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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Human T-T hybridomas were developed as a strategy for obtaining lymphokines that alter T-lymphocyte motility. Mitogen-stimulated human T lymphocytes were fused with cells of the human CEM lymphoma line and the supernatants derived from these fusion products were assessed for chemoattractant activity in a modified Boyden chamber assay. Supernatants from hybridoma 41B2 enhanced lymphocyte migration to 198 +/- 13% (mean +/- SEM) of control. Characterization by Sephadex G-100 molecular sieve chromatography revealed a single peak of chemoattractant activity corresponding to a molecular weight (MW) of 56,000. This activity eluted from a Sephadex QAE anion-exchange column at 4-6 mS. Subsequent isoelectric focusing in sucrose revealed an isoelectric point of 9.0-9.2. Fractions with activity after sequential molecular sieve and anion-exchange chromatography were concentrated, radiolabeled with 125I, and subjected to sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Autoradiography revealed a band which corresponded to a MW of 14,000 (representing four similar monomeric chains) and to the region from which chemoattractant activity could be detected in eluates from slices of unstained gels run in parallel. The biological activity of this hybridoma-derived lymphocyte chemoattractant was abolished by treatment with trypsin and neuraminidase but was unaffected by heating to 56 degrees C. We conclude that certain human T-T-cell hybridomas constitutively elaborate a lymphocyte chemoattractant that appears to be physicochemically identical to a previously described human lymphokine, lymphocyte chemoattractant factor.
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PMID:A human T-T-cell hybridoma-derived lymphocyte chemoattractant factor. 309 96

IM-9 cultured human lymphocytes were treated with N-linked glycosylation inhibitors, N-linked oligosaccharide processing inhibitors, or neuraminidase to study the effect of glycosylation modification on human growth hormone binding and molecular weight of surface hGH receptor. One mg/l tunicamycin and 20 mmol/l glucosamine decreased 125I-hGH binding to the cells to 46.3 +/- 2.4% (mean +/- SEM) and 21.9 +/- 0.2% of the controls, respectively. The hGH binding was 33.0 +/- 18.4% of the control value in the cells treated with monensin. The inhibition of binding was due to a decrease in the hGH receptor number without any affinity changes in these cells. Neither 1 mg/l swainsonine nor 100 mg/l castanospermine had any effect on the hGH binding. On the other hand, 125I-hGH binding to neuraminidase-treated cells was significantly enhanced with accompanying affinity changes. When 125I-hGH was cross-linked to IM-9 cells, there were no differences in the molecular weight of hGH receptor complexes (140 K) between untreated cells and cells treated with tunicamycin, glucosamine, monensin, or castanospermine. However, the 128 K hGH-receptor complex appeared in swainsonine-treated cells; this complex was sensitive to endoglycosidase H. These data show that the altered carbohydrate moiety changed hGH binding and the size of surface hGH receptor and suggest that glycosylation of receptor is important for the binding of hGH and for its physiological action.
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PMID:Effects of glycosylation inhibitors on human growth hormone receptor in cultured human lymphocytes. 314 7

Normal human B cell proliferation is controlled by various immunoregulatory signals including the T cell-derived lymphokine B cell growth factor (BCGF). The role of BCGF in the regulation of malignant B cell proliferation is unclear. Therefore, we studied the proliferative response of purified chronic lymphocytic leukemia (CLL) B cells to BCGF. For all CLL patients studied, CLL B cells showed a decreased proliferative response as compared with control B cells for BCGF-induced B cell proliferation (patient 291 +/- 59 cpm v control 3,942 +/- 622, mean +/- SEM). This impaired proliferative response appeared to be intrinsic to CLL B cells since it was not corrected by incubation with increasing concentrations of BCGF. Attainment of normal B cell responsiveness to BCGF requires the processing of an initial activation signal which results in the expression of cell surface receptors for BCGF. Increasing concentrations of the B cell activation signal (the F(ab')2 fragment of goat anti-human mu chain) did not improve CLL B cell responsiveness to BCGF. Three-day activated CLL B cells compared with activated control B cells demonstrated a marked impairment in their ability to absorb out the BCGF activity present in the BCGF preparation (BCGF activity absorbed out, patient 12.8% v control 53%). Pretreatment of CLL B cells with neuraminidase failed to improve either the proliferative response to BCGF or the expression of cell surface receptors for BCGF by the CLL B cells. This study suggests that the impaired responsiveness to BCGF by CLL B cells is the result of impaired expression of cell surface receptors for BCGF when CLL B cells are exposed to activation signals.
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PMID:Impaired expression of cell surface receptors for B cell growth factor by chronic lymphocytic leukemia B cells. 348 60

Differential localization of glycoconjugates was detected on microvilli and microridges of the intact cell surface of frog pronephric tumor cells in tissue culture. Alcian blue and Alcian blue/PAS staining showed a heavy concentration of dye limited to the unique short microvilli and extensive microridges of the tumor cells as previously seen with SEM (Tweedell and Williams 1976). Staining was absent or greatly reduced on microvilli of the normal pronephric cell surface. Previous exposure of each kind of cells to neuraminidase or extraction by mild hydrolysis removed the active staining sites but Alcian blue uptake was unaffected by prior digestion with testicular hyaluronidase. Fluorescein isothiocyanate (FITC) bound wheat germ agglutinin (WGA) produced a similar pattern of fluorescence on the microvilli of the tumor cells and a limited distribution on the normal cells. Digestion with neuraminidase preferentially removed but did not completely eliminate the surface binding of WGA on both the normal and tumor cells. Exposure of tumor cell monolayers to FITC bound limulin, a lectin specific for sialic acid, also produced an intense surface fluorescence on the microvilli and ridges of tumor cells. Prior treatment with neuraminidase prevented the surface fluorescence but not internal binding. Normal pronephric cells gave sparse surface fluorescence but extensive internal binding. Each procedure indicates a preferential localization of complex carbohydrates, including sialic acid, on the unique microvilli of the tumor cells. Concurrent assays for sialic acid recovered from the tumor cells indicated that lectin bound surface sialic acid was removable with neuraminidase.
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PMID:Localization of glycoconjugates on the surfaces of pronephric tumor cells in vitro. 618 38

Lymphocyte populations extracted and separated from hemal nodes (HN) and peripheral blood of 20 male healthy bovines were characterized by surface markers and the rosette-forming test. After treatment with FITC- or peroxidase-conjugated antibovine IgG, about 22% of cells from HN and peripheral blood showed superficial fluorescence (B cells) and about 13% were able to form "E rosettes" (T cells) with sheep erythrocytes pre-treated with neuraminidase. Nearly equal percentages were obtained from peripheral blood lymphocytes. On the basis of the data shown, we can conclude that the function of HN is, at least in healthy animals, analogous with that of lymph nodes. In this study we also used the SEM to evaluate the possibility of classifying the lymphoid cells as B and T lymphocytes on the basis of their surface morphology. Some authors have stated that B and T lymphocytes have a rough and smooth surface, respectively. In our experience, however, because of cells with a moderate number of surface microvilli exist, this method used on its own is not suitable for lymphocyte identification.
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PMID:Identification of lymphocytes extracted from bovine hemal nodes. 698 50

Because the terminal sialic acid of several glycoproteins regulates their intravascular half-life, and because asialo platelets have a shortened survival, we postulated that asialo platelets might affect the basal rate of thrombopoiesis. Thrombopoiesis was measured by the incorporation of intravenous 75Se-selenomethionine (a cohort label) into circulating rabbit platelets. Each animal acted as its own control. In one control group, saline was injected intravenously once daily for two days. 75Se-selenomethionine was then injected, 15 microCi/kgm on day 2 and platelets harvested on day 5 for measurement of specific activity (S.A.), cpm/10(7) platelets. The animals were allowed to rest for two weeks, and the experiment repeated. The ratio of the second SA over the first SA was utilized as the stimulation index. When saline was injected the second time, the stimulation index was 1.22 +/- 0.07 (SEM) in eight animals. Asialo platelets were prepared by incubating washed platelets with neuraminidase, 2 units/ml for 60 min. Injection of 2-4 X 10(9) asialo platelets/kgm (the second time) resulted in a stim. index of 2.08 +/- 0.23 (P less than 0.001) in 11 animals. Similar results were obtained with 1 mM DFP and neuraminidase (12 animals). Negative results were obtained when 11 rabbits were injected with a comparable number of untreated washed platelets, stim. index 1.07 +/- 0.13; when 10 rabbits were injected with sonicated asialo platelets, stim. index 1.10 +/- 0.12; or when four rabbits were injected with platelets treated with chymotrypsin, 3 mg/ml for 45 min, stim. index 0.80 +/- 0.04. We conclude that asialo intact platelets stimulate megakaryocytes to produce more platelets. It is suggested that the basal stimulus to thrombopoiesis may be regulated by desialidated older platelets.
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PMID:Asialo platelets enhance thrombopoiesis. 724 77

Although there is a growing body of information available regarding restoration of hematopoiesis with peripheral blood stem cell (PBSC) autografts, few studies have explored this procedure using allografts. In this study with healthy donors, we investigated the feasibility of a protocol for mobilizing PBSC using recombinant human granulocyte colony-stimulating factor (G-CSF) and subsequent bulk depletion of T cells from apheresis-harvested cells. Nine informed healthy donors were given G-CSF subcutaneously at two different dosing schedules (5 micrograms/kg/d in five donors and 2 micrograms/kg/d in four) for 5 consecutive days, and serial changes in blood components, including hematopoietic progenitor cells, were monitored. After 5 days of stimulation with G-CSF, PBSCs were collected by apheresis, and yields were compared. The number of white blood cells (WBC) reached a plateau level on either day 2 (5 micrograms) or 3 (2 micrograms), but the numbers of red blood cells and platelets were not affected. Circulating colony-forming unit-granulocyte/macrophage (CFU-GM) levels started to increase 1 or 2 days after the increase in the WBC count. By performing a 3L apheresis, the number of CFU-GM harvested was 4.6 +/- 3.3 x 10(6) (mean +/- standard error of the mean [SEM]) in the 5-micrograms group and 1.8 +/- 0.7 x 10(6) in the 2-micrograms group. Different procedures for depleting T cells, including the use of L-phenylalanine methyl ester (PME) and flasks coated with anti-CD5/CD8 monoclonal antibodies or neuraminidase-treated sheep red blood cells (SRBC), were also tested on the harvested cells. We found that cell lysis with PME before selective removal of T cells was very effective in reducing the number of cells that required further processing and was suitable for routine use. However, our current procedure resulted in unsatisfactory depletion of T cells (99.5% removal) while retaining hematopoietic progenitor cells (7.5% recovery). Further research is required in this area.
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PMID:Cell processing protocol for allogeneic peripheral blood stem cells mobilized by granulocyte colony-stimulating factor. 752 Mar 92

Serum neuraminidase (NA, sialidase) activity has been demonstrated in acute poststreptococcal glomerulonephritis (APSGN) and implicated in the pathogenesis of the disease. Recent investigations show that neuraminidase-treated leukocytes accumulate preferentially in kidneys; therefore, we were interested in knowing if desialized cells infiltrate the kidney in APSGN. We first tested the capacity of peanut agglutinin lectin (PNA) to detect injected NA-treated leukocytes in the kidney of rats. NA-treated leukocytes were transfused and desialized cells were identified with fluorescein-conjugated peanut lectin (FITC-PNA) in renal tissue. PNA positive cells were identified in rat kidneys 3 hours after injection (glomeruli: 1.67 +/- 0.19 cells/g.c.s.; interstitium: 0.50 +/- 0.12 cells/int). Sections from available renal biopsy material of APSGN (n = 11), other glomerulonephritis (n = 28) and normal kidneys (n = 5) were double-stained with FITC-PNA and with monoclonal antibody to the CD11b molecule, which is expressed on polymorphonuclear and monocytes the main types of infiltrating cells during APSGN. Desialized (FITC-PNA positive) cells were found in the glomeruli (2.17 +/- SEM 0.22 cells per glomerular cross section, g.c.s.) and interstitium (0.61 +/- 0.15 cells per 0.0625 mm2, int) in all biopsies of APSGN. Only in 2 of 28 other glomerulonephritis showed desialized cells. More than 80% of the PNA positive cells in APSGN expressed the CD11b molecule and the infiltration was more intense in early biopsies. In conclusion, desialized leukocytes represent a significant part of the inflammatory infiltrate in APSGN. This finding gives support for a role of NA in the disease and provides clinical validation for a mechanism of renal cellular infiltration suggested by experimental observations.
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PMID:Histological evidence of neuraminidase involvement in acute nephritis: desialized leukocytes infiltrate the kidney in acute post-streptococcal glomerulonephritis. 912 87

The microenvironment near the apical membrane of MDCK cells was studied by quantitation of the fluorescence of wheat germ agglutinin attached to fluorescein (WGA). WGA was shown to bind to sialic acid residues attached to galactose at the alpha-2,3 position in the glycocalyx on the apical membrane. Young MDCK cells (5-8 days after splitting) showed a patchy distribution of WGA at stable sites that returned to the same locations after removal of sialic acid residues by neuraminidase treatment. Other lectins also showed stable binding to patches on the apical membrane of young cells. The ratio of WGA fluorescence emission at two excitation wavelengths was used to measure near-membrane pH. The near-membrane pH was markedly acidic to the pH 7.4 bathing solution in both young and older cells (13-21 days after splitting). Patches on the apical membrane of young cells exhibited a range of near-membrane pH values with a mean +/- SEM of 6.86 +/- 0.04 (n = 121) while the near-membrane pH of older cells was 6.61 +/- 0.04 (n = 120) with a uniform WGA distribution. We conclude that the distribution of lectin binding sites in young cells reflects the underlying nonrandom location of membrane proteins in the apical membrane and that nonuniformities in the pH of patches may indicate regional differences in membrane acid-base transport as well as in the location of charged sugars in the glycocalyx.
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PMID:The apical membrane glycocalyx of MDCK cells. 1088 25

B-lineage acute leukaemia cells are generally resistant to CD95-mediated apoptosis. In this report, the CD95-resistant B-leukaemia lines SEM, RS4;11, and REH were used to investigate the mechanisms of resistance to CD95-signalling. We found that interferon-gamma (IFN-gamma) treatment increased the presence of high molecular weight forms of CD95 in these cells as judged by Western analysis, and treatment of protein extracts with Peptide: N -glycosidase F indicated that the majority of high molecular weight forms were due to N-linked glycosylation. Treatment of whole cells with neuraminidase from Vibrio cholerae substantially reduced the relative molecular mass of CD95 observed after IFN-gamma treatment and partially sensitized the three leukaemia lines to CD95-mediated death. To further characterize the different steps of oligosaccharide processing that may regulate CD95 signalling, the leukaemic cells were treated with IFN-gamma and the glycosidase inhibitors castanospermine, 1-deoxymannojirimycin (DMM), and swainsonine. Treatment with DMM, a mannosidase inhibitor, efficiently reduced the appearance of high molecular weight forms of CD95 after IFN-gamma treatment, and sensitized SEM and REH cells to CD95-mediated death. However, the IFN-gamma-induced increases of CD95 on the cell surface were not altered by treatment with any of the glycosidase inhibitors, suggesting that the generation of complex oligosaccharide structures is not required for trafficking of CD95, but may instead be used as a mechanism of partially blocking CD95 signalling in these cells. In conclusion, IFN-gamma treatment of the B-lineage leukaemia lines provides a novel, inducible system for the further characterization of post-translational modifications involved in modulating sensitivity to CD95-signalling.
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PMID:Interferon-gamma increases the expression of glycosylated CD95 in B-leukemic cells: an inducible model to study the role of glycosylation in CD95-signalling and trafficking. 1209 25


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