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T S Reese

Publications and source records attributed to T S Reese.

At least 109 records · Page 6Linked to original sources
PubMed1981

Cytoskeletal organization at the postsynaptic complex.

Postsynaptic densities and the adjacent cytoskeleton were examined in deep-etched, unfixed slices of guinea pig anteroventral cochlear nucleus. The postsynaptic density seen in conventional thin sections corresponds to a meshwork of 4-nm filaments associated with intramembrane particles at the postsynaptic active zone of inhibitory as well as excitatory synapses. These filaments intermesh with a lattice of 8- to 9-nm microfilaments, tentatively identified as F-actin, that is concentrated under the postsynaptic density. We postulate that the meshwork of 4-nm filaments anchors receptors to the adjacent microfilament lattice; this extended postsynaptic complex may limit the mobility of receptors and help maintain the curvature of the postsynaptic membrane.

Animals↗
PubMed1981

Membrane structure in mammalian astrocytes: a review of freeze-fracture studies on adult, developing, reactive and cultured astrocytes.

The application of freeze-fracture techniques to studies of brain structure has led to the recognition of two unsuspected specializations of membrane structure, each distributed in a specific pattern across the surface of astrocytes. 'Assemblies' (aggregates of uniform, small particles packed in orthogonal array into rectangular or square aggregates) are found to characterize astrocytic plasma membranes apposed to blood vessels or to the cerebrospinal fluid at the surface of the brain. These particle aggregates are much less densely packed in astrocytic processes in brain parenchyma. Assemblies are not fixation artifacts, have been shown to extend to the true outer surface of the membrane, are remarkably labile in the setting of anoxia, and are at least in part protein. The function of assemblies is unknown, but their positioning suggests that they may have a role in the transport of some material into or out of the blood and cerebrospinal fluid compartments. A second specialization of intramembrane particle distribution, the polygonal particle junction, links astrocytic processes at the surface of the brain, and also links proximal, large caliber astrocytic processes in brain parenchyma. The function of this membrane specialization also is unknown, but it may subserve a mechanical role.

Aging↗
PubMed1980

Use of aldehyde fixatives to determine the rate of synaptic transmitter release.

Aldehyde fixation continues to be useful to prepare synapses for freeze-fracture, but it may increase the rate of transmitter release. The effects of different aldehyde fixatives on spontaneous quantal release (m.e.p.p.s), and on the corresponding synaptic vesicle exocytosis at frog nerve-muscle synapses were investigated with the hope of finding a way to minimize side effects of fixation. Increases in m.e.p.p.s of up to 50 S-1 occurred during fixation, despite the species of aldehyde used in the fixative, and this fixative effect decreased only slightly as aldehyde concentration was increased. Increases in m.e.p.p frequency were not blocked by tetrodotoxin, by lowering external calcium and raising external magnesium concentration, or by lowering the total osmotic strength of the fixative. The smallest increase in m.e.p.p. frequency was in 3% glutaraldehyde and corresponded to the lowest level of synaptic vesicle exocytosis seen by freeze-fracture, 0.15 per micrometers of active zone. The effects of aldehyde fixation on m.e.p.p. frequency and synaptic vesicle exocytosis could not be avoided, but this study suggests how its effect on morphological changes in synapses might be minimized.

Aldehydes↗
PubMed1980

A freeze-substitution method for localizing divalent cations: examples from secretory systems.

This paper presents a simple method for localizing calcium in its natural distribution. This method depends on freeze-substituting rapid-frozen tissue, and combines the spatial precision of conventional plastic sections with the reliable calcium localization characteristic of direct freezing methods. Calcium is retained in the tissue during freeze-substitution and subsequent processing, and its distribution in frog skeletal muscle suggests that it is not displaced during tissue processing or in the electron probe. Examples of new findings with this method are the presence of a postsynaptic sequestration system for cations entering at the neuromuscular junction, and a nonmitochondrial system in nerve muscle synapses that sequesters cations entering during depolarization-secretion coupling.

Animals↗
PubMed1980

[Ultrastructural study of the brain and the leptomeninges in the Hy-3 hydrocephalic mouse (author's transl)].

Congenital murine hydrocephalus occuring in the Hy-3 strain has certain similarities to human congenital hydrocephalus. In order to elucidate the pathophysiology and etiology of congenital hydrocephalus, ultrastructural study of the brain and the leptomeninges in the Hy-3 hydrocephalic mice was undertaken. The cerebral cortex was invested with the thick cellular layer which had similar features of primitive arachnoid barrier cells. No appearent subarachnoid space was found. Horseradish peroxidase, introduced into the lateral ventricle, crossed the ependymal cells and penetrated into parenchymal extracellular spaces. However no horseradish peroxidase activity was found over the cerebral hemispheres. Those results suggested that the hydrocephalus in the Hy-3 strain is due to development anomaly of the leptomeninges and to defect of cerebral subarachnoid space.

Animals↗
PubMed1979

Synaptic vesicle exocytosis captured by quick freezing and correlated with quantal transmitter release.

We describe the design and operation of a machine that freezes biological tissues by contact with a cold metal block, which incorporates a timing circuit that stimulates frog neuromuscular junctions in the last few milliseconds before thay are frozen. We show freeze-fracture replicas of nerve terminals frozen during transmitter discharge, which display synpatic vesicles caught in the act of exocytosis. We use 4-aminopyridine (4-AP) to increase the number of transmitter quanta discharged with each nerve impulse, and show that the number of exocytotic vesicles caught by quick-freezing increases commensurately, indicating that one vesicle undergoes exocytosis for each quantum that is discharged. We perform statistical analyses on the spatial distribution of synaptic vesicle discharge sites along the "active zones" that mark the secretory regions of these nerves, and show that individual vesicles fuse with the plasma membrane independent of one another, as expected from physiological demonstrations that quanta are discharged independently. Thus, the utility of quick-freezing as a technique to capture biological processes as evanescent as synaptic transmission has been established. An appendix describes a new capacitance method to measure freezing rates, which shows that the "temporal resolution" of our quick-freezing technique is 2 ms or better.

Aminopyridines↗
PubMed1978

Endoplasmic reticulum sequesters calcium in the squid giant axon.

Axons were loaded with calcium, rapidly frozen, and freeze-substituted. The endoplasmic reticulum, in addition to mitochondria, contained calcium deposits, as indicated by electron probe x-ray microanalysis. Oxalate injected into living axons helped to preserve calcium-containing deposits during preparation for microscopy. It is concluded that the endoplasmic reticulum is a calcium-sequestering compartment in the squid giant axon.

Animals↗
PubMed1978

Internal organization of membranes at end bulbs of Held in the anteroventral cochlear nucleus.

The end of bulb of Held in the rostral ventral cochlear nucleus of the chinchilla and guinea pig was studied with the freeze-fracture technique. The end bulb has multiple, small active zones which are uniformly distributed within the calyceal portion of this terminal. Single or small groups of active zones are surrounded by enlarged channels of extracellular space often containing processes of astrocytes. Small plasmalemmal deformations occur at these active zones. The number of these deformations is thought to be indicative of exocytotic transmitter release because they are more frequent in animals fixed in a noisy environment compared to animals fixed in a quiet environment. Thus, our study provides a basis for the quantitative study of changes in transmitter secretion at a central nervous system synapse driven by a controllable natural stimulus. The postsynaptic active zone at end bulbs resembles other excitatory synapses in the central nervous system in having an aggregate of large particles on the external membrane leaflet. This junctional aggregate of particles is coextensive with the presynaptic active zone and with the postsynaptic density seen in thin sections. Several perisynaptic aggregates of particles are deployed around each active zone on the external membrane leaflet. These irregularly-shaped aggregates occur preferentially opposite the channels of enlarged extracellular space and along the edge of the end bulb and are not components of intercellular junctions or plasmalemmal contacts with cytoplasmic organelles. Although the function of the different particle aggregates on the postsynaptic membrane is not clear, our findings provide a basis for studying the factors controlling and maintaining their structure as well as more evidence that a consistent relationship exists between types of synaptic action and structure of the postsynaptic membrane.

Acoustic Stimulation↗
PubMed1978

T-tubule swelling in hypertonic solutions: a freeze substitution study.

Striated muscles from Rana pipiens have been exposed for variable periods of time to Ringer solutions made hypertonic by addition of either sucrose or sodium chloride. The muscles have been rapid-frozen and then prepared for electron microscopy by either freeze-substitution, freeze-fracture or cryoultramicrotomy. The only compartment greatly affected by hypertonicity is the transverse tubular system, which is visibly swollen. None of the elements of the sarcoplasmic reticulum increase in size.

Animals↗
PubMed1977

Freeze-fracture studies on the synapses in the organ of Corti.

Receptoneural junctions and synapses in the organ of Corti of the chinchilla have been examined with the freeze-fracture technique. The presynaptic membranes at the receptoneural junctions of inner and outer hair cells have many structural features in common with membranes found at chemical synapses outside the organ of Corti. However, the membranes of the postsynaptic afferent terminals are quite different depending on whether they are part of an inner or outer hair cell synapse. These differences in the distribution of intramembrane particles suggest that the transmitters, or transmitter actions, may be different at these two synapses. The distribution of particles in the postsynaptic membrane at efferent synapses with outer hair cell differs from that in the postsynaptic membrane at efferent synapses with afferent terminals or fibers, suggesting that transmitter actions at these locations could also differ.

Animals↗
PubMed1977

Structure of the Purkinje cell membrane in staggerer and weaver mutant mice.

The structure of the plasma membrane of Purkinje cell dendrites was examined in weaver and staggerer mutant mice. Purkinje spines in weaver mice have clusters of intramembrane particles which resemble those at normal synapses with parallel fibers, even though no parallel fibers are formed in this mutant. There are very few spines in the staggerer, and these manifest normal intramembrane structure at contacts with climbing fibers. The spines which would normally be involved in synapses with parallel fibers are never formed in the staggerer, and the intramembrane structures which would have been associated with these spine synapses are also lacking. Thus, during postnatal cerebellar development in the mutants, acquisition of intramembrane specializations requires Purkinje spine formation but can occur independently of the development of parallel fibers.

Animals↗
PubMed1977

Regional specialization of the hair cell plasmalemma in the organ of corti.

Nonjunctional and nonsynaptic membranes of hair cells in the chinchilla organ of Corti were examined using the freeze-fracture technique. Cytoplasmic leaflets of the apical membranes of hair cells have particles, 6-12 nm in diameter, but many more particles are found on apical membranes of outer hair cells than on inner hair cells. Cytoplasmic leaflets of the lateral membranes of outer hair cells are covered with large particles, but the corresponding regions of the inner hair cell membrane have fewer particles and these are small or medium-sized. Two types of particle aggregate also distinguish this region of the inner hair cell. The first consists of patches of particles closely spaced in rectilinear arrays. The second consists of parallel strands of widely spaced large particles similar in size, but not in distribution, to the large particles on the lateral membranes of the outer hair cells. The basal membrane of outer hair cells is distinguished from that of inner hair cells by plaques consisting of cross-hatched incisures in the external membrane leaflet. While the significance of these anatomical features is not yet apparent, they give the hair cell plasmalemma a richness or regional specialization found in few other cells and suggest that there are important functional differences between inner and outer hair cells.

Animals↗
PubMed1977

Action of brown widow spider venom and botulinum toxin on the frog neuromuscular junction examined with the freeze-fracture technique.

1. Structural changes which normally accompany transmitter release at frog neuromuscular junctions are visualized with the freeze-fracture technique. The effects of brown widow spider venom and botulinum toxin were evaluated in terms of their ability to block or produce these structural changes. Changes produced by these neuropoisons were correlated with their known effects on neurotransmitter release. 3. Fusion of synaptic vesicles with the presynaptic plasmalemma, normally evoked by electrical stimulation, was abolished at neuromuscular junctions from frogs treated with botulinum toxin. 3. The concentration of large intramembranous particles in the presynaptic plasmalemma, an indication of the excess of synaptic vesicle fusion over recovery of synaptic vesicle membrane, was increased by treatment with brown widow spider venom, even in the presence of botulinum toxin. 4. When external calcium was present, sites of vesicle fusion induced by brown widow spider venom, as well as by electrical stimulation, were located mainly in the active zone. In the absence of external calcium, many plasmalemmal deformations, also though to be sites of vesicle fusion, were more evenly dispersed over the presynaptic surface of nerve terminals. 5. Botulinum toxin decreased the number of vesicle fusion sites in the active zone induced by spider venom in the presence of external calcium but had little effect on the number of fusion sites induced by spider venom in the absence of external calcium. 6. Nerve terminals soaked in a sodium-free Ringer solution were partially depleted of vesicles. Addition of spider venom to this Ringer did not cause additional depletion of vesicles. 7. Formation of cation-permeable channels in the presynaptic membrane could account for these effects of spider venom on the frog neuromuscular junction. Botulinum toxin blocks vesicle fusion by some means which is not yet understood.

Animals↗