Formation of functional synaptic connections between heterogeneous brain formations in organotypic nerve tissue culture

The principles of oriented growth of nerve fibers and the formation of functional synaptic connections during combined culture of brain structures with no direct anatomical or functional connections (the spinal cord and olfactory bulbs of mouse embryos) were investigated by neuromorphological and electrophysiological methods. During the first week of culture connections, mainly glio-neuronal bridges, formed between the explants of spinal cord and olfactory bulb. Glial cells forming an oriented substrate, facilitating growth and fasciculation (the formation of bundles) of axons that developed subsequently, play an active role in the formation of such connections. In preparations impregnated with silver, connections formed by bundles of axons or by single nerve fibers were seen between the explants. The results of electrophysiological investigations of combined cultures of heterogeneous brain structures showed that by the second week of culture functional synaptic connections have formed between explants of spinal cord and olfactory bulbs. Electrical stimulation of spinal cord explants led to the appearance of short- and long-latency unit responses in explants of the olfactory bulbs. The formation of nonspecific functional synaptic connections for these brain structures during combined culture, revealed by this investigation, is evidence of the high level of morphogenetic plasticity of growing or regenerating axons and of the active role of neuroglial cells in preparation and provision for oriented growth of nerve fibers.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 12, No. 5, pp. 490–497, September–October, 1980.     

Interference of Factors in the Competitive Interaction of the Alien Species Pulmonaria saccharata (Mill) with a Seed Bank in the Conditions of Introduction

Biology Bulletin - In the experimental plantings of the alien species Bethlehem lungwort Pulmonaria saccharata, the transport of phytotoxic phenols with leaf leachates into the soil of the...     

Mobilization of a cryptic plasmid from the melioidosis pathogen in heterologous species of microorganisms

Cryptic plasmids with different molecular weights have been detected in B. pseudomallei strains. Mobilization of B. pseudomallei plasmid DNA in heterologous B. mallei species was performed by the conjugate plasmid RP1::Tn10. Possibility of detecting phenotypical characteristics of plasmids and behavior of B. pseudomallei non-chromosomal replicons in B. mallei have been determined.     

Influence of Bt-plants on soil biota and pleiotropic effect of δ-endotoxin-encoding genes

The critical review of experimental conclusions stating environmental safety of transgenic plants reveals that the methods and test materials employed in some studies were inadequate to the goals pursued. A large-scale application of transgenic Bt-plants may result in long-lasting negative impact on the environment. First, the cultivation of these plants leads to accumulation of Bt-toxins in soil. Second, the decomposition of transgenic plants takes significantly longer time compared to that of isogenic lines. Third, the biological activity of soils under transgenic crops is lower than in the control plots. The transfer of δ-endotoxin-encoding genes to the genome of agricultural crops affects simultaneously several entirely different traits of genetically modified plants, thus exerting pleiotropic effects. This gives rise to a paradoxical situation: the genetically engineered crops selected on the trait of resistance to herbivorous insects of the order Lepidoptera become more attractive for herbivores from the other order, Homoptera.     

Lipopolysaccharide-induced hydrolysis of plasmalogenic phosphatidylethanolamine in human platelets

The composition of human platelet major phospholipids-phosphatidylcholine (PC), phosphatidylinositol (PI), phosphatidylserine (PS), phosphatidic acid (PA), sphingomyelin (SM), plasmalogenic and diacyl species of phosphatidylethanolamine (PPE and APE, respectively) was quantitatively analyzed by high performance liquid chromatography. Incubation (10 min, 37 degrees C) of washed platelets with lipopolysaccharide B (LPS) of Salmonella typhimurium was found to produce (in the absence of aggregation) marked hydrolysis of PI (ca. 15%) and PPE (ca. 19%) containing the bulk of polyenic fatty acids. PC and APE were less degraded (8-9%), while the amounts of PS and SM were practically unchanged and the level of PA rose by 20%. Addition of thrombin to LPS-pretreated platelets resulted in their more rapid aggregation which was accompanied by a decreased and nearly equal hydrolysis of APE and PPE (7-8%) as compared with control platelets (10 and 12%, respectively). The extent to which PI was degraded (ca. 34%), by the action of thrombin was not affected by preliminary incubation with LPS. It is suggested that thrombin (as well as LPS) activating endogenous phospholipase(s) A2 can liberate from PPE not only arachidonic acid but also other essential polyenic fatty acids present in PPE in relatively high amounts. Besides, the agents studied may activate the intrinsic platelet system of rapid arachidonoyl transfer from diacyl PC and PE to PPE.     

Formation of cell structures and interneuronal connections in organotypical tissue cultures of neonatal mouse hippocampus

Cell structures and nerve fiber architectonics were studied in the neonatal mouse hippocampus in vitro. Bundles of nerve fibers (alvear tract, perforant path, axons of mossy cells) and the formed granular layer of the dentate fascia were discovered in transverse sections through the hippocampus cultured for 2 or 3 weeks. It is suggested that differentiation of cell structures continues in the explants as a result of postnatal histogenetic processes and definitive growth of nerve fibers takes place. In this way it is possible to simulate and conduct an electrophysiological analysis of the interneuronal connections characteristic of the hippocampus and formed during its postnatal development in vitro.Brain Institute, Academy of Medical Sciences of the USSR, Moscow. Translated from Neirofiziologiya, Vol. 8, No. 4, pp. 384–390, July–August, 1976.     

Protection of cultured hippocampal neurons in hypoxia and subsequent reoxygenation by antioxidant from the spatially hindered phenols class]

The influence of antioxidant from hindered phenols (U-18) on a hypoxic neurodestructive effect in mouse hippocampal cell cultures was studied. Morphological and biochemical quantitative analysis of neuronal damage showed that U-18 attenuates nerve cell death resultant from 6-7-hour hypoxia and subsequent 12-hour posthypoxic reoxygenation. This antidestructive action of U-18 was observed upon its introduction in nutrient medium both before and immediately after hypoxic period. Thus, our results suggest that peroxidant reactions play a pivotal role in hypoxic neuronal injury and probably participate in this neurodestructive process mainly during posthypoxic reoxygenation period.     

Ratio of the frequency of chromosome aberrations and sister chromatid exchanges to the dose of the mutagenic exposure to cyclophosphamide in vivo and in vitro

Cyclophosphamide (CP) and its metabolites were used to compare the rate of chromosomal aberrations (CA) and sister chromatid exchange (SCE) in the rabbit lymphocytes in vivo and in vitro. The dose-dependent increase of cytogenetic effects rate appeared to be of linear and exponential dependence for SCE and CA, respectively, both in vivo and in vitro. The regression equation coefficients coincided in in vivo and in vitro experiments.     

Characterization of Transgenic Tobacco Plants Containing Bacterial bphc Gene and Study of Their Phytoremediation Ability

Genetically modified plants can serve as an efficient tool for remediation of diverse dangerous pollutants of the environment such as pesticides, heavy metals, explosives and persistent organic compounds. Transgenic lines of Nicotiana tabacum containing bacterial bphC gene from the degradation pathway of polychlorinated biphenyls (PCBs) were tested. The product of the bphC gene – enzyme 2,3-dihydroxybiphenyl-1,2-dioxygenase is responsible for cleaving of the biphenyl ring. The presence of bphC gene in transgenic plants was detected on DNA, RNA and protein level. The expression of the bphC/His gene was verified after purification of the enzyme from plants by affinity chromatography followed by a Western blot and immunochemical assay. The enzyme activity of isolated protein was detected.Efficient transformation of 2,3-DHB by transgenic plants was achieved and the lines also exhibited high production of biomass. The transgenic plants were more tolerant to the commercial PCBs mixture Delor 103 than non-transgenic tobacco. And finally, the higher decrease of total PCB content and especially congener 28 in real contaminated soil from a dumpsite was determined after cultivation of transgenic plant in comparison with non-transgenic tobacco. The substrate specificity of transgenic plants was the same as substrate specificity of BphC enzyme.