Image reconstruction algorithm for laser-induced ultrasonic imaging: The single sensor scanning synthetic aperture focusing technique.

This paper aims to implement a laser-induced ultrasound imaging reconstruction method based on the delay-and-sum beamforming through the synthetic aperture focusing technique (SAFT) for a circular scanning, performed with a tomograph that had one acoustic sensor and a system that rotates the sample around a fixed axis. The proposed method, called the Single-sensor Scanning Synthetic Aperture Focusing Technique, considers the size of the sensor and the detection procedure inside the SAFT's algebra. This image reconstruction method was evaluated numerically, using the Green function for the laser-induced ultrasound wave equation to generate a forward problem, and experimentally, using a solid object of polylactic acid, and a Sprague-Dawley rat heart located in a tissue-mimicking phantom. The resulting images were compared to those obtained from the time reversal and the conventional delay-and-sum reconstruction algorithms. The presented method removes the sidelobe artifacts and the comet tail sign, which produces a more distinguishable target on the image. In addition, the proposed method has a faster performance and lower computational load. The implementation of this method in photoacoustic microscopy techniques for image reconstruction is discussed.

A Robust Method for the Elaboration of SiO2-Based Colloidal Crystals as a Template for Inverse Opal Structures.

Photonic crystals (PCs) are nanomaterials with photonic properties made up of periodically modulated dielectric materials that reflect light between a wavelength range located in the photonic band gap. Colloidal PCs (C-PC) have been proposed for several applications such as optical platforms for the formation of physical, chemical, and biological sensors based on a chromatic response to an external stimulus. In this work, a robust protocol for the elaboration of photonic crystals based on SiO2 particle (SP) deposition using the vertical lifting method was studied. A wide range of lifting speeds and particle suspension concentrations were investigated by evaluating the C-PC reflectance spectrum. Thinner and higher reflectance peaks were obtained with a decrease in the lifting speed and an increase in the SP concentrations up to certain values. Seven batches of twelve C-PCs employing a SP 3% suspension and a lifting speed of 0.28 µm/s were prepared to test the reproducibility of this method. Every C-PC fabricated in this assay has a wavelength peak in a range of 10 nm and a peak width lower than 90 nm. Inverse-opal polymeric films with a highly porous and interconnected morphology were obtained using the developed C-PC as a template. Overall, these results showed that reproducible colloidal crystals could be elaborated on a large scale with a simple apparatus in a short period, providing a step forward in the scale-up of the fabrication of photonic colloidal crystal and IO structures as those employed for the elaboration of photonic polymeric sensors.

Tropomyosin 1: Multiple roles in the developing heart and in the formation of congenital heart defects.

Tropomyosin 1 (TPM1) is an essential sarcomeric component, stabilising the thin filament and facilitating actin's interaction with myosin. A number of sarcomeric proteins, such as alpha myosin heavy chain, play crucial roles in cardiac development. Mutations in these genes have been linked to congenital heart defects (CHDs), occurring in approximately 1 in 145 live births. To date, TPM1 has not been associated with isolated CHDs. Analysis of 380 CHD cases revealed three novel mutations in the TPM1 gene; IVS1+2T>C, I130V, S229F and a polyadenylation signal site variant GATAAA/AATAAA. Analysis of IVS1+2T>C revealed aberrant pre-mRNA splicing. In addition, abnormal structural properties were found in hearts transfected with TPM1 carrying I130V and S229F mutations. Phenotypic analysis of TPM1 morpholino-treated embryos revealed roles for TPM1 in cardiac looping, atrial septation and ventricular trabeculae formation and increased apoptosis was seen within the heart. In addition, sarcomere assembly was affected and altered action potentials were exhibited. This study demonstrated that sarcomeric TPM1 plays vital roles in cardiogenesis and is a suitable candidate gene for screening individuals with isolated CHDs.

H2O2 augments cytosolic calcium in nucleus tractus solitarii neurons via multiple voltage-gated calcium channels.

Reactive oxygen species (ROS) play a profound role in cardiorespiratory function under normal physiological conditions and disease states. ROS can influence neuronal activity by altering various ion channels and transporters. Within the nucleus tractus solitarii (nTS), a vital brainstem area for cardiorespiratory control, hydrogen peroxide (H2O2) induces sustained hyperexcitability following an initial depression of neuronal activity. The mechanism(s) associated with the delayed hyperexcitability are unknown. Here we evaluate the effect(s) of H2O2 on cytosolic Ca2+ (via fura-2 imaging) and voltage-dependent calcium currents in dissociated rat nTS neurons. H2O2 perfusion (200 µM; 1 min) induced a delayed, slow, and moderate increase (~27%) in intracellular Ca2+ concentration ([Ca2+]i). The H2O2-mediated increase in [Ca2+]i prevailed during thapsigargin, excluding the endoplasmic reticulum as a Ca2+ source. The effect, however, was abolished by removal of extracellular Ca2+ or the addition of cadmium to the bath solution, suggesting voltage-gated Ca2+ channels (VGCCs) as targets for H2O2 modulation. Recording of the total voltage-dependent Ca2+ current confirmed H2O2 enhanced Ca2+ entry. Blocking VGCC L, N, and P/Q subtypes decreased the number of cells and their calcium currents that respond to H2O2 The number of responder cells to H2O2 also decreased in the presence of dithiothreitol, suggesting the actions of H2O2 were dependent on sulfhydryl oxidation. In summary, here, we have shown that H2O2 increases [Ca2+]i and its Ca2+ currents, which is dependent on multiple VGCCs likely by oxidation of sulfhydryl groups. These processes presumably contribute to the previously observed delayed hyperexcitability of nTS neurons in in vitro brainstem slices.

Spectrophotometric analysis at the single-cell level: elucidating dispersity within melanic immortalized cell populations.

It is widely held that the melanosome is an exemplar of the absorption features of melanin-containing cells, which are assumed to be uniform in both size and optical characteristics. In recent years, however, it has become increasingly apparent that this is a strikingly poor assumption. Indeed, melanin extracted from natural sources and synthetic melanin both show wide variability in their degree of polymerization (molecular weight) and spectroscopic characteristics. In the current study, imaging spectrophotometry performed on individual cells of immortalized melanin-producing cell lines revealed broad distributions in their sizes: 9.5-36.2 µm for Hs936 human melanoma cells, 10.9-20.8 µm for T47D human breast cancer cells, 5.3-43.5 µm for B16F1 mouse melanoma cells, and 6.4-54.2 µm for B16F10 mouse melanoma cells. The color appearance (from translucent to yellow to nearly black), absorption spectrum, and absorption (extinction) coefficient at 532 nm (28.73 to 364.75, 0.01 to 40.17, 5.88 to 977.19, and 0.01 to 1120 cm-1 for Hs936, T47D, B16F1, and B16F10 cells, respectively) of an individual cell also vary widely and cannot be adequately described by a 'typical' value. In comparison, human red blood cells are much more uniform in size (6.0-8.1 µm diameter; 1.9-3.2 µm thickness), although they too show a broad range of absorptivities, with extinction coefficients in the range of 65 to 370 cm-1 when measured at 532 nm. To further evaluate the impact of these findings on photoacoustic bioanalysis, we performed simulations of the generation of photoacoustic signals expected from these cell types. These simulations revealed that their variation in optical features exerts a pronounced effect on the amplitude and shape of the photoacoustic signals generated from these cell types. Finally, we compared the photoacoustic signal generated from these cells under ideal conditions (i.e., a single cell in isolation) versus a heterogeneous real-world sample, demonstrating that when a single or few cancer cells are present within a blood droplet, the photoacoustic signal is indistinguishable from that measured from blood alone. These outcomes have important ramifications for the early photoacoustic detection of cancer cells and circulating tumor emboli, while pointing to the potential of single-cell imaging spectrophotometry to assess heterogeneity within cell populations in more quantitative terms.

The obligatory role of the actin cytoskeleton on inward remodeling induced by dithiothreitol activation of endogenous transglutaminase in isolated arterioles.

Inward remodeling is the most prevalent structural change found in the resistance arteries and arterioles of hypertensive individuals. Separate studies have shown that the inward remodeling process requires transglutaminase activation and the polymerization of actin. Therefore, we hypothesize that inward remodeling induced via endogenous transglutaminase activation requires and depends on actin cytoskeletal structures. To test this hypothesis, isolated and cannulated rat cremaster arterioles were exposed to dithiothreitol (DTT) to activate endogenous transglutaminases. DTT induced concentration-dependent vasoconstriction that was suppressed by coincubation with cystamine or cytochalasin-D to inhibit tranglutaminase activity or actin polymerization, respectively. Prolonged (4 h) exposure to DTT caused arteriolar inward remodeling that was also blocked by the presence of cystamine or cytochalasin-D. DTT inwardly remodeled arterioles had reduced passive diameters, augmented wall thickness-to-lumen ratios and altered elastic characteristics that were reverted upon disruption of the actin cytoskeleton with mycalolide-B. In freshly isolated arterioles, exposure to mycalolide-B caused no changes in their passive diameters or their elastic characteristics. These results suggest that, in arterioles, the early stages of the inward remodeling process induced by prolonged endogenous transglutaminase activation require actin dynamics and depend on changes in actin cytoskeletal structures.

Knockdown of embryonic myosin heavy chain reveals an essential role in the morphology and function of the developing heart.

The expression and function of embryonic myosin heavy chain (eMYH) has not been investigated within the early developing heart. This is despite the knowledge that other structural proteins, such as alpha and beta myosin heavy chains and cardiac alpha actin, play crucial roles in atrial septal development and cardiac function. Most cases of atrial septal defects and cardiomyopathy are not associated with a known causative gene, suggesting that further analysis into candidate genes is required. Expression studies localised eMYH in the developing chick heart. eMYH knockdown was achieved using morpholinos in a temporal manner and functional studies were carried out using electrical and calcium signalling methodologies. Knockdown in the early embryo led to abnormal atrial septal development and heart enlargement. Intriguingly, action potentials of the eMYH knockdown hearts were abnormal in comparison with the alpha and beta myosin heavy chain knockdowns and controls. Although myofibrillogenesis appeared normal, in knockdown hearts the tissue integrity was affected owing to apparent focal points of myocyte loss and an increase in cell death. An expression profile of human skeletal myosin heavy chain genes suggests that human myosin heavy chain 3 is the functional homologue of the chick eMYH gene. These data provide compelling evidence that eMYH plays a crucial role in important processes in the early developing heart and, hence, is a candidate causative gene for atrial septal defects and cardiomyopathy.

Dietary NMN supplementation enhances motor and NMJ function in ALS.

Amyotrophic lateral sclerosis (ALS) is an adult-onset neurodegenerative disease that causes the degeneration of motor neurons in the motor cortex and spinal cord. Patients with ALS experience muscle weakness and atrophy in the limbs which eventually leads to paralysis and death. NAD+ is critical for energy metabolism, such as glycolysis and oxidative phosphorylation, but is also involved in non-metabolic cellular reactions. In the current study, we determined whether the supplementation of nicotinamide mononucleotide (NMN), an NAD+ precursor, in the diet had beneficial impacts on disease progression using a SOD1G93A mouse model of ALS. We found that the ALS mice fed with an NMN-supplemented diet (ALS+NMN mice) had modestly extended lifespan and exhibited delayed motor dysfunction. Using electrophysiology, we studied the effect of NMN on synaptic transmission at neuromuscular junctions (NMJs) in symptomatic of ALS mice (18 weeks old). ALS+NMN mice had larger end-plate potential (EPP) amplitudes and maintained better responses than ALS mice, and also had restored EPP facilitation. While quantal content was not affected by NMN, miniature EPP (mEPP) amplitude and frequency were elevated in ALS+NMN mice. NMN supplementation in diet also improved NMJ morphology, innervation, mitochondrial structure, and reduced reactive astrogliosis in the ventral horn of the lumbar spinal cord. Overall, our results indicate that dietary consumption of NMN can slow motor impairment, enhance NMJ function and improve healthspan of ALS mice.

Study of erythrocyte sedimentation in human blood through the photoacoustic signals analysis.

Introduction: In this study, we utilized the pulsed photoacoustic (PA) technique to analyze globular sedimentation in whole human blood, with a focus on distinguishing between healthy individuals and those with hemolytic anemia. Methods: Blood samples were collected from both healthy individuals (women and men) and those with hemolytic anemia, and temporal and spectral parameters of PA signals were employed for analysis. Results: Significant differences (p < 0.05) were observed in PA metrics between the two groups. The proposed spectral analysis allowed significant differentiation within a 25-minute measurement window. Anemic blood samples exhibited higher erythrocyte sedimentation rate (ESR) values, indicating increased erythrocyte aggregation. Discussion: This study underscores the potential of PA signal analysis in ESR assessment as an efficient method for distinguishing between healthy and anemic blood, surpassing traditional approaches. It represents a promising contribution to the development of precise and sensitive techniques for analyzing human blood samples in clinical settings.

Purposefully Designed Surfactants for Facile and Controllable Gold Colloidal Nanocrystal Synthesis.

Three new cationic surfactants-N-cetyl-bis(2-dimethylaminoethyl)ether bromide (CBDEB), N-dodecyl-bis(2-dimethylaminoethyl)ether bromide (DBDEB), and N-hexyl-bis(2-dimethylaminoethyl)ether bromide (HBDEB)-have been designed herein using a simple and tailorable synthesis route. CBDEB and DBDEB, the 16- and 12-carbon chain surfactants, demonstrate facile, rapid, and controllable aqueous syntheses of gold nanoparticles (AuNPs) as dual-action reducing and capping agents. The synthesis strategy, using only surfactant and HAuCl4 salt, and 4 min of heating at 80 °C, results in spherical AuNPs (average diameters of 13.4 ± 3.8 nm for CBDEB and 12.0 ± 3.8 nm for DBDEB). Microwave irradiation was also investigated as a heating method and produces AuNPs in as little as 30 s. Control over the size and shape of AuNPs was proven to be feasible (toward populations of Euclidean shapes) by appropriately tuning reaction parameters, such as the molar ratio of surfactant to Au3+, temperature, incorporation of a time delay before heating, or shape control agents, such as Cu2+. Frustratingly, the cytotoxicity of CBDEB is similar to that of cetyltrimethylammonium bromide (CTAB), a popular 16-carbon chain cationic surfactant. Notably, while the shorter HBDEB (6-carbon chain) does not produce AuNPs under the applied conditions, it does appear to improve cell viability upon cytotoxicity evaluation and may be favorable as a new biological surfactant.

Frequency-dependent modes of synaptic vesicle endocytosis and exocytosis at adult mouse neuromuscular junctions.

During locomotion, adult rodent lumbar motoneurons fire in high-frequency (80-100 Hz) 1-2 s bursts every several seconds, releasing between 10,000 and 20,000 vesicles per burst. The estimated total vesicle pool size indicates that all vesicles would be used within 30 s; thus, a mechanism for rapid endocytosis and vesicle recycling is necessary to maintain effective transmission and motor behavior. However, whether such rapid recycling exists at mouse neuromuscular junctions (NMJs) or how it is regulated has been unclear. Here, we show that much less FM1-43 dye is lost per stimulus with 100 Hz stimulation than with 10 Hz stimulation even when the same number of vesicles undergo exocytosis. Electrophysiological data using folimycin show this lesser amount of dye loss is caused in part by the rapid reuse of vesicles. We showed previously that a myosin light chain kinase (MLCK)-myosin II pathway was required for effective transmission at 100 Hz. Here, we confirm the activation of MLCK, based on increased nerve terminal phospho-MLC immunostaining, with 100 Hz but not with 10 Hz stimulation. We further demonstrate that activation of MLCK, by increased extracellular Ca(2+), by PKC (protein kinase C) activation, or by a MLCK agonist peptide, reduces the amount of dye lost even with 10 Hz stimulation. MLCK activation at 10 Hz also resulted in more vesicles being rapidly reused. Thus, MLCK activation by 100 Hz stimulation switches the mechanism of vesicle cycling to a rapid-reuse mode and is required to sustain effective transmission in adult mouse NMJs.

Confeito-like assembly of organosilicate-caged fluorophores: ultrabright suprananoparticles for fluorescence imaging.

We report ultrabright, photostable, sub-25 nm nanoparticle agglomerates (suprananoparticles) assembled from a few hundred 3.3 ± 0.9 nm units, each hosting on average a single rhodamine 6G (Rh6G) dye molecule encased in a thin organosilicate cage. These individual Rh6G-doped nanoparticle (DOSNP) units consist of a hydrophobic core containing the dye and an ultrathin, conformal silicate shell modified by CO(2) plasma to confer a beneficial 'cage effect' as well as surface hydrophilicity. The isolation of the dye within individual DOSNP units in the final 22 ± 5 nm agglomerate avoids dimerization and related spontaneous molecular interactions that otherwise lead to self-quenching in closely co-localized fluorophores. The resulting suprananoparticles are over 200 times brighter than the free Rh6G molecules in the same volume. There is no observable dye leaching, and the labels are 20-fold more resistant to photobleaching than free Rh6G in solution. We demonstrate the attractive features of DOSNPs as labels in bioimaging applications.

Plasmon-controlled shaping of gold nanostar photothermal therapy agents.

Tunable gold nanostars were synthesized through the reduction of gold salt by an aminosugar, N-methyl-D-glucamine, in a seed-less route. The nanoparticle morphology and size were facilely tuned through adjustments in reaction pH and LED light-mediated synthesis. The materials demonstrated low inherent cytotoxicity and high potential for photothermal therapy.

Arrhythmogenesis in the aged heart following ischaemia-reperfusion: role of transient receptor potential vanilloid 4.

AIMS: Cardiomyocyte Ca2+ homoeostasis is altered with ageing and predisposes the heart to Ca2+ intolerance and arrhythmia. Transient receptor potential vanilloid 4 (TRPV4) is an osmotically activated cation channel with expression in cardiomyocytes of the aged heart. The objective of this study was to examine the role of TRPV4 in Ca2+ handling and arrhythmogenesis following ischaemia-reperfusion (I/R), a pathological scenario associated with osmotic stress. METHODS AND RESULTS: Cardiomyocyte membrane potential was monitored prior to and following I/R in Langendorff-perfused hearts of Aged (19-28 months) male and female C57BL/6 mice ± TRPV4 inhibition (1 µM HC067047, HC). Diastolic resting membrane potential was similar between Aged and Aged HC at baseline, but following I/R Aged exhibited depolarized diastolic membrane potential vs. Aged HC. The effects of TRPV4 on cardiomyocyte Ca2+ signalling following I/R were examined in isolated hearts of Aged cardiac-specific GCaMP6f mice (±HC) using high-speed confocal fluorescence microscopy, with cardiomyocytes of Aged exhibiting an increased incidence of pro-arrhythmic Ca2+ signalling vs. Aged HC. In the isolated cell environment, cardiomyocytes of Aged responded to sustained hypoosmotic stress (250mOsm) with an increase in Ca2+ transient amplitude (fluo-4) and higher incidence of pro-arrhythmic diastolic Ca2+ signals vs. Aged HC. Intracardiac electrocardiogram measurements in isolated hearts following I/R revealed an increased arrhythmia incidence, an accelerated time to ventricular arrhythmia, and increased arrhythmia score in Aged vs. Aged HC. Aged exhibited depolarized resting membrane potential, increased pro-arrhythmic diastolic Ca2+ signalling, and greater incidence of arrhythmia when compared with Young (3-5 months). CONCLUSION: TRPV4 contributes to pro-arrhythmic cardiomyocyte Ca2+ signalling, electrophysiological abnormalities, and ventricular arrhythmia in the aged mouse heart.

Laser-induced sound pinging for the rapid determination of total sugar or sweetener content in commercial beverages.

We recently reported on fixed-path length laser-induced sound pinging (FPL-LISP) as a rapid photoacoustic technique employing an inexpensive benchtop tattoo-removal laser for reliably determining the speed of sound in low-volume fluids. In this contribution, we demonstrate the capacity of FPL-LISP to analyze representative commercial beverages for their natural or artificial sweetener contents. As a benchmark, the speed of sound was determined for solutions of sugars (glucose, fructose, sucrose), mock high fructose corn syrup (HFCS-55), and 12 household sweeteners (culinary sugars, syrups, honey, molasses) across the concentration range of 1-20% w/v in water, simulating the typical sweetener range found in commercial soft drinks. The setup was then employed to estimate sweetener contents of 26 popular commercial beverages using the HFCS-55 standard curve as a training data set. Our results are remarkably consistent with the label values for these representative commercial beverages, in spite of the fact that some beverages clearly employ a sweetener other than HFCS-55 or a proprietary blend, suggesting the excellent potential of the FPL-LISP setup as a quick screening tool well-suited to quality control and real-time assessment in the beverage and fermentation industrial sectors. The proposed approach represents a significant improvement over many existing methods on the basis of measurement time (down to 1 s, which can be considered real time for many applications), lenient sample requirements (tens of microliters to 1 mL), robust and user-friendly analysis, practical considerations (e.g., economical, minimal service and maintenance concerns), and prospects for advancing both online monitoring and fully portable versions of this instrumentation.

A comparative evaluation of microarray slides as substrates for the development of protease assay biosensors.

The application of commercially available microarray slides as substrates for fluorogenic protease assays has been explored in terms of binding efficiency, stability, and activity. A fluorescent, biotinylated substrate for botulinum neurotoxin A (BoNTA) was attached via self-assembled monolayer of Streptavidin to amine-reactive aldehyde, epoxy, hydrogel, and polymer slides. Nexterion Slide P® was found to have optimal protein binding efficiency and stability of the slides examined. Addition of glycerol to the printing buffer improved spot morphology significantly and polyvinylpyrrolidone provided long-term stability, allowing chips to be stored for up to 1 month with good viability. Detection of a recombinant BoNTA light chain was then carried out at 37°C and a sub-lethal dose was detected in 2 hours.

Characterization of rhythmic Ca2+ transients in early embryonic chick motoneurons: Ca2+ sources and effects of altered activation of transmitter receptors.

In the nervous system, spontaneous Ca(2+) transients play important roles in many developmental processes. We previously found that altering the frequency of electrically recorded rhythmic spontaneous bursting episodes in embryonic chick spinal cords differentially perturbed the two main pathfinding decisions made by motoneurons, dorsal-ventral and pool-specific, depending on the sign of the frequency alteration. Here, we characterized the Ca(2+) transients associated with these bursts and showed that at early stages while motoneurons are still migrating and extending axons to the base of the limb bud, they display spontaneous, highly rhythmic, and synchronized Ca(2+) transients. Some precursor cells in the ependymal layer displayed similar transients. T-type Ca(2+) channels and a persistent Na(+) current were essential to initiate spontaneous bursts and associated transients. However, subsequent propagation of activity throughout the cord resulted from network-driven chemical transmission mediated presynaptically by Ca(2+) entry through N-type Ca(2+) channels and postsynaptically by acetylcholine acting on nicotinic receptors. The increased [Ca(2+)](i) during transients depended primarily on L-type and T-type channels with a modest contribution from TRP (transient receptor potential) channels and ryanodine-sensitive internal stores. Significantly, the drugs used previously to produce pathfinding errors altered transient frequency but not duration or amplitude. These observations imply that different transient frequencies may differentially modulate motoneuron pathfinding. However, the duration of the Ca(2+) transients differed significantly between pools, potentially enabling additional distinct pool-specific downstream signaling. Many early events in spinal motor circuit formation are thus potentially sensitive to the rhythmic Ca(2+) transients we have characterized and to any drugs that perturb them.

Detection of melanoma cells in vitro using an optical detector of photoacoustic waves.

BACKGROUND AND OBJECTIVE: Circulating tumor cells have been shown to correlate positively with metastatic disease state in patients with advanced cancer. We have demonstrated the ability to detect melanoma cells in a flow system by generating and detecting photoacoustic waves in melanoma cells. This method is similar to flow cytometry, although using photoacoustics rather than fluorescence. Previously, we used piezoelectric films as our acoustic sensors. However, such films have indicated false-positive signals due to unwanted direct interactions between photons from the high laser fluence in the flow system and the film itself. We have adapted an optical detection scheme that obviates the need for piezoelectric films. STUDY DESIGN/MATERIALS AND METHODS: Our photoacoustic system comprised a tunable laser system with an output of 410-710 nm with a pulse duration of 5 nanoseconds. The light was delivered by optical fiber to a glass microcuvette that contained saline buffer suspensions of melanoma and white blood cells. We used a continuous HeNe laser to provide a probe beam that reflected off of a glass and water interface in close proximity to the microcuvette. The beam was detected by a high-speed photodiode. When a photoacoustic wave was generated in the microcuvette, the wave propagated and changed the reflectance of the beam due to index of refraction change in the water. This perturbation was used to detect the presence of melanoma cells. RESULTS: We determined a detection threshold of about one individual melanoma cell with no pyroelectric noise indicated in the signals. CONCLUSIONS: The optical reflectance method provides sensitivity to detect small numbers of melanoma cells without created false-positive signals from pyroelectric interference, showing promise as a means to perform tests for circulating melanoma cells in blood samples.

Quantitative Photoacoustic Method for the Measurement of Absorption Coefficients of Highly Absorbing Samples.

In this study, we present a quantitative photoacoustic (PA) method for performing absorption measurements on highly absorbing samples. Based on the thermoelastic mechanism, the relative changes in PA signal amplitude allowed the determination of absorption coefficients of materials in the 0.19-2500-cm-1 range, with no prior knowledge of the material's optoacoustic properties required. We have tested our new methodology by performing absorption measurements on a series of planar liquid samples as well as gelatinized spherical samples. In this approach, laser-induced ultrasound waves were detected in transmission mode. With the model presented herein and a measurement of the relative change in amplitude of the PA signal at two different known concentrations, the absorption coefficient of the sample can be straightforwardly extracted. Three important advantages are highlighted by this analytical approach. First, no previous knowledge of the optical or acoustic properties of the sample is necessary. Second, only a small quantity of sample is required. Finally, our methodology includes both short- and long-pulse regimes, validating its use for any laser pulse duration so long as the requirement for thermal confinement is fulfilled. Remarkably, this new methodology performs best for thick, highly absorbing samples where traditional spectrophotometry is most challenging and unreliable, offering a promising alternative for quantification of the absorption properties of a range of diverse liquid, and gelatinous-state materials not amenable to conventional methods.

The effect of NAMPT deletion in projection neurons on the function and structure of neuromuscular junction (NMJ) in mice.

Nicotinamide adenine dinucleotide (NAD+) plays a critical role in energy metabolism and bioenergetic homeostasis. Most NAD+ in mammalian cells is synthesized via the NAD+ salvage pathway, where nicotinamide phosphoribosyltransferase (NAMPT) is the rate-limiting enzyme, converting nicotinamide into nicotinamide mononucleotide (NMN). Using a Thy1-Nampt-/- projection neuron conditional knockout (cKO) mouse, we studied the impact of NAMPT on synaptic vesicle cycling in the neuromuscular junction (NMJ), end-plate structure of NMJs and muscle contractility of semitendinosus muscles. Loss of NAMPT impaired synaptic vesicle endocytosis/exocytosis in the NMJs. The cKO mice also had motor endplates with significantly reduced area and thickness. When the cKO mice were treated with NMN, vesicle endocytosis/exocytosis was improved and endplate morphology was restored. Electrical stimulation induced muscle contraction was significantly impacted in the cKO mice in a frequency dependent manner. The cKO mice were unresponsive to high frequency stimulation (100 Hz), while the NMN-treated cKO mice responded similarly to the control mice. Transmission electron microscopy (TEM) revealed sarcomere misalignment and changes to mitochondrial morphology in the cKO mice, with NMN treatment restoring sarcomere alignment but not mitochondrial morphology. This study demonstrates that neuronal NAMPT is important for pre-/post-synaptic NMJ function, and maintaining skeletal muscular function and structure.