Proximity Probes Research Articles

Point: The muscle metaboreflex does restore blood flow to contracting muscles

Imposed reductions in oxygen delivery to active skeletal muscle during dynamic exercise in conscious dogs evoke a powerful pressor response, termed the muscle metaboreflex. During submaximal work rates, the major mechanism used by this reflex is to increase cardiac output (CO), which generates a

Preimplantation genetic diagnosis significantly improves the pregnancy outcome of translocation carriers with a history of recurrent miscarriage and unsuccessful pregnancies

Preimplantation genetic diagnosis (PGD) for translocations has been shown to significantly reduce the risk of recurrent miscarriage, but because the majority of embryos produced are unbalanced, pregnancy rate is relatively low since 20% or more cycles have no normal or balanced embryos to transfer. The purpose of this study was to evaluate whether PGD could improve pregnancy outcome in translocation carriers with a history of two or more consecutive miscarriages and no live births. PGD for translocations was offered to translocation carriers with two or more previous miscarriages (average 3.5) and no live births (0/117 pregnancies) using a combination of distal and proximal probes to the breakpoints. After PGD, only 18.3% of embryos were normal or balanced. Only 5.3% of pregnancies were lost after PGD compared with 100% before PGD ( P < 0.001). The cumulative pregnancy rate was 57.6% and the cumulative ongoing pregnancy rate was 54.5% in the short period of time of 1.24 IVF cycles, or 46.3% and 43.9% respectively per cycle. In conclusion, PGD significantly reduced losses and increased the number of viable pregnancies ( P < 0.001). IVF plus PGD are a faster method of conceiving a live child than natural conception, at least for translocation carriers with recurrent miscarriages and no previous live births.

A compact nanopositioning stage with high vibrational eigenfrequencies

A compact nanopositioning stage is described that has high vibrational eigenfrequencies and is, therefore, insensitive to external vibrations. The high eigenfrequencies are produced by a rigid structure that is designed so that it does not degrade the motional performance of the stage. Preliminary performance evaluations are presented. We describe how a positioning stage of this type could be used as an integral part of a proximal probe.

Prevalence of Gastroesophageal Reflux in End-Stage Lung Disease Candidates for Lung Transplant

Aspiration secondary to gastroesophageal reflux has been postulated to be a contributing factor in bronchiolitis obliterans after lung transplantation. It is not clear whether gastroesophageal reflux is a preexisting condition or secondary to intraoperative vagal injury or drug-induced prolonged gastric emptying. The prevalence of gastroesophageal reflux was examined in 78 consecutive end-stage lung disease patients assessed for lung transplantation: emphysema, 21; cystic fibrosis, 5; idiopathic pulmonary fibrosis, 26; scleroderma, 10; and miscellaneous diseases, 16. All underwent esophageal manometry. Two-channel esophageal 24-hour pH testing was completed in 76 patients. Gastric emptying studies were conducted in 36 patients. Typical gastroesophageal reflux symptoms were documented in 63% of patients. The lower esophageal sphincter was hypotensive in 72% of patients, and 33% had esophageal body dysmotility. Prolonged gastric emptying was documented in 44%, and 38% had abnormal pH testing. The overall DeMeester score was above normal in 32% of patients, and 20% had abnormal proximal pH probe readings. Gastroesophageal reflux is highly prevalent in end-stage lung disease patients who are candidates for lung transplantation. Further investigation is needed to study the prevalence of gastroesophageal reflux after lung transplantation and its contribution to chronic allograft dysfunction.

Reversible electrical modification on conductive polymer for proximity probe datastorage

Reversible electrical modification of a conductive polymer is studied for ultrahigh densitydata storage based on a scanning probe microscope (SPM). Using a surface-initiatedpolymerization (SIP) method, a thin polyaniline film is formed from a self-assembledmonolayer (SAM) on an Au surface. The conductivity of the film is reversiblychanged by applying a voltage between a SPM probe and the film, depending on thepolarity of the applied voltage. This reversible electrical modification is consideredto originate in the oxidation–reduction reaction or protonation–deprotonationreaction of PANI from x-ray photoelectron spectroscopy (XPS) measurement.

Results of PGD for Translocations in 539 Cycles

To evaluate the results of Preimplantation Genetic Diagnosis (PGD) for translocations. 52 USA-based IVF centers referring PGD samples to a single reference PGD laboratory. Cycles of PGD for translocations from 1995 to February 2005 were included in the study. Samples from 52 IVF centers were received in our PGD laboratories the same or next day after biopsy. All results were provided within 30 hours after sample arrival. FISH methods evolved during this period, and included polar body biopsy using painting probes, breakpoint-spanning probes in interphase blastomeres, and the last and preferred method, the use of telomeric and proximal probes in interphase blastomeres. A total of 539 cycles were performed, with an average maternal age of 34.0 years (compared to 37.5 for PGD of aneuploidy), involving the analysis of 4,597 embryos, of which only 19.0% were normal, and the rest unbalanced. Reciprocal translocations produced 15% normal embryos while Robertsonian translocations produced 28% normal embryos. Of the 539 cycles, 422 received a replacement (78%), with an average of 1.3 normal embryos replaced. 117 cycles had no replacement as all embryos were found to be abnormal. Information regarding pregnancy results was obtained from 462 pick ups, of which 138 became pregnant with the presence of a fetal heart, producing a pregnancy rate of 30% per pick- up, and 40% per replacement. The pregnancy rate, however, varied depending on the IVF center and the etiology of patients visiting each clinic, from a low 0% to 52% per oocyte retrieval. Also it varied depending on the type of translocation, with 25% and 40% pregnancy rate per oocyte retrieval in Reciprocal and Robertsonian translocations, respectively. In total, there were 176 fetal heartbeats. Of those, 1 was ectopic, 15 spontaneously aborted (9%), 7 were elective reduced due to multiple pregnancy, 40 are still ongoing, and 113 delivered . These patients had aborted previously 88% of their pregnancies compared to 9% after PGD (p<0.001). There have not been any misdiagnoses in this group to date. PGD has been shown in the past to reduce spontaneous abortions in patients with translocations. We have confirmed this observation with the largest dataset so far on PGD of translocations. The pregnancy rate obtained is dependent on the type of translocation but also it is proportionally linked to the overall pregnancy rate of each clinic and their experience in performing embryo biopsy, indicating the presence of a learning curve in the procedure. Some European PGD laboratories emphasize biopsy of two cells rather than one to further reduce the error rate, but clearly a very acceptable error rate can be attained with only 1 cell biopsied with the advantage of a reduction personnel time and stress upon the growing embryo.

The ultrasonic/shear-force microscope: Integrating ultrasonic sensing into a near-field scanning optical microscope

An ultrasonic transducer is incorporated into a near-field scanning optical microscope (NSOM) to augment its versatility to characterize the properties of layers adsorbed to a sample’s surface. Working under typical NSOM operation conditions, the ultrasonic transducer—attached underneath the sample—demonstrates sufficient sensitivity to monitor the waves generated by the tapered NSOM probe that oscillates in the proximity of, and parallel to, the sample’s top surface. This capability makes the newly integrated ultrasonic/shear-force microscope a valuable diagnostic tool in the study of sliding friction and surface phenomena in general. Here, it is used to concurrently and independently monitor the effects that probe-sample interactions exert on the probe (that is attached to a piezoelectric tuning fork) and on the sample (that is attached to the ultrasonic transducer). The signal from the tuning fork (TF) constitutes the so called “shear-force” signal, widely used in NSOM as a feedback to control the probe’s vertical position but whose working mechanism is not yet well understood. Tests involving repeated vertical z motion of the probe towards and away from the sample’s surface reveal that the TF and ultrasonic (US) signals have distinct z dependence. Additionally, where the TF signal showed abrupt changes during the approach, the US changed accordingly. A shift in the probe’s resonance frequency that depends on the probe-sample distance is also observed through both the TF and the US responses. Within the sensitivity of the apparatus, ultrasonic signals were detected only at probe-sample distances where the probe’s resonance frequency had shifted significantly. These measured signals are consistent with a probe entering and leaving a viscoelastic fluid-like film above the sample. The film acts as the medium where waves are generated and coupled to the ultrasonic sensor located beneath the sample. To our knowledge, this is the first reported use of ultrasonic detection for detailed monitoring of the distance dependence of probe-sample interactions, and provides direct evidence of sound as an energy dissipation channel in wear-free friction. This newly integrated ultrasonic/shear-force microscope, which can be implemented with any functionalized proximal probe (including aperture and apertureless NSOM), can become a valuable metrology tool in surface science and technology.

Spatially Resolved Suzuki Coupling Reaction Initiated and Controlled Using a Catalytic AFM Probe

Appropriately modified proximal probes can be utilized in the spatially resolved chemical coupling of surface-bound and solution-phase reagents. Herein we report a chemically specific Suzuki coupling reaction between a surface-confined aryl bromide and boronic acid reagents in solution achieved using a catalytic AFM probe.

Use of Multi‐Channel Intraluminal Impedance (MII) in the Evaluation of Children with Respiratory Symptoms: A New pHenomenon?

Use of Multi‐Channel Intraluminal Impedance (MII) in the Evaluation of Children with Respiratory Symptoms: A New <i>pH</i>enomenon?

A diamond-on-silicon patch-clamp-system

Here, we present a planar multi-patch-clamp-system based on a nano-crystalline diamond patch-membrane used for the investigation of ion channels in cell-membranes. In such a system the cell-membrane is electrically stimulated through a potential difference in the electrolyte across the patch-membrane. Usually, the patch-membrane material is a highly insulating dielectric. The use of diamond allows to add highly localized probes in close proximity to the clamping area for a localized analysis of the stimulation mechanism. The technological concept, realization and first electrical characteristics of the principle structure are discussed.

Nanotribology and nanomechanics

The recent emergence and proliferation of proximal probes, in particular scanning probe microscopies (the scanning tunneling microscope and the atomic force microscope), the surface force apparatus, and of computational techniques for simulating tip-surface interactions and interfacial properties, have led to the appearance of the new field of nanotribology, which pertains to experimental and theoretical investigations of interfacial processes on scales ranging from the atomic- and molecular- to the microscope, occurring during adhesion, friction, scratching, wear, indentation, and thin-film lubrication at sliding surfaces. Nanotribological studies are needed to develop fundamental understanding of interfacial phenomena on a small scale and to study interfacial phenomena in micro/nanostructures used in magnetic storage systems, micro/nanoelectromechanical systems (MEMS/NEMS), and other applications. Proximal probes have also been used for nanomechanics and materials characterization studies. In this paper, we present a review of significant aspects of nanotribology, nanomechanics, and materials characterization studies conducted using an atomic force microscope.

Morphology and Mechanical Properties of Surfactant Aggregates at Water−Silica Interfaces: Molecular Dynamics Simulations

Dilute and concentrated surfactant systems at the solid-liquid interface are examined using classical molecular dynamics simulations. Particular emphasis is placed on understanding how surfactants aggregate and form the micellar structure, how micelles change shape at high concentrations in aqueous media and in the presence of hydrophilic surfaces, and at what force this micellar structure breaks apart during indentation of micelle-covered surfaces with a proximal probe microscope tip. The specific system of interest is C12TAB (n-dodecyltrimethylammonium bromide) surfactant in an aqueous medium that is modeled with empirical potentials. The simulations predict that the micelle structure in water is compact and either spherical or elliptical in shape. In the presence of a hydrophilic surface of silica, the structure evolves into a flat elliptical shape, in agreement with experimental findings. The simulated indentation of the micelle/silica system causes the micelle to break apart at an indentation force of about 1 nN and form a surfactant monolayer. The predicted force curve is in excellent agreement with experimental measurements.

Prevalence of Gastroesophageal Reflux in Difficult Asthma

Study objectives To determine the prevalence of gastroesophageal reflux disease (GERD)—both symptoms and objective evidence—using 24-h dual-probe pH monitoring in difficult asthma, and the relationship between the presence and treatment of GERD to clinical outcome Design and setting As part of a systematic evaluation protocol, 68 subjects with difficult-to-control asthma attending a difficult asthma clinic were referred for dual-probe ambulatory pH esophageal monitoring Results Esophageal probe data were available in 52 patients (76%) with difficult asthma. The prevalence of GERD/GERD-associated asthma symptoms was 75% (39 of 52 patients; 95% confidence interval [CI], 63 to 84.7%). The prevalence of GERD as evidenced by an abnormal pH profile at the distal esophageal probe was 55% (29 of 52 patients; 95% CI, 40 to 69%). The prevalence of GERD at the proximal probe was 34.6% (18 of 52 patients; 95% CI, 23.6 to 51%). The prevalence of GERD was similar in asthmatic subjects who responded to intervention and those who remained difficult to control (therapy resistant). Asymptomatic GERD was present in 9.6% (5 of 52 patients); 16% of cough episodes correlated with acid reflux Conclusions In difficult-to-control asthma, GERD is common, but identification and treatment of GERD do not appear to relate to improvement in asthma control in this population

Prevalence of Gastroesophageal Reflux in Difficult Asthma*

To determine the prevalence of gastroesophageal reflux disease (GERD)-both symptoms and objective evidence-using 24-h dual-probe pH monitoring in difficult asthma, and the relationship between the presence and treatment of GERD to clinical outcome. As part of a systematic evaluation protocol, 68 subjects with difficult-to-control asthma attending a difficult asthma clinic were referred for dual-probe ambulatory pH esophageal monitoring. Esophageal probe data were available in 52 patients (76%) with difficult asthma. The prevalence of GERD/GERD-associated asthma symptoms was 75% (39 of 52 patients; 95% confidence interval [CI], 63 to 84.7%). The prevalence of GERD as evidenced by an abnormal pH profile at the distal esophageal probe was 55% (29 of 52 patients; 95% CI, 40 to 69%). The prevalence of GERD at the proximal probe was 34.6% (18 of 52 patients; 95% CI, 23.6 to 51%). The prevalence of GERD was similar in asthmatic subjects who responded to intervention and those who remained difficult to control (therapy resistant). Asymptomatic GERD was present in 9.6% (5 of 52 patients); 16% of cough episodes correlated with acid reflux. In difficult-to-control asthma, GERD is common, but identification and treatment of GERD do not appear to relate to improvement in asthma control in this population.

Piezoresistive Scanning Proximity Probes for Nanoscience (Piezoresistive Raster-Kraftsonden für die Nanowissenschaften)

Abstract This article is devoted to the realization of piezoresistive sensors used in scanning probe microscopy. It is expected that in the near future major technological breakthroughs in scanning proximal probe nanotools will allow for key scientific impact on analysis and synthesis of nanostructures. All the piezoresistive cantilever sensors described here are based on advanced silicon micromachining and standard CMOS processing. Moreover, using a newly optimized piezoresistive detection scheme process comprising a Wheatstone bridge, we have designed and fabricated piezoresistive cantilevers for atomic force microscopy, which improve surface topography resolution by an order of magnitude to 0.1 nm. The elegance of this concept is that by using an almost identical detection principle and differently functionalized tips or cantilever surfaces, we can detect subtle sample interactions (mechanical, electrical, thermal, and chemical) with a significantly more compact system than with optical beam deflection techniques. For noncontact scanning force microscopy, we integrate a thermally driven bimorph actuator with the piezoresistive cantilever and make use of direct-oscillation in a higher flexural mode. The cantilever then operates in the phase-shift atomic force microscopy (AFM) detection technique.

Cricopharyngeal Muscle Electromyography in Laryngopharyngeal Reflux

The objective was to determine whether laryngopharyngeal reflux was associated with an electrophysiological abnormality of the main part of the upper esophageal sphincter, namely, the cricopharyngeal muscle, which could be related to laryngopharyngeal reflux symptoms. A prospective study of 20 patients with symptoms of laryngopharyngeal reflux. The diagnosis was based on clinical, laryngoscopic, and ambulatory 24-hour pH monitoring findings. Double-probe pH monitoring was performed with placement of the distal and proximal probes 5 cm above the proximal border of the lower esophageal sphincter and 15 cm proximal to the distal probe, in or just beneath the upper esophageal sphincter. Electromyographic recordings were obtained simultaneously on submental and cricopharyngeal muscles during water swallowing. The peak of the submental electromyographic amplitude and its duration was measured using bipolar surface electrodes placed under the chin. The electromyographic features of the cricopharyngeal muscle were investigated by means of concentric needle electrodes inserted percutaneously both in 20 normal subjects and in 20 patients with laryngopharyngeal reflux. All electrophysiological parameters were normal in all of the patients. The durations of foreburst revealed significant correlation with the number of reflux episodes and acid exposure time (P = .026 and P = .044, respectively). The duration of the foreburst correlating with acid exposure time and number of reflux episodes suggested that foreburst duration was extended because of the irritation caused by the acid reflux.

Light-Induced Protein-Matrix Uncoupling and Protein Relaxation in Dry Samples of Trehalose-Coated MbCO at Room Temperature

In humid samples of trehalose-coated carboxy-myoglobin (MbCO), thermally driven conformational relaxation takes place after photodissociation of the carbon monoxide (CO) molecule at room temperature. In such samples, because of the extreme viscosity of the external matrix, photodissociated CO cannot diffuse out of the protein and explores the whole (proximal and distal side) heme pocket, experiencing averaged protein heme pocket structures, as a result of the presence of Brownian motions. At variance, in very dry samples, a lower portion of the photodissociated CO diffuses from the distal to the proximal heme pocket side probing in nonaveraged structures. We revisit here the flash photolysis data by Librizzi et al. (2002) and report on new, room temperature experiments in MbCO-trehalose samples, shortly illuminated prior the laser pulse. In dry samples, pre-illumination increased the diffusion of CO from the distal to the proximal heme pocket side, which resulted in less structure than in non-pre-illuminated samples. Such an effect, which is absent in humid samples, stems from a decoupling of the protein internal degrees of freedom from those of the external water-sugar matrix. We suggest that such a decoupling can be brought about by the continuous attempts performed by the protein during pre-illumination to undergo relaxation toward the photodissociated deoxy state. This, in turn, causes a collapse in the hydrogen bond network, which connects the protein surface to the water-sugar matrix, as reported by Cottone et al. (2002) and Giuffrida et al. (2003). In the conclusion section, we discuss the possible involvement of the processes invoked to rationalize the present data, in the function of macromolecules and interactions in living cells.

Molecular bioelectronics

Recent work by a number of groups has highlighted the emerging potential associated with the marriage of nanoscale electronics and biological structure. Many biological macromolecules have evolved into structures typically primed for highly-specific surface recognition, analyte binding and, in some cases, facile and directional electron tunnelling. The redox-active centres of metalloproteins, for example, play a central role in photosynthesis and respiration and much progress has been made in constructively interfacing these moieties to man-made surfaces. Specifically, a variety of methodologies can be applied that not only facilitate controllable electronic coupling to underlying metallic electrode surfaces but also a highly spatially-resolved analysis of the (potentially switchable) tunnel transport characteristics. Developments in our understanding and manipulation of these entities at a molecular level has further led us to the point where nanobiotechnological advances can be realistically proposed. Strategies to exploit combined advanced lithography and molecular manipulation methods are described. Recent protein tunnel transport experiments in proximal probe junctions are discussed. In a CP-AFM metal–protein–metal tunnel junction experimental data in the low voltage regime is well-described by a non-resonant charge transfer process in which the protein matrix is modelled as a uniform tunnel barrier, the absolute magnitude of which can be controllably modulated by compressional force. Comparative analysis within STM-based junctions of metal substituted metalloproteins are additionally supportive of transport being dominantly non-resonant. Recent progress in interfacing the unique properties of nanoscale electrical junctions to biological structure, more generally, is reviewed herein.

Laryngopharyngeal Reflux: Trends in Diagnostic Interpretation Criteria

Laryngopharyngeal reflux (LPR) is becoming recognized as a clinical entity with a variety of presentations distinct from those of gastroesophreflux disease (GERD). However, much uncertainty remains as to what is considered pathologic versus physiologic reflux. The aim of the study was to determine the normal range of pharyngeal reflux (PR) occurring in healthy adults based on pH-monitoring parameters utilized in the DeMeester scoring system for GERD. We have reviewed the current pool of prospective literature examining ambulatory dual-channel pH-monitoring study data derived from hypopharyngeal proximal probes in normal adults. From our review we have identified trends in several monitoring parameters based on the DeMeester scoring system for GERD. Our discussion recognizes and accepts the limitations imposed by small sample sizes and the number of healthy individuals that would be required to determine the general adult physiologic range of PR. We also explore the possible need for separate normal PR reference intervals based on age or gender disparities. Additional discussion and the summary address future directions for LPR research notably, (1) identification of the most appropriate research paradigm for LPR (i.e., pH 4 vs. 5), (2) establishing reproducibility for the appropriate LPR research paradigm, and (3) complementary modalities to ambulatory dual-channel pH monitoring for the study of acid and nonacid bolus movement within the esophagus

DNA-PEG-DNA triblock macromolecules for reagentless DNA detection.

The sandwich assay is the most common design for electrochemical DNA sensors. This assay consists of three individual DNA components: an immobilized capture strand, a target strand, and a probe strand containing a redox-active reporter group. We report a simplified DNA assay where two strands of ssDNA, the capture and probe strands, are linked together via a flexible poly(ethylene glycol) (PEG) spacer forming an ABA triblock macromolecule. We have developed an electrochemical assay where the detection signal arises as a consequence of a large structural change induced upon hybridization with target DNA. In this system, the DNA-PEG-DNA macromolecule folds or wraps around the target DNA, bringing the ferrocene probe in close proximity to the electrode, affording an electrochemical response.