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Biomedical subjects

M Urban

Publications and source records attributed to M Urban.

At least 91 records · Page 5Linked to original sources
PubMed1998

Changes in the properties of gap junctions during neuronal differentiation of hippocampal progenitor cells.

The cellular mechanisms that regulate progenitor cell lineage elaboration and maturation during embryonic development of the mammalian brain are poorly understood. Conditionally immortalized mouse hippocampal multipotent progenitor cells (MK31 cells) were found to be strongly coupled by gap junctions comprising connexin 43 (Cx43) during early neuronal ontogeny; the presence of this Cx type was confirmed by electrophysiological, molecular biological, and immunocytochemical assays. However, as progenitor cells underwent intermediate stages of neuronal differentiation under the influence of interleukin 7 (IL-7) alone or terminal differentiation after composite exposure to basic fibroblast growth factor, IL-7, and transforming growth factor alpha, coupling strength and the level of Cx43 expression declined. An additional population of junctional channels with distinct properties was detected at an intermediate stage of neuronal differentiation. Reverse transcription-PCR assays detected mRNA encoding Cx40 in IL-7-treated cells and Cx33 after both treatment conditions. Because functional channels in exogenous expression systems are not formed by pairing Cx40 with Cx43 or by pairing Cx33 with itself or additional connexins, these experimental observations raise the possibility that the progressive loss of coupling during differentiation of neural progenitor cells may involve downregulation of Cx43 coupled with potentiation of expression of Cx33 and Cx40. Furthermore, continued expression of Cx43 in differentiating neuroblasts could mediate intercellular communication between neuronal precursor cells and astrocytes by direct signaling via homotypic gap junction channels.

Animals↗
PubMed1998

[Clinical and diagnostic imaging of labrum lesions in the hip joint].

Labral lesions are common findings in residual hip dysplasia, indicating biomechanical decompensation of the hip joint. MR-Arthrography has shown an excellent accuracy of over 90% to detect these lesions. Nevertheless, so far clinical sings, radiological diagnosis and therapeutical consequences are not well known. In a prospective study, patients suspicious for labral lesions were evaluated using a standard clinical protocol, including history, clinical signs, radiography and MR-Arthrography. Clinical signs were tested by six criteria and two provocation tests. In 11% patients clinical suspicious was wrong. Best agreement with MR-Arthrography was found for "knife sharp" groin pain (100%), impingement test (100%) and painful giving way (83%). 35% of patients showed minor (grade 2) and 52% severe (grade 3 and 4) dysplasia. Independent from grade of dysplasia, no or only slight arthrosis (grade 0 and 1) was found in 64% of patients. In 16% a single acetabular cyst could be detected on radiographs, which all could be identified as intraosseous ganglia on MR-Arthrography. Labral lesions type A (post traumatic) were found in 23% of the patients with only no or minor dysplasis (grade 1 and 2), whereas labral lesions type B (dysplastic) were found in 67% of the patients with severe dysplasia (grade 3 and 4). Clinical signs for labral lesions are typical but can also be observed in other pathologies of the hip joint. Based on the findings of this study, we recommend radiographic evaluation for dysplasia and MR-Arthrography in patients with clinical suspicion for labral lesions of the hip joint.

Acetabulum↗
PubMed1998

[MRI arthrography in labrum lesions of the hip joint. Method and diagnostic value].

Magnetic Resonance imaging with its excellent soft tissue contrast represents the method of choice for examination of intraarticular and periarticular structures of joints. However, conventional MR-imaging without intraarticular contrast application is not suitable for the diagnosis of labral lesions. MR-arthrography (MRA) of the hip clearly demonstrates labral pathology by distension of the joint space and entrance of the contrast medium into the lesion. Multiplanar 3-D-gradient echo sequences enable visualisation of the most important cranio-ventral portion of the labrum. With the MRA labral lesions can be subdivided into different, clinically relevant stages. Furthermore accompanying lesions (intra- and extraosseous ganglia, stress-bone marrow-edema) can be demonstrated. In our study including operatively verified cases, MRA showed excellent sensitivity (90%) and accuracy (91%) in detecting labral lesions. So far no complication occurred with more than 100 MRA's. Therefore this technique represents the method of choice for the radiological evaluation of labral lesions of the hip joint. In this review the technical details and results of our MRA method will be presented.

Acetabulum↗
PubMed1998

A prospective study of flexor tendon repair in zone 5.

A prospective study of postoperative mobilization of flexor tendon repairs in zone 5 was conducted over a 2-year period between 1994 and 1996 using a controlled active motion (active extension-active flexion) regimen of mobilization. Fifty-two patients, who had a total of 151 flexor digitorum superficialis (FDS) and 103 flexor digitorum profundus (FDP) divisions, were available for review at a mean follow-up of 10 months. Of the 161 fingers with division of one or both flexor tendons, 66% exhibited independent FDS function and 90% achieved good or excellent results of digital range of motion. No rupture of an FDP tendon repair occurred during the study period. The data allowed us to define a new method of classifying the results of treatment of these injuries in terms of the injured wrists as a whole and not simply as a series of isolated observations for each individual finger with divided flexor tendons. The results of recovery of independent FDS action and range of finger movement achieved for injuries in which the flexors of all four fingers had been divided indicate a statistically significant interdependence of injuries of finger flexors of adjacent fingers at the wrist. Multivariate analysis showed the presence of a "spaghetti wrist" injury to have a significant adverse effect on the recovery of the independent FDS action but not on the recovery of the digital range of motion.

Adolescent↗
PubMed1998

Myosin II-actin interaction in MDCK cells: role in cell shape changes in response to Ca2+ variations.

Cultured MDCK cell monolayers respond to a low level of extracellular calcium ([Ca2+]e < or = 5 microM) with a loss of transepithelial electrical resistance and transport function, and changes in position of a circumferential ring of actin filaments tethered to the plasma membrane at the zonula adhaerens. Keeping this cytoskeletal structure in place seems necessary to preserve the architecture of the tight junctions and therefore their sealing capacity. All three effects are reversible upon restituting normal [Ca2+]e. Recent work provided evidence of actin-myosin interactions at the filament ring, thus suggesting a contraction process involved in the alteration of the actin cytoskeleton. We now report that active contraction does occur and causes an extensive morphological transformation of MDCK cells. A marked increase in cell height simultaneous with a decrease in width and area of contact to the substratum was seen within 10 min of removal of [Ca2+]e; recovery began immediately after replacing calcium, although it took longer for completion. Conventional and confocal epifluorescence studies showed actin colocalized with myosin II at various planes of resting or contracted cells, in particular at the ring level. Electron-micrographs revealed the circumferential actin ring associated with the plasma membrane in a waist-like constriction where Ca2+ was removed from the cultures. Contraction, as well as relaxation, in response to [Ca2+]e variations were inhibited by cytochalasin-D (an actin-filament disrupting drug), by okadaic acid( an inhibitor of myosin light-chain dephosphorylation), and by 2,3-butanedione monoxime (a blocker of myosin II ATPase activity). Similarly, no response was observed in cells previously depleted of metabolic energy by 2,4-dinitrophenol and 2-deoxy-D-glucose preincubation. The actin-myosin mediated reversible structural transformation of MDCK cells in response to [Ca2+]3 poses new questions for the interpretation of in vitro experiments, as well as for the understanding of epithelial function.

2,4-Dinitrophenol↗
PubMed1998

In vitro activity of hepatitis B virus polymerase: requirement for distinct metal ions and the viral epsilon stem-loop.

Hepadnaviruses have a complex replication cycle which includes reverse transcription of the pregenomic RNA. The initial step in this process in hepatitis B virus (HBV) requires the viral polymerase to engage a highly stable region of secondary structure within the pregenomic RNA termed the epsilon stem-loop. While reverse transcriptases belonging to the retrovirus family use a specific cellular tRNA as primer, HBV polymerase utilizes a tyrosine residue located within its own N terminus. Therefore, the first deoxyribonucleotide is covalently coupled to HBV polymerase prior to extension of the DNA strand by conventional reverse transcription. We have expressed HBV polymerase in a baculovirus and following purification have found it to be active with respect to protein-priming and reverse transcription of copurified RNA. Importantly, we found both of these processes to be critically dependent on the presence of the epsilon stem-loop. The metal ion preferences of HBV polymerase were also investigated for both the protein-priming and reverse transcription activities of this enzyme. Reverse transcription was dependent on magnesium, with an optimal concentration of 5 mM. However, protein-priming was strongly favoured by manganese ions and was optimal at a concentration of 1 mM. Thus, using manganese as sole source of metal ions our activity assay is restricted to the protein-priming event and will allow the search for novel antivirals specifically blocking this unique mechanism.

Animals↗
PubMed1998

[Plastic surgery of the thoracic wall as a method of thoracic wall reconstruction after complete surgical wound disintegration after sternotomy].

During the period between January 1996 and July 1998 in our department 1920 patients were operated on account of heart disease from median sternotomy. In 17 patients, i.e. in 0.9% during the early postoperative period the surgical wound disintegrated incl. dehiscence of the sternum and the development of postoperative mediastinitis. In 14 of these patients the authors reconstructed the defect of the thoracic wall by their own modification of Jurkiewicz plastic operation using the pectoral muscles. One patient from this group died, in the remaining 13 patients the wound healed without deformity of the chest and without signs of instability, without restriction of movement and function.

Aged↗
PubMed1998

[Application of the rough set theory in the prognostication of the diabetic nephropathy prevalence. Preliminary communication].

The following aspects were evaluated by rough set methods in 107 patients aged 5-22 and suffering from insulin dependent diabetes for 2-13 years: sex, age at which the disease was diagnosed, time of disease, family anamnesis, criteria of the metabolic balance, type of the applied insulin therapy and presence or absence of microalbuminuria. Mathematical analysis showed that the most significant aspects were: age at which the disease began, HbA1c and time of the disease lasting. The above aspects influence incidence of microalbuminuria in children suffering from diabetes type I.

English Abstract↗
PubMed1998

[The analysis of exercise efficiency and autonomic function in children with nontoxic nodular goiter during suppressive L-thyroxine therapy].

UNLABELLED: The aim of the study was the analysis of exercise efficiency and the function of the autonomic system in children with a nontoxic nodular goiter (NNG) subjected to TSH suppression. The study comprised 17 children, aged 11-18 years, with NNG treated with suppressive L-thyroxine doses for 6-36 months (mean 24 months). Exercise efficiency was examined on a moving track according to the protocol of Bruce. Analysis of the autonomic function was based on functional tests of the circulatory system and monitoring of the QTc interval. A group of healthy children with a negative heart and thyroid history served as control. Statistically significant acceleration of the heart rate (p<0.01) was found in NNG patients subjected to TSH suppression, compared with controls. The remaining results included a fall in exercise efficiency parameters:work load (p<0.001) and duration (p<0.003), metabolic equivalent (p<0.005), and the maximal oxygen consumption index Vo2 (p<0.005) at normal values of double product. A significant decrease was revealed in the ejection fraction during exercise (61+/-1.9 vs 67+/-5.9 p<0.001) in the group of children with nontoxic nodular goiter. CONCLUSIONS: 1. In the subclinical state of hyperthyroidism no functional disorders were observed in the autonomic system, which controls the circulatory system. 2. Exercise tolerance was reduced in patients with nontoxic nodular goiter subjected to TSH suppression. 3. A relationship was found between the level of thyroid hormones (TSH, FT4) indicating the subclinical state of hyperthyroidism and the acceleration of heart rate, reduction in the ejection fraction of the left ventricle of the heart after exercise and shortening of load test duration. 4. Higher rest values of heart rate were observed in children treated with suppressive doses of L-thyroxine, compared with controls.

English Abstract↗
PubMed1998

[Polyglandular autoimmune syndrome in 14-year-old boy].

A case of polyglandular autoimmune syndrome (PGA) in a 14-year-old boy presented is. The case syndromes included hyperthyreosis with a high titre of antithyreoglobulin and antimicrosomal antibodies and hypofunction of adrenal glands confirmed by the test with ACTH. The boy was admitted to the clinic in an average general condition. Marked insufficiency of the body mass in comparison to the height, many pigmented moles on the skin and features of thyroid hyperfunction confirmed by laboratory examinations were observed. Thyreostatic and b-blocker were applied for treatment. The boy was discharged in the condition of clinical and biochemical euthyreosis. After two months of follow-up in the Endocrinologic Outpatient Department there was no weight gain, no appetite and general weakness. The anamnesis showed multiple faintings. The boy was hospitalized again. Suspecting adrenal hypofunction, a test with ACTH was carried out but it did not give any result. Substitutive treatment was applied resulting in a gradual improvement of the general condition and disappearance of complaints. The case is presented due to the rare incidence of the syndrome and due to the diagnostic difficulties.

English Abstract↗
PubMed1998

Penile replantation--a case report.

The authors submit a successful case of penile replantation. They discuss the course of the procedure and document the immediate and long-term result of this procedure.

Adult↗
PubMed1998

[Antibodies to glutamic acid decarboxylase (GADA) as markers of risk for development of insulin-dependent diabetes mellitus].

Autoantibodies to glutamic acid decarboxylase (GADA)-found frequently before the onset of IDDM are an important marker of the autoimmune process of B cells destruction. The aim of the present study was to evaluate the possible relationship between the frequency of GADA and ICA in first degree relatives of subjects with IDDM. The GADA were determined in 238 first degree relatives of IDDM subjects. In 32 of the investigated subjects GADA were measured second time after 12 months and in 24 of them IVGTT was performed to evaluate FPIR and GADA prevalence relationship. The results demonstrate that combination of ICA and GADA antibodies has a high sensitivity and increases the specificity for predicting IDDM in high risk siblings.

Adolescent↗
PubMed1998

[The Donauspital-Stolzalpe concept (Danube Hospital, Vienna, Austria). Corrective osteotomy with selective labrum surgery following preoperative MRI arthrography].

Concomitant pathologies (labral lesions, intra-/extra-osseous ganglia and stress bone marrow edema) in adult residual hip dysplasia (RHD) might influence the outcome of conservative hip surgery. The aim of our prospective clinical study was to assess the value of preoperative MR arthrography in diagnosing concomitant lesions and in making surgical decisions in RHD. The first 37 consecutive patients with a minimum follow-up of 18 months have been analysed. All 37 patients presented RHD with the clinical symptomatology of labral lesions and underwent routine preoperative MRA. According to clinical, radiological and MR arthrographical criteria, these 37 patients were subdivided into four therapeutic subgroups: (1) reorientation of the acetabulum using the Tönnis triple pelvic osteotomy (TPO); (2) intertrochanteric varisation osteotomy (IVO); (3) palliative decompression with only symptomatic partial resection of the torn labrum (PALL); (4) primary total hip replacement (TEP). Based on the preliminary clinical and radiological outcomes of these four subgroups, the following conclusions can be drawn: labral lesions are considered to be a sign of chronic joint instability. Therefore, acetabular malorientation should be corrected by redirectional osteotomy of the acetabulum (TPO-subgroup) even in low grades of RHD if labral lesions are present. "Palliative" labral resections without corrective osteotomy (PALL subgroup) in secondary osteoarthritis due to RHD are definitively obsolete, because they rapidly progress to severe osteoarthritis due to surgically accelerated joint instability. In RHD with highly osteoarthritic hip joints and concomitant lesions, one should not hesitate to perform primary THR even in young patients.

Acetabulum↗
PubMed1997

Tetraphocomelia and bilateral cleft lip in a historical case of Roberts syndrome [Virchow, 1898].

We discuss an unlabelled specimen of tetraphocomelia and bilaterally cleft lip from the former Virchow Museum of our Medical School. Identity of the subject with a case of what was later termed "Roberts syndrome" published by Rudolf Virchow in 1898 is demonstrated. Rediscovery of this important historical case is gratifying, since almost 95% of the specimens of Virchow's collection were lost during World War II. We have restudied Virchow's case. Recent CT scan images of the fetus are presented. We review data from the literature and present new clinical details. The fate of the original clinical data after passing through three reviews is documented briefly. We also reconstruct Virchow's view on phocomelia and its consequences for later research.

Abnormalities, Multiple↗
PubMed1997

[Modern fetal autopsy oriented to clinical demands using technical information methods].

Modern ultrasonic diagnostic instruments with high resolution and color Doppler sonography allow the obstetrician to describe pathological findings very precisely and at an early stage of pregnancy. The use of high-resolution ultrasound makes it possible to detect heart malformations already between the 8th and 10th week of gestation. This development has essentially changed the clinical requirements on fetal autopsy which in its traditional way no longer meets the increased demands. Unless the pathologists faces this challenge the importance of fetal autopsy will diminish. Modern image databases and communication techniques allow the pathologist to have direct access to text and images of pre-findings by other clinics. Great importance, however, must be attached to the interdisciplinary cooperation with obstetricians and geneticists. We report on routine fetal autopsy by using an interdisciplinary database an the Charité.

Autopsy↗
PubMed1996

Identification of the pheromone response element in Ustilago maydis.

The a mating type locus of Ustilago maydis contains the structural genes for a pheromone-based cell recognition system that governs fusion of haploid cells. Binding of pheromone to its cognate receptor includes mating competence in haploid cells and stimulates filamentous growth of the dikaryon. We have analyzed transcription of genes located in the a locus and demonstrate that all genes are induced by pheromone. Transcriptional stimulation is mediated by a 9 bp DNA element (ACAAAGGGA) that occurs in multiple copies in both alleles of the a locus. By fusing multimers containing this 9 bp sequence to the pheromone gene promoter and to a heterologous promoter we demonstrate that this sequence acts as a pheromone response element. In addition, we show that expression of the b genes, which regulate pathogenic development of the dikaryon, is also stimulated by pheromone. Pheromone-inducible genes can be divided into three classes depending on whether their expression is reduced, maintained, or increased after cell fusion. These differences may suggest some regulatory cross-talk between the a and b loci.

Alleles↗
PubMed1996

The biallelic a mating type locus of Ustilago maydis: remnants of an additional pheromone gene indicate evolution from a multiallelic ancestor.

The a mating type locus of Ustilago maydis contains the structural genes for a pheromone-based cell recognition system that governs fusion of haploid cells. The locus exists in two alleles, termed a1 and a2. We have completed the analysis of the nucleotide sequences unique to a1 and a2. Within these dissimilar regions we find two short patches of DNA sequence similarity. Interestingly, one of these segments corresponds to the transcribed region of the a1 pheromone precursor. As a result of multiple nucleotide exchanges this sequence does not code for a functional product. The existence of a second pheromone gene in the a2 allele suggests that the present locus had a multiallelic ancestor. In addition, we describe the presence of two additional genes in the a2 allele. We have investigated the role of these genes during mating and pathogenic development and speculate that they might affect mitochondrial inheritance.

Alleles↗