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Biomedical subjects

M Marko

Publications and source records attributed to M Marko.

53 records · Page 3Linked to original sources
PubMed1985

In vitro modulation of differentiation by calcium in organ cultures of human and murine epithelial tissue.

The differentiation of epithelial tissue in organ cultures of murine buccal mucosa, various human oral mucosa, and human newborn foreskin was found to be dependent on the calcium concentration of the culture media. In low calcium medium (less than or equal to 0.07 mM) epithelial differentiation was inhibited. The original stratifying layers separate and can be removed, producing a destratified explant. Histologically such an explant consists of a dorsal epithelial layer of basal keratinocytes resting on an intact basal lamina with subjacent stroma. At 0.01 mM calcium, the epithelial layer was one to two cells thick whereas at 0.07 mM it could be three or more layers in thickness with the most superficial cells being spread over the underlying cells. In addition to differentiation, keratinocyte migration over the sides of the explant (epiboly) and epithelial proliferation as determined by [3H]thymidine autoradiography were reduced by culture in low calcium medium. Redifferentiation occurs upon return to normal calcium levels (1.8 mM); addition of hydrocortisone to low calcium media was found to facilitate this redifferentiation.

Adult↗
PubMed1985

Shape changes and polarization of cells migrating through tissue. A high-voltage electron microscope and computer graphics study of serial thick sections.

Structural changes of carcinoma cells and fibroblasts migrating through small spaces in the elastic-collagen reticulum of mouse peritoneum have been studied by high-voltage electron microscopy of serial thick sections and by computer graphics reconstruction of cell profiles. The change of shape profile of an individual cell, between serial sections is large and the distribution of organelles is very non-uniform and changes markedly between sections. Conclusions about adhesion, intercell contact, cell shape and polarization of cytoplasmic organelles could only be reached by assessing a complete set of serial sections. Our preliminary results suggest that interesting structural changes occur in both carcinoma cells and fibroblasts when migrating through this tissue.

Adenocarcinoma↗
PubMed1984

Molecular structure and biochemical activity of 3,5,3'-triiodothyronamine.

The thyroid hormone decarboxylation product, 3,5,3'-triiodothyronamine (T3AM), has been shown to inhibit the cAMP production stimulated by isoproterenol in turkey erythrocytes. This adrenergic receptor binding inhibition was not shown by the thyroid hormones nor by tyramine, but was observed for 3,5-diiodotyramine, 3,5-diiodothyronamine, and thyronamine. T3AM also inhibits prolactin secretion in cultured pituitary cells as well as domperidon binding in rat corpora striata membranes. T3AM has no thyromimetic activity at the nuclear level. The molecular structure of T3AM, determined as a borosalicylate salt by X-ray diffraction techniques, is the first report of a decarboxylated thyroid hormone analogue.

Animals↗
PubMed1983

Inflammation with restricted lysosomal proteolysis during early ascites carcinoma invasion of mouse parietal peritoneum. A medium and high-voltage electron microscopic and cytochemical study.

A carcinoma invasion system (Krebs-2 and Ehrlich tetraploid ascites tumors invading mouse peritoneum) was studied by high-voltage electron microscope (HVEM) stereoscopy, conventional (medium voltage) electron microscopy (MVEM), and cytochemistry. Tumor cells entered areas of peritoneum (mainly parietal) only where mesothelial cells were damaged and where there was inflammation of the underlying stroma. The initial invasion was different from that of most other invading carcinomas in that there was minimal breakdown of basal lamina and collagen. Neither tumor cells, inflammatory leukocytes nor peritoneal fibroblasts showed significant secondary lysosome production or release of intracellular or extracellular acid phosphatase. Morphological and cytochemical criteria suggest that in some invading carcinomas, as with non-tumor migrating cells such as leukocytes, widespread proteolysis due to diffusion of proteases is not a prerequisite for invasion of stromal connective tissue.

Acid Phosphatase↗
PubMed1983

"Dark cells" in normal, hyperplastic, and promoter-treated mouse epidermis studied by conventional and high-voltage electron microscopy.

Dark cells (DC) could be reproducibly demonstrated by differential toluidine-blue staining and electron microscopy (EM) of NYLR/Nya 16- to 19-day embryo and new born skin and phorbol ester-treated or untreated young adult skin. High-voltage electron microscopy on the same or adjacent sections showed that toluidine-blue staining picks out some but not all the DC seen by EM. The ultrastructure of DC was similar in all the above situations, except that phorbol ester-induced DC showed a less contracted nucleus. No support was obtained for DC as stem cells either for basal-cell hyperplasia or for development of hair follicle or gland outgrowths. Most of the severely contracted DC (Types 3 and 4) were assumed to have undergone an apoptotic type of cell death. Two phenomena that may have caused the contraction and apoptosis were observed. Formation of a "contraction vacuole" adjacent to the DC probably led to a loss of intercellular communication. An apparent necrosis of dermal capillaries in areas of abundant follicle downgrowth probably produced local anoxia. Further characterization of DC requires a search for cytochemical or immunologic markers, analysis of intracellular calcium and other elements, and the cloning of subpopulations of basal cells that can be selectively induced to form DC.

Aging↗
PubMed1982

Ascites tumor invasion of mouse peritoneum studied by high-voltage electron microscope stereoscopy.

Interaction of Krebs-2 and Ehrlich tetraploid cells with NYLR/Nya mouse peritoneum mesothelium and penetration of basal lamina and elastic reticulum were studied. Invasion of abdominal viscera was rare. Invading cells had a shrunken nucleus and cytoplasm like the "dark cells" of hyperplastic epithelia. High-voltage electron microscope stereoscopy showed that invasive cells pass through small holes in the elastic reticulum by adherence to the reticulum and by constriction of the cells. High voltage electron microscopy stereoscopy of collagen fibers near tumor cells indicated that fragmentation and loss of collagen is minimal. Rapid progression by ascites transfer appears to produce anchorage-independent cells adapted to ascites fluid growth, but new selection steps must be adopted to concentrate strongly invasive subpopulations.

Animals↗
PubMed1980

Use of fast x-ray film for low-influence biological electron microscopy at 100 kV and 1000 kV.

A user evaluation has been made by electron microscopists of an X-ray film for routine electron microscopy. The recent improvements in mammographic X-ray films, with the attempt to reduce the patient dose required to produce a high-resolution mammogram, have resulted in some useful films for medium- and high-voltage electron microscopy. They can yield essential cytological information with a reduction of the electron fluence (exposure) applied to the specimen of more than an order of magnitude compared with conventional electron-microscope films. Their use is indicated in situations where beam damage is severe.

Electrons↗
PubMedDate not supplied

Sterecon--three-dimensional reconstructions from stereoscopic contouring.

Sterecon is a system for making 3-D reconstructions or measurements by tracing from stereopair images. The stereopair images may come directly from a microscope, such as a transmission or scanning electron microscope. Alternatively, the images may be created from a stack of thin slices, such as a confocal light microscopy depth series, an electron tomographic volume, or a set of serial histological slices. When the structure to be studied is thick or complex, a serial stack of stereoscopic images can be used. Objects are traced within the images, and their coordinates are entered into a line or contour database. The contour database can be used for 3-D structure measurement, and the contours can be displayed as a reconstruction. Sterecon has interfaces from other software which can generate the input images and to other software for further display and analysis.

Animals↗
PubMedDate not supplied

Mineralization of collagen may occur on fibril surfaces: evidence from conventional and high-voltage electron microscopy and three-dimensional imaging.

The interaction between collagen and mineral crystals in the normally calcifying leg tendons from the domestic turkey, Meleagris gallopavo, has been investigated at an ultrastructural level with conventional and high-voltage electron microscopy, computed tomography, and three-dimensional image reconstruction methods. Specimens treated by either aqueous or anhydrous techniques and resin-embedded were appropriately sectioned and regions of early tendon mineralization were photographed. On the basis of individual photomicrographs, stereoscopic pairs of images, and tomographic three-dimensional image reconstructions, platelet-shaped crystals may be demonstrated for the first time in association with the surface of collagen fibrils. Mineral is also observed in closely parallel arrays within collagen hole and overlap zones. The mineral deposition at these spatially distinct locations in the tendon provides insight into possible means by which calcification is mediated by collagen as a fundamental event in skeletal and dental formation among vertebrates.

Animals↗
PubMedDate not supplied

High-voltage electron microscopy and three-dimensional graphic study of R and T cells in head and neck carcinomas.

Individual head and neck carcinomas show extreme regional cellular differentiation. Some cells are rich in keratin filaments (T cells) and some have little keratin and a high density of free ribosomes (R or RT cells). We attempted to isolate these two cell types in order to test their relative invasiveness in an in vitro model. The high frequency of mitosis of hyperkeratinized cells showed that there was no constraint on the motility of cell division. High-voltage electron microscopy of serial thick sections and three-dimensional graphic reconstruction demonstrated that keratin cytoskeleton filaments were cross-linked into short, thick bundles. However, the keratin cytoskeleton was absent from some portions of the cytoplasm. In normal differentiated keratinized cells, a more uniform spanning of the whole cell by thin keratin intermediate-filament bundles was evident. The cytoplasm may be more mobile in the keratinized tumor cells. Even heavily keratinized T cells, like the less keratinized cell types, may have invasive motility.

Cell Separation↗
PubMedDate not supplied

Localization of interferon-induced lupus inclusions demonstrated by computer image reconstruction of monensin-treated Daudi cells.

A structural analysis of cells that contained the interferon-alpha-induced lupus inclusions (LI) was performed using a high-voltage electron microscope to determine the exact cellular location of LI and their association with normal cell organelles. LI were induced in the human B lymphoblastoid cell line, Daudi, by culturing with the pure recombinant human leukocyte interferon, IFLrA. Just prior to harvesting, a portion of the cells was treated with monensin to selectively swell the Golgi apparatus, and thereby simplify their identification using the electron microscope. Organellar associations between LI and the outer nuclear envelope and Golgi apparatus were identified in stereopairs of 1-micron sections prepared from both cells that were not treated with monensin and those that were treated with monensin. Serial 0.25-micron sections of the monensin-treated cells were prepared, and seven arbitrarily chosen cells were examined. Each of these cells contained a single LI, and it formed throughout an endoplasmic-reticulum region that made contact with both the outer nuclear envelope and the Golgi vesicles. Reconstruction of a cell by computer from the digitized negatives of serial sections clearly illustrated these relationships. This study reports the first determination of the association between LI and the Golgi apparatus. It also identifies the presence of only one LI in every cell, and the routine association of the LI with both the outer nuclear envelope and the Golgi apparatus. The unique cell location of LI formation suggests their functioning in membrane biogenesis, the trafficking of proteins to the plasma membrane or to cytoplasmic vesicles, or the processing of proteins for secretion.

Acquired Immunodeficiency Syndrome↗
PubMedDate not supplied

Topology of the mitochondrial inner membrane: dynamics and bioenergetic implications.

Electron tomography indicates that the mitochondrial inner membrane is not normally comprised of baffle-like folds as depicted in textbooks. In actuality, this membrane is pleomorphic, with narrow tubular regions connecting the internal compartments (cristae) to each other and to the membrane periphery. The membrane topologies observed in condensed (matrix contracted) and orthodox (matrix expanded) mitochondria cannot be interconverted by passive folding and unfolding. Instead, transitions between these morphological states likely involve membrane fusion and fission. Formation of tubular junctions in the inner membrane appears to be energetically favored, because they form spontaneously in yeast mitochondria following large-amplitude swelling and recontraction. However, aberrant, unattached, vesicular cristae are also observed in these mitochondria, suggesting that formation of cristae junctions depends on factors (such as the distribution of key proteins and/or lipids) that are disrupted during extreme swelling. Computer modeling studies using the "Virtual Cell" program suggest that the shape of the inner membrane can influence mitochondrial function. Simulations indicate that narrow cristae junctions restrict diffusion between intracristal and external compartments, causing depletion of ADP and decreased ATP output inside the cristae.

Animals↗