Image coregistration: quantitative processing framework for the assessment of brain lesions

The quantitative, multiparametric assessment of brain lesions requires coregistering different parameters derived from MRI sequences. This will be followed by analysis of the voxel values of the ROI within the sequences and calculated parametric maps, and deriving multiparametric models to classify imaging data. There is a need for an intuitive, automated quantitative processing framework that is generalized and adaptable to different clinical and research questions. As such flexible frameworks have not been previously described, we proceeded to construct a quantitative post-processing framework with commonly available software components. Matlab was chosen as the programming/integration environment, and SPM was chosen as the coregistration component. Matlab routines were created to extract and concatenate the coregistration transforms, take the coregistered MRI sequences as inputs to the process, allow specification of the ROI, and store the voxel values to the database for statistical analysis. The functionality of the framework was validated using brain tumor MRI cases. The implementation of this quantitative post-processing framework enables intuitive creation of multiple parameters for each voxel, facilitating near real-time in-depth voxel-wise analysis. Our initial empirical evaluation of the framework is an increased usage of analysis requiring post-processing and increased number of simultaneous research activities by clinicians and researchers with non-technical backgrounds. We show that common software components can be utilized to implement an intuitive real-time quantitative post-processing framework, resulting in improved scalability and increased adoption of post-processing needed to answer important diagnostic questions.

Imaging of occlusive thrombi in acute ischemic stroke

Thrombi, or clots, often occlude proximal segments of the cerebral arterial circulation in acute ischemic stroke. Thromboembolic occlusion or thrombi superimposed on atherosclerotic plaque are the principal focus of acute stroke therapies such as thrombolysis or thrombectomy. We review the imaging characteristics of thrombi on multimodal computed tomography and magnetic resonance imaging, angiography, and ultrasonography, summarizing recent studies that facilitate therapeutic decision-making from these noninvasive studies. Information about the location, size, and imaging characteristics can be ascertained using these techniques. Imaging findings in relation to occlusive thrombus have been correlated with clot pathology, response to therapeutic interventions, and clinical outcome. Diagnostic evaluation of occlusive thrombi on noninvasive studies now constitutes an integral component of acute stroke management.

[New Mn-chelates are radioprotectors and antioxidants for cells in vitro]

Earlier we have synthesized new Mn-chelates (Mn-compexes of ethyl ethers of salicyliden-D, L-tyrosine, -gamma-amino butyric acid and -D, L-tryptophan) bearing several free functional groups. The radioprotective and antioxidant activity of these compounds were tested on the secondary cultures of chick embryo cells. To this end the cells in vitro were gamma-irradiated with 60Co at the doses 40 and 60 Gy or treated with H2O2 at the concentration 3 mmol/l, the new Mn-chelates were added into the cultures, and the number of survived cells was determined in 24 hours. It was revealed that all the new Mn-chelates at micromolar concentrations (from 40 to 10 mumol/l) but not their precursors (Mn-acetate and ethyl ethers of salicyliden-aminoacids) effectively protect the cells from lethal effect of both gamma-irradiation and H2O2. Mn-chelates tested are considered as promising potential radioprotectors that effect seems to be reasonable to study in vivo.

[Intercellular contacts accelerate the growth of cell colonies in a chick embryo cell culture]

In sparsely seeded (1.10(3) cells/sm2) chick embryo cell cultures no cell proliferation commonly occurs. However, such factors as increasing cell density, a conditioned medium, or addition of ethanol fixed homologous cells to the culture may accelerate the cell growth. The mitogenic action of fixed cells serves as a contact stimulation of cell proliferation (Gasparian, Grigorian, 1989, 1990). Distant and contact cell-to cell interactions, that involve soluble and insoluble cell derived mitogens, are supposed to operate during the log phase of culture growth. The addition of an excess of cells to the previously sparse culture may mimic the cell microenvironment commonly existing in subconfluent cultures. The role of diverse cell-to cell contacts in the cell growth regulation is discussed. The addition of ethanol-fixed cells may improve the cell cloning technique.

[A possible pathway for mitogenic signal transmission during the contact stimulation of the multiplication of cultured cells]

Cultured cells of the Japanese quail embryo were labeled with 3H-glucosamine, fixed, suspended and inoculated into built-up cultures of the homologous cells. The transfer of insoluble components of labeled cell surface into the cells of underlaying cell sheet was revealed. A decrease in the cell incubation temperature up to 4 degrees C blocks the process. The exchange of cell surface sites between contacting cells seems to be one of the possible ways of information transmission from one cell into another during contact regulation of cell proliferation.

[The characteristics of the stimulation of the proliferation of cultured chick embryo cells during reseeding]

The growth rate of chick embryo cells in slowly proliferating cultures is activated after substitution of conditioned medium by fresh one with serum. After cell replanting, the stimulation of cell proliferation takes place in both media with the same effectiveness. In serum-less medium replanted cells do not adhere to glass and die. The results suggest that cells reversibly lose their dependence upon serum growth factors and population density, as a result of replanting, but retain anchorage-dependence for growth.

[Contact stimulation of the proliferation of cultured chick embryo cells]

It was reported elsewhere (Gasparian, Grigorian, 1989a) that in the secondary chick embryo cell culture, after its superinoculation with additional homologous cells, the cell population density increased and the cell proliferation was activated. It has been shown in the present paper that the cell proliferation rate increase after inoculation of fixed cells, as well. The results obtained are discussed as a direct evidence for growth-stimulating effect of contacts between homologous cells.

[Stimulation of multiplication of chick embryo cultured cells after an increase in density of the cellular population]

The secondary culture of chick embryo cells in 2-3 days after seeding was super-inoculated with homologous cells. Suspended cells adhere and spread on the cell layer whereby the culture density increases quickly. After adhesion of exogenous cells to the layer the stimulation of cell proliferation takes place. This activation is not connected with methodical manipulations or with the influence of conditioned medium factors. The results suggest that the increase in cell number itself does not arrest cell multiplication. It is proposed that the known phenomenon of blocking cell proliferation in dense cultures cannot be attributed only to effects of high cell density.

[Formation of the population composition of a stationary cell culture and the participation of nonproliferating cells with a doubled DNA content in regulating its density]

The conditions of the cultivation of chick embryo diploid cells were alternated (prolonged maintenance with or without medium replacement, with or without consequent cell replating in fresh medium). In different times of culture growth, the cell DNA content was assessed by cytophotometry; the percentage of non-labeled mitoses after incubating the cells with 3H-thymidine and colcemide, as well as the cell density were determined. The phenomenon, detected earlier, of the accumulation of cells containing 4c DNA during the transition of the culture from logarithmic into the stationary phase of growth, was confirmed. These cells were shown to differ in their ability to survive in conditions of stationary culture and by proliferative potential. The fraction of cells reversibly arrested in G2-period was described, by which fraction the change of the cell population size is occurring after the decrease of its proliferation rate. The transitional stage is distinguished at the beginning of the stationary phase of culture growth. During this stage the stabilization of structural and numerical composition of the population is taking place.

[Accumulation of nonproliferating cells containing 4c DNA in stationary diploid cell cultures]

The cell proliferation was stimulated in stationary cultures of chick and human embryo cells by changing the medium. The cumulative indices of labeled cells and labeled mitosis as well as the cellular DNA contents were determined in the stimulated cultures at different times of growth until their entry into the stationary phase of growth. It is established that in the case of mass entry of cells into DNA synthesis period, part of them does not complete the mitotic cycle to be arrested in the G2-period. This arrest is considered as one of the ways of the cell proliferation inhibition in cultures entering into the stationary phase.

[Studies of nucleic acid metabolism in cultured chick embryo cells infected with Mycoplasma gallisepticum]

M. gallisepticum infection of cultured chick embryo cells led to a sharp reduction the rate of 3H-thymidine and 3H-uridine incorporation into DNA and RNA cells, and almost completely suppressed the transposition of uridine label from the nucleus into the cytoplasm, this pointing to the inhibition of escape of RNA synthesized de novo into the infected cells cytoplasm. As suggested, weak labeling of the cytoplasm after prolonged (about several hours) incubation of cultured cells with labeled urine could indicate infection of cell cultures with the mycoplasmae.

[Protein SH-group concentration and RNA synthesis during the process of induction of proliferation in the stationary phase of cell culture growth]

The dynamics of intracellular protein SH-group (PSH) content was studied cytochemically in the course of stimulation of cell proliferation in stationary cultures of an established Chinese hamster cell line and of human diploid embryo fibroblasts. The results were compared with the pattern of RNA synthesis during the prereplicative period. In Chinese hamster cells immediately after medium changing in stationary cultures there is an augmentation of PSH content in parallel withe the increase in RNA synthesis rate. Later on, the rate of RNA synthesis and PSH content are seen decreasing followed by a new increase in the rate of RNA synthesis correlated with the second rise in PSH content. In stationary cultures of human diploid fibroblasts, there is also an increase in the rate of RNA synthesis and in the content of SH after medium changing, but the second wave of RNA synthesis and the second rise in PSH content are not pronounced. The variation in PSH content reflects the shift in the cell metabolism during the prereplicative period and is not attributed to changes in cell protein content.