Biology bulletin of the Academy of Sciences of the USSR最新文献

The differences in the physical organization of the membranes of normal and tumor cells are explained within the framework of the hypothesis of the presence of an intact framework on the surface of normal cells and the absence of it in tumor cells. An intact framework determines the possibility of existence of metastable states of the membrane and hysteresis phenomena in the lipid bilayer. The signals for transition to the S- and M-phases of the cycle are breakoffs of the metastable states, which occur only in the membranes of normal cells. The cell cycle in tumors is constructed only on physicochemical processes in the membrane without hysteresis phenomena, and the possibilities of regulating it are greatly weakened. This hypothesis permits: a) prediction of differences in the change in the microviscosity of the lipids of normal and tumor cells during their movement along the cycle and refinement of the concept of intactness of cells in the presence of a change in the microviscosity; b) elucidation of the role of the spreading of cells for the initiation of division in vitro; c) the proposal of a method of selective destruction of tumor cells with the aid of proteolytic and lipolytic enzymes; d) the proposal of an explanation for the weak antigenicity of many spontaneous tumors and the possibility of enhancing it. Experimental data on the properties of the membranes are discussed, and they are compared with the theoretical premises.

In this article, we present the results of long-term laboratory and field investigations designed to characterize the dynamics of the various forms of compounds of the radionuclide in the soil in relation to its biological accessibility to plants. The variations in the extent of migration of 137Cs from the soil into the harvested parts of agricultural crops on the most typical soils, the contribution of the processes of fixation of the radionuclide to these variations, and the role of various properties of the soil in the migration of 137Cs into plants and the possible fluctuations in the migration of the radionuclide into plants caused by the interspecific and varietal characteristics of the plants are also discussed. The quantitative characteristics of the migration of 137Cs into the crops determined in vegetation, microfield experiments, and field experiments are compared and the possibilities of extrapolating the results of the experiments of the first two types to natural conditions are demonstrated.

In experiments on cats anesthetized with chloralose and immobilized with flaxedil, the influence of the reticular formation (RF) of the mesencephalon on the development of habituation of evoked potentials (EP) in the cerebral cortex (CC) to repeated stimulation of the splanchnic nerve was studied. It was established that high frequency stimulation of the RF (100 counts/sec) for 15 sec before testing for habituation to visceral stimulation inhibited the amplitude of the EP and shortened the time of development of habituation to repeated stimulation of the splanchnic nerve. Low-frequency stimulation of the RF (1 pulse/sec), applied during the development of habituation, restored the amplitude of the EP to the initial level. The turnoff of the activity of the RF by intravenously injected chlorpromazine (3-6 mg/kg) was accompanied by an acceleration of the development of habituation of evoked potentials in the associative region of the cortex. The participation of the RF in processes of habituation and dehabituation is discussed.

The action of monovalent inorganic cations -Li+, Na+, K+, Rb+, Cs+, NH4+ - on assimilation of tetracycline antibiotics by Gram-positive (Staphylococcus aureus), and Gram-negative (Escherichia coli) bacteria sensitive and resistant to these antibiotics, was studied. It was found that K+ ions and, to a lesser degree, Rb+ and NH4+ ions, stimulate assimilation of tetracyclines by these microorganisms when incubated in Tris-buffer. The action of K+ ions is exhibited over a wide range of concentrations from 0.1 to 20 mM. In the case of Staph. aureus the action of K+ and Rb+ is exhibited after lag phase about 5 min in duration, but in the case of E. coli, the action of these ions is exhibited soon after their addition to the incubation medium. In all cases NH4+ ions act without a lag phase. The possible mechanisms of the effect of inorganic cations on assimilation of tetracyclines by bacteria are discussed.

In a experiment on female rats lasting two years, the influence of total gamma radiation if a dose of 100 rad on the state of the neuroendocrine system was studied. Penetrating radiation causes a disturbance of the hormonal balance and of the sexual cycle, and, as a consequence, the development of tumors of the incretory glands and target organs.

A dynamic approach was employed for a study of the reaction of the fatty acid pool of sensitive and resistant strains of E. coli K12 in response to the introduction of antibiotics. Bacteria whose resistance is controlled by plasmids exhibited a specific reaction - a reversible increase in the concentration of cis-9,10-methyl-enehexadecanoic acid. Strains of E. coli K12 (C600, J53, CSH-2) carrying plasmids RP4, R6K, R1 drd 19, pMB9, R386, RP1, RtS-1, were studied.

When 25 microgram of metenkephalin is injected subcutaneously into rats, the development of temporal associations is somewhat impaired, but the fixation of them is enhanced. The latter effect is observed more clearly when metenkephalin is injected not before, but immediately after the development of conditioned reflexes. Under the influence of metenkephalin, there is an increase in the incorporation of C14-leucine into the insoluble proteins of the hippocampus and basal ganglia. It is hypothesized that metenkephalin mainly affects the process of consolidation.

In biological systems nonuniformity of magnetic susceptibility, magnetic heterogeneity, is a reflection of their physical-chemical and morphological heterogeneity, A characteristic value of heterogeneity is delta K approximately 10(-6)-10(-7) CGS units, a quantitative measurement of susceptibility of cells and other small objects, may give qualitatively new information about their life processes. Patterns and features of movement of small biological objects and liquids affected by magnetic forces were studied. A method was developed for measuring magnetic susceptibility of single microobjects based on observation of movement of the objects in a strong heterogeneous field with parameters (formula: see text) grad H2/2 approximately 10(9)-10(10) Oe2/cm. This method does not require knowing the distribution of the field along the path of movement of the particles, and does not require preliminary calibration. Movement of human erythrocytes, rat hepatocytes, and starch granules in liquids at a point of entry into a gap with the field was observed experimentally. With sufficiently large fields Ho approximately (1-2) x 10(4) Oe, the value of the magnetic force was enough to change the rate of sedimentation movement of the objects appreciably (up to stopping it). This made it possible to compute the value delta K for cells approximately 10(-7)-10(-8) CGS units and to obtain the value of K for starch granules (-0.80 x 10(-6) cGS units). In connection with the fact that sensitivity to gravity in plants is coupled with a disturbance of the intracellular starch granules under the influence of gravity, certain problems of stimulating the effect of gravity on plants by magnetic forces were studied. Noncontact force effect on magnetically heterogeneous biological objects is a promising instrument for biophysical studies.

In recent years it has been shown on the example of primate skin that in addition to abundant cholinergic innervation, the eccrine glands are also supplied by adrenergic fibers, containing catecholamines. The presence of an adrenergic component of the innervation is demonstrated on the plantar eccrine sweat glands of a number of rodents and the cat by the detection of monoamine oxidase in it. The myelin nerve trunks, the short unmyelinated varicose terminals in direct contact with the secretory cells, as well as the mitochondria of cells of the eccrine sweat glands are rich in monoamine oxidase. Specific and nonspecific cholinesterases are localized in the dense network of nerves in lacing the secretory portions of the glands; individual fibers accompany the excretory ducts. The acetylcholinesterase concentration is lower than the concentration of nonspecific cholinesterase. In rats with chemical sympathectomy, induced by four-week administration of 25 mg/kg guanethidine from the first day of birth, in which 99% of the neurons in the stellate ganglia die, the monoamine oxidase concentration in the myelin nerves and in the mitochondria of the secretory cells drops very sharply, and acetylcholinesterase disappears from the nerves surrounding the glands.