Holger Kiesewetter

Experimental calibration of a two-stage prism-grating system for measuring cell velocity

Abstract A new optical system for the measurement of the erythrocyte velocity in microvessels is extensively applied for the first time. It is based on the projection of the erythrocyte image onto two photodiodes through a prism grating. The differential signal of the photodiodes is proportional to the velocity. The system is comparable to those of M. Anliker, M. Casty, P. Friedli, R. Kubli, and H. Keller ((1977). Noninvasive measurement of blood flow. In “Cardiovascular Flow Dynamics and Measurement” (N. H. Hwang and N. Normann, eds.), pp. 43–88. Univ. Park Press, Baltimore) and D. W. Slaaf, J. P. S. M. Rood, G. J. Tangelder, and T. Arts ((1979). Microvasc. Res. 17, S173). It measures an instantaneous velocity. The system is calibrated by a velocity which is constant over the total measuring field and by a known flow rate and profile. Concerning applicability and results the device is compared to the two-slit methods, the laser-Doppler-anemometry and high-speed cinematography.

Zur Untersuchung der Retinadurchblutung mittels Fernsehfluoreszenzangiographie

Die Fernsehfluoreszenzangiographie ist ein Verfahren, das sowohl die Registrierung von konventionellen Netzhautaufnahmen als auch von Fluoreszenzangiogrammen ermoglicht Die Aufzeichnung von Angiogrammen bei guter Auflosung und minimaler Beleuchtungsstarke ist inzwischen realisiert Mit Hilfe eines selbstentwikkelten Videotimers und -analysers ist es moglich, reproduzierbar Farbstoffdilutionskurven zu registrieren. Aus diesen lassen sich verschiedene, fur die Mikrozirkulation relevante, Parameter ermitteln.

A Measuring Device to Determine a Universal Parameter for the Flow Characteristics of Blood: Measurement of the Yield Shear Stress in a Branched Capillary

There has been an increasing attempt in recent years to search for alterations in hemorheological parameters in a variety of disease states, characterized by an increase in the viscosity of whole blood (Volger, 1980). Factors which influence this gross parameter include: hematocrit, plasma viscosity, extent of erythrocyte aggregation, and red cell deformability. A number of controversial methods exist to quantify these factors, but until recently it has been impossible to evaluate the total extent of a rheological alteration or to quantify the influence of a change in several parameters on the whole blood viscosity. The most commonly used measurement of whole blood viscosity — “rotational viscosimetry” — seems to be inappropriate because certain pathological states are concealed by phase separation in the measuring chamber due to sedimentation of large erythrocyte aggregates. This results in an apparent whole blood viscosity, as measured by rotational viscosimetry, much lower than the true viscosity in samples with greatly altered rheological parameters.

Television Fluorescein-Angiography of the Retina with On-Line Measurement of the Dilution Curves

For a long time television techniques have been employed for the imaging of the human retina. Lidley (1950) reported as early as 1950 about the application of television systems in ophthalmology. During the last years the low light level technique has rendered possible examinations with a low light stress; and computers allow an objective evaluation of the data. Van Heuven et al. (1972), Yuhasz et al. (1973) and Wessing et al. (1974) have made recordings of retinal fluorescein angiograms with a good resolution and a tolerable light stress. Some procedures are able to measure blood flow parameters of the human retina on-line as well as off-line. The essential disadvantages of these methods — especially the on-line methods — are the very high light stress and the missing reproducibility in the evaluation of the data. This leads to the fact that none of these methods are used in clinical routine as yet. The image analyzer Mikro-Videomat 3 (Carl Zeiss AG) renders the measurement of objective data from the recorded television fluorescein angiograms possible (Jung et al., 1980; Korber and Gesch, 1982). The recording method is shown in Fig. 1.

STAGNANT ANOXIA ON THE BASIS OF HEMORHEOLOGICAL OCCLUSION: RHEOLOGICAL AND PHYSIOLOGICAL ASPECTS OF THE “YIELD SHEAR STRESS” OF BLOOD

Publisher Summary This chapter describes stagnant anoxia on the basis of hemorheological occlusion and rheological and physiological aspects of the yield shear stress of blood. Mammalian blood is a highly non-Newtonian fluid; its viscosity can be as low as that of plasma and may approach infinity. The well-known phenomenon of blood stasis in the microvessels can be understood as the consequence of the thixotropic behavior of slowly flowing or stagnant red cell suspension in plasma. The rouleaux formation and the progressive increase of blood viscosity with decreasing shear stress can progress to a localized total loss of blood fluidity. Long collaterals in a hypoperfused network of capillaries are especially prone to such collateral blood viscidation because of the low shear stresses. A model of branched and converging microtubes of 120 μm diameter is constructed. Unstretched nylon threads are mounted, in a silicon-matrix, which is filled with polyester resin. After the curing of the resin, the nylon threads are stretched from their ends so that their diameter decreases and thus, they can be drawn out completely from the synthetic block. The data show that enhanced red cell aggregation at normal and elevated hematocrit leads to a curtailment of the O 2 supply to tissues.

Eine Methode zur schnellen Messung der Aggregationsgeschwindigkeit von Erythrozyten und eine hämorheologische Methoden-Kritik an der Blutsenkung

Wie im vorherigen Vortrag festgestellt, eignet sich die Messung der BKS immer dann nicht als Mas fur die Erythrozytenaggregation, wenn bei normalem Hamatokritwert die Aggregation als Netzwerk auftritt und wenn eine Aussage uber unverdunntes Blut gemacht werden soll. Auf der anderen Seite last sich mit der Messung der thixotropen bzw. Strukturviskosen Eigenschaften des Blutes die Aggregation sehr schlecht erfassen, wenn die Suspensionsstabilitat gering und eine Neigung zur Klumpenaggregation besteht (SchmidSchonbein et al., 1977). Dagegen eignet sich die photometrische Aggregometrie sehr gut, um in einem Analogsignal bei plotzlichem Stillstand einer Blutprobe nach Scherung den optischen Effekt der Zusammenlagerung vieler einzelner Erythrozyten zu wenigen Erythrozytenaggregaten zu erfassen. Das erstmals von Zijlstra so genannte „Syllektogramm“ beruht auf der Tatsache, das die Lichtstreuung nach Bildung von Aggregaten ab-, die Lichttransmission dementsprechend zunimmt.