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Speculation
Kinds of Speculation Selected Abstracts[Commentary] HAVING FUN AND DEFYING ADULTS: SPECULATIONS ON WHY MOST YOUNG PEOPLE IGNORE NEGATIVE INFORMATION ON THE DANGERS OF DRINKING ALCOHOLADDICTION, Issue 4 2009RODNEY SKAGER No abstract is available for this article. [source] Association of ablation of Barrett's esophagus with high grade dysplasia and adenocarcinoma of the gastric cardiaDISEASES OF THE ESOPHAGUS, Issue 4 2006R. E. Sampliner SUMMARY., There has been increasing application of endoscopic ablation therapy for patients with high-grade dysplasia (HGD) and Barrett's esophagus (BE). Three cases are reported in which the patient developed adenocarcinoma of the gastric cardia after thermal ablation of HGD. A definition of BE including endoscopic abnormality and intestinal metaplasia by biopsy was used. Strict and standardized criteria were utilized for the endoscopic landmarks. Three cases are reported with long-segment BE and a nodule or mass in the endoscopic cardia post-thermal ablation. Biopsies documented adenocarcinoma of the gastric cardia. The development of adenocarcinoma of the cardia is unexpected. Speculation is offered as to the potential of increased proliferation and mutations at the new squamocolumnar interface after endoscopic ablation therapy to explain this association. [source] Speculation Disguised as ResultsETHOLOGY, Issue 9 2008Article first published online: 8 AUG 200 No abstract is available for this article. [source] Anomalous energy losses for light projectiles traversing a polyvinylformyl resin,INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2001L. E. Porter Abstract Measurements of the stopping powers of the polyvinylformyl resin known as formvar for 0.67,1.75 MeV protons, 1.19,3.02 MeV alpha particles, and 3.9,10.4 MeV 7Li ions have been analyzed in terms of modified Bethe,Bloch theory for the purpose of extracting values of the dominant parameters of the formalism employed. These parameters are the target mean excitation energy and the Barkas-effect parameter, plus a single effective-charge parameter to characterize the interactions of 4He and 7Li projectiles with the target. Whereas results for the Barkas-effect parameter agreed well with the expected value of 1.4±0.1, results for the mean excitation energy lay about 20% below the value of 71.9 eV based on the assumption of linear additivity of stopping effects. Speculation as to the source of this difference is offered. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem, 2001 [source] Subjects of Speculation: Emergent Life Sciences and Market Logics in the United States and IndiaAMERICAN ANTHROPOLOGIST, Issue 1 2005KAUSHIK SUNDER RAJAN This article traces systems of exchange concerning the life sciences and capital and how they configure subjectivity in the United States and India. This is done through case studies concerning the emergence of personalized medicine in the two locales. In the U.S. case, I argue for the configuration of the subjects of personalized medicine as sovereign consumers; in the Indian case, I argue for their configuration as experimental subjects. I situate these arguments in the context of epistemologies of genomics and the consolidation of systems of speculative capitalism. [source] Fruit, Minerals, and Forest Elephant Trails: Do All Roads Lead to Rome?BIOTROPICA, Issue 3 2004Stephen Blake ABSTRACT Tropical forests are among the most heterogeneous environments on earth, and food resources for many animals are patchy both in time and space. In Africa's equatorial forest, permanent trails created and maintained by forest elephants are conspicuous features. Trails may be several meters wide and continue for tens of kilometers. Speculation on which resources determine the distribution of trails has identified fruit, browse, and mineral deposits as candidates. In this study, the relationships between these habitat variables and elephant trails were investigated. The size of individual trails and the density of the trail system increased dramatically with proximity to mineral deposits. Fruit tree basal area decreased with perpendicular distance from trails, while that of non-fruit trees did not. Fruit tree abundance and basal area were significantly higher on trail intersections than random sites and increased with intersection size. No relationship was found between monocotyledon browse abundance and elephant trail system characteristics. Clumped resources, which are at least partially reliable, provide a high nutritional payback, and are not rapidly depleted and can thus be visited repeatedly, appear to influence permanent trail formation by forest elephants. Permanent trails may allow naive individuals or those with imperfect knowledge to locate and acquire important resources. [source] Cell organization of barb ridges in regenerating feathers of the quail: implications of the elongation of barb ridges for the evolution and diversification of feathersACTA ZOOLOGICA, Issue 2 2007L. Alibardi Abstract This ultrastructural study on the regenerating feathers of quail describes the cellular organization of the barb ridges responsible for the ramification of adult feathers. Bilateral symmetry of the barb ridges determines the organization of feather cells into feather branching. The length of the barb ridges, derived from the number of cells associated to form the barbule plates, determines the length of the barbule branching. Long chains of barb cells form long barbs that branch from the rachis with an increase of feather size. Supportive cells function as spacers between the barbule cells. New cells derive from stem cells localized in the collar region of the feather follicle, as indicated from the re-organization of collar cells into barb ridges (a morphogenetic process inherited from that of embryonic feathers), production of an embryonic type of keratin (feather keratin), permanence of periderm granules (typical embryonic organelles) in barb vane ridge cells. Variations in the process of barb ridge morphogenesis allow the fusion of ridges into a rachis. The differentiation of hooklets contributes to the origin of planar feathers. Separation between rachis and merging barb ridges is by supportive cells, derived from the marginal plates of the barb ridges. Speculations on the evolution and diversification of feathers are presented. [source] The prevalence of Dyslexia among art studentsDYSLEXIA, Issue 1 2002Ulrika Wolff Abstract It is widely held opinion that dyslexia is associated with remarkably artistic creativity. Speculations on different brain structures and brain functions have been proposed as an explanation. Very few objective studies have been reported that confirm the conjectures on the relationship between dyslexia and artistic creativity. Two studies are reported on the prevalence of dyslexia among university students,one group of art students and one group of students from non-art disciplines. The admission to the art schools were extremely demanding, possibly implying that the students were genuinely talented, and that their choice of training did not reflect a compensation for failure in conventional academic fields. Art academy students reported significantly more signs of dyslexia than non-art university students. Objective testing showed that art students had significantly poorer phonological skills than non-art students. Thus, according to self-reports combined with objective testing, the incidence of dyslexia was far higher among art students. Copyright © 2002 John Wiley & Sons, Ltd. [source] Attachment, Social Rank, and Affect Regulation: Speculations on an Ethological Approach to Family Interaction,FAMILY PROCESS, Issue 3 2002F.R.C.P. (C), L.R.C.P., Leon Sloman M.R.C.P. The attachment and social rank systems are biological-evolutionary systems that can serve as models for conceptualizing family interaction. By exploring both their unique and interrelated impact on affect regulation, we can differentiate between processes that foster healthy growth and those leading to individual psychopathology. This perspective facilitates the integration of biological and psychological models, and has therapeutic implications. It also integrates well with other family therapy models. [source] Reflections and Speculations on Refractory Migraine: Why Do Some Patients Fail to Improve With Currently Available Therapies?HEADACHE, Issue 6 2008David W. Dodick MD This review considers current debate surrounding refractory migraine and poses the question, why do some patients fail to improve with currently available therapies? [source] Speculations on a Privileged State of Cognitive DissonanceJOURNAL FOR THE THEORY OF SOCIAL BEHAVIOUR, Issue 2 2001Conrad Montell [source] Instructional Design and Powerful LearningPERFORMANCE IMPROVEMENT QUARTERLY, Issue 2 2001Gordon Rowland ABSTRACT Skillfully executed, instructional design can result in effective and efficient means to meet learning goals. However, more powerful learning experiences seem to go beyond effectiveness, efficiency, appeal, and even predetermined goals. This study sought to identify the key features of instructional design, to determine the nature of powerful learning experiences, and to explore how the two might relate. A survey of experts and a series of interviews with adult learners revealed overlap in some areas, for example, in the perceived importance of active engagement in authentic situations, and clear differences in others, most significantly the importance placed by learners on continual face-to-face personal interaction with a mentor/expert teacher. Speculations are offered on what similar results from additional studies might imply with regard to design actions and choices, and questions for further research are posed. [source] Potential Errors in Detecting Earnings Management: Reexamining Studies Investigating the AMT of 1986,CONTEMPORARY ACCOUNTING RESEARCH, Issue 4 2001Won W. Choi Abstract In this paper we seek to document errors that could affect studies of earnings management. The book income adjustment (BIA) of the alternative minimum tax (AMT) created apparently strong incentives to manage book income downward in 1987. Five earlier papers using different methodologies and samples all conclude that earnings were reduced in response to the BIA. This consensus of findings offers an opportunity to investigate our speculation that methodological biases are more likely when there appear to be clear incentives for earnings management. A reexamination of these studies uncovers potential biases related to a variety of factors, including choices of scaling variables, selection of affected and control samples, and measurement error in estimated discretionary accruals. A reexamination of the argument underlying these studies also suggests that the incentives to manage earnings are less powerful than initially predicted, and are partially mitigated by tax and non-tax factors. As a result, we believe that the extent of earnings management that occurred in 1987 in response to the BIA remains an unresolved issue. [source] UNITED STATES V. BOOKER AS A NATURAL EXPERIMENT: USING EMPIRICAL RESEARCH TO INFORM THE FEDERAL SENTENCING POLICY DEBATE,CRIMINOLOGY AND PUBLIC POLICY, Issue 3 2007PAUL J. HOFER Research Summary: In United States v. Booker, the U.S. Supreme Court held that the federal sentencing guidelines must be considered advisory, rather than mandatory, if they are to remain constitutional under the Sixth Amendment. Since the decision, the U.S. Sentencing Commission has provided policy makers with accurate and current data on changes and continuity in federal sentencing practices. Unlike previous changes in legal doctrine, Booker immediately increased the rates of upward and downward departures from the guideline range. Government-sponsored downward departures remain the leading category of outside,the-range sentences. The rate of within-range sentences, although lower than in the period immediately preceding Booker, remains near rates observed earlier in the guidelines era. Despite the increase in departures, average sentence lengths for the overall caseload remain stable, because of offsetting increases in the seriousness of the crimes being sentenced and in the severity of penalties for those crimes. Analyses of the reasons that judges reported for downward departures suggest that treatment of criminal history and offender characteristics are the two leading areas of dissatisfaction with the guidelines. Policy Implications: Assessment of changes in sentencing practices following Booker by different observers depends partly on competing institutional perspectives and on different degrees of trust in the judgment of judges, prosecutors, the Sentencing Commission, and Congress. No agreement on whether Booker has bettered or worsened the system can be achieved until agreement exists on priorities among the purposes of sentencing and the goals of sentencing reform. Both this lack of agreement and an absence of needed data make consensus on Booker's effects on important sentencing goals, such as reduction of unwarranted disparity, unlikely in the near future. Similarly, lack of baseline data before Booker on the effectiveness of federal sentencing at crime control makes before-after comparisons impossible. Despite these limitations, research provides a sounder framework for policy making than do anecdotes or speculation and sets valuable empirical parameters for the federal sentencing policy debate. [source] Vertebral artery fibromuscular dysplasia: an unusual cause of stroke in a 3-year-old childDEVELOPMENTAL MEDICINE & CHILD NEUROLOGY, Issue 10 2003Ana Camacho MD Fibromuscular dysplasia (FMD) is a systemic arteriopathy which tends to affect renal arteries followed by cervicocranial vessels. It can lead to cerebral infarction if cephalic arteries are involved. FMD is an unusual cause of stroke in childhood that generally affects the carotid area. Only four cases of vertebral FMD and subsequent stroke have been reported previously and we present the youngest patient of all. A healthy 3-year-old female was admitted to Hospital Doce de Octubre in Madrid, Spain with cerebellar infarction. Angiography disclosed basilar artery thrombosis and typical signs of FMD in both vertebral arteries. No other angiographic alteration was noted in the other vessels studied. Her phenotype and other investigations were unremarkable. The patient was treated with anti-aggregation therapy (aspirin) and the outcome was excellent. Investigation of the occurrence in childhood of this kind of arteriopathy may lead to clarification of its natural history and speculation about its unclear pathogenesis. [source] Neural plasticity and human development: the role of early experience in sculpting memory systemsDEVELOPMENTAL SCIENCE, Issue 2 2000Charles A. Nelson The concept of sensitive or critical periods in the context of memory development is examined in this paper. I begin by providing examples of the role of experience in influencing sensory, linguistic and emotional functioning. This is followed by a discussion of the role of experience in influencing cognitive functioning, particularly memory. Based on this discussion, speculation is offered that the infant's proclivity for novelty, which makes its appearance shortly after birth, provides critical input into a nervous system that will eventually be set up to learn and remember for the entire lifespan. Because learning and memory are fundamental to the survival of our species, those aspects of the nervous system that permit the encoding and retention of new information are remarkably malleable from the outset, even in the face of some types of neural trauma. This flexibility is retained for many years so long as the learning and memory ,system' is challenged. The implications of this model are discussed in the context of those life events that might undermine the longevity of memory systems. [source] The role of pdx1 and HNF6 in proliferation and differentiation of endocrine precursorsDIABETES/METABOLISM: RESEARCH AND REVIEWS, Issue 2 2004Laura Wilding Abstract Ex vivo expansion of embryonic stem cells (ES cells) or pancreatic stem cells for insulin delivery to diabetic patients provides potential for the restoration of islet function in these individuals. Understanding the spatial and temporal requirements of crucial factors for endocrine progenitor specification, proliferation, and terminal differentiation remains a major challenge in the field of pancreas development. Here, we provide speculation as to the role of pdx1 and HNF6 in these different stages of pancreatic endocrine cell development. At the time when islets begin to form within the pancreas, the expression patterns of pdx1 and HNF6 diverge, suggesting distinct functions for each of the genes over the course of endocrine cell development. The current body of evidence provides support for a role of both factors in early endocrine specification as well as a requirement for pdx1 in the generation of mature pancreatic endocrine cells. The precise temporal requirement of HNF6 in the production of terminally differentiated endocrine cells remains unclear. Future studies in this area will rely on conditionally manipulatable systems in combination with lineage-tracing studies for a more accurate assessment of pdx1 and HNF6 function at different stages along the pathway of endocrine cell development. Copyright © 2004 John Wiley & Sons, Ltd. [source] Association between lymphocyte proliferation and polychlorinated biphenyls in free-ranging harbor seal (Phoca vitulina) pups from British Columbia, CanadaENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 5 2005Milton Levin Abstract Recent pinniped die-offs have led to the speculation that persistent organic pollutants (POPs) are immunomodulatory, making individuals more susceptible to viral infections. Eighteen healthy harbor seal (Phoca vitulina) pups (aged 3,4 weeks) were live-captured from southern British Columbia, Canada, and maintained temporarily in captivity for an immunotoxicological assessment. The relationships between mitogen-induced peripheral blood lymphocyte proliferation and blubber concentrations of three major immunotoxic POP classes (the polychlorinated biphenyls [PCBs], polychlorinated dibenzo- p -dioxins [PCDDs], and the polychlorinated dibenzofurans [PCDFs]) were evaluated. A significant body weight-independent positive correlation was observed between both T-cell mitogen (phytohemagglutinin [PHA])- and B-cell mitogen (lipopolysaccharide [LPS])-induced lymphocyte proliferation and the blubber concentrations of total PCB. Best subset regression analysis revealed that total PCBs, and not total PCDD or total PCDF, explained 24 and 29% of the changes in both T-cell mitogen-and B-cell mitogen-induced lymphocyte proliferation, respectively. Further regression analysis performed on the PCB classes measured in this study showed that di - ortho PCBs accounted for 25 and 30% of the changes in both T-cell and B-cell lymphocyte proliferation, respectively. Results suggest that POPs, and PCBs in particular, are associated with changes in lymphocyte proliferation, something that could result in increased susceptibility to infections in harbor seal pups. Further research is needed to evaluate the relative roles of natural and contaminant-related influences on the immune system of marine mammals. [source] Expression of a non-DNA-binding Ikaros isoform exclusively in B cells leads to autoimmunity but not leukemogenesisEUROPEAN JOURNAL OF IMMUNOLOGY, Issue 4 2007Heather Wojcik Abstract Ikaros is a transcriptional regulator whose function is essential for B cell development. It is expressed in the hematopoietic stem cell (HSC) through the mature B cell stage. Using genetically engineered mice in which the endogenous Ikaros gene is disrupted, it has been shown that a lack of Ikaros leads to a block in B cell development and that its severe diminution results in a hyperresponsive B cell compartment. Ikaros expression within the HSC has led to speculation as to whether the role of Ikaros in B cell biology is largely accomplished prior to B cell specification. In addition, widespread expression of Ikaros in hematopoietic cells leads to the possibility that some or all of the observed defects are not B cell autonomous. In this report, we demonstrate that over-expression of a dominant interfering Ikaros isoform exclusively in B cells has profound effects on mature B cell function. We provide evidence that continued high-level expression of Ikaros is essential for homeostasis of peripheral lymphocytes and maintenance of B cell tolerance. We also show that deregulation of Ikaros activity does not rapidly result in B cell leukemogenesis as it does with 100% penetrance within the T cell lineage. [source] MINIMAL SELFING, FEW CLONES, AND NO AMONG-HOST GENETIC STRUCTURE IN A HERMAPHRODITIC PARASITE WITH ASEXUAL LARVAL PROPAGATIONEVOLUTION, Issue 3 2006Charles D. Criscione Abstract Little is known about actual mating systems in natural populations of parasites or about what constitutes the limits of a parasite deme. These parameters are interesting because they affect levels of genetic diversity, opportunities for local adaptation, and other evolutionary processes. We expect that transmission dynamics and the distribution of parasites among hosts should have a large effect on mating systems and demic structure, but currently we have mostly speculation and very few data. For example, infrapopulations (all the parasites in a single host) should behave as demes if parasite offspring are transmitted as a clump from host to host over several generations. However, if offspring are well mixed, then the parasite component population (all the parasites among a host population) would function as the deme. Similarly, low mean intensities or a high proportion of worms in single infections should increase the selfing rate. For species having an asexual amplification stage, transmission between intermediate and definitive (final) hosts will control the variance in clonal reproductive success, which in turn could have a large influence on effective sizes and rates of inbreeding. We examined demic structure, selfing rates, and the variance in clonal reproductive success in natural populations of Plagioporus shawi, a hermaphroditic trematode that parasitizes salmon. Overall levels of genetic diversity were very high. An a posteriori inference of population structure overwhelmingly supports the component population as the deme, rather than individual infrapopulations. Only a single pair of 597 adult individuals was identified as clones. Thus, the variance in clonal reproductive success was almost zero. Despite being hermaphroditic, P. shawi appears to be almost entirely outcrossing. Genetic estimates of selfing (<5%) were in accordance with the proportion of parasites from single infections. Thus, it appears that individual flukes outcross whenever possible and only resort to selfing when alone. Finally, our data support the hypothesis that aquatic transmission and the use of several intermediate hosts promotes high genetic diversity and well-mixed infrapopulations. [source] THE ADAPTIVE SIGNIFICANCE OF TEMPERATURE-DEPENDENT SEX DETERMINATION: EXPERIMENTAL TESTS WITH A SHORT-LIVED LIZARDEVOLUTION, Issue 10 2005Daniel A. Warner Abstract Why is the sex of many reptiles determined by the temperatures that these animals experience during embryogenesis, rather than by their genes? The Charnov-Bull model suggests that temperature-dependent sex determination (TSD) can enhance maternal fitness relative to genotypic sex determination (GSD) if offspring traits affect fitness differently for sons versus daughters and nest temperatures either determine or predict those offspring traits. Although potential pathways for such effects have attracted much speculation, empirical tests largely have been precluded by logistical constraints (i.e., long life spans and late maturation of most TSD reptiles). We experimentally tested four differential fitness models within the Charnov-Bull framework, using a short-lived, early-maturing Australian lizard (Amphibolurus muricatus) with TSD. Eggs from wild-caught females were incubated at a range of thermal regimes, and the resultant hatchlings raised in large outdoor enclosures. We applied an aromatase inhibitor to half the eggs to override thermal effects on sex determination, thus decoupling sex and incubation temperature. Based on relationships between incubation temperatures, hatching dates, morphology, growth, and survival of hatchlings in their first season, we were able to reject three of the four differential fitness models. First, matching offspring sex to egg size was not plausible because the relationship between egg (offspring) size and fitness was similar in the two sexes. Second, sex differences in optimal incubation temperatures were not evident, because (1) although incubation temperature influenced offspring phenotypes and growth, it did so in similar ways in sons versus daughters, and (2) the relationship between phenotypic traits and fitness was similar in the two sexes, at least during preadult life. We were unable to reject a fourth model, in which TSD enhances offspring fitness by generating seasonal shifts in offspring sex ratio: that is, TSD allows overproduction of daughters (the sex likely to benefit most from early hatching) early in the nesting season. In keeping with this model, hatching early in the season massively enhanced body size at the beginning of the first winter, albeit with a significant decline in probability of survival. Thus, the timing of hatching is likely to influence reproductive success in this short-lived, early maturing species; and this effect may well differ between the sexes. [source] Intermittent hypoxia and respiratory plasticity in humans and other animals: does exposure to intermittent hypoxia promote or mitigate sleep apnoea?EXPERIMENTAL PHYSIOLOGY, Issue 3 2009Jason H. Mateika This review focuses on two phenomena that are initiated during and after exposure to intermittent hypoxia. The two phenomena are referred to as long-term facilitation and progressive augmentation of respiratory motor output. Both phenomena are forms of respiratory plasticity. Long-term facilitation is characterized by a sustained elevation in respiratory activity after exposure to intermittent hypoxia. Progressive augmentation is characterized by a gradual increase in respiratory activity from the initial to the final hypoxic exposure. There is much speculation that long-term facilitation may have a significant role in individuals with sleep apnoea because this disorder is characterized by periods of upper airway collapse accompanied by intermittent hypoxia, one stimulus known to induce long-term facilitation. It has been suggested that activation of long-term facilitation may serve to mitigate apnoea by facilitating ventilation and, more importantly, upper airway muscle activity. We examine the less discussed but equally plausible situation that exposure to intermittent hypoxia might ultimately lead to the promotion of apnoea. There are at least two scenarios in which apnoea might be promoted following exposure to intermittent hypoxia. In both scenarios, long-term facilitation of upper airway muscle activity is initiated but ultimately rendered ineffective because of other physiological conditions. Thus, one of the primary goals of this review is to discuss, with support from basic and clinical studies, whether various forms of respiratory motor neuronal plasticity have a beneficial and/or a detrimental impact on breathing stability in individuals with sleep apnoea. [source] In Memoriam: Mordecai Kaffman, M.D. (1917,2005)FAMILY PROCESS, Issue 2 2005Yoel Elizur Ph.D. A word of warning: the following ideas will be presented in plain everyday language, avoiding any type of professional lexicon. It may be that this down-to-earth form of presentation will disappoint some of my potential readers who are accustomed to peruse material presented in sophisticated meta-systemic language. All I can do is plead guilty, and in self-defense put forward two arguments. First, that I cannot escape the universal truth, "the style is the man," and second, that the simple ideas which I am to present here are all, without exception, the result of concrete clinical experience, with no admixture of theoretical armchair speculation. [source] Identification and characterization of the transcription factors involved in T-cell development, t-bet, stat6 and foxp3, within the zebrafish, Danio rerioFEBS JOURNAL, Issue 1 2010Suman Mitra The discovery of cytokines expressed by T-helper 1 (Th1), Th2, Th17 and T-regulatory (Treg) cells has prompted speculation that these types of responses may exist in fish, arising early in vertebrate evolution. In this investigation, we cloned three zebrafish transcription factors, T-box expressed in T cells (t-bet), signal transducer and activator of transcription 6 (stat6) and fork-head box p3 (foxp3), in which two transcripts are present, that are important in the development of a number of these cell types. They were found within the zebrafish genome, using a synteny approach in the case of t-bet and foxp3. Multiple alignments of zebrafish t-bet, stat6 and foxp3 amino acids with known vertebrate homologues revealed regions of high conservation, subsequently identified to be protein domains important in the functioning of these transcription factors. The gene organizations of zebrafish t-bet and foxp3 were identical to those of the human genes, with the second foxp3 transcript lacking exons 5, 6, 7 and 8. Zebrafish stat6 (21 exons and 20 introns) was slightly different from the human gene, which contained 22 exons and 21 introns. Immunostimulation of zebrafish head kidney and spleen cells with phytohaemagglutinin, lipopolysaccharide or Poly I:C, showed a correlation between the expression of t-bet, stat6 and foxp3 with other genes involved in Th and Treg responses using quantitative PCR. These transcription factors, together with many of the cytokines that are expressed by different T-cell subtypes, will aid future investigations into the Th and Treg cell types that exist in teleosts. [source] Increased glucose metabolism and ATP level in brain tissue of Huntington's disease transgenic miceFEBS JOURNAL, Issue 19 2008Judit Oláh Huntington's disease (HD) is a progressive neurodegenerative disorder characterized by multifarious dysfunctional alterations including mitochondrial impairment. In the present study, the formation of inclusions caused by the mutation of huntingtin protein and its relationship with changes in energy metabolism and with pathological alterations were investigated both in transgenic and 3-nitropropionic acid-treated mouse models for HD. The HD and normal mice were characterized clinically; the affected brain regions were identified by immunohistochemistry and used for biochemical analysis of the ATP-producing systems in the cytosolic and the mitochondrial compartments. In both HD models, the activities of some glycolytic enzymes were somewhat higher. By contrast, the activity of glyceraldehyde-3-phosphate dehydrogenase was much lower in the affected region of the brain compared to that of the control. Paradoxically, at the system level, glucose conversion into lactate was enhanced in cytosolic extracts from the HD brain tissue, and the level of ATP was higher in the tissue itself. The paradox could be resolved by taking all the observed changes in glycolytic enzymes into account, ensuing an experiment-based detailed mathematical model of the glycolytic pathway. The mathematical modelling using the experimentally determined kinetic parameters of the individual enzymes and the well-established rate equations predicted the measured flux and concentrations in the case of the control. The same mathematical model with the experimentally determined altered Vmax values of the enzymes did account for an increase of glycolytic flux in the HD sample, although the extent of the increase was not predicted quantitatively. This suggested a somewhat altered regulation of this major metabolic pathway in HD tissue. We then used the mathematical model to develop a hypothesis for a new regulatory interaction that might account for the observed changes; in HD, glyceraldehyde-3-phosphate dehydrogenase may be in closer proximity (perhaps because of the binding of glyceraldehyde-3-phosphate dehydrogenase to huntingtin) with aldolase and engage in channelling for glyceraldehyde-3-phosphate. By contrast to most of the speculation in the literature, our results suggest that the neuronal damage in HD tissue may be associated with increased energy metabolism at the tissue level leading to modified levels of various intermediary metabolites with pathological consequences. [source] Numerical taxonomic evaluation of calcium oxalate and calcium carbonate crystals in the leaves of certain Ficus species (Moraceae)FEDDES REPERTORIUM, Issue 5-6 2004S. M. Sharawy Dr. The type and the distribution of calcium oxalate and calcium carbonate crystals were investigated in the leaves of 33 taxa of Ficus belonging to the three subgenera Urostigma, Ficus and Sycomorus for a speculation to the inter-subgeneric affinity. Numerical analysis of 55 characters grouped the taxa under 13 groups. The sizes of the latter with respect to the number of taxa they contain were calculated. Some resultant groups comprised taxa from different subgenera. So far as the present data are concerned and in agreement with previous workers, the var. decora of Ficus elastica and var. comosa of Ficus benjamina are better raised to the specific levels F. decoraHort and F. comosaRoxb. respectively. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim) Numerisch-taxonomische Auswertung von Calciumoxalat- und Calciumcarbonat-Kristallen in einigen Arten der Gattung Ficus (Moraceae) An den Blättern von 33 Taxa der Gattung Ficus aus den drei Subgenera Urostigma, Ficus und Sycomorus wurden die Art und die Verteilung von Calciumoxalat- und Calciumcarbonat-Kristallen untersucht, um ihre inter-subgenerische Verwandtschaft zu ermitteln. Num-merische Analysen von 55 Eigenschaften gestatten eine Unterteilung in 13 Gruppen. Der Umfang letzterer in Bezug auf die Anzahl der sie umfassenden Taxa wurde betrachtet. Einige dieser Gruppen umfassen Taxa aus unterschiedlichen Subgenera. Auf Grund der hier gewonnenen Daten und in Übereinstimmung mit früheren Bearbeitern werden Ficus elastica var. decora und F. benjamina var. comosa in den Artrang F. decoraHort bzw. F. comosaRoxb. erhoben. [source] The effect of antibiotics and bismuth on fecal hydrogen sulfide and sulfate-reducing bacteria in the ratFEMS MICROBIOLOGY LETTERS, Issue 1 2003Hiroki Ohge Abstract Colonic bacteria produce the highly toxic thiol, hydrogen sulfide. Despite speculation that this compound induces colonic mucosal injury, there is little information concerning manipulations that might reduce its production. We studied the effect of antibiotics and bismuth on the production of hydrogen sulfide in rats. Baseline fecal samples were analyzed for hydrogen sulfide concentration and release rate during incubation and numbers of sulfate-reducing bacteria. Groups of six rats received daily doses of ciprofloxacin, metronidazole, or sulfasalazine for one week, and feces were reanalyzed. Bismuth subnitrate was then added to the antibiotic regimens. While sulfide production and sulfate-reducing bacteria were resistant to treatment with ciprofloxacin or metronidazole, bismuth acted synergistically with ciprofloxacin to inhibit sulfate-reducing bacteria growth and to reduce sulfide production. Combination antibiotic,bismuth therapy could provide insights into the importance of sulfide and sulfate-reducing bacteria in both human and animal models of colitis and have clinical utility in the treatment of antibiotic-resistant enteric pathogens. [source] Fragrances: are they safe?FLAVOUR AND FRAGRANCE JOURNAL, Issue 6 2002Peter A. Cadby In recent years it has become fashionable to criticize the use of fragrances in our society, suggesting that this use is associated with a variety of negative effects. We review the key areas of criticism, which have suggested adverse safety and environmental effects, with an emphasis on the science, rather than speculation, regarding these issues. In conclusion, an adequate review and testing mechanism exists to assure the safety of fragrance materials, and their combination in mixtures, for the consumers of fragranced products. Copyright © 2002 John Wiley & Sons, Ltd. [source] THE LAST GLACIATION OF SHETLAND, NORTH ATLANTICGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 1 2008N.R. GOLLEDGE ABSTRACT. Evidence relating to the extent, dynamics, and relative chronology of the last glaciation of the Shetland Islands, North Atlantic, is presented here, in an attempt to better illuminate some of the controversies that still surround the glacial history of the archipelago. We appraise previous interpretations and compare these earlier results with new evidence gleaned from the interpretation of a high resolution digital terrain model and from field reconnaissance. By employing a landsystems approach, we identify and describe three quite different assemblages of landscape features across the main islands of Mainland, Yell and Unst. Using the spatial interrelationship of these landsystems, an assessment of their constituent elements, and comparisons with similar features in other glaciated environments, we propose a simple model for the last glaciation of Shetland. During an early glacial phase, a coalescent British and Scandinavian ice sheet flowed approximately east to west across Shetland. The terrestrial land-forms created by this ice sheet in the north of Shetland suggest that it had corridors of relatively fast-flowing ice that were partially directed by bed topography, and that subsequent deglaciation was interrupted by at least one major stillstand. Evidence in the south of Shetland indicates the growth of a local ice cap of restricted extent that fed numerous radial outlet glaciers during, or after, ice-sheet deglaciation. Whilst the absolute age of these three landsystems remains uncertain, these new geo-morphological and palaeoglaciological insights reconcile many of the ideas of earlier workers, and allow wider speculation regarding the dynamics of the former British ice sheet. [source] Pan-glacial,a third state in the climate systemGEOLOGY TODAY, Issue 3 2009Paul F. Hoffman Radiative energy-balance models reveal that Earth could exist in any one of three discrete climate states,,non-glacial' (no continental ice-sheets), ,glacial-interglacial' (high-latitude ice-sheets) or ,pan-glacial' (ice-sheets at all latitudes),yet only the first two were represented in Phanerozoic time. There is mounting evidence that pan-glacial states existed at least twice in the Cryogenian (roughly 750,635 Ma), the penultimate period of the Neoproterozoic. Consensus is lacking on whether the world ocean was fully glaciated (,snowball' model) or largely unglaciated (,slushball' model). The first appearances of multicellular animal fossils (diapause eggs and embryos in China, and sponge-specific biomarkers in Oman), being closely associated with the last pan-glacial state, revive speculation that environmental forces had a hand in the origin of metazoa. [source] | |||||||||||||||||||||||||||||||