Wavelet Representation of the Corneal Pulse for Detecting Ocular Dicrotism

Purpose

To develop a reliable and powerful method for detecting the ocular dicrotism from non-invasively acquired signals of corneal pulse without the knowledge of the underlying cardiopulmonary information present in signals of ocular blood pulse and the electrical heart activity.

Methods

Retrospective data from a study on glaucomatous and age-related changes in corneal pulsation [PLOS ONE 9(7),(2014):e102814] involving 261 subjects was used. Continuous wavelet representation of the signal derivative of the corneal pulse was considered with a complex Gaussian derivative function chosen as mother wavelet. Gray-level Co-occurrence Matrix has been applied to the image (heat-maps) of CWT to yield a set of parameters that can be used to devise the ocular dicrotic pulse detection schemes based on the Conditional Inference Tree and the Random Forest models. The detection scheme was first tested on synthetic signals resembling those of a dicrotic and a non-dicrotic ocular pulse before being used on all 261 real recordings.

Results

A detection scheme based on a single feature of the Continuous Wavelet Transform of the corneal pulse signal resulted in a low detection rate. Conglomeration of a set of features based on measures of texture (homogeneity, correlation, energy, and contrast) resulted in a high detection rate reaching 93%.

Conclusion

It is possible to reliably detect a dicrotic ocular pulse from the signals of corneal pulsation without the need of acquiring additional signals related to heart activity, which was the previous state-of-the-art. The proposed scheme can be applied to other non-stationary biomedical signals related to ocular dynamics.     

Age-Related Changes in Corneal Deformation Dynamics Utilizing Scheimpflug Imaging

PurposeTo study age-related changes in corneal deformation response to air-puff applanation tonometry.MethodsFifty healthy subjects were recruited for a prospective study and divided into two equal age groups (≤ 28 and ≥ 50 years old). Up to three measurements by a corneal deformation analyser based on the Scheimpflug principle were performed on the left eye of each subject. Raw Scheimpflug images were used to extract changes in anterior and posterior corneal profiles, which were further modelled by an orthogonal series of Chebyshev polynomial functions. Time series of the polynomial coefficients of even order exhibited a dynamic behavior in which three distinct stages were recognized. A bilinear function was used to model the first and the third stage of corneal dynamics. Slope parameters of the bilinear fit were then tested between the two age groups using Wilcoxon rank sum test and two-way non-parametric ANOVA (Friedman) test.ResultsStatistically significant changes (Wilcoxon test, P<0.05) between the age groups were observed in the phase of the second applanation dynamics for the posterior corneal profile. In a two-way comparison, in which the corneal profile was used as a dependent variable, statistically significant changes (ANOVA/Friedman test, P = 0.017) between the groups were also observed for that phase.ConclusionCorneal biomechanics depend on age. The changes in corneal deformation dynamics, which correspond to mostly free return of the cornea to its original shape after the air pulse, indicate that the age related differences in corneal biomechanics are subtle but observable with high speed imaging.     

Changes in Cell and Organ Shape during Early Development of the Ocular Lens

It is currently fashionable to attribute changes in organ shapeduring development to the actions of microtubules and microfilamentson individual cells of the organ in question. In the case ofthe eye lens it has been proposed that cellular elongation underthe influence of microtubules and/or apical contraction by microfilamentsare responsible for the remodeling of the originally low cuboidalectoderm into the tall and wedge-shaped presumptive lens cells.Invagination of the lens is thought to follow automatically.These ideas cannot account for certain observations on lensmorphogenesis, such as the relatively fixed diameter of theorgan rudiment during early development, which is incompatiblewith the supposed contraction of the rudiment. We found that the area of contact between presumptive lens andoptic cup does become fixed after a few hours of "induction."There is a remarkable correlation in time between this fixation,and the process of lens cell elongation and increase in lenscell density. We calculated that the latter two can, in fact,be accounted for by population pressure caused by continuedcell division within the defined area of the lens rudiment.A mathematical model along these lines was developed, whichexplains lens invagination on the basis of cell number and size,extent of the area of contact between ectoderm and optic cup,and cell population doubling times. We hypothesize that the prevention of lateral cell spreadingwithin the lens territory, after the contact area becomes fixed,is a function of the build-up in extracellular materials inthis area during the "induction period." Both lens rudimentand presumptive retina contribute to this extracellular matrix.     

时间认知的年老化及其神经机制

时间认知功能的增龄性衰退表现得较晚,主要在高龄老年人中表现出时间认知功能的衰退.随着年龄的增长,老年人内部时钟的速率变慢,变异增大.注意及记忆功能随年龄增长而衰退,这些一般认知功能的改变影响老年人的时间认知功能.正常的时间认知功能依赖于"核心-背景"时间加工脑网络结构和功能的完好,这些脑区或功能通路的障碍会导致时间认知功能的损伤.老年人在一定的年龄范围内,可以通过认知补偿策略保持相对完好的时间认知功能.     

Age-Related Changes in Electroencephalographic Signal Complexity

The study of active and healthy aging is a primary focus for social and neuroscientific communities. Here, we move a step forward in assessing electrophysiological neuronal activity changes in the brain with healthy aging. To this end, electroencephalographic (EEG) resting state activity was acquired in 40 healthy subjects (age 16–85). We evaluated Fractal Dimension (FD) according to the Higuchi algorithm, a measure which quantifies the presence of statistical similarity at different scales in temporal fluctuations of EEG signals. Our results showed that FD increases from age twenty to age fifty and then decreases. The curve that best fits the changes in FD values across age over the whole sample is a parabola, with the vertex located around age fifty. Moreover, FD changes are site specific, with interhemispheric FD asymmetry being pronounced in elderly individuals in the frontal and central regions. The present results indicate that fractal dimension well describes the modulations of brain activity with age. Since fractal dimension has been proposed to be related to the complexity of the signal dynamics, our data demonstrate that the complexity of neuronal electric activity changes across the life span of an individual, with a steady increase during young adulthood and a decrease in the elderly population.     

Developmental and Age-Related Changes in Rat Brain Glycosaminoglycans

The quantities of each major class of glycosaminoglycan were determined in rat cerebrum from postnatal day 5 to 30 months of age. Chondroitin sulphate, dermatan sulphate, heparan sulphate, heparin, and hyaluronate were found, but no keratan sulphate was detected. Large and rapid changes in glycosaminoglycan content were observed during the period of brain maturation, and thereafter relatively steady levels were maintained until after the age of 12 months. The most remarkable change in the aged rat cerebrum was the ratio by weight of hyaluronate to chondroitin sulphate, which was approximately 1:1 from postnatal day 10 to 18 months but increased to 2.6:1 by the age of 30 months. In immature rats, the proportion of nonsulphated and 6-sulphated disaccharides derived from chondroitinase AC digests of brain glycosaminoglycans was much greater than in adults. In mature rats, chondroitin sulphate was composed almost entirely of 4-sulphated disaccharide subunits. The possibility that these changes could affect the permeability properties of the cerebral extracellular space and ionic equilibria in the brain is discussed.     

Age-Related Changes in Attention and Impulsivity in Young Schoolchildren

Normative values of attention, impulsivity, response time, and response time variability were determined for seven- to ten-year-old children with the continuous performance Test of Variables of Attention (TOVA). An age-related increase in attention and a decrease in impulsivity, response time, and its variability were revealed. Differences in TOVA scores were studied for students of gymnasia and schools providing general education.     

Epigenetic Changes and Its Intervention in Age-Related Neurodegenerative Diseases

Cellular and Molecular Neurobiology - Epigenetic mechanisms involving the modulation of gene activity without modifying the DNA bases are reported to have lifelong effects on mature neurons in...     

Age-Related Changes in Task Related Functional Network Connectivity

Aging has a multi-faceted impact on brain structure, brain function and cognitive task performance, but the interaction of these different age-related changes is largely unexplored. We hypothesize that age-related structural changes alter the functional connectivity within the brain, resulting in altered task performance during cognitive challenges. In this neuroimaging study, we used independent components analysis to identify spatial patterns of coordinated functional activity involved in the performance of a verbal delayed item recognition task from 75 healthy young and 37 healthy old adults. Strength of functional connectivity between spatial components was assessed for age group differences and related to speeded task performance. We then assessed whether age-related differences in global brain volume were associated with age-related differences in functional network connectivity. Both age groups used a series of spatial components during the verbal working memory task and the strength and distribution of functional network connectivity between these components differed across the age groups. Poorer task performance, i.e. slower speed with increasing memory load, in the old adults was associated with decreases in functional network connectivity between components comprised of the supplementary motor area and the middle cingulate and between the precuneus and the middle/superior frontal cortex. Advancing age also led to decreased brain volume; however, there was no evidence to support the hypothesis that age-related alterations in functional network connectivity were the result of global brain volume changes. These results suggest that age-related differences in the coordination of neural activity between brain regions partially underlie differences in cognitive performance.     

Age-Related Changes in Expectation-Based Modulation of Motion Detectability

Expecting motion in some particular direction biases sensitivity to that direction, which speeds detection of motion. However, the neural processes underlying this effect remain underexplored, especially in the context of normal aging. To address this, we examined younger and older adults'' performance in a motion detection task. In separate conditions, the probability was either 50% or 100% that a field of dots would move coherently in the direction a participant expected (either vertically or horizontally). Expectation and aging effects were assessed via response times (RT) to detect motion and electroencephalography (EEG). In both age groups, RTs were fastest when motion was similar to the expected direction of motion. RT tuning curves exhibited a characteristic U-shape such that detection time increased with an increasing deviation from the participant''s expected direction. Strikingly, EEG results showed an analogous, hyperbolic curve for N1 amplitude, reflecting neural biasing. Though the form of behavioral and EEG curves did not vary with age, older adults displayed a clear decline in the speed of detection and a corresponding reduction in EEG N1 amplitude when horizontal (but not vertical) motion was expected. Our results suggest that expectation-based detection ability varies with age and, for older adults, also with axis of motion.     

Changes of Cytochemical Markers in the Conjunctival and Corneal Epithelium After Corneal Debridement

1. The aim of this study was to determine the epithelial changes of the conjunctiva and cornea up to 7 days after corneal debridement and the changes highlighted included (1) proliferation, (2) production of growth factor, (3) changes in calcium binding protein marker, (4) production of cytokine, and (5) maturity of the regeneration corneal epithelium.2. The cytochemical changes of the corneal and conjunctival epithelia of rabbit were analyzed up to 7 days after debridement.3. An increase in proliferating cell nuclear antigen (PCNA) was observed in the limbal epithelia 12 hr after lesion and reached a peak by 48 hr.4. Some proliferating limbal cells also contained epidermal growth factor (EGF) beginning 24 hr after injury. The early limbal cell proliferation and the EGF production and their persistence until 7 days after lesion were likely involved with the process of regeneration.5. Other positive markers appeared after lesion included tumor necrosis factor (TNF) and calcium binding proteins S100A and S100B, which appeared mainly within the first 48 hr after lesion and then started to decline. The short appearance and the relatively small quantity of TNF indicated that this cytokine was probably not very important in the repair process and its appearance might be related to the injury induced. The presence of S100A and S100B could be associated with both cell death after injury and the proliferation of new epithelium.6. The cornea epithelium was still immature 7 days after lesion in that it still contained cytokeratin.7. In conclusion, the critical hours of peak conjunctival and corneal changes after corneal debridement were in the first 2 days.     

Age-Related Changes in Collagen and Glycosaminoglycans of Rat Gingiva1

Age-related changes in collagen and glycosaminoglycans (GAGs) of rat gingiva were studied biochemically and histologically. The components of isolated GAGs were identified as dermatan sulphate, hyaluronic acid, and heparan sulphate. In histological studies, hyaluronic acid was present in all regions of the gingiva, whereas dermatan sulphate and heparan sulphate were present only in gingival connective tissue. However, there was no significant difference in the relationship between aging, and the content or distribution of GAGs. On the other hand, histological findings showed that collagen fibers were markedly increased in number and the vascular composition was decreased with increasing age. In biochemical studies, the content of collagen, especially of insoluble collagen, was greatly increased with age, whereas collagen biosynthesis and collagenolytic activity were markedly decreased. In addition, lysyl oxidase activity was also significantly decreased with age. The results indicate that the rate of collagen turnover decreases and collagen fibers increase in stability in rat gingiva with increasing age. These observed age-related changes may affect the ability of gingiva to respond to local irritants.     

Corneal Changes and Strategies to Improve Survival of Hypomorphic Collagen VII-Deficient Mice for the Study of Ocular Dystrophic Epidermolysis Bullosa

Ophthalmic study of collagen CVII hypomorphic mice is uniquely challenging due to the strain’s published survival rate to weaning of 24%. Because chronic ocular fibrosis requires time to develop, optimizing the survival rate is of critical importance. In this study, standard husbandry practices were enhanced by the addition of sterilized diet and drug delivery gels, acidified water, irradiated food pellets, cellulose fiber bedding, minimal handling, removal of siblings within 2-3 wk from birth, and a preferred housing location. Survival rates per breeding cycle, sex, weight, and cause of early euthanasia were recorded and analyzed over 43 mo. Overall, 49% of mice survived to weaning and 76% of weaned mice survived to 20 wk of age. Corneal opacities were seen in 65% of mice by 20 wk, but only 10% of eyes showed the sustained opacification that was indicative of fibrosis. Corneal opacities occurred at the same rate as in humans with epidermolysis bullosa. 66% of the mice showed weight loss at 11 wk. Males required early euthanasia 4 times more often than did females. Euthanasia was required for urinary obstruction due to penile prolapse in 88% of males. With our enhanced care protocol, hypomorphic mice in our colony survived at twice the published rate. With this revised husbandry standard, experiments planned with termination endpoints of 14 wk for males and 17 wk for females are more likely to reach completion.     

Age-Related Changes in Rat Sublingual Salivary Gland Morphology1

Sublingual salivary glands were removed from 3.5-, 12-, 18- and 24-month-old Fisher 344 male rats and examined for age-related changes in morphology. Morphometric analysis revealed stability in the proportional volume of acinar tissue, connective tissue and vascular tissue across age groups. The proportion of gland volume occupied by ducts increased with age due to an increase in proportional volume of striated ducts. A number of qualitative age-related changes were noted including an increase in squamous metaplasia of duct epithelium, periductal lymphocytic foci and diffuse periductal lymphocytic infiltration. Consolidated deposits were identified in the lumen of intralobular ducts and appeared most frequent in young animals and declined in frequency with age. These morphologic changes while apparently age-related were evident by 12 months of age indicating that developmental and maturational factors rather than senescence may account for these findings.     

Age-Related Changes in Microglia of the Rat Spinal Cord

Journal of Evolutionary Biochemistry and Physiology - The aim of this study was to evaluate age-related changes in microglial cells in various regions of the cervical spinal cord in young (4...     

Learning and Age-Related Changes in Genome-wide H2A.Z Binding in the Mouse Hippocampus

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Age-Related Changes in Expression of Hippocalcin and NVP2 in Rat Brain

Expression of hippocalcin and neural visinin-like calcium-binding protein 2 (NVP2) in aging rat brain was investigated by immunoblot and immunohistochemical analyses. In 3-month old rats, hippocalcin and NVP2 were present at high concentrations in hippocampal and cerebral pyramidal cells and dentate granule cells, with hippocalcin protein levels being five to ten times higher than NVP2 levels. Hippocalcin levels in hippocampus and cerebral cortex decreased by approximately 20% at 24 months. While the number of hippocalcin-positive cells in CA3, dentate gyrus and cerebral cortex were preserved, staining intensity decreased. In contrast, the number and staining intensity of hippocalcin-positive cells in CA1 were maintained. NVP2 levels in hippocampus and cerebral cortex decreased by approximately 30% at 24 months. In cerebral cortex, the number and intensity of NVP2-positive cells decreased. In CA1 through CA3 and in dentate gyrus, NVP2-positive cell numbers were preserved, but staining intensity decreased. In summary, the loss of hippocalcin and NVP2 in aging rat brain may be associated with age-related impairment of postsynaptic functions.