ABSTRACT
A new method for the analysis of the specific activity of amino acids is described. The analysis is carried out by thin-layer chromatography of the dansylated amino acids, computerized fluorescence evaluation and activity measurement by quantitative autoradiography. Quantitative evaluation of the autoradiographs is achieved by careful calibration of the X-ray film blackening. As shown for 14C-labelled phenylalanine and tyrosine, the method allows the simultaneous determination of the specific activity of 22 amino acids. About 10(-13) mol of an amino acid with a specific activity of less than 5 GBq/mmol can be detected and measured by this method.
Subject(s)
Amino Acids/analysis , Amino Acids/isolation & purification , Autoradiography , Chromatography, Thin LayerABSTRACT
Based on results on central chemosensitivity in cats, paired stimuli were applied for therapy to infants with central respiratory insufficiency of various degrees. An unspecific respiratory stimulus, e.g. light for 1 s, was followed by a jet of either O2 or 2% CO2 in O2 for 1.5 s. The unspecific and the chemical stimuli were interspaced by 0.5 s. The combined stimulation was repeated every 10 s. The program was triggered by using threshold values of transcutaneous pO2. In infants with intratrachial tubes or tracheostoma we used the end tidal pCO2 for triggering the stimulation. The method could prevent hypoxemia during sleep in non-ventilated subjects with sleep apnea syndromes or in infants with severe hypoxemia during sleep after being rescued from Sudden Infant Death Syndrome (SIDS). In patients with Ondine's Curse Syndrome (OCS) with its CO2 insensitivity, paired stimuli were used in order to condition the chemical function of the respiratory system. Polysomnograms from 310 clinically healthy infants including healthy siblings of SIDS victims revealed instability of arterial pO2 and low CO2 sensitivity during sleep within the second month and the fourth to ninth month of life, respectively. These data challenge the described method as a potential preventive or therapeutic measure to defeat SIDS and sleep apnea syndromes in conjunction with disturbed chemical regulation of respiration.
Subject(s)
Blood Gas Monitoring, Transcutaneous/instrumentation , Monitoring, Physiologic/instrumentation , Sleep Apnea Syndromes/therapy , Sudden Infant Death/prevention & control , Arousal/physiology , Humans , Hypoxia/therapy , Infant , Infant, Newborn , Oxygen Inhalation Therapy/instrumentation , Sleep Apnea Syndromes/blood , Sleep Stages/physiologyABSTRACT
We describe the design principles of a photometric flatbed scanner with a scan area of 250 X 250 mm2, a dynamic range of 4000 gray levels, a signal/noise ratio of 2000/1, a step size of 0.1 mm, and a step frequency of 2000 steps per second. It is controlled by a microcomputer and used to acquire data for quantitative evaluation of gels or chromatograms. The performance of the instrument is demonstrated by the data obtained by scanning gratings, gray step filters, and high-resolution electropherograms.
Subject(s)
Electrophoresis/instrumentation , Photometry/instrumentation , Electronic Data Processing , Microcomputers , Photometry/standardsABSTRACT
Behind a beam-splitter in the illuminator, the irradiation of an area conjugated to the object plane is measured by a silicon photodiode and used as a reference signal. Analog division of the photomulitplier signal by this reference acts like stabilizing the light source by a factor greater than 25. A technical realization of the optical and electronical components as well as experimental results are described.
