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Biomedical subjects

T Hoffman

Publications and source records attributed to T Hoffman.

At least 91 records · Page 5Linked to original sources
PubMed1986

Suppression of B cell immunity to DNP by serotherapy with monoclonal anti-DNP antibodies. Effect of the treatment schedule on the magnitude of specific suppression and its duration.

The effect of prior administration of anti-DNP (N-[2,4-dinitrophenyl]-B-alanylglycylglycine) monoclonal antibodies on the humoral immune response of BALB/c mice was examined. One-time administration of a "cocktail" of two anti-DNP monoclonals resulted in suppression of the IgM anti-DNP response for one week after challenge but not longer. Maximal suppression of anti-DNP IgM plaque-forming cells was achieved by administration of antibody 1-2 weeks before challenge with DNP. Maximal suppression of serum IgM antibody was seen by administration of antibody 2-3 weeks before challenge with antigen. Following one-time administration of suppressive monoclonal antibody, the serum IgG antibody response to DNP was suppressed beginning 2 weeks after immunization and remained so for up to 241 days despite continual booster injections of antigen. Although most effective suppression of the humoral anti-DNP response was seen in animals receiving their single dose of suppressive antibody 2 weeks before first exposure to antigen, suppression of the IgG response was evident at all intervals examined up to 232 days in mice given monoclonal antibody between 0.1 day and 30 days before antigen, but not at earlier times. These findings suggest that regulatory networks, rather than the masking of antigenic determinants by passively administered antibody, play a role in antibody-mediated immunoregulation. They may be of use in designing strategies for optimizing immunosuppression protocols in clinical studies.

Animals↗
PubMed1985

Alteration in the membrane fatty acid composition of human lymphocytes and cultured transformed cells induced by interferon.

The effects of interferon (IFN) treatment on the lipid composition of human peripheral blood lymphocytes or transformed cell line cells were investigated. The major phospholipid classes of lymphocytes as analyzed by 2-dimensional TLC and quantified by phosphorous content were phosphatidylcholine (PC, 43%) and phosphatidylethanolamine (PE, 28%), along with phosphatidylserine (9%) and phosphatidylinositol (8%). The membrane-impermeant reagent, trinitrobenzenesulfonate was used to covalently label cell surface PE. Fatty acid (FA) composition, determined by gas-liquid chromatography, showed a distinct pattern in each lipid class, with a predominance of 16 and 18 carbon fatty acids (FA) in PC and PE respectively. Arachidonic acid (20:4) and, to a lesser extent, docosahexanoic acid (22:6) were predominant in PE. The degree of unsaturation in each class, expressed as the ratio between unsaturated and saturated FA (U/S), was higher in PE (1.72) than in derivatized trinitrophenyl cell surface PE (TNP-PE, 0.57) or PC (0.64). Treatment with IFN resulted in an increased U/S ratio in cell surface PE (1.10) but not in other PE species (1.46). A small increase in unsaturation (0.88) was also observed in PC. Most of the increase in TNP-PE U/S was accounted for by an increase in 20:4 and a concomitant decrease in 18:0. These alterations were observed in the absence of quantitative change in the principal phospholipid classes or in the FA composition of the total lipid extract. In K562, a transformed cell line with characteristics of the erythromyeloid lineage, PE was found to be the most saturated lipid class with a predominance of 18:0. In PC, 16:0 was most abundant. Among unsaturated FA, 18:1 predominated in all lipid classes studied. Treatment with natural IFN alpha for 30 hr generally resulted in a decrease in saturated FA and an increase in unsaturated FA, which was most marked in PE. The U/S ratio in PE was highest in K562 cells during the time of maximal cell proliferation as assessed by tritiated thymidine incorporation. TNP-PE simultaneously decreased. Daudi cells, a B-lymphoblastoid cell line, demonstrated changes in FA composition of lipids with decreased saturated and monoenoic FA after IFN treatment, whereas DIF3 (a clone selected for lack of sensitivity to IFN) showed no change. These studies document changes in membrane FA composition of lymphocytes treated with IFN and correlate IFN-induced changes in transformed cell line FA with effects on proliferation. They further show the existence of a transverse molecular species asymmetry of PE in the plasma membrane of these cells which is altered after IFN treatment.

Cell Line↗
PubMed1985

The effect of low osmotic potential on nitrite reduction in intact spinach chloroplasts.

The effect of water stress (reduced osmotic potential) on photosynthetic nitrite reduction was investigated using intact, isolated spinach (Spinacia oleracea) chloroplasts. Nitrite-dependent O(2) evolution was inhibited 39% at -29.5 bars osmotic potential, relative to a control at -11 bars. In the presence of an uncoupler of photophosphorylation this inhibition was not seen. Reduced osmotic potential did not inhibit either methyl viologen reduction or photosynthetic O(2) reduction. These results indicate that an inhibition of electron transport to ferredoxin cannot account for the observed inhibition of nitrite-dependent O(2) evolution. In vitro assay of nitrite reductase activity showed that the interaction of the enzyme with nitrite was not affected by changes in the concentrations of ions or molecules that might be caused by water stress conditions. These results indicate that the most likely site for the effect of water stress on chloroplastic nitrite reduction is the interaction of ferredoxin with nitrite reductase.

Journal Article↗
PubMed1984

Characterization of purified cryopreserved human monocyte function in assays of superoxide production, accessory cell function, chemotaxis, and in fluorescent cell sorter analysis.

The ability to use highly purified cryopreserved human monocytes in various in vitro assays has a number of practical and theoretical advantages, including convenience and the potential for enhanced reproducibility. Large numbers (up to 1 X 10(9)) human monocytes can be isolated from a single donor in a purified suspension state, by a combination of leukapheresis and counter-current centrifugal elutriation (CCE) technologies. Following short- and long-term periods of cryopreservation, the viability and phagocytic function of these CCE-purified monocytes was unimpaired. Cryopreserved monocytes were similar to fresh cells in their ability to release superoxide anion (O2-), although unstimulated and stimulated O2- release values tended to increase slightly following weeks to months of cryopreservation. In contrast, even short-term cryopreservation diminished both the random migration and chemotactic responses of human monocytes; however, cryopreserved monocytes could be employed in this assay provided the calculated chemotactic ratio (chemotactic migration/spontaneous migration) was used. Cryopreserved monocytes demonstrate 70% of fresh monocyte accessory cell function in pokeweed mitogen-induced lymphocyte proliferation assays. When the binding of OKT3, OKM1, anti-DR, and fluoresceinated pokeweed mitogen to monocytes was analyzed in the fluorescence activator cell sorter (FACS), cryopreserved and fresh monocytes displayed a similar pattern of membrane reactivity.

Chemotaxis, Leukocyte↗
PubMed1984

Differentiation of a human monocyte-like cell line by (2'-5') oligoisoadenylate.

Treatment of a human monocyte-like cell line (U-937) by (2'-5')ApApA, the 5' dephosphorylated product of (2'-5')oligo-isoadenylate [oligo(A)] synthetase, an interferon-induced enzyme, was able to induce differentiation, mimicking the effect of interferon treatment. Treatment of U-937 cells with (2'-5')ApApA resulted in morphologic changes, new (monocyte-associated) membrane antigen expression, and acquisition of the capacity to mediate antibody-dependent cellular cytotoxicity (ADCC). (2'-5')ApA and (3'-5')ApApA were without effect. A myeloid cell line (HL-60) which differentiates in response to other agents, but not to alpha-interferon, was not able to differentiate in response to (2'-5')ApApA, despite the ability of interferon to induce (2'-5')oligo (A) synthetase.

Antibody-Dependent Cell Cytotoxicity↗
PubMed1984

Inhibition of tumor cell line alkaline phosphatase by human peripheral blood monocytes. Correlation with growth inhibitory activity.

Alkaline phosphatase (AP) activity in intact Ag8 cells was measured by a colorimetric assay in which spectrophotometer readings were obtained directly through wells of microtiter plates using a Multiskan ELISA reader. The wide difference between enzymatic activity observed in cells of this cell line and human peripheral blood monocytes permitted an assessment of inhibition of cell line growth in the presence of plastic-adherent peripheral blood cells. Comparison at 24 h of incubation of enzymatic measurements with those obtained using 3H-thymidine uptake showed comparable results, although values obtained with the enzyme were generally lower. Similarly, direct comparison of results obtained by the enzyme-based method showed good correlation with the number of viable tumor cells remaining in culture. Inhibition of AP activity was observed earlier than inhibition of 3H-thymidine incorporation, reaching its peak after 10 h of incubation. This technique has potential application for other enzyme systems and provides a new tool for analyzing mechanisms whereby effector cells are able to control proliferation of transformed cells.

Alkaline Phosphatase↗
PubMed1984

Activation of the oxidative burst in human monocytes is associated with inhibition of methionine-dependent methylation of neutral lipids and phospholipids.

Chemotaxis and generation of the oxidative burst by phagocytes are among the biological functions thought to require methylation reaction(s) for their expression. The present study investigated the effect of different stimuli of the oxidative burst on lipid methylation by human elutriated monocytes as measured by methyl group incorporation from [methyl-3H]methionine into both phospholipid and neutral lipid extracts. Normal monocytes, incubated at 37 degrees C for 1 h with 2 microM methionine, incorporated 10.2-fmol/10(6) cells and 73.6-fmol/10(6) cells of methyl groups into neutral lipids and phospholipids, respectively. Stimulators of the respiratory burst, such as the chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine, the tumor promoter, 12-O-tetradecanoyl phorbol-13-acetate, and the calcium ionophore, A23187, decreased the incorporation of methyl groups into both neutral lipids and phospholipids in a similar manner. Increasing the concentration of methionine in the medium reversed or attenuated the inhibition achieved at lower levels. An inverse relationship existed between the degree of methylation and the extent of stimulation of the oxidative burst, measured as superoxide anion (O-2) release. Stimulated monocytes oxidized methionine to methionine sulfoxide (which cannot act as a methyl-donor), and this was dependent on activation of the respiratory burst. Elimination of the accumulated methionine sulfoxide by replacement of the medium or by prevention of extracellular methionine oxidation by catalase did not effectively restore the normal level of methylation in stimulated cells, and the reduced methylation was not primarily related to a defective methionine uptake by stimulated monocytes. These data suggest that intracellular events related to activation of the respiratory burst are responsible for the decreased lipid methylation in stimulated cells, possibly by their leading to intracellular formation of methionine sulfoxide and by their limiting the availability of methyl-donor. This mechanism may be of potential relevance for the expression of biological functions where methionine-dependent reactions are involved.

Calcimycin↗
PubMed1983

Identification of ubiquinone-50 as the major methylated nonpolar lipid in human monocytes. Regulation of its biosynthesis via methionine-dependent pathways and relationship to superoxide production.

Human blood monocytes incorporated the methyl group from methionine into their neutral lipids. The major methylated product was identified as ubiquinone-50 in monocytes, lymphocytes, and a variety of human tumor cell lines by several analytical procedures including TLC or high performance liquid chromatography and as ubiquinone-45 in a mouse tumor cell line. Up to three methyl groups were shown to be derived from methionine by mass spectrometry. The rate of synthesis of ubiquinone-50 by monocytes as assessed by measuring labeled methyl group incorporation was shown to be linear over a 3-h period. Degradation of ubiquinone proceeded slowly; 80% of the labeled compound persisted after 18 h. The dependence of ubiquinone-50 synthesis upon methionine concentration was established in monocytes, with an estimated apparent Km for methionine of about 20 microM. The tumor promoter, tetradecanoate phorbol acetate, a potent stimulator of superoxide anion (O2-) production in phagocytic cells, inhibited ubiquinone-50 synthesis at nanomolar concentrations in monocytes, but not in lymphocytes, under conditions where oxidation of methionine takes place. Degradation of the labeled ubiquinone was unaffected. Formylmethionylleucyl-phenylalanine, a chemoattractant peptide which stimulates O2- production in phagocytic cells, also inhibited ubiquinone-50 synthesis. The degree of inhibition by either stimulus was increased when the methionine concentration in the medium was low. These findings demonstrate that in human monocytes ubiquinone-50 biosynthesis is regulable and that methionine concentration modulates both its rate of synthesis and the inhibitory effects of two stimuli of O2- production.

Animals↗
PubMed1983

Differentiation of a histiocytic lymphoma cell line by lipomodulin, a phospholipase inhibitory protein.

When U 937 cells, a human histiocytic lymphoma cell line, were cultured with purified lipomodulin for 3 days, morphological and functional differentiation was induced as detected by microscopical examination of Giemsa stained smears, expression of mature monocyte antigen, and antibody dependent cellular cytotoxicity tests. Essentially similar differentiation was observed by the treatment with dexamethasone for 6 days and this differentiation by dexamethasone was blocked by monoclonal anti-lipomodulin antibody. Furthermore, the synthesis of immunoprecipitable lipomodulin in these cells was induced by dexamethasone treatment. These results, taken together, suggest that the induction of lipomodulin synthesis might be the primary event in dexamethasone-induced cellular differentiation of U 937 cells.

Annexins↗
PubMed1983

Comparative clinical trial of imipenem-cilastatin (N-formimidoyl-thienamycin-dehydropeptidase inhibitor) and cefazolin.

One hundred and eighty-six patients were randomized to receive either imipenem-cilastatin (94 patients) or cefazolin (92 patients). Imipenem-cilastatin (250 mg 6 hourly iv) or cefazolin (1000 mg 6 hourly iv) were given for 5 to 14 days. An assessment of efficacy could be made in 141 patients, 72 of whom received imipenem-cilastatin and 69 of whom received cefazolin. Reasons for exclusion included failure to isolate a causative organism (20 patients), less than 5 days of treatment (16 patients), inadequate follow up or culture (5 patients), concomitant administration of another antibiotic (1 patient), and resistance to the study drug (3 patients, all of whom were in the cefazolin group). No isolates resistant to imipenem were found. Sites of infection included skin and soft tissue (91 patients), lower respiratory tract (21 patients), urinary tract (16 patients), bone and joint (8 patients), primary bacteraemia (4 patients) and miscellaneous other sites (1 patient). Bacteria isolated included Staphylococcus aureus (65 patients), group A streptococcus (42 patients), Escherichia coli (17 patients), other Gram-negative bacilli (37 patients), anaerobic bacteria (34 patients) and other bacteria. Imipenem was more active than cephalothin in vitro against pathogenic bacteria isolated from evaluable patients. Cure or improvement was seen in 68 of the 72 imipenem-cilastatin patients (94%) and in 68 of the 69 cefazolin patients (99%). Relatively few abnormal laboratory tests and adverse experiences were noted, and there were no differences in this between the two treatment groups. We concluded that imipenem-cilastatin is safe at the dose used. It is as effective as cefazolin in mild to moderate infections caused by common pathogens.(ABSTRACT TRUNCATED AT 250 WORDS)

Adolescent↗
PubMed1983

Spontaneous cytotoxicity by monocyte-enriched subpopulations of human peripheral blood mononuclear cells against human or mouse anchorage-dependent tumour cell lines. Contribution of NK-like cells.

Human peripheral blood mononuclear cells (PBMNC) were found to be cytotoxic for mouse or human anchorage-dependent target cell lines in a 48-72 h [125I]iododeoxyuridine (IUDR) release assay. Unfractionated, adherent or nonadherent cells had significant levels of cytotoxicity, as did cells fractionated according to size into 'lymphocytes' or 'monocytes' by elutriation. Intermediate size cells, not enriched for monocytes, had high levels of cytotoxicity. In all fractions tested, including adherent populations, some cells with the morphology of large granular cells were observed. Treatment of all fractions with interferon (IFLrA, a purified, recombinant alpha-IFN) boosted cytotoxicity against four target cells lines. Treatment with lymphokines containing putative 'macrophage-activating factor' (MAF) also enhanced cytotoxicity in fractions depleted of monocytes. Culture in fetal bovine serum enhanced cytotoxicity mainly in unfractionated and nonadherent PBMNC. These experiments indicated that NK-like cells can be appreciable contaminants in elutriator-purified monocyte-enriched or adherent cell populations and thereby contribute to observed cytotoxicity, particularly after pretreatment with IFN or other stimulatory factors.

Animals↗
PubMed1983

Characterization by monoclonal antibodies of the cytotoxic effector cells in human peripheral blood mononuclear cells reactive against anchorage-dependent tumour cell lines.

The effector cells for spontaneous cytotoxicity against anchorage-dependent human or mouse tumour cell lines in a 72-h iododeoxyuridine-release assay by normal human peripheral blood cells (PBMNC) or monocyte-enriched fractions were analysed by the use of monoclonal antibodies. PBMNC or adherent or elutriated monocyte-enriched populations of PBMNC were depleted of monoclonal antibody-reactive cells by complement-dependent lysis or separated into monoclonal-antibody-positive or -negative subsets by an indirect rosetting technique followed by Ficoll-Hypaque density gradient separation. The experimental data indicated that in both PBMNC and monocyte-enriched populations, an appreciable proportion of the effector cells with cytolytic activity against adherent human or mouse tumour target cells were positive with B73.1.1 (an antibody with a high degree of selectivity for natural killer (NK) cells), B43.4.1 (or OKM1), and with OKT11a (an antibody recognizing the receptors for sheep erythrocytes), and had the morphology of large granular cells, which have previously been shown to mediate NK activity. These effector cells were mostly negative for BRL.1, BRL.2, B52.1.1, B44.1.1, B13.4.1 and DR antigens, unlike classical monocytes. Some cells which are cytotoxic for the adherent mouse, SV-40-transformed kidney tumour line, TU-5, may bear B52.1.1 or other monocyte-like antigens. Taken together, these results indicate that, in monocyte-enriched populations, both NK cells and monocytes have cytotoxic effector activity against various human and mouse adherent target cell lines.

Animals↗