Ultrastructure of soybean nodules. II: deterioration of the symbiosis in ineffective nodules

1977 ◽  
Vol 23 (7) ◽  
pp. 873-883 ◽  
Author(s):  
B. Bassett ◽  
R. N. Goodman ◽  
A. Novacky
Keyword(s):  
Electron Microscopy ◽  
Nitrogen Starvation ◽  
Host Cells ◽  
Ultrastructural Changes ◽  
Rhizobium Japonicum ◽  
Intracellular Bacteria ◽  
Seed Inoculation ◽  
Normal Manner ◽  
Infected Cells ◽  
Japonicum Strain

Ineffective nodules, formed on Clark-63 soybeans by Rhizobium japonicum strain 8-0 (Iowa), and effective nodules, formed on Clark-63 soybeans by strain 138 (U.S.D.A.), have been examined by electron microscopy at 10–12, 16, and 21 days after seed inoculation. Though strain 8-0 bacteria are able to infect the host cells in a normal manner, infection is followed closely by a progressive deterioration of the symbiosis involving selective autolysis of host cell contents and degeneration of the intracellular bacteria. The host cells, though disrupted, apparently survive the destruction of the bacteria. The observed ultrastructural changes suggest either a suddenly manifested incompatibility between host and rhizobia, or an acute, localized, nitrogen starvation in the infected cells.

scholarly journals Efficient Killing of Multidrug-Resistant Intracellular Bacteria by AIEgens in Vivo

2020 ◽  
Author(s):  
Ying Li ◽  
Fei Liu ◽  
Jiangjiang Zhang ◽  
Xiaoye Liu ◽  
Peihong Xiao ◽  
...  
Keyword(s):  
Membrane Damage ◽  
Multidrug Resistant ◽  
Host Cells ◽  
Comparable Efficacy ◽  
Intracellular Bacteria ◽  
New Agents ◽  
Immune Clearance ◽  
Infected Cells ◽  
Dose Levels

<p><a>Bacteria infected cells acting as “Trojan horses” not only protect bacteria from antibiotic therapies and immune clearance, but also increase the dissemination of pathogens from the initial sites of infection. Antibiotics are hard and insufficient to treat such hidden intracellular bacteria, especially the multidrug</a>-resistant (MDR) bacteria. Herein, aggregation-induced emission luminogens (AIEgens) such as TBPs showed potent broad-spectrum bactericidal activity against both <a></a><a>extracellular and intracellular</a> Gram-positive pathogens at low-dose levels. TBPs triggered reactive oxygen species (ROS)-mediated membrane damage to kill bacteria, regardless of light irradiation. Additionally, such AIEgens activated mitochondria dependent autophagy to eliminate intracellular bacteria in host cells. Compared to the routinely used vancomycin in clinics, TBPs showed comparable efficacy against methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) <i>in vivo</i>. Our studies demonstrate that AIEgens are promising new agents for the treatment of MDR bacteria associated infections.</p>

Ultrastructure of eastern cottonwood clones susceptible or resistant to leaf rust

1987 ◽  
Vol 65 (8) ◽  
pp. 1586-1598 ◽  
Author(s):  
L. Shain ◽  
U. Järlfors
Keyword(s):  
Electron Microscopy ◽  
Leaf Rust ◽  
Light And Electron Microscopy ◽  
Infection Process ◽  
The Other ◽  
Host Cells ◽  
Eastern Cottonwood ◽  
Melampsora Medusae ◽  
Wall Appositions ◽  
Infected Cells

The infection process in four clones of eastern cottonwood susceptible or resistant to leaf rust caused by Melampsora medusae was studied by light and electron microscopy. Infection was initiated by stomatal rather than direct entry. Typical dikaryotic haustoria were observed in all clones within 1 day of inoculation. Some healthy-appearing haustoria were observed in susceptible clones throughout the duration of the study, which was terminated during the initiation of uredial production. Incompatibility was expressed differently in the two resistant clones. In clone St 75, most haustoria and invaded host cells that were observed appeared necrotic within 2 days of inoculation. Cell wall appositions appeared during this time in cells adjoining necrotic host cells. Some infected cells disintegrated within 4 days of inoculation. Affected host cells of clone St 92, on the other hand, plasmolyzed during the first 2 to 3 days after inoculation. Necrotic host cells were not observed in this clone until the 4th day after inoculation. Hyphal ramification and host plasmolysis were extensive at 6 days after inoculation.

scholarly journals Parvoviral nuclear import: bypassing the host nuclear-transport machinery

2006 ◽  
Vol 87 (11) ◽  
pp. 3209-3213 ◽  
Author(s):  
Sarah Cohen ◽  
Ali R. Behzad ◽  
Jeffrey B. Carroll ◽  
Nelly Panté
Keyword(s):  
Electron Microscopy ◽  
Nuclear Import ◽  
Mouse Fibroblast ◽  
Host Cells ◽  
Fibroblast Cells ◽  
Dna Virus ◽  
Minute Virus Of Mice ◽  
Nuclear Lamin ◽  
Infected Cells ◽  
Minute Virus

The parvovirus Minute virus of mice (MVM) is a small DNA virus that replicates in the nucleus of its host cells. However, very little is known about the mechanisms underlying parvovirus' nuclear import. Recently, it was found that microinjection of MVM into the cytoplasm of Xenopus oocytes causes damage to the nuclear envelope (NE), suggesting that the nuclear-import mechanism of MVM involves disruption of the NE and import through the resulting breaks. Here, fluorescence microscopy and electron microscopy were used to examine the effect of MVM on host-cell nuclear structure during infection of mouse fibroblast cells. It was found that MVM caused dramatic changes in nuclear shape and morphology, alterations of nuclear lamin immunostaining and breaks in the NE of infected cells. Thus, it seems that the unusual nuclear-import mechanism observed in Xenopus oocytes is in fact used by MVM during infection of host cells.

Electron microscopy studies on infection of resistant (Sr6 gene) and susceptible near-isogenic wheat lines by Puccinia graminis f. sp. tritici

1974 ◽  
Vol 52 (12) ◽  
pp. 2615-2620 ◽  
Author(s):  
R. A. Skipp ◽  
D. E. Harder ◽  
D. J. Samborski
Keyword(s):  
Electron Microscopy ◽  
Fungal Growth ◽  
Host Cells ◽  
Wheat Line ◽  
Mesophyll Cells ◽  
Susceptible Line ◽  
Infected Cells ◽  
Mother Cells ◽  
Wheat Lines ◽  
Infection Hypha

Intracellular hyphae, haustoria, and infected host cells in young stem rust infections of a wheat line containing resistance gene Sr6 were compared by electron microscopy with those of a near-isogenic susceptible line. Mesophyll cells of the resistant line which had undergone a rapid necrotic response to haustorial invasion were collapsed and lacked the thin layer of cytoplasm that typically bounded the vacuole of infected cells of the susceptible line. Instead, the lumen was filled with an electron-dense ground material of mixed cytoplasmic and vacuolar constituents containing organelles at various stages of disorganization. Haustoria within these cells were necrotic, as were their mother cells. Apart from a dense staining of mitochondrial membranes there was little evidence of damage to the infection hypha proximal to the septum of the haustorium mother cell. The cytoplasm of host cells adjacent to those showing necrosis was often diffuse and vesiculated. A deposit of electron-dense granular material was found between the wall of a necrotic cell and its plasmalemma, and a similar deposit was present inside the adjoining wall of a contiguous non-necrotic cell.These findings are discussed in relation to the inhibition of fungal growth that accompanies host cell necrosis in the resistant wheat line.

scholarly journals Rifampicin-Loaded Mesoporous Silica Nanoparticles for the Treatment of Intracellular Infections

Antibiotics ◽  
2019 ◽  
Vol 8 (2) ◽  
pp. 39 ◽  
Author(s):  
Subramaniam ◽  
Thomas ◽  
Gustafsson ◽  
Jambhrunkar ◽  
Kidd ◽  
...  
Keyword(s):  
Mesoporous Silica ◽  
Silica Nanoparticles ◽  
Mesoporous Silica Nanoparticles ◽  
Host Cells ◽  
Economic Losses ◽  
Infection Model ◽  
Intracellular Bacteria ◽  
Infected Cells ◽  
Small Colony ◽  
Intracellular Infections

Infectious diseases remain a major burden in today’s world, causing high mortality rates and significant economic losses, with >9 million deaths per year predicted by 2030. Invasion of host cells by intracellular bacteria poses treatment challenges due to the poor permeation of antimicrobials into the infected cells. To overcome these limitations, mesoporous silica nanoparticles (MSNP) loaded with the antibiotic rifampicin were investigated as a nanocarrier system for the treatment of intracellular bacterial infection with specific interest in the influence of particle size on treatment efficiency. An intracellular infection model was established using small colony variants (SCV) of S. aureus in macrophages to systemically evaluate the efficacy of rifampicin-loaded MSNP against the pathogen as compared to a rifampicin solution. As hypothesized, the superior uptake of MSNP by macrophages resulted in an enhanced treatment efficacy of the encapsulated rifampicin as compared to free antibiotic. This study provides a potential platform to improve the performance of currently available antibiotics against intracellular infections.

Electron microscopy of vesicular-arbuscular mycorrhizae of yellow poplar. III. Host–endophyte interactions during arbuscular development

1975 ◽  
Vol 21 (12) ◽  
pp. 1930-1939 ◽  
Author(s):  
Darrell A. Kinden ◽  
Merton F. Brown
Keyword(s):  
Electron Microscopy ◽  
Arbuscular Mycorrhizae ◽  
Fungal Endophyte ◽  
Host Cells ◽  
Wall Material ◽  
Yellow Poplar ◽  
Transmission Electron ◽  
Abundant Cytoplasm ◽  
Mycorrhizal Roots ◽  
Infected Cells

Scanning- and transmission-electron microscopy were used to examine developing and mature functional arbuscules in mycorrhizal roots of yellow poplar. Arbuscules developed from intracellular hyphae which branched repeatedly upon penetration into the host cells. Intermediate and late stages of development were characterized by the production of numerous, short, bifurcate hyphae throughout the arbuscule. Mature arbuscules exhibited a coralloid morphology which resulted in a considerable increase in the surface area of the endophyte exposed within the host cells. Distinctive ultrastructural features of arbuscular hyphae included osmiophilic walls, nuclei, abundant cytoplasm, glycogen, and numerous small vacuoles. All arbuscular components were enclosed by host wall material and cytoplasm during development and at maturity. In infected cells, host nuclei were enlarged and the cytoplasm associated with the arbuscular branches typically contained abundant mitochondria, endoplasmic reticulum, and proplastids. Ultrastructural observations suggested that nutrient transfer may be predominantly directed toward the fungal endophyte during arbuscular development and while mature arbuscules remain functional.

scholarly journals An image-based screening system for the study of Mycobacterium avium persistence and drug discovery

2020 ◽  
Vol 2 (7A) ◽  
Author(s):  
Karthika Nagalekshmi ◽  
Cecilia O’Kane ◽  
Gunnar Schroeder
Keyword(s):  
Drug Discovery ◽  
Mycobacterium Avium ◽  
Opportunistic Infections ◽  
Host Cells ◽  
Steady Increase ◽  
Intracellular Bacteria ◽  
Inducible Promoters ◽  
The Past ◽  
Infected Cells ◽  
New Treatments

Mycobacterium avium infects human macrophages causing opportunistic infections. A steady increase of these infections over the past four decades and resistance to common anti-mycobacterial drugs, create an urgent need for new treatments; however, drug discovery is held back by a lack of knowledge about how M. avium replicates or persists in host cells. We implemented an image-based assay using a fluorescence dilution (FD) system to measure M. avium replication and persistence. M. avium strain 104 carrying a plasmid encoding GFP and TurboFP635 under constitutive and inducible promoters, respectively, is induced prior to infection of THP1 macrophages and the fluorescent signals are tracked over time in the absence of the inducer. Loss of the TurboFP635 signal while GFP signal is maintained, identifies replicating and retention of both signals non-replicating bacteria. In the absence of inducer, the M. avium 104 FD strain replicated in the macrophages, leading to increasing numbers of GFP-expressing intracellular bacteria and concomitant loss of TurboFP635 signal in >90% of the infected cells after 24 hours. Upon re-induction, these bacteria expressed TurboFP635, suggesting they are metabolically active and alive. We observed the presence of a small non replicating population that persisted over 96 hours pi. We applied our assay to compare the effect of a panel of anti-mycobacterial drugs, revealing different effects on killing, intracellular replication and induction of persisting, non-replicating bacteria, illustrating the power of this system to facilitate the dissection of the biology of persistence and anti-mycobacterial drug discovery in the future.

scholarly journals Essential Role for Humoral Immunity during Ehrlichia Infection in Immunocompetent Mice

2005 ◽  
Vol 73 (12) ◽  
pp. 8009-8016 ◽  
Author(s):  
Eric Yager ◽  
Constantine Bitsaktsis ◽  
Bisweswar Nandi ◽  
Jere W. McBride ◽  
Gary Winslow
Keyword(s):  
Host Defense ◽  
Humoral Immunity ◽  
Bacterial Infections ◽  
Essential Role ◽  
Host Cells ◽  
Intracellular Bacteria ◽  
Oxygen Intermediates ◽  
Subsequent Exposure ◽  
Infected Cells ◽  
Immunocompetent Mice

ABSTRACT Although cellular immunity is essential for host defense during intracellular bacterial infections, humoral immunity can also play a significant role in host defense during infection by some intracellular bacteria, including the ehrlichiae. Antibodies can protect susceptible SCID mice from fatal Ehrlichia chaffeensis infection, an observation that has been hypothesized to involve the opsonization of bacteria released from host cells. To determine whether humoral immunity plays an essential role during ehrlichia infection in immunocompetent mice, we utilized a murine model of fatal monocytotropic ehrlichiosis caused by Ixodes ovatus ehrlichia. Mice lacking either B cells or FcγRI were unable to resolve a low-dose (sublethal) I. ovatus ehrlichia infection, which suggested that humoral immunity is essential for resistance. Polyclonal sera generated in I. ovatus ehrlichia-infected mice recognized a conserved ehrlichia outer membrane protein and, when administered to infected mice, caused a significant decrease in bacterial infection. Mice experimentally depleted of complement, or deficient for complement receptors 1 and 2, were also susceptible to sublethal I. ovatus ehrlichia infection, as were mice that lacked the phox91 subunit of NADPH oxidase. The data are consistent with a mechanism whereby bacteria released from infected cells are lysed directly by complement or undergo antibody-mediated FcγR-dependent phagocytosis and subsequent exposure to reactive oxygen intermediates. The findings suggest mechanisms whereby antibodies contribute to immunity against intracellular bacteria in immunocompetent mice.

scholarly journals Efficient Killing of Multidrug-Resistant Intracellular Bacteria by AIEgens in Vivo

2020 ◽  
Author(s):  
Ying Li ◽  
Fei Liu ◽  
Jiangjiang Zhang ◽  
Xiaoye Liu ◽  
Peihong Xiao ◽  
...  
Keyword(s):  
Membrane Damage ◽  
Multidrug Resistant ◽  
Host Cells ◽  
Comparable Efficacy ◽  
Intracellular Bacteria ◽  
New Agents ◽  
Immune Clearance ◽  
Infected Cells ◽  
Dose Levels

<p><a>Bacteria infected cells acting as “Trojan horses” not only protect bacteria from antibiotic therapies and immune clearance, but also increase the dissemination of pathogens from the initial sites of infection. Antibiotics are hard and insufficient to treat such hidden intracellular bacteria, especially the multidrug</a>-resistant (MDR) bacteria. Herein, aggregation-induced emission luminogens (AIEgens) such as TBPs showed potent broad-spectrum bactericidal activity against both <a></a><a>extracellular and intracellular</a> Gram-positive pathogens at low-dose levels. TBPs triggered reactive oxygen species (ROS)-mediated membrane damage to kill bacteria, regardless of light irradiation. Additionally, such AIEgens activated mitochondria dependent autophagy to eliminate intracellular bacteria in host cells. Compared to the routinely used vancomycin in clinics, TBPs showed comparable efficacy against methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) <i>in vivo</i>. Our studies demonstrate that AIEgens are promising new agents for the treatment of MDR bacteria associated infections.</p>

Ultrastructural Changes of Canine Kidneys During 24-Hour Perfusion on a LI-400 Preservation System

1971 ◽  
Vol 29 ◽  
pp. 316-317
Author(s):  
M. O. Magnusson ◽  
D. G. Osborne ◽  
T. Shimoji ◽  
W. S. Kiser ◽  
W. A. Hawk
Keyword(s):  
Electron Microscopy ◽  
Electrolyte Solution ◽  
Ultrastructural Changes ◽  
Midline Incision ◽  
Short Term ◽  
Pentobarbital Anesthesia ◽  
Pulsatile Perfusion

Short term experimental and clinical preservation of kidneys is presently best accomplished by hypothermic continuous pulsatile perfusion with cryoprecipitated and millipore filtered plasma. This study was undertaken to observe ultrastructural changes occurring during 24-hour preservation using the above mentioned method.A kidney was removed through a midline incision from healthy mongrel dogs under pentobarbital anesthesia. The kidneys were flushed immediately after removal with chilled electrolyte solution and placed on a LI-400 preservation system and perfused at 8-10°C. Serial kidney biopsies were obtained at 0-½-1-2-4-8-16 and 24 hours of preservation. All biopsies were prepared for electron microscopy. At the end of the preservation period the kidneys were autografted.

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