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PubMed2005

Dual control mechanism in a Belousov-Zhabotinskii (B-Z) oscillator with glucose and oxalic acid as a double substrate.

Oscillations in a Belousov-Zhabotinskii (B-Z) system having oxalic acid (OA) and glucose (G) as a mixed organic substrate, neither of which acts as a bromine scavenger, have been investigated. Studies have been performed for (i) varying the concentration of G while keeping the OA concentration fixed and (ii) varying OA but keeping G fixed in a batch reactor. In both cases upper and lower critical limits occur, between which oscillations are observed. Both single and double frequency oscillations have been observed in a wide range of concentrations of G as well as of OA. The induction period in most of the cases was <1 min. When G is fixed and OA is varied, the time pause between the sequential oscillations increases with an increase in OA. On the other hand when OA is fixed and G is varied, the time-pause decreases with an increase in G. The first type of oscillation is Br(-)-controlled, whereas the second is non-Br(-)-controlled. The order of addition of G and OA in the last has no influence on the induction period. It influences, however, the oscillatory characteristics. Br(2) evolution in the G + OA + Ce(4+) + BrO(3)(-) + H(2)SO(4) reaction system has been investigated spectrophotometrically. ESR and polymerization studies indicate the important role of free radicals in influencing the reaction mechanism. A tentative dual control mechanism has been suggested involving autocatalysis of HBrO(2) and BrO2*.

Journal Article↗
PubMed2025

Genetic Evolution Between HIV-1 Groups M and O: HIV-1/MO Recombinant Forms.

HIV exhibits significant genetic diversity, with genetic recombination being a major evolutionary process. The co-circulation of HIV-1/M and HIV-1/O variants has led to the description of 20 HIV-1/M+O dual infections since 1998. Despite the genetic divergence between these variants, HIV-1/M+O dual infections have resulted in the emergence of HIV-1/MO intergroup recombinant forms, with 20 unique HIV-1/MO recombinant forms (URF_MO) currently described, raising the question of a possible benefit of the recombination and the modalities of their emergence. This review summarized the current knowledge of HIV-1/MO recombinant forms, including their virological and genetic characteristics, phylogenetic analysis, genome profiles, and breakpoints number and location. This study also identified the potential impacts of HIV-1/MO recombination on diagnosis, monitoring, and treatment, as well as the replicative capacity of such recombinants. This review highlighted the greater diversity and complexity of HIV-1/MO recombinants than originally thought, offering new research perspectives on their emergence and virological properties.

HIV-1↗
PubMed2004

Directed evolution relieves product inhibition and confers in vivo function to a rationally designed tyrosine aminotransferase.

The Escherichia coli aspartate (AATase) and tyrosine (TATase) aminotransferases share 43% sequence identity and 72% similarity, but AATase has only 0.08% and 0.01% of the TATase activities (k(cat)/K(m)) for tyrosine and phenylalanine, respectively. Approximately 5% of TATase activity was introduced into the AATase framework earlier both by rational design (six mutations, termed HEX) and by directed evolution (9-17 mutations). The enzymes realized from the latter procedure complement tyrosine auxotrophy in TATase deficient E. coli. HEX complements even more poorly than does wild-type AATase, even though the (k(cat)/K(m)) value for tyrosine exhibited by HEX is similar to those of the enzymes found from directed evolution. HEX, however, is characterized by very low values of K(m) and K(D) for dicarboxylic ligands, and by a particularly slow release for oxaloacetate, the product of the reaction with aspartate and a TCA cycle intermediate. These observations suggest that HEX exists largely as an enzyme-product complex in vivo. HEX was therefore subjected to a single round of directed evolution with selection for complementation of tyrosine auxotrophy. A variant with a single amino acid substitution, A293D, exhibited substantially improved TATase function in vivo. The A293D mutation alleviates the tight binding to dicarboxylic ligands as K(m)s for aspartate and alpha-ketoglutarate are >20-fold higher in the HEX + A293D construct compared to HEX. This mutation also increased k(cat)/K(m)(Tyr) threefold. A second mutation, I73V, elicited smaller but similar effects. Both residues are in close proximity to Arg292 and the mutations may function to modulate the arginine switch mechanism responsible for dual substrate recognition in TATases and HEX.

Amino Acids↗
PubMed1979

A histochemical study on the innervation of cerebral blood vessels in the bullfrog.

Specific histochemical techniques for the demonstration of catecholamine and acetylcholinesterase have been used to study the distribution of adrenergic and cholinergic nerves on the cerebral blood vessels of bullfrog, Rana catesbeiana. The adrenergic nerve meshworks on the cerebral arteries of bullfrog were less dense, had a more elongate appearance along the arterial axis as compared with those of mammals and were rather similar to those of snakes. The nerve plexuses on the cerebral carotid artery and its main branches were somewhat denser than those on the basilar artery. The most characteristic feature of innervation in the bullfrog cerebral vessels was that no acetylcholinesterase-positive fibres were observed on the extraparenchymal arteries, whereas, in all higher vertebrates investigated so far, the cerebral arteries have been found to be dually innervated although differences in the density of innervation of the two nerves may exist. This suggests that the peripheral adrenergic innervation on the cerebral blood vessels appeared earlier than the cholinergic one in the evolution of vertebrates. On the other hand, both adrenergic and acetylcholinesterase-positive fibres were observed in close contact with parenchymal arterioles and capillaries suggesting the possible existence of a dual central innervation. This feature, however, was by no means common. Thus, the central neurons have a significant influence on the cerebral circulation in the bullfrog is somewhat equivocal. Most of the pial and the parenchymal small vessels and the parenchymal capillaries exhibited a heavy acetylcholinesterase activity on the vascular walls. Although the significance of the enzyme is obscure as yet, this has to be considered in relation to the regulatory mechanism of the cerebral circulation.

Adrenergic Fibers↗
PubMed1997

Dual reciprocity boundary element method for solving thermal wave model of bioheat transfer.

The newly developed dual reciprocity boundary element method (DRBEM) was extended to solve the thermal wave model of bioheat transfer (TWMBT) and a practical algorithm was established. A preliminary simulation of the temperature evolution in a two dimensional zone under certain boundary conditions and micro wave heating was conducted as a numerical illustration for the method and some meaningful conclusions were drawn. The validity of DRBEM was testified through a comparison with finite difference method (FDM) under one-dimensional calculation. Owing to its unique advantages like not confined by the complex shape of biological bodies, no need of discretization of the inner domain, save vast CPU time and easy to deal with different bioheat models, DRBEM may become an important approach for predicting and controlling the transient temperature field of biological bodies under hyperthermia or hypothermia.

Algorithms↗
PubMed1998

A toxin homology domain in an astacin-like metalloproteinase of the jellyfish Podocoryne carnea with a dual role in digestion and development.

Metalloproteinases of the astacin family such as tolloid play major roles in animal morphogenesis. Cnidarians are thought to be evolutionary simple organisms and, therefore, a metalloproteinase from the marine hydrozoan Podocoryne carnea was analysed to evaluate the role of this conserved gene familiy at the base of animal evolution. Surprisingly, the proteinase domain of Podocornyne PMP1 is more similar to human meprin than to HMP1 from another hydrozoan, the freshwater polyp Hydra vulgaris. However, PMP1 and HMP1 both contain a small C-terminal domain with six cysteines that distinguishes them from other astacin-like molecules. Similar domains have been described only recently from sea anemone toxins specific for potassium channels. This toxin homology (Tox1) domain is clearly distinct from epidermal growth factor (EGF)-like domains or other cysteine-rich modules and terminates with the characteristic pattern CXXXCXXC with three out of six cysteines in the last eight residues of the protein. PMP1 is transiently expressed at various sites of morphogenetic activity during medusa bud development. In the adult medusa, however, expression is concentrated to the manubrium, the feeding organ, where the PMP1 gene is highly induced upon feeding. These disparate expression patterns suggest a dual role of PMP1 comparable to tolloid in development and, like astacin in the crayfish, also for food digestion. The Tox1 domain of PMP1 could serve as a toxin to keep the pray paralysed after ingestion, but as a sequence module such Tox1 domains with six cysteines are neither restricted to cnidarians nor to toxins.

Amino Acid Sequence↗
PubMed2000

Evolution of hemispheric specialization: advantages and disadvantages.

Lateralization of the brain appeared early in evolution and many of its features appear to have been retained, possibly even in humans. We now have a considerable amount of information on the different forms of lateralization in a number of species, and the commonalities of these are discussed, but there has been relatively little investigation of the advantages of being lateralized. This article reports new findings on the differences between lateralized and nonlateralized chicks. The lateralized chicks were exposed to light for 24 h on day 19 of incubation, a treatment known to lead to lateralization of a number of visually guided responses, and the nonlateralized chicks were incubated in the dark. When they were feeding, the lateralized chicks were found to detect a stimulus resembling a raptor with shorter latency than nonlateralized chicks. This difference was not a nonspecific effect caused by the light-exposed chicks being more distressed by the stimulus. Instead, it appears to be a genuine advantage conferred by having a lateralized brain. It is suggested that having a lateralized brain allows dual attention to the tasks of feeding (right eye and left hemisphere) and vigilance for predators (left eye and right hemisphere). Nonlateralized chicks appear to perform these dual tasks less efficiently than lateralized ones. Reference is made to other species in discussing these results.

Aggression↗
PubMed2003

Analysis of fish ZP1/ZPB homologous genes--evidence for both genome duplication and species-specific amplification models of evolution.

The vertebrate egg envelope is composed of a family of related proteins, the zona pellucida (ZP) proteins, which are characterized by the presence of a conserved zona pellucida domain. Analysis of teleost fish ZP gene sequences has demonstrated that there are no direct orthologues of the mammalian ZPB and ZP1 genes, but that teleost fish contain multiple copies of two classes of genes (ZPXa and ZPXb) that are equally related to ZPB and ZP1. The two classes of genes are further distinguished by expression in liver or ovary, respectively, indicating there was probably an initial duplication event, followed by a switch to hepatic expression of one of the paralogues. This switch was followed in some species by additional amplification of one of the paralogues with the subsequent loss of the other. It is proposed that the expansion of the number of ZPXa and ZPXb genes and the acquisition of dual sites of synthesis are the result of an ancient polyploidization event, followed by additional species-specific gene amplifications.

Animals↗
PubMed1998

Recombination, RNA evolution, and bifunctional RNA molecules isolated through chimeric SELEX.

Exchange of RNA structural domains through recombination can be used to engineer RNAs with novel functions and may have played an important role in the early evolution of life. The degree of function an RNA element retains upon recombination into a new sequence context is a measure of how deleterious or beneficial recombination will be. When we fused pairs of aptamers previously selected to bind coenzyme A, chloramphenicol, or adenosine, the chimerae retained some ability to bind both targets, but with reduced binding activity both in solution and on affinity resins, probably due to misfolding. Complex populations of recombined RNAs gave similar results. Applying dual selection pressure to recombined populations yielded the combinations that were best suited to binding both targets. Most reselected RNAs folded into the active conformation more readily than chimerae built from arbitrarily chosen aptamers, as indicated both by solution Kd measurements and affinity resin binding activity. Deletion/selection experiments confirmed that the sequences required for binding are fully contained within the respective domains and not derived from interaction between the domains, consistent with the modular architecture of their original design. The combinatorial nature of the recombination methods presented here takes advantage of the full sequence diversity of the starting populations and yields large numbers of bifunctional molecules (10(6) to more than 1012). The method can be easily generalized and should be applicable to engineering dual-function RNAs for a wide variety of applications, including catalysis, novel therapeutics, and studies of long-range RNA structure.

Base Sequence↗
PubMed1995

CHUK, a new member of the helix-loop-helix and leucine zipper families of interacting proteins, contains a serine-threonine kinase catalytic domain.

We have identified a new member of the helix-loop-helix (H-L-H) and leucine zipper gene families via a reverse transcriptase-polymerase chain reaction based strategy. This new gene, CHUK (conserved helix-loop-helix ubiquitous kinase), may represent the founding member of a new class of interacting chimeric proteins. The nucleotide sequence of a near full-length murine CHUK cDNA clone revealed an encoded polypeptide specifying: a carboxyl-terminal H-L-H domain, an amino terminal serine-threonine kinase catalytic domain, and a leucine zipper-like amphipathic alpha-helix juxtaposed in between the H-L-H and kinase domains. CHUK is highly conserved in evolution and ubiquitously expressed in diverse types of established cell lines, whereas it is differentially expressed in normal murine tissues. The structural features of the CHUK polypeptide suggest that its putative kinase activity may be targetted to H-L-H and/or leucine zipper transcription factors. Alternatively, the dual amphipathic a helices may serve to control its intrinsic kinase activity by interactions with other cellular factors. CHUK may provide new insights into the regulated transmission of cytoplasmic signals to specific nuclear factors manifesting rapid alterations in patterns of cellular gene expression.

Amino Acid Sequence↗
PubMed2002

Isotype switch-mediated CH deletions are a recurrent feature of Myc/CH translocations in peritoneal plasmacytomas in mice.

Oncogene activating chromosomal translocations that interrupt IGH switch (S) regions at 14q32 are thought to be caused by misguided IGH isotype switching in postgerminal center B-cell lymphomas and plasma cell myelomas in humans. Aberrant switching also seems to be involved in altering the fine structure of the translocation in some of these tumors, but the significance of these changes is not known. Here we report on 3 cases of IL-6 transgenic mouse plasmacytomas (PCT) that harbor T(12;15) translocations that had been modified by frustrated switch attempts that result in C(H) deletions. When considered together with 6 similar cases of PCT described previously, our observations suggest that secondary deletions in C(H) are a regular feature in the molecular evolution of T(12;15) translocations and, thereby, in the progression of PCT. We propose that the T(12;15)(+) mouse PCT offers a uniquely valuable model system for elucidating the dual role of abnormal isotype switching in causation and 'remodeling' of chromosomal translocations.

Animals↗
PubMed1994

Innovations in pulse generators and lead systems: balancing complexity with clinical benefit and long-term results.

Technologic development of implantable cardioverter defibrillators (ICDs) is now in an exponential growth phase, and many new concepts are being examined. Major innovations have occurred in pulse generators and in lead systems. This may increase ICD use for primary and secondary prevention of sudden cardiac death. Pulse generators now include hybrid pacemaker-defibrillators. Clinical data suggest a need for demand pacing in primary and secondary prevention applications, with antitachycardia pacing being most valuable in the latter group. Atrial leads will allow dual chamber sensing, pacing, and defibrillation. Low energy cardioversion with biphasic shocks can enhance shock efficacy in rapid monomorphic ventricular tachycardia and flutter. Modifications of lead design, biphasic shock waveforms, and optimal thoracic electrode location in axillary or pectoral regions will permit lower energy defibrillation and smaller pulse generators with lower maximum energy outputs of < or = 25 joules. Dual chamber sensing will improve detection of atrial flutter or fibrillation. Minimum data storage requirements for tachycardia events in ICDs still need to be defined. Intracardiac electrogram analysis is still in evolution, and better analytic methods are awaited. Lead system development is likely to support generic pacing and defibrillation catheter electrodes for atrial and ventricular application. Advances in thoracic electrode design are in progress, and a variety of intercostal electrodes are being tested. Improvements in lead design with further impact on defibrillation energy requirements have the potential to permit generator miniaturization. Significant technologic improvements in ICD devices are imminent and should improve clinical results, patient safety, and quality of life.

Algorithms↗
PubMed1993

The MAP kinase cascade is essential for diverse signal transduction pathways.

Mitogen-activated protein (MAP) kinases are activated by combined tyrosine and threonine phosphorylation catalysed by MAP kinase kinase, a novel class of protein kinases with dual specificity for both tyrosine and serine/threonine. MAP kinase kinase is turned on by serine/threonine phosphorylation catalysed by an immediate upstream kinase. The MAP kinase cascade appears to be conserved during evolution and thus might play an essential role in diverse intracellular signaling processes from yeasts to vertebrates.

Amino Acid Sequence↗
PubMed2005

Long-term reduction of atrial tachyarrhythmia recurrences in patients paced for bradycardia-tachycardia syndrome.

BACKGROUND: Atrial tachyarrhythmias (AT) are considered progressive diseases. Several rhythm control therapies for treatment of AT have been proposed. OBJECTIVES: The Italian AT500 Registry was designed to prospectively study long-term AT evolution in patients paced for the brady-tachy form of sinus node disease (BT-SND). METHODS: Three hundred forty-six BT-SND patients received an antitachycardia dual-chamber pacemaker and were followed-up for a minimum of 12 months (median 19 months). Prevention and antitachycardia pacing (ATP) features were enabled in all patients. RESULTS: During the observation period, 224 (65%) patients were treated by antiarrhythmic drugs and 45 (13%) patients were cardioverted. Five patients suffered a stroke, 4 transient ischemic attack, 22 permanent AT, and 98 AT recurrences longer than 7 days. AT mean cycle length changed from 246 to 270 ms, and the percentage of patients with AT-related hospitalizations significantly decreased with an annual 28% relative reduction. AT burden and the percentage of patients with AT recurrences longer than 2 days remained constant with time in the overall population but decreased significantly in the subgroup of patients who did not develop permanent AT. High ATP efficacy was associated with an increasingly higher prevention of AT recurrences longer than 2 days. CONCLUSION: In a long-term observation of BT-SND patients, AT-related hospitalizations decreased significantly and mean AT cycle length increased significantly. The data suggest that rhythm control therapies induce inversion of AT progression.

Aged↗
PubMed2002

Microbial glycosaminoglycan glycosyltransferases.

Glycosaminoglycans, a class of linear polysaccharides composed of repeating disaccharide units containing a hexosamine, are important carbohydrates found in many organisms. Vertebrates utilize glycosaminoglycans in structural, recognition, adhesion, and signaling roles. Certain pathogenic bacteria produce extracellular capsules composed of glycosaminoglycans or glycosaminoglycan-like polymers that enhance the microbes' ability to infect or to colonize the host. In the period from 1993 to 2001, bacterial enzymes were discovered that catalyze the polymerization of the repeating unit of hyaluronan, chondroitin, or N-acetylheparosan (unsulfated, unepimerized heparin). Depending on the specific carbohydrate and the microorganism, either a dual-action enzyme (synthase) that transfers two distinct monosaccharides or a pair of single-action transferases are utilized to synthesize the glycosaminoglycan polymer. Current views on the enzymology, structures, potential evolution, and the roles of the known glycosyltransferases from Streptococcus, Pasteurella, and Escherichia are discussed.

Bacteria↗
PubMed1987

Reporting colorectal cancer.

Reporting colorectal cancer comprises two phases: the careful collection of pathological data; and the division of patients into groups with differing prognoses. Dukes' classification of rectal cancer was the outcome of this dual approach. It evolved over many years, and full details of its final form were not published until 1958, towards the end of his career. Others modified the classification during its evolution, and numerous rival pathological and clinicopathological systems now exist. The resulting confusion that surrounds the Dukes classification may make it impossible to compare pathological findings and the results of treatment between different centres. The importance of meticulous dissection and examination of surgical specimens is emphasised and a simple set of recommendations made. It is shown how modern statistical methods may identify pathological variables that have independent clinical importance. On the basis of this information a new system of prognostic categorisation for patients receiving apparently curative surgery for rectal cancer has been developed, which is superior to the Dukes classification in that it can place many more patients into groups with clear prognostic implications.

Colonic Neoplasms↗
PubMed2006

Environmental influences on energy balance-related behaviors: a dual-process view.

BACKGROUND: Studies on the impact of the 'obesogenic' environment have often used non-theoretical approaches. In this journal's debate and in other papers authors have argued the necessity of formulating conceptual models for differentiating the causal role of environmental influences on behavior. DISCUSSION: The present paper aims to contribute to the debate by presenting a dual-process view on the environment--behavior relationship. This view is conceptualized in the EnRG framework (Environmental Research framework for weight Gain prevention). In the framework, behavior is postulated to be the result of a simultaneous influence of conscious and unconscious processes. Environmental influences are hypothesized to influence behavior both indirectly and directly. The indirect causal mechanism reflects the mediating role of behavior-specific cognitions in the influence of the environment on behavior. A direct influence reflects the automatic, unconscious, influence of the environment on behavior. Specific personal and behavioral factors are postulated to moderate the causal path (i.e., inducing either the automatic or the cognitively mediated environment - behavior relation). In addition, the EnRG framework applies an energy balance-approach, stimulating the integrated study of determinants of diet and physical activity. CONCLUSION: The application of a dual-process view may guide research towards causal mechanisms linking specific environmental features with energy balance-related behaviors in distinct populations. The present paper is hoped to contribute to the evolution of a paradigm that may help to disentangle the role of 'obesogenic' environmental factors.

Journal Article↗