Dicarboxylic acids as pH sensors for hyperpolarized 13C magnetic resonance spectroscopic imaging.

Imaging tumoral pH may help to characterize aggressiveness, metastasis, and therapeutic response. We report the development of hyperpolarized [2-13C,D10]diethylmalonic acid, which exhibits a large pH-dependent 13C chemical shift over the physiological range. We demonstrate that co-polarization with [1-13C,D9]tert-butanol accurately measures pH via13C NMR and magnetic resonance spectroscopic imaging in phantoms.

Ab Initio Construction of Magnetic Phase Diagrams in Alloys: The Case of Fe(1-x)Mn(x)Pt.

A first-principles approach to the construction of concentration-temperature magnetic phase diagrams of metallic alloys is presented. The method employs self-consistent total energy calculations based on the coherent potential approximation for partially ordered and noncollinear magnetic states and is able to account for competing interactions and multiple magnetic phases. Application to the Fe(1-x)Mn(x)Pt "magnetic chameleon" system yields the sequence of magnetic phases at T=0 and the c-T magnetic phase diagram in good agreement with experiment, and a new low-temperature phase is predicted at the Mn-rich end. The importance of non-Heisenberg interactions for the description of the magnetic phase diagram is demonstrated.

Rotary and radial forcing effects on center-of-mass locomotion dynamics.

Rotary and radial forcing are two common actuation methods for legged robots. However, these two orthogonal methods of center-of-mass (CoM) forcing have not been compared as potentially alternative strategies of actuation. In this paper, we compare the CoM stability and energetics of running with rotary and radial actuation through the simulation of two models: the rotary-forced spring-loaded inverted pendulum (rotary-forced-SLIP), and the radially-forced-SLIP. We model both radial and rotary actuation in the simplest way, applying them as a constant force during the stance portion of the gait. A simple application of constant rotary forcing throughout stance is capable of producing fully-asymptotically stable motion; however, a similarly constant application of radial forcing throughout the stance is not capable of producing stable solutions. We then allow both the applied rotary and radial forcing functions to turn on or off based on the occurrence of the mid-stance event, which breaks the symmetry of actuation during stance towards a net forward propulsion. We find that both a rotary force applied in the first half of stance and a radial force applied in the second half of stance, are capable of stabilizing running. Interestingly, these two forcing methods improve the motion stability in different ways. Rotary forcing first reduces then greatly increases the size of the stable parameter region when gradually increased. Radial forcing expands the stable parameter region, but only in a moderate way. Also, it is found that parameter region stabilized by rotary and radial forcing are largely complementary. Overall, rotary forcing can better stabilize running for both constant and event-based forcing functions that were attempted. This indicates that rotary forcing has an inherent capability of stabilizing running, even when minimal time-or-event-or-state feedback is present. Radial forcing, however, tends to be more energy efficient when compared to rotary forcing. In addition, a balanced stability and energy efficiency can be achieved by combining both forcing methods. These results may be applied in the future study of how legged animals move.

Leaf metallome preserved over 50 million years.

Large-scale Synchrotron Rapid Scanning X-ray Fluorescence (SRS-XRF) elemental mapping and X-ray absorption spectroscopy are applied here to fossil leaf material from the 50 Mya Green River Formation (USA) in order to improve our understanding of the chemistry of fossilized plant remains. SRS-XRF of fossilized animals has previously shown that bioaccumulated trace metals and sulfur compounds may be preserved in their original distributions and these elements can also act as biomarkers for specific biosynthetic pathways. Similar spatially resolved chemical data for fossilized plants is sparsely represented in the literature despite the multitude of other chemical studies performed. Here, synchrotron data from multiple specimens consistently show that fossil leaves possess chemical inventories consisting of organometallic and organosulfur compounds that: (1) map discretely within the fossils, (2) resolve fine scale biological structures, and (3) are distinct from embedding sedimentary matrices. Additionally, the chemical distributions in fossil leaves are directly comparable to those of extant leaves. This evidence strongly suggests that a significant fraction of the chemical inventory of the examined fossil leaf material is derived from the living organisms and that original bioaccumulated elements have been preserved in situ for 50 million years. Chemical information of this kind has so far been unknown for fossilized plants and could for the first time allow the metallome of extinct flora to be studied.

Trace metals as biomarkers for eumelanin pigment in the fossil record.

Well-preserved fossils of pivotal early bird and nonavian theropod species have provided unequivocal evidence for feathers and/or downlike integuments. Recent studies have reconstructed color on the basis of melanosome structure; however, the chemistry of these proposed melanosomes has remained unknown. We applied synchrotron x-ray techniques to several fossil and extant organisms, including Confuciusornis sanctus, in order to map and characterize possible chemical residues of melanin pigments. Results show that trace metals, such as copper, are present in fossils as organometallic compounds most likely derived from original eumelanin. The distribution of these compounds provides a long-lived biomarker of melanin presence and density within a range of fossilized organisms. Metal zoning patterns may be preserved long after melanosome structures have been destroyed.

Lead cap localization using ultrasound in deep brain stimulation surgery: technical note.

In deep brain stimulation (DBS) surgery, after intracranial lead implantation, lead caps are tunneled into the subgaleal space for later connection to internal pulse generator (IPG) extension wires. In the subsequent IPG implantation procedure, the lead cap must be localized by palpation in order to plan an incision in the scalp to complete this connection. However, if the IPG implantation is done the same day as the intracranial lead implantation, palpation of the lead cap may be challenging in a thick or postoperatively edematous scalp. Manufacturers suggest using fluoroscopy in these instances, but fluoroscopy provides poor soft tissue visualization, requires further unnecessary radiation exposure to both the patient and the surgical team, and can be cumbersome. Portable ultrasound (US) machines are readily available in many operating rooms, and can be used to easily and accurately localize the lead cap prior to IPG implantation.

Infrared mapping resolves soft tissue preservation in 50 million year-old reptile skin.

Non-destructive Fourier Transform InfraRed (FTIR) mapping of Eocene aged fossil reptile skin shows that biological control on the distribution of endogenous organic components within fossilized soft tissue can be resolved. Mapped organic functional units within this approximately 50 Myr old specimen from the Green River Formation (USA) include amide and sulphur compounds. These compounds are most probably derived from the original beta keratin present in the skin because fossil leaf- and other non-skin-derived organic matter from the same geological formation do not show intense amide or thiol absorption bands. Maps and spectra from the fossil are directly comparable to extant reptile skin. Furthermore, infrared results are corroborated by several additional quantitative methods including Synchrotron Rapid Scanning X-Ray Fluorescence (SRS-XRF) and Pyrolysis-Gas Chromatography/Mass Spectrometry (Py-GC/MS). All results combine to clearly show that the organic compound inventory of the fossil skin is different from the embedding sedimentary matrix and fossil plant material. A new taphonomic model involving ternary complexation between keratin-derived organic molecules, divalent trace metals and silicate surfaces is presented to explain the survival of the observed compounds. X-ray diffraction shows that suitable minerals for complex formation are present. Previously, this study would only have been possible with major destructive sampling. Non-destructive FTIR imaging methods are thus shown to be a valuable tool for understanding the taphonomy of high-fidelity preservation, and furthermore, may provide insight into the biochemistry of extinct organisms.

Dipeptidyl peptidase-4 inhibitors administered in combination with metformin result in an additive increase in the plasma concentration of active GLP-1.

The aim of the study was to investigate the effects of a dipeptidyl peptidase-4 (DPP-4) inhibitor, of metformin, and of the combination of the two agents, on incretin hormone concentrations. Active and inactive (or total) incretin plasma concentrations, plasma DPP-4 activity, and preproglucagon (GCG) gene expression were determined after administration of each agent alone or in combination to mice with diet-induced obesity (DIO) and to healthy human subjects. In mice, metformin increased Gcg expression in the large intestine and elevated the plasma concentrations of inactive glucagon-like peptide 1 (GLP-1) (9-36) and glucagon. In healthy subjects, a DPP-4 inhibitor elevated both active GLP-1 and glucose dependent insulinotropic polypeptide (GIP), metformin increased total GLP-1 (but not GIP), and the combination resulted in additive increases in active GLP-1 plasma concentrations. Metformin did not inhibit plasma DPP-4 activity either in vitro or in vivo. The study results show that metformin is not a DPP-4 inhibitor but rather enhances precursor GCG expression in the large intestine, resulting in increased total GLP-1 concentrations. DPP-4 inhibitors and metformin have complementary mechanisms of action and additive effects with respect to increasing the concentrations of active GLP-1 in plasma.

Tinnitus modulation by deep brain stimulation in locus of caudate neurons (area LC).

Tinnitus is an auditory disorder characterized by perception of internally generated phantom auditory sensations without corresponding mechanical stimuli arising from the body or external environment. Current auditory based treatment approaches, sometimes in conjunction with nonauditory based strategies, such as Tinnitus Retraining Therapy and Cognitive Behavioral Therapy, have been helpful in mitigating symptoms for the majority of patients. Yet there are over 1 million tinnitus sufferers who still endure troublesome chronic, continuous head noises that are debilitating and interfere with activities of daily living. Here we show that application of deep brain stimulation (DBS) therapy to a locus of caudate neurons (area LC) in the body of the nucleus, a subsite of the striatum that is not part of the classical auditory pathway, can decrease or increase tinnitus loudness perception. The DBS lead traversed through or was adjacent to area LC in six Parkinson's disease and essential tremor subjects with concomitant tinnitus who underwent implantation of the subthalamic or ventral intermediate nucleus. In five subjects where the DBS lead tip traversed area LC, tinnitus loudness in both ears was suppressed to a nadir of level 2 or lower on a 0-10 rating scale. In one subject where the DBS lead was outside area LC, tinnitus was not modulated. In three subjects with preoperative and postoperative audiograms, hearing thresholds were unchanged by area LC stimulation. Neuromodulation of area LC may be interrupting perceptual integration of phantom sensations generated in the central auditory system. This new, basal ganglia based approach to tinnitus modulation warrants further investigation and may be ultimately refined to treat patients with refractory symptoms.

Archaeopteryx feathers and bone chemistry fully revealed via synchrotron imaging.

Evolution of flight in maniraptoran dinosaurs is marked by the acquisition of distinct avian characters, such as feathers, as seen in Archaeopteryx from the Solnhofen limestone. These rare fossils were pivotal in confirming the dinosauria-avian lineage. One of the key derived avian characters is the possession of feathers, details of which were remarkably preserved in the Lagerstätte environment. These structures were previously simply assumed to be impressions; however, a detailed chemical analysis has, until now, never been completed on any Archaeopteryx specimen. Here we present chemical imaging via synchrotron rapid scanning X-ray fluorescence (SRS-XRF) of the Thermopolis Archaeopteryx, which shows that portions of the feathers are not impressions but are in fact remnant body fossil structures, maintaining elemental compositions that are completely different from the embedding geological matrix. Our results indicate phosphorous and sulfur retention in soft tissue as well as trace metal (Zn and Cu) retention in bone. Other previously unknown chemical details of Archaeopteryx are also revealed in this study including: bone chemistry, taphonomy (fossilization process), and curation artifacts. SRS-XRF represents a major advancement in the study of the life chemistry and fossilization processes of Archaeopteryx and other extinct organisms because it is now practical to image the chemistry of large specimens rapidly at concentration levels of parts per million. This technique has wider application to the archaeological, forensic, and biological sciences, enabling the mapping of "unseen" compounds critical to understanding biological structures, modes of preservation, and environmental context.

Physiological identification of the human pedunculopontine nucleus.

BACKGROUND: The pedunculopontine nucleus (PPN) is a brainstem structure with widespread connections to the basal ganglia. Despite the recent introduction of PPN deep brain stimulation (DBS) for the treatment of gait disorders, little is known about its physiology in humans. METHODS: Single unit discharge characteristics of neurons in the PPN region were analysed in four patients and PPN local field potentials (LFP) in one patient, recorded during the course of DBS implantation. Two patients had Parkinson disease, and two had non-sinemet responsive parkinsonism. Cell locations were plotted in the coordinate system of a human brainstem atlas. RESULTS: Fifty-six units in the PPN region were studied, of which 32 mapped to within PPN boundaries. The mean (SD) discharge rate of neurons in the PPN was 23.2 (15.6) Hz. Spontaneous neuronal firing rate and burst discharge rate were significantly different between neurons in the region dorsal to PPN and those in the PPN. Responses to passive movement of contralateral and ipsilateral limbs were found. Theta and beta band oscillations were present in the PPN LFP. CONCLUSION: PPN discharge characteristics may prove useful in the electrophysiological identification of PPN during DBS implantation surgery.

Safety and tolerability of putaminal AADC gene therapy for Parkinson disease.

BACKGROUND: In Parkinson disease (PD), the benefit of levodopa therapy becomes less marked over time, perhaps because degeneration of nigrostrial neurons causes progressive loss of aromatic l-amino acid decarboxylase (AADC), the enzyme that converts levodopa into dopamine. In a primate model of PD, intrastriatal infusion of an adeno-associated viral type 2 vector containing the human AADC gene (AAV-hAADC) results in robust response to low-dose levodopa without the side effects associated with higher doses. These data prompted a clinical trial. METHODS: Patients with moderately advanced PD received bilateral intraputaminal infusion of AAV-hAADC vector. Low-dose and high-dose cohorts (5 patients in each) were studied using standardized clinical rating scales at baseline and 6 months. PET scans using the AADC tracer [(18)F]fluoro-L-m-tyrosine (FMT) were performed as a measure of gene expression. RESULTS: The gene therapy was well tolerated, but 1 symptomatic and 2 asymptomatic intracranial hemorrhages followed the operative procedure. Total and motor rating scales improved in both cohorts. Motor diaries also showed increased on-time and reduced off-time without increased "on" time dyskinesia. At 6 months, FMT PET showed a 30% increase of putaminal uptake in the low-dose cohort and a 75% increase in the high-dose cohort. CONCLUSION: This study provides class IV evidence that bilateral intrastriatal infusion of adeno-associated viral type 2 vector containing the human AADC gene improves mean scores on the Unified Parkinson's Disease Rating Scale by approximately 30% in the on and off states, but the surgical procedure may be associated with an increased risk of intracranial hemorrhage and self-limited headache.

Sitagliptin 100 mg daily effect on DPP-4 inhibition and compound-specific glycemic improvement.

OBJECTIVE: In clinical trials, the degree of glucose lowering with sitagliptin has been correlated with the magnitude of dipeptidyl peptidase-4 (DPP-4) inhibition over 24 h. Previous studies evaluating sitagliptin doses ranging from 25 to 200 mg/day demonstrated that the daily dose of 100 mg provided maximal glucose-lowering efficacy for this compound in patients with type 2 diabetes. However, sitagliptin 200 mg once daily provided numerically greater percent plasma DPP-4 inhibition compared with 100 mg once daily. The purpose of this study was to evaluate whether sitagliptin 200 mg once daily provides greater improvement in glycemic efficacy as assessed by weighted mean glucose (WMG) over 24 h relative to sitagliptin 100 mg once daily and to relate the percent DPP-4 inhibition achieved with these doses to any between-treatment differences in glycemic efficacy. METHODS: In a double-blind crossover study, patients with type 2 diabetes (fasting plasma glucose [FPG] 130-250 mg/dL) were randomized to one of six treatment sequences over three treatment periods (placebo, sitagliptin 100 mg once daily, or sitagliptin 200 mg once daily). Each of the treatment periods was 7 days in duration, with 28-day washout periods between treatments. After each treatment period, patients underwent blood sampling at various time points over 24 h to determine 24-h WMG. Plasma DPP-4 activity was assessed at trough, 24 h following dosing on day 7; percent DPP-4 inhibition was corrected for sample assay dilution. RESULTS: The 103 randomized patients had a baseline mean FPG of 172 mg/dL. Following a planned interim analysis, the study was stopped because the 24-h WMG values were not different between the sitagliptin doses. Furthermore, a significant carryover effect across periods was observed for FPG; thus, efficacy results from period 1 are presented herein. The 24-h WMG values were significantly (p < 0.01) lower with sitagliptin relative to placebo, but the difference between sitagliptin doses was not significant (p = 0.365). Corrected percent plasma DPP-4 inhibition at trough was not significantly (p = 0.791) different with sitagliptin 200 mg (LS mean [95% CI] 96.9% [90.0, 100.0]) compared with sitagliptin 100 mg (95.6% [88.4, 100.0]). The early termination and the carryover effect described above are limitations to this study. CONCLUSION: Across sitagliptin doses in this study, the similarity of the 24-h WMG concentrations and the similarity of the corrected DPP-4 inhibition values support prior findings that the maximal glucose-lowering efficacy of sitagliptin is achieved with once-daily dosing of 100 mg. Clinicaltrials.gov: NCT00541229.

Effect of different durations of ketoconazole dosing on the single-dose pharmacokinetics of midazolam: shortening the paradigm.

Given the prominent role of cytochrome P450 3A (CYP3A) in the metabolism of drugs, it is critical to determine whether new chemical entities will be affected by the inhibition of this enzyme system and result in clinically relevant drug interactions. Ketoconazole interaction studies are frequently performed to determine a given compound's sensitivity to CYP3A metabolism. The present study evaluated whether probing a sensitive substrate (midazolam) with a potent inhibitor (ketoconazole) at earlier time points (days 1 or 2) might be used to reliably gauge the magnitude of a meaningful interaction. The geometric mean ratios (ketoconazole+midazolamday 5/ketoconazole+midazolamday 1 and ketoconazole+midazolamday 5/ketoconazole+midazolamday 2) for midazolam AUC0-infinity were 1.36 and 1.06 with corresponding 90% confidence intervals of (1.17, 1.57) and (0.83, 1.23), respectively. These findings suggest that short-term drug-drug interaction studies can predict the magnitude of change in AUC as reliably as studies using longer duration treatments.

Results from a phase I safety trial of hAADC gene therapy for Parkinson disease.

BACKGROUND: In a primate model of Parkinson disease (PD), intrastriatal infusion of an adeno-associated viral (AAV) vector containing the human aromatic l-amino acid decarboxylase (hAADC) gene results in robust gene expression. After gene transfer, low doses of systemically administered l-dopa are converted to dopamine in the transduced striatal neurons, resulting in behavioral improvement without the side effects typically associated with higher doses of l-dopa. These studies led to the initiation of a phase I safety trial. Here we report the findings for the first cohort of five patients. METHODS: Patients with moderate to advanced PD received bilateral infusion of a low dose of the AAV-hAADC vector into the putamen. PET scans using the AADC tracer, 6-[18F]fluoro-l-m-tyrosine (FMT), were performed at baseline and at 1 and 6 months after infusion as an in vivo measure of gene expression. RESULTS: PET results showed an average 30% increase in FMT uptake (K(i)(c)) in the putamen after gene transfer. Preliminary analysis of clinical data indicates a modest improvement, but absence of a control and the nonblinded analyses make interpretation difficult. CONCLUSIONS: Thus far, this gene therapy approach has been well tolerated and shows PET evidence of sustained gene expression. These initial findings demonstrate the safety of the therapy; higher doses of adeno-associated viral vector containing the human aromatic l-amino acid decarboxylase gene in the next cohort of patients may further increase dopamine production in the putamen and provide more profound clinical benefit.

Anisotropic field-of-views in radial imaging.

Radial imaging techniques, such as projection-reconstruction (PR), are used in magnetic resonance imaging (MRI) for dynamic imaging, angiography, and short-T(2) imaging. They are robust to flow and motion, have diffuse aliasing patterns, and support short readouts and echo times. One drawback is that standard implementations do not support anisotropic field-of-view (FOV) shapes, which are used to match the imaging parameters to the object or region-of-interest. A set of fast, simple algorithms for 2-D and 3-D PR, and 3-D cones acquisitions are introduced that match the sampling density in frequency space to the desired FOV shape. Tailoring the acquisitions allows for reduction of aliasing artifacts in undersampled applications or scan time reductions without introducing aliasing in fully-sampled applications. It also makes possible new radial imaging applications that were previously unsuitable, such as imaging elongated regions or thin slabs. 2-D PR longitudinal leg images and thin-slab, single breath-hold 3-D PR abdomen images, both with isotropic resolution, demonstrate these new possibilities. No scan time to volume efficiency is lost by using anisotropic FOVs. The acquisition trajectories can be computed on a scan by scan basis.

Nanomechanical properties of a Ni nanodot-patterned surface.

Nanomechanical properties of a Ni nanodot-patterned surface (NDPS) on a Si substrate were investigated using nanoindentation. The Ni NDPS was fabricated by thermal evaporation of Ni through a porous anodized aluminum oxide template onto a Si substrate. Plan-view transmission electron microscopy and nanobeam diffraction were used to characterize the Ni nanodot crystal structure. Scanning electron microscopy and atomic force microscopy were used to characterize the morphology and deformation of the Ni nanodots before and after nanoindentation. The elastic modulus and hardness of the Ni nanodots were found to be 159 ± 22 and 7.7 ± 1.0 GPa, respectively. The critical shear stress for initiating plastic deformation in the Ni nanodot was estimated to be 8.3 ± 1.0 GPa, which is close to the theoretical shear strength of 7.6 GPa in dislocation-free single crystal Ni.

Quantitative analysis of allele imbalance supports atypical ductal hyperplasia lesions as direct breast cancer precursors.

It remains unclear whether hyperplastic breast lesions, especially with atypia, are cancer precursors or markers of increased cancer risk. Quantified comparisons of genomic alterations in coexisting lesions could address this question. Therefore, we examined allele imbalance (AI), also known as loss of heterozygosity (LOH), at 20 microsatellite markers on nine chromosome arms, in DNA from 106 samples microdissected from 17 randomly selected cancer-containing breast specimens: 13 simple (DH) and 45 atypical ductal hyperplastic (ADH) lesions, 30 in situ (DCIS) and 18 invasive ductal carcinomas (IDC). Data were analysed using regression models and generalized estimating equations. We found that AI increased as histology became more aberrant and varied with histology across the chromosome arms (p<0.0001). ADH had more AIs on 1q (p=0.03) and 16q (p=0.02) and fewer AIs on 17p (p=0.06) and 17q (p<0.0001) than on other arms. In cancers, AIs remained high on 1q and 16q, and became frequent on 17p and 17q. Concordance between AIs in ADHs and cancers exceeded the 50% expected if the lesions were separate clones in 16/20 (80%) ADHs (p=0.05), from 9/11 (82%) cases (p=0.03), and involved 41/51 (80%) evaluable markers (p=0.05). The occurrence of any AI in ADH predicted greater AI (p=0.009) and possibly lower grade (p=0.05) in coexisting cancers. Nevertheless, ADHs were not genetically identical to cancers or to each other. We found AIs discordant between ADHs and cancers (always on 1q and 16q), AIs unique to ADH (usually on 11q) and some genetic heterogeneity among coexisting ADHs. We conclude that ADH lesions are genetically advanced, with frequent alterations on 1q and 16q, and are often direct cancer precursors. Their global genetic characteristics predict features of cancers in the same breast. Nevertheless, the genetic heterogeneity detected suggests that hyperplasias and cancers may arise on a field at generalized increased cancer risk.

Spin waves in nickel nanorings of large aspect ratio.

The spin dynamics of high-aspect-ratio nickel nanorings in a longitudinal magnetic field have been investigated by Brillouin spectroscopy and the results are compared with a macroscopic theory and three-dimensional micromagnetic simulations. Good agreement is found between the measured and calculated magnetic field dependence of the spin wave frequency. Simulations show that as the field decreases from saturation, the rings switch from a "bamboo" to a novel "twisted bamboo" state at a certain critical field, and predict a corresponding dip in the dependence of the spin wave frequency on the magnetic field.