Showing papers by "University of Marburg published in 1985"

Kernels for Nonparametric Curve Estimation

Abstract: SUMMARY The choice of kernels for the nonparametric estimation of regression functions and of their derivatives is investigated Explicit expressions are obtained for kernels minimizing the asymptotic variance or the asymptotic integrated mean square error, IMSE (the present proof of the optimality of the latter kernels is restricted up to order k = 5) These kernels are also of interest for the nonparametric estimation of probability densities and spectral densities A finite sample study indicates that higher order kernels-asymptotically improving the rate of convergence-may become attractive for realistic finite sample size Suitably modified kernels are considered for estimating at the extremities of the data, in a way which allows to retain the order of the bias found for interior points

Glucocorticoid and progesterone receptors bind to the same sites in two hormonally regulated promoters.

Abstract: The glucocorticoid receptor of rat liver recognizes nucleotide sequences near the promoter of mouse mammary tumour virus (MMTV) required for hormonal induction in gene transfer experiments1–4. Similar nucleotide sequences have been found in the human metallothionein gene IIA (ref. 5) and in the chicken lysozyme gene6, the latter induced also by oestrogen, progesterone and androgens. In microinjection experiments, deletion of only 44 base pairs (bp) of the lysozyme promoter (from −208 to −164) results in coordinated loss of progesterone and glucocorticoid-dependent gene expression6. We show here that purified glucocorticoid receptor from rat liver and progesterone receptor from rabbit uterus yield similar or overlapping exonuclease III footprints in the promoter regions of MMTV and chicken lysozyme. Thus, the regulatory elements for different steroid hormones may be similar or at least share structural features.

Colocalization of band 3 with ankyrin and spectrin at the basal membrane of intercalated cells in the rat kidney

Abstract: An immunoreactive form of the anion channel protein of erythrocytes, band 3, has been identified in the rat kidney. It is found in the intercalated cells of the distal tubule and collecting ducts. Immunostaining specific for band 3 is confined to the basolateral plasma membrane of these cells, where this protein probably mediates the transport of bicarbonate across the tubular wall. Double-immunolabeling studies demonstrate that band 3 is colocalized with immunoreactive forms of ankyrin and spectrin along the basolateral plasma membrane. The polarized distribution of band 3 may be the result of the association of its cytoplasmic domain with ankyrin, which in turn links band 3 to spectrin and the cytoskeleton. These observations help to explain how the collecting ducts of the kidney can direct the transport of bicarbonate ions, thus maintaining the acid-base balance.

Tumor promotion in the liver.

Abstract: Intensive research during recent years has made the rodent liver one of the best model systems to study chemical carcinogenesis and tumor promotion in vivo. As will be shown in the present paper current knowledge mainly rests on the results of histological and histochemical studies but has reached a state where broader application of the techniques of biochemistry and molecular biology is both possible and necessary for further progress. Such progress will have important implications for the design of future cancer therapies and for the toxicological evaluation of potentially carcinogenic compounds.

Observation of singular diameters in the coexistence curves of metals.

Abstract: We report the first reliable determination of the liquid-vapor coexistence curves of the metals cesium and rubidium. Both curves are noticeably different from those of nonmetallic fluids in their extreme vapor-liquid asymmetry which causes the law of rectilinear diameter to break down. The functional form of the diameter is consistent with the suggestion by Goldstein and Ashcroft that the strong state dependence of the effective interparticle forces leads to large amplitudes of the 1 -$\ensuremath{\alpha}$ anomaly.

Lifetime enhancement of two-dimensional excitons by the quantum-confined Stark effect.

Abstract: We report on picosecond luminescence studies of GaAs/AlGaAs quantum wells in the regime of the quantum-confined Stark effect. A drastic increase of the recombination lifetime is accompanied by a Stark shift of the photoluminescence of the lowest free exciton for electric fields perpendicular to the quantum-well layers. A consistent picture of the quantum-confined Stark effect is presented.

Isolation and properties of cytochrome c oxidase from rat liver and quantification of immunological differences between isozymes from various rat tissues with subunit-specific antisera.

Abstract: Cytochrome c oxidase was isolated from rat liver either by affinity chromatography on cytochrome-c-Sepharose 4B or by chromatography on DEAE-Sepharose. Dodecyl sulfate gel electrophoresis of both preparations showed the same subunit pattern consisting of 13 different polypeptides. Kinetic analysis of the two preparations gave a higher Vmax for the enzyme isolated by chromatography on DEAE-Sephacel. Specific antisera were raised in rabbits against nine of the ten nuclear endoded subunits. A monospecific reaction of each antiserum with its corresponding subunit was obtained by Western blot analysis, thus excluding artificial bands in the gel electrophoretic pattern of the isolated enzyme due to proteolysis, aggregation or conformational modification of subunits. With an antiserum against rat liver holocytochrome c oxidase a different reactivity was found by Western blot analysis for subunits VIa and VIII between isolated cytochrome c oxidases from pig liver or kidney and heart or skeletal muscle. For a quantitative analysis of immunological differences a nitrocellulose enzyme-linked immunosorbent assay was developed. Monospecific antisera against 12 of the 13 subunits of rat liver cytochrome c oxidase were titrated with increasing amounts of total mitochondrial proteins from different rat tissues dissolved in dodecyl sulfate and dotted on nitrocellulose. The absorbance of a soluble dye developed by the second peroxidase-conjugated antibody was measured. From the data the following conclusions were obtained: (a) The mitochondrial encoded catalytic subunits I–III of cytochrome c oxidase are probably identical in all rat tissues. (b) All nine investigated nuclear encoded subunits of cytochrome c oxidase showed immunological differences between two or more tissues. Large immunological differences were found between liver, kidney or brain and heart or skeletal muscle. Minor but significant differences were observed for some subunits between heart and skeletal muscle and between liver, kidney and brain. (c) Between corresponding nuclear encoded subunits of cytochrome c oxidase from fetal and adult tissues of liver, heart and skeletal muscle apparent immunological differences were observed. The data could explain cases of fatal infantile myopathy due to cytochrome c oxidase deficiency.

Histological and fine structural features of pancreatic ductal adenocarcinomas in relation to growth and prognosis: studies in xenografted tumours and clinico-histopathological correlation in a series of 75 cases.

Abstract: Histology and fine structure of pancreatic ductal adenocarcinomas were assessed with respect to their significance for tumour growth and prognosis. The histological parameters included glandular differentiation, nuclear anaplasia, nuclear size, and mitotic activity (number of mitoses per high power field). Using these criteria three grades of malignancy were distinguished. They correlated well with the growth kinetics of seven human pancreatic ductal adenocarcinomas transplanted into nude mice. The tumour doubling time of a G 3 carcinoma was about half that of a G 1 carcinoma. On electron microscopy the tumour grade was reflected in the degree of functional differentiation of the neoplastic duct cells. In an additional clinicopathological evaluation of 75 patients operated upon for ductal adenocarcinoma of the pancreatic head, a positive relationship was found between grade and duration of symptoms until diagnosis. Moreover, the G 1 tumours showed generally a lower stage symptoms until diagnosis. Moreover, the G 1 tumours showed generally a lower stage at the time of surgery than G 2 and G 3 carcinomas. Finally, the median survival times correlated significantly with the tumour grade. From the various parameters used nuclear grade proved to be the most significant prognostic criterion, since a separate morphometric study revealed a very close correlation between median nuclear size of the tumours and survival time.

Cloning and sequence analysis of human genomic DNA encoding γ subunit precursor of muscle acetylcholine receptor

Abstract: Human genomic DNA encoding the γ subunit precursor of the skeletal muscle acetylcholine receptor has been cloned by screening a gene library with a calf cDNA probe and has been subjected to nucleotide sequence analysis. Comparison of the nucleotide sequence of the cloned human genomic DNA with that of the calf cDNA has revealed that the protein-coding sequence of this gene is divided by 11 introns into 12 exons. Evidence is presented to suggest that the human muscle acetylcholine receptor γ and δ subunit genes are juxtaposed. The primary structure of the γ subunit precursor of the human muscle acetylcholine receptor has been deduced from the corresponding gene sequence. This polypeptide is composed of 517 amino acids including a hydrophobic prepeptide of 22 amino acids. The γ subunit of the human muscle acetylcholine receptor, like the α subunit of the same receptor as well as the α, β and γ subunits of its calf counterpart, shares structural features common to all four subunits of the Torpedo electroplax receptor, such as the putative disulphide bridge corresponding to that in the α subunit proposed as being in close proximity to the acetylcholine binding site and the four putative, hydrophobic transmembrane segments M1 – M4. Thus, the human γ subunit molecule apparently exhibits the same transmembrane topology as proposed for the fish receptor subunits. The 12 exons seem to correspond to different structural and functional domains of the γ subunit precursor molecule. Some exons and the protein regions encoded by them are more highly conserved between the mammalian and Torpedo sequences. The pattern of regional homology observed is consistent with the relatively high conservation of the region encompassing the putative disulphide bridge and of the region containing the putative transmembrane segments M1, M2 and M3.

Endoscopic and bioptic study of the upper gastrointestinal tract in Crohn's disease patients.

Abstract: Summary For the clinician and privately practicing physician, it is advisable to always obtain gastric biopsies in the presence of Crohn’s disease of the small and/or large bowel, even when endoscopic lesions of the gastric mucosa are not discernible In the present study, virtually all of 225 patients suffering from Crohn’s disease of the lower gastrointestinal tract (small and/or large bowel) were subjected to endoscopic examination of the upper gastrointestinal tract (esophagus, stomach, duodenum); while histologic examination of the upper gastrointestinal tract was performed in a portion of the patients (54 initial esophageal, 221 initial gastric and 210 initial duodenal examinations). Statistical evaluation of the findings from the upper gastrointestinal tract revealed that: 1. Endoscopic lesions were observed in the esophagus of 15%, the stomach of 49%, and the duodenum of 34% of the 225 Crohn’s disease patients. Of the 54 patients from which esophogeal biopsies were taken, 31 (57%) revealed histopathologic alterations. Of the 221 patients from which gastric biopsies were obtained, 60% revealed histopathologic alterations; the rate was 53% in the 210 patients from which duodenal biopsies were taken. 2. Calculated from the present data, noncaseating granulomas, i. e., Crohn’s disease, were present only in the stomach of 29.4% o the patients, only in the duodenum in 3.4% of patients, and in both the stomach and duodenum in 4.9% of patients. Gastric granulomas were confined to the region of the stomach body and fundus in 3.4% of the patients from which gastric biopsies were obtained and to the antrum in 15.6% of the respective patients. Both gastric regions were involved in 8.3% of the respective patients. 3. The incidence of gastric granulomas was significantly increased in young patients, patients with enterocolic manifestations of Crohn’s disease, and those with brief duration of disease. Patient sex or previous drug therapy had no effect on the incidence of granulomas. 4. The most frequent endoscopic findings in the stomach of patients with Crohn’s disease were mucosal edema, mucosal redness, and acute or chronic erosions. Only chronic erosions were of significant predictive value for the presence of granulomas, i. e., diagnosis of Crohn’s disease. The most frequent endoscopic lesion in the duodenum was mucosal redness, followed by mucosal edema and aphthous lesions. Ulcers, stenosis, and mucosal redness had significant predictive values for the presence of granulomas. 5. The mose frequent histopathologic findings in the stomach were diffuse and focal superficial inflammation, and granulomas — in the duodenum diffuse, discontinuous, and focal inflammation. Significant predictive values for the occurrence of granulomas in the stomach were found in the presence of focal superficial gastric inflammation and “crypt abscess” (foveolar empyema); in the duodenum in the presence of focal inflammation, “crypt abscess” and ulcers. 6. Single or multiple repetition of endoscopy with histologic evaluation did not significantly increase the incidence of granulomas.

The Permo-Triassic »Paleotethys« in mainland Southeast-Asia and adjacent parts of China

Abstract: Aspects of the geodynamic evolution of mainland Southeast Asia and China are discussed in consideration of the Permo-Triassic »Paleotethys« problem. It is shown that all sutures in Thailand, Vietnam and Yunnan already closed during the Paleozoic era and that the entire region must be regarded as part of the northern continents. The Permo-Triassic »Paleotethys« must be expected south of Tibet and in Burma.

Isolation and characterization of the Fnr protein, the transcriptional regulator of anaerobic electron transport in Escherichia coli.

Abstract: The Fnr protein, the transcriptional regulator of the expression of anaerobic respiratory functions in Escherichia coli, was purified to homogeneity from soluble extracts of a strain harbouring the fnr gene in an expression vector. 1 The identity of the isolated protein was confirmed by comparing its amino-terminal sequence with that predicted from nucleotide sequence of the fnr gene. It appeared that eight amino-terminal amino acids had been removed post-translationally from the bulk of the isolated Fnr protein. 2 The molecular mass of the isolated protein (Mr 28000) was consistent with a monomeric state, but sedimentation coefficients for the cellular (4.1 S) and the isolated (2.9 S) Fnr protein suggest that it may exist as a dimer in the bacterial cells. 3 The Fnr protein bound DNA. However, the binding activity was not specific for the regulatory regions of relevant genes and it could not be stimulated by a variety of conditions or potential effectors. 4 Two of the four cysteine residues of the Fnr protein were alkylated by iodoacetic acid and this could have functional significance in rendering the protein redox-sensitive.

Sources of heat during nonshivering thermogenesis in Djungarian hamsters: a dominant role of brown adipose tissue during cold adaptation

Abstract: To assess the thermogenic importance of BAT in Djungarian hamsters we removed about 40% of their BAT and compared their thermogenic abilities before and after the operation. BAT was weighed and assayed for its respiratory properties (Cox, mitochondria). Following removal of BAT we observed considerable reductions of NST. The comparison of NST with BAT weight and with respiratory properties of BAT following partial removal of BAT revealed that at least three different pathways for heat production were involved in NST. In cold-adapted hamsters (values for warm-adapted hamsters in parentheses) we estimated that 66.2% (37.0%) of all NST was produced by mitochondrial respiration in BAT; 16.3% (38.4%) was produced in other organ sites but required the presence of BAT, i.e. there was a mediatory action of BAT on thermogenesis in other organ sites. A further 11.5% (23%) of NST occurred outside of and independent of BAT. Mitochondrial respiration in BAT was the only compartment of NST which increased its contribution during cold adaptation (238 mW to 1,062 mW), whereas the other sources of heat remained largely unchanged.

Inhibition of human and canine diamine oxidase by drugs used in an intensive care unit: relevance for clinical side effects?

Abstract: Three hundred and forty-one drugs, commonly used in intensive care units (ICU), were chosen for an investigation of possible activation or inhibition of the histamine metabolizing enzyme diamine oxidase (DAO). After examination of 164 substances, using both canine and human DAO in anin vitro screening test, 61 agents inhibited DAO activity to various degrees. Of these, 44 inhibited the enzyme from both species, 4 inhibited the canine enzyme only and 13 the human DAO only. No. compound tested was able to enhance the enzyme activity. The inhibiting agents included representatives of all major therapeutic groups. A particlarly strong inhibition was observed with the neuromuscular blocking drugsd-tubocurarine, pancuronium and alcuronium, however, the other commonly used neuromuscular blocking drug, suxamethonium, was without effect. Similarly with the cephalosporines, cefotiame and cefuroxime caused a marked inhibition of the human DAO activity, whereas another regularly-used substance of this class, cefotaxime, inhibited neither the human nor the canine enzyme in concentrations up to 10−3 M. The observation that within a given therapeutic group some members inhibit and others do not, could be useful in choosing a therapy concept which minimizes the risk of a more severe ‘histamine’ reaction in seriously ill patients.

Mechanism of acetate oxidation to CO2 with elemental sulfur in Desulfuromonas acetoxidans

Abstract: The strict anaerobe Desulfuromonas acetoxidans can oxidize acetate to CO2 with elemental sulfur as electron acceptor. 14C-labelling experiments and enzyme studies are described revealing that acetate oxidation proceeds via the citric acid cycle with the synthesis of oxaloacetate from acetate and 2 CO2 via pyruvate as anaplerotic reaction. An oxidation of acetate via one carbon unit intermediates as proposed for anaerobic bacteria fermenting acetate to 2 CO2 and 4 H2 was excluded.

Glycosphingolipids in insects. Chemical structures of ceramide monosaccharide, disaccharide, and trisaccharide from pupae of Calliphora vicina (Insecta: Diptera).

Abstract: The presence of glycosphingolipids in the pupae of the blowfly, Calliphora vicina, was established. The thin layer chromatographic pattern of the total neutral glycolipids revealed the presence of more than 13 components, the major one being ceramide monohexoside. By the use of high performance liquid chromatography, the three simplest components were isolated and their chemical structures determined: Glc(beta 1-1)Cer, Man(beta 1-4)-Glc(beta 1-1)Cer [with minor component Gal(beta 1-4)Glc(beta 1-1)Cer] and GlcNAc(beta 1-3)Man(beta 1-4)Glc(beta 1-1)-Cer. The ceramide composition of the parent insect glycosphingolipids is dominated by the 20:0 fatty acid, arachidic acid, and the sphingoid tetradecasphing-4-enine.

Seasonal Acclimation and Thermogenesis

Abstract: Low ambient temperatures and the shortage of food during winter are confronting ail endotherms with severe challenges of thermoregulation and threaten their energy balance. In order to cope with cold mammals, birds, and endothermic insects must possess a capacity for thermoregulatory heat production large enough to compensate ail heat lost to the environment. This is especially true for small mammals where thermal insulation of fur is rather limited, and they have to rely primarily on heat production (Scholander et al. 1950; Hart 1965).

Presence of a Na + /H + antiporter in Methanobacterium thermoautotrophicum and its role in Na + dependent methanogenesis

Abstract: Methane formation from H2/CO2 by methanogenic bacteria is dependent on Na+ ions In this communication it is shown with Methanobacterium thermoautotrophicum that a Na+/H+ antiporter plays a role in methane formation from H2 and CO2 and in the regulation of the ΔpH This is based on the following findings:

Preparation and characterization of poly[oxy(2,6-dimethyl-1,4-phenylene)] with functional end groups†

Abstract: The oxidative polymerization of 2,6-dimethylphenol (1) and the halogen displacement polymerization of 4-halo-2,6-dimethylphenols (4) yielded poly[oxy(2,6-dimethyl-1,4-phenylene)] (2) with one phenolic end group. 2,2′,6,6′-Tetramethyl-4,4′-isopropylidenediphenol (9a) was used as comonomer in both polymerization reactions to obtain polymer 10a, containing two phenolic end groups. Polymers of different molecular weight were synthesized by variation of the mole ratio of the comonomers. The polymers were characterized by GPC, NMR spectroscopy and end group analysis.

Anomalous diffusion on a selfsimilar hierarchical structure

Abstract: The temporal increase of the moments in diffusion on a fractal with variable hopping range and lower cut-off is given. The essential parameters are the growth ratio, the length scaling and, as a new feature, the time scaling along the hierarchy. We find algebraical or exponential increase, logarithmic corrections, or trapping if the cut-off is removed. For the first time anomalous enhancement of the variance increase σ'0 tθ, θ larger than 2, is obtained as observed in turbulence On etudie la croissance temporelle des moments de la distribution de particules diffusant sur un fractal a portee de saut variable avec une coupure inferieure. Les parametres essentiels sont: le taux de croissance, le facteur d'echelle de la longueur et celui du temps le long de la hierarchie, ce dernier critere est nouveau. On trouve des lois de croissance algebriques et exponentielles et des corrections logarithmiques, ou un piegeage si la coupure est eliminee. Une augmentation anormale du taux de croissance de la variance σαtθ, θ>2, comme cela a deja ete observe pour la turbulence, est obtenue pour la 1ere fois

Formation of carbon monoxide from CO2 and H2 by Methanobacterium thermoautotrophicum.

Abstract: Cell suspensions of Methanobacterium thermoautotrophicum were found to reduce CO2 with H2 to CO at a maximal rate of 100 nmol − min−1− mg protein−1. Half-maximal rates were obtained at a H2 and a CO2 concentration in the gas phase of 10% and 30%, respectively. The CO concentration in the gas phase surpassed the equilibrium concentration by a factor of more than 15 which indicates that CO2 reduction with H2 to CO was energy-driven. This was substantiated by the observation that the cells only formed CO when they also generated methane and that CO formation was completely inhibited by uncouplers. CO formation by cell suspensions and by growing cells was inhibited by cyanide. Neither methane formation nor the electrochemical proton potential were affected by this inhibitor. Cyanide was shown to inactivate specifically the carbon monoxide dehydrogenase present in M. thermoautotrophicum. It is therefore concluded that reduction of CO2 to CO is catalyzed by this enzyme. CO production by growing cells was 5–10-times slower than by resting cells. This is explained by effective CO assimilation in growing cells; when CO assimilation was inhibited by propyl iodide the rate of CO production immediately increased more than tenfold.

Hopping theory of band-tail relaxation in disordered semiconductors.

Abstract: Within a new theoretical approach the current and energy decay in amorphous semiconductors is studied. The relaxation of photoexcited carriers observed by transient photoconductivity experiments in amorphous silicon and chalcogenides can well be described by an algebraic power-law decay. The theoretical explanation is based on nonequilibrium hopping transport between localized states in a band tail. The theory reproduces the typical temperature dependence of the decay param- eter commonly explained within a multiple-trapping (MT) model. The observed deviations from the simple MT relation at low temperatures can be explained by the theory. Additionally, direct calculation of the energy relaxation reveals further insight into the dissipation process.

Radical ions as chain carriers in polymerization reactions

Abstract: Certain polymerization reactions show the formation of medium molecular weights at the beginning of the reaction, although they can be considered to be polycondensations. The principle of equal reactivity of the end groups is not given in this case. Intermediates more reactive than the monomer are formed during the reaction. Poly(oxy-2,6-dimethyl-l,4-phenylene), poly(l,4-phenylene sulfide) and poly(l,4-phenylene) are examples of this type of reaction. The formation of radical ions in these reactions is discussed and they are compared to Bunnett's SRN1-reactions.