Things are not always what they seem: pacemaker dysfunction or just a technical limitation?

The precise roles of hypoxia in the initiation and progression of kidney disease remain unresolved. A major technical limitation has been the absence of methods allowing long-term measurement of kidney tissue oxygen tension (Po2) in unrestrained animals. We developed a telemetric method for the measurement of kidney tissue Po2 in unrestrained rats, using carbon paste electrodes (CPEs). After acute implantation in anesthetized rats, tissue Po2 measured by CPE-telemetry in the inner cortex and medulla was in close agreement with that provided by the “gold standard” Clark electrode. The CPE-telemetry system could detect small changes in renal tissue Po2 evoked by mild hypoxemia. In unanesthetized rats, CPE-telemetry provided stable measurements of medullary tissue Po2 over days 5− 19 after implantation. It also provided reproducible responses to systemic hypoxia and hyperoxia over this time period. There was little evidence of fibrosis or scarring after 3 wk of electrode implantation. However, because medullary Po2 measured by CPE-telemetry was greater than that documented from previous studies in anesthetized animals, this method is presently best suited for monitoring relative changes rather than absolute values. Nevertheless, this new technology provides, for the first time, the opportunity to examine the temporal relationships between tissue hypoxia and the progression of renal disease.

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Assessment of Stereoscopic Multi-resolution Images for a Virtual Reality System

International Journal of Virtual Reality ◽

10.20870/ijvr.2010.9.2.2769 ◽

2010 ◽

Vol 9 (2) ◽

pp. 31-37 ◽

Cited By ~ 1

Author(s):

Masahiko Ogawa ◽

Kazunori Shidoji ◽

Yuji Matsuki

Keyword(s):

High Resolution ◽

Field Of View ◽

Monitor System ◽

Wide Angle ◽

Camera System ◽

Technical Limitation ◽

Resolution Image ◽

The Gaze ◽

High Resolution Image ◽

Perceptual Characteristics

A camera and monitor system that projects actual real-world images has yet to be developed due to the technical limitation that the existing cameras cannot simultaneously acquire high-resolution and wide-angle images. In this research, we try to resolve this issue by superimposing images; a method which is effective because the entire wide-angle image does not necessarily need to be of high resolution because of perceptual characteristics of the human visual system. First, we examined the minimum resolution required for the field of view, which indicated that a triple-resolution image where positions more than 20 and 40 deg from the center of the visual field were decreased to 25% and approximately 11% of the resolution of the gaze point, respectively, was perceived as similar to a completely high-resolution image. Next, we investigated whether the participants could distinguish between the original completely high-resolution image and processed images, which included triple-resolution, dual-resolution, and low-resolution images. Our results suggested that the participants could not differentiate between the triple-resolution image and the original image. Finally, we developed a stereoscopic camera system based on our results

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Super-resolution shadow imaging reveals local remodeling of astrocytic microstructures and brain extracellular space after osmotic challenge

10.1101/2021.01.05.425369 ◽

2021 ◽

Author(s):

Misa Arizono ◽

V.V.G. Krishna Inavalli ◽

U. Valentin Nägerl

Keyword(s):

Brain Tissue ◽

Extracellular Space ◽

Temporal Dynamics ◽

Super Resolution ◽

Physical Contact ◽

Cellular Structures ◽

Technical Limitation ◽

Brain Physiology ◽

Shadow Imaging ◽

Osmotic Challenge

The extracellular space (ECS) plays a central role for brain physiology, shaping the time course and spread of neurochemicals, ions and nutrients that ensure proper brain homeostasis and neuronal communication. Astrocytes are the most abundant type of glia cell in the brain, whose processes densely infiltrate the brain’s parenchyma. As astrocytes are highly sensitive to changes in osmotic pressure, they are capable of exerting a potent physiological influence on the ECS.However, little is known about the spatial distribution and temporal dynamics of the ECS that surrounds astrocytes, owing mostly to a lack of appropriate techniques to visualize the ECS in live brain tissue. Mitigating this technical limitation, we applied the recent SUper-resolution SHadow Imaging technique (SUSHI) to astrocyte-labeled organotypic hippocampal brain slices, which allowed us to concurrently image the complex morphology of astrocytes and the ECS with nanoscale resolution in a live experimental setting.Focusing on ring-like astrocytic microstructures in the spongiform domain, we found them to enclose sizable pools of interstitial fluid and cellular structures like dendritic spines. Upon an experimental osmotic challenge, these microstructures remodeled and swelled up at the expense of the pools, effectively increasing the physical contact between astrocytic and cellular structures.Our study reveals novel facets of the dynamic microanatomical relationships between astrocytes, neuropil and the ECS in living brain tissue, which could be of functional relevance for neuronglia communication in a variety of (patho)physiological settings, e.g. LTP induction, epileptic seizures or acute ischemic stroke, where osmotic disturbances are known to occur.

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Adverse remodeling of cardiac cholinergic innervation and pacemaker dysfunction in Gαq overexpressing mice

The FASEB Journal ◽

10.1096/fasebj.21.6.a1263-c ◽

2007 ◽

Vol 21 (6) ◽

Author(s):

Donald B. Hoover ◽

Jennifer L. Hoard ◽

Abigail M. Mabe ◽

John C. Hancock ◽

Gianfrancesco Cormaci ◽

...

Keyword(s):

Cholinergic Innervation ◽

Adverse Remodeling ◽

Pacemaker Dysfunction

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The universe is a collection of self-driven mathematical entities; subjective consciousness is the use of mathematical models by a Turing machine

10.31219/osf.io/w964m ◽

2021 ◽

Author(s):

Xiaoyang Yu

Keyword(s):

Elementary Particle ◽

Turing Machine ◽

World Line ◽

Conscious Experience ◽

Physical Interaction ◽

External Observer ◽

Objective Reality ◽

Technical Limitation ◽

Subjective Reality ◽

The Universe

Humans are limited in what they know by the technical limitation of their cortical language network. A reality is a situation model. The universe is a collection of self-driven mathematical entities. If we are happy to accept randomness, it’s obviously possible that all other so-called “worlds” in the many-worlds interpretation don’t exist objectively. The so-called “physical interaction” (aka objective interaction) among any number of elementary particles is consistent with the so-called “physical law”. From the viewpoint of an imagined external observer (who is located somewhere outside of all worlds), in all worlds, every self-driven elementary particle is changing its state to match its fated state, together form a single fated self-driven state machine; the so-called “subjective reality” (aka the so-called “subjective conscious experience”) is actually the use of a mathematical model (MM) by a Turing machine (TM). The so-called “subjective reality” shouldn’t be able to alter/impact the fated world line of any elementary particle within this world. Except one objective MM which is a fitted MM of the objective reality, every other causality is not an objective MM but a Granger causality, and is an under-fitted MM of the objective reality.

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Development of automated annotation software for human embryo morphokinetics

Human Reproduction ◽

10.1093/humrep/deaa001 ◽

2020 ◽

Vol 35 (3) ◽

pp. 557-564 ◽

Cited By ~ 2

Author(s):

M Feyeux ◽

A Reignier ◽

M Mocaer ◽

J Lammers ◽

D Meistermann ◽

...

Keyword(s):

Human Embryo ◽

Embryo Quality ◽

Selection Criterion ◽

Time Lapse ◽

Manual Annotation ◽

Annotation Tool ◽

High Throughput Analysis ◽

Technical Limitation ◽

Automated Annotation ◽

Morphokinetic Parameters

Abstract STUDY QUESTION Is it possible to develop an automated annotation tool for human embryo development in time-lapse devices based on image analysis? SUMMARY ANSWER We developed and validated an automated software for the annotation of human embryo morphokinetic parameters, having a good concordance with expert manual annotation on 701 time-lapse videos. WHAT IS KNOWN ALREADY Morphokinetic parameters obtained with time-lapse devices are increasingly used for the assessment of human embryo quality. However, their annotation is time-consuming and can be slightly operator-dependent, highlighting the need to develop fully automated approaches. STUDY DESIGN, SIZE, DURATION This monocentric study was conducted on 701 videos originating from 584 couples undergoing IVF with embryo culture in a time-lapse device. The only selection criterion was that the duration of the video must be over 60 h. PARTICIPANTS/MATERIALS, SETTING, METHODS An automated morphokinetic annotation tool was developed based on gray level coefficient of variation and detection of the thickness of the zona pellucida. The detection of cellular events obtained with the automated tool was compared with those obtained manually by trained experts in clinical settings. MAIN RESULTS AND THE ROLE OF CHANCE Although some differences were found when embryos were considered individually, we found an overall concordance between automated and manual annotation of human embryo morphokinetics from fertilization to expanded blastocyst stage (r2 = 0.92). LIMITATIONS, REASONS FOR CAUTION These results should undergo multicentric external evaluation in order to test the overall performance of the annotation tool. Getting access to the export of 3D videos would enhance the quality of the correlation with the same algorithm and its extension to the 3D regions of interest. A technical limitation of our work lies within the duration of the video. The more embryo stages the video contains, the more information the script has to identify them correctly. WIDER IMPLICATIONS OF THE FINDINGS Our system paves the way for high-throughput analysis of multicentric morphokinetic databases, providing new insights into the clinical value of morphokinetics as a predictor of embryo quality and implantation. STUDY FUNDING/COMPETING INTEREST(S) This study was partly funded by Finox-Gedeon Richter Forward Grant 2016 and NeXT (ANR-16-IDEX-0007). We have no conflict of interests to declare. TRIAL REGISTRATION NUMBER N/A

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Balloon-based measuring system for compliance investigations

Current Directions in Biomedical Engineering ◽

10.1515/cdbme-2018-0129 ◽

2018 ◽

Vol 4 (1) ◽

pp. 539-542

Author(s):

Wolfram Schmidt ◽

Carsten Tautorat ◽

Kerstin Schümann ◽

Peter Behrens ◽

Niels Grabow ◽

...

Keyword(s):

Balloon Catheter ◽

Measuring System ◽

Lumen Area ◽

Cross Sectional ◽

Technical Limitation ◽

Elastic Tubes ◽

Starting Point ◽

Volume Relationship ◽

Pressure Volume Relationship ◽

Working Principle

AbstractFor the development of new stent designs, the compliance of the surrounding biological tissue has to be considered. We expect to obtain parameters for simulation, stent dimensioning, and the forces acting on the stent after implantation. Starting point of the investigations is the commercially available Metricath system allowing cross-sectional lumen area measurements of arteries. Its working principle is based on the pressure-volume relationship using a balloon catheter, which is inflated to a specific pressure of about 250 mmHg and conforms to the shape and size of the lumen. However, for compliance charts multiple pressure levels and a larger pressure range are needed. To overcome this technical limitation, the Metricath balloon catheter is combined with a new inflation device, called pV-Monitor. The presented cross-sectional lumen area measurements in rigid tubes and compliance investigations of elastic tubes demonstrate the feasibility of the pV-Monitor system.

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