scholarly journals Homologous Chromosome Pairing in Drosophila melanogaster Proceeds through Multiple Independent Initiations

1998 ◽  
Vol 141 (1) ◽  
pp. 5-20 ◽  
Author(s):  
Jennifer C. Fung ◽  
Wallace F. Marshall ◽  
Abby Dernburg ◽  
David A. Agard ◽  
John W. Sedat
Keyword(s):  
Three Dimensional ◽  
Motion Model ◽  
Homologous Pairing ◽  
Directed Motion ◽  
Homologous Chromosomes ◽  
Egg Deposition ◽  
Homologous Chromosome Pairing ◽  
Chromosome Arm ◽  
Kinetics Of

The dynamics by which homologous chromosomes pair is currently unknown. Here, we use fluorescence in situ hybridization in combination with three-dimensional optical microscopy to show that homologous pairing of the somatic chromosome arm 2L in Drosophila occurs by independent initiation of pairing at discrete loci rather than by a processive zippering of sites along the length of chromosome. By evaluating the pairing frequencies of 11 loci on chromosome arm 2L over several timepoints during Drosophila embryonic development, we show that all 11 loci are paired very early in Drosophila development, within 13 h after egg deposition. To elucidate whether such pairing occurs by directed or undirected motion, we analyzed the pairing kinetics of histone loci during nuclear cycle 14. By measuring changes of nuclear length and correlating these changes with progression of time during cycle 14, we were able to express the pairing frequency and distance between homologous loci as a function of time. Comparing the experimentally determined dynamics of pairing to simulations based on previously proposed models of pairing motion, we show that the observed pairing kinetics are most consistent with a constrained random walk model and not consistent with a directed motion model. Thus, we conclude that simple random contacts through diffusion could suffice to allow pairing of homologous sites.

Integration of growth hormone gene constructs in transgenic strains of coho salmon (Oncorhynchus kisutch) at centromeric or telomeric sites

Genome ◽  
2010 ◽  
Vol 53 (1) ◽  
pp. 79-82 ◽  
Author(s):  
Ruth B. Phillips ◽  
Robert H. Devlin
Keyword(s):  
Growth Hormone ◽  
Coho Salmon ◽  
Chromosomal Location ◽  
Genetically Engineered ◽  
Growth Hormone Gene ◽  
Dna Repeats ◽  
Homologous Chromosomes ◽  
Chromosome Arm ◽  
Different Strains

Very little information is currently available regarding the sites of integration of transgenes in genetically engineered fish. We examined the chromosomal location of growth hormone gene constructs containing GH1 in three different strains of transgenic coho salmon produced by microinjection into pronuclei of fertilized eggs. The constructs were labeled and used as probes in fluorescence in situ hybridization experiments on chromosome preparations from the M77, MT5750A, and H3D0474 strains of transgenic coho salmon. The constructs were localized at 1–3 different sites in different strains. In the M77 strain the construct was found at a single centromeric site on a medium-sized metacentric chromosome, while in the MT5750A strain, the construct was found at a single telomeric site on the short arm of chromosome pair 21, a subtelocentric chromosome with a large band of repetitive DNA on the short arm. In the H3D0474 strain, the construct was found at telomeric sites on the long arms of three metacentric chromosomes that appear to represent one pair of homologous chromosomes and one chromosome containing the homeologous long arm (recently duplicated chromosome arm) corresponding to the long arm of the first pair. This suggests transfer of the construct may have occurred by homologous and homeologous crossing over. All of the constructs incorporated at restricted sites characterized by the presence of tandem DNA repeats.

Kinetics of the hydrogen evolution reaction on a highly porous three-dimensional Ni catalyst in the presence of a Mo ion activator in alkaline solution

2017 ◽  
Vol 41 (9) ◽  
pp. 3344-3351 ◽  
Author(s):  
Ali Reza Madram ◽  
Samane Asadi
Keyword(s):  
Hydrogen Evolution ◽  
Hydrogen Evolution Reaction ◽  
Alkaline Solution ◽  
Three Dimensional ◽  
Electrochemical Methods ◽  
Ni Catalyst ◽  
Kinetics Of ◽  
Highly Porous

In situ activated 3D-Ni by Mo ions in alkaline solution studied by various electrochemical methods for the hydrogen evolution reaction (HER).

scholarly journals Subgenome Discrimination in Brassica and Raphanus Allopolyploids Using Microsatellites

Cells ◽  
2021 ◽  
Vol 10 (9) ◽  
pp. 2358
Author(s):  
Nicole Bon Campomayor ◽  
Nomar Espinosa Waminal ◽  
Byung Yong Kang ◽  
Thi Hong Nguyen ◽  
Soo-Seong Lee ◽  
...  
Keyword(s):  
Genome Rearrangement ◽  
Brassica Species ◽  
Root Systems ◽  
Telomeric Repeat ◽  
45S Rdna ◽  
Homologous Chromosomes ◽  
Microsatellite Repeats ◽  
Rdna Array ◽  
Homologous Chromosome Pairing

Intergeneric crosses between Brassica species and Raphanus sativus have produced crops with prominent shoot and root systems of Brassica and R. sativus, respectively. It is necessary to discriminate donor genomes when studying cytogenetic stability in distant crosses to identify homologous chromosome pairing, and microsatellite repeats have been used to discriminate subgenomes in allopolyploids. To identify genome-specific microsatellites, we explored the microsatellite content in three Brassica species (B. rapa, AA, B. oleracea, CC, and B. nigra, BB) and R. sativus (RR) genomes, and validated their genome specificity by fluorescence in situ hybridization. We identified three microsatellites showing A, C, and B/R genome specificity. ACBR_msat14 and ACBR_msat20 were detected in the A and C chromosomes, respectively, and ACBR_msat01 was detected in B and R genomes. However, we did not find a microsatellite that discriminated the B and R genomes. The localization of ACBR_msat20 in the 45S rDNA array in ×Brassicoraphanus 977 corroborated the association of the 45S rDNA array with genome rearrangement. Along with the rDNA and telomeric repeat probes, these microsatellites enabled the easy identification of homologous chromosomes. These data demonstrate the utility of microsatellites as probes in identifying subgenomes within closely related Brassica and Raphanus species for the analysis of genetic stability of new synthetic polyploids of these genomes.

Rheological Monitoring of the Formation of Polyacrylamide/Cr+3 Gels

1983 ◽  
Vol 23 (05) ◽  
pp. 804-808 ◽  
Author(s):  
Robert K. Prud'homme ◽  
Jonathan T. Uhl ◽  
John P. Poinsatte
Keyword(s):  
Metal Ions ◽  
Storage Modulus ◽  
Shear Viscosity ◽  
Polymer Concentration ◽  
Gelation Time ◽  
Three Dimensional ◽  
Reducing Agent ◽  
Chromium Ion ◽  
Kinetics Of

Abstract The formation of polyacrylamide/chromium-ion gels has been followed rheologically. The time dependence of the storage modulus has been used to analyze the kinetics of the gelation process. The kinetic theory of rubber elasticity has been used to determine the crosslink density in the gel from the measured value of the storage modulus. The effects of changing polymer, chromium ion, and reducing agent concentrations have been studied. polymer, chromium ion, and reducing agent concentrations have been studied. Introduction Water-soluble polymers of high molecular weight, such as polyacrylamides, polysaccharides, and hydroxyl ethyl celluloses, have been studied as polysaccharides, and hydroxyl ethyl celluloses, have been studied as water flooding additives since the late 1950's. These polymers are added to control fluid movement in reservoirs to improve sweep efficiencies. In addition to enhanced fluid mobility control in porous media by increased viscosities of polymer solutions, the injection of dilute (250 ppm) polyacrylamide solutions causes permeability reductions that persist after polyacrylamide solutions causes permeability reductions that persist after the mobile polymer is flushed from the pore space by water. This reduction in permeability to water is a result of the retention of polyacrylamide in the porous rock by adsorption and mechanical entrapment. Rock permeability also can be reduced deliberately by crosslinking a polyacrylamide solution in situ to form a three-dimensional (3D) gel. The polyacrylamide solution in situ to form a three-dimensional (3D) gel. The gelled polymer is capable of shutting off fractures and zones of high permeability. The rate at which this 3D gel is formed determines how far permeability. The rate at which this 3D gel is formed determines how far the solution can be pushed into the rock formation away from the injection well before gelation occurs. Polyacrylamides are known to form gels in the presence of Cr+3 ions. The process involves the reduction of Cr+6 to Cr+3 with a reducing agent such as sodium bisulfite or thiourea. When Cr+6 is reduced to Cr+3, the trivalent chromium ion and polymer react slowly to form a 3D gel structure. The mechanism by which polyacrylamide or partially hydrolyzed polyacrylamide forms gels in the presence of metal ions is not well polyacrylamide forms gels in the presence of metal ions is not well understood. One idea is that Cr+3 serves as a crosslinking agent between the polyacrylamide molecules. Another suggestion is that Cr+3 forms a stable dispersion in the polymer solution, resulting in either a highly viscous liquid or a gel. Only a limited amount of data has been published on the kinetics of the polyacrylamide/chromium ion gelation process. Terry et al. followed the increase of the steady shear viscosity with time after the introduction of a reducing agent to a polyacrylamide/Cr+6 solution. Gelation time was defined as the time required for the shear viscosity to reach an arbitrary value. The effects of varying polymer type and concentration, Cr+6 concentration, and reducing agent type and concentration were investigated. A linear relationship was found between the reciprocal of the gelation time and the reciprocal of the polymer concentration for a given polymer reducing agent system. The gelation time decreases both with increasing polymer concentration and with increasing Cr+6 and reducing agent polymer concentration and with increasing Cr+6 and reducing agent concentrations. An Arrhenius-type relationship was shown between gelation time and temperature by Willhite and Jordan. During the buildup of a 3D gel network, the shear viscosity increases, but the shearing motion imposed on the sample also tends to break down the network being formed. SPEJ p. 804

Edge-to-Edge Matching at Ti-TiH Interfaces: Kinetics of Hydride Growth and Clustering of Precipitates with Different Orientation Relationships

2011 ◽  
Vol 172-174 ◽  
pp. 242-247 ◽  
Author(s):  
Egle Conforto ◽  
Daniel Caillard
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Volume Expansion ◽  
Three Dimensional ◽  
Orientation Relationships ◽  
Edge Matching ◽  
Transmission Electron ◽  
Isotropic Distribution ◽  
Kinetics Of

The motion of steps during the growth of hydride precipitates has been observed by in situ transmission electron microscopy. Precipitates in different orientation relationships (OR) are shown to obey to the rules of three-dimensional edge-to-edge matching. They form clusters in order to realize a more isotropic distribution of the volume expansion, and to decrease their total elastic energy.

scholarly journals Directed Motion of Telomeres in the Formation of the Meiotic Bouquet Revealed by Time Course and Simulation Analysis

2003 ◽  
Vol 14 (7) ◽  
pp. 2832-2843 ◽  
Author(s):  
Peter M. Carlton ◽  
Carrie R. Cowan ◽  
W. Zacheus Cande
Keyword(s):  
Time Course ◽  
Simulation Analysis ◽  
Meiotic Chromosome ◽  
Three Dimensional ◽  
Directed Motion ◽  
Directional Bias ◽  
Homologous Chromosome Pairing ◽  
Wide Range ◽  
Dimensional Distribution

Chromosome movement is critical for homologous chromosome pairing during meiosis. A prominent and nearly universal meiotic chromosome reorganization is the formation of the bouquet, characterized by the close clustering of chromosome ends at the nuclear envelope. We have used a novel method of in vitro culture of rye anthers combined with fluorescent in situ hybridization (FISH) detection of telomeres to quantitatively study bouquet formation. The three-dimensional distribution of telomeres over time was used to obtain a quantitative profile of bouquet formation intermediates. The bouquet formed through a gradual, continuous tightening of telomeres over ∼6 h. To determine whether the motion of chromosomes was random or directed, we developed a computer simulation of bouquet formation to compare with our observations. We varied the diffusion rate of telomeres and the amount of directional bias in telomere movement. In our models, the bouquet was formed in a manner comparable to what we observed in cultured meiocytes only when the movement of telomeres was actively directed toward the bouquet site, whereas a wide range of diffusion rates were permitted. Directed motion, as opposed to random diffusion, was required to reproduce our observations, implying that an active process moves chromosomes to cause telomere clustering.

scholarly journals Face-Discriminating Dissolution Kinetics of Furosemide Single Crystals: In Situ Three-Dimensional Multi-Microscopy and Modeling

2016 ◽  
Vol 16 (8) ◽  
pp. 4421-4429 ◽  
Author(s):  
Maria Adobes-Vidal ◽  
Faduma M. Maddar ◽  
Dmitry Momotenko ◽  
Leslie P. Hughes ◽  
Stephen A. C. Wren ◽  
...  
Keyword(s):  
Single Crystals ◽  
Three Dimensional ◽  
Dissolution Kinetics ◽  
Kinetics Of

Correlated Studies of Cellular Interactions Using TEM, Freeze Etching, and SEM

1974 ◽  
Vol 32 ◽  
pp. 320-321
Author(s):  
J. P. Revel
Keyword(s):  
Developmental Stages ◽  
Three Dimensional ◽  
Cell Movement ◽  
Cellular Interactions ◽  
Serial Sections ◽  
Cell Sheets ◽  
Freeze Etching ◽  
Early Developmental

Movement of individual cells or of cell sheets and complex patterns of folding play a prominent role in the early developmental stages of the embryo. Our understanding of these processes is based on three- dimensional reconstructions laboriously prepared from serial sections, and from autoradiographic and other studies. Many concepts have also evolved from extrapolation of investigations of cell movement carried out in vitro. The scanning electron microscope now allows us to examine some of these events in situ. It is possible to prepare dissections of embryos and even of tissues of adult animals which reveal existing relationships between various structures more readily than used to be possible vithout an SEM.

In vitro and in vivo polysaccharides assembly: ultrastructural and cytochemical study of growing plant cell wall components.

1978 ◽  
Vol 36 (2) ◽  
pp. 434-435
Author(s):  
D. Reis ◽  
B. Vian ◽  
J. C. Roland
Keyword(s):  
Cell Wall ◽  
Self Assembly ◽  
Plant Cell Wall ◽  
Higher Plants ◽  
Three Dimensional ◽  
Cytochemical Study ◽  
Wall Components

Wall morphogenesis in higher plants is a problem still open to controversy. Until now the possibility of a transmembrane control and the involvement of microtubules were mostly envisaged. Self-assembly processes have been observed in the case of walls of Chlamydomonas and bacteria. Spontaneous gelling interactions between xanthan and galactomannan from Ceratonia have been analyzed very recently. The present work provides indications that some processes of spontaneous aggregation could occur in higher plants during the formation and expansion of cell wall.Observations were performed on hypocotyl of mung bean (Phaseolus aureus) for which growth characteristics and wall composition have been previously defined.In situ, the walls of actively growing cells (primary walls) show an ordered three-dimensional organization (fig. 1). The wall is typically polylamellate with multifibrillar layers alternately transverse and longitudinal. Between these layers intermediate strata exist in which the orientation of microfibrils progressively rotates. Thus a progressive change in the morphogenetic activity occurs.

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