Biomedical subjects

R Normann

Publications and source records attributed to R Normann.

3 recordsLinked to original sources

PubMed1993

Biocompatibility of silicon-based electrode arrays implanted in feline cortical tissue.

The passive biocompatibility of silicon-based electrode arrays was studied in feline cortical tissue. Three types of arrays were used: uncoated, coated with polyimide, and coated with polyimide over an adhesion promoter. Fifteen arrays were implanted for 24 h to determine early tissue reaction to the implantation procedure, and twelve arrays were implanted for 6 months to determine structural and material biocompatibility. Edema and hemorrhage were present around the short-term implants, but involved less than 6% of the total area of the tissue covered by the array. With chronic implants, leukocytes were rarely present and macrophages were found around roughly one-third of the tracks. Remnants of foreign material from the electrodes could be identified in less than 10% of the tracks. Gliosis was found around all tracks, forming an annulus between 20 and 40 microns thick. A capsule was not always present, and never exceeded a thickness of 9 microns. These results suggest that the implantation procedure produces limited amounts of tissue damage, and that the arrays are biocompatible. However, the arrays insulated with polyimide over a primer had significantly greater involvement of macrophages, gliosis, and capsule formation than uncoated arrays and arrays insulated with polyimide without printer, perhaps indicating a reaction to aluminum oxide in the primer.

Animals↗

PubMed1990

A 'puff and advance' technique for visually controlled staining of turtle retinal ganglion cells.

We describe a 'puff and advance' technique for visually controlled staining of retinal ganglion cells (GCs) in the unfixed, living retina for light and electron microscopy. Glass microelectrodes are filled with rhodamine-isothiocyanate labeled horseradish peroxidase (Rh-HRP), or Lucifer yellow (LY), or a mixture of both, or with 5,6-carboxytetramethylrhodamine (5,6-Rh) and advanced tangentially through the GC layer with microscopic observation using epifluorescence. Brief "puffs" of LY or 5,6-Rh are constantly ejected from the advancing electrode tip by a train of negative current pulses. GC penetration is signaled by virtually instantaneous staining of its soma (and eventually its axon and dendrites if the electrode is not advanced further). An impaled GC can be electron densely stained with the Rh-HRP complex by switching to positive current pulses. The extent of dye filling is monitored through the microscope using a filter combination appropriate for the dye. After fixation, standard histochemical procedures reveal HRP stained GCs in wholemount views for light microscopical examination. Furthermore, the preservation of the labeled cells and the neuropil is of a quality to allow electron microscopic analysis for synaptic input. This technique can be used in combination with LY backfiling of GCs from the optic nerve and with retinas in which GCs have been prelabeled with rhodamine beads retrogradely transported from the optic tectum as well.

Animals↗

PubMedDate not supplied

From value chain to value constellation: designing interactive strategy.

In today's fast-changing competitive environment, strategy is no longer a matter of positioning a fixed set of activities along that old industrial model, the value chain. Successful companies increasingly do not just add value, they reinvent it. The key strategic task is to reconfigure roles and relationships among a constellation of actors--suppliers, partners, customers--in order to mobilize the creation of value by new combinations of players. What is so different about this new logic of value? It breaks down the distinction between products and services and combines them into activity-based "offerings" from which customers can create value for themselves. But as potential offerings grow more complex, so do the relationships necessary to create them. As a result, a company's strategic task becomes the ongoing reconfiguration and integration of its competencies and customers. The authors provide three illustrations of these new rules of strategy. IKEA has blossomed into the world's largest retailer of home furnishings by redefining the relationships and organizational practices of the furniture business. Danish pharmacies and their national association have used the opportunity of health care reform to reconfigure their relationships with customers, doctors, hospitals, drug manufacturers, and with Danish and international health organizations to enlarge their role, competencies, and profits. French public-service concessionaires have mastered the art of conducting a creative dialogue between their customers--local governments in France and around the world--and a perpetually expanding set of infrastructure competencies.

Commerce↗