In vitro conversion of full-length mammalian prion protein produces amyloid form with physical properties of PrP(Sc)

The "protein only" hypothesis postulates that the infectious agent of prion diseases, PrP(Sc), is composed of the prion protein (PrP) converted into an amyloid-specific conformation. However, cell-free conversion of the full-length PrP into the amyloid conformation has not been achieved. In an effort to understand the mechanism of PrP(Sc) formation, we developed a cell-free conversion system using recombinant mouse full-length PrP with an intact disulfide bond (rPrP). We demonstrate that rPrP will convert into the beta-sheet-rich oligomeric form at highly acidic pH (<5.5) and at high concentrations, while at slightly acidic or neutral pH (>5.5) it assembles into the amyloid form. As judged from electron microscopy, the amyloid form had a ribbon-like assembly composed of two non-twisted filaments. In contrast to the formation of the beta-oligomer, the conversion to the amyloid occurred at concentrations close to physiological and displayed key features of an autocatalytic process. Moreover, using a shortened rPrP consisting of 106 residues (rPrP 106, deletions: Delta23-88 and Delta141-176), we showed that the in vitro conversion mimicked a transmission barrier observed in vivo. Furthermore, the amyloid form displayed a remarkable resistance to proteinase K (PK) and produced a PK-resistant core identical with that of PrP(Sc). Fourier transform infrared spectroscopy analyses showed that the beta-sheet-rich core of the amyloid form remained intact upon PK-digestion and accounted for the extremely high thermal stability. Electron and real-time fluorescent microscopy revealed that proteolytic digestion induces either aggregation of the amyloid ribbons into large clumps or further assembly into fibrils composed of several ribbons. Fibrils composed of ribbons were very fragile and had a tendency to fragment into short pieces. Remarkably, the amyloid form treated with PK preserved high seeding activity. Our work supports the protein only hypothesis of prion propagation and demonstrates that formation of the amyloid form that recapitulates key physical properties of PrP(Sc) can be achieved in vitro in the absence of cellular factors or a PrP(Sc) template.

Water-soluble hybrid nanoclusters with extra bright and photostable emissions: a new tool for biological imaging

We report the generation of a previously unknown class of water-soluble organic-inorganic hybrid nanoclusters composed of silver and thioflavin T with remarkable fluorescent properties. These hybrid nanoclusters display an extra bright fluorescence in aqueous solutions without any detectable photobleaching. Furthermore, the fluorescent nanoclusters can be generated in situ by sensitized photoreduction of Ag+. Organic-inorganic nanoclusters have remarkable advantages over the known classes of fluorescent probes for the development of ultrasensitive biological assays, cell imaging, or studies of single molecules. As an example of a practical biological application, imaging of amyloid fibrils produced from recombinant mammalian prion proteins and nonprion proteins using hybrid nanoclusters is presented.

Aqueous diffusion pathways as a part of the ventricular cell ultrastructure

The physical organization of the ventricular myocyte includes barriers for the movement of objects of varying dimensions ranging from ions to solid particles. There are two kinds of diffusion in the cell: lateral (in membranes) and aqueous. Here we examine the size constraints of aqueous diffusion pathways and discuss their impact on cellular physiology. Calibrated gold nanoparticles were used to probe the accessibility of the entire transverse-axial tubular system (TATS), the sarcoplasm, and intracellular structures. The TATS tubules, although up to 300 nm in diameter, permitted only particles </=11 nm to enter. When calibrated nanoparticles were added to permeabilized ventricular cells, particles </=11 nm were found in the sarcoplasm. The distribution of nanoparticles in the cells allowed us to conclude that 1), the TATS and the sarcoplasm are accessible only for particles </=11 nm; 2), the gaps between T-tubules and junctional sarcoplasmic reticulum (jSR), jSR and mitochondria, and intermitochondrial contacts are inaccessible for particles with physical size >3 nm; 3), the mitochondrial voltage-dependent anion channel and the nuclear pore complex in ventricular cells could not be penetrated by particles >/=6 nm; and 4), there is a difference in size clearance between transversal and longitudinal sarcoplasmic diffusional pathways.

A non-linear mathematical model for the in vivo evaluation of the RES phagocytic function

A new non-linear mathematical model was constructed in order to perform in vivo quantification of the RES phagocytic function. This method is based on the same technical facilities as used for the routine liver-spleen scintigraphy with radiocolloids [1, 2]. But kinetic modeling of dynamic Tc-99m-sulfur colloid data produced estimations of the functional RE-parameters: the clearance rate of the colloidal particles, the rate of phagocytosis, and the RES functional volume, which can not be obtained by classical approaches. This non-linear model was designed on the basis of the principal characteristics of particulate material interaction with macrophages (attachment, phagocytosis, digestion) [3, 4, 5]. The theoretically examined behavior of this in vivo mathematical model corresponds with the experimental behavior of the RES. The mathematical expression of the dynamics is the system of non-linear differential equations with constant coefficients that have no analytical solution. Fitting of the normalized heart blood time-activity curve was obtained to identify the unknown model parameters via non-linear regression. For this purpose general interactive PASCAL procedure IDPAR for a PDP-11/34 computer was used (an IBM PC version is also available). Two to three iterations were needed to estimate the set of unknown parameters for any patient study (1-1.5 min). A very good fitting was obtained between experimental and model curves in every case of different pathologies (error of the approximation is about 2-3%). Studies were performed using an in vivo bolus injection of 3.6 mg/80 kg commercially available colloid KOREN labeled with 3m-Ci 99m-Tc (analog of TCK-1). Our method was used to determine the RES functional parameters for patient groups with different levels of the RES dysfunction. Obtained results illustrate the possibilities of our technique to quantitatively estimate not only great pathology (portal cirrhosis), but also small changes of the RE-function (case of hyperlipidemia and ulcer gaster). In all patient groups marked changes of Tc-99m-sulfur colloid turnover were observed. In general, tracer clearance from the circulation was decreased, and the rate of phagocytosis and the RES volume were diminished compared with controls. The effect of a reduction of phagocytosis increases when the RES dysfunction becomes stronger. It can be shown that a non-parametric Wilcoxon-Mann-Whitney test gives a significant difference (P95%) for these patient groups. Further, we represent the possibility of using the model for monitoring changes of the RES-function parameters during and after therapy. The quantitative test of the RES function can significantly enhance the diagnosis and management of different diseases. Serial colloidal studies may document changes in the RES-function for the tumors, cirrhosis, hyperlipidemia, reticulosis, hepatitis, thrombosis, infection, AIDS, burn injury, shock and trauma patients. The technique may be useful for the different RES investigations with laboratory animals. Created computer software can be used as a tool for kinetic models, simulation, and unknown parameters identification.

[The paradoxical effect of the lymphocytes during the filtration of thrombocyte-rich heparinized plasma]

Filtration of platelet-rich heparinized plasma deprived lymphocytes and contained lymphocytes was investigated in 21 donors. Filtration of both plasmas was performed through 5 microns-pore nuclear filters at the constant perfusion pressure 100 cm H2O. The plasma contained lymphocytes filtered by 80% better, than the lymphocyte-deprived plasma. The count and adhesive activity of platelets were similar in both plasmas.

[The function of the reticuloendothelial system studied with the use of radioactive colloids]

A new method for the interpretation of data obtained during radionuclide investigation of the reticuloendothelial system (RES) was proposed. It was based on a detailed description of the mechanism of reticuloendothelial extraction of a colloid injected intravenously. A model developed for this purpose included the main stages of radioactive colloid transport. The paper also represented a comparative analysis of the results of clinical examination of the controls and patients with liver cirrhosis. A 4-fold decrease of the blood flow in portal liver cirrhosis was noted as compared with normal mean indices in a 2-fold decrease in the specific blood supply of cells of the RES and in a 2-fold decrease in its volume. An increase in phagocytosis rate in patients with liver cirrhosis needs further verification.

Field-of-view analysis of a polarization interference Fourier transform imaging spectrometer

The Fourier transform imaging spectrometer (FTIS) is an important tool for the measurement of spectral information in a scene. Advances in electro-optic crystal systems have led to the advent of the FTIS based on polarization interference filters. The operation of these devices as spectrometers has been well characterized, but the imaging capabilities have yet to be thoroughly explored. We explore the field-of-view limitations that occur when using this particular type of FTIS.

[Pharmacotherapy of endothelial dysfunction in patients with atherosclerotic brain ischemia]

We studied the effect of deproteinized hemoderivative of calf blood, thioctic acid and vinpocetine with piracetam on the endothelial function in patients with chronic cerebral ischemia stage III. After pharmacological treatment, there was the improvement in the endothelium properties of both large and small blood vessels. The index of occlusion that characterized the function of small vessels reached normal values while the phase shift did not approach to the reference values. This notion indicates that in cerebral atherosclerosis small arteries initially are subject to alterations to a lesser extent compared to the arteries of large and medium caliber. The most effective medicines of those used for the correction of endothelial dysfunction are deproteinized hemoderivative of calf blood and thioctic acid.

[Pharmacotherapy of peripheral arteriosclerosis]

Peripheral atherosclerosis was treated in 178 patients: 90 were given pyridinol carbamate for 2--4 months, 40 pentoxyphylline, 30 cetedil, and 18 received butalamine. in intermittent claudication pyridinol carbamate and trental proved most effective, cetedil (straten) was less effective. The favourable effect of pyridinol carbamate is associated with its action both on the state of microcirculation and on the content of lipids. A significant decrease in the level of blood triglycerides was observed during treatment with pyridinol carbamate. Pentoxyphylline reduced blood viscosity and platelet aggregation in patients with peripheral atherosclerosis but had no effect on the blood lipid content. Cetedil did not reduce blood viscosity although it decreased the aggregation of erythrocytes and inhibited the second phase of platelet aggregation. The objective criterion for the improvement of circulation in the affected extremities was increased tolerance to load, particularly in medication with pyridinol carbamate and trental.

[Role of leukocyte adhesion in filterability of blood cell suspensions]

We investigated blood cells suspension filterability of 16 donors. The filtration was performed trough 5 microns-pore nuclear filters at constant perfusion pressure 10(5) din/cm2. We estimated also the adherence of leukocytes and platelets on nylon. The adherence of platelets and mononuclear leukocytes reduced the level of the suspension filterability only by 21% (p > 0.05). The presence of nonadhesive polynuclear leukocytes in the suspensions did not change practically their filterability. The addition in the suspensions of adhesive polynuclear leukocytes reduced suspension filterability dramatically.

[Blood viscosity analyzer]

An analyzer that determines blood viscosity at different shift speed has been designed. Its operation principle is based on the use of rotation viscosity measurement using a rotor freely floating in the sample. A blood sample is placed between the stationary thermostabilized measuring cylinder and a free floating rotor. The system creates a rotating magnetic field which makes the rotor rotate with a preset speed, determines shift stress, calculates the magnitude of viscosity and indicates it on the display. The magnitude of viscosity is proportional to the square of the current drawn in the windings of a stator, which divided by the rotational speed of a rotor. The analyzer provides viscosity measurements in the range of 0.7-14 mPa.sec at shift rate of 20-200 sec-1, the sample volume is less than 1 cm3. The device can be used for the diagnosis of the diseases whose pathogenesis microcirculatory and coagulative disorders play an important role in.

[The blood rheological properties in patients with amputation stumps and concomitant ischemic heart disease]

Blood rheology was compared in two groups of patients with ischemic heart disease (IHD). In group 1 patients low limbs were amputated. It is in them that rheological properties of blood were changed to the most extent. This is attributed to the effect of plasmic factors in the form of hypertriglyceridemia and hyperfibrinogenemia, sharp reduction of the total cross sectional vascular area (especially in high amputation) leading to blood cell damage associated with intensive platelet aggregation and red cell microhemolysis. Reduced muscular mass and resultant reduced capillary bed and deficiency of endothelial surface may stimulate accumulation of triglyceride-enriched very low density lipoproteins.

[Significance and characteristics of disorders of rheological properties of blood in acute myocardial infarct with different indicators of central hemodynamics (clinico-experimental studies)]

Simultaneous study was conducted of the state of central hemodynamics and indices characterizing the rheologic blood properties in 25 patients with acute myocardial infarction. Patients with left ventricular insufficency were found to have considerably more marked disorders of rheologic blood properties. Experimental research conducted on dogs with a model of acute myocardial infarction confirmed the important role of disorders of rheologic and platelet-forming properties of blood in the prognosis and course of the acute period of the disease.

Diffraction light modulator based on transverse electro-optic effect in short-pitch ferroelectric liquid crystals

A diffraction modulator that exploits the transverse electro-optic effect in ferroelectric liquid crystals is proposed for applications in displays and in spatial light modulators. Experiments with a short-pitch ferroelectric liquid crystal aligned homeotropically show an achromatic contrast ratio of greater than 100:1 available with oblique readout. The sources of the contrast deterioration and the tolerance of the proposed scheme to this deterioration are analyzed. For selected directions of readout the light output obtains low sensitivity to the polarization of the readout light. Nonlaser light sources can be used in a practical display setup based on the proposed principle.

[Blood coagulation analyzer]

A ten-channel coagulometer has been designed. Its operation principle is based on the clotting method using a monitoring ball and magnetic transducers. The coagulometer consists of a recording unit and a unit of a thermostatic switch and a ball dosing apparatus. The device may operate off-line or may be connected to a personal computer. It has a specialized software and a medical manual. The analyzer may be used in clinical diagnosis laboratories for coagulation tests.

[Leukocyte filterability in whole blood]

There was investigated the leukocyte and erythrocyte filtration in blood of 25 donors men. The blood filtration was performed through 5 m pores of nuclear filters at constant perfusion pressure 100 cm H2O. Erythrocytes didn't influence on the leukocyte filtration in blood. Filtration properties of leukocytes together with their number was more important at filtration of blood.

[Early non-invasive diagnosis of cardiovascular diseases]

The study was focused on the assessment of diagnostic significance of cholesterol content in the corneal layer of epidermis detected by the method based on experimental findings that suggest positive correlation between cholesterol levels in aortic endothelium and palm corneal epidermis. Surface cholesterol level was measured with the use of digitonin conjugate. A specially developed photometer proved a valuable tool for quantitative assay of surface cholesterol. Surface cholesterol was detected in epidermis of 649 patients with angiographically confirmed stenotic atherosclerosis. Its levels were significantly different in patients with different localization of atherosclerosis and in age-matched controls. The proposed test was found to be of great prognostic value even if its results were highly variable due to the necessity of separating free and conjugate-bound cholesterol. The enzyme assay of surface cholesterol in epidermis obviates this procedure which significantly improves reproducibility of results.