Showing papers by "University of Bremen published in 1987"

Osmotic adjustment in marine eukaryotic algae: the role of inorganic ions, quaternary ammonium, tertiary sulphonium and carbohydrate solutes

Abstract: SUMMARY The unicellular marine algae, Phaeodactylum tricornutum Bohlin, Cyclotella cryptica Reimann and Cyclotella meneghiniana Kutzing (Bacillariophyceae) and Porphyridium aerugineum Geitler (Rhodophyceae) synthesized and accumulated glycine betaine and proline in response to increases of the NaCl concentration (150 to 1000 mol m-3 NaCl) of the growth medium. C. cryptica and C. meneghiniana also synthesized and accumulated homarine (N-methyl picolinic acid betaine). Both P. tricornutum and P. aerugineum synthesized increasing amounts of intracellular glycerol and P. aerugineum also formed the heteroside, floridoside [O-a-Dgalactopyranosyl (1 -+ 2)-glycerol], in response to the elevated salinities. No major low molecular weight carbohydrates were found in Cyclotella. Sucrose was not detected in the algal extracts. Only P. tricornutum synthesized the tertiary sulphonium compound, ,-dimethylsulphoniopropionate (DMSP), and the quantity of this solute in the alga was dependent on the amount of NaCl in the medium. Intracellular K+ concentrations in the algae were three to six times greater than those of Na+. Increases of the salinity of the media led to the uptake and accumulation of K+ by the cells, and smaller increases of Na+ and Cl- and loss of intracellular NO3-. The inorganic cations Na+ and K+, with their accompanying anions, and the estimated organic solutes could largely account for the osmotic balance of P. tricornutum and P. aerugineum.

Transcription activation of the tyrosine aminotransferase gene by glucocorticoids and cAMP in primary hepatocytes.

Abstract: The expression of the tyrosine aminotransferase (TAT) gene of the rat was analyzed in primary hepatocytes. The TAT gene remains active in primary cultured cells at a level similar to that in liver cells. Expression can be induced by glucocorticoids and cAMP, glucocorticoids lead to a 8–10-fold increase in TAT mRNA level, cAMP to a 20–30-fold increase. The elevation of the TAT mRNA is preceeded by a rise in the relative rate of transcription of the gene. Surprisingly transcription of the albumin gene, which steadily declines with the age of the culture, can also strongly be stimulated by glucocorticoids in primary hepatocytes. cAMP antagonists, which act as competitive inhibitors of the cAMP-dependent protein kinase, prevent induction of transcription of the tyrosine aminotransferase gene by cAMP suggesting that the effect of cAMP on expression of the tyrosine aminotransferase gene is mediated by a cAMP-dependent protein kinase. The cAMP antagonist does not interfere with induction by glucocorticoids which suggests that phosphorylation of the glucocorticoid receptor by the cAMP-dependent protein kinase is not required for its function. We thus conclude that the two inducers affect transcription by independent mechanisms.

Some structural aspects of hypergraph languages generated by hyperedge replacement

Abstract: Hyperedge replacement systems are introduced as a device for generating hypergraph languages including graph languages and string languages (where the strings are uniquely represented as certain graphs). Our concept combines a context-free type of rewriting with a comparatively large generative power. The former is indicated, for example, by a pumping lemma, the latter by the examples (among them you find the refinement of Petri nets, the analysis of flow diagrams, the structural description of molecules and some typical non-context-free string languages).

Osmotic adjustment in marine eukaryotic algae: the role of inorganic ions, quaternary ammonium, tertiary sulphonium and carbohydrate solutes. II. Prasinophytes and haptophytes

Abstract: The effects of steady state salinities (150 to 700 mol m-3 NaCl) on the growth rates and intracellular solutes of the prasinophyte algae Tetraselmis chui Butcher and Prasinocladus Kuckuck and the prymnesiophyte algae, Prymnesium parvum Carter and Ruttnera spectabilis Geitler, are described. Maximum growth rates were reached in media approximating to the NaCl concentration of oceanic waters (about 500 mol m-3 ). The following intracellular organic solutes paralleled the increases of external salinity: the tertiary sulphonium compound β-dimethylsulphoniopropionate (DMSP) in T. chui, Prasinocladus, P. parvum and R. spectabilis; the polyhydric alcohol, mannitol, in T. chui, Prasinocladus and R. spectabilis; the quaternary ammonium compounds (QACs), glycine betaine and homarine, in T. chui and Prasinocladus. QACs were not detected in P. parvum and R. spectabilis. An unknown polyol, which may be the cyclitol, 1,4/2,5 cyclohexanetetrol, was synthesized by P. parvum and R. spectabilis and in addition P. parvum contained significant concentrations of glucose. Sucrose was not detected in the algal extracts. Proline was an insignificant osmoticum in all the algae. Increases of the media NaCl concentration led to the uptake and accumulation of K+ in T. chui and Prasinocladus, with smaller increases of Na+ and Cl- . The intracellular K+ concentrations in the prasinophyte algae were about five times greater than those of Na+ . The inorganic cations Na+ and K+ , and their accompanying anions, and the organic solutes found could largely account for the osmotic balance of T. chui and Prasinocladus. The inorganic ions in P. parvum and R. spectabilis were not determined.

Quantitative neutron capture radiography for studying the biodistribution of tumor-seeking boron-containing compounds.

Abstract: Biodistribution of two compounds presently considered for use in neutron capture therapy has been studied in mice carrying a transplantable Harding-Passey melanoma. A method is described by which quantitative assessment can be made of the boron distribution in whole-body sections of such animals. An alpha-particle-sensitive film is placed in close contact with a freeze-dried section of an animal and exposed to neutrons. The tracks visible after etching are analyzed optoelectronically in fields of 0.6 X 0.6 mm2 and compared to standards of boron homogeneously distributed in liver homogenates. The dynamic range of this method is about two orders of magnitude in concentration, with a lower detection limit of 0.1 to 0.01 ppm 10B, depending on the rate of induction of spurious tracks by fast neutrons present in the neutron beam chosen. In a transplantable Harding-Passey melanoma in mice, it was found that the sulfhydryl boron hydride Na2B12H11SH presently used for therapy of glioblastoma clears blood, muscle, and brain very rapidly. Its accumulation in tumors was persistent for more than three days. A higher tumor accumulation was observed with its disulfide, which has been suggested for neutron capture therapy. For both compounds, a marked heterogeneity of boron distribution within one tumor was found.

Taphonomy of tidal flat molluscs in the northern Gulf of California; paleoenvironmental analysis despite the perils of preservation

Abstract: Taphocoenoses can be powerful indicators of ancient environments, even in depositional settings in which rates of sedimentation are low and tidal currents are strong. The rich subtropical molluscan fauna of the northern Gulf of California exhibits a distinct zonation across an extensive tidal flat atBahia la Choya (Sonora, Mexico). The distribution of live faunas is largely controlled by substrate, energy level, availability offood, and period of submergence. Despite strong tidal currents and the effects of time-averaging, the distribution of taphocoenoses closely reflects the distribution of the live communities. Indeed, the zonation of individual species is often reflected in the distribution of their shelly remains. The outerflat, middle flat, innerflat, tidal channel, and salt marsh subenvironments within the tidal flat complex can be defined by the taxonomic composition, trophicllife habit groups and taphonomic attributes of their taphocoenoses. Gastropods dominate on hard and firm substrates (rocky flats, channel and marsh) while bivalves prevail on sandy substrates. Herbivores are most common on rocky and shelly substrates; detritus feeders occur on the firm substrates of the inner flat and marsh; suspension-feeders predominate in sandy and rocky bottoms. Shell abrasion, encrustation, and boring decrease landward. We tested an integrated approach to paleoenvironmental analysis by examining a Pleistocene shell bed from Bahia la Choya. Taxonomic, ecologic, and taphonomic criteria suggest deposition by a storm event in a vety shallow subtidal to lowest intertidal environment.

Rearrangements of chromosome region 12q13----q15 in pleomorphic adenomas of the human salivary gland (PSA).

Abstract: Nine of 40 pleomorphic salivary gland adenomas (PSAs) showed clonal aberrations of chromosome 12, with a breakpoint at 12q13----q15. The cytogenetic findings in these cases and those of nine additional cases reported in the literature suggest that this type of aberration is a primary change directly involved in the genesis of PSA.

Is there a “Socratic Effect” in Nonexperimental Panel Studies? Consistency of an Attitude toward Guestworkers

Abstract: It has often been observed in experimental studies that the reliability of items increases if the same questions are asked of the same respondents more than once. This phenomenon, called the “Socratic effect,” also occurs in nonexperimental, short-wave panel studies. In the first section of this article a number of hypotheses presumed to underlie the “Socratic effect” are presented. It is argued that a distinction must be made between consistency processes at the structural level (latent attitudes) and the observational level (respondent behavior). Given this distinction, the hypotheses are tested within a LISREL framework that takes this differentiation into account. The hypotheses are then evaluated using four items to measure respondents' attitudes toward guestworkers in West Germany. By and large the central hypotheses are confirmed. It is also shown that two different models can be fit to the observed data equally well, and therefore a nonstatistical criterion has to be invoked to decide which model ...

On unique ergodicity for degenerate diffusions

Abstract: We investigate the invariant probabilities of a possible degenerate diffusion process on a manifold. Using the support theorems of stroock, Varadhan and Kunita, the possible candidates for supports of invariant probabilities can be characterized as the invariant control sets of the corresponding control system. There remains the problem of how many invariant probabilities can coexist on one invariant the problem of how many invariant probabilities can coexist on one invariant control set C. Uniqueness on C is proved under the assumption that the Lie algebra generated by the drift and diffusion vector fields is full at one point in C. This generalizes the known results obtained by PDE methods. Several versions of the ergodic theorem are given.

On the mechanism of histamine induced enhancement of the cardiac Ca2+ current.

Abstract: In guinea pig ventricular myocytes, the effect of histamine on the slow Ca2+ current (ICa) was studied and the following results were obtained: (1) Superfusion of cells with histamine resulted in a dose-dependent enhancement of the amplitude of ICa. The threshold concentration of histamine was 10−8 M, half maximal increase occurred at 3×10−7 M and maximal enhancement (about 3–4-fold) at 5×10−6 M. (2) The histamine effect was greatly reduced by the H2 antagonist cimetidine (10−5 M) but only slightly by the H1 antagonist diphenhydramine (10−5M). (3) Effects of isoprenaline (ISP) and histamine at maximal effective concentrations on ICa were not additive, suggesting that both agents use the same intracellular pathway. Intracellular infusion of a blocker of the cAMP-dependent protein kinase, Rp-cAMPS (10−4 M), prevented the histamine effect. (4) The involvement of GTP-dependent transducer proteins was studied by cell dialysis with several GTP derivatives. Intracellular application of the stable GDP-analogue, GDP-β-S, reduced the histamine effect on ICa, whereas the stable GTP analogue, GTP-γ-S, mimicked the histamine effect.

Uptake of chromium (III) complexes by erythrocytes

Abstract: Trivalent chromium is assumed to be the ultimate genotoxic form of Cr after uptake and reduction of chromate in cells. Cr(III) also is an essential trace element for mammalia; it is required for the proper control of glucose metabolism. In both kinds of biological effects, Cr(III) is assumed to act in the form of complexes with biomolecules, but there is very little information about the uptake of such complexes through membranes. By electrothermal atomic absorption we investigated the time course of the binding and uptake with human erythrocytes of [Cr(glycine)3], [Cr(2,4‐pentanedione)3], [Cr(glutathione)2]2‐, [Cr(Cysteine)2]1‐, [Cr(o‐phenanthroline)2Cl2]1+ and [Cr(bipyridine)2Cl2]1+. In all cases chromium was bound and taken up significantly except with the cysteine complex which bound to the cells but sedimented with the cell envelope after cell lysis. The uptake of Cr(III) compounds was very slow. At 1 mM concentrations and 1 hour at 37°C the intracellular chromium was estimated to be between 0.5 to 2...

Estimation of Reliability and Stability in Single-Indicator Multiple-Wave Models:

Abstract: This article focuses on three main points: (1) Because a short-wave panel study such as the ALLBUS-Retest Study 1984 is suited optimally for reliability estimations, the quality of a larger number of items concerning attitudes about the welfare state and inequality and toward a minority group in West Germany (“guestworkers”) is investigated; (2) we show that most of the items are more reliable in the subgroup with high political interest than in the low-interest group; and (3) because we cannot rely on multiple indicators in most of the cases, methods and statistical models for the analysis of single indicators in multiple-wave panels are discussed. Because we can assume that the latent attitudes are continuous and the observed variables have ordered categories (at least), we confine our analyses to metric variable models. We show that (a) the assumptions underlying the classical models proposed by Heise (1969) and by Wiley and Wiley (1970, 1974) will often be violated if the times between the panel waves...

Large deviations of linear stochastic differential equations

Abstract: We study parametric perturbations of a linear system by white noise \(\dot W_1 \left( t \right)\),...,\(\dot W_m \left( t \right)\) and by real noise ξ(t) (a nice Markov process), modelled by the linear stochastic differential equation $$dx\left( t \right) = A_0 \left( {E\left( t \right)x\left( t \right)dt} \right) + \sum\limits_{i = 1}^m {A_i \left( {E\left( t \right)} \right)x\left( t \right) \circ dW_i \left( 0 \right) = x_0 \in \mathbb{R}^d } .$$ (1) Under a mild condition every solution x(t;x0) of (1) has the same exponential growth rate (Lyapunov exponent) λ, $$\mathop {\lim }\limits_{t \to \infty } \frac{1}{t}\log \left| {x\left( {t;x_0 } \right)} \right| = \lambda \left( {law of large numbers} \right).$$ (1) is stable if λ < 0. The key tool for studying the finer properties of (1) is the Lyapunov exponent of the pth moment $$g\left( p \right) = \mathop {\lim }\limits_{t \to \infty } \frac{1}{t}\log E\left| {x\left( {t;x_0 } \right)} \right|^p ,p \in \mathbb{R}.$$

Rate of growth and longevity of a large colony of Pentapora foliacea (Bryozoa) recorded in their oxygen isotope profiles

Abstract: We studied the growth patterns and the stable oxygen isotopic composition of an individual of Pentapora foliacea (Ellis and Solander 1786) collected on October 6, 1978 from the Bristol Channel, Pembrokeshire, UK, Irish Sea. The stable oxygen isotopes are in equilibrium with the ambient seawater and show a marked seasonal variation reflecting seasonal water temperature changes. The stable oxygen isotopes further suggest that regular growth patterns of less calcified growth bands, which are secreted in winter, are perennial. These winter growth check lines can easily be used to determine longevity of these bryozoa colonies and of annual growth rates. The colony analysed is at least 3-years-old with an annual growth rate of approximately 2 cm per year.

The Influence of Dicamba on Somatic Embryogenesis and Frequency of Plant Regeneration from Cultured Immature Embryos of Wheat (Triticum aestivum L.)

Abstract: An investigation was made to discover the influence of dicamba on the somatic embryogenesis of winter wheat cultivars-. Immature embryos of Triticum aestivum cv, ‘Sage’, ‘Caribo’ and ‘Kanzler’ were cultured, on modified N6-medium with the addition of 1 mg/13,6 dichlor-2-methoxy benzoe acid (dicamba). The young embryos were placed with the embryo axis on to the medium. Under this condition the scutella of the embryos at different stage of development produced compact calli and embryoids which regenerated plants with a high frequency (70 %) four to: six weeks later. The results suggest that dicamba could be of value in the induction of somatic embryogenesis.

D-Mannitol dehydrogenase and D-mannitol-1-phosphate dehydrogenase in Platymonas subcordiformis: some characteristics and their role in osmotic adaptation.

Abstract: d-Mannitol-1-phosphate dehydrogenase (EC 1.1.1.17) and d-mannitol dehydrogenase (EC 1.1.1.67) were estimated in a cell-free extract of the unicellular alga Platymonas subcordiformis Hazen (Prasinophyceae), d-Mannitol dehydrogenase had two activity maxima at pH 7.0 and 9.5, and a substrate specifity for d-fructose and NADH or for d-mannitol and NAD+. The Km values were 43 mM for d-fructose and 10 mM for d-mannitol. d-Mannitol-1-phosphate dehydrogenase had a maximum activity at pH 7.5 and was specific for d-fructose 6-phosphate and NADH. The Km value for d-fructose 6-phosphate was 5.5 mM. The reverse reaction with d-mannitol 1-phosphate as substrate could not be detected in the extract. After the addition of NaCl (up to 800 mM) to the enzyme assay, the activity of d-mannitol dehydrogenase was strongly inhibited while the activity of d-mannitol-1-phosphate dehydrogenase was enhanced. Under salt stress the Km values of the d-mannitol dehydrogenase were shifted to higher values. The Km value for d-fructose 6-phosphate as substrate for d-mannitol-1-phosphate dehydrogenase remained constant. Hence, it is concluded that in Platymonas the d-mannitol pool is derectly regulated via alternative pathways with different activities dependent on the osmotic pressure.

On the role of trivalent chromium in chromium genotoxicity

Abstract: Trivalent chromium with high probability is one ultimate DNA damaging and mutagenic agent after chromate uptake by various cell types. It is produced and accumulated by uptake and reduction of Cr(VI) in living cells. Some complexes of Cr(III) have been shown to penetrate cell membranes and to cause gene mutations in mammalian cells, bacteria and yeast. Cr(III) compounds produced DNA‐protein crosslinks and DNA strand breaks with isolated mammalian cell nuclei. The intracellular species of Cr(III) and the possible products of their reaction with DNA are discussed.

Latitudinal shift of Pacific hotspots during the late Cretaceous and early Tertiary

Abstract: Two frames of reference, the geomagnetic field and hotspots, have been widely used to measure the past motions and interactions of lithospheric plates. Several studies have found that these reference frames have undergone as much as 19–22° of relative motion, often called true polar wander (TPW), in the past 200 Myr1–4. Moreover, it also appears that this offset did not accumulate at a uniform rate. Some evidence suggests that spurts of TPW can occur at rates as high as 1–2° per Myr3–5. Rates even an order of magnitude less could pose serious problems for tectonic studies based on the hotspot reference frame because velocities of this magnitude cannot be considered insignificant compared to those of the plates. Unfortunately, the imprecision of most palaeomagnetic data is such that large error bounds are common for many estimates of TPW rates. In this report, we present a record of TPW derived from Pacific palaeomagnetic data that are relatively well constrained in age and palaeolatitude. They show that offset between the two reference frames accumulated at ∼0.3° per Myr–1 from late Cretaceous to early Tertiary.

Structural rearrangements of chromosome Nr 8 involving 8q12--a primary event in pleomorphic ademona of the parotid gland.

Abstract: Nine pleomorphic adenomas of the human parotid gland were investigated. Within this series the group of cases having clonal aberrations of chromosome Nr 8 predominates. The occurrence of cases with trisomy-8 and cases with structural rearrangements involving a breakpoint in 8q11-8q13 allows a further subdivision of this group of tumors. Our special interest in this paper is devoted to the latter group. the hypothesis is proposed that in these cases the chromosomal rearrangement is the primary event in tumorigenesis, leading to activation of a so far unknown oncogene located most likely at 8q12. The translocations to different recipient chromosomes may serve as sign posts to transcriptionally active chromosomal domains in the salivary gland.

Penicillin Amidase from E. coli

Abstract: Penicillin amidase (EC 3.5.1.1 1) is an enzyme that can catalyze the hydrolysis and synthesis of amide bonds between phenylacetic or phenoxyacetic acid and their derivatives and 6-aminopenicillanic acid (6-APA) or 7-aminocephalosporanic acid (7-ACA) and its derivatives.' Penicillin amidases with different molecular weights (60-260 kDa), substrate specificities and pH optima have been found in more than 100 microorganisms. The biological function of these enzymes is still not known. The enzymes from E . coli (penicillin G amidase) and P. ostreatus (penicillin V amidase) are currently used on an industrial scale for the hydrolysis of penicillin G and V2 respectively. The main product-6-APA-is used for the synthesis of semisynthetic penicillins and cephalosporins. These enzymes can also be used as biocatalysts for the synthesis of the semisynthetic 8-lactam antibiotics. Two different processes can be applied here.3 In the equilibrium controlled process the enzyme is used as a hydrolase in the reverse direction that accelerates the condensation reaction to its thermodynamic equilibrium. The product yield cannot be influenced by the properties of the enzyme. In the second process-kinetically controlled-activated substrates must be used. The enzyme is here used as a transferase that catalyzes the transfer of the side-chain to the P-lactam nucleophile (6-APA, 7-ACA etc.). The maximum product yield in this process is a function of the properties of the enzyme.' Thus, for the kinetically controlled process the enzyme properties that influence the yield must be known. To obtain this information studies using pure enzyme are required. Some results on the E . coli penicillin amidase pertinent in this context are presented here.