Search PubMed⌕ Search

Biomedical subjects

H Ris

Publications and source records attributed to H Ris.

40 records · Page 3Linked to original sources
PubMed1966

Electron microscope studies on soma-somatic interneuronal junctions in the corpus pedunculatum of the wood ant (Formica lugubris Zett.).

1. The corpora pedunculata of the wood ant (Formica lugubris Zett.) contain densely packed neuron perikarya which are separated by ultrathin glial sheaths. 2. These glial sheaths are occasionally interrupted by round holes with an average surface area of 2.64 micro(2). The holes are designated glial windows since they represent intracellular gaps of glial cytoplasm. 3. The glial windows allow soma-somatic interneuronal junctions. Of all adjacent neurons in a selected neuron pool, only 42% were interconnected by such junctions. 4. The intercellular space at the soma-somatic junctions has an average diameter of 30 A; occasionally, it is collapsed and an external compound membrane ensues. The junctional membranes are characterized by the presence of a subunit pattern of cross-directional electron-opaque lines with a 50- to 70-A periodicity. 5. Morphological signs of chemical transmission are absent in these junctions. On the other hand, there is a striking similarity in structural organization between soma-somatic junctions and electrical synapses described in other species. Therefore, it is suggested that these cell contacts of the ant's "cerebral cortex" are another form of electrical junction. 6. The close proximity of the junctions to the cell nucleus is noted. Its significance could not be ascertained. 7. The suggestion is made that glial windows may have dynamic properties and may intervene in the regulation of interneuronal transfer of information.

Ants↗
PubMedDate not supplied

High-resolution field emission scanning electron microscope imaging of internal cell structures after Epon extraction from sections: a new approach to correlative ultrastructural and immunocytochemical studies.

The availability of high-resolution field emission scanning electron microscopes (FESEM) and the recent development of a less destructive method for extracting Epon from sections motivated us to investigate these techniques for the study of internal cell structures. We chose the nuclear pore complex (NPC) and insect striated muscle as test objects. Chemically fixed or rapidly cryoimmobilized samples were embedded in Epon 812. The Epon was extracted from 200- to 300-nm-thick sections with a modified potassium methoxide-crown ether complex. The samples were viewed with high-resolution FESEM at low voltages. In tangential sections of isolated nuclear envelopes from Xenopus oocytes the cytoplasmic and intranuclear components ("fishtraps") of NPCs appeared identical to what has been described from whole mounts. In cross sections, fishtraps are seen in side view, which is possible only with this technique. In longitudinal and cross sections of insect flight muscle the classical arrangement of myofilaments and cross-bridges is well preserved. This method now makes it possible to image internal cell structures from any desired angle by high-resolution FESEM. Immunolabeling studies on the rabbit psoas muscle demonstrated that antigenicity of alpha-actinin was retained in Epon-extracted sections. Immunogold labeling with antibodies against alpha-actinin conjugated to 3-nm gold beads was intense, highly specific, and restricted to the Z lines. This method can overcome the penetration problem of immunogold labeling, since any cell component can be positioned at the surface of the section. Obviously this approach can become a powerful new tool for many areas of structural cell biology.

Actinin↗