Relativistic effects on electronic pair densities: A perspective from the radial intracule and extracule probability densities.

While the effect of relativity in the electronic density has been widely studied, the effect on the pair probability, intracule, and extracule densities has not been studied before. Thus, in this work, we unveil new insights related to changes in the electronic structure caused by relativistic effects. Our numerical results suggest that the mean inter-electronic distance is reduced (mostly) due to scalar-relativistic effects. As a consequence, an increase in the electron-electron repulsion energy is observed. Preliminary results suggest that this observation is also valid when electronic correlation effects are considered.

Seminal vesicle intrafraction motion during the delivery of radiotherapy sessions on a 1.5 T MR-Linac.

PURPOSE: To evaluate seminal vesicle (SV) intrafraction motion using cinematic magnetic resonance imaging (cine-MR) during the delivery of online adaptive MR-Linac radiotherapy fractions, in preparation of MR-guided extremely hypofractionated radiotherapy for intermediate to high-risk prostate cancer patients. MATERIAL AND METHODS: Fifty prostate cancer patients were treated with 5 × 7.25 Gy on a 1.5 Tesla MR-Linac. 3D Cine-MR imaging was started simultaneously and acquired over the full beam-on period. Intrafraction motion in this cine-MR was determined for each SV separately with a previously validated soft-tissue contrast-based tracking algorithm. Motion statistics and coverage probability for the SVs and prostate were determined based on the obtained results. RESULTS: SV motion was automatically determined during the beam-on period (approx. 10 min) for 247 fractions. SV intrafraction motion shows larger spread than prostate intrafraction motion and increases over time. This difference is especially evident in the anterior and cranial translation directions. Significant difference in rotation about the left-right axis was found, with larger rotation for the SVs than the prostate. Intra-fraction coverage probability of 99% can be achieved when using 5 mm isometric expansion for the left and right SV and 3 mm for the prostate. CONCLUSION: This is the first study to investigate SV intrafraction motion during MR-guided RT sessions on an MR-Linac. We have shown that high quality 3D cine-MR imaging and SV tracking during RT is feasible with beam-on. The tracking method as described may be used as input for a fast replanning algorithm, which allows for intrafraction plan adaptation.

Prostate intrafraction motion during the preparation and delivery of MR-guided radiotherapy sessions on a 1.5T MR-Linac.

PURPOSE: To evaluate prostate intrafraction motion using MRI during the full course of online adaptive MR-Linac radiotherapy (RT) fractions, in preparation of MR-guided extremely hypofractionated RT. MATERIAL AND METHODS: Five low and intermediate risk prostate cancer patients were treated with 20 × 3.1 Gy fractions on a 1.5T MR-Linac. Each fraction, initial MRI (Pre) scans were obtained at the start of every treatment session. Pre-treatment planning MRI contours were propagated and adapted to this Pre scan after which plan re-optimization was started in the treatment planning system followed by dose delivery. 3D Cine-MR imaging was started simultaneously with beam-on and acquired over the full beam-on period. Prostate intrafraction motion in this cine-MR was determined with a previously validated soft-tissue contrast based tracking algorithm. In addition, absolute accuracy of the method was determined using a 4D phantom. RESULTS: Prostate motion was completely automatically determined over the full on-couch period (approx. 45 min) with no identified mis-registrations. The translation 95% confidence intervals are within clinically applied margins of 5 mm, and plan adaption for intrafraction motion was required in only 4 out of 100 fractions. CONCLUSION: This is the first study to investigate prostate intrafraction motions during entire MR-guided RT sessions on an MR-Linac. We have shown that high quality 3D cine-MR imaging and prostate tracking during RT is feasible with beam-on. The clinically applied margins of 5 mm have proven to be sufficient for these treatments and may potentially be further reduced using intrafraction plan adaptation guided by cine-MR imaging.

Dosimetric impact of soft-tissue based intrafraction motion from 3D cine-MR in prostate SBRT.

To investigate the dosimetric impact of intrafraction translation and rotation motion of the prostate, as extracted from daily acquired post-treatment 3D cine-MR based on soft-tissue contrast, in extremely hypofractionated (SBRT) prostate patients. Accurate dose reconstruction is performed by using a prostate intrafraction motion trace which is obtained with a soft-tissue based rigid registration method on 3D cine-MR dynamics with a temporal resolution of 11 s. The recorded motion of each time-point was applied to the planning CT, resulting in the respective dynamic volume used for dose calculation. For each treatment fraction, the treatment delivery record was generated by proportionally splitting the plan into 11 s intervals based on the delivered monitor units. For each fraction the doses of all partial plan/dynamic volume combinations were calculated and were summed to lead to the motion-affected fraction dose. Finally, for each patient the five fraction doses were summed, yielding the total treatment dose. Both daily and total doses were compared to the original reference dose of the respective patient to assess the impact of the intrafraction motion. Depending on the underlying motion of the prostate, different types of motion-affected dose distributions were observed. The planning target volumes (PTVs) ensured CTV_30 (seminal vesicles) D99% coverage for all patients, CTV_35 (prostate corpus) coverage for 97% of the patients and GTV_50 (local boost) for 83% of the patients when compared against the strict planning target D99% value. The dosimetric impact due to prostate intrafraction motion in extremely hypofractionated treatments was determined. The presented study is an essential step towards establishing the actual delivered dose to the patient during radiotherapy fractions.

Soft-tissue prostate intrafraction motion tracking in 3D cine-MR for MR-guided radiotherapy.

To develop a method to automatically determine intrafraction motion of the prostate based on soft tissue contrast on 3D cine-magnetic resonance (MR) images with high spatial and temporal resolution. Twenty-nine patients who underwent prostate stereotactic body radiotherapy (SBRT), with four implanted cylindrical gold fiducial markers (FMs), had cine-MR imaging sessions after each of five weekly fractions. Each cine-MR session consisted of 55 sequentially obtained 3D data sets ('dynamics') and was acquired over an 11 s period, covering a total of 10 min. The prostate was delineated on the first dynamic of every dataset and this delineation was used as the starting position for the soft tissue tracking (SST). Each subsequent dynamic was rigidly aligned to the first dynamic, based on the contrast of the prostate. The obtained translation and rotation describes the intrafraction motion of the prostate. The algorithm was applied to 6270 dynamics over 114 scans of 29 patients and the results were validated by comparing to previously obtained fiducial marker tracking data of the same dataset. Our proposed tracking method was also retro-perspectively applied to cine-MR images acquired during MR-guided radiotherapy of our first prostate patient treated on the MR-Linac. The difference in the 3D translation results between the soft tissue and marker tracking was below 1 mm for 98.2% of the time. The mean translation at 10 min were X: 0.0 [Formula: see text] 0.8 mm, Y: 1.0 [Formula: see text] 1.8 mm and Z: [Formula: see text] mm. The mean rotation results at 10 min were X: [Formula: see text], Y: 0.1 [Formula: see text] 0.6° and Z: 0.0 [Formula: see text] 0.7°. A fast, robust and accurate SST algorithm was developed which obviates the need for FMs during MR-guided prostate radiotherapy. To our knowledge, this is the first data using full 3D cine-MR images for real-time soft tissue prostate tracking, which is validated against previously obtained marker tracking data.

Fiducial marker based intra-fraction motion assessment on cine-MR for MR-linac treatment of prostate cancer.

We have developed a method to determine intrafraction motion of the prostate through automatic fiducial marker (FM) tracking on 3D cine-magnetic resonance (MR) images with high spatial and temporal resolution. Twenty-nine patients undergoing prostate stereotactic body radiotherapy (SBRT), with four implanted cylindrical gold FMs, had cine-MR imaging sessions after each of five weekly fractions. Each cine-MR examination consisted of 55 sequentially obtained 3D datasets ('dynamics'), acquired over a 11 s period, covering a total of 10 min. FM locations in the first dynamic were manually identified by a clinician, FM centers in subsequent dynamics were automatically determined. Center of mass (COM) translations and rotations were determined by calculating the rigid transformations between the FM template of the first and subsequent dynamics. The algorithm was applied to 7315 dynamics over 133 scans of 29 patients and the obtained results were validated by comparing the COM locations recorded by the clinician at the halfway-dynamic (after 5 min) and end dynamic (after 10 min). The mean COM translations at 10 min were X: 0.0 [Formula: see text] 0.8 mm, Y: 1.0 [Formula: see text] 1.9 mm and Z: 0.9 [Formula: see text] 2.0 mm. The mean rotation results at 10 min were X: 0.1 [Formula: see text] 3.9°, Y: 0.0 [Formula: see text] 1.3° and Z: 0.1 [Formula: see text] 1.2°. The tracking success rate was 97.7% with a mean 3D COM error of 1.1 mm. We have developed a robust, fast and accurate FM tracking algorithm for cine-MR data, which allows for continuous monitoring of prostate motion during MR-guided radiotherapy (MRgRT). These results will be used to validate automatic prostate tracking based on soft-tissue contrast.

Single Pulse Electrical Stimulation to identify epileptogenic cortex: Clinical information obtained from early evoked responses.

OBJECTIVE: Single Pulse Electrical Stimulation (SPES) probes epileptogenic cortex during electrocorticography. Two SPES responses are described: pathological delayed responses (DR, >100 ms) associated with the seizure onset zone (SOZ) and physiological early responses (ER, <100 ms) that map cortical connectivity. We analyzed properties of ERs, including frequencies >80 Hz, in the SOZ and seizure propagation areas. METHODS: We used data from 12 refractory epilepsy patients. SPES consisted of 10 pulses of 1 ms, 4-8 mA and 5s interval on adjacent electrodes pairs. Data were available at 2048 samples/s for six and 512 samples/s (22 bits) for eight patients and analyzed in the time-frequency (TF) and time-domain (TD). RESULTS: Electrodes with ERs were stronger associated with SOZ than non-SOZ electrodes. ERs with frequency content >80 Hz exist and are specific for SOZ channels. ERs evoked by stimulation of seizure onset electrodes were associated with electrodes involved in seizure propagation. CONCLUSION: Analysis of ERs can reveal aspects of pathology, manifested by association with seizure propagation and areas with high ER numbers that coincide with the SOZ. SIGNIFICANCE: Not only DRs, but also ERs could have clinical value for mapping epileptogenic cortex and help to unravel aspects of the epileptic network.

Do patients with chronic patellar tendinopathy have an altered somatosensory profile? A Quantitative Sensory Testing (QST) study.

The prevalence of tendinopathies in sports is high. The etiology and pain mechanisms of tendinopathies are not completely understood. Currently, little is known whether, or to which degree, somatosensory changes within the nervous system may contribute to the pain in tendinopathies. We conducted a patient controlled study in which we used the standardized QST protocol developed by the German Research Network on Neuropathic Pain. This protocol consists of seven different tests that measures 13 somatosensory parameters and can be seen as the gold standard to measure somatosensory function. Twelve athletes with clinically diagnosed chronic patellar tendinopathy (PT) mean duration 30 months (range 6-120) and 20 controls were included in the study. In two of the 13 QST parameters namely Mechanical Pain Threshold (P < 0.05) and Vibration Disappearance Threshold (P < 0.5) injured athletes were significantly more sensitive for the applied stimuli. None of the athletes had signs of Dynamic Mechanical Allodynia. Reduced mechanical pain thresholds or pinprick allodynia reflects the involvement of central sensitization upon the myelinated (Aδ-fibre) nociceptive input. From this explorative study, we conclude that sensitization may play a prominent role in the pain during and after sports activity in patella tendinopathy patients.

Assessment of the clinical relevance of quantitative sensory testing with Von Frey monofilaments in patients with allodynia and neuropathic pain. A pilot study.

BACKGROUND: Allodynia is a common and disabling symptom in many patients with neuropathic pain. Whereas quantification of pain mostly depends on subjective pain reports, allodynia can also be measured objectively with quantitative sensory testing. In this pilot study, we investigated the clinical relevance of quantitative sensory testing with Von Frey monofilaments in patients with allodynia as a consequence of a neuropathic pain syndrome, by means of correlating subjective pain scores with pain thresholds obtained with quantitative sensory testing. METHODS: During a 4-week trial, we administered a cannabis extract to 17 patients with allodynia. We quantified the severity of the allodynia with Von Frey monofilaments before, during and after the patients finished the trial. We also asked the patients to rate their pain on a numeric rating scale at these three moments. RESULTS: We found that most of the effect of the cannabis occurred in the last 2 weeks of the trial. In this phase, we observed that the pain thresholds, as measured with Von Frey monofilaments, were inversely correlated with a decrease of the perceived pain intensity. CONCLUSION: These preliminary findings indicate clinical relevance of quantitative sensory testing with Von Frey monofilaments in the quantification of allodynia in patients with neuropathic pain, although confirmation of our data is still required in further studies to position this method of quantitative sensory testing as a valuable tool, for example, in the evaluation of therapeutic interventions for neuropathic pain.

[The sensitization model: a method to explain chronic pain to a patient]. / Het sensitisatiemodel: een methode om een patiënt uit te leggen wat chronische pijn is.

Chronic pain is pain without a clear somatic substrate. As a result, patients with chronic pain often do not receive a clear diagnosis following a medical examination. In many patients, having pain without a proper explanation or diagnosis induces stress and the urge to search elsewhere for explanations and treatments. There is growing evidence that many chronic-pain syndromes, such as chronic low-back pain, whiplash and fibromyalgia, share the same pathogenesis: sensitisation of pain-modulating systems in the central nervous system at both spinal and supraspinal level. This central sensitisation is facilitated by numerous factors that contribute to the maintenance of pain in a way that differs from individual to individual. How sensitisation may develop and persist as a result of medical, psychological and social factors calls for research from the perspective of a bio-psycho-social model. If sensitisation is used to explain chronic pain to a patient and the patient understands the relation beween pain and the factors that play a role in the maintenance of the pain, this can lead to acceptation of a treatment learning to cope with these factors.

Structure of a pilin monomer from Pseudomonas aeruginosa: implications for the assembly of pili.

Type IV pilin monomers assemble to form fibers called pili that are required for a variety of bacterial functions. Pilin monomers oligomerize due to the interaction of part of their hydrophobic N-terminal alpha-helix. Engineering of a truncated pilin from Pseudomonas aeruginosa strain K122-4, where the first 28 residues are removed from the N terminus, yields a soluble, monomeric protein. This truncated pilin is shown to bind to its receptor and to decrease morbidity and mortality in mice upon administration 15 min before challenge with a heterologous strain of Pseudomonas. The structure of this truncated pilin reveals an alpha-helix at the N terminus that lies across a 4-stranded antiparallel beta-sheet. A model for a pilus is proposed that takes into account both electrostatic and hydrophobic interactions of pilin subunits as well as previously published x-ray fiber diffraction data. Our model indicates that DNA or RNA cannot pass through the center of the pilus, however, the possibility exists for small organic molecules to pass through indicating a potential mechanism for signal transduction.

Backbone dynamics of receptor binding and antigenic regions of a Pseudomonas aeruginosa pilin monomer.

Pilin is the major structural protein that forms type IV pili of various pathogenic bacteria, including Pseudomonas aeruginosa. Pilin is involved in attachment of the bacterium to host cells during infection, in the initiation of immune response, and serves as a receptor for a variety of bacteriophage. We have used (15)N nuclear magnetic resonance relaxation measurements to probe the backbone dynamics of an N-terminally truncated monomeric pilin from P. aeruginosa strain K122-4. (15)N-T(1), -T(2), and [(1)H]-(15)N nuclear Overhauser enhancement measurements were carried out at three magnetic field strengths. The measurements were interpreted using the Lipari-Szabo model-free analysis, which reveals the amplitude of spatial restriction for backbone N-NH bond vectors with respect to nano- to picosecond time-scale motions. Regions of well-defined secondary structure exhibited consistently low-amplitude spatial fluctuations, while the terminal and loop regions showed larger amplitude motions in the subnano- to picosecond time-scale. Interestingly, the C-terminal disulfide loop region that contains the receptor binding domain was found to be relatively rigid on the pico- to nanosecond time-scale but exhibited motion in the micro- to millisecond time-scale. It is notable that this disulfide loop displays a conserved antigenic epitope and mediates binding to the asialo-GM(1) cell surface receptor. The present study suggests that a rigid backbone scaffold mediates attachment to the host cell receptor, and also maintains the conformation of the conserved antigenic epitope for antibody recognition. In addition, slower millisecond time-scale motions are likely to be crucial for conferring a range of specificity for these interactions. Characterization of pilin dynamics will aid in developing a detailed understanding of infection, and will facilitate the design of more efficient anti-adhesin synthetic vaccines and therapeutics against pathogenic bacteria containing type IV pili.

Human CC chemokine I-309, structural consequences of the additional disulfide bond.

I-309 is a member of the CC subclass of chemokines and is one of only three human chemokines known to contain an additional, third disulfide bond. The three-dimensional solution structure of I-309 was determined by (1)H nuclear magnetic resonance spectroscopy and dynamic simulated annealing. The structure of I-309, which remains monomeric at high concentrations, was determined on the basis of 978 experimental restraints. The N-terminal region of I-309 was disordered, as has been previously observed for the CC chemokine eotaxin but not others such as MCP-1 and RANTES. This was followed in I-309 by a well-ordered region between residues 13 and 69 that consisted of a 3(10)-helix, a triple-stranded antiparallel beta-sheet, and finally a C-terminal alpha-helix. Root-mean-square deviations of 0.61 and 1.16 were observed for the backbone and heavy atoms, respectively. A comparison of I-309 to eotaxin and HCC-2 revealed a significant structural change in the C-terminal region of the protein. The alpha-helix normally present in chemokines was terminated early and was followed by a short section of extended strand. These changes were a direct result of the additional disulfide bond present in this protein. An examination of the I-309 structure will aid in an understanding of the specificity of this protein with its receptor, CCR8.

The NMR solution structure and characterization of pH dependent chemical shifts of the beta-elicitin, cryptogein.

The NMR structure of the 98 residue beta-elicitin, cryptogein, which induces a defence response in tobacco, was determined using 15N and 13C/15N labelled protein samples. In aqueous solution conditions in the millimolar range, the protein forms a discrete homodimer where the N-terminal helices of each monomer form an interface. The structure was calculated with 1047 intrasubunit and 40 intersubunit NOE derived distance constraints and 236 dihedral angle constraints for each subunit using the molecular dynamics program DYANA. The twenty best conformers were energy-minimized in OPAL to give a root-mean-square deviation to the mean structure of 0.82 A for the backbone atoms and 1.03 A for all heavy atoms. The monomeric structure is nearly identical to the recently derived X-ray crystal structure (backbone rmsd 0.86 A for residues 2 to 97) and shows five helices, a two stranded antiparallel beta-sheet and an omega-loop. Using 1H,15N HSQC spectroscopy the pKa of the N- and C-termini, Tyr12, Asp21, Asp30, Asp72, and Tyr85 were determined and support the proposal of several stabilizing ionic interactions including a salt bridge between Asp21 and Lys62. The hydroxyl hydrogens of Tyr33 and Ser78 are clearly observed indicating that these residues are buried and hydrogen bonded. Two other tyrosines, Tyr47 and Tyr87, show pKa's > 12, however, there is no indication that their hydroxyls are hydrogen bonded. Calculations of theoretical pKa's show general agreement with the experimentally determined values and are similar for both the crystal and solution structures.

Inhibition of prostatic epithelial cell proliferation by a factor secreted specifically by prostatic stromal cells.

Stromal cells from the prostate were recently shown to inhibit clonal growth of the prostatic carcinoma cell lines PC-3 (hormone-independent) and LNCaP (hormone-sensitive) in coculture. Our study revealed that stromal cell-conditioned medium strongly inhibited proliferation of PC-3 and LNCaP cells when grown in monolayer culture. Antiproliferative activity was found to be reversible, and was produced specifically by prostatic stromal cells and not by stromal cells derived from skin, foreskin, uterus, kidney, and Wilms' tumor. Inhibition was not species-specific, since the cell lines AT-2.1 and MATLyLu, derived from the Dunning rat prostate tumor, were also sensitive. No inhibition, however, occurred on breast and renal carcinoma cell lines, suggesting a prostate-specific action. The putative inhibiting factor(s) could be concentrated and partially purified by ammonium sulfate precipitation. The possible role in stromal control of epithelial cell proliferation is discussed.

Flow cytometric analysis and motility response to laminin and fibronectin of four new metastatic variants of the human renal cell carcinoma line RC43.

Using subrenal capsule implantation (SRC) in nude mice we have isolated 4 new sublines (RC43MSP, MBO, MLI, MDI) from the human renal cell carcinoma line (HRCC) RC43. These sublines exhibit an enhanced metastatic ability and a faster doubling time after subcutaneous (SC) transplantation in vivo, when compared to the parental line. With the aim of a better characterization of these new sublines we have performed a flow cytometric analysis (FA) of the DNA content and studied the motility response (MR) to laminin and fibronectin. FA results. The RC43 parental line showed a tetraploid pattern (DNA index: 2.08). Also the variant lines RC43MLI and RC43MDI were tetraploid (DNAind: 2.05 and 2.07, respectively). With RC43MDI a second peak in the tetraploid range was evident. The RC43MSP and the RC43MBO sublines both showed a hypertetraploid pattern (DNAind respectively 2.21 and 2.11). MR results. Motility studies showed that all RC43 lines, including the parental line, were stimulated to migrate in response to either laminin or fibronectin both from rat and human sources. There were no significant differences between the parental line and its variants in this respect, however. We conclude that by the use of FA at least two of the sublines (MSP and MBO) can be distinguished from the parental RC43 cell line, suggesting a different clonal origin of the various sublines. As all sublines, as well as the parental line, showed a large but similar response to migration-stimulating agents (such as laminin and fibronectin) determination of MR could not be used to obtain a further discrimination between the different sublines.