Suitable location and optimum bladder width for the occluding cuff used for indirect arterial blood pressure measurements at the wrist.

Using a finite element method (FEM) and a volume oscillometric method with a photo-electric plethysmograph, we tried to determine which location(s) and which bladder width(s) of the occluding cuff would allow the most accurate indirect blood pressure measurements at the human wrist. Nuclear magnetic resonance imaging of the wrist allowed us to determine the geometry of two-dimensional (2D) finite element models. FEM analysis showed that the pressure transmission ratio (calculated tissue pressure: externally applied pressure) from the cuff to the radial artery (RA) was 100% when the cuff was placed over the site (L1) at which the RA crosses the most protuberant spot on the volar aspect of the distal end of the radius. In fact, the mean blood pressure (BPM) measured at this site in human subjects coincided with that measured at the upper arm (BPMA). In addition, a three-dimensional (3D) FEM was constructed by extending the 2D FEM at site L1 in the longitudinal direction to investigate the relation between pressure transmission to the RA and cuff bladder width. FEM analysis using the 3D finite element model showed that for all cuff widths greater than 0.25 times the diameter of the wrist, the external pressure was transmitted almost completely to the RA beneath the cuff center. Moreover, when the cuff width was as large as 0.45 times the diameter of the wrist, the BPM measured at site L1 in human subjects was similar to the BPMA. The theoretical and experimental results in the present study both suggest that for accurate indirect blood pressure measurements at the wrist, the L1 site is a suitable location for the occluding cuff and a cuff whose bladder width is more than one-third but less than one-half the wrist diameter can be used.

Effects of acidic fibroblast growth factor on neuronal activity of the parvocellular part in rat paraventricular nucleus.

The effects of acidic fibroblast growth factor (aFGF) and its amino-terminal and carboxyl-terminal fragments (aFGF(1-15) and aFGF(114-140), respectively were examined on the neuronal activity in the parvocellular part of the paraventricular nucleus. As well known, this part contains a lot of corticotropin-releasing factor (CRF)-immunoreactive neurons. Application of 1 pg/ml and 2 pg/ml aFGF produced responses in 29.7% and 46.7% of neurons tested, respectively. Half or more than half of the responding neurons increased their discharge rate. Application of 0.2 ng/ml and 0.4 ng/ml aFGF(1-15) (1-15) also elicited response in 46.2% and 68.8% of neurons tested, respectively. Of these responding neurons, more than two third increased their firing rate. However, most of neurons tested for 0.67 ng/ml and 1.33 ng/ml aFGF(114-140) did not respond. Results suggest that aFGF and aFGF(1-15) promote the release of CRF through the activation of CRF-containing neurons.

Pressure-volume relationships of finger arteries in healthy subjects and patients with coronary atherosclerosis measured non-invasively by photoelectric plethysmography.

Knowledge of the mechanical properties of the small arteries is important for understanding physiological and pathophysiological conditions in the human peripheral circulation. We have recently developed a new method for the noninvasive measurement of arterial elastic properties in human fingers using photoelectric plethysmography. In this study, the pressure-volume relationship, an index for expressing arterial elasticity, was measured by this method in the finger arteries of 91 healthy subjects and 102 patients with coronary artery disease. Aging effects on the elastic properties of finger arteries were examined in healthy subjects classified into three groups: under 30, 31-49, and over 50 years of age. The pressure-volume curve shifted downward with increase in age, indicating that the elasticity of finger arteries decreased with age. Patients with 75% or greater coronary stenosis, as compared with age-matched healthy subjects, showed distinctly lower elasticity of finger arteries. As the number of diseased coronary arteries increased, the elasticity of finger arteries tended to decrease steadily. The elasticity of finger arteries decreased in coronary disease patients with hypertension much more than in those without hypertension. These results suggest that age-related changes in arterial elasticity can occur in peripheral small arteries, and that peripheral arteries in patients with coronary atherosclerosis are less elastic than those in healthy subjects.

Ambulatory monitoring of indirect beat-to-beat arterial pressure in human fingers by a volume-compensation method.

Using a volume-compensation technique, a portable device has been designed for the indirect measurement of beat-to-beat arterial pressure and its waveforms in the basal phalanx of fingers of ambulatory subjects. The device consists of (1) a transmission infra-red photoelectric plethysmograph (TIPP) to detect the variation of arterial volume, (2) a pneumatic cuff with an actuator, (3) a servosystem to control the cuff pressure, and (4) a stereo cassette tape recorder. Arterial pressure was determined from the cuff pressure which was controlled by the servosystem so as to maintain the arterial volume constant at the 'vascular unloading' state. This device is equipped with a compensator for any hydrostatic pressure difference between the heart and finger. Thus, the blood pressure at heart level can be obtained for any finger height. The total weight of the device was 1.6 kg. Blood pressure changes during walking, jogging, jumping, and exercises such as side-stepping, Master's two-step test and car driving, have been successfully recorded.

Electric impedance cuff for the indirect measurement of blood pressure and volume elastic modulus in human limb and finger arteries.

A new plethysmograph, the electric impedance cuff, was designed for the indirect measurement of blood pressure, volume elastic modulus Ev and compliance Ca in human limb arteries. This comprises a compression chamber filled with electrolyte solution and a tetrapolar electric impedance plethysmograph whose electrodes are placed inside the chamber; the former for controlling transmural arterial pressure Pt, and the latter for detecting total limb volume Vo, mean arterial volume Va and its variation delta Va. Systolic and mean arterial pressure in the upper arms, forearms and fingers were measured by detecting pulsatile impedance variation during the gradual (3-5 mm Hg per heart beat) increase (or decrease) in chamber pressure by the volume oscillometric technique. Diastolic and pulse pressure delta P were calculated from these pressure values. Compliance Ca = delta V/delta P and volume elastic modulus Ev = delta P/(delta Va/Va) were recorded at various Pt levels, controlled by the compression pressure. Although this is a kind of impedance plethysmograph, the volume change in a limb segment can be detected by this method without passing electric current through the limb.

Vibration technique for indirect measurement of diastolic arterial pressure in human fingers.

Diastolic pressure Pd was indirectly measured by vibrating a finger artery with a 10 Hz sinusoidal pressure variation during a gradual increase (or decrease) in occlusive cuff pressure Pc. Pulsatile arterial volume changes on which sinusoidal variations are superimposed were detected by a transmitted infra-red photoelectric plethysmograph (TIPP). It is known that volume change in an artery shows a maximum amplitude at the transmural pressure Pt level equal to 0 mm Hg due to the nonlinear viscoelastic properties of the arterial wall. For the same reason, the amplitude of the sinusoidal volume variation reached its maximum at the end-diastolic phase, when Pc was controlled to be exactly equal to Pd. The indirect Pd values determined from Pc were compared with those simultaneously measured by a direct method in rabbit forelegs and by the volume-compensation method in human fingers. Using the principle of the volume oscillometric method systolic and mean pressures were also determined by this system.

Step response analyses of the cardiovascular system and their application to the measurement of systemic and pulmonary vein compliances.

A theoretical analysis of the step response in the closed cardiovascular system induced by a sudden shift of the right cardiac output curve predicted that if the relations of the right heart output (COr) and the total systemic capillary flow (CFs) to the systemic venous pressure (Psv) are linear, then the time course of Psv change will become monoexponential with a time constant T given by T = Csv/(Gr + Gs), where Csv is the systemic vein compliance and Gr and Gs are the conductances of the transient COr-Psv and CFs-Psv relationships. A similar prediction was obtained for the time constant T of the pulmonary vein pressure (Ppv) response to the step change in the left cardiac output (COl) curve, pulmonary vein compliance (Cpv) and the conductances of the COl curve, and the pulmonary capillary flow (CFp) curve against Ppv. The actual Psv or Ppv changes following sudden alteration of the COr or COl curve by inflation and deflation of the balloon in the right or left atrium revealed monoexponential time courses. Semilogarithmic plots of the transient vein pressure changes yielded correlation coefficients of -0.995 +/- 0.006 (means +/- SD) in 11 curves for Psv and 0.977 +/- 0.017 in 16 curves for Ppv (P less than 0.01). The assumed linearity of dynamic COr and COl curves was confirmed by beat by beat COr-Psv and COl-Ppv relationships during the step responses, except for the first few beats immediately after the balloon maneuver. The linearity of the dynamic CFs curve was examined by measuring CFs with a double-step balloon maneuver so as to cause rapid equilibrium between COr and CFs at varied moments of the transient process. The correlation coefficient between CFs and Psv thus obtained was 0.98 +/- 0.04 (P less than 0.01). A similar linearity of the dynamic CFp-Ppv relationship was suggested from their steady-state curves. The values of Csv calculated from the experimental data were 1.70 +/- 0.12 ml/mmHg/kg body wt in 11 curves and those of Cpv were 0.13 +/- 0.03 ml/mmHg/kg in 15 curves. These results are mostly consistent with those previously reported.

Batatasins: New dormancy-inducing substances of yam bulbils.

Three growth inhibitors, for which the names batatasins I, II and III are proposed, occur in dormant yam bulbils. Application of these inhibitors suppresses the sprouting of bulbils, and the inhibition is reversible by low-temperature stratification. Batatasins I and III were isolated as crystals and partially characterized as phenotic compounds not identical with known inhibions.