Fine structure of the heterochromatin of the kangaroo rat Dipidomys ordii, and examination of the possible role of actin and myosin in heterochromatin condensation

1976 ◽  
Vol 21 (3) ◽  
pp. 465-477
Author(s):  
D.E. Comings ◽  
T.A. Okada
Keyword(s):  
Constitutive Heterochromatin ◽  
Divalent Cations ◽  
Random Coils ◽  
Type Complex ◽  
Kangaroo Rat ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Liver Nuclei ◽  
The Brain

Biochemical studies have suggested that some actin and myosin may be present in the nucleus. This raises the possibility that heterochromatin condensation might be the result of an actin-myosin rigour type complex. Since ATP dissociates actin and myosin, this possibility could be examined by determining the effect of ATP on heterochromatin condensation. Thin-section electron microscopy showed large amounts of condensed constitutive heterochromatin in the kidney nuclei and somewhat less in the liver nuclei of the kangaroo rat, Dipidomys ordii. Surprisingly, there were some nuclei in the brain which contained no condensed heterochromatin despite the fact that this genome is composed of 50% satellite DNA. Although washing kidney nuclei with solutions of 10 mM Tris-ATP caused marked decondensation of the heterochromatin, when they were washed with Mg-ATP the heterochromatin was more condensed than in the controls. This suggests the decondensation by Tris-ATP is due to its ability to chelate divalent cations and provides no support for condensation of heterochromatin being the result of myosin-actin interaction. Despite being decondensed, the chromatin fibres of heterochromatin were distinct from those of euchromatin. The heterochromatin formed rod-like 19-5 nm fibres, the euchromatin formed random coils of 11-0-nm fibres.

The role of the flagellar transition region: inferences from the analysis of a Chlamydomonas mutant with defective transition region structures

1991 ◽  
Vol 99 (4) ◽  
pp. 731-740
Author(s):  
JONATHAN W. JARVIK ◽  
JOSEPH P. SUHAN
Keyword(s):  
Transition Region ◽  
Basal Body ◽  
Wild Type ◽  
Central Pair ◽  
Normal Transition ◽  
Thin Section Electron Microscopy ◽  
Concomitant Reduction ◽  
Section Electron ◽  
Type Variable

Thin-section electron microscopy of the Chlamydomonas reinhardtii mutant vfl-2 revealed striking defects in the transition region between basal body and flagellum. In place of the highly organized transition cylinders and stellate fibers characteristic of wild type, variable quantities of poorly organized electron-dense material were present. In many cases the transition region was penetrated by central pair microtubules that passed from the axoneme into the basal body. On the basis of these observations we propose that an important function of the structures present in the normal transition region is to physically exclude the central pair microtubules from the basal body. The transition region is the site of flagellar autotomy – the process by which doublet microtubules are severed and flagella are released from the cell. It has been claimed that autotomy is caused by contraction of the centrin-containing stellate fibers, resulting in the mechanical severing of the doublet microtubules and a concomitant reduction of the diameter of the axoneme adjacent to the abscission point. Our observations do not support this claim in that vfl-2 cells, which lack organized stellate fibers, display effective autotomy unaccompanied by detectable narrowing of the axoneme.

scholarly journals Unmasking Novel Sporulation Genes in Bacillus subtilis

2004 ◽  
Vol 186 (23) ◽  
pp. 8089-8095 ◽  
Author(s):  
Jessica M. Silvaggi ◽  
David L. Popham ◽  
Adam Driks ◽  
Patrick Eichenberger ◽  
Richard Losick
Keyword(s):  
Bacillus Subtilis ◽  
Double Mutant ◽  
Dipicolinic Acid ◽  
Muramic Acid ◽  
Wild Type ◽  
Triple Mutant ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Sporulation Genes

ABSTRACT The Bacillus subtilis transcription factor σE directs the expression of a regulon of 262 genes, but null mutations in only a small fraction of these genes severely impair sporulation. We have previously reported that mutations in seven σE-controlled genes cause a mild (2- to 10-fold) defect in sporulation. In this study, we found that pairwise combinations of some of these seven mutations led to strong synthetic sporulation phenotypes, especially those involving the ytrHI operon and ybaN. Double mutants of ybaN and ytrH and of ybaN and ytrI had >10,000-fold lower sporulation efficiencies than the wild type. Thin-section electron microscopy revealed a block in cortex formation for the ybaN ytrH double mutant and coat defects for the ybaN single and ybaN ytrI double mutants. Sporulating cells of a ybaN ytrI double mutant and of a ybaN ytrHI triple mutant exhibited a pronounced loss of dipicolinic acid (DPA) between hours 8 and 24 of sporulation, in contrast to the constant levels seen for the wild type. An analysis of the spore cortex peptidoglycans of the ybaN ytrI and ybaN ytrHI mutants showed striking decreases in the levels of total muramic acid by hour 24 of sporulation. These data, along with the loss of DPA in the mutants, suggest that the developing spores were unstable and that the cortex underwent degradation late in sporulation. The existence of otherwise hidden sporulation pathways indicates that functional redundancy may mask the role of hitherto unrecognized sporulation genes.

The Infection of Cells by Bullet-Shaped Viruses

1969 ◽  
Vol 27 ◽  
pp. 372-373
Author(s):  
Frederick A. Murphy ◽  
Alyne K. Harrison ◽  
Sylvia G. Whitfield
Keyword(s):  
Electron Microscopy ◽  
Physical Properties ◽  
Host Cell ◽  
Thin Section ◽  
Cultured Cells ◽  
Cell Infection ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Section Electron Microscopy

The bullet-shaped viruses are currently classified together on the basis of similarities in virion morphology and physical properties. Biologically and ecologically the member viruses are extremely diverse. In searching for further bases for making comparisons of these agents, the nature of host cell infection, both in vivo and in cultured cells, has been explored by thin-section electron microscopy.

Deformation of Yeast Plasma Membrane by Ethidium Bromide

1988 ◽  
Vol 46 ◽  
pp. 254-255
Author(s):  
E. Keyhani
Keyword(s):  
Plasma Membrane ◽  
Thin Section ◽  
Ethidium Bromide ◽  
Freeze Fracture ◽  
Mutagenic Effect ◽  
Yeast Cells ◽  
Hydrophobic Region ◽  
Thin Section Electron Microscopy ◽  
Section Electron ◽  
Deep Pits

The mutagenic effect of ethidium bromide on the mitochondrial DNA is well established. Using thin section electron microscopy, it was shown that when yeast cells were grown in the presence of ethidium bromide, besides alterations in the mitochondria, the plasma membrane also showed alterations consisting of 75 to 110 nm-deep pits. Furthermore, ethidium bromide induced an increase in the length and number of endoplasmic reticulum and in the number of intracytoplasmic vesicles.Freeze-fracture, by splitting the hydrophobic region of the membrane, allows the visualization of the surface view of the membrane, and consequently, any alteration induced by ethidium bromide on the membrane can be better examined by this method than by the thin section method.Yeast cells, Candida utilis. were grown in the presence of 35 μM ethidium bromide. Cells were harvested and freeze-fractured according to the procedure previously described.

The Role of Mitochondria in the Genesis of Neuroaxonal Dystrophy in the Brains of Aging Mice

1975 ◽  
Vol 33 ◽  
pp. 372-373
Author(s):  
J.E. Johnson
Keyword(s):  
Electron Microscopy ◽  
Present Report ◽  
Light And Electron Microscopy ◽  
Dorsal Column ◽  
Neuroaxonal Dystrophy ◽  
Nucleus Gracilis ◽  
Dystrophic Axons ◽  
The Brain ◽  
Nucleus Cuneatus

Although neuroaxonal dystrophy (NAD) has been examined by light and electron microscopy for years, the nature of the components in the dystrophic axons is not well understood. The present report examines nucleus gracilis and cuneatus (the dorsal column nuclei) in the brain stem of aging mice.Mice (C57BL/6J) were sacrificed by aldehyde perfusion at ages ranging from 3 months to 23 months. Several brain areas and parts of other organs were processed for electron microscopy.At 3 months of age, very little evidence of NAD can be discerned by light microscopy. At the EM level, a few axons are found to contain dystrophic material. By 23 months of age, the entire nucleus gracilis is filled with dystrophic axons. Much less NAD is seen in nucleus cuneatus by comparison. The most recurrent pattern of NAD is an enlarged profile, in the center of which is a mass of reticulated material (reticulated portion; or RP).

Effects of Mg2+ on Chromatic Structure in Isolated Chicken Liver Nuclei

1990 ◽  
Vol 48 (3) ◽  
pp. 130-131
Author(s):  
Soichiro Arai ◽  
Yuh H. Nakanishi
Keyword(s):  
Chromatin Structure ◽  
Room Temperature ◽  
Osmium Tetroxide ◽  
Divalent Cations ◽  
Chromatin Condensation ◽  
Chicken Liver ◽  
Electron Microscopic ◽  
Razor Blade ◽  
Microscopic Studies ◽  
Liver Nuclei

Although many electron microscopic studies on extracted chromatin have provided considerable information on chromatin condensation induced by divalent cations, there is only a little literature available on the effects of divalent cations on chromatin structure in intact nuclei. In the present study, the effects of Mg2+ on chromatin structure in isolated chicken liver nuclei were examined over a wide concentration range of Mg2+ by scanning electron microscopy.Nuclei were prepared from chicken liver by the method of Chauveau et al. with some modifications. The nuclei were suspended in 25 mM triethanolamine chloride buffer (pH7.4) with 1 mM EDTA or in the buffer with concentrations of MgCl2 varying from 1 to 50 mM. After incubation for 1 min at 0°C, glutaraldehyde was added to 1.8% and the nuclei were fixed for 1 h at 4°C. The fixed nuclei were mixed with 15% gelatin solution warmed at about 40°C, and kept at room temperature until the mixture set. The gelatin containing the nuclei was fixed with 2% glutaraldehyde for 2-4 h, and cut into small blocks. The gelatin blocks were conductive-stained with 2% tannic acid and 2% osmium tetroxide, dehydrated in a graded series of ethanol, and freeze-cracked with a razor blade in liquid nitrogen.

Fibrinolytic Activity of Cerebro-Spinal Fluid and the Development of Artificial Cerebral Haematomas in Dogs

1969 ◽  
Vol 21 (02) ◽  
pp. 294-303 ◽  
Author(s):  
H Mihara ◽  
T Fujii ◽  
S Okamoto
Keyword(s):  
Cerebrospinal Fluid ◽  
Carboxylic Acid ◽  
Fibrinolytic Activity ◽  
Clinical Implications ◽  
Trans Form ◽  
Plate Method ◽  
Blood Samples ◽  
Fibrin Plate ◽  
The Brain

SummaryBlood was injected into the brains of dogs to produce artificial haematomas, and paraffin injected to produce intracerebral paraffin masses. Cerebrospinal fluid (CSF) and peripheral blood samples were withdrawn at regular intervals and their fibrinolytic activities estimated by the fibrin plate method. Trans-form aminomethylcyclohexane-carboxylic acid (t-AMCHA) was administered to some individuals. Genera] relationships were found between changes in CSF fibrinolytic activity, area of tissue damage and survival time. t-AMCHA was clearly beneficial to those animals given a programme of administration. Tissue activator was extracted from the brain tissue after death or sacrifice for haematoma examination. The possible role of tissue activator in relation to haematoma development, and clinical implications of the results, are discussed.

Neuromyelitis optica spectrum: novel concept of pathogenesis, diagnosis and treatment of Devic’s disease

2009 ◽  
Vol 150 (46) ◽  
pp. 2101-2109 ◽  
Author(s):  
Péter Csécsei ◽  
Anita Trauninger ◽  
Sámuel Komoly ◽  
Zsolt Illés
Keyword(s):  
Neuromyelitis Optica ◽  
Water Channel ◽  
Diagnostic Procedures ◽  
Diagnosis And Treatment ◽  
Clinical Settings ◽  
Permanent Disability ◽  
Therapeutic Decisions ◽  
Novel Concept ◽  
The Brain

The identification of autoantibodies generated against the brain isoform water channel aquaporin4 in the sera of patients, changed the current diagnostic guidelines and concept of neuromyelitis optica (NMO). In a number of cases, clinical manifestation is spatially limited to myelitis or relapsing optic neuritis creating a diverse. NMO spectrum. Since prevention of relapses provides the only possibility to reduce permanent disability, early diagnosis and treatment is mandatory. In the present study, we discuss the potential role of neuroimaging and laboratory tests in differentiating the NMO spectrum from other diseases, as well as the diagnostic procedures and therapeutic options. We also present clinical cases, to provide examples of different clinical settings, diagnostic procedures and therapeutic decisions.

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