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At least 199 records · Page 11Linked to original sources
PubMed1981

[The effect of the gas permeability of plastics on the stability of thiomersal. Part 49: Contributions to problems concerning the use of plastic receptacles for liquid pharmaceuticals (author's transl)].

Our studies have shown that the considerable losses of Thiomersal contained in low-density polyethylene bottles are not attributable, as suggested in the literature, to a sorption of this preserving agent. Intact Thiomersal is not sorbed by low-density polyethylene; on the contrary, the good permeability of this packing material to gas, especially oxygen, accelerates the degradation of Thiomersal. Furthermore, the ethylmercury resulting from this degradation is able to permeate through low-density polyethylene by which a displacement of the reaction equilibrium takes place in favour of the degradation products, and the degradation of Thiomersal is accelerated. The mechanism of the degradation of Thiomersal in the presence of oxygen was elucidated.

Drug Packaging↗
PubMedDate not supplied

[Plastics on the eye - plastics in the eye. Human-optic materials].

BACKGROUND: Materials of identical or similiar chemical classes are used for contact optics as well as for implantable intraocular devices. All of them derive from the chemistry of industrial product developments. PATIENTS AND METHODS: Materials used in and on the eye should behave indifferent. They should not provoke any reaction in the eye and not themselves be altered by the biological surroundings. For materials used in the eye an especially high purity of the polymers utilized as well as a long term light stability is to be demanded. Optical properties like transparency have to be stable over extended time periods under normal light influence. The long time stability of UV-absorbing additives in the materials used has to be verified. RESULTS: All materials used for IOL's - with the exception of the homopolymer of methylmethacrylate - consist of polymer mixtures forming socalled interpenetrating networks which appear as an uniform material. For the manufacturing of intraocular lense materials standardized or unanimous producer prescriptions are not existing. Based on the different polymer formulations different aging and fatigue properties are the outcome. In addition only inadequate knowledge about the long term light stability of the incorporated UV blockers is submitted. CONCLUSIONS: Polymeric materials used for IOL's should be subjected in addition to the test methods listed in EN-ISO 11 979/5 to chemical, polymeranalytic and mechanical substance examinations. As a standard in such examinations a polymethylmethacrylate, free of methylacrylate is proposed. Examinations of each lot should be compulsory. Identification of all ingredients of the intraocular materials should be prescribed and labeled in line with the revelations of common medical drugs prescriptions. The relevations commit the medical doctor to inform his patient about possible side effects of the intraocular implants.

Biocompatible Materials↗
PubMed1998

Plasticity of plasticity? Changes in the pattern of perceptual correlates of reorganization after amputation.

We report a follow-up study on seven arm amputees in whom magnetic source imaging had originally revealed a strong correlation between the amount of cortical invasion of the deafferented cortex and the amount of pain evoked sensation mislocalized to the phantom limb. This re-examination was performed in order to corroborate the phenomenon of mislocalization. On follow-up examination for mislocalization 4 weeks later, a close correlation had remained between the original amount of cortical representational reorganization of the amputation zone (at the first examination) and the number of sites from where painful stimuli evoked sensations referred to the phantom limb, i.e. the amount of perceptual mislocalization, at the second examination. However, contrary to our expectation, the topography of referred sensation had completely changed in every patient. These results suggest that while the overall extent of reorganization is a rather stable phenomenon, the concomitant changes in the pattern of sensory processing are not. This may be due to the fact that alterations of sensory processing are not hardwired, but are rather mediated by an extensive and interconnected neural network with fluctuating synaptic strengths. This mechanism may be of importance for neurological rehabilitation.

Accidents↗