Cross-linking by 1-ethyl-3- (3-dimethylaminopropyl)-carbodiimide (EDC) of a collagen/elastin membrane meant to be used as a dermal substitute: effects on physical, biochemical and biological features in vitro.

Next to in vitro-cultured autogeneic keratinocytes for the restoration of epidermis, a suitable dermal matrix is a mandatory component of an artificial skin substitute for the permanent covering of full thickness skin defects. In our model a xenogeneic membrane, consisting of processed native collagen and elastin of porcine origin is meant to serve as a template for the formation of a neo-dermis. In order to improve the resistance of this matrix against enzymatical degradation, we cross-linked it by using the carbodiimide 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) together with N-hydroxysuccinimide.

Extracellular compartments of the blowfly eye: ionic content and topology.

To analyze the elemental composition and topology of the extracellular compartments of the compound eye, the eyes of blowflies Calliphora vicina were rapidly frozen and ultrathin cryosections were freeze dried. Three zones of an ommatidium, peripheral cytosol of visual cells, rhabdomeres, and ommatidial cavities were analyzed by X-ray microprobe analysis. The ommatidial cavity was found to contain sodium and potassium in proportion similar to that in the blowfly hemolymph.

Comparing properties of brains and computers.

The criterion that pure natural science can only investigate objective phenomena which can be observed by independent observers sets certain limits to pure natural scientific understanding of brain functions. It excludes consciousness and feelings since these are only subjectively accessible and alternatives cannot be decided objectively. The limitations of brain research are discussed by comparing the properties of brains and computers.

Kinetics of rhodopsin regeneration in situ and in the excised median eye of Limulus polyphemus measured using electrophysiological methods.

The reactivation of rhodopsin after photoregeneration from metarhodopsin in the UV-sensitive cells of the median eye of Limulus was examined by means of extracellular electroretinogram (ERG) measurements. Absorbed photons convert the transducing rhodopsin (Rt) to metarhodopsin, which is thermostable and can be reconverted by another photon to non-transducing rhodopsin (Rn). The amplitude of the ERG is assumed to correlate linearly with the amount of Rt under otherwise constant conditions.

The Limulus ventral photoreceptor: light response and the role of calcium in a classic preparation.

The ventral nerve photoreceptor of the horseshoe crab Limulus polyphemus has been used for many years to investigate basic mechanisms of invertebrate phototransduction. The activation of rhodopsin leads in visual cells of invertebrates to an enzyme cascade at the end of which ion channels in the plasma membrane are transiently opened. This allows an influx of cations resulting in a depolarization of the photoreceptor cell.