An index of the physical effort required in human task performance.
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Achievement↗
Biomedical subjects
J C Hogan
Publications and source records attributed to J C Hogan.
An ultrastructural analysis of "cytoplasmic markers" in germ cells of Oryzias latipes.
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Animals↗
The role of verbal estimates of movement error in ballistic skill acquisition.
The role of verbal estimates of movement error in a ballistic movement task was investigated. Two groups performed a rapid linear movement timing task for 50 trials with KR followed by 50 trials without KR. Group I was required to give a verbal estimate of movement time immediately after the task, while Group II was not. Verbal labeling of movement error did not augment performance when KR was present. When KR was withdrawn, however, Group I maintained performance, but Group II's response accuracy declined. Implications for current motor learning theories are discussed.
Journal Article↗
Intercellular junctions, intramembranous particles and cytoskeletal elements of deep cells of the Fundulus gastrula.
The fine structure of motile deep cells of the gastrula stage of Fundulus heteroclitus was studied with transmission electron microscopy, using both thin sectioning and freeze-cleave techniques. Gastrula deep cells form extensive non-junctiona appositions with each other, in which the apposed plasma membranes are parallel and separated by a distance of 26-28 nm. They also form gap junctions. Tight junctions, desmosomes, and extensive interdigitations of apposed plasma membranes were not observed. The plasma membranes of deep cells contain numerous unclustered intramembranous particles. Cytoplasmic microtubules were found, but they appear to be small in number, sparsely distributed, and mainly randomly oriented. Microfilaments are also present and are localized largely in the cortical cytoplasm and in thin cell extensions. The significance of these findings for the contact and locomotory behavior of deep cells is discussed.
Animals↗
Intramembrane particle distribution and lectin binding of glioblastoma cells after long term subculture.
Human glioblastoma cells in long-term monolayer culture showed an even distribution of intramembrane particles (IMP) on all surfaces of the plasma membrane; junctional complexes were rarely observed and rectilinear arrays were not seen. Cells treated with Con A-ferritin and Ricin II-ferritin showed an even distribution of lectin receptors and under conditions used no capping occurred. Lectin-ferritin complexes were taken up into pinocytotic vesicles. Cleaved preparations of Ricin II-ferritin treated cells showed no change in the distribution of IMP.
Cell Membrane↗
Variation in intramembrane components of Trypanosoma brucei from intact and x-irradiated rats: a freeze-cleave study.
Additional information on host interactions with trypanosomatid membranes was obtained from studies of a monomorphic strain of Trypanosoma brucei harvested at peak parasitemia from intact and lethally irradiated rats. Pellets of trypanosomes were fixed briefly in glutaraldehyde and processed for thin section electron microscopy or freeze-cleave replicas. Observations of sectioned material facilitated orientation and comparison of details seen in replicas. Fracture faces of cell body and flagellar membranes as well as 3-dimensional views of the nuclear membrane were studied. Cell body membranes of 80% of the organisms from intact rats contained random arrays of intramembranous particles (IMP). Aggregated clusters of particles appeared on the fracture faces of 20% of the trypanosomes. Some of these membranes had nonrandomly distributed particles aligned in distinct rows on the outer fracture face of both cell body and flagellum. Many inner face fractures of the cell body membranes had a particle arrangement similar to the longitudinal alignment of cytoskeletal microtubules. No aggregated particle distribution was seen in membranes of trypanosomes harvested from lethally irradiated rats. Replicas of trypanosome pellets also had plasmanemes as a series of attached, empty, coated membrane vesicles. These structures were found in close association with, as well as widely separated from the parasites. The shedding of these vesicles and the variation of particles in cell body membranes are discussed in light of antibody-induced architectural and antigenic changes in surface properties of trypanosomatids. The convex face of the inner membrane of the nucleus also is covered with randomly arrayed particles. More IMP were observed on the inner than on the outer nuclear membranes. Images of nuclear pores were also seen. The importance of these structures in drug and developmental studies of trypanosomes is discussed. On fracture faces of the flagellar membrane there were miniature maculae adherentes, unique to the inner fracture face and occurring only at regions of membrane apposition between cell body and flagellum. Each cluster of particles exposed by the freeze-cleave method corresponds to an electron-dense plaque seen in thin section images. However, because of a unique fracture pattern, these plaques were not revealed on the apposing body membranes, as illustrated in thin sectioned organisms.
Animals↗