Percutaneous coronary interventions and cardiovascular outcomes for patients with chronic total occlusions

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Optical mechanisms regulating emmetropisation and refractive errors: evidence from animal models

Our current understanding of emmetropisation and myopia development has evolved from decades of work in various animal models, including chicks, non-human primates, tree shrews, guinea pigs, and mice. Extensive research on optical, biochemical, and environmental mechanisms contributing to refractive error development in animal models has provided insights into eye growth in humans. Importantly, animal models have taught us that eye growth is locally controlled within the eye, and can be influenced by the visual environment. This review will focus on information gained from animal studies regarding the role of optical mechanisms in guiding eye growth, and how these investigations have inspired studies in humans. We will first discuss how researchers came to understand that emmetropisation is guided by visual feedback, and how this can be manipulated by form-deprivation and lens-induced defocus to induce refractive errors in animal models. We will then discuss various aspects of accommodation that have been implicated in refractive error development, including accommodative microfluctuations and accommodative lag. Next, the impact of higher order aberrations and peripheral defocus will be discussed. Lastly, recent evidence suggesting that the spectral and temporal properties of light influence eye growth, and how this might be leveraged to treat myopia in children, will be presented. Taken together, these findings from animal models have significantly advanced our knowledge about the optical mechanisms contributing to eye growth in humans, and will continue to contribute to the development of novel and effective treatment options for slowing myopia progression in children.     

A review of the potential to restore vision with stem cells

Vision research involving stem cells is a rapidly evolving field. Animal experiments have shown that in response to environmental cues, stem cells can repopulate damaged retinas, regrow neuronal axons, repair higher cortical pathways, and restore pupil reflexes, light responses and basic pattern recognition. Viable corneas have been grown from stem cells and transplanted into humans. Similarly, human trials to repair damaged retinas in retinitis pigmentosa and age‐related macular degeneration patients have produced preliminary successes. This review attempts to place the collective contributions toward stem cell/vision research into a broader clinical model of how stem cells might ultimately be used to restore the entire visual pathway.     

Reported effects of non‐traditional treatments and complementary and alternative medicine by retinitis pigmentosa patients

Background: Benefits of complementary and alternative medicine (CAM)‐related interventions have been demonstrated for patients with chronic, systemic diseases in which stress, anxiety and disability are prevalent. Subjects with retinitis pigmentosa (RP) commonly indicate that they have ‘good’ and ‘bad’ vision days, stating that stress causes a decrease in vision and that vision improves when the stress is alleviated. We assessed CAM use by RP patients and its perceived effectiveness. Methods: We enquired about nine CAM areas: meditation, mind‐body therapies, yoga, movement therapies, energy therapies, acupuncture, massage therapy, spirituality/religion and herbal therapies/aromatherapy. Ninety‐six RP patients with any level of vision completed an anonymous internet survey. Results: Ninety‐five per cent of respondents tried at least one of the nine CAM areas. Seventy‐five per cent have used nutritional supplements, including lutein (47 per cent), bilberry (32), vitamin A palmitate (36) and docosahexaenoic acid (23 per cent). Some tried meditation (47) and yoga (31 per cent). Stress and anxiety levels were reported as improved in 93, 92 and 87 per cent of those who used yoga, meditation and mind‐body therapies, respectively. Many of those who tried mind‐body therapies (40) or acupuncture (50 per cent), used it with a desire to fight RP. Vision was subjectively affected in 65 per cent of acupuncture users and from 20 to 35 per cent of the users of the other CAM areas. Those who indicated that their vision was affected by at least one type of CAM (35 per cent) were statistically significantly more likely to require magnification to read (that is, they had lost more vision and RP had progressed), than those who did not believe vision was impacted (59 versus 84 per cent). Conclusions: RP patients are using CAM and are experiencing some impact on vision and physical/emotional well‐being. Clinicians and researchers should be aware of its use. Clinical trials with CAM interventions are necessary to attempt to validate these findings.     

Use of the Optomap with lid retraction and its sensitivity and specificity#

Background: Optomap uses the ultra‐wide field scanning laser ophthalmoscopy to provide retinal examination. It permits fundus examination without the use of a mydriatic, which is more comfortable for the patients. This paper determines the sensitivity and specificity of the Optomap for detecting retinal signs under non‐mydriatic conditions. Methods: Fifty‐four eyes identified with retinal/choroidal signs and eight normal eyes were recruited from 31 Hong Kong Chinese subjects. Photo‐documentation of fundal changes was obtained with the Optomap under non‐mydriatic conditions before a dilated fundus examination by a clinician using standard procedures. The eyelid was retracted using a cotton bud when necessary. Dilated fundus examinations were performed by another clinician using binocular indirect ophthalmoscopy and slitlamp biomicroscopy with a fundus lens. The Optomap images were evaluated by four other investigators under masked condition. The International Classification of Disease, Ninth Revision (ICD‐9‐CM) was adopted for recording retinal features. Screening results were compared with those obtained using the dilated fundus examination as the gold standard. Results: The cotton bud method for eyelid retraction showed an improvement in the area of retina that could be visualised. The sensitivity and specificity of the Optomap averaged 76.4 and 71.9 per cent, respectively. Some fundal signs were missed by all observers in the Optomap but not with the biomicroscope. These included white‐without‐pressure, lattice degeneration, paramacular drusen and pigmentary changes at central fundus. Conclusion: Optomap serves as a reliable screening tool for fundus examination especially because it covers a much wider area of the peripheral retina than other digital instruments for fundus photography.     

Altered properties of quantal neurotransmitter release at endplates of mice lacking P/Q-type Ca2+ channels

Transmission at the mouse neuromuscular junction normally relies on P/Q-type channels, but became jointly dependent on both N- and R-type Ca(2+) channels when the PQ-type channel alpha(1A) subunit was deleted. R-type channels lay close to Ca(2+) sensors for exocytosis and I(K(Ca)) channel activation, like the P/Q-type channels they replaced. In contrast, N-type channels were less well localized, but abundant enough to influence secretion strongly, particularly when action potentials were prolonged. Our data suggested that active zone structures may select among multiple Ca(2+) channels in the hierarchy P/Q >R >N. The alpha(1A)-/- neuromuscular junction displayed several other differences from wild-type: lowered quantal content but greater ability to withstand reductions in the Ca(2+)/Mg(2+) ratio, and little or no paired-pulse facilitation, the latter findings possibly reflecting compensatory mechanisms at individual release sites. Changes in presynaptic function were also associated with a significant reduction in the size of postsynaptic acetylcholine receptor clusters.     

Congenital myasthenic syndromes: II. Syndrome attributed to abnormal interaction of acetylcholine with its receptor

A 21-year-old woman had myasthenic symptoms since birth that responded poorly to anticholinesterase therapy. Tests for acetylcholine receptor (AChR) antibodies were negative. An intercostal muscle specimen was obtained to investigate the character of the neuromuscular transmission defect. There were no immune deposits at the endplates. The quantal content of the endplate potential was normal. Miniature endplate potentials and currents were very small, but the number of AChR per endplate was normal. On electron microscopy, the synaptic vesicles were of normal size, the junctional folds were intact, and the density and distribution of AChR on the folds was normal. The kinetic properties of AChR were studied by analysis of acetylcholine (ACh)-induced current noise. The mean single channel conductance was normal. The noise power spectrum was abnormal, containing two components of different time course. This could result from an abnormal interaction of ACh with AChR, or from two populations of AChR at the endplate. The second possibility is unlikely because if two populations of AChR were present at the endplate, then both would have to have low conductance to explain the small miniature endplate current, but the average conductance of the channels that did open was normal. © 1993 John Wiley & Sons, Inc.     

On the appearance of acetylcholine receptors in denervated rat diaphragm,and its dependence on nerve stump length

Acetylcholine (ACh) sensitivity and extrajunctional receptor distribution of the rat diaphragm were closely monitored during the early period following denervation. Both contracture in response to 10 μg/ml of ACh and extrajunctional binding of [¹²⁵I]alpha-bungarotoxin ([¹²⁵I]α-BTX) were first detectable 30 h after cutting the phrenic nerve in the thorax. If the nerve were cut more proximally, leaving a 3.5 cm distal nerve stump, the same level of ACh contracture and [¹²⁵I]α-BTX binding did not appear until 40 h after operation. This 10-h delay was far longer than the 3-h delay in transmission failure reportedly dependent on stump length. The earliest detectable extrajunctional [¹²⁵I]α-BTX binding appeared throughout the entire muscle fiber, and was not localized to the endplate region as would be expected if degeneration in the nerve terminal induced new receptors. However, later significant increases in [¹²⁵I]α-BTX binding at the endplate region could have resulted from such degeneration. All these results are consistent with neurotrophic regulation of muscle ACh receptors, working via a mechanism involving axonal transport.