A symposium on the structure of protoplasm / edited by William Seifriz.

Abstract

The Structure of Protoplasm matter is very probably due to a specific arrangement of parts, that is to say, to structure. Often I am asked by physicists and chemists if much can be hoped for in the way of an understanding of protoplasmic structure. Direct observation, even with the highest powers of the microscope, is too superficial to reveal anything fundamental. Chemical analysis is not productive of significant results because once protoplasm is subjected to severe treatment it is no longer living matter. The very structural features which distinguish it from the nonliving are then destroyed. The biologist interprets the basic structure of protoplasm somewhat in the same way that a chemist interprets the structure of a compound, namely, by its behavior. The chemist sees nothing of the links, rings, side chains, amino and carboxyl groups which he attaches here and there, yet he builds up a structure with considerable confidence, which is the justification of stereochemistry. Just so does the biologist work; he interprets the structure of living matter in the light of its known physical properties. But this was not the method of the older biologists, and herein lay their error. They told only of what they saw. Protoplasm viewed through the microscope appears to be a suspension of fine granules. On this fact was based the granular hypothesis of protoplasmic structure. Its weakness lay in the diversity of the granules and the undue significance given them. Some are admittedly important, as are the plastids and the mitochondria; others, such as fat droplets, are but reserve food. These last are really not granules at all but liquid droplets which make of cytoplasm a fine emulsion. The importance attributed to the "granules"-they were regarded by some as living units, morphologically and physiologically independent of the cell-and the necessary coarseness of any optically visible structure, led to the discarding of the granular hypothesis. The belief that the basic structural unit of protoplasm is a spherical body has long persisted and has given rise to numerous hypotheses expressed in terms of granules, globules, alveoli, and micellae. Such suggestions are in part supported by fact. Thus, protoplasm is unquestionably an emulsion, and when the emulsion globules are under pressure and symmetrically arranged they assume the shape of dodecaor tetrakaidecahedra which are hexagonal in cross section. These latter are alveoli.

Rhythmicity in the Protoplasmic Streaming of a Slime Mold, Physarum Polycephalum

“…Wrinkling of the periphery with a decrease in volume due to loss of protoplasm indicates that there has been no change in the total surface area and therefore, no essential role for contraction of plasmagel in the protoplasmic flow. The so called sol endoplasm is rather viscous and elastic compared with a liquid and shows a structural continuity (Seifriz, 1942). Therefore, it is more reasonable to suppose that the plasmagel and plasmasol both have the ability to contract and that the plasmasol is flowing as a thixotropic sol, while the plasmagel remains as a gel because of its denser packing.…”

“…Contraction should shorten and therefore smooth out the surface of plasmagel at the posterior end as it is emptied of protoplasm. However, photographs of slime mold (Seifriz, 1942) and of ameba (Abe, 1957) showed that the periphery of the plasmagel at the posterior end is wrinkled, whereas the periphery of the expanded protoplasmic mass at the anterior region is smooth. Wrinkling of the periphery with a decrease in volume due to loss of protoplasm indicates that there has been no change in the total surface area and therefore, no essential role for contraction of plasmagel in the protoplasmic flow.…”

“…The metabolic pattern of Physarum is very similar to that of muscle cells (Ohta, 1954). Electron microscope studies on the protoplasm of Physarum show the existence of network-like structure (Sponsler and Bath, 1953;Kishimoto and Terada, 1956). However, such submicroscopic networks of the contractile proteins may be labile compared with those of muscle cells.…”

“…Each contractile protein in the protoplasm may perhaps maintain an organized framework which would assist some aspects of protoplasmic flow (Seifriz, 1942(Seifriz, , 1943(Seifriz, , 1953Frey-Wyssling, 1949, 1953, 1955. Therefore, we can assume that there are "couplings" among contractile proteins, though perhaps not so strong as those in muscle cells.…”

Organelle Systems and Biological Organization

“…Analogous laminates of other macromolecular aggregates such as lipids and protein were proposed as the ultrastructural basis of membranes, even before the invention of the electron microscope, especially from results with polarized light and x-ray diffraction methods. Along these lines, the pioneering studies of Frey-Wyssling (33), Seifriz et al (34), Davson and Danielli (35), F. 0. Schmitt (36), and many others have been substantiated and extended (31, 3 7 ) , and the principal continuing emphasis in electron microscopy is quite justifiably at this lower level of the n~acromolecular ag-gregates.…”