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At least 217 records · Page 12Linked to original sources
PubMed2005

Conserved extracellular cysteine residues and cytoplasmic loop-loop interplay are required for functionality of the heptahelical MLO protein.

We performed a structure-function analysis of the plasma membrane-localized plant-specific barley (Hordeum vulgare) MLO (powdery-mildew-resistance gene o) protein. Invariant cysteine and proline residues, located either in extracellular loops or transmembrane domains that have been conserved in MLO proteins for more than 400 million years, were found to be essential for MLO functionality and/or stability. Similarly to many metazoan G-protein-coupled receptors known to function as homo- and hetero-oligomers, FRET (fluorescence resonance energy transfer) analysis revealed evidence for in planta MLO dimerization/oligomerization. Domain-swap experiments with closely related wheat and rice as well as diverged Arabidopsis MLO isoforms demonstrated that the identity of the C-terminal cytoplasmic tail contributes to MLO activity. Likewise, analysis of a progressive deletion series revealed that integrity of the C-terminus determines both MLO accumulation and functionality. A series of domain swaps of cytoplasmic loops with the wheat (Triticum aestivum) orthologue, TaMLO-B1, provided strong evidence for co-operative loop-loop interplay either within the protein or between MLO molecules. Our data indicate extensive intramolecular co-evolution of cytoplasmic domains in the evolutionary history of the MLO protein family.

Amino Acid Sequence↗
PubMed1989

The interplay of electrostatic fields and binding interactions determining catalytic-site reactivity in actinidin. A possible origin of differences in the behaviour of actinidin and papain.

1. The pH-dependence of the second-order rate constant (k) for the reaction of actinidin (EC 3.4.22.14) with 2-(N'-acetyl-L-phenylalanylamino)ethyl 2'-pyridyl disulphide was determined and the contributions to k of various hydronic states were evaluated. 2. The data were used to assess the consequences for transition-state geometry of providing P2/S2 hydrophobic contacts in addition to hydrogen-bonding opportunities in the S1-S2 intersubsite region. 3. The P2/S2 contacts (a) substantially improve enzyme-ligand binding, (b) greatly enhance the contribution to reactivity of the hydronic state bounded by pKa 3 (the pKa characteristic of the formation of catalytic-site-S-/-ImH+ state) and pKa 5 (a relatively minor contributor in reactions that lack the P2/S2 contacts), such that the major rate optimum occurs at pH 4 instead of at pH 2.8-2.9, and (c) reveal the kinetic influence of a pKa approx. 6.3 not hitherto observed in reactions of actinidin. 4. Possibilities for the interplay of electrostatic effects and binding interactions in both actinidin and papain (EC 3.4.22.2) are discussed.

Binding Sites↗
PubMed1992

The interplay of temperature and protons in the modulation of oxygen binding by squid blood.

An extensive set of data relating to the binding of oxygen by haemocyanin from the squid Todarodes sagittatus has been collected under various experimental conditions. The results obtained show that, within the range of physiological pH, the concentration of protons affects mainly the high-affinity state of the molecule without significantly affecting the low-affinity state. As far as the effect of temperature is concerned, the data show a characteristic feature which is very similar to that previously described in the case of haemoglobins from Arctic mammals such as reindeer (Rangifer tarandus) and musk ox. (Ovibos moschatus). The shape of the oxygen equilibrium curve shows strong temperature-dependence, since the overall heat of the binding of oxygen to the low-affinity state of the molecule is strongly exothermic and that to the high-affinity state is very close to zero. The results provide an outline of the intramolecular compromise that, through the interplay of temperature and protons, optimizes the loading and unloading of oxygen under the various environmental conditions experienced by this species of squid.

Animals↗
PubMed1999

Phenotypes in canalicular adenoma of human minor salivary glands reflect the interplay of altered secretory product, absent neuro-effector relationships and the diversity of the microenvironment.

AIMS: Uncertainty about the factors influencing phenotypes in salivary canalicular adenoma prompted the present investigation. METHODS AND RESULTS: Specimens of canalicular adenoma from 15 patients were examined with the use of histology, histochemistry for protein, mucosubstances and pigments, nerve staining and immunocytochemistry for cytoskeleton components. The tumours consisted largely of simple cells lining tubules that were occasionally cystic or branching and budding, and were set in loose, vascular and often haemorrhagic stroma. Other phenotypes recognized were mucous cells, apocrine-like cells, pigmented cells, microliths and stromal macrophages, detected in 26.6%, 20%, 33.3%, 20% and 53. 3% of the patients, respectively. Simple cells showed moderate levels of -SH groups and strong immunoreactivity for 'simple' epithelial phenotype cytokeratin. The simple cells lining cystic tubules showed additional immunoreactivity for 'stratified' epithelial phenotype cytokeratin, possibly an adaptation to mechanical pressure. Lumina showed variable levels of neutral and carboxylated glycoproteins, and chondroitin sulphate. Stroma showed high levels of chondroitin sulphate and hyaluronic acid. Mucous cells showed high levels of -SS- groups and nonsulphated glycoproteins. Apocrine-like cells contained lipofuscin. Pigmented cells contained haemosiderin, possibly a consequence of localized iron overload. Microliths contained mucosubstances. Macrophages often contained lipofuscin. No nerves were found in relation to the tumours. CONCLUSIONS: The results suggest that, contrary to popular belief, phenotypes in canalicular adenoma do not reflect histogenetic concepts but rather may derive from the interplay between an altered secretory product, consisting of glycosaminoglycan and an immature form of glycoprotein, the lack of neuro-effector relationships and the different microenvironments throughout the tumour.

Adenoma↗
PubMed2000

The interplay between social and cultural context and perceptions of cardiovascular disease.

This paper seeks to explore the impact of social and cultural factors upon perceptions of the patients' cardiovascular risk and intended lifestyle changes. Qualitative and quantitative research approaches were used. The sample was purposeful; matched groups of 10 first time post myocardial infarction (MI) patients, 10 informal (spouse, blood relative or partner) and 10 formal carers (nursing staff) were selected on a convenience basis. Personal interviews were conducted with participants, during which a semistructured questionnaire was completed. A combination of descriptive statistics and qualitative analysis of these data revealed that social and cultural factors formed the basis of patients' and informal carers' perceptions of cardiovascular risks and social information networks provided the main source of information about cardiovascular risk. For the staff, known risk factors based on epidemiological evidence (lack of exercise and diet) formed the basis of their perceptions of the patients' cardiovascular risk factors. However, for all the participant groups (i.e. patients, informal carers and staff) the risk factors - diet and exercise were indicated as being the patients' intended lifestyle changes., The results illustrate potential interplay between 'social' and 'cultural' context and perceptions of cardiovascular risk and incongruency between perceptions of risk and perceptions of the patients' intended lifestyle change. These results may assist nurses in giving effective advice to patients and relatives about lifestyle change following myocardial infarction and inform future policy for cardiac rehabilitation.

Adult↗
PubMed2004

Escherichia coli prereplication complex assembly is regulated by dynamic interplay among Fis, IHF and DnaA.

Initiator DnaA and DNA bending proteins, Fis and IHF, comprise prereplication complexes (pre-RC) that unwind the Escherichia coli chromosome's origin of replication, oriC. Loss of either Fis or IHF perturbs synchronous initiation from oriC copies in rapidly growing E. coli. Based on dimethylsulphate (DMS) footprinting of purified proteins, we observed a dynamic interplay among Fis, IHF and DnaA on supercoiled oriC templates. Low levels of Fis inhibited oriC unwinding by blocking both IHF and DnaA binding to low affinity sites. As the concentration of DnaA was increased, Fis repression was relieved and IHF rapidly redistributed DnaA to all unfilled binding sites on oriC. This behaviour in vitro is analogous to observed assembly of pre-RC in synchronized E. coli. We propose that as new DnaA is synthesized in E. coli, opposing activities of Fis and IHF ensure an abrupt transition from a repressed complex with unfilled weak affinity DnaA binding sites to a completely loaded unwound complex, increasing both the precision of DNA replication timing and initiation synchrony.

Bacterial Proteins↗
PubMed2002

The interplay of dendritic cell subsets in systemic lupus erythematosus.

Dendritic cells (DC) control immunity and tolerance. Hence, we surmised that systemic lupus erythematosus (SLE), a systemic autoimmune disease with autoreactive T and B cells, might be due to DC alterations. Based on our findings, we are proposing a model of SLE where autoimmune responses are driven by unabated activation of myeloid DC through IFN-alpha produced by plasmacytoid DC. Thus, interplay between DC subsets might represent a key component of SLE pathogenesis.

Autoantibodies↗
PubMed2000

Neuropeptide Y cotransmission with norepinephrine in the sympathetic nerve-macrophage interplay.

The CNS modulates immune cells by direct synaptic-like contacts in the brain and at peripheral sites, such as lymphoid organs. To study the nerve-macrophage communication, a superfusion method was used to investigate cotransmission of neuropeptide Y (NPY) with norepinephrine (NE), with interleukin (IL)-6 secretion used as the macrophage read-out parameter. Spleen tissue slices spontaneously released NE, NPY, and IL-6 leading to a superfusate concentration at 3-4 h of 1 nM:, 10 pM:, and 120 pg/ml, respectively. Under these conditions, NPY dose-dependently inhibited IL-6 secretion with a maximum effect at 10(-10) M: (p = 0.012) and 10(-9) M: (p < 0.001). Simultaneous addition of NPY at 10(-9) M: and the alpha-2-adrenergic agonist p-aminoclonidine further inhibited IL-6 secretion (p < 0.05). However, simultaneous administration of NPY at 10(-9) M: and the beta-adrenergic agonist isoproterenol at 10(-6) M: or NE at 10(-6) M: significantly increased IL-6 secretion (p < 0.005). To objectify these differential effects of NPY, electrical field stimulation of spleen slices was applied to release endogenous NPY and NE. Electrical field stimulation markedly reduced IL-6 secretion, which was attenuated by the NPY Y1 receptor antagonist BIBP 3226 (10(-7) M, p = 0.039; 10(-8) M, p = 0.035). This indicates that NPY increases the inhibitory effect of endogenous NE, which is mediated at low NE concentrations via alpha-adrenoceptors. Blockade of alpha-adrenoceptors attenuated electrically induced inhibition of IL-6 secretion (p < 0.001), which was dose-dependently abrogated by BIBP 3226. This indicates that under blockade of alpha-adrenoceptors endogenous NPY supports the stimulating effect of endogenous NE via beta-adrenoceptors. These experiments demonstrate the ambiguity of NPY, which functions as a cotransmitter of NE in the nerve-macrophage interplay.

Adrenergic Agonists↗
PubMed2002

Uroporphyria in the uroporphyrinogen decarboxylase-deficient mouse: Interplay with siderosis and polychlorinated biphenyl exposure.

Several methods have been used to develop rodent models with the hepatic manifestations of porphyria cutanea tarda (PCT). Acute iron administration or mutations of the hemochromatosis gene (Hfe) have been used to generate hepatic siderosis, a nearly uniform finding in PCT. Heterozygosity for a null mutation at the uroporphyrinogen decarboxylase (Uro-D+/-) locus has been developed to mimic familial PCT in humans. This study examines the interplay of these 2 genetic risk factors and their influence, alone and combined with polychlorinated-biphenyl exposure. Neither an Hfe-null mutation nor iron-dextran administration alone or in combination with polychlorinated biphenyl exposure was porphyrinogenic in a 3-week model using mice wild-type at the Uro-D locus. Homozygosity for an Hfe-null mutation significantly elevated hepatic iron but not to the extent seen with parenteral iron-dextran administration. Homozygosity for an Hfe-null mutation but not iron-dextran administration was porphyrinogenic in animals heterozygous for the Uro-D mutation. Polychlorinated biphenyls were also porphyrinogenic in these animals. Uroporphyria in Uro-D+/- animals was exacerbated by combinations of the homozygous Hfe-null mutation and polychlorinated biphenyls and iron-dextran and polychlorinated biphenyls. In all cases in which uroporphyria developed, a greater degree of experimental uroporphyria was seen in female animals. All elevated hepatic uroporphyrin concentrations were accompanied by depressed uroporphyrinogen decarboxylase activity and the presence of a factor in cytosol that inhibits recombinant human uroporphyrinogen decarboxylase. In conclusion, the expression of the uroporphyric phenotype, dependent on the susceptibility imparted by a genetic mutation, provides a uniquely facile model for dissecting the molecular pathogenesis of the disease.

Animals↗
PubMed1999

Interplay between Ca2+ release and Ca2+ influx underlies localized hyperpolarization-induced [Ca2+]i waves in prostatic cells.

Calcium seems to be a major second messenger involved in the regulation of prostatic cell functions, but the mechanisms underlying its control are poorly understood. We investigated spatiotemporal aspects of Ca2+ signals in the LNCaP cell line, a model of androgen-dependent prostatic cells, by using non-invasive external electric field pulses that hyperpolarize the anode facing membrane and depolarize the membrane facing the cathode. Using high-speed fluo-3 confocal imaging, we found that an electric field pulse (10-15 V/cm, 1-5 mA, 5 ms) initiated rapidly, at the hyperpolarized end of the cell, a propagated [Ca2+]i wave which spread through the cell with a constant amplitude and an average velocity of about 20 microns/s. As evidenced by the total wave inhibition either by the block of Ca2+ entry or the depletion of Ca2+ stores by thapsigargin, a specific Ca(2+)-ATPase inhibitor, the [Ca2+]i wave initiation may imply a localized Ca2+ influx linked to a focal auto-regenerative process of Ca2+ release. Using different external Ca2+ and Ca2+ entry blockers concentrations, Mn2+ quenching of fluo-3 and fura-2 fluorescence and inhibitors of InsP3 production, we found evidence that the [Ca2+]i wave progression required, in the presence of basal levels of InsP3, an interplay between Ca2+ release from InsP3-sensitive Ca2+ stores and Ca2+ influx through channels possibly activated by the [Ca2+]i rise.

Calcium↗
PubMed1983

[Aspects of an interplay between endocrinological and metabolic factors during birth].

The well-known rise of the levels of glucose, lactate, pyruvate, non-esterified free fatty acids (NFFA), glycerol, and ketone bodies during labour cannot be explained only by metabolic pathways. The simultaneous measurement of insulin, cortisol, hGH, and prolactin shows a striking change in secretion, especially of cortisol, after the first half of labour. It is assumed that cortisol plays an important part in the intrapartal metabolic conversions. The correlation cortisol/glucose becomes significant. There is no evidence of the known catabolic effect of cortisol under the conditions of labour, but these is evidence of a reduction of peripheral glucose utilisation. The role of cortisol for the intrapartal metabolic changes is discussed under the aspect of labour progress. The outlines of a very ingenious but also complex interplay between endocrinological and metabolic factors emerge which may provide useful tools for therapeutic use.

Fatty Acids, Nonesterified↗
PubMed1995

On the interplay between symmetry breaking, integrability, and chaos in the semiclassical limit of the Heisenberg system.

In this work we present a detailed numerical analysis of the interplay between symmetry breaking, integrability, and chaos in the two- and three-spin Heisenberg models. The results suggest that a very simple and powerful tool to convey such information are the plots of the energy level spacings Delta(n) versus the energy level index n, together with the correlation plots Delta(n+1)xDelta(n). When integrability is broken, these plots are shown to identify very sharply an energy below which one has chaotic behavior. The particularly strong point in favor of such analysis is that it can be useful in partially chaotic regimes. (c) 1995 American Institute of Physics.

Journal Article↗
PubMed2006

Interplay between two phase transitions: crystallization and liquid-liquid phase separation in a polyolefin blend.

The interplay between liquid-liquid phase separation (LLPS) and crystallization at several compositions in statistical copolymer blends of poly(ethyleneco-hexene) and poly(ethylene-cobutene) has been examined by optical microscopy (OM), atomic force microscopy (AFM), and differential scanning calorimetry (DSC). The phase contrast optical microscopy shows interconnected bicontinuous structures for deeply quenched LLPS, characteristic of spinodal decomposition. After a second quench to a temperature below the melting point, an overwhelming change in crystallization kinetics has been clearly observed, which is caused by the increase of the nucleation rate assisted by concentration fluctuations due to the spontaneous spinodal LLPS. We propose a new mechanism of "fluctuation assisted nucleation" in the crystallization process for such interactive process in a blend system. The experimental results from OM, AFM, and DSC measurements at various conditions are all consistent with the fluctuation assisted nucleation model.

Journal Article↗
PubMed2001

Interplay of antibody and T cell responses in acute myocardial infarction.

This study sought to investigate the interplay between antibody and T cell responses triggered by an acute myocardial infarction (MI) and their possible role in the progress of this disease. Serum samples were collected from two groups of patients, group A (n = 26) within the first week of MI, and group B (n = 28) at 2 weeks and 2 months after MI. Patients in group A were older and had higher prevalence of hypertension and previous attack of MI than patients in group B. The levels of anti-myosin immunoglobulin M and immunoglobulin G antibodies in the serum samples from group A were significantly higher than those in normal control subjects. In group B, the levels of both antibodies were lower than those in group A but remained significantly higher than those in normal control subjects at both 2 weeks and 2 months. The levels of intercellular adhesion molecule-1 (sICAM-1) and vascular cell adhesion molecule-1 (sVCAM-1) in the serum samples from group A patients were significantly higher than those in normal control subjects. At 2 weeks after MI (group B), only the level of sVCAM-1, but not that of sICAM-1, was significantly higher than that in normal control subjects, and there were no significant changes in the levels of these two molecules from 2 weeks to 2 months after MI. We conclude that the higher levels of anti-myosin antibodies and adhesion molecules in group A patients as compared with group B patients may be due to higher or more frequent exposures of their immune systems to heart antigens. Furthermore, the immunoglobulin M antibody response during the first week of MI had an inverse relationship with the level of interleukin-2R (sIL-2R), which suggested a possible suppressive or regulatory role of this antibody on the cellular immune response during this time.

Aged↗
PubMed2004

Computational modeling reveals how interplay between components of a GTPase-cycle module regulates signal transduction.

Heterotrimeric G protein signaling is regulated by signaling modules composed of heterotrimeric G proteins, active G protein-coupled receptors (Rs), which activate G proteins, and GTPase-activating proteins (GAPs), which deactivate G proteins. We term these modules GTPase-cycle modules. The local concentrations of these proteins are spatially regulated between plasma membrane microdomains and between the plasma membrane and cytosol, but no data or models are available that quantitatively explain the effect of such regulation on signaling. We present a computational model of the GTPase-cycle module that predicts that the interplay of local G protein, R, and GAP concentrations gives rise to 16 distinct signaling regimes and numerous intermediate signaling phenomena. The regimes suggest alternative modes of the GTPase-cycle module that occur based on defined local concentrations of the component proteins. In one mode, signaling occurs while G protein and receptor are unclustered and GAP eliminates signaling; in another, G protein and receptor are clustered and GAP can rapidly modulate signaling but does not eliminate it. Experimental data from multiple GTPase-cycle modules is interpreted in light of these predictions. The latter mode explains previously paradoxical data in which GAP does not alter maximal current amplitude of G protein-activated ion channels, but hastens signaling. The predictions indicate how variations in local concentrations of the component proteins create GTPase-cycle modules with distinctive phenotypes. They provide a quantitative framework for investigating how regulation of local concentrations of components of the GTPase-cycle module affects signaling.

GTP Phosphohydrolases↗
PubMed2005

Floral asymmetry involves an interplay between TCP and MYB transcription factors in Antirrhinum.

To understand how genes control floral asymmetry, we have isolated and analyzed the role of the RADIALIS (RAD) gene in Antirrhinum. We show that the RAD gene encodes a small MYB-like protein that is specifically expressed in the dorsal region of developing flowers. RAD has a single MYB-like domain that is closely related to one of the two MYB-like domains of DIV, a protein that has an antagonistic effect to RAD on floral development. Interactions between RAD and other genes indicate that floral asymmetry depends on the interplay between two pairs of transcription factors. First, a pair of TCP proteins is expressed in dorsal regions of the floral meristem, leading to the activation of RAD in the dorsal domain. The RAD MYB-like protein then antagonizes the related DIV MYB-like protein, preventing DIV activity in dorsal regions. In addition to its role in dorsal regions, RAD acts nonautonomously on lateral regions either directly, through RAD protein movement, or indirectly, through a signaling molecule.

Amino Acid Sequence↗
PubMed1991

Interplay of two cis-acting mRNA regions in translational control of sigma 32 synthesis during the heat shock response of Escherichia coli.

When Escherichia coli cells are transferred from 30 degrees C to 42 degrees C, transcription from specific promoters recognized by RNA polymerase containing sigma 32 (the rpoH gene product) is transiently activated, resulting in induction of heat shock proteins. Transcription from heat shock promoters is activated by an increased cellular concentration of sigma 32 due to enhanced synthesis and stabilization. We have constructed and examined the expression of mutant derivatives (deletions and base substitutions) of rpoH-lacZ gene fusion. Synthesis of a sigma 32-beta-galactosidase fusion protein was found to be regulated at the translational level involving two distinct 5'-proximal rpoH coding regions. A small region immediately downstream of the initiation codon is required for potentially high-level expression, whereas a much larger internal region is required for thermal regulation--namely, repression at low temperature or nonstress conditions. The two mRNA regions act as positive and negative cis elements, respectively, in controlling rpoH translation. We propose that an interplay between these RNA regions involving secondary structure formation is important in regulating translation initiation and that transient disruption of secondary structure represents a primary step of the heat shock response.

Base Sequence↗
PubMed1992

Extension growth of the water mold Achlya: interplay of turgor and wall strength.

When hyphae of the water mold Achlya were subjected to osmotic stress, imposed with polyethylene glycol (PEG)-300 or sucrose, turgor pressure fell in proportion to the increase in external osmotic pressure. There was no evidence of turgor regulation, even over a period of days, yet the extension rate was unaffected until turgor was reduced to less than a third of the normal level of 0.6-0.8 MPa (6-8 bars). Measurements of the pressure at which the hyphae burst indicate that they respond to osmotic stress by softening their apical cell walls, sustaining extension growth despite reduced turgor pressure. The effect of osmolytes excluded by the wall was very different; superfusion of growing hyphae with PEG-6000 or dextran-6000 reduced turgor and stopped extension but did not induce wall softening. Furthermore, the hyphae did not resume growth during an hour or more of continuous exposure to these substances. Although the two classes of osmolytes have the same effect on turgor, they may induce different strains within the cell wall; this might then affect the capacity of the organism to detect the drop in turgor or to soften its cell wall. The interplay between turgor and wall strength supports the proposition that turgor supplies the driving force for extension and that production of the standard hyphal form requires a balance between hydrostatic pressure and a resistive cell wall.

Journal Article↗