Genetic dissection of the retinotectal projection

Development ◽  
1996 ◽  
Vol 123 (1) ◽  
pp. 415-425 ◽  
Author(s):  
H. Baier ◽  
S. Klostermann ◽  
T. Trowe ◽  
R.O. Karlstrom ◽  
C. Nusslein-Volhard ◽  
...  
Keyword(s):  
Large Scale ◽  
Fish Larvae ◽  
Microscopic Analysis ◽  
Genetic Dissection ◽  
Axon Pathfinding ◽  
Retinotectal Projection ◽  
Vertebrate Brain ◽  
Retinal Axons ◽  
Assay Procedure ◽  
Homozygous Diploid

A systematic search for mutations affecting the retinotectal projection in zebrafish larvae was performed, as part of the large-scale Tubingen screen for homozygous diploid mutants in embryonic development. 2,746 inbred lines (F2 families) from males mutagenized with ethylnitroso urea were screened. In wild-type larvae, developing retinal axons travel along a stereotyped route to the contralateral optic tectum. Here, their terminals form a highly ordered retinotopic map. To detect deviations from this pattern, an axon tracing assay was developed that permits screening of large numbers of mutagenized fish. Two fluorescent tracer dyes (DiI and DiO) were injected at opposite poles of the eyes of day-5 aldehyde-fixed larvae. 12 hours later, retinal axons were labelled over their entire length, and could be observed through the intact skin. The assay procedure (aldehyde fixation, mounting, injection of dyes, microscopic analysis) took about 1 minute per fish. In total, 125,000 individual fish larvae were processed. During the screen, 114 mutations in approx. 35 genes were discovered. For the mutants subjected to complementation testing, the number of alleles per locus ranges from 1 to 15. The mutations affect distinct steps in the retinotectal pathway, from pathfinding between eye and tectum to map formation along the dorsal-ventral and the anterior-posterior axis of the tectum. Mutations that disturb axon pathfinding to the tectum for the most part do not disrupt retinotopic mapping, and vice versa. The majority of the mutants display associated defects in other tissues and die before day 10. These mutants provide new tools for studying the formation of neuronal maps. The results of this screen show that a large-scale genetic approach can be applied to relatively late and circumscribed developmental processes in the vertebrate brain.

Zebrafish mutations affecting retinotectal axon pathfinding

Development ◽  
1996 ◽  
Vol 123 (1) ◽  
pp. 427-438 ◽  
Author(s):  
R.O. Karlstrom ◽  
T. Trowe ◽  
S. Klostermann ◽  
H. Baier ◽  
M. Brand ◽  
...  
Keyword(s):  
Ganglion Cells ◽  
Fish Larvae ◽  
Retinal Ganglion ◽  
Axon Pathfinding ◽  
Class Iii ◽  
Axonal Projections ◽  
Retinal Axons ◽  
Complementation Groups ◽  
Single Allele ◽  
Neuronal Growth Cones

We have isolated mutants in the zebrafish Danio rerio that have defects in axonal connectivity between the retina and tectum. 5-day-old fish larvae were screened by labeling retinal ganglion cells with DiI and DiO and observing their axonal projections to and on the tectum. 82 mutations, representing 13 complementation groups and 6 single allele loci, were found that have defects in retinal ganglion cell axon pathfinding to the tectum. These pathfinding genes fall into five classes, based on the location of pathfinding errors between eye and tectum. In Class I mutant larvae (belladonna, detour, you-too, iguana, umleitung, blowout) axons grow directly to the ipsilateral tectal lobe after leaving the eye. Class II mutant larvae (chameleon, bashful) have ipsilaterally projecting axons and, in addition, pathfinding mistakes are seen within the eye. In Class III mutant larvae (esrom, tilsit, tofu) fewer axons than normal cross the midline, but some axons do reach the contralateral tectal lobe. Class IV mutant larvae (boxer, dackel, pinscher) have defects in axon sorting after the midline and retinal axons occasionally make further pathfinding errors upon reaching the contralateral tectal lobe. Finally, Class V mutant larvae (bashful, grumpy, sleepy, cyclops, astray) have anterior-posterior axon trajectory defects at or after the midline. The analysis of these mutants supports several conclusions about the mechanisms of retinal axon pathfinding from eye to tectum. A series of sequential cues seems to guide retinal axons to the contralateral tectal lobe. Pre-existing axon tracts seem not to be necessary to guide axons across the midline. The midline itself seems to play a central role in guiding retinal axons. Axons in nearby regions of the brain seem to use different cues to cross the ventral midline. Mutant effects are not all-or-none, as misrouted axons may reach their target, and if they do, they project normally on the tectum. The retinotectal pathfinding mutants reveal important choice points encountered by neuronal growth cones as they navigate between eye and tectum.

Characterization of seawater reverse osmosis fouled membranes from large scale commercial desalination plant

2019 ◽  
Author(s):  
Chem Int
Keyword(s):  
Reverse Osmosis ◽  
Large Scale ◽  
Retention Rate ◽  
Local Level ◽  
Microscopic Analysis ◽  
Transmembrane Pressure ◽  
Hydraulic Permeability ◽  
Seawater Reverse Osmosis ◽  
A Chain

The objective of this work is to study the ageing state of a used reverse osmosis (RO) membrane taken in Algeria from the Benisaf Water Company seawater desalination unit. The study consists of an autopsy procedure used to perform a chain of analyses on a membrane sheet. Wear of the membrane is characterized by a degradation of its performance due to a significant increase in hydraulic permeability (25%) and pressure drop as well as a decrease in salt retention (10% to 30%). In most cases the effects of ageing are little or poorly known at the local level and global measurements such as (flux, transmembrane pressure, permeate flow, retention rate, etc.) do not allow characterization. Therefore, a used RO (reverse osmosis) membrane was selected at the site to perform the membrane autopsy tests. These tests make it possible to analyze and identify the cause as well as to understand the links between performance degradation observed at the macroscopic scale and at the scale at which ageing takes place. External and internal visual observations allow seeing the state of degradation. Microscopic analysis of the used membranes surface shows the importance of fouling. In addition, quantification and identification analyses determine a high fouling rate in the used membrane whose foulants is of inorganic and organic nature. Moreover, the analyses proved the presence of a biofilm composed of protein.

scholarly journals Deciphering the role of trehalose in hindering antithrombin polymerization

2019 ◽  
Vol 39 (4) ◽  
Author(s):  
Asma Naseem ◽  
Mohammad Sazzad Khan ◽  
Hashim Ali ◽  
Irshad Ahmad ◽  
Mohamad Aman Jairajpuri
Keyword(s):  
Conformational Change ◽  
Large Scale ◽  
Guanidine Hydrochloride ◽  
Microscopic Analysis ◽  
Normal Activity ◽  
Significant Loss ◽  
Coagulation Cascade ◽  
Disulfonic Acid ◽  
Electron Microscopic ◽  
Polymer Formation

Abstract Serine protease inhibitors (serpins) family have a complex mechanism of inhibition that requires a large scale conformational change. Antithrombin (AT), a member of serpin superfamily serves as a key regulator of the blood coagulation cascade, deficiency of which leads to thrombosis. In recent years, a handful of studies have identified small compounds that retard serpin polymerization but abrogated the normal activity. Here, we screened small molecules to find potential leads that can reduce AT polymer formation. We identified simple sugar molecules that successfully blocked polymer formation without a significant loss of normal activity of AT under specific buffer and temperature conditions. Of these, trehalose proved to be most promising as it showed a marked decrease in the bead like polymeric structures of AT shown by electron microscopic analysis. A circular dichroism (CD) analysis indicated alteration in the secondary structure profile and an increased thermal stability of AT in the presence of trehalose. Guanidine hydrochloride (GdnHCl)-based unfolding studies of AT show the formation of a different intermediate in the presence of trehalose. A time-dependent fluorescence study using 1,1′-bi(4-anilino)naphthalene-5,5′-disulfonic acid (Bis-ANS) shows that trehalose affects the initial conformational change step in transition from native to polymer state through its binding to exposed hydrophobic residues on AT thus making AT less polymerogenic. In conclusion, trehalose holds promise by acting as an initial scaffold that can be modified to design similar compounds with polymer retarding propensity.

Deep abiotic weathering of pyrite

Science ◽  
2020 ◽  
Vol 370 (6515) ◽  
pp. eabb8092
Author(s):  
Xin Gu ◽  
Peter J. Heaney ◽  
Fabio D. A. Aarão Reis ◽  
Susan L. Brantley
Keyword(s):  
Large Scale ◽  
Iron Sulfide ◽  
Atmospheric Oxygen ◽  
Pyrite Oxidation ◽  
Microscopic Analysis ◽  
Sulfide Mineral ◽  
Early Atmosphere ◽  
Sulfur Oxidizing ◽  
Pyrite Weathering ◽  
Grain Surface

Pyrite is a ubiquitous iron sulfide mineral that is oxidized by trace oxygen. The mineral has been largely absent from global sediments since the rise in oxygen concentration in Earth’s early atmosphere. We analyzed weathering in shale, the most common rock exposed at Earth’s surface, with chemical and microscopic analysis. By looking across scales from 10−9 to 102 meters, we determined the factors that control pyrite oxidation. Under the atmosphere today, pyrite oxidation is rate-limited by diffusion of oxygen to the grain surface and regulated by large-scale erosion and clast-scale fracturing. We determined that neither iron- nor sulfur-oxidizing microorganisms control global pyrite weathering fluxes despite their ability to catalyze the reaction. This multiscale picture emphasizes that fracturing and erosion are as important as atmospheric oxygen in limiting pyrite reactivity over Earth’s history.

scholarly journals Formalin-Fixed Fish Larvae Could Be Effectively Identified by DNA Barcodes: A Case Study on Thousands of Specimens in South China Sea

2021 ◽  
Vol 8 ◽  
Author(s):  
Gang Hou ◽  
Yanying Chen ◽  
Sijin Wang ◽  
Jinrun Wang ◽  
Weitao Chen ◽  
...  
Keyword(s):  
South China Sea ◽  
South China ◽  
Large Scale ◽  
Fish Larvae ◽  
Morphological Characters ◽  
Dna Barcodes ◽  
High Quality ◽  
China Sea ◽  
Early Stages ◽  
Formalin Fixed

Delimiting ichthyoplankton is fundamental work for monitoring the recruitment process and identifying the spawning and nursing grounds of fishes. Nevertheless, it is extremely difficult to identify the fish during the early stages at the species level based on morphological characters because of the paucity of diagnostic features. In this study, we investigated the fish larval community through large-scale ecosystemic sampling in South China Sea (SCS) during 2013 and 2017 using DNA barcodes. To maintain the morphologies of fish larvae, we preserved the larvae in formalin and developed a technique to recover their DNA. Among the 3,500 chosen larvae, we successfully extracted DNA from 2,787 larval samples and obtained 1,006 high-quality sequences. Blast searches showed that 408 larvae (i.e., 40.5%) could be unambiguously identified to species, 413 larvae (i.e., 41.1%) were ambiguously species delimitation, and 185 larvae (i.e., 18.4%) showed a low match similarity with target sequences. A total of 101 species were identified, among which 38 and 33 species corresponded to demersal and reef-associated species, whereas the remaining 30 species corresponded to benthopelagic, pelagic-oceanic, bathypelagic, and pelagic-neritic species. High-quality larval photographs of the 101 diagnosed species showed intact morphological characters and thus provided a reference for identifying fish species during the early stages based on morphological characters. Our study highlighted the possibility of recovering and amplifying DNA from formalin-fixed samples and provided new insight into the fish larval community in the SCS.

scholarly journals Hybrid genome assembly and annotation of Danionella translucida, a transparent fish with the smallest known vertebrate brain

2019 ◽  
Author(s):  
Mykola Kadobianskyi ◽  
Lisanne Schulze ◽  
Markus Schuelke ◽  
Benjamin Judkewitz
Keyword(s):  
Large Scale ◽  
Genetic Manipulation ◽  
Large Fraction ◽  
Model Organism ◽  
Close Relative ◽  
Vertebrate Brain ◽  
Hybrid Genome ◽  
Long Read ◽  
Optical Turbidity ◽  
Low Coverage

Studying the activity of distributed neuronal circuits at a cellular resolution in vertebrates is very challenging due to the size and optical turbidity of their brains. We recently presented Danionella translucida, a close relative of zebrafish, as a model organism suited for studying large-scale neural network interactions in adult individuals. Danionella remains transparent throughout its life, has the smallest known vertebrate brain and possesses a rich repertoire of complex behaviours. Here we sequenced, assembled and annotated the Danionella translucida genome employing a hybrid Illumina/Nanopore read library as well as RNA-seq of embryonic, larval and adult mRNA. We achieved high assembly continuity using low-coverage long-read data and annotated a large fraction of the transcriptome. This dataset will pave the way for molecular research and targeted genetic manipulation of the smallest known vertebrate brain.

scholarly journals Shifts in the Assemblage of Summer Mesopelagic Fish Larvae in the Gaoping Waters of Southwestern Taiwan: A Comparison between El Niño Events and Regular Years

2021 ◽  
Vol 9 (10) ◽  
pp. 1065
Author(s):  
Hung-Yen Hsieh ◽  
Wen-Tseng Lo ◽  
Chien-Chun Liao ◽  
Pei-Jie Meng
Keyword(s):  
El Niño ◽  
Large Scale ◽  
El Nino ◽  
Fish Larvae ◽  
Seawater Temperature ◽  
Mesopelagic Fish ◽  
Hydrographic Conditions ◽  
El Niño Events ◽  
Southwestern Taiwan ◽  
El Nino Events

We investigated changes in the assemblages of summer mesopelagic fish larvae between El Niño events and regular years in 2014–2018 and evaluated their relationships with the hydrographic conditions of the Gaoping waters off southwestern Taiwan. Seventy-five taxa or morphotypes were identified, with five types of Benthosema pterotum (31.2%), Diaphus slender type (19.9%), Cyclothone alba (7.2%), Diaphus stubby type (5.9%), and Vinciguerria nimbaria (4.4%) being most common during the study period. The hydrographic conditions of the Gaoping waters were likely influenced by large-scale climate change via oceanic physical processes. Apparently higher seawater temperature, mixed layer depth, and lower salinity in the upper 100 m were observed at the end of the strong El Niño events (summer 2016). In addition, the certain dominant taxa exhibited contrasting patterns between El Niño events and regular years. In this study, although the abundance and composition of mesopelagic fish larvae assemblage were not influenced directly by changes in large-scale climatic conditions, the occurrence of mesopelagic fish larvae was related to seawater temperature, salinity, and chlorophyll a concentration. We speculated that despite the abundant food availability and the more mesopelagic fish larvae onto the Gaoping waters transported by the increased inflow of the South China Sea Surface Current during El Niño events, the higher temperature and lower salinity at the inshore upper waters might be unsuitable for mesopelagic fish larvae, possibly resulting in low egg and larval survival.

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