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At least 289 records · Page 16Linked to original sources
PubMed2005

Posterior capsule opacification-like changes in rat lens explants cultured with TGFbeta and FGF: effects of cell coverage and regional differences.

Following cataract surgery, many patients suffer secondary loss of vision because of posterior capsule opacification (PCO), which arises when residual lens epithelial cells become aberrant and migrate into the light path. Transforming growth factor-beta (TGFbeta)-induced transdifferentiation of lens cells appears to play a key role in this process. Fibroblast growth factor (FGF) may also play a role by promoting the survival of TGFbeta-affected cells and influencing their subsequent behaviour. In the present study, the effects of two different TGFbeta and FGF treatment regimes were compared in rat lens epithelial explants with either low or high initial cell coverage. Explants treated with 50 pg ml(-1) TGFbeta2 and 20 ng ml(-1) FGF-2 sequentially (day 0, day 1) or simultaneously (day 0), then cultured for up to 30 days with FGF, were assessed by light microscopy and immunolocalisation of markers for transdifferentiation (alpha-smooth muscle actin (alphaSMA) and type I collagen) or lens epithelial phenotype (Pax6) and fibre differentiation (beta-crystallin). By day 4, most cells had lost Pax6 reactivity, alphaSMA reactivity was evident, and there were differences between growth factor treatment groups, low and high initial cell coverage explants, and peripheral and central regions of explants. On day 30 of culture, all explants were well populated with cells, irrespective of treatment and initial cell coverage, and exhibited diverse PCO-like morphological changes, with expression of transdifferentiation markers and beta-crystallin in virtually all cells. Such overall resilience to variations in conditions may contribute to the insidious nature of PCO, while factors related to observed early differences between groups may contribute to PCO pleiomorphism.

Actins↗
PubMedDate not supplied

Outcome of hyperplastic persistent pupillary membrane.

PURPOSE: To evaluate the long-term visual outcome of eyes with hyperplastic persistent pupillary membrane. PATIENTS AND METHODS: We adopted a retrospective approach involving 39 eyes of 24 Korean patients diagnosed as having hyperplastic persistent pupillary membrane, excluding patients who could not be observed beyond 3 years of age and eyes that had any other ocular anomalies that affect vision. Final best-corrected visual acuity and refractive status were compared according to treatment type and laterality. Mean visual acuity was transformed to the logarithm of the minimum angle of resolution (logMAR). RESULTS: The mean final best-corrected visual acuity was 0.32 (standard deviation, +/- 0.41). Five eyes had a best-corrected visual acuity less than 20/70 at the last follow-up. Four eyes were unilateral (deprivation amblyopia) and one eye was bilateral (anisometropic amblyopia). There were no significant differences in final best-corrected visual acuity according to treatment type or laterality. Significant anisometropia was found in 11 of the 24 patients. The mean absolute value of anisometropia was greater in the surgical treatment group than in the medical treatment and observation groups (P = .048). CONCLUSIONS: The visual prognoses for individuals with hyperplastic persistent pupillary membrane can be relatively good if the condition is appropriately managed. Unilaterality and poor initial visual acuity are indicators of a poor visual outcome. Surgery is effective when the opaque membrane retards visual maturation. Close follow-up with evaluation of visual acuity and refractive status is mandatory because this condition can lead to deprivation amblyopia and anisometropic amblyopia.

Adolescent↗
PubMed1980

A mechanical oscilloscope for vision research.

A "mechanical oscilloscope" is described in which a lightbeam (Z-axis) is projected via a single front aluminized moving mirror. The mirror is mounted in a suspension frame allowing the simultaneous rotation about two mutually perpendicular axes. The linear displacements of two loudspeaker-coils are transformed mechanically into mirror rotations and an electronic position/velocity feedback control system is used to drive the loudspeakers. The bandwidth of the resulting X- and Y-axis deflection systems is of the order of 100-200 Hz. The flexibility of Z-axis control (colour, pattern, intensity, etc.) makes this instrument an attractive component of light stimulation systems for psychophysical or electrophysiological studies of vision.

Models, Neurological↗
PubMed1984

Color logic of apparent motion.

Two shapes of either the same or different color will seem to be in smooth apparent motion with like-colored mates, at proper conditions of flash timing and spacing. An experiment is reported in which the condition was tested for unlike-colored pairs, for example red-green alternated with green-red. The question of interest was how the visual system would resolve the disparity of color. An 'intelligent' solution would rotate the shapes in three dimensions. Like-colored and unlike-colored parts were found to move and transform similarly, however, the resolution being dependent more upon timing than upon color. The motion of intelligence as it might be applied to vision is discussed in light of these results.

Color Perception↗
PubMed2026

Environmental Release of Genetically Intervened Microorganisms: Towards a New Narrative.

The deliberate release of genetically engineered microorganisms for environmental applications has remained largely blocked since the early days of recombinant DNA technology, when limited ecological knowledge, lack of success stories and public apprehension shaped a culture of caution and restrictive regulation. Despite profound advances in microbial ecology, synthetic biology and genetic design, current frameworks still rely on outdated assumptions and legacy regulations that equate engineered microbes with inherent danger and demand unrealistic forms of absolute containment. This review examines how laboratory-trained microorganisms exist on a continuum with naturally evolved life, and that their risks are neither categorically different nor greater. Rather than pursuing unachievable containment, governance should shift towards traceability, stewardship and long-term monitoring through genomic barcodes, digital twins and transparent oversight. The vision moves from domination and control to care and partnership recognizing engineered microbes as live amendments capable of restoring degraded ecosystems. Achieving this transformation requires new terminology, phased field-trial frameworks, improved scaling methods, and the integration of epistemological perspectives that emphasize reciprocity and coexistence with nature. Reframing biotechnology in this way could finally unlock the capacity of engineered microorganisms to contribute responsibly and effectively to planetary repair in an era of escalating environmental crises.

Microorganisms, Genetically-Modified↗
PubMed2005

A new paradigm for graduate research and training in the biomedical sciences and engineering.

98Emphasis on the individual investigator has fostered discovery for centuries, yet it is now recognized that the complexity of problems in the biomedical sciences and engineering requires collaborative efforts from individuals having diverse training and expertise. Various approaches can facilitate interdisciplinary interactions, but we submit that there is a critical need for a new educational paradigm for the way that we train biomedical engineers, life scientists, and mathematicians. We cannot continue to train graduate students in isolation within single disciplines, nor can we ask any one individual to learn all the essentials of biology, engineering, and mathematics. We must transform how students are trained and incorporate how real-world research and development are done-in diverse, interdisciplinary teams. Our fundamental vision is to create an innovative paradigm for graduate research and training that yields a new generation of biomedical engineers, life scientists, and mathematicians that is more diverse and that embraces and actively pursues a truly interdisciplinary, team-based approach to research based on a known benefit and mutual respect. In this paper, we describe our attempt to accomplish this via focused training in biomechanics, biomedical optics, mathematics, mechanobiology, and physiology. The overall approach is applicable, however, to most areas of biomedical research.

Biological Science Disciplines↗
PubMed2001

The Gaussian derivative model for spatial-temporal vision: II. Cortical data.

Receptive fields of simple cells in the primate visual cortex were well fit in the space and time domains by the Gaussian Derivative (GD) model for spatio-temporal vision. All 23 fields in the data sample could be fit by one equation. varying only a single shape number and nine geometric transformation parameters. A difference-of-offset-Gaussians (DOOG) mechanism for the GD model also fit the data well. Other models tested did not fit the data as well as or as succinctly, or failed to converge on a unique solution, indicating over-parameterization. An efficient computational algorithm was found for the GD model which produced robust estimates of the direction and speed of moving objects in real scenes.

Animals↗
PubMed2005

Human neurobehavioral effects of long-term exposure to styrene: a meta-analysis.

Many reports in the literature suggest that long-term exposure to styrene may exert a variety of effects on the nervous system, including increased choice reaction time and decreased performance of color discrimination and color arrangement tasks. Sufficient information exists to perform a meta-analysis of these observations quantifying the relationships between exposure (estimated from biomarkers) and effects on two measures of central nervous system function: reaction time and color vision. To perform the meta-analysis, we pooled data into a single database for each end point. End-point data were transformed to a common metric of effect magnitude (percentage of baseline). We estimated styrene concentration from biomarkers of exposure and fitted linear least-squares equations to the pooled data to produce dose-effect relationships. Statistically significant relationships were demonstrated between cumulative styrene exposure and increased choice reaction time as well as increased color confusion index. Eight work-years of exposure to 20 ppm styrene was estimated to produce a 6.5% increase in choice reaction time, which has been shown to significantly increase the probability of automobile accidents. The same exposure history was predicted to increase the color confusion index as much as 1.7 additional years of age in men.

Accidents, Traffic↗
PubMedDate not supplied

The virtuous manager. Renewing the experience of work.

In healthcare, as in any other field, work can become dehumanizing, meaningless drudgery. But good managers can transform their organizations and renew the experience of work. Good management demands not only good business skills, but character, rooted in truthfulness and vision. Three virtues are particularly important: prudence, justice and fortitude. The moral skill of prudence enables healthcare managers to know what is to be done; justice creates honest relationships; and fortitude enables managers to seek a good that is difficult to achieve--to do the right thing. Businesses must also explore their potential for sacramentality and find ways in which employees--and employers--can become better, holier people through their work. Organizations should strive to achieve subsidiarity and keep employees well-informed of their missions. Establishing a sense of connectedness is important, as is open and honest communication. Finally, managers-and healthcare organizations-must always work for the common good.

Communication↗
PubMed2001

Employing the Hough Transform to locate the optic disk.

Laser surgery of the retina has become common place to treat various retinal disorders. In this surgery therapeutic lesions are placed on the retinal surface using an argon laser. Researchers have worked over the past decade to develop the control hardware and algorithms to automate the placement of therapeutic lesions. The control algorithms compensate for retinal movement during the lesion placement process. Regions of critical vision anatomy such as the retinal vessels, the fovea, and the optic disk are identified and protected from laser irradiation. Automatic recognition of the optic disk via image processing techniques has been illusive. This paper will discuss a technique and provide results which employs the Hough Transform to identify the optic disk.

Algorithms↗
PubMed1997

Reaching with cerebral tunnel vision.

We studied reaching movements in a 48-year-old man with bilateral lesions of the calcarine cortex which spared the foveal representation and caused severe tunnel vision. Three-dimensional (3D) reconstruction of brain MR images showed no evidence of damage beyond area 18. The patient could not see his hand during reaching movements, providing a unique opportunity to test the role of peripheral visual cues in limb control. Optoelectronic recordings of upper limb movements showed normal hand paths and trajectories to fixated extrinsic targets. There was no slowing, tremor, or ataxia. Self-bound movements were also preserved. Analyses of limb orientation at the endpoints of reaches showed that the patient could transform an extrinsic target's visual coordinates to an appropriate upper limb configuration for target acquisition. There was no disadvantage created by blocking the view of the reaching arm. Moreover, the patient could not locate targets presented in the hemianopic fields by pointing. Thus, residual nonconscious vision or 'blindsight' in the aberrant fields was not a factor in our patient's reaching performance. The findings in this study show that peripheral visual cues on the position and velocity of the moving limb are not critical to the control of goal directed reaches, at least not until the hand is close to target. Other cues such as kinesthetic feedback can suffice. It also appears that the visuomotor transformations for reaching do not take place before area 19 in humans.

Cerebrovascular Disorders↗
PubMed1988

Development of spatiotemporal mechanisms in infant vision.

In adult spatiotemporal vision information is processed in parallel by a number of mechanisms tuned for orientation and spatial frequency. An examination of infant neuroanatomical data suggests that three major factors are involved in the development of these mechanisms: (1) Growth of foveal cone outer segments causes an increase in mechanism sensitivity. (2) Migration of foveal cones produces a change in spatial scale and a progressive shift of mechanism tuning towards higher spatial frequencies. (3) Development of cortical inhibition transforms low-pass into bandpass spatial frequency and orientation tuning. These changes are developed into a quantitative model which is shown to provide a coherent interpretation of many of the psychophysical data on infant vision.

Adult↗
PubMed1984

Why the cortical magnification factor in rhesus is isotropic.

We examine the arguments advanced recently [by Sakitt (Vision Res. 22, 417-421, 1982), and Tootell et al. (Science 218, 902-904, 1982)] leading to the conclusion that the retino-cortical magnification factor cannot be isotropic. The relevance of the issue is discussed through the use of complex function theory as the appropriate tool to express the geometry of interconnections between neural lamina. A general expression is obtained to compute the length of a curve under a conformal transformation. When this result is applied to circles in the visual field, it is shown that Sakitt's findings imply radial asymmetry of the retino-cortical map, and not local anisotropy, as claimed. In fact, by taking Schwartz's (Vision Res. 20, 645-670, 1980) proposal that the complex log map including a constant eccentricity term be used to represent the retino-cortical mapping, we show that both local isotropy and radial asymmetry are simultaneously valid. Furthermore, the values of cortical length predicted from this approach account exactly for the data shown by Sakitt. A quantitative prediction is offered also for the ratio between the magnification factor of vertical and horizontal meridians at different eccentricities, which is precisely the value reported by Tootell et al. We conclude that these results show that (1) conformal transformations are appropriate tools to describe the geometrical interconnections between neural lamina; (2) for the case of the retino-cortical mapping the appropriate conformal transform is an eccentric complex logarithm.

Animals↗
PubMed2001

Gradation processing algorithm of digital radiological chest image.

Gradation processing technology can enhance display contrast of interested region by using linear or nonlinear transform. Current algorithms generally calculate transform parameters depended on experimental statistical values or some simple image processing method such as histogram analysis. They cannot accord with the human subjective vision mechanism nor can they intelligently acquire required parameters. Therefore, processing results are not very accurate or reliable. We propose a gradation processing algorithm of digital radiological chest images based on region growing segmentation technology. It combines self-adapted segmentation with prior knowledge of directed segmentation, and its computation cost is low. It can perform contrast enhancement of the interested regions more accurately, and accords with the human subjective vision mechanism better.

Algorithms↗
PubMed1982

Directional changes in the vestibular ocular response as a result of adaptation to optical tilt.

Before and after exposure to clockwise optical tilt, subjects' compensatory eye movements were recorded, as the head was oscillated around a vertical axis by the experimenter. An analysis of the horizontal and vertical components of eye movements showed a change in eye movement path in the clockwise direction. This corresponded to similar changes in visual spatial orientation judgments indicative of perceptual adaptation. It was suggested that long-term visual feedback serves to restore the compensatory nature of the eye movements which was altered by the introduction of the prism transformation.

Adaptation, Ocular↗
PubMed1996

Tri-axial, real-time logging of fly head movements.

We present a method to record and simultaneously display the three rotatory components of arbitrary head turns of an insect flying stationarily in a wind tunnel or walking on a treadmill. An elongated marker, placed on the fly's forehead, is video-recorded from ahead under deep red stroboscopic illumination, invisible to the insect. A fast on-board image processor of a PC video-adapter (True Vision, AT-Vista), programmed in its native code, extracts position and orientation of the marker in the video-image. The host PC transforms these data into calibrated head angles and displays stimulus and response components after 40 ms processing time at a rate of 50 frames per second. Head turns are measured relative to the fly's trunk even when the fly is rotated around its body axis provided that it is aligned with the video-axis. Technical tests, as well as recordings from live flies responding to various stimuli, illustrate the performance and accuracy of the procedure. This minimally invasive method of motion recording should be easily adaptable to other insects and to similar movements of small parts.

Animals↗
PubMed2005

The functional significance of mu rhythms: translating "seeing" and "hearing" into "doing".

Existing evidence indicates that mu and other alpha-like rhythms are independent phenomena because of differences in source generation, sensitivity to sensory events, bilateral coherence, frequency, and power. Although mu suppression and enhancement echo sensorimotor processing in frontoparietal networks, they are also sensitive to cognitive and affective influences and likely reflect more than an idling brain state. Mu rhythms are present at early stages of human development and in other mammalian species. They exhibit adaptive and dynamically changing properties, including frequency acceleration and posterior-to-anterior shifts in focus. Furthermore, individuals can learn to control mu rhythms volitionally in a very short period of time. This raises questions about the mu rhythm's open neural architecture and ability to respond to cognitive, affective, and motor imagery, implying an even greater developmental and functional role than has previously been ascribed to it. Recent studies have suggested that mu rhythms reflect downstream modulation of motor cortex by prefrontal mirror neurons, i.e., cells that may play a critical role in imitation learning and the ability to understand the actions of others. It is proposed that mu rhythms represent an important information processing function that links perception and action-specifically, the transformation of "seeing" and "hearing" into "doing." In a broader context, this transformation function results from an entrainment/gating mechanism in which multiple alpha networks (visual-, auditory-, and somatosensory-centered domains), typically producing rhythmic oscillations in a locally independent manner, become coupled and entrained. A global or 'diffuse and distributed alpha system' comes into existence when these independent sources of alpha become coherently engaged in transforming perception to action.

Animals↗