PubMed Health⌕ Search

Biomedical subjects

P E McKeever

Publications and source records attributed to P E McKeever.

15 recordsLinked to original sources
PubMed1979

Scanning electron microscopy in the evaluation of neurosurgical neoplasms: a review of new approaches.

Present and potential applications of scanning electron microscopy (SEM) to the study of solid neoplasms, the lining of cysts, exfoliated cells, mineral deposits, and supporting tissues of the central nervous system (CNS) are discussed. Special features of the SEM image include a large field of view and depth of focus, high resolution, and a three-dimensional impression of surface topography. These features have contributed a clearer understanding of similarities between colloid cyst and olfactory epithelium. They demonstrated differences between glial and nonglial fibrils of selected CNS neoplasms. These features may ultimately enhance decisions, diagnosis, and study of neoplastic origins and spread within the CNS and cerebrospinal fluid. Special features of tissue examination by SEM include processing without the need of thin sections and elemental analysis by X-ray spectroscopy. These features have been applied to studies of calcium and thorium associated with meningiomas and a schwannoma.

Adenoma↗
PubMed1979

Murine plasma cells secreting more than one class of immunoglobulin. VI. Secretion of completely assembled IgG2b and IgA molecules with segregated heavy chains and free light chains by spontaneous myeloma SAMM 368 in culture.

The antigenic and molecular characteristics of the two immunoglobulins secreted by a single cell line of plasmacytoma SAMM 368 were analyzed by polyacrylamide gel electrophoresis of biosynthesized proteins. Adapted to continuous in vitro cultivation, this BALB/c plasmacytoma secretes at least 98% of its heavy chains as components of fully assembled and isotypically uniform IgG2b and IgA molecules. The IgA is secreted as monomers, dimers, and multimers with chemical properties typical of BALB/c myeloma IgA including disulfide bonded J chain and noncovalently bonded light chains. The noncovalently bonded light chains are monomers rather than dimers. Free light chains are also secreted. The ability to segregate heavy chains is attributed either to chemical, enzymatic, or compartmental regulatory factors operating within these plasma cells.

Animals↗
PubMed1979

Two spontaneous BALB/c lymphomas synthesize IgM: monomers and half molecules are isolated and characterized whereas another molecule resembles IgD.

Spontaneous lymphomas of BALB/c mice, both in vivo tumors and cell lines established in long term tissue cultures, were investigated for their ability to synthesize IgM by using radiolabeled amino acid precursors. Immunoglobulins manufactured by lymphomas K46 and L10A had the m.w. of monomeric IgM and IgM half molecule. Both of these molecules could be immunoprecipitated with class-specific anti-IgM but not anti-IgA or anti-IgG. When precipitated with polyvalent anti-Ig L10A synthesized monomeric immunoglobulins that migrated as two peaks in contrast to their single counterpart precipitated with anti-IgM. The second peak migrated in the region expected for IgD. Monomer and half molecules were composed of similar ratios of mu-chains to light chains linked by disulfide bonds. The mu2L2 monomer of these B cell lines migrated slightly slower in SDS PAGE than a mu2L2 secreted by a myeloma. Thus, these lymphomas synthesize immunoglobulins with the chemical and antigenic characteristics typical of monomeric membrane-attached IgM and IgM half molecules, plus a molecule resembling IgD on L10A only. Lymphoma assembly of monomeric IgM may follow the same initial biosynthetic sequence as myeloma assembly.

Animals↗
PubMed1978

Electron microscopy of peroxidase and acid phosphatase in leprous and uninfected armadillo macrophages: a macrophage subpopulation contains peroxisomes and lacks bacilli.

Lepromatous tissue from armadillos inoculated 24--36 months earlier with Mycobacterium leprae was obtained for electron microscopic studies. Cytochemically stained lepromas revealed a subpopulation of macrophages containing peroxisomes. These peroxidase reactive macrophages were not infected with bacilli. Acid phosphatase was present in macrophages and many of these were infected with bacilli and contained vacuoles and lipid globules. Within the membrane-bound vacuoles, acid phosphatase surrounded bacilli. However, the reaction product ended abruptly at a 15--40 millimicron thick zone of low electron density surrounding intact bacilli. Acid phosphatase was more intensely reactive and localized less precisely in heavily infected and vacuolated macrophages than in lightly and non-infected cells. The effectiveness of this bacillary barrier and the numerous infected macrophages with substantial acid phosphatase argue against the ability of acid phosphatase to protect host cells from leprosy bacilli. Evidence suggests a protective action of peroxidase or the rapid turnover of macrophages within lepromas. Granular and membranous debris were commonly seen within vacuoles of infected macrophages. A portion of the debris was ultrastructurally similar to bacillary matrix and was nonreactive for peroxidase and acid phosphatase. Following homogenization and centrifugation, similar materials banded with bacilli above 60% sucrose. Another portion of the debris was ultrastructurally similar to host lysosomal matrix and was reactive for acid phosphatase. Results support the concept of dual host and parasitic origins of the debris found in phagolysosomes of infected macrophages. Transparent, oval Epon defects remained eccentric to the majority of intact bacilli in centrifuged fractions. Apparently, an intrinsic property of leprosy produced these Epon defects.

Acid Phosphatase↗
PubMed1978

Characteristics of BALB/C T cell lymphomas grown as continuous in vitro lines.

Transplanted lymphomas (Thy 1.2+, Ig-) of BALB/c mice, induced by the injection of 1-ethyl-1-nitrosourea, were adapted for growth as in vitro lines to provide potential tools for investigation of T lymphocyte differentiation and functions. All these tissue culture lines maintained the same pattern of surface differentiation antigens (Ly, TL, and Thy-1 antigens) as they had expressed during in vivo passages: BALENTL 13 was Thy 1.2+, TL.2-, and Ly 1+2-. BALENTL 3, 4, 5, 6, 7, 8, and 14 were Thy 1.2+, TL.2+, and Ly 1-2+. P1798 and BALENTL 9 were Thy 1.2+, TL.2+, and Ly 1-2+. There were various levels of terminal transferase activity present among these T cell tumor lines. The range of variation was from 4.6 units/10(8) cells to 29.3 units/10(8) cells (normal thymocytes, 5.0 units/10(8) cells). This 6-fold variation in TdT activity was present even among those cell lines which were Ly 1-2+, TL+. Most cultures lines had chromosome numbers near 40 and generation times of 11 to 22 hr. There were no significant morphologic changes after the adaptation of these tumors in culture except an increase in cytoplasmic C-type virus particles.

Animals↗
PubMed1978

Lysosomal activity in experimental spinal cord trauma: an ultrastructural cytochemical evaluation.

The possible role of lysosomal activity in the early post-trauma phase of severe experimental spinal cord trauma was assessed utilizing an acid phosphatase cytochemical ultrastructural study. The results indicate that there is no evidence for lysosomal alteration prior to the development of cellular degeneration or necrosis. No diffuse cytoplasmic staining was observed. This study indicates that physical lysosomal injury resulting in release of hydrolases into spinal cord cells is not a tenable hypothesis as a primary initiating event in the development of spinal cord necrosis following trauma. However, the data are consistent with the general theory that lysosomal activity is important in the secondary degradation of cells following their being altered beyond recovery.

Acid Phosphatase↗
PubMed1978

Macrophages migration through the brain parenchyma to the perivascular space following particle ingestion.

Forty-eight rats received intracerebral injections of sterile colloidal carbon. At intervals between 10 minutes and 31 days after carbon injection, the rats were perfused with glutaraldehyde, and autopsies were performed. Between 10 minutes and 3 hours after injection, carbon particles were extracellular and located strictly within the needle track. During the first few days the carbon was ingested by macrophages. Initially absent, carbon-laden macrophages spread to the neuropil immediately surrounding the injection site at 7 to 31 days following injection. These carbon-laden macrophages frequently were elongated within the neuropil and resembled microglia. Carbon-laden macrophages eventually accumulated around local vessels and in perivascular spaces. Many macrophages containing carbon remained in the injection site at the longest sampling interval of 31 days. Results indicate two macrophage responses to colloidal carbon in the central nervous system: a) an indolent population remains in the injection site for at least 1 month and b) a second population of macrophages emigrates through the neuropil. They eventually surround local vessels and enter the perivascular space. The migrating macrophages offer an explanation for the peculiar perivascular cells in Krabbe's disease and may provide a link between the CNS parenchyma and immunocompetent cells.

Animals↗
PubMed1977

Immune complex receptors on cell surfaces. III. Topography of macrophage receptors demonstrated by new scanning electron microscopic peroxidase marker.

Receptors for immune complexes have been localized on rabbit alveolar macrophages with scanning electron microscopy by exposing the cells first to a soluble immune complex composed of horseradish peroxidase and antibody to horseradish peroxidase, and then incubating with a benzidine-containing substrate that yields crystalline reaction product. Receptors were visualized by this means as sites of attachment of laminated slender crystals that were easily distinguished from macrophage surface structures. Receptors appeared most abundant on cytoplasmic veils and pseudopods and in the perinuclear region of macrophages minimally spread over the coverslip. Further macrophage spreading was associated with lighter receptor staining.

Animals↗
PubMed1976

Central pontine myelinolysis. An ultrastructural and elemental study.

Central pontine myelinolysis (CPM) has been classified as a unique disease of myelin with a peculiar localization in the central pons. Although its etiology and pathogenesis are unknown, some have compared its histopathology to that of multiple sclerosis. Ultrastructural studies of suitably preserved tissue have been lacking. We have recently studied 3 cases of CPM, selectively immunostaining 2 cases and examining the fine structure and elemental composition of the third case obtained shortly after death. IgG could not be demonstrated within or around the lesions. The findings of an increased Na/K ratio and of intramyelinic vocuoles at the periphery of the lesion sjggest that the pathogenesis of CPM might include a phase of intramyelinic edema with subsequent rupture of the distended myelin sheaths. An increase in the permeability of the blood-brain barrier might represent a complicating factor. The spheroids in our case are primarily reactive in type and do not support pior light-microscopic interpretations of concomitant neuroaxonal dystrophy. The unexplained presence of tin within the lesion indicates a need for further study of this element in CPM.

Adult↗
PubMed1976

Immune complex receptors on cell surface. I. Ultrastructural demonstration of macrophages.

A method is described for ultrastructural localization of immune complex receptors on the surface of viable peritoneal exudate cells. The technique entails incubation with a soluble complex of horseradish peroxidase (HRP) and specific antibody to HRP at 4 degrees C followed by exposure to diaminobenzidine and processing for electron microscopy. The bound immune complexes were evident as focal deposits of HRP reaction product, adhering closely to the external surface of macrophages with an uninterrupted periodicity varying between 30 and 120 nm. Following incubation with an insoluble immune complex containing a higher proportion of antibody, receptor sites stained frequently, but large aggregates adhered to the cells. Rinsing cells after staining with soluble complexes partially displaced the bound immune complexes. Fixation prior to exposure to immune complexes largely eliminated the binding capacity of the immune complex receptors.

Animals↗
PubMed1976

Immune complex receptors on cell surfaces. II. Cytochemical evaluation of their abundance on different immune cells: distribution, uptake, and regeneration.

A recently developed method for ultrastructural demonstration of cell surface receptors for immune complexes is applied to evaluation of these receptors on various cell types. The method entailing incubation with a complex of horesradish peroxidase (HRP) and antibody to HRP (anti-HRP) disclosed dense foci indicative of immune complex receptors distributed at 30- to 120-mmu intervals over macrophage surfaces. Invaginations, loop-like evaginations, and pinocytotic vasicles stained prominently. The number of stained immune complex receptors averaged 200,000 per oil-induced macrophage and 120,000 per noninduced macrophage, as determined from counts of focal deposits in electron micrographs. Receptor periodicity on giant cells present in oil-induced exudates resembled that on macrophages, but the larger giant cells contained an estimated 1.5 million sites. Although receptor periodicity on eosinophils and neutrophils equaled that on macrophages, the staining was lighter and was interrupted by intervals of unstained membrane. Neutrophils averaged 28,000 and eosinophils 35,000 receptors per cell, whereas those lymphocytes with receptors averaged 3,500 per cell. Viable cells incubated with anti-HRP sequentially exhibited about half as many reactive sites as did cells incubated with immune complex. When warmed to 37 C, viable macrophages and eosinophils pinocytosed soluble immune complexes almost completely within 30 minutes and phagocytosed insoluble complexes more slowly. The endocytosed soluble immune complexes were sequestered within tubulovesicular structures in addition to the expected phagocytic vacuoles. Receptors appeared fully active on macrophages that were restained with soluble, cold immune complex after they had endocytosed immune complex in the course of a 30-minute warming interval.

Animals↗
PubMed1976

The cytochemical demonstration of intracellular immunoglobulin. In neoplasms of lymphoreticular tissue.

An immunoglobulin-enzyme bridge technique has been employed for the selective localization of immunoglobulin-producing cells in spleen, lymph nodes, and lymphoreticular tumors fixed highly for optimal immunocytochemistry or processed routinely for surgical diagnosis. Immunostaining for immunoglobulin was encountered consistently in the specially fixed tissues and was observed in some of the surgical specimens in areas where presumably fixation was satisfactory. Many, but not all, of the tumor cells in histocytic lymphoma (reticulum cell sarcoma) of spleen and of brain stained for IgG, but none evidenced reactivity for IgM or IgA. In Hodgkin's tumors, the prevalence of IgG-reactive stromal immunocytes in or between tumor areas was greatest in the nodular sclerosing form of the disease, abundant in mixed cellular, and least in lymphocyte-predominant and lymphocyte-depleted types. Immunocytes showing reactivity for IgG greatly exceeded those staining for IgM or IgA. Hodgkin's tumor cells immunostained frequently for IgG, infrequently for IgM, not at all for IgA, and in one instance, stained for k but not for lambda light chains. Individual tumor cells failed to stain for more than one type of Ig or light chain. The proportion of Ig reactive vs. unstained tumor cells correlated with the prevalence of immunocytes in the different Hodgkin's categories. Reed-Sternberg cells differed in their fine structure in ways which possibly correspond with the presence or absence of Ig shown at the light microscope level. Tumor cells in Hodgkin's disease and reticulum cell sarcoma also disclosed argyrophilia and strong staining indicative of ribonucleic acid with a Schiff-methylene blue procedure.

Antibody-Producing Cells↗