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T Kraft

Publications and source records attributed to T Kraft.

At least 19 recordsLinked to original sources
PubMed2004

[Severe Class III malocclusion: long-term stability. Retrospective analysis of 12 cases].

PURPOSE: Long-term stability of severe class III is rarely evaluated in the literature. We present our findings with 12 patients who underwent surgery from June 1995 to December 1997 and analyze cephalometric superpositions. MATERIALS AND METHODS: Twelve operated patients were reviewed to analyze long-term results (follow-up 3 years 8 months). The sex ratio was well balanced. Mean age was 23 years. All patients were given pre- and postoperative orthodontic care and underwent bimaxillary surgery with Lefort 1 osteotomy and sagittal osteotomy of the rami. Delaire cephalometry on preoperative and early and late postoperative films was used to analyze outcome. Skeletal instability was defined as displacement greater than 4 mm. Recurrence was defined as secondary loss of the functional and esthetic result. RESULTS: Four patients (33%) developed skeletal instability. All patients achieved long-term stability. DISCUSSION: To detail the cause of skeletal instability, study of the principal factors of instability is presented together with a discussion of data in the literature.

Adolescent↗
PubMed2003

[Brain abscess and diffuse cervico-facial cellulitis: complication after mandibular third molar extraction].

The authors report a case of cervico-facial cellulitis with brain abscess after mandibular third molar removal. This is the observation of a 26 years old boy surgically treated for a cervico-facial cellulitis ten days after a third molar's removal. He was given anti-inflammatory drugs after removal for analgesia. After a phase of clinical improving, the patient developed pulmonary and brain abscess with neurological signs. He needed neurosurgery in emergency. After eight weeks of antibiotic treatment, the patient was cured with aftereffects (jaw constriction and sensory disorders of the right thigh). Cerebro-meningeal complications of diffuse cervico-facial cellulitis are exceptional but are responsible for heavy aftereffects. This observation confirms that using anti-inflammatory drugs for analgesia is associated with a higher rate of complications after dental removal.

Adult↗
PubMed2002

In vitro engineering of heart muscle: artificial myocardial tissue.

INTRODUCTION: Myocardial infarction followed by heart failure represents one of the major causes of morbidity and mortality, particularly in industrialized countries. Engineering and subsequent transplantation of contractile artificial myocardial tissue and, consequently, the replacement of ischemic and infarcted areas of the heart provides a potential therapeutic alternative to whole organ transplantation. METHODS: Artificial myocardial tissue samples were engineered by seeding neonatal rat cardiomyocytes with a commercially available 3-dimensional collagen matrix. The cellular engraftment within the artificial myocardial tissues was examined microscopically. Force development was analyzed in spontaneously beating artificial myocardial tissues, after stretching, and after pharmacologic stimulation. Moreover, electrocardiograms were recorded. RESULTS: Artificial myocardial tissues showed continuous, rhythmic, and synchronized contractions for up to 13 weeks. Embedded cardiomyocytes were distributed equally within the 3-dimensional matrix. Application of Ca(2+) and epinephrine, as well as electrical stimulation or stretching, resulted in enhanced force development. Electrocardiographic recording was possible on spontaneously beating artificial myocardial tissue samples and revealed physiologic patterns. CONCLUSIONS: Using a clinically well-established collagen matrix, contractile myocardial tissue can be engineered in vitro successfully. Mechanical and biologic properties of artificial myocardial tissue resemble native cardiac tissue. Use of artificial myocardial tissues might be a promising approach to reconstitute degenerated or failing cardiac tissue in many disease states and therefore provide a reasonable alternative to whole organ transplantation.

Animals↗
PubMed2001

Linkage disequilibrium mapping of the bolting gene in sea beet using AFLP markers.

The possibility of using linkage disequilibrium mapping in natural plant populations was assessed. In studying linkage disequilibrium among 137 mapped AFLP markers in four populations of sea beet (Beta vulgaris ssp. maritima (L.) Arcang.) it was shown that tightly linked loci could be detected by screening for associations. It was hypothesized that the short distances spanned by linkage disequilibrium enable markers that are very tightly linked to a target gene to be identified. The hypothesis was tested by whole-genome screening of AFLP markers for association with the gene for the annual growth habit, the B gene, in a sample of 106 sea beets. Despite the dominant nature of AFLP, two markers showing significant linkage disequilibrium with the B gene were detected. The results indicate the potential use of linkage disequilibrium for gene mapping in natural plant populations.

Alleles↗
PubMed2001

[Lactic acid polymer implants in the repair of traumatic defects of the orbital floor].

BACKGROUND: The criteria determining the choice of the technique used to repair traumatic orbital floor defects include the quality of the expected result, morbidity, ease of use and plasticity of the method, and its cost and availability. Among the different methods proposed, lactic acid polymer implants are particularly interesting. MATERIAL AND METHODS: Eighteen patients with an isolated blow-out fracture of the orbital floor were treated with a lactic acid polymer implant between 1995 and 1996. Ten of these patients were reviewed at 24 to 43 months follow-up. RESULTS: The mean age of the patients was 35 years (20-52 years). No residual diplopia was observed. None of the patients had an anomalous orbital volume or ocular dystopia. None of the implants migrated. One patient experienced episodes of palpebral inflammation that resolved spontaneously. The ten patients reviewed were satisfied with the outcome. DISCUSSION: The properties of lactic acid polymer implants facilitate their use, avoid morbidity and provide a quality result. This is the procedure of choice for repairing tissue loss of the orbital floor. It has several advantages over alternative methods (the implants are rigid, thin, resorbable and well tolerated) without having their defects (thickness, fragility, roughness, predetermined form, rapid alteration, specific instrumentation, iatrogenic disorders). In addition, lactic acid polymer plates can be remodeled when heated, allowing a precise adaptation of the implant to the orbital structures. Finally, the cost, compared with the advantages, is not a barrier for routine use.

Absorbable Implants↗
PubMed2000

Coupling of creatine kinase to glycolytic enzymes at the sarcomeric I-band of skeletal muscle: a biochemical study in situ.

The specific interaction of muscle type creatine-kinase (MM-CK) with the myofibrillar M-line was demonstrated by exchanging endogenous MM-CK with an excess of fluorescently labeled MM-CK in situ, using chemically skinned skeletal muscle fibers and confocal microscopy. No binding of labeled MM-CK was noticed at the I-band of skinned fibers, where the enzyme is additionally located in vivo, as shown earlier by immunofluorescence staining of cryosections of intact muscle. However, when rhodamine-labeled MM-CK was diffused into skinned fibers that had been preincubated with phosphofructokinase (PFK), a glycolytic enzyme known to bind to actin, a striking in vivo-like interaction of Rh-MM-CK with the I-band was found, presumably mediated by binding of Rh-MM-CK to the glycolytic enzyme. Aldolase, another actin-binding glycolytic enzyme was also able to bind Rh-MM-CK to the I-band, but formation of the complex occurred preferably at long sarcomere length (> 3.0 microm). Neither pyruvate kinase, although known for its binding to actin, nor phosphoglycerate kinase (PGK), not directly interacting with the I-band itself, did mediate I-band targeting of MM-CK. Anchoring of MM-CK to the I-band via PFK, but not so via aldolase, was strongly pH-dependent and occurred below pH 7.0. Labeling performed at different sarcomere length indicated that the PFK/MM-CK complex bound to thin filaments of the I-band, but not within the actomyosin overlap zones. The physiological consequences of the structural interaction of MM-CK with PFK at the I-band is discussed with respect to functional coupling of MM-CK to glycolysis, metabolic regulation and channeling in multi-enzyme complexes. The in situ binding assay with skinned skeletal muscle fibers described here represents a useful method for further studies of specific protein-protein interactions in a structurally intact contractile system under various precisely controlled conditions.

Animals↗
PubMed1999

Thin filament activation probed by fluorescence of N-((2-(iodoacetoxy)ethyl)-N-methyl)amino-7-nitrobenz-2-oxa-1,3-diazole-labeled troponin I incorporated into skinned fibers of rabbit psoas muscle.

A method is described for the exchange of native troponin of single rabbit psoas muscle fibers for externally applied troponin complexes without detectable impairment of functional properties of the skinned fibers. This approach is used to exchange native troponin for rabbit skeletal troponin with a fluorescent label (N-((2-(iodoacetoxy)ethyl)-N-methyl)amino-7-nitrobenz-2-oxa-1, 3-diazole, IANBD) on Cys(133) of the troponin I subunit. IANBD-labeled troponin I has previously been used in solution studies as an indicator for the state of activation of reconstituted actin filaments (. Proc. Natl. Acad. Sci. USA. 77:7209-7213). In the skinned fibers, the fluorescence of this probe is unaffected when cross-bridges in their weak binding states attach to actin filaments but decreases either upon the addition of Ca(2+) or when cross-bridges in their strong binding states attach to actin. Maximum reduction is observed when Ca(2+) is raised to saturating concentrations. Additional attachment of cross-bridges in strong binding states gives no further reduction of fluorescence. Attachment of cross-bridges in strong binding states alone (low Ca(2+) concentration) gives only about half of the maximum reduction seen with the addition of calcium. This illustrates that fluorescence of IANBD-labeled troponin I can be used to evaluate thin filament activation, as previously introduced for solution studies. In addition, at nonsaturating Ca(2+) concentrations IANBD fluorescence can be used for straightforward classification of states of the myosin head as weak binding (nonactivating) and strong binding (activating), irrespective of ionic strength or other experimental conditions. Furthermore, the approach presented here not only can be used as a means of exchanging native skeletal troponin and its subunits for a variety of fluorescently labeled or mutant troponin subunits, but also allows the exchange of native skeletal troponin for cardiac troponin.

Actin Cytoskeleton↗
PubMed1999

The effect of thin filament activation on the attachment of weak binding cross-bridges: A two-dimensional x-ray diffraction study on single muscle fibers.

To study possible structural changes in weak cross-bridge attachment to actin upon activation of the thin filament, two-dimensional (2D) x-ray diffraction patterns of skinned fibers from rabbit psoas muscle were recorded at low and high calcium concentration in the presence of saturating concentrations of MgATPgammaS, a nucleotide analog for weak binding states. We also studied 2D x-ray diffraction patterns recorded under relaxing conditions at an ionic strength above and below 50 mM, because it had been proposed from solution studies that reducing ionic strength below 50 mM also induces activation of the thin filament. For this project a novel preparation had to be established that allows recording of 2D x-ray diffraction patterns from single muscle fibers instead of natural fiber bundles. This was required to minimize substrate depletion or product accumulation within the fibers. When the calcium concentration was raised, the diffraction patterns recorded with MgATPgammaS revealed small changes in meridional reflections and layer line intensities that could be attributed in part to the effects of calcium binding to the thin filament (increase in I380, decrease in first actin layer line intensity, increase in I59) and in part to small structural changes of weakly attached cross-bridges (e.g., increase in I143 and I72). Calcium-induced small-scale structural rearrangements of cross-bridges weakly attached to actin in the presence of MgATPgammaS are consistent with our previous observation of reduced rate constants for attachment and detachment of cross-bridges with MgATPgammaS at high calcium. Yet, no evidence was found that weakly attached cross-bridges change their mode of attachment toward a stereospecific conformation when the actin filament is activated by adding calcium. Similarly, reducing ionic strength to less than 50 mM does not induce a transition from nonstereospecific to stereospecific attachment.

Actins↗
PubMed1999

Sarcomeric binding pattern of exogenously added intact caldesmon and its C-terminal 20-kDa fragment in skinned fibers of skeletal muscle.

Intact caldesmon and particularly the actin-binding C-terminal fragment (20-kDa) of caldesmon have been shown in skeletal muscle fibers to selectively displace low affinity, weakly bound cross-bridges from actin without significantly altering the actin attachment of force producing, strong binding cross-bridges (Brenner et al., 1991; Kraft et al., 1995a). However, the sarcomeric distribution and the specific binding of externally added caldesmon to the myofilaments of skeletal muscle fibers was not known. It was e.g., unclear whether caldesmon binds along actin in a manner similar to tropomyosin or whether it also binds to myosin. In this study, we determined the binding pattern of exogenously added intact caldesmon and its C-terminal 20-kDa fragment, respectively, in MgATP-relaxed rabbit skeletal muscle fibers using electron (EM) and confocal fluorescence microscopy (CFM). EM showed that similar to what has been demonstrated earlier for smooth muscle thin filaments (Lehman et al., 1989), intact caldesmon binds periodically every 38 nm along the thin filaments. CFM revealed that rhodamine-labeled intact caldesmon and the 20-kDa caldesmon fragment bind along nearly the entire length of the thin filaments. A portion of the I-band near the Z-line appears unlabeled, both when equilibrated at normal and long sarcomere lengths. The width of the unlabeled region seems to depend on ionic strength. The 20-kDa C-terminal caldesmon fragment binds in essentially the same pattern as intact caldesmon. This indicates that the high fluorescence intensity in the overlap region seen with intact caldesmon does not depend on caldesmon binding to myosin. X-ray diffraction was used to monitor the effects of filament lattice. Intact caldesmon at > 0.3 mg/ml induced disorder in the myofilament lattice. No such disordering was observed, however, when fibers were equilibrated with up to 0.8 mg/ml of the 20-kDa caldesmon fragment.

Actins↗
PubMed1999

A single-fiber in vitro motility assay. In vitro sliding velocity of F-actin vs. unloaded shortening velocity in skinned muscle fibers.

We describe an approach that allows us to form a micro in vitro motility assay with as little myosin as can be retrieved from a short (approximately 10 mm) segment of a single skinned skeletal muscle fiber (diameter some 100 microm). Myosin is directly extracted from the single fiber segment by a high ionic strength solution in the presence of MgATP, and the extracted myosin is immediately applied to a miniaturized flow cell that has been pretreated with BSA. The observed sliding velocities of fluorescently labeled F-actin are essentially identical with those reported in the literature. Since at the single fiber level most muscle fibers contain only a single myosin heavy chain isoform this approach allows us to determine without additional purification steps, the sliding velocity driven by myosins with different heavy chain isoforms. In addition, this approach can be used to directly correlate under identical experimental conditions unloaded shortening velocity measured in segments of skinned muscle fibers with the in vitro sliding velocity of fluorescently labeled F-actin by extraction of myosin from the same skinned fibers. Such direct correlation was performed with different myosin heavy chain isoforms as well as at different temperatures and ionic strengths. Under all conditions studied, unloaded shortening velocity was 4- to 8-fold faster than sliding velocity in the motility assay even at high temperature (22 degrees C) and ionic strengths >50 mM. This suggests that sliding velocity in the motility assay is limited by additional factors beyond those thought to limit velocity of unloaded shortening in muscle fibers. One such factor might be unspecific ionic interactions between F-actin and the substrate in the motility assay resulting in somewhat higher sensitivity for ionic strength of sliding velocity in the motility assay. This might become of special relevance when using in vitro sliding velocity in assessing functional consequences of mutations involving charged residues of actin or myosin.

Actins↗
PubMed1999

An evaluation of the use of pooled samples in studies of genetic variation.

When using molecular markers to study genetic variation, either the sampled individuals can be analysed individually or the individuals can be pooled and only the pools analysed (pooled samples). A theoretical investigation was carried out into the use of pooled samples in the detection of alleles and providing maximum likelihood estimates of allele frequency. The results show that, in many cases, pooled samples are more efficient than samples of individuals. Of the different pool sizes studied, small pools containing two or three individuals showed the smallest expected squared error of allele frequency estimates.

Alleles↗
PubMed1998

Fluorescence of NBD-labelled troponin-I as a probe for the kinetics of thin filament activation in skeletal muscle fibers.

Using fluorescence of NBD-labelled troponin I incorporated into skinned fibers of the rabbit psoas muscle by chasing native troponin by troponin with the NBD-labelled TnI subunit we attempted to study kinetics of thin filament activation at different Ca(++)-concentrations. Since fluorescence of NBD-labelled TnI is sensitive to both, changes in Ca++, and strong cross-bridge attachment, we were able to induce changes thin filament activation by rapidly dropping the fraction of strongly attached cross-bridges to very low levels, e.g. by switching from isometric to isotonic contraction conditions. At any [Ca++], the time course of the resulting changes in fluorescence of NBD-labelled TnI was found at least an order of magnitude faster than the time course of force redevelopment subsequent to the period of isotonic contraction. Modelling shows that with the kinetics of thin filament activation derived from these studies, common kinetic schemes of the actomyosin ATPase predict regulation to act via changes in cross-bridge cycling kinetics, as we had previously proposed.

Animals↗
PubMed1998

X-ray diffraction studies of the cross-bridge intermediate states.

Two dimensional x-ray diffraction was obtained from skinned rabbit psoas muscle fibers. The goal is to correlate structures of the cross-bridge population with various intermediate states in the cross-bridge cycle by using nucleotides and their analogs. It was found that in a relaxed muscle in ATP containing solutions, cross-bridges are distributed in three populations in equilibrium: those detached from actin and ordered on the myosin helix, those that are detached and disordered, and those weakly attached to actin in random orientations. The distribution among the three populations is highly dependent on temperature. Those that are detached and yet ordered in a helical structure surrounding the myosin backbone are very likely in the M.ADP.Pi state, supporting an earlier suggestion by Wray (1987). It was also found that the attached cross-bridges with bound MgADP are structurally distinct from those without nucleotide, in agreement with one of our earlier findings by osmotic compression (Xu et al., 1993). Another finding of interest is that the analog AMP-PNP was found to be an ATP analog, rather than an ADP analog as it has been reported previously by many research groups.

Adenosine Triphosphate↗
PubMed1998

Structural features of force-generating cross-bridges. A 2D-X-ray diffraction study.

In several concepts of muscle contraction it was proposed that during force generation cross-bridges assume a rigor-like conformation. However, so far 2D-X-ray diffraction patterns recorded during isometric contraction did not reveal structural features of rigor-like cross-bridges. It was therefore supposed that the number of force generating cross-bridges in isometric steady state contraction is too low to be detected in 2D-X-ray diffraction patterns. To test this concept we studied the features of 2D-X-ray diffraction patterns of different fractions of rigor-like cross-bridges by varying the concentration of the nucleotide analog ATP gamma S at high [Ca++]. Although we had a fully activated system, i.e., that weak binding cross-bridges were attached to the activated thin filament, none of the patterns was like the active pattern. Analysis of the intensity change of the actin layer lines at 1/370 A-1 and at 1/59 A-1 in diffraction patterns recorded during isometric contraction vs. relaxed and rigor conditions as well as mechanical experiments revealed that the fraction of force generating cross-bridges apparently is as high as 55-70%. Yet, in agreement with previous studies, in spite of this large fraction of force generating cross-bridges, no rigor-like features were detected in diffraction patterns recorded during isometric contraction. Moreover, the intensity distribution along the actin layer lines was clearly different in rigor compared to isometric contraction. Taken together these results provide evidence that in contrast to the above mentioned models the majority of the force generating cross-bridges seems to be in a conformation which is different from rigor.

Adenosine Triphosphate↗
PubMed1998

The isoenzyme-diagnostic regions of muscle-type creatine kinase, the M-260 and M-300 box, are not responsible for its binding to the myofibrillar M-band.

Muscle-type creatine kinase is known for its unique interaction with the myofibrillar M-band, but the molecular origin for this structural relationship is not well understood. A systematic sequence comparison between the highly homologous cytosolic isoforms, muscle-type and brain-type creatine kinase, yielded two isoenzyme-specific regions in the muscle-type creatine kinases, the M-260 box (residues 258-270) and the M-300 box (residues 300-315). These particular regions were conspicuous for the specific interaction of this CK isoenzyme, but not of brain-type creatine kinase, with the sarcomeric M-band. In situ diffusion assays with fluorescently labeled native, as well as mutated muscle-type creatine kinase variants, were used to study by laser confocal microscopy their association with the M-band of chemically skinned muscle fibers. Neither a set of charge mutants of the M-260 box and/or the M-300 box nor a hybrid construct of both isoforms with the entire C-terminal region derived from the brain-type isoform showed any significant alteration in the in situ M-band-binding properties when compared to the wild-type form of muscle-type creatine kinase. This indicates that in the intact protein of muscle type creatine kinase, these C-terminal isoenzyme-specific regions are not important for M-band interaction and that the actual M-band interaction domain(s) lay mostly within the N-terminal half of the molecule. The highly conserved motives (M-260 box and M-300 box) may serve an isoenzyme-specific purpose yet to be identified.

Amino Acid Sequence↗
PubMed1998

Positive correlation between recombination rates and levels of genetic variation in natural populations of sea beet (Beta vulgaris subsp. maritima).

The relation between the level of genetic variation and the rate of recombination per physical unit was investigated in sea beet (Beta vulgaris subsp. maritima). The rate of recombination per physical unit was estimated indirectly through marker density in an RFLP linkage map of sugar beet. From this map, we also selected RFLP markers covering two of the nine chromosomes in Beta. The markers were used to estimate the level of genetic variation in three populations of sea beet, two from Italy and one from England. Two estimates of genetic variation were employed, one based on the number of alleles in the sample and the other on heterozygosity. A statistically significant positive correlation was found between recombination rate and genetic variation. Several theoretical explanations for this are discussed, background selection being one. A correlation similar to this has been observed previously in Drosophila, one that was higher than what we obtained for Beta. This is consistent with various biological differences between the two species.

Chenopodiaceae↗
PubMed1997

X-ray diffraction studies of cross-bridges weakly bound to actin in relaxed skinned fibers of rabbit psoas muscle.

X-ray diffraction patterns were obtained from skinned rabbit psoas muscle under relaxing and rigor conditions over a wide range of ionic strengths (50-170 mM) and temperatures (1 degree C-30 degrees C). For the first time, an intensification of the first actin-based layer line is observed in the relaxed muscle. The intensification, which increases with decreasing ionic strength at various temperatures, including 30 degrees C, parallels the formation of weakly attached cross-bridges in the relaxed muscle. However, the overall intensities of the actin-based layer lines are low. Furthermore, the level of diffuse scattering, presumably a measure of disorder among the cross-bridges, is little affected by changing ionic strength at a given temperature. The results suggest that the intensification of the first actin layer line is most likely due to the cross-bridges weakly bound to actin, and that the orientations of the weakly attached cross-bridges are hardly distinguishable from the detached cross-bridges. This suggests that the orientations of the weakly attached cross-bridges are not precisely defined with respect to the actin helix, i.e., nonstereospecific. Intensities of the myosin-based layer lines are only marginally affected by changing ionic strength, but markedly by temperature. The results could be explained if in a relaxed muscle the cross-bridges are distributed between a helically ordered and a disordered population with respect to myosin filament structure. Within the disordered population, some are weakly attached to actin and others are detached. The fraction of cross-bridges in the helically ordered assembly is primarily a function of temperature, while the distribution between the weakly attached and the detached within the disordered population is mainly affected by ionic strength. Some other notable features in the diffraction patterns include a approximately 1% decrease in the pitch of the myosin helix as the temperature is raised from 4 degrees C to 20 degrees C.

Actins↗