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PubMedDate not supplied

[DNA conformation and thermostability of aqueous solutions of beta-alanine and gamma-aminobutyric acid].

It has been shown that at low concentrations of rare amino acids (from 10(-3) M to 10(-1) M of the substance) stechiometric complexes amino acid -- DNA are formed, which bring about partial substitution of counterions screening phosphate groups and to a change of spatial structure of DNA water molecules. The DNA-solvent molecular interactions are changed, accompanied by an abrupt decrease of helix-coil enthalpy transition which leads to the unwinding of DNA double helix. In the region of amino acid high concentrations (greater than 1-1,5 M) a rise of thermostability and winding of DNA double helix is observed. It has been established that B----C-like conformational transition stimulated by the rise of DNA thermostability is a result of counterions dehydration and the increase of effective ionic strength of the solution which is due to the rise of amino acid-zwitterions content in it.

Alanine↗
PubMed1984

[2-D-NMR study of the conformation characteristics of toxin 3 from Naja naja siamensis venom].

The spatial structure of "long" toxin 3 Naja naja siamensis in solution has been studied by methods of two-dimensional (2D) 1H NMR spectroscopy. The individual signal assignments for 67 out of 71 residues and analysis of nuclear Overhauser effects between distinct protons of the molecule allowed the comparison of the toxin 3 conformations at different pH values and temperatures. It was shown that the deprotonated imidazole ring of His22 residue (at pH greater than or equal to 7,5) is surrounded by the side chains of Cys17, Pro18, Val23, Cys24, Cys45, Ala46 and Thr48 residues. On the contrary, the protonated imidazole ring of His22 (at pH less than 4,0) is exposed into solvent. Ionization of His22 is accompanied by a change in the Tyr25 aromatic ring orientation and affects the conformational mobility of the Cys17, His22, Cys45 and Ala47 side chains. The revealed conformational features of toxin 3 in solution are discussed in connection with the differences between "long" and "short" neurotoxins in the kinetics of their binding to acetylcholine receptor.

Amino Acids↗
PubMedDate not supplied

[Theoretical conformation analysis of MCD peptide].

The spatial structure of the MCD-peptide from bee venom has been calculated basing on the known sequence of 22 amino acid. The a priori calculations produce a system of two disulfide bonds, identical to that observed in the native structure. The calculated structure of MCD-peptide is close to that proposed earlier for the homologues peptide tertiapin and is confirmed by NMR and CD data.

Amino Acid Sequence↗
PubMed1984

[Epizootiological evaluation of intestinal yersiniasis in Sakhalin Province].

The work presents the data obtained as the result of the study of intestinal yersiniosis in the synanthropic and natural foci of the Sakhalin region. The circle of Yersinia carriers spreading this infection in the household and natural biocenoses has been established. For the first time the data on the water-type natural focus of yersiniosis with its specific spatial structure, detected on the Tyuleny Island, are published.

Animals↗
PubMedDate not supplied

[Orbital veins and arteries in relation to the connective tissue system of the orbit].

Our study revealed that the relationships between the vessels and the connective tissue, which forms a constant and bilateral symmetrical system of connective tissue septa bordering adipose tissue compartments, are characteristics and constant but essentially different for veins and arteries. The arteries run within the adipose tissue compartments only contacting the connective tissue septa where they perforate them. As to the veins, their relationship with the connective tissue apparatus is completely different. These vessels run within the septa firmly connected with their connective tissue fibres, forming a continuity between the adventitia of the veins and the walls of the adipose tissue compartments. This difference between arteries and veins results in a different spatial structure for the two vascular systems. The arterial system is a radiating system, whereas the venous system is an anastomosing complex of venous rings which are arranged circularly inside as well as outside the muscle cone. It seems likely that the relationships of the vessels, particularly of the veins, with the connective tissue apparatus play an important role in the well-functioning of the orbital blood-circulation.

Adipose Tissue↗
PubMedDate not supplied

[Theoretical conformational analysis of delta-sleep inducing peptide].

The spatial structure of o-sleep-inducing peptide has been determined by means of semi-empirical conformational analysis of its overlapping fragments. Possible intramolecular contacts in the most stable conformations are discussed. The essential role of electrostatic interactions is emphasized.

Delta Sleep-Inducing Peptide↗
PubMedDate not supplied

[Effect of ethymisole on long-term memory].

Influence of ethymisol (bismethylamid of 1-ethylimidasol-4,5-dicarbonic acid) on learning and retention of habit was studied in experiments on rats by the method of active conditioned avoidance of electrical stimulation. At the same time optimal conformation form of the drug was determined by the method of proton magnetic resonance and by means of infrared spectra and theoretical conformation analysis. A single administration of ethymisol in the dose of 3 mg/kg reduced the deficit of the avoidance habit, when tested in 30 and 60 days following learning. A stable conformation of the ethymisol molecule with a planar arrangement of atoms of its heterocycle and amide groups was found in which the interaction of this substance with biological macromolecules was most active. The ethymisol effect on the long-term memory apparently results from a stable facilitation of synaptic transmission based on stabilization of spatial structure of biological macromolecules in the given conformation.

Animals↗
PubMedDate not supplied

[Effect of organophosphorus inhibitors, lupinine and epilupinine derivatives, on mammalian and arthropod cholinesterases].

Studies have been made on the effect of organophosphorus inhibitors on cholinesterases (CHe) from mammals (human and rabbit erythrocytes, mice brain) and arthropods (fly, spring grain aphid, rice weevil and spider tick). Organophosphorus inhibitors were presented by dialkylthiophosphates which contained normal or branching alkyls in the phosphoryl part of their molecule and lupinine or epilupinine residue in the other part of the latter. Increasing the length of alkyl in lupinine derivatives increased their inhibitory effect with respect to mammalian CHe, but decreased it in relation to all the investigated arthropod CHe. For epilupinine derivatives, the same relationship was found with mammalian CHe, being absent in arthropod enzymes. These data indicate the existence of significant differences in spatial structure of both esterase and anionic centers of the enzyme from mammals and arthropods. In arthropod CHe, hydrophobic regions of the esterase center are less developed that in mammalian CHe. The distance between the anionic and esterase centers of CHe is presumably different in the enzymes from different species.

Alkaloids↗
PubMed1980

Mitochondrial aspartate aminotransferase 27/32-410. Partially active enzyme derivative produced by limited proteolytic cleavage of native enzyme.

Native mitochondrial aspartate aminotransferase (AATase) is cleaved selectively by trypsin at the peptide bonds after Arg 26 or after Lys 31 yielding two shortened enzyme derivatives, AATase 27-410, and AATase 32-410. Recent x-ray crystallographic determination of the spatial structure of AATase has shown that the NH2-terminal segments of the two polypeptide chains of this dimeric enzyme pass in front of the active site clefts and form two separate junctions with the neighboring subunit which are not contiguous with the main subunit interface (Eichele, G., Ford, G. C., Glor, M., Jansonius, J. N., Mavrides, C., and Christen, P. (1979) J. Mol. Biol. 133, 161-180). The peptide bonds cleaved by trypsin are situated in the following stretch of the polypeptide chain which runs in exposed position on the surface of the subunit. The split-off peptide is lost during gel filtration. The molecular activity of AATase 27/32-410 (a mixture of about equal amounts of the two not readily separable derivatives) is about 3% of that of the native enzyme. In contrast, the K'm values for aspartate and 2-oxoglutarate are unchanged, indicating an unaltered geometry of the substrate binding site. A substantially diminished syncatalytic response of the reactivity of Cys 166 toward 5,5'-dithiobis-(2-nitrobenzoate) suggests that the decrease in catalytic activity is due to an interference with the syncatalytic conformational dynamics observed previously in AATase (Gehring, H., and Christen, P. (1978) J. Biol. Chem. 253, 3158-3163). Consonant with a role of the NH2-terminal segment in propagating the syncatalytic conformational rearrangements the rate of the tryptic cleavage is retarded 4-fold in the presence of the transaminating substrate pair aspartate and oxalacetate.

Amino Acids↗
PubMed1995

[New kinds of 3-dimensional atlases of the anatomy and function of the human body].

It is a drawback of classical multimedia programs for the visualization of spatial knowledge, that they are based on a limited number of predefined views. This paper describes a model that combines pictorial and symbolic knowledge about spatial structures in a way that allows arbitrary views of the scene and the interrogation of the model in the context of the actual view. The style of the pictorial presentation only depends on the objective and the phantasy of the user. The functionality of the approach is demonstrated with the example of the human head. It is furthermore shown that the model potentially allows the simulation or generation of all classical visual teaching aids for anatomy.

Anatomy, Artistic↗
PubMed1995

HBV surface antigen proteins with deletions in the preS region.

Four pairs of HBV surface antigen genes, in which the preS region was partially deleted, were constructed by the polymerase chain reaction (PCR). The comparison of the levels of the expression in mammalian cells of these genes and the ones constructed before, and the properties of these gene products showed that the missing of a part of the preS region did not affect the overall spatial structure of the S region and the surface localization of the preS region. The removal of the preS1 retention sequence (a. a. 2-19) alleviated significantly the shelter of the major antigenic determinants in the S region by the preS sequence. It was found that the long preS region seriously impaired the secretion of the surface antigen proteins from mammalian cells. In addition to the previously reported preS1 retention sequence, the preS1 sequence (a.a. 48-65) may also inhibit the secretion of the surface antigen proteins, whereas the preS2 region exerts no major influence on the retention of the large surface antigen protein. One of the expressed surface antigen proteins, in which the preS1 sequence (a.a. 21-47) and the S region were directly fused, deserves further study and may be developed into a new HBV vaccine which contains the preS1 binding site for hepatocyte receptors due to its stability, fine secretability and strong preS1 antigenicity.

Animals↗
PubMedDate not supplied

[The structural organization of the synaptic connections of the motor neurons in the mammalian spinal cord].

Peculiarities of the synaptic organization of the motor neurons of the spinal cord of the rodents (rats), predators (cats), primates (Macaca rhesus monkeys) were studied in the early stages of the postnatal ontogenesis and in the adult animals. The motor nucleus region of the lumbar thickening was studied both in normal animals and after the experimental destruction of cerebral nuclei. A new view on the structural-spatial organization of the motor neuron dendrites, the branches of which are highly specialized in the perception of the efferent inputs, is gained. By means of light and electron microscope, the types of synapses, composed of the terminations of the fibers of three major supraspinal systems of the motor control (reticulo-, vestibulo- and rubro-spinal) were studied. Lower mammals are found to have electrotonic and mixed electro-chemical synapses, along with the chemical ones. The fundamental regularities of the distribution of the synaptic inputs of different modality on the somato-dendritic membranes of the motor neurons, specifically the grouping of the chemical synapses and definitive regions of the membrane and those of electrical ones in one microzone were stated. The functional significance of the different types of synapses is discussed with the reference to modern neurology data.

Animals↗
PubMedDate not supplied

[Restructuring of the spatial organization of circular DNA molecules in liquid crystal dispersions].

The change in the spatial structure of superhelical and nicked DNA molecules in liquid-crystalline dispersions under micrococcal nuclease treatment was studied. Micrococcal nuclease digestion leads to restructuring from the "nonspecific" packing of circular DNA in dispersion particles to the cholesteric one. The transition is described by the Kolmogorov-Avramy equation; however, the parameters of the equation are essentially different for the different topological forms of circular DNA. The liquid-crystalline state of DNA expands the range of the solvent properties (ionic conditions etc.) under which the micrococcal nuclease action remain highly efficient.

Circular Dichroism↗
PubMedDate not supplied

[Intracellular interactions in the hematopoietic system after massive radiation exposure].

The review article deals with acute radiation damage to the bone marrow spatial structure, disturbances of cell-cell interactions, and stromal cytokine(s) production, hence representing limiting factors for effective postradiation recovery of blood system. The evidence for radiation-induced stromal functional activation is discussed, along with opportunity of local growth factors deficiency, thus requiring a replacement therapy with exogenous cytokines.

Animals↗
PubMed1994

Receptive field analysis and orientation selectivity of postsynaptic potentials of simple cells in cat visual cortex.

Postsynaptic potentials (PSPs) were recorded from cat striate cortical cells by the whole-cell in vivo recording technique using patch-clamp electrodes. EPSPs and IPSPs evoked by flashing bars on the receptive field at different positions and orientations revealed the spatial structure of the excitatory and inhibitory inputs. The elongation of the excitatory input field (length:width ratio) was found to be minimal (mean ratio of 1.7) and much lower than those reported for spike discharges. Two-dimensional receptive field response profiles of early PSPs were recorded by flashing a small spot of light over a square matrix covering the receptive field. These recordings also showed only mild degrees of elongations of the receptive field. Such elongations could be the result of either an excitatory input from the geniculate that is already biased for orientation or an excitatory convergence from a limited number of LGN fields arranged in a row. In most first-order cells, we found that inhibition was contributing significantly to orientation selectivity. Often prominent IPSPs could be evoked by stimuli of nonoptimum orientations. Presence of inhibition could also be inferred by the way that EPSPs were sharply cut off by inhibition. When the amplitude of an EPSP was measured at different latencies after its onset, the EPSP was found to be very broadly tuned to orientation at the beginning, but showing increasing orientation selectivity with time. It is proposed that this progressive development of orientation selectivity is due to (1) inhibitory inputs arriving after the first wave of excitation, (2) intracortical excitatory inputs from other cells tuned to similar orientations, and (3) voltage-sensitive mechanisms such as NMDA channels.

Animals↗
PubMed1994

[TOF-MR angiography in radiotherapy treated cerebral arteriovenous malformations].

Intracerebral arteriovenous malformations represent congenital anomalies with an arteriovenous shunt (nidus). The therapeutic goal is to eliminate the risk of bleeding and to improve the clinical symptoms. The exact localization of the nidus and the identification of the feeding arteries are critical for therapy planning. Up to now conventional brain angiograms have been used for treatment planning and for the assessment of therapy response. We studied whether 3D time-of-flight (TOF) MR angiography can be used for therapy planning and monitoring. MRI and TOF-MRA studies of 28 patients undergoing radiotherapy were evaluated. They were compared to conventional angiography to assess the MRA study. A Correct identification of the arterial feeder and the nidus was possible in about 75% of the patients. In combination with the MRI study, an important 3D dataset for treatment planning could be obtained that includes therapeutically relevant information on the localization and spatial structure of the AVM as well as the adjacent brain tissue. As a noninvasive technique, close-meshed follow-up studies could be performed with MRA.

Adolescent↗
PubMed1993

Morphometric and tridimensional studies of tubular cystic degeneration in rat kidney following exposure to cisplatin.

Cisplatin, a widely used chemotherapeutic agent, is characterized by a dose-limiting renal toxicity. Cystic tubular dilatation is the most typical histopathological alteration encountered in cisplatin-treated rats. The purpose of the present study was to explore by a morphometric approach the development of cystic degeneration and, in particular, to analyse, by computer-assisted tridimensional reconstructions, the spatial structure and the tubular origin of cisplatin-induced renal cysts. This study was performed on rats given 8 mg/kg cisplatin i.p. for four days and sacrificed 4, 7, 14, 21, 50 and 60 days after last drug administration. The relative area occupied by cystic tubules increased rapidly in the outer stripe of outer medulla (OSOM) and reached a maximum 21 days after the end of treatment. Cystic dilatations appeared later in the kidney cortex and the inner stripe of outer medulla (ISOM). The tridimensional study of cystic tubules located in OSOM confirmed previous reports indicating that they arise from proximal straight tubules and showed that cystic degeneration was not associated with atrophy or degeneration in more proximal parts of the nephron. Moreover, cystic tubules located in ISOM were found to originate from distal straight tubules and/or the loop of Henle, an observation which, to our knowledge, has not been reported so far in cisplatin-treated rats.

Animals↗
PubMed1993

[The interaction of angiotensin with lipid monolayers].

The studies of lipid monolayers showed the interaction of an angiotensin-2 and lipid monolayers to be a two-stage process. In the first stage peptide molecules were adsorbed due to electrical interaction in the plane of polar heads of lipid molecules. In the second stage peptide molecules incorporated into the lipid matrix owing to hydrophobic interactions. These results suggest that the lipid matrix may perform the function of a catalyst of the peptide-receptor interaction by changing the spatial structure of angiotensin molecules at the transition of the latter from hydrophobic environment.

Angiotensin II↗