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Biomedical subjects

B Ruth

Publications and source records attributed to B Ruth.

9 recordsLinked to original sources
PubMed1994

Measuring the steady-state value and the dynamics of the skin blood flow using the non-contact laser speckle method.

The non-contact laser speckle method provides a measure of skin blood flow with a time resolution of 1 s. Information about different characteristics of the blood flow can be obtained from measurements of the steady state and from the time course during ischaemia and reactive hyperaemia. Special signal processing, a microprocessor and a computer program facilitate the analysis of the data. They consider disturbances which come from a common tissue movement and from convulsions of the limbs. Measurements prove a decreased steady-state value and prolonged half-times during ischaemia and reactive hyperaemia when patients with peripheral arterial occlusive disease are compared with healthy subjects.

Arterial Occlusive Diseases↗
PubMed1993

Noncontact determination of skin blood flow using the laser speckle method: application to patients with peripheral arterial occlusive disease (PAOD) and to type-I diabetics.

The laser speckle method allows the noncontact determination of skin blood flow and its dynamics from a distance of 5 cm. The method is based on the time dependency of the speckle pattern formed by the scattered light of a 5 mW He-Ne laser (632.8 nm). Utilizing the speckle intensity measured through a pinhole, an electronic circuit generates an output signal denoted as blood flow parameter B. All measurements were carried out on the foot dorsum during steady-state, ischemia, and reactive hyperemia induced by a 3-min arterial occlusion. The investigations were carried out in four groups: healthy subjects, asymptomatic smokers, PAOD-patients, and type-I diabetics (D) with severe late complications. As shown by parallel measurements with the tcpO2-method, the initial value Binit of the blood flow parameter B indicates the steady-state blood flow. Binit decreases significantly from 5.95 +/- 2.55 (S.D.) for the control to 4.07 +/- 1.69 (PAOD) and 3.81 +/- 1.51 (D). The half-time BTrh for the increase of B at the beginning of the reactive hyperemia is significantly increased from 4.10 +/- 2.06 s (control) to 14.5 +/- 15.4 s (smokers), 17.6 +/- 32.7 s (PAOD), and 5.31 +/- 3.55 s (D). Other characteristic values such as peak value and time of peak during the reactive hyperemia as well as the final steady-state value and the time of its achievement exhibit similar effects. The correlation coefficients between the different characteristic values obtained from the laser speckle method indicate that the characteristic times of the dynamics and the absolute values of B vary separately and provide supplemental information. A two-dimensional representation of the characteristic values facilitates the differentiation between the four measured groups.

Adult↗
PubMed1993

Investigations on the photosynthetic system of spruce affected by forest decline and ozone fumigation in closed chambers.

Investigations using chlorophyll fluorescence induction kinetics provide the parameters Rfd, L, and Ap to characterize different specifications of the photosynthetic system (PS). The application of ozone, with concentrations between 100 microg m(-3) and 2000 microg m(-3) to spruce in closed chambers yields a reduction of Rfd between 6% and 23% for the current year's needles, which indicates a reduced potential photosynthetic capacity. Further measurements on the current year's needles of spruce of the damage classes S0/S1, S2 and S3 show also a reduction of Rfd of between 7% and 14% in 2 successive years. In addition, the parameter L increases for damaged trees by between 11% and 49%, indicating a change of the chlorophyll content and of the internal energy distribution between PSI and PSII. As no effect of L can be observed with ozone fumigation, it is concluded that the change of some specifications of the PS can be simulated well by ozone fumigation (e.g. Rfd) while other specifications cannot (e.g. L).

Journal Article↗
PubMed1993

Skin blood flow evaluated by the laser speckle method and the transcutaneous oxygen tension: interpretation of the dynamics using a simple model.

Spontaneous fluctuations of skin blood flow were measured by the laser speckle method in a time interval of 1024s. The frequency spectra of the resulting signal (blood flow parameter B) were calculated using the fast Fourier transformation. The mean spectrum was obtained from at least six single measurements on different days in the range 0.02 Hz-0.2 Hz. For five of six subjects no peak exists in the mean spectrum because it can be approximated by an exponential function with a mean frequency ranging between 0.05 Hz and 0.13 Hz (cycle length 7.7s - 20s). The dynamics of skin blood flow during ischaemia and reactive hyperaemia were simultaneously characterized by the blood flow parameter B and the transcutaneous oxygen tension p (24 measurements in 12 subjects). A simple theoretical model including a feedback control system for the stabilization of the tissue oxygen concentration is proposed. It provides an interpretation for the features of the dynamics of blood flow parameter B and transcutaneous oxygen tension p and their mutual relations, namely: (1) The increase in blood flow parameter B following the occlusion is determined by the arterial flow resistance. (2) The half-time for the decline of the blood flow parameter B from the peak of the reactive hyperaemia response to the final steady-state value and the existence of the spontaneous fluctuations of B indicate the active control of blood flow by the oxygen concentration in the tissue. (3) The large time constants of the oxygen tension equilibration during ischaemia and reactive hyperaemia originate from the capacity of the tissue to store oxygen. (4) The cycle length of the fluctuations (5s-50s) corresponds surprisingly well with the time constants for the decline of the blood flow parameter B from the peak to the steady-state (12.5s-42.5s).

Adult↗
PubMed1991

Measurement of the chlorophyll fluorescence induction kinetics with a 10 microseconds time resolution and its application in the forest decline research.

Measurement methods are described which determine the initial phase of the fluorescence induction kinetics with a maximum time resolution of 10 microseconds simultaneously for the two fluorescence components F685(t) and F730(t) selected by filters at the wavelengths 685 nm and 730 nm, respectively. The excitation light provided by a He-Ne laser (632.8 nm) is switched on within 0.3 microseconds (maximum intensity Ie = 12 mW/cm2). Fo, Fp, and Fs, the initial-, peak-, and steady-state intensity and the initial value Ro of the ratio R(t) = F730(t)/F685(t) can accurately be determined as well as the initial time derivative Fo* of the fluorescence intensity. Fo and Fo* are related to the quantum yield phi a of the antenna and to the photochemical quantum yield phi pc, respectively. Spruce, oak, birch, poplar, and soy bean show a decline of R(t) from Ro to a first minimum Rb at some 10 ms which has a similar value as the second minimum Rp in the time range of seconds. Furthermore, the initial value Ro and the steady-state value Rs of R(t) are also very similar. Measurements on spruce with water deficiency and with varying excitation light intensity Ie show effects on the initial phase of the fluorescence induction kinetics. Further measurements on spruce of different damage classes indicate that for the current year's needles the ratio Fp/Fo is the most sensitive parameter to differentiate between the damage classes and that Fo/Fs and Ro/Rb are also affected. As demonstrated by measurements on leaves of soy beans, the initial decrease of R(t) from Ro to Rb originates from a change of the fluorescence spectrum because no change of the leaf transmission can be observed in the time range between 10 microseconds and 1 ms.

Chlorophyll↗
PubMed1990

The fluorescence induction kinetics as a non-destructive tool for investigating spruce treated with ozone.

The scattering coefficient of yellow spruce needles exceeds that of green needles by a factor of 2, whereas the fluorescence efficiency is approximately equal for both needle colours. As shown by the angular distribution the fluorescence light is diffusely emitted. However, the scattered light consists of a diffuse and a reflecting portion below 20 degrees with a ratio of the intensities of 1 : 2 at perpendicular observation (0 degrees). Control measurements show that in the rejection region the effective transmission of cut-off-filters commonly used to separate fluorescence light and excitation light exceeds the value calculated from the filter specifications by a factor of 100. Therefore, the portion of the scattered light in the measuring signal must be controlled if the fluorescence induction kinetics is measured from specimen of different colour. A device for the determination of the fluorescence induction kinetics is described which employs a He--Ne laser, a mechanically working shutter with an opening time of 4 ms for the excitation, and a computer for data storage and device control. Two filters select the fluorescence components at 685 nm and 730 nm and they reduce the portion of the scattered light in the measuring signal to 0.18% and 0.55%, respectively. In order to consider the temporal development of the fluorescence kinetics the sampling rate is reduced from 2 kHz to 1 Hz. From the data stored in the computer maximum value Fp, and steady-state-value Fs are determined for both fluorescence components. Measurements on 4-year-old spruce exposed to ozone-concentrations of 0, 300 ppb, 600 ppb, and 1000 ppb were repeated every week. With increasing concentration and duration of treatment Rfd = (Fp-Fs)/Fs was decreased for both fluorescence components. With the highest ozone concentration a reduction of Rfd of 23% and 24%, respectively, was obtained for the two fluorescence components after three weeks.

Chemical Phenomena↗
PubMed1990

Blood flow determination by the laser speckle method.

Blood flow within the skin is measured by evaluating the dynamics of the laser speckle pattern. Laser light scattered from an object with a rough surface forms a granular structure--the speckles. When the object is moving, the speckle pattern becomes dependent on time. The measurements are performed at a distance of 6 cm which is adjusted by an auxiliary beam. The laser beam forms a spot on the skin with a diameter of approximately 1.5 mm and penetrates the skin. Part of the light is scattered back to the surface by the blood cells in the capillaries. The time dependent speckle intensity I(t) is determined by a photomultiplier. The comparison of spectra of I(t) obtained from measurements on the skin and on adhesive tape attached to the skin shows that there is a "tissue movement", the velocity of which has the same order of magnitude as the blood velocity in the capillaries. This has to be considered when measuring blood flow by the speckle method. Electronic signal processing reduces the influence from tissue movement and yields a value M being a relative measure of the blood flow. The time course of M during ischemia and reactive hyperaemia is compared with concurrent measurements of the skin temperature, the transcutaneous oxygen tension, and the laser Doppler signal. They exhibit similar tracings. Investigations in patients with leg ulcers show that measurements in open wounds can be performed.

Equipment Design↗
PubMedDate not supplied

[Experimental investigations on ultraweak photonemission form biological systems (author's transl)].

Measurements on untreated yeast cells, potato- and cucumber seedlings have confirmed the existence of photon emission from biological systems known as "ultraweak luminescence". The intensity is of the order of 10(2) counts per second, and the spectral distrubtion shows a maximum near 550 nm. The dependence of th photon emission on certain chemicals has been investigated. Some chemicals, as for instance acetone, intensify the photon emission from cucumber seedlings without essential change of the spectral distribution. On the other hand, NaCl leads to a shift to the red region of the spectrum. The treatment of EAT-cells by 4-Hydroperoxycyclofosfamide involves a nonlinear enhancement of the intensity with increasing concentration. There are some indications that collective interactions of the system are more appropriate than simple chemiluminescence reactions.

Candida↗