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Biomedical subjects

J K Koehler

Publications and source records attributed to J K Koehler.

At least 37 records · Page 2Linked to original sources
PubMed1977

Fine structure of spermatozoa of the Asiatic musk shrew, Suncus murinus.

The fine structure of spermatozoa of the Asian musk shrew, Suncus murinus, has been investigated using air-dried and critical-point-dried replicas in addition to freeze-fractured specimens. Asymmetry in the structure of the head, notable the acrosome, can be recognized in critical-point-dried replicas as a slight dorsoventral convexity not apparent in air-dried specimens. Freeze-etching reveals a dense accumulation of intramembranous particles just anterior to the posterior ring, but relatively few other characteristic membrane conformations associated with the head. Gelatin smears visualized with the light microscope show a vigorous lytic response, but preliminary efforts to remove the acrosome by physiological or enzymatic incubation have thus far not been successful.

Animals↗
PubMed1976

Fine structural localization of Concanavalin A binding sites on hamster spermatozoa.

The plasma membrane of epididymal spermatozoa of the golden hamster (Mesocricetus auratus) exhibits morphological differences over various parts of the head and tail as detected by air-dried replicas and freeze-etching techniques. In an attempt to ascertain whether any topographical differences exist in the number or distribution of carbohydrate moieties associated with the cell surface, cells were labeled with Concanavalin A and marked with hemocyanin. It was found that while the plasma membrane over the acrosomal region differed from that of the postacrosomal region in membrane components revealed by freeze fracturing, there was no apparent difference in the distribution or density of Con A binding sites detectable by hemocyanin localization. The tail regions exhibited differences in both fracture face appearance and the distribution of detectable carbohydrate moieties. It was also found that binding sites for Concanavalin A exist on the inner and outer acrosomal membranes in addition to those on the plasma membrane.

Acrosome↗
PubMed1976

Freeze-fracture study of mast cell secretion.

Within seconds after exposure of rat peritoneal mast cells to polymyxin B, bulges appear on the surface of the cells. Freeze-fracture electron microscopy reveals that each bulge overlies a mast cell granule. In contrast to the even distribution of intramembranous particles in the plasma membrane of unstimulated cells, the intramembranous particles in the stimulated cells are unevenly distributed in the membrane of the bulges with large patches of membrane lacking intramembranous particles. The membranes over the most prominent bulges are entirely free of intramembranous particles, and in some instances there is an increased concentration of intramembranous particles at the margins of the bulges. Perigranule membranes exhibit the same changes in distribution of intramembranous particles. Electron microscopy of thin sections of rapidly fixed, stimulated mast cells shows a peculiar structure of the membrane overlying some bulges; instead of the pentalaminar membranes previously demonstrated, the membrane at these sites of presumptive fusion of perigranule and plasma membrane assumes the form of a single dense lamina with a fine fuzzy coating on either side. It seems possible that membrane fusion and subsequent pore formation proceed in the stimulated mast cell through a stage of flight of intramembranous particles and molecular rearrangement of the other membrane components.

Animals↗
PubMed1976

Abnormally large lamellar bodies in type II pneumocytes in Chediak-Higashi syndrome in beige mice.

Lamellar bodies in type II pneumocytes are markedly enlarged in beige mice. The irregular shapes of some of these enlarged specialized lysosomes suggest fusion of smaller ellipsoidal bodies to form the giant organelles, consistent with the proposal of others for the mechanism of formation of abnormal lysosomes in Chediak-Higashi syndrome. Examination of the structure of lamellar bodies by the freeze-fracture technique reveals highly ordered stacking or concentric wrapping of the constituent lamellae. The corrugated patterns evident on the surfaces of normal lamellae are also present in Chediak-Higashi syndrome lamellae. Both normal and Chediak-Higashi syndrome lamellae appear free of typical intramembranous particles. The corrugations seen in the lamellae closely resemble those seen on freeze-fracture of dispersions of lecithin in water.

Animals↗
PubMed1975

Studies on the distribution of antigenic sites on the surface of rabbit spermatozoa.

Antibodies to rabbit spermatozoa isolated from immunized virgin female rabbits were conjugated to hemocyanin and have been used to determine the pattern of antigenic sites over the surface of rabbit spermatozoa under a variety of conditions. When the spermatozoa are incubated with antibody at 0 degrees C, labeling is almost entirely restricted to the postacrosomal sheath. Incubation at room temperature (22 degrees C) or at 37 degrees C results in progressively increased acrosomal labeling as well as enhanced postacrosomal sheath labeling. Initial incubation at low temperature followed by washing and high temperature incubation yields cells which indicate little tendency for postacrosomal sheath sites to migrate toward the acrosomal region. Absorption of the antibody preparation with rat lymphocytes has no effect on labeling density, whereas absorption with rabbit lymphocytes diminishes the intensity of labeling and yields cells with markers primarily over the postacrosomal sheath. It is concluded that the postacrosomal sheath plasma membrane has specific antigenic properties distinct from other regions of the head.

Animals↗