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T Nemetschek

Publications and source records attributed to T Nemetschek.

At least 19 recordsLinked to original sources
PubMed1989

Ehlers-Danlos syndrome type IV (EDS IV) as model of a defective biopolymer composite material.

The connective tissue of a lethal EDS IV case was investigated for the reasons of the manifested disturbances of the arterial wall. This functional disorder was attributed to the mechanical decoupling of elastin and collagen, with the premise of a composite material consisting of cellular, fibrillar, lamellar and other matrix components. A conceivable relation between the manifested deficiency of type III collagen and a disturbed anchoring of elastin is shown. These findings are supported by biochemical, morphological, x-ray and mechanical data.

Adult↗
PubMed1986

New aspects of the etiology of tendon rupture. An analysis of time-resolved dynamic-mechanical measurements using synchrotron radiation.

Native collagen fibers were exposed to different dynamic loads to simulate damage to tendons and ligaments relevant clinically and for sports medicine. The results suggest that the rupture of a tendon is caused at the submicroscopic fibrillar level. Not only slow or very fast elongation, but also very fast unloading of stretched fibers seems to be responsible for disseminated damage, which reduces the stability of a fiber. This damage is induced by intrafibrillar sliding processes, which occur only a few seconds before macroscopic slippage takes place. The significance of these events for the beginning and progress of repair in vivo is discussed. The conclusions are supported by simultaneous mechanical and radiological measurements, as well as by light- and electron-microscopic results.

Animals↗
PubMed1985

Stress-induced molecular rearrangement in tendon collagen.

Tension-induced molecular rearrangements in wet native fibres of rat-tail tendons and human finger flexor tendons are registered with the help of time-resolved diffraction spectra using synchrotron radiation. The tension-induced increase of the 67 nm D period is combined with changes in the intensities of some orders of the meridional small angle reflection. Both effects are reversible when unloading the fibre, but are preserved when the load is held constant until the fibre tears. The increase in the D period is partly due to a sliding of the triple helices relative to each other and partly due to a stretching of the triple helices themselves. The sliding of the triple helices results in an alteration of the D stagger, leading to a change in the length of the gap and overlap regions, and to a stretching of the cross-linked telopeptides. This interpretation is supported by comparison with the relative intensities derived from a model with varying length of gap and overlap regions, as well as by comparison with model calculations that include the telopeptides.

Adult↗
PubMed1977

[Disordered fibrillar structure in ruptured tendons (author's transl)].

Areas of disordered fibrillar structure similar to kinking deformities have been observed in specimens from ruptured tendons. It seems possible to compare this phenomenon with experimentally produced deformations. The significance for the pathomechanics of tendon rupture is discussed.

Achilles Tendon↗
PubMed1977

[Kinking deformities in collagen (author's transl)].

The affect of stretch on collagen was investigated. Alterations of mechanical dimensions and thermostability of fibrils were measured and changes in fine structure determined by x-ray diffraction and electronmicroscopy. Collagen underwent changes both in tensile strength and fine structure following stretch beyond the physiological range. The severity of these changes depended both on the degree of stretch and the cross-link density of the collagen Fibrils either became split into bundles consisting of subfibrillar units or showed circumscribed kinking deformities. The mechanism producing kinking was investigated. It is possible that a connection exists between fibrillar kinking and tendon rupture.

Animals↗
PubMed1977

[Banded filamentous associates in the intra- and extracellular space in connection with collagen degradation (author's transl)].

Banded fibrous associates are described in the extracellular space of connective tissue from human endometrium, Ehlers-Danlos syndrome and of tendon rupture. In the cases of morbus Dupuytren these associates are also found as intracellular inclusions. The banded structures are interpreted as states of an enzymatically induced degradation of collagen in correlation with Type-III collagen.

Adult↗
PubMed1976

[Aetiology of dupuytren's contracture (author's transl)].

Regarding experimental data on the multi-factorial reduction of the thermostability of collagen, the following sequence of the mechanism of Dupuytren's contracture is discussed: 1. Hereditary or acquired weakness of fibres of the palmar fascia 2. Further disturbance of the physical property of collagen by the cumulative effects of mechanical, i.e. traumatic, influence. 3. By this means an induced stepwise shrinkage of released fascial fibres in body temperature. 4. Stabilisation of the shortening (contracture) by development of collagen. This hypothesis is supported by histological, polarizing-microscopic, electron-microscopic and chemical results.

Amino Acids↗
PubMed1975

[Paracrystallic, intraplasmatic inclusion bodies in human hepatocytes: a structural analytic study (author's transl)].

Electron micrographs from intraplasmatic inclusion bodies of human hepatocytes are described; these paracrystallic aggregations consist of helically arranged filaments. All the observed periodic structures within these bodies can be indicated as originating from the same compound by the use of the Frauenhofer diffraction pattern. Concerning the genesis of these characteristically structured bodies two possibilities are discussed: 1. A special polymeric form of fibrinogen and fibrin built up in vivo. 2. Polymerization of a monomeric enzyme, for example, glutamate dehydrogenase, to paracrystallic bodies by fixation-dependent cross-linkages.

Biopolymers↗
PubMed1975

[The so-called filaments in lafora-bodies, corpora amylacea and Bielschowsky-bodies. Fasciolar substructures in accumulated intraplasmatic material of cellular dysmetabolies (author's transl)].

Both the corpora amylacea and Lafora bodies have been described in the literature as filamentous structures. On electron microscopic examination they are often composed of ribbon-like fasciolar units. The ultrastructural appearance of these structures is discussed on the example of an amylopectin model. These fasciolar substructures are also encountered in Bielschowsky bodies and are then considered to be a sign of intracellular accumulation of dysmetabolic products. The histological and electron microscopical similarity of corpora amylacea, Lafora bodies and Bielschowsky bodies suggest that all these structures are an unspecific, nearly identical endproduct of various intracellular metabolic disturbances. The pathognomonic significance of these structures depends on their regional distribution: the common corpora amylacea occur predominantly in the astroglia, the Lafora bodies typical in the neurons and the Bielschowsky bodies are restricted to the neurons of the exterior pallidum.

Amylopectin↗