Refractory Periods Observed by Intrinsic Signal and Fluorescent Dye Imaging

1998 ◽  
Vol 80 (3) ◽  
pp. 1522-1532 ◽  
Author(s):  
Andrew F. Cannestra ◽  
Nader Pouratian ◽  
Marc H. Shomer ◽  
Arthur W. Toga
Keyword(s):  
Fluorescent Dyes ◽  
Imaging Techniques ◽  
Human Subjects ◽  
Fluorescent Dye ◽  
Initial Stimulus ◽  
Intrinsic Signals ◽  
Intrinsic Signal ◽  
Refractory Periods ◽  
Auditory Cortices ◽  
The Relationship

Cannestra, Andrew F., Nader Pouratian, Marc H. Shomer, and Arthur W. Toga. Refractory periods observed by intrinsic signal and fluorescent dye imaging. J. Neurophysiol. 80: 1522–1532, 1998. All perfusion-based imaging modalities depend on the relationship between neuronal and vascular activity. However, the relationship between stimulus and response was never fully characterized. With the use of optical imaging (intrinsic signals and intravascular fluorescent dyes) during repetitive stimulation paradigms, we observed reduced responses with temporally close stimuli. Cortical evoked potentials, however, did not produce the same reduced responsiveness. We therefore termed these intervals of reduced responsiveness “refractory periods.” During these refractory periods an ability to respond was retained, but at a near 60% reduction in the initial magnitude. Although increasing the initial stimulus duration lengthened the observed refractory periods, significantly novel or temporally spaced stimuli overcame them. We observed this phenomenon in both rodent and human subjects in somatosensory and auditory cortices. These results have significant implications for understanding the capacities, mechanisms, and distributions of neurovascular coupling and thereby possess relevance to all perfusion-dependent functional imaging techniques.

scholarly journals Surgical Advances in Osteosarcoma

Cancers ◽  
2021 ◽  
Vol 13 (3) ◽  
pp. 388
Author(s):  
Marcus J. Brookes ◽  
Corey D. Chan ◽  
Bence Baljer ◽  
Sachin Wimalagunaratna ◽  
Timothy P. Crowley ◽  
...  
Keyword(s):  
Fluorescent Dyes ◽  
Imaging Techniques ◽  
Intraoperative Imaging ◽  
Survival Rates ◽  
Computer Navigation ◽  
Bone Cancer ◽  
Technical Difficulty ◽  
Implant Design ◽  
Patient Specific ◽  
Patient Specific Instruments

Osteosarcoma (OS) is the most common primary bone cancer in children and, unfortunately, is associated with poor survival rates. OS most commonly arises around the knee joint, and was traditionally treated with amputation until surgeons began to favour limb-preserving surgery in the 1990s. Whilst improving functional outcomes, this was not without problems, such as implant failure and limb length discrepancies. OS can also arise in areas such as the pelvis, spine, head, and neck, which creates additional technical difficulty given the anatomical complexity of the areas. We reviewed the literature and summarised the recent advances in OS surgery. Improvements have been made in many areas; developments in pre-operative imaging technology have allowed improved planning, whilst the ongoing development of intraoperative imaging techniques, such as fluorescent dyes, offer the possibility of improved surgical margins. Technological developments, such as computer navigation, patient specific instruments, and improved implant design similarly provide the opportunity to improve patient outcomes. Going forward, there are a number of promising avenues currently being pursued, such as targeted fluorescent dyes, robotics, and augmented reality, which bring the prospect of improving these outcomes further.

scholarly journals Recent advances in applications of multimodal ultrasound-guided photoacoustic imaging technology

2020 ◽  
Vol 3 (1) ◽  
Author(s):  
Shanshan Wang ◽  
Yunfeng Zhao ◽  
Ye Xu
Keyword(s):  
Near Infrared ◽  
Photoacoustic Imaging ◽  
Imaging Techniques ◽  
Color Doppler ◽  
Power Doppler ◽  
Infrared Region ◽  
Detection Methods ◽  
Imaging Mode ◽  
Nonlinear Imaging ◽  
The Relationship

Abstract Photoacoustic imaging (PAI) is often performed simultaneously with ultrasound imaging and can provide functional and cellular information regarding the tissues in the anatomical markers of the imaging. This paper describes in detail the basic principles of photoacoustic/ultrasound (PA/US) imaging and its application in recent years. It includes near-infrared-region PA, photothermal, photodynamic, and multimode imaging techniques. Particular attention is given to the relationship between PAI and ultrasonic imaging; the latest high-frequency PA/US imaging of small animals, which involves not only B-mode, but also color Doppler mode, power Doppler mode, and nonlinear imaging mode; the ultrasonic model combined with PAI, including the formation of multimodal imaging; the preclinical imaging methods; and the most effective detection methods for clinical research for the future.

Relationship between plasma osmolality and plasma vasopressin in human subjects

1980 ◽  
Vol 238 (4) ◽  
pp. E313-E317 ◽  
Author(s):  
M. Hammer ◽  
J. Ladefoged ◽  
K. Olgaard
Keyword(s):  
Linear Models ◽  
Human Subjects ◽  
Plasma Osmolality ◽  
Metabolic Clearance ◽  
Parabolic Model ◽  
Pronounced Increase ◽  
Plasma Vasopressin ◽  
Log Linear ◽  
The Relationship ◽  
Best Fit

The relationship between plasma osmolality (pOsm) and plasma vasopressin (pAVP) was studied in 13 human subjects during dehydration. The fit of linear, log-linear, parabolic, and exponential models was tested. For all of the data, the nonlinear models had the best fit. However, when individual differences in either gain or threshold were allowed for, the linear models were better than log-linear models. Finally, analyses were made with individual data points. Linear models had the best fit in half of the subjects, whereas for the others the parabolic model gave the best fit. For those subjects investigated in the low range of the osmoregulatory curve, a linear relationship was found, whereas, for those having the most pronounced increase in pOsm, the most significant improvement was found with the parabolic model. This finding indicates that the relationship is not stable during dehydration in the whole range and that hypovolemia probably can influence the secretion rate and/or metabolic clearance rate and thereby the relationship.

The looking/not looking dilemma

2009 ◽  
Vol 35 (4) ◽  
pp. 781-794 ◽  
Author(s):  
FRANK MÖLLER
Keyword(s):  
Human Subjects ◽  
Human Suffering ◽  
The Relationship

AbstractWhen confronted with images of war and other forms of human suffering, not looking is not an option, not only because we are permanently exposed to images but also because it would not seem to be a morally tenable position. However, looking at images of human suffering is often said to prolong this very suffering and to fix human subjects as victims. Especially when acts of violence have been committed in order to produce images of these very acts the relationship between viewing the images and participating in the acts of violence qua viewer appears to be uncomfortably close indeed. Thus, looking is not an option, either. This article, in the first part, engages with standard criticisms of photography, especially with accusations according to which photographs aestheticise that which they depict and desensitise their viewers. In the second part it discusses Alfredo Jaar's and Jeff Wall's work in order to show possible ways to circumvent the looking/not looking dilemma.

scholarly journals BDNF as a Biomarker of Cognition in Schizophrenia/Psychosis: An Updated Review

2021 ◽  
Vol 12 ◽  
Author(s):  
Rodrigo R. Nieto ◽  
Andrea Carrasco ◽  
Sebastian Corral ◽  
Rolando Castillo ◽  
Pablo A. Gaspar ◽  
...  
Keyword(s):  
Cognitive Function ◽  
High Risk ◽  
Human Subjects ◽  
Chronic Schizophrenia ◽  
Review Article ◽  
First Episode ◽  
Cognitive Symptoms ◽  
Research Gaps ◽  
Future Developments ◽  
The Relationship

Brain Derived Neurotrophic Factor (BDNF) has been linked to cognitive symptoms of schizophrenia, which has been documented in previous reviews by several authors. However, a trend has recently emerged in this field moving from studying schizophrenia as a disease to studying psychosis as a group. This review article focuses on recent BDNF studies in relation to cognition in human subjects during different stages of the psychotic process, including subjects at high risk of developing psychosis, patients at their first episode of psychosis, and patients with chronic schizophrenia. We aim to provide an update of BDNF as a biomarker of cognitive function on human subjects with schizophrenia or earlier stages of psychosis, covering new trends, controversies, current research gaps, and suggest potential future developments in the field. We found that most of current research regarding BDNF and cognitive symptoms in psychosis is done around schizophrenia as a disease. Therefore, it is necessary to expand the study of the relationship between BDNF and cognitive symptoms to psychotic illnesses of different stages and origins.

scholarly journals Determination of receptor occupancy in the presence of mass dose: [11C]GSK189254 PET imaging of histamine H3 receptor occupancy by PF-03654746

2016 ◽  
Vol 37 (3) ◽  
pp. 1095-1107 ◽  
Author(s):  
Jean-Dominique Gallezot ◽  
Beata Planeta ◽  
Nabeel Nabulsi ◽  
Donna Palumbo ◽  
Xiaoxi Li ◽  
...  
Keyword(s):  
Binding Sites ◽  
Human Subjects ◽  
Receptor Occupancy ◽  
Healthy Human ◽  
Positron Emission ◽  
Relationship Of ◽  
The Relationship ◽  
Pet Scans

Measurements of drug occupancies using positron emission tomography (PET) can be biased if the radioligand concentration exceeds “tracer” levels. Negative bias would also arise in successive PET scans if clearance of the radioligand is slow, resulting in a carryover effect. We developed a method to (1) estimate the in vivo dissociation constant Kd of a radioligand from PET studies displaying a non-tracer carryover (NTCO) effect and (2) correct the NTCO bias in occupancy studies taking into account the plasma concentration of the radioligand and its in vivo Kd. This method was applied in a study of healthy human subjects with the histamine H3 receptor radioligand [11C]GSK189254 to measure the PK-occupancy relationship of the H3 antagonist PF-03654746. From three test/retest studies, [11C]GSK189254 Kd was estimated to be 9.5 ± 5.9 pM. Oral administration of 0.1 to 4 mg of PF-03654746 resulted in occupancy estimates of 71%–97% and 30%–93% at 3 and 24 h post-drug, respectively. NTCO correction adjusted the occupancy estimates by 0%–15%. Analysis of the relationship between corrected occupancies and PF-03654746 plasma levels indicated that PF-03654746 can fully occupy H3 binding sites ( ROmax = 100%), and its IC50 was estimated to be 0.144 ± 0.010 ng/mL. The uncorrected IC50 was 26% higher.

How Neurons Communicate: Gap Junctions and Neurosecretion

The Neuron ◽  
2015 ◽  
pp. 153-186
Author(s):  
Irwin B. Levitan ◽  
Leonard K. Kaczmarek
Keyword(s):  
Synaptic Vesicles ◽  
Fluorescent Dyes ◽  
Imaging Techniques ◽  
Electrical Coupling ◽  
Snare Complex ◽  
Biologically Active ◽  
Nerve Terminals ◽  
Capacitance Measurements ◽  
Complex Process ◽  
Cytoplasmic Vesicles

Two ways that neurons communicate with one another are by direct electrical coupling and by the secretion of neurotransmitters. Electrical coupling arises from the existence of proteins, known as connexins, that form pores linking the cytoplasm of adjacent cells. Ions and small molecules can carry signals from one cell to another through these pores. Neurosecretion is a more complex process whereby different categories of molecules are sorted into cytoplasmic vesicles. Chemical processes within these vesicles ensure that they contain biologically active transmitters or hormones. SNARE complex proteins cooperate with other proteins to allow synaptic vesicles containing neurotransmitter to release their components into the external medium following calcium entry into nerve terminals. Such exocytosis of synaptic vesicles can be monitored with imaging techniques using fluorescent dyes or proteins, or by capacitance measurements. A second set of molecules retrieves the membrane of synaptic vesicles back from the plasma membrane through endocytosis.

scholarly journals Optical imaging of the intrinsic signal as a measure of cortical plasticity in the mouse

2005 ◽  
Vol 22 (5) ◽  
pp. 685-691 ◽  
Author(s):  
JIANHUA CANG ◽  
VALERY A. KALATSKY ◽  
SIEGRID LÖWEL ◽  
MICHAEL P. STRYKER
Keyword(s):  
Visual Cortex ◽  
Optical Imaging ◽  
Critical Period ◽  
Cortical Plasticity ◽  
Ocular Dominance ◽  
Screening Method ◽  
Intrinsic Signals ◽  
Intrinsic Signal ◽  
The Mean ◽  
Mouse Visual Cortex

The responses of cells in the visual cortex to stimulation of the two eyes changes dramatically following a period of monocular visual deprivation (MD) during a critical period in early life. This phenomenon, referred to as ocular dominance (OD) plasticity, is a widespread model for understanding cortical plasticity. In this study, we designed stimulus patterns and quantification methods to analyze OD in the mouse visual cortex using optical imaging of intrinsic signals. Using periodically drifting bars restricted to the binocular portion of the visual field, we obtained cortical maps for both contralateral (C) and ipsilateral (I) eyes and computed OD maps as (C − I)/(C + I). We defined the OD index (ODI) for individual animals as the mean of the OD map. The ODI obtained from an imaging session of less than 30 min gives reliable measures of OD for both normal and monocularly deprived mice under Nembutal anesthesia. Surprisingly, urethane anesthesia, which yields excellent topographic maps, did not produce consistent OD findings. Normal Nembutal-anesthetized mice have positive ODI (0.22 ± 0.01), confirming a contralateral bias in the binocular zone. For mice monocularly deprived during the critical period, the ODI of the cortex contralateral to the deprived eye shifted negatively towards the nondeprived, ipsilateral eye (ODI after 2-day MD: 0.12 ± 0.02, 4-day: 0.03 ± 0.03, and 6- to 7-day MD: −0.01 ± 0.04). The ODI shift induced by 4-day MD appeared to be near maximal, consistent with previous findings using single-unit recordings. We have thus established optical imaging of intrinsic signals as a fast and reliable screening method to study OD plasticity in the mouse.

Identification of Orientation-Specific Damage Using Guided Waves and Diagnostic Imaging

2018 ◽  
Vol 883 ◽  
pp. 16-21
Author(s):  
Chao Zhou ◽  
Chun Liang Zhang ◽  
Xia Yue ◽  
Hou Yao Zhu
Keyword(s):  
Diagnostic Imaging ◽  
Guided Waves ◽  
Imaging Techniques ◽  
Experimental Studies ◽  
Identification Accuracy ◽  
Engineering Structures ◽  
Signal Features ◽  
Rail Structure ◽  
The Relationship ◽  
Signal Correlation

Guided-waves-based diagnostic imaging techniques have been attracting much attention due to their merits including easily interpretable image, high identification accuracy and suitable for online surveillance. In this study, to envisage the difficulty in detecting orientation-specific damage (crack, notchetc.), a novel guided-waves-based diagnostic imaging technique capable of inspecting complicated engineering structures was developed, in terms of the relationship between damage parameters (location, orientation and severity) and extracted guided waves signal features (time-of-flight, signal correlation and signal energy). Experimental studies were performed to verify the developed diagnostic imaging approach, where a through-thickness crack was successfully identified in a metallic plate and a part of real rail structure respectively.

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