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Biomedical subjects

B Hartmann

Publications and source records attributed to B Hartmann.

At least 145 records · Page 8Linked to original sources
PubMed1989

[Noninvasive, continuous measurement of finger artery pressure with the servo-plethysmo-manometer Finapres].

The servo-plethysmo-manometry, as described by Penaz, represents a method for noninvasive, continuous, true-phase measurement of the finger arterial pressure. PRINCIPLES OF MEASUREMENT The light transmission plethysmograph is integrated into a pneumatic cuff for the finger (Figure 1). The light intensity is a function of the instantaneous finger blood volume. It is assumed that the pulsatory volume fluctuations are a function of the instantaneous intra-arterial blood pressure. Since the elastic arterial walls counteract the volume fluctuations with resistance, for calibrated measurements, they must be in a fully relaxed state in the absence of transmural pressure. A criterium for assessment of the transmural pressure is the extent of the volume pulse amplitude which is relatively small in the presence of higher transmural pressure due to a lesser degree of distention of the arterial walls and which increases in association with higher extravascular pressure because of the lower transmural pressure. The registered photosignal is larger with continuous cuff pressure elevation and reduced when the intravascular pressure is exceeded. At maximal amplitude, that is, complete relaxation of the arterial wall and cessation of the transmural pressure, the servosystem is activated to regulate the cuff pressure such that the pressure in the finger cuff holds the finger blood volume constant during the pulse cycle with corresponding elevation during systole and reduction during diastole. Accordingly, the cuff pressure, with minimal delay, always can be equated with the intravascular pressure. MANOMETRY WITH THE FINAPRES Currently available Finapres models 4 and 5 are electronically similar, completely automatic and easy to handle. After positioning the finger cuff, the unit is adjusted automatically through comparison of the plethysmogram at each cuff pressure level with the predicted value stored as an algorhythm++.(ABSTRACT TRUNCATED AT 250 WORDS)

Arteries↗
PubMed1989

[Consequences from key technologies for content and profile of skilled worker occupations as well as for the occupational fitness of youths].

Nearly 85% of youths start their professional life with vocational training. New technologies almost make an increase of contents as well as integration of functions in existing occupations without lost of traditional abilities and skills. New vocational contents make one's way into curriculi of all occupations in different way, only 15 professions get a new profile. Representations about origin of many new profession in consequence of new technologies didn't come true in science and practice. Conclusions for occupational fitness and medical health care of youths follow various demands to physical and psychic fitness under rising chances of development the individuality. We need more knowledge about psychic performance of healthy and disadvantaged youth, when we will use the health-promotive potential of occupations.

Adolescent↗
PubMed1989

[Career choice of youths with chronic diseases].

More than 10% of the pupils at ten-year general polytechnical schools have chronic diseases, which mean a restriction of their vocational fitness. That's why they are allowed to apply for an apprenticeship sooner than the other pupils after having had a vocational guidance under the aspect of industrial medicine. Under the conditions of large towns the multiplicity of careers can be considered as most substantially limited for these pupils.

Adolescent↗
PubMed1989

[Anthropometric differences in the physical development of apprentices of various occupational groups].

Anthropometrical examinations were conducted longitudinally on 400 male and 140 female adolescents on application for vocational training and in their second year of training. Male adolescents who chose professions entailing severe physical strain and female adolescents opting for professions entailing medium physical strain demonstrate a less favourable physical condition at the time when they selected their profession than did adolescents in either group intended to enter physically less strenuous professions. These differences which relate to physical maturity were restored by the second year of training. All that remained were special characteristics related to the individual's constitution, with a tendency to pyknomorphia in professional groups where the physical strain is greater. The muscular mass and active body mass in the case of female adolescents subject to medium physical strain show a relative decline compared with a very high fat proportion of 24.6%. According to Conrad's body type definition, a tendency to leptosomia was observed in male adolescents up to the second year of training compared with a tendency to pyknomorphia in female adolescents.

Adolescent↗
PubMed1988

[Quality assurance in Riva-Rocci blood pressure measurement: simultaneous sphygmomanometry with open and covered pressure display].

The indirect measurement of arterial blood pressure according to Riva-Rocci is one of the most frequently performed medical diagnostic procedures. When properly performed, this method yields accurate readings compared with intraarterial measurements. However, measurements by means of conventional sphygmomanometers are subject to observer error and variability. Therefore, to eliminate important sources of bias (terminal digit preference of the observer, rate of inflation and deflation of the cuff), and to quantify interobserver variability, a new sphygmomanometer has been developed. The new instrument makes possible "simultaneous-blind" blood pressure readings by two observers, according to the Riva-Rocci method. Simultaneous-blind blood pressure readings were made by four observers with experience in blood pressure determination. In 448 measurements made under resting conditions, values obtained by different observers with the new device were very consistent with each other: there were no differences in 50% of systolic and 43% of diastolic measurements. Differences of more than 5 mmHg were observed only in 9% of the systolic and 11% of the diastolic measurements. In 165 measurements made during exercise, the differences between blood pressure readings by different observers were larger (more than 5 mmHg in 40% of systolic and 35% of diastolic values). This variability among observers may be substantial in blood pressure readings made in therapeutic and epidemiologic studies, even when the observers are carefully selected and trained. Compared with the conventional open measurements, blind measurements (n = 100) gave mean values 2 mmHg lower, depending on heart rate and cuff deflation rate. The new sphygmomanometer allows quantification and control of the variability among observers during both open and blind measurements.

Adult↗
PubMed1987

Slow exchanging protons in the Z-form of G-C and A-C alternating polymers by using a rapid dialysis method.

Using a dialysis method we have measured the hydrogen exchange (HX) kinetics in poly(dG-dC).poly(dG-dC), poly(dG-m5dC).poly(dG-m5dC), poly(dG-br5dC).poly(dG-br5dC) and platinated poly(dA-br5dC).poly(dG-dT) under experimental conditions in which these polymers adopt the Z-conformation. The latter polymer has one slow exchanging proton with a half-time of about 2 h, whereas the other G-C alternating polymers display a slow class of two protons with exchange half-time of about 6 h. These exchange half-times are independent of ionic strength and of the nature of the salt for all these polymers in the Z-form. The slow proton exchange appears to be strongly correlated to the Z-conformation but rather independent of the Z-DNA sequence. The comparison of the proton exchange rates with the corresponding B in equilibrium Z transition rates is not in favour of the same rate limiting step for both processes.

Circular Dichroism↗
PubMed1986

Guanine and 7-methylguanine amino proton exchange rates as a function of buffer pK: implications for the exchange mechanism.

Using the stopped-flow kinetic method we have measured the deuteration rate of the amino protons in 2'deoxyguanosine 5'monophosphate and 7-methylguanosine 5'monophosphate. For both compounds the exchange rates are accelerated with increasing concentration of a large number of buffers with widely differing pKs. The results obtained, in conjunction with a theoretical model study, give rise to serious doubts concerning the normally accepted mechanism of amino proton exchange involving a pre-protonation at N7.

Buffers↗
PubMed1986

Poly(dA-dT).poly(dA-dT) two-pathway proton exchange mechanism. Effect of general and specific base catalysis on deuteration rates.

The deuteration rates of the poly(dA-dT).poly(dA-dT) amino and imino protons have been measured with stopped-flow spectrophotometry as a function of general and specific base catalyst concentration. Two proton exchange classes are found with time constants differing by a factor of 10 (4 and 0.4 s-1). The slower class represents the exchange of the adenine amino protons whereas the proton of the faster class has been assigned to the thymine imino proton. The exchange rates of these two classes of protons are independent of general and specific base catalyst concentration. This very characteristic behavior demonstrates that in our experimental conditions the exchange rates of the imino and amino protons in poly(dA-dT).poly(dA-dT) are limited by two different conformational fluctuations. We present a three-state exchange mechanism accounting for our experimental results.

Deuterium↗
PubMed1986

A study of the thermal stability of the Z form of (m5dC-dG)3 by resonance Raman spectroscopy.

The thermal stability of the hexanucleoside pentaphosphate m5dCpdGpm5dCpdGpm5 dCpdG has been studied by resonance Raman spectroscopy with 257 nm excitation wavelength. At low temperature and in 3M NaClO4, the Raman spectrum resembles that of poly(dG-dC).poly(dG-dC) in the Z conformation. As the temperature is increased, the position and the intensity of several bands (1312 cm-1, 1482 cm-1, 1584 cm-1 and 1632 cm-1) are modified. The variation of intensity versus temperature is biphasic. Analysis of the results suggests that the increase of temperature induces first a transition from the Z form to an intermediate stable form which then melts. These results and those previously obtained by circular dichroism and 31P nuclear magnetic resonance suggest that the intermediate form belongs to the left family but with changes in the stacking of the bases and the geometry of the phosphate groups as compared to the canonical Z form.

Circular Dichroism↗
PubMed1986

Solvation of the left-handed hexamer d(5BrC-G-5BrC-G-5 BrC-G) in crystals grown at two temperatures.

Crystals of the hexadeoxyoligomer d(5BrC-G-5BrC-G-5BrC-G) were grown at different temperatures (5 degrees C, 18 degrees C and 37 degrees C) in the absence of divalent cations. The crystals grown at 5 degrees C did not diffract X-rays, while those grown at 18 degrees C and 37 degrees C did. The oligomer adopts the left-handed ZI conformation in both crystals. The main difference resides in a more extensive hydration shell in the crystal grown at high temperature than in the crystal grown at low temperature. The high-temperature crystal displays a spine of hydration running deep in the minor groove and linking exocyclic O-2 atoms of the pyrimidine rings. In both crystalline forms, a hydrated sodium ion bound to the N-7 of a guanine ring was found. Strings of water molecules bridging phosphate anionic oxygen atoms are found along the backbone. The absolute values of the propeller-twist are also different in both structures although the values of the twist are very similar. The results point to the importance of the crystallization conditions when analysing fine structural details like solvation properties of oligomers.

Crystallization↗