Myasthenia gravis three years after thymectomy: immunological studies.
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Adult↗
Biomedical subjects
Z Malik
Publications and source records attributed to Z Malik.
Effect of interferon on the formation and release of intracellular virions in NIH/3T3 cells chronically infected with Moloney murine leukemia virus.
Using transmission electron microscopy, we demonstrate in this study the existence of intracellular Moloney murine leukemia virus particles in cytoplasmic vacuoles of chronically infected NIH/3T3 cells. Interferon (IFN) treatment for 48 h resulted in a 3-fold higher accumulation of these vacuolar virions. Intracellular virions and their accumulation in IFN-treated cells could also be shown by radioactive labeling of the cells for 48 h and isolation of labeled virus particles from the cytoplasmic fraction of the cells by banding in sucrose gradient. These virions contained typical viral RNA, proteins and glycoproteins, as determined by gel-electrophoresis. Despite their higher accumulation, the formation rate of the intracellular virions, as measured by their pulse labeling for 1 h with S35-methionine, was found to be remarkably lower in IFN-treated cells. In order to elucidate this discrepancy, we followed the kinetics of the intracellular and extracellular virus appearance. We found that the inhibitory effect of IFN on the release of virus particles to the culture medium was much stronger than its effect on the formation of the intracellular virions. This finding can explain the accumulation of intracellular virus particles in IFN-treated cells despite their reduced formation rate.
Animals↗
Distribution of sialic acid in human sperm membranes.
Sialic acid was estimated both chemically in populations of heads and tails of spermatozoa from normospermic human seminal fluid and by transmission electron microscopy, using a specific labeling technique. The results of both procedures show that sialic acid is located exclusively in the head plasma membrane and in the acrosomal membranes. It is suggested that localization of sialic acid close to that reported for neuraminidase in sperm might be of importance in the fertilization process.
Acrosome↗
Haemin affects platelet aggregation and lymphocyte mitogenicity in whole blood incubations.
The effect of haemin on platelet aggregation induced by epinephrine, ADP, collagen and arachidonic acid was examined, as well as on lymphocyte mitogenicity induced by phytohaemagglutinin (PHA). The receptor mediated platelet inducers, such as epinephrine and ADP were enhanced to maximal aggregation capacity by exogenous haemin, whereas non-receptor inducers, i.e. collagen and arachidonic acid, showed a marked decrease of platelet aggregation. The results indicate the involvement of haemin in receptor mediated platelet activation. PHA-induced lymphocytes treated with haemin showed a reduced rate of 3H-thymidine incorporation. Inhibition of lymphocyte mitogenic activity was dose-dependent on haemin concentration. Ultrastructural localization of haemin binding sites was performed by the osmiophilic reaction of benzidine. Haemin was shown to bind to the cell membrane and to the granule membrane of the platelets. The lymphocyte membrane was in practice masked by a layer of haemin.
Adenosine Diphosphate↗
Hemin stimulating effect on colony formation of leukemic and bone marrow cells.
The hemin enhancing activity on colony formation of leukemic and normal bone-marrow (BM) cells is described. The colony growth of Friend erythroleukemic cells (FL) and mastocytoma cells (M) was markedly enhanced. On the other hand, myeloid leukemic cells (P) and normal bone-marrow cells (BM) were only slightly affected. Inhibition of colony formation was observed with lymphoid leukemic cells (L). For M and BM cells, the horse serum could be replaced by BSA with preservation of hemin enhancing activity.
Animals↗
Cell membrane maturation of Friend erythroleukemic cells and tocopherol-dependent erythropoietin effect: a scanning electron microscopic study.
Typical morphological features of surface structural alterations during Friend cells differentiation are described. Scanning electron microscopy (SEM) revealed that DMSO induction switched on cell alteration of the proerythroblast-like cells, possessing microvilli projections on cell membrane with some ruffles, to an advanced stage with a blebby surface. This was followed by the formation of a pear-like polarized cell separated into two zones by a narrow cytoplasmic bridge at the equatorial plane. The polarized cells showed a smooth surface and tended to disconnect into two unequal cells. The villous leukemic erythroblast has negatively charged sialic acid residues on the glycocalyx, available for latex hydrazide probe binding, while the blebby and polarized cells lack it. Tocopherol added to culture medium of DMSO-induced erythroleukemic cells prevented the formation of blebs and the polarization phenomena, without affecting hemoglobin synthesis. The tocopherol-treated cells contain available negative charges for latex hydrazide binding similar to uninduced Friend cells. Erythropoietin potentiated a repolarization ability and morphological alteration capacity to the tocopherol-treated cells and this was accompanied by a loss of glycocalyx-negative charges. At these growth conditions erythyropoietin induced a dose-dependent proliferation effect.
Animals↗
Biochemical analysis and electron microscopic study on intracellular virions in NIH/3T3 mouse cells chronically infected with Moloney murine leukaemia virus: effect of interferon.
Radioactively labelled virus particles of intracellular origin were isolated from the cytoplasmic fraction of disrupted NIH/3T3 cells chronically infected with Moloney murine leukaemia virus [NIH/3T3 (MLV)]. Interferon (IFN) treatment for 48 h, which arrested more than 90% of virus release, resulted in a remarkable accumulation of these intracellular virions. However, no major effect of such treatment was apparent on their structural properties. Transmission electron microscopic examination revealed that these intracellular virions were located within cytoplasmic vacuoles. IFN treatment resulted in a considerable increase in the number of virus-containing vacuoles, as well as the total number of vacuolar virions. It seems that IFN inhibits the final release of vacuolar virions from the cells, thus leading to their intracellular accumulation.
Cytoplasm↗
The effects of photoactivated protoporphyrin on reticulocyte membranes, intracellular activities and hemoglobin recipitation.
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Animals↗
Ultrastructure of rabbit endosalpinx and glycoprotein pattern of the oviduct fluid in the presence of copper intrauterine devices.
Oviduct fluid was collected from 24 mature female rabbits in estrus fitted with a copper intrauterine device (IUD) in one of the uterine horns by laparotomy and examined for total sugar and protein content. The percentage of total sugar in the dry protein-containing material from the experimental side was 7.3 compared to 5.2 from the control side. The percentage of total protein was 67.0% of the total dry material from the experimental side, compared to 77.7% in the control side. Cellulose acetate electrophoresis confirmed these findings, demonstrating an increase in the strength of the periodic acid-Schiff stain bands of the glycoproteins from the copper IUD side and a weaker Ponceau-S stain of the protein bands. The ampullary-isthmic area and the uterotubal junction of both oviducts were examined with the scanning electron microscope. The secretory and ciliary cells on the copper IUD side were damaged in these two areas. These changes can be attributed to the presence and action of the copper ions in the oviduct milieu.
Animals↗
Unoccupied binding sites for oestrogen in nuclei of a breast tumour cell line (MCF-7).
1. A method to measure both occupied and unoccupied oestrogen receptors directly in the crude nuclear fraction of the MCF-7 cells was developed. The receptors had high affinity for oestradiol (Kd approx. 0.7 nM) and binding specificity characteristics of oestrogen receptors. 2. A substantial amount of the unoccupied receptors were found in the crude nuclear fraction. 3. Several experiments excluded the possibility that the unoccupied nuclear receptor might be a cytoplasmic contaminant. (a) Multiple extractions with Tris buffer released about 75% of the total receptor content, leaving the rest unextractable in the crude nuclear fraction. (b) Nuclei purified by centrifugation through 1.8M-sucrose and treatment with 0.7% Triton X-100, or by centrifugation through 50% glycerol with 0.1% Triton X-100 contained similar amounts of unoccupied receptors to that found in the crude nuclear fraction. (c) In cells cultured during 5 days after preconfluency a 3-fold increase in the amount of unoccupied cytoplasmic receptors occurred, whereas the amount of unoccupied nuclear receptors did not change significantly and conversely in cells exposed to increasing concentrations of oestradiol the unoccupied cytoplasmic receptor was continuously depleted but no considerable change in the unoccupied nuclear receptor was found.
Binding Sites↗
Lectin-bearing protoplasts of Pseudomonas aeruginosa induce capping in human peripheral blood lymphocytes.
The redistribution of surface membrane receptors and cap formation by pseudomonas aeruginosa lectins (Ps-GAL, which binds D-galactose, and Ps-MAN, which binds D-mannose and L-fucose) was studied in human peripheral blood lymphocytes by scanning electron microscopy. When Ps-GAL and Ps-MAN-bearing protoplasts of Pseudomonas aeruginosa were incubated with lymphocytes, cap formation was revealed by the accumulation of protoplasts at one pole of the lymphocyte. No adherence or capping was observed when intact Pseudomonas aeruginosa cells were used. Pretreatment of the lymphocytes by papain or neuraminidase did not enhance the capping. No capping or adherence of protoplasts to lymphocytes was observed in the presence of D-galactose, while addition of D-mannose had no effect. The inhibitory effect of D-galactose on the adherence and capping in human peripheral lymphocytes by Pseudomonas aeruginosa protoplasts suggests that the Ps-GAL lectin is responsible for both phenomena.
Galectins↗
Destruction of erythroleukemia, myelocytic leukemia and Burkitt lymphoma cells by photoactivated protoporphyrin.
The effect of protoporphyrin on erythroid, myeloid and lymphoid leukemic cells and their destruction induced by the photoactivated porphyrin was studied. Friend erythroleukemic cells (FL) and myelocytic leukemic cells (ML) accumulated protoporphyrin in a cap or patch-like pattern observed by fluorescence microscopy. Photoactivated protoporphyrin induced the appearance of "holes" on the cell membrane demonstrated by scanning electron microscopy. On the other hand, Burkitt lymphoma (BL) and mastocytoma (MS) cells accumulated porphyrin intracellularly around the nuclear envelope and as circular profiles, respectively. Photoactivated protoporphyrin induced development of multiple blebs on the cell membrane, and even complete cell destruction. Cytotoxicity of protoporphyrin at short-term incubation periods was determined by [3H]thymidine and [3H]uridine incorporation. Protoporphyrin, unexposed to light, reduced the incorporation of both precursors only to a moderate extent. On the other hand, porphyrin-treated cells exposed to light showed complete inhibition of RNA and DNA synthesis. Long-term exposure of ML and BL cells to porphyrin in the dark induced a nearly 50% inhibition of RNA and DNA synthesis. Although the cytotoxic effect of protoporphyrin in the dark was lower than that of photoactivated porphyrin, this may possess a potential activity in vivo even without illumination.
Animals↗
Cross-linking of hemoglobin and inhibition of globin synthesis in reticulocytes induced by photoactivated protoporphyrin.
The photoactivated protoporphyrin effect on reticulocyte globin synthesizing capability, cross-linking of intracellular hemoglobin and the cell ultrastructural alterations was studied. Low doses up to 15 microM of protoporphyrin markedly inhibited the globin synthesis and decreased amino acid uptake while no lytic effect or ultrastructural deformations were detected by scanning electron microscopy and transmission electron microscopy. On the other hand, at high doses of protoporphyrin, up to 60 microM, the globin synthesis was totally stopped, and the intracellular hemoglobin leaked out. The photodynamic effect induced cross-linking of hemoglobin into condensed spheres which captured numerous polyribosomes. The end-product of protoporphyrin activity was a closed ghost with a rigid membrane containing only cross-linked hemoglobin spheres closely related to the membrane.
Animals↗
Cytotoxic effect of hemin and protoporphyrin on chronic lymphocytic leukemia lymphocytes.
Hemin and protoporphyrin exerted a cytotoxic effect on lymphocytes from 24 patients with chronic lymphocytic leukemia (CLL). The porphyrins inhibited protein and RNA synthesis in a dose dependent pattern. Exposure of leukemic cells to 15 microM hemin for 10 min reduced leucine incorporation to less than 20%, and 78% of the cells were freely permeable to trypan blue. Hemin at 0.17 microM had to be bound to 10(6) cells in the dark to produce this killing effect. On the other hand, the control lymphocytes from 20 healthy subjects were relatively resistant to the hemin effect, and cell damage was reversible. Fetal calf serum (FCS) protected most leukemic lymphocytes from prophyrin toxicity. The combination of human hemoglobin with free protoporphyrin showed a synergistic toxicity, and this combination was the most potent inhibitor of protein synthesis in the presence of serum. 55Fe-hemin was preferentially bound to leukemic lymphocytes, and the binding site of protoporphyrin was observed to be on the cell surface membrane. The hemin quenching effect of diphenyl hexatriene (DPH) stained cell fluorescence indicated that hemin was apparently bound to the lipid layer of the outer membrane. Scanning electron microscopy (SEM) of hemin treated cells revealed an initial development of membranal blebs, followed by total destruction of the cell surface membrane. Transmission electron microscopy (TEM) of the treated cells showed a profound damage in the cytoplasma and nucleus. Control lymphocytes treated by hemin appeared relatively undamaged and free of membranal blebs.
Cell Membrane Permeability↗
5-Aminolevulinic acid stimulation of porphyrin and hemoglobin synthesis by uninduced Friend erythroleukemic cells.
Porphyrin synthesis and iron accumulation was stimulated by exogenous 5-aminolevulinic acid (ALA) in uninduced Friend erythroleukemic cells (FELC). Uroporphyrin and protoporphyrin were the major intermediated precursors produced. All porphyrin types were conjugated to protein insoluble cellular components and could be extracted only by methanol sulfuric acid esterification. Heme content of the uninduced FELC was increased 6-fold in the presence of 5 x 10(-4) M ALA. As a consequence, the synthesis of the minor murine hemoglobin component was preferentially induced, an effect similar to that expressed by exogenous hemin. Addition of exogenous ALA to 0.5% DMSO-induced cells increased total hemoglobin synthesis with a higher efficiency of the minor hemoglobin. The endogenous synthesis of porphyrin from exogenous ALA was markedly reduced by hemin. Uroporphyrin, coproporphyrin, protoporphyrin and heme were equally repressed, indicating an inhibitory effect of hemin on ALA dehydrase and urosynthetase activities. In addition, hemin repressed [3H]leucine incorporation into protein by uninduced cells. Incubation of uninduced cells in culture medium without serum in the presence of hemin blocked their protein synthesis activity, whereas addition of serum exerted a protective effect on living FELC.
Aminolevulinic Acid↗
Water permeability changes studied by 17O nuclear magnetic resonance during differentiation of Friend leukemia cells.
Water permeability of Friend leukemia cells was studied by 17O nuclear magnetic resonance during differentiation induced by dimethyl sulfoxide (Me2SO). While in noninduced cells water permeability was essentially constant during the growth period, in the Me2SO-induced cells there were two distinct periods at which the water permeability was increased by at least an order of magnitude. These periods correspond to approximately one doubling time and 6 days of growth. This change in water permeability is not due to direct interaction of Me2SO with the membrane but must be ascribed to structural changes in the membrane during the course of differentiation.
Animals↗
Regulation of hemoglobin synthesis, iron metabolism, and maturation of Friend leukemic cells by 5-amino levulinic acid and hemin.
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Aminolevulinic Acid↗
Ultrastructural and functional studied on the lymphocytes of a patient with chronic lymphocytic leukaemia and nuclear extrusion.
The cells of a patient with chronic lymphocytic leukaemia (CLL) showed a peculiar phenomenon of nuclear blebbing and nuclear extrusion, observed by transmission (TEM) and scanning (SEM) electron microscopy. Protein synthesis of the lymphocytes was 3 times higher than that of cells of other 3 patients with CLL, but was lower than the synthesis of cells from a patient with acute lymphoblastic leukaemia (ALL). Similar results were observed when RNA synthesizing activity of the cells was examined. On the other hand, thymidine incorporation proceeded in a similar rate in the patient's and the ALL lymphocytes, whereas in those CLL patients it was merely detected. The morphological findings and the synthesizing activities of the cells suggest that the patient's disease represents an intermediate form between CLL and ALL.
Cell Nucleus↗