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Biomedical subjects

J M Michael

Publications and source records attributed to J M Michael.

32 records · Page 2Linked to original sources
PubMed1977

Modulation of macrophage C3b receptor function by cytochalasin-sensitive structures.

A quantitative rosette assay was employed in order to determine if through pharmacologic probes we could gain an insight into the nature of the interaction between C3b-coated particles and the macrophage C3b receptor. Rabbit alveolar macrophage monolayers were challenged with chromium-labeled, complement-coated (via cold agglutinin) human erythrocytes (HEC3b) and the per cent of bound counts determined in the distilled water lysate. With this assay system in which ingestion is negligible, the cytochalasins (A greater than E greater than D greater than B) produced the most marked inhibition of rosette formation compared to control treated monolayers. No agent examined produced consistent augmentation. Cytochalasin A at 10(-5), 10(-6), and 10(-7) M inhibited rosette formation by 77+/- 2, 44 +/- 4 and 15 +/- 7 (S.E.), per cent, respectively. Cytochalasin E was also markedly inhibitory, Cytochalasins B and D produced approximately 30% inhibition at 10(-5) M. The cytochalasin effect was not secondary to an interaction between these agents and complement-sensitized erythrocytes, although cytochalasin E was also able to reduce erythrocyte-bouund C3b reactivity. Cytochalasin A and E modulation of the macrophage C3b reactivity occurred within a few minutes and was only slightly reversible. Cytochalasins A and E could also disrupt performed rosettes but the effect was not as pronounced as when these agents were present before and/or during the actual adherence phenomenon. Vinblastine and colchicine (10(-5) and 10(-6) M) also produced significant inhibition of rosette formation, although the magnitude of the effect was less than that for cytochalasins A and E. Further characterization of the vinblastine and colchicine effect demonstrated that the inhibition was rapid, irreversible over a 60-min incubation, and not explained by an alteration in macrophage attachment or in HEC3b reactivity. Agents producing insignificant inhibition of rosette formation included the following: dibutyryl cAMP and cAMP agonists (PGE1, theophylline), 8-bromo cGMP and cGMP agonists (carbachol, asorbic acid), dimethylsulfoxide, heparin, ethanol, dextran sulfate, DEAE-dextran, and poly-L-lysine. The data suggest that cytochalasin, vinblastine and colchicine sensitive membrane structures, most likely microfilaments and microtubules, are important in the interaction of C3b-coated particles with the macrophage C3b receptor.

Agglutinins↗
PubMedDate not supplied

Potassium load in CPD-preserved whole blood and two types of packed red blood cells.

The potassium load of transfused blood must be minimized. We have compared the total plasma potassium content of units of CPD-preserved stored whole blood (SWB), stored packed cells (SPC), and packed cells prepared from stored whole blood (WB-PC). Plasma potassium concentrations, unit weights, and hematocrits of 20 units of SWB, 27 units of SPC, and 20 units of WB-PC of various ages were measured. During the 21-day storage period, total plasma potassium content per unit increased in units of SPC at the same rate as in units of SWB, because plasma potassium concentration increased in SPC at three times the rate of SWB. The values for total plasma potassium per unit at 14 and 21 days in mEq/unit were: SWB, 4.4, 5.8; SPC 3.1, 4.4; and WB-PC 1.9, 2.5. Thus, SPC units may contain substantial amounts of plasma potassium when stored for two to three weeks. However, removal of most of the remaining supernatant plasma from SPC units just prior to administration provides a readily available supply of low potassium blood while allowing maximum conservation of scarce blood resources.

Blood Preservation↗
PubMedDate not supplied

Purification and use of the C3d subunit C3.

A method is described for the preparation of C3d from fresh-frozen CPD plasma. A redissolved EDTA euglobulin precipitate formed from defibrinated plasma is chromatographed on DEAE cellulose. The C3-rich peak is further chromatographed by stepwise elution from hydroxy-apatite. The highly purified C3 and C3b so obtained are then treated with commercial C3b inactivator. G-200 sephadex filtration of this material produces a low molecular weight peak containing C3d greater than 95 per cent purity. The purified C3d, which contains negligible carbohydrate, has a molecular weight of 28,000 (based on SDS polyacrylamide gel electrophoresis). When added at a final concentration of less than 70 mug per ml, it completely inhibits the anti-C3d hemagglutinin reactivity of a potent anti-C3d antiglobulin serum but does not inhibit sera with reactivities against C3c, C4b, and C5b. Two of three rabbits hyperimmunized with purified C3d produced antisera exhibiting only anti-C3d precipitin activity. After absorption of heterologous antibodies, the antisera strongly agglutinated C3d-coated RBC, failed to agglutinate RBC glutinated C3d-coated RBC, failed to agglutinate RBC coated only with C4, and reacted weakly against strongly anti-Rh coated RBC. The latter reactivity was readily absorbed by whole IgG. Preliminary studies with 125I-labeled C3d indicate its potential value in assessing potency of anti-C3d reagents.

Animals↗
PubMedDate not supplied

Identification of a C4 Subcomponent on C3d-coated erythrocytes.

Test erythrocytes (E) used to evaluate anti-complement (C') antiglobulin sera have not been adequately standardized. This report describes a previously unrecognized C4-derived antigen (temporarily called X-Ag) found on E generally believed to be coated only with the C3d subcomponent of C3, X-Ag occurred on all E coated in vitro with C' by low ionic strength-sucrose or cold agglutinin methods and on E from ten of ten patients whose cells had been C' coated in vivo. It was not removed by incubating these cells with trypsin or fresh compatible serum. This antigen was found on "C4-only-coated" red blood cells made with normal or congenitally C2-deficient serum but not on cells similarly prepared with congenitally C4-deficient serum. It was not identified on E coated with C' via the alternate pathway, normal trypsinized cells, nor cells coated only with IgG. Absorption experiments utilizing purified complement components and subcomponents and G200 Sephadex fractions of normal human serum strongly suggest that X-Ag is a subcomponent of C4(C4d). These results show that at least one C' subcomponent other than C3d occures on both in vitro and in vivo C3d-coated erythrocytes and must be taken into account when such cells are used to evaluate antiglobulin reagents.

Absorption↗
PubMedDate not supplied

Fighting smallpox on the Texas border: an episode from PHS's proud past.

The motto of the Public Health Service (PHS) is "Service with Distinction." An example of how that motto was earned can be seen in the work of the professionals of the Marine Hospital Service (as PHS was then known) in a smallpox epidemic on the Texas border in 1895. Barely 2 years after Congress had given the U.S. Surgeon General the authority to intervene and prevent the spread of contagious diseases from one State to another, Surgeon General Walter Wyman, MD, stepped in. In response to a request from the Texas State Health Officer, Wyman sent a team of officers to assist the State and prevent the spread of smallpox. At that time the Surgeon General was head of the Marine Hospital Service, which became the Public Health Service in 1912. In a period of slightly more than 2 months, the epidemic was contained in the population of 411 refugees. Sixty people had died at the camp, 51 from smallpox. Although that fatality rate would be incredibly high by current standards, it was low under the circumstances. Milton Rosenau, MD, was a key to the containment of the disease and the humanitarian treatment of the survivors, a group of black Americans who had fled from Mexico after having been lured there with the promise of land that would be their own. Rosenau would later become the head of the Hygienic Laboratory, precursor of the National Institutes of Health.

Black or African American↗