ABSTRACT
AIMS: In optic nerve hypoplasia (ONH), the extent of functional loss of retinal ganglion cells cannot be determined by ophthalmoscopic examination. The prognostic value of visual electrodiagnostic tests in infants and toddlers with ONH was assessed by comparison with visual outcome. METHODS: 85 participants with ONH had electroretinogram (ERG) and visual-evoked potential (VEP) testing to flash and to pattern-reversal checks and ocular fundus photography prior to 36 months of age. These initial measures were compared with visual acuity outcomes at 5 years of age in the better-seeing eye. RESULTS: Visual outcomes ranged from normal to no light perception. Electrodiagnostic tests with prognostic value were: the amplitude of the flash VEP (Spearman's rank correlations, p<0.001), the threshold category of stimulus (flash or check size) that elicited a VEP (p<0.001) and the amplitude of the N95 component of the pattern ERG (PERG) to 4-degree checks (p<0.02). Optic nerve size and co-existing pallor were also significant correlates. Stepwise regression analysis composed a best prediction model from VEP threshold category, optic nerve size and optic disc pallor (R(2)=58%; p<0.001). CONCLUSIONS: Optic disc diameter, observation of disc pallor, VEP and PERG testing in infancy are useful for establishing the visual prognosis at 5 years of age in children with ONH. This is consistent with the notion that these parameters are related to the anatomic and functional preservation of retinal ganglion cells.
Subject(s)
Optic Nerve/abnormalities , Vision Disorders/etiology , Age Factors , Child, Preschool , Electroretinography/methods , Epidemiologic Methods , Evoked Potentials, Visual/physiology , Female , Humans , Infant , Male , Optic Disk/pathology , Optic Nerve/pathology , Prognosis , Retinal Ganglion Cells/physiology , Signal Processing, Computer-Assisted , Vision Disorders/pathology , Vision Disorders/physiopathology , Visual Acuity/physiologyABSTRACT
The luminance-response function of the brief flash full-field photopic electroretinogram (ERG) rises to a peak before falling to a sub-maximal plateau -- the 'photopic hill'. The combination of on- and off-responses inherent in the brief flash photopic ERG suggests that this luminance-response function could be modelled by the sum of a Gaussian function and a logistic growth function. Photopic ERGs to a luminance series of brief flashes against three different background luminances recorded from seven healthy adults showed the characteristic 'photopic hill' function for b-wave amplitudes which were satisfactorily fitted with the sum of a Gaussian curve and a logistic growth curve. As background luminance increased, both components shifted to the right on the luminance axis. The Gaussian component increased in amplitude while the logistic growth function component decreased in amplitude. The luminance-response function of a complete congenital stationary night blindness patient had almost no logistic growth component.
Subject(s)
Electroretinography/methods , Adaptation, Ocular/physiology , Adolescent , Adult , Humans , Light , Logistic Models , Mathematics , Middle Aged , Models, Biological , Night Blindness/congenital , Night Blindness/physiopathology , Normal Distribution , Photic Stimulation/methods , Prospective StudiesABSTRACT
This paper examines the ethics of international clinical collaboration in stem cell research by focusing on the AlloStem project. AlloStem is an international research programme, financed by the European Union under the Sixth Framework Programme, with the aim of advancing the use of stem cells in treating leukaemia and other haematological diseases. Several areas of ethical importance are explored. Research justification and the need to consider both deontological and teleological aspects are examined. Ethical sensitivity in research and the requirement to respond to areas of ethical concern identified by the European Commission, such as the involvement of human beings, the use of human tissue, and the use of animals are also explored. Ethical issues around project structure and management, such as ethical standardization in international research, and achieving set targets are discussed. The ethical importance of dissemination of findings and teaching in clinical research is also considered. Finally, the distribution of benefits is addressed and the importance of distributive justice is emphasized.
Subject(s)
Biomedical Research/ethics , Stem Cell Transplantation/ethics , Stem Cells , Biomedical Research/economics , Biomedical Research/education , Biomedical Research/organization & administration , European Union , Humans , International Cooperation , Therapeutic Human Experimentation/ethicsABSTRACT
The potential of the aldose reductase inhibitor ponalrestat (600 mg daily) to ameliorate diabetic neuropathy was evaluated in 259 diabetes mellitus patients with peripheral neuropathy (defined by abnormal vibration perception threshold and abnormal peroneal motor conduction velocity) in a double-blind placebo-controlled clinical trial running for 18 months. Overall, no beneficial effect of ponalrestat on vibration perception thresholds, nerve conduction velocities, and nerve action potential amplitudes was detected. Because vibration perception thresholds and conduction velocities in median, peroneal, and sural nerves did not deteriorate in the placebo group, the potential of ponalrestat to prevent the expected deterioration in peripheral nerve function that occurs with an increased duration of diabetes was not tested. Patients with an abnormal heart rate reaction to standing (abnormal 30:15 ratio; n = 84) on ponalrestat did not deteriorate in this autonomic nerve function test as shown in those on placebo. In conclusion, ponalrestat did not improve peripheral nerve function in diabetes mellitus patients with signs of peripheral neuropathy, although it did ameliorate a deterioration in autonomic nerve function in diabetic patients with signs of autonomic neuropathy.
Subject(s)
Aldehyde Reductase/antagonists & inhibitors , Autonomic Nervous System/physiopathology , Diabetic Neuropathies/drug therapy , Peripheral Nerves/physiopathology , Phthalazines/therapeutic use , Autonomic Nervous System/drug effects , Diabetic Neuropathies/physiopathology , Female , Glycated Hemoglobin/analysis , Heart Rate , Humans , Male , Middle Aged , Motor Neurons/physiology , Neural Conduction , Perception , Peripheral Nerves/drug effects , Placebos , Valsalva ManeuverABSTRACT
A total hip replacement femoral component was embedded using acrylic bone cement into a full length model femur consisting of a thin-walled cylindrical fixture and was loaded anatomically. The strains in the prosthesis, the fixture and the cement were determined as was the effect of prosthesis misorientation. This method of fixation, unlike others tested, gave prosthesis stresses of magnitude and distribution similar to those which occurred in similar prostheses implanted in human femora. A metal fixture was found to be suitable for in vitro testing of femoral components, since the fixture stresses were adequately low. High stresses occurred in the cement, and in spite of acrylic precompression due to polymerization in situ, could result in acrylic fatigue fracture and interface failure, both possible causes of the loosening which occurs clinically. The load transmission from prosthesis to model femur was discussed.
