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Biomedical subjects

M Kooijman

Publications and source records attributed to M Kooijman.

9 recordsLinked to original sources
PubMed1998

Anatomic basis of Tönnis' triple pelvic osteotomy for acetabular dysplasia.

Dysplasia of the hip in adults can be treated by a pelvic osteotomy. In order to assess pelvic anatomy in relation to surgical approach and osteotomy sites, 12 cadaver hips were studied. A triple pelvic osteotomy as described by Tönnis [6] through ilium, pubis and ischium was performed, followed by an intrapelvic and anterior and posterior dissection of the hip. At the ischium, the pudendal and inferior gluteal neurovascular bundles are most at risk medially and proximally respectively. Much less in danger is the sciatic n. as it runs 1 to 3 cm lateral to the osteotomy site. At the pubis osteotomy the femoral v. lies close on the bone and is prone to damage. The artery lies further off the bone. The ilium osteotomy starts just proximal to the anterior inferior iliac spine and exits posteriorly at the sciatic notch. Here the sciatic n. and the superior gluteal neurovascular bundle may be damaged. The practical surgical implications of these three osteotomies are discussed, especially with respect to the requirement of meticulous subperiostal dissection and accurate placement of retractors.

Acetabulum↗
PubMed1997

Transient electric birefringence study of intermediate filament formation from vimentin and glial fibrillary acidic protein.

Mg2+-induced polymerization of type III intermediate filament proteins vimentin and glial fibrillary acidic protein was studied by transient electric birefringence. In the absence of MgCl2 we found a net permanent dipole moment, approximately 45-nm-long dimers for vimentin, approximately 65-nm-long tetramers, hexamers, and possibly octamers for both proteins, and 100-nm aggregates for glial fibrillary acidic protein. Controlled oligomerization occurred after the addition of MgCl2. Although the solutions contained (small) aggregates of different sizes, more or less discrete steps in polymer formation were observed, and it was possible to discriminate between an increase in width and length. At the first stage of polymerization (in 0.3 mM MgCl2 for vimentin and 0.2 mM MgCl2 for glial fibrillary acidic protein), the permanent dipole moment disappeared without a change in length of the particles. At higher MgCl2 concentrations, structures of approximately 100 nm were formed, which strongly tended to laterally assemble into full-width intermediate filament structures consisting of about 32 monomers. This contrasts with previous models where first full-width (approximately 10-nm) aggregates are formed, which then increase in length. Subsequently, two discrete elongation steps of 35 nm are observed that increase the length to 135 and 170 nm, respectively. Possible structural models are suggested for the polymerization.

Animals↗
PubMed1995

Hydrodynamic and electrical characterization of T-vimentin dimers and tetramers by transient electric birefringence measurements.

The structure and charge distribution of T-vimentin, which differs from the intact intermediate filament protein vimentin through the absence of the first 70 amino acids, has been studied by transient electric birefringence measurements. It is found that in 0.7 mM phosphate, pH 7.5 buffer, exclusively single dimers (with a hydrodynamic length of 40 to 43 nm) are present, which are considerably bent and/or flexible and which have a relatively large permanent dipole moment. This indicates a parallel alignment of two protein chains. In 0.2 mM phosphate, 0.5 mM MgCl2, pH 7.5, predominantly tetrameric T-vimentin is found with a rigid structure, no permanent dipole moment, and a length of 63 to 68 nm. Tetramer formation is likely to be induced by binding of Mg2+ to the protein. The observed length is in agreement with that of intact vimentin tetramers in which the 1B regions of the rod domains of the dimers overlap (A11 configuration). A minor part of the tetramers may be in a flexible or bent A22 form. The loss of the permanent dipole moment when tetramers are formed is, apart from charge compensation, presumably due to the antiparallel alignment of the constituting dimers in which their dipoles cancel.

Birefringence↗
PubMed1995

The assembly state of the intermediate filament proteins desmin and glial fibrillary acidic protein at low ionic strength.

The low ionic strength structures of the type III intermediate filament (IF) proteins desmin and glial fibrillary acidic protein (GFAP) have been studied by transient electric birefringence measurements. Flexible dimers with a length of around 45 nm, particles with a length of 68 +/- 6 nm (presumably tetramers and hexamers) and larger aggregates of 108 +/- 19 nm are found. GFAP has an increased tendency to aggregate upon lowering of the pH. The aggregation state of desmin does not change in the pH range studied. The results are compared with previous results on vimentin.

Animals↗
PubMed1994

Characterization of multiple oligomeric vimentin intermediate filament units by transient electric birefringence measurements.

In this work we have studied the structure of soluble vimentin units from which intermediate filaments (IFs) are built. Several oligomeric forms have been presented in the literature as IF "building blocks", but there is still no agreement on this matter. By comparing our data with various models as proposed in the literature we can favour certain models and reject others. Transient electric birefringence (TEB) measurements were performed from which information is obtained concerning electric and hydrodynamic properties of the particles under investigation. TEB decay analysis at pH 6.8 after 70 microseconds pulses (at 20 degrees C in aqueous solution) yielded three decay times: 1.1(+/- 0.3) microseconds, 4.0(+/- 1.0) microseconds and 20.0(+/- 5.0) microseconds, with amplitudes of 45% to 60%, 30% to 45%, and less than 10%, respectively. At pH 8.5 after 70 microseconds pulses, more than 90% of the TEB signal with the second decay time is obtained, while the remainder had a decay time of 15.0(+/- 4.0) microseconds. Only when the pulse duration was decreased, the fast decay time around 1 microsecond was observed, suggesting that only a minor fraction of the particles at this pH value causes such a short decay time. At both pH values, the TEB measurements indicated that, at least in part, the molecules are oriented by a permanent dipole moment. It will be shown that the shortest decay time originates from bent or flexible dimers, and the second decay time from particles with a length of 54 to 65 nm containing, at least in part, a relatively large overall dipole moment. The longest decay time is probably due to larger aggregates. These results are consistent with a model in which single dimers, antiparallel staggered tetramers and hexamers coexist. Alternatively, but less likely on the basis of literature data, a model of parallel in-register tetramers with a considerable length contribution of the head groups would fit our research.

Animals↗
PubMed1993

Flavin dynamics in reduced flavodoxins. A time-resolved polarized fluorescence study.

The time-resolved fluorescence and fluorescence anisotropy characteristics of reduced flavin mononucleotide in solution as well as bound in flavodoxins isolated from the bacteria Desulfovibrio gigas, Desulfovibrio vulgaris, Clostridium beijerinckii MP and Megasphaera elsdenii have been examined. All fluorescence and fluorescence anisotropy decays were analyzed by two different methods: (a) least-squares fitting with a sum of exponentials and (b) the maximum entropy method to yield distributed lifetimes and correlation times. The results of both approaches are in excellent agreement. The fluorescence decay of the free as well as protein-bound reduced flavin chromophore is made up of three components. The shortest component proves to be relatively sensitive to the environment and can therefore be used as a diagnostic tool to probe the microenvironment of the reduced isoalloxazine ring system. The other two longer fluorescence lifetime components are insensitive to the chromophore environment and seem therefore to be related to intrinsic, photophysical properties of the reduced chromophore. Fluorescence anisotropy decays show that the flavin mononucleotide in all four reduced flavodoxins is immobilized within the protein matrix, as indicated by the recovery of a single rotational correlation time, reflecting the rotation of the whole protein. No indications are found that rapid structural fluctuations occur in reduced flavodoxins, and the mechanism of electron transfer from flavodoxin to other redox proteins seems to involve immobilized reduced flavin.

Clostridium↗
PubMed1993

The Dutch version of the Nottingham Health Profile: investigations of psychometric aspects.

Data on the adaptation, reliability, and validity of the Dutch version of the Nottingham Health Profile are discussed. The linguistic adaptation of the English version into Dutch is described, followed by the field-testing procedure and the analyses of data from 276 selected subjects from an average general medical group practice in a village nearby Rotterdam. The internal consistency, Cronbach alphas, of the subscales varied from .70 to .85. Test-retest measures for 51 patients with cardiac problems gave Spearman correlations from .69 to .92, while the interscale relationships yielded six relatively independent areas of discomfort and stress. By means of logistic regression analysis on differences between old versus young, male versus female, and healthy versus ill individuals, discriminant validity was satisfactory. Findings suggest that the psychometric aspects of the Dutch version, also seen from a cross-cultural point of view, are sufficient. Nevertheless, further research on reliability and validity of the Dutch version is required to establish its usefulness with different patient groups.

Adult↗
PubMed1992

Fluorescence study of the nucleic acid binding site of vimentin.

A selective tyrosine fluorescence quenching is found on interaction of vimentin with poly(dT) and poly(rA). However, addition of poly(dA) does not result in tyrosine quenching. The number of nucleotides covered by vimentin upon binding (n) of poly(dT) (50 +/- 4) appeared to be approximately the same as for poly(rA) (44 +/- 4), while the apparent binding constant (K(app)) of the latter is slightly larger (5.0 +/- 2.0 x 10(7) M-1.cm-1 vs. 2.5 +/- 0.5 x 10(7) M-1.cm-1). The finding that there exists a specific strong interaction between vimentin and nucleic acids could help in the search for cellular functions of intermediate filament proteins.

Binding Sites↗