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Biomedical subjects

F J Müller

Publications and source records attributed to F J Müller.

11 recordsLinked to original sources
PubMed1989

Macro and micro rate zonal analytical centrifugation of polydisperse and slowly diffusing sedimenting systems in isovolumetric density gradients. Application to cartilage proteoglycans.

A method to study the polydispersity of zonally sedimenting and slowly diffusing macromolecules or particles in isokinetic or isovolumetric density gradients is presented. First, a brief theory is given for predicting the zonal profile after a "triangular" (or "inverse") zone is centrifuged. This type of zone is essential to preserve hydrodynamic stability of the very slowly diffusing polydisperse solutes. It is proven, both by semitheoretical considerations and by computer calculations, that the resulting concentration profile of macrosolute is almost identical with that obtainable with a rectangular zone coextensive with the triangular one and carrying the same total mass. Next, practical procedures are described for the convectionless layering of very small triangular zones (50 microL or less). The linearity and stability of the zones are experimentally tested and verified. Finally, the method is applied to cartilage proteoglycan preparations that included either the monomeric molecules only or both the monomeric and the aggregated ones. The zonal results are compared with those obtained by using conventional boundary sedimentation. The two sets of results are seen to coincide fairly well, thus proving that the present technique can add to preparative zonal centrifugation the analytical precision of boundary sedimentation. A multimodal polydisperse system is suggested to describe the aggregated proteoglycan macromolecules.

Animals↗
PubMed1989

Centrifugal characterization of proteoglycans from various depth layers and weight-bearing areas of normal and abnormal human articular cartilage.

Ultracentrifugal polydispersity differential [g(S)] distributions were determined for the proteoglycans of various postmortem human articular cartilage samples extracted from six lateral patellar grooves in nondissociative conditions after mild collagenase digestion of the tissue. The samples consisted of 53 slices (250 microns thick), from normal, mildly fibrillated, and extensively ulcerated knee joints. When statistically analyzed in various subgroupings, the obtained average sedimentation coefficients and polydispersity profiles supported the following conclusions: (a) loss of proteoglycan aggregation and sedimentability is confirmed to be a primary sign of cartilage matrix degradation; (b) higher S values for proteoglycans of the high weight (HW)-bearing areas and lower values for those of the low weight (LW)-bearing areas were a typical finding in normal cartilage samples; (c) inversion of this pattern was indicative of matrix degradation, suggesting that the HW regions are more affected than the LW-bearing areas; (d) the average S value distribution across cartilage thickness tended to resemble the corresponding proteoglycan content versus distance from articular surface; and (e) the deepest cartilage layer had, in most cases, the smallest amount of aggregates while the highest average sedimentability was observed at the middle zone of the normal samples. In the discussion, a role of proteoglycan aggregation for providing a means to "pack" more proteoglycans within the collagen meshwork and to control the generation of osmotic pressure gradients is suggested.

Adult↗
PubMed1986

Augmented glucose-6-phosphate dehydrogenase activity and normal penetration and metabolism of dehydroepiandrosterone in mononuclear leukocytes in psoriasis.

The aim of the study was to determine a biochemical basis for the augmented oxidative metabolism found in mononuclear leukocytes (MNL) of patients with active psoriasis. Dehydroepiandrosterone (DHEA) is known to inhibit glucose-6-phosphate dehydrogenase (G-6-PDH). We determined the activity of G-6-PDH as well as the penetration and metabolism of DHEA - diminished plasma concentrations of which have been found in psoriatics previously - in 16 patients with active psoriasis and 16 controls. MNL in patients with psoriasis possessed 52% more (p less than 0.05) G-6-PDH activity, based on cell number, and 34% more (p less than 0.05) activity, based on soluble protein. No difference in DHEA penetration and metabolism in MNL was found between psoriatics and controls, in contrast with previous findings of reduced penetration and increased reduction in erythrocytes of psoriatics. We conclude that the enhanced G-6-PDH activity in MNL of patients with active psoriasis is not due to altered DHEA penetration or metabolism.

Adult↗
PubMed1985

Boundary centrifugation in isovolumetric and isokinetic cesium sulfate density gradients: application to cartilage proteoglycans and other macromolecules.

A boundary sedimentation methodology is described that avoids plateau dilution and simplifies the calculation of centrifugal parameters. The technique is designed for the preparative ultracentrifuge and uses a newly developed sectorial cell. It is based on previous developments of the transport method and depends on isokinetic or isovolumetric Cs2SO4 density and viscosity gradients. These gradients are prepared with a single-chamber mixing device, and the only two parameters required for their calculations are presented in a tabulated form for general use with most available rotors and cell sizes. Conditions are specified (1) to assure that the density and shape of the sedimenting molecules remain invariant through the selected electrolytic gradient, (2) to monitor the gradient profiles, and (3) to verify attainment of isokinetic or isovolumetric sedimentations. A set of equations is presented to calculate the average and transport sedimentation coefficients and the differential sedimentation coefficient distribution for both the isokinetic and isovolumetric centrifugal regimes. The method was applied to slowly diffusing polydisperse proteoglycan monomers, to a paucidisperse DNA from bacteriophage PM2, and to a diffusible monodisperse system (purified bovine serum albumin). In all cases, the expected results were obtained.

Animals↗
PubMed1983

A simple electronic capillary microviscometer.

Inexpensive electronic components were adapted to a miniaturized version of a falling-ball viscometer. This allowed automatic determination of relative viscosities of Newtonian fluids with 1% accuracy and employing only 10 to 30 microliters of sample or about 1 microgram of some biological materials. The electronic microviscometer was tested with bidistilled water at several temperatures, with CS2SO4 and glycerol solutions, several organic liquids, and some preparations of high-molecular-weight hyaluronic acid. Details of construction, circuitry, temperature control, operating procedure, and calculations are given as well as an evaluation of the instrument's performance in terms of previously established criteria.

Animals↗