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Biomedical subjects

R Heinrich

Publications and source records attributed to R Heinrich.

At least 19 recordsLinked to original sources
PubMed1992

The definitions of metabolic control analysis revisited.

Various definitions of coefficients in metabolic control analysis are examined with respect to their theoretical consistency and practical applicability. We suggest agreement upon a definition for control coefficients which is clearly distinct from that for response coefficients, in such a way that the former describe inherent properties of the metabolic system while the latter refer to the influence of special parameters. Advantages and drawbacks of using normalized or non-normalized control coefficients are studied. It is shown that normalized control coefficients have the advantage of being invariant to a different rescaling of the particular fluxes. We demonstrate that some problems are easier to tackle if the consistency of time-independent control coefficients with their time-dependent counterparts is taken into account. It is shown that the matrix of flux control coefficients is an indempotent matrix. This allows an interpretation in terms of the transduction of the effect of parameter perturbations. Several aspects of the experimental measurement of control coefficients are discussed, with special reference to the different definitions.

Enzymes↗
PubMed1992

[Long-term results with dental treatment concepts for disabled children].

More than 10 years ago 400 mentally and physically handicapped children aged 3 to 18 years were included in a dental care program to improve their oral health status. Besides dental treatment a comprehensive preventive program (tooth brushing, application of fluorides, dietetic recommendations) was carried out. The results prove a significant caries reduction and an increase in caries free children. A reduction of dental plaque and marginal inflammations were also observed. To prevent the carious destruction of the dentition of the handicapped, these patients should receive regular prevention-oriented dental care from the age of 3 years.

Adolescent↗
PubMed1991

Kinetic parameters of enzymatic reactions in states of maximal activity; an evolutionary approach.

A theoretical investigation is presented which allows the calculation of states of maximal reaction rates for single enzymes and for unbranched enzymatic chains. As an extension to previous papers (Heinrich & Holzhütter, 1985, Biomed. biochim. Acta 44, 959-969; Heinrich et al., 1987, Bull. math. Biol. 49, 539-595) a detailed enzymatic mechanism was taken into consideration. Conclusions are drawn for the optimal values of the microscopic rate constants as well as of the maximal activities and Michaelis constants. Ten solutions are found which depend on the equilibrium constant as well as on the concentrations of substrates and products. It is shown that for high equilibrium constants one of the solutions applies to a very large range of the concentrations of the outer reactants. This solution is characterized by maximal values of the rate constants of all forward reactions and by non-maximal values of the rate constants of all backward reactions. In contrast to previous assumptions (Albery & Knowles, 1976b, Biochemistry 15, 5631-5640; Burbaum et al., 1989, Biochemistry 28, 9293-9305) states of maximal reaction rate are not always characterized by the highest possible values of the second-order rate constants which are related to the diffusion of the substrate and the product to the active site of the enzyme. Predictions are made concerning the ratios of maximal activities in optimal states as well as for the adaptation of the Michaelis constants to the concentrations of the outer reactants. Using metabolic control analysis it is shown that the solutions obtained for single enzymes may also be applied in multi-enzyme systems.

Animals↗
PubMed1991

Minimization of intermediate concentrations as a suggested optimality principle for biochemical networks. II. Time hierarchy, enzymatic rate laws, and erythrocyte metabolism.

The multiobjective problem of minimizing all intermediate concentrations is solved for a model of glycolysis, the pentose monophosphate shunt and the glutathione system in human erythrocytes. It turns out that one solution out of four obtained corresponds qualitatively to the real system. Furthermore, it is shown that for any reaction system, the mentioned optimality principle implies distinct time hierarchy in that some reactions are infinitely fast and subsist in quasi-equilibrium. Finally, the relationships to the standard method of deriving enzymatic rate laws are discussed.

Energy Metabolism↗
PubMed1991

[The diagnosis of approximal caries--a comparison of clinical, fiber optic and x-ray diagnostic procedures (the diagnosis of approximal caries)].

A comparison of the efficiency of fibre-optic transillumination with clinical and radiographic diagnosis of proximal caries in posterior teeth was carried out on 186 subjects aged 12 to 17 years. The proportion of diagnosed proximal lesions detected by fibre-optic transillumination was two times more often than by clinical examination while the increase in lesion detection by bitewing radiography was more than threefold. Taking radiographic diagnosis as the validating criteria, the sensitivity of clinical examination was 0.30 and of fibre-optic transillumination 0.68 resp. The specificity was 0.99 for both examinations. In patients with low prevalence of proximal caries and good preventive dental care fibre-optic transillumination should be used as an additional method before using of regular radiographic diagnosing of proximal caries.

Adolescent↗
PubMed1991

[Clinical controlled study on the treatment of deep carious lesions in deciduous molars].

Compared with a step-by-step procedure, the one-step excavation of deep carious lesions in primary molars proved to be the treatment of choice in a clinically, microbiologically and histologically controlled trial. The stepwise method failed to produce any significant reduction in pulp exposure. Sensitivity assessment and percussion findings did not result in a reliable and unambiguous evaluation of treatment success. Histology showed inflammation-free pulps in 67% of the deciduous molars irrespective of the treatment method used. Microbiological examination revealed slightly softened dentin to be significantly more infected than clinically acceptable, hard dentin; although only 59.3% of the cavity floors were free of microorganisms. Chronic pulp inflammations were correlated with the presence of streptococci and lactobacilli, whereas actinomycetes were associated with inflammation-free pulps.

Case-Control Studies↗
PubMed1991

[Tooth health and periodontal condition in adults with and without root caries].

In a population sample of 2261 men and women aged between 35 and 74 years the prevalence of root caries increased for both sexes consistently with age and ranged between 49 and 73%. In the mean 1.8 to 2.9 teeth were affected. Subjects with root caries had fewer teeth, more teeth with untreated coronal caries, and more teeth which needed conservative treatments. The number of extractions required was the same in subjects affected by root caries. In the age older than 65 years subjects affected by root caries had more teeth in the average of 2 teeth and significantly more fillings in their teeth. If a DMF/T-index of 15 to 19 was recorded nearly half of all subjects were affected by root caries. In individuals with root caries lesions aged between 35 and 54 years significant severe periodontal disease were seen.

Adult↗
PubMed1990

[Will root caries become a treatment problem of the future?].

Based upon the present prevalence of root caries an attempt is taken to evaluate the future importance of this carious type. A population sample of 2,261 men and women aged 35 to 74 years were examined. The participation rate was 81%. Root caries was recorded when the lesion was obviously soft and located on cementum. The prevalence of root caries increased for both sexes almost consistently with age and ranged between 49 and 73%. In the mean 1.8 to 2.9 teeth were affected. Root caries was found more often among men than women. Over the sixth decades the reduction of the relative frequency of root caries was stated. Up to this age the rates of tooth extraction were higher than the rates of incidence. If it succeeded that in the future aged people will retain more teeth than nowadays a increase of root caries can be expected.

Adult↗
PubMed1990

[The microbial colonization of the dentin close to the pulp in the permanent teeth following deep caries therapy].

In a clinical microbiological study the microflora of cavity floors in 41 permanent teeth was investigated after several month of caries excavation and with or without Calxyl application on hard dentine prior sealing with zincphosphatecementum and amalgam. The cavity floors were only lowly infected. Actinomycetes or acidogenic and aciduric streptococci and lactobacilli dominated in the CFU. After application of Calxyl actinomycetes (A. israelii) were found 3-fold more frequently in the remaining population than streptococci (S. mutans) and lactobacilli. Without application of Calxyl their ratio was 1:1. S. mutans seems to be important for the carious progression in dentin.

Actinomyces↗
PubMed1990

[Root caries--scanning electron microscopic observations].

Sound and carious root surfaces of 24 extracted human teeth with extensive periodontal attachment loss were examined by SEM. The microflora covering the radicular surfaces was a complex flora consisting of filamentous and fusiform bacteria, short and long rods. Cocci and coccoid bacteria were observed on root surfaces. Bacterial invasion in the exposed peripheral root dentin was delayed by sclerotic dentin.

Adult↗
PubMed1990

[Prevalence of root caries in a healthy adult population].

An epidemiological study involving 963 subjects aged 25 to 64 years revealed at least one carious and/or filled root surface in 40.2% of all females and in 42.7% of all males. The number of teeth and tooth surfaces affected by root caries increases continuously with age. In relation to the total number of teeth, males display a higher prevalence of root caries than females, with the exception of men aged between 55 and 64. High-risk susceptibility shows no correlation with age, although there are more surfaces at risk in males. Independent of the sex, root caries prevalence is highest in the molars and premolars of the mandible and in the canine of the maxilla; lower incisors are the teeth with the least caries involvement. Labial root surfaces are most frequently affected by caries in the mandible; the prevalence rate is twice as high in males than females. The lingual surfaces of maxillary molars of females and the proximal and buccal surfaces of incisors of males are the most frequently affected tooth surfaces.

Adult↗
PubMed1990

The structure of metabolic systems: a theoretical approach.

A theoretical approach is presented to predict the structural design of enzymatic reaction systems. It is based on the hypothesis that the kinetic properties of enzymes and of other functionally important proteins have been optimized during evolution so that the contemporary cellular metabolic systems are operating at an optimal state. As simple but instructive example we consider the optimization of the stationary flux rate of a single enzyme. In contrast to previous studies a more realistic enzymatic rate equation has been chosen according to HALDANE's reaction scheme.

Enzymes↗
PubMed1989

Influence of prostaglandin E1 on muscular tissue-PO2 in patients with diabetic gangrene.

Intraarterial infusions of short acting vasoactive drugs have been established in the treatment of peripheral occlusive disease. We studied the effect of prostaglandin E1 on the tissue pO2 of the tibialis ant. muscle. Using a fast responding polarographic pO2-probe of the hypodermic needle type, tip diameter 300 microns, we made tissue pO2 investigations in 9 patients with diabetic gangrene. pO2-measurements were done before, during and after administration of 0.2 microgram PGE1/min i.a.. PGE1 led to a slight decrease of the mean muscular pO2 during application followed by a reincrease after the end of infusion. It is known that intraarterial PGE1 infusion leads to an increase of transcutaneous pO2 of the forefoot. Our results show, that there is no increase of tissue pO2 of the tibialis ant. muscle. The reason might be a changed distribution of blood flow in favour of an increased oxygenation of the skin due to PGE1 administration.

Aged↗
PubMed1989

Development of muscular tissue PO2 after vascular reconstructive surgery.

Using a fast responding polarographic pO2-probe of the hypodermic needle type with a tip diameter of 300 microns we investigated the influence of vascular reconstructive surgery on the tissue pO2 of the tibialis ant. muscle. In 10 patients suffering from a peripheral occlusive disease state II-III according to FONTAINE measurements of tissue pO2, pain free walking distance and doppler-index were done preoperatively, 2 weeks and 6 weeks after surgery. The results show that reconstructive vascular surgery leads to an immediate improvement of the doppler-index. In contrast to that there is a time dependent increase of the mean tissue pO2 in the tibialis ant. muscle. This development of muscular oxygenation coincides with an increasing walking distance.

Female↗