Publications by authors named "Thomas J Pohida"

The tumor microenvironment consists of resident tumor cells organized within a compositionally diverse, three-dimensional (3D) extracellular matrix (ECM) network that cannot be replicated in vitro using bottom-up synthesis. We report a new self-assembly system to engineer ECM-rich 3D MatriSpheres wherein tumor cells actively organize and concentrate microgram quantities of decellularized ECM dispersions which modulate cell phenotype. 3D colorectal cancer (CRC) MatriSpheres were created using decellularized small intestine submucosa (SIS) as an orthotopic ECM source that had greater proteomic homology to CRC tumor ECM than traditional ECM formulations such as Matrigel.

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Non-mammalian model organisms have been essential for our understanding of the mechanisms that control development, disease, and physiology, but they are underutilized in pharmacological and toxicological phenotypic screening assays due to their low throughput in comparison with cell-based screens. To increase the utility of using Drosophila melanogaster in screening, we designed the Whole Animal Feeding FLat (WAFFL), a novel, flexible, and complete system for feeding, monitoring, and assaying flies in a high-throughput format. Our 3D printed system is compatible with inexpensive and readily available, commercial 96-well plate consumables and equipment.

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Commonly used monolayer cancer cell cultures fail to provide a physiologically relevant environment in terms of oxygen delivery. Here, we describe a three-dimensional (3D) bioreactor system where cancer cells are grown in Matrigel in modified six-well plates. Oxygen is delivered to the cultures through a polydimethylsiloxane (PDMS) membrane at the bottom of the wells, with microfabricated PDMS pillars to control oxygen delivery.

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Article Synopsis
  • The study focuses on the use of 3D-printed centerpieces for analytical ultracentrifugation, highlighting their ability to hold samples while enabling accurate macromolecular migration under high centrifugal forces.
  • Researchers demonstrate that these 3D-printed centerpieces are durable, reusable, and can produce data comparable to traditional epoxy resin centerpieces, making them a cost-effective alternative.
  • The paper introduces innovative centerpiece designs that improve experimental efficiency, such as designs that reduce sample volume, minimize optical aberrations, and increase sample capacity, all while maintaining high-quality results.
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Background: Naturalistic driving studies, designed to objectively assess driving behavior and outcomes, are conducted by equipping vehicles with dedicated instrumentation (eg, accelerometers, gyroscopes, Global Positioning System, and cameras) that provide continuous recording of acceleration, location, videos, and still images for eventual retrieval and analyses. However, this research is limited by several factors: the cost of equipment installation; management and storage of the large amounts of data collected; and data reduction, coding, and analyses. Modern smartphone technology includes accelerometers built into phones, and the vast, global proliferation of smartphones could provide a possible low-cost alternative for assessing kinematic risky driving.

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  • The paper discusses the importance of hemodynamic recording during interventional cardiovascular procedures and the challenges posed by electromagnetic interference (EMI) in MRI environments.
  • It outlines the development of a new system designed to minimize EMI effects on electrocardiogram (ECG) and invasive blood pressure (IBP) signals using MRI-compatible equipment and adaptive signal processing techniques.
  • Results showed an impressive 80% reduction in peak noise and the elimination of false QRS triggers during real-time MRI scanning in pediatric patients, paving the way for better high-fidelity recordings in MRI-guided procedures.
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Analytical ultracentrifugation (AUC) is a classical technique of physical biochemistry providing information on size, shape, and interactions of macromolecules from the analysis of their migration in centrifugal fields while free in solution. A key mechanical element in AUC is the centerpiece, a component of the sample cell assembly that is mounted between the optical windows to allow imaging and to seal the sample solution column against high vacuum while exposed to gravitational forces in excess of 300,000 g. For sedimentation velocity it needs to be precisely sector-shaped to allow unimpeded radial macromolecular migration.

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  • Sentinel lymph node biopsy is a common procedure in breast cancer surgery, and there's a need for quicker methods to identify cancer spread.
  • A new fluorescent method was tested, using a dye to identify breast cancer cells in lymph nodes from 38 patients, showing promising results.
  • The method demonstrated high sensitivity (97%), good specificity (79%), and an excellent negative predictive value (99%), indicating it could help surgeons make faster and more accurate decisions during operations.
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  • Researchers developed gGlu-HMRG as a fluorescent probe to detect live cancer cells by utilizing the overexpression of the enzyme GGT in cancer versus normal tissue.
  • In a study, they tested this probe during breast-conserving surgery and found it could distinguish tumors as small as 1 mm with 92% sensitivity and 94% specificity in just 5 minutes.
  • The method is considered a significant advancement in quickly and affordably assessing surgical margins to ensure all cancerous tissue is removed.
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The System for Continuous Observation of Rodents in Home-cage Environment (SCORHE) was developed to demonstrate the viability of compact and scalable designs for quantifying activity levels and behavior patterns for mice housed within a commercial ventilated cage rack. The SCORHE in-rack design provides day- and night-time monitoring with the consistency and convenience of the home-cage environment. The dual-video camera custom hardware design makes efficient use of space, does not require home-cage modification, and is animal-facility user-friendly.

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Modeling tumor growth in vitro is essential for cost-effective testing of hypotheses in preclinical cancer research. 3-D cell culture offers an improvement over monolayer culture for studying cellular processes in cancer biology because of the preservation of cell-cell and cell-ECM interactions. Oxygen transport poses a major barrier to mimicking in vivo environments and is not replicated in conventional cell culture systems.

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  • A prototype positron projection imager (PPI) was developed to visualize the biodistribution of positron-emitting compounds in small animals, particularly mice, and will be integrated into a dual-gamma camera system for flexible imaging options.
  • The imaging setup involves placing a mouse between two identical LYSO arrays to record positron-decay events, with performance tested using various positron-emitting compounds.
  • Performance results showed good imaging quality, with clear visualization of compounds like [(18)F] FDG, suggesting the PPI's potential utility in early drug development stages by providing essential biodistribution data.
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When conducting optical imaging experiments, in vivo, the signal to noise ratio and effective spatial and temporal resolution is fundamentally limited by physiological motion of the tissue. A three-dimensional (3D) motion tracking scheme, using a multiphoton excitation microscope with a resonant galvanometer, (512 × 512 pixels at 33 frames s(-1)) is described to overcome physiological motion, in vivo. The use of commercially available graphical processing units permitted the rapid 3D cross-correlation of sequential volumes to detect displacements and adjust tissue position to track motions in near real-time.

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Over the past 15 years, laser-based microdissection has improved the precision by which scientists can procure cells of interest from a heterogeneous tissue section. However, for studies that require a large amount of material (e.g.

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Laser-based microdissection facilitates the isolation of specific cell populations from clinical or animal model tissue specimens for molecular analysis. Expression microdissection (xMD) is a second-generation technology that offers considerable advantages in dissection capabilities; however, until recently the method has not been accessible to investigators. This protocol describes the adaptation of xMD to commonly used laser microdissection instruments and to a commercially available handheld laser device in order to make the technique widely available to the biomedical research community.

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Article Synopsis
  • The study aims to address challenges in testing novel optical probes on human specimens in the operating room, where tissue removal poses regulatory and privacy issues.
  • A portable benchtop fluorescence camera was developed and tested using a mouse model of ovarian cancer, demonstrating its effectiveness against standard imaging systems.
  • The results indicate that the compact camera can successfully produce comparable imaging, allowing for immediate testing of excised tissues in the operating room, which could speed up the development of new imaging probes.
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  • A new portable dual-gamma camera system called "MONICA" is designed for visualizing and analyzing the distribution of radiotracers in small animals, particularly mice.
  • The system features two miniature gamma cameras that allow for direct imaging of the mice placed on a tabletop, and its performance was validated through testing and a detailed study over a week.
  • Results indicate that MONICA is effective for whole-body imaging in mice, which may aid early drug development by providing crucial biodistribution data in a space-efficient manner.
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  • A unique high-speed optical multichannel spectrometer was created at NIH and detailed in a 1997 journal article, allowing researchers to track entire time courses using a single sample.
  • It has been utilized to explore rapid kinetic processes like the bacteriorhodopsin photocycle and electron transport in cellular respiration.
  • The latest version features significant improvements for kinetic studies, showcased by measuring proton flow alongside optical steps of the photocycle to link molecular changes to proton movements.
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  • A rapid field scan method using high frequency sweep fields on a main Zeeman field enables direct detection of signals without needing low-frequency modulation.
  • This technique, combined with rotating field gradients, allows for fast continuous wave (CW) EPR imaging, rivaling the speed of pulsed Fourier Transform (FT) EPR imaging.
  • The approach maximizes spatial encoding and improves temporal resolution, making it useful for studying spin dynamics, drug behavior, and dynamic imaging applications.
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The application of direct time-locked subsampling (TLSS) to Fourier transform electron paramagnetic resonance (FT-EPR) spectroscopy at radio frequencies (rf) is described. With conventional FT-EPR spectroscopy, the high Larmor frequencies (L(f)) often necessitate the use of intermediate frequency (IF) stages to down convert the received free induction decay (FID) signal to a frequency that can be acquired with common data acquisition technology. However, our research focuses on in vivo studies, and consequently utilizes a FT-EPR system with a L(f) of 300 MHz.

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Background: A functional blood supply is essential for tumor growth and proliferation. However, the mechanism of blood vessel recruitment to the tumor is still poorly understood. Ideally, a thorough molecular assessment of blood vessel cells would be critical in our comprehension of this process.

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The integration of modern data acquisition and digital signal processing (DSP) technologies with Fourier transform electron paramagnetic resonance (FT-EPR) imaging at radiofrequencies (RF) is described. The FT-EPR system operates at a Larmor frequency (L(f)) of 300MHz to facilitate in vivo studies. This relatively low frequency L(f), in conjunction with our approximately 10MHz signal bandwidth, enables the use of direct free induction decay time-locked subsampling (TLSS).

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Tissue microdissection is an important method for the study of disease states. However, it is difficult to perform high-throughput molecular analysis with current techniques. We describe here a prototype version of a novel technique (expression microdissection) that allows for the procurement of desired cells via molecular targeting.

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Article Synopsis
  • The study introduces a new technique combining correlation spectroscopy with stochastic excitation and the Hadamard transform to enhance time-domain Fourier transform electron paramagnetic resonance (FT-EPR) spectroscopy at a radiofrequency of 300 MHz.
  • A pseudo-random pulse sequence generator was integrated into an existing EPR spectrometer to improve signal acquisition and processing, utilizing software to apply the Hadamard transform for better data analysis.
  • Results indicated a reduction in total acquisition time and improved signal-to-noise ratio, suggesting that this method could lower RF pulse power and expand applications like in vivo FT-EPR imaging of larger samples.
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