be very low. It is reassuring that neglecting 16.7 Hz MF in childhood cancer studies appears to have little effect on findings.

Extremely low frequency magnetic fields in residences in Germany. Distribution of measurements, comparison of two methods for assessing exposure, and predictors for the occurrence of magnetic fields above background level

We examined the results of 1,835 magnetic field measurements in German residences conducted between November 1997 and September 1999. The measurements were part of an epidemiological study on the relationship between magnetic fields and childhood leukemia. We performed a fixed-location measurement of the magnetic field at 50 Hz and 16 2/3 Hz (frequency of the German railway system) over 24 h in the child's bedroom in the residence of each study participant. In addition, we conducted a second 24 h-measurement in the living room at 50 Hz, and spot measurements while walking through all rooms of the respective dwelling. Median 50 Hz magnetic fields above 0.2 muT were found to be infrequent in Germany (only 1.4% of all residences). Fields produced by high-voltage power lines (123-420 kV) were lower than expected: the median magnetic field was above 0.2 muT in only 8 (32.0%) of 25 residences located 50 m or closer to a high-voltage power line indicating that power lines in Germany are usually run well below the maximum power load. We found that magnetic fields were correlated with the type of residence and higher magnetic fields were measured in apartment buildings. There was also some evidence for a positive correlation between magnetic fields and traffic density and an inverse association between magnetic fields and family net income. The 24 h-magnetic field measurements correlated well with the spot measurements (r>0.7). However, when dichotomized with a cut-off point of 0.2 muT, there was only a poor agreement between the two measurement methods. A loss of the strength of the association after categorization was also observed when comparing the arithmetic mean and median of the same 24 h-measurement. In summary, these analyses give a valuable overview of magnetic field distributions in German residences.

Mitochondrial DNA in human hair shafts--existence of intra-individual differences?

The sequences of the hypervariable region 1 (HV1) of the mitochondrial DNA control region from multiple hair shafts from 10 unrelated individuals were compared to determine the frequency of differences in hairs from one individual. The extraction method described herein showed an average success rate of 67% for all 150 hair shafts tested in HV1. The mtDNA sequences from the hair shafts matched the sequences from the corresponding blood and saliva samples taken from the same donor and no evidence of heteroplasmy was found. The results emphasize the reliability of DNA extraction and mtDNA typing from human hair shafts for forensic purposes.

Combined risk estimates for two German population-based case-control studies on residential magnetic fields and childhood acute leukemia

From 1992 to 1996, we obtained electromagnetic field measurements in two population-based case-control studies on childhood leukemia in the northwestern part of Germany and in Berlin. Exposure assessment comprised residential 24-hour measurements and short-term measurements. We obtained 24-hour measurements for a total of 176 cases and 414 controls. We compared subjects exposed to median 24-hour measurements of 0.2 microT or more with those exposed to lower amounts. Multivariate regression analysis revealed an odds ratio of 2.3 (95% confidence interval = 0.8-6.7).

Fluoresceinyl-ethylenediamine-ouabain detects an acidic environment in the cardiac glycoside binding site of Na+/K+-ATPase

To probe the pH value in the microenvironment of the cardiac glycoside-binding site of Na+/K+-ATPase, pH-sensitive fluorescent derivatives of ouabain were synthesized. The fluoresceinyl derivative of ethylenediamino-ouabain (FEDO) had a pKs of 6.0 and showed a H+-dependent fluorescence change, when its ratio of excitation at 490 nm/450 nm was recorded at 530 nm. Binding of FEDO inactivated Na+/K+-ATPase at 37 degrees C and pH 7.25 in a slow time-dependent process under the conditions of backdoor phosphorylation with k(on) of 891 s(-1) M(-1). The complex dissociated with k(on) of 0.35 x 10(-3) s(-1) resulting in a Kd value of 0.4 microM for the FEDO x enzyme complex. Binding of FEDO was associated with a decrease of the excitatory fluorescence ratio at 490 nm/450 nm which could be used to convert this change into a pH value. A pH value of 5.1 +/- 0.2 was calculated to exist in the microenvironment of the FEDO x enzyme complex. This pH value was independent of the pH of the incubation medium used to form the FEDO x enzyme complex. Analysis of the accessibility of the fluorophore in the FEDO x enzyme complex to the dynamic quencher potassium iodide detected a decrease of the Stern-Volmer constant from 6.2 mM(-1) (free FEDO) to 1.5 mM(-1) (FEDO x enzyme complex) indicating thereby a limited accessibility of the fluorophore to anions. Analysis of the microenvironment of the fluorescein residue of the FEDO x enzyme complex by measurements of the anisotropy and the fluorescence half-life time revealed that both processes differed significantly when H2O was replaced by D2O. We conclude, therefore, that a pH of 5.1 +/- 0.2 exists in the vicinity of ouabain that is hidden in the depth of the receptor site when the ouabain receptor complex has been formed.

Childhood leukemia and electromagnetic fields: results of a population-based case-control study in Germany

The investigation of an association between increased exposure to residential extremely-low frequency electromagnetic fields (ELF-EMF) and childhood leukemia was part of a population-based case-control study carried out between 1992 and 1995 in the northwestern part of Germany. A total of 129 children with leukemia and 328 controls participated in the EMF-study. Exposure assessment comprised measurements of the magnetic field over 24 hours in the child's bedroom at the residence where the child had been living for the longest period before the date of diagnosis, and spot measurements at all residences where the child had been living for more than one year. The median of the 24h-measurement in the child's bedroom was regarded as the most valid exposure variable. For children exposed to more than 0.2 microT, an elevated but not significant odds ratio (OR) was observed (OR = 3.2, 95 percent confidence interval = 0.7-14.9). These figures are based on only four leukemia cases and three controls since only 1.5 percent of the study population was classified as highly exposed. Exploratory analyses revealed ORs that were not statistically significantly increased for other characteristics of the magnetic field at varying cut-points. The results are comparable with those from other studies. Although not statistically significant, they may indicate a positive association between EMF and childhood leukemia.

Systems analysis of yeast glycolysis using perturbations of external pH: physiological parameters, non-parametric analysis, and general properties of the system dynamics

A global systems analysis approach to yeast glycolysis is presented. Starting from a high flux steady state of anaerobic glycolysis rapid changes of external pH are applied. The dynamics of the transduction of the pH signal to the in vivo fluorescence of reduced pyridine nucleotides are investigated. Physiological studies indicate no significant influence of external pH on glycolytic flux and energy charge, but stationary concentrations of metabolites are increased after increasing the external pH from 5-7 particularly in the distal part of the glycolytic chain. Most of the changes in reduced pyridine fluorescence are due to glycolytically accessible NADH. As a first stage of system analytic investigations the premises for the approach were tested. The dynamic properties of the system are stable and the response is linear with respect to the input amplitude. The dynamic properties of the system depend on the state of adaptation to a certain external pH. The non-parametric model derived from single step experiments was used to correctly predict the response to pulses of variable duration. This indicates that the linear macroscopic approach to systems analysis with pH as input is applicable. The dynamics of the system response includes strongly damped oscillatory components. Their period lengths are similar to those found with temperature inputs and with the switching from low to high glycolytic flux under anaerobic conditions. This indicates that the three different signals may trigger common regulatory interactions. The order of the signal transduction process, indicating the number of basic processes involved, can be estimated to be 4 or higher.

Characterisation of the control of respiration in potato tuber mitochondria using the top-down approach of metabolic control analysis

Control over oxidative phosphorylation by purified potato mitochondria was determined using the top-down approach of metabolic control analysis. The control over the respiration rate, phosphorylation rate, proton-leak rate and proton motive force exerted by the respiratory chain, phosphorylation reactions and the proton leak were measured over a range of phosphorylation rates from resting (state 4) to maximal (state 3). These rates were obtained by adding different amounts of hexokinase in the presence of glucose, or different amounts of oligomycin in the presence of ADP. The respiratory substrate was NADH or succinate, both of which feed electrons directly to ubiquinone. The rate of oxygen consumption by the alternative oxidase pathway was negligible with NADH as substrate but was measurable with succinate and was subtracted. Control over the respiration rate in potato mitochondria was predominantly exerted by the respiratory chain at all rates except close to state 4, where control by the proton leak was equally or more important. For oxidation of NADH, the flux control coefficient over the respiration rate exerted by the respiratory chain in state 3 was between 0.8 and 1.0, while in state 4, control over the respiration rate was shared about equally between the chain and the proton leak. The control over the phosphorylation rate was predominantly exerted by the respiratory chain, although at low rates control by the phosphorylation system was also important. For oxidation of NADH, the flux control coefficient over the phosphorylation rate exerted by the respiratory chain in state 3 was 0.8-1.0, while near state 4 the flux control coefficients over the phosphorylation rate were about 0.8 for the phosphorylation system and 0.25 for the chain. Control over the proton leak rate was shared between the respiratory chain and the proton leak; the phosphorylation system had negative control. For oxidation of NADH, the flux control coefficients over the leak rate in state 3 were 1.0 for the leak, 0.4 for the chain and -0.4 for the phosphorylation system, while in state 4 the flux control coefficients over leak rate were about 0.5 for the leak and 0.5 for the chain. Control over the magnitude of the protonmotive force was small, between -0.2 and +0.2, reflecting the way the system operates to keep the protonmotive force fairly constant; the respiratory chain and the phosphorylation system had equal and opposite control and there was very little control by the proton leak except near state 4.

Induction of Nitrate Assimilatory Enzymes in the Tree Betula pendula

The coordinate appearance of the bispecific NAD(P)H-nitrate reductase (NR; EC 1.6.6.2) and nitrite reductase (NiR; EC 1.7.7.1) was investigated in leaves and roots from European white birch seedlings (Betula pendula Roth). Induction by nitrate and light of both enzymes was analyzed by in vitro assays and by measuring NR- and NiR-encoding mRNA pools with homologous cDNAs as probes. When birch seedlings were grown on a medium containing ammonium as the sole nitrogen source, low constitutive expression of NR and NiR was observed in leaves, whereas only NiR was significantly expressed in roots. Upon transfer of the seedlings to a nitrate-containing medium, mRNA pools and activities of NR and NiR dramatically increased in leaves and roots, with a more rapid induction in leaves. Peak accumulations of mRNA pools preceded the maximum activities of NR and NiR, suggesting that the appearance of both activities can be mainly attributed to an increased expression of NR and NiR genes. Expression of NR was strictly light-dependent in leaves and roots and was repressed by ammonium in roots but not in leaves. In contrast with NR, constitutive expression of NiR was not affected by light, and even a slight induction following the addition of nitrate was found in the dark in roots but not in leaves. No effect of ammonium on NiR expression was detectable in both organs. In leaves as well as in roots, NiR was induced more rapidly than NR, which appears to be a safety measure to prevent nitrite accumulation.

Sequence of a cDNA encoding nitrite reductase from the tree Betula pendula and identification of conserved protein regions

The sequence of an mRNA encoding nitrite reductase (NiR, EC 1.7.7.1.) from the tree Betula pendula was determined. A cDNA library constructed from leaf poly(A)+ mRNA was screened with an oligonucleotide probe deduced from NiR sequences from spinach and maize. A 2.5 kb cDNA was isolated that hybridized to an mRNA, the steady-state level of which increased markedly upon induction with nitrate. The nucleotide sequence of the cDNA contains a reading frame encoding a protein of 583 amino acids that reveals 79% identity with NiR from spinach. The transit peptide of the NiR precursor from birch was determined to be 22 amino acids in size by sequence comparison with NiR from spinach and maize and is the shortest transit peptide reported so far. A graphical evaluation of identities found in the NiR sequence alignment revealed nine well conserved sections each exceeding ten amino acids in size. Sequence comparisons with related redox proteins identified essential residues involved in cofactor binding. A putative binding site for ferredoxin was found in the N-terminal half of the protein.

Sequence of a cDNA encoding the bi-specific NAD(P)H-nitrate reductase from the tree Betula pendula and identification of conserved protein regions

Nitrate reductase (NR) assays revealed a bispecific NAD(P)H-NR (EC 1.6.6.2.) to be the only nitrate-reducing enzyme in leaves of hydroponically grown birches. To obtain the primary structure of the NAD(P)H-NR, leaf poly(A)+ mRNA was used to construct a cDNA library in the lambda gt11 phage. Recombinant clones were screened with heterologous gene probes encoding NADH-NR from tobacco and squash. A 3.0 kb cDNA was isolated which hybridized to a 3.2 kb mRNA whose level was significantly higher in plants grown on nitrate than in those grown on ammonia. The nucleotide sequence of the cDNA comprises a reading frame encoding a protein of 898 amino acids which reveals 67%-77% identity with NADH-nitrate reductase sequences from higher plants. To identify conserved and variable regions of the multicentre electron-transfer protein a graphical evaluation of identities found in NR sequence alignments was carried out. Thirteen well-conserved sections exceeding a size of 10 amino acids were found in higher plant nitrate reductases. Sequence comparisons with related redox proteins indicate that about half of the conserved NR regions are involved in cofactor binding. The most striking difference in the birch NAD(P)H-NR sequence in comparison to NADH-NR sequences was found at the putative pyridine nucleotide binding site. Southern analysis indicates that the bi-specific NR is encoded by a single copy gene in birch.

Diurnal periodicity of chalcone-synthase activity during the development of oat primary leaves

Chalcone-synthase (CHS) activity was followed during the development of primary leaves of oat (Avena sativa L.) seedlings grown under different illumination conditions. Continuous darkness and continuous light resulted in similar time courses of enzyme activity. The maximum of CHS activity in etiolated leaves was delayed by 1 d and reached about half the level of that of light-grown leaves. In seedlings grown under defined light-dark cycles a diurnal rhythm of CHS activity and its protein level was observed which followed the rhythm of CHS-mRNA translational activity (Knogge et al. 1986). This rhythm persisted in continuous light after a short-term pre-exposure to the light-dark cycle but not in continuous darkness.

Free-field sensitivity level of audiometric earphones to be used for speech audiometer calibration

Speech audiometric test results strongly depend on the frequency response of the equipment used for speech transmission. For the comparison of data measured with different kinds of acoustic transducers, e.g. earphones and loudspeakers, a common reference basis for the specification of the frequency response of speech audiometers is therefore needed. The most obvious basis is the free sound field. In order to provide data for earphone specification in terms of the equivalent free-field response, which are to be included in an IEC standard on speech audiometers under preparation, comprehensive loudness comparison measurements with free progressive sound waves were performed on various audiometric earphones. When these data are used, calibration and testing of speech audiometers are as simple as in the case of puretone audiometers.

The oxidation of exogenous NADH by mitochondria of Euglena gracilis

A novel oxidase activity of external NADH was found in mitochondria of a streptomycin-bleached mutant and the wild strain of Euglena gracilis. In contrast to higher plants the oxidation of external NADH in mitochondria of E. gracilis is sensitive to rotenone and yields the same phosphorylation efficiency as the matrix pool of NADH. Simulation of this activity by the classic complex I of the matrix side of the mitochondrial membrane, as a result of preparation-generated artefacts, is excluded. The external NADH-dehydrogenase activity is bound to the inner mitochondrial membrane with its active side facing the cytosol. State-4 enzyme activity is only slightly influenced by pH in the physiological range, whereas state-3 oxidation indicates an optimum in the physiological pH, as expected from a limitation by the ATPase. The external redox potential of NADH does not control enzyme activity. The results are discussed with respect to the metabolic status of the cells at the time of harvesting.

Threshold of hearing by bone conduction. A contribution to international standardization

Threshold measurements with a Präcitronic KH 70 bone vibrator were carried out on 25 young, otologically normal subjects (50 ears) in the frequency range between 125 Hz and 8 000 Hz. The vibrator was applied to the human mastoid as well as to the forehead. The non-test ear was masked. Equivalent threshold force levels were determined on an artificial mastoid type B & K 4930. Between 125 Hz and 2 000 Hz, the equivalent threshold force levels for mastoid placement decrease steadily by about 13.5 dB/octave, they then increase again by about 10 dB and remain constant between 4 000 Hz and 8 000 Hz. The equivalent threshold force levels for forehead application were found to be higher by about 11 dB in the whole frequency range.

Effect of temperature on the pathways of NADH-oxidation in broad-bean mitochondria

1. Respiration rates of broad-bean (Vicia faba) mitochondria were studied as a function of temperature. Arrhenius plots of all membrane-bound enzymes, as obtained with saturating substrate concentrations, revealed a break in the lower temperature range. That break was considered to indicate a phase transition of membrane phospholipids, characteristic for chilling-sensitive plants. A second discontinuity at 30°C occurred only with activities linked to energy conservation. - 2. The activation energies for the oxidation of NAD(+)-linked substrates differ between states 3 and 4. State 3 respiration of NAD(+)-linked substrates is the result a superimposition of two branches of electron transport, which can be separated by different sensibilities to rotenone. A characteristic temperature dependency of the respiratory control, as well as a shift of the low temperature break in the Arrhenius plot toward a higher temperature after state 4 to state 3 transition, are calculated to be caused by the superimposition of the two branches. - 3. The temperature dependency of the oxidation of extra-mitochondrial NADH and of succinate differs remarkably from that of the oxidation of matrix-NADH. It has been concluded that the rotenone-resistant oxidation of matrix-NADH and the oxidation of external NADH are mediated via different pathways with individual regulation sites.