Well-defined Cristae Research Articles

FEATURES OF RELATIONSHIPS BETWEEN ULTRASTRUCTURES OF THE ENERGY CAPABILITY PROFILE OF FOLLICULAR THYROCYTES IN THE CORRECTION OF ALIMENTARY IODINE DEFICIENCY WITH A LOW DOSE OF ORGANIC AND INORGANIC IODINE


 The considerable spread of dietary iodine deficiency and the medical and social significance of the pathology caused by it justifies the use of mathematical methods to study the specific activity of follicular thyrocytes when correcting the manifestations of hypothyroidism with iodine of different chemical nature. The aim of this research was to examine the features of the relationship between the energy direction ultrastructures of follicular thyrocytes when taking a low dose of organic and inorganic iodine under the conditions of dietary iodine deficiency. The study was conducted on the thyroid glands of 40 white nonlinear male rats with an initial body weight of 140-160 g using electron microscopy, linguistic description of electronograms, the method of semi-quantitative analysis of electronograms, the method of specifying the profiles of special capabilities of hormone-poietic cells, and correlation analysis. On the basis of designing the correlation portraits, the interpretation of the results from the standpoint of cytophysiology was carried out. Analysis of correlation portraits of the energy capability profile of follicular thyrocytes showed that low iodine intake of both drugs reduced the functional stress caused by iodine deficiency. This was indicated by changes in mitochondria: an increase in their number and ribosomes on their cristae, a decrease in degenerative changes, granular structure of the matrix, restoration of topographic connection with the rough endoplasmic reticulum and Golgi apparatus. Normal iodine intake was characterized by very high (r=1.000) connections between the moderate number of mitochondria with their well-defined cristae and between the granular structure of the mitochondrial matrix with no degenerative changes in the mitochondria. When consuming inorganic iodine for the energy supply of follicular thyrocytes at a level sufficient for their activity, a very high (r=1.000) connection of round shape mitochondria with the existing topographic connection of mitochondria, rough endoplasmic reticulum, and Golgi apparatus was indicated and high (r=0.881) association of moderate numbers of mitochondria with medium size mitochondria. Nevertheless, in a certain part of thyrocytes, such signs of functional stress as degenerative changes in mitochondria and their cristae, disturbance of topographic interaction of mitochondria with rough endoplasmic reticulum, and Golgi apparatus remained. The studies have established a multilevel adaptation of follicular thyrocytes to function in adverse conditions while enriching the diet with a low dose of iodine increases their energy capability. Organic iodine consumed in low doses, more than inorganic iodine increases the energy supply of follicular thyrocytes’ specific activity.

Mitochondrial Dysfunctions Contribute to Hypertrophic Cardiomyopathy in Patient iPSC-Derived Cardiomyocytes with MT-RNR2 Mutation.

SummaryHypertrophic cardiomyopathy (HCM) is the most common cause of sudden cardiac death in young individuals. A potential role of mtDNA mutations in HCM is known. However, the underlying molecular mechanisms linking mtDNA mutations to HCM remain poorly understood due to lack of cell and animal models. Here, we generated induced pluripotent stem cell-derived cardiomyocytes (HCM-iPSC-CMs) from human patients in a maternally inherited HCM family who carry the m.2336T>C mutation in the mitochondrial 16S rRNA gene (MT-RNR2). The results showed that the m.2336T>C mutation resulted in mitochondrial dysfunctions and ultrastructure defects by decreasing the stability of 16S rRNA, which led to reduced levels of mitochondrial proteins. The ATP/ADP ratio and mitochondrial membrane potential were also reduced, thereby elevating the intracellular Ca2+ concentration, which was associated with numerous HCM-specific electrophysiological abnormalities. Our findings therefore provide an innovative insight into the pathogenesis of maternally inherited HCM.

Protective Efficacy of Coenzyme Q10 Against DDVP-Induced Cognitive Impairments and Neurodegeneration in Rats

The present study was carried out to elucidate the effects of coenzyme Q(10) (CoQ(10)) against cognitive impairments induced by dichlorvos (DDVP). We have previously shown organophosphate, DDVP-induced impairments in neurobehavioral indices viz. rota rod, passive avoidance, and water maze tests. In addition to this, we have also reported that chronic DDVP exposure leads to decreased mitochondrial electron transfer activities of cytochrome oxidase along with altered mitochondrial complexes I-III activity. Administration of CoQ(10) (4.5 mg/kg, i.p. for 12 weeks prior to DDVP administration daily) to DDVP-treated rats improved cognitive performance in passive avoidance task and Morris water maze test. Furthermore, CoQ(10) treatment also reduced oxidative stress (as evident by reduced malondialdehyde, decreased ROS and increased Mn-SOD activity) in DDVP-treated rats' hippocampus region, along with enhanced activity of complexes I-III and complex IV. Electron microscope studies of rat hippocampus mitochondria revealed that CoQ(10) administration leads to near normal physiology of mitochondria with well-defined cristae compared with DDVP-treated animals where enlarged mitochondria with distorted cristae are observed. CoQ(10) administration also attenuated neuronal damage in hippocampus as evident from histopathological studies. These results demonstrate the beneficial effects of CoQ(10) against organophosphate-induced cognitive impairments and hippocampal neuronal degeneration.

Mitochondria of Retinal Müller (Glial) Cells: The Effects of Aging and of Application of Free Radical Scavengers

Age-related changes of mitochondria were studied in Müller (retinal glial) cells from guinea pigs fed with or without externally applied Ginkgo biloba extract EGb 761, an established radical scavenger. When Müller cell mitochondria from aged animals were compared with those from young adults, they displayed (1) a diminished number of well-defined cristae at the ultrastructural level, (2) a reduced membrane potential, as revealed by fluorimetry using the voltage-sensitive dye tetramethyl rhodamine methylester, and (3) a slightly reduced index of vitality assayed by tetrazolium salt colorimetry. Müller cell mitochondria were also studied in aged guinea pigs which had been fed daily by EGb 761 during the last 2 months before they were sacrificed. Such mitochondria displayed (1) many well-defined cristae at the ultrastructural level, and, compared with mitochondria from untreated aged animals, (2) a significantly enhanced membrane potential and (3) a significantly enhanced index of vitality. No age- or drug-related changes were observed in the mitochondrial content of GABA transaminase, as revealed by immunocytochemistry/densitometry. These results suggest that many but not all structural and functional parameters of aging Müller cell mitochondria are impaired by accumulating oxidative damage, and that externally applied radical scavengers may protect the organelles from the damaging actions of free radicals. As it has been shown earlier that EGb 761 treatment enhances the intrinsic glutathione content of aged guinea pig Müller cells, the protective radical-scavenging effect of the drug may be mediated both directly and indirectly.

Excretion in the house cricket Acheta domesticus: Effects of diuretics on the structure of the mid-tubule.

Most structural studies of insect Malpighian tubules focus on freshly dissected tissue, which is in fact stimulated by diuretic factors. In this study, we examine tubules from the house cricket Acheta domesticus in four discrete secretory states: control (freshly dissected); unstimulated (held in vitro for 90 min prior to fixation); corpus cardiacum-stimulated (held in vitro for 60 min, then stimulated with corpus cardiacum homogenates for 30 min prior to fixation); and cAMP-stimulated (held in vitro for 60 min, then stimulated with dibutyryl cAMP for 30 min prior to fixation). In unstimulated tubules, we see a reduction in vacuolization and a near-complete collapse of the basolateral infolds. Stimulated tubules show several major structural shifts: mitochondria are darkly stained with well-defined cristae, there is extensive vacuolization of the tissue and expansion of the basolateral spaces, and the CaPO4 spherites appear to be ejected into the lumen. cAMP-stimulated tubules showed the most pronounced structural changes, including the presence of a newly reported ultrastructural feature for A. domesticus Malpighian tubules, referred to here as paracrystalline arrays, which appear as stacks of membrane localized in the perinuclear region. © 1996 Wiley-Liss, Inc.

Ultrastructural changes in the spore and mycelia of Ascosphaera apis after treatment with benomyl (Benlate 50 W)

In Ascosphaera apis, after 8 days growth in darkness at 28° C, numerous sporocysts were observed, within which mature spores were seen aggregated into a spore ball. The mature spore of A. apis had a thick spore wall with an electron-opaque outer layer, a spore membrane with many depressions, and sporoplasm containing numerous ribosomes and mitochondria. In the cytoplasm of the mycelium, mitochondria with well-defined cristae and numerous ribosomes were observed. At a concentration of 1 μg/ml of culture medium, benomyl appeared to inhibit colony growth of A. apis, but some sporocysts containing deformed spores were found. Deformed spores possessed a thick spore wall with a grainy matrix, and depressions were no longer detected in the spore membrane. Ribosomes were lacking in the sporoplasm and mitochondria appeared degenerate. The mycelium from the treated culture contained mitochondria with an electron-lucid matrix and no well defined cristae, while ribosomes were completely depleted. The significance of these observations in relation to the use of benomyl to control chalkbrood disease in the honey bee is discussed.

Ultrastructure of the freeze-etched spore of Ascosphaera apis, an entomopathogenic fungus of the honeybee Apis mellifera

The freeze-fractured outer surface of the spore wall of Ascophaera apis is covered with granules which are 21.5 nm in diameter. The cross-fractured spore wall consists of subunits which are 9 nm in diameter. The inner surface of the spore wall is granular and has many stud-like projections measuring approximately 120 nm long × 26 nm wide. The convex face of the spore membrane carries many particles as well as many depressions which are complementary to the projections on the inner surface of the spore wall. The nucleus possesses double nuclear membranes which contain numerous well-defined nuclear pores. In the cytoplasm of the spore there are many mitochondria which have well-defined cristae and many particles on the internal membranes. The sporoplasm contains many lipid droplets which possess concentric smooth-surfaced lamellae.

Metopus, Cyclidium and Sonderia: ciliates enriched and cultured from sulfureta of a microbial mat community

Metopus contortus (Class Spirotrichea), Cyclidium borrori, Cyclidium sp., Sonderia tubigula, and two other species of Sonderia (Class Oligohymenophorea) were enriched from the sulfureta of microbial mat communities at Laguna Figueroa near San Quintin, Baja California, Mexico. The ability of some of these species to grow under anaerobic, high-sulfide conditions was demonstrated. The ultrastructural morphology of Metopus and Cyclidium revealed adaptations to anaerobic, high sulfide niches. Metopus lacks typical mitochondria and has structures which may be intracellular bacterial symbionts. Cyclidium borrori, when grown aerobically, has mitochondria with tubular cristae. When it is grown anaerobically in the presence of high amounts of hydrogen sulfide the number of mitochondria remains the same but the mitochondria dedifferentiate, becoming smaller with less well-defined cristae.

Ultrastructure of Rodlet Cells: Response to Cadmium Damage in the Kidney of the Spot Leiostomus xanthurus Lacépède

Rodlet cell ultrastructure was studied in normal and cadmium-damaged kidney tissues of the spot Leiostomus xanthurus, an estuarine teleost. Rodlet cells in control fish occurred in all parts of the nephron except the renal corpuscle, were oblong to pear-shaped (about 5x10 µm), and contained up to 30 rodlet bodies, a basally situated nucleus, poorly developed mitochondria, and a filamentous cortex. Desmosomes and tight junctions joined rodlet cells to kidney epithelial cells. After cadmium exposure, rodlet cells showed a range of responses from secretory stimulation to necrosis. Rodlet bodies, which were membrane-bound, club-shaped granules, were secreted by a merocrine process, apparently aided by contraction of the fllamentous cortex. New rodlet bodies were assembled in the Golgi apparatus. Mitochondria hypertrophied and developed well-defined cristae. The ultrastructural organization of the rodlet cells in this study and their responses to stimuli suggest that these are tissue or host cells rather than parasites as proposed by some authors. Further studies, however, are needed to confirm the nature of these cells.

Similarities in mitochondrial ultrastructure of leukemic cells and ethidium-bromide-treated normal cells

Electron micrographs of blastic human lymphocytes from phytohemagglutinin (PHA) cultures showed normal mitochondria with round, oval, and elongated shapes, containing well-defined cristae and electron-dense matrix. Micrographs of blastic lymphocytes from PHA cultures with ethidium bromide (EB) at 1 to 3 μg/ml, however, showed swollen mitochondria with fewer cristae and vacuolated matrix. Similarly damaged mitochondria were observed in micrographs of blast cells from patients with acute lymphoblastic (ALL) and acute myeloblastic leukemia (AML) and also in lymphocytes from cases of prolymphocytic leukemia (PLL). This study shows specific structural damage to mitochondrial cristae in normal proliferating lymphocytes when their mitochondrial DNA transcription, hence protein synthesis, is selectively inhibited by EB. It confirms that damaged cristae give structural evidence of inhibited mitochondrial protein synthesis. The structural damage of mitochondrial cristae observed in a variety of leukemic cells suggests that mitochondrial protein synthesis may be disturbed or abnormal in leukemic cells.

Magnesium-induced mitochondrial polymorphism and changes in respiratory metabolism in the fission yeast, Schizosaccharomyces pombe

The role of magnesium ions in controlling mitochondrial structure and function in the fission yeast, Schizosaccharomyces pombe, has been studied. Results show that in control cultures of S. pombe grown in the presence of magnesium, cells follow predominantly a fermentative pathway of metabolism. The mitochondria, as visualized by electron microscopy, are large but few in number, and appear irregularly branched with indistinct cristae. On depletion of the magnesium supply, cell division ceases after about 4 hours after which there is an increase in respiration. The mitochondria increase in number and become small with well-defined cristae. On replenishment of magnesium ions mitochondria seem to fuse and there is a gradual restoration of the respiratory metabolism characteristic of control cells.

A simple method for perfusion fixation of avian liver for electron microscopy

A simple method and apparatus are described for perfusion fixation of avian liver for electron microscopy. A constant perfusion pressure is maintained at or below a fixed value with the use of a compressed air cylinder and without the use of automatic devices. A hyperosmotic (580–600 mosm) fixative solution containing 4% glutaraldehyde, 0.0005 M CaCl2, and 0.0005 M MgCl2 in 0.05 M phosphate buffer (pH 7.4, buffer osmolality 122 mosm) produced consistent fixation without swelling or undue shrinkage. The cytoplasmic organelles were well preserved; notably, the mitochondria had electron-dense matrices and well-defined cristae. A pressure of 60 mmHg (1 mmHg = 133.322 Pa) maintained by compressed air permits a minimum to maximum flow rate of 14–19 mL∙min−1∙kg body weight−1, and optimum preservations of the architecture of sinusoids.

Mitochondrial morphology in yeast with and without mitochondrial DNA

The morphology of yeast mitochondria in Schizosaccharomyces pombe and a petite and wild-type strain of Saccharomyces cerevisiae were examined using gentle fixation procedures. The major objective was to determine the effect of the complete loss of mitochondrial DNA on the morphology of mitochondria in the strains of S. cerevisiae . The fission yeast was used as a test organism for developing a fixation procedure that would yield well-defined cristae. Optimal results were obtained when protoplasts were fixed with glutaraldehyde alone. In thin sections of wild-type S. cerevisiae which contained a full complement of mitochondrial DNA, cristae were readily discernible, while in the petite mutant strain completely lacking mitochondrial DNA, normal cristae were totally absent despite the appearance of a well-preserved innermost and outermost surface membrane. One interpretation is that the cristae membranes are different from the innermost surface membranes.