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Biomedical subjects

P Schaaf

Publications and source records attributed to P Schaaf.

At least 73 records · Page 4Linked to original sources
PubMed1989

The structure of rabbit retinal Müller (glial) cells is adapted to the surrounding retinal layers.

Radial glial (Müller) cells of the rabbit retina were studied by various techniques including Golgi impregnation, scanning electron microscopy, horseradish peroxidase application, and staining of enzymatically isolated cells. This combination of methods produced detailed information on the specialized morphology of the Müller cells within the different topographical regions of the retina, and of the Müller cell processes within the various retinal layers. As a general rule, the retinal periphery contains short thick Müller cells with big endfeet, whereas the thick central retina is occupied by long slender cells with small endfeet. Independent of their location within the retina, Müller cell processes were found to be adapted to the structure of the surrounding retinal layers. Within the outer and inner nuclear layers, Müller cell processes (and somata) extend thin cytoplasmic "bubbles" ensheathing the neuronal somata, as do the "velate" astrocytes in the brain. In the plexiform layers, Müller cells extend many fine side branches between the neuropil, comparable to the protoplasmic astrocytes of the brain. In the thick myelinated nerve fibre layer of the central retina the Müller cell processes are rather smooth, similar to those of fibrous astrocytes. It is concluded that the neuronal microenvironment determines the morphology of a given glial process, or even of a part of a glial process running through a specialized neuronal compartment.

Animals↗
PubMed1989

The course of axons within the postnatal rabbit retina.

The course of optic axons within the postnatal rabbit retina was studied by scanning electron microscopy (SEM) of the nerve fibre layer exposed by HCl and collagenase treatment, and by freeze-fracture electron microscopy. In the first days after birth, axon bundles were found to run along a rather tortuous way in between the developing Müller cell endfeet. Later on and in adults, the axon bundles show a more straight course. Single axons running into a bundle show a very irregular course before they assume their path in parallel to the other fibres of the bundle. These results support the idea that the course of growing axons is somehow determined by free "channels" in between the endfeet of glial cells.

Animals↗
PubMed1987

Band 3 is the basolateral anion exchanger of dark epithelial cells of turtle urinary bladder.

The turtle urinary bladder serves as a model for collecting duct functions in the mammalian kidney. The epithelium of both the turtle bladder and the mammalian collecting duct can generate a steep gradient for H+ ions between blood and urine. Secretion of H+ into the urine is coupled to a basolateral efflux of HCO-3 that appears to be exchanged mainly against Cl-. Here we show that approximately 80% of the dark cells of the bladder contain a 110,000 relative molecular weight (Mr) analogue of the turtle erythrocyte anion exchanger, band 3. The band 3 analogue is confined to the basolateral cell surface and is absent from the apical membrane. A minor population of the dark cells (approximately 20%), which have been previously suggested to represent reverse cells that are involved in HCO-3 secretion rather than absorption, appears not to express a band 3-like anion exchanger, at either the apical or the basolateral membrane. The bladder band 3 protein is colocalized with actin and isoforms of ankyrin (200,000 Mr) and spectrin (230,000 Mr) along the basolateral membrane. Linkage of band 3 via ankyrin to the spectrin-actin lattice may restrict this anion exchanger to the basolateral membrane surface. In view of our previous observation of a band 3-like anion exchanger in the collecting duct epithelium of the rat kidney, these findings point to a common molecular basis for acid-base transport in the mammalian collecting duct and the reptilian urinary bladder.

Animals↗