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Biomedical subjects

K Trombitás

Publications and source records attributed to K Trombitás.

At least 55 records · Page 3Linked to original sources
PubMed1990

Immunoelectron microscopic observations on tropomyosin localization in striated muscle.

Tropomyosin localization in striated muscle was studied by means of immunoelectron microscopy. Polyclonal and monoclonal antibodies to tropomyosin were allowed to diffuse into mechanically skinned single fibres dissected from frog semitendinosus muscle. Antibodies produced transverse I-band stripes with the expected periodicity of 38 nm. However, some differences were revealed among the various antibodies. While polyclonal antibodies generally showed 23 stripes, monoclonal antibodies showed an extra 24th stripe immediately adjacent to the Z-line, implying some structural/functional uniqueness of this terminal tropomyosin. Furthermore, the stripes did not always lie parallel to the Z-line. When the Z-line was straight or slightly skewed, the stripes generally were parallel to it. However, when Z-line skew was more severe, the stripes remained perpendicular to the fibre axis, indifferent to the Z-line skew. This may implay that the coupling of tropomyosin to the thin filament is not tight. Finally, the monoclonal antibodies themselves exerted an anomalous effect on the Z-line, apparently extracting or shifting some of its mass.

Animals↗
PubMed1990

A-band shortening in single fibers of frog skeletal muscle.

The question of whether A-bands shorten during contraction was investigated using two methods: high-resolution polarization microscopy and electron microscopy. During shortening from extended sarcomere lengths in the passive state, sarcomere-length changes were essentially accounted for by I-band shortening. During active shortening under otherwise identical conditions, the sarcomere length change was taken up approximately equally by A- and I-bands. Several potential artifacts that could give rise to apparent A-band shortening were considered and judged unlikely. Results obtained with polarization microscopy were similar to those obtained with electron microscopy. Thus, modest but significant thick filament shortening appears to occur during active sarcomere shortening under physiological conditions.

Animals↗
PubMed1989

Rotational motion of spin labelled microtubule protein.

Microtubule protein, isolated from porcine brain by temperature-dependent assembly-disassembly cycles, was labelled with two types of nitroxide spin labels, maleimide and isothiocyanate. Labelling was performed either in depolymerized or polymerized form of the protein. Electron paramagnetic resonance spectroscopic measurements revealed 34 ns rotational correlation time of the labels in disassembled microtubule protein which corresponds most likely to the rotational motion of the subunits. Upon polymerization, changes in the rotational dynamics of microtubule protein occurred in the temperature range of 20-30 degrees C. Polymerization process was revealed as a transition between two states, one characterizing the tubulin in its monomeric form and the other the polymeric form. In the temperature range of 20-30 degrees C, both forms (monomer-polymer) of tubulin were observed. Very slow rotational motion in the millisecond time range was detected in microtubule pellet. Orientation dependence in the distribution of spin labels in macroscopically oriented microtubules was not found.

Animals↗
PubMed1989

[Problems of the two-stage restoration of flexor tendon injuries. II. Light- and scanning electron microscopy studies of flexor tendon sheaths from hens and from humans].

Authors examined the normal flexor tendon/tendon sheat unit of the toes of the hen and in the zone Verdan 2 of the human hand with light and scanning electron microscope. The fine structure of the synovial membrane was studied with special care. It was found, in accordance with some previous literary data, that the morphology of the hen's and human tenosynovium resemble to each other. The structures of the parietal visceral synovial membranes are described and compared, and the mechanism of the secretion of the synovial fluid is discussed. The results of the present investigations may serve, over the description of the normal anatomical relations, as a comparison to other experiments of two-phase tendon transplantations with the formation of pseudo tendon sheats and also for clinical practice.

Animals↗
PubMed1989

[In vitro study of the marginal closure in adhesive fillings].

The margin closure of Dentin Adhesit composit fillings made in vitro in the dentin cavity is not the best after the cavity cleaning prescribed by the factory. After a cavity cleaning by propiol acid of 1.22% during 10 seconds better marginal closure could be obtained than by using industrial cavity cleanser (Ahydron).

Adhesiveness↗
PubMed1989

[Scanning electron microscopy and microprobe studies of fillings prepared with dentin glue].

The dentin wall of a cavity of class V prepared in vivo was, after a cavity cleaning with phosphorous acid, covered with a composite filling. The filling material penetrated into the dentin tubules. However, it did not adhere to the tubule wall. If the dentin wall of the cavity was cleaned according to factory prescriptions, the filling material did not reach the dentin. Only the preparation debris were impregnated by it.

Adhesives↗
PubMed1989

Longitudinal and vertical ultrastructural lesion of crural muscle in post-thrombotic syndrome.

The vertical and longitudinal ultrastructural changes of the crural muscle (triceps surae) were studied in a selected patient material of 18 patients suffering from post-thrombotic syndrome. The transmission and scanning electron microscopic method helped in revealing that the damage had affected the contractile system, the mitochondria and the endoplasmic reticulum and in addition marked degenerative phenomena occurred. It was shown that vertically the impairments of the fine structure were localized in foci and involved the muscle layers to the same extent. Longitudinally--distally--the muscle changes displayed an increasingly aggravating diffuse appearance. Of the several factors responsible for the development of the pathological ultrastructural picture, tissue hypoxia and metabolic disorder, as well as a decreased microcirculation (hypoperfusion) and chronic inactivity are to be emphasized.

Adult↗
PubMed1988

I-bands of striated muscle contain lateral struts.

In electron micrographs of striated muscle, the I-band often shows a distinct cross-striation. The periodicity of this striation is near 40 nm and has been attributed to troponin, which is localized along the thin filament. However, the cross-striation is often so prominent as to be suggestive of physical structures running transversely across the I-band. We examined I-band ultrastructure using three independent methods: thin sections of chemically fixed specimens; freeze-fracture; and freeze-substitution. With all three methods we found transverse structures distributed throughout the I-band, many of which bridged the gap between neighboring filaments. Such structures were observed in each of the several species studied. In fish muscle in particular, which has a highly regular lattice, it was obvious that these structures gave rise to the observed periodicity.

Animals↗
PubMed1988

Thick filaments of striated muscle are laterally interconnected.

Earlier reports from this and other laboratories indicated that thick filaments may be interconnected along their length by rung-like structures. This study was carried out to test whether these interconnections are genuine structures; whether they appear in different muscle types; and whether they arise from myosin cross-bridges. We studied insect flight muscles because of their well-known ultrastructure, and frog heart and rabbit psoas muscles secondarily. Ultrastructure was examined with freeze-fracture; with conventionally prepared thin sections; and with negative stain. All three methods showed rung-like interconnections between thick filaments. The interconnections spanned the length of the cross-bridge zone, i.e., along all but the central bare zone of the thick filament. They were observed consistently in relaxed, activated, and rigor states. We considered potential artifacts that might cause apparent interconnections where none existed in vivo, but were unable to identify a source of artifact common to all methods. Several features of the interconnections imply that for the most part they may be composed of S-1 heads from adjacent thick filaments binding to one another at their tips.

Animals↗
PubMed1988

Effect of tension on the rigor cross-bridge angle.

The effect of resting tension and external force on the rigor crossbridge angle was investigated in insect flight muscle (Honeybee, Apis mellifera). In the presence of resting tension, bridges were either perpendicular to the filament axis or tilted towards the M-line. In shortened, slack muscle, bridges remained perpendicular or were tilted towards the Z-line. Thus, the rigor bridge angle appears to depend on the state of the thick filament. With the thick filament under stress, the angle may be quite different than when it is slack. On the other hand, external force applied directly to the rigor bridges did not change their configuration. Bridge angle remained unchanged, irrespective of the amount of tension applied to the bridge. This implies that a very tight bond exists between the rigor bridge and thin filament, allowing essentially no rotation even with a large applied force.

Animals↗
PubMed1987

Morphological investigations of a porous aluminum oxide ceramic and the consequences for clinical application.

The ingrowth of bone and the tissue compatibility of a Hungarian aluminum-oxide ceramic have been investigated in animal experiments by microscopic section, by electron microscopy, and with energy-dispersion X-ray microanalysis. Surrounding bone grew into the 100- to 500-micron pores of the porous ceramic without any undesirable reaction, as well as into bored holes 500 micron in diameter. It is technically possible to make only the 1- to 2-mm deep superficial layer of such a material macroporous, so that it can be applied as an acetabular component of hip prostheses; if the surrounding bone grows into the macropores of this thin layer (as was shown in our experiment) it can perfect the connection between the living bone and the non-living ceramic material without essentially changing the much required, positive qualities of a solid acetabular component. The authors intend to apply this material in this way.

Acetabulum↗
PubMed1986

Structure of thick filaments from insect flight muscle.

The supramolecular organization of thick (myosin) filaments isolated from insect flight muscle was studied using negative staining and shadowing techniques. The electron microscopical findings favour the two-stranded arrangement of double cross-bridges rather than a four- or six-stranded structures of single cross-bridges. The thick filament backbone consists of 12-subfilaments of myosin rods with a diameter of about 4 nm in agreement with the X-ray data. Furthermore, about 4 nm stripping was observed on the filament shaft, resembling to the structure of the light meromyosin paracrystals with a periodicity of 4.8 nm. The existence of a hinge region at the origin of the projections and between the tail and myosin heads are confirmed. According to the morphological observations the stalks of the projections can be characterized with flexible properties, as well. At high level of the supramolecular organization, the myosin filaments, the connecting filaments and the Z-filaments are systematically interconnected after a remarkable myosin filament branching (trifurcation) at the Z line level, which supports the view that a continuous longitudinal filament network constitutes the structure of the myofibrils.

Animals↗
PubMed1985

How actin filament polarity affects crossbridge force in doubly-overlapped insect muscle.

We wished to find out why the internal resistance to shortening, which is negligible above rest length, becomes progressively more important with shortening below rest length. For this reason the movement of detached actin filaments in isometric sarcomeres treated with activating solution has been studied in insect flight muscle after breaking the filaments from the Z lines by stretching fibres in rigor. Evidence of sliding motion of such filaments has been produced by experimentally inducing double overlap zones in activating solution. It was deduced that the forces generated by individual crossbridges are comparable to the internal resistance to relative filament motion. Furthermore the final position of broken actin filaments indicated that wrongly polarized actin slides freely past activated crossbridges, but prevents these same bridges from exerting force on adjacent correctly polarized actin. Apparently only those bridges which are located in the normal overlap zones can generate effective force. It is therefore probable that the isometric tension is directly proportional to the number of bridges overlapped in the normal overlap zones for any sarcomere length equal to or greater than the thick filament length.

Actins↗
PubMed1985

Inter-odontoblastic fibres in human dentine observed by scanning electron microscopy.

Crowns of healthy premolars with closed apical foramina were fixed, resin-impregnated and freeze fractured. Fragments were critical-point dried and examined by scanning electron microscopy. Radial inter-odontoblastic fibres with a diameter of 0.1-0.7 micron were observed. Most of these radial fibres originated from the odontoblast cell body, but some of them arose from the pulp. Both of them entered the predentine at the rim of dentinal tubules and their branches formed the fibrous network of predentine. The odontoblast processes had only a few short side branches at the level of predentine. Some fibrils were observed in the mineralized intertubular dentine, as well.

Adolescent↗
PubMed1985

Scanning electron microscopy of the walls of tubules in human coronal dentine.

Twenty-one fully-formed healthy human premolars were fixed, resin-impregnated and freeze-fractured. Specimens were critical-point dried. The wall of the dentinal tubules was lined with a two-layered structure which extended from the pulp-predentine border to the dentine-enamel junction; there was a fibrous outer layer and an amorphous, membrane-like inner layer. The lining sheath was separated from the odontoblast process by a space which widened toward the outer surface of the dentine, although occasionally in the mid and outer dentine the lumen was constricted by transverse septa of the sheath which were in close proximity with the odontoblast process. Some tubules were divided into a system of chambers by transverse extensions of the membrane-like inner layer of the sheath.

Adolescent↗