Showing papers by "Humboldt University of Berlin published in 1993"

Chloroplast rps15 and the rpoB/C1/C2 gene cluster are strongly transcribed in ribosome-deficient plastids : evidence for a functioning non-chloroplast-encoded RNA polymerase

Abstract: Transcription of plastid genes and transcript accumulation were investigated in white leaves of the albostrians mutant of barley (Hordeum vulgare) and in heat-bleached leaves of rye (Secale cereale) as well as in normal green leaves of both species. Cells of white leaves of the mutant and cells of heat-bleached leaves bear undifferentiated plastids lacking ribosomes and, consequently, plastid translation products, among them the subunits of a putative chloroplast RNA polymerase encoded by the plastid genes rpoA, B, C1 and C2. The following results were obtained. (i) Plastid genes are transcribed despite the lack of chloroplast gene-encoded RNA polymerase subunits. The plastid origin of these transcripts was proven. This finding provides evidence for the existence of a plastid RNA polymerase encoded entirely by nuclear genes. (ii) Transcripts of the rpo genes and of rps15, but not of genes involved in photosynthesis and related processes (psbA, rbcL, atpI-H), were abundantly accumulated in ribosome-deficient plastids. In contrast, chloroplasts accumulated transcripts of photosynthetic, but not of the rpo genes. (iii) Differences in transcript accumulation between chloroplasts and ribosome-deficient plastids are due to different relative transcription rates and different transcript stability. (iv) The observed differences in transcription are not caused by an altered pattern of methylation of plastid DNA. Thus, the prokaryotic plastid genome of higher plants is transcribed by two RNA polymerases. The observed differences in transcription between chloroplasts and undifferentiated plastids might reflect different functions of the two enzymes.

Semidirect MP2 gradient evaluation on workstation computers: the MPGRAD program

Abstract: A semidirect implementation of the closed-shell MP2 gradient for efficient use on workstation computers is presented. The approach is based on the algorithm proposed by Frisch and coworkers but includes several modifications to reduce disk storage requirements and exploits nonabelian point group symmetry. The performance of the resulting program MPGRAD (BIOSYM Corp., San Diego, CA) is demonstrated in applications to the molecules [AlSi(CH3)3]4 and ferrocene. The largest calculation involved 492 basis functions and was carried out on IBM RS/6000 workstations with memory sizes of 32 and 128 Mb. The ratio of CPU to wallclock time exceeds 90% in all typical applications. © 1993 John Wiley & Sons, Inc.

Oxygenation of lipoproteins by mammalian lipoxygenases

Abstract: Oxidative modification converts low-density lipoprotein (LDL) into its atherogenic form and appears to be a necessary precondition for LDL uptake by macrophages during foam cell formation. Cellular lipoxygenases have been implicated in this process. We studied the interaction of purified mammalian lipoxygenases with human LDL in vitro and found that the arachidonate 15-lipoxygenases of rabbit and man are capable of oxygenating lipoproteins as indicated by oxygen uptake and by the formation of thiobarbituric-acid-reactive substances. Furthermore, oxygenated polyenoic fatty acids, such as 13-hydro(pero)xy-9Z,11E-octadecadienoic acid and 15-hydro(pero)xy-5,8,11,13(Z,Z,Z,E)-eicosatetraenoic acid were detected in the lipid compartment of various lipoproteins classes after lipoxygenase treatment. More than 90% of the oxygenated polyenoic fatty acids were found in the ester-lipid fraction, particularly in the cholesterol esters, whereas only small amounts of free hydro(pero)xy polyenoic fatty acids were detected. Lipoxygenase-catalyzed oxygenation of LDL is not restricted to the lipid compartment but also leads to a cooxidative modification of the apoproteins as indicated by changes in the electrophoretic mobility and by the formation of carbonyl derivatives of amino acid side chains. The possible biological significance of lipoxygenase-induced oxidative modification of lipoproteins in the pathogenesis of atherosclerosis is discussed.

A tetrameric complex of membrane proteins in the endoplasmic reticulum

Abstract: The translocation site (translocon), at which nascent polypeptides pass through the endoplasmic reticulum membrane, contains a component previously called 'signal sequence receptor' that is now renamed as 'translocon-associated protein' (TRAP). Two glycosylated subunits of the TRAP complex have been identified before (alpha and beta subunits). We now show that TRAP complex is actually comprised of four membrane proteins (alpha, beta, gamma, delta), present in a stoichiometric relation, which are genuine neighbours in intact microsomes. The amino acid sequences of the additional, non-glycosylated subunits were deduced from cloning of the corresponding cDNAs. The delta subunit spans the membrane only once and has its major portion, containing a disulfide bridge, at the lumenal side. The gamma subunit is predicted to span the membrane four times.

Rapid identification and differentiation of yeasts by DNA and PCR fingerprinting.

Abstract: We have used the techniques of DNA fingerprinting and polymerase chain reaction (PCR) with probes specific for hypervariable repetitive DNA sequences (mini- and microsatellite DNAs) to analyze 36 yeast strains belonging to 10 species and 2 genera. Using (GTG)5, (GACA)4, phage M13 DNA and the M13 sequence GAGGGTGGCGGTTCT as probes and primers, respectively, we obtained DNA polymorphisms which allowed us to discriminate 23 biotechnologically important strains of the yeast Saccaromyces cerevisiae and to distinguish them from strains of S. pastorianus, S. bayanus and S. willianus. Our results demonstrate that both DNA and PCR fingerprinting are suitable tools for an easy, fast and reliable molecular typing of yeasts. The DNA fingerprinting method seems to be more sensitive than PCR fingerprinting with respect to the individualization of strains. Nevertheless, using the PCR fingerprinting technique we were able to unambigously discriminate between genotypes of different species. Therefore, PCR fingerprinting might become a useful tool in the classification of yeasts on the basis of phylogenetic relatedness.

Basic problems of vertical Bridgman growth of CdTe

Abstract: Many efforts have been made to grow CdTe bulk crystals with a low defect content but improvements are limited. The best ingots with large extended single-crystal regions can be grown by the vertical Bridgman method. However, fundamental studies about the CdTe growth peculiarities are absent. Our investigations are concentrated on the following problems: (i) the influence of the melt structure, from which an associated state is assumed, on the crystalline quality, (ii) the composition instability in conventional ampoules, (iii) the segregation behaviour of the excess component (normally tellurium), (iv) the axial distribution of inclusions and precipitations, (v) the mass transport in modified ampoules with an additional cadmium source, (vi) the correlation between the vacancy and impurity segregation and (vii) the substrate purity as a function of the axial crystal position.

Realistic optical homodyne measurements and quasiprobability distributions.

Abstract: The deteriorating effect of low-efficiency detectors in different schemes suitable for a direct measurement of the Q function and in optical homodyne tomography is studied in some detail. It turns out that this effect amounts to smoothing the respective quasiprobability distribution that would be measured with unit-efficiency detectors. Our main result is that those smoothed distributions can be identified with certain s-parametrized quasiprobability distributions. Thus the latter gain direct experimental significance as distributions measurable under realistic experimental conditions.

Testing for Causation Between Two Variables in Higher-Dimensional VAR Models

Abstract: Different concepts of causality in vector autoregressive (VAR) models have been proposed in the literature. For instance, Granger (1969) defines a variable y 2 to be causal for y 1 if the former is helpful in predicting the latter. Formally, denoting by y 1,t (h|Ω t ) the optimal h-step predictor at origin t based on the set of all the relevant information in the universe Ω t , y 2 may be defined to be Granger-noncausal for y 1 if $$ {y_{1,t}}\left( {h|{\Omega _t}} \right) = {y_{1,t}}\left( {h|{\Omega _t}\backslash \left\{ {{y_{2,s}} \le t} \right\}} \right),\quad h = 1,2,... $$ (1.1) , where Ωt \ A denotes the set containing all elements of Ω t that are not in A. If y 1 and y 2 are generated by a bivariate VAR(p) process $$ \left[ \begin{array}{l} {y_{1t}} \\ {y_{2t}} \\ \end{array} \right] = \sum\limits_{i = 1}^p {\left[ \begin{array}{l} {\alpha _{11,i}}\quad {\alpha _{12,i}} \\ {\alpha _{21,i}}\quad {\alpha _{22,i}} \\\end{array} \right]\left[ \begin{array}{l} {y_{1,t - i}} \\ {y_{2,t - i}} \\ \end{array} \right] + {u_t}} $$ (1.2) and the information set is Ω t = {(y 1,s ,y 2,s )′|s ≤ t} then (1.1) is equivalent to $$ {\alpha _{12,i}} = 0,\quad i = 1,2, \ldots ,p $$ (1.3) . Under standard assumptions, these restrictions are easy to test.

Male rank, reproductive behavior, and reproductive success in free-ranging rhesus macaques

Abstract: Paternity assessment through DNA fingerprinting by synthetic oligonucleotide probes was applied to one birth cohort in a social group of free-ranging rhesus macaques (Macaca mulatta) on Cayo Santiago. The 11 group males and 9 males from other groups were observed mating with the females. Paternity was determined for 11 of the 15 infants. Male dominance rank was not associated with reproductive success. High-ranking resident males (N=5) sired 27% of the infants born during a one-year study. Four of the 11 infants of known paternity were sired by males of other social groups. The four infants of unknown paternity were sired either by males not observed mating with the females or the low-ranking male who was not fingerprinted. Male dominance rank was not associated with reproductive activity during conception cycles. These results suggest that the effect of rank on male reproductive success is not a predictable correlation, but a conditional probability.

Alterations in Function and Phenotype of Monocytes from Patients with Septic Disease: Predictive Value and New Therapeutic Strategies

Abstract: Recently we described the usefulness of immune monitoring as a guide for immunosuppression in allograft recipients with septic complications [1]. From cytofluorometric analyses of mononuclear cells (MNC), the HLA-DR antigen expression on monocytes seems to be the most important diagnostic parameter for the clinical management of immunosuppressed patients with sepsis. A restitution of diminished HLA-DR antigen expression on monocytes after rapid decline of immunosuppression was associated with a favorable outcome of sepsis [1]. Further studies on surgical patients suffering from septic disease (peritonitis as septic focus) not receiving therapeutically induced immunosuppression confirmed the predictive value of HLA-DR antigen expression on monocytes for clinical outcome [2, 3]. Taking a proportion of HLA-DR+ monocytes lower than 20% as the threshold for predicting fatal outcome, we correctly classified survivors and nonsurvivors in all but one case (n = 38) between the 5th and 7th days after admission to the ICU.

Sandwich enzyme immunoassay of cystatin C in serum with commercially available antibodies

Abstract: We developed a sandwich enzyme immunoassay for determining cystatin C in serum by using commercially available antibodies. We optimized each assay step (e.g., concentrations of coating rabbit anti-human cystatin C antibodies and horseradish peroxidase-conjugated antibodies) and studied the binding kinetics of antigen and antibodies. The within-assay CV was < 5%, the between-assay CV was 8.8%, the detection limit was 0.9 microgram/L, and the assay can be performed within 2 h. Cystatin C concentrations in sera from men were significantly higher than in women (mean and SD: 2.14 +/- 0.31 vs 1.78 +/- 0.26 mg/L). We studied the cystatin C concentrations in sera of 31 outpatients with suspected kidney damages to characterize the behavior of this low-M(r) protein as a possible indicator for estimating the glomerular filtration rate. The correlation with the values obtained by a standard isotopic method involving 99mTc-diethylenetriaminopentaacetic acid was rs = -0.89. The diagnostic sensitivity of cystatin C was 88.2% of that of the standard isotope clearance method and better than those of the conventional serum indicators of reduced kidney function, beta 2-microglobulin (64.7%) and creatinine (52.9%).

Identification of the cadmium vacancy in CdTe by electron paramagnetic resonance

Abstract: The isolated cadmium vacancy in CdTe is identified by means of electron paramagnetic resonance (EPR) in its single negative charge state. The spectrum reveals that the defect has trigonal symmetry, which can be explained in a model in which the hole occupies a dangling-bond ${\mathit{t}}_{2}$ orbital, and the orbital degeneracy is removed by a Jahn-Teller distortion. From the hyperfine interaction it is concluded that the hole is highly localized on one of the four tellurium neighbors. Photo-EPR measurements indicate that the 2-/- acceptor level is situated less than 0.47 eV above the valence band.

Metabolic flux determination in C6 glioma cells using carbon-13 distribution upon [1-13C]glucose incubation.

Abstract: A mathematical model of mammalian cell intermediary metabolism is presented It describes the distribution of the carbon-13 isotope (13C) at the different carbon positions of metabolites in cells fed with 13C-enriched substrates The model allows the determination of fluxes through different metabolic pathways from 13C- and 1H-NMR spectroscopy and mass spectrometry data The considered metabolic network includes glycolysis, gluconeogenesis, the citric acid cycle and a number of reactions corresponding to protein or fatty acid metabolism The model was used for calculating metabolic fluxes in a rat tumor cell line, the C6 glioma, incubated with [1-13C]glucose After evolution to metabolic and isotopic steady states, the intracellular metabolites were extracted with perchloric acid The specific enrichments of glutamate, aspartate and alanine carbons were determined from 13C-, 1H-NMR spectroscopy, or mass spectrometry data Taking into account the rate of glucose consumption and of lactate formation, determined from the evolution of glucose and lactate contents in the cell medium, and knowing the activity of the hexose monophosphate shunt, it was possible to estimate the absolute values of all the considered fluxes From the analysis the following results were obtained (a) Glucose accounts for about 78% of the pyruvate and 57% of the CoASAc (b) A metabolic channelling occurs at the citric acid cycle level; it favours the conversion of carbons 2, 3, 4, and 5 of 2-oxoglutarate into carbons 1, 2, 3, and 4 of oxaloacetate, respectively The percentage of channelled metabolites amounts to 39% (c) The pyruvate carboxylase activity and the efflux from the citric acid cycle are estimated to be very low, suggesting a lack of glutamine production in C6 cells The results emphasize different metabolic characteristics of C6 cells when compared to astrocytes, their normal counterpart

Epidemiological study of an Acinetobacter baumannii outbreak by using polymerase chain reaction fingerprinting.

Abstract: A polymerase chain reaction (PCR) technique was applied to the fingerprinting of different strains of Acinetobacter baumannii from a cluster of patients infected or colonized with the incriminated pathogen. The DNA was extracted by boiling and was subjected to PCR amplification by using the core sequence of the M13 phase as a single primer. The amplified products were separated by agarose gel electrophoresis and were detected by staining with ethidium bromide. In 1990, 49 multiresistant A. baumannii strains were isolated from 13 patients from the same intensive care unit of the Charite Hospital; 45 of these outbreak isolates obtained from 12 patients showed the same PCR patterns, indicating an epidemiological relatedness of these strains. Four strains isolated from the same patient belonged to another genetic group, as revealed by a distinct amplification pattern. Another single subtype of A. baumannii was identified as the causative agent in patients during a second outbreak at a different intensive care unit in the same hospital. Seventeen isolates recovered from 10 immunocompromised patients had the same amplification patterns, which were distinct from all other PCR profiles. Five strains were obtained from two other hospitals; three isolates from the hospital of Magdeburg, Germany, had identical PCR patterns which, however, could be clearly distinguished from the patterns of all other strains. The remaining two isolates displayed individual patterns of amplified fragments. PCR fingerprinting may provide a useful and particularly rapid identification technique for epidemiological investigations of nosocomial infections.

Phase measurement and Q function

Abstract: Generalizing a recent theoretical result obtained by Freyberger and Schleich [Phys. Rev. A 47, R30 (1993)], we show that the phase-measurement scheme proposed and realized by Noh, Foug\`eres, and Mandel [Phys. Rev. Lett. 67, 1426 (1991); Phys. Rev. A 45, 424 (1992)] amounts to measuring the Q function for the light under investigation, provided the reference beam (used for homodyne detection) is a very strong coherent field so that it can be described classically. The desired phase distribution follows from the Q function by averaging over the field amplitude. Since an analysis of an earlier proposal by Bandilla and Paul [Ann. Phys. (Leipzig) 23, 323 (1969)] to measure phase distributions via amplification led to just the same result, a perfect physical equivalence of those two approaches has thus been established.

Quantum statistics of a lossless beam splitter: SU(2) symmetry in phase space.

Abstract: A lossless beam splitter (a dielectric interface, a passive interferometer, or a linear coupler) changes the quantum state of two incident modes by an SU(2) transformation. Apart from phase shifting, the argument of the quadrature wave function of the system undergoes a rotation. Quasiprobabilities are changed by the inverse mode transformation. The use of balanced beam splitting allows the simultaneous measurement of conjugate quadrature components via homodyning the emerging beams with two strong coherent reference fields that differ in their phases by \ensuremath{\pi}/2. The measured probability distribution is given by a generalized Q function. It depends on the state of the field entering the second beam-splitter port. For a vacuum, the Q function will be obtained. The use of unbalanced beam splitting allows the measurement of a squeezed Q function without using squeezed states. Dissipation in Gaussian reservoirs corresponds exactly to a heuristic beam-splitter model. As a mathematical tool, the Fokker-Planck equation of damping in phase-sensitive reservoirs and the corresponding quantum master equation were solved. The dissipative decay of a Schr\"odinger-cat state was studied as an example. The sensitivity of quantum coherence with respect to damping can be interpreted geometrically.

Investigation of the oxygenation of phospholipids by the porcine leukocyte and human platelet arachidonate 12-lipoxygenases.

Abstract: When arachidonate 12-lipoxygenase purified from porcine leukocytes was incubated aerobically with 1-palmitoyl-2-arachidonoyl-sn-glycero-3-phosphocholine, the phospholipid reacted at up to 30% of the rate of a free fatty acid substrate; the esterified arachidonic acid was oxygenated predominantly to the (12S)-12-hydroperoxy product. The porcine leukocyte enzyme was also capable of metabolizing phosphatidylcholine containing esterified (15S)-15-hydroperoxy-5,8,11,13-eicosatetraenoic acid; oxygenation occurred predominantly at the 14R position. Reaction with mitochondrial and endoplasmic membranes of rat liver produced esterified (12S)-12-hydroperoxy-5,8,10,14-eicosatetraenoic acid and (13S)-13-hydroperoxy-9,11-octadecadienoic acid as major oxygenation products. Thus, porcine leukocyte 12-lipoxygenase is capable of oxygenating not only free polyenoic fatty acids but also more complex substrates such as phospholipids and biomembranes. In contrast, the human platelet 12-lipoxygenase is almost inactive with these esterified polyenoic fatty acids. In regard to the function of these enzymes, the leukocyte-type of 12-lipoxygenase has similar catalytic activities to the mammalian 15-lipoxygenase and its physiological function may include the structural modification of membrane lipids.

Static friction phenomena in granular materials: Coulomb law versus particle geometry.

Abstract: The static as well as the dynamic behavior of granular material are determined by dynamic and static friction. There are well known methods to inlcude static friction in molecular dynamics simulations using scarcely understood forces. We propose an ansatz based on the geometrical shape of nonspherical particles which does not involve an explicit expression for static friction. It is shown that the simulations based on this model are close to experimental results.

Comparison of Recalled and Validated Oral Contraceptive Histories

Abstract: From a case-control study of the relation between oral contraceptives and breast cancer carried out in East Germany during 1982-1986, the authors obtained information on oral contraceptive use through interviews of study subjects and from the records of prescribing gynecologists. The degree of agreement regarding information from these two sources was assessed for 234 breast cancer cases and 524 controls who had ever used oral contraceptives. Agreement between information obtained from medical records and that from interviews on total duration of use, number of episodes of use, and time since first and last use was reasonably good, and levels of agreement did not differ appreciably between cases and controls. Lower levels of agreement were observed for individual brand names and the duration of use of specific brands. Attempts should be made to obtain information on specific brands from medical records when investigating the effects of individual preparations.

Varicella-zoster virus DNA in granulomatous skin lesions following herpes zoster. A study by the polymerase chain reaction.

Abstract: Granulomatous reactions at sites of previous cutaneous herpes zosier lesions occur, but their etiology is not known. Three tissue specimens from 5 cases identified clinically and hislologically as post-zosteric granulomatous reactions were studied for the presence of varicella-zoster virus (VZV) deoxyribonucleic acid (DNA) by the polymerase chain reaction using specific primers For VZV. VZV DNA was detected in 1 of 3 cases where the granulomatous reaction occurred immediately in the wake of resolving vesicular herpes zoster lesions. Finding viral DNA in earlier reactions probably represents residue from the active herpetic process. VZV DNA was not identified in granulomatous reactions arising between 1 month and up to 4 years after resolved herpes zoster. The negative result in these cases supports the hypothesis that there is no association between persistence of VZV DNA and granuloma formation. How long VZV DNA is detectable at sites of resolved herpes zoster lesions could be the subject of further studies.

Urinary proteins and enzymes as early indicators of renal dysfunction in chronic exposure to cadmium.

Abstract: We tested the diagnostic sensitivity of various urinary analytes for detecting cadmium-induced nephropathy at an early stage. We investigated 73 healthy persons (control group 1) and individuals exposed to cadmium, either environmentally (n = 36, risk group 2) or occupationally (n = 62, exposed group 3). All data were related to limits of the central 95% reference intervals of the control group. The serum creatinine and ribonuclease values, indicators of the glomerular filtration rate, were not different in the three groups. In the exposed persons (group 3), proximal tubular indicators (low-M(r) proteins lysozyme, ribonuclease, retinol-binding protein, and alpha 1-microglobulin) were more often increased than the glomerular indices (higher-M(r) proteins transferrin, IgG, and albumin). Both the low-M(r) proteins and tubular enzymes were differently altered in their excretion rates. Alanine aminopeptidase, alkaline phosphatase, and N-acetyl-beta-D-glucosaminidase increased even in the risk group 2. alpha 1-Microglobulin was increased in the exposed persons whose cadmium excretion was < 5 mumol/mol creatinine. The combined determination of alpha 1-microglobulin and N-acetyl-beta-D-glucosaminidase exceeded the corresponding upper reference limits in 30% of group 2 and 39% of group 3. We recommend screening for these two analytes to detect cadmium-induced renal dysfunction at an early stage.

Influence of magnesium deficiency on rates of leaf expansion, starch and sucrose accumulation, and net assimilation in Phaseolus vulgaris

Abstract: Twenty one-day-old Phaseolus vulgaris‘Saxa’plants were cultured in a growth chamber and the plants supplied with either a complete or a Mg-free nutrient solution. From 6 days after transfer to the Mg-free solution, the rate of increase of the area of the second trifoliate leaf was considerably reduced; by day 11 the sucrose concentration in the first trifoliate leaf had increased 6. 2-fold at the end of the dark period and 4. 6-fold after the light period as compared with the control plants. Corresponding starch concentrations increased 6. 6-fold and 2. 9-fold respectively. After days 5 to 6 the assimilation rates declined in the first trifoliate leaf of the plants showing deficiency, in comparison with the plants fully supplied with nutrients; respiration increased during darkness. The reduction in net assimilation rate was to a great extent reversible after resupply of magnesium. The reduction of magnesium concentration in the deficient plants was much more marked in the expanding leaves than in the mature primary leaves and roots. Sucrose and starch accumulation did not occur when the first trifoliate leaf was partially shaded, although magnesium concentration, as in the unshaded leaves, was reduced to 13% of that of the control plants. The consequences of magnesium deficiency in the expanding first trifoliate leaf are discussed in terms of the possibility of sink limitation.