Scaling analysis reveals the mechanism and rates of prion replication in vivo.

Prions consist of pathological aggregates of cellular prion protein and have the ability to replicate, causing neurodegenerative diseases, a phenomenon mirrored in many other diseases connected to protein aggregation, including Alzheimer's and Parkinson's diseases. However, despite their key importance in disease, the individual processes governing this formation of pathogenic aggregates, as well as their rates, have remained challenging to elucidate in vivo. Here we bring together a mathematical framework with kinetics of the accumulation of prions in mice and microfluidic measurements of aggregate size to dissect the overall aggregation reaction into its constituent processes and quantify the reaction rates in mice. Taken together, the data show that multiplication of prions in vivo is slower than in in vitro experiments, but efficient when compared with other amyloid systems, and displays scaling behavior characteristic of aggregate fragmentation. These results provide a framework for the determination of the mechanisms of disease-associated aggregation processes within living organisms

Solid Microneedles for Transdermal Delivery of Amantadine Hydrochloride and Pramipexole Dihydrochloride

The aim of this project was to study the influence of microneedles on transdermal delivery of amantadine hydrochloride and pramipexole dihydrochloride across porcine ear skin in vitro. Microchannel visualization studies were carried out and characterization of the microchannel depth was performed using confocal laser scanning microscopy (CLSM) to demonstrate microchannel formation following microneedle roller application. We also report, for the first time, the use of TA.XT Plus Texture Analyzer to characterize burst force in pig skin for transdermal drug delivery experiments. This is the force required to rupture pig skin. The mean passive flux of amantadine hydrochloride, determined using a developed LC–MS/MS technique, was 22.38 ± 4.73 μg/cm2/h, while the mean flux following the use of a stainless steel microneedle roller was 49.04 ± 19.77 μg/cm2/h. The mean passive flux of pramipexole dihydrochloride was 134.83 ± 13.66 μg/cm2/h, while the flux following the use of a stainless steel microneedle roller was 134.04 ± 0.98 μg/cm2/h. For both drugs, the difference in flux values following the use of solid stainless steel microneedle roller was not statistically significantly (p \u3e 0.05). Statistical analysis was carried out using the Mann–Whitney Rank sum test

Magnetic resonance imaging techniques for diagnostics in Parkinson’s disease and atypical parkinsonism

Background: Parkinson’s disease (PD) is a neurodegenerative disease characterized by rigidity, hypokinesia, tremor and postural instability. PD is a clinical diagnosis based on neurological examination, patient history and treatment response. Similar symptoms can be caused by other movement disorders such as progressive supranuclear palsy (PSP) and multiple system atrophy (MSA), making it difficult to clinically separate them in early stages. However, these diseases differ in underlying pathology, treatment and prognosis. PSP and MSA have more rapid deterioration and develop additional symptoms such as impaired eye movements or autonomic dysfunction. Magnetic resonance imaging (MRI) is commonly performed as part of the clinical work-up in patients presenting with parkinsonism. There are no overt changes on structural MRI in PD. In atypical parkinsonian syndromes there are typically no visible changes until later disease stages. Purpose: The aim of this thesis is to evaluate novel MRI techniques for diagnostics and for investigation of disease processes in Parkinson’s disease, PSP and MSA. Paper I: A retrospective cohort from Karolinska University Hospital (102 participants; 62 PD, 15 PSP, 11 MSA, 14 controls) was assessed using susceptibility mapping processed from susceptibility weighted imaging. We show that there is elevated susceptibility in the red nucleus and the globus pallidus in PSP compared to PD, MSA and controls. Higher susceptibility levels were also seen in MSA compared to PD in the putamen, and in PD compared to controls in the substantia nigra. Using the red nucleus susceptibility as a diagnostic biomarker, PSP could be separated from PD with an accuracy of 97% (based on the area under the receiver operating characteristic curve, AUC), from MSA with AUC 75% and from controls with AUC 98%. We concluded that susceptibility changes, particularly in the red nucleus in PSP, could be potential biomarkers for differential diagnostics in parkinsonism. Paper II: A prospective cohort from Lund, the BioFINDER study (199 participants; 134 PD, 11 PSP, 10 MSA, 44 controls), was investigated using the susceptibility mapping pipeline developed for Paper I. The finding from Paper I with elevated susceptibility in the red nucleus was validated for PSP compared to PD, MSA and controls. The elevated putaminal susceptibility was also confirmed in MSA compared to PD. The potential role of red nucleus susceptibility as a biomarker for separating PSP from PD and MSA was also similar to the results in Paper I, with AUC 98% for separating PSP from PD and AUC 96% for separating PSP from MSA. We concluded that we could confirm our previous findings from Paper I, with the red nucleus susceptibility being a potential biomarker for separating PSP from PD and MSA. Paper III: A retrospective cohort from Karolinska University Hospital (196 participants; 140 PD, 29 PSP, 27 MSA) was evaluated to employ automated volumetric brainstem segmentation using FreeSurfer. The volumetric approach was compared to manual planimetric measurements: midbrain-pons ratio, magnetic resonance parkinsonism index 1.0 and 2.0. Intra- and inter-scanner as well as intra- and inter-rater reliability were calculated. We found good repeatability in both automated volumetric and manual planimetric measurements. Normalized midbrain volume performed better than the planimetric measurements for separating PSP from PD. We concluded that, if further developed and incorporated in a radiology workflow, automated brainstem volumetry could increase availability of brainstem metrics and possibly save time for radiologists conducting manual measurements. Paper IV: Two cohorts, a retrospective from Karolinska University Hospital (184 participants; 129 PD, 28 PSP, 27 MSA) and a prospective from Lund (185 participants; 125 PD, 11 PSP, 8 MSA, 41 controls), were studied to investigate a new method of creating T1-/T2-weighted ratio images and its diagnostic capabilities in differentiating parkinsonian disorders. In the explorative retrospective cohort, differences in white matter normalized T1-/T2- weighted ratios were seen in the caudate nucleus, putamen, thalamus, subthalamic nucleus and red nucleus in PSP compared to PD; in the caudate nucleus and putamen in MSA compared to PD and in the subthalamic nucleus and the red nucleus in PSP compared to MSA. These differences were validated externally in the prospective cohort, where the changes could be confirmed in the subthalamic nucleus and the red nucleus in PSP compared to PD and MSA. We concluded that there are different patterns of white matter normalized T1-/T2-weighted ratio between the disorders and that this reflects differences in underlying pathophysiology. The T1-/T2-weighted ratio should be further investigated for better understanding of pathological processes in parkinsonian disorders and could possibly be utilized for diagnostic purposes if further developed

Towards the Development of a Wearable Tremor Suppression Glove

Patients diagnosed with Parkinson’s disease (PD) often associate with tremor. Among other symptoms of PD, tremor is the most aggressive symptom and it is difficult to control with traditional treatments. This thesis presents the assessment of Parkinsonian hand tremor in both the time domain and the frequency domain, the performance of a tremor estimator using different tremor models, and the development of a novel mechatronic transmission system for a wearable tremor suppression device. This transmission system functions as a mechatronic splitter that allows a single power source to support multiple independent applications. Unique features of this transmission system include low power consumption and adjustability in size and weight. Tremor assessment results showed that the hand tremor signal often presents a multi-harmonics pattern. The use of a multi-harmonics tremor model produced a better estimation result than using a monoharmonic tremor model

Influence of 2,5-Hexanedione, Acrylamide, Tri-O-Tolyl Phosphate, Leptophos and Methylmercury on Endogenous Levels of Tryptophan, Serotonin and 5-Hydroxyindoleacetic Acid and Serotonin Turnover Rates in Rat Brain

Several industrial and environmental chemicals cause distal and/or central neuropathy among other diverse toxic effects. Spague-Dawley derived rats were fed doses of 2,5-hexanedione, acrylamide, tri-o-tolyl phosphate, leptophos and methylmercury via gavage. The dose levels and administration periods were established in previous experiments designed to assess clinical neuropathy using rats trained to walk on a rotorod apparatus fitted with an electrode floor. After intravenous injections of 3H-Tryptophan, whole rat brain homogenates were analyzed using liquid scintillation and spectrofluorometric techniques for levels of tryptophan, serotonin and 5-hydroxyindoleacetic acid. Serotonin turnover rates were calculated using the specific activities of tryptophan and serotonin at two different time periods. The levels of serotonin as well as the serotonin turnover rates were unaffected by dosages of 5 to 50 mg acrylamide/kg given daily doses, while whole brain concentrations of 5-hydroxyindoleacetic acid increased significantly in a dose-dependent manner. the rise in 5-hydroxyindoleacetic acid levels coupled with no effects on the other levels in acrylamide and 2,5-hexanedione-fed animals suggests a possible inhibition of the energy-dependent 5-hydroxyindoleacetic acid efflux system in the brain. Animals given five doses of Leptophos (4.5 to 45 mg/kg) or six doses from 30 to 300 mg/kg tri-o-tolyl phosphate, administered every third day, showed slightly eleveated, non-significant, serotonin turnover rates while levels of serotonin and tryptophan remained unchanged with a slight decrease in 5-hydroxyindoleacetic acid levels at the highest dosages. Levels of endogenous indole compounds in methylmercury treated rats showed no significant differences from control values; however, the turnover rates and levels of serotonin were slightly lower in the two lower treatment levels, while the highest dose level had no apparent effect on turnover rates or concentrations. Further studies involving longer treatment periods, alternate species or examination of discrete brain areas, may further clarify the effects of these chemicals on brain biochemistry

Multiscale Analysis of Biological Data by Scale-Dependent Lyapunov Exponent

Physiological signals often are highly non-stationary (i.e., mean and variance change with time) and multiscaled (i.e., dependent on the spatial or temporal interval lengths). They may exhibit different behaviors, such as non-linearity, sensitive dependence on small disturbances, long memory, and extreme variations. Such data have been accumulating in all areas of health sciences and rapid analysis can serve quality testing, physician assessment, and patient diagnosis. To support patient care, it is very desirable to characterize the different signal behaviors on a wide range of scales simultaneously. The Scale-Dependent Lyapunov Exponent (SDLE) is capable of such a fundamental task. In particular, SDLE can readily characterize all known types of signal data, including deterministic chaos, noisy chaos, random 1/fα processes, stochastic limit cycles, among others. SDLE also has some unique capabilities that are not shared by other methods, such as detecting fractal structures from non-stationary data and detecting intermittent chaos. In this article, we describe SDLE in such a way that it can be readily understood and implemented by non-mathematically oriented researchers, develop a SDLE-based consistent, unifying theory for the multiscale analysis, and demonstrate the power of SDLE on analysis of heart-rate variability (HRV) data to detect congestive heart failure and analysis of electroencephalography (EEG) data to detect seizures

Kinetic Intersections as a Source of Information on Rate Coefficients

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Aerospace Medicine and Biology: A continuing bibliography with indexes (supplement 290)

This bibliography lists 125 reports, articles and other documents introduced into the NASA scientific and technical information system in October 1986

PROBING TEMPORAL CHANGES IN MITOCHONDRIAL MEMBRANE POTENTIAL WITH IMPEDANCE SPECTROSCOPY

The electrical properties of mitochondria provide fundamental insights into metabolic processes in health and disease. This research studies electrical impedance spectroscopy as a non-invasive, sensitive, and relatively low cost technique to monitor biological processes, such as those involving changes in mitochondrial membrane potential. Our experimental strategy first involves treating suspensions of live mitochondria with the substrate succinate to stimulate activity of succinate dehydrogenase, or more simply Complex II. This triggers electron flux through Complex II and the remaining complexes of the electron transport chain, enabling them to pump protons across the inner membrane and build up a membrane potential. Subsequent variability is introduced by adding various concentrations of the uncoupler trifluorocarbonylcyanide phenylhydrazone (FCCP) and the neurotransmitter dopamine (DA) to mitochondrial suspensions, and measuring changes in impedance. Our results show that adding succinate decreases impedance, consistent with an increase in dielectric response and membrane potential. Overall, our investigation establishes real-time impedance spectroscopy as a non-destructive, potentially powerful method for membrane potential studies of mitochondria.Physics, Department o

Advanced neuroimaging methods and biomarkers applied to preclinical models of multiple sclerosis and amyothropic lateral sclerosis

New paradigms are developed in magnetic resonance imaging for the advanced diagnosis of neurodegenerative diseases. In particular, multiple sclerosis (MS) and amyotrophic lateral sclerosis (ALS) preclinical research poorly focuses on functional connectivity in brain. Available animal models of MS and ALS are extensively used for analysis such drug testing and discovery of underlying mechanisms of pathogenesis. These diseases present, since neuronal lesions formation and neuroinflammation, a multilevel heterogeneity in mechanism of neurodegeneration and brain connectivity still not well understood. Moreover, they play a key role in pharmacological research, from the identification of a therapy target to the in vivo validation of the efficacy. More recently alterations in synchronized brain activity at rest in MS patients have been reported. At the best of our knowledge, functional imaging has not been applied yet in the assessment of new therapies in the preclinical models for MS and ALS. In this study, we aim to develop an innovative platform based on functional MRI in the resting state (rsfMRI), for the pre-clinical evaluation of new markers in MS and ALS. Moreover, the advancing in MRI techniques could assess new criteria of sensitivity and specificity in diagnosis; an additional analysis on diffusion MRI outcomes in MS preclinical models is added to this study