Biomedical subjects

C F Vahl

Publications and source records attributed to C F Vahl.

93 records · Page 6Linked to original sources

PubMed1990

[Intraoperative diagnosis--measuring heart time volume and assessment of shunts].

Intraoperative measurement of hemodynamics provides objective data supporting improvement of surgical and anaesthesiological treatment. Several methods including the thermodilution method, application of ultrasonic flow meters, use of the computed pressure gradient technique, application of transoesophageal color flow mapping and other cardiovascular applications of ultrasound are discussed with respect to their benefits and limitations in a clinical routine environment in cardiac surgery. According to our experiences the application of intraoperative transoesophageal doppler echocardiography and use of electromagnetic flow measurements are today the methods of choice. However, methodological limitations have to be regarded and additional intraoperative and clinical data are necessary whenever semiquantitative measurements of ultrasound techniques are used as basis for intraoperative judgement on the hemodynamic situation.

Cardiac Output↗

PubMed1986

The temperature dependence of post-vibration tension recovery in intact and skinned rat tracheal smooth muscle.

The contraction kinetics of rat tracheal smooth muscle were studied by analysing the time course of tension recovery after the cessation of a 2 s length vibration (100 Hz, sinusoidal) in activated preparations. An initial fast component of tension recovery reflects the rearrangement of those crossbridges previously detached by vibration. The subsequent slow component could be related to the kinetics of the regular actin-myosin interaction. Both components still occur independently of the duration and type of activation (electrical field stimulation and 0.1 mM 1(-1) acetylcholine), the bath temperature (16, 22, 28 and 37 degrees C), and of the functional behaviour of the cell membrane (intact or Triton X-100 skinned preparations). The time constants of post-vibration tension recovery were increased distinctly during prolonged activation, low temperature, and after skinning (lack of calmodulin). The activation enthalpy was calculated according to Arrhenius by using the time constant of the slow component of post-vibration tension recovery. It amounted to 94.7 +/- 0.6 kJ mol-1 for the intact preparation and 97.2 +/- 1.0 kJ mol-1 for the skinned one (temperature range 16-28 degrees C). These results provide further evidence that vibration affects the contractile system directly and that the kinetics of post-vibration tension recovery reflect the kinetics of actin-myosin interaction.

Actins↗

PubMed1984

The time course of changes in contraction kinetics during the tonic activation of the rat tracheal smooth muscle.

The tension increase after onset of electrical stimulation (30 Hz square wave; 1.65 ms pulse duration) and after the cessation of inhibiting length vibration (frequency 100 Hz sinus; amplitude 6% of the muscle length) was analysed in the isolated rat tracheal smooth muscle. In the first experimental series, tonic contraction was interrupted by a 2 s vibration applied 4-256 s after a preceding stimulation. In the second series, the onset of force development was delayed by a long-term vibration stopping 6-258 s after the commencement of a simultaneously performed electrical stimulation. In both the experimental series tested, the time course of post-vibration tension recovery showed an initial fast and a subsequent slow component. The former reflects the kinetics of cross-bridge reattachment and the latter those of the normal actin-myosin interaction cycle. The time constants of both these components reached a minimum of 0.58 +/- 0.04 s (fast) and 3.49 +/- 0.28 s (slow component) when the vibration stopped 18 s after the start of stimulation. Both values increased to 1.29 +/- 0.15 s and 9.98 +/- 1.17 s after a preceding stimulation of 256 s. These changes in the time constants may reflect the slowing of cross-bridge action under prolonged contraction. Such variations in the time constants of post-vibration tension recovery occurred without any corresponding changes in the steady state tension developed after cessation of vibration. These results lend further support to the supposition that different mechanisms might control the rate and extent of smooth muscle contraction.

Actins↗