Prognostic implications of cholesterol chrystals at ACS causing culprit lesions, insights from the translational OPTICO-ACS study program

Aims

Cholesterol chrystals (CC) represent a feature of advanced plaque remodeling. Optical coherence tomography (OCT) allows for detailed morphological assessment of the culprit lesion, including the presence of CCs, in vivo. Since CCs have been identified as prognostically relevant plaque feature in coronary artery disease (CAD), the present analysis aims to further characterize their impact on adverse cardiovascular outcome in a large cohort of patients, presenting with acute coronary syndrome (ACS).

Methods

Within the translational OPTICO-ACS study program, 371 consecutive ACS-patients were included into the final analysis. OCT-characteristics, including the presence of CCs, were assessed by a standardized CoreLab analysis following universal consensus standards for OCT-derived plaque features. All patients were followed up for 12 months after the index event and major adverse cardiac events (MACE) consisting of death, myocardial infarction, target vessel revascularization plus re-hospitalization due to unstable or progressive angina pectoris were documented.

Results

215 patients (58.1%) presented with cholesterol chrystals (CCs) at the culprit lesion. Plaque rupture (RFC-ACS) represented the primary ACS-causing pathophysiology (75.3%) in those patients. Further, the presence of CCs was associated with other high-risk features within the culprit lesion, i.e. the presence of thin cap fibroatheroma (77.7% vs. 63.2%; p<0.05), plaque calcification (80.5% vs. 67.1; p<0.01) and microchannels (80.1% vs. 70.1; p<0.05) as well as an increased area stenosis (0.77 vs. 0.73 mm2; p<0.01) and a greater maximum lipid arc (282.8 vs. 242.6°; p<0.01) as compared to culprit lesions free of CCs. Of note, there was a strong association among the occurrence of macrophages within the plaque and cholesterol crystals. Finally, and most importantly MACE during 12 months follow-up, consisting of cardiac death, myocardial infarction, target vessel revascularization and re-hospitalization due to progressive or unstable angina pectoris, occurred with nearly twice the frequency in CC-patients (20.3% vs. 10.6%; p<0.01) as compared to patients without CCs at the culprit site.

Conclusion

The present analysis introduces cholesterol chrystals as a novel prognostically relevant high-risk plaque feature allowing individual risk stratification for patients after ACS.

Funding Acknowledgement

Type of funding sources: None.

Olfactory training with Aromastics: olfactory and cognitive effects

Purpose

The olfactory system can be successfully rehabilitated with regular, intermittent stimulation during multiple daily exposures to selected sets of odors, i.e., olfactory training (OT). OT has been repeatedly shown to be an effective tool of olfactory performance enhancement. Recent advancements in studies on OT suggest that its beneficial effects exceed olfaction and extend to specific cognitive tasks. So far, studies on OT provided compelling evidence for its effectiveness, but there is still a need to search for an optimal OT protocol. The present study examined whether increased frequency of OT leads to better outcomes in both olfactory and cognitive domains.

Method

Fifty-five subjects (28 females; M_age = 58.2 ± 11.3 years; 26 patients with impaired olfaction) were randomly assigned to a standard (twice a day) or intense (four times a day) OT. Olfactory and cognitive measurements were taken before and after OT.

Results

OT performed twice a day was more effective in supporting olfactory rehabilitation and interventions targeted to verbal semantic fluency than OT performed four times a day, even more so in subjects with lower baseline scores.

Conclusions

OT is effective in supporting olfactory rehabilitation and interventions targeted to verbal semantic fluency. However, it may be prone to a ceiling effect, being efficient in subjects presenting with lower baseline olfactory performance and lower verbal semantic fluency.

Supplementary Information

The online version contains supplementary material available at 10.1007/s00405-021-06810-9.

Differential tumor biological role of the tumor suppressor KAI1 and its splice variant in human breast cancer cells

The tetraspanin and tumor suppressor KAI1 is downregulated or lost in many cancers which correlates with poor prognosis. KAI1 acts via physical/functional crosstalk with other membrane receptors. Also, a splice variant of KAI1 (KAI1-SP) has been identified indicative of poor prognosis. We here characterized differential effects of the two KAI1 variants on tumor biological events involving integrin (αvß3) and/or epidermal growth factor receptor (EGF-R). In MDA-MB-231 and -435 breast cancer cells, differential effects were documented on the expression levels of the tumor biologically relevant integrin αvß3 which colocalized with KAI1-WT but not with KAI1-SP. Cellular motility was assessed by video image processing, including motion detection and vector analysis for the quantification and visualization of cell motion parameters. In MDA-MB-231 cells, KAI1-SP provoked a quicker wound gap closure and higher closure rates than KAI1-WT, also reflected by different velocities and average motion amplitudes of singular cells. KAI1-SP induced highest cell motion adjacent to the wound gap borders, whereas in MDA-MB-435 cells a comparable induction of both KAI1 variants was noticed. Moreover, while KAI1-WT reduced cell growth, KAI1-SP significantly increased it going along with a pronounced EGF-R upregulation. KAI1-SP-induced cell migration and proliferation was accompanied by the activation of the focal adhesion and Src kinase. Our findings suggest that splicing of KAI1 does not only abrogate its tumor suppressive functions, but even more, promotes tumor biological effects in favor of cancer progression and metastasis.

Structural origins of the cohesive energy in metal-terpyridine oligomer thin-films

Fe^II-terpyridine based oligomers have attracted considerable interest as key constituents for the realization of highly robust, ultra-thin ordered layers of metal center oligomers (MCOs) for organic electronics applications. By using molecular simulations and nanotribology investigations, we report on the origins of the surprisingly high mechanical and thermal stability in this type of MCO layers, which finds its expression in nanowear resistance values of up to 1.5 μN for the MCO films, as well as in a thermal stability of two-terminal MCO junctions to temperatures up to ∼100 °C under electrical load. A theoretical analysis of the fundamental cohesive forces among the constituents within the context of an electrostatic model reveal that the cohesive energy is essentially based on Coulomb interactions among the ionic constituents of the oligomers, leading to an estimated cohesive energy per molar mass of 0.0132 eV mol g^-1 for MCO layers that advantageously compare to the 0.0061 eV mol g^-1 reported for pentacene crystals.

Surface Energy and Work Function Control of AlOx/Al Surfaces by Fluorinated Benzylphosphonic Acids

The performance of organic electronic devices can be significantly improved by modifying metal electrodes with organic monolayers, which alter the physical and chemical nature of the interface between conductor and semiconductor. In this paper we examine a series of 12 phosphonic acid compounds deposited on the native oxide layer of aluminum (AlOx/Al), an electrode material with widespread applications in organic electronics. This series includes dodecylphosphonic acid as a reference and 11 benzylphosphonic acids, seven of which are fluorinated, including five newly synthesized derivatives. The monolayers are experimentally characterized by contact angle goniometry and by X-ray photoemission spectroscopy (XPS), and work function data obtained by low-intensity XPS are correlated with molecular dipoles obtained from DFT calculations. We find that monolayers are formed with molecular areas ranging from 17.7 to 42.9 Å(2)/molecule, and, by the choice of appropriate terminal groups, the surface energy can be tuned from 23.5 mJ/m(2) to 70.5 mJ/m(2). Depending on the number and position of fluorine substituents on the aromatic rings, a variation in the work function of AlOx/Al substrates over a range of 0.91 eV is achieved, and a renormalization procedure based on molecular density yields a surprising agreement of work function changes with interface dipoles as expected from Helmholtz' equation. The ability to adjust energetics and adhesion at organic semiconductor/AlOx interfaces has immediate applications in devices such as OLEDs, OTFTs, organic solar cells, and printed organic circuits.

Ultrarobust Thin-Film Devices from Self-Assembled Metal-Terpyridine Oligomers

Ultrathin molecular layers of Fe(II) -terpyridine oligomers allow the fabrication of large-area crossbar junctions by conventional electrode vapor deposition. The junctions are electrically stable for over 2.5 years and operate over a wide range of temperatures (150-360 K) and voltages (±3 V) due to the high cohesive energy and packing density of the oligomer layer. Electrical measurements reveal ideal Richardson-Shottky emission in surprising agreement with electrochemical, optical, and photoemission data.

Challenges and Opportunities in the Development of Aptamers for TNFα

RNA aptamers for tumor necrosis factor-alpha (TNFα), for which functionality was demonstrated in L929 cells, show only little affinity for the protein in vitro. Detailed investigation of the aptamer-protein interaction by surface plasmon resonance and quartz crystal microbalance analysis revealed that affinity is not the only crucial parameter for efficacy and functionality of those aptamers. Instead, the sensitive equilibrium of the monomeric and homotrimeric form of soluble TNFα decides on aptamer binding. Our results show that the field of application and the source of TNFα have to be carefully defined before selection of aptamer sequences.

Fabrication of Homogeneous High-Density Antibody Microarrays for Cytokine Detection

Cytokine proteins are known as biomarker molecules, characteristic of a disease or specific body condition. Monitoring of the cytokine pattern in body fluids can contribute to the diagnosis of diseases. Here we report on the development of an array comprised of different anti-cytokine antibodies on an activated solid support coupled with a fluorescence readout mechanism. Optimization of the array preparation was done in regard of spot homogeneity and spot size. The proinflammatory cytokines Tumor Necrosis Factor alpha (TNFα) and Interleukin 6 (IL-6) were chosen as the first targets of interest. First, the solid support for covalent antibody immobilization and an adequate fluorescent label were selected. Three differently functionalized glass substrates for spotting were compared: amine and epoxy, both having a two-dimensional structure, and the NHS functionalized hydrogel (NHS-3D). The NHS-hydrogel functionalization of the substrate was best suited to antibody immobilization. Then, the optimization of plotting parameters and geometry as well as buffer media were investigated, considering the ambient analyte theory of Roger Ekins. As a first step towards real sample studies, a proof of principle of cytokine detection has been established.

Organic dipole layers for ultralow work function electrodes

The alignment of the electrode Fermi level with the valence or conduction bands of organic semiconductors is a key parameter controlling the efficiency of organic light-emitting diodes, solar cells, and printed circuits. Here, we introduce a class of organic molecules that form highly robust dipole layers, capable of shifting the work function of noble metals (Au and Ag) down to 3.1 eV, that is, ∼1 eV lower than previously reported self-assembled monolayers. The physics behind the considerable interface dipole is elucidated by means of photoemission spectroscopy and density functional theory calculations, and a polymer diode exclusively based on the surface modification of a single electrode in a symmetric, two-terminal Au/poly(3-hexylthiophene)/Au junction is presented. The diode exhibits the remarkable rectification ratio of ∼2·10(3), showing high reproducibility, durability (>3 years), and excellent electrical stability. With this evidence, noble metal electrodes with work function values comparable to that of standard cathode materials used in optoelectronic applications are demonstrated.

Cell-free expression of a mammalian olfactory receptor and unidirectional insertion into small unilamellar vesicles (SUVs)

Although the identification of the multigene family encoding mammalian olfactory receptors were identified more than 20 years ago, we are far from understanding olfactory perception because of the difficulties in functional expression of these receptors in heterologous cell systems. Cell-free (CF) or in vitro expression systems offer an elegant alternative route to cell based protein expression, as the functional expression of membrane proteins can be directly achieved from the genetic template without the need of cell cultivation and protein isolation. Here we investigated in detail the cell-free expression and membrane insertion of the olfactory receptor OR5 in dependence of different experimental conditions like probing different origins of the cell-free expression system (from bacteria, via plants and insects toward mammalian system) and lipid composition of the respective extracts. We provided substantial biochemical indications by radioactive labeling based on [(35)S]-methionine, followed by proteolytic digestion, and we found that the insertion of the olfactory receptor OR5 into liposomes resulted in an unidirectional orientation with the binding side exposed into the aqueous space, resembling the native orientation in the cilia of the olfactory neurons. We report the different results in synthesis capacity for the different in vitro systems employed as we like to demonstrate the first in vitro kit toward and ex situ and ex vivo odorant receptor array.

Conductance modulation in tetraaniline monolayers by HCl-doping and by field-enhanced dissociation of H₂O

Oligoanilines are interesting candidates for organic electronics, as their conductivity can be varied by several orders of magnitude upon protonic doping. Here we demonstrate that tetraaniline self-assembled monolayers exhibit an unprecedented conductance on/off ratio of ∼710 (at +1 V) upon doping of the layers from the emeraldine base to the emeraldine salt form. Furthermore, a pronounced asymmetry in the current-voltage characteristics indicates dynamic doping of the tetraaniline layer by protons generated through field-enhanced dissociation of water molecules, a phenomenon known as the second Wien effect. These results point toward oligoanilines as promising substitutes for polyaniline layers in next-generation thin film devices.

Cytochrome c biosensor--a model for gas sensing

This work is about gas biosensing with a cytochrome c biosensor. Emphasis is put on the analysis of the sensing process and a mathematical model to make predictions about the biosensor response. Reliable predictions about biosensor responses can provide valuable information and facilitate biosensor development, particularly at an early development stage. The sensing process comprises several individual steps, such as phase partition equilibrium, intermediate reactions, mass-transport, and reaction kinetics, which take place in and between the gas and liquid phases. A quantitative description of each step was worked out and finally combined into a mathematical model. The applicability of the model was demonstrated for a particular example of methanethiol gas detection by a cytochrome c biosensor. The model allowed us to predict the optical readout response of the biosensor from tabulated data and data obtained in simple liquid phase experiments. The prediction was experimentally verified with a planar three-electrode electro-optical cytochrome c biosensor in contact with methanethiol gas in a gas tight spectroelectrochemical measurement cell.

Efficient electronic coupling and improved stability with dithiocarbamate-based molecular junctions

Molecular electronic devices require stable and highly conductive contacts between the metal electrodes and molecules. Thiols and amines are widely used to attach molecules to metals, but they form poor electrical contacts and lack the robustness required for device applications. Here, we demonstrate that dithiocarbamates provide superior electrical contact and thermal stability when compared to thiols on metals. Ultraviolet photoelectron spectroscopy and density functional theory show the presence of electronic states at 0.6 eV below the Fermi level of Au, which effectively reduce the charge injection barrier across the metal-molecule interface. Charge transport measurements across oligophenylene monolayers reveal that the conductance of terphenyl-dithiocarbamate junctions is two orders of magnitude higher than that of terphenyl-thiolate junctions. The stability and low contact resistance of dithiocarbamate-based molecular junctions represent a significant step towards the development of robust, organic-based electronic circuits.

Cognitive performance in elderly patients undergoing carotid endarterectomy or carotid artery stenting: a twelve-month follow-up study

BACKGROUND

It is still a matter of debate if and to what extent carotid endarterectomy (CEA) and carotid artery stenting (CAS) impair cognitive functioning in the elderly.

METHODS

We conducted a nonrandomized clinical trial on subjects with asymptomatic carotid artery stenosis comparing CEA (n = 28; 24 males and 4 females; 72.6 +/- 5.8 years old) with CAS (n = 29; 17 males and 12 females; 75.1 +/- 5.7 years old). Cognition, mood and functional status were evaluated by a broad spectrum of tests performed on the day prior to carotid reopening as well as 3 and 12 months after.

RESULTS

No significant differences in scores on cognitive tests including the Babcock story recall test and Rey's auditory verbal learning test (memory), category naming test (verbal fluency), trail-making test parts A and B (attention and executive function) and controlled oral word association test (executive functioning) were observed 3 and 12 months after carotid reopening independent of the technique used. Only scores on the copy drawing test (visuospatial and constructional abilities) slightly but significantly (p < 0.05) worsened in the CAS group 12 months after the intervention. No significant differences between the CEA and CAS groups were detected regarding mood and functional status after 3 and 12 months.

CONCLUSIONS

CEA and CAS seem to be safe procedures in elderly patients in terms of cognitive, mood and functional status in the short and long term. CAS might be preferred for the shorter hospital stay, but further studies with a larger number of old and oldest old subjects with a longer follow-up are needed to better understand the cost-effectiveness of both treatments.

Oxidative LDL modification is increased in vascular dementia and is inversely associated with cognitive performance

It is not known whether the association between increased plasma homocysteine (Hcy) associated with LDL modification and propensity for LDL uptake by macrophages in cardiovascular disease patients holds true in vascular dementia (VaD). Plasma from 83 subjects diagnosed with Alzheimer's disease (AD), VaD, mild cognitive impairment (MCI) and from controls was analysed to examine (1) whether LDL isolated from the plasma of VaD is biochemically and functionally distinct from that isolated from AD, MCI or controls; and (2) whether such biomarkers of LDL phenotype are related to plasma folate levels, Hcy levels and/or to disease severity. Folate and vitamin B6 levels were significantly lower in VaD subjects than in controls. VaD-LDL showed increased protein carbonyl content (p < 0.05) and was more susceptible to scavenging by macrophages (p < 0.05) than AD- or control-LDL. Patients from the VaD cohort were more prevalent in the lowest tertile for HDL:LDL and the upper tertile for LDL oxidation; the combined parameters of HDL cholesterol, LDL oxidation and scavenging by macrophages show 87% sensitivity towards VaD detection. The association between folate deficiency, LDL modification and dysfunction in VaD but not in AD may provide a novel biomarker assessment to discriminate between the diseases.

Band-Gap Engineering of Metal Oxides for Dye-Sensitized Solar Cells

Mixed oxides Ti(1-x)Zr(x)O2 with 0 < x < or = 0.2 were synthesized by means of thermal hydrolysis for use in dye-sensitized solar cells. The lattice parameter d is observed to increase linearly with Zr content x. The band gap of the mixed oxides was measured to increase by up to 0.2 eV. The respective shift of the conduction band edge leads to an increase of the open circuit voltage (V(OC)) by up to 0.1 V. Among others, temperature-dependent measurements of V(OC) clearly identify the correlation between band edge shift and change in V(OC).

Up-conversion fluorescence: noncoherent excitation by sunlight

We demonstrate up-conversion of noncoherent sunlight realized by ultralow excitation intensity. The bimolecular up-conversion process in our systems relies on the presence of a metastable triplet excited state, and thus has dramatically different photophysical characteristics relative to the other known methods for photon up-conversion (two-photon absorption, parametric processes, second harmonic generation, sequential multiphoton absorption, etc.).

Metal-enhanced up-conversion fluorescence: effective triplet-triplet annihilation near silver surface

Up-conversion phenomena are traditionally related to two- or multiphoton processes occurring under relatively high excitation intensities. Here we present the first results of ultralow excitation intensity (in order of Wcm(-2)) continuous-wave (CW) excited up-conversion fluorescence in Kretschmann surface plasmon geometry. The active system is a blue-emitting polymer matrix blended with metalated porphyrine macrocycles. The up-conversion fluorescence is a consequence of a two-particle triplet-triplet annihilation process (TTA).

Low-temperature fabrication of dye-sensitized solar cells by transfer of composite porous layers

Dye-sensitized solar cells have established themselves as a potential low-cost alternative to conventional solar cells owing to their remarkably high power-conversion efficiency combined with 'low-tech' fabrication processes. As a further advantage, the active layers consisting of nanoporous TiO2 are only some tens of micrometres thick and are therefore in principle suited for flexible applications. However, typical flexible plastic substrates cannot withstand the process temperatures of up to 500 degrees C commonly used for sintering the TiO2 nanoparticles together. Even though some promising routes for low-temperature sintering have been proposed, those layers cannot compete as regards electrical properties with layers obtained with the standard high-temperature process. Here we show that by a lift-off technique, presintered porous layers can be transferred to an arbitrary second substrate, and the original electrical properties of the transferred porous layers are maintained. The transfer process is greatly assisted by the application of composite layers comprising nanoparticles and nanorods.

Diffusion Properties of Dye Molecules in Nanoporous TiO2 Networks

The adsorption of ruthenium-dye molecules out of ethanol solution onto TiO2 particles of nanoporous TiO2 films was used to study the molecules' diffusion through these layers by means of optical absorption spectrometry. Dependent on pore size, porosity, and particle size, effective diffusion constants as low as D(eff) = 4 x 10(-9) cm2/s were deduced from the uptake curves by applying a simple model for combined diffusion and adsorption. These diffusion constants for diffusion through the nanoporous network are up to 3 orders of magnitude lower than in bulk ethanol and are discussed with respect to the properties of the nanoporous material.

Odd-even chain length-dependent order in pH-switchable self-assembled layers

The reversible self-assembly of a series of bipolar amphiphiles, alpha,omega-bis(3- or 4-amidinophenoxy)alkanes (chain length n = 5-12), on mercaptoalkanoic acid-functionalized gold surfaces (chain length n = 10, 11, 14, 15) has been studied by in-situ ellipsometry, IR reflection absorption spectroscopy (IRAS), and atomic force microscopy (AFM). The layer order, amphiphile orientation, and tendency to form bilayers depends on the position of the amidine substituent, the alkyl chain length of both the amidine amphiphile and the underlying acid self-assembled monolayer (SAM), and whether the amidine alkyl chain contained an even or odd number of methylene groups. Thus, para-substituted bisbenzamidines containing more than six methylene groups (n>6) and with an odd number (n = 7, 9, 11) tended to form bilayered structures, whereas those containing an even number formed monolayers when adsorbed on SAMs of the long-chain acids (n = 14, 15). This behavior also correlated with the average tilt angle of the benzene moieties of the amphiphiles, as estimated by IRAS. The odd-numbered chains gave lower tilt angles than the even-numbered ones, and a possible model that accounts for these results is proposed. IRAS also revealed a higher order of the odd-numbered chains and an increasing hydrogen-bonding contribution with increasing chain length. Additional evidence for the proposed bilayered assemblies and their reversibility was obtained by AFM. Images obtained from the assembly of decamidine on a SAM of mercaptohexadecanoic acid in a pH 9 borate buffer revealed domains of similar size to that of the underlying acid SAM (20-30 nm), but less densely packed. By acidifying the solution, the second layer was destabilized and a very smooth layer with few defects appeared. Further acidification to pH 3 also destabilized the first layer.

Impact of micropatterned surfaces on neuronal polarity

Experimental control over cellular polarity in a neuronal network is a promising tool to study synapse formation and network behavior. We aimed to exploit a mechanism described by Stenger et al. [J. Neurosci. Methods 82 (1998) 167] to manipulate the direction of axonal versus dendritic outgrowth on a micropattern. The group had used laser ablation to create patterns of aminated silanes for cell attachment on a background of repellent fluorinated silanes. The pattern offered continuous adhesive pathways for axonal and interrupted pathways for dendritic outgrowth. By microcontact printing, we created similar patterns containing continuous and interrupted pathways consisting of extracellular matrix proteins on a background of polystyrene. Neuronal polarity was determined on the functional level through double patch clamp measurements, detecting synapses and their orientation. Although our pattern reproduced the properties that were assumed to be critical for the described effect, namely contrasting pathways of different adhesiveness, we failed to reproduce the above results. It is indicated that other qualities of alternative pathways than mere differences in adhesiveness are required to orient neuronal polarity in vitro. We suggest that the effect observed by Stenger et al. has to be attributed to less universal characteristics of the micropattern, e.g. to the specific chemical groups that were utilized.

Diffusion-limited transport of I[sub 3][sup −] through nanoporous TiO[sub 2]-polymer gel networks

Tri-iodide transport in a polymer gel electrolyte embedded in nanoporous TiO(2) networks and its diffusion limits are investigated by means of current-voltage (I-V) characteristics of simple Pt-gel-Pt sandwich devices with a thin porous TiO(2) layer sintered directly onto one of the Pt electrodes. At voltages between 0.2 and 0.7 V, the I-V curves of such devices show the typical plateau of diffusion-limited redox reactions, in this case I(-)/I(3) (-), at the platinum electrodes. From the dependence of the limiting current density on layer thickness, the diffusion constants D(bulk) and D(p,eff) of tri-iodide in the bulk polymer gel and through a polymer gel penetrated TiO(2) network, respectively, have been found to be D(bulk)=3.2(+/-0.2)x10(-6) cm(2)/s and D(p,eff)=1.5(+/-0.1)x10(-6) cm(2)/s. Temperature-dependent measurements show diffusion in the gel to be activated by about 0.16 eV. The results are discussed in comparison to diffusion in liquid electrolytes as well as with respect to the implications for dye-sensitized solar cell devices.

Analysis of electrotonic coupling in patterned neuronal networks

Microcontact printing of laminin is known as an efficient approach for guiding neuronal cell migration and neurite outgrowth on artificial surfaces. In the present study, ultrathin (approximately 250 microm) brain stem slices of Sprague-Dawley rats (E15-E18) were cultured on laminin-patterned substrates, such that neuronal cells migrating out of the slices formed grid-shaped neuronal networks along the geometry defined by the pattern. The interconnections between neighbouring pairs of neurons within these artificial networks were assessed electrophysiologically by double patch-clamp recordings and optically by microinjection of fluorescent dyes. Both functional and electrotonic synapses were detected. Based on the recorded data and simulations in PSpice, an electrical model for electrotonically coupled cells was derived. In this model the neuritic pathway is described as a cylindric cable, and gap junctions are represented by an ohmic resistor. Applying this model in the data analysis, the average inner radius of neurites could be determined to be approximately 0.1 microm. In addition, evidence was found for a correlation between the path-width of the applied pattern and the diameter of neurites growing along these paths.

A functional MRI study of three motor tasks in the evaluation of stroke recovery

Functional brain imaging studies have provided insights into the processes related to motor recovery after stroke. The comparative value of different motor activation tasks for probing these processes has received limited study. We hypothesized that different hand motor tasks would activate the brain differently in controls, and that this would affect control-patient comparisons. Functional magnetic resonance imaging (MRI) was used to evaluate nine control subjects and seven patients with good recovery after a left hemisphere hemiparetic stroke. The volume of activated brain in bilateral sensorimotor cortex and four other motor regions was compared during each of three tasks performed by the right hand: index-finger tapping, four-finger tapping, and squeezing. In control subjects, activation in left sensorimotor cortex was found to be significantly larger during squeezing as compared with index-finger tapping. When comparing control subjects with stroke patients, patients showed a larger volume of activation in right sensorimotor cortex during index-finger tapping but not with four-finger tapping or squeezing. In addition, patients also showed a trend toward larger activation volume than controls within left supplementary motor area during index-finger tapping but not during the other tasks. Motion artifact was more common with squeezing than with the tapping tasks. The choice of hand motor tasks used during brain mapping can influence findings in control subjects as well as the differences identified between controls and stroke patients. The results may be useful for future studies of motor recovery after stroke.

Compensatory visual field training for patients with hemianopia after stroke

Twenty-one patients with hemianopia received 4 weeks of compensatory visual field training. Detection of and reaction time to visual stimuli were measured with eyes fixating (condition A) and with use of exploratory eye movements (condition B) before and after training. Twenty-three healthy individuals served as control subjects for measurements of parameters during both conditions. Patients with hemianopia to either side showed a marked improvement of detection and reaction time during condition B, but minimum or no change during condition A. Improvements were maintained 8 months after training. Activity of daily living skills also improved in all patients. The size of scotoma on computerized perimetry, in contrast, remained unchanged. Training improved detection of and reaction to visual stimuli without restitution of the visual field defect.

Arm Training Induced Brain Plasticity in Stroke Studied with Serial Positron Emission Tomography

We used serial positron emission tomography (PET) to study training-induced brain plasticity after severe hemiparetic stroke. Ten patients were randomized to either task-oriented arm training or to a control group and scanned before and after 22.6 +/- 1.6 days of treatment using passive movements as an activation paradigm. Increases of regional cerebral blood flow (rCBF) were assessed using statistical parametric mapping (SPM99). Before treatment, all stroke patients revealed bilateral activation of the inferior parietal cortex (IPC). After task-oriented arm training, activation was found bilaterally in IPC and premotor cortex, but also in the contralateral sensorimotor cortex (SMC). The control group only showed weak activation of the ipsilateral IPC. After treatment, the training group revealed relatively more activation bilaterally in IPC, premotor areas, and in the contralateral SMC. Five normal subjects showed no statistical significant differences between two separate PET studies. In this group of patients, task-oriented arm training induced functional brain reorganization in bilateral sensory and motor systems.

Evolution of functional reorganization in hemiplegic stroke: a serial positron emission tomographic activation study

We used serial positron emission tomography (PET) to study the evolution of functional brain activity within 12 weeks after a first subcortical stroke. Six hemiplegic stroke patients and three normal subjects were scanned twice (PET 1 and PET 2) by using passive elbow movements as an activation paradigm. Increases of regional cerebral blood flow comparing passive movements and rest and differences of regional cerebral blood flow between PET 1 and PET 2 in patients and normal subjects were assessed by using statistical parametric mapping. In controls, activation was found in the contralateral sensorimotor cortex, supplementary motor area, and bilaterally in the inferior parietal cortex with no differences between PET 1 and PET 2. In stroke patients, at PET 1, activation was observed in the bilateral inferior parietal cortex, contralateral sensorimotor cortex, and ipsilateral dorsolateral prefrontal cortex, supplementary motor area, and cingulate cortex. At PET 2, significant increases of regional cerebral blood flow were found in the contralateral sensorimotor cortex and bilateral inferior parietal cortex. A region that was activated at PET 2 only was found in the ipsilateral premotor area. Recovery from hemiplegia is accompanied by changes of brain activation in sensory and motor systems. These alterations of cerebral activity may be critical for the restoration of motor function.

Reorganization of sensory and motor systems in hemiplegic stroke patients. A positron emission tomography study

BACKGROUND AND PURPOSE

Cortical reorganization of motor systems has been found in recovered stroke patients. Reorganization in nonrecovered hemiplegic stroke patients early after stroke, however, is less well described. We used positron emission tomography to study the functional reorganization of motor and sensory systems in hemiplegic stroke patients before motor recovery.

METHODS

Regional cerebral blood flow (rCBF) was measured in 6 hemiplegic stroke patients with a single, subcortical infarct and 3 normal subjects with the [(15)O]H(2)O injection technique. Brain activation was achieved by passive elbow movements driven by a torque motor. Increases of rCBF comparing passive movements and rest were assessed with statistical parametric mapping. Significant differences were defined at P<0.01.

RESULTS

In normal subjects, significant increases of rCBF were found in the contralateral sensorimotor cortex, supplementary motor area, cingulate cortex, and bilaterally in the inferior parietal cortex. In stroke patients, significant activation was observed bilaterally in the inferior parietal cortex and in the contralateral sensorimotor cortex, ipsilateral prefrontal cortex, supplementary motor area, and cingulate cortex. Significantly larger increases of rCBF in patients compared with normal subjects were found bilaterally in the sensorimotor cortex, stronger in the ipsilateral, unaffected hemisphere, and in both parietal lobes, including the ipsilateral precuneus.

CONCLUSIONS

Passive movements in hemiplegic stroke patients before clinical recovery elicit some of the brain activation patterns that have been described during active movements after substantial motor recovery. Changes of cerebral activation in sensory and motor systems occur early after stroke and may be a first step toward restoration of motor function after stroke.