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Biomedical subjects

L F Eng

Publications and source records attributed to L F Eng.

At least 127 records · Page 7Linked to original sources
PubMed1979

Pleomorphic xanthoastrocytoma: a distinctive meningocerebral glioma of young subjects with relatively favorable prognosis. A study of 12 cases.

Twelve cases of a distinctive form of supratentorial astrocytoma occurring in young subjects (ages 7 to 25) are reported. The tumors were superficial and involved the leptomeninges extensively. The tumor cells display marked pleomorphism, including bizarre giant cells and a number of mitotic figures, but no necrosis. Many contain large amounts of lipid in their cytoplasm and are surrounded by reticulin fibers, thus simulating a mesenchymal tumor. For these reasons, some examples of this tumor have been previously interpreted to represent meningocerebral fibrous xanthomas. Immunoperoxidase technique performed in nine of the twelve cases has, however, established the presence of glial fibrillary acidic protein in the tumor cells, which are therefore considered to be astrocytic. By electron microscopy many tumor cells are surrounded by basal laminae, accounting for the abundant reticulin network demonstrable in silver preparations. Since subpial astrocytes are known to be partly covered by a basal lamina, it is likely that they are the cells of origin for this neoplasm. In contrast to its pleomorphic cytology, the biological behavior of this tumor appears to be relatively favorable, and long survival times (up to 25 years) have been recorded in some cases. (These tumors are distinct from intracranial fibrous xanthomas of mesenchymal derivation. Cells of the latter are negative on GFAP stain.)

Adolescent↗
PubMed1978

The role of glial fibrillary acidic protein in the diagnosis of central nervous system tumors.

Eighty glial and non-glial brain tumors have been studied to date using an immunologically specific and highly sensitive method of staining GFA protein which is applicable to formalin fixed and paraffin embedded tissue. Eight of these cases have been described and illustrated in some detail. GFA protein was present in all astrocytes and astrocytomas studied and in a proportion of ependymal cells and ependymomas. Some tumor cells have been demonstrated by this method to be glial despite the complete lack of blue fibrillar staining with PTAH and the absence of all morphological similarity to glial cells. In such cases the demonstration of GFA protein by this method has been valuable in establishing a diagnosis. In addition to its diagnostic value in specific cases, the method promises to shed light on unsolved problems of tumor cytogenesis.

Astrocytes↗
PubMed1978

Immunohistochemical localization of choline acetyltransferase in rabbit spinal cord and cerebellum.

Guinea pig antiserum specific for purified bovine choline acetyltransferase has been shown to cross-react with rabbit enzyme. We used the peroxidase-antiperoxidase immunohistochemical method to demonstrate the localization of choline acetyltransferase in formalin-fixed and paraffin-embedded sections of rabbit spinal cord and cerebellum. In the spinal cord, in agreement with our and others' previous results using immunofluorescent techniques, choline acetyltransferase was found in the cell bodies of the ventral horn motor neurons. In the cerebellum, choline acetyltransferase was localized exclusively in the mossy fibers and the glomeruli of the cerebellar folia. The immunohistochemical findings in the cerebellum reveal the morphological detail of cholinergic axons and their terminals. The results are consistent with published biochemical data on the cerebellar distribution of choline acetyltransferase.

Animals↗
PubMed1978

Clearance of myelin basic protein from blood of normal and EAE rabbits.

The rate of clearance of porcine myelin basic protein (MBP) from plasma of rabbits was determined following intravenous injection of 20 mg MBP. The MBP level in the plasma was measured by a 2-site immunoradiometric assay with specific antibody to guinea pig MBP produced in rabbits. Plasma MBP-antibody levels were determined by competitive binding radioimmune assay (RIA). Unsensitized and those sensitized with complete Freund's adjuvant (CFA), with porcine MBP in CFA, and with whole porcine spinal cord in CFA were studied. Unsensitized and CFA sensitized rabbits exhibited maximum MBP levels in the plasma within two minutes after injection with rapid decrease to undetectable levels in one hour. Thirty-nine of the unsensitized (control) rabbits exhibited normal, rapid clearance and no subsequent physical signs of EAE while one of the control rabbits exhibited a slightly retarded clearance rate. Histologic examination of autopsy tissues from the control group revealed that five rabbits showed lesions which could be attributed to Encephalitozoan cuniculi or Toxoplasma and one rabbit autopsied 65 days after clearance had minimal EAE lesions. Rabbits sensitized with MBP exhibited a retarded rate of clearance at the acute stage of EAE and following recovery. Rabbits sensitized with whole spinal cord in CFA also exhibited a retarded rate of MBP clearance. Anti (MBP) antibodies were detected in the plasma of all rabbits which exhibited a retarded rate of MBP clearance. Significant rates of retardation were not detected until approximately three weeks after sensitization with CFA-MBP or CFA-spinal cord. While MBP antibody levels in most animals were not detected by the immunodiffusion technique, antibodies were demonstrated by RIA. The 20 mg MBP given intravenously is probably in great antigen excess and conducive to the formation of soluble MBP-anti (MBP) complexes in the blood.

Animals↗
PubMed1977

Effects of primary antiserum dilution on staining of "antigenrich" tissues with the peroxidase antiperoxidase technique.

The effect of primary antiserum dilution on staining results with the peroxidase antiperoxidase method were investigated using frozen sections of perfused rat cerebellum and optic nerve. Results comparable to formalin fixed and paraffin embedded tissue were attainable only when low antiserum concentrations were used. Optimal staining of antigen rich tissue, such as frozen sections, with the peroxidase antiperoxidase method required low antiserum concentrations apparently to minimize the binding of both antigen-binding fragments of the bridging antibody to the tissue bound antiserum. It appears that low antiserum concentration insures that sufficient bridge antibody molecules will be only singly bound and thus free to attach the peroxidase antiperoxidase complex.

Animals↗
PubMed1977

Tumor-associated immunoglobulins in pulmonary carcinoma.

In view of the uncertainty of location and significance of immunoglobulin in tumors found by elution or rosette formation (as reported in the literature), the presence of IgG, IgM, and IgA in human carcinoma of the lung was studied by means of the peroxidase-antiperoxidase method. Surgically obtained specimens from patients with known survival times were used in this study. Membranous as well as cytoplasmic location of IgG was demonstrated more frequently than was that of IgA or IgM. The number of tumor cells carrying immunoglobulin varied greatly, even within a given case. Albumin could be demonstrated in tumor cells in 10 of 20 specimens, but there was poor correlation with immunoglobuin. In some instances, only the necrotic part of the tumor or the stroma was immunoreactive. The results are discussed and suggest that Fc receptors are not involved in the binding of immunoglobin by pulmonary carcinoma cells.

Adenocarcinoma↗
PubMed1976

The protein composition of bovine myelin-free axons.

The proteins of axons prepared from myelinated axons and isolated as myelin-free entities were separated by sodium dodecyl sulfate polyacrylamide electrophoresis and found to consist of more than 10 different molecular weight species. The molecular weights range from 13 000 to over 200 000 with a prominent protein of molecular weight 47 000. The amino acid composition of the seven major proteins showed that the protein with a molecular weigt of 47 000 is distinct from all the other proteins analyzed. A group of three low molecular weight proteins have amino acid compositions which are similar to each other as do a group of three high molecular weight proteins although the two groups are distinctly different from each other and the major axonal protein. Histones, DNA, myelin basic protein and glycoprotein were absent from the proteins but neurotubule protein was present as indicated by cochicine binding activity in the axonal preparations. The cellular origin of these proteins and their relationship to other central nervous system proteins are discussed.

Amino Acids↗
PubMed1976

The topographical distribution of S-100 and GFA proteins in the adult rat brain: an immunohistochemical study using horseradish peroxidase-labelled antibodies.

The cytological and topographical distribution of S-100 and glial fibrillary acidic (GFA) proteins in the adult rat brain has been compared using the horseradish peroxidase-labelled antibody technique. Both proteins are present in astrocytes and structures composed of astrocytic processes, namely the glial limitans and the perivascular membranes, but the cytological localization varies between the two proteins. S-100 is found in the nucleus and cytoplasm whereas GFA protein is confined to the cytoplasm. Neither is found in neurons, but S-100 is present in some oligodendroglia, suggesting a general regulatory role in glia. Although GFA protein in present in both protoplasmic and fibrous astrocytes, it is more prominent in the latter, confirming its association with astrocytic filaments.

Animals↗
PubMed1976

Human brain in tissue culture. Part. 5. Identification of glial cells by immunofluorescence.

Glial fibrillary acidic (GFA) protein was demonstrated by immunofluorescence in both primary and long-term cultures of adult human brain cells explanted from normal, neoplastic and non-neoplastic CNS diseases, and in mouse brain cells subcultivated in vitro. GFA protein was present in the cytoplasm of at least 4 distinct cell types and persisted throughout the finite lifetime of brain cell cultures.

Brain↗