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C H Hammer

Publications and source records attributed to C H Hammer.

70 records · Page 4Linked to original sources
PubMed1981

Homologous species restriction in lysis of erythrocytes by terminal complement proteins.

The cytolytic efficiency of the terminal complement protein complex, C5b-9, varies with the species of origin of C8 and C9. In the present study, we explored the susceptibility of erythrocytes from various species to lysis by C5b6,7 plus C8 and C9 from different species. EC5b6,7 intermediates were prepared on human, guinea pig, rabbit, mouse, and rat erythrocytes with human C5b6 and guinea pig C7. The degree of lysis of these intermediates by C8 and C9 was found to vary widely depending on the species of the proteins and the target cells. In all cases, lysis was least efficient when C8 and C9 were homologous with respect to the target cell species. This effect was mostly attributable to C9. The inefficient lysis in a homologous system is not due to a failure of C9 binding. Rather, the poor lysis in the homologous system may be attributable to inefficient insertion or channel formation.

Animals↗
PubMed1981

Activation of the fifth and sixth component of the complement system: similarities between C5b6 and C(56)a with respect to lytic enhancement by cell-bound C3b or A2C, and species preferences of target cell.

Brief shift of purified C5 and C6 at 0 degrees C to pH 6.4, followed by immediate neutralization, results in the generation of a factor, designated C(56)a, that lyses erythrocytes together with C7, C8, and C9. We compared C(56)a and C5b6 generated by an alternative-pathway convertase, with regard to their action on different target cells. We found tht C(56)a is similar to C5b6 in the following properties: 1) Together with C7, C(56)a forms a stable intermediate on either sheep or guinea pig erythrocytes. 2) Membrane-bound C3b, or A2C incorporated in the membrane, enhances lysis by C(56)a-9, as well as lysis by C5b6-9. We also found that the lysis of EC(56)a7 or EC5b67 intermediates by C8 and C9 depends on the species of the erythrocytes and the species of C8 and C9. Thus, lysis of sheep erythrocytes is more efficient with guinea pig C8 and C9 than with human C8 and C9. In the case of guinea pig erythrocytes, this relationship is reversed, i.e., these cells lyse more efficiently when human C8 and C9 are used. Enhancement of lysis by membrane-bound C3b or A2C does not abrogate this species incompatibility pattern.

Animals↗
PubMed1977

On the mechanism of cell membrane damage by complement: evidence on insertion of polypeptide chains from C8 and C9 into the lipid bilayer of erythrocytes.

The preceding paper (Hammer, C.H., A. Nicholson, and M. M. Mayer, 1975, Proc. Natl. Acad. Sci., 72:5076) presented evidence on insertion of polypeptide chains from the C5b and C7 subunits of C5b, 6, 7 complex into the phospholipid bilayer of erythrocyte membranes. In the present study, EAC1-8 and EAC1-9 (sheep erythrocytes carrying rabbit antibody and complement proteins C1 through C8 or C9, respectively), prepared with either 125I-C8 or 125I-C9, were incubated with trypsin or chymotrypsin and the release of 125I was measured. Only 9 to 19% of the specifically bound radioactivity was released. In addition, elution experiments were performed with 0.02 M EDTA-1.0 M NaCl. This solution did not elute C9 from EAC1-9. By contrast cellbound C9 was recovered from erythrocyte membranes with sodium dodecyl sulfate (SDS). Thus, enzymatic stripping and elution experiments indicate that cellbound C9 behaves like an integral membrane protein, presumably due to insertion into the lipid bilayer. EAC1-9 membranes that had been subjected to extended digestion with trypsin or chymotrypsin were extracted with SDS to recover the enzyme-resistant part of the C9 molecule from the membrane. Even though this domain of C9 carried 90% of the radioiodine associated with native C9, its m.w. was found to be only 18,000 daltons by analysis on SDS-PAGE. This represents one-quarter of the native C9 molecule.

Animals↗
PubMed1976

Avian riboflavinuria IX. Qualitative action of a mutant gene in chicken on riboflavin-binding protein synthesis.

Laying chickens normally produce a riboflavin-binding protein (RBP) essential for the transfer of vitamin B2 to the egg. A mutant line of chickens (rdrd) is incapable of synthesizing functional RBP. The rdrd laying hens contain a component in the liver and the magnum of the oviduct which cross-reacts with rabbit antiserum specific for RBP. No crossreacting material (CRM) was observed in eggs or blood of rdrd hens. CRM is absent in extracts of livers of rdrd males, but it can be induced in roosters of this genotype by estradiol. CRM appears to be less immunogenic on a weight basis than RBP, and it carries less net negative charge. No measurable riboflavin-binding capacity was found for newly isolated or degraded CRM.

Animals↗
PubMed1976

Increased ion permeability of planar lipid bilayer membranes after treatment with the C5b-9 cytolytic attack mechanism of complement.

The ion permeability of planar lipid bilayers, as measured electrically, was found to increase modestly upon treatment with purified complement complex C5b,6 and complement components C7 and C8. The subsequent addition C9 greatly amplified this change. No permeability changes occurred when components were added individually to the membrane, or when they were used in paired combinations, or when C5b, C7, C8, and C9 were admixed prior to addition. Thus, there is a significant parallel between the permeability changes induced in the model membrane and damage produced in biological membranes by the C5b-9 complement attack sequence. The efficiency of membrane action by C5b-9 was critically dependent on the order in whcih components were added to the membrane. There were also differences in the electrical properties of membranes treated with C5b-8 and C5b-9, though in both cases the enhanced bilayer permeability is best attributed to the formation of trans-membrane channels. Collectively, the data are consistent with the hypothesis that the mechanism of membrane action by complement involves the production of a stable channel across the lipid bilayer, resulting in cell death by colloid-osmotic lysis.

Cell Membrane Permeability↗
PubMed1976

A new activity of complement component C3: cell-bound C3b potentiates lysis of erythrocytes by C5b,6 and terminal components.

EAC4b,3b (sheep erythrocytes carrying rabbit antibody and guinea pig complement component fragments C4b and C3) adsorb human C5b,6 reversibly; the avidity of binding varies inversely with ionic strength. We believe that the receptor of C5b,6 is contributed by the cell-bound C3b because the binding capacity of EAC4b,3b varies with C3b multiplicity and can be blocked with rabbit antibody to guinea pig C3. The fixation of C5b,6 to the erythrocyte-bound C3b serves to concentrate C5b,6 on the cell surface; as a consequence, the hemolytic efficiency of C5b,6 is almost 100 times greater when assayed with EAC4b,3b than with plain erythrocytes. This potentiation represents a hitherto unrecognized function of cell-bound C3b.

Animals↗
PubMed1975

On the mechanism of cytolysis by complement: evidence on insertion of C5b and C7 subunits of the C5b,6,7 complex into phospholipid bilayers of erythrocyte membranes.

The doughnut hypothesis of cytolysis by complement [Mayer, M. M. (1972) Proc. Nat. Acad. Sci. USA 69, 2954-2958] describes an annular structure made up of C5b-9 (complement factors C5b, C6, C7, C8, and C9) which becomes inserted in the lipid bilayer of the cell membrane, thus creating a hole. We now present initial explorations of this hypothesis. EAC1-6 and EAC1-7 (sheep erythrocytes carrying rabbit antibody and complement factors C1 through C6 or C1 through C7, respectively), prepared with either 125I-C3 or 125I-C5 were incubated with trypsin and the release of bound 125I was measured. In the case of 125I-C3, all of the radioactivity was released by trypsin from both intermediates. With 125I-C5, trypsin released all of the 125I from EAC1-6, but only 40-55% from EAC1-7. Possible reasons for resistance of the C5b subunit in EAC1-7 to tryptic digestion are discussed; in terms of the doughnut hypothesis it would be due to shielding by lipid molecules as a consequence of insertion into the lipid bilayer. In accord with this interpretation we have also found that C5b in EAC1-7, but not in EAC1-6, resists elution by 0.3 M NaC1. Similarly, we have found that 125I-C7 in EAC1-7 resists stripping by trypsin. Hence, we now propose the hypothesis that hydrophobic polypeptide chains from the C5b and the C7 subunits of C5b,6,7 complex become inserted in the phospholipid bilayer and that subsequent reactions with C8 and C9 open a channel across the membrane.

Animals↗