C. elegans pronuclei fuse after fertilization through a novel membrane structure

After fertilization, parental genomes are enclosed in two separate pronuclei. In Caenorhabditis elegans, and possibly other organisms, when the two pronuclei first meet, the parental genomes are separated by four pronuclear membranes. To understand how these membranes are breached to allow merging of parental genomes we used focused ion beam scanning electron microscopy (FIB-SEM) to study the architecture of the pronuclear membranes at nanometer-scale resolution. We find that at metaphase, the interface between the two pronuclei is composed of two membranes perforated by fenestrations ranging from tens of nanometers to several microns in diameter. The parental chromosomes come in contact through one of the large fenestrations. Surrounding this fenestrated, two-membrane region is a novel membrane structure, a three-way sheet junction, where the four membranes of the two pronuclei fuse and become two. In the plk-1 mutant, where parental genomes fail to merge, these junctions are absent, suggesting that three-way sheet junctions are needed for formation of a diploid genome.

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Characterization of Nanometer-Scale Porosity in Reservoir Carbonate Rock by Focused Ion Beam–Scanning Electron Microscopy

Microscopy and Microanalysis ◽

10.1017/s1431927611012505 ◽

2012 ◽

Vol 18 (1) ◽

pp. 171-178 ◽

Cited By ~ 20

Author(s):

Bijoyendra Bera ◽

Naga Siva Kumar Gunda ◽

Sushanta K. Mitra ◽

Douglas Vick

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Carbonate Rock ◽

Focused Ion Beam ◽

Ion Beam ◽

Three Dimensional ◽

Nanometer Scale ◽

Beam Scanning ◽

Sedimentary Carbonate ◽

Scanning Electron

AbstractSedimentary carbonate rocks are one of the principal porous structures in natural reservoirs of hydrocarbons such as crude oil and natural gas. Efficient hydrocarbon recovery requires an understanding of the carbonate pore structure, but the nature of sedimentary carbonate rock formation and the toughness of the material make proper analysis difficult. In this study, a novel preparation method was used on a dolomitic carbonate sample, and selected regions were then serially sectioned and imaged by focused ion beam–scanning electron microscopy. The resulting series of images were used to construct detailed three-dimensional representations of the microscopic pore spaces and analyze them quantitatively. We show for the first time the presence of nanometer-scale pores (50–300 nm) inside the solid dolomite matrix. We also show the degree of connectivity of these pores with micron-scale pores (2–5 μm) that were observed to further link with bulk pores outside the matrix.

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Structural analysis of the C. elegans dauer larval anterior sensilla by Focused Ion Beam-Scanning Electron Microscopy

10.1101/2021.06.29.449894 ◽

2021 ◽

Author(s):

Sebastian Britz ◽

Sebastian Matthias Markert ◽

Daniel Witvliet ◽

Anna Maria Steyer ◽

Sarah Troeger ◽

...

Keyword(s):

Electron Microscopy ◽

Scanning Electron Microscopy ◽

Sensory Neurons ◽

Focused Ion Beam ◽

Ion Beam ◽

Sensory System ◽

Beam Scanning ◽

C Elegans ◽

Dauer Larvae ◽

Scanning Electron

At the end of the first larval stage, the nematode Caenorhabditis elegans developing in harsh environmental conditions is able to choose an alternative developmental path called the dauer diapause. Dauer larvae exhibit different physiology and behaviors from non-dauer larvae. Using focused ion beam scanning electron microscopy (FIB-SEM), we volumetrically reconstructed the anterior sensory apparatus of C. elegans dauer larvae with unprecedented precision. We provide a detailed description of some neurons, focusing on structural details that were unknown or unresolved by previously published studies. They include: 1) dauer-specific branches of the IL2 sensory neurons project into the periphery of anterior sensilla and motor or putative sensory neurons at the sub-lateral cords; 2) ciliated endings of URX sensory neurons are supported by both ILso and AMso socket cells near the amphid openings; 3) variability in amphid sensory dendrites among dauers; 4) somatic RIP interneurons maintain their projection into the pharyngeal nervous system. Our results support the notion that dauer larvae structurally expand their sensory system to facilitate searching for more favorable environments.

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