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D Activity (d + activity)
Selected AbstractsCalcium-Induced Membrane Microdomains Trigger Plant Phospholipase D ActivityCHEMBIOCHEM, Issue 17 2008Konstantin Kuppe Abstract Plant ,-type phospholipase D proteins are calcium-dependent, lipolytic enzymes. The morphology of the aggregates of their phospholipid substrate fundamentally defines the interaction between the enzyme and the surface. Here we demonstrate that the Ca2+ -induced generation of membrane microdomains dramatically activates ,-type phospholipase D from white cabbage. 500-fold stimulation was observed upon incorporation of 10 mol,% 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphate (POPA) into 1-palmitoyl-2-oleoyl- sn -glycero-3-phosphocholine (POPC) vesicles in the presence of Ca2+ ions. Enhanced association of PLD,2 with phospholipid surfaces containing anionic components was indicated by lag phase analysis and film balance measurements. Differential scanning calorimetry showed that the POPA-specific activation correlates with the phase behavior of the POPC/POPA vesicles in the presence of Ca2+ ions. We conclude from the results that the Ca2+ -induced formation of POPA microdomains is the crucial parameter that facilitates the binding of PLD to the phospholipid surface and suggest that this effect serves as a cellular switch for controlling PLD activity. [source] Fabrication and analysis of polymer field-effect transistorsPHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 6 2004S. Scheinert Abstract Parameters of organic field-effect transistors (OFET) achieved in recent years are promising enough for R & D activities towards a commercial low-cost polymer electronics. In spite of the fast progress, preparations dominated by trial and error are concentrated essentially on higher mobility polymers and shorter channel patterning, and the analysis of measured data is based on oversimplified models. Here ways to professionalize the research on polymer field-effect transistors are discussed exploiting experience accumulated in microelectronics. First of all, designing the devices before fabricating and subsequently analyzing them requires appropriate modelling. Almost independently from the nature of the transport process, the device physics is basically described by the drift-diffusion model, combined with non-degenerate carrier statistics. Therefore, with a modified interpretation of the so-called effective density of states, existing simulation tools can be applied, except for special cases which are discussed. Analytical estimates are helpful already in designing devices, and applied to experimental data they yield input parameters for the numerical simulations. Preparations of OFET's and capacitors with poly(3-ocylthiophene) (P3OT), poly(3-dodecylthiophene) P3HT, Arylamino-poly-(phenylene-vinylene) (PPV), poly(2-methoxy, 5 ethyl (2, hexyloxy) paraphenylenevinylene) MEH-PPV, and pentacene from a soluble precursor are described, with silicon dioxide (SiO2) or poly(4-vinylphenol) (P4VP) as gate insulator, and with rather different channel length. We demonstrate the advantage of combining all steps from design/fabrication to analysis of the experimental data with analytical estimates and numerical simulation. Of special importance is the connection between mobility, transistor channel length, cut-off frequency and operation voltage, which was the starting point for the development of a low-cost fabrication of high-performance submicrometer OFET's by an underetching technique. Finally results of simulation studies are presented concerning the formation of inversion layers, the influence of a trap distribution (as in the a-Si model) and of different types of source/drain contacts on top and bottom contact OFET's, and short-channel effects in submicrometer devices. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) [source] Laryngeal and diaphragmatic muscle activities after central nervous system lesions in catsACTA PAEDIATRICA, Issue 11 2003AA Hutchison Aim: To examine the central control and coordination of respiratory pump muscles and laryngeal valve muscles by systematic decerebration (DECER), cerebellectomy (CBELL), pontine respiratory group lesioning (PRG) and pontomedullary section (PMED). Methods: Activities of posterior cricoarytenoid (PCA), thyroarytenoid (TA) and diaphragm (D) muscles and their responses to inspiratory (I) and expiratory (E) total occlusions were determined in 10 adult cats. Results: INTACT anesthetized cats (n= 6) exhibited inspiratory PCA (PCAI) and D activities. Expiratory PCA (PCAE) was present but TA activity was absent. It was found that successive DECER, CBELL and PRG lesions attenuated PCAE, the intact pattern being noted in 7/10, 4/10 and 0/6 cats, respectively. After PMED, variable PCA, TA and continuous D activities occurred only with blood gas abnormalities. Augmented PCA and D responses to I- and E-loads occurred after PRG lesions: the I-load PCAI and D responses resembled apneusis and the E-load PCAE and D responses resembled central apnea. Conclusion: The decreasing PCAE activity observed with successive DECER, CBELL and PRG lesions suggests that these areas influence laryngeal abductor control of glottic size. The synchronous activities after PMED transection suggest a role for more rostral structures in coordinating laryngeal and diaphragmatic muscle activities. [source] Evidence for the presence of 5,-deiodinase in mammalian seminal plasma and for the increase in enzyme activity in the prepubertal testisINTERNATIONAL JOURNAL OF ANDROLOGY, Issue 4 2000Brzezi, lebodzi Thyroid hormones are critical for structural and functional development of the testis and Sertoli cells are considered true target cells for triiodothyronine (T3). However, the role of thyroid hormones in the adult testis seems to be minimal and the mechanism by which they affect testicular function is not known. Due to the existing blood,testis barrier the concentration of thyroid hormones in seminal plasma is kept lower than in blood plasma. We have found that T3 may reach the testis not only from the circulation but also from local enzymic conversion of thyroxine to T3. The presence of the enzymic activity responsible for thyroxine 5,deiodination and for generating T3 locally was also found in boar's seminal plasma. The seminal plasma 5,-deiodinase (5,-D) appeared to be predominantly the propylthiouracil (PTU)-insensitive type II isoenzyme found, so far, in tissues where it plays a role in paracrine signalling. It contains selenocysteine in its molecule (inhibition by aurothioglucose), and has an apparent Km for reverse-T3 as substrate of 0.36 n M and a Vmax 23.8 fmol I,/mg protein/min. Because the seminal plasma 5,-D is partially, but uncompetitively, inhibited by PTU, the presence in seminal plasma of two 5,-D isoenzymes (type I and II) cannot be excluded. The 5,-D activity in testes increased significantly between week 3 and 4, and this increase was concomitant with increase in testicular size. The relationship between testicular weight gain and age showed a similar characteristic change and corresponded to the change in 5,-D activity. Unlike in rodents, the testis of the prepubertal pig has thyroid hormone receptors in Sertoli cells, and suggests that in growing piglets, testicular 5,-D is a key factor regulating local supply of biologically active T3, and is an essential factor in testicular paracrine function. The present results are the first demonstration and characterization of the 5,-deiodinase in seminal plasma. [source] Effect of aroclor 1248 and two pure PCB congeners on phospholipase D activity in rat renal tubular cell culturesJOURNAL OF BIOCHEMICAL AND MOLECULAR TOXICOLOGY, Issue 2 2007Mercedes Fernández Santiago Abstract This paper elucidates the effect of different polychlorinated biphenyls (PCBs) on the phospholipase D (PLD) activity in soluble and particulate fractions of rat renal proximal tubular culture cells. Treatment with Aroclor 1248 (a commercial PCB mixture) caused a marked increase in the activity of PLD in intact renal tubular cells. The PLD activity was increased by Aroclor 1248 in the particulate fraction while the enzyme activity was unaffected in the soluble fraction. This work also shows that PCB 153 (2,2',4,4',5,5'-hexachlorobiphenyl, a di-ortho-substituted nonplanar congener) can increase the activity of PLD only in the particulate fraction. The exposure of cell cultures to PCB 77 (3,3',4,4'-tetrachlorobiphenyl, a non-ortho-substituted planar congener) does not alter PLD activity. These results suggest that PCB effects are structure dependent. Therefore, in order to clarify the molecular mechanism of activation of PLD by PCBs, the contents of immunoreactive PLD were examined by immunoblot analysis. Renal tubular cells expressed a PLD protein of 120 kDa corresponding with the PLD1 mammalian isoform in both the particulate and the soluble fraction. Aroclor 1248, PCB 153, and PCB 77 do not induce changes in the levels of PLD protein. These data indicate that PCBs, particularly nonplanar congeners, increase PLD activity. Moreover, these changes could not be demonstrated in the enzyme content in rat renal tubular cell cultures. © 2007 Wiley Periodicals, Inc. J Biochem Mol Toxicol 21:68,75, 2007; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/jbt.20160 [source] Gene position in a long operon governs motility development in Bacillus subtilisMOLECULAR MICROBIOLOGY, Issue 2 2010Loralyn M. Cozy Summary Growing cultures of Bacillus subtilis bifurcate into subpopulations of motile individuals and non-motile chains of cells that are differentiated at the level of gene expression. The motile cells are ON and the chaining cells are OFF for transcription that depends on RNA polymerase and the alternative sigma factor ,D. Here we show that chaining cells were OFF for ,D -dependent gene expression because ,D levels fell below a threshold and ,D activity was inhibited by the anti-sigma factor FlgM. The probability that ,D exceeded the threshold was governed by the position of the sigD gene. The proportion of ON cells increased when sigD was artificially moved forward in the 27 kb fla/che operon. In addition, we identified a new ,D -dependent promoter that increases sigD expression and may provide positive feedback to stabilize the ON state. Finally, we demonstrate that ON/OFF motility states in B. subtilis are a form of development because mosaics of stable and differentiated epigenotypes were evident when the normally dispersed bacteria were forced to grow in one dimension. [source] Correlations of dietary patterns with prostate healthMOLECULAR NUTRITION & FOOD RESEARCH (FORMERLY NAHRUNG/FOOD), Issue 1 2008Maria Stacewicz-Sapuntzakis Abstract Both genetic and environmental influences may be involved in etiology of prostate health and prostate cancer. These include ethnic origin, family history, smoking, and diet. Adiposity and excess energy intake are potentially distinct risk factors and positive associations with prostate cancer risk for both were observed among case-control and cohort studies. Some epidemiological studies support an association between dietary fat, particularly saturated or animal fats, and prostate cancer risk. Of these, several suggest reduced risk with low-fat diets high in n-3 fatty acids and increased risk with high-fat diets rich in n-6 fatty acids. Others suggested association with higher meat intake, possibly due to heterocyclic amines and polycyclic aromatic hydrocarbons, produced during grilling or frying. Positive association of prostate cancer risk with dairy intake could involve ,-methylacyl-CoA racemase activity (required for ,-oxidation of phytanic acid present in dairy products and red meat) or the suppression of vitamin D activity by calcium. Inverse associations were observed with dietary intake of plant foods. These include cereals, soy products, and fruit and vegetable sources of carotenoids. Numerous plant constituents may act synergistically in the prevention and inhibition of prostate disorders. These diet-risk associations may lead to future individualized diet recommendations based upon genetic polymorphisms. [source] Membrane phospholipids as a phosphate reserve: the dynamic nature of phospholipid-to-digalactosyl diacylglycerol exchange in higher plantsPLANT CELL & ENVIRONMENT, Issue 10 2008HENRIK TJELLSTRÖM ABSTRACT It is well established that phosphate deficiency induces the replacement of membrane phospholipid with non-phosphorous lipids in extra-plastidial membranes (e.g. plasma membrane, tonoplast, mitochondria). The predominant replacement lipid is digalactosyl diacylglycerol (DGDG). This paper reports that the phospholipid-to-DGDG replacement is reversible, and that when oat seedlings are re-supplied with radio-labelled phosphate, it is initially recovered primarily in phosphatidylcholine (PC). Within 2 d, the shoot contains more than half of the lipid-associated radiolabel, reflecting phosphate translocation. Oat was also cultivated in different concentrations of phosphate and the DGDG/PC ratio in roots and phospholipase activities in isolated plasma membranes was assayed after different times of cultivation. The DGDG/PC ratio in root tissue correlated more closely with plasma membrane-localized phospholipase D, yielding phosphatidic acid (PA), than with plasma membrane-localized PA phosphatase, the activity that results in a decreased proportion of phospolipids. The lipid degradation data did not reflect a significant involvement of phospholipase C, although a putative phospholipase C analogue, non-specific phospholipase C4 (NPC4), was present in oat roots. The correlation between increased phospholipase D activity and DGDG/PC ratio is consistent with a model where phospholipid-to-DGDG replacement involves formation of PA that readily is removed from the plasma membrane for further degradation elsewhere. [source] Preslaughter stress and subsequent effect on flesh quality in farmed codAQUACULTURE RESEARCH, Issue 10 2010Marit Bjørnevik Abstract The aim of this study was to investigate the effect of prehandling stress on the flesh quality of Atlantic cod (Gadus morhua). In order to stress the animal, water was reduced in the tank before a total of 30 fish were caught five at a time using a dipnet and held for 3 min, causing stress by hypoxia. This fish was compared with a control group (n=30) of fish exposed to anaesthetics directly in the tank. All fish were killed by a percussive blow to the head and exsanguinated and stored on ice before flesh quality was measured. Immediately after death and after ice storage for 3 and 8 days, 10 fish per group were measured for muscle pH, texture, fillet gaping, colour, drip loss and cathepsin D. Handling stress resulted in an initial increased fillet lightness, drip loss and decreased fillet shear force, although these differences did level off during ice storage. Stress caused by handling resulted in earlier onset of rigour mortis as compared with the control group, which reached maximum rigour tensions within 26 and 36 h postmortem respectively. We conclude that handling before harvest results in reduced time before entering rigour. After 8 days of ice storage, no effect of handling stress was seen on the muscle pH, flesh colour, fillet shear force, gaping score, drip loss or cathepsin D activity. [source] Mammalian cell expression, purification, crystallization and microcrystal data collection of autotaxin/ENPP2, a secreted mammalian glycoproteinACTA CRYSTALLOGRAPHICA SECTION F (ELECTRONIC), Issue 9 2010Jens Hausmann Autotaxin (ATX or ENPP2) is a secreted glycosylated mammalian enzyme that exhibits lysophospholipase D activity, hydrolyzing lysophosphatidylcholine to the signalling lipid lysophosphatidic acid. ATX is an ,100,kDa multi-domain protein encompassing two N-terminal somatomedin B-like domains, a central catalytic phosphodiesterase domain and a C-terminal nuclease-like domain. Protocols for the efficient expression of ATX from stably transfected mammalian HEK293 cells in amounts sufficient for crystallographic studies are reported. Purification resulted in protein that crystallized readily, but various attempts to grow crystals suitable in size for routine crystallographic structure determination were not successful. However, the available micrometre-thick plates diffracted X-rays beyond 2.0,Å resolution and allowed the collection of complete diffraction data to about 2.6,Å resolution. The problems encountered and the current advantages and limitations of diffraction data collection from thin crystal plates are discussed. [source] | ||||||||||||||||