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Biomedical subjects

R Marx

Publications and source records attributed to R Marx.

At least 91 records · Page 5Linked to original sources
PubMed1989

Oxidized fibrin(ogen) derivatives enhance the activity of tissue type plasminogen activator.

Oxidation of fibrinogen degradation products (FDP) with chloramines, results in a five- fold increase of their property to stimulate plasminogen activation by tissue type plasminogen activator (t-PA). Binding studies with immobilized stimulators demonstrated greater affinity of t-PA to oxidized than to unmodified FDP. The fibrin (ogen) domain responsible for this oxidant mediated increase in t-PA stimulation is localized in the D- subunit of fibrin(ogen). Thus, experimental data with (oxidized) I-labelled fibrin(ogen) should be interpreted with caution: the oxidized product might behave in a distinct manner than the unoxidized, native, one. As activated leukocytes release large amounts of oxidants of the chloramine type (Weiss et al., Science 222, 625-628, 1983), oxidation of fibrin might contribute significantly to fibrinolysis and proteolysis in areas of inflammation. The data give further evidence for an involvement of physiological components of haemostasis in non haemostasis but inflammation related processes.

Chloramines↗
PubMed1989

Sensitivity distribution in the central and midperipheral visual field determined by pattern electroretinography and harmonic analysis.

To investigate the value of the extrafoveal pattern electroretinogram for evaluation of local retinal defects, electroretinographic responses to contrast reversal stimulation were recorded at various locations in the central and midperipheral retina. Normal values were established in 20 eyes, and spatial selectivity at different retinal eccentricities was determined in four eyes. The response amplitude was found to decrease steeply from the fovea until about 12 degrees eccentricity and to decline only slowly thereafter. For central stimulation a clear attenuation for coarser patterns was observed. At 20 degrees and at 30 degrees eccentricity the spatial tuning function exhibited a bandpass characteristic, with the maximum amplitude shifting to lower spatial frequencies. Despite the relatively low peripheral amplitudes a satisfactory signal to noise ratio of the second harmonic responses can be obtained by Fourier analysis, which improves clinical applicability. The comparison of sensitivity in the upper and lower retina revealed a considerable asymmetry, with responses in the upper retina approximately 20% higher. No significant difference, however, was found when the temporal or nasal retina was stimulated. The reproducibility of these results is high enough to encourage clinical studies. A case of retinal venous branch occlusion exemplifies the applicability of this technique in eccentric fundus lesions.

Adult↗
PubMed1989

Social factors and trachoma: a review of the literature.

Although great advances have been made in the clinical understanding of trachoma, the disease remains endemic in many parts of the world. Economic, environmental, cultural and behavioral factors continue to play an important role in trachoma transmission and progression. The trachoma literature however, contains relatively few studies which rigorously assess the importance of social factors. A critical review of the trachoma literature implicates individual and community hygiene as important risk factors for disease. Specific risk behaviors remain to be identified and validated as independent predictors of infection in different settings. Collaboration between biomedical and social science professionals is needed to design and carry out further research.

Attitude to Health↗
PubMed1989

Limbal disease in trachoma and other ocular chlamydial infections: risk factors for corneal vascularisation.

Ocular infection with Chlamydia trachomatis, whether of genital or endemic trachoma origin, usually produces diffuse infiltration and swelling of the scleral limbus, grey infiltrates of the corneal limbus, and superficial extension of vessels onto the corneal limbus. In genitally transmitted C. trachomatis infections, subepithelial infiltrates have been reported as well. In classic endemic trachoma, limbal changes also include limbal follicles which resolve, leaving Herbert's peripheral pits, and an extensive vascular pannus. To evaluate the limbal changes in trachoma, follow-up studies were done in 1986-1987 in a group of 213 children originally seen between 1969-1972. Pannus formation occurred at a much earlier age than conjunctival scar formation and was an excellent predictor of later severe conjunctival scarring. The evidence from this study suggests that the mechanisms for corneal pannus formation from the limbus are quite different from those for scarring of the conjunctiva.

Adolescent↗
PubMed1989

[Temperature loading of resin-bonded bridges and its effect on the composite strength of the adhesive bond].

Acid-etched prostheses are exposed in the oral cavity to pressure of mastication, to corrosion due to oral fluids, to changes in temperature due to ingestion, and to iatrogenic influences. The changes in temperature which were measured in the adhesive layer were up to +/- 40 degrees C within a range from -2 degrees C up to about 80 degrees C. The bonding agents, which had a high softening temperature and little thermal expansion showed the least influence of temperature after the in-vitro tests. The fact that the tested bonding agents are different in chemistry influenced significantly the adhesive and cohesive characteristics. The thermal tests lead to the conclusion that for clinical use the following adhesives are to be preferred: Bis-GMA modified by monomeric phosphate (e.g. Panavia) and Bis-GMA (e.g. Microfill pontic).

Adhesiveness↗
PubMed1989

[Titanium in adhesive bridge technic: adhesive-metal-bond].

The application of titanium as bridge and crown metal suggests itself because of its suitable mechanical qualities and its stability against corrosion. The frequent use in medicine proofs its excellent biocompatibility. Because of the problematical casting requirements titanium has not been used very often in dentistry. As these problems had been solved recently, the question is whether titanium is suitable as resin- bonded bridge material. We compare different surface conditioning systems such as silicoating, tin plating and corrosion. The investigation shows that these surface pretreatments give stable bond strengthes.

Corrosion↗