Rheology of synovial fluid.

After a discussion of the role of synovial fluid as a joint lubricant, rheological measurements are described with both normal (healthy) synovial fluids and pathological ones. Shear stress and first normal stress difference are measured as a function of shear gradient to calculate the apparent shear viscosity eta 1 and the apparent normal viscosity psi 7 as well as an apparent shear modulus G'. It is found, that in case of diseased synoviae all rheological parameters deteriorate. Most significant changes are observed with the zero shear viscosity eta 0, the shear modulus G', and a characteristic time theta 1, which is the reciprocal of the critical shear rate Dc which determines the onset of shear thinning. The rheological deterioration of synovial fluids is explained in terms of solute structure, whereby a molecular mass of the backbone hyaluronic acid of at least 10(7) g.mol-1 is required for satisfactory function. A theory of the rheological performance of normal synovial fluid as well as its pathological deterioration is proposed.

The lectin-binding protein from the pea (Pisum sativum); properties and interactions.

The lectin-binding protein (lectin binder) from the garden pea (Pisum sativum) was studied. It is a glycoprotein composed of four subunits of about 50 000 Da. Its amino-acid composition and molecular mass differ from those of lectin and of storage proteins. The interaction between lectin and lectin binder is demonstrated and quantified by several different methods and is shown to be specifically sugar-dependent. A biological function of lectin binders and lectins is discussed.

Small-angle X-ray and light scattering studies on the influence of Mg2+ ions on the structure of the RNA from bacteriophage MS2.

The influence of Mg2+ ions on the secondary and tertiary structure of the RNA from bacteriophage MS2 was investigated by small-angle X-ray scattering and light scattering and by sedimentation experiments. The analysis of the outer part of the X-ray scattering curve obtained at low temperature in the absence of Mg2+ yielded a cross-section radius of gyration of 0.88 nm and a mass per unit length of 1720 g mol-1 nm-1. Very similar values for these parameters, which refer to the secondary structure of the RNA molecule, were also derived from the X-ray scattering curves obtained in the presence of different amounts of Mg2+ (0.07 to 1 ions per nucleotide). On the contrary, the inner part of the X-ray scattering curves turned out to be highly dependent on the Mg2+ concentration: the cross-section radius of gyration and the mass per unit length, which were determined from the scattering curves at small angles as parameters related to the tertiary structure of the RNA, amounted to 3.11 nm and 4000 g mol-1 nm-1, respectively, in the absence of Mg2+ and increased significantly upon raising the concentration of Mg2+. The increase of these structural parameters was found to be accompanied by a decrease of the overall radius of gyration (as revealed indirectly by X-ray scattering and directly by light scattering measurements) and by an increase of the sedimentation coefficient. The results from the investigations of the RNA at low temperature clearly establish the existence of double-stranded structures down to very low Mg2+ concentrations as well as the occurrence of Mg2+ induced changes of the tertiary structure.(ABSTRACT TRUNCATED AT 250 WORDS)

Internal hernia and gangrenous intestine. A rare complication of a femoral--femoral bypass graft.

An unusual case of an internal hernia related to a retropubic femoral-femoral bypass graft is presented. An orifice between the left and right inguinal ligaments and a protruding intraperitoneal portion of the prosthetic graft material resulted in herniation and strangulation of a portion of the small intestine. Technical factors (graft redundancy or misplacement) and natural factors (pulsatile erosion or age elongation) may be implicated. The potential for this complication exists in all grafts currently placed. The subcutaneous location appears to be a better technique.

[Biorheology: problems and results in medicine]. / Biorheologie. Probleme und Ergebnisse in der Medizin.

After a short explanation of the topic and a methodological introduction, several recent biorheological findings are presented and discussed. Intrinsic viscosity measurements with lipoproteins show, that a certain type associates strongly in presence of Ca ions thus representing a risk factor for infarction. A rheological theory of rheumatic deterioration of knee joint synovial fluid is presented and suggested as a diagnostic aid. Finally, recent results in blood rheology are reported and their bearing on circulation problems and arterial obstructive conditions discussed.

The interaction of calf thymus DNA with mercuric acetate and 3,6-bis-(acetatomercurimethyl)-dioxane. Small-angle X-ray scattering and viscosity studies.

The binding of Hg2+ and 3,6-bis-(acetatomercurimethyl)-dioxane (BAMD) to sonicated calf thymus DNA was studied by small-angle X-ray scattering and viscosity measurements. The scattering experiments with DNA complexed by different amounts of mercurials (for Hg2+ rb=0-0.79, for BAMD rb=0-0.86 mol of mercurial bound per mol of base pairs) established that the rod-like character of the DNA molecules is maintained up to high binding ratios. They revealed further a steady decrease of the cross-section radius of gyration Rc for the DNA X Hg2+ complex and a similar decrease of Rc for the DNA X BAMD complex up to Rb=0.35. This behaviour is certainly caused by the incorporation of both mercurials near the axis of the DNA helix. Binding of BAMD at rb greater than 0.35 led to an increase of Rc which behaviour obviously reflects the location of mercury atoms at large distances from the axis, possibly on the surface of the helix. The increase of the mass per unit length Mc upon binding of the mercurials was found to be much higher than expected. This finding established that the length of the DNA helix decreases by 0.10 +/- 0.01 nm per bound mercurial at low binding ratios (i.e. up to rb=1/3 for BAMD, up to possibly rb=0.5 for Hg2+). A similar conclusion was also drawn from the observed decrease of intrinsic viscosity [n] with increasing rb. The analysis of Mc at high binding ratios suggests that every BAMD molecule bound beyond rb=1/3 decreases the length of the DNA by 0.21 +/- 0.05 nm whereas Hg2+ when bound beyond rb=0.5 causes no change of the length.

[Biorheological contribution to the problem of rheumatic joint diseases]. / Biorheologische Beiträge zum Problem der rheumatischen Gelenkserkrankungen.

The rheological properties of synovial fluids from patients with different rheumatic diseases are discussed. Viscosities of 73 samples were determined and are compared to a standard of "healthy" human synovial fluid p. m. and to bovine synovia. Typical differences between "healthy", degenerative and inflammatory synovial fluids could be discerned. These differences can be characterized with several rheological parameters. The mechanism of lubrication in joints and the role of synovial fluid as a lubricant are discussed. Rheological properties of polymere solutions which could serve as a substitute for sick synovial fluids are described and compared to the properties of healthy synovia. Several possibilities for molecular changes which could account for the deterioration of synovial fluids in patients with different rheumatic diseases are discussed.

[A rheological study on plasma lipoproteins (author's transl)]. / Eine rheologische Studie an Plasma-Lipoproteinen

Lipoproteins of the types LpB and LP-X are studied in a microviscometer to measure intrinsic viscosity. Up to a shear rate of 1700s-1 no shear dependence of viscosity is observed. Intrinsic viscosities are 3.5 and 4.0 for LpB, and 8.5 ml/g for LP-X. Density measurements are used to calculate apparent specific volumes. The results are compatible with a spherical model. An upper limit of 0.45 is estimated for the hydration.