Biomedical subjects

J K H Hörber

Publications and source records attributed to J K H Hörber.

3 recordsLinked to original sources

PubMed2006

Secretory vesicles in live cells are not free-floating but tethered to filamentous structures: a study using photonic force microscopy.

It is well established that actin and microtubule cytoskeletal systems are involved in organelle transport and membrane trafficking in cells. This is also true for the transport of secretory vesicles in neuroendocrine cells and neurons. It was however unclear whether secretory vesicles remain free-floating, only to associate with such cytoskeletal systems when needing transport. This hypothesis was tested using live pancreatic acinar cells in physiological buffer solutions, using the photonic force microscope (PFM). When membrane-bound secretory vesicles (0.2-1.2 microm in diameter) in live pancreatic acinar cells were trapped at the laser focus of the PFM and pulled, they were all found tethered to filamentous structures. Mild exposure of cells to nocodazole and cytochalasin B, disrupts the tether. Immunoblot analysis of isolated secretory vesicles, further demonstrated the association of actin, myosin V, and kinesin. These studies demonstrate for the first time that secretory vesicles in live pancreatic acinar cells are tethered and not free-floating, suggesting that following vesicle biogenesis, they are placed on their own railroad track, ready to be transported to their final destination within the cell when required. This makes sense, since precision and regulation are the hallmarks of all cellular process, and therefore would hold true for the transport and localization of subcellular organelles such as secretory vesicles.

Actins↗

PubMed2003

Scanning probe evolution in biology.

Twenty years ago the first scanning probe instrument, the scanning tunneling microscope, opened up new realms for our perception of the world. Atoms that had been abstract entities were now real objects, clearly seen as distinguishable individuals at particular positions in space. A whole family of scanning probe instruments has been developed, extending our sense of touching to the scale of atoms and molecules. Such instruments are especially useful for imaging of biomolecular structures because they can produce topographic images with submolecular resolution in aqueous environments. Instruments with increased imaging rates, lower probe-specimen force interactions, and probe configurations not constrained to planar surfaces are being developed, with the goal of imaging processes at the single-molecule level-not only at surfaces but also within three-dimensional volumes-in real time.

Biology↗

PubMed2002

[Atomic force microscope (AFM). A nanomanipulator for biophysical studies of stereocilia of the cochlear hair cells].

OBJECTIVES: Studies of the mechanoelectrical sensor system of the hair cell bundle in the cochlea require a manipulation device that enables controlled force application and movement of individual stereocilia in the nanometer range. METHODS: In our atomic force microscope (AFM) setup, the scan is directly controlled in an upright differential interference contrast (DIC) infrared video microscope with a water immersion objective and in the measured AFM image. Here we present studies on hair cells of the mammalian cochlea. RESULTS AND CONCLUSIONS: The resulting images revealed the tips of individual stereocilia of living sensory cells of the organ of Corti and the typical shape of the ciliary bundle. Scanning electron-microscopic (SEM) images of the identical hair bundles obtained after AFM investigation demonstrated that up to four AFM manipulations on the same cell did not cause obvious damage to the surface morphology of the stereocilia.

Animals↗