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Biomedical subjects

R M Bennett

Publications and source records attributed to R M Bennett.

At least 109 records · Page 6Linked to original sources
PubMed1983

Lactoferrin binds to cell membrane DNA. Association of surface DNA with an enriched population of B cells and monocytes.

The binding of human 125I-labeled lactoferrin (LF) to a population of adherent mononuclear cells (ADMC) and nonrosetting lymphocytes (E-) was abolished by prior treatment of the cells with deoxyribonuclease (DNase), but not ribonuclease (RNase). When DNase-treated ADMC were incubated with exogenous DNA, the binding of 125I-LF was restored. Enzymatic digestion with other enzymes, trypsin, phospholipase D, and neuraminidase, did not significantly influence 125I-LF binding. Saturable binding of LF at 0 degrees C was demonstrated for both E- and ADMC, with equilibrium dissociated constants of 0.76 x 10(-6) M and 1.8 x 10(-6) M, respectively. E- cells bound 2.5 x 10(7) and ADMC bound 3.3 x 10(7) molecules of Lf at saturation. Cell membranes were isolated from ADMC, E- and E+ and reacted with 125I-labeled LF; significant binding was only seen with ADMC and E-. Prior treatment of the membranes with DNase abolished the binding. Immunofluorescence studies indicated that a population of ADMC and E-, but not E+, exhibited a peripheral staining pattern for LF. Prior treatment of ADMC and E- with DNase abolished the surface immunofluorescence. This study provides evidence that cell membrane DNA acts as a binding site for exogenous LF. This is a novel role for DNA that has not been previously reported. Furthermore, it points to a basic difference between E+ cells vs. ADMC and E- cells in respect to their possession of cell surface DNA.

B-Lymphocytes↗
PubMed1983

Dimethyl sulfoxide does not suppress an experimental model of arthritis in rabbits.

We studied the ability of dimethyl sulfoxide (DMSO) to influence the course of an experimental model of inflammatory arthritis. A Dumonde-Glynn model of arthritis was induced in both tibio-femoral joints of 10 rabbits, using ovalbumin as the immunogen. At one month post induction of the arthritis, the right tibio-femoral joint of 6 animals was treated for 3 months with topical 80% DMSO--1 g/kg body weight applied to the shaved skin for 5 out of 7 days each week. In another 4 animals, the right tibio-femoral joint was injected with 0.5 ml of 80% DMSO at one month post induction of the arthritis. Joint radiographs were taken at monthly intervals. The rabbits were sequentially sacrificed and the joint tissues evaluated by a blinded observer. Neither the topical DMSO nor the intraarticular DMSO treated joints showed any favorable responses to therapy; in fact the topically treated joints exhibited somewhat more inflammatory and destructive changes than the untreated joints. However the repeated injection of DMSO into normal joints did not, of itself, produce any deleterious effects. This study indicates a need to assess more thoroughly a possible deleterious effect of DMSO on the course of untreated inflammatory arthritis.

Administration, Topical↗
PubMed1982

Lactoferrin interacts with deoxyribonucleic acid: a preferential reactivity with double-stranded DNA and dissociation of DNA-anti-DNA complexes.

LF was found to bind to deoxyribonucleic acid as assessed by immunofluorescence studies on cell nuclei, affinity chromatography of DNA on immobilized LF, and gel chromatography of an LF-DNA reaction mixture. LF immobilized on Sepharose 4-B was reacted with 125I-labeled DNA in both its double-stranded and single-stranded configurations; dsDNA eluted with a 0.69M NaCl buffer, whereas ssDNA eluted with a 0.25M NaCl buffer. Additional evidence for a preferential reactivity with dsDNA was provided by the enzymatic treatment of preformed dsDNA-LF and ssDNA-LF complexes with S1 endonuclease, and DNAse 1--DNase digestion alone liberated free LF. The interaction of LF with DNA partially inhibited the binding of anti-DNA antibodies from patients with SLE, as assayed in a standard Farr assay. Furthermore, DNA-anti-DNA (labeled with 125I-IgG) complexes could be dispersed in vitro by the addition of LF. It is hypothesized that the release of LF by neutrophils chemotactically attracted to DNA-anti-DNA complexes may act as a feedback loop to modulate the inflammatory response in SLE.

Antigen-Antibody Complex↗
PubMed1982

Feedback regulation of granulopoiesis: polymerization of lactoferrin abrogates its ability to inhibit CSA production.

Neutrophil extracts were prepared from the peripheral blood of 40 normal volunteers and tested for their ability to inhibit CSA production by mononuclear leukocytes. Highly dilute neutrophil extracts inhibited CSA production/release, while extracts selectively depleted of lactoferrin by antibody affinity chromatography did not. In addition, higher concentrations of neutrophil extracts and higher doses of lactoferrin (10(-9)-10(-6) M) failed to inhibit CSA production/release. We found no evidence of CSA or CSA-enhancing factors in either our lactoferrin or our neutrophil extracts. However, using gel chromatography and rate zonal density sedimentation, we noted that lactoferrin undergoes concentration-dependent polymerization at 10(-9)-10(-10) M in tissue culture medium and that while monomeric lactoferrin effectively inhibits CSA production/release in vitro, the polymeric form does not. Thus, while we have confirmed that lactoferrin is the activity in neutrophil extracts that inhibits CSA production, we have also found that lactoferrin undergoes reversible polymerization at physiologic concentrations and that the polymerized molecule is inactive. The tendency of lactoferrin to polymerize in tissue culture medium and in vivo should be taken into account in any studies on its potential role as a physiologically relevant regulator of granulopoiesis.

Centrifugation, Density Gradient↗
PubMed1981

Interaction of lactoferrin, monocytes, and T lymphocyte subsets in the regulation of steady-state granulopoiesis in vitro.

Colony-stimulating activities (CSA) are potent granulopoietic stimulators in vitro. Using clonogenic assay techniques, we analyzed the degree to which mononuclear phagocytes and T lymphocytes cooperate in the positive (production/release of CSA) and feedback (inhibition of CSA production/release) regulation of granulopoiesis. We measured the effect of lactoferrin (a putative feedback regulator of CSA production) on CSA provision in three separate assay systems wherein granulocyte colony growth of marrow cells from 22 normal volunteers was stimulated by (a) endogenous CSA-producing cells in the marrow cells suspension, (b) autologous peripheral blood leukocytes in feeder layers, and (c) medium conditioned by peripheral blood leukocytes. The CSA-producing cell populations in each assay were varied by using cell separation techniques and exposure of isolated T lymphocytes to methylprednisolone or to monoclonal antibodies to surface antigens and complement. We noted that net CSA production increased more than twofold when a small number of unstimulated T lymphocytes were added to monocyte cultures. Lactoferrin's inhibitory effect was also T lymphocyte dependent. The T lymphocytes that interact with monocytes and lactoferrin to inhibit CSA production are similar to those that augment CSA production because their activities are neither genetically restricted not glucocorticoid sensitive, and both populations express HLA-DR (Ia-like) and T3 antigens but not T4 or T8 antigens. These findings are consistent with results of our studies on the mechanism of lactoferrin's inhibitory effect with indicate that mononuclear phagocytes produce both CSA and soluble factors that stimulate T lymphocytes to produce CSA, and that lactoferrin does not suppress monocyte CSA production, but does completely suppress production or release by monocytes of those factors that stimulate T lymphocytes to produce CSA. We conclude that mononuclear phagocytes and a subset of T lymphocytes exhibit important complex interactions in the regulation of granulopoiesis.

Bone Marrow Cells↗
PubMed1981

Fibrositis: misnomer for a common rheumatic disorder.

Fibrositis is a misnomer for a very common form of nonarticular rheumatism. The name implies an inflammatory process in fibroconnective tissue which has never been verified. The symptoms of fibrositis are ill-defined musculoskeletal pain made worse by stress, cold, noise and unaccustomed exercise; there is usually a significant element of depression, nonrestorative sleep, chronic fatigue and early morning stiffness. Results of physical examination are strikingly normal, apart from painful tender spots which are remarkably consistent in location from patient to patient. It is important to realize that fibrositis can complicate diseases such as rheumatoid arthritis and systemic lupus erythematosus, where its prompt recognition is essential in averting inappropriate medication. Drug therapy alone is seldom effective in alleviating symptoms; a carefully planned education program is necessary to readjust both psyche and soma.

Diagnosis, Differential↗
PubMed1979

Lactoferrin turnover in man.

1. The turnover of 125I-labelled lactoferrin was measured in ten adults. Simultaneous organ radioactivity counting was performed. 2. Ferrokinetic studies were performed in three adults after the intravenous injection of [59Fe]lactoferrin. 3. Lactoferrin was rapidly eliminated from the plasma with a mean fractional catabolic rate of 5.7/day. Apolactoferrin (one subject) was eliminated at a slower rate (fractional catabolic rate 1.22/day). 4. Of the administered 125I label 99% was recovered in the urine, as free iodine, within the first 24 h. In the 59Fe studies no appreciable activity was found in the urine. 5. Organ radioactivity counting showed that lactoferrin was rapidly taken up by the liver and spleen. In the 125I studies the rapid excretion of free 125I suggested catabolism at these sites. In the 59Fe studies, the radioactivity persisted in the liver and spleen for several weeks and was slowly transferred to the bone marrow before appearing in circulating erythrocytes. 6. From the values of fractional catabolic rate, plasma lactoferrin, neutrophil lactoferrin and plasma volume, a 'derived neutrophil turnover' was calculated for each subject. The mean value was 8 x 10(8) neutrophils/day. This is about 1% the value obtained from the actual measurement of labelled cells. It is postulated that this 'derived value' represents only that portion of neutrophil turnover accounted for by intravascular senescence.

Adult↗
PubMed1978

Neuropsychiatric problems in mixed connective tissue disease.

A group of 20 patients with mixed connective tissue disease, followed for up to five years, was found to have a 55 per cent incidence of neuropsychiatric problems. An aseptic meningitis-like syndrome was the most common presentation and was rapidly responsive to corticosteroid therapy. Other findings were psychosis, convulsions, peripheral neuropathy, trigeminal neuropathy and cerebellar ataxia. An abnormal cerebrospinal fluid was found in five patients; mild pleocytosis, an increased protein content and a first phase colloidal gold curve were the main abnormalities. These neuropsychiatric problems have not been a cause of mortality in this group of patients with mixed connective tissue disease.

Adrenal Cortex Hormones↗
PubMed1978

Lactoferrin content of peripheral blood cells.

The peripheral blood of 60 normal adults was separated into plasma, red cells, neutrophils, lymphocytes, monocytes and platelets. Lactoferrin concentrations were measured in the plasma and cell extracts and compared to those of lysozyme. The neutrophil lactoferrin content in males and post-menopausal females was found to be significantly higher than in pre-menopausal females. A small amount of lactoferrin was found in association with monocytes, but not with lymphocytes, erythrocytes and platelets. Neutrophil lysozyme concentrations did not exhibit any variation with sex and age; but the level in monocytes was higher than that in neutrophils. No correlation was observed between individual neutrophil lactoferrin values and the plasma level. Immunofluorescent studies showed neutrophils to have a lobulated pattern suggestive of nuclear staining. Monocytes did not show direct staining, but exhibited a peripheral pattern after prior exposure to lactoferrin--confirming the existence of a surface receptor. Gel chromatography indicated that neutrophil lactoferrin is in a polymerized or complexed form which elutes with the void volume on Sephadex G-200; serum lactoferrin consists of two forms, one of which also elutes with the void volume on Sephadex G-200.

Adult↗