[The secretome of mesenchymal stromal cells as a new hope in the treatment of acute brain tissue injuries]. / Sekretom mezenkhimnykh stromal'nykh kletok kak novaya nadezhda v lechenii ostrykh povrezhdenii golovnogo mozga.

Ischemic and hemorrhagic strokes, traumatic brain injury, bacterial and viral encephalitis, toxic and metabolic encephalopathies are very different pathologies. But, they have much more in common than it might seem at first glance. In this review, the authors propose to consider these brain pathologies from the point of view of the unity of their pathogenetic mechanisms and approaches to therapy. Particular attention is paid to promising therapeutic approaches, such as therapy using cells and their secretion products: an analysis of the accumulated experimental data, the advantages and limitations of these approaches in the treatment of brain damage was carried out. The review may be of interest both to specialists in the field of neurology, neurosurgery and neurorehabilitation, and to readers who want to learn more about the progress of regenerative biomedicine in the treatment of brain pathologies.

[Genetic Diversity of the Cytochrome b Gene Fragment Haplotypes in Red-Backed Vole Myodes (Clethrionomys) rutilus Pallas, 1779].

For the first time, genetic analysis of the cytochrome b gene fragment haplotypes encoding the identical and the most common cytochrome b polypeptide (F1) in M. rutilus from Eastern and Beringian mateml lineages was carried out. The F1 frequencies for the vole populations from Northern Priokhotye and the Kolyma basin were calculated. Considerable polymorphism of the cytochrome b F1 haplotypes within two major phylo- groups of red-backed vole was supported by high molecular diversity indices for these clades. The proportion of genetic variation between the maternal lineages of F1 red-backed vole individuals (60.71%) was considerably higher than inter-(24.44%) and intrapopulation (14.85%) components. The data obtained make it possible to advance a hypothesis on the convergence of the cytochrome b polypeptide structure upon sequence divergence of the corresponding gene.

Comparison of radiation dose and image quality from single-energy and dual-energy CT examinations in the same patients screened for hepatocellular carcinoma.

AIM: To compare radiation dose surrogates [volume CT dose index (CTDIvol), dose-length product (DLP), size-specific dose estimate (SSDE), and effective dose] and image noise in a cohort of patients undergoing hepatocellular carcinoma screening who underwent both single-energy CT (SECT) and dual-energy CT (DECT). MATERIALS AND METHODS: In this institutional review board-approved, Health Insurance Portability and Accountability Act-compliant retrospective study, 74 adults (mean age 59.5 years) underwent 64 section SECT (120 kVp and weight-based reference mAs) and 128 section dual-source DECT (100/Sn 140 kVp and CTDIvol, adjusted to match the CDTIvol of the SECT protocol) on different occasions. Noise levels were measured in the liver, inferior vena cava (IVC), retroperitoneal (RP) fat, and aorta. Generalized linear models were constructed to compare dose and noise, adjusting for effective diameter. RESULTS: The total DLP (1371.11 mGy-cm, SD = 527.91) and effective dose (20.57 mSv, SD = 7.92) with SECT were significantly higher than the DLP (864.84 mGy-cm, SD = 322.10) and effective dose (12.97 mSv, SD = 4.83) with DECT (p < 0.001). The differences between SECT and DECT increased as the patient's effective diameter increased (p < 0.001). Noise levels in the liver (22.4 versus 21.9 HU), IVC (22.3 versus 23.4 HU), and RP fat (23.5 versus 23 HU) were similar for DECT and SECT (p > 0.05) but were significantly lower in the aorta for DECT (25.3 versus 26.4 HU; p = 0.006). CONCLUSION: DECT imaging of the abdomen can achieve noise levels comparable to those seen with SECT imaging without a dose penalty to patients.

[Genetic structure of the Siberian Sucker (Catostomus catostomus rostratus) according to data on sequence variation of the mtDNA cytochrome B gene].

Data regarding the structure and variation of the nucleotide sequence of the cytochrome b gene of mitochondrial DNA of the Siberian Sucker from the Kolyma River were obtained. Analysis of the median network revealed that evolutionary lines diverged from a common ancestor. Penetration of the sucker into Asia from Northern America took place between the Early and Middle Pleistocene. Prolonged reproductive isolation of the Siberian and Northern American suckers led to interspecies divergence with the appearance of amino acid substitutions, which, apparently, fixed due to positive selection. The Siberian Sucker appeared to have three modifications of the Cytb protein.

[Variability of mitochondrial DNA cytochrome b gene in the red vole Clethrionomys rutilus pallas, 1779, population in the flood-plain middle stream of the Kolyma River].

The intrapopulation variability of a cytochrome b gene fragment and the corresponding amino acid sequence was studied in the red vole Clethrionomys rutilus Pallas, 1779 from the flood-plain of the Kolyma River. Wide polymorphic variability of these properties was observed. Differences in the cytochrome b gene sequence were determined between the red voles of the studied population and the species collected in neighborhoods of Novosibirsk and Omsk. The revealed results point to the urgency of the cytochrome b gene nucleotide sequence and the variants of the respective amino acid sequence as genetic markers of originality of different red vole populations.

Improved dual-energy material discrimination for dual-source CT by means of additional spectral filtration.

The use of additional spectral filtration for dual-energy (DE) imaging using a dual-source CT (DSCT) system was investigated and its effect on the material-specific DE(ratio) was evaluated for several clinically relevant materials. The x-ray spectra, data acquisition, and reconstruction processes for a DSCT system (Siemens Definition) were simulated using information provided by the system manufacturer, resulting in virtual DE images. The factory-installed filtration for the 80 kV spectrum was left unchanged to avoid any further reductions in tube output, and only the filtration for the high-energy spectrum was modified. Only practical single-element filter materials within the atomic number range of 40 < or = Z < or = 83 were evaluated, with the aim of maximizing the separation between the two spectra, while maintaining similar noise levels for high- and low-energy images acquired at the same tube current. The differences between mean energies and the ratio of the 140 and 80 kV detector signals, each integrated below 80 keV, were evaluated. The simulations were performed for three attenuation scenarios: Head, body, and large body. The large body scenario was evaluated for the DE acquisition mode using the 100 and 140 kV spectra. The DE(ratio) for calcium hydroxyapatite (simulating bone or calcifications), iodine, and iron were determined for CT images simulated using the modified and factory-installed filtration. Several filter materials were found to perform well at proper thicknesses, with tin being a good practical choice. When image noise was matched between the low- and high-energy images, the spectral difference in mean absorbed energy using tin was increased from 25.7 to 42.7 keV (head), from 28.6 to 44.1 keV (body), and from 20.2 to 30.2 keV (large body). The overlap of the signal spectra for energies below 80 keV was reduced from 78% to 31% (head), from 93% to 27% (body), and from 106% to 79% (large body). The DE(ratio) for the body attenuation scenario increased from 1.45 to 1.91 (calcium), from 1.84 to 3.39 (iodine), and from 1.73 to 2.93 (iron) with the additional tin filtration compared to the factory filtration. This use of additional filtration for one of the x-ray tubes used in dual-source DECT dramatically increased the difference between material-specific DE ratios, e.g., from 0.39 to 1.48 for calcium and iodine or from 0.28 to 1.02 for calcium and iron. Because the ability to discriminate between different materials in DE imaging depends primarily on the differences in DE ratios, this increase is expected to improve the performance of any material-specific DECT imaging task. Furthermore, for the large patient size and in conjunction with a 100/140 kV acquisition, the use of additional filtration decreased noise in the low-energy images and increased contrast in the DE image relative to that obtained with 80/140 kV and no additional filtration.

Detection of myocardial infarction by dual-source coronary computed tomography angiography using quantitated myocardial scintigraphy as the reference standard.

BACKGROUND: Dual-source coronary computed tomography angiography (DS-CTA) has the potential to assess both coronary anatomy and myocardial perfusion. We studied the ability of DS-CTA to detect myocardial infarction (MI) compared to a reference standard of technetium Tc(99)m sestamibi single photon emission computed tomography (SPECT). METHODS: 122 patients with suspected or known coronary artery disease (age 60 (SD 11) years, 36% females) were evaluated by both DS-CTA and SPECT. SPECT-MI size was quantitated using a threshold value of 60% of peak counts on the resting images. MI on DS-CTA was defined as transmural or subendocardial hypoenhancement (<50% of surrounding myocardium), which persisted in both diastolic and systolic reconstructions and was concordant with a coronary artery territory. The performance of DS-CTA to detect SPECT-MI was determined in a blinded, vessel-based analysis. RESULTS: 366 vessel territories were analysed (122 patients x3). SPECT revealed 20 vessel territories with MI (involving 17 patients). 15/20 (75%) of these vessel territories were also detected by DS-CTA. An additional seven MIs were detected by DS CTA only (considered as false positive). Thus, the sensitivity of DS-CTA for detection of SPECT-MI was 75% (95% CI 56% to 94%), specificity 98% (97% to 100%), positive predictive value 68% (49% to 88%) and negative predictive value 99% (97% to 100%). DS-CTA detected 10/11 (91%) larger MIs (involving >5% of left ventricular (LV) mass by SPECT). For the 15 concordant MIs (in both SPECT and DS-CTA) the mean difference in MI size between modalities was 0.5% (4.6%) of LV mass (95% CI -8.6% to 9.5%). CONCLUSIONS: DS-CTA myocardial perfusion imaging showed moderate sensitivity and positive predictive value but high specificity and negative predictive value for detection of SPECT-MI. Most large infarcts (>5% of LV mass) were detected by DS-CTA. When MI was detected by both modalities, there was a good correlation between infarct sizes quantitated by DS-CTA vs SPECT.

Dual-energy CT iodine overlay technique for characterization of renal masses as cyst or solid: a phantom feasibility study.

The aim of this study was to assess the ability of dual-energy computed tomography (DECT) to classify phantom renal lesions as cysts or enhancing masses. Six cylinders ranging in diameter from 0.5 to 3.0 cm were filled with distilled water or titrated iodinated contrast solutions with CT attenuation values at 120 kVp of 0 Hounsfield units (HU) for a cyst proxy or 10, 20, or 40 HU to represent enhancing masses. These were placed in a 12-cm-diameter renal phantom containing puréed beef mixed with iodinated contrast medium to simulate enhancing renal parenchyma of 100 and 250 HU and submerged within a 28-cm water bath. These combinations produced 48 individual phantom renal lesions of differing sizes, internal and parenchymal enhancement (12 cysts and 36 enhancing masses). DECT using 80 and 140 kVp was performed on a dual-source CT scanner. Commercial software created a color-encoded overlay indicating the location of iodine within the phantom. The lesions were individually graded as a cyst or enhancing mass by blinded, consensus interpretation of two genitourinary radiologists. Thirty-five of 36 enhancing masses and 10/12 cysts were correctly identified, equating to a sensitivity and specificity of 97% (95% CI 84-100%) and 83% (95% CI 51-97%), respectively. All lesions of 20- and 40-HU enhancement and 92% of 10-HU lesions were identified correctly. In a phantom model, the DECT iodine overlay technique is highly sensitive in detecting enhancing renal masses. Refinement of the technique remains necessary to improve specificity. If validated in patients, this may obviate the need for unenhanced acquisitions for renal mass characterization.

Novel ultrahigh resolution data acquisition and image reconstruction for multi-detector row CT.

We present and evaluate a special ultrahigh resolution mode providing considerably enhanced spatial resolution both in the scan plane and in the z-axis direction for a routine medical multi-detector row computed tomography (CT) system. Data acquisition is performed by using a flying focal spot both in the scan plane and in the z-axis direction in combination with tantalum grids that are inserted in front of the multi-row detector to reduce the aperture of the detector elements both in-plane and in the z-axis direction. The dose utilization of the system for standard applications is not affected, since the grids are moved into place only when needed and are removed for standard scanning. By means of this technique, image slices with a nominal section width of 0.4 mm (measured full width at half maximum=0.45 mm) can be reconstructed in spiral mode on a CT system with a detector configuration of 32 x 0.6 mm. The measured 2% value of the in-plane modulation transfer function (MTF) is 20.4 lp/cm, the measured 2% value of the longitudinal (z axis) MTF is 21.5 lp/cm. In a resolution phantom with metal line pair test patterns, spatial resolution of 20 lp/cm can be demonstrated both in the scan plane and along the z axis. This corresponds to an object size of 0.25 mm that can be resolved. The new mode is intended for ultrahigh resolution bone imaging, in particular for wrists, joints, and inner ear studies, where a higher level of image noise due to the reduced aperture is an acceptable trade-off for the clinical benefit brought about by the improved spatial resolution.

A technical solution to avoid partial scan artifacts in cardiac MDCT.

Quantitative evaluation of cardiac image data obtained using multidetector row computed tomography (CT) is compromised by partial scan reconstructions, which improve the temporal resolution but significantly increase image-to-image CT number variations for a fixed region of interest compared to full reconstruction images. The feasibility of a new approach to solve this problem is assessed. An anthropomorphic cardiac phantom and an anesthetized pig were scanned on a dual-source CT scanner using both full and partial scan acquisition modes under different conditions. Additional scans were conducted with the electrocardiogram (ECG) signal being in synchrony with the gantry rotation. In the animal study, a simple x-ray detector was used to generate a signal once per gantry rotation. This signal was then used to pace the pig's heart. Phantom studies demonstrated that partial scan artifacts are strongly dependent on the rotational symmetry of angular projections, which is determined by the object shape and composition and its position with respect to the isocenter. The degree of partial scan artifacts also depends on the location of the region of interest with respect to highly attenuating materials (bones, iodine, etc.) within the object. Single-source partial scan images (165 ms temporal resolution) were significantly less affected by partial scan artifacts compared to dual-source partial scan images (82 ms temporal resolution). When the ECG signal was in synchrony with the gantry rotation, the same cardiac phase always corresponded to the same positions of the x-ray tube(s) and, hence, the same scattering and beam hardening geometry. As a result, the range of image-to-image CT number variations for partial scan reconstruction images acquired in synchronized mode was decreased to that achieved using full reconstruction image data. The success of the new approach, which synchronizes the ECG signal with the position of the x-ray tube(s), was demonstrated both in the phantom and animal experiments.

Image reconstruction and image quality evaluation for a 64-slice CT scanner with z-flying focal spot.

We present a theoretical overview and a performance evaluation of a novel z-sampling technique for multidetector row CT (MDCT), relying on a periodic motion of the focal spot in the longitudinal direction (z-flying focal spot) to double the number of simultaneously acquired slices. The z-flying focal spot technique has been implemented in a recently introduced MDCT scanner. Using 32 x 0.6 mm collimation, this scanner acquires 64 overlapping 0.6 mm slices per rotation in its spiral (helical) mode of operation, with the goal of improved longitudinal resolution and reduction of spiral artifacts. The longitudinal sampling distance at isocenter is 0.3 mm. We discuss in detail the impact of the z-flying focal spot technique on image reconstruction. We present measurements of spiral slice sensitivity profiles (SSPs) and of longitudinal resolution, both in the isocenter and off-center. We evaluate the pitch dependence of the image noise measured in a centered 20 cm water phantom. To investigate spiral image quality we present images of an anthropomorphic thorax phantom and patient scans. The full width at half maximum (FWHM) of the spiral SSPs shows only minor variations as a function of the pitch, measured values differ by less than 0.15 mm from the nominal values 0.6, 0.75, 1, 1.5, and 2 mm. The measured FWHM of the smallest slice ranges between 0.66 and 0.68 mm at isocenter, except for pitch 0.55 (0.72 mm). In a centered z-resolution phantom, bar patterns up to 15 lp/cm can be visualized independent of the pitch, corresponding to 0.33 mm longitudinal resolution. 100 mm off-center, bar patterns up to 14 lp/cm are visible, corresponding to an object size of 0.36 mm that can be resolved in the z direction. Image noise for constant effective mAs is almost independent of the pitch. Measured values show a variation of less than 7% as a function of the pitch, which demonstrates correct utilization of the applied radiation dose at any pitch. The product of image noise and square root of the slice width (FWHM of the respective SSP) is the same constant for all slices except 0.6 mm. For the thinnest slice, relative image noise is increased by 17%. Spiral windmill-type artifacts are effectively suppressed with the z-flying focal spot technique, which has the potential to maintain a low artifact level up to pitch 1.5, in this way increasing the maximum volume coverage speed that can be clinically used.

Theory of the incommensurate smectic-A phases in dimesogenic liquid crystals.

A mechanism assuming a mismatch between the basic smectic periodicity and the amplitude and phase modulations periods of the mass density wave order parameter is proposed, for describing the incommensurate smectic-A structure found in dimesogenic liquid crystals. The different sequences of phases found in this family of compounds are described theoretically.

Bias-induced forces in conducting atomic force microscopy and contact charging of organic monolayers.

Contact electrification, a surface property of bulk dielectric materials, has now been observed at the molecular scale using conducting atomic force microscopy (AFM). Conducting AFM measures the electrical properties of an organic film sandwiched between a conducting probe and a conducting substrate. This paper describes physical changes in the film caused by the application of a bias. Contact of the probe leads to direct mechanical stress and the applied electric field results in both Maxwell stresses and electrostriction. Additional forces arise from charge injection (contact charging). Electrostriction and contact charging act oppositely from the normal long-range Coulomb attraction and dominate when a charged tip touches an insulating film, causing the tip to deflect away from the film at high bias. A bias-induced repulsion observed in spin-coated PMMA films may be accounted for by either mechanism. In self-assembled monolayers, however, tunnel current signals show that the repulsion is dominated by contact charging.

Reproducible measurement of single-molecule conductivity.

A reliable method has been developed for making through-bond electrical contacts to molecules. Current-voltage curves are quantized as integer multiples of one fundamental curve, an observation used to identify single-molecule contacts. The resistance of a single octanedithiol molecule was 900 +/- 50 megohms, based on measurements on more than 1000 single molecules. In contrast, nonbonded contacts to octanethiol monolayers were at least four orders of magnitude more resistive, less reproducible, and had a different voltage dependence, demonstrating that the measurement of intrinsic molecular properties requires chemically bonded contacts.

[Modification of a method for detecting the post-phoretic activity of mannose (Mpi, EC 5.3.1.8)- and glucose (Gpi, EC5.3.1.9)-6-phosphate isomerase]. / Modifitsirovannaia metodika vyiavleniia postforeticheskoi aktivnosti mannozo (Mpi, EC 5.3.1.8)- i gliukozo (Gpi, EC 5.3.1.9)-6-fosfatizomeraz.

A method for detecting activities of mannose- and glucose-6-phosphate isomerases based on enzyme production of the substrates is described. The results obtained for several animal taxa are illustrated by photographs.