Hormonal effects on calcium homeostasis in isolated hepatocytes.

In this article the development of fiber-optic sensors for biomedical applications is reviewed. Light-carrying fibers are potentially useful in oximetry, dye dilution measurements, laser-Doppler velocimetry, and fluorometry; as physical sensors of temperature, pressure, and radiation; and as chemical sensors of pH, partial pressure of blood gases, and glucose. Emphasis is placed on the principles and ideas used in the various devices rather than on detailed descriptions or critical discussions.

https://science.sciencemag.org/content/sci/224/4645/123.full.pdf

Fiber-optic sensors for biomedical applications

Normal mitochondrial function is a critical factor in maintaining cellular homeostasis in various organs of the body. Due to the involvement of mitochondrial dysfunction in many pathological states, the real-time in vivo monitoring of the mitochondrial metabolic state is crucially important. This type of monitoring in animal models as well as in patients provides real-time data that can help interpret experimental results or optimize patient treatment. The goals of the present review are the following: 1) to provide an historical overview of NADH fluorescence monitoring and its physiological significance; 2) to present the solid scientific ground underlying NADH fluorescence measurements based on published materials; 3) to provide the reader with basic information on the methodologies used in the past and the current state of the art fluorometers; and 4) to clarify the various factors affecting monitored signals, including artifacts. The large numbers of publications by different groups testify to the valuable information gathered in various experimental conditions. The monitoring of NADH levels in the tissue provides the most important information on the metabolic state of the mitochondria in terms of energy production and intracellular oxygen levels. Although NADH signals are not calibrated in absolute units, their trend monitoring is important for the interpretation of physiological or pathological situations. To understand tissue function better, the multiparametric approach has been developed where NADH serves as the key parameter. The development of new light sources in UV and visible spectra has led to the development of small compact units applicable in clinical conditions for better diagnosis of patients.

Mitochondrial function in vivo evaluated by NADH fluorescence: from animal models to human studies.

Functional intermediates in the reaction of membrane-bound cytochrome oxidase with oxygen.

Bacterial cytochrome oxidases: a structurally and functionally diverse group of electron-transfer proteins

A versatile time-sharing multichannel spectrophotometer, reflectometer, and fluorometer

Low temperature trapping method for cytochrome oxidase oxygen intermediates

Double beam (dual wavelength) spectrophotometers generally employ alternating, rather than simultaneous, illumination of a single sample with wavelengths λ1 and λ2 to secure large aperture viewing without optical cross‐talk. Although this technique allows the use of phase sensitive detection, which greatly reduces the effect of noise entering the system between light switch and demodulator, it also impairs the system's immunity to lamp noise, as compared to a true differential system, in which λ1 and λ2 simultaneously illuminate the sample. To improve the noise rejection, we have devised a method of compensation which uses a second photomultiplier to monitor the time shared light beam before it enters the sample. The resulting signal is normalized and subtracted from the measure signal in a differential amplifier over a bandwidth including frequencies considerably above the switching frequency fc. Details of design are presented together with experimental data showing that greatly improved performance can...

Compensation for Light Source Noise in a Sensitive Dual Wavelength Spectrophotometer

A multi-wavelength time-sharing apparatus usable in various different configurations of optical measuring equipment to provide a plurality of time-shared optical channels and including appropriate circuitry. The apparatus employs a turbine-driven filter wheel having a shaft position-encoding arrangement consisting of a hollow shaft portion which is internally illuminated. The hollow shaft portion has two sets of spaced apertures cyclically communicating with respective angularly spaced pairs of externally fixedly mounted phototransistors which are sequentially illuminated as the shaft portion rotates and which produce timing pulses which drive Schmitt triggers, which, in a typical embodiment, in turn produce pulses compatible with a logic circuit employed to decode the phototransistor signals into triggers for driving a 4-channel switched gain equalizer, a dark current clamp, and detector gates. Appropriate selection of the signals enables the instrument to function as a fluorometer or a spectrophotometer.

Multi-channel optical time-sharing apparatus having a rotating filter wheel with position-encoding means

Three methods are described for extending the time range of the dual wavelength spectrophotometric technique. First, a dual wavelength system employing interference filters (essentially a differential colorimeter) is described which employs no light modulation and thus gives operation down to the shortest time measurable in view of the system signal‐to‐noise (S/N) ratio. The second method employs dual wavelength light modulation and synchronizes the transient phenomena to the flash of the measuring light. While this method extends the time range down to that obtainable in view of S/N ratio of the optical system it is essentially a single beam method and does not compensate for optical artifacts that occur during a single flash of the measuring light. The third method extends the time range of the dual wavelength method by substituting for the vibrating mirror an air‐turbine‐driven mirror capable of rotating at several kilohertz and giving dual wavelength readout every 400 μsec or less. The three methods have been employed in time ranges of 40, 200, and 1000 μsec, respectively, in the measurement of the fast reaction of oxygen with cytochrome oxidase bound to mitochondrial membranes.

Rapid Readout from Dual Wavelength Spectrophotometers

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