Ultraflexible Nanowire Array for Label- and Distortion-Free Cellular Force Tracking

Living cells interact with their immediate environment by exerting mechanical forces, which regulate important cell functions. Elucidation of such force patterns yields deep insights into the physics of life. Here we present a top-down nanostructured, ultraflexible nanowire array biosensor capable of probing cell-induced forces. Its universal building block, an inverted conical semiconductor nanowire, greatly enhances both the functionality and the sensitivity of the device. In contrast to existing cellular force sensing architectures, microscopy is performed on the nanowire heads while cells deflecting the nanowires are confined within the array. This separation between the optical path and the cells under investigation excludes optical distortions caused by cell-induced refraction, which can give rise to feigned displacements on the 100 nm scale. The undistorted nanowire displacements are converted into cellular forces via the nanowire spring constant. The resulting distortion-free cellular force transducer realizes a high-resolution and label-free biosenor based on optical microscopy. Its performance is demonstrated in a proof-of-principle experiment with living Dictyostelium discoideum cells migrating through the nanowire array. Cell-induced forces are probed with a resolution of 50 piconewton, while the most flexible nanowires promise to enter the 100 femtonewton realm.

Reduction of olfactory sensitivity during normobaric hypoxia

OBJECTIVE

Acute mountain sickness (AMS) is caused by a low partial pressure of oxygen and may occur above 2500m. The aim of this research was to evaluate olfactory and gustatory abilities of healthy subjects during baseline conditions and after seven hours of normobaric hypoxia.

METHODS

Sixteen healthy subjects were assessed using the Sniffin' Sticks, as well as intensity and pleasantness ratings. Gustatory function was evaluated utilizing the Taste Strips. Experiments were carried out under baseline conditions (518m altitude) followed by a second testing session after seven hours of normobaric hypoxia exposure (comparable to 4000m altitude).

RESULTS

During normobaric hypoxia olfactory sensitivity and intensity estimates were significantly reduced.

CONCLUSIONS

We conclude that normobaric hypoxia leads to a significant decrease of olfactory sensitivity and intensity ratings.

[Pathomechanisms and clinical aspects of frontotemporal lobar degeneration]

BACKGROUND

Frontotemporal lobar degeneration (FTLD) includes a spectrum of heterogeneous clinical and neuropathological diseases. In a strict sense this includes the behavioral variant of frontotemporal dementia (bvFTD) and primary progressive aphasia (PPA) and both variants can be associated with amyotrophic lateral sclerosis (FTD-ALS). In a broader sense FTLD also includes progressive supranuclear palsy (PSP) and corticobasal syndrome (CBS). In recent years the strong genetic component of FTLD has become increasingly clear.

OBJECTIVE

The association between clinical presentation, neuropathology, genetics and pathophysiological mechanisms of FTLD are presented.

RESULTS

The diagnostic criteria and tools for the clinical differential diagnosis of FTLD are presented. At autopsy patients show neuronal and glial inclusions of Tau, TDP-43 or FUS. While Tau pathology is often associated with extrapyramidal symptoms, patients with TDP-43 and FUS inclusions often also show signs of ALS. Pathogenic mutations directly increase the aggregation propensity of these proteins or impair protein degradation through autophagy or the proteasome. Pathogenic mutations in most FTLD genes trigger cytoplasmic missorting and aggregation of the RNA-binding protein TDP-43 and thus lead to a nuclear loss of TDP-43 function. Microgliosis and mutations in GRN and TREM2 suggest an important role of neuroinflammation in FTLD.

CONCLUSION

There is still no causal therapy for FTLD but preclinical studies focusing on pathogenic mutations in C9orf72, GRN and Tau may lead to clinical trials soon; therefore, establishing large well characterized patient cohorts is crucial for trial readiness.

Comparison of patient-reported outcome measures in multiple sclerosis

BACKGROUND

Patient-reported outcome measurements (PROMS) have been proposed sensitive outcome parameters in multiple sclerosis (MS). In this study, we assessed a German version of the Multiple Sclerosis Impact Scale (MSIS-29) and a revised version of the Hamburg Quality of Life Questionnaire in Multiple Sclerosis (HAQUAMS) in comparison with rater- and physician-based tools.

METHODS

Consecutive MS patients (n = 117) of the MS outpatient unit were included. In addition to MSIS-29 and HAQUAMS, the following parameters were obtained: Expanded Disability Status Scale (EDSS) and modified Multiple Sclerosis Functional Composite (MSFC) [9-hole peg test (9HPT), 25-foot walk test and symbol digit modalities test]. We investigated validity, internal consistency and test-retest reliability as well as correlation between these measures.

RESULTS

Internal consistency (Cronbach's α ≤ 0.96) and test-retest coefficients (ICC ≤ 0.87) of both scales were high and satisfied psychometric standards. Convergent and discriminant validity was supported by direction, magnitude and pattern of correlation with other rater-based measures depending on the functional subdomain. Both MSIS-29 and HAQUAMS correlated with EDSS (ρ = 0.55 vs 0.62), but stronger correlation was found between MSIS-29 and HAQUAMS total score (ρ = 0.90). Both scales distinguished between patient groups of varied disease severity and cognitive impairment.

CONCLUSION

Patient-reported outcome measurements as MSIS-29 and HAQUAMS seem to be valid instruments to detect different impairment levels in comparison with traditional rater-based instruments like EDSS or MSFC.

Two-beam cross-correlation: a method to characterize transport phenomena in micrometer-sized structures

To determine flow properties, namely, the velocity and angle of the flow in microstructured channels, an experimental realization based on fluorescence correlation spectroscopy is described. For this purpose, two micrometer-sized spatially separated volume elements have been created. The cross-correlation signal from these has been recorded and evaluated mathematically. In addition to previous results, two-beam cross-correlation allows for fast and easy determination of even small (down to 200 μm/s) flow velocities, as well as simultaneous measurement of diffusion properties of single dye molecules within a rather short detection time of 5-100 s and an error rate of less than 20%. The spatial flow resolution is around 1-2 μm, limited by the diameter of the volume element. Furthermore, vectorial flow data can be obtained and evaluated. A discussion of the theoretical background and an experimental verification of the theoretical results is performed. The feasibility of fast and easy data processing is shown if the flow time is the only desired information. Possible applications of this precise and simple method are the determination of transportation effects within artificial microstructures for CE and HPLC, fast chemical kinetics, and high-throughput screening.

Salting-out phenomenon and 1-octanol/water partition coefficient of metalaxyl pesticide

In this paper, we present the effect of inorganic cations such as Na+, K+, Ca2+, Mg2+ on the salting-out phenomenon of metalaxyl from pure water to aqueous salt solutions. Moreover the 1-octanol/water partition coefficient in pure water is presented. To accomplish this, aqueous solubility of metalaxyl was determined in pure water, in different salt solution (NaCl, KCl, CaCl2 and MgCl2), and at different concentration level ranging from 0.01 to 1.5 M. The 1-octanol/water partition coefficient was determined using the static shake-flask method. Solubility was determined using dynamic saturation method for pure water in the range of 298.15-325.15 K and at 298.15 K for different salt solutions. The solubility value in pure water for studied interval was found constant (m=3.118×10(-2) mol kg(-1)). Solubility values were used to calculate the standard molar Gibbs free energy of dissolution (ΔsolG°) and transfer (ΔtrG°) at 298.15 K. The values of ΔtrG° from pure to all studied aqueous salt solutions did not exceed 2 kJ mol(-1), the value of ΔsolG° of dissolution is 18.5 ±0.72 kJ mol(-1). The 1-octanol/water partition coefficient in pure water log Ko/w is equal to 1.69. The obtained results confirm the classification of the neutral metalaxyl as a slightly hydrophobic molecule.

Simple equations to estimate light interception by isolated trees from canopy structure features: assessment with three-dimensional digitized apple trees

* Simple models of light interception are useful to identify the key structural parameters involved in light capture. We developed such models for isolated trees and tested them with virtual experiments. Light interception was decomposed into the projection of the crown envelope and the crown porosity. The latter was related to tree structure parameters. * Virtual experiments were conducted with three-dimensional (3-D) digitized apple trees grown in Lebanon and Switzerland, with different cultivars and training. The digitized trees allowed actual values of canopy structure (total leaf area, crown volume, foliage inclination angle, variance of leaf area density) and light interception properties (projected leaf area, silhouette to total area ratio, porosity, dispersion parameters) to be computed, and relationships between structure and interception variables to be derived. * The projected envelope area was related to crown volume with a power function of exponent 2/3. Crown porosity was a negative exponential function of mean optical density, that is, the ratio between total leaf area and the projected envelope area. The leaf dispersion parameter was a negative linear function of the relative variance of leaf area density in the crown volume. * The resulting models were expressed as two single equations. After calibration, model outputs were very close to values computed from the 3-D digitized databases.

Angiotensin II AT1 receptor internalization, translocation and de novo synthesis modulate cytosolic and nuclear calcium in human vascular smooth muscle cells

The present study was designed to verify if human (h) Angiotensin II (Ang II) type-1 receptor (hAT1R) undergoes internalization, nuclear translocation, and de novo synthesis in primary culture of human aortic vascular smooth muscle cells (hVSMCs) and if overexpression of this receptor modulates sustained free cytosolic ([Ca]c) and nuclear ([Ca]n) calcium. 3-dimensional (3-D) confocal microscopy was used to monitor free intracellular Ca2+ and hAT1R-green fluorescence protein (GFP) fusion protein in cultured hVSMCs. Immunofluorescence studies showed the presence of hAT1R and the absence of hAT2R in normal hVSMCs. Using 3-D imaging technique, hAT1 receptors were localized at the sarcolemma and in the cytosolic and nuclear compartments. In native as well as in normal hAT1R or hAT1R-GFP overexpressing hVSMCs, Ang II (10(-9) and 10(-4) M) induced internalization and nuclear translocation of this type of receptor. The internalization of hAT1Rs is mediated via clathrin-coated pits and vesicles pathway. This phenomenon of trancellular trafficking of receptors was associated with an increase of hAT1R. The Ang II induced increase of hAT1R density was prevented by the protein synthesis inhibitor cycloheximide. Overexpression of hAT1R and hAT1R-GFP decreased both basal cytosolic and nuclear Ca2+. In normal hVSMCs and low hAT1R-GFP overexpressing hVSMCs, Ang II (10(-15) to 10(-4) M) induced a dose-dependent sustained increase of [Ca]c and [Ca]n with an EC50 near 5 x 10(-11) and 5 x 10(-9) M, respectively. Our results suggest that hAT1Rs are the predominant type of Ang II receptors in aortic hVSMCs and are present in the sarcolemma, the cytosolic and the nuclear compartments. Ang II rapidly induces hAT1R internalization, nuclear translocation, as well as nuclear de novo synthesis of this receptor. The hAT1R overexpression in hVSMCs modulates sustained [Ca]c and [Ca]n.

Human papillomavirus infection at the United States-Mexico border: implications for cervical cancer prevention and control

The United States-Mexico border is a region comprised of a country with one of the highest rates of invasive cervical cancer (Mexico) and a country with one of the lowest rates (United States). Recent evidence clearly indicates that human papillomavirus (HPV) infection is the cause of cervical cancer. The distribution of specific types of HPV is known to vary in different regions of the world, as do the cofactors that may inhibit or promote HPV carcinogenesis. Estimating the prevalence of oncogenic HPV is needed for guiding vaccine development. The purpose of this study was to determine the prevalence of oncogenic and nononcogenic HPV types and risk factors for HPV among women residing along the United States-Mexico border. A cross-sectional study of 2319 women, ages 15-79 years, self-referring for gynecological care was conducted between 1997 and 1998. HPV was detected by PCR using the PYGMY 09/11 L1 consensus primer, and HPV genotyping was conducted using the reverse line blot method. Overall, the HPV prevalence was 14.4% with no significant differences observed by country after adjustment for age. HPV 16 was the most commonly detected HPV type in both the United States and Mexico. Among women with high-grade squamous intraepithelial lesions, HPV types 58, 45, 51, 31, 35, 55, and 73 were most common in Mexico, and HPV types 18, 31, 35, 51, 52, and 58 were most common in the United States. In both countries, HPV prevalence declined linearly with age from 25% among women ages 15-19 years to 5.3% among women 56-65 years. Factors significantly independently associated with HPV infection were older age [adjusted odds ratio (AOR) = 0.15 for ages 56-65 years compared with those 15-19 years], a marital status other than married (AOR = 1.58-3.29), increased numbers of lifetime male partners (AOR = 3.8 for > or =10 partners compared with 1 partner), concurrent infection with Chlamydia trachomatis (AOR = 1.79), ever use of Norplant (AOR = 2.69), and current use of injectable contraceptives (AOR = 2.29). Risk factors for HPV infection did not differ by country. Results from this study suggest that in addition to HPV 16 and 18, HPV types 31, 45, 51, and 58 should be considered for inclusion in an HPV prevention vaccine for distribution in Mexico.

Highly efficient single molecule detection in microstructures

For DNA single molecule sequencing, the complete detection of all dye-labeled monomers which are cleaved off during the sequencing reaction is an essential requirement. In this work we address the feasibility of single molecule detection in microstructures with a confocal multi element set-up. We present statistical data on single molecule recognition and explain a refined data evaluation technique for single molecule burst analysis. From these data the signal-to-noise ratio in microstructures is evaluated as well as the overall detection efficiency. So far, detection efficiencies of single molecule events of up to 60% have been shown in microstructures.

Towards a general procedure for sequencing single DNA molecules

In this paper we report on the latest technical advances towards single molecule sequencing, a useful method currently developed especially for fast and easy de novo sequencing. Different approaches for complete labeling of DNA with fluorescent dyes are described. In addition, the experimental set-up for the sequencing process is shown. We demonstrate the ability to purify the buffer and enzyme solutions. Inorganic buffers were purified down to at least 20 fM of remaining fluorescent impurities. The exonuclease buffer solution could be cleaned down to 0.8 pM whereby its full activity was kept. Finally, we show a selection procedure for beads and present the data of a model experiment, in which immobilized DNA is degraded by an exonuclease within a polymethylmethacrylate (PMMA) microstructure. Furthermore, the mathematical processing of the obtained raw data is described. A first complete experimental cycle is shown, combining all preparatory steps which are necessary for single molecule sequencing in microstructures.