PubMed Health⌕ Search

Biomedical subjects

G T Simon

Publications and source records attributed to G T Simon.

At least 19 recordsLinked to original sources
PubMed1990

Experimental ionization cross-sections of phosphorus and calcium by electron spectroscopic imaging.

The absolute partial electron scattering cross-section for the phosphorus L2,3-shell ionization was measured by electron spectroscopic imaging using poliovirus as a primary standard. The equivalent calcium cross-section was obtained in relation to phosphorus using the stoichiometric ratio for these two elements in hydroxyapatite, Ca10(PO4)6(OH)2. At 80 keV, the partial cross-section of phosphorus was 2.26 x 10(-20) and 2.68 x 10(-20) cm2/atom for poliovirus and hydroxyapatite, respectively, at 150 eV loss for a 15-eV energy window and an acceptance angle of 15 mrad. Under the same conditions the calcium cross-section was 0.49 x 10(-20) cm2/atom at 360 eV loss. The experimental values are slightly higher than the theoretical cross-sections calculated either by hydrogenic or Hartree-Slater approaches.

Calcium↗
PubMed1989

Immunoelectron microscopic diagnosis in nephropathology.

An immunogold postembedding method for the ultrastructural localization of immunoglobulin G (IgG), IgA, IgM, C3, fibrinogen, and kappa and lambda immunoglobulin light chains was established. The method was performed on surplus tissue from renal biopsies fixed in 2% glutaraldehyde and embedded in acrylic LR White resin. Fifteen cases were studied and the localization of antigen in the dense deposits in glomeruli compared with the immunofluorescence (IF) findings on the same cases. The results obtained by IF and immunoelectron microscopy (IEM) were comparable for IgG and IgA. In most instances, IgM and C3 were more intensely labeled by IF than IEM. Some discrepancies were noted for fibrinogen. It is postulated that these differences are related to a partial loss of antigenicity due to fixation or chemical reaction with the embedding medium. The advantage of IEM resides in localizing antigens in very small deposits seen in early stages of glomerulonephritis. The method can supplement IF in diagnostically difficult cases or be substituted for it when material for IF is not available.

Complement C3↗
PubMed1988

Cellular junctions in a spectrum of human malignant tumors.

Cellular junctions in tumors are often considered a hallmark of epithelial differentiation. However, junctions are also seen in tumors having a different differentiation. This observation prompted us to study cellular junctions in malignant nonepithelial tumors. We found a variety of cellular junctions in such tumors, although the majority were poorly formed. This observation is of importance for diagnostic purposes. We have also tried to clarify the nomenclature of cellular junctions as applied in tumor diagnosis by proposing a systematic categorization of terms in everyday use by pathologists and by referring more extensively to the term paired subplasmalemmal densities (PSD) for non-well-formed junctions.

Female↗
PubMed1988

Imaging of calcium in biological specimens: role of electron energy loss spectroscopy.

The regulation of intracytoplasmic calcium is an essential mechanism involved in many normal cytological functions. Disorders of calcium regulation are coupled to numerous pathological conditions. Calcium is such a universal participant that knowledge of its fine movements and sites of action is essential for the understanding of many biological phenomena at the cellular level. Techniques for the measurement of intracellular calcium have been dramatically improved, and we have now achieved great sensitivity to concentration changes as well as a very high time resolution. Recent advances in calcium research technology have concentrated on imaging methods permitting the visualization of calcium movements and localization of its cytoplasmic distribution. At the light microscopical level, it is now possible to trace the fluctuations of intracellular free calcium in a living cell, using sensitive calcium binding fluorescent indicators. Electron microscopic techniques are therefore necessary for the ultrastructural localization of cytoplasmic calcium stores. Electron energy loss spectroscopy is at present the most sensitive microanalytical mode in electron microscopy. It is capable of simultaneously producing high resolution images and elemental information. It therefore has application in calcium research if the specimens are prepared by an appropriate method. This review has two objectives: (1) To place electron energy loss imaging in its proper perspective in calcium research. (2) To suggest that freeze-dried embedded biological materials are appropriate for high resolution energy loss imaging of calcium.

Animals↗
PubMed1988

Electron energy loss spectroscopic imaging in biology.

One of the goals in biology is to relate the ultrastructure with the movement of elements to understand better physiological and pathophysiological mechanisms. Electron energy loss spectroscopy (EELS) imaging, which was developed in the last decade, appears to be an ideal technique to make such correlation. EELS takes advantage of the energy distribution of transmitted electrons which interacted with the specimen. All these electrons are collected and can be displayed as an energy loss spectrum for analytical purposes. Images can be produced from selected regions from the energy distribution allowing the mapping of specific elements. The main advantage of EELS imaging in biology is its spatial resolution of 0.5 nm or less and its great sensitivity allowing nearly a single atom detectability. The limitations reside essentially in specimen preparation. In order to obtain optimal results with EELS imaging, only very thin specimens can be used. This restricts the way biological specimens can be prepared. This is a real challenge for the analysis of diffusible elements. Other limitations reside in the difficulty of quantifying the results obtained. This is greatly due to the fact that theoretical considerations still have to be experimentally validated. The purpose of this review is not to repeat in length the principle of EELS but to emphasize its achievement in biology and to assess the present advantages and limitations. Also, as EELS imaging is still in its development phase, results already obtained are a strong indication that this technique has a great prospect in the analysis of dynamic biological processes.

Animals↗
PubMed1988

A carcinoid tumor of the stomach with features of a midgut tumor.

This report is, to our knowledge, the first of a gastric carcinoid tumor that, by electron microscopy, revealed pleomorphic neurosecretory granules similar to those found in carcinoid tumors arising from the midgut. On the basis of silver staining, this lesion would be classified as an argentaffin and argyrophil carcinoid tumor, of the type usually associated with midgut derivation. Immunostaining showed the presence of serotonin granules, and there was clinical evidence of intraoperative hyperserotoninemia. The lesion is believed to have arisen from foci of complete intestinal metaplasia, many of which were present in proximity to the site of the lesion and elsewhere in the stomach.

Adult↗
PubMed1988

Desmoplastic malignant melanoma. A clinicopathologic study of 14 cases.

Clinical and pathologic details in 14 cases of desmoplastic malignant melanoma were reviewed. The study group included ten men and four women with a median age of 58 years. Anatomic locations such as the head and neck area (four cases), limbs (five cases), and trunk (five cases) were involved with equal frequency. Follow-up information (median period, 4.6 years) was available for 12 patients, of whom four are alive and disease free, six have had local tumor recurrence, and two have died of their disease. Histologically, these lesions consisted of a malignant fibroblastic skin tumor intimately associated with a superficial melanoma (ten cases) or melanocytic dysplasia (four cases) that often extended deeply to the subcutaneous fat. Helpful diagnostic features included the presence of neurotropism, a lymphocytic infiltrate, and unusual patterns of triangular and periadnexal lamellar fibroplasia. Of the immunohistochemical markers employed, antisera to S100 protein and vimentin yielded the most consistent positive results. Immunostaining with NK1/C-3 (antimelanoma monoclonal antibody) was not helpful. Ultrastructural evidence of fibroblastic and schwannian differentiation was seen. We conclude that the altered morphologic melanomas is associated with a relatively favorable prognosis and believe that careful attention to light microscopic detail with immunohistochemical and electron microscopic assistance will elucidate the diagnosis in most cases.

Adolescent↗
PubMed1987

Intestinal mucosal mast cells in normal and nematode-infected rat intestines are in intimate contact with peptidergic nerves.

Inflammatory or allergic conditions, as well as situations where healing and repair processes occur, are characterized by the presence of increased numbers of mast cells. Previous work on the effect of neuropeptides on mast cell mediator release showed that only substance P caused such release from intestinal mucosal mast cells [Shanahan, F., Denburg, J. A., Fox, J., Bienenstock, J. & Befus, A. D. (1985) J. Immunol. 135, 1331-1337]. Accordingly, we investigated the microanatomical relationship between mast cells and enteric nerves in normal rat intestine and parasite-infected rat intestine, in which mucosal mast cell hyperplasia occurs. Combined immunohistochemistry for neuron-specific enolase and staining with alcian blue at pH 0.5 was employed on paraffin-embedded sections of normal and Nippostrongylus brasiliensis-infected rat jejunum. Sixty-seven percent of intestinal mucosal mast cells were touching subepithelial nerves, and an additional 20% were within 2 micron of nerves. Assessment of the proportion of the lamina propria occupied by mast cells (12.5%), the average mast cell area (121 +/- 28 microns 2), and the density of enteric nerves (one per 788 +/- 151 microns 2) suggested that the association was 5 times greater than would be expected by chance alone (P less than 0.0001). In consecutive sections, the nerves in contact with mast cells were also shown to contain substance P and/or calcitonin-gene-related peptide. Electron microscopy confirmed this association: 8% of the mast cells in infected rats exhibited membrane-membrane contact with unmyelinated axons containing 70- to 170-nm dense-core vesicles, and an additional 31% were situated less than 250 nm from nerves. Other mast cells appeared to embrace nerve bundles through the projection of lamellopodia. These data provide systematic quantitative evidence that a structural foundation for communication between the immune and nervous systems exists in the rat gastrointestinal tract.

Animals↗
PubMed1987

Solitary fibrous tumour of the pleura: an ultrastructural and immunohistochemical study.

Solitary fibrous tumour of the pleura is a benign neoplasm differing from diffuse pleural mesothelioma. It was originally thought to be a variant of mesothelioma because it consists of a spindle cell stroma associated with branching tubular structures lined by cuboidal cells. In this study of two cases the tubular structures were lined with ciliated and non-ciliated cuboidal cells. Ultrastructurally most of the non-ciliated cells had the features of type II pneumocytes, while the stromal cells had all the characteristics of fibroblasts. Immunohistochemical staining showed the epithelial cells to be positive for both keratin and carcinoembryonic antigen, whereas the stromal cells were negative. The findings support the theory that these tumours are fibroblastic in origin, and that the biphasic pattern is due to entrapment of non-neoplastic bronchiolar and alveolar epithelial cells.

Humans↗
PubMed1987

The role of mast cells in inflammatory processes: evidence for nerve/mast cell interactions.

In the rat, there is considerable evidence of mast cell/nerve interaction both in the normal and infected intestine. Between 67 and 87% of all mast cells in the intestinal lamina propria of rats infected 22-35 days earlier with Nippostrongylus brasiliensis were touching nerves. These membrane contacts were between subepithelial mast cells and nonmyelinated nerves containing substance P, calcitonin gene-related peptide and neurone specific enolase. 2.5S nerve growth factor (NGF) has a significant enhancement effect on antigen-induced histamine release without addition of phosphatidylserine, and the in vivo administration of NGF to rats causes both connective tissue and mucosal mast cells to dramatically increase in number. All of these effects are both dose dependent and NGF specific, as evidenced by inhibition with anti-NGF. 2.5S NGF also causes in vitro increase of colonies in methylcellulose cultures of human peripheral blood. The effects of NGF in this system are synergistic with other T cell-derived growth factors and relatively specific for metachromatic cell growth. These observations support the conclusions that nerves and mast cells may constantly communicate and provide a structural and conceptual framework whereby the central nervous system may communicate with inflammatory events.

Animals↗
PubMed1987

The value of morphometry in the ultrastructural diagnosis of Mycosis fungoides.

To assess the value of morphometry in the ultrastructural diagnosis of Mycosis Fungoides (MF), skin biopsy specimens from 43 patients with established MF and 28 with non-MF lymphoid skin infiltration were studied by transmission electron microscopy. Morphometrical measurements were done on the nuclei of the infiltrating lymphoid cells. The study showed that the nuclear contour index (NCI) taken alone has a very poor diagnostic value. A more reliable way to assess morphometrically the nucleus of MF cells is to combine two parameters: the nuclear surface area and the NCI, as proposed by McNutt and his group. Although the sensitivity of this method is only 43% (McNutt et al. obtained a sensitivity of 63%, analyzing a smaller number of patients), it surprisingly has a highly significant prognostic value. Most of the patients classified as positive by this method had a very aggressive course of their disease or died from it, while most of the patients who were considered as negative had an indolent course of disease or were at a stage of remission. It is suggested that other cellular expressions may be of importance in the recognition of MF cells. It is therefore proposed that, in combination with ultrastructural immunocytochemistry, such parameters be assessed. It is hoped that the results of such a study will determine the number of parameters necessary to better recognize MF cells, thus making early diagnosis of the disease possible.

Cell Nucleus↗
PubMed1987

Electron spectroscopic imaging.

Electron spectroscopic imaging (ESI) is a short term for electron energy loss spectroscopic imaging. ESI is to date the most sensitive electron microscopic analytical technique and has a spatial resolution of 0.5 nm and a mass resolution of less than 50 atoms. ESI takes advantage of filtered, inelastically scattered, transmitted electrons to form spectroscopic images. This analytical mode was developed by F. P. Ottensmeyer of the Ontario Cancer Institute in Toronto, Canada. Specimens to be analyzed by ESI should not exceed 30 nm in thickness so that multiple scattering of electrons is avoided. Isolated macromolecules constitute ideal specimens. For the analysis of diffusable elements, elaborate techniques involving quick-freezing, drying and embedded in plastic of the specimens have to be used. An example is given in which calcium was analyzed in the mitochondria of the convoluted proximal tubules in the rat kidney in normal and acute ischemic conditions. The example shows that calcium was not extracted during the preparation of the tissue. The high resolution of ESI allows the localization of calcium inside mitochondria. Experiments in progress using homogenous standards will soon render ESI entirely quantitative. It is concluded that ESI will become more and more important as a tool for the study of the pathogenesis of conditions in which modification of the distribution and concentration of elements are involved.

Animals↗
PubMed1987

Variation in physical and biological properties of solid gold sodium thiomalate on dissolution: an electron microscopic and energy dispersive spectroscopic study.

The dissolution of solid gold sodium thiomalate (GSTM) in water results in loss of yellow color. We studied the initial reaction on dissolution. It was associated with the disappearance of 2 absorption peaks on ultraviolet spectrum, one a well defined peak at 335 nm and the other a shoulder at 370 nm. This solution caused platelet aggregation and on transmission electron microscopy, dense gold containing particles measuring 125 nm are seen. Within 10 min of onset of dissolution, no gold containing particulate matter was detectable on electron microscopy. By 20 min, fibrillar particles measuring 40-150 nm appear. These resembled in general morphology and element composition the particles seen within aurosomes in platelets treated with Myochrysine (GSTM) and in synovium and other tissues by other workers. Our data elaborate on previous physical and chemical studies and correlate with morphological variations of gold containing particles at different phases. These variations in GSTM may be due to polymer size and/or structural change within the polymer. The biochemical significance of our data should provide better understanding of the biological effects of these gold thiol compounds in vivo.

Blood Platelets↗
PubMed1987

Improved preservation of cartilage extracellular matrix by freeze dried embedding.

A freeze dried embedding procedure is described and used to study the extracellular cartilage matrix of the epiphyseal growth plate. This method provides improved fine structural preservation of the extracellular matrix over conventional fixation and appears comparable to that attained by freeze substitution. The trabecular networks of expanded proteoglycan filaments are illustrated in stereo-images.

Animals↗
PubMed1986

The value of nuclear contour index in the diagnosis of mycosis fungoides. An assessment of current ultrastructural morphometric diagnostic criteria.

Skin biopsy specimens from 43 patients with established mycosis fungoides (MF) and 28 with non-MF lymphoid skin infiltrations were studied by transmission electron microscopy. The nuclear contour index (NCI) of infiltrating lymphoid cells was obtained by means of a Zeiss Videoplan computer and measuring tablet. Classification of the material into MF and non-MF groups was done according to the diagnostic criteria used by McNutt et al. (1980, 1981) and Meijer et al. (1980); this study evaluates the usefulness of these previously published criteria based on quantitative electron microscopy. Statistical analysis confirmed that the mean NCI (MNCI) of the lymphoid cells of patients with MF is significantly greater than that in patients with other lymphoid infiltrates (P less than 0.001). However, all published diagnostic criteria (McNutt et al., 1980, 1981, and Meijer et al., 1980) tested in the authors' larger patient population yielded lower sensitivity than has been reported. The diagnostic criteria based on values of MNCI, percentage of lymphoid cells with NCI greater than 7, and percentage of lymphoid cells with nuclear profile area of greater than 30 microns2 reported by McNutt et al. (1981) appear to be better than others, and provide the highest sensitivity rate, which is in the range of 44% to 47%. There were no false-positive findings. It was concluded that the use of ultrastructural morphometry according to the techniques and diagnostic criteria of McNutt et al. (1981) is useful in the diagnosis of MF.

Adolescent↗
PubMed1986

Electron microscopy of chronic eosinophilic pneumonia.

We have investigated two cases of chronic eosinophilic pneumonia using the electron microscope. The alveolar septa were thickened due to edema and an infiltrate of numerous mononuclear cells and eosinophils, with a few lymphocytes and occasional plasma cells. Macrophages were often located close to eosinophils and extracellular eosinophilic granules. Occasional eosinophilic granules were observed in the cytoplasm of mononuclear cells. The most striking finding was the presence of distinctive elongated, narrow, tubular inclusions in the cytoplasm of several of the mononuclear cells. These inclusions presented complex curved profiles which sometimes terminated in small, dilated, dense vesicles. Some of the narrow tubular sections of the inclusions presented a pentalaminar structure. Elsewhere, the tubular structures showed localized globular dilatations which contained granular material. Elongated strands of electron-dense material, identical to that forming the intracytoplasmic inclusions, were also located extracellularly, between adjacent mononuclear cells and between mononuclear cells and eosinophils. These inclusions are considered to be the product of phagocytosis of cellular debris and to be related to phagolysosomes rather than to Birbeck granules.

Adult↗
PubMed1985

Platelet fragments do not contribute to elevated levels of platelet associated IgG.

Most assays that measure platelet associated IgG (PAIgG) relate the IgG associated with the test platelets to the platelet count. This could lead to a systematic error if platelet fragments were present in the washed platelet sample but not counted. To address this issue, we studied platelets from patients with idiopathic thrombocytopenic purpura (ITP), thrombocytopenia complicating cardiopulmonary bypass, and laboratory synthesized platelet fragments (freeze-thawed) using electron microscopy. Scanning electron microscopic (SEM) examination of the platelet samples demonstrated appreciable numbers of fragments only in the freeze-thawed specimens. Yet, 'fragments' could be seen in all specimens using transmission electron microscopy (TEM). Most of these 'fragments' proved to be artefacts: we found that the ratio of 'fragments' to intact platelets observed in the TEM specimens was similar to the estimated ratio of 'fragments' to platelets that would have been generated had the specimens been sectioned at 90 degrees to the plane of the actual section. Platelets labelled with the membrane label 125I-iodosulfanilic acid were fragmented by repetitive freeze-thawing. Measurement of pellet radioactivity following washing indicated that the fragments were lost during the washing procedure. These studies indicate that elevated levels of platelet associated IgG in ITP do not represent artefacts due to contamination of the test platelets by platelet fragments.

Blood Platelets↗