Microscopy of cell cultures through thin plastic films.

Microscopy of cells growing in vessels containing plastic films as a substrate or as a transparent window is facilitated by a contact cap on the objective or the contact objectives for intravital microscopy. When applied to microscopical examination of living cells through a thin film, the cap considerably improves the conditions of observation with high-power dry objectives and makes it possible to use water- and oil-immersion objectives.

Elimination of the nucleolus from the nucleus of a living cell by centrifugation (a literature review).

The following effects involving the nucleolus take place during centrifugation of living cells at centrifugal forces of several thousand g to several hundred thousand g: settling of the nucleolus in centrifugal direction on the nuclear envelope; pulling the latter as a long stalk with the nucleolus at its end (or alternatively an easy perforation of the nuclear envelope by the nucleolus); release of the nucleolus into the cytoplasm or its expulsion out of the cell; occasional stratification of the nucleolus in the nucleus; fusion of many nucleoli together under centrifugal pressure. The asymmetric topography of the nuclear envelope is considered to be one of the causes of its different resistance to the penetration of the nucleolus. Elimination of the nucleolus from cancer cell nuclei to test the nucleolar contribution to cell malignancy is suggested as one conceivable application of the centrifugal technique of cell enucleolation.

The cell in the field of gravity and the centrifugal field.

It appears that the literature and logic that the earth's gravity has been one factor in the limitation of cell size, as well as being an important influence on the diversity of cell types and sizes throughout biological evolution. Analysis of the literature reveals an inverse relationship between the centrifugal force needed for intracellular stratification and cell size. The cells studied ranged in size from approximately 1 mm (amphibian eggs, Pelomyxa) to 0.01 mm (erythrocyte, lymphocyte), and g-forces ranged from about 100 g to 100 000 g respectively. Stratification within cell nuclei and organelles requires even greater forces, presumably because of their smaller size. Extrapolation from centrifugal forces to the force of gravity, and from the full stratification to the initial sedimentation of cell parts suggests a hypothesis for the evolutionary survival and existence of cells in the field of gravity. Average cell size results, in part, from the physical equilibrium between the destructive influence of the force of gravity and the protective role of diffusion and the cytoskeleton. At increased forces of gravity the cell size would thus be decreased, whereas at lower gravitational forces and weightlessness cell size would be expected to increase. Mechanisms of protection of giant cells against internal sedimentation are based on protoplasmic motion, thin and elongated shape of the cell body, increased cytoplasmic viscosity, and a reduced range of specific gravity of cell components, relative to the ground-plasm. The nucleolus, due to its higher density, is considered as a possible trigger of mitosis.

A hypothesis of the code of nerve impulses.

There is probably only one information system in living nature - the macromolecular system including DNA, RNA and protein. Its unity for the genetic and nervous activity can be followed in the storage of information (heredity, memory) and in its processing (recombination and selection of both genetic and mental information). According to the hypothesis of the code of nerve impulses, nucleotide triplets of the nucleus, or more likely amino acids of the surface protein of the impulse generating area of a neuron, generate a limitd variety of interspike intervals so that each amino acid corresponds to a certain interspike interval and this particular interval initiates by means of a specific neurotransmitter, the synthesis of the same amno acid (or nucleotide triplet) in the postsynaptic neuron. Thus, a series of impulses produces in the postsynaptic neuron a sequence of amino acids in a form of a polypeptide identical to the polypeptide of the presynaptic neuron.

[Interneuronal contacts and propagation mechanism in paired receptors of the propo-dactylopodite organ of the crayfish Astacus leptodactylis]. / Mezhneironnye kontakty i mekhanizm provedeniia v parnykh retseptorakh organa propo-daktilopodita rechnogo raka Astacus leptodactylis

In recordings of biopotentials from the propo-dactylopodite-organ (the PD-organ) nerve, repetitive pairs of impulses are frequently observed, which presumably reflect paired structure of receptor elements where two sensory neurons are morphologically linked by non-polarized interdendritic ephapse. It is suggested that propagation via the ephapse out to be bilateral and that each of the postephaptic fibers transmits impulses from both of the cilia of the paired receptor. However, identical impulses from different cilia reach the central nervous system at different time, this mechanisms being presumably employed for differentiation of information on each of the cilia. One of the postephaptic fibers passes, seemingly, to the right, whereas the other one - to the left half of the first thoracic ganglion.