Increase In Number Of Mitochondria Research Articles

Ultrastructural changes in mouse yolk sac associated with the initiation of vitelline circulation.

AbstractThe endodermal cells of the visceral yolk sac have been studied from the seventh to eleventh day of gestation. The absorptive capacity of the cells is established by the seventh day as indicated by the presence of microvilli, coated invaginations and vacuoles, the apical canalicular system and abundance of absorptive droplets and vacuoles in these cells. Changes in cellular structure during the next three to four days include the development of the cisternal system of the rough endoplasmic reticulum, an increase in mitochondrial number and their localization near absorptive droplets and the formation of multiple Golgi complexes. Intercellular spaces form between the endodermal cells by eight to eight and one‐half days and coincide with the disappearance of the basal lamina separating the endoderm and mesoderm (angioblastic cords); these changes correlate with the formation of the vitelline vessels. As the vitelline circulation becomes functional, the visceral basal lamina is re‐established, the intercellular clefts decrease in prominence and the absorptive storage droplets and vacuoles decrease in size and number.The apical junctional complex of the endodermal cells forms a continuous barrier for the direct passage of material from the yolk sac cavity to the developing vitelline vessels as established by the use of ruthenium red. The absorption and intracellular storage of macromolecules in the visceral endodermal cells was traced through the intermicrovillous apical coated invaginations, coated vesicles, apical canaliculi and storage vacuoles using ferritin.Immunofluorescent studies indicate the presence of immunoglobulin (anti‐mouse gamma globulin) in the cytoplasm of the visceral endodermal cells as early as 9 to 11 days. Several blast‐like cells which also were observed in the vitelline vessels at 11 days exhibited positive fluorescence for immunoglobulin.

Electron microscopic observations of hypertrophied myocardium of rat produced by injection of monocrotaline.

The right ventricular myocardium of the cor pulmonare in the rat induced by subcutaneous single injection of monocrotallne has been studied by electron microscope. The hypertrophy and wearing of myocardium was sequentially categorized into (1) preparatory stage, (2) hypertrophied stage, and (3) damaged stage.Slightly enlarged and injured mitochondria and incomplete division of mitochondria were noticed in the first stage. An increase in number of mitochondria, appearance of giant mitochondria, many free ribosomes and small bundles of myofilaments were recognized in the second stage. In the third stage, mitochondria located in the subsarcolemmal region and between the myofibrils tended to migrate to the central portion of the muscle cell, and the myofibrils were simultaneously pushed away towards the plasma membrane. A large number of spherical, electron‐opaque granules, not containing acid phosphatase, were found in the enlarged central sarcoplasmic core. The transverse cell boundary was expansively widened at the intermediate junction and its space contained many small membrane‐limited particles. Injured cells, reduced in size, were isolated and localized in the tissue space. After degeneration of this cell, it is finally replaced by collagen fibers.

Changes in the ultrastructure of salivary gland cytoplasm in Sciara ocellaris (Comstock, 1882) due to microsporidian infection

The effects of infection by a microsporidian, Thelohania sp., on the ultrastructure of the cytoplasm of salivary gland cells in Sciara ocellaris were investigated. Cytoplasm of uninfected cells contains a dense ribosomal population studding large condensations of lamellar and vesicular endoplasmic reticulum, numerous scattered Golgi areas, and typical metazoan mitochondria. In infected cells of salivary glands the ultrastructural integrity of the cytoplasm is profoundly changed due to depletion of ribosomes, disarrangement of endoplasmic reticulum, and to decrease in size and increase in number of mitochondria. The overall electron opacity of the infected cytoplasm is decreased due to a decrease in ribosomal population and to formation of cytoplasmic vacuoles. The implications of the various features observed in both normal and infected cells are discussed, and possible suggestions are made regarding alteration of the metabolic functions due to infection.

AN ELECTRON MICROSCOPE STUDY OF TOBACCO MOSAIC VIRUS LESIONS IN NICOTIANA GLUTINOSA L.

Ultra-thin sections of Nicotiana glutinosa L. leaves inoculated with a concentrated solution of tobacco mosaic virus were made at short intervals from 0 to 78 hours after inoculation. Eight hours after inoculation, the size of starch grains increased. This was followed by rupture of cytoplasmic and chloroplast membranes. At about 24 hours there was a great increase in number of mitochondria, which persisted until about 60 hours, when some became electron opaque while others appeared to disintegrate. Finally, the cell contents were compressed into one area of the cell, where they became electron opaque. This was accompanied by collapse of the rest of the cell and tearing away of the cell walls from adjacent cells. The nucleus remained stable and intact for as long as observations could be made. No identifiable virus particles were seen.

Experimental Extrahepatic Biliary Obstruction

Summary This paper records observations of disturbances of mitochondrial morphology in parenchymal liver cells of rats after ligation of the common bile duct. The changes observed include an apparent increase in number of mitochondria in some areas of cells, focal disturbances of the size and density of the matrix of mitochondria, and changes in the relative and absolute length of the cristae mitochondriales. These observations could not be related to any specific type of cell degeneration as seen in the light microscope. No explanation can be offered at present f or their occurrence beyond a general statement that they represent, at an electron microscopic level of observation, evidence of cell injury.

A quantitative electron microscopic study of mitochondria in motor neurones following axonal section

An electron microscopic study was made of the motor neurones of the hypoglossal nuclei of a series of 10 rabbits, 10–11 days after unilateral hypoglossal neurotomy. Quantitative data obtained from the micrographs showed that on the operated side there was a significantly greater number of mitochondrial profiles per unit area of cytoplasm than on the control side. There was also a 70 per cent increase in the volume ratio of mitochondria to cytoplasm, approximately three-fifths of this being attributable to mitochondrial swelling and the remaining two-fifths to the increase in mitochondrial numbers. The findings may he interpreted as indicating that the increase in number of mitochondrial profiles on the operated side, was brought about by the formation of new mitochondria resulting in an increase in total functioning mitochondrial mass. There was a highly significant increase in the number of dense bodies (“microbodies”) per unit area of cytoplasm on the operated side, and a significant correlation was found between the average increase in the number of dense bodies and the average increase in mitochondrial numbers in the individual experiments. It has already been noted that the appearances of dense bodies in motor neurones of the rabbit were consistent with their bearing a developmental relationship to mitochondria and the present results would seem to favour the possibility that dense bodies may be concerned in mitochondrial formation. In the rat, other forms of dense body, containing areas of even greater density, were also noted.

CHARACTERISTICS OF FROG CARCINOMA IN TISSUE CULTURE

The adenocarcinoma of leopard frogs may be cultivated with ease in plasma media. In such cultures two types of growth occur with regularity. The first is in the form of tubules which promptly grow out in the solid medium and retain their tubular form as long as they remain completely enveloped by plasma. When, however, they make contact with the surface of the glass, they adhere to it, the part in contact becomes flat, and its cells now grow no longer as tubules but as membranes. The manner of growth in vitro resembles the growth of transplants of the same tumor in the anterior chamber of the living eye, thus suggesting that in each case the habit of growth is determined by the same morphogenetic factors, i.e. those inherent in the cells themselves, and those depending on interfacial forces. The malignant cells of the frog carcinoma have the attributes which in general distinguish malignant cells from normal cells of corresponding type. In comparison with adult kidney cells, their normal homologues, the conspicuous properties of frog carcinoma cells are: larger and more variable size and shape of cell body, of nucleus, and nucleolus; coarser and denser structure of cytoplasm, of nucleoplasm, and of nuclear membrane; increase in number of mitochondria, and more frequent occurrence of mitosis. These cytological characteristics remain unaltered in cultures maintained for as long as six months. Frog carcinoma is a transmissible disease due to an agent which induces inclusion bodies, and which has other attributes indicating that it is a virus. The general correspondence in character between its cells and the malignant cells of mammalian tumors of diverse origin suggests that neoplastic phenomena are essentially alike, no matter in what group of animals they occur or what their causal factors may be.