Biomedical subjects
R Heinrich
Publications and source records attributed to R Heinrich.
Interpersonal skills training: comprehensive approach versus brief instruction.
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The electric potential across the erythrocyte membrane: a mathematical model.
The space-dependent electric potential of erythrocyte membranes is determined on the basis of a mathematical model which takes into account the membrane surface charges of glycophorine A, spectrin and phosphatidyl serine. The calculations are performed by numerical integration of the nonlinear Poisson-Boltzmann-equation.
[Mathematical modelling of glycolysis and of adenine nucleotide metabolism of human erythrocytes. II. Simulation of adenine nucleotide breakdown following glucose depletion].
The breakdown of adenine nucleotides in human erythrocytes in physiological and alkaline medium at 37 degrees C after glucose depletion is simulated by a mathematical model of energy metabolism. The simulation consists of time dependent solutions of a system of 16 differential equations derived from the stoichiometry of chemical pathways and kinetic properties of enzymes. Starting with the stationary characteristics of the model (M. Schauer et al.: Acta biol. med. germ. 40, 1659, 1981) the results of the simulation were analysed as a function of 1) the share of adenylate deaminase in the degradation of adenine nucleotides and 2) the interaction between adenylate kinase equilibrium and magnesium ions. The experimental data and the simulated concentration changes are in good accord, provided that the assumed activity of adenylate deaminase is very low so that the degradation of adenine nucleotides proceeds mainly via AMP-hydrolysis. The extensive activation of adenylate deaminase during incubation is explained by its sigmoid kinetics with respect to AMP. To improve the results of simulation changes in the adenylate kinase equilibrium have to taken into consideration. These have been measured during incubation of erythrocytes; they can be attributed only partly to the increasing concentration of magnesium ions and to differences among the constants of magnesium association to adenine nucleotides.
Mathematical modelling of translation of mRNA in eucaryotes; steady state, time-dependent processes and application to reticulocytes.
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Occupational exposure to hexachlorocyclohexane. I. Body burden of HCH-isomers.
In a lindane (gamma-hexachlorocyclohexane = gamma-benzenehexachloride)-producing factor 57 workers were studied with regard to their blood levels of the three hexachlorocyclohexane isomers: alpha-, beta-, and gamma-HCH. The TLV-TWA (MAK value 1979) for gamma-HCH of 0.5 mg/m3 was not exceeded at any of the workplaces where HCH is synthesized and purified to lindane. Additionally, in some of the workers samples of s.c. adipose tissue were taken for determination of HCH-isomer content. An external group of 20 clerks was examined in the same way for control purposes. In contrast to the control persons, none of whom had HCH-concentrations in serum above the respective detection limits, the values determined in serum of the exposed workers were in the following ranges: alpha-HCH: 10-273 microgram/1, beta-HCH: 17-760 microgram/l, and gamma-HCH: 5-188 microgram/1. Of special interest is the observation of a significant increase of beta-HCH-concentration in serum with the time of employment in lindane production, indicating a pronounced accumulation of this substance in the human organism. Concentrations of this isomer in s.c. adipose tissues were about 300-fold higher than in serum. A significant correlation between both parameters could be established. The results of this study show that adherence to the TLV-TWA of gamma-HCH is not sufficient for control of HCH-exposure. Furthermore, biological monitoring of exposed workers is necessary taking into account the three more important isomers alpha-, beta-, and gamma-HCH.
Immunoreactive substance P in human plasma: response to changes in posture and sodium balance.
1. In healthy volunteers plasma concentrations of immunoreactive substance P were measured in response to changes in posture and dietary salt intake. 2. In 14 subjects plasma immunoreactive substance P was 168 +/- 31 pmol/l when subjects were supine and 401 +/- 51 pmol/l (P less than 0.001) when they were ambulant. 3. Measurement of supine plasma immunoreactive substance P at 6 h intervals gave a mean value of 240 +/- 39 pmol/l at 14.00 hours and a lowest value of 76 +/- 9 pmol/l at 02.00 hours. 4. In eight healthy subjects plasma immunoreactive substance P rose only slightly from 169 +/0 41 pmol/l, on a sodium intake ad lib., to 244 +/- 45 pmol/l by day 4 of dietary sodium restriction (35 mmol/day) and significantly fell to 51 +/- 20 pmol/l (P less than 0.001) by day 4 of high sodium intake (350 mmol/day). 5. Although exogenous substance P was shown to be natriuretic in dog and rat, the present results do not favour a role of endogenous substance P as a circulating natriuretic factor in man.
[Effect of chlorhexidine inthe form of an 0.2% solution and a 1% gel upon the gingiva and the state of oral hygiene of schoolchildren (author's transl)].
A double blind experiment made twice for two weeks was used to determine the effectiveness of chlorhexidine-containing preparations (0.2% solution, 1% gel) from the oral hygiene index, the sulcal bleeding index, and the rate of flow of sulcal fluid, with a total of 64 schoolchildren serving as subjects. The results of a longitudinal comparison confirmed the plaque-inhibiting effect of the chemotherapeutic agent, whereas inflammations of the gingiva were seen to be essentially unaffected. Short-time application of chlorhexidine is recommended as a supportive measure of oral hygiene to be taken in specific cases of indication.
Analysis of the quasi-steady-state approximation for an enzymatic one-substrate reaction.
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[Use of immune serums in the management of infectious diseases].
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Interpersonal skills training: evaluation in an internal medicine residency.
To determine the effectiveness of teaching interpersonal skills in a general internal medicine residency, a program was developed utilizing videotape feedback of house-staff/patient interactions, a modification of Interpersonal Process Recall (IPR). Fifty-one randomly selected house officers at different levels of training were included in a controlled, pretest-posttest study design. The major pre-post measures were three independent ratings of videotapes of actual first-visit interviews between resident and patient. House officers in the experimental group significantly increased the proportion of each interview devoted to psychosocial issues compared with controls, although the interviews remained predominantly medical; increased the use of effective responses; and improved their level of empathy with patients. Personality and attitude measures were found not to correlate with observed interpersonal skills on pretest or posttest videotapes. House officers rated the training program as being interesting, valuable, relevant, and nonthreatening. The data suggest that interpersonal skills can be effectively taught to internal medicine residents utilizing a videotape feedback training program.
Teaching interpersonal skills in a medical residency training program.
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Measurement of potassium activity in the cat carotid body using glass microelectrodes reinforced with bitumen [proceedings].
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A mathematical model for the influence of anionic effectors on the phosphofructokinase from rat erythrocytes.
The influence of the positive effectors AMP, sulphate, glucose 1,6-bisphosphate and the negative effector 2,3-bisphosphoglycerate on rat erythrocyte phosphofructokinase has been investigated. The kinetic data have been fitted to the Monod-Wyman-Changeux model as well as to a model based on a closed association-dissociation equilibrium. The application of the fitting procedure yeilds for both models a good corresponding between theoretical and experimental data and equal results with respect to the action of the effectors on the enzyme. The corresponding dissociation constants for the binding of the positive effectors to the active state are: AMP 35 micronM, sulphate 0.43 mM and glucose 1,6-bisphosphate 15 micronM. 2,3-Bisphosphoglycerate as in inhibitor stabilizes the inactive state (dissociation constant: 1.4 mM). A preliminary discrimination between the Monod-Wyman-Changeux model and the association-dissociation model has been attempted.
[Emergency treatment of haemophilia A with factor VIII inhibitors using activated prothrombin complex concentrates (author's transl)].
Severe rectal bleeding in a 6-year-old boy with haemophilia A and factor VIII inhibitors could not be stopped with factor VIII concentrates. But a good effect was achieved with activated prothrombin complex concentrates (fraction FEIBA), given over eight days. Amaurosis occurred as a complication after injection of the first dose, but disappeared completely within several minutes. Tests revealed accelerated intravascular coagulation with increased fibrin monomers and fibrin/fibrinogen degradation products.
An extended model of the glycolysis in erythrocytes.
An extension of a previous model [2] is proposed of the glycolysis of erythrocytes which includes realistic rat laws for the hexokinase-phosphofructokinase system and for the 2,3-P2G phosphatase. Whereas most conclusions previously drawn are reinforced, the mechanism of ATP regulation is different in the present model. The ATP concentration is mainly regulated by the inhibitory action of ATP and the activating effect of AMP on the phosphofructokinase. The role of the 2,3-P2G bypass as a buffer of changes in the ATP demand is of lesser significance than previously thought. Besides the feedback action of the adenine nucleotides on the hexokinase-phosphofructokinase system in the quasisteady state the role of 2,3-P2G as an energy source is important since it can yield ATP for a certain period of time. The present version of the model describes qualitatively the experimental data on the modulation of Na+-K+-ATPase.
Regulation of anaerobic glycolysis in Ehrlich ascites tumour cells.
1) In intact Ehrlich ascites tumour cells the anaerobic glycolytic flux rate and pattern of intermediates have been investigated at different pH values of the extracellular medium. 2) As predicted from the dependence of the lactic acid dehydrogenase equilibrium on pH a strong negative correlation between log ([lactate]/[pyruvate]) and pH has been found. 3) The steady state fluxes of glycolysis at pH 8.0 and 7.4 are rather equal, despite significant differences in the intracellular concentrations of glycolytic intermediates. At pH 8.0 the concentrations of ATP, glucose 6-phosphate, and fructose 6-phosphate are lower, and the concentrations of ADP, AMP, fructose 1,6-bisphosphate, triose phosphates, phosphoglycerates, and phosphoenolpyruvate are higher than at pH 7.4. 4) From the analysis of the pH dependent changes of metabolites it follows that different mechanisms are responsible for maintaining equal actual activities of hexokinase, phosphofructokinase and pyruvate kinase at pH 7.4 and 8.0. 5) From an application of the linear theory of enzymatic chains and a calculation of the control strength of the regulatory important enzymes results that hexokinase is evidently rate-limiting for glycolysis, and phosphofructokinase is also significantly influencing the glycolytic flux. Pyruvate kinase and glyceraldehyde phosphate dehydrogenase, on the other hand, do not significantly affect the rate of the overall glycolytic flux in ascites.
Metabolic regulation and mathematical models.
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