Showing papers by "Martin Luther University of Halle-Wittenberg published in 1998"

An efficient approach to clustering in large multimedia databases with noise

Abstract: Several clustering algorithms can be applied to clustering in large multimedia databases. The effectiveness and efficiency of the existing algorithms, however, is somewhat limited, since clustering in multimedia databases requires clustering high-dimensional feature vectors and since multimedia databases often contain large amounts of noise. In this paper, we therefore introduce a new algorithm to clustering in large multimedia databases called DENCLUE (DENsity-based CLUstEring). The basic idea of our new approach is to model the overall point density analytically as the sum of influence functions of the data points. Clusters can then be identified by determining density-attractors and clusters of arbitrary shape can be easily described by a simple equation based on the overall density function. The advantages of our new approach are (1) it has a firm mathematical basis, (2) it has good clustering properties in data sets with large amounts of noise, (3) it allows a compact mathematical description of arbitrarily shaped clusters in high-dimensional data sets and (4) it is significantly faster than existing algorithms. To demonstrate the effectiveness and efficiency of DENCLUE, we perform a series of experiments on a number of different data sets from CAD and molecular biology. A comparison with DBSCAN shows the superiority of our new approach.

Adipophilin is a specific marker of lipid accumulation in diverse cell types and diseases

Abstract: We report the human DNA and protein sequence of adipophilin and its association with the surface of lipid droplets. The amino acid sequence of human adipophilin has been determined by using cDNA clones from several tissues and confirmed by the reverse transcription/polymerase chain reaction method and Edman sequencing. The open reading frame of adipophilin encodes a polypeptide with a calculated molecular weight of 48.1 kDa and an isoelectric point of 6.72. By immunofluorescence and electron-microscopic localization with newly raised specific poly- and monoclonal antibodies, we show that this protein is not restricted to adipocytes as previously indicated by studies of the mouse homologous protein, adipose-differentiation-related protein. Adipophilin occurs in a wide range of cultured cell lines, including fibroblasts and endothelial and epithelial cells. In tissues, however, expression of adipophilin is restricted to certain cell types, such as lactating mammary epithelial cells, adrenal cortex cells, Sertoli and Leydig cells of the male reproductive system, and steatosis or fatty change hepatocytes in alcoholic liver cirrhosis. Our results reveal adipophilin as a possible new marker for the identification of specialized differentiated cells containing lipid droplets and for diseases associated with fat-accumulating cells.

SET domain proteins modulate chromatin domains in eu- and heterochromatin.

Abstract: The SET domain is a 130-amino acid, evolutionarily conserved sequence motif present in chromosomal proteins that function in modulating gene activities from yeast to mammals. Initially identified as members of the Polycomb- and trithorax-group (Pc-G and trx-G) gene families, which are required to maintain expression boundaries of homeotic selector (HOM-C) genes, SET domain proteins are also involved in position-effect-variegation (PEV), telomeric and centromeric gene silencing, and possibly in determining chromosome architecture. These observations implicate SET domain proteins as multifunctional chromatin regulators with activities in both eu- and heterochromatin – a role consistent with their modular structure, which combines the SET domain with additional sequence motifs of either a cysteine-rich region/zinc-finger type or the chromo domain. Multiple functions for chromatin regulators are not restricted to the SET protein family, since many trx-G (but only very few Pc-G) genes are also modifiers of PEV. Together, these data establish a model in which the modulation of chromatin domains is mechanistically linked with the regulation of key developmental loci (e.g. HOM-C).

Compartment-specific accumulation of recombinant immunoglobulins in plant cells: an essential tool for antibody production and immunomodulation of physiological functions and pathogen activity.

Abstract: Expression and stability of immunoglobulins in transgenic plants have been investigated and optimized by accumulation in different cellular compartments as cytosol, apoplastic space and endoplasmic reticulum (ER) as will be discussed in this review. In several cases described the highest accumulation of complete active antibodies was achieved by targeting into the apoplastic space. High-level expression of active recombinant single-chain Fv antibodies (scFv's) was obtained by retention of these proteins in the lumen of the endoplasmic reticulum. This has been shown for leaves and seeds of transgenic tobacco as well as for potato tubers. Transgenic tobacco seeds, potato tubers and tobacco leaves can facilitate stable storage of scFv's accumulated in the ER over an extended (seeds, tubers) or a short (leaves) period of time. The expression of specific scFv's in different plant species, plant organs and cellular compartments offers the possibility of blocking regulatory factors or pathogens specifically. Examples are scFv's expressed in the cytosol and the apoplastic space of transgenic plant cells modulating the infection process of plant viruses and a cytosolically expressed scFv that influenced the activity of phytochrome A protein. The immunomodulation approach has been shown to be also applicable for investigating the action of the phyto-hormone abscisic acid (ABA). High-level accumulation of specific anti-ABA scFv's in the ER of all leaf cells has been used to block the influence of ABA on the stomatal functions. Seed-specific expression of high amounts of anti-ABA-scFv's at a defined time of seed-development induced a developmental switch from seed ripening to vegetative growth. It has been demonstrated that ER retention is essential for the accumulation of sufficient scFv to bind high concentrations of ABA in the transgenic seeds.

Leptomycin B‐sensitive nuclear export of MAPKAP kinase 2 is regulated by phosphorylation

Abstract: To study the intracellular localization of MAPKAP kinase 2 (MK2), which carries a putative bipartite nuclear localization signal (NLS), we constructed a green fluorescent protein-MAPKAP kinase 2 fusion protein (GFP-MK2). In transfected cells, this protein is located predominantly in the nucleus; unexpectedly, upon stress, it rapidly translocates to the cytoplasm. This translocation can be blocked by the p38 MAP kinase inhibitor SB203580, indicating its regulation by phosphorylation. Molecular mimicry of MK2 phosphorylation at T317 in GFP-MK2 led to a mutant which is located almost exclusively in the cytoplasm of the cell, whereas the mutant T317A shows no stress-induced redistribution. Since leptomycin B, which inhibits the interaction of exportin 1 with the Rev-type leucine-rich nuclear export signal (NES), blocks stress-dependent translocation of GFP-MK2, it is supposed that phosphorylation-induced export of the protein causes the translocation. We have identified the region responsible for nuclear export in MK2 which is partially overlapping with and C-terminal to the autoinhibitory motif. This region contains a cluster of hydrophobic amino acids in the characteristic spacing of a leucine-rich Rev-type NES which is necessary to direct GFP-MK2 to the cytoplasm. However, unlike the Rev-type NES, this region alone is not sufficient for nuclear export. The data obtained indicate that MK2 contains a constitutively active NLS and a stress-regulated signal for nuclear export. Keywords: nuclear export/nuclear import/protein phosphorylation/signal transduction/stress response

The deadenylating nuclease (DAN) is involved in poly(A) tail removal during the meiotic maturation of Xenopus oocytes

Abstract: Exonucleolytic degradation of the poly(A) tail is often the first step in the decay of eukaryotic mRNAs and is also used to silence certain maternal mRNAs translationally during oocyte maturation and early embryonic development. We previously described the purification of a poly(A)‐specific 3′‐exoribonuclease (deadenylating nuclease, DAN) from mammalian tissue. Here, the isolation and functional characterization of cDNA clones encoding human DAN is reported. Recombinant DAN overexpressed in Escherichia coli has properties similar to those of the authentic protein. The amino acid sequence of DAN shows homology to the RNase D family of 3′‐exonucleases. DAN appears to be localized in both the nucleus and the cytoplasm. It is not stably associated with polysomes or ribosomal subunits. Xenopus oocytes contain nuclear and cytoplasmic DAN isoforms, both of which are closely related to the human DAN. Anti‐DAN antibody microinjected into oocytes inhibits default deadenylation during progesterone‐induced maturation. Ectopic expression of human DAN in enucleated oocytes rescues maturation‐specific deadenylation, indicating that amphibian and mammalian DANs are functionally equivalent.

Lysosomal Cysteine Proteinases

Abstract: Cathepsin B has so far been the most investigated cysteine (thiol) proteinase of lysosomes. The use of cytosol proteins as substrates has allowed the detection of two new lysosomal cysteine proteinases from rat liver: the endoaminopeptidase cathepsin H and cathepsin L, which splits almost no synthetic substrates but has a more than 10-fold higher specific activity with proteins as substrates than other mammalian cysteine proteinases. The properties of cathepsin L are compared with those of other cysteine proteinases (cathepsin B,H,N,S and others) from different tissues in relation to substrate specificity and sensitivity to inhibitors. A new test system for determining cathepsin L allows us to investigate the distribution of this enzyme between different cell types and to speculate about the special role of cysteine proteinase in intracellular protein degradation.

Prophylactic thyroidectomy in 75 children and adolescents with hereditary medullary thyroid carcinoma : german and austrian experience

Abstract: RETproto-oncogene were found in 1993 to account for hereditary medullary thyroid carcinoma (MTC), surgeons obtained the opportunity to operate on patients prophylactically (ie, at a clinically asymptomatic stage) Whether this approach is justified, and, if so, when and to which extent surgery should be performed remained to be clarified A questionnaire was sent to all surgical departments in Germany and Austria All of the patients who fulfilled the following criteria were enrolled: (1) preoperatively proved RET mutation; (2) age ≤ 20 years, (3) clinically asymptomatic thyroid C cell disease; and (4) TNM classification pT0–1/pNX/pN0–1/M0 Seventy-five patients were identified, and fifteen mutations were detected in six codons Two adolescents had unilateral pheochromocytomas as part of the multiple endocrine neoplasia II (MEN-II) syndrome No hyperparathyroidism was noted All patients underwent total thyroidectomy, and 57 patients went on to have lymph node dissection Parathyroid glands were removed in 34 patients and autografted in 11 Histopathology revealed MTC in 46 patients (61%, youngest 4 years); C cell hyperplasia (CCH) only was detected in the other 29 patients Three patients had lymph node metastases (LNMs) the youngest being age 14 years Calcitonin levels were not useful for differentiating between CCH and MTC, but in all patients with LNMs at least the stimulated calcitonin levels were assayed After surgery, five patients (67%) sustained permanent hypoparathyroidism, and one patient (13%) had a permanent unilateral recurrent nerve palsy All but three patients (96%) were biochemically cured In conclusion, prophylactic total thyroidectomy can be performed safely in experienced centers We recommend prophylactic total thyroidectomy at age 6 Cervicocentral lymph node dissection should be included when calcitonin levels are elevated or if patients are older than 10 years Bilateral lymph node dissection should be performed if LNMs are suspected or when patients with elevated calcitonin are older than 15 years

Monte carlo simulations of short-time critical dynamics

Abstract: Monte Carlo simulations of the short-time critical dynamics are reviewed. The short-time universal scaling behavior of the dynamic Ising model and Potts model are discussed in detail, while extension and application to more complex systems as the XY model, the fully frustrated XY model and other dynamic systems are also presented. The investigation of the universal behavior of the short-time dynamics not only enlarges the fundamental knowledge on critical phenomena but also, more interestingly, provides possible new ways to determine not only the new critical exponents θ and θ1, but also the traditional dynamic critical exponent z as well as all static critical exponents.

Biological and prognostic significance of stratified epithelial cytokeratins in infiltrating ductal breast carcinomas.

Abstract: The biological significance of the differential expression of cytokeratin (CK) polypeptides in breast carcinomas is unclear. We examined the CK profiles of 101 primary infiltrating ductal breast carcinomas using monoclonal antibodies directed against 11 different CKs and against vimentin. Two major CK phenotypes were distinguished: first, a phenotype expressing only the simple-epithelial CKs 7 (variably), 8, 18 and 19, and secondly, a bimodal phenotype co-expressing significant amounts of one or more of the stratified-epithelial CKs 4, 14 and 17. The vast majority of G1 and G2 carcinomas had the simple-epithelium phenotype, as did a subgroup of G3 carcinomas. Interestingly, the majority (62%) of G3 carcinomas exhibited the bimodal phenotype, with the expression of CKs 4, 14 and 17 being statistically correlated with poor histological differentiation and absence of steroid hormone receptors. The distribution of vimentin only partially overlapped with that of these stratified-epithelial CKs. Prognostic analyses suggested that the presence of CKs 4, 14 and/or 17 was associated with short overall and disease-free survival in subgroups comprising G3, oestrogen-receptor-negative and vimentin-negative tumours. In node-positive tumours the correlation between these CKs and a shorter disease-free interval attained statistical significance (log rank, 0.0096). Thus, abnormal CK profiles in ductal breast carcinomas appear to reflect disturbed regulation of differentiation-related gene expression programmes and may prove to be of clinical value.

DQAsomes: a novel potential drug and gene delivery system made from Dequalinium.

Abstract: Purpose. Dequalinium, a drug known for over 30 years, is a dicationic amphiphile compound resembling bolaform electrolytes. The purpose of our work was to determine the state of aggregation of dequalinium in aqueous medium and to investigate both, its ability to bind DNA and its potential to serve as a novel non-viral transfection vector.

Small Heat-Shock Protein Family: Function in Health and Disease

Abstract: In summary, several important issues were discussed at the workshop. These included the importance of oligomer size for different functions of the sHsps, the highly significant observation that the sHsps can block apoptosis; and that some mechanisms of sHsps protection involve glutathione while others may be related to microfilament stability. Further evidence was presented for the chaperone functions of sHsps, and structural studies provided additional information relating sHsps' large oligomeric structure to chaperone function. Regulation of oligomer size by phosphorylation was also a prominent topic of discussion, as was the importance of the relationship of oligomer size to differing functions of Hsp27. An interesting contrast was noted between Hsp27, whose oligomer size is regulated by phosphorylation, and alpha beta-crystallin, whose large oligomer structure is unaffected by phosphorylation. This may prove to be of physiological significance, particularly in cell types that express both of these proteins. Observations of the translocation of MAPKAP kinase 2 from the nucleus to the cytoplasm in live cells suggest that the dynamics of phosphorylation of the sHsps may be more complex than previously thought. One topic that seems to have been settled is that the binding site of at least dimers of sHsps resides in the carboxyl-terminal region of the proteins. Ever-increasing numbers of studies are reporting interesting patterns of sHsp expression, phosphorylation, and subcellular localizations of the sHsps in various cells or tissues in normal and diseased states. Unfortunately, very little is understood about what these observations may mean. It can be expected, however, that as more is learned about the function and regulation of sHsps, the relationships between sHsps and cellular response to disease will become better understood. Lastly, the discovery that specific Hsp27-binding proteins may exist should open completely new avenues of investigation into the functions of sHsps. If the observations of unique subcellular localizations of sHsps in various cells types (e.g., striated muscle and Sertoli cells) can be related to expression of specific Hsp-binding proteins, considerable advances in our understanding of sHsps should result. It was abundantly clear from results presented and from ensuing discussions in the workshop that the study of sHsps is an exceedingly dynamic area of research (FIG. 2) with an ever-expanding significance for a number of other areas of current biological research.

Evidence for a circadian rhythm of insulin release from perifused rat pancreatic islets.

Abstract: This study aims to analyse a circadian rhythm of insulin secretion from isolated rat pancreatic islets in vitro and its potential modulation by melatonin, the concentrations of which change in vivo inversely to that of insulin The circadian rhythm was evaluated in a perifusion system, adapted to the specific conditions of pancreatic islets To determine rhythmicity of insulin secretion, 30-min fractions were collected continuously for investigative periods of 44 to 112 h Insulin secretion in 10 experiments was analysed by using the MacAnova-program for period length (tau), the chi2-periodogram for test of significance (p < 0001), and additionally the empirical cosine adaptation for amplitude and goodness-of-fit Thereby a circadian pattern was observed with periods (tau) between 218 and 262 h The period duration (mean +/- SEM) was 2359 +/- 0503 h, the overall mean insulin release 1038 +/- 13 pmol/l and the mean amplitude 88 +/- 17 pmol/l Adding melatonin (10 nmol/l, t = 2 h) as a hormonal Zeitgeber during analysis of circadian insulin secretion phase-response studies show phase-shifts with approximately 9 h phase advance Thereafter the circadian period was maintained, while the amplitude was enhanced From this it is concluded that an endogenous circadian oscillator is located within the pancreatic islets of the rat that regulates circadian insulin secretion of the insulin-producing beta cells The pacemaker is remarkably stable, because its periodicity is not affected by factors altering insulin secretion In agreement with inhibitory influences of melatonin (range 05 nmol/l to 5 micromol/l) on the insulin response in vitro, the phase-responses support the contention that pancreatic beta cells may be targets for melatonin action

Phosphorus availability, root exudates, and microbial activity in the rhizosphere

Abstract: Field and pot experiments showed that the P demand of wheat is highest in early stages of growth (up to 1.67 μg P per cm2 root surface and day). The needed orthophosphate ions H2PO4− and HPO42-move from soil to the root by diffusion. This process is controlled by the concentration gradient of the diffusible phosphate and the effective diffusion coefficient according to Pick's first law. Root excretions (rhizodeposition) are able to affect both characteristics. The water soluble portion of rhizodeposition contains more than 50% of up to 8 different sugars, 10–40% carboxylic acids and 10–15 amino acids and amides. The composition varies in dependence on the age of the root parts and on nutrition (Zea mays L., Brassica napus L., Pisum sativum L.). Diffusion experiments using small soil blocks showed that 50–75% of the root exudates were decomposed by respiration within 3 days. The rest was largely chemically converted. Originally present sugars disappeared. Due to the biosynthesis of different organic acids from the individual sugars the mobilisation of Ca3(PO4)2 by Pantoea agglomerans increased when the sugar mixture was derived from the rhizodeposition of P deficient plants with more pentoses instead of glucose and fructose (mainly effect of anions). In the rhizosphere therefore a mixture of rhizodeposition and its conversion products exists which affects the binding of phosphorus in soil and the P transport to the root. This should be considered both for the development of new soil extractants and for modelling the P supply to plants. Phosphorverfugbarkeit, Wurzelexsudate und mikrobielle Aktivitat in der Rhizosphare Vegetationsversuche zeigten, das der P-Bedarf des Weizens im Jugendstadium besonders hoch ist (bis 1.67 μg P je cm2 Wurzeloberflache und Tag). Die Anlieferung der hierfur benotigten Orthophosphationen (HPO42−, H2PO4−) erfolgt durch Diffusion, die vom Konzentrationsgradienten diffusiblen Phosphates sowie vom effektiven Diffusionskoeffizienten abhangt. Wurzelabscheidungen (Rhizodeposition) konnen beide Faktoren beeinflussen. Deren losliche Anteile bestehen meist zu mehr als 50% aus bis zu 8 Zuckern, zu 10–40% aus Carbonsauren sowie aus etwa 10–15 Aminosauren und Amiden. Ihre Zusammensetzung wechselt u. a. mit dem Alter der Wurzelteile und der Ernahrung (Zea mays L., Brassica napus L., Pisum sativum L.). Diffusionsversuche unter Verwendung kleiner Bodenblocke (30 mm × 20 mm × 10 mm) zeigten, das 50–75% der loslichen Verbindungen innerhalb von 3 d durch Mikroben veratmet werden. Der Rest ist weitgehend chemisch verandert. Ursprunglich vorhandene Zucker finden sich nicht mehr. Auf Grund der Bildung unterschiedlicher Sauren aus den einzelnen Zuckern erhoht sich beispielsweise bei Pantoea agglomerans das Losungsvermogen fur Ca3(PO4)2, wenn die Zuckermischung aus der Rhizodeposition von P-Mangelpflanzen stammt und dadurch mehr Pentosen auf Kosten eines Teils der Glucose und Fructose enthalt (vor allem Anioneneffekt). In der Rhizosphare greift also eine Mischung aus Rhizodeposition und ihren Umwandlungsprodukten in die P-Bindung und den P-Transport zur Wurzel ein, was bei der Entwicklung neuer Bodenextraktionsmittel wie bei der Modellbildung zu berucksichtigen ist.

Cardiac muscarinic receptors decrease with age. In vitro and in vivo studies.

Abstract: The M1 muscarinic receptor antagonist pirenzepine in low doses decreases resting heart rate; this effect declines with age (Poller, U., G. Nedelka, J. Radke, K. Ponicke, and O.-E. Brodde. 1997. J. Am. Coll. Cardiol. 29:187-193). To study possible mechanisms underlying this effect, we assessed (a) in six young (26 yr old) and six older volunteers (61 yr old), pirenzepine effects (0.32 and 0.64 mg intravenous [i.v.] bolus) on isoprenaline-induced heart rate increases; (b) in five heart transplant recipients, pirenzepine effects (0.05-10 mg i.v. bolus) on resting heart rate in the recipient's native and transplanted sinus nodes; and (c) in right atria from 39 patients of different ages (5 d-76 yr) undergoing open heart surgery, M2 muscarinic receptor density (by [3H]N-methyl-scopolamine binding) and adenylyl cyclase activity. (a) Pirenzepine at both doses decreased heart rate in young volunteers significantly more than in older volunteers; (b) pirenzepine (< 1 mg) decreased resting heart rate in the recipient's native but not transplanted sinus node; and (c) M2 receptor density and carbachol-induced inhibition of forskolin-stimulated adenylyl cyclase activity decreased significantly with the age of the patients. We conclude that pirenzepine decreases heart rate via inhibition of presynaptic M1 autoreceptors, thereby releasing endogenous acetylcholine, and that the heart rate-decreasing effect of acetylcholine declines with age because right atrial M2 receptor density and function decrease.

Endothelin Receptors in the Failing and Nonfailing Human Heart

Abstract: Background—In patients with chronic heart failure (CHF), plasma endothelin-1 (ET-1) levels are increased. We studied whether the cardiac ET-receptor system is altered in CHF patients. Methods and Results—We assessed ET-evoked inositol phosphate (IP) formation in slices from right atria and left ventricles from 6 potential heart transplant donors (NFH) and 15 patients with end-stage CHF; in membranes from the same tissues, we studied ET-induced inhibition of isoprenaline- and forskolin-stimulated adenylyl cyclase and ET-receptor density. ET (10−9 to 10−6 mol/L, ET-1 >>> ET-3) increased IP formation in right atria and left ventricles through ETA-receptor stimulation in a concentration-dependent manner; no difference in potency or efficacy between NFH and CHF hearts was observed. ET-1 (10−10 to 10−6 mol/L), via ETA-receptor stimulation, inhibited isoprenaline- and forskolin-stimulated adenylyl cyclase in right atria but not in left ventricles, whereas carbachol inhibited adenylyl cyclase in both tissues; aga...