22,193 research outputs found
Imaging plasticity and structure of cortical maps in cat and mouse visual cortex
The study reported in the first part of this thesis utilized optical imaging of intrinsic signals to
visualize changes in orientation maps in cat visual cortex induced by pairing a visual stimulus
with an intracortical electrical stimulation. We found that the direction of plasticity within
orientation maps depends critically on the relative timing between visual and electrical
stimulation on a millisecond time scale: a shift in orientation preference towards the paired
orientation was observed if the cortex was first visually and then electrically stimulated. In
contrast, the cortical response to the paired orientation was diminished if the electrical preceded
the visual cortical stimulation. Spike-time-dependent plasticity has been observed in single cell
studies; however, our results demonstrate an analogous effect at the systems level in the live
animal. Thus, timing-dependent plasticity needs to be incorporated into our conception of cortical
map development.
While the pairing paradigm induced pronounced shifts in orientation preference, the general setup
of the orientation preference map remained unaltered. In order to unravel potential factors
contributing to this overall stability, we determined the distribution of plasticity across the cortical
surface. We found that pinwheel centers, points were domains of all orientation meet, exhibited
less plasticity than other regions of the orientation map. The resistance of pinwheel centers to
changes in orientation preference may support maintenance of the general structure of the
orientation map.
The study that forms the second part employs optical imaging to visualize the retinotopy in mouse
visual cortex. We were able to resolve the pattern of retinotopic activity with high precision and
reliability in the primary visual cortex (area 17). Functional imaging of the position, size and
shape of area 17 corresponded exactly to the location of this area in stained histological sections.
The imaged maps were also confirmed with electrophysiological recordings. The retinotopic
structure of area 17 showed very low inter-animal variability, thus allowing averaging maps
across animals and therefore statistical analysis. These averaged maps greatly facilitated the
identification of at least four extrastriate visual areas. In addition, we detected decreases in the
intrinsic signal below baseline with a shape and location reminiscent of lateral inhibition. This
decrease of the intrinsic signal was shown to be correlated with a decrease in neuronal firing rate
below baseline.
Both studies were facilitated by the development of a signal analysis technique (part III), which
improves the quality of optical imaging data. Intrinsic signal fluctuations originating from blood
vessels were minimized based on their correlation with the actual superficial blood vessel pattern.
These fluctuation components were then extracted from images obtained during sensory stimulation. This method increases the reproducibility of functional maps from cat, rat, and mouse
visual cortex significantly and might also be applied to high resolution imaging using voltage
sensitve dyes or functional magnetic resonance
Combined midline and coronal rhytidectomy technique in the treatment of pseudoptosis in five dogs
The present report emerges in the context of the curricular internship, part
of the Integrated Master's Degree in Veterinary Medicine at the University of
Évora, held at VetOeiras Veterinary Hospital, in Portugal, from 14th September
2020 until 12th February of 2021 and from 1st of April 2021 and 30th of July of the
same year.
The report is divided into two sections. In the first part, a descriptive
quantitative analysis of the cases presented to the author throughout the
internship is given. In the second part, a five-case report series is presented
regarding the management of pseudoptosis due to reluctant skin in the dog using
a novel rhytidectomy surgical technique; Resumo:
ClÃnica e cirurgia de animais de companhia Técnica de ritidectomia mediana e
coronal combinada no tratamento de pseudoptose devido a pele redundante no
cão
O presente relatório surge no contexto do estágio curricular, parte do
Mestrado Integrado em Medicina Veterinária da Universidade de Évora,
realizado no Hospital Veterinário VetOeiras, em Portugal, a partir de 14 de
setembro 2020 até 12 de fevereiro de 2021 e de 1 de abril de 2021 e 30 de julho
do mesmo ano.
O relatório está dividido em duas seções. Na primeira parte, uma
descrição da análise quantitativa dos casos apresentados ao autor ao longo do
estágio é dado. Na segunda parte, é apresentada uma série de cinco casos
sobre o maneio da pseudoptose por pele relutante no cão, usando a nova técnica
cirúrgica de ritidectomia
Long-term in vivo imaging and measurement of dendritic shrinkage of retinal ganglion cells
PURPOSE. To monitor and measure dendritic shrinkage of retinal ganglion cells (RGCs) in a strain of transgenic mice (Thy-1 YFP) that expresses yellow fluorescent proteins in neurons under the control of a Thy-1 promoter. METHODS. A total of 125 RGCs from 16 eyes of Thy-1 YFP transgenic mice were serially imaged with a confocal scanning laser ophthalmoscope for 6 months after optic nerve crush. Quantitative analysis of cell body area, axon diameter, dendritic field, number of terminal branches, total dendritic branch length, branching complexity, symmetry, and distance from the optic disc was used to characterize the morphology of RGCs, describe the patterns of axonal and dendritic degeneration, identify the morphologic predictors for cell survival, and estimate the rate of dendritic shrinkage. RESULTS. RGC damage was observed prospectively to begin with progressive dendritic shrinkage, followed by loss of the axon and the cell body. In a small proportion of RGCs, progressive axonal changes including fragmentation, beading, retraction, and bulb formation were also observed. RGCs with a larger dendritic field and a longer total dendritic branch length in general have a better survival probability. The rate of dendritic shrinkage was variable with a slower rate observed in cells having a larger dendritic field, a longer total dendritic branch length, and a greater distance from the optic disc. CONCLUSIONS. Estimating the probability of RGC survival and measuring the rate of dendritic shrinkage could become a new paradigm for investigating neuronal degeneration and evaluating the response of neuroprotective treatment. © 2011 The Association for Research in Vision and Ophthalmology, Inc.postprin
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Differential regulation of the Drosophila sleep homeostat by circadian and arousal inputs.
One output arm of the sleep homeostat in Drosophila appears to be a group of neurons with projections to the dorsal fan-shaped body (dFB neurons) of the central complex in the brain. However, neurons that regulate the sleep homeostat remain poorly understood. Using neurogenetic approaches combined with Ca2+ imaging, we characterized synaptic connections between dFB neurons and distinct sets of upstream sleep-regulatory neurons. One group of the sleep-promoting upstream neurons is a set of circadian pacemaker neurons that activates dFB neurons via direct glutaminergic excitatory synaptic connections. Opposing this population, a group of arousal-promoting neurons downregulates dFB axonal output with dopamine. Co-activating these two inputs leads to frequent shifts between sleep and wake states. We also show that dFB neurons release the neurotransmitter GABA and inhibit octopaminergic arousal neurons. We propose that dFB neurons integrate synaptic inputs from distinct sets of upstream sleep-promoting circadian clock neurons, and arousal neurons
Quantum metrology and its application in biology
Quantum metrology provides a route to overcome practical limits in sensing
devices. It holds particular relevance to biology, where sensitivity and
resolution constraints restrict applications both in fundamental biophysics and
in medicine. Here, we review quantum metrology from this biological context,
focusing on optical techniques due to their particular relevance for biological
imaging, sensing, and stimulation. Our understanding of quantum mechanics has
already enabled important applications in biology, including positron emission
tomography (PET) with entangled photons, magnetic resonance imaging (MRI) using
nuclear magnetic resonance, and bio-magnetic imaging with superconducting
quantum interference devices (SQUIDs). In quantum metrology an even greater
range of applications arise from the ability to not just understand, but to
engineer, coherence and correlations at the quantum level. In the past few
years, quite dramatic progress has been seen in applying these ideas into
biological systems. Capabilities that have been demonstrated include enhanced
sensitivity and resolution, immunity to imaging artifacts and technical noise,
and characterization of the biological response to light at the single-photon
level. New quantum measurement techniques offer even greater promise, raising
the prospect for improved multi-photon microscopy and magnetic imaging, among
many other possible applications. Realization of this potential will require
cross-disciplinary input from researchers in both biology and quantum physics.
In this review we seek to communicate the developments of quantum metrology in
a way that is accessible to biologists and biophysicists, while providing
sufficient detail to allow the interested reader to obtain a solid
understanding of the field. We further seek to introduce quantum physicists to
some of the central challenges of optical measurements in biological science.Comment: Submitted review article, comments and suggestions welcom
Transdermal Delivery of Functional Collagen \u3cem\u3eVia\u3c/em\u3e Polyvinylpyrrolidone Microneedles
Collagen makes up a large proportion of the human body, particularly the skin. As the body ages, collagen content decreases, resulting in wrinkled skin and decreased wound healing capabilities. This paper presents a method of delivering type I collagen into porcine and human skin utilizing a polyvinylpyrrolidone microneedle delivery system. The microneedle patches were made with concentrations of 1, 2, 4, and 8% type I collagen (w/w). Microneedle structures and the distribution of collagen were characterized using scanning electron microscopy and confocal microscopy. Patches were then applied on the porcine and human skin, and their effectiveness was examined using fluorescence microscopy. The results illustrate that this microneedle delivery system is effective in delivering collagen I into the epidermis and dermis of porcine and human skin. Since the technique presented in this paper is quick, safe, effective and easy, it can be considered as a new collagen delivery method for cosmetic and therapeutic applications
Imaging of the human fundus in the clinical setting:past present and future
The human fundus is a complex structure that can be easily visualized and the world of ophthalmology is going through a golden era of new and exciting fundus imaging techniques; recent advances in technology have allowed a significant improvement in the imaging modalities clinicians have available to formulate a diagnostic and treatment plan for the patient, but there is constant on-going work to improve current technology and create new ideas in order to gather as much information as possible from the human fundus. In this article we shall summarize the imaging techniques available in the standard medical retina clinic (i.e. not limited to the research lab) and delineate the technologies that we believe will have a significant impact on the way clinicians will assess retinal and choroidal pathology in the not too distant future
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