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Biomedical subjects

P Seeman

Publications and source records attributed to P Seeman.

At least 289 records · Page 16Linked to original sources
PubMed1973

Structure of membrane holes in osmotic and saponin hemolysis.

Serial section electron microscopy of hemolysing erythrocytes (fixed at 12 s after the onset of osmotic hemolysis) revealed long slits and holes in the membrane, extending to around 1 microm in length. Many but not all of the slits and holes (about 100-1000 A wide) were confluent with one another. Ferritin and colloidal gold (added after fixation) only permeated those cells containing membrane defects. No such large holes or slits were seen in saponin-treated erythrocytes, and the membrane was highly invaginated, giving the ghost a scalloped outline. Freeze-etch electron microscopy of saponin-treated membranes revealed 40-50 A-wide pits in the extracellular surface of the membrane. If these pits represent regions from which cholesterol was extracted, then cholesterol is uniformly distributed over the entire erythrocyte membrane.

Aldehydes↗
PubMed1973

Membrane lesions in immune lysis: surface rings, globule aggregates and transient openings.

It is known that there are 100 A-wide circular structures associated with the erythrocyte membrane in immune lysis. To determine whether these structures were functional holes extending through the membrane, freeze-etch electron microscopy was carried out. Sheep erythrocytes incubated with either rabbit complement or rabbit antibody (anti-sheep erythrocyte antibody) did not hemolyze and did not reveal any abnormalities in freeze-etch or negative-stain electron microscopy. Erythrocytes incubated with both complement and antibody revealed rings on the extracellular surface (etch face) of the cell membrane. Allowing for the 30 A-thick Pt/C replica, the dimensions of the surface rings were similar to those seen by negative staining. The ring's central depression was level with the plane of the membrane; some rings were closed circles, others were crescent shaped. The cleavage face of the extracellular leaflet revealed globule aggregates, each aggregate appearing to be composed of about four fused globules. The cleavage face of the cytoplasmic leaflet was normal. When immune lysis was carried out in the presence of ferritin, ferritin was subsequently detected in all lysed erythrocytes. If ferritin was added after immune lysis was complete, only 15% of the cells were permeated by ferritin, indicating that transient openings exist in the cell membrane during immune lysis. No abnormal structures were detected when C6-deficient rabbit serum was used as a source of complement. It is concluded that antibody and complement produce surface rings, prelytic leakage of K(+), colloid osmotic swelling, membrane disruption, and membrane resealing; the surface rings persist after these events.

Animals↗