Mutations in desmin's carboxy-terminal "tail" domain severely modify filament and network mechanics

Inherited mutations in the gene coding for the intermediate filament protein desmin have been demonstrated to cause severe skeletal and cardiac myopathies. Unexpectedly, some of the mutated desmins, in particular those carrying single amino acid alterations in the non-alpha-helical carboxy-terminal domain ("tail"), have been demonstrated to form apparently normal filaments both in vitro and in transfected cells. Thus, it is not clear if filament properties are affected by these mutations at all. For this reason, we performed oscillatory shear experiments with six different desmin "tail" mutants in order to characterize the mesh size of filament networks and their strain stiffening properties. Moreover, we have carried out high-frequency oscillatory squeeze flow measurements to determine the bending stiffness of the respective filaments, characterized by the persistence length l(p). Interestingly, mesh size was not altered for the mutant filament networks, except for the mutant DesR454W, which apparently did not form proper filament networks. Also, the values for bending stiffness were in the same range for both the "tail" mutants (l(p)=1.0-2.0 microm) and the wild-type desmin (l(p)=1.1+/-0.5 microm). However, most investigated desmin mutants exhibited a distinct reduction in strain stiffening compared to wild-type desmin and promoted nonaffine network deformation. Therefore, we conclude that the mutated amino acids affect intrafilamentous architecture and colloidal interactions along the filament in such a way that the response to applied strain is significantly altered. In order to explore the importance of the "tail" domain as such for filament network properties, we employed a "tail"-truncated desmin. Under standard conditions, it formed extended regular filaments, but failed to generate strain stiffening. Hence, these data strongly indicate that the "tail" domain is responsible for attractive filament-filament interactions. Moreover, these types of interactions may also be relevant to the network properties of the desmin cytoskeleton in patient muscle.

Accessory mitral valve as a potential source of cardioembolism

An accessory mitral valve (AMV) is considered to arise from abnormal development of endocardial cushion tissue. It is a very rare entity, commonly diagnosed in childhood and associated with symptomatic left ventricular outflow tract (LVOT) obstruction. Here we describe the presence of AMV in a 58-year old patient who presented with a transient ischemic attack. Transesophageal echocardiography visualized a spherical structure attached to the ventricular aspect of the anterior mitral valve leaflet.

Severe myopathy mutations modify the nanomechanics of desmin intermediate filaments

Mutations in the intermediate filament (IF) protein desmin cause severe forms of myofibrillar myopathy characterized by partial aggregation of the extrasarcomeric desmin cytoskeleton and structural disorganization of myofibrils. In contrast to prior expectations, we showed that some of the known disease-causing mutations, such as DesA360P, DesQ389P and DesD399Y, are assembly-competent and do allow formation of bona fide IFs in vitro and in vivo. We also previously demonstrated that atomic force microscopy can be employed to measure the tensile properties of single desmin IFs. Using the same approach on filaments formed by the aforementioned mutant desmins, we now observed two different nanomechanical behaviors: DesA360P exhibited tensile properties similar to that of wild-type desmin IFs, whereas DesQ389P and DesD399Y exhibited local variations in their tensile properties along the filament length. Based on these findings, we hypothesize that DesQ389P and DesD399Y may cause muscle disease by altering the specific biophysical properties of the desmin filaments, thereby compromising both its mechanosensing and mechanotransduction ability.

Clinical, genetic, and cardiac magnetic resonance imaging findings in primary desminopathies

We report the clinical, genetic and cardiac magnetic resonance imaging (MRI) findings in 11 German patients with heterozygous E245D, D339Y, R350P and L377P desmin mutations and without cardiac symptoms. Clinical evaluation revealed a marked variability of skeletal muscle, respiratory and cardiac involvement even between patients with identical mutations, ranging from asymptomatic to severely affected. While echocardiography did not show any pathological findings in all 11 patients, cine MRI revealed focal left ventricular hypertrophy in 2 patients and MR delayed enhancement imaging displayed intramyocardial fibrosis in the left ventricle in 4 patients indicating early myocardial involvement. Our data argue against distinct genotype-phenotype correlations and suggest that comprehensive cardiac MRI is superior to conventional echocardiography for the detection of early and clinically asymptomatic stages of cardiomyopathy in desminopathy patients. Therefore, cardiac MRI may serve as a screening tool to identify patients at risk, which might benefit from early pharmacological and/or interventional (e.g. implantable cardioverter-defibrillator devices) therapy.

Intermediate filaments: from cell architecture to nanomechanics

Intermediate filaments (IFs) constitute a major structural element of animal cells. They build two distinct systems, one in the nucleus and one in the cytoplasm. In both cases, their major function is assumed to be that of a mechanical stress absorber and an integrating device for the entire cytoskeleton. In line with this, recent disease mutations in human IF proteins indicate that the nanomechanical properties of cell-type-specific IFs are central to the pathogenesis of diseases as diverse as muscular dystrophy and premature ageing. However, the analysis of these various diseases suggests that IFs also have an important role in cell-type-specific physiological functions.

Conspicuous involvement of desmin tail mutations in diverse cardiac and skeletal myopathies

Myofibrillar myopathy (MFM) encompasses a genetically heterogeneous group of human diseases caused by mutations in genes coding for structural proteins of muscle. Mutations in the intermediate filament (IF) protein desmin (DES), a major cytoskeletal component of myocytes, lead to severe forms of "desminopathy," which affects cardiac, skeletal, and smooth muscle. Most mutations described reside in the central alpha-helical rod domain of desmin. Here we report three novel mutations--c.1325C>T (p.T442I), c.1360C>T (p.R454W), and c.1379G>T (p.S460I)--located in desmin's non-alpha-helical carboxy-terminal "tail" domain. We have investigated the impact of these and four--c.1237G>A (p.E413K), c.1346A>C (p.K449T), c.1353C>G (p.I451M), and c.1405G>A (p.V469M)--previously described "tail" mutations on in vitro filament formation and on the generation of ordered cytoskeletal arrays in transfected myoblasts. Although all but two mutants (p.E413K, p.R454W) assembled into IFs in vitro and all except p.E413K were incorporated into IF arrays in transfected C2C12 cells, filament properties differed significantly from wild-type desmin as revealed by viscometric assembly assays. Most notably, when coassembled with wild-type desmin, these mutants revealed a severe disturbance of filament-formation competence and filament-filament interactions, indicating an inherent incompatibility of mutant and wild-type protein to form mixed filaments. The various clinical phenotypes observed may reflect altered interactions of desmin's tail domain with different components of the myoblast cytoskeleton leading to diminished biomechanical properties and/or altered metabolism of the individual myocyte. Our in vitro assembly regimen proved to be a very sensible tool to detect if a particular desmin mutation is able to cause filament abnormalities.

Assembly defects of desmin disease mutants carrying deletions in the alpha-helical rod domain are rescued by wild type protein

Most mutations of desmin that cause severe autosomal dominant forms of myofibrillar myopathy are point mutations and locate in the central alpha-helical coiled-coil rod domain. Recently, two in-frame deletions of one and three amino acids, respectively, in the alpha-helix have been described and discussed to drastically interfere with the architecture of the desmin dimer and possibly also the formation of tetramers and higher order complexes [Kaminska, A., Strelkov, S.V., Goudeau, B., Olive, M., Dagvadorj, A., Fidzianska, A., Simon-Casteras, M., Shatunov, A., Dalakas, M.C., Ferrer, I., Kwiecinski, H., Vicart, P., Goldfarb, L.G., 2004. Small deletions disturb desmin architecture leading to breakdown of muscle cells and development of skeletal or cardioskeletal myopathy. Hum. Genet. 114, 306-313.]. Therefore, it was proposed that they may poison intermediate filament (IF) assembly. We have now recombinantly synthesized both mutant proteins and subjected them to comprehensive in vitro assembly experiments. While exhibiting assembly defects when analyzed on their own, both one-to-one mixtures of the respective mutant protein with wild type desmin facilitated proper filament formation. Transient transfection studies complemented this fundamental finding by demonstrating that wild type desmin is also rescuing these assembly defects in vivo. In summary, our findings strongly question the previous hypothesis that it is assembly incompetence due to molecular rearrangements caused by the mutations, which triggers the development of disease. As an alternative, we propose that these mutations cause subtle age-dependent structural alterations of desmin IFs that eventually lead to disease.

Impact of disease mutations on the desmin filament assembly process

It has been documented that mutations in the human desmin gene lead to a severe type of myofibrillar myopathy, termed more specifically desminopathy, which affects cardiac and skeletal as well as smooth muscle. We showed recently that 14 recombinant versions of these disease-causing desmin variants, all involving single amino acid substitutions in the alpha-helical rod domain, interfere with in vitro filament formation at distinct stages of the assembly process. We now provide mechanistic details of how these mutations affect the filament assembly process by employing analytical ultracentrifugation, time-lapse electron microscopy of negatively stained and glycerol-sprayed/low-angle rotary metal-shadowed samples, quantitative scanning transmission electron microscopy, and viscometric studies. In particular, the soluble assembly intermediates of two of the mutated proteins exhibit unusually high s-values, compatible with octamers and other higher-order complexes. Moreover, several of the six filament-forming mutant variants deviated considerably from wild-type desmin with respect to their filament diameters and mass-per-length values. In the heteropolymeric situation with wild-type desmin, four of the mutant variants caused a pronounced "hyper-assembly", when assayed by viscometry. This indicates that the various mutations may cause abortion of filament formation by the mutant protein at distinct stages, and that some of them interfere severely with the assembly of wild-type desmin. Taken together, our findings provide novel insights into the basic intermediate filament assembly mechanisms and offer clues as to how amino acid changes within the desmin rod domain may interfere with the normal structural organization of the muscle cytoskeleton, eventually leading to desminopathy.

Forced expression of desmin and desmin mutants in cultured cells: impact of myopathic missense mutations in the central coiled-coil domain on network formation

We recently demonstrated that inherited disease-causing mutations clustered in the alpha-helical coiled-coil "rod" domain of the muscle-specific intermediate filament (IF) protein desmin display a wide range of inhibitory effects on regular in vitro assembly. In these studies, we showed that individual mutations exhibited phenotypes that were not, with respect to the severity of interference, predictable by our current knowledge of the structural design of IF proteins. Moreover, the behavior of some mutated proteins in a standard tissue culture cell expression system was found to be even more complex. Here, we systematically investigate the behavior of these disease mutants in four different cell types: three not containing desmin or the related IF protein vimentin and the standard fibroblast line 3T3, which has an extensive vimentin system. The ability of the mutants to form filaments in the vimentin-free cells varies considerably, and only the mutants forming IFs in vitro generate extended filamentous networks. Furthermore, these latter mutants integrate into the 3T3 vimentin network but all the others do not. Instead, they cause the endogenous network of 3T3 vimentin to reorganize into perinuclear bundles. In addition, most of these assembly-deficient mutant desmins completely segregate from the vimentin system. Instead, the small round to fibrillar particles formed distribute independently throughout the cytoplasm as well as between the collapsed vimentin filament arrays in the perinuclear area.

Exploring the mechanical behavior of single intermediate filaments

Intermediate filaments (IFs) are structural elements of eukaryotic cells with distinct mechanical properties. Tissue integrity is severely impaired, in particular in skin and muscle, when IFs are either absent or malfunctioning due to mutations. Our knowledge on the mechanical properties of IFs is mainly based on tensile testing of macroscopic fibers and on the rheology of IF networks. At the single filament level, the only piece of data available is a measure of the persistence length of vimentin IFs. Here, we have employed an atomic force microscopy (AFM) based protocol to directly probe the mechanical properties of single cytoplasmic IFs when adsorbed to a solid support in physiological buffer environment. Three IF types were studied in vitro: recombinant murine desmin, recombinant human keratin K5/K14 and neurofilaments isolated from rat brains, which are composed of the neurofilament triplet proteins NF-L, NF-M and NF-H. Depending on the experimental conditions, the AFM tip was used to laterally displace or to stretch single IFs on the support they had been adsorbed to. Upon applying force, IFs were stretched on average 2.6-fold. The maximum stretching that we encountered was 3.6-fold. A large reduction of the apparent filament diameter was observed concomitantly. The observed mechanical properties therefore suggest that IFs may indeed function as mechanical shock absorbers in vivo.

Severe muscle disease-causing desmin mutations interfere with in vitro filament assembly at distinct stages

Desmin is the major intermediate filament (IF) protein of muscle. Recently, mutations of the desmin gene have been reported to cause familial or sporadic forms of human skeletal, as well as cardiac, myopathy, termed desmin-related myopathy (DRM). The impact of any of these mutations on filament assembly and integration into the cytoskeletal network of myocytes is currently not understood, despite the fact that all cause the same histopathological defect, i.e., desmin aggregation. To gain more insight into the molecular basis of this process, we investigated how mutations within the alpha-helical rod domain of desmin affect both the assembly of the recombinant protein in vitro as well as the filament-forming capacity in cDNA-transfected cells. Whereas 6 of 14 mutants assemble into seemingly normal IFs in the test tube, the other mutants interfere with the assembly process at distinct stages, i.e., tetramer formation, unit-length filament (ULF) formation, filament elongation, and IF maturation. Correspondingly, the mutants with in vitro assembly defects yield dot-like aggregates in transfected cells, whereas the mutants that form IFs constitute a seemingly normal IF cytoskeleton in the cellular context. At present, it is entirely unclear why the latter mutant proteins also lead to aggregate formation in myocytes. Hence, these findings may be a starting point to dissect the contribution of the individual subdomains for desmin pathology and, eventually, the development of therapeutic interventions.

The biology of desmin filaments: how do mutations affect their structure, assembly, and organisation?

Desmin, the major intermediate filament (IF) protein of muscle, is evolutionarily highly conserved from shark to man. Recently, an increasing number of mutations of the desmin gene has been described to be associated with human diseases such as certain skeletal and cardiac myopathies. These diseases are histologically characterised by intracellular aggregates containing desmin and various associated proteins. Although there is progress regarding our knowledge on the cellular function of desmin within the cytoskeleton, the impact of each distinct mutation is currently not understood at all. In order to get insight into how such mutations affect filament assembly and their integration into the cytoskeleton we need to establish IF structure at atomic detail. Recent progress in determining the dimer structure of the desmin-related IF-protein vimentin allows us to assess how such mutations may affect desmin filament architecture.

Pathogenic effects of a novel heterozygous R350P desmin mutation on the assembly of desmin intermediate filaments in vivo and in vitro

Mutations of the human desmin gene on chromosome 2q35 cause a familial or sporadic form of skeletal myopathy frequently associated with cardiac abnormalities. Here, we report the pathogenic effects of a novel heterozygous R350P desmin missense mutation, which resides in the evolutionary highly conserved coil 2B domain of the alpha-helical coiled-coil desmin rod domain, on the assembly of desmin intermediate filaments (IF) in cultured cells and in vitro. By transfection experiments, we show that R350P desmin is incapable of de novo formation of a desmin IF network in vimentin-free BMGE+H, MCF7 and SW13 cells and that it disrupts the endogenous vimentin cytoskeleton in 3T3 fibroblast cells. Hence, transfected cells displayed abnormal cytoplasmic protein aggregates reminiscent of desmin-positive protein deposits seen in the immunohistochemical and ultrastructural analysis of skeletal muscle derived from the index patient of the affected family. To study the functional effects of the R350P desmin mutation at the protein level, we performed in vitro assembly studies with wild-type (WT) and mutant desmin protein. Our analysis revealed that the in vitro assembly process of R350P desmin is already disturbed at the unit length filament level and that further association reactions generate huge, tightly packed protein aggregates. On assessing the pathogenic effects of R350P desmin in various mixtures with WT desmin, we show that a ratio of 1 : 3 (R350P desmin/WT desmin) is sufficient to effectively block the normal polymerization process of desmin IFs. Our findings indicate that the heterozygous R350P desmin mutation exerts a dominant negative effect on the ordered lateral arrangement of desmin subunits. This disturbance of the lateral packing taking place in the first phase of assembly is ultimately leading to abnormal protein aggregation.

Upregulation of embryonic transcription factors in right ventricular hypertrophy

Increased ventricular expression of genes encoding for various structural and contractile proteins has been reported in cardiac hypertrophy. Mechanisms leading to this altered gene expression are only partly understood. Recently, various transcription factors (TF), among them GATA-4, Nkx-2.5/Csx, MEF-2 and the HAND family (eHAND and dHAND), and their role in embryonic cardiac development have been described. These transcription factors are known to have binding sites to promotor regions of many genes known to be regulated in hypertrophy of adult ventricular myocardium. We investigated the temporal and spatial expression pattern of these transcription factors in a rat model of acute pressure-overload of the right ventricle, induced by banding (coarctation) of the pulmonary artery. Expression of GATA-4, Nkx-2.5/Csx, MEF-2 and dHAND protein was found to increase in the right ventricle after the banding procedure as determined by immunohistochemistry and western blotting. A marker of the onset of cardiac hypertrophy was expression of ANP protein. We conclude that TF known to regulate embryonic heart development are involved in the adaptational response of adult ventricular myocardium to pressure overload.

[Occlusion of the arteries of the fingers after hyperextension trauma]

Acute occlusion of digital arteries due to a sport injury A 33 year old female patient with acute ischaemia of the fingers I-II of the right hand was admitted to our emergency unit. She reported that this complete ischaemia had shortly occurred after a sport injury due to an extreme hyperflexion of the right hand in a volleyball match. Four days after this trauma she felt pain and paraesthesia in the right hand. Circular areas of ischaemia were developed with skin colour change to grey and dark blue. The primary measure of the blood pressure by doppler analysis showed no signals in the first and second finger. Initially she received 500 mg Aspirin by intravenous injection. The full therapeutic dose of LMWH related to the weight of the patient was given. On the basis of the short time interval between the occurrence of the symptoms and admission of the patient we decided to perform a so called retrograde intravenous injection. The aim of this therapy was the intraarterial lysis and reperfusion. The blood pressure in all fingers were nearly normal after three days. Daily intravenous transfusion of prostaglandin were given additionally. Necrosis could be prevented as a result of our treatment over seven days. At the end of our therapy only the skin epithelium of the second finger was slightly raised and showed a tendency to desquamation. All other fingers occurred in a normal colour.

Smoothelin is an indicator of reversible phenotype modulation of smooth muscle cells in balloon-injured rat carotid arteries

Restenosis is the major obstacle interfering with a successful long-term outcome of balloon angioplasty. Neointima formation following endothelial injury is the result of phenotype modulation and proliferation of smooth muscle cells (SMC). To characterize these time-dependent changes, a rat balloon injury model of carotid artery restenosis was assessed. We applied monoclonal antibodies recognizing desmin, sm-alpha-actin and smoothelin, a novel marker specific for the differentiated phenotype of SMC. Neointima formation could be seen from day 7 after injury onwards. During early phases, the number of smoothelin-positive cells in the media was decreased compared with uninjured controls. Smoothelin staining was absent in the neointima during formation. Increased levels of smoothelin in both media and neointima were observed at days 28 and 56, correlating with a decrease in proliferation as assessed by Ki-67 antigen staining. No such changes were observed for desmin and sm-alpha-actin. Following balloon injury, SMC in both the media and the neointima underwent an early, reversible dedifferentiation, followed by proliferation. The novel SMC-specific marker protein smoothelin can be used to monitor this SMC (de)differentiation in neointima and media. These findings support the pivotal role of SMC phenotype modulation in neointima formation and restenosis.

Phosphorylation of cytokeratin 8 and 18 in human vascular smooth muscle cells of atherosclerotic lesions and umbilical cord vessels

Expression of cytokeratins (CK) is considered a hallmark of the state of epithelial differentiation. CK also occur in certain vascular smooth muscle cells (VSMC), inferring an association with a less differentiated phenotype. Recently, CK posttranslational modification was shown to occur in epithelial cells in stress, mitosis or apoptosis. The aim of this study was to determine potential CK phosphorylation patterns in human VSMC. Tissue samples of normal peripheral and coronary arteries, atherosclerotic lesions and umbilical cord vessels were evaluated by immunofluorescence microscopy applying antibodies specific for cytokeratins 8 and 18, specific cytokeratin phosphorylation sites, Ki-67-antigen as a proliferation marker and nick end labeling (TUNEL) to detect apoptosis. All samples contained cytokeratin-positive VSMC but diverse phosphorylation patterns. The C-terminal serine 431 of cytokeratin 8 (CK8Ser-431) was phosphorylated in the vast majority of CK-expressing VSMC of coronary artery lesions. Only a subset of these cells demonstrated phosphorylation of CK18Ser-33 or, to an even lesser extent, CK8Ser-73. DNA fragmentation occurred predominantly in samples containing cells with phosphorylated CK8Ser-431 domains. In contrast, occluded peripheral lesions exhibited little or no phosphorylation. Neonatal VSMC in umbilical cord vessels contain abundant phosphorylated CK domains, again predominantly CK8Ser-431, but also CK18Ser-33. Again, only single cells were found to be proliferating or to contain DNA fragmentation. Thus, abundant CK phosphorylation in VSMC of atherosclerotic lesions suggests a specific functional response to cell stress and a possible relation to apoptosis.

[Acute acral ischemia in all fingers possibly due to a Borrelia infection]

Acute interruption of circulation in the distal fingers can be both expression of an embolic event as well as the first manifestation of a vasculitis or collagenosis. The search for its cause is frequently difficult. In many cases a specialized analysis of the coagulation system as well as diagnostics such as ultrasound scan of the heart or a systematic antibody scanning do not reveal the origin of an embolus or the underlying disorder. On the basis of a case-report we would like to focus on a possible context between an infection of Borrelias stage III and consecutive deterioration of peripheral arterial perfusion in the fingers. Besides Jo-1- and positive sceleton-muscle-antibodies there were no serological and clinical indications for an autoimmune disease. It was possible to avoid acral necrosis by means of an antibiotic, immunosuppressive and rheological therapeutic concept. We recommend to control the borellia-antibody-level in cases of obscure threatening peripheral necrosis caused by arterial perfusion stop.

Zur Makro- und Mikrozirkulation am Vorfuß unter verschiedenen Kompressionsdrücken bei gesunden Probandinnen

Zielstellung und Methoden: Das Ziel dieser Studie bestand in der Untersuchung der Makro- und Mikrozirkulation am Fuß bei Gesunden unter dosierter Kompression des Beines. Die Makro- und Mikrozirkulation wurden mit Doppler-Ultraschall-Knöchelarteriendruck- Messung und Nahe-Infrarot-Rot-Remissions-Photoplethysmographie (NIRP) bzw. mit Laser-Doppler-Flowmetrie (LDF), transkutaner Sauerstoff- (tcpO2) bzw. Kohlendioxidpartialdruckmessung (tcpCO2) und NIRP an 13 weiblichen Probanden, mittleres Alter 33,4 ± 16,8 Jahre, unter Ruhebedingungen vor und nach jeweils 5-minütiger Kompression mit 10, 20, 30, 40 bzw. 50 Torr gemessen. Ergebnisse: Der Knöchelarteriendruck sowie tcpO2 und tcpCO2 blieben unverändert. Ein signifikanter Abfall zeigte sich mit steigendem Kompressionsdruck oberhalb 20 Torr beim LDF-Flux (p <0,01) und Hämatokrit (p <0,05). Der mit NIRP bestimmte periphere Mikrozirkulations- Koeffizient pMC verminderte sich signifikant (p <0,05) oberhalb 10 Torr Kompressionsdruck. Die spektrale Maßzahl MLFo veränderte sich kaum, während die Maßzahl MLFv signifikant (p <0,05 bzw. 0,01) anstieg. Der Pulsquotient PQ fiel signifikant (p <0,05) ab bei signifikanten (p <0,01) Rückgang von Gipfelzeit TG und Wendepunktzeit TW oberhalb von 10 bzw. 30 Torr. Schlußfolgerung: Bei Gesunden tritt unter Kompression bis 50 Torr keine Verschlechterung der Makrozirkulation auf, während sich die Mikrozirkulation komperessionsbedingt ändert.

Cardiac alpha-actin in smooth muscle cells: detection in umbilical cord vessels and in atherosclerotic lesions

Phenotypic modulation of smooth muscle cells (SMC) is a key event during the development of atherosclerotic and restenotic lesions. During this process, the composition of the cytoskeleton is substantially altered, with changes predominantly in actin expression reflecting a shift from smooth muscle alpha-actin to the non-muscle beta-isoform. We now demonstrate that yet another actin isoform, cardiac alpha-actin, is synthesized, de novo, in SMC of various atherosclerotic lesions. Using a highly specific monoclonal antibody against cardiac alpha-actin, we analyzed and compared the accumulation of this actin isoform in diverse SMC by immunofluorescence microscopy and immunoblotting. As expected, cardiac alpha-actin was present in human myocardium but not in healthy SMC of adult aorta, coronary arteries, trabeculae of the spleen, colon, stomach or skeletal muscle. Interestingly, the presence of cardiac alpha-actin was detected in umbilical cord vessels, human myometrium, in atherosclerotic coronary lesions and atherosclerotic lesions from peripheral vascular disease. The distribution of cardiac alpha-actin often paralleled that of cytokeratins 8 and 18, intermediate filament proteins typically found in dedifferentiated SMC. Taken together, the data presented here illustrate the expression of cardiac alpha-actin to be limited to either fetal vessels or those vessels or tissue having suffered damage or atrophy, outside its 'native' environment in the heart. The demonstration of cardiac alpha-actin in SMC of umbilical cord vessels and in atherosclerotic lesions but not in apparently healthy vessels supports the notion that SMC in atherosclerotic lesions exhibit a dedifferentiated phenotype.

Zur Makro- und Mikrozirkulation am Vorfuß unter verschiedenen Kompressionsdrücken bei Patienten mit peripherer arterieller Verschlußkrankheit

Ödeme bei Patienten mit peripherer arterieller Verschlußkrankheit (pAVK) stellen ein komplizierendes Moment der Gewebsernährung dar. In der Literatur gibt es nur ungenügende Angaben darüber, bis zu welchem arteriellen Perfusionsdruck eine Kompressionsbehandlung ohne Beeinträchtigung der Mikrozirkulation möglich ist. Ziel und Methode: Ziel dieser Studie war, die Kompressionsdrücke zu ermitteln, bei denen es zu einer nicht mehr tolerablen Einschränkung der Makrobzw. Mikrozirkulation kommt. Dazu wurden 21 pAVK-Patienten untersucht. Bei der Auswertung wurden die Patienten mit Knöchelarteriendruckwerten >65 (Gruppe A) und <65 Torr (Gruppe B) gesondert betrachtet. Ergebnis: Der Knöchelarteriendruck sowie tcpO2 und tcpCO2 änderten sich in beiden Gruppen nicht. Der LDF-Flux fiel (ebenso LDF-Speed und -Concentration) tendenziell mit steigendem Kompressionsdruck in beiden Gruppen. Der mit der nichtinvasiven NIRP-Methode bestimmte periphere Mikrozirkulationskoeffizient pMC zeigte einen signifikanten (p ≤0,001) Abfall bereits zwischen 0 und 20 Torr, der sich in beiden Gruppen bis 40 Torr fortsetzte. Der pMC war in der Gruppe B tendenziell kleiner. Die bereits vor der Kompression erhöhte spektrale Maßzahl ML, H aus dem Amplitudenspektrum, die den Gefäßtonus reflektiert, blieb unverändert. Schlußfolgerung: Der fehlende Abfall des Knöchelarteriendruckes sowie von tcpO2 und tcpCO2 zeigt, daß bei pAVK-Patienten unter Kompression bis 40 Torr keine wesentlichen Veränderungen der Makrozirkulation auftreten, aber signifikante Veränderungen in der Mikrozirkulation entstehen, wie sie insbesondere durch den sinkenden pMC widergespiegelt werden. Inwieweit diese Veränderungen als Kontraindikation für eine Kompressionstherapie angesehen werden müssen, bleibt noch unklar.

[Effect of common head gear on horses]

The functions of the most common head-gears for horses are analysed from a biomechanical point of view. With the exception of the stable halter are all of them designed to enlarge the tensile forces transmitted through the reins or the longe, and to concentrate the enlarged forces on sensitive parts of the horse's head: the nose, or the lips, mandible and tongue. Since the direction, duration and size of these tensile forces are the essential factors to modulate signals for controlling the horse, a device has been developed to measure, or at least roughly quantify these forces. The mechanical characteristics of bosal, caveçon, serreta, kappzaum and hackamore are demonstrated and compared with those of the two major types of bits: those with and without levers.

Vergleichende Untersuchung von Kompressionsstrumpfhosen der Klasse 1 mit Stützstrumpfhosen

An 20 Krankenschwestern mit einer chronisch-venösen Insuffizienz I. Grades nach Widmer wird die Wirkung einer neu entwickelten Kompressionsstrumpf-hose der Kompressionsklasse 1 (Produkt A, ca. 20 mmHg) in Hinblick auf Veränderungen der Hämodynamik in der V. fem. comm. sowie auf eine mögliche Ödemprotektion untersucht. Als Vergleich dient eine handelsübliche »Stützstrumpfhose« (Produkt B, ca. 10 mmHg). Die Ergebnisse zeigen, daß beide Produkte im Liegen eine Verbesserung der Hämodynamik bewirken, wobei Produkt A eine signifikant bessere Wirkung als Produkt B erzielt. Produkt A reduziert die Ödemneigung innerhalb eines Arbeitstages signifikant um 64%, Produkt B zeigt lediglich die Tendenz zur reduzierten Ödemneigung, signifikante Veränderungen sind hier nicht vorhanden.

Malignant melanoma in the CNS, subtyping and immunocytochemistry

Paraffin-embedded specimens from 21 patients (mean age 49 years) with malignant melanocytic tumors of the central nervous system were studied. Extraneuronal primary tumors were situated at the trunk (38%), the lower (14%) or upper extremity (10%), and the head/neck region (5%). In 33% no extraneural primary tumor could be detected. The tumor location was frontal (19%), occipital (19%), parietal, spinal, multifocally (14%, respectively), or temporal (5%). Four subtypes were distinguished according to the predominant histological cell type: pleomorphic, epithelioid, spindle- and mixed-cell tumors. 29% contained no melanin, most of them belonging to the epithelioid subtype. The morphology and immunohistochemical reactivity for different antibodies (KL-1, EMA, VIM, HMB-45, NKI-C3, S-100, and MIB-1/Ki-67) were assessed. Positive staining was demonstrated for HMB-45 (in 86% of cases), NKI-C3 (100%), S-100 (95%), vimentin (75%), and KL-1 (33%). No expression of the cytokeratin EMA could be detected. The mean proliferation index measured by MIB-1 immunoreactivity was 21%. The 4 histological subtypes were found to express different antigen patterns. In the analysis of CNS tumors of unknown origin, the panel of antibodies used for diagnosis should include HMB-45 as the most specific marker for malignant melanoma.

[Sore throat patients as the topic of a general practice quality circle. Determination and development of a practice guideline. Quality Assurance Study group for General Medicine]

The present paper describes the institutionalization of a general practitioners' quality circle and the development of management guidelines for the treatment of patients with sore throat. Doctors participating: An invitation to attend an "information meeting" on the subject quality control and a quality circle sent to 200 general practitioners and internists, evoked a response by 18 physicians, ten of whom participated in the first meeting of the quality circle. Practical procedure: Stocktaking of the procedure in the doctor's office on the basis of a documentation questionnaire, the discussion of a video of the counselling of a patient with a sore throat, interviews with patients and the personal experience of the participating physicians was compared with a current analysis of the literature. The results of the comparison were taken as a basis for the development of management guidelines following the Dutch NHG Standard (Nederlands-Huisartsen-Genootschap-Standarden).

RESULTS AND CONCLUSIONS

A wide variation was found in the treatment offered to patients with sore throats in the doctor's office. Deviation from text book information does not indicate a priori any quality deficit in the GP's practice. With respect to the management guideline worked out, it was agreed that in the individual case, a wellfounded deviation can be justified.

Modulation of DNA supercoiling by interaction with netropsin and other minor groove binders

The assay of DNA unwinding by ethidium, followed by sedimentation velocity techniques, was applied to complexes of supercoiled plasmid DNA with different non-intercalating drugs which strongly and sequence-specifically bind to DNA. Compared with the behaviour of naked DNA, most of the complexes exhibit an increase in the critical EB/nucleotide binding ratio associated with the principal minimum in the sedimentation profile. Using netropsin (Nt) as the paradigm of the minor groove binders investigated, the drug-induced alterations in various structural parameters of both the relaxed and supercoiled form of DNA are described. Whereas winding number, helical repeat (both being defined with reference to a surface normal), and linking number of the superhelical DNA remain constant in our experiments, its twist number, surface twist, number of superhelical turns as well as the absolute values of linking number difference, superhelix density, and writhing number increase on binding of Nt. Correspondingly, compared with the naked relaxed DNA a higher linking number (or twist number, or winding number), a higher average duplex winding angle and a lower helical repeat have to be assigned to the relaxed Nt-DNA complex. The various minor groove binders investigated were found to differ considerably in their efficiency to alter the structure of supercoiled DNA.

Structural differences between histone H1 molecules from sea urchin (Strongylocentrotus intermedius) sperm and calf thymus: hydrodynamic and c.d. studies

Comparative sedimentation, diffusion and circular dichroism (c.d.) measurements have been performed on two histones H1 from sperm of the sea urchin Strongylocentrotus intermedius (H1S) and from calf thymus (H1T), at a high salt concentration of M NaCl. Both the Stokes radius and the frictional ratio derived from the hydrodynamic parameters were found to be somewhat smaller for H1S than the corresponding values for H1T. In view of the considerably higher molar mass of H1S compared with that of H1T, this result indicates that H+S in 2 M NaCl has a more compact conformation than H1T, probably due to a higher degree of secondary structure in the flanking domains of H1S. The c.d. measurements likewise show that H1S has a higher content of ordered structures than H1T. Model considerations indicate that the C-terminal tail of H1S is the main candidate for accommodation of these additional secondary structure regions.

A study of drug binding to DNA by partial intercalation using a model phenazine derivative

Spectrophotometry, thermal denaturation, sedimentation, and viscometric techniques were used in a study of interaction of double helical DNA with an asymmetric phenazinium derivative, aposafranine. The results obtained indicate that aposafranine binds to DNA by a single binding mode, a wedge-like partial intercalation.

Interaction of histone H1 from sea urchin sperm with superhelical and relaxed DNA

Complexes of histone H1 from sea urchin sperm (H1S) and calf thymus (H1T) with superhelical DNA I and relaxed circular DNA II have been analyzed by analytical sedimentation. Similar to H1T, the highly basic and relatively arginine-rich histone H1S preferentially interacts with DNA I compared to DNA II under competition conditions. However, H1S induces a stronger aggregation of both forms of DNA than H1T. Below 0.05 M NaCl, the soluble complexes formed by both histones have similar properties, but aggregation proceeds in a different manner: H1S induces a stronger aggregation of DNA II as compared to DNA I, whereas H1T fails to aggregate DNA I. The results are explained on the basis of differences in amino acid sequence and structure of the two histones and related to the special chromatin condensing ability of histone H1S.

Structural changes of ultraviolet-irradiated DNA derived from hydrodynamic measurements

The paper reports on sedimentation and viscosity measurements performed on ultraviolet-irradiated DNA from T7 phage and calf thymus. From the hydrodynamic data the relative changes in the mean molecular weight, radius of gyration, and effective Kuhn statistical segment length were calculated. The results show that ultraviolet irradiation (254 nm) leads to a significant decrease of the effective statistical segment length of DNA which may be due to small local helix kinks (produced by the generation of photodimers) and a local increase of chain flexibility. Alterations in the overall DNA conformation may be observed even at low fluences where the mean molecular weight almost stays constant. The locally distorted helix regions possibly may serve as recognition sites in the first step of excision repair.