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Biomedical subjects

M Loos

Publications and source records attributed to M Loos.

At least 145 records · Page 8Linked to original sources
PubMed1980

Analysis of the anticomplementary activity in sera of three African patients with parasitic and bacteriological infections.

The sera of three different patients from Togo, Africa were investigated with respect to their complement profile. The three patients were suffering from parasitic (Onchocerca volvulus) and bacteriological (Treponema pertenue) diseases. The total hemolytic activity (50% hemolytic complement) was markedly depressed. The analysis of the individual complement components revealed the the titers of C1, C2, C3, and C4 were lowered up to 90%, indicating an activation of the classical pathway of complement. Addition of the patients' sera to normal human serum induced a temperature-dependent consumption of C4 and C2, whereas C3 was not affected. This activity in the patients' sera eluted from a Sephadex-G-200 column with the 19 S peak and could be identified as the activated form of the first component of the complement system. The reason for the presence of activated C1, C1 in the patients' sera resides in the absence of functionally active C1 inactivator.

Adult↗
PubMed1980

Killing of the S and Re forms of Salmonella minnesota via the classical pathway of complement activation in guinea-pig and human sera.

The S (wildtype) and Re form (heptose-deficient, core-defective mutant) of Salmonella minnesota were killed by treatment with normal guinea-pig serum (GPS). Using C4-deficient GPS and serum containing 0.02 M ethyleneglycol-bis-(beta-aminoethylether)-tetraacetic acid and 0.02 M MgCl2 (EGTA-Mg2+) a reduced killing rate was observed. In normal GPS diluted 1:10 containing 0.02 M EGTA-Mg2+ or in C4-deficient GPS diluted 1:10 no killing occurred, whereas the same serum dilution without EGTA-Mg2+ showed a strong bactericidal effect indicating a dependency upon C4 and Ca2+ ions. Furthermore, in contrast to normal human serum (NHS) no killing occurred in a selective complete C1q-deficient human serum. The bactericidal effect, however, could be restored by addition of highly purified C1q; this is a further indication for a dependency upon the classical pathway of C activation. The C-dependent bactericidal activity was totally abolished when phosphate buffer was used, partially reduced in the presence of veronal-buffered saline (VBS), and not affected by tris-(hydroxymethyl)-aminomethane(Tris) or thioglycollate-buffered system EGTA-Mg2+ alone slightly reduced the growth rate of the bacteria whereas disodium ethylene diaminetetraacetate (EDTA) had a bacteriostatic effect on the S-form. The inhibition of the growth of the Re-form by EDTA was amplified by the addition of serum. Pre-incubation of bacteria with serum for absorption of antibodies did not increase the killing rate of such pre-treated bacteria excluding an antibody-mediated bactericidal reaction. Furthermore, pre-treatment of the bacteria with GPS at 0 degrees reduced the serum sensitivity of both types of bacteria.

Animals↗
PubMed1979

Complement components (C1, C2, C3, C4) in bronchial secretions after intranasal infection of guinea pigs with Mycoplasma pneumoniae: dissociation of unspecific and specific defense mechanisms.

Shortly after intranasal infection of guinea pigs with Mycoplasma pneumoniae, the titers of the complement components increased significantly in bronchial secretions by the folllowing amounts, compared with the titer of a control group: C1, about 2-fold; C2, 1.6-fold; C3, 17-fold; and C4, 942-fold. Histopathological signs of inflammation were not apparent at this time. At 2 weeks after infection, when the titers of complement components in the bronchial secretions were at the level of control values or lower, the serum antibody titer increased, and it reached the highest level at 6 weeks after infection. Therefore, one can distinguish two phases of reaction of the macroorganism to intranasal inoculation. The increase in complement components shortly after infection may represent an earlyunspecific defense mechanism of the host before the specific immune response becomes effective, since the complement system can be activated by M. pneumoniae via the classical as well as the alternative pathway in the absence of antibodies.

Administration, Intranasal↗
PubMed1978

Amyloid P component--a special type of collagen?

The localization of amyloid P-components is demonstrated by immunofluorescence microscopy in normal human tissue (kidney, spleen, liver). The relation to collagen and to amyloidosis is discussed.

Amyloid↗
PubMed1978

Preparation of trinitrophenylated red cells for antibody independent lysis by complement.

Based on the earlier observation that DNP-HSA interacts directly with C1q, a subcomponent of the first component of complement (Loos and König, 1977), evidence is presented that TNP bound to erythrocytes (E-TNP) can interact with the whole complement sequence leading to the lysis of the TNP-carrying erythrocytes; in this test system the erythrocytes are used as an indicator of the TNP-complement reaction. To exclude any antibody-mediated lysis either the heterologus sera were exhaustively absorbed with the erythrocytes used in the test system or serum and erythrocytes of one individual person were taken. The strongly temperature-dependent interaction of TNP-sulfonic acid with the erythrocytes resulted in the formation of E-TNP as well as of a TNP-protein complex released into the supernatant. The TNP-protein complex strongly inhibited purified C1 similar to DNP-HSA. The antibody independent lysis of E-TNP by complement was dependent upon the TNP concentration per cell, the temperature and time as well as the complement concentration. The reaction of E-TNP with complement showed similar characteristics to those for the reaction of antibody sensitized erythrocytes (EA) with complement. E-TNP is a helpful tool to study antibody-independent activation of the complement system.

Animals↗
PubMed1978

Antibody-independent interaction of the first component of complement with Gram-negative bacteria.

The interaction of the first component of complement with two serum-sensitive strains of Escherichia coli and Klebsiella pneumoniae was studied. It could be demonstrated that highly purified C1, free of immunoglobulin G and immunoglobulin M, binds to E. coli or K. pneumoniae. C1 binding was also found with specifically absorbed human serum, after incubation of bacteria with normal serum in the presence of ethylenediaminetetraacetate or agammaglobulinemic serum; the number of C1 molecules taken up by the bacteria was not influenced, indicating that C1 binding was independent of naturally occurring antibodies. C1 bound to bacteria was still able to cleave C4, the natural substrate of C1. From these observations, it is concluded that C1 in an enzymatically active state can be bound directly to bacteria independently of antibody.

Complement C1↗
PubMed1978

Trinitrophenylated red cells (E-TNP) as a model for antibody-independent activation of the complement system via the classical pathway.

Recently, it was shown that DNP-substituted human serum albumin (DNP-HSA) bound directly C1q, a subcomponent of C1. Evidence is presented that TNP-conjugated erythrocyte (E-TNP) were lysed by autologous sera as source of complement (C). The lysis was strongly dependent on the TNP substitution rate so that the TNP-carrying erythrocytes can be used directly as an indicator for the TNP-C interaction. The TNP-induced lysis of erythrocytes required the presence of C1q, C4, and Ca++, indicating a dependency on the classical pathway of C. Purified C1 is directly bound to E-TNP; C1 bound to E-TNP could be transferred to EAC4. From E-TNP-C1 the intermediates E-TNP-C14 and E-TNP-C142 can be formed by successive addition of C4 and C2 similarly to EAC14 and EAC142. Native C1 can be activated to C1 by E-TNP in the same fashion as by EA. The E-TNP model provides evidence that the "activated" Fc part of the antibody molecule is not unique in its ability to trigger the internal activation of C1. Molecules with negatively charged groups, like polyanions, or molecules with high electron dense groups, like DNP or TNP, can activate the C system via the classical pathway by binding directly to C1q.

Animals↗
PubMed1978

Biosynthesis of the first component of complement by human and guinea pig peritoneal macrophages: evidence for an independent production of the C1 subunits.

The first component of complement, C1, was produced by human as well as guinea pig macrophages. Supernatants from serum-free cultured macrophage monolayers, tested separately for C1q and C1 activity, showed a ratio of 15:1, respectively, and a different time course of C1q and C1 production, indicating that the subcomponents of C1 are synthesized independently. Heat-inactivated fetal calf or guinea pig serum (2 hr, 56 degrees C), added to the culture medium, were found to be inhibitory for C1 but not for C1q activity, obviously due to still active C1 inhibitor in these sera. De novo synthesis was confirmed by reversible inhibition of C1 and C1q production by cycloheximide (0.5 microgram/ml) and puromycin (1 microgram/ml), by incorporation of radiolabeled amino acids into the C1s subcomponent, and by uptake of incorporated radioactivity by EA, which was sensitive to EDTA. In additional experiments, 2,2'-dipyridyl markedly reduced C1q and also C1 secretion in the supernatants. Inhibition of the prolyl and lysyl hydroxylation and, as a consequence, structural instability of the collagenous region in the C1q molecule, is discussed as the cause of this effect which is analogous to collagen biosynthesis.

2,2'-Dipyridyl↗
PubMed1977

Comparison of three instrumental methods to monitor nitrogen dioxide.

Three commercially available automated NO2-monitors, based on amperometry, chemiluminescence and coulometry respectively, were compared under simulated field conditions over a period of 45 days of continuous operation. The main purpose of this programme was the study of the reliability of the overall system, sampling line-monitors-data acquisition and handling system (PDP-8/E), the correlation between the individual half-hour averages given by the three monitors in the range 0--700 mug NO2/m3 and the comparison of the global statistics for the same NO2-pollution simultaneously seen by the three different monitors over a period of 45 days. Based on more than 1200 valid half-hour averages, a highly significant correlation between the different monitors was obtained, while the statistics of the simulated NO2-pollution were in good agreement.

Air Pollutants↗
PubMed1977

Interactions between mycoplasma pneumoniae and the first components of complement.

Mycoplasma pneumoniae cells were rounded and killed by fresh guinea pig serum (GPS) which did not contain detectable amounts of antibody. The first component of complement (C1) was bound by M. pneumoniae in considerable amounts from both GPS and purified C1. The C1 bound by the cells was reacting with C4. Sequential addition of C1, C4, C2, and C-ethylenediaminetetraacetate to glass-grown M. pneumoniae cells resulted in rounding of a significant number of cells. M. orale and M. fermentans showed a reduced binding capacity for C1 as compared with M. pneumoniae. Both species were only slowly killed by fresh GPS, whereas M. hominis was as sensitive as M. pneumoniae. The results suggest an antibody-independent interaction between some components of the membrane surface of M. pneumoniae and C1, resulting in an activation of the complement system leading to the killing of the mycoplasma cells.

Animals↗
PubMed1977

Antibodies to Acholeplasma laidlawii membrane lipids in normal guinea pig serum.

Acholeplasma laidlawii is killed and lysed by fresh normal guinea pig serum (GPS) without additional antibodies. Prior incubation of GPS with whole A. laidlawii organisms abolishes the killing activity of GPS. In the present study it was demonstrated that antibodies are present in normal GPS. The classical pathway, not the alternative pathway, of the complement sequence was activated by these antibodies in fresh normal GPS. The antibodies in GPS belong to the IgG class of immunoglobulins. They are directed predominantly against the membrane phospholipids of A. laidlawii. These antibodies may be induced either by natural infection of guinea pigs with A. laidlawii or by antigenic determinants of other microorganisms of food antigens.

Acholeplasma laidlawii↗