Biomedical subjects

F B Reitz

Publications and source records attributed to F B Reitz.

4 recordsLinked to original sources

PubMed2003

'Minimum average risk' as a new peak-detection algorithm applied to myofibrillar dynamics.

We present a new peak-detection algorithm based on the method of 'minimum average risk' proposed by Kolmogorov and developed for signal processing in various fields. In this method, translations of features within a signal scan are quantified by minimizing the integrated pointwise product of each scan relative to the first derivative of the immediately previous scan. We have adapted this method for use in a new algorithm to monitor dynamic changes of sarcomere length in single myofibrillar sarcomeres of striated muscles, but the algorithm can also be used more generally for peak localization. We find that this method results in sub-nanometer precision and higher signal-to-noise ratio than current methods. At an equal noise level, the RMS deviation of the minimum average risk algorithm was 1.3 times lower than that of the center of mass method with modeled data and 3-4 times lower with actual data.

Algorithms↗

PubMed2001

Phase transitions and molecular motion in the cell.

The cytoplasm exhibits all of the signature characteristics of a gel. The thesis put forth here is that the cytoplasm's gel-like character is central to the generation of biological movement. In artificial gels, a common vehicle for generating movement is the polymer-gel phase-transition. By undergoing phase-transition, gels produce motion of both solvent and solutes. It is argued that cells do the same. Three examples are given: the secretory system, the muscle contraction system and the biological streaming system. In each case it is shown that the characteristic motions may be created as proteins and water undergo transition from an expanded, hydrated state to a contracted, dehydrated state--or the reverse. These changes shift solutes and solvent in a characteristic way that depends on the respective organelle's structure. Phase-transitions are simple, powerful mechanisms that may be responsible for many, if not all, biological motions.

Actins↗

PubMed1997

Does regulatory protein play a role in glucokinase localization?

The enzyme glucokinase has recently been found to be largely responsible for glucose homeostatic responses of both the liver and pancreas. The mechanism(s) of these responses remains unknown but recent studies suggest that the intracellular localization of glucokinase, controlled by glucokinase regulatory protein, may be important. This protein is known to bind to and inhibit glucokinase in a phosphofructose-sensitive manner, and we present evidence for the interaction of these proteins with F-actin. Glucokinase regulatory protein gelled F-actin, and gelation was specifically inhibited by glucokinase and the regulatory protein effectors fructose-1-phosphate (F1P) and fructose-6-phosphate (F6P). These results suggest that glucokinase regulatory protein may play a role in metabolism-sensitive glucokinase localization in vivo.

Actins↗

PubMed1994

Fibre optic scrambling in light microscopy: a computer simulation and analysis.

Optical fibres bent in two mutually perpendicular planes have proven useful for randomizing illumination in light microscopes. These optical scramblers can increase the resolution and/or contrast obtained with several modes of light microscopy. Here, computer simulations are used to investigate several parameters affecting light randomization in curved optical fibres in order to further the theoretical basis for scrambler design. Light passing through 90 degrees bends of optical fibre of varying radii of curvature was modelled by ray tracing in two dimensions, and scrambling mechanisms were observed. The effects of varying the position and angle of entry of light on the phase and direction of propagation of the emergent light were determined. It was found that (a) thorough scrambling does not necessarily require high numerical aperture (NA) entry of light into the fibre, (b) considerable order persists after a single 90 degrees bend of an idealized fibre and (c) a higher degree of scrambling (at the cost of transmission efficiency) is achieved in more tightly curved fibres. The pathlength variations introduced by scrambling proved smaller than typical laser coherence lengths, requiring temporal scrambling (vibrating the fibre).

Computer Simulation↗