Electron microscopy of the sporangium of Phytophthora capsici

1970 ◽  
Vol 48 (2) ◽  
pp. 221-227 ◽  
Author(s):  
W. T. Williams ◽  
R. K. Webster
Keyword(s):  
Plasma Membranes ◽  
Structural Changes ◽  
Phytophthora Capsici ◽  
Flagellar Apparatus ◽  
Outer Wall ◽  
Wall Layer ◽  
High Concentration ◽  
Zoospore Production ◽  
Apical Papilla ◽  
Ultrastructural Cytology

This paper reports results of a study on the ultrastructural cytology of sporangia of Phytophthora capsici Leonian with emphasis on flagellum formation, general sporangial structure during zoospore cleavage, and the presence, structure, and transition of cytoplasmic organelles and inclusions during these processes.Non-cleaving sporangial cytoplasm contains a high concentration of ribosomes, mitochondria, vacuoles, lipid inclusions, and endoplasmic reticular cisternae scattered throughout the cytoplasm. Nuclei in mature sporangia are located at the periphery of the cell, with their narrow poles aligned towards the plasma membrane. The apical papilla measures 4–5 × 10 μ, and is initiated as a fibrous third layer under the two-layered cell wall several microns from the apex. The outer wall layer surrounds the papilla while the inner wall narrows and disappears near the crown. The basal septal plug is a combination of the inner wall layer and slime substances.One of the first structural changes in the cytoplasm during zoospore cleavage is the genesis of the flagellar apparatus. Paired centrioles next to the narrow poles of the nuclei elongate to form kinetosomes which extend through the cytoplasm toward receptive axonemal vesicles. Axonemes then form in the axonemal vesicles. The terminal plate and its prisms account for the appearance of the axoneme when it forms above the terminal plate in the axonemal vesicle. The axonemal cylinder has a typical 9 + 2 morphology and the axonemal sheath is continuous with the axonemal vesicle tonoplast. The nucleus is an integral part of the flagellar apparatus and appears to be connected to the kinetid (axoneme + kinetosome) base via microtubules. Golgi dictyosomes occur in the sporangia during all stages of growth and may be responsible for elaboration of needed membranes during zoospore production. Osmiophilic droplets (liposomes), located within vacuoles, are a predominant feature of precleavage cytoplasm. These globules are probably lipid in nature. As cleavage begins, the liposomes become less opaque at the margins, and striations appear, eventually encompassing all or most of the liposomes at the time of cleavage. The liposomes then become less spherical and expand, filling the vacuoles. Electron-transparent regions eventually appear throughout the liposomes and the vacuolar membrane may disappear.Cleavage of the cytoplasm into zoospores occurs by the alignment and fusion of cleavage vesicles around individual nuclei. During this period organelles migrate to these centers. The cleavage vesicles coalesce with each other and the axonemal membranes, eventually becoming the plasma membranes of the daughter zoospores.

Ultrastructural and electrophysiological changes associated with K+-evoked release of neurotransmitter at the synaptic terminals of skate photoreceptors

1991 ◽  
Vol 7 (6) ◽  
pp. 597-609 ◽  
Author(s):  
Harris Ripps ◽  
Richard L. Chappell
Keyword(s):  
Plasma Membrane ◽  
Synaptic Vesicles ◽  
Time Course ◽  
Plasma Membranes ◽  
Structural Changes ◽  
Ringer Solution ◽  
Synaptic Function ◽  
Horizontal Cells ◽  
High Concentration ◽  
Normal Ringer

AbstractBathing the skate retina in a Ringer solution containing a high concentration (100 mM) of potassium ions depolarized the visual cells, depleted the receptor terminals of synaptic vesicles, and suppressed completely the b-wave of the ERG and the intracellularly recorded response of horizontal cells (the S-potential). The depletion of synaptic vesicles was accompanied by a large increase in the extent of the plasma membrane resulting in distortion of the normal terminal profile, i.e. distension of the basal surface and elaborate infolding of protoplasmic extensions. Morphometric analysis showed that despite the changes in vesicle content and terminal structure, the combined linear extent of the vesicular and plasma membranes was unchanged from control (superfusion with normal Ringer solution); the increase in plasma membrane was equivalent to the observed loss of vesicular membrane. When returned to a normal Ringer solution, the terminals rapidly began to reform, and in about 10 min they were morphologically indistinguishable from receptor terminals seen in control preparations. After 30 min in the normal Ringer solution, the amount of membrane associated with the vesicles and the plasma membrane had reverted to control values, and once again the total membrane estimated morphometrically remained essentially the same. Thus, there is an efficient mechanism at the photoreceptor terminal for the recycling of vesicle membrane following exocytosis.The K+-induced depletion of synaptic vesicles was paralleled by a precipitous loss of responsivity in both the b-wave of the ERG and the S-potential of the horizontal cells. However, after 30-min exposure to the high K+ and a return to normal Ringer solution, the recovery of electrophysiological activity followed a much slower time course from that associated with the structural changes; 60 min or longer were required for the potentials to exhibit maximum response amplitudes. It appears that the rate-limiting step in restoring normal synaptic function following massive depletion of vesicular stores is transmitter resynthesis and vesicle loading rather than vesicle recycling.

scholarly journals Possible ecologically based ways of preserving and developing the Ukrainian Carpathians

2016 ◽  
Vol 24 (1) ◽  
pp. 157-163
Author(s):  
V. І. Nikolaichuk ◽  
M. М. Vakerich ◽  
M. V. Bilkey ◽  
O. P. Chechuy ◽  
I. Voloshchuk
Keyword(s):  
Eastern Europe ◽  
Protected Areas ◽  
Environmental Sustainability ◽  
Structural Changes ◽  
Central And Eastern Europe ◽  
Forest Cover ◽  
Ecological Crisis ◽  
Mountain Range ◽  
High Concentration ◽  
The Carpathians

Ukraine has transformed into one of the most environmentally dangerous countries in the world due to the high concentration of industrial production and agriculture and predatory use of natural resources. The current ecological situation in Ukraine is characterized by a deep ecological crisis, which is caused by the laws of operation of the command economy of the former USSR. The majority of the environmental and social indicators of Ukraine are among the worst in Europe. The Carpathian Mountains are among the most significant and interesting landscapes in Europe from the geological and geomorphological, scenic and biological perspectives. The giant arc of the Carpathians begins in southern Romania and passes through Ukraine, Slovakia, Poland, the Czech Republic and Hungary to Austria, crosses all Eastern and Central Europe. A third of the forest reserves of Ukraine are located in the Ukrainian Carpathians, at 53.5% the percentage of forest cover of the area is among the highest in the country. About 50% of the gene pool of Ukraine’s plants, many species of trees and medicinal plants grows there. The geographical location and large area of the rich natural heritage of the Carpathians have multifaceted importance for the conservation of biological, phytocoenotic and landscape diversity and maintaining the ecological balance in the central part of our continent. As with the Alps mountain range, this is an important ecological corridor between Western, Central and Eastern Europe, which promotes the migration of species and their spread into lowland landscapes. In order to preserve biodiversity an inventory of virgin forest ecosystems should be made and strict measures for their protection should be enforced. It is necessary to continue the practice of establishing bilateral areas in cross-border protected areas in order to combine efforts to solve pressing environmental challenges. Conservation of the Carpathians Biodiversity is an urgent problem. Structural changes in the economy of the region are expected to strengthen the recreational value of the Ukrainian Carpathians for the public not only in our country but also in Central and Eastern Europe, reducing the technogenic loading. International cooperation of all countries of the Carpathian region is imperative. The development of tourism in the Carpathians is highly promising, but this should be civilized tourism, taking into account the environmental sustainability of the recreational areas and protected areas. 

Microstructural Changes Induced during Hydrogen Charging Process in Stainless Steels with and without Nitrided Layers

2012 ◽  
Vol 186 ◽  
pp. 305-310 ◽  
Author(s):  
Bartosz Gołębiowski ◽  
Wiesław Świątnicki
Keyword(s):  
Hydrogen Embrittlement ◽  
Glow Discharge ◽  
Stainless Steels ◽  
Structural Changes ◽  
High Stress ◽  
High Concentration ◽  
Two Phase ◽  
Microstructural Changes ◽  
Hydrogen Charging ◽  
Expanded Austenite

The purpose of this study is to analyze the effect of glow discharge nitriding on hydrogen degradation of two types of steels: two-phase austenitic-ferritic and single-phase austenitic. The nitriding process resulted in formation of surface layers composed of expanded austenite (S phase), and in the case of two-phase steel of expanded austenite and expanded ferrite. Microstructural changes occurring under the influence of hydrogen on steels without and with nitrided layers were investigated with the use of scanning (SEM) and transmission (TEM) electron microscopy techniques. It was shown that the density of cracks formed during cathodic hydrogen charging is higher on the surface of the non-nitrided steels compared to the nitrided steels after identical hydrogen charging process. Moreover in non nitrided steel hydrogenation leads to considerable increase of dislocation density, which results from the high concentration of hydrogen absorbed to the steel during its cathodic charging. This leads in turn to high stress concentration and local embrittlement giving rise to cracks formation. Conversely nitriding reduces the absorption of hydrogen and prevents structural changes resulting in hydrogen embrittlement. The conducted studies show that glow discharge nitriding can be used to increase resistance to hydrogen embrittlement of austenitic and austenitic ferritic stainless steels.

scholarly journals Mutations in ORP1 Conferring Oxathiapiprolin Resistance Confirmed by Genome Editing using CRISPR/Cas9 in Phytophthora capsici and P. sojae

2018 ◽  
Vol 108 (12) ◽  
pp. 1412-1419 ◽  
Author(s):  
Jianqiang Miao ◽  
Yuandong Chi ◽  
Dong Lin ◽  
Brett M. Tyler ◽  
Xili Liu
Keyword(s):  
Binding Protein ◽  
Phytophthora Capsici ◽  
Control Plant ◽  
Point Mutations ◽  
Wild Type ◽  
Oxysterol Binding Protein ◽  
Type Isolate ◽  
Phytophthora Spp ◽  
Zoospore Production ◽  
Wild Type Parent

Oxathiapiprolin is a novel fungicide that was recently registered in a number of countries to control plant-pathogenic oomycetes such as Phytophthora capsici. In our previous study, point mutations G770V and G839W in oxysterol binding protein-related protein 1 (ORP1) were detected in oxathiapiprolin-resistant P. capsici isolates (PcORP1). Here, we used the CRISPR/Cas9 system to verify the effects of these two point mutations on P. capsici phenotypes. Transformants containing heterozygous G770V and G839W mutations in PcORP1 showed high levels of oxathiapiprolin resistance. The G770V transformants showed otherwise similar phenotypes compared with the wild-type isolate BYA5, including sporangia and zoospore production, cyst germination, and pathogenicity. However, two independent transformants with heterozygous G839W mutations in PcORP1 could not produce sporangia. Three transformants with an unexpected point mutation in PcORP1 (ΔN837) showed high oxathiapiprolin resistance, and either similar or significantly reduced fitness compared with BYA5. The same deletion (ΔN837) was confirmed to confer oxathiapiprolin resistance in P. sojae by using CRISPR/Cas9. These homozygous P. sojae mutants also showed either similar or strongly reduced fitness compared with the wild-type parent isolate P6497. These results improve our understanding of oxathiapiprolin resistance in Phytophthora spp., and will be useful for the development of novel oxysterol-binding protein homolog inhibitor fungicides.

Finding of artisanal uses of elemental mercury in the city of Murcia in medieval times

2021 ◽  
Author(s):  
José María Esbrí ◽  
Luis Mansilla-Plaza ◽  
María Jesús Sanchez-Gonzalez ◽  
Pablo Higueras
Keyword(s):  
Atomic Absorption ◽  
Elemental Mercury ◽  
Absorption Spectrometry ◽  
Speciation Analysis ◽  
Outer Wall ◽  
High Concentration ◽  
Entire Area ◽  
High Concentrations ◽  
Under Construction ◽  
The City

<p>Mercury (Hg) was used in gilding techniques since ancient times. This metal gilding technique consisted of applying an amalgam of Au and Hg to the surface of a metallic object and then removing the Hg to achieve adhesion of the Au to the support. The traditional preparation of amalgam was a mixture of Au with Hg (in a ratio of 1/8). After this preparation, the mixture usually was ground in a mortar, heated, and then cooled by pouring it into water. The paste was applied to the areas to be browned and then the piece was subjected to mild temperatures so that the Hg evaporated, leaving a thin layer of Au on the surface of the object.</p><p>The origin of this work is the discovery of an evident quantity of liquid Hg on a site under construction, near the old wall of the city of Murcia, at a level identified as from medieval times. To elucidate the origin of this Hg, a sampling of medieval materials has been carried out throughout the site, including both the area with liquid Hg, the entire area what appears to be the work room and the adjacent rooms. The sampling has been carried out using an Ejkelkamp sampler at various depths. These soil samples were analysed by Energy Dispersion X-Ray Fluorescence using a PanAlytical device. Total Hg and Hg speciation data were obtained by Atomic Absorption Spectrometry using a Lumex equipment. In addition to this, a gaseous mercury monitoring has been carried out using a portable atomic absorption equipment to search Hg sources and gaseous Hg dispersion in the atmosphere of the studied site. Results of the survey has shown an evident and intense soil Hg pollution in a small area of 2x2 m. This affected area was located near the outer wall of the medieval building and was very restricted, which suggests that it was a storage place for liquid Hg for later use in other areas. The degassing of these recently uncovered materials produced a significant dispersion of the Hg gas throughout the enclosure. In addition to this, samples of medieval materials have shown very high concentrations of Hg in the vicinity of the contaminated area, and high concentrations in the rest of the enclosure. Speciation analysis have shown that the Hg in this part of the enclosure is in the form of metacinnabar and Hg bound to humic acids, which suggests the presence of an atmosphere with extremely high concentration of gaseous Hg in medieval times that was later deposited in the soil, being fixed to its organic phase. Multielemental analysis has shown additional high concentrations of Pb, Cu and Sn, suggesting that the artisanal works in the enclosure involved these elements too. While waiting for more specific archaeology works that can corroborate it, the origin of this Hg in the area could be the storage for the realization of gilding work on metals with this element.</p><p>This work was funded by the company “Obras y Proyectos Soyma”.</p>

Odontoblastic Exosomes Attenuate Apoptosis in Neighboring Cells

2019 ◽  
Vol 98 (11) ◽  
pp. 1271-1278 ◽  
Author(s):  
H.S. Wang ◽  
F.H. Yang ◽  
Y.J. Wang ◽  
F. Pei ◽  
Z. Chen ◽  
...  
Keyword(s):  
Stem Cells ◽  
Signaling Pathway ◽  
Cell Apoptosis ◽  
Dental Pulp ◽  
Ex Vivo ◽  
Intercellular Signaling ◽  
High Concentration ◽  
Rescue Effect ◽  
Apical Papilla ◽  
External Stimuli

Each odontoblast is tightly linked to other odontoblasts. They form a line of defense and are capable of withstanding external stimuli, particularly the inflammation caused by caries. Thus, we investigated exosomes derived from odontoblasts as an intercellular mechanism by which inflamed odontoblasts are protected from apoptosis. CD63, an exosome marker, was expressed at high levels in caries-affected regions of the dental pulp. We conducted an ex vivo experiment by applying different concentrations of lipopolysaccharide (LPS) to the odontoblast-like cells (mineralization was induced in stem cells derived from the apical papilla). Odontoblast-like cells treated with a high concentration of LPS (20 µg/mL LPS, severely affected) exhibited an accelerated release of exosomes, which attenuated the LPS-induced cell apoptosis of odontoblast-like cells treated with a low concentration of LPS (1 µg/mL LPS, mildly affected). Next, we blocked exosome uptake with chlorpromazine, and the rescue effect vanished. Based on our findings, severely inflamed odontoblasts attenuate the apoptosis of mildly inflamed neighboring cells through an exosome-mediated intercellular signaling pathway.

Analysis of Corrosion Behavior on External Surface of 110S Tubing

2020 ◽  
Vol 993 ◽  
pp. 1242-1250
Author(s):  
Yan Han ◽  
Cheng Zheng Li ◽  
Hua Li Zhang ◽  
Yu Fei Li ◽  
Da Jiang Zhu
Keyword(s):  
Pitting Corrosion ◽  
Corrosion Test ◽  
External Surface ◽  
Sample Surface ◽  
Outer Wall ◽  
High Concentration ◽  
Surface Corrosion ◽  
Slowing Down ◽  
Threaded Connection ◽  
Acid Test

The failure analysis of 110S tubing during acidizing process was addressed. Results showed that serious pitting corrosion occurred on the outer wall of tubing, and there was no obvious pitting on the inner wall. The maximum pitting depth on the outer wall was 1019 μm. According to the results of simulation corrosion test, needle-shaped pitting appeared on the sample surface in the test without inhibitor, the maximum depth of pitting was 158 μm; and no pitting was found on the sample surface in the test within 1.5% TG501 inhibitor; the original pitting were deepened after spent acid test, and the sample with no pitting at the beginning also showed deep pitting corrosion after 96 hours spent acid test. It was indicated that the spent acid accelerated the development of pitting significantly. The external surface corrosion of the 110S tubing was caused by the chemical reaction between the high-concentration acidifying liquid and the outer wall of the tubing. There is a gap between the tubing and coupling threaded connection, which caused the acid solution entered into the thread position, and hence the severe corrosion of the thread and pin end of the tubing happened, the joint strength was continuously reduced with corrosion development till the tripping of the coupling, and then the lower string dropped. Some suggestions were proposed for avoiding or slowing down this kind of failure based on this study.

The ultrastructural development of the oocyst wall of Eimeria maxima

Parasitology ◽  
1980 ◽  
Vol 81 (1) ◽  
pp. 115-122 ◽  
Author(s):  
R. M. Pittilo ◽  
S. J. Ball
Keyword(s):  
Outer Wall ◽  
Amorphous Region ◽  
Wall Layer ◽  
Intestinal Cells ◽  
Type I ◽  
Type Ii ◽  
Oocyst Wall ◽  
Outer Membranes ◽  
Eimeria Maxima ◽  
Intracellular Process

SUMMARYOocyst wall formation in Eimeria maxima was studied during the macrogamete stage in intestinal cells of the chick and in unsporulated oocysts isolated from faeces. The outer of the 2 membranes bounding the mature macrogamete separated from the surface but remained as a veil surrounding the developing oocyst throughout the whole intracellular process. Wall-forming bodies Type I were initially applied to the limiting membrane of the zygote cytoplasm; a layer of material similar to their contents was then formed around the zygote. As this occurred a new double membrane was formed surrounding the oocyst cytoplasm. The outer wall layer was initially homogenous in appearance but later developed into 2 zones, an outer amorphous region and an inner osmiophilic region. The inner layer of the oocyst wall was formed from the contents of the wallforming bodies Type II which dispersed between the outer wall and the limiting membranes of the oocyst cytoplasm. There was evidence of an additional membrane formed external to the outer wall. The outer membranes were not present around the wall of oocysts passed in the faeces of chicks, but the same wall zonation was evident, although the inner osmiophilic zone of the outer wall layer was markedly thinner in comparison with the same zone seen in the tissues.

Ascospore germination, growth in culture, and imperfect spore formation in Cookeina sulcipes and Phillipsia crispata

1975 ◽  
Vol 53 (1) ◽  
pp. 56-61 ◽  
Author(s):  
J. W. Paden
Keyword(s):  
Germ Tube ◽  
Outer Wall ◽  
Wall Layer ◽  
Spore Formation ◽  
Spore Surface ◽  
No Formation ◽  
Ascospore Germination ◽  
Germ Tubes

Ascospores of Cookeina sulcipes germinate by one of two modes: (1) by the production of blastoconidia on sympodially proliferating conidiogenous cells which may arise from any point on the spore surface, and (2) by a thick polar germ tube. No ascospores were seen to germinate both ways. The conidiogenous cells are occasionally modified into narrow hyphae. The blastoconidia germinate readily but are evidently very short-lived. Ascospores of Phillipsia crispata germinate by two polar germ tubes; there is no formation of blastoconidia. In both species the inner ascospore wall separated from an outer wall layer during germination. In culture both C. sulcipes and P. crispata form arthroconidia. The arthroconidia are uninucleate; they germinate readily and reproduce the species when transferred to fresh plates.

scholarly journals Reversible particle movements associated with unstacking and restacking of chloroplast membranes in vitro.

1976 ◽  
Vol 71 (1) ◽  
pp. 136-158 ◽  
Author(s):  
L A Staehelin
Keyword(s):  
Plasma Membranes ◽  
Structural Changes ◽  
Freeze Fracture ◽  
Chloroplast Membranes ◽  
Ps Ii ◽  
Membrane Particles ◽  
Intramembranous Particles ◽  
Membrane Surfaces ◽  
Ps Ii Activity

Freeze-fracture and freeze-etch techniques have been employed to study the supramolecular structure of isolated spinach chloroplast membranes and to monitor structural changes associated with in vitro unstacking and restacking of these membranes. High-resolution particle size histograms prepared from the four fracture faces of normal chloroplast membranes reveal the presence of four distinct categories of intramembranous particles that are nonrandomly distributed between grana and stroma membranes. The large surface particles show a one to one relationship with the EF-face particles. Since the distribution of these particles between grana and stroma membranes coincides with the distribution of photosystem II (PS II) activity, it is argued that they could be structural equivalents of PS II complexes. An interpretative model depicting the structural relationship between all categories of particles is presented. Experimental unstacking of chloroplast membranes in low-salt medium for at least 45 min leads to a reorganization of the lamellae and to a concomitant intermixing of the different categories of membrane particles by means of translational movements in the plane of the membrane. In vitro restacking of such experimentally unstacked chloroplast membranes can be achieved by adding 2-20 mM MgCl2 or 100-200 mM NaCl to the membrane suspension. Membranes allowed to restack for at least 1 h at room temperature demonstrate a resegregation of the EF-face particles into the newly formed stacked membrane regions to yield a pattern and a size distribution nearly indistinguishable from the normally stacked controls. Restacking occurs in two steps: a rapid adhesion of adjoining stromal membrane surfaces with little particle movement, and a slower diffusion of additional large intramembranous particles into the stacked regions where they become trapped. Chlorophyll a:chlorophyll b ratios of membrane fraction obtained from normal, unstacked, and restacked membranes show that the particle movements are paralleled by movements of pigment molecules. The directed and reversible movements of membrane particles in isolated chloroplasts are compared with those reported for particles of plasma membranes.

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