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Results for “Copying Processes”

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PubMed1996

Two different but related mechanisms are used in plants for the repair of genomic double-strand breaks by homologous recombination.

Genomic double-strand breaks (DSBs) are key intermediates in recombination reactions of living organisms. We studied the repair of genomic DSBs by homologous sequences in plants. Tobacco plants containing a site for the highly specific restriction enzyme I-Sce I were cotransformed with Agrobacterium strains carrying sequences homologous to the transgene locus and, separately, containing the gene coding for the enzyme. We show that the induction of a DSB can increase the frequency of homologous recombination at a specific locus by up to two orders of magnitude. Analysis of the recombination products demonstrates that a DSB can be repaired via homologous recombination by at least two different but related pathways. In the major pathway, homologies on both sides of the DSB are used, analogous to the conservative DSB repair model originally proposed for meiotic recombination in yeast. Homologous recombination of the minor pathway is restricted to one side of the DSB as described by the nonconservative one-sided invasion model. The sequence of the recombination partners was absolutely conserved in two cases, whereas in a third case, a deletion of 14 bp had occurred, probably due to DNA polymerase slippage during the copy process. The induction of DSB breaks to enhance homologous recombination can be applied for a variety of approaches of plant genome manipulation.

Base Sequence↗
PubMed1975

Enzymatic multiplication of a chemically synthesized DNA fragment.

A synthetic DNA fragment of 19 residues was enlarged by the enzymatic addition of deoxyadenylate residues to its 3'-end with calf thymus terminal deoxynucleotidyl transferase. The 3'-terminus of this elongated DNA strand was blocked with 2', 3'-dideoxyadenylate to prevent hydrolysis by the 3'-exonuclease function of E. coli DNA polymerase I. This elongated and 3'-blocked fragment was annealed to an oligomeric primer and used as a template for the synthesis of a complementary copy of the synthetic 19-mer. The product of such a repair synthesis was separated by gel filtration and analyzed by nearest neighbor techniques. All template strands were copied with complete repair in over 90% of the chains. Facile recovery of the elongated template by virtue of its size permitted repetition of the copy process, thus allowing accumulation of the desired strand.

Animals↗
PubMed1993

Rapid direct reversal photography.

This is a description of a method which enables fast, direct-reversal photography of radiological images for slides and was designed to retain: (i) continued use of an existing small darkroom; (ii) use of Kodak Rapid Process copy film; and (iii) use of standard X-ray processors. By adaptation of a commercial photographic flash power pack, a flash head and a reflector it is possible to achieve a somewhat expensive but very successful system which enables the very rapid production of good quality image slides for lectures.

Audiovisual Aids↗
PubMed1993

[Preparation of bonded porcelain inlays and onlays using a milling-coping system].

The Celay-system offers an interesting alternative to existing systems for esthetic posterior restorations with ceramics. The basic idea of the concept is to prepare, either directly on the patient or indirectly on a plaster model, a pro-inlay using a light-curable precision material. The modelling also covers the occlusal surface. This pro-inlay is then used with the help of a milling center to machine a precise replica out of a ceramic block. The copying process is carried out via three-dimensional mechanical scanning and milling using eight axes of freedom. In this way additional corrections on the ceramic within the mouth can almost completely be avoided. The system is designed to be used as a direct chairside method by the dentist or as an indirect method by the dental technician. It is a promising but unproved restoration, more research and long-term clinical evaluation is recommended.

Adhesives↗
PubMed1996

Construction of a self-complementary nucleoside from deoxyguanosine.

The 8-hydroxyguanine:adenine mispairing scheme that spontaneously occurs in vivo through oxidative metabolism of DNA was edited to obtain a pair closely fitting the Watson-Crick geometry in which 2 purine bases of identical structure but oppositely rotated in the syn and anti configurations are hydrogen-bonded. The structure thus designed, 2-amino-8-hydroxypurine, was synthesized as a DNA precursor from deoxyguanosine in 8 steps by oxidation at carbon 8 of guanine followed by reduction at carbon 6. Polydeoxynucleotides embodying this self-complementary base are expected to undergo direct copying processes through polymerase catalysis.

Base Composition↗
PubMed1991

The dynamics of gene amplification described as a multitype compartmental model and as a branching process.

The present work is aimed at developing the mathematical tools by which the dynamics of gene amplification (GA) can be described in detail. Some discrete compartmental models of GA by disproportionate replication and a general model for other putative GA mechanisms are presented and analyzed. The dynamical distribution of gene copy number in the cell population is calculated with the loss of cells taken either as constant or as copy-number-dependent. Our analysis shows that for a one-copy GA process with constant loss of cells, the relative frequency of single-gene-copy cells (sensitive cells) converges to zero, with the rate of convergence depending on the amplification probability. In contrast, for a one-copy GA process with copy-number-dependent loss of cells, the relative frequency of single-copy cells is bounded, implying a bounded compartment of many-gene-copy cells. Using branching processes theory we calculate the dynamical distribution of the single-gene-copy compartment as well as its extinction probability. Our models are used for estimating treatment prognosis as affected by drug resistance due to GA, showing significant differences in prognosis resulting from small changes in drug dose.

Animals↗
PubMedDate not supplied

Copyright law and the nursing professor.

The copyright law affects the resources that are available to faculty for educating students. The author discusses the concept of fair use in academe, the process for obtaining permission to copy materials that have been copyrighted, and the rights of the professor who has created works during employment. An application of the copyright law to the publication of students' papers is presented.

Copying Processes↗
PubMed1986

Attribute processing in patients with graphical copying disability.

This study investigated whether defective copying of multiple-line figures in lesion patients is associated with a deficit in perceptually processing and copying elementary attributes. Lesion and Control patients were assessed on a copying test comprising multi-line figures, and on parallel perceptual and motor forms of single-attribute tasks for Size, Orientation, Angle, Position and Direction. Copying test performance was correlated with perceptual attribute performance for the Lesion but not the Control group. Mean attribute performance of the Lesion patients who showed a copying disability (defined as a copying performance below the minimum performance of the Control group) was inferior to that of the non-disabled and Control subjects. The non-disabled patients did not differ from the Controls on any of these tasks. Performance in the copying test for left- and right-hemisphere patients did not differ, but left-hemisphere patients showed less impairment in the simple attribute tasks. The results are discussed in terms of the role of elementary perceptual deficits in copying disability and hemispheric differences in the nature of this condition.

Adolescent↗
PubMed2000

Dissociation of writing processes: functional magnetic resonance imaging during writing of Japanese ideographic characters.

Dissociation between copying letters and writing to dictation has been reported in the clinical neuropsychological literature. Functional magnetic resonance imaging (fMRI) was conducted in normal volunteers to detect the neurofunctional differences between 'copying Kanji', the Japanese ideographic characters, and 'writing Kanji corresponding to phonological information'. Four tasks were conducted: the copying-Kanji task, the writing-Kanji-corresponding-to-phonogram task, the Kanji-grapheme-puzzle task, and the control task. The right superior parietal lobule was extensively activated during the copying-Kanji task (a model of the copying letters process) and the Kanji-grapheme-puzzle task. These observations suggested that this area was involved in referring the visual stimuli closely related to the ongoing handwriting movements. On the other hand, Broca's area, which is crucial for language production, was extensively activated during the writing-Kanji-corresponding-to-phonogram task (a model of the writing-to-dictation process). The Kanji-grapheme-puzzle task activated the bilateral border portions between the inferior parietal lobule and the occipital lobe, the left premotor area, and the bilateral supplementary motor area (SMA). Since the Kanji-grapheme-puzzle task involved manipulospatial characteristics, these results suggested cooperation between visuospatial and motor executive functions, which may be extensively utilized in demanding visual language processing. The neurofunctional difference between 'copying Kanji' and 'writing Kanji corresponding to phonogram' was efficiently demonstrated by this fMRI experiment.

Adult↗
PubMedDate not supplied

[Choice of electron equipment for x-ray diagnostic digital scanning system].

The paper deals with the choice of electron equipment for X-ray diagnostic devices with digital image processing which are intended for population-based mass prophylactic examinations of lung. Guidelines for the optimization of the package of electron devices for processing and storing of data and for obtaining hard copies of X-ray films.

CD-ROM↗
PubMed1991

Mutants affecting processing of DNA in macronuclear development in paramecium.

In Paramecium tetraurelia, stock 51, the A surface protein is coded by the wild type A51 gene, present in micronuclei in two copies and in macronuclei in about 1500 copies. DNA processing, comprised of DNA cleavage, copy number amplification and telomere addition occurs at autogamy and conjugation when old macronuclei degrade and new macronuclei are formed from micronuclei. In this paper we characterize mutants with macronuclear A gene deletions. These mutants are notable in three respects. First, the mutants do not appear to be simple micronuclear deletions. Although genetic analysis shows that the d12 mutant d12(-1300) is homozygous for the allele A-1300 and the mutant d12(+1) for A+1, analysis by the polymerase chain reaction indicates that the micronuclei in these two mutants contain intact, but presumably altered, micronuclear A genes. They undergo deletion during DNA processing when new macronuclei are formed. Second, the position of the deletions in these alleles has been shown to change. The deficiency present in the d12 allele A-1300 was originally determined to extend from position -1300 (relative to the start of translation of the A gene) to the end of the chromosome. Later, a derivative of this strain, homozygous for the d12 allele A+1 was isolated in which the start site of the deletion was found to have moved from -1300 to +1. Third, a surprising interaction occurs in crosses between a line homozygous for the d12 allele and one homozygous for the wild-type A51 allele. Previous work on the non-Mendelian d48 mutant (which has intact A51 genes in its micronucleus, but has truncated A51 genes in its macronucleus) has shown that intact A51 alleles must be present in the old macronucleus in order for A51 alleles to undergo proper processing. We find that d12 alleles act on A51 alleles in heterozygotes such that intact macronuclear A genes are no longer required for proper processing of A51. Thus, in crosses of 51 x d12 (either +1 or -1300) d12 exconjugants, as well as 51 exconjugants, give rise to clones carrying both intact A51 and truncated d12 alleles. Remarkably the d12 alleles, which are themselves deleted during processing, are capable in the heterozygote of fostering normal processing of the A51 allele.

Animals↗
PubMed1982

High-contrast film copying for thallium 201 cardiac image processing.

To evaluate the usefulness of high-contrast film copying as an economical means of enhancing contrast in thallium 201 cardiac images, stress and rest studies of 47 patients with and 19 patients without coronary artery disease were evaluated. A total of 66 sets of four different image formats were independently interpreted by five observers. The analysis of the receiver operating characteristic curves suggested that the high-contrast film copies were superior to their original analog images and comparable with computer-processed images in diagnostic yield. It appears that contrast enhancement by simple film copying can improve the accuracy of 201Tl image interpretation.

Coronary Disease↗
PubMedDate not supplied

The hippocampo-neocortical dialogue.

In gross anatomical terms, the hippocampal archicortex can be conceived as an "appendage' of the large neocortex. In contrast to neocortical areas, the main output targets of the hippocampus are the same as its main inputs (i.e., the entorhinal cortex). Highly processed information about the external world (the content) reaches the hippocampus via the entorhinal cortex, whereas information about the "internal world' (the context) is conveyed by the subcortical inputs. Removal of the context makes the content illegible, as demonstrated by the observation that the behavioral impairment following surgical removal of hippocampopetal subcortical inputs is as devastating as removing the hippocampus itself. From its strategic anatomical position and input-output connections, it may be suggested that the main function of the hippocampal formation is to modify its inputs by feeding back a processed "reafferent copy' to the neocortex. I hypothesize that neocortico-hippocampal transfer of information and the modification process in neocortical circuitries by the hippocampal output take place in a temporally discontinuous manner and might be delayed by minutes, hours, or days. Acquisition of information may happen very fast during the activated state of the hippocampus associated with theta/gamma oscillations. Intrahippocampal consolidation and the hippocampal-neocortical transfer of the stored representations, on the other hand, is protracted and carried by discrete quanta of cooperative neuronal bursts during slow wave sleep.

Animals↗