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Biomedical subjects

M Benthin

Publications and source records attributed to M Benthin.

9 recordsLinked to original sources
PubMed2001

13cis- and all-trans retinoic acid have antiproliferative effects on CML cells and render IFN alpha antiproliferative potency after combined treatment in vitro.

The treatment of CML with IFN alpha is limited due to resistance against this substance. Recent studies with different cells than chronic myelogenous leukemic cells revealed a synergistic effect of a combined use of Retinoids (RA) and IFN alpha. The purpose of the study was to detect possible interactions of IFN alpha and RA in CML considering also the effect of the BCR-ABL gene-product. Therefore, we investigated three CML cell lines in their proliferation after incubation with IFN alpha and Retinoids alone and in combination. We measured low susceptibility to IFN alpha but a marked influence of the Retinoids. In combination, the growth inhibition was enhanced potentially in response to an increased efficacy of IFN alpha. Even solely, ineffective concentrations of both substances lead to decreased proliferation.

Antineoplastic Agents↗
PubMed1991

Calculation of pulse-wave velocity using cross correlation--effects of reflexes in the arterial tree.

The need to investigate the elastic properties of arterial vessels in situ for the early recognition of degenerative disorders in arteries has long been apparent. Pulse-wave diagnostics has been used in traditional medicine, but only in a qualitative way. By measuring the vessel diameter change, simultaneously at two levels along an artery, it should be possible to calculate the pulse-wave velocity (PWV). A newly developed ultrasonic instrument, DIAMOVE, was designed to provide a two-dimensional, real time, B-mode image for display of the exact position of two measurement sites; a computer-controlled digital phased-locked loop detector for the measurement of diameter changes; and a personal computer for the display of the momentary displacement of the artery walls. The cross-correlation technique was used on the information from the vessel wall movements to calculate the resulting PWV. Early measurements on healthy patients showed some unexpected artifacts, which were found to be due to reflected waves, affecting the shape of the pulse-wave at the sites of measurement. A modified PWV estimation algorithm, where only the foot of the pulse-wave in every beat is utilized, seems to have solved this problem and now makes the method suitable for clinical use.

Algorithms↗
PubMed1991

Aortic diameter pulse waves and blood flow velocity in the small, for gestational age, fetus.

An ultrasound phase-locked, echo-tracking system was used for noninvasive measurements of pulsatile diameter changes in the descending aorta of 60 small, for gestational age (SGA), fetuses and of 60 fetuses appropriate for gestational age (AGA). Pulsed Doppler ultrasound was used for the recording of blood flow velocity in the aorta and in the umbilical artery of the SGA fetuses. In the SGA fetuses, a weight-related higher end-diastolic diameter and a lower relative pulse amplitude suggest that diastolic blood pressure was increased; a less steep rise of the initial ascending part of the pulse wave and a lower relative pulse amplitude suggest that the absolute stroke volume was decreased. Except for a positive correlation between relative pulse amplitude and mean velocity in the aorta, no correlation was found between diameter pulse waves and blood flow velocity. Aortic diameter pulse waves apparently yield no unequivocal information as to peripheral resistance, for which purpose blood flow velocity waveform analysis would seem, at least at present, to be the only available method.

Adult↗
PubMed1983

Automated rhinomanometry.

In order to facilitate measurements and calculations in rhinomanometry a microprocessor is used. Pressure and flow signals, obtained from microtransducers, are automatically calibrated by drawing known volumes of air through a standardized test-nose, while the signals are read by the computer. When the patient is connected, the pressure-flow curves are displayed on a screen. At adequate breathing, the computer reads the pressure and flow 200 times per second for a few breaths. It performs all calculations and presents data describing the pressure-flow relationship, e.g. in terms of the resistance, where the curve crosses a circle with a certain radius in a polar coordinate system. Automatically calculated data were compared to manually derived ones in six healthy subjects and twenty patients with symptoms of nasal obstruction. There was a close correlation between the two sets of data. It is concluded that the described automated rhinomanometer facilitates the rhinomanometric procedure and gives accurate data on nasal airway resistance.

Airway Resistance↗
PubMedDate not supplied

Pulse wave recording--development of a method for investigating foetal circulation in utero.

The need to investigate the elastic properties of arterial vessels 'in situ' for the early recognition of degenerative disorders in arteries has long been apparent. Volume pulses in defined segments of arteries can be evaluated for this purpose, and the present paper contains a survey of earlier attempts to quantify volume pulses by means of ultrasound. A presentation is given of a recently developed digital system, comprising a phase-locked echo tracker, capable of monitoring non-invasively the diameter and its pulsatile changes of a selected artery along two chosen image lines of a linear array ultrasound scanner. The physical limitations of tracking fast-moving ultrasound echoes by means of phase-locked range gating are reported and the advantage is emphasized of using a gate length of one full period. This system has been calibrated, tested and applied in measurements of pulse wave pattern and propagation velocity in the descending aorta of human foetuses in the last trimester of gestation. The present high-resolution echo-tracking method has yielded reproducible results in the foetus and appears suitable also for screening studies on adult vessels.

Blood Circulation↗
PubMedDate not supplied

An ultrasonic system for diameter pulse tracking in arteries: problems and pitfalls.

Non-invasive ultrasonic techniques for measuring the mechanical behaviour of large arteries have a potential clinical application for physiological studies of the circulation and early detection of degenerative arterial disorders. A newly developed system for such purposes, comprising two double-echo trackers with zero-crossing phase-locked circuits and interfacing a B-mode real-time scanner, has been introduced for on-line recording of the diameter in a selected aortic segment. The aim of this report is to draw attention to the limitations of the technique in order to avoid misinterpretation of results. The various problems associated with the use of phase-locked echo followers for tracking sonic echoes of vessel pulse waves are summarized. The high spatial resolution of the measuring system is essential for estimating the elastic properties of the vessel, because the fractional changes of the diameter waveform during a heart cycle are small compared with the swings of intravascular pressure. Measuring errors may originate from either human or technical sources. From several viewpoints correct alignment of the ultrasonic beam vis-à-vis the vessel segment under consideration is crucial for obtaining valid measures. A thorough knowledge of the physics involved is essential for an adequate use of the instrument. With correct use, easily reproducible and reliable estimations are obtained of the mechanical properties of large vessel walls.

Aorta, Abdominal↗