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Biomedical subjects

A W Segal

Publications and source records attributed to A W Segal.

At least 19 recordsLinked to original sources

The subcellular distribution and some properties of the cytochrome b component of the microbicidal oxidase system of human neutrophils.

A novel cytochrome b has recently been described in human neutrophils. The subcellular distribution of this cytochrome was investigated by analytical fractionation on continuous sucrose gradients and it was found to have a dual localization, the major component having a similar distribution to the plasma-membrane marker [3H]concanavalin A, and a denser peak located with the specific granules. The two components were separated on discontinuous gradients and studied independently.

Centrifugation, Density Gradient

Halothane does not inhibit human neutrophil function in vitro.

Various indices of function of neutrophils from normal healthy volunteers have been examined after in vitro exposure to halothane. Random free movement on glass was unaffected, but random migration through millipore filters was slightly increased. There was no significant change in migration in response to casein chemotaxis. Phagocytosis, degranulation and the enhanced non-mitochondrial respiration associated with phagocytosis were unaffected. Electron-microscopic appearance at 30 s after exposure to latex particles was normal in all respects.

Cell Movement

Absence of a newly described cytochrome b from neutrophils of patients with chronic granulomatous disease.

A unique cytochrome b which becomes incorporated into phagocytic vacuoles has been described in human neutrophils. This cytochrome b appears to be situated in the plasma membrane of these cells, and acts as a component of the microbicidal oxidase system. Absence or gross abnormality of this cytochrome b was demonstrated in all four patients with chronic granulomatous disease who were investigated, and reduced concentrations in two mothers known to be carriers of the disease.

Child

Tracing the fate of oxygen consumed during phagocytosis by human neutrophils with 15O2.

1. The metabolism of oxygen by phagocytosing neutrophils was traced by using 15O2. 2. The isotope did not exchange with the incubation medium or cells to an appreciable extent and unmetabolized oxygen was readily eluted by gassing the cell suspension. 3. The polarographic measurements of oxygen consumption closely paralleled the recovery of metabolized 15O2. 4. Almost all the metabolized 15O2 was converted into water, both in the presence and absence of KCN, supporting the concept that the oxygen consumed by neutrophils is converted into H2O2. It is unlikely that an appreciable proportion of this oxygen is incorporated into the organic composition of the cell or of the ingested micro-organism.

Humans

Analytical subcellular fractionation of neutrophils from patients with chronic granulomatous disease. Demonstration of the enzyme defect in four cases.

Analytical subcellular fractionation studies were performed on neutrophils from five patients, including two females, with chronic granulomatous disease. The density distribution and marker enzyme activities of the principal subcellular organelles in unstimulated cells were similar to those in unstimulated neutrophils from control subjects. NADH dependent reduction of nitroblue tetrazolium was measured in four of the patients including one female. In homogenates of whole cells the specific activity of this enzyme expressed as milliUnits/mg protein was lower in the patients than in the controls, but the difference was not statistically significant. There was however a highly significant difference between the specific activities of this enzyme in the plasma membrane fractions isolated from neutrophils of the four patients and the three controls. These findings suggest that the primary microbicidal oxidase of neutrophils, defective function of which manifests as the syndrome of chronic granulomatous disease, is a plasma membrane NADH oxidoreductase.

Adolescent

Levamisole in the treatment of Crohn's disease.

In 8 patients with active uncomplicated Crohn's disease who were not receiving any specific therapy, a clinical remission was induced with an elemental diet, and then an attempt was made to maintain this remission with levamisole. This regimen resulted in excellent control of the disease. A drug-induced arthritis developed in two patients and resolved spontaneously. There were no other significant side-effects.

Adolescent

Indium-111-labeled autologous leukocytes in man.

Autologous leukocytes have been isolated, labeled with indium-111, and administered to 15 patients suspected of inflammatory disease. The stability of the label has been demonstrated and the in vivo kinetics and distribution of the labeled cells studied. The distribution is influenced by the type and viability of the cells separated by three different techniques. Generally, there was initial accumulation of radioactivity in the lungs; approximately half of this cleared in 15 min and the remainder slowly. Twenty-five to 50 percent of the radioactivity subsequently distributed in the spleen, liver, and bone marrow, and these did not show significant change with time up to 48 hr post injection. The In-111 radioactivity administered as labeled leukocytes free from erythrocytes cleared from the circulating blood with a half-time of 7.5 hr. In three of 15 patients, the suspicion of inflammatory disease could not be confirmed, and in these a normal distribution of radioactivity was observed. In the remaining 12 patients, focal accumulation of radioactivity was detectable within 4 to 24 hr after administration, and subsequent confirmation of sepsis was obtained. From three such patients, samples of abscesses were recovered which showed markedly higher radioactivity than that in the same weight of blood.

Abscess

Indium-111-labeled cellular blood components: mechanism of labeling and intracellular location in human neutrophils.

Human neutrophils were labeled with In-111 oxine by incubation at room temperature, and the fate of the oxine and the intracellular location of the In-111 were determined. Neutral (1:3) In-111 oxine complex diffuses rapidly across the cell membrane and then dissociates. Some of the oxine leaves the cell and the In-111 binds intracellularly. After short periods of incubation the label is distributed mostly to four soluble components, a small proportion of which had a distribution similar to that of specific and azurophil granules. After longer incubation periods there was relatively less radioactivity with the soluble components and probably more attached to the particulate material. A small peak of radioactivity also appeared in the region of DNA distribution, but no confirmation could be obtained for the association of the In-111 radioactivity with DNA.

Centrifugation, Isopycnic

Indium-111-labelled leucocytes for localisation of abscesses.

Leucocytes from eight patients who were thought to have an abscess were labelled with indium-111 and reintroduced into the circulation. The distribution of radioactivity was followed by whole-body scanning and imaging with a gamma camera. Focal accumulation of radioactivity were observed in the lesion in the three patients with abscesses, in the lungs of a boy with bacterial endocarditis, in the knee of a woman with rheumatoid arthritis, and at the site of intramuscular injections in another patient. The use of radiolabelled cells for the detection of focal pathological processes would seem to be an important addition to conventional diagnostic methods.

Abscess

Neutrophil dysfunction in Crohn's disease.

The migration of neutrophils into skin windows has been examined in patients with Crohn's disease and rheumatoid arthritis and compared with normal. Leucocyte migration was significantly lower in patients with Crohn's disease than in others. This abnormality of neutrophil function in Crohn's disease appears to be secondary to a defective acute inflammatory response as the neutrophils themselves were found to behave normally on in-vitro testing. A weak acute inflammatory response to particulate or antigenic material in the bowel wall could result in the chronic inflammation observed in this condition.

Blood Sedimentation

Characterisation of the enzyme defect in chronic granulomatous disease.

Strikingly reduced activity of an enzyme, normally located in the plasma membrane of human neutrophils, has been demonstrated in a male patient with chronic granulomatous disease (C.G.D.). The subcellular distribution of N.A.D.H.-dependent reduction of nitroblue tetrazolium (N.B.T.) was determined in neutrophils because reduction of this dye by these patients is grossly impaired. Assayed at high concentrations of N.A.D.H. (1 mmol/1), N.B.T. is reduced by enzymes in the cytosol and mitochondria in addition to the plasma membrane by both normal and C.G.D. cells--properties which previously obscured the identity and location of this enzyme. At a more physiological concentration of N.A.D.H. (25 mumol/1), reduction of the dye by the plasma membrane, the principal site of N.B.T. reduction by normal neutrophils, was absent in the patient with C.G.D. It is suggested that absence or imperfect function of this reductase enzyme is the primary lesion in this disease.

Adolescent