Inductive role of mossy fibers of hippocampus in the development of dendritic spines in aberrant synaptogenesis at neurotransplantation

The dentate fascia of the hippocampal formation isolated from 20-day-old Wistar rat fetuses was subjected to heterotopic transplantation into the somatosensory area of the neocortex of adult rats of the same strain. Five months after surgery, neurotransplantates, together with neighboring area of the neocortex, were studied using light and electron microscopy. We carried out a detailed study of the ultrastructure of the ectopic synaptic endings formed by the axons of granular neurons of the dentate fascia (mossy fibers) with neurons of the neocortex unusual for them in a normal state. Ultrastructural analysis revealed that most ectopic synaptic endings produce its determinant morphological features: giant sizes of presynaptic knobs, active zones with branched dendritic spines, and adherens junctions with the surface of dendrites. The data indicate that the mossy fibers growing from neurotransplantates induce structural and chemical reorganization of dendrites of the neocortex using transmembrane adherens junctions, such as puncta adherentia junctions. This results in the differentiation of active zones and development of dendritic spines typical for giant synaptic endings that are invaginated into presynaptic endings. Thus, the ability of neurons of the dentate fascia to form aberrant synaptic connections at transplantation results from the inductive synaptogenic properties of mossy fibers.     

Mechanism of distribution of neptunium and plutonium in rats

Neptunium administered intravenously together with the high molecular weight protein fraction of blood serum was almost completely accumulated by the liver after 60 min. Then neptunium left the liver and was partially deposited in the skeleton. Plutonium, being a component of a nonprotein and a low molecular weight protein fractions, was mainly found in the skeleton where it had been accumulated throughout the entire period of observation (14 days, 52-58%); as to the nonprotein fraction, the value of accumulation was somewhat higher.     

Ultrastructure of the capillaries of nerve tissue transplants growing in the anterior chamber of the eye

Blood capillaries have been studied electron microscopically in the areas of grafts (rat embryonal hippocamp and septal cerebral parts transplanted to mature rats) containing mainly nervous, glial or connective tissue cells. Certain differences in the capillary wall structure have been revealed. In areas with a great concentration of nervous cells, the blood capillaries are characterized by a dense arrangement of cellular elements in their walls, a continuous layer of the glial end-feet, this is specific for the CNS capillaries providing the blood--brain barrier. In peripheral area of the grafts, where glial elements predominate, the capillaries have loose arrangement of the mural cellular elements, great endotheliocyte activity, thick connective tissue tunic, lack of a dense glial surrounding. These characteristics make dubious the statement whether these capillaries possess the blood--brain barrier function. In places where connective tissue cells make aggregates, the capillaries do not possess the barrier properties because of perforations and fenestrae in endothelium and interruptions of the basal membrane, absence of pericapillary glial elements. All types of the capillaries demonstrate certain signs of a high functional activity. Formation of the capillary structure depends on the surrounding tissue.     

Selection of a community of acidochemolithotrophic microorganisms with a high oxidation rate of pyrrhotite-containing sulphide ore flotation concentrate

A community of acidochemolithotrophic microorganisms with a high oxidation rate of pyrrhotite-containing sulphide ore flotation concentrate was selected. The Acidithiobacillus caldus OP-1 and Ferroplasma acidiphilum OP-2 cultures were identified to be dominating members. The presence of the Acidithiobacillus ferrooxidans OP-3, Leptospirillum ferriphilum OP-4, and Sulfobacillus thermosulfidooxidans OP-5 cultures in the community’s composition was also mentioned. The analysis results of solid residues of the process showed a greater elemental sulfur oxidation level and gold recovery when the initial pH value in tank I was maintained at a level of 1.8–2.0 (90.5%) rather than 1.6–1.8 (86.3%).     

Transmission of Megatrypanum Trypanosomes to Cervus dama by Tabanidae1

Four fallow deer, Cervus dama, became infected with Trypanosoma (Megatrypanum) sp. by oral application of triturated guts from tabanids collected in an area with deer but without any cattle; four control calves remained negative. Upon challenge with triturated guts from tabanids from an area with pastured cattle, the four calves became infected with Trypanosoma (M.) theileri. The prepatent period in deer was five days or less. Haematopota spp. and Tabanus spp. were identified as vectors of the deer trypanosomes. It is concluded that the trypanosomes of C. dama belong to a Megatrypanum species that is not identical with T. theileri.     

Involvement of Azopirillum brasilense plasmid DNA in the productio of indole acetic acid

Indole acetic acid (IAA) production in Azospirillum brasilense strain Sp245 is controlled by a 85 MDa plasmid naturally present in this bacterium. In the presence of L-tryptophan, anthranilic acid production and almost no IAA production occurs in a derivative strain harbouring a Tn5-Mob insertion in the 85 MDa plasmid. Agrobacterium tumefaciens strain GM19023, upon transfer of Tn5-Mob labelled 85 MDa plasmid of A. brasilense Sp245, gains the ability to produce anthranilic acid.     

Ultrastructure of the synaptic endings in nerve tissue transplants developing in the anterior chamber

Embryonic septum of hippocampus was grafted into the anterior eye chamber (AEC) of adult recipient rats. The fine structure and distribution of synaptic endings were studied in the hippocampus (HC) and septum (ST) grafts developing in oculo for 3-4 months. On the basis of the structure of postsynaptic regions, asymmetrical and symmetrical synapses are distinguished, whose distribution on the body and dendrites of hippocampal and septal neurons is basically similar with that in situ. As in vivo, axo-somatic, axo-dendrite and axo-spine forms of synaptic endings have been observed. Neuropile has, basically, normal structure, judging by the ratio of nerve and glial elements, but sometimes dendro-dendrite contacts and glomerular-like synaptic structures are observed which are not characteristic of the studied brain regions. Besides, the grafts contain an increased number of serial and tangential synapses, as well as axonal terminals with the signs of growth cones. The observed structural deviations appear to be due to incomplete tissue maturation in the absence of normal afferentation.     

Ultrastructure of nervous tissue developing in the anterior chamber of the eye. 1. Perikaryons and dendrites

Embryonic tissues of septum and hippocampus were transplanted into the anterior eye chamber (AEC) of adult rats. The morphology of initial embryonic tissues and of transplants within 3 to 4 months of cultivation in AEC was studied. The transplanted tissue consists of neuroblasts and immature neurones: no synaptic contacts are observed. Within 3 to 4 months, highly differentiated neurones establishing synaptic contacts can be seen in the transplants. At the same time the fine structure of perikaryons and dendrites undergoes some changes: increased vacuolization, transformation of ergastoplasm into lamellar bodies. These can be due to an elevated functional activity of some neurones. Another group of morphological abnormalities (increased number of dendrite processes and microphyllopodia, somatic spines, dendrite cones of growth, tight junctions between perikaryons) suggests incomplete tissue maturation. These might be due to the absence of normal afferent and trophic influences in AEC.     

Yeast prions, mammalian amyloidoses, and the problem of proteomic networks

Prion proteins are infective amyloids and cause several neurodegenerative diseases in humans and animals. In yeasts, prions are detected as the cytoplasmic heritable determinants of a protein nature. Yeast prion [PSI], which results from a conformational rearrangement and oligomerization of translation termination factor eRF3, is used as an example to consider the structural-functional relationships in a potentially prion molecule, specifics of its evolution, and interactions with other prions, which form so-called prion networks. In addition, the review considers the results of modeling mammalian prion diseases and other amyloidoses in yeast cells. A hypothesis of proteomic networks is proposed by analogy with prion networks, involving interactions of different amyloids in mammals.