Sensory characteristics of the cortical input of the hippocampus, the dentate fascia]

Investigation of sensory reactions of the neurones of the dentate fascia was performed in unanaesthetized rabbits. Spontaneous activity usually consisted of long aperiodic high-frequency bursts with silent periods between them. Multimodal convergence was observed in 76% of records. Responses to sensory stimuli constituted three nearly equal groups: 1 -- tonic inhibitory reactions; 2--phasic (equal to stimulus duration) activatory responses; 3--simple "specific" responses of on-type, sometimes with secondary phasic components. In one microelectrode track, perpendicular to the double lamina of granular cells, all neurones usually responded in the same fashion.     

Sensory characteristics of the cortical input to the hippocampus: the entorhinal cortex]

Sensory reactions of neurones in the medial entorhinal area were investigated in unanaesthetized rabbits. 54% of the units were multimodal. Different stimuli evoked various response patterns with complex on-off components. Differential coding of pure tones was observed in many cells, which were also sensitive to other sensory modalities. Complete habituation of responses was virtually absent; only partial reduction of the late components was observed in some cases. In 71% of units reactions were stable or incremental (gradual development and increase). It may be concluded that from the entorhinal cortex the hippocampus receives highly differentiated signals of "associative" type, which do not habituate and are of a stable or incremental nature.     

Relationship between the curve of the instantaneous pressure gradients and the enveloping heart sound]

The curve of instantaneous pressure gradients between the communicating chambers of the heart represents the "enveloping" one of the cardiac sounds. This curve is proportional to the curve of the instantaneous rates of the blood flow in the given area of the system. Consequently, the higher the pressure gradient, the greater the rate of the blood flow and the greater the oscillation range on the phonocardiogram.     

Experimental study of antibacterial activity, therapeutic effectiveness and toxic properties of the combination of tobramycin and carbenicillin

Tobramycin combination with carbenicillin was studied experimentally. Tobramycin is a new aminoglycoside antibiotic prepared at the Institute of New Antibiotics, the USSR Academy of Medical Sciences. It was shown that the combination had mainly synergistic action (67 per cent) on clinical strains of Pseudomonas aeruginosa which was confirmed in treatment of experimental sepsis caused by the organism. In acute experiments with albino mice there was observed summation of the general toxic action of the antibiotics used in the combination. The level and nature of the nephrotoxic action of the tobramycin combination with carbenicillin were shown in experiments with rats to be the same as those of the nephrotoxic action of tobramycin used alone. The presence of carbenicillin in the combination did not increase the inhibitory effect of tobramycin on excitement transmission in the neuromuscular synapses.     

Theta-bursts of hippocampal and septal neurons

Investigation of neuronal activity on non-anaesthetized rabbits in non-stress chronic conditions revealed in the hippocampus a small proportion of neurones (10-12 percent) with a weak rhythmic (theta) modulation of their activity. In the medial and lateral septal nuclei this activity was more organized and was present in about one third of neuronal population. Disruption of septo-hippocampal connections completely abolished theta-rhythm in EEG and in neuronal activity of the hippocampus. Transection of the perforant path was followed by appearance of pronounced theta-bursts in a large group of neurones (38 percent in CA1 and 43 percent in CA3). Electrical stimulation of the hippocampus suppressed theta-bursts and decreased their frequency in the lateral spetal nucleus. Disruption of hippocampo-septal connections was followed by an increase of the population of septal neurones with theta-bursts (48 percent), which became more prounced. Some theoretical implications from these data concerning the nature of hippocampal theta-activity are discussed.     

Influence of partial deproteinization on the cytochemical properties of DNP of lymphocyte nuclei

Fixed lymphocytes from mouse lymphatic nodules were treated on histological preparations with sodium chloride solutions of varying molarity. The extracts were investigated electrophoretically and were found to contain all histone fractions after treatment with 1.5 M NaCl solution and only the histone F1 after treatment with 0.6 M solution. The cytochemical properties of the cells with histones removed were investigated. The experiments showed that histone removal resulted in a marked increase of nucleic capacity to bind AO, and in a significant decrease of DNP thermal stability of these cells in denaturation test. To establish the role played by histone F1 in the course of cell activation this histone was removed from lymphocytes in states of different activity. The experiments showed that after treatment with 0.6 M sodium chloride the difference in AO-binding of cells in states of different activity disappeared. The data obtained confirm the hypothesis about histone-DNA separation at early stages of chromatin activation and suggest that the early change in physico-chemical properties of chromatin are connected with the separation of lysine-rich histone F1.     

Features of the Radial and Axial Distributions of the Toroidal Magnetic Field in the Axial Jet Ejection at the PF-3 Facility

Plasma Physics Reports - The results of experiments on the study of the features of the dynamics and internal structure of the axial plasma ejection at the PF-3 facility carried out within the...     

Formation of nanostructures in a plasma focus discharge

A new method for creating nanostructures in a plasma focus discharge is proposed. It is shown that the material of a micron-size dust target produced at the discharge axis efficiently evaporates and is then involved in the pinching process. After the pinch decays, the plasma expands with the thermal velocity and the evaporated dust material is deposited on the collectors in the form of fractal particles or nanoclusters organized into various structures. Such structures have a well-developed surface, which is important for various technological applications.