Black Squares Research Articles

Pancreatic Iron and Pancreatic Function in Thalassemia

Introduction: As patients with thalassemia major survive into middle age and beyond, there is greater need to address endocrine complications such as diabetes mellitus. Pancreatic iron deposition is common in thalassemia major patients and correlates with cardiac iron deposition. However, unlike the heart, endocrine dysfunction may not be completely reversible once functional assays become abnormal. Thus it is imperative to characterize preclinical endocrine markers similar to MRI measurements of cardiac T2*. Our aim of this study was to compare pancreatic R2* (the reciprocal of T2*) measurements with the results of an oral glucose tolerance test (OGTT) to determine the relationship between pancreatic iron and pancreatic dysfunction.Methods: We recruited 19 patients with thalassemia major to participate in a frequently sampled OGTT. Results of the OGTT were graded on NIH criteria: a 2 hour glucose level less than 140 was considered normal; between 140 and 200, impaired glucose tolerance; and greater than 200, diabetes mellitus. Acute Insulin Response (AIR) ws estimated from the OGTT measurements using the technique of Stumvall, et al. [1]. Insulin sensitivity was derived from the reciprocal of HOMA Insulin Resistance metric [2]. Pancreatic, cardiac, and hepatic iron burdens were estimated from MRI iron assessments using previously validated techniques. Where serial MRI measurements were available, we used linear interpolation to approximate the organ iron burden at the time of the OGTT. The remaining 7 patients had an MRI within 0.4 ± 0.3 years of the OGTT. The mean age was 21.9 ± 9.6 years; the mean BMI was 21.7 ± 2.3. All patients were on chronic transfusions and on standard iron chelation for their iron overload. The average pancreas R2* was 292.4 ± 259.4 Hz, cardiac R2* was 84.9 ± 64.0 Hz, and hepatic iron concentration (HIC) was 10.2 ± 10.1 mg/g dry weight. Pancreatic R2* correlated with cardiac R2* (r = 0.61, P = 0.006) in this population.Results: Of the 19 patients enrolled, 4 had diabetes, 4 had impaired glucose tolerance, and the remaining 11 had normal glucose tolerance. Figure 1 shows the expected inverse relationship between AIR and insulin sensitivity for each patient. The product of these two variables is the disposition index (DI) and is used as a measure of beta-cell function. Corresponding log-log fits to the data are shown in the same color and represent isoclines of constant DI. The patients with diabetes mellitus (gray circles) lie on a DI curve closer to the origin than normal (black squares) and glucose intolerant patients (gray triangles); lower DI indicates decreased islet cell mass or function. The patients with impaired glucose tolerance lie on a curve at the lower limit of normal. Figure 2 shows the relationship between pancreatic R2* and DI. The dashed box encloses the upper two tertiles of pancreatic R2* (boundary at 150 Hz). In this group, 7/12 had either impaired glucose tolerance or diabetes mellitus. In contrast, only 1/7 with R2* < 150 Hz had impaired glucose tolerance (p=0.08 by Fisher's exact test). Thus, 7/8 of the patients with impaired glucose tolerance or diabetes had moderate to severe pancreatic iron.Discussion: These data confirm that pancreatic iron deposition and pancreatic dysfunction are common in patients with thalassemia major. However, the relationship between pancreatic iron and function is complicated because of other risk factors such as family history, age, body habitus, as well as the type and pattern of iron chelation therapy. Although most patients with pancreatic dysfunction had moderate to severe pancreatic iron, 5/12 patients with high pancreatic iron had normal OGTT results, not unlike the normal cardiac function observed in many patients with heavy cardiac iron burdens. Serial evaluation is necessary to see if these patients will develop glucose intolerance or diabetes prospectively. Despite the complicated relationship between pancreatic function and iron, increased pancreatic R2* appears to identify a higher risk population that would likely benefit from improved chelation and more frequent endocrine evaluation. [Display omitted] [Display omitted]

Impediment of E. coli UvrD by DNA-destabilizing force reveals a strained-inchworm mechanism of DNA unwinding

Escherichia coli UvrD is a non-ring-shaped model helicase, displaying a 3'-5' polarity in DNA unwinding. Using a transverse magnetic tweezer and DNA hairpins, we measured the unwinding kinetics of UvrD at various DNA-destabilizing forces. The multiform patterns of unwinding bursts and the distributions of the off-times favour the mechanism that UvrD unwinds DNA as a dimer. The two subunits of the dimer coordinate to unwind DNA processively. They can jointly switch strands and translocate backwards on the other strand to allow slow (approximately 40 bp/s) rewinding, or unbind simultaneously to allow quick rehybridization. Partial dissociation of the dimer results in pauses in the middle of the unwinding or increases the translocation rate from approximately 40 to approximately 150 nt/s in the middle of the rewinding. Moreover, the unwinding rate was surprisingly found to decrease from approximately 45 to approximately 10 bp/s when the force is increased from 2 to 12 pN. The results lead to a strained-inchworm mechanism in which a conformational change that bends and tenses the ssDNA is required to activate the dimer.

A Pore-blocking Hydrophobic Motif at the Cytoplasmic Aperture of the Closed-state Nav1.7 Channel Is Disrupted by the Erythromelalgia-associated F1449V Mutation

Sodium channel Na(v)1.7 has recently elicited considerable interest as a key contributor to human pain. Gain-of-function mutations of Na(v)1.7 produce painful disorders, whereas loss-of-function Na(v)1.7 mutations produce insensitivity to pain. The inherited erythromelalgia Na(v)1.7/F1449V mutation, within the C terminus of domain III/transmembrane helix S6, shifts channel activation by -7.2 mV and accelerates time to peak, leading to nociceptor hyperexcitability. We constructed a homology model of Na(v)1.7, based on the KcsA potassium channel crystal structure, which identifies four phylogenetically conserved aromatic residues that correspond to DIII/F1449 at the C-terminal end of each of the four S6 helices. The model predicted that changes in side-chain size of residue 1449 alter the pore's cytoplasmic aperture diameter and reshape inter-domain contact surfaces that contribute to closed state stabilization. To test this hypothesis, we compared activation of wild-type and mutant Na(v)1.7 channels F1449V/L/Y/W by whole cell patch clamp analysis. All but the F1449V mutation conserve the voltage dependence of activation. Compared with wild type, time to peak was shorter in F1449V, similar in F1449L, but longer for F1449Y and F1449W, suggesting that a bulky, hydrophobic residue is necessary for normal activation. We also substituted the corresponding aromatic residue of S6 in each domain individually with valine, to mimic the naturally occurring Na(v)1.7 mutation. We show that DII/F960V and DIII/F1449V, but not DI/Y405V or DIV/F1752V, regulate Na(v)1.7 activation, consistent with well established conformational changes in DII and DIII. We propose that the four aromatic residues contribute to the gate at the cytoplasmic pore aperture, and that their ring side chains form a hydrophobic plug which stabilizes the closed state of Na(v)1.7.

The iron–sulphur protein Ind1 is required for effective complex I assembly

NADH:ubiquinone oxidoreductase (complex I) of the mitochondrial inner membrane is a multi-subunit protein complex containing eight iron-sulphur (Fe-S) clusters. Little is known about the assembly of complex I and its Fe-S clusters. Here, we report the identification of a mitochondrial protein with a nucleotide-binding domain, named Ind1, that is required specifically for the effective assembly of complex I. Deletion of the IND1 open reading frame in the yeast Yarrowia lipolytica carrying an internal alternative NADH dehydrogenase resulted in slower growth and strongly decreased complex I activity, whereas the activities of other mitochondrial Fe-S enzymes, including aconitase and succinate dehydrogenase, were not affected. Two-dimensional gel electrophoresis, in vitro activity tests and electron paramagnetic resonance signals of Fe-S clusters showed that only a minor fraction (approximately 20%) of complex I was assembled in the ind1 deletion mutant. Using in vivo and in vitro approaches, we found that Ind1 can bind a [4Fe-4S] cluster that was readily transferred to an acceptor Fe-S protein. Our data suggest that Ind1 facilitates the assembly of Fe-S cofactors and subunits of complex I.

Attentional capture in schizophrenia and schizotypy: Effect of attentional load

Introduction: We examined the effect of attentional load on attentional capture in schizophrenia. On the basis of the ‘‘resource limitations hypothesis’’ in schizophrenia, we propose that attentional capture by an irrelevant distractor will be differentially affected by the attentional load for patients and healthy controls. Method: 70 patients with schizophrenia, 15 schizotypals, and 54 controls were asked to attend to a central task while a lateral distractor moved. Participants were instructed either (i) to localise a black square (low-load condition), or (ii) to locate the larger number between two 1-digit numbers (medium-load condition), or (iii) to locate the larger number between two several-digit numbers (high-load condition). In the baseline condition, no distractor moved. Results: All groups showed attentional capture in the low-load condition. Patients and schizotypals resisted interference from the distractor in the medium and highload conditions. Controls resisted interference in the high-load condition. Conclusion: The results suggest that attentional modulation is impaired in schizophrenia and in the schizophrenia spectrum.

Two Orphic Poems

Research Article| March 01 2008 Two Orphic Poems Andrew Joron Andrew Joron Berkeley, CA andrew_joron@yahoo.com Andrew Joron is the author of several books of poetry, including Fathom (Black Square Editions, 2003) and The Sound Mirror (Flood Editions, forthcoming). A selection of his essays and prose poems, The Cry at Zero, was published in 2007 by Counterpath Press. He lives in Berkeley, where he works as a freelance proofreader and indexer. Search for other works by this author on: This Site Google English Language Notes (2008) 46 (1): 175–176. https://doi.org/10.1215/00138282-46.1.175 Cite Icon Cite Share Icon Share Facebook Twitter LinkedIn MailTo Permissions Search Site Citation Andrew Joron; Two Orphic Poems. English Language Notes 1 March 2008; 46 (1): 175–176. doi: https://doi.org/10.1215/00138282-46.1.175 Download citation file: Zotero Reference Manager EasyBib Bookends Mendeley Papers EndNote RefWorks BibTex toolbar search Search Dropdown Menu toolbar search search input Search input auto suggest filter your search Books & JournalsAll JournalsEnglish Language Notes Search Advanced Search The text of this article is only available as a PDF. Copyright © 2008 Regents of the University of Colorado2008 Article PDF first page preview Close Modal Issue Section: Cluster 2: Time and the Poem You do not currently have access to this content.

On 3-Harness Weaving: Cataloging Designs Generated by Fundamental Blocks Having Distinct Rows and Columns

A weaving drawdown is a rectangular grid of black and white squares with at least one black and one white square in each row and column. A pattern results from vertical and horizontal translations of the defining grid. Any such grid defines a tiling pattern. However, from a weaving point of view, some of these grids define actual fabrics while others correspond to collections of threads that fall apart. This article addresses that issue, along with a discussion of binary representations of fabric structures. The article also catalogs all weaving (or tiling) patterns defined by grids having three distinct columns and three to six distinct rows, and groups these patterns into design families based on weaving symmetries.

Springer's lines and Hermann's grid.

Hermann's grid is a complete matrix of black squares; Springer's figure has alternate squares whited out. Both figures generate illusory elements, bright and dark lines in the white spaces, with different elements seen from different distances. The visibility of these different elements is shown to be related to the detectability of sinusoidal gratings of wavenumbers corresponding to certain critical components of the Fourier decomposition of the figure. Evidence from the detection of gratings shows that near- and sub- (but not supra-) threshold contrasts are subject to a fourth power compression which shows, in the present figures, as a defect in the percept, equivalent to the deletion of (a part of) the corresponding Fourier components. There are some residual problems in understanding the perception of Hermann's grid.

What influences visual search efficiency? Disentangling contributions of preattentive and postattentive processes

The present experiments introduce a new search technique for disentangling contributions of preattentive guidance and postattentive template matching to search efficiency. Participants performed searches (for negative or positive faces in Experiment 1; pop-out search in Experiment 2; conjunction search in Experiment 3) under either standard viewing conditions or a new restricted viewing condition in which items were occluded by black placeholders and revealed only when a participant moved the mouse pointer over the black square. Under full viewing conditions, search performance can be aided by both preattentive and postattentive mechanisms, whereas the mouse-contingent search relies solely on postattentive template-matching processes. Results demonstrate the utility of this new methodology for distinguishing contributions of preattentive guidance and postattentive template-matching processes in ambiguous search situations. Furthermore, application of the new restricting viewing method to search for emotionally expressive faces suggested that emotional information is processed preattentively and influences the allocation of focal attention.

Seeing the World in Black and White

Three experiments examined the notion that rudimentary perceptual experiences can serve as powerful guides to judgments under uncertainty. The results show that exposure to certain perceptual contrast patterns can influence the direction of bias without conscious awareness. In Experiment 1a, perception of alternating black and white squares, which served as orientation markers in a lexical decision task, resulted in a reduction of the well-known anchoring bias. Similar results were obtained when alternating high- and low-pitch tones were the orientation markers (Experiment 1b). Results of a final experiment provide evidence that perceptual contrast experiences can affect judgment-relevant representations across modalities.

Perception of illusory surfaces and contours in goldfish

Goldfish (Carassius auratus) were trained to discriminate triangles and squares using a two choice procedure. In the first experiment, three goldfish were trained with food reward on a black outline triangle on a white background, while a black outline square was shown for comparison. In transfer tests, a Kanizsa triangle and a Kanizsa square were presented, perceived by humans as an illusory triangle- or square-shaped surface of slightly higher brightness than the background. The choice behavior in this situation indicates that goldfish are able to discriminate between both figures in almost the same way as in the training situation. In control experiments goldfish did not discriminate between shapes in which humans do not perceive the illusion. A series of generalization experiments was performed indicating the similarity between the tested shapes and the training triangle. From all these findings we conclude that goldfish are able to perceive an illusory triangle or square within the Kanizsa figures. In a second experiment, four goldfish were trained on a white outline triangle versus a white outline square, both on black background with white diagonal lines. In transfer tests in which the shapes were replaced by gaps within the white diagonal lines, goldfish were clearly able to discriminate between the two patterns based on the illusory contours. This was not the case in transfer tests with phase shifted abutting lines.

Interdependence of PKC-Dependent and PKC-Independent Pathways for Presynaptic Plasticity

Diacylglycerol (DAG) is a prominent endogenous modulator of synaptic transmission. Recent studies proposed two apparently incompatible pathways, via protein kinase C (PKC) and via Munc13. Here we show how these two pathways converge. First, we confirm that DAG analogs indeed continue to potentiate transmission after PKC inhibition (the Munc13 pathway), but only in neurons that previously experienced DAG analogs, before PKC inhibition started. Second, we identify an essential PKC pathway by expressing a PKC-insensitive Munc18-1 mutant in munc18-1 null mutant neurons. This mutant supported basic transmission, but not DAG-induced potentiation and vesicle redistribution. Moreover, synaptic depression was increased, but not Ca2+-independent release evoked by hypertonic solutions. These data show that activation of both PKC-dependent and -independent pathways (via Munc13) are required for DAG-induced potentiation. Munc18-1 is an essential downstream target in the PKC pathway. This pathway is of general importance for presynaptic plasticity.

A synthetic gene network for tuning protein degradation in Saccharomyces cerevisiae

Protein decay rates are regulated by degradation machinery that clears unnecessary housekeeping proteins and maintains appropriate dynamic resolution for transcriptional regulators. Turnover rates are also crucial for fluorescence reporters that must strike a balance between sufficient fluorescence for signal detection and temporal resolution for tracking dynamic responses. Here, we use components of the Escherichia coli degradation machinery to construct a Saccharomyces cerevisiae strain that allows for tunable degradation of a tagged protein. Using a microfluidic platform tailored for single-cell fluorescence measurements, we monitor protein decay rates after repression using an ssrA-tagged fluorescent reporter. We observe a half-life ranging from 91 to 22 min, depending on the level of activation of the degradation genes. Computational modeling of the underlying set of enzymatic reactions leads to GFP decay curves that are in excellent agreement with the observations, implying that degradation is governed by Michaelis–Menten-type interactions. In addition to providing a reporter with tunable dynamic resolution, our findings set the stage for explorations of the effect of protein degradation on gene regulatory and signalling pathways.

How does a patchy network affect the structure of invading percolation patterns?

Invasion percolation with trapping (TIP) is studied on two kinds of pore networks. The first class of them is the one generated through the dual site bond model [I. Kornhauser, R.J. Faccio, J.L. Riccardo, F. Rojas, A.M. Vidales, G. Zgrablich, Structure characterization of disordered porous media, Fractals 5 (3) (1997) 355–377; S. Cordero, I. Kornhauser, A. Dominguez, C. Felipe, J.M. Esparza, F. Rojas, R.H. López, A.M. Vidales, J.L. Riccardo, G. Zgrablich, Site–bond network modeling of disordered porous media, Part. Part. Syst. Charact. 21 (2004) 101–116] (DSBM). This model allows different strengths of correlations among the elements of the lattice in such a way that patches of sites and bonds with similar sizes are structured as correlations are set up. The typical size of these patches depends on the strength of correlations. The other class is a set of networks with a chessboard-like structure, i.e., patches are the “black” and “white” squares of a chessboard. Each square is made with bonds of similar sizes sampled from the same bond distribution. Black squares have sites sampled from the lower half part of the site distribution and sites in white squares belong to the other half. When a network is built, both models have the constraint imposed by a construction principle (CP) that forbids a bond to be greater than any of the sites to which it is connected. This is a common used assumption in modeling porous networks. The aim of this paper is to find whether the global patchy structure is responsible of the patterns found in TIP, or it is the local constraint imposed by the CP, which prevails. To this end, we measure different quantities, such as fractal dimensions, trapped fluid island distributions and invaded volume ratio, among others.

An open general-purposes research system for automating the development and application of information technologies in the area of image processing, analysis, and evaluation

Algorithmic/software system (ASS) referred to as “Black Square” (BS) is described. It is intended for scientific research and education in the area of image processing, analysis, recognition, and understanding. This ASS is a software environment for designing and application of algorithms for image processing, analysis, recognition and understanding with reference and information-retrieval functions. The ASS operates by means of a unified integrated software environment constructed on a common informational and methodical basis with a common navigation shell. The minimal specification necessary for launching the BS is the following: Pentium III processor 700 MHz; 128 Mb RAM; at least 100 Mb of free space on the hard disc; and Windows 98/ME/2000/XP or Linux RedHat 9. The ASS is intended for solving the following problems: (1) education and knowledge accumulation in the area of image processing, analysis, and recognition; (2) development, testing, and storage of algorithms and information technologies for solving problems of image processing, analysis, and recognition; (3) design of problem-oriented ASSs for image analysis and recognition; (4) automation of design, investigation, and application of algorithms for image processing, analysis, recognition, and understanding; (5) automation of training for methods for image processing and analysis; and (6) well-structured and user-friendly storage of various information, including information on methods and algorithms for image processing, analysis, recognition, and understanding, as well as images themselves and information about images. The main areas of application of the BS are the following: automation of scientific research and investigations in the area of image recognition and analysis; development of information technologies; solution of applied problems in the field of medicine (diagnoses of various diseases, in particular, cancer; investigation of the influence of laser and magnetic radiation on human beings; investigation of the influence of various factors on the temperature field of a human being); aerospace survey (analysis of data of remote sensing); development of tracking and detection systems; industrial and power engineering (technical diagnostics and nondestructive monitoring); as well as ecological monitoring and emergency prediction and monitoring. As an object of intellectual property, the work is protected by two patents and two inventor’s certificates.

Myelin basic protein-dependent plasma membrane reorganization in the formation of myelin

During vertebrate development, oligodendrocytes wrap their plasma membrane around axons to produce myelin, a specialized membrane highly enriched in galactosylceramide (GalC) and cholesterol. Here, we studied the formation of myelin membrane sheets in a neuron-glia co-culture system. We applied different microscopy techniques to visualize lipid packing and dynamics in the oligodendroglial plasma membrane. We used the fluorescent dye Laurdan to examine the lipid order with two-photon microscopy and observed that neurons induce a dramatic lipid condensation of the oligodendroglial membrane. On a nanoscale resolution, using stimulated emission depletion and fluorescence resonance energy transfer microscopy, we demonstrated a neuronal-dependent clustering of GalC in oligodendrocytes. Most importantly these changes in lipid organization of the oligodendroglial plasma membrane were not observed in shiverer mice that do not express the myelin basic protein. Our data demonstrate that neurons induce the condensation of the myelin-forming bilayer in oligodendrocytes and that MBP is involved in this process of plasma membrane rearrangement. We propose that this mechanism is essential for myelin to perform its insulating function during nerve conduction.

Microtubule depolymerization can drive poleward chromosome motion in fission yeast

Prometaphase kinetochores interact with spindle microtubules (MTs) to establish chromosome bi-orientation. Before becoming bi-oriented, chromosomes frequently exhibit poleward movements (P-movements), which are commonly attributed to minus end-directed, MT-dependent motors. In fission yeast there are three such motors: dynein and two kinesin-14s, Pkl1p and Klp2p. None of these enzymes is essential for viability, and even the triple deletion grows well. This might be due to the fact that yeasts kinetochores are normally juxtapolar at mitosis onset, removing the need for poleward chromosome movement during prometaphase. Anaphase P-movement might also be dispensable in a spindle that elongates significantly. To test this supposition, we have analyzed kinetochore dynamics in cells whose kinetochore-pole connections have been dispersed. In cells recovering from this condition, the maximum rate of poleward kinetochore movement was unaffected by the deletion of any or all of these motors, strongly suggesting that other factors, like MT depolymerization, can cause such movements in vivo. However, Klp2p, which localizes to kinetochores, contributed to the effectiveness of P-movement by promoting the shortening of kinetochore fibers.

Amodal completion with background determines depth from monocular gap stereopsis

Grove, Gillam, and Ono [Grove, P. M., Gillam, B. J., & Ono, H. (2002). Content and context of monocular regions determine perceived depth in random dot, unpaired background and phantom stereograms. Vision Research, 42, 1859–1870] reported that perceived depth in monocular gap stereograms [Gillam, B. J., Blackburn, S., & Nakayama, K. (1999). Stereopsis based on monocular gaps: Metrical encoding of depth and slant without matching contours. Vision Research, 39, 493–502] was attenuated when the color/texture in the monocular gap did not match the background. It appears that continuation of the gap with the background constitutes an important component of the stimulus conditions that allow a monocular gap in an otherwise binocular surface to be responded to as a depth step. In this report we tested this view using the conventional monocular gap stimulus of two identical grey rectangles separated by a gap in one eye but abutting to form a solid grey rectangle in the other. We compared depth seen at the gap for this stimulus with stimuli that were identical except for two additional small black squares placed at the ends of the gap. If the squares were placed stereoscopically behind the rectangle/gap configuration (appearing on the background) they interfered with the perceived depth at the gap. However when they were placed in front of the configuration this attenuation disappeared. The gap and the background were able under these conditions to complete amodally.

Recognition and location of the internal corners of planar checkerboard calibration pattern image

The recognition and location of the internal corners of a planar checkerboard calibration pattern image is very important to camera calibration. An effective approach is proposed to automatically recognize and locate the internal corners of the planar checkerboard calibration pattern image based on the characteristics of local intensity and the grid line architecture of the planar checkerboard pattern image. The proposed procedure consists of the detection of image corners, the recognition of the corners at the intersections of black and white squares and the recognition of the corners at the intersections of two groups of grid lines. Experiments show that compared with the commonly used interactive method, the proposed approach obviously reduces the time cost for camera calibration, speeds up calibration process and is especially adapted for automatic calibration based on multiple images.

Философия анархизма в русском художественном авангарде и “замкнутые конструкции” Даниила Хармса

The paper deals with the role of nineteenth- and twentieth-century anarchism, and in the wider sense, anarchy in the Russian Avantgarde. Anarchist ideas were a strong factor in Malevich's ideas and work, culminating in the “Black Square”. The work of Kharms is closely connected with both anarchy and Malevich, as the element of the absurd favours principles such as non-selectiveness, de-hierarchization. Moreover, for Kharms basic “closed forms” such as square, point, circle and (straight) line are of great importance.