When What's Left Is Right: Visuomotor Transformations in an Aged Population

Background: There has been little consensus as to whether age-related visuomotor adaptation effects are readily observable. Some studies have found slower adaptation, and/or reduced overall levels. In contrast, other methodologically similar studies have found no such evidence of aging effects on visuomotor adaptation. A crucial early step in successful adaptation is the ability to perform the necessary transformation to complete the task at hand. The present study describes the use of a viewing window paradigm to examine the effects of aging in a visuomotor transformation task. Methods: Two groups of participants, a young adult control group (age range 18–33 years old, mean age = 22) and an older adult group (age range 62–74, mean age = 68) completed a viewing window task that was controlled by the user via a computer touchscreen. Four visuomotor ‘‘flip’ ’ conditions were created by varying the relationship between the participant’s movement, and the resultant on-screen movement of the viewing window: 1) No flip 2) X-Axis and Y-axis body movements resulted in the opposite direction of movement of the viewing window. In each of the 3) Flip-X and 4) Flip-Y conditions, the solitary X- or Y-axes were reversed. Response times and movement of the window were recorded. Conclusions: Older participants demonstrated impairments in performing a required visuomotor transformation, as evidenced by more complex scanning patterns and longer scanning times when compared to younger control participants. These results provide additional evidence that the mechanisms involved in visuomotor transformation are negatively affected by age

Error determination in the photogrammetric assessment of shoreline changes

The evaluation of error or uncertainty in shoreline change studies is an issue of prime importance for providing an adequate framework for calculated rates of change and to allow the establishment of threshold values above which the rates would be significant. In this note, a practical, easy-to-use method is presented to estimate error involved in the calculation of shoreline changes on aerial photographs, including the three most used types of shoreline indicators: high water line, dune/cliff toe and cliff top. This approach takes into account the specific characteristics of each shoreline proxy, such as relief in the case of the cliff top or tidal oscillations in the case of the high water line. At the same time it includes the error components that are independent from the proxy, basically related to the technical aspects of the process such as photo scanning and georeferencing. A practical example of application of the method is provided for several types of data inputs, based on shoreline changes around the Bay of Cádiz (SW Spain)

Reduced Gray to White Matter Tissue Intensity Contrast in Schizophrenia

BACKGROUND: While numerous structural magnetic resonance imaging (MRI) studies revealed changes of brain volume or density, cortical thickness and fibre integrity in schizophrenia, the effect of tissue alterations on the contrast properties of neural structures has so far remained mostly unexplored. METHODS: Whole brain high-resolution MRI at 3 Tesla was used to investigate tissue contrast and cortical thickness in patients with schizophrenia and healthy controls. RESULTS: Patients showed significantly decreased gray to white matter contrast in large portions throughout the cortical mantle with preponderance in inferior, middle, superior and medial temporal areas as well as in lateral and medial frontal regions. The extent of these intensity contrast changes exceeded the extent of cortical thinning. Further, contrast changes remained significant after controlling for cortical thickness measurements. CONCLUSIONS: Our findings clearly emphasize the presence of schizophrenia related brain tissue changes that alter the imaging properties of brain structures. Intensity contrast measurements might not only serve as a highly sensitive metric but also as a potential indicator of a distinct pathological process that might be independent from volume or thickness alterations

Isolation and sequence of a tomato cDNA clone encoding subunit II of the photosystem I reaction center

We report here the isolation and nucleotide sequence of a cDNA clone encoding a phtosystem I polypeptide that is recognized by a polyclonal antibody prepared against subunit II of the photosystem I reaction center. The transit peptide processing site was determined to occur after Met 50 by N terminal sequencing. The decuced sequence of this protein predicts that the polypeptide has a net positive charge (pI=9.6) and no membrane spanning regions are evident from the hydropathy plot. Based on these considerations and the fact that subunit II is solubilized by alkali treatment of thylakoids, we concluded that subunit II is an extrinsic membrane protein. The absence of hydrophobic regions characteristic of thylakoid transfer domains furthermore implies that subunit II is localized on the stromal side of the membrane.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/43419/1/11103_2004_Article_BF00014949.pd

Evolutionary significance of inversions in legume chloroplast DNAs

Cloned genes from tobacco, spinach, and pea were used as hybridization probes to localize 36 protein genes on the chloroplast chromosomes of four legumes — mung bean, common bean, soybean, and pea. The first three chloroplast DNAs (cpDNAs), all of which retain a large inverted repeat, have an identical gene order with but one exception. A 78 kb segment encompassing nearly the entire large single copy region is inverted in mung bean and common bean relative to soybean and non-legumes. The simplest evolutionary explanation for this difference is a 78 kb inversion, with one endpoint between rps8 and inf A and the second between psb A and rpl2 . However, we can not rule out a two-step re-arrangement (consisting of successive expansion and contraction of the inverted repeat) leading to the relocation of a block of six ribosomal protein genes ( rps 19- rps 8) from one end of the large single copy region to the other. Analysis of gene locations in pea cpDNA, which lacks the large inverted repeat, combined with cross-hybridization studies using 59 clones covering the mung bean genome, leads to a refined picture of the position and nature of the numerous rearrangements previously described in the pea genome. A minimum of eight large inversions are postulated to account for these rearrangements. None of these inversions disrupt groups of genes that are transcriptionally linked in angiosperm cpDNA. Rather, the end-points of inversions are associated with relatively spacer-rich segments of the genome, many of which contain tRNA genes. All of the pea-specific inversions are shown to be positionally distinct from those recently described in a closely related legume, broad bean.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/46965/1/294_2004_Article_BF00405856.pd

Characterization of the Aspergillus niger prtT, a unique regulator of extracellular protease encoding genes

Expression of several Aspergillus niger genes encoding major secreted, but not vacuolar, protease genes including the major acid protease gene pepA, was shown to be affected in the previously isolated A. niger protease mutant, AB1.13 [Mattern, I.E., van Noort, J.M., van den Berg, P., Archer, D.A., Roberts, I.N., Hondel, C.A.M.J.J., 1992. Isolation and characterization of mutants of Aspergillus niger deficient in extracellular proteases. Molecular & General Genetics 2, 332-336]. Complementation cloning of the putative protease-regulatory gene affected in this mutant was accomplished using a functional selection approach based on the use of the A. nidulans amdS selection marker driven by the A. niger pepA promoter. As expected the PpepA::amdS selection marker is not expressed in the mutant. Introduction of a self-replicating cosmid library into the mutant strain carrying the PpepA::amdS marker allowed selection of AmdS+ transformants functionally complementing the proposed regulatory mutation. Analysis of complementing cosmid clones revealed that the complementing sequences contained a gene encoding a member of the fungal-specific Zn2Cys6-binuclear cluster protein family. Sequence comparison of the encoded protein, PrtT, showed that it has homologues among different Aspergillus species. The A. oryzae homologue was shown to govern expression of the major alkaline protease AlpA and neutral protease Np1 in this species. In contrast to several other pathway specific regulators, such as AmyR and XlnR, no PrtT orthologues could be found in any other non-Aspergillus (or related) species and surprisingly, also not in Aspergillus nidulans. Interestingly, in all Aspergillus species carrying a prtT orthologue the gene is tightly clustered to a completely syntenous region carrying an amylolytic gene cluster including another Zn2Cys6-binuclear cluster protein, AmyR. Northern analysis of the A. niger prtT gene showed (constitutive) expression from two upstream promoters about 700 bp apart. The presence of several short upstream open reading frames downstream of both the distal and the proximal transcription start point of the prtT gene suggests regulation at the post-translational level. Also regulation at the level of differential splicing is suggested by the fact that several Aspergillus EST databases carry a considerable fraction of clones in which in frame intron sequences are retained. © 2008 Elsevier Inc. All rights reserved