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A J Hudspeth

Publications and source records attributed to A J Hudspeth.

116 records · Page 7Linked to original sources
PubMed1976

Cytoarchitectonic mapping by microdensitometry.

Functional differences among various portions of the cerebral cortex are often correlated with differing cortical layering patterns. Convenient, accurate techniques for scoring layering should therefore prove useful in electrophysiological as well as anatomical investigations. We report the application of a computer-controlled scanning microdensitometer as a means of rapid measurement of optical densities in histological sections of monkey visual cortices, areas 17 and 18. The technique readily permits recognition of the previously defined cortical layers and suggests that still finer consistent layering patterns exist; it provides objective "fingerprints" of cortical regions which facilitate comparisons of structure from area to area and from animal to animal. The procedure should serve also to score the positions of autoradiographic grains, degenerating axonal terminals, and other labeled structures, and to allow the comparison of preparations stained by various techniques.

Animals↗
PubMed1975

Establishment of tight junctions between epithelial cells.

Epithelia serve as barriers to the diffusion of solutes between body compartments, and must do so despite the frequent loss of cells. When single cells are experimentally removed from the Necturus gallbladder epithelium, contiguous cells migrate to fill the defect within 30 min. Electrophysiological measurements show that the local electrical resistance across the epithelium in the region of a wound returns to normal in the same period of time; electron microscopy demonstrates that tight junctions are formed concurrently. Physiologically functional and morphologically recognizable tight junctions can thus be established within 30 min, demonstrating a mechanism for the rapid restoration of epithelial integrity after cell loss.

Animals↗
PubMed1971

Gap junctions between electrotonically coupled cells in tissue culture and in brown fat.

Although circumstantial evidence has suggested that gap junctions mediate intercellular electrotonic coupling, it has not been possible in most tissues to exclude the involvement of other, coexisting cell junctions. We have made an electron microscopic study of replicas of frozen-fractured BHK21 cells (from tissue culture) and of brown fat cells of newborn mice. Both of these cell types are known to exhibit intercellular electrical coupling. In each case, the only junctions found between the cells are small macular gap junctions (less than 1 mum in diameter) characterized by clusters of 6-nm (60 A) particles or depressions on membrane cleavage faces. Several replicas confirm the association of these particles and depressions with regions of narrowing of the intercellular space, i.e., with the sites of cell junctions. We have also determined the frequency of occurrence of gap junctions on the membrane cleavage faces of both cell types. Gap junctions occupy about 1-2% of the surface area of brown fat cells, but only 0.05% of the surface area of BHK21 cells. These observations indicate that gap junctions, when they are the only intercellular junctions present, are sufficient to account for electronic coupling between cells.

Adipose Tissue, Brown↗
PubMed1971

Coexistence of gap and sseptate junctions in an invertebrate epithelium.

The intercellular junctions of the epithelium lining the hepatic caecum of Daphnia were examined. Electron microscope investigations involved both conventionally fixed material and tissue exposed to a lanthanum tracer of the extracellular space. Both septate junctions and gap junctions occur between the cells studied. The septate junctions lie apically and resemble those commonly discerned between cells of other invertebrates. They are atypical in that the high electron opacity of the extracellular space obscures septa in routine preparations. The gap junctions are characterized by a uniform 30 A space between apposed cell membranes. Lanthanum treatment of gap junctions reveals an array of particles of 95 A diameter and 120 A separation lying in the plane of the junction. As this pattern closely resembles that described previously in vertebrates, it appears that the gap junction is phylogenetically widespread. In view of evidence that the gap junction mediates intercellular electrotonic coupling, the assignment of a coupling role to other junctions, notably the septate junction, must be questioned wherever these junctions coexist.

Animals↗
PubMedDate not supplied

Voltage- and ion-dependent conductances in solitary vertebrate hair cells.

An important function of the peripheral auditory system is the resolution of complex sounds into their constituent frequency components. It is well established that each mechanoreceptive hair cell of the cochlea is maximally sensitive to a particular frequency of sound, but the mechanisms by which this sharp frequency selectivity is achieved are still controversial. The complex mechanical and hydrodynamic properties of the receptor organs and of the hair cells themselves are certainly involved. However, in at least one auditory organ, the turtle cochlea, frequency tuning is greatly enhanced by the electrical properties of the hair-cell membrane; each cell in this organ behaves as an electrical resonator tuned to a narrow band of frequencies. Using the 'Gigaseal', whole-cell recording technique, we have investigated the biophysical basis of similar resonant behaviour in enzymatically isolated hair cells from the bullfrog sacculus. We report here the identification of three voltage- and ion-dependent conductances which may contribute to the electrical tuning mechanism: a non-inactivating calcium conductance, an A-type K+ conductance, and a Ca2+-activated K+ conductance.

Animals↗